Selective emitter using porous silicon for crystalline silicon solar cells

This study is devoted to the formation of high–low-level-doped selective emitter for crystalline silicon solar cells for photovoltaic application. We report here the formation of porous silicon under chemical reaction condition. The chemical mixture containing hydrofluoric and nitric acid, with de-ionized water, was used to make porous on the half of the silicon surface of size 125×125 cm. Porous and non-porous areas each share half of the whole silicon surface. H₃PO₄:methanol gives the best deposited layer with acceptable adherence and uniformity on the non-porous and porous areas of the silicon surface to get high- and low-level-doped regions. The volume concentration of H₃PO₄ does not exceed 10% of the total volume emulsion. Phosphoric acid was used as an n-type doping source to make emitter for silicon solar cells. The measured emitter sheet resistances at the high- and low-level-doped regions were 30–35 and 97–474 Ω/□ respectively. A simple process for low- and high-level doping has been achieved by forming porous and porous-free silicon surface, in this study, which could be applied for solar cells selective emitter doping.     

Chemical fixation of carbon dioxide to copolymers bearing cyclic carbonate group

This study is related to the investigation of the chemical fixation of carbon dioxide to copolymers bearing a cyclic carbonate group and their application to polymer blends. In the synthesis of (2-oxo-l,3-dioxolan4-yl) methyl vinyl ether (OVE) from glycidyl vinyl ether (GVE) and CO₂, quaternary ammonium salt catalysts showed good yield of OVE. The results with long alkyl chain and with lower accessibility showed a higher catalytic activity. Mixed catalyst of PEG-4000 and Nal showed higher catalytic activity than Nal alone. The copolymer of OVE and acrylonitrile (AN) was prepared by radical copolymerization in acetonitrile at 60 °C. The monomer reactivity ratios were given as r₁(OVE)=0.36 and r₂(AN)=1.21 in the copolymerization of OVE and AN. The films of poly(OVE-co-AN)/PVC blends were cast from DMF. The poly(OVE-co-AN)/PVC blends showed good miscibility over whole composition ranges.     

A trigonometric formulation of the LMS algorithm for realization on pipelined CORDIC

This paper presents an alternate formulation of the least mean square (LMS) algorithm by using a set of angle variables monotonically related to the filter coefficients. The algorithm updates the angles directly instead of the filter coefficients and relies on quantities that can be realized by simple CORDIC rotations. Two architectures based on pipelined CORDIC unit are proposed which achieve efficiency either in time or in area. Further simplifications result from extending the approach to the sign-sign LMS algorithm. An approximate convergence analysis of the proposed algorithm, along with simulation results showing its convergence characteristics are presented.     

Frequency assignment,multiple interference and binary constraints

The most accurate approaches to frequency assignment problems minimize a cost function based on signal-to-interference ratios at points where reception is required. The merits of this approach are counterbalanced by much greater requirements for computational resources than for the traditional approach using binary frequency separation constraints. This can make run times unrealistic for the largest problems. In this paper the merits of the signal-to-interference based cost function are confirmed, but it is shown that algorithms are faster and give better quality results if this cost function is combined with the binary constraint approach. Two types of algorithm are used to illustrate the combined approach, simulated annealing and a new ant colony system algorithm. The combined approach studied is applicable to all the main classes of frequency assignment problem. James Graham has B.Sc. and Ph.D. degrees in Computing Mathematics from the University of Glamorgan, UK. His Ph.D. thesis is entitled “Definition of a Common Formulation of Military Frequency Assignment Problems and the Application of Meta-Heuristic Algorithms”. Roberto Montemanni was born in Ravenna, Italy, in 1975. He received the “Laurea” degree in Computer Science from the University of Bologna, Italy, in 1999 and the Ph.D. in Mathematics from the University of Glamorgan, UK in 2002. Since November 2001 he has been a researcher at Istituto Dalle Molle di Studi sull’Intelligenza Artificiale (IDSIA), Lugano, Switzerland. His research activity covers optimization problems arising in radio frequency assignment, transportation and ad-hoc networks. Jim Moon is a Senior Lecturer in Software Engineering at the University of Glamorgan. He has a B.Sc. in Computer Studies and a Ph.D. in Multi-Agent Systems in Marine Simulation, both from the University of Glamorgan. He also qualified as a Master Mariner in an earlier career, at sea. His research interests include radio frequency assignment, software engineering, Multi-Agent Systems and marine simulation. Derek Smith is Professor of Mathematics at the University of Glamorgan, where he has worked since 1971. He has B.Sc. and Ph.D. degrees from the University of Southampton, UK and in October 2006 was awarded a D.Sc. degree from the University of Glamorgan, UK for his work on Combinatorial Mathematics applied to Radio Frequency Planning. His research interests include radio frequency assignment, graph theory, coding theory, data compression and network reliability studies.     

Cyclic redundancy check code based high-rate error-detection code for perpendicular recording

We present a particular generator polynomial for a cyclic redundancy check (CRC) code that can be used to detect all dominant error events in perpendicular recording over a broad range of densities. This polynomial is also effective in detecting error events that occur at codeword boundaries. The bit-error-rate and the sector-error-rate performances are validated that result from the use of the corresponding CRC code in conjunction with the well-known post-Viterbi error correction method.     

Approximate estimation of operational variables in fully thermally coupled distillation columns using pseudo-pinch points

An approximate procedure for the estimation of operational variables in fully thermally coupled distillation columns (FTCDCs) using two pseudo-pinch points of the feed and side draw trays is proposed, and its performance is examined with two example processes. The estimates from the proposed procedure show some 20% error compared with the results of rigorous simulation using commercial design software, the HYSYS. In addition, the relation between vapor flow rate and composition at one stage above the feed tray-required in the estimation of operational variables of the FTCDC-is analyzed to give information for the selection of the feed tray composition. A preliminary evaluation of operational variables helps to screen unrealizable design obtained often from iterative trial procedures employing the mathematical programming.     

Wire-suspended dynamical system: stability analysis by tension-closure

Based on the linear complementarity formulation of a unilaterally inextensible wire model, the behavior of motion and stability of wire-suspended dynamical systems is addressed in this paper. The concept of tension properness is developed to determine kinematical motion property, particularly the instantaneous degrees-of-freedom. Further, motion determinacy in spite of tension indeterminacy is proven. The notion of tension closure is described to help analyze the stability behavior of wire-suspended dynamical systems. By analyzing the maximal closure-domain of relative tension closure, one can assess the stability behavior of wire-suspended systems qualitatively as well as somewhat quantitatively. Some numerical examples and simulations will clarify and corroborate the theoretical results of this paper.