31 resultados para Counterexamples


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RÉSUMÉ La ruse féminine, étudiée en regard de la littérature narrative médiévale, constitue une topique spontanément associée à une idéologie misogyne. Les itérations des motifs liés à cette topique foisonnent dans le Roman de Silence et dans les fabliaux également copiés dans le manuscrit de Nottingham. Étant donné la place prépondérante du travestissement dans le Roman de Silence, ce texte a été abondamment étudié sous l’angle des Gender Studies. Toutefois, le travestissement endossé ou orchestré par des figures féminines est compris dans un ensemble de motifs liés à la ruse féminine. Cette dernière fait l’objet de nombreux commentaires de la part des narrateurs et des personnages du corpus. Or il arrive parfois que ces commentaires, sous des dehors désapprobateurs, mettent en lumière la puissance de la ruse féminine. Qui plus est, d’un point de vue narratologique, la réussite ou l’échec de ces ruses ont été étudiés, dans un corpus où le ton se fait souvent didactique, pour établir si celles-ci tenaient lieu d’exemples ou de contre-exemples. Avant d’analyser l’énonciation, les motifs de la ruse féminine ont été étudiés en regard des hypotextes qu’ils évoquaient, et ce, tout en postulant l’interlisibilité des textes d’un même manuscrit. Il a donc été possible de déterminer dans quelle mesure le corpus désamorçait ces motifs, créant des situations souvent ironiques signalant au lecteur de ne pas s’aventurer trop crédulement dans les textes, et d’être attentif autant à l’ironie de situation qu’à celle qui s’ancre dans la situation d’énonciation.

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Implications between attributes can represent knowledge about objects in a specified context. This knowledge representation is especially useful when it is not possible to list all specified objects. Attribute exploration is a tool of formal concept analysis that supports the acquisition of this knowledge. For a specified context this interactive procedure determines a miminal list of valid implications between attributes of this context together with a list of objects which are counterexamples for all implications not valid in the context. This paper describes how the exploration can be modified such that it determines a mimimal set of implications that fills the gap between previously given implications (called background implications) and all valid implications. The list of implications can be simplified further if exceptions are allowed for the implications.

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In the theory of the Navier-Stokes equations, the proofs of some basic known results, like for example the uniqueness of solutions to the stationary Navier-Stokes equations under smallness assumptions on the data or the stability of certain time discretization schemes, actually only use a small range of properties and are therefore valid in a more general context. This observation leads us to introduce the concept of SST spaces, a generalization of the functional setting for the Navier-Stokes equations. It allows us to prove (by means of counterexamples) that several uniqueness and stability conjectures that are still open in the case of the Navier-Stokes equations have a negative answer in the larger class of SST spaces, thereby showing that proof strategies used for a number of classical results are not sufficient to affirmatively answer these open questions. More precisely, in the larger class of SST spaces, non-uniqueness phenomena can be observed for the implicit Euler scheme, for two nonlinear versions of the Crank-Nicolson scheme, for the fractional step theta scheme, and for the SST-generalized stationary Navier-Stokes equations. As far as stability is concerned, a linear version of the Euler scheme, a nonlinear version of the Crank-Nicolson scheme, and the fractional step theta scheme turn out to be non-stable in the class of SST spaces. The positive results established in this thesis include the generalization of classical uniqueness and stability results to SST spaces, the uniqueness of solutions (under smallness assumptions) to two nonlinear versions of the Euler scheme, two nonlinear versions of the Crank-Nicolson scheme, and the fractional step theta scheme for general SST spaces, the second order convergence of a version of the Crank-Nicolson scheme, and a new proof of the first order convergence of the implicit Euler scheme for the Navier-Stokes equations. For each convergence result, we provide conditions on the data that guarantee the existence of nonstationary solutions satisfying the regularity assumptions needed for the corresponding convergence theorem. In the case of the Crank-Nicolson scheme, this involves a compatibility condition at the corner of the space-time cylinder, which can be satisfied via a suitable prescription of the initial acceleration.

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Esta monografía cuestiona la validez de la crítica de Gettier a la suficiencia de lo que ha sido conocido como el análisis “tradicional” del conocimiento. Este análisis establece el conocimiento como creencia, verdadera justificada. Gettier en su famoso artículo "Is Justified True Belief Knowledge?" Propone una serie de contraejemplos que parecen cumplir con las tres condiciones recién establecidas, pero no puede ser considerado conocimiento. La monografía explora dos estrategias principales para responderle a Gettier: por un lado, me pregunto sí los contraejemplos realmente cumplen con las tres condiciones. Yo argumento que los contraejemplos de Gettier son imperfectos en cuanto a que no pueden cumplir con la condición de creencia; y si esto es así los contraejemplos no serían una amenaza al análisis “tradicional” del conocimiento ni tampoco serían una prueba de su insuficiencia. Por otro lado, si uno pudiera aceptar la validez de los contraejemplos uno podría aun cuestionar su relevancia. Esto es lo que pretendo hacer en la segunda parte de este trabajo. Intento mostrar que una solución al problema de Gettier no mejora para nada nuestra investigación metodológica, ni cambia de ninguna manera la forma en que nosotros adquirimos nuestras creencias y nuestro conocimiento en general. Por lo tanto, los contraejemplos de Gettier aun si pudieran funcionar correctamente (lo cual defiendo en la primera parte de la monografía que no es así) son irrelevantes y no son una amenaza real al análisis “tradicional” del conocimiento. La monografía se propone, entonces, efectuar una disolución más que una solución al problema de Gettier.

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We construct some examples using trees. Some of them are consistent counterexamples for the discrete reflection of certain topological properties. All the properties dealt with here were already known to be non-discretely reflexive if we assume CH and we show that the same is true assuming the existence of a Suslin tree. In some cases we actually get some ZFC results. We construct also, using a Suslin tree, a compact space that is pseudo-radial but it is not discretely generated. With a similar construction, but using an Aronszajn tree, we present a ZFC space that is first countable, omega-bounded but is not strongly w-bounded, answering a question of Peter Nyikos. (C) 2008 Elsevier B.V. All rights reserved.

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This paper describes properties of upper semi-continuous homothetic preferences. First we give conditions for the existence of an upper semi-continuous representation which is homogeneous of degree one. Then we show that with the additional assumptions of monotonicity or strict convexity, the preference is continuous. Several counterexamples illustrate the tightness of the results.

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This paper investigates which properties money-demand functions have to satisfy to be consistent with multidimensional extensions of Lucasí(2000) versions of the Sidrauski (1967) and the shopping-time models. We also investigate how such classes of models relate to each other regarding the rationalization of money demands. We conclude that money demand functions rationalizable by the shoppingtime model are always rationalizable by the Sidrauski model, but that the converse is not true. The log-log money demand with an interest-rate elasticity greater than or equal to one and the semi-log money demand are counterexamples.

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Recent demographic changes have made settlement patterns in the Canadian Arctic increasingly urban. Iqaluit, capital of Canada’s newest territory, Nunavut, is home to the largest concentration of Inuit and non-Inuit populations in the Canadian North. Despite these trends, Inuit cultural identity continues to rest heavily on the perception that to learn how to be authentically Inuit (or to be a better person), a person needs to spend time out on the land (and sea) hunting, fishing, trapping, and camping. Many Inuit also maintain a rather negative view of urban spaces in the Arctic, identifying them as places where Inuit values and practices have been eclipsed by Qallunaat (‘‘white people’’) ones. Some Inuit have even gone so far as to claim that a person is no longer able to be Inuit while living in towns like Iqaluit. This article examines those aspects of Canadian Inuit identity, culture, and tradition that disfavor the acceptance of an urban cultural identity. Based on ethnographic research conducted on Baffin Island in the mid 1990s and early 2000s, the many ways Iqaluit and outpost camp Inuit express the differences and similarities between living on the land and living in town are described. Then follows an examination of how the contrast of land and town is used in the rhetoric of Inuit politicians and leaders. Finally, a series of counterexamples are presented that favor the creation of an authentic urban Inuit identity in the Arctic, including recent attempts on the part of the Nunavut Territorial Government to make education and wage employment in the region more reliant on Inuit Qaujimajatuqangit, or Inuit traditional knowledge.1

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An important problem in computational biology is finding the longest common subsequence (LCS) of two nucleotide sequences. This paper examines the correctness and performance of a recently proposed parallel LCS algorithm that uses successor tables and pruning rules to construct a list of sets from which an LCS can be easily reconstructed. Counterexamples are given for two pruning rules that were given with the original algorithm. Because of these errors, performance measurements originally reported cannot be validated. The work presented here shows that speedup can be reliably achieved by an implementation in Unified Parallel C that runs on an Infiniband cluster. This performance is partly facilitated by exploiting the software cache of the MuPC runtime system. In addition, this implementation achieved speedup without bulk memory copy operations and the associated programming complexity of message passing.

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This dissertation concerns the intersection of three areas of discrete mathematics: finite geometries, design theory, and coding theory. The central theme is the power of finite geometry designs, which are constructed from the points and t-dimensional subspaces of a projective or affine geometry. We use these designs to construct and analyze combinatorial objects which inherit their best properties from these geometric structures. A central question in the study of finite geometry designs is Hamada’s conjecture, which proposes that finite geometry designs are the unique designs with minimum p-rank among all designs with the same parameters. In this dissertation, we will examine several questions related to Hamada’s conjecture, including the existence of counterexamples. We will also study the applicability of certain decoding methods to known counterexamples. We begin by constructing an infinite family of counterexamples to Hamada’s conjecture. These designs are the first infinite class of counterexamples for the affine case of Hamada’s conjecture. We further demonstrate how these designs, along with the projective polarity designs of Jungnickel and Tonchev, admit majority-logic decoding schemes. The codes obtained from these polarity designs attain error-correcting performance which is, in certain cases, equal to that of the finite geometry designs from which they are derived. This further demonstrates the highly geometric structure maintained by these designs. Finite geometries also help us construct several types of quantum error-correcting codes. We use relatives of finite geometry designs to construct infinite families of q-ary quantum stabilizer codes. We also construct entanglement-assisted quantum error-correcting codes (EAQECCs) which admit a particularly efficient and effective error-correcting scheme, while also providing the first general method for constructing these quantum codes with known parameters and desirable properties. Finite geometry designs are used to give exceptional examples of these codes.

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We provide counterexamples to the stable equivalence problem in every dimension d ≥ 2. That means that we construct hypersurfaces H₁ , H₂ ⊂ C d+1 whose cylinders H₁ × C and H₂ × C are equivalent hypersurfaces in C d+2 , although H₁ and H₂ themselves are not equivalent by an automorphism of C d+1 . We also give, for every d ≥ 2, examples of two non-isomorphic algebraic varieties of dimension d which are biholomorphic.

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2010 Mathematics Subject Classification: Primary 35S05, 35J60; Secondary 35A20, 35B08, 35B40.

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Protecting confidential information from improper disclosure is a fundamental security goal. While encryption and access control are important tools for ensuring confidentiality, they cannot prevent an authorized system from leaking confidential information to its publicly observable outputs, whether inadvertently or maliciously. Hence, secure information flow aims to provide end-to-end control of information flow. Unfortunately, the traditionally-adopted policy of noninterference, which forbids all improper leakage, is often too restrictive. Theories of quantitative information flow address this issue by quantifying the amount of confidential information leaked by a system, with the goal of showing that it is intuitively "small" enough to be tolerated. Given such a theory, it is crucial to develop automated techniques for calculating the leakage in a system. ^ This dissertation is concerned with program analysis for calculating the maximum leakage, or capacity, of confidential information in the context of deterministic systems and under three proposed entropy measures of information leakage: Shannon entropy leakage, min-entropy leakage, and g-leakage. In this context, it turns out that calculating the maximum leakage of a program reduces to counting the number of possible outputs that it can produce. ^ The new approach introduced in this dissertation is to determine two-bit patterns, the relationships among pairs of bits in the output; for instance we might determine that two bits must be unequal. By counting the number of solutions to the two-bit patterns, we obtain an upper bound on the number of possible outputs. Hence, the maximum leakage can be bounded. We first describe a straightforward computation of the two-bit patterns using an automated prover. We then show a more efficient implementation that uses an implication graph to represent the two- bit patterns. It efficiently constructs the graph through the use of an automated prover, random executions, STP counterexamples, and deductive closure. The effectiveness of our techniques, both in terms of efficiency and accuracy, is shown through a number of case studies found in recent literature. ^

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This PhD thesis examines a phenomenon known as Monosyllabic Circumflexion (MC, hereafter) from a historical linguistics / phonological point of view. MC denotes a Lithuanian or Balto-Slavic phenomenon according to which long vowels and diphthongs in monosyllabic words exhibit a circumflex tone instead of the expected acute tone.  It is observed in the following four categories: I. 3rd person future forms of monosyllabic stems (e.g., šõks ― šókti `to jump;' vy͂s ― výti `to drive') II. reflexes of PIE root nouns (e.g., Latv. gùovs `cow;' Lith. šuõ `dog') III. prepositions/adverbs (e.g., nuõ `from' ~  nùotaka `bride;' vė͂l `again' ~ Latv. vêl `still, yet,' tė͂ (permissive particle) < *teh1) IV. pronominal forms (e.g., tuõ ~ gerúoju `the good (m.~sg.~instr.),' tie͂ ~ tíeji `id. (pl.nom)'). The unexpected circumflex tone in these categories is problematic and important for the solution of a Balto-Slavic accentological question on the etymological background of acute and non-acute tones. The aim of this thesis is to partially contribute to the solution of this problem by establishing the existence of MC and its relative chronology. The first category, the 3rd person future forms, provides a substantial number of examples and counterexamples. The examination of them has revealed the fact that the counterexamples constitute a morpho-semantic group of verbs whose future stems underwent considerable morphological changes in the prehistory, hence not exhibiting MC. This shows that the regular tonal reflex of the 3rd person future forms of monosyllabic acute stem must be circumflex, allowing for the establishment of MC as a regular phonological process, although this category does not provide much information on the relative chronology of MC. The second category, the reflexes of Proto-Indo-European root nouns, gives an important clue as to where MC is located in the relative chronology of Balto-Slavic sound changes. Next, there is a discussion of whether the results of the examinations of the first two categories can be maintained for the data of the third and fourth categories, which show an irregular distribution of the acute and circumflex tones in monosyllabic forms. It is shown that various morphological factors, such as homonymic clashes within the paradigms for pronouns, can explain why some monosyllabic forms have acute tone. Also, the linguistic feature of West Aukštaitian dialects of Lithuanian that tend to preserve the results of MC is revealed. These dialects are known to have played an important role in the formation of standard Lithuanian. In this way, the monosyllabic forms with unexpected circumflex tone in Lithuanian are explained as a combination of MC in the Proto-Balto-Slavic time and the dialectal tendency of West Aukštaitian dialects of Lithuanian.

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We describe an integration of the SVC decision procedure with the HOL theorem prover. This integration was achieved using the PROSPER toolkit. The SVC decision procedure operates on rational numbers, an axiomatic theory for which was provided in HOL. The decision procedure also returns counterexamples and a framework has been devised for handling counterexamples in a HOL setting.