• 대기
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• 제24권3호
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• pp.365-378
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• 2014

The limits of S-band dual-polarization radars in Korea are not reflected on the recent weather forecasts of Korea Meteorological Administration and furthermore, they are only utilized for rainfall estimations and hydrometeor classification researches. Therefore, this study applied four merging methods [SA (Simple Average), WA (Weighted Average), SSE (Sum of Squared Error), TV (Time-varying mergence)] to the QPE (Quantitative Precipitation Estimation) model [called RAR (Radar-AWS Rainfall) calculation system] using single-polarization radars and S-band dual-polarization radar in order to improve the accuracy of the rainfall estimation of the RAR calculation system. As a result, the merging results of the WA and SSE methods, which are assigned different weights due to the accuracy of the individual model, performed better than the popular merging method, the SA (Simple Average) method. In particular, the results of TVWA (Time-Varying WA) and TVSSE (Time-Varying SSE), which were weighted differently due to the time-varying model error and standard deviation, were superior to the WA and SSE. Among of all the merging methods, the accuracy of the TVWA merging results showed the best performance. Therefore, merging the rainfalls from the RAR calculation system and S-band dual-polarization radar using the merging method proposed by this study enables to improve the accuracy of the quantitative rainfall estimation of the RAR calculation system. Moreover, this study is worthy of the fundamental research on the active utilization of dual-polarization radar for weather forecasts.

• 천문학회보
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• 제40권1호
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• pp.74.1-74.1
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• 2015

'The one to one correspondence model' defines the relation between a dark matter halo (DM halo) and a galaxy. A basic assumption of this model is that a more massive DM subhalo hosts a brighter galaxy. In a more improved version of the model we may be able to assign a mock galaxy with a morphological type. In this study, we are building a mock galaxy catalog using massive halo merging trees from the Horizon Run 4. We test various merging models to calculate the merging time scale of a subhalo along its merging tree. And we obtain the halo mass functions for major subhalos and satellite subhalos, separately, and compare them with the observed luminosity functions of major galaxies and satellite galaxies from the SDSS group catalog. Furthermore, we are going to make a range of mock galaxy catalogs and investigate their properties, such as spatial distributions, environmental effects, and morphologies.

• Water Engineering Research
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• 제3권2호
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• pp.93-111
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• 2002

In this paper, mixing characteristics and dilution of the merging buoyant discharges from array of multiple jets has been extensively studied in the hydraulic model experiments. New equations for dilution, which include the merging effects correctly, were derived. Experiments were constructed in a 20-m long, 4.9-m wide and 0.6-m deep flume, and the model diffuser was manufactured to indicate the typical characteristics of the existing ocean wastewater outfall in South Korea. Buoyant discharge from the diffuser was reproduced using heated water. Water temperature was measured using CC-Type thermocouple sensors, which were connected to a 40-channel data logger. Experimental results show that merging between ports in a particular riser is dependent upon the discharge densimetric Froude number, whereas merging between two ports which are facing each other at 90$\circ$ at the adjacent risers is dependent upon the discharge densimetric Froude number and distance from the port and port spacing. Centerline dilution increase with distance from the port outlet until two plumes has merged. However, after merging occurs, increase of the centerline dilution almost stops. Further distance from the position where merging occurs, centerline dilution increases again.

• 한국산학기술학회논문지
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• 제4권4호
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• pp.428-433
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• 2003

본 논문은 우리나라 M＆A 시장이 선진국형의 시장 경쟁원리에 근거하여 보다 자율적이고 경쟁적인 분위기하에서 이루어 졌던 1990년부터 1997년까지의 기업합병 사례들을 대상으로 합병기업과 피 합병기업간의 M＆A사례를 표본으로 하여 합병성과를 실증 분석하였다. 합병성과 측정모형은 시장모형(market model) 과 시정조정모형(market adjusted model)을 이용하여 누적비정상 평균수익률(CAR)을 비교 검토하였다. 본 연구의 결과는 80년대의 기존 연구와는 특징적 차이가 있는 것으로 나타났으며 합병기업보다 피 합병기업에게 큰 폭의 정 (＋)의 누적초과 수익이 나타났다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2021년도 학술발표회
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• pp.134-134
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• 2021

Precipitation is a crucial component of water cycle and play a key role in hydrological processes. Traditionally, gauge-based precipitation is the main method to achieve high accuracy of rainfall estimation, but its distribution is sparsely in mountainous areas. Recently, satellite-based precipitation products (SPPs) provide grid-based precipitation with spatio-temporal variability, but SPPs contain a lot of uncertainty in estimated precipitation, and the spatial resolution quite coarse. To overcome these limitations, this study aims to generate new grid-based daily precipitation using Automatic weather system (AWS) in Korea and multiple SPPs(i.e. CHIRPSv2, CMORPH, GSMaP, TRMMv7) during the period of 2003-2017. And this study used a machine learning based Random Forest (RF) model for generating new merging precipitation. In addition, several statistical linear merging methods are used to compare with the results of the RF model. In order to investigate the efficiency of RF, observed data from 64 observed Automated Synoptic Observation System (ASOS) were collected to evaluate the accuracy of the products through Kling-Gupta efficiency (KGE), probability of detection (POD), false alarm rate (FAR), and critical success index (CSI). As a result, the new precipitation generated through the random forest model showed higher accuracy than each satellite rainfall product and spatio-temporal variability was better reflected than other statistical merging methods. Therefore, a random forest-based ensemble satellite precipitation product can be efficiently used for hydrological simulations in ungauged basins such as the Mekong River.

• 대한교통학회지
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• 제21권3호
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• pp.107-120
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• 2003

수십년동안 합류부 교통특성 및 현상을 다루는 많은 연구가 있어 왔지만 합류부 교통류를 평가하는 분석방법론은 그리 많이 개발되지 않았고 특히 합류용량에 대한 연구는 거의 이루어지지 않았었다. 본 연구는 합류부에서 강제합류를 포함한 합류용량을 확률적으로 결정하는 모형 개발을 목적으로 수행되었다. 고속도로 본선 바깥 차로의 시간차두간격 분포를 Erlang 분포로 가정하고 간격수락이론을 이용하여 합류용량 산정 모형식을 개발하였고, 이때 본선 차두간격이 임계간격보다 작은 경우 발생되는 강제합류 형태가 용량 산정식에 반영되었다. 또한. 합류용량 모형식에서 중요한 변수로 사용되는 임계간격을 결정하고자 연결로에서 진입하는 개별차량의 합류 행태를 조사하여 회귀분석을 통한 모형식을 구축하였다. 개발된 용량식을 토대로 합류용량 값들을 도로 및 교통 조건에 따라 제시하였는데 임계간격 크기가 커지고 연결로 진입교통량이 많아질수록 합류용량은 적게 산출되었다. 이러한 합류용량 값의 변화는 기존 HCM 방법에서 제시하고 있는 하나의 고정된 용량 값과는 다른 결과로 해석되고, 변화하는 합류용량 값은 앞으로 연결로 접속부 교통운영에서 고려해야 할 주요한 파라메타라고 생각된다.

• 한국안전학회지
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• 제27권4호
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• pp.108-114
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• 2012

Traffic Accident Merging Index(TAMI) is developed for TMACS(Traffic Safety Information Management Complex System). TAMI is calculated by combining 'Severity Index' and 'Frequency'. This paper suggest the accurate TAMI prediction model by time series forecasting. Preventing the traffic accident by accurately predicting it in advance can greatly improve road traffic safety. Searches the model which minimizes the error of 230 local self-governing groups. TAMI of 2007~2009 years data predicts TAMI of 2010. And TAMI of 2010 compares an actual index and a prediction index. And the error is minimized the constant where selects. Exponential Smoothing model was selected. And smoothing constant was decided with 0.59. TAMI Forecasting model provides traffic next year safety information of the local government.

• 대한교통학회지
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• 제10권1호
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• pp.5-20
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• 1992

Even though the types of ramp facilities in Korea are not various like other countries operations in these sections are very important because ramp merging and /or diverging flow affects freeway overall sections. In this study existing methodologies especially the gap acceptance model and the regression model in USHCM are evaluated with our field data. By gap acceptance model the merging capacity is founded 2.360 pcph which is increased by 7% than the capacity of freeway basic section. And in comparison of actual lane 1 volume to the estimation volume by HCM model the model slightly overestimates the actual volue.

• 대한교통학회지
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• 제24권7호
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• pp.115-128
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• 2006

도로용량편람(2004)에 제시된 합류부 분석 방법론은 수요가 용량을 초과할 경우 정체가 발생한다는 가정을 전제로 하고 있다. 그러나 많은 경우, 본선과 연결로 수요의 합이 용량을 초과하지 않은 상태에서도 합류부에서는 정체가 발생하고 있는 실정이며, 현재의 분석방법으로는 본선 및 연결로가 정체발생과 관련하여 어떠한 영향을 끼치는지에 대한 분석이 어려운 실정이다. 본 연구에서는 합류부 본선 및 연결로 수요교통량의 조합에 따라 발생할 수 있는 합류부 교통상태를 추정할 수 있는 모형을 개발하였다. 본 연구에서 제시하는 모형의 가장 큰 특징은 가변용량 개념의 도입인데 즉, 합류부 본선 및 연결로 수요교통량의 조합에 따라 정체되지 않고 통과될 수 있는 최대통과가능교통량 및 정체발생시의 최대통과교통량 산정에 있다. 이를 통해 합류부의 교통상태가 정체될 것인지, 또한 정체시 최대통과교통량 및 정체규모는 얼마가 될 것인지 추정할 수 있었다. 한편, 현재 사용하고 있는 합류부 서비스수준 평가기법은 실제 교통상황을 반영하지 못함으로 인해 고속도로 현장에서는 정체상황이 발생되고 있으나 수요가 용량을 초과하지 않았다는 이유로 정상교통류 상태로 평가하는 단점을 지니고 있다. 따라서 본 연구에서는 보다 현실적인 합류부 서비스수준 평가기법을 제시하기 위해 본 연구에서 개발한 합류부 분석방법론을 토대로 새로운 합류부 서비스수준 구분 기준을 제시하였다.

• 제어로봇시스템학회논문지
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• 제5권8호
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• pp.907-913
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• 1999

For an automated transportation system like PRT(Personal Rapid Transit) system or IVHS, an efficient vehicle-merging algorithm is required for smooth operation of the network. For management of merging, collision avoidance between vehicles, ride comfort, and the effect on traffic should be considered. This paper proposes an unmanned vehicle-merging algorithm that consists of two procedures. First, a longitudinal control algorithm is designed to keep a safe headway between vehicles in a single lane. Secondly, 'vacant slot and ghost vehicle' concept is introduced and a decision algorithm is designed to determine the sequence of vehicles entering a converging section considering energy consumption, ride comfort, and total traffic flow. The sequencing algorithm is based on fuzzy rules and the membership functions are determined first by an intuitive method and then trained by a learning method using a neural network. The vehicle-merging algorithm is shown to be effective through simulations based on a PRT model.