• 한국진공학회지
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• 제8권4A호
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• pp.432-437
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• 1999

We have fabricated an in situ ellipsometer operating at He-Ne wavelength. It can be applied to the real-time, in-situ tracking of the ellisometric change which occurs during various sample treatments. As a rotating analyzer type, all optical elements and related parts are designed to share a common hollow-axis configuration, and hence the ellipsometer is compact in shape and simple in design. It is mountable on the spare ports of vacuum chamber with ease. Using this ellipsometer, we observed the effective density variation of previously grown $TiO_2$ thin films by using electron beam evaporation. The packing density of the as-grown film was 82%. When exposed to atomsphere, the micro-void of the film was filled with water vapor. This water-filled $TiO_2$ thin film was subject to heating/cooling cycles in vacuum and the ellipsometric variation versus temperature and cycling number was measured in real time using this in situ He-Ne ellipsometer.

• ETRI Journal
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• 제22권1호
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• pp.12-19
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• 2000

Wireless communication systems using airship have been proposed in worldwide. The airship will be located at the stratosphere about $20{\sim}23\;km$ above the sea level. The position of airship will vary within the station keeping range with time due to the drag of the wind in the stratosphere. When the earth station antenna has a high gain without the tracking function, the antenna performance may be degraded by a small variation of the airship. This means that variation of airship location could result in serious degradation of the system performance. In this paper, degradation in earth station's Equivalent Isotropic Radiated Power (EIRP) and Gain to noise Temperature ratio (G/T) due to the stratospheric platform movements has been derived by calculating the deviation angle of the main beam directions between the earth station and the platform antenna. In this case, the antenna of the earth station has been assumed circular and/or patch array antennas.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.673-678
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• 2001

This paper proposes a new type of piezoactuator-driven valve system. The piezoceramic actuator bonded to both sides of a flexible beam surface makes a movement required to control the pressure at the flapper-nozzle of a pneumatic valve system. After establishing a dynamic model, an appropriate size of the valve system is designed and manufactured. Subsequently, a robust $H_{\infty}$ control algorithm is formulated in order to achieve accurate tracking control of the desired pressure. The controller is experimentally realized and control performance for the sinusoidal pressure trajectory is presented in time domain. The control bandwidth of the valve system, which directly represents the fastness, is also evaluated in the frequency domain.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.397.2-397
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• 2002

There are 4 servo systems in a DVD drive such as a focus servo system, a tracking servo system, a sled servo system and a spindle servo system. Focus servo system maintains relative distance between lens and disk. In this paper, two plant models for the focus servo system will be presented. One of them is newly developed and the other is conventional. Focus error signal between lens and disk is detected using LDV 2 beam method. (omitted)

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.554-558
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• 2000

This paper proposes a new type of piezoactuator-driven valve system. The piezoceramic actuator bonded to both sides of a flexible beam surface makes a movement required to control the pressure at the flapper-nozzle of a pneumatic system. After establishing a dynamic model, an appropriate size of the valve system is designed and manufactured. Subsequently, a sliding mode controller which is known to be robust to uncertainties such as disturbance is formulated in order to achieve accurate regulating and tracking control of the desired pressure. The controller is experimentally realized and control performances for various pressure trajectories are presented in time domain. The control bandwidth of the valve system which directly represents the fastness is also evaluated in the frequency domain.

• 한국군사과학기술학회지
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• 제6권2호
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• pp.55-64
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• 2003

Underwater acoustic noise measurement is an essential element for vulnerability assessment of modern naval platforms. But during the last few decades environmental conditions have drastically changed due to the gradually increasing sea ambient noise level and decreasing submarine radiated noise level. A real-time underwater acoustic measurement system with vertical line array is designed for the quiet submarine radiated noise assessment in challenging environment. This system has a constant directivity index in measurement frequency range and accurate tracking capability for the transmission loss compensation and navigation aids inside the submarine. This system has been validated at sea and used several times for the submarine noise measurement.

• 대한치과의사협회지
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• 제54권9호
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• pp.704-711
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• 2016

Radiologic images in dentistry are essential to perform the diagnosis, treatment, and tracking process of prognosis, thus the ability of accurate evaluation in the diagnostic images is requested for dental clinician. Radiologic interpretation means recognition of a normality and an abnormality and to report the possible diagnosis and differential diagnosis list. Therefore, dental clinicians should be familiar with the basic principle of interpretation of intraoral and extraoral radiographic images primarily used in dental clinics. Recently, dental cone beam CT is widely used for diagnositc process, thus understanding the three dimensional images is requested. The objective of this manuscript is to help the dental clinicians to interpret accurately the diagnostic images by introducing the basic principles of the step by step analytic process in the appearance of a lesion.

• 한국위성정보통신학회논문지
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• 제9권4호
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• pp.16-19
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• 2014

본 논문에서는 와이파이(WiFi) 도플러 주파수의 검파를 기반으로 무선랜 AP(Access Point)용 송신기와 수신기의 부반송파(subcarrier)비콘 방식을 설계한다. 이로서 WiFi-AP에서 도플러 주파수의 감지 및 검파를 위해 어레이(array) 안테나와 RF 빔을 추정함으로서 사람의 움직임과 침입탐지를 검출할 수 있다. 이러한 무선 탐지와 무선 동작인식을 기반으로 한 WiFi 도플러 주파수 검파방식과 적응형 비콘(beacon)의 시간영역신호를 조합하는 무선보안 서비스 설계방안을 제안하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.2299-2301
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• 2001

광 디스크의 용량을 증가시기키 위해선, 레이저 다이오드의 단파장화와 렌즈의 개구수 증가가 수년 동안 시도되어왔다. 불행히도 이러한 노력들은 디스크 틸트(tilt)로 인해 야기되는 코마(coma) 수차로 인한 부작용을 유발하였다. 이런 문제를 해결하기 위해, 램(random access memory, RAM) 디스크의 경우 몇 가지 검출과 보상 방법이 제안되었다. 그러나, 롬(read only memory, ROM) 디스크의 경우 아직까지 뚜렷한 해결책이 제시되지 않고 있다. 본 논문에서는 8분할 광 검출기에 의해 생성되는 차동 위상 검출(differential phase detection, DPD) 신호를 이용한 고밀도 롬 디스크에서 래디얼(radial) 틸트를 검출하는 방법을 제안한다. 3축 렌즈 구동형 액츄에이터(actuator)를 이용하여 개발한 래디얼 틸트 서보로 검출된 래디얼 틸트를 보상한다. 액츄에이터의 회전이 트래킹(tracking) 서보(servo)에 미치는 영향을 소개한다. 끝으로 제안된 방법의 유용성을 고밀도 롬 드라이브에 대한 실험을 통해 검증한다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.584-587
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• 2006

An energy generating greenhouse based on fluoropolymer envelope and fresnel lens is proposed. The outstanding properties of the fluoropolymer films make them very suitable for large scale solar applications. Extremely high optical transmission over the whole solar spectrum, combined with mechanical strength, and durability allows us to design a highly optimized greenhouses for both plant growing and energy generation. Systems such as photovoltaic triple junction cells are especially attractive since they have up to 35% efficiency with much less cell material when the sun beam is focused with concentrators such as fresnel lenses. Cooling such devices will enhance the efficiency and provide useful thermal energy that could be further utilized for various applications depending on the local demands. This article introduces the basic ideas and principles of the energy generating greenhouses as a first step towards the actual deployment of such systems under Korean environment.