Mostrando recursos 101 - 120 de 23.492

  1. Compositional Reactive Synthesis for Multi-Agent Systems

    Moarref, Salar
    With growing complexity of systems and guarantees they are required to provide, the need for automated and formal design approaches that can guarantee safety and correctness of the designed system is becoming more evident. To this end, an ambitious goal in system design and control is to automatically synthesize the system from a high-level specification given in a formal language such as linear temporal logic. The goal of this dissertation is to investigate and develop the necessary tools and methods for automated synthesis of controllers from high-level specifications for multi-agent systems. We consider systems where a set of controlled agents...

  2. States of Repair: Institutions of Private Life in the Postwar Anglophone Novel

    Rich, Kelly Mee
    This project proposes that one of the most enduring cultural legacies of the Second World War was the welfare state’s fantasy of rebuilding Britain. Beginning with the 1942 Beveridge Report’s promise to care for citizens “from the cradle to the grave,” the welfare state envisioned that managing individuals’ private lives would result in a more coherent and equitable community. Literature records this historic transition in order to narrate its transformative social potential, as well as its darker failures. Midcentury writers Elizabeth Bowen, George Orwell, and Muriel Spark used the militarized Home Front to present postwar Britain as a zone of...

  3. Analysis and Modeling of Advanced PIM Architecture Design Tradeoffs

    Upchurch, Ed; Sterling, Thomas; Brockman, Jay
    A major trend in high performance computer architecture over the last two decades is the migration of memory in the form of high speed caches onto the microprocessor semiconductor die. Where temporal locality in the computation is high, caches prove very effective at hiding memory access latency and contention for communication resources. However where temporal locality is absent, caches may exhibit low hit rates resulting in poor operational efficiency. Vector computing exploiting pipelined arithmetic units and memory access address this challenge for certain forms of data access patterns, for example involving long contiguous data sets exhibiting high spatial locality. But...

  4. Towards a service-led relationship in project-based firms

    Razmdoost, K; Mills, G
    Project-based firms increasingly apply practices that are in line with relationship marketing (RM), which is a shift from individuality to mutuality, and service-dominant logic (SDL), which is a shift from a focus on goods exchange to an emphasis on service exchange. These firms also adopt value co-creation processes, benefiting from both RM and SDL views. However, their overall transition towards RM, SDL and/or both is not clearly understood. Therefore, the research aim is to explain how and why project-based firms have moved away from transitional marketing. A retrospective action research between 2002 and 2009 provides process data on how a...

  5. InGaAs/GaAsSb quantum-well Tunnel-FETs for ultra-low power applications

    Yu, Tao, Ph. D. Massachusetts Institute of Technology
    The Tunnel-FET (TFET), where carrier injection is determined by gate-controlled tunneling from the source to the channel, has been attractive as one of the promising candidates for future ultra-low power applications. In this thesis, inline-TFETs with tunneling direction aligned to the gate electric field are designed, fabricated and analyzed based on InGaAs/GaAsSb material. Using ultrathin InGaAs/GaAsSb quantum-well (QW), the device fabrication technology was developed and the tunneling properties of two successive generations of QWTFETs were investigated. In the first generation QWTFETs, the limitation of gate oxide quality on InGaAs and parasitic thermal currents manifests itself in degraded subthreshold swing (SS)...

  6. Towards dissecting neural ensembles : development of genetic profiling and targeting approaches

    Li, Yinqing, Ph. D. Massachusetts Institute of Technology
    The recent development of genetic neural modulation technologies has brought about a renaissance in systems neurobiology, where manipulation of specific neural ensembles coupled with measurements of the resulting behavioral changes have begun to chart the functional organization of the brain. However, the scope of the application of this emerging paradigm depends critically on the ability to systematically identify and manipulate specific neural ensembles, which is currently lacking. In this thesis, we focus on the development of technologies towards systematic identification and targeting of specific neural ensembles. First, we present the development of single nuclei RNA sequencing methods and the application...

  7. Extracting fields from free-text

    Cattori, Pedro
    The Field Extraction Library (FEL) provides functions for named-entity extraction within free text. FEL models the content structure of the specified named-entities rather than relying on brittle, context-specific separator logic. Users specify the names of the fields they wish to extract, which determine the number of states for an underlying Hidden Markov Model. The observable emission set is pre-determined by FEL's tokenizer. Once the model topology is set, users provide training examples of the form: x = raw text, y {fieldl: val1, field2:val2, ... } FEL learns the parameters of the underlying Hidden Markov Model by maximum likelihood model-estimation on...

  8. Implementing a verified FTP client and server

    Ramseyer, Jennifer
    I present my implementation of an FTP: File Transfer Protocol system with GRASShopper. GRASShopper is a program verifier that ensures that programs are memory safe. I wrote an FTP client and server in SPL, the GRASShopper programming language. SPL integrates the program logic's pre- and post- conditions, along with loop invariants, into the language, so that programs that compile in GRASShopper are proven correct. Because of that, my client and server are guaranteed to be secure and correct. I am supervised by Professor Martin Rinard and Dr. Damien Zufferey, a post-doctoral researcher in Professor Rinard's laboratory.

  9. Object Spreadsheets : an end-user development tool for web applications backed by entity-relationship data

    McCutchen, Richard Matthew
    There is a growing demand for data-driven web applications that help automate organizational and business processes of low to medium complexity by letting users view and update structured data in controlled ways. We present Object Spreadsheets, an end-user development tool that combines a spreadsheet interface with a rich data model to help the process administrators build the logic for such applications themselves. Its all-in-one interface with immediate feedback has the potential to bring more complex tasks within reach of end-user developers, compared to existing approaches. Our data model is based on the structure of entity-relationship models and directly supports nested...

  10. The Theory of Lateral Pressure Highlights of Quantification & Empirical Analysis

    Nazli Choucri, Gaurav Agarwal
    Lateral Pressure refers to any tendency (or propensity) of individuals and societies to expand their activities and exert influence and control beyond their established boundaries, whether for economic, political, military, scientific, religious, or other purposes. Framed by Robert C. North and Nazli Choucri, the theory addresses the sources and consequences of such a tendency. Lateral Pressure theory seeks to explain the relationships between state characteristics and patterns of international behavior. The theory addresses the sources and consequences of transformation and change in international relations and provides a basis for analyzing potential feedback dynamics. To the extent that states expand their activities...

  11. Plants and the Logic of Development

    Meyerowitz, Elliot M.
    It seems likely that plants and animals have independently evolved multicellular development. Members of each kingdom are composed of different types of eukaryotic cells, implying that the two kingdoms diverged when their common eukaryotic ancestor was unicellular and that each lineage had a considerable unicellular history after they separated. This indicates that each kingdom separately evolved its mechanisms of cellular differentiation and cell-cell communication. This in turn raises a series of questions: do land plants and metazoans use the same fundamental mechanisms of development and perhaps even the same genes for similar processes, or has independent evolution of development meant...

  12. Plants, animals and the logic of development

    Meyerowitz, Elliot M.
    Multicellular plants and animals have evolved independently from a unicellular, last common ancestor. Each lineage started with a common toolkit of functioning genes and evolved to complex, multicellular forms. Comparison of the genes used to serve similar functions shows how organisms can use different genes for similar ends and thereby reveals the principles of development.

  13. Everything you always wanted to know about blank nodes (but were afraid to ask)

    Hogan, Aidan; Arenas, Macelo; Mallea, Alejandro; Polleres, Axel
    In this paper we thoroughly cover the issue of blank nodes, which have been defined in RDF as "existential variables". We first introduce the theoretical precedent for existential blank nodes from first order logic and incomplete Information in database theory. We then cover the different (and sometimes incompatible) treatment of blank nodes across the W3C stack of RDF-related standards. We present an empirical survey of the blank nodes present in a large sample of RDF data published on the Web (the BTC-2012 dataset), where we find that 25.7% of unique RDF terms are blank nodes, that 44.9% of documents and...

  14. Model predictive control from signal temporal logic specifications: a case study

    Raman, Vasumathi; Maasoumy, Mehdi; Donzé, Alexandre
    This paper describes current work on framing the model predictive control (MPC) of cyber-physical systems as synthesis from signal temporal logic (STL) specifications. We provide a case study using a simplified power grid model with uncertain demand and generation; the model-predictive control problem here is that of the ancillary service power flow from the buildings. We show how various relevant constraints can be captured using STL formulas, and incorporated into an MPC framework. We also provide preliminary simulation results to illustrate the promise of the proposed approach.

  15. Switching on Flowers: Transient LEAFY Induction Reveals Novel Aspects of the Regulation of Reproductive Development in Arabidopsis

    Wagner, Doris; Meyerowitz, Elliot M.
    Developmental fate decisions in cell populations fundamentally depend on at least two parameters: a signal that is perceived by the cell and the intrinsic ability of the cell to respond to the signal. The same regulatory logic holds for phase transitions in the life cycle of an organism, for example the switch to reproductive development in flowering plants. Here we have tested the response of the monocarpic plant species Arabidopsis thaliana to a signal that directs flower formation, the plant-specific transcription factor LEAFY (LFY). Using transient steroid-dependent LEAFY (LFY) activation in lfy null mutant Arabidopsis plants, we show that the...

  16. An Iterative Abstraction Algorithm for Reactive Correct-by-Construction Controller Synthesis

    Mattila, Robert; Mo, Yilin; Murray, Richard M.
    In this paper, we consider the problem of synthesizing correct-by-construction controllers for discrete-time dynamical systems. A commonly adopted approach in the literature is to abstract the dynamical system into a Finite Transition System (FTS) and thus convert the problem into a two player game between the environment and the system on the FTS. The controller design problem can then be solved using synthesis tools for general linear temporal logic or generalized reactivity(1) specifications. In this article, we propose a new abstraction algorithm. Instead of generating a single FTS to represent the system, we generate two FTSs, which are under- and...

  17. Sanctum : minimal architectural extensions for isolated execution

    Costan, Victor Marius
    Intel's Software Guard Extensions (SGX) have captured the attention of security practitioners by promising to secure computation performed on a remote computer where all the privileged software is potentially malicious. Unfortunately, an independent analysis of SGX reveals that it is vulnerable to software attacks, and it can only be used by developers licensed by Intel. Furthermore, significant parts of SGX are undocumented, making it impossible for researchers outside of Intel to reason about some of its security properties. Sanctum offers the same promise as SGX, namely strong provable isolation of software modules running concurrently and sharing resources, but protects against...

  18. Energy Reduction Through Voltage Scaling and Lightweight Checking

    Kadric, Edin
    As the semiconductor roadmap reaches smaller feature sizes and the end of Dennard Scaling, design goals change, and managing the power envelope often dominates delay minimization. Voltage scaling remains a powerful tool to reduce energy. We find that it results in about 60% geomean energy reduction on top of other common low-energy optimizations with 22nm CMOS technology. However, when voltage is reduced, it becomes easier for noise and particle strikes to upset a node, potentially causing Silent Data Corruption (SDC). The 60% energy reduction, therefore, comes with a significant drop in reliability. Duplication with checking and triple-modular redundancy are traditional...

  19. Imperial Enterprise: The United States International Volunteer Program, Neoliberal Empire, and Northern Youth

    Anderson, Caitlin
    In recent years, the phenomenon of Northern international volunteering has been conceived as an instance of post-collegiate “continuing education” and, as such, has been attributed to a neoliberal logic of self-enterprise. However, such accounts have neglected to interrogate how an entrenched logic of empire also animates the practice of recruiting and deploying Northern citizens to volunteer in the “developing” world. Also overlooked have been the particular intersections of these logics in the discourses of international volunteer programs, the related subject formations of Northern volunteers who come under their tutelage, and the ways in which these intersections engage broader geopolitical objectives...

  20. Cross-entropy temporal logic motion planning

    Livingston, Scott C.; Wolff, Eric M.; Murray, Richard M.
    This paper presents a method for optimal trajectory generation for discrete-time nonlinear systems with linear temporal logic (LTL) task specifications. Our approach is based on recent advances in stochastic optimization algorithms for optimal trajectory generation. These methods rely on estimation of the rare event of sampling optimal trajectories, which is achieved by incrementally improving a sampling distribution so as to minimize the cross-entropy. A key component of these stochastic optimization algorithms is determining whether or not a trajectory is collision-free. We generalize this collision checking to efficiently verify whether or not a trajectory satisfies a LTL formula. Interestingly, this verification...

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