HAZARD FUNCTION AND CHARACTERIZATIONS ON DISTRIBUTION TAILS OF NONNEGATIVE RANDOM VARIABLES

Some equivalent conditions on the classes of lighted-tailed and heavily heavy-tailed and lightly heavy-tailed d.f.s are introduced.The limit behavior of xα(x) and e λx(x) are discussed.Some properties of the subclass DKc and subclass DK 1 are obtained.

Consistency of the Estimator of Cumulative Hazard Function in Estimated Pseudo-Partial-Likelihood Approach

For multivariate failure time with auxiliary covariate information, an estimated pseudo-partial-likelihood estimator under the marginal hazard model with distinguishable baseline hazard has been proposed. However, the asymptotic properties of the corresponding estimated cumulative hazard function have not been studied. In this paper, based on counting process martingale, we use the continuous mapping theorem and Lenglart inequality and prove the consistency of the estimated cumulative hazard function in estimated pseudo-partial-likelihood approach.

ASYMPTOTIC NORMALITY OF THE NONPARAMETRIC KERNEL ESTIMATION OF THE CONDITIONAL HAZARD FUNCTION FOR LEFT-TRUNCATED AND DEPENDENT DATA

Under some mild conditions, we derive the asymptotic normality of the Nadaraya-Watson and local linear estimators of the conditional hazard function for left-truncated and dependent data. The estimators were proposed by Liang and Ould-Sa?d [1]. The results confirm the guess in Liang and Ould-Sa?d [1].

Hazard Rate Function Estimation Using Weibull Kernel

In this paper, we define the Weibull kernel and use it to nonparametric estimation of the probability density function (pdf) and the hazard rate function for independent and identically distributed (iid) data. The bias, variance and the optimal bandwidth of the proposed estimator are investigated. Moreover, the asymptotic normality of the proposed estimator is investigated. The performance of the proposed estimator is tested using simulation study and real data.

Copula joint function and its application in probability seismic hazard analysis

A mature mathematical technique called copula joint function is introduced in this paper, which is commonly used in the financial risk analysis to estimate uncertainty. The joint function is generalized to the n-dimensional Frank’s copula. In addition, we adopt two attenuation models proposed by YU and Boore et al, respectively, and construct a two-dimensional copula joint probabilistic function as an example to illustrate the uncertainty treatment at low probability. The results show that copula joint function gives us a better prediction of peak ground motion than that resultant from the simple linear weight technique which is commonly used in the traditional logic-tree treatment of model uncertainties. In light of widespread application in the risk analysis from financial investment to insurance assessment, we believe that the copula-based technique will have a potential application in the seismic hazard analysis.

Product reliability assessment based on proportional hazard degradation model

In order to evaluate the reliability of long-lifetime products with degradation data, a new proportional hazard degradation model is proposed. By the similarity between time-degradation data and stress-accelerated lifetime, and the failure rate function of degradation data which is assumed to be proportional to the time covariate, the reliability assessment based on a proportional hazard degradation model is realized. The least squares method is used to estimate the model＇s parameters. Based on the failure rate of the degradation data and the proportion function of the known time, the failure rate and the reliability function under the given time and the predetermined failure threshold can be extrapolated. A long life GaAs laser is selected as a case study and its reliability is evaluated. The results show that the proposed method can accurately describe the degradation process and it is effective for the reliability assessment of long lifetime products.

考虑时间变化的洪涝灾害损失评估

洪涝灾害是对我国影响最大的自然灾害之一。聚焦灾害损失评估问题,本文构建了考虑时间变化的洪涝灾害损失函数。一方面,表征灾害损失随着致灾因子强度先递增、而后增幅趋缓的静态S型曲线关系;另一方面,通过量级、形状和位置三个参数综合考虑灾害损失随时间的动态变化情况。基于《中国水旱灾害防御公报》提供的受灾人口、直接经济损失数据,对于各省级行政区2006—2021年洪涝灾害损失进行评估分析。结果表明:通过拟合洪涝灾害损失函数,洪涝灾害损失关于致灾因子强度和时间的三维空间散点图可有效地拓展成为连续的三维空间曲面及二维空间热力图。各省级行政区受灾人口整体上呈现出逐年下降的特征,但随致灾因子强度的增加而趋于增加。各省级行政区直接经济损失则表现出明显的差异,随时间呈现出大幅下降、缓慢下降和略有增加等不同特征。考虑时间变化的洪涝灾害损失函数是变化环境下灾害评估的有效工具,可为区域洪涝灾情评估提供借鉴和参考。

The Lambert-G Family:Properties,Inference,and Applications

This study proposes a new flexible family of distributions called the Lambert-G family.The Lambert family is very flexible and exhibits desirable properties.Its three-parameter special sub-models provide all significantmonotonic and non-monotonic failure rates.A special sub-model of the Lambert family called the Lambert-Lomax(LL)distribution is investigated.General expressions for the LL statistical properties are established.Characterizations of the LL distribution are addressed mathematically based on its hazard function.The estimation of the LL parameters is discussed using six estimation methods.The performance of this estimation method is explored through simulation experiments.The usefulness and flexibility of the LL distribution are demonstrated empirically using two real-life data sets.The LL model better fits the exponentiated Lomax,inverse power Lomax,Lomax-Rayleigh,power Lomax,and Lomax distributions.

系统安全性评估中飞行机组人为因素的分析方法

随着飞机系统日益高度综合复杂和自动化水平逐渐提高,飞行员在应对失效或应急情况时通常准备不足,纠正动作可能是不正确、不及时或不完整的,因此系统安全性评估中迫切需要考虑飞行机组人为因素问题。通过分析CCAR25.1309(b)和(c)条款的要求和飞行机组对失效的处理过程,基于功能危险性评估中的失效状态,提出人为因素需求的捕获方法和人为因素分析方法;通过在型号中应用这些方法,从失效状态向告警和程序的角度实现安全性正向设计,建立安全性评估中飞行机组人为因素的完整适航符合性证据链。结果表明:本文提出的方法可有效表明对CCAR25.1309(b)和(c)条款中人为因素相关的适航符合性。

基于高斯混合模型的采煤工作面冲击危险性评价

【目的】深入了解声发射或微震能量分布所蕴含的概率学信息,对于工作面回采过程中的冲击危险性评价具有重要意义。【方法】以陕西大佛寺煤矿4号煤层40111工作面作为工程背景,运用物理相似模拟实验、理论分析、现场监测等相关方法进行分析,研究了声发射监测数据在回采过程中的演化规律,阐明了声发射能量概率分布呈现波动性的物理意义,提出了基于高斯混合模型(Gaussianminture model,GMM)及置信区间的冲击危险性评价指标模型,并由现场微震数据进行验证。【结果和结论】结果表明:回采过程中上覆岩层周期性垮落并伴随声发射能量的集中释放。总能量的概率密度函数呈现多自由度的非对称分布,通过对比残差平方和等多项拟合效果指标,确定高斯混合模型为最佳拟合模型。基于EM(expectation maximization)算法的GMM聚类分析,将声发射事件总能量分布划分为两类:高频低能型和低频高能型,其中低频高能型与冲击事件的突发性和高能量破坏特征一致。依据概率-能量梯度变化特征,对工作面开采过程中冲击危险性进行了评估。研究成果为采煤工作面冲击危险性评价提供了概率学上的创新思路,具有在冲击地压监测预警及后续防治中的潜在应用价值。

不同构型电动垂直起降飞行器动力系统的安全性评估

安全性评估对电动垂直起降飞行器的架构开发、安全管理、设计验证及商业化有着至关重要的作用,但目前国内少有对电动垂直起降飞行器整机构型、系统设计等相关的研究。本文针对4种不同构型的电动垂直起降飞行器,包括垂起尾推固定翼构型、四轴八桨多旋翼构型、固定翼加倾转旋翼构型以及倾转机翼构型,使用功能危害分析和故障树分析方法对4种不同构型的动力系统进行了分析比较。分析表明:垂起尾推固定翼电动垂直起降飞行器动力架构在本文的特定使用场景中相对可靠性更优。2种分析方法的结合,增加了对功能危害理解的全面性和深度,并识别了减轻动力系统失效风险的多种潜在途径。安全性评估结果可以为电动垂直起降飞行器动力构型选择和产品开发提供依据。

The Cox Proportional Hazard Regression Model Vis-à-Vis ITN-Factor Impact on Mortality Due to Malaria

This study has provided a starting point for defining and working with Cox models in respect of multivariate modeling. In medical researches, there may be situations, where several risk factors potentially affect patient prognosis, howbeit, only one or two might predict patient’s predicament. In seeking to find out which of the risk factors contribute the most to the survival times of patients, there was the need for researchers to adjust the covariates to realize their impact on survival times of patients. Aside the multivariate nature of the covariates, some covariates might be categorical while others might be quantitative. Again, there might be cases where researchers need a model that has the capability of extending survival analysis methods to assessing simultaneously the effect of several risk factors on survival times. This study unveiled the Cox model as a robust technique which could accomplish the aforementioned cases. An investigation meant to evaluate the ITN-factor vis-à-vis its contribution towards death due to Malaria was exemplified with the Cox model. Data were taken from hospitals in Ghana. In doing so, we assessed hospital in-patients who reported cases of malaria (origin state) to time until death or censoring (destination stage) as a result of predictive factors (exposure to the malaria parasites) and some socioeconomic variables. We purposefully used Cox models to quantify the effect of the ITN-factor in the presence of other risk factors to obtain some measures of effect that could describe the relationship between the exposure variable and time until death adjusting for other variables. PH assumption holds for all three covariates. Sex of patient was insignificant to deaths due to malaria. Age of patient and user status were both significant. The magnitude of the coefficient (0.384) of ITN user status depicts its high contribution to the variation in the dependent variable.

STRONG REPRESENTATIONS OF THE SURVIVAL FUNCTION ESTIMATOR ON INCREASING SETS FOR TRUNCATED AND CENSORED DATA

In this paper, based on random left truncated and right censored data, the authors derive strong representations of the cumulative hazard function estimator and the product-limit estimator of the survival function. which are valid up to a given order statistic of the observations. A precise bound for the errors is obtained which only depends on the index of the last order statistic to be included.

相关标准紫外危害评估的差异研究

紫外产品目前在世界上被广泛应用于医院、学校、家庭等场所,具有净化空气、消毒环保的作用,由于产品存在紫外波段对人体有一定的危害性,评估紫外危害程度就显得尤为重要。本文从波长采样间隔、曝辐限值、紫外危害加权函数等方面,对不同的光生物标准IEC 62471:2006、GB/T 20145—2006和ANSI/IES RP-27.1-22在紫外危害评估的差异进行了分析比较,期望能够帮助读者更深入了解不同国家或地区在光化学紫外安全相关标准之间的差异。实验随机选取了三个光谱源数据,通过参考不同区域的标准来分析光化学紫外危害评估的差异。

Local Polynomial Estimation of Distribution Functions

Under the condition that the total distribution function is continuous and bounded on （ -∞,∞ ）, we constructed estimations for distribution and hazard functions with local polynomial method, and obtained the rate of strong convergence of the estimations.

某危险化学品企业GDS系统主要功能的应用

危险化学品行业面临着易燃、易爆、高温、高压等风险,气体泄漏的检测和管控显得尤为重要。介绍了GDS系统工作原理、主要功能、设置、配套设施、控制室以及供电技术等方面的内容,通过实际运行效果,有效确保了人员安全与工业安全。

以自适应巡航功能浅析功能安全概念阶段开发

文章基于ISO 26262第三部分概念阶段的要求,结合SAE J2980的补充,详细介绍了功能安全概念阶段相关项定义、危害分析与风险评估和功能安全概念开发三大活动的开发流程及方法。以自适应巡航功能为例,以功能激活这一子功能为落点,阐述了主机厂在功能安全概念阶段的分析与设计过程,包括相关性定义应包含的内容、HARA分析方法、ASIL等级的确定、安全目标及功能安全要求的导出等,对其他智能驾驶系统功能的功能安全开发具有一定的指导作用。

基于故障树定量分析的直升机振动主动控制系统安全性评估

振动主动控制系统作为直升机的重要组成设备,具有有效降低机上振动水平的作用,其安全性水平直接决定直升机的减振能力。本文以直升机振动主动控制系统为例,通过分析其功能危险因素,形成所有功能的故障状态清单。以灾难的、危险的故障状态作为顶事件进行故障树分析,并计算其发生概率,以评估振动主动控制系统安全性是否满足要求。

安全隐患排查治理在农机安全生产中的作用

农机安全隐患排查治理是农机监理部门的职责,是预防和减少农机事故,实施农机安全生产管理的重要环节。近年来,在诸多因素作用下,农业机械安全隐患排查治理很难落到实处,农机安全生产情况令人担忧。结合实际工作经验,分析了农机安全隐患排查治理在农机安全生产中的重要性,论述农机安全隐患排查存在的问题,提出了对策与建议。

基于RFID技术和ZigBee技术的危险品实验室安全监测系统设计

随着科学技术的不断发展,危险品实验室的安全问题日益引起人们的关注。为了提高实验室的安全性,基于射频识别(Radio Frequency Identification,RFID)技术和紫蜂协议(ZigBee)技术设计了一种危险品实验室安全监测系统,以提高实验室的安全性和管理效率。该系统通过RFID标签对实验室内的危险品进行追踪和管理,利用ZigBee技术实现实时的监测和报警功能。