Irradiation properties of T0 chopper components

We investigated the irradiation properties of the components of a T0 chopper. The organic materials in the rotor bearing grease, the magnetic fluids in seals, and the rubber in the timing belt, as well as the semiconductor materials in the rotation sensor and motor encoder, were all irradiated with high-energy γ-rays up to 100 kGy. No significant damage that shortens the lifetime of a T0 chopper was observed for the mechanical components. However, the semiconductor components were damaged by the irradiation. For the rotation sensor system detecting the rotor phase, the signal from a marker on the rotor shaft was transmitted outside the shielding by an optical fiber with radiation-proofing and the electrical circuits were removed from the beamline shielding. The lifetime of the motor encoder possibly meets the requirement for the maintenance period of the T0 chopper.     

Incentive‐rewarding mechanism to stimulate activities in social networking services

We have developed an incentive‐rewarding mechanism that stimulates activities in social networking services (SNSs), including content uploading and link establishment. We particularly focus on changing the reward assignment ratio based on the different risks users perceive when uploading content with different privacy settings: public‐open and friend‐limited. Learning‐based simulation allowed us to observe that SNS activity, which we measured as the amount of browsed content within a certain period, can be controlled by a rewarding assignment ratio. We then analyzed how the amount of uploaded content and the increase of established links affect SNS activity. Results suggested that the optimal reward assignment ratio to maximize SNS activity changes depending on the total amount of available reward resources. Copyright © 2011 John Wiley & Sons, Ltd.     

Preparation and characterization of stable dispersions of carbon black and nanodiamond in culture medium for in vitro toxicity assessment

Stable dispersions of carbon black and nanodiamond in culture medium were prepared by adding a pre-mixed dispersion of commercial carbon black or nanodiamond in aqueous bovine serum albumin (BSA) solution to culture medium. Dynamic light scattering revealed that carbon black and nanodiamond dispersions prepared in both NaCl solution and culture medium were highly stable. From DLVO theory and the results of zeta potential measurements, the theoretical effect of the electrostatic interactions between adsorbed BSA molecules was found to be minimal. The asymmetric flow field-flow fractionation measurements revealed that 0.05 or 0.56 mg/mL of BSA molecules were adsorbed on 0.11 or 1.09 mg/mL of carbon black, respectively, indicating 1:2 complexation of BSA with the colloidal particles. In the case of nanodiamond, 0.06 or 0.60 mg/mL of BSA molecules were adsorbed on 0.10 or 1.05 mg/mL of nanodiamond, respectively, indicating 1:2 complexation of BSA, which is the same ratio as in the case of carbon black. The adsorbed BSA molecules served as an effective stabilizing agent for the carbon black and nanodiamond, ensuring dispersion stability for at least 1 week. The preparation of the dispersions can be easily carried out by other researchers for toxicity studies.     

Prediction method of critical power by film flow rate measurement and subchannel analysis

This paper presents a method that can estimate the critical power of boiling water reactors, BWRs, with regard to spacer geometry. The current experimental method for estimating the critical power for BWR design requires many trained experts and expensive facilities to conduct the experiments. In the present method, the liquid film flow rate of adiabatic gas‐liquid two‐phase flow and a subchannel analysis of the actual BWR flow condition are measured experimentally and analyzed. In the experiment, deposition enhancement coefficients of three spacer geometries—a ferrule, an egg‐crate, and a ferrule spacer with twisted tape (CYCLONE spacer)—were estimated by measuring the liquid film flow rate of air‐water two‐phase flow flowing up in a vertical square (4 × 4) rod bundle that simulated the rod bundle of a BWR. Using these coefficients, the critical powers for bundles using each type of spacer geometry were calculated in the subchannel analysis. This method was validated using previous critical power data in the actual BWR flow condition. The critical powers predicted by this method agreed well with those of the experimental data. The result confirmed the effectiveness of this experiment‐simulation combined method, as well as the advantage over current experimental methods in terms of human and facility costs. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(5): 309–323, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20069     

Micro-flowers of poly(p-phenylene pyromelliteimide) crystals

Morphology control of poly(p-phenylene pyromelliteimide) (PPPI) crystals was examined using reaction-induced crystallization of oligomers during solution polymerization of self-polymerizable N-(4′-aminophenyl)-3-carboxyl-4-alkoxycarbonylphthalimide. Micro-flowers of the PPPI needle-like crystals were formed in which the needle-like crystals grew radially from the center part as petals. The molecules aligned regularly along the long axis of the needle-like crystal. The structure of alkoxy group in the monomer and the monomer concentration influenced the size of the needle-like crystals, and their average length and width were changeable from 640 nm to 1.69 μm and from 110 nm to 210 nm, respectively. The average thickness was 20 nm. The obtained micro-flowers possessed high crystallinity and exhibited excellent thermal stability.     

Shear-induced pre-crystallization structures of long chain branched polypropylene under steady shear flow near the melting temperature

Shear-induced crystallization of a long chain hyper-branched polypropylene (LCB-PP, denoted PP-3) was carried out at a relatively high temperature of 170 °C, close to its melting temperature of 158 °C. Small-angle X-ray scattering (SAXS) showed that the intensity ratio of the normal to the perpendicular to the shear (V/H) was always larger than 1 for PP-3, indicating that shish-like structures were predominately formed and further growth to kebab was suppressed in PP-3. The crystallization behavior of PP-3 can be explained by the nature of PP-3 that there were a large amount of crystallization nuclei due to their branching points, and the point-like precursors formed from these nuclei were arrayed linearly along the shear direction and transformed into thread-like precursors or premature shishs; however, owing to the large amount of branching, further progress in crystallization was suppressed.     

An electrochemical ionic liquid membrane reactor for NO x selective separation under excess oxygen conditions

A novel electrochemical ionic liquid membrane reactor capable of separating NO from a mixture of NO and oxygen with high current efficiency at low temperatures was designed and tested. This reactor consists of a combination of an ionic liquid and a thin film of anodised alumina with two platinum electrodes. During operation of the reactor, NO is electrically transported from the cathode side to the anode side.     

Effect of silver content on thermal fatigue life of Sn-xAg-0.5Cu flip-chip interconnects

The thermal fatigue properties of Sn-xAg-0.5Cu (x=1, 2, 3, and 4 in mass%) flip-chip interconnects were investigated to study the effect of silver content on thermal fatigue endurance. The solder joints with lower silver context (x=1 and 2) had a greater failure rate compared to those with higher silver content (x=3 and 4) in thermal fatigue testing. Cracks developed in the solders near the solder/chip interface for all joints tested. This crack propagation may be mainly governed by the nature of the solders themselves because the strain-concentrated area was similar for tested alloys independent of the silver content. From the microstructural observation, the fracture was a mixed mode, transgranular and intergranular, independent of the silver content. Higher silver content alloys (x=3 and 4) had finer Sn grains before thermal cycling according to the dispersion of the Ag₃Sn intermetallic compound, and even after the cycling, they suppressed microstructural coarsening, which degrades the fatigue resistance. The fatigue endurance of the solder joints was strongly correlated to the silver content, and solder joints with higher silver content had better fatigue resistance.