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模型比例和风洞截面对汽车流场产生影响。应用FLUENT软件,分别对不同的车模比例和风洞截面形状进行气动性能仿真。结果表明:阻塞比在一定范围内,汽车气动参数变化平缓;选用不同的阻塞比在三种典型风洞模型中进行仿真计算,结果相差很大;闭式风洞的阻力系数较开式风洞高,开式风洞的升力系数较闭式风洞高。 相似文献
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介绍吉壶公路三标段利用峒室爆破和深孔预裂爆破技术一次性开炸单侧边坡路堑的参数选择和运用情况,可为类似工程提供相应的参考数据和经验。 相似文献
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液化气体铁路罐车既是运输工具 ,又是特定的强制检定的计量器具。通常情况下液化气体铁路罐车的容积是在常压情况下检定的 ,但罐车在压力条件下使用时 ,压力可达 1 6~ 2 2MPa或更高。因此 ,就需要对常压下检定的罐车容积进行修正 ,只有这样才能确保计量检定结果的准确可靠。1 液化气体铁路罐车常压下计量检定原理液化气体铁路罐车的总容积V ,主要是由直圆筒容积V1和两边端板部分所构成容积V2 所组成(如图 1)。其总容积V =V1 V2图 1V1=π4 abL其中a—圆筒内竖直径b—圆筒内横直径L—圆筒长度V2 =2 (V2 1 V2 2 V2 3)… 相似文献
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随着最佳信号的广泛应用,只用一个序列来形成最佳信号限制了最佳信号的存在空间,两个序列组成的序列偶成为研究热点。根据有关序列偶及零/低相关区域序列的概念,定义新的序列形式,即区域(或准)最佳自相关序列偶。给出并证明了相应的变换性质.最后论证了此类信号的存在. 相似文献
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第四界长春汽车博览会上,解放品牌强势登场.不久前在上海国际车展中大放异彩的J6H6X2概念车成为解放阵营中的领军者.作为一款面向中国未来市场的重型卡车,J6H是一部融合了众多高新科技的卡车杰作.它显示了解放自主品牌的最新研发成果.其整体实力已经完全能够与国际顶级重卡相媲美. 相似文献
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An iterative transmit power allocation (PA) algorithm was proposed for group-wise space-time block coding (G-STBC) systems with group-wise successive interference cancellation (GSIC) receivers. Group-wise interference suppression (GIS) filters are employed to separate each group's transmit signals from other interferences and noise. While the total power on all transmit symbols is constrained, all transmit PA coefficients are updated jointly according to the channel information at each iteration. Through PA, each detection symbol has the same post-detection signal to interference-and-noise ratio (SINR). The simulation results verify that the proposed PA algorithm converges at the equilibrium quickly after few iterations, and it achieves much lower bit error rates than the previous single symbol SIC PA and the fixed ratio PA algorithms for G-STBC systems with GSIC receivers . 相似文献
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铁路罐车内总长检具的设计范勇,张海滨(国家铁路罐车容积计量站齐鲁分站)铁路罐车既是运输工具,又是国家强制检定计量器具。铁路罐车容积计量检定是计量工作的重要组成部分,对促进国内外贸易,节约和企业经济核算,保证铁路运输安全具有重要的作用。目前我国共有铁路... 相似文献
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ZHANG Hong-wei 《上海交通大学学报(英文版)》2005,10(4):349-353
A new improved group space-time block code (G-STBC) based on constellation rotation for four transmit antennas was proposed. In comparison with the traditional G-STBC coding scheme, the proposed space-time code has longer code length and adopts proper rotation-based symbols, which can increase the minimum distance of space-time codes and thereby improve code gain and achieve full diversity performance. The simulation results verify that the proposed group space-time code can achieve better bit error performance than both the traditional group space-time code and other quasi-orthogonal space-time codes. Compared with Ma's full diversity full rate (FDFR) codes, the proposed space-time code also can achieve the same excellent error performance. Furthermore, the design of the new space-time code gives another new and simple method to construct space-time codes with full diversity and high rate in case that it is not easy to design the traditional FDFR space-time codes. 相似文献