A class of lifetime distributions, new better than equilibrium in expectation （NBEE）, and its dual, new worse than equilibrium in expectation （NWEE）, are studied based on the comparison of the expectations of life...A class of lifetime distributions, new better than equilibrium in expectation （NBEE）, and its dual, new worse than equilibrium in expectation （NWEE）, are studied based on the comparison of the expectations of lifetime X and its equilibrium Xo. The relationships of the NBEE （NWEE） and other lifetime distribution classes are discussed. It is proved that the NBEE is very large, and increasing failure rate （IFR）, new better than used （NBU） and the L class are its subclasses. The closure properties under two kinds of reliability operations, namely, convolution and mixture, are investigated. Furthermore, a Poisson shock model and a special cumulative model are also studied, in which the necessary and sufficient conditions for the NBEE （NWEE） lifetime distribution of the systems are established. In the homogenous Poisson shock model, the system lifetime belongs to NBEE（NWEE） if and only if the corresponding discrete failure distribution belongs to the discrete NBEE（NWEE）. While in the cumulative model, the system has an NBEE lifetime if and only if the stochastic threshold of accumulated damage is NBEE.展开更多
During the launching of spacecraft,the on-board devices will undergo a series of pyroshock environments.In order to verify the reliability of these devices under these pyroshock environments,all of them are needed to ...During the launching of spacecraft,the on-board devices will undergo a series of pyroshock environments.In order to verify the reliability of these devices under these pyroshock environments,all of them are needed to take the shock test before launching.This paper has carried out an in-depth research on the simulation method of the pyroshock based on the true explosive excitation.In this study,a simulator containing multiple adjustment parameters is presented and the safety is considered by the design of the protective cover.And the working process of this setup is simulated with the explicit dynamic codes LS-DYNA.Whafs more,the effects of the adjustment parameters on the three factors of shock Response Spectrum(SRS)of the resonant board are explored carefully.The rules achieved in this paper are verified by a typical example.The results indicate that the improved simulator can avoid the danger of explosive and make full use of the advantage of actual explosive excitation.And the test condition can be quickly realized at the simulator according to the effect rules of the three adjustable parameters.展开更多
基金The National Natural Science Foundation of China(No. 10801032)
文摘A class of lifetime distributions, new better than equilibrium in expectation （NBEE）, and its dual, new worse than equilibrium in expectation （NWEE）, are studied based on the comparison of the expectations of lifetime X and its equilibrium Xo. The relationships of the NBEE （NWEE） and other lifetime distribution classes are discussed. It is proved that the NBEE is very large, and increasing failure rate （IFR）, new better than used （NBU） and the L class are its subclasses. The closure properties under two kinds of reliability operations, namely, convolution and mixture, are investigated. Furthermore, a Poisson shock model and a special cumulative model are also studied, in which the necessary and sufficient conditions for the NBEE （NWEE） lifetime distribution of the systems are established. In the homogenous Poisson shock model, the system lifetime belongs to NBEE（NWEE） if and only if the corresponding discrete failure distribution belongs to the discrete NBEE（NWEE）. While in the cumulative model, the system has an NBEE lifetime if and only if the stochastic threshold of accumulated damage is NBEE.
基金co-supported by the National Natural Science Foundation of China(No.11602073)Natural Science Foundation of Heilongjiang Province of China(No.QC2018005).
文摘During the launching of spacecraft,the on-board devices will undergo a series of pyroshock environments.In order to verify the reliability of these devices under these pyroshock environments,all of them are needed to take the shock test before launching.This paper has carried out an in-depth research on the simulation method of the pyroshock based on the true explosive excitation.In this study,a simulator containing multiple adjustment parameters is presented and the safety is considered by the design of the protective cover.And the working process of this setup is simulated with the explicit dynamic codes LS-DYNA.Whafs more,the effects of the adjustment parameters on the three factors of shock Response Spectrum(SRS)of the resonant board are explored carefully.The rules achieved in this paper are verified by a typical example.The results indicate that the improved simulator can avoid the danger of explosive and make full use of the advantage of actual explosive excitation.And the test condition can be quickly realized at the simulator according to the effect rules of the three adjustable parameters.
