Splitting Algorithms for Fast Relay Selection: Generalizations, Analysis, and a Unified View

Relay selection for cooperative communications promises significant performance improvements, and is, therefore, attracting considerable attention. While several criteria have been proposed for selecting one or more relays, distributed mechanisms that perform the selection have received relatively less attention. In this paper, we develop a novel, yet simple, asymptotic analysis of a splitting-based multiple access selection algorithm to find the single best relay. The analysis leads to simpler and alternate expressions for the average number of slots required to find the best user. By introducing a new `contention load' parameter, the analysis shows that the parameter settings used in the existing literature can be improved upon. New and simple bounds are also derived. Furthermore, we propose a new algorithm that addresses the general problem of selecting the best $Q \ge 1$ relays, and analyze and optimize it. Even for a large number of relays, the algorithm selects the best two relays within 4.406 slots and the best three within 6.491 slots, on average. We also propose a new and simple scheme for the practically relevant case of discrete metrics. Altogether, our results develop a unifying perspective about the general problem of distributed selection in cooperative systems and several other multi-node systems.Comment: 20 pages, 7 figures, 1 table, Accepted for publication in IEEE Transactions on Wireless Communication

Optimal Timer Based Selection Schemes

Timer-based mechanisms are often used to help a given (sink) node select the best helper node among many available nodes. Specifically, a node transmits a packet when its timer expires, and the timer value is a monotone non-increasing function of its local suitability metric. The best node is selected successfully if no other node's timer expires within a 'vulnerability' window after its timer expiry, and so long as the sink can hear the available nodes. In this paper, we show that the optimal metric-to-timer mapping that (i) maximizes the probability of success or (ii) minimizes the average selection time subject to a minimum constraint on the probability of success, maps the metric into a set of discrete timer values. We specify, in closed-form, the optimal scheme as a function of the maximum selection duration, the vulnerability window, and the number of nodes. An asymptotic characterization of the optimal scheme turns out to be elegant and insightful. For any probability distribution function of the metric, the optimal scheme is scalable, distributed, and performs much better than the popular inverse metric timer mapping. It even compares favorably with splitting-based selection, when the latter's feedback overhead is accounted for.Comment: 21 pages, 6 figures, 1 table, submitted to IEEE Transactions on Communications, uses stackrel.st

Supercavitating cascades with constant pressure cambered blades

Linearized theory on supercavitating cascades with constant pressure cambered blade

Experimental verification and practical application of torquewhirl theory of rotordynamic instability

A theory developed by Vance in 1978 to explain the destabilizing effect of torque on a whirling rotor was experimentally verified. The measurements made on a specially designed test apparatus are described. New computer models were also developed to investigate the effect of torque on rotordynamic stability of multidisk flexible rotor bearing systems. The effect of torque was found to be most pronounced when the system is already marginally stable from other influences. The modifications required to include torque in a typical shaft transfer matrix are described, and results are shown which identify the type of rotor design most sensitive to load torque

Performance of domestic and foreign-invested enterprises in China

Despite increasing attention paid to China's enterprise reform since the late 1970s, relatively little is known about the performance of reformed state-owned enterprises (SOEs) and newly formed private firms vis-à-vis foreign firms in China. In this study, we examine the performance of domestic Chinese firms in various ownership categories versus foreign-invested enterprises (FIEs) based on two nation-wide surveys conducted by the National Bureau of Statistics in 1998 and 2002. We found that both domestic non-state-owned firms and foreign-invested enterprises performed better than state-owned enterprises. Meanwhile, three categories of Chinese firms-privately owned, collectively owned, and shareholding-had higher performance levels than the foreign-invested enterprises. © 2005 Elsevier Inc. All rights reserved.postprin

Bio-inspired Tensegrity Soft Modular Robots

In this paper, we introduce a design principle to develop novel soft modular robots based on tensegrity structures and inspired by the cytoskeleton of living cells. We describe a novel strategy to realize tensegrity structures using planar manufacturing techniques, such as 3D printing. We use this strategy to develop icosahedron tensegrity structures with programmable variable stiffness that can deform in a three-dimensional space. We also describe a tendon-driven contraction mechanism to actively control the deformation of the tensegrity mod-ules. Finally, we validate the approach in a modular locomotory worm as a proof of concept.Comment: 12 pages, 7 figures, submitted to Living Machine conference 201

Rapid communication: Linkage mapping of the porcine immunoreceptor DAP10 and NKG2D genes

Genus and Species. Sus scrofa. Loci. DNAX-activation protein 10 (DAP10) and natural killer cell receptor D (NKG2D). Source and Description of Primers. Primers were designed from the porcine DAP10 and NKG2D sequences (GenBank accession nos. AF285446 and AF285448, respectively). The DAP10 primers were used to amplify approximately 500 bp of the fragment spanning DAP10 exon 4 and DAP12 exon 5. The DAP10 and DAP12 genes are linked in opposite transcriptional orientation, separated by 152 bp (Yim et al., 2001). The NKG2D primers were used to amplify approximately 700 bp of the fragment spanning NKG2D exons 8 and 9

On the rocking behavior of rigid objects

A novel formulation for the rocking motion of a rigid block on a rigid foundation is presented in this work. The traditional piecewise equations are replaced by a single ordinary differential equation. In addition, damping effects are no longer introduced by means of a coefficient of restitution but understood as the presence of impulsive forces. The agreement with the classical formalism is very good for both free rocking regime and harmonic forcing excitation

Validated instruments used to measure attitudes of healthcare students and professionals towards patients with physical disability: a systematic review

<p>Abstract</p> <p>Background</p> <p>Instruments to detect changes in attitudes towards people with disabilities are important for evaluation of training programs and for research. While we were interested in instruments specific for medical students, we aimed to systematically review the medical literature for validated survey instruments used to measure attitudes of healthcare students and professionals towards patients with physical disability.</p> <p>Methods</p> <p>We electronically searched Medline, EMBASE, PsycINFO, Health and Psychosocial Instruments. We included papers reporting on the development and/or validation of survey instruments to measure attitudes of healthcare students and professionals towards patients with physical disability. We excluded papers in which the attitudes were not measured in a provider-patient context. Two reviewers carried out titles and abstracts screening, full texts screening, and data abstraction in a duplicate and independent manner using standardized and pilot tested forms.</p> <p>Results</p> <p>We identified seven validated survey instruments used for healthcare students and professionals. These instruments were originally developed for the following target populations: general population (n = 4); dental students (n = 1); nursing students (n = 1); and rehabilitation professionals (n = 1). The types of validity reported for these instruments were content validity (n = 3), criterion-related validity (n = 1), construct validity (n = 2), face validity (n = 1), discriminant validity (n = 1), and responsiveness (n = 1). The most widely validated and used tool (ATDP) was developed in the late 1960s while the most recent instrument was developed in the early 1990s.</p> <p>Conclusion</p> <p>Of the seven identified validated instruments, less than half were specifically designed for healthcare students and professionals and none for medical students. There is a need to develop and validate a contemporary instrument specifically for medical students.</p