• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.9
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• pp.434-440
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• 2014

Experiments were performed to verify if performance and characteristic curves obtained from the temperature differential defrosting method, where surface temperature is measured to judge defrosting condition, can be reproduced by the photoelectric technology where defrosting condition is judged by photoelectric sensors. The output voltage of a phototransistor and heating capacity, power consumption, and surface temperature of the outdoor heat exchanger are compared. The results showed that the photoelectric sensors can be used as a defrost control device. On-off control timings in temperature differential defrosting method are in good agreement with those predicted by the high and low threshold output voltages of the photoelectric sensor.

• Journal of the Korean Solar Energy Society
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• v.25 no.2
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• pp.1-8
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• 2005

On-off differential controller is one of the very important components which affect the system performance of the active solar thermal system. In this study, analyses were made regarding the influence of "on-off" setting temperature on the system efficiency and on the electrical consumption by circulation pump. This study was performed by experiment as well as the computer simulation using TRNSYS program. The simulation system was developed in this study was verified the its reliability by the experimental results. As a results, the turn off temperature(${\Delta}T_{off}$) is much more influence than the turn on temperature(${\Delta}T_{on}$) on the system efficiency. It is more clear and sensitivity in winter season. Finally the optimum on-off setting value and the system on-off pattern according to the several different kind of system was also represented.

• Fire Science and Engineering
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• v.28 no.1
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• pp.26-30
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• 2014

A Compensation-type fire detector (CFD) is operated with two functions of a differential-temperature detector and as a fixed-temperature detector. The differential-temperature detector observes a rate of temperature increase, and the fixed-temperature detector measures a given fixed temperature. The differential-temperature detector does not observe the outbreak of fire in slowly increasing temperature conditions, whereas the fixed-temperature detector is not able to observe the outbreak of fire in conditions under predetermined temperature level. We developed a CFD to compensate for weaknesses of both detectors. To compensate for the disadvantages, a sensor of the sensor metal-insulator-transition critical-temperature sensor was used. Temperature coefficient of resistance is the sensitivity for sensor. At $55^{\circ}C$, temperature coefficient of resistance of metal-insulator-transition critical-temperature sensor was 14.15%. Temperature coefficient of resistance of thermistor was about 0.5%. This CFD was operated as two ways that fixed-temperature detector and differential-temperature detector in one sensor.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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• pp.89-94
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• 2008

Differential pressure flow meters which have a shape of triangular separate bar(TSB) were tested for investigating the flow rate characteristics of the flow meters with varying the temperature of the gas flow. Three kinds of the triangular separate bar flow meters whose aerodynamic angles are different one another are used. The mass flow rate of the flow meters are evaluated using a non-dimensional parameter which includes the gas temperature, exhaust gas pressure and differential pressure at the flow meters, and atmospheric pressure. A burner system which is similar to gas turbine was used for raising the gas flow temperature. The burner system was operated with varying the air/fuel ratio by controlling both the fuel injection rate from the fuel nozzle and air flow rate from a blower. An empirical correlation between the mass flow rate at the TSB flow meter and the non-dimensional parameter was obtained. The empirical correlation showed linear relationship between the mass flow rate and the non-dimensional parameter H. Also, the mass flow rate characteristics at the TSB flow meter was affected by the gas temperature.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.7
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• pp.1687-1692
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• 2010

In this paper, we research the method for write quality improvement by temperature characteristic of Laser diode for optical recording. Differential Resistance of Blu-ray laser diode is changed by temperature. We analyze the effect of the change of the differential resistance in low temperature and propose the method for the write quality improvement.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.321-326
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• 2004

The pressure and differential pressure(DP) transmitters are used for gas flow rate calculation on the orifice gas metering system. On site, the pressure and DP transmitters are installed in a shelter to diminish the affects of environmental change such as an ambient temperature. But there has been an argument about the effectiveness of the shelter and this brought up the necessity to verify the affects of ambient temperature. These experiments were performed to verify the ambient temperature effects as observing the output of transmitters when the ambient temperature were changed from $-30^{\circ}C$ to $50^{\circ}C$. The results showed that the most of transmitters were operated in the spec range of performance criteria presented by manufacturer but the rapid change of ambient temperature could cause the larger measurement error for the DP transmitter of low span than others. Therefore the pressure and DP transmitters need to be operated and controlled within the proper range of ambient temperature.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.860-865
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• 2006

The traditional Korean Ondol System that is a radiant floor heating system was made as warm floor and cool indoor temperature. Nowaday, Ondol is developed as the hydronic floor heating system. But unbalance of floor temperature and indoor temperature is occurred bocause strengthen thermal insulation and airtightness in building changes thermal performance. To solve these problems, we examine actual indoor environment of heating system methods in existing apartments and present the new method of floor heating system. The existing heating system made definite indoor temperatures but floor temperatures that is $22^{\circ}C-26^{\circ}C$ was maintained. To solve these problems, we adopted the differential heating system which made warm area and cool area. A differential heating system was made different pitches of heating pipe in single zone and ratio of warm area to cool area is 1 to 2. As a result of experiments, warm area temperature is $40.7^{\circ}C$, cool area temperature is $36.1^{\circ}C$. A difference of temperature between both area is 4K. A distribution of indoor vertical temperature is similar to both warm area and cool area.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.38-41
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• 2000

High temperature cure characteristics of polyester resin systems were investigated by isothermal and dynamic differential scanning calorimetries. During isothermal scanning, the experimental procedure was modified to reduce the initial Boss of heat. no kinetic equation from the isothermal experiment was compared with that from the dynamic experiment.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.221-225
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• 2004

Evaluation of turbulence models is performed for a better prediction of thermal stratification in an upper plenum of a liquid metal reactor by applying them to the experiment conducted at JNC. The turbulence models tested in the present study are the two-layer model, the $\kappa-\omega$ model, the v2-f model and the low-Reynolds number differential stress-flux model. When the algebraic flux model or differential flux model are used for treating the turbulent heat flux, there exist little differences between turbulence models in predicting the temporal variation of temperature. However, the v2-f model and the low-Reynolds number differential stress-flux model better predict the steep gradient o( temperature at the interface of thermal stratification, and only the v2-f model predicts properly the oscillation of temperature. The LES Is needed for a better prediction of the amplitude and frequency of the temperature fluctuation.

• Steel and Composite Structures
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• v.12 no.2
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• pp.129-147
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• 2012

In this paper, the thermal buckling analysis of rectangular composite laminated plates is investigated using the Differential Quadrature (DQ) method. The composite plate is subjected to a uniform temperature distribution and arbitrary boundary conditions. The analysis takes place in two stages. First, pre-buckling forces due to a temperature rise are determined by using a membrane solution. In the second stage, the critical temperature is predicted based on the first-order shear deformation theory. To verify the accuracy of the method, several case studies were used and the numerical results were compared with those of other published literatures. Moreover, the effects of several parameters such as aspect ratio, fiber orientation, modulus ratio, and various boundary conditions on the critical temperature were examined. The results confirm the efficiency and accuracy of the DQ method in dealing with this class of engineering problems.