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21.
A distributed activity scheduling algorithm for wireless sensor networks with partial coverage 总被引:1,自引:0,他引:1
One of the most important design objectives in wireless sensor networks (WSN) is minimizing the energy consumption since these
networks are expected to operate in harsh conditions where the recharging of batteries is impractical, if not impossible.
The sleep scheduling mechanism allows sensors to sleep intermittently in order to reduce energy consumption and extend network
lifetime. In applications where 100% coverage of the network field is not crucial, allowing the coverage to drop below full
coverage while keeping above a predetermined threshold, i.e., partial coverage, can further increase the network lifetime.
In this paper, we develop the distributed adaptive sleep scheduling algorithm (DASSA) for WSNs with partial coverage. DASSA
does not require location information of sensors while maintaining connectivity and satisfying a user defined coverage target.
In DASSA, nodes use the residual energy levels and feedback from the sink for scheduling the activity of their neighbors.
This feedback mechanism reduces the randomness in scheduling that would otherwise occur due to the absence of location information.
The performance of DASSA is compared with an integer linear programming (ILP) based centralized sleep scheduling algorithm
(CSSA), which is devised to find the maximum number of rounds the network can survive assuming that the location information
of all sensors is available. DASSA is also compared with the decentralized DGT algorithm. DASSA attains network lifetimes
up to 92% of the centralized solution and it achieves significantly longer lifetimes compared with the DGT algorithm. 相似文献
22.
Ammar Mahjoubi Ridha Fethi Mechlouch Belgacem Mahdhaoui Ammar Ben Brahim 《国际自然能源杂志》2013,34(5):210-224
This purpose of this paper is to develop and validate a model to accurately predict the cell temperature of a photovoltaic (PV) module that adapts to various mounting configurations, mounting locations, and climates while only requiring readily available data from the module manufacturer. Results from this model are also compared with results from published cell temperature models. The models were used to predict real-time performance from a PV water pumping systems in the desert of Medenine, south of Tunisia using 60-min intervals of measured performance data during one complete year. Statistical analysis of the predicted results and measured data highlights possible sources of errors and the limitations and/or adequacy of existing models, to describe the temperature and efficiency of PV-cells and consequently, the accuracy of performance of PV water pumping systems’ prediction models. 相似文献
23.
Oncu Akyildiz Ersin Emre Oren Tarik Omer Ogurtani 《Journal of Materials Science》2011,46(18):6054-6064
A systematic study based on the self-consistent dynamical simulations is presented for the grain boundary thermal grooving
problem by strictly following the irreversible thermodynamic theory of surfaces and interfaces with singularities [T. O. Ogurtani,
J. Chem. Phys. 124, 144706 (2006)]. This approach furnishes us to have auto-control on the otherwise free-motion of the grain
boundary triple junction without presuming any equilibrium dihedral (wetting) angles at the edges. The effects of physicochemical
properties and the anisotropic surface diffusivity on the transient grooving behavior, which takes place at the early stage
of the scenario, were considered. We analyzed the experimental thermal grooving data reported for tungsten in the literature,
and compared them with the carried simulation results. This investigation showed that the observed changes in the dihedral
angles are strictly connected to the transient behavior of the simulated global system, and manifest themselves at the early
stage of the thermal grooving phenomenon. 相似文献
24.
25.
This study aims to identify, using an extended Technology-Acceptance Model (TAM), the factors affecting the decision of using a web-based learning system among blue-collar workers in the automotive industry. A structural equation-modeling approach was applied to identify the variables that significantly affect the decision of using the system. Using LISREL 8.54, data collected from 546 blue-collar workers were used to test the proposed research model. Empirical testing of the extended TAM found all paths to be significant in the hypothesized directions, that is, the results of the study strongly support the application of extended TAM in predicting the blue-collar workers’ intention to use a web-based learning system. Among the factors, social influence is a much stronger predictor of user intention compared to others. The study concludes with the implications of this study for managers and recommendations for possible future research. 相似文献
26.
Tarik Taleb Abbas Jamalipour Nei Kato Yoshiaki Nemoto 《International Journal of Satellite Communications and Networking》2006,24(3):215-227
To meet an ever‐growing demand for wideband multimedia services and electronic connectivity across the world, development of ubiquitous broadband multimedia systems is gaining a tremendous interest at both commercial and academic levels. Satellite networks will play an indispensable role in the deployment of such systems. A significant number of satellite communication constellations have been thus proposed using Geostationary (GEO), Medium Earth Orbit (MEO), or Low Earth Orbit (LEO) satellites. These constellations, however, either require a potential number of satellites or are unable to provide data transmission with high elevation angles. This paper proposes a new satellite constellation composed of Quasi‐GeoStationary Orbit (Quasi‐GSO) satellites. The main advantage of the constellation is in its ability to provide global coverage with a significantly small number of satellites while, at the same time, maintaining high elevation angles. Based on a combination of this Quasi‐GSO satellites constellation and terrestrial networks, the paper proposes also an architecture for building a global, large‐scale, and efficient Video‐on‐Demand (VoD) system. The entire architecture is referred to as a ‘Theatre in the Sky’. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
27.
Tarik A. Almohamad M. F. M. Salleh M. N. Mahmud 《Wireless Personal Communications》2014,77(1):255-267
In wireless cooperative communication scheme, transmit diversity is achieved by coupling the distributed users. In this paper, a new partner selection algorithm is proposed. The selection scheme utilizes the basic work done by Almawgani on RS coded cooperation for wireless network. Users are classified into weak and strong ones based on the signal-to-Noise Ratio (SNR) uplink matrix. Users with good uplink channel SNR (strong users) are coupled with those experiencing weak uplink channel conditions (weak users). The proposed algorithm offers an improvement to the outage probability, \(P_{out}\) and power efficiency as compared to the established work. The algorithm shows a significant improvement of \(P_{out}\) at lower values of uplink SNR. 相似文献
28.
29.
Direct ink write deposition facilitates line-by-line extrusion of inks spanning wide viscoelastic ranges. Following deposition, post processing technologies permit tuning of the extrudate's material property characteristics—ultraviolet (UV) irradiation, facilitating the photopolymerization of UV-reactive catalyst solutions, permits targeted modification of the extrudate's microstructure and in situ tuning of extrudate macrostructure. This report analyzes the morphological, rheological, and microstructural property relationships governing the printability, and processivity, of extruded UV-curable resin inks for delineation of sufficiency and optimization of ink printability utilizing direct ink write technologies. A design-of-experiments approach is implemented to quantify significance regarding an extrudate's dimensional response to extrusion parameter variation and in situ processing parameters, identifying proportionally of nozzle velocity, nozzle height, and UV irradiation exposure with extrudate aspect ratio, reflected by respective maximum extrudate aspect ratio increases of 158% and 109%, regarding 121 and 123K resin inks. Finally, the relationship between extrudate morphology and microstructure variation was assessed via dielectric cure monitoring, whereby an extrudate's ion viscosity was calculated in relation to its rheological modulus, reflecting the relationship between an extrudate's morphology, rheological response, and printability, regarding its microstructural variation. 相似文献
30.
New numerical quasi-static model for the computer aided design (CAD) and analysis of suspended microstrip lines is reported. This model is applicable up to εr = 20 and over the range 0.001 ≤ u ≤ 1000, where u = w/h 1 is the structure’s variable (w is the width of the strip and h 1 is the air gap’s thickness). The practical cases are limited to a thickness h 1 of the same order of h 2 which is the dielectric’s thickness. This yields to choose 0.5 ≤ m ≤ 1.5. The parameter m is dependent on the structure’s variable u. This model is conceived to corroborate the results of the variational approach in any point of its ranges of validity, with a raised error with 1.2%. Although the variational approach allows accurate values of the effective permittivity, but the computing time is relatively high which quickly becomes prohibitory if the Finished Coupled Elementary Lines method is used. The present model is an improvement over the previous variational method as it not only takes lower computing time but it also valid up to high values of εr and over the range 0.001 ≤ u ≤ 1000. This work is important by the fact that it seeks to visualise the formal model of the effective permittivity, generally masked in a direct variational treatment. 相似文献