Creep-fatigue interaction properties of nickel-based superalloy 617

High-temperature fatigue properties were investigated for a nickel-based superalloy 617 as a typical candidate material for high-temperature components using an advanced ultra super critical (A-USC) power plant. Creep-fatigue data obtained by strain-controlled tests at 700 ? C was analyzed for the superalloy 617 focused on position of hold at peak strain in comparison with continuously cycled tests. The fatigue life was the shortest with the hold tensile strain wave, which showed mainly intergranular fractu...     

Oscillatory Compared with Continuous High Pressure Sterilization on Bacillus stearothermophilus Spores

TO ESTABLISH a sterilization method with minimal heating, the effect of high pressure on bacteriostasis was studied using thermoduric spores of Bacillus stearothermophilus. After exposure to 800 MPa for 60 min at 60°C, the spore count decreased from 10⁶ to 10²/mL. However, exposure to the same pressure at room temperature did not cause significant change in spore numbers. The synergistic effect of high pressurization on the bacteriostatic action of sucrose fatty acid ester at low concentration (< 10 ppm) was pronounced with sucrose palmitic acid ester but not with sucrose stearic acid ester. Oscillatory pressurization was more effective for spore sterilization. Six cycles oscillation of 5-min pressurization with 400 MPa at 70°C decreased the spore count from 10⁶ to 10²/mL, and with 600 MPa, complete sterilization was achieved.     

A High Immersive Telexistence System of the Moving Object with Full Circumference Image and Inertial Force Presentation

Currently, the remote control such as the bilateral control which enables transmitting the multimodal information has been studied. However, remote control has not been reached while perceiving the wind, gravity, and the condition of the ground on the moving object at the remote place. When it is possible to perceive the external force applied to the moving object, it is possible to perform an appropriate operation sensuously according to a remote place such as a slope or a gravel road. Therefore, we propose a high immersive telexistence system with head mounted display and the six‐axis motion base which enables transmitting the inertia and force information of the moving vehicle, and 360‐degree image of moving object's surroundings at real‐time.     

离心成型方法制备Al2O3-ZrO2梯度复合材料及力学性能

Compesitionally graded composite of alumina-20% zirconia （ volume fraction ） was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the alumina/zirconia ratio along the cent,frugal direction; zirconia tended to accumulate in the bottom section, while alumina in the .top section. Such a graded structure exhibited a considerably higher flexural strength when the alumina rich surface was subjected to a tensile stress than compositionally uniform composite of the same average composition. Fracture toughness measurement across the specimen thickness by indentation method revealed that the crack lengths along the vertical and horizontal directions were different. The anisotropy of the fracture toughness was accounted for by the variation of the residual stress across the specimen thickness.     

Sensitivity Analysis for Hygrostress Crack Formation in Cylindrical Food During Drying

A parametric analysis was performed to examine the influence of several factors on stress crack formation in cylindrical food during drying using a previously developed, validated simulation method. They included initial food moisture (W_o), air humidity (R_h) and temperature (T_a), convective surface mass transfer coefficient (h_m), convective surface heat transfer coefficient (h_t), moisture diffusivity (D_w), and initial food diameter (d_o). R_h influenced most strongly drying time for crack formation (t_cf), followed by T_a and W_o. The other 4 parameters in descending order of influence were h_m, h_t, d_o and D_w. The influence of all parameters, except W_o, was due to their influence on mass transfer Biot number, Bi_m, that was closely related to moisture concentration gradient in food. The influence of W_o was due to increased critical stress for crack formation with a reduced moisture level.     

感潮河段弯道水流的水力特性

网走湖水质主要为生物化学污染。论文利用声学多普勒流速剖面仪(ADCP)和咸水温度及深度测量仪(STD),于1996年的4月和8月在该湖出口下游河道的一个180°弯道处分别对三维流速场和咸淡异重流进行了原型观测。结果表明:在4月的融雪季节,从湖里流出的淡水主要为由上游流向下游的单向水流流动,且其流速u为矩形分布,量值与潮位有关;环流流速v与u值密切相关,下层流向指向凹岸。在8月的春潮季节,主要为上淡下咸且主流流向不同的成层异重流流动,且u的分布及流速梯度随着流向的不同而不同。经过观测数据与计算值的比较表明:融雪季节观测的主流和环流流速分布与理论计算值十分接近;春潮季节观测的环流流速表现为:(1)上、下层中的环流方向相反;(2)除过渡流外,环流强度与理论计算值较为接近。含盐度分布特征也因水流条件的不同而不同。     

Isothermal and athermal type martensitic transformations in yttria doped zirconia

The phase transformation from the high temperature tetragonal phase to the low temperature monoclinic phase of zirconia had been long considered to be a typical athermal martensitic transformation until it was recently identified to be a fast isothermal transformation. The isothermal nature becomes more apparent when a stabilizing oxide, such as yttria, is doped, by which the transformation temperature is reduced and accordingly the transformation rate becomes low.Thus it becomes easy to experimentally establish a C-curve nature in a TTT (Time-Temperature-Transformation) diagram. The C-curve approaches that of well known isothermal transformation of Y-TZP (Yttria Doped Tetragonal Zirconia Polycrystals), which typically contains 3mol% of Y2O3. In principle, an isothermal transformation can be suppressed by a rapid cooling so that the cooling curve avoids intersecting the C-curve in TTT diagram. Y-TZP is the case, where the stability of the metastable tetragonal phase is relatively high and thus the tetragonal phase persists even at the liquid nitrogen temperature. On the other hand, the high temperature tetragonal phase of pure zirconia can never be quenched-in at room temperature by a rapid cooling; instead it always turns into monoclinic phase at room temperature. This suggests the occurrence of an athermal transformation after escaping the isothermal transformation, provided the cooling rate was fast enough to suppress the isothermal transformation. Thus, with an intermediate yttria composition, it would be possible to obtain the tetragonal phase which is not only metastable at room temperature but athermally transforms into the monoclinic phase by subzero cooling. The objective of the present work is to show that, with a certain range of yttria content, the tetragonal phase can be quenched in at room temperature and undergoes isothermal transformation and athermal transformation depending on being heated at a moderate temperature or under-cooied below room temperature. Because both of the product phases are essentially the same monoclinic phase, both transformations are regarded as martensitic transformation, i. e. isothermal and athermal martensite. In some steels such as Fe-Mn-Ni and Fe-Ni-C, the occurrence of both isothermal and alhermal martensitic transformations has been reported. However, in these cases, the isothermal transformation occurs at temperatures slightly above the Ms (Martensite start) temperatures, and thus these transformations are considered to conform the same C-curve. On the other hand, the Ms temperature of the present material is well below the C-curve, which suggests that completely different mechanisms are controlling the kinetics of these two modes of transformations. Other aspects on these transformations are also to be reported..     

Parametric Analysis for Thawing Frozen Spheroidal (Prolate and Oblate) or Finitely Cylindrical Food

A screening analysis was performed to determine the influence of independent parameters (18) on thawing times of frozen spherical (prolate and oblate) and finitely cylindrical foods using a computerized simulation procedure assuming food volume shrinkage from density changes and temperature dependent physical properties. Of 18 independent parameters, 6 were significant for both foods: thawing medium temperature, initial freezing point, Biot number, radiative heat exchange, a parameter for effective specific heat and shape factor (nonsignificant influence of volumetric changes). Predictive regression equations were developed for estimating thawing time as function of significant parameters. Predictive equations were validated experimentally. A sensitivity analysis showed errors in thawing time were influenced most strongly by food dimensions, followed by operational temperatures, thermophysical properties and convective surface heat-transfer coefficient.     

Reduction Method of Fluctuation in Partial Discharge Inception Voltage for Inverter‐Fed Rectangular Wire Motors

We investigated the decisive factors that affect partial discharge inception voltage (PDIV) fluctuation between the coil wires under a sinusoidal voltage by using a rectangular wire motor. As a result, we found that PDIV under low humidity fluctuates by the surface charge, and PDIV under high humidity varies transitionally with the surface conductivity activated by predischarge. From these analyses, we proposed the measurement method of PDIV with a low fluctuation and transition for the rectangular wire motors, which will be optimized by environmental humidity, predischarge condition, and measuring frequency.     

COMPARATIVE STUDY OF TEXTURE TERMS: ENGLISH,FRENCH, JAPANESE AND CHINESE

ABSTRACT

Texture vocabularies in English, French, Japanese and Chinese languages are examined, and their characteristics are described. It wasconfirmed that most frequently used texture vocabularies concern with the mechanical and geometrical properties, and are used to describe solid‐like foods rather than liquid‐like foods. It was also shown that in all the languages, the terms used by texture experts and consumers are different. Complete agreement was not recognized even among texture experts, although it is expected that the validation of most fundamental terms could be reached through discussions. Further detailed comparison is now in progress.

PRACTICAL APPLICATIONS

In the globalization age, it is becoming more and more important to understand different languages representing texture of foods. Therefore, it is useful to compare the texture terms in different languages both for academic researchers and workers in the trade and industries.