ALBERT

Description: 〈h3〉Abstract〈/h3〉 〈p〉Double-wire double-pulsed gas metal arc welding (DP-GMAW) experiments were conducted in the double pulse synchronous (DPS), alternating (DPA), and independent (DPI) phases. The effects of current phase on weld seam formation were analyzed. Experimental results showed that a stable welding process was achieved in all three current phases and the derived weld seams demonstrated little spatter, no hump, or undercut. Different current phases had little influence on weld reinforcement and width, but had a significant influence on weld penetration and toe angle. The fish-scale ripples of weld seams were prominent; specifically, the fish-scale ripples in the DPA phase were more prominent than those in other current phases. The penetration and penetration shape factor (PSF) in the DPA phase were at their highest while those in the DPS phase were at their lowest. In the DPS phase, the ferrite was coarse and in higher quantity, while the pearlite was relatively in lower quantity. In the DPA phase, the ferrite was finer and in lower quantity, while the pearlite was relatively in higher quantity and the microstructure was more uniform. Last, in the DPI phase, the microstructure appeared in a state between the DPS and DPA phases.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Thermal issues become more serious for high-speed and high-precision motorized spindle. Thermal error compensation is cost-effective and convenient to implement for this problem. To further improve the machining accuracy of the motorized spindle with shaft core cooling, this study aims to develop simple thermal error compensation model based on only the rotational speed of spindle and without any temperature data to predict the thermal error. In this study, a special measurement system was established to measure the axial thermal deformation of a motorized spindle with shaft core cooling at various speeds. A thermal error compensation model based on the exponential function was established using the experimental data. This model needs only two parameters—operating rotational speed and duration—of the motorized spindle to predict the thermal deformation and then can be easily and quickly executed without adding any extra hardware. The model is verified by comparing with experimental data at constant speeds of 4200 rpm and 7000 rpm as well as the stepped speed. The results show that the model has higher accuracy and better robustness. Under experimental conditions, when the motorized spindle operates at constant rotational speed, its accuracy increases by about 90% after compensation; when the motorized spindle operates at stepped rotational speed, the maximum thermal deformation of the motorized spindle is 29.95 μm before compensation and 2.01 μm after compensation, the accuracy of which increases by 93.2%.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The aim of this study is to identify the limitations of self-supporting structures and evaluate the deformations associated with overhang structures fabricated without support structures. To achieve these objectives, a series of experiments involving different overhang geometries were designed, fabricated, and evaluated. The formation of defects during the fabrication of overhanging structures is detailed, and the self-supporting limits for different overhangs are established. A segmentation strategy for the support structure addition is proposed and evaluated in different configurations for ledge overhangs to reduce the amount of support structures without affecting the overhang accuracy. Based on the inferences of this study, design rules are proposed for producing overhang structures through electron beam melting. The results identified the self-supporting limits for different overhang geometries. In addition, the proposed segmentation strategy for support generation in ledge overhangs resulted in reduction of support structure materials and post-processing time without any effect on the quality of the fabricated overhang.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Shrub encroachment has profound influences on regional carbon cycling. However, few studies have examined the changes in soil organic carbon (SOC) components at the molecular level along a climate gradient. In this study, we aimed to investigate the effects of biotic and abiotic factors on the patterns of SOC components in the shrub patches and the grassy matrix.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉We analyzed the distribution and controlling factors of SOC components (including free lipids, bound lipids, and lignin-derived phenols) in the topsoil of shrub-encroached grasslands along natural climate gradients in Inner Mongolia, China.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉 We found that the concentrations of bound lipids and lignin-derived phenols were significantly higher and the vanillic acid to vanillin ratio ((Ad/Al)〈sub〉v〈/sub〉) was significantly lower in the shrub patches than in the grassy matrix (〈em〉p〈/em〉 〈 0.05). After excluding variables exhibiting collinearity, redundancy analysis showed that shrub patch cover and soil pH were the most important variables that influenced SOC composition in the shrub patches, while herb characteristics and shrub density were the most important in the grassy matrix. Structural equation modeling showed that shrub characteristics at the plot scale greatly contributed to the variance in all components in the grassy matrix, whereas soil properties were more important in the shrub patches.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Our results highlight that although the topsoil carbon content did not change, shrub encroachment altered the SOC components and their drivers in the Inner Mongolian grasslands.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Background and aims〈/h3〉 〈p〉While the coupled effects of root exudates and microbial feedbacks on soil processes are well-recognized, we still lack an understanding of differences in root exudate fluxes and the associated ecological consequences among tree growth forms.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Two deciduous tree species (i.e., 〈em〉Cercidiphyllum japonicum〈/em〉 and 〈em〉Larix kaempferi〈/em〉) and two evergreen tree species (i.e., 〈em〉Pinus armandi〈/em〉 and 〈em〉Pinus tabulaeformis〈/em〉) were selected to perform an in-situ collection of root exudates during the growing season in 2016. The net N mineralization rates and associated microbial enzyme activities were measured in rhizosphere and bulk soils to evaluate rhizosphere effects. Moreover, we compiled the dataset related to root exudation and their associated biological traits and the soil chemical properties for 21 tree species from temperate forests.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉The root exudation rates and the annual root exudate carbon (C) fluxes of two deciduous tree species were significantly higher than those of the two evergreen tree species. Correspondingly, the rhizosphere effects of deciduous tree species on the microbial biomass, enzyme activity and net N mineralization rate were approximately 1.9, 1.6 and 2.4 times greater than those of the evergreen tree species, respectively. Rhizosphere effects were positively correlated with the root exudation rate. The compiled dataset also suggest that deciduous tree species tend to have higher exudation rates than evergreen tree species in temperate forests.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Collectively, these results suggest that the two tree growth forms exhibit different patterns in root exudate inputs and associated rhizosphere microbial processes. Generally, deciduous tree species tend to exude more C into the soil and consequently induce greater microbial feedback on soil N transformations during the growing season in temperate regions, implying that deciduous tree species induced a greater effect on the C and nutrient cycling in rhizosphere soil than evergreen tree species.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper addresses the use of two algorithms based on symbolic dynamics analysis of vibration signal for fault diagnosis in gearboxes. The symbolic dynamics algorithm (SDA) works by subdividing the phase space described by the Poincaré plot into several angular regions; then, a symbol is assigned to each region. The probability distributions generated by the set of symbols are considered as features for classification of faults in a gearbox. The peak symbolic dynamics algorithm (PSDA) is a variant that extracts a sequence of peaks from the vibration signals and then performs the phase-space subdivision and symbol coding. A gearbox vibration signal dataset is analyzed for classifying 10 types of faults. Fault classification is attained using a multi-class support vector machine. The highest accuracy attained using 〈em〉k〈/em〉-fold cross-validation is 100.0% for load L3 with SDA and 100% with load L2 with PSDA. The accuracy considering all signals in the gearbox dataset is 99.2% with SDA and 99.8% with PSDA. The algorithms proposed have the advantage of being simple, accurate, and fast, and they could be adapted for online condition monitoring.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Culture media compositions and bioprocess conditions were studied to improve the production of cell biomass and indolic phytohormones by 〈em〉Herbaspirillum seropedicae〈/em〉 BR11471, a plant growth promoting bacterium, and different inoculant formulations were also produced and tested for their stability and shelf life.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Response surface methodology (RSM) based on central composite rotation designs (CCRD) was used to find bioprocess variables that lead to an increase in bacterial biomass and yield of indolic compounds. The major components of DYGS medium were optimized in small-scale shaken cultivations, in two sets of CCRD. High performance liquid chromatography was used to determine nutrient consumption and to correlate it with cell biomass production, and the Salkowski method was used to quantify indoles. Hydrolytic activity in the formulations was quantified with the fluorescein diacetate assay.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Glycerol (5.5 g L〈sup〉−1〈/sup〉) and yeast extract (2.8 g L〈sup〉−1〈/sup〉), as the main carbon and nitrogen sources, respectively, increased biomass production by 87.5% when compared to original DYGS medium, reaching 3.0 g L〈sup〉−1〈/sup〉 of dry cell weight (DCW). In a 2.0 L bioreactor, the optimized medium was used to enhance process conditions for DCW and indole-3-acetic acid (IAA). Biomass production reached 3.4 g L〈sup〉−1〈/sup〉 and was restrained at highest air flow levels. The conditions of 34-36 °C, 150 rpm and 4.0 L min〈sup〉−1〈/sup〉 of air flow rate resulted in 11.97 mg L〈sup〉−1〈/sup〉 of IAA, an increase of 370% over original DYGS at 30 °C. Peat can still be regarded as a good cell carrier for solid state inoculants, whilst the additives tested for liquid formulations are individually more efficient than the mixture.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The production of inoculants containing 〈em〉H. seropedicae〈/em〉 strain BR11471 can be efficiently improved with the use of the RSM approach i.e. it maximizes the production of biomass and indolic compounds, and reduces culture media components, both key factors for large-scale industrial production.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉We examined how mechanical management of invasive macrophyte, 〈em〉Typha × glauca〈/em〉 alters plant-soil interactions underlying carbon processes and nutrient cycling, which are important to wetland function but under-represented in restoration research.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉In the northern Great Lakes, we compared plant biomass, light transmittance, soil nutrient availability and carbon mineralization rates of 〈em〉Typha〈/em〉-dominated controls with 〈em〉Typha〈/em〉 stands harvested above the waterline (harvest) and at the soil surface (submerged harvest).〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Relative to controls, harvested stands had 50% less litter and twice as much light transmittance to the water surface after one year. However, 〈em〉Typha〈/em〉 stems re-grew, and soil nutrient availability rates were similar to controls. Submerged harvest eliminated 〈em〉Typha〈/em〉 litter and stems, and increased light transmittance through the water column. P and K soil availability rates were 70% greater with submerged harvest than in controls. Soil C mineralization rates were not affected by treatment (mean ± 1 SE; 40.11 ± 2.48 μg C-CO〈sub〉2〈/sub〉 and 2.44 ± 0.85 μg C-CH〈sub〉4〈/sub〉 g〈sup〉−1〈/sup〉 soil C hr.〈sup〉−1〈/sup〉), but were positively correlated with soil Fe availability.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉While submerged harvest effectively decreased invasive 〈em〉Typha〈/em〉 biomass after one year, it increased soil nutrient availability, warranting further examination of macronutrient cycling and export during invasive plant management.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Background and aims〈/h3〉 〈p〉〈em〉Malus prunifolia〈/em〉 (Chinese name: Fu Ping Qiu Zi), a wild relative of cultivated apple (〈em〉Malus〈/em〉 x 〈em〉domestica〈/em〉 Borkh), is extremely resistant to drought compared with domesticated cultivars, such as ‘Golden Delicious’. However, the molecular mechanisms underlying drought resistance of 〈em〉M. prunifolia〈/em〉 have not been characterized. This study investigates a new regulatory mechanism to improve apple drought resistance.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉〈em〉M. prunifolia〈/em〉 and ‘Golden Delicious’ were each grafted on 〈em〉M. hupehensis〈/em〉 for gene expression analysis. The methylation level of the 〈em〉DREB2A〈/em〉 promoter was determined by bisulfite sequencing and ChIP-qPCR. Chromatin immunoprecipitation sequencing (ChIP-seq) was used to identify target genes of MpDREB2A in apple.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉The exposure to drought stress stimulated the expression level of 〈em〉DREB2A〈/em〉 gene more than 100-fold in 〈em〉M. prunifolia,〈/em〉 but only 16-fold in ‘Golden Delicious’. This difference in gene expression could not be explained in terms of difference in leaf relative water content. Correspondingly, the methylation level of 〈em〉M. prunifolia DREB2A〈/em〉 (〈em〉MpDREB2A〈/em〉) promoter region was significantly reduced. Additionally, 〈em〉MpDREB2A〈/em〉 conferred enhanced drought resistance when ectopically expressed in 〈em〉Arabidopsis〈/em〉. Over 2800 potential downstream target genes of MpDREB2A were identified by ChIP-seq and these downstream genes have diverse potential functions related to stress resistance.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Methylation regulation in promoter of 〈em〉MpDREB2A〈/em〉 may contribute to the drought resistance of 〈em〉M. prunifolia〈/em〉.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The monitoring of tool condition in machining processes has significant importance to control the quality of machined parts and to reduce equipment downtime. This study investigates the application of a special variant of artificial neural networks (ANNs), in particular, wavelet neural network (WNN) for tool wear monitoring in CNC end milling process of high-speed steel. A mixed level design of experiments with machining parameters of cutting speed, feed rate, cutting depth, and machining time is developed, from which 126 experiments are conducted. For each experiment, tool wear and surface roughness of machined workpiece are measured. The tool wear images are processed, and the descriptor of wear zone is extracted. The WNN is then applied to predict the flank wear of the cutting tool and compared with commonly used types of ANNs and the statistical model. Different input combinations with the inclusion of wear zone descriptor and surface roughness of machined parts are used to evaluate the performance of all models. Results show that the WNN with the input parameters of cutting speed, feed rate, depth of cut, machining time, and descriptor of wear zone predicts the degree of tool wear most accurately.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The centrifugal disc finishing process is an abrasive technique of mass machining, and it is very effective but very frequently time consuming. In this paper, a simulation of the centrifugal disc finishing process was presented in order to estimate the kinetic energy distribution of the working medium and to find its regions that make the process more efficient. Numerical results were obtained using an explicit method in the Ansys/Ls-Dyna program. Due to the fact that the physical properties of numerous objects in free motion need to be calculated in a simulation process, the discrete element method (DEM) was used. Results from the numerical simulations indicate that the velocity and energy of particles is variable in an axial cross-section of working medium. The article presents particle velocity distributions in the working chamber for various rotational speeds of the rotor. The typical changes in velocity in the function of time are also discussed. Statistical important functions of the average kinetic energy of the working medium and accumulated energy by machining surface have been estimated in respect to the rotational speed and machining time with a high value of adjustment coefficients. This article constitutes the first stage of research, which is continued in order to experimentally verify the results in the real process, as presented in the companion paper (Part 2: Experimental analysis with the use of acoustic emission signal).〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Characterization of barley-tissue–colonization efficiency (〈em〉Hordeum vulgare〈/em〉 L.) by 〈em〉Paraburkholderia tropica〈/em〉 MTo-293 after seed inoculation was studied in two plant-growth systems: (1) in flasks with semisolid agar-containing sterile medium, as a suitable environment to study plant-bacteria interaction and also optimize molecular-biology techniques, and (2) in a pot-substrate system as an approach to understand their potential behavior as bioinput.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Culture-dependent techniques were implemented to quantify surface and endophytic bacterial populations in plant tissues. Culture-independent techniques were employed to detect and localize the inoculated bacteria in tissue samples along with evaluating the biofilm-forming capability by epifluorescent, confocal-laser-scanning, and scanning-electron microscopy. Plant-growth parameters were measured to evaluate the effects of the inoculated bacteria on the development of the barley plants.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉〈em〉Paraburkholderia tropica〈/em〉 grew as a biofilm on both abiotic and biotic surfaces and efficiently colonized barley roots and stems in plants grown in flasks in presence of other microorganisms. The bacteria was localized on root surfaces, hairs, and central-cylinder areas. 〈em〉Paraburkholderia tropica〈/em〉 also colonized the roots and stems in plants grown in the pot-substrate system. Although no endophytic root colonization occurred, the presence of the inoculated bacteria improved the aerial weight. A nested PCR detected 〈em〉P. tropica〈/em〉 in the tissue samples.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉〈em〉Paraburkholderia tropica〈/em〉 MTo-293 was characterized as an efficient biofilm-forming and barley-tissue–colonizing bacterium despite the presence of other microorganisms, but root endophytic colonization resulted dependent on the plant-growth system. Molecular-biology techniques were optimized, and also, its presence was correlated with plant-growth–promoting activity.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Nickel alloys such as Inconel 718 have been widely used in the aerospace, oil and gas, and chemical industries, since they have excellent properties that combine high creep resistance and high mechanical strength, fatigue and corrosion. However, these properties make these alloys extremely difficult to machine, due to a high level of heat generation during material removal, causing rapid wear of cutting tools and a detrimental effect on the surface integrity, reducing the fatigue life of the machined component and lowering the productivity. Looking at the literature, it seemed that there is an opportunity to study the surface integrity of Inconel 718, turned under cryogenic conditions at cutting speeds of 250, 275 and 300 m/min. For these reasons, this work aims to evaluate the influence of the cutting parameters on the surface integrity of Inconel 718 turned under cryogenic conditions using liquid nitrogen (LN2) at high cutting speeds. A whisker-reinforced ceramic tool was used in order to provide wear and shock resistance at high cutting speeds; these are factors that are associated with surface integrity in terms of roughness Ra, residual stresses, microhardness and cutting forces. A central composite design was chosen as factorial planning for the independent variables including cutting speed, feed rate and depth of cut when carrying out the experiments. Cryogenic cooling resulted in an average cutting force of 267 N, where the penetration force was higher. The roughness Ra was 0.52 μm and was influenced by the feed rate and depth of cut. The highest tensile residual stresses in the circumferential direction with LN2 and under dry conditions were 1394 MPa and 1237 MPa, respectively and were influenced by the depth of cut. Small changes in microhardness occurred at a depth of 0.3 mm from beneath machine surface and the presence of a white layer was not observed. Although tensile residual stresses were slightly higher when using LN2 compared to dry machining on the surface, the use of LN2 caused higher compressive residual stresses at the subsurface, which can improve the fatigue life of machined components at high cutting speeds. The results showed that lower cutting parameters tend to give the best results in terms of the cutting force and surface integrity.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The modular design of reconfigurable machine tools (RMTs) is the key enabling technology to reconfigurability. A systematic methodology for setting the constituent modules of RMTs is proposed in this paper. According to the structural and functional characteristics of the components that construct the machine tools, the geometry modules and the basic structure modules are generated, and on this basis, the conceptual autonomous functional modules of RMTs can be constructed. According to the reconfigurable manufacturing process planning for a part family, the optimal processing plans of a family of parts can be obtained, which include a series of processing segments. And through the generated motion-schemes of a RMT of each processing segment, the RMT configurations can be constructed from a set of the autonomous functional modules to meet the process requirements. Finally, a set of RMT modules with particular sizes and structures can be generated, which will be used to construct RMTs to accommodate required changes in existing products or parts. Taking the production of a gearbox part family as an example, the validity of the method is verified.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Robots are widely used in automation because of their flexibility. However, there are still challenges to enhance the effective use of robots in machining process due to unexpected vibration/chatter. Instead of time-consuming trial and error, this paper proposes an expanded mode coupling chatter theory that suits robot kinematics and enables industrial application due to accurate mode coupling chatter prediction. This research allows determination of mode coupling chatter occurrence with respect to constantly changing parameters of robotic kinematic and practical contemplation before setting up the physical robot, workpiece and tool for machining. Firstly, the mathematical model of the robot structure is established and combined with chatter theory. A deepened analysis of stability criteria is carried out followed by experimental validation of the theory. By carrying out this chatter analysis, a software tool based on an algorithm was developed to help determine the stable setup, including machining parameters, robot pose, travel direction and workpiece setup, for a certain robotic machining application. The developed prediction algorithm ties vibration occurrence to machining force direction and magnitude that makes it applicable to various machining operations.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In virtual cardiovascular surgery and human-robot micro interaction surgery, the force feedback is transmitted via the flexible guide wire. Flexible deformation would make it hard to ensure fidelity only by rendering the force feedback in actuators. This study develops a dynamic model of the guide wire, which is used to simulate the collision of guide wire in the blood vessel or pipeline of the force feedback device. Its dynamic characteristic can be adapted to the design of control strategy of the force feedback and its parameter adjustment. As the force is low, it is easily affected by the motion and friction of the actuator and hand tremor. It puts up the requirement for system robustness. Then, the terminal sliding mode controller is designed to improve the robustness and convergence of the force feedback control. And the research quantitatively evaluates the fidelity of the force feedback control.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉In the face of problems caused by ‘intensive agriculture’ dominated by large areas of monocultures, mixed intercropping mimicking natural ecosystems has been reported to constitute a viable solution to increase and stabilize productivity. When designing such systems, root niche separation was thought to be a prerequisite to optimize production.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉This paper reviews the beneficial and adverse effects of trees and crops on water acquisition and redistribution in agroforestry ecosystems using the concepts of competition and facilitation between plants in link with root functional traits.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉The results of the review showed that the reality was more complex leading agroforestry practitioners to adopt management practices to induce a separation in root activities thus avoid competition, particularly for water. Water uptake by plant roots is triggered by the water potential difference between the soil and the atmosphere when leaf stomata are open and depends largely on the root exploration capacity of the plant. Thus, root water uptake dynamics are strongly related to root-length densities and root surface areas. In addition, plants with deep roots are able to lift up or redistribute water to the upper layers through a process known as hydraulic lift, potentially acting as “bioirrigators” to adjacent plants. The redistributed water could be of importance not only in regulating plant water status, e.g. by enhancing transpiration, but also in increasing the survival and growth of associated crops in mixed systems.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Even though some more work is still needed to assess the volume of water transferred to neighbors, hydraulic lift could constitute an ecological viable mechanism to buffer against droughts and ensure productivity in regions with erratic rainfall. Giving the difficulty in measuring the above-mentioned aspects in the field, modeling of some of the most relevant parameters to quantify them might inform the design of future empirical studies.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The effects of process parameters on microstructure and mechanical properties of the 316L stainless steel helical micro-diameter spring (316L HMDS) fabricated by selective laser melting (SLM) were explored. By optimizing SLM process parameters, the near-full density (〉 99%) SLM-316L HMDS can be manufactured. The SLM-316L HMDS exhibits typical layered morphology consisting of micron-sized melt pools and columnar grains whose growth orientations are consistent with the temperature gradient. Lower hatch space reduces the formation of voids, resulting in better density, elongation, and ultimate tensile strength of the SLM-316L HMDS. The form angle significantly affects the yield strength and ultimate tensile strength, and obvious dimples appear on the fracture surface, demonstrating toughness fracture. The experimental results establish the correlation between the process parameters of SLM and the microstructure and macro-mechanical properties of the SLM-316L HMDS.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this study, the effect of particle size and particle content of silicon carbide fillers in epoxy matrix on the mechanical properties and microstructure of the developed composites was investigated. Silicon carbide fillers sized to 〈 45 μm and 90–45 μm were incorporated to epoxy composites to obtain volume fractions of 2, 4, 6 and 8 wt% of SiC. Mechanical properties including flexural strength, compressive strength and hardness tests of the composite samples were performed according to ASTM D790-03 (2003), ASTM D695-15 (2015) and EN 1534 standards. Surface morphology, crack propagation and particulate dispersion were observed using scanning electron microscopes (SEM). The results of the mechanical properties obtained were examined statistically and the results that a strong negative correlation between hardness and flexural strength but the individual correlation between hardness and flexural modulus, compressive stress and compressive modulus were positive. Results also showed that the inclusion of small particulate silicon carbide (〈 45 μm) displayed superior mechanical properties in term of flexural, compressive and hardness characterizations at a given volume fraction. Flexural properties of the composite samples decrease with increase in filler concentrations while the compressive strength and hardness increase as particulate loading increase. In terms of microstructure, uniform dispersion of silicon carbide particulates was observed within epoxy matrix with linear crack propagation.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Alpine ecosystems are important terrestrial carbon (C) pools, and microbial decomposers play a key role in cycling soil C. Microbial metabolic limitations in these ecosystems, however, have rarely been studied. The objectives of this study are to reveal the characteristics of microbial nutrient limitation, and decipher the drivers in the alpine ecosystems.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Models of extracellular enzymatic stoichiometry were applied to examine and compare the metabolic limitations of the microbial communities in bulk and rhizosphere soils along an altitudinal gradient (2800–3500 m a.s.l.) under the same type of vegetation (〈em〉Abies fabri〈/em〉) on Gongga Mountain, eastern Tibetan Plateau.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉The soil microbial communities suffered from relative C and phosphorus (P) limitations in the alpine ecosystem despite of high soil nutrient contents here. Partial least squares path modelling (PLS-PM) revealed that the limitations were directly regulated by soil nutrient stoichiometry, followed by nutrient availability. The C and P limitations were higher at the high altitudes (3000–3500 m) than that at the low altitude (2800 m), which mainly attribute to changes of soil temperature and moisture along the altitudinal gradient. This suggested that global warming may relieve microbial metabolic limitation in the alpine ecosystems, and then is conducive to the retention of organic C in soil. Furthermore, the C and P limitations varied significantly between the bulk and rhizosphere soils at the high altitudes (3200–3500 m), but not at the low altitudes. This indicated the influences of vegetation on the microbial metabolisms, while the influences could decrease under the scenario of global warming.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Our study suggests that the alpine ecosystems with high organic C storage harbour abundant microbial populations limited by relative C and P, which have sensitive metabolic characteristics. This could thus potentially lead to large fluctuations in the soil C turnover under climate change. The study provides important insights linking microbial metabolisms to the environmental gradients, and improves our understanding of C cycling in alpine ecosystems.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Motion trajectory commands are usually generated using CAD/CAM software and a specified motion controller. At the CAD/CAM stage, the motion commands are generated with respect to the constrains on the contouring error and the application. These commands are also related to the motion controller, which incorporates an advanced blending interpolation method in its function core. Although, high-speed motion can be achieved using blending interpolation, the accuracy of the trajectory is decreased. This study proposes a new blending method that uses a predefined absolute accuracy to optimize both the speed and the accuracy of the generated motion trajectory. The proposed method uses two strategies: the first accelerates or decelerates the velocity profile and the second inserts an arc trajectory command and the corresponding blending accuracy in a critical segment, in order to achieve the speed and the contouring error that is predefined by the user. Four cases are used to determine the performance of the proposed method: (a) line-to-line, (b) line-to-arc, (c) arc-to-arc, and (d) arc-to-line interpolations. The experiments use a predefined speed and accuracy for the motion trajectory. The results demonstrate that the proposed motion trajectory planning process satisfies the needs of industrial applications such as laser cutting and dispensing.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Background and aims〈/h3〉 〈p〉Nitrogen (N) deposition affects litter decomposition. However, how nutrients, especially deposited N are immobilized and released in decomposing litters with different qualities (C/N and C/P) remains unclear.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉We conducted a laboratory microcosm experiment with four litter types and a combination of a coniferous and deciduous litter treated with N addition (6 mg 99.99% 〈sup〉15〈/sup〉N g〈sup〉−1〈/sup〉 litter) and control by measuring N-deposition effect on mass (NDEM), N (NDEN), and P remaining percentages (NDEP), deposited 〈sup〉15〈/sup〉N immobilized abundance, and microbial composition and enzyme activities in decomposing litters during two years of incubation.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉The values of NDEM, NDEN, and NDEP were generally greater for the litters with intermediate C/N and C/P than those with the highest and lowest ratios after 360 days, although these parameters varied among different quality litters before 180 days. Immobilized exogenous 〈sup〉15〈/sup〉N abundance by microbes showed an increasing trend with increasing litter C/N and C/P across the whole 720-day period. Both C/N and C/P were generally correlated with decomposition rate, 〈sup〉15〈/sup〉N immobilization abundance, the microbial richness, and main enzyme activities in decomposing litters.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉N-deposition effects on N and P dynamics in decomposing litters varied with their C/N and C/P, generally exerting an unimodal curve at later decomposition stages. Lower quality litter with higher C/N and C/P favoured N immobilization in response to N addition.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉The information of nitrogen uptake by subtropical, ever-green broad-leaf plants at cold temperatures of winter is very limited. The present field experiment was conducted to investigate whether 〈sup〉15〈/sup〉N is taken up by tea (〈em〉Camellia sinensis〈/em〉 L.) plants in winter dormancy in the absence of active shoot growth and utilization in young spring shoots.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉We applied 〈sup〉15〈/sup〉N-labeled urea to soil at five different times i.e. mid-January, early February, mid-February, and early and mid-March. 〈sup〉15〈/sup〉N abundance was determined in fibrous roots, twigs and mature leaves after 3, 7 and 15 days after application and in young shoots the following spring.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉〈sup〉15〈/sup〉N was taken up by fibrous roots and transported to above-ground tissues within 3 days after application under low winter temperatures. Earlier application significantly increased nitrogen derived from 〈sup〉15〈/sup〉N-urea (N〈sub〉dff〈/sub〉) and 〈sup〉15〈/sup〉N amount in young spring shoots. N〈sub〉dff〈/sub〉 values and 〈sup〉15〈/sup〉N amount in young spring shoots were described well by quadratic or linear regressions against soil growing degree days (GDD, T ≥ 8 °C, depth 20 cm) between 〈sup〉15〈/sup〉N application and harvesting dates (R〈sup〉2〈/sup〉 = 0.58–0.90, 〈em〉p〈/em〉 〈 0.001).〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Nitrogen was absorbed and translocated in dormant tea plants in the absence of active root and shoot growth throughout the late winter until early spring. Absorbed N was stored and remobilized to support shoot growth the following spring. Soil GDD between N application and harvesting could predict N〈sub〉dff〈/sub〉 and 〈sup〉15〈/sup〉N amount in young spring shoots.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉To identify the rhizobia nodulating 〈em〉Vicia sativa〈/em〉 in Northwestern China and to estimate their geographic distribution.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Rhizobia trapped with 〈em〉V. sativa〈/em〉 plants from soils at six sites in the northwest of China were classified into genotypes by PCR-based restriction fragment length polymorphism (RFLP) of 16S–23S rRNA intergenic spacer (IGS) and 16S rRNA genes, and phylogenetic analyses of housekeeping (16S rRNA, 〈em〉recA〈/em〉, 〈em〉atpD〈/em〉) and symbiotic genes were performed for the representative strains. Soil physicochemical characteristics were recorded and canonical correlation analysis was performed to examine the correlations between soil features and distribution of rhizobial genotypes.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉A total of 202 rhizobial isolates were discriminated by RFLP analyses into 15 IGS types and a single 16S rRNA type, which were identified as 〈em〉Rhizobium〈/em〉 by 16S rRNA gene phylogeny and as four clusters by multilocus sequence analysis (MLSA). Cluster 1 covering 86 strains and 7 IGS types prevalent in all sites was identified as 〈em〉Rhizobium laguerreae〈/em〉; cluster 2 was 〈em〉R. sophorae〈/em〉 with 18 strains in 2 IGS types found in the site Q-GD. Each of cluster 3 and cluster 4 contained three IGS types representing two novel 〈em〉Rhizobium〈/em〉 genospecies specific to Gansu Province and Shanxi Province, respectively. Four 〈em〉nodC〈/em〉 phylogenetic clades were defined among the isolates.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉〈em〉R. sophorae〈/em〉, 〈em〉R. laguerreae〈/em〉, and two novel 〈em〉Rhizobium〈/em〉 genospecies with diverse symbiotic genotypes are associated with 〈em〉Vicia sativa〈/em〉 L. in Northwest China. Their biogeographic patterns are mainly directed by soil pH and salinity. This is the first study on the diversity of rhizobia nodulating 〈em〉Vicia sativa〈/em〉 in China.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The influence of the welding and tool rotation speed on morphology and mechanical behavior of friction spot stir welds made on polycarbonate is investigated. The welds were performed in butt configuration. The mechanical behavior of the welds was assessed by means of tensile tests. Digital image correlation (DIC) analysis was performed to determine the strain distribution (over the cross section) during the tests. This enabled to determine the precise position of crack onset and simplified the determination of the welds’ failure. These data were crossed with observation of the welds morphology to better understand the mutual relation among process conditions-morphology and mechanical behavior. The results indicated that the welds produced under low welding speed were characterized by adhesive failure between the stirred region and the substrate. The welds produced under higher speed were affected by excessive thinning. This led to failure in the stirred region or in some cases within the base material due to localized thinning. The mechanical characteristics of the welds were highly correlated to the temperature of the stirred region. This suggests the possibility to use IR thermography for online control and qualitative assessment of the mechanical behavior of the FSW welds made on amorphous thermoplastics.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Background and aim〈/h3〉 〈p〉Root-associated microbial communities influence plant phenotype, growth and local abundance, yet the factors that structure these microbial communities are still poorly understood. California landscapes contain serpentine soils, which are nutrient-poor and high in heavy metals, and distinct from neighboring soils making them ideal for studying the factors that structure root microbiomes and their functions.〈/p〉 〈/span〉 〈span〉 〈h3〉Method〈/h3〉 〈p〉Here, we surveyed the rhizoplane of serpentine-indifferent plants, which grow on and off serpentine soil, to determine the relative influence of plant identity and soil chemistry on rhizoplane microbial community structure using 16S rRNA metabarcoding. Additionally, we experimentally examined if serpentine vs. non-serpentine microorganisms differentially affected plant growth in serpentine soil.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Rhizoplane bacterial communities differed among plant species, soil types, and the interaction between them in both the field and experimental soils. In the experiment, soil microbial community source influenced seedling survival, but plant growth phenotypes were largely invariant to microbial community with a few exceptions.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Rhizosplane bacterial species composition differed between plant species and soil types, and Amplicon Sequence Variants (ASVs) from the phyla Acidobacteria and Proteobacteria (Genus: 〈em〉Microvirga〈/em〉) were characteristic of serpentine soils. While soil microbial community composition influenced seedling survival in the current study, further study is required to disentangle the role of microbial associations and plant tolerance to serpentine.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Plants can optimize the allocation of phosphorus (P) among their foliar P fractions to increase the P utilization efficiency (PUE). Identifying the genetic relationships between foliar P fractionation and PUE could provide opportunities to improve the P efficiency of barley (〈em〉Hordeum vulgare〈/em〉 L.).〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉The differences in the concentrations and proportions of inorganic P, ester P, nucleic acid P and insoluble P between a wild barley cultivar CN4027 and a commercial cultivar Baudin were studied, and their quantitative trait loci (QTLs) at normal P (NP) and low P (LP) fertilisations were mapped. The PUE that was determined in the previous study was used to analyze the relationship between PUE and foliar P fractionation in this research.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Both cultivars of barley could increase their metabolic P fractions as an LP stress tolerance strategy to ensure their continued metabolic activities in response to LP stress. Cultivar CN4027 showed higher nucleic acid P concentration (NPC), nucleic acid P proportion (NPP) and insoluble P proportion (IPP) than cultivar Baudin under LP stress. This abundant organic P (Po) pool of CN4027 ensured the normal functioning of its metabolic pathways under LP stress. The close relationships between the foliar P fractionation and PUE could be explained by two QTL clusters, 〈em〉Cl-3H.02〈/em〉 and 〈em〉Cl-5H.01〈/em〉. The QTL cluster 〈em〉Cl-3H.02〈/em〉 is flanked by the markers 〈em〉bPb3256099-bPb3255630〈/em〉 on chromosome 3H and controls the ester P concentration (EPC), ester P proportion (EPP), insoluble P concentration (IPC) and IPP.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The QTL cluster 〈em〉Cl-3H.02〈/em〉 might have great potential for the future genetic improvement of barley PUE and may offer clues for the genetic relationships between the foliar P fractionation and PUE.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Roots are vital organs for plants, but the assessment of root traits is difficult, particularly in deep soil layers under natural field conditions. A popular technique to investigate root growth under field or semi-field conditions is the use of minirhizotrons. However, the subsequent manual quantification process is time-consuming and prone to error.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉We developed a multispectral minirhizotron imaging system and a subsequent image analysis strategy for automated root detection. Five wavelengths in the visible (VIS) and near-infrared (NIR) spectrum are used to enhance living roots by a multivariate grouping of pixels based on differences in reflectance; background noise is suppressed by a vesselness enhancement filter. The system was tested against manual analysis of grid intersections for both spring barley (〈em〉Hordeum vulgare L.〈/em〉) and perennial ryegrass (〈em〉Lolium perenne L.)〈/em〉 cultivars at two time-points. The images of living roots were captured in wet subsoil conditions with dead roots present from a previous crop.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Under the soil conditions used in the study, NIR reflectance (940 nm), provided limited ability to separate between rhizosphere components, compared to reflectance in the violet and blue light spectrum (405 nm and 450 nm). Multivariate image analysis of the spectral data, combined with vesselness enhancement and thresholding allowed for automated detection of living roots. Automated image analysis largely replicated the root intensity found during manual grid intersect analysis of the same images. Although some misclassification occurred, caused by elongated structures of dew and chalkstone with similar reflectance pattern as living root, the system provided similar or in some cases improved detection of genotypic differences in the total root length within each tube.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusion〈/h3〉 〈p〉The multispectral imaging system allows for automated detection of living roots in minirhizotron studies. The system requires considerably less time than traditional manual recording using grid intersections. The flexible training strategy used for root segmentation offers hope for the transfer to other rhizosphere components and other soil types of interest.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉The objective of this research was to develop a three-dimensional (3D) rhizosphere modeling capability for plant-soil interactions by integrating plant biophysics, water and ion uptake and release from individual roots, variably saturated flow, and multicomponent reactive transport in soil.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉We combined open source software for simulating plant and soil interactions with parallel computing technology to address highly-resolved root system architecture (RSA) and coupled hydrobiogeochemical processes in soil. The new simulation capability was demonstrated on a model grass, 〈em〉Brachypodium distachyon〈/em〉.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉In our simulation, the availability of water and nutrients for root uptake is controlled by the interplay between 1) transpiration-driven cycles of water uptake, root zone saturation and desaturation; 2) hydraulic redistribution; 3) multicomponent competitive ion exchange; 4) buildup of ions not taken up during kinetic nutrient uptake; and 5) advection, dispersion, and diffusion of ions in the soil. The uptake of water and ions by individual roots leads to dynamic, local gradients in ion concentrations.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusion〈/h3〉 〈p〉By integrating the processes that control the fluxes of water and nutrients in the rhizosphere, the modeling capability we developed will enable exploration of alternative RSAs and function to advance the understanding of the coupled hydro-biogeochemical processes within the rhizosphere.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This study investigated an influence of the temperature field on thickness distribution of thermoformed products using complex and high-aspect-ratio mold. The optimum temperature field was obtained to achieve a more uniform thickness distribution in the thermoformed products by using finite element simulation. The material properties of acrylonitrile-butadiene-styrene (ABS) polymer sheet were obtained by two rheological measurement tests. The linear viscoelastic properties, such as the storage modulus and loss modulus, were measured by a small amplitude oscillatory shear (SAOS) test for wide ranges of frequency and temperature. The discrete relaxation time and discrete relaxation modulus were obtained by nonlinear regression. The fitting parameters 〈em〉C〈/em〉〈sub〉1〈/sub〉 and 〈em〉C〈/em〉〈sub〉2〈/sub〉 for the WLF model were obtained by curve fitting. The nonlinear viscoelastic property, such as stress relaxation modulus, was measured by a step strain test. The damping function and fitting parameter 〈em〉α〈/em〉 of Wagner-Demarmels (WD) model were determined by curve fitting. Then, the Kaye–Bernstein-Kearsley-Zapas (K-BKZ) constitutive equation was utilized to the thermoforming simulation in order to investigate the material behavior of the polymer sheet. The numerical results showed that a more uniform thickness distribution could be achieved with the optimum temperature field of the sheet. The thinnest part of the products was improved by more than 30%.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A simulated annealing algorithm combined with an adaptive large neighborhood search (ALNS) has been proposed in this paper to minimize the laser cutting path in a two-dimensional cutting process. The proposed algorithm was capable of finding a near-optimum cutting path from a given layout of cut profiles. In this study, the layout was taken from an image, in which image processing algorithms were employed to extract cut profiles from the input image and to assign coordinates to the contours’ pixels. The optimization algorithm was based on generalized traveling salesman problem (GTSP), where all pixels of the input image were considered as the potential piercing locations. A laser beam made a single visit and then did a complete cut of each profile consecutively. The simulation results revealed that the proposed algorithm can successfully solve several datasets from GTSP-Lib database with a good solution quality. A compromise between the path distance and computing time was achievable by considering only 30% of the total pixels of the input image examined in this study. In addition, the cutting path generated by the proposed method was shorter than that recommended by the commercial CAM software and other previous works in terms of path distance with the same profile sample.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉As a major plant-derived soil organic carbon (SOC) component, lignin-derived phenolic compounds show varying biogeochemical characteristics compared to plant-derived lipid moieties. Comparing their distribution patterns can provide information on mechanisms governing SOC preservation and dynamics. However, the large-scale distribution pattern and stability of lignin versus plant-derived lipids are still poorly constrained. Here we investigated the distribution of lignin phenols versus plant-derived lipids in the surface soils across the alpine versus temperate grasslands of China and Mongolia.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Lignin phenols were isolated by cupric oxide oxidation method and compared with the previously analyzed plant-derived lipids (cutin and suberin). A comprehensive list of environmental variables was compiled to disentangle the climatic, edaphic and vegetation influences on lignin phenols’ distribution in the soil.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Lignin phenols showed similar SOC-normalized concentrations in the alpine and temperate grassland soils despite a higher plant input to the latter, suggesting better lignin preservation in the cold region. However, compared with plant-derived lipids (cutin and suberin), lignin seems to be less stabilized. The variation of lipid versus lignin components is mainly related to climate (particularly aridity) in the alpine grassland soils, while the relative abundance of plant lipids and lignin phenols is more related to reactive mineral contents in the temperate grassland soils.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Lignin contributes differentially to SOC accumulation in the alpine and temperate soils: while lignin seems to be better preserved in the cold region, lignin phenols decrease relative to other carbon components with SOC accrual in the temperate region. Overall, lignin distribution and fate may be more sensitive to carbon source variations than temperature shifts in the grasslands.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The novel generation of production facilities fostered by the fourth industrial revolution widely adopts different technologies to digitalise the manufacturing and assembly processes. In this context, work measurement techniques are one of the main candidates for the application of these new technologies because of the time, cost, and competences required to analyse manual production activities and considering the limited precision of the traditional approaches. This paper proposes a new hardware/software architecture devoted to the motion and time analysis of the activities performed by human operators within whatsoever industrial workplace. This architecture, called Human Factor Analyser (HFA), is constituted by a network of ad hoc depth cameras able to track the worker movements during the task execution without any interference with the monitored process. The data provided by these cameras are then elaborated in a post-process phase by the HFA to automatically and quantitatively measure the work content of the considered activities through an accurate motion and time analysis. The developed architecture evaluates the worker in a 3D environment considering his interaction with the industrial workplace through the definition of appropriate control volumes within the layout. To test the accuracy of HFA, an extensive experimental campaign is performed at the Bologna University Laboratory for Industrial Production adopting several realistic industrial configurations (different workplaces, operators and tasks). Finally, the HFA is applied to a real manufacturing case study of an Italian company producing refrigerator metal grates. A wide and deep analysis of the obtained key results is presented and discussed.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉A century of atmospheric deposition of sulfur and nitrogen has acidified soils and undermined the health and recruitment of foundational tree species in the northeastern US. However, effects of acidic deposition on the forest understory plant communities of this region are poorly documented. We investigated how forest understory plant species composition and richness varied across gradients of acidic deposition and soil acidity in the Adirondack Mountains of New York State.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉We surveyed understory vegetation and soils in hardwood forests on 20 small watersheds and built models of community composition and richness as functions of soil chemistry, nitrogen and sulfur deposition, and other environmental variables.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Community composition varied significantly with gradients of acidic deposition, soil acidity, and base cation availability (63% variance explained). Several species increased with soil acidity while others decreased. Understory plant richness decreased significantly with increasing soil acidity (〈em〉r〈/em〉 = 0.60). The best multivariate regression model to predict richness (〈em〉p〈/em〉 〈 0.001, adjusted〈em〉-R〈/em〉〈sup〉〈em〉2〈/em〉〈/sup〉 = 0.60) reflected positive effects of pH and carbon-to-nitrogen ratio (C:N).〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The relationship we found between understory plant communities and a soil-chemical gradient, suggests that soil acidification can reduce diversity and alter the composition of these communities in northern hardwood forests exposed to acidic deposition.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In the orbital mode of electrical discharge machining (EDM), an electrode with a complex profile causes deviation in the cavity profile from the design objective. In this paper, electrode compensation techniques according to the envelope theory are presented to eliminate deviation errors. The succession of orbits traced out a family of electrode curves based on kinematic geometry integrated with the motion path of tool bodies and constraints. The boundary of the family of electrode curves is referred to as the orbiting profile. The deviation error between the orbiting and objective profiles can be eliminated by using a compensation electrode in the orbiting process. Thus, the generated orbiting profile conforms to the objective profile. Experimental results of the tested example for the machining profile of the compensation electrode by using the orbital process revealed that profile deviation can be eliminated to ensure that the EDM profile closely conforms to the objective profile. This compensation method for orbiting EDM provided an exact process to engineers for easy control of the machining precision of EDM.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Background and aims〈/h3〉 〈p〉Endophytic fungi colonization is an eco-friendly strategy to respond to environmental stresses and confer tolerance to the host plant. Here, the responses of wheat plant inoculated with an indole acetic acid (IAA) -producing endophytic fungus to drought stress and water recovery were evaluated.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉The inoculation of wheat plants with 〈em〉Alternaria alternata〈/em〉 (LQ1230) was conducted to evaluate drought resistance under adequate water, water deficit and water recovery conditions by examining the growth parameters and various physiological indicators of wheat seedlings.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉The LQ1230 isolated from 〈em〉Elymus dahuricus〈/em〉 Turcz could secrete indole acetic acid (IAA) by both the tryptophan-dependent (319.24 ± 14.88 μg/mL) and independent (40.12 ± 8.59 μg/mL) pathways. LQ1230 inoculation enhanced wheat growth and drought tolerance through regulation of antioxidant enzyme activities and the content of compatible solutes such as soluble sugars and proline. Additionally, LQ1230 inoculated plants demonstrated significantly improved photosynthesis, C and N accumulation of wheat plants, leading to a positive relationship with plant dry biomass under water deficit and re-watering conditions.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉We found that the improved wheat plant growth, photosynthesis and nutrient accumulations by the inoculation of 〈em〉Alternaria alternata〈/em〉 LQ1230 might be attributed to the reprogramming of wheat plant metabolism, thus enhancing wheat drought tolerance. Inoculation with fungal endophytes such as LQ1230 has the potential to increase crop drought resistance.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Subtropical ecosystems are generally characterized by phosphorus (P)-deficient soils; however, extreme P-rich soils develop on phosphate rocks. We aimed to integrate metabolomic and ionomic analyses to survey how in situ trees adaptively respond to such contrasting P soils.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Gas (GC-MS) or liquid (LC-MS) chromatography-mass spectrometry and inductively coupled plasma-optical emission spectrometer (ICP-OES) were used to analyze leaf metabolome and ionome of 〈em〉Quercus variabilis〈/em〉, which grew at two geologic P-rich and P-deficient sites in subtropical China.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Two 〈em〉Q. variabilis〈/em〉 populations were significantly discriminated in terms of metabolome and ionome, with major contributions from 25 identified metabolites (e.g. sugars and P-containing compounds) and P and four other chemical elements. And of these 25 metabolites, orthophosphate was predominant in influencing the variation in the metabolomes of 〈em〉Q. variabilis〈/em〉 between the two P-type sites. Moreover, orthophosphate was correlated with leaf P (〈em〉r〈/em〉 = 0.85, 〈em〉p〈/em〉 〈 0.001), while leaf P was significantly influenced only by soil resident P at the P-rich site. Furthermore, the metabolic pathway analysis indicated four critical metabolic pathways: galactose metabolism, amino sugar and nucleotide sugar metabolism, glyoxylate and dicarboxylate metabolism, fructose and mannose metabolism.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉These findings suggested that there were distinct ionome-metabolome interactions in 〈em〉Q. variabilis〈/em〉 populations, between P-rich and P-deficient sites, which contributed to novel insights into how plants interactively adapt to P-limiting soils.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The main objective of this work is to evaluate the tool life and the workpiece surface roughness when applying a vegetable-based cutting fluid by minimum quantity of lubricant (MQL) at three different directions (main tool flank face, secondary tool flank face, and overhead) in turning AISI D6 hardened steel with polycrystalline cubic boron nitride (PCBN) tools with Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 ceramic binder and TiN coating. Dry cutting was also tested for comparisons. Tool wear analyses were performed on the tools at the end of their lives within a scanning electron microscope (SEM). The application of the cutting fluid by MQL technique in the direction between the main tool flank face and the workpiece showed better results than the dry condition. The application of MQL through other directions (overhead and between the secondary tool flank face and the workpiece) also showed competitive results. Abrasion and adhesion were the prevailing mechanisms for the wear of the tools.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Cutting tools may heat up during use, causing them to deform. Such an effect degrades the surface microstructure of potassium dihydrogen phosphate (KDP) crystals via ultra-precision fly cutting. In this process, thermal expansion of the tool displaces the tool tip perpendicular to the workpiece processing surface. Such displacement is difficult to measure experimentally due to the limited sensitivity of displacement sensors and the severe conditions present during cutting processes. In this study, a cutting surface simulation model based on machine kinematics of the fly cutting and a thermal model based on the experimental results of the principal cutting forces are established in KDP crystal ultra-precision flying cutting to explore the specific impact on the workpiece due to the thermal deformation of the tool. The relationships between cutting parameters and principal cutting forces are thereby determined. The relationships between tip heat inflow, tip displacement perpendicular to the workpiece processing surface, and crystal surface microstructure were simulated. The results demonstrate that the heat deformation of the tool slightly influences the roughness and waviness of KDP crystal surfaces, and increases their surface slope, thus influencing surface precision. This directly affects the optical performance of such crystals.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Although nitrogen (N) fertilization is widely used to increase rice yield, its impact on the distribution, transformation, and fates of photosynthetic carbon (C) in rice–soil systems is poorly understood. To address this, we quantified the C flows into various pools in a rice–soil system.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Rice (〈em〉Oryza sativa〈/em〉 L.) was pulse-labeled with 〈sup〉13〈/sup〉CO〈sub〉2〈/sub〉 at the tillering stage. Samples were collected six times during the 26 days following labeling. We quantified the partitioned photosynthesized C into various pools using stable isotopic techniques and estimated C flows.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Although the net distribution of assimilated C to belowground pools did not change, N fertilization promoted C assimilation in aboveground biomass. C allocation into soil was enhanced by N fertilization during early growth, but decreased during late growth. N fertilization induced higher mass-specific rhizodeposition (per unit root dry weight) and its turnover rate compared with the unfertilized system. However, with higher microbial turnover, the daily C allocation from roots to soil was similar at both fertilization levels.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Although total C input into soil is enhanced by N fertilization, its further fate is N fertilization independent, thus leading to a net accumulation of C input in rice paddy soil similar to that observed unfertilized soil.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Micro dry wire electrical discharge machining (μDWEDM) is a process where gas is used as the dielectric fluid instead of a liquid. In this process, certain modifications of wire electrical discharge machining (WEDM) are needed during the machining operation to achieve stable machining. Smooth and stable machining operation in μDWEDM process remains as a critical issue. Thus, this paper presents the investigation of process parameters for a stable μDWEDM process. The investigation was performed on a stainless steel (SS304) with a tungsten wire as the electrode using integrated multi-process machine tool, DT 110 (Mikrotools Inc., Singapore). The experimentation method used in this phase was a conventional experimental method, one-factor-at-a-time (OFAT). Types of dielectric fluid, dielectric fluid pressure, polarity, threshold, wire tension, wire feed rate, wire speed, gap voltage, and capacitance were the controlled parameters. The machined microchannels were observed using scanning electron microscope (SEM). Stable and smooth machining operation of μDWEDM was found to be with compressed air as the dielectric fluid, workpiece positive polarity, 24% threshold, 0.0809 N wire tension, 0.2 μm/s wire feed rate, and 0.6 rpm wire speed.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Five-axis machine tool is widely used in freeform surface machining. The freeform surface’s tool path is usually discretized as G01 segments and the freeform surface machined with linear interpolation in five-axis machine. Due to the two additional rotary axes, there are the nonlinear coupling relationship between the workpiece coordinate system (WCS) and machine coordinate system (MCS). Hence, there are many uncertain errors produced by the nonlinear coupling relationship, especially via linear interpolation. In order to represent the motion trajectory accurately and generate G01 tool path appropriately, this paper proposes an irredundant G01 tool path generation method for five-axis machine. Firstly, a new tool tip error (TTE) definition is given to reflect the influence of the rotation axis on the tool tip. And then, a new tool orientation error (TOE) definition is given to mirror the tool orientation error caused by rotary axis’ linear interpolation. Finally, an adaptive iterative method (AIM) is proposed to obtain irredundant G01 tool path. By using this method, the G01 tool path can be generated based on the given error limits and the proposed method is verified both in the simulation and experiment. The results show that the proposed method can significantly reduce the number of G01 segments and limit the actual error.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper reported the facile fabrication of high-vanadium high-speed steel (HVHSS) by the conventional powder metallurgy process for the wear-resistant applications. The effect of compaction pressure and of subsequent sintering temperatures on the formability and structural evolution of HVHSS was assessed by scanning electron microscopy (SEM) with electron-dispersive spectra (EDS), and X-ray diffraction (XRD) analysis. The results well revealed the primary constitution composed of mixed hardening phases MC and M〈sub〉6〈/sub〉C existing within the α-ferrite matrix after hot solidification, and the association of microstructural alteration with the sintering temperatures was discussed for as-obtained HVHSS specimens. The HVHSS attained the desirable values of mechanical hardness and bending strength and thereby delivered the capability of friction reduction and wear inhibition, closely depending on the sintering temperature. The optimal sintering condition was determined on the basis of bulk density, shrinkage, and capability assessments. A well-established fabricating route for producing high-quality HVHSS was explored through the combined process of cold compaction and subsequent sintering on the conceptual design of chemical composition and alloying design of commercial M2 steel.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Long-duration drought can alter ecosystem plant species composition with subsequent effects on carbon cycling. We conducted a rainfall manipulation field experiment to address the question: how does drought-induced vegetation change, specifically shrub encroachment into grasslands, regulate impacts of subsequent drought on soil CO〈sub〉2〈/sub〉 efflux (R〈sub〉s〈/sub〉) and its components (autotrophic and heterotrophic, R〈sub〉a〈/sub〉 and R〈sub〉h〈/sub〉)?〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉We conducted a two-year experiment in Inner Mongolia plateau, China, using constructed steppe communities including graminoids, shrubs and their mixture (graminoid + shrub) to test the effects of extreme-duration drought (60-yr return time) on R〈sub〉s〈/sub〉, R〈sub〉h〈/sub〉 and R〈sub〉a.〈/sub〉〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Our results indicated that extreme-duration drought reduced net primary production, with subsequent effects on R〈sub〉s〈/sub〉, R〈sub〉h〈/sub〉 and R〈sub〉a〈/sub〉 in all three vegetation communities. There was a larger relative decline in R〈sub〉a〈/sub〉 (35–54%) than R〈sub〉s〈/sub〉 (30–37%) and R〈sub〉h〈/sub〉 (28–35%). Interestingly, we found R〈sub〉s〈/sub〉 in graminoids is higher than in shrubs under extreme drought. Meanwhile, R〈sub〉h〈/sub〉 declines were largest in the shrub community. Although R〈sub〉a〈/sub〉 and R〈sub〉h〈/sub〉 both decreased rapidly during drought treatment, R〈sub〉h〈/sub〉 recovered quickly after the drought, while R〈sub〉a〈/sub〉 did not, limiting the 〈em〉R〈/em〉〈sub〉〈em〉s〈/em〉〈/sub〉 recovery.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉This study suggests that plant species composition regulates several aspects of soil CO〈sub〉2〈/sub〉 efflux response to climate extremes. This regulation may be limited by above- and below-ground net primary production depending on soil water availability〈em〉.〈/em〉 The results of this experiment address a critical knowledge gap in the relationship between soil respiration and plant species composition. With shrub encroachment into grasslands, total soil respiration is reduced and can partly offset the effect of reduction in productivity under drought stress.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The keyhole behaviors were observed directly by laser welding experiment with quartz glass. Based on Fresnel absorption of laser beam and multi-reflection combined with volume of fluid (VOF) method, a three-dimensional mathematical model was established to study the role of welding speed on keyhole behaviors and keyhole-induced porosity formation in laser welding of aluminum alloy. The keyhole behaviors and weld pool fluid flow were discussed, and the result shows that, although the welding speed varies, the mechanism of keyhole collapse was similar. However, the keyhole stability at higher welding speed was improved due to reduced weld depth fluctuations, spatter number, keyhole depth to width ratio, and keyhole collapse frequency. Furthermore, the improved keyhole stability impeded the keyhole collapse, and the lower weld depth and solidification rate facilitated bubble escaping from the weld pool easily, which are the main factors for suppression of porosity at higher welding speed.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Ultrasonic welding (UW) process offers the ability to create highly efficient solid-state joints for lightweight metal alloys with low power consumption. During the process, a distinct diffusion layer is observed at the joint interface that undergoes severe plastic deformation at elevated temperature. A hierarchical multiscale method is proposed in this study to predict the diffusion behavior of the UW process of dissimilar materials. The method combines molecular dynamics and classical diffusion theory to calculate the thickness of the diffusion layer at the welded interface. A molecular dynamics model is developed for the first time that considers the effect of transverse ultrasonic vibration to simulate the evolution of the diffusion layer. The effect of ultrasonic vibration at the atomic level is assumed to provide thermal energy at the joint interface and the mechanical movement of atoms. The influence of sinusoidal velocity change during ultrasonic vibration is incorporated by numerically time integrating the diffusivity at different ultrasonic velocity. The simulation result shows that the solid-state diffusivity depends on temperature, pressure, and transverse ultrasonic velocity. Higher temperature, pressure, and ultrasonic velocity result in higher diffusivity leading to larger diffusion layer thickness. This article provides a comprehensive review of the diffusion bonding behavior and its dependence on process variables. It also presents a numerical approach combining molecular dynamics and hierarchical multiscale calculation to predict the diffusion layer thickness for the UW process of dissimilar materials.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Tube hydroforming (THF) is a unique forming technique, which can transform metal tubes into complex hollow parts using hydraulic fluid as the forming medium. The initial non-uniform thickness of as-received practical tubes significantly affects their formability in the hydroforming process. A forming limit diagram (FLD), also called as the forming limit curve (FLC), is often adopted to evaluate the forming behaviour of sheet metals in plastic forming processes to avoid forming failures. The purposes of this research are fivefold, namely to establish the FLCs of tubular blanks with varied initial thickness deviations in tensile and compressive strain states by means of finite element (FE) modelling of THF, to construct a non-uniform geometric model for practical tubes, to analyse the impact of initial thickness deviation on the FLCs, to clarify the differences in the FLCs obtained using three different instability criteria, and to validate the proposed non-uniform geometric model by conducting hydro-bulging experiments. Results show that it is possible to accurately predict the FLCs of practical tubes with initial non-uniform thicknesses using FE simulation combined with the proposed non-uniform geometric model. We found that the displacement of FLCs occurred in the major- and minor-strain coordinates because the thickness is initially not uniform; however, no significant discrepancies were observed in the FLCs obtained using the three instability criteria. The proposed approach, which combines FE simulation with a non-uniform geometric model, can be easily employed to predict the ultimate strains of tubes with initial non-uniform thicknesses in THF to avoid forming defects.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The ‘pre-design + optimization’ is one of the main methods to obtain appropriate cooling pipe parameters in hot stamping tools for satisfied quenching quality of hot stamping parts. Since good ‘pre-design’ can effectively reduce the workload of optimization, a novel pre-design method of cooling pipe parameters was put forward and applied in this paper. Firstly, the concept of pipe parameter window and its related building method were proposed, by which the domain of satisfied cooling pipe parameters, under certain quenching process and quality demand, could be obtained. Secondly, the pipe parameter window of drilled cooling pipes, suitable for flat die surface, was built based on the above method, and then used to pre-design the cooling pipes in flat die for application. Finally, the satisfied cooling performance of pre-designed cooling pipes demonstrated the validity of proposed method in guiding the pre-designing of cooling pipe parameters in hot stamping tools.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Transient thermo-mechanical analysis of welding problem requires tremendous computation cost. To accelerate the thermal analysis of large-scale welded structures, an efficient computation scheme based on heat transfer localization and dual meshes was proposed. The computation accuracy is guaranteed by a local fine mesh model with size determined by a theoretical solution and a global coarse mesh model with equivalent heat input. The validity and accuracy of the dual-mesh method were verified using an experimental bead-on-plate model. By extending the weld length, the computation time of the proposed method was proved to be almost linearly dependent on the model scale. The thermal analysis of fillet welding of a large panel structure with 6-m-long weld was accelerated by 10 times over conventional finite element analysis and 2.2 times over adaptive mesh method. Meanwhile, the physical memory consumption was also greatly reduced by the dual-mesh method. Such efficient computation method enables fast evaluation of welding stress and distortion which are vital for manufacturing process and structure performance.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A type of simulation model for a hot stamping forming process was developed for TA32 high-temperature titanium alloy to study the fracture of a complex aircraft skin by using the forming limit stress diagram (FLSD) as a tool to evaluate the formability. After derivation, the theoretical FLSD of TA32 in the hot forming process is strain rate-dependent and temperature-dependent, which is understood from the constitutive relationship of an Arrhenius-type model. Different stress states were used in this study to evaluate the quality of forming via FLSDs. The results show that the materials develop a resistance to fractures in response to an increase in temperature and a decrease in the formation speed. The predicted results also show that the shape of the blank is an important factor that affects part forming. Tests were performed on the TA32 high-temperature titanium alloy to investigate the effects of the processing parameters and the blank shapes. Several indicators were used to assess forming with respect to the thickness distributions in the safe and dangerous areas by comparing the results of the simulations and experiments. Finally, tensile tests under different states were used to indicate that the experimental and simulation results meet practical engineering requirements.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Through fabricating the micro-textures to improve surface property, the surface texturing technology has become a widely used way to prepare the functionalized surface. This study proposed a surface texturing method of one-dimensional ultrasonic vibration–assisted turning to generate micro-textured end face. The generation principle for the micro-textured end face was presented through the description of cutting conditions, the theoretical analysis of textured features, and the simulation prediction of surface topography. The polycrystalline diamond cutting tools with different clearance angles (7° and 20°) and nose radiuses (400 μm, 200 μm, and 100 μm) were used in the experimental tests to investigate the influence of tool geometry on the micro-dimple features. The results show that the micro-dimples with different sizes and shapes can be successfully fabricated on the end face of Copper 1100. Same as the theoretical analysis and simulation prediction, through changing the cross-sectional profile of dimple along cutting direction, the clearance angle and the radius of observed point were verified to play a key role in the shape of micro-dimple. The oval-like dimples and the scale-like dimples can be respectively manufactured under the different intersection states between the flank face and the cutting trace. It was also confirmed that by choosing proper nose radius and the corresponding feed rate, the textured surface covered by micro-dimples of different widths can be generated. This texturing method used for fabricating the micro-textured end face was verified to be feasible and efficient, which laid a foundation for further research on the application of the textured surface.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Background and aims〈/h3〉 〈p〉The effects of root glutathione (GSH) supplementation on leaf chlorophyll, Fe concentrations and contents in leaves, stems and roots, and traits associated to Fe deficiency were studied in 〈em〉Medicago scutellata〈/em〉 plants grown in rock sand under conditions of Fe deficiency, in the presence of different concentrations of bicarbonate.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Plants were grown in acid-washed rock sand irrigated with a zero Fe solution (pH 7.8 with 0.5 g L〈sup〉−1〈/sup〉 CaCO〈sub〉3〈/sub〉) or a 45 μM Fe(III)-EDDHA solution (5 mM MES, pH 5.5), with 0, 5 or 15 mM NaHCO〈sub〉3〈/sub〉, and 250 mL of 1 mM GSH was added daily to half of the pots.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Iron deficiency caused characteristic symptoms in plants, with GSH supplementation relieving them. Glutathione supplementation led to increases in total Fe, chlorophyll and leaf total and extractable Fe, whereas root Fe concentrations decreased. Traits associated to Fe deficiency, including changes in biomass, root morphology, carboxylate contents and antioxidant parameters became less intense with GSH supplementation.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Glutathione supplementation allowed plants to take up Fe from the rock sand via a reductive solubilization mechanism. Also, the distribution of Fe within the plant changed, with more Fe being allocated to the shoot tissues and less to the roots.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A considerable interest has been generated in recent years in the use of thermoplastic polymers as matrices in the manufacture of advanced composites that require high reliability during long-term operations. In this research, a new Elium® acrylic matrix developed by Arkema was studied to evaluate the accelerated test methodology based on time-temperature superposition principle of Carbon Fiber/Elium® 150 composites. The results show that the high frequencies increase the glass transition (Tg) to higher values because the free volume is favored by polymer chains movement. In addition, artificial neural network has been used to model the temperature-frequency dependence of dynamic mechanical over the wide range of temperatures and frequencies due to its complex non-linear behavior. It has been observed that low frequencies result in low damping due to the lower internal friction, while high frequencies provide greater stiffness to the chains, resulting in a high damping. The long-term life prediction using master curves confirms that this new material can be considered to acoustic or vibrational damping purposes, considering its use in temperatures above Tg.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Product miniaturisation is one of the key aspects of modern manufacturing technology. One of the ways to fabricate miniaturised product is micromachining using sophisticated computer numerically controlled (CNC) machine tools. However, conventional CNC machines are bulky, stationary, and unable to carry out parallel operations. This research aims to develop a modular robotic platform which would be able to carry out machining operation in mesoscale. Hexapod robots are legged mobile robots which are used for verities of applications. Here, we have implemented a hexapod robotic platform to support and move the cutting tool (in this case, a drilling tool). The robot was controlled from the host computer through serial communication. A graphical user interface (GUI) was designed and implemented to operate the robot and the drilling spindle. Several machining operations were carried out with the system to assess its performance. An innovative compensation algorithm has been proposed to improve the positional accuracy of the robot movement. The proposed algorithm takes into account spindle speed and linear velocity to mitigate the positional error. The positional accuracy was improved by more than 60% after implementing the error compensation scheme. In this research we managed to achieve sub-10 μm repeatability (≤ 10 μm) at the lowest spindle and point to point linear speed of 2500 RPM and 200 mm/min, respectively. The performance (in terms of positional accuracy) of the robot was also compared with that of an existing commercial micromachining system where the robot was found to be almost ~ 2× time poorer to that of the commercial machine. Finally, the machined holes’ quality was measured in terms of circularity and taperness. It was observed that at the best machining parameters circularity deviation was as low as 29.4 μm while taperness was 0.54 degree.〈/p〉

Description: 〈p〉The name of one author was omitted in the initially published version.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Micro components have been demanded increasingly due to the global trend of miniaturization of products and devices. Micro milling is one of the most promising processes for micro-scale production and differs from conventional milling due to the size effect introducing phenomena like the minimum chip thickness, making the prediction of micro milling process hard. Among challenges in micro milling, tool life and tool wear can be highlighted. Understanding tool wear and modelling in micro milling is challenging and essential to maintaining the quality and geometric tolerances of workpieces. This work investigates how to model the diameter reduction of a tool caused by tool wear for micro milling of H13 tool steel. Machining experiments were carried out in order to obtain cutting parameters affecting tool wear by considering the diameter reduction. Dry full slot milling with TiAlN (titanium aluminium nitride)-coated micro tools of diameter 〈em〉d〈/em〉 = 400 μm was performed. Three levels of feed per tooth (〈em〉f〈/em〉〈sub〉z〈/sub〉 = 2 μm, 4 μm and 5 μm) and two spindle speed levels (〈em〉n〈/em〉 = 30,000 rpm and 46,000 rpm) were used and evaluated over a cutting length of 〈em〉l〈/em〉〈sub〉c〈/sub〉 = 1182 mm. The results show that lower levels of feed per tooth and spindle speed lead to higher tool wear with a total diameter reduction over 22%. The magnitude of the cutting parameters affecting tool wear was determined by ANOVA (analysis of variance), and the model validation meets the statistical requirements with a coefficient of determination 〈em〉R〈/em〉〈sup〉2〈/sup〉 = 83.5% showing the feasibility of the approach to predict tool wear using diameter reduction modelling in micro milling.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this paper, a new additive manufacturing (AM) process based on extrusion and solid-state bonding is presented. The process uses metal feedstock wire which is processed in a continuous rotary extruder in order to disperse the surface oxides of the feedstock and to provide the required bonding pressure. Simultaneously, the die outlet is scraping the contact surface to provide an oxide-free interface between the extrudate and the substrate. Optical analyses of samples from a layered structure produced from AA6082 reveal that the stringers are fully merged; however, some voids and cracks are observed between the individual stringers. Still, this initial demonstration indicates that the process, upon further development, has high potential of producing near-net-shape parts at high deposition rates.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Laser cleaning has been widely used in manufacturing industries due to its lower pollution and higher cleaning precision and efficiency compared with traditional ways. However, laser cleaning would inevitably induce processing roughness on the workpiece surface and only a few researches have been conducted to this field. In this work, the influence of process parameters on surface roughness was explored in detail. The results showed that process parameters changed surface roughness by changing energy density and overlap ratio. And surface roughness was showed linear positive correlation with energy density. At same energy density, surface roughness will first increase and then decrease with increasing overlap ratios. The maximum roughness was in the range of 50 to 66.7%. It could be explained that after laser irradiation, the sample surface absorbed pulse energy and formed craters. The rim and craters made the sample surface coarse. Due to the depth and diameter of craters were dependent on energy density, the roughness increased with increasing energy densities. The adjacent craters will also change the height of rim and depth of crater with different overlap ratios. It led to different surface roughness.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Mycorrhizae and root exudates have been considered the two important pathways for nitrogen (N) transfer from legume to non-legume plants. The present study aimed to investigate contribution of the relative importance of arbuscular mycorrhizal fungi and root exudates in short-term N transfer.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉A field experiment was conducted to explore N transfer from alfalfa to maize under two different N application levels using 〈sup〉15〈/sup〉N leaf labeling.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉N transfer amount ranged from 7 to 10 mg N plant〈sup〉−1〈/sup〉 from alfalfa to maize and significantly decreased (by 11%–22%) with N fertilizer application. Intercropping of 4 rows of maize and 6 rows of alfalfa with 30 cm intra-row spacing (IMA43) was the optimal intercropping mode, which increased N transfer, total N uptake and yield by 18%, 15% and 11%, respectively. The relative importance of arbuscular mycorrhizal fungi and root exudates on N transfer was dependent on soil N availability. Under no N addition, hyphal length density (HLD) of rhizosphere soil explained the largest significant amount (50%) of the variability in N transfer and crop yield. However, root exudates explained 77% of the variability in N transfer and crop yields with N fertilizer application.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Our findings highlighted that N transfer is reliant more on arbuscular mycorrhizal fungi than root exudates in N-deficient soil, whereas root exudates play a more important role in N-fertilized soil.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Additive manufacture (AM) enables the fabrication of highly efficient lattice structures. However, the mathematical efficiency of characterising AM lattice geometry can be poor, potentially restricting the commercial application of AM lattice structures. This research quantifies the effect of the polygon order used to characterise the geometric resolution of lattice strut elements on the associated manufacturability and geometric qualities of the manufactured lattice. The effect of these design parameters on manufactured quality is experimentally determined for aluminium and titanium specimens fabricated by selective laser melting (SLM), although the method can be generally applied to any AM technology. This research finds that geometric thresholds exist, below which additional geometric resolution does not result in increased part quality. These thresholds are a function of material, lattice inclination angle, cross-sectional area and the polynomial order used to represent the cross section. These findings enable significantly reduced computational cost in managing AM lattice structures, and can be directly integrated with algorithmic methods for the optimisation of AM lattice structures.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A new energy-efficient welding method, flux bands constricting arc (FBCA) welding, is proposed to solve the fabrication of metal sandwich panels. This method is suitable for welding T-joints in special structures where the welding gun is unable to reach the welding position, such as welding thick face-plate metal sandwich panels. The characteristics of FBCA welding, key welding technologies, and corresponding defects and resolutions are discussed. Pull-out tests between T-joints welded by laser and FBCA welding were conducted. Results indicate that complete penetration and good fusion of three-sided T-joint can be produced by FBCA welding. The typical cross section morphology is unlike other common welding methods. T-joints without defects, such as weld asymmetry, root leakage, slag inclusion, and pores, show better ultimate tensile strength than T-joints welded by laser welding. The FBCA welding method can compensate for shortage of insufficient weld width of laser welding.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper is about adding magnetic and ethanol to explore the accuracy of electrochemical discharge machining processing quartz glass. The tool electrode is tungsten carbide rod, the auxiliary electrode is platinum, the power source uses square wave pulse voltage, the KOH electrolyte is added with ethanol, and the tool is added with 3 T magnetic force. The experimental results show that ethanol can stabilize the square wave power supply wave shape, which can reduce the contact angle between the electrode and the bubble. The low contact angle electrolyte can increase the wettability of the tool electrode and improve the electrochemical processing stability. Therefore, under the action of ethanol and a magnetic field, the processing result can be improved, so that the generated bubbles are reduced and the film gets thinned. When the voltage frequency is higher, the film formation thickness will decrease, and the magnetic force and voltage will induce the magnetohydrodynamics of the electrolyte, which will make the electrolyte and bubble flow around the electrode relatively stable, the circumference around the aperture is flat, and the roundness is obviously improved. The overall improvement in the taper of the machined hole is increased by about 30%, and the amount of undercut of the hole is reduced.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Due to the complicated deformation of the billet in roll forming process and the lack of the theoretical understanding, there are still no unified methods to design and optimize roll profiles. Theoretical analysis of the deformation in roll forming process based on mathematical method is efficient and necessary. A qualified roll profile optimization method should be based on the accurate calculation of the spatial configuration of the billet. However, the existing models for calculating the spatial configuration of the billet in roll forming process cannot calculate the springback of the billet. In this paper, according to the mathematical model established by the author for calculating the spatial configuration of the billet, a roll profile optimization method for high-strength V channel roll forming process was proposed by taking the maximum edge membrane longitudinal strain as constraint conditions. After optimization, the number of roll stands required for final V channels was reduced from 8 to 5. Through analyzing and comparing the deformation of the billet in simulation results of bending and roll forming process, it is found that bending tests can also be used to verify the feasibility of the roll profile optimization method proposed in this paper. The bending tests were carried out using the original and optimized process parameters, respectively. The results show that the shape of the V channel obtained by the optimized process parameters is much closer to that of the designed V channel.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A process variant of electromagnetic sheet forming, known as radial Lorentz force augmented deep drawing, has been recently developed to promote the material flow control in high-velocity forming process. Unlike conventional electromagnetic sheet forming, this new process introduces an additional radial inward Lorentz force at the flange region to enhance the draw-in material flow. Previous works have illustrated the feasibility of the process for altering the dynamic deformation behavior and, therefore, the final deformation morphology. This paper further explores the versatility of this process on deformation control by scheduling a wider range of the discharge voltage combinations. While previous works reported two potential types of the final deformation profiles, i.e., convex and flat shapes, this paper further suggests a concave shape and shows adjustment of the deformation profile in a flexible manner by altering the process parameters. To reveal the control rule for forming shape, we established two process windows in terms of two discharge voltages or in terms of draw-in and forming height, based on experimental and numerical results. In addition, new insights into the mechanisms behind different deformation modes have been gained from the analysis of the dynamic deformation process. This work demonstrates the versatility of the process, which offers an improved ability for deformation control in the context of electromagnetic sheet forming.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Background and aims〈/h3〉 〈p〉Magnesium (Mg) deficiency impacts many metabolic processes in 〈em〉Brassica napus〈/em〉 (〈em〉B. napus〈/em〉), leading to yield loss. However, the mechanism of Mg〈sup〉2+〈/sup〉 uptake and translocation in 〈em〉B. napus〈/em〉 remains unknown.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉After screening 39 genotypes of 〈em〉B. napus〈/em〉 under Mg-deficient conditions, the cultivars P160 and P153 were selected according to their Mg transfer factor (TF) from root to shoot. We further characterized these two genotypes under Mg-deficiency by analyzing chlorophyll concentration, malondialdehyde and peroxidase activity, and reducing sugar concentration in leaves. Additionally, we performed transcriptomics and qRT-PCR assays on P153 and P160 shoots and roots. The identified functional genes involved in Mg transport were characterized by functional assays in yeast and Arabidopsis mutants.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉The physiological analysis revealed that P160 (Mg tolerance cultivar; Mg-T) is more tolerant than P153 (Mg sensitive cultivar; Mg-S) under magnesium-deficient environments. Transcriptomics and qRT-PCR assays revealed that transcript levels of 〈em〉BnMGT1–2〈/em〉 and 〈em〉BnMGT6–1〈/em〉 were more significantly up-regulated in the shoot of Mg-T cultivar than that of the Mg-S cultivar under Mg limitation. Functional assays of BnMGT1–2 and BnMGT6–1 reveals that BnMGT1–2 and BnMGT6–1 are the two main functional Mg transporters mediating Mg translocation from root to shoot under low Mg conditions.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusion〈/h3〉 〈p〉Mg-T is more efficient in the translocation of Mg from root to shoot than Mg-S. BnMGT1–2 and BnMGT6–1 should be the two main Mg transporters associated with Mg translocation under Mg deficiency condition, which caused the different Mg efficiency between the Mg-T and Mg-S.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Global climate change is characterized by enhanced atmospheric carbon dioxide concentration ([CO〈sub〉2〈/sub〉]) and temperature, with unknown consequences for soil nematode communities. Soil nematode in response to elevated [CO〈sub〉2〈/sub〉], warming and their interaction in paddy field remain largely unknown. Here we aimed to understand how factorial combinations of elevated [CO〈sub〉2〈/sub〉] and canopy warming affect soil nematode in a rice paddy field.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉A rice paddy field was consistently treated with elevated [CO〈sub〉2〈/sub〉] (500 ppm), canopy warming (+2 °C) or their combinations. Soil samples after a two-year treatment were collected during the rice growing season and nematode communities were extracted with a modified Baermann funnel extraction to examine the changes in nematode abundance and composition under climate change.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Soil nematode communities were altered by elevated [CO〈sub〉2〈/sub〉] and warming, but these responses were dependent on rice growing stages. When averaged over the four stages, total nematode abundances were increased by 31.5% under elevated [CO〈sub〉2〈/sub〉], and by 25.7% under warming. Elevated [CO〈sub〉2〈/sub〉] had no effect on nematode diversity, but slightly altered the composition of different trophic groups. In contrast, warming decreased nematode diversity, but increased plant parasite index, which was negative correlated with crop production. This was attributed to increases in the relative abundance of herbivores under simulated climate change conditions.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Elevated [CO〈sub〉2〈/sub〉] and warming had a positive effect on nematode abundance, but potentially reduced nematode diversity and soil health. These results suggest that multi-factors interactively affect the responses of soil nematode communities, which is important for food productivity under climate change.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Residual stress in additive manufacturing (AM) is one of the key challenges in terms of structural integrity and the finish quality of printed components. Estimating the distribution of residual stresses in additively manufactured components is complex and computationally expensive with full-scale thermo-mechanical FE analysis. In this study, a point heat source is utilized to predict the thermal field and residual stress distribution during the manufacturing processes. Numerical results show that the residual stress at a single material point can be expressed as a function of its spatial position and the peak nodal temperature it has experienced during thermal cycles. The distribution of residual stress can be divided into three segments according to the peak nodal temperature. The peak nodal temperature only depends on the heat flux and the distance to the point heat source center. A semi-analytical approach to predict the peak nodal temperature and residual stresses, once the heat flux is known, is proposed. The proposed approach is further validated by a numerical case study, and a very good agreement has been achieved. Compared with traditional thermo-mechanical FE analysis of additive manufacturing, the proposed method significantly improves the computational efficiency, showing great potential for prediction of residual stresses and distortion.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Background and aims〈/h3〉 〈p〉Atmospheric nitrogen (N) deposition alters the priming effect (PE), which is defined as the change in native soil organic carbon (SOC) decomposition by exogenous C inputs. However, how the priming intensity varies under chemically heterogeneous N deposition, particularly with increasing labile C input, remains unclear.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉We collected soils from a temperate forest in northeastern China that had received simulated organic and/or inorganic N deposition for 6 years. The soils were incubated with or without three levels of 〈sup〉13〈/sup〉C-labelled glucose solution for 152 days. CO〈sub〉2〈/sub〉 emission and its 〈sup〉13〈/sup〉C value were continuously measured to calculate the PE.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Enhanced SOC decomposition (i.e., a positive PE) was observed after glucose addition, regardless of the N deposition form. The PE intensity increased with the increase in the glucose addition level. However, organic N decreased the PE by 12.3-23.2%. The SOC-derived microbial biomass was 16.2-34.3% lower in organic N-treated soil, indicating that preferential utilization of exogenous labile C by microorganisms was responsible for the decrease in PE. The PE inhibition by organic N increased nonlinearly as a function of glucose level. Furthermore, the net annual change in SOC as a balance between the replenishment of added glucose-C and primed C was larger in organic N-treated soil due to a decrease in soil microbial metabolic quotient.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉In this study, we found that organic N deposition inhibited the PE, and the inhibition effect was intensified with increasing C inputs, favouring SOC sequestration.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Despite the high economic benefits of using an intensive agriculture system, the sustainable development of 〈em〉Lycium barbarum〈/em〉 L〈em〉.〈/em〉 cultivation in Northwest China is hindered by serious negative plant–soil feedback, which may be paralleled by the variation in the microbial rhizosphere community.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Here, we assessed the shift in the bacterial and fungal rhizosphere communities of 〈em〉L. barbarum〈/em〉 across a 20-year-old chronosequence of stands at two independent experimental sites in Ningxia, China via real-time PCR and high-throughput sequencing.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Stand age significantly influenced the α-diversity and abundance of the fungal rhizosphere community (〈em〉p〈/em〉 〈 0.05) but did not affect the bacterial community. Phytopathogenic fungi, including 〈em〉Alternaria〈/em〉, 〈em〉Fusarium〈/em〉, 〈em〉Gibberella〈/em〉, and 〈em〉Stemphylium〈/em〉, were progressively enriched in the rhizosphere as the plant aged. Structure equation model suggested that soil abiotic properties were the direct drivers for bacterial community, whereas stand age and edaphic factor coexplained the succession of the fungal rhizosphere community.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusion〈/h3〉 〈p〉Long-term monocropping decoupled plant–bacteria interaction and strengthened the colonization of fungal phytopathogens in 〈em〉L. barbarum〈/em〉 rhizosphere. This study presents novel assessments of the links between the shifts in microbial rhizosphere community and the negative plant–soil feedback of 〈em〉L. barbarum〈/em〉.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Background and aims〈/h3〉 〈p〉Twenty-four species of eucalypts were studied regarding their ability to grow under low P and their responsiveness to P inputs.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Growth and photosynthesis-related parameters were evaluated.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Growth of all species was influenced by low P availability. No significant correlation was found between leaf P concentration and biomass, indicating that P concentrations in leaves cannot be solely considered an indication of the responsiveness to P in eucalypts. Species responsive to P-input (high agronomic P efficiency values, APE) were those with low P use efficiency - PUE (here assessed as relative efficiency of P-use, REP) and low P uptake efficiency (PUpE). But, non-responsive species were related to higher P-efficiency under low soil P-availability. 〈em〉Eucalyptus tereticornis〈/em〉, 〈em〉E. cladocalyx〈/em〉, 〈em〉E. globulus〈/em〉 and 〈em〉E. camaldulensis〈/em〉 were efficient under low-P availability. Whereas, 〈em〉E. crebra〈/em〉 and 〈em〉E acmenoides〈/em〉 were the most responsive species, with high APE, suggesting that for these species P-inputs are needed to guarantee plant growth. The root:shoot ratio remained constant at different P availabilities, suggesting that biomass allocation towards the root in response to P and greater investment in roots were not correlated with greater PUE. Under limited P, 〈em〉E. robusta〈/em〉 and 〈em〉E. botryoides〈/em〉 exhibited low foliar P contents and higher root:shoot ratios than those of other species with higher P contents, indicating that greater root investment does not necessarily result in greater PUE.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusion〈/h3〉 〈p〉The results suggest that the divergence among species is probably related to different mechanisms, which may improve P-use efficiency.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Excessive boron (B) can pose toxicity to many plant species, and consequently restricts land utilization in B-laden regions. The purpose of this study was to identify “agretti” (〈em〉Salsola soda〈/em〉) as an alternative B-tolerant food crop.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Both pot and hydroponic experiments were conducted for measuring biomass, total phenolic content and B absorption of 〈em〉S. soda〈/em〉 exposed to varied B treatments. Mineral element accumulation in 〈em〉S. soda〈/em〉 growing in pots was also determined.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉No typical B toxicity symptoms were observed in pot experiment, and only slight B toxicity symptoms were observed in hydroponically-grown plants at 50, 100 and 200 mg B L〈sup〉−1〈/sup〉 treatments. Biomass production was not affected in either experiment. The response of total phenolic content to B exposure varied with growing medium, parts of tissues, B treatments, and exposure times. Boron predominantly accumulated in leaves and increased with increasing B treatments in both experiments. Increased exposure time increased the transport of B from root to shoot. Increasing B treatment generally reduced the accumulation of phosphorus, manganese, selenium and arsenic, but increased the accumulation of B, molybdenum and cadmium in 〈em〉S. soda〈/em〉 under specific B treatments, even the accumulation of such elements was still safe for human consumption.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉〈em〉S. soda〈/em〉 appears to be a promising alternative crop to grow in B-laden regions such as the western SJV of Central California.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Rhizosheath is known as a layer of adhering soil particle to the root surface. Despite several speculations, the positive function of rhizosheath in acquisition of water and nutrients from drying soil has not yet been experimentally proven. The objective of this study was to experimentally show whether an enhanced rhizosheath formation could help plants to better access water from drying soil.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Eight wheat cultivars were grown in a sandy-loam soil. When plants were 35 days old let dry soil to a water content at which evident wilting symptoms appeared on the plant leaves. During this drying cycle, soil water content and transpiration rate of plants were gravimetrically measured by weighing the plant pots. At the end of this drying cycle, the roots were excavated out of the soil and the rhizosheath formation was gravimetrically quantified by weighing the soil attached to the root system.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉The results showed that plant cultivars with greater rhizosheath formation could sustain higher transpiration rates at dry condition (water content of 0.07 cm〈sup〉3〈/sup〉 cm〈sup〉−3〈/sup〉) while the plant cultivars with lower rhizosheath formation suffered from drought stress and reached their permanent wilting points at the same water content.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusion〈/h3〉 〈p〉The findings of this study gathered evidence that under severe drought condition plant cultivars with an enhanced rhizosheath formation could better survive by sustaining their transpirational and nutritional demands.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Background〈/h3〉 〈p〉Agroforestry systems have enhanced diversity of cultivated plants compared to monocultures, and are expected to affect associated biodiversity. Despite a growing body of literature on the importance of soil fauna, the known effects of different agroforestry types on soil fauna communities and functions have not yet been synthesized.〈/p〉 〈/span〉 〈span〉 〈h3〉Scope〈/h3〉 〈p〉We scanned publications on soil fauna in agroforestry systems. Our aim was to give an overview of strengths and weaknesses of the existing data, in terms of spatial coverage and representation of diverse agroforestry types and soil fauna groups and functions.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Our database includes sixty-seven articles, mostly focusing on tropical regions and perennial crop agroforestry systems. Soil macrofauna are the most studied fauna group. The most common question addressed is the comparison of the effect of land use types on communities. Effects on fauna abundance and diversity are mainly positive when agroforestry is compared to cropland, and neutral or negative when compared to forests. Few publications actually measure soil fauna functions, or characterize their interactions and evolution in time and space depending on system design and management. Further work on soil fauna in agroforestry should harness ecological theory and address questions of spatial structure and scale, temporal dynamics and ecological interaction networks and how they determine ecosystem functioning.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Rising atmospheric CO〈sub〉2〈/sub〉 causes an increase in dissolved inorganic carbon (DIC) availability in aquatic ecosystems, further affecting plant growth and aquatic ecosystem production. Belowground carbon input can strongly influence microbial processes (carbon or nitrogen cycling). However, changes in sediment microbial abundance and community structure have not been thoroughly assessed in freshwater ecosystems under rising atmospheric CO〈sub〉2〈/sub〉. A pot experiment was conducted using fragments of the submerged macrophyte 〈em〉Myriophyllum spicatum〈/em〉 L. to study plant and sediment microbial responses to increasing aquatic carbon availability under rising atmospheric CO〈sub〉2〈/sub〉. Three DIC levels of overlying water were set up by continuous bubbling with different concentrations of CO〈sub〉2〈/sub〉. Higher biomass accumulation, chlorophyll content, nitrate reductase activity, and leaf N content were observed in 〈em〉M. spicatum〈/em〉 under high DIC level in CO〈sub〉2〈/sub〉 treatment. The increased DIC level in CO〈sub〉2〈/sub〉 treatment reduced sediment ammonium nitrogen, dissolved organic nitrogen content, microbial biomass carbon content and phenol oxidase activity, but not microbial biomass nitrogen content, urease and N-acetyl-β-D-glucosaminidase activities. 〈em〉NifH〈/em〉 abundance significantly decreased with the increasing DIC levels in CO〈sub〉2〈/sub〉 treatment, while bacterial 16S rRNA abundance was not affected. Redundancy analysis results indicated a modest but obvious shift in sediment microbial community compositions among different levels of DIC. Variation partitioning revealed a strong interaction between plant traits and sediment properties and their regulation of sediment microbial compositions at different DIC levels. It seemed that an intensified competition for essential resources between 〈em〉M. spicatum〈/em〉 and sediment microbes occurred under increased aquatic DIC availability caused by rising atmospheric CO〈sub〉2〈/sub〉.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Aim to unveil the functions of VcLon1 in plant Fe use efficiency.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉RT-PCR was used to analyze the expression profile of 〈em〉VcLon1〈/em〉. 〈em〉VcLon1〈/em〉 was expressed in 〈em〉Nicotiana benthamiana〈/em〉, and its homologous tobacco gene was silenced using RNAi. The differences in biomass growth, oxidative stress and chloroplast ultrastructure between wild type and transgenic 〈em〉Nicotiana benthaminana〈/em〉 were analyzed after being subjected to Fe deficiency stress〈em〉.〈/em〉〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉The RT-PCR showed that the expression of 〈em〉VcLon1〈/em〉 was significantly higher in young leaves than in old leaves or in leaves treated with Fe deficiency stress, indicating that VcLon1 is involved in reactive oxygen species (ROS) homeostasis induced by senescence or Fe deficiency. Compared with wild-type, overexpression of 〈em〉VcLon1〈/em〉 in 〈em〉Nicotiana benthamiana〈/em〉 reduced damage to chloroplast structure induced by Fe deficiency. Furthermore, the contents of H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉, MDA and carbonylated protein in leaves were kept at a low level, and antioxidant enzyme activities in chloroplasts such as SOD and APX are also generally higher in chloroplasts with 〈em〉VcLon1〈/em〉 overexpression. In contrast, the oxidative stress levels in 〈em〉NbLon1〈/em〉 RNAi silenced 〈em〉Nicotiana benthamiana〈/em〉 leaves showed opposite trends.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Under Fe deficiency stress, VcLon1 reduces oxidative damage in plants by degrading carbonylated proteins in organelles such as chloroplasts and effectively maintains the structure and function of organelles and the activity of functional proteins, contributing to Fe use efficiency in plants.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aim〈/h3〉 〈p〉Plant-endophytic associations exist only when equilibrium is maintained between both partners. This study analyses the properties of endophytic fungi inhabiting a halophyte growing in high soil salinity and tests whether these fungi are beneficial or detrimental when non-host plants are inoculated.〈/p〉 〈/span〉 〈span〉 〈h3〉Method〈/h3〉 〈p〉Fungi were isolated from 〈em〉Salicornia europaea〈/em〉 collected from two sites differing in salinization history (anthropogenic and naturally saline) and analyzed for plant growth promoting abilities and non-host plant interactions.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Most isolated fungi belonged to Ascomycota (96%) including dematiaceous fungi and commonly known plant pathogens and saprobes. The strains were metabolically active for siderophores, polyamines and indole-3-acetic acid (mainly 〈em〉Aureobasidium〈/em〉 sp.) with very low activity for phosphatases. Many showed proteolytic, lipolytic, chitinolytic, cellulolytic and amylolytic activities but low pectolytic activity. Different activities between similar fungal species found in both sites were particularly seen for 〈em〉Epiccocum〈/em〉 sp., 〈em〉Arthrinium〈/em〉 sp. and 〈em〉Trichoderma〈/em〉 sp. Inoculating the non-host 〈em〉Lolium perenne〈/em〉 with selected fungi increased plant growth, mainly in the symbiont (〈em〉Epichloë〈/em〉)-free variety. 〈em〉Arthrinium gamsii〈/em〉 CR1-9 and 〈em〉Stereum gausapatum〈/em〉 ISK3-11 were most effective for plant growth promotion.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉This research suggests that host lifestyle and soil characteristics have a strong effect on endophytic fungi, and environmental stress could disturb the plant-fungi relations. In favourable conditions, these fungi may be effective in facilitating crop production in non-cultivable saline lands.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉To optimize assay conditions of two common methods for measuring potential free-living nitrogen-fixation (FLNF), acetylene reduction assay (ARA) and 〈sup〉15〈/sup〉N〈sub〉2〈/sub〉-incorporation (〈sup〉15〈/sup〉N〈sub〉2〈/sub〉), for use with soil/rhizosphere samples.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉We tested the impact of different carbon (C) sources, oxygen concentrations (O〈sub〉2〈/sub〉), and incubation times on FLNF rates of two low-fertility Michigan soils via ARA and 〈sup〉15〈/sup〉N〈sub〉2〈/sub〉.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉FLNF rates were greatest with addition of a C cocktail, at low O〈sub〉2〈/sub〉, and with 7-day incubations for both methods. FLNF via ARA was 1700x greater with a C cocktail versus glucose only and via 〈sup〉15〈/sup〉N〈sub〉2〈/sub〉 was 17x greater with a C cocktail compared to other C sources and no-C controls. Specific O〈sub〉2〈/sub〉 optimum varied by method and site. A 7-day incubation was needed for the ARA, but a 3-day incubation was suitable for 〈sup〉15〈/sup〉N〈sub〉2〈/sub〉. Lastly, we confirm previously identified issues with the ARA of acetylene-independent ethylene production/consumption resulting in potential FLNF measurement error of 1.3–52.3 μg N g〈sup〉−1〈/sup〉 day〈sup〉−1〈/sup〉.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉We present an optimized method for measuring potential FLNF in soil/rhizosphere samples which will allow for consistent and comparable FLNF rate measurements. Researchers should account for C source, O〈sub〉2〈/sub〉, and incubation time when assessing FLNF and use the ARA method with caution.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Backgrounds〈/h3〉 〈p〉There are growing concerns regarding the restoration of karst rocky desertification (KRD) areas. However, the soil conditions and its residing microorganisms, which are essential for the plants, remain largely unclear.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉We studied soil characteristics and microbial communities in natural forests (non-KRD) and shrubs with eroded soil and surface soil run-off, using Illumina Miseq sequencing.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Our results showed that despite KRD reduced soil fertility and altered microbial community structures, microbial diversity did not diminish. Interestingly, bacterial OTU richness and diversity were greater in the KRD areas than in the non-KRD areas, which had relatively greater plant density and diversity. Fungal OTU richness and diversity remained unchanged by KRD. Although the KRD areas had been clear-cut and trees were mostly absent, ectomycorrhizal fungi did not differ in diversity and relative abundance between the two land types, indicating that the KRD shrubs hosted surprisingly diverse and abundant ectomycorrhizal fungi.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Our results highlight the highly diverse microbes under environmental and anthropogenic stresses in KRD areas. Despite the fact that degraded soil properties and an altered microbial community structure remain, KRD did not erode ectomycorrhizal fungal species richness, which is crucial in the revegetation of trees in KRD areas.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Abrasive fluidized bed (AFB) machining of aluminum samples was studied with a specific focus on surface roughness formation, according to the sample position inside AFB operating in a minimum fluidization regime. The experimentation was aimed at defining optimum process conditions in terms of morphology uniformity and developing a mathematical model which relates the sample position to the final roughness. Measurements performed by profilometry have shown that a uniform average roughness lower than 1 μm can be obtained, starting from 3.5 μm, when the process parameters and handling are optimized. The analysis of variance (ANOVA) was performed to support the experimental and modeling strategy. This study led to the definition of a rapid and efficient procedure for finding the optimal positioning of samples in terms of finishing and surface uniformity. The proposed procedure does not require complex systems for component movement, and it is based on the study of just two reference positions of samples. The advantage of the procedure developed and validated in this study consists in its ease of implementation and its applicability in industrial strategies, where short decision times are essential.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Initial substrate chemical characteristics are the most important factor in the regulation of fine root decomposition. However, it remains unclear how nitrogen (N) deposition changes the decomposition process by affecting initial substrate chemical characteristics with different fine root diameter sizes.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉We compared the root decomposition processes across three diameter sizes (very fine roots, 〈 0.5 mm; intermediate fine roots, 0.5–1.0 mm; largest fine roots, 1.0–2.0 mm) of 〈em〉Pinus tabulaeformis〈/em〉 treated with N addition (control, low, medium, high N are 0, 3, 6, and 9 g N m〈sup〉−2〈/sup〉 y〈sup〉−1〈/sup〉 respectively) for two years.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉(1) The root decomposition rates, which were mainly determined by initial N, phosphorus (P), cellulose and lignin concentrations, and carbon (C)/N and lignin/N ratios, increased with the root diameters. (2) The effect of N addition on fine root decomposition rate was not significant (〈em〉P〈/em〉 〉 0.05), but low N addition enhanced the correlation coefficients between initial chemical indexes and decomposition rates. (3) Low N addition increased the release rates of C and cellulose in the very fine roots but not intermediate fine and largest fine roots, while the medium and high N addition decreased the release rates of N, P, cellulose and lignin in the very fine and intermediate fine roots by affecting the initial C, N, P, starch, cellulose and lignin concentrations. (4) Release of compounds from large diameter fine roots is less responsive to N addition than that from the small ones.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The initial substrate chemistry plays an important role during the N addition affecting fine root decomposition and release of chemical compounds. Our results suggest that N deposition may change the biogeochemical processes of forest ecosystems by affecting the release of compounds from fine roots.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Background and aims〈/h3〉 〈p〉Root niche partitioning among trees/shrubs and grasses facilitates their coexistence in savannas, but little is known regarding root distribution patterns of co-occurring woody plants, and how they might differ on contrasting soils.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉We quantified root distributions of co-occurring shrubs to 2 m on argillic and non-argillic soils.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Root biomass in the two shrub communities was 3- to 5- fold greater than that in the grassland community. 〈em〉Prosopis glandulosa〈/em〉, the dominant overstory species was deep-rooted, while the dominant understory shrub, 〈em〉Zanthoxylum fagara〈/em〉, was shallow-rooted (47% vs. 25% of root density at depths 〉0.4 m). Shrubs on argillic soils had less aboveground and greater belowground mass than those on non-argillic soils. Root biomass and density on argillic soils was elevated at shallow (〈 0.4 m) depths, whereas root density of the same species on non-argillic soils were skewed to depths 〉0.4 m. Root density decreased exponentially with increasing distance from woody patch perimeters.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Belowground biomass (carbon) pools increased markedly with grassland-to-shrubland state change. The presence/absence of a restrictive barrier had substantial effects on root distributions and above- vs. belowground biomass allocation. Differences in root distribution patterns of co-occurring woody species would facilitate their co-existence.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Milling freeform surfaces using a STEP-compliant CNC machine tool highly reflect the intelligence of STEP-NC, especially when the toolpaths can be generated and adjusted online. However, in contrast to the 2.5D manufacturing features, there are very seldom entities defined in the standard ISO 14649-11 for milling freeform surfaces. Basically, there are only four freeform strategies used for finish milling a freeform surface, and no roughing operations are provided for milling a freeform surface from a raw piece to the shape before the (semi-)finishing operation. Obviously, both of the rough and finish operations are fundamental to machine a freeform surface from the raw piece. This paper extends the EXPRESS definitions for rough milling freeform surfaces, so as to enrich the related operations. Both 2.5D and freeform operations are improved, and individual operations, strategies, and technologies are added to fulfill the need of 2.5D and freeform roughing tasks respectively. The related online toolpath generation algorithms are developed and integrated into a STEP-CNC prototype. The STEP-CNC system is equipped to a three-axis machine tool and finally drives the machine tool to cut a T-spline surface.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Amid diversification, high performance, high integration, and low-cost development in consumer electronic products, the conventional system on board function integration model is giving way to system on chip (SoC). Layout of solder balls under ball grid array (BGA) is getting irregular as system in package (SiP) is integrating multi-chip module and couple of active and passive components along with more complex circuit design. Due to the shortening life cycles of consumer electronic products and frequent new product launches, the incoming inspection operation of electronic components is getting tedious, let alone the component database updates required by mounter are also getting more frequent and time consuming due to increasingly complex and diversified components and soaring demands in characteristic measurement and identification difficulties. This study is aimed at building automated characteristic capture and analysis image processing model for BGA packages of irregular solder ball layout. It employs edge detection to get component body looks and dimensions by enhanced component edge characteristics. A image pre-processing model is used to identify consistency of individual solder ball characteristics with median filter, highlight image characteristics with binary conversion, remove noise with morphology, and connected component labeling to segment area covered by individual characteristic. In addition, a roundness and aspect ratio of the least rectangle-based solder ball characteristics identification method is proposed to determine number of, diameter of, and coordinates of center of border solder balls. The component characteristics acquired by the model comes in ± 3% difference against the actual one in terms of dimension. The model appears a good reference for system packaging operator in component database creation for the launch of new products in terms of reduced time for manual measurement and error as well as loss in mounter capacity. It also serves for electronic components incoming inspection to reduce inspection operation time and simplify the process.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉In this study, we investigated the effects of reduced snow depth on plant phenology, productivity, nitrogen (N) cycling, and N use in canopy and understory vegetation. We hypothesized that decreased snow depth would hasten the timing of leaf flushing and N uptake in understory vegetation, increasing its N competitive advantage over canopy trees.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Snow removal did not directly affect the phenology of either canopy or understory vegetation. Understory vegetation took up more N in the snow removal plots than in the control plots, particularly in the mid- to late-growing season. Leaf production and N uptake in canopy trees also did not differ between the control and snow removal plots, but N resorption efficiency in the snow removal plots (57.6%) was significantly higher than those in control plots (50.0%).〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Increased N uptake by understory plants may induce N limitation in canopy trees, which in turn may cause canopy trees to increase their N use efficiency. Such competitive advantage of understory vegetation over canopy trees against snow reduction may affect N cycling via litter quality and quantity not only just after the growing season but also in subsequent seasons.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Background and aims〈/h3〉 〈p〉Whilst several studies have shown that edaphic variability influences species composition in nutrient-poor tropical forests, the determinants of local species distributions and, in particular, how these change from younger to mature individuals in such forests are still under debate, and have been poorly explored in tropical heath forests that are among the least fertile tropical forest ecosystems.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉We investigated the influence of soil fertility and topography on a Bornean heath forest species composition, α-, β-diversity and tree size structure among size classes by recording all trees ≥1 cm DBH in 16 forest plots totalling 0.36 ha.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Tree species distributions generally followed gradients in available Al and soil depth; α- and β-diversity were linked to soil depth, and to some extent also to pH and the H:Al ratio. In contrast, forest structural attributes (basal area and stem density) were negatively correlated with both available and total P and a wider suite of soil nutrients, although trees ≥10 cm DBH were positively correlated with total P.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusion〈/h3〉 〈p〉Our study shows that heath forest species distribution, richness and structure is related to both edaphic and topographic characteristics and that soil acidity might have a strong influence in shaping these forests’ features. Among size classes, small trees are less influenced by soil and topography, whereas the sensitivity to these variables increases with tree size. We thus highlight that multiple edaphic factors influence different aspects of tropical forest structure, including different tree life stages, and species composition.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Global interference detection and avoidance are key issues in tool path planning for five-axis machining of complex surfaces. Improving the detection accuracy and efficiency has always been the main goal of global interference research. In this paper, a novel method for fast interference judgment is proposed. First, the four planes with X or Y extremum are obtained by the intersection operation between the plane and the machined surface and solving extremum, respectively. Then, the four boundaries of the initial interference detection area are obtained by intersecting the four extreme planes with the machined surface. To determine whether there is collision interference between the tool and the machined part, the shortest distance between the tool axis and the detection area is used for interference judgment. The shortest distance can be obtained by calculating the distance between the discrete point in the detection area and the tool axis. In order to ensure the uniformity of the discrete points, the discretization of points was carried out in the projection area of the initial detection area on the XOY plane, rather than on the part surface. For improving the efficiency of interference detection, the four-sided constraint method is used to screen the discrete points in the initial detection area. Only the points satisfying the screening conditions can be used as effective detection points to calculate the distances, and the shortest distance can be found from all the calculated distances. In this paper, the subdivision technology is used to achieve high-precision interference detection. At the end of the paper, the interference detection algorithm was tested by two examples, and the correctness of the test results was verified by the VERICUT simulation and cutting experiment. The proposed algorithm can be applied to interference detection of five-axis end milling of complex surfaces.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Background and aims〈/h3〉 〈p〉The trend of soil degradation in intensive open coffee systems is well-documented. This study highlights the impact of young shade trees on soil quality only 4 years after their intercropping with coffee.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉18 young shade trees belonging to three tree species (〈em〉Cinnamomum camphora〈/em〉, 〈em〉Bishofia javanica〈/em〉 and 〈em〉Jacaranda mimosifolia〈/em〉) were selected in an intensive coffee system in Southern Yunnan. Soil samples (0–20 cm) were tested for chemical composition, soil communities and soil enzyme activities under their canopies and in open areas, both in coffee rows and inter-rows, once during the rainy and once during the dry season. Additionally, root systems were characterized using trenches. Soil water profiles and litterfall were monitored along the production cycle. Coffee yield was recorded for two consecutive years.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉We detected a positive impact of all shade tree species on soil chemical, biological and biochemical components, especially during the dry season. This positive impact included higher soil organic matter (+10%) and more abundant soil microbial communities (+64%) under shaded coffee than under open coffee. Furthermore, shaded coffee trees yielded as much as open coffee trees, except under 〈em〉C. camphora〈/em〉, probably due to high below-ground competition.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉These results demonstrate that carefully selected shade trees can rapidly contribute to preserving and/or restoring soil quality in intensive coffee systems, while maintaining high coffee yield.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Traits of the plant root system architecture (RSA) play a key role in crop performance. Therefore, architectural root traits are becoming increasingly important in plant phenotyping. In this study, we use a mathematical model to investigate the sensitivity of characteristic root system measures, obtained from different classical field root sampling schemes, to RSA parameters.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Root systems of wheat and maize were simulated and sampled virtually to mimic real field experiments using the root system architecture (RSA) model CRootBox. By means of a sensitivity analysis, we found RSA parameters that significantly influenced the virtual field sampling results. To identify correlations between sensitivities, we carried out a principal component analysis.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉We found that the parameters of zero order roots are the most sensitive, and parameters of higher order roots are less sensitive. Moreover, different characteristic root system measures showed different sensitivity to RSA parameters. RSA parameters that could be derived independently from different types of field observations were identified.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Selection of characteristic root system measures and parameters is essential to reduce the problem of parameter equifinality in inverse modeling with multi-parameter models and is an important step in the characterization of root traits from field observations.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Moso bamboo (〈em〉Phyllostachys edulis〈/em〉) invasions into adjacent forests are becoming increasingly common. Moso bamboo invasions affect litter quality, soil nutrients, and microbial community composition. Although these effects likely vary among invaded sites and forest types, this has not been investigated.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉We investigated moso bamboo invasion effects on carbon (C) and other major nutrients of litter and soil, as well as soil microbial community composition determined by phospholipid fatty acids (PLFAs) in broadleaf or coniferous forests at three different sites in China.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Ordinations indicated that the effects of invasions on soil nutrients, litter nutrients, and soil microbial composition each varied among forest types and sites. Invasions consistently decreased litter C. Invasions tended to have larger effects on soil nutrients in coniferous forests. Except for bacterial groups in one coniferous forest site, invasions had positive effects on every soil group.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Variations in direction and magnitude of invasion effects on litter properties, soil properties, and soil communities among community types and sites suggest that studies of effects of invasions on soils in a single invaded community may not be able to predict effects of an invasion at other locations, even when the original community is similar or occurs in the same site.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Background and aims〈/h3〉 〈p〉Mine tailings are challenging substrates for ecological restoration, as the establishment of diverse native plant communities can be constrained by a range of edaphic factors. Thus, the ability to restore native vegetation communities will depend upon developing a clear evidence-base as to what types of species and communities are likely sustainably reinstated on such altered substrates. As global tailings production and the cumulative footprint of tailings storage facilities continue to grow, understanding the effect of edaphic filters on community establishment is foundational for developing effective restoration solutions for tailings.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉We standardised growth rate estimates derived from nine root and shoot parameters for plants grown in magnetite tailings and natural topsoil, using crops (eight species) to characterise previously identified plant responses and native plants (40 species) to understand the impact of edaphic conditions on the species pool available for restoration.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉The edaphic conditions of unweathered magnetite tailings select against the majority of native plant species and nutrient-acquisition guilds (approximately 75% of reference floristic biodiversity), with plant development on tailings compared with natural topsoil compromised in a number of variables in all but six species. Plant growth on tailings was limited by a lack of available nitrogen (N) and high alkalinity (pH 〉9), and seedling growth and development was positively associated with seed N concentration. Calcicole species and species from N〈sub〉2〈/sub〉-fixing and cluster root-producing strategies performed better on tailings than calcifuge species and species without specialised nutrient-acquisition strategy or those reliant upon mycorrhizal associations.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉The return of plant communities native to highly weathered, acidic soils on magnetite tailings is likely unsuccessful, unless strategies to ameliorate substrate hostility through acidification of the soil profile and improving N availability are prioritised.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉The low phosphorus (P) fertilizer use efficiency in weathered, P deficient soils calls for better fertilizer formulations. We previously formulated nanoparticles containing P (NP-P) that were a successful fertilizer in nutrient solution. This study was set up to test the fate and the bioavailability of nanofertilizer-P and of that of native (colloid) P naturally present in soil.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉The NP-P consisted of nano-ferrihydrite (~ 10 nm) loaded with phosphate (P-〈em〉n〈/em〉Fh) and stabilized with either natural organic matter (NOM) or hexametaphosphate (HMP). Natural colloid concentrations were increased with KOH addition, as deflocculating agent, to soil; all tests used samples from P deficient, highly weathered soils.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Pot trials with rice seedlings did not reveal larger P uptake in the NP-P amended soils compared to equal doses of soluble PO〈sub〉4〈/sub〉 or soluble HMP. Total Fe concentrations in soil solutions were unaffected by NP-P addition, whereas natural colloidal Fe and P markedly increased by KOH addition. The bioavailability of native colloidal P, mobilized by KOH addition, could not be assessed due to lack of growth, likely related to collapse of the soil structure.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉This study showed that P-loaded iron oxyhydroxide NPs insufficiently enhanced soluble P in soil to offer benefits over soluble fertilizers, likely because of a combined effect of lower diffusivity of NPs compared to P〈sub〉i〈/sub〉 and lower bioavailability of NP-P than P〈sub〉i〈/sub〉. Smaller particles or small labile organic colloids might offer an improvement in both aspects.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Conventional volumetric error compensation strategies for five-axis machines directly generate compensation values without considering the RTCP (rotation tool center point) effects, which causes additional movements of translational axes with the movement of rotary axes, so the compensation values for three linear axes need to be recalculated. In this paper, a volumetric error compensation model considering RTCP is proposed. In the model, the compensation values for translational axes totally consist of three parts, i.e., position errors caused by the volumetric error, position variations caused by the compensation of rotary axes, and caused by RTCP. Firstly, the compensation values for rotary axes are obtained based on the volumetric error model and the inverse kinematics. Then, the compensation values for three linear axes are calculated in detail based on the compensation values of rotary axes and RTCP effects. Finally, ballbar tests of a cone-frustum toolpath are selected to verify the proposed compensation model.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Wetlands play vital roles as sinks for metal contaminants. Some wetland plants accumulate manganese (Mn) oxides in the black biofilm around roots and rhizomes, although the underlying mechanism is still unclear. Our aim is to determine the role of endophytic bacteria in the formation of Mn deposits in the wetland plant 〈em〉Suaeda salsa〈/em〉 Pall. as well as the underlying chemical and molecular mechanisms.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Manganese-oxidizing endophytic bacteria were isolated with leucoberbeline blue (LBB) and further identified via the phylogenetic analysis. The Mn content and black deposit characteristics of laboratory-cultivated plants before/after co-cultivation of bacteria were investigated by inductively-coupled plasma optical emission spectrometry (ICP-OES), a scanning electron microscope equipped with an energy energy-dispersive X-ray spectroscopye (SEM-EDX), and X-ray fluorescence (XRF). The chemical structures of the biogenic Mn minerals were characterized via spectra of X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and selected area electron diffraction (SAED). Proteomic analyses, coupled with the enzymic assays were performed to identify the enzymes involved in the Mn oxidation.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉We observed black deposits containing Mn oxides in the belowground and aboveground tissues of 〈em〉S. salsa〈/em〉. Three Mn-tolerant bacterial strains were isolated from the plants, and two of them possessed Mn(II) oxidation capacities, which were identified as 〈em〉Pantoea eucrina〈/em〉 SS01 and 〈em〉Pseudomonas composti〈/em〉 SS02. Co-cultivation of the two isolates with 〈em〉S. salsa〈/em〉 showed promoted plant growth and facilitated the formation of black precipitations on roots. Further results showed the different chemical compositions and cellular localizations of biogenic Mn oxides from the two strains. Hydrogen peroxide-detoxifying enzymes were involved in Mn oxidation, most likely mitigating oxidative stresses.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉We suggest a role of endophytic bacteria in Mn uptake and accumulation in the wetland plant 〈em〉S. salsa〈/em〉; our study thereby contributes to a better understanding of the plant-endophyte symbiosis in biogeochemical Mn cycling and wetland soil phytoremediation.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The remanufacturing technology of aero-engine blade is one of the effective ways to save expensive materials such as titanium alloy, make full use of resources, and solve the problem of resource hiding. Laser-cladding technology has been widely used in the remanufacturing of blades due to its ability to fabricate high-performance alloy surfaces on metal substrates without affecting the properties of the matrix. In order to solve the problem that the grinding precision is difficult to guarantee due to the deformation and residual distribution of the blade in laser cladding remanufacturing, the self-adaptive grinding process of abrasive belt is repaired based on online inspection and reconstruction model. Firstly, the distribution of theoretical measuring points is planned based on the curvature of cross-section curve, and then the theoretical measurement points are adaptively extracted according to the improved firefly algorithm, so that the CMM measurement path planning of laser cladding and remanufacturing blades is realized. Taking the layer as the unit, the measurement data are processed, and the iterative nearest point algorithm is used for data registration to realize the laser-cladding remanufacturing blade measurement data processing. On this basis, the blade surface model is obtained based on NURBS interpolation. Finally, a laser cladding and remanufacturing blade of an aero-engine was tested. The experimental results show that the blade surface roughness is 0.4 μm, the blade edge accuracy is less than 0.05 mm, and the blade edge error is less than 10%. The experimental results show that this method can effectively solve the grinding process of laser-cladding remanufacturing blade.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Northern peatlands store large amounts of soil organic carbon (C) that can be very sensitive to ongoing global warming. Recently it has been shown that temperature-enhanced growth of vascular plants in these typically moss-dominated ecosystems may promote microbial peat decomposition by increased C input via root exudates. To what extent different plant functional types (PFT) and soil temperature interact in controlling root C input is still unclear. In this study we explored how root C input is related to the presence of ericoid shrubs (shrubs) and graminoid sedges (sedges) by means of a factorial plant clipping experiment (= PFT effect) in two peatlands located at different altitude (= temperature effect).〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉By selective clipping of shrub and sedge shoots in mixed vegetation at two Alpine peatland sites we interrupted the above- to belowground translocation of C, thus temporarily inhibiting root C release. Subsequent measurements of soil respiration, dissolved organic carbon (DOC) concentration and stable isotope composition (〈sup〉13〈/sup〉C) of DOC in pore water were used as proxies to estimate the above- to belowground transfer of C by different PFT.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉We found that soil respiration rates and DOC concentrations temporarily decreased within 24 h after clipping, with the decrease in soil respiration being most pronounced at the 1.4 °C warmer peatland after clipping shrubs. The transient drop in DOC concentration coincided with a shift towards a heavier C isotope signature, indicating that the decrease was associated with inhibition of a light C source that we attribute to root exudates. Together these results imply that shrubs translocated more C into the peat than sedges, particularly at higher temperature.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉We showed that plant functional type and temperature interact in controlling root C input under field conditions in peatlands. Our results provide a mechanistic evidence that shrubs may potentially promote the release of stored soil C through root-derived C input.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Background and aims〈/h3〉 〈p〉Root-rot disease, a catastrophic disease of 〈em〉Panax quinquefolium〈/em〉 L. causes yield reduction and serious economic losses. However, knowledge of the relationship between rhizosphere microbial community and root-rot disease is limited. This study is aim to test whether the bacteria and fungi community differed between the soil attached to healthy and rotten roots of American ginseng. Moreover, the effects of American ginseng cultivation for 4 years on changes of soil physiochemical properties and microbial community were also investigated.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉High-throughput sequencing (Illumina MiSeq) was used to investigate the difference of microbial communities in the soils of new farmland (C) and the rhizosphere soils around healthy (H) and root rot diseased ginseng (R).〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Cultivation of American ginseng for 4 years not only changed the soil physicochemical properties, but also significantly increased the richness of the soil bacteria and decreased the fungal richness and diversity. Compared with other genera, the bacterial genera 〈em〉Nitrospira〈/em〉 and the fungal genera 〈em〉Gibberella〈/em〉 and 〈em〉Podospora〈/em〉 were strongly enriched in the soil of new farmland. However, the relative abundance of 〈em〉Janthinobacterium, Nitrospira〈/em〉 and 〈em〉Pedomicrobium〈/em〉 in bacterial community, and 〈em〉Mrakia, Paradendryphiella, Sporopachydermia, Myrothecium〈/em〉 and 〈em〉Racocetra〈/em〉 in fungal community were significantly decreased after culture of American ginseng. The results also showed that the bacteria and fungi community differs between the soil attached to healthy and rotten roots of American ginseng. The richness indices of fungal community showed a significant decrease in rhizosphere soils of R comparing with H. The bacteria 〈em〉Rhodoplanes〈/em〉 and 〈em〉Kaistobacter〈/em〉 were the dominant genera in the H sample, whereas 〈em〉Sphingobium〈/em〉 was dominant in the R sample. Notably, 〈em〉Monographella〈/em〉 was significantly higher in the R sample (23.13%) than that of H sample (2.90%). In addition, the fungi 〈em〉Melanophyllum〈/em〉 and 〈em〉Staphylotrichum〈/em〉 were the most differently abundant in the H sample, whereas 〈em〉Mortierella〈/em〉 and 〈em〉Cistella〈/em〉 were the differently abundant genera in the R sample.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉Our results indicate that cultivation of American ginseng changed the edaphic factors and the soil microbial community, and there are significant differences in the microbial community between the soil attached to healthy and rotten roots of American ginseng.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉 We evaluated the effect of 〈em〉Azospirillum brasilense〈/em〉 strain HM053 inoculation on maize seeds, a spontaneous mutant that excrete ammonium and fix nitrogen constitutively.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Maize was grown with different nitrogen (urea) concentration and inoculated with 〈em〉A. brasilense〈/em〉 Ab-V5 (Brazilian commercial strain) or HM053 strain in four field experiments, in three regions of Parana State, Southern Brazil. We evaluated yield components, nutrient content on leaves and grains and productivity during the crop cycle.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Inoculation with 〈em〉A. brasilense〈/em〉 strain Ab-V5 and HM053 associated with base fertilization (30 kg ha〈sup〉−1〈/sup〉 N) improved crop yield in all trials. Ab-V5 increased production between 2.2 to 10.4%, or 178.0 to 759.9 kg ha〈sup〉−1〈/sup〉, respectively. HM053, by itself, increased production between 4.7 to 29%, or 460.5 to 1769.3 kg ha〈sup〉−1〈/sup〉, respectively.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusion〈/h3〉 〈p〉The new strain HM053 showed to be a great biofertilizer for maize seeds and a new alternative for a more sustainable agriculture.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉X-ray computed tomography (CT) is widely recognized as a powerful tool for in-situ quantification of root system architecture (RSA) in soil. However, employing X-ray CT to identify the spatio-temporal dynamics of RSA still remains a challenge due to non-automatic, time-consuming image processing protocols and their poor recovery of fine roots in soil.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Here we present a new protocol (Rootine) to segment roots rapidly and precisely down to fine roots with two voxels in diameter (90 μm in pots with 70 mm in diameter). This is facilitated by feature detection of the tubular shape of roots, an approach that was originally developed for detecting blood vessels in medical imaging.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉In comparison to established root segmentation methods, Rootine produced a more accurate root network, i.e. more roots and less over-segmentation. Root length quantified by X-ray CT showed high correlation with results by root washing combined with 2D light scanning (R〈sup〉2〈/sup〉 = 0.92). Tests with different soil materials showed that the recovery of roots depends on signal-to-noise ratio but can be up to 99% for a favorable contrast between fine roots and background.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉This new protocol provides great efficiency to study RSA in undisturbed soil. As it is fully automated it has the potential for high-throughput root phenotyping and related modelling.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Litter inputs are closely related to both forest productivity and nutrient cycling under climate change and local management. This study investigated the effect of litter inputs on litter decomposition, changes in litter chemistry and nitrogen (N) dynamics during eucalyptus leaf litter decomposition.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉Two parallel in situ litter decomposition experiments were conducted at two sites with high-quality (HQ) and low-quality (LQ) litters in a eucalyptus-dominated forest of southeast Queensland, Australia. At each site, leaf litters with either a single (SL) or double mass load (DL) of litter inputs were decomposed for 15 months. Litter mass loss, chemical composition and N content of decomposing litters were measured seasonally during the decomposition period. The chemical composition of the collected litters was determined by solid-state 〈sup〉13〈/sup〉C nuclear magnetic resonance (NMR) spectroscopy.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉The HQ litters decomposed faster than the LQ litter, with a decomposition constant of 0.53 and 0.33 y〈sup〉−1〈/sup〉 at the HQ and LQ site, respectively. Litter addition rates had no effect on litter decomposition, changes in chemical composition and N content during decomposition regardless of differences in initial litter quality. The HQ and LQ litters showed the same pattern of chemical changes during decomposition, with an increase in alkyl C and a decrease in di-O-alkyl C and aryl C. The relative intensity of O-aryl C and carboxyl C converged, while the relative intensity of di-O-alkyl C and 〈em〉δ〈/em〉〈sup〉15〈/sup〉N diverged as the decomposition progressed. N immobilization during decomposition depended on litter quality, with N consistently immobilized in LQ litters over the whole decomposition period.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉In subtropical eucalyptus-dominated forests, the dynamics of organic C and N during litter decomposition were resistant to the increased inputs of aboveground litters. Litter chemistry of different initial qualities converged at the early stages of decomposition, and the implications of chemical convergence on the formation and stabilization of soil organic matter need to be assessed in the future.〈/p〉 〈/span〉

Description: 〈h3〉Abstract〈/h3〉 〈span〉 〈h3〉Aims〈/h3〉 〈p〉Previous studies suggest that organic carbon (C) and nitrogen (N) can stimulate soil nitrification, but whether autotrophic or heterotrophic nitrification is stimulated and who are active nitrifiers for the nitrification activity is still in debate. We elucidated which nitrification dominated and the active nitrifiers during the decomposition of rice callus.〈/p〉 〈/span〉 〈span〉 〈h3〉Methods〈/h3〉 〈p〉〈sup〉15〈/sup〉N-labeled callus and acetylene (C〈sub〉2〈/sub〉H〈sub〉2〈/sub〉) inhibition were used to explore the autotrophic or heterotrophic nitrification during the decomposition of callus and DNA-based stable isotope probing (SIP) and high-throughput sequencing were used to investigate the active nitrifiers.〈/p〉 〈/span〉 〈span〉 〈h3〉Results〈/h3〉 〈p〉Autotrophic nitrification dominated the nitrification activity, driven by oxidation of ammonia (NH〈sub〉3〈/sub〉) produced from mineralization of the callus-derived organic N. Callus significantly stimulated nitrification activity, which was paralleled by changes in the abundance and community composition of AOA. DNA-SIP further demonstrated that the active AOA outnumbered their bacterial counterparts in the 〈sup〉13〈/sup〉C-DNA from the soil with callus amendment. Phylogenetic analysis revealed the functional importance of soil fosmid 29i4-like and 54d9-like AOA within soil group 1.1b during the active nitrification with callus cells.〈/p〉 〈/span〉 〈span〉 〈h3〉Conclusions〈/h3〉 〈p〉NH〈sub〉3〈/sub〉 released from the mineralization of callus was the main substrate for autotrophic nitrification and preferentially stimulated the growth of AOA within group 1.1b in the paddy soil.〈/p〉 〈/span〉