| 1. |
- Chatterjee, Kalyan, et al.
(author)
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Bidding rings : a bargaining approach
- 2017
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In: Games and Economic Behavior. - : Elsevier BV. - 0899-8256.
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Journal article (peer-reviewed)abstract
- We address the issue of bidder ring formation in single and multi-unit Vickrey auctions. We analyze this issue in a bargaining game set up under the assumption that valuation of bidders is commonly known only amongst themselves. In the single unit case, we show that the equilibrium coalition structure can only be an order preserving r-ring , that includes the winner and the top (r−1)(r−1) losers. In the multiple units case, we specify sufficient conditions for formation of an interesting class of equilibrium coalition structures, which we call single winner ring with free riding, where exactly one winner colludes with all the losers and generates maximum possible bidders' surplus, and, depending on the protocol, the remaining winners free ride either by staying alone or by colluding in pairs.
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| 2. |
- Kong, Xiangrui, et al.
(author)
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Molecular characterization and optical properties of primary emissions from a residential wood burning boiler
- 2021
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In: Science of the Total Environment. - : Elsevier B.V.. - 0048-9697 .- 1879-1026. ; 754
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Journal article (peer-reviewed)abstract
- Modern small-scale biomass burners have been recognized as an important renewable energy source because of the economic and environmental advantages of biomass over fossil fuels. However, the characteristics of their gas and particulate emissions remain incompletely understood, and there is substantial uncertainty concerning their health and climate impacts. Here, we present online measurements conducted during the operation of a residential wood-burning boiler. The measured parameters include gas and particle concentrations, optical absorption and chemical characteristics of gases and particles. Positive matrix factorization was performed to analyze data from a high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) equipped with a filter inlet for gases and aerosols (FIGAERO). Six factors were identified and interpreted. Three factors were related to the chemical composition of the fuel representing lignin pyrolysis products, cellulose/hemicellulose pyrolysis products, and nitrogen-containing organics, while three factor were related to the physical characteristics of the emitted compounds: volatile compounds, semi-volatile compounds, and filter-derived compounds. An ordinal analysis was performed based on the factor fractions to identify the most influential masses in each factor, and by deconvoluting high-resolution mass spectra fingerprint molecules for each factor were identified. Results from the factor analysis were linked to the optical properties of the emissions, and lignin and cellulose/hemicellulose pyrolysis products appeared to be the most important sources of brown carbon under the tested burning conditions. It is concluded that the emissions from the complex combustion process can be described by a limited set of physically meaningful factors, which will help to rationalize subsequent transformation and tracing of emissions in the atmosphere and associated impacts on health and climate.
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| 3. |
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| 4. |
- Mitra, Kalyan
(author)
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Formation and Transformation of Atmospheric Brown Carbon (BrC)
- 2022
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Doctoral thesis (other academic/artistic)abstract
- Atmospheric brown carbon (BrC) aerosol absorbs light in the UV-Vis spectrum and has poorly constrained but potentially large climate forcing impacts. Most current climate models lack detailed chemistry and interlinked properties of atmospheric BrC, that induce large uncertainties in radiative forcing predictions. BrC lifecycle and its atmospheric lifespan have not been fully explored. It is suggested that strongly light absorbing primary BrC (PBrC) may rapidly evolve into weakly light absorbing secondary BrC (SBrC) in the atmosphere, which is considered as bleaching of PBrC. Therefore, formation, transformation and optical properties of PBrC from biomass and fossil-fuel combustion system were investigated in lab and field studies. On the other hand, non-absorbing secondary/primary organic aerosol (SOA/POA) evolve into weakly light absorbing SBrC referred as browning of SOA/POA. The chemical processes underlying SOA aging and the subsequent formation and transformation of SBrC are not well understood. The presence of reactive nitrogen, acidity and water is also thought to further drive the chemistry of SBrC evolution and hence contribute to the global radiative forcing budget. These possibilities, and others, were explored in detail and are presented in this PhD thesis. Biomass is a major source of PBrC emissions, but also it is an important renewable bioenergy source because of its economic and environmental advantages over fossil fuels. The formation of PBrC and its optical properties in a modern Swedish small-scale biomass burner were explored. The measured parameters include gas and particle concentrations, optical absorption and chemical characteristics of gases and particles. Positive matrix factorization (PMF) was performed to analyze data from a HR-ToF-CIMS equipped with FIGAERO and PASS-3. Results from the factor analysis were linked to the optical properties of the emissions, and lignin and cellulose/hemicellulose pyrolysis products were the most important sources of PBrC under the tested burning conditions. Further, formation of PBrC and its atmospheric transformation was studied at a remote rural site, the Indo-Gangetic Plains – Centre for Air Research and Education (IGP-CARE) in India,in the Indo Gangetic Plain in India where some of the most severe air pollution episodes occur on Earth. The field measurements of short-lived climate pollutants including BrC, black carbon (BC) and ozone (O3) were conducted over a period of one year. In this study, the elevated concentrations of BrC co-emitted BC were identified, which was mostly PBrC and can largely be attributed to the local biomass burning activities in the neighbouring rural communities. This study's most important finding is that the BrC concentration normalized by BC concentration (BrC/BC ratio) showed a very pronounced diurnal variation throughout the year with distinct morning and evening peaks in general and a minimum at around noon time i.e. boat shape pattern of BrC/BC. The profile of the BrC/BC ratio evolved astonishingly during the day-time. An extremely sharp decline in the BrC/BC ratio at the time of dawn each morning indicates the dominance of photochemical processes in the transformation of PBrC. This is hypothesized to be associated with daytime photochemical bleaching of the PBrC and transforming it into SBrC. PBrC formation and its optical properties were investigated in three distinct premixed fossil-fuelled i.e. propane, flames. POA containing BrC constituted a high fraction (20–40% by mass) of aerosol mass and was predominantly (i.e., 92–97% by mass) internally mixed with soot particles. In these flames, aerosol mixture containing BrC, POA and BC was found to be highly light absorptive, i.e., an Ångström absorption exponent (AAE) value at 405/781 nm > 1.5. The mass absorption cross-section (MAC - 5 m2g-1) of POA containing BrC at 405 nm under a specific flame i.e. fuel-rich setting, was comparable to MACs of BC particles (8–9 m2 g-1). SBrC formation, transformation and its optical properties were explored under the influence of reactive nitrogen (NOx, NH3)-, acidity (H2SO4)-, and water-mediated chemistry during the photo-oxidation of toluene and subsequent aging of its SOA. The pattern of toluene SOA formation at [NOx]/[ΔHC] molar ratios 0.15 or below was distinctly different (i.e. constant SOA mass) than that was observed at [NOx]/[ ΔHC] ratios higher than 0.15 (i.e. here, SOA mass decreased). These distinguish between SOA formed under nitrogen-poor (NP) conditions i.e. with low initial NOx concentrations, and nitrogen-rich (NR) SOA formed at higher initial NOx concentrations, which has a higher content of compounds such as organo-nitrates. This distinction is valuable for understanding trends in the formation and properties of SOA containing BrC in the presence of varying concentrations of NOx. Hereafter, NP SOA and NR SOA are referred to SOA formed under nitrogen poor and nitrogen rich conditions, respectively. The light absorption coefficient (Babs) and mass absorption cross-section (MAC) of the SOA increased with [NOx/ΔHC] under both the NP and NR regimes. For NP SOA, the MAC increased with [NOx/ΔHC] independently of the relative humidity (RH). However, the MAC of NR SOA was RH-dependent. Under both NP and NR regimes, NH3 and acidity promoted SOA browning. The highest MAC was observed at the lowest RH (20%) for acidic NR SOA, and it was postulated that the MAC of SOA depends mainly on the pH and the [H+]free/[SOA mass] ratio of the aqueous SOA phase. In the same preceding experiments, I additionally analyzed data from HR-ToF-CIMS. I found that several m/z (i.e. mass to charge ratio of a chemically ionized molecule detected in mass spectrometry) mimicked the trend of observed bulk Babs – against [NOx/ΔHC] increase, of SOA containing BrC. These m/z hereafter termed BrC molecules containing chromophores. An interesting observation was that the key m/z contributing to the Babs were distinct for each experiment. However, we found m/z 296 as a common dominant BrC chromophore (m/z), under several experimental conditions. The RH played a vital role in determining the BrC composition i.e. m/z distribution. The BrC molecules containing chromophores corresponding to various identified m/z are suggested to be nitro-aromatic compounds (NAC), which are primarily formed via OH oxidation of toluene followed by the nitration processing of the oxidized aromatic ring. The suggested key BrC molecules containing chromophores are the nitro-derivatives of the phenols, catechol, benzoic acid, benzaldehyde and benzonitriles.
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| 5. |
- Mitra, Kalyan, et al.
(author)
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Secondary Organic Aerosol (SOA) from Photo-Oxidation of Toluene: 1 Influence of Reactive Nitrogen, Acidity and Water Vapours on Optical Properties
- 2022
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In: Atmosphere. - : MDPI AG. - 2073-4433. ; 13:7
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Journal article (peer-reviewed)abstract
- Many climate models treat the light-absorbing SOA component called “brown carbon” (BrC) as non-light absorbing because its formation and transformations are poorly understood. We therefore investigated the influence of reactive nitrogen (NOx, NH3)-, acidity (H2SO4)-, and water-mediated chemistry on SOA formed by the photo-oxidation of toluene, the subsequent formation and transformation of BrC, and its optical properties. We discovered that nitrogen-poor (NP) SOA is formed when the molar ratio of NOx to reacted toluene (henceforth, [NOx/ΔHC]) is 0.15 or less, whereas nitrogen-rich (NR) SOA is formed when [NOx/ΔHC] > 0.15. NR and NP SOA have markedly different characteristics. The light absorption coefficient (Babs) and mass absorption cross-section (MAC) of the SOA increased with [NOx/ΔHC] under both the NP and NR regimes. For NP SOA, the MAC increased with [NOx/ΔHC] independently of the relative humidity (RH). However, the MAC of NR SOA was RH-dependent. Under both NP and NR regimes, acidity promoted SOA browning while NH3 increased Babs and MAC at 80% RH. The highest MAC was observed at the lowest RH (20%) for acidic NR SOA, and it was postulated that the MAC of SOA depends mainly on the pH and the [H+]free/[SOA mass] ratio of the aqueous SOA phase.
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| 6. |
- Prakash, Jai, et al.
(author)
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Characterization of Propane Fueled Flames: A Significant Source of Brown Carbon
- 2022
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In: Atmosphere. - : MDPI AG. - 2073-4433. ; 13:8
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Journal article (peer-reviewed)abstract
- In this study, we developed a framework for interpreting the in situ morphological properties of black carbon (BC, also referred to as “soot” due to combustion relevance) mixed with primary organic aerosol. Integration of the experiment considering primary organic aerosol (POA) evaporation from the soot particles was examined using a Differential mass–mobility analyzer (DMA) and showed the untold story of the mixing of BC and POA. We also hypothesize that morphological transformation of soots and determined such as (i) the evaporation of externally and internally mixed POA led to a decline in the particle number and size of monodisperse aerosol; (ii) presence of externally mixed BC was interpreted from the occurrence of two peaks of soot upon heating; (iii) heat-induced collapse of the BC core possibly resulted from the evaporation of material from the voids and effect of heat; (iv) volume equivalent to changes in the mobility diameter represented evaporation of POA from the surface and collapse upon heating. POA constituted a high fraction (20–40% by mass) of aerosol mass from these flames and was predominantly (i.e., 92–97% by mass) internally mixed with BC. POA was found to be highly light absorptive, i.e., an Ångström absorption exponent (AAE) value of (in general) >1.5 was estimated for BC + POA at 405/781 nm wavelengths. Interestingly, a much more highly absorptive POA [mass absorption cross-section (MAC)-5 m2 g−1] at 405 nm was discovered under a specific flame setting, which was comparable to MACs of BC particles (8–9 m2 g−1).
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| 7. |
- Prakash, Jai, et al.
(author)
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Characterization, sources, and atmospheric transformation of a few key short-lived climate pollutants (SLCPs) at a rural super-site in the Indo-Gangetic Plain (IGP) of India
- 2022
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In: Environmental Science: Atmospheres. - : Royal Society of Chemistry (RSC). - 2634-3606. ; 2, s. 517-538
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Journal article (peer-reviewed)abstract
- The Indo-Gangetic Plain (IGP) region of India faces some of the most severe air pollution problems on Earth that threaten human health, food security, ecosystems, environmental sustainability, and the climate. The aim of this study is to identify and characterize the sources of key short-lived climate pollutants (SLCPs) - black carbon (BC), brown carbon (BrC), and ozone (O3) - as well as other pollutants [carbon monoxide (CO) and nitrogen oxides NOX = NO and NO2], and interlinked atmospheric processes of their formation and transformation at our long-term air pollution monitoring station in a remote rural IGP site, the Indo-Gangetic Plains Centre for Air Research and Education (IGP-CARE). Because of its location, measurements acquired at IGP-CARE provide otherwise new information on the key SLCPs in the IGP region at a remote and rural location. The year-long measurement data at this remote site provided new insights into the variability of SLCP concentration and interlinked atmospheric processes that affect air quality in the rural IGP region. Thirteen episodic events (E1-E13) of elevated BC and BrC concentrations were identified, which can largely be attributed to the local biomass burning activities in the neighboring rural communities. It is suggested that high concentrations of BrC were mostly primary in nature and thought to be co-emitted with BC from biomass burning. Also, secondary pollutant tropospheric O3 showed elevated concentration. O3 peaks were mostly attributed to local ozone formation. Nevertheless, on several occasions, O3 emission was also attributed to regional urban areas. This study's most important finding is that BrC concentrations were relatively high throughout the year with very pronounced diurnal variation with distinct morning and evening peaks in general and a minimum at around noon time; this is hypothesized to be associated with daytime photochemical processes. Analyses using a conditional bivariate probability function (CBPF) and potential source contribution function (PSCF) suggest that regional sources likely affected the local concentrations of SLCPs. These results partly explain the high concentrations and spatial distributions of SLCPs at the local and regional scales at the IGP-CARE site in winter and autumn. In contrast, in the summer and monsoon seasons, strong convection likely favored the dilution of pollutants.
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| 8. |
- Sharma, Nikhil, 1986, et al.
(author)
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Characterization from Diesel and Renewable Fuel Engine Exhaust: Particulate Size/Mass Distributions and Optical Properties
- 2023
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In: Aerosol Science and Engineering. - : Springer Science and Business Media LLC. - 2510-375X .- 2510-3768. ; 7, s. 182-191
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Journal article (peer-reviewed)abstract
- Combustion of fossil fuel produces emissions and is one of the major environmental problems leading to climate change. Diesel engines are highly efficient but produce particulate emissions. These particulate emissions are considered dangerous to human health because inhaling particulates may cause respiratory and heart disease. Substituting fossil diesel fuel with renewable diesel fuel and using diesel particulate filters is one possibility to meet stringent legislative requirements. With this motivation, the present experimental investigation aimed to evaluate the particle size distribution (PSD), optical properties of particulate matter (PM) emitted, and the outcome of using an after-treatment system comprising of a diesel particle filter (DPF). This investigation aimed to make a comparative analysis of particulate emission upstream and downstream of the DPF with and without ultraviolet (UV) light (405 nm and 781 nm wavelength) turned on/off. Experiments were performed at (a) engine idle with a torque of 6 Nm at 750 rpm, IMEP of 1.35 bar and power of 0.5 kW, (b) engine at part load with a torque of 32 Nm at 1200 rpm, IMEP of 8.5 bar and power of 4.5 kW. Diesel engine was operated on two fuels (a) Diesel and (b) EHR7. Results showed that as and when UV light was turned on, a distinct nucleation mode that dominated the number concentration for both test fuels were observed. Downstream of the filter had relatively higher AAE values which show the contribution to climate change. Present experimental research is important for renewable fuel industries, industrial innovation's future, and the exhaust gas after-treatment system (EATS) community. The results contribute to knowledge for occupational exposure, human health, and the environment.
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