Research plan for divertor simulation making use of a large tandem mirror device

We are planning to start a study of divertor simulation under the closely resemble to actual fusion plasma environment making use of the advantage of open magnetic field configuration and to contribute the solution for realizing the divertor in ITER as a future research plan of Plasma Research Center of the University of Tsukuba. In the research plan, the concepts of two divertor devices are introduced. One has an axi-symmetric divertor configuration with the separatrix which is similar to toroidal divertor of torus systems and the other is a high heat flux divertor simulator by using an end-mirror exit of the existing tandem mirror device. Development of magnetic field configuration for ensuring the MHD stability is under way and a designed example is investigated under the optimal condition for plasma production. Consideration of plasma heating scheme using Fokker-Planck simulation code was successfully performed at both axi-symmetric divertor and end-mirror regions. Preparative experiments using calorimeter, Mach probe and high-speed camera have been started at the end-mirror region and the heat flux density of the level in 1-10 MW m⁻² was achieved in standard hot-ion mode plasma-confining experiments, which gives a clear prospect of generating the required heat flux density for divertor studies.     

Optimization of key factors affecting hydrogen production from food waste by anaerobic mixed cultures

Key factors (inoculums concentration, substrate concentration and citrate buffer concentration) affecting hydrogen yield (HY) and specific hydrogen production rate (SHPR) from food waste in batch fermentation by anaerobic mixed cultures were optimized using Response Surface Methodology with Central Composite Design. The experiments were conducted in 120 ml serum bottles with a working volume of 70 mL. Under the optimal condition of 2.30 g-VSS/L of inoculums concentration, 2.54 g-VS/L of substrate concentration, and 0.11 M of citrate buffer concentration, the predicted maximum HY and SHPR of 104.79 mL H₂/g-VS_added and 16.90 mL H₂/g-VSS.h, respectively, were obtained. Concentrations of inoculums, substrate and citrate buffer all had an individual effect on HY and SHPR (P < 0.05). The substrate concentration and citrate buffer concentration had the greatest interactive effect on SHPR (P = 0.0075) while their effects on HY (P = 0.0131) were profound. These results were reproduced in confirmation experiments under optimal conditions and generated an HY of 104.58 mL H₂/g-VS_added and an SHPR of 16.86 mL H₂/g-VSS.h. This was only 0.20% and 0.24%, respectively, different from the predicted values. Microbial community analysis by PCR-DGGE indicated that Clostridium was the pre-dominant hydrogen producer at the optimum and worst conditions. The presence of Lactobacillus sp. and Enterococcus sp. might be responsible for the low HY and SHPR at the worst condition.     

The effect of polyesterurethane belt surface roughness on Listeria monocytogenes biofilm formation and its cleaning efficiency

Contamination of surfaces in direct contact with food in the processing line is the major cause of finished product cross-contamination, especially conveyor belt surfaces that transfer food products. Polyesterurethane (PSU) is one of the materials widely used in conveyor belt systems; therefore, the objective of this study was to examine the effect of PSU conveyor belt surface roughness on the ability of biofilm formation by two strains of Listeria monocytogenes, i.e. ATCC19114 and ATCC51782. Additionally, the efficiency of a cleaning and sanitizing procedure adopted by a chicken meat plant in Thailand in eliminating biofilm formation on belt surfaces was assessed. The roughness values (Ra) were 0.05 ± 0.00 μm and 1.44 ± 0.01 μm for new (unused) and old conveyor belts (in use for 5 years), respectively. It was found that at 30 °C, both strains of L. monocytogenes formed robust biofilms regardless of differences in surface roughness. Conversely, at 15 °C, the ability of L. monocytogenes to form biofilms decreased with the lower Ra value. Under a simulated processing environment, cleaning and sanitizing reduced L. monocytogenes biofilms from both old and new conveyor belt surfaces to certain levels; however, a total reduction could not be achieved. In addition, more highly concentrated cleaning and sanitizing agents resulted in greater reduction. Results from this study clearly illustrate that surface roughness of material is also an important factor which may hinder effective cleaning and sanitizing. Therefore, the roughness value may be used as an indicator for evaluating the life of conveyor belts being used in the food industry.     

A method of identifying influential data in fuzzy clustering

In multivariate statistical methods, it is important to identify influential observations for a reasonable interpretation of the data structure. In this paper, we propose a method for identifying influential data in the fuzzy C-means (FCM) algorithm. To investigate such data, we consider a perturbation of the data points and evaluate the effect of a perturbation. As a perturbation, we consider two cases: one is the case in which the direction of a perturbation is specified and the other is the case in which the direction of a perturbation is not specified. By computing the change in the clustering result of FCM when given data points are slightly perturbed, we can look for data points that greatly affect the result. Also, we confirm an efficacy of the proposed method by numerical examples     

Properties of the solution set of a fuzzy relation equation from the viewpoint of attainability

 In a fuzzy relation equation, many properties of the solution set are known, especially when the basic spaces are all finite sets. However, when the basic spaces are infinite, only a few properties are known. In this paper, we introduce a new binary relation that is weaker than the ordinary one defined on fuzzy sets, and we show that an unattainable solution is partly characterized by the proposed binary relation.     

Computational analysis of water residence on ceramide and sphingomyelin bilayer membranes

Many physical chemical properties of lipid membranes, for example, the thickness, phase state, order parameter, and fluidity, can be understood straightforwardly. Water residence on a membrane is, however, an exception. To tackle this problem, we have performed molecular dynamics simulations of the distribution of water normal to the surface of several lipid membranes and from this deduced the associated water residence time. Our analysis of the results clearly indicates that lipid membranes have hydration shells on their surface, just as a solute in an aqueous solution does, and that the water residence time can be estimated from the potential for the mean force field derived from the distribution function of the water. We have done this atomic-scale analysis for ceramide bilayers and contrasted the calculation results with those for sphingomyelin bilayers, revealing that sphingomyelin bilayers can retain water molecules longer than ceramide bilayers and that the total number of water molecules retained on the membrane surface of sphingomyelin is larger than that for ceramide. In addition, we find that not only polar atoms of lipid molecules, such as oxygen, but also non-polar atoms, such as carbon, influence the motion of water on the membranes.     

Improvement of damping performance by splitting damping material

Damping materials in the carriage arm of a hard disk drive reduce flow-induced vibrations. As recording tracks become narrower, better damping is required. In this paper, a technique of splitting damping materials to improve the damping performance is described. We assumed a structural damping and examined the damping performance using the strain energy stored in a viscoelastic material. At first, we classified deformations of the viscoelastic material into three kinds: bending, shearing and thickness deformation (change in thickness). For the bending and the shearing deformation, we clarified that the splitting technique does not increase the strain energy. For the thickness deformation, we derived equations for the deformation shape and the strain energy. Then we found the splitting increases the strain energy if the parameter ϕ, which is proportional to the length and related to the stiffness of the damping material, is more than 5. Finally, we demonstrated the effectiveness of the splitting technique by numerical simulations and experiments.     

A MEMS electromagnetic optical scanner for a commercial confocal laser scanning microscope

A MEMS electromagnetic optical scanner for horizontal scanning of a commercial confocal laser scanning microscope has been developed. The purpose is to replace the currently used commercially available scanner with our new MEMS scanner in an existing microscope product, and therefore, the scanner specifications have to be compatible with those of the current one. Electromagnetic actuation is selected because of the millimeter-sized mirror, and a single crystal silicon hinge is used for realizing high-speed scanning with sufficient scan angle. In order to maintain mirror flatness for high quality optics requirement, the whole wafer thickness (300 /spl mu/m) is used as the mirror, resulting in a large moment of inertia, and this has been taken into consideration in the actuator design. Although few MEMS actuators have been commercialized to date, it has successfully satisfied all the specifications including not only the fundamentals such as resonant frequency and scan angle but also those for the commercial product such as scanning stability and reliability. It has been commercialized as a part of our product, Olympus OLS1100 (remodeled as OLS1200 in August 2002).     

Design-in-play: improving the variability of indoor pervasive games

Treasure is a pervasive game playing in the context of people’s daily living environments. Unlike previous pervasive games that are based on the predefined contents and proprietary devices, Treasure exploits the “design-in-play” concept to enhance the variability of a game in mixed-reality environments. Dynamic and personalized role design and allocation by players is enabled by exploring local smart objects as game props. The variability of the game is also enhanced by several other aspects, such as user-oriented context-aware action setting and playing environment redeployment. The effectiveness of the “design-in-play” concept is validated through a user study, where 15 subjects were recruited to play and author the trial game.     

On various eigen fuzzy sets and their application to image reconstruction

In this study, we formulate and solve a problem of image reconstruction using eigen fuzzy sets. Treating images as fuzzy relations, we propose two algorithms of generating eigen fuzzy sets that are used in the reconstruction process. The first one corresponds to a convex combination of eigen fuzzy set equations, i.e., fuzzy relational equations involving convex combination of max-min and min-max compositions. In the case of the first algorithm, various eigen fuzzy sets can be generated by changing the parameter controlling the convex combination of the corresponding equations. The second algorithm generates various eigen fuzzy sets with respect to the original fuzzy relation using a permutation matrix. A thorough comparison of the proposed algorithms and a conventional algorithm which reconstructs an image using the greatest and smallest eigen fuzzy sets is presented as well. In the experiments, 10,000 artificial images of size 5 × 5 pixels. The approximation error in the case of the first/second algorithm is decreased to 68.2%/97.9% of that of the conventional algorithm, respectively. Furthermore, through the experimentation using real images extracted from Standard Image DataBAse (SIDBA), it is confirmed that the approximation error of the first algorithm is decreased to 41.5% of that of the conventional one.