Modelling of Non-Darcy Flows through Porous Media Using Extended Incompressible Smoothed Particle Hydrodynamics

In this article, a novel numerical method is presented for the simulation of non-Darcy flows through porous media by the incompressible smooth particle hydrodynamics (ISPH) method with a predictor-corrector scheme. In the ISPH algorithm, a semi-implicit velocity-correction procedure is used and the pressure is obtained by solving the pressure Poisson equation. The key point for the application to non-Darcy flows is to include porosity and drag forces of the medium (the Darcy term and the Forcheimer term) in the ISPH method. Unsteady lid-driven flow, natural convection in non-Darcy porous cavities, and natural convection at a porous medium–fluid interface are examined separately by our extended ISPH method. The results are presented with flow configurations, isotherms, and average Nusselt numbers for different Darcy numbers from 10^?4 to 10^?2, porosity values from 0.4 to 0.9, and Reynolds/Rayleigh numbers. The flow pattern and rate of heat transfer inside the cavity are affected by these parameters. The results demonstrate the important effect of the Darcy number on both the heat transfer rate and the flow regime. The results from this investigation are well validated and compare favorably with previously published results.     

Characteristics of Introduction of Fatty Acids into Gajutsu (Curcuma zedoaria Roscoe) and Teppǒ-yuri (Lilium longiflorum Thunb.) Starches

Starch granules, normally, contain naturally occurring lipids which are firmly embraced in starch granules and hardly extractable with Et₂O. In this paper, the characteristics of introduction of free fatty acids (FFAs) into Gajutsu (Curcuma zedoaria), Teppǒ-yuri (Lilium longiflorum) and potato starches, being very low in the above “embraced lipids” contents (9.2-25.6 mg%), were investigated. It was found that the saturated FFAs were more abundantly introduced into them (41.2-174.7 mg%) than the unsaturated ones (15.9-46.5 mg%), and the respective starches differed from one another in capacity of introducing each FFA. There was also found some characteristic changes in pasting feature after introduction of FFAs depending upon the respective starches. Furthermore, their Nägeli-amylodextrins were prepared as a model of their crystalline protion and were subjected to introduction of FFAs. On these results, a possible distributing diagram of the introduced FFAs in a granule of the respective starch was proposed.     

Machine parameters and performance of interior permanent magnet synchronous motors with different permanent magnet volume

Permanent magnet synchronous motors are widely used for several industrial applications. Some applications such as electric vehicles and compressor drives require a constant power operation. The operating limits and the constant power speed range deeply depend on the machine parameters. The relationships between the motor parameters and the operating performance have been theoretically examined. This paper examines the performances of the prototype synchronous motors, where the stator structure and the rotor structure of all motors are the same. The permanent magnets are inserted into the rotor slits and the volume of the permanent magnet is adjusted to control the magnet‐flux linkage. The effects of adding the magnet to the rotor on the machine parameters and the operating performance are examined based on the various experimental results. The prototype motor has flexibility as to speed versus power performance by adjusting the volume of the permanent magnet. The theoretical results with respect to the operating limits and the motor parameters are also confirmed experimentally. © 2000 Scripta Technica, Electr Eng Jpn, 131(4): 70–77, 2000     

Natural convection heat transfer in an anisotropic porous cavity heated from the side: Part 1. Theory

Natural convection heat transfer and flow structure in an anisotropic porous medium in a square cavity saturated with a Boussinesq fluid have been studied analytically and numerically. Based on an asymptotic analysis, three distinctive regimes are found depending on the magnitude of the permeability ratio K. In the vicinity of K = 1 the average Nusselt number and fluid velocity are scaled with (KRa) ^1/2 when either K or the Rayleigh number Ra is varied. In the limit of K → 0 the heat transfer across the cavity approaches the conductive state, and the convecting velocity, which is primarily in the vertical direction, is scaled with KRa. At the other end of the spectrum, namely, K → ∞, the average Nusselt number and the convecting velocity are scaled with Ra and independent of K. The asymptotic results are verified with two‐dimensional numerical calculations. The ranges of K of the respective regimes are also determined based on the numerical results. © 2000 Scripta Technica, Heat Trans Asian Res, 29(5): 373–384, 2000     

A control scheme for a three‐phase current source inverter in utility interactive photovoltaic system

A novel PWM control scheme for a three‐phase current source inverter of a photovoltaic (PV) generation system connected to a utility is proposed. The PV‐array output power can be adjusted by controlling the modulation factor in the proposed PWM pattern. The harmonic components of the output currents can be decreased sufficiently to satisfy the requirements of the Interactive Guidelines. Furthermore, a new Maximum Power Point Tracking control is proposed. The inverter output current should be detected, and the modulation factor may be controlled so as to obtain the maximum effective current. The inverter output power can be maintained at the maximum power point despite fluctuations of panel temperatures, insolation levels, and system voltages. © 2001 Scripta Technica, Electr Eng Jpn, 135(1): 43–55, 2001     

Morphology and electrical properties of short carbon fiber-filled polymer blends: High-density polyethylene/poly(methyl methacrylate)

Morphology and electrical properties of short carbon fiber-filled high-density polyethylene (HDPE)/poly(methyl methacrylate)(PMMA) polymer blends have been studied. The percolation threshold of HDPE50/PMMA50 blends filled with vapor-grown carbon fiber (VGCF), 1.25 phr VGCF content, is much lower than those of the individual polymers. The SEM micrographs verified that the enhancement of conductivity could be attributed to the selective location of VGCF in the HDPE phase. A double percolation is the basic requirement for the conductivity of the composites, i.e., the percolation of carbon fibers in the HDPE phase and the continuity of this phase in the blends, which hereby are defined as the first percolation and the second percolation, respectively. The SEM micrographs also showed that the short carbon fibers could affect the morphology of the blends. With the increase of VGCF content, the HDPE domains are elongated from spherical into strip shape, finally develop to a continuous structure. As a result, the second percolation threshold of the blends filled with 2.5 phr VGCF, 20 wt % HDPE, is lower than that of the blends filled with 1.5 phr VGCF, 30 wt % HDPE. The influence of molding temperature and time on the second percolation threshold has also been investigated. For the composites molded at a lower temperature, the second percolation threshold is shifted to a higher VGCF content, but there is little influence of molding time on the second percolation threshold. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1813–1819, 1998     

Theory of film condensation on shock-tube endwall behind reflected shock wave (Part II: Theoretical basis for determination of condensation coefficient)

This paper is concerned with the theoretical basis for the determination of the condensation coefficient of vapor by means of a shock tube. Film condensation on the shock-tube endwall behind a reflected shock wave is analyzed on the basis of the first author's gas-dynamics theory. It is clarified that there exists a transition phenomenon during the growth of a liquid film, that is, the liquid film grows in proportion to time immediately after the reflection of the shock wave, and after a transition time, it grows in proportion to the square root of time. The transition phenomenon between these growths is caused by the change in heat conduction characteristics at the endwall. The reason why the condensation coefficient must be determined before the transition is clarified. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res 25(3): 166–177, 1996     

Analysis of counter ions of cyanine dye in Langmuir–Blodgett films by PIXE

Langmuir–Blodgett (LB) films of 1-methyl-1^′-octadecylquinocyanine bromide, iodide and perchlorate were prepared from subphases containing NaClO₄, KBr and/or KI. Each sample consists of an arachidic cadmium layer and about 100 cyanine dye layers on a Si substrate. Anions incorporated into the film as counter ions from the subphase were analyzed by particle induced X-ray emission (PIXE) using a 2.5 MeV He²⁺ beam. It was found that the dissociation of the cationic dye molecule in the monolayer at the air/water interface leads to the substitution of counter anions of the dye molecules, and the subsequent incorporation of the counter anions in the LB films. Some of the dissociation constants of cyanine halide dyes were estimated.     

High Capacity Li2S–Li2O–LiI Positive Electrodes with Nanoscale Ion-Conduction Pathways for All-Solid-State Li/S Batteries

All-solid-state lithium–sulfur (Li/S) batteries are promising next-generation energy-storage devices owing to their high capacities and long cycle lives. The Li₂S active material used in the positive electrode has a high theoretical capacity; consequently, nanocomposites composed of Li₂S, solid electrolytes, and conductive carbon can be used to fabricate high-energy-density batteries. Moreover, the active material should be constructed with both micro- and nanoscale ion-conduction pathways to ensure high power. Herein, a Li₂S–Li₂O–LiI positive electrode is developed in which the active material is dispersed in an amorphous matrix. Li₂S–Li₂O–LiI exhibits high charge–discharge capacities and a high specific capacity of 998 mAh g⁻¹ at a 2 C rate and 25 °C. X-ray photoelectron spectroscopy, X-ray diffractometry, and transmission electron microscopy observation suggest that Li₂O–LiI provides nanoscale ion-conduction pathways during cycling that activate Li₂S and deliver large capacities; it also exhibits an appropriate onset oxidation voltage for high capacity. Furthermore, a cell with a high areal capacity of 10.6 mAh cm^–2 is demonstrated to successfully operate at 25 °C using a Li₂S–Li₂O–LiI positive electrode. This study represents a major step toward the commercialization of all-solid-state Li/S batteries.     

Fabrication and Training of 3D Conductive Polymer Networks for Neuromorphic Wetware

The human brain possesses an exceptional information processing capability owing to the 3D and dense network architecture of numerous neurons and synapses. Brain-inspired neuromorphic hardware can also benefit from 3D architectures, such as high integration of circuits and acquisition of highly complex dynamical systems. In this study, for future 3D neuromorphic engineering, 3D conductive polymer networks consisting of poly(3,4-ethylenedioxy-thiophene) doped with poly(styrene sulfonate) anions (PEDOT:PSS) are successfully and stably fabricated between multiple electrodes from scratch in precursor solution by electropolymerization. The networks efficiently emulate the 3D local connections between neighboring neurons observed in the cortex. This novel technology, which allows 3D conductive wiring only between desired electrodes, is unprecedented and has potential as an underlying technology for 3D integration. Furthermore, the experimental results also conclusively prove that conductance modification can be performed by manipulating the physical and chemical properties of 3D branch-wired conductive polymer wires, thus demonstrating for the first time the feasibility of neuromorphic wetware with enhanced biological plausibility in the subsequent post-Moore era.