155 research outputs found

    Semantic Visual Localization

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    Robust visual localization under a wide range of viewing conditions is a fundamental problem in computer vision. Handling the difficult cases of this problem is not only very challenging but also of high practical relevance, e.g., in the context of life-long localization for augmented reality or autonomous robots. In this paper, we propose a novel approach based on a joint 3D geometric and semantic understanding of the world, enabling it to succeed under conditions where previous approaches failed. Our method leverages a novel generative model for descriptor learning, trained on semantic scene completion as an auxiliary task. The resulting 3D descriptors are robust to missing observations by encoding high-level 3D geometric and semantic information. Experiments on several challenging large-scale localization datasets demonstrate reliable localization under extreme viewpoint, illumination, and geometry changes

    Development of the Theoretical and Experimental Framework of a Heliostat Field Calibration Method

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    Solarturmkraftwerke verwenden tausende bis mehr als hundertausend individuell, zweiachsig der Sonne nachgeführte Heliostaten, um direkte Solarstrahlung auf eine als Receiver bezeichnete zentrale Absorberstruktur oben auf einem Turm zu reflektieren. Aufgrund der daraus resultierenden hohen Solarstrahlungsflussdichte auf dem Receiver sind Solarturmkraftwerke in der Lage, hohe Betriebstemperaturen zu erreichen. Dies ist besonders nützlich unter anderem zur Realisierung von hohen Gesamtwirkungsgraden bei Betrieb eines Clausius-Rankine-Kreisprozesses oder für solarchemische Verfahren zur Herstellung von solaren Kraftstoffen. Solarturmkraftwerke haben jedoch den Nachteil, dass jeder Heliostat die Sonnenbahn mit eigenen zweiachsigen Antrieben mit hoher Genauigkeit nachführen muss. Idealerweise sollte die Nachführgenauigkeit ≤1 mrad betragen (Sattler et al. 2020). Dies stellt jedoch auch heutzutage noch immer ein Problem dar, da die Nachführgenauigkeit von mehreren Fehlerquellen beeinflusst wird. Um die Ausrichtung der Heliostaten zu vermessen, ist es notwendig, ein Kalibriersystem einzusetzen. Die meisten Solarturmkraftwerke verwenden die dem aktuellen Stand der Technik entsprechende Kamera-Target-Methode, die jedoch Nachteile hat, beispielsweise dass der Kalibrierprozess für ein gesamtes Heliostatfeld sehr langsam ist. In der vorliegenden Arbeit lag der Fokus auf der Erforschung und Entwicklung einer Kalibriermethode, die den Einsatz eines zweiachsig nachgeführten zentralen Lasersystems und zweier Kameras vorsieht. Diese Kalibriermethode wird als zentrales Laser-Kamera-System (CLCS) bezeichnet. Das Ziel war, eine Genauigkeit von 0.1 mrad für die Messung der Ausrichtung eines Heliostaten zu erreichen. Die Auswahl einer optimalen Konfiguration des Laser- und Kamerasystems ist komplex. Um die Theorie des CLCS zu bestätigen, wurde ein Simulationsmodell entwickelt und validiert sowie mehrere Laborversuche und ein Außenversuch durchgeführt. Die Experimente und die Theorie zeigten, dass es mit einer spezifischen Konfiguration des Laser- und Kamerasystems realistisch ist, dass das CLCS prinzipiell in einer realen Anwendung in der Zukunft funktionieren kann. Zur Bewertung der Messgenauigkeit des CLCS wurde eine Simulationsstudie unter Verwendung von Bildaufnahmen von Laserstrahlen vom Außenversuch durchgeführt, die zu dem Ergebnis kam, dass mit der verwendeten Kamera eine mittlere Messgenauigkeit von 0.37 mrad realistisch ist, was ausreichend gut ist. Für das CLCS ist eine Messrate von 10 Hz realistisch. Verglichen mit der aktuellen Kamera-Target-Methode kann das CLCS potentiell mit einer weit höheren Messgeschwindigkeit betrieben werden und zwar bis zu 300-mal schneller, wenn bei der Vermessung der Ausrichtung eines Heliostaten lediglich eine einzelne Spiegelfacette verwendet wird. Die Vermessung mehrerer Spiegelfacetten pro Heliostat, um daraus die Gesamt-Heliostatennormale zu bestimmen, ist ebenfalls möglich. Darüber hinaus kann das Laser-Kamera-Verfahren auch nachts eingesetzt werden

    High-Temperature Thermal Storage System for Solar Tower Power Plants with Open-Volumetric Air Receiver Simulation and Energy Balancing of a Discretized Model

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    This paper describes the modeling of a high-temperature storage system for an existing solar tower power plant with open volumetric receiver technology, which uses air as heat transfer medium (HTF). The storage system model has been developed in the simulation environment Matlab/Simulink®. The storage type under investigation is a packed bed thermal energy storage system which has the characteristics of a regenerator. Thermal energy can be stored and discharged as required via the HTF air. The air mass flow distribution is controlled by valves, and the mass flow by two blowers. The thermal storage operation strategy has a direct and significant impact on the energetic and economic efficiency of the solar tower power plants

    High-Temperature Thermal Storage System for Solar Tower Power Plants with Open-Volumetric Air Receiver Simulation and Energy Balancing of a Discretized Model

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    This paper describes the modeling of a high-temperature storage system for an existing solar tower power plant with open volumetric receiver technology, which uses air as heat transfer medium (HTF). The storage system model has been developed in the simulation environment Matlab/Simulink®. The storage type under investigation is a packed bed thermal energy storage system which has the characteristics of a regenerator. Thermal energy can be stored and discharged as required via the HTF air. The air mass flow distribution is controlled by valves, and the mass flow by two blowers. The thermal storage operation strategy has a direct and significant impact on the energetic and economic efficiency of the solar tower power plants

    CAP-reform and the provision of non-commodity outputs in Brandenburg

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    This paper presents an attempt to model the response of selected farms to decoupled direct payments and the associated impact on the provision of a defined set of non-commodity outputs (NCO’s) using a combined modelling approach consisting of the AgriPoliS and MODAM models. AgriPoliS focuses on the socio-economic dimension of multifunctionality at the individual farm and regional levels and explicitly models heterogeneous farms (in size, location and efficiency) within a competitive and dynamic environment. The linear-programming model MODAM allows a detailed representation of production processes and their impact on the environmental dimension of multifunctionality at the farm level. We simulate the impact of a uniform area payment and a fully decoupled single farm payment. Our case study region is the district Ostprignitz-Ruppin in Brandenburg. Results show that the decoupling schemes create a trade-off between the NCO’s and that adjustment reactions differ between farms depending on their legal form, size, and production.decoupling, multifunctionality, non-commodity outputs, modelling, simulation, policy analysis, ecological indicators, Agricultural and Food Policy, Land Economics/Use,

    Evaluating the Benefits: Quantifying the Effects of TCP Options, QUIC, and CDNs on Throughput

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    To keep up with increasing demands on quality of experience, assessing and understanding the performance of network connections is crucial for web service providers. While different measures, like TCP options, alternative transport layer protocols like QUIC, or the hosting of services in CDNs, are expected to improve connection performance, no studies are quantifying such impacts on connections on the Internet. This paper introduces an active Internet measurement approach to assess the impacts of mentioned measures on connection performance. We conduct downloads from public web servers considering different vantage points, extract performance indicators like throughput, RTT, and retransmission rate, and survey speed-ups due to TCP option usage. Further, we compare the performance of QUIC-based downloads to TCP-based downloads considering different option configurations. Next to significant throughput improvements due to TCP option usage, in particular TCP window scaling, and QUIC, our study shows significantly increased performance for connections to domains hosted by different giant CDNs.Comment: Presented at the ACM/IRTF Applied Networking Research Workshop 2023 (ANRW23

    Rusty Clusters? Dusting an IPv6 Research Foundation

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    The long-running IPv6 Hitlist service is an important foundation for IPv6 measurement studies. It helps to overcome infeasible, complete address space scans by collecting valuable, unbiased IPv6 address candidates and regularly testing their responsiveness. However, the Internet itself is a quickly changing ecosystem that can affect longrunning services, potentially inducing biases and obscurities into ongoing data collection means. Frequent analyses but also updates are necessary to enable a valuable service to the community. In this paper, we show that the existing hitlist is highly impacted by the Great Firewall of China, and we offer a cleaned view on the development of responsive addresses. While the accumulated input shows an increasing bias towards some networks, the cleaned set of responsive addresses is well distributed and shows a steady increase. Although it is a best practice to remove aliased prefixes from IPv6 hitlists, we show that this also removes major content delivery networks. More than 98% of all IPv6 addresses announced by Fastly were labeled as aliased and Cloudflare prefixes hosting more than 10M domains were excluded. Depending on the hitlist usage, e.g., higher layer protocol scans, inclusion of addresses from these providers can be valuable. Lastly, we evaluate different new address candidate sources, including target generation algorithms to improve the coverage of the current IPv6 Hitlist. We show that a combination of different methodologies is able to identify 5.6M new, responsive addresses. This accounts for an increase by 174% and combined with the current IPv6 Hitlist, we identify 8.8M responsive addresses

    The COMT p.Val158Met Polymorphism and Cognitive Performance in Adult Development, Healthy Aging and Mild Cognitive Impairment

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    Background: The impact of genetic polymorphisms on cognition is assumed to increase with age as losses of brain resources have to be compensated for. We investigate the relation of catechol-O-methyltransferase (COMT) p.Val158Met polymorphism and cognitive capacity in the course of adult development, healthy aging and the development of mild cognitive impairment (MCI) in two birth cohorts of subjects born between 1930 and 1932 or between 1950 and 1952. Methods: Thorough neuropsychological assessment was conducted in a total of 587 participants across three examination waves between 1993 and 2008. The COMT genotype was determined as a restriction fragment length polymorphism after PCR amplification and digestion with Nla III. Results: Significant effects of the COMT p.Val158Met polymorphism were identified for attention and cognitive flexibility in the younger but not the older cohort. Conclusion: These results confirm the importance of the COMT p.Val158Met genotype on tasks assessing attention and cognitive flexibility in midlife but not in healthy aging and the development of MCI. Our findings suggest that the influence of COMT changes as a function of age, decreasing from midlife to aging

    Application of Electrochemical Impedance Spectroscopy on Different Battery Circuits

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    For the operation of a battery pack, the cell state estimation plays a central role. For that, enough information about the current charge condition (SoC, state of charge) and the health status (SoH, state of health) of the individual cells or cell strings must be available. One way to draw out conclusions about the state of charge and health provides the electrochemical impedance spectroscopy (EIS) [1]. The test cells are thereby stimulated with an alternating current signal, and the resulting voltage signal is detected. These results in cell impedances, which are addicted to the signal frequencies and the respective cell states. This poster shows an experimental platform which uses the EIS to detect asymmetries in SoC and/or SoH on circuited cells. For that, the behavior of the amplitudes and frequencies of the signals should be analyzed, because for the calculation of the precise impedance, these factors are crucial. Thereby the required alternating current and voltage signals are acquired and analyzed separately for each single cell. As cell type lithium iron-phosphate round cells of the size 18650 are used. The investigations are made on a series circuit (Fig.1) made up of three cells and on a parallel circuit made up of two strings, each having two cells in series. It shows that both a series and a parallel connection within the working range the experimental platform impedances of individual cells can be determined. For these cases, differences in state of charge and state of health can be highlighted and assigned to the respective cells

    Packed to the Brim: Investigating the Impact of Highly Responsive Prefixes on Internet-wide Measurement Campaigns

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    Internet-wide scans are an important tool to evaluate the deployment of services. To enable large-scale application layer scans, a fast, stateless port scan (e.g., using ZMap) is often performed ahead of time to collect responsive targets. It is a common expectation that port scans on the entire IPv4 address space provide a relatively unbiased view as they cover the complete address space. Previous work, however, has found prefixes where all addresses share particular properties. In IPv6, aliased prefixes and fully responsive prefixes, i.e., prefixes where all addresses are responsive, are a well-known phenomenon. However, there is no such in-depth analysis for prefixes with these responsiveness patterns in IPv4. This paper delves into the underlying factors of this phenomenon in the context of IPv4 and evaluates port scans on a total of 161 ports (142 TCP & 19 UDP ports) from three different vantage points. To account for packet loss and other scanning artifacts, we propose the notion of a new category of prefixes, which we call highly responsive prefixes (HRPs). Our findings show that the share of HRPs can make up 70 % of responsive addresses on selected ports. Regarding specific ports, we observe that CDNs contribute to the largest fraction of HRPs on TCP/80 and TCP/443, while TCP proxies emerge as the primary cause of HRPs on other ports. Our analysis also reveals that application layer handshakes to targets outside HRPs are, depending on the chosen service, up to three times more likely to be successful compared to handshakes with targets located in HRPs. To improve future scanning campaigns conducted by the research community, we make our study's data publicly available and provide a tool for detecting HRPs. Furthermore, we propose an approach for a more efficient, ethical, and sustainable application layer target selection
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