Thermal and mechanical properties of bio-based polymer networks by thiol-ene photopolymerizations of gallic acid and pyrogallol derivatives

Allylated pyrogallol (A3PG) and acrylated pyrogallol (Ac3PG) as bio-based trienes, and allylated gallic acid (A4GA) and acrylated allyl gallate (Ac3A1GA) as bio-based tetraenes were synthesized from pyrogallol and gallic acid, respectively. Thiol-ene photopolymerizations of the bio-based polyenes and a pentaerythritol-based primary tetrathiol (pS4P) at the allyl/SH ratio of 1/1 produced photo-cured resins (A3PG-pS4P, Ac3PG-pS4P, A4GA-pS4P and Ac3A1GA-pS4P). The FT-IR spectral analysis revealed that thiol-ene reactions of thiol/allyl and thiol/acryloyl groups smoothly proceeded. Gel fractions of acryl-based cured resins were a little higher than those of allyl-based cured resins. The swelling test and dynamic mechanical analysis revealed that GA- and acryl-based cured resins exhibited higher crosslinking densities than PG- and allyl-based cured resins, respectively. A higher order of tan δ peak temperature was Ac3PG-pS4P (48.3 ° C) > Ac3A1GA-pS4P (24.1 ° C) > A4GA-pS4P (22.1 ° C) > A3PG-pS4P (?7.8 ° C). Ac3PG-pS4P displayed the highest 5 % weight loss temperature, tensile strength and tensile modulus among all of the cured resins.     

Synthesis and Sintering of Cerium(II) Monosulfide

Cerium monosulfide (CeS) powder was synthesized by the reduction of Ce₂S₃ powder with metallic Ce, which was obtained from ceria (CeO₂) powder using carbon disulfide (CS₂) gas. To obtain the maximum amount of CeS from a mixture of Ce₂S₃ and Ce, an excess amount of metallic Ce, a stoichiometric composition, was necessary in the synthesis at 1273 K for 10.8 ks. The preliminary sintering experiments also were performed using a synthetic CeS powder containing a small amount of Ce, Ce₂O₂S, and β-Ce₂S₃ as impurities. It was found that the oxygen content in the sintered compact decreases gradually as the sintering temperature increases, because of the removal of the impurities due to the evaporation of the volatile CeO. Single-phase CeS was formed by sintering at 2173 K. To evaluate the activation energy for densification of single-phase CeS, a CeS powder was prepared by milling an initial sintered compact and was used as an ingredient for hot-press experiments. Densification data during hot-press sintering were analyzed using a kinetic equation, showing that boundary diffusion is a rate-limiting process. The results suggest that this boundary diffusion model can explain well the densification data, with an apparent activation energy of 479 kJ·mol^-1.     

Novel Fabrication of High-Quality ZrO2 Ceramic Thin Films from Aqueous Solution

We report on the direct deposition of high-quality ZrO₂ thin films on various kinds of substrates by the liquid phase deposition method. After reaction for 24 h, thin films formed on various kinds of substrates, and the obtained thin film was comprised of densely packed nano-sized particles. The film annealed at 500°C showed a tetragonal phase at room temperature and this phenomenon has been discussed from the viewpoint of crystallite size effect. The result of optical transmittance measurement revealed that high transparency, more than 70% transmittance, has been achieved for the film after annealing at 900°C.     

Combining UASB and the "fourth generation" down-flow hanging sponge reactor for municipal wastewater treatment.

A "fourth generation" down-flow hanging sponge (DHS) Reactor has been developed and proposed as an improved variant of post-treatment system for UASB treating domestic wastewater. This paper evaluates the potential of the proposed combination of UASB and DHS as a sewage treatment system, especially for developing countries. A pilot-scale UASB (1.15 m3) and DHS (0.38 m3; volume of sponge) was installed in a municipal sewage treatment site and constantly monitored for 2 years. UASB was operated at an HRT of 6 h corresponding to an organic load of 2.15 kg-COD/m3 per day. Subsequently, the organic load in DHS was 2.35 kg-COD/m3 per day, operated at an HRT of 2 h. Organic removal by the whole system was satisfactory, accomplishing 96% of unfiltered BOD removal and 91% of unfiltered COD removal. However, nitrification decreased from 56% during the startup period to 28% afterwards. Investigation on DHS sludge was made by quantifying it and evaluating oxygen uptake rates with various substrates. Average concentration of trapped biomass was 26 g-VSS/L of sponge volume, increasing the SRT of the system to 100-125 d. Removal of coliforms obtained was 3-4 log10 with the final count of 10(3) to 10(4) MPN/100 ml in DHS effluent.     

Potential of renewable energy sources and its applications in Yakushima Island

A study was carried out to see if the potential of renewable energy sources other than hy droelectric power, such as wind, photovoltaic, solar thermal, biomass and waste energy sources, can meet the current energy consumption in Yakushima. The current electricity consumption can be covered by wind and photovoltaic energy sources. The total potential of wind and photovoltaic energy sources is 5.4 times as much as the current electricity consumption. LP gas and kerosene can be replaced by solar thermal and biogas energy. The potential of plant biomass and municipal waste is not sufficient (approximately one third) to cover the rest of the fossil fuels (gasoline, diesel oil and heavy oil). Also, plant biomass and municipal waste must be converted into fluid form. This shortage can be covered by the po tential of wind and photovoltaic energy sources. We also investigated the possibility of tourism expansion using the potential of wind and photovoltaic energy sources. Taking into account three types of capacity (energy, accommodation and transportation), Yakushima can accept approximately four times as many tourists as the current number of tourists.     

Thermoelectromechanical Interaction Among Multiparallel Cracks in a Piezoelectric Material

This paper investigates the thermoelectromechanical interaction among multi parallel cracks in a piezoelectric material under a uniform heat flow and a uniform mechanical load far away from the crack region. The crack faces are supposed to be insulated thermally and electrically. By using the Fourier transform, the thermal and electromechanical problems are reduced to systems of singular integral equations, respectively. The singular integral equations are solved numerically. Numerical calculations are carried out, and detailed results are presented to illustrate the influence of the thermoelectromechanical interaction on the stress and electric displacement intensity factors.     

Spatial indexing of high-dimensional data based on relative approximation

We propose a novel index structure, the A-tree (approximation tree), for similarity searches in high-dimensional data. The basic idea of the A-tree is the introduction of virtual bounding rectangles (VBRs) which contain and approximate MBRs or data objects. VBRs can be represented quite compactly and thus affect the tree configuration both quantitatively and qualitatively. First, since tree nodes can contain a large number of VBR entries, fanout becomes large, which increases search speed. More importantly, we have a free hand in arranging MBRs and VBRs in the tree nodes. Each A-tree node contains an MBR and its children VBRs. Therefore, by fetching an A-tree node, we can obtain information on the exact position of a parent MBR and the approximate position of its children. We have performed experiments using both synthetic and real data sets. For the real data sets, the A-tree outperforms the SR-tree and the VA-file in all dimensionalities up to 64 dimensions, which is the highest dimension in our experiments. Additionally, we propose a cost model for the A-tree. We verify the validity of the cost model for synthetic and real data sets. Edited by T. Sellis. Received: December 8, 2000 / Accepted: March 20, 2002 Published online: September 25, 2002     

Electronic Synthesis of the Avian Retina

An electronic model, based upon reported physiological and anatomical findings and capable of replicating the optical-to-electrical transformations performed by the avian retina has been constructed.     

Mie scattering from sphere structures in polymer blends

Polymer blends of transparent poly(methyl methacrylate) and polystyrene become opaque due to light scattering at the boundaries of the two polymers. The polymer blend is light brown when it is illuminated by white light. The coloring depends on the spherical domain structures existing in the polymer blend. The coloring was analyzed by using the rigorous Mie theory. The Mie results were compared with the semiempirical results previously reported by the authors. The wavelength dependence of theoretical scattering efficiencies on radii of scattering spheres from 0.05 to 1.2 μm was obtained for polystyrene spheres in poly(methyl methacrylate) matrix, and vice versa. The scattering at the short wavelength region is stronger than at the long wavelength region. The scattering efficiencies become almost constant in the visible wavelength region for sufficiently large spheres.     

Aldol condensation of butanal over alkali metal zeolites

Alkali metal zeolites and metal oxides were used for the aldol condensation of n-butanal to 2-ethyl-2-hexenal. The order of activity at 150 °C and 1 atm. was: CsNaY > NaY > LiNaY > MgO >Al₂O₃. Selectivity to 2-ethyl-2-hexenal was 100% for both pure and mixed isomer feed. Infrared spectroscopic studies showed that stable catalysts were produced by propene pretreatments which blocked Lewis acid sites. Adsorption of ammonia and carbon dioxide on CsNaY during aldol condensation of n-butanal causes a decrease in rate. This result, along with the order of activity, suggests that the presence of both acid and basic sites produce higher activity than strongly basic MgO.Work performed at San Jose State University.