Página 7 dos resultados de 1418 itens digitais encontrados em 0.004 segundos

## Impacto da utilização de motores de alto rendimento e sua aplicação no leilão de eficiência energética.; Impact of the use of high performance engines and its application in the auction of energy efficiency.

Micerino, Fabio José
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 14/05/2012 PT
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O trabalho apresentado tem como objetivo principal pesquisar e demonstrar através de simulações as implicações da utilização de motores de alto rendimento com viés de Eficiência Energética. Além disso, pretende-se estabelecer uma ligação entre o uso eficiente da energia com a possibilidade dos leilões de eficiência energética virem a se tornar uma realidade no Brasil. É de fundamental importância que se tenha a preocupação com sistemas de conservação de energia e não somente com novas fontes de geração. A eficiência Energética vem ganhando cada vez mais espaço no setor elétrico, se tornando muito mais que um indicador, mas também uma forma de tornar o sistema mais robusto e capaz de suprir deficiências por problemas estruturais. Procurou-se demonstrar o cenário atual da matriz energética atual, conceituar leilões de eficiência energética e os certificados brancos que é um subproduto deste. Por fim, realizou-se várias simulações estudando a substituição dos motores de alto rendimento e os ganhos técnicos e financeiros atrelados aos leilões de eficiência energética. Além disso, foi demonstrado também o impacto da utilização dos motores de alto rendimento em leilões de eficiência energética por segmentos da indústria brasileira.; The present study has as main objective the analysis...

## Análise dos fatores de influência nas propostas ofertadas nos leilões de transmissão de energia elétrica; Initially changes that have happened in Brazilian Electricity Sector since the 1990s were described, including Transmission Lines and Substations Auctions for the Expansion of the National Interconnected System in Brazil

Nascimento, Rodrigo Limp
Tipo: Dissertação
POR
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## Uma visão sobre o mercado leiloeiro lisboeta e a sua importância no conhecimento da produção de mobiliário civil português no século XVIII

Nunes, Marta Marinho
Fonte: Instituto Universitário de Lisboa Publicador: Instituto Universitário de Lisboa
Tipo: Dissertação de Mestrado
Publicado em 29/07/2010 POR
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## Rationality, Irrationality and Escalating Behavior in Lowest Unique Bid Auctions

Radicchi, Filippo; Baronchelli, Andrea; Amaral, Luís A. N.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 18/01/2012 EN
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Information technology has revolutionized the traditional structure of markets. The removal of geographical and time constraints has fostered the growth of online auction markets, which now include millions of economic agents worldwide and annual transaction volumes in the billions of dollars. Here, we analyze bid histories of a little studied type of online auctions – lowest unique bid auctions. Similarly to what has been reported for foraging animals searching for scarce food, we find that agents adopt Lévy flight search strategies in their exploration of “bid space”. The Lévy regime, which is characterized by a power-law decaying probability distribution of step lengths, holds over nearly three orders of magnitude. We develop a quantitative model for lowest unique bid online auctions that reveals that agents use nearly optimal bidding strategies. However, agents participating in these auctions do not optimize their financial gain. Indeed, as long as there are many auction participants, a rational profit optimizing agent would choose not to participate in these auction markets.

## On Revenue-Optimal Dynamic Auctions for Bidders with Interdependent Values

Constantin, Florin; Parkes, David C.
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Monograph or Book
EN_US
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In a dynamic market, being able to update one’s value based on information available to other bidders currently in the market can be critical to having profitable transactions. This is nicely captured by the model of interdependent values (IDV): a bidder’s value can explicitly depend on the private information of other bidders. In this paper we present preliminary results about the revenue properties of dynamic auctions for IDV bidders. We adopt a computational approach to design single-item revenue-optimal dynamic auctions with known arrivals and departures but (private) signals that arrive online. In leveraging a characterization of truthful auctions, we present a mixed-integer programming formulation of the design problem. Although a discretization is imposed on bidder signals the solution is a mechanism applicable to continuous signals. The formulation size grows exponentially in the dependence of bidders’ values on other bidders’ signals. We highlight general properties of revenue-optimal dynamic auctions in a simple parametrized example and study the sensitivity of prices and revenue to model parameters.; Engineering and Applied Sciences

## An Options-Based Method to Solve the Composability Problem in Sequential Auctions

Juda, Adam I.; Parkes, David C.
Fonte: Springer Verlag Publicador: Springer Verlag
Tipo: Monograph or Book
EN_US
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Current auctions often expose bidding agents to two difficult, yet common, problems. First, bidding agents often have the opportunity to participate in successive auctions selling the same good, with no dominant bidding strategy in any single auction. Second, bidding agents often need to acquire a bundle of goods by bidding in multiple auctions, again with no dominant bidding strategy in any single auction. This paper introduces an options-based infrastructure that respects the autonomy of individual sellers but still enables bidders to utilize a dominant, truthful strategy across multiple auctions.; Engineering and Applied Sciences

## Worst-case optimal redistribution of VCG payments in heterogeneous-item auctions with unit demand

Guo, M.
Fonte: International Foundation for Autonomous Agents and Multiagent Systems; UK Publicador: International Foundation for Autonomous Agents and Multiagent Systems; UK
Tipo: Conference paper
Publicado em //2012 EN
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Many important problems in multiagent systems involve the allocation of multiple resources among the agents. For resource allocation problems, the well-known VCG mechanism satisfies a list of desired properties, including efficiency, strategy-proofness, individual rationality, and the non-deficit property. However, VCG is generally not budget-balanced. Under VCG, agents pay the VCG payments, which reduces social welfare. To offset the loss of social welfare due to the VCG payments, VCG redistribution mechanisms were introduced. These mechanisms aim to redistribute as much VCG payments back to the agents as possible, while maintaining the aforementioned desired properties of the VCG mechanism. We continue the search for worst-case optimal VCG redistribution mechanisms -- mechanisms that maximize the fraction of total VCG payment redistributed in the worst case. Previously, a worst-case optimal VCG redistribution mechanism (denoted by WCO) was characterized for multi-unit auctions with nonincreasing marginal values [7]. Later, WCO was generalized to settings involving heterogeneous items [4], resulting in the HETERO mechanism. [4] conjectured that HETERO is feasible and worst-case optimal for heterogeneous-item auctions with unit demand. In this paper...

## Leilão combinatório : estudo de abordagens computáveis para o Setor Elétrico Brasileiro; Combinatorial auction : study of computable approaches to the brazilian electric sector

Elisa Bastos Silva
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 23/02/2015 PT
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Leilões de novos empreendimentos de energia envolvem o compromisso de construí-los e o direito de explorá-los por meio de contratos de outorga. O leiloeiro, cujo objetivo é minimizar o pagamento pela energia contratada, buscando a redução de seu preço para os consumidores finais, fornece o direito de outorga da usina para o vencedor. O licitante é um investidor, e.g., uma empresa de geração que procura maximizar seu benefício com a venda de energia proveniente do empreendimento. Quando a natureza desses empreendimentos é complementar, torna-se possível proporcionar maiores benefícios aos licitantes, e maior eficiência ao leilão, caso sejam negociados em conjunto. Atualmente, o projeto de leilão instituído é composto por uma abordagem híbrida, sequencial e simultânea, que não permite a extração das sinergias entre empreendimentos. Esta tese examina duas metodologias híbridas de leilões reversos, considerando-se o ponto de vista do leiloeiro. O primeiro modelo, centralizado, é composto por duas fases: uma simultânea de lance aberto e outra combinatória de lance fechado. A fase simultânea incentiva a revelação do preço da energia, enquanto a fase combinatória oferece oportunidade aos licitantes de submeterem ofertas mais agressivas através de pacotes de empreendimentos complementares. O modelo centralizado é formulado como um problema de otimização inteiro e combinatório. A função-objetivo consiste em minimizar o pagamento...

## Optimize-and-Dispatch Architecture for Expressive Ad Auctions

Parkes, David C.; Sandholm, Tuomas
Fonte: Association for Computing Machinery Publicador: Association for Computing Machinery
Tipo: Monograph or Book
EN_US
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Ad auctions are generating massive amounts of revenue for online search engines such as Google. Yet, the level of expressiveness provided to participants in ad auctions could be significantly enhanced. An advantage of this could be improved competition and thus improved revenue to a seller of the right to advertise to a stream of search queries. In this paper, we outline the kinds of expressiveness that one might expect to be useful for ad auctions and introduce a high-level “optimize-and-dispatch” architecture for expressive ad auctions. The architecture is designed to enable expressiveness while retaining real-time response to search queries.; Engineering and Applied Sciences

## Hybrid Keyword Search Auctions

Goel, Ashish; Munagala, Kamesh
Tipo: Artigo de Revista Científica
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Search auctions have become a dominant source of revenue generation on the Internet. Such auctions have typically used per-click bidding and pricing. We propose the use of hybrid auctions where an advertiser can make a per-impression as well as a per-click bid, and the auctioneer then chooses one of the two as the pricing mechanism. We assume that the advertiser and the auctioneer both have separate beliefs (called priors) on the click-probability of an advertisement. We first prove that the hybrid auction is truthful, assuming that the advertisers are risk-neutral. We then show that this auction is superior to the existing per-click auction in multiple ways: 1) It takes into account the risk characteristics of the advertisers. 2) For obscure keywords, the auctioneer is unlikely to have a very sharp prior on the click-probabilities. In such situations, the hybrid auction can result in significantly higher revenue. 3) An advertiser who believes that its click-probability is much higher than the auctioneer's estimate can use per-impression bids to correct the auctioneer's prior without incurring any extra cost. 4) The hybrid auction can allow the advertiser and auctioneer to implement complex dynamic programming strategies. As Internet commerce matures...

## Experiments with Probabilistic Quantum Auctions

Chen, Kay-Yut; Hogg, Tad
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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We describe human-subject laboratory experiments on probabilistic auctions based on previously proposed auction protocols involving the simulated manipulation and communication of quantum states. These auctions are probabilistic in determining which bidder wins, or having no winner, rather than always having the highest bidder win. Comparing two quantum protocols in the context of first-price sealed bid auctions, we find the one predicted to be superior by game theory also performs better experimentally. We also compare with a conventional first price auction, which gives higher performance. Thus to provide benefits, the quantum protocol requires more complex economic scenarios such as maintaining privacy of bids over a series of related auctions or involving allocative externalities.; Comment: extended description of experiment setup and results

## The Computational Complexity of Truthfulness in Combinatorial Auctions

Dobzinski, Shahar; Vondrak, Jan
Tipo: Artigo de Revista Científica
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One of the fundamental questions of Algorithmic Mechanism Design is whether there exists an inherent clash between truthfulness and computational tractability: in particular, whether polynomial-time truthful mechanisms for combinatorial auctions are provably weaker in terms of approximation ratio than non-truthful ones. This question was very recently answered for universally truthful mechanisms for combinatorial auctions \cite{D11}, and even for truthful-in-expectation mechanisms \cite{DughmiV11}. However, both of these results are based on information-theoretic arguments for valuations given by a value oracle, and leave open the possibility of polynomial-time truthful mechanisms for succinctly described classes of valuations. This paper is the first to prove {\em computational hardness} results for truthful mechanisms for combinatorial auctions with succinctly described valuations. We prove that there is a class of succinctly represented submodular valuations for which no deterministic truthful mechanism provides an $m^{1/2-\epsilon}$-approximation for a constant $\epsilon>0$, unless $NP=RP$ ($m$ denotes the number of items). Furthermore, we prove that even truthful-in-expectation mechanisms cannot approximate combinatorial auctions with certain succinctly described submodular valuations better than within $n^\gamma$...

## Bidding to the Top: VCG and Equilibria of Position-Based Auctions

Aggarwal, Gagan; Muthukrishnan, S.; Feldman, Jon
Tipo: Artigo de Revista Científica
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Many popular search engines run an auction to determine the placement of advertisements next to search results. Current auctions at Google and Yahoo! let advertisers specify a single amount as their bid in the auction. This bid is interpreted as the maximum amount the advertiser is willing to pay per click on its ad. When search queries arrive, the bids are used to rank the ads linearly on the search result page. The advertisers pay for each user who clicks on their ad, and the amount charged depends on the bids of all the advertisers participating in the auction. In order to be effective, advertisers seek to be as high on the list as their budget permits, subject to the market. We study the problem of ranking ads and associated pricing mechanisms when the advertisers not only specify a bid, but additionally express their preference for positions in the list of ads. In particular, we study "prefix position auctions" where advertiser $i$ can specify that she is interested only in the top $b_i$ positions. We present a simple allocation and pricing mechanism that generalizes the desirable properties of current auctions that do not have position constraints. In addition, we show that our auction has an "envy-free" or "symmetric" Nash equilibrium with the same outcome in allocation and pricing as the well-known truthful Vickrey-Clarke-Groves (VCG) auction. Furthermore...

## Bundling Equilibrium in Combinatorial auctions

Holzman, Ron; Kfir-Dahav, Noa; Monderer, Dov; Tennenholtz, Moshe
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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This paper analyzes individually-rational ex post equilibrium in the VC (Vickrey-Clarke) combinatorial auctions. If $\Sigma$ is a family of bundles of goods, the organizer may restrict the participants by requiring them to submit their bids only for bundles in $\Sigma$. The $\Sigma$-VC combinatorial auctions (multi-good auctions) obtained in this way are known to be individually-rational truth-telling mechanisms. In contrast, this paper deals with non-restricted VC auctions, in which the buyers restrict themselves to bids on bundles in $\Sigma$, because it is rational for them to do so. That is, it may be that when the buyers report their valuation of the bundles in $\Sigma$, they are in an equilibrium. We fully characterize those $\Sigma$ that induce individually rational equilibrium in every VC auction, and we refer to the associated equilibrium as a bundling equilibrium. The number of bundles in $\Sigma$ represents the communication complexity of the equilibrium. A special case of bundling equilibrium is partition-based equilibrium, in which $\Sigma$ is a field, that is, it is generated by a partition. We analyze the tradeoff between communication complexity and economic efficiency of bundling equilibrium, focusing in particular on partition-based equilibrium.

## Linear Programming helps solving large multi-unit combinatorial auctions

Gonen, Rica; Lehmann, Daniel
Tipo: Artigo de Revista Científica
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Previous works suggested the use of Branch and Bound techniques for finding the optimal allocation in (multi-unit) combinatorial auctions. They remarked that Linear Programming could provide a good upper-bound to the optimal allocation, but they went on using lighter and less tight upper-bound heuristics, on the ground that LP was too time-consuming to be used repetitively to solve large combinatorial auctions. We present the results of extensive experiments solving large (multi-unit) combinatorial auctions generated according to distributions proposed by different researchers. Our surprising conclusion is that Linear Programming is worth using. Investing almost all of one's computing time in using LP to bound from above the value of the optimal solution in order to prune aggressively pays off. We present a way to save on the number of calls to the LP routine and experimental results comparing different heuristics for choosing the bid to be considered next. Those results show that the ordering based on the square root of the size of the bids that was shown to be theoretically optimal in a previous paper by the authors performs surprisingly better than others in practice. Choosing to deal first with the bid with largest coefficient (typically 1) in the optimal solution of the relaxed LP problem...

## Multi-Unit Auctions: Beyond Roberts

Dobzinski, Shahar; Nisan, Noam
Tipo: Artigo de Revista Científica
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We exhibit incentive compatible multi-unit auctions that are not affine maximizers (i.e., are not of the VCG family) and yet approximate the social welfare to within a factor of $1+\epsilon$. For the case of two-item two-bidder auctions we show that these auctions, termed Triage auctions, are the only scalable ones that give an approximation factor better than 2. "Scalable" means that the allocation does not depend on the units in which the valuations are measured. We deduce from this that any scalable computationally-efficient incentive-compatible auction for $m$ items and $n \ge 2$ bidders cannot approximate the social welfare to within a factor better than 2. This is in contrast to arbitrarily good approximations that can be reached under computational constraints alone, and in contrast to the fact that the optimal social welfare can be obtained under incentive constraints alone.

## Simulation-Based Game Theoretic Analysis of Keyword Auctions with Low-Dimensional Bidding Strategies

Vorobeychik, Yevgeniy
Tipo: Artigo de Revista Científica
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We perform a simulation-based analysis of keyword auctions modeled as one-shot games of incomplete information to study a series of mechanism design questions. Our first question addresses the degree to which incentive compatibility fails in generalized second-price (GSP) auctions. Our results suggest that sincere bidding in GSP auctions is a strikingly poor strategy and a poor predictor of equilibrium outcomes. We next show that the rank-by-revenue mechanism is welfare optimal, corroborating past results. Finally, we analyze profit as a function of auction mechanism under a series of alternative settings. Our conclusions coincide with those of Lahaie and Pennock [2007] when values and quality scores are strongly positively correlated: in such a case, rank-by-bid rules are clearly superior. We diverge, however, in showing that auctions that put little weight on quality scores almost universally dominate the pure rank-by-revenue scheme.; Comment: Appears in Proceedings of the Twenty-Fifth Conference on Uncertainty in Artificial Intelligence (UAI2009)

## Draft Auctions

Devanur, Nikhil R.; Morgenstern, Jamie; Syrgkanis, Vasilis
Tipo: Artigo de Revista Científica
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We introduce draft auctions, which is a sequential auction format where at each iteration players bid for the right to buy items at a fixed price. We show that draft auctions offer an exponential improvement in social welfare at equilibrium over sequential item auctions where predetermined items are auctioned at each time step. Specifically, we show that for any subadditive valuation the social welfare at equilibrium is an $O(\log^2(m))$-approximation to the optimal social welfare, where $m$ is the number of items. We also provide tighter approximation results for several subclasses. Our welfare guarantees hold for Bayes-Nash equilibria and for no-regret learning outcomes, via the smooth-mechanism framework. Of independent interest, our techniques show that in a combinatorial auction setting, efficiency guarantees of a mechanism via smoothness for a very restricted class of cardinality valuations, extend with a small degradation, to subadditive valuations, the largest complement-free class of valuations. Variants of draft auctions have been used in practice and have been experimentally shown to outperform other auctions. Our results provide a theoretical justification.

## Optimal Strategies for Simultaneous Vickrey Auctions with Perfect Substitutes

Gerding, Enrico H.; Dash, Rajdeep Kumar; Byde, Andrew; Jennings, Nicholas Robert
Tipo: Artigo de Revista Científica