• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.4
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• pp.364-374
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• 2006

Natural ventilation technique could be the substitute for or the complement to the local exhaust ventilation system in the sense of protecting work environment. Moreover, it has many strong points ; almost no mechanical parts, no energy use and no noise. If applied appropriately, it could have the very high ventilation rate and save a lot of energy expense. But, it depends on the outdoor environment, especially temperature and wind speed/direction. Predicting the capacity of natural ventilation is not an easy job because it comes from both buoyancy and wind effect. Another problem is too much flow through the ventilator especially in winter time due to too much difference between indoor and outdoor temperature. Thus some ventilators in industries are sealed by door or plastic sheet, resulting in bad work environment. Various types of dampers are used to control the flow rate through ventilators. The capabilities of flow control by damper has not been estimated. In addition, it was not tested whether the damper could obstruct the flow through ventilator when fully opened. To answer these questions, 4 types of dampers were tested by using computational fluid dynamics. 10 different configurations includes no damper, full open and half open. Flow rates were estimated and airflow fields were analysed to clarify the before-mentioned questions. The dual type damper was the best choice for controling the capability of ventilator. In addition, the upward grill type damper was the best for not obstructing the air flow when fully opened.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.892-897
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• 2020

Previous plastic heat exchangers are expensive because the mold must be newly manufactured depending on the air conditioning space. On the other hand, danpla is so thin that the heat exchange performance is excellent. Moreover, danpla can be used easily in ventilation systems in view of fabrication. This study proposes correlations for the cooling performance of an indirect evaporative cooling system. The experimental apparatus consisted of a heat exchanger, spray nozzle, fan, thermostat, pump, and measuring sensors for temperature, humidity, and airflow rate. The results showed that the effectiveness decreased gradually as the airflow rate increased. In addition, there was an optimal condition in terms of effectiveness. The performance prediction correlations were determined using the experimental data from various conditions. The proposed correlations showed performance accuracies within 4 % error.

• Membrane Journal
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• v.26 no.1
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• pp.55-61
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• 2016

Organic fouling observed in submerged membrane filtration as a pretreatment for seawater desalination increases energy consumption for membrane operation because of requiring frequent chemical cleaning and membrane replacement. In membrane pretreatment for seawater facing with algae blooms, membrane fouling was observed in submerged microfiltration using sodium alginate model compound which is one of the main components of extracellular polymeric substances. Without aeration, aglinate fouling increased with its concentration while aeration reduced the alginate fouling effectively regardless of its concentration tested. In the absence of aeration, alingate fouling tended to be decreased with increasing calcium concentration. However, this effectiveness was reduced by increasing sodium chloride concentration. At high concentration of sodium chloride and calcium similar to the seawater conditions, aeration reduced initial fouling. However, as time progressed, the effect of increased airflow rate on fouling reduction was not significant, implying that optimum airflow rate to control alginate fouling in submerged microfiltration can exist.

• Phonetics and Speech Sciences
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• v.7 no.4
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• pp.93-99
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• 2015

In case of PAS test, the air is sometimes leaked although the mask is tightly attached to the face, which is not reliable on the measured values. Therefore, this study aimed to assist the clinical practice suggesting the test method of PAS without air leakage. In the healthy subjects with 12 males and 12 females over 19 years old, three types of tests were performed on the voicing efficiency among the protocol of PAS Model 6600. They are; first, to attach the mask tightly to the face holding the handle of PAS with the subject's two hands (Method 1); second, to attach the mask tightly to the face holding the handle of PAS with the subject's one hand and pushing the body of PAS strongly with the other hand (Method 2); and third, to attach the mask tightly to the face pushing the upper part of the mask by the tester when the subject attached the mask to his or her face holding the handle of PAS with two hands (Method 3). Upon the study analyses, the mean negative pressure, the mean phonogram, subglottic air pressure, and voicing efficiency were shown to be statistically significantly different during PAS test in males depending on the methods. (p<.05) In case of females, only the target airflow rate showed significant difference depending on the methods during PAS test. (p<.001) In conclusion, Method 2 enhanced the noise level and strength while Method 1 was likely to leak the air more compared to the other two methods in males. In case of females, Method 1 showed significant leakage of the air flow. Not to allow the air flow leakage without affecting the outcome of PAS test, it will be the most useful for the tester to push the mask to the subject's face tightly (Method 3).

• KIEAE Journal
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• v.13 no.5
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• pp.43-50
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• 2013

Recent researches on plant factory system deal with the convergence of lighting technology, agricultural technology inclusive to the high-tech industries worldwide in order to respond to the decreasing crop harvest due to global warming and abnormal weather phenomena. However, the fundamental performance standard is not currently being introduced in the case of plants factory and its commercialization is not activated because of high initial investment and operating cost. Large portion of the initial investment and operating cost of a plant factory is ascribed to artificial light sources and thermal control facilities, therefore, innovation should be provided in order to improve the economics of the plant factory. As an alternative, new plant factory could harness solar thermal and geothermal systems for heating, cooling and ventilation. In this study, a natural light dependent multi-layer plant factory's thermal environment was analyzed with two-dimensional numerical methods to elicit efficient operation conditions for optimized internal physical environment. Depending on the supply air temperature and airflow rate introduced in the facility, the temperature changes around the crops was interpreted. Since the air supplied into the plant factory does not stay long enough, the ambient temperature predicted around the plating trays was not significantly different from that of the supplied air. However, the changes of airflow rate and air flow pattern could cause difference to the temperature around the planting trays. Increasing the amount of time of air staying around the planting trays could improve energy performance in case the thermal environment of a natural light based multi-layer plant factory is considered.

• Journal of the Korean Applied Science and Technology
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• v.35 no.4
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• pp.1393-1406
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• 2018

In this study, three parameters (Pressure ($X_1$), Airflow rate ($X_2$), Operation time ($X_3$)) were experimentally designed and the predicted model and optimal conditions were established by using the terminal rise velocity of the microbubbles as the response value. The polynomial regression analysis showed that the optimum value for the terminal rise velocity at the Pressure ($X_1$) of 4.5 bar, Airflow rate ($X_2$) of 3.3 L/min and Operation time ($X_3$) of 2.2 min was 5.14 cm/min ($85.7{\mu}m/sec$). Also, the highest microbubble diameter size distribution in the range of 2 to $5{\mu}m$ and 25 to $50{\mu}m$ was confirmed by using a laser particle counting apparatus.

• Phonetics and Speech Sciences
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• v.4 no.3
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• pp.143-149
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• 2012

The purpose of this study is to investigate the speech rate of an esophageal speech group that is capable of vocalization after surgery. The subjects in this experiment were 10 male esophageal speakers and 10 male laryngeal speakers. Each group read a reading passage that was recorded by a DAT recorder (Rolando, EDIROL R-09). These records were analyzed by using CSL (Computerized Speech Lab, model 4150). The results were as follows: (1) the overall speech rate of esophageal speech was 2.50 SPS (syllable per second) while the overall speech rate of laryngeal speech was 4.23 SPS. (2) The articulatory rate of esophageal speech was 3.14 SPS (syllable per second) while the articulatory rate of laryngeal speech was 4.75 SPS. Speech rates as well as articulatory rates of esophageal speech were significantly lower than laryngeal speech. These differences between the two groups may be due to reduced efficiency of airflows across the pharyngeal-esophageal segment for esophageal speakers when compared to airflow through the glottis for laryngeal speakers. These results would provide a guideline in speech rates for esophageal speakers in clinical settings.

• Journal of Biomedical Engineering Research
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• v.33 no.4
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• pp.177-183
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• 2012

The inspiratory flow rate of a human is changed with the amount of the workload. The flow characteristic is affected by the inspiratory flow rate. In the flow field of airway, the both of turbulence intensity and secondary flow affect the deposition pattern of particles which is important for the drug-aerosol targeting. Thus the analysis of the flow characteristic in a human airway is important. The purpose of this study is to investigate the effects of the inspiratory flow rate on the flow characteristics in a human airway. The tubular airway is consistent with the oral cavity, pharynx, larynx and trachea. The relatively inspiratory flow rate is used at each case of human states regarding the workload. By the effect of geometric airway changes, transition to turbulent airflow after the larynx can occur with relaminarization further downstream. The low Reynolds number k-${\omega}$ turbulence model is used for analysis with flow regime. As the inspiratory flow rate is larger, the turbulence kinetic energy and secondary flow intensity increase in airway. On the other hand, the area of recirculation zone is smaller.

• Speech Sciences
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• v.15 no.2
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• pp.177-189
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• 2008

This study was to investigate diadochokinetic (DDK) rate, regularity and mean flow rate of articulation valves in dysarthria. DDK rate, mean airflow rate (MFR) and regularity of DDK syllable repetitions of vocal function /ihi/, tongue function /ta/, velopharyngeal function /bm/, and labial function /pa/ in 24 normal and dysarthric speakers were measured. Aerophone Ⅱ and Motor Speech Profile were used for data recording and analysis. The results of the findings were as follows: First, there were significant differences between the dysarthria and the normal group in DDK rate. DDK rates in ataxic dysarthria were the lowest and spastic, flaccid, and hypokinetic dysarthria followed in sequence. Second, there was a significant difference between the dysarthria and the normal group in DDK regularity. Third, there was a significant difference between dysarthria groups and normal group in DDK MFR. Finally, there was a significant difference between the 4 groups of dysarthria and the normal group in DDK air flow tracking. The results of this study can be guidelines for normal DDK rate, regularity and flow rate in dysarthria groups. In addition, their differential diagnoses and descriptions are important to make a decision on medical and behavioral management of the individuals with disorders according to DDK characteristics.

• Journal of Environmental Science International
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• v.21 no.7
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• pp.855-863
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• 2012

This study analyzed mass concentrations of TSP, PM10 and PM2.5 and elemental constituents according to the isentropic backward trajectories of air parcel from Cheongwonin East Asia during the period January - October, 2011. Mass concentrations of the continental polluted airflow (CP) showed levels of TSP and PM10 mass concentrations higher than the continental background airflow (CB). Also, PM2.5 mass concentrations of anthropogenic fine particles ran higher in CP than in CB. The elemental constituents and elemental constituent ratio ended up varying depending on the origin of atmospheric aerosols generated. The average absolute content of elemental constituents reached its height in CB, the ratio of anthropogenically originating elements (PE) among the all elements (AE) analyzed marked a high in CP, and Mg+Na/AE reached its height in the oceanic airflow (OA). At the same time, TSP, PM10 and PM2.5 mass concentrations, the ratio of PM2.5/TSP and PE/AE element ratio ran higher in CP than CB. Episodes of large-scale transport of atmospheric pollutants as observed at Cheongwon were 8 cases and 22 days. The ratios of PM10, PM2.5 among TSP mass concentrations showed different results and the ratios of PM2.5 showed an increasing trend in the episodes of anthropogenic air pollution transport. Overall, dustfall episodes show a level of elemental constituents higher than those of anthropogenic air pollution.Dustfall episodes were observed to contain more of Fe, Al and Ca originating from continental soils and those of air pollution were observed to contain more of Zn, Mn, Cu and Pb. By difference in contents of absolute elemental constituents, episodes of anthropogenic air pollution showed a high PE/AE rate, and dustfall episodes a high SE/AE rate.