In this study, the damage-plasticity model for concrete that was verified by the model experiment was used to calculate the damage to a spiral case structure based on the damage mechanics theory. The concrete structur...In this study, the damage-plasticity model for concrete that was verified by the model experiment was used to calculate the damage to a spiral case structure based on the damage mechanics theory. The concrete structure surrounding the spiral case was simulated with a three-dimensional finite element model. Then, the distribution and evolution of the structural damage were studied. Based on investigation of the change of gap openings between the steel liner and concrete structure, the impact of the non-uniform variation of gaps on the load-beating ratio between the steel liner and concrete structure was analyzed. The comparison of calculated results of the simplified and simulation algorithms shows that the simulation algorithm is a feasible option for the calculation of spiral case structures. In addition, the shell-spring model was introduced for optimization analysis, and the results were reasonable.展开更多
An explicit simulation with a fine mesh at intervals of 6 km is used to explore the inner-core structures of Vongfong (0214). The dynamic mechanism for the inshore strengthening of Vongfong is examined. It is found as...An explicit simulation with a fine mesh at intervals of 6 km is used to explore the inner-core structures of Vongfong (0214). The dynamic mechanism for the inshore strengthening of Vongfong is examined. It is found as follows. (1) The radius of maximum wind of the axisymmetric structures of the typhoon decreased with height during its mature stage. When Vongfong was inshore, the strongest low-layer inflow located in front of it and the outflow was to the rear of it, which was just reversed from the Atlantic hurricanes and other Pacific typhoons. (2) The dynamic and thermodynamic fields were highly asymmetric in structure. Convection was stronger in the northwest quadrant of the typhoon than in the southeast; the strongest convective cloud bands were consistent with the maximum wind region. During its strengthening stage, it was cold west of and warm east of the eye in the lower layer but warm in the west and cold in the east of the mid-upper layer. During its mature stage, a warm-core structure was evident in the lower and middle-upper layer. (3) The interactions between a mid-latitude cold low in the middle-upper troposphere and the typhoon were responsible for the latter to strengthen inshore. Firstly, the outer circulation of the cold low entered the typhoon from the middle troposphere when an outer cold airflow from the cold low flowed into the northwest quadrant of the typhoon so that geopotentially instable energy increased and convection developed. Secondly, the downdraft in the cold low was just the corresponding branch of the secondary circulation of the typhoon system; when the cold low weakened while moving south, the typhoon strengthened inshore. Due to the CISK mechanism, these two phenomena might be realized.展开更多
The structure of the La-LaCl_3-KCl molten system at 1223K has been investigated by computer simulation using Monte Carlo method.The partial radial distribution functions of some ion pair as well as the potential and i...The structure of the La-LaCl_3-KCl molten system at 1223K has been investigated by computer simulation using Monte Carlo method.The partial radial distribution functions of some ion pair as well as the potential and internal energy of the system at 1223K have been calculated.The results implies that about 50% of La(Ⅲ)is six coordinated and LaCl_4^(2-) tetrahedron is the predominant configuration for La(Ⅱ). It is also concluded that the distribution of free space in the molten system is not uniform.There exist many fissures and empty holes in the molten salt.展开更多
This paper provides a computer modeling method for the study of nanocrystals. Structural features,such as the boundary component proportion, the reduced density proportion, the excess lattice parameter, and the radial...This paper provides a computer modeling method for the study of nanocrystals. Structural features,such as the boundary component proportion, the reduced density proportion, the excess lattice parameter, and the radial distribution function, have been atomistically simulated. The energy and elastic properties also have been investigated. Simulation results indicate that the structure of grain boundaries in nanocrystals is different from those of the amorphous and the gas, or rather, it is a special structure with some degree of short-range order. Moreover, the structure of crystallites is not entirely the same as that in the perfect crystal lattice. The present simulation method may become one of the foundations of the theoretical study of nanocrystals.展开更多
A new Monte Carlo simulation of the track structure of low-energy electrons （〈10keV） in liquid water is presented. The feature of the simulation is taken into consideration of the condensed-phase effect of liquid w...A new Monte Carlo simulation of the track structure of low-energy electrons （〈10keV） in liquid water is presented. The feature of the simulation is taken into consideration of the condensed-phase effect of liquid water on electron elastic scattering with the use of the Champion model, while the dielectric response formalism incorporating the optical-data model developed by Emfietzoglou et al. is applied for calculating the electron inelastic scattering. The spatial distributions of energy deposition and inelastic scattering events of low-energy electrons with different primary energies in liquid water are calculated and compared with other theoretical evaluations. The present work shows that the condensed-phase effect of liquid water on electron elastic scattering may be of the influence on the fraction of absorbed energy and distribution of inelastic scattering events at lower primary energies, which also indicate potential effects on the DNA damage induced by low-energy electrons.展开更多
The wind tunnel simulations of wind loading on a solid structure of revolution with one smooth and five rough surfaces were conducted using wind tunnel tests. Timemean and fluctuating pressure distributions on the sur...The wind tunnel simulations of wind loading on a solid structure of revolution with one smooth and five rough surfaces were conducted using wind tunnel tests. Timemean and fluctuating pressure distributions on the surface were obtained, and the relationships between the roughness Reynolds number and pressure distributions were analyzed and discussed. The results show that increasing the surface roughness can significantly affect the pressure distribution, and the roughness Reynolds numbers play an important role in the change of flow patterns. The three flow patterns of subcritical, critical and supercritical flows can be classified based on the changing patterns of both the mean and the fluctuating pressure distributions. The present study suggests that the wind tunnel results obtained in the supercritical pattern reflect more closely those of full-scale solid structure of revolution at the designed wind speed.展开更多
Quantum cascade lasers(QCLs) have broad application potentials in infrared countermeasure system,free-space optical communication and trace gas detection.Compared with traditional Fabry-Pérot(FP) cavity and exter...Quantum cascade lasers(QCLs) have broad application potentials in infrared countermeasure system,free-space optical communication and trace gas detection.Compared with traditional Fabry-Pérot(FP) cavity and external cavity,distributed feedback quantum cascade lasers(DFB-QCLs) can obtain narrower laser linewidth and higher integration.In this paper,the structure design,numerical simulation and optimization of the Bragg grating of DFB-QCLs are carried out to obtain the transmission spectrum with central wavelength at 4.6 μm.We analyze the relationship among the structure parameters,the central wavelength shift and transmission efficiency using coupled-wave theory and finite-difference time-domain(FDTD) method.It is shown that the increase in the number of grating periods enhances the capabilities of mode selectivity,while the grating length of a single period adjustment directly determines the Bragg wavelength.Additionally,variations in etching depth and duty cycle lead to blue and red shifts in the central wavelength,respectively.Based on the numerical simulation results,the optimized design parameters for the upper buffer layer and the upper cladding grating are proposed,which gives an optional scheme for component fabrication and performance improvement in the future.展开更多
The structure factors of any crystal structure can be simulated from its atomic coordinates (and temperature factors) in a SHELXL-97 run on a dummy hkl in which only the scale factor is refined. The squares of the str...The structure factors of any crystal structure can be simulated from its atomic coordinates (and temperature factors) in a SHELXL-97 run on a dummy hkl in which only the scale factor is refined. The squares of the structure factors are retrieved from the fcf, and such simulated data are used in the revision of the space groups of several incorrectly-refined crystal structures. Two cases, a P1 to P1 revision and a chemically-incorrect structure that is refined in a correct space group, are discussed.展开更多
Sand/dust storms are some of the main hazards in arid and semi-arid zones. These storms also influence global environmental changes. By field observations, empirical statistics, and numerical simulations, pioneer rese...Sand/dust storms are some of the main hazards in arid and semi-arid zones. These storms also influence global environmental changes. By field observations, empirical statistics, and numerical simulations, pioneer researchers on these natural events have concluded the existence of a positive relationship between thermodynamic effects and sand/dust storms. Thermodynamic effects induce an unsteady stratified atmosphere to influence the process of these storms. However, studies on the relationship of thermodynamic effects with particles (i.e., sand and dust) are limited. In this article, wind tunnel with heating was used to simulate the quantitative relationship between thermodynamic effects and particle movement on different surfaces. Compared with the cold state, the threshold wind velocity of particles is found to be significantly decrease under the hot state. The largest decrease percentage exceedes 9% on fine and coarse sand surfaces. The wind velocity also has a three-power function in the sand transport rate under the hot state with increased sand transport. Thermodynamic effects are stronger on loose surfaces and fine particles, but weaker on compacted surfaces and coarse particles.展开更多
To investigate the differences and the development trends of the 400 kA aluminum reduction cell, four representative cells were deeply analyzed. By using numerical simulation methods in ANSYS software, the structure p...To investigate the differences and the development trends of the 400 kA aluminum reduction cell, four representative cells were deeply analyzed. By using numerical simulation methods in ANSYS software, the structure parameters were firstly compared, and then three-dimensional models of electric-magnetic-flow field were built and solved with finite element method(FEM). The comparison of the structures reveals that the cell bodies are similar while the current flow path and distribution ratio of bus bars are different. It appears that most of the current(70%-80%) in side A are used as the magnetic field compensation current and flow through two ends. The numerical simulation results indicate that the distributions of magnetic fields are different but all satisfy with the magnetohydrodynamics(MHD) stabilization, and the flow patterns are all two or multi vortexes with appropriate velocities. The comparison shows that all studied cells can satisfy with the physical field requirement, and the commercial applications also verify that the 400 kA cells have become the product of the mature and world's leading technology.展开更多
We present numerical simulations of simplified models for swimming organisms or robots, using chordwise flexible elastic plates. We focus on the tip vortices originating from three-dimensional effects due to the finit...We present numerical simulations of simplified models for swimming organisms or robots, using chordwise flexible elastic plates. We focus on the tip vortices originating from three-dimensional effects due to the finite span of the plate. These effects play an important role when predicting the swimmer＇s cruising velocity, since they contribute significantly to the drag force. First we simulate swimmers with rectangular plates of different aspect ratios and compare the results with a recent experimental study. Then we consider plates with expanding and contracting shapes. We find the cruising velocity of the contracting swimmer to be higher than the rectangular one, which in turn is higher than the expanding one. We provide some evidence that this result is due to the tip vortices interacting differently with the swimmer.展开更多
In the ultra-deep strata of the Tarim Basin,the vertical growth process of strike-slip faults remains unclear,and the vertical distribution of fractured-cavity carbonate reservoirs is complex.This paper investigates t...In the ultra-deep strata of the Tarim Basin,the vertical growth process of strike-slip faults remains unclear,and the vertical distribution of fractured-cavity carbonate reservoirs is complex.This paper investigates the vertical growth process of strike-slip faults through field outcrop observations in the Keping area,interpretation of seismic data from the Fuman Oilfield,Tarim Basim,NW China,and structural physical simulation experiments.The results are obtained mainly in four aspects.First,field outcrops and ultra-deep seismic profiles indicate a three-layer structure within the strike-slip fault,consisting of fault core,fracture zone and primary rock.The fault core can be classified into three parts vertically:fracture-cavity unit,fault clay and breccia zone.The distribution of fracture-cavity units demonstrates a distinct pattern of vertical stratification,owing to the structural characteristics and growth process of the slip-strike fault.Second,the ultra-deep seismic profiles show multiple fracture-cavity units in the strike-slip fault zone.These units can be classified into four types:top fractured,middle connected,deep terminated,and intra-layer fractured.Third,structural physical simulation experiments and ultra-deep seismic data interpretation reveal that the strike-slip faults have evolved vertically in three stages:segmental rupture,vertical growth,and connection and extension.The particle image velocimetry detection demonstrates that the initial fracture of the fault zone occurred at the top or bottom and then evolved into cavities gradually along with the fault growth,accompanied by the emergence of new fractures in the middle part of the strata,which subsequently connected with the deep and shallow cavities to form a complete fault zone.Fourth,the ultra-deep carbonate strata primarily develop three types of fractured-cavity reservoirs:flower-shaped fracture,large and deep fault and staggered overlap.The first two types are larger in size with better reservoir conditions,suggesting a significant exploration potential.展开更多
A series of electron donors,including 1,1-cyclopentanecarboxylic acid diethyl ester (CPCADEE),1,1cyclopentanedimethanol acetic diester (CPDMAD),1,1-biethoxymethyl pentane (BEMP),2,2-diethyl diethylmalonate (DEDEM)and ...A series of electron donors,including 1,1-cyclopentanecarboxylic acid diethyl ester (CPCADEE),1,1cyclopentanedimethanol acetic diester (CPDMAD),1,1-biethoxymethyl pentane (BEMP),2,2-diethyl diethylmalonate (DEDEM)and 2,2-diethyl-1,3-propanediol acetic diester (DEPDADE),were synthesized by diethyl malonate (DEM).The purities and structures of the above products were characterized by gas chromatography (GC) and gas chromatography-mass spectrometer (GC-MS),respectively.Furthermore,the possible optimal three-dimensional structures of these donors were simulated by means of Gaussian 03 and Chem 3D.Then these electron donors were coordinated with tetrachloro titanium (TiCl 4) and chloride magnesium (MgCl 2)to obtain the catalysts for the polymerization of propylene.The catalytic activities and properties of polypropylene are greatly improved by adding external donor(ED) when CPCADEE or DEPDADE is used as internal donor(ID).However,when BEMP was used as ID,the highest catalytic activity is obtained without adding ED,which can reduce production costs and simplify catalytic synthesis.The experiments indicate that BEMP has the shortest distance of oxygen atoms and the highest electronegativity.展开更多
The soft rock's heterogeneity and nonlinear mechanical behavior cause extremely difficult maintenance on the soft rock roadway. Aiming at the asymmetric deformation and destruction phenomenon appearing after excav...The soft rock's heterogeneity and nonlinear mechanical behavior cause extremely difficult maintenance on the soft rock roadway. Aiming at the asymmetric deformation and destruction phenomenon appearing after excavating and supporting the 7101 air return way in Meihe mine, this paper comprehensively adopted a variety of methods to analyze the roadway surrounding rock deformation rule, obtaining the roadway surrounding rock stress and plastic zone distribution rule under no supporting condition and the roadway surrounding rock deformation features under original symmetric supporting condition.Furthermore, this paper revealed the catastrophe mechanism, and proposed the concept of ‘‘weak structure'' and the disaster countermeasure of ‘‘overall stabilizing the roadway and strengthening the support of weak structure''. The industrial test shows that the disaster control technology can realize the coordination deformation of the supporting structure and roadway surrounding rock, thus significantly controlling the deformation of roadway surrounding rock.展开更多
The ecological environment quality is an important constraint and an optimization objective for land resource allocation.Integrating ecological service value(ESV)accounting and ecological security pattern(ESP)delineat...The ecological environment quality is an important constraint and an optimization objective for land resource allocation.Integrating ecological service value(ESV)accounting and ecological security pattern(ESP)delineation,and combining with the land use structure of 2004/2010/2016 in Ezhou City,this research laid out the urban ESP based on ESV with Net Primary Productivity(NPP),and made it as the main influence factor to simulate land use structure in 2022.The results indicated that:1)The water body has the biggest contribution to ESV,while the construction land has the minimum;2)91 ecological corridors are extracted,of which 28 were important ecological corridors;there were 36 ecological nodes extracted,including 17 important nodes;3)According to ESV,Ezhou City was divided into four security zones.The area of ecological restoration zone was the largest,and human activity core zone area was the smallest;4)In the no ESP protection scenarios and ESP protection scenarios separately,the net increase area of construction land is from 868.5 hm^(2) to 52.74 hm^(2) in the ecological core protection area;the construction land in the human activity core area has been increased by 2342.31 hm^(2) in protected scene,766.23 hm^(2) more than that of the unprotected scene.The results show that the division of security zones promoted the relocation of construction land from ecological protection core zone to human activity core zone,which can protect the ecological environment effectively,and the ESP-based simulation can provide the decision-making reference to coordinate the relationship of regional land resource allocation and the ecological environment protection.展开更多
Ultrasound simulation for carotid arteries is helpful to the performance assessments of vessel wall detection and signal processing methods by using ultrasound techniques. An ul- trasound simulation method of carotid ...Ultrasound simulation for carotid arteries is helpful to the performance assessments of vessel wall detection and signal processing methods by using ultrasound techniques. An ul- trasound simulation method of carotid artery wall with a three-membrane structure is proposed in present study. According to the ultrasound speckle distributions varying with the shapes and densities of scatterer distributions, as well as the statistic results of the clinical images, the parameters of distributions, densities and intensities of scatterers for different kinds of tissues in the carotid artery phantoms are determined. Each region is acoustically characterized using FIELD II software to produce the radio frequency echo signals, from which ultrasound images are derived. The results based on 30 simulations show that the echo distributions of the intimae, mediae, adventitias and blood are consistent with the clinical ones. Moreover, compared with the results from the central frequency of 8 MHz, the mean measurements for thicknesses of the intima, media and adventitia membranes, as well as the lumen diameter from the simulation images based on 12 MHz are the same as the preset ones, and the maximum relative errors are the 4.01%, 1.25%, 0.04% and 0.15%, respectively. The simulation under this condition is more realistic.展开更多
In recent years, microstrip antennas have been more widely applied in satellite communications, mobile phones, unmanned aerial vehicle （UAV）, and weapons. A micro-electro-mechanical systems-based （MEMS-based） high...In recent years, microstrip antennas have been more widely applied in satellite communications, mobile phones, unmanned aerial vehicle （UAV）, and weapons. A micro-electro-mechanical systems-based （MEMS-based） high-resistance silicon C-band microstrip antenna array has been designed for the intelligent ammunition. The center frequency is 4.5 GHz. A cavity has been designed in substrate to reduce the dielectric constant of silicon and high-resistance silicon has been used as the material of substrate to improve the gain of antenna. It is very easy to be manufactured by using MEMS technology because of the improved structure of the antenna. The results show that the gain of the antenna is 8 dB and voltage standing wave ratio （VSWR） is less than 2 by the analysis and simulation in high freauencv structure simulator （HFSS）.展开更多
In this paper, an efficient multi-conductor simplification technique is proposed to model the electromagnetic immunity on cable bundles within a braid shielding structure over a large frequency range. By grouping toge...In this paper, an efficient multi-conductor simplification technique is proposed to model the electromagnetic immunity on cable bundles within a braid shielding structure over a large frequency range. By grouping together the conductors based on the knowledge of Z-Smith chart, the required computation time is markedly reduced and the complexity of modeling the completely shielding cable bundles is significantly simplified with a good accuracy. After a brief description of the immunity problems in shielding structure, a six-phase procedure is detailed to generate the geometrical characteristics of the reduced cable bundles. Numerical simulation is carried out by using a commercial software CST to validate the efficiency and advantages of the proposed approach. The research addressed in this paper is considered as a simplified modeling technique for the electromagnetic immunity within a shielding structure.展开更多
The ion cyclotron resonance of frequency heating（ICRH） plays an important role in plasma heating.Two ICRH antennas were designed and applied on the EAST tokamak.In order to meet the requirement imposed by high-power...The ion cyclotron resonance of frequency heating（ICRH） plays an important role in plasma heating.Two ICRH antennas were designed and applied on the EAST tokamak.In order to meet the requirement imposed by high-power and long-pulse operation of EAST in the future,an active cooling system is mandatory to be designed to remove the heat load deposited on the components.Thermal analyses for high heat-load components have been carried out,which presented clear temperature distribution on each component and provided the reference data to do the optimization.Meanwhile,heat pipes were designed to satisfy the high requirement imposed by a Faraday shield and lateral limiter.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 51079020)the He'nan Provincial Research Foundation for Basic and Advanced Technology (Grant No. 122300410001)the Foundation of He'nan Educational Committee (Grant No. 13A570715)
文摘In this study, the damage-plasticity model for concrete that was verified by the model experiment was used to calculate the damage to a spiral case structure based on the damage mechanics theory. The concrete structure surrounding the spiral case was simulated with a three-dimensional finite element model. Then, the distribution and evolution of the structural damage were studied. Based on investigation of the change of gap openings between the steel liner and concrete structure, the impact of the non-uniform variation of gaps on the load-beating ratio between the steel liner and concrete structure was analyzed. The comparison of calculated results of the simplified and simulation algorithms shows that the simulation algorithm is a feasible option for the calculation of spiral case structures. In addition, the shell-spring model was introduced for optimization analysis, and the results were reasonable.
基金Joint Supporting Foundation for Natural Science of China (U0733002)Natural Science Foundation of China (40775066)National project "973" (2006CB403601)
文摘An explicit simulation with a fine mesh at intervals of 6 km is used to explore the inner-core structures of Vongfong (0214). The dynamic mechanism for the inshore strengthening of Vongfong is examined. It is found as follows. (1) The radius of maximum wind of the axisymmetric structures of the typhoon decreased with height during its mature stage. When Vongfong was inshore, the strongest low-layer inflow located in front of it and the outflow was to the rear of it, which was just reversed from the Atlantic hurricanes and other Pacific typhoons. (2) The dynamic and thermodynamic fields were highly asymmetric in structure. Convection was stronger in the northwest quadrant of the typhoon than in the southeast; the strongest convective cloud bands were consistent with the maximum wind region. During its strengthening stage, it was cold west of and warm east of the eye in the lower layer but warm in the west and cold in the east of the mid-upper layer. During its mature stage, a warm-core structure was evident in the lower and middle-upper layer. (3) The interactions between a mid-latitude cold low in the middle-upper troposphere and the typhoon were responsible for the latter to strengthen inshore. Firstly, the outer circulation of the cold low entered the typhoon from the middle troposphere when an outer cold airflow from the cold low flowed into the northwest quadrant of the typhoon so that geopotentially instable energy increased and convection developed. Secondly, the downdraft in the cold low was just the corresponding branch of the secondary circulation of the typhoon system; when the cold low weakened while moving south, the typhoon strengthened inshore. Due to the CISK mechanism, these two phenomena might be realized.
文摘The structure of the La-LaCl_3-KCl molten system at 1223K has been investigated by computer simulation using Monte Carlo method.The partial radial distribution functions of some ion pair as well as the potential and internal energy of the system at 1223K have been calculated.The results implies that about 50% of La(Ⅲ)is six coordinated and LaCl_4^(2-) tetrahedron is the predominant configuration for La(Ⅱ). It is also concluded that the distribution of free space in the molten system is not uniform.There exist many fissures and empty holes in the molten salt.
文摘This paper provides a computer modeling method for the study of nanocrystals. Structural features,such as the boundary component proportion, the reduced density proportion, the excess lattice parameter, and the radial distribution function, have been atomistically simulated. The energy and elastic properties also have been investigated. Simulation results indicate that the structure of grain boundaries in nanocrystals is different from those of the amorphous and the gas, or rather, it is a special structure with some degree of short-range order. Moreover, the structure of crystallites is not entirely the same as that in the perfect crystal lattice. The present simulation method may become one of the foundations of the theoretical study of nanocrystals.
文摘A new Monte Carlo simulation of the track structure of low-energy electrons （〈10keV） in liquid water is presented. The feature of the simulation is taken into consideration of the condensed-phase effect of liquid water on electron elastic scattering with the use of the Champion model, while the dielectric response formalism incorporating the optical-data model developed by Emfietzoglou et al. is applied for calculating the electron inelastic scattering. The spatial distributions of energy deposition and inelastic scattering events of low-energy electrons with different primary energies in liquid water are calculated and compared with other theoretical evaluations. The present work shows that the condensed-phase effect of liquid water on electron elastic scattering may be of the influence on the fraction of absorbed energy and distribution of inelastic scattering events at lower primary energies, which also indicate potential effects on the DNA damage induced by low-energy electrons.
文摘The wind tunnel simulations of wind loading on a solid structure of revolution with one smooth and five rough surfaces were conducted using wind tunnel tests. Timemean and fluctuating pressure distributions on the surface were obtained, and the relationships between the roughness Reynolds number and pressure distributions were analyzed and discussed. The results show that increasing the surface roughness can significantly affect the pressure distribution, and the roughness Reynolds numbers play an important role in the change of flow patterns. The three flow patterns of subcritical, critical and supercritical flows can be classified based on the changing patterns of both the mean and the fluctuating pressure distributions. The present study suggests that the wind tunnel results obtained in the supercritical pattern reflect more closely those of full-scale solid structure of revolution at the designed wind speed.
基金supported by the Scientific Research Project of Beijing Municipal Education Commission (No.KM202411232020)the Young Backbone Teacher Support Plan (No.YBT202408)the Scientific Researchof Beijing Information Science and Technology University (No.2023XJJ08)。
文摘Quantum cascade lasers(QCLs) have broad application potentials in infrared countermeasure system,free-space optical communication and trace gas detection.Compared with traditional Fabry-Pérot(FP) cavity and external cavity,distributed feedback quantum cascade lasers(DFB-QCLs) can obtain narrower laser linewidth and higher integration.In this paper,the structure design,numerical simulation and optimization of the Bragg grating of DFB-QCLs are carried out to obtain the transmission spectrum with central wavelength at 4.6 μm.We analyze the relationship among the structure parameters,the central wavelength shift and transmission efficiency using coupled-wave theory and finite-difference time-domain(FDTD) method.It is shown that the increase in the number of grating periods enhances the capabilities of mode selectivity,while the grating length of a single period adjustment directly determines the Bragg wavelength.Additionally,variations in etching depth and duty cycle lead to blue and red shifts in the central wavelength,respectively.Based on the numerical simulation results,the optimized design parameters for the upper buffer layer and the upper cladding grating are proposed,which gives an optional scheme for component fabrication and performance improvement in the future.
文摘The structure factors of any crystal structure can be simulated from its atomic coordinates (and temperature factors) in a SHELXL-97 run on a dummy hkl in which only the scale factor is refined. The squares of the structure factors are retrieved from the fcf, and such simulated data are used in the revision of the space groups of several incorrectly-refined crystal structures. Two cases, a P1 to P1 revision and a chemically-incorrect structure that is refined in a correct space group, are discussed.
基金Under the auspices of National Natural Science Foundation of China(No.40930741,41071009,41001005)Knowledge Innovation Programs of Chinese Academy of Sciences(No.KZCX2-YW-329)
文摘Sand/dust storms are some of the main hazards in arid and semi-arid zones. These storms also influence global environmental changes. By field observations, empirical statistics, and numerical simulations, pioneer researchers on these natural events have concluded the existence of a positive relationship between thermodynamic effects and sand/dust storms. Thermodynamic effects induce an unsteady stratified atmosphere to influence the process of these storms. However, studies on the relationship of thermodynamic effects with particles (i.e., sand and dust) are limited. In this article, wind tunnel with heating was used to simulate the quantitative relationship between thermodynamic effects and particle movement on different surfaces. Compared with the cold state, the threshold wind velocity of particles is found to be significantly decrease under the hot state. The largest decrease percentage exceedes 9% on fine and coarse sand surfaces. The wind velocity also has a three-power function in the sand transport rate under the hot state with increased sand transport. Thermodynamic effects are stronger on loose surfaces and fine particles, but weaker on compacted surfaces and coarse particles.
基金Projects(51104187,51274241,61321003) supported by the National Natural Science Foundation of ChinaProject(20100162120008) supported by Doctoral Fund of Ministry of Education of China
文摘To investigate the differences and the development trends of the 400 kA aluminum reduction cell, four representative cells were deeply analyzed. By using numerical simulation methods in ANSYS software, the structure parameters were firstly compared, and then three-dimensional models of electric-magnetic-flow field were built and solved with finite element method(FEM). The comparison of the structures reveals that the cell bodies are similar while the current flow path and distribution ratio of bus bars are different. It appears that most of the current(70%-80%) in side A are used as the magnetic field compensation current and flow through two ends. The numerical simulation results indicate that the distributions of magnetic fields are different but all satisfy with the magnetohydrodynamics(MHD) stabilization, and the flow patterns are all two or multi vortexes with appropriate velocities. The comparison shows that all studied cells can satisfy with the physical field requirement, and the commercial applications also verify that the 400 kA cells have become the product of the mature and world's leading technology.
文摘We present numerical simulations of simplified models for swimming organisms or robots, using chordwise flexible elastic plates. We focus on the tip vortices originating from three-dimensional effects due to the finite span of the plate. These effects play an important role when predicting the swimmer＇s cruising velocity, since they contribute significantly to the drag force. First we simulate swimmers with rectangular plates of different aspect ratios and compare the results with a recent experimental study. Then we consider plates with expanding and contracting shapes. We find the cruising velocity of the contracting swimmer to be higher than the rectangular one, which in turn is higher than the expanding one. We provide some evidence that this result is due to the tip vortices interacting differently with the swimmer.
基金Supported by the National Natural Science Foundation of China(42362026)Key R&D Project of Xinjiang Uygur Autonomous Region(2024B01015).
文摘In the ultra-deep strata of the Tarim Basin,the vertical growth process of strike-slip faults remains unclear,and the vertical distribution of fractured-cavity carbonate reservoirs is complex.This paper investigates the vertical growth process of strike-slip faults through field outcrop observations in the Keping area,interpretation of seismic data from the Fuman Oilfield,Tarim Basim,NW China,and structural physical simulation experiments.The results are obtained mainly in four aspects.First,field outcrops and ultra-deep seismic profiles indicate a three-layer structure within the strike-slip fault,consisting of fault core,fracture zone and primary rock.The fault core can be classified into three parts vertically:fracture-cavity unit,fault clay and breccia zone.The distribution of fracture-cavity units demonstrates a distinct pattern of vertical stratification,owing to the structural characteristics and growth process of the slip-strike fault.Second,the ultra-deep seismic profiles show multiple fracture-cavity units in the strike-slip fault zone.These units can be classified into four types:top fractured,middle connected,deep terminated,and intra-layer fractured.Third,structural physical simulation experiments and ultra-deep seismic data interpretation reveal that the strike-slip faults have evolved vertically in three stages:segmental rupture,vertical growth,and connection and extension.The particle image velocimetry detection demonstrates that the initial fracture of the fault zone occurred at the top or bottom and then evolved into cavities gradually along with the fault growth,accompanied by the emergence of new fractures in the middle part of the strata,which subsequently connected with the deep and shallow cavities to form a complete fault zone.Fourth,the ultra-deep carbonate strata primarily develop three types of fractured-cavity reservoirs:flower-shaped fracture,large and deep fault and staggered overlap.The first two types are larger in size with better reservoir conditions,suggesting a significant exploration potential.
基金Supported by National Natural Science Foundation of China (No. 20476080)Tianjin Natural Science Foundation (No. 07JCYBJC00600)
文摘A series of electron donors,including 1,1-cyclopentanecarboxylic acid diethyl ester (CPCADEE),1,1cyclopentanedimethanol acetic diester (CPDMAD),1,1-biethoxymethyl pentane (BEMP),2,2-diethyl diethylmalonate (DEDEM)and 2,2-diethyl-1,3-propanediol acetic diester (DEPDADE),were synthesized by diethyl malonate (DEM).The purities and structures of the above products were characterized by gas chromatography (GC) and gas chromatography-mass spectrometer (GC-MS),respectively.Furthermore,the possible optimal three-dimensional structures of these donors were simulated by means of Gaussian 03 and Chem 3D.Then these electron donors were coordinated with tetrachloro titanium (TiCl 4) and chloride magnesium (MgCl 2)to obtain the catalysts for the polymerization of propylene.The catalytic activities and properties of polypropylene are greatly improved by adding external donor(ED) when CPCADEE or DEPDADE is used as internal donor(ID).However,when BEMP was used as ID,the highest catalytic activity is obtained without adding ED,which can reduce production costs and simplify catalytic synthesis.The experiments indicate that BEMP has the shortest distance of oxygen atoms and the highest electronegativity.
基金provided by the National Natural Science Foundation of China(Nos.51204166 and51174195)the Jiangsu Province ordinary university graduate research innovation projects(No.CXZZ12_0954)
文摘The soft rock's heterogeneity and nonlinear mechanical behavior cause extremely difficult maintenance on the soft rock roadway. Aiming at the asymmetric deformation and destruction phenomenon appearing after excavating and supporting the 7101 air return way in Meihe mine, this paper comprehensively adopted a variety of methods to analyze the roadway surrounding rock deformation rule, obtaining the roadway surrounding rock stress and plastic zone distribution rule under no supporting condition and the roadway surrounding rock deformation features under original symmetric supporting condition.Furthermore, this paper revealed the catastrophe mechanism, and proposed the concept of ‘‘weak structure'' and the disaster countermeasure of ‘‘overall stabilizing the roadway and strengthening the support of weak structure''. The industrial test shows that the disaster control technology can realize the coordination deformation of the supporting structure and roadway surrounding rock, thus significantly controlling the deformation of roadway surrounding rock.
基金supported by the National Natural Science Foundation of China(Grant No.41871172).
文摘The ecological environment quality is an important constraint and an optimization objective for land resource allocation.Integrating ecological service value(ESV)accounting and ecological security pattern(ESP)delineation,and combining with the land use structure of 2004/2010/2016 in Ezhou City,this research laid out the urban ESP based on ESV with Net Primary Productivity(NPP),and made it as the main influence factor to simulate land use structure in 2022.The results indicated that:1)The water body has the biggest contribution to ESV,while the construction land has the minimum;2)91 ecological corridors are extracted,of which 28 were important ecological corridors;there were 36 ecological nodes extracted,including 17 important nodes;3)According to ESV,Ezhou City was divided into four security zones.The area of ecological restoration zone was the largest,and human activity core zone area was the smallest;4)In the no ESP protection scenarios and ESP protection scenarios separately,the net increase area of construction land is from 868.5 hm^(2) to 52.74 hm^(2) in the ecological core protection area;the construction land in the human activity core area has been increased by 2342.31 hm^(2) in protected scene,766.23 hm^(2) more than that of the unprotected scene.The results show that the division of security zones promoted the relocation of construction land from ecological protection core zone to human activity core zone,which can protect the ecological environment effectively,and the ESP-based simulation can provide the decision-making reference to coordinate the relationship of regional land resource allocation and the ecological environment protection.
基金supported by the National Natural Science Foundation of China(Grant 61261007)the Key Program of Yunnan Natural Science Foundation(Grant 2013FA008)
文摘Ultrasound simulation for carotid arteries is helpful to the performance assessments of vessel wall detection and signal processing methods by using ultrasound techniques. An ul- trasound simulation method of carotid artery wall with a three-membrane structure is proposed in present study. According to the ultrasound speckle distributions varying with the shapes and densities of scatterer distributions, as well as the statistic results of the clinical images, the parameters of distributions, densities and intensities of scatterers for different kinds of tissues in the carotid artery phantoms are determined. Each region is acoustically characterized using FIELD II software to produce the radio frequency echo signals, from which ultrasound images are derived. The results based on 30 simulations show that the echo distributions of the intimae, mediae, adventitias and blood are consistent with the clinical ones. Moreover, compared with the results from the central frequency of 8 MHz, the mean measurements for thicknesses of the intima, media and adventitia membranes, as well as the lumen diameter from the simulation images based on 12 MHz are the same as the preset ones, and the maximum relative errors are the 4.01%, 1.25%, 0.04% and 0.15%, respectively. The simulation under this condition is more realistic.
基金supported by the Chinese PLA General Armament Department under Grant No.51318020305
文摘In recent years, microstrip antennas have been more widely applied in satellite communications, mobile phones, unmanned aerial vehicle （UAV）, and weapons. A micro-electro-mechanical systems-based （MEMS-based） high-resistance silicon C-band microstrip antenna array has been designed for the intelligent ammunition. The center frequency is 4.5 GHz. A cavity has been designed in substrate to reduce the dielectric constant of silicon and high-resistance silicon has been used as the material of substrate to improve the gain of antenna. It is very easy to be manufactured by using MEMS technology because of the improved structure of the antenna. The results show that the gain of the antenna is 8 dB and voltage standing wave ratio （VSWR） is less than 2 by the analysis and simulation in high freauencv structure simulator （HFSS）.
基金Project supported by the National Natural Science Foundation of China(Grant No.51675086)the National Defense Pre-Research Foundation of China(Grant No.6140758010116DZ02002)
文摘In this paper, an efficient multi-conductor simplification technique is proposed to model the electromagnetic immunity on cable bundles within a braid shielding structure over a large frequency range. By grouping together the conductors based on the knowledge of Z-Smith chart, the required computation time is markedly reduced and the complexity of modeling the completely shielding cable bundles is significantly simplified with a good accuracy. After a brief description of the immunity problems in shielding structure, a six-phase procedure is detailed to generate the geometrical characteristics of the reduced cable bundles. Numerical simulation is carried out by using a commercial software CST to validate the efficiency and advantages of the proposed approach. The research addressed in this paper is considered as a simplified modeling technique for the electromagnetic immunity within a shielding structure.
基金supported by National Natural Science Foundation of China(Grant No.11375233)
文摘The ion cyclotron resonance of frequency heating（ICRH） plays an important role in plasma heating.Two ICRH antennas were designed and applied on the EAST tokamak.In order to meet the requirement imposed by high-power and long-pulse operation of EAST in the future,an active cooling system is mandatory to be designed to remove the heat load deposited on the components.Thermal analyses for high heat-load components have been carried out,which presented clear temperature distribution on each component and provided the reference data to do the optimization.Meanwhile,heat pipes were designed to satisfy the high requirement imposed by a Faraday shield and lateral limiter.
