• The Journal of Korea Robotics Society
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• v.13 no.2
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• pp.142-149
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• 2018

$RRT^*$ (Rapidly exploring Random $Tree^*$) based algorithms are widely used for path planning. Informed $RRT^*$ uses $RRT^*$ for generating an initial path and optimizes the path by limiting sampling regions to the area around the initial path. $RRT^*$ algorithms have several limitations such as slow convergence speed, large memory requirements, and difficulties in finding paths when narrow aisles or doors exist. In this paper, we propose an algorithm to deal with these problems. The proposed algorithm applies the image skeletonization to the gridmap image for generating an initial path. Because this initial path is close to the optimal cost path even in the complex environments, the cost can converge to the optimum more quickly in the proposed algorithm than in the conventional Informed $RRT^*$. Also, we can reduce the number of nodes and memory requirement. The performance of the proposed algorithm is verified by comparison with the conventional Informed $RRT^*$ and Informed $RRT^*$ using initial path generated by $A^*$.

• IEMEK Journal of Embedded Systems and Applications
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• v.16 no.3
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• pp.107-111
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• 2021

A 3D point cloud map is an essential elements in various fields, including precise autonomous navigation system. However, generating a 3D point cloud map using a single sensor has limitations due to the price of expensive sensor. In order to solve this problem, we propose a precise 3D mapping system using low-cost sensor fusion. Generating a point cloud map requires the process of estimating the current position and attitude, and describing the surrounding environment. In this paper, we utilized a commercial visual-inertial odometry sensor to estimate the current position and attitude states. Based on the state value, the 2D LiDAR measurement values describe the surrounding environment to create a point cloud map. To analyze the performance of the proposed algorithm, we compared the performance of the proposed algorithm and the 3D LiDAR-based SLAM (simultaneous localization and mapping) algorithm. As a result, it was confirmed that a precise 3D point cloud map can be generated with the low-cost sensor fusion system proposed in this paper.

• International Journal of Advanced Culture Technology
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• v.10 no.4
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• pp.518-528
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• 2022

Virtual Reality (VR) has been widely used in various applications to generate realistic virtual environments. A sense of immersion can be increased by providing additional stimuli such as tactile sensation to VR contents. However, it is still challenging to provide a realistic feel for the wind blowing over the whole body by smoothly controlling the airflow. To address this issue, we employ a household electric fan as a wind generating device to provide users with wind experience in VR environments. The wind generating device targets the whole body to mimic the wind we feel outside in our daily life. To do so, we present a low-cost method to smoothly control household fan speed using an Arduino microcontroller. Here, we use the Sinusoidal Pulse Width Modulation (SPWM) technique to generate the sinusoidal voltage required to drive the fan motor. Our experimental results show how Variable Voltage Variable Frequency (VVVF) is implemented at a low cost using our method for household fan speed control. The results can be applied to various VR applications to enhance the sense of immersion by providing users with realistic wind.

• Environmental and Resource Economics Review
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• v.20 no.4
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• pp.761-796
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• 2011

The purpose of this paper is to derive fuel mix of electricity generating system with the lowest cost considering energy security and climate change mitigations as the target of energy policy. Energy Security Price Index(ESPI), based on the measure of market concentration in fossil fuel market and political risk of exporting countries, is chosen to assess the level of energy security. The methodology of Energy Conservation Supply Curve(CSC) is applied to fuel mix to meet the carbon emission mitigation through increasing the alternatives participation and introduction of new technologies. These also represent an improvement on the level of energy security, having the complementarity between two objectives. The alternative measure for improving energy security is exploration and production(E&P) of fossil fuel for energy sufficiency. Fuel mix of electricity generating system to achieve certain objectives in 2020 can be derived with the lowest cost considering energy security and carbon emission mitigations.

• New & Renewable Energy
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• v.7 no.4
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• pp.10-17
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• 2011

Recently, electricity industry is facing high market uncertainty which has ever had and which increase risks in power market. In this study, we analyze risk factors such as discount rates, initial investment (overnight cost), plant factor, fuel cost, carbon price, etc, for the perspective of investor. For the analysis of risk factors, we used LCOE method. The results of this study show that renewable energy is more affected by plant factor and overnight cost than other risk factors. First, Renewable energy has higher proportion of overnight cost in the total investment than that of other technologies. Second, renewable energy is free of fuel cost and carbon price so plant factor is the most important factor, in other words, competitiveness of renewable energy depends on plant factor. Furthermore, we conducted economic feasibility of wind power and PV in domestic case study. The minimum requirement condition to get profitability is that plant factor 15% and overnight cost \6,000,000/kW and 26%, \2,200,000/kW for PV and Wind Power, respectively.

• Journal of Communications and Networks
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• v.17 no.6
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• pp.582-591
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• 2015

A massive distributed storage system is the foundation for big data operations. Access latency performance is a key metric in distributed storage systems since it greatly impacts user experience while existing codes mainly focus on improving performance such as storage overhead and repair cost. By generating parity nodes from parity nodes, in this paper we design new XOR-based erasure codes hierarchical tree structure code (HTSC) and high failure tolerant HTSC (FH HTSC) to reduce access latency in distributed storage systems. By comparing with other popular and representative codes, we show that, under the same repair cost, HTSC and FH HTSC codes can reduce access latency while maintaining favorable performance in other metrics. In particular, under the same repair cost, FH HTSC can achieve lower access latency, higher or equal failure tolerance and lower computation cost compared with the representative codes while enjoying similar storage overhead. Accordingly, FH HTSC is a superior choice for applications requiring low access latency and outstanding failure tolerance capability at the same time.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.7
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• pp.181-193
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• 2021

Thailand's tourism industry contributed to over three trillion baht in 2019. Tourist attractions across Thailand attract tourists around the world with their natural scenery, lifestyles, and cultures, especially in those called "second-tier cities". Community enterprises play a vital role to drive the tourism industry to local areas. However, most community enterprises lack professional accounting knowledge. This research aims to provide guidelines for ecotourism cost management of community enterprises in Thailand. Participatory Action Research (PAR) was employed to investigate the current circumstances of the Banlaem enterprise by using in-depth interviews to identify problems in cost management. Then, the focus and small group meetings were organized to monitor and evaluate solutions. The results reveal that the cost of VIP-Two Days trip was generating the highest net profit and margin, followed by VIP-One Day trip, but net losses were detected on the Students-One Day trip, even though income was greater than the variable costs, revenues didn't cover fixed costs. Thus, accounting knowledge could be a major concern of these enterprises. They should systematically record revenues and expenses, set appropriate labor costs, reduce production costs by using seasonal seafood and make use of vegetables in their gardens, and price products according to their production costs.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1999.06a
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• pp.119-124
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• 1999

This paper proposes an evolutionary model for automatically generating artificial creatures of various shapes and colors according to insect ecology. This model offers a novel way to naturally evolve the shapes and colors of artificial creatures. The evolutionary model used in our research is based on Genetic Algorithms (GA). In this paper, artificial Computer Graphics(CG) creatures develop into various shapes and colors according to the evolutionary model. Later, they can be used as CG animated characters. This model also solves the problem of reducing the time and labor cost for mass production of various characters. It could be used in such areas as the cavalry battle scene in Disney's animation, “Mulan”. Our approach has two steps. At first, artificial creatures move according to information gathered form the five senses. This information is also used for generating the shapes of the five sense organs[1]. Then, based on the GA, evolutionary mode[2], we prepare prototype creatures, which evolve into various shapes and different colors in alternating generations. Finally, our evolutionary model successfully generates various character shapes and colors automatically.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.8
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• pp.1467-1472
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• 2011

This paper presents an optimal operation of microgrid systems and considering a tie-lines capacities that concerned each grid. The microgrid system consists of a wind turbine, a diesel generator, and a fuel cell. An one day load profile and wind resource for wind turbine generator were used for the study. For the grid interconnection, tie-line capacities were applied as constraints. The capacity constraints of tie-lines in production cost analysis are very important issues in the operation and planning of microgrid. In optimization, the Harmony Search (HS) algorithm is used for solving the problem of microgrid system operation which a various generation resources are available to meet the customer load demand with minimum operating cost. The application of HS algorithm to optimal operation of microgrid proves its effectiveness to determine optimally the generating resources without any differences of load mismatch.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.7
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• pp.1287-1293
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• 2009

This paper presents an application of Harmony Search (HM) meta-heuristic optimization algorithm for optimal operation of microgrid system. The microgrid system considered in this paper consists of a wind turbine, a diesel generator, and a fuel cell. An one day load profile which divided 20 minute data and wind resource for wind turbine generator were used for the study. In optimization, the HS algorithm is used for solving the problem of microgrid system operation which a various generation resources are available to meet the customer load demand with minimum operating cost. The application of HS algorithm to optimal operation of microgrid proves its effectiveness to determine optimally the generating resources without any differences of load mismatch and having its nature of fast convergency time as compared to other optimization method.