基于目标函数梯度向量的相邻方向共轭法

从共轭梯度法的基本思想出发,在前一寻优方向起点和终点的负梯度向量平移所决定的平面内确定共轭方向,并提出二维和三维优化问题的共轭方向计算公式。根据向量的几何关系和矢量加减运算的几何意义,推导由任一寻优方向起点和终点的梯度所确定的共轭方向。此方法可用于多维优化问题的求解。提出新算法的寻优步骤,并与众多经典共轭方向计算公式相比。该算法不仅具有理论严密性,而且寻优有效,具有二次终止性。     

建设“文化强国”给公共图书馆带来新的契机和挑战

基于党的十七届六中全会的有关精神,探讨了建设"文化强国"给公共图书馆带来的新的契机和挑战,指出图书馆应以高度文化自觉推动图书馆事业的发展与繁荣,阐述了通过建设文化强国应使公共图书馆惠及更多百姓的问题,从机制体制建设、服务内容创新、图书馆新文化等方面提出了图书馆推动社会主义文化大发展的思路。     

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。     

论涉油非法产业链的几个问题

涉油非法产业链成因隐蔽,发展势头猛、危害性大,冲击我国的石油安全形势,对其内涵、本质和发展态势需要加以研究,尤其需要创新视角,增强预见性.     

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.