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  1. Article: Estimate of the critical exposure time based on 70 confirmed COVID-19 cases.

    Lee, Handol / Ahn, Kang-Ho

    The journal of the Korean Physical Society

    2021  Volume 79, Issue 5, Page(s) 492–498

    Abstract: The transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) occurs via contact with contaminated surfaces and inhalation of large airborne droplets and aerosols. As growing evidence of airborne SARS-CoV-2 transmission has been ... ...

    Abstract The transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) occurs via contact with contaminated surfaces and inhalation of large airborne droplets and aerosols. As growing evidence of airborne SARS-CoV-2 transmission has been reported worldwide, ventilation is an effective method of reducing the infection probability of SARS-CoV-2. This leads to such questions as "What is a sufficient ventilation rate for avoiding the risk of COVID-19 infection?" Therefore, this study evaluates the critical ventilation rates according to room size and exposure time when a susceptible person is in the same room as an infector. The analytical results were based on data obtained from 70 confirmed COVID-19 cases transmitted in confined spaces without an operational ventilation system. The results reveal that even with active ventilation (20 h
    Language English
    Publishing date 2021-06-18
    Publishing country Korea (South)
    Document type Journal Article
    ZDB-ID 2046361-3
    ISSN 1976-8524 ; 0374-4884
    ISSN (online) 1976-8524
    ISSN 0374-4884
    DOI 10.1007/s40042-021-00225-9
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Accurate measurements of particle emissions from a three-dimensional printer using a chamber test with a mixer-installed sampling system.

    Lee, Handol / Kwak, Dong-Bin / Choi, Chi Young / Ahn, Kang-Ho

    Scientific reports

    2023  Volume 13, Issue 1, Page(s) 6495

    Abstract: Recently, three-dimensional (3D) printing has attracted attention as a new manufacturing technology. However, there is lack of data and regulations regarding the emissions of ultrafine particles from 3D printers. Therefore, we investigated particle ... ...

    Abstract Recently, three-dimensional (3D) printing has attracted attention as a new manufacturing technology. However, there is lack of data and regulations regarding the emissions of ultrafine particles from 3D printers. Therefore, we investigated particle emissions from a 3D printer using a chamber system. The test system was improved by installing a developed mixer for accurate measurement. Without a mixer, the particle concentration was unstable depending on the sampling point; however, reliable data with good uniformity were obtained by installing a mixer. Using the test system with a mixer, we investigated particle emissions from a 3D printer during operation. Filaments made each of acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) were used as the printing material. The effects of nozzle temperature and printing time were investigated. Compared to the effect of the printing time, the nozzle temperature had greater impact on the particle emissions. The dominant particle size for the emissions from a 3D printer is less than 10 nm, and the particle concentration decreased with increasing particle size.
    Language English
    Publishing date 2023-04-20
    Publishing country England
    Document type Journal Article
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-023-33538-9
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Modeling pressure drop values across ultra-thin nanofiber filters with various ranges of filtration parameters under an aerodynamic slip effect.

    Lee, Songhui / Bui-Vinh, Dai / Baek, Minwoo / Kwak, Dong-Bin / Lee, Handol

    Scientific reports

    2023  Volume 13, Issue 1, Page(s) 5449

    Abstract: Computational fluid dynamics simulations of fibrous filters with 56 combinations of different fiber sizes, packing densities, face velocities, and thicknesses were conducted for developing models that predict pressure drops across nanofiber filters. The ... ...

    Abstract Computational fluid dynamics simulations of fibrous filters with 56 combinations of different fiber sizes, packing densities, face velocities, and thicknesses were conducted for developing models that predict pressure drops across nanofiber filters. The accuracy of the simulation method was confirmed by comparing the numerical pressure drops to the experimental data obtained for polyacrylonitrile electrospun nanofiber filters. In the simulations, an aerodynamic slip effect around the surface of the small nanofibers was considered. The results showed that, unlike in the case of conventional filtration theory, pressure drops across the thin layers of electrospun nanofiber filters are not proportional to the thickness. This might be a critical factor for obtaining precise pressure drops across the electrospun nanofiber filters with extremely thin layers. Finally, we derived the product of drag coefficient and Reynolds number as a function of packing density, Knudsen number, and ratio of thickness to fiber diameter to get the correlation equation for pressure drop prediction. The obtained equation predicted the pressure drops across the nanofiber filters with the maximum relative difference of less than 15%.
    Language English
    Publishing date 2023-04-03
    Publishing country England
    Document type Journal Article
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-023-32765-4
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Modeling pressure drop values across ultra-thin nanofiber filters with various ranges of filtration parameters under an aerodynamic slip effect

    Songhui Lee / Dai Bui-Vinh / Minwoo Baek / Dong-Bin Kwak / Handol Lee

    Scientific Reports, Vol 13, Iss 1, Pp 1-

    2023  Volume 14

    Abstract: Abstract Computational fluid dynamics simulations of fibrous filters with 56 combinations of different fiber sizes, packing densities, face velocities, and thicknesses were conducted for developing models that predict pressure drops across nanofiber ... ...

    Abstract Abstract Computational fluid dynamics simulations of fibrous filters with 56 combinations of different fiber sizes, packing densities, face velocities, and thicknesses were conducted for developing models that predict pressure drops across nanofiber filters. The accuracy of the simulation method was confirmed by comparing the numerical pressure drops to the experimental data obtained for polyacrylonitrile electrospun nanofiber filters. In the simulations, an aerodynamic slip effect around the surface of the small nanofibers was considered. The results showed that, unlike in the case of conventional filtration theory, pressure drops across the thin layers of electrospun nanofiber filters are not proportional to the thickness. This might be a critical factor for obtaining precise pressure drops across the electrospun nanofiber filters with extremely thin layers. Finally, we derived the product of drag coefficient and Reynolds number as a function of packing density, Knudsen number, and ratio of thickness to fiber diameter to get the correlation equation for pressure drop prediction. The obtained equation predicted the pressure drops across the nanofiber filters with the maximum relative difference of less than 15%.
    Keywords Medicine ; R ; Science ; Q
    Subject code 621
    Language English
    Publishing date 2023-04-01T00:00:00Z
    Publisher Nature Portfolio
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article: Application of an aerosol electrical mobility spectrum analyzer: Charged-particle polarity ratio measurement in the Antarctic and Arctic regions.

    Lee, Handol / Chung, Hyeok / Ahn, Kang-Ho

    Journal of environmental sciences (China)

    2021  Volume 105, Page(s) 81–89

    Abstract: An aerosol electrical mobility spectrum analyzer (AEMSA), developed at Hanyang University, was employed to investigate the particle charge characteristics in the Antarctic and Arctic regions. The particle charge characteristics in these areas were ... ...

    Abstract An aerosol electrical mobility spectrum analyzer (AEMSA), developed at Hanyang University, was employed to investigate the particle charge characteristics in the Antarctic and Arctic regions. The particle charge characteristics in these areas were compared with the charging state in Ansan, South Korea, located in the midlatitude, where artificial factors, such as human activity, urbanization, and traffic, might result in a higher total concentration. Furthermore, in Ansan, South Korea, the charged-particle polarity ratio was very stable and was close to 1. However, notably different particle charge characteristics were obtained in the Antarctic and Arctic regions. The imbalance between the numbers of positively and negatively charged particles was evident, resulting in more positive charges on the atmospheric particles. On average, the positively charged particle concentrations in the Antarctic and Arctic areas were 1.4 and 2.8 times higher, respectively, compared with the negatively charged particles. The developed AEMSA system and the findings of this study provide useful information on the characteristics of atmospheric aerosols in the Antarctic and Arctic regions and can be further utilized to study particle formation mechanisms.
    MeSH term(s) Aerosols ; Antarctic Regions ; Arctic Regions ; Humans ; Particle Size ; Republic of Korea
    Chemical Substances Aerosols
    Language English
    Publishing date 2021-01-14
    Publishing country Netherlands
    Document type Journal Article
    ZDB-ID 1092300-7
    ISSN 1878-7320 ; 1001-0742
    ISSN (online) 1878-7320
    ISSN 1001-0742
    DOI 10.1016/j.jes.2020.12.028
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    In stock of ZB MED Bonn / Germany

    Z 7630: Show issues

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  6. Article: Numerical simulation of a multi-port differential mobility analyzer (MP-DMA) used in a real-time nano-particle sizer (NPS)

    Lee, Handol / Lee, Hong Ku / Ahn, Kang-Ho

    Powder technology. 2020 Feb. 15, v. 362

    2020  

    Abstract: In a recently conducted study, we developed a nano-particle sizer (NPS) that consists of a multi-port differential mobility analyzer (MP-DMA) and two multi condensation particle counters (M-CPCs) for achieving fast measurements of aerosol particles; ... ...

    Abstract In a recently conducted study, we developed a nano-particle sizer (NPS) that consists of a multi-port differential mobility analyzer (MP-DMA) and two multi condensation particle counters (M-CPCs) for achieving fast measurements of aerosol particles; however, the performance of MP-DMA was not detailed in the study. Therefore, the objective of this study is to perform numerical simulations to obtain the transfer function of each port in the MP-DMA, which is the main component of the NPS. We observed good agreement between the numerically obtained central particle size of each port and the experimental data under the same operating conditions. The transmission probability and resolution of each port were determined and analyzed under various conditions using the transfer function. The findings of this study shall help in understanding the advantages of NPS.
    Keywords aerosols ; counters ; mathematical models ; nanoparticles ; particle size ; probability
    Language English
    Dates of publication 2020-0215
    Size p. 135-144.
    Publishing place Elsevier B.V.
    Document type Article
    ISSN 0032-5910
    DOI 10.1016/j.powtec.2019.11.055
    Database NAL-Catalogue (AGRICOLA)

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  7. Article ; Online: Extensive evaluation and classification of low-cost dust sensors in laboratory using a newly developed test method.

    Ahn, Kang-Ho / Lee, Handol / Lee, Hae Dong / Kim, Sang Chul

    Indoor air

    2019  Volume 30, Issue 1, Page(s) 137–146

    Abstract: An extensive evaluation of low-cost dust sensors was performed using an exponentially decaying particle concentration. A total of 264 sensors including 27 sensors with light-emitting diodes (LEDs) and 237 sensors with laser lighting sources were tested. ... ...

    Abstract An extensive evaluation of low-cost dust sensors was performed using an exponentially decaying particle concentration. A total of 264 sensors including 27 sensors with light-emitting diodes (LEDs) and 237 sensors with laser lighting sources were tested. Those tested sensors were classified into 4 groups based on the deviation from the reference data obtained by a reference instrument. The response linearities of all the tested samples for PM
    MeSH term(s) Air Pollutants/analysis ; Air Pollution, Indoor/analysis ; Dust/analysis ; Environmental Monitoring/economics ; Environmental Monitoring/instrumentation ; Environmental Monitoring/methods ; Particulate Matter/analysis
    Chemical Substances Air Pollutants ; Dust ; Particulate Matter
    Language English
    Publishing date 2019-11-12
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 1081722-0
    ISSN 1600-0668 ; 0905-6947
    ISSN (online) 1600-0668
    ISSN 0905-6947
    DOI 10.1111/ina.12615
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    In stock of ZB MED Bonn / Germany

    Z 7724: Show issues

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  8. Article ; Online: Hydrothermal synthesis of CuO@MnO

    Kakani, Vijay / Ramesh, Sivalingam / Yadav, H M / Bathula, Chinna / Basivi, Praveen Kumar / Palem, Ramasubba Reddy / Kim, Heung Soo / Pasupuletti, Visweswara Rao / Lee, Handol / Kim, Hakil

    Scientific reports

    2022  Volume 12, Issue 1, Page(s) 12951

    Abstract: Nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs) have been used to fabricate nanostructured materials for various energy devices, such as supercapacitors, sensors, batteries, and electrocatalysts. Nitrogen-doped carbon-based electrodes have been ... ...

    Abstract Nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs) have been used to fabricate nanostructured materials for various energy devices, such as supercapacitors, sensors, batteries, and electrocatalysts. Nitrogen-doped carbon-based electrodes have been widely used to improve supercapacitor applications via various chemical approaches. Based on previous studies, CuO@MnO
    Language English
    Publishing date 2022-09-20
    Publishing country England
    Document type Journal Article
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-022-16863-3
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article: Modeling transport of colloidal particles through polydisperse fibrous membrane filters under unfavorable chemical and physical conditions

    Lee, Handol / Kang, Seungkoo / Kim, Seong Chan / Pui, David Y.H

    Powder technology. 2019 Oct., v. 355

    2019  

    Abstract: Numerical simulations of filters with polydisperse fibers under chemically and physically unfavorable conditions were conducted to predict particle retentions on polypropylene fibrous filters. The fibrous filters were analyzed by a scanning electron ... ...

    Abstract Numerical simulations of filters with polydisperse fibers under chemically and physically unfavorable conditions were conducted to predict particle retentions on polypropylene fibrous filters. The fibrous filters were analyzed by a scanning electron microscopy to obtain fiber size distributions, and on the basis of a randomized algorithm, 2-D calculation domains were generated, and flow field calculations were conducted. For tracking particles, the standard Lagrangian tracking method in ANSYS Fluent software was modified by user-defined functions to incorporate particle deposition via interception and interaction energy calculations. Particle release from collector surfaces was considered by performing torque analysis for particles attached to the surfaces. Numerical retention efficiencies of fibrous filters showed very good agreement with experimental data without any free parameters or empirical correction factors. The parametric studies of polydisperse fibrous filters were conducted, and the retention efficiency was varied from 0 to 100% depending on chemical and physical conditions.
    Keywords algorithms ; colloids ; computer software ; energy ; filters ; mathematical models ; polypropylenes ; scanning electron microscopy ; torque
    Language English
    Dates of publication 2019-10
    Size p. 7-17.
    Publishing place Elsevier B.V.
    Document type Article
    ISSN 0032-5910
    DOI 10.1016/j.powtec.2019.07.025
    Database NAL-Catalogue (AGRICOLA)

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  10. Article: Deposition and reentrainment of colloidal particles in disordered fibrous filters under chemically and physically unfavorable conditions

    Lee, Handol / Kang, Seungkoo / Kim, Seong Chan / Pui, David Y.H

    Journal of membrane science. 2019 July 15, v. 582

    2019  

    Abstract: This study is to establish computational fluid dynamics (CFD) simulations of disordered fibrous filters under unfavorable conditions to investigate the effects of chemical and physical factors on filtration performance. We employed a discrete phase model ...

    Abstract This study is to establish computational fluid dynamics (CFD) simulations of disordered fibrous filters under unfavorable conditions to investigate the effects of chemical and physical factors on filtration performance. We employed a discrete phase model (DPM) to track individual particles, and user-defined functions were implemented to consider the particle deposition to the collector surface via interception and interaction energy. During the DPM process, calculations based on interactional and fluid hydrodynamic effects were proceeded for all injected individual colloids. The results of filtration and collision efficiencies of the single collectors obtained by our CFD simulations showed a very good agreement with the existing expressions and data, accurately predicting the trends of particle deposition and reentrainment. After the validation of the developed particle tracking method, the disordered fibrous filters with randomly distributed monodisperse fibers were studied. The results showed that the reentrainment of deposited particles was enhanced with increasing fluid velocity and solid volume fraction and decreasing fiber size due to the hydrodynamic effects. Moreover, the combined effect with ionic strength, Hamaker constant and zeta potential determined particle deposition behavior by altering particle/filter interactions. The developed simulation method for predicting filtration performance does not contain any free parameters or empirical factors.
    Keywords artificial membranes ; collectors ; colloids ; energy ; filters ; filtration ; hydrodynamics ; ionic strength ; models ; prediction ; zeta potential
    Language English
    Dates of publication 2019-0715
    Size p. 322-334.
    Publishing place Elsevier B.V.
    Document type Article
    ZDB-ID 194516-6
    ISSN 0376-7388
    ISSN 0376-7388
    DOI 10.1016/j.memsci.2019.03.092
    Database NAL-Catalogue (AGRICOLA)

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    In stock of ZB MED Bonn / Germany

    Z 78/706: Show issues

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