Experimental study of wear interaction between piston ring and piston groove in a radial piston hydraulic motor

The wear interaction between piston ring and piston groove in a radial piston hydraulic motor was studied in regard to mass loss and changes in form and surface roughness. A specially developed test rig that simulates the tilting movements of pistons at the end of strokes was used in the test. The results show that wear on the piston ring groove can be up to 10 times greater than the wear on the piston ring. For both interacting surfaces, the dominant wear mechanism was mild wear. The results from a factorial design show that the form of the piston groove significantly influences the amount of wear.     

发电公司报价决策行为的分析

在电力市场环境下,发电公司从传统的完成发电任务转变为报价竞标发电负荷以获得最大的利润,其目标和行为发生了本质的变化。文中利用博弈论中n人对策理论,对独自竞标和联盟竞标情况下发电公司的行为和市场状况进行了研究。算例表明,联盟未必获得更大的利润,产权不同是防止市场完全垄断的根本。     

基于光纤微弯的缠绕式管道形变传感器

利用多模光纤的微弯特性 ,提出并实现了一种新颖的光纤缠绕式管道形变传感器 ;也给出了它的基本实验原理 .研究表明多模光纤的微弯损耗对导管的变形响应灵敏 ,其灵敏度可达 3.5 d B/ με.并且实验与理论符合的很好     

HMAC􀀁MD5 算􀀂法的硬件实现

信息安全体系中的消息验证是一个非常重要的方面。采用以散列函数为基础的消息验证编码是其中的一种重要方法。现提出了硬件实现一种以MD5算法为基础的消息验证编码（HMAC－MD5）的电路结构。该电路结构通过对MD5核心运算模块的复用,缩小了电路规模,达到了较高的处理速度。用Verilog HDL描述电路结构,并且在FPGA上验证了该结构的正确性。     

电子乐谱的设计与实现

本文介绍了了电子乐谱的硬件系统设计和软件设计的总体框架,以及各部分的接口电源的设计。通过基于该硬件系统平台上开发出来的软件,电子乐谱实现了自动翻谱,作曲,选曲,自动搜索新曲等功能。     

Evidence that leptin contributes to intestinal cholesterol absorption in obese (ob/ob) mice and wild-type mice

In the present study, the effect of leptin on intestinal cholesterol absorption was investigated in C57 BL/6 OlaHsd Lep^ob/Lep^ob obese (ob/ob) mice and lean C57 BL/6 (wild-type) mice. Animals were treated either with or without recombinant leptin for 2 wk. Cholesterol absorption was measured by the constant isotope feeding method and indirectly by the ratio of campesterol to cholesterol in serum. In ob/ob mice, cholesterol absorption was significantly higher compared to wild-type mice [83.4±2.3% (SD) vs. 77.6±1.5%, P<0.01]. Treatment with leptin significantly reduced cholesterol absorption in both ob/ob and wild-type mice by 8.5 (P<0.001) and 5.2% (P<0.05), respectively. Serum concentrations of campesterol and the ratio of campesterol to cholesterol in ob/ob mice were significantly higher compared to wild-type mice (2.2±0.3 mg/dL vs. 1.2±0.3 mg/dL, P<0.001; and 36.8±2.8 μg/mg vs. 28.0±3.3 μg/mg, P<0.001). After treatment of ob/ob mice with leptin, concentrations of campesterol and its ratio to cholesterol were significantly lower (2.2±0.3 mg/dL vs. 1.0±0.2 μg/mg, P<0.001; and 36.8±2.8 μg/mg vs. 13.2±2.2 μg/mg, P<0.001, respectively). In wild-type mice, the ratio of campesterol to cholesterol in serum was also significantly lower after treatment with leptin (28.0±3.3 μg/mg vs. 22.6±5.0 μg/mg, P<0.05). A significant positive correlation (r=0.701, P<0.01) between cholesterol absorption and the ratio of campesterol to cholesterol, in serum was found. It is concluded that leptin contributes to intestinal cholesterol absorption in ob/ob mice and lean wild-type mice.