• Journal of Astronomy and Space Sciences
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• v.25 no.4
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• pp.361-374
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• 2008

Recently, satellite formation flying has been a topic of significant research interest in aerospace society because it provides potential benefits compared to a large spacecraft. Some techniques have been proposed to design optimal formation trajectories minimizing fuel consumption in the process of formation configuration or reconfiguration. In this study, a method is introduced to build fuel-optimal trajectories minimizing a cost function that combines the total fuel consumption of all satellites and assignment of fuel consumption rate for each satellite. This approach is based on collocation and nonlinear programming to solve constraints for collision avoidance and the final configuration. New constraints of nonlinear equality or inequality are derived for final configuration, and nonlinear inequality constraints are established for collision avoidance. The final configuration constraints are that three or more satellites should form a projected circular orbit and make an equilateral polygon in the horizontal plane. Example scenarios, including these constraints and the cost function, are simulated by the method to generate optimal trajectories for the formation configuration and reconfiguration of multiple satellites.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.321-324
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• 2003

There are two steps to solve the self-collision avoidance problems for redundant manipulators. First, all links are regarded as cylinders. and then the collisions should be checked among all pairs of the links. Between two cylinders. we can get the collision information derived from the concept or configuration space obstacle in real time. Therefore. it is possible to detect the links where collisions are likely in real time by setting the risk radius which is larger than actual radius. Second. the configuration control points (CCP) should be placed at the ends of the detected links. A cost function is the sum of the distances between the CCPs. To maximize the cost function means the links go far away each other without self-collisions.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.5
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• pp.791-798
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• 2020

The share of advanced technology in modern weapon systems are gradually increasing, and life cycle of components are shortened due to the rapid speed of technological development. On the other hand, the weapon systems have a characteristic that takes a long time in the requirement stage of weapon to the operation and maintenance stage. Due to inevitably, obsolescence of the main components for parts occurs in the acquisition phase. The obsolescence parts could cause delays in mass production schedules, and further adversely affects operational availability due to poor supply of repair parts during in the maintenance phase. However, business managers are obliged to maximize the performance while minimizing the cost of the total life cycle of the design, production, and operation stages. It is necessary to establish and implement an appropriate components and parts of life cycle management plan. In this research, we analyzed the effectiveness of parts obsolescence management through cost avoidance and total life cycle cost that can be reduced through proper parts obsolescence management.

• Journal of Neurocritical Care
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• v.11 no.2
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• pp.110-118
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• 2018

Background: The role of clinical pharmacists in medication therapy to improve clinical and economic outcomes has been reported in the literature. This study was conducted to analyze the changes in details of medication interventions before and after the introduction of clinical pharmacists into the care of neurocritical care unit (NCU) patients, and to evaluate the economic effects of clinical pharmacists by calculating the avoidance cost. Methods: A retrospective study was conducted reviewing the electronic medical records from June 2013 to May 2014 (before), and from June 2016 to May 2017 (after). We calculated the number and rates of intervention, the acceptance rates of it, and also reviewed the list of interventions. We calculated avoidance cost if there was no intervention. Results: The monthly mean number of interventions increased from 8.0 (${\pm}5.7$) to 31.7 (${\pm}12.8$) (P<0.001) and the frequency of intervention also increased from 0.8% to 1.6% (P=0.003). The most frequently provided pharmacist intervention was nutritional support before introduction of clinical pharmacists and discussions on the medication plan after. The number of classified interventions was 14 before introduction of clinical pharmacist services and 33 after. The calculated cost avoidance associated with a clinical pharmacists' integration was 77,990,615 won per year. Conclusion: Introduction of clinicals pharmacist into the NCU was associated with increased intervention rates and expanded types of clinical interventions. The cost avoidance achieved by the pharmacists' interventions can be further explored to evaluate if similar expansions of pharmacists' services achieve similar results in other settings.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.1
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• pp.89-93
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• 2009

This paper deals with obstacle avoidance for unmanned vehicle using stereo system. The "DARPA Grand Challenge 2005" shows that the robot can move autonomously under given waypoint. RADAR, IMS (Inertial Measurement System), GPS, camera are used for autonomous navigation. In this paper, we focus on stereo system for autonomous navigation. Our approach is based on Singh et. al. [5]'s approach that is successfully used in an unmanned vehicle and a planetary robot. We propose an improved algorithm for obstacle avoidance by modifying the cost function of Singh et. al. [5]. Proposed algorithm gives more sharp contrast in choosing local path for obstacle avoidance and it is verified in experimental results.

• International Journal of Aeronautical and Space Sciences
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• v.11 no.4
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• pp.351-359
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• 2010

This paper proposes a linear system control algorithm with collision avoidance in multiple satellites. Consideration of collision avoidance is augmented by adding a weighting term in the cost function of the original tracking problem in linear quadratic control (LQC). Because the proposed algorithm relies on a similar solution procedure to the original LQC, its inherent advantages, including gain-robustness and optimality, are preserved. To confirm and visualize the derived algorithm, a simple example of two-vehicle motion in the two-dimensional plane is illustrated. In addition, the proposed collision avoidance control is applied to satellite formation flying, and verified by numerical simulations.

• Journal of the Korean Society for Library and Information Science
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• v.39 no.2
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• pp.35-55
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• 2005

This study attempts feasibility analysis of cataloging outsourcing. The economic analysis model based on information economics categorizes the benefit into direct benefit and value linking. We measure direct benefit by cost savings and cost avoidance, value linking by the degree of improvement in cataloging quality The results show that there is no feasibility overall, because librarians spent more time to control the quality due to vendor's lack of professionalism, resulting little effect on cost savings. When cataloging outsourcing is forcibly used under the economically infeasible condition, it is impossible to achieve the basic purpose of operating cost savings and improvement of service function.

• Journal of Information Processing Systems
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• v.16 no.6
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• pp.1324-1342
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• 2020

Various modified algorithms of rapidly-exploring random tree (RRT) have been previously proposed. However, compared to the RRT algorithm for collision avoidance with global and static obstacles, it is not easy to find a collision avoidance and local path re-planning algorithm for dynamic obstacles based on the RRT algorithm. In this study, we propose boundary-RRT*, a novel-algorithm that can be applied to aerial vehicles for collision avoidance and path re-planning in a three-dimensional environment. The algorithm not only bounds the configuration space, but it also includes an implicit bias for the bounded configuration space. Therefore, it can create a path with a natural curvature without defining a bias function. Furthermore, the exploring space is reduced to a half-torus by combining it with simple right-of-way rules. When defining the distance as a cost, the proposed algorithm through numerical analysis shows that the standard deviation (σ) approaches 0 as the number of samples per unit time increases and the length of epsilon ε (maximum length of an edge in the tree) decreases. This means that a stable waypoint list can be generated using the proposed algorithm. Therefore, by increasing real-time performance through simple calculation and the boundary of the configuration space, the algorithm proved to be suitable for collision avoidance of aerial vehicles and replanning of local paths.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.12
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• pp.1132-1138
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• 2012

The MPC (Model Predictive Control) is one of the techniques that can be used to control an unmanned vehicle. It predicts the future vehicle trajectory using the dynamic characteristic of the vehicle and generate the control value to track the reference path. If some obstacles are detected on the reference paths, the MPC can generate control value to avoid the obstacles imposing the inequality constraints on the MPC cost function. In this paper, we propose an obstacle modeling algorithm for MPC with inequality constraints for obstacle avoidance and a method to set selective constraint on the MPC for stable obstacle avoidance. Simulations with the field test data show successful obstacle avoidance and way point tracking performance.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.241-249
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• 2014

This paper presents a path planning algorithm of an autonomous vehicle (ADAM III) for collision avoidance in the presence of multiple obstacles. Under the requirements that a low-cost GPS is used and its computation should be completed with a sampling time of sub-second, heading angle estimation is proposed to improve performance degradation of its measurement and a hierarchical structure for path planning is used. Once it is decided that obstacle avoidance is necessary, the path planning consists in three steps: waypoint generation, trajectory candidate generation, and trajectory selection. While the waypoints and the corresponding trajectory candidates are generated based on position of obstacles, the final desired trajectory is determined with considerations of kinematic constraints as well as an optimal condition in a term of lateral deviation. Finally the proposed algorithm was validated experimentally through field tests and its demonstration was performed in Autonomous Vehicle Competition (AVC) 2013.