• Korean Journal of Food Science and Technology
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• v.45 no.5
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• pp.531-536
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• 2013

We developed a simple, sensitive, and specific analytical method for prometryn using gas chromatography-mass spectrometry (GC-MS). Prometryn is a selective herbicide used for the control of annual grasses and broadleaf weeds in cotton and celery crops. On the basis of high specificity, sensitivity, and reproducibility, combined with simple analytical operation, we propose that our newly developed method is suitable for use as a Ministry of Food and Drug Safety (MFDS, Korea) official method in the routine analysis of individual pesticide residues. Further, the method is applicable in clams. The separation condition for GC-MS was optimized by using a DB-5MS capillary column ($30m{\times}0.25mm$, 0.25 ${\mu}m$) with helium as the carrier gas, at a flow rate of 0.9 mL/min. We achieved high linearity over the concentration range 0.02-0.5 mg/L (correlation coefficient, $r^2$ >0.998). Our method is specific and sensitive, and has a quantitation limit of 0.04 mg/kg. The average recovery in clams ranged from 84.0% to 98.0%. The reproducibility of measurements expressed as the coefficient of variation (CV%) ranged from 3.0% to 7.1%. Our analytical procedure showed high accuracy and acceptable sensitivity regarding the analytical requirements for prometryn in fishery products. Finally, we successfully applied our method to the determination of residue levels in fishery products, and showed that none of the analyzed samples contained detectable amounts of residues.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.136-152
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• 2017

The thermodynamic models, PC-SAFT (Perturbed-Chain Statistical Associated Fluid Theory) state equation and the Two-model approach liquid activity coefficient model NRTL (Non Random Two Liquid) + Henry + Peng-Robinson, for modeling the Rectisol process using methanol aqueous solution as the $CO_2$ removal solvent were compared. In addition, to determine the new binary interaction parameters of the PC-SAFT state equations and the Henry's constant of the two-model approach, absorption equilibrium experiments between carbon dioxide and methanol at 273.25K and 262.35K were carried out and regression analysis was performed. The accuracy of the newly determined parameters was verified through the regression results of the experimental data. These model equations and validated parameters were used to model the carbon dioxide removal process. In the case of using the two-model approach, the methanol solvent flow rate required to remove 99.00% of $CO_2$ was estimated to be approximately 43.72% higher, the cooling water consumption in the distillation tower was 39.22% higher, and the steam consumption was 43.09% higher than that using PC-SAFT EOS. In conclusion, the Rectisol process operating under high pressure was designed to be larger than that using the PC-SAFT state equation when modeled using the liquid activity coefficient model equation with Henry's relation. For this reason, if the quantity of low-solubility gas components dissolved in a liquid at a constant temperature is proportional to the partial pressure of the gas phase, the carbon dioxide with high solubility in methanol does not predict the absorption characteristics between methanol and carbon dioxide.

• Clean Technology
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• v.25 no.1
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• pp.81-90
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• 2019

A dielectric barrier discharge (DBD) plasma reactor packed with $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst was used for the dry ($CO_2$) reforming of propane (DRP) to improve the production of syngas (a mixture of $H_2$ and CO) and the catalyst stability. The plasma-catalytic DRP was carried out with either thermally or plasma-reduced $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst at a $C_3H_8/CO_2$ ratio of 1/3 and a total feed gas flow rate of $300mL\;min^{-1}$. The catalytic activities associated with the DRP were evaluated in the range of $500{\sim}600^{\circ}C$. Following the calcination in ambient air, the ${\gamma}-Al_2O_3$ impregnated with the precursor solution ($Ni(NO_3)_2$ and $Ce(NO_3)_2$) was subjected to reduction in an $H_2/Ar$ atmosphere to prepare $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst. The characteristics of the catalysts were examined using X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectrometry (EDS), temperature programmed reduction ($H_2-TPR$), temperature programmed desorption ($H_2-TPD$, $CO_2-TPD$), temperature programmed oxidation (TPO), and Raman spectroscopy. The investigation revealed that the plasma-reduced $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst exhibited superior catalytic activity for the production of syngas, compared to the thermally reduced catalyst. Besides, the plasma-reduced $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst was found to show long-term catalytic stability with respect to coke resistance that is main concern regarding the DRP process.

• Korean Chemical Engineering Research
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• v.52 no.6
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• pp.814-820
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• 2014

In this work, hydrate inhibition performance of water-soluble polymers including pyrrolidone, caprolactam, acrylamide types were evaluated using torque measurement and high pressure differential scanning calorimeter (HP ${\mu}$-DSC). The obtained experimental results suggest that the studied polymers represent the kinetic hydrate inhibition (KHI) performance. 0.5 wt% polyvinylcaprolactam (PVCap) solution shows the hydrate onset time of 34.4 min and subcooling temperature of 15.9 K, which is better KHI performance than that of pure water - hydrate onset time of 12.3 min and subcooling temperature of 6.0 K. 0.5 wt% polyvinylpyrrolidone (PVP) solution shows the hydrate onset time of 27.6 min and the subcooling temperature of 13.2 K while polyacrylamide-co-acrylic acid partial sodium salt (PAM-co-AA) solution shows less KHI performance than PVP solution at both 0.5 and 5.0 wt%. However, PAM-co-AA solution shows slow growth rate and low hydrate amount than PVCap. In addition to hydrate onset and growth condition, torque change with time was investigated as one of KHI evaluation methods. 0.5 wt% PVCap solution shows the lowest average torque of 6.4 N cm and 0.5 wt% PAM-co-AA solution shows the average torque of 7.2 N cm. For 0.5 wt% PVP solution, it increases 11.5 N cm and 5.0 wt% PAM-co-AA solution shows the maximum average torque of 13.4 N cm, which is similar to the average torque of pure water, 15.2 N cm. Judging from the experimental results obtained by both an autoclave and a HP ${\mu}$-DSC, the PVCap solution shows the best performance among the KHIs in terms of delaying hydrate nucleation. From these results, it can be concluded that the torque change with time is useful to identify the flow ability of tested solution, and the further research on the inhibition of hydrate formation can be approached in various aspects using a HP ${\mu}$-DSC.

• Journal of the Korean Vacuum Society
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• v.17 no.1
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• pp.16-22
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• 2008

We studied plasma etching of polycarbonate in $O_2/SF_6$, $O_2/N_2$ and $O_2/CH_4$. A capacitively coupled plasma system was employed for the research. For patterning, we used a photolithography method with UV exposure after coating a photoresist on the polycarbonate. Main variables in the experiment were the mixing ratio of $O_2$ and other gases, and RF chuck power. Especially, we used only a mechanical pump for in order to operate the system. The chamber pressure was fixed at 100 mTorr. All of surface profilometry, atomic force microscopy and scanning electron microscopy were used for characterization of the etched polycarbonate samples. According to the results, $O_2/SF_6$ plasmas gave the higher etch rate of the polycarbonate than pure $O_2$ and $SF_6$ plasmas. For example, with maintaining 100W RF chuck power and 100 mTorr chamber pressure, 20 sccm $O_2$ plasma provided about $0.4{\mu}m$/min of polycarbonate etch rate and 20 sccm $SF_6$ produced only $0.2{\mu}m$/min. However, the mixed plasma of 60 % $O_2$ and 40 % $SF_6$ gas flow rate generated about $0.56{\mu}m$ with even low -DC bias induced compared to that of $O_2$. More addition of $SF_6$ to the mixture reduced etch of polycarbonate. The surface roughness of etched polycarbonate was roughed about 3 times worse measured by atomic force microscopy. However examination with scanning electron microscopy indicated that the surface was comparable to that of photoresist. Increase of RF chuck power raised -DC bias on the chuck and etch rate of polycarbonate almost linearly. The etch selectivity of polycarbonate to photoresist was about 1:1. The meaning of these results was that the simple capacitively coupled plasma system can be used to make a microstructure on polymer with $O_2/SF_6$ plasmas. This result can be applied to plasma processing of other polymers.

• Tuberculosis and Respiratory Diseases
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• v.47 no.5
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• pp.609-617
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• 1999

Background: The aims of this study were to assess the etiologies, survival and prognostic factors of patients with chronic cor pulmonale visited Pusan National University Hospital. Methods : This study included 103 patients with chronic cor pulmonale. There were 67 men and 36 women. The diagnosis of chronic cor pulmonale was primarily based on the presence of underlying lung disorder and echocardiographic finding of enlarged or hypertrophied right ventricle. Other clinical data including patients' symptoms and signs, findings of arterial blood gas analysis, hematologic and biochemical laboratory and pulmonary function test were assessed. Results: The most common underlying lung disorder was pulmonary tuberculosis(59.2%) and chronic obstructive pulmonary disease was the next(28.2%). The survival rate was 57% in one year, 45% in two years, and 34% in three years. The prognostic factors were maximal voluntary ventilation(MVV), forced vital capaoity(FVC), $FEV_1$ serum Na, vital capacity(VC), serum albumin and peak expiratory flow(PEF) in univariate analysis. And in multivariate analysis, serum albumin(p=0.0144) and VC(p=0.0078) were statistically significant. Conclusion: Pulmonary tuberculosis was the most important underlying lung disorder in chronic cor pulmonale. The survival rate was 57% in one year, 45% in two years, and 34% in three years. Serum albumin (p=0.0144) and VC(p=0.0078) were statistically significant prognostic factors.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.2
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• pp.94-101
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• 2015

To mitigate the greenhouse gas emission, many carbon capture and storage projects are underway all over the world. In Korea, many studies focus on the storage of $CO_2$ in the offshore sediment. Assurance of safety is one of the most important issues in the geological storage of $CO_2$. Especially, the assessment of possibility of leakage and amount of leaked $CO_2$ is very crucial to analyze the safety of marine geological storage of $CO_2$. In this study, the leakage of injected $CO_2$ through fault was numerically studied. TOUGH2-MP ECO2N was used to simulate the subsurface behavior of injected $CO_2$. The storage site was 150 m thick saline aquifer located 825 m under the continental shelf. It was assumed that $CO_2$ leak was happened through the fault located 1,000 m away from the injection well. The injected $CO_2$ could migrate through the aquifer by both pressure difference driven by injection and buoyancy force. The enough pressure differences made it possible the $CO_2$ to migrate to the bottom of the fault. The $CO_2$ could be leaked to seabed through the fault due to the buoyancy force. Prior to leakage of the injected $CO_2$, the formation water leaked to seabed. When $CO_2$ reached the seabed, leakage of formation water stopped but the same amount of sea water starts to flow into the underground as the amount of leaked $CO_2$. To analyze the effect of injection rate on the leakage behavior, the injection rate of $CO_2$ was varied as 0.5, 0.75, and $1MtCO_2/year$. The starting times of leakage at 1, 0.75 and $0.5MtCO_2/year$ injection rates are 11.3, 15.6 and 23.2 years after the injection, respectively. The leakage of $CO_2$ to the seabed continued for a period time after the end of $CO_2$ injection. The ratios of total leaked $CO_2$ to total injected $CO_2$ at 1, 0.75 and $0.5MtCO_2/year$ injection rates are 19.5%, 11.5% and 2.8%, respectively.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.6
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• pp.1092-1099
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• 2022

Research on exhaust aftertreatment devices to reduce air pollutants and greenhouse gas emissions is being actively conducted. However, in the case of the particulate matters/nitrogen oxides (PM/NOx) simultaneous reduction device for ships, the problem of back pressure on the diesel engine and replacement of the filter carrier is occurring. In this study, for the optimal design of the integrated device that can simultaneously reduce PM/NOx, an appropriate standard was presented by studying the flow inside the device and change in back pressure through the inlet/outlet pressure. Ansys Fluent was used to apply porous media conditions to a diesel particulate filter (DPF) and selective catalytic reduction (SCR) by setting porosity to 30%, 40%, 50%, 60%, and 70%. In addition, the ef ect on back pressure was analyzed by applying the inlet velocity according to the engine load to 7.4 m/s, 10.3 m/s, 13.1 m/s, and 26.2 m/s as boundary conditions. As a result of a computational fluid dynamics analysis, the rate of change for back pressure by changing the inlet velocity was greater than when inlet temperature was changed, and the maximum rate of change was 27.4 mbar. This was evaluated as a suitable device for ships of 1800kW because the back pressure in all boundary conditions did not exceed the classification standard of 68mbar.

• Ecology and Resilient Infrastructure
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• v.9 no.3
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• pp.183-193
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• 2022

The growth inhibitory effect of Microcystis aeruginosa according to the ultrasonic irradiation time was evaluated using a large algae sample volume (10 L) for various ultrasonic irradiation times (0.5, 1, 1.5, 2, 2.5 and 3 hr) at a laboratory scale. Based on the analysis of Chl-a and cell number of M. aerginosa, algae growth inhibition was observed with the decrease in Chl-a and cell number in all experimental groups after the ultrasonic irradiation. For the experimental group (T_B, T_C, T_D) with an ultrasonic irradiation time of less than 2 hours, rapid regrowth of algae was observed after growth inhibition, but the experimental group (T_E, T_F, T_G) with an irradiation time of more than 2 hours successfully inhibited algal growth lasting one or two more days. Based on the comparison of the recovery time to initial cell number the experimental group (T_B, T_C, T_D) took less than 20 days whereas the experimental group (T_E, T_F, T_G) took about 30 days. Correspondingly, the experimental group showed a high first order decay rate (𝜅) in proportion to the ultrasonic irradiation time during the growth inhibition period. Additionally, the specific growth rates (𝜇) during regrowth in the experimental group with irradiation time of more than 2 hours were relatively low compared to those in the experimental group with less than 2 hours. Therefore, ultrasonic irradiation for more than 2 hours is required for long-term (30 days) inhibition of algal growth in stagnant waters. However, the appropriate ultrasonic irradiation time for algae growth inhibition should be determined according to various field conditions such as the volume of stagnant water, water depth, flow rate, algae concentration, etc. Finally, damages to the algal cell surface and cell membrane were clearly observed, and both destruction and disturbance of gas vesicles of M. aeruginosa in the experimental group were discovered, indicating the growth inhibitory effect of Microcystis aeruginosa according to the ultrasonic irradiation time was confirmed.

• Tuberculosis and Respiratory Diseases
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• v.45 no.4
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• pp.813-822
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• 1998

Background: Extubation is recommended to be performed at minimum pressure support (PSmin) during the pressure support ventilation (PSV). In field, physicians sometimes perform additional 1 hr T-piece trial to the patient at PSmin to reduce re-intubation risk. Although it provides confirmation of patient's breathing reserve, weaning could be delayed due to increased airway resistance by endotracheal tube. Methods: To investigate the effect of additional 1 hr T-piece trial on weaning outcome, a prospective study was done in consecutive 44 patients who had received mechanical ventilation more than 3 days. Respiratory mechanics, hemodymic, and gas exchange measurements were done and the level of PSmin was calculated using the equation (PSmin=peak inspiratory flow rate $\times$ total ventilatory system resistance) at the 15cm $H_2O$ of pressure support. At PSmin, the patients were randomized into intervention (additional 1 hr T-piece trial) and control (extubation at PSmin). The measurements were repeated at PSmm, during weaning process (in cases of intervention), and after extubation. The weaning success was defined as spontaneous breathing more than 48hr after extubation. In intervention group, failure to continue weaning process was also considered as weaning failure. Results: Thirty-six patients with 42 times weaning trial were satisfied to the protocol. Mean PSmin level was 7.6 (${\pm}1.9$)cm $H_2O$. There were no differences in total ventilation times (TVT), APACHE III score, nutritional indices, and respiratory mechanics at PSmin between 2 groups. The weaning success rate and re-intubation rate were not different between intervention group (55% and 18% in each) and control group (70% and 20% in each) at first weaning trial. Work of breathing, pressure time product, and tidal volume were aggravated during 1 hr T-piece trial compared to those of PSmin in intervention group ($10.4{\pm}1.25$ and $1.66{\pm}1.08$ J/L in work of breathing) ($191{\pm}232$ and $287{\pm}217$cm $H_2O$ s/m in pressure time product) ($0.33{\pm}0.09$ and $0.29{\pm}0.09$ L in tidal volume) (P<0.05 in each). As in whole, TVT, and tidal volume at PSmin were significantly different between the patients with weaning success ($246{\pm}195$ hr, $0.43{\pm}0.11$ L) and the those with weaning failure ($407{\pm}248$ hr, $0.35{\pm}0.10$L) (P<0.05 in each). Conclusion : There were no advantage to weaning outcome by addition of 1 hr T-piece trial compared to prompt extubation to the patient at PS min.