排序方式: 共有13条查询结果,搜索用时 17 毫秒
1.
Karl Heinz Kienitz 《IEEE transactions on aerospace and electronic systems》2006,42(4):1485-1492
On-off thrusters are frequently used as actuators for attitude control. Typically these thrusters are subject to switching constraints. A limit cycle is the normal steady state operation mode of such attitude control systems. This contribution deals with controller design for precision attitude stabilization using actuators whose switching restrictions are explicitly considered. An exact approach is presented using ideas from established relay control methods. The design procedure is illustrated with an attitude controller design to attain a limit cycle with prescribed characteristics 相似文献
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Sebastian Heinz 《Space Science Reviews》2014,183(1-4):405-425
In this chapter, we will explore the interaction of jets with their environments. Jets can transport a sizable fraction of accretion energy away from black holes and neutron stars. Because they are collimated, they can travel to distances far beyond the gravitational sphere of influence of the black hole. Yet, their interaction with the interstellar and intergalactic medium must eventually halt their advance and dissipate the energy they carry. The termination of the jet, and the inflation of large scale cavities of relativistic plasma offers one of the most powerful ways to constrain the physics of jets. In this chapter, we will review the inflation of radio lobes, the propagation of hot spots, the creation of shells and cavities, and the bending of jet by proper motion through their environment, both in the context of AGN jets and microquasars. 相似文献
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George L. Withbroe John L. Kohl Heinz Weiser Richard H. Munro 《Space Science Reviews》1982,33(1-2):17-52
Measurements of the intensities and profiles of UV and EUV spectral lines can provide a powerful tool for probing the physical conditions in the solar corona out to 8 R
and beyond. We discuss here how measurements of spectral line radiation in conjunction with measurements of the white light K-corona can provide information on electron, proton and ion temperatures and velocity distribution functions; densities; chemical abundances and mass flow velocities. Because of the fundamental importance of such information, we provide a comprehensive review of the formation of coronal resonance line radiation, with particular emphasis on the H i L line, and discuss observational considerations such as requirements for rejection of stray light and effects of emission from the geocorona and interplanetary dust. Finally, we summarize some results of coronal H i L and white light observations acquired on sounding rocket flights.Paper presented at the IX-th Lindau Workshop The Source Region of the Solar Wind. 相似文献
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Peter J. Cargill Loukas Vlahos Rim Turkmani Klaus Galsgaard Heinz Isliker 《Space Science Reviews》2006,124(1-4):249-259
Particle acceleration in large-scale turbulent coronal magnetic fields is considered. Using test particle calculations, it
is shown that both cellular automata and three dimensional MHD models lead to the production of relativistic particles on
sub-second timescales with power law distribution functions. In distinction with the monolithic current sheet models for solar
flares, particles gain energy by multiple interactions with many current sheets. Difficulties that need to be addressed, such
as feedback between particle acceleration and MHD, are discussed. 相似文献
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Protoplanetary evolution is discussed in both its global and local aspects. The global turbulent evolution implies large scale average chemical fractionation and chondrule-sized grains as the building blocks of planetary and possibly also cometary material. Local processes such as electric discharges and associated flash heating of grains allow for chemical, mineralogical, and morphological alterations of the disk material. Large scale turbulence keeps the disk well stirred, however, time dependent (or intermittent) turbulence, associated with e.g. optical depth variations, could lead to dust sedimentation within the disk and subsequent planetesimal formation. Recent relevant astronomical observations of young T Tauri stars are briefly reviewed. 相似文献
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Heinz Neckel 《Space Science Reviews》1984,38(3-4):187-202
This paper reviews shortly the most reliable observations, which are available at present to describe the basic characteristics of the solar radiation: absolute measurements of the disk-center intensity, high resolution spectra of disk-center intensity and irradiance, and scans of the center to limb variation at continuum wavelengths and for the line-averaged radiation. Further it reports recent results obtained by the merging of these observations, namely high precision data for disk-center intensity and irradiance, which concern not only the line-averaged radiation, but also the position of the continuum. 相似文献
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Theodor Meyer's 1908 doctoral dissertation, with Ludwig Prandtl (1875–1953) as his advisor, introduced much of what has now become basic gas dynamics: not only the Prandtl–Meyer expansion but also the oblique-shock-wave theory as well. It is arguably the most influential dissertation in all of fluid dynamics. Yet no biography or even a photograph of Meyer has been available in the intervening century. This biography provides some insight into his character and covers his education, dissertation, World War I combat service and long career as an engineer and a teacher of math and physics. 相似文献