The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Jonathan P. Caulkins - One of the best experts on this subject based on the ideXlab platform.
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Might Randomization in Queue Discipline Be Useful When Waiting Cost is a Concave Function of Waiting Time?
2018Co-Authors: Jonathan P. CaulkinsAbstract:This paper raises the question of whether some degree of randomization in queue discipline might be welfare enhancing in certain queues for which the cost of waiting is a Concave Function of waiting time, so that increased variability in waiting times may be good not bad for aggregate customer welfare. Such concavity may occur if the costs of waiting asymptotically approach some maximum (e.g., for patients seeking organ transplants who will not live beyond a certain threshold time) or if the customer incurs a fixed cost if there is any wait at all (e.g., for knowledge workers seeking a service or piece of information that is required to proceed with their current task, so any delay forces them to incur the “set up charge” associated with switching tasks)
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Might randomization in queue discipline be useful when waiting cost is a Concave Function of waiting time
Socio-Economic Planning Sciences, 2010Co-Authors: Jonathan P. CaulkinsAbstract:This paper suggests that introducing randomization in queue discipline might be welfare enhancing in certain queues for which the cost of waiting is a Concave Function of waiting time. Concavity can make increased variability in waiting times good not bad for aggregate customer welfare. Such concavity may occur if the costs of waiting asymptotically approach some maximum or if the customer incurs a fixed cost if there is any wait at all. As examples, cost might asymptotically approach a maximum for patients seeking organ transplants who will not live beyond a certain threshold time, and fixed costs could pertain for knowledge workers seeking a piece of information that is required to proceed with their current task, so any delay creates a "set up charge" associated with switching tasks.
Zhi Ding - One of the best experts on this subject based on the ideXlab platform.
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globally optimal linear precoders for finite alphabet signals over complex vector gaussian channels
IEEE Transactions on Signal Processing, 2011Co-Authors: Chengshan Xiao, Yahong Rosa Zheng, Zhi DingAbstract:We study the design optimization of linear precoders for maximizing the mutual information between finite alphabet input and the corresponding output over complex-valued vector channels. This mutual information is a nonlinear and non-Concave Function of the precoder parameters, posing a major obstacle to precoder design optimization. Our work presents three main contributions: First, we prove that the mutual information is a Concave Function of a matrix which itself is a quadratic Function of the precoder matrix. Second, we propose a parameterized iterative algorithm for finding optimal linear precoders to achieve the global maximum of the mutual information. The proposed iterative algorithm is numerically robust, computationally efficient, and globally convergent. Third, we demonstrate that maximizing the mutual information between a discrete constellation input and the corresponding output of a vector channel not only provides the highest practically achievable rate but also serves as an excellent criterion for minimizing the coded bit error rate. Our numerical examples show that the proposed algorithm achieves mutual information very close to the channel capacity for channel coding rate under 0.75, and also exhibits a large gain over existing linear precoding and/or power allocation algorithms. Moreover, our examples show that certain existing methods are susceptible to being trapped at locally optimal precoders.
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design optimization of linear precoders for complex vector gaussian channelswith finite alphabet inputs
International Conference on Acoustics Speech and Signal Processing, 2011Co-Authors: Chengshan Xiao, Yahong Rosa Zheng, Zhi DingAbstract:We study the design optimization of linear precoders that maximize the mutual information in complex-valued vector Gaussian channels under finite alphabet inputs. It is well known that mutual information of a vector channel with discrete constellation source is a highly nonlinear and nonConcave Function of the linear precoder matrix G, thereby complicating the precoder design optimization. In this paper, we show that the mutual information is a Concave Function of W = GhHhHG, where H is the complex-valued channel matrix and superscript “h” represents conjugate transpose. We further propose an iterative algorithm for solving the globally optimal linear precoder G. Illustrative results show that the proposed iterative algorithm is very robust and efficient for global convergence.
Yichen Huang - One of the best experts on this subject based on the ideXlab platform.
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entanglement criteria via Concave Function uncertainty relations
Physical Review A, 2010Co-Authors: Yichen HuangAbstract:A general theorem as a necessary condition for the separability of quantum states in both finite and infinite dimensional systems, based on Concave-Function uncertainty relations, is derived. Two special cases of the general theorem are stronger than two known entanglement criteria based on the Shannon entropic uncertainty relation and the Landau-Pollak uncertainty relation, respectively; other special cases are able to detect entanglement where some famous entanglement criteria fail.
Andrew R Solow - One of the best experts on this subject based on the ideXlab platform.
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unintended biological invasions does risk vary by trading partner
Journal of Environmental Economics and Management, 2007Co-Authors: Christopher Costello, Michael R Springborn, Carol Mcausland, Andrew R SolowAbstract:Abstract International trade is the primary conduit for unintentional and damaging species introductions. But biogeographic heterogeneity, and differences in historical trade exposure across trade partners suggest that not all imports are equally risky. We develop an analytical model linking exotic species introductions and discoveries to trade volumes. The model is estimated using a novel historical data set on global trade and species introductions by region. Our estimates support theoretical predictions that trade from different regions poses different risks and that the cumulative number of introductions from a region is a Concave Function of imports. For each trade region we then calculate the marginal and cumulative invasion risk from additional trade. Simple volume restrictions on imports to reduce NIS introductions are not advisable based on coarse cost–benefit calculations.
Arthur Van Soest - One of the best experts on this subject based on the ideXlab platform.
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measuring inequity aversion in a heterogeneous population using experimental decisions and subjective probabilities
Econometrica, 2008Co-Authors: Charles Bellemare, Sabine Kroger, Arthur Van SoestAbstract:We combine choice data in the ultimatum game with the expectations of proposers elicited by subjective probability questions to estimate a structural model of decision making under uncertainty. The model, estimated using a large representative sample of subjects from the Dutch population, allows both nonlinear preferences for equity and expectations to vary across socioeconomic groups. Our results indicate that inequity aversion to one's own disadvantage is an increasing and Concave Function of the payoff difference. We also find considerable heterogeneity in the population. Young and highly educated subjects have lower aversion for inequity than other groups. Moreover, the model that uses subjective data on expectations generates much better in- and out-of-sample predictions than a model which assumes that players have rational expectations. Copyright Copyright 2008 by The Econometric Society.