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| 2. |
- Bower, K. N., et al.
(författare)
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ACE-2 HILLCLOUD. An overview of the ACE-2 ground-based cloud experiment
- 2000
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Ingår i: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509. ; 52:2, s. 750-778
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Tidskriftsartikel (refereegranskat)abstract
- The ACE-2 HILLCLOUD experiment was carried out on the island of Tenerife in June-July 1997 to investigate the interaction of the boundary layer aerosol with a hill cap cloud forming over a ridge to the north-east of the island. The cloud was used as a natural flow through reactor to investigate the dependence of the cloud microphysics and chemistry on the characteristics of the aerosols and trace gases entering cloud, and to simultaneously study the influence of the physical and chemical processes occurring within the cloud on the size distribution, chemical and hygroscopic properties of the aerosol exiting cloud. 5 major ground base sites were used, measuring trace gases and aerosols upwind and downwind of the cloud, and cloud microphysics and chemistry and interstitial aerosol and gases within the cloud on the hill. 8 intensive measurement periods or runs were undertaken during cloud events, (nocturnally for seven of the eight runs) and were carried out in a wide range of airmass conditions from clean maritime to polluted continental. Polluted air was characterised by higher than average concentrations of ozone (> 50 ppbv), fine and accumulation mode aerosols (> 3000 and > 1500 cm -3 , respectively) and higher aerosol mass loadings. Cloud droplet number concentrations N, increased from 50 cm -3 in background maritime air to > 2500 cm -3 in aged polluted continental air, a concentration much higher than had previously been detected. Surprisingly, N was seen to vary almost linearly with aerosol number across this range. The droplet aerosol analyser (DAA) measured higher droplet numbers than the corrected forward scattering spectrometer probe (FSSP) in the most polluted air, but at other times there was good agreement (FSSP = 0.95 DAA with an r 2 = 0.89 for N < 1200 cm -3 ). Background ammonia gas concentrations were around 0.3 ppbv even in air originating over the ocean, another unexpected but important result for the region. NO 2 was present in background concentrations of typically 15 pptv to 100 pptv and NO 3 . (the nitrate radical) was observed at night throughout. Calculations suggest NO 3 . losses were mainly by reaction with DMS to produce nitric acid. Low concentrations of SO 2 (~30 pptv), HNO 3 and HCl were always present. HNO 3 concentrations were higher in polluted episodes and calculations implied that these exceeded those which could be accounted for by NO 2 oxidation. It is presumed that nitric and hydrochloric acids were present as a result of outgassing from aerosol, the HNO 3 from nitrate rich aerosol transported into the region from upwind of Tenerife, and HCl from sea salt aerosol newly formed at the sea surface. The oxidants hydrogen peroxide and ozone were abundant (i.e., were well in excess over SO 2 throughout the experiment). Occasions of significant aerosol growth following cloud processing were observed, particularly in cleaner cases. Observations and modelling suggested this was due mainly to the take up of nitric acid, hydrochloric acid and ammonia by the smallest activated aerosol particles. On a few occasions a small contribution was made by the in-cloud oxidation of S(IV). The implications of these results from HILLCLOUD for the climatologically more important stratocumulus Marine Boundary Layer (MBL) clouds are considered.
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| 5. |
- He, Ying, et al.
(författare)
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Distribution automation : impact of communication system on reliability of automatic control
- 2001
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Ingår i: Power Tech Proceedings, 2001 IEEE Porto. ; , s. 6-3
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Konferensbidrag (refereegranskat)abstract
- The communication system is essential to the performance of automated distribution systems. It is necessary to perform reliability assessments of communication facilities in carrying out the control functions. The paper describes an approach for reliability evaluation of the communication and control. This approach is based on the event tree methodology, and by using it sensitivity studies are performed to predict the impact of a communication system. The results of the studies are discussed and the importance of the communication system on the reliable automation performance is demonstrated in the paper
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| 6. |
- Johansson, Allan, et al.
(författare)
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From megaplants to mini-mills - a trend in steelmaking - a prospect for papermaking
- 2004
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Ingår i: Resources, Conservation & Recycling. - 0921-3449. ; 40:2, s. 173-183
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Tidskriftsartikel (refereegranskat)abstract
- A comparison is made between the development trends experience over the last decades by the steel and papermaking industries, respectively. These two industrial branches, although totally different in their technical nature, are subject to similar pressures from their external environment, notably increasing requirements for environmental protection and more efficient raw material management. Such new dimensions of technical development may in fact require alternatives to the familiar search for efficiency through "economy of scale" that has prevailed virtually over the whole industrial era. It is suggested that some of the structural changes that already have taken place in the steel industry may serve as indicators for what might happen also in the paper industry. (C) 2003 Elsevier B.V. All rights reserved.
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| 8. |
- Ringqvist, L., et al.
(författare)
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Poorly humified peat as an adsorbent for metals in wastewater
- 2002
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Ingår i: Water Research. - 0043-1354 .- 1879-2448. ; 36:9, s. 2394-2404
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Tidskriftsartikel (refereegranskat)abstract
- Metal adsorption and surface charge determinations were performed previously on well-characterised Sphagnum and Carex peat samples. The aim of this investigation was to determine metal adsorption from complex wastewaters onto these peat samples and compare it to the adsorption onto peat granules, clinoptilolite, glauconite and a flue dust from steel production. A sulphide mine leachate, a landfill leachate and a laundry wastewater were chosen, giving a variation in pH, ionic strength, total organic carbon and concentrations of metals. Metal adsorption was determined in batch and column experiments. The wastewater composition was of great importance for metal removal efficiency, mainly due to the difference in dominating metal species. In the sulphide mine leachate, containing free metal ions, a high metal adsorption was observed onto both peat and inorganic adsorbents. In the landfill leachate the metals formed carbonate and organic complexes and a low metal removal was achieved. Contrary to the leachates, the laundry wastewater contained suspended particles. The high amount of metals removed, 80% of the Cu and 30-60% of the Zn concentration, was probably withdrawn bound to the particle fraction. The highest removal of metal ions was obtained in the sulphide mine leachate with Carex peat, removing 97-99% of the Zn and 85-100% of the Cu content. The Sphagnum peat sample removed 37-77% of the Zn and 80-100% of the Cu content. The differences found between Sphagnum and Carex peat were attributed to the original chemistry of the plant material and the habitat conditions at the time of peat formation. Generally, the combination of glauconite or clinoptilolite with the peat samples in column experiments gave a minor improvement in metal removal.
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| 9. |
- Wang, Zeng, et al.
(författare)
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Zeolite coated ATR crystals for new applications in FTIR-ATR spectroscopy
- 2004
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; :24, s. 2888-2889
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Tidskriftsartikel (refereegranskat)abstract
- Thin silicalite-1 films were grown on ATR crystals and used for detection of low amounts of organic molecules in a gas flow by FTIR spectroscopy.
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