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61.
We consider the effects of projection, internal absorption, and gas-or stellar-velocity dispersion on the measured rotation curves of galaxies with edge-on disks. Axisymmetric disk models clearly show that the rotational velocity in the inner galaxy is highly underestimated. As a result, an extended portion that imitates nearly rigid rotation appears. At galactocentric distances where the absorption is low (i.e., it does not exceed 0.3–0.5m kpc?1), the line profiles can have two peaks, and a rotation curve with minimum distortions can be obtained by estimating the position of the peak that corresponds to a higher rotational velocity. However, the high-velocity peak disappears in high-absorption regions and the actual shape of the rotation curve cannot be reproduced from line-of-sight velocity estimates. In general, the optical rotation curves for edge-on galaxies are of little use in reconstructing the mass distribution in the inner regions, particularly for galaxies with a steep velocity gradient in the central region. In this case, estimating the rotation velocities for outer (transparent) disk regions yields correct results. 相似文献
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64.
SORPTION AND DESORPTION CHARACTERISTICS OF CADMIUM BY FOUR DIFFERENT SOILS IN NORTHEAST CHINA 总被引:3,自引:0,他引:3
ZHANG Lei SONG Feng-bin 《中国地理科学(英文版)》2005,15(4):343-347
1IN TR O D U C TIO NA s a persistentand toxic pollutant, cadm ium (C d) canresultin m any adverse health effects in a variety oftis-suesand organssuch asthe lung,kidney,urinary,blad-der,pancreas,breast and prostate (SA TA R U G etal.,2003).C adm ium in so… 相似文献
65.
DEVELOPMENTSTRATEGIESOFWATERANDLANDRESOURCESINTHEHEXIREGION,CHINA肖洪浪,高前兆,李福兴DEVELOPMENTSTRATEGIESOFWATERANDLANDRESOURCESINTHE... 相似文献
66.
J. I. Read M. I. Wilkinson N. W. Evans G. Gilmore Jan T. Kleyna 《Monthly notices of the Royal Astronomical Society》2006,366(2):429-437
We present an improved analytic calculation for the tidal radius of satellites and test our results against N -body simulations.
The tidal radius in general depends upon four factors: the potential of the host galaxy, the potential of the satellite, the orbit of the satellite and the orbit of the star within the satellite . We demonstrate that this last point is critical and suggest using three tidal radii to cover the range of orbits of stars within the satellite. In this way we show explicitly that prograde star orbits will be more easily stripped than radial orbits; while radial orbits are more easily stripped than retrograde ones. This result has previously been established by several authors numerically, but can now be understood analytically. For point mass, power-law (which includes the isothermal sphere), and a restricted class of split power-law potentials our solution is fully analytic. For more general potentials, we provide an equation which may be rapidly solved numerically.
Over short times (≲1–2 Gyr ∼1 satellite orbit), we find excellent agreement between our analytic and numerical models. Over longer times, star orbits within the satellite are transformed by the tidal field of the host galaxy. In a Hubble time, this causes a convergence of the three limiting tidal radii towards the prograde stripping radius. Beyond the prograde stripping radius, the velocity dispersion will be tangentially anisotropic. 相似文献
The tidal radius in general depends upon four factors: the potential of the host galaxy, the potential of the satellite, the orbit of the satellite and the orbit of the star within the satellite . We demonstrate that this last point is critical and suggest using three tidal radii to cover the range of orbits of stars within the satellite. In this way we show explicitly that prograde star orbits will be more easily stripped than radial orbits; while radial orbits are more easily stripped than retrograde ones. This result has previously been established by several authors numerically, but can now be understood analytically. For point mass, power-law (which includes the isothermal sphere), and a restricted class of split power-law potentials our solution is fully analytic. For more general potentials, we provide an equation which may be rapidly solved numerically.
Over short times (≲1–2 Gyr ∼1 satellite orbit), we find excellent agreement between our analytic and numerical models. Over longer times, star orbits within the satellite are transformed by the tidal field of the host galaxy. In a Hubble time, this causes a convergence of the three limiting tidal radii towards the prograde stripping radius. Beyond the prograde stripping radius, the velocity dispersion will be tangentially anisotropic. 相似文献
67.
山区公路软基病害研究 总被引:2,自引:0,他引:2
随着高等级公路建设规模的扩大,山区公路所面临的路基病害特别是软土路基病害问题也逐渐增多。结合对陕南勉(县)一宁(强)高速公路工程实例分析,对山区软土成因及其特性进行了初步分析,认为山区软土属以坡洪积、湖积和冲积为主的软土,也有少量是由坡残积物堆积而形成。山区软土的特殊性表现在成分的复杂性、分布的不均匀性、隐蔽性和物理力学性质的特殊性。根据其特性以及中国山区公路软基普遍存在的病害问题,总结了山区公路软基的主要病害类型为剪切拉裂破坏、浸水沉陷破坏、剥蚀坍塌破坏、推挤滑动破坏。还提出了相应的软基处理方法及建议。 相似文献
68.
形变大地测量学的进展、问题与地震预报 总被引:12,自引:7,他引:5
简要概括了形变大地测量学的革命性进展,研讨了它的科学特色、功能和定义以及对地球科学和防灾减灾的推动。形变大地测量学有助于从根本上击破多年来制约地震预报的“瓶颈”,但也存在不少急待解决的问题。着重研讨了在21世纪前10年,形变大地测量学如何依托多年的学科积累并充分受益于人造卫星和数字化等新技术,开展创新性研究和试验以推进地震预报。为此,对当前的研究工作提出了12条科学技术途径。最后对学科名称提出了建议。 相似文献
69.
依据岩性组合、古生物特征及地震事件层研究,对胶辽鲁西徐淮地区新元古代地层可作如下多重划分对比:鲁西黑山官组、二青山组分别与辽东的钓鱼台组,南芬组相当,胶东豹山口组可与南芬组对比,它们同属青白口系。辽东南关岭组下部、鲁西石旺庄组下部、苏皖北部贾园组、淮南九里桥组皆为一套砂灰岩组合,都发育第一期地震事件层,并开始含有后生动物化石,为等时地层单位,与其以上各前寒武岩石地层单位同属灯影峡阶,鲁西的佟家庄组、浮来山组可分别与辽东桥头组、长岭子组、胶东辅子夼组、南庄组、苏皖北部兰陵组一城山组、淮南伍山组一四十里长山组对比,归属《中国区域年代地层(地质年代)表》新划分的陡山陀阶。 相似文献
70.
Advanced material constitutive models are used to describe complex soil behaviour. These models are often used in the solution of boundary value problems under general loading conditions. Users and developers of constitutive models need to methodically investigate the represented soil response under a wide range of loading conditions. This paper presents a systematic procedure for probing constitutive models. A general incremental strain probe, 6D hyperspherical strain probe (HSP), is introduced to examine rate‐independent model response under all possible strain loading conditions. Two special cases of HSP, the true triaxial strain probe (TTSP) and the plane‐strain strain probe (PSSP), are used to generate 3‐D objects that represent model stress response to probing. The TTSP, PSSP and general HSP procedures are demonstrated using elasto‐plastic models. The objects resulting from the probing procedure readily highlight important model characteristics including anisotropy, yielding, hardening, softening and failure. The PSSP procedure is applied to a Neural Network (NN) based constitutive model. It shows that this probing is especially useful in understanding NN constitutive models, which do not contain explicit functions for yield surface, hardening, or anisotropy. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献