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Dive into the research topics where Yoonkyung Kang is active.

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Featured researches published by Yoonkyung Kang.


Indoor and Built Environment | 2014

Thermal and non-thermal germicidal effects of microwave radiation on microbial agents

Yoonkyung Kang; Shinsuke Kato

To assess possible applications of evaporative humidifier elements of air-conditioning systems, the germicidal effect of microwave irradiation on fungal spores (e.g. Cladosporium herbarum and Fusarium solani), vegetative bacteria and bacterial spores (e.g., Bacillus subtilis) was investigated by this study. A general purpose microwave oven and a specifically assembled microwave source placed in a 2.45 GHz magnetron were used. Initially, the optimal radiation output power and exposure time were determined to achieve the desired germicidal effects using both wet and dry sample filters. The study also investigated whether the germicidal effect could be a direct result of the microwave irradiation or rather a result of the radiation-induced heat. The results of our study have indicated that microbial degradation could be dependent on the fungal strain type, microwave output power, exposure time and sample moisture. Our results have also illustrated that the germicidal effect shown in the experiments could be attributed to the associated rise in temperature particularly above 60℃ during the microwave irradiation of the fungal buffer solutions.


Hvac&r Research | 2014

A study on the effectiveness of microwave heating for disinfection of humidifier elements

Yoonkyung Kang; Shinsuke Kato

In this study, microwave irradiation was tested as a possible means to disinfect evaporative humidifiers in air-conditioning systems. A mock-up of a humidifier was prepared to identify the applicability of the microwave irradiation system. To characterize the heating properties of this system under optimum operating conditions, the temperature distribution of the humidifier element was measured as a function of various parameters. Variables included the use of ventilation and water spraying during microwave irradiation, the level of radiation output power and whether the element was dry or wet. The results showed that microwave irradiation can heat the evaporative humidifier element about 60°C at 1200 W for exposure times greater than 3 min under nonoperating conditions (without air blower and water spraying). However, the temperature distribution of the element was nonuniform, regardless of whether the conditions were dry or wet. The effectiveness of microwave heating is limited due to nonuniform distribution of temperature. To achieve a uniform surface temperature on the element, further studies are necessary.


Hvac&r Research | 2014

The germicidal effects of microwave heating on microbes on evaporative humidifier elements

Yoonkyung Kang; Shinsuke Kato

To identify the germicidal effects of microwave radiation for evaporative humidifiers, we measured the germicidal effects of fungal spores of Fusarium solani and vegetative cells and spores of the bacterium Bacillus subtilis using a mock-up system. The germicidal effect was compared to the output powers, irradiation times, and water contents of the element to establish effective disinfection conditions of humidifier element surfaces. The results demonstrated that the fungal and bacterial strains were inhibited at 1200 W for 20 min, except for the B. subtilis spores under the nonoperation condition involving water spray and the blower. In general, the germicidal effects appear to be stronger on the upper portion of the elements than on the lower portion. The germicidal effect was stronger at higher output power and longer exposure time under wet conditions. To achieve a uniform disinfection on the element faces, it is necessary to consider variations of these methods to produce a uniform heating pattern.


Science and Technology for the Built Environment | 2016

Field measurement of indoor air quality and airborne microbes in a near-zero energy house with an earth tube in the cold region of Japan

Yoonkyung Kang; Katsunori Nagano

This study was conducted to evaluate the level of microbial contamination of indoor air during 3 years for two residences in one building equipped with heat recovery ventilation devices and located in Kimobetsu town of Hokkaido, Japan. This article documents a case study aimed at monitoring the microbes contaminations indoors for a safe use of energy saving ventilation devices and sanitary indoor air. This articles describes an investigative approach with three components. First, the authors evaluated the indoor air quality and microbial concentration by comparing the concentrations of particulate matter (PM10 and PM2.5), carbon dioxide, and airborne bacteria and fungi of indoor air and outdoor air during spring, summer and winter. Second, the microbial concentration inside an earth tube and a fixed sensible heat exchanger was evaluated by measuring the airborne microbial concentration of the supply air. Third, the authors assessed the possibility of microbial contamination inside the earth tube using the fungal index and by measuring temperature and relative humidity at the tubes outlet airflow. The results showed that the total concentration of airborne fungi was higher in summer than in spring or winter and that the fungal genera Cladosporium sp. and Penicillium sp. were dominant in the samples. Additionally, it was found that the environment inside the earth tube allowed easy growth of fungi from May to September with the highest fungal index measured in August. It was also confirmed that the earth tube did not affect the supply air for a building constructed 4 years ago.


Science and Technology for the Built Environment | 2016

A study of the energy consumption and airborne microbe concentration in the Sapporo underground walkway, in a cold region of Japan

Yoonkyung Kang; Katsunori Nagano

The present study sought to evaluate the energy consumption, indoor air quality and concentration of airborne bacteria and fungi in the Sapporo underground walkway, which is in a cold region of Japan. The energy consumption, temperature, relative humidity, and carbon dioxide concentrations of the underground walkway were investigated for 4 years from its opening in 2011 (until 2014). The temperature, relative humidity, and carbon dioxide concentrations were automatically detected using sensors and data from Sapporo city hall. To evaluate the microbial contamination in the ventilation system and indoors, the concentrations of airborne bacteria and fungi were measured on 2 days (a weekday and a weekend day) during opening hours in both summer and winter. The concentration of airborne microbes in the supply air, indoor air, and outside air was compared. Species of airborne bacteria were identified using 16S rDNA sequence analysis. The energy use intensities were decreased in 2013, when the walkway temperature was changed during both winter and summer. The carbon dioxide concentration in the walkway was maintained below 1000 ppm. The number of airborne bacteria and fungi in the supply air from the ceiling diffuser was lower than those in the outdoor and indoor air. These results indicate that both energy consumption and indoor air quality were maintained in the walkway throughout the 4-year period. This study could be helpful for developing the related standards for indoor air quality and for developing control strategies to properly operate air conditioning and ventilation systems in underground spaces.


Hvac&r Research | 2014

An electromagnetic simulation study of the distribution of the power absorbed in evaporative humidifier elements

Yoonkyung Kang; Shinsuke Kato

To resolve the uneven microwave heating of an evaporative humidifier element, the distribution of the electric field in the humidifier cavity and the power absorbed in the humidifier element were investigated using a microwave simulation. The dielectric constant and loss tangent from changes in the water content of the humidifier element were measured using a rectangular waveguide method and calculated using microwave simulation to perform the electric field calculations. Then the penetration depth of microwaves in the element was identified for different water densities. The results demonstrated that the microwave could penetrate a 100-mm-thick element with a water density of 0.054 g/cm3. The simulation results indicated that the average power density lost across the cross-section of the element (thickness) was attenuated from the front face to the rear face with increasing water density. The depth profile of the power absorbed in the element agrees with the experimental results. However, the vertical profile of the power absorbed into the element did not match with heating patterns. An air fluid analysis should be undertaken in future simulations to predict the temperature change of the evaporative humidifier element.


Journal of Applied Phycology | 2008

Isolation, identification and characterization of algicidal bacteria against Stephanodiscus hantzschii and Peridinium bipes for the control of freshwater winter algal blooms

Yoonkyung Kang; Soo-Yeon Cho; Yoon-Ho Kang; Toshiya Katano; EonSeon Jin; Dong-Soo Kong; Myung-Soo Han


Indoor Environment and Technology | 2008

A Study on VOCs and HCHO Emission of Building Materials Using the 20L Test Chamber

Yoonkyung Kang; 김현진; Yun-Gyu Lee


Summaries of technical papers of annual meeting | 2015

41416 The assessment of microbial contamination on energy recovery ventilation devices of a residential building in Kimobetsu-cho, Hokkaido

Yoonkyung Kang; Katsunori Nagano


Journal of Environmental Engineering (transactions of Aij) | 2013

THE GERMICIDAL EFFECT ON A FULL-SCALE EVAPORATION TYPE HUMIDIFIER ELEMENT BY MICROWAVE IRRADIATION

Yoonkyung Kang; Shinsuke Kato; U Yanagi

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Mitsuo Harada

Tokyo Electric Power Company

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Dong-Soo Kong

National Institute of Environmental Research

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