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  • Articles  (8)
  • De Gruyter  (8)
  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (6)
  • Technology  (2)
  • Sociology
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  • Articles  (8)
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  • 1
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    Quantitative structural characterization of the lignins from the stem and pith of bamboo (Phyllostachys pubescens) (2013)
    De Gruyter
    Details
    Publication Date: 2013-08-01
    Description: Milled wood lignins (MWL) were isolated from the stem (MWLS) and pith (MWLP) of bamboo (Phyllostachys pubescens). The nonacetylated and acetylated bamboo MWLs were investigated by Fourier transform infrared, quantitative 13C-nuclear magnetic resonance (NMR), 2D heteronuclear single quantum coherence (HSQC) NMR, and 31P-NMR spectroscopy. The MWL consists of p-hydroxyphenyl (1–2%), guaiacyl (21–31%), and syringyl (67–78%) units associated with p-coumarates and ferulates. A modified quantitative 13C-NMR and 2D-HSQC analysis has demonstrated that the predominant intermonomeric linkages are of the type β-O-4 (45–49 per 100 C9 units, i.e., per C900) along with small amounts of other structural units such as resinols (3.6–7.4 per C900), tetrahydrofuran (2.0–2.3 per C900), phenylcoumaran (2.8–4.5 per C900), spirodienones (1.3–2.3 per C900), and α,β-diaryl ethers (2.8–2.9 per C900). MWLP contained more p-coumarates than MWLS. The various degrees of γ-acylation (17–27%) were positively associated with S/G ratios in the lignins; however, γ-acylation was inversely correlated to the ratio between β-β and β-O-4 side chains in these lignin fractions. Moreover, a flavonoid compound (tricin) was also detected in the MWLS but not in MWLP. The two MWLs are very similar in terms of molecular weights and the contents of OHphen and OHaliph.
    Print ISSN: 0018-3830
    Electronic ISSN: 1437-434X
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 2
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    Enhancement of the physical and mechanical properties of wood using a novel organo-montmorillonite/hyperbranched polyacrylate emulsion (2020)
    De Gruyter
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    Publication Date: 2020-10-23
    Description: In this work, a novel waterborne hyperbranched polyacrylate (HBPA) dispersed organo-montmorillonite (OMMT) emulsion was synthesized and used for the treatment of wood in a vacuum environment in order to enhance the physical and mechanical properties of the wood. The sapwood of Cathay poplar (Populus cathayana Rehd.) and Radiata pine (Pinus radiata D.Don) were used as the samples for experimentation. The results showed that the physical and mechanical properties of the wood improved significantly due to the successful penetration of the OMMT and HBPA into the wood cell wall. From it was also observed that OMET completely exfoliated from the HBPA matrix and formed a hydrophobic film covering on the inside walls of the cell lumen. Further, it was observed that the poplar sample displayed better mechanical properties than the pine sample because the pine has a more compact structure when compared to poplar and contains rosin. Furthermore, it was also observed that the mechanical properties of the modified wood sample gradually improved with an increase in the concentration of the emulsion. However, excessive concentration (〉4 wt%) did not lead to further improvement.
    Print ISSN: 0018-3830
    Electronic ISSN: 1437-434X
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 3
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    Research on Key Process Technology for Profile Electrolytic Finishing of Large Marine Propeller Impeller (2018)
    De Gruyter
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    Publication Date: 2018-08-01
    Description: An electrolysis process method for free-form blade surface finishing is proposed for a free-form surface impeller, and a stepwise method is used to process the inter-blade channel of the overall impeller. The forming cathode is then used to finish the blade to meet the blade processing requirements. In the design, the forming cathode structure was improved by using motion simulation software, and the flow field simulation software was used to simulate and analyze the cathode flow channel. The cathode shape and the electrolyte flow rate between the electrodes meet the processing requirements. In the process of processing experiments, the motion path of the cathode was analyzed and optimized. The effect of the feed direction on the uneven distribution of the blade machining gap was reduced through optimization, and high-frequency pulse power processing was used to reduce the machining gap and improve the machining accuracy of the blade. The experimental results show that the process scheme is feasible and the precision of the processed impeller free-form surface is significantly improved. The material is a monolithic turbine disk of high-temperature alloys, and its large twisted blade processing has always been a problem in the manufacturing industry.
    Print ISSN: 1233-2585
    Electronic ISSN: 2083-7429
    Topics: Technology , Economics
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  • 4
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    Water Entry of A Wedge Into Waves in Three Degrees Offreedom (2019)
    De Gruyter
    Details
    Publication Date: 2019-03-01
    Description: The hydrodynamic problem of a two-dimensional wedge entering into a nonlinear wave in three degrees of freedom is investigated based on the incompressible velocity potential theory. The problem is solved through the boundary element method in the time domain. To avoid numerical difficulties due to an extremely small contact area at the initial stage, a stretched coordinate system is used based on the ratio of the Cartesian system in the physical space to the distance travelled by the wedge in the vertical direction. The mutual dependence of body motion and wave loading is decoupled by using the auxiliary function method. Detailed results about body accelerations, velocities and displacements at different Froude numbers or different waves are provided, and the mutual effect between body motion and wave loading is analysed in depth.
    Print ISSN: 1233-2585
    Electronic ISSN: 2083-7429
    Topics: Technology , Economics
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  • 5
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    Characteristics and discrimination of five types of wood-plastic composites by FTIR spectroscopy combined with principal component analysis (2010)
    De Gruyter
    Details
    Publication Date: 2010-10-01
    Description: The analytical potential of attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy has been tested on the following wood-plastic composites (WPCs): high and low density polyethylene (HDPE and LDPE), polypropylene (PP), polystyrene (PS), and a recycled plastic (rHDPE). The data set of ATR-FTIR spectra has been analyzed by principal component analysis (PCA) and the studied samples could be grouped according to their polymeric matrixes. Additionally, ATR-FTIR spectroscopy proved to be a useful tool for determining the distribution profile of wood and plastic materials within different types of WPCs. Accordingly, the plastic content of the surface layers of HDPE, rHDPE, and PP composites was significantly higher than that of the core layer, whereas homogenous dispersion was observed in the LDPE composite. Among all WPCs, the PS composite displayed the worst dispersion.
    Print ISSN: 0018-3830
    Electronic ISSN: 1437-434X
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 6
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    Effects of polymeric matrix on accelerated UV weathering properties of wood-plastic composites (2012)
    De Gruyter
    Details
    Publication Date: 2012-12-01
    Description: The purpose of this work is to compare the weathering properties of different types of wood-plastic composites (WPCs) based on high-density polyethylene (HDPE), recycled high-density polyethylene (rHDPE-I and rHDPE-II), low-density polyethylene (LDPE), polypropylene (PP), recycled polypropylene (rPP), polystyrene (PS), and recycled polystyrene (rPS). The modulus of rupture (MOR) and modulus of elasticity (MOE) of all WPCs decreased with increasing exposure time of weathering. Of these, the rHDPE-II-based composite exhibited the highest MOR and MOE retention ratios after 2000 h of accelerated ultraviolet (UV) weathering, while the PS-based WPC had the lowest values. In addition, the carbonyl index difference (CID) of various WPCs increased significantly as a function of exposure time. Among them, the PS-based WPCs exhibited the most severe degradation due to photo-oxidation on the surface, while the degradation of PE-based WPCs was the mildest. These results are consistent with the change in the surface cracking and flexural properties of the composites. The PS-based WPCs also exhibited higher moisture diffusion coefficients. The mechanical behavior of WPCs after weathering is influenced by a combination of factors, such as surface oxidation, morphology changes, and moisture absorption.
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    Electronic ISSN: 1437-434X
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 7
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    Three-dimensional elastic-plastic damage constitutive model of wood (2020)
    De Gruyter
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    Publication Date: 2020-10-30
    Description: A 3D combined elastic-plastic damage constitutive model for wood is proposed within the theoretical framework of classical plasticity and continuum damage mechanics (CDM). The model is able to describe the various behavior of wood under loading, including the orthotropic elasticity, strengths inequality under tension and compression in each orthotropic direction, ductile softening under longitudinal compression, brittle failure under transverse tension, and parallel shearing, densification hardening under transverse compression. Hoffman criterion and a set of eight separate failure criteria were used to define wood yielding and damage initiation, respectively. Isotropic hardening was assumed after yielding and defined by an exponential type function. The constitutive model was implicitly discretized using backward Euler method, solved through the return mapping algorithm and implemented into ABAQUS through the user-defined material subroutine (UMAT). The proposed model was firstly verified by material property tests considering different stress states: monotonic and repeated tension and compression (in both parallel and perpendicular-to-grain directions), parallel-to-grain shearing, and the interactions between perpendicular-to-grain compression/tension and parallel-to-grain shearing, etc. Mechanical behavior of typical structural elements was further simulated to validate the proposed constitutive model.
    Print ISSN: 0018-3830
    Electronic ISSN: 1437-434X
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 8
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    Superhydrophobic wood surface fabricated by Cu2O nano-particles and stearic acid: its acid/alkali and wear resistance (2021)
    De Gruyter
    Details
    Publication Date: 2021-04-20
    Description: Reducing the hydrophilic nature of wood could enhance dimensional stability and improve life cycle performance. Masson pine and pecan wood were modified to create superhydrophobic, self-cleaning functions by spray-coating with Cu2O nano-particles (Cu2O NPs)/phenol formaldehyde (PF) resin mixed solution followed by immersion in a stearic acid ethanol solution. Two types of Cu2O NPs, derived from different concentrations of copper chloride (CuCl2) were evaluated for their ability to improve hydrophobicity of wood surface. A special petal-shaped structure on the edge of Cu2O NPs was found on modified pecan wood, and water contact angles (WCA) of both kind of modified wood reached around 155° and sliding angles (SA) less than 10°. Meanwhile, low liquid permeability and excellent repellency to aqueous solutions with pH = 1 to 13 were achieved. The critical WCA around 150° was also maintained on modified wood surfaces after being immersed in strong acid (pH = 2) and strong alkali (pH = 12) solutions for 12 h. Furthermore, remarkable mechanical durability was obtained after harsh abrading test, which could be attributed to the high bond strength from cured PF resin adhesive. Such highly waterproof, acid/alkali resistant and hard-wearing superhydrophobic surface must have potential to be widely applied in wood products industry.
    Print ISSN: 0018-3830
    Electronic ISSN: 1437-434X
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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