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A dark photon is a hypothetical particle that has a similar role to a photon in the Standard Model (SM) electromagnetic interaction but has been proposed as a force carrier with a potential link to dark matter. Detecting dark photon in particle collider experiments poses significant challenges owing to the interference from the SM events. This paper presents how effectively machine learning can reduce background events that pose a major problem in search for dark photons at future electron–positron accelerators/detectors: CEPC/CEPC, FCC-ee/IDEA and ILC/ILD. Based on the simplified model, we focus on the signal modes of e+e-→A′A′and e+e-→A′A′γ, where A′is a dark photon decaying into a muon pair. The dominant background originates from the SM. The background mode for the e+e-→A′A′is e+e-→μ+μ-μ+μ-, and for the e+e-→A′A′γ, it is e+e-→μ+μ-μ+μ-γ.The signal events are generated using MadGraph5 with the simplified model, while the background events are generated with the SM. We simulated detector responses using Delphes. Machine learning classification was performed using a Boosted Decision Trees classifier built on the Toolkit for Multivariate Data Analysis. Our study demonstrates a significant improvement in the signal-to-background ratio by an order of 100–10000 by effectively reducing background events using machine learning. Finally, we show the detector efficiencies from well-separated signal events.

Particle collider experiments would be continued even when one is not present at the laboratory (on-site). To achieve this, we require an e-Science paradigm of studying particle physics anytime anywhere. One of the components for establishing this paradigm is a remote control room for data acquisition (DAQ). We developed and embedded a remote control room at the Korea Institute of Science and Technology Information (KISTI). Since then, we have been adopting on/offline shifts for conducting collider experiments at KISTI, that is, the experiments are done even when we are not on-site. In this paper, we introduce our experience of our remote control room for both CDF and Belle II experiments. This remote control room includes international networks, security, DAQ systems, data transfers, and monitoring systems. We also presented the results of the shifts done in the remote control room at KISTI.

The material loss caused by bubble collapse during the micro-nano bubbles auxiliary chemical mechanical polishing (CMP) process cannot be ignored. In this study, the material removal mechanism of cavitation in the polishing process was investigated in detail. Based on the mixed lubrication or thin film lubrication, bubble—wafer plastic deformation, spherical indentation theory, Johnson—Cook (J—C) constitutive model, and the assumption of periodic distribution of pad asperities, a new model suitable for micro-nano bubble auxiliary material removal in CMP was developed. The model integrates many parameters, including the reactant concentration, wafer hardness, polishing pad roughness, strain hardening, strain rate, micro-jet radius, and bubble radius. The model reflects the influence of active bubbles on material removal. A new and simple chemical reaction method was used to form a controllable number of micro-nano bubbles during the polishing process to assist in polishing silicon oxide wafers. The experimental results show that micro-nano bubbles can greatly increase the material removal rate (MRR) by about 400% and result in a lower surface roughness of 0.17 nm. The experimental results are consistent with the established model. In the process of verifying the model, a better understanding of the material removal mechanism involved in micro-nano bubbles in CMP was obtained.

Laser-induced breakdown spectroscopy (LIBS) was applied to rapidly detect elements in flowback water samples from shale gas wells in Oklahoma. Two types of LIBS systems (aerosolization and collection on a substrate) were used. The LIBS with an aerosolization system provided rapid determination of elements in flowback water, but moisture present in the chamber and variation in the water droplet size could make quantification difficult. In the substrate collection system, a comparison among substrate types showed that a hydrophilic cellulose filter gave the most homogeneous sample distribution after drying and provided the best performance. The elements in flowback water samples were also determined by inductively coupled plasma–optical emission spectroscopy (ICP-OES). ICP-OES data showed spatial variations for the elements among the different wells. Among the elements, K showed the highest variation (relative standard ${\rm deviation} = {62.8}\% $deviation=62.8%) and Mg the lowest (relative standard ${\rm deviation} = {39.1}\% $deviation=39.1%). Good correlations (${ r} = {0.98 - 0.99}$r=0.98−0.99) were observed between Ca, K, Mg, and Na LIBS peak areas determined using the cellulose filter and their mass concentrations (ppm) measured by ICP-OES for aqueous solutions. The limits of detection for Ca, K, Mg, and Na by LIBS were 122 ppm, 68 ppm, 36 ppm, and 142 ppm, respectively. Both the LIBS and ICP-OES data showed that element concentrations in the flowback water samples were in the order of Na, Ca, Mg, and K from highest to lowest. Our data suggest that the LIBS technique could rapidly detect elements in flowback water samples on site. However, accurate quantification of elements present in low concentrations in water samples is limited.

As a trend of using colloidal and smaller ceria nanoparticles (CNPs) at the shallow trench isolation (STI) chemical mechanical polishing (CMP) in semiconductor manufacturing, post-CMP cleaning challenges in the removal of residual CNPs on the SiO2film surface became much more challenging. We investigated the reduction/oxidation of ceria nanoparticles (CNPs) by hydrogen gas-dissolved water (H2GDW), carbon dioxide gas-dissolved water (CO2GDW), and oxygen gas-dissolved water (O2GDW). The concentration of Ce3+on the CNPs changed from 18.64% to 19.48%, 20.31% to 21.94%, and 21.27% to 19.22%, respectively, after immersion in H2GDW, CO2GDW, and O2GDW for 3 to 12 h. Following the Ce3+concentration of the CNP surface, adhesion energies between CNPs immersed in H2GDW, CO2GDW, and O2GDW for 6 h with SiO2surface were 6.06E-16 J, 6.18E-16 J, and 4.83E-16 J. Cleaning experiments under megasonic conditions revealed the efficacy of H2GDW and O2GDW in removing residual CNPs from SiO2surfaces. The residual cerium (Ce) ion concentrations remaining on the SiO2film surface after cleaning, were 0.06, 0.41, and 0.10 ppb for H2GDW, CO2GDW, and O2GDW, respectively.

Chemical mechanical polishing (CMP) has undergone rapid advancements in global and local planarization. The synergy between the process control and the consumables is critical to overall CMP performance. In addition to optimizing consumables and equipment including a polisher, metrology, and inspection, the polishing protocol plays a crucial role in effective process management. In fabrication scenarios, protocol revision is a convenient and practical approach for problem-solving. This research focuses on the study of head sweep direction, head sweep distance, and slurry sweep effects in oxide film polishing. Sweeping toward the outside resulted in an average increase of 12.66% removal amount for ceria and 11.57% for silica compared to fixed head polishing. Moreover, a longer head sweep distance reduced non-uniformity. While the slurry sweep exhibited a non-significant effect on the removal amount, it proved valuable in optimizing the removal amount profile.

The sources of primary and secondary aerosols in the Arctic are still poorly known. A number of surface seawater samples—with varying degrees of Arctic riverine and sea ice influences—were used in a sea spray generation chamber to test them for their potential to produce sea spray aerosols (SSA) and cloud condensation nuclei (CCN). Our interdisciplinary data showed that both sea salt and organic matter (OM) significantly influenced the SSA production. The number concentration of SSA in the coastal samples was negatively correlated with salinity and positively correlated with a number of OM tracers, including dissolved and chromophoric organic carbon (DOC, CDOM), marine microgels and chlorophyll a(Chl-a) but not for viral and bacterial abundances; indicating that OM of riverine origin enhances primary aerosol production. When all samples were considered, transparent exopolymer particles (TEP) were found to be the best indicator correlating positively with the ratio number concentration of SSA/salinity. CCN efficiency was not observed to differ between the SSA from the various samples, despite differences in organic characteristics. It is suggested that the large amount of freshwater from river runoff have a substantial impact on primary aerosols production mechanisms, possibly affecting the cloud radiative forcing.

Laser-induced breakdown spectroscopy (LIBS) has been increasingly used in recent years to rapidly detect the elemental compositions of various materials in different media (i.e., solids, liquids, and gases). In this study, an aerosol-LIBS system was developed for the real-time monitoring of process-induced particles generated during semiconductor manufacturing. The developed system consists primarily of a laser, a spectrometer, optics, and an aerosol chamber; the last element was constructed for the application of the aerosol-LIBS to various semiconductor manufacturing processes and comprises exhaust tubes and low pressure and high temperature chambers. The system was evaluated for its sensitivity to various elements using laboratory-generated aerosols and successfully detected P, Fe, Mg, Cu, Co, Ni, Ca, Na, and K emission lines. Further evaluation of the aerosol-LIBS is ongoing.

ABSTRACTThe size distribution and chemical components of a fine fraction (<2.5 μm) of road dust collected at urban sites in Korea (Gwangju) and Mongolia (Ulaanbaatar) where distinct urban characteristics exist were measured. A clear bimodal size distribution was observed for the resuspended fine road dust at the urban sites in Korea. The first mode peaked at 100–110 nm, and the second peak was observed at 435–570 nm. Ultrafine mode (~30 nm) was found for the fine road dust at the Mongolia site, which was significantly affected by residential coal/biomass burning. The contribution of the water-soluble ions to the fine road dust was higher at the sites in Mongolia (15.8–16.8%) than at those in Korea (1.2–4.8%). Sulfate and chloride were the most dominant ionic species for the fine road dust in Mongolia. As (arsenic) was also much higher for the Mongolian road dust than the others. The sulfate, chloride, and As mainly come from coal burning activity, suggesting that coal and biomass combustion in Mongolia during the heating season should affect the size and chemical components of the fine road dust. Cu (copper) and Zn (zinc), carbonaceous particles (organic carbon [OC] and elemental carbon [EC]) increased at sites in Korea, suggesting that the fine road dust at these sites was significantly affected by the high volume of traffic (engine emission and brake/tire wear). Our results suggest that chemical profiles for road dust specific to certain sites should be applied to more accurately apportion road dust source contributing to the ambient particulate matter.Implications: Size and chemical characteristics of fine road dust at sites having distinct urban characteristics were examined. Residential coal and biomass burning and traffic affected physiochemical properties of the fine road dust. Different road dust profiles at different sites should be needed to determine the ambient PM2.5 sources more accurately.

A stand-off laser-induced breakdown spectroscopy (LIBS) system was developed to determine the elemental composition of contamination particles during semiconductor manufacturing. It successfully detected laboratory-generated monodisperse (size=200  nm and 300 nm) CaCl_2 particles and internally mixed particles of CaCl_2, MgCl_2, NaCl, and KCl. Temperature and pressure effects on the LIBS emission signals were investigated. The peak area and signal-to-noise ratio of the emission lines increased with the temperature (25°C–250°C). Stronger emission lines were observed at higher pressure. Although temperature and pressure affect the LIBS signals, the developed stand-off LIBS could be employed for real-time detection of the elemental composition of contamination particles.

Chemical characteristics of aerosols (PM1(on-line measurement) and PM2.5(off-line measurement) were investigated in coastal and urban atmospheres. Organics were the most dominant species in PM1at both sites, exhibiting little difference in the relative fractions of chemical constituents in PM1(organics, sulfate, black carbon (BC), nitrate, ammonium and chloride) between two sites. However, a clear difference in the types of organics was found between the two sites. The fraction of oxidized (aged) organics was much higher at coastal site than at urban site. The nitrate fraction significantly increased at both sites in PM2.5compared with that in PM1, suggesting that a significant amount of nitrate exists at particle sizes of 1 μm–2.5 μm. Additionally, the aerosols observed at coastal site were acidic. At both sites, photochemical activity played an important role in enhancing sulfate and oxidized organics in the afternoon, thereby overcoming the dilution effect. More distinct diurnal patterns were observed for nitrate, BC and organics at the urban site compared to the coastal site. Chemical characteristics also varied with different air masses. The highest PM concentration was associated with the northwest continental air mass (the air mass passed over heavy industrial areas before arriving at the site and moved slowly compared to other air masses). Three PM events (sulfate-dominant versus organic-dominant) were observed during the sampling periods and were considered long-range transport (LTP) events. The water-soluble organic carbon (WSOC) and oxidized organic contents significantly increased during LTP events, suggesting that organics were highly aged during transport.

Cloud condensation nuclei (CCN) activation of black carbon (BC) particles coated with different amounts of inorganic (sulfuric acid) and organic (levoglucosan or succinic acid) compounds was investigated. An evaporation-condensation method was used to produce coated BC particles, and the volume fractions of coating species were measured using the tandem differential mobility analyzer method. Furthermore, the CCN activation of the coated BC particles was measured using a differential mobility analyzer-CCN counter method. Coating with both aforementioned compounds engendered the activation of the BC particles as CCN at a supersaturation of 0.5%. Sulfuric acid coating was associated with the highest CCN activation fraction (= CCN/condensation nuclei), followed by levoglucosan coating and then succinic acid coating; this indicates that the water solubility of the coating compounds played a crucial role in the CCN activation of the coated BC particles. In general, the CCN activation fraction of the coated BC particles increased with the volume fraction of the coating species, but the manner of increase differed with the coating compounds and generation method. A premixed solution method was also used to produce mixed BC particles, and among the coating compounds, sulfuric acid was associated with the highest CCN activation fraction. For a given volume fraction, sulfuric-acid-coated BC particles produced using the premixed solution method showed a higher CCN activation fraction compared with those obtained using the evaporation-condensation method, and this was due to the presence of residual water in the sulfuric-acid-coated BC particles produced using the premixed solution method.

AbstractParticle light scattering (Bsp) from nephelometers and fine particulate matter (PM2.5) mass determined by filter samplers are compared for summer and winter at 35 locations in and around California’s San Joaquin Valley from December 2, 1999 to February 3, 2001. The relationship is described using particle mass scattering efficiency (σsp) derived from linear regression of Bspon PM2.5that can be applied to estimated PM2.5from nephelometer data within the 24-hr filter sampling periods and between the every-6th-day sampling frequency. An average of σsp=4.9 m2/g was found for all of the sites and seasons; however, σspaveraged by site type and season provided better PM2.5estimates. On average, the σspwas lower in summer than winter, consistent with lower relative humidities, lower fractions of hygroscopic ammonium nitrate, and higher contributions from fugitive dust. Winter average σspwere similar at non-source-dominated sites, ranging from 4.8 m2/g to 5.9 m2/g. The σspwas 2.3 m2/g at the roadside, 3.7 m2/g at a dairy farm, and 4.1 m2/g in the Kern County oilfields. Comparison of Bspfrom nephelometers with and without a PM2.5inlet at the Fresno Super-site showed that coarse particles contributed minor amounts to light scattering. This was confirmed by poorer correlations between Bspand coarse particulate matter measured during a fall sampling period.

AbstractContinuous measurements of particle size distributions of 3–407 nm were collected from August 2002 to July 2004 at the Fresno Supersite to understand their number concentrations, size distributions, and formation processes. Measurements for fine particulate matter (PM2.5) mass, sulfate (SO42−), nitrate (NO3−), black carbon (BC), particle-bound polycyclic aromatic hydrocarbons (PAHs), nitrogen oxides (NOx), carbon monoxide (CO), ozone (O3), and meteorological data (wind speed, wind direction, temperature [T], relative humidity [RH], and solar radiation) were used to determine the causes of nanoparticle (3–10 nm) and ultrafine (10–100 nm) particle events. These events were found to be divided into four types: (1) 3- to 10-nm morning nucleation; (2) 10- to 30-nm morning traffic; (3) 10- to 30-nm afternoon photochemical; and (4) 50- to 84-nm evening home heating, including residential wood combustion. Intense examples of the first type (>104number [#]/cm3) were observed on 29 days, nearly always during the summer. The second type of event was observed on more than 73 days and occurred throughout the year. The third type was observed on 36 days, from spring through summer. The fourth type was found on 109 days, all of them during the winter. Although sulfur dioxide (SO2) emissions in Central California are low, the small residual amounts in gasoline and diesel fuel are apparently sufficient to initiate nucleation events. These were measured in the morning, soon after the shallow surface inversion coupled with layers aloft where nucleation probably was initiated. PM2.5concentrations were poorly correlated with nanoparticle number.

AbstractResults from six continuous and semicontinuous black carbon (BC) and elemental carbon (EC) measurement methods are compared for ambient samples collected from December 2003 through November 2004 at the Fresno Supersite in California. Instruments included a multi-angle absorption photometer (MAAP; λ = 670 nm); a dual-wavelength (λ = 370 and 880 nm) aethalometer; seven-color (λ = 370, 470, 520, 590, 660, 880, and 950 nm) aethalometers; the Sunset Laboratory carbon aerosol analysis field instrument; a photoacoustic light absorption analyzer (λ = 1047 nm); and the R&P 5400 ambient carbon particulate monitor. All of these acquired BC or EC measurements over periods of 1 min to 1 hr. Twenty-four-hour integrated filter samples were also acquired and analyzed by the Interagency Monitoring of Protected Visual Environments (IMPROVE) thermal/optical reflectance carbon analysis protocol. Site-specific mass absorption efficiencies estimated by comparing light absorption with IMPROVE EC concentrations were 5.5 m2/g for the MAAP, 10 m2/g for the aethalometer at a wavelength of 880 nm, and 2.3 m2/g for the photoacoustic analyzer; these differed from the default efficiencies of 6.5, 16.6, and 5 m2/g, respectively. Scaling absorption by inverse wavelength did not provide equivalent light absorption coefficients among the instruments for the Fresno aerosol measurements. Ratios of light absorption at 370 nm to those at 880 nm from the aethalometer were nearly twice as high in winter as in summer. This is consistent with wintertime contributions from vehicle exhaust and from residential wood combustion, which is believed to absorb more shorter-wavelength light. To reconcile BC and EC measurements obtained by different methods, a better understanding is needed of the wavelength dependence of light-absorption and mass-absorption efficiencies and how they vary with different aerosol composition.

ABSTRACTCarbonaceous components (organic carbon [OC] and elemental carbon [EC]) and optical properties (light absorption and scattering) of fine particulate matter (aerodynamic diameter <2.5 μm; PM2.5) were simultaneously measured at an urban site in Gwangju, Korea, during the winter of 2011. OC was further classified into OC1, OC2, OC3, and OC4, based on a temperature protocol using a Sunset OC/EC analyzer. The average OC and EC concentrations were 5.0 ± 2.5 and 1.7 ± 0.9 μg C m−3, respectively. The average single-scattering albedo (SSA) at a wavelength of 550 nm was 0.58 ± 0.11, suggesting that the aerosols observed in the winter of 2011 had a local warming effect in this area. During the whole sampling period, “stagnant PM” and “long-range transport PM” events were identified. The light absorption coefficient (babs) was higher during the stagnant PM event than during the long-range transport PM event due to the existence of abundant light-absorbing OC during the stagnant PM event. In particular, the OC2 and OC3 concentrations were higher during the stagnant PM event than those during the long-range transport event, suggesting that OC2 and OC3 might be more related to the light-absorbing OC. The light scattering coefficient (bscat) was similar between the events. On average, the mass absorption efficiency attributed to EC (σEC) was 9.6 m2g−1, whereas the efficiency attributed to OC (σOC) was 1.8 m2g−1at λ = 550 nm. Furthermore, the σECis comparable among the PM event days, but the σOCfor the stagnant PM event was significantly higher than that for the long-range transport PM event (1.7 vs. 0.5).Implications: Optical and thermal properties of carbonaceous aerosol were measured at Gwangju, and carbonaceous aerosol concentration and optical property varied between “stagnant PM” and “long-range transport PM” events. More abundant light absorbing OC was observed during the stagnant PM event.

Carbonaceous species (organic carbon [OC] and elemental carbon [EC]) and inorganic ions of particulate matter less than 2.5 μm (PM2.5) were measured to investigate the chemical characteristics of long-range-transported (LTP) PM2.5at Gosan, Jeju Island, in Korea in the spring and fall of 2008–2012 (excluding 2010). On average, the non-sea-salt (nss) sulfate (4.2 µg/m3) was the most dominant species in the spring, followed by OC (2.6 µg/m3), nitrate (2.1 µg/m3), ammonium (1.7 µg/m3), and EC (0.6 µg/m3). In the fall, the nss-sulfate (4.7 µg/m3) was also the most dominant species, followed by OC (4.0 µg/m3), ammonium (1.7 µg/m3), nitrate (1.1 µg/m3), and EC (0.7 µg/m3). Both sulfate and OC were higher in the fall than in the spring, possibly due to more common northwest air masses (i.e., coming from China and Korea polluted areas) and more frequent biomass burnings in the fall. There was no clear difference in the EC between the spring and fall. The correlation between OC and EC was not strong; thus, the OC measured at Gosan was likely transported across a long distance and was not necessarily produced in a manner similar to the EC. Distinct types of LTP events (i.e., sulfate-dominant LTP versus OC-dominant LTP) were observed. In the sulfate-dominant LTP events, air masses directly arrived at Gosan without passing over the Korean Peninsula from the industrial area of China within 48 hr. During these events, the aerosol optical depth (AOD) increased to 1.63. Ionic balance data suggest that the long-range transported aerosols are acidic. In the OC-dominant LTP event, a higher residence time of air masses in Korea was observed (the air masses departing from the mainland of China arrived at the sampling site after passing Korea within 60–80 hr).Implications: In Northeast Asia, various natural and anthropogenic sources contribute to the complex chemical components and affect local/regional air quality and climate change. Chemical characteristics of long-range-transported (LTP) PM2.5were investigated during spring and fall of 2008, 2009, 2011, and 2012. Based on air mass types, sulfate-dominant LTP and OC-dominant LTP were observed. A long-term variation and chemical characteristics of PM2.5along with air mass and satellite data are required to better understand long-range-transported aerosols.

During three separate studies involving characterization of diesel particulate matter, carbon nanotubes (CNTs) were found among diesel exhaust particles sampled onto transmission electron microscopy (TEM) grids. During these studies, samples were collected from three different diesel engines at normal operating conditions with or without an iron catalyst (introduced as ferrocene) in the fuel. This paper is to report the authors’ observation of CNTs among diesel exhaust particles, with the intent to stimulate awareness and further discussion regarding the formation mechanisms of CNTs during diesel combustion.Implications:Increased attention is being given to CNTs and other nanomaterials and a recent review paper showed that CNTs are capable of inflammation in the lung when inhaled. For this reason and because diesel engines are so common, it is important to acknowledge the existence of CNTs among diesel particles and possible regulation and online measurement method development.

In order to investigate the chemical characteristics of atmospheric aerosol measured during a severe winter haze event, 12-hr PM2.5(particulate matter with an aerodynamic diameter ≤2.5 μm) samples were collected at an urban site in Ulaanbaatar, Mongolia, from January 9 to February 17, 2008. On average, 12-hr PM2.5mass concentration was 105.1 ± 34.9 μg/m3. Low PM2.5mass concentrations were measured when low pressure developed over central Mongolia. The 12-hr average organic mass by carbon (OMC) varied from 6.4 to 132.3 μg/m3, with a mean of 54.9 ± 25.4 μg/m3, whereas elemental carbon (EC) concentration ranged from 0.1 to 3.6 μgC/m3, with a mean of 1.5 ± 0.8 μgC/m3. Ammonium sulfate was found to be the most abundant water-soluble ionic component in Ulaanbaatar during the sampling period, with an average concentration of 11.3 ± 5.0 μg/m3. In order to characterize the effect of air mass pathway on fine particulate matter characteristics, 5-day back-trajectory analysis was conducted, using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. The haze level was classified into three categories, based on the 5-day air mass back trajectories, as Stagnant (ST), Continental (CT), and Low Pressure (LP) cases. PM2.5mass concentration during the Stagnant condition was approximately 2.5 times higher than that during the Low Pressure condition, mainly due to increased pollutant concentration of OMC and secondary ammonium sulfate.Implications:Mongolia is experiencing rapid rates of urbanization similar to other Asian countries, resulting in air pollution problems by the growing number of automobiles and industrialization. Ulaanbaatar, capital of Mongolia, is inherently vulnerable to air pollution because of its emission sources, topography, and meteorological characteristics. Very limited measurements on chemical characteristics of particulate matter have been carried out in Ulaanbaatar, Mongolia.

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., NO2, SO2, 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 5.53×103cm−3, 4.68×103cm−3, 5.32×103cm−3, 3.99×103cm−3, and 2.16×103cm−3in 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.

Biomass burning emitted aerosols are subject of concern in different disciplinary researches from different perspectives (climate change science from shift of balance in radiative forcing having severe repercussions on global ecosystem, while air pollution science from public health concern). By exploring particle number emission factors (PNEF), particle size distributions, and volatility of emitted ultrafine particles from burning rice straw, potential annual release of aerosols from rice straw combustion to the global atmosphere is estimated, and the issue of their management from such interdisciplinary perspectives is discussed. Between an estimated as low as 15% and as high as 75% of rice straw being burnt globally, the global annual estimate of emitted aerosols mounted from an order of 1021particles/yr to the order of 1022particles/yr. From looking at different estimates made therein, we advocate Dp= 0.25 µm (PN0.25equivalent) for adopting emission control standards. In volatility analysis flaming combustion and open burning indicated internal mixing of black carbon and organic carbon in emitted ultrafine particles, while smoldering combustion emitted ultrafine particles having little black carbon component. Up to 65% contrast in remaining volume in volatility analysis between the flaming and smoldering combustions, and positioning of open burning in between them, give us the idea of potential management of such biomass burning with controllable distinct choices. Therefore, the concept of exploiting potential from interdisciplinary dimensions is coined to enable more efficient management with least amounts of additional resources utilized, by resolving complexities through mutual cooperation of concerned disciplinary researches. It also shows a new avenue in our affairs in managing global atmosphere for the global ecosystem and public health.

A new methodology for creating patterned fluorescence images was developed based on acrylate polymers that have pendant triphenylmethane derivatives as precursor fluorophores. Photoinduced oxidation of the substituted nonfluorescent triphenylmethane substituents on the polymers results in the generation of fluorescent cationic species. Patterned fluorescence images were obtained when the polymer film was subjected to photomasked UV‐irradiation. The rate of formation and quality of the patterned images were found to be dependent on the nature of substituents on the methane carbon of the triphenylmethane group. Inefficient image formation takes place with the polymer derived from the H‐substituted derivative owing to the inefficient oxidation of the triphenylmethane group. In contrast, photomasked UV‐irradiation of a thin polymer film derived from the CN‐substituted triphenylmethane derivative leads to fast (1 s irradiation, 12 mW · cm−2) and finely resolved patterned fluorescence images.

ABSTRACTThe application of Laser-Induced Fluorescence (LIF) into soil remediation process is not popular due to the difficulties of the interpretation of remediation process. The monitoring for the lab-scale surfactant enhanced electrokinetic remediation process using the LIF was performed. The variation of the fluorescence intensity and the change of the fluorescence spectral signature reflecting the nature of the surrounding environment were investigated. The diffuse reflectance correction method for the soil matrix properties on fluorescence, and the time resolution for isolation of surfactant which can be overlapped with PAHs spectra of interest were considered to provide the information of contaminants taking place during the remediation process. Eletrokinetic (EK) remediation process as control experiment was also performed and this result was compared with the surfactant-enhanced EK process especially in terms of the spectral signature of PAHs. The LIF monitoring for soil remediation process showed that the relative quantities and the state of contaminant in soil media which can be an important key to assess the feasibility of remediation process.

Abstract: In this research, an enhanced lateral stability control system has been developed for a vehicle. The system consists of a vehicle parameter estimation part and an enhanced ESP control logic part. The vehicle parameter estimation was conducted by considering the physical relationship among the longitudinal dynamic components. The enhanced ESP logic was designed so that the controller gains change adaptively to the vehicle parameter variation. All the system components were tested in a simulation environment, while the vehicle mass estimation algorithm was also tested in the field. The results indicated that the lateral vehicle stability limit can be improved with the designed ESP system.

Particulate matter (PM) causes several diseases, including cardiovascular diseases (CVDs). Previous studies compared the gene expression patterns in airway epithelial cells and keratinocytes exposed to PM. However, analysis of differentially expressed gene (DEGs) in endothelial cells exposed to PM2.5 (diameter less than 2.5 μm) from fossil fuel combustion has been limited. Here, we exposed human umbilical vein endothelial cells (HUVECs) to PM2.5 from combustion of gasoline, performed RNA-seq analysis, and identified DEGs. Exposure to the IC50 concentrations of gasoline engine exhaust PM2.5 (GPM) for 24 h yielded 1081 (up-regulation: 446, down-regulation: 635) DEGs. The most highly up-regulated gene is NGFRfollowed by ADM2and NUPR1. The most highly down-regulated gene is TNFSF10followed by GDF3and EDN1. Gene Ontology enrichment analysis revealed that GPM regulated genes involved in cardiovascular system development, tube development and circulatory system development. Kyoto Encyclopedia of Genes and Genomes and Reactome pathway analyses showed that genes related to cytokine–cytokine receptor interactions and cytokine signaling in the immune system were significantly affected by GPM. We confirmed the RNA-seq data of some highly altered genes by qRT-PCR and showed the induction of NGFR, ADM2 and IL-11 at a protein level, indicating that the observed gene expression patterns were reliable. Given the adverse effects of PM2.5 on CVDs, our findings provide new insight into the importance of several DEGs and pathways in GPM-induced CVDs.

Wide-spread deployment of infrastructure WLANs has made Wi-Fi an integral part of today's Internet access technology. Despite its crucial role in affecting end-to-end performance, past research has focused on MAC protocol enhancement, analysis and simulation-based performance evaluation without sufficient consideration for modeling inaccuracies stemming from inter-layer dependencies, including physical layer diversity, that significantly impact performance. We take a fresh look at IEEE 802.11 WLANs, and using a combination of experiment, simulation, and analysis demonstrate its surprisingly agile performance traits. Our main findings are two-fold. First, contention-based MAC throughput degrades gracefully under congested conditions, enabled by physical layer channel diversity that reduces the effective level of MAC contention. In contrast, fairness and jitter significantly degrade at a critical offered load. This duality obviates the need for link layer flow control for throughput improvement but necessitates traffic control for fairness and QoS. Second, TCP-over-WLAN achieves high throughput commensurate with that of wireline TCP under saturated conditions, challenging the widely held perception that TCP throughput fares poorly over WLANs when subject to heavy contention. We show that TCP-over-WLAN prowess is facilitated by the self-regulating actions of DCF and TCP congestion control that jointly drive the shared physical channel at an effective load of 2--3 wireless stations, even when the number of active stations is very large. Our results highlight subtle inter-layer dependencies including the mitigating influence of TCP-over-WLAN on dynamic rate shifting.

We describe a new technique to measure the size dependent inherent material density of chain agglomerate particles. Measurements were carried out for diesel soot and aluminum/alumina agglomerate particles in the nanometer size range. Transmission electron microscopy was used to measure the volumes of agglomerate particles that were preselected by mass using an aerosol particle mass analyzer. We found that the density of diesel exhaust particles increased from 1.27 to 1.78g/cm3as particle mobility size increased from 50 to 220nm. When particles are preheated to remove volatile components, the density was 1.77±0.07g/cm3, independent of particle size. The densities measured after heating correspond to the inherent material density of diesel soot. Measurements with aluminum nanoparticles were made downstream of a furnace where aluminum (Al) was converted to alumina (Al2O3). From measurements of inherent material density we were able to infer the extent of reaction, which varied with furnace temperature.

Triphenylamine(TPA) substituted polysiloxane was synthesized as the hole-transporting material. Field dependence of the hole mobility and photoconductivity were measured using the time-of flight and simple DC photocurrent measurement, respectively. We demonstrated that the film of polysiloxane with pendant TPA units higher hole mobility (3.2×10 −5 cm 2 /Vsec at E=6×10 5 ) than that of the conventional poly( N -vinylcarbazole) and carbazole substituted polysiloxane. Further experiments are required to test these new materials as hole transporting layers in photorefractive and electroluminescent devices.

AbstractNew styryl dyes for the recording layer of digital versatile disc-recordable (DVD-R) were synthesized and analyzed by UV-vis spectroscopy and thermal analyzer. Using these dyes, we prepared two-type DVD-R discs, with/without metallic thin film between substrate and organic buffer layer. The metal-polymer deformation 4.7 GB DVD-R discs were recorded by high-power 658nm-wavelength laser diode and their recording characteristics were evaluated at 650nm wavelength. The optimum writing power and jitter value was in the range of 10 mW and 12∽13 %, respectively.

Denial of service (DoS) attack on the Internet has become a pressing problem. In this paper, we describe and evaluate route-based distributed packet filtering (DPF), a novel approach to distributed DoS (DDoS) attack prevention. We show that DPF achieves proactiveness and scalability, and we show that there is an intimate relationship between the effectiveness of DPF at mitigating DDoS attack and power-law network topology.The salient features of this work are two-fold. First, we show that DPF is able to proactively filter out a significant fraction of spoofed packet flows and prevent attack packets from reaching their targets in the first place. The IP flows that cannot be proactively curtailed are extremely sparse so that their origin can be localized---i.e., IP traceback---to within a small, constant number of candidate sites. We show that the two proactive and reactive performance effects can be achieved by implementing route-based filtering on less than 20% of Internet autonomous system (AS) sites. Second, we show that the two complementary performance measures are dependent on the properties of the underlying AS graph. In particular, we show that the power-law structure of Internet AS topology leads to connectivity properties which are crucial in facilitating the observed performance effects.

The semi-active suspension system is getting widely adopted in passenger vehicles for its ability to improve ride comfort with low cost and light weight. A key to the success is to develop practical controllers that yield performance enhancement over the passive damper under various driving conditions. To this end, several control strategies have been studied and evaluated in this research in consideration of practical aspects such as nonlinearity and dynamics of the damper. From simulation results, it has been observed that, with the proposed control schemes, ride comfort can be significantly upgraded while suppressing degradation of driving safety.

With the proliferation of workstation clusters connected by high-speed networks, providing efficient system support for concurrent applications engaging in nontrivial interaction has become an important problem. Two principal barriers to harnessing parallelism are: (1) efficient mechanisms that achieve transparent dependency maintenance while preserving semantic correctness and (2) scheduling algorithms that match coupled processes to distributed resources while explicitly incorporating their communication costs. This paper describes a set of performance features and their properties and implementation in a system support environment called DUNES that achieves transparent dependency maintenance—IPC, file access, memory access, process creation/termination, process relationships—under dynamic load balancing. The two principal performance features are push/pull-based active and passive end-point caching and communication-sensitive load balancing. Collectively, they mitigate the overhead introduced by the transparent dependency maintenance mechanisms. Communication-sensitive load balancing, in addition, affects the scheduling of distributed resources to application processes where both communication and computation costs are explicitly taken into account. DUNES' architecture endows commodity operating systems with distributed operating system functionality while achieving transparency with respect to their existing application base. DUNES also preserves semantic correctness with respect to single processor semantics. We show performance measurements of a UNIX-based implementation on Sparc and x86 architectures over high-speed LAN environments. We show that significant performance gains in terms of system throughput and parallel application speedup are achievable.

AbstractThe poling process in nonlinear optical (NLO) polymer films is studied by the second harmonic generation (SHG) and optical retardation measurements. The PMSt polymer is used as a NLO chromophore whose dipole moment is aligned transverse to the main-chain backbone. Both the optical retardation and the SHG intensity increase during poling process and decay after poling in the same fashion. The optical retardation is found to be more sensitive to the thermal fluctuations than the SHG.

This paper presents a distributed, end-to-end congestion control protocol for use in high-traffic, packet-switched networks. The network is represented as a stochastic single-server queue, with arrival rates being the control variables. A time-stamp based measure of network state called warp is defined, and it is shown to be an estimator of network utilization. Congestion is modeled explicitly using unimodal load-throughput functions, and its mono tonicity property is exploited to yield characterizations of the interplay between optimality and stability. First, a protocol based on “perfect” information is analyzed, whose prowess is then shown to be emulated by one which only uses locally computable, delayed information. Both are subject to the unimodality assumption which has the effect of inducing a division of the phase space into stable and unstable regions, the optimal operating point lying at its boundary. Protocols are devised for dealing with each regime separately, rate adjustment protocol being the control that guides the system to the optimal operating point, pro active and reactive rate protocols dealing with the issue of maintaining near optimal throughput in the long-run. Protocols for handling fairness and structural perturbation augment the basic suite. The potential instability of the optimal operating point, even with control, carries implications for the different costs associated with proactive versus reactive congestion control mechanisms and their feasibility in high-speed networks. The analysis is supported by simulations showing the global dynamical properties of the system.