• Journal of Energy Engineering
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• v.23 no.4
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• pp.240-246
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• 2014

The present study has been carried out to reduce the heat loss from a refrigerator by changing thermal conductivity and partial removal of rubber magnet near refirgerator gasket. To perform this purpose, two dimensional heat transfer analysis for the horizontal cross sectional plane of a refrigerator has been accomplished. From the present study, it could be seen that the heat loss could be reduced nearly 7% by changing thermal conductivity of rubber magnet from 10W/mK to 1W/mK. The heat loss reduction, 17%, could be achieved by removal of rubber magnet near hotline and the effect on the heat loss reduction by partial removal of rubber magnet might be helpful for the refrigerator power consumption.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.27 no.4
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• pp.423-432
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• 2017

Objectives: This study was conducted to evaluate asbestos handling history of workers at automobile manufacturing plants in Korea. Methods: National regulations on asbestos and Korea Occupational Safety and Health Agency(KOSHA) database on the information of asbestos containing products were reviewed. We investigated asbestos related materials from one automobile manufacturing plant. Material safety data sheets(MSDS) collected in 2010, work environment monitoring results reported from 2000 to 2013, trade union reports and asbestos survey reports were reviewed. We also interviewed workers with long career and did walk-through survey. Results: The Ministry of Labor in Korea has permitted asbestos manufacturing since 1990. In 1997, the use of crocidolite and amosite asbestos were banned. In 2007, the Korean government announced a total ban on the manufacturing, importation and use of all kinds of asbestos, which took full effect in 2009. A total of 174 asbestos products information from KOSHA database was analyzed. Extruded cement panel for building, special brake for crane farm machinery, gasket, joint sheet and thermal insulator were produced until 2007. From automobile manufacturing plant survey, we confirmed that asbestos containing materials(ACM) such as gasket, heating induction materials have been used until 2011. Asbestos containing building materials(ACBM) such as bamlites, slate and ceiling tex were reported at 122 asbestos dismantling projects in 2014. Conclusion: Although the use of all kinds of asbestos were banned from 2009, ACMs and ACBMs installed before 2009 were still found at automobile manufacturing plant until 2011 and 2014 respectively. In particular, asbestos slates should be managed because most of slates had not been removed until 2014.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.1
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• pp.34-41
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• 2018

A flange joint is a pipe connection used to prevent the leakage of high-pressure fluids by inserting a gasket and tightening the bolts. Among several kinds of gaskets available, metal ring type joint gaskets are most widely used in conditions that require high-temperature and high-pressure fluid flow, such as oil pipelines, gas pipes, pumps, valve joints, etc. The purpose of this study is to investigate the contact pressure and stress characteristics closely related to the sealing performance of Class 900 flange joints used in high temperature and high pressure environments. The dimensions of flange joints with five different nominal pipe sizes were determined with reference to those specified in ASME 16.5. The metal ring gaskets inserted in the joints were octagonal and oval gaskets. The bolt tensile forces calculated from the tightening torques were input as the bolt pretension loads in order to determine the contact pressure and stress levels after fastening. Loading was composed of three steps, including the fastening step, and different amounts of applied pressures were used in each analysis to investigate the effect of fluid pressure on the contact force of the joints. A general-purpose software, ANSYS 17.2, was used for the analysis.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.470-475
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• 2013

In this study, we report that effects of a filler with a high coefficient of thermal expansion on a sealant for high-temperature ($750{\sim}850^{\circ}C$) SOFC. We designed a $SiO_2-BaO-ZnO-B_2O_3-Al_2O_3$ glass system with a softening temperature higher than $750^{\circ}C$. The properties of the glass system show not only low volumetric shrinking but also low swelling. The glass system did not create a crystal phase during along-term heat treatment. We fabricated a seal gasket with 0, 10, 15, and 20 wt% cristobalite added as filler materials with glass powder. The coefficient of thermal expansion of the seal gasket increased according to cristobalite content. During along-term heat treatment, the leak rate decreased by about 5% after a heat treatment in an oxidizing atmosphere at $750^{\circ}C$ for 2000 h, also decreasing by about 6% after a heat treatment in a reducing atmosphere at $750^{\circ}C$ for 1000 h.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.9-17
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• 2012

This study is dealt with the experimental seam strength of deep corrugated steel plate which is used as underpasses, storm sewers and other buried applications. The soil-metal structure using deep corrugated plate should be sufficient to ensure safety for compressive loading. The experimental and theoretical results on the seam strength are accumulated enough to take the design guideline, even if the seam strength at the bolt connected lap joint in construction site can be varied depending on the connection detailing and the thickness of plate. In this study, compressive behavior of bolted lap jointed plates using various connection detail such as gasket, slot hole, washer was experimentally analyzed. From the test, failure pattern with an increases in the thickness of specimens was changed from plate bearing to bolt shearing. In case of thicker plates than 6.0mm, the structural performance of lap joint using gasket and slot hole is more effective than it of the plate adopted washer.

• Earthquakes and Structures
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• v.17 no.4
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• pp.411-424
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• 2019

In this study, a numerical model of a shield tunnel with an assembled segmental lining was built. The seismic response of the segmental lining of the section of the shield tunnel in Line 1 of the Chengdu Metro is analyzed as it passes through the interface of sand-cobble and mudstone layers. To do so, the node-stress seismic-motion input method was used to input the seismic motion measured during the 2008 Wenchuan earthquake, and the joint openings and dislocations associated with the earthquake action were obtained. With reference to the Ethylene-Propylene-Diene Monomer (EPDM) sealing gaskets used in the shield tunnels in the Chengdu Metro, numerical simulation was applied to analyze the contact pressure along the seepage paths and the waterproof property under different joint openings and dislocations. A laboratory test on the elastic sealing gasket was also conducted to study its waterproof property. The test results accord well with the numerical results and the occurrence of water seepage in the section of the shield tunnel in Line 1 of the Chengdu Metro during the 2008 Wenchuan earthquake was verified. These research results demonstrate the deformation of segmental joint under earthquake, also demonstrate the relationship between segmental joint deformation and waterproof property.

• Applied Chemistry for Engineering
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• v.22 no.2
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• pp.149-154
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• 2011

In order to explore properties of various rubber compounds after thermal aging under the condition similar to the operating environment of a fuel cell-stack, heat resistance and compression set of those compounds were investigated for a long term operation in $H_2SO_4$, $H_2O$, and LLC (ethylene glycol : $H_2O=50:50$) solution. It was assumed that aging Acrylonitrile butadiene rubber (NBR) and Elthylene Propylene diene rubber (EDPM) compound in the solution resulted in discoloration as time passed. It was also found that hydrolysis was developed on the Silicone rubber (VMQ) compound intentionally aged under acidic condition by means of TGA, SEM, and EDS analysis.

• New Physics: Sae Mulli
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• v.69 no.10
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• pp.1107-1114
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• 2019

Producing extremely stable high temperature and pressure condition is crucial in order to synthesize novel materials with various functions and to investigate their static and dynamic properties. Already a high pressure in the Mbar range, which is necessary to make novel materials, can be acquired by using a Diamond Anvil Cell (DAC), In this study, a laser-heating system combined with the DAC was designed and installed using two 1064-nm, 100-W fiber lasers on different sides of the DAC to heat the sample and three spectrometers to measure the temperature, pressure, and Raman spectra. A stainless-steel gasket, which is generally used as a sample chamber in high-pressure experiments, was heated to make a thermal radiation source, and the temperature of the heated gasket was obtained by measuring the spectrum of the radiation. By applying this technique, we were able to make various materials and to investigate their physical properties under extreme conditions.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.123.1-123.1
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• 2010

The solid oxide fuel cell (SOFC) has attracted great deal of attention due to its high electrical efficiency, high waste-heat utilization, fuel flexibility, and application versatility. However, SOFC technology is still not matured enough to fulfill the practical requirements for commercialization. Therefore, all the research and development activities are mainly focused on a development of practically viable SOFCs with higher performance and better reliability. We were successful in fabricating high-performance anode-supported unit cells by employing hierarchically controlled multi-layered electrodes for both structural reliability and high performance. In addition, a novel composite sealing gasket made it possible to achieve excellent sealing integrity even with considerable surface irregularities in a multi-cell planar arrayed stack.

• Bulletin of the Korean Chemical Society
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• v.26 no.11
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• pp.1723-1727
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• 2005

A generalized fractional diffusion equation (FDE) is presented, which describes the time-evolution of the spatial distribution of a particle performing continuous time random walk (CTRW) on a fractal lattice. For a case corresponding to the CTRW with waiting time distribution that behaves as $\psi(t) \sim (t) ^{-(\alpha+1)}$, the FDE is solved to give analytic expressions for the Green’s function and the mean squared displacement (MSD). In agreement with the previous work of Blumen et al. [Phys. Rev. Lett. 1984, 53, 1301], the time-dependence of MSD is found to be given as < $r^2(t)$ > ~ $t ^{2\alpha/dw}$, where $d_w$ is the walk dimension of the given fractal. A Monte-Carlo simulation is also performed to evaluate the range of applicability of the proposed FDE.