• Journal of Korea Water Resources Association
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• v.52 no.7
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• pp.493-503
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• 2019

This study presents a new method of estimating the size distribution of river bed gravel through image processing. The analysis was done in two steps; first the individual grain images were analyzed and then the grain particle segmentation of river-bed images were processed. In the first part of the analysis, the relationships (long axes, intermediate axes and projective areas) between grain features from images and those measured were compared. For this analysis, 240 gravel particles were collected at three river stations. All particles were measured with vernier calipers and weighed with scales. The measured data showed that river gravel had shape factors of 0.514~0.585. It was found that the weight of gravel had a stronger correlation with the projective areas than the long or intermediate axes. Using these results, we were able to establish an area-weight formula. In the second step, we calculated the projective areas of the river-bed gravels by detecting their edge lines using the ImageJ program. The projective areas of the gravels were converted to the grain-size distribution using the formula previously established. The proposed method was applied to 3 small- and medium- sized rivers in Korea. Comparisons of the analyzed size distributions with those measured showed that the proposed method could estimate the median diameter within a fair error range. However, the estimated distributions showed a slight deviation from the observed value, which is something that needs improvement in the future.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.138-149
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• 2014

This study proposes an estimation method of strain distribution for multi-span steel beam structure under unspecific loading conditions. The estimation method in this paper employs the curve fitting using the least square method from measured strain data, not analytical method. To verify the proposed estimation method, a static loading test for multi-span steel beam on which distributed and concentrated loads act was conducted. The strain data for verification was measured by FBG sensors that have multiplexing technology. The analysis of the accuracy of strain estimation for distributed and concentrated loads and the errors by considering the number of measured points used in the estimation were conducted. In the maximum strain points, the strains could be estimated with the errors of 5.89% (loading step 1) and 6.26% (loading step 2). In case of decreasing the number of sensors, it was also confirmed that the errors increased (0.26~0.37%). Through the curve fitting method, it is possible to estimate the strain distribution (maximum strains and their locations) of multi-span beam for unspecific loads and go over the limit of the analytical estimation method which is suitable for specific distributed loads.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.7
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• pp.576-579
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• 2017

Due to the existence of flash lobe caused by the radome structure, a radar return in general contains clutter component added to target echo. Unlike jammer, clutter is apt to simultaneously coexist with target echo, which hinders a monopulse radar from estimating the angle difference between target echo direction and radar steering direction. In this paper, we propose a clutter estimation algorithm applicable to generalized sidelobe canceller(GSC) based monopulse radar. We show that clutter estimation can be achieved via iterative process of the orthogonal projections. Through simulations, the proposed GSC-based system combined with the clutter estimation can outperform the conventional monopulse system in terms of target angle estimation.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.2
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• pp.108-113
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• 2009

MFL(magnetic flux leakage) inspection is a general method of non-destructive evaluation(NDE) of underground gas pipelines. Pipelines are magnetized by permanent magnets when MFL PIG(pipeline inspection gauge) gets through them. If defects or corrosions exist in pipelines, effective thickness is changed and thus variation of leakage flux occurs. The leakage flux signals detected by hall-sensors are analyzed to characterize defect's geometries such as length, width, depth, and so on. This paper presents several methods for estimating defect's length using MFL signals and their performances are compared for real defects carved in KOGAS pipeline simulation facility. It is found that 80% and 90% of minimum values for axial and peak values for radial signals respectively show the best performance in the point of length estimation error.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1288-1293
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• 2014

This paper proposes a new method to estimate the striking velocity for ballistic limit velocity in MIL-STD-662F. The method from MIL-STD-662F needs relative air density, drag coefficient, form factor, ballistic coefficient for estimating striking velocity. So precedent studies are essential. However, the new method can estimate striking velocity only using measured velocities and distance between the screen and the target. To prove new method, we compared estimation of striking velocity from both the new method and the method from MIL-STD-662F on the basis of datain PRODAS. The new method shows bigger errors in some velocity ranges. But it could still calculate ballistic limit velocity. It also shows smaller errors in most velocity ranges.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.2
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• pp.15-22
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• 2020

In this paper, seismic ground motion generation method based on the observbation data from the Korea Meteorological Administration is proposed to predict the acceleration time history at an arbitrary location after earthquake. The proposed method assumes that the magnitude of the seismic accelrations obtained from the near stations decreases linearly with the distance from the epicenter to the corresponding station and the accelerations measured at the adjacent stations are assumed to have similar maximum acceleration and time shape functions. These two assumptions allow for the prediction of seismic acceleartion motion without geotechnical information where no seismic accelerometer is installed. This study verified the applicability of the prediction method using seismic observation data from Gyeongju Earthquake (2016), Pohang Earthquake (2017) and Sangju Earthuqkae (2019). The comparison results show that the proposed method is effective for predicting the seismic acceleration response spectrum and time history at arbitary locations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.6
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• pp.785-791
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• 2021

In this paper, we propose a methodology for estimating the optimal traversable destination from the location-based information of the object recognized by the mobile robot to perform the object delivery service. The location estimation process is to apply the generalized Voronoi graph to the grid map to create an initial topology map composed of nodes and links, recognize objects and extract location data using RGB-D sensors, and collect the shape and distance information of obstacles. Then, by applying the hybrid approach that combines the center of gravity and thinning method, the optimal moving position for the service robot to perform the task of grabbing is estimated. And then, the optimal node information for the robot's work destination is updated by comparing the geometric distance between the estimated position and the existing node according to the node update rule.

• The Journal of the Convergence on Culture Technology
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• v.8 no.3
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• pp.277-282
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• 2022

The sleeper floating track (STEDEF) in this study was a track type in which a very soft resilience pad was installed under a relatively thin concrete sleeper (RC Block). Therefore it was expected that the resilience pad could affect the estimation results of the concrete strength. In this study, field applicability evaluation was performed to apply the rebound hardness test method, which was a general method for estimating the compressive strength of concrete in civil structures, to concrete sleepers of railway tracks. In order to analyze the strength estimation technique of concrete sleepers reflecting the characteristics of track structures different from those of civil structures, the parameter experiments that could affect the strength estimation results of concrete sleepers in a serviced line were performed. As a result of the study, the appropriate hitting position was suggested considering the shape of the concrete sleeper, and the difference in strength estimation results according to the condition of the concrete sleeper and supporting conditions was derived.

• Bulletin of Food Technology
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• v.15 no.1
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• pp.62-68
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• 2002

사과급여가 지질대사에 미치는 효과를 40마리의 Wistar rats에 0.3% 콜레스테롤을 첨가한 반정제식이를 급여하여 조사하였다. 사과첨가군는 일반식이중 전분함량(15%)을 동결건조시킨 사과(Gala 품종)로 대체하였으며, 대조군은 사과에서 유래되는 당함량을 대신하여 전분중 13%를 과당/포도당/ 전분의 혼합물로 대체하였다. 실험식이에서 지방원은 옥배유 사용하였으며, 식이중 비타민E는 요구량의 1/3정도 첨가하였다. 실험쥐는21일간의 적응기간을 걸쳐 선별하였다. 사과급여군에서, 사과에서 유래되는 식이섬유소량이 소량(약 2%)임에도 불구하고 혈장내 콜레스테롤이 유의적으로 낮아지는 경향을 보였으나, 콜레스테롤 첨가군에서는 간에 콜레스테롤 에스테르가 축적되는 결과를 보였다. 사과급여군에서 지단백질 형상이 크게 다르게 나타났는데, 이는 중성지방이 많은 지단백질(TGRLP) 콜레스테롤이 감소되고 HDL 콜레스테롤은 증가되는 결과를 보여 심장관련질환 예방에 효과가 있을 것으로 추정되었다. 또한, 사과가 콜레스테롤 흡수를 크게 저하시키는 것으로 추정되나 담즙산의 분해에는 영향을 주지 않는 것으로 나타났다. 이와 같은 결과로 사과식이군이 대조군에 비해 혈장 FRAP가 높고 뇨중의 MDA 추출물이 감소하는 경향을 보여 산화억제효과도 있는 것으로 나타났다. 따라서 후식으로 적당량의 사과를 섭식하는 것이 지질과 과산화성 인자에 바람직한 영향을 주는 것으로 나타났다.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2476-2481
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• 2007

An inverse radiation analysis is presented for the estimation of the wall emissivities for an absorbing, emitting, and scattering media with diffusely emitting and reflecting opaque boundaries. In this study, a repulsive particle swarm optimization(RPSO) algorithm which is a relatively recent heuristic search method is proposed as an effective method for improving the search efficiency for unknown parameters. To verify the performance of the proposed RPSO algorithm, it is compared with a basic particle swarm optimization(PSO) algorithm and a hybrid genetic algorithm(HGA) for the inverse radiation problem with estimating the wall emissivities in a two-dimensional irregular medium when the measured temperatures are given at only four data positions. A finite-volume method is applied to solve the radiative transfer equation of a direct problem to obtain measured temperatures.