In an effort to find suitable wood from natural forest to meet the demand for veneer products, the yield and tensile strength of veneers produced from Brachystegia nigerica were investigated. Two trees of B. nigerica ...In an effort to find suitable wood from natural forest to meet the demand for veneer products, the yield and tensile strength of veneers produced from Brachystegia nigerica were investigated. Two trees of B. nigerica were separately selected from 10 different natural forest zones while two logs were obtained from each tree. The logs were debarked and steamed in a vat prior to rotary peeling and slicing for veneer production. The optimum steam temperature was determined by considering different temperatures： 50℃, 60℃, 70℃, 80℃ and 90℃ for 24 h. Thereafter, optimum steam time was determined at the optimum temperature by considering durations of 24, 48, 72 and 96 h. The average taper of 0.75 mm per 1.0 m length was recorded for B. nigerica, indicating that the logs were reasonably cylindrical; thereby its logs are good for the production of veneer. The yield ranged from 44% to 61% with an average of 52% of the log input. The tensile strength of the veneer was tested perpendicular to grain and both peeled and sliced veneers had the highest tensile strength between 70℃ and 90℃, suggesting that softening of wood polymers, especially lignin, is between 70℃ and 90℃. The optimum temperature and time for veneer production are 70℃ and 48 h, respectively. Commercial production of veneer from B. nigerica is feasible based on the yield and mechanical properties of the obtained veneer, thereby encouraging the expansion of the scope of its utilization.展开更多
Theory and concepts of boundary layer mass transfer is applied to correlate experimental data on extraction of essential oils from vegetable leaves and stems, using steam. From these theory, concepts and experimental ...Theory and concepts of boundary layer mass transfer is applied to correlate experimental data on extraction of essential oils from vegetable leaves and stems, using steam. From these theory, concepts and experimental data with seven systems, two correlations are developed to predict the Sherwood number and mass transfer coefficient as function of Reynolds and Schmidt numbers. From these equations, the molar flux, the amount of solute extracted, and the yield of extraction is predicted. A steam of higher temperature normally improves the mass transfer and the yield. A method to estimate the enhancement for temperature increase is proposed. The correlations developed are applied to a case with industrial size that was no part of the data for correlation generation. Theory may be applied for industrial applications.展开更多
目的:研究活血丹风干前后挥发油的化学成分,比较两者之间的异同。方法:采用水蒸气蒸馏法提取自然风干处理前后活血丹的挥发油,计算挥发油含油率并进行比较。利用GC-MS分析其化学组分,峰面积归一法比较各组分间的相对含量。色谱条件:采...目的:研究活血丹风干前后挥发油的化学成分,比较两者之间的异同。方法:采用水蒸气蒸馏法提取自然风干处理前后活血丹的挥发油,计算挥发油含油率并进行比较。利用GC-MS分析其化学组分,峰面积归一法比较各组分间的相对含量。色谱条件:采用毛细管柱(30 m×0.25 mm×0.25μm),柱温为程序升温(起始柱温60℃,保持2 min,以10℃·min^(-1)升温速率升至230℃,保持1 min),载气为高纯氦气,柱流速为1.0 m L·min^(-1),进样量1.0μL,挥发油用乙醚稀释100倍,不分流;质谱条件:EI离子源,电子能量70 e V,扫描范围33~350 amu,四极杆温度和离子源温度分别为150℃和230℃。结果:自然风干前后活血丹挥发油平均含量分别为0.15%和0.01%;分别检出32个和27个色谱峰,鉴定了其中的23个和18个化合物,各占挥发油总量的91.8%和90.2%。主要成分包括柠檬烯、薄荷酮、胡薄荷酮、γ-榄香烯、石竹烯等。结论:经自然风干处理后,活血丹的含油率下降,自然风干处理前后的活血丹挥发油化学成分基本一致,但各主要成分含量存在明显差异。展开更多
文摘In an effort to find suitable wood from natural forest to meet the demand for veneer products, the yield and tensile strength of veneers produced from Brachystegia nigerica were investigated. Two trees of B. nigerica were separately selected from 10 different natural forest zones while two logs were obtained from each tree. The logs were debarked and steamed in a vat prior to rotary peeling and slicing for veneer production. The optimum steam temperature was determined by considering different temperatures： 50℃, 60℃, 70℃, 80℃ and 90℃ for 24 h. Thereafter, optimum steam time was determined at the optimum temperature by considering durations of 24, 48, 72 and 96 h. The average taper of 0.75 mm per 1.0 m length was recorded for B. nigerica, indicating that the logs were reasonably cylindrical; thereby its logs are good for the production of veneer. The yield ranged from 44% to 61% with an average of 52% of the log input. The tensile strength of the veneer was tested perpendicular to grain and both peeled and sliced veneers had the highest tensile strength between 70℃ and 90℃, suggesting that softening of wood polymers, especially lignin, is between 70℃ and 90℃. The optimum temperature and time for veneer production are 70℃ and 48 h, respectively. Commercial production of veneer from B. nigerica is feasible based on the yield and mechanical properties of the obtained veneer, thereby encouraging the expansion of the scope of its utilization.
文摘Theory and concepts of boundary layer mass transfer is applied to correlate experimental data on extraction of essential oils from vegetable leaves and stems, using steam. From these theory, concepts and experimental data with seven systems, two correlations are developed to predict the Sherwood number and mass transfer coefficient as function of Reynolds and Schmidt numbers. From these equations, the molar flux, the amount of solute extracted, and the yield of extraction is predicted. A steam of higher temperature normally improves the mass transfer and the yield. A method to estimate the enhancement for temperature increase is proposed. The correlations developed are applied to a case with industrial size that was no part of the data for correlation generation. Theory may be applied for industrial applications.
文摘目的:研究活血丹风干前后挥发油的化学成分,比较两者之间的异同。方法:采用水蒸气蒸馏法提取自然风干处理前后活血丹的挥发油,计算挥发油含油率并进行比较。利用GC-MS分析其化学组分,峰面积归一法比较各组分间的相对含量。色谱条件:采用毛细管柱(30 m×0.25 mm×0.25μm),柱温为程序升温(起始柱温60℃,保持2 min,以10℃·min^(-1)升温速率升至230℃,保持1 min),载气为高纯氦气,柱流速为1.0 m L·min^(-1),进样量1.0μL,挥发油用乙醚稀释100倍,不分流;质谱条件:EI离子源,电子能量70 e V,扫描范围33~350 amu,四极杆温度和离子源温度分别为150℃和230℃。结果:自然风干前后活血丹挥发油平均含量分别为0.15%和0.01%;分别检出32个和27个色谱峰,鉴定了其中的23个和18个化合物,各占挥发油总量的91.8%和90.2%。主要成分包括柠檬烯、薄荷酮、胡薄荷酮、γ-榄香烯、石竹烯等。结论:经自然风干处理后,活血丹的含油率下降,自然风干处理前后的活血丹挥发油化学成分基本一致,但各主要成分含量存在明显差异。
