Performance of the Vickrey auction for digital goods under various bid distributions

The generalized Vickrey auction is analysed as a mechanism for setting prices of digital goods. A selection of models of the bidders' behaviour (embodied by the probability distribution of their bids' values) are employed to derive the optimal auctioneer's choice as to the number of items to sell. The satisfaction levels of both the auctioneer and the bidders are taken into account through the evaluation of the expected revenues, the percentage of winning bidders and their aggregated utilities under each of the probabilistic scenarios considered. (C) 2007 Elsevier B.V. All rights reserved

Stochastic simulation techniques as related to innovation in communications-navigation-surveillance and air traffic management (CNS/ATM)

The design and operational tuning of the instruments and procedures employed in communications-navigation-surveillance (CNS) and air traffic management (ATM) often relies on stochastic simulation techniques. In this paper the application areas of simulation in the CNS/ATM context are reviewed together with the simulation methods that can help solve the main problems encountered, i.e. quick simulation techniques for the simulation of rare events, and the bootstrap technique for the evaluation of the accuracy of the results

The value of location in keyword auctions

Sponsored links on search engines are an emerging advertising tool, whereby a number of slots are put on sale through keyword auctions. This is also known as contextual advertising. Slot assignment and pricing in keyword auctions are then essential for the search engine\u2019s management since provide the main stream of revenues, and are typically accomplished by the Generalized Second Price (GSP) mechanism. In GSP the price of slots is a monotone function of the slot location, being larger for the highest slots. Though a higher location is associated with larger revenues, the lower costs associated with the lowest slots may make them more attractive for the advertiser. The contribution of this research is to show, by analytical and simulation results based on the theory of order statistics, that advertisers may not get the optimal slot they aim at (the slot maximizing their expected profit) and that the GSP mechanism may be unfair to all the winning bidders but the one who submitted the lowest bid

Regularization Techniques for Inverse Problem in DOT Applications

Diffuse optical tomography (DOT) is an emerging diagnostic technique which uses near-infra-red light to investigate the optical coefficients distribution in biological tissues. The surface of the tissue is illuminated by light sources, then the outgoing light is measured by detectors placed at various locations on the surface itself. In order to reconstruct the optical coefficients, a mathematical model of light propagation is employed: such model leads to the minimization of the discrepancy between the detected data and the corresponding theoretical field. Due to severe ill-conditioning, regularization techniques are required: common procedures consider mainly \u2113 1-norm (LASSO) and \u2113 2-norm (Tikhonov) regularization. In the present work we investigate two original approaches in this context: The elastic-net regularization, previously used in machine learning problems, and the Bregman procedure. Numerical experiments are performed on synthetic 2D geometries and data, to evaluate the performance of these approaches. The results show that these techniques are indeed suitable choices for practical applications, where DOT is used as a cheap, first-level and almost real-Time screening technique for breast cancer detection

Approximation of 2d and 3d models of chemotactic cell movement in vasculogenesis

Cell migration plays a central role in a wide variety of biological phenomena. In the case of chemotaxis, cells (or an organism) move in response to a chemical gradient. Chemotaxis underlies many events during embrio development and in the adult body. An understanding of chemotaxis is not only gained through laboratory experiments but also through the analysis of model systems, which often are much more amenable to experimental manipulation. This work is concerned with the relaxation schemes for the numerical approximation of a 2D and 3D model for cell movement driven by chemotaxis. More precisely, we consider models arising in the description of blood vessels formation and network formation starting from a random cell distribution

Related and unrelated industry variety and the internationalization of start-ups

We study the relationship between industry variety in a start-up's home location and the start-up's internationalization in terms of both the likelihood of and persistence in exporting. Using a unique sample of Swedish start-ups, we find that related industry variety is positively associated with exporting likelihood and persistence, whereas unrelated industry variety is positively associated with exporting likelihood and persistence when the start-ups’ employees possess technological knowledge. We also find that employees’ international experience strengthens the positive relationship between related industry variety and start-ups’ export persistence. We provide auxiliary evidence of the proposed mechanisms through which related and unrelated industry variety affects start-ups’ internationalization—that is, through their effects on start-ups’ ability to launch novel products in foreign markets. The findings of our study provide policymakers preliminary evidence on th

Related and unrelated industry variety and the internationalization of start-ups

We study the relationship between industry variety in a start-up's home location and the start-up's internationalization in terms of both the likelihood of and persistence in exporting. Using a unique sample of Swedish start-ups, we find that related industry variety is positively associated with exporting likelihood and persistence, whereas unrelated industry variety is positively associated with exporting likelihood and persistence when the start-ups’ employees possess technological knowledge. We also find that employees’ international experience strengthens the positive relationship between related industry variety and start-ups’ export persistence. We provide auxiliary evidence of the proposed mechanisms through which related and unrelated industry variety affects start-ups

Understanding Cerebellum Granular Layer Network Computations through Mathematical Reconstructions of Evoked Local Field Potentials

Background: The cerebellar granular layer input stage of cerebellum receives information from tactile and sensory re- gions of the body. The somatosensory activity in the cerebellar granular layer corresponds to sensory and tactile input has been observed by recording Local Field Potential (LFP) from the Crus-IIa regions of cerebellum in brain slices and in anesthetized animals. Purpose: In this paper, a detailed biophysical model of Wistar rat cerebellum granular layer net- work model and LFP modelling schemas were used to simulate circuit\u2019s evoked response. Methods: Point Source Ap- proximation and Line Source Approximation were used to reconstruct the network LFP. The LFP mechanism in in vitro was validated in network model and generated the in vivo LFP using the same mechanism. Results: The network simulations distinctly displayed the Trigeminal and Cortical (TC) wave components generated by 2 independent bursts implicating the generation of TC waves by 2 independent granule neuron populations. Induced plasticity was simulated to estimate granule neuron activation related population responses. As a prediction, cerebellar dysfunction (ataxia) was also studied using the model. Dysfunction at individual neurons in the network was affected by the population response. Conclusion: Our present study utilizes available knowledge on known mechanisms in a single cell and associates network function to population responses