• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.1
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• pp.145-152
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• 2001

Thermal deformation of a machine tool structure can be evaluated from the analysis of the whole temperature field. However, it is extremely inefficient and impossible to know the whole temperature field by measuring temperatures at every point. So, the temperature estimator is required, which can predict the whole temperature field from the temperatures of just a few points. In this paper, a 1-dimensional heat transfer problem is modeled with modal analysis and state space equations. And then the state observer is designed to estimate the intensity of heat source and the whole temperature field in real time. The reliability of the estimator is verified by making comparison between solutions obtained from the proposed method and the exact solutions of examples. The proposed method is applied to the estimation of temperature distribution in a ball screw system.

• Journal of the Korean Society of Combustion
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• v.4 no.1
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• pp.1-15
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• 1999

In order to analyze the sensitivity on the pulverized coal flames of the several variables, a numerical study was conducted at the gasification process. Eulerian approach is used for the gas phase, whereas lagrangian approach is used for the solid phase. Turbulence is modeled using the standard $k-{\varepsilon}$ model. The turbulent combustion incorporates eddy dissipation model. The radiation was solved using a Monte-Carlo method. One-step two-reaction model was employed for the devolatilization of Kideco coal. In pulverized flame of long liftoff height, the initial turbulent intensity seriously affects the position of flame front. The radiation heat transfer and wall heat loss ratio distort the temperature distributions along the reactor wall, but do not influence the reactor performance such as coal conversion, residence time and flame front position. The primary/secondary momentum ratio affects the position of flame front, but the coal burnout is only slightly influenced. The momentum ratio is a variable only associated with the flame stabilization such as flame front position. The addition of steam in the reactor has a detrimental effect on all the aspects, particularly reactor temperature and coal burnout.

• Atmosphere
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• v.20 no.4
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• pp.505-518
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• 2010

We investigated the impacts of the diabatic heating location, vertical profile and basic state on the Rossby wave propagation. To examine the dynamical process of individual responses on the regional heat source, a dry version of the linear baroclinic model was used with climatological summertime (JJA) mean basic state and vertical structure of the diabatic heating for 1979-2008. Two sets of diabatic heating were constructed of those positioned in the mid-latitudes (Tibetan Plateau, eastern Mediterranean Sea, and the west-central Asia) and the tropics (the southern India, Bay of Bengal, and western Pacific). It was found that using the principal component analysis, atmospheric response to diabatic heating reaches to the steady state in 19th days in time. The prescribed mid-latitude forcing forms equivalent barotropic Rossby wave propagation along the westerly Asia jets, whereas the tropical forcing generates the Rossby wave train extending from the tropics to mid-latitudes. In relation to the maximum vertical profile, the mid-level forcing reveals a stronger response than the lower-level forcing, which may be caused by more effective Rossby wave response by the upper-level divergent flow. Under the different sub-seasonal mean state, both of the tropical and mid-latitude forcing induce the different sub-seasonal response intensity, due to the different basic-state wind.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1253-1263
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• 1994

The experimental study is carried out to identify the combustion generated noise mechanism in free turbulent jet diffusion flames. Axial mean fluctuating velocities in cold and reacting flow fields were measured using hot-wire anemometer and LDv.The overall sound pressure level and their spectral distribution in far field with and without combustion were also measured in an anechoic chamber. The axial mean velocity is 10-25% faster and turbulent intensities are about 10 to 15% smaller near active reacting zone than those in nonreacting flow fields. And sound pressure level is about 10-20% higher in reacting flow fields. It is also shown that the spectra of the combustion noise has lower frequency characteristics over a broadband spectrum. These results indicate that the combustion noise characteristics in jet diffusion flames are dominated by energy containing large scale eddies and the combusting flow field itself. Scaling laws correlating the gas velocity and heat of combustion show that the acoustic power of the combustion noise is linearly proportional to the 3.8th power of the mean axial velocity rather than 8th power in nonreacting flow fields, and the SPL increases linearly with logarithmic 1/2th power of the heat of combustion.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1322-1327
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• 2007

Many automotive companies have tried to apply the aluminum alloy sheet to car body because reducing the car weight can improve the fuel efficiency of vehicle. In order to do that, sheet materials require of weldablity, formability, productivity and so on. Aluminum alloy was not easy to join these metals due to its material properties. Thus, the laser is good heat source for aluminum alloy welding because of its high heat intensity. However, the welding quality was not good by porosity, underfill, and magnesium loss in welded metal for AA5182 aluminum alloy. In this study, Nd:YAG laser welding of AA 5182 with filler wire AA 5356 was carried out to overcome this problem. The weldability of AA5182 laser welding with AA5356 filler wire was investigated in terms of tensile strength and Erichsen ratio. For full penetration, mechanical properties were improved by filler wire. In order to optimize the process parameters, model to estimate tensile strength by artificial neural network was developed and fitness function was defined in consideration of weldability and productivity. Genetic algorithm was used to search the optimal point of laser power, welding speed, and wire feed rate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1503-1510
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• 2012

In this research, various cases of centrifugal impeller for HVAC system have been numerically analyzed by changing center angle of blades and length of outlet. Commercial CFD code, FLUENT has been used to calculate velocity, pressure, turbulence intensity, and temperature that can lead numerous results. Regardless of warming up, when the heater power level was increased, the temperature inside surrounding impeller also increased due to flowing outer air, but the temperature decreased because of flowing inner air. Consequently, the variation of central angle of blades and length of outlet led difference of velocity and flow rate which can reduce $CO_2$ in gas emission.

• Journal of the Korean Institute of Oriental Medical Informatics
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• v.15 no.2
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• pp.93-99
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• 2009

Objective: The aim of this study is to show one case of cerebral infarction patient with chest discomfort, insomnia and constipation improved by Daehwanghwangryeonsasim-tang. Methods: The patient was treated with herbal medicine (Daehwanghwangryeonsasim-tang) and acupuncture. Changes in symptoms for treatment period were observed. Result: Intensity and frequency of chest discomfort was decreased. Sleep time was increased and constipation was improved. Conclusion: Daehwanghwangryeonsasim-tang is effective on symptoms of the pattern of heart heat and fire-heat.

• Journal of the Korean Solar Energy Society
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• v.32 no.5
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• pp.11-17
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• 2012

In this study, a simulation program was developed with heat transfer model in the thermal storage tank for a solar collector and burner combined heating and hot water supply system. Analysis was conducted with variation of operating condition and schedule to analyze performance of a hot water supply and panel heating system with a solar collector and burner combined thermal storage tank. The simulation program is divided two sections. One part is calculation of temperature variation of water which flows through the panel in the floor for heating of the residential house during 24 hours, and the other part is heat transfer calculation for the reaction time to get desired water temperature in the thermal storage tank. As results, light oil consumption and system performance during operation period were analyzed with variation of climate condition and with or without solar collector. Most of the case, oil could be saved about from 24 to 41% with installing the solar collector. The performance of the system is more dependent on radiation time of the solar collector rather than the intensity of the solar radiation which was adopted for the climate analysis.

• KIEAE Journal
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• v.10 no.2
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• pp.3-8
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• 2010

Many countermeasures are presented to make excessive earth circumstance pollution better in the earth. A lot of researches are in progress to lessen $CO_2$ among the industries exhausting it. The industries manufacturing cement are making many countermeasures. Many concernments on ECO-friendly materials, rather than cement, are increased, and researches are in progress to develop them. Lime, material mostly used before Portland cement appeared, attracts the Occident as well as the Orient. In the Occident, lime mortar was used in common, for maintaining and repairing cultural properties, too. This study is aimed at offering basic materials for the modern use of lime, ECO-friendly material. This study measured the change of intensity and weight with lime, sand, and earth, basic materials of Samhoimool. As a result, at the beginning, hydrated lime displayed its density late, but as time was gone, density was promoted continuously. In addition, density was promoted, when it was given heat at the beginning. If heat-generation reaction of quicklime and water was used, density was promoted at the beginning, but liquidity showed a drop.

• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.139-144
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• 2016

The dependence of the microwave dielectric properties of the glass-ceramic composite $0.9CaMgSi_2O_6-0.1MgSiO_3$ on the crystallization behaviour was investigated as functions of the $TiO_2$ content and heat-treatment temperature. The crystallization behaviour of the specimens was evaluated via a combination of the Rietveld and reference-intensity ratio methods. For specimens with a $TiO_2$ content of up to 1 wt.%, a monoclinic diopside phase was formed, whereas a secondary $TiO_2$ phase was formed with further increases in the $TiO_2$ content. The quality factor (Qf) of the specimens was strongly dependent on the degree of crystallization. The highest Qf value was obtained with a $TiO_2$ content of 0.5 wt.%, which was improved by increasing the heat-treatment temperature. The dielectric constant (K) was affected by the size of the crystallites and the $TiO_2$ content. The temperature coefficient of the resonant frequency (TCF) was nearly constant for all of the specimens, regardless of the $TiO_2$ content or heattreatment temperature.