THE UPGRADING OF SOLVENT REFINED COALS AND LIGNITES: DETERMINATION OF AN EFFECTIVE HETEROGENOUS CATALYST CARRIER

The hydrodenitrogenation, hydrodesulfurization and hydrocracking of solvent refined coals and lignites was accomplished with catalysts comprising high surface area, large pore diameter bases impregnated with MoO₃,CoOand WO₃. The most effective catalysts were those which performed well in hydrodenitrogenating nitrocellulose. This indicates that most of the pore diameter is consistently large enough to accommodate molecules of the size of liquified coal and lignite.     

Comparison of yield and metabolites according to the types of hilling materials utilized during Glehnia littoralis sprout vegetable cultivation

Food Science and Biotechnology - Various hilling materials (rice hulls, pine sawdust, and perlite) were compared to produce sprout vegetables using beach silvertop (Glehnia littoralis Fr. Schm. ex...     

Characterization of waterborne polyurethane for ecofriendly functional floor plate

Three types of nonmetallic mineral particles (CaCO₃, TiO₂ and loess) were incorporated into waterborne polyurethane acrylate (PUA) to improve the surface properties of ecofriendly floor tiles. Several properties of PUA containing nonmetallic mineral materials were measured by Fourier transform infrared spectroscopy (FT-IR), a dynamic mechanical thermal analyzer (DMTA), swelling tests, and contact angle measurement. Upon decreasing the molecular weight between crosslinks (variation of molecular weight of the polyol), the modulus and glass transition temperature (T_g) of the PUA film increased because of the increase in crosslinking density. Resistance properties such as swelling and contact angle against water were enhanced with the addition of nonmetallic mineral particles because of the increase in the hydrophobic nature of the polymer matrix.     

Grain Boundary Conformed Volumetric Mesh Generation from a Three-Dimensional Voxellated Polycrystalline Microstructure

We present a new comprehensive scheme for generating grain boundary conformed, volumetric mesh elements from a three-dimensional voxellated polycrystalline microstructure. From the voxellated image of a polycrystalline microstructure obtained from the Monte Carlo Potts model in the context of isotropic normal grain growth simulation, its grain boundary network is approximated as a curvature-maintained conformal triangular surface mesh using a set of in-house codes. In order to improve the surface mesh quality and to adjust mesh resolution, various re-meshing techniques in a commercial software are applied to the approximated grain boundary mesh. It is found that the aspect ratio, the minimum angle and the Jacobian value of the re-meshed surface triangular mesh are successfully improved. Using such an enhanced surface mesh, conformal volumetric tetrahedral elements of the polycrystalline microstructure are created using a commercial software, again. The resultant mesh seamlessly retains the short- and long-range curvature of grain boundaries and junctions as well as the realistic morphology of the grains inside the polycrystal. It is noted that the proposed scheme is the first to successfully generate three-dimensional mesh elements for polycrystals with high enough quality to be used for the microstructure-based finite element analysis, while the realistic characteristics of grain boundaries and grains are maintained from the corresponding voxellated microstructure image.     

Effect of Nafion ionomer and catalyst in cathode layers for the direct formic acid fuel cell with complex capacitance analysis on the ionic resistance

Using platinum (Pt) black and carbon-supported Pt (Pt/C) as cathode catalysts, membrane-electrode assemblies (MEAs) were fabricated with various Nafion ionomer content, and their direct formic acid fuel cell (DFAFC) performances were investigated. In MEAs incorporating Pt black catalysts, the current density at 0.6 V was highest at ionomer/catalyst volume ratio of 1.0, which was consistent with the electrochemical active area (EAS) variation measured by cyclic voltammetry. However, the current density measured at 0.3 V, the cell performance increased with Nafion ionomer content, especially at low ionomer loading, indicating that proton transport rate played an important role. The variation in ionic resistance (R_ion) of cathode layers with Nafion ionomer content was experimentally confirmed by using the complex capacitance analysis of impedance data implemented with nitrogen (cathodes)/hydrogen (anodes) atmosphere. For Pt/C, the layer thickness and EAS of cathode were larger than those of MEA cathode using Pt black; and the current densities at 0.6 V were lower than those of Pt black, suggesting that smaller fraction of EAS was utilized.     

Desulfurization in a plate-type gas-lift photobioreactor using light emitting diodes

Hydrogen sulfide gas was removed in a 2-dimensional gas-lift reactor by the photosynthetic microorganismChlorobium thiosulfatophilum using light emitting diodes (LEDs) as a light source. LEDs saved light energy by 99% compared with the incandescent light source. The plate-type gas-lift reactor removed hydrogen sulfide five times better per unit mg of protein, and performed two times better in the maximum performance per unit luminous flux, compared with cylindrical fermentors.     

Analysis for a two-dissimilar-component cold standby repairable system with repair priority

In this paper, a cold standby repairable system consisting of two dissimilar components and one repairman is studied. Assume that working time distributions and repair time distributions of the two components are both exponential, and Component 1 has repair priority when both components are broken down. After repair, Component 1 follows a geometric process repair while Component 2 obeys a perfect repair. Under these assumptions, using the perfect repair model, the geometric process repair model and the supplementary variable technique, we not only study some important reliability indices, but also consider a replacement policy T, under which the system is replaced when the working age of Component 1 reaches T. Our problem is to determine an optimal policy T^? such that the long-run average loss per unit time (i.e. average loss rate) of the system is minimized. The explicit expression for the average loss rate of the system is derived, and the corresponding optimal replacement policy T^? can be found numerically. Finally, a numerical example for replacement policy T is given to illustrate some theoretical results and the model's applicability.     

Nano Si-coated graphite composite anode synthesized by semi-mass production ball milling for lithium secondary batteries

Nano-sized silicon particles were uniformly coated onto a natural graphite surface by a 1 ton/month-based semi-mass production ball milling method in order to prepare Si-based anodes for Li ion batteries. The structure, surface morphology and Si coating properties of the as-synthesized powders were analyzed by XRD, Raman, SEM, TEM and EDS mapping tools. The initial gravimetric discharge capacity of the Si-coated graphite measured using a half cell was 761 mAh/g at a rate of 0.2 C. Additionally, the discharge capacity retention of a full cell system was 71.4% at a 1 C rate even after 300 cycles as well as 96.6% of initial coulombic efficiency. The cycled composite powders were further analyzed by SEM and EDS mapping techniques. This method is proposed for commercial extension to the manufacture of lithium secondary batteries.