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991.
本文通过对近期国产厚板试验资料的整理和分析,求得了它们的材性统计参数。可作为有关标准(如钢结构设计规范)的补充和有关分析(如高层钢结构设计计算)的基础。 相似文献
992.
戴梅 《云南工业大学学报》1992,(3)
考察分析了大理、丽江两城镇的外部空间构成。主要结论是:1)该两城镇具有易于识别、软硬相间、融物质功能与精神生活于一体的外部空间构成特色;2) 自然环境、文化意识、使用功能对该两城镇的外部空间构成具有重要的影响和限定作用。 相似文献
993.
应用红外光谱和电子顺磁共振对西曲煤显微组分的分子结构和自由基性质进行了研究。结果表明:镜质组、半镜质组和惰质组的芳碳率分别为0.84、0.91和0.93,镜质组分子结构单元中含有较多的脂肪取代基和螯形醌基;显微组分的自由基浓度(10~(18)spins/g):镜质组3.87,半镜质组18.98,惰质组40.10。镜质组自由基为较小的含氧型芳香π自由基,情质组自由基为巨大的纯芳香π自由基;半镜质组的分子结构和自由基性质均介于镜质组和惰质组之间。 相似文献
994.
压阻式压力传感器的动态特性 总被引:2,自引:2,他引:0
综合分析了敏感元件构形与尺寸及传感器的封装结构对动态压力测量的影响。给出了几种CYG压阻式压力传感器在动态压力测量时的频响特性的理论计算值与实验值。 相似文献
995.
The synthesis and characterization of composite materials based on calcium–aluminum layered double hydroxides (Ca–Al-LDHs), intercalated with organic polycarboxylate (PC) polymers, is described. The PC polymers, which exhibit a “comb-like” architecture, contain ethylene oxide side chains of different lengths. They are intercalated between the cationic Ca–Al–OH-layers when tricalcium aluminate is rehydrated in the presence of PC polymers. The intercalation compounds are characterized by X-ray diffraction (XRD), elemental analysis, IR spectroscopy and TEM. The basal spacings of the PC-LDH composite materials, determined by XRD, are dependent on the number of the ethylene oxide units (EOUs) in the side chain. Accordingly, first TEM micrographs reveal approximately similar layer distances. Elemental analysis as well as IR-spectroscopy proves the existence of the intercalated organic material. 相似文献
996.
Treatment of solidification latent heat is a key point in solidification simulation by the finite difference method. When latent heat is dealt with in a traditional method of equivalent latent heat, it was found that heat was increased when casting with a high cooling rate, and then the simulation result was distorted. In this paper, a new method is proposed to deal with solidification latent heat. Moreover, a mathematical model was suggested, in which the latent heat can be dealt with accurately under high or normal cooling rates. By contrasting the simulation results from this new method with the traditional one, it was indicated that this new model can obtain more accurate simulation results than the traditional model under high or normal cooling rates. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(2): 115–121, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20104 相似文献
997.
On the Diversity Order of Spatial Multiplexing Systems With Transmit Antenna Selection: A Geometrical Approach 总被引:3,自引:0,他引:3
Zhang H. Dai H. Zhou Q. Hughes B. L. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2006,52(12):5297-5311
In recent years, the remarkable ability of multiple-input-multiple-output (MIMO) wireless communication systems to provide spatial diversity or multiplexing gains has been clearly demonstrated. For MIMO diversity schemes, it is well known that antenna selection methods that optimize the postprocessing signal-to-noise ratio (SNR) can preserve the diversity order of the original full-size MIMO system. On the other hand, the diversity order achieved by antenna selection in spatial multiplexing systems, especially those exploiting practical coding and decoding schemes, has not thus far been rigorously analyzed. In this paper, a geometrical framework is proposed to theoretically analyze the diversity order achieved by transmit antenna selection for separately encoded spatial multiplexing systems with linear and decision-feedback receivers. When two antennas are selected from the transmitter, the exact achievable diversity order is rigorously derived, which previously only appears as conjectures based on numerical results in the literature. If more than two antennas are selected, we give lower and upper bounds on the achievable diversity order. Furthermore, the same geometrical approach is used to evaluate the diversity-multiplexing tradeoff in spatial multiplexing systems with transmit antenna selection 相似文献
998.
Ionic liquids with ammonium cations as lubricants or additives 总被引:3,自引:0,他引:3
A new class of more effective lubricants could lead to huge energy savings. Limited recent literature has suggested potential for using room-temperature ionic liquids as lubricants, however, only a few out of millions (or more) of species possible have been evaluated. In this study, a series of new protic alkylammonium ionic liquids were synthesized by neutralization and metathesis reactions, and have demonstrated promising lubricating properties as neat lubricants or lubricant additives, particularly for use with difficult-to-lubricate metals like aluminum. More than a 30% friction reduction was observed with ammonium-based ionic liquids compared to conventional hydrocarbon oils in reciprocating sliding tests of 52100 bearing steel on aluminum alloy 6061-T6511. The inherent polarity of ionic liquids is believed to provide strong adsorption to contact surfaces and can form a boundary lubricating film leading to friction and wear reductions. Other advantages of ionic liquids include (1) negligible volatility, (2) high thermal stability, (3) non-flammability, and (4) better intrinsic properties that may eliminate the need for more complex and expensive additive packages. With very flexible molecular structures, this new class of lubricants, particularly ammonium-based ionic liquids, can be tailored to fit a variety of applications. 相似文献
999.
1000.
The demands being placed on CAD systems by current advances in packaging technology, in particular, the need to design interconnecting networks for thin-film multichip modules (MCMs), are discussed. The approaches embodied in several recently developed software packages are described. These include interactive placement and routing, warping, shape-based routing, rubber-band routing, and correct by design. The role of concurrent engineering in the design process is examined 相似文献