| 1. |
- Arnby, Karl, 1974, et al.
(författare)
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The effect of platinum distribution in monolithic catalysts on the oxidation of CO and hydrocarbons
- 2005
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 233:1, s. 176-185
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Tidskriftsartikel (refereegranskat)abstract
- Monolithic Pt/gamma-Al2O3 catalysts were prepd. by depositing of the platinum phase, either homogeneously or heterogeneously (i.e., local high platinum concn.), in the washcoat. The influence of the platinum distribution on the ignition and extinction processes for oxidn. of CO, propene, and propane, resp., was investigated by both temp.-programmed and oxygen step-response flow-reactor expts. In addn., in situ XANES spectroscopy was used to follow changes in the chem. state of platinum during propane oxidn. For samples with heterogeneous platinum distribution, the results show an improved low-temp. activity for CO oxidn., whereas no clear improvement is obsd. for oxidn. of propene or propane. Comparison of the results for CO and hydrocarbon oxidn. shows that the improved activity cannot be explained by thermal effects. Moreover, calcns. indicate that the enhanced activity for CO oxidn. can be due to mass-transfer phenomena. This could not be confirmed by our expts., however. Instead, the improved activity for CO oxidn. can be due to varying platinum particle size between the samples. Furthermore, the oxidn. of propane is shown to be highly influenced by the oxygen concn., showing an activity max. for gas compositions close to the stoichiometric. High oxygen levels result most probably in a predominantly oxygen-covered surface, which inhibits the reaction and, as supported by the in situ XANES experiments, passivates the surface by forming platinum oxide.
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| 2. |
- Aad, G., et al.
(författare)
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- 2014
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Hudson, D.S., et al.
(författare)
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Hospitalizations for immersion-related injuries in Alaska 1991-2000
- 2006
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Ingår i: Safety Science. - : Elsevier BV. - 0925-7535 .- 1879-1042. ; 44:6, s. 479-489
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Tidskriftsartikel (refereegranskat)abstract
- Objective: This study analyzed factors associated with injuries to hospitalized victims of nonfatal immersion-related events in Alaska from 1991 through 2000. Data: Alaska Trauma Registry (ATR) records of victims of nonfatal immersion events requiring hospitalization were examined to identify factors associated with injury outcomes. Subjects were divided into two groups: the "immersion only" (IO) group had no additional injuries associated with their immersion-related events, while subjects in the "associated injury" (AI) group incurred additional trauma during injury events. Results: There were 176 ATR records of nonfatal immersion events. In 87 (49.5%) cases, hospitalizations were due to the effects of immersion only (IO group). In 89 (50.5%) cases, hospitalizations were due not only to the effects of immersion, but also due to additional injuries occurring immediately before or while immersion took place (AI group). The final logistic regression model revealed statistically significant relationships between age greater than 12 years, female gender, white ethnicity, and operation of water transport vehicles, and increased risk for associated injury outcomes (p < 0.05). Discussion: This study is the first of its kind to analyze factors associated with the most severe nonfatal immersion-related injuries in Alaska, and identifies target populations for future safety campaigns. © 2005 Elsevier Ltd. All rights reserved.
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| 4. |
- Shukla, Padma Kant, et al.
(författare)
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Nonlinear interactions between electromagnetic waves and electron plasmas oscillations in quantum plasmas
- 2007
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 99:9
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Tidskriftsartikel (refereegranskat)abstract
- We consider nonlinear interactions between intense circularly polarized electromagnetic (CPEM) waves and electron plasma oscillations (EPOs) in a dense quantum plasma, taking into account the electron density response in the presence of the relativistic ponderomotive force and mass increase in the CPEM wave fields. The dynamics of the CPEM waves and EPOs is governed by the two coupled nonlinear Schrödinger equations and Poisson's equation. The nonlinear equations admit the modulational instability of an intense CPEM pump wave against EPOs, leading to the formation and trapping of localized CPEM wave pipes in the electron density hole that is associated with a positive potential distribution in our dense plasma. The relevance of our investigation to the next generation intense laser-solid density plasma interaction experiments is discussed.
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| 5. |
- Zietsman, Grant, et al.
(författare)
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Modelling of a Speech-to-Text Recognition System for Air Traffic Control and NATO Air Command
- 2022
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Ingår i: Journal of Internet Technology. - : Angle Publishing Co., Ltd.. - 1607-9264 .- 2079-4029. ; 23:7, s. 1527-1539
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Tidskriftsartikel (refereegranskat)abstract
- Accent invariance in speech recognition is a chal- lenging problem especially in the are of aviation. In this paper a speech recognition system is developed to transcribe accented speech between pilots and air traffic controllers. The system allows handling of accents in continuous speech by modelling phonemes using Hidden Markov Models (HMMs) with Gaussian mixture model (GMM) probability density functions for each state. These phonemes are used to build word models of the NATO phonetic alphabet as well as the numerals 0 to 9 with transcriptions obtained from the Carnegie Mellon University (CMU) pronouncing dictionary. Mel-Frequency Cepstral Co-efficients (MFCC) with delta and delta-delta coefficients are used for the feature extraction process. Amplitude normalisation and covariance scaling is implemented to improve recognition accuracy. A word error rate (WER) of 2% for seen speakers and 22% for unseen speakers is obtained.
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