Fuzzy relational algebra for possibility-distribution-fuzzy-relational model of fuzzy data

In the real world, there exist a lot of fuzzy data which cannot or need not be precisely defined. We distinguish two types of fuzziness: one in an attribute value itself and the other in an association of them. For such fuzzy data, we propose a possibility-distribution-fuzzy-relational model, in which fuzzy data are represented by fuzzy relations whose grades of membership and attribute values are possibility distributions. In this model, the former fuzziness is represented by a possibility distribution and the latter by a grade of membership. Relational algebra for the ordinary relational database as defined by Codd includes the traditional set operations and the special relational operations. These operations are classified into the primitive operations, namely, union, difference, extended Cartesian product, selection and projection, and the additional operations, namely, intersection, join, and division. We define the relational algebra for the possibility-distribution-fuzzy-relational model of fuzzy databases.     

Atomic Layer Epitaxy of Silicon

Two methods are proposed and demonstrated successfully for low temperature atomic layer epitaxy (ALE) of Si, where H atoms play essential roles. The first method is the use of H as a self-limiting factor. Trisilane (Si₃H₈) was used as source gas and the substrate temperature was modulated in order to alternate steps in an ALE cycle. When the temperature was less than 380°C in the adsorption step and more than 520°C in the desorption step, respectively, the grown layer thickness per cycle was 0.8 ML/cycle. The second method is the use of atomic H as an active reducer of a self-limiting factor. A clean surface was exposed to dichlorosilane (SiH₂Cl₂) as source gas to grow an Si monolayer covered with CI. Next, atomic H was injected to reduce CI from the surface. An ideal monolayer growth was obtained with the substrate temperature over 540°C.     

Direct Observation of the Collection Process for Dust Particles from an Air Stream by a Charged Water Droplet

One of the most effective precipitation methods for submicrometer particles is the charged droplet scrubber. The dust collection in the charged droplet scrubber is considered to consist of some processes with respect to the interaction between charged dust particles and a charged water droplet. That is, the charged dust particles are attracted to, collide with, adhere to, penetrate into, rebound from, accumulate on, and reentrain from a charged water droplet. The direct observation of the collection process for dust particles by a charged water droplet was conducted by using the experimental setup designed by the authors. It was found from the experiments that particles with good wettability were captured inside the water droplet, particles with poor wettability floated at regular intervals on the droplet surface, and particles with medium wettability were trapped on or inside the water droplet. When particles were trapped on the droplet surface the growth of dendritic depositions was found, and their behavior was very distinct from those obtained on the fibrous filter due to the fluidity of the droplet surface. The deposition mechanisms of charged particles on the charged water droplet are discussed qualitatively.     

Development of three-dimensional electric field analysis by segment arrangement based on a charge simulation method

This paper describes the development of three-dimensional electric field analysis by using the so-called segment method which enables the electric field to be calculated with high accuracy and with enhanced efficiency, for high-voltage apparatus. In the segment method, electrode configuration of high-voltage apparatus is simulated by small components which are called segments and by the arrangement of several kinds of such segments. In this calculation, the charge simulation method is used which is suitable for segment application. As basic segments, spherical, cylindrical and ring segments are used and in addition to these, as subsegments, disc and elbow segments are adopted for good simulation of the total electrode configuration. In this paper, the fundamental construction and arrangement parameter of segments were discussed. Moreover, the segment method was applied to an actual high-voltage apparatus and the calculation accuracy was discussed. It was clarified that the segment method has sufficient calculation accuracy and is a very efficient means for three-dimensional electric field analysis.     

Electron-microscopic imaging of single-walled carbon nanotubes grown on silicon and silicon oxide substrates

Direct imaging of single-walled carbon nanotubes (SWNTs) suspended on pillar-patterned Si or SiO2 substrates is investigated using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The suspended nanotubes are successfully observed by direct TEM imaging and it is seen that they have either individual or bundles of SWNTs. Low energy (< or =2 keV) SEM produces high contrast images of suspended SWNTs. On the contrary, when SWNTs contact a SiO2 substrate, they are imaged using electron-beam induced current. The image brightness depends on the length of SWNTs.     

In situ high-temperature visible microspectroscopy for volcanic materials

In situ high-temperature visible microspectroscopy has been developed in order to study color change kinetics of volcanic materials. Olivine thin sections put on a synthetic alumina plate are heated on a heating stage at 600-800 degrees C under a visible microspectroscope. Changes in visible absorption spectra are monitored every 60 s for 5 hours. The obtained high-temperature visible spectra showed a gradual increase with time in absorbance in the shorter wavelength region (400-600 nm). The 430 nm absorbance (ligand field transition of Fe3+ increased more with time at higher temperatures. Assuming diffusional transport in plane sheets, apparent diffusion coefficients were determined at temperatures of 600-800 degrees C. The activation energy for this diffusion in olivine is 208 +/- 17 kJ/mol. This activation energy value is similar to those for the metal vacancy diffusion in olivine. This newly developed in situ high-temperature visible microspectroscopy can provide kinetic measurements of visible spectral change of materials at high temperatures such as volcanic materials.     

Preparation and properties of fine hematite powders by hydrolysis of iron carboxylate solutions

Submicrometer, crystalline hematite (α-Fe₂O₃) particles were prepared by hydrolysis of organic iron carboxylate solutions using water at 175 °C for 30 minutes. The particle size of hematite was significantly dependent on the liquid-phase stirring speed and the organic compositions. The precipitation rate of hematite from the organic solution followed first-order kinetics. The precipitation rate increased markedly with increasing temperature, and the activation energy for the process was 94.6 kJ mol⁻¹. At 220 °C, the hydrolysis of iron carboxylate solution led to a mixture of hematite and magnetite (Fe₃O₄). The iron oxides prepared at 175 °C to 220 °C were found to be free from organic contamination by the starting material.     

Development of in-process visualization system for laser-assisted three-dimensional microfabrication using photocatalyst nanoparticles

Recently, microfabrication technology has been used to develop micro-electro-mechanical systems (MEMSs), micro-total analysis systems (μ-TASs), and photonic crystals. Various microfabrication techniques have been proposed; however, a technique that can be used to efficiently fabricate 3-D structures via a simple procedure has not been reported thus far. Because 3-D metal structures have not only mechanical functions but also electromagnetic functions, it is desirable to develop such a technique. Our research group is in the process of developing a new technique for 3-D microfabrication that involves the use of a lower power continuous wave laser. Our technique is characterized by the reduction of silver ions via the photocatalysis of titanium dioxide (TiO2) excited at the laser beam waist. For the analysis and development of our microfabrication technique, we developed a microscope system that enabled us to observe the microfabrication process along the fabrication beam optical axis and its radial direction. We successfully visualized the microfabrication process in 3-D. The visualization showed that when the beam waist was swept, the silver structure grew in 3-D following its path. The effect of the substrate on the deposition condition was examined.