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在模型检验中建立了一种新方法:检验可计算时态逻辑(CTL)公式描述的系统属性是否为空属性.根据原子命题的极性,用TRUE 或FALSE替换原子命题,得到一系列的CTL公式,再对这些CTL公式用模型检验工具验证,若CTL公式中有一个通过了验证,则可得出该系统属性是一个空属性.该方法对CTL公式的空属性的探测不需要对它的所有子公式用TRUE 或FALSE替换,只需对原子命题替换,这样检验的次数与原子命题的个数呈线性关系.利用验证综合系统对十字路口交通控制器规范的空属性进行了检验. 相似文献
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地铁机车采用直流牵引,具有波动性强、系统谐波含量丰富等特点.极大地威胁到电力系统的安全稳定运行。为了分析西安地铁对公共电网的影响,应用MATLAB/Simulink软件对即将投运的西安地铁2号线24脉波整流设备和牵引供电系统建模,并对其接入西安市公共电网后产生的谐波进行计算。结果表明:地铁负荷的变化对公网谐波含量的百分比影响较小;地铁供电系统23、25、11、13次谐波所在的比例最大,对公共电网电能质量的影响也最为严重。建议对以上4种谐波采取相应的治理和防护措施;随着地铁牵引负荷的增大。建议预留谐波抑制设备的安装位置。 相似文献
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A. Plumtree Nai-yong Tang 《Fatigue & Fracture of Engineering Materials & Structures》1989,12(5):377-386
Abstract— —A series of tests has been carried out to investigate the effect of sequential high frequency fatigue cycles interspersed with hold times on elevated temperature crack growth rates in AISI type 304 stainless steel. Each test sequence included different combinations of fatigue cycles and hold-times. Those sequences which included the smallest number of fatigue cycles resulted in the fastest crack propagation rates. The sequence with a block of 1000 cycles and a 120min hold time had the slowest crack propagation rate, similar to that for a reference 5 Hz fatigue test. Examination of the fracture surfaces revealed alternating regions of transgranular and intergranular fracture corresponding to the respective fatigue block and hold-time period. Intergranular fracture was observed to be characteristic of maximum time-dependent and time-independent damage interaction, which was associated with those specimens subjected to sequences including a block of 50 fatigue cycles, possessing the fastest crack propagation rates. The results may be explained using a model based on fatigue-creep-environment interaction. During the hold-time a damaged zone due to oxidation induced cavitation formed at the crack tip. Depending on the stress intensity factor range, the subsequent fatigue cycles continued to extend the crack through part or whole of the remaining portion of this region. For the remainder of the fatigue block the crack propagated in its normal transgranular mode. Oxide induced closure at low Δ K levels brought about the lowest crack propagation rate for the sequence consisting of a block of 1000 cycles and a 120 min hold period. 相似文献
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在对大型光伏电站并网运行特性理论研究和实验分析的基础上,建立了双级变换并网光伏电站整体模型,并爿析了光伏电站的动态输出特性和等值阻抗。然后以某1.6MW实际并网光伏电站工程为算例,着重研究了光伏电站接,配网对系统潮流、母线电压、短路电流和继电保护等方面目影响。 相似文献
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T91钢表面Ni和Ni/CeO_2镀层的氧化行为研究 总被引:3,自引:0,他引:3
采用电沉积法在T91钢基体上制备Ni与Ni/CeO2镀层,研究该镀层试样在温度分别为750℃和800℃,ω(Ar)=90%、ω(H2O)=10%气氛中的氧化行为。测量试样氧化动力学曲线并利用X射线衍射仪测定样品氧化后表面产物的相,利用带能谱分析功能EDS的扫描电镜SEM观察样品表面和截面形貌。结果表明:Ni和Ni/CeO2镀层对T91钢高温水蒸气氧化具有一定防护作用;此外,Ni/CeO2镀层中纳米CeO2颗粒抑制了氧化膜的开裂,改善了氧化膜的黏附性,提高了T91钢镀Ni试样的耐高温水蒸气氧化性能。 相似文献