激光微造型凸轮副的摩擦磨损

采用UMT-2多功能摩擦磨损实验机,模拟内燃机凸轮/滚轮工况条件,考察了多种激光微造型形貌试样表面的摩擦磨损特性.实验结果发现,与未处理光滑表面相比,激光微造型试样表面的耐磨、抗擦伤性显著提高,其中,凹坑造型表面的摩擦因数显著下降,而凹槽表面的摩擦因数相对较大.这说明凹槽形貌会增大表面摩擦,而凹坑形貌具有一定的减摩效果.合理选择凹坑的深度及其面积占有率,并进行微形貌几何参数的优化组合,可达到最佳减摩效果.     

计算机控制激光扫描识别木段横断面图形的研究

针对原木在确定最佳旋切回转中心时,需要识别原木横断面外形几何尺寸而研究、设计了采用计算机控制的激光扫描检测系统,对原木进行动态测试、数据转换及图形显示。其方法是沿木段长度方向均匀设置５～７个激光传感器,当木段旋转时,起动激光传感器进行数据采集,每隔１５°扫描一个点,在各横断面圆周上共采集２４个点的数据,由计算机计算出每个角度上原木表面到中心轴的距离,并对这些数据通过坐标变换,在计算机上绘制出原木横断面几何图型。测试结果表明,该系统的综合测量精度达到±１ｍｍ。     

Thermal constants of wood during the heating process measured with the laser flash method

The thermal diffusivity, specific heat, and thermal conductivity of 13 species of wood were measured by means of the laser flash method to investigate the thermal properties of wood during the heating process. The temperature ranged from room temperature to 270°C in air or under vacuum. The thermal diffusivity varied little during the heating process up to 240°C. The values in air were larger than those under vacuum. There was a linear relation between the specific heat and the ambient temperature, and the specific heat under vacuum was larger than that in air at high temperature. The thermal conductivity increased with density and the ambient temperature. To discuss the effects of the atmospheric conditions on the thermal constants of wood, a theoretical model of thermal conductivity was proposed and its validity examined, where the wood was assumed to be a uniformly distributed material composed of cell walls and air.Part of this paper was presented at the 47th annual meeting of Japan Wood Research Society at Kochi, April 1997     

珠江河口及其附近水域银鲳生长与死亡参数估计

对珠江河口及其附近水域银鲳的生长与死亡参数进行估算,得von Bertalanffy生长方程的相关参数为：L∞=36．0cm,K=0．230,t0=-1．137;根据生长方程进一步计算得到自然死亡系数为0．586;20世纪9H0年代捕捞死亡系数为0．944,是20世纪80年代的近2倍;根据等渔获量曲线图分析,若在当前的捕捞规格(开捕叉长为12．0cm)下仍维持现行的捕捞强度(捕捞死亡系数),资源将受到破坏,而且不符合经济效益的要求。依据性成熟特征,开捕叉长最小应为15．0cm;综合考虑性成熟特征、当前可能的捕捞强度及经济效益,在提高产量而不破坏资源的前提下,建议珠江河口及附近水域银鲳的开捕叉长应由12．0cm增加至15．0cm。     

Agronomic and economic response to furrow diking tillage in irrigated and non-irrigated cotton (Gossypium hirsutum L.)

The Southeast U.S. receives an average of 1300 mm annual rainfall, however poor seasonal distribution of rainfall often limits production. Irrigation is used during the growing season to supplement rainfall to sustain profitable crop production. Increased water capture would improve water use efficiency and reduce irrigation requirements. Furrow diking has been proposed as a cost effective management practice that is designed to create a series of storage basins in the furrow between crop rows to catch and retain rainfall and irrigation water. Furrow diking has received much attention in arid and semi-arid regions with mixed results, yet has not been adapted for cotton production in the Southeast U.S. Our objectives were to evaluate the agronomic response and economic feasibility of producing cotton with and without furrow diking in conventional tillage over a range of irrigation rates including no irrigation. Studies were conducted at two research sites each year from 2005 to 2007. Irrigation scheduling was based on Irrigator Pro for Cotton software. The use of furrow diking in these studies periodically reduced water consumption and improved yield and net returns. In 2006 and 2007, when irrigation scheduling was based on soil water status, an average of 76 mm ha⁻¹ of irrigation water was saved by furrow diking, producing similar cotton yield and net returns. Furrow diking improved cotton yield an average of 171 kg ha⁻¹ and net return by $245 ha⁻¹ over multiple irrigation rates, in 1 of 3 years. We conclude that furrow diking has the capability to reduce irrigation requirements and the costs associated with irrigation when rainfall is periodic and drought is not severe.     

激光衍射法测定中国典型土壤颗粒分布的模型建立与验证

【目的】探讨快速测定中国典型土壤粒径分布的方法,提高土壤颗粒粒径分布测定的准确性。【方法】采用激光衍射法和传统吸管法（简称吸管法）对比研究中国15个省20种不同类型土壤的颗粒分布。【结果】激光法和吸管法测定的砂粒、粉粒和黏粒含量均呈显著的线性正相关。其中,激光法测定的黏粒和砂粒含量比吸管法测定的值平均低73.4 g•kg-1和59.6 g•kg-1,而粉粒含量平均较吸管法高131.2 g•kg-1。通过建立土壤粒径的累积分布曲线函数,建立了两种方法测定结果的转换模型。激光法测出的土壤颗粒粒径累积分布曲线函数为：y=1 000x/（b+x）（x代表粒径大小,y代表小于该粒径的颗粒所占的质量）。吸管法测得的相应粒径累积曲线函数为y=1 000x/（1.32b-1.01+x）。根据该函数得到的土壤颗粒粒径质量百分含量查质地分类三角图,即可判断土壤的质地类型。【结论】激光粒度仪检测结果通过转换模型修正,可以较好地反映土壤机械组成及土壤质地情况,可以快速准确地用于土壤颗粒组成的测定。     

静电喷粉颗粒沉积过程数值模拟与实验研究

以经典的圆柱绕流为例,通过对建立的颗粒群模型进行数值模拟和应用激光多普勒测速技术,从理论和实验上研究了静电喷粉的沉积特性,发现颗粒荷电对颗粒运动特性有明显的影响;在相同的荷质比时,颗粒荷电的影响随颗粒尺寸的增加而增加,影响的结果是增加了颗粒向农作物沉积的趋势。数值模拟和实验结果的对比表明,颗粒群模型合理地描述了荷电颗粒的运动特性。     

中国海洋捕捞学科发展的研究

21世纪是海洋的世纪。然而，由于资源的过度利用、环境污染和全球气候变化，海洋渔业资源不断衰退，海洋捕捞业的发展遇到了困境。传统上海洋渔业主要研究学科之一的海洋捕捞学科，如何适应形势的发展，拓展研究领域，开创海洋捕捞学科研究的新局面，这是海洋捕捞学科面临的一个问题。本文从海洋捕捞学科的发展现状，海洋捕捞学科研究涉及的领域，海洋捕捞学科研究的发展方向，更新充实知识等方面进行探讨，提出关于海洋捕捞学科发展的一些有建设性的看法。     

微生物菌种筛选技术方法研究进展

微生物菌种筛选能帮助人类全面认识地球环境中微生物群落的组成与功能,具有重要的科研价值、生态环境与社会经济效益.传统的菌种筛选方法过程繁琐、费时费力.近期新兴的现代菌种筛选方法因其操作简便快捷而成为当前的国际研究热点.本文综合国内外相关研究进展,重点介绍了传统菌种筛选方法和以基于光学镊子结合拉曼光谱的细胞分选技术、荧光活...