Efficiency and fairness in team search with self-interested agents

We consider team-work settings where individual agents incur costs on behalf of the team. In such settings it is frequently the custom to reimburse agents for the costs they incur (at least in part) in order to promote fairness. We show, however, that when agents are self-interested, such reimbursement can result in degradation in efficiency—at times severe degradation. We thus study the relationship between efficiency and fairness in such settings, distinguishing between ex-ante and ex-post fairness. First, we analyze reimbursement policies that reimburse solely based on purchase receipts (as is customary), and show that with such policies the degradation in both efficiency and fairness can be unbounded. We thus introduce two other families of reimbursement policies. The first family guarantees optimal efficiency and ex-ante fairness, but not ex-post fairness. The second family improves (at times) on ex-post fairness, but at the expense of efficiency, thus providing a tradeoff between the two.     

Lead‐Free Polycrystalline Ferroelectric Nanowires with Enhanced Curie Temperature

Ferroelectrics are important technological materials with wide‐ranging applications in electronics, communication, health, and energy. While lead‐based ferroelectrics have remained the predominant mainstay of industry for decades, environmentally friendly lead‐free alternatives are limited due to relatively low Curie temperatures (T _C) and/or high cost in many cases. Efforts have been made to enhance T _C through strain engineering, often involving energy‐intensive and expensive fabrication of thin epitaxial films on lattice‐mismatched substrates. Here, a relatively simple and scalable sol–gel synthesis route to fabricate polycrystalline (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ nanowires within porous templates is presented, with an observed enhancement of T _C up to ≈300 °C as compared to ≈90 °C in the bulk. By combining experiments and theoretical calculations, this effect is attributed to the volume reduction in the template‐grown nanowires that modifies the balance between different structural instabilities. The results offer a cost‐effective solution‐based approach for strain‐tuning in a promising lead‐free ferroelectric system, thus widening their current applicability.     

Not all faces are processed equally: Evidence for featural rather than holistic processing of one's own face in a face-imaging task.

The present work considers the mental imaging of faces, with a focus in own-face imaging. Experiments 1 and 3 demonstrated an own-face disadvantage, with slower generation of mental images of one's own face than of other familiar faces. In contrast, Experiment 2 demonstrated that mental images of facial parts are generated more quickly for one's own face. Finally, Experiment 4 established that a bias toward local processing is advantageous for one's own face, whereas a global-processing bias produces an enhanced own-face disadvantage. The results suggest that own-face imaging is more synchronized with retrieval of face features and less attuned to a face's holistic pattern than is imaging of other people's faces. The authors propose that the salient information for own and other face identification reflects, in part, differences in the purpose and experiences (expertise) generally associated with processing of own and other faces. Consistent with work examining the range of face processing, including other-race faces, our results suggest that not all faces receive the same holistic emphasis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Repetition priming effects for newly formed associations are perceptually based: Evidence from shallow encoding and format specificity.

This article is concerned with memory for newly formed associations as displayed on implicit and explicit tests of memory. After studying a list of word pairs, participants were shown the original intact pairs and pairs formed by recombining the original pairs. Pairs were simultaneously presented both at study and at test. In a lexical-decision task in which participants were asked to indicate whether both items were words, responses to intact pairs were faster than to recombined pairs. The size of this association-specific repetition effect was relatively unaffected by a levels-of-processing manipulation, indicating that conceptual processes did not likely contribute to the production of the effect. Furthermore, the effect was not produced when pairs were presented simultaneously at study but sequentially at test, thus highlighting the importance of format of presentation. Finally, in an explicit speeded-recognition task the size of the association-specific effect was largely affected by levels-of-processing manipulation and was revealed even under sequential test presentation suggesting that the associative repetition effects were not contaminated by conscious recollection.?.?.?.? (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Call routing to distributed queues: Is FIFO really better than MED?

New services providing automatic call distribution in the network have been one of the most hotly contested areas in the USA telecommunications arena in recent years. This has been fueled by increasing demand from large corporations for intelligent network routing that will keep their geographically distributed telemarketing/service centers operating with maximum efficiency. This paper compares two basic strategies for a network call distributor: a centralized FIFO queue and a distributed queueing strategy called Minimum‐Expected‐Delay (MED). According to MED, a central controller routes each arrival to the node that minimizes its expected delay (waiting time). Our main result qualifies the conventional wisdom that perceives FIFO as optimal. We show that the waiting time under FIFO is not stochastically smaller than that under MED. Furthermore, we prove that the waiting time distribution functions intersect at a single point. Numerical experiments suggest that, for certain performance criteria and over a range of parameters of interest, MED can actually outperform FIFO. This revised version was published online in June 2006 with corrections to the Cover Date.     

Flame retardant polyesters based on bromine derivatives

Unsaturated polyesters containing halogens in the backbone of the polymer chain were synthesized. Derivatives used had brominated functional groups such as tetrabromobisphenol A, tetrabromophthalic anhydride, and dibromoneopentyl glycol. These were compared to chlorine-containing polyesters based on HET acid and tetrachlorophthalic anhydride and an additive exhibiting a synergistic effect of phosphorus and halogen, trichloroethyl phosphate. Optical properties before and after artificial weathering (up to 1650 hr), were determined on cast specimens, and mechanical properties (flexural strength, modulus, and hardness) and flame retardancy were determined on glass fiber laminates. The flammability tests consisted of the “oxygen index” and the “self-extinguishing time” tests, which were correlated for various halogen concentrations and different compositions. The efficiency of bromine in flame retardancy has been found to be much higher than that of chlorine. The minimal concentration of bromine required for self-extinguishing is 10–12%, as compared with 20–25% for chlorine. A general performance index for polyesters has been derived which incorporates both flame and weather resistivity factors of the modified polyesters.     

Native-oxide-based selective area growth of InP nanowires via metal-organic molecular beam epitaxy mediated by surface diffusion

The growth of InP nanowires on an InP(111) B substrate is reported. The substrate native oxide was not removed from the surface prior to growth. Nanowires were grown at 400 °C from gold catalysts in a selective area manner, without bulk growth. Unlike SiO(2)-based metal-organic molecular beam epitaxy selective area growth, the growth reported here is mediated by surface diffusion with a characteristic diffusion length of 4 μm, about an order of magnitude larger than values for diffusion on bare substrates. A pre-growth heating treatment at 450 °C was found to increase the yield of nanowire nucleation from the gold catalysts.     

Deformable M-Reps for 3D Medical Image Segmentation

M-reps (formerly called DSLs) are a multiscale medial means for modeling and rendering 3D solid geometry. They are particularly well suited to model anatomic objects and in particular to capture prior geometric information effectively in deformable models segmentation approaches. The representation is based on figural models, which define objects at coarse scale by a hierarchy of figures—each figure generally a slab representing a solid region and its boundary simultaneously. This paper focuses on the use of single figure models to segment objects of relatively simple structure.A single figure is a sheet of medial atoms, which is interpolated from the model formed by a net, i.e., a mesh or chain, of medial atoms (hence the name m-reps), each atom modeling a solid region via not only a position and a width but also a local figural frame giving figural directions and an object angle between opposing, corresponding positions on the boundary implied by the m-rep. The special capability of an m-rep is to provide spatial and orientational correspondence between an object in two different states of deformation. This ability is central to effective measurement of both geometric typicality and geometry to image match, the two terms of the objective function optimized in segmentation by deformable models. The other ability of m-reps central to effective segmentation is their ability to support segmentation at multiple levels of scale, with successively finer precision. Objects modeled by single figures are segmented first by a similarity transform augmented by object elongation, then by adjustment of each medial atom, and finally by displacing a dense sampling of the m-rep implied boundary. While these models and approaches also exist in 2D, we focus on 3D objects.The segmentation of the kidney from CT and the hippocampus from MRI serve as the major examples in this paper. The accuracy of segmentation as compared to manual, slice-by-slice segmentation is reported.     

Borders: An Efficient Algorithm for Association Generation in Dynamic Databases

We consider the problem of finding association rules in a database with binary attributes. Most algorithms for finding such rules assume that all the data is available at the start of the data mining session. In practice, the data in the database may change over time, with records being added and deleted. At any given time, the rules for the current set of data are of interest. The naive, and highly inefficient, solution would be to rerun the association generation algorithm from scratch following the arrival of each new batch of data. This paper describes the Borders algorithm, which provides an efficient method for generating associations incrementally, from dynamically changing databases. Experimental results show an improved performance of the new algorithm when compared with previous solutions to the problem.