CFD analysis of a high‐speed unsteady jet

The flow of a high‐speed unsteady jet is analyzed using computational fluid dynamics for an incompressible flow with the k–ε turbulence model. The pseudo‐nozzle concept is applied to the inlet condition with a large pressure gradient. The results show that the time history of the jet development agrees with the experimental data for methane and hydrogen fuels. In addition, the effect of the injection condition on the development of the jet tip is well described with this model. Furthermore, the effects of inlet conditions of the turbulence intensity and scale on the flow are investigated. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(1): 1– 12, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20141     

Optical properties of C60/a-C superlattice structures for solar cell applications

C₆₀/amorphous carbon superlattice structures were fabricated by shutter-controlled molecular beam deposition. The periodic structure of resulted films was confirmed by X-ray diffraction measurements. From the UV–vis reflectance/transmittance measurements, the energy shift of absorption edge was observed in the superlattice structures as a function of their well width. The carbon-based superlattice structure is the useful technique to control the band gap energy of carbon materials.     

Liquefaction and dechlorination of hydrothermally treated waste mixture containing plastics with glass powder

Additive effects of glass powder upon the product yields and chlorine distribution after liquefaction of hydrothermally pretreated mixed waste (HMW) are compared with liquefaction of HMW with any one of water, quartz sand, or glass powder plus water. As a result, addition of either water or quartz sand did not affect liquefaction and dechlorination of HMW. Further, water (5 g) addition did not enhance liquefaction and dechlorination of HMW with glass powder. On the other hand, after liquefaction of HMW with glass powder, the yields of chlorine in the gas and water insoluble constituents decreased and the chlorine yield in the water-soluble constituent increased significantly. Because sodium in glass powder dissolved in a small amount (0.5 g) of water resulted from dehydration of HMW during liquefaction. Further, hydrogen chloride derived from polyvinylchloride in HMW was neutralized by ion exchange between H(+) and Na(+) dissolved in a small amount of water forming NaCl in the Residue (water-soluble) constituent. Therefore, most of chlorine in HMW was removed easily by water extraction of the Residue constituent after liquefaction of HMW with glass powder. Further, upgrading of HMW into the oil constituent was enhanced due to inhibition of production of chlorine containing organic compounds. Accordingly, it was clarified that glass powder was the most effective additive for liquefaction and dechlorination of HMW.     

Nanometer resolution stress measurement of the Si gate using illumination-collection-type scanning near-field Raman spectroscopy with a completely metal-inside-coated pyramidal probe

We have proposed an illumination-collection-type scanning near-field Raman spectroscopy (SNRS) with a completely gold metal-inside-coated (MIC) pyramidal probe without an optical aperture in order to detect the Raman spectra of fine Si devices for local stress measurements. The gold MIC pyramidal probe has been studied to act as a plasmon resonance near-field optical probe with high power using a finite differential time domain (FDTD) simulation and the prototyped SNRS. In the simulation, the propagated optical power can be made available for SNRS. In the experiments, it is clear that the prototyped SNRS enhanced the Si Raman peak signal by plasmon resonance and could measure the Si Raman peak shift by line scanning the Si gate region and the Si active layer. Furthermore, compressive and tensile stresses localized around the Si gate were demonstrated by the Si Raman peak shift with a resolution of about 10 nm. It is clarified that the proposed SNRS has the possibility of detecting the Raman spectra of a local area.     

Interplay Between Vorticity and Chirality Inside the Vortex Core in Chiral p-Wave Superconductors

The vortex core in chiral p-wave superconductors exhibits various properties owing to the interplay between the vorticity and chirality inside the vortex core. In the chiral p-wave superconductors, the site-selective nuclear spin-lattice relaxation rate T ^–1 ₁ is theoretically studied inside the vortex core within the framework of the quasiclassical theory of superconductivity. T ^–1 ₁ at the vortex center depends on the sense of the chirality relative to the sense of the magnetic field. The effect of a tilt of the magnetic field upon T ^–1 ₁ is investigated. The effect of the anisotropy in the superconducting gap and the Fermi surface is then investigated. The result is expected to be experimentally observed as a sign of the chiral pairing state in a superconducting material Sr₂RuO₄.     

A series‐connected hybrid triple converter system

This paper proposes a hybrid multiconverter system aiming at a large‐capacity high‐voltage high‐efficiency converter system free from harmonics in its input/output. The system consists of n (n: integer) GTO converters and a single neutral‐point‐clamped IGBT converter connected in series by n + 1 output transformers. The GTO converters operate in a square‐wave switching mode while the IGBT converter operates in a PWM switching mode. The former produces a base part of the resultant output voltage. The latter not only produces an additional part of the resultant output voltage, but offsets the voltage harmonics generated by the GTO converters. A basic voltage control strategy for the hybrid converter system is proposed, and its validity is verified by experimental results. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(3): 64–70, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20210     

High-efficiency electroabsorption in quaternary AlGaInAsquantum-well optical modulators

Quaternary AlGaInAs quantum-well optical modulators operating at 1.55 μm are introduced and demonstrated for the first time. An electron-to-heavy-hole exciton absorption peak shift of over 600 Å is observed for a bias voltage of 6 V. An extinction ratio of 19 dB and high-speed operation over 4 GHz is obtained for this optical modulator     

A dry phantom material composed of ceramic and graphite powder

Details of an artificially synthesized dry phantom material developed for experimental studies of microwave exposure to the human body are shown. The material is solid and can simulate electrical characteristics of high water content biological tissues such as muscles and the brain. The material is composed of high-ϵ_r ceramic powder, graphite powder, and bonding resin. Any shape of phantom models can be constructed to simulate different parts of the body, as well as the head. The paper reports the synthesis technique to obtain the desired complex permittivity and the fabrication technique of the phantom models for usage of specific absorption rate (SAR) estimation at 900 MHz     

Measurement of Rising R-Curve Behavior in Toughened Silicon Nitride by Stable Crack Propagation in Bending

A simple procedure for measuring the R -curve properties of ceramics by a stable fracture test in three-point bending is described. As a typical case, data are displayed for a Si₃N₄ material toughened by the presence of acicular grains in situ grown during the sintering process. The fracture mechanics specimen was a single-edge double-notched beam (SEDNB), whose notch was sharpened to a radius of <10 μm in order to reduce the amount of elastic energy stored at its root prior to crack extension. Furthermore, a stabilizer, specially designed for the bending geometry, was used to control crack stability. During stable extension, the crack could be easily arrested at selected locations of the load-displacement curve, the load quickly released, and the stable crack extension directly measured by the die-penetration technique. The crack resistance, K _R, of the material was calculated from the measured crack extent and the onset load value before unloading. This method enabled us to precisely monitor the critical load value at which the load-displacement curve deviated from linear behavior, as well as crack extensions from a few tens of micrometers to about 1 mm. As an application of this method, the fracture resistance of a Si₃N₄ material with rising R -curve behavior was measured and found to increase from about 5.5 to 9.0 MPaμm^1/2 within a 0.8-mm extension.