Yutaka Ishikawa

A concurrent object-oriented knowledge representation language Orient84/K: its features and implementation

Orient84/K is an object oriented concurrent programming language for describing knowledge systems. In Orient84/K, an object is composed of the behavior part , the knowledge-base part , and the monitor part , in order to provide object-oriented, logic-based, demon-oriented , and concurrent-programming paradigms in the object framework. Every object is capable of concurrent execution in Orient84/K. In this paper, after describing an overview of Orient84/K, we will describe implementation issues in a concurrent object oriented language. Then, a new method for an efficient implementation of concurrent objects is proposed and formally described. A new virtual machine for Orient84/K is designed using this method, and some preliminary results of evaluation are presented.

Oxidation enhanced and concentration dependent diffusions of dopants in silicon

Diffusions of impurities in silicon under oxidizing ambient and under extrinsic conditions have been analyzed by developing the Hu’s model. The general expression of diffusion coefficient, which includes both the vacancy and interstitialcy mechanisms, is used. The temperature dependences of a fraction of interstitialcy mechanism for arsenic fAs, phosphorus fP, and boron fB are obtained from the data of oxidation enhanced diffusion (OED) and oxidation induced stacking faults.  fAs =42 exp(−0.542/kT), fP =156 exp(−0.666/kT), and fB =860 exp(−0.829/kT). Time dependence of OED and the concentration dependence of the diffusion coefficient of arsenic and boron under extrinsic conditions can be explained by this model.Diffusions of impurities in silicon under oxidizing ambient and under extrinsic conditions have been analyzed by developing the Hu’s model. The general expression of diffusion coefficient, which includes both the vacancy and interstitialcy mechanisms, is used. The temperature dependences of a fraction of interstitialcy mechanism for arsenic fAs, phosphorus fP, and boron fB are obtained from the data of oxidation enhanced diffusion (OED) and oxidation induced stacking faults.  fAs =42 exp(−0.542/kT), fP =156 exp(−0.666/kT), and fB =860 exp(−0.829/kT). Time dependence of OED and the concentration dependence of the diffusion coefficient of arsenic and boron under extrinsic conditions can be explained by this model.

An object-oriented approach to knowledge systems

ABSTRACT A method for an object oriented modeling of knowledge systems called DKOM (Distributed Knowledge Object Modeling) is proposed. In this modeling method, a knowledge system consists of cooperative knowledge objects, where each knowledge object consists of a behavior part, a knowledge part, and a monitor part. An object oriented language called ORIENT84/K has been designed based on the DKOM. The behavior part of an object contains methods like those in Smalltalk; the knowledge part contains rules and facts like those in Prolog; and the monitor part monitors and controls the object. The relation between class and object, the relation between the behavior part and knowledge part, inference from knowledge, addition and deletion of knowledge, addition and deletion of methods, and access control of objects are described. An expert system is built using ORIENT84/K and the performance of ORIENT84/K is compared with some other programming languages/systems.

The design of an object oriented architecture

This paper proposes a new object model, called the distributed object model, wherein the model is unified as a protection unit, as a method of data abstraction, and as a computational unit, so as to realize reliable, maintainable, and secure systems. An object oriented architecture called ZOOM is designed based on this object model. A software simulator and cross assembler for this architecture have been implemented. The feasibility and performance of the architecture are discussed according to program sizes and estimated hardware size and execution speed.

Metalevel Decomposition in AL-1/D

Research has shown that metalevel architectures and the concept of reflection are useful for modifying programming systems dynamically in a controlled way. To modify the system flexibly, it is necessary to represent various abstraction levels, from the programing language level to the OS level, as well as users multiple views, such as the view where the distributed environment is transparent and the view where that is not transparent, in a programming system. In traditional reflective systems, it is, however, difficult to represent these aspects of the system because these systems are modeled by one metalevel. To overcome this problem, we have proposed a new reflection framework: Multi-Model Reflection Framework (MMRF), and implemented a programming system AL-1/D based on this framework. This paper gives a clearer definition of MMRF than in our previous paper. MMRF is a framework for decomposing a metalevel into multiple conceptual models according to the abstraction levels and users views. These conceptual models may overlap each other in their functions and resources. The decomposed models should run concurrently because models represents system components running concurrently in a system. The definition of MMRF includes the conditions to enable models to run simultaneously without violenting consistently. The structure of a model includes information to decide whether or not these conditions are satisfied.

Low-temperature oxidation of silicon in dry O2 ambient by UV-irradiation

The mechanism of thermal oxidation of silicon in dry O2 ambient with UV-irradiation has been discussed. The dependence of SiO2 thickness on oxidation time follows the model proposed by Cabrera and Mott for relatively short oxidation time. Such dependence follows the model by Deal and Grove for longer time. The main oxidizing species is ozone (O3) or some other reactive species generated from O3 at lower temperatures and this gradually changes to O2 with an increase in temperature. The SiO2 film formed at 500°C for 1 h by the present technique has a similar quality to that of SiO2 formed at high temperatures in dry O2 ambient, as evaluated from Fourier Transform-Infrared (FT-IR), Auger Electron Spectroscopy (AES) and Capacitance-Voltage (C-V) characteristics.

Low-Temperature Thermal Oxidation of Silicon in N2O by UV-Irradiation

A new thermal oxidation method using UV-irradiation has been proposed. Silicon dioxide of 3.5–4.0 nm thickness can be formed in 0.5 h at 200–500°C under N2O flow with UV-irradiation. Oxide formed by the present method is determined to be silicon dioxide. The fixed charge density at the Si/SiO2 interface is relatively low for 500°C oxidation. It is estimated to be about 2×1011 cm-2 without any thermal annealing.

Effect of Tungsten on Synthesis of Multiwalled Carbon Nanotubes Using Cobalt as Catalyst

The effect of W and W2C on the synthesis of multi-walled carbon nanotubes (MWCNTs) by hot-filament-assisted chemical vapor deposition (HFCVD) using Co particles as a catalyst was examined. W or W2C was vacuum-evaporated onto Co particles supported by zeolite and used as a catalyst in CNT synthesis. Methanol was used as a carbon source. Synthesis of CNTs was carried out at about 400°C. The density of the MWCNTs synthesized using only Co as a catalyst was the lowest, and was sequentially higher when using Co combined with W (Co + W) and Co combined with W2C (Co + W2C). The mechanism of the enhancement of CNT growth upon the addition of W or W2C was considered.

Diffusion of Phosphorus and Boron into Silicon at Low Temperatures by Heating with Light Irradiation

The diffusion of phosphorus and boron from a doped oxide into silicon upon heating with light irradiation was investigated at low temperatures. A tungsten halogen lamp was used as a light source. The diffusion coefficient for the 280-nm-thick doped oxide at 760° C upon light irradiation corresponded to that at 900° C upon heating in a furnace for both impurities, indicating enhanced diffusion in the former case. Arsenic diffusion was not enhanced upon heating with light irradiation. The reason for the enhanced diffusion may be that excess self-interstitials are generated at the interface between the doped oxide and silicon during light irradiation. This enhances the diffusion of impurities in silicon, which diffuse mainly by the interstitialcy mechanism.

The enhanced diffusion of low-concentration phosphorus, arsenic and boron in silicon during IR-heating

The diffusion of P, As and B in silicon during IR-heating has been investigated quantitatively under low-concentration conditions. A spin-on source was used for the diffusion of the dopants. The diffusion coefficient was determined by fitting the measured concentration profile to the complementary error function. Enhanced diffusion was obtained for these three impurities. The degree of the enhancement became larger in the order of As, P and B. The cause of the enhancement was found to be the generation of excess self-interstitials during IR-heating.