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.

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.

A PENALTY FUNCTION METHOD FOR THE PRINCIPAL-AGENT PROBLEM WITH AN INFINITE NUMBER OF INCENTIVE-COMPATIBILITY CONSTRAINTS UNDER MORAL HAZARD

In this paper,we propose an iterative algorithm to find the optimal incentive mechanism for the principal-agent problem under moral hazard where the number of agent action profiles is infinite,and where there are an infinite number of results that can be observed by the principal.This principal-agent problem has an infinite number of incentive-compatibility constraints,and we transform it into an optimization problem with an infinite number of constraints called a semi-infinite programming problem.We then propose an exterior penalty function method to find the optimal solution to this semi-infinite programming and illustrate the convergence of this algorithm.By analyzing the optimal solution obtained by the proposed penalty function method,we can obtain the optimal incentive mechanism for the principal-agent problem with an infinite number of incentive-compatibility constraints under moral hazard.

Lung Function Impairment among Gasoline Attendants: A Cross-Sectional Study

Background: Occupational health is an important consideration, especially for people that work in an environment with pollutants. Gasoline attendants are individuals that work in filling stations. They are constantly exposed to gasoline fumes and automobile engine products from vehicle exhaust. This increases the risk of acute and chronic respiratory diseases and carcinogenesis among them. The risk of health complications tends to increase with the duration of exposure. The study aimed to determine the proportion of gasoline attendants with lung function impairment. Methods and Materials: Two hundred and eight eligible participants were recruited for this study. A cross-sectional analytical study was carried out in Esan West local government area of Edo state, Nigeria. The study was carried out for a period of six months from December 2015 to May 2016. A questionnaire was used to obtain information on demographic characteristics, work history, mode of exposure and duration of exposure to petrol fumes. Lung function was assessed using a DTspiro spirometer (Model POP 10. Serial no 110843-005);also the anthropometric parameters of the respondent were measured. Statistical analysis was done using IBM SPSS version 20.0. Frequency and percentages were used to present categorical data. The mean and standard deviation of continuous variables were calculated and compared using the student’s t-test. The criteria of significant association were assumed for a p-value less than 0.05. Results: A total of one hundred and forty petrol pump attendants and one hundred and forty controls participated in this study. The mean age for petrol pump attendants was 24 ± 3.1 years and 23 ± 2.8 years for the control group. There were no significant differences in the gender distribution and anthropometric parameters as observed in this study. The lung impairment pattern observed in this study was obstructive in twelve (8.6%) gasoline pump attendants and restrictive pattern in thirty-nine (27.9%) gasoline pump attendants, while only four (2.9%) had an obstructive pattern and twelve (8.6%) had a restrictive pattern of lung impairment among the control group. This implies that a restrictive pattern was predominant. This study also observed that there was an increase in the number of gasoline pump attendants with declined lung function compared to the control group. Conclusion: Restrictive pattern of lung impairment was more predominant than the obstructive pattern among gasoline pump attendants. As a result, public health interventions should be instituted among these individuals, especially in developing countries.

Lung Function Impairment among Gasoline Attendants: A Cross-Sectional Study

Background: Occupational health is an important consideration, especially for people that work in an environment with pollutants. Gasoline attendants are individuals that work in filling stations. They are constantly exposed to gasoline fumes and automobile engine products from vehicle exhaust. This increases the risk of acute and chronic respiratory diseases and carcinogenesis among them. The risk of health complications tends to increase with the duration of exposure. The study aimed to determine the proportion of gasoline attendants with lung function impairment. Methods and Materials: Two hundred and eight eligible participants were recruited for this study. A cross-sectional analytical study was carried out in Esan West local government area of Edo state, Nigeria. The study was carried out for a period of six months from December 2015 to May 2016. A questionnaire was used to obtain information on demographic characteristics, work history, mode of exposure and duration of exposure to petrol fumes. Lung function was assessed using a DTspiro spirometer (Model POP 10. Serial no 110843-005);also the anthropometric parameters of the respondent were measured. Statistical analysis was done using IBM SPSS version 20.0. Frequency and percentages were used to present categorical data. The mean and standard deviation of continuous variables were calculated and compared using the student’s t-test. The criteria of significant association were assumed for a p-value less than 0.05. Results: A total of one hundred and forty petrol pump attendants and one hundred and forty controls participated in this study. The mean age for petrol pump attendants was 24 ± 3.1 years and 23 ± 2.8 years for the control group. There were no significant differences in the gender distribution and anthropometric parameters as observed in this study. The lung impairment pattern observed in this study was obstructive in twelve (8.6%) gasoline pump attendants and restrictive pattern in thirty-nine (27.9%) gasoline pump attendants, while only four (2.9%) had an obstructive pattern and twelve (8.6%) had a restrictive pattern of lung impairment among the control group. This implies that a restrictive pattern was predominant. This study also observed that there was an increase in the number of gasoline pump attendants with declined lung function compared to the control group. Conclusion: Restrictive pattern of lung impairment was more predominant than the obstructive pattern among gasoline pump attendants. As a result, public health interventions should be instituted among these individuals, especially in developing countries.

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。

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。

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.

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。

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。

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。

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。

危化品安全风险监测预警系统建设

随着我国工业化进程的加快和经济的快速发展,危化品的使用量和储存量不断增加,由此带来的安全风险也日益凸显。为保障人民群众的生命财产安全,建立一个高效可靠的危化品安全风险监测预警系统显得尤为重要。基于某市危化品安全风险监测预警系统的建设,文章从监测预警系统业务流程、系统架构、功能设计、系统部署等方面进行详细探讨。实践表明,该系统通过视频监控及智能分析、物联监测和预警等功能,实现了对危化品企业的实时智能监管,提高了企业现场安全管理水平,为监管部门提升监管效能奠定了基础。

某关停铅蓄电池企业土壤重金属污染特征及生态风险评价

为探明江苏省某铅蓄电池企业生产6年关停后对该地块土壤是否造成污染,对土壤中Pb、Cu、Zn、Hg、As、Cd、Ni、Cr这8种重金属采样分析,基于主成分分析和径向基函数(RBF)插值法分析地块土壤重金属的污染分布特征。利用单因子指数法和Nemerow综合指数法对污染地块土壤环境质量分析,对于涉及人体健康生态风险评价采用Hakanson潜在生态危害指数法开展综合评价。结果表明:研究区域土壤已遭受明显的人为外源重金属污染,且局部重金属富集程度较高,纵向污染区域主要集中在100cm以上土壤中,区域整体污染程度达到轻度污染,其中危废库局部土壤受污染程度已为中度污染,建议对该单元土壤开展进一步风险评估和修复;研究区域土壤尚不存在潜在生态风险,但是需重点关注危废库构筑物单元的土壤环境质量,主要威胁来自土壤中的镉,其EiCd潜在生态风险指数等级已达到强的级别。建议该地块后续开发利用时不作为农用地使用或进行局部区域土壤修复治理。

Accelerated proportional degradation hazards-odds model in accelerated degradation test

An accelerated proportional degradation hazards-odds model is proposed. It is a non-parametric model and thus has path- free and distribution-free properties, avoiding the errors caused by faulty assumptions of degradation paths or distribution of degra- dation measurements. It is established based on a link function which combines the degradation cumulative hazard rate function and the degradation odds function through a transformation pa- rameter, and this makes the accelerated proportional degradation hazards model and the accelerated proportional degradation odds model special cases of it. Hypothesis tests are discussed, and the proposed model is applicable when some model assumptions are satisfied. This model is utilized to estimate the reliability of minia- ture bulbs under low stress levels based on the degradation data obtained under high stress levels to validate the effectiveness of this model.

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.

ADDITIVE HAZARDS MODEL WITH TIME-VARYING REGRESSION COEFFICIENTS

This article discusses regression analysis of failure time under the additive hazards model, when the regression coefficients are time-varying. The regression coefficients are estimated locally based on the pseudo-score function [12] in a window around each time point. The proposed method can be easily implemented, and the resulting estimators are shown to be consistent and asymptotically normal with easily estimated variances. The simulation studies show that our estimation procedure is reliable and useful.