• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.198-204
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• 2019

For the removal of carbon dioxide from the chemical process, a chemical absorption method is typically used industrially. Development of new processes for the removal of carbon dioxide by the chemical absorption method has been developing new absorbents by using various absorbents. Thermodynamic data of the sorbent mixture in the new process design using hybrid absorbent is essential to reduce the equipment cost and operating costs of the process. In this study, densities of water+diisopropanolamine (DIPA), DIPA+MDEA(Methyldiethanolamine) binary systems and Water+DIPA+MDEA ternary system were measured over the full range of composition at temperatures from 303.15 K to 333.15 K by using an Anton Paar digital vibrating tube densimeter (DMA4500). The experimental excess volumes have been obtained from the experimental density results and have been fitted using the Redlich-Kister-Muggianu expression. The parameters obtained from the binary excess volume data were used for the correlation of ternary system with one additional ternary parameter for each isotherm. All investigated binary and ternary systems are completely miscible, because the values of excess volume are negative under the examined conditions.

• Composites Research
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• v.32 no.1
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• pp.78-84
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• 2019

This study focused on the prediction of the long-term performance of carbon fiber/epoxy composites using Dynamic Mechanical Analysis (DMA) and Time-Temperature Superposition (TTS). Single-frequency test, multi-frequency test, and creep TTS test were performed. A sinusoidal load of $20{\mu}m$ amplitude was applied while increasing the temperature from $-30^{\circ}C$ to $240^{\circ}C$ at $2^{\circ}C/min$ for the single-frequency test and the multi-frequency test. The frequencies applied to the multi-frequency test were 0.316, 1, 3.16, 10 and 31.6 Hz. In the creep TTS test, a stress of 15 MPa was applied for 10 minutes at every $10^{\circ}C$ from $-30^{\circ}C$ to $230^{\circ}C$. The glass transition temperature was determined by single-frequency test. The activation energy and the storage modulus curve for each temperature were obtained from glass transition temperature for each frequency by the multi-frequency test. The master curve for the reference temperature was obtained by applying the shift factor using the Arrhenius equation. Also, TTS test was used to obtain the creep compliance curves for each temperature and the master curve for the reference temperature by applying the shift factors using the manual shift technique. The master curve obtained through this process can be applied to predict the long-term performance of carbon fiber/epoxy composites for a given environmental condition.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.623-626
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• 2011

Various poly(amic acid)s were synthesized from PMDA/BPDA/p-PDA/ODA with different mole ratios and effectively converted into 4-component polyimide films by thermal imidization. The chemical structures and thermo-mechanical properties of polyimide films were examined using Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric analyzer (TGA), thermo-mechanical analyzer (TMA), dynamic mechanical analyzer (DMA) and universal tensile machine (UTM). The tensile strength, modulus, and thermal properties of polyimides films increased with the amount of rigid PMDA and p-PDA, while the elongation and moisture absorption of polyimide films increased with the amount of flexible BPDA and ODA. One of 4-component polyimide films exhibited a similar coefficient of thermal expansion (CTE) value to that of copper when it was composed of PMDA : BPDA : p-PDA : ODA with the ratio of 5 : 5 : 4 : 6. Thus, this polyimide film could be useful for a base film for flexible copper clad laminates (FCCL) of flexible printed circuit boards.

• Bulletin of the Korean Chemical Society
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• v.32 no.spc8
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• pp.3074-3080
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• 2011

We synthesized three novel poly(norbornene bisimide)s by ring opening metathesis polymerization (ROMP) and subsequent hydrogenation. Their thermal, mechanical and optical properties were investigated with TGA, DMA, UV-Vis spectrometer, and optical reflectometer. The new polymers showed high glass transition temperatures over $260^{\circ}C$ and good thermal stability with 5% wt-loss temperature higher than $390^{\circ}C$. When solvent casted, they yielded optically transparent and dimensionally stable films with a relatively low coefficient of thermal expansion of about 50 ppm $K^{-1}$. Therefore, the bisimide moieties substantially enhanced thermal and dimensional stabilities, as compared with normal ROMP-prepared polynorbornene films. Though the water uptake was increased to 0.6 wt-%, this water uptake is still considerably lower than that for polyethersulfones (1.4 wt-%) or polyimides (2.0 wt-%). Hence, the new poly(norbornene bisimide)s may become attractive candidates for flexible substrates of optoelectronic devices such as displays and photovoltaic solar cells.

• Biomaterials and Biomechanics in Bioengineering
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• v.2 no.4
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• pp.237-248
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• 2015

"Dynamic stabilization" systems have been developed in recent years to treat degenerative disorders of the spinal column. In contrast to arthrodesis (fusion), the aim here is to conserve intervertebral mobility to maximize comfort. When developing innovative concepts, many mechanical tests need to be carried out in order to validate the different technological solutions. The present study focuses on the B Dyn$^{(R)}$ "dynamic stabilization" device (S14$^{(R)}$ Implants, Pessac, France), the aim being to optimize the choice of polymer material used for one of the implant's components. The device allows mobility but also limit the range of movement. The stiffness of the ring remains a key design factor, which has to be optimized. Phase one consisted of static tests on the implant, as a result of which a polyurethane (PU) was selected, material no.2 of the five elastomers tested. In phase two, dynamic tests were carried out. The fatigue resistance of the B Dyn$^{(R)}$ system was tested over five million cycles with the properties of the polymer elements being measured using dynamic mechanical analysis (DMA) after every million cycles. This analysis demonstrated changes in stiffness and in the damping factor which guided the choice of elastomer for the B Dyn$^{(R)}$ implant.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.2
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• pp.251-259
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• 2000

The ionic wind formed in a nonuniform electric field has been recognized to have a significant effect on particle collection in an electrostatic precipitator(ESP). Under normal operating conditions the effect of ionic wind is not pronounced. However, as the flow velocity becomes smaller, the ionic wind becomes pronounced and induces secondary flow, which has a significant influence on the flow field and the particle collecting efficiency. In this paper, experiments for investigating the effect of secondary flow on collection efficiencies were carried out by changing the flow velocities in 0.2-0.7m/s and the applied voltages in 9-11kV/cm. The particle size distributions and concentrations are measured by DMA and CNC. To analyze the experimental results, numerical analysis of electric filed in ESP was carried out. It shows that particle collection is influenced by two independent dimensionless numbers, $Re_{ehd}\;and\;Re_{flow}$ not by $N_{ehd}$ alone. When $Re_{flow}$, decreases for constant $Re_{ehd}$, the secondary flow prohibits the particle collection. But when $Re_{ehd}$ increases for constant $Re_{flow}$, it enhances the particle collection by driving the particles into the collection region.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.349-358
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• 2004

A low pressure impactor is an impaction device to separate airborne particles into aerodynamic size classes at low pressure condition. We designed a two-stage low-pressure impactor to classify submicron sized environmental aerosols. Performance evaluation was carried out for stages 1 and 2 by using an electrical method. Monodisperse liquid dioctyl sebacate (DOS) particles were generated using evaporation-condensation process followed by electrostatic classification using a DMA (differential mobility analyzer). The test particles were in the range of 0.08∼0.8$\mu\textrm{m}$. For the evaluation of the impactor we used two electrometers; one was connected to the impaction plate of the impactor and the other was to the Faraday cage used as a backup filter. The effect of polydispersity of test aerosols on the performance was investigated. The results showed that the experimental 50-% cutoff diameters at each impactor's operation pressure were 0.53 and 0.187$\mu\textrm{m}$ for stages 1 and stage 2, respectively. The effects of operation pressure on the cutoff diameter and the steepness of collection efficiency curves were also investigated.

• YAKHAK HOEJI
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• v.38 no.1
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• pp.24-30
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• 1994

Nitric oxide(NO) synthase was identified and characterized by determining the L-citrulline formed in the NO-Arg pathway in pancreatic tissues. NO synthase activities in chicken pancreas were dependent upon the concentration of L-Arg which is the substrate molecule for the NO synthase, the amount of the enzyme protein used, and linearly on the incubation time. NO synthase in mouse pancreas was found to be constitutive, not induced by lipopolysaccharide treatment. In vitro NO synthase activities of chicken pancreas were inhibited 36%, 21%, 12% and 44% by $200\;{\mu}M$ of MMA, DMA, D'MA and NAME respectively. These results suggest the presence of NO and NO synthase in the pancreas.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.4 s.175
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• pp.824-829
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• 2000

The industries use polymer materials for many purposes because they have many merits. But these materials' costs take up too much proportion in overall cost of products that use these materials as their major material. So it is very economical for polymer industries to reduce these costs. Microcellular foaming process appeared in 1980's to solve this problem and it proved to be quite successful. This process uses inert gases such as CO2, N2. As these gases are dissolved into polymer matrices. many properties are changed. Glass transition temperature is one of these properties. DSC, DMA are devices that measures this temperature, but these are not sufficient to measure the temperature of polymer containing gas. In this paper, we devised a new tester that uses magnetism. We used this device to acquire data of the change of glass transition temperature and made Cha-Yoon model that can predict the change of glass transition temperature. Using this model, the change of this temperature can be estimated as a function of weight gain of gas. Cha-Yoon model proved that Chow's model is inappropriate to predict the change of glass transition temperature of polymer matrices containing gas.

• Journal of Food Hygiene and Safety
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• v.12 no.2
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• pp.125-131
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• 1997

Gulbi, salted and dried yellow corvenia, is a favorite diet food in Korea from the ancient times. A Few studies have dealt with sanitary concerns related to its products, while a number of investigators studied its taste compounds. This study attemps to establish the basic data for ensuring the safety of Gulbi. The contents of nitrate and nitrite were detected 1.2 and <0.1 mg/kg in raw sample, but their contents were detected 3.6~3.9 and 1.2~2.0 mg/kg during its processing and storage of Gulbi, respectively. TMAO contents decreased while betaine, TMA, DMA and formaldehyde increased in yellow corvenia during its processing and storage. Recovery from raw, salted, salt-dried and stored sample spiked with 10$\mu\textrm{g}$/kg for NDBA was 83.2~102.7% average 92.7%). N-nitrosamine such as NDMA, NDEA and NDPA was not detected in raw sample and drastically increased during Gulbi processing and storage. The levels of NDMA, NDEA and NDPA in Gulbi stored for 30 days were about 2.7,4.5 and 5.3 times higher than those in salted sample, respectively. Regardless of cooking methods, NDMA, NDEA and NDPA during cooking when sample were cooked using direct heating methods such as a gas and a briquet fire than when sample were cooked using indirect methods such as an microwave oven and a fried pan. Indirect cooking methods was effective to minimize the N-nitrosamine formation such as NDMA, NDEA and NDPA during cooking of Gulbi.