Research perspective: Japan

The new director of the Building Research Institute of Japan describes an interwoven pattern in which work is done by the Institute for the policies of government through the Ministry of Construction, for other government agencies and for private firms; researchers from private laboratories are also accepted each year and can then take back the results learned. The number of staff, including 120 researchers and research assistants, is relatively small, highly qualified and has an average age of 37. International collaboration is an important activity.     

Processing and photocatalytic properties of Cu-grafted TiO2 powder from acid treated BaTiO3

The respective influences of calcination, drying methods, and washing conditions on the morphologies, surface properties, and photocatalytic activities of TiO₂ powders prepared from acid treatments of BaTiO₃ were investigated. Rutile powder was obtained using the treatment under strong acid conditions. It possesses a bundle-like shape and comprises rutile nanorods. After calcination, characteristic voids were observed in the particles. Anatase powder was obtained by adjusting pH values of a BaTiO₃ suspension to 2.5-3. Drying at 110 °C engendered the formation of spheroidal anatase, although freeze-dried anatase particles assembled into a flake-like shape. The freeze-dried samples show lower crystallinity. With grafting Cu ions, rutile exhibited better photocatalytic performance for the decomposition of gaseous 2-propanol (IPA) under visible light, although it did not work effectively for anatase.     

Fundamental welding R&D results for manufacturing vacuum vessel of JT-60SA

The real vacuum vessel (VV) manufacturing of JT-60SA has started since November 2009 at Toshiba. Prior to starting manufacturing, fundamental welding R&Ds had been performed by three stages. In the first stage, primary tests for screening welding method were performed. In the second stage, the trial welding for 1 m-long straight and curved double shell samples were conducted. The dependences of welding quality and distortion on the welding conditions, such as arc voltage and current, setting accuracy, welding sequence, and the shape of grooves were studied. In addition, welding condition with low heat input was explored. In the last stage, fabrication sequence was confirmed and established by the trial manufacturing of the 20° upper half mock-up [1]. This paper presents the R&D results obtained in the first and second stages.     

A communication protocol based on IR-space division transceivers for mobile robots

In this article, we propose MAC protocols based on our infrared-space division transceiver (IR-SDT) for mobile robots. The IR-SDT has eight communication modules, so it can communicate with a maximum of eight other nodes simultaneously. The number of parallel multiple accesses will be improved by using this transceiver and its specialized protocol. In addition, we consider situations in which a packet collision occurs, and propose a protocol that resolves communication conflicts using the signal collision-detection function of IR-SDT. Finally, we consider the performance of these protocols, and discuss the influence of signal collision-detection accuracy.     

Thermal Feasibility Analyses for the 1356MWe High Conversion-Type Innovative Water Reactor for Flexible Fuel Cycle

A new reactor concept of innovative water reactor for flexible fuel cycle (FLWR) is under development at Japan Atomic Energy Agency in cooperation with Japanese reactor suppliers. A design of 1,356 MWe high conversion boiling water reactor-type FLWR core, which has an instantaneous conversion ratio of 1.04, negative void coefficient, high burnup of 65 GWd/t, and 15-month operational cycle length, has been constructed. So far, studies on thermal-hydraulic characteristics have been performed for tight lattice core. Evaluation methods for the critical power and the pressure drop under both the steady and the transient states have been established, and a modified TRAC-BF1 code has been developed for the thermal-hydraulic design of the FLWR. In this paper, the thermal feasibility of the designed 1356MWe FLWR core is analyzed by using the modified TRAC-BF1 code. The analysis is first carried out for the current core design. It is confirmed that no boiling transition (BT) occurs under the steady state. However, the minimum critical power ratio (MCPR) is only about 1.08, and the BT is confirmed occurring under the postulated abnormal transient processes. Therefore, concretizations of the conditions that ensure the thermal feasibility of a natural circulation-type FLWR and a forced circulation-type FLWR are performed. As for the results, for a forced circulation-type FLWR, the operation-limited MCPR (OLMCPR) is 1.32, and the necessary minimum core coolant flow rate is 640 kg/(m²s). For a natural circulation-type FLWR, the OLMCPR is 1.19, and the necessary minimum core coolant flow rate is 560 kg/(m²s).     

Natural convection heat transfer from a horizontal cylinder in liquid sodium: Part 2: generalized correlation for laminar natural convection heat transfer

Rigorous numerical solution of natural convection heat transfer, from a horizontal cylinder with uniform surface heat flux or with uniform surface temperature, to liquid sodium was derived by solving the fundamental equations for laminar natural convection heat transfer without the boundary layer approximation. It was made clear that the local and average Nusselt numbers experimentally obtained and reported in part 1 of this paper were described well by the numerical solutions for uniform surface heat fluxes, but that those for uniform surface temperatures could not describe the angular distribution of the local Nusselt numbers and about 10% underpredicted the average Nusselt numbers. Generalized correlation for natural convection heat transfer from a horizontal cylinder with a uniform surface heat flux in liquid metals was presented based on the rigorous theoretical values for a wide range of Rayleigh numbers. It was confirmed that the correlation can describe the authors’ and other workers’ experimental data on horizontal cylinders in various kinds of liquid metals for a wide range of Rayleigh numbers. Another correlation for a horizontal cylinder with a uniform surface temperature in liquid metals, which may be applicable for special cases such as natural convection heat transfer in a sodium-to-sodium heat exchanger etc. was also presented based on the rigorous theoretical values for a wide range of Rayleigh numbers. These correlations can also describe the rigorous numerical solutions for non-metallic liquids and gases for the Prandtl numbers up to 10.     

Theoretical studies on the charge trap mechanism of MONOS type memories – Relationship between atomistic information and program/erase actions

We have investigated atomistic structural changes of two types of defects (N vacancies and O substitutional defects) in a SiN layer in MONOS type memories during program/erase actions. N vacancy type defects reveal reversible structural change, whereas O substitutional defects are expected to reveal irreversible structural changes, indicating that detailed atomistic structure is crucial for clarifying the characteristics of MONOS type memory operation.     

Influence of heating and laser irradiation on the Raman D band in single-wall carbon nanotubes

Fine structure of the Raman D band in single-wall carbon nanotubes (SWNTs) was investigated by heating and laser irradiation. It is shown that the D band is composed of three components at ～ 1313, 1340, and 1355 cm^? 1, denoted by D₁, D₂, and D₃, respectively. The D₁ and D₂ intensities significantly increase with laser irradiation in air and vacuum, respectively. The D₃ intensity drastically increases with heating in air. From these results, it is suggested that the fine structure of the D band is attributed to different kinds of defects introduced in SWNTs.     

Application of polymer gels containing side‐chain phosphate groups to drug‐delivery contact lenses

Hydrogels that contain phosphate groups in side chains were studied for their usefulness in drug‐delivery soft contact lenses (SCLs). Naphazoline, a model drug having a cationic group, was incorporated into an SCL because of its phosphate groups and was released over a period of about 14 h. For the SCL, the naphazoline content was equivalent to the phosphate group content. It is suggested that drug‐delivery SCLs can be designed to contain the needed amount of a drug through the choice of the ionic group for the ligand. Furthermore, the SCL having amide groups and phosphate groups had high transparency and an unchanged shape. It is suggested that amide groups and phosphate groups must be introduced into the polymer in equimolar amounts to give the necessary polymer–drug interaction. Therefore, hydrogels having a drug‐delivery system were synthesized by the inclusion of a phosphate group and an amide group. These hydrogels are also applicable to SCL materials. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 731–735, 2005