浅谈中小企业如何引进和留住人才

作为资本有限的中小企业,不可能拿出大笔资金用于培训和招揽人才,但作为中小企业的经营者,在头脑中必须要有人才第一的观念,想尽一切办法去引进人才,留住人才,只有这样才能更好地适应新环境,促进新发展.     

Ponderomotive Forces in Cosmos

This review is devoted to ponderomotive forces and their importance for the acceleration of charged particles by electromagnetic waves in space plasmas. Ponderomotive forces constitute time-averaged nonlinear forces acting on a media in the presence of oscillating electromagnetic fields. Ponderomotive forces represent a useful analytical tool to describe plasma acceleration. Oscillating electromagnetic fields are also related with dissipative processes, such as heating of particles. Dissipative processes are, however, left outside these discussions. The focus will be entirely on the (conservative) ponderomotive forces acting in space plasmas. The review consists of seven sections. In Section 1, we explain the rational for using the auxiliary ponderomotive forces instead of the fundamental Lorentz force for the study of particle motions in oscillating fields. In Section 2, we present the Abraham, Miller, Lundin–Hultqvist and Barlow ponderomotive forces, and the Bolotovsky–Serov ponderomotive drift. The hydrodynamic, quasi-hydrodynamic, and ‘`test-particle’' approaches are used for the study of ponderomotive wave-particle interaction. The problems of self-consistency and regularization are discussed in Section 3. The model of static balance of forces (Section 4) exemplifies the interplay between thermal, gravitational and ponderomotive forces, but it also introduces a set of useful definitions, dimensionless parameters, etc. We analyze the Alfvén and ion cyclotron waves in static limit with emphasis on the specific distinction between traveling and standing waves. Particular attention has been given to the impact of traveling Alfvén waves on the steady state anabatic wind that blows over the polar regions (Section~5). We demonstrate the existence of a wave-induced cold anabatic wind. We also show that, at a critical point, the ponderomotive acceleration of the wind is a factor of 3 greater than the thermal acceleration. Section 6 demonstrates various manifestations of ponderomotive forces in the Earth's magnetosphere, for instance the ionospheric plasma acceleration and outflow. The polar wind and the auroral density cavities are considered in relation to results from the Freja and Viking satellites. The high-altitude energization and escape of ions is discussed. The ponderomotive anharmonicity of standing Alfvén waves is analyzed from ground based ULF wave measurements. The complexity of the many challenging problems related with plasma processes near the magnetospheric boundaries is discussed in the light of recent Cluster observations. At the end of Section 6, we consider the application of ponderomotive forces to the diversity of phenomena on the Sun, in the interstellar environment, on newborn stars, pulsars and active galaxies. We emphasize the role of forcing of magnetized plasmas in general and ponderomotive forcing in particular, presenting some simple conceivable scenarios for massive outflow and jets from astrophysical objects.     

Calculation of the effect of opacity in the solar spectral lines of carbon ions

In this paper, using the intensity ratio of carbon ions emission lines, we determined the optical depths at the line center of the CI at about 165.7 nm, CII at about 133.5 nm, CIII at about 117.5 nm and CIV at about 154.9 nm emission lines by escape factor treatment. For CI and CII emission lines, we discuss the intensity ratio of two lines arising from the common upper levels; while for CIII and CIV emission lines, we discuss the intensity ratio of two lines arising from the common lower levels. By introducing the measured abundance of carbon and the results of ionization balance calculations, we make an estimate of the line-of-sight physical thickness of the regions of carbon ions. This discussion will provide some results in the discussion of opacity on the solar ultraviolet (UV) or extreme-ultraviolet (EUV) spectrum.     

电荷交换离子对栅极系统束流影响的数值研究

采用二维网格质点法(PIC)计算离子在离子发动机栅极系统中的运动, 通过在模型中添加离子和中性粒子电荷交换的Monte Carlo碰撞模块, 得到了电荷交换离子在栅极周围的分布及电荷交换离子的运动规律.计算结果表明:考虑电荷交换离子后, 屏栅极电流较不考虑电荷交换离子情况时增大了1.42%, 所受影响不大, 加速栅极电流由0增大到主束流电流的1.41%.模拟结果表明:加速栅极下游较远处产生的电荷交换离子, 是造成加速栅极下游面腐蚀及加速栅极电流的主要原因.      

An update about recent developments of the PHITS code

PHITS (Particle and Heavy-Ion Transport code System) is a general-purpose three-dimensional Monte Carlo code, developed and maintained by RIST, JAEA and KEK in Japan together with Sihver et al. at Chalmers in Sweden. PHITS can deal with the transports of all varieties of hadrons and heavy ions with energies up to around 100 GeV/nucleon, and in this paper the current status of PHITS is presented. We introduce a relativistically covariant version of JQMD, called R-JQMD, that features an improved ground state initialization algorithm, and we will present the introduction of electron and photon transport in PHITS using EGS5, which have increased the energy region for the photon and energy transport from up to around 3 GeV to up to several hundred GeV depending on the atomic number of the target. We show how the accuracy in dose and fluence calculations can be improved by using tabulated cross sections. Benchmarking of shielding and irradiation effects of high energy protons in different materials relevant for shielding of accelerator facilities is also presented. In particular, we show that PHITS can be used for estimating the dose received by aircrews and personnel in space. In recent years, many countries have issued regulations or recommendations to set annual dose limitations for aircrews. Since estimation of cosmic-ray spectra in the atmosphere is an essential issue for the evaluation of aviation doses, we have calculated these spectra using PHITS. The accuracy of the atmospheric propagation simulation of cosmic-ray performed by PHITS has been well verified by experimental cosmic-ray spectra taken under various conditions. Based on a comprehensive analysis of the simulation results, an analytical model called “PARMA” has been proposed for instantaneously estimating the atmospheric cosmic-ray spectra below the altitude of 20 km. We have also performed preliminary simulations of long-term dose distribution measurements at the ISS performed with the joint ESA-FSA experiment MATROSHKA-R (MTR-R) led by the Russian Federation Institute of Biomedical Problems (IMBP) and the ESA supported experiment MATROSHKA (MTR), led by the German Aerospace Center (DLR). For the purpose of examining the applicability of PHITS to the shielding design in space, the absorbed doses in a tissue equivalent water phantom inside an imaginary space vessel has been estimated for different shielding materials of different thicknesses. The results confirm previous results which indicate that PHITS is a suitable tool when performing shielding design studies of spacecrafts.     

高能重离子径迹结构对单粒子翻转的影响

利用解析法计算了高能重离子的径迹结构,通过MonteCarlo方法研究了径迹结构对微电子芯片单粒子翻转的影响.结果表明,考虑了径迹结构的影响后,当离子能量较高时,具有小尺寸灵敏单元、低翻转阈值的芯片的翻转截面较传统的LET描述结果小许多;当离子更重时,这种差别对灵敏单元尺寸较大、翻转阈值较高的芯片也变得较明显.即离子径迹结构的影响是通过其有效地沉积到灵敏单元中的能量与翻转阈值相比较而表现出来的.还研究了作用距离较深、结构宽大的径迹造成的相邻多个灵敏单元的同时翻转,即多位翻转现象,这是用LET所不能反映的.      

Radiative transitions in few-electron quasi-molecules

The review is aimed at the discussion of recent results on spectral profiles produced in collisions of few-electron atoms/ions. Calculations of spectral profiles produced by atom/ion collisions need some preliminary quantum-chemical information such as potential energy surfaces, dipole transition moments, etc. The main advantage of few-electron systems is that all input data can be obtained ab initio or analytically, thus the profiles calculated do not include any fit parameters. Two specific examples have been discussed. The first one deals with radiative transitions accompanying charge-exchange in collisions of one-electron ions with bare nuclei. The second example concerns radiative transitions produced by H⁻ + H collisions.     

太阳极区低日冕重离子的回旋波加热机制

采用电子、质子、氦核和另外一种微量离子代替氧离子的4组元模型分别计算了Fe^11 ,Mg^9 ,Mg^7 ,Ne^7 和Si^7 等微量离子的漂移速度和温度，并和SUMER的观测结果进行了比较。     

Pickup Ions and Cosmic Rays from Dust in the Heliosphere

The combination of recent observational and theoretical work has completed the catalog of the sources of heliospheric Pickup Ions (PUIs). These PUIs are the seed population for Anomalous Cosmic Rays (ACRs), which are accelerated to high energies at or beyond the Termination Shock (TS). For elements with high First Ionization Potentials (high-FIP atoms: e.g., H, He, Ne, etc.), the dominant source of PUIs and ACRs is from neutral atoms that drift into the heliosphere from the Local Interstellar Medium (LISM) and, prior to ionization, are influenced primarily by solar gravitation and radiation pressure (for H). After ionization, these interstellar ions are pickup up by the solar wind, swept out, and are either accelerated near the TS or beyond it. Elements with low first ionization potentials (low-FIP atoms: e.g., C, Si, Mg, Fe, etc.) are also observed as PUIs by Ulysses and as ACRs by Wind and Voyager. But the low-FIP composition of this additional component reveals a very different origin. Low-FIP interstellar atoms are predominantly ionized in the LISM and therefore excluded from the heliosphere by the solar wind. Remarkably, a low-FIP component of PUIs was hypothesized by Banks (J. Geophys. Res. 76, 4341, 1971) over twenty years prior to its direct detection by Ulysses/SWICS (Geiss et al., J. Geophys. Res. 100(23), 373, 1995) The leading concept for the generation of Inner Source PUIs involves an effective recycling of solar wind on grains near the Sun, as originally suggested by Banks. Voyager and Wind also observe low-FIP ACRs, and a grain-related source appears likely and necessary. Two concepts have been proposed to explain these low-FIP ACRs: the first concept involves the acceleration of the Inner Source of PUIs, and the second involves a so-called Outer Source of PUIs generated from solar wind interaction with the large population of grains in the Kuiper Belt. We review here the observational and theoretical work over the last decade that shows how solar wind and heliospheric grains interact to produce pickup ions, and, in turn, anomalous cosmic rays. The inner and outer sources of pickup ions and anomalous cosmic rays exemplify dusty plasma interactions that are fundamental throughout the cosmos for the production of energetic particles and the formation of stellar systems.     

The extension of the INCL model for simulation of shielding in space

Radiation hazard for space missions is mainly due to cosmic ray protons, helium nuclei and light ions, whose energy spectrum is maximum around 1 GeV per nucleon but remains non-negligible for energies up to 15 GeV per nucleon. Nuclear reactions induced by high energy protons are often described by intranuclear cascade plus evaporation models. The attention is focused here on the Liège Intranuclear Cascade model (INCL), which has been shown to reproduce fairly well a great deal of experimental data for nucleon-induced reactions in the 200 MeV to 2 GeV range, when coupled with the ABLA evaporation-fission code. In order to extend the model to other conditions relevant for space radiation, three improvements of INCL are under development. They are reported on here. First, the reaction model has been extended to nucleon–nucleus reactions at incident energies up to 15 GeV, mainly by the inclusion of additional pion production channels in nucleon–nucleon collisions during the cascade. Second, a coalescence mechanism for the emission of light charged particles has been implemented recently. Finally, the model has been modified in order to accommodate light ions as projectiles. First results are shown and compared with illustrative experimental data. Implications for issues concerning radiation protection in space are discussed.