“Non-adhesion grain boundaries” are formed when low-quality coal grains do not adhere to other grains in the carbonization process because of the low dilation of coke. To better understand the effects of non-adhesion grain boundaries on coke strength, the relationship between the existence ratio of non-adhesion grain boundaries and coke strength was investigated quantitatively. The existence ratio of non-adhesion grain boundaries were measured quantitatively by observing the fracture cross-section of coke using scanning electron microscopy (SEM). Coke strength was measured with a diametral-compression test and an I-shape drum index test. As a result, non-adhesion grain boundaries increased with an increase in the blending ratio of low-quality coal. In particular, non-adhesion grain boundaries increased rapidly when the blending ratio of low-quality coal was over 50%. When the ratio was less than 50%, low-quality coals adhered to other caking coal. However, not many low-quality coals adhered to other caking coals when the ratio was over 50%. The tensile strength of coke was not affected by the porosity of coke. However, the tensile strength and the drum index were affected by the existence ratio of non-adhesion grain boundaries. Tensile strength decreased rapidly even for a few non-adhesion grain boundaries because significant defects caused a fracture in the diametral-compression test. However, the I-shape drum index decreased linearly with the existence ratio of the non-adhesion grain boundaries because many fractures occurred during 600 rotations in the drum. The strength of coke containing low-quality coal is governed by the existence ratio of non-adhesion grain boundaries rather than mean values such as the porosity of coke.
This study describes nanoparticle pigmented coatings used in controlling the radiative properties of surfaces exposed to sunlight. The effect of particle dispersed state to reflectance of the coating is discussed. As the dispersed particles, TiO2 and Fe2O3 are used. From Raman spectral intensity measurements made on the coating, the dispersed state of particles was investigated. The spectral reflectance of the coating was measured by spectroscopy. The reflectivity of the coating is analyzed theoretically. In this calculation, the dispersed state is assumed to be monodispersed and homogeneous. Comparison between experimental and numerical results shows that the difference between the measured and calculated reflectance increases as the volume fraction increases. The maximum absolute error of reflectance is about 10% when the volume fraction is 0.05. In contrast, the maximum absolute error of reflectance is about 3% when the volume fraction is 0.01. The control of dispersed state affects the radiative properties of pigmented coatings.
We report and discuss an experiment and numerical simulation of heat transfer by natural convection inside an autoclave for the solvothermal growth of bulk crystalline GaN. The inner diameter and height of the autoclave were φ 20 and 335 mm, respectively. When the bottom heater of the autoclave is removed and the space between the top and bottom heaters is increased, the crystal growth rate increases. The axisymmetric numerical simulation showed that a rising flow from the center hole in the baffle allows a fast growth rate because the rising fluid is GaN-rich and it reaches the GaN seed crystal quickly. The direction of natural convection can be controlled by changing the vertical position of the heater or baffle.
Marxman's diffusion-limited analysis of hybrid rocket combustion has been often used to investigate various combustion problems in hybrid rocket motors. This analysis was developed on the basis of the Reynolds analogy in turbulent boundary layers. This analogy assumes that both molecular and turbulent Prandtl numbers are equal to one. In the present study, a semi-empirical correlation between the Stanton number and the skin-friction coefficient in a turbulent boundary layer was obtained. This is applicable to hybrid rocket combustion, and also includes the effects of the Prandtl numbers variation. Using this correlation, a fuel regression rate equation for standard-flow hybrid rocket motors was obtained, and its characteristics were examined. In addition, the calculated regression rate characteristics were compared with the experimental data from the laboratory-scale hybrid rocket motors that used gaseous oxygen (GOX) as oxidizer and polymethylmethacrylate (PMMA) as fuel.
Non-thermal air plasma can kill cancer cells. However, there is no selectivity between normal and cancer cells. Therefore, cancer specific antibody conjugated gold nanoparticle (GNP) was pretreated before plasma irradiation. Stimulation of antibody conjugated GNP by plasma treatment resulted in a significant decrease in viability of cancer cells. This technology shows the feasibility of using plasma therapy for killing cancer cells selectively.