A single-machine scheduling with preventive periodic maintenance activities in a remanufacturing system including resumable and non-resumable jobs is studied.The objective is to find a schedule to minimize the makespa...A single-machine scheduling with preventive periodic maintenance activities in a remanufacturing system including resumable and non-resumable jobs is studied.The objective is to find a schedule to minimize the makespan and an LPT-LS algorithm is proposed.Non-resumable jobs are first scheduled in a machine by the longest processing time（LPT） rule,and then resumable jobs are scheduled by the list scheduling（LS） rule.And the worst-case ratios of this algorithm in three different cases in terms of the value of the total processing time of the resumable jobs（denoted as S2） are discussed.When S2 is longer than the spare time of the machine after the non-resumable jobs are assigned by the LPT rule,it is equal to 1.When S2 falls in between the spare time of the machine by the LPT rule and the optimal schedule rule,it is less than 2.When S2 is less than the spare time of the machine by the optimal schedule rule,it is less than 2.Finally,numerical examples are presented for verification.展开更多
This paper analyzed the reliability and put forward the reliability index of overload protection for moulded case circuit breaker. The success rate was adopted as its reliability index of overload protection. Based on...This paper analyzed the reliability and put forward the reliability index of overload protection for moulded case circuit breaker. The success rate was adopted as its reliability index of overload protection. Based on the reliability index and the reli- ability level, the reliability examination plan was analyzed and a test device for the overload protection of moulded case cir- cuit-breaker was developed. In the reliability test of overload protection, two power sources were used, which reduced the time of conversion and regulation between two different test currents in the overload protection test, which made the characteristic test more accurate. The test device was designed on the base of a Windows system, which made its operation simple and friendly.展开更多
Although favourable results of pentoxifylline （PTX） used in treatment of severe alcoholic hepatitis patients with a Maddrey discriminant function score ≥ 32 have been previously reported, it is not currently recomm...Although favourable results of pentoxifylline （PTX） used in treatment of severe alcoholic hepatitis patients with a Maddrey discriminant function score ≥ 32 have been previously reported, it is not currently recommended as a first line treatment for alcoholic hepatitis owing to lack of evidence for its efficacy as compared to the standard treatment with corticosteroids. In a very recent issue of World Journal of Gastroenterology, Dr. De BK and colleagues compared for the first time the two treatment modalities head to head in a randomized controlled study, demonstrating the advantage of PTX over corticosteroids in terms of patients＇ survival and risk-benefit profile. The advantage of PTX over corticosteroids in survival of patients with severe alcoholic hepatitis was found to be related to the prevention of hepatorenal syndrome in their study. This study raises the question of the use of PI-X as a standard treatment for severe alcoholic hepatitis. Considering the fact that PTX presented a spectacular efficiency in prevention of hepatorenal syndrome in their study as well as that previous studies have shown that this effect is possibly related to a primary renoprotective action because it is irrelevant of tumor necrosis factor-c~ synthesis inhibition or improved liver function, we tempted to speculate that PXT might be an effective option for prevention and/or treatment of hepatorenal syndrome complicating other forms of advanced liver disease. This attractive theory remains to be elucidated by pressing future studies in view of the lack of effective treatment modalities for hepatorenal syndrome.展开更多
The Oscillating Water Column(OWC) wave energy convertor with the advantage of its simple geometrical construction and excellent stability is widely employed.Recently,perforated breakwaters have been often used as they...The Oscillating Water Column(OWC) wave energy convertor with the advantage of its simple geometrical construction and excellent stability is widely employed.Recently,perforated breakwaters have been often used as they can effectively reduce the wave reflection from and wave forces acting on the structures.Considering the similarity between the compartment of perforated caisson and the air chamber of OWC wave energy convertor,a new perforated caisson of breakwater is designed in this paper.The ordinary caisson is modified by installing facilities similar to the air chamber of OWC converter,but here they are utilized to dissipate the wave energy inside the caisson.Such an arrangement improves the stability of the caisson and reduces the construction cost by using the compartment of perforated caisson like using an air chamber.This innovation has both academic significance and important engineering value.For a new type of caisson,reliability analysis of the structure is necessary.Linear potential flow theory is applied to calculate the horizontal wave force acting on the caisson.The calculated results are compared with experimental data,showing the feasibility of the method.The Importance Sampling Procedure(ISP) is used to analyse the reliability of this caisson breakwater.展开更多
The reliability of a vertical breakwater is calculated using direct integration methods based on joint density functions.The horizontal and uplifting wave forces on the vertical breakwater can be well fitted by the lo...The reliability of a vertical breakwater is calculated using direct integration methods based on joint density functions.The horizontal and uplifting wave forces on the vertical breakwater can be well fitted by the lognormal and the Gumbel distributions,respectively.The joint distribution of the horizontal and uplifting wave forces is analyzed using different probabilistic distributions,including the bivariate logistic Gumbel distribution,the bivariate lognormal distribution,and three bivariate Archimedean copulas functions constructed with different marginal distributions simultaneously.We use the fully nested copulas to construct multivariate distributions taking into account related variables.Different goodness fitting tests are carried out to determine the best bivariate copula model for wave forces on a vertical breakwater.We show that a bivariate model constructed by Frank copula gives the best reliability analysis,using marginal distributions of Gumbel and lognormal to account for uplifting pressure and horizontal wave force on a vertical breakwater,respectively.The results show that failure probability of the vertical breakwater calculated by multivariate density function is comparable to those by the Joint Committee on Structural Safety methods.As copulas are suitable for constructing a bivariate or multivariate joint distribution,they have great potential in reliability analysis for other coastal structures.展开更多
The over-load protective relay is widely used directly affects the safe running of a motor. The reliability for motor protection. The reliability of the over-load protective relay testing and reliability analysis of t...The over-load protective relay is widely used directly affects the safe running of a motor. The reliability for motor protection. The reliability of the over-load protective relay testing and reliability analysis of the over-load protective relay is an important way to improve the reliability of products. In this paper, the reliability test method of the over-load protective relay is studied, and the reliability tests of the typical products are carried out on a reliability tester developed by authors. In terms of the testing results, the reliability analysis is finished. The failure reasons are found and the measures are put forward to improve the reliability of the products.展开更多
VFDs （variable frequency drives） are an integral part of many industrial plants and stations. Reliable operation and maintenance of these drives is vital to ensure sustained plant operation and availability. Underst...VFDs （variable frequency drives） are an integral part of many industrial plants and stations. Reliable operation and maintenance of these drives is vital to ensure sustained plant operation and availability. Understanding of the principles of operation of VFD systems as well as knowledge about their required operating environment is necessary for all operating personnel. Many times the operating personnel do not get involved with different technical issues until a complete failure has occurred. Hence, the awareness of the most dominant failure causes has a significant impact on assisting operators to avoid catastrophic failures and tremendous economic losses due to VFD shutdown. Proper plant design, accurate monitoring and data logging, following manufacturer preventive maintenance schedule, and choosing qualified team of operators can be the key to an efficient operation and a long lifetime for any VFD system. In this paper, we have analyzed the electrical and non-electrical causes of VFD failures based on a case study of a typical medium voltage VFD pumping station. Finally, recommendations are given from field analysis and observations.展开更多
The effect of Pentoxifylline (PTX) on type 1 diabetes was investigated by means of the studies on the expressions of cytokine mRNA in pancreas and the Fas-FasL on islet cells of NOD mice. NOD mice were treated with PT...The effect of Pentoxifylline (PTX) on type 1 diabetes was investigated by means of the studies on the expressions of cytokine mRNA in pancreas and the Fas-FasL on islet cells of NOD mice. NOD mice were treated with PTX from 4-6?wk, and then from 8-12?wk. After treatment, it was found that the incidence of diabetes in NOD mice at ages of 30?wk was reduced to 25% in group of mice treated with PTX, in comparison to 73.3% in case of mice injected with PBS, and the degree of insulitis in the PTX treated mice was lower than that of the PBS injected mice. RT-PCR analysis revealed down-regulatory effect on the expressions of IFN-γ and TNF-α mRNA in PTX treated mice, but there was no any effect on the expression of IL-10. As to the expression of Fas, there was marked decrease in the mean cytoplasmic integral optical density (IOD) in PTX treated mice, but there was little difference between PTX and PBS groups in the expression of FasL. These results indicated that PTX could prevent the development of diabetes in NOD mice, which might be related to the regulation of Th1/Th2 imbalance and the decreased expression of Fas in islet cells.展开更多
This paper presents an application of the hazard model reliability analysis on wind generators, based on a condition monitoring system. The hazard model techniques are most widely used in the statistical analysis of t...This paper presents an application of the hazard model reliability analysis on wind generators, based on a condition monitoring system. The hazard model techniques are most widely used in the statistical analysis of the electric machine＇s lifetime data. The model can be utilized to perform appropriate maintenance decision-making based on the evaluation of the mean time to failures that occur on the wind generators due to high temperatures. The knowledge of the condition monitoring system is used to estimate the hazard failure, and survival rates, which allows the preventive maintenance approach to be performed accurately. A case study is presented to demonstrate the adequacy of the proposed method based on the condition monitoring data for two wind turbines. Such data are representative in the generator temperatures with respect to the expended operating hours of the selected wind turbines. In this context, the influence of the generator temperatures on the lifetime of the generators can be determined. The results of the study can be used to develop the predetermined maintenance program, which significantly reduces the maintenance and operation costs.展开更多
基金The National Natural Science Foundation of China (No.70971022,71271054)the Scientific Research Innovation Project for College Graduates in Jiangsu Province(No.CXLX_0157)the Scientific Research Foundation of the Education Department of Anhui Province(No.2011sk123)
文摘A single-machine scheduling with preventive periodic maintenance activities in a remanufacturing system including resumable and non-resumable jobs is studied.The objective is to find a schedule to minimize the makespan and an LPT-LS algorithm is proposed.Non-resumable jobs are first scheduled in a machine by the longest processing time（LPT） rule,and then resumable jobs are scheduled by the list scheduling（LS） rule.And the worst-case ratios of this algorithm in three different cases in terms of the value of the total processing time of the resumable jobs（denoted as S2） are discussed.When S2 is longer than the spare time of the machine after the non-resumable jobs are assigned by the LPT rule,it is equal to 1.When S2 falls in between the spare time of the machine by the LPT rule and the optimal schedule rule,it is less than 2.When S2 is less than the spare time of the machine by the optimal schedule rule,it is less than 2.Finally,numerical examples are presented for verification.
基金Project (No. E2005000039) supported by the Natural Science Foun-dation of Hebei Province, China
文摘This paper analyzed the reliability and put forward the reliability index of overload protection for moulded case circuit breaker. The success rate was adopted as its reliability index of overload protection. Based on the reliability index and the reli- ability level, the reliability examination plan was analyzed and a test device for the overload protection of moulded case cir- cuit-breaker was developed. In the reliability test of overload protection, two power sources were used, which reduced the time of conversion and regulation between two different test currents in the overload protection test, which made the characteristic test more accurate. The test device was designed on the base of a Windows system, which made its operation simple and friendly.
文摘Although favourable results of pentoxifylline （PTX） used in treatment of severe alcoholic hepatitis patients with a Maddrey discriminant function score ≥ 32 have been previously reported, it is not currently recommended as a first line treatment for alcoholic hepatitis owing to lack of evidence for its efficacy as compared to the standard treatment with corticosteroids. In a very recent issue of World Journal of Gastroenterology, Dr. De BK and colleagues compared for the first time the two treatment modalities head to head in a randomized controlled study, demonstrating the advantage of PTX over corticosteroids in terms of patients＇ survival and risk-benefit profile. The advantage of PTX over corticosteroids in survival of patients with severe alcoholic hepatitis was found to be related to the prevention of hepatorenal syndrome in their study. This study raises the question of the use of PI-X as a standard treatment for severe alcoholic hepatitis. Considering the fact that PTX presented a spectacular efficiency in prevention of hepatorenal syndrome in their study as well as that previous studies have shown that this effect is possibly related to a primary renoprotective action because it is irrelevant of tumor necrosis factor-c~ synthesis inhibition or improved liver function, we tempted to speculate that PXT might be an effective option for prevention and/or treatment of hepatorenal syndrome complicating other forms of advanced liver disease. This attractive theory remains to be elucidated by pressing future studies in view of the lack of effective treatment modalities for hepatorenal syndrome.
基金supported by the National Natural Science Foundation of China (Grant No 4087-6047)
文摘The Oscillating Water Column(OWC) wave energy convertor with the advantage of its simple geometrical construction and excellent stability is widely employed.Recently,perforated breakwaters have been often used as they can effectively reduce the wave reflection from and wave forces acting on the structures.Considering the similarity between the compartment of perforated caisson and the air chamber of OWC wave energy convertor,a new perforated caisson of breakwater is designed in this paper.The ordinary caisson is modified by installing facilities similar to the air chamber of OWC converter,but here they are utilized to dissipate the wave energy inside the caisson.Such an arrangement improves the stability of the caisson and reduces the construction cost by using the compartment of perforated caisson like using an air chamber.This innovation has both academic significance and important engineering value.For a new type of caisson,reliability analysis of the structure is necessary.Linear potential flow theory is applied to calculate the horizontal wave force acting on the caisson.The calculated results are compared with experimental data,showing the feasibility of the method.The Importance Sampling Procedure(ISP) is used to analyse the reliability of this caisson breakwater.
基金supported by the National Natural Science Foundation of China (51279186,51479183)the 111 Project (B14028)The first author thanks the Chinese Scholarship Council for funding his research in University of Washington
文摘The reliability of a vertical breakwater is calculated using direct integration methods based on joint density functions.The horizontal and uplifting wave forces on the vertical breakwater can be well fitted by the lognormal and the Gumbel distributions,respectively.The joint distribution of the horizontal and uplifting wave forces is analyzed using different probabilistic distributions,including the bivariate logistic Gumbel distribution,the bivariate lognormal distribution,and three bivariate Archimedean copulas functions constructed with different marginal distributions simultaneously.We use the fully nested copulas to construct multivariate distributions taking into account related variables.Different goodness fitting tests are carried out to determine the best bivariate copula model for wave forces on a vertical breakwater.We show that a bivariate model constructed by Frank copula gives the best reliability analysis,using marginal distributions of Gumbel and lognormal to account for uplifting pressure and horizontal wave force on a vertical breakwater,respectively.The results show that failure probability of the vertical breakwater calculated by multivariate density function is comparable to those by the Joint Committee on Structural Safety methods.As copulas are suitable for constructing a bivariate or multivariate joint distribution,they have great potential in reliability analysis for other coastal structures.
基金Project (No. E2005000039) supported by the Natural Science Foun-dation of Hebei Province, China
文摘The over-load protective relay is widely used directly affects the safe running of a motor. The reliability for motor protection. The reliability of the over-load protective relay testing and reliability analysis of the over-load protective relay is an important way to improve the reliability of products. In this paper, the reliability test method of the over-load protective relay is studied, and the reliability tests of the typical products are carried out on a reliability tester developed by authors. In terms of the testing results, the reliability analysis is finished. The failure reasons are found and the measures are put forward to improve the reliability of the products.
文摘VFDs （variable frequency drives） are an integral part of many industrial plants and stations. Reliable operation and maintenance of these drives is vital to ensure sustained plant operation and availability. Understanding of the principles of operation of VFD systems as well as knowledge about their required operating environment is necessary for all operating personnel. Many times the operating personnel do not get involved with different technical issues until a complete failure has occurred. Hence, the awareness of the most dominant failure causes has a significant impact on assisting operators to avoid catastrophic failures and tremendous economic losses due to VFD shutdown. Proper plant design, accurate monitoring and data logging, following manufacturer preventive maintenance schedule, and choosing qualified team of operators can be the key to an efficient operation and a long lifetime for any VFD system. In this paper, we have analyzed the electrical and non-electrical causes of VFD failures based on a case study of a typical medium voltage VFD pumping station. Finally, recommendations are given from field analysis and observations.
文摘The effect of Pentoxifylline (PTX) on type 1 diabetes was investigated by means of the studies on the expressions of cytokine mRNA in pancreas and the Fas-FasL on islet cells of NOD mice. NOD mice were treated with PTX from 4-6?wk, and then from 8-12?wk. After treatment, it was found that the incidence of diabetes in NOD mice at ages of 30?wk was reduced to 25% in group of mice treated with PTX, in comparison to 73.3% in case of mice injected with PBS, and the degree of insulitis in the PTX treated mice was lower than that of the PBS injected mice. RT-PCR analysis revealed down-regulatory effect on the expressions of IFN-γ and TNF-α mRNA in PTX treated mice, but there was no any effect on the expression of IL-10. As to the expression of Fas, there was marked decrease in the mean cytoplasmic integral optical density (IOD) in PTX treated mice, but there was little difference between PTX and PBS groups in the expression of FasL. These results indicated that PTX could prevent the development of diabetes in NOD mice, which might be related to the regulation of Th1/Th2 imbalance and the decreased expression of Fas in islet cells.
文摘This paper presents an application of the hazard model reliability analysis on wind generators, based on a condition monitoring system. The hazard model techniques are most widely used in the statistical analysis of the electric machine＇s lifetime data. The model can be utilized to perform appropriate maintenance decision-making based on the evaluation of the mean time to failures that occur on the wind generators due to high temperatures. The knowledge of the condition monitoring system is used to estimate the hazard failure, and survival rates, which allows the preventive maintenance approach to be performed accurately. A case study is presented to demonstrate the adequacy of the proposed method based on the condition monitoring data for two wind turbines. Such data are representative in the generator temperatures with respect to the expended operating hours of the selected wind turbines. In this context, the influence of the generator temperatures on the lifetime of the generators can be determined. The results of the study can be used to develop the predetermined maintenance program, which significantly reduces the maintenance and operation costs.
