Constrained Location Problems in the Plane and on a Sphere

This paper presents a unified approach for the solution of the minimax and maximin location problems subject to constraints in the plane and on the sphere. The constraints limit the solution to be inside some circles and/or outside some other circles. Four distance measures are considered: Euclidean in the plane, shortest arc distance on the sphere, and general monotonic functions of each. Computational results are presented.     

Energy Efficient Reliable Data Collection in Wireless Sensor Networks with Asymmetric Links

Field measurements reveal that radio link asymmetry has a severe impact on reliable data delivery. We analyze the energy efficiencies of selected reliability schemes for asymmetric radio links using theoretical models. The analysis provides guidelines for retransmission control so as to balance between reliability and energy consumption. We also design two enhancements to the “implicit” ARQ scheme addressing the negative effects of asymmetric radio links. The energy efficiencies of these algorithms are explicitly derived using our theoretical model and validated by simulations and field trials. Based on the analysis of the two enhanced algorithms, we propose an improvement, referred to as Energy Efficient Reliable Data Collection (EERDC) that controls the retransmissions of the enhanced ARQ schemes. Simulations and field trials confirm our theoretical findings and demonstrate that our proposed EERDC algorithm alleviates the impact of link asymmetry and achieves energy savings.

An adjustable-torque slipping clutch

A slipping clutch capable of delivering a constant torque is described. This is based on the resistance to rolling offered by a steel cylinder rolling under pressure between two bonded layers of a suitably compounded rubber formulation.     

Concurrent Formation of Metallic Glass During Laser Forward Transfer 3D Printing

In recent years, bulk metallic glasses (BMGs) have drawn much research attention and are shown to be of industrial interest due to their superior mechanical properties and resistance to corrosion. In spite of the interest in harnessing MG for microelectromechanical systems devices, there are limitations in manufacturing such micrometer‐scale structures. A novel approach for the fabrication of 3D MG structures using laser‐induced forward transfer (LIFT) is demonstrated. Inherent tremendous cooling rates associated with the metal LIFT process (≈10¹⁰ k s^?1) make the formation of a variety of BMGs accessible, including also various binary compositions. In this work, it is demonstrated that LIFT printing of ZrPd‐based metallic glass microstructures can also be performed under ambient conditions. X‐ray diffraction analysis of the printed structures reveals > 95% of amorphous metal phase. Taking advantage of the properties of BMG, high quality printing of high aspect ratio BMG pillars, and microbridges are demonstrated. It is also shown how a composite, amorphous‐crystalline metal structure with a required configuration can be fabricated using multimaterial LIFT printing. The inherent high resolution of the method combined with the noncontact and multimaterial printing capacity makes LIFT a valuable additive manufacturing technique to produce metallic glass‐based devices.     

An approximate method for the study of large deformations of membranes

A method is described to give approximate solutions to problems concerned with the deformation of highly extensible, rubberlike membranes. This is based on a principle first described by Rayleigh, involving the minimization of the elastic strain energy of the membrane. The method, which enables rapid solution under a variety of boundary conditions, is applied to three typical problems with no known closed-form solutions, namely: the stretching of a clamped rubber sheet; the stretching of a rubber tube; and the axial movement of the inner ring of an annulus with respect to its outer periphery.     

On the power of uniform power: capacity of wireless networks with bounded resources

The throughput capacity of arbitrary wireless networks under the physical Signal to Interference Plus Noise Ratio (SINR) model has received much attention in recent years. In this paper, we investigate the question of how much the worst-case performance of uniform and non-uniform power assignments differ under constraints such as a bound on the area where nodes are distributed or restrictions on the maximum power available. We determine the maximum factor by which a non-uniform power assignment can outperform the uniform case in the SINR model. More precisely, we prove that in one-dimensional settings the capacity of a non-uniform assignment exceeds a uniform assignment by at most a factor of \(O(\log L_{\max })\) when the length of the network is \(L_{\max }\). In two-dimensional settings, the uniform assignment is at most a factor of \(O(\log P_{\max })\) worse than the non-uniform assignment if the maximum power is \(P_{\max }\). We provide algorithms that reach this capacity in both cases. These bounds are tight in the sense that previous work gave examples of networks where the lack of power control causes a performance loss in the order of these factors. To complement our theoretical results and to evaluate our algorithms with concrete input networks, we carry out simulations on random wireless networks. The results demonstrate that the link sets generated by the algorithms contain around 20–35 % of all links. As a consequence, engineers and researchers may prefer the uniform model due to its simplicity if this degree of performance deterioration is acceptable.     

On high-speed computing with a programmable linear array

It has been observed by many researchers that systolic arrays are very suitable for certain high-speed computations. Using a formal methodology, we present a design for a single simple programmable linear systolic array capable of solving large numbers of problems drawn from a variety of applications. The methodology is applicable to problems solvable by sequential algorithms that can be specified as nested for-loops of arbitrary depth. The algorithms of this form that can be computed on the array presented in this paper include 25 algorithms dealing with signal and image processing, algebraic computations, matrix arithmetic, pattern matching, database operations, sorting, and transitive closure. Assuming bounded I/O, for 18 of those algorithms the time and storage complexities are optimal, and therefore no improvement can be expected by using dedicated special-purpose linear systolic arrays designed for individual algorithms. We also describe another design which, using a sufficient large local memory and allowing data to be preloaded and unloaded, has an optimal processor/time product.An earlier version of this paper was presented at Supercomputing '88.This work was partially supported by ONR under the contract N00014-85-K-0046 and by NSF under Grant Number CCR-8906949.     

Outdoor attractancy of males ofMatsucoccus josephi (Homoptera: Matsucoccidae) andElatophilus hebraicus (Hemiptera: Anthocoridae) to synthetic female sex pheromone ofMatsucoccus josephi

The active component of the sex pheromone ofMatsucoccus josephi is (2E,6E,8E)-5,7-dimethyl-2,6,8-decatrien-4-one; the chemical is also a powerful kairomone of adult males and females of the bugElatophilus hebraicus the principal predator ofM. josephi. The presence of theZ isomer (2E,6Z,8E)-5,7-dimethyl-2,6,8-decatrien-4-one does not interfere with the attractancy of the activeE component forM. josephi males or the bug. Our results show a clear dose-response between trap catch ofM. josephi males andE. hebraicus. Conversely, increasing amounts of theZ isomer in the mixture did not affect the attraction of the scale insect males or the bug. The catch ofM. josephi males did not differ significantly among traps of different color, and was significantly higher with traps attached to the tree trunk than those suspended between trees. Comparison of the catch ofM. josephi among the three forests and between pine species suggests that the level of infestation ofPinus halepepsis andPinus brutia ssp.brutia is similar, despite the fact that the latter pine is resistant to the scale insect. Both sexes ofE. hebraicus were trapped in much lower numbers at the more infested sites. This may be related to interference with the activity ofE. hebraicus due to deterioration and drying of parts of the tree crowns and heavy colonization by generalist predators in injured trees.     

Chirality of israeli pine bast scale,Matsucoccus josephi (homoptera: Matsucoccidae) sex pheromone

The absolute configuration of the sex pheromone of the Israeli pine bast scale,Matsucoccus josephi, was determined as (2E,5R,6E,8E)-5,7-dimethyl-2,6,8-decatrien-4-one, designated here asR-E with 10% (2E,5S,6E,8E)-5,7-dimethyl-2,6,8-decatrien-4-one, designated asS-E. The chirality of the quantitatively minorZ isomer was (2E,5R,6Z,8E)-5,7-dimethyl-2,6,8-decatrien-4-one (R-Z). Chiral assignments were made by comparative gas chromatographic (GC) analysis of naturalM. josephi pheromone with stereoselectively synthesized stereoisomers on a chiral Cyclodex-B column, which separated the enantiomers with baseline resolution. In gas chromatographic-electroantennographic detection (GC-EAD) analysis of the racemicZ andE isomers, the latter elicited the stronger antennal response by maleM. josephi. In GC-EAD of all four stereoisomers, employing the chiral column,R-E was the most active stereoisomer. In field testsR-E attracted 10 times more males ofM. josephi than didS-E. The racemicE/Z pheromone mixture, containing all four stereoisomers in approximately equal amounts, attracted as many maleM. josephi as did an equivalent amount ofR-E, indicating that the other stereoisomers are not inhibitory. The same keto-diene moiety with the same chiral center and configuration in all three known Matsucoccidae sex pheromones implies a common biosynthetic pathway and phylogenetic relationship.Contribution from the Agricultural Research Organization, the Volcani Center, No. 1496-E, 1994 series.Part of the work was performed during a sabbatical leave of E.D. at Simon Fraser University.     

Association of personal, process, and outcome variables in group counseling: Testing an exploratory model.

This study measured relationships among personal, process, and outcome variables in a student population (n = 205) participating in group counseling. Personal variables included intention to disclose, self-esteem, risk taking, and interpersonal relationships. Process variables included bonding with group members, bonding with leader, impression of therapy, self-disclosure, and resistance. Analyses were conducted with hierarchical models and Mplus. Results indicated gains in interpersonal relationships, which were associated with their own initial scores, with intention to disclose mediated by impression of therapy, and with self-disclosure. Three of the four personal variables (risk taking being the exception) were associated with the process variables of bonding with group and leader and impression of therapy, all moderately interrelated. Self-disclosure was unrelated to any personal or process variables. (PsycINFO Database Record (c) 2010 APA, all rights reserved)