共查询到20条相似文献，搜索用时 15 毫秒
1.
为了在短时间内获得真空荧光显示器(VFD)的寿命信息,通过加大其灯丝温度建立了加速寿命试验模型,开展了4组恒定应力加速寿命试验.采用威布尔函数描述VFD寿命分布,利用极大似然法(MLE)及其迭代流程图估计出形状参数和尺度参数.通过最小二乘法确定了VFD加速寿命方程,对VFD寿命是否符合威布尔分布进行了Kolmogorov-Smirnov检验,并利用自行开发的寿命预测软件计算出平均寿命和可靠寿命.数据统计分析结果表明,试验设计方案正确可行,VFD的寿命服从威布尔分布,VFD加速模型符合线性阿伦尼斯方程.所提出的试验方法和估计出的VFD寿命对生产厂商和用户有很强的指导意义. 相似文献
2.
设备的寿命损耗是企业设备管理部门进行设备检修和更换的重要依据.根据寿命服从Weibull分布,结合Weibull分布的特征构建了预测设备寿命损耗的2参数的数学模型,根据寿命损耗可以确定设备检修和更换的最佳时机,可用于避免发生重大事故和节约检修成本. 相似文献
3.
运用综合参数及非参数估计方法对服从威布尔分布的寿命试验的下一个失效时间的预测问题进行了详细的讨论,这对寿命服从威布尔分布的产品的寿命试验有指导意义. 相似文献
4.
论述了Weibull分布下双应力交叉步加试验的时间折算公式及数据统计分析的逆矩估计法。 相似文献
5.
利用自适应舍选抽样和Gibbs抽样对CE模型下Weibull分布场合恒定应力加速寿命试验进行了Bayes估计.最后通过模拟实例表明该估计是有效的. 相似文献
6.
重点阐述BRM12型新型高速杆端关节轴承与PHS12型普通球面关节轴承的寿命设计与韦布尔寿命对比试验论证。试验结果表明：BRM12型高速杆端轴承使用寿命是PHS12型使用寿命的7.4倍。 相似文献
7.
12 bonnet macaque (Macaca radiata) mother-infant dyads were studied. For 14 weeks, beginning when the infants were a mean age of 11.2 weeks, the dyads were housed and observed under different foraging-demand conditions for the mothers: 6 dyads in a low-foraging-demand (LFD) condition and 6 dyads in a variable-foraging-demand (VFD) conditions. For VFD mothers, demand varied between low and high in 2-week blocks. Differences between the LFD and VFD groups were minimal during this period; there was, however, more maternal grooming and shorter separation bouts in the VFD group than in the LFD group. The dyads were then challenged by brief introductions to a novel environment. The challenge revealed that frequency of breaking dyadic contact and levels of play were significantly lower for the VFD infants than for the LFD infants, perhaps as a consequence of less secure attachment. 相似文献
8.
A newly developed pure rolling fatigue test rig with three contact points for bearing balls was used to perform rolling contact fatigue (RCF) tests. The fatigue properties of GCr15 steel balls and two kinds of Si3N4 ceramic balls (GSN-200 and NBD-200) produced with different technologies were compared. Ball surfaces were examined after failure with optical microscope and scanning electron microscope (SEM). It was identified by tests that the failure mode of ceramic balls was surface spall. The main factor of ceramic ball failure was principal tensile stress. Life tests data, summarized in accordance with the Weibull theory, showed that the life of GSN-200 balls was close to that of GCr15 balls, whereas the life of NBD-200balls was much longer than those of GSN-200 and GCr15. Under the same working condition, the temperature rise of all ceramic balls was lower than that of steel balls, and their crack propagation rates were slower than that of steel balls. 相似文献
9.
加速寿命试验(ALT)是用加大试验应力来缩短试验周期的一种基本寿命试验方法,其目的在于:以较低的试验代价(例如试验样本、试验周期等)获取具有足够精度的寿命信息.在现有方法的基础上,基于试验应力加载顺序的变化将可能使试验效率发生重大改善的设想,该文提出了一种新的试验方法——序降应力加速寿命试验,然后根据失效物理的退化模型,与其它几种试验方法比较了其有效性,并且给出了序降应力加速寿命试验在we ibu ll分布场合下的分布函数. 相似文献
10.
威布尔分布的参数估计 总被引：1，自引：0，他引：1
威布尔分布是常见的寿命分布之一。对其密度函数中参数的估计方法有很多,常见的有矩法极大法Menond方法等。本文将利用最小二乘的思想给出定数结尾试验下双参数威布尔分布的参数估计的一种计算公式,以列表的方式给出计算时所需要的部分顺序统计量的期望,并通过模拟给出一个例子来说明该方法的可行性。 相似文献
11.
Application of the Bayes＇ theory to the failure rate evaluation of electrical apparatus 总被引：2，自引：0，他引：2
JIN Shao-hua LU Jian-guo WAN Yan-ping SUN Shu-guang 《浙江大学学报(A卷英文版)》2007,8(3):501-505
The Weibull distribution has been widely used in reliability fields. A mixed Weibull distribution represents a population that consists of several Weibull subpopulations. In this paper, a new approach which combines the least-squares method with Bayes＇ theorem, takes advantage of the parameter estimation for single Weibull distribution is developed to estimate the parameters of each subpopulation. The estimates given by this paper also satisfy the maximum likelihood equation. The estimates of the failure rate of the mixed Weibull population are given. An actual test data is computed by using the proposed method. The Kolmogorov-Smirnov goodness-of-fit test turns out that the proposed method yields more accurate result. 相似文献
12.
范绍佳 《中山大学学报论丛》1993,(1)
本文利用北京市大气自动监测系统冬季逐时SO_2、CO、NO_x资料研究城市大气污染物浓度分布的一般规律。发现:①不存在一个统一的分布模型;②对数正态分布适用于大部分SO_2和CO资料;③韦伯分布最适于高浓度的SO_2资料;④指数分布不适于城市大气污染物的浓度分布;⑤NO_x的分布较复杂。 相似文献
13.
Vacuum interrupter, high reliability component of distribution switches, circuit breakers and contactors 总被引：1，自引：0，他引：1
SLADE Paul G LI Wang-pei MAYO Stephen SMITH R. Kirkland TAYLOR Erik D 《浙江大学学报(A卷英文版)》2007,8(3):335-342
The use of vacuum interrupters(VIs)as the current interruption component for switches,circuit breakers,reclosers and contactors operating at distribution voltages has escalated since their introduction in the mid-1950’s.This electrical product has developed a dominating position for switching and protecting distribution circuits.VIs are even being introduced into switching products operating at transmission voltages.Among the reasons for the VI’s popularity are its compactness,its range of application,its low cost,its superb electrical and mechanical life and its ease of application.Its major advantage is its well-established reliability.In this paper we show how this reliability has been achieved by design,by mechanical life testing and by electrical performance testing.We introduce the“sealed for life”concept for the VI’s integrity.We discuss this in terms of what is meant by a practical leak rate for VIs with a life of over 30 years.We show that a simple high voltage withstand test is an easy and effective method for monitoring the long-term vacuum integrity.Finally we evaluate the need for routine inspection of this electrical product when it is used in adverse ambient environments. 相似文献
14.
The Development of Affiliative and Agonistic Social Patterns in Differentially Reared Monkeys 总被引：1，自引：0，他引：1
Bonnet macaques that had been reared from 3 to 6 months of age in experimental environments that appeared to adversely affect their ability to separate from mother to explore a novel physical environment in dyadic assessments shortly after the rearing experience were tested during late adolescence, an average of 2.5 years later, under conditions of increasing unfamiliarity and complexity of the social milieu. 6 monkeys, the low-foraging-demand (LFD) group, were reared by mothers having constant easy access to food during the experimental rearing period. Another 6 monkeys, the variable-foraging-demand (VFD) group, were reared by mothers having a foraging task that varied between easy and difficult in 2-week blocks during the experimental rearing period. Although no treatment group differences were evident during the initial rearing period, during subsequent social challenges VFD monkeys exhibited a diminished capacity for affiliative social engagement relative to LFD monkeys and were socially subordinate to LFD monkeys. 相似文献
15.
为解决在定数截尾的情况下混合weibull分布的参数估计问题,给出了混合weibull分布的后验参数估计形式,设计了用于参数Bayes估计的Gibbs抽样方案.通过随机模拟,结果显示,采用Gibbs抽样算法的参数估计具有一定的有效性和良好的稳定性,特别在样本较少的情况下优于使用EM算法的估计结果. 相似文献
16.
针对机采油井油管经常发生疲劳断裂的问题,加工了J55油管疲劳试件,通过成组多级疲劳试验法,获得了J55油管高周疲劳分组试验数据。通过疲劳寿命的参数估计和疲劳寿命的分布类型检验,获得了J55油管在不同轴向应力水平下的疲劳寿命、分布规律和P-S-N曲线。结果显示,J55油管的疲劳寿命服从对数状态分布,其S-N曲线服从一般金属的疲劳S-N曲线形式。在疲劳寿命一定时,欲获得较高的可靠性,需大幅度降低油管的疲劳应力。 相似文献
17.
This study examined the effects of a training programme on students’ acquisition of life skills, life satisfaction, life orientation and expectations about academic achievement. Participants were allocated to either an intervention group (n?=?41) that took part in a life skills programme, or a control group (n?=?43). Participants completed the Youth Experiences Scale 2.0, the satisfaction with life scale, the life orientation test-revised and the expectations about academic achievement. Results showed that students who received the intervention reported having more developmental experiences related to life skills, greater life satisfaction and a stronger tendency to be optimistic. Expectations about academic achievement were higher for the intervention group before and after the intervention. In conclusion, there are benefits to providing life skills training to adolescents in educational contexts. 相似文献
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19.
加工中心MTBF值的点估计与区间估计 总被引：2，自引：0，他引：2
应用基于截尾数据的似然函数理论和Weibull分布下的似然比方法,对加工中心有替换定时截尾试验数据分别进行了加工中心平均故障时间间隔(MTBF)值的点估计与区间估计。根据似然函数的重要引理,用迭代方法进行了Weibull模型两个参数的区间估计,并进行了MTBF值的区间估计。本研究解决了加工中心可靠性评估工作中的难题。 相似文献
20.
主要运用问卷调查法,在某中等发达城市的四所学校采用分层随机抽样抽取440名小学生、500名初中生、500名高中生共1 440人对其学校生活满意度进行调查。结果表明：（1）总体上看,中小学生生活满意度成负偏态分布,整体水平较高;（2）学业成绩依然是影响学生学校生活满意度最重要的因素;学生在学校普遍缺乏自我展示的机会;自由度较低;（3）中小学生的校内人际关系自我评价较高,但师生关系和同伴关系对中学生和小学生的学校生活满意度影响呈现出明显差异。 相似文献