• 전자공학회논문지D
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• 제35D권3호
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• pp.39-45
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• 1998

SrBi$_{2}$Ta$_{2}$O$_{9}$ (SBT) ferroelectric thin films for nonvolatile memory were prepared on Pt/Ti/SiO$_{2}$/Si and RuO$_{2}$/SiO$_{2}$/Si substrates by RF magnetron sputtering. The dependences of crystalline and electrical properties on the lower electrode type(Pt and RuO$_{2}$) and the annealing temperatures were investigated. SBT films regardless of their electrode types showed typeical Bi layered peroviskite crystal structures. The crystalline quality of as-deposited SBT films was improved by the rapid thermal annealing at 650.deg. C for 30 sec. The remanetn polarization of 2Pr (Pr+-Pr-) of the annealed SBT films deposited on Pt/Ti/SiO$_{2}$/Si substrates were about 11 .mu.C/cm$^{2}$ and 3 .mu.C/cm$^{2}$, respectively. The leakage currents at 3 V bias voltage were about 0.8 .mu.A/cm$^{2}$ for SBT/ Pt/Ti/SiO$_{2}$/Si and about 1 .mu.A/cm$^{2}$ for SBT/RuO$_{2}$/SiO$_{2}$/Si sample. SBT films annealed at 650 .deg. C showed no degradation in Pr values after 10$^{11}$ polarization switching cycles, indicating good fatigue properties. In addition, for SBT samples deposited on Pt/Ti/SiO$_{2}$/Si, Pr values increased to more than that of initial state, suggesting the increament of leakage current caused by repeated polarization.

• 전력전자학회논문지
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• 제20권5호
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• pp.456-463
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• 2015

Nowadays, small quantity batch production, which is so-called a flexible manufacturing system, is a major trend in the modern factory automation industry. The demands for new transportation system are increased gradually, with which multiple passive carriers carrying materials and semi-products are precisely and individually controlled along a single closed rail. Thus, a new type of permanent magnet linear synchronous motor (PMLSM), which consists of state coils on a single rail and PM movers as many as carriers, is proposed in this paper. The rail can be segmented as modules with pairs of coils and a current amplifier, which makes the transportation system simple; therefore, the rail can be easily extended and repaired. A design method of the new PMLSM with a single carrier is proposed, which can be thought as a new version of PMLSM, a coil-segmented coreless PMLSM (CS-CLPMLSM). Experimental setup for it is made, and propulsion results show that with the help of a new effective coil selection and switching algorithms, the conventional current-based vector control is sufficient to fulfill the position and velocity control of the new PMLSM. The proposed PMLSM is expected to fulfill seamless servo-control of multiple carriers also in process line, such as a new generation of flat panel display manufacturing line.

• Molecules and Cells
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• 제43권3호
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• pp.251-263
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• 2020

Flagellin, a major structural protein of the flagellum found in all motile bacteria, activates the TLR5- or NLRC4 inflammasome-dependent signaling pathway to induce innate immune responses. Flagellin can also serve as a specific antigen for the adaptive immune system and stimulate anti-flagellin antibody responses. Failure to recognize commensal-derived flagellin in TLR5-deficient mice leads to the reduction in anti-flagellin IgA antibodies at steady state and causes microbial dysbiosis and mucosal barrier breach by flagellated bacteria to promote chronic intestinal inflammation. Despite the important role of anti-flagellin antibodies in maintaining the intestinal homeostasis, regulatory mechanisms underlying the flagellin-specific antibody responses are not well understood. In this study, we show that flagellin induces interferon-β (IFN-β) production and subsequently activates type I IFN receptor signaling in a TLR5- and MyD88-dependent manner in vitro and in vivo. Internalization of TLR5 from the plasma membrane to the acidic environment of endolysosomes was required for the production of IFN-β, but not for other pro-inflammatory cytokines. In addition, we found that anti-flagellin IgG2c and IgA responses were severely impaired in interferon-alpha receptor 1 (IFNAR1)-deficient mice, suggesting that IFN-β produced by the flagellin stimulation regulates anti-flagellin antibody class switching. Our findings shed a new light on the regulation of flagellin-mediated immune activation and may help find new strategies to promote the intestinal health and develop mucosal vaccines.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 추계종합학술대회
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• pp.465-468
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• 2005

기존의 MMA(Multi-Modulus Algorithm)는 심벌간 간섭(Intersymbol Interference: ISI)이 심한 등화 초기에는 부정확한 판단을 할 가능성이 매우 높기 때문에 눈모형을 열리게 하는데 어려움이 있다. 이러한 문제점을 피하기 위해 최근에 MCMA(Modified Constant Modulus Algorithm)를 기반으로 한 SMMA(Sliced MMA)가 제안되었다. SMMA는 높은 SNR 조건에서는 MMA보다 개선된 성능을 보이나, 낮은 SNR 조건에서는 비용함수에 사용되는 판정 값이 부정확할 가능성이 매우 높다는 사실을 알 수 있다. 그러므로 본 논문에서는 등화 초기에 블라인드 수렴 특성을 저하시키지 않으면서 정상상태 성능을 개선하는 다중 modulus 블라인드 등화 알고리즘 기법을 제시한다. 제안한 방법에서는 단일 modulus와 다중 modulus의 선택적 적용을 위해 등화기 출력의 잔류심벌간 간섭 양을 이용한 초기수렴검출 기법을 고안${\cdot}$적용하여 최적의 전환 시점을 자동으로 겨??ㅇ하였다. 제안 알고리즘의 성능을 모의실험을 통하여 수렴 속도와 잔류 ISI 성능에서 기존방식에 비해 제안한 방식의 유용성을 확인하였다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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• pp.141-144
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• 2006

The deviations in the injection orbital parameters, resulting from launcher dispersions, need to be estimated and used for autonomous satellite operations. For the proposed small satellite mission of the university there will be two GPS receivers onboard the satellite to provide the instantaneous orbital state to the onboard data handling system. In order to meet the power requirements, the satellite will be sun-tracking whenever there is no imaging operation. For imaging activities, the satellite will be maneuvered to nadir-pointing mode. Due to such different modes of orientation the geometry for the GPS receivers will not be favorable at all times and there will be instances of poor geometry resulting in no output from the GPS receivers. Onboard the satellite, the orbital information should be continuously available for autonomous switching on/off of various subsystems. The paper presents the strategies to make use of small arcs of data from GPS receivers to compute the mean orbital parameters and use the updated orbital parameters to calculate the position and velocity whenever the same is not available from GPS receiver. Thus the navigation message from the GPS receiver, namely the position vector in Earth-Centered-Earth-Fixed (ECEF) frame, is used as measurements. As for estimation, two techniques - (1) batch least squares method, and (2) Kalman Filter method are used for orbit estimation (in real time). The performance of the onboard orbit estimation has been assessed based on hardware based multi-channel GPS Signal simulator. The results indicate good converge even with short arcs of data as the GPS navigation data are generally very accurate and the data rate is also fast (typically 1Hz).

• Journal of Power Electronics
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• 제16권1호
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• pp.297-309
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• 2016

Grid-connected inverters (GCIs) with an LCL output filter have the ability of attenuating high-frequency (HF) switching ripples. However, by using only grid-current control, the system is prone to resonances if it is not properly damped, and the current distortion is amplified significantly under highly distorted grid conditions. This paper proposes a synchronous reference frame equivalent proportional-integral (SRF-EPI) controller in the αβ stationary frame using the parallel virtual resistance-based active damping (PVR-AD) strategy for grid-interfaced distributed generation (DG) systems to suppress LCL resonance. Although both a proportional-resonant (PR) controller in the αβ stationary frame and a PI controller in the dq synchronous frame achieve zero steady-state error, the amplitude- and phase-frequency characteristics differ greatly from each other except for the reference tracking at the fundamental frequency. Therefore, an accurate SRF-EPI controller in the αβ stationary frame is established to achieve precise tracking accuracy. Moreover, the robustness, the harmonic rejection capability, and the influence of the control delay are investigated by the Nyquist stability criterion when the PVR-based AD method is adopted. Furthermore, grid voltage feed-forward and multiple PR controllers are integrated into the current loop to mitigate the current distortion introduced by the grid background distortion. In addition, the parameters design guidelines are presented to show the effectiveness of the proposed strategy. Finally, simulation and experimental results are provided to validate the feasibility of the proposed control approach.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기물성,응용부문
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• pp.212-214
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• 2004

In this study, we fabricated the organic thin film by self-assembly method by using nitro-group and methoxy-group organic molecule. Also, we selected the organic single molecule in organic thin film and measured current-voltage characteristics by using scanning tunneling microscopy. The Organic molecules that use in an experiment is 4,4'-(diethynylphenyl)-2'-nitro-1-benzen ethiol and 4-[2,5-dimethoxy-4-ph enylethynylphenyl]ethynylphenylethanthiol. 4,4'-(dimet hynylphenyl)-2'-nitro-1-benzenethiol is applied widely in molecular electronic device and 4-[2,5-dime thoxy-4-phenylethynylphenyl]ethynylphenylethanthiol composed in Korea Research Institute of Chemical Technology. To be confirmed the formation of the self-assembled monolayers, we observed the real time frequency shift of the QCM and investigated surface of the self-assembled monolayers the using STM. With this, we measured current to the organic single molecule, in condition of the air state. As a result, we confirmed in constant voltage that properties of negative differential resistance. Using properties of negative differential resistance to get from this study, application is expected to be molecular switching device, memory device and logic device.

• 전력전자학회논문지
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• 제6권5호
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• pp.400-409
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• 2001

대용량 승압형 응용을 위한 새로운 위상천이 병렬입력/직렬출력 듀얼 컨버터가 제안된 바 있다. 제안된 컨버터는 종래의 펄스 폭 변조(PWM) 방식의 병렬입력/직렬출력 듀얼 컨버터에 비해 낮은 스위치 전압 스트레스를 보여 저 손실의 소자를 사용할 수 있으므로 높은 효율을 보인다. 또한, 출력 캐패시터의 실효(RMS) 전류 스트레스가 낮고 입력 전류와 출력 전압의 맥동이 작으며, 제어 입력에 대한 출력 전압의 동역학(dynamics)이 빠른 장점이 있다. 본 논문에서는 제안된 컨버터의 정상상태 동작을 심도 있게 분석하고 그 수학적 모델 및 정상상태 해를 제시하며, 제안된 컨버터의 특징을 종래의 PWM 방식의 컨버터와의 비교를 통해 정량적으로 분석한다. 또한, 제안된 회로의 동작, 특성 및 유효성을 검증하기 위해 800W급 24-350Vdc 사양의 시작품으로부터의 실험 결과를 제시한다.

• Transactions on Electrical and Electronic Materials
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• 제18권4호
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• pp.199-202
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• 2017

Silicon carbide (SiC) is being spotlighted as a next-generation power semiconductor material owing to the characteristic limitations of the existing silicon materials. SiC has a wider band gap, higher breakdown voltage, higher thermal conductivity, and higher saturation electron mobility than those of Si. When using this material to implement Schottky barrier diode (SBD) devices, SBD-state operation loss and switching loss can be greatly reduced as compared to that of traditional Si. However, actual SiC SBDs exhibit a lower dielectric breakdown voltage than the theoretical breakdown voltage that causes the electric field concentration, a phenomenon that occurs on the edge of the contact surface as in conventional power semiconductor devices. Therefore in order to obtain a high breakdown voltage, it is necessary to distribute the electric field concentration using the edge termination structure. In this paper, we designed an edge termination structure using a field plate structure through oxide etch angle control, and optimized the structure to obtain a high breakdown voltage. We designed the edge termination structure for a 650 V breakdown voltage using Sentaurus Workbench provided by IDEC. We conducted field plate experiments. under the following conditions: $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $75^{\circ}$. The experimental results indicated that the oxide etch angle was $45^{\circ}$ when the breakdown voltage characteristics of the SiC SBD were optimized and a breakdown voltage of 681 V was obtained.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.77.1-77.1
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• 2013

Atomic layer deposition (ALD) is known for its self-limiting reaction, which offers atomic-level controllability of the growth of thin films for a wide range of applications. The self-limiting mechanism leads to very useful properties, such as excellent uniformity over a large area and superior conformality on complex structures. These unique features of ALD provide promising opportunities for future electronics. Although the ALD of Al2O3 film (using trimethyl-aluminum and water as a metal precursor and oxygen source, respectively) can be regarded as a representative example of an ideal ALD based on the completely self-limiting reaction, there are many cases deviating from the ideal ALD reaction in recently developed ALD processes. The nonconventional aspects of the ALD reactions may strongly influence the various properties of the functional materials grown by ALD, and the lack of comprehension of these aspects has made ALD difficult to control. In this respect, several dominant factors that complicate ALD reactions, including the types of metal precursors, non-metal precursors (oxygen sources or reducing agents), and substrates, will be discussed in this presentation. Several functional materials for future electronics, such as higher-k dielectrics (TiO2, SrTiO3) for DRAM application, and resistive switching materials (NiO) for RRAM application, will be addressed in this talk. Unwanted supply of oxygen atoms from the substrate or other component oxide to the incoming precursors during the precursor pulse step, and outward diffusion of substrate atoms to the growing film surface even during the steady-state growth influenced the growth, crystal structure, and properties of the various films.