• Title/Summary/Keyword: Characteristic Parameter

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Assessment of the Damage in High Performance Fiber-Reinforced Cement Composite under Compressive Loading Using Acoustic Emission (AE기법에 의한 압축력을 받는 고인성 섬유보강 시멘트 복합체의 손상 평가)

  • Kim, Sun-Woo;Yun, Hyun-Do
    • Journal of the Korea Concrete Institute
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    • v.21 no.5
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    • pp.589-597
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    • 2009
  • High Performance Fiber-reinforced Cement Composite (HPFRCC) shows the multiple crack and damage tolerance capacity due to the interfacial bonding of the fibers to the cement matrix. For practical application, it is needed to investigate the fractural behavior of HPFRCC and understand the micro-mechanism of cement matrix with reinforcing fiber. This study is devoted to the investigation of the AE signals in HPFRCC under monotonic and cyclic uniaxial compressive loading, and total four series were tested. The major experimental parameters include the type and volume fraction of fiber (PE, PVA, SC), the hybrid type and loading pattern. The test results showed that the damage progress by compressive behavior of the HPFRCC is a characteristic for the hybrid fiber type and volume fraction. It is found from acoustic emission (AE) parameter value, that the second and third compressive load cycles resulted in successive decrease of the amplitude as compared with the first compressive load cycle. Also, the AE Kaiser effect existed in HPFRCC specimens up to 80% of its ultimate strength. These observations suggested that the AE Kaiser effect has good potential to be used as a new tool to monitor the loading history of HPFRCC.

Real-Time Variation of Water Quality with Water Depth in the Han River during the Spring Season (춘계 한강 수질의 실시간 수심별 변동특성)

  • Jung, Jin-Hong;Lim, Hyun-Man;Yoon, Young H.;Park, Jae-Roh;Kim, Weon-Jae
    • Journal of Korean Society of Environmental Engineers
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    • v.38 no.4
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    • pp.184-192
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    • 2016
  • A profiling monitoring system has been developed to monitor the water quality variations according to each water depth and applied for a test-bed. The key parameters were derived to disclose the aquatic ecology and environment of river systems, and the real-time monitoring techniques to profile the variations of each parameter were verified. Monitoring parameters were configured to include water quality, hydrodynamic, and weather conditions. Considering the water depth of the 4 major rivers in Korea, a profiling monitoring system with 1.0 m water depth interval for each monitoring has been established. To understand the real-time variation properties in the Han river, the monitoring system has been installed and operated at the YangHwa-Dock as a test-bed. Based on the results of the detailed analyses on the spring season, as the characteristic diurnal and water-depth-related variations for water temperature, pH, dissolved oxygen (DO), and chlorophyll-a were observed, it could be concluded that the real-time water-depth profiling monitoring system is a very effective tool for the proper management of river environment.

Development and Implementation of a 2-Phase Calibration Method for Gravity Model Considering Accessibility (접근성 지표를 도입한 중력모형의 2단계 정산기법 개발 및 적용)

  • CHOI, Sung Taek;RHO, Jeong Hyun
    • Journal of Korean Society of Transportation
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    • v.33 no.4
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    • pp.393-404
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    • 2015
  • Gravity model has had the major problem that the model explains the characteristics of travel behavior with only deterrence factors such as travel time or cost. In modern society, travel behavior can be affected not only deterrence factors but also zonal characteristics or transportation service. Therefore, those features have to be considered to estimate the future travel demand accurately. In this regard, there are two primary aims of this study: 1. to identify the characteristics of inter-zonal travel, 2. to develop the new type of calibration method. By employing accessibility variable which can explain the manifold pattern of trip, we define the zonal travel behavior newly. Furthermore, we suggest 2-phase calibration method, since existing calibration method cannot find the optimum solution when organizing the deterrence function with the new variables. The new method proceeds with 2 steps; step 1.estimating deterrence parameter, step 2. finding balancing factors. The validation results with RMSE, E-norm, C.R show that this study model explains the inter-zonal travel pattern adequately and estimate the O/D pairs precisely than existing gravity model. Especially, the problem with estimation of short distance trip is overcomed. In conclusion, it is possible to draw the conclusion that this study suggests the possibility of improvement for trip distribution model.

The Evaluation of CR and DDR chest image using ROC analysis (ROC평가 방법을 이용한 CR과 DDR 흉부 영상의 비교)

  • Park, Yeon-Ok;Jung, Eun-Kyung;Park, Yeon-Jung;Nam, So-Ra;Jung, Ji-Young;Kim, Hee-Joung
    • Journal of the Korean Society of Radiology
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    • v.1 no.1
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    • pp.25-30
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    • 2007
  • ROC(Receiver Operating Characteristic)curve is the method that estimate detected insignificant signal from the human's sense of sight, it has been raised excellent results. In this study, we evaluate image quality and equipment character by obtaining a chest image from CR(Computed Radiography) and DDR(Direct Digital radiography) using the human chest phantom, The parameter of exposure for obtaining chest image was 120 kVp/3.2 mAs and the SID(Source to Image Distance) was 180cm. The images were obtained by CR(AGFA MD 4.0 General plate, JAPAN) and DDR(HOLOGIC nDirect Ray, USA). Using some pieces of Aluminum and stone for expressing regions, then attached them on the heart, lung and thoracic vertebrae of the phantom. 29 persons hold radiology degrees were participated in ROC analysis. As a result of the ROC analysis, TPF(true positive fraction) and FPF(false positive fraction) of DDR and CR are 0.552 and 0.474 and 0.629 and 0.405, respectively. By using the results, the ROC curve of CR has higher image quality than DDR. According to the theory, DDR has the higher image quality than CR in chest X-ray image. But, CR has the higher image quality than DDR. quality of DDR inserted the enhance board. The results confirmed that image post-processing is important element decipherment of clinical.

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Estimation and Assessment of Bivariate Joint Drought Index based on Copula Functions (Copula 함수 기반의 이변량 결합가뭄지수 산정 및 평가)

  • So, Jae Min;Sohn, Kyung Hwan;Bae, Deg Hyo
    • Journal of Korea Water Resources Association
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    • v.47 no.2
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    • pp.171-182
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    • 2014
  • The objective of this study is to evaluate the utilization of bivariate joint drought index in South Korea. In order to develop the bivariate joint drought index, in this study, Clayton copula was used to estimate the joint distribution function and the calibration method was employed for parameter estimation. Precipitation and soil moisture data were selected as input data of bivariate joint drought index for period of 1977~2012. The time series analysis, ROC (Receiver Operating Characteristic) analysis, spatial analysis were used to evaluate the bivariate joint drought index with SPI (Standardized Precipitation Index) and SSI (Standardized Soil moisture Index). As a result, SPI performed better for drought onset and SSI for drought demise. On the other hand the bivariate joint drought index captured both drought onset and demise very well. The ROC score of bivariate joint drought index was higher than that of SPI and SSI, and it also reflected the local drought situations. The bivariate joint drought index overcomes the limitations of existing drought indices and is useful for drought analysis.

Characteristics of Tidal Current and Tidal Residual Current in the Chunsu Bay, Yellow Sea, Korea based on Numerical Modeling Experiments (수치모델링 실험을 통한 서해 천수만의 조류와 조석잔차류 특성)

  • Jung, Kwang Young;Ro, Young Jae;Kim, Baek Jin
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.25 no.4
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    • pp.207-218
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    • 2013
  • This study is based on a series of numerical modeling experiments to understand the circulation and its change in the Chunsu Bay (CSB), Yellow Sea of Korea. A skill analysis was performed for the tidal height and tidal current of the observation data using the amplitude and phase of the 4 major tidal constituents respectively for verification of modeling experimental results. As a result, most of the skill score was seen to be over 90%, so numerical model experiment results can be said to be in good agreement with the observed tidal height and tidal current. Tidal wave proceeded from the entrance of the CSB towards inside, and the tidal range gradually increased to the north. It took about 10 to 30 minutes for the tidal wave to reach to northern end. The tidal wave showed a characteristic to rotate counter-clockwise in the southern part. The tidal current flowed to the north-south direction along the bottom topography; the angle of the major axis appeared alongside the isobath. It showed the characteristics of reversing tidal current with the minor axis less than 10% of the major axis. The strength of the tidal residual current that is influenced by geographical factors including bathymetry and coastline showed the range of 1~30 cm/sec, greater in the south channel and smaller in northern Bay. Two pairs of cyclonic/anti-cyclonic eddies around Jukdo and 3~4 pairs of strong eddies at the southern part of CSB in hundreds of m to a few km size by relative vorticity derived from the tidal residual current.

A Comparative Study of Trophic State in Lake Andong, Korea (안동호의 수역별 영양상태와 평가방법간 상관성 비교)

  • Park, Jung-Won;Kim, Dae-Hyun;Shin, Jae-Ki;Lee, Hee-Moo;Park, Jae-Chung
    • Korean Journal of Ecology and Environment
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    • v.38 no.1 s.110
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    • pp.95-104
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    • 2005
  • Using TSI, TSIm and LTSI, we compared physico-chemical water quality and trophic state of 5 stations in Lake Andong from June 2002 to June 2003 and examined the correlation of them. It is difficult to evaluate trophic state of waters by each parameter, TP, Chl-a and SD, because TSI and TSIm in each section show different results, oligo-, meso- and eutrophic state. But three methods, TSI, TSIm and LTSI, show the same result that trophic degree lows as it goes to a lower area of the lake. The correlation among them is closer in the upper shallow waters than in the lower deep waters. The reciprocal application of trophic state indices is possible because the coefficient of mean correlation ranges 0.9117 to 0.9909. In conclusion, it seems that LTSI reflects a characteristic of water quality in each section better than TSI, TSIm and is very effective to simplify trophic state evaluation and minimize researcher's subjectivity.

Development of Analytical Method of Organophosphates in Sea water by Finger Printing Fluorescence Spectroscopy (형광분석을 이용한 지문방식의 해수중 유기인의 분석 방법)

  • PARK Mi-Ok
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.30 no.3
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    • pp.377-387
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    • 1997
  • Primary fluorescence characteristics of ten standard solutions of organophosphates, sea water, and water from agricultural land were investigated by fluorescence contour. All the standard solutions of organophosphates has shown characteristics countours. Their emission maxima were shown between 296 nm and 437 nm. According to their numbers of emission maxima on the fluorescence contours, the organophosphates can be categorized in two different groups. Ateric and Diazinon are the first group with two emission maxima. DDVP with other seven standard organophosphates belong to the second group. The second group has two subgroups. One is characterized by the similar emission and excitation maxima, which are 310 nm and 280 nm, respectively. Those are DDVP, Hinosan, Kitazin, Locsion, Meta. The other sub-group shows quite different emission and excitation maxima from the first sub-group. They are Monopho, Thaconyl and Gropho and their emisson maxima were in far longer (437 nm) or shorter wavelength (296 nm). From agricutural samples, one of the investigated organophosphates was detetected by its characteristic retention time $(t_r=12min)$. HPIC-fluorescence data gave an additional parameter for differentiation between two organophosphates which has similar excitation and emission maxima.

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A Propeller Design Method with a New Blade Section : Applied to Container Ships (새로운 날개단면을 이용한 프로펠러 설계법 - 콘테이너선에 응용 -)

  • J.T. Lee;M.C. Kim;J.W. Ahn;S.H. Van;H.C. Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.28 no.2
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    • pp.40-51
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    • 1991
  • A Propeller design method using the newly developed blade section(KH18), which behaves better cavitation characteristics, is presented. Experimental results for two-dimensional foil sections show that the lift-drag curve and the cavitation-free bucket diagram of the new blade section are wider comparing to those of the existion NACA sections. This characteristic of the new section is particularly important for marine propeller applications since angle of attack variation of the propeller blade operating behind a non-uniform ship's wake is relatively large. A lifting surface theory is used for the design of a propeller with the developed section for a 2700 TEU container ship. Since the most suitable chordwise loading shape is not known a priori, chordwise loading shape is chosen as a design parameter. Five propellers with different chordwise loading shapes and different foil sections are designed and tested in the towing tank and cavitation tunnel at KRISO. It is observed by a series of extensive model tsets that the propeller(KP197) having the chordwise loading shape, which has less leading edge loading at the inner radii and more leading edge loading at the outer radii of 0.7 radius, has higher propulsive efficiency and better cavitation characteristics. The KP197 propeller shows 1% higher efficiency, 30% cavitation volume reduction and 9% reduction of fluctuating pressure level comparing to the propeller with an NACA section. More appreciable efficiency gain for the new blade section propeller would be expected by reduction of expanded blade area considering the better cavitation characteristics of the new blade section.

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Determination of the Optimal Parameters in Data Processing for the Precision Geoid Construction (정밀 지오이드 구축을 위한 자료처리의 최적 변수 결정)

  • Lee, Ji-Sun;Kwon, Jay-Hyoun
    • Spatial Information Research
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    • v.17 no.3
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    • pp.397-404
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    • 2009
  • To solve the problems of distribution and quality on land gravity data, airborne gravity survey was performed in 2008 obtaining the airborne gravity data with accuracy of 1.56mGal. Since airborne gravity data is the obtained at the flight height, it is necessary to convert the airborne gravity data to the surface to combine various gravity data and compute precision geoid. In addition, Stokes' integral radius, Stokes' kernel and the radius of terrain effect computation should be optimally determined to calculate precision geoid. In this study, we made an effort to decide the optimal parameters based on the distribution and the characteristic of gravity data. Then, two geoid models were calculated using the selected parameters and the difference of geoid was calculated with mean of -16.95cm and the standard deviation of ${\pm}8.50cm$. We consider that this difference is due to the distribution and errors on the gravity data. For future work, the study on the effect of geoid with newly obtained land gravity data ship-borne gravity data and GPS/Leveling data should be conducted. Furthermore, the study on the downward continuation and terran effect calculation should be studied in detail for better precision geoid construction.

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