The non-linear effects of different initial melt temperatures on the microstructure evolution during the solidification process of liquid Mg7Zn3 alloys were investigated by molecular dynamics simulation, The microstru...The non-linear effects of different initial melt temperatures on the microstructure evolution during the solidification process of liquid Mg7Zn3 alloys were investigated by molecular dynamics simulation, The microstructure transformation mechanisms were analyzed by several methods. The system was found to be solidified into amorphous structures from different initial melt temperatures at the same cooling rate of 1×10^12 K/s, and the 1551 bond-type and the icosahedron basic cluster （12 0 12 0 ） played a key role in the microstructure transition. Different initial melt temperatures had significant effects on the final microstructures. These effects only can be clearly observed below the glass transition temperature Tg; and these effects are non-linearly related to the initial melt temperatures, and fluctuated in a certain range. However, the changes of the average atomic energy of the systems are still linearly related with the initial melt temperatures, namely, the higher the initial melt temperature is, the more stable the amorphous structure is and the stronger the glass forming ability will be.展开更多
The maintenance of an aero-engine usually includes three levels,and the maintenance cost and period greatly differ depending on the different maintenance levels.To plan a reasonable maintenance budget program, airline...The maintenance of an aero-engine usually includes three levels,and the maintenance cost and period greatly differ depending on the different maintenance levels.To plan a reasonable maintenance budget program, airlines would like to predict the maintenance level of aero-engine before repairing in terms of performance parameters,which can provide more economic benefits.The maintenance level decision rules are mined using the historical maintenance data of a civil aero-engine based on the rough set theory,and a variety of possible models of updating rules produced by newly increased maintenance cases added to the historical maintenance case database are investigated by the means of incremental machine learning.The continuously updated rules can provide reasonable guidance suggestions for engineers and decision support for planning a maintenance budget program before repairing. The results of an example show that the decision rules become more typical and robust,and they are more accurate to predict the maintenance level of an aero-engine module as the maintenance data increase,which illustrates the feasibility of the represented method.展开更多
A monitoring and comparison experiment with two types of sensors on a turbojet engine is carried out. Compared with a probe-typed sensor,which is designed successfully before,signals are collected to verify the validi...A monitoring and comparison experiment with two types of sensors on a turbojet engine is carried out. Compared with a probe-typed sensor,which is designed successfully before,signals are collected to verify the validity and better feasibility of the circular sensor.According to the signals monitored over 131h,the typical signals of 125—129 phases are analyzed.The results show that the unusual exhaust particles are carbon depositions from fuel spray nozzle.Therefore,with the electrostatic sensor,early warning can be provided for initial fault condition, as well as real-time reference for the condition-based maintenance.展开更多
Traditional coning algorithms are based on the first-order coning correction reference model.Usually they reduce the algorithm error of coning axis(z)by increasing the sample numbers in one iteration interval.But the ...Traditional coning algorithms are based on the first-order coning correction reference model.Usually they reduce the algorithm error of coning axis(z)by increasing the sample numbers in one iteration interval.But the increase of sample numbers requires the faster output rates of sensors.Therefore,the algorithms are often limited in practical use.Moreover,the noncommutivity error of rotation usually exists on all three axes and the increase of sample numbers has little positive effect on reducing the algorithm errors of orthogonal axes(x,y).Considering the errors of orthogonal axes cannot be neglected in the high-precision applications,a coning algorithm with an additional second-order coning correction term is developed to further improve the performance of coning algorithm.Compared with the traditional algorithms,the new second-order coning algorithm can effectively reduce the algorithm error without increasing the sample numbers.Theoretical analyses validate that in a coning environment with low frequency,the new algorithm has the better performance than the traditional time-series and frequency-series coning algorithms,while in a maneuver environment the new algorithm has the same order accuracy as the traditional time-series and frequency-series algorithms.Finally,the practical feasibility of the new coning algorithm is demonstrated by digital simulations and practical turntable tests.展开更多
In view of the complexity of landing on the deck of aircraft carrier,a systematic model,composed of sixdegree-of-freedom mathematic model of carrier-based aircraft,four-degree-of-freedom model of landing gears and six...In view of the complexity of landing on the deck of aircraft carrier,a systematic model,composed of sixdegree-of-freedom mathematic model of carrier-based aircraft,four-degree-of-freedom model of landing gears and six-degree-of-freedom mathematic model of carrier,is established in the Matlab-Simulink environment,with damping function of landing gears and dynamic characteristics of tires being considered.The model,where the carrier movement is introduced,is applicable for any abnormal landing condition.Moreover,the equations of motion and relevant parameter are also derived.The dynamic response of aircraft is calculated via the variable step-size RungeKuta algorithm.The effect of attitude angles of aircraft and carrier movement during the process of landing is illustrated in details.The analytical results can provide some reference for carrier-based aircraft design and maintenance.展开更多
An efficient LDPC-coded multi-relay cooperation architecture is proposed based on virtual vertical Bell Labs layered space-time （V-BLAST） processing for uplink communication, where minimum-mean-square-error （MMSE）...An efficient LDPC-coded multi-relay cooperation architecture is proposed based on virtual vertical Bell Labs layered space-time （V-BLAST） processing for uplink communication, where minimum-mean-square-error （MMSE） and BP-based joint iterative decoding based on the introduced muhi-layer Tanner graph are effectively de- signed to detect and decode the corrupted received sequence at the destination. By introducing V-BLAST transmis- sion to the coded multi-relay cooperation, relays send their streams of symbols simultaneously, which increases the data rate and significantly reduces the transmission delay. The theoretical analysis and numerical results show that the new LDPC coded cooperation scheme outperforms the coded non-cooperation under the same code rate, and it also achieves a good trade-off among the performance, signal delay, and the encoding complexity associated with the number of relays. The performance gain can be credited to the proposed V-BLAST processing architecture and BP-based joint iterative decoding by the introduced multi-layer Tanner graph at a receiver-side.展开更多
The non-linear behavior of continuous fiber reinforced C/SiC ceramic matrix composites(CMCs)under tensile loading is modeled by three-dimensional representative volume element(RVE)models of the composite. The theoreti...The non-linear behavior of continuous fiber reinforced C/SiC ceramic matrix composites(CMCs)under tensile loading is modeled by three-dimensional representative volume element(RVE)models of the composite. The theoretical background of the multi-scale approach solved by the finite element method(FEM)is recalled firstly.Then the geometric characters of three kinds of damage mechanisms,i.e.micro matrix cracks,fiber/matrix interface debonding and fiber fracture,are studied.Three kinds of RVE are proposed to model the microstructure of C/SiC with above damage mechanisms respectively.The matrix cracking is modeled by critical matrix strain energy(CMSE)principle while a maximum shear stress criterion is used for modeling fiber/matrix interface debonding. The behavior of fiber fracture is modeled by the famous Weibull statistic theory.A numerical example of continuous fiber reinforced C/SiC composite under tensile loading is performed.The results show that the stress/strain curve predicted by the developed model agrees with experimental data.展开更多
A fast feature ranking algorithm for classification in the presence of high dimensionahty and small sample size is proposed. The basic idea is that the important features force the data points of the same class to mai...A fast feature ranking algorithm for classification in the presence of high dimensionahty and small sample size is proposed. The basic idea is that the important features force the data points of the same class to maintain their intrinsic neighbor relations, whereas neighboring points of different classes are no longer to stick to one an- other. Applying this assumption, an optimization problem weighting each feature is derived. The algorithm does not involve the dense matrix eigen-decomposition which can be computationally expensive in time. Extensive exper- iments are conducted to validate the significance of selected features using the Yale, Extended YaleB and PIE data- sets. The thorough evaluation shows that, using one-nearest neighbor classifier, the recognition rates using 100-- 500 leading features selected by the algorithm distinctively outperform those with features selected by the baseline feature selection algorithms, while using support vector machine features selected by the algorithm show less prominent improvement. Moreover, the experiments demonstrate that the proposed algorithm is particularly effi- cient for multi-class face recognition problem.展开更多
With the increase of complexity of electromagnetic environment and continuous appearance of advanced system radars,signals received by radar reconnaissance receivers become even more intensive and complex.Therefore,tr...With the increase of complexity of electromagnetic environment and continuous appearance of advanced system radars,signals received by radar reconnaissance receivers become even more intensive and complex.Therefore,traditional radar sorting methods based on neural network algorithms and support vector machine(SVM) cannot process them effectively.Aiming at solving this problem,a novel radar signal sorting method based on the cloud model theory and the geometric covering algorithm is proposed.By applying the geometric covering algorithm to divide input signals into different covering domains based on their distribution characteristics,the method can overcome a typical problem that it is easy for traditional sorting algorithms to fall into the local extrema due to the use of complex nonlinear equation to describe input signals.The method uses the cloud model to describe the membership degree between signals to be sorted and their covering domains,thus it avoids the disadvantage that traditional sorting methods based on hard clustering cannot deinterleave the signal samples with overlapped parameters. Experimental results show that the presented method can effectively sort advanced system radar signals with overlapped parameters in complex electromagnetic environment.展开更多
In this paper, we study entanglement dynamics of a two-qubit extended Werner-like state locally, interacting with independent noisy channels, i.e., amplitude damping, phase damping, and depolarizing channels. We show ...In this paper, we study entanglement dynamics of a two-qubit extended Werner-like state locally, interacting with independent noisy channels, i.e., amplitude damping, phase damping, and depolarizing channels. We show that the purity of initial entangled state has direct impacts on the entanglement robustness in each noisy channel. That is, if the initial entangled state is prepared in mixed instead of pure form, the state may exhibit entanglement sudden death （ESD） and/or be decreased for the critical probability at which the entanglement disappear.展开更多
Objective： To provide a kinetic model（s） and reveal the mechanism of thymoquinone and Poloxin blocking an emerging anti-cancer target, human Polo-like kinase 1 （hPlkl） Polo-box domain （PBD）. Methods： The bindi...Objective： To provide a kinetic model（s） and reveal the mechanism of thymoquinone and Poloxin blocking an emerging anti-cancer target, human Polo-like kinase 1 （hPlkl） Polo-box domain （PBD）. Methods： The binding kinetics was determined by using a fluorescence polarization based assay. The putative mechanism was examined with a competition test. Results： Thymoquinone follows a one-step binding with an association rate constant （k1） of 6.635× 10^3 L.mol^-1 min^-1.Poloxin fit a two-step binding with a dissociation constant （Ki） of 118 μmol/L for the intermediate complex and its isomerization rate （k4） of 0.131 5 minJ to form an irreversible adduct. No significant dissociation was observed for either ligand up to 13 h. The inhibitors responded insignificantly to the presence of Michael donors as hPIkl-PBD competitors. Conclusion： Thymoquinone and Poloxin are slow-tight ligands to the hPlkl-PBD with kinetic models distinct from each other. Michael addition as the mechanism is excluded.展开更多
A high cycle fatigue reliability analysis approach to helicopter rotor hub is proposed under working load spectrum. Automatic calculation for the approach is implemented through writing the calculating programs. In th...A high cycle fatigue reliability analysis approach to helicopter rotor hub is proposed under working load spectrum. Automatic calculation for the approach is implemented through writing the calculating programs. In the system, the modification of geometric model of rotor hub is controlled by several parameters, and finite element method and S-N curve method are then employed to solve the fatigue life by automatically assigned parameters. A database between assigned parameters and fatigue life is obtained via Latin Hypercube Sampling （LHS） on toler- ance zone of rotor hub. Different data-fitting technologies are used and compared to determine a highest-precision approximation for this database. The parameters are assumed to he independent of each other and follow normal distributions. Fatigue reliability is then computed by the Monte Carlo （MC） method and the mean-value first order second moment （MFOSM） method. Results show that the approach has high efficiency and precision, and is suit- able for engineering application.展开更多
Coupling with the periodical displacement boundary condition,a representative volume element(RVE) model is established to simulate the progressive damage behavior of 2D1×1 braided composites under unidirectional ...Coupling with the periodical displacement boundary condition,a representative volume element(RVE) model is established to simulate the progressive damage behavior of 2D1×1 braided composites under unidirectional tension by using the nonlinear finite element method.Tsai-Wu failure criterion with various damage modes and Mises criterion are considered for predicting damage initiation and progression of yarns and matrix.The anisotropic damage model for yarns and the isotropic damage model for matrix are used to simulate the microscopic damage propagation of 2D1×1braided composites.Murakami′s damage tensor is adopted to characterize each damage mode.In the simulation process,the damage mechanisms are revealed and the tensile strength of 2D1×1braided composites is predicted from the calculated average stress-average strain curve.Numerical results show good agreement with experimental data,thus the proposed simulation method is verified for damage mechanism analysis of 2D braided composites.展开更多
基金Projects(50831003,51071065,51101022,51102090) supported by the National Natural Science Foundation of China
文摘The non-linear effects of different initial melt temperatures on the microstructure evolution during the solidification process of liquid Mg7Zn3 alloys were investigated by molecular dynamics simulation, The microstructure transformation mechanisms were analyzed by several methods. The system was found to be solidified into amorphous structures from different initial melt temperatures at the same cooling rate of 1×10^12 K/s, and the 1551 bond-type and the icosahedron basic cluster （12 0 12 0 ） played a key role in the microstructure transition. Different initial melt temperatures had significant effects on the final microstructures. These effects only can be clearly observed below the glass transition temperature Tg; and these effects are non-linearly related to the initial melt temperatures, and fluctuated in a certain range. However, the changes of the average atomic energy of the systems are still linearly related with the initial melt temperatures, namely, the higher the initial melt temperature is, the more stable the amorphous structure is and the stronger the glass forming ability will be.
基金Supported by the National Natural Science Foundation of China(60939003)
文摘The maintenance of an aero-engine usually includes three levels,and the maintenance cost and period greatly differ depending on the different maintenance levels.To plan a reasonable maintenance budget program, airlines would like to predict the maintenance level of aero-engine before repairing in terms of performance parameters,which can provide more economic benefits.The maintenance level decision rules are mined using the historical maintenance data of a civil aero-engine based on the rough set theory,and a variety of possible models of updating rules produced by newly increased maintenance cases added to the historical maintenance case database are investigated by the means of incremental machine learning.The continuously updated rules can provide reasonable guidance suggestions for engineers and decision support for planning a maintenance budget program before repairing. The results of an example show that the decision rules become more typical and robust,and they are more accurate to predict the maintenance level of an aero-engine module as the maintenance data increase,which illustrates the feasibility of the represented method.
基金Supported by the National Natural Science Foundation of China(60939003,61079013)the Natural Science Fund Project in Jiangsu Province(BK2011737)the Fundamental Research Funds for the Central Universities(NS2012059)
文摘A monitoring and comparison experiment with two types of sensors on a turbojet engine is carried out. Compared with a probe-typed sensor,which is designed successfully before,signals are collected to verify the validity and better feasibility of the circular sensor.According to the signals monitored over 131h,the typical signals of 125—129 phases are analyzed.The results show that the unusual exhaust particles are carbon depositions from fuel spray nozzle.Therefore,with the electrostatic sensor,early warning can be provided for initial fault condition, as well as real-time reference for the condition-based maintenance.
基金Supported by the National Natural Science Foundation of China(61104188,91016019)the National Basic Research Program of China(2009CB724002)the Research Funding of Nanjing University of Aeronautics and Astronautics(NS2010084,NP2011049)
文摘Traditional coning algorithms are based on the first-order coning correction reference model.Usually they reduce the algorithm error of coning axis(z)by increasing the sample numbers in one iteration interval.But the increase of sample numbers requires the faster output rates of sensors.Therefore,the algorithms are often limited in practical use.Moreover,the noncommutivity error of rotation usually exists on all three axes and the increase of sample numbers has little positive effect on reducing the algorithm errors of orthogonal axes(x,y).Considering the errors of orthogonal axes cannot be neglected in the high-precision applications,a coning algorithm with an additional second-order coning correction term is developed to further improve the performance of coning algorithm.Compared with the traditional algorithms,the new second-order coning algorithm can effectively reduce the algorithm error without increasing the sample numbers.Theoretical analyses validate that in a coning environment with low frequency,the new algorithm has the better performance than the traditional time-series and frequency-series coning algorithms,while in a maneuver environment the new algorithm has the same order accuracy as the traditional time-series and frequency-series algorithms.Finally,the practical feasibility of the new coning algorithm is demonstrated by digital simulations and practical turntable tests.
基金Supported by the National Natural Science Foundation of China(51075203,51105197)the Research Funding of Nanjing University of Aeronautics and Astronautics(NS2010023)
文摘In view of the complexity of landing on the deck of aircraft carrier,a systematic model,composed of sixdegree-of-freedom mathematic model of carrier-based aircraft,four-degree-of-freedom model of landing gears and six-degree-of-freedom mathematic model of carrier,is established in the Matlab-Simulink environment,with damping function of landing gears and dynamic characteristics of tires being considered.The model,where the carrier movement is introduced,is applicable for any abnormal landing condition.Moreover,the equations of motion and relevant parameter are also derived.The dynamic response of aircraft is calculated via the variable step-size RungeKuta algorithm.The effect of attitude angles of aircraft and carrier movement during the process of landing is illustrated in details.The analytical results can provide some reference for carrier-based aircraft design and maintenance.
基金Supported by the Science and Technology on Avionics Integration Laboratory and National Aeronautical Science Foundation of China(20105552)
文摘An efficient LDPC-coded multi-relay cooperation architecture is proposed based on virtual vertical Bell Labs layered space-time （V-BLAST） processing for uplink communication, where minimum-mean-square-error （MMSE） and BP-based joint iterative decoding based on the introduced muhi-layer Tanner graph are effectively de- signed to detect and decode the corrupted received sequence at the destination. By introducing V-BLAST transmis- sion to the coded multi-relay cooperation, relays send their streams of symbols simultaneously, which increases the data rate and significantly reduces the transmission delay. The theoretical analysis and numerical results show that the new LDPC coded cooperation scheme outperforms the coded non-cooperation under the same code rate, and it also achieves a good trade-off among the performance, signal delay, and the encoding complexity associated with the number of relays. The performance gain can be credited to the proposed V-BLAST processing architecture and BP-based joint iterative decoding by the introduced multi-layer Tanner graph at a receiver-side.
基金Supported by the National Natural Science Foundation of China(51075204,51105195)the Aeronau-tical Science Foundation of China(2011ZB52024)
文摘The non-linear behavior of continuous fiber reinforced C/SiC ceramic matrix composites(CMCs)under tensile loading is modeled by three-dimensional representative volume element(RVE)models of the composite. The theoretical background of the multi-scale approach solved by the finite element method(FEM)is recalled firstly.Then the geometric characters of three kinds of damage mechanisms,i.e.micro matrix cracks,fiber/matrix interface debonding and fiber fracture,are studied.Three kinds of RVE are proposed to model the microstructure of C/SiC with above damage mechanisms respectively.The matrix cracking is modeled by critical matrix strain energy(CMSE)principle while a maximum shear stress criterion is used for modeling fiber/matrix interface debonding. The behavior of fiber fracture is modeled by the famous Weibull statistic theory.A numerical example of continuous fiber reinforced C/SiC composite under tensile loading is performed.The results show that the stress/strain curve predicted by the developed model agrees with experimental data.
基金Supported by the National Natural Science Foundation of China(71001072)the Natural Science Foundation of Guangdong Province(9451806001002294)
文摘A fast feature ranking algorithm for classification in the presence of high dimensionahty and small sample size is proposed. The basic idea is that the important features force the data points of the same class to maintain their intrinsic neighbor relations, whereas neighboring points of different classes are no longer to stick to one an- other. Applying this assumption, an optimization problem weighting each feature is derived. The algorithm does not involve the dense matrix eigen-decomposition which can be computationally expensive in time. Extensive exper- iments are conducted to validate the significance of selected features using the Yale, Extended YaleB and PIE data- sets. The thorough evaluation shows that, using one-nearest neighbor classifier, the recognition rates using 100-- 500 leading features selected by the algorithm distinctively outperform those with features selected by the baseline feature selection algorithms, while using support vector machine features selected by the algorithm show less prominent improvement. Moreover, the experiments demonstrate that the proposed algorithm is particularly effi- cient for multi-class face recognition problem.
基金Supported by the National Natural Science Foundation of China(61240007)the Fundamental Re-search Funds for the Central Universities(HEUCF130805)+3 种基金the Key Science and Technology Project of Harbin(2011AA2CG007-2)the Chinese Postdoctoral Science Foundation Funded Projects(20080430903)the Chinese Postdoctoral Science Foundation Specially Funded Projects(200902411)the Heilongjiang Post-doctoral Research Foundation(LBH-Q10140,LBH-Q12122,LBH-Q12136)
文摘With the increase of complexity of electromagnetic environment and continuous appearance of advanced system radars,signals received by radar reconnaissance receivers become even more intensive and complex.Therefore,traditional radar sorting methods based on neural network algorithms and support vector machine(SVM) cannot process them effectively.Aiming at solving this problem,a novel radar signal sorting method based on the cloud model theory and the geometric covering algorithm is proposed.By applying the geometric covering algorithm to divide input signals into different covering domains based on their distribution characteristics,the method can overcome a typical problem that it is easy for traditional sorting algorithms to fall into the local extrema due to the use of complex nonlinear equation to describe input signals.The method uses the cloud model to describe the membership degree between signals to be sorted and their covering domains,thus it avoids the disadvantage that traditional sorting methods based on hard clustering cannot deinterleave the signal samples with overlapped parameters. Experimental results show that the presented method can effectively sort advanced system radar signals with overlapped parameters in complex electromagnetic environment.
基金Supported by Natural Science Foundation of Hubci Province under Grant No. 2006ABA055Postgraduate Program of Hubei Normal University of China under Grant No. 2007D20
文摘In this paper, we study entanglement dynamics of a two-qubit extended Werner-like state locally, interacting with independent noisy channels, i.e., amplitude damping, phase damping, and depolarizing channels. We show that the purity of initial entangled state has direct impacts on the entanglement robustness in each noisy channel. That is, if the initial entangled state is prepared in mixed instead of pure form, the state may exhibit entanglement sudden death （ESD） and/or be decreased for the critical probability at which the entanglement disappear.
基金a co-sponsored graduate research project by China Pharmaceutical University and Shanghai Medicilon Inc
文摘Objective： To provide a kinetic model（s） and reveal the mechanism of thymoquinone and Poloxin blocking an emerging anti-cancer target, human Polo-like kinase 1 （hPlkl） Polo-box domain （PBD）. Methods： The binding kinetics was determined by using a fluorescence polarization based assay. The putative mechanism was examined with a competition test. Results： Thymoquinone follows a one-step binding with an association rate constant （k1） of 6.635× 10^3 L.mol^-1 min^-1.Poloxin fit a two-step binding with a dissociation constant （Ki） of 118 μmol/L for the intermediate complex and its isomerization rate （k4） of 0.131 5 minJ to form an irreversible adduct. No significant dissociation was observed for either ligand up to 13 h. The inhibitors responded insignificantly to the presence of Michael donors as hPIkl-PBD competitors. Conclusion： Thymoquinone and Poloxin are slow-tight ligands to the hPlkl-PBD with kinetic models distinct from each other. Michael addition as the mechanism is excluded.
文摘A high cycle fatigue reliability analysis approach to helicopter rotor hub is proposed under working load spectrum. Automatic calculation for the approach is implemented through writing the calculating programs. In the system, the modification of geometric model of rotor hub is controlled by several parameters, and finite element method and S-N curve method are then employed to solve the fatigue life by automatically assigned parameters. A database between assigned parameters and fatigue life is obtained via Latin Hypercube Sampling （LHS） on toler- ance zone of rotor hub. Different data-fitting technologies are used and compared to determine a highest-precision approximation for this database. The parameters are assumed to he independent of each other and follow normal distributions. Fatigue reliability is then computed by the Monte Carlo （MC） method and the mean-value first order second moment （MFOSM） method. Results show that the approach has high efficiency and precision, and is suit- able for engineering application.
基金Supported by the National Natural Science Foundation of China(10672075)
文摘Coupling with the periodical displacement boundary condition,a representative volume element(RVE) model is established to simulate the progressive damage behavior of 2D1×1 braided composites under unidirectional tension by using the nonlinear finite element method.Tsai-Wu failure criterion with various damage modes and Mises criterion are considered for predicting damage initiation and progression of yarns and matrix.The anisotropic damage model for yarns and the isotropic damage model for matrix are used to simulate the microscopic damage propagation of 2D1×1braided composites.Murakami′s damage tensor is adopted to characterize each damage mode.In the simulation process,the damage mechanisms are revealed and the tensile strength of 2D1×1braided composites is predicted from the calculated average stress-average strain curve.Numerical results show good agreement with experimental data,thus the proposed simulation method is verified for damage mechanism analysis of 2D braided composites.
