204 research outputs found
Long reads: Pepijn Brandon on revolution in the Netherlands (part 1)
No full textThe Dutch Revolt of the sixteenth century defeated the Spanish monarchy, the great European superpower of its day. It may not be as well remembered as the English Civil War or the French Revolution. But it was a watershed moment in the development of modern Europe.Pepijn Brandon joins Long Reads to discuss the Dutch Revolt. He’s an historian at VU University in Amsterdam and the author of War, Capital, and the Dutch State. This is the first part of a two-part interview.Long Reads is a Jacobin podcast looking in-depth at political topics and thinkers, both contemporary and historical, with the magazine’s longform writers. Hosted by features editor Daniel Finn. Produced by Conor Gillies, music by Knxwledge
Insight into the local bed-level dynamics to assist management of multi-functional rivers
No full textGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Rivers, Ports, Waterways and Dredging Engineerin
Aerosol Absorption from Global Satellite Measurements in the Ultra-Violet: From Qualitative Aerosol Index to Quantitative Aerosol Absorptive Properties
No full textAtmospheric aerosols are solid or liquid particles suspended in the air. The majority of them are produced by natural processes, including sea salt from oceans, mineral dust from (semi-)arid regions, carbon containing particles from wildfires, and sulfates and ash from volcanic activities. Anthropogenic aerosols are produced by industrial activities, power generation, transportation, agriculture, and human-induced biomass burning events. Depending on the meteorological conditions, aerosol particles can stay in the atmosphere for several hours to several months and can be transported over long distances, causing adverse effects on human health, visibility and climate.This thesis focuses on the aerosol optical properties, particularly the light absorption of the aerosol particles that has significant effects on the Earth’s climate system. This thesis starts with a general introduction of atmospheric aerosols, including its sources, categories, physical properties and measurement techniques (Chapter 1). Next, the Ultra-Violet Aerosol Index (UVAI) is introduced, which is calculated from satellite measurements of the radiance at two wavelengths in the UV. UVAI contains information of aerosol absorption, and it has a very long andalmost continuous data record starting in 1978. Direct use of UVAI is challenging because it is not a geophysical quantity, but a numerical index. The objective of this thesis is to derive quantitative properties on aerosol absorption from the UVAI (e.g. single scattering albedo, absorption aerosol optical depth) that can be directly used in aerosol radiative transfer assessments. Two types of methods have been developed, i.e. physically-based methods and statistically-based methods. The first compares the observed UVAI to the one simulated by radiative transfer models. The second uses Machine Learning algorithms trained by existing data sets.The physically-based methods have been applied to quantify aerosol absorption of several large scale wildfires (Chapter 2 and 3). An important challenge of these method is that assumptions have to be made on the aerosol micro-physical properties, leading to significant uncertainties in the results, whereas theMachine Learning-based methods can avoid this kind of assumptions. Chapter 3 investigates the feasibility to quantify aerosol absorption from UVAI using a Machine Learning algorithm. Despite the higher computational efficiency and better results, the application of such data-driven methods is still restricted by the limited data on the aerosol vertical distribution. Therefore, in Chapter4, a database of aerosol height is created from a chemistry transport model. This database is applied in Chapter 5, where a Deep Neural Network method is used to derive the quantitative aerosol absorptive properties from the OMI/Aura UVAI for the period from 2006 to 2019. In comparison to ground-based observations, the results of the Deep Neural Network agree better than satellite retrievals and also better than chemistry transport model simulations.This thesis demonstrates the feasibility of deriving quantitative aerosol absorptive properties from the satellite retrieved UVAI.We use traditional radiative transfer simulations meanwhile investigating the new possibilities of data-driven methods in aerosol remote sensing. Although the retrieval results are encouraging, there remain limitations and challenges which need to be addressed. These are discussed in Chapter 6 with corresponding suggestions and prospects. Despite the challenges, it is expected that a synthetic database of global aerosol absorption can be derived fromUVAI observations provided by multiple satellite products. Such a data set will make great contributions to quantify the effect of absorbing aerosols on the climate system.Atmospheric Remote Sensin
Analysing confidence intervals with a strict method: The difference between the classic and a conditional testing-estimation
No full textIncremental nonlinear control allocation for an aircraft with distributed electric propulsion: An application to the scaled flight demonstrator
No full textTo meet the demanding requirements on the environmental impact of aircraft, radically new aircraft concepts need to be developed. Within the NOVAIR project, Royal Netherlands Aerospace Centre (NLR) tests these new concepts on a Scaled flight demonstrator (SFD). Using an SFD allows for testing of dynamic and flight physical behavior of new aircraft concepts, which is difficult with more theoretical methods. Furthermore, by using an SFD, the risks associated with full-scale testing in terms of cost and time are minimized. One of the new concepts developed for the SFD is Distributed electric propulsion (DEP). Here, the two jet engines are replaced by six electric propellers. As these can be used actively for control, this results in an over-actuated system. These propellers interact with the aerodynamics of the wing resulting in Propulsion airframe interaction (PAI) effects. Although using the PAI effects for control has the potential to improve capabilities, efficiency and robustness of the aircraft, research into controllers using these effects actively is limited.This thesis, therefore, presents a new control method including control allocation for the DEP-SFD aircraft, based on the nonlinear Incremental nonlinear dynamic inversion (INDI) controller. INDI enables controlling the nonlinear dynamics of the DEP aircraft over the complete flight envelope with one controller. By feeding back real-time sensor measurements, robustness to modeling errors and external disturbances is increased. Using the Incremental nonlinear control allocation (INCA) method, the full control authority of the DEP can be used. This technique enables taking into account nonlinear allocation relations and control effector interactions, while solving the control allocation real-time, which is key in actively using the PAI effects for control. The INCA method is used for two performance improvements: tracking performance and propeller power efficiency. To compensate for actuator dynamics, this thesis implements an Model predictive control (MPC) controller which results in improved tracking and higher efficiency. The performance of the controller was analyzed in simulation, where a reference square signal input on the roll angle was applied, while minimizing the sideslip angle and maintaining a steady altitude and velocity. The INCA controller with MPC is compared to a conventional INDI controller, showing a significant decrease in rise time from 2.46 s to 0.703 s with minimal tracking error. Furthermore, the effective bandwidth of the system was increased from 0.186 Hz to 0.663 Hz and the power consumption reduced by 6.3%. Modeling uncertainties, external disturbances and a propeller fault were introduced to verify the robustness of the controller. Finally, the reference altitude and velocity were varied, demonstrating controller performance over a large part of the flight envelope.Mechanical Engineering | Systems and Contro
UN City Hub Beirut: A metro station in the city centre of Beirut
No full textArchitecture, Urbanism and Building Sciences | Complex Project
Life cycle sustainability of novel monopropellant systems: A comparative LCSA of a LEO minisatellite case study
No full textFor over 50 years, hydrazine has been the industry standard for monopropellant propulsion systems, widely used in satellite attitude and orbit control systems. However, hydrazine’s toxicity necessitates expensive handling procedures and may lead to a future ban of the propellant in Europe. This has motivated the development of novel monopropellants, featuring reduced toxicity compared to hydrazine. Separately, life cycle assessments (LCAs) are becoming increasingly prevalent in the space industry. As very few assessments have been made so far for monopropellant systems, this thesis performs a comparative life cycle sustainability assessment (LCSA) of a hydrazine and three novel monopropellant systems for a single use case, evaluating the environmental, economic and social sustainability of each. This research provides new insights into the life cycle impact of the differences between the various propulsion systems and identifies hotspots in each sustainability dimension, informing a more sustainable development of novel monopropellant systems in the future.Aerospace Engineerin
The Business Ecosystem of the Quantum Computing Market: Cooperation and Competition
No full textThe current second quantum revolution heralds the biggest technological advancements of the twenty-first century. At the forefront of this is the development of quantum computers, which promise to bring transformations to almost all sectors, from banking to drug research. With rising investments in developing full-scale, fault-tolerant quantum computers, the quantum computing provider market is starting to saturate with incumbents. In order to succeed, firms operating in this market need to start acting competitively. However, despite vast research on the potential applications, technological development and responsible innovation, little is known about strategic factors that drive the market.To address this issue, this work identifies, describes and contextualises the use of alliances in firms’ business strategy in the quantum computing business ecosystem. Through literature review, publications of various types of collaborations on firms's websites, and interviews with four experts in the industry, the work describes the quantum computing business ecosystem, links the cooperations to literature on strategies, and provides contextual implementations of various alliances.First, a value proposition is constructed, containing five components: Hardware providers, cloud service providers, quantum software providers, managed services providers and end-users, each with its own set of challenges and strategies attached to it. Furthermore, two technology strategies pursued by firms can be identified: an open innovation approach and a full-stack approach. The use of various types of collaborations are described, including licensing, standards agreements, business networks, joint marketing, selling and offering agreements, consortia, strategic partnerships, mergers and acquisitions, and joint ventures.For SMEs, alliances through bidding consortia, formed for tenders and subsidies, are the main use of cooperation. Strategies herein are the acquisition of capital, reduction of R\&D costs, early product show-off, and staying in the loop for technological decision making on standards. Other partnerships are aimed at figuring out relationships with other firms in the industry, and fostering standardisation through the release of open-source software. The former is characteristic of the nascent ecosystem's formation, as the value proposition is still unclear and the industry's architecture is not set. The use of open-source software has also played a key role in the development of the classical computer, and firms are seen to adhere to a similar approach. Furthermore, we contextualise the strategic differences between the full-stack and open innovation approaches that are seen within the ecosystem. Where firms in the former are challenged by technical inflexibility, low sales volume and vast investment costs, firms in the latter need to balance an appropriability-adoption dilemma, create sufficient alignment with their value proposition and use extensive cooperation to ensure compatibility and modularity. However, through this, they get to enjoy increased economies of scale and agility.All in all, the strategies can be summarised in two main categories: procurement of resources and embedding into the ecosystem. The work in this thesis encompasses a multitude of related fields including competitive strategy, ecosystems and alliances, and discusses the quantum computing industry from the standpoint of the technology providers and developers, which should aid managers in evaluating their strategic position in the ecosystem and in drafting cooperation strategies. From an academic perspective, this work provides the first managerial study of the quantum computing market from the standpoint of the technology providers. In addition to strategies, it identifies a lack of alignment of end-users as a key inhibitor to the constitution of the value proposition. Moreover, the findings of this thesis support the hypothesis that pre-adaptation-phase strategies are aimed at constituting Ortt and Kamp's technological innovation system (TIS) framework's building blocks, an important step to understanding ecosystem formation dynamics.Lastly, we identify several key areas for future studies. This includes validating and strengthening the conclusions of this work through additional expert interviews, which should also help in exposing nuances in strategy between firm sizes, position in the value chain and geolocation, as well as similarities and differences with the development of the classical computer. Furthermore, future studies are suggested to investigate the differences in efficiency and effectiveness of governmental funding in the quantum industry, characterise end-users based on their expected moment of engagement with the quantum computing market, the role of alliances in quantum computing platform formation, and the link between innovation-phase strategies and the TIS framework's building blocks.Management of Technology (MoT
The performance of Earth System Models in simulating droughts
No full textThis research evaluated the performance of Land Surface Models (LSMs) in simulating droughts, examining Land-Hist offline simulations from the Land, Surface, Snow and Soil Moisture Intercomparison Project (LS3MIP). It is well known that LSMs possess uncertainties and biases due to oversimplifications or the absence of certain physical processes (e.g., groundwater interactions and lateral connectivity). Therefore, the objective of this research was to identify the strengths and weaknesses of various LSMs and how this relates to the performances in simulating soil moisture droughts. To address this objective, eight LSMs were evaluated: CESM2, CMCC-ESM2, E3SM-1-1, EC-Earth3-Veg, HadGEM3-GC31-LL, IPSL-CM6A-LR, MIROC6, and UKESM1-0-LL. Two reference evaporation data sets (DOLCE V3 and an ensemble of FLUXCOM-RS, BESS and PML) and a reference soil moisture data set (SoMo.ml) were utilized for the evaluation. After a global analysis on the LSM evaporation characteristics, six climate diverse study areas were selected for further investigation. A long-term analysis was performed by examining the water balance and implementing the LSMs into the Budyko Framework. Subsequently, soil moisture deficits were calculated for the driest periods in time, and the resulting accumulated deficits were compared with the reference evaporation data. The timing and progression of the deficits were evaluated utilizing the reference soil moisture data. Finally, the sensitivity of the model was evaluated by examining the response of evaporation anomalies to precipitation anomalies and comparing this with the reference evaporation data. The results showed that there was a large spread in output and performance among the LSMs across all parts of the evaluation. The greatest contrasts among the LSMs were found in the dry to wet transition zones within the tropics. In this latitudinal range, the worst performing LSMs overestimated the accumulation of soil moisture deficits and the severity of droughts, while the opposite was found for the extratropical regions. Additionally, the models showed, in general, to be overly sensitive to precipitation anomalies. When ranking the implemented model bases in the LSMs based on their performance during droughts, the findings showed that the Community Land Model (implemented in CMCC-ESM2, E3SM-1-1 and CESM2) was predominantly the best performing, followed by ORCHIDEE (IPSL-CM6A-LR) and HTESSEL (EC-Earth3-Veg). MATSIRO (MIROC6) and JULES (HadGEM3-GC31-LL and UKESM1-0-LL) were the least performing model bases. From a hydrological perspective, the findings of this research could be linked to some known limitations of LSMs. Oversimplified soil and vegetation dynamics could contribute to the LSMs being overly sensitive to precipitation anomalies while the contrasts between the tropical and extratropical regions could be attributed to the representation of the soil moisture-evaporation coupling, which plays a greater role in the tropical study areas. Ultimately, this research could contribute to LS3MIP and the Land Surface Modeling community, as the results highlight the strengths and weaknesses of the LSMs in simulating soil moisture droughts. From there, this research could contribute to improving LSMs, understanding drought mechanisms, and addressing climate change impacts, especially in drought-prone regions.Water Managemen
Global Mapping of Atmospheric Composition from Space: Retrieving Aerosol Height and Tropospheric NO2 from OMI
No full textThe main objective of this thesis is to design a new aerosol layer height retrieval in order to improve the operational NO2 retrieval, both in the troposphere, from space-borne instruments for highly polluted events and under cloud-free conditions. This thesis focuses on the exploitation of the OMI satellite measurements acquired in the visible wavelength range (405-490 nm). In addition, we develop numerical methods and tools (e.g. machine learning) in order to support the operational processing of big data amounts from the forthcoming new-generation satellite instruments for air quality and climate research.Atmospheric Remote Sensin
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