vol.10 (1997)

Bulletin of Computer Center
Vol.10, 1997 ISSN 0913-8420 Published March 31, 1997

CFD Analysis of Flow in Highly Loaded Turbines
Wataru Hirohata, Seisho Inaoka, Kanto Shibatani, Hoshio Tsujita, Shimpei Mizuki
PDF   Abstract
In this study, four types of super highly loaded turbine blades are analyzed by a numerical method for the two-dimensional incompressible viscous flow. The governing equations employ the standard κ – ε model are solved in the physical component tensor form with a boundary-fitted coordinate system. The geometries of super highly loaded blades posses the limiting turning angles of about 160 degrees. The pressure distributions on the blade surfaces are compared for four turbine cascades. As the results, it is found that the pressure distribution on the blade surface strongly depend on the blade configuraion.
Inverse Problems in Magnetic Fields and lts Wavelets Analysis
Yoshifuru Saito
PDF   Abstract
This article describes about the definition and approach for the inverse problems in electromagnetic fields. At first, it is discussed to the definition and some examples of the inverse problems. Second, it is introduced the wavelet analysis extensively used in the image processing fields for the inverse analysis. Third, wavelet analysis is applied to the inverse problems. Key idea for the wavelet based inverse approach is that the system matrix of inverse problem is regarded as one of the two dimensional image data. Thereby, wavelet transformation makes it possible to derive the most dominant elements from the system matrix, and then we can get an approximate solution of the inve・rse problem based on the most dominant elements of the system.
Leg Motion Control with Considering Stride Length
Hajime Minamisawa, Kuniaki Kawabata, Hisato Kobayashi
PDF   Abstract
It is difficult to control walking robot by analytical approach. Recently, a biological approach has been studied for controlling such complex system. However, it may not be practical to apply every aspects of biological system to real walking robots. The proposed system also has a similar structure of mammal’s automic nerves systems, but its leg motion control is designed by engineering aspects. Especially, the new method considers stride length which depends on a mammals travelling speed. This paper also verifies the validity of the proposed system by some computer simulations.
On A Decision Making System with Emotion
Kakyu Inoue, Kuniaki Kawabata, Hisato Kobayashi
PDF   Abstract
This paper proposes a decision making system and its process of the evolution. By evolving, this system comes to decide its action as if it has an emotion. According to the URGE theory asserted by Masanao Toda, emotion is the most optimized and fundamental decision making system [1]-[4]. If it is able to generate such system artificially, it may be applied in various engineering fields. Conventional decision making system never have such emotional nature. Thus, we started the research of the decision making system with emotion, which may have many possibilities. As the first step, we are trying to make an emotional feature that is included in the decision making system of evoulating. This paper reports about an example of evolutional system that determines actions of virtual creatures in a virtual environment.
Improved Multistep Method for Wide-Angle Beam Propagation
Junji Yamauchi, Jun Shibayama, Minoru Sekiguchi, Hisamatsu Nakano
PDF   Abstract
To improve a wide-angle beam propagation method using a finite-difference technique, the generalized Douglas scheme for variable coefficients is applied to a multistep method. A truncation error of O(⊿x2) is a.chieved in the transverse direction. The effectiveness of the present method is demonstrated in the analysis of a tilted step-index slab waveguide.
Extention of Simulation System for Communications Protocol Performance Evaluation
Miho Kosuge, utaka Yoshida
PDF   Abstract
Computer simulation analysis is suitable for communications protocol performance evaluations. Usually, general simulation systems arc used for such evaluations, but they are inconvenient to make up detail mechanisms of communications protocols and require much time for execution of simulation. We design simulation supporting tool for communications protocols, special purpose simulation system SLCP. Generally, communications protocols may involve many specification items, and it is difficult to support all of them. This system is designed using C++ language and includes new functions for interruptive transmission and transient state performance analysis.
A Basic Study on Line Drawing of Facial Image
Mitsuo Oguro, Yutaka Yoshida
PDF   Abstract
In visual conmmunications systems, such as TV couference, facial images of participants play an important role for them to identify each other and understand their feeling or intents from the expressions on their faces. Such image data occupies most of transmission data. Reconstruction of facial images in the form of line-drawing is studied in this paper. Dividing the process into five steps, various problems at each step are shown. ln particular, abstraction of facial images from total original input images is discussed.
Scattered Photons During Gamma Ray Transmission CT
Yukinori Kawamura, koichi Ogawa
PDF   Abstract
Quantitative image reconstruction in SPECT (single photon emission CT) requires an accurate attenuation map of a cross section of an object. Several data acquisition geometries have been proposed to obtain the true attenuation map by means of gamma-ray transmission CT (TCT). In the transmission data scattered photons are sometimes measured and they reduce the accuracy of reconstructed TCT images. To investigate the effects of scattered photons in gamma-ray transmission CT, we performed Monte Carlo simulations for several types of data acquisition systems. The results showed that a fan beam collimator and a line source rejected most of the scattered photons generated inside an object, and that if we collimated emitted photons at the source side, almost all the scattered photons could be rejected at the collimator on the detector side.
Research on a Pinhole SPECT
Takahisa Kawade, Koichi Ogawa
PDF   Abstract
High spatial resolution SPECT is required to evaluate radio-labeled monoclonal antibodies and receptor-specific radiopharmaceuiticals in targeted radiotherapy. This study was carried out to obtain ultla high resolution pinhole SPECT images. The pinhole SPECT was conducted using a Toshiba GCA-7200A gamma camera system. The diameter of the pinhole was lmm and the pinhole aperture insert made of tungsten was used to reduce the penetration of gamma rays though the edge of the aperture. Data were acquired by a 128xl28 matrix, and the distance from the center of the rotation and the pinhole was 20mm. The Feldkamp method was used for image reconstruction. The imaging voxel was 0.27×0.27×0.27mm. From the experiments the spatial resolution was 1.05mm FWHM.
Helical scan CT by Tilted Fan Beam Data Acquisition
Yasuharu Yamada, Koichi Ogawa, Tsutomu Uno
PDF   Abstract
The helical scan x-ray CT is useful for high speed acquisition of three dimensional image data. In image reconstruction from helical scan data, the data are interpolated to produce projection data which reconstruct an image. This interpolation causes artifacts in the reconstructed image. We propose a new data acquisition method which minimizes the effect of scanning slice position in the axial direction. The proposed method inclines an x-ray detector array in the direction of rotation. The tilted angle is defined as arctan(θL/2Rπtanθ), where L is the moving distance of a table per rotation and R is the radius of rotation of the x-ray source. The angle θ is the orthogonal projection of the half of a fan angl. Simulation results showed that our method eliminated the low frequency distortion and slightly improved the spatia] resolution in the axial direction.
High Speed Photon Transport in Monte Carlo Method
Satoru Takahashi, Koichi Ogawa
PDF   Abstract
Monte Carlo simulations in nuclear science and medicine are usually performed using a model which describes an object by a combination of small voxels. The model named voxel-based(VB) method takes long time to transport photons. To reduce the calculation time we proposed a new photon transportation method. In this method we do not move a photon to the next voxel, but move it to a boundary of different media directoly or by a mean free path. The proposed method was compared with the conventional methods (the VB method and the Quadtree method). The results showed the proposed method accomplislted to reduce the calculation time to half of the VB method.
Rational points on algebraic curves over finite fields and linear codes
Toyokazu Hiramatsu
PDF   Abstract
In 1981, D.Goppa found a surprising link between coding theory and algebraic geometry. Namely he used algebraic curves to construct codes over a finite field. This paper gives a short survey of the work done on algebraic geometric codes, modular forms and number theory during the last 15 years.
Applications of the Wavelet Transformation to the Finite Element Analysis
Minoru Katsumoto, Hiroshi Takeda
PDF   Abstract
This paper considers applicability of the wavelet based transformation, which is widely accepted in time-flequency analysis and picture condensation algorithm, to the finite element numerical analysis. Formulations of wavelet transformation for the finite element method are presented in the global based equations and element based equations.
Algorithms for the Bottleneck Assingnment Problem
Takashi Kobayashi
PDF   Abstract
We have presented two algorithms for obtaining the min-max assignment which minimizes the sum of costs. We compared their computing-times for various sizes of problems. As a result, it is seen that the algorithm such that we once get the minimum cost assignment after the maximum is minimized becomes faster as the size increases.
Formulations of Normalized Orthogonal Discrete Wavelet Transforms
Yuko Oguchi
PDF   Abstract
Though wavelet analysises have been used in many fields of science and technology, it is quite difficult for students to understand the transform’s mathematical bases. In this report, he intends to clear up the elementary foundations of normalized orthogonal discrete wavelet transforms by way of Fourier transform. It will be understood bow to construct orthogonal systems in time space or frequency space, and the relations between both spaces.
Development of CAL System By Dynamic Path
Norimichi Ishida
PDF   Abstract
Nowaday, CAL(or CAl) system is a high demand from class in simultaneous education because of difference level after the exercise computer programming knowledge. We are development CAL system for support on the class level. This CAL system is character at flame presentation by dynamic path in stead of static path. Contents of teaching material is COBOL which by use authoring tool of Navigware(Trade mark by Fujitsu) for computer class at college of Economics. This project work cooperate with Fujitsu Ltd. and member of Fujitsu users group. From now, Authoring tool is in need of being changed for the use multimedia component(audio and motion picture) a demand. And CAL system will be change in use new material.
Development of Teaching Materials with the WWW Browser
Sawa Matsuyama
PDF   Abstract
An educational system with the WWW(world Wide Web) browser is a suitable for all subjects in faculty. This system fast spreads all over the world. The similar system is developed as one of the electronic teaching material in Hosei University. In this system, the professor makes the teaching text with HTML(HyperText Markup Language) before his lecture. Before and after the lecture, the students can see the contents of the lecture by the personal computer or work station everywhere. In near future, we will show interactive-type educational materials using CGI and Java language.
Approximately Analysis to Linear System Used Wavelet Transformation
Harumi Iwasaki, Yuko Oguchi, Yashifuru Saito
PDF   Abstract
In the present paper, an approximate solution methodology employing the wavelet transformation for the huge linear system is proposed. A linear system is transformed into a wavelet spectrum space, and an approximate solution in wavelet spectrum space is evaluated from a reduced small size system including the mother wavelet spectrum. Inverse wavelet transform to thjs spectram solution yields an approximate solution. Several examples demonstrate the usefulness of our methodology.