Dissertations / Theses: 'Mechanical computation'

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Moore, Darren William. "Quantum state reconstruction and computation with mechanical networks." Thesis, Queen's University Belfast, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.728195.

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Networks of mechanical resonators embedded in the platform of optomechanics are studied in two quantum information contexts: quantum state reconstruction and measurement based quantum computation. The optomechanical setup considered consists of a harmonically interacting network of resonators one of which is coupled via radiation pressure to a resonant mode of a cavity electromagnetic field. We develop a protocol for reconstructing the state of the network from measurements on the output cavity field. An interaction profile tuned to a set of mechanical quadratures ensures that the cavity field carries a copy of the quadratures’ information. Homodyne detection of the output field provides measurement statistics directly linked to the statistics of the mechanical quadratures from which their marginals can be estimated and standard tomographic techniques applied, recovering the phase space distribution for the network. We provide a method for determining the interaction profiles required and analyse the effectiveness of the scheme for Gaussian states in the case of finite measurements. We also provide some further examples of state reconstruction in similar optomechanics settings. An equivalent setup is that in which the cavity field interacts simultaneously with a collection of noninteracting mechanical modes. Here we implement measurement based quantum computation, giving a summary of cluster state generation in optomechanics and providing a scheme for applying multimode Gaussian operations. Adapting QND measurements on movable mirrors we continuously monitor individual resonators in order to assess the feasibility of using indirect measurements for computation compared to projective measurements performed directly on the cluster. Using a linear cluster state of five modes and taking advantage of the decomposition of single-mode Gaussian operations into four steps, we perform a numerical assessment of a large array of experimental parameters, paring down the list until those that most significantly affect the outcome are distilled. These are the mechanical bath temperature, the mechanical dissipation rate and the cluster squeezing. They place strong restrictions on the experimental parameters in order to ensure high fidelities, with stronger requirements for more highly squeezed clusters. We conclude with a small discussion of currently available experimental settings and remarks on further research possibilities.

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Erhan, Inci. "Quantum Mechanical Computation Of Billiard Systems With Arbitrary Shapes." Phd thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/2/1104082/index.pdf.

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An expansion method for the stationary Schrodinger equation of a particle moving freely in an arbitrary axisymmeric three dimensional region defined by an analytic function is introduced. The region is transformed into the unit ball by means of coordinate substitution. As a result the Schrodinger equation is considerably changed. The wavefunction is expanded into a series of spherical harmonics, thus, reducing the transformed partial differential equation to an infinite system of coupled ordinary differential equations. A Fourier-Bessel expansion of the solution vector in terms of Bessel functions with real orders is employed, resulting in a generalized matrix eigenvalue problem. The method is applied to two particular examples. The first example is a prolate spheroidal billiard which is also treated by using an alternative method. The numerical results obtained by using both the methods are compared. The second exampleis a billiard family depending on a parameter. Numerical results concerning the second example include the statistical analysis of the eigenvalues.

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Su, Yunde. "High-fidelity Computation and Modeling of Turbulent Premixed Combustion." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595513943378125.

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Ulrich, Karl T. "Computation and Pre-Parametric Design." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/6845.

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My work is broadly concerned with the question "How can designs bessynthesized computationally?" The project deals primarily with mechanical devices and focuses on pre-parametric design: design at the level of detail of a blackboard sketch rather than at the level of detail of an engineering drawing. I explore the project ideas in the domain of single-input single-output dynamic systems, like pressure gauges, accelerometers, and pneumatic cylinders. The problem solution consists of two steps: 1) generate a schematic description of the device in terms of idealized functional elements, and then 2) from the schematic description generate a physical description.

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Chen, Chao 1974. "A direct kinematic computation algorithm for all planar 3-legged platforms /." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33962.

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An analysis and comprehensive solution to the direct kinematics problem (DK) of all planar 3-legged platforms with lower pairs, called general planar Stewart-Gough platform (PSGP), is presented. There are 10 types of PSGP DK problem formulation including those with mixed leg architecture.
Planar kinematic mapping expresses pole position and rotation angle of a planar displacement as a point in 3-dimensional projective space represented by 4 homogeneous coordinates. This provides a universal tool for kinematic analysis. Its application will be demonstrated in the derivation of a general algorithm for planar DK. For each type of PSGP, the problem is reduced to a 6th order univariate polynomial whose roots reveal all solutions. An example of a PSGP with 6 real assembly configurations is presented. Furthermore, this algorithm was implemented and tested exhaustively. A complete self-contained version, coded in C, is available at http://www.cim.mcgill.ca/∼paul/. It should be easy to customize and adapt to any given real time micro-controller application.

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Kalakkad, Jayaraman Suganth Kumar. "Computation of economic rebound effect in different sectors of the U.S. economy." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/46068.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.
Includes bibliographical references.
Economic rebound effect is the phenomenon in which price reduction in products and services, induced by energy efficiency increase will cause more consumption leading to an "eat away" of the potential decreases in energy usage. Several researchers have expressed their views on the existence of the effect and the related consequences of such an effect in the micro economic scale. It is recognized that the microeconomic rebound effect will depend on how the price of a good will vary when an efficiency increase is brought about and also on how the quantity consumed may vary when the price changes by a certain amount. A mathematical formulation for this effect is then developed and the two parameters required are found separately for two relevant sectors of the economy. In the first case, the rebound effect is evaluated for the US Aluminum production sector taking into consideration both primary and secondary production. Several models for determining the price elasticity of demand are developed and the share of energy cost in total costs is also found in order to estimate the rebound. The values indicate very low rebound effect in the aluminum industry. A similar trial is conducted for system wide U.S air travel and the rebound estimates are arrived at. Low to moderate take back is observed in this case due to the increased price elasticity unlike the aluminum case where a very low price elasticity of demand pulled down rebound values. In the final sections of the report, discussions including the future trends in rebound effect in the wake of the higher fuel prices and low cost product introduction etc are made. A qualitative description of the macroeconomic rebound effect is also made and conclusions regarding the presence and significance of this effect are drawn. In summarizing it is inferred that even if the rebound effect is statistically significant, it cannot be big enough to completely mask the gains in efficiency improvement. Hence efficiency improvement is inferred as a definite method to decrease energy usage despite the fact that it has its own effectiveness limit set by the rebound.
by Suganth Kumar Kalakkad Jayaraman.
S.M.

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Razavi, Seyed Esmail. "Far field boundary conditions for computation of compressible aerodynamic flows." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28896.

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The formulation and implementation of a far field boundary condition (FFBC) model for compressible flows is reported in this thesis. This FFBC model, developed for quasi-one-dimensional and two-dimensional flows, aims to permit a substantial reduction of the computational domain, leading to a considerable improvement in the computational efficiency. The present FFBC approach uses asymptotic expansions of the Riemann variables, which are truncated up to the required degree of accuracy. Then, the far field perturbation equations are integrated in time and applied in conjunction with the solution calculated within the computational domain. The propagating information from the computational domain is determined along the outgoing characteristic fronts, based on the estimation of the wave front orientation.
The proposed FFBC model is implemented in conjunction with an implicit finite-difference flow field solver using an alternating direction implicit (ADI) scheme for solving the Euler equations. The discretized form of the governing equations are solved using a time-marching technique until the steady-state solution is reached. An accurate procedure for the solid boundary treatment was also used.
The proposed FFBC model was used for solving typical problems of confined and external compressible flows in subsonic and transonic regimes. For the transonic regime, the proposed FFBC model has been extended for the case of non-isentrophic outgoing flows, which appear behind the shock waves. The solutions obtained are compared with previous theoretical and numerical results. This comparison shows that the proposed FFBC model can generate accurate solutions using a substantially reduced computational domain, which reduces by an order of magnitude the size of the block tridiagonal matrices to be inverted. This leads to a corresponding improvement in the overall computational efficiency.

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Chan, Godine Kok Yan. "Computation of nonlinear hydrodynamic loads on floating wind turbines using fluid-impulse theory." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104254.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 199-202).
Wind energy is one of the more viable sources of renewable energy and offshore wind turbines represent a promising technology for the cost effective harvesting of this abundant source of energy. To capture wind energy offshore, horizontal-axis wind turbines can be installed on offshore platforms and the study of hydrodynamic loads on these offshore platforms becomes a critical issue for the design of offshore wind turbine systems. A versatile and efficient hydrodynamics module was developed to evaluate the linear and nonlinear loads on floating wind turbines using a new fluid-impulse formulation - the Fluid Impulse Theory(FIT). The new formulation allows linear and nonlinear loads on floating bodies to be computed in the time domain, and avoids the computationally intensive evaluation of temporal and spatial gradients of the velocity potential in the Bernoulli equation and the discretization of the nonlinear free surface. The module computes linear and nonlinear loads - including hydrostatic, Froude-Krylov, radiation and diffraction, as well as nonlinear effects known to cause ringing, springing and slow-drift loads - directly in the time domain and a stochastic seastate. The accurate evaluation of nonlinear loads by FIT provides an excellent alternative to existing methods for the safe and cost-effective design of offshore floating wind turbines. The time-domain Green function is used to solve the linear and nonlinear free-surface problems and efficient methods are derived for its computation. The body instantaneous wetted surface is approximated by a panel mesh and the discretization of the free surface is circumvented by using the Green function. The evaluation of the nonlinear loads is based on explicit expressions derived by the fluid-impulse theory, which can be computed efficiently.
by Godine Kok Yan Chan.
Ph. D.

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Huang, Geng S. M. Massachusetts Institute of Technology. "Computation of safety control for hybrid system with applications to intersection collision avoidance system." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101543.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 69-74).
In this thesis, I consider the problem of designing a collision avoidance system for the scenario in which two cars approach an intersection from perpendicular directions. One of the cars is a human driven vehicle, and the other one is a semi-autonomous vehicle, equipped with a driver-assist system. The driver-assist system should warn the driver of the semi-autonomous vehicle to brake or accelerate if potential dangers of collision are detected. Then, if the system detects that the driver disobeys the warning, the system can override the behavior of the driver to guarantee safety if necessary. A hybrid automaton model with hidden modes is used to solve the problem. A disturbance estimator is used to estimate the driver's reaction to the warning. Then, with the help of a mode estimator, the hybrid system with hidden modes is translated to a hybrid system with perfect state information. Finally, we generalize the solution for the application example to the solution of safety control problem for general hybrid system with hidden modes when the hybrid system satisfies some proposed constraints and assumptions.
by Geng Huang.
S.M.

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Muñiz, Pablo E. (Muñiz Aponte). "Detection of launch frame in long jump videos using computer vision and discreet computation." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123277.

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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (page 44).
Pose estimation, a computer vision technique, can be used to develop a quantitative feedback training tool for long jumping. Key performance indicators (KPIs) such as launch velocity would allow a long jumping athlete to optimize their technique while training. However, these KPIs need a prior knowledge of when the athlete jumped, referred to as the launch frame in the context of videos and computer vision. Thus, an algorithm for estimating the launch frame was made using the OpenPose Demo and Matlab. The algorithm estimates the launch frame to within 0.8±0.91 frames. Implementing the algorithm into a training tool would give an athlete real-time, quantitative feedback from a video. This process of developing an algorithm to flag an event can be used in other sports as well, especially with the rise of KPIs in the sports industry (e.g. launch angle and velocity in baseball).
by Pablo E. Muniz.
S.B.
S.B. Massachusetts Institute of Technology, Department of Mechanical Engineering

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Goldman, Avrum. "Some issues pertaining to computation of flow through large domains linked by a small slot." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69745.

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Potential difficulties involved in Computational Fluid Dynamics (CFD) approaches to the investigation of primary-flow domains linked by multiple orifices are identified. Practices that involve detailed simulation of the complete flow field, including flow through the orifices, are limited by the need for extensive grid refinement near each orifice, and by slow convergence rates. Other approaches, such as modeling of the flow in each domain separately, and linking these flows by one-dimensional flow networks, reduce the accuracy of the solution. In this thesis, an alternative treatment is developed in which finite-volume modeling (FVM) inside the slot is replaced by specified flow conditions at the slot boundaries. These conditions are updated once per iteration by a correlation function, based on flow conditions local to the slot, as generated by the primary-domain FVM solution. The correlation function is derived empirically, using data from detailed numerical simulations. Application of this approach to laminar flow in two parallel channels linked by a small slot has produced encouraging results.

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Gupta, Jatin. "Application Of Conjugate Heat Transfer (Cht) Methodology For Computation Of Heat Transfer On A Turbine Blade." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1230064860.

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Alrudainy, Haider M. "Non-invasive power gating techniques for bursty computation workloads using micro-electro-mechanical relays." Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3818.

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Electrostatically-actuated Micro-Electro-Mechanical/Nano-Electro- Mechanical (MEM/NEM) relays are promising devices overcoming the energy-efficiency limitations of CMOS transistors. Many exploratory research projects are currently under way investigating the mechanical, electrical and logical characteristics of MEM/NEM relays. One particular issue that this work addresses is the need for a scalable and accurate physical model of the MEM/NEM switches that can be plugged into the standard EDA software. The existing models are accurate and detailed but they suffer from the convergence problem. This problem requires finding ad-hoc workarounds and significantly impacts the designer’s productivity. In this thesis we propose a new simplified Verilog-AMS model. To test scalability of the proposed model we cross-checked it against our analysis of a range of benchmark circuits. Results show that, compared to standard models, the proposed model is sufficiently accurate with an average of 6% error and can handle larger designs without divergence. This thesis also investigates the modelling, designing and optimization of various MEM/NEM switches using 3D Finite Element Analysis (FEA) performed by the COMSOL multiphysics simulation tool. An extensive parametric sweep simulation is performed to study the energy-latency trade-offs of MEM/NEM relays. To accurately simulate MEMS/NEMS-based digital circuits, a Verilog-AMS model is proposed based on the evaluated parameters obtained from the multiphysics simulation tool. This allows an accurate calibration of the MEM/NEM relays with a significant reduction in simulation speed compared to that of 3D FEA exercised on COMSOL tool. The effectiveness of two power gating approaches in asynchronous micropipelines is also investigated using MEM/NEM switches and sleep transistors in reducing idle power dissipation with a particular target throughput. Sleep transistors are traditionally used to power gate idle circuits, however, these transistors have fundamental limitations in their effectiveness. Alternatively, MEM/NEM relays with zero leakage current can achieve greater energy savings under a certain data rate and design architecture. An asynchronous FIR filter 4 phase bundled data handshake protocol is presented. Implementation is accomplished in 90nm technology node and simulation exercised at various data rates and design complexities. It was demonstrated that our proposed approach offers 69% energy improvements at a data rate 1KHz compared to 39% of the previous work. The current trends for greater heterogeneity in future Systems-on- Chip (SoC) do not only concern their functionality but also their timing and power aspects. The increasing diversity of timing and power supply conditions, and associated concurrently operating modes, within an SoC calls for more efficient power delivery networks (PDN) for battery operated devices. This is especially important for systems with mixed duty cycling, where some parts are required to work regularly with low-throughput while other parts are activated spontaneously, i.e. in bursts. To improve their reaction time vs energy efficiency, this work proposes to incorporate a power-switching network based on MEM relays to switch the SoC power-performance state (PPS) into an active mode while eliminating the leakage current when it is idle. Results show that even with today0s large and high pull-in voltages, a MEM-relay-based power switching network (PSN) can achieve a 1000x savings in energy compared to its CMOS counterpart for low duty cycle. A simple case of optimising an on-chip charge pump required to switch-on the relay has been investigated and its energy-latency overhead has been evaluated. Heterogeneous many-core systems are increasingly being employed in modern embedded platforms for high throughput at low energy cost considerations. These applications typically exhibit bursty workloads that provide opportunities to minimize system energy. CMOS-based power gating circuitry, typically consisting of sleep transistors, is used as an effective technique for idle energy reduction in such applications. However, these transistors contribute high leakage current when driving large capacitive loads, making effective energy minimization challenging. This thesis proposes a novel MEMS-based idle energy control approach. Core to this approach is an integrated sleep mode management based on the performance-energy states and bursty workloads indicated by the performance counters. A number of PARSEC benchmark applications are used as case studies of bursty workloads, including CPU- and memory- intensive ones. These applications are exercised on an Exynos 5422 heterogeneous many-core platform, engineered with a performance counter facilities, showing 55.5% energy savings compared with an on-demand governor. Furthermore, an extensive trade-off analysis demonstrates the comparative advantages of the MEMS-based controller, including zero-leakage current and non-invasive implementations suitable for commercial off-the-shelf systems.

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Chue, Bryan C. "Efficient Hessian computation in inverse problems with application to uncertainty quantification." Thesis, Boston University, 2013. https://hdl.handle.net/2144/21138.

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Thesis (M.Sc.Eng.) PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
This thesis considers the efficient Hessian computation in inverse problems with specific application to the elastography inverse problem. Inverse problems use measurements of observable parameters to infer information about model parameters, and tend to be ill-posed. They are typically formulated and solved as regularized constrained optimization problems, whose solutions best fit the measured data. Approaching the same inverse problem from a probabilistic Bayesian perspective produces the same optimal point called the maximum a posterior (MAP) estimate of the parameter distribution, but also produces a posterior probability distribution of the parameter estimate, from which a measure of the solution's uncertainty may be obtained. This probability distribution is a very high dimensional function with which it can be difficult to work. For example, in a modest application with N = 104 optimization variables, representing this function with just three values in each direction requires 3^10000 U+2248 10^5000 variables, which far exceeds the number of atoms in the universe. The uncertainty of the MAP estimate describes the shape of the probability distribution and to leading order may be parameterized by the covariance. Directly calculating the Hessian and hence the covariance, requires O(N) solutions of the constraint equations. Given the size of the problems of interest (N = O(10^4 - 10^6)), this is impractical. Instead, an accurate approximation of the Hessian can be assembled using a Krylov basis. The ill-posed nature of inverse problems suggests that its Hessian has low rank and therefore can be approximated with relatively few Krylov vectors. This thesis proposes a method to calculate this Krylov basis in the process of determining the MAP estimate of the parameter distribution. Using the Krylov space based conjugate gradient (CG) method, the MAP estimate is computed. Minor modifications to the algorithm permit storage of the Krylov approximation of the Hessian. As the accuracy of the Hessian approximation is directly related to the Krylov basis, long term orthogonality amongst the basis vectors is maintained via full reorthogonalization. Upon reaching the MAP estimate, the method produces a low rank approximation of the Hessian that can be used to compute the covariance.
2031-01-01

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Shary, Stephen. "Java Simulator of Qubits and Quantum-Mechanical Gates Using the Bloch Sphere Representation." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1298044339.

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Adhikari, Sudip. "Accelerating the Computation of Chemical Reaction Kinetics for Modeling Turbulent Reacting Flows." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1510259399348102.

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Orselli, Erdem. "Computation Of Drag Force On Single And Close-following Vehicles." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607619/index.pdf.

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In this study, application of computational fluid dynamics to ground vehicle aerodynamics was investigated. Two types of vehicle models namely, Ahmed Body and MIRA Notchback Body and their scaled models were used. A commercial software "
Fluent"
was used and the effects of implementing different turbulence models with wall functions were observed. As a result, an appropriate turbulence model was selected to use in the study. The drag forces, surface pressure distributions and wake formations were investigated in simulation of various test cases available in the literature. The study was extended to simulate the aerodynamics of the vehicles in close-following situation. The results were then compared with available wind tunnel test data.

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Sexton, Scott Michael. "Progress Toward Analytic Predictions of Supersonic Hydrocarbon-Air Combustion| Computation of Ignition Times and Supersonic Mixing Layers." Thesis, University of California, San Diego, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10687717.

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Combustion in scramjet engines is faced with the limitation of brief residence time in the combustion chamber, requiring fuel and preheated air streams to mix and ignite in a matter of milliseconds. Accurate predictions of autoignition times are needed to design reliable supersonic combustion chambers. Most efforts in estimating non-premixed autoignition times have been devoted to hydrogen-air mixtures. The present work addresses hydrocarbon-air combustion, which is of interest for future scramjet engines.

Computation of ignition in supersonic flows requires adequate characterization of ignition chemistry and description of the flow, both of which are derived in this work. In particular, we have shown that activation energy asymptotics combined with a previously derived reduced chemical kinetic mechanism provides analytic predictions of autoignition times in homogeneous systems. Results are compared with data from shock tube experiments, and previous expressions which employ a fuel depletion criterion.

Ignition in scramjet engines has a strong dependence on temperature, which is found by perturbing the chemically frozen mixing layer solution. The frozen solution is obtained here, accounting for effects of viscous dissipation between the fuel and air streams. We investigate variations of thermodynamic and transport properties, and compare these to simplified mixing layers which neglect these variations. Numerically integrating the mixing layer problem reveals a nonmonotonic temperature profile, with a peak occurring inside the shear layer for sufficiently high Mach numbers.

These results will be essential in computation of ignition distances in supersonic combustion chambers.

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Labaki, Wassim. "Computation of free vibration frequencies and mode shapes of cantilever plates with finite discontinuities in properties moving outward from the clamped edge." Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/8988.

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The study of rectangular cantilever plates with step discontinuities in properties is of interest in many areas of industry. Cantilever plates are assigned different properties to represent change in stiffness and mass creating therefore the concept of step discontinuities in properties. The step discontinuity in properties is best represented by dividing the cantilever plate into separate segments called spans, with each span having its own stiffness and/or mass distribution as one moves outwards from the clamped edge. This thesis presents the concept of dividing the cantilever plate into spans and provides accurate analytical solutions for free vibration frequencies and mode shapes. Chapter 1 introduces the reader to the theory of rectangular plates while chapter 2 concentrates on introducing the general solutions as applied to rectangular plates. Although there is no limit to the number of plate spans to be studied, three and four span cantilever plates were analysed in chapter 3. The computed eigenvalues are validated against previously published uniform rectangular cantilever plate free vibration results. They were found converging to the known values. Free vibration eigenvalues and mode shapes are then calculated for a variety of cantilever plates of different aspect ratios and with different span thicknesses creating a discontinuity in mass and flexural rigidity along the plate. The results are presented in chapter 4 and discussed in chapter 5.

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Sharkey, Keeper Layne. "Very Accurate Quantum Mechanical Non-Relativistic Spectra Calculations of Small Atoms & Molecules Employing All-Particle Explicitly Correlated Gaussian Basis Functions." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/560835.

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Due to the fast increasing capabilities of modern computers it is now feasible to calculate spectra of small atom and molecules with the greater level of accuracy than high-resolution measurements. The mathematical algorithms developed and implemented on high performance supercomputers for the quantum mechanical calculations are directly derived from the first principles of quantum mechanics. The codes developed are primarily used to verify, refine, and predict the energies associated within a given system and given angular momentum state of interest. The Hamiltonian operator used to determine the total energy in the approach presented is called the internal Hamiltonian and is obtained by rigorously separating out the center-of-mass motion (or the elimination of translational motion) from the laboratory-frame Hamiltonian. The methods utilized in the articles presented in this dissertation do not include relativistic corrections and quantum electrodynamic effects, nor do these articles assume the Born-Oppenheimer (BO) approximation with the exception of one publication. There is one major review article included herein which describes the major differences between the non-BO method and the BO approximation using explicitly correlated Gaussian (ECG) basis functions. The physical systems studied in this dissertation are the atomic elements with Z < 7 (although the discussion is not limited to these) and diatomic molecules such as H₂⁺ and H₂ including nuclear isotopic substitution studies with deuterium and tritium, as well as electronic substitutions with the muon particle. Preliminary testing for triatomic molecular functionals using a model potential is also included in this dissertation. It has been concluded that using all-particle ECGs with including the addition of nonzero angular momentum functions to describe nonzero angular momentum states is sufficient in determining the energies of these states for both the atomic and molecular case.

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Tupek, Michael Ronne. "Lagrangian methods for ballistic impact simulations/." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/69216.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 85-92).
This thesis explores various Lagrangian methods for simulating ballistic impact with the ultimate goal of finding a universal, robust and scalable computational framework to assist in the design of armor systems. An overview is provided of existing Lagrangian strategies including particle methods, meshless methods, and the peridynamic approach. We review the continuum formulation of mechanics and its discretization using finite elements. A rigid body contact algorithm for explicit dynamic finite elements is presented and used to model a rigid sphere impacting a confined alumina tile. The constitutive model for the alumina is provided by the Deshpande-Evans ceramic damage model. These simulations were shown to capture experimentally observed radial crack patterns. An adaptive remeshing strategy using finite elements is then explored and applied, with limited success, to the problem of predicting the transition from dwell to penetration for long-rod penetrators impacting confined ceramic targets at high velocities. Motivated by the difficulties of mesh-based Lagrangian approaches for modeling impact, an alternative Lagrangian approach is investigated which uses established constitutive relations within a particle-based computational framework. The resulting algorithm is based on a discretization of the peridynamic formulation of continuum mechanics. A validating benchmark example using a Taylor impact test is shown and compared to previous results from the literature. Further numerical examples involving ballistic impact and the crushing of an aluminum sandwich structures provide further demonstration of the method's potential for armor applications.
by Michael Ronne Tupek.
S.M.

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Losey, Bradley. "Analysis of Magnetic Gear End-Effects to Increase Torque and Reduce Computation Time." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595514209192582.

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AL-AZMI, BADER SHABEEB. "ANALYSIS OF TRANSPORT MODELS AND COMPUTATION ALGORITHMS FOR FLOW THROUGH POROUS MEDIA." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1051059625.

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Hayward, Kevin. "Application of evolutionary algorithms to engineering design." University of Western Australia. School of Mechanical Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2009.0018.

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The efficiency of the mechanical design process can be improved by the use of evolutionary algorithms. Evolutionary algorithms provide a convenient and robust method to search for appropriate design solutions. Difficult non-linear problems are often encountered during the mechanical engineering design process. Solutions to these problems often involve computationally-intensive simulations. Evolutionary algorithms tuned to work with a small number of solution iterations can be used to automate the search for optimal solutions to these problems. An evolutionary algorithm was designed to give reliable results after a few thousand iterations; additionally the scalability and the ease of application to varied problems were considered. Convergence velocity of the algorithm was improved considerably by altering the mutation-based parameters in the algorithm. Much of this performance gain can be attributed to making the magnitude of the mutation and the minimum mutation rates self-adaptive. Three motorsport based design problems were simulated and the evolutionary algorithm was applied to search for appropriate solutions. The first two, a racing-line generator and a suspension kinematics simulation, were investigated to highlight properties of the evolutionary algorithm: reliability; solution representation; determining variable/performance relationships; and multiple objectives were discussed. The last of these problems was the lap-time simulation of a Formula SAE vehicle. This problem was solved with 32 variables, including a number of major conceptual differences. The solution to this optimisation was found to be significantly better than the 2004 UWA Motorsport vehicle, which finished 2nd in the 2005 US competition. A simulated comparison showed the optimised vehicle would score 62 more points (out of 675) in the dynamic events of the Formula SAE competition. Notably the optimised vehicle had a different conceptual design to the actual UWA vehicle. These results can be used to improve the design of future Formula SAE vehicles. The evolutionary algorithm developed here can be used as an automated search procedure for problems where performance solutions are computationally intensive.

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Wojtacki, Kajetan Tomasz. "Coupling between transport, mechanical properties and degradation by dissolution of rock reservoir." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS153/document.

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L'objectif de cette thèse est d'analyser l'évolution des propriétés mécaniques et de transport effectives de roches aquifères,qui sont soumises à une dégradation progressive par attaque chimique due à la dissolution par CO2.L'étude proposée porte sur les conditions à long terme et en champ lointain, lorsque la dégradation de la matrice poreuse peut être supposée homogène à l'échelle de l'échantillon.La morphologie du réseau de pores et du squelette solide définissant les propriétés macroscopiques majeures de la roche (perméabilité, élasticité),la modélisation d'un tel matériau poreux doit être basée sur une caractérisation morphologique et statistique des roches étudiées.Tout d'abord, une méthode de reconstruction inspirée du processus naturel de formation des grès est développée afin d'obtenir des représentations statistiquement équivalentes à de véritables échantillons.Les échantillons générés sont sélectionnés afin de satisfaire les informations morphologiques extraites de l'analyse des images microtomographiques d'échantillons de roche naturelle.Une méthodologie afin d'estimer les propriétés mécaniques équivalentes des échantillons générés, fondées directement sur des maillages réguliers considérés comme images binaires, est présentée.Le comportement mécanique équivalent est obtenu dans le cadre de l'homogénéisation périodique.Mais en raison du manque de périodicité géométrique des échantillons considérés, deux approches différentes sont développées :la reconstruction de VER par symétrie de réflexion ou l'addition d'une couche homogène associée à une méthode de point fixe.L’évolution de la perméabilité est estimée de manière classique en utilisant la méthode de mise à l'échelle dans la forme de la loi de Darcy. Enfin, la dissolution chimique du matériau est abordée par dilatation morphologique de la phase poreuse.De plus, une analyse détaillée de l'évolution des descripteurs morphologiques liée aux modifications de la microstructure lors des étapes de dissolution est présentée.La relation entre les propriétés morphologiques - perméabilité - modules d'élasticité est également fournie.La méthodologie développée dans ce travail pourra être facilement appliquée à d'autres classes de matériaux hétérogènes
The aim of this thesis is to analyse evolution of effective mechanical and transport properties of rock aquifer, which is subjected to progressive chemical degradation due to CO2 dissolution. The proposed study focuses on long-term and far field conditions, when degradation of porous matrix can be assumed to be homogeneous at sample scale. It is very well known that morphology of pore network and solid skeleton defines important macroscopic properties of the rock (permeability, stiffness). Therefore, modelling of such porous material should be based on morphological and statistical characterisation of investigated rocks. First of all, in order to obtain statistically equivalent representations of real specimen a reconstruction method inspired by natural process of sandstone formation is adapted. Then the selected generated samples satisfy morphological informations which are extracted by analysing microtomography of the natural rock sample. Secondly, a methodology to estimate effective mechanical properties of investigated material, based directly on binary images, is featured. Effective mechanical behaviour is obtain within the framework of periodic homogenization, However due to lack of geometrical periodicity two different approaches are used (reflectional symmetry of considered RVE and a fixed point method, using additional layer spread over the considered geometry). Evolution of permeability is estimated in classical way using upscaling method in the form of Darcy's law. Finally, chemical dissolution of material is tackled in a simplified way by performing morphological dilation of porous phase. Detailed analysis of chosen morphological descriptors evolution, triggered by modifications of microstructures is provided. The relation between morphological properties – permeability – elastic moduli is also provided. The methodology developed in this work could be easily applied to other heterogeneous materials

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26

Polad, Serkan. "Quantum Mechanical Treatment Of Fullerene-based Systems Doped With Various Metal And Non-metal Elements As Prospective Spin-qubits." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612173/index.pdf.

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In this thesis, We have calculated the optimized geometries, electronic structures and spin distributions of metal and non-metal elements Li, Na, N and P doped C60 fullerene dimers and trimers with different spin multiplicities using hybrid density functional theory (DFT) at the B3LYP/6-31G level of theory. Natural population analysis and Mulliken population analysis show that non-metal elements (N, P) inside the C60 fullerene dimers and trimers are well isolated and preserve their electronic structures while charge transfer processes occur between metal elements(Li, Na) and C60 structures. Energy calculations showed that both doped and undoped linear C60 structures are energetically lower than triangular C60 structures. Calculated spin density distributions make non-metal doped C60 structures advantageous over metal doped C60 cages as spin cluster qubits.

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27

Mitlin, Sergey. "Studies of Interaction of Small Molecules with Water Condensed Media." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/1273.

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STUDIES OF INTERACTION OF SMALL MOLECULES WITH WATER CONDENSED MEDIA

The present work reports experimental and theoretical studies of the intermolecular interactions in condensed water media. The chemical objects comprise pristine ice and polar organic substances: acetone, acetaldehyde, methanol and chloroform and bi-component water-organic deposits. The experimental part of the studies includes the Fourier Transform Infrared Reflection Absorption spectral (FTIR RAS) examination of the processes of film growth by vapor deposition on cold metal substrate and subsequent annealing. The theoretical studies include ab initio (MP2) and semi-empirical (B3LYP) calculations on the small water and water-organic clusters and classical molecular dynamics simulations of the adsorption of inert guests (Xe/Rn) on the ice surface. The FTIR RA spectral studies reveal that depending on the deposition conditions condensed water media exist in two principal structural forms: noncrystalline and polycrystalline. The former is characterized by porous structure while the latter exists as a non-porous medium with smooth external interface. On annealing, characteristic spectral changes indicate on a rapid crystallization occurring at a certain temperature range. The initial adsorption of organic molecules is accompanied by the hydrogen-bonded coordination between the functional group of organic species and non-coordinated hydroxyl group of the ice surface, the topology of which depends on the electronic properties of the functional group. The computational studies of small water-organic clusters reveal, in particular, two major coordination minima for carbonyl group: a single hydrogen-bonded in-plane complex and a double hydrogen-bonded in-plane complex. The classical molecular dynamics of Xe/Rn species on the ice interface is consistent with two distinctly different surface adsorption sites: one that delocalized over the entire surface and one that confined to small opening in the top ice layer, disrupted by the thermal molecular motion. The penetration barrier is associated with van der Walls repulsion of guest species from the ordered water hexagonal arrangement. A thermo-disruption of latter leads to a rapid diffusion of guest species inside ice medium.

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Singh, Mahendra [Verfasser]. "Quantenmechanische Berechnung der Dispersionsenergie in Fluiden Systemen und Anwendung in Zustandsgleichungen : Quantum Mechanical Computation of the Dispersion Energy in Fluid Systems and Application in Equations of State / Mahendra Singh." Aachen : Shaker, 2010. http://d-nb.info/1120864682/34.

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29

Larson, Rudolph Scott. "Computationally Efficient Modeling of Transient Radiation in a Purely Scattering Foam Layer." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1871.pdf.

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30

Tien, Meng-Hsuan. "Analyzing and Exploiting the Dynamics of Complex Piecewise-Linear Nonlinear Systems." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1586039513469825.

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31

Matek, Christian C. A. "Statistical mechanics of nucleic acids under mechanical stress." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:ce44cf50-2001-4f54-8e57-d1757f709fd6.

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In this thesis, the response of DNA and RNA to linear and torsional mechanical stress is studied using coarse-grained models. Inspired by single-molecule assays developed over the last two decades, the end-to-end extension, buckling and torque response behaviour of the stressed molecules is probed under conditions similar to experimentally used setups. Direct comparison with experimental data yields excellent agreement for many conditions. Results from coarse-grained simulations are also compared to the predictions of continuum models of linear polymer elasticity. A state diagram for supercoiled DNA as a function of twist and tension is determined. A novel confomational state of mechanically stressed DNA is proposed, consisting of a plectonemic structure with a denaturation bubble localized in its end-loop. The interconversion between this novel state and other, known structural motifs of supercoiled DNA is studied in detail. In particular, the influence of sequence properties on the novel state is investigated. Several possible implications for supercoiled DNA structures in vivo are discussed. Furthermore, the dynamical consequences of coupled denaturation and writhing are studied, and used to explain observations from recent single molecule experiments of DNA strand dynamics. Finally, the denaturation behaviour, topology and dynamics of short DNA minicircles is studies using coarse-grained simulations. Long-range interactions in the denaturation behaviour of the system are observed. These are induced by the topology of the system, and are consistent with results from recent molecular imaging studies. The results from coarse-grained simulations are related to modelling of the same system in all-atom simulations and a local denaturation model of DNA, yielding insight into the applicability of these different modelling approaches to study different processes in nucleic acids.

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32

Wu, Fei. "Parallel computational methods for constrained mechanical systems." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282561.

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Two methods suitable for parallel computation in the study of mechanical systems with holonomic and nonholonomic constraints are presented: one is an explicit solution based on generalized inverse algebra; the second solves problems of this class through the direct application of Gauss' principle of least constraint and genetic algorithms. Algorithms for both methods are presented for sequential and parallel implementations. The method using generalized inverses is able to solve problems that involve redundant, degenerate and intermittent constraints, and can identify inconsistent constraint sets. It also allows a single program to perform pure kinematic and dynamic analyses. Its computational cost is among the lowest in comparison with other methods. In addition, constraint violation control methods are investigated to improve integration accuracy and further reduce computational cost. Constrained dynamics problems are also solved using optimization methods by applying Gauss' principle directly. An objective function that incorporates constraints is derived using a symmetric scheme, which is implemented using genetic algorithms in a parallel computing environment. It is shown that this method is capable of solving the same cases of constraints as the former method. Examples and numerical experiments demonstrating the applications of the two methods to constrained multiparticle and multibody systems are presented.

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33

Ward, Paul. "A computational and experimental study on respiratory oscillation mechanics for the control of mechanical ventilation." Thesis, King's College London (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435804.

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Ballage, Marion. "Algorithmes de résolution rapide de problèmes mécaniques sur GPU." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30122/document.

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Dans le contexte de l'analyse numérique en calcul de structures, la génération de maillages conformes sur des modèles à géométrie complexe conduit à des tailles de modèles importantes, et amène à imaginer de nouvelles approches éléments finis. Le temps de génération d'un maillage est directement lié à la complexité de la géométrie, augmentant ainsi considérablement le temps de calcul global. Les processeurs graphiques (GPU) offrent de nouvelles opportunités pour le calcul en temps réel. L'architecture grille des GPU a été utilisée afin d'implémenter une méthode éléments finis sur maillage cartésien. Ce maillage est particulièrement adapté à la parallélisation souhaitée par les processeurs graphiques et permet un gain de temps important par rapport à un maillage conforme à la géométrie. Les formulations de la méthode des éléments finis ainsi que de la méthode des éléments finis étendue ont été reprises afin d'être adaptées à notre méthode. La méthode des éléments finis étendus permet de prendre en compte la géométrie et les interfaces à travers un choix adéquat de fonctions d'enrichissement. Cette méthode discrétise par exemple sans mailler explicitement les fissures, et évite surtout de remailler au cours de leur propagation. Des adaptations de cette méthode sont faites afin de ne pas avoir besoin d'un maillage conforme à la géométrie. La géométrie est définie implicitement par une fonction surfaces de niveau, ce qui permet une bonne approximation de la géométrie et des conditions aux limites sans pour autant s'appuyer sur un maillage conforme. La géométrie est représentée par une fonction surfaces de niveau que nous appelons la densité. La densité est supérieure à 0.5 à l'intérieur du domaine de calcul et inférieure à 0.5 à l'extérieur. Cette fonction densité, définie par ses valeurs aux points noeuds du maillage, est interpolée à l'intérieur de chaque élément. Une méthode d'intégration adaptée à cette représentation géométrique est proposée. En effet, certains éléments sont coupés par la fonction surfaces de niveau et l'intégration de la matrice de raideur ne doit se faire que sur la partie pleine de l'élément. La méthode de quadrature de Gauss qui permet d'intégrer des polynômes de manière exacte n'est plus adaptée. Nous proposons d'utiliser une méthode de quadrature avec des points d'intégration répartis sur une grille régulière et dense. L'intégration peut s'avérer coûteuse en temps de calcul, c'est pour cette raison que nous proposons une technique d'apprentissage donnant la matrice élémentaire de rigidité en fonction des valeurs de la fonction surfaces de niveau aux sommets de l'élément considéré. Cette méthode d'apprentissage permet de grandes améliorations du temps de calcul des matrices élémentaires. Les résultats obtenus après analyse par la méthode des éléments finis standard ou par la méthode des éléments finis sur maillage cartésien ont une taille qui peut croître énormément selon la complexité des modèles, ainsi que la précision des schémas de résolution. Dans un contexte de programmation sur processeurs graphiques, où la mémoire est limitée, il est intéressant d'arriver à compresser ces données. Nous nous sommes intéressés à la compression des modèles et des résultats éléments finis par la transformée en ondelettes. La compression mise en place aidera aussi pour les problèmes de stockage en réduisant la taille des fichiers générés, et pour la visualisation des données
Generating a conformal mesh on complex geometries leads to important model size of structural finite element simulations. The meshing time is directly linked to the geometry complexity and can contribute significantly to the total turnaround time. Graphics processing units (GPUs) are highly parallel programmable processors, delivering real performance gains on computationally complex, large problems. GPUs are used to implement a new finite element method on a Cartesian mesh. A Cartesian mesh is well adapted to the parallelism needed by GPUs and reduces the meshing time to almost zero. The novel method relies on the finite element method and the extended finite element formulation. The extended finite element method was introduced in the field of fracture mechanics. It consists in enriching the basis functions to take care of the geometry and the interface. This method doesn't need a conformal mesh to represent cracks and avoids refining during their propagation. Our method is based on the extended finite element method, with a geometry implicitly defined, wich allows for a good approximation of the geometry and boundary conditions without a conformal mesh.To represent the model on a Cartesian grid, we use a level set representing a density. This density is greater than 0.5 inside the domain and less than 0.5 outside. It takes 0.5 on the boundary. A new integration technique is proposed, adapted to the geometrical representation. For the element cut by the levet set, only the part full of material has to be integrated. The Gauss quadrature is no longer adapted. We introduce a quadrature method with integration points on a cartesian dense grid.In order to reduce the computational effort, a learning approach is then considered to form the elementary stiffness matrices as function of density values on the vertices of the elements. This learning method reduces the stiffness matrices time computation. Results obtained after analysis by finite element method or the novel finite element method can have important storage size, dependant of the model complexity and the resolution scheme exactitude. Due to the limited direct memory of graphics processing units, the data results are compressed. We compress the model and the element finite results with a wavelet transform. The compression will help for storage issue and also for data visualization

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35

Betancourt, Arturo. "Computational study of the heat transfer and fluid structure of a shell and tube heat exchanger." Thesis, Florida Atlantic University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10172609.

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A common technique to improve the performance of shell and tube heat exchangers (STHE) is by redirecting the flow in the shell side with a series of baffles. A key aspect in this technique is to understand the interaction of the fluid dynamics and heat transfer. Computational fluid dynamics simulations and experiments were performed to analysis the 3-dimensional flow and heat transfer on the shell side of an STHE with and without baffles. Although, it was found that there was a small difference in the average exit temperature between the two cases, the heat transfer coefficient was locally enhanced in the baffled case due to flow structures. The flow in the unbaffled case was highly streamed, while for the baffled case the flow was a highly complex flow with vortex structures formed by the tip of the baffles, the tubes, and the interaction of flow with the shell wall.

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36

Tang, Baobao. "Development of Mathematical and Computational Models to Design Selectively Reinforced Composite Materials." Thesis, University of Louisiana at Lafayette, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10163313.

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Different positions of a material used for structures experience different stresses, sometimes at both extremes, when undergoing processing, manufacturing, and serving. Taking the three-point bending as an example, the plate experiences higher stress in the middle span area and lower stress in both sides of the plate. In order to ensure the performance and reduce the cost of the composite, placement of different composite material with different mechanical properties, i.e. selective reinforcement, is proposed.

Very few study has been conducted on selective reinforcement. Therefore, basic understanding on the relationship between the selective reinforcing variables and the overall properties of composite material is still unclear and there is still no clear methodology to design composite materials under different types of loads.

This study started from the analysis of composite laminate under three point bending test. From the mechanical analysis and simulation result of homogeneously reinforced composite materials, it is found that the stress is not evenly distributed on the plate based on through-thickness direction and longitudinal direction. Based on these results, a map for the stress distribution under three point bending was developed. Next, the composite plate was selectively designed using two types of configurations. Mathematical and finite element analysis (FEA) models were built based on these designs. Experimental data from tests of hybrid composite materials was used to verify the mathematical and FEA models. Analysis of the mathematical model indicates that the increase in stiffness of the material at the top and bottom surfaces and middle-span area is the most effective way to improve the flexural modulus in three point bending test. At the end of this study, a complete methodology to perform the selective design was developed.

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37

Denzer, Ralf. "Computational configurational mechanics." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=978669797.

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Dhruv, Akash. "A Multiphase Solver for High-Fidelity Phase-Change Simulations over Complex Geometries." Thesis, The George Washington University, 2021. http://pqdtopen.proquest.com/#viewpdf?dispub=28256871.

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Complex interactions between solid, liquid and gas occur in many practical engineering applications, and are often difficult to quantify experimentally. A few examples include boiling over solid heaters, solidification melt-dynamics in metal casting, and convective cooling of electronic components. With the availability of scalable computational tools, high-fidelity simulations can provide new insight into these phenomena and answer open questions. In the present work, a multiphase solver is presented which can simulate problems involving phase transition over complex geometries. The dynamics of liquid-gas interface are modeled using a level-set technique, which utilizes Ghost Fluid Method (GFM) to account for sharp jump in pressure, velocity, and temperature across the multiphase boundary. The fluid-solid interactions are modeled using an Immersed Boundary Method (IBM) which uses a Moving Least Squared (MLS) reconstruction to calculate fluid-flow around the solid, along with an additional GFM forcing to model its effect on pressure, temperature and Conjugate Heat Transfer (CHT). The resulting three dimensional solver is fully explicit in time and uses a fractional step method for Navier-Stokes, energy, and mass transfer equations. Validation and verification cases are presented to demonstrate the accuracy of the solver in comparison to experimental and analytical problems, and results of high fidelity pool boiling simulations in varying gravity environments are discussed in detail.

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39

Emmanuelli, Gustavo. "An Assessment of State Equations of Air for Modeling a Blast Load Simulator." Thesis, Mississippi State University, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10979719.

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When an explosive detonates above ground, air is principally the only material involved in the transmission of shock waves that can result in damage. Hydrodynamic codes that simulate these explosions use equations of state (EOSs) for modeling the behavior of air at these high-pressure, high-velocity conditions. An investigation is made into the effect that the EOS selection for air has on the calculated overpressure-time waveforms of a blast event. Specifically, the ideal gas, Doan-Nickel, and SESAME EOSs in the SHAMRC code were used to reproduce experiments conducted at the Blast Load Simulator (BLS), a large-scale shock tube operated by the U.S. Army Engineer Research and Development Center, that consisted of subjecting an instrumented rigid box at three angles of orientation inside the BLS to a blast environment. Numerical comparisons were made against experimentally-derived confidence intervals using peak values and several error metrics, and an attempt was made to rank the EOS based on performance. Issues were noted with the duration of decay from maximum pressure to negative phase that resulted in a general underprediction of the integrated impulse regardless of EOS, while the largest errors were noted for gages on faces at 45 to 90 degrees from the initial flow direction. Although no significant differences were noticed in the pressure histories from different EOSs, the ideal gas consistently ranked last in terms of the error metrics considered and simultaneously required the least computing resources. Similarly, the Doan-Nickel EOS slightly performed better than SESAME while requiring additional wallclock time. The study showed that the Doan-Nickel and SESAME EOSs can produce blast signatures with less errors and more matches in peak pressure and impulse than the ideal gas EOS at the expense of more computational requirements.

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40

Schmidt, Peter. "Computational Models of Adhesively Bonded Joints." Doctoral thesis, Linköping : Division of Mechanics, Department of Management and Engineering, Linköping University, 2007. http://www.bibl.liu.se/liupubl/disp/disp2007/tek1076s.pdf.

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41

Lakkis, Issam Adnan 1970. "Lagrangian computations of radiating fire plumes." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/89262.

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42

Starling, Alexander Charles. "Performance-based computational synthesis of parametric mechanical systems." Thesis, University of Cambridge, 2004. https://www.repository.cam.ac.uk/handle/1810/251925.

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43

Marshall, G. S. "Muiticomponent fluid flow computation." Thesis, Teesside University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384659.

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Smart, Ronald S. "Automated Multidisciplinary Optimizations of Conceptual Rocket Fairings." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/3058.

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The purpose of this research is to develop and architect a preliminary multidisciplinary design optimization (MDO) tool that creates multiple types of generalized rocket fairing models. These models are sized relative to input geometric models and are analyzed and optimized, taking into account the primary objectives, namely the structural, thermal, and aerodynamic aspects of standard rocket flights. A variety of standard nose cone shapes is used as optimization proof of concept examples, being sized and compared to determine optimal choices based on the input specifications, such as the rocket body geometry and the specified trajectory paths. Any input models can be optimized to their respective best nose cone style or optimized to each of the cone styles individually, depending on the desired constraints. Two proof of concept example rocket model studies are included with varying sizes and speeds. Both have been optimized using the processes described to provide delineative instances into how results are improved and time saved. This is done by optimizing shape and thickness of the fairings while ascertaining if the remaining length downstream on the designated rocket model remains within specified stress and temperature ranges. The first optimized example exhibits a region of high stress downstream on the rocket body model that champions how these tools can be used to catch weaknesses and improve the overall integrity of a rocket design. The second example demonstrates how more established rocket designs can decrease their weight and drag through optimization of the fairing design.

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45

Zhu, Tulong. "Meshless methods in computational mechanics." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/11795.

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46

Alipour, Skandani Amir. "Computational and Experimental Nano Mechanics." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/64869.

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The many advances of nano technology extensively revolutionize mechanics. A tremendous need is growing to further bridge the gap between the classical mechanics and the nano scale for many applications at different engineering fields. For instance, the themes of interdisciplinary and multidisciplinary topics are getting more and more attention especially when the coherency is needed in diagnosing and treating terminal diseases or overcoming environmental threats. The fact that how mechanical, biomedical and electrical engineering can contribute to diagnosing and treating a tumor per se is both interesting and unveiling the necessity of further investments in these fields. This dissertation presents three different investigations in the area of nano mechanics and nano materials spanning from computational bioengineering to making mechanically more versatile composites. The first part of this dissertation presents a numerical approach to study the effects of the carbon nano tubes (CNTs) on the human body in general and their absorbability into the lipid cell membranes in particular. Single wall carbon nano tubes (SWCNTs) are the elaborate examples of nano materials that departed from mere mechanical applications to the biomedical applications such as drug delivery vehicles. Recently, experimental biology provided detailed insights of the SWCNTs interaction with live organs. However, due to the instrumental and technical limitations, there are still numerous concerns yet to be addressed. In such situation, utilizing numerical simulation is a viable alternative to the experimental practices. From this perspective, this dissertation reports a molecular dynamics (MD) study to provide better insights on the effect of the carbon nano tubes chiralities and aspect ratios on their interaction with a lipid bilayer membrane as well as their reciprocal effects with surface functionalizing. Single walled carbon nano tubes can be utilized to diffuse selectively on the targeted cell via surface functionalizing. Many experimental attempts have smeared polyethylene glycol (PEG) as a biocompatible surfactant to carbon nano tubes. The simulation results indicated that SWCNTs have different time-evolving mechanisms to internalize within the lipid membrane. These mechanisms comprise both penetration and endocytosis. Also, this study revealed effects of length and chirality and surface functionalizing on the penetrability of different nano tubes. The second part of the dissertation introduces a novel in situ method for qualitative and quantitative measurements of the negative stiffness of a single crystal utilizing nano mechanical characterization; nano indentation. The concept of negative stiffness was first introduced by metastable structures and later by materials with negative stiffness when embedded in a stiffer (positive stiffness) matrix. However, this is the first time a direct quantitative method is developed to measure the exact value of the negative stiffness for triglycine sulfate (TGS) crystals. With the advancements in the precise measuring devices and sensors, instrumented nano indentation became a reliable tool for measuring submicron properties of variety of materials ranging from single phase humongous materials to nano composites with heterogeneous microstructures. The developed approach in this chapter of the dissertation outlines how some modifications of the standard nano indentation tests can be utilized to measure the negative stiffness of a ferroelectric material at its Curie temperature. Finally, the last two chapters outline the possible improvements in the mechanical properties of conventional carbon fiber composites by introducing 1D nano fillers to them. Particularly, their viscoelastic and viscoplastic behavior are studied extensively and different modeling techniques are utilized. Conventional structural materials are being replaced with the fiber-reinforced plastics (FRPs) in many different applications such as civil structures or aerospace and car industries. This is mainly due to their high strength to weight ratio and relatively easy fabrication methods. However, these composites did not reach their full potential due to durability limitations. The majorities of these limitations stem from the polymeric matrix or the interface between the matrix and fibers where poor adhesion fails to carry the desired mechanical loadings. Among such failures are the time-induced deformations or delayed failures that can cause fatal disasters if not taken care of properly. Many methodologies are offered so far to improve the FRPs' resistance to this category of time-induced deformations and delayed failures. Several researchers tried to modify the chemical formulation of polymers coming up with stiffer and less viscous matrices. Others tried to modify the adhesion of the fibers to the matrix by adding different chemically functional groups onto the fibers' surface. A third approach tried to modify the fiber to matrix adhesion and at the same time improve the viscous properties of the matrix itself. This can be achieved by growing 1D nano fillers on the fibers so that one side is bonded to the fiber and the other side embedded in the matrix enhancing the matrix with less viscous deformability. It is shown that resistance to creep deformation and stress relaxation of laminated composites improved considerably in the presence of the nano fillers such as multiwall carbon nano tubes (MWCNTs) and zinc oxide nano wires (ZnO- NWs). The constitutive behaviors of these hybrid composites were investigated further through the use of the time temperatures superposition (TTS) principle for the linear viscoelastic behavior and utilizing phenomenological models for the viscoplastic behavior.
Ph. D.

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Sessions, Blake A. "A computational bow-spring model." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/65303.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2011.
"May 2010." Cataloged from PDF version of thesis.
Bow-springs find few applications in industry. Principally, they are used in archery. In addition, they have found some use in a compression-spring mode in the field of biomechatronics, to emulate elastic human legs. The mechanical behavior (characterized by deflected shape and deformation force) is difficult to model, because internal forces and moments and the geometry are both unknown. The only closed-form solutions to such systems are relatively useless to a mechanical engineer. This work comprises an iterative model developed in MATLAB that computes the mechanical behavior of buckled beam (or bow-spring) sections, over a range of parameters and geometries, to be used in the development and testing of compression bow-springs as parallel loading systems to the human leg.
by Blake A. Sessions.
S.B.

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Li, Shuai Ph D. Massachusetts Institute of Technology. "Computational imaging through deep learning." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122070.

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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 143-154).
Computational imaging (CI) is a class of imaging systems that uses inverse algorithms to recover an unknown object from the physical measurement. Traditional inverse algorithms in CI obtain an estimate of the object by minimizing the Tikhonov functional, which requires explicit formulations of the forward operator of the physical system, as well as the prior knowledge about the class of objects being imaged. In recent years, machine learning architectures, and deep learning (DL) in particular, have attracted increasing attentions from CI researchers. Unlike traditional inverse algorithms in CI, DL approach learns both the forward operator and the objects' prior implicitly from training examples. Therefore, it is especially attractive when the forward imaging model is uncertain (e.g. imaging through random scattering media), or the prior about the class of objects is difficult to be expressed analytically (e.g. natural images).
In this thesis, the application of DL approaches in two different CI scenarios are investigated: imaging through a glass diffuser and quantitative phase retrieval (QPR), where an Imaging through Diffuser Network (IDiffNet) and a Phase Extraction Neural Network (PhENN) are experimentally demonstrated, respectively. This thesis also studies the influences of the two main factors that determine the performance of a trained neural network: network architecture (connectivity, network depth, etc) and training example quality (spatial frequency content in particular). Motivated by the analysis of the latter factor, two novel approaches, spectral pre-modulation approach and Learning Synthesis by DNN (LS-DNN) method, are successively proposed to improve the visual qualities of the network outputs. Finally, the LS-DNN enhanced PhENN is applied to a phase microscope to recover the phase of a red blood cell (RBC) sample.
Furthermore, through simulation of the learned weak object transfer function (WOTF) and experiment on a star-like phase target, we demonstrate that our network has indeed learned the correct physical model rather than doing something trivial as pattern matching.
by Shuai Li.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering

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Bansod, Yogesh Deepak. "Computational Simulation of Mechanical Tests of Isolated Animal Cells." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-263397.

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Buňka tvoří složitý biologický systém vystavený mnoha mimobuněčným mechanickým podnětům. Hlubší pochopení jejího mechanického chování je důležité pro charakterizaci její odezvy v podmínkách zdraví i nemoci. Výpočtové modelování může rozšířit pochopení mechaniky buňky, která může přispívat k vytvoření vztahů mezi strukturou a funkcí různých typů buněk v různých stavech. Za tímto účelem byly pomocí metody konečných prvků (MKP) vytvořeny dva bendotensegritní modely buňky v různých stavech: model vznášející se buňky pro analýzu její globální mechanické odezvy, jako je protažení nebo stlačení, a model buňky přilnuté k podložce, který vysvětluje odezvu buňky na lokální mechanické zatížení, jako třeba vtlačování hrotu při mikroskopii atomárních sil (AFM). Oba zachovávají základní principy tensegritních struktur jako je jejich předpětí a vzájemné ovlivnění mezi komponentami, ale prvky se mohou nezávisle pohybovat. Zahrnutí nedávno navržené bendotensegritní koncepce umožňuje těmto modelům brát v úvahu jak tahové, tak i ohybové namáhání mikrotubulů (MTs) a také zahrnout vlnitost intermediálních filament (IFs). Modely předpokládají, že jednotlivé složky cytoskeletu mohou měnit svůj tvar a uspořádání, aniž by při jejich odstranění došlo ke kolapsu celé buněčné struktury, a tak umožňují hodnotit mechanický příspěvek jednotlivých složek cytoskeletu k mechanice buňky. Model vznášející se buňky napodobuje realisticky odezvu síla-deformace během protahování a stlačování buňky a obě odezvy ilustrují nelineární nárůst tuhosti s růstem mechanického zatížení. Výsledky simulací ukazují, že aktinová filamenta i mikrotubuly hrají klíčovou úlohu při určování tahové odezvy buňky, zatímco k její tlakové odezvě přispívají podstatně jen aktinová filamenta. Model buňky přilnuté k podložce dává odezvu síla-hloubka vtlačení ve dvou různých místech odpovídající nelineární odezvě zjištěné experimentálně při AFM. Výsledky simulací ukazují, že pro chování buňky je rozhodující místo vtlačení a její tuhost určují aktinová povrchová vrstva, mikrotubuly a cytoplazma. Navržené modely umožňují cenný vhled do vzájemných souvislostí mechanických vlastností buněk, do mechanické úlohy komponent cytoskeletu jak individuálně, tak i ve vzájemné synergii a do deformace jádra buňky za různých podmínek mechanického zatížení. Tudíž tato práce přispívá k lepšímu pochopení mechaniky cytoskeletu zodpovědné za chování buňky, což naopak může napomáhat ve zkoumání různých patologických podmínek jako je rakovina a cévní choroby.

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(unal), Kutlu Ozge. "Computational 3d Fracture Analysis In Axisymmetric Media." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609872/index.pdf.

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In this study finite element modeling of three dimensional elliptic and semielliptic cracks in a hollow cylinder is considered. Three dimensional crack and cylinder are modeled by using finite element analysis program ANSYS. The main objectives of this study are as follows. First, Ansys Parametric Design Language (APDL) codes are developed to facilitate modeling of different types of cracks in cylinders. Second, by using these codes the effect of some parameters of the problem like crack location, cylinder&rsquo
s radius to thickness ratio (R/t), the crack geometry ratio (a/c) and crack minor axis to cylinder thickness ratio (a/t) on stress intensity factors for surface and internal cracks are examined. Mechanical and thermal loading cases are considered. Displacement Correlation Technique (DCT) is used to obtain Stress Intensity Factors.

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Dissertations / Theses on the topic 'Mechanical computation'

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