The correlation coefficients of random variables of mechanical structures are generally chosen with experience or even ignored,which cannot actually reflect the effects of parameter uncertainties on reliability.To dis...The correlation coefficients of random variables of mechanical structures are generally chosen with experience or even ignored,which cannot actually reflect the effects of parameter uncertainties on reliability.To discuss the selection problem of the correlation coefficients from the reliability-based sensitivity point of view,the theory principle of the problem is established based on the results of the reliability sensitivity,and the criterion of correlation among random variables is shown.The values of the correlation coefficients are obtained according to the proposed principle and the reliability sensitivity problem is discussed.Numerical studies have shown the following results：（1） If the sensitivity value of correlation coefficient ρ is less than（at what magnitude 0.000 01）,then the correlation could be ignored,which could simplify the procedure without introducing additional error.（2） However,as the difference between ρs,that is the most sensitive to the reliability,and ρR,that is with the smallest reliability,is less than 0.001,ρs is suggested to model the dependency of random variables.This could ensure the robust quality of system without the loss of safety requirement.（3） In the case of ｜Eabs｜ρ0.001 and also ｜Erel｜ρ0.001,ρR should be employed to quantify the correlation among random variables in order to ensure the accuracy of reliability analysis.Application of the proposed approach could provide a practical routine for mechanical design and manufactory to study the reliability and reliability-based sensitivity of basic design variables in mechanical reliability analysis and design.展开更多
Distributed generation (DG) is the future of energy. This technology allows the bidirectional flow of power within an electrical network. Researchers are faced with many challenges to the accurate implementation of pr...Distributed generation (DG) is the future of energy. This technology allows the bidirectional flow of power within an electrical network. Researchers are faced with many challenges to the accurate implementation of protection schemes for DG-connected distribution network. The schemes designed must satisfy the performance requirements of selectivity, reliability, and sensitivity. Most researchers opine that conventional protection schemes based on over current detection are insufficient to completely and accurately protect a DG-connected distributed power system. There are many challenges?that?need to be tackled before embarking upon the journey to successfully implement these schemes. This paper summarizes the major challenges which one can encounter while designing protection schemes for DG-connected distribution networks. Some possible solutions from the literature are also mentioned. Moreover, a suggested solution for protecting future active distribution networks is provided. It is expected that this paper will act as a benchmark for future researchers in this field to tackle the challenges related to the protection of active distribution networks.展开更多
Meloidogyne vitis is a new root-knot nematode parasitic on grape root in Yunnan Province,China.In order to establish a rapid,reliable and specific molecular detection method for M.vitis,the species-specific primers we...Meloidogyne vitis is a new root-knot nematode parasitic on grape root in Yunnan Province,China.In order to establish a rapid,reliable and specific molecular detection method for M.vitis,the species-specific primers were designed with rDNA-ITS(ribosomal DNA internal transcribed spacer)gene fragment as the target.The reaction system was optimized and the reliability,specificity and sensitivity of primer were testified,therefore,a rapid PCR detection method for M.vitis was established.The result showed that the optimal annealing temperature of the primers was 53℃,which was suitable for the detection of different life stages of M.vitis.Specificity test showed that the specific fragment size of 174 bp was obtained from M.vitis,but other five non-target nematodes did not have any amplification bands,thus effectively distinguish M.vitis and the other five species,and could specifically detect the M.vitis from mixed populations.Sensitivity test showed that this PCR technique could detect the DNA of a single second-stage juvenile(J_(2))and 10^(-4)female.Futhermore,this PCR technique could be used to detect directly M.vitis from soil samples.The rapid,sensitive and specific PCR molecular detection technique could be used for the direct identification of a single J_(2)of M.vitis and the detection of M.vitis in mixed nematode populations and the detection of two J_(2)s or one male in 0.5 g soil samples,which will provide technical support for the investigation of the occurrence and damage of M.vitis and the formulation of efficient green co ntrol strategies.展开更多
基金supported by Changjiang Scholars and Innovative Research Team in University of China (Grant No. IRT0816)Key National Science & Technology Special Project on "High-Grade CNC Machine Tools and Basic Manufacturing Equipments" of China (Grant No. 2010ZX04014-014)+1 种基金National Natural Science Foundation of China (Grant No. 50875039)Key Projects in National Science & Technology Pillar Program during the 11th Five-year Plan Period of China (Grant No. 2009BAG12A02-A07-2)
文摘The correlation coefficients of random variables of mechanical structures are generally chosen with experience or even ignored,which cannot actually reflect the effects of parameter uncertainties on reliability.To discuss the selection problem of the correlation coefficients from the reliability-based sensitivity point of view,the theory principle of the problem is established based on the results of the reliability sensitivity,and the criterion of correlation among random variables is shown.The values of the correlation coefficients are obtained according to the proposed principle and the reliability sensitivity problem is discussed.Numerical studies have shown the following results：（1） If the sensitivity value of correlation coefficient ρ is less than（at what magnitude 0.000 01）,then the correlation could be ignored,which could simplify the procedure without introducing additional error.（2） However,as the difference between ρs,that is the most sensitive to the reliability,and ρR,that is with the smallest reliability,is less than 0.001,ρs is suggested to model the dependency of random variables.This could ensure the robust quality of system without the loss of safety requirement.（3） In the case of ｜Eabs｜ρ0.001 and also ｜Erel｜ρ0.001,ρR should be employed to quantify the correlation among random variables in order to ensure the accuracy of reliability analysis.Application of the proposed approach could provide a practical routine for mechanical design and manufactory to study the reliability and reliability-based sensitivity of basic design variables in mechanical reliability analysis and design.
文摘Distributed generation (DG) is the future of energy. This technology allows the bidirectional flow of power within an electrical network. Researchers are faced with many challenges to the accurate implementation of protection schemes for DG-connected distribution network. The schemes designed must satisfy the performance requirements of selectivity, reliability, and sensitivity. Most researchers opine that conventional protection schemes based on over current detection are insufficient to completely and accurately protect a DG-connected distributed power system. There are many challenges?that?need to be tackled before embarking upon the journey to successfully implement these schemes. This paper summarizes the major challenges which one can encounter while designing protection schemes for DG-connected distribution networks. Some possible solutions from the literature are also mentioned. Moreover, a suggested solution for protecting future active distribution networks is provided. It is expected that this paper will act as a benchmark for future researchers in this field to tackle the challenges related to the protection of active distribution networks.
基金supported by the grants from the National Key Research and Development Program of China(2018YFD0201202 and 2017YFD0200601)。
文摘Meloidogyne vitis is a new root-knot nematode parasitic on grape root in Yunnan Province,China.In order to establish a rapid,reliable and specific molecular detection method for M.vitis,the species-specific primers were designed with rDNA-ITS(ribosomal DNA internal transcribed spacer)gene fragment as the target.The reaction system was optimized and the reliability,specificity and sensitivity of primer were testified,therefore,a rapid PCR detection method for M.vitis was established.The result showed that the optimal annealing temperature of the primers was 53℃,which was suitable for the detection of different life stages of M.vitis.Specificity test showed that the specific fragment size of 174 bp was obtained from M.vitis,but other five non-target nematodes did not have any amplification bands,thus effectively distinguish M.vitis and the other five species,and could specifically detect the M.vitis from mixed populations.Sensitivity test showed that this PCR technique could detect the DNA of a single second-stage juvenile(J_(2))and 10^(-4)female.Futhermore,this PCR technique could be used to detect directly M.vitis from soil samples.The rapid,sensitive and specific PCR molecular detection technique could be used for the direct identification of a single J_(2)of M.vitis and the detection of M.vitis in mixed nematode populations and the detection of two J_(2)s or one male in 0.5 g soil samples,which will provide technical support for the investigation of the occurrence and damage of M.vitis and the formulation of efficient green co ntrol strategies.
