A Single-Stage High-Power-Factor Electronic Ballast Based on Integrated Buck Flyback Converter to Supply Metal Halide Lamps

In this paper, a novel single-stage electronic ballast with a high power factor is presented. The ballast circuit is based on the integration of a buck converter to provide the power factor correction, and a flyback converter to control the lamp power and to supply the lamp with a low-frequency square-waveform current. Both converters work in discontinuous conduction mode, which simplifies the control. In spite of being an integrated topology, the circuit does not present additional stress of voltage or current in the main switch, which handles only the flyback or buck current, depending on the operation mode. To supply the lamp with a low-frequency square-wave current to avoid acoustic resonances, the flyback has two secondary windings that operate complementarily at a low frequency. The design procedure of the converters is also detailed. Experimental results from a 35-W metal halide lamp are presented, where the proposed ballast reached a power factor of 0.95, a total harmonic distortion of 30% (complying with IEC 61000-3-2), and an efficiency of 90%.     

An intrinsic order criterion to evaluate large, complex fault trees

A new efficient algorithm is introduced to evaluate (non) coherent fault trees, obtaining exact lower & upper bounds on system unavailability, with a prespecified maximum error. The algorithm is based on the canonical normal form of the Boolean function, but overcomes the large number of terms needed, by using an intrinsic order criterion (IOC) to select the elementary states to evaluate. This intrinsic order implies lexicographic (truth table) order. The criterion guarantees a priori that the probability of a given elementary system state is always greater than or equal to the probability of another state, for any set of basic probabilities. IOC is exclusively based on the positions of 0 & 1 in the binary n-tuples defining the elementary states. The algorithm does not require any qualitative analysis of the fault tree. The computational cost mainly depends on the basic event probabilities, and is related to system complexity, only because the Boolean function must be evaluated.     

Silver versus white sheet as a back reflector for microcrystalline silicon solar cells deposited on LPCVD‐ZnO electrodes of various textures

We compare the performance of two back reflector designs on the optoelectrical properties of microcrystalline silicon solar cells. The first one consists of a 5‐µm‐thick low‐pressure chemical vapor deposition (LPCVD)‐ZnO electrode combined with a white sheet; the second one incorporates an Ag reflector deposited on a thin LPCVD‐ZnO layer (with thickness below 200 nm). For this latter design, the optical loss in the nano‐rough Ag reflector can be strongly reduced by smoothing the surface of the thin underlying ZnO layer, by means of an Ar‐plasma treatment. Because of its superior lateral conductivity, the thin‐ZnO/Ag back reflector design provides a higher fill factor than the dielectric back reflector design. When decreasing the roughness of the front electrode with respect to our standard front LPCVD‐ZnO layer, the electrical cell performance is improved; in addition, the implementation of the thin‐ZnO/Ag back reflector leads to a significant relative gain in light trapping. Applying this newly optimized combination of front and back electrodes, the conversion efficiency is improved from 8.9% up to 9.4%, for cells with an active‐layer thickness of only 1.1 µm. We thereby highlight the necessity to optimize simultaneously the front and back electrodes. Copyright © 2014 John Wiley & Sons, Ltd.     

Design and Implementation of Super Wide Band Triple Band-Notched MIMO Antennas

Wireless Personal Communications - Semantic Web content extracting are the augmentation of the present web where the data is given in the better importance and allowing users to work close by close...     

Localized Ligand Induced Electroless Plating (LIEP) Process for the Fabrication of Copper Patterns Onto Flexible Polymer Substrates

The “ligand induced electroless plating (LIEP) process” is a simple process to obtain localized metal plating onto flexible polymers such as poly(ethylene terephtalate) and polyvinylidene fluoride sheets. This generic and cost‐effective process, efficient on any common polymer surface, is based on the covalent grafting by the GraftFast process of a thin chelating polymer film, such as poly(acrylic acid), which can complex copper ions. The entrapped copper ions are then chemically reduced in situ and the resulting Cu⁰ species act as a seed layer for the electroless copper growth which, thus, starts inside the host polymer. The present work focuses on the application of the LIEP process to the patterning of localized metallic tracks via two simple lithographic methods. The first is based on a standard photolithography process using a positive photoresist masking to prevent the covalent grafting of PAA in designated areas of the polymer substrate. In the second, the patterning is performed by direct printing of the mask with a commercial laser printer. In both cases, the mask was lifted off before the copper electroless plating step, which provides ecological benefits, since only the amount of copper necessary for the metallic patterning is used.     

Multiplexer model for RTL satisfiability using MILP

New approaches to the satisfiability problem (SAT) for register transfer level (RTL) designs combine arithmetic blocks with Boolean logic to form a mixed integer linear program (MILP). Two-to-one multiplexers with word-level inputs can be decomposed to logic gates, but it is more efficient to describe them in MILP constraints as arithmetic operators. Larger multiplexers are built using a multilevel selection tree. However, such an approach should be improved to optimise the overall efficiency in solving the SAT problem. Proposed is a new MILP model for multiplexers. Experimental results indicate a 50% decrease in the number of constraints and a reduction in MILP complexity from /spl Omega/(N/sup 2.4/) to /spl Omega/(N/sup 1.7/), measured in CPU time.     

Connectivity Based k-Hop Clustering in Wireless Networks

In this paper we describe several new clustering algorithms for nodes in a mobile ad hoc network. The main contribution is to generalize the cluster definition and formation algorithm so that a cluster contains all nodes that are at distance at most k hops from the clusterhead. We also describe algorithms for modifying cluster structure in the presence of topological changes. We also proposed an unified framework for most existing and new clustering algorithm where a properly defined weight at each node is the only difference in otherwise the same algorithm. This paper studied node connectivity and node ID as two particular weights, for k=1 and k=2. Finally, we propose a framework for generating random unit graphs with obstacles.     

Brain-computer interface in multimedia communication

This article raises various issues in the design of an efficient BCI system in multimedia applications. The main focus is on one specific modality, namely an electroencephalography (EEG)-based BCI. In doing so, we provide an overview of the most recent progress achieved in this field, with an emphasis on signal processing aspects.     

Design optimization and characterization of high-gain GaInP/GaAsHBT distributed amplifiers for high-bit-rate telecommunication

The design methodology, processing technology, and characterization of high-gain GaInP/GaAs heterojunction-bipolar-transistor-based distributed amplifiers are described in this paper. Distributed amplifiers with different active cells and number of stages have been compared for high-gain (>12 dB) and high-bandwidth (>25 GHz) performance. Based on the results, a three-stage attenuation-compensated distributed amplifier with a flat gain (S₂₁) of 12.7 dB over a bandwidth of 27.5 GHz was successfully fabricated and tested. Eye-diagram tests at 10 Gb/s show very open eye characteristics with no signal skewing. The amplifier achieves a minimum noise figure of 4 dB at 3 GHz and a sensitivity of -25 dBm for 10-Gb/s nonreturn-to-zero 2¹⁵-1 pseudorandom bit sequence with a bit error rate of 10^-9     

Cholesterol content and fatty acid composition of rhea meat

The influence of species and muscle on the intramuscular fat content, cholesterol content and fatty acid composition of Greater and Lesser Rhea meat were evaluated. Muscle has no influence (P>0.05) on any of these characteristics. Neither intramuscular fat (1.23%) nor cholesterol content (57 mg/100 g) differed (P>0.05) between species. Despite differences (P<0.05) in the percentage of individual fatty acids, total saturated fatty acids (33.1%) did not differ (P>0.05) between species, while total monounsaturated fatty acids (26.8 vs 32.2%) was lower (P<0.05) and total polyunsaturated fatty acids (39.7 vs 33.6%) higher (P<0.05) for Greater than Lesser Rhea.