纳米铜晶胞体积弹性模量变化规律的分子动力学模拟

用分子动力学的方法详细模拟纳米铜晶胞随温度与压强变化的规律,得到了铜晶胞体积弹性模量突变的敏感压强点.模拟结果表明:单晶铜的在压强小于75GPa时体积弹性模量随温度升高而降低,随压强增大而增大;在压强大于75GPa时,体积弹性模量随温度升高而增大,随压强增大而减小.     

油气弹簧力学特性仿真

提出了针对油气弹簧力学特性研究的一种力学模型,根据分段线性速度特性的计算方法,运用薄板力学和流体力学基础理论,分别对开阀点和最大开阀点处的缝隙宽度、阀片预变形量以及限位挡圈等阻尼阀结构参数进行了设计,并通过修正的理想气体状态方程对油气弹簧弹性力进行了推导。通过台架性能试验与建模的仿真数据比较,验证了设计方法的正确性,最后编程分析了不同缸体和特性参数对油气弹簧速度特性的影响规律,为研究减振装置的内特性提供了参考依据。     

Numerical simulation of deformations and forces of a floating fish cage collar in waves

The dynamic behavior of a fish cage collar in waves was investigated using a numerical model based on the finite element method. The floating collar and mooring system were divided into a series of line segments modeled by straight massless model segments with a node at each end. To verify the validity of the numerical model, research data from other authors were cited and compared with the simulated results, the comparison of results showed a good agreement. The numerical model was then applied to a dynamic simulation of a floating cage collar in waves to analyze its elastic deformation and mooring line tension. The simulated results indicated that the greatest deformation of the collar taken place in the position of the mooring line connection point when incident waves were in the same direction. An increase in the length of mooring line would help to decrease the mooring line tension of the collar. Furthermore, the effects of collar dimension, including collar circumference, pipe diameter in cross-section, and pipe thickness, on the dynamic behavior of the floating collar were discussed. The results of this study provided a better understanding of the dynamic behavior of the fish cage collar.     

Effect of drying on soil strength and corn emergence

Summary Laboratory studies were conducted to evaluate the effects of drying on soil strength and corn emergence (Zea mays L.). Corn was germinated in Billings silty clay under a bank of heat lamps which operated 9, 14, 19, or 24 h per day. Soil strength (modules of rupture), soil moisture content and emergence were measured daily.The relationship of soil strength to corn seedling emergence as influenced by the four light and heat durations and bare and mulched soil surfaces was determined. As soil strength increased emergence decreased until it ceased at soil strengths of about 80 kPa. Strength of this soil had a high negative correlation with soil water content and increased with time. Mulching decreased initial rate of drying, decreased crust strength, and improved corn emergence. The 14-hour light and heat treatment resulted in the highest corn emergence.Contribution from Colorado State Experiment Station, USDA-ARS Snake River Conservation Research Center, and USDA-ARS Fort Collins, respectively     

土壤侵蚀强度分级标准适用性初探

以水利部颁发的土壤分蚀强度分级拟定标准为基础,利用前人的研究成果,比较了不同植被覆盖度下的土壤侵蚀模数。结果表明,土壤侵蚀强度分级拟定标准与前人研究成果间均存在一定差距,说明该拟定标准的适用性值得进一步斟酌。     

内蒙古京津风沙源治理工程土壤风蚀控制效益研究

2000—2013年内蒙古风沙源治理工程区风蚀模数整体呈现下降趋势,风蚀程度有所减轻。5个亚治理区风蚀模数差异较大,其中浑善达克沙地治理区风蚀模数最高,其他依次为科尔沁沙地南缘治理区﹥乌兰察布高平原退化草原、荒漠草原治理区﹥锡林郭勒高平原-乌珠穆沁沙地盆地退化草原治理区﹥华北北部丘陵山地水源涵养治理区。工程区土壤风蚀量明显减少,2001—2013年累计净减少1 370 446.65×104t,其中,乌兰察布高平原退化草原、荒漠草原治理区累计净减少风蚀量最大;其次为锡林郭勒高平原-乌珠穆沁沙地盆地退化草原治理区。风力是造成内蒙古风沙源工程区土壤侵蚀的最主要营力。2000—2013年,工程区风蚀模数与风蚀量的逐步降低说明,京津风沙源治理工程实施十余年以来,通过实施各类治理措施,工程区土壤风蚀得到初步控制,工程区生态状况趋向好转,随着森林资源总量与质量的提高,水土流失状况进一步改善,沙化土地治理初见成效。     

梨树在自然水分亏缺下的生理反应

１９９４～１９９６年对梨树在自然水分亏缺和水分充足条件下的主要水分生理参数、气孔相对开张度（ＲＳＯＤ）、蒸腾速率（Ｔｒ）和光合速率（Ｐｎ）进行了比较研究。结果表明，梨树属于低水势耐旱类型，在自然水分亏缺下，其叶水势（ψｗ）显著降低，膨压（ψｐ）明显增高，而ＲＳＯＤ、Ｔｒ和Ｐｎ则无显著变化。梨树具有明显的渗透调节和一定的弹性调节作用，在中度水分亏缺下，其渗透调节能力△π１００或△π０分别为０．４４ＭＰａ和０．７７ＭＰａ，弹性调节能力△｜β｜和△εｍａｘ分别为２．７８和３．１９。另外，在自然水分亏缺下，梨树叶片还具有较强的保水能力，反映在基本无变化的膨压消失点的相对含水量（Ｒ０）、叶表面水分散失率（ＷＬ０）和明显高于ＣＫ的一定ψｗ下的相对含水量（Ｒ）值以及无灌溉园较高的εｍａｘ或｜β｜等方面。     

杨木纤维/PF树脂制取木陶瓷的研究

采用XRD、SEM等技术,对以杨木纤维/PF树脂为基材制备的木陶瓷进行了研究,结果表明:木陶瓷呈三维网状结构,保持了木材结构的部分特征,随着烧结温度的升高有可石墨化倾向;随着树脂含量的增加和烧结温度的升高,木陶瓷的抗压强度、弹性模量以及耐磨性能增强,表观密度和显气孔率升高,而体积电阻率迅速降低。     

Impact of alum on crust prevention and aggregation of calcareous soil: laboratory studies

Alum was applied at rates of 0.01, 0.02, 0.05, 0.1 and 0.2% by weight to a calcareous silty clay soil in an attempt to reduce soil crusting and improve soil aggregation. Results indicated that the modulus of rupture (MR) was reduced from 176 to 60 kPa with the addition of 0.2% alum. The mean weight diameter (MWD) was doubled when the application rate of alum increased from 0 to 0.2%. Alum apparently modified the soil physical environment by making the soil fluffy which in turn reduces its MR. Gypsum was formed by the reaction of alum with calcium carbonate in proportion to the amount of alum applied, increasing from 0.2% in the control soil to 1.1% with the highest rate of alum applied. This increase may have lead to the reduction in the MR and an increase in the MWD. This research showed that alum was effective in improving soil aggregate stability and decreasing aggregate rupture stress.     

Changes in sediment discharge in a sediment-rich region of the Yellow River from 1955 to 2010： implications for further soil erosion control

The well-documented decrease in the discharge of sediment into the Yellow River has attracted considerable attention in recent years. The present study analyzed the spatial and temporal variation of sediment yield based on data from 46 hydrological stations in the sediment-rich region of the Yellow River from 1955 to 2010. The results showed that since 1970 sediment yield in the region has clearly decreased at different rates in the 45 sub-areas controlled by hydrological stations. The decrease in sediment yield was closely related to the intensity and extent of soil erosion control measures and rainstorms that occurred in different periods and sub-areas. The average sediment delivery modulus(SDM) in the study area decreased from 7,767.4 t/(km2?a) in 1951–1969 to 980.5 t/(km2?a) in 2000–2010. Our study suggested that 65.5% of the study area with the SDM below 1,000 t/(km2?a) is still necessary to control soil deterioration caused by erosion, and soil erosion control measures should be further strengthened in the areas with the SDM above 1,000 t/(km2?a).