• Advances in materials Research
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• 제6권1호
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• pp.1-12
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• 2017

The aim of the work was to evaluate the effect of ultraviolet-ozone ($UV-O_3$) irradiation with different times on the structure and thermal properties of hydroxypropyl methylcellulose (HPMC) in the form of a thin film to be used as bioequivalent materials according to their important broad practical and medical applications. HPMC thin films were exposed to $UV-O_3$ radiation in air at a wavelength of 184.9 nm.The beneficial effects of this treatment on the crystallinity and amorphousity regions were followed by X-ray diffraction technique and FTIR spectroscopy. Differential scanning calorimetry, thermogravimetric and differntial thermal analyses were used in order to study the thermal properties of HPMC samples following the process of photodegradation. The obtained results indicated that the rate of degradation process was increased with increasing the exposure time. Variations in shape and area of the thermal peaks were observed which may be attributed to the different degrees of crystallinity after exposing the treated HPMC samples. This meant a change in the amorphousity of the treated samples, the oxidation of its chemical linkages on its surface and its bulk, and the formation of free radical species as well as bond formation.

• Journal of Dairy Science and Biotechnology
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• 제33권3호
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• pp.223-229
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• 2015

Milk is a food with high nutritional value as it contains abundant water, proteins, vitamins, lactose, fat, minerals, enzymes, etc. However, in order to make milk suitable for intake, it should be thermally treated to eliminate microbiologically hazardous factors. Heat treatment is an essential sanitation process for milk, but various precautions must be taken in order to process and preserve it. Therefore, various techniques should be developed to minimize the nutrient loss and to ensure that milk is safe for consumption, conservation, and distribution. However, the existing thermal pasteurization methods are harmful and increase the nutrient loss; moreover, no new thermal pasteurization methods are being researched that are safe for the human health and minimize the nutrient loss. Hence, this study aims to review new processes for thermal (low temperatures) and no thermal pasteurization methods that can minimize the nutrient loss during milk pasteurization.

• 한국압력기기공학회 논문집
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• 제12권1호
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• pp.41-48
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• 2016

To investigate the effect of long-term thermal aging on the microstructural and mechanical characteristics of weldment made of nickel base alloy and its weld metal, an accelerated heat treatment was applied to simulate the process of long-term thermal aging in the operating condition of nuclear power plant. A representative nickel-based weldment with Alloy 600 and Alloy 182 was fabricated and heat-treated at $400^{\circ}C$ for 1,713 h and 3,427 h to simulate the thermal aging for the period equivalent to 15 and 30 years in operating pressurized water reactors, respectively. The microstructural and mechanical characteristics were analyzed by using optical microscopy, scanning electron microscopy and Vickers microhardness measurement. Changes were observed in precipitation behavior and microhardness of each specimen, and these changes were mainly attributed to the change in precipitated morphology and residual stress across the weld during the thermal aging process.

• 한국전기전자재료학회논문지
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• 제21권1호
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• pp.35-43
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• 2008

Aviation obstacle lights including controller for the safe night aviation service have applied to high voltage transmission line of which height is from $60{\sim}180 m$, Fresnel lens made by Augustine Fresnel have been applied to light houses, These Fresnel lens were applied to aviation obstacle lights and have been universally used, It was reported that Fresnel lens for aviation obstacle light was used in the first place in Korea in 1987, LEDs have recently been applied to aviation obstacle lights, So, the optimum physical design is essential to the design of aviation obstacle light. In this study, optical and three dimensional modeling of LED module and globe lens were performed, And thermal analysis due to LED thermal source and service thermal condition in high voltage transmission line was performed and was analyzed comparing with experiments, The optimum design process of medium intensity LED aviation obstacle lights was constructed with three dimensional modeling, thermal analysis, and thermal experimental technique.

• 한국기계가공학회지
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• 제11권1호
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• pp.50-55
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• 2012

The important problem in high speed spindle is to reduce and minimize the thermal effect by motor and bearing. This paper presents the thermal characteristic analysis for a high speed spindle with and without cooling at the rear part, considering the viscosity and the flow rate of cooling oil. A high speed spindle is composed of angular contact ceramic ball bearings, high speed built-in motor, oil jacket cooling and so on. The thermal analyses of high speed spindle need to minimize the thermal effect and maximize the cooling effect and they are carried out under the various cooling conditions. Heat generations of the bearing and the high speed motor are estimated from the theoretical and experimental data. This result can be applied to the design and manufacture of a high speed motor spindle.

• 한국기계가공학회지
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• 제6권1호
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• pp.50-56
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• 2007

Exhaust manifold is generally subjected to thermal cycle loadings ; at hot condition, large compressive plastic deformations are generated, and at cold condition, tensile stresses are remained in highly deformed critical zones. These phenomena originate from the fact that thermal expansions of the runners are restricted by inlet flange clamped to the cylinder head, because the former is less stiff than the latter and, the temperature of the inlet flange is lower than that of the runners. Since the failure of an exhaust manifold is mainly caused by geometric constraints between the cylinder head and the manifold, the thermal stress can be controlled by geometric factors. The generic geometric factors include the inter distance (2R), the distance from the head to the outlet (L), the tube diameter(d) and the tube thickness (t). This criteria based on elastic analysis up to onset of yield apparently indicate that the pre-stress also reduces the factor; however, high temperature relaxation may reduce this effect at later operation stage.

• 한국기계가공학회지
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• 제11권2호
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• pp.105-111
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• 2012

High speed machining is the core technology that influences the performance of machine tools, and the high speed motor spindle is widely used for the high speed machine tools. The important problem in high speed spindle is to minimize the thermal effect by motor and bearing and frequency effect. This paper presents the thermal characteristic analysis and frequency experiment for a high speed spindle considering the flow rate of cooling oil. A high speed spindle is composed of angular contact ceramic ball bearings, high speed built-in motor, oil cooling jacket and so on. The thermal analyses of high speed spindle need to minimize the thermal effect and maximize the cooling effect and they are carried out under the various cooling conditions. Heat generations of the bearing and the high speed motor are estimated from the theoretical and experimental data. To find out the characteristic of vibration, the high speed spindle is excited in operational range. This result can be applied to the design and manufacture of a high speed tapping spindle.

• 비파괴검사학회지
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• 제34권1호
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• pp.10-17
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• 2014

A 3D model based on the finite element method (FEM) was built to simulate the infrared thermography (IRT) inspection process. Thermal contrast is an important parameter in IRT and was proven to be a function of defect parameters. Parametric studies were conducted on internal defects with different depths, thicknesses, and orientations. Thermal contrast evolution profiles with respect to the time of the defect and host material were obtained through numerical simulation. The thermal contrast decreased with defect depth and slightly increased with defect thickness. Different orientations of thin defects were detected with IRT, but doing so for thick defects was difficult. These thermal contrast variations with the defect depth, thickness, and orientation can help in optimizing the experimental process and interpretation of data from IRT.

• Food Science and Biotechnology
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• 제18권6호
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• pp.1336-1341
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• 2009

Quantitative changes in functional constituents of waxy corn (Zea mays L.) by 5 different thermal pretreatments, including roasting, steaming, microwave, puffing, and extruding, were determined and compared with those of the raw waxy corn. There were no significant differences in fatty acid compositions among the corn treated with 5 thermal treatments. Levels of $\alpha$- and $\gamma$-tocopherols, soluble amino acids, and phytosterols decreased by thermal treatments, while those of p-coumaric and ferulic acids considerably increased by thermal treatments. In particular, the contents of tocopherols and phytosterols, and souble amino acid decreased significant in the steaming and puffing processes, respectively, whereas those of 2 free cinnamic acids increased significantly in the steaming and puffing processes. The extruding process showed smaller quantitative changes in tocopherols, phytosterols, and hydroxycinnamic acid derivatives compared to other heat pretreatments. These results suggest that the extruding process have a positive effect on valuable phytochemicals in waxy corn.

• 한국태양에너지학회 논문집
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• 제27권4호
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• pp.43-49
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• 2007

This study is conducted to improve the efficiency of a thermal storage tank. The thermal storage tank was designed to store heat energy that obtained from the solar or the others heat sources. However, it has difficulties in storing heat with nonuniform temperature through the entire tank with respect to the vertical direction, This study is focused on the thermal stratification to improve thermal comfort for the resident in house. To enhance temperature stratification of the tank, a distributor was designed and installed in the middle of the storage tank vertically. The vertically designed distributor could supply the return water with stratified temperature in the storage tank with respect to the height. The water velocity from the distributor hole is the same with the other outlet in the distributor. However, gravity effect on the flow in the storage tank is much higher than that of the velocity effect due to that Froude Number is less than 1. During the heat charging process in the storage tank, temperature maintained with little difference with respect to the height. However the charging process takes long time to get a effective temperature for the heating or hot water supply because of all of water in the storage tank needs to be heated.