Piezoelectric Properties of Pb(Mg1/3Nb2/3)O3 PbTiO3 -PbZrO3 Ceramics Modified with Certain Additives

Effects of additives on the piezoelectric properties of Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃-PbZrO₃ ceramics in a perovskite-type structure are described. The tetragonality of Pb(Mg_1/3Nb_2/3)_0.375-Ti_0.375Zr_0.25O₃ ceramics increased with the addition of NiO, Cr₂O₃, or Fe₂O₃ 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(Mg_1/2Nb_2/3)_0.4375Ti_0.4375 zr_0.125O₃ 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 Cr₂O₃ retarded grain growth and addition of MnO₂, NiO, CoO, or Fe₂O₃ promoted grain growth in the ternary system.     

水平圆管内高普朗特数流体的凝固

本文从高普朗特数流体所具有的共同特性出发,用数值计算方法对在壁温一定的水平圆管内、伴随着非稳态自然对流换热的高普朗特数流体的凝固过程进行了解析。从而使管内发生的自然对流的流动样相随时间之推移的变化、液固两相非稳态温度分布与自然对流换热的关系、凝固界面的形状及其随时间的变化、自然对流对于凝固速度的影响等原来所不清楚的问题得以明确。     

Relative Activity of Oxygen Ions in Molten Sodium Phosphate as Determined from the Solubility of Sulfur Trioxide

The solubility of sulfur trioxide in sodium phosphate melts with Na₂O/P₂O₅ ratios from 1.0 to 1.4 was investigated at 653° to 1021°C. The oxygen-ion activity estimated from the solubility of SO₃ increased exponentially as the Na₂O/P₂O₅ ratio increased. This compositional dependence of the activity is discussed on the basis of a polymer model.     

Quality Evaluation of Fish Meat by 31 Phosphorus-Nuclear Magnetic Resonance

³¹Phosphorus-Nuclear Magnetic Resonance (³¹P-NMR) was used to evaluate degree of freshness of loach muscle depending on metabolic changes of high energy phosphate compounds. The phosphocreatine ([PCr])/inorganic phosphate ([Pi]) ratio was found to be a sensitive index of early metabolic hypofunction. Ratios of [PCr]/β-phosphate of ATP ([β-ATP]), and [Pi]/[β-ATP] were demonstrated to be appropriate indexes to estimate such metabolic changes in fresh fish. The intramuscular levels of creatine phosphate, ATP and pH were maintained at higher levels in blood-drained loach than in untreated fish. The freshness of fish which were bled and washed at lower temperatures were better preserved.     

Characteristics of Wheat-Flour Dough Using Enterobacter cloacae GAO With and Without Yeast

The Leavening bacterium Enterobacter cloacae GAO made dough rise, without shrinkage or flattening due to refrigeration. The GAO plus yeast mixture was allowed to ferment from 20 to 25% of the time for the GAO alone. The ratio of 0.5% yeast volume to wheat flour was acceptable. The yeast was used in the dough to make mantou (a type of bun). Both mantou volume and pH declined after 3 days refrigeration. The GAO and yeast mixture could withstand 5-7 days refrigeration before falling.     

Calculation of radiation from a quasi-optical reflector antenna for whispering gallery mode

We propose a method to calculate the radiation characteristics of a quasi-optical reflector antenna for whispering gallery mode called Vlasov's antenna. Correction of the shape of the reflector, which was a parabolic cylinder in the original paper by Vlasov et al. (1975), is performed using wave-normal rays. The radiation field is calculated by means of an image source which is obtained with the geometrical optics. Some numerical results show that the radiated beam is gaussian-like in far zone. A scheme of high-power application (500kW, 106·4GHz, TE_12,2) to a beam transmission system is also presented     

Complex-number analysis for non-linear oscillator circuits and the physical meaning of synchronization phenomena

A general method of analysis for non-linear oscillation phenomena by means of complex-number expression is presented together with some examples. The results are simple in form and physically comprehensible. Utilizing the analysis, the physical meaning of the synchronization phenomena of oscillators is elucidated. This paper may provide a heuristic approach to the non-linear oscillation     

Piezoelectric Properties of Pb(Mg1/3Nb2/3)O3—PbTiO3—PbZrO3 Solid Solution Ceramics

Ceramic and electrical properties and crystal structures of the system Pb(Mg_l/3Nb_2/3- PbTiO₃-PbZrO₃ are described. The system is composed of three crystal phases at room temperature: pseudocubic, tetragonal, and rhombohedral. A high dielectric constant and radial coupling coefficient and low resonant resistance were obtained for the compositions near the morphotropic transformation. The composition Pb(Mg_l/3Nb_2/3)_0.4375Ti_0.4375Zr_0.125O₃ had the lowest temperature coefficient of resonant frequency.     

Focusing of high power millimeter-wave radiation by a quasi-optical antenna system

The focusing of millimeter-wave radiation from a high power 60 GHz gyrotron is studied using a two-dimensional ellipso-parabolic focusing antenna system. Fine focusing with an elliptic reflector gives a sheet beam of about 10 mm in thickness even at a high power input of about 100 kW. The addition of a parabolic reflector produces a finely focused and nearly Gaussian beam of about 10 mm in diameter with an energy density higher than lOOkWcm^-2. Spatial distributions of beam power are compared with calculations and good agreement is obtained.