• Title/Summary/Keyword: Finite Field Division

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Development of Insulation Sheet Materials and Their Sound Characterization

  • Ni, Qing-Qing;Lu, Enjie;Kurahashi, Naoya;Kurashiki, Ken;Kimura, Teruo
    • Advanced Composite Materials
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    • v.17 no.1
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    • pp.25-40
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    • 2008
  • The research and development in soundproof materials for preventing noise have attracted great attention due to their social impact. Noise insulation materials are especially important in the field of soundproofing. Since the insulation ability of most materials follows a mass rule, the heavy weight materials like concrete, lead and steel board are mainly used in the current noise insulation materials. To overcome some weak points in these materials, fiber reinforced composite materials with lightweight and other high performance characteristics are now being used. In this paper, innovative insulation sheet materials with carbon and/or glass fabrics and nano-silica hybrid PU resin are developed. The parameters related to sound performance, such as materials and fabric texture in base fabric, hybrid method of resin, size of silica particle and so on, are investigated. At the same time, the wave analysis code (PZFlex) is used to simulate some of experimental results. As a result, it is found that both bundle density and fabric texture in the base fabrics play an important role on the soundproof performance. Compared with the effect of base fabrics, the transmission loss in sheet materials increased more than 10 dB even though the thickness of the sample was only about 0.7 mm. The results show different values of transmission loss factor when the diameters of silica particles in coating materials changed. It is understood that the effect of the soundproof performance is different due to the change of hybrid method and the size of silica particles. Fillers occupying appropriate positions and with optimum size may achieve a better effect in soundproof performance. The effect of the particle content on the soundproof performance is confirmed, but there is a limit for the addition of the fillers. The optimization of silica content for the improvement of the sound insulation effect is important. It is observed that nano-particles will have better effect on the high soundproof performance. The sound insulation effect has been understood through a comparison between the experimental and analytical results. It is confirmed that the time-domain finite wave analysis (PZFlex) is effective for the prediction and design of soundproof performance materials. Both experimental and analytical results indicate that the developed materials have advantages in lightweight, flexibility, other mechanical properties and excellent soundproof performance.

Effects of the Remanent Magnetization on Detecting Signals in Magnetic Flux Leakage System (자기누설탐상시스템에서 배관의 잔류자화가 결함신호에 미치는 영향)

  • Seo, Kang;Jeong, Hyun-Won;Park, Gwan-Soo;Rho, Yong-Woo;Yoo, Hui-Ryong;Cho, Sung-Ho;Kim, Dong-Kyu
    • Journal of the Korean Magnetics Society
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    • v.15 no.6
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    • pp.325-331
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    • 2005
  • The magnetic Hut leakage (MFL) type nondestructive testing (NDT) method is widely used to detect corrosion and defects, mechanical deformation of the underground gas pipelines. The object pipeline is magnetically saturated by the magnetic system with permanent magnet and yokes. Because of the strong magnetic field enough to saturate the pipe, there could be distortion of the sensing signals because of the magnetization of the pipeline itself, To detect the defects precisely, the sensing signals are need to be compensated to eliminate the distortions coming from the media hysteresis. In this paper, the magnetizations of the pipeline in MFL type NDT are analyzed by Preisach model and 3D FEM. The distortions of the sensing signals are analyzed.

The Study for Performance Analysis of Software Reliability Model using Fault Detection Rate based on Logarithmic and Exponential Type (로그 및 지수형 결함 발생률에 따른 소프트웨어 신뢰성 모형에 관한 신뢰도 성능분석 연구)

  • Kim, Hee-Cheul;Shin, Hyun-Cheul
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.9 no.3
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    • pp.306-311
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    • 2016
  • Software reliability in the software development process is an important issue. Infinite failure NHPP software reliability models presented in the literature exhibit either constant, monotonic increasing or monotonic decreasing failure occurrence rates per fault. In this paper, reliability software cost model considering logarithmic and exponential fault detection rate based on observations from the process of software product testing was studied. Adding new fault probability using the Goel-Okumoto model that is widely used in the field of reliability problems presented. When correcting or modifying the software, finite failure non-homogeneous Poisson process model. For analysis of software reliability model considering the time-dependent fault detection rate, the parameters estimation using maximum likelihood estimation of inter-failure time data was made. The logarithmic and exponential fault detection model is also efficient in terms of reliability because it (the coefficient of determination is 80% or more) in the field of the conventional model can be used as an alternative could be confirmed. From this paper, the software developers have to consider life distribution by prior knowledge of the software to identify failure modes which can be able to help.

Three-dimensional Imaging of Subsurface Structures by Resistivity Tomography (전기비저항 토모그래피에 의한 지하구조의 3차원 영상화)

  • Yi Myeong-Jong;Kim Jung-Ho;Chung Seung-Hwan;Suh Jung Hee
    • Geophysics and Geophysical Exploration
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    • v.5 no.4
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    • pp.236-249
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    • 2002
  • We have extended the three-dimensional (3-D) resistivity imaging algorithm to cover the 3-D resistivity tomography problem, where resistivity data are acquired using electrodes installed in several boreholes as well as at the earth surface. The imaging algorithm consists of the 3-D finite element forward modeling and least-squares inversion scheme, where the ACB (Active Constraint Balancing) is adopted to enhance the resolving power of the inversion. Sensitivity analysis with numerical verifications shows that 3-D resistivity tomography is a very appealing method and can be used to get 3-D attitude of subsurface structures with very high-resolution. Moreover, we could accurately handle the topography effect, which could cause artifacts in the resistivity tomography. In the application of 3-D resistivity tomography to the real field data set acquired at the quarry mine, we could derive a very reasonable and accurate image of the subsurface.

Design of External Coil System for Reducing Artifact of MR Image due to Implantable Hearing Aid (이식형 보청기에 의한 자기공명 영상의 인공음영 축소를 위한 외부 코일 시스템 설계)

  • Ahn, Hyoung Jun;Lim, Hyung-Gyu;Kim, Myoung Nam;Cho, Jin-Ho
    • Journal of Korea Multimedia Society
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    • v.19 no.2
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    • pp.375-385
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    • 2016
  • Recently, several implantable hearing aids such as cochlear implant, middle ear implant, etc., which have a module receiving power and signal from outside the body, are frequently used to treat the hearing impaired patients. Most of implantable hearing aids are adopted permanent magnet pairs to couple between internal and external devices for the enhancement of power transmission. Generally, the internal device which containing the magnet in the center of receiving coil is implanted under the skin of human temporal bone. In case of MRI scanning of a patient with the implantable hearing aid, however, homogeneous magnetic fields of the MRI might be interfered by the implanted magnet. For the above reasons, the MR image is degraded by large area of artifact, so that diagnostics are almost impossible in deteriorated region. In this paper, we proposed an external coil system that can reduce the artifact of MR image due to the internal coupling magnet. By finite element analysis estimating area of MR artifact according to varying current and shape of the external coil, optimal coil parameters were extracted. Finally, the effectiveness of the proposed external coil system was verified by confirming the artifact at real MRI scan.

A Study on Feasibility of Surface Wave Application for the Assessment of Physical Properties of Dam (표면파 적용 댐체 물성 조사 타당성 연구)

  • Kim, Hyoung-Soo;Min, Dong-Ju;Kim, Jung-Yul;Ha, Ik-Soo;Oh, Suk-Hoon
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.384-391
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    • 2005
  • Three dimensional finite difference elastic wave model was developed to estimate the feasibility of surface wave applications in geotechnical problems. The wave motions calculated by the developed program in this study shows good agreement with well known analytic solutions. The surface wave motions calculated from layered dam type structure can be interpreted as a infinite layer structure using dispersion curve but it is need a special source of which high energy in frequency band lower than 10 Hz to get information of physical properties in few tens meter deep. The source which has high energy in the low frequency band, however, can give defect on dam and this will make some limitation in real field applications. The dispersion curves calculated from the surface wave motion of homogeneous and center core type dam models will give rise to fatal errors if the conventional infinite layer structure used in their interpretation because the surrounding materials and boundaries of dam make some distortion in dispersion curve of surface wave. So it is strongly recommended to use three dimensional inversion model for correct interpretation and estimation of physical properties of dam materials.

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Influences of Geometric Configurations of Bypass Grafts on Hemodynamics in End-to-Side Anastomosis

  • Choi, Jae-Sung;Hong, Sung-Chul;Kwon, Hyuck-Moon;Suh, Sang-Ho;Lee, Jeong-Sang
    • Journal of Chest Surgery
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    • v.44 no.2
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    • pp.89-98
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    • 2011
  • Background: Although considerable efforts have been made to improve the graft patency in coronary artery bypass surgery, the role of biomechanical factors remains underrecognized. The aim of this study is to investigate the influences of geometric configurations of the bypass graft on hemodynamic characteristics in relation to anastomosis. Materials and Methods: The Numerical analysis focuses on understanding the flow patterns for different values of inlet and distal diameters and graft angles. The Blood flow field is treated as a two-dimensional incompressible laminar flow. A finite volume method is adopted for discretization of the governing equations. The Carreau model is employed as a constitutive equation for blood. In an attempt to obtain the optimal aorto-coronary bypass conditions, the blood flow characteristics are analyzed using in vitro models of the end-to-side anastomotic angles of $45^{\circ}$, $60^{\circ}$ and $90^{\circ}$. To find the optimal graft configurations, the mass flow rates at the outlets of the four models are compared quantitatively. Results: This study finds that Model 3, whose bypass diameter is the same as the inlet diameter of the stenosed coronary artery, delivers the largest amount of blood and the least pressure drop along the arteries. Conclusion: Biomechanical factors are speculated to contribute to the graft patency in coronary artery bypass grafting.

Analysis of an Actual Slope Failure in the Residual Soil by Suction Stress Based Effective Stress (흡수응력에 기반한 유효응력에 의한 실제 잔류토 사면 붕괴의 해석)

  • Oh, Seboong;Lu, Ning;Park, Young Mog;Lee, Junsuk
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.32 no.3C
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    • pp.113-120
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    • 2012
  • An actual slope failure was analyzed in residual soils at Jinju. Due to rainfall infiltration, the safety factor decreases in the unsaturated layers, since the effective stress and shear strength decrease. In this study, the effective stress is based on suction stress using soil water retention curve. Unsaturated properties were evaluated on soil water retention curve, hydraulic conductivity and shear strength with samples from the site. After infiltration analysis of unsaturated flow under the actual rainfall, the distribution of pore water pressure could be calculated in the slope layers. In the stress field of finite elements, an elastic analysis calculated total stress distribution in the layers and also shear stresses on the slip surface using elastic model. On the slip surface, suction stress and effective stress evaluated the shear strength. As a result, the factor of safety was calculated due to rainfall, which could simulate the actual slope failure. In particular, it was found that the suction stress increases and both the effective stress and the shear strength decrease simultaneously on the slip surface.

A study on the design optimization of the head stucture of 5-axis machining center using finite element analysis (유한요소해석을 이용한 5축 복합가공기 헤드 구조물의 최적 설계에 관한 연구)

  • Kim, Jae-Seon;Lee, Meong-Ho;Youn, Jae-Woong
    • Journal of the Korea Convergence Society
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    • v.12 no.9
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    • pp.161-168
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    • 2021
  • As the demand for high speed and high precision increases in the field of machine tool, interest in stiffness and vibration of machine tool is increasing. However, it takes a lot of time to develop a detailed design of machine tool based on experience, and it is difficult to design appropriately. Recently, structural optimization using FEM are increasingly used in machine tool design. But, it is difficult to optimize in consideration of the vibration state of the structure since optimization through stress distribution of a structure is mainly used, In this paper, Static structural analysis, mode analysis, and harmonic analysis using FEM were conducted to optimize the head structure that has the most influence on machining in a 5-axis machine tool. It is proposed a topology optimization analysis method that considers both static stiffness and dynamic stiffness using objective function design.

A Public-Key Crypto-Core supporting Edwards Curves of Edwards25519 and Edwards448 (에드워즈 곡선 Edwards25519와 Edwards448을 지원하는 공개키 암호 코어)

  • Yang, Hyeon-Jun;Shin, Kyung-Wook
    • Journal of IKEEE
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    • v.25 no.1
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    • pp.174-179
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    • 2021
  • An Edwards curve cryptography (EdCC) core supporting point scalar multiplication (PSM) on Edwards curves of Edwards25519 and Edwards448 was designed. For area-efficient implementation, finite field multiplier based on word-based Montgomery multiplication algorithm was designed, and the extended twisted Edwards coordinates system was adopted to implement point operations without division operation. As a result of synthesizing the EdCC core with 100 MHz clock, it was implemented with 24,073 equivalent gates and 11 kbits RAM, and the maximum operating frequency was estimated to be 285 MHz. The evaluation results show that the EdCC core can compute 299 and 66 PSMs per second on Edwards25519 and Edwards448 curves, respectively. Compared to the ECC core with similar structure, the number of clock cycles required for 256-bit PSM was reduced by about 60%, resulting in 7.3 times improvement in computational performance.