Global dust density in two-dimensional complex plasma

The driven-dissipative Langevin dynamics simulation is used to produce a two-dimensional(2D) dense cloud, which is composed of charged dust particles trapped in a quadratic potential. A 2D mesh grid is built to analyze the center-to-wall dust density. It is found that the local dust density in the outer region relative to that of the inner region is more nonuniform,being consistent with the feature of quadratic potential. The dependences of the global dust density on equilibrium temperature, particle size, confinement strength, and confinement shape are investigated. It is found that the particle size, the confinement strength, and the confinement shape strongly affect the global dust density, while the equilibrium temperature plays a minor effect on it. In the direction where there is a stronger confinement, the dust density gradient is bigger.

基于网格Grid技术和Spaces模型构建高校大学生利益诉求处理系统

大学生利益诉求体系的建设与健全是构建和谐校园的重要内容之一,将信息技术领域中的网格Grid技术和Spaces空间模型引入大学生利益诉求体系的构建,是对传统利益诉求体系建设的一次尝试与创新,以期不断健全完善大学生利益诉求表达渠道,提高大学生利益诉求系统的运作效率,提升利益诉求事件处理的成功率,培养学生的利益诉求主体意识,切实维护学生的权益。

Thermal Comfort Measurement and Landscape Reconstruction Strategy of Street Space Based on Decomposition Grid Method:A Case Study of Yangmeizhu Street

As an important public space in the city,street space is the second residence of people.Taking Yangmeizhu Street as the research object,this study established a street microclimate model in Beijing through microclimate measurement and simulation,and then calculated thermal comfort index of the street and evaluated thermal comfort of the street space and distribution model.The evaluation method used grid method to decompose and study and made several 10m×10m grids for inner space of the street,so as to compare deeply difference of microclimate environment in the street and analyze quantitatively relevance between street space elements(street pavement,street greening,building shadow coverage)and thermal comfort(physiological equivalent temperature PET)in the data.Finally,adaptive strategy of microclimate on street level was put forward to improve the environmental quality of public space in the old city by means of landscape design,aiming at creating a resilient and humanized street space and improving adaptability of microclimate and thermal comfort for living.

General decay of energy to a nonlinear viscoelastic two-dimensional beam

A viscoelastic beam in a two-dimensional space is considered with nonlinear tension. A boundary feedback is applied at the right boundary of the beam to suppress the undesirable vibration. The well-posedness of the problem is established. With the multiplier method, a uniform decay result is proven.

Influence and hazard of disastrous space weather on power grid in China

Based on the measured data of geomagnetically induced currents （GIC） in Guangdong Ling＇ ao 500 kV power networks during several magnetic storms at the peak years of 23rd Solar Cycle, the GIC calculation results of 750 kV planning power grid in Shartxi, Gansu, Qinghai and Ningxia, the structure and characteristics of power networks from 500 kV to 1 000 kV, and super magnetic storm in 1859 are analyzed in this paper. Through the analysis, the possible impacts of extreme space weather on the future ultra-high voltage （UHV） grid, the security of large-scale power system in China are expounded, and the research suggestions coping with the strong solar storms are proposed.

Power Control Based on State Space Strategies for Grid⁃Oriented Inverters with LCL Filters

Through a third⁃order mathematical model of grid⁃oriented LCL⁃type converters,this paper analyzes the complicated dynamic characteristics and resonance problems which may influence the system stability.To realize active damping for LCL filters and improve dynamic performance of current regulators,a state space current PI controller is proposed whose parameters can be tuned based on the polynomial equations approach.An extended state observer is integrated with the regulation scheme,where additional sensors are not necessary in contrast with conventional active damping strategies.Synchronous reference frame PLL(SRF⁃PLL)equipped with filter technology is proposed for grid voltage disturbance suppression.This method is then applied to establish a double⁃closed⁃loop power regulator that demonstrates improved performance compared with other controllers.The simulation results are displayed to illustrate the efficiency of the regulation methods.

GRID探测器的SiPM质子辐照研究

使用100 MeV质子对SensL MicroFJ-60035-TSV SiPM进行地面辐照实验,得到了SiPM漏电流增长与质子注量的关系,漏电流增长率为每片SiPM 3.98×10^(-7)μA·cm^(-2),并与其他文章的地面辐照实验结果进行对比,验证了结果一致性;实验结果与GRID-02载荷在轨漏电流增长进行对比,在量级上一致,增长斜率低约40%,进一步定量分析需要详细讨论空间在轨辐射环境的粒子能谱与类型。此外,实验中还设置了开偏压与关偏压两种测试条件,探究了工作电压对SiPM辐照损伤可能的影响。

时空网格(ST-GRID)移动对象数据库模型

有效的存储和查询数据库管理系统中的移动对象受到了大量的关注,有一些是针对管理移动对象动态改变信息的应用。在本文中,把时间和空间变换成时空网格模型(ST-GRJD),把移动对象的运动轨迹转换成时空网格上的折线,用这种存储结构来管理移动对象,并给出产生折线轨迹的RippleInsert算法及移动对象突然改变目的地的解决方案。

ARC/INFO GRID模块支持下的内蒙古土地利用与覆盖宏观空间结构分析

本文的研究中主要在遥感信息和ARC/INFOGISGRID模块支持下可视化分 析了2000年度内蒙古土地利用/覆盖在1km空间尺度下的宏观空间结构,有效地把握了各种 土地利用/覆盖类型的空间分布规律,在此基础上提出了基于宏观空间结构的内蒙古中西部草 原地区、内蒙古西部荒漠地区、东北部森林地区以及东部和南部农林牧交错地区的人类土地利 用模式。

Architecture Design of Global Distributed Storage System for Data Grid

This paper describes the architecture of global distributed storage system for data grid. It focue on the management and the capability for the maximum users and maximum resources on the Internet, as well as performance and other issues.

A flexible architecture for job management in a grid environment

Job management is a key issue in computational grids, and normally involves job definition, scheduling, executing and monitoring. However, job management in the existing grid middleware needs to be improved in terms of efficiency and flexibility. This paper addresses a flexible architecture for job management with detailed design and implementation. Frameworks for job scheduling and monitoring, as two important aspects, are also presented. The proposed job management has the advantages of reusability of job definition, flexible and automatic file operation, visual steering of file transfer and job execution, and adaptive application job scheduler. A job management wizard is designed to implement each step. Therefore, what the grid user needs to do is only to define the job by constructing necessary information at runtime. In addition, the job space is adopted to ensure the security of the job management. Experimental results showed that this approach is user-friendly and system efficient.

Grid-connected inverter for wind power generation system

In wind power generation system the grid-connected inverter is an important section for energy conversion and transmission, of which the performance has a direct influence on the entire wind power generation system. The mathematical model of the grid-connected inverter is deduced firstly. Then, the space vector pulse width modulation （SVPWM） is analyzed. The power factor can be controlled close to unity, leading or lagging, which is realized based on H-type current controller and grid voltage vector-oriented control. The control strategy is verified by the simulation and experimental results with a good sinusoidal current, a small harmonic component and a fast dynamic response.

Simulation method for measurement of the cross-section of the^(14)N(n,a)^(11)B reaction using a gridded ionization chamber

A simulation method for measurement of the cross-section of the^(14)N(n,a)^(11)B reaction with gas and solid samples using a gridded ionization chamber(GIC)has been established.Using the simulation,the experimental spectra of both^(14)N(n,a)^(11)B events and background from other reactions can be predicted,and the experimental scheme can be optimized.According to the simulation results,the optimal experimental parameters,including the pressure of the working gas and the compositions of the working gas and the sample,can be determined.In addition,the simulation results can be used to determine the valid event area and calculate the detection efficiency for valid events.A measurement of the cross-sections of the^(14)N(n,a)^(11)B reaction at E_(n)=4.25,4.50,4.75,5.00,5.25,and 5.50 MeV,based on the 4.5-MV Van de Graff accelerator at Peking University(PKU)using a GIC as the detector for the outgoing a particles,has been performed.The good agreement of the spectra from the simulation and experiment demonstrated the universality of this simulation method,which can be used to accurately measure neutroninduced light-charged particle emission reactions.

Arcinfo-Grid模块在三峡库区洪水预报系统中的应用

地理信息系统(Geographical Information System,简称GIS)是处理地理空间数据的信息系统,它集现实世界中对象的空间位置和人文经济信息的管理于一体.全面阐述了如何将Arcinfo软件的Grid模块应用到水利,进行洪水预报系统的开发.将地理信息系统与Grid模块的水文表面分析工具相结合,形成直观的流域环境显示,再通过计算、统计、分析,可获得精确的水文因子数据,为洪水预报系统提供快速、准确的实时流域参数.

Experimental Study on Optimal Layout of Grid Desilting Gallery

Based on the desilting research of one scheduling project in the southwest of China, the method of setting grid desilting gallery before the desilting tunnel is put forward to expand the scope of the scouring funnel before the dam and solve the problem of sediment deposition at the power station water intake. The experimental results show that, in the design of a grid desilting gallery, the width of the grid gallery should not be smaller than that of the desiring bottom intake, the size of the grid orifice should be in the range of 1.5 m--2.0 m along the flow direction, and the grid spacing should be 3--5 times the size of the grid orifice. The discharging ability of the desilting bottom intake will decrease after the grid desilting gallery is added. The average of the decrease rates is about 5%-10%. The scouring funnel draws in the longitudinal direction before the dam obviously after the construction of the grid desilting gallery.

Improved VSVPWM Modulation Method for Three-level NPC Inverter in Rural Power Grid

With the acceleration of agricultural electrification,a lot of nonlinear and shock loads appear in the rural power grid,and the resulting harmonic and reactive currents pollute the rural power grid more and more seriously.To solve the above problem,three-level neutral point clamped(NPC)inverters have been widely used,but their development is greatly restricted by the defect of neutral point voltage imbalance.In this paper,an improved virtual space vector pulse width modulation(VSVPWM)was proposed.Firstly,the mathematical models of various space vectors were established,and the influence of various space vectors on neutral point voltage was analyzed.The sum of the vector current at the neutral point was zero and the voltage control at the neutral point was completed by.introducing the time offset into different switching times of the redundant small vector.This method was simple in design and avoided the redundant calculation of the traditional VSVPWM method and tedious switch sequence design.This balancing control strategy could greatly reduce the influence of virtual vectors on neutral point voltage and effectively control the low-frequency oscillation of neutral point voltage.The validity of the method was verified by establishing a matlab simulation model.

Research of Sensitivity Encoding Reconstruction for MRI with Non-Cartesian K-Space Trajectories

The Sensitivity Encoding (SENSE) parallel reconstruction scheme for magnetic resonance imaging (MRI) is implemented with non-cartesian sampled k-space trajectories in this paper. SENSE has the special capability to reduce the scanning time for MRI experiments while maintaining the image resolution with under-sampling data sets. In this manner, it has become an increasingly popular technique for multiple MRI data acquisition and image reconstruction schemes. The gridding algorithm is also implemented with SENSE due to its ability in evaluating forward and adjoin operator with non-cartesian sampled data. In this paper, the sensitivity map profile, field map information and the spiral k-space data collected from an array of receiver coils are used to reconstruct unaliased images from under-sampled data. The performance of SENSE with real data set identifies the computational issues to be improved for researched.

基于space-oz思政网格化的高校意识形态责任制项目化落实研究

互联网技术方兴未艾,以"互联网+思政"思路塑造大学生思政工作网格化,构筑思政教育主体平台、内容、课堂、介体为一体的网格化体系,充分发挥"互联网+"独特的育人功效,发挥政治统领和主导作用,牢固占据高校意识形态主导权、话语权、统治权。发现问题,明确权责,整合资源,形成合力,推动高校思政工作和谐可持续发展。