• Proceedings of the Korea Information Processing Society Conference
• /
• 2006.11a
• /
• pp.295-298
• /
• 2006

본 논문에서는 극 좌표계에서의 벡터 표현 방식을 이용한 per-pixel displacement mapping 방법을 제시한다. per-pixel displacement mapping은 triangle mesh의 처리 방식에 상관없이 변위매핑을 수행할 수 있도록 한 것으로, 2차원 screen space로 projection 된 triangle의 각 pixel의 위치를 객체 표면 정보에 따라 displacement 해주는 방법이다. 이는 기 검증된 범프매칭 하드웨어에 약간의 하드웨어를 추가함으로써 변위매핑을 수행할 수 있도록 한 효과적인 구조이다. 제안 방식에 의해 생성된 영상과 기존 방식에 의해 생성된 영상을 비교해본 결과, 시각적으로 거의 차이가 없음을 알 수 있다.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.7 no.6
• /
• pp.71-80
• /
• 2003

Though a nonlinear time history analysis may be provided to estimate more exactly the seismic performance of building structure, approximation methods are still needed in the aspect of practicality and simplicity, In converting a multi-story structure to an equivalent SDOF system, the mode vectors of the multi-story structure are assumed as the mode shape in elastic state regardless of elastic or elastic-plastic state. However, the characteristics of displacement mode are also changed after the yielding made in the structural elements, because the structure becomes inelastic in each incremental load step. In this research, a method of converting MDOF system to ESDOF system is presented by using nonlinear displacement mode considering the mode change of structures after the yielding. Also, the accuracy and efficiency of the method of the nonlinear displacement mode method of the estimate of seismic response of Mixed Building Structures were examined by comparing the displacements of the roof level of the multi-story building structures estimated from this converted displacement response of ESDOF with the displacement of the roof level through the nonlinear dynamic analysis of the multi-story building structures subjected to an actual earthquake excitation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.1C
• /
• pp.47-55
• /
• 2003

This paper proposes a composition method of mosaic image from the compressed MPEG-2 video stream, in which the displacement between successive frames according to the camera operation is estimated directly from the information involved in the stream. In the proposed method. the approximated optical flow is constructed from motion vectors of macro blocks, and it is used to determine the parameters of the displacements according to the camera operation associated with pan and tilt. The extracted parameters are used to determine the geometric transform of successive video frames in order to construct a mosaic image. The construction of mosaic uses several blending techniques including the one proposed by Nichols in which an analytic weight is used to determine pixel values. Through the experiment, the blending technique based on analytic weights was superior to the others such as averaging and median-based techniques. It provided more smooth changes in background and made use of instantaneous frame information to construct a mosaic. The mosaic in the paper puts the emphasis on the reduction of computation because it is constructed from the motion vectors included in the compressed video without decoding and recalculating exact optical flows. The constructed mosaic can be used in the retrieval of the compressed video as the representative frame of a shot.

• Journal of the Korean Geotechnical Society
• /
• v.22 no.7
• /
• pp.5-12
• /
• 2006

In this study, 2D shallow tunnel model test using close range photogrammetric technique was conducted with aluminium rods simulating continuum granular material. Numerical analysis was also carried out in order to identify the behaviour of subsurface deformations caused by shallow tunnelling. Direction and magnitude of displacement vectors from the model test were identical to the result of numerical analysis based on the model data. In particular, it is shown that the vector direction was toward a point below the tunnel invert level. A narrow "chimney or tulip like" pattern of vertical displacement was confirmed by both the model test and numerical analysis. This behaviour is consistent with the field data. In addition to the qualitative comparison, the quantitative result of subsurface settlements according to 2D volume loss showed good agreement between the model test and numerical analysis. Therefore, close range photogrammetric technique applied in the model test may be used to validate the result from the continuum numerical analysis.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.4 no.1
• /
• pp.13-18
• /
• 1999

This paper proposes a new overmodulation stategy to give a better voltage by the full utilization of the hexagon voltage range in the space vector PWM(SVPWM) inverter. This overmodulation strategy can apply to the vector control, leading to better output torque capability in the ac motor drive system. This strategy is that in the overmodulation range, the d-axis output current is given a priority to regulate the flux well, instead the q-axis output curent is sacrificed. Therefore, the vector control even in the overmodulation PWM operation can be achieved well. For this purpose, the d-axis output voltage of a current controller to control the flux is conserved. the q-axis output voltage to control the torque is controlled to place the reference voltage vector on the hexagon boundary in case of the overmodulation. The validity of the proposed overall scheme is confirmed by simulation and experiments for a 22[kW] induction motor drive system

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.16 no.4
• /
• pp.387-402
• /
• 2014

In congested urban areas, constructions of tunnel structures have became necessary due to a lack of surface space. The excavation of any tunnel generated the ground disturbances of surrounding ground and displacements is major concern. Therefore, a study of tunnel stability is necessary. In this study, the authors have investigated the stability and failure pattern of tunnel through the model tunnel test. In this study, the close range photogrammetry was used to measure the ground deformation. The measured data was converted to displacement vectors and contours. And then it compared to FE analysis and empirical formula. In addition, this study presented the comparison between steel pipe reinforced model tunnel and unreinforced model tunnel. The ground deformation for both the steel pipe reinforced model tunnel and the unreinforced model tunnel was analysed.

• The Journal of Engineering Geology
• /
• v.23 no.1
• /
• pp.47-55
• /
• 2013

To analyze lateral displacement of excavation walls exposed during the construction of Subway Line 1 in the Daegu region, inclinometer measurement data for sites D4, D5, and Y6 are investigated from the perspective of engineering geology. The study area, in the Banyawol Formation, Hayang Group, Gyeongsang Supergroup, is in the lower part of bedrock of andesitic volcanics, calcareous shale, sandstone, hornfels, and felsite dykes that are unconformably overlain by soil. The rock mass around the D4 site is classified as RMR-V grade and the maximum lateral displacement of 101.39 mm, toward N34W, was measured at a bedding-parallel fault, at a depth of 12 m. The rock mass around the D5 site is classified as RMR-IV grade and the maximum lateral displacement of 55.17 mm, toward the south, was measured at a lithologic contact between shale and felsite, at a depth of 14 m. The rock mass around the Y6 site is classified as RMR-III grade and the maximum lateral displacement of 12.65 mm, toward S52W, was measured at an unconformity between the soil and underlying bedrocks, at a depth of 7 m. The directions of lateral displacement in the excavation walls are vector sums of the directions perpendicular to the excavation wall and horizontally parallel to the excavation wall. Lateral displacement graphs according to depth in the soil profile show curvilinear trajectories, whereas those in bedrock show straight and rapid-displacement trajectories.

• Journal of the Korean Society for Precision Engineering
• /
• v.17 no.4
• /
• pp.203-208
• /
• 2000

2진 로봇 머니퓰레이터는 기하학적 형상이 가변트러스 구조로 되어 있으며 조인트의 구동원으로 사용되는 엑츄에이터는 2가지의 변위, 즉 최대 및 최소 변위만으로 동작한다. 따라서 작업영역은 연속적으로 주어지는 일반 로봇 머니퓰레이터와는 달리 유한 개의 위치 벡터의 집합 형태로 나타난다. 기존의 역기구학적 해석방법을 적용하기 어려운 2진 로봇 머니퓰레이터의 불연속적인 특성에 대해 새로운 작업영역과 역기구학 문제를 정의하였다. 유전 알고리즘을 사용하여 새로이 정의된 문제의 역기구학적 해석을 수행하였으며 유전 알고리즘이 2진 로봇 머니퓰레이터의 역기구학적 해석에 있어서 효과적이고 강건한 방법임을 보여주었다.

• Proceedings of the Korean Information Science Society Conference
• /
• 2002.10d
• /
• pp.562-564
• /
• 2002

본 논문에서는 자기상관함수의 국소적 특징을 사용하여 에지 특징을 추출한 후, 이를 이용해 유사이미지를 검색하는 방법을 제시한다. 자기상관함수의 국소적 특징을 이용하여 이미지를 검색할 경우 크기, 밝기, 색상등과 같은 이미지 요소가 서로 다를 경우에도 영향을 받지 않고 에지 특징정보를 추출해 낼 수 있다. 이는 얻어진 에지 특징을 이미지 크기와 고차 국소 자기상관함수의 변위에 의해 변하지 않도록 정규화를 하고, 동일 이미지에 대해 밝기가 조금 달라지면 검색효율이 떨어지는 점을 해결하기 위해 거리척도로서 방향여현거리(direction cosine distance)를 이용함으로써 가능하다. 이렇게 추출된 특징벡터를 자기조직화 맵에 의하여 클러스터링하고, 유사이미지 검색의 효율성을 비교해본 결과, 본 논문에서 제시한 방법을 사용하여 검색한 경우 재현율이 기존의 방법에 비해서 비교적 높은 수치를 나타냈다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2002.11a
• /
• pp.649-652
• /
• 2002

PCA 방법은 입력 차원을 수학적으로 줄일 수 있는 장점 때문에 패턴인식 부분에서 널리쓰이고 있다. 얼굴인식에서의 PCA는 학습 패턴의 분산을 최대로 하는 기저 벡터들인 고유얼굴을 만들어 얼굴인식이 필요한 영상을 이 기저 벡터에 투사시켜 이때 나온 인자들과 원래 각 개인의 대표 인자값과의 거리 비교로 얼굴을 인식하는 방법이다. 그러나 조명등의 영향에 매우 민감하며 거리값으로 얼굴을 인식하기 때문에 다양한 변화에 따라 오인식률이 높아진다. 이는 인식률을 높이고자 임계값을 높게 설정하는 과정에서 발생하는 오류이며, 이를 방지하기 위해 임계치를 낮게 설정하면 오거부율이 높아진다. 이에 본 연구에서는 PCA에 입력되는 패턴들을 사전에 비교, 분류하여 PCA 연산시에 분산과 변위를 최대한으로 가질 수 있도록 하였다. 그러하여, 기존의 PCA보다 상당히 낮은 임계값으로도 오거부율의 증가를 막았으며, 낮은 임계값 설정으로 인하여 오인식률을 낮추는 결과를 얻을 수 있었다. 이는 기존의 PCA 방법을 사용하는 인식시스템에서 종종 발생하는 허가되지 않아야 하는 외부인을 인증시키는 사례를 줄일 수 있다.