Recursos de colección

DSpace at MIT (90.784 recursos)

This site is a university repository providing access to the publication output of the institution. Registered users can set up email alerts to notify them of newly added relevant content. A certain level of encryption and security is embedded in the site which may cause some users accessibility problems.

Electrical Engineering and Computer Sciences - Master's degree

Mostrando recursos 1 - 20 de 5.860

  1. Magnetometry with ensembles of nitrogen vacancy centers in bulk diamond

    Teale, Carson (Carson Arthur)
    This thesis summarizes experiments conducted to develop a high sensitivity vector magnetometer using nitrogen vacancy (NV) centers in a bulk diamond sample. This project began by analyzing the sensitivity of a single NV orientation using a continuous wave electron spin resonance approach. A protocol for determining the diamond's orientation was developed to map vector magnetic field readings in the diamond reference frame to the lab frame. Preliminary vector field measurements and differential vector measurements were performed. Although these showed promising results, significant instrument and ambient magnetic noise limited the achievable sensitivity. A new frequency locking measurement technique was developed to...

  2. Wide-field magnetic field imaging with nitrogen vacancy centers in nanodiamonds at high frame-rates

    Foy, Christopher, S.M. Massachusetts Institute of Technology
    The nitrogen vacancy center (NV) is a promising single spin system in diamond with optical polarization, readout and optically detected magnetic resonances (ODMR). The NV has been shown to be a sensitive magnetometer at room temperature. In particular, owing to their small size, NV centers in nanocrystals (nanodiamonds) offer magnetic field imaging with high spatial resolution. Competitive magnetic field imaging methods such as magnetic force microscopy (MFM) or superconducting quantum interference devices (SQUID) either image serially, and are thus slow, or are limited in their use for biological systems. Nanodiamonds in contrast have the advantage that they can be attached...

  3. Inferring the properties of transcription factor regulation

    Grzadkowski, Michal R
    The regulatory targets of transcription factors are costly to directly detect using existing technologies. Many computational models have thus been developed to infer the genes targeted by TFs using gene expression profiles, position weight matrices modeling TF protein binding, histone modifications, and other secondary datasets. We develop a framework for scoring the potential targets of various TFs using models that take the profile of motif hits on the proximity of transcription start sites as input, and describe methods to validate this framework using expression datasets. These models are then extended to include cis-regulatory regions inferred from epigenetic data.

  4. Vuvuzela : scalable private messaging that hides metadata

    Lazar, David, S.M. Massachusetts Institute of Technology
    Private messaging over the Internet has proven challenging to implement, because even if message data is encrypted, it is difficult to hide metadata about who is communicating in the face of traffic analysis. Systems that offer strong privacy guarantees, such as Dissent [39], scale to only several thousand clients, because they use techniques with superlinear cost in the number of clients (e.g., each client broadcasts their message to all other clients). On the other hand, scalable systems, such as Tor, do not protect against traffic analysis, making them ineffective in an era of pervasive network monitoring. Vuvuzela is a new...

  5. Comprehensive geometric modeling of human cerebral vasculature for quantitative vascular analysis

    Linghu, Changyang
    In this work we developed a comprehensive and structured geometric model of human cerebral vasculature for quantitative anatomical analysis. We first proposed a general and structured geometric representation of the interconnected vascular network as a framework. We then described an image processing pipeline for the segmentation of vascular anatomy from discrete scalar field images, and applied the pipeline to segment the anatomical structures of cerebral vasculatures from whole brain magnetic resonance angiography (MRA) scans of healthy adult subjects. Next, we employed the proposed geometric representation to generate the comprehensive geometric model of human cerebral vasculature from those segmented anatomies. In...

  6. Sublinear-time algorithms for counting star subgraphs with applications to join selectivity estimation

    Peebles, John Lee Thompson, Jr
    We study the problem of estimating the value of sums of the form ... when one has the ability to sample xi ;> 0 with probability proportional to its magnitude. When p = 2, this problem is equivalent to estimating the selectivity of a self-join query in database systems when one can sample rows randomly. We also study the special case when {x} is the degree sequence of a graph, which corresponds to counting the number of p-stars in a graph when one has the ability to sample edges randomly. Our algorithm for a ...-multiplicative approximation of Sp has query...

  7. Reinforcement learning with natural language signals

    Sidor, Szymon
    In this thesis we introduce a technique that allows one to use Natural Language as part of the state in Reinforcement Learning. We show that it is capable of solving Natural Language problems, similar to Sequence-to-Sequence models, but using multistage reasoning. We use Long Short-Term Memory Networks to parse the Natural Language input, whose final hidden state is used to compute action scores for the Deep Q-learning algorithm. First part of the thesis introduces the necessary theoretical background, including Deep Learning approach to Natural Language Processing, Recurrent Neural Networks and Sequence-to-Sequence modeling. We consider two case studies: translation and dialogue....

  8. A systems approach to software security in aviation

    Helfer, Jonas
    Field Loadable Software in commercial aviation is indispensable for vital avionics functions yet its security has never been studied in depth. Due to the recent introduction of wireless software loading capabilities and Internet-connected in-flight entertainment systems along with several high-profile information security breaches in other sectors, the security of Field Loadable software has come under closer scrutiny. Conventional information systems security analysis approaches focus on finding and preventing vulnerabilities in the implementation of a system, but they are not designed to include the organizational "soft" components of a system. The aim of this thesis is to provide a comprehensive security...

  9. Authentication protocol using trapdoored matrices

    Sotiraki, Aikaterini
    In this thesis, we propose a new type of public-key authentication protocol, which is based on timing gaps. The honest user's secret key allows him to perform a task faster than any adversary. In our construction, the public key is a n x n matrix and the secret key is a trapdoor of this matrix. The task which an honest user has to perform in order to authenticate himself is a matrix-vector multiplication, where the vector is supplied by the verifier. We provide specific constructions of the trapdoor and analyze them both theoretically and practically.

  10. Computational perception of physical object properties

    Wu, Jiajun, S.M. Massachusetts Institute of Technology
    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...

  11. Area display of obstacle location for use with a guidance device for the blind

    Sokal, Nathan O
    by Nathan O. Sokal.

  12. Terapixel image processing and simulation with distributed halide

    Denniston, Tyler
    Many image processing and simulation tasks are naturally expressed as a pipeline of small computational kernels known as stencils. Halide is a popular domain-specific language and compiler designed to implement stencil algorithms. Halide uses simple language constructs to express what to compute and a separate scheduling co-language for expressing how to perform the computation. This approach has demonstrated performance comparable to or better than hand-optimized code. Until now, Halide has been restricted to parallel shared memory execution, limiting its performance and applicability to tomorrow's terapixel image processing tasks. In this thesis we present an extension to Halide to support distributed-memory...

  13. Let's make robots! : automated co-generation of electromechanical devices from user specifications using a modular robot library

    DelPreto, Joseph (Joseph Jeff)
    Personalized on-demand robots have a vast potential to impact daily life and change how people interact with technology, but so far this potential has remained largely untapped. Building robots is typically restricted to experts due to the extensive knowledge, experience, and resources required. This thesis aims to remove these barriers with an end-to-end system for intuitively designing robots from high-level specifications. By describing an envisioned structure or behavior, casual users can immediately build and use a robot for their task. The presented work encourages users to treat robots for physical tasks as they would treat software for computational tasks. By...

  14. Learning and enforcing diversity with Determinantal Point Processes

    Mariet, Zelda Elaine
    As machine-learning techniques continue to require more data and become increasingly memory-heavy, being able to choose a subset of relevant, high-quality and diverse elements among large amounts of redundant or noisy data and parameters has become an important concern. Here, we approach this problem using Determinantal Point Processes (DPPs), probabilistic models that provide an intuitive and powerful way of balancing quality and diversity in sets of items. We introduce a novel, fixed-point algorithm for estimating the maximum likelihood parameters of a DPP, provide proof of convergence and discuss generalizations of this technique. We then apply DPPs to the difficult problem...

  15. Towards practical theory : Bayesian optimization and optimal exploration

    Kawaguchi, Kenji, S.M. Massachusetts Institute of Technology
    This thesis presents novel principles to improve the theoretical analyses of a class of methods, aiming to provide theoretically driven yet practically useful methods. The thesis focuses on a class of methods, called bound-based search, which includes several planning algorithms (e.g., the A* algorithm and the UCT algorithm), several optimization methods (e.g., Bayesian optimization and Lipschitz optimization), and some learning algorithms (e.g., PAC-MDP algorithms). For Bayesian optimization, this work solves an open problem and achieves an exponential convergence rate. For learning algorithms, this thesis proposes a new analysis framework, called PACRMDP, and improves the previous theoretical bounds. The PAC-RMDP framework...

  16. Cryptographically enforced access control for user data in untrusted clouds

    Wang, Frank Yi-Fei
    Modern web services rob users of low-level control over cloud storage; a user's single logical data set is scattered across multiple storage silos whose access controls are set by the web services, not users. The result is that users lack the ultimate authority to determine how their data is shared with other web services. In this thesis, we introduce Sieve, a new architecture for selectively exposing user data to third party web services in a provably secure manner. Sieve starts with a user-centric storage model: each user uploads encrypted data to a single cloud store, and by default, only the...

  17. Optimization as estimation with Gaussian processes in bandit settings

    Wang, Zi, S.M. Massachusetts Institute of Technology
    Optimizing an expensive unknown function is an important problem addressed by Bayesian optimization. Motivated by the challenge of parameter tuning in both machine learning and robotic planning problems, we study the maximization of a black-box function with the assumption that the function is drawn from a Gaussian process (GP) with known priors. We propose an optimization strategy that directly uses a maximum a posteriori (MAP) estimate of the argmax of the function. This strategy offers both practical and theoretical advantages: no tradeoff parameter needs to be selected, and, moreover, we establish close connections to the popular GPUCB and GP-PI strategies....

  18. WMM : a resilient Weak Memory Model

    Zhang, Sizhuo
    A good memory model should have a precise definition that can be understood by any computer architect readily. It should also be resilient in the sense that it should not break when new microarchitecture optimizations are introduced to improve single-threaded performance. We introduce WMM, a new weak memory model, which meets these criteria. WMM permits all load-store reorderings except a store is not allowed to overtake a load. WMM also permits both memory dependency speculation and load-value prediction. We define the operational semantics of WMM using a novel conceptual device called invalidation buffer, which achieves the effect of out-of-order instruction...

  19. Design and construction of an artificial reverberation producer

    Redmond, William Guy
    by William Guy Redmond, Jr.

  20. Optimum design of a static single-phase frequency tripler

    Reichard, Robert William
    by Robert William Reichard.

Aviso de cookies: Usamos cookies propias y de terceros para mejorar nuestros servicios, para análisis estadístico y para mostrarle publicidad. Si continua navegando consideramos que acepta su uso en los términos establecidos en la Política de cookies.