• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2010년도 하계학술대회
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• pp.164-167
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• 2010

`신호 공간 다이버시티(Signal Space Diversity)'기술은 DVB-T2 표준에 포함된 기술로써, 추가적인 전력이나 대역폭의 희생없이 검파에 있어 성능 이득을 얻을 수 있어 DVB-T2 물리계층 핵심적인 기술 중 하나로 평가받으며, 후속 표준인 DVB-NGH 에도 적용 가능성이 높은 기술이다. 본 논문에서는 '신호 공간 다이버시티' 기술을 MIMO 시스템으로 확장하기 위해서 발생하는 문제점에 대해서 분석한 뒤, 이를 해결하기 위해 제안된 '성분 맞교환(Component-Swapping)' 기술을 현재 논의 중에 있는 DVB-NGH 시스템에 적용하여 주어진 실험 환경에서 2.2~3.0dB 가량의 이득을 가짐을 실험적으로 확인하였다.

• 한국소음진동공학회논문집
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• 제23권11호
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• pp.1012-1019
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• 2013

Recently, awareness of noise is increased and high performance sound insulation performance wall is designed. But in spite of installing high performance sound insulation performance wall, sound insulation performance in space is reduced by door. In this study, Sound insulation performance of doors which commonly used in buildings was measured to analyze current situation in the field and effect of method which increase sound insulation performance is analyzed quantitatively. As a result, sound insulation performance of doors which commonly used in buildings is FSTC 17~29 and can be increased about 2~3 dB by install rubber seal or mohair.

• Journal of Magnetics
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• 제19권2호
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• pp.126-129
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• 2014

We report the crystallographic and magnetic properties of $Ni_{0.3}Fe_{0.7}Ga_2S_4$ by means of X-ray diffractometer (XRD), a superconducting quantum interference device (SQUID) magnetometer, and a M$\ddot{o}$ssbauer spectroscopy. In particular, $Ni_{0.3}Fe_{0.7}Ga_2S_4$ was studied by M$\ddot{o}$ssbauer analysis for evidence of spin reorientation. The chalcogenide material $Ni_{0.3}Fe_{0.7}Ga_2S_4$ was fabricated by a direct reaction method. XRD analysis confirmed that $Ni_{0.3}Fe_{0.7}Ga_2S_4$ has a 2-dimension (2-D) triangular lattice structure, with space group P-3m1. The M$\ddot{o}$ssbauer spectra of $Ni_{0.3}Fe_{0.7}Ga_2S_4$ at spectra at various temperatures from 4.2 to 300 K showed that the spectrum at 4.2 K has a severely distorted 8-line shape, as spin liquid. Electric quadrupole splitting, $E_Q$ has anomalous two-points of temperature dependence of $E_Q$ curve as freezing temperature, $T_f=11K$, and N$\acute{e}$el temperature, $T_N=26K$. This suggests that there appears to be a slowly-fluctuating "spin gel" state between $T_f$ and $T_N$, caused by non-paramagnetic spin state below $T_N$. This comes from charge re-distribution due to spin-orientation above $T_f$, and $T_N$, due to the changing $E_Q$ at various temperatures. Isomer shift value ($0.7mm/s{\leq}{\delta}{\leq}0.9mm/s$) shows that the charge states are ferrous ($Fe^{2+}$), for all temperature range. The Debye temperature for the octahedral site was found to be ${\Theta}_D=260K$.

• 한국전자파학회논문지
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• 제23권2호
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• pp.151-158
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• 2012

본 논문에서는 Y-junction을 이용한 H-평면 8-way 구형 도파관 전력 분배기를 제안한다. 일반적인 N-way 전력분배기의 경우 T-junction을 이용하여 다단 형태로 구성이 되는데, 출력 포트 간의 간격이 가까운 경우 T-junction 만으로는 공간상의 제약으로 인하여 매칭 특성을 개선할 수 없다. 따라서 이 같은 경우에는 T-junction과 함께 다른 형태의 3포트 junction이 최종 출력단에 사용되어야 하는데, 본 논문에서는 Y-junction이 사용되었다. 제안된 Y-junction은 임피던스 매칭 특성을 향상시키기 위해 테이퍼드-라인 임피던스 변환기와 유도성 iris가 적용되었다. Y-junction을 이용한 8-way 전력 분배기를 제작하여 측정한 결과, 동작 주파수에서 반사 손실 값은 -30.8 dB, 삽입 손실은 약 -9.5 dB로 측정되었다. 또한, 출력 포트 간의 최대 위상차는 약 $1^{\circ}$로 측정되었다. 따라서 제안된 전력 분배기는 배열 안테나의 급전 구조와 같이 입력 전력을 동일한 크기와 위상으로 분기하는데 필요한 다양한 마이크로파 시스템에 적용하는데 있어서 매우 유용할 것으로 판단된다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.429-431
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• 2002

Metabolic analysis of biological tissues, the interventional radiology in MRT (Magnetic Resonance Treatment) and for clinical diagnoses, representation of 4-Dimensional (4D) structural information (x,y,z,t) of biological tissues is required. This paper discusses image representation techniques for those 4D MR Images. We have proposed an image reconstruction method for ultra-fast 3D MRI. It is based on image interpolation and prediction of un-acquired pictorial data in both of the real and the k-space (the acquisition domain in MRI). A 4D MR image is reconstructed from only two 3D MR images and acquired a few echo signals that are optimized by prediction of the tissue motion. This prediction can be done by the phase of acquired echo signal is proportioned to the tissue motion. On the other hand, reconstructed 4D MR images are represented as a 3D-movie by using computer graphics techniques. Rendered tissue surfaces and/or ROIs are displayed on a CRT monitor. It is represented in an arbitrary plane and/or rendered surface with their motion. As examples of the proposed representation techniques, the finger and the lung motion of healthy volunteers are demonstrated.

• Journal of Astronomy and Space Sciences
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• 제25권2호
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• pp.113-128
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• 2008

Solar wind dynamic pressure enhancements are known to cause various types of disturbances to the magnetosphere. In particular, dynamic pressure enhancements may affect the evolution of magnetic storms when they occur during storm times. In this paper, we have investigated the statistical significance and features of dynamic pressure enhancements during magnetic storm times. For the investigation, we have used a total of 91 geomagnetic storms for 2001-2003, for which the Dst minimum $(Dst_{min})$ is below -50 nT. Also, we have imposed a set of selection criteria for a pressure enhancement to be considered an event: The main selection criterion is that the pressure increases by ${\geq}50%\;or\;{\geq}3nPa$ within 30 min and remains to be elevated for 10 min or longer. For our statistical analysis, we define the storm time to be the interval from the main Dst decrease, through $Dst_{min}$, to the point where the Dst index recovers by 50%. Our main results are summarized as follows. $(i){\sim}$ 81% of the studied storms indicate at least one event of pressure enhancements. When averaged over all the 91 storms, the occurrence rate is ${\sim}$ 4.5 pressure enhancement events per storm and ${\sim}$ 0.15 pressure enhancement events per hour. (ii) The occurrence rate of the pressure enhancements is about three times higher for CME-driven storm times than for CIR-driven storm times. (iii) Only 21.1% of the pressure enhancements show a clear association with an interplanetary shock. (iv) A large number of the pressure enhancement events are accompanied with a simultaneous change of IMF $B_y$ and/or $B_z$: For example, 73.5% of the pressure enhancement events are associated with an IMF change of either $|{\Delta}B_z|>2nT\;or\;|{\Delta}B_y|>2nT$. This last finding suggests that one should consider possible interplay effects between the simultaneous pressure and IMF changes in many situations.

• 천문학회지
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• 제53권1호
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• pp.9-26
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• 2020

At q = 1.81 ± 0.20 × 10^-5, KMT-2018-BLG-0029Lb has the lowest planet-host mass ratio q of any microlensing planet to date by more than a factor of two. Hence, it is the first planet that probes below the apparent "pile-up" at q = 5-10 ×10^-5. The event was observed by Spitzer, yielding a microlens-parallax π_E measurement. Combined with a measurement of the Einstein radius θ_E from finite-source effects during the caustic crossings, these measurements imply masses of the host M_host = 1.14^+0.10_-0.12 M_⊙ and planet M_planet = 7.59^+0.75_-0.69 M_⊕, system distance D_L = 3.38^+0.22_-0.26 kpc and projected separation a_⊥ = 4.27^+0.21_-0.23 AU. The blended light, which is substantially brighter than the microlensed source, is plausibly due to the lens and could be observed at high resolution immediately.

• 전자통신동향분석
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• 제33권1호
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• pp.11-19
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• 2018

IoT is used not only as a technical terminology but also as a paradigm representation. As the number of IoT devices spread tremendously throughout the world, they are able to be located anywhere,recognize their environment, and achieve adaptable reactions. All market investigation agencies expect the number of IoT devices to reach tens to hundreds of billions in number. They also expect various technical problems owing to the huge number of connected things and data that will emerge during the AI era. The decentralization of centralized computing for AI is the one of the technical solutions to such problems, and the computing roles for AI will be soon distributed into the things, which can be located anywhere. In this article, the traditional distributed intelligence and its current research activities are introduced, and the next distributed intelligence target for the IoT 2.0 era is briefly touched upon using the keyword Socio-Things.

• 한국항공우주학회지
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• 제38권8호
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• pp.806-812
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• 2010

회전익항공기 연료탱크는 추락시 승무원의 생존성과 직결되는 구성품이다. 1950년대부터 미육군에서는 항공기 추락 후 화재에 의한 사상자를 줄일 수 있는 방안으로 내충돌성 연료탱크에 적합한 특성을 갖는 소재를 개발하기 위해 다양한 노력을 기울여왔다. 그 결과로 1961년에 MIL-T-27422A라는 항공기 연료탱크 설계규격이 처음 등장하였고, 1970년부터 2002년까지 수회의 개정을 거쳐 2007년 MIL-DTL-27422D라는 미군사 규격으로 발전되었다. 한국형 기동헬기의 연료탱크는 미군사규격(MIL-DTL-27422D)에 따라 개발 및 성능인증시험이 수행되었으며, 연료탱크의 내추락 성능은 미군사 규격에 구체화된 충돌/충격시험으로 검증되도록 규정되어 있다. 본 연구는 한국형기동헬기 연료탱크의 내추락 성능 검증을 위해 수행된 충돌/충격시험 결과를 제시하고 있다.

• Journal of applied mathematics & informatics
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• 제8권1호
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• pp.45-57
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• 2001

A parametric scheme is proposed for the numerical solution of the nonlinear Boussinesq equation. The numerical method is developed by approximating the time and the space partical derivatives by finite-difference re placements and the nonlinear term by an appropriate linearized scheme. The resulting finite-difference method is analyzed for local truncation error and stability. The results of a number of numerical experiments are given for both the single and the double-soliton wave. AMS Mathematics Subject Classification : 65J15, 47H17, 49D15.