• 한국응용과학기술학회지
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• 제33권1호
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• pp.23-29
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• 2016

육방정계 우르자이츠형의 산화아연은 n형 반도체로써 3.37 eV의 넓은 밴드갭 에너지와 60 meV의 큰 엑시톤 바인딩 에너지를 가진 물질이다. 가스센서, 발광 다이오드, 염료 감응 태양 전지, 염료오염의 분해 등의 넓은 범위에서 활용이 가능하다. 합성 시 마이크로파 수열합성법을 사용하게 되면 높은 수율, 빠른 반응속도, 에너지 절약의 장점이 있다. 아민첨가제는 수산이온 생성 및 킬레이트 효과로 인해 산화아연 입자 형상을 조정하는 역할을 한다. 본 논문에서는 전구체로는 질산아연육수화물을 사용하였고, 형상조정제로는 에탄올아민, 에틸렌디아민, 디에틸렌트리아민, 헥사메틸렌테트라민을 사용하였다. 수산화소듐을 사용하여 용액을 pH 11로 조정하였다. 합성된 산화아연은 별모양, 막대형, 꽃모양, 원추형의 다양한 형상을 확인할 수 있었다. 아민첨가제에 의한 물리 화학적 특성과 광학적 특성을 분석하기 위해 XRD, SEM, EDS, FT-IR, UV-vis 스펙트럼, PL 스펙트럼을 사용하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.331-332
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• 2008

Couplings between electric, magnetic, and structural order parameters result in the so-called multiferroic phenomena with two or more ferroic phenomena such as ferroelectricity, ferromagnetism, or ferroelasticity. The simultaneous ferroelectricity and ferromagnetism (magnetoelectricity) permits potential applications in information storage, spintronics, and magnetic or electric field sensors. The perovskite BiFeO3(BFO) is known to be antiferromagnetic below the Neel temperature of 647K and ferroelectric with a high Curie temperature of 1043K. It exhibits weak magnetism at room temperature due to the residual moment from a canted spin structure. It is likely that non-stoichiometry and second-phase formation are the factors responsible for leakage current in BFO. It has been suggested that oxygen non-stoichiometry leads to valence fluctuations of Fe ions in BFO, resulting in high conductivity. To reduce the large leakage current of BFO, one attempt is to make donor-doped BFO compounds and thin films. In this study, (Bi1-x,Ndx)(Fe1-y,Tiy)O3 thin films have been deposited on Pt(111)/TiO2/SiO2/Si substrates by pulsed laser deposition. The effect of dopants on the phase evolution and surface morphology are analyzed. Furthermore, electrical and magnetic properties are measured and their coupling characteristics are discussed.

• 제어로봇시스템학회논문지
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• 제16권5호
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• pp.463-468
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• 2010

An obstacle avoidance method for a mobile robot is proposed in this paper. Our research was focused on the obstacles that can be found indoors since a robot is usually used within a building. It is necessary that the robot maintain the desired direction after successfully avoiding the obstacles to achieve a good autonomous navigation performance for the specified project mission. Sensors such as laser, ultrasound, and PSD (Position Sensitive Detector) can be used to detect and analyze the obstacles. A PSD sensor was used to detect and measure the height and width of the obstacles on the floor. The PSD sensor was carefully calibrated before measuring the obstacles to achieve better accuracy. Data obtained from the repeated experiments were used to plot an error graph which was fitted to a polynomial curve. The polynomial equation was used to navigate the robot. We also obtained a direction-error model of the robot after avoiding the obstacles. The prototypes for the obstacle and direction-error were modeled using a neural network whose inputs are the obstacle height, robot speed, direction of the wheels, and the error in direction. A mobile robot operated by a notebook computer was setup and the proposed algorithm was used to navigate the robot and avoid the obstacles. The results showed that our algorithm performed very well during the experiments.

• 대한전자공학회논문지SD
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• 제41권3호
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• pp.39-44
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• 2004

광섬유 브래그 격자 센서는 광섬유의 코어의 굴절률 변조에 의해서 제작되며, 이 센서는 외부의 스트레인에 따라 브래그 파장이 변화하게 된다. 본 논문에서는 광섬유 브래그 격자 센서를 파장 영역에서 신호처리 할 수 있는 방법에 대하여 연구하였다. SLD와 F-P 필터로 구성된 sweep 반도체 광원과 F P 필터내의 PZT의 히스테리시스 특성을 보상하기 위한 에탈론 필터와 장기 계측을 위해 절대 파장 기준으로 온도 안정된 광섬유 브래그 격자를 사용하였다. 콘크리트 흄관에서 FBG 센서의 스트레인 응답 특성을 전기저항 센서와 비교하였다. 그리고 광섬유 격자 센서를 이용하여 장거리 변위의 측정 가능성을 확인하였다.

• 센서학회지
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• 제12권5호
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• pp.225-230
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• 2003

최근 최소 침습적 수술(minimal invasive surgery)방법에 대한 관심이 높아지면서 인체 내부의 악성 종양을 치료하는 방법 중의 하나로 레이저를 이용한 온열 치료법(laserthermia)이 사용되고 있다. 인체 심부의 암세포에 대한 레이저 열 치료는 레이저를 조직에 흡수시키면서 발생되는 열을 이용하여 암세포를 제거하는 방법이다. 본 시스템은 레이저 전달용 광섬유, 영상 획득용 내시경, 온도 측정 센서 등으로 구성된다. 온열 요법은 치료할 암세포를 적절한 온도($42{\sim}43^{\circ}C$)로 유지시켜주면서 정상 세포는 레이저의 조사에 의한 열 발생을 최소화시키는 것이 중요한데 이러한 온도 유지를 위해서는 신속 정착한 온도 측정이 요구되고 있다. 본 연구에서는 새로운 형태의 LC(liquid crystal)-광섬유 온도 측정 센서를 개발하기 위해 온도 변화에 따른 LC물질의 색 변화 정도를 수광-발광 광섬유로서 측정하였고 측정된 수광량과 온도 변화 사이의 관계식을 도출하였다. 그리고 광섬유와 LC물질간의 복잡한 거리 문제를 해결하고, 보다 향상된 실험 결과를 얻기 위해 Y-coupler를 제작하여 LC물질의 반사 광량과 온도 사이의 관계도 알아보았다.

• Journal of Biosystems Engineering
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• 제34권2호
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• pp.120-126
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• 2009

The purpose of this study was to develop a visibility evaluation system for cabin type combine. Human's field of view was classified into five levels (perceptive, effective, stable gaze, induced, and auxiliary) depending on rotation of human's head and eye. Divider, reaper lever, gearshift, dashboard, and conveying part were considered as major viewpoints of combine. Visibilities of combine was evaluated quantitatively using the viewpoints and the human's field of view levels. The visibility evaluation system for cabin type combine was consisted of a laser pointer, stepping motors to control the direction of view, gyro sensors to measure horizontal and vertical angle, and I/O interface to acquire the signals. Tests were conducted with different postures ('sitting straight', 'sitting with $15^{\circ}$ tilt', 'standing straight', and 'standing with $15^{\circ}$ tilt'). The LSD (least significant difference) multiple comparison tests showed that the visibilities of viewpoints were different significantly as the operator's postures were changed. The results showed that the posture at standing with $15^{\circ}$ tilt provided the best visibility for operators. The divider of the combine was invisible due to blocking with the cabin frame at many postures. The reaper lever showed good visibilities at the postures of sitting or standing with $15^{\circ}$ tilt. The gearshift, the dashboard, and the conveying part had reasonable visibilities at the posture of sitting with $15^{\circ}$ tilt. However, most viewpoints of the combine were out of the stable gaze field of view level. Modifications of the combine design will be required to enhance the visibility during harvesting operation for farmers' safety and convenience.

• 한국항공운항학회지
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• 제17권4호
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• pp.8-16
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• 2009

An experimental study was carried out to investigate aerodynamic characteristics on reduced frequency of flapping wings. The half span of the wing is 28cm, and the mean chord length of wing is 10cm. In flight, the Reynolds Number range of birds is about $10^4$, and the reduced frequency during a level flight is 0.25. The experimental variables of present study were set to have similar conditions with the bird flight's one. The freestream velocities in a wind tunnel were 2.50, 3.75 and $5.00^m/s$, and the corresponding Reynolds numbers were $1.7{\times}10^4$, $2.5{\times}10^4$ and $3.3{\times}10^4$, respectively. The wing beat frequencies of an experimental model were 2, 3 and 4Hz, and the corresponding reduced frequency was decided between 0.1 and 0.5. Aerodynamic forces of an experimental flapping model were measured by using 2 axis load-cell. Inertial forces measured in a vacuum chamber were removed from measuring forces in the wind tunnel in order to acquire pure aerodynamic forces. Hall sensors and laser trigger were used to make sure the exact position of wings during the flapping motion. Results show that the ratio of downstroke in a wing beat cycle is increased as a wing beat frequency increases. The instantaneous lift coefficient is the maximum value at the end of downstroke of flapping wing model. It is found that a critical reduced frequency with large lift coefficient is existed near k=0.25.

• 한국결정성장학회지
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• 제31권2호
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• pp.84-88
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• 2021

레이저, 광학센서 등에 사용되고 있는 La2O3-CaF2-Al2O3-SiO2 계 유리에 희토류 물질을 첨가하였을 때, 열처리 온도에 따른 결정화유리의 발광 특성 변화에 대하여 연구하였다. 결정화유리를 얻기 위한 열처리 조건은 비등온 열분석을 통해 얻었으며, 열처리 온도에 따른 결정성장 정도 및 생성된 결정상 종류를 파악하기 위해 XRD 분석을 진행하였다. Scherrer's equation을 이용한 결과, 결정화유리 내부에 25~40 nm 크기의 결정들이 생성된 것으로 계산되었다. Photoluminescence (PL) 분석결과, 660~670℃에서 1시간 열처리 된 시편이 가장 우수한 PL 강도를 보였으며, CIE 색좌표계 분석결과, 열처리 유무와 관계없이 모든 결정화유리 시편들은 red-orange 빛을 발광하는 것으로 나타났다.

• 대기
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• 제29권3호
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• pp.283-294
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• 2019

For the upper air observations, a temperature measurement using radiosonde is a common method, and the compensation of solar radiation effects in the radiosonde temperature sensor is an important factor. In this paper, we present various experiments and compensation methods of the radiosonde temperature sensor to overcome the errors caused by the movement of the radiosonde rotation, etc. The methods and procedures of this study are as follows. First, we used the solar simulator to analyze the temperature variation and solar effect of the temperature sensor in the radiosonde according to the insolation. We also analyzed the temperature variation and solar effect of the temperature sensor according to the incident angle between the solar simulator and radiosonde. Second, we measured and analyzed solar radiation absorbed by solar cells attached to radiosonde. Third, we present combined compensate solution of the first and the second experiment results, to overcome errors caused by insolation effects in the radiosonde temperature sensors. Fourth, we compared that the reference temperature in similar environment with the upper air conditions, to verify the new radiated compensation performance of the radiosonde temperature sensor. Finally, the radiosonde fabricated in this study was raised to the atmosphere, and the laser correction algorithm proposed through experiments was reviewed. As a result of the radiosonde SRS-10 produced in this study, the temperature deviation from Vaisala RS92 was $0.057^{\circ}C$ in nighttime observation, $0.17^{\circ}C$ in daytime observation, It is expected that the GRUAN under WMO will be able to obtain a high test rating of 5.0.

• 한국지반환경공학회 논문집
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• 제20권1호
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• pp.57-65
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• 2019

본 연구에서는 원통형 대책 구조물의 설치변화가 토석류의 흐름에 미치는 영향을 확인하기 위해, 대책 구조물을 설치 가능한 소형수로를 제작한 후에 실내모형실험을 실시하였다. 실험은 수로 내에 설치된 구조물의 높이와 종방향 열의 개수를 변화시켜가면서 수행하였다. 대책 구조물이 설치된 수로 측면과 상부에는 초고속 카메라와 레이저 수위센서를 설치하여, 토석류가 구조물을 통과하기 전 후의 흐름변화를 측정하였다. 이를 바탕으로 대책구조물 설치에 따른 토석류의 에너지 저감효과를 비교, 분석하였다. 실험결과, 원통형 대책 구조물의 설치는 토석류의 유속과 흐름깊이를 감소시키는 것으로 나타났다. 또한 구조물의 설치높이와 종방향 열의 개수가 증가할수록 그 영향은 더욱 커지는 것으로 나타났다.