• 한국산학기술학회논문지
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• 제17권4호
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• pp.59-73
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• 2016

지하 수송에 대한 수요가 증가함에 따라 도로터널 사용자와 운영자는 다양한 원인에 의한 위험에 노출되어 있으며, 주요 원인은 각각 사고 이벤트가 될 수 있는 교통상황이다. QRA(정량적 위험평가)의 중요성은 도로터널의 안전성을 정량화하고, 다수의 이해관계자들의 관점(용량, 신뢰성, 가용성, 유지보수 및 안전)에서의 요구조건에 밸런스를 유지하려는 의도에서 커지기 시작했다. 위험평가에 사용되는 고전적 방법은 ETA, FTA이지만, 변수의 다양함과 상호관계를 반영하지 못한다는 이유에서 이 방법들은 상대적으로 단순한 경우에만 적용할 수 있다. 특정위험평가에 필요한 객체, 이벤트, 결과 및 가정, 경계조건 등의 총체는 도로 터널시설 위험평가를 위해 필수적인 내용으로 관찰되어야 하는 시스템을 만들고, 정보, 데이터, 모델 등 관련 항목들이 그 시스템을 서술하게 된다. 시스템은 위험모델에 기반한 계층적 지표들을 사용하여 모델링되고 분석되며, 시스템의 모든 가능한 구성은 지표의 적절한 선택을 통하여 표현될 수 있다. 따라서 본 연구에서는 일반터널에서뿐만 아니라 복층터널 같은 복합적인 지하시스템 변수들간의 상호의존성을 고려하여 정량화할 수 있는 베이지안 네트워크를 근거로 한 정량적 위험평가방법을 소개한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권8호
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• pp.1933-1954
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• 2013

Multiple wireless devices are being widely deployed in Intelligent Transportation System (ITS) services on the road to establish end-to-end connection between vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) networks. Vehicular ad hoc networks (VANETs) play an important role in supporting V2V and V2I communications (also called V2X communications) in a variety of urban environments with distinct topological characteristics. In fact, obstacles such as big buildings, moving vehicles, trees, advertisement boards, traffic lights, etc. may block the radio signals in V2X communications. Their impact has been neglected in VANET research. In this paper, we present a realistic and efficient radio propagation model to handle different sizes of static and moving obstacles for V2X communications. In the proposed model, buildings and large moving vehicles are modeled as static and moving obstacles, and taken into account their impact on the packet reception rate, Line-of-sight (LOS) obstruction, and received signal power. We use unsymmetrical city map which has many dead-end roads and open faces. Each dead-end road and open faces are joined to the nearest edge making a polygon to model realistic obstacles. The simulation results of proposed model demonstrates better performance compared to some existing models, that shows proposed model can reflect more realistic simulation environments.

• Biotechnology and Bioprocess Engineering:BBE
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• 제11권1호
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• pp.72-79
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• 2006

Kojic acid production by Aspergillus flavus strain S44-1 using sucrose as a carbon source was carried out in a 250-mL shake flask and a 2-L stirred tank fermenter. For comparison, production of kojic acid using glucose, fructose and its mixture was also carried out. Kojic acid production in shake flask fermentation was 25.8 g/L using glucose as the sole carbon source, 23.6 g/L with sucrose, and 6.4 g/L from fructose. Reduced kojic acid production (13.5 g/L) was observed when a combination of glucose and fructose was used as a carbon source. The highest production of kojic acid (40.2 g/L) was obtained from 150 g/L sucrose in a 2 L fermenter, while the lowest kojic acid production (10.3 g/L) was seen in fermentation using fructose as the sole carbon source. The experimental data from batch fermentation and resuspended cell system was analysed in order to form the basis for a kinetic model of the process. An unstructured model based on logistic and Luedeking-Piret equations was found suitable to describe the growth, substrate consumption, and efficiency of kojic acid production by A. flavus in batch fermentation using sucrose. From this model, it was found that kojic acid production by A. flavus was not a growth-associated process. Fermentation without pH control (from an initial culture pH of 3.0) showed higher kojic acid production than single-phase pH-controlled fermentation (pH 2.5, 2.75, and 3.0).

• Spatial Information Research
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• 제14권2호
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• pp.245-260
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• 2006

이동성을 지원하는 모바일 환경에서 위치정보의 활용과 사용자 요구가 증가되고 GIS 공간 DB와 연계된 다양한 서비스가 진행되고 있다. 일반적으로 도로 DB를 구성하는 교통 네트워크의 논리적 관계의 표현은 노드-링크 구조를 사용한다. 이러한 단일 수준에 적합하게 설계된 구조는 다양한 모형 적용에 유연하지 못하고, 데이터베이스 검색과 유지관리 측면에서 비효율적이다. 본 연구에서는 동적 분할(Dynamic Segmentation)을 이용한 네트워크 모델의 설계와 구축을 통해 기존 도로망 모델의 문제점과 구축상의 한계점을 보완하고, 네트워크의 검색과 표현에 효율적인 계층 모델을 구현하고자 하였다. 설계된 모델은 다양한 수준의 단계별 표현과 계층 간 개체 관계성을 지원하며, GIS가 지닌 네트워크 공간 모델링 기능을 대폭 보완할 수 있을 것으로 기대 된다.

• 산업경영시스템학회지
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• 제35권4호
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• pp.118-125
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• 2012

When monitoring an instrumental process, one often collects a host of data such as characteristic signals sent by a sensor in short time intervals. Characteristic data of short time intervals tend to be autocorrelated. In the instrumental processes often the practice of adjusting the setting value simply based on the previous one, so-called 'adjacent point operation', becomes more critical, since in the short run the deviations are harder to detect and in the long run they have amplified consequences. Stochastic modelling using ARIMA or AR models are not readily usable here. Due to the difficulty of dealing with autocorrelated data conventional practice is resorting to choosing the time interval where autocorrelation is weak enough then to using I-MR control chart to judge the process stability. In the autocorrelated instrumental processes it appears that using the Shewhart chart and the time interval data where autocorrelation is relatively not existent turns out to be a rather convenient and very useful practice to determine the process stability. However in the autocorrelated instrumental processes we intend to show that one would presumably do better using the EWMA control chart rather than just using the Shewhart chart along with some arbitrarily intervalled data, since the former is more sensitive to shifts given appropriate weights.

• 한국환경과학회지
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• 제15권8호
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• pp.745-757
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• 2006

We focus on the improvement of accuracy of sea surface wind over complex coastal area doling the warm season. Local Analysis Prediction System (LAPS) was used to improve the initial values in Mesoscale Meteorological model (MM5). During the clear summer days with weak wind speed, sea surface wind simulated with LAPS was compared with the case without LAPS. The results of modeling with LAPS has a good agreement mesoscale circulation such as mountain and valley winds on land and in case of modeling without LAPS, wind speed overestimated over the sea in the daytime. And the results of simulation with LAPS indicated similar wind speed values to observational data over the sea under influence of data assimilation using BUOY, QuikSCAT, and AMEBAS. The present study suggests that MM5 modelling with LAPS showed more improved results than that of without LAPS to simulate sea surface wind over the complex coastal area.

• 한국농공학회논문집
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• 제50권4호
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• pp.67-75
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• 2008

In construction facilities such as bridges, the fluid boundary layer(or water film) is formed at the structure-soil interface by the inflow into the system due to rainfall or/and rising ground-water. As a result, the structure-soil interaction(SSI) state changes into the structure-fluid-soil interaction(SFSI) state. In general, construction facilities may be endangered by the inflow of water into the soil foundation. Thus, it is important to predict the dynamic SFSI responses accurately so that the facilities may be properly designed against such dangers. It is desired to have the robust tools of attaining such a purpose. However, there has not been any report of a method for the SFSI analyses. The objective of this study is to propose an efficient method of finite element modelling using the new interface element named hybrid interface element capable of giving reasonable predictions of the dynamic SFSI response. This element enables the simulation of the limited normal tensile resistance and the tangential hydro-plane behaviour, which has not been preceded in the previous studies. The hybrid interface element was tested numerically for its validity and employed in the analysis of SFSI responses of the continuous bridge subjected to seismic load under rainfall or/and rising ground-water condition. It showed that dynamic responses of the continuous bridge resting on direct foundation may be amplified under rainfall condition and consequently lead to significant variation of stresses.

• 한국정보시스템학회지:정보시스템연구
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• 제29권1호
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• pp.75-91
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• 2020

Purpose Retrofit, defined to be addition of new technologies or features to the old system to increase efficiency or to abate GHG emissions, is considered as an important alternative for the old coal-fired power plant. The purpose of this study is to propose mathematical method to model multiple alternative retrofit in Generation Capacity Expansion Planning(GCEP) problem, and to get insight to the retrofit patterns from realistic case studies. Design/methodology/approach This study made a multi-alternative retrofit GECP model by adopting some new variables and equations to the existing GECP model. Added variables and equations are to ensure the retrofit feature that the life time of retrofitted plant is the remaining life time of the old power plant. We formulated such that multiple retrofit alternatives are simultaneously compared and the best retrofit alternative can be selected. And we found that old approach to model retrofit has a problem that old plant with long remaining life time is retrofitted earlier than the one with short remaining life time, fixed the problem by some constraints with some binary variables. Therefore, the proposed model is formulated into a mixed binary programming problem, and coded and run using the GAMS/cplex. Findings According to the empirical analysis result, we found that approach to model the multiple alternative retrofit proposed in this study is comparing simultaneously multiple retrofit alternatives and select the best retrofit satisfying the retrofit features related to the life time. And we found that retrofit order problem is cleared. In addition, the model is expected to be very useful in evaluating and developing the national policies concerning coal-fired power plant retrofit.

• 대한조선학회지
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• 제27권1호
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• pp.35-44
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• 1990

근년에 이르러 에너지 절약형선(節約型船) 개발이 촉진됨에 따라 디이젤엔진이 대구경(大口徑) 장행정(長行程) 소수(小數)실린더 저회전수화(低回轉數化)함으로써 불균형(不均衡)모멘트가 커져서 특히 중형선(中型船)에 대해 저진동수영역(低振動數領域)의 선체진동(船體振動) 방진설계(防振設計)가 주요과제로 대두되고 있다. 자동차운반선(自動車運搬船)의 경우 구조적(構造的) 특성(特性) 및 선형기하학적(船型幾何學的)인 특성(特性)이 일반상선(一般商船)과는 매우 다르다. 본 논문에서는 선체상하진동(船體上下振動), 선체수평(船體水平) 비틂연성진동(聯成振動)에 대하여 보유추(類推)이론에 의거한 해석방법의 정립을 위하여 전기 특성을 고려한 적정한 모델링방법, 부가수질량(附加水質量) 및 동 중심(中心), 부가수질량(附加水質量) 극관성(極慣性) 모멘트, 단면(斷面)의 전단계수(剪斷係數) 등의 적정한 산정방법, 수평(水平) 비틂거동(擧動)의 연성도(聯成度), modal해석(解析) 즉 mode중 첩법에 의한 강제진동응답(强制振動應答)의 계산 등에 관하여 실선(實船)에 대한 수치실험적(數値實驗的) 계산예(計算例)를 통해 일련의 고찰을 거쳐 합리적인 해석방법을 제시하였다.

• Structural Engineering and Mechanics
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• 제74권2호
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• pp.157-173
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• 2020

In the finite element modelling of long-span cable-stayed bridges, there are a lot of uncertainties brought about by the complex structural configuration, material behaviour, boundary conditions, structural connections, etc. In order to reduce the discrepancies between the theoretical finite element model and the actual static and dynamic behaviour, updating is indispensable after establishment of the finite element model to provide a reliable baseline version for further analysis. Traditional sensitivity-based updating methods cannot support updating based on static and dynamic measurement data at the same time. The finite element model is required in every optimization iteration which limits the efficiency greatly. A convenient but accurate Kriging surrogate model for updating of the finite element model of cable-stayed bridge is proposed. First, a simple cable-stayed bridge is used to verify the method and the updating results of Kriging model are compared with those using the response surface model. Results show that Kriging model has higher accuracy than the response surface model. Then the method is utilized to update the model of a long-span cable-stayed bridge in Hong Kong. The natural frequencies are extracted using various methods from the ambient data collected by the Wind and Structural Health Monitoring System installed on the bridge. The maximum deflection records at two specific locations in the load test form the updating objective function. Finally, the fatigue lives of the structure at two cross sections are calculated with the finite element models before and after updating considering the mean stress effect. Results are compared with those calculated from the strain gauge data for verification.