Small-Amplitude Disturbances in a Radiating and Scattering Grey MediumIII. Gravitational Effects on the Solutions of Given Real Wave Number k     

Noboru Kaneko  Kazuhiko Morita 《Astrophysics and Space Science》2006,305(4):349-376

We study the fundamental modes of radiation hydrodynamic linear waves that arise from one-dimensional small-amplitude initial fluctuations with wave number k in a radiating and scattering grey medium by taking into account the gravitational effects. The equation of radiative acoustics is derived from three hydrodynamic equations, Poisson’s equation, and two moment equations of radiation, by assuming a spherical symmetry for the matter and radiation and by using the Eddington approximation. We solve the dispersion relation as a quintic function of angular frequency ω, the wave number k being a real parameter. Numerical results reveal that wave patterns of five solutions are distinguished into three types: the radiation-dominated, type 1, and type 2 matter-dominated cases. In the case of no gravitaional effects (Kaneko et al., 2005), the following wave modes appear: radiation wave, conservative radiation wave, entropy wave, Newtonian-cooling wave, opacity-damped and cooling-damped waves, constant-volume and constant-pressure diffusions, adiabatic sound wave, cooling-damped and drag-force-damped isothermal sound waves, isentropic radiation-acoustic wave, and gap mode. Meanwhile, the gravitaional effects being taken into account, the growing gravo-diffusion mode newly arises from the constant-pressure diffusion at the point that k agrees with Jeans’ wave number specified by the isothermal sound speed. This mode changes to the growing radiation-acoustic gravity mode near the point that k becomes Jeans’ wave number specified by the isentropic radiation-acoustic speed. In step with a transition between them, the isentropic radiation-acoustic wave splits into the damping radiation-acoustic gravity mode and constant-volume diffusion. The constant-volume diffusion emerges twice if the gravitational effects are taken into account. Since analytic solutions are derived for all wave modes, we discuss their physical significance. The critical conditions are given which distinguish between radiation-dominated and type 1 matter-dominated cases, and between type 1 and type 2 matter-dominated cases. Waves in a self-gravitating scattering grey medium are also analyzed, which provides us some hints for the effects of energy and momentum exchange between matter and radiation.  相似文献   

A new stereo‐analytical method for determination of removal blocks in discontinuous rock masses     

Zixin Zhang  P. H. S. W. Kulatilake 《国际地质力学数值与分析法杂志》2003,27(10):791-811

The paper provides a new stereo‐analytical method, which is a combination of the stereographic method and analytical methods, to separate finite removable blocks from the infinite and tapered blocks in discontinuous rock masses. The methodology has applicability to both convex and concave blocks. Application of the methodology is illustrated through examples. Addition of this method to the existing block theory procedures available in the literature improves the capability of block theory in solving practical problems in rock engineering. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

A simple model for the evolution of disc galaxies: the Milky Way     

Thorsten Naab  Jeremiah P. Ostriker 《Monthly notices of the Royal Astronomical Society》2006,366(3):899-917

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Measurement of radiative lifetimes and determination of transition probabilities of astrophysical interest in Ho iii     

E. Biémont  P. Palmeri  P. Quinet  G. Paquin  Z. G. Zhang  G. Somesfalean  S. Svanberg 《Monthly notices of the Royal Astronomical Society》2001,328(4):1085-1090

Lifetimes of six levels belonging to the 4f¹⁰6p configuration of Ho  iii have been measured for the first time using the time-resolved laser-induced fluorescence method. They are compared with multiconfigurational pseudo-relativistic Hartree–Fock calculations. A very good agreement is found. Using the experimental lifetimes and theoretical branching fractions, a first set of transition probabilities of astrophysical interest has been obtained for this ion.  相似文献   

国外软骨藻酸的研究概况   总被引：4，自引：0，他引：4  

刘伟斌 《海洋湖沼通报》1997,(1):67-70

软骨藻酸相继从一些海洋红藻和硅藻中被发现并分离出,研究表明其为神经毒素、递质,当它进入中枢神经系统后,会发生胞溶现象,从而破坏边缘系统结构而产生记忆力丧失等症状。目前,检测其含量有化学和生化二类分析方法。  相似文献   

Internal generation of waves: Delta source function method and source term addition method     

Gunwoo Kim  Changhoon Lee  Kyung-Duck Suh   《Ocean Engineering》2007,34(17-18):2251-2264

In this study, we investigate two internal wave generation methods in numerical modeling of time-dependent equations for water wave propagation, i.e., delta source function method and source term addition method, the latter of which has been called the line source method in literatures. We derive delta source functions for the Boussinesq-type equations and extended mild-slope equations. By applying the fractional step splitting method, we show that the delta source function method is equivalent to the source term addition method employing the energy velocity. This suggests that the energy velocity should be used rather than the phase velocity for the transport of incident wave energy in the source term addition method. Finally, the performance of the delta source function method is verified by accurately generating nonlinear cnoidal waves as well as linear waves for horizontally one-dimensional cases.  相似文献   

Freely floating-body simulation by a 2D fully nonlinear numerical wave tank     

Weoncheol Koo  Moo-Hyun Kim 《Ocean Engineering》2004,31(16):221-2046

Nonlinear interactions between large waves and freely floating bodies are investigated by a 2D fully nonlinear numerical wave tank (NWT). The fully nonlinear 2D NWT is developed based on the potential theory, MEL/material-node time-marching approach, and boundary element method (BEM). A robust and stable 4th-order Runge–Kutta fully updated time-integration scheme is used with regriding (every time step) and smoothing (every five steps). A special φ_n-η type numerical beach on the free surface is developed to minimize wave reflection from end-wall and wave maker. The acceleration-potential formulation and direct mode-decomposition method are used for calculating the time derivative of velocity potential. The indirect mode-decomposition method is also independently developed for cross-checking. The present fully nonlinear simulations for a 2D freely floating barge are compared with the corresponding linear results, Nojiri and Murayama’s (Trans. West-Jpn. Soc. Nav. Archit. 51 (1975)) experimental results, and Tanizawa and Minami’s (Abstract for the 6th Symposium on Nonlinear and Free-surface Flow, 1998) fully nonlinear simulation results. It is shown that the fully nonlinear results converge to the corresponding linear results as incident wave heights decrease. A noticeable discrepancy between linear and fully nonlinear simulations is observed near the resonance area, where the second and third harmonic sway forces are even bigger than the first harmonic component causing highly nonlinear features in sway time series. The surprisingly large second harmonic heave forces in short waves are also successfully reproduced. The fully updated time-marching scheme is found to be much more robust than the frozen-coefficient method in fully nonlinear simulations with floating bodies. To compare the role of free-surface and body-surface nonlinearities, the body-nonlinear-only case with linearized free-surface condition was separately developed and simulated.  相似文献   

The weakening role of science in the management of groundfish off the east coast of Canada     

Shelton  Peter A. 《ICES Journal of Marine Science》2007,64(4):723-729

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台湾海峡海洋捕捞业管理策略和投资方向   总被引：1，自引：0，他引：1  

戴天元 《台湾海峡》1997,16(2):239-244

本文收集了１９８５￣１９９４年福建省在台湾海峡生产的具有代表性的５０对拖网渔船、１２０艘单拖渔船、４８组灯光围网渔船、３８对大围缯渔船、３１艘定置网渔船的技术参数及生产资料，计算并分析了其适正捕捞力量、经济指标，得出了一些有益的结论：（１）根据台湾海峡渔业资源，把握正确的投资方向，已成为进一步发展海洋捕捞业的关键。（２）由于台湾海峡的渔业资源正遭受越来越大的压力，为了保护渔业资源，应当限制捕捞力量  相似文献   

海底沉积物分析测试方法标准的研究   总被引：3，自引：0，他引：3  

夏宁  宋苏顷  刘昌岭  张红  林学辉 《海洋科学》2002,26(11):53-56

依据海底沉积物分析测试方法标准研究的总体设计，完成了40个分析项目的21份验证报告，进行了实验室间精密度协作性检验工作，在海底沉积物CaCo3,H2Os^-，H2O^ 的分析方法研究中取得新进展，并建立了ICP－AES法测定海底沉积物中常量、微量、稀土元素分析方法。  相似文献