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1.
The tetragonal (t) to monoclinic (m) transformation behaviour and its relationship to microstructural evolution were investigated by means of dilatometry and transmission electron microscopy for ZrO2–9.7 mol% MgO during cyclic heating and cooling between room temperature and 1490 K. In the as-sintered specimens, fine oblate ellipsoidal t-phase precipitates, 20–50 nm in diameter and 100–200 nm long, were distributed in the cubic (c)-phase matrix. They were below a critical size for transformation and exhibited no transformation in the first three cycles. In the fourth and further cycles, transformation occurred in two distinct stages. A low-temperature stage appeared at 850–1000 K on heating and at 400–700 K on cooling, while a high-temperature stage appeared at 1350–1400 K on heating and at 1000–1200 K on cooling. With the increasing number of cycles, at first the size of low-temperature stages increased and then decreased above ten cycles accompanying the development of the high-temperature stage. During cyclic heating and cooling, coarsening of ellipsoidal precipitates and decomposition of c- and t-phases occurred. As a result of the decomposition, MgO particles and a new m-phase containing a very low concentration of MgO were produced. The coarsened ellipsoidal t-phase precipitates were responsible for the low-temperature stage. The new m- or t-phase containing very low MgO produced by the decomposition was responsible for the high-temperature stage. 相似文献
2.
HIRAMITSU SUZUKI SHUN WADA SEIICHI HAYAKAWA SINPATIRO TAMURA 《Journal of food science》1985,50(2):358-360
To prevent loss of w3 polyunsaturated fatty acids over long-term preservation, the effects of temperature and oxygen absorber on the fatty acids of sardine oil stored in air-tight film were studied. The fatty acids of sardine oil and lipids in the diet of experimental animals rapidly decreased over 1 month at 22°C. The amounts in the diet decreased slowly at 2°C; however, no alterations in the oil samples were observed for 6 months. Also, the amounts did not change at -30°C. Significant changes in samples treated with oxygen absorber were not observed under all temperatures during 6 months storage (P > 0.05). These results indicate that treatment with an oxygen absorber and/or freezing can prevent ω3 polyunsaturated fatty acids of fish oil from decreasing during storage. 相似文献
3.
Piezoelectric Properties of Pb(Mg1/3 Nb2/3 )O3 PbTiO3 -PbZrO3 Ceramics Modified with Certain Additives
HIROMU OUCHI MASAMITSU NISHIDA SHIGERU HAYAKAWA 《Journal of the American Ceramic Society》1966,49(11):577-582
Effects of additives on the piezoelectric properties of Pb(Mg1/3 Nb2/3 )O3 -PbTiO3 -PbZrO3 ceramics in a perovskite-type structure are described. The tetragonality of Pb(Mg1/3 Nb2/3 )0.375 -Ti0.375 Zr0.25 O3 ceramics increased with the addition of NiO, Cr2 O3 , or Fe2 O3 but decreased with the addition of MnO2 or CoO. The dielectric and piezoelectric properties of the base composition were improved markedly through selection of additives in proper amounts. Addition of NiO yielded a high dielectric constant and planar coupling coefficient for compositions at the morphotropic transition boundary. High mechanical Q -factors and low electrical dissipation factors were obtained by addition of MnO2 . Addition of both NiO and MnO2 produced a mechanical Q -factor of 2051 and a planar coupling coefficient of 0.553. The resonant frequency of Pb(Mg1/2 Nb2/3 )0.4375 Ti0.4375 zr0.125 O3 containing MnO2 had very low temperature and time dependence. The microstructure indicated that ceramics with a high mechanical Q -factor had a fine, uniform grain structure. Addition of Cr2 O3 retarded grain growth and addition of MnO2 , NiO, CoO, or Fe2 O3 promoted grain growth in the ternary system. 相似文献
4.
缓变弯道河道冲刷试验研究 总被引:2,自引:0,他引:2
有关弯道水流及其河道演变特性的研究一直为人们所关注。本文引入了在直线段和单一曲率圆弯道间插入曲率渐变的过渡段这一新的弯道型式,舒缓水流冲击力和离心力作用,以减轻水流对河床及堤身、堤脚的冲蚀破坏。作者首先对这一弯道和圆弯道的水流流速、副流强度进行了数值模拟的计算和比较;又通过变换床沙、流量及放水时间,进行了24组合的动床试验;最后,通过整理分析所有实验数据,对插有缓变曲线的弯道的减蚀作用进行了探讨。结果表明:插有缓变曲线的弯道可以减轻水流对两岸堤身和堤脚的冲蚀破坏;在弯道同一横断上的最大冲深与沙洲波高的比值最终稳定在0.58。 相似文献
5.
SEIICHI NAKAMORI 《International journal of systems science》2013,44(12):2573-2584
The optimal fixed-point smoother is designed based on an innovations theory for the white gaussian plus coloured observation noise in linear continuous systems. The signals to be estimated are non-stationary or stationary stochastic processes. The proposed fixed-point smoothing algorithm calculates estimates sequentially by using the observed value, the autocovariance function of the signal plus the coloured observation noise process and the cross-covariance function of the signal with the observed value. 相似文献
6.
Acid Urease: Reduction of Ethyl Carbamate Formation in Sherry under Simulated Baking Conditions 总被引:1,自引:0,他引:1
Acid urease derived from Lactobacillus fermentum was applied to reduce ethyl cthe target level (90 μg/L). However, complete prearbamate (EC) formation in California sherry production. Commercial sherry and sherry base were treated with urease under different conditions. Amounts of urea were determined and EC amounts were monitored by gas chromatography. Urea removal by acid urease reduced EC formation during the baking process and effectively maintained EC concentrations below vention of EC was not achieved because of precursors other than urea. 相似文献
7.
Through dual step simulations, theoretical regression formulae were obtained for estimating the dimensionless thawing time of rectangular or cylindrical food. These formulae contain independent variables related to an initial uniform food temperature, final central food temperature, thawing medium temperature, highest freezing point of food, empirical constant for estimating food enthalpy, shape factor of food and Biot number. The formulae were verified for their reliability by comparing thawing times estimated by these formulae with those determined experimentally. Error analyses were performed by using the formulae to examine the errors of thawing times due to uncertainty in parametric values. 相似文献
8.
A procedure was developed to determine simultaneously convective and radiative heat transfer coefficients applicable to the nonsymmetric freezing or thawing of planar food. The transient state temperature distribution and transient state locations of thermal centers in a sample were used for this development together with computer programs for simulating heat transfer in the food. The coefficients were determined by minimizing squared residuals related to the temperature distributions and thermal centers. The developed method was used to determine the boundary coefficients of slabs made from a crystallized methyl cellulose gel subjected to freezing and thawing. The influence of thermophysical characteristics of the sample material on the determined coefficients was examined qualitatively. 相似文献
9.
N. HAYASHI I. HAYAKAWA Y. FUJIO 《International Journal of Food Science & Technology》1991,26(6):567-574
A newly developed capillary viscometer, having an airtight sample cell and capillary system, was utilized to determine the flow properties of moisturized [70% dry basis (d.b.)] soy protein isolate (SPI) melt at 140°C. Pressure drop measurement with an orifice die was done to clarify the large end effect. An end effect correction method was performed by subtracting the orifice die data from the capillary tube data, and reasonable results were obtained. The flow properties of the SPI melt were thus elucidated and could be classified as those of a power law fluid with flow behaviour index of 0.35. It was concluded that SPI with 70% d.b. moisture is an extremely high pseudoplastic fluid at 140°C. 相似文献
10.
Semolina extrudates were reshaped, immediately after extrusion to form 0.5 mm thick × 2 mm wide × 130 mm long strips. Moisture content (W) was adjusted to 5 to 39% (dry basis) equilibrating in desiccators containing saturated salt solutions. The following tensile rheological properties of the prepared samples were determined at room temperature (21-24°C) using a Rheometrics solid analyzer: Young modulus (E), yield stress (σy), fracture stress (σc) and fracture stain (?c). Each of E, σy and σc was fitted by a semilogorithmically linear function of W with a negative slope. The property ?c fitted two semilogarithmically linear functions: for W < 24.2% a line with a positive slope and for W > 24.2% a line with near zero slope. Such data for moisture ranges used in conventional pasta drying can help to optimize conditions for pasta production without stress cracking. 相似文献