Evaluation of the effect of strength mismatch in undermatched joints on the static tensile strength of welded joints by considering microstructure

High-tensile strength 950 MPa steel, HT950, which is steel used in penstocks, was developed to provide two vital properties: fracture arrest to stop brittle fracture and high weldability. This steel has been already used for penstocks in some hydropower plants in Japan. To widely apply high-tensile strength steels in penstocks in the future, fewer restrictions against their welding conditions such as pre-heat and post-heat temperature controls are required. One proposed solution is to undermatch the strength of the filler metal to that of the base material. This allows less pre-heating, or no pre-heating at all, and the use of conventional rod and process management is easier. Previous studies have shown that there are softening conditions under which the strength of the joint can be considered as that of the base material. However, the shape and distribution of the soft region are assumed to be ideal. In this study, the method for calculating the change of the strength in heat-affected zone (HAZ) during the welding process is discussed. Then, the influence of the strength distribution of HAZ and welded zone to the strength of the joint is investigated by a wide plate test in both experiment and elastic–plastic analysis. Applicability of undermatched joints to penstock fabrication is considered by these discussions. As a result, it is concluded that the Vickers hardness distribution in the HAZ can be estimated by the method which is proposed in this study and the strength of the under-matched joints is high enough in both experiment and analysis in which the Vickers hardness distribution is considered. From these conclusions, the applicability of undermatched joints, of which the weld metal is the HT570 class, to penstock fabrication is conformed.     

不同热处理制度对T250钢性能的影响

在不同的固溶温度、时效温度和时效时间的条件下,时真空感佑行热处理,研究不同热处理制度对其性能的影响.结果显示:在750～975 ℃不同的固溶温度下,固溶温度的变化对T250钢性能的影响很小;在450～570 ℃不同的时效温度下,T250钢的抗拉强度、屈服强度、冲击韧性和断裂韧性受到时效温度的显著影响,时效温度的变化对T250钢其他性能指标影响不大;时效时间大于5 h后,延长时效时间对T250马氏体时效钢性能的影响很小,T250钢在时效时间5 h时具有最佳的力学性能.     

Optimization of process parameters for high-efficiency polymer photovoltaic devices based on P3HT:PCBM system

Here, we report the fabrication of high-efficiency poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C₆₁-butyric acid methyl ester (PCBM) blend photovoltaic device. Process parameters like solvent, solvent drying conditions, electron donor to acceptor ratio and cathodes structures are optimized in making the devices. For the first time, we used cosolvent systems to make active layer of P3HT:PCBM composite and G-PEDOT:PSS, made by mixing 6 wt% glycerol to PEDOT:PSS, is used as a buffer layer. Highest efficiency of 4.64% was obtained for the device made with 1:0.7 ratio of P3HT to PCBM, o-dichlorobenzene:chloroform cosolvent, newly developed slow process and G-PEDOT:PSS. Film morphology is evaluated by atomic force microscopy (AFM). Time-of-flight (TOF) and incident photon-to-current conversion efficiency (IPCE) measurements are also performed for the best device.     

基于CAN总线的电锅炉温度控制网络

在已有温度控制系统的前提下,首先选取SJA1000芯片作为CAN总线的控制器、82C250芯片作为CAN总线的收发器,来设计电锅炉温度控制网络,然后通过CAN—USB转换器与通用PC相连。形成形式上以通用PC机为上位机,独立锅炉温度控制系统为下位机的电锅炉温度控制网络。     

T250钢离子渗氮后的组织和性能

对固溶态的T250钢进行不同渗氮时间和渗氮温度的离子渗氮试验。采用金相分析、硬度试验、XRD测定了渗氮层的深度、硬度、显微组织和物相。试验表明,T250钢渗氮后表面硬度大于900 HV0.3,基体硬度在500 HV0.3左右。渗层中的扩散层与基体边界明显。T250钢的渗氮温度与时效温度相近,可以在渗氮过程中实现材料的时效强化。     

考马斯亮兰G-250法测定苹果浓缩汁生产中的蛋白含量

考马斯亮兰G-250法(Bradford法)是目前灵敏度最高的蛋白质测定法。将其用于检测果汁中的蛋白．研究发现，苹果汁中的几种主要成分，如；果糖、葡萄糖、蔗糖和苹果酸等不会对测定造成干扰，其最大吸收波长不变，标准曲线的线性较好，并对苹果浓缩汁生产中不同工序物料中的蛋白含量进行测定，测定结果的精密度较好，加标回收率在97．76％～103．20％之间。     

A Quasi 2D Model of a High Temperature Polymer Fuel Cell for the Interpretation of Impedance Spectra

Electrochemical impedance spectroscopy is a widely recognized tool for in situ diagnostics of polymer fuel cells. The main drawback of this measurement is that it includes several features, which are not directly related to physical phenomena and the interpretation is often difficult. In this work, a physical quasi 2D model is applied to experimental data of a high temperature proton exchange fuel cell based on polybenzimidazole doped with phosphoric acid. The quasi 2D approach is applied in order to decrease the computational cost of the model, without decreasing the prediction capability. The model is able to simulate polarization curves and impedance spectra and it is fitted on six polarization data and impedance spectra recorded in different conditions. The model is able to capture the main features of a typical spectrum of a polybenzimidazole based high temperature polymer fuel cell. A sensitivity analysis is also performed on the model parameters to show the effect of each physical parameter.     

Decision of mobile devices enabling high throughput and non‐high throughput medium access control of 802.11n based on the consideration of energy efficiency

To be compatible with the legacy 802.11, there are two major medium access control (MAC) behaviors, high throughput (HT) and non‐high throughput (non‐HT), in the 802.11n. In this paper, we analyze and compare the energy efficiencies of different MAC behaviors in 802.11n on the basis of the Bianchi model and our previous works to evaluate the performance of the different MAC behaviors regarding HT and non‐HT. Our studies try to provide the decision for the mobile stations to enable the HT of 802.11n or not based on the consideration of energy efficiency. Studies show that owing to the large power consumption in HT, it is not suitable for limited power devices to carry WWW traffics by multiple‐input multiple‐output transmission because of large overheads of physical layer in the HT mode. However, if large file transmissions by File Transfer Protocol are considered, the energy efficiency in HT MAC can be very high because of the large aggregated frame size. It is especially true when the number of active stations is large because of the decrease in idle listening time by using the techniques applied in HT MAC such as Aggregate MAC Protocol Data Unit and Block‐ACK. These characteristics in the HT mode can overwhelm the larger overheads of physical layer compared with that in the non‐HT mode when large files are needed to be uploaded. Copyright © 2012 John Wiley & Sons, Ltd.     

OVM250平行钢绞线拉索单根换索试验研究

本介绍了针对台湾省国道六号南投段第C608标埔里隧道及爱兰交流道工程脊背式斜拉桥（下面简称台湾C608斜拉桥工程）设计及施工要求，采用的一种0VM250平行钢绞线拉索钢绞线单根换索的新工法的试验研究，该工法与常规换索所不同的是：常规换索时是将需要更换的无粘结钢绞线整根（连同PE护套）替换掉，本工法在钢绞线更换过程中将无粘结钢绞线里的钢绞线抽出的同时，新的钢绞线也一同被带入原无粘结筋PE护套内，原无粘结筋的PE护套仍然保留，大大简化了钢绞线更换工艺。