• KSBB Journal
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• v.24 no.5
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• pp.432-438
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• 2009

Here, we demonstrated simple nucleic acid, RNA, concentration method using polymer micro chip containing glass bead ($100\;{\mu}m$). Polymer micro chip was fabricated by PDMS ($1.5\;cm\;{\times}\;1.5\;cm$, $100\;{\mu}m$ in the height) including pillar structure ($160\;{\mu}m\;(I)\;{\times}\;80\;{\mu}m\;(w)\;{\times}\;100\;{\mu}m\;(h)$, gap size $50\;{\mu}m$) for blocking micro bead. RNA could be adsorbed on micro glass bead at low pH by hydrogen bonding whereas RNA was released at high pH by electrostatic force between silica surface and RNA. Amount of glass beads and flow rate were optimized in aspects of adsorption and desorption of RNA. Adsorption and desorption rate was measured with real time PCR. This concentrated RNA was applied to amplification micro chip in which NASBA (Nucleic Acid Sequence Based Amplification) was performed. As a result, E.coli O157 : H7 in the concentration of 10 c.f.u./10 mL was successfully detected by these serial processes (concentration and amplification) with polymer micro chips. It implies this simple concentration method using polymer micro chip can be directly applied to ultra sensitive method to measure viable bacteria and virus in clinical samples as well as environmental samples.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.4
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• pp.204-211
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• 2011

A dynamic analysis procedure is developed to provide a better estimation of the dynamic responses of bridge during the passage of high speed railway vehicles. Particularly, a three dimensional numerical model including the structural interaction between high speed vehicles, bridges and railway endures to analyse accurately and evaluate with in-depth parametric studies for dynamic responses of various bridge span lengths running KTX railway locomotive up to increasing maximum speed(450km/h). Three dimensional frame element is used to model the simply supported pre-stressed concrete (PSC) box bridges for four span lengths(40~25m). Track irregularity employed as a stationary random process from the given spectral density functions and irregularities of both sides of the track are assumed to have high correlation. The high-speed railway vehicle (KTX) is used as 38-degree of freedom system. Three displacements (Vertical, lateral, and longitudinal) as well as three rotational components (Pitching, rolling, and yawing) are considered in the 38-degree of freedom model. The dynamic amplification factors are evaluated by the developed procedure under various traveling conditions, such as track irregularity camber, train speed and ballast. The dynamic analysis such as Newmark-${\beta}$ and Runge-Kutta methods which are able to analyse considering the dynamic impact factors are compared and contrasted.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.1
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• pp.1-8
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• 2009

In order to evaluate the effect of shear wave velocity of a seismic control point on site response analysis, one-dimensional equivalent linear site response analysis were performed on the model soil profile based on the results of a detailed site investigation of sedimentary layers at Incheon and Busan. The results of the analysis show that an increase of shear wave velocity on the seismic control point (base rock) results in an increase of acceleration in the soil layers. This was mainly due to an unclear definition of the seismic control point. For this reason, the Korean Seismic Design Standard requires a specific definition of the seismic control point, including spatial conditions and soil properties, similar to the MCE (Maximum Considered Earthquake) in FEMA 369.

• Journal of the Korean Geotechnical Society
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• v.38 no.8
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• pp.17-27
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• 2022

To characterize the dynamic properties of Gimhae Plains sediments, we calculated natural frequencies using microtremor horizontal-to-vertical spectral ratios and derived shear wave velocity profiles by inversion of Rayleigh-wave dispersion curves obtained by the high frequency-wavenumber and modified spatial autocorrelation methods. Our results suggest that in this region, strong amplification of ground motion is expected in the vibration frequency (f ≥ 1 Hz). Additionally, obtained velocity profiles show that shear wave velocities are ~200 and 400 m/s for the shallow marine and old fluvial sediments, respectively. Bedrock is possibly encountered at depths of 60-100 m at most sites. We developed a simplified shear wave velocity model of shallow sediments based on the obtained profiles. Our results suggest that a large area in the Gimhae Plains could be categorized as an S6 site based on the Korean seismic design code (KDS 17 10 00).

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.10
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• pp.63-67
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• 2003

This paper proposes a new BLSA(Bit Line Sense Amplifier) for MRAM. Current BLSA employs a latch-type circuit to amplify a signal from the selected memory cell. The proposed BLSA simplifies the circuit by amplifying the signal using cross-coupled PMOS transistors. It shows the same operation speedas the latch-type BLSA in simulation and occupies only 85% of the area taken by the latch-type BLSA.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.377-382
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• 2004

The dynamic material characteristics on some mild steel sheets were observed. The dynamic tests were conducted on the ESH servo-hydraulic test machine. It was observed that the mechanical properties of mild steel are highly sensitive to the value of strain rate. The well known Cowper-Symonds constitutive equation was used to generalize the strain rate sensitivity effect. Modified constitutive equations were suggested to couple the strain hardening to the strain rate sensitivity. The dynamic stress-strain relationships for the mild steel sheets used in the present study were reasonably predicted using these modified constitutive equations.

• Electronics and Telecommunications Trends
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• v.29 no.6
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• pp.1-13
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• 2014

GaN(Gallium Nitride)는 3.4eV의 넓은 에너지 갭으로 인하여 고전압에서 동작이 가능하고, 분극전하를 이용한 캐리어 농도가 높아 높은 전류밀도와 전력밀도를 얻을 수 있으며, 높은 전자 이동도와 포화 속도로부터 고속 동작이 가능하여 고주파 고출력 고효율 소형의 전력증폭기 소자의 재료로 적합하다. 본고에서는 민수 및 군수 겸용 Ku-대역 및 Ka-대역 GaN 고출력 전력증폭기(SSPA: Solid-State Power Amplifier)와 관련된 GaN 전력증폭 소자, GaN 전력증폭기 MMIC(Microwave Monolithic Integrated Circuit), 내부정합 패키지형 GaN 전력증폭기 및 GaN SSPA에 대하여, 국내외 특허 기술동향과 연구개발 기술동향을 중심으로 고찰하고자 한다. 국외의 GaN 고주파 고출력 전력증폭기 기술의 연구동향이나 특허동향을 심층분석하여 연구개발에 활용하고자 한다.

• Journal of the KSME
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• v.35 no.8
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• pp.725-736
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• 1995

소노루미네센스(SL)현상은 액체 내에서 초음파에 동기화되어 진동하는 미소기포$~10\mu\textrm{m}$)가 수축할 때 기포내부의 온도가 고온이 됨에 따라 기포중심으로부터 빛이 나오는 현상을 말한다. 단일기 포가 초음파에 가진 될 경우 그 스펙트럼이 X선에 가까운 것임이 밝혀질뿐더러 촉매물 질의 개발이나 활성화, 고분자 합성뿐만 아니라 용액 내에서의 불순물 제거 등에 대한 응용의 가능성이 속속 발견되자, 현재 과학계뿐만 아니라 일반 매스컴에서도 화제의 대상이 되고 있다. SL현상은 원자당 $10^{11}eV$ 에 해당되는 초음파 에너지의 파장이 0.19.mu. 이하인 X선, 즉 6eV 이상의 광자에너지로 증폭됨에 따라 기포수축시 기포내 가스의 온도가 수만 도에 이르는 것, 레이저에 상응하는 광펄스 폭(50 ps)과 초음파에 동기되어 현존하는 최상의 수정시계에 필적하는 SL펄스의 규칙성, 기포수축시의 $10^{10}W/m^{2}$에 해당되는 열의 방출과 10억분의 수 초 동안에 $10^{4}K$의 고온상태에서 200K 정도의 저온상태로 바뀜에 따른 급격한 냉각속도 등 으로 특징지어질 수 있다. 이 글에서는 현재 실험을 통하여 알려진 SL에 관한 현상의 특징과 응용에 대해 구체적으로 기술하였다.

• Korean Journal of Optics and Photonics
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• v.5 no.2
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• pp.340-346
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• 1994

2.5Gbps 광통신시스템용 수광소자로서 charge plate층을 갖는 링구조의 separate absorption grading multiplication avalanche photodiode를 제작하고 그 특성을 조사 분석하였다. Avalanche Photodiode의 제작은 Metal-Organic Chemical Vapor Deposition 과 Liquid Phase Epitaxy법을 이용한 에피성장과 Br:Methanol을 이용한 채널식각 방법을 사용하였고, passivation과 평탄화는 photosensitive polyimide를 이용하였다. 제작된 ADP는 10nA 이하의 작은 누설전류를 나타내었고, -38~39 V의 항복전압을 나타내었다. 제작된 ADP를 GaAs FET hybrid 전치증폭기와 결합하여 2.5Gbps 속도에서 $2^{23}-1$의 길이를 갖는 입력 광신호에 대해 $ 10^{-10}$ Bit Error Rate에서 -31.0dBm의 수신감도를 얻었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.46-46
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• 2011

본 논문에서는 전세계적으로 차세대 화합물반도체 플랫폼으로 각광을 받고 있는 GaN 전력소자의 연구개발 동향에 관하여 발표하고자 한다. GaN 반도체는 와이드 밴드갭(Eg=3.4eV)과 고온 안정성($700^{\circ}C$)등 재료적인 특징으로 인하여 고출력 RF 전력증폭기와 고전력용 전력반도체 응용에 큰 장점을 가진다. 전반부에서는 미국, 유럽을 중심으로 한 대형 국책 연구프로젝트등 RF 전력증폭기 연구개발 동향을, 후반부에서는 일본, 미국, 유럽에서 급속도로 진행되는 전력반도체 연구개발 동향에 관하여 알아본다. 이러한 총체적인 동향 분석을 통하여 차세대 반도체의 신시장 개척과 선진입을 위한 GaN 반도체의 연구개발 방향과 상용화의 중요성을 함께 생각해보고자 한다.