• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.342-344
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• 2002

This paper presents a new strategy to find starting points for placing optimally Phasor Measurement Units(PMUs). The performance of the starting point, initial placement set of PMUs, affect critically the computational burden and/or time, because the Optimal PMU Placement (OPP) problem is formulated the combinatorial optimization. By analyzing the properties of OPP solutions on IEEE sample systems in detail, a new strategy for initial PMU placement, in this paper, is proposed. To verify the performance of the suggested strategy, the comparison with the existing strategy and the new one, on IEEE sample systems. is performed. By using the new strategy, the numbers of search spaces to solve the OPP problem is drastically decreased.

• Korean Journal of Occupational Health Nursing
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• v.32 no.4
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• pp.141-151
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• 2023

Purpose: This study explored caregivers' support needs to relieve their physical burden while working in long-term care facilities. Methods: Participants were 12 caregivers with more than 10 years of experience working at six long-term care facilities in Gwangju, South Korea. Data were collected through individual interviews conducted between June and July 2023. The results were analyzed using qualitative content analysis. Results: Of the four sub-categories and 13 codes, two categories emerged: "need for welfare medical devices" and "need for improved working conditions." Conclusion: Caregivers working in long-term care facilities require support in deploying and utilizing welfare medical devices to reduce their physical burden, along with improving staffing standards and ensuring they receive the proper amount of days off. Therefore, it is necessary to mandate the provision of a certain level of welfare medical devices to ease the physical burden on caregivers and improve the standards for the placement of caregivers in long-term care facilities.

• Smart Structures and Systems
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• v.31 no.3
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• pp.247-257
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• 2023

In structural health monitoring of large-scale structures, optimal sensor placement plays an important role because of the high cost of sensors and their supporting instruments, as well as the burden of data transmission and storage. In this study, a vibration sensor placement algorithm based on deep reinforcement learning (DRL) is proposed, which can effectively solve non-convex, high-dimensional, and discrete combinatorial sensor placement optimization problems. An objective function is constructed to estimate the quality of a specific vibration sensor placement scheme according to the modal assurance criterion (MAC). Using this objective function, a DRL-based algorithm is presented to determine the optimal vibration sensor placement scheme. Subsequently, we transform the sensor optimal placement process into a Markov decision process and employ a DRL-based optimization algorithm to maximize the objective function for optimal sensor placement. To illustrate the applicability of the proposed method, two examples are presented: a 10-story braced frame and a sea-crossing bridge model. A comparison study is also performed with a genetic algorithm and particle swarm algorithm. The proposed DRL-based algorithm can effectively solve the discrete combinatorial optimization problem for vibration sensor placements and can produce superior performance compared with the other two existing methods.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.7
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• pp.313-322
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• 2000

This paper presents optimal placement of minimal set of Phasor Measurement Units (PMU's) and observability analysis of the network with PMU's. In order to find a observable system, a symbolic method which directly assigns an appropriate symbol for measurement or pseudo-measurement to every entry of node-branch incidence matrix is proposed. It is much simpler and easier to analyze the observability of the network with PMU's than the conventional ones. For the optimal PMU placement problem, two approaches which are based on a modified Simulated-Annealing (SA) method and a Direct Combination method are proposed. Some case studies with IEEE sample system are made to show the performance of the proposed methods are almost alike and more effective than the conventional simulated-annealing method. It is also shown that the Direct Combination method is more effective than the modified simulated-annealing one in the sense of computation burden. The results of this study showed also that the accuracy of power system estimation and system observability can be improved the proposed PMU placements.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.4
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• pp.364-370
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• 1990

In this paper, we propose a self-tuning PID controller for unknown systems with time-varying delay. Using pole placement equations, we derive the controller that can be extended to the multi-step time delay case. The time-varying delays are estimated by a prediction error delay method using multiple predictors. Since the order of the estimation vector is not increased, the persistant exciting condition of control input is alleviated. Since the least square method gives biased parameter estimates for colored noise cases, the recursive instrumental variable method is used to estimate system parameters. The computational burden of the proposed method is less than the conventional adaptive methods. Computer simulations are performed to illustrate the efficiency of the proposed method.

• Journal of Advanced Technology Convergence
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• v.3 no.3
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• pp.47-56
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• 2024

This study analyzes the field practicum experiences of adult learners in social welfare and discusses areas for improvement. The field practicum is an essential process and training course for becoming a social worker. Through the practicum experience, learners gain a valuable opportunity to apply theoretical knowledge in real-world settings and understand their future roles as prospective social workers. However, if the field practicum does not adequately reflect the characteristics of adult learners, it may be difficult to ensure a successful practicum experience. For adult learners to successfully complete their social welfare practicum, integrated and consistent support from both the university and practicum institutions is essential. In particular, the challenges adult learners may face, such as difficulties in time management, psychological stress, and the gap between theory and practice, must be addressed. Most importantly, thorough preparation before the practicum is necessary to ensure success.

• Journal of the Korean Institute of Educational Facilities
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• v.26 no.2
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• pp.11-18
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• 2019

There is a growing demand for public kindergartens due to the problem of private kindergartens. However, when the kindergarten is built in the residential land development area, the cost of purchasing the land increases, and the overall project cost is increasing. This situation puts a lot of burden on educational finances. Therefore, to reduce the cost of establishing a kindergarten, it is required to revise related laws including act on the special cases concerning the procurement, etc. of school sites. The purpose of this study is to propose the revised laws to expand public kindergartens. In this study, the present situation of infants and kindergartens was analyzed through policy data and statistics. And the analysis of the investment evaluation data also analyzed the problems in establishing kindergarten. In addition, we conducted surveys and FGI analyzes on school sites and kindergarten related laws and regulations. Finally, this study aims to find a way to amend related acts of urban and architectural Planning for Invigoration of Public kindergarten establishment by analysis data.

• Journal of Power Electronics
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• v.19 no.4
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• pp.1000-1010
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• 2019

The use of internal-model-based linear controller, such as resonant controller, is a well-established technique for the current control of grid-connected systems. Attractive properties for resonant controllers include their two-sequence tracking ability, the simple control structure, and the reduced computational burden. However, in the case of continuous-designed resonant controller, the transient performance is inevitably degraded at a low switching frequency. Moreover, available design methods for resonant controller is not able to realize the direct design of transient performances, and the anticipated transient performance is mainly achieved through trial and error. To address these problems, the zero-order-hold (ZOH) characteristic and inherent time delay in digital control systems are considered comprehensively in the design, and a corresponding hold-equivalent discrete model of the grid-connected converter is then established. The relationship between the placement of closed-loop poles and the corresponding transient performance is comprehensively investigated to realize the direct mapping relationship between the control gain and the transient response time. For the benefit of automatic tuning and real-time adaption, analytical expressions for controller gains are derived in detail using the required transient response time and system parameters. Simulation and experimental results demonstrate the validity of the proposed method.

• The Journal of Korean Academy of Prosthodontics
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• v.53 no.1
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• pp.58-65
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• 2015

For the rehabilitation of fully edentulous patients, implant-supported removable partial dentures can be considered as one of the treatment options with complete dentures or implant-supported overdentures. If removable partial dentures are used in combination with a small number of implants placed in strategically important positions, it can offer additional stability, retention and support through implants and reduce a burden of surgical procedures compared with fixed implant-supported prostheses with extensive implant placement. Moreover, the economical benefit can be expected as well. The purpose of this case report is to present a treatment in which an implant-supported removable partial denture was fabricated considering residual alveolar bone status and demands after teeth loss in a patient who had been using a distal extension removable partial denture for a long period of time. In anterior area, fixed prostheses were fabricated with implant placement and in posterior area, short implants provide only support for the removable partial denture. In addition, denture base and clasp were made of thermoplastic acrylic resin. Finally, functionally and aesthetically satisfying treatment results can be achieved.

• Journal of Practical Engineering Education
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• v.12 no.2
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• pp.309-319
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• 2020

Billiards is a fun and popular sport, but both route planning and cueing prevent beginners from becoming skillful. A beginner in billiards requires constant concentration and training to reach the right level, but without the right motivating factor, it is easy to lose interests. This study aims to induce interest in billiards and accelerate learning by utilizing billiard path prediction and visualization on a highly immersive augmented reality platform that combines a stereo camera and a VR headset. For implementation, the placement of billiard balls is recognized through the OpenCV image processing program, and physics simulation, path search, and visualization are performed in Unity Engine. As a result, accurate path prediction can be achieved. This made it possible for beginners to reduce the psychological burden of planning the path, focus only on accurate cueing, and gradually increase their billiard proficiency by getting used to the path suggested by the algorithm for a long time. We confirm that the proposed AR billiards is remarkably effective as a learning assistant tool.