Numerical simulation of natural convection heat transfer in the open space between two horizontal circular planes

Numerical simulations were conducted for natural convection heat transfer in a narrow gap between two horizontal plates in air. The lower plate is an infinite plate with a circular heating zone. The upper one is the bottom of a vertical cylinder, which is placed right above the circular heated plate and kept at room temperature. A set of Navier–Stokes equations and an energy equation are analyzed for a variety of combinations of gap clearance and Rayleigh number. The calculated average heat transfer values are shown to be in good agreement with the experimentally obtained ones reported in a previous paper. From the obtained isotherms, streamlines, and local Nusselt numbers, it is found that two types of convection appear in the gap space according to the conditions of Rayleigh number and gap clearance: one is a simple convection due to a single renewal flow which replaces heated air with ambient air and the other is a combined convection due to several vortex flows and a renewal flow. Furthermore, the flow rate of each flow controls the rate of heat transfer from the limited area which is covered by each flow. From this fact, the validity of the previously proposed heat transfer correlation is briefly discussed. © 2001 Scripta Technica, Heat Trans Asian Res, 30(6): 485–502, 2001     

Recent Advances in Prion Inactivation by Plasma Sterilizer

Prions, which cause transmissible spongiform encephalopathies (TSEs), are a notorious group of infectious agents with possibly the highest resistance to complete inactivation. Although various gas plasma instruments have been developed, studies on prion inactivation using gas plasma instruments are limited. Among them, the hydrogen peroxide gas plasma instrument, STERRAD^® (Advanced Sterilization Products; ASP, Johnson & Johnson, Irvine, CA, USA), is recommended for prion inactivation of heat-sensitive medical devices. However, STERRAD^® is not a plasma sterilizer but a hydrogen peroxide gas sterilizer. In STERRAD^®, plasma generated by radio frequency (RF) discharge removes excess hydrogen peroxide gas and does not contribute to sterilization. This is also supported by evidence that the instrument was not affected by the presence or absence of RF gas plasma. However, recent studies have shown that other gas plasma instruments derived from air, nitrogen, oxygen, Ar, and a mixture of gases using corona, dielectric barrier, microwave, and pulse discharges can inactivate scrapie prions. As inactivation studies on prions other than scrapie are limited, further accumulation of evidence on the effectiveness of gas plasma using human-derived prion samples is warranted for practical purposes.     

Toward Mega-pixel Neutron Imager Using Current-Biased Kinetic Inductance Detectors of Nb Nanowires with ^{10}B Converter

We present not the results but the idea of a superconducting nanowire detector with \(^{10}\) B conversion layer for sensing a single neutron. We use \(^{7}\) Li ion and \(^{4}\) He ion emitted as two independent heat sources, which appear in opposite direction associated with nuclear reaction \(^{10}\) B(n, \(^{4}\) He) \(^{7}\) Li. We probe a change in the kinetic inductance \(L_\mathrm{k}\) coming from inertia of the Cooper pairs. Our detector is different from a conventional kinetic inductance detector (KID), but is named as a current-biased KID. We use two sets of Nb nanowires with superconducting readout taps to monitor the local signal. In between the X meander and the Y meander, we inserted a \(^{10}\) B layer acting as a conversion layer from neutrons to charged particles. We plan to fabricate a mega-pixel neutron imager by coupling 10 bit linear position-sensitive arrays along the X and Y directions with the single flux quantum readout circuits.     

R dependence of electronic structure in perovskite type structure compounds, RBRh3 (R: Sc, Y and La)

The electronic structures of perovskite type structure, RBRh₃ (R: Sc, Y and La) were studied by X-ray photoelectron spectroscopy and calculation with full potential linearized augmented plane wave (FLAPW) method. As the lattice constant of the crystals increases with the atomic number of R, it can be discussed how the bond length between boron and rhodium atoms effect on the bonding character. The valence band XPS profiles of the samples are well coincided with the calculated profiles. The calculated electron density maps of the valence bands indicate the following. The charge transfer directions are from R to rhodium atoms and from boron to rhodium atoms. The bonds of RRh and BRh atoms have also covalent character. The covalency of RRh bond increases with the order of the atomic number of R atoms. On the other hand, the covalent bond of BRh decreases with the order atomic number.     

ON THE DRYING MECHANISM OF SHRINKAGE MATERIALS

ABSTRACT

Effects of moisture content on Liquid transport properties (Permeability and suction pressure) and mechanical properties (Young's modulus, yield stress and tensile strength) of drying shrinkage materials (Kibnshi, IIaido and mixed clay) were measured and a strong dependence was found. When glass beads are added to the Kibushi, permeability increase and Young's modulus and yield stress decrease in spite of the same suction pressure and tensile strength. Changes in local moisture content and stress during drying was calculated by using finite-element method, taking into account the stress gradient in addition to the pressure gradient due to osmotic suction.     

Numerical simulation of ice accretion phenomena on rotor blade of axial blower

Ice accretion is the phenomenon that super-cooled water droplets impinge and accrete on a body. It is well known that ice accretion on blades and airfoils leads to performance degradation and severe accidents. For this reason, experimental investigations have been carried out using flight tests or icing tunnels. However, it is too expensive, dangerous, and difficult to set actual icing conditions. Hence, computational fluid dynamics is useful to predict ice accretion. A rotor blade is one of jet engine components where ice accretes. Therefore, the authors focus on the ice accretion on a rotor blade in this study. Three-dimensional icing phenomena on the rotor blade of a commercial axial blower are computed here, and ice accretion on the rotor blade is numerically investigated.     

Asymmetric anionic polymerization of 7-cyano-7-phenyl-1,4-benzoquinone methide

Asymmetric anionic polymerizations of a prochiral monomer, 7-cyano-7-phenyl-1,4-benzoquinone methide (3), using chiral initiators were performed under various conditions, and optically active polymers having configurational chirality in the main chain were obtained though their specific rotation values are quite small. The optically active polymer with a negative specific rotation value of −4.4° was obtained by polymerization of 3 with a lithium isopropylphenoxide (ⁱPrPhOLi)/(−)-sparteine ((−)-Sp) in a mixture solution of dichloromethane/toluene ratio of 30/70 (in vol%) at −40 °C. Stereostructures of 1-mer, 2-mer, and oligomers obtained by asymmetric anionic oligomerization of 3 with ⁱPrPhOLi/(−)-Sp were examined in detail. It was found that the stereoselectivity turned out to be the opposite between the initiation reaction and the propagation one.