A frequency-aware and energy-saving strategy based on DVFS for Spark

The Journal of Supercomputing - With the fast growth of big data applications, it has brought about a huge increase in the energy consumption for big data processing in Cloud data centers. In this...     

Mold-filling characteristics of AZ91 magnesium alloy in the low-pressure expendable pattern casting process

The magnesium (Mg) alloy low-pressure expendable pattern casting (EPC) process is a newly developed casting technique combining the advantages of both EPC and low-pressure casting. In this article, metal filling and the effect of the flow quantity of inert gas on the filling rate in the low-pressure EPC process are investigated. The results showed that the molten Mg alloy filled the mold cavity with a convex front laminar flow and the metal-filling rate increased significantly with increasing flow quantity when flow quantity was below a critical value. However, once the flow quantity exceeded a critical value, the filling rate increased slightly. The influence of the flow quantity of inert gas on melt-filling rate reveals that the mold fill is controlled by flow quantity for a lower filling rate, and, subsequently, controlled by the evaporation of polystyrene and the evaporation products for higher metal velocity. Meanwhile, the experimental results showed that the melt-filling rate significantly affected the flow profile, and the filling procedure for the Mg alloy in the low-pressure EPC process. A slower melt-filling rate could lead to misrun defects, whereas a higher filling rate results in folds, blisters, and porosity. The optimized filling rate with Mg alloy casting is 140 to 170 mm/s in low-pressure EPC.     

基于Visual Basic 开发机床主传动非常规变速系统的设计--重复转速的传动系统(实例之二)

本文介绍利用Visual Basic工具开发金属切削机床主传动非常规变速系统的设计总体结构，功能和方法，以重复转速的传动系统为例，重点介绍转速图的拟定过程，本系统具有界面美观，操作方便，易于理解的特点。     

火焰原子吸收光谱法测定高纯石英粉中痕量钙

系统地研究了用空气——乙炔火焰原子吸收光谱分析法测定高纯石英粉中钙的最佳条件，建立了14％的乙醇作为增感剂，在2％盐酸介质中，0．4％ LaCl3溶液作为释放剂，用塞曼火焰原子吸收法测定的可行性方案，探讨了共存元素对钙的干扰及其消除。方法操作简便快速，干扰少，方法相对标准偏差小于3％，适用于日常分析石英粉中的杂质。     

2003年上半年我国染料、有机颜料生产及进出口情况浅析（一）

20 0 2年我国染料及有机颜料生产和进出口数量达到历史最好水平 ,2 0 0 3年上半年虽然经受了SARS的影响 ,但我国染料及有机颜料工业仍然取得了稳定增长的成绩。上半年染料产量总计 19 5 9万t,同比增长 2 4 7%;颜料产量为 4 30万t,同比增长 2 1 6 9%。上半年出口增长幅度减缓 ,染料出口总量为 9 92万t,同比增长 3 1%;有机颜料出口为 4 2万t,同比增长 3 1%。进口基本稳定 ,上半年染料进口量为 3 2 5万t,同比增长 9 1%;有机颜料进口为1 6 9万t,同比增长为 11 5 %。总之 ,上半年主要经济指标完成情况良好 ,进出口数量和经济效益继续保持稳定增长。但染料和纺织品的生产与出口都遇到一定的困难 ,纺织品出口又直接影响染料的内销市场 ,由于内外市场的变化 ,使染料生产和进出口的增长幅度减缓。     

Morphologies-Controlled Synthesis and Optical Properties of Bismuth Tungstate Nanocrystals by a Low-Temperature Molten Salt Method

Well-crystallized bismuth tungstate (Bi₂WO₆) powders with different morphologies were successfully synthesized via a low-temperature molten salt method. The powders were characterized by X-ray diffraction, transmission electron microscopy, and UV-Vis, respectively. It was found that the variation of morphology of the obtained Bi₂WO₆ powder mainly depends on the different reaction temperatures and the weight ratio of LiNO₃–NaNO₃ salt to precursor. In addition, the UV-Visible absorption spectra showed that the synthesized powders had strong light absorption properties not only in the ultraviolet light but also in the visible light region.     

Zinc hydroxystannate and zinc stannate as flame‐retardant agents for flexible poly(vinyl chloride)

The flame‐retardant and smoke‐suppressant properties of inorganic tin compounds such as zinc hydroxystannate (ZHS) and zinc stannate (ZS) were investigated in a comparison with alumina trihydrate, magnesium hydroxide, and Sb₂O₃ through the limiting oxygen index test and smoke density test. The flame‐retardant mechanisms were studied through the char yield test, SEM, quantitative analysis, thermogravimetry and differential thermal analysis. The thermal degradation in air of flexible PVC treated with the above compounds was studied by thermal analysis from ambient temperature to 800°C. The results showed that tin compounds such as ZHS and ZS could be used as a highly effective flame retardant for flexible PVC, and it appears that the tin compound may exert its action in both the condensed and vapor phases, but mainly in condensed phases as a Lewis acid. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1469–1475, 2005     

离心制冷机组冷凝/蒸发系统的化学清洗

针对该厂离心制冷机组冷凝 /蒸发系统严重积垢危及设备安全运行这一现状 ,研究出了一种适宜的清洗方案并成功地应用于现场。为化学清洗技术如何有效地用于制冷行业特殊污垢的处理 ,提供了一个成功的范例     

卡尔曼滤波算法在MEMS热式风速风向传感器中的应用

针对MEMS热式风速风向传感器在实际使用过程中因噪声问题导致输出不稳定的现象,本文首次采用了卡尔曼(Kalman)滤波算法对本征白噪声进行滤波处理,从而优化传感器的输出性能.本文分别通过理论分析和仿真模拟证明了Kalman滤波算法的可行性.实验结果表明,通过调节相关参数,Kalman滤波算法在滤波效果、响应速度及误差上均优于传统的加权滑动均值滤波算法.除此之外,在消耗较少资源的前提下,Kalman滤波算法可以有效减少本征白噪声的干扰,且调节空间较大,可以适应不同的应用需求.