• Journal of the Korea Organic Resources Recycling Association
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• v.19 no.4
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• pp.53-59
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• 2011

In this study, as a tool of evaluating biological stability of landfilled waste, influencing factors of $AT_4$ method was studied for standardizing the method. As influencing factors, initial lag time, exchanging period of $CO_2$ absorbing agent, and interval of pressure measurement were discussed, and also the relationship between content of dried food waste and $AT_4$ value were compared. Considering heterogeneity of landfilled waste and statistical error range of measurement, authors suggest that the criteria of stabilized landfill waste is $10mg\;O_2/g\;DM$ by $AT_4$ method.

• Composites Research
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• v.22 no.2
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• pp.7-13
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• 2009

With the wide application of fiber-reinforced composite material in aero-structures and mechanical parts, the design of composite joint have become a very important research area because they are often the weakest areas in composite structures. In this paper, the failure strengths of the hybrid composite joints which were composed of a combination of an adhesive joint and a mechanical joint were evaluated and predicted. The 10 hybrid joint specimens which have different w/d, e/d and adherend thickness were manufactured and tested. The damage zone theory and the failure area index method were used for the failure prediction of the adhesive joint and the mechanical joint, respectively and the hybrid joints were assumed to be failures if either of the two failure criteria was satisfied. From the results of experiments and analyses, the failure strengths of the hybrid joints could be predicted to within 25.5%.

• Journal of Korean Society of Transportation
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• v.25 no.6
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• pp.19-31
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• 2007

When estimating the benefits from an investment project in the transportation sector, errors caused by many factors may exist. This study focuses on user equilibrium traffic assignment methods and stopping criteria. According to previous studies, when using a user equilibrium assignment model, the benefits of travel time savings can be effected by the relative gap value. As the stopping criteria decreases, the time needed for traffic assignment increases, so that lowering the criteria cannot be the best solution. Therefore, an effort is necessary to reduce this change rate and thus improve reliability. This paper considers three methods: reducing the links subject to benefit calculation, extracting sub-area O/D tables and networks, and applying the mean value of successive traffic assignment results. The results of the analysis show that the method using the mean value of five results is more proper than the other methods. Using the sub-area analysis method, if the study area is small the benefits of a project might be over- or under-estimated. This paper used a nationwide O/D table and network at peak time as a case study. The resulting patterns can differ according to basic data to be used in analysis. So further analysis using the data from metropolitan areas are needed.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.1068-1072
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• 2005

조석이란, 해면의 완만한 주기적 승강을 말하며, 보통 그 승강은 1일 약 2회이나, 곳에 따라서는 1일 1회의 곳도 있다. 조석에 있어서는 이 밖에 수일의 주기를 갖는 약간 불규칙한 승강, 반년, 또는 1년을 주기로 하는 다소 규칙적인 승강까지 포함하여 취급한다. 그러나, 각 항만마다 갖는 특정적인 주기인 수분내지 수십분의 주기의 승강은 조석으로 취급하지 않는다. 조석은 해양의 제현상 중에서 예측가능성이 가장 큰 현장으로 이는 조석이 천체의 운행과 연관되기 때문이다. 조석이란 지구로부터 일정한 거리에서 각 고유의 속도를 가지는 적도상을 운행하는 무수의 가상천체에 기인하는 규칙적인 개개의 조석을 합성한 것이며 이 개개의 조석을 분조(Constituent)라 한다. 여기에서 사용되는 신경망 모형은 입력과 출력으로 구성되는 블랙박스 모형으로서 하나의 시스템을 병렬적으로 비선형적으로 구축할 수 있다는 장점 때문에 과거 하천유역의 강우-유출과정에서의 경우 유출현상을 해석하고 유출과정을 모형화 하기 위해 사용하였다. 본 연구에서는 기존의 조위 예측방법인 조화분석법이 아닌 인공신경망을 이용하여 조위예측을 실시하였다. 학습이라는 최적화 과정을 통해 구조와 기능이 복잡한 자연현상을 그대로 받아들여 축적시킴으로써 이를 지식으로 현상에 대한 재현능력이 뛰어나고, 또한 신경회로망의 연상기억능력에 적용하여 수학적으로 표현이 불가능한 불확실한 조위곡선에 적용하기에 유리한 장점을 가지고 있다. 본 연구의 목적은 과거 조위이론을 통해 이루었던 조위예측을 우리가 알기 쉬운 여러 기후인자(해면기압, 풍향, 풍속, 음력 등)에 따른 조위곡선을 예측하기 위해 신경망 모형을 이용하여 여수지역의 조위에 적용하여 비교 분석하고자 한다. May가 제안한 공식을 더 확장하여 적용할 수 있는 실험 공식으로 개선하였으며 다양한 조건에 대한 실험을 수행하여 보다 정밀한 공식으로 개선할 수 있었다.$10,924m^3/s$ 및 $10,075m^3/s$로서 실험 I의 $2,757m^3/s$에 비해 통수능이 많이 개선되었음을 알 수 있다.함을 알 수 있다. 상수관로 설계 기준에서는 관로내 수압을 $1.5\~4.0kg/cm^2$으로 나타내고 있는데 $6kg/cm^2$보다 과수압을 나타내는 경우가 $100\%$로 밸브를 개방하였을 때보다 $60\%,\;80\%$ 개방하였을 때가 더 빈번히 발생하고 있으므로 대상지역의 밸브 개폐는 $100\%$ 개방하는 것이 선계기준에 적합한 것으로 나타났다. 밸브 개폐에 따른 수압 변화를 모의한 결과 밸브 개폐도를 적절히 유지하여 필요수량의 확보 및 누수방지대책에 활용할 수 있을 것으로 판단된다.8R(mm)(r^2=0.84)$로 지수적으로 증가하는 경향을 나타내었다. 유거수량은 토성별로 양토를 1.0으로 기준할 때 사양토가 0.86으로 가장 작았고, 식양토 1.09, 식토 1.15로 평가되어 침투수에 비해 토성별 차이가 크게 나타났다. 이는 토성이 세립질일 수록 유거수의 저항이 작기 때문으로 생각된다. 경사에 따라서는 경사도가 증가할수록 증가하였으며 $10\% 경사일 때를 기준으로 $Ro(mm)=Ro_{10}{\times}0.797{\times}e^{-0.021s(\%)}$로 나타났다.천성 승모판 폐쇄 부전등을 초래하는 심각한 선

• Journal of Environmental Impact Assessment
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• v.27 no.5
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• pp.431-446
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• 2018

In this study, chemical characteristics of $PM_{2.5}$ samples collected in an agricultural area in Nonsan of Korea were investigated focusing on of black carbon, 3 inorganic ions and 22 trace elements. It was found that the relative error and relative standard deviation of many trace elements fell below 10%, which indicates good analytical accuracy and precision. The mean values of $PM_{2.5}$ in an agricultural area were exceeded by new Korean air quality standard of March 2018. The concentration of $PM_{2.5}$ was well correlated with those of black carbon and ions. The concentrations of trace elements were in a wide range of seven orders of a magnitude. Based on these $PM_{2.5}$ data sets, a total of 6 sources were identified using PMF (Positive Matrix Factorization; secondary aerosol (34.4%), soil/road dust (20.1%), biomass burning (16.9%), incineration/fuel combustion (13.2%), vehicle exhaust(12.2%), sea-salt (3.17%). Results of our study indicate that it is very important to control illegal burning activities in agricultural area.

• Journal of Korea Water Resources Association
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• v.53 no.9
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• pp.647-660
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• 2020

The objectives of this study are to develop a framework for selecting multi-GCMs considering Asia monsoon characteristics and assess it's applicability. 12 climate variables related to monsoon climates are selected for GCM selection. The framework for selecting multi-GCMs includes the evaluation matrix of GCM performance based on their capability to simulate historical climate features. The climatological patterns of 12 variables derived from individual GCM over the summer monsoon season during the past period (1976-2005) and they are compared against observations to evaluate GCM performance. For objective evaluation, a rigorous scoring rule is implemented by comparing the GCM performance based on the results of statistics between historical simulation derived from individual GCM and observations. Finally, appropriate 5 GCMs (NorESM1-M, bcc-csm1-m, CNRM-CM5, CMCC-CMS, and CanESM2) are selected in consideration of the ranking of GCM and precipitation performance of each GCM. The selected 5 GCMs are compared with the historical observations in terms of monsoon season and monthly mean to validate their applicability. The 5 GCMs well capture the observational climate characteristics of Asia for the 12 climate variables also they reduce the bias between the entire GCM simulations and the observational data. This study demonstrates that it is necessary to consider various climate variables for GCM selection and, the method introduced in this study can be used to select more reliable climate change scenarios for climate change assessment in the Asia region.

• Korean Journal of Remote Sensing
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• v.36 no.5_4
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• pp.1209-1220
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• 2020

In the case of forest areas, the installation of ground control points (GCPs) and the selection of terrain features, which are one of the unmanned aerial photogrammetry work process, are limited compared to urban areas, and safety problems arise due to non-visible flight due to high forest. To compensate for this problem, the drone equipped with a real time kinematic (RTK) sensor that corrects the position of the drone in real time, and a 3D flight method that fly based on terrain information are being developed. This study suggests to present a method for investigating damage using drones in forest areas. Position accuracy evaluation was performed for three methods: 1) drone mapping through GCP measurement (normal mapping), 2) drone mapping based on topographic data (3D flight mapping), 3) drone mapping using RTK drone (RTK mapping), and all showed an accuracy within 2 cm in the horizontal and within 13 cm in the vertical position. After evaluating the position accuracy, the volume of the landslide area was calculated and the volume values were compared, and all showed similar values. Through this study, the possibility of utilizing 3D flight mapping and RTK mapping in forest areas was confirmed. In the future, it is expected that more effective damage investigations can be conducted if the three methods are appropriately used according to the conditions of area of the disaster.

• Journal of Cadastre & Land InformatiX
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• v.48 no.1
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• pp.111-121
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• 2018

RIn this research, digital elevation models, true-ortho image and 3-dimensional digital complied data was generated and evaluated using unmanned aircraft vehicle stereoscopic images by applying photogrammetric principles. In order to implement stereoscopic vision, digital Photogrammetric Workstation should be used necessarily. For conducting this, in this study GEOMAPPER 1.0 is used. That was developed by the Ministry of Trade, Industry and Energy. To realize stereoscopic vision using two overlapping images of the unmanned aerial vehicle, the interior and exterior orientation parameters should be calculated. Especially lens distortion of non-metric camera must be accurately compensated for stereoscope. In this work. photogrammetric orientation process was conducted using commercial Software, PhotoScan 1.4. Fixed wing KRobotics KD-2 was used for the acquisition of UAV images. True-ortho photo was generated and digital topographic map was partially produced. Finally, we presented error analysis on the generated digital complied map. As the results, it is confirmed that the production of digital terrain map with a scale 1:2,500~1:3,000 is available using stereoscope method.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.1
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• pp.37-45
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• 2012

In an effort to further exploit the peak ground-motion acceleration (PGA) information per second available in real time by the enacted law, bracketed summations of the PGA per second ($BSPGA_k$) for 30 seconds based on the records with a rate of 100 samples were compared with the cumulative absolute velocity (CAV) and earthquake intensities based on a worldwide database of records from small-to-large earthquakes. The CAV, currently in use as an earthquake damage indicator for nuclear power plants due to its strong correlation with the earthquake intensity, has the disadvantage of requiring a massive amount of digital data with a rate of more than 100 samples per second. The comparative study shows that the $BSPGA_k$ is well correlated with the CAV over the wide range of strong ground-motion levels, which suggests that the $BSPGA_k$ is one of the new promising ground-motion parameters especially useful for rapid earthquake alert notifications through an earthquake monitoring network. Based on the domestic database of records from small-to-moderate earthquakes with felt reports, it is also observed that the $BSPGA_k$ is comparable to the CAV and better than the PGA in predicting the intensity by using the correlation relation.

• Journal of Aerospace System Engineering
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• v.15 no.5
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• pp.8-15
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• 2021

This paper describes a design method using an optimization technique to satisfy the longitudinal handling quality of high maneuverable jet aircraft. The dynamic inversion technique was applied to the target aircraft, and the control gain optimization satisfied the longitudinal short-period handling quality, however, the stability margin was not considered. If the stability margin is not satisfied, it is necessary to directly readjust the gains through trial and error methods for improvement. To improve this, an additional compensator and an optimization constraint were added to the control gain optimization procedure. In addition, the degree of handling quality satisfaction with the optimization result was reevaluated, and additional control evaluation criteria for the convergence of the time response and the steady state error that the flight performance requirement set as the optimization constraint cannot be reflected, and the results are described.