| 1. |
- Erlandsson, Ragnar, et al.
(författare)
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Gas-induced restructuring of palladium model catalysts studied with atomic force microscopy
- 1991
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 9:2, s. 825-828
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Tidskriftsartikel (refereegranskat)abstract
- The structure of thin Pd films evaporated onto planar SiO2 substrates changes dramatically during oxygen/hydrogen exposures in ultrahigh vacuum. In this work we have used an atomic force microscope(AFM), operated in the attractive mode, to obtain the three‐dimensional morphology of the Pd surface for different film thicknesses and treatments, and compared the data with transmission electron microscopy(TEM) micrographs. During restructuring, a 100‐Å film changes from being a smooth continuous film with cracks into metal clusters dispersed on the SiO2 support. In the 5‐Å case the metal films are already well dispersed as fabricated. Here the gas exposure instead results in a clustering effect resulting in larger particles. The AFM gives results which are consistent with TEM micrographs but also gives additional information on metal particle shape which can lead to a further understanding of the restructuring process.
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| 2. |
- Nilsson, Hans-Erik, et al.
(författare)
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A semi-analytic model of the Permeable Base Transistor
- 1994
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Ingår i: Physica scripta. T. - 0281-1847. ; T54, s. 159-164
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Tidskriftsartikel (refereegranskat)abstract
- The I-V characteristics of the Permeable Base Transistor (PBT) has been investigated in order to find a simple and practical model for use in circuit designs. Two possible approaches has been discussed, a one-dimensional analytical solution and a semi-analytical solution mixing analytical and empirical methods. The semi-analytical model developed in this paper offers high accuracy and a simple and fast evaluation. All model parameters can be extracted from a set of I-V curves from two typical transistors with different threshold voltages. An analytical small signal model has been developed that agrees very well with two-dimensional simulations.
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| 3. |
- Nilsson, Hans-Erik, et al.
(författare)
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Different methods of noise reduction in Monte Carlo simulations of a Schottky diode
- 1994
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Ingår i: Physica scripta. T. - 0281-1847. ; T54, s. 268-272
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Tidskriftsartikel (refereegranskat)abstract
- Methods of decreasing the noise and increasing the computational efficiency in Monte Carlo simulations of semiconductor devices are investigated. A lookup table approach to the charge assignment to mesh points has been implemented which is independent of the complexity of the assignment function. Using this approach reduces the CPU time of the charge assignment to about one third. Potential fluctuations in low field regions are compared for different assignment function, which shows the advantage of using more complex schemes than those generally used. Results from a full band Monte Carlo simulation of a submicron Schottky diode are presented and the values of the current density for different assignment schemes are compared, showing a lower noise for the higher order schemes. Statistical enhancements by splitting of superparticles in the depletion region has been investigated. The combination of a high order assignment scheme and statistical enhancement by splitting decreases simulation runtimes considerable for a given noise tolerance.
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| 4. |
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| 5. |
- Ramnäs, Olle Jerker, 1941, et al.
(författare)
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Assessment by gas chromatography - mass spectrometry of hexenes emitted to air
- 1993
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Ingår i: Journal of Chromatography. ; 638, s. 65-69
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Tidskriftsartikel (refereegranskat)abstract
- Hexenes and cyclohexenes in vapours of conventional petrol were separated by gas chromatography on an aluminium oxide column. All hexenes appear in a favourable chromatographic position between hexanes and heptanes. The seventeen isomeric acyclic hexenes were identified by mass spectra and single-ion monitoring on an ion-trap mass spectrometer. The rapidly photooxidant-forming isomers with a non-terminal double bond constitute 70% of the total amount of acyclic hexenes. The proportions of isomers in petrol vapour are similar to those in urban air and in exhaust from petrol-fuelled vehicles.
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| 6. |
- Ramnäs, Olle Jerker, 1941, et al.
(författare)
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Characterization of sixty alkenes in a cat-cracked gasoline naphtha by gas chromatography
- 1994
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Ingår i: Chromatographia. ; 38, s. 222-226
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Tidskriftsartikel (refereegranskat)abstract
- The alkene-rich petrol fraction from refinery fluid catalytic cracking (FCC) has been characterized by GC and GC-MS. Quantitative proportions and retention data of 52 acyclic and 11 cyclic C5–C7 alkenes are given. Relative retentions are reported for methylsilicone and aluminium oxide stationary phases as methylene units (MU). Applications of mass spectra, single-ion GC-MS monitoring and retention data for identifications are demonstrated.
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| 7. |
- Östermark, Ulf, 1967, et al.
(författare)
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Assessment of hydrocarbons in vapours of conventional and alkylate-based petrol
- 1992
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Ingår i: Chemosphere. ; 25, s. 763-768
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Tidskriftsartikel (refereegranskat)abstract
- Vapours of recently introduced alkylate-based petrol for power saws, lawn mowers and other petrol-fuelled machines were compared with vapours of conventional petrol varieties. The composition of C4-C8 hydrocarbons was determined by adsorption sampling and gas chromatography on an aluminium oxide column. Results are given for 22 specific arenes, alkenes and alkanes. Major advantages of the reformulated petrol with respect to health and environment are the virtual absence of benzene and alkenes in the vapours. The proportions of methylbenzene, hexane and cycloalkanes are also very low.
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| 8. |
- Östermark, Ulf, 1967, et al.
(författare)
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Volatile hydrocarbons in exhaust from alkylate-based petrol
- 1993
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Ingår i: Chemosphere. ; 27, s. 1719-1728
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Tidskriftsartikel (refereegranskat)abstract
- The non-methane hydrocarbon composition was studied for emissions from new alkylate-based fuels marketed for applications of special concern to human health and the environment. Proportions of 27 selected C2-C8 hydrocarbons were determined in moped exhaust for an alkylate-based fuel and a conventional reformate-based fuel. Samples were taken on an adsorbent cartridge behind the moped during driving, and were analyzed by thermal desorption and gas chromatography on an alumina column. About 90% of the hydrocarbons emitted from the two-stroke moped engine were unburnt fuel hydrocarbons.
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