• Title/Summary/Keyword: 베

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A study on structural safety evaluation of jet vane under very high temperature and dynamic pressure (초고온 동압을 받는 제트 베인의 구조 안전성 평가에 대한 연구)

  • Park Sunghan;Lee Sangyeon;Park Jongkyoo;Kim Wonhoon;Moon Soonil
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • v.y2005m4
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    • pp.99-105
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    • 2005
  • To evaluate structural safety factor of the jet vane for the thrust deflection system under the dynamic pressure and very high temperature($2700^{\circ}C$) of the combustion gas flow, the high temperature tension tests of refractory metals and 3-D nonlinear numerical simulations are performed. Through the analysis of high temperature structural behavior for jet vane, the structural safety of jet vane is evaluated, and numerical results are compared with static pound tests of jet vanes. It has been found that most of structural and thermal loading is concentrated on the vane shaft which worked as safe under $1400^{\circ}C$. From the comparison of static ground tests and numerical results, the evaluation criterion using the vane load and shaft displacement is more useful to estimate the structural safety than using the equivalent stress.

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Separated Control Signaling Protocol for WDM Optical Networks (파장 분할 다중화 방식을 사용하는 광 전송망을 위한 분리 제어 신호 방식)

  • 소원호;김영천
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.37 no.6
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    • pp.361-361
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    • 2000
  • In this paper, we propose a novel control signaling protocol that efficiently controls connection setup and increases the utilization of network resources. The proposed protocol, Separated Control Signaling Protocol(SCSP), separates bearer control from call control lot WDM optical networks. The main function of call control is to check the availability of network resources such as wavelengths and receivers at destination node. Bearer control is to reserve and assign wavelengths. The signaling architecture of this protocol consists of call controller and hearer controller The call controller handles call setup and release, activates the beater controller, and manages the status of call and bearer. The bearer controller reserves wavelengths, sets up bearer, tears down bearer. and notifies the status of beater to call controller. The state transition diagrams of each controller are designed. Using control messages and related primitives, the information flows for call setup and bearer setup, hearer teardown and call release, and reaction for setup failures are described to evaluate the performance. The simulation results show that the separated control signaling protocol is superior to conventional one in terms of call blocking probability and resource utilization.

A Courseware for the Learning of Visual Basic on the Web (초등학생을 위한 비주얼베이식 교육 시스템 개발)

  • Jin, Hyun-Sik;Park, Phan-Woo
    • Journal of The Korean Association of Information Education
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    • v.7 no.3
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    • pp.299-308
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    • 2003
  • Programming education in the area of ICT instruction is usually considered as contributing to the improvement of one's analytical power, logic in thinking, and procedural problem-solving capabilities. However, it is hard to get access to adequate web coursewares in suit with their intellectual level of development of Korean elementary students. Most of the existing coursewares, if any, are dealing with high level and theory-oriented contents, and accordingly are quite difficult for the elementary students to understand them. In addition, it is very difficult to practice them on the Web. Drawing upon some ideas on the theories of Web-based design and learning, this study tries to develop and materialize a fresh learning courseware for Visual Basic. The Web courseware thus developed allows students to learn the basics of visual basic programming as well as the basic grammar. It also provides students with an environment that enables students to code and run programs on the Web.

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Evaluation of Acceleration Effect of Ancillary Services on Cavitation and Fatigue of a Water Turbine in Pumped-Storage Plants (부수적 서비스 제공에 따른 양수발전소 수차의 캐비테이션 및 피로에 대한 가속효과 평가)

  • Kim, Jong Sung;Kim, Se Na
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.3
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    • pp.225-232
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    • 2017
  • Several maintenance issues related to cavitation erosion and fatigue cracks in the water turbine subcomponents of pumped-storage plants, such as a runner and a draft tube, have been reported in the past. Generally, the pumped-storage plants provide ancillary services, such as black-start and system stabilization. The ancillary services are responsible for cyclic low opening operation of the guide vanes. It has been empirically established that this low opening operation further damages the water turbine subcomponents. In this study, the acceleration effect of the low opening operation on the cavitation erosion and fatigue of the water turbine is quantitatively assessed through finite element flow analysis, finite element stress analysis, and fatigue analysis. As a result of the assessment, it is identified that the cavitation potential increases and the turbine efficiency decreases with a decrease in the opening of the guide vane. Also, the low opening operation has an insignificant effect on the fatigue even though it increases the maximum stress values at the runner blade roots.

Synthesis of Boehmite by Hydrothermal Homogeneous Precipitation Reaction (수열균일 침전반응에 의한 Boehmite 합성)

  • Ham, Yong-Mook;Kim, Jo-Woong;Choi, Choul-Ho
    • Applied Chemistry for Engineering
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    • v.2 no.2
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    • pp.119-126
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    • 1991
  • This investigation was undertaken to study the synthesis of Boehmite by the hydrothermal homogeneous precipitation reaction of alum with urea. The reactions were carried out at a temperature of 100 to $250^{\circ}C$, 1 : 2 to 1 : 5 in a mole ratio of alum to urea and a reaction time of 0.5 to 20 hrs. The reaction precipitates were examined by X-ray diffraction analysis, scanning electron microscope, and chemical analysis. Under the condition of mole ratio 1 : 4 of alum to urea, the spherical and monodispersed amorphous aluminum sulfate hydrate was formed at $100^{\circ}C$, the mixture of spherical amorphous aluminum sulfate hydrate and Boehmite was formed at $150^{\circ}C$, Boehmite was formed at above $200^{\circ}C$, respectively. The reaction precipitates were dense, superior precipitable and filterable particle of average $2-4{\mu}m$.

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Is There a Stochastic Non-fundamental Trend in Korean Stock Price?: Inference under Transformed Error Correction Model (우리나라 주가에는 펀더멘털과 무관한 비정상 추세가 존재하는가?: 공적분 및 베버리지-넬슨 분해 접근)

  • Kim, Yun-Yeong
    • KDI Journal of Economic Policy
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    • v.35 no.2
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    • pp.107-131
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    • 2013
  • In this paper, we test and estimate the stochastic non-fundamental trend in Korean stock market. For this, following Kim (2011), we exploit that the long-run equilibrium stock price may be decomposed into fundamental and stochastic non-fundamental trends (i.e., the sum of dividend innovations and a part that are orthogonal with the dividend innovations) by using the Beveridge-Nelson decomposition and projections. In this VAR construction, there is an error correction mechanism through which stock prices converge to their long-run equilibrium, which also contain the stated stochastic non-fundamental trend as well as fundamental trend. The estimation and test results using yearly data from the Korea (1976-2012) indicated that fluctuations in stock prices during that period can be explained mainly not by the stochastic non-fundamental trend but by the dividend trend. However, during some periods like after Seoul Olympic Games, we may observe the non-fundamental trend affected to the stock price variation.

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Effect of Active Gluten Supplementation on the Processing and Quality of Rice Bagel (활성 글루텐 첨가가 쌀베이글의 품질 특성에 미치는 영향)

  • Lee, Young-Tack;Park, Young-Seo
    • Food Engineering Progress
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    • v.13 no.1
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    • pp.50-55
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    • 2009
  • The effect of active gluten supplementation on the quality properties of rice bagel was investigated. Water hydration capacity of rice flour increased as the amount of gluten increased, whereas alkaline water retention capacity decreased. Pelshenke value and sedimentation value were incerased as the amount of gluten increased, but these values are lower than those of strong wheat flour. Peak viscosity, setback, peak height, and peak width decreased as the amount of gluten increased. When the active gluten of 23% was added to the rice flour, the specific loaf volume of bagel increased more that two times compared with the active gluten of 11%. Hardness, gumminess, and chewiness were decreased as the amount of gluten increased. Specific loaf volume of bagel showed highly positive correlation in water hydration capacity, Pelshenke value, and sedimentation value of which values were r=0.962, r =0.964, and r =0.966, respectively.

Carbon and Nitrogen Inputs by Litterfall of Chamaecyparis obtusa Planted in Pine Wilt Disease-disturbed Forests (소나무재선충병 피해지에 식재된 편백의 낙엽·낙지에 의한 탄소 및 질소 유입량)

  • Kang, Hyeon Cheol;Baek, Gyeongwon;Choi, Byeonggil;Ha, Jiseok;Kim, Choonsig
    • Journal of Korean Society of Forest Science
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    • v.110 no.1
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    • pp.43-52
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    • 2021
  • In this study, carbon (C) and nitrogen (N) inputs by the litterfall of Japanese cypress (Chamaecyparis obtusa Endlicher) planted in pine wilt disease-disturbed forests were determined. The study sites were located in Sacheon-si, Gyeongsangnam-do. Eight plots under two regeneration sites (DR: four plots of C. obtusa planted under slightly disturbed Pinus thunbergii stands; CR: four plots of C. obtusa planted following the clear-cutting of severely disturbed pine stands) were established to collect litterfall from December 2018 to December 2019. The growth of diameter at breast height (DBH) was significantly higher in the CR treatment (12.10 cm) than that in the DR treatment (9.42 cm). C and N concentrations and the C/N ratio in C. obtusa leaf litter did not differ significantly between the two regeneration treatments, but the C/N ratio was significantly lower in the leaf litter collected in October (93) relative to that collected in December (143). The C concentration of litterfall components was significantly higher in C. obtusa leaf litter and in P. thunbergii needle litter than in broadleaved and miscellaneous litter, whereas the N concentration in broadleaved and miscellaneous litter was significantly higher than that in the leaf litter of C. obtusa and in branch litter. Thus, the C/N ratio was significantly higher in C. obtusa leaf litter and branch litter compared with that in miscellaneous and broadleaved litter. Respective C and N inputs by leaf litter were 773 kg C ha-1 yr-1 and 6.95 kg N ha-1 yr-1 for the CR treatments, and 78 kg C ha-1 yr-1 and 0.70 kg N ha-1 yr-1 for the DR treatment. Total C and N inputs were higher for the DR treatment (3,765 kg C ha-1 yr-1 and 47.6 kg N ha-1 yr-1, respectively) than for the CR treatment (1,290 kg C ha-1 yr-1 and 17.2 kg N ha-1 yr-1, respectively). These results indicate that, for C. obtusa, the DBH growth in the CR treatment was superior to that in the DR treatment, but the C and N inputs by litterfall were considerably reduced in CR treatments.