Effects of annealing on performance of InP solar cells on GaAs substrates

Effects of annealing on crystal structure and device characteristics of InP solar cells on GaAs substrates were studied. Two different methods, thermally cycled annealing during the growth, and rapid thermal annealing after the growth, were applied. The results obtained for the annealed solar cells were compared with those obtained for nonannealed and homoepitaxial solar cells. The dislocation density was significantly reduced by annealing from that of the non-annealed heteropitaxial solar cells, and most of the device characteristics were improved.     

A Comparision of the Number of Rational Places of Certain Function Fields to the Hasse-Weil Bounds

We give explicitly the number of rational places of certain function fields in terms of the reciprocals of the zeros of the function fields in question. The results are then compared with the Hasse-Weil bounds by using the approximation theorems of Dirichlet and Kronecker and it turns out that in many of these function fields the number of rational places is near the upper Hasse-Weil bound. Keywords:Function fields, Diophantine approximation, Exponential sums.     

A note on language equations involving morphisms

Language equations, ETOL systems, L systems     

BMC via on-the-fly determinization

This paper develops novel bounded model checking (BMC) techniques for asynchronous parallel systems. The aim is to increase the efficiency of BMC by exploiting the inherent concurrency in such systems. This added efficiency is gained by covering more reachable states within a given bound using two techniques. Firstly, a nonstandard execution model, step executions, where multiple actions can take place simultaneously is applied. Secondly, the number of executions the system can have is reduced by modeling the execution of the system components as if they were determinized. This determinization technique also enables the removal of the internal transitions of the components. Step executions can be further restricted to a subclass called process executions without losing any reachable states.The paper presents a translation scheme for BMC of reachability properties. The translation is from an asynchronous system where the components are modeled as labeled transition systems (LTSs) to a propositional formula. The models of the formula correspond to the step executions of the original system where each component is replaced with its determinized counterpart. The formula for step executions can be easily extended in such a way that its models correspond to the process executions of the system. The translation scheme has been implemented and some experimental comparisons performed. The results show that the bound needed to detect a violation of a reachability property is, for step and process executions, in most cases lower than in interleaving executions and that the running time of the model checker using process executions is smaller than of that using steps. Moreover, the performance compares favorably to a state-of-the-art interleaving BMC implementation in the NuSMV system.     

近于零污染排放的浆厂

１由于环境和经济两方面的原因，增强浆厂化学品封闭循环成为新千年的发展趋势。事实上，这意味着在纸浆生产中降低水的消耗，减少对大气的排放，最后也是最重要的一点，建设几乎无臭味的浆厂。此外，纸浆生产的原料来源也同样重要，造纸生产不应再消耗雨林和其他重要的原始森林。在澳大利亚新南威尔士的TumutVisyPaper正在建设由松木生产牛皮挂面纸的综合浆纸厂。该项目于２００１年年中完成。建成后，该厂每年将用８０万t的锯木厂边角料、松木、枝丫材以及５万t废纸生产２４万t的高质量牛皮挂面纸。本文是对新建项目的一个整体概述。文…     

Direct tomography with chemical-bond contrast

Three-dimensional (3D) X-ray imaging methods have advanced tremendously during recent years. Traditional tomography uses absorption as the contrast mechanism, but for many purposes its sensitivity is limited. The introduction of diffraction, small-angle scattering, refraction, and phase contrasts has increased the sensitivity, especially in materials composed of light elements (for example, carbon and oxygen). X-ray spectroscopy, in principle, offers information on element composition and chemical environment. However, its application in 3D imaging over macroscopic length scales has not been possible for light elements. Here we introduce a new hard-X-ray spectroscopic tomography with a unique sensitivity to light elements. In this method, dark-field section images are obtained directly without any reconstruction algorithms. We apply the method to acquire the 3D structure and map the chemical bonding in selected samples relevant to materials science. The novel aspects make this technique a powerful new imaging tool, with an inherent access to the molecular-level chemical environment.     

A carrier phase control suitable for conducted EMI noise reduction in a multiple‐converter system

The conducted EMI noise flowing from power converters to an AC utility line is regulated by international commissions such as the International Electrotechnical Commission (IEC). Adherence to the IEC regulations requires that EMI filters should be used in power electronics equipment. This paper proposes a method for analyzing conducted EMI noise in multiple power converters connected to the same power line. In this method, the phase difference between subharmonic modulated carrier signals at each power converter is taken into account. The phase difference among the power converters determines the EMI noise level in a multiple converter system, as is evident from the analysis of the waveform of the common mode current. In addition, EMI noise suppression using carrier phase control is proposed. In order to reduce the size of the EMI filter effectively, the phase difference θ should be set to 360/nN°, where n is a high‐order harmonic component near 150 kHz and N is the number of power converters. Therefore, the conducted EMI noise can be reduced effectively with the help of the proposed phase control. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(3): 56–66, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21305     

Vacuum extraction based response equipment for recovery of fresh fuel spills from soil

Accidental overturns of fuel tankers can have, depending on soil types, severe consequences. This applies, particularly in areas of shallow soils where the groundwater is located 2-4m below the ground surface. By rapid, vacuum extraction based recovery emergency services, which would normally be the first to arrive on the scene, could minimize consequences of fresh fuel spills and even prevent groundwater contamination, the primary purpose of emergency response. Powerful vacuum extraction-based response (PER), equipment has been developed to recover freshly spilt volatile fuels from the soil, primary by emergency services, but also by other trained responders. The main components of mobile PER-equipment are perforated extraction pipes, a recovery vacuum tank, a vacuum pump and an incinerator. The PER-equipment has been tested in summer and sub-zero winter conditions, and in both cases 50-80% of fresh gasoline spilled into sandy soil was recovered during the first 2h of operation. Gasoline was recovered in both liquid and vapor form, and hydrocarbon vapors were destroyed by controlled incineration at a safe distance from the spill. Recovery of less volatile diesel oil is not so effective from the sandy soil, but about 30% of it could be pumped from a fresh pool directly after a seepage time of 15 min.     

An efficient swap algorithm for the lattice Boltzmann method

During the last decade, the lattice-Boltzmann method (LBM) as a valuable tool in computational fluid dynamics has been increasingly acknowledged. The widespread application of LBM is partly due to the simplicity of its coding. The most well-known algorithms for the implementation of the standard lattice-Boltzmann equation (LBE) are the two-lattice and two-step algorithms. However, implementations of the two-lattice or the two-step algorithm suffer from high memory consumption or poor computational performance, respectively. Ultimately, the computing resources available decide which of the two disadvantages is more critical. Here we introduce a new algorithm, called the swap algorithm, for the implementation of LBE. Simulation results demonstrate that implementations based on the swap algorithm can achieve high computational performance and have very low memory consumption. Furthermore, we show how the performance of its implementations can be further improved by code optimization.