• KIEE International Transactions on Power Engineering
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• v.4A no.2
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• pp.69-72
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• 2004

Nowadays, one of the serious problems in the KEPCO system is a much higher fault current than the SCC (Short Circuit Capacity) of the circuit breaker. Since superconductivity technology has become more developed, the HTS-FCL (High Temperature Superconductor-Fault Current Limiter) may become an attractive alternative to solving the fault current problem. In order to achieve the best performance, the parameters of HTS-FCL should be designed optimally. Under this setting, this paper presents the optimal design method of parameters for resistive type HTS-FCL using the Monte Carlo technique.

• Bulletin of the Society of Naval Architects of Korea
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• v.21 no.2
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• pp.1-7
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• 1984

This paper is concerned with an optimum design study of containerships in preliminary stage by applying economic criteria. The Net Present Value Index (NPVI) and the Required Freight Rate(RFR) are used as measures of merit. Hooke & Jeeves direct search method and External Penalty Function method of Sequential Unconstrained Minimization Techniques(SUMT) are used for solving constrained nonlinear optimization problem. Sensitivity analysis is carried out to investigate the effect on the optimum solution due to change of values in some parameters such as crane capacity, load factor, oil price, ship speed and the ratio between loaded FEU and TEU.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.5
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• pp.661-666
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• 2015

This paper proposes a method for solving running cost problem by minimizing switching reactive power compensation devices. An objective function was modeled by calculating the weighting value of cost, and a solution was derived using ILP. This paper suggests optimal coordinative control method between FACTS, Shunt Reactors, Capacitors and OLTC. Therefore, it is valuable for decision maker in determining order and capacity of devices which gaining a voltage stabilization. As a result, the objectives of voltage stabilization and cost minimization were achieved simultaneously. This realizes the economic efficiency of the system. We start by showing how to solve systems of linear equations using the language of pivots and tableaus. The effectiveness of this technique is demonstrated in modified PSS/E MIGUM 45 bus system. The simulation results show the effectiveness of this algorithm by comparing the outcome withseveral established methods.

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.675-685
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• 2013

Generation capacities and transmission line constraints in a competitive electricity market make it troublesome to compute Nash Equilibrium (NE) for analyzing participants' strategic generation quantities. The NE can cause a mixed strategy NE rather than a pure strategy NE resulting in a more complicated computation of NE, especially in a multiplayer game. A two-level hierarchical optimization problem is used to model competition among multiple participants. There are difficulties in using a mathematical programming approach to solve a mixed strategy NE. This paper presents heuristics applied to the mathematical programming method for dealing with the constraints on generation capacities and transmission line flows. A new formulation based on the heuristics is provided with a set of linear and nonlinear equations, and an algorithm is suggested for using the heuristics and the newly-formulated equations.

• Geomechanics and Engineering
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• v.24 no.3
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• pp.227-235
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• 2021

A criterion and a method for solving a problem on the prevention of mine working fracture under the action of tectonic and gravitational forces are offered. Based on minimal criterion, theoretical analysis of the definition of the optimal shape of working in the rock mass weakened by arbitrarily located rectilinear cracks was carried out. A closed system of algebraic equations allowing to minimize the stress state and stress intensity factors depending on mechanical and geometrical characteristics of the rock, is constructed. The relation between the shape of the working and the stress intensity factors and also location and sizes of the cracks is obtained. The found optimal shape of working increases load-bearing capacity of the rock.

• Journal of Environmental Health Sciences
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• v.37 no.5
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• pp.335-341
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• 2011

The Goseong abandoned mine accident was a typical case of long-term sequela resulting from environmental disruption during the rapid economic development of Korea. While the final conclusion of epidemiologic investigation was that residents surrounding the abandoned mine were simply exposed to cadmium from the abandoned mine without any patient contracting 'itai-itai' disease, not only did residents around the abandoned mine suffer enormous psychological and economic damage, but people in neighbouring communities did as well when the entire area was stigmatized as an contaminated area. Environmental civic groups and the government worked together to solve the problem by forming a joint committee which held the right of decision in any matter to be determined. By inviting all the stakeholders to participate in the joint committee, a transparent investigation was guaranteed and the results of investigation and recommendations to solve the problem were accepted by all involved. Even though the environmental health division in Ministry of Environment has developed considerably and built up a capacity to deal with environmental accidents, the process which was adopted to solving the Goseong abandoned mine accident can be useful to settle environmental health issues with severe conflicts among stakeholders.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1540-1546
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• 2014

In order to resolve coverage hole problems caused by indoor-BS (IBS) faults, we propose a new frame structure and practical algorithm based on optimization technique. Our main contributions can be described as follows: 1) a frame structure with healing channels for solving abnormal IBS faults; and 2) an efficient heuristic resource allocation algorithm with fixed IBS selection to reduce the complexity for the optimization problem. Through intensive simulations, we evaluate the performance excellency of our proposed algorithm with respect to average cell capacity and user fairness compared with conventional algorithms.

• Journal of Communications and Networks
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• v.12 no.3
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• pp.275-284
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• 2010

The current multihome-aware protocols (like stream control transmission protocol (SCTP) or parallel TCP for concurrent multipath data transfer (CMT) are not designed for high-capacity and large-latency networks; they often have performance problems transferring large data files over shared long-distance wide area networks. It has been shown that SCTP-CMT is more sensitive to receive buffer (rbuf) constraints, and this rbuf-blocking problem causes considerable throughput loss when multiple paths are used simultaneously. In this research paper, we demonstrate the weakness of SCTP-CMT rbuf constraints, and we then identify that rbuf-blocking problem in SCTP multihoming is mostly due to its loss-based nature for detecting network congestion. We present a simulation-based performance comparison of FAST TCP versus SCTP in high-speed networks for solving a number of throughput issues. This work proposes an end-to-end transport layer protocol (i.e., FAST TCP multihoming as a reliable, delaybased, multihome-aware, and selective ACK-based transport protocol), which can transfer data between a multihomed source and destination hosts through multiple paths simultaneously. Through extensive ns-2 simulations, we show that FAST TCP multihoming achieves the desired goals under a variety of network conditions. The experimental results and survey presented in this research also provide an insight on design decisions for the future high-speed multihomed transport layer protocols.

• Korean Journal of Materials Research
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• v.30 no.11
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• pp.636-640
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• 2020

Due to the serious air pollution problem, interest in eco-friendly vehicles is increasing. Solving the problem of pollution will necessitate the securing of high energy storage technology for batteries, the driving force of eco-friendly vehicles. The reason for the continuing interest in the transition metal oxide LiMO₂ as a cathode material with a layered structure is that lithium ions reveal high mobility in two-dimensional space. Therefore, it is important to investigate the effective intercalation and deintercalation pathways of Li⁺, which affect battery capacity, to understand the internal structure of the cathode particle and its effect on the electrochemical performance. In this study, for the cathode material, high nickel Ni_0.8Co_0.1Mn_0.1(OH)₂ precursor is synthesized by controlling the ammonia concentration. Thereafter, the shape of the primary particles of the precursor is investigated through SEM analysis; X-ray diffraction analysis is also performed. The electrochemical properties of LiNi_0.8Co_0.1Mn_0.1O₂ are evaluated after heat treatment.

• Journal of the Korean Chemical Society
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• v.63 no.6
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• pp.486-504
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• 2019

This study analyzed achievement standards in the 2015 Science Education Standards as well as activities and assessment items in the Integrated Science, Chemistry I, and Chemistry II textbooks using science core competencies and subcomponents. All five scientific core competencies, in order of scientific thinking capacity, scientific inquiry capacity, scientific communication capacity, scientific problem solving capacity, and scientific participation and lifelong learning capacity, were included in the achievement standards of Integrated Science. Scientific thinking capacity, scientific inquiry capacity, and scientific communication capacity were included in the achievement standards of Chemistry I. The achievement standards of Chemistry II only included scientific thinking capacity. All five scientific core competencies were involved in activities of Integrated Science, Chemistry I, and Chemistry II textbooks and the highest propotion was scientific thinking capacity and scientific inquiry capacity. All five scientific core competencies were involved in assessment items of Integrated Science, Chemistry I, and Chemistry II textbooks and the highest proportion was scientific thinking capacity.