• The Journal of Engineering Geology
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• v.32 no.4
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• pp.499-511
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• 2022

In this study, a vertical drop test was carried out to identify the performance of flexible wire rope rockfall protection fence by 100 kJ rockfall energy according to ETAG 027. The flexible wire rope, which consists of wire rope and spring. is especially enhanced the elasticity and flexibility so that it can be longer elongated when the rope is impacted by rockfall compared to original wire rope, and that results longer increase of contact time between rockfall and wire rope and increase rockfall energy absorption capability and decreases rockfall impact force. The test results shows that the plastic deformation occurred in middle post and the final deflection of the middle post was 1.15 m, which is lower than 2.0 m determined by ETAG 027. This vertical test verified the flexible wire rope rockfall protection fence can successfully absorb 102.9 kJ rockfall energy.

• International Journal of Highway Engineering
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• v.6 no.2 s.20
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• pp.25-36
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• 2004

The pressuremeter test can be used as an effective tool for evaluating stiffness of lower pavement layers including subgrade and subbase. At present, the most practical and applicable methods for evaluation of the stiffness of the subgrade and subbase are PBT and CBR in Korea. However, these methods have inherent drawbacks and large variabilities of test results themselves. In this study, an evaluation method and a test procedure that can be used for decision of pavement stiffness using pressuremeter were developed. The obtained results representing stiffness of the subgrade and subbase can replace PBT's soil reaction value k and CBR in design methods. It is found that the developed procedure based on the pressuremeter can provide an effective correaltion between the PBT's soil reaction value k and PMT's reloading modulus ($E_R$).

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.5
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• pp.27-33
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• 2010

In this study, a monotonic loading test to estimate structural capacity of 12 meter long full scale precast pre-stressed concrete beam specimen was performed with a 2,000 kN dynamic actuator. A couple of embedded steel plate was installed at the ends of the beam and specimens were connected to steel girder frame with high tension bolts. Nominal compressive strength of pre-stressed concrete beam and slab were 50 MPa and 24 MPa respectively. Two HD25 tensile steel reinforcements were welded on vertical plate of embedded steel plate. Pre-stressed concrete beam specimen was loaded by displacement control method with a certain loading pattern which was repeated loading and unloading with 10mm increment displacement. About 88.34%, 86.97% and 66.83% of displacement restoration ratios were evaluated at elastic, inelastic and plastic behavior region of specimen respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.2
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• pp.121-131
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• 1986

The stiffness matrix of circularly curved frame elements including the warping effects is formulated by the solutions of vlasov's differential equations, and the procedure for the elastic static analysis of curved girder systems by the displacement method is presented. The validity of this method has been demonstrated by comparing the analysis results with other solutions. And if the tangential lines of the two frame element axes connected at any nodal point coincide, the transformation to the global coordinate system can be omitted when we analyze the structures consisting of circularly curved elements. The theory introduced in this thesis can be applied with sufficient accuracy to the structures built up with horizontally circular curved frame elements which have closed or open cross sections and are symmetric to the axis perpendicular to the plane of the curvature, such as prestressed concrete box girder bridges.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.456-456
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• 2011

최근 차세대 디스플레이, 터치스크린, 전자파 차폐 및 흡수 등의 다양한 응용분야에 적합한 소재를 개발하기 위한 연구가 진행되고 있다. 현재 주로 사용되는 ITO박막은 희소원소인 인듐의 매장량 한계와 높은 비용이 문제시 되고 있기 때문에, 대체 재료의 개발이 시급하게 요구되고 있다. 탄소나노튜브(CNT)는 금속을 능가하는 이론적인 전기전도도를 갖고 있으며 높은 탄성등의 우수한 기계적 성질을 갖고 있어 다양한 차세대 응용에 있어서 최적의 재료로 주목을 받고 있다. 특히, CNT 기반의 투명전도막은 기존의 ITO 박막 보다 우수한 유연성이 기대되어 더욱 기대를 모으고 있다. 본 연구에서는, 최종 고순도 재료를 얻기까지 합성 및 정제에 많은 공정과 시간이 요구되는 고가의 단층벽 나노튜브(SWNT)를 이용하지 않고, 웨이퍼 기판 위에 수직배향 합성한 상태의 다층벽 나노튜브(MWNT)를 별도의 정제과정 없이 초음파 분산한 뒤, 스프레이 코팅법을 이용하여 고분자 기판 위에 투명전도막을 제작하였고, 이때 각기 다른 길이의 수직배향 MWNT를 이용하여 유연성 투명전도막의 전기적 특성에 미치는 MWNT 길이의 영향에 대해 알아보았다. MWNT는 아세틸렌가스를 이용하여 열CVD법으로 합성하였고, 합성시간을 제어함으로써 길이가 다른 MWNT를 얻을 수 있었다. 투명전도막 제조공정의 단순화를 위하여 이용한 MWNT의 초음파 분산 결과, $500{\mu}m$ 이하 길이의 MWNT에서 분산성이 현저히 빨라지는 것을 확인하였다. 한편, 제작한 MWNT 기반의 유연성 투명전도막은 원자간힘현미경 및 면저항 측정기를 이용하여 막 두께에 따른 면저항 특성을 조사하였다. 그 결과 응용 가능한 면저항을 갖는 MWNT 투명전도막의 두께는 최소 50 nm 이상이어야 함을 알았고, 특히 MWNT등의 접촉점(node) 수에 따른 접촉저항 및 전기전도경로(electric conductivity path)를 고려했을 때 최적의 MWNT 길이가 존재하는 것을 확인하였다.

• Korean Journal of Applied Biomechanics
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• v.18 no.2
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• pp.29-39
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• 2008

This study was to provide for Tippelt technique which was a basic technique used in parallel bars. The program was applied to players for 8 weeks. Then it was analyzed by using 3Dmotion Analysis system to seek the difference between before and after using the program. Moreover establish the improvement and trait for newly made program. The program was made up of down-swing, up-swing and composite connection-phase training. Through down-swing training, shoulder angle made extension and chest closed quickly. As a result, players' performance have improved. Through up-swing training, legs kicking to vertical direction and trunk stood up fastly. As a result, players' performance have improved. When going upward, the center of mass must be in control not to have a lot of movement and hip angle extension using the bar is very positive coaching. When coaching composite connection in training from down-swing to up-swing, must have enough air phase time using center of mass vertically to have extension of leg. As a result, players' performance have improved by having increase of air phase time.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.2
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• pp.145-154
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• 2020

Steel set is a structure that stabilize the NATM tunnel until the installation of shotcrete, and it is combined after the shotcrete is installed to improve stability. In this study, determination approach for the equivalent elastic modulus of shotcrete-lattice girder composite is newly suggested for tunneling simulation. Also, a method was presented to calibrate the equivalent elastic modulus through the comparison of the full 3D model and equivalent model. When the conventional equivalent elastic modulus is used for shotcrete-lattice girder composite, the flexural strength of equivalent model is 130% smaller than that of full 3D model. Equivalent elastic modulus is adjusted considering the error of flexural strength. It is found that the error of flexural strength obtained from adjusted equivalent model using adjusted equivalent elastic modulus is reduced less than 1%.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.89-94
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• 2006

In order to increase the signal-to-noise ratio in multi-component seismic data, we developed new polarization filters based on the method of multicomponent complex trace analysis. Unlike the previous polarization filters, the present filters separately compute linear and elliptic components at each time sample using amplitude ratio of horizontal and vertical components of body waves and ellipticity of Rayleigh waves. The polarization filters work ideally even with low S/N data. Application of the filters to both synthetic and real seismic data shows that Rayleigh waves of elliptic motions are effectively eliminated and both P and S waves of linear motions are well separated each other.

• The korean journal of orthodontics
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• v.27 no.5 s.64
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• pp.711-721
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• 1997

The purpose of this study was to investigate the stress distribution and intensity derived from the transpalatal lingual arch in the investing bone composed of photoelastic material(PL-3). The transpalatal lingual arch wire was deflected in the horizontal and vertical direction to give the various conditions. The two-dimensional photoelastic stress analysis was performed, and the stress distrebution was recored by photography The results were as follows: 1. In bilateral expansion, as horizontal deflection was singly applied, the stress was more concentrated on the root apex in square free end than round. In square free end, as vertical deflection was increased gradually, the black line meaning center of rotation moved inferiorly together with the increment of whole fringes. 2. In application of vertical deflection on anchorage side for unilateral expansion, the stress distribution that expansive force leaned to expansion side was observed. As vortical deflection increased, the extruding stress was observed on molar of expansion side. And as horizontal deflection increased, the tipping stress on the molar of anchorage side was observed. 3. In unilateral rotation with the asymmetric toe-in, the fringe appeared on the distal aspect of root apex.

• Journal of the Korean Geotechnical Society
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• v.38 no.10
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• pp.49-60
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• 2022

Underground urbanization appears to be a promising solution in response to the shortage of construction sites in the above-ground space. In this context, an accurate evaluation of a construction site ensures the long-term performance of geosystems. This study characterizes potential sites for complex plants built in underground space using geophysical methods (i.e., seismic refraction exploration and electrical resistivity survey) and in situ tests (i.e., standard penetration tests (SPTs) and downhole tests). SPTs are conducted in nine boreholes BH-1-BH-9 to estimate the groundwater level and vertical distribution of geological structures. The seismic refraction method enables us to obtain the elastic wave velocity and thickness of each soil layer for each cross-sectional area. An electrical resistivity survey conducted using the dipole array method provides the electrical resistivity profiles of the cross-sectional area. Data obtained using geophysical techniques are used to assess the classification of the soil layer and bedrock, particularly the fracture zone. This study suggests that geotechnical information using in situ tests and geophysical methods are useful references to design an underground complex plant construction.