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本文研究核电站稳压器抗震分析模型的建立方法。针对某堆型的稳压器,分析内部冷却剂的液面晃动效应及处理方法;对比分析节点个数、筒体壁厚、集中质量等因素对简化模型固有频率的影响,确定了稳压器抗震分析模型的简化原则。针对最终模型进行模态分析,并对计算结果进行评价。 相似文献
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针对我国通信电源交流供电状况不良的现状,论述了移动通信基站交流稳压器选型应注意的几个问题,详细介绍了国内生产的机械调压补偿式稳压器、参数稳压器,感应式稳压器、可控硅补偿式稳压器等产品性能,并进行了比较,最后提出了移动通信基站交流稳压器选型的建议。 相似文献
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本文讨论了人工神经网络技术在语音压缩编码方面的应用,提出了一种用Kohonen网络实现语音多脉冲激励分析模型的矢量量化方法。该方法将参数分析和量化编码熔为一体,和传统的先分析、后量化方法相比较,具有许多优良的特性,如全并行处理、过程简化等。本文针对语音多脉冲激励模型,提出了量化网络的结构和学习规则,并将此方法和传统方法进行了比较。最后对网络的压缩性能进行了计算机模拟,结果表明应用人工神经网络进行语音信源的压缩是切实可行的。 相似文献
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通常情况下,降压稳压器的设计针对的是连续模式工作,这就简化了输出电压计算及系统设’计。然而,如果系统非同步,而且要求在轻载条件下工作,情况就变得更复杂了。在这些条件下,降压稳压器可能转而采用不连续模式工作。占空比从输出电压与输入电压之比(Vout/Vin)变为涉及电感值、输入电压、开关频率及输出电流的一项复杂函数。 相似文献
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本文应用平均值技术和描述函数法推导的开关稳压器小信号、低频线性平均值模型,分析了开关稳压器的频率特性及音频敏感度。采用校正网络来改善开关稳压器对低频纹波的抑制能力。合适的校正,可以使稳压器获得高增益、宽带宽的稳定工作状态。最后提供一个设计实例并进行了试验,理论分析与实验结果基本一致。 相似文献
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核电厂稳压器加热器功率调节器通过调节电路的导通和关断时间实现对加热器功率的调节.由于可控硅击穿故障,造成功率调节器工作异常.通过对功率调节器运行状况及故障可控硅的解剖分析,最终确定造成可控硅击穿故障的原因是器件内部存在绝缘薄弱点,并通过更换质量可靠的可控硅后,恢复了设备的正常运行. 相似文献
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Vibration fatigue test and analysis methodology for flip chip solder joint fatigue life assessment have been developed by performing vibration tests with constant G-level and varying G-level input excitation. The linear cumulative damage analysis method (Miner’s rule) predicts non-conservative result for vibration fatigue life of flip chip solder joint. Finite element analysis (FEA) using a global-local-beam modeling method was used to calculate the natural frequency and were compared to experimental data. A quasi-static finite element analysis method was developed to investigate solder joint stress strain behavior for solder joint vibration fatigue life prediction. Harmonic finite element analysis was also carried out to predict solder joint fatigue life. Results from quasi-static analysis and harmonic analysis were compared. Based on Miner’s rule and stress amplitude results from FEA results, different assumed cumulative damage index (CDI) factors were investigated in fatigue life prediction. 相似文献
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基于人工神经网络的IC互连可靠性研究 总被引:1,自引:0,他引:1
鉴于有限元分析耗时耗资源的缺点,为了加速集成电路的互连可靠性分析,提出将传统的有限元建模和人工神经网络(ANN)建模技术结合来实现IC的建模和仿真分析.采用有限元ANSYS参数化设计语言(APDL)实现IC三维模型的自动构建和原子通量散度(AFD)计算,之后通过对计算所得的可靠性数据进行训练和测试,采用神经网络技术对模型的输入输出关系进行建模,使模型达到足够高的精度.神经网络模型构建好之后,可以在短时间产生一个可靠性数据库.通过对数据的统计分析可以得到电路在不同条件下的互连可靠性,进而分析各因素对电路互连可靠性的影响,为集成电路的互连可靠性分析和设计提供重要指导. 相似文献
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为了研究激光技术应用于区分不同金相组织的可行性,采用不同的热处理方法分别得到珠光体+铁素体和马氏体这两种不同的金相组织的钢样,选择合适的激光脉冲能量,对比分析了激光诱导击穿光谱的谱线强度与金相组织的关系,用主成分分析法对不同金相组织进行了区分。结果表明,不同金相组织的谱线强度不同,其中珠光体+铁素体组织的谱线强度较大,基体元素Fe的谱线强度差异比合金元素Mn的谱线强度差异大;不同金相组织呈现一定分布特性,主成分分析法能对不同金相组织进行区分,其中在波长范围280nm~320nm内区分效果最好。该研究验证了激光技术具有区分不同金相组织的能力。 相似文献
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Effect of substrate flexibility on solder joint reliability. Part II: finite element modeling 总被引:1,自引:1,他引:0
Solder joint fatigue failure is a serious reliability concern in area array technologies, such as flip chip and ball grid array packages of integrated-circuit chips. The selection of different substrate materials could affect solder joint thermal fatigue life significantly. The mechanism of substrate flexibility on improving solder joint thermal fatigue was investigated by thermal mechanical analysis (TMA) technique and finite element modeling. The reliability of solder joints in real flip chip assembly with both rigid and compliant substrates was evaluated by accelerated temperature cycling test. Finite element simulations were conducted to study the reliability of solder joints in flip chip on flex assembly (FCOF) and flip chip on rigid board assembly (FCOB) applying Anand model. Based on the finite element analysis results, the fatigue lives of solder joints were obtained by Darveaux’s crack initiation and growth model. The thermal strain/stress in solder joints of flip chip assemblies with different substrates were compared. The results of finite element analysis showed a good agreement with the experimental results. It was found that the thermal fatigue lifetime of FCOF solder joints was much longer than that of FCOB solder joints. The thermal strain/stress in solder joints could be reduced by flex buckling or bending and flex substrates could dissipate energy that otherwise would be absorbed by solder joints. It was concluded that substrate flexibility has a great effect on solder joint reliability and the reliability improvement was attributed to flex buckling or bending during temperature cycling. 相似文献
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空气动力学粒径谱仪和微量振荡天平法测尘仪的工作原理不同,数据表示形式不同.用APS3321空气动力学粒径谱仪对北京2008年冬、春、夏进行大气颗粒物粒径分布和质量浓度测量,同步使用3台R&P1400a的微量振荡天平法测尘仪分别测量空气中的PM10、PM2.5和PM1.0的质量浓度,对两种方法测量的数据进行相关比较,获得微量振荡天平法测尘仪与空气动力学粒径谱仪的测量数据的相关性,建立了回归方程. 相似文献
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