• Title/Summary/Keyword: Cross-anisotropy

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High Fatigue Life and Tensile Strength Characteristics of Low Activation Ferritic Steel(JLE-1) by TIG Welding (TIG용접한 저방사화 페라이트강(JLF-1)의 고온강도 및 피로수명특성)

  • Yoon, H.K.;Lee, S.P.;Kim, S.W.;Park, W.J.;Kohyama, A.
    • Proceedings of the KSME Conference
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    • 2001.06a
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    • pp.181-186
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    • 2001
  • JLF-1 steel (Fe-9Cr-2W-V-Ta), low activation ferritic steel, is one of the promising candidate materials fer fusion reactor applications. High temperature fatigue life and tensile strength of JLF-1 steel and its TIG welded joints were investigated at the room temperature and $400^{\circ}C$. The strength of base metal (JLF-1) is in between those of weld metal and the HAZ. When the test temperature was increased from room temperature to $400^{\circ}C$, both strength and ductility decreased for base metal, weld metal and the HAZ. The longitudinal specimens of base metal showed similar strength and ductility compared with those of the transverse specimens at room temperature and $400^{\circ}C$. Little anisotropy was observed in the JLF-1 steel base metal in terms of rolling direction. Fatigue limit of weld metal which was obtained from cross-weld specimen is 495MPa. Thus, the weld metal showed the higher fatigue limit than those of base metal at both room temperature and $400^{\circ}C$. Little anisotropy of fatigue properties was observed for JLF-1 base metal in terms of rolling direction. When the test temperature was increased from room temperature to $400^{\circ}C$, the fatigue limit of both base metal and weld metal decreased substantially.

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Program Development to Evaluate Permeability Tensor of Fractured Media Using Borehole Televiewer and BIPS Images and an Assessment of Feasibility of the Program on Field Sites (시추공 텔리뷰어 및 BIPS의 영상자료 해석을 통한 파쇄매질의 투수율텐서 계산 프로그램 개발 및 현장 적용성 평가)

  • 구민호;이동우;원경식
    • The Journal of Engineering Geology
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    • v.9 no.3
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    • pp.187-206
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    • 1999
  • A computer program to numerically predict the permeability tensor of fractured rocks is developed using information on discontinuities which Borehole Televiewer and Borehole Image Processing System (BIPS) provide. It uses orientation and thickness of a large number of discontinuities as input data, and calculates relative values of the 9 elements consisting of the permeability tensor by the formulation based on the EPM model, which regards a fractured rock as a homogeneous, anisotropic porous medium. In order to assess feasibility of the program on field sites, the numerically calculated tensor was obtained using BIPS logs and compared to the results of pumping test conducted in the boreholes of the study area. The degree of horizontal anisotropy and the direction of maximum horizontal permeability are 2.8 and $N77^{\circ}CE$, respectively, determined from the pumping test data, while 3.0 and $N63^{\circ}CE$ from the numerical analysis by the developed program. Disagreement between two analyses, especially for the principal direction of anisotropy, seems to be caused by problems in analyzing the pumping test data, in applicability of the EPM model and the cubic law, and in simplified relationship between the crack size and aperture. Aside from these problems, consideration of hydraulic parameters characterizing roughness of cracks and infilling materials seems to be required to improve feasibility of the proposed program. Three-dimensional assessment of its feasibility on field sites can be accomplished by conducting a series of cross-hole packer tests consisting of an injecting well and a monitoring well at close distance.

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Seismic First Arrival Time Computation in 3D Inhomogeneous Tilted Transversely Isotropic Media (3차원 불균질 횡등방성 매질에 대한 탄성파 초동 주시 모델링)

  • Jeong, Chang-Ho;Suh, Jung-Hee
    • Geophysics and Geophysical Exploration
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    • v.9 no.3
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    • pp.241-249
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    • 2006
  • Due to the long tectonic history and the very complex geologic formations in Korea, the anisotropic characteristics of subsurface material may often change very greatly and locally. The algorithms commonly used, however, may not give sufficiently precise computational results of traveltime data particularly for the complex and strong anisotropic model, since they are based on the two-dimensional (2D) earth and/or weak anisotropy assumptions. This study is intended to develope a three-dimensional (3D) modeling algorithm to precisely calculate the first arrival time in the complex anisotropic media. Considering the complex geology of Korea, we assume 3D TTI (tilted transversely isotropy) medium having the arbitrary symmetry axis. The algorithm includes the 2D non-linear interpolation scheme to calculate the traveltimes inside the grid and the 3D traveltime mapping to fill the 3D model with first arrival times. The weak anisotropy assumption, moreover, can be overcome through devising a numerical approach of the steepest descent method in the calculation of minimum traveltime, instead of using approximate solution. The performance of the algorithm developed in this study is demonstrated by the comparison of the analytic and numerical solutions for the homogeneous anisotropic earth as well as through the numerical experiment for the two layer model whose anisotropic properties are greatly different each other. We expect that the developed modeling algorithm can be used in the development of processing and inversion schemes of seismic data acquired in strongly anisotropic environment, such as migration, velocity analysis, cross-well tomography and so on.

Flexural and Buckling Analysis of Laminated Composite Beams with Bi- and Mono-Symmetric Cross-Sections (이축 및 일축 대칭단면 적층복합 보의 휨과 좌굴해석)

  • Hwoang, Jin-Woo;Back, Sung Yong
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.12
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    • pp.614-621
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    • 2019
  • A generalized laminated composite beam element is presented for the flexural and buckling analysis of laminated composite beams with double and single symmetric cross-sections. Based on shear-deformable beam theory, the present beam model accounts for transverse shear and warping deformations, as well as all coupling terms caused by material anisotropy. The plane stress and plane strain assumptions were used along with the cross-sectional stiffness coefficients obtained from the analytical technique for different cross-sections. Two types of one-dimensional beam elements with seven degrees-of-freedom per node, including warping deformation, i.e., three-node and four-node elements, are proposed to predict the flexural behavior of symmetric or anti-symmetric laminated beams. To alleviate the shear-locking problem, a reduced integration scheme was employed in this study. The buckling load of laminated composite beams under axial compression was then calculated using the derived geometric block stiffness. To demonstrate the accuracy and efficiency of the proposed beam elements, the results based on three-node beam element were compared with those of other researchers and ABAQUS finite elements. The effects of coupling and shear deformation, support conditions, load forms, span-to-height ratio, lamination architecture on the flexural response, and buckling load of composite beams were investigated. The convergence of two different beam elements was also performed.

Effects of the Combination Herbal Extract on Working Memory and White Matter Integrity in Healthy Individuals with Subjective Memory Complaints : A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

  • Kwon, Oran;Lee, Sunho;Ban, Soonhyun;Im, Jooyeon J.;Lee, Doo Suk;Lee, Eun Hee;Kim, Joohee;Lim, Soo Mee;Lee, Sang Gon;Kang, Ilhyang;Kim, Kyung-Hee;Yoon, Sujung;Lee, Sun Hea
    • Korean Journal of Biological Psychiatry
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    • v.22 no.2
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    • pp.63-77
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    • 2015
  • Objectives The combination extract of four kinds of herbs, Gastrodia elata, Liriope platyphylla, Dimocarpus longan, and Salvia miltiorrhiza, has shown to have memory improving effects in mice. The aim of this study was to investigate the efficacy and safety of the herbal mixture for improving working memory as well as microstructural changes in white matter integrity in individuals with subjective memory complaints. Methods Seventy-five individuals with subjective memory complaints were assigned to receive either placebo (n = 15) or herbal mixture (low-dose group, n = 30 and high-dose group, n = 30) supplementation in an 8-week, randomized, double-blind, placebo-controlled clinical trial. Changes in working memory performance and fractional anisotropy (FA) values reflecting white matter integrity from baseline to 8-week endpoint were assessed. Results The herbal mixture group showed an increase in working memory performance compared to the placebo group (p for interaction = 0.001). In addition, the herbal mixture group showed an increase in FA values in the temporo-parietal regions (corrected p < 0.05), which are crucially involved in working memory function and are among the most affected regions in patients with cognitive impairments. Conclusions Findings from this study indicate that the herbal mixture may be a promising therapeutic option for individuals with subjective memory complaints.

Effect of Kerfing and Incising Pretreatments on High-Temperature Drying Characteristics of Cedar and Larch Boxed-Heart Timbers with Less than 150 mm in Cross Section Size (배할 및 인사이징 전처리가 횡단면 크기 150 mm 이하 삼나무와 낙엽송 수심재의 고온건조특성에 미치는 영향)

  • LEE, Chang-Jin
    • Journal of the Korean Wood Science and Technology
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    • v.48 no.3
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    • pp.345-363
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    • 2020
  • This study was conducted to identify the effect of kerfing and incising pretreatments on high-temperature drying characteristics of cedar and larch boxed-heart timbers with a cross section of less than 150 mm. The result showed that the pretreatments have made a significant difference regarding surface check and shrinkage. Although the kerfing was suitable as a pretreatment to reduce the occurrence of surface check, the incising was not suitable as a pretreatment since the knives of timber joined together, causing the conversion to the surface checks. The shrinkage showed a significant result that the final moisture content was reduced in the order of incising, kerfing, and kerfing-incising after the drying process based on the pretreatment condition. Twist was more affected by the grain angle than the anisotropy of the juvenile wood, and there was no effect of pretreatments.

Analysis of Stability Condition and Wideband Characteristics of 3D Isotropic Dispersion(ID)-FDTD Algorithm (3차원 ID-FDTD 알고리즘의 Stability Condition과 광대역 특성 분석)

  • Kim, Woo-Tae;Koh, Il-Suek;Yook, Jong-Gwan
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.22 no.4
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    • pp.407-415
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    • 2011
  • The stability condition and wideband characteristics of 3D ID-FDTD algorithm which has low dispersion error with isotropic dispersion are presented in this paper. 3D ID-FDTD method was proposed to improve the defect of the Yee FDTD such as the anisotropy and large dispersion error. The published paper calculated the stability condition of 3D ID-FDTD algorithm by using numerical method, however, it is thought that the examples were not sufficient to verify the stability condition. Thus, in this paper, various simulations are included in order to hold reliability under the conditions that the plane wave propagation is assumed with a single frequency and a wideband frequency. Also, the 3D ID-FDTD algorithm is compared to those that have the similar FDTD algorithm with ID-FDTD such as Forgy's method and non-standard FDTD method in a wideband. Finally, the radar cross section(RCS) for the large sphere with high dielectric constant is calculated.

Elastic-plastic Micromechanics Modeling of Cross-anisotropic Granular Soils: II. Micromechanics Analysis (직교 이방적 사질토의 미시역학적 탄소성 모델링: II. 미시역학적 해석)

  • Jung, Young-Hoon;Chung, Choong-Ki
    • Journal of the Korean Geotechnical Society
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    • v.23 no.3
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    • pp.89-100
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    • 2007
  • In the companion paper, we provided the novel elastic-plastic constitutive model based on the micromechanics theory. Herein, the elastic and elastic-plastic deformation of granular soils is meticulously analyzed. To guarantee high accuracy of the microscopic parameter, the systematic procedure to evaluate the parameters is provided. The analysis of the elastic response during the isotropic and triaxial compression shows that the stress-level dependency of cross-anisotropic elastic moduli is induced by the power relationship of the contact force in the normal contact stiffness, while the evolution of fabric anisotropy is more pronounced during triaxial compression. The micromechanical analysis indicates that the plastic strains are likely to occur at very small strains. The plastic deformation of tangential contacts has an important role in the reduction of soil stiffness during axial loading.

Thermal Stability Analysis of a Flexible Beam Spacecraft Appendage (위성체 유연 보 구조물의 열 안정성 해석)

  • 윤일성;송오섭
    • Composites Research
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    • v.15 no.3
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    • pp.18-29
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    • 2002
  • The bending vibration and thermal flutter instability of spacecraft booms modeled as circular thin-walled beams of closed cross-section and subjected to thermal radiation loading is investigated in this paper. The thin-walled beam model incorporates a number of nonclassical effects of transverse shear, primary and secondary warping, rotary inertia and anisotropy of constituent materials. Thermally induced vibration response characteristics of a composite thin walled beam exhibiting the circumferantially uniform system(CUS) configuration are exploited in connection with the structural flapwise bending-lagwise bending coupling resulting from directional properties of fiber reinforced composite materials and from ply stacking sequence. The numerical simulations display deflection time-history as a function of the ply-angle of fibers of the composite materials, damping factor, incident angle of solar heat flux, as well as the boundary of the thermal flutter instability domain. The adaptive control are provided by a system of piezoelectric devices whose sensing and actuating functions are combined and that are bonded or embedded into the host structure.

Texture Development of Cold Rolled and T-6 Treated 7X1X Al-alloy with 0.1% Sc (0.1% Sc이 첨가된 7X1X Al-합금의 압연과 T-6열처리에 따른 집합조직의 발달)

  • Jea, C.W.;Jin, S.J.;Chung, D.S.;Lim, S.T.;Park, N.J.
    • Journal of the Korean Society for Heat Treatment
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    • v.17 no.2
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    • pp.101-105
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    • 2004
  • After extrusion, cold rolling and T-6 treatment, texture development of 7x1x Al-alloy with 0.1% Sc is studied. During extrusion the very strong <111>+weak <100> fiber texture is developed, which is Influenced on the formation of rolling texture. The texture after 80% cold rolling can be described by strong{112}<111>(Cu)+{123}<634>(S) component in the cross section of the extruded rod, the strong -fiber+weak{110}<001>(Goss) components in the longitudinal section, and the strong {110}<112>(Bs)+weak{001}<100>(Cube) components in the transverse section. The components of rolling texture are remained after T-6 treatment, but the maximum density of ODF is higher. The calculated mean r-values and the planar anisotropy are relatively high, which are dependent on the texture. After T-6 treatment, recrystallized equiaxed grains with average grain size of $1{\sim}2{\mu}m$ are obtained.