Microstructural evolution and mechanical properties of in situ TiB2/Al composites under high-intensity ultrasound

Microstructural evolution and mechanical properties of in situ TiB2/Al composites fabricated with exothermic reaction process under high-intensity ultrasound produced by the magnetostrictive transducer were investigated. In this method, the microstructure and grain refining performance of the TiB2/Al composites were characterized by optical morphology(OM), scanning electron microscopy(SEM), energy-dispersive spectrometer(EDS), and X-ray diffraction(XRD) analysis.Microstructural observations show a decreasing trend in the grain size of the composites due to the ultrasound and the content of TiB2 particles in the composites. Compared with the process without ultrasound, the morphology and agglomeration of TiB2 particles are improved by high-intensity ultrasound. Meanwhile, it is proposed that the formation of TiB2 particles occurs via the transformation from Ti Al3, and at the optimal amount of the reactants, the conversion efficiency of Ti Al3 into TiB2 almost reaches up to 100 %. Finally, the effects of high-intensity ultrasound and TiB2 particles on the mechanical properties of the TiB2/Al composites were also discussed.     

高层建筑结构中关于上部结构嵌固部位的选取和设计建议

文章阐述了高层建筑结构嵌固部位的基本概念,并以2010版新规范《抗规》及《高规》的要求及基本思想为出发点,介绍了在运用结构计算软件进行电算分析时,如何确定高层建筑上部结构嵌固部位的一些处理办法,尤其在地下室顶板作为上部结构嵌固部位的问题上进行深入探讨,最后对与之相关的主要技术措施及实际工程应用作出一些设计建议.     

防止离心开关损坏的两项措施

A186C、D型梳棉机上的离心开关,主要是用来控制主电机启动后,锡林、刺辊达到一定转速时,接通热继电器,保证主电机的正常运行,并接通传动道夫的双速电机电路,实现刺辊速度与双速电机的电气连锁。因而,离心开关是梳棉机重要零部件之一。离心开关主要由离心块、连杆、输入转轴、滑动轴、微动开关和传动件等组成。从使     

Functional properties of Lactobacillus strains isolated from kimchi

The objective of this study was to evaluate the functional properties of lactic acid bacteria (LAB) from kimchi, a traditional Korean fermented vegetable product generally consumed raw as a side-dish with practically every meal.Twelve mild acid producing facultatively heterofermentative Lactobacillus strains were selected for their potential as starter cultures for fermentation of kimchi, and evaluated for their functional properties. Eleven strains were identified as Lactobacillus sakei and one as Lactobacillus plantarum. The strains identified as L. sakei differed in some physiological features; of particular interest was the fact that 9 of these strains produced L(+) lactic acid from glucose in presence of acetate.All strains were able to survive gastrointestinal conditions simulating stomach and duodenum passage. In addition, they showed higher adherence to HT-29 cells than Lactobacillus rhamnosus GG, a commercial probiotic strain used worldwide. These strains also showed antimicrobial activity against a number of food-borne pathogens. Their ability to lower cholesterol was demonstrated by BSH (bile salt hydrolytic) activity, and cholesterol assimilation tests in vitro. The results suggest the probiotic potential of these strains for use in kimchi fermentation.     

Gas evolution characteristics of three kinds of no-bake resin-bonded sands for foundry in production

No-bake resin-bonded sand is commonly used in casting production.However,its air pollution is relatively serious,especially in the molding and pouring process.For this reason,it is necessary to study the gas evolution characteristics of no-bake resin-bonded sand from room temperature to high temperatures,and not only the amount of gaseous products,but also the composition of the gaseous products.No-bake furan resin-bonded sand(#1),phenolic urethane no-bake resin-bonded sand(#2),and alkaline phenolic no-bake resin-bonded sand(#3)are the three most common no-bake resin-bonded sands in casting.The gas evolution volume and rate of these three no-bake resin-bonded sands were studied.Thermogravimetry-mass spectrometer(TG-MS),headspace-gas chromatography/mass spectrometer(HS-GC/MS),and pyrolysis-gas chromatography/mass spectrometer(PY-GC/MS)were used to measure the composition of the gaseous products emitted from binders at room temperature and high temperatures.The differences between formaldehyde,heterocyclic aromatic compounds(HAC),monocyclic aromatic hydrocarbons(MAH),and polycyclic aromatic hydrocarbons(PAHs)gaseous products from the three types of no-bake resin-bonded sands during the molding and casting process were compared.From the perspective of environmental protection,alkaline phenolic no-bake resin-bonded sand and no-bake furan resin-bonded sand are better than phenolic urethane no-bake resin-bonded sand.     

微波辐射辅助柠檬酸络合法制备的Ho3+/Tm3+/Yb3+共掺杂CaWO4的白光性能（英文）

采用微波辐射辅助柠檬酸络合法制备Ho3+/Tm3+/Yb3+共掺杂CaWO4纳米晶升频转换荧光粉。将柠檬酸络合物前驱体在300~700°C热处理3 h。Ho3+/Tm3+/Yb3+共掺杂CaWO4C在400°C时开始结晶,在600°C时结晶完成。经600°C热处理的Ho3+/Tm3+/Yb3+共掺杂CaWO4主要呈球形,且形态均匀。在980 nm的激光激发下,Ho3+/Tm3+/Yb3+共掺杂CaWO4纳米晶出现肉眼可见的明亮的白色升频转换发射,这种现象来自Tm3+的475 nm蓝光发射以及Ho3+的543 nm绿光和651 nm红光发射。通过调整Tm3+和Ho3+的浓度可以控制Ho3+/Tm3+/Yb3+共掺杂CaWO4的CIE色度图从冷到暖白色之间变化。讨论了Tm3+和Ho3+浓度对升频转换光性能的影响以及与激光泵功率相关的影响机制。     

实时技术之影响

一、实时企业正在成为时下企业竞争的主流 商务速度对于一家企业而言,已经变得越来越重要。随便拜访一下你的客户就会发现,没有一个客户会抱怨你的反应时间太快,恰恰相反,所有的客户在投诉的时候都恨不得几秒钟内就得到响应。同样,一个企业的CEO可能不是要等到第2天,而是在几分钟内就要得到整个公司的财务状况。所以说商务速度对企业的经营而言,已经是关键的资源。随着企业用     

Development of Fiber Lasers and Their Applications

1 Introduction Fiber lasers have been developed for more than forty years since Snitzer!s proposal and the demonstration of Nd- doped fiber in 1961 [1]. But fiber lasers have not been attracted considerable attention until the develop- ment of the low- loss fiber fabrication technology and the high power semiconductor laser technology recently. Actually,it is the application and development of fiber communication technology that has promoted the rapid development of fiber laser. Fiber laser, …