• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.388-388
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• 2022

하수처리 공정 중 생물반응조에서는 미생물의 산화 반응을 통해 하수 내 각종 유기물들을 처리하고 있다. 블로워는 호기조를 유리산소상태로 만들어 미생물들의 유기물 제어, 질산화가 원활하게 이루어질 수 있도록 지원하는 역할을 담당하고 있다. 그러나 실제 하수처리장에서는 유기물을 원활하게 처리하기 위하여 과도하게 블로워를 가동하고 있어 경제적인 측면에서 문제를 겪고 있다. 블로워를 통해 수중에 산소를 부족하게 공급할 경우 활성슬러지의 침전성이 저해되어 방류수 수질이 저해되는 반면, 용존산소가 과도하게 공급되어도 유기물질의 처리 효율은 증대되지 않으며 잉여용존산소는 대기 중으로 방류된다. 이러한 이유로 국내 하수처리장에서는 강화된 방류수 수질 기준을 만족하기 하고자 유입수질에 관계없이 과도하게 송풍기를 운영하고 있다. 이러한 하수처리장의 운영 및 경제적인 문제점을 해결하고자, 본 연구에서는 하수처리장으로 유입되는 원수의 수질을 처리하는 데 실제로 미생물이 필요한 산소요구량 및 공기공급량을 산정하는 프로그램을 개발하였다. 이를 통해 실제 하수처리장에서 필요한 산소요구량, 공기공급량을 산출하여 효율적인 하수처리장 운영이 가능하다. 실제 하수처리장에서의 프로그램을 통한 송풍량 절감 효율을 분석하고자 한 달간의 A 하수처리장 수질 데이터를 기반으로 하수처리에 필요한 산소요구량 및 공기공급량을 산정하였다. 실험 결과 프로그램 적용시 약 평균적으로 10%의 송풍량을 절감이 가능하며, 연구 결과를 바탕으로 효율적이고 경제적인 송풍기 운영조건의 기준을 제시하고자 한다.

• Wind and Structures
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• v.38 no.4
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• pp.261-275
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• 2024

Before performing an experimental study on the downburst-generated wave, it is necessary to examine the scale effects and corresponding corrections or compensations. Analysis of similarity is conducted to conclude the non-dimensional force ratios that account for the dynamic similarity in the interaction of downburst with wave between the prototype and the scale model, along with the corresponding scale factors. The fractional volume of fluid (VOF) method in association with the impinging jet model is employed to explore the characteristics of the downburst-generated wave numerically, and the validity of the proposed scaling method is verified. The study shows that the location of the maximum radial wind velocity in a downburst-wave field is a little higher than that identified in a downburst over the land, which might be attributed to the presence of the wave which changes the roughness of the underlying surface of the downburst. The impinging airflow would generate a concavity in the free surface of the water around the stagnation point of the downburst, with a diameter of about two times the jet diameter (D_jet). The maximum wave height appears at the location of 1.5D_jet from the stagnation point. Reynolds number has an insignificant influence on the scale effects, in accordance with the numerical investigation of the 30 scale models with the Reynolds number varying from 3.85 × 10⁴ to 7.30 × 10⁹. The ratio of the inertial force of air to the gravitational force of water, which is denoted by G, is found to be the most significant factor that would affect the interaction of downburst with wave. For the correction or compensation of the scale effects, fitting curves for the measures of the downburst-wave field (e.g., wind profile, significant wave height), along with the corresponding equations, are presented as a function of the parameter G.

• Journal of Periodontal and Implant Science
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• v.53 no.5
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• pp.376-387
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• 2023

Purpose: Peri-implantitis (PI) is an inflammatory condition associated with the destruction of bone tissue around a dental implant, and diode lasers can be used to treat this disease. In this study, we aimed to evaluate the effectiveness of a 940-nm diode laser for the nonsurgical treatment of PI. Methods: Twenty patients (8 women and 12 men) were enrolled in a split-mouth randomized controlled study. In the control group (CG), mechanical debridement with titanium curettes accompanied by airflow was performed around the implants. The test group (TG) was treated similarly, but with the use of a diode laser. Clinical measurements (plaque index, gingival index [GI], probing pocket depth [PPD], bleeding on probing [BOP], clinical attachment level, and interleukin-1β [IL-1β] in the peri-implant crevicular fluid) were evaluated and recorded at baseline and 3 months. IL-1β levels were determined using the enzyme-linked immunosorbent assay method. Results: The symptoms were alleviated in both groups at 3 months as assessed through clinical measurements. GI, BOP, and PPD were significantly lower in the TG than in the CG (P<0.05). The IL-1β level increased post-treatment in both groups, but this increase was only statistically significant (P<0.05) in the CG. Conclusions: The diode laser enabled improvements in clinical parameters in the periimplant tissue. However, it did not reduce IL-1β levels after treatment. Further studies about the use of diode lasers in the treatment of PI will be necessary to evaluate the effects of diode lasers in PI treatment.

• Tuberculosis and Respiratory Diseases
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• v.87 no.3
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• pp.221-233
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• 2024

The 2023 Global Initiative for Chronic Obstructive Lung Disease (GOLD) revised the definition of chronic obstructive pulmonary disease (COPD) to broadly include a variety of etiologies. A new taxonomy, composed of etiotypes, aims to highlight the heterogeneity in causes and pathogenesis of COPD, allowing more personalized management strategies and emphasizing the need for targeted research to understand and manage COPD better. However, controversy arises with including some diseases under the umbrella term of COPD, as their clinical presentations and treatments differ from classical COPD, which is smoking-related. COPD due to infection (COPD-I) and COPD due to environmental exposure (COPD-P) are classifications within the new taxonomy. Some disease entities in these categories show distinct clinical features and may not benefit from conventional COPD treatments, raising questions about their classification as COPD subtypes. There is also controversy regarding whether bronchiectasis with airflow limitations should be classified as an etiotype of COPD. This article discusses controversial issues associated with the proposed etiotypes for COPD in terms of COPD-I, COPD-P, and bronchiectasis. While the updated COPD definition by GOLD 2023 is a major step towards recognizing the disease's complexity, it also raises questions about the classification of related respiratory conditions. This highlights the need for further research to improve our understanding and approach to COPD management.

• Tuberculosis and Respiratory Diseases
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• v.44 no.5
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• pp.1051-1062
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• 1997

Background : In asthma, airway obstruction is usually reversible, either spontaneously or with treatment. However, the responses to treatment are variable and some patients show an irreversible component of airflow obstruction. This may be associated with structural changes in the airway. To assess the relationship between the difference in airway reversibility and structural changes, we evaluated the HRCT findings and pulmonary function test. Methods : We studied 40 asthmatic subjects who had had acute exacerbation of symptoms and had showed normal chest X-ray findings. They had monitered PEFR daily, and had performed PFT and HRCT within three days after initiation of treatment. According to serial PEFR, they were grouped into 3 categories (Group 0 ; initial PEFR was within normal limit, Group 1 ; revealed increment of 30% in PEFR within 3 days after initiation of treatment, Group 2 ; revealed within 2 weeks) and then grouped again into 4 (Group 0, Group 3 ; reached to normal value of PEFR within 3 days after initiation of treatment, Group 4 ; within 2 weeks, Group 5 ; not within 2 weeks). Results : (1) Age in Group 0 was significantly lower than other groups(p<0.05), but there was no significance in other groups. (2) Duration of asthma in Group 2 was significantly longer than Group 0, 1(p<0.05). (3) FVC(%) and FEV1(%) were significantly decreased with delayed response to the treatment (p<0.05). (4) $FEV_1$/FVC(%) in Group 1, 2 were significantly lower than Group 0(p<0.05). $FEV_1$/FVC(%) in Group 5 was significantly lower than Group 0,3,4 (p<0.05). (5) Air trapping was increased significantly with delayed response to the treatment (p<0.05). (6) Mucus impaction in Group 0 was significantly larger than Group 1,2 (p<0.05). $FEV_1$/FVC(%) in Group 0,4,5 were significantly larger than Group 3 (p<0.05). Conclusion : Difference in reversibility of airway obstruction was associated with age, duration of asthma and severity of initial airflow obstruction There was no definite difference in HRCT findings in asthma.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.50 no.6
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• pp.406-410
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• 2005

This study was conducted to establish the efficient protocols of the germination and cryopreservation of dehisced Korean ginseng seeds for long-term germ­plasm conservation. $GA_3$ and BA treated on seed for 24 hr facilitated germination at 5 and $10^{\circ}C$. Germination percentage of desiccated seeds was decreased under moisture content (MC) of below $7.2\%$. Dehisced ginseng seeds were dried under airflow of laminar floor cabinet and seed drying room. The high levels (more than $90\%$) of germination after cryogenic exposure were obtained after drying under vertical airflow of laminar floor for 12-30 hours (MC $10.6{\~}7.2\%$). Decrease in germination percentage of ginseng seeds due to desiccation damage and freezing injury was observed at MC of below $7.2\%$ and of above $12.1\%$, respectively. Therefore, MC of ginseng seeds need to be controlled with a range of $8{\~}10\%$ to avoid damages from both desiccation and freezing.

• Membrane Journal
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• v.21 no.1
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• pp.46-54
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• 2011

In this study, combined effect of airflow rate, $TiO_2$ concentration, solution pH and $Ca^{+2}$ addition on HA (humic acid) fouling in submerged, photocatalytic hollow-fiber microfiltraiton was investigated systematically. Results showed that UV irradiation alone without $TiO_2$ nanoparticles could reduce HA fouling by 40% higher than the fouling obtained without UV irradiation. Compared to the HA fouling without UV irradiation and $TiO_2$ nanoparticles, the HA fouling reduction was about 25% higher only after the addition of $TiO_2$ nanoparticles. Both adsorptive and hydrophilic properties of $TiO_2$ nanoparticles for the HA can be involved in mitigating membrane fouling. It was also found that the aeration itself had lowest effect on fouling mitigation while the HA fouling was affected significantly by solution pH. Transient behavior of zeta potential at different solution pHs suggested that electrostatic interactions between HA and $TiO_2$ nanoparticles should improve photocatalytic efficiency on HA fouling. $TiO_2$ concentration was observed to be more important factor than airflow rate to reduce HA fouling, implying that surface reactivity on $TiO_2$ naoparticles should be important fouling mitigation mechanisms in submerged, photocatalyic microfiltraiton. This was further supported by investigating the effect of $Ca^{+2}$ addition on fouling mitigation. At higher pH (= 10), addition of $Ca^{+2}$ can play an important role in bridging between HA and $TiO_2$ nanoparticles and increasing surface reactivity on nanoparticles, thereby reducing membrane fouling.

• Journal of The Korean Society of Grassland and Forage Science
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• v.42 no.2
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• pp.73-78
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• 2022

This experiment was conducted to establish the technology for artificial hay preparation in Korea. Using far-infrared heater, a device that can control temperature, airflow, and far-infrared radiation was produced and conducted on the fourth harvested alfalfa. The drying conditions were carried out by selecting a total of four conditions. For each condition, the radiation rate was set to around 40% (33-42%), and the temperature was set at 58~65℃, and the speed of the airflow was fixed at 60m/s. The overall drying time was set to 30 min in the single and 60 min (30-30 min) and 90 min (30-30-30 min) in the complex condition, and the radiation rate and temperature were changed by time period. In the case of drying condition 1, the final dry matter (DM) content was 46.26%, which did not reach a DM suitable for hay. However, all of the alfalfa corresponding to the remaining drying conditions 2 to 7 showed a DM content of 80% or more, resulting in optimal alfalfa hay production. In power consumption according to the drying conditions, the second drying condition showed the lowest at 4.7 KW, and the remaining drying conditions were as high as 6.5 to 7.1 KW. The crude protein content was found to be high at an average of 25.91% and it showed the highest content in the 5th drying condition (26.93%) and the lowest value in the 6th drying condition (25.16%). The digestibility showed a high value with an average of 84.90%, and there was no significant difference among treatments (p>0.05). Considering the above results, it was judged that drying condition 2 was the most advantageous.

• Journal of the Korean Society for Railway
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• v.19 no.3
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• pp.280-287
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• 2016

In railway tunnels, dust is generated when trains run due to the contact between the wheels and the rails. The generated dust is suspended due to the train-induced airflow, with some of it deposited due to gravitational sedimentation. In this study, the diurnal variation of the dust concentration was investigated in a railway tunnel. A single lane of a tunnel was selected in which to observe more easily the dust concentration due to the passing of a train. Four particle-measuring instruments were utilized to detect dust ranging from 5nm to $20{\mu}m$. To synchronize the train passing time at the measuring location, a three-dimensional ultrasonic anemometer and a video camera were used. It was found that the dust concentration was significantly increased from $50{\mu}g/m^3$ to $150{\mu}g/m^3$ due to the train. Particularly, the dust concentration was greatly increased to more than $250{\mu}g/m^3$ during the morning rush-hour times.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.6
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• pp.587-597
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• 2010

Air-staged combustion is known to be one of the techniques of NOx reduction. The objective of this study is to determine the optimal ratio of air flow distributed for CCOFA and SOFA; at this optimal ratio, the combustion and exhaust emission characteristics of a pulverized coal-fired boiler are maintained at a satisfactory level. A numerical investigation was performed at various airflow ratios of 16.7/83.3%, 25/75%, 50/50%, 75/25%, and 83.3/16.7%. An inert gas was considered as a substitute for air to isolate the effects of the cooling process and chemical reaction on NOx reduction; during NOx reduction in air-staged combustion, both the effects typically occur simultaneously. The results of our study show that the optimum condition, under which the maximum NOx reduction and highest boiler efficiency can be obtained, corresponds to the equal splitting of the over-fire air between CCOFA and SOFA.