• 한국전기전자재료학회논문지
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• 제19권8호
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• pp.707-711
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• 2006

ZnO was doped up to 0.3 wt% for improving the electrical properties of lead-free $[Li_{0.04}(Na_{0.44}Ko_{0.52})-(Nb_{0.86}\;Ta_{0.10}\;Sb_{0.04})]O_3$ piezoelectric ceramics. The ceramics were fabricated with the conventional sintering processes. Crystal structure of the samples was tetragonal phase regardless of ZnO amount. However, the piezoelectric properties were varied with the ZnO amount. The electro-mechanical coupling factor $(k_p)$ was with the ZnO amount up to 0.2 wt% but decreased with the further addition. the maximum value of $k_p$ was 0.475. Density, piezoelectric charge constant and relative dielectric constant was also showed maximum value at 0.2 wt%. The maximum values are $4.75g/cm^3$, 275 pC/N, 1403, respectively. In contrast, the mechanical quality factor $(Q_m)$ was not varied with increasing the ZnO addition up to 0.2 wt% but rapidly increased at 0.3 wt%.

• 전기학회논문지P
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• 제52권4호
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• pp.161-166
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• 2003

This paper proposes a sensorless vector control of interior permanent magnet synchronous motor(IPMSM) using a reduced order observer. This method introduce the auxiliary control inputs that can eliminate the nonlinear term in the electrical equations and realize the linearization of the motor model. The rotor speed estimate with the observer that needs only the q-axis current. The rotor position calculate using the estimated rotor speed. The speed and position control implement with the estimated value. The validity of the proposed scheme is confirmed by various response characteristics.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.305-307
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• 1996

Because most LIM is driven by inverter, input voltage is involved with the time harmonics. Therefore the equiLlQ/ent circuit for an inverter-fed LIM has to be modified to represent every harmonics present in supply voltage. This paper analyzes the characteristics and loss of LIM to construct the equivalent circuit for each time harmonics through the static test and theoretical analysis. To make an analysis of nonsinusoidal supply waveforms, it is developed the simulation program to calculate the RMS, peak value and THD for any waveforms expressing Fourier series.

• 전기학회논문지
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• 제66권1호
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• pp.66-71
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• 2017

In this paper, we study the robustness of disturbance observer based controller for DC motor in the presence of unmodeled dynamics. It is well known that the robustness property usually becomes weaker as the control gain becomes larger. On the contrary to this expectation, it is shown that the phase margin of DOB controller remains quite a large value even though the time constant of Q-filter becomes smaller. The computer simulation results show that DOB controller is able to stabilize the motor system even in the presence of unmodeled dynamics. On the contrary, the unity-feedback system fails to maintain stability when a high gain feedback is employed for the purpose of achieving better disturbance attenuation performance.

• 한국컴퓨터산업학회논문지
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• 제6권2호
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• pp.357-364
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• 2005

최근 들어 우리나라에서는 설치의 간편성과 높은 신뢰도를 가진 전력케이블의 사용이 증가하고 있다. 전력케이블은 출고 전에 IEEE std. 404-1993 시험을 거쳐 안정성을 확인하고 있지만 포설시 발생하는 접속부 내부의 결함으로 인하여 많은 문제가 발생하고 있다. 특히 불순물 혼입 또는 공극 발생시 고장율은 증가하게 된다 부분방전 검출은 포설 후 전력케이블의 상태를 관측할 수 있는 유용한 방법이다. 본 연구에서는 부분방전 특성을 평가하고자 케이블 접속재인 EPR과 케이블 절연체인 XPLE 사이에 인공 결함을 발생시킨 후 데이터 취득 시스템을 이용하여 $\Phi-q-n$ 특성을 검출하였으며, 부분방전의 정량적 해석을 위해 필요한 통계량을 계산하였으며, 신경망 모델을 적용하여 패턴 분석을 수행하여 $88\~96\%$의 구별이 가능하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1993년도 추계학술대회 논문집
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• pp.6-9
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• 1993

본 연구에서는 소량(lmol%)의 MnO$_2$를 첨가한 Ba(Zn$_{1}$3Ta$_{2}$3)O$_3$에서 미량(x)외 Ba를 결핍 시켜가면서 마이크로파 유전 특성과 소결성, 구조적 특성을 관찰하였다. XRD분석을 통하여 Ba의 부족량이 증가함에 따라 Ba(Zn$_{1}$3/Ta$_{2}$3/)O$_3$B site의 규칙화와 격자 비틀림(Lattice Distortion)이 촉진되었다. 무부하 Q값은 10.5GHz에서 x가 0.01일때 가장 높은 간(8500)을 나타내었으나 이 후에는 급격히 감소하였고 온도 계수는 Ba의 부족량이 중가함에 따라 중가하였고, x가 0.01일때는 약 2ppm/$^{\circ}C$였다.

• E2M - 전기 전자와 첨단 소재
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• 제10권3호
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• pp.274-283
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• 1997

These days, according to surprising development of communication enterprises, every soft of devices is getting smaller and cheaper. Among these Devices, microwave dielectric ceramics are studied and progressed briskly as the materials of dielectric resonator. Dielectric properties of BaO-S $M_{2}$ $O_{3}$-Ti $O_{2}$, one of the BaO Lnsub 2/ $O_{3}$-Ti $O_{2}$ (Ln=La, Sm, Nd, Pr…) system, synthesized by solid-reaction and coprecipitation method were investigated. Disk-type samples were sintered at 1250-1400.deg. C for 2hrs. As a result, single phase was not synthesized in both method. First created the second phase of S $M_{2}$ $Ti_{2}$ $O_{7}$, and then the last phase of $Ba_{3.75}$S $m_{9.5}$ $Ti_{18}$ $O_{54}$, Ti $O_{2}$, and $Ba_{2}$ $Ti_{9}$ $O_{20}$. When the sample was sintered at 1280.deg. C (in solid reaction method) and at 1310.deg. C (in coprecipitation method), it obtained highest dielectric constant (72.96 and 71.70, respectively) and high Q value. Above that temperature, dielectric constant and Q value decreased because of lattice defect according to oxygen vacancies........

• E2M - 전기 전자와 첨단 소재
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• 제10권8호
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• pp.819-829
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• 1997

The microwave dielectric materials of the BaO-Nd$_2$O$_3$-TiO$_2$and BaO-(Sm, Nd)$_2$O$_3$-TiO$_2$system were synthesized by conventional ceramic processing and sintered 1220 to 140$0^{\circ}C$ for 2 hours respectively. Their crystallization and dielectric properties were examined. In the BaO-Nd$_2$O$_3$-TiO$_2$ and BaO-(Sm, Nd)$_2$O$_3$-TiO$_2$system. Nd$_2$Ti$_2$O$_{7}$ and (Sm, Nd)$_2$Ti$_2$O$_{7}$ were observed as a second phase respectively. The maximum relative dielectric constant were 79,99 for the BaO-Nd$_2$O$_3$-TiO$_2$system and 105.07 for the BaO-(Sm,Nd)$_2$O$_3$-TiO$_2$system and their Q-value were over 2000 at 3GHz.GHz.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.298-298
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• 2007

Influence of $TiO_2$ on the dielectric properties of the $Bi(Nb_{0.7}Ta_{0.3})O_4$ ceramic with 7 wt% zinc borosilicate(ZBS) glass was investigated as a function of the $TiO_2$ contents with a view to applying this system to LTCC technology. The $Bi(Nb_{0.7}Ta_{0.3})O_4$ ceramic addition of 7 wt% ZBS glass ensured successful sintering below $900^{\circ}C$. But, TCF of $Bi(Nb_{0.7}Ta_{0.3})O_4$ ceramic is large negative values, respectively, it is necessary to adjust to zero TCF for practical applications Therefore, the addition of materials having positive TCF, such as $TiO_2$, might be an effective method for the improvement. In general, increasing addition of $TiO_2$ increased dielectric constant and TCF but it decreased the sinterability and $Q{\tiems}f$ value significantly due to the dielectric property and high sintering temperature of $TiO_2$. $Bi(Nb_{0.7}Ta_{0.3})O_4$ ceramic with 7 wt% ZBS glass and then addition 0.5 wt% $TiO_2$ sintered at $900^{\circ}C$ demonstrated 42 in the dielectric constant(${\varepsilon}_r$), 1,000 GHz in the $Q{\times}f$ value, and $10{\pm}5\;ppm/^{\circ}C$ in the temperature coefficient of resonant frequency(${\tau}_f$).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1958-1960
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• 2003

Here we describe a unique self-oscillating mixer (SOM) design using a modified defected ground structure (DGS) for down-converter. Proposed SOM is consisted of self-oscillator, which can produce negative resistance and select resonance frequency, and input/output matching filter. As the advantage of this SOM can be reused by module that mix signals with transistor that is used to oscillator, it is simply and low-costly designed Also, there is easy advantage to be applied in RFIC/ MMIC technology because it offers excellent high Q value in spite of using micro-strip structure. Designed self-oscillating frequency is 1.04GHz and RF frequency established is 0.8GHz. It was achieved 20dB conversion loss and phase noise of -95dBc/Hz at 100KHz offset frequency over intermediate frequency (IF). The equivalent circuit parameters for DGS are extracted by using a three dimensional EM simulator and simple circuit analysis method.