Development of air purification device through application of thin-film photocatalyst

TiO₂ photocatalyst was prepared by hydrothermal method using titanium isopropoxide as a precursor. This photocatalyst had higher content of anatase structure and larger surface area than commercial P-25 photocatalyst. The air purification device with a filter coated with photocatalyst film was excellent in its capabilities to decompose organic materials and to kill germs. When the device was installed in hospitals, it was powerful for the sterilization of floating germs in the air. In addition, the number of germs after 7 months operation was almost the same as that obtained in the first operation.     

Phase equilibria of poly(methyl methacrylate) in supercritical mixtures of carbon dioxide and chlorodifluoromethane

Phase behavior data are presented for poly(methyl methacrylate) (PMMA: M_w= 15,000, 120,000) in supercritical solvent mixtures of carbon dioxide (CO₂) and chlorodifluoromethane (HCFC-22). Experimental cloud point curves, which were the phase boundaries between single and liquid-liquid phases, were measured by using a high-pressure equilibrium apparatus equipped with a variable-volume view cell at various CO₂ compositions up to about 63 wt% (on a polymer-free basis) and at temperatures up to about 100 °C. The cloud point curves exhibited the characteristics of a lower critical solution temperature phase behavior. As the CO₂ content in the solvent mixture increased, the cloud point pressure at a fixed temperature increased significantly. Addition of CO₂ to HCFC-22 caused a lowering of the dissolving power of the mixed solvent due to the decrease of the solvent polarity. The cloud point pressure increased with increasing the molecular weight of PMMA.     

Design and experimental validation of doubly salient permanent magnet linear synchronous motor for precision position control

A typical iron-core permanent magnet linear synchronous motor (PMSLM) suffers force ripple originated from detent force. Rare earth permanent magnets (PMs) in stationary part cause cost issue. This paper introduces a doubly salient PMLSM (DSPMLSM) which reduces force ripple and number of PMs in stationary part. A prototype DSPMLSM is made based on geometry optimization by response surface methodology (RSM) considering multiple responses combined with 2D finite element analysis (FEA). Analysis and experimental results show promising results that the proposed DSPMLSM displays low force ripple and good positionability.     

The compressive response of new composite truss cores

New approaches for fabricating truss cellular cores using pultruded unidirectional fiber-reinforced composite rods and yarns are described. Based on the performance and observed failure mechanism of two initial ideas, a final design named “semi-wire-woven bulk Kagome” (semi-WBK) core is developed. Under compressive load, three types of semi-WBK core specimens (which differ in the type and the amount of adhesive bond used) failed, mainly by premature collapse at the ends of the pultruded rods (defibration). In terms of strength, equivalent Young’s modulus, and density, the semi-WBK cores showed performance comparable to honeycomb cores and pyramidal CFRP lattices.     

PL and PLE studies of KMgF3:Sm crystal and the effect of its wavelength conversion on CdS/CdTe solar cell

We studied the effect on conversion efficiency of a CdS/CdTe solar cell by applying a wavelength conversion of a rare earth ion. Both photoluminescence (PL) and photoluminescence excitation (PLE) spectra of the Sm-doped KMgF₃ crystal were investigated. As a result, we found that both the divalent and the trivalent Sm ions coexist in the grown KMgF₃ crystals. Also, all the PLE spectra below 500 nm were effectively converted to PL spectra above 540 nm and the solar cell possessed a high spectral response. The quantum efficiency of Sm ions was estimated to be 0.84 from the comparison of the experimental curve with the calculated one for the increased spectral response below 500 nm. When a thin disc crystal of KMgF₃:Sm was placed on the top of CdS/CdTe solar cell as a precursor for wavelength conversion, both the maximum output power and the conversion efficiency increased by 5% as compared with the case of a pure KMgF₃ crystal.     

Phase behavior of water-insoluble simvastatin drug in supercritical mixtures of chlorodifluoromethane and carbon dioxide

Phase behavior data are presented for simvastatin, a water-insoluble drug, in supercritical solvent mixtures of chlorodifluoromethane (CHClF₂) and carbon dioxide (CO₂). The solubilities of the simvastatin drug in the solvent mixtures of CHClF₂ and CO₂ were determined by measuring the cloud point pressures using a variable-volume view cell apparatus as functions of temperature, solvent composition, and amount of the drug loaded into the solution. The cloud point pressure increased with increasing the system temperature. As the CHClF₂ composition in the solvent mixture increased, the cloud point pressure at a fixed temperature decreased. Addition of CHClF₂ to CO₂ caused an increase of the dissolving power of the mixed solvent for the simvastatin drug due to the increase of the solvent polarity. CHClF₂ acted as a solvent for simvastatin, while CO₂ acted as an anti-solvent. The cloud point pressure increased as the amount of the simvastatin drug in the solvent mixture increased. Consequently, the solubility of the simvastatin drug in the solvent mixture of CHClF₂ and CO₂ decreased with increasing the CO₂ content in the solvent mixture as well as with increasing the system temperature.     

Solubility of carbon dioxide in ammonium-based ionic liquids: Butyltrimethylammonium bis(trifluoromethylsulfonyl)imide and methyltrioctylammonium bis(trifluoromethylsulfonyl)imide

Solubility results of carbon dioxide (CO₂) in two ammonium-based ionic liquids, butyltrimethylammonium bis(trifluoromethylsulfonyl)imide ([N4,1,1,1][Tf₂N]) and methyltrioctylammonium bis(trifluoromethylsulfonyl)imide ([N1,8,8,8][Tf₂N]), are presented at pressures up to approximately 45 MPa and temperatures ranging from 303.15 K to 343.15 K. The solubility was determined by measuring bubble point pressures of mixtures of CO₂ and ionic liquid using a high-pressure equilibrium apparatus equipped with a variable-volume view cell. Sharp increase of equilibrium pressure was observed at high CO₂ compositions. The CO₂ solubility in ionic liquids increased with the increase of the total length of alkyl chains attached to the ammonium cation of the ionic liquids. The experimental data for the CO₂+ionic liquid systems were correlated using the Peng-Robinson equation of state.     

High-pressure phase behavior of carbon dioxide in ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

Phase equilibrium data of carbon dioxide in the ionic liquid 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf₂N]) are presented at high pressures up to about 30 MPa and at temperatures between 298.15 K and 343.15 K. The solubilities at a given temperature were determined by measuring the bubble point pressure of the ionic liquid solution with carbon dioxide dissolved using the high-pressure equilibrium apparatus equipped with a variable-volume view cell. Solubility results are reported for carbon dioxide concentrations ranging from 0.21 up to 0.80 mole fraction. Carbon dioxide gave very high solubilities in the ionic liquid at lower pressures, while the equilibrium pressure increased very steeply at higher concentrations of carbon dioxide. The solubility of carbon dioxide in the ionic liquid decreased with an increase in temperature.     

Sensitivity of fuel failure detection by the delayed neutron measurement in the primary cooling circuit of HANARO

The sensitivity of the fuel failure detection system based on the delayed neutron measurement in the primary cooling circuit of a research reactor, HANARO is investigated. The neutrons around the primary cooling pipe during normal operation of HANARO are measured with BF₃ detector, and their count rate is 900 cps. They are regarded as photoneutrons due to the high energy gamma-rays from N-16 and delayed neutrons from the fission of the uranium contaminated on the fuel surface. The contribution of each neutron source is analyzed by measuring the changes of the neutron counts before and after the abrupt shutdown of reactor. In order to estimate the sensitivity of the fuel failure detection, the neutron count rate of BF₃ detector is predicted by Monte Carlo calculation. The generation, transportation and detection of the photoneutrons and the delayed neutrons are simulated for the geometry similar to the experiments. From the calculations and experiments, it is ascertained that the photoneutron contribution to the total count rate is about 20–30%, and that the delayed neutron count rate is expected to about 720 cps. The fission rate in the flow tube of the reactor core by the surface contamination is obtained from the deduced delayed neutron count rate, and it is estimated to 1.66 × 10⁵ fissions/cm³ s. From the MCNP calculation, it is confirmed that this fission rate can originate from the contaminated uranium of 120 μg, which is about 13% of the maximum allowable surface contamination on the fuel surface. The sensitivity of U-235 mass detection by the delayed neutron measurement can be concluded to about 0.2 μg-U²³⁵/cps. Thus, it is confirmed that the delayed neutron detection is sensitive enough to monitor the fuel failure, and that the neutron count rate is high enough for stable signal with short counting time.     

An investigation of methanol and methanol blended sprays using laser scattering images

The characteristics of methanol and methanol blended (M85) sprays were investigated under atmospheric conditions at various temperatures, ranging from non-vaporizing to vaporizing ambient conditions (298–353 K). From laser scattering images, the macroscopic characteristics of the spray, such as the spray tip penetration and the spray angle, were determined. Entropy concept was introduced to represent homogeneity and PIV analysis was adopted to determine the fluid dynamic information at each location of the spray. The correlation between entropy and vorticity strength enabled us to find their relations. The effect of ambient composition, mainly of viscous effect as affected by CO₂ levels, was investigated using PIV and entropy analysis. Spray width and entropy value were found to tend to decrease at increased CO₂ levels.