Numerical simulation of blow‐down closed‐cycle disk MHD generator

Numerical simulations of the closed‐cycle disk MHD generation experiment with Tokyo Institute of Technology's Fuji‐1 blow‐down facility are performed. In the calculations, the r–z two‐dimensional time‐dependent simulation code developed by the authors that can take the effect of water contamination into account is used, and the experimental conditions of Run A4109 operated by Disk‐F4 generator are selected as the numerical conditions. When the water contamination is the lowest level realized in the experiments, the simulation results coincide with the experimental results reasonably well, though there exist some discrepancies caused by inaccuracy of used basic plasma parameters, limitations of the two‐dimensional approximation, and so on. The voltage–current curve is almost linear, indicating that the MHD interaction is relatively weak and the flow field is mainly determined by the back‐pressure. The increase of the water contamination level results in decreased seed ionization rate at the generator channel inlet, leading to the steep deterioration of the generator performance. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(2): 46–54, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10335     

Aligning vapor-grown carbon fibers in polydimethylsiloxane using dc electric or magnetic field

A trace amount of vapor-grown carbon fibers (VGCFs), which, as received, had an aggregated lump form, was completely dispersed in polydimethylsiloxane, a nonpolar viscous liquid, at room temperature by mechanical stirring. Using this uniformly dispersed sample as a starting material, a dc electric or magnetic field was applied to induce the formation of an aligned structure. In situ transmission optical microscopy was carried out to observe the structural development of VGCFs in polydimethylsiloxane under the dc electric or magnetic field, which was applied both parallel and perpendicular to the observation direction. Upon application of a dc electric field, an aligned ramified network structure of VGCFs developed between the electrodes. In the formation of the network structure, ends of VGCFs became connected to ends of other VGCFs, which was followed by rotation and orientation of the VCGFs. On the other hand, upon application of a magnetic field, the VGCFs were only rotated, without the formation of a network. The electric resistivity of the network structure was evaluated. Additionally, the influence of the viscosity of the polydimethylsiloxane matrix on the structural formation process was examined.     

Monotonic and Cyclic Behavior of Unsaturated Sandy Soil Under Drained and Fully Undrained Conditions

Changes in air pressure during monotonic and cyclic loading are in some cases important for the behavior of unsaturated soil. For example, in order to investigate the stability of embankments and slope failure during earthquakes, it is necessary to consider the effect of the pore air or the pore gas pressure as well as the pore water pressure and the interaction between the soil and the pore fluids. In the present study, we carried out a series of monotonic and cyclic loading tests on sandy soil used for the improvement of river embankments. The effects of the initial suction, the confining pressure, and the degree of compaction under fully undrained conditions, namely, constant water and constant air shearing tests, as well as under drained conditions for both air and water, were studied. For the stress variables of the unsaturated soil, the skeleton stress was used to describe the experimental results and was defined as the difference between the total stress tensor and the average pore pressure of water and gas (Oka et al., 2010). From the monotonic and cyclic test results, we found that the stress-strain behavior of unsaturated sandy soil strongly depends on the initial suction, especially under fully undrained conditions, due to the difference in pore pressures. In the cyclic loading tests under fully undrained conditions, the mean skeleton stress decreased due to the increase in air pressure and led to the failure of the specimen in the case of a lower level of initial suction. In addition, the test results exhibited the strain rate effect on the stress-strain behavior during cyclic loading under fully undrained conditions.     

Organization of gold nanorods on a substrate using a strong magnetic field

The effects of magnetic processing on the organization of gold nanorods (AuNRs)/poly(styrenesulfonate) (PSS) composites using a strong magnetic field were examined by absorption spectra corresponding to surface plasmon on a glass plate and TEM images. The results in the absorption spectra and the TEM images showed that the side-to-side aggregation of AuNRs/PSS composites formed in the presence of a magnetic field directed horizontally to the surface of the sample. In the absence of the magnetic field, side-to-side AuNRs/PSS aggregates were not observed. The effects of magnetic processing are attributed to the induced magnetic dipoles of the AuNRs.     

Thermal uniformity and rapid cooling inside refrigerators

The authors developed a new air-supply system for improving the thermal uniformity and the cooling rate inside a fresh food cabinet of a household refrigerator. For these purposes, we added a blower and jet slots to a conventional cooled air supply system. The jet slots circulate the air inside the cabinet at a higher velocity to optimize airflow velocity and its distribution. The jet stirs the air inside the cabinet and improves thermal uniformity, which resulted in half the temperature deviation in the cabinet as that of the conventional systems. The jet also improves the heat transfer on the surface of foods. We achieved a four times higher cooling rate with the new system than that with the conventional ones. In order to cut down the development period, we applied computational fluid dynamics to study air distribution inside the cabinet with the new system. We also derived the model of the cooling process by the jet using theoretical and empirical equations and applied it to decide the jet velocity for the rapid cooling.     

Preparation of aluminium hydroxide by reacting sodium aluminate solutions with mineral acid

The preparation of aluminium hydroxide from sodium aluminate solutions by varying the alkaline concentration at a fixed molar ratio of Na₂O: Al₂O₃ has been investigated on addition of hydrochloric or nitric acids. The resulting materials have been examined by X-ray diffraction study, infrared spectrophotometry, thermogravimetrical and differential analyses. As a result, it was found that precipitates generally exist as pseudoboehmite or bayerite, but the formation of bayerite is enhanced by a low rate of addition of acid, higher temperature or higher alkaline concentration. In this case, the composition of the precipitates was little influenced at different molar ratios of Na₂O: Al₂O₃. When the precipitates from sodium aluminate solutions at low and higher alkali concentrations were aged in the mother liquors, pseudoboehmite therein transformed to hydrargillite and bayerite, respectively.     

3D structuring of dense alumina ceramics using fiber-based stereolithography with interparticle photo-cross-linkable slurry

In this paper, we demonstrated optical fiber-based stereolithography of alumina ceramics using concentrated slurry with low monomer content for enabling rapid firing of the printed green objects. Photo-cross-linkable alumina slurries were designed using a partial complex of polyethyleneimine and oleic acid (PEI-OA) as reactive polymer dispersants and multifunctional acrylates (MA) as monomers. The effects of the processing parameters, such as oleic acid contents, MA contents, particle contents, and particle sizes, on photocuring properties were systematically investigated. We found that the reactive amine sites of PEI-OA attached to particles and MA volume concentrations in the liquid phase were the most dominant factors to improve the photocuring properties. Therefore, a slurry composed of larger alumina particles with higher solid contents and PEI-OA with lower OA contents was more favorable for achieving photocuring under reduced MA content. The designed photocurable slurry was then applied to ceramic stereolithography using optical fiber. 3D alumina green parts were drawn by passing blue laser beam through an optical fiber in a droplet of photocuring slurry and dense sintered alumina were successfully fabricated by rapid drying (<10 min) and debinding (<1 h) without any structural collapse.     

Efficient spin resolved spectroscopy observation machine at Hiroshima Synchrotron Radiation Center

Highly efficient spin- and angle-resolved photoelectron spectrometer named ESPRESSO (Efficient SPin REsolved SpectroScopy Observation) machine has been developed at the beamline BL-9B in Hiroshima Synchrotron Radiation Center. Combination of high-resolution hemispherical electron analyzer and the high-efficient spin detector based on very low energy electron diffraction by the ferromagnetic target makes the high-energy resolution and angular resolution compatible with spin- and angle-resolved photoemission (SARPES) measurement. 7.5 meV in energy and ±0.18° in angular resolution have been achieved with spin resolution. The ESPRESSO machine, combination of quick energy-band dispersion measurement and Fermi surface mapping by two-dimensional electron detector for the spin integrated ARPES and the high-efficient spin analysis by the efficient spin detector realizes the comprehensive investigation of spin electronic structure of materials.     

Near lossless coding of sparse histogram images based on zero-skip quantization

Multimedia Tools and Applications - This paper introduces a zero-skip quantization (ZS.Q) scheme for the near lossless coding of sparse histogram images. Increases in the range of pixel values and...