Simplified edge isolation of buried contact solar cells

The aim of this work is to implement simple edge isolation techniques in buried contact solar cell (BCSC) process by preserving the active cell area. Here we present results of two simplified edge isolation techniques for BCSC and they are compared with the standard process incorporating mechanical edge isolation using a dicing saw. The first technique is chemical wet etching of the solar cell's rear side in an inline system recently developed by University of Konstanz and Rena. The second technique is edge removal carried out in a fluoride/oxide radicals environment of a Asyntis plasma etcher. While the shunt resistance R_sh obtained with wet etching is between 1500 and 7000 Ω cm², the standard process shows R_sh values ranging from 2100–6300 Ω cm². The R_sh after plasma processing is between 1000 and 3600 Ω cm². These cell results show that both wet and plasma etching achieve results close to mechanical edge isolation.However, a slight reduction of short circuit current is observed for the cells undergone standard as well as plasma processing. This is due to the presence of floating volume shunts formed at the rear n–p⁺ junction, which are not removed by either the standard or plasma process. These shunts do not influence the IV-curve of the solar cells and are nearly invisible with conventional thermography, as they are not connected to the front side emitter grid. Hence, light-modulated lock-in thermography measurements were carried out to analyse these shunts.     

GTC Simulation of Ideal Ballooning Mode in Tokamak Plasmas

In the present paper,we first derive the eigenmode equation of the ideal ballooning mode in tokamak plasmas using a gyrokinetic equation.It is shown that the gyrokinetic eigenmode equation can be reduced to the magnetohydrodynamic(MHD) form in the long wavelength limit when kinetic effects are ignored.Then,the global gyrokinetic toroidal code(GTC) is applied for simulations of the edge-localized ideal ballooning modes.The obtained mode structures are compared with the results of ideal MHD simulations.The observed scaling of the linear growth rate with the toroidal mode number is consistent with the ideal MHD theory.The simulation results verify the GTC capability of simulating MHD processes in toroidal plasmas.     

A versatile approach to develop porous hydrogels with a regular pore distribution and investigation of their physicomechanical properties

Porous polyacrylamide (PAAm) hydrogels with enhanced mechanical properties and regular pore distribution have been synthesized by a unique and facile methodology, which involves formation of the hydrogel pores by leaching out chemically modified silica particles. To improve the pore distribution and mechanical properties of the hydrogel network, porogen particles have been modified with PAAm chains chemically attached to the silica surface. Grafting polymerization initiated by peroxide groups immobilized on the particle surface has been used for this modification. The grafted PAAm layer on the silica surface improves the dispersibility of the porogen material in the hydrogel composition, and simultaneously forms pore “walls” reinforcing the hydrogel network, after leaching out the silica particles. The proposed synthetic way for the development of porous hydrogels includes three steps: (i) tethering of PAAm chains to silica particles due to the grafting polymerization initiated by an adsorbed polyperoxide macroinitiator (PPM), (ii) simultaneous crosslinking of grafted PAAm chains and PAAm forming hydrogel network, and (iii) pore formation by leaching out silica particles in the presence of hydrofluoric acid. The PPM has been synthesized by a free radical copolymerization of the peroxide monomer (PM) N‐(tert‐butylperoxymethyl)acrylamide with acrylamide. Both PM and PPM have been developed in our lab, and applied for the synthesis of porous polymeric hydrogels. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Field-directed self-assembly with locking nanoparticles

A reversible locking mechanism is established for the generation of anisotropic nanostructures by a magnetic field pulse in liquid matrices by balancing the thermal energy, short-range attractive and long-range repulsive forces, and dipole-dipole interactions using a specially tailored polymer shell of nanoparticles. The locking mechanism is used to precisely regulate the dimensions of self-assembled magnetic nanoparticle chains and to generate and disintegrate three-dimensional (3D) nanostructured materials in solvents and polymers.     

Effect of hydrogen treatment on the discharge properties of electrodes made of ZrCrNi alloy

For metal-hydride electrodes based on ZrCrNi alloy, we have established an increase in their activation rate (two charge-discharge cycles) and discharge capacitance after homogenization of the Laves phase with a C14-type structure at the expense of treatment of the alloy by the method of partial disproportionation in hydrogen at 873 K and recombination in vacuum at 1223 K. The discharge capacitance decreases after disproportionation at 1083 K and recombination accompanied by the formation of the Laves phase with a C15-type structure. We have also determined the optimal milling conditions for this alloy in a planetary mill in hydrogen: rotational speed 100 rpm and milling time 30 min. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 6, pp. 49–54, November–December, 2005.     

Hydrogen as a working atmosphere for manufacturing permanent magnets based on rare-earth metals

The phase compositions and magnetic properties of permanents magnets of the systems Sm – Co and Nd – Fe – B are analyzed. Features of the hydrogenation–disproportionation–desorption–recombination (HDDR) process in the Nd₂ Fe₁₄ B intermetallic are considered. Using the Dd – Fe – B system as an example, we assess stages of manufacture of commercial permanent magnets and show the prospect of using hydrogen as a working atmosphere for the manufacture of magnetic powder. It is established that the HDDR of Dd – Fe – B alloys leads to their homogenization, grain refinement to a grain size of 0.2 to 0.5 μm, and an increase in the volume content of the main ferromagnetic phase Dd₂ Fe₁₄ B. By optimizing such a treatment, we managed to increase the magnetic energy (by 10%) and the lift force (by 25 – 27%) of Dd – Fe – B commercial permanent magnets.     

Modification of Wiley-Mclaren Tof Analyzers for Laser Desorption

ABSTRACT

Conversion of Wiley-McLaren type TOF instruments for laser desorption is described, including laser optics, timing circuitry, postacceleration detection for high mass and data acquisition. Results are shown to illustrate signal averaging capabilities, detection limits and high mass measurements.     

Structural integrity analysis of HDPE pipes for water supplying network

A problem of reliability of polymer pipes manufactured with the high‐density polyethylene (HDPE) for drinking water supply was considered. The safety of the pipelines network was analyzed with taking into account two main factors: arising of sudden overpressure (water hammer phenomenon) and presence of defects on pipe surface. Based on elastoplastic fracture mechanics and using of J‐integral approach, the numerical model of cracked pipe was developed and verified by direct experimental test. The formula for calculation of crack initiation pressure, which is the function of pipe size and size of external surface defect, was derived. The validity of this relation was proved for pipes of diameter 450 to 800 mm. It was also shown that the pressure peaks of the water hammer phenomenon are quickly damped because of the high deformability of the polyethylene pipes and the defect depth that is equivalent to 40% of pipe wall thickness can be considered as acceptable. The applicability of developed tools was demonstrated under analysis in the real state of South Tunisian water supply network.     

Optimizing Scalable Video Compression for Efficient Implementation on a VLIW Media Processor

State-of-the-art digital multimedia platforms contain a powerful very-long instruction word (VLIW) processing core. To obtain optimum performance on such a platform, a media-processing algorithm should exploit all the advantages provided by the VLIW processor's architecture. This paper focuses on a method for adapting a video compression algorithm for implementation on a VLIW processor using algorithm-architecture co-design. We demonstrate the importance of our adaptation approach and show the improved efficiency of the algorithm implementation