Accurate measurement of the transverse position of a beam is crucial in particle accelerators because it plays a key role in determining the beam parameters.Existing methods for beam-position measurement rely on the d...Accurate measurement of the transverse position of a beam is crucial in particle accelerators because it plays a key role in determining the beam parameters.Existing methods for beam-position measurement rely on the detection of image currents induced on electrodes or narrow-band wake field induced by a beam passing through a cavity-type structure.However,these methods have limitations.The indirect measurement of multiple parameters is computationally complex,requiring external calibration to determine the system parameters in advance.Furthermore,the utilization of the beam signal information is incomplete.Hence,this study proposes a novel method for measuring the absolute electron beam transverse position.By utilizing the geometric relationship between the center position of the measured electron beam and multiple detection electrodes and by analyzing the differences in the arrival times of the beam signals detected by these electrodes,the absolute transverse position of the electron beam crossing the electrode plane can be calculated.This method features absolute position measurement,a position sensitivity coefficient independent of vacuum chamber apertures,and no requirement for a symmetrical detector electrode layout.The feasibility of this method is validated through numerical simulations and beam experiments.展开更多
Road Side Units(RSUs)are the essential component of vehicular communication for the objective of improving safety and mobility in the road transportation.RSUs are generally deployed at the roadside and more specifical...Road Side Units(RSUs)are the essential component of vehicular communication for the objective of improving safety and mobility in the road transportation.RSUs are generally deployed at the roadside and more specifically at the intersections in order to collect traffic information from the vehicles and disseminate alarms and messages in emergency situations to the neighborhood vehicles cooperating with the network.However,the development of a predominant RSUs placement algorithm for ensuring competent communication in VANETs is a challenging issue due to the hindrance of obstacles like water bodies,trees and buildings.In this paper,Ruppert’s Delaunay Triangulation Refinement Scheme(RDTRS)for optimal RSUs placement is proposed for accurately estimating the optimal number of RSUs that has the possibility of enhancing the area of coverage during data communication.This RDTRS is proposed by considering the maximum number of factors such as global coverage,intersection popularity,vehicle density and obstacles present in the map for optimal RSUs placement,which is considered as the core improvement over the existing RSUs optimal placement strategies.It is contributed for deploying requisite RSUs with essential transmission range for maximal coverage in the convex map such that each position of the map could be effectively covered by at least one RSU in the presence of obstacles.The simulation experiments of the proposed RDTRS are conducted with complex road traffic environments.The results of this proposed RDTRS confirmed its predominance in reducing the end-to-end delay by 21.32%,packet loss by 9.38%with improved packet delivery rate of 10.68%,compared to the benchmarked schemes.展开更多
To alleviate the distortion of XRII X-ray image intensifier images in the C-arm CT computer tomography imaging system an algorithm based on the Delaunay triangulation interpolation is proposed.First the causes of the ...To alleviate the distortion of XRII X-ray image intensifier images in the C-arm CT computer tomography imaging system an algorithm based on the Delaunay triangulation interpolation is proposed.First the causes of the phenomenon the classical correction algorithms and the Delaunay triangulation interpolation are analyzed.Then the algorithm procedure is explained using flow charts and illustrations. Finally experiments are described to demonstrate its effectiveness and feasibility. Experimental results demonstrate that the Delaunay triangulation interpolation can have the following effects.In the case of the same center the root mean square distances RMSD and standard deviation STD between the corrected image with Delaunay triangulation interpolation and the ideal image are 5.760 4 ×10 -14 and 5.354 2 ×10 -14 respectively.They increase to 1.790 3 2.388 8 2.338 8 and 1.262 0 1.268 1 1.202 6 after applying the quartic polynomial model L1 and model L2 to the distorted images respectively.The RMSDs and STDs between the corrected image with the Delaunay triangulation interpolation and the ideal image are 2.489 × 10 -13 and 2.449 8 ×10 -13 when their centers do not coincide. When the quartic polynomial model L1 and model L2 are applied to the distorted images they are 1.770 3 2.388 8 2.338 8 and 1.269 9 1.268 1 1.202 6 respectively.展开更多
According to the theory of laser triangulation measurement,it can be used to test not only plane but also curving surface profile. As a non-contact measurement of optic-electro on a single spot,its advantages are high...According to the theory of laser triangulation measurement,it can be used to test not only plane but also curving surface profile. As a non-contact measurement of optic-electro on a single spot,its advantages are high measurement speed,high precision,great anti-jamming,small measurement spot,easy operation,wide application range and so on. Laser triangulation measurement based on PSD makes system perfect with small volume,high sensitivity,low noise,high resolution. The system’s precision is above 0.5%. It shows that with simpler specified PSD software it can be found a convenient way to optimize system design,improve reliability,shrink volume,reduce power and shorten exploitation period.展开更多
A method for quality mesh generation of parametric curved surfaces isproposed. It is shown that the main difference between the proposed method and previous ones is thatour meshing process is done completely in the pa...A method for quality mesh generation of parametric curved surfaces isproposed. It is shown that the main difference between the proposed method and previous ones is thatour meshing process is done completely in the parametric domains with the guarantee of meshquality. To obtain this aim, the Delaunay method is extended to anisotropic context of 2D domains,and a Riemannian metric map is introduced to remedy the mapping distortion from object space toparametric domain. Compared with previous algorithms, the approach is much simpler, more robust andspeedy. The algorithm is implemented and examples for several geometries are presented todemonstrate the efficiency and validity of the method.展开更多
The paper presents the utilization of the adaptive Delaunay triangulation in the finite element modeling of two dimensional crack propagation problems, including detailed description of the proposed procedure which co...The paper presents the utilization of the adaptive Delaunay triangulation in the finite element modeling of two dimensional crack propagation problems, including detailed description of the proposed procedure which consists of the Delaunay triangulation algorithm and an adaptive remeshing technique. The adaptive remeshing technique generates small elements around crack tips and large elements in the other regions. The resulting stress intensity factors and simulated crack propagation behavior are used to evaluate the effectiveness of the procedure. Three sample problems of a center cracked plate, a single edge cracked plate and a compact tension specimen, are simulated and their results assessed.展开更多
A new deghosting method based on the generalized triangulation is presented. First, two intersection points corresponding to the emitter position are obtained by utilizing two azimuth angles and two elevation angles f...A new deghosting method based on the generalized triangulation is presented. First, two intersection points corresponding to the emitter position are obtained by utilizing two azimuth angles and two elevation angles from two jammed 3-D radars （or 2-D passive sensors）. Then, hypothesis testing based deghosting method in the multiple target scenarios is proposed using the two intersection points. In order to analyze the performance of the proposed method, the correct association probability of the true targets and the incorrect association probability of the ghost targets are defined. Finally, the Monte Carlo simulations are given for the proposed method compared with the hinge angle method in the cases of both two and three radars. The simulation results show that the proposed method has better performance than the hinge angle method in three radars case.展开更多
The triangulation of red sprites was obtained, based on concurrent observations over a mesoscale convective system(MCS) in North China from two stations separated by about 450 km. In addition, broadband sferics from t...The triangulation of red sprites was obtained, based on concurrent observations over a mesoscale convective system(MCS) in North China from two stations separated by about 450 km. In addition, broadband sferics from the sprite-producing lightning were measured at five ground stations, making it possible to locate and identify the individual causative lightning discharges for different elements in this dancing sprite event. The results of our analyses indicate that the sprites were produced above the trailing stratiform region of the MCS, and their parent strokes were located mainly in the peripheral area of the stratiform. The lateral offset between sprites and causative strokes ranges from a few km to more than 50 km. In a particularly bright sprite, with a distinct halo feature and streamers descending down to an altitude of approximately 48 km, the sprite current signal identified in the electric sferic, measured at a range of about 1,110 km, peaked at approximately 1 ms after the return stroke.展开更多
Incremental algorithm is one of the most popular procedures for constructing Delaunay triangulations （DTs）. However, the point insertion sequence has a great impact on the amount of work needed for the construction ...Incremental algorithm is one of the most popular procedures for constructing Delaunay triangulations （DTs）. However, the point insertion sequence has a great impact on the amount of work needed for the construction of DTs. It affects the time for both point location and structure update, and hence the overall computational time of the triangulation algorithm. In this paper, a simple deterministic insertion sequence is proposed based on the breadth-first-search on a Kd-tree with some minor modifications for better performance. Using parent nodes as search-hints, the proposed insertion sequence proves to be faster and more stable than the Hilbert curve order and biased randomized insertion order （BRIO）, especially for non-uniform point distributions over a wide range of benchmark examples.展开更多
Boundary recovery is one of the main obstacles in applying the Delaunay criterion to mesh generation. A stan- dard resolution is to add Steiner points directly at the intersection positions between missing boundaries ...Boundary recovery is one of the main obstacles in applying the Delaunay criterion to mesh generation. A stan- dard resolution is to add Steiner points directly at the intersection positions between missing boundaries and triangulations. We redesign the algorithm with the aid of some new concepts, data structures and operations, which make its implementation routine. Furthermore, all possible intersection cases and their solutions are presented, some of which are seldom discussed in the litera- ture. Finally, numerical results are presented to evaluate the performance of the new algorithm.展开更多
It is important to quantify and analyze forest spatial patterns for studying biological characteristics,population interaction and the relationship between the population and environment.In this study,the forest spati...It is important to quantify and analyze forest spatial patterns for studying biological characteristics,population interaction and the relationship between the population and environment.In this study,the forest spatial structure unit was generated based on the Delaunay triangulation model(DTM),and the weights were generated using the comprehensive values of the tree diameter at breast height,total height and crown width.The distance between neighbors determined by the DTM was weighted to transform the original coordinates of trees into logical coordinates.Then,a weighted spatial pattern(WSP)was developed.After weighting,the neighboring trees were replaced,the replacement ratio was 38.3%,and there was 57.4%of the central tree.Correlation analysis showed that the uniform angle index of the WSP was significantly correlated with the tree size standard deviation under uniformity(r=0.932)and randomness(r=0.711).The DTM method not only considers the spatial distance between trees,but also considers the non-spatial attributes of trees.By changing the spatial topological relation between trees,this method further improves the spatial structure measurement of forest.展开更多
Adaptive Delaunay triangulation is combined with the cell-centered upwinding algorithm to analyze inviscid high-speed compressible flow problems. The multidimensional dissipation scheme was developed and included in t...Adaptive Delaunay triangulation is combined with the cell-centered upwinding algorithm to analyze inviscid high-speed compressible flow problems. The multidimensional dissipation scheme was developed and included in the upwinding algorithm for unstructured triangular meshes to improve the computed shock wave resolution. The solution accuracy is further improved by coupling an error estimation procedure to a remeshing algorithm that generates small elements in regions with large change of solution gradients, and at the same time, larger elements in other regions. The proposed scheme is further extended to achieve higher-order spatial and temporal solution accuracy. Efficiency of the combined procedure is evaluated by analyzing supersonic shocks and shock propagation behaviors for both the steady and unsteady high-speed compressible flows.展开更多
In the paper, an improved algorithm is presented for Delaunay triangulation of the point-set in the plain. Based on the original algorithm, we propose the notion of removing circle. During the process of triangulation...In the paper, an improved algorithm is presented for Delaunay triangulation of the point-set in the plain. Based on the original algorithm, we propose the notion of removing circle. During the process of triangulation, and the circle dynamically moves, the algorithm which is simple and practical, therefore evidently accelerates the process of searching a new point, while generating a new triangle. Then it shows the effect of the algorithm in the finite element mesh.展开更多
Exploratory data analysis is increasingly more necessary as larger spatial data is managed in electro-magnetic media. Spatial clustering is one of the very important spatial data mining techniques which is the discove...Exploratory data analysis is increasingly more necessary as larger spatial data is managed in electro-magnetic media. Spatial clustering is one of the very important spatial data mining techniques which is the discovery of interesting rela-tionships and characteristics that may exist implicitly in spatial databases. So far, a lot of spatial clustering algorithms have been proposed in many applications such as pattern recognition, data analysis, and image processing and so forth. However most of the well-known clustering algorithms have some drawbacks which will be presented later when ap-plied in large spatial databases. To overcome these limitations, in this paper we propose a robust spatial clustering algorithm named NSCABDT (Novel Spatial Clustering Algorithm Based on Delaunay Triangulation). Delaunay dia-gram is used for determining neighborhoods based on the neighborhood notion, spatial association rules and colloca-tions being defined. NSCABDT demonstrates several important advantages over the previous works. Firstly, it even discovers arbitrary shape of cluster distribution. Secondly, in order to execute NSCABDT, we do not need to know any priori nature of distribution. Third, like DBSCAN, Experiments show that NSCABDT does not require so much CPU processing time. Finally it handles efficiently outliers.展开更多
Rotationally symmetric triangulation(RST)sensor has more flexibility and less uncertainty limits because of the abaxial rotationally symmetric optical system.But if the incident laser is eccentric,the symmetry of the ...Rotationally symmetric triangulation(RST)sensor has more flexibility and less uncertainty limits because of the abaxial rotationally symmetric optical system.But if the incident laser is eccentric,the symmetry of the image will descend,and it will result in the eccentric error especially when some part of the imaged ring is blocked.The model of rotationally symmetric triangulation that meets the Schimpflug condition is presented in this paper.The error from eccentric incident laser is analysed.It is pointed out that the eccentric error is composed of two parts,one is a cosine in circumference and proportional to the eccentric departure factor,and the other is a much smaller quadric factor of the departure.When the ring is complete,the first error factor is zero because it is integrated in whole ring, but if some part of the ring is blocked,the first factor will be the main error.Simulation verifies the result of the a- nalysis.At last,a compensation method to the error when some part of the ring is lost is presented based on neural network.The results of experiment show that the compensation will make the absolute maximum error descend to half,and the standard deviation of error descends to 1/3.展开更多
Laser triangulation theory was used to develop a novel contact-free method for measuring the coal level in a silo under harsh environmental conditions found in coal mines, such as the presence of dense dust, high humi...Laser triangulation theory was used to develop a novel contact-free method for measuring the coal level in a silo under harsh environmental conditions found in coal mines, such as the presence of dense dust, high humidity, and low illumination. A laser source and a camera were mounted at the top of the silo. The laser spot projected into the silo was imaged by the camera. The pinhole imaging principle allows the level to be found from the lateral shift of the spot image on the sensor. A pre-calibrated look-up table of the coal depth versus spot position was used to obtain the depth. The measurement accuracy depends on the step size used during pre-calibration. The actual application of a device designed according to these principles shows that it is easy to implement. The detection of the coal level in a silo at the low illumination level found in coal mines is demonstrated.展开更多
An algorithm of trimmed surface triangulation is put forward by using the isoparametric curves of aircraft surfaces to evenly allocate the mesh nodes. Further refinements are made to deal with the trimming loops and e...An algorithm of trimmed surface triangulation is put forward by using the isoparametric curves of aircraft surfaces to evenly allocate the mesh nodes. Further refinements are made to deal with the trimming loops and ensure the mesh consistency.展开更多
A new method of view synthesis is proposed based on Delaunay triangulation. The first step of this method is making the Delaunay triangulation of 2 reference images. Secondly, matching the image points using the epipo...A new method of view synthesis is proposed based on Delaunay triangulation. The first step of this method is making the Delaunay triangulation of 2 reference images. Secondly, matching the image points using the epipolar geometry constraint. Finally, constructing the third view according to pixel transferring under the trilinear constraint. The method gets rid of the classic time consuming dense matching technique and takes advantage of Delaunay triangulation. So it can not only save the computation time but also enhance the quality of the synthesized view. The significance of this method is that it can be used directly in the fields of video coding, image compressing and virtual reality.展开更多
A harmonic condition that can distinguish whether the dimension of spline space S 1 3( △ ) depends on the geometrical character of triangulation is presented, then on a type of general triangulation the dimension...A harmonic condition that can distinguish whether the dimension of spline space S 1 3( △ ) depends on the geometrical character of triangulation is presented, then on a type of general triangulation the dimension is got.展开更多
基金supported by the National Key R&D Program of China(No.2022YFA1602201)。
文摘Accurate measurement of the transverse position of a beam is crucial in particle accelerators because it plays a key role in determining the beam parameters.Existing methods for beam-position measurement rely on the detection of image currents induced on electrodes or narrow-band wake field induced by a beam passing through a cavity-type structure.However,these methods have limitations.The indirect measurement of multiple parameters is computationally complex,requiring external calibration to determine the system parameters in advance.Furthermore,the utilization of the beam signal information is incomplete.Hence,this study proposes a novel method for measuring the absolute electron beam transverse position.By utilizing the geometric relationship between the center position of the measured electron beam and multiple detection electrodes and by analyzing the differences in the arrival times of the beam signals detected by these electrodes,the absolute transverse position of the electron beam crossing the electrode plane can be calculated.This method features absolute position measurement,a position sensitivity coefficient independent of vacuum chamber apertures,and no requirement for a symmetrical detector electrode layout.The feasibility of this method is validated through numerical simulations and beam experiments.
文摘Road Side Units(RSUs)are the essential component of vehicular communication for the objective of improving safety and mobility in the road transportation.RSUs are generally deployed at the roadside and more specifically at the intersections in order to collect traffic information from the vehicles and disseminate alarms and messages in emergency situations to the neighborhood vehicles cooperating with the network.However,the development of a predominant RSUs placement algorithm for ensuring competent communication in VANETs is a challenging issue due to the hindrance of obstacles like water bodies,trees and buildings.In this paper,Ruppert’s Delaunay Triangulation Refinement Scheme(RDTRS)for optimal RSUs placement is proposed for accurately estimating the optimal number of RSUs that has the possibility of enhancing the area of coverage during data communication.This RDTRS is proposed by considering the maximum number of factors such as global coverage,intersection popularity,vehicle density and obstacles present in the map for optimal RSUs placement,which is considered as the core improvement over the existing RSUs optimal placement strategies.It is contributed for deploying requisite RSUs with essential transmission range for maximal coverage in the convex map such that each position of the map could be effectively covered by at least one RSU in the presence of obstacles.The simulation experiments of the proposed RDTRS are conducted with complex road traffic environments.The results of this proposed RDTRS confirmed its predominance in reducing the end-to-end delay by 21.32%,packet loss by 9.38%with improved packet delivery rate of 10.68%,compared to the benchmarked schemes.
基金The Natural Science Foundation of Anhui Province(No.1308085MF96)the Project of Chuzhou University(No.2012qd06,2011kj010B)+1 种基金the Scientific Research Foundation of Education Department of Anhui Province(No.KJ2014A186)the National Basic Research Program of China(973 Program)(No.2010CB732503)
文摘To alleviate the distortion of XRII X-ray image intensifier images in the C-arm CT computer tomography imaging system an algorithm based on the Delaunay triangulation interpolation is proposed.First the causes of the phenomenon the classical correction algorithms and the Delaunay triangulation interpolation are analyzed.Then the algorithm procedure is explained using flow charts and illustrations. Finally experiments are described to demonstrate its effectiveness and feasibility. Experimental results demonstrate that the Delaunay triangulation interpolation can have the following effects.In the case of the same center the root mean square distances RMSD and standard deviation STD between the corrected image with Delaunay triangulation interpolation and the ideal image are 5.760 4 ×10 -14 and 5.354 2 ×10 -14 respectively.They increase to 1.790 3 2.388 8 2.338 8 and 1.262 0 1.268 1 1.202 6 after applying the quartic polynomial model L1 and model L2 to the distorted images respectively.The RMSDs and STDs between the corrected image with the Delaunay triangulation interpolation and the ideal image are 2.489 × 10 -13 and 2.449 8 ×10 -13 when their centers do not coincide. When the quartic polynomial model L1 and model L2 are applied to the distorted images they are 1.770 3 2.388 8 2.338 8 and 1.269 9 1.268 1 1.202 6 respectively.
文摘According to the theory of laser triangulation measurement,it can be used to test not only plane but also curving surface profile. As a non-contact measurement of optic-electro on a single spot,its advantages are high measurement speed,high precision,great anti-jamming,small measurement spot,easy operation,wide application range and so on. Laser triangulation measurement based on PSD makes system perfect with small volume,high sensitivity,low noise,high resolution. The system’s precision is above 0.5%. It shows that with simpler specified PSD software it can be found a convenient way to optimize system design,improve reliability,shrink volume,reduce power and shorten exploitation period.
基金This project is supported by National Natural Science Foundation of China(No.59990470).
文摘A method for quality mesh generation of parametric curved surfaces isproposed. It is shown that the main difference between the proposed method and previous ones is thatour meshing process is done completely in the parametric domains with the guarantee of meshquality. To obtain this aim, the Delaunay method is extended to anisotropic context of 2D domains,and a Riemannian metric map is introduced to remedy the mapping distortion from object space toparametric domain. Compared with previous algorithms, the approach is much simpler, more robust andspeedy. The algorithm is implemented and examples for several geometries are presented todemonstrate the efficiency and validity of the method.
文摘The paper presents the utilization of the adaptive Delaunay triangulation in the finite element modeling of two dimensional crack propagation problems, including detailed description of the proposed procedure which consists of the Delaunay triangulation algorithm and an adaptive remeshing technique. The adaptive remeshing technique generates small elements around crack tips and large elements in the other regions. The resulting stress intensity factors and simulated crack propagation behavior are used to evaluate the effectiveness of the procedure. Three sample problems of a center cracked plate, a single edge cracked plate and a compact tension specimen, are simulated and their results assessed.
基金supported partly by the Foundation for the Author of National Excellent Doctoral Dissertation of China(200443)the National Natural Science Foundation of China(60541001)+1 种基金the Program for New Century Excellent Talents inUniversity(05-0912)the Foundation of Taishan Scholars.
文摘A new deghosting method based on the generalized triangulation is presented. First, two intersection points corresponding to the emitter position are obtained by utilizing two azimuth angles and two elevation angles from two jammed 3-D radars （or 2-D passive sensors）. Then, hypothesis testing based deghosting method in the multiple target scenarios is proposed using the two intersection points. In order to analyze the performance of the proposed method, the correct association probability of the true targets and the incorrect association probability of the ghost targets are defined. Finally, the Monte Carlo simulations are given for the proposed method compared with the hinge angle method in the cases of both two and three radars. The simulation results show that the proposed method has better performance than the hinge angle method in three radars case.
基金supported by the National Key Basic Research and Development Program (2017YFC1501501)National Natural Science Foundation of China (41574179, 41875006)+4 种基金National Natural Science Foundation for Excellent Youth of China (41622501)"The Hundred Talents Program" of Chinese Academy of Sciences (2013068)supported by funding from the NOAA Office of Global Programs for the Global Precipitation Climatology Project (GPCP)by NASA via the Tropical Rainfall Measuring Mission (TRMM)supported by NASA's HQ Earth S cience Data Systems (ESDS) Program
文摘The triangulation of red sprites was obtained, based on concurrent observations over a mesoscale convective system(MCS) in North China from two stations separated by about 450 km. In addition, broadband sferics from the sprite-producing lightning were measured at five ground stations, making it possible to locate and identify the individual causative lightning discharges for different elements in this dancing sprite event. The results of our analyses indicate that the sprites were produced above the trailing stratiform region of the MCS, and their parent strokes were located mainly in the peripheral area of the stratiform. The lateral offset between sprites and causative strokes ranges from a few km to more than 50 km. In a particularly bright sprite, with a distinct halo feature and streamers descending down to an altitude of approximately 48 km, the sprite current signal identified in the electric sferic, measured at a range of about 1,110 km, peaked at approximately 1 ms after the return stroke.
基金supported by the National Natural Science Foundation of China (10972006 and 11172005)the National Basic Research Program of China (2010CB832701)
文摘Incremental algorithm is one of the most popular procedures for constructing Delaunay triangulations （DTs）. However, the point insertion sequence has a great impact on the amount of work needed for the construction of DTs. It affects the time for both point location and structure update, and hence the overall computational time of the triangulation algorithm. In this paper, a simple deterministic insertion sequence is proposed based on the breadth-first-search on a Kd-tree with some minor modifications for better performance. Using parent nodes as search-hints, the proposed insertion sequence proves to be faster and more stable than the Hilbert curve order and biased randomized insertion order （BRIO）, especially for non-uniform point distributions over a wide range of benchmark examples.
基金Project (No. 60225009) supported by the National Natural ScienceFoundation of China through the National Science Fund for Distin-guished Young Scholars
文摘Boundary recovery is one of the main obstacles in applying the Delaunay criterion to mesh generation. A stan- dard resolution is to add Steiner points directly at the intersection positions between missing boundaries and triangulations. We redesign the algorithm with the aid of some new concepts, data structures and operations, which make its implementation routine. Furthermore, all possible intersection cases and their solutions are presented, some of which are seldom discussed in the litera- ture. Finally, numerical results are presented to evaluate the performance of the new algorithm.
基金funded by National Natural Science Foundation of China(31570627)Hunan Forestry Science and Technology Project(XLK201740)+1 种基金Hunan Science and Technology Innovation Platform and Talent Plan(2017TP1022)Hunan Science and Technology Plan Project(2015WK3017)。
文摘It is important to quantify and analyze forest spatial patterns for studying biological characteristics,population interaction and the relationship between the population and environment.In this study,the forest spatial structure unit was generated based on the Delaunay triangulation model(DTM),and the weights were generated using the comprehensive values of the tree diameter at breast height,total height and crown width.The distance between neighbors determined by the DTM was weighted to transform the original coordinates of trees into logical coordinates.Then,a weighted spatial pattern(WSP)was developed.After weighting,the neighboring trees were replaced,the replacement ratio was 38.3%,and there was 57.4%of the central tree.Correlation analysis showed that the uniform angle index of the WSP was significantly correlated with the tree size standard deviation under uniformity(r=0.932)and randomness(r=0.711).The DTM method not only considers the spatial distance between trees,but also considers the non-spatial attributes of trees.By changing the spatial topological relation between trees,this method further improves the spatial structure measurement of forest.
文摘Adaptive Delaunay triangulation is combined with the cell-centered upwinding algorithm to analyze inviscid high-speed compressible flow problems. The multidimensional dissipation scheme was developed and included in the upwinding algorithm for unstructured triangular meshes to improve the computed shock wave resolution. The solution accuracy is further improved by coupling an error estimation procedure to a remeshing algorithm that generates small elements in regions with large change of solution gradients, and at the same time, larger elements in other regions. The proposed scheme is further extended to achieve higher-order spatial and temporal solution accuracy. Efficiency of the combined procedure is evaluated by analyzing supersonic shocks and shock propagation behaviors for both the steady and unsteady high-speed compressible flows.
文摘In the paper, an improved algorithm is presented for Delaunay triangulation of the point-set in the plain. Based on the original algorithm, we propose the notion of removing circle. During the process of triangulation, and the circle dynamically moves, the algorithm which is simple and practical, therefore evidently accelerates the process of searching a new point, while generating a new triangle. Then it shows the effect of the algorithm in the finite element mesh.
文摘Exploratory data analysis is increasingly more necessary as larger spatial data is managed in electro-magnetic media. Spatial clustering is one of the very important spatial data mining techniques which is the discovery of interesting rela-tionships and characteristics that may exist implicitly in spatial databases. So far, a lot of spatial clustering algorithms have been proposed in many applications such as pattern recognition, data analysis, and image processing and so forth. However most of the well-known clustering algorithms have some drawbacks which will be presented later when ap-plied in large spatial databases. To overcome these limitations, in this paper we propose a robust spatial clustering algorithm named NSCABDT (Novel Spatial Clustering Algorithm Based on Delaunay Triangulation). Delaunay dia-gram is used for determining neighborhoods based on the neighborhood notion, spatial association rules and colloca-tions being defined. NSCABDT demonstrates several important advantages over the previous works. Firstly, it even discovers arbitrary shape of cluster distribution. Secondly, in order to execute NSCABDT, we do not need to know any priori nature of distribution. Third, like DBSCAN, Experiments show that NSCABDT does not require so much CPU processing time. Finally it handles efficiently outliers.
基金Supported by China Scholarship Council(CSC),Deutscher Akademischer Austausch Dienst(DAAD),National Natural Science Foundation of China(60375011,60575028)Natural Science Foundation of Anhui Province(04042044)Supported by Program for New Century Excellent Talents in University(NCET-04-0560)
文摘Rotationally symmetric triangulation(RST)sensor has more flexibility and less uncertainty limits because of the abaxial rotationally symmetric optical system.But if the incident laser is eccentric,the symmetry of the image will descend,and it will result in the eccentric error especially when some part of the imaged ring is blocked.The model of rotationally symmetric triangulation that meets the Schimpflug condition is presented in this paper.The error from eccentric incident laser is analysed.It is pointed out that the eccentric error is composed of two parts,one is a cosine in circumference and proportional to the eccentric departure factor,and the other is a much smaller quadric factor of the departure.When the ring is complete,the first error factor is zero because it is integrated in whole ring, but if some part of the ring is blocked,the first factor will be the main error.Simulation verifies the result of the a- nalysis.At last,a compensation method to the error when some part of the ring is lost is presented based on neural network.The results of experiment show that the compensation will make the absolute maximum error descend to half,and the standard deviation of error descends to 1/3.
基金supported by the National Natural Science Foun-dation of China (No. 51074169)
文摘Laser triangulation theory was used to develop a novel contact-free method for measuring the coal level in a silo under harsh environmental conditions found in coal mines, such as the presence of dense dust, high humidity, and low illumination. A laser source and a camera were mounted at the top of the silo. The laser spot projected into the silo was imaged by the camera. The pinhole imaging principle allows the level to be found from the lateral shift of the spot image on the sensor. A pre-calibrated look-up table of the coal depth versus spot position was used to obtain the depth. The measurement accuracy depends on the step size used during pre-calibration. The actual application of a device designed according to these principles shows that it is easy to implement. The detection of the coal level in a silo at the low illumination level found in coal mines is demonstrated.
文摘An algorithm of trimmed surface triangulation is put forward by using the isoparametric curves of aircraft surfaces to evenly allocate the mesh nodes. Further refinements are made to deal with the trimming loops and ensure the mesh consistency.
文摘A new method of view synthesis is proposed based on Delaunay triangulation. The first step of this method is making the Delaunay triangulation of 2 reference images. Secondly, matching the image points using the epipolar geometry constraint. Finally, constructing the third view according to pixel transferring under the trilinear constraint. The method gets rid of the classic time consuming dense matching technique and takes advantage of Delaunay triangulation. So it can not only save the computation time but also enhance the quality of the synthesized view. The significance of this method is that it can be used directly in the fields of video coding, image compressing and virtual reality.
文摘A harmonic condition that can distinguish whether the dimension of spline space S 1 3( △ ) depends on the geometrical character of triangulation is presented, then on a type of general triangulation the dimension is got.
