• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.4
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• pp.49-57
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• 1988

A new analytical inversion technique is developed to determine the shear wave velocity profiles of natural soils and pavement systems from the dispersion curves of Rayleigh waves. Haskell's theory on the dispersion of the surface waves in multi-layered elastic solids is utilized. A frequency-unlimited dispersion equation is developed by use of the delta matrix technique. Rigid halfspace is assumed at the depth of the one wavelength of Rayleigh waves. Computer program is coded and validity of the technique is verified through the numerical model tests.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.461-469
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• 2001

Existing area-based stereo algorithms rely heavily on rectangular windows for computing correspondence. While the algorithms with the rectangular windows are efficient, they generate relatively large matching errors due to variations of disparity profiles near depth discontinuities and doesnt take into account local deformations of the windows due to projective distortion. In this paper, in order to deal with these problems, a new correlation function with 4 directional line masks, based on robust estimator, is proposed for the selection of potential matching points. These points is selected to consider depth discontinuities and reduce effects on outliers. The proposed matching method finds an arbitrarily-shaped variable window around a pixel in the 3d array which is constructed with the selected matching points. In addition, the method take into account the local deformation of the variable window with a constant disparity, and perform the estimation of sub-pixel disparities. Experiments with various synthetic images show that the proposed technique significantly reduces matching errors both in the vicinity of depth discontinuities and in continuously smooth areas, and also does not be affected drastically due to outlier and noise.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.5
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• pp.103-110
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• 2003

The grounding system is necessary to provide means to dissipate electric currents into the earth without exceeding any operating and equipment limits. The ground is composed of various soils and the resistivity of the soil depends on many parameters. It depends on the type of soil and varies with distance as well as with depth. Especially, soil resistivity of volcanic area such as Jeju is ve교 high and it is difficult to acquire necessary grounding resistivity. This paper introduces the efficient grounding construction using coring technique for proper grounding resistance in high resistivity area. Because it is difficult to measure the accurate resistivity of soils, their resistivities are estimated using measured value of ground resistance and equivalent radius method. Estimated resistivities are used for grounding resistance in scheduled construction region.

• The Journal of Korea Robotics Society
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• v.11 no.3
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• pp.156-162
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• 2016

For the underwater localization, acoustic sensor systems are widely used due to greater penetration properties of acoustic signals in underwater environments. On the other hand, the good penetration property causes multipath and interference effects in structured environment too. To overcome this demerit, a localization method using the attenuation of electro-magnetic(EM) waves was proposed in several literatures, in which distance estimation and 2D-localization experiments show remarkable results. However, in 3D-localization application, the estimation difficulties increase due to the nonuniform (doughnut like) radiation pattern of an omni-directional antenna related to the depth direction. For solving this problem, we added a depth sensor for improving underwater 3D-localization with the EM wave method. A micro scale pressure sensor is located in the mobile node antenna, and the depth data from the pressure sensor is calibrated by the curve fitting algorithm. We adapted the depth(z) data to 3D EM wave pattern model for the error reduction of the localization. Finally, some experiments were executed for 3D localization with the fast calculation and less errors.

• Journal of the Korean Society for information Management
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• v.20 no.4 s.50
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• pp.159-193
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• 2003

This study is a case study that attempt to quantify the economic efficiency of 'digital library program(DLP) of the National Library of Korea' by means of cost-benifit analysis. Results indicate that the B/C ratio is 1.70 which can be interpreted the economic efficiency of DLP is very high. Of particular significance is the fact that this study empirically proves that the digital library program is economically efficient.

• The Korean Journal of Malacology
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• v.3 no.1
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• pp.44-67
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• 1987

담수 저서 생물군 중의 하나인 연체동물은 인간 생활에 있어 매우 중요하다. 이들은 먹이사슬(food chain)과 깊이 연관되어 있고 하상 퇴적물의 찌꺼기를 섭취하는 청소자로서의 역할 뿐 아니라 안간의 식용으로 이용되기도 한다. 어떤 종은 생태학적 지표종으로서의 역할을 하며, 어떤 종들은 지리적 특성과 연관성을 연구하는데 대상이 될 뿐 아니라 과거의 수계 형성과정을 추정하는데 중요한 역할을 한다. 부정적 측면으로는 한국 담수산 권패류의 몇몇 종류는 인체의 흡충류 기생충을 전달하는 그들의 역할 때문에 실제 문제시 되고 있다. 그들의 이 같은 중요성에도 불구하고, 한국산 담수 연체동물에 대한 깊은 연구가 이루어지지 않고 있는바, 이는 부분적으로 한국에 서식하는 연체동물상을 동정함에 있어 쉽게 이용될 수 있는 적당한 분류체계가 부족하였기 때문이다. 본 논문의 첫째 목적은 한국산 담수 권패류를 속(genus)수준까지 동정할 수 있는 색인을 마련하고 그 분류기준을 세우는데 있으며, 둘째로는 한국산 담수 권패류에 대한 광범한 문헌을 수집하고 중요한 문헌의 순서에 따라 그 내용을 간략히 요약하여 앞으로의 연구자득에게 도움을 주고자 한 것이다.

• Journal of the Society of Naval Architects of Korea
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• v.36 no.2
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• pp.105-113
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• 1999

This paper resents a prediction method of natural frequencies of coupled horizontal and torsional vibration of hull girder based on design sensitivity analysis in case of the changes of system parameters. The sensitivity analysis is formulated applying the direct differentiation method and transfer matrix method. In the analysis, warping, shear deformation due to torsion and the continuity condition at the connected part of open and closed hull section are considered. Using the presented method. The affection for natural frequencies by the change of system parameters, especially cargo and added mass and their centers, is numerically investigated for a real large container carrier.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.1
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• pp.33-41
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• 2011

For the assessment of ultimate longitudinal strengths of damaged hull girders, it is preliminarily necessary to determine the extents and locations of the damages due to severe accidents. This paper deals with the estimation of the damages from collisions and groundings of large-sized vessels where deterministic and probabilistic approaches are investigated. Deterministic damages estimated from MARPOL(or ICLL), ABS and DNV are compared with probabilistic damages from IMO guideline and some references including damage statistic data. Damages from MARPOL show largest one among all the investigated damage estimation, since it was developed not for the residual strength of hull girder but for the damage stability calculation. IMO guideline with high level probability of damage(eg. 95% probability level) also forecasts even severer damage extents than MARPOL. On the other hand, assuming average probability level of damage, the calculated damage sizes are around the one from deterministic approaches.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.4
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• pp.95-101
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• 2008

Purpose: The aim of this research was to propose a program that can be used the Binocular Eye Visual Perception Training. Methods: This program can be used as a tool for binocular vision and vision training. The system that was made up of module was available in the stereosis and the vergence training. Results: In case of input module, this program could estimate the distance by using fixation disparity. Also, our margin of erroe is less then 5%. In case of output module, 28 trainers were examined by stereoscopic vision and visual depth perception. Conclusions: Therefore, the system can be used as a tools for the vision training.

• Journal of Broadcast Engineering
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• v.24 no.5
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• pp.765-774
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• 2019

In this paper, we propose a point cloud matching algorithm for multiple RGB-D cameras. In general, computer vision is concerned with the problem of precisely estimating camera position. Existing 3D model generation methods require a large number of cameras or expensive 3D cameras. In addition, the conventional method of obtaining the camera external parameters through the two-dimensional image has a large estimation error. In this paper, we propose a method to obtain coordinate transformation parameters with an error within a valid range by using depth image and function optimization method to generate omni-directional three-dimensional model using 8 low-cost RGB-D cameras.