• KSTLE International Journal
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• v.3 no.1
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• pp.1-6
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• 2002

The purpose of this paper is to investigate the effects of design parameters on the friction loss in piston skirt. An analytical model to describe the friction characteristics of piston skirt has been presented, which is based on the secondary motion of piston and mixed lubrication theory, It could be shown that the skirt friction closely depends on the side force acted on the piston pin. The side force is inf1uenced by cylinder pressure at low engine speed, but by inertia force at high engine speed. The usage of extensive skirt area and low weight piston is effective to reduce the friction loss at high speed. The low viscosity oil considerably decreases viscous friction as engine speed increases, but it increases boundary friction at low engine speed. From the parametric study, it is found that the skirt axial profile is the most important design parameter related to the reduction of skirt friction.

• Journal of ILASS-Korea
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• v.22 no.2
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• pp.47-54
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• 2017

$CO_2$ emission regulation will be prescribed and main issue in automotive industry. Mostly, vehicle's fuel efficiency deeply related to $CO_2$ emission is regulated by qualified driving test cycle by using chassis dynamometer and exhaust gas analyser. But, real driving fuel consumption rate depends so much on the individual usage profile and where it is being driven: city traffic, road conditions. In this study, vehicle model of fuel consumption rate for ICEV and PHEV was developed through co-simulation with CRUISE model and Simulink based on driving control model. The simulation results of fuel consumption rate were analysed with on-road vehicle data and compared with its official level.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.401-401
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• 2009

Recently, demands for the development of compact, lightweight power supplies with higher power density and higher efficiency have been increased. Since Piezoelectric Transformer (PT) was emerged in device and material industry, it has been suggested as a viable alternative to the magnetic transformer in some applications. PT has some advantages such as low profile and mechanical energy transfer with little electromagnetic interface (EMI). Also, PT can provide high voltage stepping ratio with good isolation and requires no copper windings saving copper usage especially for large voltage conversion differences. Conventional control of PT converter has mainly two-way. One is the pulse frequency modulation (PFM) control method and the other is the pulse width modulation (PWM) control with frequency fixed method. It is known that the maximum PT efficiency can be obtained when it operates near the resonant frequency of the PT. And, also PT's resonant frequency moves according to the load condition. Therefore, selection of PT converter control method is very difficult. This paper analyzes general piezo-electric converter modeling and proposes a guide-line to selection of control method and stabilization control.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.445-450
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• 1997

Self-Powered Neutron Detectors(SPNDs) are currently used to estimate the power generation distribution and fuel burn-up in several nuclear power reactors in Korea. In this paper, Monte Carlo simulation is accomplished to calculate the escape probability of beta particle as a function of their birth position fur the typical geometry of rhodium-based SPNDs. Also, a simple numerical method calculates the initial generation rate of beta particles and the change of generation rate due to rhodium burn-up. Using the simulation and the numerical method, the burn-up profile of rhodium density and the neutron sensitivity are calculated as a function of burn-up time in the reactor. The sensitivity of the SPNDs decreases non-linearly due to the high absorption cross-section and the non-uniform burn-up of rhodium in the emitter rod. In addition, for improvement of some properties of rhodium-based SPNDs which are currently used, this paper presents a new material. The method used here can be applied to the analysis of other types of SPNDs and will be useful in the optimum design of new SPNDs for long term usage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.5
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• pp.1077-1084
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• 2017

In this paper, we propose a electrical safety management architecture based on IoT (Internet of things) platform, especially IoTivity which is open source platform organized by OCF. With the advent of various ICT technologies, researches on convergence between power facilities and ICT technology are actively under way. The application of ICT technology to high voltage electrical equipment has been studied in terms of improving power efficiency and measuring accurate usage in real time. We focused on safety data and described the components of the electrical safety architecture, the requirement of reference interface, and available services. We defined the data profile for the electrical facilities subject to electrical safety management and examined feasibility through testing.

• Korean journal of food and cookery science
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• v.25 no.2
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• pp.219-226
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• 2009

Red ginseng extract was added to Yanggaeng to determine a practical use for the herb which has medical usage and functionality. We examined the antioxidant activity and quality characteristics of Yanggaeng prepared with different amounts (as ratios of 1%, 2%, 3% to the total materials) of red ginseng extract, as well as those of commercial red ginseng Yanggaeng. The antioxidant activity of the Yanggaengs samples was estimated by the DPPH free radical scavenging activity, $ABTS^{+\cdot}$ scavenging activity, and reducing power. The antioxidant activity of the Yanggaeng increased as a result of the addition of the red ginseng extract. Levels of polyphenol compounds and flavonoids increased according to the extract concentration. The quality characteristics of the red ginseng Yanggaeng were estimated in terms of pH, sugar content, viscosity, color, texture profile analysis, and sensory evaluations. With increasing concentrations of the extract, viscosity and sugar content increased, but pH decreased. In terms of the overall palatability, color, taste, flavor, and hardness, the 3% red ginseng Yanggaeng was determined as the best among the tested samples. Also, the 3% red ginseng Yanggaeng had higher scores than the commercial red ginseng Yanggaeng.

• The Korean Journal of Applied Statistics
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• v.33 no.6
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• pp.791-804
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• 2020

Residential electricity consumption can be predicted more accurately by utilizing the realtime household electricity consumption reference that can be collected by the AMI as the ICT developed under the smart grid circumstance. This paper studied the model that predicts residential power load using the ARIMA, TBATS, NNAR model based on the data of hour unit amount of household electricity consumption, and unlike forecasting the consumption of the whole households at once, it computed the anticipated amount of the electricity consumption by aggregating the predictive value of each established model of cluster that was collected by the households which show the similiar load profile. Especially, as the typical time series data, the electricity consumption data chose the clustering analysis method that is appropriate to the time series data. Therefore, Dynamic Time Warping and Periodogram based method is used in this paper. By the result, forecasting the residential elecrtricity consumption by clustering the similiar household showed better performance than forecasting at once and in summertime, NNAR model performed best, and in wintertime, it was TBATS model. Lastly, clustering method showed most improvements in forecasting capability when the DTW method that was manifested the difference between the patterns of each cluster was used.