Mechanical phenomena of a new-type anisotropic conductive film adhering to the outer lead bonding

In this study the adhesive strength and swelling effect of a new-type anisotropic conductive film (ACF) adhering to the outer lead bonding (OLB) are investigated by experiments. The new-type ACF offers lower bonding temperature and less curing time than the conventional-type ACF in manufacturing processes. For further investigating the mechanical behaviors of this new-type ACF, the finite element analysis is used to assess the states of both adhesion and pressured conductive particle in detail. It can be found that the delamination occurs on the interface between ACF and glass substrate and it can cause the distribution of indium tin oxides (ITOs) pattern on the glass substrate which would affect the growing path of delamination in particular. Then the range of the temperature cycling between −40 °C and 125 °C is used to estimate the elastic-plastic behaviors of Au-coating conductive particles at different positions.     

浅析钢铁企业发展循环经济的措施

介绍了循环经济的概念及发展模式,简述了我国钢铁行业的现状,对钢铁企业如何实现循环经济进行了分析,提出了解决途径。     

Damage predictions in a chip resistor solder joint on flexible circuit board

Flexible circuit boards are being widely used in the electronic packages. Solders are often used to assemble chip resistors and other components on them. In practice, solder alloys work in high homologous temperatures and experience cyclic temperature loadings. As a result, damage may accumulate in solder materials quickly and this will eventually lead to the failure of the solder joints. In this work, computer modelling technique has been used to predict such damage accumulations in chip resistor solder joints under a range of thermal cycling conditions. It has been documented that the higher and the lower dwell temperatures of a thermal cycle dominate the damages in solder joints. Both the ramp time and the cycle duration have strong influence on the damage accumulation. In general, faster ramp time and longer cycle duration cause more damages. The types of materials used to produce flexible circuit board have also significant impact on the damage accumulation. Polyimide (PI), Polyethylene Naphthalate (PEN) and Liquid Crystal Polymer (LCP) based flexible circuit boards have been compared for their effect on damage in solder joints and the results show that the highest damage could be found in the chip resistor solder joint on the PI-based flexible circuit boards and least damage could be found for the LCP based flexible circuit boards. The results also show that the thicknesses of the constituent layers of different materials in flexible circuit boards are linearly proportional to the damage accumulation in solder joints.     

Characteristics and performance of membrane electrode assemblies with operating conditions in polymer electrolyte membrane fuel cell

The degradation behavior of a membrane-electrode assembly (MEA) was investigated in accelerated degradation tests under constant voltage (0.8 V and 0.7 V) and load cycling (from open circuit voltage to 0.35 V) conditions. Changes in the structural and electrochemical characteristics of MEA after the durability tests give information as to the degradation mechanism of MEAs. The results of cyclic voltammogram and postmortem analysis by X-ray diffraction and high resolution-transmission electron microscopy indicate that the cathode catalyst layers of the MEAs showed no extreme degradation under constant voltage mode, whereas MEAs under repetition of load cycling mode showed very severe degradation after 280 h. However, the single cell performance of the MEA under repetition of load cycling mode was higher than under constant voltage mode. In addition, although the Pt band in the membrane of the MEA under repetition of load cycling mode was observed by field emission scanning electron microscopy, it did not affect the ohmic resistance.     

Design of a two‐step pulsed pressure‐swing adsorption‐based oxygen concentrator

A two‐step pulsed pressure‐swing adsorption (PPSA) process has been modeled to assess the extent to which an oxygen concentrator might be miniaturized for medical applications. The process consists of a single bed of packed adsorbent particles that is alternately pressurized and depressurized at the feed end. An enriched oxygen product is withdrawn at ambient pressure from the product end when the bed is pressurized at the feed end. The product end remains closed during depressurization. The model development addresses the manner in which axial dispersion enters into the describing equations and the formulation of proper boundary conditions, both of which have not been handled rigorously in some prior modeling studies. The describing equations are solved using COMSOL® Multiphysics software. The effect on the performance of the adsorption time, desorption time, bed length, particle diameter, and imposed pressure drop across the bed have been investigated. An interesting novel result is that for a chosen particle size, bed length, and applied pressure drop, there is an optimum combination of adsorption and desorption times that maximizes the product purity. The results suggest that there are operating windows for both 5A and partially Ag‐exchanged Li‐substituted 13X zeolite adsorbents wherein the product oxygen purity is greater than 90%. At a given product flow rate within this operating window, the extent of miniaturization is limited by the (maximum) cycling frequency that is practically achievable. Sizing of an oxygen concentrator for personal medical applications is also discussed. A principal conclusion is that a compact oxygen concentrator capable of producing a highly oxygen‐enriched product is possible using commercially available adsorbents and implementable operating conditions. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

钻孔灌注桩泥浆循环处理方法

结合钻孔灌注桩工程施工实例,从技术、经济、环保等方面比较了泥浆外运处理方案和场内泥浆循环处理方案,指出泥浆循环处理方案节约了钻孔用水,泥浆处理费用和土地资源,具有很好的经济效益和社会效益。     

A prospective cohort study on minor accidents involving commuter cyclists in Belgium

The purpose of this study is to gain insight into bicycle accidents. Bicycle accident data and weekly exposure data were prospectively collected for one year to calculate the incidence rate (IR) of bicycle accidents. An accident was included if it occurred during utilitarian cycling, resulting in an acute injury with corporal damage. If an accident occurred, a detailed questionnaire was filled out to collect detailed information about its circumstances and consequences.     

Numerical evaluation of thermal cycling reliability of high performance flip‐chip package assembly using submodeling analysis

Abstract

This paper applies the submodeling technique in analyzing thermal cycling reliability of high performance flip‐chip ball grid array package assemblies. The packages have one‐piece tunnel‐type heat spreaders with different lead widths, connected to chips using different thermal interface materials. The global model contains no solder bumps to simplify the analysis. The calculated displacement field of the global model is then interpolated on the boundary of the submodel that contains the critical solder bump. The submodel is solved using the prescribed displacement boundary conditions together with external thermal loads to evaluate thermomechanical reliability of the critical solder bump.     

干湿循环环境下膨胀土地区桩基设计

对苏丹膨胀土地区数个工程案例进行了调查分析,以常用的干作法钻孔灌注桩基础为例,分别采用理论计算与现场工程案例相结合的方式进行了论证,结果表明,干湿循环交替的膨胀土环境对单桩最终极限承载力影响非常大,并提出了经过实践检验的膨胀土地区桩基工程灾害防治措施。