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Hidden feature extraction for unstructured agricultural environment based on supervised kernel locally linear embedding modeling

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Advances in Manufacturing 2018年第4期6卷 409-418页

作者： Zhong-Hua Miao Chen-Hui Ma Zhi-Yuan Gao Ming-Jun Wang Cheng-Liang Liu School of Mechatronic Engineering and Automation Shanghai University Shanghai 200072 People's Republic of China School of Mechanical Engineering Shanghai Jiao Tong University Shanghai 200240 People's Republic of China

An online hidden feature extraction algorithm is proposed for unknown and unstructured agricultural environments based on a supervised kernel locally linear embedding (SKLLE) algorithm. Firstly, an online obtaining method for scene training samples is given to obtain original feature data. Secondly, Bayesian estimation of the a posteriori probability of a cluster center is performed. Thirdly, nonlinear kernel mapping function construction is employed to map the original feature data to hyper-high dimensional kernel space. Fourthly, the automatic deter mination of hidden feature dimensions is performed using a local manifold learning algorithm. Then, a low-level manifold computation in hidden space is completed. Finally, long-range scene perception is realized using a 1-NN classifier. Experiments are conducted to show the effectiveness and the influence of parameter selection for the proposed algorithm. The kernel principal component analysis (KPCA), locally linear embedding (LLE), and supervised locally linear embedding (SLLE) methods are compared under the same experimental unstructured agricultural environment scene. Test results show that the proposed algorithm is more suitable for unstructured agricultural environments than other existing methods, and that the computational load is significantly reduced.

关键词： Long-range scene perception Hidden feature extraction Agricultural vehicle unstructured agricultural environment

A Coastal Ocean Model of Semi-Implicit Finite Volume unstructured Grid

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China Ocean Engineering 2012年第2期26卷 277-290页

作者：耿艳芬王志力 Transportation College Southeast University State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Nanjing Hydraulic Research Institute

A two-dimensional coastal ocean model based on unstructured C-grid is built, in which the momentum equation is discretized on the faces of each cell, and the continuity equation is discretized on the cell. The model is discretized by semi-implicit finite volume method, in that the free surface is semi-implicit and the bottom friction is implicit, thereby removing stability limitations associated with the surface gravity wave and friction. The remaining terms in the momentum equations are discretized explicitly by integral finite volume method and second-order Adams-Bashforth method. Tidal flow in the polar quadrant with known analytic solution is employed to test the proposed model. Finally, the performance of the present model to simulate tidal flow in a geometrically complex domain is examined by simulation of tidal currents in the Pearl River Estuary.

关键词： finite volume method unstructured C-grid coastal ocean modeling

WENO Schemes for Mixed-Element unstructured Meshes

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Communications in Computational Physics 2010年第8期8卷 585-609页

作者： V.A.Titarev P.Tsoutsanis D.Drikakis Fluid Mechanics and Computational Sciences Group Aerospace Sciences DepartmentCranfield UniversityCranfieldMK430ALUK

The paper extends weighted essentially non-oscillatory(WENO)schemes to two-dimensional quadrilateral and mixed-element unstructured *** key element of the proposed methods is a reconstruction procedure suitable for arbitrarilyshaped *** resulting schemes achieve the designed uniformly high-order of accuracy and compute discontinuous solutions without spurious oscillations at interfaces between cells of two different types.

关键词： WENO unstructured mixed-element triangular quadrilateral finite volume

Implicit unstructured-Mesh Method for Calculating Poiseuille Flows of Rarefied Gas

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Communications in Computational Physics 2010年第7期8卷 427-444页

作者： V.A.Titarev Fluid Mechanics and Computational Sciences Group Aerospace Sciences DepartmentCranfield UniversityCranfieldMK430ALUK

An implicit high-order accurate method for solving model kinetic equations is *** method is an extension of earlier work on the construction of an explicit TVD method for hybrid unstructured meshes in physical space and is illustrated on the Poiseuille flow of rarefied *** of calculations are provided for different Knudsen numbers and mesh resolutions,which illustrate the efficiency and high accuracy of the new scheme.

关键词： Poiseuille kinetic unstructured mixed-element micro rarefied implicit

3D magnetotelluric inversions with unstructured finite-element and limited-memory quasi-Newton methods

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Applied Geophysics 2018年第3期15卷 556-565页

作者： Cao Xiao-Yue Yin Chang-Chun Zhang Bo Huang Xin Liu Yun-He Cai Jing College of Geo-exploration Science and Technology Jilin UniversityChangchun 130026China Department of Earth Sciences Memorial University of NewfoundlandSt.John'sNLA1BCanada

Traditional 3D Magnetotelluric(MT) forward modeling and inversions are mostly based on structured meshes that have limited accuracy when modeling undulating surfaces and arbitrary structures. By contrast, unstructured-grid-based methods can model complex underground structures with high accuracy and overcome the defects of traditional methods, such as the high computational cost for improving model accuracy and the difficulty of inverting with topography. In this paper, we used the limited-memory quasi-Newton(L-BFGS) method with an unstructured finite-element grid to perform 3D MT inversions. This method avoids explicitly calculating Hessian matrices, which greatly reduces the memory requirements. After the first iteration, the approximate inverse Hessian matrix well approximates the true one, and the Newton step(set to 1) can meet the sufficient descent condition. Only one calculation of the objective function and its gradient are needed for each iteration, which greatly improves its computational efficiency. This approach is well-suited for large-scale 3D MT inversions. We have tested our algorithm on data with and without topography, and the results matched the real models well. We can recommend performing inversions based on an unstructured finite-element method and the L-BFGS method for situations with topography and complex underground structures.

关键词： Magnetotelluric(MT) 3D inversion unstructured fi nite-element method quasi-Newton method L-BFGS

Two Modified QUICK Schemes for Advection-Diffusion Equation of Pollutants on unstructured Grids

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Journal of Water Resource and Protection 2009年第5期1卷 362-367页

作者： Linghang XING 不详

In this paper, two modified QUICK schemes, namely Q-QUICK and UQ-QUICK, for improving the preci-sion of convective flux approximation are verified in advection-diffusion equation of pollutants on unstruc-tured grids. The constructed auxiliary nodes for Q-QUICK/UQ-QUICK are composed of two neighboring nodes plus the next upwind node, the later node is generated from intersection of the line of current neighboring nodes and their corresponding interfaces. 2D unsteady advection-diffusion equation of pollut-ants is conducted for their verifications on unstructured grids. The numerical results show that Q-QUICK and UQ-QUICK have similar computational accuracy to the central difference scheme and similar numerical stability to upwind difference scheme after applying the deferred correction method. In addition, their corre-sponding CPU times are approximately equivalent to those of traditional difference schemes and their abili-ties for adapting high grid deformation are robust.

关键词： unstructured Grids Q-QUICK/UQ-QUICK Numerical Computation Advection-Diffusion Equation of Pollutants

A Comparative Study of unstructured Data with SQL and NO-SQL Database Management Systems

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Journal of Computer and Communications 2020年第4期8卷 59-71页

作者： Ahsan Malik Aqil Burney Fawad Ahmed Department of Computer Science CCSIS Iobm Korangi Creek Karachi Pakistan

This paper aims to establish a relative study between a relational Microsoft SQL Server database and a non-relational MongoDB database within the unstructured representation of data in JSON format. There is a great amount of work done regarding comparison of multiple database management applications on the basis of their performances, security etc., but we have limited information available where these databases are assessed on the basis of provided data. This study will mainly focus on looking at all the possibilities that both these database types offer us when handling data in JSON. We will accomplish this by implementing a series of experiments while taking into consideration that the subjected data does not require to be normalized;and therefore, evaluate the outcome to conclude the result.

关键词： SQL NoSql MongoDB Databases unstructured Data JSON

A new numerical method on unstructured grids

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Science China(Physics,Mechanics & Astronomy) 2009年第12期52卷 2016-2026页

作者： WU WangYi & XIE WenJun State Key Laboratory for Turbulence and Complex System,Department of Mechanics and Aerospace Engineering,College of En-gineering,Peking University,Beijing 100871,China

A new numerical method-basic function method is proposed. This method can directly discrete differential operators on unstructured grids. By using the expansion of basic function to approach the exact function,the central and upwind schemes of derivative are constructed. By using the polynomial as basic function,applying the technique of flux splitting method and the combination of central and upwind schemes,the non-physical fluctuation near the shock wave is suppressed. The first-order basic function scheme of polynomial type for solving inviscid compressible flow numerically is constructed in this paper. Several numerical results of many typical examples for one-,two-and three-dimensional inviscid compressible steady flow illustrate that it is a new scheme with high accuracy and high resolution for shock wave. Especially,combining with the adaptive remeshing technique,the satisfactory results can be obtained by these schemes.

关键词： basic function scheme new numerical method unstructured grids

GENERATION AND APPLICATION OF unstructured ADAPTIVE MESHES WITH MOVING BOUNDARIES

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Transactions of Nanjing University of Aeronautics and Astronautics 2001年第Z1期18卷 56-59页

作者： Geng J. H.Department of Power Engineering,Nanjing University of Science & Technology Nanjing 210094,P.R.ChinaWu H. Z. (Department of Information, Nanjing University of Science & Technology Nanjing 210094,P.R.China) Department of Power Engineering Nanjing University of Science & Technology Nanjing 210094P. R. China Department of Information Nanjing University of Science & Technology Nanjing 210094P. R. China

This paper presents a method to generate unstructured adaptive meshes with moving boundaries and its application to CFD. Delaunay triangulation criterion in conjunction with the automatic point creation is used to generate 2 D and 3 D unstructured grids. A local grid regeneration method is proposed to cope with moving boundaries. Numerical examples include the interactions of shock waves with movable bodies and the movement of a projectile within a ram accelerator, illustrating an efficient and robust mesh generation method developed.

关键词： Delaunay triangulation adaptive unstructured grid moving boundary