• Proceedings of the Optical Society of Korea Conference
• /
• 2004.02a
• /
• pp.352-353
• /
• 2004

• Current Optics and Photonics
• /
• v.2 no.6
• /
• pp.595-605
• /
• 2018

The two-photon process of microscopy provides good spatial resolution and optical sectioning ability when observing quasi-static endogenous fluorescent tissue within an in vivo animal model skin. In order to extend the use of such systems, we developed a two-photon laser scanning microscopy system capable of also capturing $512{\times}512$ pixel images at 90 frames per second. This was made possible by incorporating a 72 facet polygon mirror which was mounted on a 55 kRPM motor to enhance the fast-scan axis speed in the horizontal direction. Using the enhanced temporal resolution of our high-speed two-photon laser scanning microscope, we show that rapid processes, such as fluorescently labeled erythrocytes moving in mouse blood flow at up to 1.2 mm/s, can be achieved.

• Proceedings of the KIEE Conference
• /
• 2006.10b
• /
• pp.199-203
• /
• 2006

무선통신 환경에서 단말의 이동에 의해 발생되는 끊김 현상을 제거하고, 지속적인 서비스를 제공하기 위해서는 빠른 핸드오프(Handoff) 방식이 필요하다. 본 논문에서는 모든 채널을 탐색한 후, 가장 상태가 좋은 채널을 선택하는 기존 방식을 개선한다. 각 AP(Access Point)가 현재 사용하고 있는 채널정보와 ACR(Access Control Router)가 제공하는 인접 AP들 정 보의 주기적인 NEB-ADV에 포함하여 이동단말에 제공 한다. 본 논문에서는 정보를 습득한 단말이 인접한 AP들의 사용 채널만 탐색하는 새로운 Fast Channel Detection(FCD)방식을 제안한다. 제안하는 방식은 기존 방식과 비교하여 채널탐색 시간이 감소되므로 총 지연시간을 감소시킨다. 제안된 방식에 대한 시뮬레이션 모델을 통해서 링크 효율성과 블록킹 확률의 비교 분석을 통하여 제안방식의 우수성을 입증한다.

• Proceedings of the KIPE Conference
• /
• 2014.11a
• /
• pp.91-92
• /
• 2014

본 논문은 고속 Scanning 전자석 전원공급 장치를 제작하여 한국 원자력 의학원에 납품하였고, 전원 장치성능을 확인하였다. 한국 원자력 의학원에서 요구 사양은 전류 기울기가 440 kA/s와 출력 전압 / 전류는 ${\pm}530V$ / ${\pm}80A$이며, 과도상태 이후의 전류 정밀도는 ${\pm}100ppm$ 이하를 만족하는 전원장치 이다. 전류가 고속으로 증가하기 때문에 출력 케이블과 전자석 자체의 표피효과로 인해 구간별 성능에 미진한 부분이 확인되어 추가 연구개발이 요구된다.

• Journal of the Optical Society of Korea
• /
• v.16 no.1
• /
• pp.42-46
• /
• 2012

We have developed a fluorescence optical detection system using a digital micromirror device (DMD) for monitoring 3D cell culture matrices in situ. Full 3D imaging with fast scanning speed was implemented by the combined action of a DMD and a motorized stage. Imaging results with fluorescent microbeads measure the minimum axial resolution of the system as $6.3{\mu}m$, while full 1-mm scanning through 3D alginate-based matrix was demonstrated. For cell imaging, improved images were obtained by removing background fluorescence although the scanning distance was reduced because of low intracellular fluorescence efficiency. The system is expected to be useful to study various dynamics and behaviors of 3-dimensionally cultured cells in microfluidic systems.

• Journal of the Korean Society for Precision Engineering
• /
• v.23 no.9 s.186
• /
• pp.102-110
• /
• 2006

We discuss two possibilities of using femtosecond pulse lasers as a new interferometric light source for enhanced precision surface-profile metrology. First, a train of ultra-fast laser pulses yields repeated low temporal coherence, which allows unequal-path scanning interferometry, which is not feasible with white light. Second, the high spatial coherence of femtosecond pulse lasers enables large-sized optics to be tested in nonsymmetric configurations with relatively small-sized reference surfaces. These two advantages are verified experimentally using Fizeau and Twyman-Green type scanning interferometers.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2009.04a
• /
• pp.115-117
• /
• 2009

Terrestrial Laser Scanner and Airborne Laser Scanning is one of the state of art surveying equipments. So This study deals with the combined use of mobile TLS(Terrestrial Laser Scanner) with ALS(Airborne Laser Scanning) to extract shoreline's topography information. These two systems have their own pros and cons. Mobile TLS can capture the facades of a low story building along the shoreline fast and quickly. Meanwhile, Due to viewpoint restrictions of ALS data collection, the amount of detail, which is available for the building facades is very limited. Therefore, it is recommended that the co-registration and geo-referencing methods of both two should be developed and the application of both system for shoreline mapping also should be investigated.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.54 no.7
• /
• pp.453-457
• /
• 2005

With the expansion of Internet, a variety of image databases are widely used and it is needed to select the part of an image what he wants. In contents-based image retrieval system, Zernikie moment and ART Descriptors are used fur shape descriptors in MPEC-7. This paper presents a fast computation method to determine the radius of a bounding circle that encloses an object in a binary image. With conventional methods, the whole area of the image should be scanned first and the distance from every pixel to the center point be computed. The proposed 4-directional scan method and fast circle-drawing algorithm is utilized to minimize the scanning area and reduce the number of operations fur computing the distance. Experimental results show that proposed method saves the computation time to determine the radius of a bounding circle efficiently.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.653-656
• /
• 2005

This paper introduces design, fabrication and experiment process of a novel scanner for the high speed AFM(Atomic Force Microscope). A proper design modification is proposed through analyses on the dynamic characteristics of the existing linear motion stages using a dynamic analysis program, Recurdyn. Since the scanning speed of each direction is allowed to be different, the linear motion stage for the high-speed scanner of AFM can be so designed to have different resonance frequencies for the modes with one dominant displacement in the desired directions. One way to achieve this objective is to use one-direction flexure mechanism for each direction and to mount one stage for fast motion on the other stage for slow motion. This unsymmetrical configuration separates the frequencies of the two vibration modes with one dominant displacement in each desired direction, hence, the coupling between the motions in the two directions. In addition, a pair of actuators is used for each axis to decrease the cross talks in the two motions and gives a force large enough to actuate the slow motion stage, which carries the fast motion stage. After these design modifications, a novel scanner with scanning speed higher than 10 Hz can be achieved to realize undistorted images in the high speed AFM.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2008.10a
• /
• pp.732-735
• /
• 2008

In order for fast calculation for the modular multiplication which plays an essential role in RSA cryptography algorithm, the Montgomery algorithm has been studed and developed in varous ways. Since there is no division operation in the algorithm, it is able to perform a fast modular multiplication. However, the Montgomery algorithm requires a few extra operations in the progress of which transformation from/to ordinary modular form to/from Montgomery form should be made. Concept of high radix operation can be considered by splitting the key size into word-defined units in the RSA cryptosystems which use longer than 1024 key bits. In this paper, We adopted the concept of operand scanning methods to enhance the traditional Montgomery algorithm. The methods consider issues of optimization, memory usage, and calculation time.