• Journal of Korean Society of Water and Wastewater
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• v.38 no.3
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• pp.165-175
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• 2024

The dissolved air at the bottom layer of the deep aeration tank transforms into fine gas bubbles within the MLSS (Mixed Liquor Suspended Solid) floc when exposed to the atmosphere. MLSS floc flotation occurs when MLSS from the deep aeration tank enters the secondary clarifier for solid-liquid separation, as dissolved air becomes fine air within the MLSS floc. The floated MLSS floc causes a high SS (Suspended Solid) concentration in the secondary effluent. The fine air bubbles within the MLSS floc must be removed to achieve stable sedimentation in the secondary clarifier. Fine bubbles within the MLSS floc can be removed by air sparging. The settleability of MLSS was measured by sludge volume indexes (SVIs) after air sparging MLSS taken at the end of the deep aeration tank. MLSS settling tests were performed at MLSS heights of 200, 300, 400, and 500 mm, and compressed air was fed at the bottom of the settling column with air flow rates of 100, 300, and 500 ml/min at each MLSS height, respectively. Also, at each height and air flow rate, air was sparged for 3, 5, and 7 minutes, respectively. SVI was determined for each height, air flow rate, and sparging time, respectively. Experimental results showed that a 300 mm MLSS height, 300 ml/min air flow rate, and 3 minutes of sparging time were the least conditions to achieve less than 120 ml/g of SVI, which was the criterion for good MLSS settling in the secondary clarifier.

• Applied Microscopy
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• v.52
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• pp.5.1-5.10
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• 2022

The use of Pipelines for long-distance transportation of crude oil, natural gas and similar applications is increasing and has pivotal importance in recent times. High specific strength plays a crucial role in improving transport efficiency through increased pressure and improved laying efficiency through reduced diameter and weight of line pipes. TRIP-based high-strength and high-ductility alloys comprise a mixture of ferrite, bainite, and retained austenite that provide excellent mechanical properties such as dimensional stability, fatigue strength, and impact toughness. This study performs microstructure analysis using both Nital etching and LePera etching methods. At the time of Nital etching, it is difficult to distinctly observe second phase. However, using LePera etching conditions it is possible to distinctly measure the M/A phase and ferrite matrix. The fraction measurement was done using OM and SEM images which give similar results for the average volume fraction of the phases. Although it is possible to distinguish the M/A phase from the SEM image of the sample subjected to LePera etching. However, using Nital etching is nearly impossible. Nital etching is good at specific phase analysis than LePera etching when using SEM images.

• Tuberculosis and Respiratory Diseases
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• v.40 no.3
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• pp.267-273
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• 1993

Background: Panting method for airway resistance measurement has the disadvantages of departing from the normal breathing pattern and of difficult for some patients to perform. We can measure airway resistance during quiet breathing under more physiologic conditions. Airway resistance is often measured during panting but attempts have been made to facilitate resistance measurements during quiet breathing. This study was designed to compare airway resistance measurements during panting with those during quiet breathing. Method: The 24 normal persons and 29 pulmonary disease patients were included in this study. Spirometry was performed and airway resistance measurement was also done during panting and quiet breathing concomittently. Results: The results were as follows; 1) High correlations were found between airway resistance measurements during panting and quiet breathing. 2) Resistance fell during panting, 21.2% in Raw tot, and 22.1% in Raw 0.5. 3) In normal persons, airway resistance fell more during panting when comparing to those in pulmonary disease patients. 4) This was largely independent of thoracic gas volume differences, because the specific airway conductance rose significantly during panting 5) The patients in whom resistance didn't fell during panting was supposed to the patients who couldn't perform panting successively because of high resistance. Conclusions: Although airway resistance can be measured during panting or quiet breathing according to the patient's performance, we must consider resistance fell during panting, by a mean 20%. It may be concluded that quiet breathing is more likely than panting to provide a relevant measurement of airway resistance.

• Journal of Animal Environmental Science
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• v.9 no.2
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• pp.93-102
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• 2003

This study designed and constructed an experimental column far adhesion efficiency test and conducted experiment to investigate the offensive odor adhesion efficiency of filter bed materials. The offensive odor adhesion experiment was conducted using mixture of high physical adhesion efficiency material, and the fixity of deodorization microorganism of selected filter bed material was tested using ammonia exclude microorganism A4-­2 and sulfur oxidation microorganism S5­-5.2 those were cultured at the Agricultural Chemical Department of Chungnam National University, and deodorization efficiency of selected filter bed material mixture was tested. Following are summary of these tests results. 1. Amount of elimination of the offensive odor gas of ammonia and hydrogen sulfide per unit volume was 0.054 and 0.016$\ell/\textrm{cm}^3$ in rice hull, 0.01 and 0.004 $\ell/\textrm{cm}^3$ in rice straw 0.158 and 0.01 $\ell/\textrm{cm}^3$ in coconut, 0.014 and 0.02$\ell/\textrm{cm}^3$ perlite, 0.004 and 0.003$\ell/\textrm{cm}^3$ in high road ball, and 0.112 and 0.015 $\ell/\textrm{cm}^3$ in chaff of pine, respectively. 2. Amount of elimination of offensive odor gas of ammonia and hydrogen sulfide per unit volume was 0.045 and 0.014$\ell/\textrm{cm}^3$ in mixture 1, 0.079 and 0.016$\ell/\textrm{cm}^3$ in mixture 2, 0.123 and 0.017 $\ell/\textrm{cm}^3$ in mixture 3, 0.031 and 0.015$\ell/\textrm{cm}^3$ in mixture 4, 0.055 and 0.016$\ell/\textrm{cm}^3$ in mixture 5, and 0.111 and 0.020$\ell/\textrm{cm}^3$ in mixture 6, respectively. 3. The offensive odor elimination microorganism inoculated to mixture of chaff of pine(70%) and perlite(30%) showed the elimination efficiency of 99.06% and 96.61% against the ammonia and hydrogen sulfide, respectively, during 24 hours period.

• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.146-152
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• 2005

The activated carbon was produced from Sancheong bamboo by carbon dioxide gas activation methods. The carbonization of raw material was conducted at $900^{\circ}C$, and $CO_2$ activation reactions were conducted under various conditions: activation temperatures of $750-900^{\circ}C$, flow rates of carbon dioxide $5-30cm^3/g-char{\cdot}min$, and activation time of 2-5 h. The yield, adsorption capacity of iodine and methylene blue, specific surface area and pore size distribution of the prepared activated carbons were measured. The adsorption capacity of iodine (680.8-1450.1 mg/g) and methylene blue (23.5-220 mg/g) increased with increasing activation temperature and activation time. The adsorption capacity of iodine and methylene blue increased with the $CO_2$ gas quantity in the range of $5-18.9cm^3/g-char{\cdot}min$. But those decreased over those range due to the pore shrinkage. The specific volume of the mesopore and macropore of bamboo activated carbon were $0.65-0.91cm^3/g$. Because of this large specific volume, it can be used to the biological activated carbon process. Bamboo activated carbon phisically adsorbed the $CO_2$ of maximum 106 mg/g-A.C in the condition of 90% $CO_2$ and adsorption temperature of $20^{\circ}C$. The $CO_2$ adsorption ability of bamboo activated carbon was not changed in the 5 cyclic test of desorption and adsorption.

• Tuberculosis and Respiratory Diseases
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• v.45 no.1
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• pp.169-175
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• 1998

Background: Heliox is known to decrease $PaCO_2$ in patients with increased airway resistance by increasing minute ventilation and reducing work of breathing(WOB). Besides these effect, heliox is expected to decrease functional anatomic dead space owing to improvement of peak expiratory flow rate(PEFR) and enhancement of gas distribution. We investigated whether heliox can decrease $PaCO_2$ even at the same minute ventilation (VE) and WOB with $N_2-O_2$ to speculate the effect of the heliox on the anatomic dead space. Material and Method: The subjects were 8 mechanically ventilated patients with asthma or upper airway obstruction(M : F=5 : 3, $68{\pm}10$years) who were under neuromuscular paralysis. The study was consisted of three 15-minutes phases: basal $N_2-O_2$ heliox and washout Heliox was administered via the low pressure inlet of servo 900C, and respiratory parameters were measured by pulmonary monitor(CP-100 pulmonary monitor, Bicore, Irvine, CA, USA). To obtain the same tidal volume(Vt) in heliox phase, the Vt on monitor was adjusted by the factor of relative flow rate of heliox to $N_2-O_2$. Dead space was calculated by Bohr equation. Results: 1) Vt, VE, peak inspiratory pressure(PIP) and peak inspiratory flow rate(PIFR) were not different between $N_2-O_2$ and heliox. 2) PEFR was higher on heliox($0.52{\pm}0.19$L/sec) than $N_2-O_2$($0.44{\pm}0.13$L/sec)(p=0.024). 3) $PaCO_2$(mmHg) were decreased with heliox($56.1{\pm}14.1$) compared to $N_2-O_2$($60.5{\pm}15.9$)(p=0.027). 4) Dead space ventilation(%) were decreased with heliox($73{\pm}9$ with $N_2-O_2$ and $71{\pm}10$ with heliox)(p=0.026). Conclusion: Heliox decreased $PaCO_2$ even at the same VE and WOB with $N_2-O_2$, and the effect was considered to be related with the reduction of anatomic dead space.

• Tuberculosis and Respiratory Diseases
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• v.41 no.4
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• pp.379-388
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• 1994

Background : In sleep apnea syndrome, arterial oxygen saturation($SaO_2$) decreases at a variable rate and to a variable degree for a given apneic period from patient to patient, and various kinds of cardiac arrythmia are known to occur. Factors supposed to affect arterial oxygen desaturation during apnea are duration of apnea, lung voulume at which apnea occurs, and oxygen consumption rate of the subject. The lung serves as preferential oxygen source during apnea, and there have been many reports related with the influence of lung volume on $SaO_2$ during apnea, but there are few, if any, studies about the influence of oxygen consumption rate of an individual on $SaO_2$ during breath holding or about the profile of arterial oxygen resaturation after breathing resumed. Methods : To investigate the changes of $SaO_2$ and heart rate(HR) during breath holding(BH) and rebreathing(RB) and to evaluate the physiologic factors responsible for the changes, lung volume measurements, and arterial blood gas analyses were performed in 17 healthy subjects. Nasal airflow by thermistor, $SaO_2$ by pulse oxymeter and ECG tracing were recorded on Polygraph(TA 4000, Gould, U.S.A.) during voluntary BH & RB at total lung capacity(TLC), at functional residual capacity(FRC) and at residual volume(RV), respectively, for the study subjects. Each subject's basal metabolic rate(BMR) was assumed on Harris-Benedict equation. Results: The time needed for $SaO_2$ to drop 2% from the basal level during breath holding(T2%) were $70.1{\pm}14.2$ sec(mean${\pm}$standard deviation) at TLC, $44.0{\pm}11.6$ sec at FRC, and $33.2{\pm}11.1$ sec at RV(TLC vs. FRC, p<0.05; FRC vs. RV, p<0.05). On rebreathing after $SaO_2$ decreased 2%, further decrement in $SaO_2$ was observed and it was significantly greater at RV($4.3{\pm}2.1%$) than at TLC($1.4{\pm}1.0%$)(p<0.05) or at FRC($1.9{\pm}1.4%$)(p<0.05). The time required for $SaO_2$ to return to the basal level after RB(Tr) at TLC was not significantly different from those at FRC or at RV. T2% had no significant correlation either with lung volumes or with BMR respectively. On the other hand, T2% had significant correlation with TLC/BMR(r=0.693, p<0.01) and FRC/BMR (r=0.615, p<0.025) but not with RV/BMR(r=0.227, p>0.05). The differences between maximal and minimal HR(${\Delta}HR$) during the BH-RB manuever were $27.5{\pm}9.2/min$ at TLC, $26.4{\pm}14.0/min$ at RV, and $19.1{\pm}6.0/min$ at FRC which was significantly smaller than those at TLC(p<0.05) or at RV(p<0.05). The mean difference of 5 p-p intervals before and after RB were $0.8{\pm}0.10$ sec and $0.72{\pm}0.09$ sec at TLC(p<0.001), $0.82{\pm}0.11$ sec and $0.73{\pm}0.09$ sec at FRC(p<0.025), and $0.77{\pm}0.09$ sec and $0.72{\pm}0.09$ sec at RV(p<0.05). Conclusion Healthy subjects showed arterial desaturation of various rates and extent during breath holding at different lung volumes. When breath held at lung volume greater than FRC, the rate of arterial desaturation significantly correlated with lung volume/basal metabolic rate, but when breath held at RV, the rate of arterial desaturation did not correlate linearly with RV/BMR. Sinus arrythmias occurred during breath holding and rebreathing manuever irrespective of the size of the lung volume at which breath holding started, and the amount of change was smallest when breath held at FRC and the change in vagal tone induced by alteration in respiratory movement might be the major responsible factor for the sinus arrythmia.

• Tuberculosis and Respiratory Diseases
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• v.52 no.1
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• pp.14-23
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• 2002

Background: The opitmal ventilator setting during partial liquid ventilation(PLV) is controversial. This study investigated the effects of various gas exchange parameters during PLV in normal rabbit lungs in order to aid in the development of an optimal ventilator setting during PLV. Methods: Seven New-Zealand white rabbits were ventilated in pressure-controlled mode with the following settings; tidal volume($V_T$) 8 mL/kg, positive end-expiratory pressure(PEEP) 4 $cmH_2O$, inspiratory-to-expiratory ratio(I:E ratio) 1:2, fraction of inspired oxygen($F_TO_2$) 1.0. The respiration rate(RR) was adjusted to keep $PaCO_2$ between 35~45 mmHg. The ventilator settings were changed every 30 min in the following sequence : (1) Baseline, as the basal ventilator setting, (2) Inverse ratio, I:E ratio 2:1, (3) high PEEP, adjust PEEP to achieve the same mean inspiratory pressure (MIP) as in the inverse ratio, (4) High $V_T$, $V_T$ 15 mL/kg, (5) high RR, the same minute ventilation (MV) as in the High $V_T$. Subsequently, the same protocol was repeated after instilling 18 mL/kg of perfluorodecalin for PLV. The parameters of gas exchange, lung mechanics, and hemodynamics were examined. Results: (1) The gas ventilation(GV) group showed no significant changes in the $PaO_2$ at all phases. The $PaCO_2$ was lower and the pH was higher at the high $V_T$ and high RR phases(p<0.05). No significant changes in the lung mechanics and hemodynamics parameters were observed. (2) The baseline $PaO_2$ for the PLV was $312{\pm}$ mmHg. This was significantly lower when decreased compared to the baseline $PaO_2$ for GV which was $504{\pm}81$ mmHg(p=0.001). During PLV, the $PaO_2$, was significantly higher at the high PEEP($452{\pm}38$ mmHg) and high $V_T$ ($461{\pm}53$ mmHg) phases compared with the baseline phase. However, it did not change significantly during the inverse I:E ratio or the high RR phases. (3) The $PaCO_2$ was significantly lower at high $V_T$ and RR phases for both the GV and PLV. During the PLV, $PaCO_2$ were significantly higher compared to the GV (p<0.05). (4) There were no important or significant changes in of baseline and high RR phases lung mechanics and hemodynamics parameters during the PLV. Conclusion: During PLV in the normal lung, adequate $V_T$ and PEEP are important for optimal oxygenation.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.6
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• pp.590-598
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• 2005

An adequate method to identify chromium separation, Cr(III) and Cr(VI), in water samples were studied by using High Performance Liquid Chromatography(HPLC) coupled with Inductively Coupled Plasma Mass Spectometer(ICP-MS) equipped with Dynamic Reaction Cell(DRC). The characteristic distribution of Cr(III) and Cr(VI) in the raw water taken at the six water intake stations in Seoul, was analyzed by the method developed by the authors. The chromium species separated by HPLC was isocratically conducted by using tetrabutylammonium phosphate monobasic(1.0 mM TBAP), ethylenediaminetetraacetic acid(0.6 mM EDTA) and 2% v/v methanol as the mobile phase. 5% v/v methanol was used as flushing solvent. A reactive ammonia($NH_3$) gas was used to eliminate the potential interference of $ArC^+$. Several Parameters such as solvent ratio, pH, flow rate and sample injection volume were optimized for the successful separation and reproducibility. Although it has been reported thai the separation sensitivity of Cr(III) is superior to that of Cr(VI), the authors observed Cr(VI) was more sensitive than Cr(III) when ammonia($NH_3$) gas was used as the reaction gas. It took less than 3 minutes to analyze chromium species with this method and the estimated detection limits were $0.061\;{\mu}g/L$ for Cr(III) and $0.052\;{\mu}g/L$, for Cr(VI). According to the results from the analysis on chromium species in the raw water of the six intake stations, the concentrations of Cr(III) ranged from 0.048 to $0.064\;{\mu}g/L$(ave. $0.054\;{\mu}g/L$) while that of Cr(VI) ranged from 0.014 to $0.023\;{\mu}g/L$(ave. $0.019\;{\mu}g/L$). Recovery ratio was very high($90.1{\sim}94.1%$). There were two or three times more Cr(III) than Cr(VI) in the raw water.

• Tuberculosis and Respiratory Diseases
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• v.45 no.6
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• pp.1223-1235
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• 1998

Background and Objective : Although prone positioning has been reported to improve gas exchange, prone positioning alone does not seem to be sufficient to increase systemic oxygen transport in an acute lung injury. The objective of this study was to investigate whether the combined therapy of low dose nitric oxide (NO) inhalation and prone positioning has an additive effect on the oxygenation and hemodynamics in patients with severe ARDS. Patients and Methods : Twelve patients with ARDS were included. Prone positioning alone, later combined with nitric oxide inhalation (5~10 ppm) from the supine position (baseline) were performed with serial measurement of gas exchange, respiratory mechanics and hemodynamic at sequential time points. The patient was regarded as a responder to prone positioning if an increase in $PaO_2/FiO_2$ of more than 20 mm Hg at 30 min or 120 min intervals after prone positioning was observed compared to that of the baseline. The same criterion was applied during nitric oxide inhalation. Results : Eight patients (66.5%) responded to prone positioning and ten patients (83.3%) including the eight just mentioned responded to the addition of NO inhalation. The $AaDO_2$ level also decreased promptly with the combination of prone positioning and NO inhalation compared to that of prone positioning alone ($191{\pm}109$ mm Hg vs. $256{\pm}137$ mm Hg, P<0.05). Hemodynamic parameters and lung compliance did not change significantly during prone positioning only. Following the addition of NO inhalation to prone positioning, the mean pulmonary artery pressure and pulmonary artery occlusion pressure decreased and cardiac output, stroke volume and oxygen delivery increased (P < 0.05) compared to those of prone 120 min. Conclusion : These findings indicate that NO inhalation would provide additional improvement in oxygenation and oxygen transport to mechanically ventilated patients with ARDS who are in a prone position.