• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.21-31
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• 2008

response surface method (RSM) is widely used to evaluate th e extremely smal probability of ocurence or toanalyze the reliability of very complicated structures. Althoug h Monte-Carlo Simulation (MCS) technique can evaluate any system, the procesing time of MCS dependson the reciprocal num ber of the probability of failure. The stochastic finite element method could solve thislimitation. However, it is limit ed to the specific program, in which the mean and coeficient o f random variables are programed by a perturbation or by a weigh ted integral method. Therefore, it is not aplicable when erequisite programing. In a few number of stage analyses, RSM can construct a regresion model from the response of the c omplicated structural system, thus, saving time and efort significantly. However, the acuracy of RSM depends on the dist ance of the axial points and on the linearity of the limit stat e functions. To improve the convergence in exact solution regardl es of the linearity limit of state functions, an improved adaptive response surface method is developed. The analyzed res ults have ben verified using linear and quadratic forms of response surface functions in two examples. As a result, the be st combination of the improved RSM techniques is determined and programed in a numerical code. The developed linear adapti ve weighted response surface method (LAW-RSM) shows the closest converged reliability indices, compared with quadratic form or non-adaptive or non-weighted RSMs.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.5
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• pp.58-66
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• 2012

The IR signature and radiative base heating from an aircraft plume have been important factors for aircraft survivability in modern battle fields. In order to enhance the aircraft survivability and reduce the base heating, infrared signatures emitted from an aircraft exhaust plume should be determined. In this work, therefore, IR signatures and radiative base heating characteristics are examined in the plume exhausted from the aircraft with operating at altitude of 5 km in M=0.9 and 1.6, respectively. As a result, it is found that the particular wavelength IR signature has high spectral characteristics because of $H_2O$ and $CO_2$ gases in the plume, and the radiative heat flux coming into the base plane increases with higher Mach number and shorter distance.

• Journal of Korean Society of Disaster and Security
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• v.9 no.2
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• pp.33-42
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• 2016

Domestic harbor yard storage facilities are a place specifically located in a container terminal for import and export of packaged dangerous goods, and due to the recent relaxed criteria for the secured open area, concerns for the extended damage upon accidents are increasing. In this study, the impact of damages by radiant heat was analyzed through a simulation of a pool fire caused by the leakage of flammable liquids from a tank container. As a result, it was analyzed that the distance of radiant heat according to threshold damage levels was beyond the current criteria of the secured open area, and the structural damage of adjacent containers could happen within a very short time if they were exposed to the early pool fire continuously. It is considered that this study will be helpful in preparing the proper criteria for the secured open area between yard storage facilities in a container terminal.

• Journal of the Korean Society for Railway
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• v.19 no.3
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• pp.388-396
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• 2016

The metropolitan subway network of Seoul has gone through many evolutionary processes in past decades to disperse the floating population and improve the traffic flow. In this study, we analyzed how the structural characteristics and the efficiency of the subway network have changed according to the dynamic evolutionary processes of the metropolitan subway network of Seoul. We have also proposed new measures that can be used to characterize the structural properties of the subway network more practically. It is shown that the global efficiency is about 74%, which is higher than those of subway networks of foreign countries. It should also be considered that passenger flow between stations is even higher, at about 85%. Since the private lines, including line 9, the New Bundang line, the Uijeongbu line, and the Ever line do not release their traffic data since September, 2013, only 5 years of data from September, 2008 to September, 2013 is available. So, in this study we limit the analysis period to these 5 years.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.1
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• pp.147-155
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• 2015

In this paper, we consider a mobile sensor network for monitoring a polluted area where human beings cannot access. Due to the limited sensing range of individual unmanned vehicles, they need to cooperate to achieve an effective sensing coverage and move to a more polluted region. In order to address the limitations of sensing and communication ranges, we propose a hazardous substance monitoring network based on virtual force algorithms, and develop a testbed. In the considered monitoring network, each unmanned vehicle achieves an optimal coverage and move to the highest interest area based on neighboring nodes sensing values and locations. By using experiments based on the developed testbed, we show that the proposed monitoring network can autonomously move toward a more polluted area and obtain a high weighted coverage.

• Journal of Digital Convergence
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• v.13 no.10
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• pp.287-293
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• 2015

This study proposed signal processing techniques and neural network with weighted fuzzy membership functions(NEWFM) to detect epileptic seizure from EEG signals. This study used wavelet transform(WT), sequential increment method, and phase space reconstruction(PSR) as signal processing techniques. In the first step of signal processing techniques, wavelet coefficients were extracted from EEG signals using the WT. In the second step, sequential increment method was used to extract peaks from the wavelet coefficients. In the third step, 3D diagram was produced from the extracted peaks using the PSR. The Euclidean distances and statistical methods were used to extract 16 features used as inputs for NEWFM. The proposed methodology shows that accuracy, specificity, and sensitivity are 97.5%, 100%, 95% with 16 features, respectively.

• Journal of Soil and Groundwater Environment
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• v.13 no.6
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• pp.85-92
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• 2008

Water in Soyang River is an essential source for citizens of Chuncheon and Seoul areas. In 2006, turbid water in Soyang River aggravated by the typhoon Ewiniar, sustained for over 280 days unlike conventional years, then which interrupted water supply of Chuncheon and Seoul areas. Soil erosion derived from high cool lands constituting about 55% of Soyang River area is considered one of main causes for the turbid water, including imprudent development of mountainous area, road expansion, and road construction for forestry. According to analysis of turbidity, precipitation and reservoir level in Soyang River region for June 2006${\sim}$August 2008, the turbidity showed a peak correlation (r = 0.28) at a lag time of 49 days and especially did an excellent correlation (r = 0.60) with the reservoir level at a lag of 4 days. In the meantime, a critical turbidity of 31 NTU at Soyanggang Dam was estimated, over which would cause turbid water at Paldang Dam. In addition, a master recession curve was suggested, from which sustaining time of turbid water can be predicted.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1607-1611
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• 2009

본 연구에서는 현재 가뭄을 관측하는데 주로 이용되는 가뭄지수의 단점 등을 보완하고자 가뭄에 관련되는 식생지수를 연계한 공간해상도 높은 가뭄지수를 제시하였다. 우리나라 지상관측을 통해 산출할 수 있는 PDSI(Palmer Drought Severity Index)와 SPI(Standardized Precipitation Index) 같은 가뭄지수는 기온과 강수량 등의 기후자료만을 이용하여 산정할 수 있다. 두 가뭄지수는 관측하기 어려운 가뭄의 시기와 심도를 설명하고자 여러 연구를 통해 개발한 지수이지만, 두 가뭄지수만을 가지고 우리나라 전역의 가뭄의 공간적인 분포를 설명하기에는 다소 무리가 있다. PDSI의 경우 강수량과 기온과 토양의 수분함유량을 가지고 산출하는데, 전 관측지점을 똑같은 토양수분함유량을 가지고 있다는 가정 하에 계산되고, SPI의 경우 강수량만을 이용하여 산정한다. PDSI의 경우 과거의 가뭄의 정도를 판단하는데 매우유용하다고 알려져 있다. 하지만, 현재의 가뭄정도를 나타내는 데는 문제를 가지고 있고, SPI의 경우는 누적강수량을 가지고 시간단위로 계산한다는 점에서 다양한 가뭄의 정도를 예측할 수 있지만, 입력 자료로 강수량만 들어간다는 점에서 약점을 가진다. 이런 기후지수만을 이용한 가뭄정보 생산이 공간정보를 구현하는데 한계를 가지는 문제점을 개선하고자 가뭄에 직간접적으로 관련이 있는 보다 세밀한 공간정보를 가진 식생, 토지이용, 고도 등의 자료와 기후정보로부터 산정된 가뭄지수간의 관계를 분석하였다. 나아가 기존의 기후지수보다 고해상도를 가진 위성의 정규식생지수(NDVI; Normalized Difference Vegetation Index)와 같은 식생지수를 이용하여 기존보다 더 향상된 해상도의 가뭄지수를 산정하고자 하였다. 우리나라 지상관측소 76개 지점 중에 MODIS(Moderate Resolution Imaging Spectroradiometer) 정규식생지수 자료와의 관계를 분석하고자 자료의 보유기간이 짧은 지점과 섬지점 등을 제외한 57개 지점을 선정하고, 연구기간동안의 강수량과 기온자료를 이용하여 PDSI와 SPI를 산출하였다. PDSI와 SPI자료를 고해상도 가뭄지수 산정의 기본 변수로 사용하기 위하여 역거리가중평균법을 이용한 연구기간동안의 한반도 지역 PDSI와 SPI 가뭄지수 지도를 생산하였다. 각각의 가뭄지수와 식생 상태를 나타내는 NDVI와의 상관특성과 계절 변화에 따른 변화특성을 분석하고, CART(Classification and Regression Trees) 알고리즘을 이용하여, 지상 자료만을 사용한 가뭄지수가 가지는 시공간적 변화 특성 제시에 대한 문제점을 개선한 보다 해상도가 높은 조합가뭄지수를 제시하였다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.3
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• pp.221-228
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• 2011

For service-area-widening and commercialization of DGNSS service, Ministry of Land, Transport and Maritime Affairs is developing a DGNSS service based on VRS using T-DMB. In this study, three PRC generation algorithms are developed for VRS DGNSS and their accuracies were evaluated. Three DGNSS correction generation algorithms are based on inverse distance weighting, 1st- and 2nd- multiple linear regression, and their positioning accuracies were compared in terms of the number of reference stations used for network composition and the algorithm type. As a result, the positioning accuracy of the case of using 16 sites is better than that of 6 sites. And the algorithm using the multiple linear regression showed the best performance. When the positioning accuracy of VRS DGNSS was compared with the traditional single-reference DGNSS, the improvement ratio was 20-23% and 20-36% for the horizontal and vertical directions, respectively.

• Journal of Korea Multimedia Society
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• v.12 no.9
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• pp.1333-1341
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• 2009

Tactical path-finding in computer games is path-finding where a path is selected by considering not only basic elements such as the shortest distance or the minimum time spend but also tactical information of surroundings when deciding character's moving trajectory. One way to include tactical information in path-finding is to represent a heuristic function as a sum of tactical quality multiplied by a weighting factor which is.. determined based on the degree of its importance. The choice of weighting factors for tactics is very important because it controls search performance and the characteristic of paths found. In this paper. we propose a method for improving a heuristic function by adjusting weights based on the difference between paths on examples given by a level designer and paths found during the search process based on the CUITent weighting factors. The proposed method includes the search algorithm modified to detect search errors and learn heuristics and the perceptron-like weight updating formular. Through simulations it is demonstrated how different paths found by tactical path-finding are from those by traditional path-finding. We analyze the factors that affect the performance of learning and show the example applied to the real game environments.