• Journal of Korean Institute of Industrial Engineers
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• v.43 no.1
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• pp.12-18
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• 2017

This study presents a plant concept design for a smart factory which is mainly targeted to machine airplane parts. The plant layout is based on the TOC-DBR approach together with autonomous distributed factory control considered, while discrete event simulation is also performed in order to validate its layout. The resulting layout and its procedure turn out to be quite a useful guideline in realizing those smart factories especially for machining-oriented manufacturing industries.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.1
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• pp.99-108
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• 2005

This paper represents an efficient modeling method of a suspension system for the vehicle dynamic simulation. The suspension links are modeled as composite joints. The motion of wheel is defined as relative one degree of freedom motion with respect to car body. The unique relative kinematic constraint formulation between the car body and wheel enables to derive equations of motion in terms of wheel vertical motion. Thus, vehicle model has ten degrees of freedom. By using velocity transformation method, the equations of motion of the vehicle is systematically derived without kinematic constraints. Various vehicle simulation such as J-turn, slowly increasing steer, sinusoidal sweep steer and bump run has been performed to verify the validity of the suggested vehicle model.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.2
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• pp.173-182
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• 2001

Ascent trajectory optimization and optimal explicit guidance problems for a satellite launch vehicle in a 2-dimensional pitch plane are studied. The trajectory optimization problem with boundary conditions is formulated as a nonlinear programming problem by parameterizing the pitch attitude control variable, and is solved by using the SQP algorithm. The flight constraints such as gravity-turn are imposed. An optimal explicit guidance algorithm in the exoatmospheric phase is also presented, the guidance algorithm provides steering command and time-to-go value directly using the current states of the vehicle and the desired orbit insertion conditions. To verify the optimality and accuracy of the algorithm simulations are performed.

• Journal of Korea Society of Industrial Information Systems
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• v.6 no.2
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• pp.63-73
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• 2001

An alternative approach to formulating a special class of linear goal programming (LGP) models is presented. We propose a formulation of the LGP model that can include the decision variables in the objective function. We specifically propose that the position of the decision variables in the objective function be used to eliminate goal constraints whose sole purpose is to indirectly optimize decision variables. For the select group of LGP problems wherever indirect optimization of decision variables are sought, the alternative LGP model formulation is able to reduce the size of these LGP models and in turn the computational effort required for their solution.

• The Journal of Information Technology and Database
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• v.7 no.1
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• pp.42-53
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• 2000

The major goal of this research is to develop an optimal route search algorithm for an intelligent route guidance system, one sub-area of ITS. ITS stands for intelligent Transportation System. ITS offers a fundamental solution to various issues concerning transportation and it will eventually help comfortable and swift moves of drivers by receiving and transmitting information on humans, roads and automobiles. Genetic algorithm, and fuzzy logic are utilized in order to implement the proposed algorithm. Using genetic algorithm, the proposed algorithm searches shortest routes in terms of travel time in consideration of stochastic traffic volume, diverse turn constraints, etc. Then using fuzzy logic, it selects driver-preference optimal route among the candidate routes searched by GA, taking into account various driver's preferences such as difficulty degree of driving and surrounding scenery of road, etc. In order to evaluate this algorithm, a virtual road-traffic network DB with various road attributes is simulated, where the suggested algorithm promptly produces the best route for a driver with reference to his or her preferences.

• Journal of Aerospace System Engineering
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• v.14 no.2
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• pp.1-11
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• 2020

Detecting obstacles and generating a suitable path to avoid obstacles in real time is a prime mission requirement for UAVs. In areas, close to buildings and people, detecting obstacles in the path and estimating its own position (egomotion) in GPS degraded/denied environments are usually addressed with vision-based Simultaneous Localization and Mapping (SLAM) techniques. This presents possibilities and challenges for the feasible path generation with constraints of vehicle dynamics in the configuration space. In this paper, a near real-time feasible path is shown to be generated in the ORB-SLAM framework using a chain-based path planning approach in a force field with dynamic constraints on path length and minimum turn radius. The chain-based path plan approach generates a set of nodes which moves in a force field that permits modifications of path rapidly in real time as the reward function changes. This is different from the usual approach of generating potentials in the entire search space around UAV, instead a set of connected waypoints in a simulated chain. The popular ORB-SLAM, suited for real time approach is used for building the map of the environment and UAV position and the UAV path is then generated continuously in the shortest time to navigate to the goal position. The principal contribution are (a) Chain-based path planning approach with built in obstacle avoidance in conjunction with ORB-SLAM for the first time, (b) Generation of path with minimum overheads and (c) Implementation in near real time.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.7
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• pp.1823-1840
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• 2023

In order to improve spectral efficiency and reduce power consumption for reconfigurable intelligent surface (RIS) assisted wireless communication systems, a joint design considering irregular RIS topology, RIS on-off switch, power allocation and phase adjustment is investigated in this paper. Firstly, a multi-dimensional variable joint optimization problem is established under multiple constraints, such as the minimum data requirement and power constraints, with the goal of maximizing the system energy efficiency. However, the proposed optimization problem is hard to be resolved due to its property of nonlinear nonconvex integer programming. Then, to tackle this issue, the problem is decomposed into four sub-problems: topology design, phase shift adjustment, power allocation and switch selection. In terms of topology design, Tabu search algorithm is introduced to select the components that play the main role. For RIS switch selection, greedy algorithm is used to turn off the RISs that play the secondary role. Finally, an iterative optimization algorithm with high data-rate and low power consumption is proposed. The simulation results show that the performance of the irregular RIS aided system with topology design and RIS selection is better than that of the fixed topology and the fix number of RISs. In addition, the proposed joint optimization algorithm can effectively improve the data rate and energy efficiency by changing the propagation environment.

• Korean Journal of Culture and Social Issue
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• v.29 no.1
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• pp.101-123
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• 2023

As an effort to further extend the existing understanding on the Psychology of Working Theory, this study examined gender differences in the paths to the attainment of decent work with Korean emerging adults. A total of 311 South Korean employees (mean age = 25.96, men = 94, women = 217) completed online questionnaires. We found that economic constraints inversely predicted work volition and career adaptability, which were positively relatedin turn, led to decent work. The overall indirect effect of work volition and career adaptability between economic constraints and decent work was significant., hHowever, the specific indirect effect of work volition and career adaptability was not significant. Further analyses showed a gender difference in the paths. Specifically, economic constraint was significantly negatively associated with work volition, and work volition predicted decent work only for women, but not for men. Moreover, economic constraint was significantly inversely associated with career adaptability, and career adaptability positively predicted decent work only for men, but not for women. Work volition mediated between economic constraints and decent work for women, while career adaptability had a mediating effect for men. It suggests that career resources for obtaining a decent work may be distinctive by genderdifferent groups.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.204-205
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• 2015

Demands for free-form buildings are on the rise, but such building designs require most cost and longer construction schedule, with less constructability due to challenges in construction member production and installation. FCP production technology has been developed using CNC machine in a bid to resolve the difficulties of member production. Exterior finishing panels of free-form building design must be divided in size and shape that can be produced by CNC machine. To solve this problem, constraints of CNC machine and correlations between CNC machine and panel need to be reviewed. Thus, the purpose of this study is to analyze decision factors on free-form concrete panel sizes produced by CNC machines. Through this study, FCP size can be optimized, which in turn can lead to improved FCP productivity and aesthetical quality of free-form building designs determined by the pattern of exterior finishing panels. CNC machine-enabled free-form concrete panel production technology will apply on site in the future, which will not only maximize the economic benefits of the technology but also support shorter construction schedule and better constructability.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.7
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• pp.613-623
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• 2002

Ascent trajectory optimization and explicit guidance problems for a satellite launch vehicle with yaw maneuver in a 3-dimension are considered. The trajectory optimization problem with boundary conditions is formulated as a nonlinear programming problem by parameterizing the inertial pitch and yaw attitude control variables, and is solved by using the SQP algorithm. The flight constraints such as gravity-turn and range safety conditions are imposed. An explicit inertial guidance algorithm in the exoatmospheric phase is also presented. The guidance algorithm provides steering command and time-to-go value directly using the current states of the vehicle and the desired orbit insertion conditions. The liquid propelled Delta 2910 launch vehicle is used as a numerical model.