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101.
E. M. Ahmed 《Crystal Research and Technology》2012,47(6):689-695
Zn‐ 22 wt.% Al (Zn ‐ 40 Al in atomic%) eutectoid alloys with different Cerium (Ce) contents of 0, 1, 2, and 6 (in wt.%), 0.35, 0.70 and 2.1 (in atomic%) were rapidly solidified by melt spun technique. The effects of high cooling rate and alloying element (Ce) on microstructure of the studied alloys were analyzed by X‐ray diffractometry (XRD), scanning electron microscopy (SEM) and electrical resistance measurements. The results showed that the dendrites as well as grains size were refined by the additions of Ce. The main phases in melt spun alloys were α‐Al and η‐Zn, in addition to intermetallic CeZn5 and Al4Ce. Additional metastable intermetallic Al0.71Zn0.29 phase has been observed only for melt spun alloy of 6 wt.% Ce content. XRD peaks of melt spun alloys demonstrated a considerable broadening with percentage of Ce due to the grain refinement and lattice distortion. Moreover, increase of Ce content results in a decrease of Al lattice constant which could be related to formation of supersaturated solid solution of Zn and/or Ce in α‐Al. Crystallite size of all phases were in the range of nanometer scale which reflects the role of the high cooling rate and the existence of Ce as alloying element for producing nanocrystalline structure. Resistance measurements of melt spun alloys show that the relative resistance rate for the alloys of higher Ce content relaxed faster to lower value than that of lower Ce content. Electrical resistance and microstructure exhibit strongly Ce content dependence. 相似文献
102.
An interconnecting bus power optimization method combining interconnect wire spacing with wire ordering 下载免费PDF全文
On-chip interconnect buses consume tens of percents of dynamic power in a nanometer scale integrated circuit and they will consume more power with the rapid scaling down of technology size and continuously rising clock frequency, therefore it is meaningful to lower the interconnecting bus power in design. In this paper, a simple yet accurate interconnect parasitic capacitance model is presented first and then, based on this model, a novel interconnecting bus optimization method is proposed. Wire spacing is a process for spacing wires for minimum dynamic power, while wire ordering is a process that searches for wire orders that maximally enhance it. The method, i.e., combining wire spacing with wire ordering, focuses on bus dynamic power optimization with a consideration of bus performance requirements. The optimization method is verified based on various nanometer technology parameters, showing that with 50% slack of routing space, 25.71% and 32.65% of power can be saved on average by the proposed optimization method for a global bus and an intermediate bus, respectively, under a 65-nm technology node, compared with 21.78% and 27.68% of power saved on average by uniform spacing technology. The proposed method is especially suitable for computer-aided design of nanometer scale on-chip buses. 相似文献
103.
Self-organization that leads to the discontinuous emergence of optimized new patterns is related to entropy generation and the export of entropy. Compared to the original pattern that the new, self-organized pattern replaces, the new features could involve an abrupt change in the pattern-volume. There is no clear principle of pathway selection for self-organization that is known for triggering a particular new self-organization pattern. The new pattern displays different types of boundary-defects necessary for stabilizing the new order. Boundary-defects can contain high entropy regions of concentrated chemical species. On the other hand, the reorganization (or refinement) of an established pattern is a more kinetically tractable process, where the entropy generation rate varies continuously with the imposed variables that enable and sustain the pattern features. The maximum entropy production rate (MEPR) principle is one possibility that may have predictive capability for self-organization. The scale of shapes that form or evolve during self-organization and reorganization are influenced by the export of specific defects from the control volume of study. The control volume (CV) approach must include the texture patterns to be located inside the CV for the MEPR analysis to be applicable. These hypotheses were examined for patterns that are well-characterized for solidification and wear processes. We tested the governing equations for bifurcations (the onset of new patterns) and for reorganization (the fine tuning of existing patterns) with published experimental data, across the range of solidification morphologies and nonequilibrium phases, for metallic glass and featureless crystalline solids. The self-assembling features of surface-texture patterns for friction and wear conditions were also modeled with the entropy generation (MEPR) principle, including defect production (wear debris). We found that surface texture and entropy generation in the control volume could be predictive for self-organization. The main results of this study provide support to the hypothesis that self-organized patterns are a consequence of the maximum entropy production rate per volume principle. Patterns at any scale optimize a certain outcome and have utility. We discuss some similarities between the self-organization behavior of both inanimate and living systems, with ideas regarding the optimizing features of self-organized pattern features that impact functionality, beauty, and consciousness. 相似文献
104.
The focus of this paper is to investigate the methods for Four Wave Mixing (FWM) suppression. Modified techniques equal and unequal-channel spacing with polarization, equal channel spacing with alternate channel delay, optical coupling and varied laser power have been proposed to reduce the impact of FWM on Dense Wave Length Division Multiplexing (DWDM) optical communication system. Further the comparison of reduction of FWM for existing and proposed techniques has been discussed by varying the dispersion of fiber from 0 to 16 ps/nm/km. It has been observed that the suggested techniques are simpler to design optical communication system and superior to the existing methods. 相似文献
105.
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107.
为了制备高性能的聚合物/蒙脱土纳米复合材料, 必须对蒙脱土(MMT)进行有机改性来改善蒙脱土表面的疏水性、提高蒙脱土与聚合物之间的相容性, 同时也需要尽可能地增大蒙脱土的层间距. 为此, 提出了一种采用不同链长的聚醚铵阳离子协同插层MMT 的新方法, 即采用D2000(或T5000)聚醚铵盐与D400 聚醚铵盐协同插层MMT, 并采用X射线衍射分析(XRD)和热重分析(TGA)研究了协同插层对改性MMT 的层间距、有机含量以及耐热性的影响. 另外, 也研究了插层过程中的搅拌方式和D400 聚醚铵盐多次插层对改性MMT 的层间距、有机含量等的影响. 研究结果表明,采用长链聚醚铵阳离子协同插层更有利于提高D400 聚醚铵盐改性MMT 的层间距和有机含量; T5000 协同插层MMT中总的有机含量(64.06%)进一步增加, 这可能是因为T5000 的支链在MMT 层间形成的笼型结构既提供了更大的空隙,又起到了屏蔽作用, 同时也得到了较大的层间距(6.86 nm). 相似文献
108.
Smiley W. Cheng 《Annals of the Institute of Statistical Mathematics》1983,35(1):407-414
Summary The most powerful test of the null hypothesisH
0:σ=σ
0 versus the alternative hypothesisH
1:σ=σ
1 based on a few selected sample quantiles is proposed here where σ is the scale parameter of the distribution and the location
parameter μ is known. The quantiles are chosen from a large sample that is either complete or censored (singly-censored or
doubly-censored). The relationship between the proposed test and the asymptotically best linear unbiased estimate (ABLUE)
of the scale parameter is discussed. 相似文献
109.
The synthesis of pillared clays have led to the development of new materialswith suitable pore size and sufficient stability to be used as shape-selective catalystsand molecular sieves. There are numerous layered inorganic oxides which havethe potential to undergo ion-exchange reactions analogous to those observed withclays, but the nonswelling nature of most ionic layered oxides generally prevents 相似文献
110.
Roohollah Torabi Kachoosangi Gregory G. Wildgoose Richard G. Compton 《Electroanalysis》2008,20(15):1714-1718
A sensitive electroanalytical method is presented for the determination of 4‐hexylresorcinol using adsorptive stripping voltammetry (AdsSV) at a multiwalled carbon nanotube modified basal plane pyrolytic graphite electrode (MWCNT‐BPPGE). This method is also extended to the use of a MWCNT modified screen‐printed electrode (MWCNT‐SPE), thereby demonstrating that this approach can easily be incorporated into a facile and inexpensive electrochemical sensor. 相似文献