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Boost斩波器在功率源负载下的动态特性与控制方法   总被引:1,自引:1,他引:0  
为更方便、经济地研究分布式发电单元的电特性,可用Boost斩波器对发电单元直流特性进行模拟。分布式发电单元在功率变化过程中的直流特性较为复杂,因此在功率源负载下将Boost斩波器的二阶非线性状态方程近似线性化,并根据其特点采用输出反馈控制法,对输出电压和电流分别加以调节。由于采用数字控制,故对斩波器及控制器离散化模型进行了详细分析,根据稳定性判据得出控制参数取值范围。给出并分析了斩波器在恒功率、恒压、变压变功率情况下的实验波形,验证了该控制方法的有效性。  相似文献   
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The correlation averaging algorithm frequently used to enhance micrographs of repeating structures contains an inherent bias that favours images with larger pixel values or positive noise levels. This bias not only skews the composite image toward higher pixel values, but also distorts the image by increasing the value of high-valued pixels more than that of low-valued pixels. These errors are especially important in scanning probe microscopy images where the pixel value reflects a distinct height. A similar algorithm that uses a structure function in place of the correlation function eliminates this bias.  相似文献   
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在日本,用水单位可自由使用取水设施,干旱季节水资源的合理配置就成为一个突出的问题.目前,日本的干旱季节会有多种用水分配分式.对于KOKAI河流域的水资源分配,水的配给制度沿用了传统的方式,即地形条件占有决定性的地位,没有特殊的手段去控制水资源的公平配置.而对于YAHAGI河流域的水资源分配,各用水单位建立了一个非政府的水资源配置委员会.尽管灌溉部门掌握用水优先权,但是在严重干旱期农民会将水资源转让给供水部门.  相似文献   
4.
本文描述了把扩展句节数最小法进行形态素解析的结果登录在网络[定向图]上,并把这个网络[定向图]保留在计算机的内存中直到修改操作结束,实现了在不同句节切分的各种选择候补中取出所需候补。再根据所选候补去检索网络[定向图]上的路径,就可以得到符合操作者意图的全句的转换结果,从而使日文汉字输入时所需的假名汉字转换操作简单易行,提高了操作性能。  相似文献   
5.
In the case of sudden valve closure, water hammer creates the most powerful pressure and damage to pipeline systems. The best way to protect the pipeline system is to eliminate water hammer. The main reasons for water hammer occurrence are valve closure, high initial velocity, and static pressure. However, it is difficult to eliminate water hammer. Water hammer tends to occur when the valve is being closed. In this study, the pipe fracture caused by static water pressure, gradually increasing pressure, and suddenly increasing pressure were compared experimentally in a breaking PVC test pipe. The quasi-static zone, the dynamic zone, and the transition zone are defined through the results of those experiments, with consideration of the fracture patterns of test pipes and impulses. The maximum pressure results were used to design the pipeline even though it is in the dynamic zone.  相似文献   
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Patients with hemodialysis (HD) are at risk of death due to cardiac arrhythmias, worsening congestive heart failure (CHF), and noncardiac causes. This study reviews our experience with the use of implantable cardioverter defibrillators (ICDs) in patients with ventricular tachycardia who are under maintenance HD. We retrospectively reviewed 71 consecutive patients who underwent an ICD implantation in our hospital. There were 11 patients under maintenance HD and 60 patients without HD. The group of patients with HD (HD group) was compared with the patients without HD (control group). The mean follow-up period was 30±9 vs. 39±4 months in the HD group vs. the control group, respectively. Among these patients, 6 in the HD group and 26 in the control group received appropriate ICD therapies. There was no difference in appropriate ICD therapy, time to the first therapy, and electrical storm between the 2 groups. In the HD group, 1 patient underwent surgical removal of the ICD system due to infective endocarditis. There were 5 deaths in the HD group (4 from CHF) and 8 deaths in the control group (4 from CHF). There were no sudden cardiac deaths or arrhythmic deaths in both groups of patients during the follow-up period. However, the overall death rate was significantly higher in the HD group (P<0.01). In HD patients, ICD therapy prevented arrhythmic death, but their rate of nonarrhythmic adverse outcomes was high. This risk-benefit association should be considered before implantation of the device.  相似文献   
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2024 aluminum matrix composites reinforced with different size AIN particles (0.5, 4 and 10 μm) were fabricated by the squeeze-casting technology. The aging behavior and microstructure of AINp/2024AI composites were investigated by Brinell hardness measurement and transmission electron microscopy (TEM). The results show that the precipitation sequence of AINJ2024AI composites is similar to that of the matrix alloy aged at 160 and 190 ℃, but the age hardening rate of composites is improved, and the AIN particles with large size promote the precipitation process more obviously, in comparison with smaller AIN particles. With increasing temperature, the precipitation processes are accelerated, and the time to reach the peak hardness is shortened. The acceleration of the formation of GP region and phase S' in the composites is attributed to the interfaces (between particles and the matrix) and the high density of dislocations introduced by addition of AIN particles.  相似文献   
9.
This paper describes two types of rotary loop flow controller, one is series type and the other is unified power flow controller (UPFC) type. Both of them can maintain the suitable voltage level of distribution system even with a large and uneven penetration of distributed generation. The configurations of proposed controllers are essentially same as wound rotor induction machine with no slip rings. The proposed controllers are less costly, more efficient, and more tolerant to overvoltages/currents as compared to power electronics‐type controllers. Further, UPFC‐type rotary loop flow controller has additional advantages like relatively smaller capability and ability to control reactive power than the series type of rotary loop flow controller. The proper functioning of the proposed controllers is confirmed through simulations and experiments.  相似文献   
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