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Dissertations / Theses on the topic 'Mechanical methods'
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1
Jonsson, Anders. "Integral equation methods for fracture mechanics and micro-mechanical problems." Doctoral thesis, KTH, Solid Mechanics, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3336.
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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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Ruedin, Laurent. "Statistical mechanical methods and continued fractions /." [S.l.] : [s.n.], 1994. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10796.
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Neupane, Manish. "Mechanical Joining Methods in Aluminum Sheets." University of Toledo / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1574853232358122.
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Kostic, Peter. "New methods for optimization of mechanical ventilation." Doctoral thesis, Uppsala universitet, Anestesiologi och intensivvård, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-249172.
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Mechanical ventilation saves lives, but it is an intervention fraught with the potential for serious complications. Prevention of these complications has become the focus of research and critical care in the last twenty years. This thesis presents the first use, or the application under new conditions, of three technologies that could contribute to optimization of mechanical ventilation. Optoelectronic plethysmography was used in Papers I and II for continuous assessment of changes in chest wall volume, configuration, and motion in the perioperative period. A forced oscillation technique (FOT) was used in Paper III to evaluate a novel positive end-expiratory pressure (PEEP) optimization strategy. Finally, in Paper IV, FOT in conjunction with an optical sensor based on a self-mixing laser interferometer (LIR) was used to study the oscillatory mechanics of the respiratory system and to measure the chest wall displacement. In Paper I, propofol anesthesia decreased end-expiratory chest wall volume (VeeCW) during induction, with a more pronounced effect on the abdominal compartment than on the rib cage. The main novel findings were an increased relative contribution of the rib cage to ventilation after induction of anesthesia, and the fact that the rib cage initiates post-apneic ventilation. In Paper II, a combination of recruitment maneuvers, PEEP, and reduced fraction of inspired oxygen, was found to preserve lung volume during and after anesthesia. Furthermore, the decrease in VeeCW during emergence from anesthesia, associated with activation of the expiratory muscles, suggested that active expiration may contribute to decreased functional residual capacity, during emergence from anesthesia. In the lavage model of lung injury studied in Paper III, a PEEP optimization strategy based on maximizing oscillatory reactance measured by FOT resulted in improved lung mechanics, increased oxygenation, and reduced histopathologic evidence of ventilator-induced lung injury. Paper IV showed that it is possible to apply both FOT and LIR simultaneously in various conditions ranging from awake quiet breathing to general anesthesia with controlled mechanical ventilation. In the case of LIR, an impedance map representing different regions of the chest wall showed reproducible changes during the different stages that suggested a high sensitivity of the LIR-based measurements.
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Liu, Xianhua Mechanical & Manufacturing Engineering Faculty of Engineering UNSW. "Blind source separation methods and their mechanical applications." Awarded by:University of New South Wales. School of Mechanical and Manufacturing Engineering, 2006. http://handle.unsw.edu.au/1959.4/24961.
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Blind Source Separation is a modern signal processing technique which recovers both the unknown sources and unknown mixing systems from only measured mixtures of signals. It has application in diverse fields such as communication, image processing, geological exploration and biomedical signal processing etc. This project studies the BSS problem, develop separation methods and reveal the potential for mechanical engineering applications. There are two models for blind source separation corresponding to the two ways that the sources are mixed, the instantaneous mixing model and the convolved mixing model. The author carried out a theoretical study of the first model by proposing an idea called Redundant Data Elimination which leads to geometric interpretation of the model, explains that circular distribution property is the reason why Gaussian signal mixtures can not be separated, and showed that this idea can improve separation accuracy for unsymmetrically distributed sources. This new idea enabled evaluation and comparison of two well-known algorithms and proposal of a simplified algorithm based on Joint Approximate Diagonalization of fourth order cumulant matrices, which is further developed by determining an optimized parameter value for separation convergence. Also based on the understanding from the RDE, an outlier spherical projection method is proposed to improve separation accuracy against outlier errors. Mechanical vibration or acoustic problems belong to the second model. After some theoretical study of the problem and the model, a novel application of the Blind Least Mean Square algorithm using Gray's variable norm as cost function is applied to engine vibration data to separate piston slap, fuel injection noise and cylinder pressure effects. Further, the algorithm is combined with a deflation algorithm for successive subtraction of recovered source responses from the measured mixture to enable the recovery of more sources. The algorithms are verified to be successful by simulation, and the separated engine sources are proved reasonable by analysing the engine operation and physical properties of the sources. The author also studied the relationship between these two models, the problems of different approaches for solving the model such as the frequency domain approach and the Bussgang approach, and sets out future research interests.
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Martin, Jessica E. "Humane mechanical methods for killing poultry on-farm." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6634/.
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Worldwide, an estimated 9.1 billion birds may need to be killed on farm each year. As of January 2013 the use of manual cervical dislocation (MCD) as a killing method for poultry on-farm has been heavily restricted through new EU legislation (EC 1099/2009) on the Welfare of Animals at the Time of Killing, following reported welfare concerns. The method by which birds are killed on farm is crucial to poultry welfare on a large scale. The overall aim of this project was to design a mechanical device conforming to the new legislation to kill poultry humanely on-farm and provide a competitive replacement for MCD. Following a survey and a literature review, four mechanical devices were designed and prototyped: Modified Armadillo (MARM); Modified Pliers (MPLI); Modified Rabbit Zinger (MZIN) and a Novel mechanical cervical dislocation glove (NMCD). The devices were tested for killing efficacy in three laboratory experiments, assessing their performance in poultry cadavers (Study 1), anaesthetised birds (Study 2) and live conscious birds (Study 3). The reliability and welfare impact of the devices, along with comparisons with a control method (MCD) were evaluated via post-mortem analysis, reflex and behaviour durations, and characteristics of electroencephalography (EEG) analysis. Due to consistently high kill success rates and rapid loss of reflexes, as well as short durations of EEG activity indicating consciousness across three laboratory experiments, the NMCD device was shown to have the most promise as a mechanical device to be used as an alternative to MCD for poultry stock-workers and keepers. The final experiment explored the user-reliability and practicality of the NMCD device in two relevant commercial environments (a layer hen farm and a broiler farm). When applied by multiple users, the NMCD device did not match the killing performance of MCD, however it did show promise and the study highlighted the need for further refinement in the training protocol in order to encompass the wide variation in MCD techniques and experience. The result of this project is a novel on-farm mechanical killing device, which shows great potential in laboratory experiments and competed with the traditional MCD method in commercial environments. Further training refinements are required in order to develop the device into a marketable product which any individual could purchase and use as a humane method for killing poultry.
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Wang, Zhiguo. "Mechanical and optical methods for breast cancer imaging." Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/618.
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It has been recognized that mechanical and optical properties of tissues can be the indicators to identify and characterize breast tumors. The objective of this study is to develop new mechanical and optical modalities for qualification of the elastic and optical properties of normal and cancerous breast tissues.
First, a mammography-based elastography (called elasto-mammography) is proposed to generate the elastogram of breast tissues based on conventional X-ray mammography. The displacement information is extracted from mammography projections before and after breast compression. With the incorporation of the displacement measurements, an elastography reconstruction algorithm is specially developed to estimate the elastic moduli of heterogeneous breast tissues. Case studies with numerical breast phantoms are conducted to demonstrate the capability of the proposed elasto-mammogrpahy. It is shown that the proposed methodology is stable and robust for characterization of the elastic moduli of breast tissues from the projective displacement measurement.
Second, a nonlinear elastogrpahy is proposed to extend breast material model to nonlinear cases. A three-dimensional (3D) model is developed for heterogeneous breast tissues extracting from real images including fatty tissue, glandular tissue, and tumors. An exponential-form of nonlinear material model is applied. Based on the finite-deformation constitutive law, discretized nonlinear equations are solved for displacement, strain, and stress fields in breast tissues with given tumors under external compression at breast boundaries. We develop a 3D inverse-problem algorithm to reconstruct the material parameters for nonlinear elastic constitutive relation of breast phantoms with tumors. For the first time, a nonlinear adjoint gradient method is introduced to improve the numerical efficiency and enhance the stability of elastogrpahy reconstruction.
Third, encouraged by the success of linear elasto-mammography and nonlinear elastography, a nonlinear elasto-mammography method is proposed. Mammography projections are taken before and after breast compression and displacement information is extracted for reconstruction of nonlinear breast tissue properties. Numerical phantom study is conducted and results show the proposed nonlinear elasto-mammography is potential to identify and characterize breast tumors in clinic.
Finally, we switch from mechanical to optical method for breast cancer imaging. We develop a finite-element-based algorithm to solve the inverse problem of frequent-domain diffusion equation. With the analytical form of gradients, the adjoint method is expanded to complex domain for the reconstruction of optical parameters in diffuse optical tomography. Specific numerical simulation is carried out and compared with phantom experiment. The results show that the adjoint-based algorithm is efficient and robust for reconstructing the optical parameters.
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Levitan, Jeremy Asher 1977. "Methods for self-fabrication chips." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/89313.
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Sarathy, Sudarshan. "Enhanced condensation with active methods." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107064.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 59-64).
Condensation of low surface tension fluids is important in liquefied natural gas processing and refrigeration systems. Current state of the art low surface energy low hysteresis coatings are not able to achieve dropwise condensation below 10 mN/m. Surface acoustic waves are proposed as an active method to shed thin condensate films to reduce their thermal resistance and improve heat transfer coefficients. Interdigitated electrode patterns were fabricated on piezoelectric LiNbO3 wafers and SAW waves were generated with RF voltages in the 12.5 - 100 MHz regime. These were tested in the in-house condensation rig with Ethanol, Pentane, Hexane and Perfluorohexane. Heat transfer coefficients showed more than 2X improvement over standard filmwise condensation. Further, the effect of refrigerant side heat transfer enhancement in a condenser operating in a vapor compression refrigeration cycle is studied as a potential application.
by Sudarshan Sarathy.
S.M.
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Lee, Moshin. "Methods for configuring manufacturing systems." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/11400.
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Lomangino, F. Paul. "Grammar- and optimization-based mechanical packaging." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/15848.
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Bausch, John Jacob. "Kinematic methods for automated fixture design." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/13978.
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Kao, Chung-Yao 1972. "Efficient computational methods for robustness analysis." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/29258.
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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.Includes bibliographical references (p. 209-215).
Issues of robust stability and performance have dominated the field of systems and control theory because of their practical importance. The recently developed Integral Quadratic Constraint (IQC) based analysis method provides a framework for systematically checking robustness properties of large complex dynamical systems. In IQC analysis, the system to be analyzed is represented as a nominal, Linear Time-Invariant (LTI) subsystem interconnected with a perturbation term. The perturbation is characterized in terms of IQCs. The robustness condition is expressed as a feasibility problem which can be solved using interiorpoint algorithms. Although the systems to be analyzed have nominal LTI subsystems in many applications, this is not always the case. A typical example is the problem of robustness analysis of the oscillatory behavior of nonlinear systems, where the nominal subsystem is generally Linear Periodically Time-Varying (LPTV). The objective of the first part of this thesis is to develop new techniques for robustness analysis of LPTV systems. Two different approaches are proposed. In the first approach, the harmonic terms of the LPTV nominal model are extracted, and the system is transformed into the standard setup for robustness analysis. Robustness analysis is then performed on the transformed system based on the IQC analysis method. In the second approach, we allow the nominal system to remain periodic, and we extend the IQC analysis method to include the case where the nominal system is periodically time-varying.
(cont.) The robustness condition of this new approach is posed as semi-infinite convex feasibility problems which requires a new method to solve. A computational algorithm is developed for checking the robustness condition.In the second part of the thesis, we consider the optimization problems arising from IQC analysis. The conventional way of solving these problems is to transform them into semi-definite programs which are then solved using interior-point algorithms. The disadvantage of this approach is that the transformation introduces additional decision variables. In many situations, these auxiliary decision variables become the main computational burden, and the conventional method then becomes very inefficient and time consuming. In the second part of the thesis, a number of specialized algorithms are developed to solve these problems in a more efficient fashion. The crucial advantage in this development is that it avoids the equivalent transformation. The results of numerical experiments confirm that these algorithms can solve a problem arising from IQC analysis much faster than the conventional approach does.
by Chung-Yao Kao.
Sc.D.
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Eigen, Gary Fredric. "Smoothing methods for discrete die forming." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13178.
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Singh, Jagmeet 1980. "Comparative analysis of robust design methods." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35630.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (p. 161-163).
Robust parameter design is an engineering methodology intended as a cost effective approach to improve the quality of products, processes and systems. Control factors are those system parameters that can be easily controlled and manipulated. Noise factors are those system parameters that are difficult and/or costly to control and are presumed uncontrollable. Robust parameter design involves choosing optimal levels of the controllable factors in order to obtain a target or optimal response with minimal variation. Noise factors bring variability into the system, thus affecting the response. The aim is to properly choose the levels of control factors so that the process is robust or insensitive to the variation caused by noise factors. Robust parameter design methods are used to make systems more reliable and robust to incoming variations in environmental effects, manufacturing processes and customer usage patterns. However, robust design can become expensive, time consuming, and/or resource intensive. Thus research that makes robust design less resource intensive and requires less number of experimental runs is of great value. Robust design methodology can be expressed as multi-response optimization problem.
(cont.) The objective functions of the problem being: maximizing reliability and robustness of systems, minimizing the information and/or resources required for robust design methodology, and minimizing the number of experimental runs needed. This thesis discusses various noise factor strategies which aim to reduce number of experimental runs needed to improve quality of system. Compound Noise and Take-The-Best-Few Noise Factors Strategy are such noise factor strategies which reduce experimental effort needed to improve reliability of systems. Compound Noise is made by combing all the different noise factors together, irrespective of the number of noise factors. But such a noise strategy works only for the systems which show effect sparsity. To apply the Take-The-Best-Few Noise Factors Strategy most important noise factors in system's noise factor space are found. Noise factors having significant impact on system response variation are considered important. Once the important noise factors are identified, they are kept independent in the noise factor array. By selecting the few most important noise factors for a given system, run size of experiment is minimized.
(cont.) Take-The-Best-Few Noise Factors Strategy is very effective for all kinds of systems irrespective of their effect sparsity. Generally Take-The-Best-Few Noise Factors Strategy achieves nearly 80% of the possible improvement for all systems. This thesis also tries to find the influence of correlation and variance of induced noise on quality of system. For systems that do not contain any significant three-factor interactions correlation among noise factors can be neglected. Hence amount of information needed to improve the quality of systems is reduced.
by Jagmeet Singh.
Ph.D.
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Persons, Jeffrey B. "Assessment of adaptive one-factor-at-a-time method vs. fractional factorial methods using reconfigurable paper aircraft." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36717.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaf 46).
Recent research has suggested that under certain conditions, adaptive one-factor-at-a-time (aOFAT) methods outperform more commonly used fractional factorial methods. This study sought to corroborate these claims by analyzing a case study of a real-life experiment. A full factorial experiment was conducted to collect data for simulations of fractional factorial and adaptive one-factor-at-a-time experiments. The experiment used a reconfigurable paper aircraft template with four three-level control factors. Results indicated that the exploitation of control factor interactions by adaptive one-factor-at-a-time occurred at similar rates as predicted by Frey and Wang (2006). AOFAT experiments proved particularly effective at avoiding factor levels that led to poor performance. with rates of avoidance approaching 100% for the worst levels. When bias in the full factorial experiment was eliminated, aOFAT methods even returned a higher (weighted average) leading quality indicator value than full factorial methods.
by Jeffrey B. Persons, Jr..
S.B.
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Mahoney, Phillip. "Novel mechanical test methods applied to bulk metallic glasses." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/13397/.
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By their nature Bulk Metallic Glasses (BMGs) are generally available with limited volumes. Therefore, to understand their mechanical behaviour, innovative small scales tests are required. Here aspects of mechanical behaviour covering elastic, time dependent and plastic deformation are explored. For indentation (elastic moduli and hardness measurements), test data contained displacement burst signals; dependent on indentation load and loading rates; hypothesised to be due to shear bands and Shear Transformation Zones (STZs). Measurements of the energy associated with these signals were heavily influenced by data smoothing. Nevertheless, shear banding is seen to be more energetic process than STZ activation, and STZ activation during loading is more energetic than in load-hold or unloading. Teter’s empirical relationship [1] provided the best estimate of elastic properties from hardness data. Whilst indentation size effects made the method unreliable for bulk estimates, these effects are suggested as a means to map free volume distributions within BMG structures. Poor reproducibility of indentation creep data and the influence of analysis methods led to the conclusion that indentation creep measurements are unreliable. Practices to improve this reliability are given, however the fundamentals of the test limits its usefulness. Finally, shear banding of BMGs was explored through a new testing methodology based on the dynamic measurement of resistivity. Two types of signal were detected; both accountable through the shear band process. Analysis of the signals indicated that thermal and structural changes were required to explain the observed resistivity changes. Monte-Carlo and Ising based models were used to relate the observed signals to structure and temperature. Whilst these require further work, the method provides the means to measure shear band structure evolution.
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Haynes, P. "Linear-scaling methods in ab initio quantum-mechanical calculations." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603888.
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The work described in this dissertation concerns the development of new methods for performing computer simulations of real materials from first principles or ab initio i.e. using the fundamental equations of quantum mechanics and only well-controlled approximations. In particular, these methods have been developed within the framework of density-functional theory and therefore lie in the realms of both quantum chemistry and computational condensed matter physics. The work is particularly concerned with methods which are efficient in the sense that the computational effort required scales only linearly with system-size (i.e. the volume or number of electrons) whereas traditional methods have scaled with the cube of the system-size which has restricted their range of applicability. The aim of this work is therefore to extend the scope of ab initio quantum-mechanical calculations beyond what is currently possible. Density-functional theory has traditionally been applied by making use of a mapping from the system of interacting electrons to a fictitious system of non-interacting particles. However, the need to maintain the mutual orthogonality of the wave functions of the fictitious system leads to the cubic scaling mentioned above, and is ultimately responsible for limiting the maximum size of systems which can be treated. Making use of a reformulation of the problem in terms of the single-particle density-matrix eliminates the need to work with the wave functions directly. Moreover, exploiting the short-ranged nature of the density-matrix leads in principle to a linear-scaling method. The dissertation tackles two issues which are relevant to obtaining practical schemes for performing linear-scaling calculations. Firstly a localised basis set is developed which is used to describe the density-matrix computationally. Analytic results for several key quantities required by the calculation are derived, namely the overlap, kinetic energy and non-local pseudopotential matrix elements. These results allow accurate calculation of the total energy of the system and have been implemented and tested computationally. Secondly, the dissertation discusses several methods for imposing the difficult non-linear idempotency constraint on the density-matrix.
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Magnevall, Martin. "Methods for Simulation and Characterization of Nonlinear Mechanical Structures." Licentiate thesis, Karlskrona : Blekinge Institute of Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00430.
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Trial and error and the use of highly time-consuming methods are often necessary for modeling, simulating and characterizing nonlinear dynamical systems. However, for the rather common special case when a nonlinear system has linear relations between many of its degrees of freedom there are particularly interesting opportunities for more efficient approaches. The aim of this thesis is to develop and validate new efficient methods for the theoretical and experimental study of mechanical systems that include significant zero-memory or hysteretic nonlinearities related to only small parts of the whole system. The basic idea is to take advantage of the fact that most of the system is linear and to use much of the linear theories behind forced response simulations. This is made possible by modeling the nonlinearities as external forces acting on the underlying linear system. The result is very fast simulation routines where the model is based on the residues and poles of the underlying linear system. These residues and poles can be obtained analytically, from finite element models or from experimental measurements, making these forced response routines very versatile. Using this approach, a complete nonlinear model contains both linear and nonlinear parts. Thus, it is also important to have robust and accurate methods for estimating both the linear and nonlinear system parameters from experimental data. The results of this work include robust and user-friendly routines based on sinusoidal and random noise excitation signals for characterization and description of nonlinearities from experimental measurements. These routines are used to create models of the studied systems. When combined with efficient simulation routines, complete tools are created which are both versatile and computationally inexpensive. The developed methods have been tested both by simulations and with experimental test rigs with promising results. This indicates that they are useful in practice and can provide a basis for future research and development of methods capable of handling more complex nonlinear systems.
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Jamali, Hamadi. "Adaptive control methods for mechanical manipulators: a comparative study." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26847.
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Norlander, Hans. "Modelling and Control Methods with Applications to Mechanical Waves." Doctoral thesis, Uppsala universitet, Avdelningen för systemteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-229793.
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Models, modelling and control design play important parts in automatic control. The contributions in this thesis concern topics in all three of these concepts. The poles are of fundamental importance when analyzing the behaviour of a system, and pole placement is an intuitive and natural approach for control design. A novel parameterization for state feedback gains for pole placement in the linear multiple input case is presented and analyzed. It is shown that when the open and closed loop poles are disjunct, every state feedback gain can be parameterized. Other properties are also investigated. Hammerstein models have a static non-linearity on the input. A method for exact compensation of such non-linearities, combined with introduction of integral action, is presented. Instead of inversion of the non-linearity the method utilizes differentiation, which in many cases is simpler. A partial differential equation (PDE) can be regarded as an infinite order model. Many model based control design techniques, like linear quadratic Gaussian control (LQG), require finite order models. Active damping of vibrations in a viscoelastic beam, modelled as a PDE, is considered. The beam is actuated by piezoelectric elements and its movements are measured by strain gauges. LQG design is used, for which different finite order models, approximating the PDE model, are constructed. The so obtained controllers are evaluated on the original PDE model. Minimization of the measured strain yields a satisfactory performance, but minimization of transversal deflection does not. The effect of the model accuracy of the finite order model approximations is also investigated. It turns out that a model with higher accuracy in a specified frequency interval gives controllers with better performance. The wave equation is another PDE. A PDE model, with one spatial dimension, is established. It describes wave propagation in a tube perforated with helical slots. The model describes waves of both extensional and torsional type, as well as the coupling between the two wave types. Experimental data are used for estimation of model parameters, and for assessment of the proposed model in two different cases. The model is found adequate when certain geometrical assumptions are valid.
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Malik, Khalid Masood. "Chemometric and quantum mechanical methods to analyse CD data." Thesis, King's College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267279.
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Chen, Yousheng. "Model calibration methods for mechanical systems with local nonlinearities." Doctoral thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-57638.
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Most modern product development utilizes computational models. With increasing demands on reducing the product development lead-time, it becomes more important to improve the accuracy and efficiency of simulations. In addition, to improve product performance, a lot of products are designed to be lighter and more flexible, thus more prone to nonlinear behaviour. Linear finite element (FE) models, which still form the basis of numerical models used to represent mechanical structures, may not be able to predict structural behaviour with necessary accuracy when nonlinear effects are significant. Nonlinearities are often localized to joints or boundary conditions. Including nonlinear behaviour in FE-models introduces more sources of uncertainty and it is often necessary to calibrate the models with the use of experimental data. This research work presents a model calibration method that is suitable for mechanical systems with structural nonlinearities. The methodology concerns pre-test planning, parameterization, simulation methods, vibrational testing and optimization. The selection of parameters for the calibration requires physical insights together with analyses of the structure; the latter can be achieved by use of simulations. Traditional simulation methods may be computationally expensive when dealing with nonlinear systems; therefore an efficient fixed-step state-space based simulation method was developed. To gain knowledge of the accuracy of different simulation methods, the bias errors for the proposed method as well as other widespread simulation methods were studied and compared. The proposed method performs well in comparison to other simulation methods. To obtain precise estimates of the parameters, the test data should be informative of the parameters chosen and the parameters should be identifiable. Test data informativeness and parameter identifiability are coupled and they can be assessed by the Fisher information matrix (FIM). To optimize the informativeness of test data, a FIM based pre-test planning method was developed and a multi-sinusoidal excitation was designed. The steady-state responses at the side harmonics were shown to contain valuable information for model calibration of FE-models representing mechanical systems with structural nonlinearities. In this work, model calibration was made by minimizing the difference between predicted and measured multi-harmonic frequency response functions using an efficient optimization routine. The steady-state responses were calculated using the extended multi-harmonic balance method. When the parameters were calibrated, a k-fold cross validation was used to obtain parameter uncertainty. The proposed model calibration method was validated using two test-rigs, one with a geometrical nonlinearity and one with a clearance type of nonlinearity. To attain high quality data efficiently, the amplitude of the forcing harmonics was controlled at each frequency step by an off-line force feedback algorithm. The applied force was then measured and used in the numerical simulations of the responses. It was shown in the validation results that the predictions from the calibrated models agree well with the experimental results. In summary, the presented methodology concerns both theoretical and experimental aspects as it includes methods for pre-test planning, simulations, testing, calibration and validation. As such, this research work offers a complete framework and contributes to more effective and efficient analyses on mechanical systems with structural nonlinearities.
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Allen, Katherine Ruth. "Methods of testing the mechanical properties of orthodontic wires /." Title page, table of contents and summary only, 1994. http://web4.library.adelaide.edu.au/theses/09DM/09dma427.pdf.
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Johansson, Ludvig. "On the Mechanical Recycling of Woven Fabrics : Improving the Reusable Fibre Yield of Mechanical Methods." Thesis, Uppsala universitet, Tillämpad materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-414569.
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This master thesis studies the recycling prospects of textiles. The textile industry contributes negatively to the global environmentthrough the release of greenhouse gases and consumption of resources. In order to achieve a circular textile industry, textiles must be recyclable by both chemical and mechanical means. Here, the focus is on mechanical extraction of staple fibres, particularly cotton, for reentry into yarn production. Experiments show that used, but undamaged, cotton sateen and cotton twill responds differently to abrasion with stochastic surfaces. Previous studies on the conventional shredding processes have shown positive impact from lubricants on extracted fibre lengths, by reducing inter-fibre friction. In the present study on abrasion, variables such as alignment of the weave pattern, lubrication and load are shown to have little to no impact on extracted fibre length, but notable effects on overall fibre quality. These analyses are supported by manual length assessment, electron micrographs and tensile tests using load cells. Furthermore, simple tests and observations on structured diamond surfaces constructed through chemical vapor deposition are promising for mechanical fibre release directly from a woven fabric. Suggestions are made on continued research in this field.
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van, Drunen Erwin Johan. "Mechanical Ventilation Modelling and Optimisation." Thesis, University of Canterbury. Mechanical Engineering, 2013. http://hdl.handle.net/10092/8400.
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Acute Respiratory Distress Syndrome (ARDS) is associated with lung inflammation and fluid filling, resulting in a stiffer lung with reduced intrapulmonary gas volume. ARDS patients are admitted to the Intensive Care Unit (ICU) and require Mechanical Ventilation (MV) for breathing support. Positive End Expiratory Pressure (PEEP) is applied to aid recovery by improving gas exchange and maintaining recruited lung volume. However, high PEEP risks further lung injury due to overstretching of healthy lung units, and low PEEP risks further lung injury due to the repetitive opening and closing of lung units. Thus, selecting PEEP is a balance between avoiding over-stretching and repetitive opening of alveoli. Furthermore, specific protocols to determine optimal PEEP do not currently exist, resulting in variable PEEP selection. Thus, ensuring an optimal PEEP would have significant impact on patient mortality, and the cost and duration of MV therapy.
Two important metrics that can be used to aid MV therapy are the elastance of the lungs as a function of PEEP, and the quantity of recruited lung volume as a function of PEEP. This thesis describes several models and model-based methods that can be used to select optimal PEEP in the ICU. Firstly, a single compartment lung model is investigated for its ability to capture the respiratory mechanics of a mechanically ventilated ARDS patient. This model is then expanded upon, leading to a novel method of mapping and visualising dynamic respiratory system elastance. Considering how elastance changes, both within a breath and throughout the course of care, provides a new clinical perspective. Next, a model using only the expiratory portion of the breathing cycle is developed and presented, providing an alternative means to track changes in disease state throughout MV therapy. Finally, four model-based methods are compared based on their capability of estimating the quantity of recruited lung volume due to PEEP.
The models and model-based methods described in this thesis enable rapid parameter identification from readily available clinical data, providing a means of tracking lung condition and selecting optimal patient-specific PEEP. Each model is validated using data from clinical ICU patients and/or experimental ARDS animal models.
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Brooks, Christopher Allen 1978. "Terrain identification methods for planetary exploration rovers." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/30303.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (leaves 77-82).
Autonomous mobility in rough terrain is becoming increasingly important for planetary exploration rovers. Increased knowledge of local terrain properties is critical to ensure a rover's safety, especially when driving on slopes or rough surfaces. This thesis presents two methods for using on-board sensors to identify local terrain conditions. The first method visually measures sinkage of a rover wheel into deformable terrain, based on a single color or grayscale image from a camera with a view of the wheel- terrain interface. Grayscale intensity is computed along the rim of the wheel, and the wheel-terrain interface is identified as the location with maximum change in intensity. The algorithm has been shown experimentally to give accurate results in identifying the terrain characteristics under a wide range of conditions. The second method classifies terrain based on vibrations induced in the rover structure by rover-terrain interaction during driving. Vibrations are measured using an accelerometer on the rover structure. The method uses a supervised learning approach to train a classifier to recognize terrain based on representative vibration signals during an off-line learning phase. Real-time terrain classification uses linear discriminant analysis in the frequency domain to identify gross terrain classes such as sand, gravel, or clay. The algorithm is experimentally validated on a laboratory testbed and on a rover in outdoor conditions. Results demonstrate the robustness of the algorithm on both systems.
by Christopher Allen Brooks.
S.M.
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Ku, Jason (Jason Stoutsenberger). "Methods of invisibility and multi-dimensional display." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54501.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 49).
Modern methods of multidimensional display are extremely limited in their depiction of three dimensional environments. Improving upon modern integral imaging displays with respect to viewing angle and angular resolution, a new method is proposed consisting of spherical lenses to focus incident light to an imaging surface. A theoretically exact model is provided in addition to a number of feasible physical approximation alternatives for different components of the model. This model can be extended for applications in multidimensional display and invisibility.
by Jason Ku.
S.B.
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Timm, Richard W. (Richard William). "Visual-based methods in compliant mechanism optimization." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35649.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (p. 103-105).
The purpose of this research is to generate visual-based methods for optimizing compliant mechanisms (CMs). Visual-based optimization methods use graphical representations (3-D plots) of CM performance to convey design information. They have many advantages over traditional optimization methods, such as enabling judgment-based design tradeoffs and ensuring robustness of optimized solutions. This research fulfilled the primary aims of determining (1) how to best convey decision-driving design information, and (2) how to interpret and analyze the results of a visual-based optimization method. Other useful tools resulting from this work are (3) a nondimensional model of a CM (a compliant four-bar mechanism) that may be used to maximize the information density of optimization plots, and (4) a new model of a compliant beam that establishes a link between beam stiffness and instant center location. This work presents designers with an optimization tool that may either be used to augment or replace current optimization methods.
by Richard W. Timm.
S.M.
31
Hover, Franz S. "Methods for positioning deeply-towed underwater cables." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12605.
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Dong, Wei S. M. Massachusetts Institute of Technology. "Innovative color management methods for RGB printing." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38292.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaf 50).
Re-calibrating a printer in response to systematic changes is measurement and labor intensive. In this study, a fast correction method with cycle-to-cycle control was proposed. The process includes two steps: the creation of look-up table using a characterization data set, and image color compensation in conjunction with Windows printing architecture. Several types of correction models for determining printer characterization were proposed and evaluated, including polynomial models and neural network models. The most successful of these methods was the quadratic spline interpolation model, which removed most errors introduced by the changes of colorant and printing substrate. A significant reduction in error was realized by incorporating this technique into the color management program.
by Wei Dong.
M.Eng.
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Vanderpuije, Curtis N. "Innovative color management methods for RGB printing." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38285.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaf 57).
The demand for printing excellent quality images has increased tremendously in parallel to the growth spurts in the digital camera market. Printing good quality images consistently, however, remains a difficult and/or expensive venture despite the numerous advances in color technology and printing. To alleviate these issues, a color compensating software solution was developed to utilize the unique Kikuze calibration chart to improve printer output. The software solution integrates with the windows printing process at the operating system level through a UNIDRV plug-in. The plug-in retrieves the data within the print stream, passes it on to the color compensation engine which corrects the color data by mapping input and output colors obtained via a B-spline interpolation algorithm. The rendered image is re-introduced into the print stream for final printing. The prototype achieved successful results and can be packaged with commercial printers after a few refinements.
by Curtis N. Vanderpuije.
M.Eng.
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Chang, Minho. "Input methods for solid models of assemblies." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12348.
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Yiğit, Konuralp. "Path planning methods for Autonomous Underwater Vehicles." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67807.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 75-81).
From naval operations to ocean science missions, the importance of autonomous vehicles is increasing with the advances in underwater robotics technology. Due to the dynamic and intermittent underwater environment and the physical limitations of autonomous underwater vehicles, feasible and optimal path planning is crucial for autonomous underwater operations. The objective of this thesis is to develop and demonstrate an efficient underwater path planning algorithm based on the level set method. Specifically, the goal is to compute the paths of autonomous vehicles which minimize travel time in the presence of ocean currents. The approach is to either utilize or avoid any type of ocean flows, while allowing for currents that are much larger than the nominal vehicle speed and for three-dimensional currents which vary with time. Existing path planning methods for the fields of ocean science and robotics are first reviewed, and the advantages and disadvantages of each are discussed. The underpinnings of the level set and fast marching methods are then reviewed, including their new extension and application to underwater path planning. Finally, a new feasible and optimal time-dependent underwater path planning algorithm is derived and presented. In order to demonstrate the capabilities of the algorithm, a set of idealized test-cases of increasing complexity are first presented and discussed. A real three-dimensional path planning example, involving strong current conditions, is also illustrated. This example utilizes four-dimensional ocean flows from a realistic ocean prediction system which simulate the ocean response to the passage of a tropical storm in the Middle Atlantic Bight region.
by Konuralp Yiğit.
S.M.
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Tsai, Geoffrey T. "Design for surprise and idea generation methods." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67804.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 58-59).
This thesis explores the meaning of surprise in product design and how surprise can be created in the early phase of the design process, specifically during ideation. In product and service markets with multiple competitors and where product differentiation is difficult, surprise, if used correctly, can be an indispensable differentiator-creating emotional attachment and fostering brand loyalty. A two-part experiment tests three different idea generation methods-brainstorming, multiple perspectives, and counter attributes (a new method proposed in this thesis)-and how ideation sketches from these methods are rated by workers on Amazon's Mechanical Turk. Findings reveal that counter attributes may be less effective at generating surprising ideas. Brainstorming and multiple perspectives perform similarly to each other, but small differences in the structure of an idea generation method may either inhibit or encourage creativity and surprise. The findings also reveal that how clearly an idea is expressed in a sketch greatly influences the variance for how it will be rated upon review.
by Geoff T. Tsai.
S.M.
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Shur, Maiya 1980. "Microfabrication methods for the study of chemotaxis." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/27130.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (leaves 59-60).
We have developed a system for studying chemotaxis in a microfabricated system. The goal was to develop a system capable of generating spatially and temporally stable concentration gradients of a chemotactic molecule while providing a viable environment for the cell. Numerical models were generated to investigate fluid flow in microchannels for given geometries. Through computational modeling and experimentally-driven iteration of the design, features of the chamber were determined and geometry was established. Prototypes of the system were fabricated using soft lithography and multi-layer soft lithography techniques. Three fluid delivery methods for establishing gradients in the system have been studied: gravity feed system, dual-syringe pump feed system, and integrated individually-controlled peristaltic pump feed system. We were able to create spatially and temporally stable gradients using the dual-syringe feed setup. Two syringes were used to pump a chemokine and a buffer in parallel channels that are connected by a cross-channel and terminated to a single output. Microbeads in the flow were used to confirm the lack of movement in the cross-channel. Human neutrophil viability over the course of several hours and directed cell movement was demonstrated in microchannels.
by Maiya Shur.
S.M.
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Bachrach, Hillel E. "Formal methods for design automation application development." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43427.
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Voxakis, Petros. "Ship hull resistance calculations using CFD methods." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74895.
Full textAbstract:
Thesis (Nav. E. and S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 77-78).
In past years, the computational power and run-time required by Computational Fluid Dynamics (CFD) codes restricted their use in ship design space exploration. Increases in computational power available to designers, in addition to more efficient codes, have made CFD a valuable tool for early stage ship design and trade studies. In this work an existing physical model (DTMB #5415, similar to the US Navy DDG-51 combatant) was replicated in STAR-CCM+, initially without appendages, then with the addition of the appendages. Towed resistance was calculated at various speeds. The bare hull model was unconstrained in heave and pitch, thus allowing the simulation to achieve steady dynamic attitude for each speed run. The effect of dynamic attitude on the resistance is considered to be significant and requires accurate prediction. The results were validated by comparison to available data from tow tank tests of the physical model. The results demonstrate the accuracy of the CFD package and the potential for increasing the use of CFD as an effective tool in design space exploration. This will significantly reduce the time and cost of studies that previously depended solely on physical model testing during preliminary ship design efforts.
by Petros Voxakis.
Nav.E.and S.M.
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Cho, Dong-Il. "Nonlinear control methods for automotive powertrain systems." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14682.
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Walczyk, Daniel Francis 1963. "Rapid fabrication methods for sheet metal dies." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10566.
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Quiñones, Lisandro E. (Quiñones Ortiz). "Carbon nanotubes : a study on assembly methods." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45289.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (p. 31-32).
The urgent stipulation is to manufacture CNTs of desired properties and dimensions. The heart of this yearning lies in understanding the growth and assembly methods of CNTs, which are not yet clear. In this study, hence, we concentrate on the synthesis and assemblage, pointing out the parameters, issues, and limitations of the available techniques. While there have been many interesting and successful attempts to grow and assemble CNTs by various methods, this study focuses on the conventional growing techniques and proposes unconventional assembly methods.
by Lisandro E. Quiñones.
S.B.
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Steindl, Riley M. "Choosing methods and metrics for design feedback." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123267.
Full textAbstract:
Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 18-19).
Collecting feedback is an invaluable part of the design process because it helps inform useful and effective changes to products. With a multitude of different methods for gathering feedback and metrics for evaluation, it can be difficult to select the method and/or metrics that will provide the most useful feedback for a given stage of design. There is currently no condensed guide for selecting methods and metrics for feedback on the bases of stage of design, effort level, and data type. This study filled this gap through a literature review of 9 academic papers related to design evaluation methods and metrics. Following review, the information in these papers was analyzed to establish how evaluation methods and metrics relate to different stages of design, different data types, and relative effort levels. The result is description of the relationships between stage of design and suitability, evaluation method and data type, evaluation method and effort level, and evaluation metric vs data type. In all, this study provides useful information for designers to use when selecting the right evaluation methods and metrics to collect feedback on their designs.
by Riley M. Steindl.
S.B.
S.B. Massachusetts Institute of Technology, Department of Mechanical Engineering
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Abu, Zeid Houda, and Tanya Syed. "Suitable textile recycling methods for implementation inSweden : A study in mechanical and chemical recycling methods." Thesis, KTH, Energiteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-226867.
Full textAbstract:
Detta projekt undersöker de ekonomiska, tekniska och miljömässiga aspekterna avtextilproduktion samt textilåtervinning. Paralleller dras mellan olika naturfibrer ochsyntetfibrer där såväl positiva som negativa aspekter belyses. I rapporten exemplifieras demest omdiskuterade textilierna; bomull, polyester, viskos och lyocell. Vidare görs en analyspå diverse textilåtervinningstekniker som finns i dagsläget och hur dessa är lämpade fördagens samhälle. På så sätt kan man undersöka vilka framtida möjligheter och begränsningarsom finns för utvecklingen av den textila återvinningen. En SWOT-analys utförs för attutreda möjligheterna för implementering av någon av de befintliga återvinningsteknikerna,kemisk respektive mekanisk återvinning, i Sverige. Utifrån SWOT-analysen som även räknassom rapportens resultat och även utifrån forskning i litteraturstudien dras slutsatsen attkemisk återvinning är tekniken som bäst lämpar sig utifrån Sveriges förhållanden. Slutsatserdras också kring vilka områden som landet måste fokusera på för att möjliggöra en storskaligåtervinning och detta involverar sorteringsteknologier, insamling och hantering av återvunnatextilfibrer. De specifika slutsaterna är:● Fokus bör ligga på att öka insamlingen av textilier då kemisk återvinning är mesteffektiv när det gäller återvinning av större volymer.● Majoriteten av all sortering av textilier bör automatiseras för att underlättahanteringen av insamlingen av textilier● Till en början bör endast textilier som gjorda på endast en fibertyp återvinnas, dettaeftersom att blandtextilier är mycket mer komplexa att hantera.Rapporten är uppdelad i två delar där den första delen innehåller introduktion, projektetsfrågeställningar samt målbeskrivning. Den senare delen är en längre litteraturstudie där faktaom olika typer av textilfibrer och hur produktion samt återvinning av dessa fibrer påverkarmiljö och samhälle. Litteraturstudien följs upp av en modellbeskrivning och en djupgåendeanalys av de slutgiltiga resultaten. I litteraturstudien återfinns även en intervju som ärgenomförd med klädföretaget Houdini Sportswear AB.This report strives to examine the economical, technical and environmental aspects of textileproduction, but mainly textile recycling. Comparisons between natural fibers and syntheticones will be made, comparing both positive and negative aspects. The textile fibers that willbe discussed are cotton, viscose, polyester and lyocell. Furthermore, an analysis of varioustextile recycling technologies currently available and how suited they are for today’s societywill be made. By doing so one can explore the future possibilities and limitations for thedevelopment of textile recycling. A SWOT-analysis will be conducted in order to examinethe possibility to implement one of the recycling techniques in Sweden. The conclusion thatformed from the SWOT-analysis was that the chemical recycling technique is better fitted fora country of Sweden’s nature. Furthermore, in order for Sweden to be able to implement alarge scale recycling system there is a need for development of certain areas, such as sortingtechnologies, collection and general managing of recycled textile fibers. Some furtherconclusions from this study are that:● Greater focus is needed in order to increase the collection of textiles, since thechemical recycling method is the most efficient when it comes to the recycling oflarger volumes of textiles.● The majority of the sorting of textiles should be done automatically to facilitate thehandling of the collection of textiles.● In the beginning one should focus on recycling textiles that only consist of one type offiber, this since the recycling of textiles consisting of more than one type of fiber ismore complex and the technique for it is not yet fully developed.There are two parts to the report. The first part contains an introduction and a description ofthe project’s research questions and mission. The second part is a literature study whichcontains information about different types of textile fibers currently available and how theproduction and recycling of these fibers affect the environment and society as a whole. Theliterature study is followed by a description of the model used in this report and also ananalysis of the final results. An interview conducted with the sportswear company HoudiniSportswear AB can also be found in the literature study.
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Snyman, H. "Second order analyses methods for stirling engine design." Thesis, Stellenbosch : University of Stellenbosch, 2007. http://hdl.handle.net/10019.1/16102.
Full textAbstract:
Thesis (MScIng( Mechanical Engineering)--University of Stellenbosch, 2007.121 Leaves printed single pages, preliminary pages a-l and numbered pages 1-81.
ENGLISH ABSTRACT:In the midst of the current non-renewable energy crises specifically with regard to fossil fuel, various research institutions across the world have turned their focus to renewable and sustainable development. Using our available non.renewable resources as efficiently as possible has been a focal point the past decades and will certainly be as long as these resources exist Various means to utilize the world's abundant and freely available renewable energy has been studied and some even introduced and installed as sustainable energy sources, Electricity generation by means of wind powered turbines, photo-voltaic cells, and tidal and wave energy are but a few examples. Modern photo-voltaic cells are known to have a solar to electricity conversion efficiency of 12% (Van Heerden, 2003) while wind turbines have an approximate wind to electricity conversion efficiency of 50% (Twele et aI., 2002). This low solar to electricity conversion efficiency together with the fact that renewable energy research is a relatively modern development, lead to the investigation into methods capable of higher solar to electricity conversion efficiencies. One such method could be to use the relatively old technology of the Stirling cycle developed in the early 1800's (solar to electricity conversion efficiency in the range of 20.24 % according Van Heerden, 2003). The Stirling cycle provides a method for converting thermal energy to mechanical power which can be used to generate electricity, One of the main advantages of Stirling machines is that they are capable of using any form of heat source ranging from solar to biomass and waste heat. This document provides a discussion of some of the available methods for the analysis of Stirling machines. The six (6) different methods considered include: the method of Beale, West, mean-pressurepower- formula (MPPF), Schmidt, idea! adiabatic and the simple analysis methods. The first three (3) are known to be good back-of-the-envelope methods specifically for application as synthesis tools during initialisation of design procedures, while the latter three (3) are analysis tools finding application during Stirling engine design and analysis procedures. These analysis methods are based on the work done by Berchowitz and Urieli (1984) and form the centre of this document. Sections to follow provide a discussion of the mathematical model as well as the MATlAB implementation thereof. Experimental tests were conducted on the Heinrici engine to provide verification of the simulated resutls. Shortcomings of these analyses methods are also discussed in the sections to follow. Recommendations regarding improvements of the simulation program, possible fields of application for Stirling technology, as well as future fields of study are made in the final chapter of this document. A review of relevanl literature regarding modern applications of Stirling technology and listings of companies currently manufacturing and developing Stirling machines and findings of research done at various other institutions are provided.
AFRIKAANSE OPSOMMING:Die tempo van uitputling van die wereld se nie-hernubare energiebronne die afgelope jare het aanleiding gegee daartoe dal daar loenemend fokus toegespits word op die ontwikkeling van hernubare alternatiewe. Meer doeltreffende benutting van die wereld se nie-hernubare energie is reeds 'n fokus punt, vir navorsers reg oor die wereld, vir die afgelope dekades. Die aarde se oorvloedryke hernubare energie bronne word reeds met verskeie metodes ontgin. Die omskakeling van wind-, son- en gety energie na elektrisieteids is net 'n paar voorbeelde. Die effektiwiteid van sonkrag na elektrisietyds omskakeling van moderne fotovo!la'iese selle is in die orde van 12% (Van Heerden, 2003) terwyl die doeltreffendeid van wind energie na elektrisiteit omskakelling in die orde van 50% (Twele et at, 2002) is. Hierdie relatief lae omskelings doeltreffendeid van sonkrag na elektrisietyd, tesame met die feit dat die hernubare industrie nag relatief jonk is, lei lot die soeke na ander meer doellreffende moontlikhede Die Stirling siklus is nie 'n mod erne beginsel nie, maar die toepassing daarvan veral in die hernubare energie industrie is wei 'n relatiewe nuwe beg rip, veral in teme van die omskakeling van sonkrag na elektriese energie (gemiddelde sonkrag na lektriese energie omskakelings doellreffendeid in die orde van 20-24% is gevind deur Van Heerden, 2003). Die omskakeling van lermiese energie na meganiese energie is sekerlik die hoof uitkomsle van die Stirling siklus, alhoewel dit ook toepassing vind in die verkoefingsindustrie. Die feit dat die Stirling siklus van enige vorm van termiese energie (bv. son. biomassa, asook hilte geproduseer as byproduk tydens sekere prosesse) gebruik kan maak. is een van die redes wat die tegnologie 56 aanloklik maak, spesifiek !.o,v. die hernubare energie sektor. Ses (6) metodes vir die analise van die Stirling siklus word in hierdie dokument bespreek. Dit slui! die volgnde in: Beale-, West-, die gemiddelde-druk-krag-metode (GDKM), Schmidt-, adiabatiese- en die eenvoudige analise melodes. Die eerste drie (3) metodes is handige berekenings metodes Iydens die aanvangs en sinlesefase van Stirling enjin ontwerp, lerwyl die laaste drie (3) meer loegespils is op die volledige ontwerps- en analisefases gedurende die Stirling eniin ontwerps proses. Die drie (3) analise melodes is gebaseer op die werk wat deur Berchowitz en Urieli (1984) gedoen is en maak die kern van die dokument uit. Die wiskundige model, implimentering daarvan in MATlAB, sowel as die eksperimentele verifieering van die resultate word bespreek. Tekortkominge van die analise metodes word ook aangespreek in elke hoofsluk. Moontlikke verbeterings len opsigte van die verskeie aannames word in die finale hoofsluk van die dokumenl aangespreek. Verskeie voorgestelde riglings vir toekomslige navorsings projekle word ook in die finale hoofstuk van die dokument genoem. 'n Kort oorsig van die relevanle lileraluur in verband mel huidige loepassings van die Stirling legnologie, asook die name van maatskappye wal tans hierdie tegnologiee ontwikkel en vervaardig, word genoem.
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Kaufmann, Matthew Vernon 1969. "Finite element and analytical methods for analyzing interfacial thermal resistance." Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/278334.
Full textAbstract:
In this thesis, the phenomena of thermal contact resistance is examined from both an analytical and numerical standpoint. Strong emphasis is made on the differentiation between the macroscopic and microscopic mechanisms and their separate effects on the thermal resistance at the interface of two unbonded materials. Of particular interest is the interface between two dissimilar materials. A full analysis of the macroscopic influence of thermal strains on the deformations at the interface is presented. The dependence of interfacial thermal resistance on the direction of heat flow is explained. The theory of microscopic-based contact resistance is also reviewed. A computer code enabling coupled thermal-mechanical finite element analyses of models was developed to investigate the complex interplay between thermal strains, interface separation, and contact conductance. The program is used to examine past and current methods of experimentally determining thermal contact resistance. A unique procedure, based on observed interfacial phenomena, for experimentally measuring true thermal contact resistance is presented and numerically verified. Finally, the technology developed in this thesis is used to analyze some interface problems in electronic packages.
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Dee, H. Devin (Herbert Devin). "Analyzing manufacturing methods of carbon nanotubes for commercialization." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/83706.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013.Cataloged from PDF version of thesis. "June 2013."
Includes bibliographical references (pages 38-41).
This research explores the history and structure of carbon nanotubes and the current technologies and methods available for synthesizing, purifying, and assembling carbon nanotubes. Furthermore, the current state of fabrication of carbon nanotubes has not reached a level where they can be commercialized. The most commonly used techniques of chemical vapor deposition (CVD), arc discharge, and laser ablation are discussed in detail with emphasis placed on three criteria: cost, rate, and flexibility. Satisfactory achievement in these three areas will result in the ability to have carbon nanotubes as a product. Assembly methods like nanopelleting and individual transplanting has helped make great strides towards reaching a state of commercialization, but several advancements need to take place with respect to carrying current processes out on a larger scale at affordable prices.
by H. Devin Dee.
S.B.
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Schantz, Christopher James. "Methods for non-intrusive sensing and system monitoring." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92173.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references.
Improving the efficiency of collection, transmission, and consumption of resources is the focus of a wide swath of engineering research. Current technological solutions for capturing or mitigating energy and resource waste are asymmetrical. A dilemma is becoming increasingly apparent in monitoring and control systems. Networking tools provide potentially inexpensive remote access to information, but gathering useful information, however, may require the installation of an array of costly and intrusive sensors. The promise of highly effective and useful networked solutions is hemmed in by a sensing frontier consisting of significant challenges. At any time in the service life of a machine or system it may perform below its design efficiency. Valves may leak, belts might slip, and equipment may be left on when not needed. Systems under feedback control like HVAC plants will mask the effect of incipient faults from the user by increasing their duty cycle and wasting energy. Water distribution networks will supply healthy and leaky loads alike without obvious change save in perhaps a monthly bill delivered in the mail. To meet these challenges, this thesis uses easily installed non-intrusive sensors coupled with advanced signal processing algorithms to provide a collated corrected picture of consumption and to provide opportunities for fault detection. Specific contributions are made in three areas: Electric motor driven machine fault detection; a motor like an induction machine can serve as its own fine resolution speed and torque sensor with performance to rival optical shaft encoders and exceeding most torque sensors, all from simple voltage and current signals. Full time fluid flow and hydraulic load tracking from clamp on vibration and magnetic field sensing. Non intrusive techniques for capturing vibration data for rotating machine fault detection, and methods to combine electrical and vibration information to create virtual inputs for performing output only or single sensor system identification.
by Christopher James Schantz.
Ph. D.
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Harutunian, Vigain. "Representation methods for an axiomatic design process software." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/39768.
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Hayeck, Tristan J. "Stochastic methods for modeling hydrodynamics of dilute gases." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36745.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaf 18).
When modeling small scale sub-micron gas flows, continuum methods, i.e. Navier Stokes equations, no longer apply. Molecular Dynamics (MD) approaches are then more appropriate. For dilute gases, where particles travel in straight lines for the overwhelming majority of the time, MD methods are inefficient compared to kinetic theory approaches because they require the explicit calculation of each particle's trajectory. An effective way to model the hydrodynamics of dilute gases is a stochastic particle method known as Direct Simulation Monte Carlo (DSMC). In DSMC the motion and collision of particles are decoupled to increase computational efficiency. The purpose of this thesis is to evaluate a variant of the DSMC algorithm, in which particles have discrete velocities. The most important modification to the DSMC algorithm is the treatment of collisions between particles with discrete velocities in a way which ensures strict conservation of momentum and energy. To achieve that an algorithm that finds all possible pairs of discrete post-collision velocities given a pair of discrete pre-collision velocities was developed and coded.
(cont.) Two important discretization ingredients were introduced: the number of discrete velocities and the maximum discrete velocity allowed. A number of simulations were performed to compare the discrete DSMC (IDSMC) and the regular DSMC method. Our results show that the difference between the two methods is small when the allowed discrete velocity spectrum extends to high speeds. In this case the error is fairly insensitive to the number of discrete velocities used. On the other hand, when the maximum velocity allowed is small compared to the most probably particle speed (approximately equivalent to the speed of sound), large errors are observed (in our case up to 450% in the stress).
by Tristan J. Hayeck.
S.B.