Investigations on the reduction of false-alarms of smoke detectors caused by nuisance aerosols

Das Ausmaß der Schäden die durch einen Brand verursacht werden steht in direktem Zusammenhang mit seiner Dauer, bzw. mit der Zeit zwischen dem Beginn des Brandes und der Löschung. Um den Schaden zu minimieren ist es demzufolge notwendig, den Brand möglichst früh zu erkennen. Automatische Systeme, die einen Brand in seiner frühen Phase erkennen, sind bereits für viele Einsatzgebiete erhältlich. Im Betrieb einer Brandmeldeanlage zeigt sich jedoch, dass nicht allein die frühzeitige Alarmierung im Falle eines Brandes wichtig ist. In der Zeit, in der kein Brand vorliegt (meist die überwiegende Zeit), sollte das Brandentdeckungssystem auch keinen Alarm melden. Die Unterdrückung von möglichen Fehlalarmen erweist sich als eine noch komplexere Aufgabe als die tatsächliche Branderkennung, zumal die strenge Vorgabe besteht, dass alle Brände entdeckt werden müssen. Thema dieser Arbeit ist die optische Erkennung und Unterscheidung von Rauch und möglichen Störaerosolen wie Staub oder Wasserdampf. Dabei wurden zwei Ansätze verfolgt: einerseits die Aerosolcharakterisierung anhand von hoch aufgelösten Streulichtaufnahmen und andererseits die Unterscheidung von Rauch und Störaerosolen anhand von polarimetrischen Streulichtmessungen. Diese Ansätze können zur optimalen Störunterdrückung auch kombiniert werden. Durch die bildgestützte Messung von Streulicht ist es möglich, Informationen über die Partikelgrößenverteilung des überwachten Aerosols zu erhalten. Der besondere Vorteil eines videogestützten Systems gegenüber Systemen mit Photodioden, die lediglich die mittlere Intensität des Streulichts auswerten, liegt darin, dass kleine Partikel auch dann erkannt werden können, wenn große, stärker streuende Partikel im Aerosol vorhanden sind. Messungen mit verschiedenen Brand- und Nichtbrandaerosolen haben gezeigt, dass Wasserdampf und Staub von Rauch unterschieden werden kann. Ein weiterer Vorteil des Einsatzes von Bildsensoren zur Streulichtmessung bietet die Möglichkeit der Richtungsschätzung der strömenden Rauchwolken. Diese kann zur Ortung des Brandherdes beitragen und in Verbindung mit automatischen Löschanlagen eingesetzt werden. Das zweite vorgestellte Verfahren basiert auf der polarimetrischen Streulichtmessung. Dabei wird zwar nur eine Polarisationsrichtung untersucht, aber auch die Depolarisation der Strahlung wird gemessen. Das System zeigt eine ähnliche Empfindlichkeit für Rauch von offenen Bränden und Rauch von Schwelbränden. Es ist möglich, Staub we-gen seiner stark unregelmäßigen Partikelform anhand der Depolarisation zu erkennen. Das Verfahren ist unabhängig von der Strömungsgeschwindigkeit und kann Rauch auch dann erkennen, wenn die Luft bereits mit Staub verunreinigt ist. Ein weiterer Vor-teil ist, dass auch Rauch von Schwelbränden mit geringer Temperatur von feinen Stäuben unterschieden werden kann.The extent of damage of a fire is related to the time between its ignition and its extinction. Therefore it is necessary to detect a fire as soon as possible. Fast automatic fire-detection systems are available on the market for different fields of application. However, during its lifetime, the fire-detection system will probably “see” more non-fire situations than real fires. During this period of no fire the system should raise no alarm. This simple target is, apart from the fire-detection itself, one of the most complex tasks. Fire-like scenarios may lead to a false-alarm. For detectors which are based on the light scattering principle such scenarios may be caused by clouds of steam or dust. The topic of this work is the fire-detection based on the detection of smoke and its differentiation from nuisance aerosols like steam or dust. Two approaches have been followed: the aerosol characterisation by light scattering measurements performed with an optical sensor with a high spatial resolution, and the characterisation of the monitored aerosol by polarised light scattering measurements. Both methods may be combined for an optimal discrimination of smoke, dust and steam, without losing the sight of a fast fire-detection. Image based light scattering measurements provide information about the size distribution of the observed aerosol. The advantage over simple measurements with a photodiode is that small particles can be monitored even if larger, stronger scattering particles are present in the atmosphere. Measurements with different fire and nuisance aerosols have shown that a discrimination of smoke, dust and steam is possible. Further on the recorded images provide information about the flow direction of the aerosol, which may be important for the localisation of the fire source. This information can be used by automatic extinguishing systems, for a directed operation. The second presented method analyses the polarisation of the scattered light. With it, it is not only possible to achieve a similar sensitivity for smoke from open and smouldering fires, but also a discrimination between smoke and dust is possible. Due to the compact, irregular shaped particles present in dust, part of the polarised light is depolarised. This effect is negligible when light is scattered by smoke particles, which are usually spherical or have a low fractal dimension. The method is independent of the flow velocity of the aerosol and allows a detection of smoke even in dusty atmospheres. By the analysis of the depolarisation of the scattered light it is possible to discern dust even from smoke from fires with low temperature

Publikationsprozesse für Forschungsdaten mit PubFlow : von der Erhebung und Verarbeitung zur Archivierung und Publikation

Project report. Die Ergebnisse des DFG-geförderten Projektes PubFlow werden präsentiert. PubFlow zielt darauf ab, Publikationsprozesse für Forschungs- daten von der Erhebung und der Verarbeitung bis hin zur Archivierung und Publikation zu unterstützen. Die exemplarische Implementierung von PubFlow orientiert sich an etablierten Arbeitsabläufen des Forschungsdatenmanagements in den Meereswissenschaften

Multitrophic diversity in a biodiverse forest is highly nonlinear across spatial scales

Date of Acceptance: 10/11/2015 Acknowledgements We thank the administration of the Gutianshan National Nature Reserve and members of the BEF-China consortium for support, the many people involved in the plant and arthropod censuses, and T. Fang, S. Chen, T. Li, M. Ohl and C.-D. Zhu for help with species identification. G. Seidler kindly calculated forest cover and T. Scholten and P. Kühn provided soil data. The study was funded by the German Research Foundation (DFG FOR 891/1, 891/2), the Sino-German Centre for Research Promotion (GZ 524, 592, 698, 699, 785 and 1020) and the National Science Foundation of China (NSFC 30710103907 and 30930005).Peer reviewedPublisher PD

Multitrophic diversity in a biodiverse forest is highly nonlinear across spatial scales

Subtropical and tropical forests are biodiversity hotspots, and untangling the spatial scaling of their diversity is fundamental for understanding global species richness and conserving biodiversity essential to human well-being. However, scale-dependent diversity distributions among coexisting taxa remain poorly understood for heterogeneous environments in biodiverse regions. We show that diversity relations among 43 taxa - including plants, arthropods and microorganisms - in a mountainous subtropical forest are highly nonlinear across spatial scales. Taxon-specific differences in β-diversity cause under- or overestimation of overall diversity by up to 50% when using surrogate taxa such as plants. Similar relationships may apply to half of all (sub)tropical forests - including major biodiversity hotspots - where high environmental heterogeneity causes high biodiversity and species turnover. Our study highlights that our general understanding of biodiversity patterns has to be improved - and that much larger areas will be required than in better-studied lowland forests - to reliably estimate biodiversity distributions and devise conservation strategies for the world's biodiverse regions

Eddy Study to Understand Physical-Chemical-Biological Coupling and the Biological Carbon Pump as a Function of Eddy Type off West Africa, Cruise No. M160, 23.11.2019 - 20.12.2019, Mindelo (Cabo Verde) - Mindelo (Cabo Verde)

Cruise M160 is part of concerted MOSES/REEBUS Eddy Study featuring three major research expeditions (M156, M160, MSM104). It aims to develop both a qualitative and quantitative understanding of the role of physical-chemical-biological coupling in eddies for the biological pump. The study is part of the MOSES “Ocean Eddies” event chain, which follows three major hypotheses to be addressed by the MOSES/REEBUS field campaigns: (1) Mesoscale and sub-mesoscale eddies play an important role in transferring energy along the energy cascade from the large-scale circulation to dissipation at the molecular level. (2) Mesoscale and sub-mesoscale eddies are important drivers in determining onset, magnitude and characteristics of biological productivity in the ocean and contribute significantly to global primary production and particle export and transfer to the deep ocean. (3) Mesoscale and sub-mesoscale eddies are important for shaping extreme biogeochemical environments (e.g., pH, oxygen) in the oceans, thus acting as a source/sink function for greenhouse gases. In contrast to the other two legs, MOSES Eddy Study II during M160 did not include any benthic work but focused entirely on the pelagic dynamics within eddies. It accomplished a multi-disciplinary, multi-parameter and multi-platform study of two discrete cyclonic eddies in an unprecedented complexity. The pre-cruise search for discrete eddies suitable for detailed study during M160 had already started a few months prior to the cruise. Remote sensing data products (sea surface height, sea surface temperature, ocean color/chlorophyll a) were used in combination with eddy detection algorithms and numerical modelling to identify and track eddies in the entire eddy field off West Africa. In addition, 2 gliders and 1 waveglider had been set out from Mindelo/Cabo Verde for pre-cruise mapping of the potential working area north of the Cabo Verdean archipelago. At the start of M160, a few suitable eddies – mostly of cyclonic type – had been identified, some of which were outside the safe operation range of the motorglider plane. As technical problems delayed the flight operations, the first eddy (center at 14.5°N/25°W) for detailed study was chosen to the southwest of the island of Fogo. It was decided to carry out a first hydrographic survey there followed by the deployment of a suite of instruments (gliders, waveglider, floats, drifter short-term mooring). Such instrumented, we left this first eddy and transited – via a strong anticyclonic feature southwest of the island of Santiago – to the region northeast of the island of Sal, i.e. in the working range of the glider plane. During the transit, a full suite of underway measurements as well as CTD/RO section along 22°W (16°-18.5°N) were carried in search for sub-surface expressions of anticyclonic eddy features. In the northeast, we had identified the second strong cyclonic eddy (center at 18°N/22.5°W) which was chosen for detailed study starting with a complete hydrographic survey (ADCP, CTD/RO, other routine station work). After completion of the mesoscale work program, we identified a strong frontal region at the southwestern rim of the cyclonic eddy, which was chosen for the first sub-mesoscale study with aerial observation component. There, the first dye release experiment was carried out which consisted of the dye release itself followed by an intense multi-platforms study of the vertical and horizontal spreading of the initial dye streak. This work was METEOR-Berichte, Cruise M160, Mindelo – Mindelo, 23.11.2019 4 – 20.12.2019 supported and partly guided by aerial observation of the research motorglider Stemme, which was still somewhat compromised by technical issues and meteorological conditions (high cloud cover, Saharan dust event). Nevertheless, this first dye release experiment was successful and showed rapid movement of the dynamic meandering front. After completion of work on this second eddy and execution of a focused sampling program at the Cape Verde Ocean Observation, RV METEOR returned to the first eddy for continuation of the work started there in the beginning of the cruise. This was accompanied by a relocation of the airbase of Stemme from the international airport of Sal to the domestic airport of Fogo. The further execution of the eddy study at this first eddy, which again included a complete hydrographic survey followed by a mesoscale eddy study with dye release, was therefore possible with aerial observations providing important guidance for work on RV METEOR. Overall, M160 accomplished an extremely intense and complex work program with 212 instrument deployments during station work, 137 h of observation with towed instruments and a wide range of underway measurements throughout the cruise. Up to about 30 individually tracked platforms (Seadrones, glider, wavegliders, drifters, floats) were in the water at the same time providing unprecedented and orchestrated observation capabilities in an eddy. All planned work components were achieved and all working groups acquired the expected numbers of instrument deployments and sampling opportunities

Traces of trauma – a multivariate pattern analysis of childhood trauma, brain structure and clinical phenotypes

Background: Childhood trauma (CT) is a major yet elusive psychiatric risk factor, whose multidimensional conceptualization and heterogeneous effects on brain morphology might demand advanced mathematical modeling. Therefore, we present an unsupervised machine learning approach to characterize the clinical and neuroanatomical complexity of CT in a larger, transdiagnostic context. Methods: We used a multicenter European cohort of 1076 female and male individuals (discovery: n = 649; replication: n = 427) comprising young, minimally medicated patients with clinical high-risk states for psychosis; patients with recent-onset depression or psychosis; and healthy volunteers. We employed multivariate sparse partial least squares analysis to detect parsimonious associations between combinations of items from the Childhood Trauma Questionnaire and gray matter volume and tested their generalizability via nested cross-validation as well as via external validation. We investigated the associations of these CT signatures with state (functioning, depressivity, quality of life), trait (personality), and sociodemographic levels. Results: We discovered signatures of age-dependent sexual abuse and sex-dependent physical and sexual abuse, as well as emotional trauma, which projected onto gray matter volume patterns in prefronto-cerebellar, limbic, and sensory networks. These signatures were associated with predominantly impaired clinical state- and trait-level phenotypes, while pointing toward an interaction between sexual abuse, age, urbanicity, and education. We validated the clinical profiles for all three CT signatures in the replication sample. Conclusions: Our results suggest distinct multilayered associations between partially age- and sex-dependent patterns of CT, distributed neuroanatomical networks, and clinical profiles. Hence, our study highlights how machine learning approaches can shape future, more fine-grained CT research

Performance Enhancement of UWB Material Characterization and Object Recognition for Security Robots

By means of UWB Radar sensors the tasks of material characterisation and object recognition can be performed on the basis of a previous imaging of the whole environment. A UWB version of the microwave ellipsometry method is applied for estimating the permittivity of homogenous objects. The object recognition task is performed using bistatic sensor nodes on the basis of Radar measurements. The simulation-based performance evaluations show a very robust behavior due to suitable preprocessing of Radar data. The applications comprise the detection of fire sources, the detection of metallic object hidden under clothing, and the recognition of building structures

Analysis of Dust Properties to Solve the Complex Problem of Non-fire Sensitivity Testing of Optical Smoke Detectors

AbstractThe purpose of an automatic fire detection system is the fast and reliable detection of arising fires in order to keep damage as low as possible. The European Standard EN54 defines a series of tests to prove and certify the functionality of smoke detectors, i.e. to prove that the detector is able to detect a fire in a prescribed period of time. Unfortunately the complex task of avoiding false alarms is not completely addressed. In contrast to the well standardized methods for the evaluation of the detection capability of a smoke detector, there is a lack of a reproducible and representative test method concerning the false alarm susceptibility with regard to nuisance aerosols. The consequences of false alarms should not be underestimated, as they may cause costs to serve the operator, especially in airborne applications. Many false alarms are caused by construction works in the surrounding of smoke detectors. For that reason several dust sources have been analyzed. Several approaches are possible and have been implemented to reduce the false alarm susceptibility of optical smoke detectors caused by dust and steam, e.g. different wavelengths and scattering angles. Unfortunately the developer has no representative test methods to quantify improvements and to point out the false-alarm resistance with e.g. a seal of quality due to new developments. Important is the knowledge of dust and steam properties such as the particle size distribution in comparison to particle size distribution of smoke of a fire. This paper presents a new approach for the test of smoke detectors regarding their susceptibility to false alarms due to nuisance aerosols, like steam and dust. The presented test apparatus is a very helpful and important tool for developers as well as for test houses during the developing and certification process. System designer will have a quantitative decision criterion to find the optimal detector for a specific place of installation. The paper compares the analysis of dust properties caused by construction works with standardized test dusts and shows how to solve the problem

Spatiotemporal measurement of light extinction coefficients in compartment fires

In case of fire, the visibility plays a major role as it limits the occupants’ orientation capabilities and the perception of signs. These effects are determined by the light extinction due to smoke or other aerosols produced in fires. The presented method is based on the optical observation of an array of light sources during a fire in a laboratory experiment. The smoke induced into the compartment leads to a drop in intensity of each individual light source. This information is used to deduce the extinction along the line-of-sight to the camera. Once the data are captured, an automated processing is used to locate the diodes on the images and determine their intensity. Here, the optical image of the small diodes is assumed to have a known shape, so that the optimisation algorithm is capable to identify the location of the diode’s centre and quantify the luminosity in a sub-pixel range. The result is a time series for each diode, indicating the change of the relative luminosity, w.r.t. the initial values. Finally, a model for the extinction along each line-of-sight is formulated. It assumes that the light extinction coefficient is distributed in homogeneous layers. The number of layers is a free model parameter. Given this spatial distribution of the extinction coefficient and the experimental geometry, each line-of-sight is impacted by a number of layers, of yet unknown coefficient values. An inverse modelling approach is used here to find coefficient values that match the modelled line-of-sight extinction with the observed luminosity drops. The final result is a time- and height-dependent distribution of the light extinction coefficient during the full experiment