浅谈高压变频调速变压器及高压变频系统结构

介绍了高压变频调速变压器及高压变频器系统的基本原理及结构,详细论述了系统各组成部分的功能,并进行了举例说明。     

基准信号的低相噪声长距离光纤传输设计

介绍了基准光传输设备的基本组成和原理,指出低相噪长距离光纤传输中的问题所在,并提供了解决问题的方法,即数模混合器件的选择及改进滤波器设计.     

Qualification of bumping processes: Experimental and numerical investigations on mechanical stress and failure modes induced by shear test

In the past few years, novel assembly schemes, such as Flip Chip, 3D assemblies, and advanced low-k/ultralow-k dielectric materials have been introduced in the semiconductor industry. Aiming to develop and grant maturity milestones, standardized procedures are used to assess the assembly reliability. Among them, bump shear test provides a quantitative measure of the bonding strength between the Bump, UBM and pad structure. In this paper, some investigations on the failure mechanism induced by shear test are proposed. At first, it is shown experimentally that, for similar structures, the failure mode depends on the shear tool standoff. More precisely, high height values promote the cratering mode (i.e. fracture in the interconnect layers) whereas low ones induce a ductile mode (i.e. fracture in the bulk Aluminum layer). A numerical model is carried out to provide a better understanding of the mechanisms. Finite element simulations highlight a strong variation of the peeling stress according to the shear height, whereas the shear stress component remains quite stable. Based on these experimental and numerical findings, distinct scenarii and criterion are proposed to explain the fails. This approach is consolidated by extending the comparisons with additional experimental results. At last, the preliminary results of a time dependent study (effect of the shear tool speed and a non linear copper law) are discussed. These first insights aim at giving additional input on the physics occurring during the test.The present work proposes a validated numerical basis to explain and forecast the failure mode preference during a bump shear test. This provides some clues for design guidelines, process integration and product developments.     

Shear and mode II fracture of PUR foams

Polyurethane (PUR) foam materials are widely used as cores in sandwich composites, for packing and cushioning. They are made of interconnected networks of solid struts and cell walls incorporating voids with entrapped gas. The main characteristics of foams are lightweight, high porosity, high crushability, and good energy absorption capacity. Fracture toughness in mixed mode loading is of particular interest because foam cracking weakens the structure’s capacity for carrying loads.Present paper assesses the shear elastic (shear modulus) and mechanical (shear strength) properties of polyurethane foams. Also, three different types of specimens were used to determine mode I and mode II fracture toughness. The shear modulus, shear strength and fracture toughness increases with increasing foam density. Also the effect of loading direction and loading speed is investigated. The authors propose a micromechanical model to estimate fracture toughness based on the tensile strength of the solid material and the topology of the cellular structure.     

影像设备OM测试法解读(能源之星2.0版)

美国能源之星对影像设备能效测试2.0版操作模式功率法(OM法)主要反应被测样品在完成准备状态、睡眠状态、低耗能状态或关闭状态的能耗情况。分析了OM法的各测试项目以及相应指标,归纳总结了该标准规范在实施中应注意的问题,对影像设备附加功能进行了详细说明。     

Sliding mode based fault detection,reconstruction and fault tolerant control scheme for motor systems

The fault-tolerant control problem belongs to the domain of complex control systems in which inter-control-disciplinary information and expertise are required. This paper proposes an improved faults detection, reconstruction and fault-tolerant control (FTC) scheme for motor systems (MS) with typical faults. For this purpose, a sliding mode controller (SMC) with an integral sliding surface is adopted. This controller can make the output of system to track the desired position reference signal in finite-time and obtain a better dynamic response and anti-disturbance performance. But this controller cannot deal directly with total system failures. However an appropriate combination of the adopted SMC and sliding mode observer (SMO), later it is designed to on-line detect and reconstruct the faults and also to give a sensorless control strategy which can achieve tolerance to a wide class of total additive failures. The closed-loop stability is proved, using the Lyapunov stability theory. Simulation results in healthy and faulty conditions confirm the reliability of the suggested framework.     

High-efficiency Silicon Solar Cells: A Review

Over the past few decades, crystalline silicon solar cells have been extensively studied due to their high efficiency, high reliability, and low cost. In addition, these types of cells lead the industry and account for more than half of the market. For the foreseeable future, Si will still be a critical material for photovoltaic devices in the solar cell industry. In this paper, we discuss key issues, cell concepts, and the status of recent high-efficiency crystalline silicon solar cells.     

Data collection mode effect on feeling thermometer questions: A comparison of face-to-face and Web surveys

Feeling thermometer questions are widely used in political science research to estimate people’s attitudes and feelings toward a political object, like a political figure or an organization. Given the popularity of the feeling thermometer question in population surveys, more work is needed to explore the measurement of this question type. This study examines the data collection mode effect on feeling thermometers. Using the 2012 American National Election Studies, we find that the measurement of feeling thermometers is not exactly comparable between face-to-face and Web surveys. Face-to-face respondents tend to provide warmer feelings, while Web respondents give relatively more reliable responses in comparison. In both survey modes, respondents are most likely to select the response options that are verbally labeled although the effect is more striking in face-to-face than Web survey. The item nonresponse between these two modes does not differ in a meaningful way. This study ends by discussing future research directions on feeling thermometer questions.     

冷轧平整机机前甩尾轧制工艺的开发与应用

本文介绍了柳钢冷轧板带厂1550 mm单机架平整机机前甩尾轧制的工艺。改进前轧制每卷钢卷生产效率低,钢卷成材率低,改进后生产效率、成材率明显提高,部分规格的钢卷能实现带尾剪切长度为零。     

机械工厂三坐标测量室的设计探讨

对三坐标测量机(CMM)的分类和结构形式进行分析,围绕三坐标测量室设计中的选址、起吊方式、暖通空调、地坪、隔振、照明等问题进行探讨.结合设计实践,重点针对待测工件的起吊运输方式,给出相应的解决方案,并分析了各种方案的优缺点.