• Journal of Power Electronics
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• v.15 no.3
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• pp.602-609
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• 2015

In this paper, a zero current transition (ZCT) double-ended flyback converter is proposed. All of the switching elements act under soft switching conditions and the voltage stress of the main switches is limited to the input voltage due to the innate behavior of the double-ended flyback converter. Providing soft switching conditions and clamping the voltage stress improves the efficiency and electromagnetic compatibility (EMC). The Proposed converter is analyzed in detail and its operating modes are discussed in detail. Experimental results are presented to verify the theoretical predictions. Moreover, the conducted electromagnetic emissions of the proposed ZCT double-ended flyback converter are measured to show another merit of the proposed converter in addition to providing soft switching conditions. The measured electromagnetic interference (EMI) of the proposed converter demonstrates that its EMI is lower than the conventional double-ended flyback converter. Furthermore, two simple and cost effective EMI reduction methods are applied to satisfy the EMC standard.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.5 no.2
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• pp.101-115
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• 2001

Recent theoretical analysis of numerical methods for solving nonlinear systems of equations is represented by alpha theory of Newton method developed Smale et al. The theory was extended to Secant method by providing convergence conditions by Yakoubsohn which the Secant method is treated as an operator defined for analytical functions. We use Secant methods as an iterative scheme with approximations, which results in new convergence conditions. We compare the two conditions and show that the new conditions represent the features of Secant method in a more precise way.

• Journal of the Korean housing association
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• v.12 no.2
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• pp.55-63
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• 2001

The purpose of this study was to develop the community programs of multihousing in Korea through evaluating and analyzing the actual conditions of community in multihousing in U.S.A. This study was conducted by using a field survey and questionaire at the 2 multihousing complexes located in the City of Blacksburg, Virginia, U.S.A. The major findings were as follows: 1) There was a variety of community programs and facilities, such as a monthly newsletter which allowed information to be exchanged among all residents. The programs also provided news on events for the children, teenagers, college students, adults and seniors. These events were held at the club house or pond area. 2) The average degree of satisfaction of these programs and facilities was high. 3) Korea need to follow the example of the U.S.A by i) providing a monthly newsletter periodically to exchange information ii) offering a variety of community programs iii) providing programs regarding district bureau of public administration, kindergarten service, telecommunications office and holding service for package, registered mail, drycleaning, etc.

• Journal of applied mathematics & informatics
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• v.37 no.3_4
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• pp.183-200
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• 2019

We have constructed a robust numerical method on Shishkin mesh for a class of convection diffusion type turning point problems with Robin type boundary conditions. Supremum norm is used to derive error estimates which is of order O($N^{-1}$ ln N). Theoretical results are verified by providing numerical examples.

• Journal of Platform Technology
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• v.6 no.4
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• pp.78-86
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• 2018

In this paper, a VR-based cyber hiking system was designed to provide virtual reality for famous mountains that can offer the real senses and feelings of hiking in supporting environmental factors of actual mountains such as the temperature, air, sound, echoes, etc., of the mountain the user wants to climb. The VR-based cyber hiking system that reflects real-time site conditions is largely consisted of the data collection module that collects data from the live site, multiple drive modules that enables the user to feel real senses using data from the sites, and sensor module to detect the stimuli provided by the drive modules and the user's physical body transition. Unlike existing VR-based hiking systems, the proposed cyber hiking system not only provides simple virtual reality for the wanted mountain, but can also provide the natural conditions of real mountains and implement the uphill and downhill of hiking routes. In particular, it has the effect of providing fun and game elements to users by excluding unnecessary conditions and risks that may arise in actual hiking and instead supporting augmented realities such as squirrels on actual hiking paths. In addition, in providing users with the changes in their body before and after hiking, it is expected to be effective in providing diverse feedback such as the height, gradient, and speed of mountain hiking.

• Korean Journal of Applied Biomechanics
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• v.32 no.4
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• pp.121-127
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• 2022

Objective: The purpose of this study was to investigate potential effects of transcranial direct current stimulation (tDCS) on bimanual force control capabilities in healthy young adults. Method: Eighteen right-handed healthy young adults (10 females and 8 males; age: 23.55 ± 3.56 yrs) participated in this crossover design study. All participants were randomly allocated to both active-tDCS and sham-tDCS conditions, respectively. While receiving 20 min of active- or sham-tDCS interventions, all participants performed bimanual isometric force control tasks at four submaximal targeted force levels (i.e., 5%, 10%, 15, and 20% of maximal voluntary contraction: MVC). To compare bimanual force control capabilities including force accuracy, variability, and regularity between active-tDCS and sham-tDCS conditions, we conducted two-way repeated measures ANOVAs (2 × 4; tDCS condition × Force levels). Results: We found no significant difference in baseline MVC between active-tDCS and sham-tDCS conditions. Moreover, our findings revealed that providing bilateral tDCS including anodal tDCS on left primary motor cortex (M1) and cathodal on right M1 while conducting bimanual force control trials significantly decreased force variability and regularity at 5%MVC. Conclusion: These findings suggest that providing bilateral tDCS on M1 areas may improve bimanual force control capabilities at a relatively low targeted force level.

• Advances in nano research
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• v.14 no.3
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• pp.285-294
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• 2023

The dynamic and sensing performances of nanomechanical resonators with their different boundary conditions are studied based on surface elasticity-based modeling and simulation. Specifically, the effect of surface stress is included in Euler-Bernoulli beam model for different boundary conditions. It is shown that the surface effect on the intrinsic elastic property of nanowire is independent of boundary conditions, while these boundary conditions affect the frequency behavior of nanowire resonator. The detection sensitivity of nanowire resonator is remarkably found to depend on the boundary conditions such that double-clamping boundary condition results in the higher mass sensitivity of the resonator in comparison with simple-support or cantilever boundary condition. Furthermore, we show that the frequency shift of nanowire resonator due to mass adsorption is determined by its length, whereas the frequency shift is almost independent of its thickness. This study enables a design principle providing an insight into how the dynamic and sensing performances of nanomechanical resonator is determined and tuned.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.6
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• pp.573-583
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• 2005

Fugitive dust, which is emitted in the ambient air without first passing through a stack or duct designed to control flow, is frequently generated by means of wind erosion from storage yards at Pohang Steel Wokrs. The size distribution of fugitive dust is mostly in the range of coarse particulate which is deposited as soon as emitted and less harm to human health; however $20\%$ of fugitive dust contains PM 10 known as one of most harmful airborne pollutant. Consequently, effective control and reduction of fugitive dust is strongly requested by the local society, but it is not easy so far because the generation and dispersion of fugitive dust highly depends on meteorological conditions, and it being occurred for irregularity. This research presented a fugitive dust control system for each meteorological condition by providing statistical prediction data obtained from a statistical analysis on the probability of generating the threshold velocity at which the fugitive dust begins to occur, and the frequency occurring by season and by time of the wind direction that can generate atmospheric pollution when the dispersed dust spreads to adjacent residential areas. The research also built a fugitive dust detection system which monitors the weather conditions surrounding storage yards and the changes in air quality on a real-time basis and issues a warning message by identifying a situation where the fugitive dust disperses outside the site boundary line so that appropriate measures can be taken on a timely basis. Furthermore, in respect to the spraying of water to prevent the generation of fugitive dust from the storage piles at the storage yard, an advanced statistical meteorological analysis on the weather conditions in Pohang area and a case study of fugitive dust dispersion toward outside of working field during $2002\∼2003$ were carried out in order to decide an optimal water-spraying time and the number of spraying that can prevent the origin of fugitive dust emission. The results of this research are expected to create extremely significant effects in improving surrounding environment through actual reduction of the fugitive dust produced from the storage yard of Pohang Steel Works by providing a high-tech warning system capable of constantly monitoring the leakage of fugitive dust and water-spray guidance that can maximize the water-spraying effects.

• 한국경영정보학회:학술대회논문집
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• 2007.06a
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• pp.378-381
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• 2007

Traditional intermediaries refer to service providers such as travel agents, real estate brokers, job agencies and insurance agents which matching services for buyers and suppliers in a traditional market. The introduction of Electronic commerce resulted in the automation of many tasks provided by intermediaries and seemed to eliminate the role of many traditional intermediaries, which is called disintermediation. However, depending on their market power, traditional intermediaries either will be disintermediated or fill new roles by providing added value and assistance, which is called reintermediation. According to the research of Alina M. Chircu et al. there are three conditions for reintermediation for traditional intermediaries. Three conditions are weak appropriability of EC innovations, ownership of co-specialized assets for both market intermediation and EC innovations and economies of scale. Besides these three reintermediation conditions, we hypothesize that leveraging BPO can be a suitable strategy for traditional intermediaries to be transformed into reintermediaries. Business Process Outsourcing (BPO) is the leveraging of technology or specialist process vendors to provide and manage an organization's critical and/or non-critical enterprise processes and applications. This paper will investigate the relationship between above reintermediation conditions including BPO and reintermediation.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.4
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• pp.351-362
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• 2000

To set the similarity conditions between a prototype usually in the field and its reduced-scale model is a crucial part in model tests. No technique is available to keep perfect similarity for this procedure so far. The experimental work using a wind tunnel is not exceptional. based on the field measurements, the effect of stack parameters and wind conditions on the dispersion of stack plume has been investigated in the laboratory. in this paper intensive methodology is focused on matching these similarities. Due to the limitations to keep perfect similarity conditions some simplifications are involved in common. In this study geometric conditions and kinematic conditions using Froude number and Reynolds number have been con-sidered to keep the similarity conditions required. From the tests it is found that the critical Reynolds number (Recrit) is 2,700 when the height of stack discharge is 50mm. The dispersion has a similar trend for the higher Reynolds number than the critical Reynolds number. It is also found that different Froude number does not make any significant influence for the normalized tracer gas concentrations at the recipient providing the same ratio of the wind speed to the discharge speed. No significant effect of stack diameter is observed in the normalized tracer gas concentrations with the same Frounde number. The similarity conditions therefore used in this study are reliable to simulate the conditions in prototype into the wind tunnel tests.