• Title/Summary/Keyword: Joint Orientation

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Geological Survey in a Construction Area of Taegu-Pohang Highway (대구-포항간 고속도로 7공구의 지질조사 연구)

  • 이병주;선우춘;한공창
    • Tunnel and Underground Space
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    • v.10 no.4
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    • pp.497-505
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    • 2000
  • The surveyed area is mainly distributed by the sedimentary rocks, tuffs, and esites in Cretaceous age and acidic and basic dikes are intruded in these rocks. The principle discontinuities are represented by beddings, joints and faults. The trends of the beddings of sedimentary rocks develop as E-W direction in the start area. However, they are gradually bending and finally their trends are N-S direction in terminal area. In the sedimentary rocks the 3∼4 joint sets are distributed and in dikes joints are more scattered. The majority of joints are highly dipped. Sampo fault which has NE-SW trend makes a valley and NW trending normal faults are well developed at 50k+600 to 51k+000 area. During the construction of tunnel the orientation of discontinuities will not significantly influence on the stability of excavation. Since the rock mass is extensively jointed, the overbreak in tunnel wall may be placed.

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Effect of Kinematic Motion on Changes in Coefficients of Friction of Porcine Knee Joint Cartilage (기구학적 운동이 돼지 무릎 관절연골의 마찰계수 변화에 미치는 영향)

  • Kim, Hwan;Kim, ChoongYeon;Lee, KwonYong;Kim, DaeJoon;Kim, DoHyung
    • Tribology and Lubricants
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    • v.29 no.1
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    • pp.46-50
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    • 2013
  • In this study, the frictional behaviors of articular cartilage against a Co-Cr alloy in two types of kinematic motions were compared. Cartilage pins were punched from the femoral condyles of porcine knee joints, and Co-Cr alloy disks were machined from orthopedic-grade rods and polished to a surface roughness ($R_a$) of 0.002. Friction tests were conducted by using a pin-on-disk-type tribotester in phosphate buffered saline (PBS) under pressures of 0.5, 1, and 2 MPa. All tests were performed in the repeat pass rotational (ROT) and the linear reciprocal (RCP) sliding motions with the same sliding distance and speed of 50 mm/s. The coefficients of friction of the cartilage against the Co-Cr alloy increased with the sliding time in both kinematic motions for all contact pressures. The maximum coefficients of friction in RCP motion were 1.08, 2.82, and 1.96 times those in ROT motion for contact pressures of 0.5, 1, and 2 MPa, respectively. As the contact pressure increased, the coefficients of friction gradually increased in RCP motion, whereas they decrease and then increased in ROT motion. The interaction between the directional change of the shear stress and the orientation of collagen fiber in the superficial layer of the cartilage could affect the change in the frictional behaviors of the cartilage. A large difference in the coefficients of friction between the two kinematic motions could be interpreted as differences in the directional change of shear stress at the contact surface.

The effect of the shape factor of an underground cavern in good rock conditions on its stability by 2D discontinuum analysis (2차원 불연속체 해석에 의한 양호한 암반 내의 지하공동 형상비가 안정성에 미치는 영향 검토)

  • You, Kwang-Ho;Jung, Ji-Suug
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.11 no.2
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    • pp.189-198
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    • 2009
  • Recently the concern about the construction of underground structures such as oil and food storage caverns is increasing in Korea and abroad. The stability of those underground caverns is greatly influenced by shape factor and the size of excavation area as well as the joint conditions. In this study, therefore, the effect of the shape factor of an underground cavern on its stability was analyzed in terms of safety factor. To this end, four different shape factors of a cavern excavated in good rock conditions were investigated and sensitivity analyses were performed based on overburden, lateral earth pressure coefficient, joint spacing, properties, and orientation. The stability of a cavern is evaluated in terms of safety factor estimated numerically based on the shear strength reduction technique. In future, this study is expected to be helpful in designing and evaluating the stability of caverns excavated in discontinuous rock masses.

LASER WELDING OF SINGLE CRYSTAL NICKEL BASE SUPERALLOY CMSX-4

  • Yanagawa, Hiroto;Nakamura, Daisuke;Hirose, Akio;Kobayashi, Kojiro F.
    • Proceedings of the KWS Conference
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    • 2002.10a
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    • pp.193-198
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    • 2002
  • In 1his paper, applicability of laser welding to joining process of single crystal nickel base superalloy turbine blades was investigated. Because heat input of laser welding is more precisely controlled 1han TIG welding, it is possible to optimize solidification microstructure of the welds. Since in single crystal nickel base superalloy the crystal orientation have a significant effect on the strength, it is important to control the solidification microstructure in the fusion zone. A single crystal nickel base supera1loy, CMSX-4, plates were bead-on welded and butt welded using a $CO_2$ laser. The effects of microstructure and crystal orientation on properties of the weld joints were investigated. In bead-on weldling, welding directions were deviated from the base metal [100] direction by 0, 5, 15 and 30 degrees. The welds with deviation angles of 15 and 30 degrees showed fusion zone transverse cracks. As the deviation angles became larger, the fusion zone had more cracking. In the cross section microstructure, the fusion zone grains in 0 and 5 degrees welds grew epitaxially from the base metal spins except for the bead neck regions. The grains in the bead neck regions contained stray crystals. As deviation angles increased, number of the stray crystals increased. In butt welding, the declinations of the crystal orientation of the two base metals varied 0, 5 and 10 degrees. All beads had no cracks. In the 5 degrees bead, the cross section and surface microstructures showed that the fusion zone grains grew epitaxially from the base metal grains. However, the 10 degrees bead, the bead cross section and surface contained the stray crystals in the center of the welds. Orientations of the stray crystals accorded with the heat flow directions in the weld pool. When the welding direction was deviated from the base metal [100] direction, cracks appeared in the area including the stray crystals. The cracks developed along the grain boundaries of the stray crystals with high angles in the final solidification regions at the center of the welds. The fracture surfaces were covered with liquid film. The cracks, therefore, found to be solidification cracks due to the presence of low melting eutectic. As the results, in both bead-on welding and butt welding the deviation angles should be control within 5 degrees for preventing the fusion zone cracks. To investigate the mechanical properties of the weld joints, high temperature tensile tests for bead-on welds with deviation angles of 0 and 5 degrees and the butt welds with dec1ination angles of 0, 5 and 10 degrees were conducted at 1123K. The the tensile strength of all weld joints were more 1han 800MPa that is almost 80% of the tensile strength of the base metal. The strength of the laser weld joints were more than twice that of tue TIG weld joints with a filler metal of Inconel 625. The results reveals 1hat laser welding is more effective joining process for single crystal nickelbase superalloy turbine blades 1han TIG welding.

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A study of the Sampling Bias Correction on Joint Data from 1D Survey Line (1D 측선에 의한 절리 자료에 대한 편향 보정 기법에 관한 연구)

  • 엄정기
    • Tunnel and Underground Space
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    • v.13 no.5
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    • pp.344-352
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    • 2003
  • The procedures to correct sampling biases for discontinuity data obtained from 1D survey line(borehole or scanline) is addressed. The Probability of intersection between the survey line and a circular discontinuity is considered, and a correction far orientation bias is developed assuming discontinuities as equivalent circular disks. The correction incorporates the effect of the angle between the direction of survey line and each discontinuity plane belonging to the discontinuity cluster, size of each discontinuity and length of the survey line. A procedure is provided to estimate unbiased discontinuity spacing parameters using the discontinuity spacing data based on the measurements carried out on a finite length of the survey line.

Stability analysis of a rock slope in Himalayas

  • Latha, Gali Madhavi;Garaga, Arunakumari
    • Geomechanics and Engineering
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    • v.2 no.2
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    • pp.125-140
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    • 2010
  • Slope stability analysis of the right abutment of a railway bridge proposed at about 350 m above the ground level, crossing a river and connecting two huge hillocks in the Himalayas, India is presented in this paper. The site is located in a highly active seismic zone. The rock slopes are intensely jointed and the joint spacing and orientation are varying at different locations. Static slope stability of the rock slope is studied using equivalent continuum approach through the most commonly used commercial numerical tools like FLAC and SLOPE/W of GEOSTUDIO. The factor of safety for the slope under static conditions was 1.88 and it was reduced by 46% with the application of earthquake loads in pseudo-static analysis. The results obtained from the slope stability analyses confirmed the global stability of the slope. However, it is very likely that there could be possibility of wedge failures at some of the pier locations. This paper also presents the results from kinematics of right abutment slope for the wedge failure analysis based on stereographic projections. Based on the kinematics, it is recommended to flatten the slope from 50o to 43o to avoid wedge failures at all pier locations.

Fatigue Creak Growth Properties of Welded Joint for the Railway Bridge Steel (철도교량(鐵道橋梁)의 용접부(鎔接部)에서 피로(疲勞)균열의 성장특성(成長特性))

  • Chang, Dong Il;Yong, Hwan Sun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.4 no.1
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    • pp.125-136
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    • 1984
  • In the weled structures, fatigue fracture mainly depends upon crack growth behavior. Specially anisotropy of crack growth orientation and welding direction become important factor of fracture in the welding jone. When fatigue stressed steel welded with nonfatigue stressed steel, at the low stress intensity factor range, residual stress become more important factor of growth behavior then properties of base metal but when the crack growth in the weld metal, toughness of weld metal become the most important factor. Especially nonhomgeniety of toughness for the weld metal make more scatter the relations of $da/dN-{\Delta}K$.

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Error Analysis of a Parallel Mechanism Considering Link Stiffness and Joint Clearances

  • Park, Woo-Chun;Song, Jae-Bok;Daehie Hong;Shim, Jae-Kyung;Lim, Seung-Reung;Kyungwoo Kang;Park, Sungchul
    • Journal of Mechanical Science and Technology
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    • v.16 no.6
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    • pp.799-809
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    • 2002
  • In order to utilize a parallel mechanism as a machine tool component, it is important to estimate the errors of its end-effector due to the uncertainties in parts. This study proposes an error analysis for a new parallel device, a cubic parallel mechanism. For the parallel device, we consider two kinds of errors. One is a static error due to link stiffness and the other is a dynamic error due to clearances in the parts. In this study, we propose a stiffness model for the cubic parallel mechanism under the assumption that the link stiffness is a linear function of the link length. Also, from the fact that the errors of u-joints and spherical joints are changed with the direction of force acting on the link, they are regarded as a part of link errors, and then the error model is derived using forward kinematics. Lastly, both the error models are integrated into the total error, which is analyzed with a test example that the platform moves along a circular path. This analysis can be used in predicting the accuracy of other parallel devices.

An Improved Approach for 3D Hand Pose Estimation Based on a Single Depth Image and Haar Random Forest

  • Kim, Wonggi;Chun, Junchul
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.9 no.8
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    • pp.3136-3150
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    • 2015
  • A vision-based 3D tracking of articulated human hand is one of the major issues in the applications of human computer interactions and understanding the control of robot hand. This paper presents an improved approach for tracking and recovering the 3D position and orientation of a human hand using the Kinect sensor. The basic idea of the proposed method is to solve an optimization problem that minimizes the discrepancy in 3D shape between an actual hand observed by Kinect and a hypothesized 3D hand model. Since each of the 3D hand pose has 23 degrees of freedom, the hand articulation tracking needs computational excessive burden in minimizing the 3D shape discrepancy between an observed hand and a 3D hand model. For this, we first created a 3D hand model which represents the hand with 17 different parts. Secondly, Random Forest classifier was trained on the synthetic depth images generated by animating the developed 3D hand model, which was then used for Haar-like feature-based classification rather than performing per-pixel classification. Classification results were used for estimating the joint positions for the hand skeleton. Through the experiment, we were able to prove that the proposed method showed improvement rates in hand part recognition and a performance of 20-30 fps. The results confirmed its practical use in classifying hand area and successfully tracked and recovered the 3D hand pose in a real time fashion.

New Surveying Methods for Rock Slopes (암반사면의 새로운 조사기법)

  • Hwang, Sang-Gi
    • Proceedings of the KSR Conference
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    • 2009.05a
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    • pp.1016-1019
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    • 2009
  • Detailed survey of the rock mass is essential for design, construction and maintenance of rock slope. However, geological survey of poor outcrops and various geophysical aids provides limited information for slope engineering. Remote measurement system for excavation surface (Surface Mapper) and projection s/w for borehole data (Fracjection) are developed for further support of slope surveying. The Surface Mapper measures orientation of joint, fault, foliation on excavated rock surface and database the measured data. The Fracjection projects measurements in boreholes, which are obtained by BIPS, Televideo and DOM operation, to any expected excavation space. These methods promise new approaches for surveying, designing, constructing and maintaining processes of slope.

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