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
To increase the detectability of split Hopkinson pressure bar （SHPB） of low-impedance materials, modifications were conducted on traditional SHPB apparatus with a PMMA tube to output transmitted signal, and weak sig...To increase the detectability of split Hopkinson pressure bar （SHPB） of low-impedance materials, modifications were conducted on traditional SHPB apparatus with a PMMA tube to output transmitted signal, and weak signals were further amplified by semiconductor strain gauges. Experiments on soft rubbers and cushioning foam materials were carried out. In order to analyze the accuracy of the experimental results, the stress equilibrium issues involved in the assumptions of SHPB were investigated. First, by way of re-constructing loading process of incident wave, the stress- strain curve was obtained, along with the stress equilibrium ratio of specimen. Secondly, the influences on the accuracy of stress-strain curves were investigated through the elastic modulus comparisons. And the results illustrate that the bilinear incident wave from experiments can ensure the stress equilibrium deformation of specimen after 2 normalized times, much sooner than ramp incident waves. Moreover, it even facilitates specimen deformation with a constant strain rate. The results confirm that the detectability of the modified SHPB can be down to tens kPa with enough accuracy level.展开更多
Background:Previous studies had shown that short-term acute heat stress(HS)affected the host’s metabolism and intestinal microbiota independent of feed intake(FI)reduction,and long-term calorie restriction caused int...Background:Previous studies had shown that short-term acute heat stress(HS)affected the host’s metabolism and intestinal microbiota independent of feed intake(FI)reduction,and long-term calorie restriction caused intestinal morphological injuries and gut microbial alterations.However,research on the effects of constant chronic HS on intestinal microbial composition and the roles of FI reduction played in is limited.This study aimed to investigate the effects of 7-day constant chronic HS on the composition of intestinal microbes in growing-finishing pigs,and its relationship with pigs’performance,intestinal morphology,and ileal immune response.Twenty-four growingfinishing pigs(Duroc×Large White×Landrace,30±1 kg body weight)were randomly assigned to three treatments(n=8),1)thermal neutral(TN)conditions(25±1℃)with ad libitum FI,2)HS conditions(35±1℃)with ad libitum FI,3)pair-fed(PF)with HS under TN conditions to discriminate the confounding effects of dissimilar FI,and the FI was the previous day’s average FI of HS.The small intestinal segments(duodenum,jejunum,and ileum)and feces were collected on d 8.Results:Results indicated that HS drastically declined(P<0.05)average daily gain(ADG)and average daily feed intake(ADFI)(about 61%)in comparison with TN,and caused hyperpyrexia,meanwhile PF caused hypothermia.Morphological observation by light and electron microscopes showed that both HS and PF treatment decreased(P<0.05)the villus and microvillus height compared with TN.Additionally,HS increased(P<0.05)protein expression of heat shock protein 70 in the duodenum,jejunum,and ileum.Furthermore,the expression of tight junction protein zonula occluden-1(ZO-1)in the duodenum and ileum,and Occludin in the ileum were enhanced(P<0.05)compared with TN and PF.Moreover,HS significantly enhanced(P<0.05)the mRNA relative expression of inflammatory cytokines(TLR-2,TLR-4,and tumor necrosis factor-α(TNF-α),IL-6,IL-8,PG1–5,β-defensin 2(pBD-2)),mucins(mucin-1 and mucin-2)and P65 protein level in the ileal mucosa tis展开更多
Gas wiping is a decisive operation in hot-dip galvanizing process. In special, it has a crucial influence on the thickness and uniformity in coating film, but may be subsequently responsible for the problem of splashi...Gas wiping is a decisive operation in hot-dip galvanizing process. In special, it has a crucial influence on the thickness and uniformity in coating film, but may be subsequently responsible for the problem of splashing. The progress of industry demands continuously the reduction of production costs which may relate directly with the increase of coating speed, and the speed up of coating results in the increase of stagnation pressure in gas wiping system in final. It is known that the increase of stagnation pressure may accompany a harmful problem of splashing in general. Together with these, also, from the view point of energy consumption, it is necessary to design a nozzle optimally. And there is known that the downward tilting of nozzle using in air knife system is effective to prevent in somewhat the harmful problem of splashing. In these connections, first, we design a nozzle with constant expansion rate. Next, for the case of actual coating conditions in field, the effects of tilting of the constant expansion rate nozzle are investigated by numerical analysis. Under the present numerical conditions, it was turned out that the nozzle of constant expansion rate of p = having a downward jet angle of 5^0 is the most effective to diminish the onset of splashing, while the influence of small tilting of the nozzle on impinging wall pres- sure itself is not so large.展开更多
Accelerated life test (ALT) is an important branch of reliability test and is a focus of research both for statisticians and reliability engineers. The paper outlines the four topics of study embodied in ALT: statisti...Accelerated life test (ALT) is an important branch of reliability test and is a focus of research both for statisticians and reliability engineers. The paper outlines the four topics of study embodied in ALT: statistical analysis of constant-stress test, step-stress test and progressive stress test, and optimal design of ALT. It gives a general review of engineering applications of ALT, and points out some possible directions in ALT, gives some suggestions for further study.展开更多
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.
基金Supported by the National Natural Science Foundation(11272267,11102168,10932008)111 Project(B07050)
文摘To increase the detectability of split Hopkinson pressure bar （SHPB） of low-impedance materials, modifications were conducted on traditional SHPB apparatus with a PMMA tube to output transmitted signal, and weak signals were further amplified by semiconductor strain gauges. Experiments on soft rubbers and cushioning foam materials were carried out. In order to analyze the accuracy of the experimental results, the stress equilibrium issues involved in the assumptions of SHPB were investigated. First, by way of re-constructing loading process of incident wave, the stress- strain curve was obtained, along with the stress equilibrium ratio of specimen. Secondly, the influences on the accuracy of stress-strain curves were investigated through the elastic modulus comparisons. And the results illustrate that the bilinear incident wave from experiments can ensure the stress equilibrium deformation of specimen after 2 normalized times, much sooner than ramp incident waves. Moreover, it even facilitates specimen deformation with a constant strain rate. The results confirm that the detectability of the modified SHPB can be down to tens kPa with enough accuracy level.
基金supported by National Key Research and Development Program of China(2016YFD0500501)the China Agriculture Research System of MOF and MARA+1 种基金the Science and Technology Program of Guangdong Academy of Agricultural Sciences(R2020PY-JG009,202106TD)the Project of Swine Innovation Team in Guangdong Modern Agricultural Research System(2021KJ126)。
文摘Background:Previous studies had shown that short-term acute heat stress(HS)affected the host’s metabolism and intestinal microbiota independent of feed intake(FI)reduction,and long-term calorie restriction caused intestinal morphological injuries and gut microbial alterations.However,research on the effects of constant chronic HS on intestinal microbial composition and the roles of FI reduction played in is limited.This study aimed to investigate the effects of 7-day constant chronic HS on the composition of intestinal microbes in growing-finishing pigs,and its relationship with pigs’performance,intestinal morphology,and ileal immune response.Twenty-four growingfinishing pigs(Duroc×Large White×Landrace,30±1 kg body weight)were randomly assigned to three treatments(n=8),1)thermal neutral(TN)conditions(25±1℃)with ad libitum FI,2)HS conditions(35±1℃)with ad libitum FI,3)pair-fed(PF)with HS under TN conditions to discriminate the confounding effects of dissimilar FI,and the FI was the previous day’s average FI of HS.The small intestinal segments(duodenum,jejunum,and ileum)and feces were collected on d 8.Results:Results indicated that HS drastically declined(P<0.05)average daily gain(ADG)and average daily feed intake(ADFI)(about 61%)in comparison with TN,and caused hyperpyrexia,meanwhile PF caused hypothermia.Morphological observation by light and electron microscopes showed that both HS and PF treatment decreased(P<0.05)the villus and microvillus height compared with TN.Additionally,HS increased(P<0.05)protein expression of heat shock protein 70 in the duodenum,jejunum,and ileum.Furthermore,the expression of tight junction protein zonula occluden-1(ZO-1)in the duodenum and ileum,and Occludin in the ileum were enhanced(P<0.05)compared with TN and PF.Moreover,HS significantly enhanced(P<0.05)the mRNA relative expression of inflammatory cytokines(TLR-2,TLR-4,and tumor necrosis factor-α(TNF-α),IL-6,IL-8,PG1–5,β-defensin 2(pBD-2)),mucins(mucin-1 and mucin-2)and P65 protein level in the ileal mucosa tis
文摘Gas wiping is a decisive operation in hot-dip galvanizing process. In special, it has a crucial influence on the thickness and uniformity in coating film, but may be subsequently responsible for the problem of splashing. The progress of industry demands continuously the reduction of production costs which may relate directly with the increase of coating speed, and the speed up of coating results in the increase of stagnation pressure in gas wiping system in final. It is known that the increase of stagnation pressure may accompany a harmful problem of splashing in general. Together with these, also, from the view point of energy consumption, it is necessary to design a nozzle optimally. And there is known that the downward tilting of nozzle using in air knife system is effective to prevent in somewhat the harmful problem of splashing. In these connections, first, we design a nozzle with constant expansion rate. Next, for the case of actual coating conditions in field, the effects of tilting of the constant expansion rate nozzle are investigated by numerical analysis. Under the present numerical conditions, it was turned out that the nozzle of constant expansion rate of p = having a downward jet angle of 5^0 is the most effective to diminish the onset of splashing, while the influence of small tilting of the nozzle on impinging wall pres- sure itself is not so large.
文摘Accelerated life test (ALT) is an important branch of reliability test and is a focus of research both for statisticians and reliability engineers. The paper outlines the four topics of study embodied in ALT: statistical analysis of constant-stress test, step-stress test and progressive stress test, and optimal design of ALT. It gives a general review of engineering applications of ALT, and points out some possible directions in ALT, gives some suggestions for further study.
