590 research outputs found
Hy Care - Hydrogen Energy Chances and Risks for the Environment: Proceedings of the first HyCARE meeting, Hamburg, 16-17 December 2004
In order to discuss the most pressing research needs and structure the research activities regarding the environmental impact of large-scale hydrogen use in Europe, a workshop was held at the Max Planck Institute for Meteorology, Hamburg, Germany on Dec. 16 and 17, 2004. Thirty-two internationally recognized experts in atmospheric chemistry, soil microbiology, fuel cell technology, and scenario development came to Hamburg for two days of exchange of knowledge. This report summarizes the meeting presentations and discussions and is intended to support governments and funding agencies in structuring their agenda with respect to hydrogen impact research. All presentations from the workshop are also available as pdf documents on the HyCARE web pages
Modeling of an upper Midwest forest boundary layer and vehicle indoor air quality
The key to understanding tropospheric chemistry begins with the hydroxyl and hydroperoxy radicals. Recent research suggests that there is still considerable uncertainty in our understanding of the sources of these radicals and their role as sinks. The work detailed in this thesis describes a computational approach to modeling the hydroxyl and hydroperoxy radicals in a forest environment and attempts to shed further light on the radical budget in a typical Northern Hardwood forest. Additionally, research was conducted with United States Council for Automotive Research in collaboration with Ford, General Motors, and Chrysler to develop a global standard for vehicle indoor air quality test methodologies. An initial evaluation of materials to validate test and analysis process has been completed. In addition to establishing the identity of a material for an internal standard, a VOC specific emission algorithm to predict cabin VOC concentrations for a given set of control parameters was established
A systematic review of perception system and simulators for autonomous vehicles research
This paper presents a systematic review of the perception systems and simulators for autonomous vehicles (AV). This work has been divided into three parts. In the first part, perception systems are categorized as environment perception systems and positioning estimation systems. The paper presents the physical fundamentals, principle functioning, and electromagnetic spectrum used to operate the most common sensors used in perception systems (ultrasonic, RADAR, LiDAR, cameras, IMU, GNSS, RTK, etc.). Furthermore, their strengths and weaknesses are shown, and the quantification of their features using spider charts will allow proper selection of different sensors depending on 11 features. In the second part, the main elements to be taken into account in the simulation of a perception system of an AV are presented. For this purpose, the paper describes
simulators for model-based development, the main game engines that can be used for simulation, simulators from the robotics field, and lastly simulators used specifically for AV. Finally, the current state of regulations that are being applied in different countries around the world on issues concerning the implementation of autonomous vehicles is presented.This work was partially supported by DGT (ref. SPIP2017-02286) and GenoVision (ref. BFU2017-88300-C2-2-R) Spanish Government projects, and the “Research Programme for Groups of Scientific Excellence in the Region of Murcia" of the Seneca Foundation (Agency for Science and Technology in the Region of Murcia – 19895/GERM/15)
Transport impacts on atmosphere and climate: Land transport
Emissions from land transport, and from road transport in particular, have significant impacts on the atmosphere and on climate change. This assessment gives an overview of past, present and future emissions from land transport, of their impacts on the atmospheric composition and air quality, on human health and climate change and on options for mitigation. In the past vehicle exhaust emission control has successfully reduced emissions of nitrogen oxides, carbon monoxide, volatile organic compounds and particulate matter. This contributed to improved air quality and reduced health impacts in industrialised countries. In developing countries however, pollutant emissions have been growing strongly, adversely affecting many populations. In addition, ozone and particulate matter change the radiative balance and hence contribute to global warming on shorter time scales. Latest knowledge on the magnitude of land transport's impact on global warming is reviewed here. In the future, road transport's emissions of these pollutants are expected to stagnate and then decrease globally. This will then help to improve the air quality notably in developing countries. On the contrary, emissions of carbon dioxide and of halocarbons from mobile air conditioners have been globally increasing and are further expected to grow. Consequently, road transport's impact on climate is gaining in importance. The expected efficiency improvements of vehicles and the introduction of biofuels will not be sufficient to offset the expected strong growth in both, passenger and freight transportation. Technical measures could offer a significant reduction potential, but strong interventions would be needed as markets do not initiate the necessary changes. Further reductions would need a resolute expansion of low-carbon fuels, a tripling of vehicle fuel efficiency and a stagnation in absolute transport volumes. Land transport will remain a key sector in climate change mitigation during the next decades
Aircraft Emissions and the Global Atmosphere
Emissions from airplanes and their potential global effects on the atmosphere have become the subject of intensive study by scientists, and are now drawing the interest of governments. Global fuel consumption has risen much faster for aviation than for other energy-use sectors. Concerns have focused on the contribution of nitrogen oxides (NOx), carbon dioxide (C02), water vapor (H20) and other engine effluents to the buildup of the atmosphere\u27s greenhouse effect. Future aircraft emissions also may affect the stratosphere\u27s ozone layer.
This report describes an effort to develop long-term scenarios for emissions from aviation in order to provide a basis for assessing their potential environmental impact throughout the 21st century. Carbon dioxide and nitrogen oxides from the current and projected subsonic aircraft fleets are the main focus of this study. The scenarios in this report were produced by a model that builds on technological and operational assumptions made by industry and government for the period through 2015.
It is important to state from the outset what this report is not about. It is not a detailed examination of the environmental effects of aviation. It is not an assessment of the potential for technological or operational changes that could reduce emissions from expected levels. It does not set forth a comprehensive and detailed policy prescription for limiting emissions from aviation. This report does not analyze the potential emissions of a vastly expanded fleet of supersonic aircraft, such as the proposed High-Speed Civil Transport (HSCT), although its possible environmental impacts are discussed briefly
Applications of aerospace technology in the public interest: Pollution measurement
This study of selected NASA contributions to the improvement of pollution measurement examines the pervasiveness and complexity of the economic, political, and social issues in the environmental field; provides a perspective on the relationship between the conduct of aerospace R and D and specific improvements in on site air pollution monitoring equipment now in use; describes the basic relationship between the development of satellite-based monitoring systems and their influence on long-term progress in improving environmental quality; and comments on how both instrumentation and satellite remote sensing are contributing to an improved environment. Examples of specific gains that have been made in applying aerospace R and D to environmental problem-solving are included
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Towards secure & robust PNT for automated systems
This dissertation makes four contributions in support of secure and robust position, navigation, and timing (PNT) for automated systems. The first two relate to PNT security while the latter two address robust positioning for automated ground vehicles.
The first contribution is a fundamental theory for provably-secure clock synchronization between two agents in a distributed automated system. All one-way synchronization protocols, such as those based on the Global Positioning System (GPS) and other Global Navigation Satellite Systems (GNSS), are shown to be vulnerable to man-in-the-middle delay attacks. This contribution is the first to identify the necessary and sufficient conditions for provably secure clock synchronization.
The second contribution, also related to PNT security, is a three-year study of the world-wide GPS interference landscape based on data from a dual-frequency GNSS receiver operating continuously on the International Space Station (ISS). This work is the first publicly-reported space-based survey of GNSS interference, and unveils previously-unreported GNSS interference activity.
The third contribution is a novel ground vehicle positioning technique that is robust to GNSS signal blockage, poor lighting conditions, and adverse weather events such as heavy rain and dense fog. The technique relies on sensors that are commonly available on automated vehicles and are insensitive to lighting and inclement weather: automotive radar, low-cost inertial measurement units (IMUs), and GNSS. Remarkably, it is shown that, given a prior radar map, the proposed technique operating on data from off-the-shelf all-weather automotive sensors can maintain sub-50-cm horizontal position accuracy during 60 min of GNSS-denied driving in downtown Austin, TX.
This dissertation’s final contribution is an analysis and demonstration of the feasibility of crowd-sourced digital mapping for automated vehicles. Localization techniques, such as the one described in the previous contribution, rely on such digital maps for accuracy and robustness. A key enabler for large-scale up-to-date maps is enlisting the help of the very consumer vehicles that need the map to build and update it. A method for fusing multi-session vision data into a unified digital map is developed. The asymptotic limit of such a map’s globally-referenced position accuracy is explored for the case in which the mapping agents rely on low-cost GNSS receivers performing standard code-phase-based navigation. Experimental validation along a semi-urban route shows that low-cost consumer vehicles incrementally tighten the accuracy of the jointly-optimized digital map over time enough to support sub-lane-level positioning in a global frame of reference.Electrical and Computer Engineerin
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