• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1341-1343
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• 1996

This paper presents a design method for an on-line adaptive neural networks based intelligent controller. The proposed neural controller, assuming PID controller is initially presented, learns the equivalent behaviors of the existing PID controller initially and switches to take over the PID control system. Then, it executes on-line adaptation via evaluating its performance and minimizing user defined cost function constantly so that the optimal control can be achieved. The PID controller and the proposed neural controller are investigated and compared in computer simulation.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.789-795
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• 2014

In a demand response (DR) market run by independent system operators (ISOs), load aggregators are important market participants who aggregate small retail customers through various DR programs. A load aggregator can minimize the allocation cost by efficiently allocating its demand response resources (DRRs) considering retail customers' characteristics. However, the uncertain response behaviors of retail customers can influence the allocation strategy of its DRRs, increasing the economic risk of DRR allocation. This paper presents a risk-based DRR allocation method for the load aggregator that takes into account not only the physical characteristics of retail customers but also the risk due to the associated response uncertainties. In the paper, a conditional value-at-risk (CVaR) is applied to deal with the risk due to response uncertainties. Numerical results are presented to illustrate the effectiveness of the proposed method.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.485-486
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• 2007

In the deregulated power market, suppliers, consumers and transmission companies try to maximize their profits by economical behaviors. In particular, generating companies like to sell more electricity for the revenue. Their situations will lead to various power system planning as optimal solutions for each supplier. In this paper, fundamental approaches of optimal power system planning under market positions of generating company are presented. The profit-maximizing approaches are modeled mathematically. By this analysis, each optimal planning is proved in risk of cost and monetary risk will be the economical signal for participants.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.766-771
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• 2001

The package used to transport radioactive materials, which is called by cask, must be safe under normal and hypothetical accident conditions. These requirements for the cask design must be verified through test or finite element analysis. Since the cost for FE analysis is less than one for test. the verification by FE analysis is mainly used. But due to the complexity of mechanical behaviors. the results depends on how users apply the codes and it can cause severe errors during analysis. In this paper, finite element analysis is carried out for the 9 meters free drop and the puncture condition of the hypothetical accident conditions using LS-DYNA3D and ABAQUS/Explicit. We have investigated the analyzing technique for the free drop impact test of the cask and found several vulnerable cases to errors. The analyzed results were compared with each other. We have suggested a reliable and relatively simple analysis technique for the drop test of spent nuclear fuel casks.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.295-302
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• 2003

A quantitative approach for the retrofit prioritization of bridges is developed based on the damage risk of seismic vulnerable components. In the developed approach, seismic damage risk is estimated in the probabilistic perspectives with an analytical bridge model, which can consider various phenomena found in the seismic behaviors of girder-type bridges and damage models of various vulnerable components. Based on the total cost due to failure of structural components, weighting factors are proposed. Finally, the ranking index and retrofit priority of bridges are estimated from the overall damage risk and weighting factors of bridges. As a result, the retrofit priority of four PSC girder bridges is evaluated by using the proposed approach. The vulnerable components in need of seismic retrofit are selected accordingly. From simulated results, the validity of the proposed approach is verified by comparison with the existing approach. In addition, the proposed approach is found to be appropriate in evaluating the priority of existing bridges.

• Korean Journal of Metals and Materials
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• v.46 no.8
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• pp.471-476
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• 2008

There has been a growing interest for the use of natural fibers in composite applications due to their low cost, environmental friendliness, and good mechanical properties. It was demonstrated to determine the characteristic of tensile behaviors under the variation of test temperature on sisal fiber reinforced polymer composites by RTM process. Especially, the permanganate-treated-fibers improved tensile strength by increasing the coherence with matrix. Material deformation is restricted to increment of cohesion for surface treatment of fiber and then elongation decreas.

• Journal of Power Electronics
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• v.19 no.1
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• pp.296-306
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• 2019

The flyback topology is being widely used in power adapters. The coupling capacitance between primary and secondary windings of a flyback transformer is the main path for common-mode (CM) noise conduction. A Y-cap is usually used to effectively suppress EMI noise. However, this results in problems in space, cost, and the danger of safety leakage current. In this paper, the CM noise behaviors due to the electric field coupling of the transformer windings in a flyback adapter with synchronous rectification are analyzed. Then a scheme with balance winding is proposed to reduce the CM noise with a transformer winding design that eliminates the Y-cap. The planar transformer has advantages in terms of its low profile, good heat dissipation and good stray parameter consistency. Based on the proposed scheme, with the help of a full-wave simulation tool, the key parameter influences of the transformer PCB winding design on CM noise are further analyzed. Finally, a PCB transformer for an 18W adapter is designed and tested to verify the effectiveness of the balance winding scheme.

• Structural Engineering and Mechanics
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• v.78 no.5
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• pp.529-543
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• 2021

Inevitable source-uncertainties in geometry configuration, boundary condition, and material properties may deviate the structural dynamics from its expected responses. This paper aims to examine the influence of these uncertainties on the vibration of functionally graded beams. Finite element procedures are presented for Timoshenko beams and utilized to generate reliable datasets. A prerequisite to the uncertainty quantification of the beam vibration using Monte Carlo simulation is generating large datasets, that require executing the numerical procedure many times leading to high computational cost. Utilizing artificial neural networks to model beam vibration can be a good approach. Initially, the optimal network for each beam configuration can be determined based on numerical performance and probabilistic criteria. Instead of executing thousands of times of the finite element procedure in stochastic analysis, these optimal networks serve as good alternatives to which the convergence of the Monte Carlo simulation, and the sensitivity and probabilistic vibration characteristics of each beam exposed to randomness are investigated. The simple procedure presented here is efficient to quantify the uncertainty of different stochastic behaviors of composite structures.

• International conference on construction engineering and project management
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• 2007.03a
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• pp.50-60
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• 2007

The endeavor of this paper focuses on designing a monitoring system to provide a cost-effective solution on quality assurance for construction projects. The construction site monitoring system integrates a long-range wireless network, network cameras, and a web-based collaborative platform. The users of the system could obtain the most updated status of construction sites, such as behaviors of workers, project progress, and site events anywhere with Internet connectivity. It was carefully configured in order to maintain the reliability under the reactive conditions of the construction sites. This paper reports the architecture of the monitoring system and reviews the related technologies. The system has been implemented and tested on a construction site and promising results were obtained.

• Journal of Nutrition and Health
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• v.52 no.3
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• pp.297-309
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• 2019

Purpose: This study examined the relationship among the use of food-related content (FRC), dietary behaviors, and dietary self-efficacy to demonstrate the need for nutrition education to help adolescents build healthy eating habits and provide evidence for developing nutrition education programs for adolescents. Methods: Three hundred and eighty-one high school students in Seoul and Gyeonggi areas participated in the study. The subjects were divided into three groups (low, medium, and high) according to the level of use of the FRC, and their general characteristics, dietary behaviors, and dietary self-efficacy were analyzed. Correlation analysis was performed between FRC usage, dietary behaviors, and dietary self-efficacy, and the mediating effects of dietary self-efficacy on the relationship between the level of the use of FRC and dietary behaviors were estimated. Results: A higher level of FRC usage was associated with an increased daily cost of eating out and snacking, but no difference was observed in the BMI range. The subjects in a group with a high level of FRC usage ate convenience store or instant foods instead of homemade meals (p = 0.033), had a late-night meal or snack (p = 0.024), and turned to emotional eating under stress (p < 0.001) more than those in the low level group. In addition, the high level group checked the nutrition facts label more carefully when purchasing processed foods (p = 0.016) and exercised at least 30 minutes daily, not considering physical education classes (p = 0.057). The higher level of FRC use, the lower the dietary self-efficacy, whereby the subscales 'environmental stimulus control efficacy' and 'affective factor control efficacy' showed complete mediating effects. Conclusion: Given that FRC has been increased recently, adolescents are in need of support to help them control and enhance their dietary self-efficacy as well as develop healthy dietary behaviors through proper nutrition education programs.