• Journal of Power Electronics
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• 제11권4호
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• pp.583-590
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• 2011

Three-level NPC inverters have been put into practical use for years especially in high voltage high power grids. This paper researches three-level active power filters (APFs). In this paper a mathematical model in the d-q coordinates is presented for 3-phase 3-wire NPC APFs. The deadbeat control scheme is obtained by using state equations. Canceling the delay of one sampling period and providing the predictive value of the harmonic current is a key problem of the deadbeat control. Based on this deadbeat control, the predictive output current value is obtained by the state observer. The delay of one sampling period is remedied in this digital control system by the state observer. The predictive harmonic command current value is obtained by the repetitive predictor synchronously. The repetitive predictor can achieve a better prediction of the harmonic current with the same sampling frequency, thus improving the overall performance of the system. The experiment results indicate that the steady-state accuracy and the dynamic response are both satisfying when the proposed control scheme is implemented.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2344-2353
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• 2018

A coupled recursive total least squares (CRTLS) algorithm is proposed for parameter estimation of permanent magnet synchronous machines (PMSMs). TLS considers the errors of both input variables and output ones, and thus achieves more accurate estimates than standard least squares method does. The proposed algorithm consists of two recursive total least squares (RTLS) algorithms for the d-axis subsystem and q-axis subsystem respectively. The incremental singular value decomposition (SVD) for the RTLS obtained by an approximate calculation with less computation. The performance of the CRTLS is demonstrated by simulation and experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.163-168
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• 2002

The voting algorithm for action selection performs self-improvement by Reinforcement learning algorithm in the dynamic environment. The proposed voting algorithm improves the navigation of the robot by adapting the eligibility of the behaviors and determining the Command Set Generator (CGS). The Navigator that using a proposed voting algorithm corresponds to the CGS for giving the weight values and taking the reward values. It is necessary to decide which Command Set control the mobile robot at given time and to select among the candidate actions. The Command Set was learnt online by means as Q-learning. Action Selector compares Q-values of Navigator with Heterogeneous behaviors. Finally, real-world experimentation was carried out. Results show the good performance for the selection on command set as well as the convergence of Q-value.

• 한국전자파학회논문지
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• 제23권4호
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• pp.468-474
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• 2012

본 논문은 기판 직접형 도파관(SIW)에 complementary split ring resonator(CSRR)이 탑재된 저위상 잡음 발진기를 제안한다. SIW 캐비티의 unloaded Q-factor는 CSRR을 삽입하여 높아졌고, 그 값은 1960을 나타내고 있다. 높은 Q-factor를 나타내는 SIW 캐비티 공진기에 대한 이론적인 분석과 설계 과정이 제시되어 있으며, 설계된 회로가 11.3 dBm의 출력 파워와 1-MHz 오프셋에서 -127.9 dBc/Hz의 위상 잡음을 갖는 9.3 GHz의 신호를 발생시킴을 실험적으로 보여주고 있다.

• E2M - 전기 전자와 첨단 소재
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• 제7권5호
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• pp.403-408
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• 1994

Dielectric and structural properties of $Ba_{1-x}$(Z $n_{1}$3/T $a_{2}$3/) $O_{3}$+1 mol% Mn $O_{2}$ (x=0, 0.01, 0.02, 0.03, 0.04) ceramics was investigated at microwave frequencies. With $Ba_{+2}$ shortage, the sinterability and the unloaded Q( $Q_{u}$) were much improved, and the ordering in B site and the lattice distortion was greatly enhanced and the structure approached the completely ordered structure. $Q_{u}$ was strongly correlated with these factors such as ordering ratio, lattice distortion and sinterability, and had the maximum value of 7500 at x=0.01. The dielectric constant was near 30 and the temperature coefficient of the resonant frequency was 2 ppm/.deg. C at x=0.01.1.1.1.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.252-252
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• 2007

$Al_2O_3-TiO_2$(AT)ceramics shows great promise as a dielectric material for millimeter-wave use. The sintering temperature of AT ceramics was approximately $1450^{\circ}C$ and decreased to $900^{\circ}C$ with the addition of BaCu(B2O5) (BCB) ceramic powder. The presence, of the liquid phase was responsible for the decrease of the sintering temperature. The liquid phase is considered to have a composition similar to the BaO-deficient BCB. The Q-value initially increased with the addition of BCB, but decreased considerably when a large amount of BCB was added, because of the presence of the liquid phase. Good microwave dielectric properties of $Q{\times}f\;=\;16,200\;GHz$, ${\varepsilon}_r\;=\;9$ and ${\tau}_f\;=\;-4\;ppm/^{\circ}C$ were obtained for the 20.0 mol% BCB-added AT ceramics sintered at $900^{\circ}C$ for 2 h.

• 전기전자학회논문지
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• 제15권4호
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• pp.354-362
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• 2011

인공신경망회로에서 아직도 안 풀리는 문제 중 하나는 회로의 처리용량에 관한 것이다. 본 논문은 인공신경망회로의 가장 기본이 되는 하나의 입력과 하나의 출력을 갖은 단층 다단 코어넷을 제안하고 그 처리 용량에 관한 수식을 유도하였다. 제안된 코어넷의 처리 용량으로 p단 입력과 q단 출력을 갖는 코어넷의 처리용량(구현 가능한 함수의 수)은 $a_{p,q}=\frac{1}{2}p(p-1)q^2-\frac{1}{2}(p-2)(3p-1)q+(p-1)(p-2)$ 이며, 입력단 p 값이 짝수이고, 출력단 q가 홀수값이면 추가로 (p-1)(p-2)(q-2)/2 만큼 감해진다. 입력 값으로 3단(level), 출력 값으로 6단을 갖는 1(3)-1(6) 모델을 시뮬레이션하여 분석한 결과, 총 216가지의 함수 조합에서 입력 레벨링 방법으로 cot(x)를 이용하여 82가지의 함수가 구현가능 함을 보였다. 이 모델의 시뮬레이션 결과 80개의 함수가 수렴(구현 가능)하였고, 나머지 수렴되지 않은 함수 중에서 2개의 함수는 무게값 공간에서 무게값 좌표를 미리 계산하여 구현 가능함으로 나와, 총 82개의 구현 가능한 함수가 있음을 보였으며, 이는 위 코어넷 처리용량에 의한 계산 값과 일치하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권7호
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• pp.305-310
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• 2002

The microwave dielectric properties of Ba(Mg$_{1}$3/Ta$_{2}$3/O$_3$-Ba(Co$_{1}$3/Nb$_{2}$3/O$_3$[BMT-BCN] ceramics were investigated. The specimens were prepared by the conventional mixed oxide method with the sintering temperature of 15$25^{\circ}C$~1575$^{\circ}C$. It was found that Ba(Mg$_{1}$3/Ta$_{2}$3/O$_3$[BMT] and BCN formed a solid solution with complex perovskite structure. As increasing the mole fraction of BCN, dielectric constant increased while the temperature coefficient of resonant frequency was changed from positive to negative value. The highest value of quality factor, Q$\times$f$_{0}$=138,205GHz, obtained in the 0.9BMT-0.1BCN ceramics sintered at 1575$^{\circ}C$. In the range of x$\geq$0.4, the dielectric constant was about 30. The 0.55BMT-0.45BCN ceramics sintered at 15$25^{\circ}C$ for 5 hours showed the microwave dielectric properties of $\varepsilon$$_{r}$=30.21, Q$\times$f$_{0}$=85,789GHz and $\tau$$_{f}$=2.9015ppm/$^{\circ}C$.EX>.

• Transactions on Electrical and Electronic Materials
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• 제13권6호
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• pp.283-286
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• 2012

(1-X)$(Na_{0.5}K_{0.5})NbO_3-XK_{5.4}Cu_{1.3}Ta_{10}O_{29}$ (NKN-KCT) lead-free piezoelectric ceramics have been synthesized by the conventional solid state sintering method, and their sinterability and piezoelectric properties were investigated. Typically, this material is sintered between 1,025 and $1,100^{\circ}C$ for 2 hours to achieve the required densification. Crystalline structures and Microstructures were analyzed by X-ray diffraction and scanning electron microscope. The density, dielectric constant (${\varepsilon}_r$), piezoelectric constant $d_{33}$, electromechanical coupling factor $k_p$ and mechanical quality factor $Q_m$ value of the NKN ceramics depended upon the KCT content and the sintering temperature. In particular, the KCT addition to NKN greatly improved the mechanical quality factor $Q_m$ value. The ceramic with X = 1.0 mol% sintered at $1,050^{\circ}C$ exhibited optimum properties (${\varepsilon}_r$=246, $d_{33}$=95, $k_p$=0.38 and $Q_m$=1,826). These results indicate that the ceramic is a promising candidate material for applications in lead free piezoelectric transformer and filter materials.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.260-260
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• 2007

Low-temperature sintering and dielectric properties of the $1-xBiNbO_4-xZnNb_2O_6$ ceramics (x=0.3, 0.5, and 0.7) with 10 wt% zinc borosilicate (ZBS) glass was investigated as a function of the substitution of $ZnNb_2O_6$ with a view to applying this system to LTCC technology. The all composition addition of 10 wt% ZBS glass ensured a successful sintering below $900^{\circ}C$. The the amount of $ZnNb_2O_6$ on $ZnNb_2O_6$ ceramics increased the $Q{\times}f$ values, but it decreased the sinterability and dielectric constant due to the higher $Q{\times}f$ value and sintering temperature of $ZnNb_2O_6$ than that of $ZnNb_2O_6$ ceramics. The increase of $ZnNb_2O_6$ content from 0.3 to 0.7 in the $1-xBiNbO_4-xZnNb_2O_6$ ceramics with 10 wt% ZBS glass sintered at $900^{\circ}C$ demonstrated 30~20 in the dielectric constant (${\varepsilon}_r$), 3,500~4,500 GHz in the $Q{\times}f$ value.