Key Engineering Materials Vols. 321-323

Abstract: This paper presents a new image fingerprinting scheme which embeds a multi-bits fingerprinting code and is robust against the geometric attack such as rotation, scaling and translation. We construct a 64 bits fingerprinting code and embed into wavelet subband of 512x512 images repeatedly. In order to restore an image from geometric distortion a noise reduction filter is performed and a rectilinear tiling pattern is used as a template. Results of experimental studies show that our method is robust against geometric distortions and JPEG compression.

Abstract: The ZnSe epilayers were grown on the GaAs substrate by hot wall epitaxy. After the ZnSe epilayers treated in the vacuum-, Zn-, and Se-atmosphere, respectively. The defects of the epilayer were investigated by means of the low-temperature photoluminescence measurement. The dominant peaks at 2.7988 eV and 2.7937 eV obtained from the PL spectrum of the as-grown ZnSe epilayer were found to be consistent with the upper and the lower polariton peak of the exciton, I2 (Do, X), bounded to the neutral donor associated with the Se-vacancy. This donorimpurity binding energy was calculated to be 25.3 meV. The exciton peak, I1 d, at 2.7812 eV was confirmed to be bound to the neutral acceptor corresponded with the Zn-vacancy.

Abstract: CFRP laminate is sensitive to impacts. Even a low impact creates delamination, bringing deterioration of the structural reliability. Monitoring for delamination is, therefore, indispensable to maintain the reliability of a CFRP structure. In this study, asymmetrical dual charge electric potential change method was introduced to estimate a delamination in the CFRP laminate. Delaminations were estimated using response surfaces as solver of the inverse problem. Learning data of response surfaces were calculated by FEM analyses. Actual delaminations in the CFRP laminate were successfully identified.

Abstract: Resin transfer molding (RTM) process is getting popular for fabrications of complicated commercial products made from Glass Fiber Reinforced Polymer (GFRP) at low cost. Cure monitoring is indispensable for RTM process. In the present study, polyester resin is adopted for matrix resin of the GFRP components. The polyester is usually adopted as matrix resin of the low-cost GFRP products. Existing methods for the cure monitoring are, however, expensive for the GFRP products. The polyester resin usually changes its optical property during curing. This enables us to monitor the degree of cure by means of measurements of luminance change of the transmitted light. Since the electrical circuit for measuring luminance change is not expensive, this system utilizes the luminance change for monitoring cure is not expensive system. In the present study, the sensing system employs a LED as a light source and plastic optical fibers as light paths. A photodiode is adopted as a light power sensor. This low-cost cure-monitoring system is applied to monitoring of degree of cure of polyester resin. Degree of cure is measured by means of commercially available dielectric sensors, and results are compared with the results of luminance change. The effectiveness of the method is confirmed experimentally here.

Abstract: We investigated the effect of SiO
cap layer on the thermal stability of nickel and nickel-cobalt silicide by measuring its sheet resistance. The stability of nickel silicide was deteriorated as a function of annealing temperature, while that of nickel-cobalt silicide was not. In case of both silicides, the SiO
cap layer improved the stability. Tensile stress from the difference of thermal expansion coefficients between SiO2 and nickel silicide may suppress the agglomeration of nickel silicide.

Abstract: The corrosion behavior of pure titanium and Ti-6Al-4V alloy in NaF solutions and the wettability of pure water on the specimens after corrosion were investigated. The relation between the change of surface chemistry and roughness of specimens after corrosion and the wettability of pure water droplets on such surfaces were discussed.

Abstract: We developed a device that makes possible the normal generation of low-temperature plasma under atmospheric pressure. For plasma generation, a radio frequency of rf (13.56 MHz) was used, for plasma gas, helium (He), and for material gases, acetylene (C2H2) and toluene (C6H5CH3) were used. As a result of measuring Fourier transform infrared (FT-IR) after adding the CO2 gas to the generated plasma, the absorption of C=O (carboxyl group) was observed around 1715 cm-1. When the flow rates of the added CO2 increased, the absorption peak increased at the same time, and we knew that this originated from the CO2 molecules.

Abstract: We investigated the structural and electrical properties of the 0.5% Ce-doped Ba(ZrxTi1-x)O3 (BZT) thin films with a mole fraction of x=0.2 and a thickness of 150 nm for the MLCC (Multilayer Ceramic Capacitor) application. Ce-doped BZT films were prepared on Pt/Ti/SiO2/Si substrates by a RF magnetron sputtering system as a function of Ar/O2 ratio and substrate temperature. X-ray diffraction patterns were recorded for the samples deposited with three different substrate temperatures. The thickness and the surface roughness of the films deposited with different Ar/O2 ratios were measured. The oxygen gas, which was introduced during the film deposition, had an influence on the growth rate and the roughness of the film. The surface roughness and dielectric constant of the Ce-doped BZT film varied with Ar to O2 ratios (5:1, 2:1, and 1:1) from 1.21 nm to 2.33 nm and 84 to 149, respectively. The Ce-doped BZT film deposited at lower temperature has small leakage current and higher breakdown voltage.

Abstract: Present study was conducted in order to expand the applications of acoustic emission (AE) as a tool in evaluation of the recovery behavior of pure magnesium after deformation at room temperature. From our previous research, we confirmed that AE from magnesium and its alloys during recovery process at room temperature is a unique characteristic and AE measurement should also be a promising approach in investigating such characteristic phenomenon. In present research, magnesium with purity of 99.95% was selected as the main research objective, and the cylinder specimen was compressed with strain rate of 1.67×10-4/s and unloaded with extremely high strain rate of 0.56/s for the forthcoming AE evaluation in anelastic recovery process. The AE behavior during anelastic recovery process and parameters such as anelastic recovery strain and twin densities etc. were analyzed in detail. Pseudoelastic behavior of pure magnesium was considered to be related to the detwinning and dislocation motions by the driving force of internal stress.

Abstract: The fretting wear arises when contacting surfaces undergo oscillatory tangential displacement of small amplitude. Depending on the degree of stick and slip there are three kinds of the contact motions, such as gross-slip, partial-slip and stick-slip. The fretting damage occurs most severely when the transition from gross-slip to partial-slip happens. In this paper, the transitions of friction and wear under fretting were investigated by ball-on-disk wear tests in various environments, which were dry friction of air and nitrogen, and wet friction of mineral oil and engine oil. The transition from partial-slip to stick-slip firstly occurred in nitrogen environment, and then in air. Later, the transition occurred at higher load in mineral oil, and then lastly in engine oil.