Visualization on the behavior of inert gas jets impinging on a single glass tube submerged in liquid sodium

In order to accurately model sodium–water reaction jets in steam generators of fast breeder reactors, knowledge of size distributions or mean diameters of liquid sodium droplets entrained into the reaction jets is prerequisite. In the present study, argon-gas jet behaviors, without chemical reaction, injected into liquid sodium were successfully visualized using an endoscope and a glass tube, and the size distributions and mean diameters of liquid sodium droplets entrained into the gas jet were also obtained in the bubbling regime. Most of the liquid sodium droplets were observed to be intermittently produced in the vicinity of a gas nozzle in the present study. The droplet size distributions of entrained sodium droplets were found to agree well with the Nukiyama–Tanasawa distribution function when the arithmetic mean diameter was used. The Sauter mean diameters obtained in the present study were also found to be well correlated with an empirical equation proposed by Epstein et al. The present study shows that the existing knowledge, which is based on the results of water experiments, is suitable in terms of accuracy in practice.     

Response of organic photodiode fabricated directly on plastic scintillator to X-rays

Organic photodiodes (OPDs) have attracted considerable interest in the field of photonic devices because they are useful for large and flexible photodetectors. To assess their applicability to radiation measurement, the authors have been studying their response to X-ray irradiation. For a previous study, OPDs with a bulk heterojunction structure were fabricated. Then, their response to X-rays was evaluated. However, the X-ray-induced current was extremely low and the necessity to increase the efficiency was apparent. In this study, to increase X-ray-induced current, the authors fabricated OPDs directly on plastic scintillator plates. The device structure was a plastic scintillator substrate (1 or 5 mm)/ITO (150 nm) or IZO (100 nm)/PEDOT: PSS (30 nm)/P3HT:PCBM (200 nm)/Al (70 nm). The fabricated devices were irradiated with X-rays. Then their responses were evaluated. Results demonstrated that the X-ray-induced current can be increased by fabricating OPDs directly on plastic scintillator plates. The measured energy responses of the devices were compared with the energy deposition calculated using EGS5 code. Both results show coincident tendencies. However, because the collected charges were smaller than expected from simulations in the low-energy region, further study should be conducted to specify the factors.     

Selection of eutectic systems in AI2O3–Y2O3 ceramics

There are two eutectic reactions in the Al₂0₃–rich portion of the AI₂O₃-Y₂O₃ pseudo–binary system; one is the equilibrium A1₂0₃–YAG eutectic reaction at 1826%C, and the other is the metastable A1₂0₃–YAP eutectic reaction at 1702%C. Selection of the A1₂0₃–YAG and the A1₂0₃–YAP eutectics was examined in terms of cooling rate, nucleation temperature and maximum melt temperature. When the melt was cooled from 2100%C at any cooling rate, it always nucleated below the Al₂0₃–YAP eutectic temperature, therefore the Al₂0₃–YAP eutectic was selected. The Al₂0₃–YAG eutectic was selected when the melt was cooled from 1900%C at a cooling rate of less than 1 K s^-1. The selection of the two eutectic systems was determined by the nucleation temperature, although the maximum holding temperature of the melt and the cooling rate significantly affected the nucleation temperature. The structure of the melt, such as coordination of oxygen and chemical order when being heated to 2100%C may affect the nucleation behavior.     

Extraction of Exotic Fullerenes and Purification of Single-Walled Nanotubes

Abstract

In this report, we presented a novel and simple extraction method, namely Hydrothermally Initiated Dynamic Extraction (HIDE) method, which allows the extraction of exotic fullerenes remaining in the fullerene soot. In the HIDE method, the soot was treated in boiling water that neither dissolved fullerenes nor produced minimal by-products but untangles the fullerenes from the soot, prior to the extraction by organic solvent. As a result, the HIDE method allowed the extraction of exotic fullerenes, such as dimeric fullerene oxides, higher fullerenes having a low symmetry and oxidized higher fullerenes. Accordingly, the single walled nanotubes (SWNTs) with a purity of 99% by wt was achieved for the first time with the application of the HIDE method.     

Water-soluble metal working fluids additives derived from the esters of acid anhydrides with higher alcohols for aluminum alloy materials

Water-soluble metal working fluids are used for processing of aluminum alloy materials. This short article describes properties of new additives in water-soluble metal working fluids for aluminum alloy materials. Many half esters or diesters were prepared from the reactions of higher alcohols with acid anhydrides. Interestingly, diesters of PTMG (tetrahydrofuran oligomer, MW = 650 and 1000) and polybutylene oxide (MW = 650) with maleic anhydride and succinic anhydride showed both of an excellent anti-corrosion property for aluminum alloy and a good hard water tolerance. The industrial soluble type processing oils including these additives also showed anti-corrosion property and hard water tolerance.     

Hydrogen fermentation properties of undiluted cow dung

Anaerobic treatment of undiluted cow dung (15% total solids), so-called dry fermentation, produced hydrogen (743 ml-H(2)/kg-cow dung) at an optimum temperature of 60 degrees C, with butyrate and acetate formation. The hydrogen production was inhibited by the addition of NH(4)(+) in a dose-dependent manner. A bacterium with similarity to Clostridium cellulosi was detected in the fermented dung by a 16S rDNA analysis.     

Center of excellence for atomically controlled fabrication technology

This short review aims to show the introduction of the educational and research program of "Center of excellence of atomically controlled fabrication technology" supported ministry of education, culture, sports, science and technology--Japan. We would like to introduce research activity and a unique trait of educational system.     

Airflow and thermal conductance in a totally enclosed induction motor

Heat transfer coefficients of air‐cooled fins located on the outer surface of a totally enclosed induction motor were measured. It was found that the heat transfer coefficient decreases in the downstream direction in relation to the outer fins. It was also found that increasing the axial length of the fan cover (i.e., so that the fan cover overlaps the fin) increases the average heat transfer coefficient of the outer fins. Internal airflow induced by the rotor fan inside the motor end‐bracket coincides with the rotational speed of the rotor fan. Airflow velocity between the stator coil end and the housing in the motor is low, so a cooling structure with an inside ventilation passage for airflow was introduced to increase the heat transfer of the stator coil. By using an actual motor, the effect of resin (varnish) between the stator and the motor housing on the thermal‐contact conductance was determined; the thermal‐contact conductance of a motor with resin was 1.58 times higher than that of one without resin. © 2001 Scripta Technica, Heat Trans Asian Res, 31(1): 7–20, 2002     

An optimum design of antireflection coating for spherical silicon solar cells

Antireflection (AR) coatings for spherical crystalline silicon solar cells are theoretically optimized from the viewpoint of achieving the largest photon densities in the spherical crystalline silicon solar cells. Because the AR film thickness is optimized with regard to the photon densities in the spherical crystalline silicon solar cells, tolerance in the film thickness can be evaluated. Also, the optimized AR film thicknesses for the spherical crystalline silicon solar cells and planar crystalline silicon solar cells are compared, and analytic expressions for the optimized AR film thicknesses are derived as a function of a quarter-wavelength film thickness.     

Control of conduction band offset in wide-gap Cu(In,Ga)Se2 solar cells

The effects of conduction band offset of window/Cu(In,Ga)Se₂ (CIGS) layers in wide-gap CIGS based solar cells are investigated. In order to control the conduction band offset, a Zn_1−xMg_xO film was utilized as the window layer. We fabricated CIGS solar cells consisting of an ITO/Zn_1−xMg_xO/CdS/CIGS/Mo/glass structure with various CIGS band gaps (E_g≈0.97–1.43 eV). The solar cells with CIGS band gaps wider than 1.15 eV showed higher open circuit voltages and fill factors than those of conventional ZnO/CdS/CIGS solar cells. The improvement is attributed to the reduction of the CdS/CIGS interface recombination, and it is also supported by the theoretical analysis using device simulation.