A hybrid method for inversion of 3D AC resistivity logging measurements

In this paper, we propose the use of a hybrid algorithm for the inversion of 3D Alternate Current (AC) resistivity logging measurements. The forward problem is solved using a goal-oriented self-adaptive hp-Finite Element Method (hp-FEM) that provides exponential convergence of the numerical error with respect to the mesh size. The inverse problem is solved using a Hierarchical Genetic Search (HGS) coupled with a Broyden–Fletcher–Goldfar–Shanno (BFGS) method. Individuals from the genetic populations represent the resistivity of the formation layers. The fitness function is estimated based on hp-FEM results. The hybrid method controls the accuracy of evaluation of particular individuals, as well as the accuracy of the genetic coding. After finding those regions where the fitness function has small values, the local search method by means of BFGS algorithm is executed. The paper is concluded with numerical results for the hybrid algorithm.     

Using artificial neural networks to invert 2D DC resistivity imaging data for high resistivity contrast regions: A MATLAB application

MATLAB is a high-level matrix/array language with control flow statements and functions. MATLAB has several useful toolboxes to solve complex problems in various fields of science, such as geophysics. In geophysics, the inversion of 2D DC resistivity imaging data is complex due to its non-linearity, especially for high resistivity contrast regions. In this paper, we investigate the applicability of MATLAB to design, train and test a newly developed artificial neural network in inverting 2D DC resistivity imaging data. We used resilient propagation to train the network. The model used to produce synthetic data is a homogeneous medium of 100 Ω m resistivity with an embedded anomalous body of 1000 Ω m. The location of the anomalous body was moved to different positions within the homogeneous model mesh elements. The synthetic data were generated using a finite element forward modeling code by means of the RES2DMOD. The network was trained using 21 datasets and tested on another 16 synthetic datasets, as well as on real field data. In field data acquisition, the cable covers 120 m between the first and the last take-out, with a 3 m x-spacing. Three different electrode spacings were measured, which gave a dataset of 330 data points. The interpreted result shows that the trained network was able to invert 2D electrical resistivity imaging data obtained by a Wenner–Schlumberger configuration rapidly and accurately.     

A hybrid method based on linear programming and tabu search for routing of logging trucks

In this paper, we consider an operational routing problem to decide the daily routes of logging trucks in forestry. This industrial problem is difficult and includes aspects such as pickup and delivery with split pickups, multiple products, time windows, several time periods, multiple depots, driver changes and a heterogeneous truck fleet. In addition, the problem size is large and the solution time limited. We describe a two-phase solution approach which transforms the problem into a standard vehicle routing problem with time windows. In the first phase, we solve an LP problem in order to find a destination of flow from supply points to demand points. Based on this solution, we create transport nodes which each defines the origin(s) and destination for a full truckload. In phase two, we make use of a standard tabu search method to combine these transport nodes, which can be considered to be customers in vehicle routing problems, into actual routes. The tabu search method is extended to consider some new features. The solution approach is tested on a set of industrial cases from major forest companies in Sweden.     

A new hybrid method for 3D object recovery from 2D drawings and its validation against the cubic corner method and the optimisation-based method

This paper uses a hybrid method to reconstruct 3D polyhedral objects from 2D line drawings by combining two known methods, the cubic corner method and the optimisation-based method, and presents comprehensive test results comparing the three methods. The cubic corner method is deterministic and very efficient. It recovers accurate 3D objects from accurate drawings but for inaccurate drawings, the quality of its results varies with the accuracy of the input. In general, the optimisation-based method produces approximate 3D objects that conform to human perception of the drawings. But it is computationally demanding, and can sometimes converge to incorrect results, partly due to poor initial values for the optimisation. The hybrid method starts with the cubic corner method, and uses its output as the initial guess for the optimisation process, which then produces a better quality 3D object than either method on its own. Tests are conducted for each method using drawings of varying degrees of accuracy. The results of the cubic corner method and the hybrid method are consistent, with accurate inputs producing good results and inaccurate input producing poor results. The results of the optimisation-based method are inconsistent. The hybrid method produces the best results in general, but it is less efficient than the cubic corner method and more efficient than the optimisation-based method.     

全桥DC/DC电源模块三维组装技术研究

针对宇航DC/DC电源的体积和重量已接近极限的现状,设计了一种新型的三维立体组装电源模块,将各种器件以不同的堆叠和互连方式在三维空间内进行组装,使用裸芯片替代分立器件,采用陶瓷基板和柔性电路实现阻容器件预埋和板间堆叠互连,解决集成密度提高后功率变换电路的组装工艺、高效散热等问题。建立模态和振动模型分析模块内部的器件布局和受力情况,对模块的力学性能进行了验证。完成了开关频率为100 kHz、输入50～70 V、输出功率120 W的DC/DC功率开关电源的研制,相同输出功率下比现用模块化电源体积减小50%。     

A retargeting method for stereoscopic 3D video

Computational Visual Media - We propose a disparity-constrained retargeting method for stereoscopic 3D video, which simultaneously resizes a binocular video to a new aspect ratio and remaps the...     

A direct method for BBD matrix inversion

Published in Kibernetika i Sistemnyi Analiz, No. 2, pp. 51–64, March–April, 1994.     

A coral-like macroporous gold-platinum hybrid 3D electrode for enzyme-free glucose detection

We are introducing a macroporous Au-Pt hybrid 3D electrode to be used for enzyme-free glucose detection. The proposed hybrid electrode was fabricated with a three dimensional structure by electroplating platinum nanoparticles onto the surface of the coral-like macroporous Au. It was then physically analyzed by using field emission scanning electron microscopy (FESEM). The porosity and window pore size of the macroporous Au electrode were 50% and 100-300 nm, respectively. The diameters of the Pt nanoparticles ranged from 10 to 15 nm. Through cyclic voltammograms in a 1 M sulfuric acid solution, we confirmed that the hybrid electrode exhibited a much larger surface activation area with a roughness factor (RF) of 2024.7 than the macroporous Au electrode with a roughness of 46.07. The highly improved surface activation area was caused by the electroplated Pt nanoparticles. The hybrid electrode exhibited a much stronger electrocatalytic activity due to glucose oxidation than the macroporous Au electrode. At 0.4 V, it responded linearly to the glucose up to 20 mM in a neutral media with a detection limit of 0.025 mM and detection sensitivity of 39.53 μA mM⁻¹ cm⁻² without being affected by interfering species. It also showed a stable recovery response to the step changes of the glucose concentration.     

分层的线性迭代三维重建方法

为了重建三维物体,提出了一种基于分层的线性迭代三维重建方法,该方法首先利用所有图像序列构成的行向量生成的线性子空间之和与空间结构点构成的行向量生成的子空间是同一线性子空间及在该子空间中任何一个基底都可以作为射影重建的特性,线性迭代地完成射影重建,然后利用相机参数之间的相互约束关系,线性迭代地实现相机的自定标,完成到欧氏重建的过渡.模拟实验和真实实验表明:该重建方法具有鲁棒性好、收敛性好及重投影误差小等优点.     

基于影子页面和混合日志的MMDB恢复方法

为了提升内存数据库从各种故障中恢复的速度,提出了基于影子页面技术、混合日志策略以及模糊检查点思想的内存数据库恢复方法。在分析内存数据库运行过程中主要的时间消耗点的基础上建立了内存数据库的系统模型,通过分析事务过程和检查点过程,讨论了该恢复策略的执行过程以及优点,讲述了内存数据库在此系统模型和恢复策略下的事务故障和系统故障的恢复过程以及系统的性能分析。     

A mesh-geometry based method for coupling 1D and 3D elements

When conducting a finite element analysis (FEA) one way to reduce the total number of degrees of freedom is to use a mixed-dimensional model. Using beam elements to model long and slender components can significantly reduce the total number of elements. Problems arise when trying to connect elements with different dimensions in part due to incompatible degrees of freedom between different types of finite elements. This paper focuses on problems that occur in coupling beams and solids, which means coupling 1D and 3D finite elements. This paper presents a mesh-based solution to these problems only using specific arrangements of classical 1D and 3D finite elements without requiring the use of additional constraint equations. Two alternative solutions are detailed, evaluated and compared in this paper through series of computational experiments. The implementation of both solutions is also presented and involves mesh and geometry processing operations along with an adaptation of boundary representation (BREP) classical data structures.     

一种改进的遗传算法的三维人脸建模方法

采用网格重采样算法提取人脸特征实现了真实人脸与原型三维人脸之间的精确对应,在此基础上,提出了基于改进的方向自学习遗传算法的模型匹配算法,该算法在局部搜索中引入方向信息,提高了算法的收敛速度和重建精度,实验结果表明:新算法可有效实现真实人脸与原型三维人脸之间的精确对应,减少了优化参数,提高了模型重建精度和速度,缩短了模型...     

Application of asymptotic waveform approximation technique to hybrid FE/BI method for 3D scattering

The asymptotic waveform evaluation (AWE) technique is a rational function ap- proximation method in computational mathematics, which is used in many appli- cations in computational electromagnetics. In this paper, the performance of the AWE technique in conjunction with hybrid finite element/boundary integral (FE/BI) method is firstly investigated. The formulation of the AWE applied in hybrid FE/BI method is given in detail. The characteristic implementation of the application of the AWE to the hybrid FE/BI method is discussed. Numerical results demonstrate that the AWE technique can greatly speed up the hybrid FE/BI method to acquire wide-band and wide-angle backscatter radar-cross-section (RCS) by complex tar- gets.     

Validation of plant part measurements using a 3D reconstruction method suitable for high-throughput seedling phenotyping

In plant phenotyping, there is a demand for high-throughput, non-destructive systems that can accurately analyse various plant traits by measuring features such as plant volume, leaf area, and stem length. Existing vision-based systems either focus on speed using 2D imaging, which is consequently inaccurate, or on accuracy using time-consuming 3D methods. In this paper, we present a computer-vision system for seedling phenotyping that combines best of both approaches by utilizing a fast three-dimensional (3D) reconstruction method. We developed image processing methods for the identification and segmentation of plant organs (stem and leaf) from the 3D plant model. Various measurements of plant features such as plant volume, leaf area, and stem length are estimated based on these plant segments. We evaluate the accuracy of our system by comparing the measurements of our methods with ground truth measurements obtained destructively by hand. The results indicate that the proposed system is very promising.     

A subspace trust-region method for seismic migration inversion

In seismic exploration, regularized migration inversion of seismic data usually requires solving a weighted least-squares problem with constrains. It is well known that directly solving this problem using some decomposition techniques is very time-consuming, which makes it less possible for practical use. For iterative methods, previous research is mainly on solving the inverse model in a full space. In this paper, a robust subspace method is applied to seismic migration inversion with Gaussian beam representations of Green's function. The problem is first formulated by incorporating regularizing constraints, and then, it is changed from full space to subspace and solved by a trust-region method. To test the potential of the application of the developed method, synthetic data simulations are performed. The results show that this method is very promising for ill-posed seismic migration inversion problems.     

用于大型LED显示屏的混合直流电源

设计了一种直流电源系统,可以根据LED显示屏模块的数量进行电源输出模块的自适应配置,能够通过GPRS无线通信模块对电源参数进行远程监控与配置,并且通过专家控制算法实现了太阳能光伏、蓄电池、AC-DC的自动切换.     

A fast singular boundary method for 3D Helmholtz equation

This paper presents a fast singular boundary method (SBM) for three-dimensional (3D) Helmholtz equation. The SBM is a boundary-type meshless method which incorporates the advantages of the boundary element method (BEM) and the method of fundamental solutions (MFS). It is easy-to-program, and attractive to the problems with complex geometries. However, the SBM is usually limited to small-scale problems, because of the operation count of $O\left(N^3\right)$ with direct solvers or $O\left(N^2\right)$ with iterative solvers, as well as the memory requirement of $O\left(N^2\right)$. To overcome this drawback, this study makes the first attempt to employ the precorrected-FFT (PFFT) to accelerate the SBM matrix–vector multiplication at each iteration step of the GMRES for 3D Helmholtz equation. Consequently, the computational complexity can be reduced from $O\left(N^2\right)$ to $O\left(NlogN\right)$ or $O\left(N\right)$. Three numerical examples are successfully tested on a desktop computer. The results clearly demonstrate the accuracy and efficiency of the developed fast PFFT-SBM strategy.     

A finite element method for 3D hydrostatic water flows

In this paper we propose a numerical method for the solution of the “Quasi-3D” hydrodynamic equations. This approach uses a combination of standard linear finite elements along the vertical direction and non-conforming Raviart-Thomas elements in the horizontal planes. We describe, also, a suitable approximation for the convective terms. Received: 17 March 1999 / Accepted: 17 June 1999