Non‐destructive detection of corrosion applied to steel and galvanized steel coated with organic paints by the pulsed phase thermography

Organic coatings in the automobile industry have to resist corrosion and mechanical damage from stone chipping. Currently, no tool is established in industrial non‐destructive applications for analyzing the damage of stone‐impacts and the following corrosion after accelerated corrosion tests. Measurement methods such as the scanning Kelvin probe can analyze the corrosion progress in a detailed manner, but with a long measurement time. The pulsed phase thermography (PPT) is a non‐destructive tool to analyze inhomogeneities and defects in materials, with a huge field of applications existing. The present work shows advances in using the PPT to detect propagation of corrosion under coatings. Physical principles of the mechanism of the corrosion detection under coatings are described. Results of measurements of organic coatings on carbon steel as well as of organic coated galvanized steel show the corrosion propagation. Influencing factors to the measurement such as the thickness of the coatings are investigated, but no significant effect on the quality of the analysis was found. The corrosion progress can be monitored by the PPT fast and reliably. The achieved results correlate with the theoretical basis and the test results after surface characterization and destructive analysis of samples.     

微波相关器散射参数推导与MATLAB仿真

运用矩阵代数分析方法,推导了由功分器、定向耦合器和延迟线组成的微波相关器在忽略各部件互连传输线情况下的散射参数表达式,形式简明,物理概念清晰。结合S参数表达式利用Matlab数值计算,全面分析了功分器输出幅度、相位不一致,定向耦合器耦合度变化、直通端和耦合端相位差非90°等情况对微波相关器鉴相带来的影响,为分析设计微波相关器提供了参考。     

多相滤波宽带信道化数字接收机

宽带雷达电子战数字接收机是当前国内外研究的重点，信道化接收机能够处理同时到达的多个信号并有较高的截获概率。多相滤波信道化接收机运算量小且易于实现。为克服因D倍抽取而产生的多相滤波信道化数字接收机的接收盲区，引入了重叠一半的多相滤波信道化数字接收机。利用瞬时自相关接收机，可在消除信道化接收机虚假输出的同时提高信道化接收机的测频精度。文中给出了上述数字接收机的实现方法，并通过仿真实验证明了以上结论的有效性。     

相位推算法瞬时测频研究

相位推算法瞬时测频是基于数字接收机的计算方法。本文介绍了该算法的原理,分析、仿真了其误差,给出了校码处理原则,并进行了技术验证。结果表明,该算法具有测频精度高、瞬时性好的优点。     

Experimental Presentation of an Integrated Flow Model

Abstract

Integrated flow modeling (IFMing) is an expanding area of research since it was introduced less than a decade ago. It is a combination of the traditional flow simulator with a petrophysical algorithm. This article introduces an experimental apparatus that allows for simultaneous monitoring of fluid flow and elastic wave velocities. In addition to fluid flow monitoring and elastic wave velocities measurement, apparatus provides a means to calculate elastic moduli needed for the petrophysical algorithm in the IFM. Also, apparatus makes possible to evaluate the petrophysical algorithm by history matching experimental fluid flow data.     

Fitting Drought Duration and Severity with Two-Dimensional Copulas

This study aims to model the joint drought duration and severity distribution using two-dimensional copulas. The method of inference function for margins (IFM method) is employed to construct copulas. Two separate maximum likelihood estimations of univariate marginal distributions are performed first, then followed by a maximization of the bivariate likelihood as a function of the dependence parameters. The drought duration and severity are assumed to be exponential and gamma distributions, respectively. Several copulas are tested to determine the best data fitted copula. Droughts, defined using the Standardized Precipitation Index (SPI), of Wushantou (Taiwan) are employed as an example to illustrate the proposed methodology. The copula fitting results for drought duration and severity are quite satisfactory. The bivariate drought analyses, including the joint probabilities and bivariate return periods, based on the derived copula-based joint distribution are also investigated to demonstrate the advantages of bivariate modeling of droughts.     

A directional control method for interface flow considering static voltage stability

A directional control method (DCM) for power flows on a set of interface lines between two regions of power system considering static voltage stability margin is developed in this paper. A surface approximation approach is firstly used to obtain the relationship between the interface flow solution and the generation direction of generator (the portion of generation variation in each participating generator to satisfy the desired power increase on the interface and the system loss). Then, an optimization model is built to determine the optimum dispatching scheme of generators. This method not only can control the total power on the interface to satisfy the power demand but also can realize the directional control of power on each interface line based on the needs of operation. The proposed DCM is further extended to determine the optimum dispatching scheme of generators for maximizing the interface flow margin (IFM), which is the active power margin of the key transmission lines between two regions of power system constrained by static voltage stability. A modified continuation power flow (MCPF) is used to show and evaluate the impacts of the DCM on the IFM. The New England 39-bus system and the IEEE 300-bus system have been employed to verify the effectiveness of the DCM.     

基于Copula函数的区域降水联合分布与特征分析

为深入研究降水时空分布特性,以便为流域水资源合理配置提供科学依据,以广东省东江流域内32个代表雨量站1956~2009年月降雨量资料为例,根据泰森多边形法计算四个子区间的面雨量,采用边际插值函数法（IFM）估计Copula函数参数,通过AIC信息准则确定研究时段内任意两相邻区间面雨量指标的联合分布。结合历史雨量极值组合所对应的重现期计算结果表明,东江流域降水时空分布不均匀,前汛期时段流域水资源状况较为安全,流域上游水资源状况也较为安全,后汛期与枯季时段流域下游水资源状况最为严峻。基于Copula函数方法与传统面雨量频率分析方法相比,能更全面地反映降水的分布特征。     

弹载雷达侦察干扰设备设计

论述了弹载雷达侦察干扰设备的天线设计、接收机设计和信号处理硬件设计,并从实际需求出发,重点讨论了信号处理算法中的信号检测技术、瞬时测频技术、雷达信号脉内调制识别技术和干扰信号产生技术.仿真结果表明所采用的信号处理算法可行,对于弹载平台雷达侦察干扰设备的设计具有指导意义.     

基于累积释放模型的测量电路研究

在谐振式传感器、多普勒频移等应用中测量频率的相对变化更有用,因此探索对频率变化的精确测量有很现实的意义.以圆映射动力学为理论基础,按照累积-释放模型的变化规律设计测量电路.在一定的条件下,使电路处于混沌状态,这时的输出对频率的变化非常敏感.在输出轨道的符号序列与输入信号的频率之间建立对应关系,频率的微小变化可以转化为符...