• Transactions of Materials Processing
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• v.4 no.4
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• pp.345-352
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• 1995

Warm deep drawing for optimum forming conditions to give the maximum drawing depth is investigated and compared with the results from experiments performed at room temperature. Experiments which draw square cups of STS 304 stainless steel sheet under the constant lubrication condition of teflon film are made both in a crank and hydraulic press for two kinds of specimens. The maximum drawing depth at warm forming condition reaches 1.4 times the drawing depth at room temperature in a crank press, whereas 1.6 times in a hydraulic press, and also more uniform distribution of thickness in case of warm deep drawn cup is observed. The effects of other factors on formability, such as forming temperature, speed of press and cooling of punch are examined and discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.209-214
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• 1995

This paper describes that the effects of punch speed and temperatures of the die and the blank holder on the drawability are examined. Up to now, multi-stage of dies sets have been used generally at room temperature in deep drawing of rectangular shaped components. But using local heating, it is shown that one stage of die set was capable of deep drawing and the drawability was increased and sheet thickness of component was drawn somewhat uniformly. Rectangular deep drawing experiments on two kinds of stainless steel STS316L, STS430 of 1.0 mm thickness have been conducted using local heating. The limiting drawing height can be increased by heating the die and the blank holder up to 100 .deg. C at STS316L. Commercial lubricants hadn't an effect on drawability in rectangular deep drawing, but vinyl and teflon film had an effect on it.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.698-703
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• 2004

In this study, mode I interlaminar fracture phenomena of carbon fabric/epoxy composite for tilting train were investigated. Specimens were 25mm $\times$ 180mm $\times$ 4.7mm with an initial artificial delamination of 65mm at one end. This delamination with the thickness of 12.5$\mu$m and 25$\mu$m (teflon film) was used. Mode I interlaminar fracture toughness was measured using the double cantilever beam and the fractured surfaces were examined through a scanning electron microscope. The experimental results obtained in this study would be applicable in the design and structural analysis of the composite structures.

• Korean Journal of Materials Research
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• v.18 no.2
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• pp.69-72
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• 2008

A sensor element array for combinatorial solution deposition research was fabricated using LTCC (Low-temperature Co-fired Ceramics). The designed LTCC was co-fired at $800^{\circ}C$ for 1 hour after lamination at $70^{\circ}C$ under 3000 psi for 30 minutes. $SnO_2$ sol was prepared by a hydrothermal method at $200^{\circ}C$ for 3 hours. Tin chloride and ammonium carbonate were used as raw materials and the ammonia solution was added to a Teflon jar. 20 droplets of $SnO_2$ sol were deposited onto a LTCC sensor element and this was heat treated at $600^{\circ}C$ for 5 hours. The gas sensitivity ($S\;=\;R_a/R_g$) values of the $SnO_2$ sensor and 0.04 wt% Pd-added $SnO_2$ sensor were measured. The 0.04 wt% Pd-added $SnO_2$ sensor showed higher sensitivity (S = 8.1) compared to the $SnO_2$ sensor (S = 5.95) to 200 ppm $CH_3COCH_3$ at $400^{\circ}C$.

• Journal of Chest Surgery
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• v.10 no.1
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• pp.82-89
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• 1977

A rupture of a dissecting aneurysm of the aorta is life threatening disease and calls for emergency surgical treatment. The author recently experienced one case of ruptured dissecting aneurysm of the descending thoracic aorta complicated with left hemothorax who was recovered after emergency operation of Aug. 11, 1976. The patient was a 43 years old farmer with known hypertension [260/120] for 20 years but without any venereal disease and had experienced sudden throbbing chest pain. Chest film and aortogram revealed this case ruptured aneurysm of descending thoracic aorta complicated with left hemothorax. In this case, large dissecting aneurysm extend from proximal part of left subclavian artery below diaphragm and involved with 3.0 and 4.0cm sized elliptical rupture in proximal part of descending thoracic aorta. And so, neither fenestration procedure nor replacement of dacron artificial vessel was suitable for this case. Finally, only the rupture site of aneurysm was treated by covering with fibrous pleura and teflon patch. The post-operative management of this case was planned to control hypertension with antihypertensive drugs. The follow-up was possible up to date about 2months. The patient has been doing well with ordinary activities except mild chest discomfort.

• Journal of the Korean Society for Railway
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• v.8 no.6 s.31
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• pp.573-580
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• 2005

Model I interlaminar fracture behaviors of the carbon/epoxy composite, one of the candidate composites for a tilting train carbody, were investigate by the use of DCB(Double cantilever beam) specimens. These specimens were made of CF3327 plain woven fabric with epoxy resin, and an artificial starter delamination was fabricated by inserting Teflon film with the thickness of $12.5{\mu}m$ of $25.0{\mu}m$ at the one end of the specimen. Mode I interlaminar fracture toughness was evaluated for the specimens with the different thickness of an inserter. Also delamination propagating behaviors and interlaminar fracture surface were examined through an ooptical travelling scope and a scanning electron microscope. We found that abruptly unstable crack propagation called as stick-slip phenomena was observed. In addition, interlaminar fracture behaviors were affected on the location and the morphology of a crack tip as well as an interface region.

• Journal of the Korean Applied Science and Technology
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• v.40 no.4
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• pp.913-923
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• 2023

In this study, a triboelectric nanogenerator was fabricated using the composite of teflon-based polymer and graphene flower, which are stable in air and have relatively high electronegativity. The composite was used to fabricate an electronegative layer of a nanogenerator using a spin-coating method. For the electropositive layer, a zinc oxide film was prepared using a sol-gel method. The fabricated triboelectric nanogenerator produced a maximum power of about 44 ㎼. In conclusion, since all the active layers of the triboelectric nanogenerator was made by the solution process, it is scalable to a large area.

• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2592-2598
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• 2022

Research groups in the field of PET instrumentation are studying time-of-flight(TOF) technology to improve the signal-to-noise ratio of PET images. Scintillation light transport and collection plays an important role in improving the coincidence resolving time(CRT) of PET detector based on a pixelated crystal array. Four crystal arrays were designed by the different optical reflection configuration such as external reflectors and surface treatment on the CRT and compared with the light output, energy resolution and CRT. The design proposed in the study was composed of 8 × 8 LYSO crystal array consisted of 3 × 3 × 15 mm³ pixels. The entrance side was roughened while the other five surfaces were polished. Four sides of all crystal pixels were wrapped with ESR-film, and the entrance surface was covered by Teflon-tape. The design provided an excellent timing resolution of 210 ps and improved the CRT by 16% compared to the conventional method using a polishing treatment and ESR-film. This study provided a method for improving the light output and CRT of a pixelated scintillation crystal-based brain TOF PET detector. The proposed configuration might be an attractive detector design for TOF brain PET requiring fast timing performance with high cost-effectiveness.

• Membrane Journal
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• v.14 no.2
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• pp.173-184
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• 2004

For the application of direct methanol fuel cell (DMFC), sulfonated polystyrene/teflon (PS/PTFE) composite membranes were developed by changing monomer ratio of styrene and DVB. The composite membranes were prepared as follows: first, the monomer mixtures consisting of styrene, divinyl benzene and AIBN were impregnated in porous PTFE film and then, polymerized under 8$0^{\circ}C$ to give PS/PTFE membranes. Finally, the membranes were reacted with chlorosulfonic acid in 1,2-dichloroethane to give the sulfonated composite membranes. The measurements of ATR-FTIR, SEM, solvent uptake test and ion exchange capacity (IEC) were done for the resulting membranes before or after sulfonation, respectively, which showed the composite membranes with proper crosslinking degree and sulfonic acid content were prepared well as a function of styrene/DVB ratio. ion conductivity and methanol permeability were studied for the sulfonated membranes. It was found that with decreasing the ratio of styrene/DVB, methanol permeability decreased from $6.6{\times}10^{-7}∼1.3{\timas}10^{-7}$ $\textrm{cm}^2$/s, which are much lower values than that of Nafion$^{(R)}$117($1.02{\times}10^{-6}$ $\textrm{cm}^2$/s). Under the same monomer condition, ion conductivity decreased from 0.11 S/cm ($25^{\circ}C$) to 0.08 S/cm ($25^{\circ}C$), which are similar or a little higher values compared with $Nafion^{(R)}117 (1.02{\times}10^{-6}$ $\textrm{cm}^2$/s, 0.0824 S/cm). These two results confirmed the composite membranes prepared could be applied successfully to DMFC.C.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.3
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• pp.353-363
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• 2007

To differentiate temperature effect from the light intensity effect on the formation of secondary products during the photooxidation of toluene-$NO_x$-air mixtures, steady-state air temperature was changed from $20^{\circ}C\;to\;33^{\circ}C$ at the same light intensity of $0.39min^{-1}$ in an indoor smog chamber. Smog chamber consisted of 64 blacklights and a $5.8m^3$ reaction bag made of Teflon film. Air temperature was controlled by an air-conditioning system. The starting time for rapid conversion of NO to $NO_2$ was slightly delayed with decreasing air temperature. In contrast to light intensity effect, the ozone formation time and the ozone production rate were insensitive to air temperature. Although the formation time for secondary organic aerosols was not changed, the particle number concentration increased with temperature. However, the newly formed secondary organic aerosol mass at lower temperature was higher than that at higher temperature. Since light intensity significantly affected the starting time and quantity of ozone and aerosol formation, it is considered that the temperature could contribute partly the quantity of aerosol formation during the photooxidation of toluene-$NO_x$-air mixtures.