• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.3
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• pp.261-266
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• 1992

In this paper, we investigated the stability of TeS1100-xTGeS1xT( x = 15,33,50 at. %) thin films by observing the transmittance and reflectance changes with annealing and exposure of diode laser(780nm). As results of transmittance changes in constant tenperature and humidity atmosphere, it was shown that TeS150TGeS150T thin film has the smallest transmittance change. From the XRD patterns, it was confirmed that the transmittance changes in TeS150TGeS150T thin film before and after annealing are due to crystalization. The transmittance changes in TeS150TGeS150T thin film with annealing are largest at diode laser wavelength and the trasmittance changes with laser exposure are decreased fast.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.1
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• pp.124-132
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• 2004

A hydraulic system is difficult to keep the performance due to non-linearity, load pressure which changes according to working condition and system parameter variation, the requirement of control algorithm has been risen in order to satisfy them. An adaptive control is a control method which is suggested to achieve a control object though plant characteristics change. In spite of the case that plant characteristics and the degree of variation are difficult to grasp, adaptive control can keep the characteristics of closed-loop system regularly. In this study GMVAC(generalized minimum variance adaptive control) combined with output error feedback is proposed in order to solve problems of non-minimum phase, vibration and overshoot in initial response of the plant. The control performance according to the variation of characteristics of the plant is evaluated by changing the supply pressure only.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.1
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• pp.71-79
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• 1990

An analog phase shifter is designed at the operating frequency 10GHz that is coupled with a hybrid ring and the network connecting an inductor series with a varactor to extend a continuous chage in the phase of the reflected output wave to be produced from a variation in the terminated varactor reactance as a variation in the reverse bias voltage. It is manufactured in a microstripline in consideration of an effect of the dispersion characteristics and discontinuities. As a resuls of an experiment, a change in the phase is achieved over 180 degree from $52.34^{\circ}$ degrees to $235.01^{\circ}$degrees, the transmission loss is -3.6~-14.3dB, and the return loss is -16~-8dB(1.37

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.11
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• pp.899-905
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• 2014

This paper describes preliminary research conducted for developing a high-efficiency clean large cauldron using the liquid-vapor phase change heat transfer. To improve the isothermal environment of the cauldron, naphthalene and FC-40 were selected as the working fluids to operate well in the temperature range of $100-200^{\circ}C$ and used in experimental investigations of the heat transfer characteristics. A two-phase closed thermosyphon was designed and built to demonstrate the functionality of the working fluids. Startup, boiling, and condensation tests were performed, and the test results were used to examine the possibility of complementary effects of the startup and heat transfer characteristics of the two-phase closed thermosyphon using a mixture of naphthalene and FC-40.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.2
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• pp.169-175
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• 2006

This study investigated variation leakage current maximum value and waveform considering applied voltage phase angel by simulating three environmental conditions, such as fog, salt fog, and kaolin contamination .As the result of applied voltage phase angel characteristics, leakage currents presented almost in phases in the early stage regardless of environmental conditions just after applying the voltage, and the phase of leakage currents certain phase lags for the discharge of the applied voltage when surface discharges occurred due to the continuous environmental contamination. In addition, the difference in phase significantly increased according to the intensity of discharges. The change in distortion rates according to the environmental contamination presented a nearly same level just after applying the voltage. The distortion rate of third harmonic for the fundamental wave presented by the order of fog>salt fog>kaolin when surface discharges occurred due to the applied voltage for certain continued periods. In the case of the fog and salt fog, the scale of spectrums decreased according to the increase in frequencies from the results of the analysis of high frequencies. In addition, the even number frequency presented a relatively large level compared to the odd number frequency under the kaolin contamination.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.12
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• pp.647-653
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• 2013

TABS (Thermally Activated Building System) has recently applied by huge commercial buildings, airports, and convention centers in Europe. TABS provides night-time thermal storage by heating or cooling. The embedded water-based heating and cooling system uses the high thermal inertia of concrete in the building construction, in which a heating or cooling pipe is embedded. The aim of this study is to analyze the thermal storage and thermal output of TABS applied with PCM (Phase Change Material). To achieve this, prototypes of TABS and the thermal properties of various PCMs were investigated. By using the simulation program Physibel Voltra 6.0 W, the thermal storage and thermal output were evaluated according to a heating and cooling operation schedule.

• Solar Energy
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• v.6 no.2
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• pp.43-53
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• 1986

The objective of this study is to report on the characterics of convective flow and heat transfer during metling process in order to provide design information for thermal energy storage systems which use phase change material. In present study, flow and heat transfer characteristics of the Phase Change Material in the Open Top Model (O.T.M) and in the Closed Top Model (C.T.M) were studied numerically by the control volume formulation using the algebraic non-orthogonal coordinate transformation. For the calculation procedure, the physical properties of fluid are assumed to be constant except density which is linely dependent on temperature in the bouyancy term of momentum equations. At start of melting process, the thickness of melting layer is assumed from the Stefan Problem assumption. The heat transfer results of Open Top Model and Closed Top Model are compared with the parameters of Grashof number and aspect ratio. It was found that heat transfer phenomena in melted region was greatly affected by buoyancy-driven natural convection and the melting distance of Open Top Model at the upper region is greater than that of Closed Top Model.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.154-155
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• 2007

PRAM(Phase-Change RAM) is a promising memory that can solve the problem of conventional memory and has the nearly ideal memory characteristics. We reviewed the issues for high density PRAM integration. Writing current reduction is the most urgent problem for high density PRAM realization. So, we studied new constitution of $Ge_1Se_1Te_2$ chalcogenide material and presented the method of reducing the contact size between $Ge_1Se_1Te_2$ and electrode. A small-contact-area electrode is used primarily to supply current into and minimize heat loss from the chalcogenide. In this letter, we expect the method of reducing the contact size between $Ge_1Se_1Te_2$ and electrode to decrease writing current.

• Journal of KIISE
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• v.42 no.9
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• pp.1071-1077
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• 2015

In this paper, we adopt PCM (phase-change memory) as a virtual memory swap device and present a new page replacement policy that considers the characteristics of PCM. Specifically, we aim to reduce the write traffic to PCM by considering the dirtiness of pages when making a replacement decision. The proposed policy tracks the dirtiness of a page at the granularity of a sub-page and replaces the least dirty page among the pages not recently used. Experimental results show that the proposed policy reduces the amount of data written to PCM by 22.9% on average and up to 73.7% compared to CLOCK. It also extends the lifespan of PCM by 49.0% and reduces the energy consumption of PCM by 3.0% on average.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.98-100
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• 2007

This paper presents a analysis on the torque and power characteristics of standard 3-phase induction motor. An induction motor changes its characteristics parameters under the operation condition with the same capacity. In this paper, we analyzed that how the power and torque characteristics of induction motor would be changed according to the change of these parameters.