• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.15 no.2
• /
• pp.95-101
• /
• 2016

In this paper, miniaturized ${\lambda}/4$ folded microstrip antennas is presented for parking monitoring base station system. The proposed antenna reduced a width of the radiating element for miniaturizing a size and we changed an aperture such as folded shape for reducing a length of the antenna by the pertubation effect by reducing a width of the antenna. Finally, the ${\lambda}/2$ length of the folded microstrip antenna to ${\lambda}/4$ folded microstrip antenna was miniaturized by reducing the length. The proposed antenna was designed to receive 425 MHz of center frequency that can be used without permission. Dimensions are $134mm{\times}143.85mm{\times}20.1mm$($0.19{\lambda}{\times}0.2{\lambda}{\times}0.028{\lambda}$, ${\lambda}$ is wavelength at 425 MHz) that are compared with basic microstrip patch antenna miniaturized 97.2%. Also, Measured -10 dB bandwidth was 2.44 MHz(0.57%). On the other hand, measured radiation patterns was 1.82 dBi at E-plane $15^{\circ}$.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.32 no.4
• /
• pp.647-660
• /
• 2022

Recent works demonstrate that the semi-supervised anomaly detection method functions quite well in the environment with normal data and some anomalous data. However, abnormal data shortages can occur in an environment where it is difficult to reserve anomalous data, such as an unknown attack in the cyber security fields. In this paper, we propose ADA-PH(Abnormal Data Augmentation Method using Perturbation based on Hypersphere), a novel anomalous data augmentation method that is applicable in an environment where abnormal data is insufficient to secure the performance of the semi-supervised anomaly detection method. ADA-PH generates abnormal data by perturbing samples located relatively far from the center of the hypersphere. With the network intrusion detection datasets where abnormal data is rare, ADA-PH shows 23.63% higher AUC performance than anomaly detection without data augmentation and even performs better than the other augmentation methods. Also, we further conduct quantitative and qualitative analysis on whether generated abnormal data is anomalous.

• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.2
• /
• pp.130.2-130.2
• /
• 2011

지상의 관측소에서 특정 인공위성을 찾아내기 위해서는 위성의 정밀궤도 계산이 필요하다. 궤도상의 인공위성의 위치는 시간에 따라 계속 변하므로 이러한 위성의 위치를 실시간으로 추적하기 위해서는 컴퓨터를 이용한 계산이 필수적이다. 정밀한 계산 결과를 얻기 위하여 태양과 지상 관측소의 위치는 Astronomical Almanac과 지구 타원체 모델을 이용하여 계산 하였다. 인공위성의 궤도는 미공군 북미방공사령부(NORAD)에서 발표하는 TLE를 초기값으로 이용하여 J2 섭동효과를 포함한 위성의 위치 및 속도의 변화를 계산하여 SkyView로 나타내었다. 이렇게 나타낸 SkyView의 결과를 실제 위성의 궤적과 비교하여 위성의 궤도를 검증하였으며, 시간에 따른 위성의 광도 곡선 변화 계산 루틴을 작성하여 실제 위성을 찾아내기 위한 기초자료로 활용이 가능하도록 하였다. 모든 계산을 위한 프로그램을 Visual Studio.net 2010 환경에서 C++ 언어를 이용하여 작성하였으며, 결과를 나타내기 위하여 Nokia 사의 Cross Platform 라이브러리인 Qt를 이용하여 UI 제작 및 Visualization을 수행하였다. Qt 라이브러리는 C++ 언어를 기반으로 작성된 플랫폼 독립적인 GUI 라이브러리로써 MS Windows, Linux, MacOS 환경에서 사용이 가능하다. 이를 통해 운영체제에 관계없이 모든 컴퓨터 환경에서 동일한 유저 인터페이스를 이용하여 계산을 할 수 있다. 본 연구는 향후 우주물체탐색에 있어 독자적인 운영을 위한 프로그램으로 활용할 예정이다.

• Journal of Astronomy and Space Sciences
• /
• v.22 no.4
• /
• pp.463-472
• /
• 2005

In this paper, the dynamic model development for interplanetary navigation has been discussed. The Cowell method for special perturbation theories was employed to develop an interplanetary trajectory propagator including the perturbations due to geopotential, the Earth's dynamic polar motion, the gravity of the Sun, the Moon and the other planets in the solar system, the relativistic effect of the Sun, solar radiation pressure, and atmospheric drag. The equations of motion in dynamic model were numerically integrated using Adams-Cowell 11th order predictor-corrector method. To compare the influences of each perturbation, trajectory propagation was performed using initial transfer orbit elements of the Mars Express mission launched in 2003, because it can be the criterion to choose proper perturbation models for navigation upon required accuracy. To investigate the performance of dynamic model developed, it was tested whether the spacecraft can reach the Mars. The interplanetary navigation tool developed in this study demonstrated the spacecraft entering the Mars SOI(Sphere of Influence) and its velocity .elative to the Mars was less than the escape velocity of the Mars, hence, the spacecraft can arrive at the target planet. The obtained results were also verified by using the AGI Satellite Tool Kit. It is concluded that the developed program is suitable for supporting interplanetary spacecraft mission for a future Korean Mars mission.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.17 no.5
• /
• pp.86-94
• /
• 2013

Research on dynamic characteristics of injectors gives us insight for preventing combustion instability in a rocket engine. While lots of studies have been done about swirl injectors' dynamic characteristics, little is known about impinging jet injectors' dynamic characteristics. For this reason, this study was aimed to reveal the dynamic characteristics of an impinging jet injector based on experiment using a hydraulic mechanical pulsator. Gain, which is the relationship between input pressure and output value(pressure or velocity) was analyzed with the frequency and manifold pressure change. Pulsating frequency was chosen in the low range: 5, 10, 15 Hz. As a background work, Methods to determine the jet velocity were discussed. Klystron effect was also considered as a factor of this experiment.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.20 no.4
• /
• pp.83-94
• /
• 2021

In this paper, we proposed a microstrip antenna (center frequency 118 MHz) with an omnidirectional radiation pattern that can replace the antennae used in VDB systems in GBAS. First, to obtain an omnidirectional radiation pattern from a microstrip antenna, we constructed a folded antenna. We then designed a miniaturized triple-folded antenna using perturbation effects. Thus we obtained suitable characteristics with a S₁₁ of -13.91dB, -10 dB bandwidth of 1.5 MHz (1.27%) in the center frequency of 118 MHz. Furthermore, in the yz-plane and xy-plane, the component exhibits an omnidirectional radiation pattern, and the size of the antenna achieves miniaturization of 64.2% compared to the reference antenna. Finally, it is suitable as an antenna for VDB systems in GBAS.

• Economic and Environmental Geology
• /
• v.21 no.2
• /
• pp.165-169
• /
• 1988

Negative induced polarization (IP) responses are examined for two-dimensional structures using a modeling technique with finite difference method. Percent frequency effect is used for IP parameter because it can be efficiently computed by a perturbation method. Thin conductive, polarizable overburden causes obvious negative IP responses on IP pseudosection. This fact means that IP responses from resistive, polarizable body below the overburden can be masked solely as a function of the resistivity distribution. Resistive, non-polarizable body below the overburden, however, can be detected by the negative IP responses.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2007.11a
• /
• pp.17-20
• /
• 2007

Effect of radial position of half-wave resonator is investigated experimentally for acoustic damping of tangential mode in a combustion chamber by adopting acoustic cold test. When resonator with optimal tuning length is installed， damping is enhanced as its radial location is away from the center of the faceplate. And, radial profile of damping factor is similar to that of the amplitude of the acoustic mode to be damped. As the location is close to the center, acoustic damping is mitigated and independent on the resonator length. on the other hand， the resonator with non-optimal length dose not show any effect of its radial position.

• Journal of the Korean Chemical Society
• /
• v.47 no.5
• /
• pp.447-459
• /
• 2003

Generalized 2D correlation spectroscopy has been applied extensively to the analysis of spectral data sets obtained during the observation of a system under some external perturbation. It is used in various fields of spectroscopy including IR, Raman, UV, fluorescence, X-ray diffraction, and X-ray absorption spectroscopy (XAS) as well as chromatography. 2D hetero-spectral correlation analysis compares two completely different types of spectra obtained for a system under the same perturbation. Because of the wide range of applications of this technique, it has become one of the standard analytical techniques for the analytical chemistry, physical chemistry, biochemistry, and so on, and for studies of polymers, biomolecules, nanomaterials, etc. In this paper, we will introduce the principle of generalized 2D correlation spectroscopy and its applications that we have studied.

• Journal of Astronomy and Space Sciences
• /
• v.12 no.1
• /
• pp.78-89
• /
• 1995

We solved n-body problem about 9 planets, moon, and 4 minor planets with relativistic effect related to the basic equation of motion of the solar system. Perturbations including flgure potential of the earth and the moon and solid earth tidal effect were considered on this relativistic equation of motion. The orientations employed precession and nutation for the earth, and lunar libration model with Eckert's lunar libration model based on J2000.0 were used for the moon. Finally, we developed heliocentric ecliptic position and velocity of each planet using this software package named the SSEG (Solar System Ephemerides Generator) by long-term (more than 100 years) simulation on CRAY-2S super computer, through testing each subroutine on personal computer and short-time(within 800 dyas) running on SUN3/280 workstation. Epoch of input data JD2440400.5 were adopted in order to compare our results to the data archived from JPL's DE 200 by Standish and Newhall. Above equation of motion was integrated numerically having 1-day step-size interval through 40,000 days (about 110 years long) as total computing interval. We obtained high-precision ephemerides of the planets with maximum error, less $than\pm2\times10^{-8}AU(\approx\pm3km)$ compared with DE200 data (except for mars and moon).