• 한국지반공학회논문집
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• 제24권9호
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• pp.23-32
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• 2008

본 논문에서는 계단식 형태로 시공되는 블록식 보강토 옹벽의 전체 안정성이 고려된 설계에 관한 내용을 다루었다. 다양한 계원과 이격거리로 설계된 네 가지 설계사례에 대해 현재 통용되고 있는 FHWA 및 NCMA 설계기준에 근거하여 내 외적 안정해석을 수행하고 그 결과를 토대로 두 설계기준의 차이점을 검토하였다. 아울러 대상옹벽에 대해 한계평형해석에 근거한 사면안정해석과 연속체역학 기반의 강도감소기법 해석을 수행하여 계단식 옹벽의 설계를 지배하는 파괴 메카니즘을 고찰하였다. 그 결과 내 외적 안정성 공히 FHWA에서 채택하고 있는 설계기준이 NCMA 보다 보수적인 결과(낮은 안전율)를 주는 것으로 나타났다. 또한 계단식 옹벽의 보강재의 소요 포설 길이는 전반적으로 전체 안정성에 좌우되는 것으로 검토되었으며 상부 옹벽의 보강재의 길이는 현 설계기준 보다 현저히 증가시켜야 하는 것으로 검토되었다.

• The Journal of Asian Finance, Economics and Business
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• 제7권3호
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• pp.149-156
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• 2020

The study aims to investigate a close relation between macro and non-macro variables on stock performance of tourism companies in Korea. The sample used in this study includes monthly data from January 2001 to December 2018. The stock price index of the tourism companies as a dependent variable are obtained from Sejoong, HanaTour, and RedcapTour as three leading Korean tourism companies that have been listed on the Korea Stock Exchange. This study assesses the tourism stock performance using the quantile regression approach. This study also investigates whether global crisis events as the Iraq War and the global financial crisis as non-macro variables have a significant effect on the stock performance of tourism companies in Korea. The results show that the oil prices, exchange rate and industrial production have negative coefficients on stock prices of tourism companies, while the effects of tourist expenditure and consumer price index are positive and significant. We estimate the result of quantile regression that non-macro determinants have statistically a significant and negative effect on tourism stock performance because the global crisis could threaten traveler's safety and economy. Overall, empirical results suggest that the effects of macro and non-macro variables are statistically asymmetric and highly related to tourism stock performance.

• International Journal of Control, Automation, and Systems
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• 제4권4호
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• pp.405-413
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• 2006

A novel approach based on genetic algorithms (GA) is developed to find a global minimum-jerk trajectory of a space robotic manipulator in joint space. The jerk, the third derivative of position of desired joint trajectory, adversely affects the efficiency of the control algorithms and stabilization of whole space robot system and therefore should be minimized. On the other hand, the importance of minimizing the jerk is to reduce the vibrations of manipulator. In this formulation, a global genetic-approach determines the trajectory by minimizing the maximum jerk in joint space. The planning procedure is performed with respect to all constraints, such as joint angle constraints, joint velocity constraints, joint angular acceleration and torque constraints, and so on. We use an genetic algorithm to search the optimal joint inter-knot parameters in order to realize the minimum jerk. These joint inter-knot parameters mainly include joint angle and joint angular velocities. The simulation result shows that GA-based minimum-jerk trajectory planning method has satisfactory performance and real significance in engineering.

• Journal of Information Processing Systems
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• 제16권1호
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• pp.201-209
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• 2020

The graph data structure is popular because it can intuitively represent real-world knowledge. Graph databases have attracted attention in academia and industry because they can be used to maintain graph data and allow users to mine knowledge. Mining reachability relationships between two nodes in a graph, termed reachability query processing, is an important functionality of graph databases. Online traversals, such as the breadth-first and depth-first search, are inefficient in processing reachability queries when dealing with large-scale graphs. Labeling schemes have been proposed to overcome these disadvantages. The state-of-the-art is the 2-hop labeling scheme: each node has in and out labels containing reachable node IDs as integers. Unfortunately, existing 2-hop labeling schemes generate huge 2-hop label sizes because they only consider local features, such as degrees. In this paper, we propose a more efficient 2-hop label size reduction approach. We consider the topological sort index, which is a global feature. A linear combination is suggested for utilizing both local and global features. We conduct experiments over real-world and synthetic directed acyclic graph datasets and show that the proposed approach generates smaller labels than existing approaches.

• Structural Engineering and Mechanics
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• 제68권5호
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• pp.549-561
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• 2018

Sobol method is applied as a powerful variance decomposition technique in the field of global sensitivity analysis (GSA). The paper is devoted to increase convergence speed of the extracted Sobol indices using a new proposed sampling technique called genetic based Latine hypercube sampling (GBLHS). This technique is indeed an improved version of restricted Latine hypercube sampling (LHS) and the optimization algorithm is inspired from genetic algorithm in a new approach. The new approach is based on the optimization of minimax value of LHS arrays using manipulation of array indices as chromosomes in genetic algorithm. The improved Sobol method is implemented to perform factor prioritization and fixing of an uncertain comprehensive high speed rotor-bearing system. The finite element method is employed for rotor-bearing modeling by considering Eshleman-Eubanks assumption and interaction of axial force on the rotor whirling behavior. The performance of the GBLHS technique are compared with the Monte Carlo Simulation (MCS), LHS and Optimized LHS (Minimax. criteria). Comparison of the GBLHS with other techniques demonstrates its capability for increasing convergence speed of the sensitivity indices and improving computational time of the GSA.

• Nuclear Engineering and Technology
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• 제55권9호
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• pp.3493-3505
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• 2023

Reactor containment buildings serve as the last barrier to prevent radioactive leakage due to accidents and their safety is crucial in overpressurization conditions. Thus, the Regulatory Guide (RG) 1.216 has mentioned the global strain as one of failure criteria in the free-field for cylindrical prestressed concrete containment vessels (PCCV) subject to internal pressure. However, there is a limit that RG 1.216 shows the free-field without the specific locations of failure criteria and also the global strain corresponding to only azimuth 135° has been mentioned in NUREG/CR-6685, regardless of the elevations of the structure. Therefore, in order to reevaluate the failure criteria of the 1:4 scaled PCCV, the high fidelity simulation model based on the experimental test was significantly validated in this study, and it was interesting to find that the experimental and numerical result was very close to each other. In addition, for the consideration of the material uncertainties, the Latin hypercube method was used as a statistical approach. Consequently, it was revealed that the radial displacements of various azimuth area such as 120°, 135°, 150°, 180° and 210° at elevations 4680 mm and 6,200 mm can represent as the global deformation at the free-field, obtained from the statistical approach.

• 한국정보처리학회논문지
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• 제1권2호
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• pp.172-183
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• 1994

멀티 데이타베이스 시스템에서 가장 중요한 사항은 지역 자치성의 보장과 전역적 일관성을 유지하는 것이다. 전역적 일관성은 전역 동시성 제어 알고리즘과 회복 알고 리즘에 의해 유지될 수 있다. 본 논문은 지역 자치성을 보장하면서 전역적 직렬성을 만족하는 전역 동시성 제어 알고리즘과 지역 자치성을 보장하면서 각종 고장으로부터 멀티 데이타베이스를 회복할 수 있는 전역 회복 알고리즘을 제안한다. 제안된 전역 동시성 제어 알고리즘은 상향식 방법으로 3단계 트랜잭션 처리 모델에 기반을 두고, 지역 트랜잭션들로 인하여 부트랜잭션들 사이에 간접 충돌이 발생할 때 서버에서 가상 연산을 사용하여 지역 데이타베이스 시스템에서 수행되는 부트랜잭션들의 수행 순서와 직렬화 순서가 동일하게 유지할 수 있도록 함으로써 간접 충돌 문제를 해결할 수 있다. 저 전역 모듈에서는 충돌 관계가 있는 전역 트랜잭션들에 대해서만 전역적 직렬성을 검사 함으로써 전역적 직렬성 검사를 더욱 효율적으로 할 수 있다.

• 한국산업정보학회논문지
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• 제20권6호
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• pp.57-65
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• 2015

제조최적화 문제는 비선형 형태의 설계변수로 표시되며, 다양하고 복잡한 제약들을 만족하는 조건하에서 최적해를 구하는 문제이다. 이러한 제조최적화 문제 해결을 위하여 본 연구에서는 혼합형접근법을 제안한다. 제안된 혼합형접근법은 기존의 유전알고리즘(Genetic algorithm: GA)과 쿠쿠탐색(Cuckoo search: CS) 및 언덕오르기법(Hill climbing method: HCM)을 혼합한 형태로 구성된다. 제안된 혼합형접근법에서 GA는 전역적탐색(Global search)를 위해 사용되고, CS는 GA탐색과정에서 발생하는 단점을 개선하기 위해 적용되고, 마지막으로 HCM은 GA와 CS 탐색 이후의 수렴된 지역을 정밀하게 탐색하기 위한 지역적탐색(Local search)을 위해 적용된다. 실험분석에서는 다양한 형태의 제조최적화 문제가 제시되어 본 연구에서 제안된 혼합형접근법와 기존접근법들의 수행도를 각각 비교, 분석하였으며, 그 결과는 본 연구에서 제안한 혼합형접근법의 수행도가 기존접근법들의 수행도보다 더 우수한 것을 확인하였다.

• Journal of Positioning, Navigation, and Timing
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• 제3권1호
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• pp.31-36
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• 2014

Precise Point Positioning (PPP) is a stand-alone precise positioning approach. As the quality of satellite orbit and clock products from analysis centers has been improved, PPP can provide more precise positioning accuracy and reliability. A combined use of Global Positioning System (GPS) and Global Orbiting Navigation Satellite System (GLONASS) in PPP is now available. In this paper, we explained about an approach for combined GPS and GLONASS PPP measurement processing, and validated the performance through the comparison with GPS-only PPP results. We also used the measurement obtained from the GRAS reference station for the performance validation. As a result, we found that the combined GPS/GLONASS PPP can yield a more precise positioning than the GPS-only PPP.

• 제어로봇시스템학회논문지
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• 제9권10호
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• pp.832-835
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• 2003

The objective of this study is to investigate the possibility of chemical process synthesis purely based on mathematical programming when given an objective, feed conditions, product specifications, and model equations for available process units. A method based on a state space approach is proposed, and applied to an example problem with a reactor, a heat exchanger, and a separator. The results indicate that a computer can automatically synthesize an optimal process without any heuristics or expertise in process design provided that global optimization techniques are improved to be suitable for large problems.