| 1. |
- Bjerkeli, Per, 1977, et al.
(författare)
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Water around IRAS 15398-3359 observed with ALMA
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 595, s. Art no A39-
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Tidskriftsartikel (refereegranskat)abstract
- Context. Understanding how protostars accrete their mass is one of the fundamental problems of star formation. High dust column densities and complex kinematical structures make direct observations challenging. Moreover, direct observations only provide a snapshot. Chemical tracers provide an interesting alternative to characterise the infall histories of protostars. Aims. We aim to map the distribution and kinematics of gaseous water towards the low-mass embedded protostar IRAS 15398-3359. Previous observations of H13CO+ showed a depression in the abundance towards IRAS 15398-3359. This is a sign of destruction of HCO+ by an enhanced presence of gaseous water in an extended region, possibly related to a recent burst in the accretion. Direct observations of water vapour can determine the exact extent of the emission and confirm the hypothesis that HCO+ is indeed a good tracer of the water snow-line. Methods. IRAS 15398-3359 was observed using the Atacama Large Millimeter/submillimeter Array (ALMA) at 0.5? resolution in two setups at 390 and 460 GHz. Maps of HDO (101-000) and were taken simultaneously with observations of the CS (8-7) and N2H+ (5-4) lines and continuum at 0.65 and 0.75 mm. The maps were interpreted using dust radiative transfer calculations of the protostellar infalling envelope with an outflow cavity. Results. HDO is clearly detected and extended over the scales of the H13CO+ depression, although it is displaced by ~500 AU in the direction of the outflow. HO is tentatively detected towards the red-shifted outflow lobe, but otherwise it is absent from the mapped region, which suggests that temperatures are low. Although we cannot entirely exclude a shock origin, this indicates that another process is responsible for the water emission. Conclusions. Based on the temperature structure obtained from dust radiative transfer models, we conclude that the water was most likely released from the grains in an extended hour-glass configuration during a recent accretion burst. HDO is only detected in the region closest to the protostar, at distances of up to 500 AU. These signatures can only be explained if the luminosity has recently been increased by orders of magnitudes. Additionally, the densities in the outflow cones must be sufficiently low.
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| 2. |
- Lindberg, Johan E., et al.
(författare)
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EXTERNALLY HEATED PROTOSTELLAR CORES in the OPHIUCHUS STAR-FORMING REGION
- 2017
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 835:1, s. 3-
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Tidskriftsartikel (refereegranskat)abstract
- We present APEX 218 GHz observations of molecular emission in a complete sample of embedded protostars in the Ophiuchus star-forming region. To study the physical properties of the cores, we calculate H2CO and c-C3H2 rotational temperatures, both of which are good tracers of the kinetic temperature of the molecular gas. We find that the H2CO temperatures range between 16 K and 124 K, with the highest H2CO temperatures toward the hot corino source IRAS 16293-2422 (69-124 K) and the sources in the ? Oph A cloud (23-49 K) located close to the luminous Herbig Be star S1, which externally irradiates the ? Oph A cores. On the other hand, the c-C3H2 rotational temperature is consistently low (7-17 K) in all sources. Our results indicate that the c-C3H2 emission is primarily tracing more shielded parts of the envelope whereas the H2CO emission (at the angular scale of the APEX beam; 3600 au in Ophiuchus) mainly traces the outer irradiated envelopes, apart from in IRAS 16293-2422, where the hot corino emission dominates. In some sources, a secondary velocity component is also seen, possibly tracing the molecular outflow.
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| 3. |
- Vagnoni, Giovanni, et al.
(författare)
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Predictive engine and aftertreatment control concepts for a heavy-duty long-haul truck
- 2018
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Ingår i: Aachen Colloquium Automobile and Engine Technology.
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Konferensbidrag (refereegranskat)abstract
- This paper considers the modular control framework for energy and emissions management developed within the IMplementation of Powertrain Control for Economic and Clean Real driving emIssion and fuel ConsUMption (IMPERIUM) project. The framework is proposed for a long haul truck equipped with a 13 L Volvo Diesel engine and it aims to improve the operating system efficiency. Its main function blocks are: Transport Mission Management, Vehicle Environment, Route Situation, Traffic Situation, Vehicle Motion Management and Device Abstractions. The focus of the paper is the development and the evaluation of three key functions of the control framework: the Integrated Engine and After-Treatment System (EATS) Supervisory Controller and two local controllers, for the engine and the after-treatment. Whilst for the last two only a brief introduction is given, for the Integrated Engine and EATS Supervisory Controller a detailed description of the Optimal Control Problem (OCP) formulation and its solution strategies is provided. A controller is proposed based on a moving horizon Nonlinear Model Predictive Control (NMPC), which is tested in a simulation environment and benchmarked against Dynamic Programming (DP) strategies.
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