Modeling of static concentrator modules incorporating lambertian or v-groove rear reflectors

Ray tracing modeling has been used to calculate the performance of static concentrator modules with a geometric concentration ratio of 2 and incorporating very narrow (1–2 mm), long and bifacial cells. The modules utilize either a v-groove or a lambertian rear reflector. It is shown that the use of very narrow cells allows a performance improvement of 5% or more compared to structures incorporating wider cells, in the case of v-groove reflectors. The averaged yearly performance for both types of reflectors is found to be rather similar, with expected light collection in the range 82–86% of that of a module with 100% cell coverage. Experimental measurements on modules with lambertian reflectors are shown to be in good agreement with the results of modeling.     

Limited-trial Chase decoding

Chase decoders permit flexible use of reliability information in algebraic decoding algorithms for error-correcting block codes of Hamming distance d. The least complex version of the original Chase algorithms uses roughly d/2 trials of a conventional binary decoder, after which the best decoding result is selected as the final output. On certain channels, this approach achieves asymptotically the same performance as maximum-likelihood (ML) decoding. In this correspondence, the performance of Chase-like decoders with even less trials is studied. Most strikingly, it turns out that asymptotically optimal performance can be achieved by a version which uses only about d/4 trials.     

Gallium gradients in Cu(In,Ga)Se2 thin‐film solar cells

The gallium gradient in Cu(In,Ga)Se₂ (CIGS) layers, which forms during the two industrially relevant deposition routes, the sequential and co‐evaporation processes, plays a key role in the device performance of CIGS thin‐film modules. In this contribution, we present a comprehensive study on the formation, nature, and consequences of gallium gradients in CIGS solar cells. The formation of gallium gradients is analyzed in real time during a rapid selenization process by in situ X‐ray measurements. In addition, the gallium grading of a CIGS layer grown with an in‐line co‐evaporation process is analyzed by means of depth profiling with mass spectrometry. This gallium gradient of a real solar cell served as input data for device simulations. Depth‐dependent occurrence of lateral inhomogeneities on the µm scale in CIGS deposited by the co‐evaporation process was investigated by highly spatially resolved luminescence measurements on etched CIGS samples, which revealed a dependence of the optical bandgap, the quasi‐Fermi level splitting, transition levels, and the vertical gallium gradient. Transmission electron microscopy analyses of CIGS cross‐sections point to a difference in gallium content in the near surface region of neighboring grains. Migration barriers for a copper‐vacancy‐mediated indium and gallium diffusion in CuInSe₂ and CuGaSe₂ were calculated using density functional theory. The migration barrier for the In_Cu antisite in CuGaSe₂ is significantly lower compared with the Ga_Cu antisite in CuInSe₂, which is in accordance with the experimentally observed Ga gradients in CIGS layers grown by co‐evaporation and selenization processes. Copyright © 2014 John Wiley & Sons, Ltd.     

Visualizing the electric grid

In the new world of competition, power traders, grid managers, public service boards, and the public itself all need to take in what's happening at a glance. Visualization software enables viewers to interpret the data more rapidly and more accurately than ever before. This kind of software will become still more useful, even indispensable, as electricity grids are integrated over ever-larger areas, as transmission and generation become competitive markets, and as transactions grow in number and complexity. Concepts like power flow, loop flow, and reactive power, which once mattered only to the engineers directly involved in grid operations, now must be made intuitive. This is because they must be communicated to public service commissions and the consumer-voters to whom such boards are answerable. In short, whether the client/user is a power marketer, a grid operator or manager, a public authority, or a member of the public, power system visualization tools can aid their comprehension by lifting the truly significant above background noise. Such tools can expedite decision-making for congestion management, power trading, market organization, and investment planning for the long term     

On the application of the Neuron MOS transistor principle formodern VLSI design

In this paper, the speed performance, power consumption, and layout area of Neuron MOS transistor circuits are monitored considering the requirements of modern VLSI design. The Neuron MOS transistor is a recently discovered device principle which has a number of input gates that couple capacitively to a floating gate. The floating gate potential controls the current of a transistor channel. This device can be used in logic circuits. A threshold current through the Neuron MOS transistor can be defined that causes a switching of the output of the logic circuits as soon as the channel current surmounts or falls below the specified value. We designed two different multiplier cells, one based on a Neuron MOS inverter, and the other on a Neuron MOS n-MOSFET which is used as one input device of a comparator circuit. Functionality of both cells is proven for data rates up to 50 MHz which represents the first high-speed measurement of a circuit based on this new design principle. A perspective for the upper speed limit found at more than 500 MHz is given by simulation. The new design principle has a layout area reduced by more than a factor of two compared to usual multiplier cells. Moreover, it is shown, that depending on the design chosen, high speed operation leads to considerable power savings. In view of those advantages it is concluded that the principle of threshold logic qualifies for a major breakthrough for packing density improvement of CMOS-based applications     

A new method for the calculation of the emission spectrum of DFBand DBR lasers

A method based on transmission matrices that allows the emission spectra of arbitrarily complicated semiconductor laser structures to be computed below and above threshold has been developed. These can include active and passive periodic or uniform sections. As examples, the authors compute the emission spectra of a normal distributed feedback (DFB) laser, a DFB laser with a λ/4 phase shifter, and a surface-emitting distributed Bragg reflector (DFB) laser. To do that, Petermann's method for calculating the spontaneous emission coupling coefficient has been extended to the case of a periodic waveguide. It is shown how the spontaneous emission, when treated correctly, can be used to measure the coupling coefficient of the grating in a DFB laser with a λ/4 phase shifter     

Carbohydrate content of apolipoprotein B-48 from rat chylomicrons of varying density

Monosaccharide composition was determined in apolipoprotein B-48 (apoB) of chylomicrons of rat mesenteric lymph. Chylomicrons were separated into three fractions based on density. Triglyceride and apolipoprotein content were determined in each. ApoB was isolated and quantified using precipitation with isopropanol. Chylomicrons were collected in lymph under normal conditions, and with Poloxalene 2930 when chylomicron secretion was inhibited. Most of the triglyceride was carried in the least dense fraction, while the highest apoB content was in the most dense fraction under normal conditions. Mannose and galactosamine contents of apoB were similar in all fractions while contents of both glucosamine and galactose were highest in the least dense fraction. When chylomicron secretion was inhibited by Poloxalene, the amount of triglyceride recovered in the least dense fraction was significantly reduced. Despite the inhibition of lipid transport in the least dense fraction of chylomicrons by Poloxalene, there was little change in apoB recoveries and in the relative content of various monosaccharides in the apoB from each of the three fractions as compared to results obtained during lipid absorption under normal conditions. In conclusion, carbohydrate composition of apoB of chylomicrons is heterogeneous and varies with chylomicron density.     

Performance analysis of partially coherent SSD systems

The performance analysis of a system employing co-ordinate interleaving and constellation rotation, over Nakagami-m fading channels, in the presence of phase noise as well as additive white Gaussian noise, is presented. An upper bound for the average probability of bit error for M-ary phase shift keying is derived. It is shown that the derived upper bound is tight for high signal-to-noise ratios and in the presence of phase noise the optimum rotation angle does not change. Furthermore, it is shown that a system employing co-ordinate interleaving and constellation rotation is more robust against phase estimation errors.     

Limits of the output power in Er3+:ZBLAN singlemodefibre lasers

The saturation of the 2.71 μm laser output has been measured in erbium-doped ZBLAN singlemode fibres with Er³⁺ concentrations of 1000, 5000 and 10000 ppm mol. Limits of the single-mode-laser output are discussed