Electron swarm parameters and dielectric strength of C5F10O and its mixtures with CO2 and dry air

2021 ◽  
Author(s):  
Mai Hao ◽  
Boya Zhang ◽  
Xingwen Li ◽  
Jiayu Xiong
Keyword(s):  
Fluid Model ◽  
Dielectric Strength ◽  
Rate Coefficients ◽  
Electron Drift ◽  
Mixing Ratio ◽  
Data Set ◽  
Dry Air ◽  
Electron Diffusion Coefficient ◽  
Electrical Insulation Properties ◽  
Effective Ionization

Abstract Perfluoroketone C5F10O is considered as a potential SF6 alternative. The GWP (Global warming potential) of C5F10O is extremely low and even close to that of air. We investigated the electrical insulation properties of the C5F10O by pulsed Townsend (PT) experiment. The rate coefficients of ionization, attachment, and effective ionization, as well as the electron drift velocity and the longitudinal electron diffusion coefficient in pure C5F10O were obtained. We conclude that the density-reduced critical electric field of pure C5F10O is (768±5)Td and ion kinetics are not exist or negligible in C5F10O. Furthermore, the swarm parameters of C5F10O /CO2 and C5F10O /Air mixtures with C5F10O percentage up to 30% were measured in a wide E/N-range. C5F10O has good synergism with both CO2 and dry air and air behaves better. The synergistic effect coefficients were also calculated. To have the same (E/N)crit as pure SF6, the mixing ratio of C5F10O should be 30% in the mixture with CO2 and 26% in the mixture with dry air. The obtained electron swarm parameters in this paper provide a supplement for the fundamental data set of these novel gases, and also lay the foundation for fluid model simulations of gas discharge.

scholarly journals Global distributions of CO<sub>2</sub> volume mixing ratio in the middle and upper atmosphere from daytime MIPAS high-resolution spectra

2016 ◽  
Vol 9 (12) ◽  
pp. 6081-6100 ◽  
Author(s):  
Á. Aythami Jurado-Navarro ◽  
Manuel López-Puertas ◽  
Bernd Funke ◽  
Maya García-Comas ◽  
Angela Gardini ◽  
...  
Keyword(s):  
High Resolution ◽  
General Circulation ◽  
Lower Thermosphere ◽  
Michelson Interferometer ◽  
General Circulation Models ◽  
Rate Coefficients ◽  
Kinetic Temperature ◽  
Mixing Ratio ◽  
Atmospheric Parameters ◽  
Data Set

Abstract. Global distributions of the CO2 vmr (volume mixing ratio) in the mesosphere and lower thermosphere (from 70 up to  ∼  140 km) have been derived from high-resolution limb emission daytime MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) spectra in the 4.3 µm region. This is the first time that the CO2 vmr has been retrieved in the 120–140 km range. The data set spans from January 2005 to March 2012. The retrieval of CO2 has been performed jointly with the elevation pointing of the line of sight (LOS) by using a non-local thermodynamic equilibrium (non-LTE) retrieval scheme. The non-LTE model incorporates the new vibrational–vibrational and vibrational–translational collisional rates recently derived from the MIPAS spectra by [Jurado-Navarro et al.(2015)]. It also takes advantage of simultaneous MIPAS measurements of other atmospheric parameters (retrieved in previous steps), such as the kinetic temperature (derived up to  ∼  100 km from the CO2 15 µm region of MIPAS spectra and from 100 up to 170 km from the NO 5.3 µm emission of the same MIPAS spectra) and the O3 measurements (up to  ∼  100 km). The latter is very important for calculations of the non-LTE populations because it strongly constrains the O(3P) and O(1D) concentrations below  ∼  100 km. The estimated precision of the retrieved CO2 vmr profiles varies with altitude ranging from  ∼  1 % below 90 km to 5 % around 120 km and larger than 10 % above 130 km. There are some latitudinal and seasonal variations of the precision, which are mainly driven by the solar illumination conditions. The retrieved CO2 profiles have a vertical resolution of about 5–7 km below 120 km and between 10 and 20 km at 120–140 km. We have shown that the inclusion of the LOS as joint fit parameter improves the retrieval of CO2, allowing for a clear discrimination between the information on CO2 concentration and the LOS and also leading to significantly smaller systematic errors. The retrieved CO2 has an improved accuracy because of the new rate coefficients recently derived from MIPAS and the simultaneous MIPAS measurements of other key atmospheric parameters (retrieved in previous steps) needed for non-LTE modelling like kinetic temperature and O3 concentration. The major systematic error source is the uncertainty of the pressure/temperature profiles, inducing errors at midlatitude conditions of up to 15 % above 100 km (20 % for polar summer) and of  ∼  5 % around 80 km. The errors due to uncertainties in the O(1D) and O(3P) profiles are within 3–4 % in the 100–120 km region, and those due to uncertainties in the gain calibration and in the near-infrared solar flux are within  ∼  2 % at all altitudes. The retrieved CO2 shows the major features expected and predicted by general circulation models. In particular, its abrupt decline above 80–90 km and the seasonal change of the latitudinal distribution, with higher CO2 abundances in polar summer from 70 up to  ∼  95 km and lower CO2 vmr in the polar winter. Above  ∼  95 km, CO2 is more abundant in the polar winter than at the midlatitudes and polar summer regions, caused by the reversal of the mean circulation in that altitude region. Also, the solstice seasonal distribution, with a significant pole-to-pole CO2 gradient, lasts about 2.5 months in each hemisphere, while the seasonal transition occurs quickly.

scholarly journals Update on GOSAT TANSO-FTS performance, operations, and data products after more than 6 years in space

2016 ◽  
Vol 9 (6) ◽  
pp. 2445-2461 ◽  
Author(s):  
Akihiko Kuze ◽  
Hiroshi Suto ◽  
Kei Shiomi ◽  
Shuji Kawakami ◽  
Makoto Tanaka ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Near Infrared ◽  
Satellite System ◽  
Fourier Transform Spectrometer ◽  
Infrared Sensor ◽  
Data Set ◽  
Dry Air ◽  
Retrieval Accuracy ◽  
Carbon Dioxide Co2

Abstract. A data set containing more than 6 years (February 2009 to present) of radiance spectra for carbon dioxide (CO2) and methane (CH4) observations has been acquired by the Greenhouse gases Observing SATellite (GOSAT, available at http://data.gosat.nies.go.jp/GosatUserInterfaceGateway/guig/GuigPage/open.do), nicknamed “Ibuki”, Thermal And Near infrared Sensor for carbon Observation Fourier Transform Spectrometer (TANSO-FTS). This paper provides updates on the performance of the satellite and TANSO-FTS sensor and describes important changes to the data product, which has recently been made available to users. With these changes the typical accuracy of retrieved column-averaged dry air mole fractions of CO2 and CH4 (XCO2 and XCH4, respectively) are 2 ppm or 0.5 % and 13 ppb or 0.7 %, respectively. Three major anomalies of the satellite system affecting TANSO-FTS are reported: a failure of one of the two solar paddles in May 2014, a switch to the secondary pointing system in January 2015, and most recently a cryocooler shutdown and restart in August 2015. The Level 1A (L1A) (raw interferogram) and the Level 1B (L1B) (radiance spectra) of version V201 described here have long-term uniform quality and provide consistent retrieval accuracy even after the satellite system anomalies. In addition, we discuss the unique observation abilities of GOSAT made possible by an agile pointing mechanism, which allows for optimization of global sampling patterns.

scholarly journals Interrogation of O-ATRP Activation Conducted by Singlet and Triplet Excited States of Phenoxazine Photocatalysts

2021 ◽  
Author(s):  
Yisrael M. Lattke ◽  
Daniel Corbin ◽  
Steven M. Sartor ◽  
Blaine G. McCarthy ◽  
Garret Miyake ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Driving Force ◽  
Catalyst Design ◽  
Rate Coefficients ◽  
Quantum Yields ◽  
Collisional Quenching ◽  
Initiator Concentration ◽  
Data Set ◽  
Back Electron Transfer ◽  
Electron Transfer Theory

Organocatalyzed ATRP (O-ATRP) is a growing field exploiting organic chromophores as photoredox catalysts (PCs) that engage in dissociative electron transfer (DET) activation of alkyl halide initiators following absorption of light. Characterizing DET rate coefficients (<i>k<sub>act</sub></i>) and photochemical yields across various reaction conditions and PC photophysical properties will inform catalyst design and efficient use during polymerization. The studies described herein consider a class of phenoxazine PCs where synthetic handles of core-substitution and <i>N</i>-aryl substitution enable tunability of the electronic and spin character of the catalyst excited state as well as DET reaction driving force ( ). Using Stern-Volmer quenching experiments through variation of diethyl 2-bromo-2-methylmalonate (DBMM) initiator concentration, collisional quenching is observed. Eight independent measurements of <i>k<sub>act </sub></i>are reported as a function of for four PCs: four triplet reactants and four singlets with <i>k<sub>act</sub></i> values ranging from 1.1´10<sup>8</sup> M<sup>-1</sup>s<sup>-1</sup> where DET itself controls the rate to 4.8´10<sup>9</sup> M<sup>-1</sup>s<sup>-1</sup> where diffusion is rate limiting. This overall data set, as well as a second one inclusive of five literature values from related systems, is readily modeled with only a single parameter of reorganization energy under the frameworks of adiabatic Marcus electron transfer theory and Marcus-Savéant theory of DET. The results provide a predictive map where <i>k<sub>act</sub></i> can be estimated if is known and highlight that DET in these systems appears insensitive to PC reactant electronic and spin properties outside of their impact on driving force. Next, on the basis of measured <i>k<sub>act</sub></i> values in selected PC systems and knowledge of their photophysics, we also consider activation yields specific to the reactant spin states as the DBMM initiator concentration is varied. In <i>N</i>-naphthyl-containing PCs characterized by near-unity intersystem crossing, the T<sub>1</sub> is certainly an important driver for efficient DET. However, at DBMM concentrations common to polymer synthesis, the S<sub>1</sub> is also active and drives 33% of DET reaction events. Even in systems with low yields of ISC, such as in <i>N</i>-phenyl-containing PCs, reaction yields can be driven to useful values by exploiting the S<sub>1</sub> under high DBMM concentration conditions. Finally, we have quantified photochemical reaction quantum yields, which take into account potential product loss processes after electron-transfer quenching events. Both S<sub>1</sub> and T<sub>1</sub> reactant states produce the PC<sup>·+</sup> radical cation with a common yield of 71%, thus offering no evidence for spin selectivity in deleterious back electron transfer. The sub-unity PC<sup>·+</sup> yields suggest that some combination of solvent (DMAc) oxidation and energy-wasting back electron transfer is likely at play and these pathways should be factored in subsequent mechanistic considerations.

scholarly journals Cluster analysis of European surface ozone observations for evaluation of MACC reanalysis data

2016 ◽  
Vol 16 (11) ◽  
pp. 6863-6881 ◽  
Author(s):  
Olga Lyapina ◽  
Martin G. Schultz ◽  
Andreas Hense
Keyword(s):  
Cluster Analysis ◽  
Statistical Tests ◽  
Surface Ozone ◽  
Atmospheric Composition ◽  
Regional Differentiation ◽  
Mixing Ratio ◽  
Data Set ◽  
Diurnal Cycles ◽  
Mixing Ratios ◽  
Weekly Cycles

Abstract. The high density of European surface ozone monitoring sites provides unique opportunities for the investigation of regional ozone representativeness and for the evaluation of chemistry climate models. The regional representativeness of European ozone measurements is examined through a cluster analysis (CA) of 4 years of 3-hourly ozone data from 1492 European surface monitoring stations in the Airbase database; the time resolution corresponds to the output frequency of the model that is compared to the data in this study. K-means clustering is implemented for seasonal–diurnal variations (i) in absolute mixing ratio units and (ii) normalized by the overall mean ozone mixing ratio at each site. Statistical tests suggest that each CA can distinguish between four and five different ozone pollution regimes. The individual clusters reveal differences in seasonal–diurnal cycles, showing typical patterns of the ozone behavior for more polluted stations or more rural background. The robustness of the clustering was tested with a series of k-means runs decreasing randomly the size of the initial data set or lengths of the time series. Except for the Po Valley, the clustering does not provide a regional differentiation, as the member stations within each cluster are generally distributed all over Europe. The typical seasonal, diurnal, and weekly cycles of each cluster are compared to the output of the multi-year global reanalysis produced within the Monitoring of Atmospheric Composition and Climate (MACC) project. While the MACC reanalysis generally captures the shape of the diurnal cycles and the diurnal amplitudes, it is not able to reproduce the seasonal cycles very well and it exhibits a high bias up to 12 nmol mol−1. The bias decreases from more polluted clusters to cleaner ones. Also, the seasonal and weekly cycles and frequency distributions of ozone mixing ratios are better described for clusters with relatively clean signatures. Due to relative sparsity of CO and NOx measurements these were not included in the CA. However, simulated CO and NOx mixing ratios are consistent with the general classification into more polluted and more background sites. Mean CO mixing ratios are within 140–145 nmol mol−1 (CL1–CL3) and 130–135 nmol mol−1 (CL4 and CL5), and NOx mixing ratios are within 4–6 nmol mol−1 and 2–3 nmol mol−1, respectively. These results confirm that relatively coarse-scale global models are more suitable for simulation of regional background concentrations, which are less variable in space and time. We conclude that CA of surface ozone observations provides a powerful and robust way to stratify sets of stations, being thus more suitable for model evaluation.

Characterising sediments of a tropical sediment-starved shelf using cluster analysis of physical and geochemical variables

2015 ◽  
Vol 12 (2) ◽  
pp. 204 ◽  
Author(s):  
Lynda C. Radke ◽  
Jin Li ◽  
Grant Douglas ◽  
Rachel Przeslawski ◽  
Scott Nichol ◽  
...  
Keyword(s):  
Large Data ◽  
High Energy ◽  
Rate Coefficients ◽  
Geochemical Data ◽  
Clustering Methods ◽  
Data Set ◽  
Β Diversity ◽  
Published Evidence ◽  
Baseline Information ◽  
Geochemical Variables

Environmental context Australia's tropical marine estate is a biodiversity hotspot that is threatened by human activities. Analysis and interpretation of large physical and geochemistry data sets provides important information on processes occurring at the seafloor in this poorly known area. These processes help us to understand how the seafloor functions to support biodiversity in the region. Abstract Baseline information on habitats is required to manage Australia's northern tropical marine estate. This study aims to develop an improved understanding of seafloor environments of the Timor Sea. Clustering methods were applied to a large data set comprising physical and geochemical variables that describe organic matter (OM) reactivity, quantity and source, and geochemical processes. Arthropoda (infauna) were used to assess different groupings. Clusters based on physical and geochemical data discriminated arthropods better than geomorphic features. Major variations among clusters included grain size and a cross-shelf transition from authigenic-Mn–As enrichments (inner shelf) to authigenic-P enrichment (outer shelf). Groups comprising raised features had the highest reactive OM concentrations (e.g. low chlorin indices and C:N ratios, and high reaction rate coefficients) and benthic algal δ13C signatures. Surface area-normalised OM concentrations higher than continental shelf norms were observed in association with: (i) low δ15N, inferring Trichodesmium input; and (ii) pockmarks, which impart bottom–up controls on seabed chemistry and cause inconsistencies between bulk and pigment OM pools. Low Shannon–Wiener diversity occurred in association with low redox and porewater pH and published evidence for high energy. Highest β-diversity was observed at euphotic depths. Geochemical data and clustering methods used here provide insight into ecosystem processes that likely influence biodiversity patterns in the region.

scholarly journals Volume cross section of auroral radar backscatter and RMS plasma fluctuations inferred from coherent and incoherent scatter data: a response on backscatter volume parameters

2011 ◽  
Vol 29 (6) ◽  
pp. 1081-1092 ◽  
Author(s):  
M. V. Uspensky ◽  
P. Janhunen ◽  
A. V. Koustov ◽  
K. Kauristie
Keyword(s):  
Electron Density ◽  
Cross Section ◽  
Drift Velocity ◽  
Density Fluctuations ◽  
Electron Drift Velocity ◽  
Electron Drift ◽  
Data Set ◽  
Flow Angle ◽  
Effective Electron ◽  
Rate Of Increase

Abstract. Norway and Finland STARE radar measurements in the eastward auroral electrojet are combined with EISCAT CP-1 measurements of the electron density and electric field vector in the common scattering volume to investigate the variation of the auroral radar volume cross section (VCS) with the flow angle of observations (radar look direction with respect to the E×B electron drift). The data set available consists of ~6000 points for flow angles of 40–85° and electron drifts between 500 and 2000 m s−1. The EISCAT electron density N(h)-profile data are used to estimate the effective electron density, aspect angle and thickness of the backscattering layer. It is shown that the flow angle variation of the VCS is rather weak, only ~5 dB within the range of the considered flow angles. The VCS values themselves respond almost linearly to the square of both the electron drift velocity magnitude and the effective electron density. By adopting the inferred shape of the VCS variation with the flow angle and the VCS dependence upon wavelength, the relative amplitude of electrostatic electron density fluctuations over all scales is estimated. Inferred values of 2–4 percent react nearly linearly to the electron drift velocity in the range of 500–1000 m s−1 but the rate of increase slows down at electron drifts >1000 m s−1 and density fluctuations of ~5.5 percent due to, perhaps, progressively growing nonlinear wave losses.

scholarly journals Revising the retrieval technique of a long-term stratospheric HNO<sub>3</sub> data set: from a constrained matrix inversion to the optimal estimation algorithm

2011 ◽  
Vol 29 (7) ◽  
pp. 1317-1330 ◽  
Author(s):  
I. Fiorucci ◽  
G. Muscari ◽  
R. L. de Zafra
Keyword(s):  
Optimal Estimation ◽  
Matrix Inversion ◽  
The Arctic ◽  
Inversion Method ◽  
Data Sets ◽  
Vertical Profiles ◽  
Mixing Ratio ◽  
Data Set ◽  
The Antarctic

Abstract. The Ground-Based Millimeter-wave Spectrometer (GBMS) was designed and built at the State University of New York at Stony Brook in the early 1990s and since then has carried out many measurement campaigns of stratospheric O3, HNO3, CO and N2O at polar and mid-latitudes. Its HNO3 data set shed light on HNO3 annual cycles over the Antarctic continent and contributed to the validation of both generations of the satellite-based JPL Microwave Limb Sounder (MLS). Following the increasing need for long-term data sets of stratospheric constituents, we resolved to establish a long-term GMBS observation site at the Arctic station of Thule (76.5° N, 68.8° W), Greenland, beginning in January 2009, in order to track the long- and short-term interactions between the changing climate and the seasonal processes tied to the ozone depletion phenomenon. Furthermore, we updated the retrieval algorithm adapting the Optimal Estimation (OE) method to GBMS spectral data in order to conform to the standard of the Network for the Detection of Atmospheric Composition Change (NDACC) microwave group, and to provide our retrievals with a set of averaging kernels that allow more straightforward comparisons with other data sets. The new OE algorithm was applied to GBMS HNO3 data sets from 1993 South Pole observations to date, in order to produce HNO3 version 2 (v2) profiles. A sample of results obtained at Antarctic latitudes in fall and winter and at mid-latitudes is shown here. In most conditions, v2 inversions show a sensitivity (i.e., sum of column elements of the averaging kernel matrix) of 100 ± 20 % from 20 to 45 km altitude, with somewhat worse (better) sensitivity in the Antarctic winter lower (upper) stratosphere. The 1σ uncertainty on HNO3 v2 mixing ratio vertical profiles depends on altitude and is estimated at ~15 % or 0.3 ppbv, whichever is larger. Comparisons of v2 with former (v1) GBMS HNO3 vertical profiles, obtained employing the constrained matrix inversion method, show that v1 and v2 profiles are overall consistent. The main difference is at the HNO3 mixing ratio maximum in the 20–25 km altitude range, which is smaller in v2 than v1 profiles by up to 2 ppbv at mid-latitudes and during the Antarctic fall. This difference suggests a better agreement of GBMS HNO3 v2 profiles with both UARS/ and EOS Aura/MLS HNO3 data than previous v1 profiles.

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