Dependence of the Thermal Conductivity of PMMA, PS and PE on Temperature and Crystallinity

B. Salameh,S. Yasin,D. Abu Fara,A. M. Zihlif 한국고분자학회 2021 폴리머 Vol.45 No.2

This study presents measurements of the thermal conductivity as a function of temperature for different polymers: poly(methyl methacrylate) (PMMA), polystyrene (PS) and polyethylene (PE). The effects of varying the polymer structure, sample thickness and degree of crystallinity on the thermal conductivity are reported. The thermal conductivity increases with temperature for amorphous and semicrystalline polymers with crystallinity less than 50%, and decreases with temperature for semicrystalline polymers with crystallinity larger than 50%. Moreover, the thermal conductivity of the crystalline polymer is found to be larger than that of the amorphous polymer at the same temperature. The contact resistance of PMMA and PE could be calculated from the sample thickness dependence of the thermal resistance.

History of atmospheric SF6 from 1973 to 2008

Rigby, M.,Mü,hle, J.,Miller, B. R.,Prinn, R. G.,Krummel, P. B.,Steele, L. P.,Fraser, P. J.,Salameh, P. K.,Harth, C. M.,Weiss, R. F.,Greally, B. R.,O&,apos,Doherty, S.,Simmonds, P. G.,Vollmer, M Copernicus GmbH 2010 Atmospheric Chemistry and Physics Vol.10 No.21

<P>Abstract. We present atmospheric sulfur hexafluoride (SF6) mole fractions and emissions estimates from the 1970s to 2008. Measurements were made of archived air samples starting from 1973 in the Northern Hemisphere and from 1978 in the Southern Hemisphere, using the Advanced Global Atmospheric Gases Experiment (AGAGE) gas chromatographic-mass spectrometric (GC-MS) systems. These measurements were combined with modern high-frequency GC-MS and GC-electron capture detection (ECD) data from AGAGE monitoring sites, to produce a unique 35-year atmospheric record of this potent greenhouse gas. Atmospheric mole fractions were found to have increased by more than an order of magnitude between 1973 and 2008. The 2008 growth rate was the highest recorded, at 0.29 ± 0.02 pmolmol−1 yr−1. A three-dimensional chemical transport model and a minimum variance Bayesian inverse method was used to estimate annual emission rates using the measurements, with a priori estimates from the Emissions Database for Global Atmospheric Research (EDGAR, version 4). Consistent with the mole fraction growth rate maximum, global emissions during 2008 were also the highest in the 1973-2008 period, reaching 7.4 ± 0.6 Gg yr−1 (1-σ uncertainties) and surpassing the previous maximum in 1995. The 2008 values follow an increase in emissions of 48 ± 20% since 2001. A second global inversion which also incorporated National Oceanic and Atmospheric Administration (NOAA) flask measurements and in situ monitoring site data agreed well with the emissions derived using AGAGE measurements alone. By estimating continent-scale emissions using all available AGAGE and NOAA surface measurements covering the period 2004-2008, with no pollution filtering, we find that it is likely that much of the global emissions rise during this five-year period originated primarily from Asian developing countries that do not report detailed, annual emissions to the United Nations Framework Convention on Climate Change (UNFCCC). We also find it likely that SF6 emissions reported to the UNFCCC were underestimated between at least 2004 and 2005. </P>

Hydrochlorofluorocarbon and hydrofluorocarbon emissions in East Asia determined by inverse modeling

Stohl, A.,Kim, J.,Li, S.,O&,apos,Doherty, S.,Mü,hle, J.,Salameh, P. K.,Saito, T.,Vollmer, M. K.,Wan, D.,Weiss, R. F.,Yao, B.,Yokouchi, Y.,Zhou, L. X. Copernicus GmbH 2010 Atmospheric Chemistry and Physics Vol.10 No.8

<P>Abstract. The emissions of three hydrochlorofluorocarbons, HCFC-22 (CHClF2), HCFC-141b (CH3CCl2F) and HCFC-142b (CH3CClF2) and three hydrofluorocarbons, HFC-23 (CHF3), HFC-134a (CH2FCF3) and HFC-152a (CH3CHF2) from four East Asian countries and the Taiwan region for the year 2008 are determined by inverse modeling. The inverse modeling is based on in-situ measurements of these halocarbons at the Japanese stations Cape Ochi-ishi and Hateruma, the Chinese station Shangdianzi and the South Korean station Gosan. For every station and every 3 h, 20-day backward calculations were made with the Lagrangian particle dispersion model FLEXPART. The model output, the measurement data, bottom-up emission information and corresponding uncertainties were fed into an inversion algorithm to determine the regional emission fluxes. The model captures the observed variation of halocarbon mixing ratios very well for the two Japanese stations but has difficulties explaining the large observed variability at Shangdianzi, which is partly caused by small-scale transport from Beijing that is not adequately captured by the model. Based on HFC-23 measurements, the inversion algorithm could successfully identify the locations of factories known to produce HCFC-22 and emit HFC-23 as an unintentional byproduct. This lends substantial credibility to the inversion method. We report national emissions for China, North Korea, South Korea and Japan, as well as emissions for the Taiwan region. Halocarbon emissions in China are much larger than the emissions in the other countries together and contribute a substantial fraction to the global emissions. Our estimates of Chinese emissions for the year 2008 are 65.3±6.6 kt/yr for HCFC-22 (17% of global emissions extrapolated from Montzka et al., 2009), 12.1±1.6 kt/yr for HCFC-141b (22%), 7.3±0.7 kt/yr for HCFC-142b (17%), 6.2±0.7 kt/yr for HFC-23 (>50%), 12.9±1.7 kt/yr for HFC-134a (9% of global emissions estimated from Velders et al., 2009) and 3.4±0.5 kt/yr for HFC-152a (7%). </P>

Global emissions of HFC-143a (CH3CF3) and HFC-32 (CH2F2) from in situ and air archive atmospheric observations

O&,apos,Doherty, S.,Rigby, M.,Mü,hle, J.,Ivy, D. J.,Miller, B. R.,Young, D.,Simmonds, P. G.,Reimann, S.,Vollmer, M. K.,Krummel, P. B.,Fraser, P. J.,Steele, L. P.,Dunse, B.,Salameh, P. K.,Harth, Copernicus GmbH 2014 Atmospheric chemistry and physics Vol.14 No.17

<P>Abstract. High-frequency, in situ observations from the Advanced Global Atmospheric Gases Experiment (AGAGE), for the period 2003 to 2012, combined with archive flask measurements dating back to 1977, have been used to capture the rapid growth of HFC-143a (CH3CF3) and HFC-32 (CH2F2) mole fractions and emissions into the atmosphere. Here we report the first in situ global measurements of these two gases. HFC-143a and HFC-32 are the third and sixth most abundant hydrofluorocarbons (HFCs) respectively and they currently make an appreciable contribution to the HFCs in terms of atmospheric radiative forcing (1.7 ± 0.04 and 0.7 ± 0.02 mW m−2 in 2012 respectively). In 2012 the global average mole fraction of HFC-143a was 13.4 ± 0.3 ppt (1σ) in the lower troposphere and its growth rate was 1.4 ± 0.04 ppt yr−1; HFC-32 had a global mean mole fraction of 6.2 ± 0.2 ppt and a growth rate of 1.1 ± 0.04 ppt yr−1 in 2012. The extensive observations presented in this work have been combined with an atmospheric transport model to simulate global atmospheric abundances and derive global emission estimates. It is estimated that 23 ± 3 Gg yr−1 of HFC-143a and 21 ± 11 Gg yr−1 of HFC-32 were emitted globally in 2012, and the emission rates are estimated to be increasing by 7 ± 5% yr−1 for HFC-143a and 14 ± 11% yr−1 for HFC-32. </P>

Global and regional emission estimates for HCFC-22

Saikawa, E.,Rigby, M.,Prinn, R. G.,Montzka, S. A.,Miller, B. R.,Kuijpers, L. J. M.,Fraser, P. J. B.,Vollmer, M. K.,Saito, T.,Yokouchi, Y.,Harth, C. M.,Mü,hle, J.,Weiss, R. F.,Salameh, P. K.,Kim, J Copernicus GmbH 2012 Atmospheric chemistry and physics Vol.12 No.21

<P>Abstract. HCFC-22 (CHClF2, chlorodifluoromethane) is an ozone-depleting substance (ODS) as well as a significant greenhouse gas (GHG). HCFC-22 has been used widely as a refrigerant fluid in cooling and air-conditioning equipment since the 1960s, and it has also served as a traditional substitute for some chlorofluorocarbons (CFCs) controlled under the Montreal Protocol. A low frequency record on tropospheric HCFC-22 since the late 1970s is available from measurements of the Southern Hemisphere Cape Grim Air Archive (CGAA) and a few Northern Hemisphere air samples (mostly from Trinidad Head) using the Advanced Global Atmospheric Gases Experiment (AGAGE) instrumentation and calibrations. Since the 1990s high-frequency, high-precision, in situ HCFC-22 measurements have been collected at these AGAGE stations. Since 1992, the Global Monitoring Division of the National Oceanic and Atmospheric Administration/Earth System Research Laboratory (NOAA/ESRL) has also collected flasks on a weekly basis from remote sites across the globe and analyzed them for a suite of halocarbons including HCFC-22. Additionally, since 2006 flasks have been collected approximately daily at a number of tower sites across the US and analyzed for halocarbons and other gases at NOAA. All results show an increase in the atmospheric mole fractions of HCFC-22, and recent data show a growth rate of approximately 4% per year, resulting in an increase in the background atmospheric mole fraction by a factor of 1.7 from 1995 to 2009. Using data on HCFC-22 consumption submitted to the United Nations Environment Programme (UNEP), as well as existing bottom-up emission estimates, we first create globally-gridded a priori HCFC-22 emissions over the 15 yr since 1995. We then use the three-dimensional chemical transport model, Model for Ozone and Related Chemical Tracers version 4 (MOZART v4), and a Bayesian inverse method to estimate global as well as regional annual emissions. Our inversion indicates that the global HCFC-22 emissions have an increasing trend between 1995 and 2009. We further find a surge in HCFC-22 emissions between 2005 and 2009 from developing countries in Asia - the largest emitting region including China and India. Globally, substantial emissions continue despite production and consumption being phased out in developed countries currently. </P>

HFC-43-10mee atmospheric abundances and global emission estimates : ARNOLD ET. AL.; HFC-43-10mee IN THE GLOBAL ATMOSPHERE

Arnold, Tim,Ivy, Diane J.,Harth, Christina M.,Vollmer, Martin K.,Mü,hle, Jens,Salameh, Peter K.,Paul Steele, L.,Krummel, Paul B.,Wang, Ray H. J.,Young, Dickon,Lunder, Chris R.,Hermansen, Ove,Rhee, American Geophysical Union 2014 Geophysical Research Letters Vol.41 No.6

Characterization of uncertainties in atmospheric trace gas inversions using hierarchical Bayesian methods

Ganesan, A. L.,Rigby, M.,Zammit-Mangion, A.,Manning, A. J.,Prinn, R. G.,Fraser, P. J.,Harth, C. M.,Kim, K.-R.,Krummel, P. B.,Li, S.,Mü,hle, J.,O&,apos,Doherty, S. J.,Park, S.,Salameh, P. K.,Ste Copernicus GmbH 2014 Atmospheric chemistry and physics Vol.14 No.8

<P>Abstract. We present a hierarchical Bayesian method for atmospheric trace gas inversions. This method is used to estimate emissions of trace gases as well as 'hyper-parameters' that characterize the probability density functions (PDFs) of the a priori emissions and model-measurement covariances. By exploring the space of 'uncertainties in uncertainties', we show that the hierarchical method results in a more complete estimation of emissions and their uncertainties than traditional Bayesian inversions, which rely heavily on expert judgment. We present an analysis that shows the effect of including hyper-parameters, which are themselves informed by the data, and show that this method can serve to reduce the effect of errors in assumptions made about the a priori emissions and model-measurement uncertainties. We then apply this method to the estimation of sulfur hexafluoride (SF6) emissions over 2012 for the regions surrounding four Advanced Global Atmospheric Gases Experiment (AGAGE) stations. We find that improper accounting of model representation uncertainties, in particular, can lead to the derivation of emissions and associated uncertainties that are unrealistic and show that those derived using the hierarchical method are likely to be more representative of the true uncertainties in the system. We demonstrate through this SF6 case study that this method is less sensitive to outliers in the data and to subjective assumptions about a priori emissions and model-measurement uncertainties than traditional methods. </P>

Continued Emissions of the Ozone-Depleting Substance Carbon Tetrachloride From Eastern Asia

Lunt, M. F.,Park, S.,Li, S.,Henne, S.,Manning, A. J.,Ganesan, A. L.,Simpson, I. J.,Blake, D. R.,Liang, Q.,O'Doherty, S.,Harth, C. M.,Mü,hle, J.,Salameh, P. K.,Weiss, R. F.,Krummel, P. B.,Fraser, P American Geophysical Union 2018 Geophysical research letters Vol.45 No.20