• Title/Summary/Keyword: 온도진폭

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Thw Characteristic of Supersonic Flow with Condensation along a Wavy Wall of Small Amplitute in Channel (미소진폭 파형벽을 가진 유로내에서 凝縮을 수반하는 超音速 유동의 特性 - 수치해석 결과)

  • 김병지;권순범
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.10
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    • pp.1990-1997
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    • 1992
  • The characteristic of supersonic flow with condensation along a wavy wall of small amplitude in channel is investigated through the direct marching method of characteristics. The very complex problem that may appear where the overlapping of the same family characteristics occurs, can be satisfactorily solved by means of the modified method suggested by Zucrow. In the present study for the case of supersonic moist air flow, the dependency of location of formation and reflection of oblique shock wave generated by the wavy wall, and the distributions of flow properties, on the relative humidity and temperature at the entrance of wavy wall is clarified by plots of streamline, ios-Mach umber and ios-flow properties. Also, it is confirmed that the wavy wall plays an important key role in the formation of oblique shock wave, and that the effect of condensation on the flow field appears apparently.

Effect of Temperature on the Luminous Properties of Remote-Phosphor White Light-Emitting Diodes (이격 형광체 구조가 적용된 백색 LED 광원의 온도변화에 따른 발광 특성 분석)

  • Choi, Min-Hyouk;Lee, Hun Jae;Ko, Jae-Hyeon
    • Korean Journal of Optics and Photonics
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    • v.25 no.5
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    • pp.254-261
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    • 2014
  • Two types of white light-emitting diodes (LEDs) with different phosphor structures were fabricated and compared in terms of their optical characteristics. Their spectroscopic properties were analyzed as a function of temperature, from room temperature to $80^{\circ}C$. The temperature dependence of the luminance and the color coordinates showed that the decrease in luminance and change in the color coordinates of the remote-phosphor type LED were much smaller compared to the conventional white LED. These improvements were attributed to the decrease in phosphor temperature, due to the distance between the LED chip and the phosphor layer, as well as to the reduced absorption by the LED chip of the light emitted from the phosphor layer.

Changes in Mechanical Properties and Magnetic Parameters of Neutron Irradiated Mn-Mo-Ni Low Alloy Steels (중성자에 조사된 Mn-Mo-Ni 저합금강의 기계적 및 자기적 성질 변화)

  • Jang, Gi-Ok;Ji, Se-Hwan;Park, Seung-Sik;Kim, Byeong-Cheol;Kim, Jong-O
    • Korean Journal of Materials Research
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    • v.8 no.11
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    • pp.1020-1025
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    • 1998
  • Irradiation-induced changes in mechanical properties and magnetic parameters were measured and compared to explore possible correlations for Mn-Mo-Ni low alloy steel surveillance specimens which were irradiated to a neutron fluence of $2.3\times10^{19}n/cm^2$(E>1.0MeV) in a typical pressurized water reactor environment at about $288^{\circ}C$. For mechanical property parameters, microvickers hardness, tensile and Charpy impact test were performed and Barkhausen noise amplitude, coercivity, remanence, maximum induction were measured for magnetic parameters. respectively. Results of mechanical property measurements showed an increase in yield and tensile strength, microvickers hardness. 41J indexed $RT_{NDT}$ and a decrease in upper shelf energy irrespective of base and weld metals. However, in the case of tensile properties, the changes in weld metal were negligible compared to the base metal. In the case of magnetic measurements, it is found that magnetic remanence, BN amplitude. BN energy have dropped significantly but coercivity(H,) has increased rapidly after irradiation. In this study. the measurements conducted on surveillance specimens of Mn-Mo-Ni low alloy steel showed that there were strong correlations between mechanical properties and magnetic properties.

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Combustion Characteristics of the Atomized Hydrocarbon Liquid-fuel Spray Injected through a Slit-jet Nozzle (Slit-jet 노즐을 통해 분사되는 탄화수소계 액체연료 분무의 연소특성)

  • Kim, Min Sung;Kim, Jeong Soo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.20 no.1
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    • pp.43-49
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    • 2016
  • An experimental study was performed to investigate the combustion characteristics of the liquid hydrocarbon fuel atomized by an ultrasonic oscillator. Configuration of the flame was caught by the DSLR camera, and images were analyzed in detail through a post-processing. Temperature of the flame zone was measured using thermocouple. It is resulted that the flame area is proportional to the mass flow rate of carrier gas as well as the voltage applied to the ultrasonic oscillator. Temperature of the flame zone is measured and analyzed according to variation in the operating condition of the burner, too.

Oxygen Isotope Profile and Age Determination of Venus Clam Mercenaria stimpsoni ( Bivalvia : Veneridae ) from the East Sea (동해산 뷔나스백합 ( Mercenaria stimpsoni ) 의 산소동위원소상과 연령추정)

  • Khim, Boo-Keun;Je, Jong-Geel;Han, Sang-Joon;Woo, Kyung-Sik;Park, Yong-Ahn
    • The Korean Journal of Malacology
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    • v.14 no.1
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    • pp.9-17
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    • 1998
  • 동해 연안에서 채취된 뷔나스백합(Mercenaria stimpsoni)의 연령과 성장률을 이매패의 표면에서 확인된 연륜과 이매패 각질에서 분석된 산소동위원소비의 성장에 따른 변화를 이용하여 비교하였다. 뷔나스백합의 산소동위원소상은 일련의 주기적인 변화를 뚜렷하게 보여주며 이러한 변화진폭은 이매패가 성장한 해수의 온도변화에 일차적으로 제어된다. 산소동위원소상의 주기화 연륜의 관계로부터 뷔나스백합의 연륜이 해마다 여름철에 형성됨을 보여준다. 해수 온도의 계절적 변화와 산소동위원소비에서 얻어진 예측 온도와의 비교로부터, 뷔나스백합은 겨울철에 성장이 멈추는 것으로 사료된다. 또한 산소도위원소비는 뷔나스백합의 성장에 따른 전형적인 노화현상을 보여준다. 따라서 이매패가 성장하는 해수의 물리화학적 조건에 의해 제어되는 산소동위원소비는 뷔나스백합의 경우 연령과 성장률을 측정하는 독립적인 시간 척도가 될 수 있다.

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A Study on the Thermal Response Characteristics of Snow Removing Facilities using Heat Pipe (히트파이프식 제설설비의 열응답 특성에 관한 연구)

  • Lee, Yong-Soo;Jang, Yeong-Suk
    • Solar Energy
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    • v.17 no.4
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    • pp.45-56
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    • 1997
  • The purpose of this research was to study the characteristics of heat transfer of snow removing facilities using heat pipe by experimental method. Heat pipes was constructed a flexible tube connected between evaporator and condenser ends for altitude adjustment of evaporator and it was constituted an internal diameter of 25.4mm, a length of 950mm for heating section and a length of 6000mm for condenser section with copper material for closed system. The results showed that the effect of heat transfer was increased when inclination angle and inlet temperature of heating water increased. Wall temperature response by inclined angle $4.5^{\circ}c-9^{\circ}c$ and working fluid amount 0.96 from to 1.3 times of evaporator volume were better than those of other working fluid and angle.

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A digital closed-loop processor with a stabilizer for an open-loop fiber-optic gyroscope (개회로 FOG용 폐회로 신호처리기의 안정화)

  • 김도익;예윤해
    • Korean Journal of Optics and Photonics
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    • v.13 no.5
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    • pp.377-383
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    • 2002
  • An all-digital closed-loop (ADCL) signal processor for an open-loop FOG was developed to replace the analog circuitry of a Digital Phase Tracking (DPT) signal processor with new digital circuitry. When the ADCL signal processor without a stabilizer for fiber phase modulator (FPM) was attached to the FOG, temperature drift of FOG was about 0.26$\mu$rad/$^{\circ}C$, which makes the FOG unusable in medium or higher-grade applications. This drift was due to variations of phase modulation amplitude and phase delay of the FPM. The stabilizer controls its phase modulation amplitude and phase delay by regulating the ratio of harmonics of the FOG output. Thus, the stabilizer reduces the drift of the FOG to negligible.

Variation of the Sea Surface Height around the Korean Peninsula with the Use of Multi-satellite Data (Topex/Poseidon, Jason-1, ERS, Envisat) and its Association with Sea Surface Temperature (복합위성자료(Topex/Poseidon, Jason-1, ERS, Envisat)를 이용한 한반도 주변해역에서의 해수면 고도 변화와 해수면 온도의 상관성 연구)

  • Ha, Kyung-Ja;Jeong, Gi-Yong;Jang, Sae-Rom;Kim, Ki-Young
    • Korean Journal of Remote Sensing
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    • v.22 no.6
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    • pp.519-531
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    • 2006
  • Sea surface height (SSH) around fe Korean Peninsula was investigated as a rising rate of $3.89mm\;yr^{-1}$ on the average from 1993 to 2005, which is 1.3 times higher rising rate, compared to the world ocean. In the present study, to investigate SSH changes in regional sections of the East Sea, the Yellow Sea, the South Sea, and the Korea Strait, DT-MSLA (Delayed Time-Maps of Sea Level Anomalies) with multi-satellite data (Topex/Poseidon, Jason-1, ERS, Envisat), provided by AVISO (Archiving, Validation and Interpretation of Satellite Oceanographic data), was used. The periodicity in interannual variability was dominant for $4\sim5$ year in summer, and 3 year in winter as well as an increasing trend. The amplitude and phase for the annual and semi-annual mode in SSH and SST were investigated with harmonic analysis. The geographical distribution of amplitudes for comparison of SSH and SST are slightly reverse in southwest-northeast tilted direction. The monthly SST and SSH is highly correlated correlation coefficient about 0.7 with lag of one or two months over the East Sea and the South Sea during June-August. These results suggest that the Kuroshio stream is dominant during summer over these regions.

Temporal and Spatial Variation of the Sea Surface Temperature Differences Derived from Argos Drifter Between Daytime and Nighttime in the Whole East Sea (위성추적 표류부이를 이용한 동해 표면수온의 주야간 온도차에 대한 중규모 시공간 변동)

  • 서영상;장이현;이동규
    • Korean Journal of Remote Sensing
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    • v.17 no.3
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    • pp.219-230
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    • 2001
  • The daytime and nighttime sea surface temperature (SST) differences and their seasonal variabilities in the East Sea were studied using Argos drifters data during 1996~1999. The SST differences for 1,438 data set were derived from 30 Argos drifters related to the NOAA satellite-based location and data collection system. The horizontal variation of SST differences in summer in the East Sea were higher than those in winter. The relationship between the SST differences and the half day moving distances of Argos drifters was studied. Monthly SST difference in the northern and southern part of 38$^{\circ}$N in the East Sea was considered. The SST differences derived from NOAA-14 satellite were compared with those from Argos drifter between daytime and nighttime in the turbulent eddy off Wonsan coast of Korea.

Simulation of Spatio-Temporal Distributions of Winter Soil Temperature Taking Account of Snow-melting and Soil Freezing-Thawing Processes (융설과 토양의 동결-융해 과정을 고려한 겨울철 토양온도의 시공간 분포 모의)

  • Kwon, Yonghwan;Koo, Bhon K.
    • Journal of Korea Water Resources Association
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    • v.47 no.10
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    • pp.945-958
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    • 2014
  • Soil temperature is one of the most important environmental factors that govern hydrological and biogeochemical processes related to diffuse pollution. In this study, considering the snowmelting and the soil freezing-thawing processes, a set of computer codes to estimate winter soil temperature has been developed for CAMEL (Chemicals, Agricultural Management and Erosion Losses), a distributed watershed model. The model was calibrated and validated against the field measurements for three months at 4 sites across the study catchment in a rural area of Yeoju, Korea. The degree of agreement between the simulated and the observed soil temperature is good for the soil surface ($R^2$ 0.71~0.95, RMSE $0.89{\sim}1.49^{\circ}C$). As for the subsurface soils, however, the simulation results are not as good as for the soil surface ($R^2$ 0.51~0.97, RMSE $0.51{\sim}5.08^{\circ}C$) which is considered resulting from vertically-homogeneous soil textures assumed in the model. The model well simulates the blanket effect of snowpack and the latent heat flux in the soil freezing-thawing processes. Although there is some discrepancy between the simulated and the observed soil temperature due to limitations of the model structure and the lack of data, the model reasonably well simulates the temporal and spatial distributions of the soil temperature and the snow water equivalent in accordance with the land uses and the topography of the study catchment.