Freezing phenomena of supercooled water under impacts of ultrasonic waves

In order to clarify effects of ultrasonic waves on supercoold water, ultrasonic waves were applied to supercooled water. Frequency of the ultrasonic waves applied was 45 kHz, and the intensities of the waves were 0.13 and 0.28 W cm⁻², respectively. Four cases of experimental conditions were selected; a case of a free surface, a case of an oil-water surface, a case of a free surface with a dipped metal bar and a case of an oil–water surface with a dipped metal bar. For each experimental condition, water was cooled at a constant cooling rate and the ultrasonic wave was applied from underneath until the water in a test tube solidified. It was found that in the case of 0.28 W cm⁻², the ultrasonic wave had distinct effects on freezing of supercooled water for all experimental conditions. On the other hand, in the case of 0.13 W cm⁻², the ultrasonic wave had an effect on freezing of supercooled water only under existence of a free surface and a metal bar.     

Vacuum freezing type ice slurry production using ethanol solution 1st report: Measurement of vapor–liquid equilibrium data of ethanol solution at 20 °C and at the freezing temperature

In this study, an original method for the production of ice slurry from ethanol solution without using a refrigerator is proposed. This system has advantages compared with similar existing systems using materials other than ethanol solution. In this paper, the vapor–liquid equilibrium data of ethanol solution at 20 °C and at the freezing temperature are measured, which is necessary to calculate the COP of this ice slurry producing system. In the experiments, two experimental methods are proposed to measure the saturated pressure and the vapor composition of ethanol solution. Each method has an advantage in their operating temperature range. As a result, the vapor–liquid equilibrium diagrams of ethanol solution at 20 °C and at the freezing temperature, and approximations of saturated pressure of various concentrations of ethanol solution for varying liquid temperature, are obtained.     

大米加工精度与碾白程度检测的研究

本研究对不同品种稻谷进行碾米实验，测定碾米全过程的不同碾白程度米粒样品的糙出白率、碾白卒、大米白度、表面色及染色后呈色，分析和比较了各测定值的特性及其相互关系，结果表明：用碾白率表示碾白程度和加工精度较准确，米粒染色后呈色测定的a值和b值与碾白率的关系反映了糙米籽粒结构的特征．可以根据碾白是否到达或超过临界碾白率来检测大米加工精度和碾白程度。     

Experimental identification of the phenomenon triggering the net vapor generation in upward subcooled flow boiling of water at low pressure

Observation of the bubble behavior was made using a high-speed camera to investigate the mechanisms to cause the net vapor generation in subcooled flow boiling. In the experiments, water was used as the test fluid, the flow direction was vertical upward, and the pressure was kept close to the atmospheric pressure. At high liquid subcooling close to the condition of the onset of nucleate boiling, all the bubbles were lifted off the heated surface immediately after the nucleation to disappear quickly in the subcooled bulk liquid due to condensation. It was found that the void fraction did not increase significantly unless the liquid subcooling became low enough for some bubbles to be reattached to the heated surface after the lift-off. When the reattachment took place, the bubble lifetime was substantially elongated since the bubbles slid up the vertical heated surface for a long distance after the reattachment. The reattachment therefore contributed to an increase in the void fraction. It was concluded that in the experimental conditions tested in this work, the bubble reattachment to the heated surface was a key phenomenon to cause the sharp increase of the void fraction at the point of net vapor generation.     

Nucleation of supercooled water on solid surfaces

Heterogeneous nucleation of water was investigated using molecular dynamics simulation. Solid with fcc (111) surface was placed at the bottom of a cell consisting of 864 water molecules. ST2 model with NPT ensemble was used. The pressure and temperature were set to be 0.1 MPa and 275 K, respectively. The interaction between water and the solid was based on the equations proposed by Spohr. Exception was made on the lattice constant which was slightly modified to fit with that for ice structure. The shape of the solid surface was considered. It was found that the only one layer of water molecules was adsorbed in a case of a flat surface, whereas ice nucleation occurred by removing some of the atoms from the surface. Spohr's interaction was also modified so that the dipole moment of water became anti-ferroelectric. It was found that the modification increased the ice growth, further. The effect of lattice constant of solid on nucleation was also investigated. It was found that the variation on lattice constant with a few percent from that of ice was acceptable for nucleation, especially on shrinking side. On expanding side, however, it gave some gaps for water molecules to fit in other than that for ice structure, and it prevented the growth of ice. Hence, a guideline for the selection of ice nucleus material was obtained.     

Effect of crystal orientation on freeze concentration of solutions

Freeze concentration is one of the methods to concentrate solution by making pure ice in the solution. In general, the ratio of condensation is focused on, and so the research on the concentration captured in ice is very limited. However, quality improvement of eliminating impurities from wastewater is a very important task. In this study, the difference of initial morphology of ice was focused on and the influence on the freeze concentration was studied. It was found that the concentration of solute captured in ice was in the following order, from bigger value, multi-crystal ice, a single crystal ice with growth direction in a-axis and a single crystal ice with growth direction in c-axis. It was clarified that the ratio of concentration between the solute captured in ice and the solute in the mother solution varied from 1/10 to 1/250, depending on the crystal orientation of the ice.     

Direct contact melting with asymmetric load

In this study, direct contact melting with an asymmetric load was investigated both experimentally and by numerical analysis. A rectangular parallelepiped solid on a heating surface was melted under various asymmetric loads, while total load acting on the solid and brine temperature were kept constant. In the numerical analysis, the melting process keeping the force balance between the pressure in the liquid film and the loads at all times was calculated. It was found that the average heat flux into the solid was independent of the moment acting on the solid. Analytical results of the time dependencies of the amount of melting and the inclination of the solid agreed with experimental ones for each condition.     

Microscopic tomography with ultra-HVEM and applications

The ultra-HVEM with an accelerating voltage of 3 MV at Osaka University is capable of achieving excellent penetration and resolution for thick specimens. We obtained images of 5-microm-thick slices tilted at angles of up to 70 degrees for biological samples and observed stick-shaped samples of Si devices free from missing zone. These features make the ultra-HVEM an invaluable extension of 3D observation by electron tomography. In this paper, we introduce aspects of ultra-HVEM tomography; specifically, the magnification, the amount of image blurring for thick samples and the electron staining method. Finally, we give some typical applications in the fields of cell biology, pathology and electrical engineering.     

Effects of shapes of electrodes on freezing of supercooled water in electric freeze control

In order to clarify the effects of electric charge on freezing of supercooled water, experiments were carried out. Two kinds of shapes were used for tips of electrodes. One was the sharp end surface. The other was the flat end surface. Aluminum was selected as the material. Water sample was kept in a test tube and cooled down at a constant cooling rate. When the water sample was maintained under a supercooling state, an electric charge was applied to the water sample with a small electric current. The degree of supercooling and the electric current were measured, continuously. Then the degree of supercooling at freezing was determined. It was found that the effects of electric charge were distinct according to the shapes of electrodes. The degree of supercooling at freezing was the lower in the case of flat end surface of the anode than that in the case of sharp end surface of the anode.     

Silica-based 2.5%-/spl Delta/ arrayed waveguide grating using simple polarisation compensation method with core width adjustment

Silica-based 2.5%-Delta arrayed waveguide gratings using a polarisation compensation method with simple circuit design are demonstrated based on core width adjustment in the array. Experimental results show that the polarisation-dependent wavelength shift can be adjusted by optimising chirping parameters for core width