A genetic algorithm for the optimal sequential partitioning problem

The optimal sequential problem is defined as the problem of finding the minimum cost partition of the nodes of a directed acyclic graph into subsets of a given size, subject to the constraint that the precedence relationships among the elements are satisfied. A heuristic algorithm based on tabu search has been proposed for this problem [2]. However, there is a tendency for the solutions obtained by tabu search to become trapped in bad local optima in parallel graphs with random edge costs. In this paper we present a genetic algorithm for the optimal sequential partitioning problem. We develop an effective two‐point partial order crossover satisfying sequential conditions, which preserve better blocks that have a larger sum of edge costs. In this crossover we introduce the roulette selection method to escape local optima. We also assess the effectiveness of the algorithm. The results show that this proposed algorithm outperforms any other algorithm using tabu search in terms of solution quality. © 2001 Scripta Technica, Electr Eng Jpn, 135(4): 43–51, 2001     

Back surface reflectors with periodic textures fabricated by self-ordering process for light trapping in thin-film microcrystalline silicon solar cells

Back surface reflectors (BSRs) with grating structures have been developed to enhance light trapping in thin-film hydrogenated microcrystalline Si (μc-Si:H) solar cells. As a grating structure, a periodic honeycomb-like dimple pattern with a period of ～450 nm has been fabricated on Al substrates by a self-ordering process using anodic oxidation of Al. The clear diffraction effect has been confirmed on the patterned Al from the angle-dependent reflection. From quantum efficiency measurements, we found that the periodically patterned BSR can confine the incident light more effectively than the random textured BSR, especially at longer wavelengths.     

INTERFACIAL ADSORPTION OF 2-HYDROXY-5-NONYLBENZOPHENONE OXIME IN STATIC AND VIGOROUSLY STIRRED DISTRIBUTION SYSTEMS

ABSTRACT

The interfacial adsorption of 2-hydroxy-5-nonylbenzo-phenone oxime (LIX65N) at a n-heptane/water interphase was examined under static and vigorously stirred conditions, varying the aqueous pH from 2 to 12. In static systems, the pH and the concentration dependences of the interfacial tension were analysed on the basis of the Gibbs equation. The acid dissociation equilibrium at the interface was evaluated. In vigorously stirred systems, the interfacial adsorption was observed as a reversible, reproducible decrease of the organic phase concentration in response to stirring. A Langmuir isotherm was applicable for the adsorption of neutral LIX65N in acidic condition. The greater adsorption of the anionic form of LIX65N occurring in alkaline condition required an alternative isotherm.     

An electrochemical ionic liquid membrane reactor for NO x selective separation under excess oxygen conditions

A novel electrochemical ionic liquid membrane reactor capable of separating NO from a mixture of NO and oxygen with high current efficiency at low temperatures was designed and tested. This reactor consists of a combination of an ionic liquid and a thin film of anodised alumina with two platinum electrodes. During operation of the reactor, NO is electrically transported from the cathode side to the anode side.     

Performances of metal fluoride added carbon anodes with pre-electrolysis for electrolytic synthesis of NF3

Metal fluoride added carbon anodes treated by pre-electrolysis were investigated for electrolytic production of nitrogen trifluoride (NF₃) in molten NH₄F·KF·4HF at 100 °C. The conditions for pre-electrolysis were first optimized using a graphite sheet anode as a model anode. The formation of fluorine-graphite intercalation compounds (fluorine-GICs) with semi-covalent C–F bonds, (C_xF)_n, on the MgF₂ and CaF₂ added carbon anode surface was accelerated by pre-electrolysis at potentials less than 4.0 V. Critical current densities (CCD) on the MgF₂ added carbon anodes pre-electrolyzed under various conditions were determined, and the highest CCD was 290 mA cm⁻² obtained for that pre-electrolyzed at 3.5 V for 500 C cm⁻². This anode was successfully used in the electrolysis at 100 mA cm⁻² for 290 h and the maximum NF₃ current efficiency was 55%. From these results, it was concluded that the metal fluoride added carbon anode treated by pre-electrolysis has a high potential for electrolytic production of NF₃ at higher current density.     

Thermotropic and Barotropic Phase Behavior of Phosphatidylcholine Bilayers

Bilayers formed by phospholipids are frequently used as model biological membranes in various life science studies. A characteristic feature of phospholipid bilayers is to undergo a structural change called a phase transition in response to environmental changes of their surroundings. In this review, we focus our attention on phase transitions of some major phospholipids contained in biological membranes, phosphatidylcholines (PCs), depending on temperature and pressure. Bilayers of dipalmitoylphosphatidylcholine (DPPC), which is the most representative lipid in model membrane studies, will first be explained. Then, the bilayer phase behavior of various kinds of PCs with different molecular structures is revealed from the temperature–pressure phase diagrams, and the difference in phase stability among these PC bilayers is discussed in connection with the molecular structure of the PC molecules. Furthermore, the solvent effect on the phase behavior is also described briefly.     

A Comparison Between Machine Flexibility and Routing Flexibility

In this paper, we evaluate two types of flexibility, machine flexibility and routing flexibility, in terms of manufacturing performance in various shop environments. A simulation-based investigation was conducted to analyze the impact of these types of flexibility on the average flow time of parts under various job flow pattern conditions, which characterize the shop nature from a random job shop to a flow shop, operation time variance, setup time, and shop load. The experimental results show how these types of flexibility affect the average flow time of parts and which type is superior under what conditions. Management can obtain better insight and guidelines for determining priorities or the scale, or scope, of various decision items relating to design standardization, process and operations improvement, investment in new equipment and tools, and the like.     

Micro-/nanostructural investigation of laser-cut surfaces of single- and polycrystalline diamonds

Micrometer- to nanometer-scale structures of the cut surfaces of single- and polycrystalline diamonds by a pulsed ultraviolet laser have been thoroughly investigated by scanning and transmission electron microscopy. Within the laser-cut grooves, the processed diamond surfaces are extensively covered with laser-modified debris which consists of complex layered units of graphite with various crystallinities. The units consist of 1) highly oriented graphite, 2) corrugated graphite, and 3) nanocrystalline graphite, which are sequentially located from the surface of the underlying diamond substrate to the center of the grooves. Detailed textural examinations revealed that the highly oriented graphite unit is a product of the initial graphitization of diamond by a solid-state diffusion process, whereas the latter two units are deposition products from the liquid and/or vapor phases of carbon in the later stage. The present study demonstrates that the laser-cutting of diamonds proceeds in a two-step process: 1) extensive graphitization of laser-scanning path and 2) subsequent sublimation of the pre-formed graphite. These processes are basically identical among the three different types of diamonds (single crystal type Ib, single crystal type IIa and nano-polycrystalline aggregate) tested in this study.     

Creating educational Web sites

This article deals with the issue of educators creating their own educational Web sites equipped with original Web-based teaching materials developed by themselves. As an illustrative example, teaching of English as a foreign language in Japan is taken. Several concrete ideas in building up educational Web sites are illustrated, including an example of Web-based rapid reading exercise pages, an example of Web pages implementing instant feedback to students' quiz responses, and semi-automatic creation of students' study history files using standard commercially available software. Introduction of the next-generation Web server, developed at Graz University of Technology, for effective document management and organized access rights control is also discussed     

Molecular screening of both the promoter and the protein coding regions in the human ob gene in Japanese obese subjects with non-insulin-dependent diabetes mellitus

OBJECTIVE: Although the molecular mechanism of obesity has been poorly understood, recent studies indicate that leptin plays a critical role in regulating both food intake and body weight. Because obesity decreases the sensitivity to insulin, the human ob gene is presumed to be one of the candidate genes for non-insulin-dependent diabetes mellitus (NIDDM) associated with obesity. Although the protein coding region in the ob gene has been screened for mutations, the promoter region and the non-coding first exon have not yet been studied. We investigated the involvement of the human ob gene, especially mutations at the promoter region and the non-coding first exon, in the development of NIDDM associated with obesity. SUBJECTS: The study group comprised 60 Japanese obese subjects with NIDDM (body mass index (BMI) 43.6 > or = BMI > or = 26.4, 29.0+/-0.41 (mean+/-S.E.M.)) and 24 obese individuals with impaired glucose tolerance (IGT) (30 > or = BMI > or = 26.4, 27.1+/-0.22). METHODS: Mutations at both the promoter region and all three exons in the human ob gene were screened by the single-stranded conformational polymorphism analysis. When aberrantly migrated bands were recognized, the PCR-amplified DNA fragment was directly sequenced. RESULTS: In the protein coding region a silent mutation in the second exon was detected. The non-coding first exon and the about 100 bp 5'-flanking region of the gene which contains a proximal CCAAT/enhancer-binding protein site were screened, but no mutations were found. CONCLUSION: These results suggest that no mutations in either the promoter region at the about 100 bp 5'-flanking region of the gene, or in any of the three exons, are involved in the development of NIDDM or IGT associated with obesity.