Dynamic simulation of rod-like and plate-like particle dispersed systems

A particle simulation method (PSM) is presented to simulate the dynamics of rod-like and plate-like particle dispersed systems. In this method, the particle is modeled with arrays of spheres connected by three types of springs. The motion of particles in flow is followed by solving the translational and rotational equations of motion for each constituent sphere. The mobility matrix for each particle is calculated to obtain the hydrodynamic force and torque exerted on each sphere. For the hydrodynamic interaction among particles, the near-field lubrication force is considered. The method was applied to the simulation of the transient behavior of particles in a shear flow by dispersing them into a cell with periodic boundaries. In semi-dilute to concentrated systems, the overshoot of viscosity was observed for rigid rod-like particle dispersed systems, but not for flexible ones. This was due to the transient change of the microstructure from the flow-directional orientation to the planar one of particles. The normal stress appeared in the flexible particle dispersed systems because of the deformation of particles. In the rectangular plate-like particle dispersed system, the planar orientation of particles was observed and furthermore the orientation of the major axis of particles in the shear direction appeared.     

Evolution of cooperative behavior among heterogeneous agents with different strategy representations in an iterated prisoner’s dilemma game

The iterated prisoner’s dilemma (IPD) game has frequently been used to examine the evolution of cooperative behavior among agents. When the effect of representation schemes of IPD game strategies was examined, the same representation scheme was usually assigned to all agents. That is, in the literature, a population of homogeneous agents was usually used in computational experiments. In this article, we focus on a slightly different situation where every agent does not necessarily use the same representation scheme. That is, a population can be a mixture of heterogeneous agents with different representation schemes. In computational experiments, we used binary strings of different lengths (i.e., three-bit and five-bit strings) to represent IPD game strategies. We examined the evolution of cooperative behavior among heterogeneous agents in comparison with the case of homogeneous ones for the standard IPD game with typical payoff values of 0, 1, 3, and 5. Experimental results showed that the evolution of cooperative behavior was slowed down by the use of heterogeneous agents. It was also demonstrated that a faster evolution of cooperative behavior is achieved among majority agents than among minority ones in a heterogeneous population.     

Device design guidelines for FC-SGT DRAM cells with high soft-error immunity

This paper describes the device design guidelines for floating channel type surrounding gate transistor (FC-SGT) DRAM cells with high soft-error immunity. One FC-SGT DRAM cell consists of an FC-SGT and a three-dimensional storage capacitor. The cell itself arranges the bit line (BL), storage node, and body region in a silicon pillar vertically and hence, achieves a cell area of 4F/sup 2/ (F: feature size) per bit. A thin-pillar FC-SGT with a metal gate can maintain a low leakage current without using a heavy doping concentration in the body region. Furthermore, as the silicon pillar thickness is reduced, the device enters into the fully depleted operation and as a result can realize excellent switching characteristics. In FC-SGT DRAM cells, the parasitic bipolar current is a major factor that causes soft errors to occur. However, the parasitic bipolar current can be suppressed and its duration can be shortened as the silicon pillar thickness is reduced. As a result, the amount of stored charge lost in the storage capacitor can be effectively decreased by using a thin-pillar FC-SGT. In the case of a 10-nm-thick FC-SGT, the amount lost due to the parasitic bipolar current is decreased to about 28% of that due to the leakage current. Therefore, FC-SGT DRAM is a promising candidate for future nanometer high-density DRAMs having high soft-error immunity.     

Identification of a Molecular Target of a Novel Fungal Metabolite,Pyrrolizilactone, by Phenotypic Profiling Systems

In the course of screening our microbial metabolite fraction library, we identified a novel pyrrolizidinone compound, pyrrolizilactone. In this study, we report the identification and characterization of a molecular target for pyrrolizilactone by using two phenotypic profiling systems. Cell morphology‐based profiling analysis using an imaging cytometer (MorphoBase) classified pyrrolizilactone as a proteasome inhibitor. Consistently, proteome‐based profiling analysis using 2D difference gel electrophoresis (DIGE; ChemProteoBase) also demonstrated that pyrrolizilactone is associated with proteasome inhibition. On the basis of these predictions, we determined that pyrrolizilactone is a novel type of proteasome inhibitor inhibiting the trypsin‐like activity of the proteasome.     

Structural characterization and electrochemical properties of non-graphitizable carbons for a lithium ion battery

Structural characteristics and electrochemical properties of non-graphitizable carbons were investigated. The carbons were obtained by heat-treating the oxidized graphitizable carbon precursors with various molar ratios of aromatic compounds and cross-linking agent. The discharge profiles of the non-graphitizable carbons heat-treated at 600°C had one plateau discharge region at 1.0 V vs. Li/Li⁺, which is similar to graphitizable ones heat-treated at the temperature. However, the discharge profiles of the non-graphitizable carbons heat-treated above 800°C exhibited two plateau discharge regions at 0.2 and 1.0 V vs. Li/Li⁺. The discharge capacities of the non-graphitizable carbons increased with an increase of cavity volume, which was controlled by molar ratios of aromatic compound and cross-linking agent. The structural parameters proposed were measured to compare with each other, and it was found that they showed good correlation.     

Nonstationary hot wire method with silica-coated probe for measuring thermal conductivities of molten metals

The nonstationary hot wire method with a silica-coated probe has been developed to measure thermal conductivities of molten metals at high temperatures. Measurements were carried out on mercury and lead as test liquids. The thermal conductivities of liquid mercury ranged between 7.6 and 8.1 W/m K at temperatures between 273 and 293 K, and those of molten lead displayed constant values of about 15 W/m K at temperatures between 673 and 973 K. Factors affecting the thermal conductivity measurement using this method have been discussed. It has been concluded that the nonstationary hot wire method with an insulator-coated probe can be applied to various molten metals, as long as materials for probe coating are pertinent.     

Noninvasive online measurement of particle size and concentration in liquid–particle mixture by estimating equivalent circuit of electrical double layer

ABSTRACT

Three electrical elements (i.e., resistance, capacitance, and relaxation frequency) of electrical double layer (EDL) formed around particles have been extracted by a measuring–fitting combination for a novel noninvasive online measurement technique of particle size and concentration in a liquid–particle mixture. The measuring–fitting combination means measuring the impedances with electrical-impedance spectroscopy (EIS) method, and fitting the equivalent circuit with Levenberg–Marquardt method. The liquid–particle mixture in the impedance measurement is made of sodium chloride solution and stainless particles; the equivalent circuit is established corresponding to the contents in the liquid–particle mixture. As a result, the influence of the particle size and concentration on the electrical elements in the EDL which are the resistance, capacitance, and relaxation frequency in the EDL are clarified and discussed. This method is useful for determination of the particle size and concentration in liquid–particle mixture.     

Consultation system with contact person through on‐demand calling of a proper expert for a problem

Local branches of financial institutions offer to their customers a wide spectrum of advisory services which must be upgraded from time to time to keep up with changes in the mix of financial products offered and with the growing sophistication of the customers' inquiries. However, keeping the full staff of experts trained in various aspects of banking business is not practical from the standpoint of cost‐effectiveness, while without them it is difficult to provide high‐quality services. In this paper we propose a window consultation system for customers at the branch office using the on‐demand calling of an expert specializing in the subject related to the inquiry. The proposed system is based on the multimedia network technology and it has two main functions: selection of an on‐line expert and tele‐consultation providing the replies or expert advises to the inquiries. A customer visiting his branch office is interviewed by a clerk who determines the contents of the request and, if he is unable to give the customer satisfactory advice, contacts through the proposed system an appropriate expert. This system makes it possible to provide high‐quality services and to avoid mistakes, which can be made by customers if they operate the consultation systems on their own. The proposed system has a three‐layered structure: application component layer, middleware component layer, and fundamental component layer. This structure allows for an easy installation and modifications depending on the scale of specific branch offices of financial institutions and the mix of financial products offered by them. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(2): 57–66, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20518     

Hydrogen production by catalytic near-critical water gasification and steam reforming of glucose

Near-critical water gasification (NCWG) and steam reforming (SR) were investigated for the production of hydrogen from a biomass model compound (glucose) using fixed bed tubular reactor. Ruthenium/carbon and nickel/yttria stabilized zirconia (YSZ) were utilized to enhance the reaction rates of the two processes for NCWG and SR, respectively. NCWG experiments were performed at 200 bar and 360–450 °C, while SR experiments were conducted at 500–800 °C and atmospheric pressure. Although in both cases complete carbon gasification is achieved, gas composition, hydrogen selectivity and overall energy efficiency show strong dependencies on the type of process itself and the associated operating conditions. It is shown that operating the reforming reaction of glucose at high pressures and low temperatures (NCWG) results in a significant amount of methane and trace amounts of carbon monoxide. In contrast, gasification of glucose at atmospheric pressures and high temperatures (SR) leads to a methane-free gas stream that contains few percents of carbon monoxide. Considering energy recovery and neglecting the heat losses, the maximum cold gas efficiency of the NCWG and SR reached 78% and 91%, respectively. The features of the two catalytic reaction processes are discussed in terms of the experiments and process simulations.     

Characterization of simple and reproducible vascular stenosis model in hypercholesterolemic hamsters

The importance of low-density lipoprotein (LDL) in the etiology of atherosclerosis is well recognized. We have established a reproducible stenosis model in hypercholesterolemic hamsters, and the process of arterial stenosis by thrombus or neointima was studied and compared with that in normal hamsters. The level of plasma LDL was 4.6 times higher in hamsters fed a high-cholesterol diet than in hamsters fed normal food. Endothelial injury in right common carotid arteries was induced using a modified catheter. Arterial blood flow was monitored continuously using a Doppler flow probe. Arterial patency after the initiation of injury in high-cholesterol hamsters was significantly changed as compared with that of normal hamsters. Neointima was observed 2 wk after the vascular injury. The neointimal area of high-cholesterol hamsters was significantly larger than that of normal hamsters. To characterize the stenosis in hypercholesterolemic hamsters, we measured platelet aggregation, thrombin time, activated partial thromboplastin time, and proliferating smooth muscle cells (SMC) in vitro and in vivo. The half-maximal inhibitory concentration value for platelet aggregation induced by thrombin or collagen, the DNA synthesis stimulated by plateletderived growth factor (PDGF)-BB, and 5-bromo-2-deoxy-uridine labeling indices (proliferating index of SMC in vivo) in high-cholesterol hamsters were each significantly higher than the comparable value from normal hamsters. However, specific binding of PDGF-BB in SMC was not different between the two types of hamsters. Furthermore, we investigated the inhibitory effects of probucol or losartan on neointima formation using this model. Probucol, but not losartan, significantly reduced the neointimal area in hypercholesterolemic hamsters. These findings indicated that high levels of plasma LDL strongly contributed to the development of thrombus and neointima formation via both up-regulation of platelet aggregation and the enhancement of SMC proliferation. This stenosis model may be useful for the investigation of hypercholesterolemia-associated cardiovascular diseases.