高维欧氏空间中正则曲线的微分中值定理

将拉格朗日中值定理和柯西中值定理分别推广到R^n中的正则曲线情形,结果表明平面曲线的某些几何性质在高维空间的曲线情形仍成立．     

正交试验法合成柠檬酸三丁酯

采用柠檬酸和正丁醇为原料合成柠檬酸三丁酯。通过正交试验考察了催化剂种类、醇酸摩尔比、反应时间及反应温度对酯化率的影响,从而确定了最佳合成工艺条件为:采用一水合硫酸氢钠为催化剂,醇酸摩尔比为4:1,反应时间为2.5h,反应温度为115℃,柠檬酸三丁酯的酯化率可达96.94%。     

Experimental investigation of an adjustable ejector for CO2 heat pump water heaters

An adjustable ejector expansion device for a CO2 heat pump water heater （HPWP） is proposed to improve the system performance. It has been designed to investigate experimentally the effects of the motive nozzle throat area of the ejector, entrained flow pressure, back pressure and primary flow pressure on the entrainment ratio. Experiments based on different motive nozzle throat areas were conducted and the results of the prototype ejector using CO2 as working fluid are presented. The results show that an adjustable ejector can achieve high performance and work well in a wide range of working conditions.     

Effect of CO2 enrichment on the glucosinolate contents under different nitrogen levels in bolting stem of Chinese kale (Brassica alboglabra L.)

The effects of CO₂ enrichment on the growth and glucosinolate (GS) concentrations in the bolting stem of Chinese kale (Brassica alboglabra L.) treated with three nitrogen (N) concentrations (5, 10, and 20 mmol/L) were investigated. Height, stem thickness, and dry weights of the total aerial parts, bolting stems, and roots, as well as the root to shoot ratio, significantly increased as CO₂ concentration was elevated from 350 to 800 μl/L at each N concentration. In the edible part of the bolting stem, 11 individual GSs were identified, including 7 aliphatic and 4 indolyl GSs. GS concentration was affected by the elevated CO₂ concentration, N concentration, and CO₂×N interaction. At 5 and 10 mmol N/L, the concentrations of aliphatic GSs and total GSs significantly increased, whereas those of indolyl GSs were not affected, by elevated atmospheric CO₂. However, at 20 mmol N/L, elevated CO₂ had no significant effects on the concentrations of total GSs and total indolyl GSs, but the concentrations of total aliphatic GSs significantly increased. Moreover, the bolting stem carbon (C) content increased, whereas the N and sulfur (S) contents decreased under elevated CO₂ concentration in the three N treatments, resulting in changes in the C/N and N/S ratios. Also the C/N ratio is not a reliable predictor of change of GS concentration, while the changes in N and S contents and the N/S ratio at the elevated CO₂ concentration may influence the GS concentration in Chinese kale bolting stems. The results demonstrate that high nitrogen supply is beneficial for the growth of Chinese kale, but not for the GS concentration in bolting stems, under elevated CO₂ condition. Project (No. 2007CB109305) supported by the National Basic Research Program (973) of China     

成人高校招生报名比率的实证分析

近年来,成人高校招生报名人数总体呈下降趋势,是否继续现行成人高校招生制度,以及如何完善成人高校招生制度成为高等教育战线比较关注的热点问题。本文选取影响成人高校招生报名人数的几个关键因素进行实证分析,以期明晰成人高校招生制度的改革方向,也尝试为高校招生改革提供一种新的研究路径。     

《情报理论与实践》1980-2007年发文的被引分析

通过对<情报理论与实践>1980-2007年发文的被引情况,分别从论文被引年代分布、频次分布、被引期刊分布、高频被引论文分布、高频作者分布和基金论文被引分布6个方面进行了统计分析,揭示了<情报理论与实践>研究的现状.     

充分利用实验室资源加强地质专业本科教学实践环节

本文以地质专业本科教学中实验室利用情况的现状为例,提出了存在的实验室利用率不高、实验室的整体规划和日常管理制度不完善等现象。通过剖析问题的原因所在,提出可通过拓宽实验室建设和维护经费来源、完善实验室管理体系、激励师生利用实验室进行教学科研活动等举措,提高实验室资源在地质专业本科生教学和科研活动中的利用率。     

中心极限定理应用举例

本文通过举例讨论了中心极限定理在参数区间估计及求数列极限中的应用.     

磁场中电子荷质比的测定

介绍了磁场中测定电子荷质比的方法,详细讨论了威尔尼特管法及磁聚焦方法的基本原理,并采用这两种方法对电子荷质比进行测定,最后分析了测量过程中时测量结果影响较大的因素.     

可分生成域扩张的生成元

设K为域, L= K(a1;…… ; an) 为K的可分生成的扩域, tr:deg:(L/K) = r。证明了存在有限多个非零n(r + 1) 元 多项式 , 使得对任意 ,只要某一个 ,令 就有 ,结论中多 项式的系数范围控制得足够好。