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- Baranzahi, Amir, et al.
(författare)
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Response of metal-oxide-silicon carbide sensors to simulated and real exhaust gases
- 1997
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 43:1-3, s. 52-59
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Tidskriftsartikel (refereegranskat)abstract
- Field effect devices based on catalytic metal-oxide-silicon carbide (MOSiC) structures can be used as high temperature gas sensors. The devices are sensitive to hydrocarbons and hydrogen and can be operated up to at least 900 degrees C, which make them suitable for several combustion applications, Simulated and real exhaust gases from a car engine have been studied at sensor temperatures from 200 to 650 degrees C, and it was round that the sensor signal is high for excess hydrocarbon and low for excess oxygen. The response time is less than 100 ms and only a small degradation of the devices was observed after several days of operation. The devices also react to changes of the gas composition In the fuel-rich and fuel-lean region. The devices show an interesting temperature dependence in the fuel rich region.
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| 2. |
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| 3. |
- Sagalowicz, Laurent, et al.
(författare)
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Structure of the wafer fused InP (001)-GaAs (001) interface
- 1997
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Ingår i: Philosophical Magazine Letters. - : Informa UK Limited. - 0950-0839 .- 1362-3036. ; 76:6, s. 445-452
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Tidskriftsartikel (refereegranskat)abstract
- A structural study of wafer fused InP-GaAs interfaces has been carried out. The geometry of the dislocation network which accommodates the twist and the lattice mismatch is first given using a geometrical approach. Cross-sectional transmission electron microscopy and plan view observations are presented. Two different misfit cases are observed. (1) When no twist is present, the 3.7% lattice mismatch is relaxed by a regular square network of dislocations with pure edge character. (2) When an additional twist is present, a square network of dislocations results as well but here the dislocations have a mixed character; 60° dislocations are also observed, some form closed defect circuits and others very likely accommodate a small tilt. The interaction between the 60° dislocations and the edge dislocations is explained in detail. Voids or inclusions are also observed as well as additional dislocations which may accommodate part of the thermal mismatch. © 1997 Taylor & Francis Ltd.
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| 4. |
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| 5. |
- Salomonsson, P., et al.
(författare)
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Temperature-dependent performance of 1.55 ÎŒm vertical-cavity lasers with InGaAsP/InP bottom mirror
- 1999
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Ingår i: Conference Proceedings - International Conference on Indium Phosphide and Related Materials. - Davos, Switz. ; :Piscataway, NJ, United States, s. 223-226
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Tidskriftsartikel (refereegranskat)abstract
- We have fabricated and evaluated a long-wavelength vertical-cavity laser (VCL) based on an epitaxially integrated InP distributed Bragg reflector (DBR) under continuous wave (CW) and pulsed conditions. We conclude that, for an InP-DBR-down configuration, the high-temperature performance is limited by the heat conductivity of the bottom mirror. The highest operating temperature for CW and pulsed condition is 17 °C and 101 °C respectively, indicating a substantial self-heating for CW. To investigate the prospect for improved performance in other mounting configurations, we have applied a two-dimensional finite element analysis to the heat transfer problem. It is suggested that for top-side-down mounting with the AlGaAs/GaAs DBR closest to the heat sink, a performance comparable to that of so called double-fused VCLs could be possible.
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| 6. |
- Strand, V, et al.
(författare)
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Immediate and delayed effects of nitrogen dioxide exposure at an ambient level on bronchial responsiveness to histamine in subjects with asthma
- 1996
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Ingår i: The European respiratory journal. - : European Respiratory Society (ERS). - 0903-1936 .- 1399-3003. ; 9:4, s. 733-740
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Tidskriftsartikel (refereegranskat)abstract
- The time-kinetics of NO2 induced effects on bronchial responsiveness are poorly known as most observations have been made shortly after exposure. The aim of this study was to measure nonspecific bronchial responsiveness, lung function and inflammatory markers at different times after NO2 exposure in asthmatics. Nineteen subjects with mild asthma were exposed to either purified air or 488 micrograms.m-3 (0.26 ppm) NO2 for 30 min during intermittent exercise. Airway responsiveness to histamine, specific airway resistance (sRaw) and thoracic gas volume (TGV) were measured 30 min, 5 h, 27 h and 7 days after exposure. Peripheral blood inflammatory mediators and the expression of an adhesion molecule, (Mac1) on granulocytes, were analysed 30 min and 27 h after exposure. Bronchial responsiveness to histamine was significantly increased 5 h after NO2 exposure when compared to air (median provocative dose of histamine required to cause 100% increase of sRaw ((PDsRaw,100%) 110 micrograms after NO2 exposure vs 203 micrograms on air). There was a tendency for an increase after 30 min, which was nonsignificant (median PDsRaw,100% 100 vs 153 micrograms). NO2 exposure did not affect sRaw, but TGV was significantly reduced after exposure. We found an increased expression of Mac-1 on granulocytes 30 min after NO2 exposure when compared to pre-exposure values. No effect was seen on tryptase, eosinophil cationic protein (ECP), or myeloperoxidase (MPO). These results suggest that exposure to an ambient level of NO2 causes a delayed effect on bronchial responsiveness in asthmatics. The increased expression of an adhesion molecule in peripheral blood may indicate a NO2-induced priming of human granulocytes.
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| 7. |
- Unéus, Lars, et al.
(författare)
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Schottky diodes with thin catalytic gate metals for potential use as ammonia sensors for exhaust gases
- 1999
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Ingår i: Sensors and materials. - : Scientific Publishing Division Myu. - 0914-4935. ; 11:5, s. 305-318
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Tidskriftsartikel (refereegranskat)abstract
- Selective catalytic reduction (SCR) is a method in which ammonia reacts with nitric oxides in a catalytic converter to form water and nitrogen. We show that catalytic Metal Insulator Silicon Carbide (MISiC) devices can be used as ammonia sensors for a SCR system in a diesel engine. Different catalytic metals, Pt and Ir, with a thickness of 30 or 50 nm were investigated. The temperature dependence of the ammonia response of the sensors was characterized. Maximum responses were found at temperatures between 225-250 degrees C. Preliminary experiments were performed to investigate how annealing in different gas ambient influences the response-temperature curve of the sensors. In synthetic diesel exhausts with ammonia added, the sensors showed very good selectivity for ammonia and a small interaction effect with oxygen. The influence of other gas components was almost negligible. Temperature in the diesel exhaust system can reach 550 degrees C; however, operating at temperatures above 400 degrees C limited the lifetime of the sensor. Anger electron spectroscopy (AES) revealed that island formation of the metal due to structural changes was the main reason for failure of the sensor.
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