Lung computed axial tomography image segmentation using possibilistic fuzzy C-means approach for computer aided diagnosis system

Soft computing is an associate rising field that plays a crucial half in the area of engineering and science. One of the most significant applications of soft computing is image segmentation. It focuses on an exploiting tolerance of imprecision and uncertainty. Segmentation supported soft computing remains a difficult task within the medical field. Medical images are habitually used in the segmentation process to extract the meaningful portions and to know and clarify the condition of the particular patient. In this article, we implement an efficient possibilistic fuzzy C-means (PFCM) approach to segment the lung portion in the computed tomography (CT) image and the result shows that it improves the segmentation accuracy upto 98.5012% and results are compared with existing segmenting approaches like fuzzy possibilistic C-means method, fuzzy bitplane method and so forth. Also, the PFCM approach increases the diagnostic accuracy of the computer aided diagnosis system using CT images. The radiologist may utilize this computer aided diagnosis system results as a second opinion of their diagnosed results.     

大挠度索结构的非线性有限元分析

本文基于有限元理论,将大挠度索离散为一系列小挠度索单元,推导出索结构的刚 度矩阵的显式。应用本文介绍的方法,可以计算任意挠度、作用有任意荷载的索结构。经过 算例对比,表明本文方法对于求解索结构是一种很好的方法。     

冷弯薄壁箱形梁柱构件局部与整体稳定相关作用的弹塑性分析

本文将局部屈曲的薄壁构件等效成由若干个局部屈曲的波段在局部屈曲节平面处连接而成的梁柱构件。首先分析该波段(或短柱段)局部屈曲后的弹塑性M-P-Φ曲线,进而应用有限积分法求解薄壁构件的极限承载能力。这一处理方法,使得薄壁构件局部与整体稳定相关作用这一难度较大的问题得到了很好的解决,并且具有较高的精度。     

基于粒子群优化聚类的汽轮机组振动故障诊断

针对模糊C-均值聚类算法(FCM)容易陷入局部极值和对初始值敏感的不足,提出了一种新的模糊聚类算法(PFCM),新算法利用粒子群优化算法(PSO)全局寻优、快速收敛的特点,代替了FCM算法的基于梯度下降的迭代过程,使算法具有很强的全局搜索能力,很大程度上避免了FCM算法易陷入局部极值的缺陷,同时也降低了FCM算法对初始值的敏感度。将该算法应用于汽轮机组振动故障诊断中,与电厂运行实际故障状态对照,仿真结果表明该算法提高了故障诊断的正确率。为汽轮机振动故障诊断方法的研究提供了一种新的思路。     

Large deflections and large-amplitude free vibrations of straight and curved beams

This paper is concerned with the large-deflection (bending and free vibration)analysis of thin elastic curved beams by conventional and mixed finite element methods. The conventional finite element method is based on the total potential energy expression, whereas the mixed method is based on a Reissner-type variational statement and involves the bending moments and deflections as primary dependent variables. Incremental and direct formulations are presented for both methods. The nonlinearity is included in the numerical method via an iterative procedure (i.e. the in-plane force due to the large deflection is not treated as constant but included under the integral in the energy expression). In the case of vibrations, the transverse shear and rotary inertia effects are also included. A number of numerical examples of beams with various edge conditions are analysed for deflections and natural frequencies, and the results are compared with those reported in the literature.     

A computational procedure for flexible beams with frictional contact constraints

This paper deals with the application of a parametric quadratic programming (PQP) method to the numerical solution of large-deflection beams involving frictional contact constraints. The flexibility of the structure is modelled by an intrinsic spatial beam theory which is approximated by transverse-shear deformable linear beam elements. The linear complementary problem (LCP) without the penalty function resulting from PQP is made part of a Newton-Raphson search. The tool for solving the complementary equations is Lemke's algorithm, in which frictional contact conditions are enforced and new contact surfaces are updated during iteration. Applying the resulting contact element, a more accurate approximation of the contact point can be guaranteed, and the contact force can be directly computed by the adjacent beam elements. Three numerical examples are analysed to show the effectiveness and validity of the method.     

在波浪作用下悬挂点Z向运动及刚体摆动对SCR位移影响分析

针对钢悬链式立管刚体摆动对横流向响应影响开展研究。在大挠度细长梁模型、波浪荷载、顶部运动及刚体摆动模型基础上,采用有限元方法求解结构响应。采用李萨如图形实现结构计算校核。计算表明运动响应从顶部悬挂点的YZ平面较窄幅度的振荡逐渐向底部触地点的ZX平面较宽幅度的八字形振荡发展。总体而言,随着水深增加,响应减小。顶部区域位移响应降低幅度较为剧烈。底部区域位移降低幅度较弱。刚体摆动响应表现为幅值的增大、减小甚至抵消,与矢径s线性相关。总之,刚体摆动对结构位移响应影响可通过一定的安全系数进行计算处理。希望上述研究对钢悬链式立管横流向计算提供一些合理建议。     

Techniques based on genetic algorithms for large deflection analysis of beams

A couple of non-convex search strategies, based on the genetic algorithm, are suggested and numerically explored in the context of large-deflection analysis of planar, elastic beams. The first of these strategies is based on the stationarity of the energy functional in the equilibrium state and may therefore be considered weak. The second approach, on the other hand, attempts to directly solve the governing differential equation within an optimisation framework and such a solution may be thought of as strong. Several numerical illustrations and verifications with ‘exact’ solutions, if available, are provided For communication     

Characterisation of mechanical behaviour and damage analysis of 2D woven composites under bending

In this paper, flexural loading of woven carbon fabric-reinforced polymer laminates is studied using a combination of experimental material characterisation, microscopic damage analysis and numerical simulations. Mechanical behaviour of these materials was quantified by carrying out tensile and large-deflection bending tests. A substantial difference was found between the materials' tensile and flexural properties due to a size effect and stress stiffening of thin laminates. A digital image-correlation technique capable of full-field strain-measurement was used to determine in-plane shear properties of the studied materials. Optical microscopy and micro-computed tomography were employed to investigate deformation and damage mechanisms in the specimens fractured in bending. Various damage modes such as matrix cracking, delaminations, tow debonding and fibre fracture were observed in these microstructural studies. A two-dimensional finite-element (FE) model was developed to analyse the onset and propagation of inter-ply delamination and intra-ply fabric fracture as well as their coupling in the fractured specimen. The developed FE model provided a correct prediction of the material's flexural response and successfully simulated the sequence and interaction of damage modes observed experimentally.     

Experimental and Numerical Analysis of Damage in Woven GFRP Composites Under Large-deflection Bending

Textile-reinforced composites such as glass fibre-reinforced polymer (GFRP) used in sports products can be exposed to different in-service conditions such as large bending deformation and multiple impacts. Such loading conditions cause high local stresses and strains, which result in multiple modes of damage and fracture in composite laminates due to their inherent heterogeneity and non-trivial microstructure. In this paper, various damage modes in GFRP laminates are studied using experimental material characterisation, non-destructive micro-structural damage evaluation and numerical simulations. Experimental tests are carried out to characterise the behaviour of these materials under large-deflection bending. To obtain in-plane shear properties of laminates, tensile tests are performed using a full-field strain-measurement digital image correlation technique. X-ray micro computed tomography (Micro CT) is used to investigate internal material damage modes – delamination and cracking. Two-dimensional finite element (FE) models are implemented in the commercial code Abaqus to study the deformation behaviour and damage in GFRP. In these models, multiple layers of bilinear cohesive-zone elements are employed to study the onset and progression of inter-ply delamination and intra-ply fabric fracture of composite laminate, based on the X-ray Micro CT study. The developed numerical models are capable to simulate these features with their mechanisms as well as subsequent mode coupling observed in tests and Micro CT scanning. The obtained results of simulations are in agreement with experimental data.     

The nonlinear response of unsymmetric multilayered plates using smeared laminate and layerwise models

A continually growing interest in the response of unsymmetric multilayered plates is apparent. Analyses were recently completed addressing the load-deflection behaviour of these plate geometries. The characteristic feature of the analyses is the use of nonlinear strain-displacement relations, even at low loading levels, in reaction to the large-deflection effect enhanced by the bending-extension and twisting-shearing coupling. Approaches where use is made of Higher Order Shear Deformation Theories (HSDT) for predicting global quantities, such as deflections and critical loads, are not found in the open literature. Such modelling approaches, in particular those of the layerwise type, are reserved to predict distributions across the thickness. Thus, a further assessment of the influence of the transverse shear effect on global quantities should be required. To give some preliminary contributions on this subject, the load-deflection behaviour of a [90₄/0₄] cross-ply plate with pinned edges, subjected to cylindrical bending under uniform transverse pressure, is investigated. Use is made of the Layerwise Higher Order Shear Deformation Layerwise Theory (RHSD) to serve this purpose. From the numerical results presented, the influence of modelling is enhanced or reduced, depending on the sign of loading. It is concluded that, depending on the loading, boundary conditions and lay-up, higher-order approaches can be used for predicting global quantities in unsymmetric multilayered plates. In order to investigate stability, nonlinear equations are developed where critical points are located under boundary and combined loading conditions which vary during perturbation.     

半解析有限元法分析环向加劲圆柱壳外压稳定性

采用一般有限元法分析环向加劲圆柱壳外压稳定性需要用确定的单元结点位移描述待定的各种失稳波形的变化,从而造成单元划分较多,基函数复杂,所需计算机内存大,往往使稳定性分析难于实现。本文利用半解析有限元法来分析圆柱壳的稳定性,可以利用解析的成果代替一般有限元法的离散化处理,有效地解决了用一般有限元法要遇到的难题。半解析有限元法的特点是:在位移模式中,周向引入圆环板和圆柱壳的解析函数,轴向和径向采用了离散型的内插多项式函数。由于采用了解析函数与离散函数相结合的位移模式,所以不但减少了自由度,并提高了计算精度,而且也能方便地处理各种复杂的结构及其不同的连接方式。本研究采用了几何非线性大挠度理论,据此,推导了单元的弹性刚度矩阵和几何刚度矩阵。在稳定性计算中,把求解失稳荷载和失稳变形形态的问题,转化为数学上求实矩阵的最大特征根及其特征向量的问题。本文最后给出了计算实例,计算结果与理论解吻合较好,说明此法是切实可行的,并且具有广泛的使用范围。     

Pulse pressure loading of clamped mild steel plates

Some results of a large series of pulse pressure loading tests on 1 m×1 m, clamped mild steel plates with different in-plane edge conditions are presented. A novel experimental device was used to produce uniform, repeatable pulse pressure loads of an approximate triangular form. The behaviour of the restrained plates was dominated by membrane effects leading to substantial spring-back. An assumed-modes, elastic–plastic analytical approach was used to predict the maximum and residual deflections of the test plates under dynamic loading with reasonably good success. Multi-element models of the test plates were developed in which the bi-axial behaviour of the plate was represented by one-dimensional finite strips. The in-plane restraint of the plate was approximated using non-linear translation springs and a slippage allowance. Satisfactory results were achieved owing to the careful determination and definition of the boundary conditions, which can significantly influence the results particularly if non-linear membrane forces and slippage occur. It has been shown that a simple methodology such as the one proposed in this paper can provide adequate predictions of the dynamic, large-deflection behaviour of pulse-loaded plates.     

Optimization of Short Load Forecasting in Electricity Market of Iran Using Artificial Neural Networks

Accurate short-term load forecasting (STLF) is one of the essential requirements for power systems. In this paper, two different seasonal artificial neural networks (ANNs) are designed and compared in terms of model complexity, robustness, and forecasting accuracy. Furthermore, the performance of ANN partitioning is evaluated. The first model is a daily forecasting model which is used for forecasting hourly load of the next day. The second model is composed of 24 sub-networks which are used for forecasting hourly load of the next day. In fact, the second model is partitioning of the first model. Time, temperature, and historical loads are taken as inputs for ANN models. The neural network models are based on feed-forward back propagation which are trained and tested using data from electricity market of Iran during 2003 to 2005. Results show a good correlation between actual data and ANN outcomes. Moreover, it is shown that the first designed model consisting of single ANN is more appropriate than the second model consisting of 24 distinct ANNs. Finally ANN results are compared to conventional regression models. It is observed that in most cases ANN models are superior to regression models in terms of mean absolute percentage error (MAPE).     

波轮式全自动洗衣机振动模型的建立

为建立波轮式全自动洗衣机(以下简称波轮式洗衣机)显含悬挂系统设计参数的振动模型,首先分析了波轮式洗衣机组成结构,对各部件分类描述,并推导出相应的动能描述形式;进而在分析悬挂系统作用力成分的基础上,建立了悬挂系统空气动力学模型与摩擦模型,对其计算结果进行了讨论,并与实验结果进行了对比,两者非常接近;最后,结合悬挂系统模型,并引入液体平衡环的稳态平衡机理,应用第二类Lagrange方程,建立了整机振动模型.根据最小势能原理,应用遗传算法估算整机静平衡位置,在此基础上,采用四阶Runge-Kutta法求解整机运动轨迹,给出了仿真结果并分析了系统振动与悬挂系统中一些设计参数间的关系.     

Application Study on 3D Modeling of Axial Compressor Blades Based on CFD and CAD

A new method for design of turbomachinery blades is presented. The parameters of a compressor blade are created from the Computational Fluid Dynamics (CFD) software CFX-BladeGen, and are inputted to the Computer Aided Design (CAD) software UG for building a curve surface model to create an entity model in UG. The result shows that the blade model is favorable from the entity effect and reflection analysis and the model process is useful for the CAD model creation of turbomachinery blades.     

System identification application using Hammerstein model

Generally, memoryless polynomial nonlinear model for nonlinear part and finite impulse response (FIR) model or infinite impulse response model for linear part are preferred in Hammerstein models in literature. In this paper, system identification applications of Hammerstein model that is cascade of nonlinear second order volterra and linear FIR model are studied. Recursive least square algorithm is used to identify the proposed Hammerstein model parameters. Furthermore, the results are compared to identify the success of proposed Hammerstein model and different types of models.     

Topology-dependent thermoluminescence kinetics

Standard kinetic models for thermoluminescence (TL) relate to the simple trap model (STM) and the model of localised transitions (LT). This paper presents a review of TL properties in various spatially correlated systems (SCS), which span the two limiting cases. A classification of kinetic models for SCS is proposed. Numerical results are presented for the isolated clusters model (IC) and the interacting one-dimensional (1-D) and three-dimensional (3-D) systems. For these systems an influence of external electric field on TL is demonstrated. Analytical formulation for the IC model is possible using trap structural functions (TSFs). To calculate the TSFs (analytically or numerically) it is convenient to use their structural and symmetry properties. Analytical equations are presented also for the semi-localised transitions (SLT) model, which is a generalised version of LT. It is shown that in some cases the SLT model leads to the cascade detrapping (CD) phenomenon. The CD mechanism produces very narrow TL peaks that are apparently well described by the first order kinetics with very high frequency factors and very high activation energies.     

Bending buckling behavior of perfect and defective single-walled carbon nanotubes via a structural mechanics model

A structural mechanics model is employed for the investigation of the bending buckling behavior of perfect and defective single-walled carbon nanotubes (SWCNTs). The effects of different types of defects (vacancies and Stone–Wales defects) at various locations on the critical bending buckling moments and curvatures are also studied for zigzag and armchair nanotubes with various aspect ratios (length/diameter). The locations of defects are along the length of the nanotube and around the circumference. Moreover, the results of this structural mechanics model are compared with a finite element model. The simple continuum model, especially, could be adopted to predict the critical buckling moments and curvatures of SWCNTs with large aspect ratio. Finally, the results of the present structural model are compared with those from molecular dynamics (MD) simulation, and there is good agreement between our model and the MD model.