Prediction of acoustic absorption performance of a perforated plate with air jets

The present study focuses on the prediction of acoustic absorption performance of a perforated plate with air jets by theoretical calculations.In addition,we experimentally measured the flow rate,internal pressure,acoustic pressure,and transfer function using an acoustic impedance tube.The normal incidence absorption coefficient was calculated from the measured transfer function using transfer function methods.We investigated the influences of background air space,flow velocity,thickness,aperture rate,and aperture diameter of a perforated plate on the acoustic absorption characteristics.The frequency characteristics of the acoustic absorption coefficient showed a maximum value at a local frequency.As the background air space increased,the peak frequency of acoustic absorption characteristics decreased.As the flow velocity passing through the apertures increased,the peak level of the acoustic absorption coefficient also increased.The theoretical results agreed well with the experimental ones qualitatively.     

Effect of the Amount of H2O on the Crystallization of TiO2 Films Prepared from Alkoxide Solutions Containing Acetylacetone

Sol–gel‐derived TiO₂ films were prepared by dip‐coating from Ti(OC₃H₇ⁱ)₄–CH₃COCH₂COCH₃–HNO₃–H₂O–C₂H₅OH solutions, and the effect of the H₂O content in solutions on the crystallization of TiO₂ films during the heat treatment at 800°C was discussed. The crystalline phase, crystallite size, grain size, and refractive index of the TiO₂ films depended on the H₂O/Ti(OC₃H₇ⁱ)₄ mole ratios (x) in the coating solutions. Highly dense and crystalline rutile films were obtained at x = 0.5–10, where the crystallites and grains became larger with increasing x. The further increase in x from 10 to 50 reduced the crystallite size and refractive index of the films, where anatase phase appeared at x = 30–50.     

Tachyon Condensation and Brane Annihilation in Bose-Einstein Condensates: Spontaneous Symmetry Breaking in Restricted Lower-Dimensional Subspace

In brane cosmology, the Big Bang is hypothesized to occur by the annihilation of the brane–anti-brane pair in a collision, where the branes are three-dimensional objects in a higher-dimensional Universe. Spontaneous symmetry breaking accompanied by the formation of lower-dimensional topological defects, e.g. cosmic strings, is triggered by the so-called ‘tachyon condensation’, where the existence of tachyons is attributable to the instability of the brane–anti-brane system. Here, we discuss the closest analogue of the tachyon condensation in atomic Bose–Einstein condensates. We consider annihilation of domain walls, namely branes, in strongly segregated two-component condensates, where one component is sandwiched by two domains of the other component. In this system, the process of the brane annihilation can be projected effectively as ferromagnetic ordering dynamics onto a two-dimensional space. Based on this correspondence, three-dimensional formation of vortices from a domain-wall annihilation is considered to be a kink formation due to spontaneous symmetry breaking in the two-dimensional space. We also discuss a mechanism to create a ‘vorton’ when the sandwiched component has a vortex string bridged between the branes. We hope that this study motivates experimental researches to realize this exotic phenomenon of spontaneous symmetry breaking in superfluid systems.     

High-speed and low-driving-voltage X-cut LiNbO3 opticalmodulator with two step backside slot

A newly designed low-driving-voltage X-cut lithium niobate optical modulator with a two step backside slot is proposed. This modulator was fabricated with micro-machining technology utilising excimer laser ablation. The modulation bandwidth of this modulator achieves 25 GHz and the driving voltage is 2.8 V at 1 kHz     

Synthesis of europium-doped yttrium hydroxide and yttrium oxide nanosheets

A new approach has been developed for the preparation of Y(OH)₃:Eu and Y₂O₃:Eu nanosheets using the sol–gel method and hydrothermal reactions. XRD patterns showed that the product was purely hexagonal-phase Y(OH)₃. TEM images revealed that the nanosheets are square shaped (1 × 1 μm²) with a thickness of several tens of nanometers. In addition, it was found that cubic-phase Y₂O₃ nanosheets can be obtained by calcination of Y(OH)₃ at 900 °C for 1 h. More importantly, the thus-prepared Y(OH)₃:Eu and Y₂O₃:Eu nanosheet phosphors were found to exhibit a relatively high photoluminescence (PL) intensity.     

Bending strength of concrete-filled narrow-width steel box girder

A new type of partially concrete filled steel box girder is proposed. The distance between the two webs is narrower than that of a conventional steel box girder, and concrete is filled inside the box girder at the intermediate supports of the continuous girder. Static bending loading tests were conducted with these new type girders, showing that the ultimate bending strength of the concrete filled steel box girder model was 40% larger than that of the steel box girder model. The ductility also increased about 8 times. The tests with the half concrete filled steel box girder model showed that the ultimate bending strength was 25% larger than the steel box girder model and the ductility was about 6.5 times larger. The half concrete filled steel box girder model without vertical stiffeners had the same ultimate bending strength of that of the girder with vertical stiffeners but the ductility was about half. The simple calculation method was developed using fibre models. The calculated results agreed with the test results and the calculation method has been verified.     

Reassuring evacuation guidance with mobile terminal communication and RFID system in absence of power supply

In this paper, we propose a method which aims to allow people inside a building to evacuate when a disaster occurs. In particular, it is very difficult for them to evacuate safely in blackout conditions with servers down. In the proposed method, passive RFID tags are placed on the walls of the building and each evacuee carries a mobile terminal that is battery‐powered and equipped with an RFID reader‐writer. This device finds evacuation routes based on the information from passive RFID tags touched by the evacuee. The method identifies safety of evacuation routes from the movement of people who have evacuated safely. Mobile terminal communication and RFID tags achieve sharing of information on safe routes among many evacuees. An experiment was conducted, letting people evacuate by two routes in an actual building, and giving about half of them mobile terminals. We easured the increases in the blood pressure and heart rates of the evacuees before and after the evacuation. In both routes, the rates of increase of these two characteristics in the evacuees with terminals were smaller than those in the evacuees without terminals, demonstrating that the proposed method provides assurance to evacuees. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 177(2): 19–31, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21165     

Polarization-Dependent Total-Reflection Fluorescence X-ray Absorption Fine Structure for 3D Structural Determination and Surface Fine Tuning

This short review reports the three dimensional structure analysis of oxide-supported metal species and the origin of the metal-support interaction, using single crystal oxide surfaces and polarization-dependent total-reflection X-ray absorption fine structure (PTRF-XAFS) method. The PTRF-XAFS revealed that metal species interact strongly with oxygen anions of oxide surfaces and that surface pre-modification is a promising way to stabilize the surface monoatomic species of easily-aggregating Cu and Au and to prepare finely-tuned surface metal–organic species with regulated molecular structures and orientations.     

Stabilization of higher-order structure of poly(phenyleneethynylene)s by metathesis polymerization at the side chains

Novel poly(m-phenyleneethynlene-p-phenyleneethynylene)s bearing polymerizable diene or norbornene groups were synthesized by the Sonogashira–Hagihara coupling polymerization of the corresponding d-hydroxyphenylglycine-derived diiodo monomers with p-diethynylbenzene. These polymers exhibited strong Cotton effects derived from a predominantly one-handed helical conformation in CHCl₃ and tetrahydrofuran, but exhibited weak or no Cotton effects in N,N-dimethylformamide. The metathesis polymerization of the diene and norbornene moieties was performed at the side chains of the polymers under diluted conditions in the presence of a chain-transfer agent, if necessary. The reaction took place intramolecularly, which was confirmed by size exclusion chromatography (SEC) measurements. The polymers exhibited stronger Cotton effects even in polar media after the intramolecular crosslinking, which indicated stabilization of the predominantly one-handed helical structures.