Design and Prototyping of Micro Centrifugal Compressor

In order to establish the design methodology of ultra micro centrifugal compressor, which is the most important component of ultra micro gas turbine unit, a 10 times of the final target size model was designed, prototyped and tested. The problems to be solved for downsizing were examined and 2-dimensional impeller was chosen as the first model due to its productivity. The conventional ID prediction method, CFD and the inverse design were attempted. The prototyped compressor was driven by using a turbocharger and the performance characteristics were measured.     

a-Si/mc-Si hybrid solar cell using silicon sheet substrate

A hybrid junction solar cell with amorphous silicon (a-Si) and multicrystalline silicon (mc-Si) was fabricated using a mc-Si sheet substrate, which is produced directly from molten silicon using a novel rotational solidification method. The efficiency of 11.6% was obtained for the hybrid junction cell, while 10.2% for the single junction cell made of a mc-Si sheet substrate, which confirmed that the hybrid structure is effective to improve the solar cell property made of a mc-Si substrate. With introducing light trapping structure, the efficiency was improved to be 12.0%. Moreover, the possibility of Jsc improvement was investigated using the advanced light trapping structure. Jsc of 15.6 mA/cm² was obtained and it was confirmed that the hybrid junction is a promising structure.     

In-situ analysis of positive and negative energetic ions generated during Sn-doped In2O3 deposition by reactive sputtering

Using a quadrupole mass spectrometer combined with an energy analyser, we have investigated the in-situ energy distribution of highly energetic ions generated during reactive sputtering of In-Sn alloy (IT) targets and non-reactive sputtering of Sn-doped In₂O₃ (ITO) ceramic targets. Ar⁺, In⁺, O⁺, O⁻, O₂⁻, InO⁻ and InO₂⁻ ions with kinetic energies greater than 40 eV were clearly observed. Upon increasing the O₂ flow ratio for reactive sputtering, the surface of the IT target changes from metal (metal mode) to oxide (oxide mode) via a state of mixed metal and oxide (transition region). O⁻ ions with the kinetic energy corresponding to cathode voltage are generated at the oxide layer, which expands upon the target surface with increasing O₂ flow ratio in the metal mode and the transition region. In contrast, the flux of 60-eV Ar⁺ ions decreases with increasing O₂ flow ratio. The presence of 125- and 200-eV In⁺ ions is attributed to the dissociation of InSnO₂⁻ and InO₂⁻ with the kinetic energy corresponding to cathode voltage, respectively, while the presence of 40- and 150-eV O⁺ ions is attributed to the dissociation of InO₂⁻ and O₂⁻ with the kinetic energy corresponding to cathode voltage, respectively.     

Low-temperature synthesis of boron carbide powder from condensed boric acid-glycerin product

Crystalline boron carbide (B₄C) powder was synthesized by the carbothermal reduction of a condensed product formed from boric acid (H₃BO₃) and glycerin (C₃H₈O₃). The condensed product was prepared by dehydration after directly mixing equimolar amounts of H₃BO₃ and glycerin, which was followed by pyrolysis in air to obtain a precursor powder from which the excess carbon had been eliminated. The prepared precursor powder had a bicontinuous boron oxide (B₂O₃)/carbon network structure. Crystalline B₄C powder without residual carbon was successfully synthesized from this precursor powder by heating at 1250 °C for 5 h in an Ar flow.     

Magnetic and optical properties of MgAl2O4-(Ni0.5Zn0.5)Fe2O4 thin films prepared by pulsed laser deposition

Thin films composed of MgAl₂O₄ and (Ni_0.5Zn_0.5)Fe₂O₄ ([MA(100-x)-NZFx] films) were grown on fused SiO₂ substrates by pulsed laser deposition. X-ray diffraction measurements revealed that the films were polycrystalline, and that their lattice constant varied linearly with composition, indicating the formation of a solid solution. The film with x=60 was paramagnetic and those with x ≥ 70 were ferromagnetic. The films had a transparency above 75% in the visible range, but the transparency decreased with the x value. The optical band gaps were 2.95, 2.55, 2.30 and 1.89 eV for x=20, 40, 60, 80 and 100, respectively. The Faraday rotation angle increased with x in the visible range, and the film with x=70 exhibited a value of 2000 degrees cm^-1 at 570 nm, which is comparable to the rotation angle of Y₃Fe₅O₁₂. Owing to their high transparency, which extends into the visible range, the [MA(100-x)-NZFx] films can be used in novel magneto-optical devices.     

Inter-laboratory evaluation studies for development of notified ELISA methods for allergic substances (wheat)

Extracts of sausage, sauce, pasta sauce, fish paste and cereal spiked with wheat standard protein at a level of 5-20 ng/mL as sample solutions were analyzed in replicate in 10 laboratories. Coefficients of variation (CVs) of both ELISA methods using a Wheat Protein ELISA Kit (Gliadin kit) and a FASTKIT Wheat ELISA Kit (Wheat ELISA kit) were mostly below 10%. Mean recoveries of the wheat standard protein from the food extracts were over 40% in the two ELISA methods except those from cereal extract determined using the Wheat ELISA kit. Repeatability relative standard deviations of wheat standard protein in the five food extracts were in the ranges of 16-26.9% and 3.7-36.2% for the Gliadin kit and the Wheat ELISA kit, respectively. Reproducibility relative standard deviations of wheat standard protein in the five food extracts were 21.6-38.5%, 29.7-53.8% for the Gliadin kit and the Wheat ELISA kit, respectively. The recoveries of wheat standard protein from the cereal extract were improved by the increasing the amount of antibody coated on the plate in the Wheat ELISA kit. The detection limits of both ELISA methods were 1 ng/mL in sample solutions. These results suggested that the notified ELISA methods are reliable and reproducible for the inspection of wheat protein levels in extracts of sausage, sauce, pasta sauce, fish paste and cereal.     

Changes during ensilage in fermentation products,tea catechins,antioxidative activity and in vitro gas production of green tea waste stored with or without dried beet pulp

Wet green tea waste (GTW) was ensiled in laboratory silos with or without dried beet pulp at a ratio of 2:1 on a fresh weight basis. The silos were opened at 15, 30 and 60 days after anaerobic storage; fermentation products, tea catechins, antioxidative activity and in vitro gas production were determined. Acetic acid prevailed over the fermentation and the pH declined to below 4.2 when wet GTW was ensiled alone. Addition of dried beet pulp greatly enhanced lactic acid production and the pH further decreased to below 3.8 with no butyric acid being detected. Approximately 90% and 80% of (?)‐epicatechin gallate and (?)‐epigallocatechin gallate, respectively, were degraded in silage prepared from wet GTW alone, while the degradation was ameliorated in mixed silage to about 55% and 70%, respectively. Antioxidative activity was not markedly altered by ensiling and 70–80% of the initial activity was detected after 60 days. Changes were small in (?)‐epigallocatechin, caffeine and total phenols with or without mixing with dried beet pulp. In vitro gas production was similar between materials and their silages, indicating that reduction of tea catechins would not elicit an improvement in digestibility. It is concluded that wet GTW can be ensiled successfully without bacterial inoculants when mixed with other materials containing certain sugars. Ensiling may degrade part of the components of tea catechins, while not affecting total phenols, antioxidative activity and digestibility of wet GTW. Copyright © 2007 Society of Chemical Industry     

Cutting characteristics of twist drill having cutting edges for drilling and reaming

In this study, the cutting characteristics of a drill reamer, which has conventional twist drill cutting edges appended for reaming, were investigated. A drill reamer has three types of cutting edges, whose roles are drilling, semi-finishing, and finishing. The cutting characteristics of a conventional twist drill were compared to those of the drill reamer. The cutting characteristics were evaluated using the thrust force, cutting torque, surface roughness, wear behavior of the cutting edges, and cutting edge temperature. The study used a workpiece made of carbon steel. The temperature of the cutting edge for reaming reached a maximum value of approximately 420°C, even though the depth of the cut was very small. The inner surface roughness with the drill reamer was superior to that with the conventional drill, even under dry and low-speed cutting conditions. The abrasive wear observed on the margin face of the cutting edge used for reaming.     

Demineralisation of whey by a combination of nanofiltration and anion‐exchange treatment: a preliminary study

Demineralisation is an important process for the utilisation of whey in the food industry. Sodium (Na⁺) and potassium (K⁺) ions pass through nanofiltration (NF) membranes in ion pairs with chloride (Cl^?) to maintain electroneutrality, but NF processing can only partially remove these ions from whey, because the total Na and K content of whey generally exceeds the Cl content. In this work, a preliminary study of a new demineralisation method was made. A reconstituted sweet whey powder solution was first treated by Cl‐form anion‐exchange resin to increase the molar ratio of Cl to Na and K from ~0.5 to ~1.0. Subsequently, NF removed >90% of Na and K from the anion‐exchange treated whey compared with <60% from the control whey. This new process could be useful for producing 70% demineralised whey with very low levels of the monovalent ions Na⁺, K⁺ and Cl^?.