• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.151-151
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• 2020

표면영상유속측정법은 영상을 이용한 비접촉식 유속 측정 방법으로 카메라 외에 별도로 고가의 장비를 구매할 필요가 없을 뿐 아니라 현장 상황을 영상으로 확인할 수 있기 때문에 현장조사인력이 필요 없어 경제적이고, 안전하다는 장점을 갖고 있는 하천 유속 측정 방법이다. 표면영상유속측정법은 일반적으로 상호상관법을 이용하여 수표면을 촬영한 연속된 두 영상에서 입자군의 명암값 분포를 계산하여 입자군의 변위를 계산하고 이를 두 영상 사이의 시간 간격으로 나누어 입자군의 이동 속도를 산정하는 방법이다. 따라서 표면영상유속측정법으로 산정한 유속의 정확도를 높이기 위해서는 영상 내 두 입자군의 변위를 정확하게 계산하는 것이 무엇보다 중요하다. 즉, 분석하고자 하는 영상의 물리거리를 정확하게 계산할 수 있어야 한다. 카메라를 이용하여 실제 하천 영상을 촬영한 영상은 카메라 렌즈에 의한 왜곡이 필연적으로 발생하게 되고 이는 영상 내의 변위 산정 시에도 영향을 미친다. 특히 드론을 활용하여 넓은 하천 영역을 촬영할 경우 카메라 렌즈에 의한 왜곡은 실제 물리 변위 계산 정확도에 큰 영향을 미치게 된다. 이에 본 연구에서는 카메라 왜곡이 영상 내 변위 산정 결과의 정확도에 미치는 영향을 분석하였다. 연구 결과 카메라 렌즈 왜곡은 영상 중심에서 방사방향으로 점점 크게 발생하고 왜곡 정도는 비선형적으로 나타났으며, 변위 측정 오차는 영상의 중앙부에서는 거의 차이가 없었으며, 영상 외곽부에서 최대 오차가 발생하는 것으로 나타났다. 그리고 카메라 렌즈 왜곡 보정을 실시하게 되면 영상 전체적으로 변위측정 오차는 모두 제거할 수 있는 것으로 확인하였다. 따라서 카메라 렌즈 왜곡 보정을 실시하여 표면영상유속 측정 결과의 정확도를 개선할 수 있는 것으로 나타났다. 향후 카메라 렌즈 왜곡 보정을 실시한다면 하천의 표면유속을 보다 정확하게 측정할 수 있을 것으로 기대한다.

• Ecology and Resilient Infrastructure
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• v.8 no.1
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• pp.1-8
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• 2021

A surface image velocimeter (SIV) measures the velocity of a particle group by calculating the intensity distribution of the particle group in two consecutive images of the water surface using a cross-correlation method. Therefore, to increase the accuracy of the flow velocity calculated by a SIV, it is important to accurately calculate the displacement of the particle group in the images. In other words, the change in the physical distance of the particle group in the two images to be analyzed must be accurately calculated. In the image of an actual river taken using a camera, camera lens distortion inevitably occurs, which affects the displacement calculation in the image. In this study, we analyzed the effect of camera lens distortion on the displacement calculation using a dense and uniformly spaced grid board. The results showed that the camera lens distortion gradually increased in the radial direction from the center of the image. The displacement calculation error reached 8.10% at the outer edge of the image and was within 5% at the center of the image. In the future, camera lens distortion correction can be applied to improve the accuracy of river surface flow rate measurements.

• Journal of Korean Society of Transportation
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• v.3 no.1
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• pp.86-93
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• 1985

1965년에 출판된 고속도로용량교범(Highway Capacity Manual)은 고속도로, 도시 및 지방도로의 용량과 서비스수준을 판단하는데 기본서 역할을 해왔다. 도시내 신호등이 있는 교차로의 서비스수준은 빈하율(load factor) 개념을 이용하여 산정해 왔다. 그러나 푸른신호 주기동안 차량의 교차로이용도를 기준으로 하는 빈하율 개념은 서비스 수준의 측정치로서 한계가 있고 또 그동안 신호체계가 많이 개선되었고 운전자의 통행행태가 크게 변화하여 1970년대 중반부터 한계통행분석법(Critical Movement Analysis)과 차량의 교차로지체시간 측정법(Intersection Delay)등과 같은 새로운 기법이 소개되었다. 본 논문은 최근에 많이 이 용되고 있는 교차로지체시간측정법의 유용성을 검증하기 위해 15개 교차로의 차량통행량을 기준으로 하여 V/C비를 계산하는 한계통행분석법에 의한 측정치와 비교, 분석하였다. 그 결 과 교차로의 서비스수준을 측정하는데 양자의 방법에 의한 측정치가 크게 다르지 않음을 발 견하였다. 즉 도시내 신호등이 있는 교차로시설을 개선하기 위해 대략적인 교차로 서비스수 준을 측정할 경우 조사인원 및 비용이 많이 소요되는 한계통행분석법보다 조사가 간편하고 비용이 적게 드는 교차로지체시간측정법이 유용함을 밝혔다.

• Journal of Korea Water Resources Association
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• v.54 no.11
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• pp.933-942
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• 2021

The surface image velocimetry was developed to measure river flow velocity safely and effectively in flood season. There are a couple of methods in the surface image velocimetry. Among them the spatio-temporal image velocimetry is in the spotlight, since it can estimate mean velocity for a period of time. For the spatio-temporal image velocimetry analyzes a series of images all at once, it can reduce analyzing time so much. It, however, has a little drawback to find out the main flow direction. If the direction of spatio-temporal image does not coincide to the main flow direction, it may cause singnificant error in velocity. The present study aims to propose a new method to find out the main flow direction by using a fast Fourier transform(FFT) to a spatio-temporal (image) volume, which were constructed by accumulating the river surface images along the time direction. The method consists of two steps; the first step for finding main flow direction in space image and the second step for calculating the velocity magnitude in main flow direction in spatio-temporal image. In the first step a time-accumulated image was made from the spatio-temporal volume along the time direction. We analyzed this time-accumulated image by using FFT and figured out the main flow direction from the transformed image. Then a spatio-temporal image in main flow direction was extracted from the spatio-temporal volume. Once again, the spatio-temporal image was analyzed by FFT and velocity magnitudes were calculated from the transformed image. The proposed method was applied to a series of artificial images for error analysis. It was shown that the proposed method could analyze two-dimensional flow field with fairly good accuracy.

• Journal of Korean Society of Transportation
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• v.34 no.6
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• pp.523-534
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• 2016

The purpose of this study is to develope a method for measuring social benefit by mitigating in-vehicle congestion level in intercity buses. Contingent valuation method and Tobit model are adopted for social benefit evaluation method. One thousand passengers were interviewed with 992 obtained valid samples. Tobit models with age, income level, and bus boarding times as explanatory variables are selected to estimate the willingness to pay for the mitigation of intercity bus in-vehicle congestion. Statistically and logically, two models with age or income level as explanatory variables are turned out to be valid. The intercity bus service supply status and usage are examined and the bus users who have willingness-to-pay for the intercity bus in-vehicle congestion mitigation have been identified. In case of the 'no standing' rules implemented to the intercity bus, the annual economic benefit from the service is estimated to be 14.7 billion won.

• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.311-315
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• 2010

The effects of $SO_2$ on the performance of proton exchange membrane(PEMFC) were investigated by introduction air containing $SO_2$ into cathode inlet of PEMFC. And the recovery of the cell performance by applying clean air, cycle voltammetry(CV) and high voltage holding following exposure contaminated air was studied. The $SO_2$ concentration range used in the experiments was from 20 ppb to 1.3 ppm. The performance degradation and recovery were measured by constant-current discharging, I-V polarization and electrochemical impedance spectroscopy(EIS). The cell voltage gradually decayed with time and decreased by 17 mV after 200 hours of 20 ppb $SO_2$ injection. The cell performance can be recovered partially by clean air flushing, CV and high voltage holding due to desorption of S from Pt catalyst.

• Journal of the Korean Society for Library and Information Science
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• v.46 no.4
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• pp.61-76
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• 2012

The research reports the results from an investigation of various measurement elements and techniques appropriate for the economic assessment of academic libraries, with a view to apply them in future evaluation of academic libraries in Korea. Two libraries participated in the pilot study. In one library, CVM (contingency valuation method) was applied to services ranging from circulation, electronic collection, reference, user education and facility. In the second library, three different methodologies--time value, alternative service value and CVM--were all applied to measure the value of electronic collection. The research provides analyses of measurement elements used, study procedures and measurement results. Based on these analyses, the study also makes suggestions in the areas of measurement goals, service, users and the calculation of B/C ratios that need to be taken into consideration in order to execute reliable and valid assessment of academic library's value.

• Korean Journal of Food Science and Technology
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• v.32 no.5
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• pp.1009-1014
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• 2000

In order to detect pantothenic acid (PA), conditions for enzyme-linked immunosorbent assay (ELISA) were established. Anti-PA-BSA antibody was produced from rabbits immunized with PA-bovine serum albumin (BSA) conjugates which were prepared by the bromoacetyl chloride [Bc] method (PA-BSA[Bc]) and by the periodate oxidation [Po] method (PA-BSA[Po]). PA-BSA[Bc] and PA-BSA[Po] was used as a coating antigen for competitive indirect(ci)ELISA. The Anti-PA-BSA[Po] antibody on ciELISA showed no competitive reaction. The detection limit of PA by ciELISA using Anti-PA-BSA[Bc] antibody was 1 ppm. The Anti-PA-BSA[Bc] antibody showed little cross-reactivity to PA derivatives such as pantoyllactone, pantetheine, pantothenyl alcohol, and acetyl CoA. The detection limit of PA by microbiological assay (MBA) was 10 ppb. Assay recoveries of PA in egg, cow's liver, and lettuce by ciELISA were 109, 64, and 344%, respectively, comparing with the MBA results.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.5 s.98
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• pp.132-144
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• 1999

In this study, the complexity of the product was evaluated quantitatively considering the product structure, assembly process and disassembly process. To evaluate the complexity of the product, subassemblies of automobile were analyzed and then characteristics of part and subassembly were determined according to product structure, assembly process and disassembly process. Evaluation criteria of complexity were determined considering each characteristics of part and subassembly. Experiential evaluation was accomplished by classified evaluation criteria and time-motion evaluation was accomplished by the relational motion factor with characteristics of part and subassembly in MTM(Methods Time Measurement) and WF(Work Factor). The total complexity of product was determined by experiential evaluation and time-motion evaluation.

• Journal of Life Science
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• v.14 no.3
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• pp.441-444
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• 2004

This study was performed to establish a simple and rapid method for measuring thrombin activity based on weight of fibrin clot formed. The new method was based on the weight measurement of fibrin clot after enzymatic reaction of thrombin with fibrinogen. The fibrin formation depended upon the activities of thrombin used, temperature, incubation time, and centrifugation time. The fibrin formation was increased proportionally up to 1.0 unit/ml of thrombin activity, 4.0mg/ml of fibrinogen concentration, and 5 min of incubation time at 37$^{\circ}C$. The fibrin clot formed was stable by centrifugation at 3,000$\times$g for 5min. This simple assay based on weight of fibrin after centrifugation would be useful for identifying natural food anticoagulants by inhibiting thrombin.