• 한국공작기계학회논문집
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• 제17권1호
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• pp.29-34
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• 2008

A modeling technique for the 2-way coupling of heat transfer and conduction currents has been performed to inspire a combined analytical simulation. The 3-D finite element method is used to solve steady conduction currents and heat generation in an aluminum film deposited on a silicon substrate. The model investigates the temperature in the device after the current is applied. The conservation equation of energy, the Maxwell equations for conduction currents, the unsteady state heat transfer equation and the Fourier's law for heat transfer are implemented as a bidirectionally coupled problem. It is found that the strongly coupled temperature and time dependent heat equations give a reasonable results and an explicit solving technique.

• 산업기술연구
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• 제32권A호
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• pp.103-107
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• 2012

Due to improvement of the semiconductor technology, the LED replaces the conventional lighting source and LED drivers have been studied and developed. The LED is driven by the constant current control method according to its characteristics. For the constant current control method, the linear regulator and the switching regulator is used. The switching regulator is usually used to LED drivers because it has specific characteristics as the wide input dynamic range and the high efficiency. In this paper, we have described the principle and the implement of the switching regulator, using the drive IC and the low cost DSP chip. Also, both methods have been implemented and its electrical characteristics had almost same experimental results in the steady state and the transient state.

• 대한전기학회논문지
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• 제41권6호
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• pp.579-587
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• 1992

This paper is to study on the step-up DC-DC converter for power system which yields output characteristics of low voltage and high current, such as fuel cell generation system. DC-AC-DC scheme is suggested for high ratio of voltage conversion. Three phase MOSFET-SPWM inverter is adopted for intermediate AC conversion and inverter output frequency is chosen at 400[Hz] in order to reduce the size of magnetic circuit and DC filter. Since control strategy which combines voltage controller with current controller in parallel is used, good output performance is obtained both in steady state and in transient state like load variation, not only in single unit operation but also in parallel operation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 학술대회 논문집 전문대학교육위원
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• pp.98-101
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• 2002

The switching-mode power converter has been widely used because of its features of high efficiency and small weight and size. These features are brought by the ON-OFF operation of semiconductor switching devices. However, this switching operation causes the surge and EMI(Electromagnetic Interference) which deteriorate the reliability of the converter themselves and entire electronic systems. This problem on the surge and noise is one of the most serious difficulties in AC-to-DC converter. In the case of carrier frequency selection, output-voltage of steady state and transient state is fully regulated. A RPWM control method was proposed in order to smooth the switching noise spectrum and reduce it's level. Experimental results are verified by converter operating at 300V/1kW with 5%${\sim}$30% white noise input. Spectrum analysis is performed on the Phase current and the CM noise voltage. The former is measured with Current Probe and the latter is achieved with USN. which are connected to the spectrum analyzer respectively.

• 전기학회논문지P
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• 제51권3호
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• pp.120-125
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• 2002

The switching-mode power converter has been widely used because of its features of high efficiency and small weight and size. These features are brought by the ON-OFF operation of semiconductor switching devices. However, this switching operation causes the surge and EMI(Electromagnetic Interference) which deteriorate the reliability of the converter themselves and entire electronic systems. This problem on the surge and noise is one of the most serious difficulties in AC-to-DC converter. In the switching-mode power converter, the output voltage is generally controlled by varying the duty ratio of main switch. When a converter operates in steady state, duty ratio of the converter is kept constant. So the power of switching noise is concentrated in specific frequencies. Generally, to reduce the EMI and improve the immunity of converter system, the switching frequency of converter needs to be properly modulated during a rectified line period instead of being kept constant. Random Pulse Width Modulation (RPWM) is performed by adding a random perturbation to switching instant while output-voltage regulation of converter is performed. RPWM method for reducing conducted EMI in single switch three phase discontinuous conduction mode boost converter is presented. The more white noise is injected, the more conducted EMI is reduced. But output-voltage is not sufficiently regulated. This is the reason why carrier frequency selection topology is proposed. In the case of carrier frequency selection, output-voltage of steady state and transient state is fully regulated. A RPWM control method was proposed in order to smooth the switching noise spectrum and reduce it's level. Experimental results are verified by converter operating at 300V/1kW with 5%~30% white noise input. Spectrum analysis is performed on the Phase current and the CM noise voltage. The former is measured with Current Probe and the latter is achieved with LISN, which are connected to the spectrum analyzer respectively.

• 한국통신학회논문지
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• 제21권12호
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• pp.3069-3085
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• 1996

This paper shows an accurate charge-pump PLL model which considers the wave-form distortion in high speed operation of charge-pump PLL, the leakage current in loop filter, and a physical limit in charge-pump. With proposed model of charge-pump PLL, overload and stability are derived theoretically and the results are compared to the conventional model. Unlike the ideal charge-pump PLL that simplifies calculations, it is possible to analyze the transient-state and the steady-state at the same time with proposed accurate model. Thus, charge-pump over load, in the transient-state and the stead-state of charge-pump, is accuragely analyzed and the results are confirmed with simulation.

• 대한전기학회논문지:전력기술부문A
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• 제53권3호
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• pp.161-167
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• 2004

Zone 3 of the distance relay is used to provide the remote back-up protection in case of the failure of the primary protection. However, the risk lot mal-operations under stressed conditions such as heavy loading, voltage and transient instability is usually high. Zone 3 is used in combination with the derivatives of the voltage, and current, etc to prevent mal-operations. Sometimes, the impedance characteristics that restrict the tripping area of relay are used to avoid the mal-operations due to load encroachment. This paper presents a novel Zone 3 scheme based on combining the steady-state components (i.e. 60Hz) and the transient components (TCs) using a state diagram that visualizes the sequence of studies that emanate from the sequence of events. The simulation results show that the novel zone 3 distance relay elements using the proposed method operates correctly for the various events.

• 한국임상약학회지
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• 제19권2호
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• pp.120-130
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• 2009

The objective of this study was to analyze and to improve therapeutic drug monitoring(TDM) service of vancomycin in a local hospital. Patients with TDM service between September 2005 and December 2008 were included and the data were collected for vancomycin use and components of TDM. During that period, 421 cases of TDM service of vancomycin in 236 patients were retrospectively reviewed. The first dosages of vancomycin were appropriate in 135(57.2%) patients and administration of vancomycin was discontinued in 126(53.4%) patients due to therapeutic failure or adverse drug reaction. MRSA was identified in 191(80.9%) patients and 135(70.7%) samples for the identification were sputum. According to the TDM reports, 232(55.1%) serum samples were obtained at the steady-state conditions and 55.5% of the samples that were drawn before the steady-state was due to the physician's inappropriate knowledge about the steady-state. Based on the time of vancomycin administration, 35.8% of the samples were not obtained at the recommended sampling time. For the patients in general wards, the most common reason for the incorrect samples was routine serum sampling by the laboratory medicine phlebotomists between 6 and 8 a.m. except sunday. In contrast, samples drawn by nurses or physicians at inappropriate time were the most common reason for the incorrect samples with patients in the intensive care units. Physicians accepted 68.5% of the recommendations for vancomycin dosage and administration. In conclusion, TDM service of vancomycin needs to be improved in inappropriate sampling time and vancomycin dosage. For solving these problems, current team made of TDM pharmacists and physicians of laboratory medicine can be expanded to include a physician of infectious diseases, nurses and laboratory medicine phlebotomists as new members. Through the TDM service of vancomycin by the new team, we can settle the problems and make the guideline for the scientific controversies associated with therapeutic monitoring of vancomycin.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2003년도 춘계공동학술대회논문집
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• pp.157-164
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• 2003

복잡한 수심을 가진 연안해역에서 조석, 바람과 파에 의해 발생된 흐름의 영향까지를 고려한 파랑모델의 도입은 대부분의 해안공학 설계나 방재 문제에 매우 중요한 요소이다. 근해역에서 수심변화에 의한 굴절 및 천수효과, 흐름에 의해 유발되는 굴절효과, 파형경사에 따른 쇄파, 회절, 바람에 의한 파의 성장, 파랑 상호간의 간섭 및 에너지 재분포 등을 다를 수 있다는 점에서 정상상태 스펙트럼 모델의 현장 적용은 지금까지 여러 모델이 다루지 못한 부분을 해소하게 될 것이다. 본 연구에서는 부만 신항만 건설이 이루어지고 있는 가덕인접의 및은 수역에 대해 파랑의 변환과정을 보다 합리적으로 해석하기 위해 스펙트럼 모델을 적용하고 기존의 모델 결과와 비교 분석하는 것을 골자로 하고 있다. 이러한 시도가 가까운 장래에 항만설계 및 방재시스템 분야에서 보다 안전하고 널리 스펙트럼 모델을 적용하게 하는 계기가 되도록 의도하였다.

• 한국인터넷방송통신학회논문지
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• 제19권5호
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• pp.101-106
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• 2019

본 논문에서는 nonconstant modulus 신호 전송에서 채널에서 발생되는 부호간 간섭 영향을 줄이기 위한 FC-MMA 적응 등화 알고리즘에 가변 스텝 크기를 적용하여 등화 성능을 개선할 수 있는 VSS-FC-MMA 알고리즘을 제안한 후, 이의 개선된 성능을 확인하였다. FC-MMA 는 적응 등화를 위한 오차 신호를 얻을 때 신호 심볼의 레벨수를 고려한 수정된 dispersion constant와 고정 스텝 크기를 적용하여 MMA의 수렴 속도를 개선할 수 있지만 정상 상태에서 등화 성능이 열화된다. 논문에서 제안하는 VSS-FC-MMA는 기존 FC-MMA와 가변 스텝 크기를 적용하므로서 정상 상태에서 등화 성능을 개선할 수 있으며, 이를 컴퓨터 시뮬레이션을 통해 확인하였다. 이를 위하여 동일한 채널과 신호대 잡음비를 적용할 때 알고리즘의 신호 복원 능력 및 성능 비교를 위한 지수로는 잔류 isi, MSE와 SER을 적용하였다. 시뮬레이션의 결과 제안 VSS-FC-MMA는 FC-MMA보다 잔여량과 SER 성능이 개선되지만, 수렴 속도에서는 1.7배 정도 늦어짐을 확인하였다.