利用广义诺顿定理调整输电线路参数不对称性的方法

为了降低高压输电线路上的不对称电压,维持电网的稳定运行,提出基于三相高压输电线路的诺顿等值电路.将不对称的线路参数看作诺顿等值电路的等效导纳,通过调节末端变电站中静止无功补偿设备的投切量,使其端口电压接近三相对称,从而达到降低线路上不对称电压的目的.理论计算结果及Matlab仿真分析表明,该方法可以使得线路末端电压的不平衡度降到最低,从而改善整条线路的不对称状况.     

单管放大电路输出电阻教学方法探讨

输出电阻是单管放大器的一个主要参数,在教学中一般用电压源模型进行定义,用外加电源法求解,学生容易产生困惑.本文用电流源模型定义输出电阻,提出了"诺顿加替代"法用于输出电阻求解,得到了物理意义明确的输出电阻.并根据三极管的等效简化模型,对射极偏置放大器的外加电源求解输出电阻的方法进行了分析.     

A front-tracking method with projected interface conditions for compressible multi-fluid flows

A front-tracking method for compressible multi-fluid flows is presented, where marker points are used both for tracking fluid interfaces and also for constructing the Riemann problem on the interfaces. The Riemann problem between the two fluid phases (defined in the interface normal direction) is solved using the exact Riemann solver on the marker points. The solutions are projected onto fixed grid points and then extrapolated into the corresponding ghost-fluid regions, to be used as boundary conditions. Each fluid phase is solved separately as in the ghost-fluid method. The proposed procedures, especially the projection of the exact Riemann solutions onto the fluid grids, are designed to be simple and consistent in any spatial dimensions. Several multi-fluid problems, including the breakup of a water cylinder induced by the passage of a shock wave were computed in order to demonstrate the capability of the proposed method.     

Comparison of wipe materials and wetting agents for pesticide residue collection from hard surfaces

Different wipe materials and wetting agents have been used to collect pesticide residues from surfaces, but little is known about their comparability. To inform the selection of a wipe for the National Children's Study, the analytical feasibility, collection efficiency, and precision of Twillwipes wetted with isopropanol (TI), Ghost Wipes (GW), and Twillwipes wetted with water (TW), were evaluated. Wipe samples were collected from stainless steel surfaces spiked with high and low concentrations of 27 insecticides, including organochlorines, organophosphates, and pyrethroids. Samples were analyzed by GC/MS/SIM. No analytical interferences were observed for any of the wipes. The mean percent collection efficiencies across all pesticides for the TI, GW, and TW were 69.3%, 31.1%, and 10.3% at the high concentration, respectively, and 55.6%, 22.5%, and 6.9% at the low concentration, respectively. The collection efficiencies of the TI were significantly greater than that of GW or TW (p < 0.0001). Collection efficiency also differed significantly by pesticide (p < 0.0001) and spike concentration (p < 0.0001). The pooled coefficients of variation (CVs) of the collection efficiencies for the TI, GW, and TW at high concentration were 0.08, 0.17, and 0.24, respectively. The pooled CV of the collection efficiencies for the TI, GW, and TW at low concentration were 0.15, 0.19, and 0.36, respectively. The TI had significantly lower CVs than either of the other two wipes (p = 0.0008). Though the TI was superior in terms of both accuracy and precision, it requires multiple preparation steps, which could lead to operational challenges in a large-scale study.     

针对Ghost还原的木马隐蔽驻留技术研究

Ghost还原系统已经被广泛应用于计算机的系统还原,该技术在使用方便的同时,也存在着安全隐患。文中首先介绍了Ghost映像文件的格式,并阐述其解析的过程和原理。然后在此基础上引出针对Ghost还原系统映像的木马隐蔽驻留技术,并剖析了所实现的Ghost映像文件穿越的命令行工具。该工具读取解析Ghost映像文件,然后往其中写入后门文件来实现木马的隐蔽驻留。最后提出了如何预防和检测利用该方法隐蔽驻留的木马,确保系统还原后的完整和安全。     

ZEMAX软件在曝光光源设计中的应用

以光学设计软件ZEMAX为依托,结合曝光光源设计思路,并以实例展示设计方法和描述它的实用性,利用ZEMAX计算机辅助设计分析了曝光光源的鬼点。     

改进Center-Net网络的自主喷涂机器人室内窗户检测

室内自主喷涂机器人可以实现室内墙面喷涂的自动化以此提升喷涂的效率,减少人力物力的投入。而基于计算机视觉的室内窗户检测算法则是该机器人的关键技术。对于室内窗户检测,由于环境光照、窗户形状和窗户透光属性的存在,传统方法无法得到较好的效果。针对此问题,设计一种基于深度学习的室内窗户检测算法。该算法主要对中心点网络(CenterNet)的特征提取网络进行修改,减少部分卷积操作,使用Ghost模块替换原始的卷积模块,降低特征冗余,并引入注意力机制,让网络尽可能表达重要信息。实验结果表明,改进的CenterNet在不损失网络精度的前提下,大幅度提高了网络的运算速度,使得该检测算法即使在机器人端的嵌入式系统上也可以达到实时检测的效果。     

随机扰动三维流体界面不稳定性的并行计算

对三维流体界面不稳定性的数值模拟引进了新的数值计算方法,并在 MPI 并行计算环境下进行了数值模拟。利用 Level Set 方法确定界面位置,零水平集对应界面位置。对应离散 Level Set 方程和界面两侧的两套 Euler 方程,借助于 Ghost 网格方法完成离散。如何确定临近界面的网格点的状态量,涉及到跨界面点的两套 Euler方程,借助于 Ghost 网格点思想实现在全流场用二阶 TVD 格式的统一计算。对最后网格点上的两套状态量的辨认依赖于该点的 LevelSet 值的符号。数值计算结果表明,TVD 格式结合 Ghost 方法较好地保持了跨界面密度的 Heaviside 剖面。采用区域分解方法对多处理机分配计算负载,每一个处理机有自己的内存和 CPU。讨论了缓冲区设定和数据交换方式。实际计算网格数为 102.4 万。得到Rayleigh-Taylor 不稳定性随机扰动的图象。     

基于PXE网络克隆技术的探讨与实现

论述了PXE网络克隆技术的原理,并阐述了利用Ghost8.3企业版的多播功能,将DHCP服务和TFTP文件传输与PXE功能相结合,实现局域网计算机在无光驱和软驱的情况下硬盘数据恢复技术。     

浅谈高职院校计算机机房管理

目前高职院校计算机机房由于使用频率较高,学生误操作及上网常被病毒破坏等原因,造成计算机故障多,设备维护量大。因此如何加强计算机机房管理成为每一名机房管理人员的当务之急。