• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.3
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• pp.71-77
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• 2016

Characteristic of thermal reaction of Kevlar/EPDM internal insulator used in a solid rocket motor chamber was investigated at 1,030 psi, 35.86 s and 1,406 psi, 36.63 s. Surface status after test was similar each other and thermal destruction depth was 4.10 mm and 4.18 mm, respectively. Kinetic constant ${\xi}$, ${\zeta}$ and thermal destruction velocity $V_{TD}$ were also similar. It was concluded that characteristics of thermal reaction of Kevlar/EPDM internal insulator were not affected by change of chamber pressure.

• The Journal of Engineering Geology
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• v.6 no.1
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• pp.33-43
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• 1996

In this study, hypocentor parameters of some local and regional earthquakes and explosions, including focal depth and origin time, were redetermined by using a single station of three-component. We attempt to do the job by the combination of polarization analyses, by which azimuths and trial epicenters of earthquakes can be figured out, and a layered constant velocity model, on the basis of which theoretical travel times can be computed to match a series of input seismic phases of the event. Magnitudes were determined by using coda duration. Results, which correspond to the least misfit, showed that the average focal depth of all earthquakes in this study is around 15km, which fits well to that by investigation (Kang and Choi, 1993).

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.2
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• pp.95-101
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• 1999

The electron energy distributions function were analysed in sulIitur hexaflowide at E/N : 500~800(Td) for a case of non-equilibrium region in the nran electron energy. This papa- describes the electron transport characteristics in $ SF_6$ gas calculated for range of E/N values from 150~800(Td) by the Monte Carlo simulation and Boltzmann equation Irethod using a set of electron collision cross sectioos determined by the authors and the values of electron swarm parameters. The results gained that the value of an electron swarm parameter such as the electron drift velocity, the electron ionization or attachment coefficients, longitudinal and transverse diffusion coefficients agree with the experimental and theoretical for a range of E/N. The properties of electron avalanches in an electron energy non-equilibrium region.region.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.8
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• pp.1191-1200
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• 2002

The measurements of velocity vectors are made in the near wake(X/d=5.0) of a circular cylinder with serrated fins. Velocity of fluid which flow through fins decreases as increasing fin height and freestream velocity and decreasing fin pitch. Therefore the velocity distribution at X/d=0.0 has lower gradient with increasing freestream velocity and fin height and decreasing fin pitch. The discontinuity of the streamwise velocity gradient is observed near the fin edge and causes significant changes in V-component velocity distribution in the near wake. This change attributes to the differences in Strouhal number and entraintment flow behavior. Increased turbulent intensity around a circular cylinder due to the serrated fins and entrainment flow are important factors for the recovery of velocity defect. The widths of velocity and turbulent intensity distribution of fin tubes are wider than those of a circular cylinder. The normalized velocity and turbulent intensity distributions with a hydraulic diameter which is proposed in this paper are in closer agreement with those of a circular cylinder.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1994.04a
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• pp.201-201
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• 1994

항암 및 면역조절작용을 가지고 있으며 그자체가 서방성 prodrug으로서 약효를 나타낼것으로 기대되는 ara-C와 etherphospholipid의 conjugate인 ara-CDP-DL-PCA.2Na의 실험동물(rat)에서의 체내동태를 HPLC 정량법으로 시행 하였다. Ara-CDP-DL-PCA.2Na의 정맥내 투여(20mg/300g)의 경우 혈장중 반감기는 분포상에 있어서는 평균 20min, 소실상 에서는 4.42hr이었다. 분포 용적은 0.1635Lㆍkg$^{-1}$이었고, 전신 clearance 는 25.63ml.$hr^{-1}$.kg$^{-1}$이었다. 한편 AUC는 2601$\mu\textrm{g}$.hr.ml$^{-1}$이었다. 복강내 주사(1g/kg)의 경우 소실상의 반감기는 3.28hr, AUC는 439.3$\mu\textrm{g}$.hr.ml$^{-1}$이었다. 최고 혈중농도 도달시간은 4.4hr이었으며 그때의 농도는 33.19$\mu\textrm{g}$.ml$^{-1}$이었다. 한편 흡수속도 정수는 0.2493$hr^{-1}$이었다. 정맥내 투여에 대한 복강내 투여의 생체 이용율은 1.1252%로 복강내 투여시 흡수율이 좋지 않음을 시사하고 있다. 이는 투여 시료인 micellar solution이 일종의 약물저장 형태로 작용하여 활성물질을 서서히 방출 하기 때문인 것으로 사료된다. 한편 예비적 대사연구결과 TLC에서 뇨나 담즙으로 배설되는 유의한 농도수준의 ara-CDP-DL-PCA.2Na가 없는 것으로 평가되었다. 이는 생체내에서 enzyme등에 의한 대사과정을 거치는 것으로 사료되는바 방사성 동위원소 표지화합물을 이용한 충분한 대사연구가 필요한 것으로 사료된다.

• Microbiology and Biotechnology Letters
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• v.9 no.4
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• pp.231-236
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• 1981

Studies were made on the optimal conditions of sterilization for Streptococcus pyogenes treated with heat. The results were as follows: The optimal temperature on growth of Streptococcus pyogenes was 37$^{\circ}C$ and mean generation time was 20 minutes in the logarithmic growth phase. The suspension of Streptococcus pyogenes, adjusted to pH 6-9 and treated with heat at 5$0^{\circ}C$, showed logarithmic death rate. Specific death rate constant(k) values at pH 6-9 were 0.1448, 0.1194. 0.1273 and 0.1707 minute$^{-1}$ , respectively.

• Journal of the Korea Computer Industry Society
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• v.2 no.11
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• pp.1373-1382
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• 2001

Traditionally, Mobile Teletraffic model consists of two sub-models, i.e. the network traffic model and the traffic source model. In this paper, we present the traffic source model by developing MobCall(Mobile Call Simulator) which analyses various mobile wireless environments based on regional characteristics that the base stations are located. User mobility is presented by regional average vehicle speeds and the transportation share rate. Moreover, the user mobility on subway, which is increasing in urban area, is considered in MobCall. Using MobCall, the accumulated number of calls in residential and commercial regions, the handoff rate with respect to traffic sources of Seoul, the handoff rate on highway, and the handoff rate according to the call duration are presented. MobCall enables the simulation of dynamic handoff buffering and functional entity control of one base station according to the changes in user's calling pattern at the design phase.

• Annual Conference on Human and Language Technology
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• 2018.10a
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• pp.210-214
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• 2018

본 논문에서는 한국어 대화 엔진에서의 문장 분류 방법에 대해서 소개한다. 문장 분류시 말뭉치에서 관찰되지 않은 표현들을 포함한 입력 발화를 처리하기 위하여, 태깅되지 않은 뉴스 데이터로부터 일반적인 단어 의미 벡터들이 훈련 및 성능 평가되었고, 이를 문장 분류기에 적용하였다. 또한, 실 서비스에 적용 가능한 빠른 분류 속도를 유지함과 동시에 문제에 특화된 의미 벡터들을 학습하기 위하여, 기존에 사용되던 캐릭터 기반 의미 벡터 대신 도메인 특화 단어 의미 벡터의 사용이 제안되었다. 실험 결과, 자체 구축된 테스트 말뭉치에 대하여 본 논문에서 제안된 시스템은 문장 단위 정확률 96.88, 문장당 평균 실행 시간 12.68 msec을 기록하였다.

• Journal of IKEEE
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• v.23 no.4
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• pp.1408-1414
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• 2019

Deep artificial neural network with transfer learning is applied to compressed sensing cardiovascular MRI. Transfer learning is a method that utilizes structure, filter kernels, and weights of the network used in prior learning for current learning or application. The transfer learning is useful in accelerating learning speed, and in generalization of the neural network when learning data is limited. From a cardiac MRI experiment, with 8 healthy volunteers, the neural network with transfer learning was able to reduce learning time by a factor of more than five compared to that with standalone learning. Using test data set, reconstructed images with transfer learning showed lower normalized mean square error and better image quality compared to those without transfer learning.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.2
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• pp.111-117
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• 2013

A valveless pump consisting of a pumping chamber with an elastic tube was simulated using an immersed boundary method. The interaction between the motion of the elastic tube and the pumping chamber generated a net flow toward the outlet through a full cycle of the pump. The net flow rate of the valveless pump was examined by varying the stretching coefficient, bending coefficient, and aspect ratio of the elastic tube. Photographs of the fluid velocity vectors and the wave motions of the elastic tube were examined over one cycle of the pump to gain a better understanding of the mechanism underlying the valveless pump. The relationship between the gap in the elastic tube and the average flow rate of the pump was analyzed.