• Journal of the Korean Society of Marine Environment & Safety
• /
• v.22 no.1
• /
• pp.129-137
• /
• 2016

In the present study we verified performance of feed-forward control algorithm using short term prediction of ship motion information by taking advantage of developed numerical simulation model of FPSO motion. Up until now, various studies have been conducted about thrust control and allocation for dynamic positioning systems maintaining positions of ships or marine structures in diverse sea environmental conditions. In the existing studies, however, the dynamic positioning systems consist of only feedback control gains using a motion of vessel derived from environmental loads such as current, wind and wave. This study addresses dynamic positioning systems which have feedforward control gain derived from forecasted value of a motion of vessel occurred by current, wind and wave force. In this study, the future motion of vessel is forecasted via Brown's Exponential Smoothing after calculating the vessel motion via a selected mathematical model, and the control force for maintaining the position and heading angle of a vessel is decided by the feedback controller and the feedforward controller using PID theory and forecasted vessel motion respectively. For the allocation of thrusts, the Lagrange Multiplier Method is exploited. By constructing a simulation code for a dynamic positioning system of FPSO, the performance of feedforward control system which has feedback controller and feedforward controller was assessed. According to the result of this study, in case of using feedforward control system, it shows smaller maximum thrust power than using conventional feedback control system.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.37 no.5
• /
• pp.879-890
• /
• 2017

The US Pavement Design method (AASHTO) and HDM-4, a road pavement maintenance decision system, are not suitable for domestic pavement design, construction and maintenance. KPRP(Korea Pavement Research Program) has been developed to reflect Korea's environmental conditions and vehicle characteristics, thereby, extending pavement life. The main objective of this study is to select the best alternative through Life Cycle Cost $CO_2$ (LCCC) calculations among three representative maintenance strategies using KPRP design software since the environment cost resulting from the extended pavement life will also differ. The analysis of this study illustrates that cumulative carbon emissions for 40 years in alternative 2 (Cutting and Overlaying at Year 30) is the lowest option among them, and the basic cost of $CO_2$ emission by various road maintenance and repair work can be used for suggesting an optimal maintenance strategy for highway agency.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.12 no.4
• /
• pp.3-14
• /
• 2002

In this paper we classify the possible threat and introduce the method that measures the loss resulted from the threat in the university. This is the method that the amount of the loss minimized in the case of the same quality in damage as establish a economical prediction model. The method of measuring the loss is as follows. First, asset should be clearly identified and valued. Second, threats which may result in harm to asset should be classified. Third, vulnerabilities which is weaknesses associated with asset should be analyzed. Fourth, measure the value of the loss. we explain the valued method by the example.

• Journal of Korean Society of Forest Science
• /
• v.32 no.1
• /
• pp.9-15
• /
• 1976

Financial rotations of Pinus koraiensis stands are calculated and compared on the basis of five basic financial maturity concepts. The rotations given by the forest rent and average annual gross revenue models are in excess of sixty years by adopting zero interest rates of capital and forest lands. IRR model also neglects land value and highly sensitive to the changes of fixed and regeneration costs. The Faustmann doctrine recommands rotation ages of 23-39 years depend upon applied interest rates and site indices, and seems to be most adequate for determining financial maturity. It is however the situation in Korea that economic conditions are changing rapidly, and thus a model which does not require many exogenous variables in calculation process is preferable. The Duerr's solution has a basic simplicity and logic which is appealing from both a theoritical and practical viewpoint, and most adaptable to the Korean situation, even though the model completly neglects the opportunity cost for forest land. There is a tendency to reduce rotation length with the increase of site quality, but the difference is negligible.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 1995.09a
• /
• pp.16-42
• /
• 1995

변환기에 있는 국내 외주위탁 시장의 특징은 대기업을 중심으로 시장이 형 성되어 있다는 것이다. 즉, 전체 시장규모의 약 절반 가량을 대기업들의 그 룹내 정보시스템 관리 비용이 차지하고 있으며, 자본금 10억 이상의 대형 외 주업체가 전체 70%정도를 점유하고 있다. 대부분의 그룹들은 계열사들의 정 보 시스템 부문을 통합하여 시스템 통합 회사를 설립하고, 이를 통해 내부 정보 시스템의 관리 및 운영을 실시하고 있다. 따라서, 계열사들은 기업의 환경과 요구 사항에 관계없이 무조건적으로 그룹내 시스템 통합 업체에 정 보 시스템을 외주 위탁하여 왔다. 하지만, 기업의 미래는 정보 시스템이 제 공하는 정보의 질에 의해 좌우된다고 해도 과언이 아니므로, 계열사들은 외 주위탁을 위해 그룹내 시스템 통합 업체 뿐 아니라 전문 기술과 경험을 가 지고 있는 외부 회사들을 고려하여야 한다. 즉, 기업의 환경과 필요한 정보 기술에 적합한 외주 위탁 회사를 선정하도록 하여야 한다. 계열사들이 기업 내부의 상황과 그룹의 환경에 따라 최적의 외주위탁 전략을 결정하도록 하 기 위해 본 연구에서는 두 가지 요소 -조직의 정보강도, 그룹의 영향지수-를 도입하였다. 이 요소들을 사용하여 계열사들의 독특한 업무의 환경에 적합한 외주위탁 상황 모형을 제시하고, 제시된 모델의 적합성 여부를 검증하기 위 해 시스템 통합 업체를 가진 국내 대기업의 사례들을 분석, 평가해 보았다. 6개의 그룹에서 11개의 계열사들을 선정하여 각 계열사들의 현재의 외주위 탁 전략, 조직의 정보강도, 그룹의 영향요소 및 정보 시스템에 대한 사용자 만족도를 상위 관리자들과의 인터뷰를 통해 조사하였다. 이 사례 연구들의 결과는 각 계열사들의 상황에 따라 제시된 외주위탁 전략과 현재의 외주위 탁 전략이 일치할 때 정보 시스템에 대한 사용자 만족도가 보다 높은 것으 로 나타났다. 할 수 있는 효율적인 distributed system를 개발하는 것을 제시하였다. 본 논문은 데이타베이스론의 입장에서 아직 정립되어 있지 않은 분산 환경하에서의 관계형 데이타베이스의 데이타관리의 분류체계를 나름대로 정립하였다는데 그 의의가 있다. 또한 이것의 응용은 현재 분산데이타베이스 구축에 있어 나타나는 기술적인 문제점들을 어느정도 보완할 수 있다는 점에서 그 중요성이 있다.ence of a small(IxEpc),hot(Tex> SOK) core which contains two tempegatlue peaks at -15" east and north of MDS. The column density of HCaN is (1-3):n1014cm-2. Column density at distant position from MD5 is larger than that in the (:entral region. We have deduced that this hot-core has a mass of 10sR1 which i:s about an order of magnitude larger those obtained by previous studies.previous studies.업순서들의 상관관계를 고려하여 보다 개선된 해를 구하기 위한 연구가 요구된다. 또한, 준비작업비용을 발생시키는 작업장의 작업순서결정에 대해서도 연구를 행하여, 보완작업비용과 준비비용을 고려한 GMMAL 작업순서문제를 해결하기 위한 연구가 수행되어야 할 것이다.로 이루어 져야 할 것이다.태를 보다 효율적으로 증진시킬 수 있는 대안이 마련되어져야 한다고 사료된다.$\ulcorner$순응$\lrcorner$의 범위를 벗어나지 않는다. 그렇기 때문에도 $\ulcorner$순응$\lrcorner$

• KIPS Transactions on Software and Data Engineering
• /
• v.12 no.3
• /
• pp.133-140
• /
• 2023

The performance of lithium ion batteries depends on the usage environment and the combination ratio of cathode materials. In order to develop a high-performance lithium-ion battery, it is necessary to manufacture the battery and measure its performance while varying the cathode material ratio. However, it takes a lot of time and money to directly develop batteries and measure their performance for all combinations of variables. Therefore, research to predict the performance of a battery using an artificial intelligence model has been actively conducted. However, since measurement experiments were conducted with the same battery in the existing published battery data, the cathode material combination ratio was fixed and was not included as a data attribute. In this paper, we define a training data model required to develop an artificial intelligence model that can predict battery performance according to the combination ratio of cathode materials. We analyzed the factors that can affect the performance of lithium-ion batteries and defined the mass of each cathode material and battery usage environment (cycle, current, temperature, time) as input data and the battery power and capacity as target data. In the battery data in different experimental environments, each battery data maintained a unique pattern, and the battery classification model showed that each battery was classified with an error of about 2%.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.3
• /
• pp.100-109
• /
• 2019

Maintainability indicates the extent to which maintenance can be done easily and quickly. The consideration of maintainability is crucial to reduce the operation and support costs of weapon systems, but if the maintainability is evaluated after the prototype production is done and necessitates design changes, it may increase the cost and delay the schedule. The evaluation should verify whether maintenance work can be performed, and support the designers in developing a design to improve maintainability. In previous studies, the maintainability index was calculated using the graph theory at the early design phase, but evaluation accuracy appeared to be limited. Analyzing the methods of evaluating the maintainability using fuzzy logic and 3D modeling indicate that the design of a system with good maintainability should be done in an integrated manner during the whole system life cycle. This paper proposes a method to evaluate maintainability using SysML-based modeling and simulation technique and fuzzy logic. The physical design structure with maintainability attributes was modeled using SysML 'bdd' diagram, and the maintainability was represented by an AHP matrix for maintainability attributes. We then calculated the maintainability using AHP-based weighting calculation and fuzzy logic through the use of SysML 'par' diagram that incorporated MATLAB. The proposed maintainability model can be managed efficiently and consistently, and the state of system design and maintainability can be analyzed quantitatively, thereby improving design by early identifying the items with low maintainability.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.20 no.5
• /
• pp.23-36
• /
• 2010

Signcryption is a cryptographic primitive which offers authentication and confidentiality simultaneously with a cost lower than signing and encrypting the message independently. We propose a new cryptographic notion called Identity-based online/offline signcryption. The notion of online/offline scheme can be divided into two phases, the first phase is performed offline prior to the arrival of a message to be signed or encrypted and the second phase is performed online phase after knowing the message and the public key of recipient. The Online phase does not require any heavy computations such as pairings or exponents. It is particularly suitable for power-constrained devices such as smart cards. In this paper, we propose ID-based signcryption scheme and ID-based online/offline signcryption scheme where the confidentiality and authenticity are simultaneously required to enable a secure and trustable communication environment. To our best knowledge, this is the first ID-based online/offline signcryption scheme that can be proven secure in the standard model.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2010.05a
• /
• pp.1134-1138
• /
• 2010

호소의 수질오염 문제를 해결하기 위해선 우선 소하천에서 강우유출에 의한 비점오염물질이 어디서 얼마나 발생하는지에 대한 정량적인 조사가 필요하다. 그러나 유역의 오염원에 대한 정량적인 조사가 이루어지려면 많은 비용과 시간 그리고 노력이 필요하다. 따라서 본 연구에서는 대청호 상류유역의 소하천인 안내천을 대상으로 강우유출수 조사를 실시하고, 높은 예측 정확성 때문에 세계적으로 널리 쓰이고 있는 Long-Term Hydrologic Impact Assessment(L-THIA)을 이용하여 실측데이터와 L-THIA 모델의 결과를 비교하였다. 안내천의 유역면적은 16.5 $km^2$로 유역의 약 69.5%가 산림, 농업 및 초지지역이 25.3% 그리고 주거지역이 2.6%로 조사되었다. 수질분석을 위하여 자동수질시료채취기(ISCO sampler 6712)를 설치하여 시간단위의 시료를 채취한 뒤 수질농도를 측정하였다. 수질항목은 유기물질인 $BOD_5$, TOC, T-N, T-P 항목에 대하여 수질오염 공정시험법으로 분석하였다. WHAT 시스템을 이용하여 분리된 직접유출량은 315.5~161,835.1 $m^3$의 범위로 나타났다. 직접유출량을 이용하여 산정한 유역의 EMC 농도는 안내천 유역의 $EMC_{BOD}$는 1.0~2.4 mg/L, $EMC_{TOC}$는 1.429~5.491 mg/L, $EMC_{COD}$는 2.2~10.2 mg/L, $EMC_{TN}$은 2.906~10.864 mg/L, $EMC_{TP}$는 0.029~0.285 mg/L의 범위를 보였다. 또한 실측된 유량과 농도를 이용하여 산정한 오염부하는 안내천 유역이 $BOD_5$ 37.9~390.9 g, $COD_{Mn}$ 0.8~1,657.5 g, TOC 0.54~791.83 g, T-N 0.968~1,758.174 g, T-P 0.011~42.139 g의 범위로 나타났다. L-THIA 모델을 이용하여 직접유출량의 산정된 결과와 실측 결과를 비교 분석한 결과 결정계수와 유효지수가 0.95와 0.93으로 높게 나타나 대청호 상류유역에서 발생하는 유출량을 모의하는데 적절할 것으로 판단된다. 토지이용도와 토양도 그리고 일 강우자료만으로 구축되는 L-THIA 모델을 이용하여 대청호 상류의 소하천 유역에 대하여 비점오염원 유출특성을 해석하는 것이 가능 할 것으로 판단된다.

• Journal of the Society of Disaster Information
• /
• v.19 no.4
• /
• pp.976-983
• /
• 2023

Purpose: The dynamic behavior of a bridge structure under seismic loading depends on many uncertainties, such as the nature of the seismic waves and the material and geometric properties. However, not all uncertainties have a significant impact on the dynamic behavior of a bridge structure. Since probabilistic seismic performance evaluation considering even low-impact uncertainties is computationally expensive, the uncertainties should be identified by considering their impact on the dynamic behavior of the bridge. Therefore, in this study, a global sensitivity analysis was performed to identify the main parameters affecting the dynamic behavior of bridges with I-curved girders. Method: Considering the uncertainty of the earthquake and the material and geometric uncertainty of the curved bridge, a finite element analysis was performed, and a surrogate model was developed based on the analysis results. The surrogate model was evaluated using performance metrics such as coefficient of determination, and finally, a global sensitivity analysis based on the surrogate model was performed. Result: The uncertainty factors that have the greatest influence on the stress response of the I-curved girder under seismic loading are the peak ground acceleration (PGA), the height of the bridge (h), and the yield stress of the steel (fy). The main effect sensitivity indices of PGA, h, and fy were found to be 0.7096, 0.0839, and 0.0352, respectively, and the total sensitivity indices were found to be 0.9459, 0.1297, and 0.0678, respectively. Conclusion: The stress response of the I-shaped curved girder is dominated by the uncertainty of the input motions and is strongly influenced by the interaction effect between each uncertainty factor. Therefore, additional sensitivity analysis of the uncertainty of the input motions, such as the number of input motions and the intensity measure(IM), and a global sensitivity analysis considering the structural uncertainty, such as the number and curvature of the curved girders, are required.