• Journal of the Korean Chemical Society
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• v.26 no.4
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• pp.195-204
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• 1982

Semi-empirical MO calculations, EHT, CNDO/2, MINDO/3, and MNDO met hods, were performed on various geometries of n-butane, n-alkyl radical and tetramethylene diracal (triplet) in order to compare eigenvalue and eigenvector properties with those obtained by STO-3G method. All methods predicted the same relative order of stabilities of various geometries for n-butane; geometrical preferences were found to be dominated by one-electron factor, ${\pi}$-orbital energy changes being more impotant in the semi-empirical methods. The hyperconjugative energy changes accompanying structural changes from $(n-{\sigma}{\ast})_{trans}$ to (n-{\sigma}{\ast})cis were underestimated in the EHT, CNDO/2 and MINDO/3, whereas those were overestimated in the MNDO. The net destabilizing effect of $(n-{\sigma}{\ast})_{trans}$ structure was mainly due to the large internuclear energy involved in the structure. Through-space interaction between $n_1$ and $n_2$ orbitals of diradical caused energy gap narrowing of ${\Delta}E_{sp}$ and ${\Delta}{\varepsilon}={\varepsilon}_0$-${\varepsilon}_{av}$; through-space interaction had opposing effect to that of through-bond interaction. Due to the less severe neglect of differential overlaps in the MNDO, this energy gap narrowing effect appeared amplified in the MNDO. In general orbital properties were found to be reproduced satisfactorily, but eigenvalue properties were not, in all the semi-empirical methods especially when ${\sigma}-{\sigma}{\ast}$ and n-$n-{\sigma}{\ast}$interactions were involved.

• The korean journal of orthodontics
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• v.38 no.4
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• pp.228-239
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• 2008

Objective: The aim of this study was to evaluate the strain induced in the cortical bone surrounding an orthodontic microimplant during insertion. Methods: A 3D finite element method was used to model the insertion of a microimplant (AbsoAnchor SH1312-7, Dentos Co., Daegu, Korea) Into 1 mm thick cortical bone with a pre-drilled hole of 0.9 mm in diameter. A total of 1,800 analysis steps was used to simulate the 10 turns and 5 mm advancement of the microimplant. A series of remesh in the cortical bone was allowed to accommodate the change in the geometry accompanied by the implant insertion. Results: Bone strains of well higher than 4,000 microstrain, the reported upper limit for normal bone remodeling, was observed in the bone along the whole length of the microimplant. At the bone in the vicinity of the screw tip, strains of higher than 100% was recorded. The insertion torque was calculated at approximately 1.2 Ncm which was slightly lower than those measured from the animal experiment using rabbit tibias. Conclusions: The insertion process of a microimplant was successfully simulated using the 3D finite element method which showed that bone strains from a microimplant insertion might have a negative impact on physiological remodeling of bone.

• Journal of the Korean Geotechnical Society
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• v.31 no.4
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• pp.45-55
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• 2015

The stability of the adjcent structures or slopes under blasting is typically evaluated using an empirical vibration attenuation curve or dynamic numerical analysis. To perform a dynamic analysis, it is necessary to determine the blast load and the damping ratio of rock mass. Various empirical methods have been proposed for the blast load. However, a study on representative values of damping ratio of a rock mass has not yet been performed. Therefore, the damping ratio was either ignored or selected without a clear basis in performing a blast analysis. Selection of the dampring ratio for the rock mass is very difficult because the vibration propagation is influenced by the layout and properties of the rock joints. Besides, the vibration induced by blasting is propagated spherically, whereas plane waves are generated by an earthquake. Since the geometrical spreading causes additional attenuation, the damping ratio should be adjusted in the case of a 2D plane strain analysis. In this study, we proposed equivalent damping ratios for use in continuum 2D plane strain analyses. To this end, we performed 2D dynamic analyses for a wide range of rock stiffness and investigated the characteristics of blast vibration propagation. Based on numerical simulations, a correlation between the attenuation equation, shear wave velocity, and equivalent damping ratio of rock mass is presented. This novel approach is the first attempt to select the damping ratio from an attenuation relationship. The proposed chart is easy to be used and can be applied in practice.

• Journal of the Korean Society of Radiology
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• v.15 no.3
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• pp.321-327
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• 2021

Wrist PA-grip view is used to diagnose triangular fibrocartilage complex (TFCC) tear because it can easily diagnose damage to the surrounding wrist ligaments. However, despite advances in radiology equipment, distortion of images due to geometric elements still has many limitations. In this paper, we propose a method that can minimize the distortions of images by analyzing the distortions occurring in the wrist PA-grip view. A source of image distance (SID) were set at 130 cm and 150 cm for comparison with 110 cm. Depending on the SID, the phantom of wrist was moved at 0, 2, 4, 6, 8, and 10 cm in the X-axis and Y-axis directions, respectively. For quantitative evaluation, the difference of distance between the radius and ulna was measured in picture archiving and communication system (PACS) system. As a qualitative evaluation, survey was conducted among 20 radiologic technologists who examined the Wrist PA-grip view. The Kruskal Wallis test was performed to compare the distortion according to the phantom movement in the X-axis and Y-axis directions based on the SID, and the Tukey test was performed as a post-test. In the quantitative evaluation results, the measured values obtained in the X-axis was not significantly different in all groups (p>0.05). The measured values obtained in the Y-axis was significantly different in the most groups (p<0.05). Therefore, to reduce distortion while maintaining image quality, we recommend what examine the SID at 150 cm than 110 cm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.9-17
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• 2021

Curved beams are increasingly used in buildings, vehicles, ships, and aircraft, which has resulted in considerable effort being directed toward developing an accurate method for analyzing the dynamic behavior of such structures. The stability behavior of elastic circular arches has been the subject of a large number of investigations. One of the efficient procedures for the solution of ordinary differential equations or partial differential equations is the differential quadrature method DQM. This method has been applied to a large number of cases to overcome the difficulties of the complex computer algorithms, as well as excessive use of storage due to conditions of non-linear geometries, loadings, or material properties. This study uses DQM to analyze the in-plane vibration of the circular arches considering the effects of midsurface extension and rotatory inertia. Fundamental frequency parameters are calculated for the member with various parameter ratios, boundary conditions, and opening angles. The solutions from DQM are compared with exact solutions or other numerical solutions for cases in which they are available and given to analyze the effects of midsurface extension and rotatory inertia on the frequency parameters of the circular arches.

• Journal of the Korean Geotechnical Society
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• v.25 no.10
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• pp.17-30
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• 2009

Underground construction such as tunneling can induce damages on the surrounding rock mass, due to the stress concentration of in situ stresses and excessive energy input during construction sequence, such as blasting. The developed damage on the rock mass can have substantial influence on the mechanical and hydraulic behaviors of the rock masses around a tunnel. In this study, investigation on the generation of damage around an opening in a jointed rock model under biaxial compression condition was conducted. The joint dip angles employed are 30, 45, and 60 degrees to the horizontal, and the synthetic rock mass was made using early strength cement and water. From the biaxial compression test, initiation and propagation of tensile cracks at norm to the joint angle were found. The propagated tensile cracks eventually developed rock blocks, which were dislodged from the rock mass. Furthermore, the propagation process of the tensile cracks varies with joint angle: lower joint angle model shows more stable and progressive tensile crack propagation. The development of the tensile crack can be explained under the hypothesis that the rock segment encompassed by the joint set is subjected to the developing moment, which can be induced by the geometric irregularity around the opening in the rock model. The experiment results were simulated by using discrete element method PFC 2D. From the simulation, as has been observed from the test, a rock mass with lower joint angle produces wider damage region and rock block by tensile cracks. In addition, a rock model with lower joint angle shows progressive tensile cracks generation around the opening from the investigation of the interacted tensile cracks.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2010.06a
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• pp.183-183
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• 2010

위치기반서비스(Location Based Service)는 갈수록 고도화 되어 가고 있다. 특히 최근의 대형 포털을 중심으로 지오웹 서비스가 활성화 되어 있고 이를 스마트폰과 같은 개인용 이용기기를 통해 연속적으로 제공하려는 경향이 뚜렷하다. 이와 같은 시점에서 정부와 민간에서 구축 중이거나 보유 중인 전국적 규모의 데이터 간 상호 연동과 융합을 도모하려는 시도 또한 불가결하다. 이는 고도화된 LBS를 위하여 반드시 필요한 과정이기 때문이다. 이에 따라 몇 가지 주요한 전국 데이터를 대상으로 상호 연동과 융합을 위한 기술개발을 시도하였다. 우선 도로명주소기본도와 수치지형도 간 POI의 연계를 위한 연구를 수행하고 있다. 이 연구에서는 두도면 내의 POI를 대상으로 다양한 매칭과 이에 기반 한 의사결정 방법론을 이용하여 자동으로 상호 인식 및 연계가 될 수 있도록 하고 있다. 다음으로 지적도와 수치지형도 간의 객체 매칭에 관한 연구이다. 수치지형도와 지적도의 불부합으로 인하여 그 동안 지적도를 수치지형도에 맞춘 형태의 편집지적도를 지속적으로 생산하여 왔고 앞으로도 그럴 것이다. 문제는 여기에 필요한 많은 예산이다. 만일 수치지형도와 지적도를 자동으로 매칭하여 편집지적도를 자동으로 생산할 수 있게 된다면 많은 예산 절감과 함께 편집지적도의 현시성을 확보할 수 있게 될 것이다. 다음으로 항공사진과 도로망도의 매칭이다. 현재 주요 포털에서 제공하고 있는 항공사진 기반의 도로망도는 기복변위와 같은 문제로 인하여 시각적으로 많은 위치오차를 보이고 있다. 만일 항공사진의 도로영역을 자동으로 추출하여 벡터 도로망도와 매칭을 할 수 있다면 보다 시각적으로 안정된 항공사진 상의 도로망도를 제공할 수 있게 되고 나아가 이는 차량이나 보행자 네비게이션에 매우 요긴하게 이용될 수 있을 것이다. 다음으로 서로 LOD가 다른 도로망도의 매칭 문제이다. 많은 기관에서 독자적으로 생산한 도로망도는 LOD의 상이에 기인한 문제가 많아 서로 연계 활용되지 않는다. 이를 자동으로 매칭하여 서로 연계할 수 있다면 두 도로망도가 보유하고 있는 속성정보를 공동으로 이용할 수 있는 이익을 얻게 된다. 다음으로 지도 일반화 기술이다. 지도일반화는 지적도내 수치지형도와 같은 대규모 데이터를 스마트폰과 같은 저용량 사양의 기기에 서비스 할 때 불가결한 기술이다. 지도상 객체들의 기하학적 정보 손실을 최소화하면서 메모리 측면에서 경량의 지도를 자동으로 만들어 낸다면 이는 매우 요긴하게 이용될 것이다. 마지막으로 보행자 네트워크의 생성기술이다. 보행자 네트워크는 그 상세함과 정보용량에 있어서 차량용 네트워크에 견줄 수 없다. 이를 현행의 차량용 네트워크와 같이 수동으로 생성하는 데에는 경제적으로나 시간적으로 막대한 투자가 필요하다. 따라서 이를 기존의 공간정보들을 활용하여 자동으로 생성해 낼 수 있다면 그 파급효과는 매우 크리라 판단된다. 본 발표에서는 위와 같은 주제에 관하여 그간의 연구 성과를 개략적으로 소개해본다.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.290-297
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• 2009

A two-phase (gas and liquid) flow analysis solver, named CUPID, has been developed for a realistic simulation of transient two-phase flows in light water nuclear reactor components. In the CUPID solver, a two-fluid three-field model is adopted and the governing equations are solved on unstructured grids for flow analyses in complicated geometries. For the numerical solution scheme, the semi-implicit method of the RELAP5 code, which has been proved to be very stable and accurate for most practical applications of nuclear thermal hydraulics, was used with some modifications for an application to unstructured non-staggered grids. This paper is concerned with the effects of interpolation schemes on the simulation of two-phase flows. In order to stabilize a numerical solution and assure a high numerical accuracy, the second-order upwind scheme is implemented into the CUPID code in the present paper. Some numerical tests have been performed with the implemented scheme and the comparison results between the second-order and first-order upwind schemes are introduced in the present paper. The comparison results among the two interpolation schemes and either the exact solutions or the mesh convergence studies showed the reduced numerical diffusion with the second order scheme.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.6
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• pp.201-211
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• 2013

In this paper, we propose a hand tracking and gesture recognition system. Our system employs a depth capture device to obtain 3D geometric information of user's bare hand. In particular, we build a flexible tracking volume and restrict the hand tracking area, so that we can avoid diverse problems caused by conventional object detection/tracking systems. The proposed system computes running average of the hand position, and tracking volume is actively adjusted according to the statistical information that is computed on the basis of uncertainty of the user's hand motion in the 3D space. Once the position of user's hand is obtained, then the system attempts to detect stretched fingers to recognize finger gesture of the user's hand. In order to test the proposed framework, we built a NUI system using the proposed technique, and verified that our system presents very stable performance even in the case that multiple objects exist simultaneously in the crowded environment, as well as in the situation that the scene is occluded temporarily. We also verified that our system ensures running speed of 24-30 frames per second throughout the experiments.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.33-49
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• 2016

The study area, located in Sinam-ri, Ulsan, in the southeastern part of the Korean Peninsula, is mainly composed of hornblende granite (ca. 65 Ma). Fracturing and reactivation of a fault striking ENE-WSW was strongly controlled by the intrusion of a mafic dyke (ca. 44 Ma), which behaves as a discontinuity in the mechanically homogeneous pluton, increasing the instability of the basement in this area. A geometric and kinematic study undertaken to interpret the faults and fractures was performed in a trench excavated almost perpendicular to the orientation of the dyke. The analysis of structural elements, such as dykes, veins, and faults, is used to infer the deformation history and to determine the paleostress orientations at the time of formation of the structures. The deformation history established based on this analysis is as follows: (1) NNE-SSW, E-W, ENE-WSW, and NE-SW trending fractures had already developed in the pluton before dyke intrusion; (2) felsic dykes intruded under conditions of σ_Hmax oriented N-S and σ_Hmin oriented E-W; (3) mafic dykes intruded under conditions of σ_Hmax oriented E-W and σ_Hmin oriented N-S; (4) dextral reactivation of the main fault associated with the development of hydrothermal quartz veins under conditions of σ_Hmax oriented E-W and σ_Hmin oriented N-S; (5) sinistral reactivation of the main fault and high-angle normal faults under conditions of σ_Hmax oriented NE-SW and σ_Hmin oriented NW-SE; and (6) dextral reactivation of the main fault and NE-SW low-angle reverse faults under conditions of σ_Hmax oriented NW-SE and σ_Hmin oriented NE-SW. These results are consistent with the tectonic history of the Pohang-Ulsan block in the southeastern part of the Korean Peninsula, and indicates the tectonic deformation of the southern area of the Ulsan fault bounded by Yangsan fault was analogous to that of the Pohang-Ulsan area from the Cenozoic. This work greatly aids the selection of sites for critical facilities to prevent potential earthquake hazards in this area.