1,721,089 research outputs found
Performance comparison of route metrics for wireless mesh networks
No full textWhen designing the route metrics for wireless mesh networks, we can improve network capacity by considering the traffic load, the link loss rate, and the medium contention. In this letter, we propose as the route metrics for wireless mesh networks the number of contention nodes that reflects both the traffic load and the medium contention as well as the aggregated traffic bandwidth that reflects the traffic load. To the best of our knowledge, no studies to date have compared the performances of route metrics with different features in the wireless mesh network. We therefore compared the performances of the proposed route metrics and the, existing route metrics of the hop count and the expected transmission count to reflect the link loss rate. Simulation results show that the proposed route metrics perform better than the existing route metrics.This research was supported by the MIC, Korea, under the ITRC support program supervised by the IITA
Lateral-shearing interferometer using square prisms for optical testing of aspheric lenses
No full textWe present a lateral-shearing interferometer specially devised for production-line inspection of aspheric lenses. The interferometer constitutes four right-angle prisms, whose relative sliding motions provide the lateral shearing and phase shifts necessary for measuring the beam wavefront collimated by the lens under test. The prisms are held together face to face using index-matching oil, so environmental disturbances from external vibration and atmospheric turbulence can be minimized. Furthermore, a special phase-measuring algorithm of least-squares type is adopted to compensate for the phase shift error caused by the variation in thickness of the index-matching oil holding the prisms. Experimental results prove that the interferometer provides a measuring reproducibility of the order of one hundredth of the light's wavelength
Enhanced Ad Hoc On-demand Distance Vector (EAODV) Routing Protocol with Route Distribution
No full textThis research was supported by the MIC (Ministry of Information and Communication), Korea, under the ITRC (Information Technology Research Center) support program
supervised by the IITA (Institute of Information Technology Assessment
Investigation of coating failure on the surface of water ballast tank of an oil tanker
No full textThe current crude oil tanker is constructed as a double-hull structure which consists of an oil tank and a water ballast tank whose surface is coated with epoxy paint to prevent corrosion. Since the cracks that developed in the epoxy coating have caused corrosion of the interface of the water ballast tank, the identification of the parameters for crack development is important. In addition, the moisture absorption by the epoxy coating can cause deterioration of bond strength, which results in delamination of the coating and accelerates the corrosion at the interface. In this study, after the mechanical and thermo-mechanical properties of epoxy paints were measured, the residual stresses induced by the temperature change and cure shrinkage were calculated by the finite element analysis, which were compared with the experimental results. Also, the pull-off tests were performed to investigate the deterioration of the bond strength of epoxy coatings due to moisture absorption. It was found that the thermo-mechanical properties such as the coefficient of thermal expansion and glass transition temperature of the coating materials had dominant effects on the crack resistance rather than the cure shrinkage; the moisture penetration to the bonding interface caused interfacial failure and a significant deterioration of bond strength
Fatigue characteristics of the bolted joints for unidirectional composite laminates
No full textWhen composites are employed as structural materials, joining of composites to other materials is necessary because manufacturing structures with composites only is not generally feasible. Although the maximum static strength of the composite bolted joint is frequently realized by quasi-isotropic patterns, these patterns are seldom used in structural members under general load, such as bending, compressive, and tensile load. To increase the efficiency of whole structures with the composite bolted joints, the laminate with stacking sequence of [+/- theta/0(8)](s) was proposed in this work. The fatigue characteristics of the [+/- theta/0(8)](s) laminate bolted joint were investigated with respect to the angle 0 and the bolt clamping pressure and compared with the result of the [0(2)/+/- 453/90(2)](s) laminate, which was proposed as one of the optimum stacking sequence under the static load. From the experiments on the bolted joints, it has been found that the laminates whose major plies are stacked in the axial direction can be used for the bolted joint structures under fatigue load when an appropriate clamping pressure is applied to the bolted joint. (C) 2004 Elsevier Ltd. All rights reserved
Stress Analysis and Evaluation of Cracks Developed on the Coatings for Welded Joints of Water Ballast Tanks
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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