Characterisation of radionuclides formed by high-energy neutron irradiation

The physicochemical properties of radionuclides suspended in the air are important parameters in order to evaluate internal doses due to the inhalation of the airborne radionuclides and to develop the air-monitoring system in high-energy proton accelerator facilities. This study focuses on the property of radioactive airborne chlorine (38Cl and 39Cl) and sulphur (38S) produced in Ar gas by irradiation with high-energy neutrons. As a result of the irradiation of a mixture of Ar gas and dry air, 38Cl and 39Cl existed as non-acidic gas and 38S was present as acidic gas. Furthermore, it has been found that in the high-energy neutron irradiation of aerosol containing Ar gas, the higher the amount of radioactive aerosols, the lower will be the amount of radioactive acidic gas.     

A new method for preparing plan-view TEM specimen of multilayered films using focused ion beam

A new method is proposed for preparing plan-view specimens of a CeO(2)/Gd(2)Zr(2)O(7) multilayer on a metal substrate using focused ion beam milling. In the plan-view specimen, a membrane from the surface region of the CeO(2) to the Gd(2)Zr(2)O(7) layer was thinned to electron transparence so that the entire span of the multilayer can be observed in a single sample. The in-plane alignments of the CeO(2) layer and the Gd(2)Zr(2)O(7) layer were analysed using selected-area diffraction patterns (SADPs). The boundaries between the CeO(2) grains were also examined using SADPs.     

System boundary selection in life-cycle inventories using hybrid approaches

Life-cycle assessment (LCA) is a method for evaluating the environmental impacts of products holistically, including direct and supply chain impacts. The current LCA methodologies and the standards by the International Organization for Standardization (ISO) impose practical difficulties for drawing system boundaries; decisions on inclusion or exclusion of processes in an analysis (the cutoff criteria) are typically not made on a scientific basis. In particular, the requirement of deciding which processes could be excluded from the inventory can be rather difficult to meet because many excluded processes have often never been assessed by the practitioner, and therefore, their negligibility cannot be guaranteed. LCA studies utilizing economic input-output analysis have shown that, in practice, excluded processes can contribute as much to the product system under study as included processes; thus, the subjective determination of the system boundary may lead to invalid results. System boundaries in LCA are discussed herein with particular attention to outlining hybrid approaches as methods for resolving the boundary selection problem in LCA. An input-output model can be used to describe at least a part of a product system, and an ISO-compatible system boundary selection procedure can be designed by applying hybrid input-output-assisted approaches. There are several hybrid input-output analysis-based LCA methods that can be implemented in practice for broadening system boundary and also for ISO compliance.     

Electron transport behaviors across single grain boundaries in <Emphasis Type="Italic">n</Emphasis>-type BaTiO<Subscript>3</Subscript>, SrTiO<Subscript>3</Subscript> and ZnO

In some electroceramic materials, their unique electrical properties are due to potential barriers, i.e., double Schottky barriers (DSBs), formed at grain boundaries. So far, some researchers have revealed that the electrical properties of DSB are closely related to grain boundary characters, especially grain boundary coherency. For example, highly coherent boundary does not give PTCR or varistic property, while random types exhibit clear resistivity jump or abrupt current increment. Therefore, a concept of grain boundary design will be required for future device manufacturing, even in bulk materials. But it has not been clarified yet why the electron transport behaviors depend on them. In order to address this question, it is necessary to carry out a systematic experiment focusing on single grain boundaries using well-defined bicrystals.In the present study, we have summarized our studies with a special interest in electron transport behavior across single grain boundaries for n-type BaTiO₃, SrTiO₃ and ZnO.     

Forecasting daily peak load by a deterministic prediction method employing Gram-Schmidt orthonormalization

A technique for forecasting daily peak load in a utility power system is presented. After embedding time series data of daily peak load into a reconstructed state space, a nonlinear mapping is constructed by a local approximation method based on the orthonormal Gram-Schmidt bases. This method utilizes only the past load data for short-term prediction of the daily peak load, while many conventional methods make predictions with various kinds of data such as temperature and weather. The quality of prediction by the proposed method is as good as those with other prediction methods. Moreover, the results of short-term prediction by this method are satisfactory even with data as small as 250 points.     

Novel fast atom beam (FAB) processes for fabricating functional nanostructures on three-dimensional microstructures

 We have developed four manufacturing processes that use a fast atom beam (FAB) for fabricating functional nanostructures on three-dimensional (3-D) microstructures. Such fabrication involves two steps: (1) producing the 3-D microstructure; and (2) producing the nanometer-size functional structures at a local point on this microstructure. The FAB methods that we developed for the first step are the separated (non-contact) mask FAB (SM-FAB) and moving mask FAB (MM-FAB), and those for the second step are the nanometer-motion moving mask FAB (NMM-FAB) and electron-beam deposition-pattern FAB (ED-FAB). We previously demonstrated the capability of the SM-FAB, by producing a multi-faced microstructure, a micro gojyunoto (named after an old Japanese temple tower). In this study, we describe and demonstrate the capability of the MM-FAB, by producing multiple, multi-curved and sloped structure, a diffraction grating structure; the NMM-FAB, by producing ultra-fine stairs, 30 nm wide and 30 nm high; and the ED-FAB, by producing a GaAs line structure, 55.3 nm wide and 13.6 nm high. These results show that these FAB methods are effective in producing 3-D microstructures and nano-structures. Combinations of these methods will make it possible to produce functional nanostructures on 3-D microstructures. Received: 3 November 1996 / Accepted: 13 November 1996     

Complete remission after radiotherapy for recurrent rectal cancer

Although the efficacy of radiotherapy for the palliation of recurrent or inoperable cancer has been proven, it results in complete tumor remission only rarely. We report a case of pelvic recurrence in which complete histological remission followed radiotherapy. A 68-year-old man developed a small pelvic recurrence near the rectal stump 8 months after a Hartmann procedure for rectal cancer. Histologic examination of the biopsy specimens revealed adenocarcinoma consistent with the primary tumor. He received radiotherapy to the whole pelvis, with a total dose of 39.4 Gy administered in 22 fractions over 4 weeks, with a continuous infusion of 5-fluorouracil as a radiosensitizer. After regression of the tumor was confirmed, resection of the pelvic recurrence was performed. Histologic examination of the resected specimen revealed no tumor. Thirty-six months after the second operation, the patient was alive with no evidence of disease. The experience of our case and a review of the literature suggests that small pelvic recurrences may be more responsive to radiotherapy than larger ones.     

A small-scale flame test for fire-resistance evaluation of rubber conveyor belts with fabric skeletons

Small-scale flame tests were conducted on samples of six different rubber conveyor belts with fabric skeletons for use in Japanese coal mines. Each sample was claimed to be ‘flame-resistant’ under the test condition prescribed in JIS K 6324-1977, but results show that there are problems in this kind of test. Every sample tested sustains flame continuously when the flame exposure time exceeds a certain value or ‘ignition time’. In addition, flame duration seems to depend on the flame-resistance of the fabric skeleton as well as on flame exposure time.     

A future satellite communications system using millimetre-wave bands and an on-board processor

This paper proposes the system concept of a personal satellite communications system that will be available in the first decade of the 21st century. Technologies of millimetre-wave bands and an onboard processor with baseband switching promise to meet the requirements of a personal communications system: portability, low-cost, and large capacity. Based on the prospects of these technologies, the most likely parameters for the future personal satellite communications system and the configuration of a suitable on-board processor are proposed. A trial model of such an on-board processor has been made. In this paper, details of the trial model on-board processor and its future developments are described.     

Laminated polarizers exhibiting high performance over a wide rangeof wavelength

A laminated polarizer exhibiting high performance over a wide range of wavelengths has been fabricated for the first time. The polarizer consists of alternate layers of laminated silica film and metal-included semiconductor ultra-thin film as the transparent and absorptive layers, respectively. Extinction ratios of greater than 50 dB with insertion losses of less than 0.4 dB have been obtained over the wavelength range of 0.8-1.55 μm. At the wavelength 0.98 μm where previously no viable laminated polarizer had been available, the extinction ratio is as high as greater than 60 dB and the insertion loss less than 0.3 dB