Critical Heat Flux for Downward Facing Boiling on a Coated Hemispherical Surface

An experimental study was performed to investigate the effect of surface coating on the critical heat flux for downward facing boiling on the outer surface of a hemispherical vessel. Steady-state boiling experiments were conducted in the subscale boundary layer boiling (SBLB) facility using test vessels with metallic microporous coatings to obtain the local boiling curves and the local critical heat flux (CHF) limits. Similar heat transfer performance was observed for microporous aluminum and microporous copper coatings. When compared to the corresponding data without coatings, the boiling curves for the coated vessels were found to shift upward and to the right. This meant that the CHF limit was higher with surface coating and that the minimum film boiling temperatures were located at higher wall superheats. In particular, the microporous coatings were found to enhance the local CHF values appreciably at all angular locations explored in the experiments. Results of the present study showed that the microporous aluminum coating was very durable. Even after many cycles of steady state boiling, the vessel coating remained rather intact, with no apparent changes in color or structure. Although similar heat transfer performance was observed for microporous copper coatings, the latter were found to be much less durable and tended to degrade after several cycles of boiling.     

Real Hypersurfaces in Complex Two-Plane Grassmannians with GTW Reeb Lie Derivative Structure Jacobi Operator

Mediterranean Journal of Mathematics - Using GTW connection, we considered a real hypersurface M in a complex two-plane Grassmannian $${G_{2}({\mathbb{C}}^{m+2})}$$ when the GTW Reeb Lie derivative...     

Separation and purification of 99mTc from 99Mo produced by electron linear accelerator

The medical radionuclide ⁹⁹Mo was produced by the ¹⁰⁰Mo(γ,n) reaction using bremsstrahlung photons generated by an electron linear accelerator. The amount of ⁹⁹Mo produced was compared to that predicted by calculation using the particles and heavy ion transport code system. From the ⁹⁹Mo produced, highly pure ^99mTc was separated using the so-called technetium master milker, and the chemical yield of ^99mTc was 83–99 %. The installation of a new complex using this method and the electron linear accelerator with the preferable specification was suggested, and a possibility to supply the demand of ^99mTc was discussed and shown.

     

Gas Storage in Single-Walled Carbon Nanotubes

Abstract

X-ray diffraction (XRD) and electrical resistance measurement on single-walled carbon nan-otube (SWNT) samples prepared by the arc-discharge method are reported. The XRD profile of heat-treated sample indicated that air (oxygen, and/or nitrogen and/or water) can be condensed inside the SWNTs. We also found that the electrical resistance of SWNT soot is significantly affected by exposing to the oxygen gas and humid air.     

Nonlinear obstacle problems with double phase in the borderline case

In this paper we study a double phase problem with an irregular obstacle. The energy functional under consideration is characterized by the fact that both ellipticity and growth switch between a type of polynomial and a type of logarithm, which can be regarded as a borderline case of the double phase functional with $(p,q)$-growth. We obtain an optimal global Calderón–Zygmund type estimate for the obstacle problem with double phase in the borderline case.     

Cyclization from Higher Excited States of Diarylethenes Having a Substituted Azulene Ring

The cyclization reaction of diarylethenes having an azulene ring occurs only via higher excited states. Novel diarylethenes having an azulene ring with a strong donor or acceptor were synthesized and examined in these reactions. A derivative having an electron-donating 1,3-benzodithiol-2-ylidenemethyl group at the 1-position of the azulene ring showed photochromism, whereas neither a derivative having a π-conjugated electron-donating group at the 3-position of the azulene ring nor derivatives having a π-conjugated electron-withdrawing group at the 1- or 3-position of the azulene ring showed any photochromism. The photoreactivities of these compounds were explained by calculating forces and bond orders on the excited states using density functional theory (DFT) and time-dependent (TD)-DFT.     

Composite of SiO2 and Hydrogel Having Microphase Separated Structure: Physical Properties Dependence on pH

Abstract

Organic-inorganic composite gel was prepared by using PEG-modified urethane acrylate (PMUA) gel and tetraethoxysilane (TEOS). PMUA gel was prepared by the phase-inversion emulsion polymerization of PMUA emulsion. The gelation of PMUA emulsion using this method enables PMUA gel to swell with H₂O, TEOS, and ethanol. Hydrolysis and condensation reaction rates of the sol-gel process are strongly influenced by the pH controlled by catalysts such as HCl and NH₄OH. Additionally, the morphology on the cross section of composite and the amount of silica ingredient incorporated into the composite gel were dependent on solvent, the molar ratio of H₂O to TEOS, as well as the pH value.

As the silica content increased, due to hydrogen bonds interacting between PMUA gel and SiO₂, particles, the tensile strength of composites considerably increased, whereas the elongation at break decreased. The incorporation of silica ingredient in PMUA gel/silica composites was verified with FTIR/ATR and SEM. The amount of the silica component in the composite was indirectly investigated by using TGA thermal analysis.     

Viscosity Properties for Aqueous Solution of Urethane Acrylate Cationomer

Abstract

Water-soluble and UV-curable urethane acrylate cationomer was synthesized incorporating N-methyldiethanol amine (MDEA) on the molecular backbone and its viscosity properties were examined with respect to shear rate, temperature, and weight fraction of resin. All shear rates showed shear rate independence within given fraction regions. The viscosity trends of urethane acrylate cationomer solutions followed the Arrhenius equation well. The logarithmic infinite viscosity and activation energy showed linear relationship with the fraction below the weight fraction of 0. 325. However, above the fraction of 0. 325, the deviation from linear relationship was observed. This was believed to be attributed to the intermolecular interactions among molecular chains. From the obtained linear correlation of the logarithmic infinite viscosity and activation energy with the fraction, rheological equation of state was proposed. The viscosities obtained from the equation of state successfully corresponded to the results of experiments.