3GPP在版本16(R16,Release 16)中升级了最小化路测(MDT,minimization of drive test)技术,提出移动终端可利用4G/5G网络自主上报Wi-Fi信号的接收信号强度指示(RSSI,received signal strength indicator),为运营商度量Wi-Fi网络的覆盖率...3GPP在版本16(R16,Release 16)中升级了最小化路测(MDT,minimization of drive test)技术,提出移动终端可利用4G/5G网络自主上报Wi-Fi信号的接收信号强度指示(RSSI,received signal strength indicator),为运营商度量Wi-Fi网络的覆盖率带来了可能性。然而,现有基于MDT技术的网络覆盖度量方法严重依赖GPS提供的位置坐标,但全球定位系统(GPS,global positioning system)不能提供室内精准定位,无法用于室内Wi-Fi网络的覆盖度量。为此,提出了一种不依赖位置坐标的RSSI聚类方法,充分利用室内相近位置RSSI的统计相似性,区分不同位置的RSSI测量差异,在无位置坐标条件下准确估计出室内Wi-Fi网络的覆盖率。实验结果表明,所提方法估计的覆盖率与基于真实位置坐标测量的覆盖率相近,度量准确度明显优于现有的其他方法。展开更多
To study the seismic behavior of high strength concrete fi lled double-tube(CFDT) columns,each consisting of an external square steel tube and an internal circular steel tube,quasi-static tests on eight CFDT column sp...To study the seismic behavior of high strength concrete fi lled double-tube(CFDT) columns,each consisting of an external square steel tube and an internal circular steel tube,quasi-static tests on eight CFDT column specimens were conducted.The test variables included the width-to-thickness ratio(β1) and the area ratio(β2) of the square steel tube,the wall thickness of the circular steel tube,and the axial force(or the axial force ratio) applied to the CFDT columns.The test results indicate that for CFDT columns with a square steel tube with β1 of 50.1 and 24.5,local buckling of the specimen was found at a drift ratio of 1/150 and 1/50,respectively.The lateral force-displacement hysteretic loops of all specimens were plump and stable.Reducing the width-to-thickness ratio of the square steel tube,increasing its area ratio,or increasing the wall thickness of the internal circular steel tube,led to an increased fl exural strength and deformation capacity of the specimens.Increasing the design value of the axial force ratio from 0.8 to 1.0 may increase the fl exural strength of the specimens,while it may also decrease the ultimate deformation capacity of the specimen with β1 of 50.1.展开更多
We calculated the crustal stress field using the composite focal mechanism method based on the P-wave initial motion polarity data of the Tengchong volcanic area from January 2011 to April 2019 obtained from the Bulle...We calculated the crustal stress field using the composite focal mechanism method based on the P-wave initial motion polarity data of the Tengchong volcanic area from January 2011 to April 2019 obtained from the Bulletin of Seismological Observations of Chinese stations.The magnitude range of earthquakes used in this study is 0–4,and their magnitudes are mainly approximately 1.0.To investigate the infl uence of the source location on the stress fi eld and obtain reliable stress fi elds of the study area,we applied the double-diff erence algorithm to relocate the seismic events,obtaining more accurate and reliable relative positions of seismic events with a clearer seismic belt.On the basis of relocation results,the study on the stress fi eld along the fault zone was conducted,and the infl uence of seismic event position on the stress fi eld was analyzed.Results show that,fi rst,the current stress regime in the shallow crust of the Tengchong volcanic area is strike-slip faulting,the orientation of the principal compressive stress axis is NE–SW,the orientation of the principal extension stress axis is SE–NW,the principal compressive and extension stress axes are nearly horizontal,and the dip angle of intermediate principal stress axis is relatively large.This reflects that the volcanic and seismic activities in the Tengchong volcanic area are mainly controlled by the collision and squeezing eff ect of the Indian–Eurasian plate.It also refl ects that the current tensile action caused by deep magma activity has little infl uence on the shallow crustal stress field.Second,the stress field along fault zones reveals that there exist local stress fi elds,such as the thrust stress regime at the strike-slip fault terminal area,which is consistent with the compressional area at the intersection of conjugate strike-slip faults indicated by previous study.Third,the stress fi eld results are consistent,regardless of using the original location in the bulletin or the relocated location,indicating that the infl uence of the event location error can be neglected when there are suffi cient data and refl ecting the stability of the composite focal mechanism method.The findings can serve as a reference for investigating geological structure movement,seismic activities,and volcanic activities in the Tengchong volcanic area.展开更多
Magnetic field gradient tensor technique provides abundant data for delicate inversion of subsurface magnetic susceptibility distribution. Large scale magnetic data inversion imaging requires high speed and accuracy f...Magnetic field gradient tensor technique provides abundant data for delicate inversion of subsurface magnetic susceptibility distribution. Large scale magnetic data inversion imaging requires high speed and accuracy for forward modeling. For arbitrarily distributed susceptibility data on an undulated surface, we propose a fast 3D forward modeling method in the wavenumber domain based on(1) the wavenumber-domain expression of the prism combination model and the Gauss–FFT algorithm and(2) cubic spline interpolation. We apply the proposed 3D forward modeling method to synthetic data and use weighting coefficients in the wavenumber domain to improve the modeling for multiple observation surfaces, and also demonstrate the accuracy and efficiency of the proposed method.展开更多
Gravity and magnetic exploration areas are usually irregular,and there is some data defi ciency.Missing data must be interpolated before the vertical derivative conversion in the wavenumber domain.Meanwhile,for improv...Gravity and magnetic exploration areas are usually irregular,and there is some data defi ciency.Missing data must be interpolated before the vertical derivative conversion in the wavenumber domain.Meanwhile,for improved processing precision,the data need to be edge-padded to the length required by the fast Fourier transform algorithm.For conventional vertical derivative conversion of potential fi eld data(PFD),only vertical derivative conversion is considered,or interpolation,border padding,and vertical derivative conversion are executed independently.In this paper,these three steps are considered uniformly,and a vertical derivative conversion method for irregular-range PFD based on an improved projection onto convex sets method is proposed.The cutoff wavenumber of the filter used in the proposed method is determined by fractal model fi tting of the radial average power spectrum(RAPS)of the potential fi eld.Theoretical gravity models and real aeromagnetic data show the following:(1)The fitting of the RAPS with a fractal model can separate useful signals and noise reasonably.(2)The proposed iterative method has a clear physical sense,and its interpolation,border padding error,and running time are much smaller than those of the conventional kriging and minimum curvature methods.展开更多
Large-scale,fine,and efficient numerical simulation of a geothermal field plays an important role in geothermal energy development.Confronted with the problem of large computation and high storage requirements for com...Large-scale,fine,and efficient numerical simulation of a geothermal field plays an important role in geothermal energy development.Confronted with the problem of large computation and high storage requirements for complex underground models in a three-dimensional(3-D)numerical simulation of a geothermal fi eld,a mixed space-wavenumber domain 3-D numerical simulation algorithm is proposed in this paper.According to the superposition principle of temperature field,the geothermal field is decomposed into background and abnormal temperature fi elds for calculation.The uniform layered model is used to solve the background field.When the abnormal field is solved,the horizontal two-dimensional(2-D)Fourier transform is used to transform the 3-D diff erential equation satisfi ed by an abnormal field into a series of one-dimensional ordinary differential equations with diff erent wavenumbers,which greatly reduces the calculation and storage.The unit division of an ordinary diff erential equation is fl exible,and the calculation amount is small.The algorithm fully takes advantage of the effi ciency of the Fourier transform and the quickness of the catch-up method to solve linear equations with a fixed bandwidth,which effectively improves the computational efficiency.Compared with the COMSOL Multiphysics professional simulation finite element software,the time consumption and memory requirements of the algorithm proposed in this paper are reduced by multiple orders of magnitude in terms of ensuring accuracy and the same mesh division.The more the number of calculated nodes is,the more obvious is the advantage.We design models to study the thermal conductivity,heat fl ux boundary,regional tectonic morphology,and topographic relief of the geothermal fi eld distribution.A 3-D geophysical model is developed based on topographic elevation data,geothermal geology,and geophysical exploration data in the Qiabuqia area of Gonghe Basin,Qinghai Province,China.Numerical simulation of the geothermal fi eld in this area is realized,which shows that the algorithm is suitable for precise and effi cient simulation of an arbitrary complex terrain and geological conditions.展开更多
The downward continuation of potential fields is a process of calculating their values in a lower plane based on those of a certain plane.This technology is not only a data processing method for resource exploration b...The downward continuation of potential fields is a process of calculating their values in a lower plane based on those of a certain plane.This technology is not only a data processing method for resource exploration but also plays an extremely important role in military applications.However,the downward continuation of potential fields is a typical linear inverse problem that is ill-posed.Generalized minimal residuals(GMRES)is an eff ective solution to ill-posed inverse problems,but it is unstable under the condition wherein the GMRES is directly applied in the calculation process.Moreover,the long-term behavior of its iterative computation is a disordered,divergent result.Therefore,to obtain stable solutions,GMRES is applied to solve the normal equations of the downward continuation of potential fields;it is also used to prequalify for occasional interruptions in the operation process by adding the damping coefficient,thus strengthening the stability conditions of the equations of residual minimization.Finally,the stable downward continuation of the potential fields method is proposed.As indicated by the theoretical data and the measured testing data,the method proposed in this paper has the advantages of high-precision and excellent stability.Furthermore,compared with the Tikhonov iteration method,the proposed method avoids the need to choose regularization parameters.展开更多
由于GPS无法在楼宇内使用,而目前的楼宇内定位技术一般都需要预先部署额外的设施,因此楼宇内无基础设施定位成为了一个热点研究问题.提出了一种利用Wi-Fi接入点的MAC地址和RSSI(received signal strength indication)值,通过机器分类的...由于GPS无法在楼宇内使用,而目前的楼宇内定位技术一般都需要预先部署额外的设施,因此楼宇内无基础设施定位成为了一个热点研究问题.提出了一种利用Wi-Fi接入点的MAC地址和RSSI(received signal strength indication)值,通过机器分类的方式实现楼宇内房间级定位的算法R-kNN(relativity k-nearest neighbor).R-kNN是一种属性加权k近邻算法,它通过将AP之间的相关性反应在权值的分配上,有效地降低了维度冗余对分类准确率的负面影响.R-kNN没有对房间和AP的物理位置做出任何假设,只需要使用环境中现存的AP就可以取得较好的定位效果,无需部署任何额外设施或修改现有设施.实验结果表明,在AP数量较多的楼宇环境中,R-kNN能够取得比k近邻算法和朴素贝叶斯分类器更好的定位效果.展开更多
文摘3GPP在版本16(R16,Release 16)中升级了最小化路测(MDT,minimization of drive test)技术,提出移动终端可利用4G/5G网络自主上报Wi-Fi信号的接收信号强度指示(RSSI,received signal strength indicator),为运营商度量Wi-Fi网络的覆盖率带来了可能性。然而,现有基于MDT技术的网络覆盖度量方法严重依赖GPS提供的位置坐标,但全球定位系统(GPS,global positioning system)不能提供室内精准定位,无法用于室内Wi-Fi网络的覆盖度量。为此,提出了一种不依赖位置坐标的RSSI聚类方法,充分利用室内相近位置RSSI的统计相似性,区分不同位置的RSSI测量差异,在无位置坐标条件下准确估计出室内Wi-Fi网络的覆盖率。实验结果表明,所提方法估计的覆盖率与基于真实位置坐标测量的覆盖率相近,度量准确度明显优于现有的其他方法。
基金the National Natural Science Foundation of China under Grants Nos.51261120377 and 51008173
文摘To study the seismic behavior of high strength concrete fi lled double-tube(CFDT) columns,each consisting of an external square steel tube and an internal circular steel tube,quasi-static tests on eight CFDT column specimens were conducted.The test variables included the width-to-thickness ratio(β1) and the area ratio(β2) of the square steel tube,the wall thickness of the circular steel tube,and the axial force(or the axial force ratio) applied to the CFDT columns.The test results indicate that for CFDT columns with a square steel tube with β1 of 50.1 and 24.5,local buckling of the specimen was found at a drift ratio of 1/150 and 1/50,respectively.The lateral force-displacement hysteretic loops of all specimens were plump and stable.Reducing the width-to-thickness ratio of the square steel tube,increasing its area ratio,or increasing the wall thickness of the internal circular steel tube,led to an increased fl exural strength and deformation capacity of the specimens.Increasing the design value of the axial force ratio from 0.8 to 1.0 may increase the fl exural strength of the specimens,while it may also decrease the ultimate deformation capacity of the specimen with β1 of 50.1.
基金the National Scholarship Fundthe National Natural Science Foundation of China(Nos.41704053,42174074,41674055)the East China University of Technology Research Foundation for Advanced Talents(ECUT)(DHBK2019084)for financial support。
文摘We calculated the crustal stress field using the composite focal mechanism method based on the P-wave initial motion polarity data of the Tengchong volcanic area from January 2011 to April 2019 obtained from the Bulletin of Seismological Observations of Chinese stations.The magnitude range of earthquakes used in this study is 0–4,and their magnitudes are mainly approximately 1.0.To investigate the infl uence of the source location on the stress fi eld and obtain reliable stress fi elds of the study area,we applied the double-diff erence algorithm to relocate the seismic events,obtaining more accurate and reliable relative positions of seismic events with a clearer seismic belt.On the basis of relocation results,the study on the stress fi eld along the fault zone was conducted,and the infl uence of seismic event position on the stress fi eld was analyzed.Results show that,fi rst,the current stress regime in the shallow crust of the Tengchong volcanic area is strike-slip faulting,the orientation of the principal compressive stress axis is NE–SW,the orientation of the principal extension stress axis is SE–NW,the principal compressive and extension stress axes are nearly horizontal,and the dip angle of intermediate principal stress axis is relatively large.This reflects that the volcanic and seismic activities in the Tengchong volcanic area are mainly controlled by the collision and squeezing eff ect of the Indian–Eurasian plate.It also refl ects that the current tensile action caused by deep magma activity has little infl uence on the shallow crustal stress field.Second,the stress field along fault zones reveals that there exist local stress fi elds,such as the thrust stress regime at the strike-slip fault terminal area,which is consistent with the compressional area at the intersection of conjugate strike-slip faults indicated by previous study.Third,the stress fi eld results are consistent,regardless of using the original location in the bulletin or the relocated location,indicating that the infl uence of the event location error can be neglected when there are suffi cient data and refl ecting the stability of the composite focal mechanism method.The findings can serve as a reference for investigating geological structure movement,seismic activities,and volcanic activities in the Tengchong volcanic area.
基金supported by the National Special Plan for the 13th Five-Year Plan of China(No.2017YFC0602204-10)Independent Exploration of the Innovation Project for Graduate Students at Central South University(No.2017zzts176)+3 种基金National Natural Science Foundation of China(Nos.41574127,41404106,and 41674075)Postdoctoral Fund Projects of China(No.2017M622608)National Key R&D Program of China(No.2018YFC0603602)Natural Science Youth Fund Project of the Hunan Province,China(No.2018JJ3642)
文摘Magnetic field gradient tensor technique provides abundant data for delicate inversion of subsurface magnetic susceptibility distribution. Large scale magnetic data inversion imaging requires high speed and accuracy for forward modeling. For arbitrarily distributed susceptibility data on an undulated surface, we propose a fast 3D forward modeling method in the wavenumber domain based on(1) the wavenumber-domain expression of the prism combination model and the Gauss–FFT algorithm and(2) cubic spline interpolation. We apply the proposed 3D forward modeling method to synthetic data and use weighting coefficients in the wavenumber domain to improve the modeling for multiple observation surfaces, and also demonstrate the accuracy and efficiency of the proposed method.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41804136, 41774156, 61773389)the Young Talent Fund of University Association for Science and Technology in Shaanxi,China (Grant No.20180702)
文摘Gravity and magnetic exploration areas are usually irregular,and there is some data defi ciency.Missing data must be interpolated before the vertical derivative conversion in the wavenumber domain.Meanwhile,for improved processing precision,the data need to be edge-padded to the length required by the fast Fourier transform algorithm.For conventional vertical derivative conversion of potential fi eld data(PFD),only vertical derivative conversion is considered,or interpolation,border padding,and vertical derivative conversion are executed independently.In this paper,these three steps are considered uniformly,and a vertical derivative conversion method for irregular-range PFD based on an improved projection onto convex sets method is proposed.The cutoff wavenumber of the filter used in the proposed method is determined by fractal model fi tting of the radial average power spectrum(RAPS)of the potential fi eld.Theoretical gravity models and real aeromagnetic data show the following:(1)The fitting of the RAPS with a fractal model can separate useful signals and noise reasonably.(2)The proposed iterative method has a clear physical sense,and its interpolation,border padding error,and running time are much smaller than those of the conventional kriging and minimum curvature methods.
基金supported by National Natural Science Foundation of China (No. 41574127, 42174080)Innovation research team project of Guangxi Natural Science Foundation (No. GXNSFGA380004)Central South University independent exploration and innovation project for Postgraduates (Nos. 2021zzts0831, 2021zzts0271)
文摘Large-scale,fine,and efficient numerical simulation of a geothermal field plays an important role in geothermal energy development.Confronted with the problem of large computation and high storage requirements for complex underground models in a three-dimensional(3-D)numerical simulation of a geothermal fi eld,a mixed space-wavenumber domain 3-D numerical simulation algorithm is proposed in this paper.According to the superposition principle of temperature field,the geothermal field is decomposed into background and abnormal temperature fi elds for calculation.The uniform layered model is used to solve the background field.When the abnormal field is solved,the horizontal two-dimensional(2-D)Fourier transform is used to transform the 3-D diff erential equation satisfi ed by an abnormal field into a series of one-dimensional ordinary differential equations with diff erent wavenumbers,which greatly reduces the calculation and storage.The unit division of an ordinary diff erential equation is fl exible,and the calculation amount is small.The algorithm fully takes advantage of the effi ciency of the Fourier transform and the quickness of the catch-up method to solve linear equations with a fixed bandwidth,which effectively improves the computational efficiency.Compared with the COMSOL Multiphysics professional simulation finite element software,the time consumption and memory requirements of the algorithm proposed in this paper are reduced by multiple orders of magnitude in terms of ensuring accuracy and the same mesh division.The more the number of calculated nodes is,the more obvious is the advantage.We design models to study the thermal conductivity,heat fl ux boundary,regional tectonic morphology,and topographic relief of the geothermal fi eld distribution.A 3-D geophysical model is developed based on topographic elevation data,geothermal geology,and geophysical exploration data in the Qiabuqia area of Gonghe Basin,Qinghai Province,China.Numerical simulation of the geothermal fi eld in this area is realized,which shows that the algorithm is suitable for precise and effi cient simulation of an arbitrary complex terrain and geological conditions.
基金This research is supported by the National Key Research and Development Program of China under Grant No.2018YFC1505401the Key Research and Development Projects of the Sichuan Science and Technology Department under Grant Nos.2019YFG0460,2020YFG0303,and 2021YJ0031+1 种基金the Technology Research and Development Program of China Railway Group Limited under Grant No.CZ01-Key Point-05the Fundamental Research Funds for the Central Universities under Grant No.2682021GF019.
文摘The downward continuation of potential fields is a process of calculating their values in a lower plane based on those of a certain plane.This technology is not only a data processing method for resource exploration but also plays an extremely important role in military applications.However,the downward continuation of potential fields is a typical linear inverse problem that is ill-posed.Generalized minimal residuals(GMRES)is an eff ective solution to ill-posed inverse problems,but it is unstable under the condition wherein the GMRES is directly applied in the calculation process.Moreover,the long-term behavior of its iterative computation is a disordered,divergent result.Therefore,to obtain stable solutions,GMRES is applied to solve the normal equations of the downward continuation of potential fields;it is also used to prequalify for occasional interruptions in the operation process by adding the damping coefficient,thus strengthening the stability conditions of the equations of residual minimization.Finally,the stable downward continuation of the potential fields method is proposed.As indicated by the theoretical data and the measured testing data,the method proposed in this paper has the advantages of high-precision and excellent stability.Furthermore,compared with the Tikhonov iteration method,the proposed method avoids the need to choose regularization parameters.