Context/Objective: High blood pressure (HBP) currently represents the most widespread chronic non-communicable disease in Cameroon. The increase in its prevalence in the country is the result of multiple factors inclu...Context/Objective: High blood pressure (HBP) currently represents the most widespread chronic non-communicable disease in Cameroon. The increase in its prevalence in the country is the result of multiple factors including economic stress imposed by precariousness, poor living conditions, sources of anxiety, anguish, depression and other behavioral disorders. Economic stress is a globalizing concept that integrates into a purely hermeneutic approach, a particular functioning of the nervous system of an individual who faces employment problems and precarious remuneration conditions. The non-satisfaction by an individual of his basic needs due to insufficient financial means can cause him to become irritable, aggressive, and socially and symbolically isolated, thereby increasing the desire to resort to morbid life models such as excessive consumption of narcotics and other psychoactive substances often associated with high blood pressure. The fight against the emergence of BPH is a complex, multifaceted and multifactorial reality that requires taking into account economic stress. The main objective of this survey is to describe the situation of economic stress within the Cameroonian population, which imposes precariousness and life models at risk of high blood pressure. Specifically, we determined the level of household income and the sources of income. Methods: A cross-sectional survey with a descriptive aim among five hundred households in the Central Region of Cameroon was conducted. A probabilistic technique called simple randomness was used. The number of households to be surveyed was determined indirectly using the Cochrane formula. Data collection in face-to-face mode using a physical questionnaire took place from July 1 to August 31, 2023, after obtaining ethical clearance from the Regional Health Research Ethics Committee, Human from the Center and an administrative authorization for data collection. Regarding their processing, the data was grouped during processing in Excel sheets. Normality and reliability tests of the collected data were carried out. For this, the Chi-square test was used for data with a qualitative value and that of Kolmogorov-Sminorf for data with a quantitative value. Descriptive analysis was possible using R software version 3.2, SPSS version 25.0, XLSTAT 2016, PAST and EXCEL programs from Microsoft Office 2013. Results: The main results highlight economic stress, with 45.60% of households surveyed earning less than US$154 per month;55% of household heads were women in single-parent families;14% of household heads were unemployed, 22% worked in the private sector and 19% were self-employed. This general economic situation leads to precarious living conditions, thereby increasing the risk of high blood pressure among the Cameroonian population.展开更多
The optimum design of equivalent accelerated life testing plan based on proportional hazards-proportional odds model using D-optimality is presented. The defined equivalent test plan is the test plan that has the same...The optimum design of equivalent accelerated life testing plan based on proportional hazards-proportional odds model using D-optimality is presented. The defined equivalent test plan is the test plan that has the same value of the determinant of Fisher information matrix. The equivalent test plan of step stress accelerated life testing （SSALT） to a baseline optimum constant stress accelerated life testing （CSALT） plan is obtained by adjusting the censoring time of SSALT and solving the optimization problem for each case to achieve the same value of the determinant of Fisher information matrix as in the baseline optimum CSALT plan. Numer- ical examples are given finally which demonstrate the equivalent SSALT plan to the baseline optimum CSALT plan reduces almost half of the test time while achieving approximately the same estimation errors of model parameters.展开更多
AIM: To provide a structural model of the relationship between personality traits, perceived stress, coping strategies, social support, and psychological outcomes in the general population.METHODS: This is a cross sec...AIM: To provide a structural model of the relationship between personality traits, perceived stress, coping strategies, social support, and psychological outcomes in the general population.METHODS: This is a cross sectional study in which the study group was selected using multistage cluster and convenience sampling among a population of 4 million. For data collection, a total of 4763 individuals were asked to complete a questionnaire on demographics, personality traits, life events, coping with stress, social support, and psychological outcomes such as anxiety and depression. To evaluate the comprehensive relation-ship between the variables, a path model was fitted.RESULTS: The standard electronic modules showed that personality traits and perceived stress are important determinants of psychological outcomes. Social support and coping strategies were demonstrated to reduce the increasing cumulative positive effects of neuroticism and perceived stress on the psychological outcomes and enhance the protective effect of extraversion through decreasing the positive effect of perceived stress on the psychological outcomes. CONCLUSION: Personal resources play an important role in reduction and prevention of anxiety and depression. In order to improve the psychological health, it is necessary to train and reinforce the adaptive coping strategies and social support, and thus, to moderate negative personality traits.展开更多
The effects of ambient temperature and shaft power variations on creep life consumption of compressor turbine blades of LM2500+ industrial gas turbine engine are investigated in this work. An engine model was created ...The effects of ambient temperature and shaft power variations on creep life consumption of compressor turbine blades of LM2500+ industrial gas turbine engine are investigated in this work. An engine model was created in PYTHIA (Cranfield University’s gas turbine software) for the analysis. Blade thermal and stress models were developed and used together with Larson-Miller Parameter method for life analysis. Mean life reduction index, which is the propensity of a given effect to reduce engine life by half, is developed for each effect and applied in this research to compare the impacts of the different effects on the blade creep life. It was observed that blade life will be halved when ambient temperature is increased by 8.11 units while 13.64% increase in shaft power reduces blade life by a factor of 2. The results of this work will guide engine operators in making decisions concerning operating at part loads.展开更多
为了解决多层片式陶瓷电容器(MLCC)在高可靠产品应用、研发验证和产品改进等环节对快速可靠性评价技术的需求,提出了一种基于Procopowicz-Vaskas模型(P-V模型)的高加速寿命试验(HALT)评价方法,开展了某10μF 6.3 V MLCC产品在9组不同高...为了解决多层片式陶瓷电容器(MLCC)在高可靠产品应用、研发验证和产品改进等环节对快速可靠性评价技术的需求,提出了一种基于Procopowicz-Vaskas模型(P-V模型)的高加速寿命试验(HALT)评价方法,开展了某10μF 6.3 V MLCC产品在9组不同高温、高电压下的HALT研究。获得了样品在不同温度和电压应力下的失效分布特征,其P-V寿命模型参数的激活能为1.30 eV、电场加速因子为3.79。建立了高容量MLCC产品的HALT寿命模型,为其可靠性快速评价提供了参考。展开更多
研究了平均应力效应对7075-T651铝合金疲劳性能的影响,选取了R=0.5、0.3、0.1和-0.1四组应力比进行疲劳试验。结果表明,同一应力比下,随着峰值应力水平的增加,疲劳寿命逐渐降低;而同一峰值应力水平下,随着应力比的提高,疲劳寿命则呈现...研究了平均应力效应对7075-T651铝合金疲劳性能的影响,选取了R=0.5、0.3、0.1和-0.1四组应力比进行疲劳试验。结果表明,同一应力比下,随着峰值应力水平的增加,疲劳寿命逐渐降低;而同一峰值应力水平下,随着应力比的提高,疲劳寿命则呈现出逐渐升高的趋势。同时,使用扫描电子显微镜(Scanning Electron Microscopy,SEM)观察疲劳断口形貌发现,在峰值应力相同的情况下,裂纹萌生及扩展区的扇形面积随平均应力的增大而增大。最后,基于7075-T651铝合金疲劳实验结果,提出了一种考虑S-N-R的改进型预测模型,结果对比显示相较于其他模型,此模型在一定程度上对7075-T651铝合金具有更好的疲劳寿命预测效果。展开更多
Abstract With the recent products being more reliable, engineers cannot obtain enough failure or degradation information through the design period and even the product lifetime, therefore, accel erated life test （ALT...Abstract With the recent products being more reliable, engineers cannot obtain enough failure or degradation information through the design period and even the product lifetime, therefore, accel erated life test （ALT） ihas become the most popular way to quantify the life characteristics of prod ucts. Test design is the most essential topic, such as testing duration, stress profile, data inference, etc. In this paper, a method and procedure based on theoretical life models is proposed to determine the accelerated stress profile. Firstly, the method for theoretical life calculation is put forward based on the main failure mechanism analysis and the theoretical life models. Secondly, the method is pro vided to determine the accelerated stress profile, including the method to determine the accelerated stress types and the stress range on the basis of the main failure mechanism analysis, the method to determine the acceleration factor and the accelerated stress level based on life quantitative calcula tion models, and the collaborative analysis method of the accelerated test time while taking the mul tiple failure mechanisms into consideration. Lastly, the actuator is taken as an example to describe the procedure of the method and the engineering applicability and the validity are verified.展开更多
文摘Context/Objective: High blood pressure (HBP) currently represents the most widespread chronic non-communicable disease in Cameroon. The increase in its prevalence in the country is the result of multiple factors including economic stress imposed by precariousness, poor living conditions, sources of anxiety, anguish, depression and other behavioral disorders. Economic stress is a globalizing concept that integrates into a purely hermeneutic approach, a particular functioning of the nervous system of an individual who faces employment problems and precarious remuneration conditions. The non-satisfaction by an individual of his basic needs due to insufficient financial means can cause him to become irritable, aggressive, and socially and symbolically isolated, thereby increasing the desire to resort to morbid life models such as excessive consumption of narcotics and other psychoactive substances often associated with high blood pressure. The fight against the emergence of BPH is a complex, multifaceted and multifactorial reality that requires taking into account economic stress. The main objective of this survey is to describe the situation of economic stress within the Cameroonian population, which imposes precariousness and life models at risk of high blood pressure. Specifically, we determined the level of household income and the sources of income. Methods: A cross-sectional survey with a descriptive aim among five hundred households in the Central Region of Cameroon was conducted. A probabilistic technique called simple randomness was used. The number of households to be surveyed was determined indirectly using the Cochrane formula. Data collection in face-to-face mode using a physical questionnaire took place from July 1 to August 31, 2023, after obtaining ethical clearance from the Regional Health Research Ethics Committee, Human from the Center and an administrative authorization for data collection. Regarding their processing, the data was grouped during processing in Excel sheets. Normality and reliability tests of the collected data were carried out. For this, the Chi-square test was used for data with a qualitative value and that of Kolmogorov-Sminorf for data with a quantitative value. Descriptive analysis was possible using R software version 3.2, SPSS version 25.0, XLSTAT 2016, PAST and EXCEL programs from Microsoft Office 2013. Results: The main results highlight economic stress, with 45.60% of households surveyed earning less than US$154 per month;55% of household heads were women in single-parent families;14% of household heads were unemployed, 22% worked in the private sector and 19% were self-employed. This general economic situation leads to precarious living conditions, thereby increasing the risk of high blood pressure among the Cameroonian population.
文摘The optimum design of equivalent accelerated life testing plan based on proportional hazards-proportional odds model using D-optimality is presented. The defined equivalent test plan is the test plan that has the same value of the determinant of Fisher information matrix. The equivalent test plan of step stress accelerated life testing （SSALT） to a baseline optimum constant stress accelerated life testing （CSALT） plan is obtained by adjusting the censoring time of SSALT and solving the optimization problem for each case to achieve the same value of the determinant of Fisher information matrix as in the baseline optimum CSALT plan. Numer- ical examples are given finally which demonstrate the equivalent SSALT plan to the baseline optimum CSALT plan reduces almost half of the test time while achieving approximately the same estimation errors of model parameters.
文摘AIM: To provide a structural model of the relationship between personality traits, perceived stress, coping strategies, social support, and psychological outcomes in the general population.METHODS: This is a cross sectional study in which the study group was selected using multistage cluster and convenience sampling among a population of 4 million. For data collection, a total of 4763 individuals were asked to complete a questionnaire on demographics, personality traits, life events, coping with stress, social support, and psychological outcomes such as anxiety and depression. To evaluate the comprehensive relation-ship between the variables, a path model was fitted.RESULTS: The standard electronic modules showed that personality traits and perceived stress are important determinants of psychological outcomes. Social support and coping strategies were demonstrated to reduce the increasing cumulative positive effects of neuroticism and perceived stress on the psychological outcomes and enhance the protective effect of extraversion through decreasing the positive effect of perceived stress on the psychological outcomes. CONCLUSION: Personal resources play an important role in reduction and prevention of anxiety and depression. In order to improve the psychological health, it is necessary to train and reinforce the adaptive coping strategies and social support, and thus, to moderate negative personality traits.
文摘The effects of ambient temperature and shaft power variations on creep life consumption of compressor turbine blades of LM2500+ industrial gas turbine engine are investigated in this work. An engine model was created in PYTHIA (Cranfield University’s gas turbine software) for the analysis. Blade thermal and stress models were developed and used together with Larson-Miller Parameter method for life analysis. Mean life reduction index, which is the propensity of a given effect to reduce engine life by half, is developed for each effect and applied in this research to compare the impacts of the different effects on the blade creep life. It was observed that blade life will be halved when ambient temperature is increased by 8.11 units while 13.64% increase in shaft power reduces blade life by a factor of 2. The results of this work will guide engine operators in making decisions concerning operating at part loads.
文摘为了解决多层片式陶瓷电容器(MLCC)在高可靠产品应用、研发验证和产品改进等环节对快速可靠性评价技术的需求,提出了一种基于Procopowicz-Vaskas模型(P-V模型)的高加速寿命试验(HALT)评价方法,开展了某10μF 6.3 V MLCC产品在9组不同高温、高电压下的HALT研究。获得了样品在不同温度和电压应力下的失效分布特征,其P-V寿命模型参数的激活能为1.30 eV、电场加速因子为3.79。建立了高容量MLCC产品的HALT寿命模型,为其可靠性快速评价提供了参考。
文摘研究了平均应力效应对7075-T651铝合金疲劳性能的影响,选取了R=0.5、0.3、0.1和-0.1四组应力比进行疲劳试验。结果表明,同一应力比下,随着峰值应力水平的增加,疲劳寿命逐渐降低;而同一峰值应力水平下,随着应力比的提高,疲劳寿命则呈现出逐渐升高的趋势。同时,使用扫描电子显微镜(Scanning Electron Microscopy,SEM)观察疲劳断口形貌发现,在峰值应力相同的情况下,裂纹萌生及扩展区的扇形面积随平均应力的增大而增大。最后,基于7075-T651铝合金疲劳实验结果,提出了一种考虑S-N-R的改进型预测模型,结果对比显示相较于其他模型,此模型在一定程度上对7075-T651铝合金具有更好的疲劳寿命预测效果。
基金supported by the Ministry Level Project of China
文摘Abstract With the recent products being more reliable, engineers cannot obtain enough failure or degradation information through the design period and even the product lifetime, therefore, accel erated life test （ALT） ihas become the most popular way to quantify the life characteristics of prod ucts. Test design is the most essential topic, such as testing duration, stress profile, data inference, etc. In this paper, a method and procedure based on theoretical life models is proposed to determine the accelerated stress profile. Firstly, the method for theoretical life calculation is put forward based on the main failure mechanism analysis and the theoretical life models. Secondly, the method is pro vided to determine the accelerated stress profile, including the method to determine the accelerated stress types and the stress range on the basis of the main failure mechanism analysis, the method to determine the acceleration factor and the accelerated stress level based on life quantitative calcula tion models, and the collaborative analysis method of the accelerated test time while taking the mul tiple failure mechanisms into consideration. Lastly, the actuator is taken as an example to describe the procedure of the method and the engineering applicability and the validity are verified.
