• Structural Engineering and Mechanics
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• 제60권4호
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• pp.633-653
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• 2016

One of the major threats to the stability of classical columns and colonnades are earthquakes. The behavior of columns under high seismic excitation loads is non-linear and complex since rocking, wobbling and sliding failure modes can occur. Therefore, three dimensional simulation approaches are essential to investigate the in-plane and out-of-plane response of such structures during harmonic and seismic loading excitations. Using a software based on the Distinct Element Method (DEM) of analysis, a three dimensional numerical study has been performed to investigate the parameters affecting the seismic behaviour of colonnades' structural systems. A typical section of the two-storey colonnade of the Forum in Pompeii has been modelled and studied parametrically, in order to identify the main factors affecting the stability and to improve our understanding of the earthquake behaviour of such structures. The model is then used to compare the results between 2D and 3D simulations emphasizing the different response for the selected earthquake records. From the results analysis, it was found that the high-frequency motion requires large base acceleration amplitude to lead to the collapse of the colonnade in a shear-slip mode between the drums. However, low-frequency harmonic excitations are more prominent to cause structural collapse of the two-storey colonnade than the high-frequency ones with predominant rocking failure mode. Finally, the 2D analysis found to be unconservative since underestimates the displacement demands of the colonnade system when compared with the 3D analysis.

• Steel and Composite Structures
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• 제26권6호
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• pp.771-791
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• 2018

This paper deals with the low velocity impact response and dynamic stresses of composite sandwich truncated conical shells (STCS) with compressible or incompressible core. Impacts are assumed to occur normally over the top face-sheet and the interaction between the impactor and the structure is simulated using a new equivalent three-degree-of-freedom (TDOF) spring-mass-damper (SMD) model. The displacement fields of core and face sheets are considered by higher order and first order shear deformation theory (FSDT), respectively. Considering continuity boundary conditions between the layers, the motion equations are derived based on Hamilton's principal incorporating the curvature, in-plane stress of the core and the structural damping effects based on Kelvin-Voigt model. In order to obtain the contact force, the displacement histories and the dynamic stresses, the differential quadrature method (DQM) is used. The effects of different parameters such as number of the layers of the face sheets, boundary conditions, semi vertex angle of the cone, impact velocity of impactor, trapezoidal shape and in-plane stresses of the core are examined on the low velocity impact response of STCS. Comparison of the present results with those reported by other researchers, confirms the accuracy of the present method. Numerical results show that increasing the impact velocity of the impactor yields to increases in the maximum contact force and deflection, while the contact duration is decreased. In addition, the normal stresses induced in top layer are higher than bottom layer since the top layer is subjected to impact load. Furthermore, with considering structural damping, the contact force and dynamic deflection decrees.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.55-56
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• 2006

This paper describes a new concept of the robot that can climb on the vertical plane. The engineering design problem of the main structure is presented and the experimental results regarding a new mechanism of climbing on the vertical wall are discussed. The locomotive motion of the robot is realized by using a series chain of two caterpillar wheels on which 24-suction pads are installed. White each caterpillar wheel rotates on the vertical plane surface, the vacuum pads are activated in sequence based on the sequential opening by specially designed mechanical valves. The detail design feature of the valve is also described in this paper. The overall size of the robot is around 460 mm in width and length, respectively, and 200 mm in height. Its mass is slightly over 14 kg. The main mechanical structure of the robot consists of driving motors, vacuum caterpillar system, steering part, vacuum pump and battery. The performance of the robot is verified on the vertical wall.

• 대한토목학회논문집
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• 제7권2호
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• pp.141-153
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• 1987

고층 건물의 정확한 거동을 구하기 위한 구조 해석은 컴퓨터 적용의 중요한 분야로 취급되어 왔다. 본 논문에서는 건축구조물에 대한 3차원적인 해석방법을 연구하였다. 이 해석 방법은 건물을 각각의 독립된 프레임의 조합체로 보고 해석하므로 매우 효율적이며, 건물의 3차원적인 거동에 관한 고려는 건물이나 하중이 대칭이 아닐 때는 특히 중요하다. 그리고 matrix condensation 기법을 이용함으로써 컴퓨터의 용량과 해석 시간이 상당히 절약되므로 매우 경제적이다. 본 논문의 건물 구조해석 컴퓨터 프로그램 PFS의 정확성과 효율성을 증명하기 위해 여러가지 예제들에 대해서 SAPIV 에 의한 해석 결과와 비교하였다. 그러므로, 본 논문에서 제안한 해석방법은 고층 건물의 구조 설계에서 매우 효율적이라 할 수 있다.

• Steel and Composite Structures
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• 제43권1호
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• pp.79-90
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• 2022

In this study, the dynamic behavior of functionally graded layered deep beams with viscoelastic core is investigated including the porosity effect. The material properties of functionally graded layers are assumed to vary continuously through thickness direction according to the power-law function. To investigate porosity effect in functionally graded layers, three different distribution models are considered. The viscoelastically cored deep beam is exposed to harmonic sinusoidal load. The composite beam is modeled based on plane stress assumption. The dynamic equations of motion of the composite beam are derived based on the Hamilton principle. Within the framework of the finite element method (FEM), 2D twelve -node plane element is exploited to discretize the space domain. The discretized finite element model is solved using the Newmark average acceleration technique. The validity of the developed procedure is demonstrated by comparing the obtained results and good agreement is detected. Parametric studies are conducted to demonstrate the applicability of the developed methodology to study and analyze the dynamic response of viscoelastically cored porous functionally graded deep beams. Effects of viscoelastic parameter, porosity parameter, graduation index on the dynamic behavior of porous functionally graded deep beams with viscoelastic core are investigated and discussed. Material damping and porosity have a significant effect on the forced vibration response under harmonic excitation force. Increasing the material viscosity parameters results in decreasing the vibrational amplitudes and increasing the vibration time period due to increasing damping effect. Obtained results are supportive for the design and manufacturing of such type of composite beam structures.

• 한국운동역학회지
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• 제31권3호
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• pp.155-161
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• 2021

Objective: There is a lack of studies using the 3D-2D image registration techniques on the mechanism of a shoulder injury for ice hockey players. This study aimed to analyze in vivo 3D glenohumeral joint arthrokinematics in collegiate ice hockey athletes and compare shoulder scaption with or without a hockey stick using the 3D-2D image registration technique. Method: We recruited 12 male elite ice hockey players (age, 19.88 ± 0.65 years). For arthrokinematic analysis of the common shoulder abduction movements of the injury pathogenesis of ice hockey players, participants abducted their dominant arm along the scapular plane and then grabbed a stick using the same motion under C-arm fluoroscopy with 16 frames per second. Computed tomography (CT) scans of the shoulder complex were obtained with a 0.6-mm slice pitch. Data from the humerus translation distances, scapula upward rotation, anterior-posterior tilt, internal to external rotation angles, and scapulohumeral rhythm (SHR) ratio on glenohumeral (GH) joint kinematics were outputted using a MATLAB customized code. Results: The humeral translation in the stick hand compared to the bare hand moved more anterior and more superior until the abduction angle reached 40°. When the GH joint in the stick hand was at the maximal abduction of the scapula, the scapula was externally rotated 2~5° relative to 0°. The SHR ratio relative to the abduction along the scapular plane at 40° indicated a statistically significant difference between the two groups (p < 0.05). Conclusion: With arm loading with the stick, the humeral and scapular kinematics showed a significant correlation in the initial section of the SHR. Although these correlations might be difficult in clinical settings, ice hockey athletes can lead to the movement difference of the scapulohumeral joints with inherent instability.

• 한국화재소방학회논문지
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• 제30권4호
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• pp.82-87
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• 2016

초고층 건물의 환기계획에서 설비의 효율적인 운영을 위해 환기설비는 제연설비 겸용으로 사용되고 있다. 본 연구에서는 지하 4층 지상 59층의 초고층 건물을 분석모델로 선정하고 수치해석을 통해 연기이동력에 의한 층별 압력분포를 검토하였으며, 분석모델 건물에서의 연기이동력이 환기 및 제연에 미치는 영향을 규명하였다. 또한 이들 결과를 바탕으로 분석모델 건물의 환기계획에서 주방용 환기댐퍼를 환기-제연 겸용으로 설계할 때 연기이동의 복합력과 요구되는 댐퍼의 개폐력과의 관계를 운동해석 시뮬레이션을 통해 결정하였고, 그 결과로부터 적합한 댐퍼의 구동장치를 선정하였다.

• 대한정형도수물리치료학회지
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• 제13권1호
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• pp.36-43
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• 2007

Purpose: An objective analysis and observations were to be done on hemiplegia patients that are wearing a walking support device, Stroke shoes. Their improvements in walking pace, the reduction of distance between the two knee joint, the increase of curve angle of the knee joint and their steps and the reduction of ankle joint upon swing phase were analyzed using a 20 walking analyzer. Methods: An examination was carried out to see the patients' communication skill and independent walking and then let them walk with the Stroke shoes on to get results before and after wearing it. Simi Reality Motion Systems GmbH (Germany, 2007) was used to analyze the results regarding knee joint and ankle joint angle changes of sagitta plane and coronal plane, stepping distances, distances between the knees and walking pace. Results: 1. The articulation angle of ankle joint during swing phase decreased and knee joint has shown a statistically significant increase in such value(p<0.05). 2. Only knee joint showed a significant increase in articulation angle during heel strike(p<0.05). 3. Knee joint showed a significant increase in articulation angle during toe off(p<0.05). 4. The distance between the two knees as well as their foot steps significantly decreased compared with when Stroke shoes were not worn(p<0.05). 5. Stroke shoes with FES have shown positive effects on the patients in improving their walking styles overall. (p<0.05). Conclusion: There was an improvement in rotation walking pattern by a reduction in the distance between the knees after wearing Stroke shoes with FES. Plantar flexion reduced that occurred in ankle joint during walking and flexion angle increased in knee joint, both of which improved foot drop which was a major problem in hemiplegia patients. Also it is believed that the device will have some positive influences on knee joint stiffening paralysis to aid in improving inefficient walking phases.

• 한국자동차공학회논문집
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• 제23권5호
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• pp.463-470
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• 2015

When a camera installed on a vehicle is used, estimation of the camera pose including tilt, roll, and pan angle with respect to the world coordinate system is important to associate camera coordinates with world coordinates. Previous approaches using huge calibration patterns have the disadvantage that the calibration patterns are costly to make and install. And, previous approaches exploiting multiple vanishing points detected in a single image are not suitable for automotive applications as a scene where multiple vanishing points can be captured by a front camera is hard to find in our daily environment. This paper proposes a camera pose estimation method. It collects multiple images of lane markings while changing the horizontal angle with respect to the markings. One vanishing point, the cross point of the left and right lane marking, is detected in each image, and vanishing line is estimated based on the detected vanishing points. Finally, camera pose is estimated from the vanishing line. The proposed method is based on the fact that planar motion does not change the vanishing line of the plane and the normal vector of the plane can be estimated by the vanishing line. Experiments with large and small tilt and roll angle show that the proposed method outputs accurate estimation results respectively. It is verified by checking the lane markings are up right in the bird's eye view image when the pan angle is compensated.

• Journal of Advanced Marine Engineering and Technology
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• 제39권4호
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• pp.437-442
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• 2015

본 연구에서는 SI 엔진의 정상유동장치에서 충격식 스월미터로 측정한 스월비와 PIV(입자영상유속계) 속도장을 적분하여 구한 스월비를 비교 고찰하였다. PIV 속도장으로부터 스월비를 산출하는 방식에 있어서는 토크를 실린더의 기하학적 중심과 스월 중심에서 각각 계산하여 비교하였다. 또한, 정상유동장치에서 토크의 측정 위치를 변화하여 그에 따른 영향도 고찰하였다. 그 결과, 와류가 안정화되지 못한 상류에서는 충격식 스월미터의 측정값이 PIV로 측정한 값보다 크게 나타났다. PIV 측정에 있어서는 유동 상류에서 실린더 중심을 기준으로 산출한 값이 스월 중심으로 산출한 값보다 작게 나타났다. 측정위치가 하류로 이동하여 스월이 안정화되면서 측정방법에 따른 차이점이 줄어든다.