北斗GEO卫星广播星历的直接拟合算法研究

针对因北斗地球静止轨道(GEO)卫星的小倾角特性,经典全球卫星定位系统(GPS)广播星历拟合算法不能直接应用于北斗GEO卫星这一问题,提出了一种基于无奇点变换的北斗GEO卫星广播星历直接拟合算法.该算法采用一组无奇点轨道根数代替经典轨道根数,解决了由GEO轨道的小倾角特性引起的经典广播星历拟合过程中法化矩阵奇异的问题;同时,避免了接收机GEO广播星历参数用户算法中坐标旋转的过程,减少了GEO用户算法的计算步骤.经仿真验证:该算法可很好地适用于北斗GEO卫星广播星历拟合,且拟合精度高,完全满足接收机导航定位的精度.但对于圆地球轨道(MEO)和倾斜地球同步轨道(IGSO)卫星,该算法实用性较差,仍须进一步研究和改进.     

基于数据库的教务信息化管理的开发和应用

随着计算机及其应用软件的发展,教务信息化管理能够减轻学校和教务管理部门的压力,已经越来越得到重视。教务管理的对象主要是大批量的信息,例如:学生成绩、师生的个人信息、课程信息等等,这就需要一个能够对大批量的信息进行有效管理的工具。在计算机系统中,数据库就是这样一个工具。基于数据库的教务信息化管理是借助数据库创建、数据库访问、数据库存储和界面开发等技术在计算机上建立教务管理的数据库应用系统。     

Visualization of the complex structure and stress field inside rock by means of 3D printing technology

Accurate characterization and visualization of the complex inner structure and stress distribution of rocks are of vital significance to solve a variety of underground engineering problems. In this paper, we incorporate several advanced technologies, such as CT scan, three-dimensional（3D） reconstruction, and 3D printing, to produce a physical model representing the natural coal rock that inherently contains complex fractures or joints. We employ 3D frozen stress and photoelastic technologies to characterize and visualize the stress distribution within the fractured rock under uniaxial compression. The 3D printed model presents the fracture structures identical to those of the natural prototype. The mechanical properties of the printed model,including uniaxial compression strength, elastic modulus,and Poisson’s ratio, are testified to be similar to those of the prototype coal rock. The frozen stress and photoelastic tests show that the location of stress concentration and the stress gradient around the discontinuous fractures are in good agreement with the numerical predictions of the real coalsample. The proposed method appears to be capable of visually quantifying the influences of discontinuous,irregular fractures on the strength, deformation, and stress concentration of coal rock. The method of incorporating3 D printing and frozen stress technologies shows a promising way to quantify and visualize the complex fracture structures and their influences on 3D stress distribution of underground rocks, which can also be used to verify numerical simulations.     

风电场向孤岛输电的VSC-HVDC Light的建模与仿真

介绍了以VSC控制为基础的HVDC Light的系统结构和工作原理,在MATLAB中创建了风电场向孤岛输电的VSC-HVDC Light系统仿真模型,并对其进行了稳态仿真研究.对仿真结果进行分析可知,系统直流电压基本稳定在给定的电压值,两端直流电压实现了协调配合,有功功率实现了协调控制和自动平衡传输,各状态量都符合理论值,模型准确模拟出了VSC-HVDC Light系统的稳态工作状况,为实际工程提供了科学的理论依据.     

Parallel scheduling strategy of web-based spatial computing tasks in multi-core environment

In order to improve the concurrent access performance of the web-based spatial computing system in cluster,a parallel scheduling strategy based on the multi-core environment is proposed,which includes two levels of parallel processing mechanisms.One is that it can evenly allocate tasks to each server node in the cluster and the other is that it can implement the load balancing inside a server node.Based on the strategy,a new web-based spatial computing model is designed in this paper,in which,a task response ratio calculation method,a request queue buffer mechanism and a thread scheduling strategy are focused on.Experimental results show that the new model can fully use the multi-core computing advantage of each server node in the concurrent access environment and improve the average hits per second,average I/O Hits,CPU utilization and throughput.Using speed-up ratio to analyze the traditional model and the new one,the result shows that the new model has the best performance.The performance of the multi-core server nodes in the cluster is optimized; the resource utilization and the parallel processing capabilities are enhanced.The more CPU cores you have,the higher parallel processing capabilities will be obtained.     

二机流水作业带不可用区间、工件可拒绝的调度问题

考虑了二机流水作业第一台机器带不可用区间、工件可拒绝的调度问题.所有的工件都是加工可中断的,即当某一工件在不可用区间出现之前开始加工但在机器不可用时并未加工完成,在不可用区间结束后可以接着加工.目标函数是最小化接受加工工件的最大完工时间与拒绝工件的惩罚之和.此问题是NP-难的.首先提出了一个动态规划的最优算法以求解小规模问题,并给出了数值计算实例.所提出的动态规划算法的运算时间随着问题的规模成指数增长,进而又提出了一个启发式算法,并证明了该启发式算法的最坏性能比是3.     

基于DEA模型的中原城市群城市效率研究

运用数据包络分析方法,对2012年中原城市群9个城市的城市效率进行定量研究.结果表明:郑州、洛阳和济源的城市效率达到最优,处于高水平阶段;平顶山、新乡的城市效率均在0.90以上,城市效率水平较高;漯河、许昌的城市效率水平处于中等;开封和焦作的城市效率则位于低水平阶段.通过对各市的投入产出分析发现,郑州、洛阳、济源3个城市的资源投入量和产出量为合理值,而平顶山、新乡、漯河、许昌、开封和焦作均存在不同程度的投入冗余现象.     

偏序内P-集合模型及其特征

利用层次内P-集合理论,研究层次内P-集合基于依赖关系偏序性质,研究层次内P-集合元素间的关系以及普通P-集合与层次P-集合的关系.层次P-集合是普通P-集合的扩展,提供了多角度、多层次分析和研究问题的方法.     

一类分数阶微分方程边值问题正解的存在性

研究了一类分数阶微分方程的边值问题:{Dα0+u(t)+f(u(t))=0,u(0)=0,u(1)=0,其中α(1α2)是实数,Dα0+是标准的Riemann-Liouville微分,f:[0,+∞)→[0,+∞)连续,t∈[0,1].利用范数形式的锥拉伸与锥压缩不动点定理,在满足适当的条件下,证明了该边值问题正解的存在性.     

地理科学背景下的全球导航卫星系统教学探索

全球导航卫星系统是由多学科相互渗透而形成的一门科学.该课程涉及内容众多,需要较多先修课程与基础知识,是一门理论性和实践性都很强的课程.对于非测绘专业而言,欲在先修课程严重不足、而学时紧张情况下取得较好的教学效果极具挑战性.作者在多年的教学实践中,对该课程的教学内容、教学手段、实践教学以及考核体系进行了一些有益的探索,取得了较好的效果.