• Transactions of the Society of Information Storage Systems
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• v.2 no.1
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• pp.21-25
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• 2006

The new multimedia information environment requires smaller optical data storage systems. However, one of the difficulties encountered in designing small form factor(SFF) optical pick-up is to emit the heat which is generated from laser diode(LD). Heat generated at the LD can reduce the optical performance of the system and the lifetime of LD. Therefore, it is important to include the thermal design in the design stage of SFF optical pick-up system for high performance and the longer lifetime of LD, and furthermore, to analyze the thermal characteristics of LD in detail micro heat transfer analysis is necessary. In the present study, micro heat transfer analysis was performed using the finite element method for the $28{\times}11{\times}2mm^3$ super slim swing-arm type optical pick-up actuator for Blu-ray disk. Two different materials were used for a swing-arm; a double layer polycarbonate/steel structure and a single aluminum structure.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.169-170
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• 2022

Due to the higher use of nonrenewable fossil fuel energy, environment friendly sustainable energy from waste materials is attracting attention of the researchers. Considering that, jute stick (JS) biochar has been considered for this study for ecofriendly and sustainable thermal energy storage application. Waste jute sticks (JS), which are being mainly used as a fuel for cooking purpose, have been pyrolyzed to produce porous biochar and have been used for shape stabilization of stearic acid (SA) as phase change material (PCM). SA at 1:1 ratio has been incorporated into the activated JS biochar to concoct shape-stabilized phase change composite (SAJS). The SAJS has been evaluated by different techniques such as Fourier transform-infrared spectroscope (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The obtained composite PCM has shown excellent shape stability with a high latent heat storage, suggesting its suitability for thermal energy storage applications.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.601-603
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• 2005

Refocusing methods are used to compensate optical performance degradation of high resolution satellite camera during on-orbit operation. Due to mechanical vibration during launch and thermal vacuum environment of space where camera is exposed, the alignment of optical system may have error. The focusing error is dominant of misalignment and caused by the de-space error of secondary mirror of catoptric camera, which is most sensitive to vibration and space environment. The high resolution camera of SPOT, Pleiades and KOMPSAT2 have refocusing device to adjust focusing during orbital operation while QuickBird of US does not use on orbit refocusing method. For the Korsch type optical configuration which is preferred for large aperture space remote sensing camera, secondary mirror and folding mirror are available as refocusing element.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.4
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• pp.436-442
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• 2005

Rapid development of electronic technology requires small size, high density packaging and high power of electronic devices. In this paper, characteristics on oscillating heat pipe according to operating conditions (environment temperature, charging ratio of working fluid, inclination) based on experimental study was investigated From the experimental results $25^{\circ}C$(environment temperature) R-141b (working fluid) $40\%$ (charging ratio) was best performace at others of inclination angle and the top heating mode of OCHP performed $80\%$ efficiency of the bottom heating mode.

• Journal of Urban Science
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• v.6 no.2
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• pp.17-27
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• 2017

Recently, civil complaints have increased due to water pollution and bad smell in rivers. Therefore, attention is focused on improving the river environment. The purpose of this study is to acquire RGB and thermal infrared images using UAV for sewage outlet and to monitor the status of stream pollution and the applicability UAV based images for river embankment maintenance plan was examined. The accuracy of the 3D model was examination by SfM(Structure from Motion) based images analysis on river embankment maintenance area. Especially, The wastewater discharged from the factory near the river was detected as an thermal infrared images and the flow of wastewater was monitored. As a result of the study, we could monitor the cause and flows of wastewater pollution by detecting temperature change caused by wastewater inflow using UAV images. In addition, UAV based a high precision 3D model (DTM, Digital Topographic Map, Orthophoto Mosaic) was produced to obtain precise DSM(Digital Surface Model) and vegetation cover information for river embankment maintenance.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.4
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• pp.317-326
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• 2020

In this study, damages caused by flash fire, overpressure, and thermal radiation based on the sizes of leak holes were evaluated using the areal location of hazardous atmospheres when natural gas leaked owing to the damage of pipeline in a LNG fueled ship. In addition, environmental variables (wind speed, atmospheric temperature, and atmospheric stability) and process variables (pipe pressure and pipe length) were classified to analyze the damage impact ranges caused by various scenarios. From the results, the damage range caused by the environmental variables was the largest, followed by overpressure and thermal radiation. Additionally, for the process variables, regardless of the pressure, length, or size of the leak holes, the damage range attributed to flash fire was the most significant, and the damage range was high in the order of overpressure and thermal radiation, similar to the environmental variables. The larger the size of the leak holes, the higher the values of the environmental and process variables, and the higher the damage range caused by jet fire compared to the environmental variables.

• KIEAE Journal
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• v.14 no.6
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• pp.93-97
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• 2014

Curtain wall system of office buildings has recently become very common in Korea. As the multi-layer curtain glazing is exposed to outdoor environment, it is very subjected to direct environmental impact. Consequently, breakage and cracks of glazing due to heat expansion is frequently observed. This study explores various causes and aspects for destruction of multi-layer glazing. A sensitivity analysis was performed on the basis that thermal changes causes damage to the multi-layer glazing. Air temperature in air cavity within the multi-layer glazing was examined to find its effect on multi-layer glazing breakage. Analysis showed high deflection to depth ratio of 1:1.8 and that higher the aspect ratio, smaller is the deflection. Allowable pressure showed that the weakest value is for aspect ratio of 1:2.9. Sensitivity analysis by the area of the glazing showed that as area of glazing becomes higher, allowable pressure and deflection-depth ratio becomes smaller. For allowable pressure and allowable deflection-depth within air cavity, the glazing breakage occurred at least $107^{\circ}C$. The results from glazing breakage by thermal factor shows that it is hard to break the glazing with only an increase in air cavity temperature in multi-layer glazing applied in buildings.

• Journal of Radiation Protection and Research
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• v.24 no.3
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• pp.143-154
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• 1999

Panasonic UD-809P type albedo neutron TL dosimeters mounted on a water phantom were used to measure neutron personal dose equivalent in a Korean nuclear power plant. From the measured TL readings, personal dose equivalents from thermal, epithermal and fast neutrons were evaluated by using a method adopted in a neutron dose calculation algorithm for Panasonic UD-809P type albedo neutron TL dosimeters, which was suggested in a Panasonic TLD System User's Manual. The results showed that personal dose equivalent from fast neutrons could not be adequately evaluated in a field with high thermal neutron fraction to be encountered in a nuclear power plant. This seems to be related to the incomplete incidence of albedo thermal neutrons to the TL dosimeters. In order to evaluate appropriately the personal dose equivalent from fast neutrons in the field condition, new method fer the neutron dose calculation algorithm was suggested. In this new method, neutrons are grouped into thermal neutrons and fast neutrons. For each neutron component, equations for TL response, sensitivity factor, calibration factor and personal dose equivalent were derived.

• Journal of Bio-Environment Control
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• v.5 no.1
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• pp.57-64
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• 1996

To use effectively the solar energy in greenhouse heating, a high performance solar collector should be developed. And then the size of the solar collector and thermal storage tank should be determined through the calculation of heating load. The solar collector must be set in the optimum tilt angle and direction to take daily solar radiation maximally, and the flow rate of heat transfer fluid through the solar collector should be kept in the optimum range. In this research, the performance tests of a capillary tube solar collector were performed to determine the optimum water flow rate and the results summarized as follows. 1. The regressive equations for efficiency estimations of the capillary tube solar collector in the open loop were modeled in the water flow rate of 700-l,000 $\ell$/hr. 2. The optimum water flow rate of the solar collector was estimated by the second order polynomial regression and the maximum efficiency was 80% at the water flow rate of 850 $\ell$/hr. 3. The solar thermal storage system consisted of a capillary tube solar collector and a water storage tank was tested at the water flow rate of 850 $\ell$/hr in the closed loop, and obtained the solar thermal storage efficiency of 55.2%. 4. As the capillary tube solar collector engaged in this experiment was made of non-corrosive polyolefin tubes, its weight was as light as 1/30 of the flat plate solar collector made of copper tubes. Therefore it was considered to be suitable for the greenhouse heating system.

• Clean Technology
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• v.10 no.4
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• pp.203-213
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• 2004

Natural gas thermal decomposition method is the technology of converting natural gas (methane) into hydrogen and carbon at high temperature. The most advantage of thermal decomposition method is that hydrogen and carbon can be produced without emitting carbon dioxide. In this study, the generation of hydrogen and carbon was investigated by this natural gas (methane) thermal decomposition method. We found that pyrocarbon was created on the surface of reactor, carbon black was deposited on the pyrocarbon and final plugging phenomenon took place. To solve this problem, we tried several attempts such as introduction of double pipe reactor instead of single pipe reactor or oxidization of carbon black using $O_2$ or $CO_2$ at regular intervals of reaction. Therefore, some plugging phenomenon was resolved by this methods. Also, carbon particle size was measured by SEM (Scanning Electron Microscope) image and the size was about 200 nm.