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31.
Enning B. Vodhanel R.S. Dietrich E. Patzak E. Meissner P. Wenke G. 《Lightwave Technology, Journal of》1989,7(3):459-464
Polarization diversity is an alternative technique for coherent receivers to prevent loss to signal due to variations in the states of polarization (SOP) of the received signal field. It is shown experimentally and theoretically that there is no significant power penalty difference between a receiver with optimally adjusted gains and receivers with linear envelope detection and square-law detection. Experimentally, two amplitude-shift keying (ASK) heterodyne polarization diversity receivers with envelope detectors were demonstrated at 560 Mb/s, one using linear rectifiers, the other using square-law rectifiers. In both cases, the receiver sensitivity of -35 dBm at BER=10 -9 was degraded by less than 1 dB as the received signal SOP was varied, in agreement with theory 相似文献
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以某大型数据中心内气流组织为研究对象,采用6SigmaRoom软件进行数值模型,求解获取不同送风方式下数据中心内温度场和速度场分布,进而对比不同空调位置方案和不同通道封闭方案的优劣,最后运用供热指数(SHI)、回热指数(RHI)、机架冷却指数(RCI)和回风温度指数(RTI)详细分析其优劣.结果发现:相同机房空调布置情况下,与未封闭通道方案相比,封闭通道方案冷热气流掺混少,采用地板下送风+冷通道封闭+空调单侧布置时,相对于地板下送风+空调两侧布置SHI指标可降低98.3%.无论封闭通道方案或未封闭通道方案,将空调布置在机房同一侧比各一半相对布置的气流组织更好,流线和温度场更加均匀.综合可得,该数据中心最优空调方案为冷通道封闭+空调布置在机房同一侧结合应用方式. 相似文献
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为分析整形器对入射波形的影响规律,以紫铜T2材料为研究对象,在14.5 mmSHPB试验设备上开展整形器的直径和厚度、撞击杆速度和长度改变对入射波形状影响规律研究。结果表明:直径增大,整形器的广义强度增大,导致第1个拐点T1提高;厚度增加,整形器受冲击压缩应变率降低、压缩时间增加,拐点T1降低,拐点T2右移;撞击杆速度提高使第1个拐点T1提高,拐点T2位置左移;撞击杆长度对整形器调整入射波形状不产生影响,整形器吸收能量相同。 相似文献
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膨胀土是在我国分布范围较广的一种由亲水性矿物蒙脱石与伊利石组成的高塑性土,其多裂隙性、强胀缩性和超固结性,往往给边坡工程造成滑坡、溜塌、塌陷等灾害,严重影响交通、房屋和水利工程安全。为此,国内外做过很多的处治方法,耗费了巨大的工程费用,但收效并不理想。为了给膨胀土边坡的治理提供更科学合理的理论依据,根据国内外对膨胀土已有的研究成果进行系统分析与评价,提出了膨胀土边坡不宜采取单一的支挡防护措施,应根据膨胀土的成因与微结构特征进行综合治理,以柔性支挡、刚性支挡和植被防护措施的有机结合方为妥当,既能对膨胀土边坡的灾害治理起到长期、有效的作用,又可取得绿化工程环境的双重效果。 相似文献
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Polysulfide adhesives are often subjected to breakage or even fracture caused by highly loaded vibrations and large deformations from the wing, limiting their practical use in aircraft fuel tanks. Inserting polyurethanes into liquid polysulfide systems is a viable approach to strengthening their mechanical properties and avoiding nonuniform dispersion of the curing agent. In this contribution, a series of sulfur-containing curing agents were prepared by liquid polysulfide and trimethylolpropane tris(3-mercapto propionate) (TMPMP) to minimize the effect of the polysulfide-urea (-NHCOS-) groups on water resistance. Subsequently, the two-component polysulfide adhesives were successfully synthesized via the prepolymerization method, and their chemical structure, mechanical properties, and solvent resistance were systematically evaluated. As expected, the large introduction of sulfur linkages and -NHCOS- groups provided excellent oil resistance and strong mechanical properties for polysulfide adhesives. Notably, Samples 2-4 exhibited the highest tensile strength of 1.11 ± 0.02 MPa, the greatest shear strength of 1.87 ± 0.04 MPa, and the best hardness of 81 ± 2 Shore A, with 122.0%, 523.3%, and 170.0% improvement over the control, respectively. Furthermore, the oil absorption rate of all samples was less than 3.0%, and their tensile strength remained almost unchanged after 30 days of immersion than before. We believe our paradigm can provide a valuable guideline for designing high-performance polysulfide adhesives. 相似文献
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Wenke Zhang Hongxing Yang Lin Lu Zhaohong Fang 《International Journal of Heat and Mass Transfer》2012,55(21-22):6023-6031
The application of ground heat exchangers (GHEs) has attracted much attention for its advantages in terms of energy-saving and emission-reduction. Therefore, it is significant to introduce heat transfer into investigation, the paper illustrated the existing heat transfer models in order to analyze the GHEs with buried coils. Line heat source, cylindrical heat source and ring-coil heat source are introduced step by step. For the present, the borehole GHEs are the mainstream, and in recent years pile foundation GHEs have been followed with interest on account of heat transfer superiority as well as lowering initial cost and saving land area. Concerning that groundwater flow exist in geological stratum sometimes, so that the thermal analysis about heat transfer should be composed of two cases, i.e. models under the condition of both pure conduction and combination that include conduction and advection. It is obvious that ring-coil model is on the verge of actual situation for pile foundation GHEs with buried coils from the academic research perspectives, nevertheless for some engineering computation problems which the result error can be permitted in the certain range, other heat transfer models can be chosen in order to simplify the calculation process. 相似文献