We show how to combine in a natural way(i.e.,without any test nor switch)the conservative and non-conservative formulations of an hyperbolic system that has a conservative form.This is inspired from two different clas...We show how to combine in a natural way(i.e.,without any test nor switch)the conservative and non-conservative formulations of an hyperbolic system that has a conservative form.This is inspired from two different classes of schemes:the residual distribution one(Abgrall in Commun Appl Math Comput 2(3):341–368,2020),and the active flux formulations(Eyman and Roe in 49th AIAA Aerospace Science Meeting,2011;Eyman in active flux.PhD thesis,University of Michigan,2013;Helzel et al.in J Sci Comput 80(3):35–61,2019;Barsukow in J Sci Comput 86(1):paper No.3,34,2021;Roe in J Sci Comput 73:1094–1114,2017).The solution is globally continuous,and as in the active flux method,described by a combination of point values and average values.Unlike the“classical”active flux methods,the meaning of the point-wise and cell average degrees of freedom is different,and hence follow different forms of PDEs;it is a conservative version of the cell average,and a possibly non-conservative one for the points.This new class of scheme is proved to satisfy a Lax-Wendroff-like theorem.We also develop a method to perform nonlinear stability.We illustrate the behaviour on several benchmarks,some quite challenging.展开更多
An improved finite difference method （FDM）is described to solve existing problems such as low efficiency and poor convergence performance in the traditional method adopted to derive the pressure distribution of aero...An improved finite difference method （FDM）is described to solve existing problems such as low efficiency and poor convergence performance in the traditional method adopted to derive the pressure distribution of aerostatic bearings. A detailed theoretical analysis of the pressure distribution of the orifice-compensated aerostatic journal bearing is presented. The nonlinear dimensionless Reynolds equation of the aerostatic journal bearing is solved by the finite difference method. Based on the principle of flow equilibrium, a new iterative algorithm named the variable step size successive approximation method is presented to adjust the pressure at the orifice in the iterative process and enhance the efficiency and convergence performance of the algorithm. A general program is developed to analyze the pressure distribution of the aerostatic journal bearing by Matlab tool. The results show that the improved finite difference method is highly effective, reliable, stable, and convergent. Even when very thin gas film thicknesses （less than 2 Win）are considered, the improved calculation method still yields a result and converges fast.展开更多
The Dividing Distribution Function (DDF) method is one of the methods by which the particle size distribution of ultrafine powder can be evaluated from its small angle X-ray scattering data. In this paper, the stabili...The Dividing Distribution Function (DDF) method is one of the methods by which the particle size distribution of ultrafine powder can be evaluated from its small angle X-ray scattering data. In this paper, the stability of the solution obtained from DDF method has been investigated through optimizing the coefficient matrix, introducing a damping factor and a least square treatment. All calculations were accomplished with a microcomputer. It was shown that the average deviations of the size distribution obtained are not larger than the assigned random errors to the scattering intensities as long as the corresponding requirements are satisfied.展开更多
Considering the ocean water＇s optical attenuation and the roughness of the sea surface, we analyze the security of continuous-variable （CV） quantum key distribution （QKD） based Mr-to-water channel. The effects of...Considering the ocean water＇s optical attenuation and the roughness of the sea surface, we analyze the security of continuous-variable （CV） quantum key distribution （QKD） based Mr-to-water channel. The effects of the absorp- tion and scattering on the transmittance of underwater quantum channel and the maximum secure transmission distance are studied. Considering the roughness of the sea surface, we simulate the performance bounds of CV QKD with different wind speeds using the Monte Carlo method. The results show that even if the secret key rate gradually reduces as the wind speed increases, the maximum transmission distance will not be affected obviously. Compared to the works regarding short-distance underwater optical communication, our research represents a significant step towards establishing secure communication between air platform and submarine vehicle.展开更多
In order to research possible influences of the adjustment of plant distribution on the development frequency of thunderstorms over the Leizhou Peninsula, mathematic statistic methods, including correlation analyses, ...In order to research possible influences of the adjustment of plant distribution on the development frequency of thunderstorms over the Leizhou Peninsula, mathematic statistic methods, including correlation analyses, 11 kinds of fitting models and all-variable regression methods, were used for analyses and research. The results show that the average trend of the number of annual thunderstorm days is descending obviously, and there are thunderstorms in all seasons, in which warm post-midday thunderstorms have taken up the most part, and high frequency is found from May to September, and the starting and ending dates of thunderstorms have a great annual discrepancy. The vegetation structure has been improved along with the reduction of rice fields and the area increment of sugarcane and fruits planting, which results in the decrease of the number of thunderstorm days; the change in the characteristics of winter spare fields, which is caused by the planting of vegetables, limits the formation of thunderstorms in early winter and late spring. Meanwhile, the area adjustment of peanut planting has little influence on the variation of thunderstorm days. The adjustment of principal crop distribution, such as rice, sugarcane, fruits and vegetables, may have obvious influence on the formation of thunderstorms, and sugarcane has the largest effect, followed in turn by rice, vegetables and fruits, and the adjustment of crop distribution has little influence on the starting and ending dates of thunderstorms.展开更多
In recent years,the Indian smartphone market has grown rapidly,and Xiaomi's expansion in this market has never stopped.However,Xiaomi India has and would face even more changes and challenges due to the impact of ...In recent years,the Indian smartphone market has grown rapidly,and Xiaomi's expansion in this market has never stopped.However,Xiaomi India has and would face even more changes and challenges due to the impact of the COVID-19 pandemic.This paper focuses on how Xiaomi India can adhere to its ethical business practices in changes and developments that will improve its distribution layout.展开更多
The g-factor hence the magnetic moment,of the isomeric state <sup>43</sup>Sc（|9/2<sup>-</sup>,3.1232 MeV）has been measured by the time differential perturbed angular distributionmethod.The me...The g-factor hence the magnetic moment,of the isomeric state <sup>43</sup>Sc（|9/2<sup>-</sup>,3.1232 MeV）has been measured by the time differential perturbed angular distributionmethod.The measured values are g=0.3279（19）and μ=3.108（18）nm.展开更多
How to distribute total sum of funds among different investment priorities？ It is not only a theoretical problem in Management Accounting, but also a realistic problem in the investment decision of an enterprise. In ...How to distribute total sum of funds among different investment priorities？ It is not only a theoretical problem in Management Accounting, but also a realistic problem in the investment decision of an enterprise. In this paper, the author queries the method of ＂use linear programming to find out optimum combination＂, which put forward in management accounting, and gives a convenient and reasonable method---effective gradient method.展开更多
Objective To study the feasibility of the crossover trial design and the minimal imbalance index random distribution method in the clinical small-sample-size randomized controlled trial（RCT） research of thalamic pai...Objective To study the feasibility of the crossover trial design and the minimal imbalance index random distribution method in the clinical small-sample-size randomized controlled trial（RCT） research of thalamic pain treated with acupuncture under the guidance of evidence-based medicine（EBM）.Methods The crossover trial design was adopted.Eleven cases with the definite diagnosis were randomized into a program-I group（6 cases,treated with acupuncture before western medicine） and a program-II group（5 cases,treated with western medicine before acupuncture） according to the minimal imbalance index method.In the statistical analysis,the groups were named as an acupuncture group and a western medicine group separately,11 cases in each one.Acupuncture was applied to Xìmén（郄门 PC 4）,Yīnxì（阴郄 HT 6）,Xuèhǎi（血海 SP 10）,etc.In the control treatment,Carbamazepine was prescribed for oral administration.Either the duration of treatment or the wash-out period was 10 days.The visual analogue scale（VAS） was adopted for the efficacy assessment.Results The total effective was 100.0%（11/11） after treatment in either group.The remarkably effective rates were 63.6%（7/11） and 36.4%（4/11） in the acupuncture group and the western medicine group separately,without statistically significant difference in comparison.Conclusion The crossover trial design and the minimal imbalance index distribution method can accomplish RCT of the clinical acupuncture and moxibustion research with the small sample size involved.They can provide the high-quality evidences for clinical acupuncture research.Acupuncture therapy can achieve the same therapeutic effect as Carbamazepine,the common western medicine,and the efficacy of it is potentially superior to that of western medicine.展开更多
The potential energy curves of the ground state X2∑＋g of the fluorine molecule have been accurately reconstructed employing the Ryderg-Klein-Rees （RKR） method extrapolated by a Hulburt and Hirschfeler potential fu...The potential energy curves of the ground state X2∑＋g of the fluorine molecule have been accurately reconstructed employing the Ryderg-Klein-Rees （RKR） method extrapolated by a Hulburt and Hirschfeler potential function for longer internuclear distances. Solving the corresponding radial one-dimensional Schr？dinger equation of nuclear motion yields 22 bound vibrational levels above v=0. The comparison of these theoretical levels with the experimental data yields a mean absolute deviation of about 7.6 cm^-1 over the 23 levels. The highest vibrational level energy obtained using this method is 13308.16 cm？1 and the relative deviation compared with the experimental datum of 13408.49 cm^-1 is only 0.74%. The value from our method is much closer and more accurate than the value obtained by the quantum mechanical ab initio method by Bytautas. The reported agreement of the vibrational levels and dissociation energy with experiment is contingent upon the potential energy curve of the F2 ground state.展开更多
为识别铝合金板孔损伤位置及区域,以Lamb波为研究基础,提出基于魏格纳-威利分布(WVD,WignerVille distribution)和到达时间差值法(ATDM,arrival time difference method)的损伤识别技术。首先,采集实验铝合金板健康和有损模型的Lamb信号...为识别铝合金板孔损伤位置及区域,以Lamb波为研究基础,提出基于魏格纳-威利分布(WVD,WignerVille distribution)和到达时间差值法(ATDM,arrival time difference method)的损伤识别技术。首先,采集实验铝合金板健康和有损模型的Lamb信号,对其差值信号进行WVD分析,准确提取损伤反射信号到达时间;其次,通过ATDM建立各传感器间的距离差值关系,确定孔损伤位置中心并预测最大损伤半径,从而实现对孔损伤关键指标的识别;最后,通过数值模拟进一步验证该方法,结果表明,基于WVD/ATDM的损伤识别技术不仅能准确识别出孔损伤位置,而且能够有效地识别损伤区域面积。展开更多
Multi-phase flowfield simulation has been performed on solid rocket motor and effect of multi-phases on the performance prediction of the solid rocket motor(SRM) is investigation.During the combustion of aluminized pr...Multi-phase flowfield simulation has been performed on solid rocket motor and effect of multi-phases on the performance prediction of the solid rocket motor(SRM) is investigation.During the combustion of aluminized propellant,the aluminum particles in the propellant melt and formliquid aluminum at the burning propellant surface.So the flow within the rocket motor is multi phase or two phase because it contains droplets and smoke particles of Al2O3.Flowsi mulations have been performed on a large scale motor,to observe the effect of the flowfield onthe chamber and nozzle as well.Uniform particles diameters and Rosin-Rammler diameter distribution method that is based on the assumption that an exponential relationship exists betweenthe droplet diameter,dand mass fraction of droplets with diameter greater thandhave been used for the si mulation of different distribution of Al2O3 droplets present in SRM.Particles sizes in the range of 1-100μm are used,as being the most common droplets.In this approachthe complete range of particle sizes is dividedinto a set of discrete size ranges,eachto be defined by single streamthat is part of the group.Roe scheme-flux differencing splitting based on approxi mate Riemann problem has been used to si mulate the effects of the multi-phase flowfeild.This is second order upwind scheme in which flux differencing splitting method is employed.To cater for the turbulence effect,Spalart-All maras model has been used.The results obtained show the great sensitivity of this diameters distribution and particles concentrations to the SRMflowdynamics,primarily at the motor chamber and nozzle exit.The results are shown with various sizes of the particles concentrations and geometrical configurations including models for SRM and nozzle.The analysis also provides effect of multi-phase on performance prediction of solid rocket motor.展开更多
Because of the randomness of many impact factors influencing the dynamic assembly relationship of complex machinery, the reliability analysis of dynamic assembly relationship needs to be accomplished considering the r...Because of the randomness of many impact factors influencing the dynamic assembly relationship of complex machinery, the reliability analysis of dynamic assembly relationship needs to be accomplished considering the randomness from a probabilistic perspective. To improve the accuracy and efficiency of dynamic assembly relationship reliability analysis, the mechanical dynamic assembly reliability（MDAR） theory and a distributed collaborative response surface method（DCRSM） are proposed. The mathematic model of DCRSM is established based on the quadratic response surface function, and verified by the assembly relationship reliability analysis of aeroengine high pressure turbine（HPT） blade-tip radial running clearance（BTRRC）. Through the comparison of the DCRSM, traditional response surface method（RSM） and Monte Carlo Method（MCM）, the results show that the DCRSM is not able to accomplish the computational task which is impossible for the other methods when the number of simulation is more than 100 000 times, but also the computational precision for the DCRSM is basically consistent with the MCM and improved by 0.40-4.63% to the RSM, furthermore, the computational efficiency of DCRSM is up to about 188 times of the MCM and 55 times of the RSM under 10000 times simulations. The DCRSM is demonstrated to be a feasible and effective approach for markedly improving the computational efficiency and accuracy of MDAR analysis. Thus, the proposed research provides the promising theory and method for the MDAR design and optimization, and opens a novel research direction of probabilistic analysis for developing the high-performance and high-reliability of aeroengine.展开更多
The stripped solar sail whose membrane is divided into separate narrow membrane strips is believed to have the best structural efficiency.In this paper,the stripped solar sail structure is regarded as an assembly made...The stripped solar sail whose membrane is divided into separate narrow membrane strips is believed to have the best structural efficiency.In this paper,the stripped solar sail structure is regarded as an assembly made by connecting a number of boom-strip components in sequence.Considering the coupling effects between booms and membrane strips,an exact and semianalytical method to calculate structural dynamic responses of the stripped solar sail subjected to solar radiation pressure is established.The case study of a 100 m stripped solar sail shows that the stripped architecture helps to reduce the static deflections and amplitudes of the steady-state dynamic response.Larger prestress of the membrane strips will decrease stiffness of the sail and increase amplitudes of the steady-state dynamic response.Increasing thickness of the boom will benefit to stability of the sail and reduce the resonant amplitudes.This proposed semi-analytical method provides an efficient analysis tool for structure design and attitude control of the stripped solar sail.展开更多
To make three-dimensional electromagnetic exploration achievable,the distributed wide field electromagnetic method(WFEM)based on the high-order 2^(n) sequence pseudo-random signal is proposed and realized.In this meth...To make three-dimensional electromagnetic exploration achievable,the distributed wide field electromagnetic method(WFEM)based on the high-order 2^(n) sequence pseudo-random signal is proposed and realized.In this method,only one set of high-order pseudo-random waveforms,which contains all target frequencies,is needed.Based on high-order sequence pseudo-random signal construction algorithm,the waveform can be customized according to different exploration tasks.And the receivers are independent with each other and dynamically adjust the acquisition parameters according to different requirements.A field test in the deep iron ore of Qihe−Yucheng showed that the distributed WFEM based on high-order pseudo-random signal realizes the high-efficiency acquisition of massive electromagnetic data in quite a short time.Compared with traditional controlled-source electromagnetic methods,the distributed WFEM is much more efficient.Distributed WFEM can be applied to the large scale and high-resolution exploration for deep resources and minerals.展开更多
The plane strain asymmetrical rolling was analyzed using slab method. The contact arc was replaced by parabola, and the constant surface friction status was adopted during the analysis. The deformation area was divide...The plane strain asymmetrical rolling was analyzed using slab method. The contact arc was replaced by parabola, and the constant surface friction status was adopted during the analysis. The deformation area was divided into three zones according to the direction of the friction. Then, the three zones were studied, respectively. A rolling force model and a rolling torque model were developed based on the analysis, and they were used to analyze the influ- ence of asymmetrical rolling factors on deformation area and unit pressure if they had good precision which was determined by comparing the calculated results with the measured ones.展开更多
Britholites with the general formula Ca10-xLnx（PO4）6-x（SiO4）xF2, （0≤x≤6） are considered to be promising matrices for the confinement of the by-products in the nuclear industry. A thermodynamic study showed tha...Britholites with the general formula Ca10-xLnx（PO4）6-x（SiO4）xF2, （0≤x≤6） are considered to be promising matrices for the confinement of the by-products in the nuclear industry. A thermodynamic study showed that the stability of these compounds de-creased as the substitution rate increased. The present work was an attempt to gain more information about the structural changes in-duced by the substitution, in order to understand the observed stability decrease. The samples were successfully synthesized as a sin-gle-phase apatite by a solid-state reaction between 1200 and 1400 °C. The structural refinement indicated that the La3＋ions preferen-tially occupied the 6（h） sites. A progressive shift of F-along the c-axis outside its ideal position occurred as a result of the substitution increase. This might be the cause of the observed stability decrease, especially as the energies of the La-O, La-F and Si-O bonds are higher than those of Ca-O, Ca-F and P-O. The distribution of La3＋ between the two non-equivalent sites was confirmed by the charge distribution method.展开更多
The fluid flow induced by light-density, low-stiffness structures was treated as inviscid, incompressible irrotational and steady plane flow. On the basis of the dipole configuration method, a singularity distribution...The fluid flow induced by light-density, low-stiffness structures was treated as inviscid, incompressible irrotational and steady plane flow. On the basis of the dipole configuration method, a singularity distribution method of distributing sources/sinks and dipoles on interfaces of the structure and fluid was developed to solve the problem of fluid flow induced by the vibration of common structures, such as columns and columns with fins, deduce the expression of kinetic energy of the fluid flow, and obtain the added mass finally. The calculational instances with analytical solutions prove the reliability of this method.展开更多
The sedimentation of a single circular particle between two parallel walls was studied by means of direct numerical simulation (DNS) and experiment. The improved implementation of distributed Lagrange multiplier/ficti...The sedimentation of a single circular particle between two parallel walls was studied by means of direct numerical simulation (DNS) and experiment. The improved implementation of distributed Lagrange multiplier/fictitious domain method used in our DNS is a promising new way for simulation of particulate flows. The settling behaviors of the particle are presented ranging in Reynolds number from 0 to about 700, which showed that our results for low Reynolds numbers agreed well with that reported before. Nevertheless, for higher Reynolds numbers our results were different from theirs. The long-term mean equilibrium positions in our results were all on the centerline, but not at off-center position as reported before. In order to validate our simulation, experiments were also conducted. The results showed that the sedimenting behavior simulated in this paper agreed well with our experiment result.展开更多
基金the author was partially funded by the SNF project 200020_175784.
文摘We show how to combine in a natural way(i.e.,without any test nor switch)the conservative and non-conservative formulations of an hyperbolic system that has a conservative form.This is inspired from two different classes of schemes:the residual distribution one(Abgrall in Commun Appl Math Comput 2(3):341–368,2020),and the active flux formulations(Eyman and Roe in 49th AIAA Aerospace Science Meeting,2011;Eyman in active flux.PhD thesis,University of Michigan,2013;Helzel et al.in J Sci Comput 80(3):35–61,2019;Barsukow in J Sci Comput 86(1):paper No.3,34,2021;Roe in J Sci Comput 73:1094–1114,2017).The solution is globally continuous,and as in the active flux method,described by a combination of point values and average values.Unlike the“classical”active flux methods,the meaning of the point-wise and cell average degrees of freedom is different,and hence follow different forms of PDEs;it is a conservative version of the cell average,and a possibly non-conservative one for the points.This new class of scheme is proved to satisfy a Lax-Wendroff-like theorem.We also develop a method to perform nonlinear stability.We illustrate the behaviour on several benchmarks,some quite challenging.
基金The National Natural Science Foundation of China(No50475073,50775036)the High Technology Research Program of Jiangsu Province(NoBG2006035)
文摘An improved finite difference method （FDM）is described to solve existing problems such as low efficiency and poor convergence performance in the traditional method adopted to derive the pressure distribution of aerostatic bearings. A detailed theoretical analysis of the pressure distribution of the orifice-compensated aerostatic journal bearing is presented. The nonlinear dimensionless Reynolds equation of the aerostatic journal bearing is solved by the finite difference method. Based on the principle of flow equilibrium, a new iterative algorithm named the variable step size successive approximation method is presented to adjust the pressure at the orifice in the iterative process and enhance the efficiency and convergence performance of the algorithm. A general program is developed to analyze the pressure distribution of the aerostatic journal bearing by Matlab tool. The results show that the improved finite difference method is highly effective, reliable, stable, and convergent. Even when very thin gas film thicknesses （less than 2 Win）are considered, the improved calculation method still yields a result and converges fast.
文摘The Dividing Distribution Function (DDF) method is one of the methods by which the particle size distribution of ultrafine powder can be evaluated from its small angle X-ray scattering data. In this paper, the stability of the solution obtained from DDF method has been investigated through optimizing the coefficient matrix, introducing a damping factor and a least square treatment. All calculations were accomplished with a microcomputer. It was shown that the average deviations of the size distribution obtained are not larger than the assigned random errors to the scattering intensities as long as the corresponding requirements are satisfied.
基金Supported by the National Natural Science Foundation of China under Grant No 61572529
文摘Considering the ocean water＇s optical attenuation and the roughness of the sea surface, we analyze the security of continuous-variable （CV） quantum key distribution （QKD） based Mr-to-water channel. The effects of the absorp- tion and scattering on the transmittance of underwater quantum channel and the maximum secure transmission distance are studied. Considering the roughness of the sea surface, we simulate the performance bounds of CV QKD with different wind speeds using the Monte Carlo method. The results show that even if the secret key rate gradually reduces as the wind speed increases, the maximum transmission distance will not be affected obviously. Compared to the works regarding short-distance underwater optical communication, our research represents a significant step towards establishing secure communication between air platform and submarine vehicle.
文摘In order to research possible influences of the adjustment of plant distribution on the development frequency of thunderstorms over the Leizhou Peninsula, mathematic statistic methods, including correlation analyses, 11 kinds of fitting models and all-variable regression methods, were used for analyses and research. The results show that the average trend of the number of annual thunderstorm days is descending obviously, and there are thunderstorms in all seasons, in which warm post-midday thunderstorms have taken up the most part, and high frequency is found from May to September, and the starting and ending dates of thunderstorms have a great annual discrepancy. The vegetation structure has been improved along with the reduction of rice fields and the area increment of sugarcane and fruits planting, which results in the decrease of the number of thunderstorm days; the change in the characteristics of winter spare fields, which is caused by the planting of vegetables, limits the formation of thunderstorms in early winter and late spring. Meanwhile, the area adjustment of peanut planting has little influence on the variation of thunderstorm days. The adjustment of principal crop distribution, such as rice, sugarcane, fruits and vegetables, may have obvious influence on the formation of thunderstorms, and sugarcane has the largest effect, followed in turn by rice, vegetables and fruits, and the adjustment of crop distribution has little influence on the starting and ending dates of thunderstorms.
文摘In recent years,the Indian smartphone market has grown rapidly,and Xiaomi's expansion in this market has never stopped.However,Xiaomi India has and would face even more changes and challenges due to the impact of the COVID-19 pandemic.This paper focuses on how Xiaomi India can adhere to its ethical business practices in changes and developments that will improve its distribution layout.
基金supported by National Natural Science Foundation of ChinaNuclear Industry Science Foundation of China
文摘The g-factor hence the magnetic moment,of the isomeric state <sup>43</sup>Sc（|9/2<sup>-</sup>,3.1232 MeV）has been measured by the time differential perturbed angular distributionmethod.The measured values are g=0.3279（19）and μ=3.108（18）nm.
文摘How to distribute total sum of funds among different investment priorities？ It is not only a theoretical problem in Management Accounting, but also a realistic problem in the investment decision of an enterprise. In this paper, the author queries the method of ＂use linear programming to find out optimum combination＂, which put forward in management accounting, and gives a convenient and reasonable method---effective gradient method.
基金Supported by research project of "Innovation Engineering" of The First Affiliated Hospital of Tianjin University of TCM:Academy 0804
文摘Objective To study the feasibility of the crossover trial design and the minimal imbalance index random distribution method in the clinical small-sample-size randomized controlled trial（RCT） research of thalamic pain treated with acupuncture under the guidance of evidence-based medicine（EBM）.Methods The crossover trial design was adopted.Eleven cases with the definite diagnosis were randomized into a program-I group（6 cases,treated with acupuncture before western medicine） and a program-II group（5 cases,treated with western medicine before acupuncture） according to the minimal imbalance index method.In the statistical analysis,the groups were named as an acupuncture group and a western medicine group separately,11 cases in each one.Acupuncture was applied to Xìmén（郄门 PC 4）,Yīnxì（阴郄 HT 6）,Xuèhǎi（血海 SP 10）,etc.In the control treatment,Carbamazepine was prescribed for oral administration.Either the duration of treatment or the wash-out period was 10 days.The visual analogue scale（VAS） was adopted for the efficacy assessment.Results The total effective was 100.0%（11/11） after treatment in either group.The remarkably effective rates were 63.6%（7/11） and 36.4%（4/11） in the acupuncture group and the western medicine group separately,without statistically significant difference in comparison.Conclusion The crossover trial design and the minimal imbalance index distribution method can accomplish RCT of the clinical acupuncture and moxibustion research with the small sample size involved.They can provide the high-quality evidences for clinical acupuncture research.Acupuncture therapy can achieve the same therapeutic effect as Carbamazepine,the common western medicine,and the efficacy of it is potentially superior to that of western medicine.
基金This work was supported by the National Natural Science Foundation of China （No.20273066）.
文摘The potential energy curves of the ground state X2∑＋g of the fluorine molecule have been accurately reconstructed employing the Ryderg-Klein-Rees （RKR） method extrapolated by a Hulburt and Hirschfeler potential function for longer internuclear distances. Solving the corresponding radial one-dimensional Schr？dinger equation of nuclear motion yields 22 bound vibrational levels above v=0. The comparison of these theoretical levels with the experimental data yields a mean absolute deviation of about 7.6 cm^-1 over the 23 levels. The highest vibrational level energy obtained using this method is 13308.16 cm？1 and the relative deviation compared with the experimental datum of 13408.49 cm^-1 is only 0.74%. The value from our method is much closer and more accurate than the value obtained by the quantum mechanical ab initio method by Bytautas. The reported agreement of the vibrational levels and dissociation energy with experiment is contingent upon the potential energy curve of the F2 ground state.
文摘为识别铝合金板孔损伤位置及区域,以Lamb波为研究基础,提出基于魏格纳-威利分布(WVD,WignerVille distribution)和到达时间差值法(ATDM,arrival time difference method)的损伤识别技术。首先,采集实验铝合金板健康和有损模型的Lamb信号,对其差值信号进行WVD分析,准确提取损伤反射信号到达时间;其次,通过ATDM建立各传感器间的距离差值关系,确定孔损伤位置中心并预测最大损伤半径,从而实现对孔损伤关键指标的识别;最后,通过数值模拟进一步验证该方法,结果表明,基于WVD/ATDM的损伤识别技术不仅能准确识别出孔损伤位置,而且能够有效地识别损伤区域面积。
文摘Multi-phase flowfield simulation has been performed on solid rocket motor and effect of multi-phases on the performance prediction of the solid rocket motor(SRM) is investigation.During the combustion of aluminized propellant,the aluminum particles in the propellant melt and formliquid aluminum at the burning propellant surface.So the flow within the rocket motor is multi phase or two phase because it contains droplets and smoke particles of Al2O3.Flowsi mulations have been performed on a large scale motor,to observe the effect of the flowfield onthe chamber and nozzle as well.Uniform particles diameters and Rosin-Rammler diameter distribution method that is based on the assumption that an exponential relationship exists betweenthe droplet diameter,dand mass fraction of droplets with diameter greater thandhave been used for the si mulation of different distribution of Al2O3 droplets present in SRM.Particles sizes in the range of 1-100μm are used,as being the most common droplets.In this approachthe complete range of particle sizes is dividedinto a set of discrete size ranges,eachto be defined by single streamthat is part of the group.Roe scheme-flux differencing splitting based on approxi mate Riemann problem has been used to si mulate the effects of the multi-phase flowfeild.This is second order upwind scheme in which flux differencing splitting method is employed.To cater for the turbulence effect,Spalart-All maras model has been used.The results obtained show the great sensitivity of this diameters distribution and particles concentrations to the SRMflowdynamics,primarily at the motor chamber and nozzle exit.The results are shown with various sizes of the particles concentrations and geometrical configurations including models for SRM and nozzle.The analysis also provides effect of multi-phase on performance prediction of solid rocket motor.
基金supported by National Natural Science Foundation of China(Grant Nos.51175017,51245027)Innovation Foundation of Beihang University for PhD Graduates,China(Grant No.YWF-12-RBYJ008)Research Fund for the Doctoral Program of Higher Education of China(Grant No.20111102110011)
文摘Because of the randomness of many impact factors influencing the dynamic assembly relationship of complex machinery, the reliability analysis of dynamic assembly relationship needs to be accomplished considering the randomness from a probabilistic perspective. To improve the accuracy and efficiency of dynamic assembly relationship reliability analysis, the mechanical dynamic assembly reliability（MDAR） theory and a distributed collaborative response surface method（DCRSM） are proposed. The mathematic model of DCRSM is established based on the quadratic response surface function, and verified by the assembly relationship reliability analysis of aeroengine high pressure turbine（HPT） blade-tip radial running clearance（BTRRC）. Through the comparison of the DCRSM, traditional response surface method（RSM） and Monte Carlo Method（MCM）, the results show that the DCRSM is not able to accomplish the computational task which is impossible for the other methods when the number of simulation is more than 100 000 times, but also the computational precision for the DCRSM is basically consistent with the MCM and improved by 0.40-4.63% to the RSM, furthermore, the computational efficiency of DCRSM is up to about 188 times of the MCM and 55 times of the RSM under 10000 times simulations. The DCRSM is demonstrated to be a feasible and effective approach for markedly improving the computational efficiency and accuracy of MDAR analysis. Thus, the proposed research provides the promising theory and method for the MDAR design and optimization, and opens a novel research direction of probabilistic analysis for developing the high-performance and high-reliability of aeroengine.
基金supported by the National Natural Science Foundation of China(No.11572001)。
文摘The stripped solar sail whose membrane is divided into separate narrow membrane strips is believed to have the best structural efficiency.In this paper,the stripped solar sail structure is regarded as an assembly made by connecting a number of boom-strip components in sequence.Considering the coupling effects between booms and membrane strips,an exact and semianalytical method to calculate structural dynamic responses of the stripped solar sail subjected to solar radiation pressure is established.The case study of a 100 m stripped solar sail shows that the stripped architecture helps to reduce the static deflections and amplitudes of the steady-state dynamic response.Larger prestress of the membrane strips will decrease stiffness of the sail and increase amplitudes of the steady-state dynamic response.Increasing thickness of the boom will benefit to stability of the sail and reduce the resonant amplitudes.This proposed semi-analytical method provides an efficient analysis tool for structure design and attitude control of the stripped solar sail.
基金funded by the National Natural Science Foundation of China(No.42004056)the Natural Science Foundation of Shangdong Province,China(No.ZR2020QD052)China Postdoctoral Science Foundation(No.2019M652386)。
文摘To make three-dimensional electromagnetic exploration achievable,the distributed wide field electromagnetic method(WFEM)based on the high-order 2^(n) sequence pseudo-random signal is proposed and realized.In this method,only one set of high-order pseudo-random waveforms,which contains all target frequencies,is needed.Based on high-order sequence pseudo-random signal construction algorithm,the waveform can be customized according to different exploration tasks.And the receivers are independent with each other and dynamically adjust the acquisition parameters according to different requirements.A field test in the deep iron ore of Qihe−Yucheng showed that the distributed WFEM based on high-order pseudo-random signal realizes the high-efficiency acquisition of massive electromagnetic data in quite a short time.Compared with traditional controlled-source electromagnetic methods,the distributed WFEM is much more efficient.Distributed WFEM can be applied to the large scale and high-resolution exploration for deep resources and minerals.
基金Item Sponsored by National Natural Science Foundation of China (50104006)National Key Technology Research and Development Program of China(2006BAE03A08)
文摘The plane strain asymmetrical rolling was analyzed using slab method. The contact arc was replaced by parabola, and the constant surface friction status was adopted during the analysis. The deformation area was divided into three zones according to the direction of the friction. Then, the three zones were studied, respectively. A rolling force model and a rolling torque model were developed based on the analysis, and they were used to analyze the influ- ence of asymmetrical rolling factors on deformation area and unit pressure if they had good precision which was determined by comparing the calculated results with the measured ones.
文摘Britholites with the general formula Ca10-xLnx（PO4）6-x（SiO4）xF2, （0≤x≤6） are considered to be promising matrices for the confinement of the by-products in the nuclear industry. A thermodynamic study showed that the stability of these compounds de-creased as the substitution rate increased. The present work was an attempt to gain more information about the structural changes in-duced by the substitution, in order to understand the observed stability decrease. The samples were successfully synthesized as a sin-gle-phase apatite by a solid-state reaction between 1200 and 1400 °C. The structural refinement indicated that the La3＋ions preferen-tially occupied the 6（h） sites. A progressive shift of F-along the c-axis outside its ideal position occurred as a result of the substitution increase. This might be the cause of the observed stability decrease, especially as the energies of the La-O, La-F and Si-O bonds are higher than those of Ca-O, Ca-F and P-O. The distribution of La3＋ between the two non-equivalent sites was confirmed by the charge distribution method.
文摘The fluid flow induced by light-density, low-stiffness structures was treated as inviscid, incompressible irrotational and steady plane flow. On the basis of the dipole configuration method, a singularity distribution method of distributing sources/sinks and dipoles on interfaces of the structure and fluid was developed to solve the problem of fluid flow induced by the vibration of common structures, such as columns and columns with fins, deduce the expression of kinetic energy of the fluid flow, and obtain the added mass finally. The calculational instances with analytical solutions prove the reliability of this method.
文摘The sedimentation of a single circular particle between two parallel walls was studied by means of direct numerical simulation (DNS) and experiment. The improved implementation of distributed Lagrange multiplier/fictitious domain method used in our DNS is a promising new way for simulation of particulate flows. The settling behaviors of the particle are presented ranging in Reynolds number from 0 to about 700, which showed that our results for low Reynolds numbers agreed well with that reported before. Nevertheless, for higher Reynolds numbers our results were different from theirs. The long-term mean equilibrium positions in our results were all on the centerline, but not at off-center position as reported before. In order to validate our simulation, experiments were also conducted. The results showed that the sedimenting behavior simulated in this paper agreed well with our experiment result.
