Spatio-temporal fMRI data in the spiking neural network

Deep learning machine that employs Spiking Neural Network (SNN) is currently one of the main techniques in computational intelligence to discover knowledge from various fields. It has been applied in many application areas include health, engineering, finances, environment and others. This paper addresses a classification problem based on a functional Magnetic Resonance Image (fMRI) brain data experiment involving a subject who reads a sentence or looks at a picture. In the experiment, Signal to Noise Ratio (SNR) is used to select the most relevant features (voxels) before they were propagated in an SNN-based learning architecture. The spatio-temporal relationships between Spatio Temporal Brain Data (STBD) are learned and classified accordingly. All the brain regions are taken from data with label starplus-04847-v7.mat. The overall results of this experiment show that the SNR method helps to get the most relevant features from the data to produced higher accuracy for Reading a Sentence instead of Looking a Picture

Isogeometric analysis: an overview and computer implementation aspects

Isogeometric analysis (IGA) represents a recently developed technology in computational mechanics that offers the possibility of integrating methods for analysis and Computer Aided Design (CAD) into a single, unified process. The implications to practical engineering design scenarios are profound, since the time taken from design to analysis is greatly reduced, leading to dramatic gains in efficiency. The tight coupling of CAD and analysis within IGA requires knowledge from both fields and it is one of the goals of the present paper to outline much of the commonly used notation. In this manuscript, through a clear and simple Matlab implementation, we present an introduction to IGA applied to the Finite Element (FE) method and related computer implementation aspects. Furthermore, implemen- tation of the extended IGA which incorporates enrichment functions through the partition of unity method (PUM) is also presented, where several examples for both two-dimensional and three-dimensional fracture are illustrated. The open source Matlab code which accompanies the present paper can be applied to one, two and three-dimensional problems for linear elasticity, linear elastic fracture mechanics, structural mechanics (beams/plates/shells including large displacements and rotations) and Poisson problems with or without enrichment. The Bezier extraction concept that allows FE analysis to be performed efficiently on T-spline geometries is also incorporated. The article includes a summary of recent trends and developments within the field of IGA

Numerical Simulation and Customized DACM Based Design Optimization

PhD thesis in Offshore technologyThe diverse numerical modelling, analysis and simulation tools that have been developed and introduced to markets are intended to perform the virtual design and testing of products and systems without the construction of physical prototypes. Digital prototyping in the form of computer modelling and simulation are important means of numerical model predictions, i.e. design validation and verification. However, as the tools advance to more precise and diverse applications, the operation eventually becomes more complex, computationally expensive and error prone; this is particularly true for complex multi-disciplinary and multidimensional problems; for instance, in multi-body dynamics, Fluid-Structure Interaction (FSI) and high-dimensional numerical simulation problems. On the other hand, integrating design optimization operations into the product and system development processes, through the computer based applications, makes the process even more complex and highly expensive. This thesis analyses and discusses causes of complexity in numerical modelling, simulation and optimization operations and proposes new approaches/frameworks that would help significantly reduce the complexity and the associated computational costs. Proposed approaches mainly integrate, simplify and decompose or approximate complex numerical simulation based optimization problems into simpler, and to metamodel-based optimization problems. Despite advancing computational technologies in continuum mechanics, the design and analysis tools have developed in separate directions with regard to ‘basis functions’ of the technologies until recent developments. Basis functions are the building blocks of every continuous function. Continuous functions in every computational tool are linear combinations of specific basis functions in the function space. Since first introduced, basis functions in the design and modelling tools have developed so rapidly that various complex physical problems can today be designed and modelled to the highest precision. On the other hand, most analysis tools still utilize approximate models of the problems from the latter tools, particularly if the problem involves complex smooth geometric designs. The existing gap between the basis functions of the tools and the increasing precision of models for analysis introduce tremendous computational costs. Moreover, to transfer models from one form of basis function to another, additonal effort is required. The variation of the basis functions also demands extra effort in numerical simulation based optimization processes. This thesis discusses the recently developed integrated modelling and analysis approach that utilizes the state-of-the-art basis function (NURBS function) for both design and analysis. A numerical simulation based shape optimization framework that utilizes the state-of-the-art basis function is also presented in a study in the thesis. One of the common multidisciplinary problem that involves multiple models of domains in a single problem, fluid-structure interaction (FSI) problem, is studied in the thesis. As the name implies, the two models of domains involved in any FSI problems are fluid and structure domain models. In order to solve the FSI problems, usually three mathematical components are needed: namely, i) fluid dynamics model, ii) structural mechanics model and, iii) the FSI model. This thesis presents the challenges in FSI problems and discusses different FSI approaches in numerical analysis. A comparative analysis of computational methods, based on the coupling and temporal discretization schemes, is discussed using a benchmark problem, to give a better understanding of what a multidisciplinary problem is and the challenge for design optimizations that involve such problems. [...

A framework for geometric modeling and structural analysis of composite laminates

Laminated fiber-reinforced polymer (FRP) composites show considerable promise in structural applications due to their good combination of low weight and high strength. However, the manufacturing costs of laminated composites is significantly higher than their metallic counterparts. As a consequence, estimating the residual life of composites becomes critical, and can enable reusability in applications that demand lower mechanical strength requirements. One of the major factors affecting the residual life of the laminated composites is the defects introduced during manufacturing or in service. A common way of determining defects in the composite laminates is using non-destructive evaluation (NDE) techniques. In this study, a framework for modeling and structural analysis of composite laminates is presented. The framework follows the laminate manufacturing process and incorporates structural elements, such as stiffeners, as well as defects, such as delaminations, determined using NDE techniques. Each layer composing the laminate is modeled separately and combined to generate the final laminate. The layer combination process is called bonding and involves computation of boundary conditions for the constitutional model being selected for the analysis. Then, the final laminate model and the computed boundary conditions are used during the structural analysis. The initial framework used commercial off-the-shelf (COTS) software, i.e. 3D ACIS Modeler for 3-dimensional modeling and SIMULIA Abaqus for structural analysis via finite element modeling. The framework was then extended to use the NURBS library, NURBS-Python, and the isogeometric analysis library, gIGA, which were developed as a part of this study and released as free and open-source software on GitHub. Using NURBS for modeling and isogeometric analysis for structural analysis provide several advantages, such as directly operating on the exact geometry, and therefore; achieving better estimations on interlaminar and intralaminar stresses and strains, which has significant importance in determining the residual life of the composite laminates

Razvoj izogeometrijske metode konačnih elemenata i njena primena u strukturnoj analizi nosećih struktura transportnih mašina

The subject of doctoral dissertation is the isogeometric structural analysis. The isogeometric analysis represents a special approach in the finite element method (FEM) which aims at closing the gap between the actual geometry of modeled structures and the geometry generated upon the finite element discretization. In the isogeometric FE analysis, NURBS (non-uniform rational basis spline) functions usually form the basis for the definition of both the geometric models and interpolation functions of the FE models. Regardless of the mesh density, the geometry is exactly described in the FE model. The aim of the dissertation is the systematization of procedures and methods necessary for isogeometric analysis by creating general mathematical forms and program procedures. Isogeometric FE models are defined by using the NURBS and T-spline basis functions. An isogeometric solid element is formulated as well as a Kirchhoff-Love shell element with the NURBS basic functions. The method of modeling complex structures formed from several surfaces by using Kirchhoff-Love elements is presented. The results of the performed isogeometric analyses were compared with analytical results, the results yielded by the classical finite element method and experimental results. The developed isogeometric models were tested in the field of linear static, modal and explicit dynamic analyses. A particular part of the dissertation is dedicated to the benefits of isogeometric analysis in the field of structural analysis of transport machines complex structures. The conclusions related to advantages and disadvantages of NURBS ant Tsplines basis functions in the finite element method are presented through examples and tests done in this dissertation. The directions of further research are proposed

Energy yield enhancement of bifacial photovoltaic modules

The bifacial photovoltaic (BPV) module is an emerging renewable technology that produces augmented energy yield due to its capability of receiving sunlight both on the front and rear sides. This contrasts with conventional monofacial PV, which captures sunlight only on the front side. The extensive deployment of bifacial PV is expected to reduce the cost of solar energy considerably. However, there is limited evidence regarding the field performance of bifacial PV. Uncertainty exists in modelling the ground-reflected irradiance received by the rear side of BPV, which depends on ground albedo and the view factor (VF) from solar PV to the ground. Existing research on the view factor considers infinite lengths of the PV array, which prevents accurate determination of ground-reflected irradiance for PV arrays with finite lengths. In this research, the finite element method (FEM) is used to develop a view factor computation model for the finite length of the PV array. The model can be utilised to analyse the ground-reflected irradiance at the rear side of bifacial PV, which is necessary to predict bifacial PV's energy generation correctly, adding scientific value to this research. The developed model is verified with the analytical solution with an error margin of ±2%. The model is validated by comparing calculated and measured reflected irradiance, which shows a strong agreement at a root mean square error (RMSE) of 16 W/m2 and a mean bias error (MBE) of 7 W/m2 . An investigation into the performance of BPV for four ground surfaces: soil, white pebbles, concrete, and white tiles is undertaken to quantify the gain BPV can achieve. Six empirical models are developed based on the measured data, which can be utilized to estimate rear irradiance gain, bifacial energy gain and power output. A probability distribution of bifacial energy gain data at a 95% confidence level shows that the bifacial energy gain varies within 2%-25% depending on the reflectance of the ground surface and the probability is low that the bifacial energy gain will be more than 30%. Based on the annual bifacial energy gain analysis, the highest gain range is found for white tiles ground surface, followed by concrete and white pebbles. Simulations have been performed for various utility-scale PV arrays across the UK to verify the reliability of measured field data. The results are found to be consistent with the measured bifacial energy gain which showed a clear agreement of about 2%-5%. The findings of this research will remove some uncertainty about BPV performance, which is crucial to predict its energy generation accurately