Transaction of the Japan Society for Simulation Technology
Online ISSN : 1883-5058
Print ISSN : 1883-5031
ISSN-L : 1883-5058
Volume 4, Issue 3
Displaying 1-6 of 6 articles from this issue
Paper
  • Kun Zhao, Naohisa Sakamoto, Koji Koyamada
    2012 Volume 4 Issue 3 Pages 62-70
    Published: 2012
    Released on J-STAGE: December 05, 2012
    JOURNAL FREE ACCESS
      The hyper streamline of diffusion tensor fields is a key technique to visualize the continuous behaviors of biological tissues such as neural or muscle fibers. However, due to the difficulty to handle possible rotational inconsistency (degeneracy), the visualization of hyper stramline is always a hard problem. In a previous research, a visualization result of the degenerate lines in the diffusion 3D Tensors have been showed without considering the possible linear double degenrate point. In this paper, we present an approach to finding the degenerate surfce of the 3D diffusion tensors by locating the possible degeneracy and removing the linear double degenerate point. To visualize the degenerate surface, we use the isosurface as the basic method to approximate the degenerate surface. By rendering the isosurface as an animation, we can obtain a precise degenerate surface in 3D diffusion tensor field.
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  • Yuta Kitamura, Noriyuki Miyazaki, Naoto Nagakura, Yasuhiro Hashimoto, ...
    2012 Volume 4 Issue 3 Pages 71-80
    Published: 2012
    Released on J-STAGE: December 05, 2012
    JOURNAL FREE ACCESS
      CaF2 single crystal is expected being used as high performance optical elements for semiconductor lithography technology. When the wavelength of the light becomes down to the vacuum ultraviolet region such as in the lithography, this single crystal shows intrinsic birefringence phenomenon. Therefore we developed an analysis system for simulating birefringence of CaF2 single crystal, which is used as a chamber window of an ArF excimer laser light source, with consideration of intrinsic birefringence. The analysis system consists of a stress analysis and a birefringence analysis. In the stress analysis, the finite element method was applied to obtain the mechanical stress caused by a window holder and gas pressure. In the birefringence analysis, we treated the wave vector dependence of dielectric constant in order to consider the intrinsic birefringence, in addition to the photo-elastic effect. The crystal anisotropy of CaF2 single crystal was taken into account. We performed the analyses of two crystals with a surface vertical to the ⟨111⟩ direction under the Brewster's angle of incidence and several rotation angles. From these analyses, we obtained reasonable results of the optical path difference in comparison with experimental results. Then we evaluated the optical performance and optimum condition of single crystal window.
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  • Amane Takei, Kouhei Murotani, Shinobu Yoshimura, Hiroshi Kanayama
    2012 Volume 4 Issue 3 Pages 81-95
    Published: 2012
    Released on J-STAGE: December 15, 2012
    JOURNAL FREE ACCESS
      This paper describes a method of making mesh models for large-scale full-wave analysis of electromagnetic fields by the finite element method with an iterative domain decomposition method using numerical human body models. Numerical human body models by National Institute of Information and Communications Technology (NICT) composed by the voxel data with all sides of 2mm include skins, blood vessels, bones etc. and internal organs distinguishing with the material flag. The user can evaluate electromagnetic filed distribution inside the body using NICT numerical human models. A stationary vector wave equation for the 3D full-wave electromagnetic field analysis is solved taking an electric field as an unknown function. The mesh is efficiently divided by using the domain decomposition data structure when elements of 200 million or more are generated from the voxel data of NICT numerical human body models. The mesh generation method corresponds to a past 32-bit I/O library in the ADVENTURE System. Numerical analyses are done using torso models and whole body models. The results prove that our method can precisely predict the distribution of the electromagnetic field in human bodies inside.
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  • Anup Kumar Paul, Yanwei Li, Takuro Sato
    2012 Volume 4 Issue 3 Pages 96-106
    Published: 2012
    Released on J-STAGE: February 06, 2013
    JOURNAL FREE ACCESS
      The accurate distance estimation between anchor nodes and sensor nodes based on the hop count information is an important research problem in Wireless Sensor Networks (WSNs). The accuracy of the localization algorithm greatly impacts the performance of the location dependent protocols and applications such as routing and storage. In anisotropic network where the transmission path between anchor nodes and sensor nodes is not straight but curved, Euclidean distance between a pair of sensor nodes is not always proportional to their hop count distance, which undermines the assumption of many existing range free localization algorithms. Most of the existing works focus on increasing the accuracy by using the heuristics or mathematical techniques. In this paper, we proposed Friendly Anchor Selection Strategy (FASS). in which we show that the selection of friendly anchor nodes instead of using all the anchor nodes for accurate localization is a very important factor especially in anisotropic network. We first demonstrate that using all the anchor nodes in anisotropic network does not give accurate position estimation. Then we devised the method of selecting friendly anchor nodes for each sensor node in order to get accurate localization. Extensive simulation results show that, FASS can effectively select the friendly anchors from all the anchors in anisotropic network and therefore improve the localization accuracy by finally adjusting the average hop distance by utilizing the information from friendly anchors only.
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  • Kenta Onishi, Kazuhiko Tamesue, Takuro Sato
    2012 Volume 4 Issue 3 Pages 107-115
    Published: 2012
    Released on J-STAGE: February 16, 2013
    JOURNAL FREE ACCESS
      We propose a resource allocation method which guarantees a throughput of each mobile station (MS) in a Base Station (BS) cooperated MIMO. A previously proposed method for guaranteeing MS throughputs allocates resource to MSs which can not guarantee throughput with a bad channel quality. Our method excludes MSs with a bad channel quality and allocates resource to the other MSs with a good channel quality. The simulation result showed our method guaranteed more MSs' throughput and achieved a higher system throughput than the previous method.
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  • Yi Jiang, Zhenyu Zhou, Gen-ichiro Ohta, Takuro Sato
    2012 Volume 4 Issue 3 Pages 116-125
    Published: 2012
    Released on J-STAGE: February 21, 2013
    JOURNAL FREE ACCESS
      By combining two complex signals into one, Four Orthogonal Single Sideband Elements (4-SSB) Modulation has the potential to double the information rate of any transmission system using Quadrature Amplitude Modulation (QAM), including multi-carrier systems, such as Orthogonal Frequency Division Multiplexing (OFDM) or Single Carrier Frequency Division Multiple Access (SC-FDMA). However, effective demodulation of 4-SSB signals remained until now an open issue. This paper shows for the first time that 4-SSB modulation applied to QPSK can be demodulated with vanishing error rate in both AWGN and Rayleigh fading conditions when using a turbo structure at the receiver. We design a turbo equalization technique specifically designed to tackle the challenges of the demodulation of 4-SSB signals. Computer simulations show that Bit Error Rate (BER) performances of 4-SSB QPSK can converge toward the performances of QPSK with the proposed receiver structure. To improve the convergence toward the performance limit, we also present a feedback interference canceller (FIC) at the receiver. Incorporated into the turbo structure, this filter enables a trade-off between transmitter and receiver complexity levels, so as to adapt to different types of links such as uplink and downlink, while preserving performances.
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