扩频信号探测器的性能比较与分析

目前,跳频扩频信号探测器的种类很多,从原理和性能角度比较各种探测器类型的优缺点,并提出在实际应用和理论研究中的建议。     

数字图像中扩频水印的盲提取方法

提出了一种图像中采用扩频方法嵌入的数字水印的盲提取方法。在扩频序列及其长度均未知条件下,该方法采用遗传算法,通过求解扩频序列长度及序列构成的两变量优化问题,可较好地估计出嵌入时使用的扩频序列。通过获取的扩频序列与藏密信号的相关性分析,可实现扩频水印的盲提取。在微机上,采用该方法对多幅标准测试图像进行了模拟实验。实验结果表明,估计出的扩频序列正确率较高,盲提取的水印图像具有较好的可辨认性。     

A study on wear coefficients and mechanisms of steam generator tube materials

Reciprocating sliding wear tests were performed to evaluate wear properties of Inconel 600MA and 690TT steam generator (SG) tube materials against 405 and 409 ferritic stainless steels. With increasing normal loads and sliding amplitudes, the wear rate of tube materials increased but a wear transition occurred only in Inconel 690TT. Subsurface deformation strengthening seemed to be an important factor that determines the wear resistance of tube materials. After the wear test, the worn surfaces were observed to investigate the wear mechanism of tube materials using SEM. The results indicated that there are different mechanisms of wear particle removal between the tube materials. The differences are related to the degree of work hardening due to the differences in chromium content in the tube materials. Based on the present results, wear coefficient values for the life estimation of SG tubes were calculated according to the work-rate model at each test condition. The wear rate is lower for Inconel 690TT compared to that for Inconel 600MA. Finally, parameters that should be considered for evaluation of wear coefficients were discussed.     

Decision‐tree‐based methods for differential diagnosis of β‐thalassemia trait from iron deficiency anemia

Several discrimination indices have been proposed to distinct between β‐thalassemia trait (βTT) and iron deficiency anemia (IDA). This study is the first application of tree‐based methods for differential diagnosis of βTT from IDA. One hundred forty‐four patients with hypochromic microcytic anemia aged 18–40 years old from Ayat Hospital of Tehran were recruited. Classification and Regression tree, CHi‐squared Automatic Interaction Detector (CHAID), Exhaustive CHi‐squared Automatic Interaction Detector (E‐CHAID), Quick, Unbiased, Efficient Statistical Tree (QUEST), Classification Rule with Unbiased Interaction Selection and Estimation (CRUISE), and Generalized, Unbiased, Interaction Detection and Estimation (GUIDE) have been used to discriminate the diagnosis. Mean corpuscular volume (MCV) was found as the main predictor in discrimination. All the mentioned tree‐based methods showed acceptable sensitivity, specificity, accuracy, Youden's index, false positive and negative rate, positive and negative predictive values and AUC in differential diagnosis of βTT from IDA. However, Classification Rule with Unbiased Interaction Selection and Estimation revealed more precise classification with an area under the curve value of 0.99. Decision‐tree‐based methods can be used to develop sensitive and accurate diagnostic methods for differentiating βTT from IDA.     

Effects of dissolved oxygen on corrosion fatigue cracking of Alloy 690(TT) in pressurized water reactor environments

Alloy 690(TT) is widely used for steam generator tubes in pressurized water reactor (PWRs), where it is susceptible to corrosion fatigue. In this study, the effects of dissolved oxygen on the corrosion fatigue cracking behavior of Alloy 690(TT) in simulated PWR environments were investigated under small scale yielding conditions. Dissolved oxygen, combined with the monotonic plastic zone size (r_p), had a significant influence on out-of-plane cracking of corrosion fatigue crack and environment factor (F_en).     

可修改PSI调制器在数字电视中的应用

本文简述了数字电视中PSI/SI表结构和作用,并举例说明TT6120可修改PSI调制器在数字电视中的应用,具有很强的实用性.     

Tara tannin a natural product with antifouling coating application

The international trade by marine transportation has increased continuously since the 70s. The undesirable accumulation of a wide variety of marine organisms (biofouling) on ship hulls can lead to significant increased costs, principally by increased fuel consumption. On the other hand, there is a great concern about the biocides commonly used in commercial antifouling (AF) protective systems due to the high concentration encountered in coastal areas and the potential damage they could cause to marine organisms. As a consequence, the development of alternative AF coatings with new natural products as biocides inhibit is a key factor. In this approach, tara tannin (TT) is being proposed as a promising solution. It is important to note that TT is obtained from the pods of the tree avoiding its cutting down. The aim of this research was, primarily, to explore the possible application of a natural and abundant product, such as the TT, in the preparation of AF coatings. So, a TT derivative was obtained and characterized to be employed as the bioactive compound in AF coatings. Previous to the immersion in natural environments, the dissolution of TT from AF coating in artificial sea water (ASW) was studied. TT was incorporated into the coating as zinc “tannate”. One of the tested coatings proved to be efficient in AF protection in natural sea water (NSW) at Mar del Plata (38°08′17″S–57°31′18″W) harbor during eight months. The addition of 2% by weight of zinc oxide to the coating extended its service life until the year.     

基于STK二次开发的链路测控仿真

在航空航天任务过程中,测控覆盖率高就能提供实时、连续、可靠的信息支持。利用VC结合STK二次开发,建立了测控链路仿真模型。软件利用STK/X模块较好的显示效果与Access模块计算、显示测控链路的余量和测控链路覆盖范围。针对不同的地面站部署,可计算空间飞行器的测控覆盖率。实现VC与STK集成的二次开发可大幅节省了开发时间,该仿真方法对测控系统的设计具有参考价值。     

SPD“3+1”接线模式及间接触电防护分析

介绍了TT系统中SPD的"3+1"保护模式。重点分析采用"3+1"接线模式时,其N-PE放电间隙的失效短路使TT系统暂时成为局部TN系统运行,电气设备外露导电部分可能出现的危险对地故障电压。并指出,为满足间接触电防护要求、避免电击事故的发生,应尽量降低电源端系统中性点接地电阻。