• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.771-772
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• 2014

In this paper, the integrated design method of suction muffler in compressor was studied. There are three things to consider when designing this. First, the transmission loss was maximized to consider the noise reduction. Second, dissipation energy of fluid flow was minimized for energy efficiency. Finally, acoustical resonance frequency of suction muffler was controlled because energy efficiency can be increased by supercharging of refrigerant. Therefore, suction muffler was designed to have the specific resonance frequency. The input impedance was used for designing target acoustical resonance frequency. Topology optimization was used for optimization method.

• 전기학회논문지
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• 제63권6호
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• pp.841-849
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• 2014

Urban railway with rectifiers is connected by parallel circuits because substations are joined by the power rail. Thus, if an input voltage of a substation is increased, then the voltage of rectifiers is also increased, and which leads to an increase in the peak power of the substation. To solve this problem, this paper proposes a new method reducing the peak power of substations by adjusting the operation number of rectifiers. Its feasibility is exemplified by some simulations performed for Incheon subway Line 1 and GA(Genetic Algorithm) method has been applied to obtain the optimal input. Simulation results show that peak power can significantly be reduced using the method proposed in this paper.

• 한국통신학회논문지
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• 제18권4호
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• pp.481-489
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• 1993

등간격의 전극구조를 갖는 탄성표면파 필터의 정전계적 임피던스 해석을 위하여 무한개의 인접전극의 정전계적 상호작용을 해석하여 전극의 구조에 따른 전하분포를 구현하였는데, 이는 Element Factor와 Array Factor로 분리하여 계산할 수 있었다. 임의의 전극 구조를 갖는 탄성표면과 필터의 입력 및 출력 전극의 Radiation Conductionce, Susceptance 및 static Capacitance는 이러한 전극에서의 전하분포를 통하여 구하였고 Apodized IDT의 임피던스는 Multi-Track 해석에 의하여 다수의 Uniform Track의 병렬 연결로써 계산하였다. 이와 같이 얻어진 입.출력 전극의 임피던스를 실제로 제작된 필터의 측정 임피던스와 비교한 결과 잘 일치하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.273-277
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• 1999

A cold cathode flourescent lamp for the backlight in the notebook computer requires high input voltage about 1300(V) when it turns on. But once a discharge starts, the input voltage can be dropped by about one-third for continued output. The equivalent impedance also varies from open to several dozens of kilo-ohms. The piezoelectric transformer converts electrical energy into mechanical energy and then converts it back to electrical energy at a high voltage. Its high output voltage, high efficiency and small size are suitable for driving the LCD backlight in the notebook computer. The piezoelectric transformer operates near the resonance frequency and the output waveform is close to sine wave with very little noise. This paper suggests an inverter for LCD backlight of notebook computer using piezoelectric transformer that includes voltage to frequency converter for gate signal which is useful for tracking of variable resonance frequency depending on load impedance.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(1)
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• pp.267-270
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• 2000

The feasibility of small linear antenna for near range wireless communications was studied. The requirement of the system are frequency range 9∼12 MHz and antenna size 15 cm. The communication range is about 15 m. The antenna input impedance is very small radiation resistance and very large capacitive reactance. The lossless impedance matching is nearly impossible, therefore lossy matching is considered. The antenna has very low radiation efficiency. The near field calculation has a large uncertainty, but the results can be used as the guideline of a small linear antenna system for a near range wireless communication.

• 대한의용생체공학회:의공학회지
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• 제16권3호
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• pp.301-308
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• 1995

A high-precision pre-amplifier is designed for general use in EEG measurement system. It consists of signal generator, signal amplifier with a impedance converter, shield driver, body driver, differential amplifier, and isolation amplifier. The combination of minimum use of inaccurate passive components and the appropriate matching of each monolithic amplifiers results in good noise behavior, low leakage current, high CMRR, high input impedance, and high IMRR. The performance of EEG pre-amplifier has been verified by showing the typical EEG pattevn of a nomad person through the clinical experiments.

• 소음진동
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• 제6권6호
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• pp.749-754
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• 1996

In this paper, a design method of matching layers is presented for the sandwich type broad band underwater acoustic vibrators. The characteristic impedances of matching layers are determined to be matched to the characteristic impedance of head mass material. For the dynamic characteristic analysis of the sandwich type transducers, one dimensional FEM technique is also introduced. A test vibrator with the quarter wave matching layers has been designed to verify the proposed method. And the wide band characteristics of the input impedance and transmitting voltage response (TVR) are investigated.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(1)
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• pp.447-450
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• 2002

In this paper, we present design methods for a series-fed microstrip patch array operating at X-band frequency. The array consists of 18 rectangular patches connected to 3 quarter-wave impedance transformers. The power divider is designed for the uniform element excitation. The element excitation is then made to be tapered by increasing the input impedance of elements located at array edges. The designed antenna is fabricated and tested. Results of test show a fair agreement with the prediction.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.617-618
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• 2013

• 전기학회논문지
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• 제63권10호
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• pp.1364-1370
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• 2014

Power system fault analysis has been based on symmetrical component method, which describes power system elements by positive, negative and zero sequence impedance. Obtaining accurate line impedances as possible are very important for estimating fault current magnitude and setting distance relay accurately. Especially, accurate calculation of zero sequence impedance is important because most of transmission line faults are line-to-ground faults, not balanced three-phase fault. Since KEPCO has started measuring of transmission line impedance at 2005, it has been revealed that the measured and calculated line impedances are well agreed within reasonable accuracy. In case of underground transmission lines, however, large discrepancies in zero sequence impedance were observed occasionally. Since zero sequence impedance is an important input data for distance relay to locate faulted point correctly, it is urgently required to analyze, detect and consider countermeasures to the source of these discrepancies. In this paper, development of pre/post processor to ATP (Alternative Transient Program) version of EMTP (Electro-Magnetic Transient Program) for sequence impedance calculation was described. With the developed processor ATP-cable, effects of ground resistance and ECC (Earth Continuity Conductor) on sequence impedance were analyzed.