• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.2
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• pp.97-105
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• 2008

This paper presents simulated and experimental test results of optimal control algorithm for an encapsulated ice thermal storage system with full capacity chiller operation. The algorithm finds an optimal combination of a chiller and/or a storage tank operation for the minimum total operation cost through a cycle of charging and discharging. Dynamic programming is used to find the optimal control schedule. The conventional control strategy of chiller-priority is the baseline case for comparing with the optimal control strategy through simulation and experimental test. Simulation shows that operating cost for the optimal control with chiller on-off operation is not so different from that with chiller part load capacity control. As a result from the experimental test, the optimal control operation according to the simulated operation schedule showed about 14 % of cost saving compared with the chiller-priority control.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.863-868
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• 2001

It is necessary to design th anti-vibration system of precision machinery for a sound operation and a quality assurance. However, in general. the allowable vibration limit is not well known. In the paper, the vibration criteria for foundation of vibration sensitive machinery is proposed and anti-vibration system is designed by using vibration measurement results of foundation. Also, the F.E. analysis is performed to verify the effectiveness of a designed anti-vibration system and to determine allowable dynamic load of machinery

• ETRI Journal
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• v.37 no.6
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• pp.1096-1107
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• 2015

This paper presents a dynamic retry adaptation scheme for H.264 HD video, called DRAS.264, which dynamically adjusts the retry limits of frames at the medium access control (MAC) layer according to the impact those frames have on the streamed H.264 HD video. DRAS.264 is further improved with a bandwidth estimation technique, better prediction of packet delays, and expanded results covering multi-slice video. Our study is performed using the Open Evaluation Framework for Video Over Networks as a simulation environment for various congestion scenarios. Results show improvements in average peak signal-to-noise ratios of up to 4.45 dB for DRAS.264 in comparison to the default MAC layer operation. Furthermore, the ability of DRAS.264 to prioritize data of H.264 bitstreams reduces error propagation during video playback, leading to noticeable visual improvements.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.927-935
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• 2011

In-situ California Bearing Ratio(CBR) test has been widely used for evaluating the subgrade condition in pavements. However, because the in-situ CBR test is expensive and takes time for operation, it is difficult to figure out the in-situ characteristics of subgrade strength in detail. For faster and economical operation, the Dynamic Cone Penetrometer(DCP) has been often utilized for estimating the subgrade strength in the field. The purpose of this paper is to determine the relationship between CBR value and DCP index of the embankment constructed with mixtures of soil and waste lime. Waste lime used in this study is producted as a by-product in the manufacturing process of making $Na_2CO_3$ from local chemical factory in Incheon. In this field measurement, the geotechnical tests such as field water content, field density, field CBR test, and dynamic cone penetration test were conducted.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.480-485
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• 2005

In the respect of the environmental protection viewpoint, the $CO_2$ may be regarded as one of the most attractive alternative refrigerants for an automotive air-conditioning system. Control methods for a $CO_2$ system should be newly developed, because properties of $CO_2$ are different compared with those of classical refrigerants. Especially, high-side pressure of a $CO_2$ system should be controlled for the effective operation of the system. In this study, intelligent control algorithms for a $CO_2$ system were developed ‘ These are a high-side pressure control algorithm and an indoor air temperature control algorithm. These algorithms were analysised by using dynamic models of a $CO_2$ system.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.5
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• pp.511-518
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• 2016

The dynamic positioning system (DPS) maintains an offshore vessel's position and heading under various environmental conditions by using its own thrust. DPS is regarded as one of the most important systems in offshore vessels. So, efficient operation and maintenance of the DPS are important issues. To monitor the DPS, it is necessary to define an appropriate key performance indicator (KPI) that can express the condition of the DPS from the perspective of operational efficiency and maintenance. In this study, a new KPI for the DPS is proposed considering the efficiency of the machinery and controller, the energy efficiency, and the environmental conditions in which the DPS is operated. The KPI is defined as a function of control deviation, energy consumption, and environmental load. A normalization factor is used to normalize the effect of environmental load on the KPI. The KPI value is calculated from DPS simulation and model test data. The possibility of applying the KPI to monitoring of DPS condition is discussed by comparing the values. The result indicates the feasibility of the new KPI.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1047_1048
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• 2009

This paper describes comparative analysis results about the dynamic interaction of interconnected wind power system using the actual-size hardware simulator and the simulation model with PSCAD/EMTDC. The hardware simulator, which is composed of 2.0MVA induction motor with drive system and 1.5MW doubly-fed induction generator, was built and tested in Go-Chang Test Site of KEPCO for analyzing the dynamic interaction with the interconnected distribution system. The operation of hardware simulator was verified through comparative analysis between experimental results and simulation results obtained by simulation model with PSCAD/EMTDC. The developed hardware simulator and simulation model could be effectively used for analyzing the dynamic interaction, which has various phenomena depending on the wind variation and the network state of interconnected power system.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.37-40
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• 2014

Capturing the carbon dioxide emitted from coal-fired power plants will be necessary if targeted reduction in carbon emissions is to be achieved. Modelling and simulation are the base for optimal operation and control in thermal power plant and also play an important role in energy savings. This study aims to analyze the performance of supercritical coal fired power plant through steady and dynamic simulation using a commercial software gCCS. A whole power plant has been modeled and validated with design data of 500 MWe power plant, base and part load operations of the plant were also evaluated, consequently it had been proven that the simulated result had a good agreement with actual operating data. In addition, the effect of co-firng on the plant efficiency and flue gases were investigated using gCCS simulator.

• Tribology and Lubricants
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• v.33 no.1
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• pp.9-14
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• 2017

This paper presents a rotordynamic analysis and the operation of a power turbine applied to a 250 kW super-critical $CO_2$ cycle. The power turbine consists of a turbine wheel and a shaft supported by two fluid film bearings. We use a tilting pad bearing for the power turbine owing to the high speed operation, and employ copper backing pads to improve the thermal management of the bearing. We conduct a rotordynamic analysis based on the design parameters of the power turbine. The dynamic coefficients of the tilting pad bearings were calculated based on the iso-thermal lubrication theory and turbine wheel was modeled as equivalent inertia. The predicted Cambell diagram showed that there are two critical speeds, namely the conical and bending critical speeds under the rated speed. However, the unbalance response prediction showed that vibration levels are controlled within 10 mm for all speed ranges owing to the high damping ratio of the modes. Additionally, the predicted logarithmic decrement indicates that there is no unstable mode. The power turbine uses compressed air at a temperature of $250^{\circ}C$ in its operation, and we monitor the shaft vibration and temperature of the lubricant during the test. In the steady state, we record a temperature rise of $40^{\circ}C$ between the inlet and outlet lubricant and the measured shaft vibration shows good agreement with the prediction.

• Journal of Electrical Engineering and information Science
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• v.3 no.1
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• pp.103-109
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• 1998

A new flux-weakening scheme for an Interior Permanent Magnet Synchronous Motor (IPMSM) is proposed. This control scheme enables the maximum torque operation for the fast acceleration in the constant power region according to the current and voltage limit condition. Especially the dynamic performance of the braking in the flux-weakening region is improved with the compensation of the stator resistance. Also since the onset of the flux weakening operation is adjusted according to the load conditions, the machine parameters, and whether motoring or braking region, the stable and precise transition operation into or out of the flux weakening region can be achieved. The effectiveness of the proposed scheme is verified through experiments with an IPMSM drive system.