提高线阵CCD相机MTF的细分采样理论与方法

文章从理论上推导了线阵CCD相机间歇细分采样和连续细分采样成像所得到的光电图像调制度和MTF公式,并讨论了这两种采样方法对提高动态成像MTF的不同效果,分析比较了它们的特点和工程应用的可能性。     

高速公路融合式联网收费系统设计与实现

随着高速公路的迅猛发展以及计算机网络、通信等高新技术的发展 ,高速公路逐步走向智能化 ,并将最终发展成为智能交通系统 ( ITS Intelligent Transport System)。相应地 ,高速公路的收费技术呈现出网络化和智能化的趋势。文中介绍一种新型的融合式的自动收费系统 ,它采用智能卡技术 ,融合了人工收费方式和半自动收费方式 ,不仅支持现有系统的收费方式 ,而且还为将来采用电子收费 ( ETC Electronic Toll Collection)技术提供了接口功能 ,使系统具有较强的适应性和较好的扩展性 ,满足高速公路建设的要求     

Semi-automatic determination of the Azores Current axis using satellite altimetry: Application to the study of the current variability during 1995–2006

Satellite altimetry has been widely used to study the variability of the ocean currents such as the Azores Current (AzC) in the North Atlantic. Most analyses are performed over the region that encloses the current, thus being somehow affected by other oceanographic signals, e.g., eddies. In this study, a new approach for extracting the axis of a zonal current solely based on satellite altimetry is presented. This is a semi-automatic procedure that searches for the maximum values of the gradient of absolute dynamic topography (ADT), using the geostrophic velocity as auxiliary information. The advantage of this approach is to allow the analyses to be performed over a buffer centered on the current axis instead of using a wider region. It is here applied to the AzC for the period June 1995–October 2006.     

Tearing,coalescence and fragmentation processes in solar flare current sheet and drifting pulsating structures

The paper presents a summary of results from two different simulations which study the tearing, coalescence and fragmentation of current sheets, the associated production of energetic electrons and of plasma waves from these electrons which could explain drifting pulsation structures observed at radio wavelengths. Using a 2.5-D particle-in-cell (PIC) model of the current sheet it is shown that due to the tearing mode instability the current sheet tears into plasmoids and these plasmoids later on coalesce into larger ones. During these processes electrons are accelerated and they produce observable electromagnetic waves. Furthermore, the 3-D PIC model with two current sheets extended in the electric current direction shows their fast fragmentation associated with the exponential dissipation of the free magnetic field energy. An example of the drifting pulsating structure which is considered to be a radio signature of the above mentioned processes in solar flares is shown.     

Kink-like mode of a double gradient instability in a compressible plasma current sheet

A linear MHD instability of the electric current sheet, characterized by a small normal magnetic field component, varying along the sheet, is investigated. The tangential magnetic field component is modeled by a hyperbolic function, describing Harris-like variations of the field across the sheet. For this problem, which is formulated in a 3D domain, the conventional compressible ideal MHD equations are applied. By assuming Fourier harmonics along the electric current, the linearized 3D equations are reduced to 2D ones. A finite difference numerical scheme is applied to examine the time evolution of small initial perturbations of the plasma parameters. This work is an extended numerical study of the so called “double gradient instability”, – a possible candidate for the explanation of flapping oscillations in the magnetotail current sheet, which has been analyzed previously in the framework of a simplified analytical approach for an incompressible plasma. The dispersion curve is obtained for the kink-like mode of the instability. It is shown that this curve demonstrates a quantitative agreement with the previous analytical result. The development of the instability is investigated also for various enhanced values of the normal magnetic field component. It is found that the characteristic values of the growth rate of the instability shows a linear dependence on the square root of the parameter, which scales uniformly the normal component of the magnetic field in the current sheet.     

智能化交流磁化电流控制器设计中的若干问题

本文对设计智能化交流磁化电流控制器过程中所必须解决的非正弦交流磁化电流的测量、退磁速率的线性化等问题进行了讨论，详细分析了磁化回路中电流与触发角及负载功率因数角之间的关系，并在此基础上提出相应的解决方案，同时叙述了以单片机技术为核心的交流磁化电流控制器的组成及工作原理。对进一步提高我国磁粉探伤设备的技术水平具有一定的促进意义。     

Fronts and thermohaline structure of the Brazil–Malvinas Confluence System

Fronts and thermohaline structure of the Brazil–Malvinas Confluence System (BMCS) are studied from climatic data, “Marathon Exp. Leg.8, 1984” data, and Sea surface temperature (SST) data base “ds277-Reynolds” (1981–2000). The South Atlantic Central Water (SACW) is divided in two main types: tropical (TW) and subtropical water (ST). Water masses, Fronts, Inter-Frontal and Frontal Zones are analysed and classified: (a) the water masses: Tropical Low-Salinity Water, Tropical Surface Water, Tropical Tropospheric Water, Subtropical Low-Salinity Water, Subtropical Surface Water, Subtropical Tropospheric Water. T,S characteristics of intermediate, deep and bottom water defined by different authors are confirmed and completed; (b) the Inter-Frontal Zones: Tropical/Brazil Current Zone, Subtropical Zone and Subantarctic Zone; (c) the Frontal Zones: Subtropical, Subantarctic and Polar, and (d) the Fronts: Subtropical Front of the Brazil Current, Principal Subtropical Front, North Subtropical Front, Subtropical Surface Front, South Subtropical Front, Subantarctic Surface Front, Subantarctic Front and Polar Front. Several stable T–S relationships are found below the friction layer and at the Fronts. The maximum gradient of the oceanographic characteristics occurs at the Brazil Current Front, which can be any of the subtropical Fronts, depending on season. Minimum mean depth of the pycnocline coincides with the Fronts of the BMCS, indicating the paths of low-salinity shelf waters into the open ocean. In the work it is shown how to recover the horizontal and vertical thermohaline structure of waters from satellite data RSMAS SST.     

分流条件下不锈钢交流点焊电流波形的频谱特征与熔核直径的关系

通过对分流条件下不锈钢点焊焊接电流波形进行快速傅立叶变换(FFT),获得了焊接电流波形的幅频图,并将熔核直径与对应的幅频进行了对比分析,发现了一次及三次电流谐波幅值与熔核直径成线性反比关系.利用这一规律,可方便地实现点焊熔核直径的实时无损检测.     

基于虚拟仪器的飞行参数记录系统的软件设计

介绍了一套基于飞行参数记录系统硬件，用Lab VIEW和C语言设计的飞参激励器测试系统软件。该软件采用最新的虚拟仪器软件模式，使用模块化思想，建立起了飞行参数采集记录的自动化和智能化的测试系统。该系统采用数据对比的形式进行显示，具有精度高，使用方便，界面友好，系统开放，容易扩展等特点；并有着强大的交互和控制功能，能够及时准确快速的对飞参系统进行测试和维护。     

全动模拟机数据记录器的开发

模拟机数据记录器是参照飞行数据记录器（FDR）开发出的模拟机的数据记录工具，其原理是用软件记录模拟飞行过程中各种飞行参数并存储在介质上供飞行品质评估，飞行训练再现和工程研究使用。