• Korean Journal of Hydrosciences
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• 제2권
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• pp.39-59
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• 1991

Scour at bridge pier is a complicated three-dimensional problem involving interaction of fluld force on movable aid nonuniformily distributed sand grains. Although several analytical solution approaches, experimental research and field investigations for scout at piers have been conducted, no comprehensive and universally acceptable solution is so far available. Even though many methods and equations for predicting scour at piers are available in the literature, hydraulic and/or bridge design engineers are often at a loss over which method or equation is applicable for the specific bridge sites. To provide better understanding about scour phenomena and better predicting of scour at piers, intensive research is conducted through comprehensive review of published literature. Based on the research the state-of-the-art of pier scour prediction for design application is provided as a design guide for practicing engineers in this field. Recommendations for applying aggradation and degradation, contraction scour, and local scour prediction methods or equations are suggested. It is hoped that this paper may provide good information for the prediction of scour at piers.

• 한국시뮬레이션학회논문지
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• 제12권1호
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• pp.73-83
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• 2003

This paper presents armed vehicle BAttle Group Simulation model(called BAGSim) which is an object-oriented simulation system for representing battle group engagement consisting of tanks and helicopters. BAGSim is designed in the evolutionary software life cycle approach with the Unified Software Development Process, and implemented with C++ language. BAGSim consists of a preprocessor for engagement scenario definition and simulation data set up, a main processor for triggering engagement event and advancing simulation clock, and a post processor to record simulation histories. Application scenario covers several type of engagement among command tanks, fight tanks, scout helicopters, attack helicopters, anti-tank guided missiles, and decoys. Thus, BAGSim can be effectively used as an analytic tool to examine some operational concepts and tactics, further experimentally fine tune tank design options.

• Journal of Information Processing Systems
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• 제8권3호
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• pp.471-482
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• 2012

For disaster exploration and surveillance application, this paper aims to present a novel application of a multi-robot agent based on WSN and to evaluate a multi-hop communication caused by the robotics correspondingly, which are used in the uncertain and unknown subterranean tunnel. A Primary-Scout Multi-Robot System (PS-MRS) was proposed. A chain topology in a subterranean environment was implemented using a trimmed ZigBee2006 protocol stack to build the multi-hop communication network. The ZigBee IC-CC2530 modular circuit was adapted by mounting it on the PS-MRS. A physical experiment based on the strategy of PS-MRS was used in this paper to evaluate the efficiency of multi-hop communication and to realize the delivery of data packets in an unknown and uncertain underground laboratory environment.

• International Journal of Computer Science & Network Security
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• 제21권11호
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• pp.312-320
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• 2021

Increase in computational cost and exhaustive search can lead to more complexity and computational energy. Thus, there is need for effective and efficient scheme to reduce the complexity to achieve optimal energy utilization. This will improve the energy efficiency and enhance the proficiency in terms of the resources needed to achieve convergence. This paper primarily focuses on the development of hybrid swarm intelligence scheme for reducing the computational complexity in binary optimization. In order to reduce the complexity, both artificial bee colony (ABC) and particle swarm optimization (PSO) have been employed to effectively minimize the exhaustive search and increase convergence. First, a new approach using ABC and PSO has been proposed and developed to solve the binary optimization problem. Second, the scout for good quality food sources is accomplished through the deployment of PSO in order to optimally search and explore the best source. Extensive experimental simulations conducted have demonstrate that the proposed scheme outperforms the ABC approaches for reducing complexity and energy consumption in terms of convergence, search and error minimization performance measures.

• 한국수자원학회논문집
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• 제36권6호
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• pp.893-899
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• 2003

본 연구에서는 하상이 단단한 지질구조로 이루어진 하상조건에서의 실제적인 세굴현상을 파악하기 위해 실시간 교량세굴 모니터링 시스템을 설치하여 홍수시의 세굴심을 측정하였다. 또한, 홍수 전$\cdot$후의 지반구조를 측정할 수 있는 GPR(Ground Penetrating Radar)탐사를 통하여 홍수로 인한 세굴가능성을 면밀히 파악하였다. 이와 같은 연구과정을 통해 지질구조에 따른 세굴심 산정공식의 적용성 여부를 판단하였고 하상특성과 흐름특성이 동시에 고려된 실제적인 세굴의 영향을 평가하였다.

• Journal of Korean Neurosurgical Society
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• 제56권5호
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• pp.400-404
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• 2014

Objective : Clip artifacts limit the visualization of intracranial structures in CT scans from patients after aneurysmal clipping with cobalt alloy clips. This study is to analyze the parameters influencing the degree of clip artifacts. Methods : Postoperative CT scans of 60 patients with straight cobalt alloy-clipped aneurysms were analyzed for the maximal diameter of white artifacts and the angle and number of streak artifacts in axial images, and the maximal diameter of artifacts in three-dimensional (3-D) volume-rendered images. The correlation coefficient (CC) was determined between each clip artifact type and the clip blade length and clip orientation to the CT scan (angle a, lateral clip inclination in axial images; angle b, clip gradient to scan plane in lateral scout images). Results : Angle b correlated negatively with white artifacts (r=-0.589, p<0.001) and positively with the angle (r=0.636, p<0.001) and number (r=0.505, p<0.001) of streak artifacts. Artifacts in 3-D images correlated with clip blade length (r=0.454, p=0.004). Multiple linear regression analysis revealed that angle b was the major parameter influencing white artifacts and the angle and number of streak artifacts in axial images (p<0.001), whereas clip blade length was a major factor in 3-D images (p=0.034). Conclusion : Use of a clip orientation perpendicular to the scan gantry angle decreased the amount of white artifacts and allowed better visualization of the clip site.

• Advances in Energy Research
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• 제7권1호
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• pp.35-52
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• 2020

The paper proposes a hybrid approach of artificial bee colony (ABC) and grey wolf optimizer (GWO) algorithm for multi-objective and multidimensional engine optimization of a converted plug-in hybrid electric vehicle. The proposed strategy is used to optimize all emissions along with brake specific fuel consumption (FC) for converted parallel operated diesel plug-in hybrid electric vehicle (PHEV). All emissions particulate matter (PM), nitrogen oxide (NOx), carbon monoxide (CO) and hydrocarbon (HC) are considered as optimization parameters with weighted factors. 70 hp engine data of NOx, PM, HC, CO and FC obtained from Oak Ridge National Laboratory is used for the study. The algorithm is initialized with feasible solutions followed by the employee bee phase of artificial bee colony algorithm to provide exploitation. Onlooker and scout bee phase is replaced by GWO algorithm to provide exploration. MATLAB program is used for simulation. Hybrid ABC-GWO algorithm developed is tested extensively for various values of speeds and torque. The optimization performance and its environmental impact are discussed in detail. The optimization results obtained are verified by real data engine maps. It is also compared with modified ABC and GWO algorithm for checking the effectiveness of proposed algorithm. Hybrid ABC-GWO offers combine benefits of ABC and GWO by reducing computational load and complexity with less computation time providing a balance of exploitation and exploration and passes repeatability towards use for real-time optimization.

• 제어로봇시스템학회논문지
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• 제18권12호
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• pp.1122-1131
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• 2012

This paper presents obstacle avoidance method for scout robot or industrial robot in unknown environment by using IR sensor and vision system. In the proposed method, robots share the information where the obstacles are located in real-time, thus the robots can choose the best path for obstacle avoidance. Using IR sensor and vision system, multiple robots efficiently evade the obstacles by the proposed cooperation method. No landmark is used at wall or floor in experiment environment. The obstacles don't have specific color or shape. To get the information of the obstacle, vision system extracts the obstacle coordinate by using an image labeling method. The information obtained by IR sensor is about the obstacle range and the locomotion direction to decide the optimal path for avoiding obstacle. The experiment was conducted in $7m{\times}7m$ indoor environment with two-wheeled mobile robots. It is shown that multiple robots efficiently move along the optimal path in cooperation with each other in the space where obstacles are located.

• 천문학논총
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• 제38권2호
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• pp.25-36
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• 2023

Since interstellar objects like 1I/'Oumuamua and 2I/Borisov originate from exoplanetary systems, even if we do not visit the exoplanetary systems, flyby, rendezvous, and sample return missions of interstellar objects can provide clues to solve the mysteries of cosmic life phenomena such as the origin of exoplanetary systems, galactic evolution, biosignatures (or even technosignatures), and panspermia. In this paper, we review space missions for interstellar object exploration in the stage of mission design or concept study such as Project Lyra, Bridge, Comet Interceptors, and Lightcraft^TM. We also review space missions, OSIRIS-REx and NEA Scout, designed for Near Earth Asteroids(NEA) explorations, to investigate the current state of basic technologies that can be extended to explore interstellar objects in a velocity of ~ 6AU/year. One of the technologies that needs to be developed for interstellar object exploration is a spacecraft propulsion method such as solar sail, which can catch up with the fast speed of interstellar objects. If this kind of propulsion becomes practical for space explorations, interstellar object explorations will mark a new era and serve as a driving force to provide evidences of cosmic life.

• 한국IT서비스학회지
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• 제17권3호
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• pp.117-138
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• 2018

The purpose of this study is to empirically analyze the relationships between the Boundary Spanning Activities (BSA) of project team and system performance in ERP system development projects. We could theoretically classify the BSA in the ERP development projects into five categories on the basis of existing studies on the BSA in the research fields of organization theory, new product development, and information systems development. These five categories are 'Ambassador' activities, 'Task-coordinator' activities, 'Scout' activities, 'Sentry' activities and 'Guard' activities. And the relationship between the implementation level of activities included in each category and the project performance (system usage and users' satisfaction) was hypothesized with respect to five BSA categories. In order to test the hypotheses, we conducted on/offline survey of the participants who were involved in the ERP system development projects, and received 345 valid responses. The unit of analysis was the project team, and the total number of teams that survey participants belonged to were 103 ones. The Structural Equation Model Analysis using the SMART PLS 3.0 was applied to statistically testing the hypotheses. The results showed that 10 hypotheses among 12 hypotheses could be supported. The theoretical implications of this study can be summarized as following; first, redefining and categorizing the BSA (Boundary Spanning Activities) in the ERP system development projects, secondly, deriving measurement indicators of the implementation level for each BSA category and statistically proving the validity and the reliability of them, and finally, suggesting the theoretical background of expanding the management area of ERP systems development projects. Furthermore, the practical implication of this study is that concrete BSA items which are empirically derived can be utilized as effective guidelines for successfully implementing the BSA in the process of managing the ERP system development projects.