• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.4
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• pp.279-290
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• 2004

The differential quadrature method (DQM) for a system of coupled differential equations governing the elastic stability of thin-walled curved members is presented, and is applied to computation of the eigenvalues of out-of-plane buckling of curved beams subjected to uniformly distributed radial loads including a warping contribution. Critical loads with warping, which were found to be significant, are calculated for a single-span wide-flange beam with various end conditions, opening angles, and stiffness parameters. The results are compared with the exact methods available. New results are given for the case of both ends clamped and clamped-simply supported ends without comparison since no data are available The differential quadrature method gives good accuracy and stability compared with previous theoretical results.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.4
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• pp.39-49
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• 2001

In this paper, inelastic analysis procedures are presented for the seismic performance evaluation of RC bridge piers with premature termination of main reinforcement. The mechanical characteristic of cracked concrete and reinforcing bar in concrete has been modeled, considering the bond effect between reinforcing bars and concrete, the effect of aggregate interlocking at crack surface and the stiffness degradation after the crack. The smeared crack approach is incorporated. In boundary plane at which each member with different thickness is connected, local discontinuous deformation due to the abrupt change in their stiffness can be taken into account by introducing interface element. The increase of concrete strength due to the lateral confining reinforcement has been also taken into account to model the confined concrete. The proposed numerical method for seismic performance evaluation of RC bridge piers with premature termination of main reinforcement will be verified by comparison with reliable experimental results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.8
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• pp.728-733
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• 2008

Unsteady aerodynamic analysis of an air-pressure-levitated high-speed ground vehicle moving over the nonplanar ground surface are performed using the boundary-element method. The potential flow solution is included in a time-stepping loop and the wake is captured as part of the solution. When the vehicle moving inside the channel, the lift coefficient and the pitching moment coefficient of the vehicle are increased further because the air trapped by the channel increases the ground effect. In other words, the nonplanar ground surface such as the channel decreases further the longitudinal stability of the vehicle. On the other hand, there is little difference between the ground and the channel in the lateral stability of the vehicle because the lift increment due to the nonplanar ground surface such as the channel takes place on both sides of the wing with the same rate of increase.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.6
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• pp.846-851
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• 2010

A liquid-air interface sensing system using the flat end surfaces of a fused-silica fiber coupler has been demonstrated. The principle is based on the additional optical loss caused by changing the refractive index of the external material at the boundary of the end face made of a fiber. The immersion characteristics of this system with respect to the different splitting ratios of the couplers were investigated to determine the sensitivity when it responses to water and air. These experimental data are very useful for selecting the coupling ratio of a coupler in order to develop a multiple sensing probe system. In the proposed sensor structure, it can be emphasize that the sensing probe can be appropriately arrayed on the basis of splitting ratio of the coupler. As a result, it is expected that the proposed liquid-air interface sensors can also be applied to monitor flooding that occurs in multiple areas at the same time.

• Economic and Environmental Geology
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• v.29 no.3
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• pp.345-355
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• 1996

The effectiveness of various electrode configurations in horizontal mappings and 1-D inversions of vertical sounding data for delineating 2-D structures was studied. Apparent resistivity values of three point, dipole-dipole, Wenner, and Schlumberger mappings were simulated for such structures as vertical dyke, tabular prism, buried vertical fault, ramp and complex structure by finite difference method (FDM) and they were compared with each other. Also 2-D cross sections for three structures obtained by interpolation of 1-D inverted sounding data in terms of three layers were compared for Schlumberger and Wenner arrays. On these cross sections, horizontal and vertical resistivity interfaces of the 2-D structures are revealed relatively clearly. Apparent resistivity curves of Schlumberger mapping show vertical resistivity discontinuities very well. On the whole, Schlumberger array is superior to the other arrays in electric sounding as well as mapping. This study clearly indicates that interpretations of 2-D structures based on 1-D inversion are possible.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.04a
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• pp.97-98
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• 2002

최근 들어 구제역과 같은 세균에 대한 경계와 관심이 늘어가고 있다. 하지만, 관심에 비하여 이에 대한 연구가 부족한 실정이고 대기질과 상호 연계한 연구는 더욱 미미한 상태이다. 따라서, 본 연구에서는 광주광역시의 시간대별 교통량과 대기질 그리고 낙하세균의 수를 함께 조사하여 상호연관성을 찾아보고자 하였다. 낙하세균은 탄저균이나 구제역처럼 전염성이나 인체에 미치는 영향은 크지 않지만 공중보건과 대기질 관리의 관점에서 이에 대한 정보 확보와 관련대책이 시급하다. (중략)

• The Journal of the Korean dental association
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• v.47 no.10
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• pp.628-636
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• 2009

낭은 상피세포로 싸여있는 병적인 공간으로 내부가 액체나 반액체로 채워져 있다. 악골에서 낭은 다른 골 부위에서보다 더 흔하게 발생하는데 이는 대부분의 낭이 치아 형성 후에 악골에 남아있는 치성잔류물로부터 발생하는 경우가 많기 때문이다. 구강악안면부에서 발생하는 낭은 연조직에서 발생할 수도 있지만 대부분 골내에서 발생하고, 법랑질 상피나 치배와 관련해 악골내에 발생하는 치낭성이다. 치낭성은 WHO분류에서 발생근원에 따라 크게 염증성과 발육성 기원의 두 가지 군으로 분류되고, 발육성 낭은 치성과 비치성으로 세분할 수 있다. 악골에 발생하는 낭은 대부분이 치낭성이며 가장 흔한 악골 낭종은 치근단낭으로 염증성이고, 발육성인 함치성낭과 치성각화낭도 다음으로 발생률이 높은 편이다. 소아환자에서 함치성낭과 치성각화낭의 발병률이 성인보다 더 높았다. 비치성낭 중에서 비구개관낭이 가장 많이 발생하며, 연조직에서 발생하는 낭과 상피세포 경계가 없는 낭성 병소인 가성낭(pseudocyst)은 드물게 관찰된다. WHO에서 치성각화낭과 서회화치성낭은 파괴적 성장을 하고 재발 경향이 높으므로 양성 낭성 종양으로 재분류하고 있다.

• Journal of the Korea Safety Management & Science
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• v.13 no.2
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• pp.97-102
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• 2011

본 연구에서는 원형 박판 구조물의 안정성에 대하여 해석 하였다. 임계하중은 하중을 점차적으로 증가하여 구조물이 파괴가 발생하여 안정성을 상실 하는 상태에서 가장 작은 하중을 의미한다. 판구조의 안정성을 임계하중의 크기로 기초를 두고 해석 하였다. 원형 박판구조의 차분해석은 일반 판구조와 같으므로 최근에 많은 연구의 대상이 되어왔다. 차분법은 복잡한 구조물에서도 물론, 다양한 경계조건을 포함하는 문제에 이르기까지 효과적인 수치방법이다. 본 연구에서는 기본 박판구조의 지배방정식을 유도하고 차분화 하여 직접적으로 접근하였다. 원 둘레 의 지점이 힌지 받침으로, 등분포 하중을 받고 있는 박판을 기하학적 비선형 해석으로 수행하여 원형 박판의 처짐 및 응력을 해석 하였다.

• Journal of the Korean Association of Geographic Information Studies
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• v.24 no.1
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• pp.80-91
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• 2021

The purpose of this study is to present the applicability to the effective survey into the actual condition of lands such as analysis of occupied location of government owned lands based on orthoimages created from aerial photographs taken by UAV. The boundary point coordinates and areas of the parcels were observed respectively by VRS-GNSS surveying and orthoimages for each land use of two categories of land, i.e. building site and farmland. As a result of comparing boundary point coordinates and areas extracted from UAV orthoimages with VRS-GNSS surveying data which were used as reference data, the RMS error of the coordinates for the boundary points was ±0.074m for both X and Y in the building site, and ±0.150m and ±0.127m for the X and Y respectively in the farmland. The positional error of the boundary point was 1.7~ 2 times higher in the farmland than in the building site where the boundary points were relatively clear. The RMS error of ±8.964㎡ of areas in the farmland was 4.7 times higher than that of ±1.898㎡ of areas in the building site. The area errors of all 22 parcels measured from the orthoimage were found to be within the allowed error range, indicating that it is feasible to apply the orthoimage generated by UAV to survey of government owned lands in terms of accuracy.

• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.691-700
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• 1998

Based on Von Karman-Donnell kinematic assumptions for laminated shells, the nonlinear vibration behaviour of antisymmetrically or asymmetrically laminated cross-ply circular cylindrical shells with clamped and simply-supported ends are studied by a multi-mode approach. A equation is formulated and satisfies the associated compatibility equation and all boundary conditions. The displacement function is assumed to take the form of the lowest linear vibration mode and to satisfy continuity of the circumferential displacement. The nonlinear vibration equation is derived by the Galerkin's method. And nonlinear frequency is obtained by using the harmonic balance method as a function of lamination parameters, material constants, aspect ratio and amplitude of vibration. The effect of initial imperfection is also included. Results of the non-linear vibration are presented for different amplitudes of initial imperfection and four sets of boundary conditions. Present results are compared well with existing analysis results.