• 한국정보통신설비학회:학술대회논문집
• /
• 2003.08a
• /
• pp.12-15
• /
• 2003

이동체 탑재형 안테나는 특성상 소형화 및 신호 추적 시간 단축이 중요한 요소이다. 이러한 특성은 위상변위기를 이용한 전자적인 빔 조향 방식으로 한층 더 보완할 수 있다. 현재 이동체에서 주로 사용되고 있는 DBS (Direct Broadcasting Satellite) 수신용 안테나는 패치 및 슬롯 형태의 안테나 소자를 배열하여 사용한다. 하지만 이러한 안테나 소자는 전방위각에 대해 인공위성 방향(앙각 45도)에서 이득 손실이 있기 때문에 위상변위기를 이용한 빔 조향 방식에서 사용하기에는 문제점을 가지고 있다. 따라서 모든 방위각에 대해 앙각 45도에서 최대 이득 특성을 갖는 안테나 소자를 이용해 이득 손실을 줄이는 것은 큰 의미가 있다. 본 논문에서는 monopole 주변에 PBG(Photonic Band Gap) 구조를 구현함으로써 표면파를 억제하여 앙각 45도 방향에서 최대 이득 특성을 보이는 안테나 소자를 제안한다.

• Journal of Korean Elementary Science Education
• /
• v.23 no.3
• /
• pp.182-191
• /
• 2004

In this research a questionary survey was implemented to investigate how elementary school students in $3^{rd}-6^{th}$ grade understood articles or terminology using electromagnetic wave technology in contemporary culture. Also, part of students who had participated in questionnaire survey was interviewed 2 times for each 20 minute personally to investigate students＇ perceptions about some household articles in their every day life using electromagnetic wave technology. As a result, first, elementary school students had pretty higher perceptions of the artificial satellite provided in their curriculum and the technology of electromagnetic wave released from cartoons, computer games or advertisements. Second, because they were concerned about appearances of household articles, they perceived some household articles in their every day life with conceptions of electricity or visual mechanism.

• International Journal of Aeronautical and Space Sciences
• /
• v.8 no.1
• /
• pp.129-139
• /
• 2007

In this paper, attitude control laws for simultaneous pointing of multiple spacecrafts are considered under a formation flying scenario. The basic approach lies in adaptive feedback gains using relative attitude information or maneuver time approximation for coordinated attitude control. Each control law is targeted to balancing mean motion or to correcting system response to the slowest satellite. The control gain adaptation is constructed by two approaches. The first one is using variable damping gain to manipulate speed of a fast system response, and the second one uses alternate natural frequency of the system under control. The validity and stability of the proposed approaches are examined analytically and tested through numerical simulations.

• Proceedings of the Korean Information Science Society Conference
• /
• 2007.10d
• /
• pp.221-224
• /
• 2007

홍수 예보 시스템은 관측소의 우량계와 수위계로부터 데이터를 수집하여, VHF, SATELLITE 등의 통신망을 이용하여 통제소의 TM 주장비로 수집한 데이터를 송신한다. 그리고 통제소에서는 수신된 데이터를 분석하여 홍수예보에 활용하고 있다. 그러나 현 시스템은 제한적인 무선 시스템으로 관측소의 자료 확인이나 테스트를 위해서는 직접적인 수동접속 또는 엔지니어의 대국이 불가피하다. 본 연구에서는 기존의 홍수예보 시스템에 CDMA라 Bluetooth 기능을 적용하여 지능적 홍수예보시스템(IFFS, Intelligence Flood Forecast System)의 개발하였다. 지능적 통수예보시스템의 도입 시 항시 휴대 가능한 PDA를 이용, 관측소의 수위, 우량데이터를 Bluetooth를 이용하여 백업하며 수집된 데이터를 통제소로 간편하게 전승할 수 있으며, 관측소의 S/N 측정을 인력과 시간의 낭비 없이 효율적으로 수행할 수 있다.

• Proceedings of the KIEE Conference
• /
• 2006.07c
• /
• pp.1613-1614
• /
• 2006

In this paper, a $4{\times}4$ rectangular patch array antenna operated at 20 GHz is implemented for the satellite communication. Two $2{\times}2$ subarrays are designed and more efficient $2{\times}2$ subarray is used for the design of $4{\times}4$ patch array. The sixteen patch antennas and microstrip feeding line are printed on the single-layered substrate. The spacing between the array elements is chosen to be $0.736{\lambda}$. HPBW (Half-Power Beam Width) is 17.6 degrees in the E-plane and 18.7 degrees in the H-plane with a gain of 17.2SdBi in the simulation results.

• Korean Journal of Remote Sensing
• /
• v.22 no.5
• /
• pp.439-443
• /
• 2006

Image co-registration is the process of overlaying two images of the same scene. One of which is a reference image, while the other (sensed image) is geometrically transformed to the one. Numerous methods were developed for the automated image co-registration and it is known as a timeconsuming and/or computation-intensive procedure. In order to improve efficiency and effectiveness of the co-registration of satellite imagery, this paper proposes a pre-qualified area matching, which is composed of feature extraction with Laplacian filter and area matching algorithm using correlation coefficient. Moreover, to improve the accuracy of co-registration, the outliers in the initial matching point should be removed. For this, two outlier detection techniques of studentized residual and modified RANSAC algorithm are used in this study. Three pairs of Landsat images were used for performance test, and the results were compared and evaluated in terms of robustness and efficiency.

• Molecules and Cells
• /
• v.42 no.2
• /
• pp.97-103
• /
• 2019

Androgens act in almost all tissues throughout the lifetime and have important roles in skeletal muscles. The levels of androgens increase during puberty and remain sustained at high levels in adulthood. Because androgens have an anabolic effect on skeletal muscles and muscle stem cells, these increased levels of androgens after puberty should lead to spontaneous muscle hypertrophy and hyperplasia in adulthood. However, the maintenance of muscle volume, myonuclei number per myofiber, and quiescent state of satellite cells in adulthood despite the high levels of androgens produces paradoxical outcomes. Our recent study revealed that the physiological increase of androgens at puberty initiates the transition of muscle stem cells from proliferation to quiescence by the androgen-Mindbomb1-Notch signaling axis. This newly discovered androgen action on skeletal muscles underscores the physiological importance of androgens on muscle homeostasis throughout life. This review will provide an overview of the new androgen action on skeletal muscles and discuss the paradoxical effects of androgens suggested in previous studies.

• Journal of Positioning, Navigation, and Timing
• /
• v.12 no.2
• /
• pp.149-155
• /
• 2023

In urban areas it can be difficult to utilize global navigation satellite systems (GNSS) due to signal reflections and blockages. It is thus crucial to detect reflected or blocked signals because they lead to significant degradation of GNSS positioning accuracy. In a previous study, a classifier for global positioning system (GPS) signal reception conditions was developed using three features and the support vector machine (SVM) algorithm. However, this classifier had limitations in its classification performance. Therefore, in this study, we developed an improved machine learning based method of classifying GPS signal reception conditions by including an additional feature with the existing features. Furthermore, we applied various machine learning classification algorithms. As a result, when tested with datasets collected in different environments than the training environment, the classification accuracy improved by nine percentage points compared to the existing method, reaching up to 58%.

• Journal of Korean Library and Information Science Society
• /
• v.28
• /
• pp.61-91
• /
• 1998

In contemporary education, a school library is considered and valued as a vital and integral component of a school's instructional program. Especially, school library materials should contribute to execution of school curriculums through wide provision of resources. The results of the study are as follows. 1. The term 'library materials' should be changed into 'library resources' with a broad meaning. And, the scope of school library materials should include printed materials, audio-visual materials, electronic materials, associated equipment and other library resources. 2. It is desirable that the minimal standards of total collection is 5 books and 3 AV for a student in elementary schools, 7 books and 5 AV for a student in middle schools, 10 books and 7 AV for a student in high schools. 3. Annual growth is 0.5 for a student in elementary schools, 1 for a student in middle schools and 1.5 copy for a student in high schools. And, the number of minimal serials is 20 titles in elementary schools, 30 titles in middle schools and 50 tides in high schools. 4. Besides, basic collection, with the advances of technology, the school library collection should include new formats and delivery systems such as CD, video discs, videotex, computer software, satellite transmission etc. 5. The recommendable annual ratio of withdrawl is 3 to 5% for update and functional materials.

• 전자공학회논문지 IE
• /
• v.45 no.1
• /
• pp.44-49
• /
• 2008

In this paper, the performance for the non-linear satellite channel including the characteristics of group delay and gain ripple of transponder is analyzed with multi-level QAM-OFDM schemes. Comparing the BER performances between general OFDM and CI(Carrier Interferometry)-OFDM for various QAM schemes, the degree of performance improvement is presented in AWGN environments for specified nonlinear characteristics. The simulations are performed with the 36MHz bandwidth of transponder channel and 120Mbps transmission rate for QPSK, 8QAM, 16QAM, 32QAM, 64QAM schemes between normal and worst case condition. It is shown that the improvement measure by the CI-OFDM for the group delay of channel and nonlinear characteristic of HPA outperforms that for the gain ripple in the case of higher level QAM scheme in normal condition. And the simulation results show that the additional techniques like the channel coding and compensation scheme against the nonlinear characteristic are required for 32QAM and higher level QAM in worst case condition.