A combined regularization algorithm for three-dimensional electrical impedance tomography system

By studying the reconstructed algorithms of Tikhonov regularization and the Newtons one-step error reconstructor (NOSER),a combined regularization algorithm is proposed. Two evaluation parameters of reconstructed algorithms,i.e. normalization mean square distance criterion(NMSD)and normalized mean absolute distance criterion(NMAD)are used to evaluate the results precision of inverse problem quantificationally. The comparison among Tikhonov regularization,NOSER and the combined regularization shows that the ill-condition and error of inverse problem are reduced. This new algorithm can decrease the condition number by 97%,NMSD by 51% and NMAD by 41% at least. Simulate results show that the combined regularization algorithm can reconstruct the target image in the depth from 10 mm to 40 mm. The performance of this system and the combined regularization algorithm demonstrate significantly better spatial resolution and less reconstructed error.     

响应面法不确定性参数对行星架静强度的影响

不确定性参数对行星架静强度的影响,取行星架强度最薄弱的部位-前轴承支座挖根(清根处)为研究对象,采用参数方差分析法从不确定性参数中挑选显著参数,并利用D最优抽样法选取样本点组合,计算精细有限元模型清根处应力响应值,继而基于最小二乘估计建立多项式回归响应面模型。基于快速响应面模型,利用蒙特卡洛模拟法和统计分析法研究显著性参数过盈量、铸造圆角和腹板公差对清根处第一主应力的影响,并从可靠度角度对清根处静强度进行评估。研究发现过盈量和前后腹板偏差的离散性对清根处静强度影响明显,同时行星架可靠度达到99.3%,表明在考虑了GL和IEC安全系数后,行星架可靠度仍然非常高。     

Open-electrical impedance tomography with variation regularization algorithm

Open electrical impedance tomography (OEIT) with fixed electrode row is proposed to overcome the clinical application problems in closed electrical impedance tomography such as poor model adaptability, electrode position error, and inflexibility. Variation regularization algorithm (VRA) using variations function as regularization penalty term is proposed to save the more serious ill-posed inverse problem of OEIT. Simulation and experiment results show that the inverse problem of OEIT can be efficiently solved by VRA. The position, size and the relative value of conductivity of target at shallower position below electrodes can be clearly reflected by the restored image. OEIT is more potentially practical and effective in clinical applications.     

Computation method of magnetic field inverse problem on grounding grids fault diagnosis

Grounding grids are the guarantee of substation running safety. The fault of grounding grids is a threat to people and equipment in substations. A method to diagnose the fault of grounding grids based on magnetic field inverse problem. The inverse problem of magnetic field is established by injecting and extracting a low frequency current. The morbid of inverse problem is solved through regularization and Newton iteration method to obtain the distribution of the mesh currents. The approximate distribution of the magnetic field is calculated to diagnose the fault of the grounding grid. A 4×4 substation grounding grids is taken as an example. By comparison of the forward problem result, the error is under 3%, so the prposed method of inverse problem is verified. The selection of measurement point is discussed, and 40% of the number of meshes is accounted to approximate the real distribution of the magnetic field on the grounding grids.     

Defects detection in the inner surface of pipes based on inverse heat conduction problem

It is a typical ill posed inverse heat conduction problem to estimate the geometry boundary of the inner surface of pipe by the temperature of outer surface. With the establishment of a two dimensional steady model for pipe with irregular inner surface, the inverse problem is transformed into a direct problem and an optimization problem. Based on the temperature at the outer surface obtained from the infrared thermography and the variation of the object function, the conjugate gradient method (CGM) is introduced into the geometry problem. With the numerical analysis of three typical defects, the effects of the measurement errors, choice of the initial value, boundary conditions and number of discrete temperature points are discussed and the proposed methodology is approved.     

THE THREE-DIMENSIONAL CALCULATING MODEL OF INVERSE PROBLEM IN ECG AND A SPECIAL BOUNDRYVALUE PROBTEM

In this paper, the mathematical model and the three-dimensional finite clement formulation of inverse problem in electrocardiography (ECG) under a general inhomogcneous and anisotropic configuration of the torso conductor is focused on. The following points are especially considered: 1. The mathamatical model is described by a differential equation instead of the Fredholm integral equation. 2. A kind of special boundary value problem is defined as ill-posed boundary value problem. 3. A group of finite element formulation, in which the method that treats anisotropic medium, is built up. 4. The calculating method of ill-posed boundary value problem is discussed.     

Analysis of fast optimization algorithm for inverse detecting faulty insulators

In order to improve the computational efficiency of the insulator electric field inverse problem, the fast multi-pole method has been introduced to the traditional simulation charge method. Tikhonov regularization is used to process the ill-posed characteristic of inverse problem solution caused by the interference. Newton method is used to search the optimum solution, and then the actual field source parameters of insulators and the practical voltage distribution on the surface of the insulators can be obtained. The fast optimization algorithm has been verified in point charge model. And 110 kV insulator string is carried out to demonstrate that the fast optimization algorithm is much faster and more efficient than traditional method.     

A domain decomposition algorithm in meshless method for discontinuous problem

A domain decomposition algorithm for material and displacement discontinuity problems in meshless method is presented. The domain is decomposed into sub-domains along the discontinuous interface. The continuity of the displacements on the interface is satisfied through the introduction of two transformation matrixes. The partitioned-matrix method is proposed to calculate the transferred stiffness matrix,which is sparse and bandy. By means of coupling meshless method and finite element method, the essential boundary condition can be imposed directly. The computer program based on the presented method is developed and two numerical examples, a beam consisted with two kinds of materials and an edge-cracked plate under uniform tension, are employed to demonstrate the correctness and efficiency of the method.     

Optimization of quenching parameters for ultra high strength steel using response surface method

In order to optimize the quenching parameters of ultra high strength steel 22MnB5,orthogonal experimental design method is applied to design the experiments and response surface methodology (RSM) is used to analyze the experimental results. Austenitizing temperature and soaking time are taken as the optimization factors. The effect of these factors on quenching hardness and elongation are investigated. The optimization results of each single objective are firstly obtained. Then,ideal point method is used to find the solution to the multi-objective programming,and global optimums are gained. Finally,the optimal results are discussed from the microstructure angle and the reliability of the prediction models is demonstrated.     

考虑剪切变形影响的桩基m法计算理论

考虑桩基的剪切变形影响,利用单广义位移深梁理论,建立了桩基m法的计算方法,导出了水平位移、转角、弯矩和剪力的初参数表达式和无量纲参数函数的统一表达式,根据桩底边界条件建立了初参数解的计算公式;给出了无量纲参数函数随换算深度和弯剪刚度比的变化图形。研究表明,换算深度小于3.0时,弯剪刚度比对无量纲参数函数影响较小,换算深度大于4.0时,弯剪刚度比对无量纲参数函数影响的趋势非常明显,桩基剪切变形的影响程度与桩的边界条件有关。算例结果表明,桩身的剪切变形有增大桩顶水平位移、提高弯矩零点位置、改变弯矩分布特征、扩大桩侧土压力大小等影响。     

A new boundary treatment of lattice boltzmann method (LBM) for fully developed pressure-driven periodic incompressible fluid flow

This paper proposeds a new boundary treatment of Lattice Boltzmann Method (LBM) for fully developed pressure-driven periodic incompressible fluid flow. The pressure gradient, instead of equivalent body force, is applied to determine the particle distribution function on the periodic traverse sections for the fully developed pressure-driven periodic flow. Numerical simulations, including 2D pressure-driven poiseuille flow and fluid flow passing periodic square obstacles, are carried out using this new boundary treatment. Simulation results show that the proposed approach not only overcomes the nonphysical inlet and outlet flow disturbances (which the LBM simulation always suffers from using the existing pressure boundary methods), but also preserves the system periodicity and generates consistent pressure distribution with macroscopic periodic boundary conditions for the pressure-driven incompressible fluid flow.     

A new measurement method for mass property parameters

Mass property parameters (mass, center of mass, moment of inertia) are important technology parameters of aircraft. The traditional mass and center of mass measurement uses centroid units, and the moment of inertia measurement torsion units, which can only get results in installing direction. Because of the structural reasons, there is a need to get all high accurate physical parameters in clamping once. To solve this problem, this study merges centroid units and torsion units into one composite unit, installs a table which can tilt and rotation to measure the moment of inertia in different conditions. The moment of inertia and product of inertia relative to three axis are calculated by the method of coordinate transformation. Measurement theory of mass, center of mass and mass moment of inertia are described, the main reason of causing measurement errors is discussed, and the measurement accuracy affected by tilt error is analyzed.     

QTLs for chlorophyll and chlorophyll fluorescence parameters in barley under post-flowering drought

Drought is one of the major factors limiting barley yields in many developing countries worldwide. The identification of molecular markers linked to genes controlling drought tolerance in barley is one way to improve breeding efficiency. In this study, we analyzed the quantitative trait loci (QTL) controlling chlorophyll content and chlorophyll fluorescence in 194 recombinant inbred lines (RILs) developed from the cross between the cultivar ‘Arta’ and Hordeum spontaneum 41-1. Five traits, chlorophyll content, and four chlorophyll fluorescence parameters, namely initial fluorescence (F_o), maximum fluorescence (F_m), variable fluorescence (F_v), and maximum quantum efficiency of PSII (F_v/F_m) which are related to the activity of the photosynthetic apparatus, were measured under well-watered and drought stress conditions at post-flowering stage. QTL analysis identified a total of nine and five genomic regions, under well-watered and drought stress conditions, respectively, that were significantly associated with the expression of the five target traits at post-flowering stage. No common QTL was detected except one for chlorophyll content, which was identified in both growth conditions, demonstrating that the genetic control of the expression of the traits related to photosynthesis differed under different water conditions. A QTL for F_v/F_m, which is related to the drought tolerance of photosynthesis was identified on chromosome 2H at 116 cM in the linkage map under drought stress. This QTL alone explained more than 15% of phenotypic variance of maximum quantum yield of PSII, and was also associated with the expression of four other traits. In addition, another QTL for F_v/F_m was also located on the same chromosome (2H) but at 135.7 cM explaining around 9% of the phenotypic variance under drought conditions. The result presented here suggest that two major loci, located on chromosome 2H, are involved in the development of functional chloroplast at post-flowering stage for drought tolerance of photosynthesis in barley under drought stress. If validated in other populations, chlorophyll fluorescence parameters could be used as selection criteria for drought tolerance.     

The Taylor series multipole boundary element method (TSM BEM)and its applications in rolling engineering

Rainfall is the main input for probabilistic analysis and prediction of rainfall-triggered landslide. The joint probabilistic structure of daily rainfall (DR) and cumulative rainfall (CR), which are dominant parameters of rainfall related on landslide in Chongqing region, was analyzed. Following the traditional technology, daily rainfall was translated into discrete variable by rainfall grade and cumulative rainfall became continuous variable if records with very small cumulative rainfall were ignored. Then joint probabilistic model of discrete variable and continuous one was derived, and transiting solution of conditional density function was put forward, together with its approximation via a family of Dirac δ sequences. Naturally, the proposed method was used to analyze conditional density function of cumulative rainfall in Chongqing region, and the numerical results were verified by comparison. However, most of the conditional density functions were irregular and not modeled by simple probability density function, thus the finite mixture distribution was introduced, which is of uncomplicated format and relatively high precision. At last, the joint probabilistic model of daily rainfall and cumulative rainfall was built up by combining frequency function of grade of daily rainfall with conditional density model of cumulative rainfall.     

对偶性与特大增量步算法在复杂平面框架中的应用

特大增量步算法（LIM）是一种基于力法和广义逆矩阵理论的迭代算法,在简单桁架和刚架非线性初步应用中,达到相同计算精度下有同等甚至超过位移有限元的计算效率。针对工程中的复杂杆系结构,利用平衡与协调的对偶性,探讨LIM在复杂平面框架结构中的应用,建立了平面框架结构的LIM基本方程,提出了针对典型支座约束以及组合结点的处理方法。该处理方法的线弹性问题算例表明,与位移有限元相比具有至少同等的精度和相当的计算效率。在支座本身不考虑塑性的情况下,该处理方法同样适用于弹塑性问题,为LIM在复杂杆系结构的弹塑性分析中奠定了基础。     

Topology optimization for constrained layerdamping material in structures using ESO method

Topology optimization for constrained damping material in structures is investigated in order to suppress structural vibration through the optimal placement of constrained damping material in structure. A mathematical model to describe the topology optimization problem is established. In the topology optimization approach, structural modal damping ratio is designed as objection function, while constrained damping material consumption is considered as constraint condition. The sensitivity of modal damping ratio to the place is analyzed. An evolutionary criterion for placement of constrained damping material in a structure is presented. The formula of sensitivity is derived and used to determine the optimized placement of constrained damping material in structure. The topology optimization problem is further solved by evolutionary structural optimization (ESO) method. The numerical examples are given. The results show that a stable and dramatic increase of the modal damping ratio during the course of iterations can be observed. Therefore, an optimal layout of constrained damping material in structure is obtained. The comparison of amplitude frequency characteristics with the optimal and fully covered layout validates the effectiveness of proposed topology optimized approach.     

早熟柑橘黄龙病空间格局参数特征及其应用

为了揭示柑橘早熟宫川黄龙病的空间分布信息和病株行为特征,2004-2009年采取多级抽样法于每年11月上旬在果实成熟期对2块定点样地逐株进行病级调查,取得了12组样本资料,应用聚集度指标法、Iwao 法和Taylor法等对其空间分布型进行测定检验,结果表明柑橘黄龙病在早熟宫川果园呈聚集分布,其聚集强度是随着病级升高而增加。其聚集原因经Blackith种群聚集均数测定,当m<2.1184时,其聚集是由于某些环境如气候、栽培条件、植株生育状况等所引起的;当m≥2.1184时,其聚集是由病株本身的聚集行为与环境条件综合影响所致。在此基础上提出了理论抽样数和序贯抽样模型：n=(1/D)2?[1/m+0.6761] 和Tn=1.831 /[D02-0.1581 /n]。     

The BEM for Elliptic Unilateral Problems

Unilateral problems is a kind of important partial differential problems. It can be solved by treating it as a complementary problem. As the complementary conditions lie in the boundary of the region,it is suitable for BEM. This paper is based on the switching algorithm,which is first used by J. M. Aitchison for the Signorini Problems of Laplace operator,then extends it to the elliptic operator,and conjunct it with the BEM. At last the detail of the algorithm is given. The new algorithm is easy to be implied effectively and quickly. It only needs the minimal change of the BEM programming. The numerical tests show the algorithm is effective and conventional.     

Fast multi-pole preconditioned GMRES high order boundary element method for power frequency electric field of multi-medium

In order to improve the computational accuracy and cost for multi-medium power frequency electric field (PFEF) solved by low order boundary element method (BEM) and preconditioned generalized minimal residual (GMRES),a hybrid technique combining the high order BEM and fast multi-pole (FM) method has been introduced to low order BEM. The FM preconditioned GMRES high order BEM is proposed to solve three dimension electric field distribution. The high order BEM model for three dimension electric field distribution is built, and the basic principles and implementation steps of the FM preconditioned GMRES high order BEM are given. The higher accuracy has verified in two medium test models. Part key devices in 500 kV substation is carried out to demonstrate that FM preconditioned GMRES high order BEM is much faster and more efficient than the preconditioned GMRES BEM in the computational cost and the storage of computer. The simulation values of this method are compared with measured values in 500 kV substation. It is found that the max relative error is 8.65%, so this method is suggested for use in large-scale and multi-medium PFEF problems.     

A method for considering parameter errors in power system harmonic state estimation

Total least squares (TLS) is proposed to complete harmonic state estimation when parameter and measurement errors are both taken into consideration. The buses are partitioned into subsets of non source buses and suspicious buses, thereby reducing the number of unknown state variables. The validity and practicability of this approach is validated using the IEEE 14bus harmonic testing system. The estimation precision is analyzed by random sampling 10 000 times in Matlab when measurement errors and parameter errors followed a Gaussian distribution. The results show that an accurate estimate can be obtained using TLS if parameter and measurement errors are considered.