957 resultados para Self-organizing Feature Maps


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Durant els darrers anys, s’han publicat un gran nombre de materials multimèdia destinats a l’aprenentatge de llengües, la major part dels quals son CD-ROM dissenyats com a cursos per l’autoaprenentatge. Amb aquests materials, els alumnes poden treballar independentment sense l’assessorament d’un professor, i per aquest motiu s’ha afirmat que promouen i faciliten l’aprenentatge autònom. Aquesta relació, però, no es certa, com Phil Benson i Peter Voller 1997:10) han manifestat encertadament:(…) Such claims are often dubious, however, because of the limited range of options and roles offered to the learner. Nevertheless, technologies of education in the broadest sense can be considered to be either more or less supportive of autonomy. The question is what kind of criteria do we apply in evaluating them? En aquest article presentem una investigació conjunta on es defineixen els criteris que poden ser utilitzats per avaluar materials multimèdia en relació a la seva facilitat per permetre l’aprenentatge autònom. Aquests criteris son la base d’un qüestionari que s’ha emprat per avaluar una selecció de CD-ROM destinats a l’autoaprenentatge de llengües. La estructura d’aquest article és la següent: - Una introducció de l’estudi - Els criteris que s’han utilitzar per la creació del qüestionari - Els resultats generals de l’avaluació - Les conclusions que s’han extret i la seva importància pel disseny instructiu multimèdia

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Són molts els estudis que avui en dia incideixen en la necessitat d’oferir un suport metodològic i psicològic als aprenents que treballen de manera autònoma. L’objectiu d’aquest suport és ajudar-los a desenvolupar les destreses que necessiten per dirigir el seu aprenentatge així com una actitud positiva i una major conscienciació envers aquest aprenentatge. En definitiva, aquests dos tipus de preparació es consideren essencials per ajudar els aprenents a esdevenir més autònoms i més eficients en el seu propi aprenentatge. Malgrat això, si bé és freqüent trobar estudis que exemplifiquen aplicacions del suport metodològic dins els seus programes, principalment en la formació d’estratègies o ajudant els aprenents a desenvolupar un pla de treball, aquest no és el cas quan es tracta de la seva preparació psicològica. Amb rares excepcions, trobem estudis que documentin com s’incideix en les actituds i en les creences dels aprenents, també coneguts com a coneixement metacognitiu (CM), en programes que fomenten l’autonomia en l’aprenentatge. Els objectius d’aquest treball son dos: a) oferir una revisió d’estudis que han utilitzat diferents mitjans per incidir en el CM dels aprenents i b) descriure les febleses i avantatges dels procediments i instruments que utilitzen, tal com han estat valorats en estudis de recerca, ja que ens permetrà establir criteris objectius sobre com i quan utilitzar-los en programes que fomentin l’aprenentatge autodirigit.

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One of the features of pneumococcus which has deserved the attention of investigators is the capsule. Since Pasteur, Chamberland and Roux (1881) several functions have been ascribed to it as well as peculiar properties. In the present paper, we take into consideration one only aspect of this problem; it is the relationship which there possibly may be between acidity of the culture medium and the power of capsule formation by pneumococcus. As it is known, this germ requires for its development 7.8 as an optimum pH, but maintains its biological activities down to 5.6. These variations do not take place without large alterations, particularly of the capsule, not only from the morphological but also from the chemical viewpoint. The diameter of the mucous envelopment of the pneumococcus decreases in proportion to the increase of acidity down to its complete extinction. This fact has been regarded by investigators as a biological feature inhe¬ring to the germ itself and as proceeding of self-defense. In an acid medium the existing capsule is destroyed and the germ does not produce it again; consequently, acidity inhibits the formation of the capsule. We tried to check how this phenomenon comes to pass and to elucidated it. As we know, the fundamental compound of the pneumococcus capsule is mucin. In the first place, we experimented the action of acidity on same in the following manner: Mucin extracted from bovine submaxillary gland is precipitated by HC1 at a determined concentration degree; the mucin dissolves again and precipi¬tates in function of this concentration. This property of mucin (solubility in acid medium) modifies a little the interpretation of the mechanism of disappearance of the capsule from the said germ in the culture medium. Indeed: The acidification of the medium consecutive to the growth of pneumococcus reduces the dimensions of the capsule until causing its com¬plete disappearance; but on transferring this strain to new optimum cultiva¬ting conditions the capsule appears again exhuberantly, at times as anteriorly, although with biased virulence. Linking these two facts we draw the following conclusions: Pneumo¬coccus does not lose its capacity of capsule formation in an acid medium; but mucin, whilst being produced, is entirely dissolved in this medium by the aid of acidity; we venture to state that, in spite of medium acidity, the capacity of capsule production is a constant feature of pneumococcus and that the disappearance of the capsule does not depend on the pneumococcus in itself when it produces smooth colonies, but on the chemical properties of mucin, mainly on its solubility in acid medium.

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Vegeu el resum a l'inici del document del fitxer adjunt

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"Vegeu el resum a l'inici del document del fitxer adjunt."

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Constitutional arrangements affect the decisions made by a society. We study how this effect leads to preferences of citizens over constitutions; and ultimately how this has a feedback that determines which constitutions can survive in a given society. Constitutions are stylized here, to consist of a voting rule for ordinary business and possibly different voting rule for making changes to the constitution. We deffine an equilibrium notion for constitutions, called self-stability, whereby under the rules of a self-stable constitution, the society would not vote to change the constitution. We argue that only self-stable constitutions will endure. We prove that self-stable constitutions always exist, but that most constitutions (even very prominent ones) may not be self-stable for some societies. We show that constitutions where the voting rule used to amend the constitution is the same as the voting rule used for ordinary business are dangerously simplistic, and there are (many) societies for which no such constitution is self-stable rule. We conclude with a characterization of the set of self-stable constitutions that use majority rule for ordinary business.

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This paper studies collective choice rules whose outcomes consist of a collection of simultaneous decisions, each one of which is the only concern of some group of individuals in society. The need for such rules arises in different contexts, including the establishment of jurisdictions, the location of multiple public facilities, or the election of representative committees. We define a notion of allocation consistency requiring that each partial aspect of the global decision taken by society as a whole should be ratified by the group of agents who are directly concerned with this particular aspect. We investigate the possibility of designing envy-free allocation consistent rules, we also explore whether such rules may also respect the Condorcet criterion.

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Report for the scientific sojourn at the Research Institute for Applied Mathematics and Cybernetics, Nizhny Novgorod, Russia, from July to September 2006. Within the project, bifurcations of orbit behavior in area-preserving and reversible maps with a homoclinic tangency were studied. Finitely smooth normal forms for such maps near saddle fixed points were constructed and it was shown that they coincide in the main order with the analytical Birkhoff-Moser normal form. Bifurcations of single-round periodic orbits for two-dimensional symplectic maps close to a map with a quadratic homoclinic tangency were studied. The existence of one- and two-parameter cascades of elliptic periodic orbits was proved.

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Bathsheba's actions in 2 Sam. 11.2-4 identify crucial aspects of her character. Past commentators interpret these words in connection with menstrual purification, stressing the certain paternity of David's adulterine child. This article demonstrates that the participles rōheset and mitqaddesšet and the noun mittum'ātāh do not denote menstrual cleansing. Bathsheba's washing is an innocent bath. She is the only individual human to self-sanctify, placing her in the company of the Israelite deity. The syntax of the verse necessitates that her action of self-sanctifying occurs simultaneously as David lies with her. The three focal terms highlight the important legitimacy of Bathsheba before the Israelite deity, her identity as a non-Israelite, her role as queen mother of the Solomonic line, and her full participation in the narrative.

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We establish a one-to-one correspondence between the renormalizations and proper totally invariant closed sets (i.e., α-limit sets) of expanding Lorenz map, which enable us to distinguish periodic and non-periodic renormalizations. We describe the minimal renormalization by constructing the minimal totally invariant closed set, so that we can define the renormalization operator. Using consecutive renormalizations, we obtain complete topological characteriza- tion of α-limit sets and nonwandering set decomposition. For piecewise linear Lorenz map with slopes ≥ 1, we show that each renormalization is periodic and every proper α-limit set is countable.