弹上电缆,作为导弹设备进行信号、能量传输的重要载体,质量是否符合要求,直接决定了设备的可靠性。与传统电缆不同,弹上电缆,具备多芯、多头、大规模等特点。传统的测试设备往往存在线缆支持规模较小、测试针对性太强、扩展性差、自动...弹上电缆,作为导弹设备进行信号、能量传输的重要载体,质量是否符合要求,直接决定了设备的可靠性。与传统电缆不同,弹上电缆,具备多芯、多头、大规模等特点。传统的测试设备往往存在线缆支持规模较小、测试针对性太强、扩展性差、自动化程度低等缺点,本文提出了基于Test On Demand平台的弹上电缆测技术,阐述了测试原理和测试流程设计,使用该技术完成了对最多达300芯弹上电缆的导通、绝缘、耐压测试,可扩展多种型号电缆,具备通用性、扩展性强、测试速度快、自动化程度高、智能化等特点。展开更多
Quantitative safety assessment of safety systems plays an important role in decision making at all stages of system lifecycle, i.e., design, deployment and phase out. Most safety assessment methods consider only syste...Quantitative safety assessment of safety systems plays an important role in decision making at all stages of system lifecycle, i.e., design, deployment and phase out. Most safety assessment methods consider only system parameters, such as configuration, hazard rate, coverage, repair rate, etc. along with periodic proof-tests （or inspection）. Not considering demand rate will give a pessimistic safety estimate for an application with low demand rate such as nuclear power plants, chemical plants, etc. In this paper, a basic model of IEC 61508 is used. The basic model is extended to incorporate process demand and behavior of electronic- and/or computer-based system following diagnosis or proof-test. A new safety index, probability of failure on actual demand （PFAD） based on extended model and demand rate is proposed. Periodic proof-test makes the model semi-Markovian, so a piece-wise continuous time Markov chain （CTMC） based method is used to derive mean state probabilities of elementary or aggregated state. Method to determine probability of failure on demand （PFD） （IEC 61508） and PFAD based on these state probabilities are described. In example, safety indices of PFD and PFAD are compared.展开更多
【目的】验证美国加州大学开发的作物蒸散量-SIMETAW(simulation of evapotranspiration of applied water)模型在中国辽西北地区应用的有效性。【方法】利用辽西北地区的作物、土壤和气候数据运行模型,将当地主要作物蒸散量的模型模拟...【目的】验证美国加州大学开发的作物蒸散量-SIMETAW(simulation of evapotranspiration of applied water)模型在中国辽西北地区应用的有效性。【方法】利用辽西北地区的作物、土壤和气候数据运行模型,将当地主要作物蒸散量的模型模拟值与田间实测值进行对比分析;同时,在模型验证的基础上模拟分析当地主要作物生育期内蒸散量和所需灌水量的多年平均情况。【结果】主要作物生育时期内模型模拟的蒸散强度曲线和实测曲线变化趋势基本一致,蒸散总量模拟值和实测值比较接近,相对误差均在10%之内。利用模型模拟当地玉米、大豆和谷子生育期内蒸散量多年平均值分别为514.15、449.64和389.12mm,所需灌水量分别为208.4、220.93和116.17mm。【结论】SIMETAW模型在辽西北地区对玉米、大豆和谷子蒸散量的模拟比较准确,模型有效,可以进一步应用该模型开展作物的水分管理研究和指导灌溉。展开更多
文摘弹上电缆,作为导弹设备进行信号、能量传输的重要载体,质量是否符合要求,直接决定了设备的可靠性。与传统电缆不同,弹上电缆,具备多芯、多头、大规模等特点。传统的测试设备往往存在线缆支持规模较小、测试针对性太强、扩展性差、自动化程度低等缺点,本文提出了基于Test On Demand平台的弹上电缆测技术,阐述了测试原理和测试流程设计,使用该技术完成了对最多达300芯弹上电缆的导通、绝缘、耐压测试,可扩展多种型号电缆,具备通用性、扩展性强、测试速度快、自动化程度高、智能化等特点。
文摘Quantitative safety assessment of safety systems plays an important role in decision making at all stages of system lifecycle, i.e., design, deployment and phase out. Most safety assessment methods consider only system parameters, such as configuration, hazard rate, coverage, repair rate, etc. along with periodic proof-tests （or inspection）. Not considering demand rate will give a pessimistic safety estimate for an application with low demand rate such as nuclear power plants, chemical plants, etc. In this paper, a basic model of IEC 61508 is used. The basic model is extended to incorporate process demand and behavior of electronic- and/or computer-based system following diagnosis or proof-test. A new safety index, probability of failure on actual demand （PFAD） based on extended model and demand rate is proposed. Periodic proof-test makes the model semi-Markovian, so a piece-wise continuous time Markov chain （CTMC） based method is used to derive mean state probabilities of elementary or aggregated state. Method to determine probability of failure on demand （PFD） （IEC 61508） and PFAD based on these state probabilities are described. In example, safety indices of PFD and PFAD are compared.
文摘【目的】验证美国加州大学开发的作物蒸散量-SIMETAW(simulation of evapotranspiration of applied water)模型在中国辽西北地区应用的有效性。【方法】利用辽西北地区的作物、土壤和气候数据运行模型,将当地主要作物蒸散量的模型模拟值与田间实测值进行对比分析;同时,在模型验证的基础上模拟分析当地主要作物生育期内蒸散量和所需灌水量的多年平均情况。【结果】主要作物生育时期内模型模拟的蒸散强度曲线和实测曲线变化趋势基本一致,蒸散总量模拟值和实测值比较接近,相对误差均在10%之内。利用模型模拟当地玉米、大豆和谷子生育期内蒸散量多年平均值分别为514.15、449.64和389.12mm,所需灌水量分别为208.4、220.93和116.17mm。【结论】SIMETAW模型在辽西北地区对玉米、大豆和谷子蒸散量的模拟比较准确,模型有效,可以进一步应用该模型开展作物的水分管理研究和指导灌溉。
