Numerical simulation on liquid jet behavior issued into still air

Numerical simulations have been conducted to clarify the effects of turbulence, in the onset of protrusions on liquid jet surfaces. The turbulences in the liquid jet were simulated by the Rankin vortices. The liquid jet surface was tracked numerically by the VOF method. From numerical simulations, the protrusions on the liquid jet surface are induced by the vortices in the liquid, whose rotational direction decelerates the jet surface. Despite the distance between vortices, the displacement of the liquid jet surface from the initial surface location increases linearly, in time, at almost the same growth rate. In the initial region, the growth rate of the displacement increases as the major semiaxis‐to‐minor semiaxis ratio of the ellipsoidal vortex increases. The initial growth rate of displacement is almost proportional to the vortex intensity. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(2): 141–152, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10078     

Modification of cyanate ester resin by soluble polyimides

Soluble polyimides (PIs) were prepared as random or multiblock types with 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (s‐BPDA) as acid dianhydride components and 4,4′‐bis(m‐aminophenoxy) diphenyl sulfone (m‐BAPS) as a diamine component by a one‐pot process and used to improve the brittleness of the cyanate ester resin. Random‐type PIs were more effective as modifiers than multiblock‐type PIs. The morphologies of the modified resins depended on PI structure, molecular weight, and concentration. The most effective modification of the cyanate ester resin was attained because of a heterogeneous phase structure composed of a flat matrix phase and phase‐inverted structures of the modified resin; a 15 wt % inclusion of a random PI (weight‐average molecular weight = 63,400) composed of 6FDA, s‐BPDA, and m‐BAPS (0.5/0.5/1.0 molar ratio) led to a 65% increase in the fracture toughness for the modified resin with a slight loss of flexural strength and a retention of flexural modulus and glass‐transition temperature, compared with the values for the unmodified resin. Water absorptivity of the modified resin was comparable to that of the unmodified resin up to 400 h, and then, water absorption of the modified resins increased considerably. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1–11, 2003     

MTT-hybrid assay incorporates the advantages of both clonogenic and MTT assay radiosensitivity testing for fresh tumor samples

Microspheres of theophylline, with both ethylcellulose of high and low molecular weight and also their mixtures as a coating material, were prepared using the solvent evaporation technique. No permeability through intact isolated polymer films was found. Therefore, this study investigated the drug release dependence of structure and mechanical properties of the polymer matrix. In vitro dissolution studies exhibited the square-root of time (Higuchi model) release characteristics. The size distribution of microspheres was dependent on the ratio of ethylcellulose mixtures with high and low molecular weights.     

Study of point defects in CuGaSe2 single crystals by means of electron paramagnetic resonance and photoluminescence

Point defects in CuGaSe₂ single crystals as vacancies V_Se, V_Cu and defect pair (2V_Cu⁻+Ga_Cu²⁺) have been studied by means of electron paramagnetic resonance (EPR) and low-temperature photoluminescence (PL). EPR hyperfine structure has been found at temperatures as low as 1.45–45 K and the temperature dependence of EPR line is discussed. Photo-EPR spectrum reveals optically active behavior of intrinsic point defects in CuGaSe₂ crystals. Three bands of PL emission show different origins and two low-energy bands at 1.55 and 1.58 eV have been found to be steady despite H₂-, O₂- and Se₂-annealings. The experimental data added with electric characterization in accordance with the used annealings and together with a defect physics model allow consideration of the point defect ensemble in CuGaSe₂ in more detail.     

Good trellises for IC implementation of Viterbi decoders for linearblock codes

This paper investigates trellis structures of linear block codes for the integrated circuit (IC) implementation of Viterbi decoders capable of achieving high decoding speed while satisfying a constraint on the structural complexity of the trellis in terms of the maximum number of states at any particular depth. Only uniform sectionalizations of the code trellis diagram are considered. An upper-bound on the number of parallel and structurally identical (or isomorphic) subtrellises in a proper trellis for a code without exceeding the maximum state complexity of the minimal trellis of the code is first derived. Parallel structures of trellises with various section lengths for binary BCH and Reed-Muller (RM) codes of lengths 32 and 64 are analyzed. Next, the complexity of the IC implementation of a Viterbi decoder based on an L-section trellis diagram for a code is investigated. A structural property of a Viterbi decoder called add-compare-select (ACS)-connectivity which is related to state connectivity is introduced. This parameter affects the complexity of wire-routing (interconnections within the IC). The effect of five parameters namely: (1) effective computational complexity; (2) complexity of the ACS-circuit; (3) traceback complexity; (4) ACS-connectivity; and (5) branch complexity of a trellis diagram on the very large scale integration (VLSI) complexity of a Viterbi decoder is investigated. It is shown that an IC implementation of a Viterbi decoder based on a nonminimal trellis requires less area and is capable of operation at higher speed than one based on the minimal trellis when the commonly used ACS-array architecture is considered     

Japanese research and development on metallic biomedical,dental, and healthcare materials

There is considerable demand for metallic materials for use in medical and dental devices. Metals and alloys are widely used as biomedical materials and are indispensable in the medical field. In dentistry, metal is used for restorations, orthodontic wires, and dental implants. This article describes R&D on metallic biomaterials primarily conducted by the members of the Japan Institute of Metals. For more information, contact Mitsuo Niinomi, Toyohashi University of Technology, Department of Production Systems Engineering, 1-1 Hibarigaoka, Tempaku-cho.Toyohashi 441-8580, Japan     

Numerical simulation of separated flow transition and heat transfer around a two‐dimensional rib

Numerical simulations of separated flow transition and heat transfer around a two‐dimensional rib mounted in a laminar boundary layer were performed. The separated shear layer becomes unstable due to the Kelvin–Helmholtz instability and generates a two‐dimensional vortex. This vortex becomes three‐dimensional and collapses in the downstream part of the separation bubble. As a result, transition from laminar to turbulent flow occurs in the separated shear layer. Streamwise vortices exist downstream of the reattachment flow region. The low‐frequency flapping motion and transition of the separated shear layer are influenced by three‐dimensional dynamics upstream of the separation bubble. Large‐scale vortices around the reattachment flow region have substantial effects on heat transfer. Downstream of the reattachment point, the surface friction coefficient and Nusselt number are different from their profiles in the laminar boundary layer and approach the distributions seen in the turbulent boundary layer. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(8): 513–528, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20177     

燃料挥发性对柴油机性能及排放的影响

针对不同的发动机热状态及压缩比，试验研究了燃料物化特性对柴油机稳态及过渡工况下性能、排放的影响规律。应用自行开发的柴油机过渡工况控制系统及排气采集装置，模拟车用柴油机实际工作时的加速状态，对具有相同十六烷值但有不同挥发性能燃料的HC排放特性进行了研究，利用气相色谱仪对HC排放成分进行了分析。研究结果表明，采用挥发性好的燃料，可有效降低排气烟度，提高有效热效率，在发动机热状态不好及压缩比较低等燃烧条件恶劣、HC排放高的情况下，可有效地降低HC排放。