Spatial structure and energy spectrum of ion beams studied with CN detectors within a small PF device

The paper reports the application of Solid-State Nuclear Track Detectors to study the pulsed plasma-ion streams emitted from plasma-focus (PF) type discharges, which were performed within a low-energy PACO device constructed at Instituto de Fisica Arroyo Seco. The PACO device was operated under static initial gas conditions or with dynamic gas puffing. Studies of the structure of the fast deuteron beams were carried out within an energy range from 80 keV to about 2 MeV. Studies of ion energy and an ion angular distribution were also performed. The measurements showed that the fast deuterons are emitted in many “narrow” micro-beams, as in other larger PF devices. The anisotropy of the deuteron angular distribution was explained by the stochastic character of the formation of local ion sources within the PF discharge column.     

NUMERICAL LOCALIZATION OF ELECTROMAGNETIC IMPERFECTIONS FROM A PERTURBATION FORMULA IN THREE DIMENSIONS

This work deals with the numerical localization of small electromagnetic inhomogeneities. The underlying inverse problem considers, in a three-dimensional bounded domain, the time-harmonic Maxwell equations formulated in electric field. Typically, the domain contains a finite number of unknown inhomogeneities of small volume and the inverse problem attempts to localize these inhomogeneities from a finite number of boundary measurements. Our localization approach is based on a recent framework that uses an asymptotic expansion for the perturbations in the tangential boundary trace of the curl of the electric field. We present three numerical localization procedures resulting from the combination of this asymptotic expansion with each of the following inversion algorithms： the Current Projection method, the MUltiple Signal Classification （MUSIC） algorithm, and an Inverse Fourier method. We perform a numerical study of the asymptotic expansion and compare the numerical results obtained from the three localization procedures in different settings.     

Straightness Measurement Using Laser Diode and CCD Camera

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Direct synthesis, crystal structure and thermal analyses of 2-nitroterephthalate and carbohydrazide bridged staircase-like 3D packing grids of lead(II)

X-ray single crystal diffraction demonstrates that in {[Pb₂(HNTP)₂(NTP)(CHZ)(H₂O)₂] · 2.5H₂O} _n (polymer, NTP = nitroterephthalate, CHZ = carbohydrazide), there are two kinds of Pb centers. By means of the bridging ligands–two water, two CHZ and two NTP molecules, four Pb centers (two Pb1 and two Pb2) are joined together to form the rectangular grid, and by the intense static electric interactions among the two O atoms of nitro groups in NTP, the extending two-dimensional grids are linked together to form the three-dimensional frameworks. Thermal analyses DSC and TG-DTG have been performed on the polymer to study its thermal decomposition mechanism and thermal kinetic properties. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Steady-state solutions in a three-dimensional nonlinear pool-boiling heat-transfer model

We consider a relatively simple model for pool-boiling processes. This model involves only the temperature distribution within the heater and describes the heat exchange with the boiling medium via a nonlinear boundary condition imposed on the fluid-heater interface. This results in a standard heat-transfer problem with a nonlinear Neumann boundary condition on part of the boundary. In a recent paper [Speetjens M, Reusken A, Marquardt W. Steady-state solutions in a nonlinear pool-boiling model. IGPM report 256, RWTH Aachen. Commun Nonlinear Sci Numer Simul, in press, doi:10.1016/j.cnsns.2006.11.002] we analysed this nonlinear heat-transfer problem for the case of two space dimensions and in particular studied the qualitative structure of steady-state solutions. The study revealed that, depending on system parameters, the model allows both multiple homogeneous and multiple heterogeneous temperature distributions on the fluid-heater interface. In the present paper we show that the analysis from Speetjens et al. (doi:10.1016/j.cnsns.2006.11.002) can be generalised to the physically more realistic case of three space dimensions. A fundamental shift-invariance property is derived that implies multiplicity of heterogeneous solutions. We present a numerical bifurcation analysis that demonstrates the multiple solution structure in this mathematical model by way of a representative case study.     

Three-dimensional radiative transfer in an isotropically scattering, plane-parallel medium: generalized X- and Y-functions

The topic of this work is the generalized X- and Y-functions of multidimensional radiative transfer. The physical problem considered is spatially varying, collimated radiation incident on the upper boundary of an isotropically scattering, plane-parallel medium. An integral transform is used to reduce the three-dimensional transport equation to a one-dimensional form, and a modified Ambarzumian's method is used to derive coupled, integro-differential equations for the source functions at the boundaries of the medium. The resulting equations are said to be in double-integral form because the integration is over both angular variables. Numerical results are presented to illustrate the computational characteristics of the formulation.     

一种新型面阵CCD航天立体摄影测量光学系统

采用一台大面阵CCD和广角摄影物镜的组合，研制成功一种新型的单面阵CCD航天立体摄影测量系统.该系统焦距为23.3 mm;视场角为40°;在空间分辨率为36 lp/mm时，MTF均值达到0.8以上;光谱适应范围为0.5 μm~0.75 μm.和国内外常用的三线阵CCD遥感立体测量相机相比，本系统结构更简单、体积更小，重量更轻，更加适用于航天遥感应用环境.     

软X射线条纹相机用于激光等离子体辐射温度的测量方法

本文提出了软X射线条纹相机与吸收膜相耦合测量等离子体温度的实验原理与方法,编制了数值计算程序SCC,给出了平面金靶在1.06μm激光(LF—II~=激光装置)作用下,靶面功率密度约10~(14)W/cm~2的辐射温度。并对温度处理中存在的误差,以及把此方法推广到能谱的时间分辨和温度的空间分辨测量中的可能性进行了讨论。     

Numerical simulation of the horizontal Bridgman growth. Part II: Three-dimensional flow

We study the steady-state three-dimensional flow which occurs in a horizontal crucible of molten metal under the action of a horizontal temperature gradient. The geometry and the boundary conditions are similar to those encountered in the Bridgman growth process of semiconductor crystals. We find that three-dimensional effects can have a dramatic influence upon the flow, which, before the onset of periodic disturbances, differs appreciably from its two-dimensional counterpart. We also investigate the sensitivity of the flow to non-symmetric disturbances.     

溶蚀岩体三维随机洞体数学模型的设计

溶蚀岩体是地质体中一种特定的岩体 ,它在水流等自然因素作用下 ,生成了许多溶蚀洞体 ,本文首先对作为其载体的三维地质体进行数学描述和显示 ,然后对如何确定椭球洞体形状和大小、复杂洞体的生成、三维随机洞体的数学模型以及确定性洞体的数学描述和计算机显示进行了详尽的阐述。本文提出的溶蚀岩体三维随机洞体的数学模型为溶蚀岩体的溶蚀率和渗透特性的研究提供了可视化手段 ,能够有力地指导溶蚀岩体三维随机洞体的计算机显示的编程实践