• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.341-347
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• 2003

Single flighted screw extrusion is the most cost effective method for the production of film, sheet, pipe and the fundamental step in other processes including blow molding and injection molding The temperature and injection pressure in barrel play a very important role in quality of products. Because thermal distortion and displacement of barrel by temperature difference and injection pressure difference cause irregular resine melting and flow. In this paper thermal distortion and stress of barrel includes pressure and temperature distributions by finite element analysis to understand dynamic characteristics of barrel.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.707-710
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• 2004

This paper reported the results of mock-up test on mass concrete for transfer girder using setting time difference of super retarding agent(SRA). According to test results, two mock-up structures were made. Plain concrete without placing layer reached maximum temperature after 24hours since placement and caused surface hydration cracks at top section. However, concrete with placing layer reached maximum temperature after 72hours and surface temperature was higher than center temperature, which did not cause surface crack. After form removing, no crack was observed at side surface of plain concrete, while concrete using SRA at mid section had surface scaling and settling crack. According to coring results, concrete with placing layer had a penetration crack from top section to bottom section. Therefore, the setting time difference method to reduce hydration heat will have difficulty in applying the mass concrete for transfer girder.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.212-220
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• 2000

Single flighted screw extrusion is the most cost effective method for the production of film, sheet, pipe and the fundamental step in other processes including blow molding and injection molding. The temperature of polymer melts and injection pressure play a very important role in the injection molding machine. Thermal distortion and displacement of screw by temperature difference and injection pressure difference cause adhesive wear by metal-to-metal contact. In this paper we analyze thermal distortion and stress of screw includes pressure and temperature distributions by finite element analysis to understand dynamic characteristics of screw.

• Fibers and Polymers
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• 제3권1호
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• pp.38-42
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• 2002

Polypropylene filaments were spun from a mixture of PP chips of two different Melt Flow Index (MFI) (3 MFI and 35 MFI). A significant difference was observed in the melting characteristics of the resultant filaments from either of the individual components as observed from the DSC. The main difference being in the degree of melting achieved at any temperature in the initial stages of the melting range, which was found to be higher in case of the filaments spun from the b]end. These filaments were then thermally bonded using silicon oil bath and heated roller method. Subsequently the bond strength of the filaments was measured on the Instron Tensile Tester using the loop technique. The values of the world strengths obtained from the blend were compared with those made from the individual component. It was found that the bond strength of the bonds obtained from the blended filament at a given temperature was higher than that of the bonds made from the filaments of either of the individual components, which is also suggested by the DSC curves. The difference in the bond strength was found to be as high as 25% in case of the blend with 60:40 composition ratios of the 3 MFI and 35 MFI components respectively.

• 한국도로학회논문집
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• 제17권5호
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• pp.1-10
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• 2015

PURPOSES : A finite difference model considering snow melting process on porous asphalt pavement was derived on the basis of heat transfer and mass transfer theories. The derived model can be applied to predict the region where black-ice develops, as well as to predict temperature profile of pavement systems where a de-icing system is installed. In addition, the model can be used to determined the minimum energy required to melt the ice formed on the pavement. METHODS : The snow on the porous asphalt pavement, whose porosity must be considered in thermal analysis, is divided into several layers such as dry snow layer, saturated snow layer, water+pavement surface, pavement surface, and sublayer. The mass balance and heat balance equations are derived to describe conductive, convective, radiative, and latent transfer of heat and mass in each layer. The finite differential method is used to implement the derived equations, boundary conditions, and the testing method to determine the thermal properties are suggested for each layer. RESULTS: The finite differential equations that describe the icing and deicing on pavements are derived, and we have presented them in our work. The framework to develop a temperature-forecasting model is successfully created. CONCLUSIONS : We conclude by successfully creating framework for the finite difference model based on the heat and mass transfer theories. To complete implementation, laboratory tests required to be performed.

• 오토저널
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• 제3권3호
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• pp.24-29
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• 1981

This paper is studied an efficient temperature distribution and heat transfer of two-dimensional rectangular cross-section by the higher-order triangular finite dynamic element and finite difference. This is achieved by employing a discretization technique based on a recently developed concept of finite dynamic elements, involving higher order dynamic correction terms in the associated stiffness and convection matrices. Numerical solution results of temperature distribution presented herein clearly optimum element and show that FEM10 is the most accurate temperature distribution, but heat transfer and computational effort is the most acquired.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.625-628
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• 2003

This paper presents the behaviors of reinforced concrete columns under high temperature. When columns are exposed high temperature, temperature distribution of a section becomes nonlinear and it is calculated by using finite difference method(F.D.M). The interaction curves show the strength of columns at various exposure times. The strength of columns decreases according to the increase of the exposure time and the decrease of concrete cover.

• 조명전기설비학회논문지
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• 제27권4호
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• pp.1-7
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• 2013

Optical characteristics including the view angle and color temperature uniformity of LED packages with an integrated lens fabricated by compression molding method are investigated according to lens shape, lens materials, and phosphor coating methods. Four types of lens shape are designed and their optical output power dependence on the refractive index of silicone encapsulant are evaluated. Also, spatial color temperature uniformities of packages fabricated with different phosphor coating methods-direct coating on a chip vs. uniformly mixed with silicone encapsulant- are compared at various view angles. As the result, it is found that phosphor coating method is more effective on color temperature uniformity than lens shape. The maximum color temperature difference of a package with direct coating of phosphor on a chip is 1,340K according to the view angle at the color temperature of 5,000K, and that of a package with uniformly mixed phosphor is 250K, which indicates 1,090K improvement of color uniformity for the latter case.

• 대기
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• 제23권4호
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• pp.471-483
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• 2013

Nighttime sea fog detection from satellite is very hard due to limitation in using visible channels. Currently, most widely used method for the detection is the Dual Channel Difference (DCD) method based on Brightness Temperature Difference between 3.7 and 11 ${\mu}m$ channel (BTD). However, this method have difficulty in distinguishing between fog and low cloud, and sometimes misjudges middle/high cloud as well as clear scene as fog. Using CALIPSO Lidar Profile measurements, we have analyzed the intrinsic problems in detecting nighttime sea fog from various satellite remote sensing algorithms and suggested the direction for the improvement of the algorithm. From the comparison with CALIPSO measurements for May-July in 2011, the DCD method excessively overestimates foggy pixels (2542 pixels). Among them, only 524 pixel are real foggy pixels, but 331 pixels and 1687 pixels are clear and other type of clouds, respectively. The 514 of real foggy pixels accounts for 70% of 749 foggy pixels identified by CALIPSO. Our proposed new algorithm detects foggy pixels by comparing the difference between cloud top temperature and underneath sea surface temperature from assimilated data along with the DCD method. We have used two types of cloud top temperature, which obtained from 11 ${\mu}m$ brightness temperature (B_S1) and operational COMS algorithm (B_S2). The detected foggy 1794 pixels from B_S1 and 1490 pixel from B_S2 are significantly reduced the overestimation detected by the DCD method. However, 477 and 446 pixels have been found to be real foggy pixels, 329 and 264 pixels be clear, and 989 and 780 pixels be other type of clouds, detected by B_S1 and B_S2 respectively. The analysis of the operational COMS fog detection algorithm reveals that the cloud screening process was strictly enforced, which resulted in underestimation of foggy pixel. The 538 of total detected foggy pixels obtain only 187 of real foggy pixels, but 61 of clear pixels and 290 of other type clouds. Our analysis suggests that there is no winner for nighttime sea fog detection algorithms, but loser because real foggy pixels are less than 30% among the foggy pixels declared by all algorithms. This overwhelming evidence reveals that current nighttime sea fog algorithms have provided a lot of misjudged information, which are mostly originated from difficulty in distinguishing between clear and cloudy scene as well as fog and other type clouds. Therefore, in-depth researches are urgently required to reduce the enormous error in nighttime sea fog detection from satellite.

• Journal of Biosystems Engineering
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• 제33권1호
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• pp.21-29
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• 2008

In this study, the thermal properties of peeled chestnuts were measured, and the mathematical prediction model of freezing time was also developed for various interior positions from center to rind (surface). The measured thermal properties were showed that heat conductivity is $0.43W/m^{\circ}C$, specific heat is $2.7206J/m^3^{\circ}C$, latent heat is $216.9{\times}10^6J/m^3$ and freezing point is $-2.8^{\circ}C$. The entire process about reaching to the freezing time of peeled chestnuts was analyzed with its each regular depth position using the finite difference method (FDM) based on computer simulation. In case of regular freezing temperature, it was showed an that surface (rind) position is more rapidly reached into the freezing point rather than the center position, and also reaching time to the freezing point is more fast at the lower freezing temperature. Comparison results between simulation and experiments showed linear relationship. In regularly varying condition for freezing temperature, this method would give an information to predict a freezing time of the interior points for peeled chestnuts and more similar agricultural products.