Mostrando recursos 121 - 140 de 23.502

  1. Morphometric parameters and outlines of 62 landslides off central Chile

    Völker, David; Scholz, Florian; Geersen, Jacob
    The comparison of bathymetric datasets compiled before and after the Mw = 8.8 Maule Earthquake of the 27 February 2010 offshore Central Chile proves that no new submarine landslides on a size scale detectable with hull-mounted bathymetric echosounders (features of a horizontal size of > 1 km) formed as a direct consequence of the ground shaking. Gravity coring around a pre-existing slide feature offshore Concepción (BioBio Slide), however, documents that (1) a number of events occurred as retrogressive failures of the BioBio Slide wall, the youngest of which is 700-1000 years old, and that (2) a very recent small scale...

  2. The intensification of rankings logic in an increasingly marketised higher education environment

    Locke, W
    Rankings and online comparison sites have both facilitated and shaped the marketisation of higher education in England, the UK as a whole and elsewhere. They have facilitated marketisation by introducing greater competition between and within higher education institutions. Ultimately, they accomplish the transformation of qualities into quantities, which is both required by, and a consequence of, the commodification and privatisation of higher education. Rankings have also helped to embed the logic of the market within organisational structures and processes and within the minds and practices of organisational members. In some ways, in a highly regulated UK higher education market, rankings...

  3. Optimal Control of Nonlinear Systems with Temporal Logic Specifications

    Wolff, Eric M.; Murray, Richard M.
    We present a mathematical programming-based method for optimal control of nonlinear systems subject to temporal logic task specifications. We specify tasks using a fragment of linear temporal logic (LTL) that allows both finite- and infinite-horizon properties to be specified, including tasks such as surveillance, periodic motion, repeated assembly, and environmental monitoring. Our method directly encodes an LTL formula as mixed-integer linear constraints on the system variables, avoiding the computationally expensive process of creating a finite abstraction. Our approach is efficient; for common tasks our formulation uses significantly fewer binary variables than related approaches and gives the tightest possible convex relaxation....

  4. Selling online versus offline: theory and evidences from Sotheby's

    Kazumori, Eiichiro
    We consider a recent business and policy question of "how and why does a firm use online markets versus traditional offline markets ?" using a unique dataset of more than 3000 auctions held by Sotheby's online at eBay and offline at New York in June-July2002. We find robust empirical regularities in our dataset about the use of online markets. First, the average transaction price is more than 10 times higher in offline markets. This fact strongly suggests that the seller is not simply randomly assigning assets between online and offline markets. Second, the higher the mean and spread of pre-auction...

  5. Tunable thermal bioswitches for in vivo control of microbial therapeutics

    Piraner, Dan I.; Abedi, Mohamad H.; Moser, Brittany A.; Lee-Gosselin, Audrey; Shapiro, Mikhail G.
    Temperature is a unique input signal that could be used by engineered microbial therapeutics to sense and respond to host conditions or spatially targeted external triggers such as focused ultrasound. To enable these possibilities, we present two families of tunable, orthogonal, temperature-dependent transcriptional repressors providing switch-like control of bacterial gene expression at thresholds spanning the biomedically relevant range of 32–46°C. We integrate these molecular bioswitches into thermal logic circuits and demonstrate their utility in three in vivo microbial therapy scenarios, including spatially precise activation using focused ultrasound, modulation of activity in response to a host fever, and self-destruction after fecal...

  6. Stochastic, spatial routing for hypergraphs, trees, and meshes

    Huang, Randy; Wawrzynek, John; DeHon, André
    FPGA place and route is time consuming, often serving as the major obstacle inhibiting a fast edit-compile-test loop in prototyping and development and the major obstacle preventing late-bound hardware and design mapping for reconfigurable systems. Previous work showed that hardware-assisted routing can accelerate fanout-free routing on Fat-Trees by three orders of magnitude with modest modifications to the network itself. In this paper, we show how these techniques can be applied to any FPGA and how they can be implemented on top of LUT networks in cases where modification of the FPGA itself is not justified. We further show how to...

  7. A framework for evaluating operations control on a metro line: integrating multiple perspectives and automatically collected train and passenger movement data

    Carrel, Andre; Mishalani, Rabi G.; Wilson, Nigel H. M.; Attanucci, John P
    Transit operations control, the task of implementing the operations plan in daily operations on a metro line, plays a key role in service delivery because it determines the quality of the service experienced by passengers. Yet, it is one of the most poorly understood aspects of rail transit operations. Faced with a disruption or infeasibility, dispatchers typically choose between several response strategies. However, to date, it has been very difficult to evaluate the positive and negative effects of individual control strategies with respect to operations and passenger travel times under real-world conditions. This paper proposes a framework for the study...

  8. Mechanized meta-reasoning using a hybrid HOAS/de bruijn representation and reflection

    Hickey, Jason; Nogin, Aleksey; Yu, Xin; Kopylov, Alexei
    We investigate the development of a general-purpose framework for mechanized reasoning about the meta-theory of programming languages. In order to provide a standard, uniform account of a programming language, we propose to define it as a logic in a logical framework, using the same mechanisms for definition, reasoning, and automation that are available to other logics. Then, in order to reason about the language's meta-theory, we use reflection to inject the programming language into (usually richer and more expressive) meta-theory. One of the key features of our approach is that structure of the language is preserved when it is reflected, including...

  9. Mechanized meta-reasoning using a hybrid HOAS/de bruijn representation and reflection

    Hickey, Jason; Nogin, Aleksey; Yu, Xin; Kopylov, Alexei
    We investigate the development of a general-purpose framework for mechanized reasoning about the meta-theory of programming languages. In order to provide a standard, uniform account of a programming language, we propose to define it as a logic in a logical framework, using the same mechanisms for definition, reasoning, and automation that are available to other logics. Then, in order to reason about the language's meta-theory, we use reflection to inject the programming language into (usually richer and more expressive) meta-theory. One of the key features of our approach is that structure of the language is preserved when it is reflected, including...

  10. A Systems Approach to Molecular Electronics

    Heath, James R.
    Molecular electronics is an area of research in which molecules are employed to yield the active and passive device components (switches, diodes, resistors) of an electronic circuit or integrated circuit. Consider the crossbar circuits of nanowires in the electron micrograph at the left [1]. The smallest (100 element) crossbar in this image is patterned at a density approach 10^12/cm^2, and the wire diameter is approximately 8 nm. At a doping level (with species like Boron or Arsenic) of 10^18/cm^3, a similar 8 nm diameter, micrometer-long segment of silicon wires would have 20-30 dopant atoms, and a junction of two crossed...

  11. Resolução de problemas de dedução lógica na promoção da comunicação matemática na oralidade

    Dias, Cátia Filipa Madaleno
    Relatório de Estágio apresentado à Escola Superior de Educação do Instituto Politécnico de Castelo Branco para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Educação Pré-Escolar e Ensino do 1º Ciclo do Ensino Básico.

  12. A coalgebraic decision procedure for NetKAT

    Foster, N; Kozen, D; Milano, M; Silva, A; Thompson, L
    Copyright © 2015 by the Association for Computing Machinery, Inc. (ACM).NetKAT is a domain-specific language and logic for specifying and verifying network packet-processing functions. It consists of Kleene algebra with tests (KAT) augmented with primitives for testing and modifying packet headers and encoding network topologies. Previous work developed the design of the language and its standard semantics, proved the soundness and completeness of the logic, defined a PSPACE algorithm for deciding equivalence, and presented several practical applications. This paper develops the coalgebraic theory of NetKAT, including a specialized version of the Brzozowski derivative, and presents a new efficient algorithm for...

  13. No crisol das lógicas de territorialização educativa nas escolas portuguesas se frágua a ação do poder político local e das parcerias

    Martins, Ernesto
    Abordamos hermenêuticamente a descentralização e a territorialização educativa em Portugal, numa tríade de relações: ‘escola-comunidade educativa’, parceria socioeducativa e política educativa local. A intervenção do poder local na educação processa-se numa perspetiva instrumental virada para o desenvolvimento e coesão social. As autarquias são os parceiros responsáveis pela educação e os professores valorizam a relação escola-comunidade educativa, principalmente na promoção da qualidade. A relação ’escola-poder local’ efetua-se numa interação participativa dos laços redutores e promotores da administração e gestão escolar, com lógicas de ação e racionalização das parcerias.

  14. Admissible Rules and the Leibniz Hierarchy

    Raftery, James G.
    This paper provides a semantic analysis of admissible rules and associated completeness conditions for arbitrary deductive systems, using the framework of abstract algebraic logic. Algebraizability is not assumed, so the meaning and significance of the principal notions vary with the level of the Leibniz hierarchy at which they are presented. As a case study of the resulting theory, the nonalgebraizable fragments of relevance logic are considered.

  15. An Abelian Rule for BCI—and Variations

    Kowalski, Tomasz; Humberstone, Lloyd
    We show the admissibility for $\mathsf{BCI}$ of a rule form of the characteristic implicational axiom of abelian logic, this rule taking us from $(\alpha\to\beta)\to\beta$ to $\alpha$ . This is done in Section 8, with surrounding sections exploring the admissibility and derivability of various related rules in several extensions of $\mathsf{BCI}$ .

  16. Modal Consequence Relations Extending $\mathbf{S4.3}$ : An Application of Projective Unification

    Dzik, Wojciech; Wojtylak, Piotr
    We characterize all finitary consequence relations over $\mathbf{S4.3}$ , both syntactically, by exhibiting so-called (admissible) passive rules that extend the given logic, and semantically, by providing suitable strongly adequate classes of algebras. This is achieved by applying an earlier result stating that a modal logic $L$ extending $\mathbf{S4}$ has projective unification if and only if $L$ contains $\mathbf{S4.3}$ . In particular, we show that these consequence relations enjoy the strong finite model property, and are finitely based. In this way, we extend the known results by Bull and Fine, from logics, to consequence relations. We also show that the lattice...

  17. Algebraic Logic Perspective on Prucnal’s Substitution

    Citkin, Alex
    A term $\mathit{td}(p,q,r)$ is called a ternary deductive (TD) term for a variety of algebras $\mathcal{V}$ if the identity $\mathit{td}(p,p,r)\approxr$ holds in $\mathcal{V}$ and $(\mathsf{c},\mathsf{d})\in\theta(\mathsf{a},\mathsf{b})$ yields $\mathit{td}(\mathsf{a},\mathsf{b},\mathsf{c})\approx\mathit{td}(\mathsf{a},\mathsf{b},\mathsf{d})$ for any $\mathscr{A}\in\mathcal{V}$ and any principal congruence $\theta$ on $\mathscr{A}$ . A connective $f(p_{1},\dots,p_{n})$ is called $\mathit{td}$ -distributive if $\mathit{td}(p,q,f(r_{1},\dots,r_{n}))\approx$ $f(\mathit{td}(p,q,r_{1}),\dots,\mathit{td}(p,q,r_{n}))$ . If $\mathsf{L}$ is a propositional logic and $\mathcal{V}$ is a corresponding variety (algebraic semantic) that has a TD term $\mathit{td}$ , then any admissible in $\mathsf{L}$ rule, the premises of which contain only $\mathit{td}$ -distributive operations, is derivable, and the substitution $r\mapsto\mathit{td}(p,q,r)$ is a projective $\mathsf{L}$ -unifier for any formula containing...

  18. Deciding Unifiability and Computing Local Unifiers in the Description Logic $\mathcal{E\!L}$ without Top Constructor

    Baader, Franz; Binh, Nguyen Thanh; Borgwardt, Stefan; Morawska, Barbara
    Unification in description logics has been proposed as a novel inference service that can, for example, be used to detect redundancies in ontologies. The inexpressive description logic $\mathcal{E\!L}$ is of particular interest in this context since, on the one hand, several large biomedical ontologies are defined using $\mathcal{E\!L}$ . On the other hand, unification in $\mathcal{E\!L}$ has been shown to be NP-complete and, thus, of considerably lower complexity than unification in other description logics of similarly restricted expressive power. ¶ However, $\mathcal{E\!L}$ allows the use of the top concept ( $\top$ ), which represents the whole interpretation domain, whereas the large medical...

  19. When commitment matters : essays on social evaluation and its market outcomes

    Ha, Jae-Kyung; Gosline, Renée Ann Richardson; Zuckerman, Ezra W; Hahl, Oliver
    In my doctoral dissertation, I attempt to understand why and how an individual or organization's perceptions of commitment affect different market outcomes. This dissertation consists of three essays. In the first essay, I study the effect of organizational form on market performance in the diamond retail industry. Building on the notion that profit-oriented motives create the risk that sellers may not be committed to customers, I develop the argument that the chain form of organization generates beliefs about profit-oriented motives that give rise to the perception that small retailers have higher moral standing. I argue that when organizational actions are...

  20. Street capitalism : informal property rights and their enforcement in Bogotá's on-street parking system

    Lasema, Diego
    This thesis explores how informal property rights are defined and enforced in the business of onstreet parking in Bogotá. It establishes that informal businesses could not operate without such property rights and that the value of force has been underestimated in the scant literature devoted to the subject. To contribute to the construction a currently non-existent informal property rights theory this thesis contrasts the research findings with traditional property rights theory and attempts to redefine classic property rights concepts to fit the context of the urban informal economy. Finally, the thesis explains how mafias can enforce informal property rights, the...

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