• Korean Journal of Remote Sensing
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• v.33 no.5_1
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• pp.571-585
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• 2017

The number of spaceborne optical sensors including red-edge band has been increasing since red-edge band is known to be effective to enhance the information content on biophysical characteristics of vegetation. Considering that the Agriculture and Forestry Satellite is planning to carry an imaging sensor having red-edge band, we tried to analyze the current status and potential of red-edge band. As a case study, we analyzed the effect of using red-edge band and tried to find the optimum band width and wavelength region of the red-edge band to estimate leaf area index (LAI) of very dense tree canopy. Field spectral measurements were conducted from April to October over two tree species (white oak and pitch pine) having high LAI. Using the spectral measurement data, total 355 red-edge bands reflectance were simulated by varying five band width (10 nm, 20 nm, 30 nm, 40 nm, 50 nm) and 71 central wavelength. Two red-edge based spectral indices(NDRE, CIRE) were derived using the simulated red-edge band and compared with the LAI of two tree species. Both NDRE and CIRE showed higher correlation coefficients with the LAI than NDVI. This would be an alternative to overcome the limitation of the NDVI saturation problem that NDVI has not been effective to estimate LAI over very dense canopy situation. There was no significant difference among five band widths of red-edge band in relation to LAI. The highest correlation coefficients were obtained at the red-edge band of center wavelength near the 720 nm for the white oak and 710 nm for the pitch pine. To select the optimum band width and wavelength region of the red-edge band, further studies are necessary to examine the relationship with other biophysical variables, such as chlorophyll, nitrogen, water content, and biomass.

• Journal of Broadcast Engineering
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• v.12 no.1 s.34
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• pp.41-52
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• 2007

The 3DTV services can be seen as a general case of the multi-view video that has been receiving a significant attention lately. However, the key factors that influence the success of 3DTV are the availability of content, the ease of use, the quality of contents, and the reduction of cost. This paper deals primarily with the perceptual improvement in image quality, especially based on human factors. An optimal asymmetrical coding method for binocular and multi-view images is presented. The quantitative value of asymmetrical rate to maintain optimized subjective image quality is explored. Also we analyze how edges of 2D images affect on 3D perceptions and propose an edge-preserving algorithm to perform perceptual improvements. Experimental results demonstrate that the proposed algorithm enhances subjective image quality much better than conventional methods.

• Journal of the Korea Computer Graphics Society
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• v.28 no.1
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• pp.11-19
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• 2022

In this paper we present a new method for interactive segmentation of a triangle mesh by using the concavity-sensitive harmonic field and anisotropic geodesic. The proposed method only requires a single vertex in a desired feature region, while most of existing methods need explicit information on segmentation boundary. From the user-clicked vertex, a candidate region which contains the desired feature region is defined and concavity-senstive harmonic field is constructed on the region by using appropriate boundary constraints. An initial isoline is chosen from the uniformly sampled isolines on the harmonic field and optimal points on the initial isoline are determined as interpolation points. Final segmentation boundary is then constructed by computing anisotropic geodesics passing through the interpolation points. In experimental results, we demonstrate the effectiveness of the proposed method by selecting several features in various 3D models.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.4
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• pp.198-204
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• 2003

In this paper, we presented a new algebraic iterative algorithm for the optimal control of the nonlinear systems. The algorithm is based on two steps. The first step transforms nonlinear optimal control problem into a sequence of linear optimal control problem using the quasilinearization method. In the second step, TPBCP(two point boundary condition problem) is solved by algebraic equations instead of differential equations using the new integral operational matrix of BPF(block pulse functions). The proposed algorithm is simple and efficient in computation for the optimal control of nonlinear systems and is less error value than that by the conventional matrix. In computer simulation, the algorithm was verified through the optimal control design of synchronous machine connected to an infinite bus.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.371-374
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• 1999

현재까지 초음파 모터는 소형 경량이면서도 저속에서 큰 출력을 가지며 정확한 위치 제어가 가능하다는 점에서 큰 관심을 끌고 있다. 대부분 회전형 로우터리 모터가 주종을 이루고 있으며 특수한 용도로 초음파 리니어 모터가 일부 사용되고 있다. 본 연구에서는 진행파를 이용하여 쌍방향으로 움직일 수 있는 새로운 구조의 진행파형 초음파 리니어 모터를 설계하고 제작하였다. 설계는 유한요소해석법을 이용하여 구조의 가능성과 진행파가 왜곡되지 않는 최적구조, 계질, 크기, 경계조건을 결정하였다. 그 결과에 따라 리니어 모터를 실제로 제작하여 알루미늄판 위에서 주파수 변화 및 부하질량 변화에 대한 모터의 성능을 측정하였는데, 제작된 모터는 부하질량이 100 g일 때 14.6cm/s로 가장 빠른 속도특성을 보였다. 본 모터는 다양한 정밀위치제어 및 이동 소자로서 활용될 수 있을 것이다.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.307-308
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• 2014

듀얼 액티브 브릿지 컨버터는 고전력 전달에 유용한 절연형 양방향 컨버터이다. 듀얼 액티브 브릿지 (DAB) 컨버터의 가장 간단한 제어 방식은 고주파 변압기의 일차단과 이차단의 위상 차이를 통해 전달 전력을 제어하는 위상천이변조 (PSM) 방식이다. 그러나 위상 변동 방식을 이용하면 경부하 상황에서 소프트 스위칭이 이루어지지 않으며 순환 전류 또한 크게 발생하여 변환 효율이 낮아지게 된다. 본 논문에서는 위상 및 듀티가 변동된 컨버터의 최적 동작점을 파악하기 위한 DAB 컨버터의 운용 특성 연구를 수행하였다. 컨버터의 위상과 듀티에 따른 동작 파형, 경계 조건, RMS 전류, 소프트스위칭의 여부 등이 분석되었다.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.2
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• pp.21-31
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• 1999

This paper presents a new possibility of calculating optimal control for large scale which consist of non-linear dynamic sub-systems using two level hierarchical structures method. And the proposed method is based on the idea of block pulse transformation to simplify the algorithm and its calculation. This algorithm used an expansion around the equilibrium point of the system to fix the second and higher order terms. These terms are compensated for iteratively at the second level by providing a prediction for the states and controls which form of a part of the higher order terms. In this new approach the quadratic penalty terms are not used in the cost function. This allows convergence over a longer time horizon and also provides faster convergence. And the method is applied to the problem of optimization of the synchronous machine. Results show that the new approach is superior to conventional numerical method or other previous algorithm.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.5
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• pp.441-448
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• 2011

Lately, digital restitution was became common using digital aerial photos. Therefore, we can obtain three-dimensional data. As a plotting-maker is checked by naked eye, plotting original data is very useful for making reliable three-dimensional data including contour and elevation point layers. In this study, we want to make precise and accurate digital elevation model using plotting original data. Contour and elevation point layers was extracted in digital map and break line was extracted in plotting original data. And then, compared both of results. For comparison, we selected slight slope and complex topography area like a residence area, mountain and agricultural land. We extracted break line deleting layer until obtaining ideal digital elevation model. As the results, We could extract contour, elevation points, eight road and two boundary layers using break lines. And We could obtain precise elevation model. Editing break lines, the distortion of digital elevation model could be minimized in the complex and sharp slope area.

• Journal of Korea Water Resources Association
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• v.38 no.7 s.156
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• pp.537-544
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• 2005

For the proper management of high pressurized gas storage caverns, analysis of groundwater flow field and inflow quantity according to the groundwater head, gas storage pressure and water curtain head should be performed. The finite element method has been widely used for the groundwater flow analysis surrounding underground storage cavern because it can reflect the exact shape of cavern. But the various simulations according to the change of design factors such as the width of water curtain, shape of cavern etc. are not easy when elements were set up. To overcome these limitations, two dimensional groundwater flow model is established based on the boundary element method which compute the unknown variable by using only the boundary shape and condition. For the exact computation of drainage rate into cavern, the model test is performed by using the exact solution and pre-developed finite element model. The test result shows that the model could be used as an alternative to finite element model when various flow simulations are needed to determine the optimizing cavern shape and arrangement of water curtain holes and so forth.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.3
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• pp.1-12
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• 1985

The linear tracking theory has a great merit that its solution can be analytically obtained under the quadratic performance measure. However, this theory has not been applied to reservoir system operation yet, because the tracking assumes no boundness of the control and state vectors. This paper presents deriving the optimal control law and solving the Riccati equations for the discrete time horizon, and its application to the real system. And the additional necessary conditions for the saturated vectors of the control and/or state are also derived using the concept of the Pontryagin's minimum principle. The logic and its algorithm in this work are not so positive to give a general solution. In fact, it is a matter of modeling in terms of relative magnitude of disturbance and time-step size. However its application to the real environment of the Han river, which comprises six major reservoirs in series/parallel, demonstrated satisfactory results over 36 monthly stages.