• Journal of Welding and Joining
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• v.16 no.3
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• pp.74-84
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• 1998

The microstructures of the HAZ (Heat Affected Zone) are generally different from the base metal due to rapid thermal cycle during welding process. Particuraly, CGHAZ (Coarsened Grain Heat Affected Zone) near the fusion line is the most concerned region in which many metallurgical and mechanical discontinuities have been normally generated. A computer program by the numerical formularization of phase transformation during cooling with different rates was developed to generate the CCT diagram, and to predict microstructural (phase) changes in the CGHAZ. In order to verify simulated results, isothermal and continuous cooling transformation experiments were conducted. The simulated and experimental results showed that the developed computer model could successfully predict the room temperature microstructural changes (changes in volume fraction of phases) under various welding conditions (heat input & cooling rate $(Δt_{8/5})$).

• ETRI Journal
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• v.19 no.2
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• pp.59-70
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• 1997

A study on the operation of a heat pipe with two heat sources has been performed to optimize the heat distribution of satellite equipment. A numerical modeling is used to predict the temperature profile for the heat pipe assuming cylindrical two-dimensional laminar flow for the vapor, and the conduction heat transfer for the wall and wick. An experimental study using the copper-water heat pipe with the length of 0.45 m has been performed to evaluate the numerical model and to compare the temperature distribution at the outer wall for the non-uniform heat distribution. The results on temperature profiles for the heat input range from 29 W to 47 W on each heater are presented. Also the correlation between the heat input and the temperature increase is presented for the optimum distribution on two heaters. The result shows that the outer wall temperature can be controlled by redistribution of heat sources. It is also concluded that the heat source closer to the condenser can carry more heat while maintaining lower temperatures at the outer wall.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.863-868
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• 2004

Reheating furnace is an essential facility of a rod mill plant where a billet is heated to the required rolling temperature so that it can be milled to produce wire. Sometimes, it is also necessary to control a transient billet temperature pattern according to the material characteristics to prevent a wire from breaking. Though it is very important objective to obtain a correct information of a billet temperature during furnace operation. Consequently, a billet temperature profile must be estimated. In this paper, a billet heat transfer model based on FEM (Finite Element Method) with spatially distributed emission factors is proposed and a measurement is also carried out for two different furnace operation conditions. Finally, the difference between the model outputs and the measurements is minimized by using the new optimization algorithm named uDEAS(Univariate Dynamic Encoding Algorithm for Searches) with multi-step tuning strategy. Hence, the information of billet temperatures can be obtained by using proposed model on various furnace operation conditions.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.1
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• pp.9-14
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• 2004

In this paper, temperature dependence of effective ionization coefficient in Si is formulated as a single polynomial function of temperature, which allows analytical expressions for breakdown voltage of Si $p^+n$ junction as a function of temperature. The analytical breakdown voltages agree well with the simulation as well as the experimental ones reported within $3\%$ in error for the doping concentrations in the range of $10^{14}cm^{-3}{\~} 10^{17}cm^{-3}$ at 100K, 300K and 500K.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.35 no.4
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• pp.313-318
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• 2017

Land surface temperature is essential for monitoring abnormal climate phenomena such as UHI (Urban Heat Islands), and for modeling weather patterns. However, the quality of surface temperature obtained from the optical space imagery is affected by many factors such as, revisit period of the satellite, instance of capture, spatial resolution, and cloud coverage. Landsat 8 imagery, often used to obtain surface temperatures, has a high resolution of 30 meters (100 meters rearranged to 30 meters) and a revisit frequency of 16 days. On the contrary, MODIS imagery can be acquired daily with a spatial resolution of about 1 kilometer. Many past attempts have been made using both Landsat and MODIS imagery to complement each other to produce an imagery of improved temporal and spatial resolution. This paper applied machine learning methods and performed downscaling which can obtain daily based land surface temperature imagery of 30 meters.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.7
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• pp.559-563
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• 2002

A threshold voltage model of SiC N-channel MOSFETs for high-temperature and hard radiation environments has been developed and verified by comparing with experimental results. The proposed model includes the difference in the work functions, the surface potential, depletion charges and SiC/$SiO_2$acceptor-like interface state charges as a function of temperature. Simulations of the model shoved that interface slates were the most dominant factor for the threshold voltage decrease as the temperature increase. To verify the model, SiC N-chnnel MOSFETS were fabricated and threshold voltages as a function of temperature were measured and compared wish model simulations. From these comparisons, extracted density of interface slates was $4{\times}10^{12}\textrm{cm}^{-2}eV^{-1}$.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.12
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• pp.98-103
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• 2019

With the increasing need for environmental protection, it is particularly important to improve the energy saving and reliability of refrigerators. Generally, the cold air flowing into the freezer compartment transits to the bottom of the refrigerating compartment, which can lead to uneven temperature distribution. This paper proposes two design solutions for improving the temperature distribution problem. Of these, the optimal refrigeration design was selected and tested using Computational Fluid Dynamics (CFD) modeling and simulation. The results showed improved uniformity of the temperature distribution inside the refrigerator, thus benefitting food storage while reducing energy consumption.

• Journal of Korean Society for Atmospheric Environment
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• v.33 no.1
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• pp.45-53
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• 2017

A high resolution model is proposed for calculating the temperature field of a large city, based upon a Lagrangian particle model. Utilizing the analogy between the heat and mass transport phenomena in turbulent flows, a Lagrangian particle model, originally developed for air pollutant dispersion problems, is adapted for simulating heat transport. In the model conceptual heat particles are released into the atmosphere from the heat sources and move along with the turbulent winds in accordance with the Markov process. The potential temperature assumed to be conserved along with heat particles serves as a tag, so the temperature fields can be deduced from the distribution of particles. The wind fields are constructed from a diagnostic meteorology model incorporating a morphological model designed for building flows. Test run shows the robustness of the modeling system.

• Journal of the Semiconductor & Display Technology
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• v.5 no.4 s.17
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• pp.35-40
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• 2006

This paper shows that the effect of exposing on the top area and a solution which using a water circulation system. Semiconductor substrate stage is made from Aluminum and is repeated the sequence of exposing (150), turning OFF shutter, taking 30 sec. interval at the top area of stage. So the temperature of substrate temperature rises continuously. On this, we made a waterway at the inner part of the substrate stage and operated a water circulation system. We measured the temperature of a substrate stage surface with a thermocouple attached to the substrate stage. To analyze the top area's temperature, we used Analysis Program ANSYS for analysis and 3D CAD program Solid-Works for modeling.

• Journal of the Korea Institute of Building Construction
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• v.14 no.3
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• pp.273-284
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• 2014

Ultra-high-performance concrete (UHPC) consists of cement, silica fume (SF), sand, fibers, water and superplasticizer. Typical water/binder ratios are 0.15 to 0.20 with 20 to 30% silica fume. In the production of ultra-high performance concrete, a significant temperature rise at an early age can be observed because of the higher cement content per unit mass of concrete. In this paper, by considering the production of calcium hydroxide in cement hydration and its consumption in the pozzolanic reaction, a numerical model is proposed to simulate the hydration of ultra-high performance concrete. The heat evolution rate of UHPC is determined from the contributions of cement hydration and the pozzolanic reaction. Furthermore, by combining a blended-cement hydration model with the finite-element method, the temperature history in the hardening of UHPC is evaluated using the degree of hydration of the cement and the silica fume. The predicted temperature-history curves were compared with experimental data, and a good correlation was found.