• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.15-26
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• 2014

This paper proposes a Modified Particle Swarm Optimization with Time Varying Acceleration Coefficients (MPSO-TVAC) for solving economic load dispatch (ELD) problem. Due to prohibited operating zones (POZ) and ramp rate limits of the practical generators, the ELD problems become nonlinear and nonconvex optimization problem. Furthermore, the ELD problem may be more complicated if transmission losses are considered. Particle swarm optimization (PSO) is one of the famous heuristic methods for solving nonconvex problems. However, this method may suffer to trap at local minima especially for multimodal problem. To improve the solution quality and robustness of PSO algorithm, a new best neighbour particle called 'rbest' is proposed. The rbest provides extra information for each particle that is randomly selected from other best particles in order to diversify the movement of particle and avoid premature convergence. The effectiveness of MPSO-TVAC algorithm is tested on different power systems with POZ, ramp-rate limits and transmission loss constraints. To validate the performances of the proposed algorithm, comparative studies have been carried out in terms of convergence characteristic, solution quality, computation time and robustness. Simulation results found that the proposed MPSO-TVAC algorithm has good solution quality and more robust than other methods reported in previous work.

• Journal of Electrical Engineering and Technology
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• v.4 no.4
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• pp.457-466
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• 2009

This paper presents efficient parallel genetic algorithm (EPGA) based decomposed network for optimal power flow with various kinds of objective functions such as those including prohibited zones, multiple fuels, and multiple areas. Two coordinated sub problems are proposed: the first sub problem is an active power dispatch (APD) based parallel GA; a global database generated containing the best partitioned network: the second subproblem is an optimal setting of control variables such as generators voltages, tap position of tap changing transformers, and the dynamic reactive power of SVC Controllers installed at a critical buses. The proposed approach tested on IEEE 6-bus, IEEE 30-bus and to 15 generating units and compared with global optimization methods (GA, DE, FGA, PSO, MDE, ICA-PSO). The results show that the proposed approach can converge to the near solution and obtain a competitive solution with a reasonable time.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.80-89
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• 2013

This paper presents an efficient approach for solving economic dispatch (ED) problems with nonconvex cost functions using a 'Mean-Variance Optimization (MVO)' algorithm with Kuhn-Tucker condition and swap process. The aim of the ED problem, one of the most important activities in power system operation and planning, is to determine the optimal combination of power outputs of all generating units so as to meet the required load demand at minimum operating cost while satisfying system equality and inequality constraints. This paper applies Kuhn-Tucker condition and swap process to a MVO algorithm to improve a global minimum searching capability. The proposed MVO is applied to three different nonconvex ED problems with valve-point effects, prohibited operating zones, transmission network losses, and multi-fuels with valve-point effects. Additionally, it is applied to the large-scale power system of Korea. The results are compared with those of the state-of-the-art methods as well.

• Journal of the Korea Convergence Society
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• v.12 no.2
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• pp.201-213
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• 2021

Recently, personal mobility has been spreading and using increasing, but the pedestrian environment is getting worse and accidents are also rapidly increasing. Therefore, this study conducts a status survey related to the elements of pedestrian disturbances in personal mobility and identifies the problems. The following measures are presented to improve the pedestrian environment for the mobility handicapped through expert opinion surveys. The movement of individual mobility means in the walking space is prohibited, and the speed limit shall be stipulated to enable the mobility handicapped to walk safely and conveniently. Parking spaces will have to create obstacle zones in the parking area next to the roadway or at the border of sidewalks and roads, and regulations are needed to collect illegally parked vehicles. It is necessary to switch from the existing automobile-oriented road to the road structure considering the use of low and medium-speed vehicles.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.68-74
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• 2007

Critical Chain Project Management(CCPM) is a new project management system paradigm which maintains the advantages of PERT/CPM and improves the shortcomings of it. In CCPM the task durations are determined as 50% time estimates, ie average time discarding the their contingency. CCPM determines the critical chain the constraint of a projects considering the logical precedence relationship and resource conflict resolution. Project buffer is located at the end of critical chain to absorb the variations of critical chain. The size of project buffer is usually calculated as the half of the sum of critical chain length. Also feeding buffer is inserted after each non-critical chain which feeding into the critical chain to prevent the time delay of critical chain from uncertainties of non-critical chains. Resource buffer can be utilized to improve the availability of resources of critical chain. Buffer management is a project execution and control mechanism. Buffers are classified into 3 zones. They are OK zone, Watch and Plan zone and Expediting zone. If the project status is within Watch and Plan zone, contingency plan is established. And if it changes into Expediting zone, the preplanned contingency plan are executed to recover the time delay. In CCPM the workers are asked to work with relay runner work mechanism that they work fast if possible and report their completion to project manager for the succeeding task to start as soon as possible. The task durations are not considered as the promised time schedule. The multi-tasking is prohibited.

• Journal of the Korean Institute of Landscape Architecture
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• v.50 no.1
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• pp.1-19
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• 2022

The Geumgang Pine (Pinus densiflora) Forest in Sogwang-ri, Uljin has traditionally been a pine tree protection area (prohibited forest) for timber production purposes, and is now designated and managed as a protected area for forest genetic resource conservation by the Korea Forest Service. This study, we analyzed topographical characteristics, existing vegetation, tree age, and plant community structure, and proposed a sustainable management method for the Geumgang Pine (Pinus densiflora) Forest in Sogwang-ri, Uljin for timber havesting purposes. The topographical characteristics of the target area were 36.7% ridges and 38.7% valleys; the ratio of ridges to valleys was similar, and the slopes formed 24.7% of the total area. The types of pine forest communities are divided into six types based on the progress of pine forest renewal, the competition with other species such as deciduous broadleaf trees, and the formation of layered structures. It has been confirmed that the age of the large-diameter pine trees (40~60cm in diameter) is approximately 60~70 years, which is relatively low. As a result of the analysis of the relative importance percentage and layered structure, differences depended on the progress of the pine forest renewal project, and not only the maintenance of the pine forest, but also the creation of a secondary growth forest, the density adjustment of pine trees, and the active management of competitive trees. The average basal area by the community was 12,642.1~25,424.4cm² for the tree layer and 1.8~1,956.5cm² for the low tree layer based on a quadrat of 400m². The difference in the basal area appeared to depend on the size and number of trees forming the tree layer and the degree of pine forest renewal (the degree of time elapsed after thinning pine trees). The average number of species that appeared in each community was 8.7-20.3; there were many species located in valleys, and the type competes with deciduous broadleaf trees due to the lack of management. The diversity of species ranged from 0.6915-1.0942, and was evaluated as low compared to pine communities in central temperate zones. In this paper, we determined the management goals of Geumgang Pine (Pinus densiflora) Forest in Sogwang-ri, Uljin to produce timber with high economic value, and suggested efficient vegetation management for continuous afforestation, the establishment of a timber production system, and improvement of wood production as a management direction.

• The Korean Journal of Air & Space Law and Policy
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• v.32 no.2
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• pp.189-217
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• 2017

Declaration of Air Defense and Identification Zones started with the United States in 1950, which was followed by declaration of KADIZ by the Republic of Korea in 1951. Initial ADIZ were solely linked with air defense missions, but their roles have changed as nations around the globe manifested a tendency to expand their influence over maritime resources and rights. In particular, China declared ADIZ over the East China Sea in October 2013 and forced all passing aircraft to submit flight plan to ATC or military authority, saying failure of submission will be followed by armed engagement. China announced it would declare another zone over the South China Sea despite the ongoing conflict in the area, clearly showing ADIZ's direct connection with territorial claim and EEZ and that it serves as a zone within which a nation can execute its rights. The expanded KADIZ, which was expanded in Dec 15, 2013 in response to Chinese actions, overlaps with the Chinese ADIZ over the East China Sea and the Japanese ADIZ. The overlapping zone is an airspace over waters where not only the Republic of Korea but also of China and Japan argue to be covering their continental shelf and EEZ. Military conventions were signed to prevent contingencies among the neighboring nations while conducting identifications in KADIZ, including the overlapping zone. If such military conventions and practice of air defense identification continue to be respected among states, it is under the process of turning into a regional customary law, although ADIZ is not yet recognized by international law or customary law. Moreover, identification within ADIZ is carried out by military authorities of states, and misguided customary procedures may cause serious negative consequences for national security since it may negatively impact neighboring countries in marking the maritime border, which calls for formulation of operation rules that account for other state activities and military talks among regional stake holders. Legal frameworks need to be in place to guarantee freedom of flights over international seas which UN Maritime Law protects, and laws regarding military aircraft operation need to be supplemented to not make it a requirement to submit flight plan if the aircraft does not invade sovereign airspace. Organizational instructions that require approval of Chairman of Joint Chiefs of Staff for entrance and exit of ADIZ for military aircraft need to be amended to change the authority to Minister of National Defense or be promoted to a law to be applicable for commercial aircraft. Moreover, in regards to operation and management of ADIZ, transfer of authority should be prohibited to account for its evolution into a regional customary law in South East Asia. In particular, since ADIZ is set over EEZ, military conventions that yield authority related to national security should never be condoned. Among Korea, China, Japan and Russia, there are military conventions that discuss operation and management of ADIZ in place or under negotiation, meaning that ADIZ is becoming a regional customary law in North East Asia region.