Influence of Cyclic Strain-Hardening Exponent on Fatigue Ductility Exponent for a Sn-Ag-Cu Micro-Solder Joint

The fatigue ductility exponent in the Coffin–Manson law for a Sn-Ag-Cu micro-solder joint was investigated in terms of the cyclic strain-hardening property and the inelastic strain energy in fracture for isothermal fatigue. The fatigue ductility exponent was found to increase with temperature and holding time under strain at high temperature. This exponent is closely related to the cyclic strain-hardening exponent, which displays the opposite behavior in that it decreases with increasing temperature and with coarsening of intermetallic compound particles while holding under strain at high temperature. This result differs from the creep damage mechanism (grain boundary fracture), which is a primary reason for the significant reduction in fatigue life for all strain ranges for large-size specimens.     

日本寒地北海道的优质糯米育种（网络首发、推荐阅读）

北海道糯米一直以来由于硬化性低而不易变硬,所以适合做糯米小豆饭和日式点心等。但与东北以南的品牌糯米相比,其精米蛋白含量（蛋白质）高,精米白度和捣年糕口感等较差。近年来为了扩大需求,还要求培育用于切块年糕、成型年糕以及适合米制点心的捣年糕硬化性高的品种。因此,对早期开发新品种进行了世代促进栽培及药物培养等,为提高选拔效率,从初期世代就开始对糙米和精米的白度、蛋白质以及和硬化性相关的糊化特性等用仪器进行了分析,并用少量糯米实测了硬化性;从中期世代开始进行了糯米小豆饭和捣年糕的品尝试验等,在推进改善其农艺性状的同时促进了品质改良。其结果是：近年来培育的糯米品种颗粒很大,穗孕期和开花期两个障碍型耐冷性都很强,提高了生产稳定性。进而,培育年份上,越是新品种蛋白质越低,与蛋白质呈负相关关系的精米白度就越高,而糯米小豆饭和捣年糕的口感也提高了。另一方面,关于捣年糕的硬化性,不仅培育出了传统的硬化性低的品种,而且培育出了以黏性品种为母本的硬化性高的两个新品种。但与东北以南的品牌糯米相比,捣年糕的口感和硬化性还不高,还需要进一步改良。     

Automated segmentation of optic disc region on retinal fundus photographs: Comparison of contour modeling and pixel classification methods

The automatic determination of the optic disc area in retinal fundus images can be useful for calculation of the cup-to-disc (CD) ratio in the glaucoma screening. We compared three different methods that employed active contour model (ACM), fuzzy c-mean (FCM) clustering, and artificial neural network (ANN) for the segmentation of the optic disc regions. The results of these methods were evaluated using new databases that included the images captured by different camera systems. The average measures of overlap between the disc regions determined by an ophthalmologist and by using the ACM (0.88 and 0.87 for two test datasets) and ANN (0.88 and 0.89) methods were slightly higher than that by using FCM (0.86 and 0.86) method. These results on the unknown datasets were comparable with those of the resubstitution test; this indicates the generalizability of these methods. The differences in the vertical diameters, which are often used for CD ratio calculation, determined by the proposed methods and based on the ophthalmologist's outlines were even smaller than those in the case of the measure of overlap. The proposed methods can be useful for automatic determination of CD ratios.     

Blood flow velocity waveforms in the middle cerebral artery at rest and during exercise

Blood flow velocities in the middle cerebral artery (MCA) were measured under steady-state and incremental cycle exercises using a transcranial Doppler ultrasound velocimeter. The peak systolic velocity was found to rise markedly under exercise, while the end diastolic velocity tended to remain at the resting value. The relationship between peak systolic velocity and systolic blood pressure, and that between peak systolic velocity and heart rate were found to show a statistically significant correlation. The mean MCA blood velocity also showed a significant correlation with the mean arterial pressure and heart rate. The fluctuations of velocity and the resistance index were calculated in order to evaluate the hemodynamic load on the vessel wall; these also increased markedly under exercise. Such hemodynamic changes in activity might be important in understanding the genesis of vascular diseases, as well as the physiology of cerebral circulation.     

Network-supported TCP rate control for high-speed power line communications environments

High-speed power line communications (PLC) technology has great potential to serve as an infrastructure for home networking. To investigate the performance of end-to-end data flows over high definition (HD)-PLC, we have developed a new module on the NS-2 network simulator for HD-PLC that is driven by the particular patterns of the time-varying packet-error-rate as measured by experiments. To solve the problem on coexisting multiple TCP flows, a novel network-supported TCP rate control that appropriately modifies the advertized-window value in a TCP-ACK packet in response to the PLC network condition is presented and is shown to be effective through simulations.     

Use of chitosan for removal of bisphenol a from aqueous solutions through quinone oxidation by polyphenol oxidase

In this study, a combined use of biopolymer chitosan and oxidoreductase polyphenol oxidase (PPO) was applied to the removal of bisphenol A (BPA) as an endocrine disrupting chemical from aqueous solutions. The optimum conditions for the enzymatic quinone oxidation of BPA were determined to be pH 7.0 and 40°C. Quinone derivatives generated were chemisorbed on chitosan beads, and BPA was completely removed at 4–7 h. The removal time was shortened with an increase in the amount of dispersed chitosan beads or the PPO concentration. In addition, the initial velocity of quinone oxidation increased with an increase in the amount of chitosan beads. The use of chitosan in the form of porous beads was more effective than the use of chitosan in the form of solutions or powder. It was found that an important factor for this procedure was a high‐specific surface area of chitosan beads and heterogeneous reaction of quinone derivatives enzymatically generated with chitosan. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

均质箱梁在分布动载作用下考虑剪力滞效应的稳态解

动力响应计算是薄壁箱梁设计中需要考虑的重要问题之一。本文基于Hamilton原理,考虑薄壁截面翼缘的剪力滞效应,推出了均质箱梁在分布动载作用下的控制微分方程和边界条件,采用分离变量法求出了简支均质薄壁箱梁在均布简谐动载下的稳态解。通过数字算例,研究了不同频率动载作用下,结构的动挠度、动应力、剪力滞系数、挠度放大系数和应力放大系数在共振区和非共振区的变化情况,以及与简谐动载相位的关系,分析了剪力滞效应对薄壁箱梁动力响应的影响,为薄壁箱梁的动力设计与计算提供了依据。     

锥形超高层建筑脉动风荷载特性

采用同步测压技术,进行了具有不同锥率的超高层建筑刚性模型风洞试验,对该类建筑物的脉动风荷载特性进行了研究。结果表明：超高层建筑采用锥形轮廓后,延长了来流在建筑物侧风面漩涡脱落的卓越频率,横风向升力系数功率谱谱峰小幅下降,有利于缓解风荷载作用下建筑物横风向风荷载及其风致效应,这对横向风风致效应起控制性作用的超高层建筑十分重要。对比分析表明：随着建筑物锥率的增加,横风向升力系数归一化功率谱谱峰下降,功率谱带宽增大,升力系数根方差减小。但是,超高层建筑锥率的变化对顺风向阻力及扭转向扭矩影响较小。锥形超高层建筑的相关系数、相干函数的变化规律与普通棱柱形超高层建筑基本一致,但其升力以及升力与扭矩之间的相关性有所减弱,相干系数小幅增加。