• Smart Structures and Systems
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• 제3권2호
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• pp.189-200
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• 2007

As a functional material, shape memory alloy (SMA) has attracted much attention and research effort to explore its unique properties and its applications in the past few decades. Some of its properties, in particular the electrical resistance (ER) based self-sensing property of SMA, have not been fully studied. Electrical resistance of an SMA wire varies during its phase transformation. This variation is an inherent property of the SMA wire, although it is highly nonlinear with hysteresis. The relationship between the displacement and the electrical resistance of an SMA wire is deterministic and repeatable to some degree, therefore enabling the self-sensing ability of the SMA. The potential of this self-sensing ability has not received sufficient exploration so far, and even the previous studies in literature lack generality. This paper concerns the utilization of the self-sensing property of a spring-biased Nickel-Titanium (Nitinol) SMA actuator for two applications: ER feedback position control of an SMA actuator without a position sensor, and estimation of the opening of a SMA actuated valve. The use of the self-sensing property eliminates the need for a position sensor, therefore reducing the cost and size of an SMA actuator assembly. Two experimental apparatuses are fabricated to facilitate the two proposed applications, respectively. Based on open-loop testing results, the curve fitting technique is used to represent the nonlinear relationships between the displacement and the electrical resistance of the two SMA wire actuators. Using the mathematical models of the two SMA actuators, respectively, a proportional plus derivative controller is designed for control of the SMA wire actuator using only electrical resistance feedback. Consequently, the opening of the SMA actuated valve can be estimated without using an extra sensor.

• 한국의류학회지
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• 제34권10호
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• pp.1742-1753
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• 2010

This study clarifies the importance, advantages, and constituents of the professional image by appearance management in the workplace. In-depth interviews were conducted with 8 participants who have over 8 years experience in their respective fields. The transcripts of the interview were classified according to a card classification method. The results of the study were as follows: First, the professional image by appearance management is important, because there is a special treatment by image in interaction on business. Second, the advantages of the professional image were to achieve a career opportunity, improve interpersonal relationships, obtain special treatment or protection from a biased angle, and increase business reliability. Third, the constituents of the professional image were conscientiousness and self-management skills, assertive and open attitudes, leadership, interpersonal skills, customer-satisfaction spirit, expert knowledge and skills, and confidence in the business results.

• Journal of Magnetics
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• 제15권4호
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• pp.194-198
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• 2010

In our present work, we developed a GMI (giant magnetoimpedance) sensor system to detect magnetic fields in the milli gauss range based on the asymmetric magnetoimpedance (AGMI) effect in Co-based amorphous ribbon with self bias field produced by field-annealing in open air. The system comprises magnetoimpedance sensor probe, signal conditioning circuits, A/D converter, USB controller, notebook computer, and program for measurement and display. Sensor probe was constructed by wire-bonding the cobalt based amorphous ribbon with dimensions $10\;mm\;{\times}\;1\;mm\;{\times}\;20\;{\mu}m$ on a printed circuit board. Negative feedback was used to remove the hysteresis and temperature dependence and to increase the linearity of the system. Sensitivity of the milli gauss meter was 0.3 V/Oe and the magnetic field resolution and environmental noise level were less than 0.01 Oe and 2 mOe, respectively, in an unshielded room.

• 전자공학회논문지A
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• 제30A권3호
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• pp.76-87
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• 1993

We present a self-consistent, 2-dimensional solution of the Poisson and Sch rodinger equation based on the finite difference method with a nonuniform mesh size for a AlGaAs/GaInAs/GaAs HEMT devide. During the interative self-consistent calculation, however, we calculate Schrodinger equation only a some region of device, not a fully region in order to save the moemory and the speed-up of computation, and then use the approximated data for the other region using by a interpolation method with a given values. Also we adopt the proper matrix transformation method that allows preservation of the symmetric, form of the discretized Schrodinger equation, even with the use of a nonumiform mesh size, therefor, can reduce the computation time. We calculate the wavefunction, eigenstates and the electron concentration uat channel layer nder the thermal equilibrium and the biased conditions, respectively. Also,these parameters are used to solve 2-dimensional tdistribution of potential in he entire region of device. It is proved that the method is very efficient in finding eigenstages extending over relatively large spatial area without loss of accuracy. So, it can be used rather easily in any sarbitrary modulation doped utucture.

• 대한전자공학회논문지TE
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• 제39권4호
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• pp.409-412
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• 2002

IMT-2000 전 대역(1920∼2170MHz, BW=250MHz)에서 사용되는 중계기용 2단 저잡음 증폭기를 설계하였다. Ansoft사의 Serenade를 이용하여 첫째 단 PHEMT의 소스와 접지간 source lead의 인덕턴스 값을 최적화하여 기판 선고로 등가화하고, 첫째 단의 잡음 정합은 물론 각 단의 정합회로가 간단하도록 high pass 구조로 설계하였다. 바이어스 회로는 단일 능동회로로 구성하였고, 인가전압은 8V, 총 전류는 180mA이다. 이때, 첫째 단 PHEMT의 Vgs = -0.4V, Vds = 4V이고, 둘째 단 AH1의 Vds = 5V이다. 상업화가 가능하도록 설계 기준을 정하여 제작되었고, 측정 결과 이득은 20dB, NF는 1dB, 입력 VSWR은 1.14∼l.3dB, P1dB는 22.4dBm, gain flatness는 ±0.45dB로 상업용 저잡음 증폭기로 사용될 수 있다.

• 한국콘텐츠학회논문지
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• 제22권1호
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• pp.148-161
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• 2022

한국의 디자인은 경제성장과 밀접한 연관이 되어 발전하였고 오늘날에도 물질적인 성장이나 부의 증대, 소비촉진을 위한 핵심적인 역할을 담당하고 있다. 물론 한국의 디자인 수준이 크게 성장한 것은 사실이나 트렌드를 선도하는 수준에는 이르지 못하고 있다. 그 이면에는 대다수의 디자인 기업에서 트렌드 리서치와 벤치마킹등의 공급자적인 관점으로 편중되어 디자인 조형창작이 이루어지는 것도 여러 원인들 중 한가지라고 생각된다. 세계의 디자인 트렌드를 선도하는 사례를 살펴보면 창작자의 작가적인 관점에서 비롯된 그들의 주관적인 사고가 디자인 조형창작에서 적지 않은 비중을 차지하는 것을 알 수 있다. 자기 표현적 디자인 개발 사례를 살펴보고 사고의 스펙트럼 양 극단에 있는 디자이너와 예술가들과의 심층 인터뷰를 통해 자기표현적 디자인 조형창작의 개념모델 제안을 위한 시사점을 얻고자 한다. 이를 통해 공급자적인 관점에 따른 사고가 지배적인 대다수의 디자인 조형창작에 작가적인 관점에 따른 사고체계와 프로세스를 융합한 균형적인 사고가 이루어지는 5단계 디자인 조형창작 과정으로 체계화한 개념모델을 제안 하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.697-700
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• 1999

This Paper presents the design, fabrication, analysis of the measured date of a voltage controlled oscillator(VCO) for the application of Personal Communication Systems. Main VCO circuit consists of self biased emitter resonating circuit with microstrip line resonator on FR4 epoxy substrate. A varactor diode is used for 90MHz frequency tuning with center frequency of 1635MHz Phase noise of -114.67㏈C/Hz at 100KHz off set has been achieved with 3.3 V supply. The size of the fabricated VCO circuit is 1.25 cm$\times$ 1.25 cm.

• 한국자기학회지
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• 제5권4호
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• pp.294-298
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• 1995

A shielded magnetoresistive (SMR) head which has double MR films and linearizes each other has been designed and studied by applying the transmission-line model. We have analyzed the yoke efficiency, bias efficiency and read efficiency of the SMR head. The read efficiency strongly depends on the height of the sensor and slightly on the other geometric parameters. The yoke and bias efficiencies vary with gap length, insulated layer thickness and relative permeability. A quasi-index reduction in the signal flux is observed when the displacement moves away from the medium.

• 한국자기학회지
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• 제5권4호
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• pp.299-303
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• 1995

In order to improve the read-out signal waveform, a shielded magnetoresistive (SMR) head has been designed and studied by applying the transmission-line model. The bias and signal field distribution, the voltage output, the harmonic output signal and resistance value of MR element are simulated as functions of bias current and recording displacement. The results show that the SMR head has good linear character with respect to the medium recording signal in high recording frequency of about 2.5 MHz. The amplitude and waveform of reroduction signal have been obviously improved. The saturation effect on the symmetry and amplitude of reproducing output have also been analyzed.

• 한국측량학회지
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• 제36권6호
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• pp.565-572
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• 2018

최근 들어 운용비용이 저렴하고 신속한 데이터 획득 및 처리가 가능한 무인항공기(드론)를 이용한 측량 및 지도 제작이 활발히 진행되고 있으며, 그 활용도는 지형 변화분석, 시설물 모니터링, 농업, 임업 등 여러 분야로 확장되고 있다. 드론의 높은 활용도의 바탕에는 높은 공간 정확도의 획득이 가능하다는데 있으며, 관련하여 드론 기반 공간 정확도의 평가 결과가 여러 연구를 통해 보고되었다. 대부분의 연구는 잘 분포된 지상기준점을 활용하여 획득 가능한 정확도를 분석한 경우이며, 부분적으로 기준점의 개수의 변화에 따른 정확성을 평가한 경우가 있다. 본 연구에서는 도로, 관로, 철도 등 선형 대상지에 드론을 이용한 측량을 수행할 경우 획득 가능한 공간 정확성을 확인하기 위해, 기준점 배치를 여러 조합으로 나누어 정확성을 평가 해보았다. 선형 대상지를 따라 기준점의 편위 및 밀도에 따른 정확성을 평가하였고, 추가적으로 카메라 캘리브레이션의 영향, 횡중복 스트립 개수에 따른 정확성 또한 평가하였다. 실험 결과 기준점의 밀도에 비해 기준점 배치의 편위가 정확성에 더 큰 악영향을 주었으며, 미리 카메라 캘리브레이션을 수행하고 사용하는 것이 현장 셀프 캘리브레이션에 비해 기준점의 배치나 개수가 충분치 못한 경우에 오차를 줄일 수 있었다. 또한, 선형 방향으로의 스트립 수를 늘리는 것은 정확도 향상에 큰 도움이 되지 않았다.