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21.
Local residence time,residence revolution,and residence volume distributions in twin‐screw extruders
Xian‐Ming Zhang Lian‐Fang Feng Sandrine Hoppe Guo‐Hua Hu 《Polymer Engineering and Science》2008,48(1):19-28
This work was aimed at studying the overall, partial, and local residence time distributions (RTD); overall, partial and local residence revolution distributions (RRD) and overall, partial and local residence volume distributions (RVD) in a co‐rotating twin screw extruder, on the one hand; and establishing the relationships among them, on the other hand. Emphasis was placed on the effects of the type and geometry of mixing elements (a gear block and various types of kneading elements differing in staggering angle) and process parameters on the RTD, RRD and RVD. The overall and partial RTD were directly measured in‐line during the extrusion process and the local ones were calculated by deconvolution based on a statistical theory. The local RTD allowed comparing the mixing performance of mixing elements. Also it was confirmed both experimentally and theoretically that specific throughput, defined as a ratio of throughput (Q) over screw speed (N), controlled all the above three types of residence distributions, be they local, partial or overall. The RRD and RVD do not provide more information on an extrusion process than the corresponding RTD. Rather they are different ways of representing the same phenomena. POLYM. ENG. SCI., 48:19–28, 2008. © 2007 Society of Plastics Engineers 相似文献
23.
Zhenghong Yang Yongjian Hu 《Automatic Control, IEEE Transactions on》2004,49(10):1783-1792
In this note, a generalized Bezoutian matrix with respect to a polynomial sequence of interpolatory type is introduced. The operator representation relative to a pair of dual bases and the generalized Barnett-type factorization formula are derived. An intertwining relation and a Bezoutian reduction to a block diagonal form by congruence via a generalized Vandermonde matrix are presented. Fujiwara-Hermite and Routh-Hurwitz criteria in terms of this generalized Bezout matrix are obtained. 相似文献
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Fei Hu Ankur Teredesai 《Pervasive Computing, IEEE》2007,6(1):88-91
Today, there's an urgent need for well-trained pervasive computing engineers and scientists. Pervasive computing has evolved into a critical field, influencing a broad range of industries from healthcare to manufacturing to defense. However, most computer engineering and computer science programs pay marginal attention, at best, to the field. In this issue, the authors of the Rochester Institute of Technology describes a set of courses on pervasive computing topics and a supporting laboratory designed for both computer engineering and computer science students 相似文献
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Electromigration reliability of interconnect under bidirectional current stress has been studied in a wide frequency range (mHz to 200 MHz). Experimental results show that the AC lifetime rises with the stress current frequency. The current density exponent and the activation energy of AC lifetime are found to be twice that of DC lifetime. Pure AC current stress failure at extremely high current density is believed to result from thermal migration of metal at hot/cold transition points 相似文献
29.
When melting processes are associated with an exothermic heat of mixing, unique coupled transport phenomena take place. In
this article, a mathematical model has been developed to simulate these unique coupled heat and mass transfer events. The
model was based on the control-volume finite difference approach and on an enthalpy method. In order to verify the mathematical
model, a low-temperature physical model was established consisting of ice and sulfuric acid solutions. In this physical model,
both temperature and velocity measurements were carried out. The model predictions were compared with experimental measurements,
and they were found to be in good agreement. The model was also applied to a high-temperature system, namely, the melting
of silicon metal in liquid high carbon iron. The predictions distinguished two periods present in the entire melting process.
In the first period, the silicon was heated up. The second period, i.e., free melting period, occurred in tandem with the exothermic reaction, and consequently, the melting process was greatly
accelerated. As was the case with the low-temperature physical model, as with the high-temperature system, good agreement
was obtained between the predicted results and the experimental measurements. 相似文献
30.
中国的三种非同步轨道卫星移动通信系统星座方案 总被引:6,自引:1,他引:5
本文介绍基于我国的三种非同步轨道卫星移动通信系统星座方案:低、中轨系统各有24和18颗星,轨道高度分别为1326和8035km,两系统各以5°和30°的仰角对我国的覆盖率为99.78%和99.96%;椭圆轨道系统12颗星,近、远地点分别为427和2906km,以7°和15°仰角对我国北纬20°以上地区覆盖率分别为97.90%和89.61%,若增加4颗中轨卫星,以15°仰角对我国的覆盖率为99.99%。 相似文献