• Title/Summary/Keyword: temperature estimation

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Thermal Analysis Comparison of IMO with USCG Design Condition for the INGC During the Cool-down Period (급냉각기간에서 IMO설계조건과 USCG 설계조건에 대한 LMGC 화물탱크의 열해석 비교)

  • Lee, Jung-Hye
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.11
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    • pp.1390-1397
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    • 2004
  • This study is concerned with the thermal analysis during the cool-down period of 135,000㎥ class GT-96 membrane type LNG carrier under IMO and USCG design condition. During the cool-down period, the spraying rate for the NG cooling decreases as the temperature of NG falls down from -4$0^{\circ}C$ to -l3$0^{\circ}C$, and the spraying rate for the cooling of the insulation wall increases as the temperature gradient of the insulation wall is large. It was confirmed that there existed the largest temperature decrease at the first barrier and the first insulation, which are among the insulation wall, especially in the top side of the insulation wall under IMO and USCG design condition. Also, as the NG temperature distribution is fixed, the outer temperature condition under the design condition has influence on the temperature variation at the insulation. By the 3-D numerical calculation about the cargo tank and the cofferdam during the cool-down period, the temperature variation in hulls and insulations is precisely predicted under IMO and USCG design condition. From the comparison between two conditions; IMO design condition shows more severe temperature gradient than USCG design condition, therefore, it provides the conservative estimation of the BOG.

Error Compensation due to Environmental Temperature for Diaphragm-Type Pressure Sensor (다이어프램형 압력센서에서 주변 온도에 의한 오차 보상)

  • Yun, Dae Jhonng;Ahn, Jung Hwan;Lee, Gil Seung;Kim, Hwa Young
    • Journal of Sensor Science and Technology
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    • v.28 no.3
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    • pp.177-181
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    • 2019
  • Pressure sensors are used in various industries such as automobiles, airplanes, medical equipment, and coolers. Even if the ambient temperature changes, the measurement is reliable and stable. In this study a diaphragm-type pressure sensor was used to derive a temperature-compensated pressure estimation equation for accurate pressure measurement at $100^{\circ}C$ and $-40^{\circ}C$. To understand the characteristics of the pressure sensor diaphragm with respect to temperature and pressure, experiments were conducted in temperature-variable chamber using FEM analysis to confirm that the influence of temperature effect was nonlinear. Based on the experimental results, a nonlinear method for calculating the pressure by compensating for the error due to temperature was derived. The calculated pressure value is lower than 0.5 % at low and high temperatures, and lower than 0.4 % at $22^{\circ}C$, thereby eliminating the effect of temperature.

Estimation of Duration of Low-temperature in Winter Season Using Minimum Air Temperature on January (1월 최저기온을 이용한 겨울철 저온발생일수 추정)

  • Moon, Kyung-Hwan;Son, In-Chang;Seo, Hyeong-Ho;Choi, Kyung-San;Joa, Jae-Ho
    • Korean Journal of Agricultural and Forest Meteorology
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    • v.14 no.3
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    • pp.119-123
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    • 2012
  • The duration of low temperature in winter season is one of the important agrometeorological characteristics in crop growing fields. This study was conducted to develop a method to estimate the duration of low-temperature with monthly meteorological data. Using daily meteorological data from 61 observation sites from 1981 to 2010, we analyzed the relationships between the averages of monthly temperature minima and the durations of low-temperature ranging from -15 to $5^{\circ}C$, The monthly mean of the January minimum air temperature was appropriate for theestimation of the durations of lowtemperature below $0^{\circ}C$. We tested a simple second order equation to predict durations of low-temperature. To apply the equation to various temperature ranges, we suggested two different equations for the estimation of coefficients a and b, which are dependent on the base temperatures from -15 to $0^{\circ}C$. Thevalidation of the equations using other daily meteorological datasets from 1971 to 2000 showed that they were appropriate for the range from -10 to $0^{\circ}C$, but underestimated at $-15^{\circ}C$.

Creep Property Assessment and Creep Life Estimation for High-Temperature Tube Material(2.25Cr1Mo Steel) in Power Plants by LMP (발전용 고온 배관재료 2.25Cr1Mo 강의 크리프 특성과 LMP에 의한 크리프 수명의 예측)

  • Lee, Sang-Guk;Jeong, Min-Hwa;O, Se-Gyu;Song, Jeong-Geun
    • Journal of Ocean Engineering and Technology
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    • v.12 no.2 s.28
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    • pp.65-70
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    • 1998
  • In this report, the creep properties and creep life estimation by Larson-Miller Parameter(LMP) Method for 2.25Cr1Mo steel to be used as power plant tubes or other components were presented at the high temperatures of 500, 550, and $600^{\circ}C$. It was confirmed experimentally and quantitatively that a creep life estimation equation at such various high temperatures was well derived by LMP and could be used very effectively within the creep life of 10$^3$ hours, but very unreliable and even dangerous for design in a long term of creep life such as 10$^4$ or $10^5$ hours.

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Adaptive Suppression of Mechanical Resonance in High-Density Disk Drives (고밀도 디스크 드라이브의 적응형 공진 보상 알고리즘)

  • 강창익;김창환
    • Journal of Institute of Control, Robotics and Systems
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    • v.9 no.9
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    • pp.679-691
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    • 2003
  • The band-width of disk drive servo system is rapidly increasing for the robustness to external disturbance as the track density is increasing. The increase of the band-width may cause mechanical resonance of an actuator. In disk drive servo system, a notch filter is usually used to suppress the mechanical resonance of the actuator. However, the resonance frequency differs from drive to drive because of manufacturing tolerance and varies with temperature even within a single drive. The variation of resonance frequency degrades the suppression performance of the notch filter. In this paper, we present an adaptive digital notch filter that identifies the resonance frequency of the disk drive servo actutaor precisely and adjusts automatically its center frequency. For this, we design an adaptive FIR digital filter for the estimation of the resonance frequency. The estimation filter identifies the resonance frequency adaptively using the output signal generated from the servo system, which is excited with an excitation signal including all the expected resonance frequency components. We prove mathematically the convergence of the resonance frequency estimation filter. Furthermore, in order to demonstrate the practical use of our work, we present some experimental results using a commercially available disk drive.

Study on Statistical Analysis of Measured Fluid Leakage Data and Estimation of the Leakage Rate for Power Plant Valve (발전용 밸브 유체누설 측정 데이터의 통계적 평가 및 누설량 예측 연구)

  • Lee, S.G.;Kim, D.W.;Kim, Y.S.;Park, J.H;Jeong, H.
    • Journal of Power System Engineering
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    • v.13 no.5
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    • pp.59-66
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    • 2009
  • High temperature and pressure valves in power plant have been used for fluid flowing and leakage occurred owing to valve internal damage such as disc wear, crack and inserting of foreign objects etc. in these valves. Recently, multi-measuring technique applied both ultrasonic and acoustic method have been used for evaluation of valve internal leakage in order to raise measurement reliability. Therefore, we have performed various leakage tests using ultrasonic and acoustic measuring system and acquired leakage data for the various leakage conditions. In this study, we developed the estimation method of regression model through leakage data, and expectation method for valve opening ratio, which is directly proportion to leakage rate, using the established estimation model from the measured data, valve size and fluid pressure so as to enhance data reliability. As a result of this study, it was founded that expectation method of leakage rate by statistical analysis method is appropriate to valve leakage evaluation.

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Improved Mutual MRAS Speed Identification Based on Back-EMF

  • Zheng, Hong;Zhao, Jiancheng;Liu, Liangzhong
    • Journal of Electrical Engineering and Technology
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    • v.11 no.3
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    • pp.769-774
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    • 2016
  • In the design of sensorless control system for induction motor, high-precision speed estimation is one of the most difficult problems. To solve this problem, the common method is model reference adaptive method (MRAS). MRAS requires accurate motor parameters to estimate rotor speed precisely. However, when motor is running, the variety of temperature and magnetic saturation will lead to the change of motor parameters such as stator resistance and rotor resistance, which will lower the accuracy of the speed estimation. To improve the accuracy and rapidity of speed estimation, this paper analyses the mutual MRAS speed identification based on rotor flux linkage, and proposes an improved mutual MRAS speed identification based on back-EMF. The improved method is verified by Simulink simulation and motor experimental platform based on DSP2812. The results of simulation and experiment indicate that the method proposed by this paper can significantly improve the accuracy of speed identification, and speed up the response of identification.

Estimation of Temporal Surface Air Temperature under Nocturnal Inversion Conditions (야간 역전조건 하의 지표기온 경시변화 추정)

  • Kim, Soo-ock
    • Korean Journal of Agricultural and Forest Meteorology
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    • v.19 no.3
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    • pp.75-85
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    • 2017
  • A method to estimate hourly temperature profiles on calm and clear nights was developed based on temporal changes of inversion height and strength. A meteorological temperature profiler (Model MTP5H, Kipp and Zonen) was installed on the rooftop of the Highland Agriculture Research Institute, located in Daegwallyeong-myeon, Pyeongchang-gun, Gangwon-do. The hourly vertical distribution of air temperature was measured up to 600 m at intervals of 50 m from May 2007 to March 2008. Temperature and relative humidity data loggers (HOBO U23 Pro v2, Onset Computer Corporation, USA) were installed in the Jungdae-ri Valley, located between Gurye-gun, Jeollanam-do and Gwangyang-si, Jeollanam-do. These loggers were used to archive measurements of weather data 1.5 m above the surface from October 3, 2014, to November 23, 2015. The inversion strength was determined using the difference between the temperature at the inversion height, which is the highest temperature in the profile, and the temperature at 100 m from the surface. Empirical equations for the changes of inversion height and strength were derived to express the development of temperature inversion on calm and clear nights. To estimate air temperature near the ground on a slope exposed to crops, the equation's parameters were modified using temperature distribution of the mountain slope obtained from the data loggers. Estimated hourly temperatures using the method were compared with observed temperatures at 19 weather sites located within three watersheds in the southern Jiri-mountain in 2015. The mean error (ME) and root mean square error (RMSE) of the hourly temperatures were $-0.69^{\circ}C$ and $1.61^{\circ}C$, respectively. Hourly temperatures were often underestimated from 2000 to 0100 LST the next day. When temperatures were estimated at 0600 LST using the existing model, ME and RMSE were $-0.86^{\circ}C$ and $1.72^{\circ}C$, respectively. The method proposed in this study resulted in a smaller error, e.g., ME of $-0.12^{\circ}C$ and RMSE of $1.34^{\circ}C$. The method could be improved further taking into account various weather conditions, which could reduce the estimation error.

The Estimation of Urbanization Effect in Global Warming over Korea using Daily Maximum and Minimum Temperatures (최고, 최저기온을 이용한 우리나라 기온변화에서의 도시화효과 분석)

  • Koo, Gyo-Sook;Boo, Kyung-On;Kwon, Won-Tae
    • Atmosphere
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    • v.17 no.2
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    • pp.185-193
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    • 2007
  • This study investigates urbanization effect in warming trend of surface air temperature over Korea. The data used in this study consist of the daily minimum and maximum temperatures during the period of 32 years(1968-1999) from 16 stations of KMA. To calculate magnitude and trend of urbanization effect, stations were classified into urban and rural stations using population statistics. Urban stations were defined as those with population densities greater than 1000 persons per kilometer squared in 1995. The others were defined as rural stations. The urban stations were also subdivided into two groups according to their population totals. For estimates of urban effect magnitude, temperature change was calculated by comparing 16-year mean values between 1968-83 and 1984-99. Then, the difference between each urban station and every rural station was calculated. During the analysis period of 32 years, maximum temperature increase is $1.22^{\circ}C$. In the total temperature increase, urban effect is estimated by 28.7%. For minimum temperature, it becomes larger by about 10% than that in maximum temperature. Therefore, urban effect in an increasing trend of minimum temperature is 38.9% in the change of $1.13^{\circ}C$.

Estimation of Electrical Parameters of OD Organic Semiconductor Diode from Measured I-V Characteristics

  • Moiz, Syed Abdul;Ahmed, Mansoor M.;Karimov, Kh. S.
    • ETRI Journal
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    • v.27 no.3
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    • pp.319-325
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    • 2005
  • In this paper the effect of temperature on the electrical properties of organic semiconductor disperse orange dye 25 (OD) have been examined. Thin films of OD have been deposited on $In_{2}O_{3}$ substrates using a centrifugal machine. DC current-voltage (I-V) characteristics of the fabricated devices $(Al/OD/In_{2}O_{3)$ have been evaluated at varying temperatures ranging from 40 to $60^{\circ}C$. A rectification behavior in these devices has been observed such that the rectifying ratio increases as a function of temperature. I-V characteristics observed in $Al/OD/In_{2}O_{3)$ devices have been classified as low temperature $({\leq} 50^{\circ}C)$ and high temperature characteristics (approximately $60^{\circ}C$). Low temperature characteristics have been explained on the basis of the charge transport mechanism associated with free carriers available in OD, whereas high temperature characteristics have been explained on the basis of the trapped space-charge-limited current. Different electrical parameters such as traps factor, free carrier density, trapped carrier density, trap density of states, and effective mobility have been determined from the observed temperature dependent I-V characteristics. It has been shown that the traps factor, effective mobility, and free carrier density increase with increasing values of temperature, whilst no significant change has been observed in the trap density of states.

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