Relation between the superstructures and the tree deterioration in polypropylene

The initiation and growth of the electrical tree in crystalline polymers are influenced by the superstructure. However, there are still many unclear points in the relationship between the tree deterioration and the superstructure (spherulites). To study the relationship between the tree deterioration and the spherulite, we designed the measuring apparatus which allows simultaneous observation of these phenomena. The sample was set on the stage of the polarizing microscope to make observations of the tree initiation and growth in polypropylene. This paper reports the results of some observations concerning the tree initiation and growth in polypropylene with 60-Hz ac voltage. The results are as follows:

• 1 Prior to the initiation of trees, a fine deterioration zone is formed on spherulite surfaces. Thereafter, the discharge occurs along the spherulite surface, and the trees occur.
• 2 Tree shapes change under the influence of the distribution state of spherulite.
• 3 Tree initiation voltage is 5.8 kV for the spherulite inside and 5.1 kV for the spherulite boundary, respectively.

     

Fabrication of highly efficient full-color electroluminescent device composed of nanocrystalline silicon

We fabricated a highly-efficient full-color electroluminescent device composed of nanocrystalline silicon (nc-Si). High luminance red, green and blue luminescence from the device was achieved by using hydrofluoric acid solution and oxidation techniques, because these techniques lead to reduction of both nc-Si size and P(b)-center on the surface, which is related closely to luminescent color and luminance, respectively. Moreover, direct current (DC) operating voltage on red/green/blue light emission of the device was realized at a relative low value below 10.0 V by controlling the thickness of the oxidized layer on the nc-Si surface. These results are a strong indication that the device developed in this study can be adapted to future flat panel display and illumination fields.     

Compatibility between ecocement produced from incinerator ash and reactive aggregates in ASR expansion of mortars

Recently, in Japan, two new-type hydraulic cements, high early strength type ecocement (HEC) and normal type ecocement (NEC), have been developed using incinerator ashes up to 50% of the raw materials. In this study, the compatibility of these ecocements with various types of reactive aggregates with respect to alkali-silica reaction (ASR) was studied. Ordinary Portland cement (OPC) and blast furnace slag cement (BFSC) were also used for a comparative study. Two types of the accelerated mortar bar expansion test, the JIS A1146 and the Danish methods, were used to clarify the expansion behavior of mortars made with the above cements. The influence of a combination of the chemical and mineralogical compositions of cement and the reactive components of aggregate on both the amount of ASR gel and the expansion rate of the mortar was also investigated. From the results, it was found that the expansion behaviors of mortars due to ASR varied significantly depending on a combination of both the mineralogical composition of cement and the reactive component of aggregate.     

Development of triode type RF plasma enhanced CVD equipment for low temperature growth of carbon nanotube

Triode-type radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) equipment has been developed in order to grow well-aligned carbon nanotubes on Si and glass substrates at 550 °C. The CVD equipment employs a grid electrode in addition to the cathode and anode electrodes. The grid electrode allows the growth of a well-aligned carbon nanotube with an inside and an outside diameter of 7 and 17 nm, respectively. Moreover, the patterning growth of the well-aligned CNT on a glass substrate was also demonstrated.     

Study of ultimate seismic response and fragility evaluation of nuclear power building using nonlinear three-dimensional finite element model

The probabilistic safety assessment (PSA) is important for nuclear power buildings in Japan because the risk of the occurrence of seismic ground motions beyond the design assumption cannot be denied. In this paper, the building fragility of the seismic PSA was evaluated using a high accuracy analysis model (three-dimensional nonlinear FEM building model considering soil-structure interaction and basemat uplift behavior). First, the response analyses were conducted increasing the input acceleration up to 3500 Gal, until the damage of the building reached the ultimate condition. The damage of the building was estimated from the shear strain, the axial stress, and the consumed strain energy of the shear walls. Then, the influence on the response given by the vertical ground motion and the basemat uplift was evaluated. In addition, considering the shear destruction of the web wall and compressive crash of the flange wall as the fracture modes, the building fragility was evaluated. As a result, it was shown that the investigated method is efficient for more accurate seismic PSA estimation.     

Influence of free‐air CO2 enrichment (FACE) on the eating quality of rice

Rice plants (Oryza sativa L cv Akitakomachi) were grown under free‐air CO₂ enrichment (FACE) in farmers' fields in Shizukuishi, Iwate, Japan during 1999 and 2000. The grains were harvested and subsequently analyzed for protein and amylose contents as well as the traits related to cooked‐rice viscosity. The cooked rice was also subjected to sensory evaluation. The protein content of rice grains grown under elevated CO₂ was significantly lower than that of rice grown under ambient conditions. In addition, CO₂ enrichment increased the whiteness of the grains in both brown and milled rice and reduced their surface hardness. Although the amylose content of rice grains was unaffected, starch pasting properties demonstrated that rice grains in elevated CO₂ had higher maximum viscosity and breakdown than those grown in ambient conditions. Sensory evaluation of cooked rice with respect to umami (deliciousness), appearance, aroma, hardness, stickiness and overall palatability index indicated that the sensory properties were not significantly altered by the CO₂ enrichment treatment. Therefore, we conclude that the growth of the rice cultivar Akitakomachi under elevated CO₂ concentration decreased the protein content, but did not change the palatability to a level that may be detected by sensory taste panel evaluation. Copyright © 2005 Society of Chemical Industry     

Suppression of overtone oscillation and low‐current operation using novel‐design scheme for quartz crystal oscillators

A novel design is proposed for a low‐frequency quartz crystal oscillator circuit. Negative resistance in a low‐frequency CMOS‐inverter quartz oscillator was reviewed for the fundamental mode at 32 kHz and the overtone oscillation at 200 kHz. Suppression of the overtone oscillation, appropriate gain, and drive current reduction are realized by adding only three circuit components. Experimental results and an estimate of the absolute value of the negative resistance are presented for the conventional Colpitts circuit and two types of the quartz crystal oscillator circuit. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Bubble dynamics at boiling incipience in subcooled upward flow boiling

Bubble dynamics in water subcooled flow boiling was investigated through visualization using a high-speed camera. The test section was a vertical rectangular channel, and a copper surface of low contact angle was used as a heated surface. Main experimental parameters were the pressure, mass flux and liquid subcooling. Although all the experiments were conducted under low void fraction conditions close to the onset of nucleate boiling, no bubbles stayed at the nucleation sites at which they were formed. Depending on the experimental conditions, the following two types of bubble behavior were observed after nucleation: (1) lift-off from the heated surface followed by collapsing rapidly in subcooled bulk liquid due to condensation, and (2) sliding along the vertical heated surface for a long distance. Since the bubble lift-off was observed only when the wall superheat was high, the boundary between the lift-off and the sliding could be determined in terms of the Jakob number. Based on the present experimental results, discussion was made for the possible mechanisms governing the bubble dynamics.     

Temperature effect on single bubble rise characteristics in stagnant distilled water

Rise characteristics of spherical and ellipsoidal bubbles in normal- and high-temperature distilled water were visually observed. In the high-temperature experiments, the measured results of the rise velocity of a single bubble and the existence of rise path oscillation roughly agreed with the correlations for the bubbles in contaminated liquid. Also, applicability of an available correlation for the frequency of rise path oscillation was confirmed and a new correlation was developed to evaluate the amplitude of oscillation. It is expected that these results are to contribute to the further improvement of the prediction methods of multidimensional void distribution.     

Bromide removal by hydrotalcite-like compounds in a continuous system.

Bromide ion removal from a real water matrix by hydrortalcite-like compounds (HTCs) was attempted in a column reactor to control the formation of brominated disinfection by-products in drinking water treatment process. The performance of HTCs was found to be comparable to a commercially available ion exchange resin for relatively low alkalinity water. Also, it was deduced that HTCs are better than ion exchange resins for high sulfate water because of their unique ion selectivity. In addition, the ion exchange reactions by HTCs were faster than a commercially available resin. Thus, HTCs are expected to provide similar performance to organic resins without the concern about secondary contamination (i.e., elution of organic compounds from resins).