Mechanism design for coalition formation and cost sharing in group-buying markets

We study the mechanism design problem of coalition formation and cost sharing in a group-buying electronic marketplace, where buyers can form coalitions to take advantage of volume based discounts. The desirable mechanism properties include stability (in the core), and incentive compatibility with good efficiency. We show the impossibility to simultaneously satisfy efficiency, budget balance and individual rationality at a Bayesian–Nash equilibrium, and propose a mechanism in the core of the game. We then present and evaluate a group of reasonable mechanisms. Empirical results show positive correlation between stability and incentive compatibility (which is in turn related to efficiency).     

Message delivery in heterogeneous networks prone to episodic connectivity

We present an efficient message delivery framework, called MeDeHa, which enables communication in an internet connecting heterogeneous networks that is prone to disruptions in connectivity. MeDeHa is complementary to the IRTF’s Bundle Architecture: besides its ability to store messages for unavailable destinations, MeDeHa can bridge the connectivity gap between infrastructure-based and multi-hop infrastructure-less networks. It benefits from network heterogeneity (e.g., nodes supporting more than one network and nodes having diverse resources) to improve message delivery. For example, in IEEE 802.11 networks, participating nodes may use both infrastructure- and ad-hoc modes to deliver data to otherwise unavailable destinations. It also employs opportunistic routing to support nodes with episodic connectivity. One of MeDeHa’s key features is that any MeDeHa node can relay data to any destination and can act as a gateway to make two networks inter-operate or to connect to the backbone network. The network is able to store data destined to temporarily unavailable nodes till the time of their expiry. This time period depends upon current storage availability as well as quality-of-service needs (e.g., delivery delay bounds) imposed by the application. We showcase MeDeHa’s ability to operate in environments consisting of a diverse set of interconnected networks and evaluate its performance through extensive simulations using a variety of scenarios with realistic synthetic and real mobility traces. Our results show significant improvement in average delivery ratio and a significant decrease in average delivery delay in the face of episodic connectivity. We also demonstrate that MeDeHa supports different levels of quality-of-service through traffic differentiation and message prioritization.     

The Plan B OS for ubiquitous computing. Voice control, security, and terminals as case studies

The conventional approach to building pervasive environments relies on middleware to integrate different systems. Instead, we have built a system that can deal with these environments by exporting system resources through distributed virtual file systems. This requires no middleware, simplifies interoperation, and permits the application of general purpose tools to any system resource. A constraint-based file system import mechanism allows the system to adapt to changes in the environment and permits users to customize the environment and tailor adaptations according to their needs. The system has been in use for over a year to carry out our daily work and is underlying the smart space that we built for our department. The system, and some novel services, including ubiquitous voice interfaces, a distributed security architecture, and remote terminals for smart spaces, are also described in this paper.     

A Roadmap of Agent Research and Development

This paper provides an overview of research and development activities in the field of autonomous agents and multi-agent systems. It aims to identify key concepts and applications, and to indicate how they relate to one-another. Some historical context to the field of agent-based computing is given, and contemporary research directions are presented. Finally, a range of open issues and future challenges are highlighted.     

Return on capital of Brazilian electricity distributors: A comparative analysis

This paper analyzes the electricity distribution segment in Brazil from 1998 to 2005—after the conclusion of privatization process—trying to assess whether the return on capital invested was in line with the risk required in the segment. It concludes that the return on equity in Brazil was systematically negative until 2003. Only in 2005 did the distribution segment really begin to recover, showing profitability consistent with the estimated cost of equity. Comparisons with Argentine, Chilean and American companies reveal that firms in the latter two countries, generally managed to reward shareholders according to the opportunity cost of capital. Estimates are that to sustain annual growth of roughly 3.7% for the next decade, the entire electricity sector will demand US$ 7 billion in capital expenditures a year for the next decade, 67% for generation, 16% for transmission and 17% for distribution. In order to stimulate private capital investment, it is fundamental for the regulator, in the tariff revision processes, to consistently assure a rate of return on capital in line with the segment's real opportunity cost and therefore maintain the health of all the three segments without the burden of subsidies.     

The impact of depression on social economic decision making.

[Correction Notice: An erratum for this article was reported in Vol 119(3) of Journal of Abnormal Psychology (see record 2010-15289-020). In the article, the last revision received date printed on the final page of the article was incorrect due to an error in the production process. The correct publication dates are as follows: Received April 14, 2009; Revision received November 6, 2009; Accepted November 9, 2009.] Although the role of emotion in social economic decision making has been increasingly recognized, the impact of mood disorders, such as depression, on such decisions has been surprisingly neglected. To address this gap, 15 depressed and 23 nondepressed individuals completed a well-known economic task, in which they had to accept or reject monetary offers from other players. Although depressed individuals reported a more negative emotional reaction to unfair offers, they accepted significantly more of these offers than did controls. A positive relationship was observed in the depressed group, but not in controls, between acceptance rates of unfair offers and resting cardiac vagal control, a physiological index of emotion regulation capacity. The discrepancy between depressed individuals' increased emotional reactions to unfair offers and their decisions to accept more of these offers contrasts with recent findings that negative mood in nondepressed individuals can lead to lower acceptance rates. This suggests distinct biasing processes in depression, which may be related to higher reliance on regulating negative emotion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tunable wettability on Pendelic marble: could an inorganic marble surface behave as a “self-cleaning” biological surface?

The sustainable protection of the Greek cultural heritage aims to strengthen Pendelic marble, to preserve its unique esthetic properties and its resistance to long weathering. Our main purpose was to design, apply, and study a system of controllable wettability appropriate to the hydrophilic nature of the surface of Pendelic marble. A very simple, cost effective, and easily reproducible method has been developed, to fabricate a composite protective hybrid nanostructured film via a bio-mimetic route. This is a modern technological method for self-cleaning surfaces mimicking nature’s phenomena and structures, such as the Lotus leaf hierarchical nano/microstructure. Our approach differs from the conventional conservation methods in that it is based on a top coating with nanostructured synthesis, consisting of a hydrophilic/hydrophobic silica mixture dispersed in organic solvents, applied by “alla prima” technique onto a fluorosilanic base matrix that has been coated onto Pendelic marble. The behavior of this new surface is critically examined in this document.     

Tailored One-Way and Two-Way Shape Memory Capabilities of Poly(ε-Caprolactone)-Based Systems for Biomedical Applications

This paper investigates the shape memory capabilities of semicrystalline networks, focusing the attention on poly(ε-caprolactone) (PCL) systems, a class of materials that allows to satisfy important requirements for their applications as biomedical devices, such as the good biocompatibility, the fast recovery of large “temporary” shape configurations, and the easy tailoring of the transformation temperatures. The materials were prepared with various crosslink densities and crosslinking methodologies; in particular, beside a thermal crosslinking based on reactive methacrylic end groups, a novel type of covalently crosslinked semicrystalline systems was prepared by a sol-gel approach from alkoxysilane-terminated PCL precursors, so as to avoid potentially toxic additives typically used for free-radical thermal curing. The materials were subjected to biological tests, to study their ability in sustaining cell adhesion and proliferation, and to thermal characterizations, to evaluate the possibility to tailor their melting and crystallization temperatures. The one-way shape memory (i.e., the possibility to set the material in a given configuration and to recover its pristine shape) and the two-way shape memory response (i.e., the triggered change between two distinguished shapes on the application of an on-off stimulus) were studied by applying optimized thermo-mechanical cyclic histories. The ability to fix the applied shape and to recover the original one on the application of heating (i.e., the one-way effect) was evaluated on tensile bars; further, to investigate a potential application as self-expandable stents, isothermal shape memory experiments were carried out also on tubular specimens, previously folded in a temporary compact configuration. The two-way response was studied through the application of a constant load and of a heating/cooling cycle from above melting to below the crystallization temperature, leading to a reversible elongation/contraction effect, involving maximum strain changes up to about 80%, whose extent may be controlled through the crosslink density.     

Characterization of Active Dry Wine Yeast During Starter Culture (Pied de Cuve) Preparation for Sparkling Wine Production

The preparation of yeast starter culture (Pied de Cuve) for producing sparkling wine with the traditional method is a key factor for manufacturing a good Prise de mousse. In this paper, the evolution of total yeast population, its viability during Pied de Cuve preparation, and the pressure profile during the 2nd fermentation in 2 different base wines made from Bombino bianco and Chardonnay grapes were investigated using 4 different commercial active dried yeasts. The study proves that despite the initial differences observed throughout the acclimatization phase, all the tested strains showed similar results on either the total population (from 8.2 × 10⁷ cells/mL to 1.3 × 10⁸ cells/mL) or cellular viability (from 70% to 84%). Independently from the base wine tested, the kinetic of sugar consumption was faster during the gradual acclimatization to the alcoholic medium (phase II) and slower during the preparation of starter culture in active growth phase (phase III). During both of these phases Saccharomyces cerevisiae bayanus Vitilevure DV10^® (Station ?notechnique de Champagne) proved to have a higher sugar consumption rate than the other strains. During the Prise de mousse, S. cerevisiae bayanus Lalvin EC‐1118^® (Lallemand) reached the maximum pressure increase within time in both base wines.     

Flooding for Reliable Multicast in Multi-Hop Ad Hoc Networks

Ad hoc networks are gaining popularity as a result of advances in smaller, more versatile and powerful mobile computing devices. The distinguishing feature of these networks is the universal mobility of all hosts. This requires re-engineering of basic network services including reliable multicast communication. This paper considers the special case of highly mobile fast-moving ad hoc networks and argues that, for such networks, traditional multicast approaches are not appropriate. Flooding is suggested as a possible alternative for reliable multicast and simulation results are used to illustrate its effects. The experimental results also demonstrate a rather interesting outcome that even flooding is insufficient for reliable multicast in ad hoc networks when mobility is very high. Some alternative, more persistent variations of flooding are sketched out.