• 대한원격탐사학회지
• /
• 제19권1호
• /
• pp.43-52
• /
• 2003

EOC (Electro-Optical Camera) of KOMPSAT-1 (Korea Multi-Purpose SATellite) has been producing land imageries of the world since January 2000. After image data are acquired by EOC, they are transmitted from satellite to ground via X-band RF signal. Then, EOC image data are retrieved and pass through radiometric and geometric corrections to generate standard products of EOC images. After radiometric correction on EOC image data, Modulation Transfer Function (MTF) compensation is applicable on EOC images with user's request for better image quality. MTF compensation is concerned with filtering EOC images to minimize the effect of degradations. For Image Receiving and Processing System (IRPE) at KOMPSAT Ground Station (KGS), Wiener filter is used for MTF compensation of EOC images. If the Pointing Spread Function (PSF) of EOC system is known, signal-to-noise (SNR) power spectra ratio is the only variable which determines the shape of Wiener filter In this paper, MTF compensation in IRPE at KGS is briefly addressed, and MTF compensated EOC images are generated using Wiener filters with various SNR power spectra ratios. MTF compensated EOC images are compared with original EOC 1R images to observe correlations between them. As a result, the effect of SNR power spectra ratio on MTF compensated EOC images is shown.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2009년도 춘계학술대회
• /
• pp.180-185
• /
• 2009

우주비행체의 정밀 자세제어에 있어서 자세지향 및 안정성을 저해하는 구동기 교란의 효과는 매우 중요한 요소 중 하나라 할 수 있다. 최근 CMG는 그 구조의 복잡성에도 불구하고 반작용휠에 비교할 때 고출력 저중량이라는 장점에 근거하여 인공위성의 차세대 구동기로 많은 연구가 진행되고 있다. 정밀자세제어가 요구되는 인공위성의 구동기로 이용되기 위해서는 CMG가 위성 동체에 주게 될 교란력의 특성을 파악하는 것이 필수적이다. 본 논문에서는 CMG의 교란토크 및 교란력를 분석하기 위해 정적 동적 불균형을 가정하고, 라그랑지안 방법을 이용하여 해석적 모델을 유도하고 휠을 제작하여 진동을 분석하였다.

• 한국컴퓨터정보학회논문지
• /
• 제6권4호
• /
• pp.146-153
• /
• 2001

본 논문에서는 웹 페이지 운영자가 웹 서버에 패스워드로 보호된 웹 영역을 배치시키는데 편리함을 제공하는 목적으로 새로운 패스워드 인증 방안을 제안한다. 이 방법에 따라 웹 영역은 접근 제한된 웹 페이지가 저장된 웹서버의 보안 디렉토리에 연결된다. 패스워드는 보안 디렉토리의 이름을 생성하는데 사용되며, 자바스크립트 코드는 보안 디렉토리영역 외부의 인증 웹 페이지에 포함된다. 이 스크립트 코드는 사용자가 입력한 패스워드를디렉토리 이름으로 변환시키고, 보안 디렉토리 내부의 접근 제한된 웹 페이지를 지시하는 완전한 URL을 형성한다. 따라서, 패스워드를 아는 사용자만이 유효한 URL을 구성할 수 있고, 접근 제한된 웹 페이지를 검색할 수 있다. 이 방법에 따라, 웹 페이지 운영자는 서버 독립적인 방식으로 패스워드로 보호된 웹 영역을 배치할 수 있다.

• Current Optics and Photonics
• /
• 제5권2호
• /
• pp.114-120
• /
• 2021

Free-space optical (FSO) communication is considered to be a potential solution to congestion in the radio-frequency spectrum and last-mile-access bottleneck issues in future cellular communication networks, such as 5G and beyond. However, FSO link performance may degrade significantly due to irradiance fluctuations and random temporal fluctuations from atmospheric turbulence. Therefore, in this work the main objective is to reduce the effect of the atmospheric turbulence by considering a multihop FSO communication system with amplify-and-forward relaying supported by a radio-frequency (RF) link, which form a hybrid FSO/RF communication system. The FSO link is assumed to follow the gamma-gamma fading model, which represents strong turbulence. Also, the RF link is modeled by a Rayleigh distribution. The performance of the considered system, in terms of the outage probability and average bit-error rate (BER), is investigated and analyzed under various weather conditions and pointing errors. Furthermore, the effect of the number of employed relay nodes on the performance of the system is investigated. The results indicate that the considered system reduces outage probability and average BER significantly, especially for low channel quality. Finally, the closed-form expressions derived in this work are compared to the results of Monte Carlo simulations, for verification.

• 한국멀티미디어학회논문지
• /
• 제24권7호
• /
• pp.903-912
• /
• 2021

Eye tracking research for upper limb disabilities is showing an effect in the aspect of device control. However, the reality is that it is not enough to perform web interaction with only eye tracking technology. In the Eye-Voice interface, a previous study, in order to solve the problem that the existing gaze tracking interfaces cause a malfunction of pointer execution, a gaze tracking interface supplemented with a voice command was proposed. In addition, the reduction of the malfunction rate of the pointer was confirmed through a comparison experiment with the existing interface. In this process, the difficulty of pointing due to the small size of the execution object in the web environment was identified as another important problem of malfunction. In this study, we propose an auto-magnification interface of objects so that people with upper extremities can freely click web contents by improving the problem that it was difficult to point and execute due to the high density of execution objects and their arrangements in web pages.

• 통합자연과학논문집
• /
• 제11권4호
• /
• pp.192-196
• /
• 2018

The mobile agent paradigm can be exploited in a variety of ways, ranging from low-level system administration tasks to middle ware to user-level applications. Mobile agents can be useful in building middle-ware services such as active mail systems, distributed collaboration systems, etc. An active mail message is a program that interacts with its recipient using a multimedia interface, and adapts the interaction session based on the recipient's responses. The mobile agent paradigm is well suitable to this type of application, since it can carry a sender-defined session protocol along with the multimedia message. Mobile agent communication is possible via method invocation on virtual references. Agents can make synchronous, one-way, or future-reply type invocations. Multicasting is possible, since agents can be aggregated hierarchically into groups. A simple check-pointing facility has also been implemented. Another proposed solution is to use multi agent computer systems to access, filter, evaluate, and integrate this information. We will present the overall architectural framework, our agent design commitments, and agent architecture to enable the above characteristics. Besides, the each information needed a mobile agent system such as text, graphic, image, audio and video etc, constructed a great capacity multimedia database system. However, they have problems in establishing connections over multiple subnetworks, such as no end-to-end connections, transmission delay due to ATM address resolution, no QoS protocols. We propose a new connection management scheme in the thesis to improve the connection management involved of mobile agent systems.

• 지식경영연구
• /
• 제20권3호
• /
• pp.1-16
• /
• 2019

Jobless Growth, one of the most issue keywords for Korea's economy at this moment, stands for an economic situation where the unemployment rate once edging up at the downturn does not fall sharply even after a business cycle is on the stage of its recovery. A remarkable progress of ICT has intensified the apprehension of technology displacing human labor. A remarkable progress of ICT has intensified the apprehension of technology displacing human labor historically. Nowadays, ICT as the main cause for recent jobless growth in Korea ends up with pointing out. This study is to investigate whether the ICT leads to an economic situation of jobless growth. We served an empirical analysis using firm-level panel data from 2009 to 2013 and estimated the effects of ICT on both firm's employment and productivity. A result suggests not only does the employment increase with the rise of ICT investment, but also the employment becomes a complete mediator in terms of linking ICT and firm's productivity. It turns out to be a groundless fear that the ICT rules out human labor causing jobless growth for Korea's economy according to the result revealed.

• 한국항공우주학회지
• /
• 제47권5호
• /
• pp.371-378
• /
• 2019

정밀지향위성은 반작용휠로 자세제어를 수행하며, 반작용휠의 모멘텀 덤핑은 3개의 자기토커로 이뤄진다. 본 논문에서는 자기토커 고장 시의 모멘텀 덤핑 영향성에 대해서 살펴본다. 높은 경사각을 가지는 궤도에 위치한 위성이 지구지향자세를 유지하고 있을 때 피치축 방향 자기토커가 고장나면 모멘텀 덤핑이 불가능하다. 하지만 다른 방향의 자기토커가 고장나면 성능 저하만 있을 뿐 모멘텀 덤핑은 여전히 가능하다. 피치축 방향의 자기토커가 고장났을 때도 위성자세변화를 통해서 모멘텀 덤핑을 할 수 있다. 또한 자기토커 배치를 변경하면, 어느 자기토커가 고장나더라도 모멘텀 덤핑이 항상 가능하다.

• 천문학회보
• /
• 제44권1호
• /
• pp.82.2-82.3
• /
• 2019

Korea Astronomy and Space Science Institute (KASI), in collaboration with the NASA Goddard Sparce Flight Center (GSFC), will develop a next generation coronagraph for the International Space Station (ISS). COronal Diagnostic EXperiment (CODEX) uses multiple filters to obtain simultaneous measurements of electron density, temperature, and velocity within a single instrument. CODEX's regular, systematic, comprehensive dataset will test theories of solar wind acceleration and source, as well as serve to validate and enable improvement of space-weather/operational models in the crucial source region of the solar wind. CODEX subsystems include the coronagraph, pointing system, command and data handling (C&DH) electronics, and power distribution unit. CODEX is integrated onto a standard interface which provides power and communication. All full resolution images are telemeters to the ground, where data from multiple images and sequences are co-added, spatially binned, and ratioed as needed for analysis.

• 천문학회보
• /
• 제44권1호
• /
• pp.72.3-72.3
• /
• 2019

The observation of transient objects such as supernovae or variable stars requires a survey of the wide sky and quickly extracting the results. In accordance with this purpose, we have been developing an automatic observing software, KAOS (Kyung Hee University Automatic Observing Software) as a series. KAOS30 was the first series of KAOS and it was applied to the 30-inch platform at the McDonald Observatory in the United States of America. KAOS76 controls the 76-cm telescope at Kyung Hee Astronomical Observatory. In this poster, we introduce KAOS10 for controlling a portable telescope with a small aperture size attaching a guiding camera as QHY-5L II. Kyung Hee University auto-guiding package which includes the auto-guiding function for small aperture size telescope was also developed. Additionally, the Telescope Control Package(TCP) can communicate with the main server to do astrometry for pointing and identifying targets efficiently. KAOS10 has a universal interface that will be useful for the research of both amateurs and professionals.