ALBERT

Description: To identify genetic diversity, genetic structure and the relationship among accessions, and further establish a core collection for the long-term breeding of cypress (Cupressus funebris Endl.), the genealogy of breeding parents was reconstructed using simple sequence repeat (SSR) molecular markers. Seventeen SSR markers were used to detect molecular polymorphisms among 290 cypress accessions from five provinces and 53 accessions with unknown origin in China. A total of 92 alleles (Na) were detected with 5.412 alleles per locus and an average polymorphism information content (PIC) of 0.593. The haplotype diversity (H) ranged from 0.021 to 0.832, with an average of 0.406. The number of alleles (Na) and the effective number of alleles (Ne) ranged from 4.294 to 5.176 and from 2.488 to 2.817 among five populations, respectively. The pairwise population matrix of Nei’s genetic distance ranged from 0.008 to 0.023. Based on the results of unweighted pair group method average (UPGMA) cluster and population structure analyses, 343 breeding parents were divided into two major groups. Lower genetic differentiation coefficients and closer genetic relationships were observed among cypress breeding parents, suggesting that the genetic basis was narrow, and the genetic relationship was confused by frequent introduction and wide cultivation. Moreover, we reconstructed the genealogy between breeding parents and 30 accessions of breeding parents from an identified core collection. According to the present study, not only geographic origin but also the relationship of the individuals should be considered in future crossbreeding work.

Description: In order to study the flashover mechanism of polluted insulators under AC voltage, a new arc propagation criterion which is based on an arc root voltage gradient is proposed. This criterion can explain the variation of the arc root voltage gradient in the arc propagation process. Based on this criterion, a new distributed parameter electrical circuit flashover model of polluted insulators is presented. The arc channel is considered as an equivalent distributed parameter circuit model instead of using the arc voltage-gradient equation. The parameters of the arc model are obtained from the electromagnetic field distribution of the arc and the gas discharge theories. The arc root is considered as parallel paths including the polluted layer. The variation of the voltage on the arc root is related to the capability of arc propagation. This model takes the microscopic mechanism of arc root ionization into consideration, which can improve the accuracy of the flashover model. The results obtained from the presented model are in good agreement with other mathematical and experimental results.

Description: Using box-counting and spatial regression, this paper analyzes the morphological characteristics of coastal settlement patterns and their spatial determinants, with a case of the Wen-Tai region on the Chinese eastern coast. Coastal settlement patterns, which reflect the interactions between people and the surrounding environment, can indicate the anthropogenic pressure sustained in the coastal zones. Characterization of settlement patterns in coastal zones is definitely needed for coastal management. Results indicate that coastal settlement patterns in the Wen-Tai region present significant fractal characteristics, and exhibit obvious spatial variations. The morphological characteristics of settlement patterns are significantly correlated with the standard deviation value of elevation and slope, as well as percentage of loam soils. In particular, cities with greater relief amplitude, higher slope variability, and higher percentage of loam soils would present more complexity in form. Proximity to roads and rivers are insignificant determinants. Our study contributes to the understanding of the spatial determinants of the morphological characteristics of settlement patterns in coastal zones. We argue that fractal dimension provides a useful tool to facilitate the identification of vulnerability hotspots for coastal studies.

Description: In order to study the flashover mechanism of polluted insulators under AC voltage, a new arc propagation criterion which is based on an arc root voltage gradient is proposed. This criterion can explain the variation of the arc root voltage gradient in the arc propagation process. Based on this criterion, a new distributed parameter electrical circuit flashover model of polluted insulators is presented. The arc channel is considered as an equivalent distributed parameter circuit model instead of using the arc voltage-gradient equation. The parameters of the arc model are obtained from the electromagnetic field distribution of the arc and the gas discharge theories. The arc root is considered as parallel paths including the polluted layer. The variation of the voltage on the arc root is related to the capability of arc propagation. This model takes the microscopic mechanism of arc root ionization into consideration, which can improve the accuracy of the flashover model. The results obtained from the presented model are in good agreement with other mathematical and experimental results.

Description: In the dual-axis rotation inertial navigation system (INS), besides the gyro error, accelerometer error, rolling misalignment angle error, and the gimbal angle error, the shaft swing angle and the axis non-orthogonal angle also affect the attitude accuracy. Through the analysis of the structure, we can see that the shaft swing angle and axis non-orthogonal angle will produce coning errors which cause the fluctuation of the attitude. According to the analysis of the rotation vector, it can be seen that the coning error will generate additional drift velocity along the rotating shaft, which can reduce the navigation precision of the system. In this paper, based on the establishment of the modulation average frame, the vector projection is carried out, and then the attitude conversion matrix and the attitude error matrix mainly including the shaft swing angle and axis non-orthogonal are obtained. Because the attitude angles are given under the static condition, the shaft swing angle and the axis non-orthogonal angle are estimated by the static Kalman filter (KF). This kind of KF method has been widely recognized as the standard optimal estimation tool for estimating the parameters such as coning angles (α1 , α2), initial phase angles (ϕ1,ϕ2), and the non-perpendicular angle (η). In order to carry out the system level verification, a dual axis rotation INS is designed. Through simulation and experiments, the results show that the amplitudes of the attitude angles’ variation are reduced by about 20%–30% when the shaft rotates. The attitude error equation is reasonably simplified and the calibration method is accurate enough. The attitude accuracy is further improved.

Description: Energies, Vol. 10, Pages 1241: Simulation Study on the Effect of Fracturing Technology on the Production Efficiency of Natural Gas Hydrate Energies doi: 10.3390/en10081241 Authors: Chen Chen Lin Yang Rui Jia Youhong Sun Wei Guo Yong Chen Xitong Li Natural gas hydrate (NGH) concentrations hold large reserves of relatively pure unconventional natural gases, consisting mainly of methane. Depressurization is emerging as the optimum conversion technology for converting NGH in its reservoir to its constituent water and natural gas. NGH concentrations commonly have a pore fill of over 80%, which means that NGH is a low-permeability reservoir, as NGH has displaced water in terms of porosity. Fracturing technology (fracking) is a technology employed for increasing permeability-dependent production, and has been proven in conventional and tight oil and gas reservoirs. In this work, we carried out numerical simulations to investigate the effects on depressurization efficiency of a variably-fractured NGH reservoir, to make a first order assessment of fracking efficiency. We performed calculations for the variations in original NGH saturation, pressure distribution, CH4 gas production rate, and cumulative production under different fracturing conditions. Our results show that the rate of the pressure drop within the NGH-saturated host strata increases with increased fracturing. The CH4 gas production rate and cumulative production are greatly improved with fracturing. Crack quantity and spacing per volume have a significant effect on the improvement of NGH conversion efficiencies. Possibly most important, we identified an optimum fracking value beyond which further fracking is not required.

Description: The Stipa grandis steppe is a type of steppe in the Central Asian sub-region, and it is an important resource for livestock production in China. Mowing is one of the main management methods for this steppe. Verifying the response of the Stipa grandis steppe communities to different mowing frequencies is essential for the rational utilization of pastures and the protection and recovery of natural steppe. In this study, we investigated the community characteristics and compensatory growth of important species of the Stipa grandis steppe community under four mowing frequencies (TAY: twice a year; OAY: once a year; OTY: once every other year; NM: no mowing/enclosure), and found that different frequencies of mowing significantly influenced the community characteristics and the compensatory growth of dominant plant species. In the enclosure, species density was significantly lower, and height and biomass were significantly greater than in the mowing treatments. At the beginning of the growing season, mowing had a significant impact on the individual miniaturization of Stipa grandis, Leymus chinensis, and Anemarrhena asphodeloides. Mowing also had a significant impact on the diversity of the community. The Shannon diversity index, the Pielou evenness index, and the richness index were higher under OTY than other mowing frequencies. Under different mowing frequencies, growth rates were significantly different after the aboveground portions were cut, while the levels of biomass were not significantly different. Stipa grandis, Leymus chinensis, and Anemarrhena asphodeloides had less compensatory height growth under OAY compared to the other treatments; however, there were no significant differences in the relative growth rates of the three species under different treatments. Stipa grandis exhibited equivalent compensatory height growth; both Leymus chinensis and Anemarrhena asphodeloides exhibited over-compensatory growth. Based on the results of community characteristics and the compensatory growth of the dominant species, mowing every other year is currently the most practical mowing system.

Description: This paper presents a joint estimation method of source range and depth using a bottom-deployed vertical line array (VLA). The method utilizes the information on the arrival angle of direct (D) path in space domain and the interference characteristic of D and surface-reflected (SR) paths in frequency domain. The former is related to a ray tracing technique to backpropagate the rays and produces an ambiguity surface of source range. The latter utilizes Lloyd’s mirror principle to obtain an ambiguity surface of source depth. The acoustic transmission duct is the well-known reliable acoustic path (RAP). The ambiguity surface of the combined estimation is a dimensionless ad hoc function. Numerical efficiency and experimental verification show that the proposed method is a good candidate for initial coarse estimation of source position.

Description: Forests, Vol. 8, Pages 404: The Floral Biology, Breeding System and Pollination Efficiency of Schima superba Gardn. et Champ. (Theaceae) Forests doi: 10.3390/f8100404 Authors: Hanbo Yang Rui Zhang Ping Song Zhichun Zhou Schima superba Gardn. et Champ. is a perennial, evergreen tree valued for its eco-protection and commercial values in China. In this study, we investigate the breeding system, reproductive ecology and pollination biology of S. superba in a seed orchard. The flowers are hermaphrodite and protogynous. The viability of the pollen is inactivated rapidly, and the stigma maintains a high receptivity within the flower lifespan. Flowers typically offer pollen and nectar to visitors. The flowers possess a typical insect pollination syndrome, and three visitors (Apis cerana cerana Fabricius, Protaetia brevitarsis Lewis, and Popillia mutans Newman) are observed on flowers during the study period. The visitation frequency per minute and capability of pollen removal and deposition of A. cerana are significantly higher than P. brevitarsis and P. mutans, although the pollinator efficiency is lower than those shown by the two beetles. Fruit set (28.27%) and seed set (6.57%) percentages resulting from open-pollination are significantly lower than those resulting from cross-pollination (fruit/seed set, 43.73%/11.66%), and the pollen limitation index (L) was 0.34, suggesting that seed production is pollen-limited in the seed orchard. The pollen/ovule ratio (P/O) and outcrossing index (OCI) values are 6686.67 and 4, respectively. The self-incompatibility index (ISI) was estimated to be 0.95. Results from hand-pollination, pollen tube growth experiments and the ISI value show that S. superba is late-acting self-incompatible. The synthetic results indicate that A. cerana is the most efficient pollinator of S. superba, and seed production is frequently limited by pollinators, fruit abortion, and pollen quality.

Description: Sensors, Vol. 18, Pages 2053: Sensitivity Analysis of Geometrical Parameters on the Aerodynamic Performance of Closed-Box Girder Bridges Sensors doi: 10.3390/s18072053 Authors: Yongxin Yang Rui Zhou Yaojun Ge Yanliang Du Lihai Zhang In this study, the influence of two critical geometrical parameters (i.e., angles of wind fairing, α; and lower inclined web, β) in the aerodynamic performance of closed-box girder bridges was systematically investigated through conducting a theoretical analysis and wind tunnel testing using laser displacement sensors. The results show that, for a particular inclined web angle β, a closed-box girder with a sharper wind fairing angle of α = 50° has better flutter and vortex-induced vibration (VIV) performance than that with α = 60°, while an inclined web angle of β = 14° produces the best VIV performance. In addition, the results from particle image velocimetry (PIV) tests indicate that a wind fairing angle of α = 50° produces a better flutter performance by inducing a single vortex structure and a balanced distribution of the strength of vorticity in both upper and lower parts of the wake region. Furthermore, two-dimensional three-degrees-of-freedom (2D-3DOF) analysis results demonstrate that the absolute values of Part A (with a reference of flutter derivative A2*) and Part D (with a reference of A1*H3*) generally decrease with the increase of β, while the change of the participation level of heaving degrees of freedom (DOF) in torsion-dominated coupled flutter initially increases, reaches its peak, and then decreases with the increase of β.