The emerging millimeter-wave microphones have garnered considerable attention in recent years due to their potential for sound detection in various applications,particularly in situations where traditional microphones...The emerging millimeter-wave microphones have garnered considerable attention in recent years due to their potential for sound detection in various applications,particularly in situations where traditional microphones may be impractical.However,despite their promise,there is a notable lack of evidence demonstrating high-quality sound recovery of moving sources,which remains a significant challenge in thefield.This paper addresses this critical gap by proposing a novel method for displacement alignment that improves the detection and recovery of sound signals from moving sources.The proposed method works byfirst aligning the displacement of the sound source over time,which ensures that the signals are synchronized and avoids interference from movement of sources.Subsequently,precise surface vibrations are extracted from the aligned signals,providing data for sound recovery.Afinite impulse response(FIR)filter is applied to remove low-frequency motion,which often interferes with the clarity of the detected sound.Experimental results demonstrate the method’s effectiveness in recovering high-quality sound from moving sources,offering a promising solution for advancing the emerging millimeter-wave microphone technology in real-world applications.This work could pave the way for more accurate and reliable sound detection systems,particularly in dynamic environments.展开更多
Doppler effect widely exists in the signal from the moving acoustic source. In order to solve such problems as frequency shift and frequency band expansion, a time domain cor- rection method is presented in this paper...Doppler effect widely exists in the signal from the moving acoustic source. In order to solve such problems as frequency shift and frequency band expansion, a time domain cor- rection method is presented in this paper. First, the discrete time vector for interpolation and the amplitude restoration formula is derived based on the moving relationship and the Morse acoustic theory, then the amplitude weights are corrected and the distortion signal is interpolated. Every point of the discrete signal is operated separately in time domain. Compared with the existing frequency domain methods, this method does not need to know the characteristic frequency beforehand and would not be influenced by the blending of the frequency band. Hence, this method can be employed to correct multiple frequency signals and it is also a simple and effective Doppler effect reduction method.展开更多
In this paper the properties of space- time correlation function of the noise field of moving source in layered statistic inhomogeneous medium are studied and the effects of random fluctuating boundary are considered ...In this paper the properties of space- time correlation function of the noise field of moving source in layered statistic inhomogeneous medium are studied and the effects of random fluctuating boundary are considered as well.It has been shown, theoretically and experimentally, multi-path propergating effects cause the dispersion of the correlation function and fluctuations of the medium refraction index and the boundary cause the fluctuation of it.The effect of the movement of the noise source on the output of real- time correlator is equivalent to a low- pass filter added the drift of space- time correlation function.These properties of the correlation function cause grave degradation of the signal processing gain of noise ranging sonar system.The fluctuating and the distortion of conrrelation function made it difficult to realize the noise ranging.So in this paper, a method of space correlation ranging by a linear array of four points with short separation and long span and a technigue of dual- correlation signal processing are presented. By this, the influences of previously mentioned factors are greatly overcomed.Futhermore, for the long period and great delay fluctuation of the dual- correlation function output caused by internal wave, a method of limited memory Quasi- Kalman filtering is developed and the effective accurate ranging and tracing of noise ranging sonar are able to be tralized finally.展开更多
Classical thermo-viscoelastic models may be challenged to predict the precise thermo-mechanical behavior of viscoelastic materials without considering the memorydependent effect.Meanwhile,with the miniaturization of d...Classical thermo-viscoelastic models may be challenged to predict the precise thermo-mechanical behavior of viscoelastic materials without considering the memorydependent effect.Meanwhile,with the miniaturization of devices,the size-dependent effect on elastic deformation is becoming more and more important.To capture the memory-dependent effect and the size-dependent effect,the present study aims at developing a modified fractional-order thermo-viscoelastic coupling model at the microscale to account for two fundamentally distinct fractional-order models which govern the memory-dependent features of thermal conduction and stress-strain relation,respectively.Then,the modified theory is used to study the dynamic response of a polymer micro-rod heated by a moving heat source.The governing equations are obtained and solved by the Laplace transform method.In calculation,the effects of the fractional-order parameter,the fractional-order strain parameter,the mechanical relaxation parameter,and the nonlocal parameter on the variations of the considered variables are analyzed and discussed in detail.展开更多
This paper is devoted to the blow-up properties of solutions to the porous medium equations with a nonlocal boundary condition and a moving localized source. Conditions for the existence of global or blow-up solutions...This paper is devoted to the blow-up properties of solutions to the porous medium equations with a nonlocal boundary condition and a moving localized source. Conditions for the existence of global or blow-up solutions are obtained. Moreover, we prove that the unique solution has global blow-up property whenever blow-up occurs.展开更多
The harmonic metric for Schwarzschild black hole with a uniform velocity is presented. In the limit of weak field and low velocity, this metric reduces to the post-Newtonian approximation for one moving point mass. As...The harmonic metric for Schwarzschild black hole with a uniform velocity is presented. In the limit of weak field and low velocity, this metric reduces to the post-Newtonian approximation for one moving point mass. As an application, we derive the dynamics of particle and photon in the weak-field limit for the moving Schwarzschild black hole with an arbitrary velocity. It is found that the relativistic motion of gravitational source can induce an additional centripetal force on the test particle, which may be comparable to or even larger than the conventional Newtonian gravitational force.展开更多
The wide application of carbon fiber reinforced plastic(CFRP)components in modern aerospace manufacturing field puts high demands on the manufacturing process.Especially,the temperature increase during continuous mill...The wide application of carbon fiber reinforced plastic(CFRP)components in modern aerospace manufacturing field puts high demands on the manufacturing process.Especially,the temperature increase during continuous milling process becomes a key factor affecting the performance of composites,and the high milling temperature induces a variety of processing defects.This paper obtained the temperature variation data during the end milling process of CFRP laminates through experiments.After data fitting,the data were transformed into a function of heat flux density varying with time.In the finite element analysis,a double-ellipsoid moving heat source model was introduced,and a moving heat source subrou-tine was written based on the time-varying function of heat flux density to more accurately describe the thermal effects dur-ing the milling process and simulate the changes in the temperature field during milling.The Hashin failure criterion is a-dopted as the basis of fiber and matrix failure,and the simulation results of the temperature field are input into the thermal-force coupling simulation model as the predefined field conditions for solving and analyzing by means of sequential thermal-force coupling,so as to establish a thermal-force coupling simulation and analysis model for milling processing of CFRP end faces.The model simulation results can provide a basis for exploring the damage evolution law of CFRP material under the influence of temperature.展开更多
In this article,the physics informed neural networks(PINNs)is employed for the numerical simulation of heat transfer involving a moving source under mixed boundary conditions.To reduce computational effort and increas...In this article,the physics informed neural networks(PINNs)is employed for the numerical simulation of heat transfer involving a moving source under mixed boundary conditions.To reduce computational effort and increase accuracy,a new training method is proposed that uses a continuous time-stepping through transfer learning.A single network is initialized and used as a sliding window function across the time domain.On this single network each time interval is trained with the initial condition for(+1)t n h iteration as the solution obtained at nth iteration.Thus,this framework enables the computation of large temporal intervals without increasing the complexity of the network itself.The proposed framework is used to estimate the temperature distribution in a homogeneous medium with a moving heat source.The results from the proposed framework is compared with traditional finite element method and a good agreement is seen.展开更多
Heat moving source models along with transient heat analysis by finite element method were used to determine weld thermal cycles and isothermal sections obtained from the application of a gas tungsten arc welding bead...Heat moving source models along with transient heat analysis by finite element method were used to determine weld thermal cycles and isothermal sections obtained from the application of a gas tungsten arc welding beads on Inconel 718 plates. Analytical (Rosenthal’s thick plate model) and finite element results show an acceptable approximation with the experimental weld thermal cycles. The isothermal sections determined by numerical simulation show a better approximation with the experimental welding profile for double-ellipse model heat distribution than Gauss model. To analyze the microstructural transformation produced by different cooling rates in the fusion and heat affected zones, Vickers microhardness measurements (profile and mapping representation) were conducted. A hardness decrement for the heat affected zone (~200 HV0.2) and fusion zone (~240 HV0.2) in comparison with base material (~350 HV0.2) was observed. This behavior has been attributed to the heterogeneous solubilization process of the γ″ phase (nickel matrix), which, according to the continuous-cooling-transformation curve, produced the Laves phase,δ and MC transition phases, generating a loss in hardness close to the fusion zone.展开更多
Based on schematically formulation of the vibrations induced by moving trains, this paper analyses the waveforms along the Datong-Qinhuangdao railroad in Northern China recorded in the suburban Huairou district of Be...Based on schematically formulation of the vibrations induced by moving trains, this paper analyses the waveforms along the Datong-Qinhuangdao railroad in Northern China recorded in the suburban Huairou district of Beijing on March 8, 2003. It is illustrated that vibrations induced by train, except traditional recognized noises and interfer- ence effects, could be used as a seismic source to detect crustal structures with its advantage of abundant frequency spectrum, repeatability and no additional harm to the environment. It will bring lights to the traditional exploration seismology with the further studies of signal processing and interpretation methods, and related models and new observing systems.展开更多
Using the slot method, the moving boundary problem caused by the change of the tide water elevation is treated. A two-dimensional advection - diffusion model with moving boundary is proposed, and the input pollutant i...Using the slot method, the moving boundary problem caused by the change of the tide water elevation is treated. A two-dimensional advection - diffusion model with moving boundary is proposed, and the input pollutant is considered as moving source to meet the water level variation. The model given in this paper has been used to simulate the pollutant transport in the Bohai Gulf, the computational results are in good agreement with the measured data.展开更多
Line heating method is widely used to manufacture curved surfaces in ship building. The main factors governing the quality of the manufactured products are the moving velocity of the heating source, heating strength, ...Line heating method is widely used to manufacture curved surfaces in ship building. The main factors governing the quality of the manufactured products are the moving velocity of the heating source, heating strength, and heating ways. In this study, the temperature distributions of the heated plate were investigated with the condition that the line heating process was automatic. The temperature variations were also investigated with the changes of those three variables. The numerical results showed that the peak temperature decreased as the moving velocity of the heating source increased. It also revealed that the peak temperatures changed linearly with the changes of the heating source.展开更多
This paper studies the close-contact melting around a moving, horizontal elliptical heat source thatmelts its way through a phase change material under its own weight. The heat source velocity andthe volume of the mat...This paper studies the close-contact melting around a moving, horizontal elliptical heat source thatmelts its way through a phase change material under its own weight. The heat source velocity andthe volume of the material melted are obtained by analysis. The effects of compression coefficient andtemperature distribution in the melt are investigated. The results include that for melting around amoving cylindrical heat source.展开更多
Near-field acoustical holography (NAH) is a powerful tool for identifying noise sources and visualizing acoustic field. By recording the acoustic pressures in the near-field, the acoustic quantities in the whole 3-D f...Near-field acoustical holography (NAH) is a powerful tool for identifying noise sources and visualizing acoustic field. By recording the acoustic pressures in the near-field, the acoustic quantities in the whole 3-D field can be reconstructed and predicted. However, the current theory of NAH is not applicable to tracking large scale moving noise sources. Therefore, the hybrid near-field acoustical holography is developed for reconstructing acoustic radiation, which is derived from statistically optimized near-field acoustical holography (SONAH) and moving frame acoustical holography (MFAH). The theoretical formulation is systematically addressed. This method enables us to visualize the noise generated by moving noise sources and the measurement array can be smaller than the source, which improves the practicability and efficiency of this technology. Numerical simulations are presented to demonstrate the advantages of hybrid NAH. Then, two experiments have been carried out with a line array of hydrophones. The results of simulations and experiments support the proposed theory, which shows the advantage of hybrid NAH in the reconstruction of an acoustic field in an underwater holographic measurement.展开更多
Research on the distribution of smoke in tunnels is significant for the fire emergency rescue after an operating metro train catches fire. A dynamic grid technique was adopted to research the law of smoke flow diffusi...Research on the distribution of smoke in tunnels is significant for the fire emergency rescue after an operating metro train catches fire. A dynamic grid technique was adopted to research the law of smoke flow diffusion inside the tunnel when the bottom of a metro train was on fire and to compare the effect of longitudinal ventilation modes on the smoke motion when the burning train stopped. Research results show that the slipstream curves around the train obtained by numerical simulation are consistent with experimental data. When the train decelerates, the smoke flow first extends to the tail of the train. With the decrease of the train's speed, the smoke flow diffuses to the head of the train. After the train stops, the slipstream around the train formed in the process of train operation plays a leading role in the smoke diffusion in the tunnel. The smoke flow quickly diffuses to the domain in front of the train. After forward mechanical ventilation is provided, the smoke flow inside the tunnel continues to diffuse downstream. When reverse mechanical ventilation operates, the smoke in front of the train flows back rapidly and diffuses to the rear of the train.展开更多
Based on the problem that the generating method of random array structure is inefficient, a method is proposed to generate the random target arrays by using coaxial circu- lar array in the polar coordinates in the pre...Based on the problem that the generating method of random array structure is inefficient, a method is proposed to generate the random target arrays by using coaxial circu- lar array in the polar coordinates in the premise that the array angular resolution of source identification is guaranteed. According to the principle of moving sound source identification, this work deduces the basic non-equidistance coaxial circular rings＇ radius, and generates target random arrays which were suitable for moving sound source identification through array partitioning, condition filtering in the polar coordinates and simulation evaluation. Finally, numerical simulation and moving car sound source identification test have been done. The analytical results show that using this method to generate random array is effective. Compared with the traditional regular arrays, the target random array has more accurate moving sound source identification performance.展开更多
Analytically solving a three-dimensional （3-D） bioheat transfer problem with phase change during a freezing process is extremely difficult but theoretically important. The moving heat source model and the Green func...Analytically solving a three-dimensional （3-D） bioheat transfer problem with phase change during a freezing process is extremely difficult but theoretically important. The moving heat source model and the Green function method are introduced to deal with the cryopreservation process of in vitro biomaterials. Exact solutions for the 3-D temperature transients of tissues under various boundary conditions, such as totally convective cooling, totally fixed temperature cooling and a hybrid between them on tissue surfaces, are obtained. Furthermore, the cryosurgical process in living tissues subject to freezing by a single or multiple cryoprobes is also analytically solved. A closed-form analytical solution to the bioheat phase change process is derived by considering contributions from blood perfusion heat transfer, metabolic heat generation, and heat sink of a cryoprobe. The present method is expected to have significant value for analytically solving complex bioheat transfer problems with phase change.展开更多
International and domestic research progress in theory and experiment and applications of the air-to-water sound transmission are presented in this paper. Four classical numerical methods of calculating the underwater...International and domestic research progress in theory and experiment and applications of the air-to-water sound transmission are presented in this paper. Four classical numerical methods of calculating the underwater sound field gener- ated by an airborne source, i.e., the ray theory, the wave solution, the normal-mode theory and the wavenumber integration approach, are introduced. Effects of two special conditions, i.e., the moving airborne source or medium and the rough air-water interface, on the air-to-water sound transmission are reviewed. In experimental studies, the depth and range distributions of the underwater sound field created by different kinds of airborne sources in near-field and far-field, the longitudinal horizontal correlation of underwater sound field and application methods for inverse problems are reviewed.展开更多
The results of experiments on measuring the energy spectra of alpha particles in reactions with heavy ions are presented.The measurements were performed using the high-resolution magnetic analyzer MAVR with beams of ^...The results of experiments on measuring the energy spectra of alpha particles in reactions with heavy ions are presented.The measurements were performed using the high-resolution magnetic analyzer MAVR with beams of ^(48)Ca(280 MeV)and ^(56)Fe(320 and 400 MeV)on ^(181)Ta and ^(238)U targets at an angle of 0°.A strong dependence of the double differential cross sections for production of alpha particles on the atomic number of the target nucleus was observed,which indicates that fast alpha particles are mainly emitted from the target nucleus;this conclusion was also confirmed by calculations within the time-dependent Schrödinger equation approach.An analysis of the obtained experimental data was carried out within the model of moving sources modified to consider the kinematic limits for two-body and three-body exit channels.展开更多
Fused deposition rapid prototyping is an important technology of rapid prototyping. In order to improve the processing technology,the process plan to change its scanning mode is put forward,through the finite element ...Fused deposition rapid prototyping is an important technology of rapid prototyping. In order to improve the processing technology,the process plan to change its scanning mode is put forward,through the finite element simulation. The verification in the accumulation of fewer layers change the long and short side scanning to improve the rationality of fused deposition rapid prototyping. Based on the ANSYS version of the classic Gauss heat source on the use of mobile technology,it is reasonable to describe the formation process of fused deposition rapid prototyping,and put forward the improvement scheme is put forward.展开更多
基金supported by the National Natural Science Foundation of China under Grant No.51905341the Natural Science Foundation of Shanghai under Grant 22ZR1433900.
文摘The emerging millimeter-wave microphones have garnered considerable attention in recent years due to their potential for sound detection in various applications,particularly in situations where traditional microphones may be impractical.However,despite their promise,there is a notable lack of evidence demonstrating high-quality sound recovery of moving sources,which remains a significant challenge in thefield.This paper addresses this critical gap by proposing a novel method for displacement alignment that improves the detection and recovery of sound signals from moving sources.The proposed method works byfirst aligning the displacement of the sound source over time,which ensures that the signals are synchronized and avoids interference from movement of sources.Subsequently,precise surface vibrations are extracted from the aligned signals,providing data for sound recovery.Afinite impulse response(FIR)filter is applied to remove low-frequency motion,which often interferes with the clarity of the detected sound.Experimental results demonstrate the method’s effectiveness in recovering high-quality sound from moving sources,offering a promising solution for advancing the emerging millimeter-wave microphone technology in real-world applications.This work could pave the way for more accurate and reliable sound detection systems,particularly in dynamic environments.
基金supported by the National Science Foundation of China(51075379)
文摘Doppler effect widely exists in the signal from the moving acoustic source. In order to solve such problems as frequency shift and frequency band expansion, a time domain cor- rection method is presented in this paper. First, the discrete time vector for interpolation and the amplitude restoration formula is derived based on the moving relationship and the Morse acoustic theory, then the amplitude weights are corrected and the distortion signal is interpolated. Every point of the discrete signal is operated separately in time domain. Compared with the existing frequency domain methods, this method does not need to know the characteristic frequency beforehand and would not be influenced by the blending of the frequency band. Hence, this method can be employed to correct multiple frequency signals and it is also a simple and effective Doppler effect reduction method.
文摘In this paper the properties of space- time correlation function of the noise field of moving source in layered statistic inhomogeneous medium are studied and the effects of random fluctuating boundary are considered as well.It has been shown, theoretically and experimentally, multi-path propergating effects cause the dispersion of the correlation function and fluctuations of the medium refraction index and the boundary cause the fluctuation of it.The effect of the movement of the noise source on the output of real- time correlator is equivalent to a low- pass filter added the drift of space- time correlation function.These properties of the correlation function cause grave degradation of the signal processing gain of noise ranging sonar system.The fluctuating and the distortion of conrrelation function made it difficult to realize the noise ranging.So in this paper, a method of space correlation ranging by a linear array of four points with short separation and long span and a technigue of dual- correlation signal processing are presented. By this, the influences of previously mentioned factors are greatly overcomed.Futhermore, for the long period and great delay fluctuation of the dual- correlation function output caused by internal wave, a method of limited memory Quasi- Kalman filtering is developed and the effective accurate ranging and tracing of noise ranging sonar are able to be tralized finally.
基金Project supported by the National Natural Science Foundation of China(Nos.11972176 and12062011)。
文摘Classical thermo-viscoelastic models may be challenged to predict the precise thermo-mechanical behavior of viscoelastic materials without considering the memorydependent effect.Meanwhile,with the miniaturization of devices,the size-dependent effect on elastic deformation is becoming more and more important.To capture the memory-dependent effect and the size-dependent effect,the present study aims at developing a modified fractional-order thermo-viscoelastic coupling model at the microscale to account for two fundamentally distinct fractional-order models which govern the memory-dependent features of thermal conduction and stress-strain relation,respectively.Then,the modified theory is used to study the dynamic response of a polymer micro-rod heated by a moving heat source.The governing equations are obtained and solved by the Laplace transform method.In calculation,the effects of the fractional-order parameter,the fractional-order strain parameter,the mechanical relaxation parameter,and the nonlocal parameter on the variations of the considered variables are analyzed and discussed in detail.
基金The NSF (10771085) of China,the Key Lab of Symbolic Computation and Knowledge Engineering of Ministry of Education and the 985 program of Jilin University
文摘This paper is devoted to the blow-up properties of solutions to the porous medium equations with a nonlocal boundary condition and a moving localized source. Conditions for the existence of global or blow-up solutions are obtained. Moreover, we prove that the unique solution has global blow-up property whenever blow-up occurs.
基金Supported by the Program for New Century Excellent Talents in University under Grant No.NCET-10-0702the National Basic Research Program of China(973 Program)under Grant No.2013CB328904the Ph.D.Programs Foundation of Ministry of Education of China under Grant No.20110184110016
文摘The harmonic metric for Schwarzschild black hole with a uniform velocity is presented. In the limit of weak field and low velocity, this metric reduces to the post-Newtonian approximation for one moving point mass. As an application, we derive the dynamics of particle and photon in the weak-field limit for the moving Schwarzschild black hole with an arbitrary velocity. It is found that the relativistic motion of gravitational source can induce an additional centripetal force on the test particle, which may be comparable to or even larger than the conventional Newtonian gravitational force.
文摘The wide application of carbon fiber reinforced plastic(CFRP)components in modern aerospace manufacturing field puts high demands on the manufacturing process.Especially,the temperature increase during continuous milling process becomes a key factor affecting the performance of composites,and the high milling temperature induces a variety of processing defects.This paper obtained the temperature variation data during the end milling process of CFRP laminates through experiments.After data fitting,the data were transformed into a function of heat flux density varying with time.In the finite element analysis,a double-ellipsoid moving heat source model was introduced,and a moving heat source subrou-tine was written based on the time-varying function of heat flux density to more accurately describe the thermal effects dur-ing the milling process and simulate the changes in the temperature field during milling.The Hashin failure criterion is a-dopted as the basis of fiber and matrix failure,and the simulation results of the temperature field are input into the thermal-force coupling simulation model as the predefined field conditions for solving and analyzing by means of sequential thermal-force coupling,so as to establish a thermal-force coupling simulation and analysis model for milling processing of CFRP end faces.The model simulation results can provide a basis for exploring the damage evolution law of CFRP material under the influence of temperature.
文摘In this article,the physics informed neural networks(PINNs)is employed for the numerical simulation of heat transfer involving a moving source under mixed boundary conditions.To reduce computational effort and increase accuracy,a new training method is proposed that uses a continuous time-stepping through transfer learning.A single network is initialized and used as a sliding window function across the time domain.On this single network each time interval is trained with the initial condition for(+1)t n h iteration as the solution obtained at nth iteration.Thus,this framework enables the computation of large temporal intervals without increasing the complexity of the network itself.The proposed framework is used to estimate the temperature distribution in a homogeneous medium with a moving heat source.The results from the proposed framework is compared with traditional finite element method and a good agreement is seen.
基金CONACyT-México for the scholarship providedCONACyT (Project 736)SIP-IPN are also acknowledged for funds given to conduct this research
文摘Heat moving source models along with transient heat analysis by finite element method were used to determine weld thermal cycles and isothermal sections obtained from the application of a gas tungsten arc welding beads on Inconel 718 plates. Analytical (Rosenthal’s thick plate model) and finite element results show an acceptable approximation with the experimental weld thermal cycles. The isothermal sections determined by numerical simulation show a better approximation with the experimental welding profile for double-ellipse model heat distribution than Gauss model. To analyze the microstructural transformation produced by different cooling rates in the fusion and heat affected zones, Vickers microhardness measurements (profile and mapping representation) were conducted. A hardness decrement for the heat affected zone (~200 HV0.2) and fusion zone (~240 HV0.2) in comparison with base material (~350 HV0.2) was observed. This behavior has been attributed to the heterogeneous solubilization process of the γ″ phase (nickel matrix), which, according to the continuous-cooling-transformation curve, produced the Laves phase,δ and MC transition phases, generating a loss in hardness close to the fusion zone.
基金National Natural Science Foundations of China (No. 40234038 and 40174014).
文摘Based on schematically formulation of the vibrations induced by moving trains, this paper analyses the waveforms along the Datong-Qinhuangdao railroad in Northern China recorded in the suburban Huairou district of Beijing on March 8, 2003. It is illustrated that vibrations induced by train, except traditional recognized noises and interfer- ence effects, could be used as a seismic source to detect crustal structures with its advantage of abundant frequency spectrum, repeatability and no additional harm to the environment. It will bring lights to the traditional exploration seismology with the further studies of signal processing and interpretation methods, and related models and new observing systems.
文摘Using the slot method, the moving boundary problem caused by the change of the tide water elevation is treated. A two-dimensional advection - diffusion model with moving boundary is proposed, and the input pollutant is considered as moving source to meet the water level variation. The model given in this paper has been used to simulate the pollutant transport in the Bohai Gulf, the computational results are in good agreement with the measured data.
基金supported by the post BK21 project of the MEST of Koreapartly supported by the NRL program of NRF of Korea (2008-0060153)
文摘Line heating method is widely used to manufacture curved surfaces in ship building. The main factors governing the quality of the manufactured products are the moving velocity of the heating source, heating strength, and heating ways. In this study, the temperature distributions of the heated plate were investigated with the condition that the line heating process was automatic. The temperature variations were also investigated with the changes of those three variables. The numerical results showed that the peak temperature decreased as the moving velocity of the heating source increased. It also revealed that the peak temperatures changed linearly with the changes of the heating source.
文摘This paper studies the close-contact melting around a moving, horizontal elliptical heat source thatmelts its way through a phase change material under its own weight. The heat source velocity andthe volume of the material melted are obtained by analysis. The effects of compression coefficient andtemperature distribution in the melt are investigated. The results include that for melting around amoving cylindrical heat source.
基金supported by the Fundamental Research Funds For the Central Universities (Grant No. HEUCFR1013)
文摘Near-field acoustical holography (NAH) is a powerful tool for identifying noise sources and visualizing acoustic field. By recording the acoustic pressures in the near-field, the acoustic quantities in the whole 3-D field can be reconstructed and predicted. However, the current theory of NAH is not applicable to tracking large scale moving noise sources. Therefore, the hybrid near-field acoustical holography is developed for reconstructing acoustic radiation, which is derived from statistically optimized near-field acoustical holography (SONAH) and moving frame acoustical holography (MFAH). The theoretical formulation is systematically addressed. This method enables us to visualize the noise generated by moving noise sources and the measurement array can be smaller than the source, which improves the practicability and efficiency of this technology. Numerical simulations are presented to demonstrate the advantages of hybrid NAH. Then, two experiments have been carried out with a line array of hydrophones. The results of simulations and experiments support the proposed theory, which shows the advantage of hybrid NAH in the reconstruction of an acoustic field in an underwater holographic measurement.
基金Project(U1134203)supported by the Major Program of the National Natural Science Foundation of ChinaProject(51105384)supported by the National Natural Science Foundation of China
文摘Research on the distribution of smoke in tunnels is significant for the fire emergency rescue after an operating metro train catches fire. A dynamic grid technique was adopted to research the law of smoke flow diffusion inside the tunnel when the bottom of a metro train was on fire and to compare the effect of longitudinal ventilation modes on the smoke motion when the burning train stopped. Research results show that the slipstream curves around the train obtained by numerical simulation are consistent with experimental data. When the train decelerates, the smoke flow first extends to the tail of the train. With the decrease of the train's speed, the smoke flow diffuses to the head of the train. After the train stops, the slipstream around the train formed in the process of train operation plays a leading role in the smoke diffusion in the tunnel. The smoke flow quickly diffuses to the domain in front of the train. After forward mechanical ventilation is provided, the smoke flow inside the tunnel continues to diffuse downstream. When reverse mechanical ventilation operates, the smoke in front of the train flows back rapidly and diffuses to the rear of the train.
基金supported by the National Natural Science Foundation of China(61271387)the Natural Science Foundation of Shandong Province(ZR2012FZ001)
文摘Based on the problem that the generating method of random array structure is inefficient, a method is proposed to generate the random target arrays by using coaxial circu- lar array in the polar coordinates in the premise that the array angular resolution of source identification is guaranteed. According to the principle of moving sound source identification, this work deduces the basic non-equidistance coaxial circular rings＇ radius, and generates target random arrays which were suitable for moving sound source identification through array partitioning, condition filtering in the polar coordinates and simulation evaluation. Finally, numerical simulation and moving car sound source identification test have been done. The analytical results show that using this method to generate random array is effective. Compared with the traditional regular arrays, the target random array has more accurate moving sound source identification performance.
基金Project supported by the National Natural Science Foundation of China (No. 50776097)
文摘Analytically solving a three-dimensional （3-D） bioheat transfer problem with phase change during a freezing process is extremely difficult but theoretically important. The moving heat source model and the Green function method are introduced to deal with the cryopreservation process of in vitro biomaterials. Exact solutions for the 3-D temperature transients of tissues under various boundary conditions, such as totally convective cooling, totally fixed temperature cooling and a hybrid between them on tissue surfaces, are obtained. Furthermore, the cryosurgical process in living tissues subject to freezing by a single or multiple cryoprobes is also analytically solved. A closed-form analytical solution to the bioheat phase change process is derived by considering contributions from blood perfusion heat transfer, metabolic heat generation, and heat sink of a cryoprobe. The present method is expected to have significant value for analytically solving complex bioheat transfer problems with phase change.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11434012 and 11674349)
文摘International and domestic research progress in theory and experiment and applications of the air-to-water sound transmission are presented in this paper. Four classical numerical methods of calculating the underwater sound field gener- ated by an airborne source, i.e., the ray theory, the wave solution, the normal-mode theory and the wavenumber integration approach, are introduced. Effects of two special conditions, i.e., the moving airborne source or medium and the rough air-water interface, on the air-to-water sound transmission are reviewed. In experimental studies, the depth and range distributions of the underwater sound field created by different kinds of airborne sources in near-field and far-field, the longitudinal horizontal correlation of underwater sound field and application methods for inverse problems are reviewed.
文摘The results of experiments on measuring the energy spectra of alpha particles in reactions with heavy ions are presented.The measurements were performed using the high-resolution magnetic analyzer MAVR with beams of ^(48)Ca(280 MeV)and ^(56)Fe(320 and 400 MeV)on ^(181)Ta and ^(238)U targets at an angle of 0°.A strong dependence of the double differential cross sections for production of alpha particles on the atomic number of the target nucleus was observed,which indicates that fast alpha particles are mainly emitted from the target nucleus;this conclusion was also confirmed by calculations within the time-dependent Schrödinger equation approach.An analysis of the obtained experimental data was carried out within the model of moving sources modified to consider the kinematic limits for two-body and three-body exit channels.
文摘Fused deposition rapid prototyping is an important technology of rapid prototyping. In order to improve the processing technology,the process plan to change its scanning mode is put forward,through the finite element simulation. The verification in the accumulation of fewer layers change the long and short side scanning to improve the rationality of fused deposition rapid prototyping. Based on the ANSYS version of the classic Gauss heat source on the use of mobile technology,it is reasonable to describe the formation process of fused deposition rapid prototyping,and put forward the improvement scheme is put forward.
