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251.
Large-scale structure formation, accretion and merging processes, AGN activity produce cosmological gas shocks. The shocks
convert a fraction of the energy of gravitationally accelerated flows to internal energy of the gas. Being the main gas-heating
agent, cosmological shocks could amplify magnetic fields and accelerate energetic particles via the multi-fluid plasma relaxation
processes. We first discuss the basic properties of standard single-fluid shocks. Cosmological plasma shocks are expected
to be collisionless. We then review the plasma processes responsible for the microscopic structure of collisionless shocks.
A tiny fraction of the particles crossing the shock is injected into the non-thermal energetic component that could get a
substantial part of the ram pressure power dissipated at the shock. The energetic particles penetrate deep into the shock
upstream producing an extended shock precursor. Scaling relations for postshock ion temperature and entropy as functions of
shock velocity in strong collisionless multi-fluid shocks are discussed. We show that the multi-fluid nature of collisionless
shocks results in excessive gas compression, energetic particle acceleration, precursor gas heating, magnetic field amplification
and non-thermal emission. Multi-fluid shocks provide a reduced gas entropy production and could also modify the observable
thermodynamic scaling relations for clusters of galaxies. 相似文献
252.
Frits Paerels Jelle Kaastra Takaya Ohashi Philipp Richter Andrei Bykov Jukka Nevalainen 《Space Science Reviews》2008,134(1-4):405-418
We briefly review capabilities and requirements for future instrumentation in UV- and X-ray astronomy that can contribute
to advancing our understanding of the diffuse, highly ionised intergalactic medium. 相似文献
253.
Vasconcelos Maria Jaqueline Jatenco-Pereira Vera Opher Reuven 《Space Science Reviews》2003,107(1-2):383-386
In this work we examine the damping of Alfvén waves as a source of plasma heating in disks and magnetic funnels of young solar
like stars, the T Tauri stars. We apply four different damping mechanisms in this study: viscous-resistive, collisional, nonlinear
and turbulent, exploring a wide range of wave frequencies, from 10−5Ωi to 10−1Ωi (where Ωi is the ion-cyclotron frequency). The results show that Alfvénic heating can increase the ionization rate of accretion disks
and elevate the temperature of magnetic funnels of T Tauri stars opening possibilities to explain some observational features
of these objects.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
254.
脉冲电晕放电对减少内燃机有害排放的研究 总被引:1,自引:0,他引:1
本文对脉冲电晕放电对减少内燃机有害排放的可行性进行了研究,实验中用NDIR(非分散红外线)气体分析仪测量了SY492Q-1型汽油机在等离子装置工作或不工作时排气中CO、CO2和HC的浓度,并通过等离子发生装置结构的变化调整阴极与阳极间的放电间隙,观察并测量其对实验结果的影响。初步实验结果证明,利用等离子体技术减少汽车尾气中的HC和CO的排放是可行的,并且等离子发生装置的放电电压和放电间隙对实验结果有重要影响。 相似文献
255.
声发射技术在复合材料损伤模式识别中的应用 总被引:1,自引:0,他引:1
应用模态分析技术,分析复合材料拉伸破坏试验中的声发射信号,提取复合材料不同破坏阶段下的声发射源信号的特征,进行了有关复合材料损伤模式识别的工作。 相似文献
256.
257.
YANG Shu-bo WANG Xi LONG Yi-fu LI Zhi-peng HU Zhong-zhi YIN Kai ZHANG Rong 《航空动力学报》2016,31(12):3042-3053
Since ambient conditions vary in a wide range within the full flight envelope, the existing piecewise linear model (PLM), which is based on sea-level static condition with use of corrected parameters for other points in the flight envelope, cannot meet the accuracy for replacing the nonlinear model. To obtain more accurate linear models, a method of partitioning the flight envelope over a grid of Mach number and altitude boxes was suggested. Then, a set of linear models for a given operating condition was selected by picking the nearest (Mach number, altitude) box in the flight envelope. Through the selected set of linear models, interpolating for power level based on a weighted sum of corrected rotor speeds can obtain a linear model with acceptable accuracy. Simulation results of different points within the full flight envelope showed that the maximum error between nonlinear model and the existing PLM was more than 50%, while the maximum error between nonlinear model and the improved PLM was within 8%. It is concluded that the improved PLM performs accurately, especially under the non-standard conditions. In addition, the improved PLM can satisfy the real-time requirement better than the existing PLM. 相似文献
258.
259.
为了掌握采用富油-淬熄-贫油低排放燃烧技术的驻涡燃烧室(RQL-TVC)在起飞-着陆(LTO)循环各状态中的排放特性,采用数值模拟的方法开展了研究。数值模拟结果表明:在LTO循环中,RQL驻涡燃烧室的氮氧化物(NOX)与未燃碳氢化合物(UHC)的排放指数EI均低于传统燃烧室的;但一氧化碳(CO)的排放指数(Emission Indext, EI)偏大。RQL驻涡燃烧室NOX的LTO排放数少,是国际民航组织颁布的航空发动机排放标准CAEP6的29.1%;UHC的LTO排放数接近于0;CO的LTO排放数在慢车状态下的数值明显高于其它状态下的。RQL-TVC具有良好的低排放潜力。 相似文献
260.
民用飞机全航线排放预测 总被引:2,自引:1,他引:2
针对民用飞机全航线的排放预测问题,运用飞机升阻特性模型、发动机性能模型和飞机航线性能模型计算了民用飞机在全航线上的飞机升阻特性与发动机性能,并将以上模型与基于T3-p3法与波音流量法所建立的排放计算模型相耦合,详细计算了飞机在实际飞行过程中未燃碳氢化合物(UHC)、一氧化碳(CO)、氮氧化合物(NOx)的排放指数,并得到了全航线的各种污染排放物排放总量,完善了民用航空发动机排放预测分析体系,为低污染民用航空发动机的设计与评估提供理论依据.计算结果表明,飞机处在起飞以及爬升阶段时,NOx的排放指数较高,而UHC与CO的排放指数较低;当飞机处在下降以及进场时,NOx的排放指数较低,而UHC与CO的排放指数较高.NOx的总排放量在3种污染排放产物中最高. 相似文献