Growth of whiskered ZrO2 crystals by hydrothermal decomposition of zirconium oxide sulphate pseudo-crystals

Several kinds of metastable compounds, pseudo zirconium oxide sulphates (PZOS) with a chemical composition of Zr₃O₅SO₄·nH₂O, were previously synthesized by the thermal hydrolysis of solutions containing zirconium sulphate at 200 or 240°C. The obtained PZOS samples were again hydrothermally treated in different sulphuric acid solutions (<1.0 mol l^-1) at 240°C, and their hydrothermal decomposition behaviour was investigated by TEM observation. The PZOS samples mostly crystallized to plate-like zirconium oxide sulphate (ZOS) in the concentrated sulphuric acid solution (>0.5 mol l^-1), but long-whiskered monoclinic ZrO₂ crystals grew with decomposition of the PZOS samples obtained from the starting mixtures with added Zr(OH)₄ when rapidly heated to the hydrothermal treatment temperatures. It was found that many ultrafine monoclinic ZrO2 crystals were simultaneously formed during the hydrothermal preparation of the PZOS samples, and during the following hydrothermal decomposition of the PZOS samples, the whiskered crystals of monoclinic ZrO2 grew with the consumption of PZOS from the coexisting ultrafine monoclinic ZrO2 particles which act as seed crystals. This revised version was published online in November 2006 with corrections to the Cover Date.     

Model reference adaptive control for spectral systems

In this paper, we investigate a model reference adaptive control problem for the class of distributed parameter systems generated by spectral operators. First we present an equivalent static input-output representation for the spectral system using filtered values generated from the inputs and the outputs. Next, we design and analyse a model reference adaptive control system for systems with unknown input and output distribution functions.     

Finite-time stabilization of continuous-time systems with constant disturbances

Finite-time stabilization is investigated for continuous-time systems with constant disturbance. A new feedback control law is presented which stabilizes the continuous-time systems in finite time.     

Improvement of forest type classification by SPOT HRV with 20 m mesh DTM

Abstract

For multispectral analysis of forest land in mountainous areas, the estimation of true reflectance without the terrain having an effect on the sensor response is indispensable. To study this subject, the authors carried out the following experiment. First, we made a precise digital terrain model (DTM) at an interval of 10 m for a test forest site covered with Lambertian-type crown surface. Analysing the forest land from the SPOT data with the precise DTM, we obtained a classification result of forest type about 20 per cent higher accuracy than the result without application of this method.     

FEM Modeling of Crack Propagation in a Model Multiphase Alloy

In this paper, several widely applied fracture criteria were first numerically examined and the crack-tip-region Jntegral criterion was confirmed to be more applicable to predict fracture angle in an elastic-plastic multiphase material. Then, the crack propagation in an idealized an elastic-plastic finite element method. The variation dendritic two-phase AI-7%Si alloy was modeled using of crack growth driving force with crack extension was also demonstrated. It is found that the crack path is significantly influenced by the presence of α-phase near the crack tip, and the crack growth driving force varies drastically from place to place. Lastly, the simulated fracture path in the two-phase model alloy was compared with the experimentally observed fracture path.     

Scanning electron microscopic structure of the prismatic layer in the Bivalvia

The shell structure of the Bivalvia has been observed with the use of optical and electron microscopes since the early 1900’s. The prismatic structure is one of the more attractive shell structures in bivalved mollusks. This structure is composed of the aggregation of polygonal prisms arranged densely. Each prism is made of small calcite crystallites arranged perpendicular to a growth shell surface. Organic materials, named organic sheaths, accumulate around prisms and stain well with heamatoxylin-eosin.The Bivalvia, which make prismatic structures, are divided into two groups. One group has the inner shell layer made up of a nacreous structure, and the other has the inner shell layer made up of a foliated structure. The aragonite prismatic layer and the prismatic layer are closely related to each other, as is the aragonite prismatic layer to the composite prismatic one.     

Enthalpy of Denaturation and Surface Functional Properties of Heated Egg White Proteins in the Dry State

The enthalpy of denaturation (ΔH) and surface properties of proteins were related to elucidate the mechanisms of foaming and emulsifying properties by using various heated egg white proteins in the dry state. Foaming and emulsifying properties of all sample proteins were greatly increased with a decrease in the enthalpy of denaturation as determined by differential scanning calorimetry analysis. In plots, foaming and emulsifying properties correlated linearly with ΔH values for various dry-heated egg white proteins. Thus, the enthalpy of denaturation of proteins seemed to be a significant structural factor governing surface functional properties.     

Optimized Logarithmic Roller Crowning Design of Cylindrical Roller Bearings and Its Experimental Demonstration

A logarithmic profile is essentially an optimal geometry for rolling machine elements such as bearing rollers and raceways. Under most conditions of loading, it yields lower stresses to give longer endurance. Lundberg first suggested the basic profile, and some researchers followed him by modifying it to satisfy engineering requirements. In this article, the authors propose a mathematical optimization method for logarithmic profiles in roller bearing applications. Moreover, rolling contact fatigue life tests are carried out to make a comparison among logarithmically crowned, standard partially crowned, and modified partially crowned rollers. Results show that the logarithmically crowned rollers are beyond the modified partially crowned rollers in fatigue life, especially in poor lubrication conditions, although the logarithmic rollers require less workload to process the crowning.     

Dynamic Fracture Toughnesses of Reaction-Bonded Silicon Nitride

Dynamic fracture toughness specimens consisting of 5.1-mm thick, modified wedge-loaded, tapered double-cantilever-beam (WL-MTDCB) specimens, which are side-grooved on one side, were used to establish the room-temperature dynamic fracture toughness, K _ID vs crack velocity, a , relations of two reaction-bonded silicon nitrides. The measured dynamic crack extension histories were then used to drive a dynamic finite-element code in its generation mode which computes the dynamic stress intensity factors for a given crack extension. Results indicate that the K _ID vs a relations of reaction-bonded silicon nitrides do not follow the general trend in those relations of brittle polymer and steel. The slow initial crack velocity which was reported for glass was observed again in silicon nitride and resulted in a nonunique K _ID vs a relation, in contrast to the unique K _ID vs a material properties reported for brittle polymers and metals.     

新型中点钳位三电平电池储能变流器设计及控制系统

基于新型中点钳位(A-NPC)拓扑结构的三电平变流器可以提高输出电压波形质量,有利于降低绝缘栅双极型晶体管(IGBT)耐压,以减小开关器件成本、IGBT损耗和电感损耗,来提高系统整体效率,因此在电力储能领域具有广泛的应用前景。基于A-NPC三电平拓扑结构,设计了电池储能变流器主电路,开发了变流器系统控制器软硬件,研究了变流器中点电压控制机理。样机实验结果表明:所搭建的A-NPC三电平电池储能变流器系统运行良好,与当前储能系统常用的两电平拓扑相比,在略微增加综合成本的基础上,实现了输出电流波形畸变小和输出电流谐波小、效率高等特点,应用在储能系统中,获得了很小的稳态总谐波畸变率和非常好的功耗特性。