It has been repeatedly observed that the mechanical properties of microtomed wood sections are significantly lower than those of samples of normal size, but few investigations have been conducted to deal with this top...It has been repeatedly observed that the mechanical properties of microtomed wood sections are significantly lower than those of samples of normal size, but few investigations have been conducted to deal with this topic, especially based on theoretical approaches. We measured the longitudinal MOE of Chinese fir on microtomed sections ranging in thickness from 70 to 200 μm and compared these with the values of samples of normal size. The results indicate that the MOE of microtomed wood sections increases with thickness from 70 to 200 μm, but is significantly less than that of normal samples. A size effect coefficient of 2.63 is inferred based on statistical data for samples of normal size and 200 μm thick microtomed sections. Finally, an explanation based on a complete shear restraint model of cell walls and a single fiber multi-ply model is proposed for the size effect on stiffness of microtomed wood sections.展开更多
Similar to transpiration,the formulation of interfacial solar evaporation has been designed to perform water treatment.The concept involves wood-based support(tree)with a graphene-based layer acting as leaves.To enhan...Similar to transpiration,the formulation of interfacial solar evaporation has been designed to perform water treatment.The concept involves wood-based support(tree)with a graphene-based layer acting as leaves.To enhance light absorption and solar-thermal conversion capacity,a novel holly-leaf graphene(HLG)layer with an individual hollowed-out structure was engineered.The formation mechanism of this HLG was shown to be linked to the strong capillarity forces in the polyporous wood.By creating biomimetic leaves made of graphene,the light-to-heat conversion performance can be improved,while exhibiting substantially lower thermal conductivity(0.074 W/(m K))than natural wood.Under solar irradiation,HLG/wood exhibits an outstanding evaporation rate of 1.96 kg/(m^(2)h),with an impressive ef-ficiency of 94.2%.A theoretical model of HLG/wood based on the thermal management capability was built to further confirm its structural superiority in facilitating photothermal conversion.Consequently,a bilayer evaporator based on HLG/wood has the potential to revolutionize water purification processes,including desalination of seawater,removal of heavy metal ions,and treatment of organic dye-contaminated wastewater.展开更多
It is very difficult to characterize the fracture surface of wood with traditional way because of its irregularity and complexity. This paper, inspired from slit island method (SIM) and mass fractal method, proposes a...It is very difficult to characterize the fracture surface of wood with traditional way because of its irregularity and complexity. This paper, inspired from slit island method (SIM) and mass fractal method, proposes a new method, by which the change of sectional area with spatial location in wood fractures can be determined, to quantify the character of fracture surfaces. The experiment is done by continuously microtoming a fractured sample embedded with paraffin at intervals of hundreds micron along the longitudinal axis from tip to end of fracture. The results indicate there exists a linear correlation between the area and the corresponding location in a double logarithm coordinate. The slope, here termed as section variation dimension (D-L), is located between 2.23 to 2.75 with the D-L of pressed zone being smaller than that of tensile zone for a wood fractured by static bending, and D-L can be used to describe quantitatively the complexity of fracture surface of wood.展开更多
This paper initially applied the non-destructive evaluation-computerized tomography and the fractal theory to research the feature of wood fracture. Pinus elliottii, Populus×canadensis cv. ‘I-214’ and Larix gme...This paper initially applied the non-destructive evaluation-computerized tomography and the fractal theory to research the feature of wood fracture. Pinus elliottii, Populus×canadensis cv. ‘I-214’ and Larix gmelinii were choosed as samples. The author established the logarithm-logarithm relationship between the section area of wood fracture and its location, then defined the slope-D_L regressed by the two factors above as the section variation fractal dimension of wood fracture. The results showed: the non-destructive evaluation-computerized tomography can effectively analysis the feature of wood fracture. All the samples exist an marked linear relationship between the section area of fracture and its location, D_L is a new effective parameter to quantitatively characterize the feature of wood fracture, the delta of -2 described the complexity of fracture surface of wood. Due to the anisotropy and variation of wood properties, D_L is the statistically fractal dimension. All the results are tested by the statistic software——SARS, there exists remarkable difference between the D_L from different species. The average fractal dimension of fracture surface of Pinus elliottii is 2.25, Populus×canadensis cv. ‘I-214’ is 2.46, Larix gmelinii is 2.65.展开更多
基金the National Natural Science Foundation of China (Grant No. 30730076 and 30400337) for financial support
文摘It has been repeatedly observed that the mechanical properties of microtomed wood sections are significantly lower than those of samples of normal size, but few investigations have been conducted to deal with this topic, especially based on theoretical approaches. We measured the longitudinal MOE of Chinese fir on microtomed sections ranging in thickness from 70 to 200 μm and compared these with the values of samples of normal size. The results indicate that the MOE of microtomed wood sections increases with thickness from 70 to 200 μm, but is significantly less than that of normal samples. A size effect coefficient of 2.63 is inferred based on statistical data for samples of normal size and 200 μm thick microtomed sections. Finally, an explanation based on a complete shear restraint model of cell walls and a single fiber multi-ply model is proposed for the size effect on stiffness of microtomed wood sections.
基金supported by the National Natural Science Foun-dation of China(Nos.32171709 and 32271791)the Forestry Science and Technology Innovation of Hunan Province(No.XLK202107-3)the Scientific Research Project of Hunan Education Department(No.21B0242).
文摘Similar to transpiration,the formulation of interfacial solar evaporation has been designed to perform water treatment.The concept involves wood-based support(tree)with a graphene-based layer acting as leaves.To enhance light absorption and solar-thermal conversion capacity,a novel holly-leaf graphene(HLG)layer with an individual hollowed-out structure was engineered.The formation mechanism of this HLG was shown to be linked to the strong capillarity forces in the polyporous wood.By creating biomimetic leaves made of graphene,the light-to-heat conversion performance can be improved,while exhibiting substantially lower thermal conductivity(0.074 W/(m K))than natural wood.Under solar irradiation,HLG/wood exhibits an outstanding evaporation rate of 1.96 kg/(m^(2)h),with an impressive ef-ficiency of 94.2%.A theoretical model of HLG/wood based on the thermal management capability was built to further confirm its structural superiority in facilitating photothermal conversion.Consequently,a bilayer evaporator based on HLG/wood has the potential to revolutionize water purification processes,including desalination of seawater,removal of heavy metal ions,and treatment of organic dye-contaminated wastewater.
文摘It is very difficult to characterize the fracture surface of wood with traditional way because of its irregularity and complexity. This paper, inspired from slit island method (SIM) and mass fractal method, proposes a new method, by which the change of sectional area with spatial location in wood fractures can be determined, to quantify the character of fracture surfaces. The experiment is done by continuously microtoming a fractured sample embedded with paraffin at intervals of hundreds micron along the longitudinal axis from tip to end of fracture. The results indicate there exists a linear correlation between the area and the corresponding location in a double logarithm coordinate. The slope, here termed as section variation dimension (D-L), is located between 2.23 to 2.75 with the D-L of pressed zone being smaller than that of tensile zone for a wood fractured by static bending, and D-L can be used to describe quantitatively the complexity of fracture surface of wood.
文摘This paper initially applied the non-destructive evaluation-computerized tomography and the fractal theory to research the feature of wood fracture. Pinus elliottii, Populus×canadensis cv. ‘I-214’ and Larix gmelinii were choosed as samples. The author established the logarithm-logarithm relationship between the section area of wood fracture and its location, then defined the slope-D_L regressed by the two factors above as the section variation fractal dimension of wood fracture. The results showed: the non-destructive evaluation-computerized tomography can effectively analysis the feature of wood fracture. All the samples exist an marked linear relationship between the section area of fracture and its location, D_L is a new effective parameter to quantitatively characterize the feature of wood fracture, the delta of -2 described the complexity of fracture surface of wood. Due to the anisotropy and variation of wood properties, D_L is the statistically fractal dimension. All the results are tested by the statistic software——SARS, there exists remarkable difference between the D_L from different species. The average fractal dimension of fracture surface of Pinus elliottii is 2.25, Populus×canadensis cv. ‘I-214’ is 2.46, Larix gmelinii is 2.65.
