Preparation of acetylcellulose/silica composites by sol-gel method and their mechanical properties

Acetylcellulose (AC)/silica composites were prepared by sol-gel method in an attempt to realize materials with Young's moduli and bending strengths similar to those of cortical bones. Si(OCH₃)₄ (TMOS)-AC-H₂O-HNO₃-tetrahydrofuran-CH₃OC₂H₄OH solutions were allowed to be gelled, where AC/TMOS mole ratios were defined for AC monomers, and the gels were dried at 30–70^∘C to obtain composites. The composites prepared from solutions of mole ratios of AC/TMOS = 0.5 and 1.0 were composed of micrometer-sized particles rich in silica surrounded by the matrix rich in AC. The composites from solutions of AC/TMOS = 2.0, on the other hand, the interface between the particles and the matrix was much less distinct. All the composite samples showed good machinability, which could be cut into 5 mm × 2 mm × 4.4 mm rectangular specimens by an electric saw without cracking or fracture. The specimens were subjected to three-point bending test, where the degree of plastic deformation and the fracture strain increased, and Young's modulus and bending strength decreased with increasing AC/TMOS ratio in the starting solutions. When the gels were dried at higher temperatures, Young's modulus and strength increased. Young's modulus and bending strength could be varied in the range of 1.8–3.9 GPa and 48–100 MPa, respectively, by varying the AC/TMOS ratio in solutions and the drying temperature.     

Electron transport behaviors across single grain boundaries in <Emphasis Type="Italic">n</Emphasis>-type BaTiO<Subscript>3</Subscript>, SrTiO<Subscript>3</Subscript> and ZnO

In some electroceramic materials, their unique electrical properties are due to potential barriers, i.e., double Schottky barriers (DSBs), formed at grain boundaries. So far, some researchers have revealed that the electrical properties of DSB are closely related to grain boundary characters, especially grain boundary coherency. For example, highly coherent boundary does not give PTCR or varistic property, while random types exhibit clear resistivity jump or abrupt current increment. Therefore, a concept of grain boundary design will be required for future device manufacturing, even in bulk materials. But it has not been clarified yet why the electron transport behaviors depend on them. In order to address this question, it is necessary to carry out a systematic experiment focusing on single grain boundaries using well-defined bicrystals.In the present study, we have summarized our studies with a special interest in electron transport behavior across single grain boundaries for n-type BaTiO₃, SrTiO₃ and ZnO.     

Shape and Structure of Zinc Oxide Particles Prepared by Vapor-Phase Oxidation of Zinc Vapor

The shape and structure of granular and tetrapod-like ZnO particles prepared by a vapor-phase method were analyzed by electron microscopy, and the growth mechanism is discussed. Only the wurtzite structure exists in ultrafine particles less than 50 nm, indicating that the ZnO particles have the wurtzite structure from the early stages of growth. The legs of the tetrapod-like particles are hexagonal prisms grown along the <001> direction. With regard to the geometrical orientation relationship between any two of the four legs, it was found that the (1¯0) planes of the two legs are parallel to each other.     

Size distribution of large grain-boundary cracks in the creep-ruptured specimens of a cobalt-based alloy

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Equilibrium Oxygen Pressures of Mn-Zn Ferrites

The equilibrium oxygen pressures of Mn-Zn ferrites with various oxygen/metal ratios were obtained at 1000° to 1400°C. The method used is the dependence of the lattice constant on oxygen content obtained in Mn ferrites and the relation between oxygen content and the equilibrium oxygen pressure found in Mn and Ni ferrites. Previous results were compared with those of the present study.     

Partial Characterization of Muscle Collagens from Prawns and Lobster

The abdominal muscle tissues of giant river prawn, fleshy prawn and spiny lobster contained 2.4–2.6% collagen of the total tissue protein. Alkali-insoluble proteins were prepared from the muscle tissues by treatment with 0. 1N NaOH at 4°C and found to exhibit the amino acid composition typical of collagen. The muscle collagens, consisting of α chain-sized components, were then isolated by limited pepsin digestion and characterized by a high content of hydroxylysine and its glycoside and a low content of alanine. In addition, subcuticular membranes covering the muscle tissues were found to be comprised mainly of such an alkali-insoluble collagen.     

CHANGES DURING FERMENTATION AND PROPERTIES OF SOM-FUG PRODUCED FROM DIFFERENT MARINE FISH

ABSTRACT

Microbiological, chemical and physical changes of Som‐fug produced from six marine fish during fermentation were monitored. During the fermentation (0–72 h) at 30C, the increase in lactic acid bacteria (LAB) count and total acidity (TA) with the concomitant decrease in pH was observed. After the fermentation was completed, Som‐fug samples contained 1.5–7.9 × 10⁹ cfu/g LAB count and TA ranging from 2.00 to 2.28% with the pH range of 4.53–4.60. Trimethylamine N‐oxide content decreased, whereas trimethylamine content increased throughout the fermentation (P < 0.05). Proteolysis of Som‐fug proteins and lipid oxidation occurred during fermentation. As the fermentation proceeded, hardness, adhesiveness, springiness and cohesiveness of all samples increased, and L*, a*and b*values also increased (P < 0.05). Generally, Som‐fug produced from bigeye snapper showed a greater acceptability than those produced from other species. However, its acceptability was slightly lower than a commercial Som‐fug produced from freshwater fish (P < 0.05).

PRACTICAL APPLICATIONS

This research indicates that some marine fish can be used as the raw material for Som‐fug production with the quality almost comparable to those prepared from fresh water fish, which are commercially availalble. Therefore, the improvement of process for Som‐fug production from marine fish should be further conducted to obtain the better quality and higher acceptability. As a consequence, Som‐fug from marine fish with the high nutritive value can become a novel product for the consumers.

     

Fatigue thresholds of holed components under in‐phase and out‐of‐phase torsional and axial loadings

The resistance‐curve (R‐curve) method was applied to the prediction of the fatigue thresholds of notched components under in‐phase and out‐of‐phase combinations of cyclic torsion and axial loadings. The prediction was compared with the experimental data obtained from thin‐walled tubular specimen of medium‐carbon steel with a hole. The stress was completely reversed and the mean stress was zero. The crack was nucleated at the position of the maximum range of the circumferential stress on the periphery of a hole, and propagated almost straight for all cases examined. The experimental data of the thresholds for crack initiation and fracture agreed well with the predictions for in‐phase and for out‐of‐phase loadings with 45° phase difference. For out‐of‐phase loading with 90°, the threshold for fracture was close to the crack initiation limit, because of the reduction of crack closure due to crack face rubbing by mode II shear cycling.     

温轧细化亚晶7475铝合金板材的力学性能

研究了温轧下过渡元素对7475铝合金板材晶粒细化的影响。经350℃温轧、480℃固溶热处理后,用Zr代替Cr的7475铝合金具有稳定亚晶超细组织;平均亚晶直径接近3μm。结果表明,溶液中的Zr能稳定亚晶是因为温轧中析出了细小的Al3Zr粒子;另一方面,含Cr粒子化合物在温轧之前析出,并且在温轧过程中会变粗大。与传统冷轧7475铝合金板材相比,温轧细化亚晶板材具有独特的性能。固溶处理后的温轧板材,在厚度截面的亚晶组织具有高比例小于150的小角度晶界;温轧T6态合金板材的强度高于传统7475铝合金板材强度10％。温轧铝合金板材最显著的特点是,在与轧制方向呈45°时高Lankford（r）值为3．5,而其平均Lankford（r）值为2．2。高Lankford（r）值有利于组织演变为β-fiber织构,特别是强{011}（211）黄铜部分。同时,温轧板材也具有高的抗应力腐蚀开裂性能（SCC）。根据Kikuchi线和透射电镜分析,温轧T6板材形成的小角度晶界导致无沉淀析出带（PFZs）难以形成,这是导致抗应力腐蚀开裂性能提高的重要因素,其原因是晶界和晶内的电化学性能存在差异。     

业务应用软件框架的一种分析方法

为了开发成熟的、可重用的软件框架和组件,提倡尽量地抽出和组入软件模式.讨论了基于软件模式的面向对象软件开发方法.在分析业务应用领域需求规格的基础上,给出了软件框架的分析方法和基本角色模型,抽出了框架的体系结构分析模式、基本角色类及其结构并设计了数据存取的"抽象工厂”模式.该方法适用于应用框架和软组件的开发.