• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.129-131
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• 1994

Rectangular type hybrid step motor is designed to generate thirty percents higher torque than existing step motors. The torque for the motor is generated by the electromagnetic force at the air gap between the stator and rotor. The generating torque is proportioned to the rotor volume, i. e. rotor diameter. The main idea in this study is that the diameter of rotor is increased to generate more torque for the same overall motor size. This motors are manufactured by varying the shape of the teeth width of the stator and rotor. The optimum shape of the teeth is selected from the standpoint as smaller step angular accuracy.

• Progress in Superconductivity
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• 제4권1호
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• pp.90-93
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• 2002

The sintering process of BSCCO 2223 tapes is a complex process that is very sensitive to parameters, such as temperature, oxygen partial pressure, heating and cooling rate and holding time. During the first heat treatment, 2212 phase of precursor powder is partially transformed into 2223 phase and some residual secondary phases, such as $(Bi,Pb)_2$$Sr_2$CuO／sub y／(2201), $(Ca,Sr)_2$CuO／sub y／(2/1AEC), (Ca,Sr)／sub 14／Cu／sub 24／O／sub 41／(14／24 AEC) etc. The secondary phases are difficult to be removed from the BSCCO 2223 matrix on the heat treatment. These secondary phases degrade the critical current density. In order to minimize the amount and size of alkaline earth cuprate(AEC) particles step heat treatment is applied during the first heat treatment under the varying atmosphere. Experimental results showed that by adapting the step heat treatment process, the amount and particle size of the secondary phases in the final tapes are decreased. Consequently, the BSCCO 2223grain texture and Jc properties are improved.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.192-193
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• 2006

A 16Mb ITIC FeRAM device was fabricated with BLT capacitors. The average value of the switchable 2 polarization obtained m the 32k-array (unit capacitor size: 068 ${mu}m^2$) capacitors was about 16 ${\mu}C/cm^2$ at 3V and the uniformity within an 8-inch wafer was about 2.8%. But a lot of cells were failed randomly during the measuring the bit-line signal of each cell. It was revealed that the Grain size and orientation of the BLT thin film were severely non-uniform. Therefore, the uniformity of the grain size and orientation was improved by changing the process conditions of post heat treatment. The temperature of nucleation step was the very effective on varying the microstructure of the BLT thin film. The optimized temperature of the nucleation step was $560^{\circ}C$.

• 전자공학회논문지B
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• 제31B권7호
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• pp.49-57
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• 1994

An efficient approach for the computationtion of the optimum convergence factor is proposed for the LMS algorithm applied to a transversal FIR structure in this study. The approach automatically leads to an optimum step size algorithm at each weight in every iteration that results in a dramatic reduction in terms of convergence time. The algorithm is evaluated in system identification application where two alternative computer simulations are considered for time-invariant and time-varying system cases. The results show that the proposed algorithm needs not appropriate convergence factor and has better performance than AGC(Automatic Gain Control) algorithm and Karni algorithm, which require the convergence factors controlled arbitrarily in computer simulation for time-invariant system and time-varying systems. Also, itis shown that the proposed algorithm has the excellent adaptability campared with NLMS(Normalized LMS) algorithm and RLS (Recursive least Square) algorithm for time-varying circumstances.

• 한국멀티미디어학회논문지
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• 제9권5호
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• pp.585-594
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• 2006

휴대폰 카메라에서는 자동 초점 제어를 위하여, 스텝 모터보다 크기 면에서 소형인 보이스 코일 모터가 많이 사용되고 있다. 보이스 코일 모터를 이용하는 광학계에서는 인가되는 동일한 전류 값에 대하여, 초점값이 달라지는 특정이 있다. 이는 보이스 코일 모터의 특성으로 인하여 발생하는 현상으로서, 렌즈 위치에 대한 오차가 발생하였음을 의미한다. 이러한 보이스 코일 모터의 특성에 의한 렌즈 위치 오차를 보상하기 위하여, 본 논문에서는 검색 단계별 스텝 간격 및 검색 횟수에 따른 렌즈 위치 오차 보상 알고리즘을 제안하였다. 이 방법에서는, 고속 초점 제어를 위하여 검색 단계를 기존 검색 방법에 -7의 중간 스텝 간격을 추가하고, 정교한 초점 제어를 위하여 최종 검색 단계 스텝 사이즈를 +1로 설정한다. 제안한 방법은 기존의 방법보다 더 빠르게 자동 초점 조절을 수행하며, 촬영된 결과 영상 또한 주관적 및 객관적인 측면에서 더 우수함을 실험 결과를 통해 확인하였다.

• Macromolecular Research
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• 제12권2호
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• pp.240-245
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• 2004

Monodisperse PMMA micro spheres are prepared by means of a simple soap-free emulsion polymerization in methanol-enriched aqueous medium in a single step process. The size and uniformity of the microspheres are dependent on the polymerization temperature. In a stable system, the uniformity is improved with the polymerization time. The most uniform and stable micro spheres are obtained under mild agitation speed of 100 rpm at 70$^{\circ}C$. The monodisperse PMMA microspheres in the size range of 1.4-2.0 $\mu\textrm{m}$ having less than 5% size variation are successfully achieved with varying concentrations of monomer and initiator. As the monomer and initiator concentrations increase, the larger micro spheres with enhanced uniformity are obtained. However, the decreased amount of water induces the polydisperse PMMA particles due to the generation of secondary particles.

• 제어로봇시스템학회논문지
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• 제5권2호
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• pp.166-173
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• 1999

Reference models are used in many control algorithms for improvement of transient response characteristics. They provide desired trajectories that the plant should follow Most control systems have bounded control inputs to avoid saturation of the plant. If we design the reference models that do not account for limits of the control inputs, control performance of the system may be deteriorated. In this paper a new approach of avoiding saturation by varying the reference model for TDC(time delay control) based systems subject to step changes in the reference input. In this scheme, the variable reference model is determined based on the information on control inputs and the size of the step changes in the reference inputs. This scheme was verified by application to the BLDC motor position control system in simulations and experiments. The responses of the TDC with the variable reference model showed better tracking performance than that with the fixed reference model.

• Structural Engineering and Mechanics
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• 제31권4호
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• pp.423-437
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• 2009

In order to perform a step-by-step force-displacement response analysis or dynamic time-history analysis of large buildings with masonry infilled R/C frames, a continuous force-deformation model based on an equivalent strut approach is proposed for masonry infill panels containing openings. The model, which is applicable for degrading elements, can be implemented to replicate a wide range of monotonic force-displacement behaviour, resulting from different design and geometry, by varying the control parameters of the model. The control parameters of the proposed continuous model are determined using experimental data. The experimental program includes fifteen 1/3-scale, single-story, single-bay reinforced concrete frame specimens subjected to lateral cyclic loading. The parameters investigated include the shape, the size, the location of the opening and the infill compressive strength. The actual properties of the infill and henceforth the characteristics needed for the diagonal strut model are based on the assessment of its lateral resistance by the subtraction of the response of the bare frame from the response of the infilled frame.

• 한국인터넷방송통신학회논문지
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• 제21권2호
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• pp.61-66
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• 2021

본 논문은 16-QAM 신호 전송시 비선형 통신 채널에서 발생되는 부호간 간섭을 줄일 수 있는 mSE-MMA와 mDSE-MMA 적응 등화 알고리즘의 성능 비교에 관한 것이다. 이들은 이동 통신 단말에 적용되기 위하여 알고리즘은 기존 MMA의 연산량을 줄일 수 있지만, 이로 인하여 등화 성능의 열화되는 문제점이 있다. 이와 같은 성능 열화를 개선하기 위하여 적응을 위한 스텝 크기를 등화기의 출력이 송신 신호점을 중심으로 임의 반경내의 존재 여부에 따라 조절하게 된다. 이와 같은 원리에 따라 스텝 크기를 변화시키는 개념을 SE-MMA와 DSE-MMA에 적용한 mSE-MMA와 mDSE-MMA 알고리즘의 성능을 비교하였으며, 이를 위하여 동일 채널과 잡음 환경에서 컴퓨터 시뮬레이션을 수행하였다. 시뮬레이션 결과 모든 성능 지수의 잔여량과 SER 성능에서 mSE-MMA가 mDSE-MMA 보다 우월하였으나, 수렴 속도에서는 mDSE-MMA가 mSE-MMA보다 약간 우월하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.368-370
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• 2007

AAO(Anodic Aluminum Oxidation) method has been known that it is practically useful for the fabrication of nano-structures and makes it possible to fabricate the highly ordered nano masters on large surface and even on the 2.5 or 3D surface at low cost comparing to the expensive e-beam lithography or the conventional silicon processing. In this study, by using the multi-step anodizing and etching processes, highly ordered nano patterned master with concave shapes was fabricated. By varying the processing parameters, such as initial matter and chemical conditions; electrical and thermal conditions; time scheduling; and so on, the size and the pitch of the nano pattern can be controlled. Consequently, various alumina/aluminum nano structures can be easily available in any size and shape by optimized anodic oxidation in various aqueous acids. The resulting good filled uniform nano molded structure through hot embossing molding process shows the validity of the fabricated nano pattern masters.