• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.5
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• pp.251-258
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• 2018

In construction site, conventional methods such as jackhammer or explosive methods(dynamite) have been often used for the demolition of structures. Use of those methods are more carefully treated in environmentally and historically sensitive area. For those reasons, use of Soundless Chemical Demolition Agent(SCDA) is getting the spotlight. The SCDA is a powder which has expansive strength when it is mixed with water. In these Characteristics, SCDA can destroy the concrete or rock as it is poured into boreholes of the concrete or rock structures. However, there is no industrial standard for the use of SCDA effectively yet. In this study, experimental study to measure the expansive pressure was conducted depending on various boundary conditions such as waterproof, length of the steel pipe, submerged of steel pipe. Furthermore, computational analysis using damage plasticity model to predict the minimum required pressure of the SCDA for the concrete demolition depending on spacing between holes(k-factor) and compressive strength of the concrete was conducted. Obtained results indicates that water heat dissipation with submerged steel pipe shows the stable pressure for measuring the SCDA and hole distance(k-factor) is the most important factor for crack initiation of concrete.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.2
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• pp.121-141
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• 2017

The thermal analysis of an underground power conduit for electrical cables is essential to determine their current capacity with an increasing number of demands for high-voltage underground cables. The temperature rises around a buried cable, caused by excessive heat dissipation, may increase considerably the thermal resistance of the cables, leading to the danger of "thermal runaway" or damaging to insulators. It is a key design factor to develop the mechanism on thermal behavior of backfilling materials for underground power conduits. With a full-scale field test, a numerical model was developed to estimate the temperature change as well as the thermal resistance existing between an underground power conduit and backfill materials. In comparison with the field test, the numerical model for analyzing thermal behavior depending on density, moisture content and soil constituents is verified by the one-year-long field measurement.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.2
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• pp.11-15
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• 2017

As the heat dissipation problem is increased in 3D multi flip chip packages, an improvement of thermal conductivity in bonding interfaces is required. In this study, the effect of alumina filler addition was investigated in non-conductive paste(NCP). The fine alumina filler having average particles size of 400 nm for the fine pitch interconnection was used. As the alumina filler content was increased from 0 to 60 wt%, the thermal conductivity of the cured product was increased up to 0.654 W/mK at 60 wt%. It was higher value than 0.501 W/mK which was reported for the same amount of silica. It was also found out that the addition of fine sized alumina filler resulted in the smaller decrease in thermal conductivity than the larger sized particles. The viscosity of NCP with alumina addition was increased sharply at the level of 40 wt%. It was due to the increase of the interaction between the filler particles according to the finer particle size. In order to achieve the appropriate viscosity and excellent thermal conductivity with fine alumina fillers, the highly efficient dispersion process was considered to be important.

• Journal of Aerospace System Engineering
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• v.12 no.1
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• pp.57-67
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• 2018

The APD (Antenna Pointing Driver) is an electronic equipment tool that is used to drive the two-axis gimbal-type antenna for the image data transmission of CAS (Compact Advanced Satellite). In this study, a heat dissipation of EEE (Electrical, Electronic and Electromechanical) is reviewed, to identify the parts that directly affected its efficiency, lifetime as well as the reliability of the structure. This event eventually incurs a failure of the EEE part itself, or even the entire satellite system as noted in experiments in this case. To guarantee reliability of electronic equipment during the mission, the junction temperature of EEE parts is considered a significant and important design factor, and subsequently must be secured within the allowable range. Therefore, the notation of the thermal analysis considering the derating is indispensable, and a proper thermal mathematical model should be constructed for this case. In this study, the thermal design and thermal analysis are performed to confirm the temperature requirement of the APD. In addition, we noted that the validity of the thermal model, according to each of the identified modeling methods, was therefore compared through the thermal analysis utilized in this case.

• Clean Technology
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• v.27 no.2
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• pp.132-138
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• 2021

Research is being conducted on graphene to provide graphene having both excellent physical as well as electrical properties in addition to unique physical properties. In this study, Hummer's method, which is a representative method for chemical exfoliation, was applied in order to investigate the possibility of the mass production of high-quality graphene oxide. Three types of graphite (graphite, crystalline graphite, and expanded graphite) were used in the preparation of graphene oxide with variations in the amount of potassium permanganate added, reaction temperature, and reaction time. Then a Fourier transform infrared spectroscopy (FT-IR), a Raman spectrometer, and a transmission electron microscope (TEM) were used to measure the quality of the prepared graphene oxide. Of the three types of graphite used in this experiment, crystalline graphite showed the highest quality. The prepared graphene oxide was then purified with an organic solvent, and an analysis conducted using energy dispersive X-ray spectroscopy (EDS). From the results of the residual values, we were able to confirm that both acid wastewater and wastewater were best purified using cyclohexane. The method for manufacturing graphene oxide as well as the method of purification using organic solvents that are presented in this study are expected to have less of an environmental impact, making them environmentally friendly. This makes them suitable for use in various industrial fields such as the film industry and for heat dissipation and as coating agents.

• Tunnel and Underground Space
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• v.32 no.1
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• pp.59-77
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• 2022

Currently, the design reference temperature of the buffer material for disposing of high-level radioactive waste is less than 100℃, so if the heat dissipation capacity of the buffer material is improved, the spacings of the disposal tunnel and the deposition hole in the repository can be reduced. First of all, this study tries to analyze the criteria for thermal-hydraulic-mechanical performance of the buffer materials and to investigate the researches regarding the enhanced buffer materials with improved thermal conductivity. First, the thermal conductivity should be as high as possible and is affected by dry density, water content, temperature, mineral composition, and bentonite type. the organic content of the buffer material can have a significant effect on the corrosion performance of a canister, so the organic content should be low. In addition, hydraulic conductivity of the buffer material should be less than that of near-field rock and swelling pressure should be appropriate for buffer materials to function properly. For the development of enhanced buffer materials, additives such as sand, graphite, and graphite oxide are typically used, and a thermal conductivity can be greatly improved with a very small amount of graphite addition compared to sand.

• Composites Research
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• v.36 no.3
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• pp.162-166
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• 2023

Although composite materials are increasingly utilized in general high-strength structures, the demand of performance characteristics as the multifunctional materials has been increased especially in the area of complex electronic devices. While the heat dissipation properties of devices are typically required properties, control of thermal property of composite material especially in the vertical direction is one of the problems to be solved due to its lamination process. In this study, CFRP was manufactured using the Vacuum filtration method for three types of solvent and CFs. In the composite material manufacturing process, the effect of solvent was examined using three solvents where solvents are most frequently used for the dispersion of fibers. Morphology of fiber was observed through a microscope to confirm the arrangement of CFs in the vertical direction. The alignment of fiber was examined through the measurement of the thermal conductivity of the manufactured specimen. For the thermal conductivity measurement, the higher thermal conductivity was obtained with the lower aspect ratio of CF. For the thermal conductivity in the through-plane direction, 8.687 W/m·K, 10.322 W/m·K, and 13.005 W/m·K of thermal conductivity was measured in the DMF, NMP and Acetone, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.3
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• pp.1-9
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• 2024

This paper addresses the significance of Cu/Polymer Hybrid Bonding technology in the advancement of semiconductor packaging. As the demands of the AI era increase, the semiconductor industry is exploring heterogeneous integration packaging technologies to achieve high I/O counts, low power consumption, efficient heat dissipation, multifunctionality, and miniaturization. The conventional Cu/SiO₂ Hybrid Bonding structure faces limitations such as achieving compatibility with CMP processes to attain surface roughness below 1nm and the occurrence of bonding defects due to particles. However, Cu/Polymer Hybrid Bonding technology, utilizing polymers, is gaining attention as a promising alternative to overcome these challenges. This study focuses on the deposition, patterning, and material properties of polymers essential for Cu/Polymer Hybrid Bonding, highlighting the advantages and potential applications of this technology compared to existing methods. Specifically, the use of polymers with low glass transition temperatures (Tg) is discussed for their benefits in low-temperature bonding processes and improved mechanical properties due to their high coefficients of thermal expansion. Furthermore, the study explores surface property modifications of polymers and the enhancement of bonding mechanisms through plasma treatment. This research emphasizes that Cu/Polymer Hybrid Bonding technology can serve as a critical breakthrough in developing high-performance, low-power semiconductor devices within the industry.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.75-82
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• 2019

Flexible solar cells have attracted enormous attention in recent years due to their wide applications such as portable batteries, wearable devices, robotics, drones, and airplanes. In particular, the demands of the flexible silicon and compound semiconductor solar cells with high efficiency and high reliability keep increasing. In this study, we fabricated a flexible InGaP/GaAs double-junction solar module. Then, the effects of the wind speed and ambient temperature on the operating temperature of the solar cell were analyzed with the numerical simulation. The temperature distributions of the solar modules were analyzed for three different wind speeds of 0 m/s, 2.5 m/s, and 5 m/s, and two different ambient temperature conditions of 25℃ and 33℃. The flexibility of the flexible solar module was also evaluated with the bending tests and numerical bending simulation. When the wind speed was 0 m/s at 25 ℃, the maximum temperature of the solar cell was reached to be 149.7℃. When the wind speed was increased to 2.5 m/s, the temperature of the solar cell was reduced to 66.2℃. In case of the wind speed of 5 m/s, the temperature of the solar cell dropped sharply to 48.3℃. Ambient temperature also influenced the operating temperature of the solar cell. When the ambient temperature increased to 33℃ at 2.5 m/s, the temperature of the solar cell slightly increased to 74.2℃ indicating that the most important parameter affecting the temperature of the solar cell was heat dissipation due to wind speed. Since the maximum temperatures of the solar cell are lower than the glass transition temperatures of the materials used, the chances of thermal deformation and degradation of the module will be very low. The flexible solar module can be bent to a bending radius of 7 mm showing relatively good bending capability. Neutral plane analysis was also indicated that the flexibility of the solar module can be further improved by locating the solar cell in the neutral plane.