Effect of Surface Condition of Electrode on the Surface Melting of Material by Laser-Guided Micro-Arc Discharge

This paper studies the surface melting in the atmosphere by YAG laser-guided micro-arc discharge. In three kinds of surface conditions (free, oiled, and polyethylene covered), we try to control the diameter and the power density of discharge pit. It is found that the power density of 3 x 10(6) W/cm(2) of discharge pit on the oiled surface is moderate to form the melted layer thicker than that of the others, adapting to strengthen the surface of material, and the power density of 1.07 x 10(7) W/cm(2) of discharge pit on the polyethylene-covered surface is highest to form the deepest discharge pit among them, adapting to remove the material.

El optimismo metafísico en la escatología de San Ireneo

Resumen: Mucho antes de que San Agustín y Santo Tomás afirmaran que las cosas son buenas por el mero hecho de ser, ya en el siglo II de nuestra era Ireneo expresaba su confianza en la bondad fundamental de la materia. En los últimos seis capítulos del Adversus haereses (V, 31-36), el Obispo de Lyon plantea una verdadera teología de la historia que tiene como centro al hombre plasmado por Dios y llamado a su plenificación definitiva en la temporalidad y en el mismo mundo que lo vio caer. Al describir este tramo final y decisivo de la experiencia humana en la historia, nuestro autor nos revela su peculiar concepción del tiempo a la par que despliega un realismo escatológico totalmente opuesto al gnosticismo espiritualista de la época, que consideraba todo lo material como proveniente del error y la defección. A su vez, esta concepción de Ireneo supera tanto a los milenarismos ingenuos de su tiempo como a las utopías posteriores, en que el realismo escatológico es trocado en escatologismo radical. Se trata, en definitiva, de un optimismo metafísico propio de la visión cristiana que resultó novedoso para el ambiente espiritual de la época en que se gestó y que alienta a una prometedora relación del hombre con la naturaleza, ya sea desde la perspectiva del trabajo humano como fuerza transformadora de la misma, o desde un enfoque ecológico sin compromiso con posturas extremas, tales como el panteísmo o la explotación y sojuzgamiento brutal de los recursos naturales.

Observation and modeling for terrestrial processes in alpine meadow

The water-heat transfer process between land and atmosphere in Haibei alpine meadow area has been systematically observed. A multi-layer coupling model for land-atmosphere interaction was presented with special attention paid to the moisture transfer in leaf stomata under unsaturated condition. A profound investigation on the physical process of turbulent transfer inside the vegetation has been performed with a revised formula of water absorption for root system. The present model facilitates the study of vertically distributed physical variables in detail. Numerical simulation was conducted according to the transfer process of Kinesia humility meadow in the area of Haibei Alpine Meadow Ecosystem Station, CAS. The calculated results agree well with observation.

Growth of liquid bridge in AFM

Capillary forces are dominant in adhesive forces measured with an atomic force microscope (AFM) in ambient air, which are thought to be dependent on water film thickness, relative humidity and the free energy of the water film. In this paper, besides these factors, we study the nature of the 'pull-off' force on a variety of atmospheres as a function of the contact time. It is found that capillary forces strongly depend on the contact time. In lower relative humidity atmosphere, the adhesion force is almost independent of the contact time. However, in higher relative humidity, the adhesion force increases with the contact time. Based on the experiment and a model that we present in this paper, the growth of the liquid bridge can be seen as undergoing two processes: one is water vapour condensation; the other is the motion of the thin liquid film that is absorbed on the substrate. The experiment and the growth model presented in this paper have direct relevance to the working mechanism of AFM in ambient air.

Experiment on the thermocapillary convection of a mercury liquid bridge in a floating half zone

A liquid bridge of a floating half zone consisting of liquid mercury sealed in a glass tube with nitrogen atmosphere was used for the experiment of thermocapillary convection with a low Prandtl number liquid. A non-contacted diagnostic method was developed to monitor the surface flow and the surface oscillation. A growing surface film (or skin) is a crucial source to suppress thermocapillary convection, and is discussed in this paper. For the case of a mercury Liquid bridge, the critical Marangoni number was obtained as 900, and the oscillatory frequency was around 5 Hz.

Air flow over a mountain and the convective boundary-layer

In this paper, the analytical model coupling the convective boundary layer (CBL) with the free atmosphere developed by Qi and Fu (1992) is improved. And by this improved model, the interaction between airflow over a mountain and the CBL is further discussed. The conclusions demonstrate: (1) The perturbation potential temperatures in the free atmosphere can counteract the effect of orographic thermal forcing through entraining and mixing in the CBL. If u(M)BAR > u(F)BAR, the feedback of the perturbation potential temperatures in the free atmosphere is more important than orographic thermal forcing, which promotes the effect of interfacial waves. If u(M)BAR < u(F)BAR, orographic thermal forcing is more important, which makes the interfacial height and the topographic height identical in phase, and the horizontal speeds are a maximum at the top of the mountain. (2) The internal gravity waves propagating vertically in the free atmosphere cause a strong downslope wind to become established above the lee slope in the CBL and result in the hydraulic jump at the top of the CBL. (3) With the CBL deepening, the interfacial gravity waves induced by the potential temperature jump at the top of the CBL cause the airflow in the CBL to be subcritical.

Equilibrium of isolated magnetostatic flux structure

Two-dimensional magnetostatic models of flux structure confined in stratified atmosphere are discussed in the present paper. The magnetic field in the flux structure is assumed to be force-free at the first step. Numerical solutions for this nonlinear free boundary problem are obtained by finite element method. Results show clearly the relation between the inside fields and outside pressure, especially the influence of atmospheric pressure distribution on the flux structure.

Magnetostatic configuration of a confined magnetic-flux tube

In this paper an isolated magnetic flux tube confined in stratified atmosphere is studied for slender and axisymmetric model. The functions of the pressure, density, and temperature are expanded as a Taylor series of magnetic surface function psi. Several models of an isolated magnetic flux tube confined in a stratified atmosphere are constructed, and the external pressure of the stratified atmosphere decreases reasonably with increasing height. The distribution of thermal dynamic quantities and the magnetic pressure in the flux tube are also obtained.

The progress of solar-terrestrial sciences in china

 SOLAR-TERRESTRIAL SCIENCESThe solar-terrestrial sciences study how the solar energy, momentum and mass transfer through the interplanetary space, the earth magnetosphere, the ionosphere and the neutral atmosphere, and their influence on earth environment. The solar-terrestrial sciences are also called, sometimes, the solar-terrestrial physics, solar-terrestrial relations, solar-terrestrial 更多还原

A ground hydrologic model with inclusion of a layer of vegetation canopy that can interact with general-circulation model

In this paper, a ground hydrologic model(GHM) is presented in which the vapor, heat and momentum exchanges between ground surface covers (including vegetation canopy) and atmosphere is described more realistically. The model is used to simulate three sets of field data and results from the numerical simulation agree with the field data well. GHM has been tested using input data generated by general circulation model (GCM) runs for both the North American regions and the Chinese regions, The results from GHM are quite different from those of GHMs in GCMs. It shows that a more active concerted effort on the land surface process study to provide a physically realistic GHM for predicting the exchange between land and atmosphere is important and necessary.

The mechanism of energy storage by shearing the solar magnetic field

In this paper, a complete set of MHD equations have been solved by numerical calculations in an attempt to study the dynamical evolutionary processes of the initial equilibrium configuration and to discuss the energy storage mechanism of the solar atmosphere by shearing the magnetic field. The initial equilibrium configuration with an arch bipolar potential field obtained from the numerical solution is similar to the configuration in the vicinity of typical solar flare before its eruption. From the magnetic induction equation in the set of MHD equations and dealing with the non-linear coupling effects between the flow field and magnetic field, the quantitative relationship has been derived for their dynamical evolution. Results show that plasma shear motion at the bottom of the solar atmosphere causes the magnetic field to shear; meanwhile the magnetic field energy is stored in local regions. With the increase of time the local magnetic energy increases and it may reach an order of 4×10^25 J during a day. Thus the local storage of magnetic energy is large enough to trigger a big solar flare and can be considered as the energy source of solar flares. The energy storage mechanism by shearing the magnetic field can well explain the slow changes in solar active regions.

A consistent model of isolated force-free magnetic arches

The magnetic flux tube concentrating strong magnetic field is the basic configuration of magneticfield in the solar atmosphere. In the present paper, the equilibrium of isolated magnetic flux tube inthe solar atmosphere is discussed. In the viewpoint of mathematics, the boundary condition is nonlinearand the position of boundary needs to be determined by the physical condition although the equation ofmagnetic potential is linear for the linear force-free field. Analytical solutions to the arches of bothuniform circular cross-section and non-uniform cross section have been obtained. The results show thatthe nonlinear problem may have or not have any solution according to different azimuthal components of the magnetic field; the number of solutions to the nonlinear problem is four at most, and two in some cases. In the present paper, the analytical solutions to the approximations of both fat and slender arches are given in detail, and the general features of magnetic arch structure are shown.

高寒草甸生态系统陆地生物圈模式研究及应用

改进了适合于高寒草甸生态系统的陆地生态圈模式，分析了模式中温度变化与水分运动分层的物理原因，说明了气候状况对地表面能量交换的影响，给出了净辐射和蒸散量新的计算方法，提出了有很差分计算中具有二阶精度的Euler隐式格式，介绍了中国科学院海北高寒草甸生态站的气候概况和野外观测情况。最后利用本模式对高寒草甸生态站地区的土壤-植被-大气间水热交换过程进行了数值模拟，模拟值与实测值吻合较好。

考虑生物结皮影响的陆气湍流模式研究

在以前工作基础上，针对腾格里沙漠人工植被区陆气水热传输过程，提出了一个多层陆气耦合模式。特别给出了导水率的计算模型和修正后的根系吸水模式，考虑了结皮层对土壤水分入渗的影响以及植被演化的过程。陆面过程耦合模式分别对大气、植被、土壤作多层划分，以助于细致了解沿度分布的各物理量。同时，利用本模式对中国科学院沙坡头沙漠站人工植被区陆气水热交换过程进行了数值模拟，模拟结果与实测值吻合较好，可为当地合理利用水热资源和沙漠治理提供科学依据。

含尘大气近地层流底层流动特性及其摩阻系数

采用双向耦合的双流体模型，了大气悬浮沙尘的存在对大气边界层中流底层流动特性及摩阻系数的影响，计算并讨论了不同沙尘含量下含尘大气相对于无尘大气摩阻系数的变化，结果表明，摩阻系数的变化取决于悬浮沙尘的初始运动状态和质量载荷率。