• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2007년도 추계학술대회 논문집
• /
• pp.1303-1308
• /
• 2007

Recently, precast concrete tracks are replacing ballast track for efficient and economic maintenance of track. Precast concrete railroad tracks are manufactured in factory, and transported to railroad construction site for installation. Therefore, quality of precast concrete track itself should be sufficiently good. On the contrary to the convenient manufacturing of precast concrete track, the installation of a precast concrete track requires careful steps. Typically, a precast concrete track is placed on an approximately 15-cm thick lean concrete layer. A mortar is filled between lean concrete layer and precast concrete track to adjust the sloping angle of a precast concrete track for a safe train operation at a curvy section. Then, the use of filled mortarproduces a void underneath a precast concrete track, which is harmful to structural safety of a precast concrete track undercyclic loading. Therefore, it is essential to make sure that there is no void left beneath a precast concrete track after mortar filling. In the continuous resonance method, the amplitude of frequency response measured using an instrumented hammer and an accelerometer is plotted against a pseudo-depth, which is half of the wave velocity divided by frequency. The frequency response functions are measured at consecutive measurement locations, 6-cm interval between measurement points, and then combined together to generate a 2-D plot of frequency response. The sections with strong reflections or large amplitude of frequency response are suspicious areas with internal voids and unfilled areas. The 2-D frequency response plot was efficient in locating problematic sections just by examining the color shade of a visualized plot in 2-D format. Some of the problematic sections were drilled to make a visual inspection of mortar filling. The visual image of interface between mortar and precast concrete track was verified using the validity of the continuous resonance technique adopted in this research.

• 한국전기전자재료학회논문지
• /
• 제16권12S호
• /
• pp.1278-1285
• /
• 2003

This study investigated the phase transformation of the REBa$_2$Cu$_3$$O_{7-x}$ (RE=Nd, Gd, Dy) superconductor, and CCT (Continuous-Cooling-Transformation) along with the TTT (Time-Temperature-Transformation) diagrams are suggested according to the isothermal and continuous cooling heat-treatments. The peritectic temperature of the 123 phases decreased approximately 3$0^{\circ}C$ when the ionic radius of the rare-earth elements was reduced. The optimum cooling rate where BC and Cu-free phases do not exist was 0.001$^{\circ}C$/s. At this cooling late, the 123 phase grew with a c-axis Perpendicular to the surface and had a well-distributed 211 phase. When the oxygen partial pressure was reduced Outing isothermal heat-treatment, the formation temperature of the 211 phase decreased. In addition, the formation temperature of the 123 phases decreased from 100$0^{\circ}C$ (Nd-123) to 9$25^{\circ}C$ (Gd-123), and finally 875$^{\circ}C$ (Dy-123) according to the decrease in the ionic radius of the tare-earth elements. Compared to Nd-123, Gd- and Dy-123 had a better texture with a well-distributed 211 phase.e.

• Nuclear Engineering and Technology
• /
• 제50권1호
• /
• pp.140-144
• /
• 2018

Isotopic analyses of plutonium and low-enriched uranium mixtures with particle sizes of $0.6-3.3{\mu}m$ were performed using thermal ionization mass spectrometry with a continuous heating method to verify its effectiveness for the accurate analysis of minor isotopes without sample pretreatment. The mixed particles used in this study were prepared from a mixed solution of plutonium (SRM 947) and uranium (U010, $^{235}U$ 1% enriched) reference materials. The isotope ratios for plutonium in the individual mixed particles, including $^{238}Pu/^{239}Pu$, $^{241}Pu/^{239}Pu$ as well as $^{240}Pu/^{239}Pu$, and $^{242}Pu/^{239}Pu$, were in good agreement with the certified values despite the isobaric interference of $^{238}U$ and $^{241}Am$. The isotope ratios for uranium in the mixed particles also agreed well with the certified values within the range of error. However, the isotope ratios for minor isotopes, such as $^{234}U$ and $^{236}U$, in the particles with diameters of less than approximately $1.8{\mu}m$ could not be measured because numbers of $^{234}U$ and $^{236}U$ atoms in analyzed particles are too low. These results indicate that thermal ionization mass spectrometry with a continuous heating method is applicable for the analysis of trace amounts of plutonium isotopes, including $^{238}Pu$ and $^{241}Pu$, despite the presence of the respective isobars $^{238}U$ and $^{241}Am$ in the microsamples.

• 한국광학회지
• /
• 제20권5호
• /
• pp.276-280
• /
• 2009

Cr:YAG 결정을 포화흡수체로 사용하여 수동형 Q-스위치시킨 다이오드 레이저 여기 Nd:$YVO_4$ 레이저를 제작하였다. Cr:YAG 결정의 한 면에 여기 빛 파장(808 nm)에 대해 고반사 코팅을 한 후, Nd:$YVO_4$ 결정과 접촉시켜 공진기를 구성하였다. Cr:YAG의 한 면에 여기 다이오드 레이저를 반사시키는 코팅을 입혀 공진기의 광변환 효율을 높임과 동시에, 여기빔에 의한 포화흡수체의 표백현상을 방지하여 안정된 출력이 나오게 하였다. 레이저 이득 매질 및 포화흡수체의 온도는 열전 냉각기와 냉각수를 사용하여 안정화 시켰다. 온도안정화를 시킨 상태에서 발진되는 펄스의 첨두 출력 요동(peak to peak)은 4%였다. 다이오드 레이저의 출력이 1 W일 때, 출력 펄스의 반복률은 평균 9 KHz 였으며, 최소 펄스폭은 7.11 ns, 최고 출력은 16.27 mW였다.

• Smart Structures and Systems
• /
• 제12권3_4호
• /
• pp.415-426
• /
• 2013

Condition assessment and monitoring of bridges is critical for safe passenger travel, public transportation, and efficient freight. In monitoring, displacement measurement capability is important to keep track of performance of bridge, in part or as whole. One of the most important parts of a bridge is the expansion joint, which accommodates continuous cyclic thermal expansion of the whole bridge. Though expansion joint is critical for bridge performance, its inspection and monitoring has not been considered significantly because the monitoring requires long-term data using cost intensive equipment. Recently, a wireless smart sensor network (WSSN) has drawn significant attention for transportation infrastructure monitoring because of its merits in low cost, easy installation, and versatile on-board computation capability. In this paper, a rapid wireless displacement monitoring system, wireless hybrid sensor (WHS), has been developed to monitor displacement of expansion joints of bridges. The WHS has been calibrated for both static and dynamic displacement measurement in laboratory environment, and deployed on an in-service highway bridge to demonstrate rapid expansion joint monitoring. The test-bed is a continuous steel girder bridge, the Founders Bridge, in East Hartford, Connecticut. Using the WHS system, the static and dynamic displacement of the expansion joint has been measured. The short-term displacement trend in terms of temperature is calculated. With the WHS system, approximately 6% of the time has been spent for installation, and 94% of time for the measurement showing strong potential of the developed system for rapid displacement monitoring.

• Environmental Engineering Research
• /
• 제19권3호
• /
• pp.283-287
• /
• 2014

Cultivation of microalgae using wastewater exhibits several advantages such as nutrient removal and the production of high valuable products such as lipid and pigments. With this study, two types of wastewater from instant noodle factory; mixed liquor suspended solids (MLSS) and effluents after sedimentation tank were investigated for green microalga Scenedesmus sp. cultivation under laboratory condition. Optimal wastewater dilution percentage was evaluated in 24 wells microplate. MLSS and effluent without dilution showed the highest specific growth rate (${\mu}$) of $1.63{\pm}0.11day^{-1}$ and $1.57{\pm}0.16day^{-1}$, respectively, in which they were significantly (p < 0.05) higher than Scenedesmus sp. grown in BG11 medium ($1.08{\pm}0.14day^{-1}$). Ten days experiment was also conducted using 2000 ml Duran bottle as culture vessel under continuous light at approximately 5000 lux intensity and continuous aeration. It was found that maximum biomass density of microalgae cultivated in MLSS and effluent were $344.16{\pm}105.60mg/L$ and $512.89{\pm}86.93mg/L$ respectively and there was no significant (p < 0.05) difference on growth to control (BG11 medium). Moreover, cultivation microalgae in wastewater could reduce COD in wastewater by 39.89%-73.37%. Therefore, cultivation of Scenedesmus sp. in wastewater from instant noodle factory can yield microalgae biomass production and wastewater reclamation using photobioreactor simultaneously.

• KSBB Journal
• /
• 제21권2호
• /
• pp.118-122
• /
• 2006

본 연구에서는 연속확산식 무세포 단백질 발현 시스템을 이용한 이황화결합 함유 단백질의 생산 시, 발현된 단백질의 응집으로 인한 비활성화의 문제점이 분파샤페론을 통한 발현 단백질의 용해도 증가, 세포 파쇄액의 화학적 처리를 통한 환원활성 제거, 산화환원완충액을 이용한 적절한 산화환원전위의 제공 등을 통해 단백질의 폴딩에 유리한 반응조건을 구축함으로써 해결될 수 있음을 보였다. 이러한 연구 결과는 각종 게놈 시퀀싱 프로젝트의 빠른 진척에 따라 현재 요구되고 있는 고속, 고효율의 단백질 발현 수단으로써 무세포 단백질 발현 시스템이 적용될 수 있는 가능성을 높여 줄 수 있을 것으로 기대된다.

• 한국항공운항학회지
• /
• 제26권4호
• /
• pp.36-42
• /
• 2018

Although continuous passenger injuries and physical damages are repeated due to the unexpected aviation turbulence encountered during operations, there is still exist the limitation for preventing recurrence of similar events because the lack of real-time information and delay in technological developments regarding various operating conditions and variable weather phenomena. The purpose of this study is to compare and analyze the meteorological data of the aviation turbulence occurred and actual flight data extracted from the Quick Access Recorder(QAR) to provide some precursors that the pilot can identify aviation turbulence early by referring thru the flight instrumentation indications. The case applied for this study was recent event, a scheduled flight from Incheon Airport, Korea to Narita Airport, Japan that suddenly encountered turbulence at an altitude of approximately 14,000 feet during approach. According to the Korea Meteorological Administration(KMA)'s Regional Data Assessment and Prediction System(RDAPS) data, it was observed that the strong amount of vorticity in the rear area of jet stream, which existed near Mount Fuji at that time. The QAR data analysis shows significant changes in the aircraft's parameters such as Pitch and Roll angle, Static Air Temperature(SAT), and wind speed and direction in tens of seconds to minutes before encounter the turbulence. If the accumulate reliability of the data in addition and verification of various parameters with continuous analysis of additional cases, it can be the precursors for the pilot's effective and pre-emptive action and conservative prevention measures against aviation turbulence to reduce subsequent passenger injuries in the aviation operations.

• 한국광학회지
• /
• 제34권6호
• /
• pp.225-234
• /
• 2023

모드 잠금 레이저는 주기성을 가지고 짧은 시간 동안 레이저 출력이 펄스로 동작한다. 그러나 시간-주파수 영역에서 모드 잠금된 펄스 레이저의 펄스 반복률의 주기성은 푸리에 변환으로 일정한 주파수 간격을 가진 광 주파수 빗과 같이 이해된다. 이때 광 주파수 빗의 각 주파수 성분은 연속적으로 발진하는 수십만 개의 단일 주파수 성분을 가진 continuous-wave 레이저들과 같다. 광 주파수 빗은 약 20년 전에 개발되어 세계에서 가장 정밀한 원자 시계의 개발을 가능케 하고 안정된 광 주파수를 정밀하게 전송하는 데에 사용되었으며, 다양한 응용연구로도 발전했다. 본 논문에서는 광 주파수 빗의 단일 주파수 구성 요소를 선택적으로 추출하고, 광 빗의 주파수 구성 요소를 제어하는 연구를 소개한다. 또한 광 주파수 빗의 개념과 원리를 해설함으로써 시간-주파수 도메인에서 빛의 특성을 이해하고, 광 주파수 빗을 활용한 다양한 응용 연구를 개발하는 데 도움을 주고자 한다.

• 전기전자학회논문지
• /
• 제28권1호
• /
• pp.14-19
• /
• 2024

주택용 BESS에 적용하기 위한 재활용 셀 성능을 파악하기 위해 지난 5년 동안 사용한 셀을 선택하였다. 시험에 사용된 셀의 기본 사양은 공칭 전압이 3.7[V], 공칭 용량이 2,200[mAh], 충전 전압이 4.05[V], 연속방전전류가 1[C](2,200[mA]), 연속충전전류가 0.5[C](1,100[mA]) 이다. 새 셀의 경우 내부저항은 21.3±1[mΩ]인데, 재활용 셀의 경우 평균 내부저항이 25.38[mΩ]로 나타나 약 19.1[%] 상승하였다. 충·방전 용량은 새 셀에 비해 약 18.9~19.3[%] 정도 낮게 나타났다. 내부저항과 충·방전 용량이 셀의 노화에 상호 밀접하게 연관되어 있으므로 BESS에 적용할 셀은 초기 내부저항보다 1.5배 이하이고 70[%] 이상의 충·방전 용량 성능을 갖는 제품을 사용할 필요가 있다.