• Polymer(Korea)
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• v.32 no.5
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• pp.440-445
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• 2008

The failure mechanism and failure morphology of linear low density polyethylene (LLDPE) tubing under hydrostatic pressure were investigated. Microscopic observations using video microscope and scanning electron microscope indicate that the failure mode is a brittle fracture including cracks propagated from inner wall to outer wall. In addition, oxidation induction time and Fourier transform infrared spectroscopy results show the presence of exothermic peak and the increase in carbonyl index on the surface of fractured LLDPE tubing, due to thermal-degradation. An accelerated life test methodology and testing system for LLDPE tubing are developed using the relationship between stresses and life characteristics by means of thermal acceleration. Statistical approaches using the Arrhenius model and Weibull distribution are implemented to estimate the long-term life time of LLDPE tubing under hydrostatic pressure. Consequently, the long-term life time of LLDPE tubing at the operating temperature of $25^{\circ}C$ could be predicted and also be analyzed.

• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.210-218
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• 2019

Batch experiment studies were carried out on the adsorption of the major tar compound, 2-picoline, derived from the plant cell cultures of Taxus chinensis, using Sylopute while varying parameters such as initial 2-picoline concentration, contact time and adsorption temperature. The experimental data were fitted to the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. Comparison of results revealed that the Langmuir isotherm model could account for the adsorption isotherm data with the highest accuracy among the four isotherm models considered. From the analysis of adsorption isotherms, it was found that adsorption capacity decreased with increasing temperature and the adsorption of 2-picoline onto Sylopute was favorable. The kinetic data were well described by the pseudo-second-order kinetic model, while intraparticle diffusion and boundary layer diffusion did not play a dominated role in 2-picoline adsorption according to the intraparticle diffusion model. Thermodynamic parameters revealed the exothermic, irreversible and non-spontaneous nature of adsorption. The isosteric heat of adsorption decreased as surface loading ($q_e$) increased, indicating a heterogeneous surface.

• Fire Science and Engineering
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• v.33 no.1
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• pp.7-14
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• 2019

While wood pellets are often used as a fuel in thermoelectric power plants and firewood boilers, there is a risk of ignition temperature when strong wood pellets, which have a high calorific value, for prolonged periods of time. In this research study, the minimum auto ignition temperature and the ignition limitation temperature according to the change in flow rate depending on the size of the test vessel were calculated, and based on these temperatures, the apparent activation energy was calculated to predict the combustive properties of the material. The apparent activation energy was calculated to be 190.224 kJ/mol. The thicker the sample is storage in the vessel, the longer the ignition induction time was due to the increased difficulty in heat being transferred from the surface of the vessel to the middle section area of the vessel. For vessel of the same size, the higher the flow rate, the lower the auto ignition temperature was. It was also confirmed that increases in the size of the test vessel lowered the auto ignition temperature and increased the ignition induction time.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.6
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• pp.271-276
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• 2020

In this study, an amorphous SiC block was manufactured using polycarbosilane (PCS), an organosilicon polymer. The dense SiC blocks were easily fabricated in various shapes via pyrolysis at 1100℃, 1200℃, 1300℃, 1400℃ after manufacturing a PCS molded body using cured PCS powder. Physical and chemical properties were analyzed using a thermogravimetric analyzer (TGA), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and universal testing machine (UTM). The prepared SiC block was decomposed into SiO and CO gas as the temperature increased, and β-SiC crystal grains were grown in an amorphous structure. In addition, the density and flexural strength were the highest at 1.9038 g/㎤ and 6.189 MPa of SiC prepared at 1100℃. The manufactured amorphous silicon carbide block is expected to be applicable to other fields, such as the previously reported microwave assisted heating element.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.19-31
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• 2022

With the advent of technologies based on big data, the trend of electronics towards high performance and high integration density continues. However, this development of electronics suffers from overheating issues, which seriously threaten the reliability of the devices. To develop effective strategies for thermal management, it is crucial to accurately evaluate the temperature distribution and design the heat dissipation path within the device in the operating condition. This paper introduces thermoreflectance microscopy that can observe the temperature distribution of a device with high spatial and temporal resolutions in a non-contact way. Specifically, the working principle and various forms of thermoreflectance microscopy are presented along with the latest research trends to improve the temperature, space, and time resolutions. We further review several examples in which thermoreflectance microscopy is applied to investigate the temperature and thermal characteristics of electronic devices.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.4
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• pp.1-10
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• 2021

Recently, electronic components are becoming smaller and highly integrated. As a result, electromagnetic interference (EMI) and heat generation problems must be solved simultaneously with a small area and thickness. Graphene composites and graphite composites are lightweight materials that can simultaneously solve EMI shielding and heat dissipation problems with excellent electrical and thermal conductivity. With the recent development of synthetic technology and composite manufacturing technology, the research to application of their composites is increasing. In this paper, we reviewed the latest researches on composite films of graphene and graphite for EMI shielding and heat dissipation.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.28 no.2
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• pp.143-149
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• 2022

PCS needs to freely switch AC and DC to connect the battery, external AC loads and renewable energy in both directions for energy efficiency. Whenever converting happens, power loss inevitably occurs. Minimization of the power loss to save electricity and convert it for usage is a very critical function in PCS. PCS plays an important role in the ESS(Energy Storage System) but the importance of stabilizing semiconductors on PCB(Printed Circuit Board) should be empathized with a risk of failure such as a fire explosion. In this study, the temperature variation inside PCS was reviewed by cooling fan on top of PCS, and the vibration characteristics of PCS were analyzed during truck transportation for reliability of the product. In most cases, a cooling fan is mounted to control the inner temperature at the upper part of the PCS and components generating the heat placed on the internal aluminum cooling plate to apply the primary cooling and the secondary cooling system with inlet fans for the external air. Results of CFD showed slightly lack of circulating capacity but simulated temperatures were durable for components. The resonance points of PCS were various due to the complexity of components. Although they were less than 40 Hz which mostly occurs breakage, it was analyzed that the vibration displacement in the resonance frequency band was very insufficient. As a result of random-vibration simulation, the lower part was analyzed as the stress-concentrated point but no breakage was shown. The steel sheet could be stable for now, but for long-term domestic transportation, structural coupling may occur due to accumulation of fatigue strength. After the test completed, output voltage of the product had lost so that extra packaging such as bubble wrap should be considered.

• Journal of the Korean Society of Safety
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• v.38 no.1
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• pp.25-33
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• 2023

In this study, we determined the failure rate and fire status of electric motors widely used in domestic and industrial devices and analyzed the associated fire risks by identifying the electrical and temperature characteristics of electric motors under the normal and restrained operation modes in industrial sites and laboratories. A 2.2kW motor used for driving a conveyor during the vulcanization process in a rubber product manufacturing plant was employed as the study object and was exposed to a high- temperature environment as this motor is widely used in industrial sites. The current amplitude was 4.45-4.50 A during normal operation and 38.2-41.5 A during restrained operation due to the pinching of products and semi-finished products (i.e., 8.5 times higher than that during normal operation). The leakage current amplitude was 0.33 mA during both operation modes. The temperature of the workplace in summer was 42.38℃, indicating a poor environment for the installed motor. In the laboratory, the current and temperature of the coil inside a 3.7kW motor were measured under the restrained operation mode as performing measurements of the coil inside the motor in industrial sites is challenging. The current amplitude during normal operation was 3.5 A, whereas that during restrained operation for 30 s was 51.7-58.6 A, which is 14.8-16.7 times higher than that of normal operation. Moreover, the temperature of the motor coil increased from 22.9℃ to 101℃. Based on the experimental data, we derived the temperature increase formula according to the restrained operation time by performing a regression analysis and verified the time at which the temperature exceeded the stipulated limit for the insulation grade. The findings presented in this paper can be utilized to establish fire-prevention measures and perform safety management of motors of the same type or with a similar capacity.

• Journal of Aerospace System Engineering
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• v.18 no.4
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• pp.96-101
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• 2024

The Synthetic Aperture Radar (SAR) is equipped with a Transmitter/Receiver (TR) module, which serves as the signal transmission and reception unit for acquiring image data. The TR module generates significant heat during signal generation and amplification, potentially degrading performance or causing mission failure. Furthermore, launch and operational environments may result in structural damage to the components. Thus, assessing the thermal and structural safety of the TR module through thermal and vibration tests is essential to guarantee its safety. Safety assessments can be verified through environmental tests prescribed in MIL-STD-883. This paper explores the thermal and structural safety characteristics of the TR module by simulating test environments using finite element analysis prior to conducting environmental tests.

• Polymer(Korea)
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• v.39 no.3
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• pp.506-513
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• 2015

Ethylidene norbornene (ENB) and its blends with endo-dicyclopentadiene (endo-DCPD) were prepared and reacted via the ring-opening metathesis polymerization (ROMP) reaction with the $1^{st}$ and $2^{nd}$ generation Grubbs' catalysts. Dynamic exothermic behaviors during ROMP and tensile properties after ROMP were evaluated using a differential scanning calorimeter (DSC) and a universal testing machine (UTM) for the samples, respectively. It revealed that the ROMP rate was accelerated with the less contents of endo-DCPD and under the $2^{nd}$ generation catalyst. Also, the addition of endo-DCPD and the $1^{st}$ generation catalyst resulted in higher tensile modulus and strength but lower toughness. Gel fraction measurement and fracture surface observation were made to understand the tensile properties.