点到平面距离公式的一种新证法

该文根据球面上一点切平面的方程和平移变换,对空间任一点P(x0,y0,z0),分P点为坐标原点和P点不是坐标原点两种情形,给出了到平面π:Ax By Cz D=0的距离公式d=|Ax0 By0 Cz0 D|/√A2 B2 C2 的一种新证法.     

一类非光滑非凸分式半无限规划的最优性

在一致Fb-凸函数，一致Fb-伪凸和一致Fb-拟凸等广义凸性函数的基础上，研究了一类分式半无限规划问题，得到了涉及这些广义凸性函数的一类非光滑分式半无限规划的一些最优条件。     

Experimental investigation on the detachable thermosiphon for conduction-cooled superconducting magnets

A detachable thermosiphon, as a transient thermal switch for conduction-cooled superconducting magnet, is designed, fabricated and tested. A thermosiphon between the first and second stages of a cryocooler can reduce the cool-down time of a conduction-cooled superconducting magnet by using the large cooling capacity of the first stage. The thermosiphon is a very efficient heat transfer device until all the working fluid in it freezes (off-state). After the working fluid freezes and the second stage temperature becomes lower than that of the first stage, however, the thermosiphon then becomes a conduction heat leak path between two stages of the cryocooler. Considering a very small cooling capacity of the second stage of the cryocooler around 4.2 K, the conduction heat loss is not negligible. Therefore, a detachable thermosiphon, made of a metal bellows, is considered to be able to eliminate such a conduction heat leak. The mock-up magnet is cooled down with the thermosiphon and the thermodynamic states of the thermosiphon and the mock-up magnet are precisely examined during the whole cool-down process. At off-state, the thermosiphon is detached mechanically from the magnet. In this way, the conduction heat leak path through the thermosiphon wall is completely eliminated. This paper describes the detailed transient operation of the detachable thermosiphon using nitrogen as the working fluid.     

论梁启超政治功能小说观

梁启超发起“小说界革命”，将小说直接承载政治使命，并提出“小说为文学之最上乘”的口号，客观上消融了一直以来存在于人们脑海的“小说为小道”的观念痼疾。小说也因此成为当时最受欢迎的文学样式。“小说界革命”对小说地位的提升与当时特定的社会环境及梁启超本人的社会地位是密不可分的。     

电子设备的建模研究

本文首先介绍了开关电源的基本工作原理和电路构成,在此基础上,通过试验研究,建立了计算机和电视机等电子设备的静态负荷模型。所得结论,为电力系统稳定分析计算提供了依据。     

Symbol error rate of selection amplify-and-forward relay systems

Cooperative diversity schemes significantly improve the performance of wireless networks by transmitting the same information through several nodes. The amplify-and-forward (AF) relaying method is one of the most attractive cooperative diversity schemes due to its low complexity. Selection AF relaying has recently been proven to achieve the same diversity order as and lower outage probability than all-participate relays. In this letter, we present an asymptotic analysis of the symbol error rates of a selection AF network, and compare it with the conventional all-participate scheme     

Modeling and simulation for a drop-impact analysis of multi-layered printed circuit boards

Multi-layered printed circuit boards (PCBs) contain a multi-layered structure that is suitable for high-speed and high-frequency applications. Hence, they are used extensively in electronic packaging assemblies for high-density applications. However, numerous composite parts and complex material properties of multi-layer PCBs complicate the reliability simulation of PCB model. This paper deals with a finite element analysis intended to describe numerically the behavior of multi-layered multi-materials PCB model (combination of metallic and composite plies) in the drop-impact performance. Through the comparison of physical drop test results, the fully multi-layered model illustrates higher accuracy if compared with that of the traditional simplified isotropic model and orthotropic model. The effects of material properties for the multi-layer PCB under drop-impact shock have also been investigated.     

Structural reliability assessment of multi-stack package (MSP) under high temperature storage (HTS) testing condition

Wire ball open failure at the interface of the gold wire and bonding pad of a multi-stack package (MSP) under high temperature storage (HTS) condition of 150 °C is studied. Failure analysis using FIB-SEM was conducted by in-plane moiré interferometry and FEA to clarify the failure mechanism. The ball open failure due to Kirkendall void that results from metal diffusion at high temperature was accelerated by the tensile stress imposed at the gold wire. The tensile stress developed at the gold wire when packages showing different warpage behaviours were stacked. Mechanical interaction between top and bottom packages caused unstable warpage, readily twisted and saddled. The wire came in contact with the photo-sensitive solder resist (PSR) dam because of the unstable warpage and this contact resulted in tensile stress at the gold wires. Solder flux residues reacted with the encapsulant, and as a result, the encapsulant of the top package adhered to the chip of the bottom package, and this adherence created additional tensile stress at the gold wires. To reduce the tensile stress at the wires, the PSR dam was removed, loop shape was altered from 45° to 90°, water soluble flux was applied, and cleaning process was added. HTS reliability was significantly improved and guaranteed after reducing the tensile stress at the wires.     

基于PLC的配料计量装置的设计

冶金生产中，各种原料之间的配比精度对生产过程的稳定和产品的质量有重要的影响。目前使用的配料系统计量精度低，瞬时物料流量波动大，系统复杂。本文介绍的计量装置的计量过程是对料斗内物料的减少量进行计量，以减重秤为主，配料精度达到0．5％级。     

攀钢1450mm热连轧机层流冷却控制系统的开发及应用

阐述了攀钢1 450 mm热连轧机层流冷却控制新系统的开发与应用。该系统采用α机过程控制系统,通过预设定、在线前馈和自适应三大功能,对层流冷却模式、冷却速率和最终卷取温度进行控制,卷取温度控制精度较原系统有较大提高,±20℃的命中率由原来的88.6%提高到现在的96.4%。