• Title/Summary/Keyword: M-G set

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Estimation of the air temperature over the sea using the satellite data

  • Kwon B. H.;Hong G. M.;Kim Y. S.
    • Proceedings of the KSRS Conference
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    • 2005.10a
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    • pp.392-393
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    • 2005
  • Due to the temporal and spatial simultaneity and the high-frequency repetition, the data set retrieved from the satellite observation is considered to be the most desirable ones for the study of air-sea interaction. With rapidly developing sensor technology, satellite-retrieved data has experienced improvement in the accuracy and the number of parameters. Nevertheless, since it is still impossible to directly measure the heat fluxes between air and sea, the bulk method is an exclusive way for the evaluation of the heat fluxes at the sea surface. It was noted that the large deviation of air temperature in the winter season by the linear regression despite good correlation coefficients. We propose a new algorithm based on the Fourier series with which the SST and the air temperature. We found that the mean of air temperature is a function of the mean of SST with the monthly gradient of SST inferred from the latitudinal variation of SST and the spectral energy of air temperature is related linearly to that of SST. An algorithm to obtain the air temperature over the sea was completed with a proper analysis on the relation between of air temperature and of SST. This algorithm was examined by buoy data and therefore the air temperature over the sea can be retrieved based on just satellite data.

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Dendrite Arm Spacing and Carbide Morphology with Thermal Gradient and Solidification Rate in Directionally Solidified Ni-Base Superalloy (일방향 초내열합금에서 응고속도 및 온도구배 따른 수지상간격 및 탄화물 형상 변화)

  • Son, S.D.;Kim, Y.H.;Choi, G.S.;Lee, J.H.;Seo, S.M.;Jo, C.Y.
    • Journal of Korea Foundry Society
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    • v.27 no.2
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    • pp.77-82
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    • 2007
  • The effects of thermal gradient and solidification rate on the dendrite arm spacing and carbide morphology were investigated in directionally solidified Ni-base superalloy, CM 247LC. Thermal gradient was controlled by changing the position of the cold chamber and the furnace set temperature. The interface morphology changed from the planar to dendritic as increasing solidification rate. It was found that the dendrite spacing decreased as increasing the thermal gradient as well as the solidification rate. Also, as increasing solidification rate, carbide morphology changed from blocky shape to script and spotty shapes.

Performance of Air-Water Direct Contact Heat Exchanger Linked to Heat Pump (히트펌프에 연계된 공기-물 직접접촉식 열교환기의 성능)

  • Kim, Y.H.;Keum, D.H.;Ryou, Y.S.;Kang, Y.K.;Kim, J.G.;Jang, J.K.;Lee, H.M.
    • 한국신재생에너지학회:학술대회논문집
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    • 2011.05a
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    • pp.80.2-80.2
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    • 2011
  • Fossil fuel was a major energy resource but the consumption of fossil fuel will decrease gradually because of limited deposits and non-environmental features. In contrast, because the renewable energy resources are infinite and sustainable, their consumption has increased annually. To promote the supply of these infinite natural energy we have to develop more efficient and inexpensive heat recovery system. In this study a simple device was designed as a heat exchanger, that is a direct contact heat exchanger. This heat exchanger was manufactured in cylindrical shape with height of 1,500 mm and diameter of 1,000 mm. To test the efficiency of this heat exchanger, it was connected to the evaporator of heat pump system. During the experimental tests, the humid air of $10{\sim}30^{\circ}C$ was supplied to this air-to-water heat exchanger and then the water flow rate was set to 2500~3500 L/h. Heat recovery rate of this heat exchanger increased in proportion to entering air temperature and water flow rate.

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A Study on Electromagnetic Retarder's Power Recovery System and Regenerating Voltage Control (전자기형 리타더의 전력회수장치 및 회생전압제어에 대한 연구)

  • Jung, Sung-Chul;Ko, Jong-Sun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.66 no.8
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    • pp.1207-1214
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    • 2017
  • In the case of frequent braking, when driving downhill or long distance, conventional brakes using friction are problematic in braking safety due to brake rupture and fading phenomenon. Therefore auxiliary brakes is essential for heavy vehicles. And several research has been actively conducted to improve energy efficiency by regenerating mechanical energy into electric energy when the vehicles brake. In this paper, a voltage control method is utilized to recover the electric energy generated in the electromagnetic retarder instead of the eddy current. To regenerate the braking energy into the electrical energy, a resonant L-C circuit is configured in the retarder. The retarder can be modeled as self-excited induction generator due to its operating principle. The driving conditions according to the retarder's parameters are made into 3-D maps. Also, the voltage of the resonant circuit changing depending on the driving pulse applied to the FET was analyzed. For the control of this voltage, we proposed an algorithm using the PI controller. The controlled voltage is converted by a 3-phase AC/DC converter and then charged to a battery inside the heavy vehicles through a DC/DC converter. Electromagnetic retarder and its controller are validated using Matlab Simulink. We also demonstrate the voltage controller through the actual M-G set experiment.

The effects of uncertainties in structural analysis

  • Pellissetti, M.F.;SchueIler, G.I.
    • Structural Engineering and Mechanics
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    • v.25 no.3
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    • pp.311-330
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    • 2007
  • Model-based predictions of structural behavior are negatively affected by uncertainties of various type and in various stages of the structural analysis. The present paper focusses on dynamic analysis and addresses the effects of uncertainties concerning material and geometric parameters, mainly in the context of modal analysis of large-scale structures. Given the large number of uncertain parameters arising in this case, highly scalable simulation-based methods are adopted, which can deal with possibly thousands of uncertain parameters. In order to solve the reliability problem, i.e., the estimation of very small exceedance probabilities, an advanced simulation method called Line Sampling is used. In combination with an efficient algorithm for the estimation of the most important uncertain parameters, the method provides good estimates of the failure probability and enables one to quantify the error in the estimate. Another aspect here considered is the uncertainty quantification for closely-spaced eigenfrequencies. The solution here adopted represents each eigenfrequency as a weighted superposition of the full set of eigenfrequencies. In a case study performed with the FE model of a satellite it is shown that the effects of uncertain parameters can be very different in magnitude, depending on the considered response quantity. In particular, the uncertainty in the quantities of interest (eigenfrequencies) turns out to be mainly caused by very few of the uncertain parameters, which results in sharp estimates of the failure probabilities at low computational cost.

Experimental Study on Turbulent Ethylene Diffusion Flame (에틸렌 난류확산 화염에 관한 실험적 연구)

  • Yang, G.S.;Kim, Y.M.
    • Journal of the Korean Society of Combustion
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    • v.4 no.2
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    • pp.23-33
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    • 1999
  • A turbulent non-premixed ethylene flame, which was set up in a vertical wind tunnel, was examined to understand the effect of turbulent mixing on formations of soot and gaseous species in the flames. Temperature and velocity profiles were measured using uncoated thermocouples and LDV system. Gaseous samples were withdrawn by using a water cooled stainless iso-kinetic gas sampling probe. The samples for inorganic compounds and light hydrocarbons were collected with sampling bottles and were analyzed by a gas chromatography. The samples for aromatic hydrocarbons were collected on a sorbent tube and were analyzed on a GC/MS system. Some of main results were followed. CO and $CO_2$ were measured relatively in early part of flame and the concentration of CO was greater than that of $CO_2$ all over the early flame region due to the scavenging of the oxidizing species OH by soot particles. Aromatic hydrocarbons were measured at x/D=122 along the radial direction and main important species were benzene, xylene, toluene, styrene, indene, naphthalene. The peak points of these compounds occurred at r/D=0.8 apart from the center of flame, around in which the concentration of $C_2H_2$ decayed relatively rapidly from the maximum value.

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Taming of large diameter triaxial setup

  • Nair, Asha M.;Madhavi Latha, G.
    • Geomechanics and Engineering
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    • v.4 no.4
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    • pp.251-262
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    • 2012
  • Triaxial tests are essential to estimate the shear strength properties of the soil or rock. Normally triaxial tests are carried out on samples of 38 mm diameter and 76 mm height. Granular materials, predominantly used in base/sub-base construction of pavements or in railways have size range of 60-75 mm. Determination of shear strength parameters of those materials can be made possible only through triaxial tests on large diameter samples. This paper describes a large diameter cyclic triaxial testing facility set up in the Geotechnical Engineering lab of Indian Institute of Science. This setup consists of 100 kN capacity dynamic loading frame, which facilitates testing of samples of up to 300 mm diameter and 600 mm height. The loading ram can be actuated up to a maximum frequency of 10 Hz, with maximum amplitude of 100 mm. The setup is capable of carrying out static as well as dynamic triaxial tests under isotropic, anisotropic conditions with a maximum confining pressure of 1 MPa. Working with this setup is a difficult task because of the size of the sample. In this paper, a detailed discussion on the various problems encountered during the initial testing using the equipment, the ideas and solutions adopted to solve them are presented. Pilot experiments on granular sub-base material of 53 mm down size are also presented.

A Study on the Volatilization of Particulate Nitrate (NO3-) During Fine Particle (PM2.5) Measurement (미세입자(PM2.5) 측정시 발생되는 질산염(NO3-) 휘발에 관한 연구)

  • 강병욱;이학성
    • Journal of Korean Society for Atmospheric Environment
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    • v.18 no.4
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    • pp.297-303
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    • 2002
  • Fine particles (d$_{p}$ < 2.5 $\mu$m) were measured using an annular denuder system (ADS) in Chongju. The data set was collected on fifty-eight different days with a 24-hr sampling period from October 27, 1995 through August 25, 1996. Particulate nitrate in the ADS was also measured on teflon and nylon filters in series behind denuders to collect HNO$_3$, HNO$_2$, SO$_2$and NH$_3$. From this study. the mean concentration of particulate nitrate of PM$_{2.5}$ in the ADS were seen with the following order: winter (5.05) >fall (4.36) >spring (3.92) > summer (1.10 $\mu\textrm{g}$/㎥). Nitrate losses, which calculated from the ratio of nylon filter nitrate to the sum of teflon and nylon filter nitrates, varied in the following manner summer (72.2%) > spring (42.6%) > fall (23.5%)> winter (0.4%). Especially, gaseous nitric acid was dominant at temperature higher than 8$^{\circ}C$ while particulate nitrate was major species in total nitrate below that temperature. This indicates the particulate nitrate loss is strongly correlated rather with ambient temperature.e.e.

Test method for Motor/controller for Electric Vehicle (전기자동차용 전동기/제어기의 시험 방법)

  • 오성철
    • The Transactions of the Korean Institute of Power Electronics
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    • v.8 no.4
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    • pp.328-335
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    • 2003
  • Test procedure for Electric Vehicle(EV) motor/controller has been developed. Most of existing standards mainly focus on minimum requirements for safe operation. However, detailed test procedures are not covered in the standard. In order to develop test items, methods and procedures which should be strictly applied to EV motor and controller, existing standards have been reviewed by the expert group in Korea. Based on their feedback, standard test procedure was proposed. Test procedure especially for combined motor and controller has been proposed. As a load lot the tested motor, M-G set, eddy current type engine dynamo and AC dynamo were used. Test procedures for the driving cycle test and regeneration test were proposed.

Measurement of Particle Deposition Velocity toward a Horizontal Semiconductor Wafer Using a Wafer Surface Scanner (Wafer Surface Scanner를 이용한 반도체 웨이퍼상의 입자 침착속도의 측정)

  • Bae, G.N.;Park, S.O.;Lee, C.S.;Myong, H.K.;Shin, H.T.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.5 no.2
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    • pp.130-140
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    • 1993
  • Average particle deposition velocity toward a horizontal semiconductor wafer in vertical airflow is measured by a wafer surface scanner(PMS SAS-3600). Use of wafer surface scanner requires very short exposure time normally ranging from 10 to 30 minutes, and hence makes repetition of experiment much easier. Polystyrene latex (PSL) spheres of diameter between 0.2 and $1.0{\mu}m$ are used. The present range of particle sizes is very important in controlling particle deposition on a wafer surface in industrial applications. For the present experiment, convection, diffusion, and sedimentation comprise important agents for deposition mechanisms. To investigate confidence interval of experimental data, mean and standard deviation of average deposition velocities are obtained from more than ten data set for each PSL sphere size. It is found that the distribution of mean of average deposition velocities from the measurement agrees well with the predictions of Liu and Ahn(1987) and Emi et al.(1989).

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