• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.75-81
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• 2006

슬관절 전치환술은 관절염이나 사고로 인해 일상적인 활동의 제약을 받는 환자의 슬관절을 인공 관절로 대체함으로써 본래의 기능을 복원하고자 하는 수술이다. 이 수술은 인공 관절의 위치 및 정렬에 매우 민감하게 영향을 받기 때문에 수술이 잘못되는 경우 정렬 이상으로 인한 해리, 삽입물의 파손, 인공 슬관절 주위 골절, 슬개골 탈구, 굴곡 각도의 제한 등의 증상이 발생할 수 있다. 현재의 인공 관절은 임상에 적용되는 다양한 인공 관절 중에서 적당한 형상의 관절을 선택하여 시술되고 있지만 환자의 골 형상에 정확히 일치하는 인공 관절 선택의 어려움 때문에 종종 시술 후 부작용이 발생한다든지 심지어는 재수술을 해야 될 경우도 발생하게 된다. 본 논문은 Mechanical CAD 소프트웨어인 CATIA에서 제공하는 절단, Assembly, Analysis, Kinematic Simulation 기능 등을 이용하여 가상 수술을 수행하는 과정을 보여준다. 슬관절 전치환술 과정을 그대로 재현하여 절단량과 절단각을 결정하고 환자의 골격 형상에 적합한 최적의 인공 관절을 실제 수술 전에 미리 선정할 수 있다. CAD 시스템을 이용함으로써 외과의들이 실제 수술 시에 시행착오법을 통해 인공 관절을 선택하는 과정을 줄이고 수술의 정확도를 높일 수 있다. 향후 ADAMS나 ANSYS와 연계하여 수술 후 동작이나 하중을 분석할 수 있으며, 수술 과정에 대한 교육용으로 활용될 수 있다.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.2132-2135
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• 2008

최근 우리나라에서는 하천의 생태 및 환경에 대한 관심이 고조되면서 기능을 상실한 보들이 철거되고 있으나, 보 철거에 따른 하천의 변화에 대한 연구는 아직까지 미흡한 실정이다. 본 연구에서는 한탄강의 고탄보 철거 전 후의 물리적 변화를 살펴보기 위하여 하상변동, 하상재료의 변화, 가시적인 하천 형태의 변화등을 조사하여 그 결과를 정리, 분석하였다. 물리적 변화는 크게 대규모 평면 변화와 소규모 종단 및 횡단 변화로 나눌 수 있다. 평면 변화는 퇴적지, 하중도 및 제방 등의 변화를 포함하며, 이러한 변화 양상을 분석하기 위하여 주기적으로 촬영된 사진과 영상을 비교 분석 하였다. 또한, 하상의 종 횡단 변화를 연구하기 위해 철거 전 후와 홍수 후에 하천 단면 측량을 실시하여, 보 철거에 따른 미세 지형 변동을 파악하였다. 또한, 하상 재료의 변화를 연구하기 위해 홍수 전후의 하상 재료에 대한 입도분석을 실시하였으며, 홍수 시에는 부유사를 채취하여 유사량을 분석하였다. 본 연구를 통해 보철거 전 후의 물리적 변화를 관찰하기 위한 방법을 제시하였으며, 하상변동 관찰 결과보 철거로 인해 상류에서는 침식현상이, 하류에서는 퇴적현상이 발생하여 점차 평형 하상 경사로 복원되어가는 것으로 판단할 수 있었다. 고탄보의 경우는 하상이 자갈과 거석으로 구성되어 있어, 하상재료의 변화는 미미하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.2
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• pp.1-8
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• 2004

Sliding mode control (SMC), which is one of active control algorithms showing remarkable control performance, requires the excessive control force for control of seismically excited civil structures. Therefore, controller saturation should be considered in design of SMC. In this study, a method for determining the maximum control force is developed in terms of the fraction of the lateral restoring force using a design response spectrum. Numerical analyses of MDOF structures with one or multiple control devices verify the effectiveness of the proposed method for the control of seismically excited civil structures with saturation problem.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.2
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• pp.87-96
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• 1999

To analyze the dynamic behavior of structure, direct integration and mode superposition may be utilized in time domain analysis. As finite number of frequencies can give relatively exact solutions, mode superposition is preferable in analyzing structural behavior. In non-linear analysis, however, mode superposition is seldom used since time-varying element stiffness changes stiffness matrix, and the change of stiffness matrix leads to the change of essential constants - natural frequencies and mode shapes. In spite of these difficulties, there are some attempts to adopt mode superposition because of low cost compared to direct integration, but the result is not satisfactory. In this paper, a method using mode superposition in non-linear analysis is presented by separating local element stiffness from global stiffness matrix with the difference between linear and non-linear restoring forces to the external force vectors included. Moreover, the hysteresis model changing with the relative deformation in each floor makes it possible to analyze non-linear behavior of structure. The proposed algorithm is applied to shear beam model and the maximum displacement is compared with the result using direct integration method.

• International Journal of Highway Engineering
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• v.1 no.1
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• pp.107-119
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• 1999

The joints in the jointed concrete pavement provide a control against transverse or longitudinal cracking at slab, which may be caused by temperature or moisture variation during or after hydration. Without control of cracking, random cracks cause more serious distresses and result in structural or functional failure of pavement system. However, joints nay cause distresses due to its inherent weakness in structural integrity. Thus, the evaluation at joint is very important. and the joint-related distresses should be evaluated reasonably for economic rehabilitation. The purpose of this paper was to develop an evaluation system at joints of jointed concrete pavement using finite element analysis program, ILLI-SLAB, and nondestructive testing device. FWD. To develop an evaluation system for JCP, a sensitivity analysis was performed using ILLI-SLAB program with a selected variables which might affect fairly to on the performance of transverse joints. The most significant variables were selected from precise analysis. An evaluation charts were made for jointed concrete pavement by adopting the field FWD data. It was concluded that the variables which most significantly affect to pavement deflections are the modulus of subgrade reaction(K) and the modulus of dowel/concrete interaction(G), and limiting criteria on the performance of joints at JCP are 300pci. 500,000 lb/in. respectively. Using these variables and FWD test, a charts of load transfer ratio versus surface deflection at joints were made in order to evaluate the performance of JCP. Practically, Chungbu highway was evaluated by these evaluation charts and FWD field data for jointed concrete pavement. For Chungbu highway, only one joint showed smaller value than limiting criterion of the modulus of dowel/concrete interaction(G). The rest joints showed larger values than limiting criteria of the modulus of subgrade reaction(K) and the modulus of dowel/concrete interaction(G).

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.5
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• pp.628-636
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• 2018

Because large buoys are mainly made of steel, they are heavy and vulnerable to corrosion by sea water. This makes buoy installation and maintenance difficult. Moreover, vessel collision accidents with buoys and damage to vessels due to the material of buoys (e.g., steel) are reported every year. Recently, light buoys adopting eco-friendly and lightweight materials have come into the spotlight in order to solve the previously-mentioned problems. In Korea, a new lightweight buoy with a 7-Nautical Mile lantern adopting expanded polypropylene (EPP) and aluminum to create a buoyant body and tower structure, respectively, was developed in 2017. When these light buoys are operated in the ocean, the visibility and angle of light from the lantern installed on the light buoys changes, which may cause them to function improperly. Therefore, research on the performance of light buoys is needed since the weight distribution and motion characteristics of these new buoys differ from conventional models. In this study, stability estimation and motion analyses for newly-developed buoys under various environmental conditions considering a mooring line were carried out using ANSYS AQWA. Numerical simulations for the estimation of wind and current loads were performed using commercial CFD software, Siemens STAR-CCM+, to increase the accuracy of motion analysis. By comparing the estimated maximum significant motions of the light buoys, it was found that waves and currents were more influential in the motion of the buoys. And, the estimated motions of the buoys became larger as the sea state became worser, which might be the reason that the peak frequencies of the wave spectra got closer to those of the buoys.

• Journal of Korean Society of Steel Construction
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• v.27 no.6
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• pp.493-501
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• 2015

Superelastic shape memory alloys (SMAs) are metallic materials that can automatically recover to their original condition without heat treatment only after the removal of the applied load. These smart materials have been wildly applied instead of steel materials to the place where large deformation is likely to concentrate. In spite of many advantages, superelastic SMA materials have been limited to use in the construction filed because there is lack of effort and research involved with the development of the material model, which is required to reproduce the behavior of superelastic SMA materials. Therefore, constitutive material models as well as algorithm codes are mainly treated in this study for the purpose of simulating their hysteretic behavior through numerical analyses. The simulated curves are compared and calibrated to the experimental test results with an aim to verify the adequacy of material modeling. Furthermore, structural analyses incorporating the material property of the superelastic SMAs are conducted on simple and cantilever beam models. It can be shown that constitutive material models presented herein are adequate to reliably predict the behavior of superelastic SMA materials under cyclic loadings.

• Journal of the Korean Wood Science and Technology
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• v.44 no.1
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• pp.57-66
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• 2016

In order to develop materials with a low environmental load for restoring the destroyed forest, seven types of wood-concrete hybrid laminated materials were manufactured with four softwoods, three hardwoods and concrete, and the effect of wood density on bending creep property was investigated. The bending creep curves showed a shape to considerably increase at the upper right side, and the curves were found to show a linear behavior beyond about 30 min - 1 hour, as behaviors of solid woods and wood-based materials. The initial compliances of wood-concrete hybrid-laminated materials decreased with an increase in the wood density, and those values showed 0.9 - 1.2 times of the concrete one. The creep compliances of hybrid laminated materials showed very low values, which were 0.4 - 0.8 times of the concrete ones. The relative creep were very low with a range from 8.2% to 17.0% range, which were 0.3 - 0.7 times of the concrete ones. These results indicate that these materials can be applied for restoring the destroyed forest to reduce creep deformation of the conventional concrete materials by hybrid-laminating concrete and woods.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.131-136
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• 2008

We performed a non-destructive geophysical survey such as an elastic wave survey, electric specific resistance survey, plate loading test, etc. in order to grasp the structure and status of the ground around the pillar gate and to provide the directions and design data for preservation and maintenance during reconstruction. The result of electric specific resistance survey shows 50-1300 ohm-m range of general electric specific resistance distribution. Besides, the positions around 1m south of stone pillars, between stone pillar No.3 and 4, and 1m north of stone pillar No.2 and 3 show abnormality of relatively lower electric specific resistance than their surroundings. The abnormality of low electric specific resistance appearing between stone pillar No.3 and 4 shows consistency with the abnormal section appearing from the result of elastic wave reflection survey. The result of a plate loading test shows that allowable bearing force is over $10.70tf/m^2$, and the settlement amount at this time was calculated as 19.635mm. The design load during reconstruction of pillar gates was calculated as $16.37t/m^2$ by applying assumption values, which is far more than the allowable bearing force, so it is judged that a measure to strengthen the foundation ground is necessary.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.3 s.55
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• pp.23-31
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• 2007

Fast bridge construction has been increasingly needed according to the changed construction environment. This paper deals with quasi-static tests on precast piers for bridge substructures. One of the most crucial aspect of the design of precast prestressed concrete bridge piers is the seismic performance. Seven precast pier elements were fabricated. The amount of prestressing bars, the prestressing force, and the location and number of the joint between segments were the main test parameters. Test results showed that the introduced axial prestress made the restoration of the deformation under small lateral displacement and minor damage. However, there was no effect of the prestress when the plastic hinge region was damaged severely due to large lateral displacement. Judging from the observed damage, the design of the joints in precast piers should be done for the first joint between the foundation and the pier segment. The amount of the necessary prestressing steel may be designed to satisfy the P-M diagram according to the service loads, not by having the same steel ratio as normal RC bridge piers. In order to satisfy the current required displacement ductility, it is necessary to have the same amount of the transverse reinforcements as RC piers. As the steel ratio increases, the energy absorption capacity increases. The number of joints showed a little influence on the energy absorption capacity.