• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.230-236
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• 2001

We developed a built-in sensor bearing to measure the rotor motion of a rolling piston type compressor for the air conditioner. Because of needs for the high efficiency and long life span of compressor, and the usage of alternative refrigerants, the operating condition of the compressor becomes more severe. The accurate measurement of the rotor motion of the compressor can contribute greatly to the design and analysis of the hydrodynamic bearing. However, it is difficult to measure accurately the shaft behavior of small compressor because of the small space for the sensor mount, high temperature and pressure of compressor, oil mixed with refrigerant, and electromagnetic noise of the motor. To overcome these difficulties, we develop the cylindrical capacitive sensor that is built in the hydrodynamic bearing and calibrate the built-in sensor bearing indirectly through measuring the oil relative permittivity. We measured the rotor motion as well as suction and discharge pressures in various conditions. The several experimental results show that the developed built-in sensor bearing can measure the rotor motion not only in steady state but also in transient state.

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.3
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• pp.63-71
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• 2001

This paper presents a model-based method for detecting and diagnosing some faults in the cooling tower of healing, ventilating, and air-conditioning systems. A simple model for the cooling tower is employed. Faults in cooling tower operation are detected through the deviations in the values of system characteristic parameters such as the heat transfer coefficient-area product, the tower approach, the tower effectiveness, and fan power. Three distinct faults are considered: cooling tower inlet water temperature sensor fault, cooling tower pump fault, and cooling tower fan fault. As a result, most values of the system characteristics parameter variations due to a fault are much higher or lower than the values without faults. This allows the faults in a cooling tower to be detected easily using above methods. The diagnostic rules for the faults were also developed through investigating the changes in the different parameter due to each faults.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.7
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• pp.552-559
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• 2002

The fault detection and diagnosis (FDD) technology may be applied in order to decrease the energy consumption and the maintenance cost of the air conditioning system. In this study, rule bases and curve fitting models were used to detect faults in an air handling unit. Gradually progressed faults, such as the fan speed degradation, the coil water leakage, the humidifier nozzle clogging, the sensor degradation and the damper stoppage, were applied to the developed FBD system. Simulation results show good detections and diagnoses of these faults. Therefore, this method may be effectively used for the fault detection and diagnosis of the air handling unit.

• Journal of Power Electronics
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• v.7 no.2
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• pp.174-180
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• 2007

In this paper, a simple control method for two-stage utility grid-connected photovoltaic power conditioning systems (PCS) is proposed. This approach enables maximum power point (MPP) tracking control with post-stage inverter current information instead of calculating solar array power, which significantly simplifies the controller and the sensor. Furthermore, there is no feedback loop in the pre-stage converter to control the solar array voltage or current because the MPP tracker drives the converter switch duty cycle. This simple PCS control strategy can reduce the cost and size, and can be utilized with a low cost digital processor. For verification of the proposed control strategy, a 2.5kW two-stage photovoltaic grid-connected PCS hardware which consists of a boost converter cascaded with a single-phase inverter was built and tested.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.263-266
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• 2009

In the photovoltaic applications, MPPT(maximum power point tracking) method is essential due to the non-lineality of photovoltaic output characteristics. To ensure stable tracking response, two sensors are required in conventional popular MPPTs. In modularized PV system as an AC module system, the cost of a sensor can have an effect on entire system cost because a power conditioning device is connected in a PV module. Because only a current sensor is required for proposed MPPT, it is helpful in the cost reduction point of view. In this paper, a novel MPPT using current sensor is proposed In the proposed MPPT, the voltage is derived from sensed current value. The proposed method is verified by simulation results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.581-584
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• 2003

The phase differences and noise signals are in general serious on output of a instrumentation amplifier for signal conditioning of a sensor driven at high frequency due to a time-varying input signal. In this study, we get the better amplification and S/N ratio using the rectified signal for the input of instrumentation amplifier. This driving circuits were designed and constructed by OrCAD and laboratory PCB process. All of the elements used on the circuit including highly speedy OP-Amp. was SMD type and the MI sensor was fabricated by meander-patterned amorphous ribbon. The output sensitivity of this circuit was $105.3mV/V{\cdot}Oe$. That's why this driving circuit is good at detection of fine magnetic field.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.825-828
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• 2007

This paper presents a thermally adaptive driving (TAD) technology for response time compensation of LCD with integrated sensor. The TAD is comprised of analog sensor signal conditioning and a digital feedback algorithm. Utilizing with a digital feedback system, TAD reduces response time of nearly 50% over the temperature range $0^{\circ}C-60^{\circ}C$.

• Journal of the Institute of Convergence Signal Processing
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• v.2 no.1
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• pp.108-112
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• 2001

Heart sound contains rich information regarding the dynamics of the heart and the auscultation has been a first choice of routine procedures for diagnosis of the heart. However, heart sounds captured using a conventional stethoscope are not often loud or clear enough for doctors to precisely classify their characteristics, especially, under the noisy environments of the hospital. A simple auscultation device that removed shortcomings of the conventional stethoscope was constructed in the study. The device employed a polymer based adherent differential output sensor which was on contact with skin through a coupling medium and appropriated electronic circuits for signal amplification and conditioning An ordinary headphone is taken to hear the captured heart sounds and the volume can be adjusted to hear well. It is also possible that the device sends the captured heart sound signals to a PC where the signals are further processed and viualized.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.454-459
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• 2006

There are two main streams for pattern classification technology One is the method using PCA (Principal Component Analysis) and the other is the method using Neural network. Both of them have merits and demerits. In general, using PCA is so simple while using neural network can improve algorithm continually. Algorithm using neural network needs so many calculations rendering very slow response. In this work, an attempt is made to develop algorithms adopting both PCA and neural network merits for simpler, but faster and smarter.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.53-54
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• 2007