美军倾转旋翼机的发展和事故分析

倾转旋翼机综合了固定翼飞机和直升机的优点,可以垂直起降并能以大速度前飞.倾转旋翼机起降只需要很小的场地,可以改善城市的交通,在军事方面也有很好的前景.在发展的过程中,倾转旋翼机从无到有,经历了关键技术和稳定性难题的阻碍.美军在倾转旋翼机的研究方面一直处于领先地位,文章简单回顾了美军发展的历程,并进行了事故分析,为避免类似事故的发生提供借鉴.     

多变量情形下的Newton—Leibniz公式

对单变量情形下的牛顿－莱布尼兹公式借助于定向体积化和外微分形式，给出了统一、简明的多变量情形下的Newton-Leibniz公式。     

Kinetic study on the direct nitridation of silicon powders diluted with α-Si3N4 at normal pressure

Silicon nitride (Si₃N₄) powders were prepared by the direct nitridation of silicon powders diluted with α-Si₃N₄ at normal pressure. Silicon powders of 2.2 μm in average diameter were used as the raw materials. The nitriding temperature was from 1623 to 1823 K, and the reaction time ranged from 0 to 20 min. The phase compositions and morphologies of the products were analyzed by X-ray diffraction and scanning electron microscopy, respectively. The effects of nitriding temperature and reaction time on the conversion rate of silicon were determined. Based on the shrinking core model as well as the relationship between the conversion rate of silicon and the reaction time at different temperatures, a simple model was derived to describe the reaction between silicon and nitrogen. The model revealed an asymptotic exponential trend of the silicon conversion rate with time. Three kinetic parameters of silicon nitridation at atmospheric pressure were calculated, including the pre-exponential factor (2.27 cm·s^?1) in the Arrhenius equation, activation energy (114 kJ·mol^?1), and effective diffusion coefficient (6.2×10^?8 cm²·s^?1). A formula was also derived to calculate the reaction rate constant.     

吕梁山隧道3#斜井及正洞通风技术总结

针对吕梁山隧道3#斜井及正洞的特点,采取分阶段通风的方法,取得良好的通风效果,以保证工程的顺利进行.     

A Novel Switching Architecture for IP Over WDM Networks

Integrating IP and WDM is an attractive direction for research.Many solutions have been presented but it is noted that the existing switching technologies still need more concern. Since optical packet switching is not practical yet, there are just two possible solutions left. One is wavelength routing(WR), which is circuit switching in essence and the other is newly proposed optical burst switching (OBS). In this paper, characteristics of WR and OBS are first described, then, compared in several aspects. It is notice that in many aspects, the wavelength routing and burst switching are complement. This stimulates us to propose a new switching architecture, which may be considered as “mixture” of WR and OBS. We beleve the network built on new switching structure can accommodate the requirements of practicability, flexibility, robustness, effciency and etc. simultaneously. However, many related problems still need to be further researched.     

铝（Ⅲ）—5′—硝基水杨基荧光酮—溴化十六烷基三甲铵体系的荧光反应及应用研究

基于铝（Ⅲ）5′－硝基水杨基荧光酮的荧光具有猝灭的特性，拟定了一种测定铝的新方法。该方法的激发波长为246nm，发射波长为552nm，线性范围为1.6-28ng/ml，检出限为1.6ng/ml。本方法灵敏度高、选择性好，用于多种茶叶中微量铝的测定，获得了满意的结果。     

诗坛上永恒的幽灵——语义格式塔现象浅论

古代诗歌中有一种人们屡见不鲜的现象，常常以为是写作技法，至多被认为是一种句法结构，从《诗经》始，这种回环结构就已存在，历代诗家自觉不自觉地运用着，心有灵犀地丰富着，使这种回环结构成为诗的一种基本结构。现代诗更是借鉴和延伸了这种结构。词语破碎处，万物皆存。     

化工制图教学初探

化工制图在与机械制图有着紧密联系的同时又具有明显的专业特征，通过分析这二的差异，掌握化工制图的特点，并采用适当的教学方法可收到较好的教学效果。     

A Case Study of Search Engine on World Wide Web for Chemical Fiber Engineering

Search engine is an effective approach to promote the service quality of the World Wide Web. On terms of the analysis of search engines at home and abroad, the developing principle of search engines is given according to the requirement of Web information for chemical fiber engineering. The implementation method for the communication and dynamic refreshment of information on home page of the search engines are elaborated by using programming technology of Active Server Page 3.0 (ASP3.0). The query of chemical fiber information and automatic linking of chemical fiber Web sites can be easily realized by the developed search engine under Internet environment according to users' requirement.     

超薄注塑充模中的次相剪切效应

为克服超薄注塑充模的困难,定义了主、次相剪切的概念,分析了超薄注塑剪切场.根据泊肃叶方程,通过狭缝流变实验,重点讨论了超薄注塑过程中次相剪切对表观黏度、表观剪应力的影响,分析了次相剪切与粘性升温、入口压力的关系,发现次相剪切能有效改善超薄注塑中的熔体充模.文中还提出了超薄导光板的表面微特征混排设计方法,使熔体在流动平面内形成次相剪切,有效提高了制件填充率,验证了次相剪切效应的理论正确性.