• Smart Structures and Systems
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• 제25권1호
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• pp.23-35
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• 2020

It is important to take into account the thermal behavior in assessing the structural condition of bridges. An effective method of studying the temperature effect of long-span bridges is numerical simulation based on the solar radiation models. This study aims to develop a time-varying solar radiation model which can consider the real-time weather changes, such as a cloud cover. A statistical analysis of the long-term monitoring data is first performed, especially on the temperature data between the south and north anchors of the bridge, to confirm that temperature difference can be used to describe real-time weather changes. Second, a defect in the traditional solar radiation model is detected in the temperature field simulation, whereby the value of the turbidity coefficient t_u is subjective and cannot be used to describe the weather changes in real-time. Therefore, a new solar radiation model with modified turbidity coefficient γ is first established on the temperature difference between the south and north anchors. Third, the temperature data of several days are selected for model validation, with the results showing that the simulated temperature distribution is in good agreement with the measured temperature, while the calculated results by the traditional model had minor errors because the turbidity coefficient t_u is uncertainty. In addition, the vertical and transverse temperature gradient of a typical cross-section and the temperature distribution of the tower are also studied.

• 산업경영시스템학회지
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• 제37권2호
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• pp.27-34
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• 2014

In this paper, we investigate the statistical correlation of the time series for temperature measured at the heat box in the automobile drying process. We show, in terms of the sample variance, that a significant non-linear correlation exists in the time series that consist of absolute temperature changes. To investigate further the non-linear correlation, we utilize the volatility, an important concept in the financial market, and induce volatility time series from absolute temperature changes. We analyze the time series of volatilities in terms of the de-trended fluctuation analysis (DFA), a method especially suitable for testing the long-range correlation of non-stationary data, from the correlation perspective. We uncover that the volatility exhibits a long-range correlation regardless of the window size. We also analyze the cross correlation between two (inlet and outlet) volatility time series to characterize any correlation between the two, and disclose the dependence of the correlation strength on the time lag. These results can contribute as important factors to the modeling of forecasting and management of the heat box's temperature.

• 한국연소학회지
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• 제18권4호
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• pp.12-20
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• 2013

The ignition delay time is an important factor to understand the combustion characteristics of internal combustion engine. In this study, ignition delay times of cool and thermal flame were observed separately in homogeneous charge compression ignition(HCCI) engine. This study presents numerical investigation of ignition delay time of n-heptane and alcohol(ethanol and n-butanol) binary fuel. The $O_2$ concentration in the mixture was set 9-10% to simulate high exhaust gas recirculation(EGR) rate condition. The numerical study on the ignition delay time was performed using CHEMKIN codes with various blending ratios and EGR rates. The results revealed that the ignition delay time increased with increasing the alcohol fraction in the mixture due to a decrease of oxidation of n-heptane at the low temperature. From the numerical analysis, ethanol needed more radical and higher temperature than n-butanol for oxidation. In addition, thermal ignition delay time is sharply increasing with decreasing $O_2$ fraction, but cool flame ignition delay time changes negligibly for both binary fuels. Also, in high temperature regime, the ignition delay time showed similar tendency with both blends regardless of blending ratio and EGR rate.

• 한국정밀공학회지
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• 제22권7호
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• pp.155-163
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• 2005

Pressure heating rollers with temperature control were mounted to a flat cable laminating machine (FCLM). Pressure heating rollers should be heated up to the setting temperature $(175^{\circ}C)$ and kept on to producing good quality flexible flat cables (FFC). Existing Pressure heating rollers took more than 70minutes to the setting temperature and did not keep on the setting temperature in production. Temperature controller, electric power controller, material and diameter of rollers and heat capacities were changed to improve the temperature control of the pressure heat rollers for better production of the FFC. Thus, the reaching time to the setting temperature (RT), temperature stability time (TST) and temperature hunting (TH) were measured and compared with the existing pressure rollers case. The RT of A roller was shortened by 50minutes, and B roller was shortened by 15minutes. The TST of A roller was shortened by 13minutes, and B roller was shortened by 15minutes. The THs of both A and B rollers were settled up to ${\pm}5^{\circ}C$. Finally, the productivity of the FCLM and the quality of the FFC were increased.

• Journal of the Korean Wood Science and Technology
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• 제39권4호
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• pp.303-310
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• 2011

본 연구에서는 압체온도와 시간에 따른 열압밀화 라디에타 소나무재의 역학적 특성을 조사하였다. 종압축강도와 휨강도는 압체온도와 시간의 증가와 함께 증가하였다. 그러나 압체온도 $220^{\circ}C$에서는 열화로 인해 오히려 감소된 값을 나타내었다. 표면경도는 압체온도의 증가와 함께 증가하였으며, 압체시간이 표면경도에 미치는 영향은 미약하였다. 못뽑기저항의 경우 접선단면의 저항력이 가장 높았으며, 압체온도와 시간에 의한 영향은 거의 나타나지 않았다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 학술대회지
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• pp.872-875
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• 2004

In this paper, thermal response analysis of a temperature controlled three-axis accelerometer for high temperature environments with integrated micro-heaters and temperature sensors is investigated with finite element method (FEM) program, ANSYS and infrared thermal measurement systems. And availability to application fields from a viewpoint about short thermal response time is discussed. In this paper, the time of three-axis accelerometer for high temperatures becoming $300^{\circ}C$ by integrated micro-heaters and temperature sensors to reduce thermal drift characteristics was analyzed as a thermal response time of this device. The simulated thermal response time (time until SOI piezoresistors actually becomes $300^{\circ}C$) of three-axis accelerometer for high temperatures with ANSYS is about 0.6s, and measured result with infrared temperature measurement systems is about 0.64s. Experimental results using infrared thermal measurement systems agreed well with these theoretical results.

• 대한가정학회지
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• 제29권1호
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• pp.13-25
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• 1991

We measured change of peripheral skin temperature and mean skin temperature when the upper arm and thigh are pressured in order to know the effect of skin pressure applied by clothing on blood circulation. After release from pressure, we observed also recovery condition. At the same time, we examined relation between pressure and a feeling of thightness. Three physiques of healthy females, namely slender, standard and plump, served as subjects. We used continuous restraint method with skin pressure applied by experimental fabric for 10 min. As a result of this experiment, we obtained following findings. 1. The significant difference was marked at the pressure, measuring time and physique with change of skin temperature under upper arm restraint. The peripheral and mean skin temperature decreased with the lapse of restraint time. A remarkable tendency observed according to the increase of restraint pressure. Recovery condition after release from pressure not yet recovered to original state, for all after a lapse of 10 min. 2. The significant difference was marked at the pressure, measuring time and physique with change of skin temperature under thigh restraint, especially different physique was remarkable among them. The peripheral skin temperature decreased or decreased. Recovery condition after release from pressure was the same upper arm. 3. Main factor affecting the evaluation of a feeling of tightness was restraint pressure. The value of pressure sensation made remarkable declined after a lapse of 10 min restraint time. Individual differences, however, were shown in pressure sensation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 추계학술대회 논문집
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• pp.356-359
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• 1997

The Effects of different melting temperature and holding time in the melting temperature on J$\sub$c/ of YBa$_2$Cu$_3$O$\sub$x/ based superconducting bulk using MPMG process were investigated. the value of critical current density was the largest at l120$^{\circ}C$, the melting temperature which is appointed to the mid point of (Y$_2$BaCuO$\sub$5/ + Liquid)region. With the melting temperature in which the value of J$\sub$c/ is the largest, J$\sub$c/ was again measured to see whether the holding time at this proper melting temperature has the effect on the critical characteristics. From the result above it was concluded that the melting temperature and holding time were important to improve the J$\sub$c/ and the formation of the Y$_2$BaCuO$\sub$5/. In this paper, the melting temperature obtained was l120$^{\circ}C$ and propel holding time could be obtained as 20 minute and the more holding time was not effective in the J$\sub$c/ improvement as well as the formation of Y$_2$BaCuO$\sub$5/.

• 한국방사선학회논문지
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• 제6권3호
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• pp.201-206
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• 2012

진단적 초음파가 태아에 미치는 영향에 대하여는 대부분의 연구결과, 심각한 영향을 미칠 가능성이 매우 낮다고 보고되고 있으나, 장시간의 과도한 조사는 초음파가 인체조직에 온도 상승이나 물리적인 영향을 줄 수 있어 초음파 검사시간에 따라 허벅지의 온도 변화를 조사하여 태아 초음파 검사 시 영향이 없는 시간을 알아보았다. 그 결과 초음파 검사 전보다 40분 안에는 온도가 떨어졌고 50분에는 허벅지의 온도가 검사 전보다 $1^{\circ}C$이상 올라가는 것을 확인하였다. 그러므로 40분 안에 초음파 검사를 한다면 안전한 것으로 추론해 본다.

• 대한기계학회논문집A
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• 제30권8호
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• pp.976-984
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• 2006

Time-temperature superposition has been studied to determine the long-term fatigue life over millions of cycles for glassy polymers. π le superposition is supposed to make an accelerated lifetime testing (ALT) technique possible. Dog-bone shaped specimens made of carbon filled Polycarbonate (PC) were tested under fatigue, based on the stress-lifetime approach (S-N curve). Fatigue-induced localized yield-like deformation is considered as the defect leading to fatigue and its evolution behavior is characterized by a modified energy activation model in which temperature is considered as fatigue acceleration factor. This model allows the reduced time concept to account for effects of different temperature in short-term fatigue data to determine long-term fatigue life through the use of time-temperature superposition that is applicable under a low frequency and isothermal conditions. The experimental results validated that the proposed technique could be a possible method for accelerated lifetime testing (ALT) of time-dependent polymeric materials.