Exact solution of entanglement of the double Jaynes—Cummings model without rotating wave approximation

This paper investigates the influences of atom--field coupling and dipole--dipole coupling for atoms on the entanglement between two atoms by means of concurrence. The results show that the sudden death occurs when the atom--field coupling is strong enough, and the collapse and the revival appear when the dipole--dipole interaction is strong enough.     

面向三维地质建模的领域本体逻辑结构与构建方法

结合三维地质建模的应用,分析面向三维地质建模的领域本体的组成和层次结构.结合地质语义的特点,提出突出概念间关系的五元组逻辑结构和基于迭代思想的构建方法.该逻辑结构由概念、概念间语义关系、概念间层次关系、属性和实例组成.基于迭代思想的构建方法分为需求分析、领域共享词语的字典库构建、本体表示、本体集成和本体评估等步骤.以OWL语言描述工具,结合正断层本体实例探讨了面向三维地质建模领域本体逻辑结构的描述和构建方法.     

The Canary Islands swell: a coherence analysis of bathymetry and gravity

The Canary Archipelago is an intraplate volcanic chain, located near the West African continental margin, emplaced on old oceanic lithosphere of Jurassic age, with an extended volcanic activity since Middle Miocene. The adjacent seafloor does not show the broad oceanic swell usually observed in hotspot-generated oceanic islands. However, the observation of a noticeable depth anomaly in the basement west of the Canaries might indicate that the swell is masked by a thick sedimentary cover and the influence of the Canarian volcanism. We use a spectral approach, based on coherence analysis, to determine the swell and its compensation mechanism. The coherence between gravity and topography indicates that the swell is caused by a subsurface load correlated with the surface volcanic load. The residual gravity/geoid anomaly indicates that the subsurface load extends 600 km SSW and 800 km N and NNE of the islands. We used computed depth anomalies from available deep seismic profiles to constrain the extent and amplitude of the basement uplift caused by a relatively low-density anomaly within the lithospheric mantle, and coherence analysis to constrain the elastic thickness of the lithosphere ( T_e ) and the compensation depth of the swell. Depth anomalies and coherence are well simulated with T_e =28–36 km, compensation depth of 40–65 km, and a negative density contrast within the lithosphere of ∼33 kg m⁻³. The density contrast corresponds to a temperature increment of ∼325°C, which we interpret to be partially maintained by a low-viscosity convective layer in the lowermost lithosphere, and which probably involves the shallower parts of the asthenosphere. This interpretation does not require a significant rejuvenation of the mechanical properties of the lithosphere.     

走滑断裂带中挤压阶区内部剪切构造初探

野外地质调查和航片立体镜下解译发现,小江断裂带北段蒙姑和东支大营盘两个挤压阶区内部发育有剪切构造,它们在地表主要表现为断裂槽地、断层陡坎、地裂缝等。挤压阶区内部剪切构造和拉张阶区内部剪切构造一样,是阶区形成后,随着走滑断裂的进一步活动而形成的新生性构造     

Analysis of the positive ionospheric response to a moderate geomagnetic storm using a global numerical model

Current theories of F-layer storms are discussed using numerical simulations with the Upper Atmosphere Model, a global self-consistent, time dependent numerical model of the thermosphere-ionosphere-plasmasphere-magnetosphere system including electrodynamical coupling effects. A case study of a moderate geomagnetic storm at low solar activity during the northern winter solstice exemplifies the complex storm phenomena. The study focuses on positive ionospheric storm effects in relation to thermospheric disturbances in general and thermospheric composition changes in particular. It investigates the dynamical effects of both neutral meridional winds and electric fields caused by the disturbance dynamo effect. The penetration of short-time electric fields of magnetospheric origin during storm intensification phases is shown for the first time in this model study. Comparisons of the calculated thermospheric composition changes with satellite observations of AE-C and ESRO-4 during storm time show a good agreement. The empirical MSISE90 model, however, is less consistent with the simulations. It does not show the equatorward propagation of the disturbances and predicts that they have a gentler latitudinal gradient. Both theoretical and experimental data reveal that although the ratio of [O]/[N₂] at high latitudes decreases significantly during the magnetic storm compared with the quiet time level, at mid to low latitudes it does not increase (at fixed altitudes) above the quiet reference level. Meanwhile, the ionospheric storm is positive there. We conclude that the positive phase of the ionospheric storm is mainly due to uplifting of ionospheric F2-region plasma at mid latitudes and its equatorward movement at low latitudes along geomagnetic field lines caused by large-scale neutral wind circulation and the passage of travelling atmospheric disturbances (TADs). The calculated zonal electric field disturbances also help to create the positive ionospheric disturbances both at middle and low latitudes. Minor contributions arise from the general density enhancement of all constituents during geomagnetic storms, which favours ion production processes above ion losses at fixed height under day-light conditions.     

On crustal corrections in surface wave tomography

Mantle models from surface waves rely on good crustal corrections. We investigated how far ray theoretical and finite frequency approximations can predict crustal corrections for fundamental mode surface waves. Using a spectral element method, we calculated synthetic seismograms in transversely isotropic PREM and in the 3-D crustal model Crust2.0 on top of PREM, and measured the corresponding time-shifts as a function of period. We then applied phase corrections to the PREM seismograms using ray theory and finite frequency theory with exact local phase velocity perturbations from Crust2.0 and looked at the residual time-shifts. After crustal corrections, residuals fall within the uncertainty of measured phase velocities for periods longer than 60 and 80 s for Rayleigh and Love waves, respectively. Rayleigh and Love waves are affected in a highly non-linear way by the crustal type. Oceanic crust affects Love waves stronger, while Rayleigh waves change most in continental crust. As a consequence, we find that the imperfect crustal corrections could have a large impact on our inferences of radial anisotropy. If we want to map anisotropy correctly, we should invert simultaneously for mantle and crust. The latter can only be achieved by using perturbation theory from a good 3-D starting model, or implementing full non-linearity from a 1-D starting model.     

Lymanα forests and the evolution of the universe

The Lyα forest absorption lines in the spectra of quasars are interpreted as caused by the crossings of the light beam with the walls of a bubble structure (expanding with the Hubble flow only). Then, the typical separation between the absorption lines is proportional to the mean size of the bubbles. The variable factor is the expansion rate H[z]. The Friedmann regression analysis of the observed line separations determines the density parameter ω₀ and the normalized cosmological term λ₀ = λc²/3H²₀ of the appropriate cosmological model: ω₀ = 0.014 ± 0.002, λ₀ = 1.080 ± 0.006. Depending on the Hubble parameter this method reveals the values of the present mean matter density pm,0 = 2.6 h² · 10⁻²⁸ kg m⁻³ and of the cosmological constant Λ = 3.77 h² · 10⁻⁵² m⁻² (with h = H₀/(100 km/s·Mpc)). According to our analysis all models with Λ = 0 must be excluded. The curvature of space is positive. The curvature radius R₀ is 3.3 times the Hubble radius (c/H₀). The age t₀ is 2.8 times the Hubble age (H₀⁻¹).     

Invariant manifolds, phase correlations of chaotic orbits and the spiral structure of galaxies

In the presence of a strong   m = 2  component in a rotating galaxy, the phase-space structure near corotation is shaped to a large extent by the invariant manifolds of the short-period family of unstable periodic orbits terminating at L ₁ or L ₂. The main effect of these manifolds is to create robust phase correlations among a number of chaotic orbits large enough to support a spiral density wave outside corotation. The phenomenon is described theoretically by soliton-like solutions of a Sine–Gordon equation. Numerical examples are given in an N -body simulation of a barred spiral galaxy. In these examples, we demonstrate how the projection of unstable manifolds in configuration space reproduces essentially the entire observed bar–spiral pattern.     

基于时间序列法的北京市需水量预报(英文)

It is essential to establish the water resources exploitation and utilization planning,which is mainly based on recognizing and forecasting the water consumed structure rationally and scientifically.During the past 30 years(1980-2009),mean annual precipitation and total water resource of Beijing have decreased by 6.89% and 31.37% compared with those perennial values,respectively,while total water consumption during the same period reached pinnacle historically.Accordingly,it is of great significance for the harmony between socio-economic development and environmental development.Based on analyzing total water consumption,agricultural,industrial,domestic and environmental water consumption,and evolution of water consumed structure,further driving forces of evolution of total water consumption and water consumed structure are revealed systematically.Prediction and discussion are achieved for evolution of total water consumption,water consumed structure,and supply-demand situation of water resource in the near future of Beijing using Time Series Forecasting Method.The purpose of the endeavor of this paper is to provide scientific basis for the harmonious development between socio-economy and water resources,for the establishment of rational strategic planning of water resources,and for the social sustainable development of Beijing with scientific bases.     

GPS高程转换的神经元网络方法分析

GPS高程转换是GPS高程应用的关键问题之一，试图应用神经元网络方法来进行GPS高程的转换，并在网络的拓扑结构与网络结构的改进等方面作了分析，通过GPS高程转换的二次曲面法和神经元网络法进行了比较试验，结果表明了神经元网络转换GPS高程的可行性和可靠性，对于应用神经网络转换GPS高程具有实际的指导意义。