• New & Renewable Energy
• /
• v.3 no.4
• /
• pp.22-30
• /
• 2007

An expansion device plays an important role in optimizing the heat pumps by controlling refrigerant flow and balancing the system pressures. Conventional expansion devices are being gradually replaced with electronic expansion valves due to increasing focus on comfort, energy conservation, and application of a variable speed compressor. In addition, the amount of refrigerant charge in a heat pump is another primary parameter influencing system performance. In this study, the flow characteristics of the expansion devices are analyzed, and the effects of refrigerant charge amount on the performance of the heat pump and the variation of compressor speed are investigated at various operating conditions. Mass flow rate through capillary tube, short tube orifice, and EEV was strongly dependent on the upstream pressure and subcooling. The heat pump system is very sensitive with a variation of refrigerant charge amount. The performance of it can be optimized by adjusting the flow rate through expansion device to maintain a constant superheat at all test conditions.

• Proceedings of the KIEE Conference
• /
• 1999.11c
• /
• pp.706-708
• /
• 1999

In recent years, analog to digital converter is significant component in high frame rate system. But, in the future. as long as minimum line width is reduced, matching between speed and resolution may be worse. In this paper, first-order $\Sigma-\Delta$ analog to digital converter is adopted and designed as its solutions. Hspice simulation is performed, using $0.65{\mu}m$ CMOS 2-poly 2-metal model parameter.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2003.07a
• /
• pp.32-35
• /
• 2003

Nonlinear parameterization of OLED device from measurements of bias dependence of impedance spectra and parameter extraction using Levenberg-Marquardt complex nonlinear least square regression algorithm based on resistor-capacitor equivalent circuit model enables computer simulation of OLED power driving characteristics in forms of square-wave or sinusoidal output signal at arbitrary conditions. We introduce developed OLED power driving simulation software and discuss transient responses in voltage-or current-controlled operations as well as nonlinear characteristics of OLED, by presenting both the simulation and experimental results. This OLED simulation technique using impedance spectroscopy is extremely useful in predicting performance of the nonlinear device, especially in time-domain analysis of device operation.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.11a
• /
• pp.538-541
• /
• 2007

An expansion device plays an important role in optimizing the heat pumps by controlling refrigerant flow and balancing the system pressures. Conventional expansion devices are being gradually replaced with electronic expansion valves due to increasing focus on comfort, energy conservation, and application of a variable speed compressor. In addition, the amount of refrigerant charge in a heat pump is another primary parameter influencing system performance. In this study, the flow characteristics of the expansion devices are analyzed, and the effects of refrigerant charge amount on the performance of the heat pump are investigated at various operating conditions. Cooling capacity of the heat pump system is strongly dependent on load conditions. The heat pump system is very sensitive with a variation of refrigerant charge amount. But, the performance of it can be optimized by adjusting the flow rate through expansion device to maintain a constant superheat at all test conditions.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.30A no.9
• /
• pp.38-45
• /
• 1993

In this study, the degradation characteristics of drain output resis-tance was described due to hot electron effects. An semi-empirical model for the degraded drain output resistance was derived from the measured device characteristics. The suggested model was verified from the measured data and the device parameter dependence was also analyzed. The degradation of drain output resistance was increased with stress time and had linear relationship with the degradation of drain current. The device lifetime which was defined by failure criteria of drain output resistance (such as $\Delta$ro/roo=5%) was equivalent to that of failure criteria of drain current (such as $\Delta$ID/ID=5%)

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2000.04a
• /
• pp.75-81
• /
• 2000

This study for the roundness and perpendicularity of machining center is classified into two ways. One is the way that progresses the roundness amending the parameter of machining center based on the measured value after the measurement of the roundness of machaning center by means of a existing measuring device, another is the way that measures the roundness by remodeling the existing measuring device. the former is studied by pack hei jae team in Seoul university, the later is studied by TSUTSUMI. Especially TSUTSUMI measures the roundness according to circular compensation after the insertion of developed measuring device using a rotary encoder to the spindle of machining tool. we study how regulation velocity occuring with circular motion of machining center table influences the roundness after measuring the roundness using Circular Test method by a 2 dimention probe and a standard discus in this experiment.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.1609-1612
• /
• 2008

RQ(Respiratory Quotient) value is obtained from the ratio of the consumed oxygen and the produced carbon dioxide during the patient's respiration. To investigate the efficacy of insulin and diagnosis the metabolic disorder in short time, the RQ value can be used as important parameter. The measurement of oxygen and carbon dioxide amounts is needed large chamber and complex sensors. But If the atmospheric oxygen and carbon dioxide concentrations do not change, the expiratory oxygen and carbon dioxide can be used to obtain RQ value. A convenient RQ measuring device has been developed by using two sensors for O2 and CO2. The estimation of RQ devices confirms that the RQ device can obtain accurate data by eliminating uncertain factor such as delay time and remaining gases.

• International Journal of Aerospace System Engineering
• /
• v.5 no.1
• /
• pp.9-18
• /
• 2018

The longitudinal flight parameters of a light airplane are estimated from flight test data by use of the output error method. The reliability of the flight test measurement is examined in engineering judgment, scatter and Cramer-Rao bound, which turns out to be satisfactory with minor defects. Estimated parameter values are validated by comparing the simulated responses with the ones from actual flight tests. The FTD(Flight Training Device) of a light airplane turns out to satisfy the qualification of FAA Level 5 FTD in longitudinal motion. All the necessary practices for generation of high-fidelity data in longitudinal motion of a light aircraft are successfully performed in this study.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.24 no.5
• /
• pp.818-822
• /
• 1987

Gate capacitances have been measured directly on small-geometry MOSFET's with the drain voltage as a parameter for various channel lengths and for p and n channel types and the characteristics have been compared with each other. The influence of 'hot carrier effect' of short channel devices on capaciatance has been compared with long channel devices. The results show that gate capacitance characteristics of short channel device deviate from those of long channel device. The accuracy of the measurement system is less than a few femto Farad, and the minimum geometry (W/L) of device for which reliable measurement can be obtained is 6/3.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.10 no.1
• /
• pp.61-65
• /
• 2010

Threshold voltage is one of the most important factors in a device modeling. In this paper, analytical method to calculate threshold voltage for recessed channel (RC) MOSFETs is studied. If we know the fundamental parameter of device, such as radius, oxide thickness and doping concentration, threshold voltage can be obtained easily by using this model. The model predicts the threshold voltage which is the result of 2D numerical device simulation.