The gears of new energy vehicles are required to withstand higher rotational speeds and greater loads,which puts forward higher precision essentials for gear manufacturing.However,machining process parameters can caus...The gears of new energy vehicles are required to withstand higher rotational speeds and greater loads,which puts forward higher precision essentials for gear manufacturing.However,machining process parameters can cause changes in cutting force/heat,resulting in affecting gear machining precision.Therefore,this paper studies the effect of different process parameters on gear machining precision.A multi-objective optimization model is established for the relationship between process parameters and tooth surface deviations,tooth profile deviations,and tooth lead deviations through the cutting speed,feed rate,and cutting depth of the worm wheel gear grinding machine.The response surface method(RSM)is used for experimental design,and the corresponding experimental results and optimal process parameters are obtained.Subsequently,gray relational analysis-principal component analysis(GRA-PCA),particle swarm optimization(PSO),and genetic algorithm-particle swarm optimization(GA-PSO)methods are used to analyze the experimental results and obtain different optimal process parameters.The results show that optimal process parameters obtained by the GRA-PCA,PSO,and GA-PSO methods improve the gear machining precision.Moreover,the gear machining precision obtained by GA-PSO is superior to other methods.展开更多
In this paper,we propose a neural network approach to learn the parameters of a class of stochastic Lotka-Volterra systems.Approximations of the mean and covariance matrix of the observational variables are obtained f...In this paper,we propose a neural network approach to learn the parameters of a class of stochastic Lotka-Volterra systems.Approximations of the mean and covariance matrix of the observational variables are obtained from the Euler-Maruyama discretization of the underlying stochastic differential equations(SDEs),based on which the loss function is built.The stochastic gradient descent method is applied in the neural network training.Numerical experiments demonstrate the effectiveness of our method.展开更多
The concept of TNT(Trinitrotoluene,C_7H_5N_3O_6)equivalence is often invoked to evaluate the performance and predict the explosion parameters of different types of explosives.However,due to its low prediction accuracy...The concept of TNT(Trinitrotoluene,C_7H_5N_3O_6)equivalence is often invoked to evaluate the performance and predict the explosion parameters of different types of explosives.However,due to its low prediction accuracy and limited application range,the use of TNT equivalence for predicting explosion parameters in a confined space is rare.Compared with explosions in free fields,the process of explosive energy release in a confined space is closely related to various factors such as oxygen balance,combustible components content,and surrounding oxygen content.Studies have shown that in a confined space,negative oxygen balance explosives react with surrounding oxygen during afterburning,resulting in additional energy release and enhanced blast effects.The mechanism of energy release during afterburning is highly complex,making it challenging to determine the TNT equivalence for blast effects in a confined space.Therefore,this remains an active area of research.In this study,internal blast experiments were conducted using TNT and three other explosives under both air and N_2(Nitrogen)conditions to obtain explosion parameters including blast wave overpressure,quasi-static pressure,and temperature.The influences of oxygen balance and external oxygen content on energy release are analyzed.The author proposes principles for determining TNT equivalence for internal explosions while verifying the accuracy of obtained blast parameters through calculations based on TNT equivalence.These findings can serve as references for predicting blast performance.展开更多
Based on 310 horizontal-component digital seismograms recorded at 14 seismic stations in Shanxi Digital Seis-mograph Network, the inelastic attenuation coefficient in Shanxi region is studied. By the methods of Atkins...Based on 310 horizontal-component digital seismograms recorded at 14 seismic stations in Shanxi Digital Seis-mograph Network, the inelastic attenuation coefficient in Shanxi region is studied. By the methods of Atkinson and Moya, the site response of each station and several source parameters are obtained and the inversion results from both methods are compared and analyzed. The frequency-dependent inelastic attenuation coefficient Q is estimated as Q( f )=323.2 f 0.506. The site responses of 14 seismic stations do not show significant amplification, which is consistent with their basement on rock. We also found the dependence of corner frequency on seismic moment, seismic moment on stress drop, source radius on stress drop.展开更多
Using the data of regional seismic network, this paper analyzes the current faulting behaviors of different segments of the Anninghe-Zemuhe fault zone, western Sichuan, and identifies the likely risky segments for pot...Using the data of regional seismic network, this paper analyzes the current faulting behaviors of different segments of the Anninghe-Zemuhe fault zone, western Sichuan, and identifies the likely risky segments for potential large earthquakes. The authors map the probable asperities from the abnormally low b-value distribution, develop and employ a method for identifying current faulting behaviors of individual fault segment from the combinations of multiple seismicity parameter values, and make an effort to estimate the average recurrence intervals of character-istic earthquakes by using the parameters of magnitude-frequency relationship of the asperity segment. The result suggests that the studied fault zone contains 5 segments of different current faulting behaviors. Among them, the Mianning-Xichang segment of the Anninghe fault has been locked under high stress, its central part is probably an asperity with a relatively large scale. The Xichang-Puge segment of the Zemuhe fault displays very low seismicity under low stress. Both the locked segment and the low-seismicity segment can be outlined on the across-profile of relocated hypocenter depths. The Mianning-Xichang segment is identified to be the one with potential large earth-quake risk, for which the average recurrence interval between the latest M = 6.7 earthquake in 1952 and the next characteristic event is estimated to be 55 to 67 years, and the magnitude of the potential earthquake between 7.0 and 7.5. Also, it has been preliminarily suggested that for a certain fault segment, its faulting behaviors may change and evolve with time gradually.展开更多
Influence of multiple structural parameters on the performance of a gun launch system driven by highpressure reactive gases is important for structural design and performance adjustment.A coupled lumped parameter mode...Influence of multiple structural parameters on the performance of a gun launch system driven by highpressure reactive gases is important for structural design and performance adjustment.A coupled lumped parameter model was utilized to predict the propellant combustion,and a dynamic finite element method was applied to approximate the mechanical interactions between the projectile and the barrel.The combustion and the mechanical interactions were coupled through a user subroutine interface in ABAQUS.The correctness and the capability of the finite element approximations in capturing small structural changes were validated by comparing predicted resistance with experiments.Based on the coupled model,the influence of structural parameters of a medium-caliber gun on the system performance was investigated.In order to reduce the research costs,orthogonal tests were designed to investigate the comprehensive effects of the parameters.According to statistical analysis,the important order of the structural parameters on the launching process was obtained.The results indicate that the influence of the width of the rotating band stands out among the studied parameters in the gun.The work provides a method to investigate the influence of multiple parameters on system performance and gives guidance for controlling the system performance.展开更多
A more general form of projective synchronization, so called linear generalized synchronization （LGS） is proposed, which includes the generalized projective synchronization （GPS） and the hybrid projective synchron...A more general form of projective synchronization, so called linear generalized synchronization （LGS） is proposed, which includes the generalized projective synchronization （GPS） and the hybrid projective synchronization （HPS） as its special cases, Based on the adaptive technique and Lyapunov stability theory, a general method for achieving the LGS between two chaotic or hyperehaotic systems with uncertain parameters in any scaling matrix is presented. Some numerical simulations are provided to show the effectiveness and feasibility of the proposed synchronization method.展开更多
By using the sparsity of frequency hopping（FH） signals,an underdetermined blind source separation（UBSS） algorithm is presented. Firstly, the short time Fourier transform（STFT） is performed on the mixed signals. ...By using the sparsity of frequency hopping（FH） signals,an underdetermined blind source separation（UBSS） algorithm is presented. Firstly, the short time Fourier transform（STFT） is performed on the mixed signals. Then, the mixing matrix, hopping frequencies, hopping instants and the hooping rate can be estimated by the K-means clustering algorithm. With the estimated mixing matrix, the directions of arrival（DOA） of source signals can be obtained. Then, the FH signals are sorted and the FH pattern is obtained. Finally, the shortest path algorithm is adopted to recover the time domain signals. Simulation results show that the correlation coefficient between the estimated FH signal and the source signal is above 0.9 when the signal-to-noise ratio（SNR） is higher than 0 d B and hopping parameters of multiple FH signals in the synchronous orthogonal FH network can be accurately estimated and sorted under the underdetermined conditions.展开更多
When the training data are insufficient, especially when only a small sample size of data is available, domain knowledge will be taken into the process of learning parameters to improve the performance of the Bayesian...When the training data are insufficient, especially when only a small sample size of data is available, domain knowledge will be taken into the process of learning parameters to improve the performance of the Bayesian networks. In this paper, a new monotonic constraint model is proposed to represent a type of common domain knowledge. And then, the monotonic constraint estimation algorithm is proposed to learn the parameters with the monotonic constraint model. In order to demonstrate the superiority of the proposed algorithm, series of experiments are carried out. The experiment results show that the proposed algorithm is able to obtain more accurate parameters compared to some existing algorithms while the complexity is not the highest.展开更多
Laser Induced Breakdown Spectroscopic(LIBS)technique was used to detect calcium and silicon in an unknown sample.In this method plasma was generated by Nd∶YAG laser of wavelength 1 064 nm with energy 400 mJ and pulse...Laser Induced Breakdown Spectroscopic(LIBS)technique was used to detect calcium and silicon in an unknown sample.In this method plasma was generated by Nd∶YAG laser of wavelength 1 064 nm with energy 400 mJ and pulse duration between 5~10ns.The method was applied for the qualitative as well as quantitative analysis.In the qualitative analysis,the electron number density(Ne)of plasma containing calcium and silicon is determined showing that Neof neutral particles is equivalent to 1016(cm-3)whereas for ionized particles it is 1017(cm-3).Plasma temperature is measured using Boltzmann plot method which must be greater than 10 000 k.Intensity ratio method is used for the quantitative analysis shows various elements in abundance with calcium and silicon in majority.展开更多
The existing trajectory clustering （TRACLUS） is sensitive to the input parameters c and MinLns. The parameter value is changed a little, but cluster results are entirely different. Aiming at this vulnerability, a sh...The existing trajectory clustering （TRACLUS） is sensitive to the input parameters c and MinLns. The parameter value is changed a little, but cluster results are entirely different. Aiming at this vulnerability, a shielding parameters sensitivity trajectory cluster （SPSTC） algorithm is proposed which is insensitive to the input parameters. Firstly, some definitions about the core distance and reachable distance of line segment are presented, and then the algorithm generates cluster sorting according to the core dis- tance and reachable distance. Secondly, the reachable plots of line segment sets are constructed according to the cluster sorting and reachable distance. Thirdly, a parameterized sequence is extracted according to the reachable plot, and then the final trajectory cluster based on the parameterized sequence is acquired. The parameterized sequence represents the inner cluster structure of trajectory data. Experiments on real data sets and test data sets show that the SPSTC algorithm effectively reduces the sensitivity to the input parameters, meanwhile it can obtain the better quality of the trajectory cluster.展开更多
Since the joint actuator of the space robot executes the control instructions frequently in the harsh space environment,it is prone to the partial loss of control effectiveness(PLCE)fault.An adaptive fault-tolerant co...Since the joint actuator of the space robot executes the control instructions frequently in the harsh space environment,it is prone to the partial loss of control effectiveness(PLCE)fault.An adaptive fault-tolerant control algorithm is designed for a space robot system with the uncertain parameters and the PLCE actuator faults.The mathematical model of the system is established based on the Lagrange method,and the PLCE actuator fault is described as an effectiveness factor.The lower bound of the effectiveness factors and the upper bound of the uncertain parameters are estimated by an adaptive strategy,and the estimated value is fed back to the control algorithm.Compared with the traditional fault-tolerant algorithms,the proposed algorithm does not need to predetermine the lower bound of the effectiveness factor,hence it is more in line with the actual engineering application.It is proved that the algorithm can guarantee the stability of the closed-loop system based on the Lyapunov function method.The numerical simulation results show that the proposed algorithm can not only compensate for the uncertain parameters,but also can tolerate the PLCE actuator faults effectively,which verifies the effectiveness and superiority of the control scheme.展开更多
To explore a new evaluation method for spontaneous combustion tendency of different areas in sulfide ore heap, ore samples from a pyrite mine in China were taken as experimental materials, and the temperature variatio...To explore a new evaluation method for spontaneous combustion tendency of different areas in sulfide ore heap, ore samples from a pyrite mine in China were taken as experimental materials, and the temperature variations of the measuring points of simulated ore heap were measured. Combined with wavelet transform and nonlinear parameters extraction, a new method for spontaneous combustion tendency of different areas in sulfide ore heap based on nonlinear parameters was proposed and its reliability was verified by field test. The results indicate that temperature field evolution of the simulated ore heap presents significant spatial difference during self-heating process. Area with the maximum increasing extent of temperature in sulfide ore heap changes notably with the proceeding of self-heating reaction. Self-heating of sulfide ore heap is a chaotic evolution process, which means that it is feasible to evaluate spontaneous combustion tendency of different areas by nonlinear analysis method. There is a relatively strong correlation between the maximum Lyapunov exponent and spontaneous combustion tendency with the correlation coefficient of 0.9792. Furthermore, the sort of the maximum Lyapunov exponent is consistent with that of spontaneous combustion tendency. Therefore, spontaneous combustion tendency of different areas in sulfide ore heap can be evaluated by means of the maximum Lyapunov exponent method.展开更多
In the traditional strength reduction method,the cohesion and the friction angle adopt the same reduction parameter,resulting in equivalent proportional reduction.This method does not consider the different effects of...In the traditional strength reduction method,the cohesion and the friction angle adopt the same reduction parameter,resulting in equivalent proportional reduction.This method does not consider the different effects of the cohesion and friction angle on the stability of the same slope and is defective to some extent.Regarding this defect,a strength reduction method based on double reduction parameters,which adopts different reduction parameters,is proposed.The core of the double-parameter reduction method is the matching reduction principle of the slope with different angles.This principle is represented by the ratio of the reduction parameter of the cohesion to that of the friction angle,described as η.With the increase in the slopeangle,ηincreases; in particular,when the slope angle is 45°,tηis 1.0.Through the matching reduction principle,different safety margin factors can be calculated for the cohesion and friction angle.In combination with these two safety margin factors,a formula for calculating the overall safety factor of the slope is proposed,reflecting the different contributions of the cohesion and friction angle to the slope stability.Finally,it is shown that the strength reduction method based on double reduction parameters acquires a larger safety factor than the classic limit equilibrium method,but the calculation results are very close to those obtained by the limit equilibrium method.展开更多
The study was designated to explore the physiological mechanism of cold tolerance enhanced by phosphate in rice. An experiment was conducted to investigate the effects of different levels of phosphate fertilizer on co...The study was designated to explore the physiological mechanism of cold tolerance enhanced by phosphate in rice. An experiment was conducted to investigate the effects of different levels of phosphate fertilizer on cold tolerance and its related physiological parameters in rice seedings （chilling-sensitive cv. Changbai 9 and chilling-tolerant cv. Jijing 81） under low temperature stress. At the same time, the identification of cold tolerance was conducted. Compared with the normal temperature treatment, the relative chlorophyll content, photosynthesis rate, Fv/Fm and qP decreased and index of unsaturated fatty acid increased in rice under low temperature stress. The effect of chilling-sensitive cultivars was more than that of chilling-tolerant cultivars, more phosphorus fertilizer properly improved seedling quality of rice, slowed relative chlorophyll content dropping degree of rice seeding, increased photosynthesis rate, Fv/Fm, qP and index of unsaturated fatty acids, and enhanced the ability to chilling-tolerant cultivars under low temperature. The effect on chilling-tolerant cultivars was significantly higher than that on chilling sensitive cultivars by applying more phosphorus fertilizer. Phosphate regulated photosynthetic physiology and membrane fluidity to reduce injury by low temperature, and increasd the cold tolerance capacity of rice.展开更多
The influence of enlarged section parameters on pressure transients of high-speed train passing through a tunnel was investigated by numerical simulation.The calculation results obtained by the structured and unstruct...The influence of enlarged section parameters on pressure transients of high-speed train passing through a tunnel was investigated by numerical simulation.The calculation results obtained by the structured and unstructured grid and the experimental results of smooth wall tunnel were verified.Numerical simulation studies were conducted on three tunnel enlarged section parameters,the enlarged section distribution along circumferential direction,the enlarged section area and the enlarged section distribution along tunnel length direction.The calculation results show that the influence of the different enlarged section distributions along tunnel circumferential direction on pressure transients in the tunnel is basically consistent.There is an optimal enlarged section area for the minimum value of the pressure variation amplitude and the average pressure variation in the tunnel.The law of the pressure variation amplitude and the average pressure variation of the enlarged section distribution along tunnel length direction are obtained.展开更多
Blast vibration analysis is one of the important foundations for studying the control technology of blast vibration damage. According to blast vibration live data that have been collected and the characteristics of sh...Blast vibration analysis is one of the important foundations for studying the control technology of blast vibration damage. According to blast vibration live data that have been collected and the characteristics of short-time non-stationary random signals, the wavelet packet energy spectrum analysis for blast vibration signal has made by wavelet packet analysis technology and the signals were measured under different explosion parameters （the maximal section dose, the distance of blast source to measuring point and the section number of millisecond detonator）. The results show that more than 95% frequency band energy of the signals sl-s8 concentrates at 0-200 Hz and the main vibration frequency bands of the signals sl-s8 are 70.313-125, 46.875-93.75, 15.625-93.75, 0-62.5, 42.969-125, 15.625-82.031, 7.813-62.5 and 0-62.5 Hz. Energy distributions for different frequency bands of blast vibration signal are obtained and the characteristics of energy distributions for blast vibration signal measured under different explosion parameters are analyzed. From blast vibration signal energy, the decreasing law of blast seismic waves measured under different explosion parameters was studied and the wavelet packet analysis is an effective means for studying seismic effect induced by blast.展开更多
The high-flowing sand-concrete （HFSC） containing natural sands as aggregate was carried out. The high fluidity and stability of HFSC can be achieved by tailoring the mix design parameters, such as fine to coarse san...The high-flowing sand-concrete （HFSC） containing natural sands as aggregate was carried out. The high fluidity and stability of HFSC can be achieved by tailoring the mix design parameters, such as fine to coarse sand ratio, dosage of additions, water to binder ratio and dosage of admixtures. Mini-cone slump test, v-fl.mnel time test and viscosity model parameters were used to characterize the behaviour of HFSC in fresh state. The mechanical compressive strength in 28 d was also determined. A factorial design approach was used to establish models highlighting the effect of each mix-parameter on measured properties of HFSC. The derived models are valid for mixtures made with 0 to 0.3 of dune sand to total sand ratio, 82 to 418 kg/m3 of marble powder, 0.42 to 0.46 of water/binder ratio and 1.3% to 1.9% of superplasticizer high water-reducer. The results show that the derived models constitute very efficient means for understanding the influence of key mix-parameters on HFSC properties and are useful in selecting the optimum mix proportions, by simulating their impact on fluidity, stability and compressive strength.展开更多
The influences of hot stamping parameters such as heating temperature,soaking time,deformation temperature and cooling medium on the phase transformation,microstructure and mechanical properties of 30MnB5 and 22MnB5 a...The influences of hot stamping parameters such as heating temperature,soaking time,deformation temperature and cooling medium on the phase transformation,microstructure and mechanical properties of 30MnB5 and 22MnB5 are investigated and analyzed in this work.The quenching experiment,tensile testing,hardness measurement and microstructure observation were conducted to obtain the mechanical and microstructural data.The results indicate that 30MnB5 possesses a higher tensile strength but a lower elongation than 22MnB5,if hot stamped at the same process parameter.The tensile strength and hardness of the hot stamped specimens decrease under inappropriate heating conditions for two reasons,insufficient austenitization or coarse austenite grains.The austenitic forming rate of 30MnB5 is higher than that of 22MnB5,because more cementite leads to higher nucleation rate and diffusion coefficient of carbon atom.More amount of fine martensite forms under the higher deformation temperature or the quicker cooling rate.展开更多
基金Projects(U22B2084,52275483,52075142)supported by the National Natural Science Foundation of ChinaProject(2023ZY01050)supported by the Ministry of Industry and Information Technology High Quality Development,China。
文摘The gears of new energy vehicles are required to withstand higher rotational speeds and greater loads,which puts forward higher precision essentials for gear manufacturing.However,machining process parameters can cause changes in cutting force/heat,resulting in affecting gear machining precision.Therefore,this paper studies the effect of different process parameters on gear machining precision.A multi-objective optimization model is established for the relationship between process parameters and tooth surface deviations,tooth profile deviations,and tooth lead deviations through the cutting speed,feed rate,and cutting depth of the worm wheel gear grinding machine.The response surface method(RSM)is used for experimental design,and the corresponding experimental results and optimal process parameters are obtained.Subsequently,gray relational analysis-principal component analysis(GRA-PCA),particle swarm optimization(PSO),and genetic algorithm-particle swarm optimization(GA-PSO)methods are used to analyze the experimental results and obtain different optimal process parameters.The results show that optimal process parameters obtained by the GRA-PCA,PSO,and GA-PSO methods improve the gear machining precision.Moreover,the gear machining precision obtained by GA-PSO is superior to other methods.
基金Supported by the National Natural Science Foundation of China(11971458,11471310)。
文摘In this paper,we propose a neural network approach to learn the parameters of a class of stochastic Lotka-Volterra systems.Approximations of the mean and covariance matrix of the observational variables are obtained from the Euler-Maruyama discretization of the underlying stochastic differential equations(SDEs),based on which the loss function is built.The stochastic gradient descent method is applied in the neural network training.Numerical experiments demonstrate the effectiveness of our method.
文摘The concept of TNT(Trinitrotoluene,C_7H_5N_3O_6)equivalence is often invoked to evaluate the performance and predict the explosion parameters of different types of explosives.However,due to its low prediction accuracy and limited application range,the use of TNT equivalence for predicting explosion parameters in a confined space is rare.Compared with explosions in free fields,the process of explosive energy release in a confined space is closely related to various factors such as oxygen balance,combustible components content,and surrounding oxygen content.Studies have shown that in a confined space,negative oxygen balance explosives react with surrounding oxygen during afterburning,resulting in additional energy release and enhanced blast effects.The mechanism of energy release during afterburning is highly complex,making it challenging to determine the TNT equivalence for blast effects in a confined space.Therefore,this remains an active area of research.In this study,internal blast experiments were conducted using TNT and three other explosives under both air and N_2(Nitrogen)conditions to obtain explosion parameters including blast wave overpressure,quasi-static pressure,and temperature.The influences of oxygen balance and external oxygen content on energy release are analyzed.The author proposes principles for determining TNT equivalence for internal explosions while verifying the accuracy of obtained blast parameters through calculations based on TNT equivalence.These findings can serve as references for predicting blast performance.
基金National Scientific Research Target Project of China (2001-BA601B01-01-05) during the tenth Five-year Plan.
文摘Based on 310 horizontal-component digital seismograms recorded at 14 seismic stations in Shanxi Digital Seis-mograph Network, the inelastic attenuation coefficient in Shanxi region is studied. By the methods of Atkinson and Moya, the site response of each station and several source parameters are obtained and the inversion results from both methods are compared and analyzed. The frequency-dependent inelastic attenuation coefficient Q is estimated as Q( f )=323.2 f 0.506. The site responses of 14 seismic stations do not show significant amplification, which is consistent with their basement on rock. We also found the dependence of corner frequency on seismic moment, seismic moment on stress drop, source radius on stress drop.
基金Chinese Joint Seismological Science Foundation (102002).
文摘Using the data of regional seismic network, this paper analyzes the current faulting behaviors of different segments of the Anninghe-Zemuhe fault zone, western Sichuan, and identifies the likely risky segments for potential large earthquakes. The authors map the probable asperities from the abnormally low b-value distribution, develop and employ a method for identifying current faulting behaviors of individual fault segment from the combinations of multiple seismicity parameter values, and make an effort to estimate the average recurrence intervals of character-istic earthquakes by using the parameters of magnitude-frequency relationship of the asperity segment. The result suggests that the studied fault zone contains 5 segments of different current faulting behaviors. Among them, the Mianning-Xichang segment of the Anninghe fault has been locked under high stress, its central part is probably an asperity with a relatively large scale. The Xichang-Puge segment of the Zemuhe fault displays very low seismicity under low stress. Both the locked segment and the low-seismicity segment can be outlined on the across-profile of relocated hypocenter depths. The Mianning-Xichang segment is identified to be the one with potential large earth-quake risk, for which the average recurrence interval between the latest M = 6.7 earthquake in 1952 and the next characteristic event is estimated to be 55 to 67 years, and the magnitude of the potential earthquake between 7.0 and 7.5. Also, it has been preliminarily suggested that for a certain fault segment, its faulting behaviors may change and evolve with time gradually.
基金the financial support from the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYLX_0399)
文摘Influence of multiple structural parameters on the performance of a gun launch system driven by highpressure reactive gases is important for structural design and performance adjustment.A coupled lumped parameter model was utilized to predict the propellant combustion,and a dynamic finite element method was applied to approximate the mechanical interactions between the projectile and the barrel.The combustion and the mechanical interactions were coupled through a user subroutine interface in ABAQUS.The correctness and the capability of the finite element approximations in capturing small structural changes were validated by comparing predicted resistance with experiments.Based on the coupled model,the influence of structural parameters of a medium-caliber gun on the system performance was investigated.In order to reduce the research costs,orthogonal tests were designed to investigate the comprehensive effects of the parameters.According to statistical analysis,the important order of the structural parameters on the launching process was obtained.The results indicate that the influence of the width of the rotating band stands out among the studied parameters in the gun.The work provides a method to investigate the influence of multiple parameters on system performance and gives guidance for controlling the system performance.
基金the National Natural Science Foundation of China (60574045 10661006).
文摘A more general form of projective synchronization, so called linear generalized synchronization （LGS） is proposed, which includes the generalized projective synchronization （GPS） and the hybrid projective synchronization （HPS） as its special cases, Based on the adaptive technique and Lyapunov stability theory, a general method for achieving the LGS between two chaotic or hyperehaotic systems with uncertain parameters in any scaling matrix is presented. Some numerical simulations are provided to show the effectiveness and feasibility of the proposed synchronization method.
基金supported by the National Natural Science Foundation of China(6120113461201135)+2 种基金the 111 Project(B08038)the Fundamental Research Funds for the Central Universities(72124669)the Open Research Fund of the Academy of Application(2014CXJJ-TX06)
文摘By using the sparsity of frequency hopping（FH） signals,an underdetermined blind source separation（UBSS） algorithm is presented. Firstly, the short time Fourier transform（STFT） is performed on the mixed signals. Then, the mixing matrix, hopping frequencies, hopping instants and the hooping rate can be estimated by the K-means clustering algorithm. With the estimated mixing matrix, the directions of arrival（DOA） of source signals can be obtained. Then, the FH signals are sorted and the FH pattern is obtained. Finally, the shortest path algorithm is adopted to recover the time domain signals. Simulation results show that the correlation coefficient between the estimated FH signal and the source signal is above 0.9 when the signal-to-noise ratio（SNR） is higher than 0 d B and hopping parameters of multiple FH signals in the synchronous orthogonal FH network can be accurately estimated and sorted under the underdetermined conditions.
基金supported by the National Natural Science Foundation of China(6130513361573285)the Fundamental Research Funds for the Central Universities(3102016CG002)
文摘When the training data are insufficient, especially when only a small sample size of data is available, domain knowledge will be taken into the process of learning parameters to improve the performance of the Bayesian networks. In this paper, a new monotonic constraint model is proposed to represent a type of common domain knowledge. And then, the monotonic constraint estimation algorithm is proposed to learn the parameters with the monotonic constraint model. In order to demonstrate the superiority of the proposed algorithm, series of experiments are carried out. The experiment results show that the proposed algorithm is able to obtain more accurate parameters compared to some existing algorithms while the complexity is not the highest.
文摘Laser Induced Breakdown Spectroscopic(LIBS)technique was used to detect calcium and silicon in an unknown sample.In this method plasma was generated by Nd∶YAG laser of wavelength 1 064 nm with energy 400 mJ and pulse duration between 5~10ns.The method was applied for the qualitative as well as quantitative analysis.In the qualitative analysis,the electron number density(Ne)of plasma containing calcium and silicon is determined showing that Neof neutral particles is equivalent to 1016(cm-3)whereas for ionized particles it is 1017(cm-3).Plasma temperature is measured using Boltzmann plot method which must be greater than 10 000 k.Intensity ratio method is used for the quantitative analysis shows various elements in abundance with calcium and silicon in majority.
基金supported by the National High Technology Research and Development Program of China(863 Program)(2007AA01Z404)the Funding of Jiangsu Provincial Innovation Program for Graduate Education(CXLX110206)
文摘The existing trajectory clustering （TRACLUS） is sensitive to the input parameters c and MinLns. The parameter value is changed a little, but cluster results are entirely different. Aiming at this vulnerability, a shielding parameters sensitivity trajectory cluster （SPSTC） algorithm is proposed which is insensitive to the input parameters. Firstly, some definitions about the core distance and reachable distance of line segment are presented, and then the algorithm generates cluster sorting according to the core dis- tance and reachable distance. Secondly, the reachable plots of line segment sets are constructed according to the cluster sorting and reachable distance. Thirdly, a parameterized sequence is extracted according to the reachable plot, and then the final trajectory cluster based on the parameterized sequence is acquired. The parameterized sequence represents the inner cluster structure of trajectory data. Experiments on real data sets and test data sets show that the SPSTC algorithm effectively reduces the sensitivity to the input parameters, meanwhile it can obtain the better quality of the trajectory cluster.
基金supported by the National Natural Science Foundation of China(11372073,11072061)
文摘Since the joint actuator of the space robot executes the control instructions frequently in the harsh space environment,it is prone to the partial loss of control effectiveness(PLCE)fault.An adaptive fault-tolerant control algorithm is designed for a space robot system with the uncertain parameters and the PLCE actuator faults.The mathematical model of the system is established based on the Lagrange method,and the PLCE actuator fault is described as an effectiveness factor.The lower bound of the effectiveness factors and the upper bound of the uncertain parameters are estimated by an adaptive strategy,and the estimated value is fed back to the control algorithm.Compared with the traditional fault-tolerant algorithms,the proposed algorithm does not need to predetermine the lower bound of the effectiveness factor,hence it is more in line with the actual engineering application.It is proved that the algorithm can guarantee the stability of the closed-loop system based on the Lyapunov function method.The numerical simulation results show that the proposed algorithm can not only compensate for the uncertain parameters,but also can tolerate the PLCE actuator faults effectively,which verifies the effectiveness and superiority of the control scheme.
基金Projects(51304238,51534008)supported by the National Natural Science Foundation of ChinaProject(2015CX005)supported by Innovation Driven Plan of Central South University,China
文摘To explore a new evaluation method for spontaneous combustion tendency of different areas in sulfide ore heap, ore samples from a pyrite mine in China were taken as experimental materials, and the temperature variations of the measuring points of simulated ore heap were measured. Combined with wavelet transform and nonlinear parameters extraction, a new method for spontaneous combustion tendency of different areas in sulfide ore heap based on nonlinear parameters was proposed and its reliability was verified by field test. The results indicate that temperature field evolution of the simulated ore heap presents significant spatial difference during self-heating process. Area with the maximum increasing extent of temperature in sulfide ore heap changes notably with the proceeding of self-heating reaction. Self-heating of sulfide ore heap is a chaotic evolution process, which means that it is feasible to evaluate spontaneous combustion tendency of different areas by nonlinear analysis method. There is a relatively strong correlation between the maximum Lyapunov exponent and spontaneous combustion tendency with the correlation coefficient of 0.9792. Furthermore, the sort of the maximum Lyapunov exponent is consistent with that of spontaneous combustion tendency. Therefore, spontaneous combustion tendency of different areas in sulfide ore heap can be evaluated by means of the maximum Lyapunov exponent method.
基金Project(KZCX2-YW-T12)supported by the Chinese Academy of Science,China
文摘In the traditional strength reduction method,the cohesion and the friction angle adopt the same reduction parameter,resulting in equivalent proportional reduction.This method does not consider the different effects of the cohesion and friction angle on the stability of the same slope and is defective to some extent.Regarding this defect,a strength reduction method based on double reduction parameters,which adopts different reduction parameters,is proposed.The core of the double-parameter reduction method is the matching reduction principle of the slope with different angles.This principle is represented by the ratio of the reduction parameter of the cohesion to that of the friction angle,described as η.With the increase in the slopeangle,ηincreases; in particular,when the slope angle is 45°,tηis 1.0.Through the matching reduction principle,different safety margin factors can be calculated for the cohesion and friction angle.In combination with these two safety margin factors,a formula for calculating the overall safety factor of the slope is proposed,reflecting the different contributions of the cohesion and friction angle to the slope stability.Finally,it is shown that the strength reduction method based on double reduction parameters acquires a larger safety factor than the classic limit equilibrium method,but the calculation results are very close to those obtained by the limit equilibrium method.
基金Supported by the Special Agricultural Project of Agricultural Department (200903003)the Agricultural Modernization Project in the Science and Technology Development Plan of Jilin Province (2009-2010) the High-yield Project of Science and Technology Department (2011BAD16B10)
文摘The study was designated to explore the physiological mechanism of cold tolerance enhanced by phosphate in rice. An experiment was conducted to investigate the effects of different levels of phosphate fertilizer on cold tolerance and its related physiological parameters in rice seedings （chilling-sensitive cv. Changbai 9 and chilling-tolerant cv. Jijing 81） under low temperature stress. At the same time, the identification of cold tolerance was conducted. Compared with the normal temperature treatment, the relative chlorophyll content, photosynthesis rate, Fv/Fm and qP decreased and index of unsaturated fatty acid increased in rice under low temperature stress. The effect of chilling-sensitive cultivars was more than that of chilling-tolerant cultivars, more phosphorus fertilizer properly improved seedling quality of rice, slowed relative chlorophyll content dropping degree of rice seeding, increased photosynthesis rate, Fv/Fm, qP and index of unsaturated fatty acids, and enhanced the ability to chilling-tolerant cultivars under low temperature. The effect on chilling-tolerant cultivars was significantly higher than that on chilling sensitive cultivars by applying more phosphorus fertilizer. Phosphate regulated photosynthetic physiology and membrane fluidity to reduce injury by low temperature, and increasd the cold tolerance capacity of rice.
基金Project (2016YFB1200602-11) supported by National Key R&D Plan of China
文摘The influence of enlarged section parameters on pressure transients of high-speed train passing through a tunnel was investigated by numerical simulation.The calculation results obtained by the structured and unstructured grid and the experimental results of smooth wall tunnel were verified.Numerical simulation studies were conducted on three tunnel enlarged section parameters,the enlarged section distribution along circumferential direction,the enlarged section area and the enlarged section distribution along tunnel length direction.The calculation results show that the influence of the different enlarged section distributions along tunnel circumferential direction on pressure transients in the tunnel is basically consistent.There is an optimal enlarged section area for the minimum value of the pressure variation amplitude and the average pressure variation in the tunnel.The law of the pressure variation amplitude and the average pressure variation of the enlarged section distribution along tunnel length direction are obtained.
基金Foundation item: Project(51064009) supported by the National Natural Science Foundation of ChinaProject(201104356) supported by the China Postdoctoral Science FoundationProject(20114BAB206030) supported by the Natural Science Foundation of Jiangxi Province,China
文摘Blast vibration analysis is one of the important foundations for studying the control technology of blast vibration damage. According to blast vibration live data that have been collected and the characteristics of short-time non-stationary random signals, the wavelet packet energy spectrum analysis for blast vibration signal has made by wavelet packet analysis technology and the signals were measured under different explosion parameters （the maximal section dose, the distance of blast source to measuring point and the section number of millisecond detonator）. The results show that more than 95% frequency band energy of the signals sl-s8 concentrates at 0-200 Hz and the main vibration frequency bands of the signals sl-s8 are 70.313-125, 46.875-93.75, 15.625-93.75, 0-62.5, 42.969-125, 15.625-82.031, 7.813-62.5 and 0-62.5 Hz. Energy distributions for different frequency bands of blast vibration signal are obtained and the characteristics of energy distributions for blast vibration signal measured under different explosion parameters are analyzed. From blast vibration signal energy, the decreasing law of blast seismic waves measured under different explosion parameters was studied and the wavelet packet analysis is an effective means for studying seismic effect induced by blast.
文摘The high-flowing sand-concrete （HFSC） containing natural sands as aggregate was carried out. The high fluidity and stability of HFSC can be achieved by tailoring the mix design parameters, such as fine to coarse sand ratio, dosage of additions, water to binder ratio and dosage of admixtures. Mini-cone slump test, v-fl.mnel time test and viscosity model parameters were used to characterize the behaviour of HFSC in fresh state. The mechanical compressive strength in 28 d was also determined. A factorial design approach was used to establish models highlighting the effect of each mix-parameter on measured properties of HFSC. The derived models are valid for mixtures made with 0 to 0.3 of dune sand to total sand ratio, 82 to 418 kg/m3 of marble powder, 0.42 to 0.46 of water/binder ratio and 1.3% to 1.9% of superplasticizer high water-reducer. The results show that the derived models constitute very efficient means for understanding the influence of key mix-parameters on HFSC properties and are useful in selecting the optimum mix proportions, by simulating their impact on fluidity, stability and compressive strength.
基金Projects(51705018,U1564202)supported by the National Natural Science Foundation of China
文摘The influences of hot stamping parameters such as heating temperature,soaking time,deformation temperature and cooling medium on the phase transformation,microstructure and mechanical properties of 30MnB5 and 22MnB5 are investigated and analyzed in this work.The quenching experiment,tensile testing,hardness measurement and microstructure observation were conducted to obtain the mechanical and microstructural data.The results indicate that 30MnB5 possesses a higher tensile strength but a lower elongation than 22MnB5,if hot stamped at the same process parameter.The tensile strength and hardness of the hot stamped specimens decrease under inappropriate heating conditions for two reasons,insufficient austenitization or coarse austenite grains.The austenitic forming rate of 30MnB5 is higher than that of 22MnB5,because more cementite leads to higher nucleation rate and diffusion coefficient of carbon atom.More amount of fine martensite forms under the higher deformation temperature or the quicker cooling rate.
