Current Issue : July - September Volume : 2011 Issue Number : 3 Articles : 6 Articles
Wireless sensor networks (WSNs) have great potential for many distributed applications in different scenarios. As they grow in popularity and importance, it becomes increasingly desirable and necessary to share their data over the Internet. This paper presents an energy-aware middleware that focuses on integrating the Internet and WSNs at service level by providing transparency of access, location, and technology. In particular, it describes and evaluates the implemented strategies to reduce the energy consumption, which are essential for prolonging the WSN lifetime....
This study presents a simple model of monthly mean daily global solar radiation on horizontal surfaces in Agenebode and Ekpoma, Nigeria. The modelling was based on the earlier proposed temperature model and was computed using monthly mean daily data set for minimum and maximum ambient temperatures. Our estimated results were verified to be statistically significant at the 95% confidence level with excellent performance accuracy....
The design space of FPGA-based processor systems is huge, because many parameters can be modified at design- and runtime to achieve an efficient system solution in terms of performance, power and energy consumption. Such parameters are, for example, the number of processors and their configurations, the clock frequencies at design time, the use of dynamic frequency scaling at runtime, the application task distribution, and the FPGA type and size. The major contribution of this paper is the exploration of all these parameters and their impact on performance, power dissipation, and energy consumption for four different application scenarios. The goal is to introduce a first approach for a developer's guideline, supporting the choice of an optimized and specific system parameterization for a target application on FPGA-based multiprocessor systems-on-chip. The FPGAs used for these explorations were Xilinx Virtex-4 and Xilinx Virtex-5. The performance results were measured on the FPGA while the power consumption was estimated using the Xilinx XPower Analyzer tool. Finally, a novel runtime adaptive multiprocessor architecture for dynamic clock frequency scaling is introduced and used for the performance, power and energy consumption evaluations....
A design scenario examined in this paper assumes that a circuit has been designed initially for high speed, and it is redesigned for low power by downsizing of the gates. In recent years, as power consumption has become a dominant issue, new optimizations of circuits are required for saving energy. This is done by trading off some speed in exchange for reduced power. For each feasible speed, an optimization problem is solved in this paper, finding new sizes for the gates such that the circuit satisfies the speed goal while dissipating minimal power. Energy/delay gain (EDG) is defined as a metric to quantify the most efficient tradeoff. The EDG of the circuit is evaluated for a range of reduced circuit speeds, and the power-optimal gate sizes are compared with the initial sizes. Most of the energy savings occur at the final stages of the circuits, while the largest relative downsizing occurs in middle stages. Typical tapering factors for power efficient circuits are larger than those for speed-optimal circuits. Signal activity and signal probability affect the optimal gate sizes in the combined optimization of speed and power....
This study is aimed at realizing a portable self defence weapon that generates a high voltage with small current to help escape from a potentially dangerous situation by stunning the attacker. This was realized using the basic principle of Cockcroft Walton theory and voltage transformation ratio of a transformer. The snubber network was also introduced to regulate the rate of change of the output voltage. The output of the device when implemented was found to produce 30kV at 3mA sufficient to deter the attacker, which justifies the theoretical value without causing any permanent deformity....
The role of 4-tert butyl pyridine (4TBP) adsorption on TiO2 surface band bending has been studied using photoelectron spectroscopy. Surface oxygen vacancies pin the Fermi level near the conduction band edge on rutile (110). 4TBP preferentially adsorbs in those vacancies and shift the Fermi level to lower binding energy in the band gap. This is done by transferring vacancy excess charge into the empty ?* orbital in the pyridine ring. The anatase (100) surface contains much less oxygen vacancies although the surface is much rougher than the rutile (110). 4TBP adsorption does not have any significant effect on the surface band bending. Thus the positive role associated with 4TBP addition to solar cell electrolytes is suggested to protection against adsorption of other electrolyte components such as Li and I....
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