Effect of chromium on the phase evolution and microstructure of ZnO doped with bismuth and antimony

Crystalline phase formation and microstructure of ZnO varistors with a basic composition ZnO–Bi₂O₃–Sb₂O₃ were examined. Addition of chromium oxide to this basic varistor resulted in an α-spinel (α-Zn₇Sb₂O₁₂) phase dissolving a significant amount of Cr, while the β-spinel did not. β-spinel transformed to pyrochlore during cooling, whereas α-spinel hardly transformed to pyrochlore irrespective of the cooling conditions. When Sb₂O₃ was completely replaced by Cr₂O₃, ZnCr₂O₄ was formed instead of spinel. α-spinel particles were 1–2 μm in size and intra- as well as intergranular. ZnCr₂O₄ particles, smaller than 1 μm in size, however, were present as aggregates in the bismuth-rich matrix phase at the grain boundaries. This revised version was published online in November 2006 with corrections to the Cover Date.     

Investigation of the drying temperature dependence of the orientation in sol–gel processed PZT thin films

The crystal orientations of lead zirconate titanate (PZT) thin films have been investigated by using various drying temperatures in the sol–gel process. The films were dried at different temperatures between 310 and 350°C for pyrolysis and then were heat treated at 650°C using rapid thermal annealing (RTA). TG/DTA and FTIR spectroscopy were used to detect the remnants of organic materials in the thin films prior to the final heat treatment. In order to examine the relationship between the film orientation and the remaining organic materials for the prior and final heat treatment, the films were fabricated with different coating cycles and dried for different holding times and then annealed at 650°C. The preferred orientations were investigated using X-ray diffraction. This revised version was published online in November 2006 with corrections to the Cover Date.     

Forecasting Winning Bid Prices on an Online Auction Market - Data Mining Approaches -

To solve information asymmetry problem on online auction, this study suggests and validates a forecasting model of winning bid prices. Especially, it explores the usability of data mining approaches, such as neural network and Bayesian network in building a forecasting model. This research empirically shows that, in forecasting winning bid prices on online auction, data mining techniques have showed better performance than traditional statistical analysis, such as logistic regression and multivariate regression.     

Surface properties of Al-doped ZnO thin film before and after CF4/Ar plasma etching

Al-doped ZnO (AZO) is considered as an alternative to transparent conductive oxide materials. Patterning and achieving a stable surface are important challenges in the development and optimization of dry etching processes, which must be overcome for the application of AZO in various devices. Therefore, in this study, the etch rate and surface properties of an AZO thin film after plasma etching using the adaptive coupled plasma system were investigated. The fastest etch rate was achieved with a CF₄/Ar ratio of 50:50 sccm. Regardless of the ratio of CF₄ to Ar, the transmittance of the film in the visible region exceeded 80%. X-ray photoelectron spectroscopy analysis of the AZO thin film confirmed that metal-F bonding persists on the surface after plasma etching. It was also shown that F eliminates O vacancies. Consequently, the work function and bandgap energy increased as the ratio of CF₄ increased. This study not only provides information on the effect of plasma on AZO thin film, but identifies the cause of changes in the device characteristics during device fabrication.     

Degradation Products of 2-tert-Butylhydroquinone at Frying Temperature

Decomposed products of 2-tert-butylhydroquinone (TBHQ) at frying temperature in model system were identified and characterized. An attempt was made to determine the functions of the decomposed compounds in foods using model system. Tert-butylbenzoquinone (TBBQ) was identified as the primary and major oxidation product of TBHQ. Interconversion between TBHQ and TBBQ was the most important role in antioxidant effectiveness and carry-through effect of TBHQ. Several types of dimers by ether linkage resulting from thermolysis at frying temperature were identified. In addition, significant reactivity of a phenolic antioxidant with the functional carboxyl group of a fatty acid, which might lower antioxidant effectiveness, was determined using a simple model system.     

QUANTITATIVE ANALYSIS OF TEXTURE CHANGE IN COD MUSCLE DURING FROZEN STORAGE

The textural deterioration of cod muscle during frozen storage was investigated by objective measurement using the Instron Universal Testing Machine. The rates of texture change as a function of storage time revealed that the increased toughness and decreased cohesiveness could be described by a first-order relationship. Higher storage temperatures resulted in more rapid rates of textural deterioration. Larger activation energy constants for toughness of cod muscle as compared to cohesiveness indicated that toughening was more temperature dependent than cohesiveness. The increased toughness and the decreased cohesiveness of frozen-stored fish appeared to be related to the protein denaturation of the cod muscle and the loss of water-holding capacity, respectively.