71 research outputs found
Improved MAX-DOAS measurements and retrievals focused on the marine boundary layer
A ground-based MAX-DOAS system was updated and used in multiple campaigns focused on measurements of halogens (especially iodine monoxide) as well as NO2 and formaldehyde in the remote marine boundary layer. In addition, spectral effects of liquid water (absorption, VRS and Brillouin scattering) and their influences on the DOAS retrieval are analyzed. The impact of insufficiently removed liquid water structures as a potential error source for trace gas retrievals is demonstrated and correction spectra for existing water cross-sections were retrieved. In the visible spectral range, an improvement of the DOAS fit quality of the order of 10% was achieved by introducing the retrieved correction spectra
Computer-aided Optical Plasma Postprocessing Applied on Model Spark Gaps
Spark gaps are used as surge protective devices (SPD class 1) for low voltage grids protection against surge currents and overvoltages. For practical research of the narrow gap plasma of spark gaps, high-speed camera recordings are used in modified transparent test models. In this test setup, current densities of 1010 A/m2 are generated.
In order to optimize and automate the evaluation process of camera recordings, an image analysis tool is developed further in this contribution. After basic image improvement and segmentation, this research optimizes a detection algorithm for plasma location and distribution. As a result, the known plasma distribution gives access to significantly more information about the plasma behaviour and the spatial distribution of radiation
Optimizing Postprocessing of Range-Gated Viewing Data for Maritime Search and Rescue Operations at Night and in Bad Weather Conditions
At night and in bad weather conditions the detection of persons and objects floating in the sea represents a major challenge for search and rescue operations (SAR). If conventional searchlights are used, backscattering from rain, fog and snow decreases detection range. Therefore, a compact and inexpensive range-gated viewing system which significantly reduces atmospheric backscattering was developed. The instrument was designed for detection ranges of several hundred meters. In this study, different image processing techniques were analyzed in terms of improved object detectability for a human observer and for a machine learning-based object detector, based on a real-world image dataset. On the one hand, noise of the camera is reduced by performing a non-uniformity correction (NUC) and on the other, the dynamic range of the images is adjusted and dark objects are accentuated by equalizing (EQ). The aim of this field study with the subsequent post processing steps was to improve visibility for both human observers and machine learning-based object detectors with low computing power, based on real-world image datasets. The results show that processing requirements are different in both cases, mainly due to human eye perception, which an automated detector does not rely on and therefore the performance of the object detector before the equalizing step is slightly better. However, the NUC improves the image quality in any case
Simulation of a Gated-Viewing instrument for helicopter deck-landing assistance and vision enhancement
A simulation of an existing Gated-Viewing instrument for integration in a flight simulator was developed based on real sensor characteristics. The simulation was compared to measurements of the instrument in a surrounding that was recreated in a 3D computer model. It was clearly found that the assumption of pure Lambertian reflectors in the simulation did not reproduce even the most dominant observed phenomena in the measurements sufficiently. When including the Phong reflection model the agreement was improved.
The simulation enables to easily investigate the potential of the sensor for use on airborne (in particular helicopter) platforms without the need of deploying the instrument physically, therefore also avoiding extensive regulation and certification issues. In addition, different sensor characteristics can be easily changed in the simulation enabling to study the effect in the respective scenario and allowing for a more purposeful further development of the real sensor.
In particular, sensor simulations were performed in two scenarios, aiming at investigating the added value of the instrument for 1) deck-landing assistance, and 2) for observing and reconnaissance tasks. In both scenarios, the effect of different optical power and field of view was studied
Vision enhancement for maritime search and rescue operations at night and bad weather conditions
During search and rescue operations (SAR) at night and bad weather conditions, the detection of persons in water represents a major challenge. When conventional searchlights are used, the backscattering from rain and fog decreases the detection range. For these conditions, the transportable angegated viewing system (TRAGVIS) was developed, aiming to reduce the effect of backscatter, in particular from close ranges (up to several hundred meters). After data acquisition, image post processing techniques were applied. The objective of the study presented here is to enchance the vision of the image for better object recognition by the operator. In addition automatic object detection methods were tested
Studies of the horizontal inhomogeneities in NO2 concentrations above a shipping lane using ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements and validation with airborne imaging DOAS measurements
This study describes a novel application of an “onion-peeling” approach to multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of shipping emissions aiming at investigating the strong horizontal inhomogeneities in NO2 over a shipping lane. To monitor ship emissions on the main shipping route towards the port of Hamburg, a two-channel (UV and visible) MAX-DOAS instrument was deployed on the island Neuwerk in the German Bight, 6–7 km south of the main shipping lane. Utilizing the fact that the effective light path length in the atmosphere depends systematically on wavelength, simultaneous measurements and DOAS retrievals in the UV and visible spectral ranges are used to probe air masses at different horizontal distances to the instrument to estimate two-dimensional pollutant distributions. Two case studies have been selected to demonstrate the ability to derive the approximate plume positions in the observed area. A situation with northerly wind shows high NO2 concentrations close to the measurement site and low values in the north of the shipping lane. The opposite situation with southerly wind, unfavorable for the on-site in situ instrumentation, demonstrates the ability to detect enhanced NO2 concentrations several kilometers away from the instrument. Using a Gaussian plume model, in-plume NO2 volume mixing ratios can be derived from the MAX-DOAS measurements.
For validation, a comparison to airborne imaging DOAS measurements during the NOSE campaign in July 2013 is performed, showing good agreement between the approximate plume position derived from the onion-peeling MAX-DOAS and the airborne measurements as well as between the derived in-plume NO2 volume mixing ratios (VMRs)
Ultrabright and narrowband intra-fiber biphoton source at ultralow pump power
Nonclassical photon sources of high brightness are key components of quantum communication technologies. We here demonstrate the generation of narrowband, nonclassical photon pairs by employing spontaneous four-wave mixing in an optically-dense ensemble of cold atoms within a hollow-core fiber. The brightness of our source approaches the limit of achievable generated spectral brightness at which successive photon pairs start to overlap in time. For a generated spectral brightness per pump power of up to 2 × 10⁹ pairs/(s MHz mW) we observe nonclassical correlations at pump powers below 100 nW and a narrow bandwidth of 2π × 6.5 MHz. In this regime we demonstrate that our source can be used as a heralded single-photon source. By further increasing the brightness we enter the regime where successive photon pairs start to overlap in time and the cross-correlation approaches a limit corresponding to thermal statistics. Our approach of combining the advantages of atomic ensembles and waveguide environments is an important step toward photonic quantum networks of ensemble-based elements
Дослідження структури порушених відкритою розробкою земель й пошук шляхів вдосконалення рекультивації залишкових виробок кар'єрів
Стаття присвячена дослідженням структури порушених земель, на ділянках з видобутку корисних копалин відкритим способом. Наведено площі порушень земель при розробці основних видів корисних копалин. Проаналізовано ризики, що виникають із несвоєчасною рекультивацією земель гірничого відводу, а також від покинутих гірничих виробок старих кар'єрів. Паралельно розглянуті обсяги відходів гірничого виробництва та їх повторне використання в якості заповнювача для залишкових вироблених просторів кар'єрів.The article is devoted to the research of land violation indicators at the extraction of minerals by surface mining method. Data gives about the land violations area at the mining key minerals. Ana-lyzed the risks from the not-on-time reclamation of the mining clam and abandoned excavations of the old quarries. In parallel considered the volumes of mining wastes and their reuse as aggregate for filling residual spaces of surface mines.Статья посвящена исследованиям площадей нарушения земель, связанных с добычей полезных ископаемых открытым способом. Приведены площади нарушений земель при разработке основных видов полезных ископаемых. Проанализированы риски, представляемые несвоевременной рекультивацией земель горного отвода, а также заброшенными горными выработками старых карьеров. Параллельно рассмотрены объемы отходов горного производства и их повторное использование в качестве заполнителя для остаточных выработанных пространств карьеров
Intercomparison of NO2, O4, O3 and HCHO slant column measurements by MAX-DOAS and zenith-sky UV¿visible spectrometers during CINDI-2
40 pags., 22 figs., 13 tabs.In September 2016, 36 spectrometers from 24 institutes measured a number of key atmospheric pollutants for a period of 17¿d during the Second Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI-2) that took place at Cabauw, the Netherlands (51.97¿¿N, 4.93¿¿E). We report on the outcome of the formal semi-blind intercomparison exercise, which was held under the umbrella of the Network for the Detection of Atmospheric Composition Change (NDACC) and the European Space Agency (ESA). The three major goals of CINDI-2 were (1) to characterise and better understand the differences between a large number of multi-axis differential optical absorption spectroscopy (MAX-DOAS) and zenith-sky DOAS instruments and analysis methods, (2) to define a robust methodology for performance assessment of all participating instruments, and (3) to contribute to a harmonisation of the measurement settings and retrieval methods. This, in turn, creates the capability to produce consistent high-quality ground-based data sets, which are an essential requirement to generate reliable long-term measurement time series suitable for trend analysis and satellite data validation.
The data products investigated during the semi-blind intercomparison are slant columns of nitrogen dioxide (NO2), the oxygen collision complex (O4) and ozone (O3) measured in the UV and visible wavelength region, formaldehyde (HCHO) in the UV spectral region, and NO2 in an additional (smaller) wavelength range in the visible region. The campaign design and implementation processes are discussed in detail including the measurement protocol, calibration procedures and slant column retrieval settings. Strong emphasis was put on the careful alignment and synchronisation of the measurement systems, resulting in a unique set of measurements made under highly comparable air mass conditions.
The CINDI-2 data sets were investigated using a regression analysis of the slant columns measured by each instrument and for each of the target data products. The slope and intercept of the regression analysis respectively quantify the mean systematic bias and offset of the individual data sets against the selected reference (which is obtained from the median of either all data sets or a subset), and the rms error provides an estimate of the measurement noise or dispersion. These three criteria are examined and for each of the parameters and each of the data products, performance thresholds are set and applied to all the measurements. The approach presented here has been developed based on heritage from previous intercomparison exercises. It introduces a quantitative assessment of the consistency between all the participating instruments for the MAX-DOAS and zenith-sky DOAS techniques.CINDI-2 received funding from the Netherlands Space Office (NSO). Funding for this study was provided
by ESA through the CINDI-2 (ESA contract no. 4000118533/16/ISbo) and FRM4DOAS (ESA contract no. 4000118181/16/I-EF)
projects and partly within the EU 7th Framework Programme
QA4ECV project (grant agreement no. 607405). The BOKU
MAX-DOAS instrument was funded and the participation of Stefan F. Schreier was supported by the Austrian Science Fund
(FWF): I 2296-N29. The participation of the University of Toronto
team was supported by the Canadian Space Agency (through
the AVATARS project) and the Natural Sciences and Engineering Research Council (through the PAHA project). The instrument was primarily funded by the Canada Foundation for Innovation and is usually operated at the Polar Environment Atmospheric Research Laboratory (PEARL) by the Canadian Network
for the Detection of Atmospheric Change (CANDAC). Funding for
CISC was provided by the UVAS (“Ultraviolet and Visible Atmospheric Sounder”) projects SEOSAT/INGENIO, ESP2015-71299-
R, MINECO-FEDER and UE. The activities of the IUP-Heidelberg
were supported by the DFG project RAPSODI (grant no. PL
193/17-1). SAOZ and Mini-SAOZ instruments are supported by the
Centre National de la Recherche Scientifique (CNRS) and the Centre National d’Etudes Spatiales (CNES). INTA recognises support
from the National funding projects HELADO (CTM2013-41311-P) and AVATAR (CGL2014-55230-R). AMOIAP recognises support from the Russian Science Foundation (grant no. 16-17-10275) and the Russian Foundation for Basic Research (grant nos. 16-05-
01062 and 18-35-00682). Ka L. Chan received transnational access funding from ACTRIS-2 (H2020 grant agreement no. 654109).
Rainer Volkamer recognises funding from NASA’s Atmospheric Composition Program (NASA-16-NUP2016-0001) and the US National Science Foundation (award AGS-1620530). Henning Finkenzeller is the recipient of a NASA graduate fellowship. Mihalis Vrekoussis recognises support from the University of Bremen and the DFG Research Center/Cluster of Excellence “The Ocean in the
Earth System-MARUM”. Financial support through the University of Bremen Institutional Strategy in the framework of the
DFG Excellence Initiative is gratefully appreciated for Anja Schönhardt. Pandora instrument deployment was supported by Luftblick
through the ESA Pandonia Project and NASA Pandora Project at the Goddard Space Flight Center under NASA Headquarters’ Tropospheric Composition Program. The article processing charges for
this open-access publication were covered by BK Scientific
Framework and baseline examination of the German National Cohort (NAKO)
The German National Cohort (NAKO) is a multidisciplinary, population-based prospective cohort study that aims to investigate the causes of widespread diseases, identify risk factors and improve early detection and prevention of disease. Specifically, NAKO is designed to identify novel and better characterize established risk and protection factors for the development of cardiovascular diseases, cancer, diabetes, neurodegenerative and psychiatric diseases, musculoskeletal diseases, respiratory and infectious diseases in a random sample of the general population. Between 2014 and 2019, a total of 205,415 men and women aged 19–74 years were recruited and examined in 18 study centres in Germany. The baseline assessment included a face-to-face interview, self-administered questionnaires and a wide range of biomedical examinations. Biomaterials were collected from all participants including serum, EDTA plasma, buffy coats, RNA and erythrocytes, urine, saliva, nasal swabs and stool. In 56,971 participants, an intensified examination programme was implemented. Whole-body 3T magnetic resonance imaging was performed in 30,861 participants on dedicated scanners. NAKO collects follow-up information on incident diseases through a combination of active follow-up using self-report via written questionnaires at 2–3 year intervals and passive follow-up via record linkages. All study participants are invited for re-examinations at the study centres in 4–5 year intervals. Thereby, longitudinal information on changes in risk factor profiles and in vascular, cardiac, metabolic, neurocognitive, pulmonary and sensory function is collected. NAKO is a major resource for population-based epidemiology to identify new and tailored strategies for early detection, prediction, prevention and treatment of major diseases for the next 30 years. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10654-022-00890-5
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