Дисертації з теми "Computational Science, Engineering"
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1
Sidiropoulos, Anastasios. "Computational metric embeddings." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44712.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 141-145).
We study the problem of computing a low-distortion embedding between two metric spaces. More precisely given an input metric space M we are interested in computing in polynomial time an embedding into a host space M' with minimum multiplicative distortion. This problem arises naturally in many applications, including geometric optimization, visualization, multi-dimensional scaling, network spanners, and the computation of phylogenetic trees. We focus on the case where the host space is either a euclidean space of constant dimension such as the line and the plane, or a graph metric of simple topological structure such as a tree. For Euclidean spaces, we present the following upper bounds. We give an approximation algorithm that, given a metric space that embeds into R1 with distortion c, computes an embedding with distortion c(1) [delta]3/4 (A denotes the ratio of the maximum over the minimum distance). For higher-dimensional spaces, we obtain an algorithm which, for any fixed d > 2, given an ultrametric that embeds into Rd with distortion c, computes an embedding with distortion co(1). We also present an algorithm achieving distortion c logo(1) [delta] for the same problem. We complement the above upper bounds by proving hardness of computing optimal, or near-optimal embeddings. When the input space is an ultrametric, we show that it is NP-hard to compute an optimal embedding into R2 under the ... norm. Moreover, we prove that for any fixed d > 2, it is NP-hard to approximate the minimum distortion embedding of an n-point metric space into Rd within a factor of Q(n1/(17d)). Finally, we consider the problem of embedding into tree metrics. We give a 0(1)approximation algorithm for the case where the input is the shortest-path metric of an unweighted graph.
(cont.) For general metric spaces, we present an algorithm which, given an n-point metric that embeds into a tree with distortion c, computes an embedding with distortion (clog n)o ... . By composing this algorithm with an algorithm for embedding trees into R1, we obtain an improved algorithm for embedding general metric spaces into R1.
by Anastasios Sidiropoulos.
Ph.D.
2
Castillo, Andrea R. (Andrea Redwing). "Assessing computational methods and science policy in systems biology." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/51655.
Анотація:
Thesis (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2009.Includes bibliographical references (p. 109-112).
In this thesis, I discuss the development of systems biology and issues in the progression of this science discipline. Traditional molecular biology has been driven by reductionism with the belief that breaking down a biological system into the fundamental biomolecular components will elucidate such phenomena. We have reached limitations with this approach due to the complex and dynamical nature of life and our inability to intuit biological behavior from a modular perspective [37]. Mathematical modeling has been integral to current system biology endeavors since detailed analysis would be invasive if performed on humans experimentally or in clinical trials [17]. The interspecies commonalities in systemic properties and molecular mechanisms suggests that certain behaviors transcend specie differentiation and therefore easily lend to generalizing from simpler organisms to more complex organisms such as humans [7, 17]. Current methodologies in mathematical modeling and analysis have been diverse and numerous, with no standardization to progress the discipline in a collaborative manner. Without collaboration during this formative period, successful development and application of systems biology for societal welfare may be at risk. Furthermore, such collaboration has to be standardized in a fundamental approach to discover generic principles, in the manner of preceding long-standing science disciplines. This study effectively implements and analyzes a mathematical model of a three-protein biochemical network, the Synechococcus elongatus circadian clock.
(cont.) I use mass action theory expressed in kronecker products to exploit the ability to apply numerical methods-including sensitivity analysis via boundary value formulation (BVP) and trapiezoidal integration rule-and experimental techniques-including partial reaction fitting and enzyme-driven activations-when mathematically modeling large-scale biochemical networks. Amidst other applicable methodologies, my approach is grounded in the law of mass action because it is based in experimental data and biomolecular mechanistic properties, yet provides predictive power in the complete delineation of the biological system dynamics for all future time points. The results of my research demonstrate the holistic approach that mass action method-ologies have in determining emergent properties of biological systems. I further stress the necessity to enforce collaboration and standardization in future policymaking, with reconsiderations on current stakeholder incentive to redirect academia and industry focus from new molecular entities to interests in holistic understanding of the complexities and dynamics of life entities. Such redirection away from reductionism could further progress basic and applied scientific research to embetter our circumstances through new treatments and preventive measures for health, and development of new strains and disease control in agriculture and ecology [13].
by Andrea R. Castillo.
S.M.in Technology and Policy
3
Vanek, Christopher Michael. "Computational hurricane hazard analysis a performance based engineering view." Master's thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4543.
Анотація:
Results show that both the time and frequency content of the dynamic signal could be accurately captured through CFD simulations in a much more cost effective manner than laboratory experimentation. Structural FEM models showed the poor performance of two coastal structures designed using deterministic principles, as serviceability and strength limit states were exceeded. Additionally, the response curves created for the prototype structure could be further developed for multiple wind directions and wave periods. Thus CFD is a viable option to wind and wave laboratory studies and a key tool for the development of PBE in the field of hurricane engineering.; Widespread structural damage to critical facilities such as levees, buildings, dams and bridges during hurricanes has exemplified the need to consider multiple hazards associated with hurricanes as well as the potential for unacceptable levels of performance even if failure is not observed. These inadequate standards warrant the use of more accurate methods to describe the anticipated structural response, and damage for extreme events often termed performance based engineering (PBE). Therefore PBE was extended into the field of hurricane engineering in this study. Application of performance-based principles involves collection of the numerous hazards data from sources such as historical records, laboratory experiments or stochastic simulations. However, the hazards associated with a hurricane typically include spatial and temporal variation therefore, more detailed collection of data from each hazard of this loading spectrum is required. At the same time, computational power and computer-aided design have advanced and potentially allows for collection of the structure-specific hazard data. This novel technique, known as computational fluid dynamics (CFD), was applied to the wind and wave hazards associated with hurricanes to accurately quantify the spectrum of dynamic loads in this study. Numerical simulation results are presented on verification of this technique with laboratory experimental studies and further application to a typical Florida building and bridge prototype. Both the time and frequency domain content of random process signals were analyzed and compared through basic properties including the spectral density, autocorrelation, and mean. Following quantification of the dynamic loads on each structure, a detailed structural FEM was constructed of each structure and response curves were created for various levels of hurricane categories.ID: 029050946; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.C.E.)--University of Central Florida, 2010.; Includes bibliographical references (p. 183]-186).
M.S.C.E.
Masters
Department of Civil, Environmental, and Construction Engineering
Engineering and Computer Science
4
Gupta, Gaurav. "Computational material science of carboncarbon : composites based on carbonaceous mesophase matrices." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83865.
Анотація:
Carbon/Carbon composites belong to the generic class of fiber reinforced composites and are widely used because of their high strength as well as chemical and thermal stability. Like other fiber reinforced composites they consist of the fibers which act as reinforcements and matrix which acts as a glue that binds the fibers. c/c composites from pitch based precursor are unique since the matrix in this case is a liquid crystal or mesophase. This makes them remarkable in the sense that unlike c/c composites from other precursors such as PAN, rayon etc. they have extremely high degree of molecular orientation and exhibit texture. An important characteristic of their textures is the presence of topological defects. It is hence of great interest to understand and elucidate the principles that govern the formation of textures so as to optimize their properties. In this work we present a computational study of structure formation in carbon-carbon composites that describes the emergence of topological defects due to the distortions in the oriented matrix created by the presence of fiber matrix interaction. Dynamical and structural features of texture formation were characterized using gradient elasticity and defect physics.
5
Yadala, Bhavya Sree. "Understanding Participants’ Feedback from Workshop Promoting Diversity and Inclusion in Computational Science and Engineering." Youngstown State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1620987134533065.
6
Doshi, Manan(Manan Mukesh). "Energy-time optimal path planning in strong dynamic flows." Thesis, Massachusetts Institute of Technology, 2021. https://hdl.handle.net/1721.1/130905.
Анотація:
Thesis: S.M., Massachusetts Institute of Technology, Center for Computational Science & Engineering, February, 2021Cataloged from the official PDF version of thesis.
Includes bibliographical references (pages 55-61).
We develop an exact partial differential equation-based methodology that predicts time-energy optimal paths for autonomous vehicles navigating in dynamic environments. The differential equations solve the multi-objective optimization problem of navigating a vehicle autonomously in a dynamic flow field to any destination with the goal of minimizing travel time and energy use. Based on Hamilton-Jacobi theory for reachability and the level set method, the methodology computes the exact Pareto optimal solutions to the multi-objective path planning problem, numerically solving the equations governing time-energy reachability fronts and optimal paths. Our approach is applicable to path planning in various scenarios, however we primarily present examples of navigating in dynamic marine environments. First, we validate the methodology through a benchmark case of crossing a steady front (a highway flow) for which we compare our results to semi-analytical optimal path solutions. We then consider more complex unsteady environments and solve for time-energy optimal missions in a quasi-geostrophic double-gyre ocean flow field.
by Manan Doshi.
S.M.
S.M. Massachusetts Institute of Technology, Center for Computational Science & Engineering
7
Wang, Hong Feng. "IGP traffic engineering : a comparison of computational optimization algorithms." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/20877.
Анотація:
Thesis (MSc)--Stellenbosch University, 2008.ENGLISH ABSTRACT: Traffic Engineering (TE) is intended to be used in next generation IP networks to optimize the usage of network resources by effecting QoS agreements between the traffic offered to the network and the available network resources. TE is currently performed by the IP community using three methods including (1) IGP TE using connectionless routing optimization (2) MPLS TE using connection-oriented routing optimization and (3) Hybrid TE combining IGP TE with MPLS TE. MPLS has won the battle of the core of the Internet and is making its way into metro, access and even some private networks. However, emerging provider practices are revealing the relevance of using IGP TE in hybrid TE models where IGP TE is combined with MPLS TE to optimize IP routing. This is done by either optimizing IGP routing while setting a few number of MPLS tunnels in the network or optimizing the management of MPLS tunnels to allow growth for the IGP traffic or optimizing both IGP and MPLS routing in a hybrid IGP+MPLS setting. The focus of this thesis is on IGP TE using heuristic algorithms borrowed from the computational intelligence research field. We present four classes of algorithms for Maximum Link Utilization (MLU) minimization. These include Genetic Algorithm (GA), Gene Expression Programming (GEP), Ant Colony Optimization (ACO), and Simulated Annealing (SA). We use these algorithms to compute a set of optimal link weights to achieve IGP TE in different settings where a set of test networks representing Europe, USA, Africa and China are used. Using NS simulation, we compare the performance of these algorithms on the test networks with various traffic profiles.
AFRIKAANSE OPSOMMING: Verkeersingenieurswese (VI) is aangedui vir gebruik in volgende generasie IP netwerke vir die gebruiksoptimering van netwerkbronne deur die daarstelling van kwaliteit van diens ooreenkomste tussen die verkeersaanbod vir die netwerk en die beskikbare netwerkbronne. VI word huidiglik algemeen bewerkstellig deur drie metodes, insluitend (1) IGP VI gebruikmakend van verbindingslose roete-optimering, (2) MPLS VI gebruikmakend van verbindingsvaste roete-optimering en (3) hibriede VI wat IGP VI en MPLS VI kombineer. MPLS is die mees algemene, en word ook aangewend in metro, toegang en selfs sommige privaatnetwerke. Nuwe verskaffer-praktyke toon egter die relevansie van die gebruik van IGP VI in hibriede VI modelle, waar IGP VI gekombineer word met MPLS VI om IP roetering te optimeer. Dit word gedoen deur `of optimering van IGP roetering terwyl ’n paar MPLS tonnels in die netwerk gestel word, `of optimering van die bestuur van MPLS tonnels om toe te laat vir groei in die IGP verkeer `of die optimering van beide IGP en MPLS roetering in ’n hibriede IGP en MPLS situasie. Die fokus van hierdie tesis is op IGP VI gebruikmakend van heuristieke algoritmes wat ontleen word vanuit die berekeningsintelligensie navorsingsveld. Ons beskou vier klasse van algoritmes vir Maksimum Verbindingsgebruik (MVG) minimering. Dit sluit in genetiese algoritmes, geen-uitdrukkingsprogrammering, mierkoloniemaksimering and gesimuleerde temperoptimering. Ons gebruik hierdie algoritmes om ’n versameling optimale verbindingsgewigte te bereken om IGP VI te bereik in verskillende situasies, waar ’n versameling toetsnetwerke gebruik is wat Europa, VSA, Afrika en China verteenwoordig. Gebruikmakende van NS simulasie, vergelyk ons die werkverrigting van hierdie algoritmes op die toetsnetwerke, met verskillende verkeersprofiele.
8
Dreany, Harry Hayes. "Safety Engineering of Computational Cognitive Architectures within Safety-Critical Systems." Thesis, The George Washington University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10688677.
Анотація:
This paper presents the integration of an intelligent decision support model (IDSM) with a cognitive architecture that controls an autonomous non-deterministic safety-critical system. The IDSM will integrate multi-criteria, decision-making tools via intelligent technologies such as expert systems, fuzzy logic, machine learning, and genetic algorithms.
Cognitive technology is currently simulated within safety-critical systems to highlight variables of interest, interface with intelligent technologies, and provide an environment that improves the system’s cognitive performance. In this study, the IDSM is being applied to an actual safety-critical system, an unmanned surface vehicle (USV) with embedded artificial intelligence (AI) software. The USV’s safety performance is being researched in a simulated and a real-world, maritime based environment. The objective is to build a dynamically changing model to evaluate a cognitive architecture’s ability to ensure safe performance of an intelligent safety-critical system. The IDSM does this by finding a set of key safety performance parameters that can be critiqued via safety measurements, mechanisms, and methodologies. The uniqueness of this research lies in bounding the decision-making associated with the cognitive architecture’s key safety parameters (KSPs). Other real-time applications (RTAs) that would benefit from advancing cognitive science associated with safety are unmanned platforms, transportation technologies, and service robotics. Results will provide cognitive science researchers with a reference for the safety engineering of artificially intelligent safety-critical systems.
9
Blount, Steven Michael 1958. "Computational methods for stochastic epidemics." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/288714.
Анотація:
Compartmental models constructed for stochastic epidemics are usually difficult to analyze mathematically or computationally. Researchers have mostly resorted to deterministic approximations or simulation to investigate these models. This dissertation describes three original computational methods for analyzing compartmental models of stochastic epidemics. The first method is the Markov Process Method which computes the probability law for the epidemic by solving the Chapman-Kolmogorov ordinary differential equations as an initial value problem using standard numerical analysis techniques. It is limited to models with small populations and few compartments and requires sophisticated numerical analysis tools and relatively extensive computer resources. The second method is the Probability Vector Method which can estimate the first few moments of a discrete time epidemic model over a limited time period (i.e. if Y(t) is the number of individuals in a given compartment then this method can estimate E[ Yr for small positive integers r. Size restrictions limit the maximum order of the moment that can be computed. For compartmental models with a constant, homogeneous population, this method requires modest computational resources to estimate the first two moments of Y(t). The third method is the Linear Extrapolation Method, which computes the moments of a compartmental model with a large population by extrapolating from the given moments of the same model with smaller populations. This method is limited to models that have some alternate way of calculating the moments for small populations. These moments should be computed exactly from probabilistic principles. When this is not practical, any method that can produce accurate estimates of these moments for small populations can be used. Two compartmental epidemic models are analyzed using these three methods. First, the simple susceptible/infective epidemic is used to illustrate each method and serves as a benchmark for accuracy and performance. These computations show that each algorithm is capable of producing acceptably accurate solutions (at least for the specific parameters that were used). Next, an HIV/AIDS model is analyzed and the numerical results are presented and compared with the deterministic and simulation solutions. Only the probability vector method could compete with simulation on the larger (i.e. more compartments) HIV/AIDS model.
10
Raina, Priyanka. "Architectures for computational photography." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82393.
Анотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 93-94).
Computational photography refers to a wide range of image capture and processing techniques that extend the capabilities of digital photography and allow users to take photographs that could not have been taken by a traditional camera. Since its inception less than a decade ago, the field today encompasses a wide range of techniques including high dynamic range (HDR) imaging, low light enhancement, panorama stitching, image deblurring and light field photography. These techniques have so far been software based, which leads to high energy consumption and typically no support for real-time processing. This work focuses on hardware architectures for two algorithms - (a) bilateral filtering which is commonly used in computational photography applications such as HDR imaging, low light enhancement and glare reduction and (b) image deblurring. In the first part of this work, digital circuits for three components of a multi-application bilateral filtering processor are implemented - the grid interpolation block, the HDR image creation and contrast adjustment blocks, and the shadow correction block. An on-chip implementation of the complete processor, designed with other team members, performs HDR imaging, low light enhancement and glare reduction. The 40 nm CMOS test chip operates from 98 MHz at 0.9 V to 25 MHz at 0.9 V and processes 13 megapixels/s while consuming 17.8 mW at 98 MHz and 0.9 V, achieving significant energy reduction compared to previous CPU/GPU implementations. In the second part of this work, a complete system architecture for blind image deblurring is proposed. Digital circuits for the component modules are implemented using Bluespec SystemVerilog and verified to be bit accurate with a reference software implementation. Techniques to reduce power and area cost are investigated and synthesis results in 40nm CMOS technology are presented
by Priyanka Raina.
S.M.
11
Kirmani, Ghulam A. (Ghulam Ahmed). "Computational time-resolved imaging." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/97803.
Анотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 151-159).
Classical photography uses steady-state illumination and light sensing with focusing optics to capture scene reflectivity as images; temporal variations of the light field are not exploited. This thesis explores the use of time-varying optical illumination and time-resolved sensing along with signal modeling and computational reconstruction. Its purpose is to create new imaging modalities, and to demonstrate high-quality imaging in cases in which traditional techniques fail to even form degraded imagery. The principal contributions in this thesis are the derivation of physically-accurate signal models for the scene's response to timevarying illumination and the photodetection statistics of the sensor, and the combining of these models with computationally tractable signal recovery algorithms leading to image formation. In active optical imaging setups, we use computational time-resolved imaging to experimentally demonstrate: non line-of-sight imaging or looking around corners, in which only diffusely scattered light was used to image a hidden plane which was completely occluded from both the light source and the sensor; single-pixel 3D imaging or compressive depth acquisition, in which accurate depth maps were obtained using a single, non-spatially resolving bucket detector in combination with a spatial light modulator; and high-photon efficiency imaging including first-photon imaging, in which high-quality 3D and reflectivity images were formed using only the first detected photon at each sensor pixel despite the presence of high levels of background light.
by Ghulam A. Kirmani.
Ph. D.
12
Li, Zheng Ph D. Massachusetts Institute of Technology. "Computational Raman imaging and thermography." Thesis, Massachusetts Institute of Technology, 2021. https://hdl.handle.net/1721.1/130673.
Анотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, February, 2021Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 185-201).
Thermography tools that perform accurate temperature measurements with nanoscale resolution are highly desired in our modern society. Although researchers have put extensive efforts in developing nanoscale thermography for more than three decades and a significant amount of achievements have been made in this field, the mainstream thermography tools have not fully met the requirements from the industry and the academia. In this thesis, we present our home-built Raman microscope for Raman imaging and thermography. The performance of this instrument is enhanced by computational approaches. The body of the thesis will be divided into three parts. First, the instrumentation of our setup are introduced. Second, we present the results of Raman imaging with computational super-resolution techniques. Third, this instrument is used as a thermography tool to map the temperature profile of a nanowire device. These results provide insights in combining advanced instrumentation and computational methods in Raman imaging and Raman thermography for the applications in modern nano-technology.
by Zheng Li.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering
13
Alabdulkareem, Ahmad. "Analyzing cities' complex socioeconomic networks using computational science and machine learning." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119325.
Анотація:
Thesis: Ph. D. in Computational Science & Engineering, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 133-141).
By 2050, it is expected that 66% of the world population will be living in cities. The urban growth explosion in recent decades has raised many questions concerning the evolutionary advantages of urbanism, with several theories delving into the multitude of benefits of such efficient systems. This thesis focuses on one important aspect of cities: their social dimension, and in particular, the social aspect of their complex socioeconomic fabric (e.g. labor markets and social networks). Economic inequality is one of the greatest challenges facing society today, in tandem with the eminent impact of automation, which can exacerbate this issue. The social dimension plays a significant role in both, with many hypothesizing that social skills will be the last bastion of differentiation between humans and machines, and thus, jobs will become mostly dominated by social skills. Using data-driven tools from network science, machine learning, and computational science, the first question I aim to answer is the following: what role do social skills play in today's labor markets on both a micro and macro scale (e.g. individuals and cities)? Second, how could the effects of automation lead to various labor dynamics, and what role would social skills play in combating those effects? Specifically, what are social skills' relation to career mobility? Which would inform strategies to mitigate the negative effects of automation and off-shoring on employment. Third, given the importance of the social dimension in cities, what theoretical model can explain such results, and what are its consequences? Finally, given the vulnerabilities for invading individuals' privacy, as demonstrated in previous chapters, how does highlighting those results affect people's interest in privacy preservation, and what are some possible solutions to combat this issue?
by Ahmad Alabdulkareem.
Ph. D. in Computational Science & Engineering
14
Wang, Billie. "Integrated Computational Microstructure Engineering for Single-Crystal Nickel-base Superalloys." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1228147112.
15
Qiu, Kanjun. "Developing a computational textiles curriculum to increase diversity in computer science." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/85222.
Анотація:
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 97-98).
The current culture surrounding computer science is quite narrow, resulting in a participating population that lacks diversity in both gender and interests. The field of computational textiles has shown promise as a domain for diversifying computer science culture by drawing a population with broader, less traditional interests and backgrounds into creating technology; however, little effort has been made to build resources and communities around computational textiles. This thesis presents a curriculum that teaches computer science and computer programming through a series of lessons for building and programming computational textile projects, along with systematic considerations that support the real-world implementation of such a curriculum. In 2011-12, we conducted three workshops to evaluate the impact of our curriculum methods and projects on students' technological self-efficacy. As a result of data obtained from these workshops, we conclude that working with our curriculum's structured computational textile projects both draws a gender-diverse population, and increases students' comfort with, enjoyment of, and interest in working with electronics and programming. Accordingly, we are transforming the curriculum into a published book in order to provide educational resources to support the development of a computer science culture around computational textiles.
by Kanjun Qiu.
M. Eng.
16
Huang, Liangliang. "Computational Study of Toxic Gas Removal by Reactive Adsorption." Thesis, North Carolina State University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3538542.
Анотація:
Growing concerns about the environment and terrorist attacks prompt a search for effective adsorbents for removal of small molecule toxic gases, such as ammonia and hydrogen sulfide, under ambient conditions in the presence of moisture, where physical adsorption is not adequate. We use graphene oxide and CuBTC metal-organic framework as the adsorbents to explore toxic gas removal by reactive adsorption. Using ab initio density functional theory, atomistic reactive molecular dynamics and Monte Carlo simulation strategies, theoretical understanding of the underlying reaction and adsorption mechanisms of ammonia and hydrogen sulfide on graphene oxide and CuBTC metal-organic framework have been gained.
The ab initio calculation results show that ammonia and hydrogen sulfide decompose on carboxyl and epoxy functional groups and vacancy defects of graphene oxide. The existence of water molecules substantially reduces the adsorption/dissociation of ammonia or hydrogen sulfide on graphene oxide because the water molecules either form hydrogen bonds with the functional groups or adsorb more easily on the vacancy defects. Reactive molecular dynamics calculations by the ReaxFF method have been performed to propose realistic graphene oxide models for theoretical calculations. We also use reactive molecular dynamics simulation to study the thermal and hydrostatic stabilities of the CuBTC metal-organic framework and its application for ammonia removal. We predict the collapse temperature for CuBTC crystal structure and observe the partial collapse of CuBTC at lower temperatures upon ammonia adsorption. The results agree well with experiment data and provide insights on the reaction mechanism involved in such an ammonia removal process.
The research in this thesis can provide fundamental understanding, at the electronic and atomistic levels, of the roles of surface defects and functionalities for reactive adsorption of toxic gas molecules. In addition to developing experimental and theoretical algorithms to design effective adsorbents, the results are expected to find applications in air cleaning, energy storage, fuel cell technology and other scientific challenges where the separation of reactive molecules is involved.
17
Ristad, Eric Sven. "Computational Structure of Human Language." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/7038.
Анотація:
The central thesis of this report is that human language is NP-complete. That is, the process of comprehending and producing utterances is bounded above by the class NP, and below by NP-hardness. This constructive complexity thesis has two empirical consequences. The first is to predict that a linguistic theory outside NP is unnaturally powerful. The second is to predict that a linguistic theory easier than NP-hard is descriptively inadequate. To prove the lower bound, I show that the following three subproblems of language comprehension are all NP-hard: decide whether a given sound is possible sound of a given language; disambiguate a sequence of words; and compute the antecedents of pronouns. The proofs are based directly on the empirical facts of the language user's knowledge, under an appropriate idealization. Therefore, they are invariant across linguistic theories. (For this reason, no knowledge of linguistic theory is needed to understand the proofs, only knowledge of English.) To illustrate the usefulness of the upper bound, I show that two widely-accepted analyses of the language user's knowledge (of syntactic ellipsis and phonological dependencies) lead to complexity outside of NP (PSPACE-hard and Undecidable, respectively). Next, guided by the complexity proofs, I construct alternate linguisitic analyses that are strictly superior on descriptive grounds, as well as being less complex computationally (in NP). The report also presents a new framework for linguistic theorizing, that resolves important puzzles in generative linguistics, and guides the mathematical investigation of human language.
18
Chin, Toshio M. "Dynamic estimation in computational vision." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13072.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1992.Includes bibliographical references (leaves 213-220).
by Toshio Michael Chin.
Ph.D.
19
Baggett, David McAdams. "A system for computational phonology." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36535.
Анотація:
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (p. 127-129).
by David McAdams Baggett.
M.S.
20
Sither, Matthew C. (Matthew Christian). "Adaptive consolidation of computational perspectives." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37098.
Анотація:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (p. 81).
This thesis describes the design and implementation of machine learning algorithms and real-time recommendations within EWall, a software system used for individual and collaborative information management. In the EWall workspace, users collect and arrange cards, which are compact visual abstractions of information. A significant problem that often arises when humans try to collect information is information overload. Information overload refers to the state of having too much information, and it causes difficulty in discovering relevant information. When affected by information overload, the user loses focus and spends more time filtering out irrelevant information. This thesis first presents a simple solution that uses a set of algorithms that prioritize information. Based on the information the user is working with, the algorithms search for relevant information in a database by analyzing spatial, temporal, and collaborative relationships. A second, more adaptive solution uses agents that observe user behavior and learn to apply the prioritization algorithms more effectively. Adaptive agents help to prevent information overload by removing the burden of search and filter from the user, and they hasten the process of discovering interesting and relevant information.
by Matthew C. Sither.
M.Eng.
21
Bylinskii, Zoya. "Computational understanding of image memorability." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/97256.
Анотація:
Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 77-82).
Previous studies have identified that images carry the attribute of memorability, a predictive value of whether a novel image will be later remembered or forgotten. In this thesis we investigate the interplay between intrinsic and extrinsic factors that affect image memorability. First, we find that intrinsic differences in memorability exist at a finer-grained scale than previously documented. Moreover, we demonstrate high consistency across participant populations and experiments. We show how these findings generalize to an applied visual modality - information visualizations. We separately find that intrinsic differences are already present shortly after encoding and remain apparent over time. Second, we consider two extrinsic factors: image context and observer behavior. We measure the effects of image context (the set of images from which the experimental sequence is sampled) on memorability. Building on prior findings that images that are distinct with respect to their context are better remembered, we propose an information-theoretic model of image distinctiveness. Our model can predict how changes in context change the memorability of natural images using automatically computed image features. Our results are presented on a large dataset of indoor and outdoor scene categories. We also measure the effects of observer behavior on memorability, on a trial-bytrial basis. Specifically, our proposed computational model can use an observer's eye movements on an image to predict whether or not the image will be later remembered. Apart from eye movements, we also show how 2 additional physiological measurements - pupil dilations and blink rates - can be predictive of image memorability, without the need for overt responses. Together, by considering both intrinsic and extrinsic effects on memorability, we arrive at a more complete model of image memorability than previously available.
by Zoya Bylinskii.
S.M.
22
Herzog, Jonathan 1975. "Computational soundness of formal adversaries." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/87334.
Анотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2003.Includes bibliographical references (p. 50-51).
by Jonathan Herzog.
S.M.
23
Banks, Eric 1976. "Computational approaches to gene finding." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/81523.
24
Sealfon, Rachel (Rachel Sima). "Computational investigation of pathogen evolution." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99858.
Анотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 105-118).
Pathogen genomes, especially those of viruses, often change rapidly. Changes in pathogen genomes may have important functional implications, for example by altering adaptation to the host or conferring drug resistance. Accumulated genomic changes, many of which are functionally neutral, also serve as markers that can elucidate transmission dynamics or reveal how long a pathogen has been present in a given environment. Moreover, systematically probing portions of the pathogen genome that are changing more or less rapidly than expected can provide important clues about the function of these regions. In this thesis, I (1) examine changes in the Vibrio cholerae genome shortly after the introduction of the pathogen to Hispaniola to gain insight into genomic change and functional evolution during an epidemic. I then (2) use changes in the Lassa genome to estimate the time that the pathogen has been circulating in Nigeria and in Sierra Leone, and to pinpoint sites that have recurrent, independent mutations that may be markers for lineage-specific selection. I (3) develop a method to identify regions of overlapping function in viral genomes, and apply the approach to a wide range of viral genomes. Finally, I (4) use changes in the genome of Ebola virus to elucidate the virus' origin, evolution, and transmission dynamics at the start of the outbreak in Sierra Leone.
by Rachel Sealfon.
Ph. D.
25
Hinuma, Yoyo. "Computational structure analysis of multicomponent oxides." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44208.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references.
First principles density functional theory (DFT) energy calculations combined with the cluster expansion and Monte Carlo techniques are used to understand the cation ordering patterns of multicomponent oxides. Specifically, the lithium ion battery cation material LiNi0.5Mn0.5O2 and the thermoelectric material P2-NaxCoO2 (0.5 =/< x =/< 1) are investigated in the course of this research. It is found that at low temperature the thermodynamically stable state of LiNi0.5Mn0.5O2 has almost no Li/Ni disorder between the Li-rich and transition metal-rich (TM) layer, making it most suitable for battery applications. Heating the material above ~600°C causes an irreversible transformation, which yields a phase with 10~12% Li/Ni disorder and partial disorder of cations in the TM layer. Phase diagrams for the NaxCoO2 system were derived from the results of calculations making use of both the Generalized Gradient Approximation (GGA) to DFT and GGA with Hubbard U correction (GGA+U). This enabled us to study how hole localization, or delocalization, on Co affects the ground states and order-disorder transition temperatures of the system. Comparison of ground states, c lattice parameter and Na1/Na2 ratio with experimental observations suggest that results from the GGA, in which the holes are delocalized, matches the experimental results better for 0.5 =/< x =/< 0.8. We also present several methodological improvements to the cluster expansions. An approach to limit phase space and methods to deal with multicomponent charge balance constrained open systems while including both weak, long-range electrostatic interactions and strong, short-range interactions in a single cluster expansion.
by Yoyo Hinuma.
Ph.D.
26
Wang, Mengyi S. M. Massachusetts Institute of Technology. "Multiscale computational modeling of nanofluidic transport." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/128996.
Анотація:
Thesis: S.M., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2020Cataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 56-61).
Water scarcity is one of the largest global challenges, affecting two-thirds of the world population. Water desalination and purification technologies, such as novel membrane processes and materials, are in great demand to produce clean water from contaminated sources or the sea. However, the lack of fundamental understanding of structure-property-performance has hindered the advancement of these techniques. In this study, we address this critical knowledge gap by adapting multiscale computational modeling to better understand the mechanisms of intrinsic molecular interaction in nanofluidic applications. We performed ab initio molecular dynamics to study the nanoscale solvation behavior of selected ions on finite graphene models. The degree of charge transfer between ion and water, and the effect of defects on dynamics and solvation has been investigated. Furthermore, a quantum mechanics/molecular mechanics (QM/MM) model for the accurate description of free energy changes in ion adsorption process has been developed. Lastly, we combined classical molecular dynamics and density functional theory (DFT) to elucidate the dielectric-driven mechanism of ionization behavior in nanoporous polyamide films. We seek to utilize this knowledge for the design of next-generation membranes for separation and water purification.
by Mengyi Wang.
S.M.
S.M. Massachusetts Institute of Technology, Department of Materials Science and Engineering
27
Zumbro, Emiko. "Computational insights into multivalently binding polymers." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/129045.
Анотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2020Cataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 253-264).
Multivalent binding is commonly used throughout biology to create strong, conformal bonds using multiple weak binding interactions simultaneously. Bonds are considered multivalent when multiple ligands on one species simultaneously bind to multiple receptors on another species. Together, this bond can be much stronger than the sum of its parts. Throughout this thesis, we use theory and coarse-grain Brownian dynamics simulations with specific reactive-binding to explore general characteristics of multivalent polymer interactions. Our simulations bridge length and timescales and can sample large polymer systems that bind targets at the sub-nanometer lengthscale. While the simulation and theory presented is very general and can be applied to many different systems of multivalent polymers, this thesis specifically explores consequences for two applications: multivalent polymers as decoys to inhibit infection and polymers as scaffolds for biocondensates.
Many pathogens use multivalent bonds to attach to our cell surfaces before entering and causing infection. Therefore, there is significant interest in preventing infection from viruses, bacteria, and toxic proteins by inhibiting this attachment step using multivalent decoys. There have been many experiments showing successful binding of long polymers or other large multivalent architectures to colloids or small proteins that pathogens use to bind to our cells. While these experiments have shown how promising multivalent inhibitors are for preventing infection, a theoretical understanding of why design parameters of multivalent polymers result in a particular binding affinity is still missing. Simulations can easily isolate a single design parameter to provide direct links between structure and function, when experiments cannot always do so. This research is intended to provide a systematic study linking structure of multivalent polymers to their binding behavior.
In the first half of this thesis, we explore design properties of polymeric binders and how degree of polymerization, solvent quality, binding site affinity patterns, backbone stiffness, and target concentration change the multivalent binding affinity. We provide simple theory to show that multivalent polymers are limited by their ability and the energetic costs of forming polymer loops. We go on to show how these results and theory have implications on the binding affinity of polymers with heterogeneous binding sites and determines the effect of polymer backbone flexibility and solvent quality on binding affinity. Multivalent polymers are also an essential component of biocondensates, liquid-like droplets comprised of proteins and nucleic acids are found throughout cells. Although the function of these biocondensates is still an active field of study, it is clear that multivalent polymers are essential to their formation through liquid-liquid phase separation (LLPS).
There is little theoretical study of biocondensates that contain binding between species of asymmetric size and valency and the effects of multivalent polymers on the dynamics of these liquid droplets is not well understood. Studying how multivalent polymers modulate droplet dynamics is important because droplet crystallization or solidification is often associated with neurodegenerative disorders such as dementia and amyotrophic lateral sclerosis (ALS). Therefore, in the second half of this thesis, we present research on the role multivalent polymers play in LLPS droplets and their resulting dynamics. We consider how a host of design parameters can change the phase boundary of systems with multivalent polymers binding to smaller targets including solvent quality, valency, binding affinity, specific versus non-specific binding sites, and backbone stiffness.
We found that consistent with previous work on other systems, asymmetric valency systems also showed increased phase separation with increased binding affinities and valencies. We show that phase separation due to non-specific bonds is highly sensitive to changes in attraction, but that phase separation through specific-bonds is much more robust. By combining specific and non-specific multivalency, systems can precisely tune the phase separation boundary. Polymer stiffness can also modulate the phase boundary, where stiff, rod-like polymers were less able to cause phase separation than their flexible counterparts. We also elucidate how polymer-target binding affinities can be used to form micro-phase separated droplets. Lastly, we show that increasing attraction to polymers can slow target diffusion inside droplets while decreasing the density of droplets, with implications for droplet solidification.
We hope that this work will provide direction for the rational design of synthetic multivalent polymer systems such as pathogen inhibitors as well as improve understanding of native biological systems like biocondensates.
by Emiko Zumbro.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering
28
Bose, Prosenjit. "Geometric and computational aspects of manufacturing processes." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28686.
Анотація:
Two of the fundamental questions that arise in the manufacturing industry concerning every type of manufacturing process are: (1) Given an object, can it be built using a particular process? (2) Given that an object can be built using a particular process, what is the best way to construct the object? The latter question gives rise to many different problems depending on how best is qualified. We address these problems for two complimentary categories of manufacturing processes: rapid prototyping systems and casting processes. The method we use to address these problems is to first define a geometric model of the process in question and then answer the question on that model.In the category of rapid prototyping systems, we concentrate on stereolithography, which is emerging as one of the most popular rapid prototyping systems. We model stereolithography geometrically and then study the class of objects that admit a construction in this model. For the objects that admit a construction, we find the orientations that allow a construction of the object.
In the category of casting processes, we concentrate on gravity casting and injection molding. We first model the process and its components geometrically. We then characterize and recognize the objects that can be formed using a re-usable two-part cast. Given that a cast of an object can be formed, we determine a suitable location for the pin gate, the point from which liquid is poured or injected into a mold. Finally, we compute an orientation of a mold that ensures a complete fill and minimizes the number of venting holes for molds used in gravity casting processes.
29
Hwang, Dae Kun 1972. "Computational optical science of textured liquid crystals for biosensors, rheooptics, and carbon composites." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102509.
Анотація:
Liquid crystals are functional materials used in displays, sensors, and biosensor applications, as well as structural materials used as precursors in the manufacturing of polymer superfibers and high performance carbon composites. While consumer display applications are based on defect-free homogeneous liquid crystals, the performance of biosensors devices and the characterization of structural material precursors is based on the presence of defects, textures, and heterogeneities. This thesis uses theory, modeling, and simulation to formulate the computational optical science of textured liquid crystals, and its applications in biosensors and material characterization methods.The computational optical science of textured liquid crystals is established by a comprehensive study of light propagation through cross-polars in thin liquid crystal films containing defects of significant complexity. Optical matrix methods widely used in display applications, including the aggregate model and the well-known Berreman method are quantitatively compared with the direct numerical simulation (DNS) of the Maxwell equations for anisotropic liquid crystal media.
Biosensors based on liquid crystal vision offer an affordable, fast, transportable means to detect viruses and proteins, through the disruption of the liquid crystal orientation upon protein surface adsorption. This thesis presents simulations of the texture formation process relevant to the LC biosensors based on the nematodynamic model and the matrix and DNS optical methods and identifies the optical factors that lead to optimal performance.
Rheooptics is an experimental tool used to better characterize the flow properties of liquid crystal polymer solutions. The rheooptics of Poly-gamma-Benzyl-L-Glutamate (PBLG) solutions under shear start-up flow between parallel plates was computed using the Berreman method and the FDTD method. The ubiquitous banded textures were reproduced using the Leslie-Ericksen equation for flowing liquid crystals. The optical signal of each band revealed the presence of characteristic double peak structures which correlated with the underlying defect texture of the flowing polymer solutions.
Carbonaceous mesophases are precursors materials used in the manufacturing of high performance carbon fiber composites. Reflection polarized optical microscopy (RPOM) is used to characterize the experimentally observed defects and heterogeneities in these materials.
30
Peraino, Jim. "Architectural epidemiology : a computational framework." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127877.
Анотація:
Thesis: S.M., Massachusetts Institute of Technology, Department of Architecture, May, 2020Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, May, 2020
Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 73-76).
Architecture affects our health, especially in hospitals. However, our ability to learn from existing hospitals to design buildings that improve patient outcomes is limited. If we want to leverage large datasets of health outcomes to build knowledge about how architecture affects health, then we need new methods for analyzing spatial data and health data jointly. In this thesis, I present several steps toward the goal of developing a computational model of architectural epidemiology that aims to leverage both human and machine intelligence to do so. First, I outline the need for structured architectural datasets that capture spatial information in schemas that current drawing formats do not allow. These datasets need to be wide to capture multifaceted and qualitative aspects of the built environment, and so we need new methods to generate this data. Finally, we need strategies for surfacing insight from these datasets by involving both humans and machines in the process.
Next, I propose a framework to satisfy these criteria that consists of four components: 1) data sources, 2) feature engineering, 3) statistical analyses, and 4) decision-making activities. Two case studies provide in-depth illustrations of these components: The first presents a 3D interface that enables developers to create 3D visualizations of large health outcome datasets in architectural space while taking advantage of the Kyrix details-on-demand system's backend performance optimizations. The second tests the efficacy of neural network ablation to surface relationships between architectural characteristics and health outcomes using a synthetic dataset. It is not necessary to ignore human intuition if we want to take advantage of computational power, and it is not necessary to leave behind computational power if we want to take advantage of human intuition. By overcoming current technical barriers with the methods proposed in this thesis, we can work toward achieving both.
Ultimately, we can learn from our current environments to design buildings that improve our health.
by Jim Peraino.
S.M.
S.M.
S.M. Massachusetts Institute of Technology, Department of Architecture
S.M. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
31
Li, Weichang 1972. "Computational reconstruction of images from optical holograms." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/91356.
Анотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (leaves 103-105).
by Weichang Li.
S.M.
32
Ellis, Daniel Patrick Whittlesey. "Prediction-driven computational auditory scene analysis." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/11006.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (p. 173-180).
by Daniel P.W. Ellis.
Ph.D.
33
Edwards, Matthew Douglas. "Information-sharing models for computational genetics." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105572.
Анотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 97-105).
Modern genetics has been transformed by a dramatic explosion of data. As sample sizes and the number of measured data types grow, the need for computational methods tailored to deal with these noisy and complex datasets increases. In this thesis, we develop and apply integrated computational and biological approaches for two genetic problems. First, we build a statistical model for genetic mapping using pooled sequencing, a powerful and efficient technique for rapidly unraveling the genetic basis of complex traits. Our approach explicitly models the pooling process and genetic parameters underlying the noisy observed data, and we use it to calculate accurate intervals that contain the targeted regions of interest. We show that our model outperforms simpler alternatives that do not use all available marker data in a principled way. We apply this model to study several phenotypes in yeast, including the genetic basis of the surprising phenomenon of strain-specific essential genes. We demonstrate the complex genetic basis of many of these strain-specific viability phenotypes and uncover the influence of an inherited virus in modifying their effects. Second, we design a statistical model that uses additional functional information describing large sets of genetic variants in order to predict which variants are likely to cause phenotypic changes. Our technique is able to learn complicated relationships between candidate features and can accommodate the additional noise introduced by training on groups of candidate variants, instead of single labeled variants. We apply this model to a large genetic mapping study in yeast by collecting multiple genome-wide functional measurements. By using our model, we demonstrate the importance of several molecular phenotypes in predicting genetic impact. The common themes in this thesis are the development of computational models that accurately reflect the underlying biological processes and the integration of carefully controlled biological experiments to test and utilize our new models.
by Matthew Douglas Edwards.
Ph. D.
34
Martin, Keith Dana. "A computational model of spatial hearing." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36573.
Анотація:
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (leaves 60-62).
by Keith Dana Martin.
M.S.
35
Kamvysselis, Manolis 1977. "Computational comparative genomics : genes, regulation, evolution." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/7999.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references (p. 95-99).
Understanding the biological signals encoded in a genome is a key challenge of computational biology. These signals are encoded in the four-nucleotide alphabet of DNA and are responsible for all molecular processes in the cell. In particular, the genome contains the blueprint of all protein-coding genes and the regulatory motifs used to coordinate the expression of these genes. Comparative genome analysis of related species provides a general approach for identifying these functional elements, by virtue of their stronger conservation across evolutionary time. In this thesis we address key issues in the comparative analysis of multiple species. We present novel computational methods in four areas (1) the automatic comparative annotation of multiple species and the determination of orthologous genes and intergenic regions (2) the validation of computationally predicted protein-coding genes (3) the systematic de-novo identification of regulatory motifs (4) the determination of combinatorial interactions between regulatory motifs. We applied these methods to the comparative analysis of four yeast genomes, including the best-studied eukaryote, Saccharomyces cerevisiae or baker's yeast. Our results show that nearly a tenth of currently annotated yeast genes are not real, and have refined the structure of hundreds of genes. Additionally, we have automatically discovered a dictionary of regulatory motifs without any previous biological knowledge. These include most previously known regulatory motifs, and a number of novel motifs. We have automatically assigned candidate functions to the majority of motifs discovered, and defined biologically meaningful combinatorial interactions between them. Finally, we defined the regions and mechanisms of rapid evolution, with important biological implications.
(cont.) Our results demonstrate the central role of computational tools in modem biology. The analyses presented in this thesis have revealed biological findings that could not have been discovered by traditional genetic methods, regardless of the time or effort spent. The methods presented are general and may present a new paradigm for understanding the genome of any single species. They are currently being applied to a kingdom-wide exploration of fungal genomes, and the comparative analysis of the human genome with that of the mouse and other mammals.
by Manolis (Kellis) Kamvysselis.
Ph.D.
36
Murmann, Lukas. "Computational bounce flash for indoor portraits." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111928.
Анотація:
Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 31-33).
Portraits taken with direct flash look harsh and unflattering because the light source comes from a small set of angles very close to the camera. Advanced photographers address this problem by using bounce flash, a technique where the flash is directed towards other surfaces in the room, creating a larger, virtual light source that can be cast from different directions to provide better shading variation for 3D modeling. However, finding the right direction to point a bounce flash towards requires skill and careful consideration of the available surfaces and subject configuration. Inspired by the impact of automation for exposure, focus and flash metering, we automate control of the flash direction for bounce illumination. We first identify criteria for evaluating flash directions, based on established photography literature, and relate these criteria to the color and geometry of a scene. We augment a camera with servomotors to rotate the flash head, and additional sensors (a fisheye and 3D sensors) to gather information about potential bounce surfaces. We present a simple numerical optimization criterion that finds directions for the flash that consistently yield compelling illumination and demonstrate the effectiveness of our various criteria in common photographic configurations.
by Lukas Murmann.
S.M.
37
Apichitsopa, Nicha. "Intrinsic cytometry based on computational microscopy." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107030.
Анотація:
Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 123-131).
With the goal of understanding cells, we propose to study the intrinsic properties of individual cells by combining visual observation from large field-of-view computational microscopy with separation of cells via an integrated label-free microfluidic platform. This intrinsic cytometry will benefit from the parallel and gentle separation of label-free cells via a microfluidic platform and parallel tracking of multiple cells via a large field-of view microscopy in contrast to the gold standard, flow cytometry, which is able to rapidly and singly identify multiple cell properties via scattering of external fluorescent cell markers. In this thesis, a prototype of this integrated platform was designed and fabricated. The prototype consisted of a large field-of-view digital in-line holographic microscopy system and a microfluidic deterministic lateral displacement array which separated particles based on size. Each system was first characterized separately and later integrated such that individual cells inside the deterministic lateral displacement array could be recorded and tracked with the large field-of-view digital in-line holographic microscopy system, showing the promise of our proposed intrinsic cytometry. In future studies, if a microfluidic platform can be designed to investigate multiple intrinsic properties of individual cells on the same platform, the intrinsic cytometer will enable a large pool of quantitative measurement data of cell intrinsic properties that can potentially be used for cell characterization and diagnostics.
by Nicha Apichitsopa.
S.M.
38
Pătrașcu, Mihai. "Computational geometry through the information lens." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40526.
Анотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 111-117).
This thesis revisits classic problems in computational geometry from the modern algorithmic perspective of exploiting the bounded precision of the input. In one dimension, this viewpoint has taken over as the standard model of computation, and has led to a powerful suite of techniques that constitute a mature field of research. In two or more dimensions, we have seen great success in understanding orthogonal problems, which decompose naturally into one dimensional problems. However, problems of a nonorthogonal nature, the core of computational geometry, have remained uncracked for many years despite extensive effort. For example, Willard asked in SODA'92 for a o(nlg n) algorithm for Voronoi diagrams. Despite growing interest in the problem, it was not successfully solved until this thesis. Formally, let w be the number of bits in a computer word, and consider n points with O(w)-bit rational coordinates. This thesis describes: * a data structure for 2-d point location with O(n) space, and 0( ... )query time. * randomized algorithms with running time 9 ... ) for 3-d convex hull, 2-d Voronoi diagram, 2-d line segment intersection, and a variety of related problems. * a data structure for 2-d dynamic convex hull, with O ( ... )query time, and O ( ... ) update time. More generally, this thesis develops a suite of techniques for exploiting bounded precision in geometric problems, hopefully laying the foundations for a rejuvenated research direction.
by Mihai Pǎtraşcu.
S.M.
39
Khan, Zeeshan Rahman. "A computational linguistic analysis of Bangla." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/35460.
Анотація:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (p. 77-78).
by Zeeshan Rahman Khan.
M.Eng.
40
Khodor, Julia 1974. "DAN-based string rewrite computational systems." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8339.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (p. 89-97).
We describe a DNA computing system called programmed mutagenesis. prove that it is universal, and present experimental results from a prototype computation. DNA is a material with important characteristics, such as possessing all the information necessary for self-reproduction in the presence of appropriate enzymes and components, simple natural evolution mechanism, and miniature scale, all of which make it an attractive substrate for computation. For computer science, using single DNA molecules to represent the state of a computation holds the promise of a new paradigm of composable molecular computing. For biology, the demonstration that DNA sequences could guide their own evolution under computational rules may have implications as we begin to unravel the mysteries of genome encoding. Programmed mutagenesis is a DNA computing system that uses cycles of DNA annealing, ligation, and polymerization to implement programmatic rewriting of DNA sequences. We report that programmed mutagenesis is theoretically universal by showing how Minsky's 4-symbol 7-state Universal Turing Machine can be implemented using a programmed mutagenesis system. Each step of the Universal Turing Machine is implemented by four cycles of programmed mutagenesis, and progress is guaranteed by the use of alternate sense strands for each rewriting cycle. We constructed a unary counter, an example programmed mutagenesis system, and operated it through three cycles of mutagenesis to gather efficiency data. We showed that the counter operates with increasing efficiency, but decreasing overall yield.
(cont.) The measured efficiency of an in vitro programmed mutagenesis system suggests that the segregation of the products of DNA replication into separate compartments would be an efficient way to implement molecular computation. Naturally occurring phenomena such as gene conversion events and RNA editing processes are also discussed as possible manifestations of programmed mutagenesis-like systems.
by Julia Khodor.
Ph.D.
41
Bell, Rebekah L. "Computational support for media ecosystems research." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119921.
Анотація:
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 67-71).
This thesis summarizes the design, implementation, and evaluation of two end-user web tools for automated content analysis of online news data. The first tool is a visualization that displays neural word embeddings data, allowing a user to explore words used in similar contexts within a text corpus. The second tool is an interface that guides users through a supervised machine learning pipeline, enabling novices to train their own binary classification models to detect the presence of a specific frame within the text of a news story. The visualization and interface were evaluated in a user study and think-aloud test respectively. These tools were developed for integration into Media Cloud, an open-source platform for media analysis, which is part of a larger effort to facilitate and advance media ecosystems research.
by Rebekah L. Bell.
M. Eng.
42
Williams, Reid E. (Reid Edward) 1980. "Training architectural computational critics by example." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/16691.
Анотація:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references (p. 63-65).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
New building technologies and materials coupled with a modular construction system offer consumers an unprecedented chance to customize their living spaces. At the center of this customization process is a computational tool that guides consumers through the process of designing a home or apartment. Algorithms for architectural computational critics that are trained by a designer through examples and that can then critique designs is proposed as part of the design tool. A prototype system encompassing two apartment design scenarios is built and tested. The prototype demonstrates the ability to learn architectural concepts through training.
by Reid E. Williams.
M.Eng.
43
Ghazi, Badih. "Computational aspects of communication amid uncertainty." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115638.
Анотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 203-215).
This thesis focuses on the role of uncertainty in communication and effective (computational) methods to overcome uncertainty. A classical form of uncertainty arises from errors introduced by the communication channel but uncertainty can arise in many other ways if the communicating players do not completely know (or understand) each other. For example, it can occur as mismatches in the shared randomness used by the distributed agents, or as ambiguity in the shared context or goal of the communication. We study many modern models of uncertainty, some of which have been considered in the literature but are not well-understood, while others are introduced in this thesis: Uncertainty in Shared Randomness -- We study common randomness and secret key generation. In common randomness generation, two players are given access to correlated randomness and are required to agree on pure random bits while minimizing communication and maximizing agreement probability. Secret key generation refers to the setup where, in addition, the generated random key is required to be secure against any eavesdropper. These setups are of significant importance in information theory and cryptography. We obtain the first explicit and sample-efficient schemes with the optimal trade-offs between communication, agreement probability and entropy of generated common random bits, in the one-way communication setting. -- We obtain the first decidability result for the computational problem of the noninteractive simulation of joint distributions, which asks whether two parties can convert independent identically distributed samples from a given source of correlation into another desired form of correlation. This class of problems has been well-studied in information theory and its computational complexity has been wide open. Uncertainty in Goal of Communication -- We introduce a model for communication with functional uncertainty. In this setup, we consider the classical model of communication complexity of Yao, and study how this complexity changes if the function being computed is not completely known to both players. This forms a mathematical analogue of a natural situation in human communication: Communicating players do not a priori know what the goal of communication is. We design efficient protocols for dealing with uncertainty in this model in a broad setting. Our solution relies on public random coins being shared by the communicating players. We also study the question of relaxing this requirement and present several results answering different aspects of this question. Uncertainty in Prior Distribution -- We study data compression in a distributed setting where several players observe messages from an unknown distribution, which they wish to encode, communicate and decode. In this setup, we design and analyze a simple, decentralized and efficient protocol. In this thesis, we study these various forms of uncertainty, and provide novel solutions using tools from various areas of theoretical computer science, information theory and mathematics.
"This research was supported in part by an NSF STC Award CCF 0939370, NSF award numbers CCF-1217423, CCF-1650733 and CCF-1420692, an Irwin and Joan Jacobs Presidential Fellowship and an IBM Ph.D. Fellowship"--Page 7.
by Badih Ghazi.
Ph. D.
44
Elia, Nicola. "Computational methods for multi-objective control." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10679.
45
Ruhl, Jan Matthias 1973. "Efficient algorithms for new computational models." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/17018.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references (p. 155-163).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Advances in hardware design and manufacturing often lead to new ways in which problems can be solved computationally. In this thesis we explore fundamental problems in three computational models that are based on such recent advances. The first model is based on new chip architectures, where multiple independent processing units are placed on one chip, allowing for an unprecedented parallelism in hardware. We provide new scheduling algorithms for this computational model. The second model is motivated by peer-to-peer networks, where countless (often inexpensive) computing devices cooperate in distributed applications without any central control. We state and analyze new algorithms for load balancing and for locality-aware distributed data storage in peer-to-peer networks. The last model is based on extensions of the streaming model. It is an attempt to capture the class of problems that can be efficiently solved on massive data sets. We give a number of algorithms for this model, and compare it to other models that have been proposed for massive data set computations. Our algorithms and complexity results for these computational models follow the central thesis that it is an important part of theoretical computer science to model real-world computational structures, and that such effort is richly rewarded by a plethora of interesting and challenging problems.
by Jan Matthias Ruhl.
Ph.D.
46
Pass, Rafael (Rafael Nat Josef). "A precise computational approach to knowledge." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38303.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (p. 100-103).
The seminal work of Goldwasser, Micali and Rackoff put forward a computational approach to knowledge in interactive systems, providing the foundation of modern Cryptography. Their notion bounds the knowledge of a player in terms of his potential computational power (technically defined as polynomial-time computation). In this thesis, we put forward a stronger notion that precisely bounds the knowledge gained by a player in an interaction in terms of the actual computation he has performed (which can be considerably less than any arbitrary polynomial-time computation). Our approach not only remains valid even if P = NP, but is most meaningful when modeling knowledge of computationally easy properties. As such, it broadens the applicability of Cryptography and weakens the complexity theoretic assumptions on which Cryptography can be based.
by Rafael Pass.
Ph.D.
47
Korsky, Samuel A. "On the computational power of RNNs." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/127704.
Анотація:
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019
Cataloged from student-submitted PDF of thesis.
Includes bibliographical references (page 27).
Recent neural network architectures such as the basic recurrent neural network (RNN) and Gated Recurrent Unit (GRU) have gained prominence as end-to-end learning architectures for natural language processing tasks. But what is the computational power of such systems? We prove that finite precision RNNs with one hidden layer and ReLU activation and finite precision GRUs are exactly as computationally powerful as deterministic nice automata. Allowing arbitrary precision, we prove that RNNs with one hidden layer and ReLU activation are at least as computationally powerful as pushdown automata. If we also allow infinite precision, infinite edge weights, and nonlinear output activation functions, we prove that GRUs are at least as computationally powerful as pushdown automata. All results are shown constructively.
by Samuel A. Korsky.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
48
Wu, Jiajun Ph D. Massachusetts Institute of Technology. "Computational perception of physical object properties." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103736.
Анотація:
Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 49-50).
We study the problem of learning physical object properties from visual data. Inspired by findings in cognitive science that even infants are able to perceive a physical world full of dynamic content at a early age, we aim to build models to characterize object properties from synthetic and real-world scenes. We build a novel dataset containing over 17, 000 videos with 101 objects in a set of visually simple but physically rich scenarios. We further propose two novel models for learning physical object properties by incorporating physics simulators, either a symbolic interpreter or a mature physics engine, with deep neural nets. Our extensive evaluations demonstrate that these models can learn physical object properties well and, with a physic engine, the responses of the model positively correlate with human responses. Future research directions include incorporating the knowledge of physical object properties into the understanding of interactions among objects, scenes, and agents.
by Jiajun Wu.
S.M.
49
Chollacoop, Nuwong 1977. "Computational and experimental study of instrumented indentation." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/16624.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004.Includes bibliographical references (p. 167-175).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
The effect of characteristic length scales, through dimensional and microstructural miniaturizations, on mechanical properties is systematically investigated by recourse to instrumented micro- and/or nanoindentation. This technique is capable of extracting mechanical properties accurately down to nanometers, via rigorous interpretation of indentation response. Such interpretation requires fundamental understandings of contact mechanics and underlying deformation mechanisms. Analytical, computational and experimental approaches are utilized to elucidate specifically how empirical constitutive relation can be estimated from the complex multiaxial stress state induced by indentation. Analytical formulations form a framework for parametric finite element analysis. The algorithms are established to predict indentation response from a constitutive relation (hereafter referred to as "forward algorithms") and to extract mechanical properties from indentation curve (hereafter referred to as "reverse algorithms"). Experimental verifications and comprehensive sensitivity analysis are conducted. Similar approaches are undertaken to extend the forward/reverse algorithms to indentations using two ore more tip geometries. Microstructural miniaturization leads to novel class of materials with a grain size smaller than 100 nm, hereafter referred to as "nanocrystalline" material. Its mechanical properties are observed to deviate greatly from the microcrystalline counterparts.
(cont.) In this thesis, experimental, analytical and computational approaches are utilized to elucidate the rate and size dependent mechanical properties observed in nanocrystalline materials. Indentations, as well as micro-tensile tests, are employed to attain various controllable deformation rates. A simple analytical model, hereafter referred to as Grain-Boundary-Affected-Zone (GBAZ) model, is proposed to rationalize possible rate-sensitivity mechanism. Systematic finite element analysis integrating GBAZ model is conducted with calibration against the experiments. The same GBAZ model, further utilized in the parametric finite element study, is capable of predicting the inverse Hall-Petch-type phenomenon (weakening with decreasing grain size) at the range consistent with the literature.
by Nuwong Chollacoop.
Ph.D.
50
Charous, Aaron (Aaron Solomon). "High-order retractions for reduced-order modeling and uncertainty quantification." Thesis, Massachusetts Institute of Technology, 2021. https://hdl.handle.net/1721.1/130904.
Анотація:
Thesis: S.M., Massachusetts Institute of Technology, Center for Computational Science & Engineering, February, 2021Cataloged from the official PDF version of thesis.
Includes bibliographical references (pages 145-151).
Though computing power continues to grow quickly, our appetite to solve larger and larger problems grows just as fast. As a consequence, reduced-order modeling has become an essential technique in the computational scientist's toolbox. By reducing the dimensionality of a system, we are able to obtain approximate solutions to otherwise intractable problems. And because the methodology we develop is sufficiently general, we may agnostically apply it to a plethora of problems, whether the high dimensionality arises due to the sheer size of the computational domain, the fine resolution we require, or stochasticity of the dynamics. In this thesis, we develop time integration schemes, called retractions, to efficiently evolve the dynamics of a system's low-rank approximation. Through the study of differential geometry, we are able to analyze the error incurred at each time step. A novel, explicit, computationally inexpensive set of algorithms, which we call perturbative retractions, are proposed that converge to an ideal retraction that projects exactly to the manifold of fixed-rank matrices. Furthermore, each perturbative retraction itself exhibits high-order convergence to the best low-rank approximation of the full-rank solution. We show that these high-order retractions significantly reduce the numerical error incurred over time when compared to a naive Euler forward retraction. Through test cases, we demonstrate their efficacy in the cases of matrix addition, real-time data compression, and deterministic and stochastic differential equations.
by Aaron Charous.
S.M.
S.M. Massachusetts Institute of Technology, Center for Computational Science & Engineering