430 research outputs found

    A Domain-Specific Language and Editor for Parallel Particle Methods

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    Domain-specific languages (DSLs) are of increasing importance in scientific high-performance computing to reduce development costs, raise the level of abstraction and, thus, ease scientific programming. However, designing and implementing DSLs is not an easy task, as it requires knowledge of the application domain and experience in language engineering and compilers. Consequently, many DSLs follow a weak approach using macros or text generators, which lack many of the features that make a DSL a comfortable for programmers. Some of these features---e.g., syntax highlighting, type inference, error reporting, and code completion---are easily provided by language workbenches, which combine language engineering techniques and tools in a common ecosystem. In this paper, we present the Parallel Particle-Mesh Environment (PPME), a DSL and development environment for numerical simulations based on particle methods and hybrid particle-mesh methods. PPME uses the meta programming system (MPS), a projectional language workbench. PPME is the successor of the Parallel Particle-Mesh Language (PPML), a Fortran-based DSL that used conventional implementation strategies. We analyze and compare both languages and demonstrate how the programmer's experience can be improved using static analyses and projectional editing. Furthermore, we present an explicit domain model for particle abstractions and the first formal type system for particle methods.Comment: Submitted to ACM Transactions on Mathematical Software on Dec. 25, 201

    BEM-FEM of Coupling for Prosthetic Socket

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    In this study, the investigating of the mechanical interaction between the residual limb and its prosthetic socket, and in computer-aided design and computer-aided manufacturing of prosthetic sockets is solving numerically by using FEM-BEM coupling approach. This work tried to improve the deflection of the loading of Socket. The BEM techniques has been used to estimate a deflection at each distance for the main part of loading  that applied on Socket .In addition, a simplified stiffener has been added to optimize a moment of inertia of this main part thereby the deflection will be better , for this purpose a case study has been considered according to international standard for the Socket specification that investigated to illustrate the goal of this work Moreover, a physical problem governed by a linear elliptic partial deferential equation but with a socket (where this paper approximate Socket to shell ) discontinuity in the domain cannot be efficiently solved using the traditional boundary element method. This paper also shows how the Laplace equation can be solved in an interior region containing shell discontinuities by recasting it as an integral equation known as a boundary and shell integral equation and applying collocation to derive a method termed the boundary and Socket element method. Direct and indirect methods are derived and applied to a test problem.  The results show that using stabilized method enables us to get stable and accurate numerical approximations consistent with the physical configuration of the problem over rough mesh by using ANSYS Workbench 14.0 ,AutoCAD and COMSOL 5.2. Keywords: Finite element model; boundary element method; discontinuity; Socke

    Transient Analysis of Thermal Bending and Vibration of Steam Turbine Rotor

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    Rotor-bearing systems often exhibit nonlinear behavior due to hydrodynamic effects and external forces. Finite element methods based on linear analysis are commonly used for rotor dynamic analyses, where nonlinear bearing/damping forces are linearized into equivalent stiffness and damping coefficients. However, this method may not accurately describe strongly nonlinear systems. Engineers use transient analysis and nonlinear models to improve rotor behavior analysis. This study investigates the effects of transient-thermal bending and vibration on a high-pressure steam turbine rotor using the finite element method. A scaled rotor-shaft was used to study thermal bending and vibrations caused by steam heat. The design of the shaft was based on an existing power station high-pressure turbine rotor. Numerical modal analyses were performed using ANSYS software to obtain a partial level of integrity between the numerical model and the analytical model. Natural frequencies were compared between the experimental, numerical, and analytical results, which showed good correlations

    Design and finite element analysis of formula student braking system

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    The present project focuses on the research and design of a braking system for sports vehicles. The braking system will be included in a vehicle being developed by the IPB Motorsport Team in order to participate in an annual worldwide collegiate design competition called Formula Student. The competition evaluates a Formula style car's engineering, performance, and cost. Since it was the first vehicle of this style to be designed at IPB, the values were analysed and estimated for the under-design vehicle. A methodology has been developed using the theory of vehicle dynamics to design a braking system capable of meeting the technical requirements of the competition. Another part of this research included analysing the behaviour of brake rotors made of various materials (Gray Cast Iron, Aluminium Alloy) and Geometry (Drilled, Solid) using Finite Element Analysis (FEA) more precisely the ANSYS software version 21. Static and thermal simulations were conducted for the design. As a result, a brake system assembly capable of achieving a four-wheel lock is demonstrated. Gray cast iron has superior thermal and static capabilities than aluminium, and the rotor geometry has an effect on the stress distribution. The simulations proved to be very useful in determining the most suitable brake rotor material and cooling shape for the brake rotors.O presente projeto centra-se na investigação e concepção de um sistema de travagem para veículos desportivos. O sistema de frenagem será incluído em um veículo que está sendo desenvolvido pela IPB Motorsport Team para participar de uma competição universitária anual de design chamada Formula Student. A competição avalia a engenharia, o desempenho e o custo de um carro estilo Fórmula. Por ter sido o primeiro veículo desse estilo a ser projetado no IPB, os valores foram analisados e estimados para o veículo em projeto. Foi desenvolvida uma metodologia a partir da teoria da dinâmica veicular para projetar um sistema de frenagem capaz de atender aos requisitos técnicos da competição. Outra parte desta pesquisa incluiu a análise do comportamento dos rotores dos freios feitos de diversos materiais (Ferro Fundido Cinza, Liga de Alumínio) e da Geometria (Perfurada, Sólida) utilizando a Análise de Elementos Finitos (FEA), mais precisamente o software ANSYS versão 21. Estático e térmico simulações foram realizadas para o projeto. Como resultado, é demonstrado um conjunto de sistema de freio capaz de obter um travamento nas quatro rodas. O ferro fundido cinzento tem capacidades térmicas e estáticas superiores do que o alumínio, e a geometria do rotor tem um efeito na distribuição de tensões. As simulações provaram ser muito úteis para determinar o material do rotor do freio e a forma de refrigeração mais adequados para os rotores do freio

    Comparative analysis of a transient heat flow and thermal stresses by analytical and numerical methods

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    The study of heat flow problems is of extreme importance in engineering, there is a need to know the temperatures imposed and generated, when appropriate, in the structural parts to be able to evaluate the stresses that can arise due to the thermal variations. These stresses arise due to imposed constraints, ie bodies can not move freely and consequently undesirable cracks may arise when the stresses are greater than the resistive capacity of the stressed parts. The analysis of these problems can be done in both analytical or numerical way, with the use of calculation methods, such as the Finite Difference Method (FDM) and the Finite Element Method (FEM), with aid of computational programs such as MATLAB, PYTHON and ANSYS, as used in this work. The results presented here show simple cases of transient thermal variation and thermomechanical coupling by two methods of analysis, aiming at the validation of the numerical methods and softwares used. The solutions were satisfactory, the temperatures and stresses were coincident for different methods, making possible to start studying more complex problems with confidence in the implemented code

    Building Blocks for a Model for using EDI and ERP to Improve Supply Chain Performance in Ugandan PDEs

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    The study's overarching goal is to provide a theoretical foundation for the integration of EDI and ERP systems into Ugandan procurement and disposal entities' supply chains to optimize their performance. A design science approach was used as a research strategy and for data collection; a cross-sectional survey using qualitative techniques, including in-depth interviews was employed. From the findings, a model was developed for data visualization, report production, analytics, and transformation. This study therefore provides an in-depth evaluation of the effectiveness of procurement and disposal organizations in Uganda with the help of EDI and ERP technologies to enhance supply chain management

    The Effects of Acute and Chronic Selective Phosphodiesterase 1 Inhibition on Smooth Muscle Cell-Associated Aging Features

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    Age-related cardiovascular diseases (CVDs) remain among the leading global causes of death, and vascular smooth muscle cell (VSMC) remodeling plays an essential role in its pathology. Reduced NO-cGMP pathway signaling is a major feature and pathogenic mechanism underlying vasodilator dysfunction. Recently, we identified phosphodiesterase (PDE) 1, an enzyme that hydrolyzes and inactivates the cyclic nucleotides cAMP and cGMP, and thereby provides a potential treatment target for restoring age-related vascular dysfunction due to aging of VSMC. Based on this hypothesis, we here tested the effects of PDE1 inhibition in a model of SMC-specific accelerated aging mice. SMC-KO and their WT littermates received either vehicle or the PDE1 inhibitor lenrispodun for 8 weeks. Vascular function was measured both in vivo (Laser Doppler technique) and ex vivo (organ bath). Moreover, we deployed UV irradiation in cell culture experiments to model accelerated aging in an in vitro situation. SMC-KO mice display a pronounced loss of vasodilator function in the isolated aorta, the cutaneous microvasculature, and mesenteric arteries. Ex vivo, in isolated vascular tissue, we found that PDE1 inhibition with lenrispodun improves vasodilation, while no improvement was observed in isolated aorta taken from mice after chronic treatment in vivo. However, during lenrispodun treatment in vivo, an enhanced microvascular response in association with upregulated cGMP levels was seen. Further, chronic lenrispodun treatment decreased TNF-α and IL-10 plasma levels while the elevated level of IL-6 in SMC-KO mice remained unchanged after treatment. PDE1 and senescence markers, p16 and p21, were increased in both SMC-KO aorta and cultured human VSMC in which DNA was damaged by ultraviolet irradiation. This increase was lowered by chronic lenrispodun. In contrast, lenrispodun increased the level of PDE1A in both situations. In conclusion, we demonstrated that PDE1 inhibition may be therapeutically useful in reversing aspects of age-related VSMC dysfunction by potentiating NO-cGMP signaling, preserving microvascular function, and decreasing senescence. Yet, after chronic treatment, the effects of PDE1 inhibition might be counteracted by the interplay between differential PDE1A and C expression. These results warrant further pharmacodynamic profiling of PDE enzyme regulation during chronic PDE1 inhibitor treatment

    Theoretical and numerical investigations of the parametric resonance of the mechanical vibrissa

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    In nature, vibrissae are tactile hairs of mammals used as sensor elements for the exploring the surrounding area. These hairs, also known as whiskers, can be found in different locations on an animals body. Mystacial vibrissae are distributed over a whiskerpad on a muzzle. Carpal vibrissae are located on the downside aspect of the forelimbs of mammals. The vibrissal hair has a conical shape and grows from a special heavily innervated hair follicle incorporating a capsule of blood. As the hair itself has no receptors along its length, the vibrissa may be considered as a system for transmitting forces and torques that arise from the contact between the hair and an object to sensory receptors inside the follicle. The present thesis deals with the vibrational motion of vibrissae dur- ing natural exploratory behaviour from the mechanical point of view. The phenomenon of the parametric resonance of the vibrissa is investigated the- oretically and numerically. In the first part of this thesis, two mechanical models of an elastic beam are presented based on findings in the literature. The first model considers a straight beam with the linearly decreasing radius of the circular cross-section. The second model takes into account the circu- lar natural configuration of the cylindrical beam. Within these models, the small transverse vibration of the beam under a periodic following force at the tip are analysed using the Euler-Bernoulli beam theory and asymptotic methods of mechanics. In the second part of the thesis, the numerical analysis of the problems is performed based on the finite element method using ANSYS 16.2 software. For each model, the dynamical response of the system on the parametric excitation is simulated for different frequency values. It is shown theoretically and numerically that at specific ranges of the excitation frequency the phenomenon of the parametric resonance of the beam takes place. That means that the amplitude of vibrations of the beam increases exponentially with time, when it is stimulated within one of the frequency ranges of the parametric resonance. These ranges depend on the geometrical and material parameters of the beam model, as well as the am- plitude of the periodic excitation.Tesi

    CFD Evaluation of Blood Flow in an Improved Blalock-Taussig Shunt Using Patient Specific Geometries

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    Blalock-Taussig (BT) Shunt is a palliative surgical procedure used during a Norwood surgery on a newborn baby suffering from cyanotic heart defects. The BT Shunt can increase blood flow in patients’ pulmonary artery which can ease the “Blue Baby Syndrome.” Currently used BT Shunts do not produce a balanced flow distribution to the pulmonary arteries (PAs) which can cause high wall shear stress (WSS) and blood flow separation resulting in blood clots. A modified BT Shunt was designed to partially solve this problem. In our previous work [1], the modified BT Shunt was shown by numerical simulations to have the ability to better control the flow distribution between Innominate Artery (IA) and PA with lower and gradually varying WSS and with improved flow balance to the pulmonary artery at the T-junction of the shunt. The goal of this paper is to computationally evaluate the flow in the modified BT shunt model between innominate and pulmonary artery using a patient specific aorta model. The simulations are performed using the commercial CFD software ANSYS Fluent. The improved modified BT shunt is connected between IA and PA. A change in the length of the shunt can be made to fit it under different conditions of actual patients. In numerical simulations, a full geometry of patient’s aorta is considered. Results for different lengths of the shunt are compared to determine the length that generates the lowest WSS and improved flow distribution to the PAs. It was found that the length of nearly 26mm creates lower WSS and flow rate difference between the two sides of PA at the T-junction attachment of the shunt. A sophisticated computational model was created using SolidWorks and Blender software to create the realistic geometry which included the IA, PA and modified BT shunt. The numerical simulations provide details of the flow field including velocity and pressure field, WSS, and blood damage. Several parameters in shunt design weigh heavily in reducing the thrombosis. This study demonstrates how CFD can be effectively utilized in the design of a medical device such as BT shunt to improve the clinical outcomes in patients
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