• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.481-482
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• 2016

병렬 운전 시 인터리빙 기술은 인버터 최종 출력 전류에 포함되는 스위칭 주파수 성분의 고조파를 제거하는 장점을 가지고 있지만 이로 인해 고주파 성분의 영상분 순환 전류를 만든다. 따라서 이 성분을 억제하기 위해 커플드 인덕터가 같이 사용된다. 하지만 커플드 인덕터를 사용할 경우에는 파라메타의 오차로 인해 안정성에 문제가 발생 할 수 있다. 따라서 본 논문에서는 인터리빙 및 커플드 인덕터를 사용한 병렬 운전 인버터 시스템에서 전류 품질 개선을 위해 고조파 보상을 할 경우 발생 할 수 있는 안정성 문제에 대한 원인을 규명하고 새로운 순환전류 제어 방법에 대해 제안하고 실험을 통해 검증하였다.

• Journal of the Korean Chemical Society
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• v.16 no.3
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• pp.149-156
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• 1972

The responsive characteristics of hydrogen-responsive glass electrode in various buffer solutions of methanol, N,N-dimethylformamide and acetonitrile were examined. The potentials were attained more rapidly with an electrode stored in the same solvent medium than that stored in water before use. However, the time to be required for a stable potential increased with the basicity of buffer solution, and it was not provide a constant potential in the strong basic solution of these solvent. Even in acidic solution, the potential was varied according to the past usage of the electrode.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2519-2523
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• 2008

When constructing a high-speed railroad, the reduction of the distance between track centers and the width of track bed will save the construction cost. However the shortening the distance between track centers may cause the stability problems due to higher wind pressure. Therefore the extensive technical review and aerodynamical study should be performed to determine the adequate distance between track centers. In this study, the impact that the increase in wind pressure due to the change of aerodynamic phenomena with the change of the distance between track centers may have on two trains passing by each other was predicted, and the stability of train operation was analyzed in order to review the distance between track centers suitable to Honam HSR trains. We conducted the parametric study of the effects of train wind on the running stability.

• Journal of the KSME
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• v.23 no.3
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• pp.200-206
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• 1983

FAM의 기본적인 구상은 해석 하고자하는 선형 또는 비선형 편미분 방정식을 국부적으로 해석 적인 해를 구하여 이용하자는 것이다. 그러기 위하여 유한차분법(FDM)과 유한변분법(FEM)에 서와 같이 전체유동장을 작은 요소로 나누고 그 요소 내에서 국부해를 구한 다음 이들 요소를 중첩시킴으로써 각 요소의 미지수에 대한 대수식을 얻어서 수치해를 구하자는 것이다. 그러나 FDM에서와 같이 국부요소에서 미분항을 구하지 않고, FEM 에서와 같이 요소에서 형상함수를 도입하지 않는 상태에서 해석적인 해를 구하고 있기 때문에 수치해석에서 얻어지는 미분양들은 비교적 정확하게 구해진다. 따라서 Navier-Stokes 방정식이나 에너지 방정식에서 최고차항이 작은 파라메타, 즉 레이놀즈수나 피크리수의 역수로 곱하여서 있는 경우에도 안정된 해를 구할 수 있다고 알려져 있다. 요소자체의 계수를 구하는 데는 계산시간이 많이 소요되지만 수치해석 상의 안정성이나 수렴성이 좋기 때문에 전체계산시간은 오히려 적게 걸리는 경우도 있다고 한다.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.12
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• pp.36-45
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• 1998

In this paper, a method of on-line PI gain-tuninng is proposed for the speed control of brushless D.C. motor by investigating the pattern of input and output without estimating parameter. Proportional gain is tuned in the process to obtain a fast speed response by supplying the maximum constant input. And integral gain is appropriately tuned in the process of proportional control so that the response may be stably converged and the overshoot may be prevented. Therefore because both control and gain-tuning are executed concurrently, additional works that estimate parameters and so on aren't required in the proposed method. In the proposed method, both fast-response and overshoot problem are well solved, and it is more useful and convenient than existing auto-tuning methods in the speed control of D.C. motor. It is illustrated by simulations and experimental results that the proposed method is useful and stable.

• Elastomers and Composites
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• v.49 no.2
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• pp.117-126
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• 2014

Methylene diisocyanate (MDI) was investigated as a novel interfacial modifier to enhance the performances of poly(methyl methacrylate)-modified starch/styrene-butadiene rubber (PMMA-modified starch/SBR) composites. Owing to the formation urethane linkage on one side and ${\pi}-{\pi}$ adhesion on the other side, MDI acted as an intermediated linkage role in the PMMA-modified starch/SBR interfaces, which was evidenced by the morphological, mechanical, dynamic mechanical and thermal decomposition studies. As a result, the presence of MDI significantly improved the mechanical properties and thermal stability of PMMA-modified starch/SBR composites. In addition, the effect of starch concentration on the various performances of the resulted MDI/PMMA-modified starch/SBR composites, such as morphology, vulcanization characteristics, mechanical properties, toluene swelling behavior, and thermal stability were investigated and discussed in detail. The obtained MDI/PMMA-modified starch/SBR composites exhibited superior mechanical properties to carbon black/SBR (CB/SBR) composites, demonstrating the potential use of the renewable starch as a substitute for CB in the rubber compounds.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.32 no.11
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• pp.394-403
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• 1983

This paper discusses a model reference adaptive control for a multi-input multi-output continuos system in matrix fraction description. The controller is of Monopoli-Narendra type with a time-varying gain matrix in the parameter adaptation law. The transfer matrix of the given plant with an adjustable controller is made to approach to that of the reference model asymptotically. It is shown that, under some plausible assumptions such as on the knowlidge of an interactor matrix, the algorithm for a single-input single-output system can be appropriately extended to a multi-input multi-output system. The convergence of an adaptation law is estavlished with some stability theory and stability of the overall system is asserted by an analytical investigation.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.4
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• pp.21-27
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• 2003

The copolymers with various composition of methyl methacrylate (MMA), ethyl methacrylate (EMA), methacrylic acid (MA) and hydroxyethyl methacrylate (HEMA) were synthesized for capacitive humidity sensitive materials. The capacitive humidity sensor consisted of a polymethacrylate film coated on both sides with gold electrode. Capacitance versus relative humidity increased with HEMA content in the copolymer. In the case of self-crosslinkable MMA/MA/HEHA= 40/10/10, the average capacitance at 30%RH, 60%RH and 90%RH are 102, 134 and 166 pF, respectively. And also, the hysteresis, temperature cycle and long-term stability were evaluated as a capacitance humidity sensor.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2006.05a
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• pp.63-72
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• 2006

정보화 시대에 있어 급변하는 기술발전과 함께 인간의 문화적 욕구가 증대됨에 따라 3차원 공간정보에 대한 수요가 증가하고 있다. 하지만 현재 3차원 공간정보를 구축하는 과정은 일반적으로 수작업 또는 반자동에 의해 이루어지고 있다. 이는 데이터의 구축 및 표현에 많은 시간과 비용이 소요된다는 제약을 가지고 있다. 따라서 본 연구에서는 3차원 symbol 라이브러리를 구축하여 분류된 객체에 부합되는 3차원 symbol을 자동으로 선택하며, 선택된 3차원 symbol을 파라메타를 이용하여 자동으로 mapping 하는 과정을 구축하였다. 이를 통해 3차원 공간데이터의 구축 및 표현에 요구되는 시간과 오류를 최소화할 수 있었다. 또한 LiDAR(Light Detection And Range) 데이터의 3차원 정보를 활용하여 symbol의 자동 mapping을 위한 파라메타들을 산출하였고, symbol의 분류를 위한 기본 데이터로 활용하였다. 구축된 알고리즘의 평가를 위하여 실재 데이터의 3차원 공간데이터베이스를 구축하였다. 구축된 데이터에 대해 symbol선택 및 자동 mapping 과정에 대한 오류 검사를 수행하였고, 더불어 구축된 3차원 데이터의 활용 가능성을 평가하였다. 그 결과 본 연구로부터 구축된 알고리즘들은 3차원 공간정보를 표현함에 있어 신속하고 안정적으로 기여할 수 있을 것으로 판단되었다.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.6 no.2
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• pp.27-34
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• 1995

In this paper, an X-band TDRO(transistor dielectric resonator oscillator) is designed and experimented with the oscillator constructed. Design of the TDRO is carried out by deriving analycally the coupling parameters between a microstrip line and a dielectric resonator. The coupling parameters take account of the relations among substrate material, ground plane, metallic boundaries surrounding the resonator, distance between a microstrip line and a resonator. Two criteria, external quality factor and coupling coefficient, have been chosen in order to evaluate the performance of the TDRO designed. TDRO studed in this paper may be useful for the application of a microwave system requiring a stable and effective oscillator frequency.