| 1. |
- Wetzel, G., et al.
(författare)
-
Validation of MIPAS-ENVISAT H2O operational data collected between July 2002 and March 2004
- 2013
-
Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 13:11, s. 5791-5811
-
Tidskriftsartikel (refereegranskat)abstract
- Water vapour (H2O) is one of the operationally retrieved key species of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument aboard the Environmental Satellite (ENVISAT) which was launched into its sun-synchronous orbit on 1 March 2002 and operated until April 2012. Within the MIPAS validation activities, independent observations from balloons, aircraft, satellites, and ground-based stations have been compared to European Space Agency (ESA) version 4.61 operational H2O data comprising the time period from July 2002 until March 2004 where MIPAS measured with full spectral resolution. No significant bias in the MIPAS H2O data is seen in the lower stratosphere (above the hygropause) between about 15 and 30 km. Differences of H2O quantities observed by MIPAS and the validation instruments are mostly well within the combined total errors in this altitude region. In the upper stratosphere (above about 30 km), a tendency towards a small positive bias (up to about 10 %) is present in the MIPAS data when compared to its balloon-borne counterpart MIPAS-B, to the satellite instruments HALOE (Halogen Occultation Experiment) and ACE-FTS (Atmospheric Chemistry Experiment, Fourier Transform Spectrometer), and to the millimeter-wave airborne sensor AMSOS (Airborne Microwave Stratospheric Observing System). In the mesosphere the situation is unclear due to the occurrence of different biases when comparing HALOE and ACE-FTS data. Pronounced deviations between MIPAS and the correlative instruments occur in the lowermost stratosphere and upper troposphere, a region where retrievals of H2O are most challenging. Altogether it can be concluded that MIPAS H2O profiles yield valuable information on the vertical distribution of H2O in the stratosphere with an overall accuracy of about 10 to 30% and a precision of typically 5 to 15% - well within the predicted error budget, showing that these global and continuous data are very valuable for scientific studies. However, in the region around the tropopause retrieved MIPAS H2O profiles are less reliable, suffering from a number of obstacles such as retrieval boundary and cloud effects, sharp vertical discontinuities, and frequent horizontal gradients in both temperature and H2O volume mixing ratio (VMR). Some profiles are characterized by retrieval instabilities.
|
|
| 2. |
- Neumann, Patrick, et al.
(författare)
-
An artificial potential field based sampling strategy for a gas-sensitive micro-drone
- 2011
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a sampling strategy for mobile gas sensors. Sampling points are selected using a modified artificial potential field (APF) approach, which balances multiple criteria to direct sensor measurements towards locations of high mean concentration, high concentration variance and areas for which the uncertainty about the gas distribution model is still large. By selecting in each step the most often suggested close-by measurement location, the proposed approach introduces a locality constraint that allows planning suitable paths for mobile gas sensors. Initial results in simulation and in real-world experiments witha gas-sensitive micro-drone demonstrate the suitability of the proposed sampling strategy for gas distribution mapping and its use for gas source localization.
|
|
| 3. |
- Neumann, Patrick, et al.
(författare)
-
Gas source localization with a micro-drone using bio-inspired and particle filter-based algorithms
- 2013
-
Ingår i: Advanced Robotics. - : Informa UK Limited. - 0169-1864 .- 1568-5535. ; 27:9, s. 725-738
-
Tidskriftsartikel (refereegranskat)abstract
- Gas source localization (GSL) with mobile robots is a challenging task due to the unpredictable nature of gas dispersion,the limitations of the currents sensing technologies, and the mobility constraints of ground-based robots. This work proposesan integral solution for the GSL task, including source declaration. We present a novel pseudo-gradient-basedplume tracking algorithm and a particle filter-based source declaration approach, and apply it on a gas-sensitivemicro-drone. We compare the performance of the proposed system in simulations and real-world experiments againsttwo commonly used tracking algorithms adapted for aerial exploration missions.
|
|
| 4. |
- Neumann, Patrick P., et al.
(författare)
-
A Probabilistic Gas Patch Path Prediction Approach for Airborne Gas Source Localization in Non-Uniform Wind Fields
- 2014
-
Ingår i: Sensor Letters. - Valencia, USA : American Scientific Publishers. - 1546-198X .- 1546-1971. ; 12:6-7, s. 1113-1118
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we show that a micro unmanned aerial vehicle (UAV) equipped with commercially available gas sensors can addressenvironmental monitoring and gas source localization (GSL) tasks. To account for the challenges of gas sensing under real-world conditions,we present a probabilistic approach to GSL that is based on a particle filter (PF). Simulation and real-world experiments demonstrate thesuitability of this algorithm for micro UAV platforms.
|
|
| 5. |
- Neumann, Patrick P., et al.
(författare)
-
Autonomous gas-sensitive microdrone wind vector estimation and gas distribution mapping
- 2012
-
Ingår i: IEEE robotics & automation magazine. - : Institute of Electrical and Electronics Engineers (IEEE). - 1070-9932 .- 1558-223X. ; 19:1, s. 50-61
-
Tidskriftsartikel (refereegranskat)abstract
- This article presents the development and validation of an autonomous, gas sensitive microdrone that is capable of estimating the wind vector in real time using only the onboard control unit of the microdrone and performing gas distribution mapping (DM). Two different sampling approaches are suggested to address this problem. On the one hand, a predefined trajectory is used to explore the target area with the microdrone in a real-world gas DM experiment. As an alternative sampling approach, we introduce an adaptive strategy that suggests next sampling points based on an artificial potential field (APF). Initial results in real-world experiments demonstrate the capability of the proposed adaptive sampling strategy for gas DM and its use for gas source localization.
|
|
| 6. |
- Ulmschneider, Martin B., et al.
(författare)
-
Spontaneous transmembrane helix insertion thermodynamically mimics translocon-guided insertion
- 2014
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- The favourable transfer free energy for a transmembrane (TM) alpha-helix between the aqueous phase and lipid bilayer underlies the stability of membrane proteins. However, the connection between the energetics and process of membrane protein assembly by the Sec61/SecY translocon complex in vivo is not clear. Here, we directly determine the partitioning free energies of a family of designed peptides using three independent approaches: an experimental microsomal Sec61 translocon assay, a biophysical (spectroscopic) characterization of peptide insertion into hydrated planar lipid bilayer arrays, and an unbiased atomic-detail equilibrium folding-partitioning molecular dynamics simulation. Remarkably, the measured free energies of insertion are quantitatively similar for all three approaches. The molecular dynamics simulations show that TM helix insertion involves equilibrium with the membrane interface, suggesting that the interface may play a role in translocon-guided insertion.
|
|
