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- 저자 : Maskey, Dhiraj (검색결과 54 건)
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Maskey, S.,Chae, H.,Lee, K.,Dan, N.P.,Khoi, T.T.,Park, K. Elsevier Scientific Pub. Co 2016 Journal of hazardous materials Vol.317 No.-
Morphology and elemental composition of individual fine ambient particles varied among types of PM events and between two different urban environments having different major transportation systems (gasoline/diesel vehicles versus motorcycles). Carbonaceous particles were the most dominant in PM events, whereas S-rich particles were the highest in non-events at urban Gwangju in Korea. The aged soot, semi-volatile organic (SVO), and non-volatile organic (NVO) particles were more abundant in the polluted-long range transport (LTP) event than those in the dust-LTP event and non-event. In the dust-LTP event, the aged mineral dust particles outnumbered the fresh ones, suggesting the mineral dust particles were aged during their long-range transport. At HoChiMinh (HCM) in Vietnam, the fraction of carbonaceous particles was much higher than Gwangju (66% versus 30%) possibly due to more abundant two-stroke motor vehicles at HCM. Of the carbonaceous particles, combustion soot (19%) was the highest, followed by NVO (18%), SVO (17%), and biological particles (11%) at HCM, whereas SVO (11%) and NVO (10%) particles were the highest, followed by combustion soot particles (8%) at Gwangju. The higher fraction of mineral dust particles was also observed at HCM, indicating the sampling site was influenced by dust from unpaved roads and construction sites.
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Maskey, Shila,Kang, TaeHee,Jung, Hae‐,Jin,Ro, Chul‐,Un Blackwell Publishing Ltd 2011 Indoor Air Vol.21 No.1
<P><B>Abstract </B> In this study, single‐particle characterization of aerosol particles collected at an underground shopping area was performed for the first time. A quantitative single‐particle analytical technique, low‐<I>Z</I> particle electron probe X‐ray microanalysis, was used to characterize a total of 7900 individual particles for eight sets of aerosol samples collected at an underground shopping area in Seoul, Korea. Based on secondary electron images and X‐ray spectral data of individual particles, fourteen particle types were identified, in which primary soil‐derived particles were the most abundant, followed by carbonaceous, Fe‐containing, secondary soil‐derived, and secondary sea‐salt particles. Carbonaceous particles exist in three types: organic carbon, carbon‐rich, and CNO‐rich. A significant number of textile particles with chemical composition C, N, and O were encountered in some of the aerosol samples, which were from the textile shops and/or from clothes of passersby. Primary soil‐derived particles showed seasonal variation, with peak values in spring samples, reflecting higher air exchange between indoor and outdoor environments in the spring. Secondary soil‐derived, secondary sea‐salt, and ammonium sulfate particles were frequently encountered in winter samples. Fe‐containing particles, contributed from a nearby subway station, were in the range of about 19% relative abundances for all samples.</P><P><B>Practical Implications</B></P><P>In underground shopping areas, particulate matters can be a considerable health hazard to the workers, shoppers, passersby, and shop‐keepers as they spend their considerable time in this closed microenvironment. However, no study on the characteristics of indoor aerosols in an underground shopping area has been reported to our knowledge. This work provides detailed information on characteristics of underground shopping area aerosols on a single particle level.</P>
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MASKEY, DHIRAJ,KIM, HYUNG GUN,SUH, MYUNG-WHAN,ROH, GU SEOB,KIM, MYEUNG JU D.A. Spandidos 2014 INTERNATIONAL JOURNAL OF MOLECULAR MEDICINE Vol.34 No.2
<P>The increasing use of mobile communication has triggered an interest in its possible effects on the regulation of neurotransmitter signals. Due to the close proximity of mobile phones to hearing-related brain regions during usage, its use may lead to a decrease in the ability to segregate sounds, leading to serious auditory dysfunction caused by the prolonged exposure to radiofrequency (RF) radiation. The interplay among auditory processing, excitation and inhibitory molecule interactions plays a major role in auditory function. In particular, inhibitory molecules, such a glycine, are predominantly localized in the auditory brainstem. However, the effects of exposure to RF radiation on auditory function have not been reported to date. Thus, the aim of the present study was to investigate the effects of exposure to RF radiation on glycine receptor (GlyR) immunoreactivity (IR) in the auditory brainstem region at 835 MHz with a specific absorption rate of 4.0 W/kg for three months using free-floating immunohistochemistry. Compared with the sham control (SC) group, a significant loss of staining intensity of neuropils and cells in the different subdivisions of the auditory brainstem regions was observed in the mice exposed to RF radiation (E4 group). A decrease in the number of GlyR immunoreactive cells was also noted in the cochlear nuclear complex [anteroventral cochlear nucleus (AVCN), 31.09%; dorsal cochlear nucleus (DCN), 14.08%; posteroventral cochlear nucleus (PVCN), 32.79%] and the superior olivary complex (SOC) [lateral superior olivary nucleus (LSO), 36.85%; superior paraolivary nucleus (SPN), 24.33%, medial superior olivary nucleus (MSO), 23.23%; medial nucleus of the trapezoid body (MNTB), 10.15%] of the mice in the E4 group. Auditory brainstem response (ABR) analysis also revealed a significant threshold elevation of in the exposed (E4) group, which may be associated with auditory dysfunction. The present study suggests that the auditory brainstem region is susceptible to chronic exposure to RF radiation, which may affect the function of the central auditory system.</P>
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Ultrafine Particle Events in the Ambient Atmosphere in Korea
Maskey, Shila,Kim, Jae-Seok,Cho, Hee-Joo,Park, Kihong Korean Society for Atmospheric Environment 2012 Asian Journal of Atmospheric Environment (AJAE) Vol.6 No.4
In this study, real time measurements of particle number size distribution in urban Gwangju, coastal Taean, and industrial Yeosu in Korea were conducted in 2008 to understand the occurrence of ultrafine particle (UFP) (<100 nm) events, the variation of its concentration among different sampling sites, and UFP formation pathways. Also, to investigate seasonal and long-term variation of the UFP number concentration, data were collected for the period of 5 years (2007, 2008, 2010, 2011, and 2012) in urban Gwangju. Photochemical and combustion events were found to be responsible for the formation of UFP in the urban Gwangju site, whereas only photochemical event led to the formation of UFP in the coastal Taean site. The highest UFP concentration was found in industrial Yeosu (the average UFP number fractions were 79, 59 and 58% in Yeosu, Gwangju, and Taean, respectively), suggesting that high amount of gas pollutants (e.g., $NO_2$, $SO_2$, and volatile organic carbon (VOC)) emitted from industries and their photochemical reaction contributed for the elevated UFP concentration in the industrial Yeosu site. The UFP fraction also showed a seasonal variation with the peak value in spring (61.5, 54.5, 50.5, and 40.7% in spring, fall, summer, and winter, respectively) at urban Gwangju. Annual average UFP number concentrations in urban Gwangju were $5.53{\times}10^3\;cm^{-3}$, $4.68{\times}10^3\;cm^{-3}$, $5.32{\times}10^3\;cm^{-3}$, $3.99{\times}10^3\;cm^{-3}$, and $2.16{\times}10^3\;cm^{-3}$ in the year 2007, 2008, 2010, 2011, and 2012, respectively. Comparison of the annual average UFP number concentration with urban sites in other countries showed that the UFP concentrations of the Korean sites were lower than those in other urban cities, probably due to lower source strength in the current site. TEM/EDS analysis for the size-selected UFPs showed that the UFPs were classified into various types having different chemical species. Carbonaceous particles were observed in both combustion (soot and organics) and photochemical events (sulfate and organics). In the photochemical event, an internal mixture of organic species and ammonium sulfate/bisulfate was identified. Also, internal mixtures of aged Na-rich and organic species, aged Ca-rich particles, and doughnut shaped K-containing particles with elemental composition of a strong C with minor O, S, and K-likely to be originated from biomass burning nearby agricultural area, were observed. In addition, fly ash particles were also observed in the combustion event, not in the photochemical event.
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Use of Exploratory Factor Analysis in Maritime Research
Reenu MASKEY,Jiangang FEI,Hong-Oanh Nguyen 한국해운물류학회 2018 The Asian journal of shipping and Logistics Vol.34 No.2
The purpose of this paper is to discuss the approaches that are undertaken while applying exploratory factor analysis (EFA) in maritime journals to attain a factor solution that fulfils the criteria of EFA, achieves the research objectives and makes interpretation easy. To achieve the aim of this paper, published articles across maritime journals will be examined to discuss the use of EFA. This will be followed by an example of EFA using an empirical data set to emphasise the approaches that can be undertaken to make appropriate decisions as to whether to retain or drop an item from the analysis to attain an interpretable factor solution. The results of this study demonstrate that majority of maritime studies employing EFA retain a factor solution based on the researchers‟ subjective judgement. However, the researchers do not provide sufficient information to allow readers to evaluate the analysis. The majority of the reviewed papers failed to provide important information related to EFA explaining how the final factor structure has been acquired. Furthermore, some papers have failed to justify their decisions, for example, for deleting an item or retaining factors with single measured variable. The first contribution of this study is the analysis of how studies carried out in the maritime sector have been applying EFA in their studies. The second contribution of this study is to provide future researchers aiming to use EFA in their studies for the first time an example of a complete EFA process, explaining different steps that can be undertaken while carrying out EFA.
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SNUSAT Mission and System for CanSat Competition Korea 2014
Abhas Maskey,Ju Hyeon Kim,Hee Jae Gwon,Ji Hyun Park,Jae Young Lim,In-Seuck Jeung 한국항공우주학회 2014 한국항공우주학회 학술발표회 논문집 Vol.2014 No.11
Seoul National University’s small satellite group, the SNUSAT, participated in SaTRec’s annual CanSat Competition Korea 2014. In an attempt to differentiate from previous missions in the past and to incorporate more complexity in the design and development process, SNUSAT group for this year decided to take panoramic 360° images for search and rescue operations. This paper discusses the mission and system development while remarking on the hurdles and challenges the group had to face on the road to the final competition.
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