During 7th-15th October 2023,an earthquake sequence with four MW6.2-6.3 occurred in the Herat region,Afghanistan,causing damage to buildings,fire,and loss of life.The co-seismic deformation induced by the earthquake s...During 7th-15th October 2023,an earthquake sequence with four MW6.2-6.3 occurred in the Herat region,Afghanistan,causing damage to buildings,fire,and loss of life.The co-seismic deformation induced by the earthquake sequence helps us invert the rupture model of these earthquakes to constrain the geometric characteristics of the Herat fault system,and estimate the future seismic risk at this fault system.In this work,we utilized the line-of-sight(LOS)displacements from Interferometric Synthetic Aperture Radar(InSAR)observations to determine the optimal fault geometry and slip distribution of the 2023 Afghanistan earthquake sequence through a two-step inversion method.Our results indicated that these four MW6.2-6.3 earthquakes ruptured the western and northwestern segments of the Herat fault system,which are dominated by thrust motions.We identified two fault models from InSAR LOS displacement data,with two different strikes,and the same dip angle range of about 35-45°.The source model with the strike of 280.5°has a peak slip of about 2.2 m,a central rupture zone with about 25 km along-strike length,and a depth range of 5-10 km,corresponding to a MW6.67 earthquake.The following source model with the strike direction of about 240°has smaller rupture length and width,and a peak slip of about 2.5 m,corresponding to a MW6.65 earthquake.We also calculated the Coulomb Failure Stress of the Herat fault system around this rupture area caused by this earthquake sequence.Our results indicated that the stress loading at the western segment of the Herat Fault system is greater than the triggering threshold,suggesting that the future seismic risk in this area is at a relatively high stage.In summary,the rupture model of these earthquakes indicates that two unidentified thrust faults between the western and northwestern segments of the Herat fault system are in a compression-stress environment.展开更多
A new approach to conductive electromagnetic interference （EMI） noise source modeling, i. e. the source internal impedance extraction, is presented. First, the impedance magnitude is achieved through an exciting pro...A new approach to conductive electromagnetic interference （EMI） noise source modeling, i. e. the source internal impedance extraction, is presented. First, the impedance magnitude is achieved through an exciting probe and a detecting probe, or through calculations based on insertion loss measurement results when inserting a series nigh-value known impedance or a shunt low-value known impedance in the circuit. Then the impedance phase is extracted by the Hilbert transform （HT） of the logarithm of the obtained impedance magnitude. Performance studies show that the estimated phase error can increase greatly at a zero frequency in the Hilbert transform because of the existence of a singular point, and this effect can be eliminated by introducing a zero-point when the noise source does not include a series-connected capacitive component. It is also found that when the frequency is nigher than 150 kHz, the estimated phase error is not sensitive to the inductive source but sensitive to the capacitive source. Finally, under the conditions of the same measurement accuracies for impedance magnitude, the accuracy of complex impedance based on the HT can be improved about 10 times when compared with the accuracy of estimated parameters based on the impedance magnitude fitting method （IMFM）.展开更多
： The first step in any seismic hazard study is the definition of seismogenic sources and the estimation of magnitude-frequency relationships for each source. There is as yet no standard methodology for source modeli...： The first step in any seismic hazard study is the definition of seismogenic sources and the estimation of magnitude-frequency relationships for each source. There is as yet no standard methodology for source modeling and many researchers have worked on this topic. This study is an effort to define linear and area seismic sources for Northern Iran. The linear or fault sources are developed based on tectonic features and characteristic earthquakes while the area sources are developed based on spatial distribution of small to moderate earthquakes. Time-dependent recurrence relationships are developed for fault sources using renewal approach while time-independent frequency-magnitude relationships are proposed for area sources based on Poisson process. GIS functionalities are used in this study to introduce and incorporate spatial- temporal and geostatistical indices in delineating area seismic sources. The proposed methodology is used to model seismic sources for an area of about 500 by 400 square kilometers around Tehran. Previous researches and reports are studied to compile an earthquake/fault catalog that is as complete as possible. All events are transformed to uniform magnitude scale; duplicate events and dependent shocks are removed. Completeness and time distribution of the compiled catalog is taken into account. The proposed area and linear seismic sources in conjunction with defined recurrence relationships can be used to develop time-dependent probabilistic seismic hazard analysis of Northern Iran.展开更多
In this study, a composite source model has been used to calculate the realistic strong ground motions in Beijing area, caused by 1679 Ms8.0 earthquake in Sanhe-Pinggu. The results could provide us the useful physical...In this study, a composite source model has been used to calculate the realistic strong ground motions in Beijing area, caused by 1679 Ms8.0 earthquake in Sanhe-Pinggu. The results could provide us the useful physical parameters for the future seismic hazard analysis in this area. Considering the regional geological/geophysical background, we simulated the scenario earthquake with an associated ground motions in the area ranging from 39.3°N to 41. 1°N in latitude and from 115.35°E to 117.55°E in longitude. Some of the key factors which could influence the characteristics of strong ground motion have been discussed, and the resultant peak ground acceleration （PGA） distribution and the peak ground velocity （PGV） distribution around Beijing area also have been made as well. A comparison of the simulated result with the results derived from the attenuation relation has been made, and a sufficient discussion about the advantages and disadvantages of composite source model also has been given in this study. The numerical results, such as the PGA, PGV, peak ground displacement （PGD）, and the three-component time-histories developed for Beijing area, have a potential application in earthquake engineering field and building code design, especially for the evaluation of critical constructions, government decision making and the seismic hazard assessment by financial/insurance companies.展开更多
Based on the comprehensive analysis of data from petrology and mineralogy,well logging,seismic surveys,paleontology,and geochemistry,a detailed research was conducted on paleoenvironmental and paleoclimatic conditions...Based on the comprehensive analysis of data from petrology and mineralogy,well logging,seismic surveys,paleontology,and geochemistry,a detailed research was conducted on paleoenvironmental and paleoclimatic conditions,and modeling of the source rocks in the second member of the Eocene Wenchang Formation(Wen 2 Member)in the Northern Shunde Subsag at the southwestern margin of the Pearl River Mouth Basin.The Wen 2 Member hosts excellent,thick lacustrine source rocks with strong longitudinal heterogeneity and an average total organic carbon(TOC)content of over 4.9%.The Wen 2 Member can be divided into three units(I,II,III)from bottom to top.Unit I features excellent source rocks with Type I organic matters(average TOC of 5.9%)primarily sourced from lake organisms;Unit II hosts source rocks dominated by Type II2 organic matters(average TOC of 2.2%),which are originated from mixed sources dominated by terrestrial input.Unit III contains good to excellent source rocks dominated by Type II1 organic matters(average TOC of 4.9%),which are mainly contributed by lake organisms and partially by terrestrial input.Under the background of rapid subsidence and limited source supply during intense rifting period in the Eocene,excellent source rocks were developed in Wen 2 Member in the Northern Shunde Subsag under the coordinated control of warm and humid climate,volcanic activity,and deep-water reducing conditions.During the deposition of Unit I,the warm and humid climate and volcanic activity promoted the proliferation of lake algaes,primarily Granodiscus,resulting in high initial productivity,and deep-water reducing conditions enabled satisfactory preservation of organic matters.These factors jointly controlled the development and occurrence of excellent source rocks.During the deposition of Unit II,a transition from warm to cool and semi-arid paleoclimatic conditions led to a decrease in lake algaes and initial productivity.Additionally,enhanced terrestrial input and shallow-water,weakly oxidizing water conditions caused a significant dilution and decomposition of organic matters,degrading the quality of source rocks.During the deposition of Unit III,when the paleoclimatic conditions are cool and humid,Pediastrum and Botryococcus began to thrive,leading to an increase in productivity.Meanwhile,the reducing environment of semi-deep water facilitated the preservation of excellent source rocks,albeit slightly inferior to those in Unit I.The study results clarify the differential origins and development models of various source rocks in the Shunde Sag,offering valuable guidance for evaluating source rocks and selecting petroleum exploration targets in similar marginal sags.展开更多
In this paper, the common heat source model of point and linear heat source in the numerical simulation of electron beam welding （EBW） were summarized and introduced. The combined point-linear heat source model was ...In this paper, the common heat source model of point and linear heat source in the numerical simulation of electron beam welding （EBW） were summarized and introduced. The combined point-linear heat source model was brought forward and to simulate the welding temperature fields of EBW and predicting the weld shape. The model parameters were put forward and regulated in the combined model, which included the ratio of point heat source to linear heat source Qpr and the distribution of linear heat source Lr. Based on the combined model, the welding temperature fields of EBW were investigated. The results show that the predicted weld shapes are conformable to those of the actual, the temperature fields are reasonable and correct by simulating with combined point-linear heat source model and the typical weld shapes are gained.展开更多
To develop a sound ozone（O_3） pollution control strategy,it is important to well understand and characterize the source contribution due to the complex chemical and physical formation processes of O_3.Using the ＂Sh...To develop a sound ozone（O_3） pollution control strategy,it is important to well understand and characterize the source contribution due to the complex chemical and physical formation processes of O_3.Using the ＂Shunde＂ city as a pilot summer case study,we apply an innovative response surface modeling（RSM） methodology based on the Community Multi-Scale Air Quality（CMAQ） modeling simulations to identify the O_3 regime and provide dynamic analysis of the precursor contributions to effectively assess the O_3 impacts of volatile organic compound（VOC） control strategy.Our results show that Shunde is a typical VOC-limited urban O_3 polluted city.The ＂Jiangmen＂ city,as the main upper wind area during July 2014,its VOCs and nitrogen oxides（NO_x） emissions make up the largest contribution（9.06%）.On the contrary,the contribution from local（Shunde） emission is lowest（6.35%） among the seven neighbor regions.The local VOCs industrial source emission has the largest contribution comparing to other precursor emission sectors in Shunde.The results of dynamic source contribution analysis further show that the local NO_x control could slightly increase the ground O_3 under low（10.00%） and medium（40.00%）reduction ratios,while it could start to turn positive to decrease ground O_3 under the high NO_x abatement ratio（75.00%）.The real-time assessment of O_3 impacts from VOCs control strategies in Pearl River Delta（PRD） shows that the joint regional VOCs emission control policy will effectively reduce the ground O_3 concentration in Shunde.展开更多
Real traffic information was analyzed in the statistical characteristics and approximated as a Gaussian time series. A data source model, called two states constant bit rate (TSCBR), was proposed in dynamic traffic mo...Real traffic information was analyzed in the statistical characteristics and approximated as a Gaussian time series. A data source model, called two states constant bit rate (TSCBR), was proposed in dynamic traffic monitoring sensor networks. Analysis of autocorrelation of the models shows that the proposed TSCBR model matches with the statistical characteristics of real data source closely. To further verify the validity of the TSCBR data source model, the performance metrics of power consumption and network lifetime was studied in the evaluation of sensor media access control (SMAC) algorithm. The simulation results show that compared with traditional data source models, TSCBR model can significantly improve accuracy of the algorithm evaluation.展开更多
To accelerate the large-scale integration of renewable energy and support the strategic goals of“carbon peaking and carbon neutrality,”High Voltage Direct Current(HVDC)transmission technology has made significant br...To accelerate the large-scale integration of renewable energy and support the strategic goals of“carbon peaking and carbon neutrality,”High Voltage Direct Current(HVDC)transmission technology has made significant breakthroughs.Among the various approaches,a hybrid DC transmission system that combines a line-commutated converter(LCC)and a voltage source converter(VSC)retains the inherent fault self-clearing capability of the LCC topology while mitigating the risk of commutation failure when connected to a weak grid.In this paper,based on the harmonic generation mechanisms of hybrid DC transmission systems,an improved 3-pulse harmonic source model of the LCC and a dynamic phase-sequence harmonic analysis model of the VSC are developed.The integrated harmonic model demonstrates strong adaptability in accurately calculating DC-side harmonics under the influence of power imbalances and background harmonics.Based on this model,the fundamental characteristics of DC-side harmonics in hybrid DC transmission systems are analyzed.To mitigate harmonic effects,this paper proposes an LCLC-trap2 high-order filter structure with parallel RC damping circuits and a co-optimized design of filter parameters.Finally,a±500 kV hybrid DC transmission systemismodeled using theMATLAB/Simulink platform,and the harmonic filtering performances of the conventional LC filter,the Butterworth filter,and the proposed filter are simulated and compared.The results verify that the proposed filter offers superior performance in suppressing low-order harmonics under nonideal operating conditions.展开更多
The welding mechanism of laser-TIG hybrid welding process is analyzed. Withthe variation of arc current, the welding process is divided into two patterns: deep-penetrationwelding and heat conductive welding. The heat ...The welding mechanism of laser-TIG hybrid welding process is analyzed. Withthe variation of arc current, the welding process is divided into two patterns: deep-penetrationwelding and heat conductive welding. The heat flow model of hybrid welding is presented. As todeep-penetration welding, the heat source includes a surface heat flux and a volume heat flux. Theheat source of heat conductive welding is composed of two Gaussian distribute surface heat sources.With this heat source model, a temperature field is calculated. The finite element code MARC isemployed for this purpose. The calculation results show a good agreement with the experimental data.展开更多
Two cardiac functional models are constructed in this paper. One is a single current model and the other is a current multipole model. Parameters denoting the properties of these two models are calculated by a least-s...Two cardiac functional models are constructed in this paper. One is a single current model and the other is a current multipole model. Parameters denoting the properties of these two models are calculated by a least-square fit to the measurements using a simulated annealing algorithm. The measured signals are detected at 36 observation nodes by a superconducting quantum interference device （SQUID）. By studying the trends of position, orientation and magnitude of the single current dipole model and the current multipole model in the QRS complex during one time span and comparing the reconstructed magnetocardiography （MCG） of these two cardiac models, we find that the current multipole model is a more appropriate model to represent cardiac electrophysiological activity.展开更多
The DLBSW（ dual laser-beam bilateral synchronous welding） technology of T-type joint has been widely used for the connection of skins and stringers in airplane industry. To understand the thermodynamic and mechanica...The DLBSW（ dual laser-beam bilateral synchronous welding） technology of T-type joint has been widely used for the connection of skins and stringers in airplane industry. To understand the thermodynamic and mechanical behavior of this process, it is necessary to establish a reasonable heat source model. Two different surface-body combination heat source models are adopted in this paper. Both models use the Gaussian surface heat source model and one is combined with the cone body heat source model and the other is combined with Gaussian rotator body heat source model. The simulation results of these two different models are investigated. And the temperature field results of DLBSW process for T-joint with two different heat sources are discussed. It is indicated that the combination heat source model is effective to simulate the DLBSW process and the current study is useful for more profound research in this field.展开更多
The static comer frequency and dynamic comer frequency in stochastic synthesis of ground motion from fi- nite-fault modeling are introduced, and conceptual disadvantages of the two are discussed in this paper. Further...The static comer frequency and dynamic comer frequency in stochastic synthesis of ground motion from fi- nite-fault modeling are introduced, and conceptual disadvantages of the two are discussed in this paper. Furthermore, the non-uniform radiation of seismic wave on the fault plane, as well as the trend of the larger rupture area, the lower comer frequency, can be described by the source spectral model developed by the authors. A new dynamic comer frequency can be developed directly from the model. The dependence of ground motion on the size of subfault can be eliminated if this source spectral model is adopted in the synthesis. Finally, the approach presented is validated from the comparison between the synthesized and observed ground motions at six rock stations during the Northridge earthquake in 1994.展开更多
In this paper, we present a magnetocardiogram （MCG） simulation study using the boundary element method （BEM） and based on the virtual heart model and the realistic human volume conductor model. The different contr...In this paper, we present a magnetocardiogram （MCG） simulation study using the boundary element method （BEM） and based on the virtual heart model and the realistic human volume conductor model. The different contributions of cardiac equivalent source models and volume conductor models to the MCG are deeply and comprehensively investigated. The single dipole source model, the multiple dipoles source model and the equivalent double layer （EDL） source model are analysed and compared with the cardiac equivalent source models. Meanwhile, the effect of the volume conductor model on the MCG combined with these cardiac equivalent sources is investigated. The simulation results demonstrate that the cardiac electrophysiological information will be partly missed when only the single dipole source is taken, while the EDL source is a good option for MCG simulation and the effect of the volume conductor is smallest for the EDL source. Therefore, the EDL source is suitable for the study of MCG forward and inverse problems, and more attention should be paid to it in future MCG studies.展开更多
Since programing complex and dynamic heat source model for welding simulation is a complex job,the parametric methods are studied in this paper.Firstly,an overall flow to achieve automatically modeling welding was int...Since programing complex and dynamic heat source model for welding simulation is a complex job,the parametric methods are studied in this paper.Firstly,an overall flow to achieve automatically modeling welding was introduced.Secondly,an expert module rule for selecting welding heat source model was founded,which is based on simulation knowledge and experiences.Thirdly,a modularity routine method was investigated using writing with C++programing,which automatically creates subroutines of 3D dynamic heat source model for user.To realize the dynamic weld path,the local weld path coordinate system was moved in the global coordinate system and it is used to model the direction of weld gun,welding path and welding pose.The weld path data file was prepared by the automatic tool for the welding heat source subroutines.All above functions were integrated in the user interface and the connection with architecture was introduced.At last,a laser beam welding heat source modeling was automatically modeled and the weld pool geometry was compared with the reported literature.It demonstrated that the automated tool is valid for welding simulation.Since modeling became convenient for welding simulation using the tool proposed,it could be easy and useful for welding engineers to acquire the needed information.展开更多
High-precision time-varying gravity field is an effective way to study the internal mass movement and understanding the spatio-temporal evolution process of the geodynamic system.Compared to the satellite gravity meas...High-precision time-varying gravity field is an effective way to study the internal mass movement and understanding the spatio-temporal evolution process of the geodynamic system.Compared to the satellite gravity measurement,the repeated terrestrial gravity observation can provide a more high-order signal related to the shallow crust and subsurface.However,the suitable and unified method for gravity model estimation is a key problem for further applications.In this study,we introduce the spherical hexahedron element to simulate the field source mass and forward model the change of gravity field located at the Sichuan-Yunnan region(99—104°E,23—29°N)in the four epochs from 2015 to 2017.Compared to the experimental results based on Slepian or spherical harmonics frequency domain method,this alternative approach is suitable for constructing the equivalent mass source model of regional-scale gravity data,by introducing the first-order smooth prior condition of gravity time-varying signal to suppress the high-frequency component of the signal.The results can provide a higher spatial resolution reference for regional gravity field modeling in the Sichuan-Yunnan region.展开更多
The noise prediction of the turbocharger is studied.The broadband noise source model is employed to predict the near-field noise of the turbocharger.The 3D software Solidworks is adopted to establish the model blades ...The noise prediction of the turbocharger is studied.The broadband noise source model is employed to predict the near-field noise of the turbocharger.The 3D software Solidworks is adopted to establish the model blades and inlet of turbocharger compressor,then this 3D model is introduced into the software CFD to calculate the flow-field under different inlet shapes,different blades shapes and different clearances between casing and impeller.On the base of the above simulation,the broadband noise source model is employed to calculate and analyze the near-field noise.The calculation shows that compressor static pressure values and the sound power values near the impeller outlet are the largest.Through the noise calculation by using broadband noise source model under different inlet shapes and blade shapes,we find that the noise level of the inlet of cylindrical and cone types are smaller.Compared with the current widespread used backward skewed or radial blades,there is little difference of the noise value of the inlet of the forward skewed blades.展开更多
In this paper, a new theoretical expression of dissipation term is presented on the basis of statistical model of breaking wave, which is an improvement to LAGFD-WAM wave model. The computational results in three typi...In this paper, a new theoretical expression of dissipation term is presented on the basis of statistical model of breaking wave, which is an improvement to LAGFD-WAM wave model. The computational results in three typical wind fields show a good improvement to LAGFD-WAM model and a better accuracy in comparison with the observed data in the South China Sea.展开更多
A frequency domain analysis method based on the three-dimensional translating-pulsating （3DTP） source Green function is developed to investigate wave loads and free motions of two ships advancing on parallel course ...A frequency domain analysis method based on the three-dimensional translating-pulsating （3DTP） source Green function is developed to investigate wave loads and free motions of two ships advancing on parallel course in waves. Two experiments are carried out respectively to mea- sure the wave loads and the free motions for a pair of side-by- side arranged ship models advancing with an identical speed in head regular waves. For comparison, each model is also tested alone. Predictions obtained by the present solution are found in favorable agreement with the model tests and are more accurate than the traditional method based on the three dimensional pulsating （3DP） source Green function. Numer- ical resonances and peak shift can be found in the 3DP pre- dictions, which result from the wave energy trapped in the gap between two ships and the extremely inhomogeneous wave load distribution on each hull. However, they can be eliminated by 3DTP, in which the speed affects the free sur- face and most of the wave energy can be escaped from the gap. Both the experiment and the present prediction show that hydrodynamic interaction effects on wave loads and free motions are significant. The present solver may serve as a validated tool to predict wave loads and motions of two ves- sels under replenishment at sea, and may help to evaluate the hydrodynamic interaction effects on the ships safety in replenishment operation.展开更多
By applying the empirical Green＇s function method, we first proved that the source spectra in the middle eastern area of North Tianshan follow the ω^-2 Brune model, and then, on this basis, obtained the source spect...By applying the empirical Green＇s function method, we first proved that the source spectra in the middle eastern area of North Tianshan follow the ω^-2 Brune model, and then, on this basis, obtained the source spectra for 105 earthquakes of ML 2.5 - 5.7 in the studied area upon removing the noise, instrument, propagation and site effects in the observational seismic S waveforms. Finally, we determined the source parameters such as the seismic moment, stress drop, source dimension, etc., based on the Brune model. The results show that there is a good linear correlation between scalar seismic moment, M0, and ML, which is Log10 M0 = 1.10 ML ＋ 17.20; The source radii range between 100- 1500m; the stress drop, 1-16MPa with a predominant range of 1 - 10MPa. The relationship of the seismic moment versus corner frequencies indicates that there may exist two source scaling, that is, when M0 〈 4×10^21 dyne. cm （equal to an ML4.0 event）, stress drop is weakly dependent on M0： whereas, when M0 〉 4×10^21 dyne·cm, stress drop is independent of M0.展开更多
基金funded by the PhD Starting Research Fund in East China Jiaotong University,Grant No.2003423017the National Natural Science Foundation of China(Grant Nos.42304009)。
文摘During 7th-15th October 2023,an earthquake sequence with four MW6.2-6.3 occurred in the Herat region,Afghanistan,causing damage to buildings,fire,and loss of life.The co-seismic deformation induced by the earthquake sequence helps us invert the rupture model of these earthquakes to constrain the geometric characteristics of the Herat fault system,and estimate the future seismic risk at this fault system.In this work,we utilized the line-of-sight(LOS)displacements from Interferometric Synthetic Aperture Radar(InSAR)observations to determine the optimal fault geometry and slip distribution of the 2023 Afghanistan earthquake sequence through a two-step inversion method.Our results indicated that these four MW6.2-6.3 earthquakes ruptured the western and northwestern segments of the Herat fault system,which are dominated by thrust motions.We identified two fault models from InSAR LOS displacement data,with two different strikes,and the same dip angle range of about 35-45°.The source model with the strike of 280.5°has a peak slip of about 2.2 m,a central rupture zone with about 25 km along-strike length,and a depth range of 5-10 km,corresponding to a MW6.67 earthquake.The following source model with the strike direction of about 240°has smaller rupture length and width,and a peak slip of about 2.5 m,corresponding to a MW6.65 earthquake.We also calculated the Coulomb Failure Stress of the Herat fault system around this rupture area caused by this earthquake sequence.Our results indicated that the stress loading at the western segment of the Herat Fault system is greater than the triggering threshold,suggesting that the future seismic risk in this area is at a relatively high stage.In summary,the rupture model of these earthquakes indicates that two unidentified thrust faults between the western and northwestern segments of the Herat fault system are in a compression-stress environment.
基金The Natural Science Foundation of Jiangsu Province(No.BK2008429)Open Research Foundation of State Key Laboratory of Millimeter Waves of Southeast University(No.K200603)+1 种基金China Postdoctoral Science Foundation(No.20080431126)Jiangsu Postdoctoral Science Foundation(No.2007-337)
文摘A new approach to conductive electromagnetic interference （EMI） noise source modeling, i. e. the source internal impedance extraction, is presented. First, the impedance magnitude is achieved through an exciting probe and a detecting probe, or through calculations based on insertion loss measurement results when inserting a series nigh-value known impedance or a shunt low-value known impedance in the circuit. Then the impedance phase is extracted by the Hilbert transform （HT） of the logarithm of the obtained impedance magnitude. Performance studies show that the estimated phase error can increase greatly at a zero frequency in the Hilbert transform because of the existence of a singular point, and this effect can be eliminated by introducing a zero-point when the noise source does not include a series-connected capacitive component. It is also found that when the frequency is nigher than 150 kHz, the estimated phase error is not sensitive to the inductive source but sensitive to the capacitive source. Finally, under the conditions of the same measurement accuracies for impedance magnitude, the accuracy of complex impedance based on the HT can be improved about 10 times when compared with the accuracy of estimated parameters based on the impedance magnitude fitting method （IMFM）.
文摘： The first step in any seismic hazard study is the definition of seismogenic sources and the estimation of magnitude-frequency relationships for each source. There is as yet no standard methodology for source modeling and many researchers have worked on this topic. This study is an effort to define linear and area seismic sources for Northern Iran. The linear or fault sources are developed based on tectonic features and characteristic earthquakes while the area sources are developed based on spatial distribution of small to moderate earthquakes. Time-dependent recurrence relationships are developed for fault sources using renewal approach while time-independent frequency-magnitude relationships are proposed for area sources based on Poisson process. GIS functionalities are used in this study to introduce and incorporate spatial- temporal and geostatistical indices in delineating area seismic sources. The proposed methodology is used to model seismic sources for an area of about 500 by 400 square kilometers around Tehran. Previous researches and reports are studied to compile an earthquake/fault catalog that is as complete as possible. All events are transformed to uniform magnitude scale; duplicate events and dependent shocks are removed. Completeness and time distribution of the compiled catalog is taken into account. The proposed area and linear seismic sources in conjunction with defined recurrence relationships can be used to develop time-dependent probabilistic seismic hazard analysis of Northern Iran.
基金The One Hundred Individual Program of Chinese Academy of Sciences and National Natural Science Foundation of China (40574022).
文摘In this study, a composite source model has been used to calculate the realistic strong ground motions in Beijing area, caused by 1679 Ms8.0 earthquake in Sanhe-Pinggu. The results could provide us the useful physical parameters for the future seismic hazard analysis in this area. Considering the regional geological/geophysical background, we simulated the scenario earthquake with an associated ground motions in the area ranging from 39.3°N to 41. 1°N in latitude and from 115.35°E to 117.55°E in longitude. Some of the key factors which could influence the characteristics of strong ground motion have been discussed, and the resultant peak ground acceleration （PGA） distribution and the peak ground velocity （PGV） distribution around Beijing area also have been made as well. A comparison of the simulated result with the results derived from the attenuation relation has been made, and a sufficient discussion about the advantages and disadvantages of composite source model also has been given in this study. The numerical results, such as the PGA, PGV, peak ground displacement （PGD）, and the three-component time-histories developed for Beijing area, have a potential application in earthquake engineering field and building code design, especially for the evaluation of critical constructions, government decision making and the seismic hazard assessment by financial/insurance companies.
基金Supported by the Research Project of China National Offshore Oil Corporation(SCKY-2023-HN-3)。
文摘Based on the comprehensive analysis of data from petrology and mineralogy,well logging,seismic surveys,paleontology,and geochemistry,a detailed research was conducted on paleoenvironmental and paleoclimatic conditions,and modeling of the source rocks in the second member of the Eocene Wenchang Formation(Wen 2 Member)in the Northern Shunde Subsag at the southwestern margin of the Pearl River Mouth Basin.The Wen 2 Member hosts excellent,thick lacustrine source rocks with strong longitudinal heterogeneity and an average total organic carbon(TOC)content of over 4.9%.The Wen 2 Member can be divided into three units(I,II,III)from bottom to top.Unit I features excellent source rocks with Type I organic matters(average TOC of 5.9%)primarily sourced from lake organisms;Unit II hosts source rocks dominated by Type II2 organic matters(average TOC of 2.2%),which are originated from mixed sources dominated by terrestrial input.Unit III contains good to excellent source rocks dominated by Type II1 organic matters(average TOC of 4.9%),which are mainly contributed by lake organisms and partially by terrestrial input.Under the background of rapid subsidence and limited source supply during intense rifting period in the Eocene,excellent source rocks were developed in Wen 2 Member in the Northern Shunde Subsag under the coordinated control of warm and humid climate,volcanic activity,and deep-water reducing conditions.During the deposition of Unit I,the warm and humid climate and volcanic activity promoted the proliferation of lake algaes,primarily Granodiscus,resulting in high initial productivity,and deep-water reducing conditions enabled satisfactory preservation of organic matters.These factors jointly controlled the development and occurrence of excellent source rocks.During the deposition of Unit II,a transition from warm to cool and semi-arid paleoclimatic conditions led to a decrease in lake algaes and initial productivity.Additionally,enhanced terrestrial input and shallow-water,weakly oxidizing water conditions caused a significant dilution and decomposition of organic matters,degrading the quality of source rocks.During the deposition of Unit III,when the paleoclimatic conditions are cool and humid,Pediastrum and Botryococcus began to thrive,leading to an increase in productivity.Meanwhile,the reducing environment of semi-deep water facilitated the preservation of excellent source rocks,albeit slightly inferior to those in Unit I.The study results clarify the differential origins and development models of various source rocks in the Shunde Sag,offering valuable guidance for evaluating source rocks and selecting petroleum exploration targets in similar marginal sags.
基金co-supported by the National Basic Research Program (No.61362)the National Natural Science Foundation of China(No. 50935008 and 10902113)Science Foundation of Aeronautics (No. 2010ZE25006)
文摘In this paper, the common heat source model of point and linear heat source in the numerical simulation of electron beam welding （EBW） were summarized and introduced. The combined point-linear heat source model was brought forward and to simulate the welding temperature fields of EBW and predicting the weld shape. The model parameters were put forward and regulated in the combined model, which included the ratio of point heat source to linear heat source Qpr and the distribution of linear heat source Lr. Based on the combined model, the welding temperature fields of EBW were investigated. The results show that the predicted weld shapes are conformable to those of the actual, the temperature fields are reasonable and correct by simulating with combined point-linear heat source model and the typical weld shapes are gained.
基金Financial support for this work is provided by the Shunde Environment ProtectionTransportation and Urban Administration Bureau(no.0851-1361FS02CL51)+5 种基金the Guangdong Provincial Science and Technology Plan Projects(no.2014A050503019)Guangzhou Environmental Protection Bureau(no.x2hjB2150020)supported by the funding of State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complexthe project of Atmospheric Haze Collaboration Control Technology Design(no.XDB05030400)from Chinese Academy of Sciencesthe Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund(U1501501)(the second phase)the Guangdong Provincial Engineering and Technology Research Center for Environmental Risk Prevention and Emergency Disposal(no.b2152120)
文摘To develop a sound ozone（O_3） pollution control strategy,it is important to well understand and characterize the source contribution due to the complex chemical and physical formation processes of O_3.Using the ＂Shunde＂ city as a pilot summer case study,we apply an innovative response surface modeling（RSM） methodology based on the Community Multi-Scale Air Quality（CMAQ） modeling simulations to identify the O_3 regime and provide dynamic analysis of the precursor contributions to effectively assess the O_3 impacts of volatile organic compound（VOC） control strategy.Our results show that Shunde is a typical VOC-limited urban O_3 polluted city.The ＂Jiangmen＂ city,as the main upper wind area during July 2014,its VOCs and nitrogen oxides（NO_x） emissions make up the largest contribution（9.06%）.On the contrary,the contribution from local（Shunde） emission is lowest（6.35%） among the seven neighbor regions.The local VOCs industrial source emission has the largest contribution comparing to other precursor emission sectors in Shunde.The results of dynamic source contribution analysis further show that the local NO_x control could slightly increase the ground O_3 under low（10.00%） and medium（40.00%）reduction ratios,while it could start to turn positive to decrease ground O_3 under the high NO_x abatement ratio（75.00%）.The real-time assessment of O_3 impacts from VOCs control strategies in Pearl River Delta（PRD） shows that the joint regional VOCs emission control policy will effectively reduce the ground O_3 concentration in Shunde.
基金The National Natural Science Foundation ofChia(No60372076)The Important cienceand Technology Key Item of Shanghai Science and Technology Bureau ( No05dz15004)
文摘Real traffic information was analyzed in the statistical characteristics and approximated as a Gaussian time series. A data source model, called two states constant bit rate (TSCBR), was proposed in dynamic traffic monitoring sensor networks. Analysis of autocorrelation of the models shows that the proposed TSCBR model matches with the statistical characteristics of real data source closely. To further verify the validity of the TSCBR data source model, the performance metrics of power consumption and network lifetime was studied in the evaluation of sensor media access control (SMAC) algorithm. The simulation results show that compared with traditional data source models, TSCBR model can significantly improve accuracy of the algorithm evaluation.
基金funded by the Natural Science Foundation of Chongqing(CSTB2023NSCQMSX0279)the Science and Technology Research Program of Chongqing Municipal Education Commission(KJQN202201119).
文摘To accelerate the large-scale integration of renewable energy and support the strategic goals of“carbon peaking and carbon neutrality,”High Voltage Direct Current(HVDC)transmission technology has made significant breakthroughs.Among the various approaches,a hybrid DC transmission system that combines a line-commutated converter(LCC)and a voltage source converter(VSC)retains the inherent fault self-clearing capability of the LCC topology while mitigating the risk of commutation failure when connected to a weak grid.In this paper,based on the harmonic generation mechanisms of hybrid DC transmission systems,an improved 3-pulse harmonic source model of the LCC and a dynamic phase-sequence harmonic analysis model of the VSC are developed.The integrated harmonic model demonstrates strong adaptability in accurately calculating DC-side harmonics under the influence of power imbalances and background harmonics.Based on this model,the fundamental characteristics of DC-side harmonics in hybrid DC transmission systems are analyzed.To mitigate harmonic effects,this paper proposes an LCLC-trap2 high-order filter structure with parallel RC damping circuits and a co-optimized design of filter parameters.Finally,a±500 kV hybrid DC transmission systemismodeled using theMATLAB/Simulink platform,and the harmonic filtering performances of the conventional LC filter,the Butterworth filter,and the proposed filter are simulated and compared.The results verify that the proposed filter offers superior performance in suppressing low-order harmonics under nonideal operating conditions.
文摘The welding mechanism of laser-TIG hybrid welding process is analyzed. Withthe variation of arc current, the welding process is divided into two patterns: deep-penetrationwelding and heat conductive welding. The heat flow model of hybrid welding is presented. As todeep-penetration welding, the heat source includes a surface heat flux and a volume heat flux. Theheat source of heat conductive welding is composed of two Gaussian distribute surface heat sources.With this heat source model, a temperature field is calculated. The finite element code MARC isemployed for this purpose. The calculation results show a good agreement with the experimental data.
基金Project supported by the State Key Development Program for Basic Research of China (Grant No 2006CB601007)the National Natural Science Foundation of China (Grant No 10674006)the National High Technology Research and Development Program of China (Grant No 2007AA03Z238)
文摘Two cardiac functional models are constructed in this paper. One is a single current model and the other is a current multipole model. Parameters denoting the properties of these two models are calculated by a least-square fit to the measurements using a simulated annealing algorithm. The measured signals are detected at 36 observation nodes by a superconducting quantum interference device （SQUID）. By studying the trends of position, orientation and magnitude of the single current dipole model and the current multipole model in the QRS complex during one time span and comparing the reconstructed magnetocardiography （MCG） of these two cardiac models, we find that the current multipole model is a more appropriate model to represent cardiac electrophysiological activity.
基金The research is sponsored by the Shanghai STCSM Project of the Postdoctoral Science Research Assistant Plan （10R21421200）, the National Natural Science Foundation of China （50904038） and the China Postdoctoral Science Foundation （20100470064）.
文摘The DLBSW（ dual laser-beam bilateral synchronous welding） technology of T-type joint has been widely used for the connection of skins and stringers in airplane industry. To understand the thermodynamic and mechanical behavior of this process, it is necessary to establish a reasonable heat source model. Two different surface-body combination heat source models are adopted in this paper. Both models use the Gaussian surface heat source model and one is combined with the cone body heat source model and the other is combined with Gaussian rotator body heat source model. The simulation results of these two different models are investigated. And the temperature field results of DLBSW process for T-joint with two different heat sources are discussed. It is indicated that the combination heat source model is effective to simulate the DLBSW process and the current study is useful for more profound research in this field.
基金supported by National Natural Science Foundation of China under grant No. 50778058 and 90715038National Key Technology Research and Development Program under grant No. 2006BAC13B02
文摘The static comer frequency and dynamic comer frequency in stochastic synthesis of ground motion from fi- nite-fault modeling are introduced, and conceptual disadvantages of the two are discussed in this paper. Furthermore, the non-uniform radiation of seismic wave on the fault plane, as well as the trend of the larger rupture area, the lower comer frequency, can be described by the source spectral model developed by the authors. A new dynamic comer frequency can be developed directly from the model. The dependence of ground motion on the size of subfault can be eliminated if this source spectral model is adopted in the synthesis. Finally, the approach presented is validated from the comparison between the synthesized and observed ground motions at six rock stations during the Northridge earthquake in 1994.
基金supported by the State Key Development Program for Basic Research of China (Grant Nos. 2007CB512100 and2006CB601007)the National Natural Science Foundation of China (Grant No. 10674006)+2 种基金the National High Technology Research and Development Program of China (Grant No. 2007AA03Z238)China Postdoctoral Science Foundation (Grant No. 20090461376)the Fundamental Research Funds for the Central Universities (Grant No. KYJD09001)
文摘In this paper, we present a magnetocardiogram （MCG） simulation study using the boundary element method （BEM） and based on the virtual heart model and the realistic human volume conductor model. The different contributions of cardiac equivalent source models and volume conductor models to the MCG are deeply and comprehensively investigated. The single dipole source model, the multiple dipoles source model and the equivalent double layer （EDL） source model are analysed and compared with the cardiac equivalent source models. Meanwhile, the effect of the volume conductor model on the MCG combined with these cardiac equivalent sources is investigated. The simulation results demonstrate that the cardiac electrophysiological information will be partly missed when only the single dipole source is taken, while the EDL source is a good option for MCG simulation and the effect of the volume conductor is smallest for the EDL source. Therefore, the EDL source is suitable for the study of MCG forward and inverse problems, and more attention should be paid to it in future MCG studies.
基金supported by Young Innovative Talents Training Plan of Heilongjiang(UNPYSCT-2018133).
文摘Since programing complex and dynamic heat source model for welding simulation is a complex job,the parametric methods are studied in this paper.Firstly,an overall flow to achieve automatically modeling welding was introduced.Secondly,an expert module rule for selecting welding heat source model was founded,which is based on simulation knowledge and experiences.Thirdly,a modularity routine method was investigated using writing with C++programing,which automatically creates subroutines of 3D dynamic heat source model for user.To realize the dynamic weld path,the local weld path coordinate system was moved in the global coordinate system and it is used to model the direction of weld gun,welding path and welding pose.The weld path data file was prepared by the automatic tool for the welding heat source subroutines.All above functions were integrated in the user interface and the connection with architecture was introduced.At last,a laser beam welding heat source modeling was automatically modeled and the weld pool geometry was compared with the reported literature.It demonstrated that the automated tool is valid for welding simulation.Since modeling became convenient for welding simulation using the tool proposed,it could be easy and useful for welding engineers to acquire the needed information.
基金funded by National Natural Science Foundation of China(U1839207,U1939205)the earthquake tracking directional work task of China Earthquake Administration(No.DZ2022010214)+1 种基金Key project of Spark Program of Seismic Science and Technology of China Earthquake Administration(No.XH20008)S&T Program of Hebei(21375411D)。
文摘High-precision time-varying gravity field is an effective way to study the internal mass movement and understanding the spatio-temporal evolution process of the geodynamic system.Compared to the satellite gravity measurement,the repeated terrestrial gravity observation can provide a more high-order signal related to the shallow crust and subsurface.However,the suitable and unified method for gravity model estimation is a key problem for further applications.In this study,we introduce the spherical hexahedron element to simulate the field source mass and forward model the change of gravity field located at the Sichuan-Yunnan region(99—104°E,23—29°N)in the four epochs from 2015 to 2017.Compared to the experimental results based on Slepian or spherical harmonics frequency domain method,this alternative approach is suitable for constructing the equivalent mass source model of regional-scale gravity data,by introducing the first-order smooth prior condition of gravity time-varying signal to suppress the high-frequency component of the signal.The results can provide a higher spatial resolution reference for regional gravity field modeling in the Sichuan-Yunnan region.
基金Sponsored by the National Natural Science Foundation of China (50875022)Research Foundation of Beijing Institute of Technology(20070342012)
文摘The noise prediction of the turbocharger is studied.The broadband noise source model is employed to predict the near-field noise of the turbocharger.The 3D software Solidworks is adopted to establish the model blades and inlet of turbocharger compressor,then this 3D model is introduced into the software CFD to calculate the flow-field under different inlet shapes,different blades shapes and different clearances between casing and impeller.On the base of the above simulation,the broadband noise source model is employed to calculate and analyze the near-field noise.The calculation shows that compressor static pressure values and the sound power values near the impeller outlet are the largest.Through the noise calculation by using broadband noise source model under different inlet shapes and blade shapes,we find that the noise level of the inlet of cylindrical and cone types are smaller.Compared with the current widespread used backward skewed or radial blades,there is little difference of the noise value of the inlet of the forward skewed blades.
文摘In this paper, a new theoretical expression of dissipation term is presented on the basis of statistical model of breaking wave, which is an improvement to LAGFD-WAM wave model. The computational results in three typical wind fields show a good improvement to LAGFD-WAM model and a better accuracy in comparison with the observed data in the South China Sea.
基金supported by the National Natural Science Foundation of China(50879090)the Key Research Program of Hydrodynamics of China(9140A14030712JB11044)
文摘A frequency domain analysis method based on the three-dimensional translating-pulsating （3DTP） source Green function is developed to investigate wave loads and free motions of two ships advancing on parallel course in waves. Two experiments are carried out respectively to mea- sure the wave loads and the free motions for a pair of side-by- side arranged ship models advancing with an identical speed in head regular waves. For comparison, each model is also tested alone. Predictions obtained by the present solution are found in favorable agreement with the model tests and are more accurate than the traditional method based on the three dimensional pulsating （3DP） source Green function. Numer- ical resonances and peak shift can be found in the 3DP pre- dictions, which result from the wave energy trapped in the gap between two ships and the extremely inhomogeneous wave load distribution on each hull. However, they can be eliminated by 3DTP, in which the speed affects the free sur- face and most of the wave energy can be escaped from the gap. Both the experiment and the present prediction show that hydrodynamic interaction effects on wave loads and free motions are significant. The present solver may serve as a validated tool to predict wave loads and motions of two ves- sels under replenishment at sea, and may help to evaluate the hydrodynamic interaction effects on the ships safety in replenishment operation.
文摘By applying the empirical Green＇s function method, we first proved that the source spectra in the middle eastern area of North Tianshan follow the ω^-2 Brune model, and then, on this basis, obtained the source spectra for 105 earthquakes of ML 2.5 - 5.7 in the studied area upon removing the noise, instrument, propagation and site effects in the observational seismic S waveforms. Finally, we determined the source parameters such as the seismic moment, stress drop, source dimension, etc., based on the Brune model. The results show that there is a good linear correlation between scalar seismic moment, M0, and ML, which is Log10 M0 = 1.10 ML ＋ 17.20; The source radii range between 100- 1500m; the stress drop, 1-16MPa with a predominant range of 1 - 10MPa. The relationship of the seismic moment versus corner frequencies indicates that there may exist two source scaling, that is, when M0 〈 4×10^21 dyne. cm （equal to an ML4.0 event）, stress drop is weakly dependent on M0： whereas, when M0 〉 4×10^21 dyne·cm, stress drop is independent of M0.
