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991.
Levent Aksoy Eduardo Costa Paulo Flores José MonteiroAuthor vitae 《Microprocessors and Microsystems》2011,35(8):729-741
Over the years many efficient algorithms for the multiplierless design of multiple constant multiplications (MCMs) have been introduced. These algorithms primarily focus on finding the fewest number of addition/subtraction operations that generate the MCM. Although the complexity of an MCM design is decreased by reducing the number of operations, their solutions may not lead to an MCM design with optimal area at gate-level since they do not consider the implementation costs of the operations in hardware. This article introduces two approximate algorithms that aim to optimize the area of the MCM operation by taking into account the gate-level implementation of each addition and subtraction operation which realizes a constant multiplication. To find the optimal tradeoff between area and delay, the proposed algorithms are further extended to find an MCM design with optimal area under a delay constraint. Experimental results clearly indicate that the solutions of the proposed algorithms lead to significantly better MCM designs at gate-level when compared to those obtained by the solutions of algorithms designed for the optimization of the number of operations. 相似文献
992.
Thermal drift analysis using a multiphysics model of bulk silicon MEMS capacitive accelerometer 总被引:1,自引:0,他引:1
Gang Dai Mei LiXiaoping He Lianming DuBeibei Shao Wei Su 《Sensors and actuators. A, Physical》2011,172(2):369-378
An interpretation of the thermal drift of the bulk silicon MEMS capacitive accelerometer using multiphysics analysis is proposed in this paper. Stress, strain, electrostatics, thermal and structural interactions are simulated based on the finite element method. The thermal drift is generated by both the stiffness asymmetry of the U-springs of the structure and relative displacement caused by the mismatch in thermal expansion coefficients between the Pyrex glass substrate and heavily boron-doped silicon structure, neither of which is dispensable. Although the layout design is symmetrical, the asymmetric widths of the U-springs, which cause stiffness asymmetry, are observed by scanning electron microscopy. To achieve a fast and feasible simulation, we divide the model into two components with different configurations. During the simulation, boundary conditions are carefully set up according to the fabrication process. A series of experiments is designed to verify the result, including a temperature experiment from −40 to 100 °C and DC voltage polarity experiment. To verify the conclusion, a new layout design that gradually increases the width of the U-springs without changing any other dimension is simulated, fabricated, and tested. The simulation and experiment results are compared and discussed. 相似文献
993.
文中就微波功率计在测量微波功率时可能出现的哪些误差以及它们的性质和处理方法(有效效率ηe或校准系数Kb)做一个概括性介绍。 相似文献
994.
分析了采用布喇格光纤光栅的FH-OCDMA系统中不同群速度失配的光纤信道对系统性能的影响. 群速度失配造成的光脉冲位置偏移, 在没有补偿措施的情况下, 普通单模光纤不适于现有的FH-OCDMA系统. 提出了解决多波长群速度失配问题的补偿方案. 相似文献
995.
996.
通道间延迟时间差的测量不确定度 总被引:14,自引:3,他引:11
介绍了用正弦波拟合法评价测量系统通道间延迟时间差不确定度的分析和评定过程。讨论了几个主要的不确定度来源,包括信号源误差、采集序列的谐波失真、噪声及非谐波失真、抖动、软件拟合运算误差等。结合一个实例,给出了通道间延迟时间差测量不确定度的评定结果。该过程可用于相应计量标准的不确定度分析与评定。 相似文献
997.
Takuo Kuwahara Chiharu Tohara Takehiro Kohno Hidefumi Shibamoto 《Propellants, Explosives, Pyrotechnics》2005,30(6):425-429
By using partitions in smoke generators, luminous flame agents or other pyrotechnic agents, the vapor and sublimated materials are confined in a chamber. Titanium (Ti), polytetrafluoroethylene (Teflon), and Viton pyrolants (TTV), which generate high temperature products, can be used in a partition type igniter. The ignition delay time, τig, decreased with the increase of the concentration of Ti, ξ(Ti), and also the physical ignition delay time, τp, decreased with the increase of ξ(Ti). On the other hand the chemical ignition delay time, τc, remained unchanged in the range of ξ(Ti) from 0.4 to 0.7. As τp of TTV pyrolants is larger than τc, the ignition delay time is dominated by physical processes. 相似文献
998.
一种时延约束的多点到多点组播路由启发式算法 总被引:2,自引:0,他引:2
多点到多点组播路由是组播研究领域内的一个重要问题。当单棵共享组播树不能满足时延约束时,需要建立多棵共享组播树,但同时又会增加管理开销。因此,如何尽量减少共享组播树的个数成为关键问题。本文提出了一种启发式算法DCMMHA,用来解决时延约束的多共享组播树问题(DCMSMT),该问题已被证明为NP完全问题。本文算法按照特定规则生成候选中心列表,在不违反时延约束条件下,将源节点和目的节点加入共享树,并且对已选择中心进行更新。仿真实验将DCMMHA算法同其它四种同类算法进行比较,结果表明本文的算法所获得的中心数最少,显著降低了共享树的管理开销。 相似文献
999.
为了深入研究与控制SWRS82B钢中氧化铝夹杂,针对添加稀土元素铈研究其对氧化铝的改性问题,通过热力学以及边-边匹配模型对稀土夹杂物的析出条件和Al2O3与稀土氧(硫)化物之间、γ-Fe和稀土氧(硫)化物之间的原子间错配度进行计算,探究稀土铈夹杂物作为Al2O3和γ-Fe异质形核的有效性,进而证明稀土铈元素对B类氧化铝夹杂物改性的有效性,提高钢材性能。计算结果表明,在0~2 000 K的温度区间上,生成CeAlO3夹杂物反应的吉布斯自由能最低,且在同等条件下铈氧(硫)化物生成的可能性偏低,稀土铈氧(硫)化物可以作为Al2O3异质形核的核心,且稀土铈氧(硫)化物可以作为γ-Fe异质形核的核心;Al2O3可在稀土铈氧(硫)化物上有效形核,且Al2O3优先在Ce2O2S上发生异质形核;γ-Fe可在Al2O3和稀土铈氧(硫)化物上有效形核,且γ-Fe优先在Al2O3上发生异质形核,使得形状不规则的氧化铝夹杂物转变为近球形的铈铝酸盐夹杂,揭示SWRS82B钢中非金属夹杂物的变性机理,为提高SWRS82B钢中脆性夹杂物转变为塑性夹杂物处理的实际效果提供理论依据。 相似文献
1000.
The phase diagrams of Fe–Pt and Ni–Pt liquid alloy systems show the existence of FePt and NiPt intermetallic compounds, respectively, in their solid intermediate states, and the associative tendency between unlike atoms in these liquid alloys has been analysed using the self-association model. The concentration dependences of mixing properties such as the free energy of mixing, GM; the concentration fluctuations, Scc(0), in the long-wavelength limits; the chemical short-range order (CSRO) parameter, α1; as well as the chemical diffusion, enthalpy and entropy of the mixing of Fe–Pt and Ni–Pt liquid alloys have been investigated to determine the nature of ordering in the liquid alloys. The results show that heterocoordination occurs in the alloys at all concentrations. The effect of CSRO on Scc(0), chemical diffusion, D, and the order parameter, α1, has been considered. The ordering phenomenon in the liquid alloys is also related to the effect of the atomic size mismatch volume on Scc(0). 相似文献