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Attacks on Federated Learning (FL) can severely reduce the quality of the generated models and limit the usefulness of this emerging learning paradigm that enables on-premise decentralized learning. However, existing untargeted attacks are not practical for many scenarios as they assume that i) the attacker knows every update of benign clients, or ii) the attacker has a large dataset to locally train updates imitating benign parties. In this paper, we propose a data-free untargeted attack (DFA) that synthesizes malicious data to craft adversarial models without eavesdropping on the transmission of benign clients at all or requiring a large quantity of task-specific training data. We design two variants of DFA, namely DFA-R and DFA-G, which differ in how they trade off stealthiness and effectiveness. Specifically, DFA-R iteratively optimizes a malicious data layer to minimize the prediction confidence of all outputs of the global model, whereas DFA-G interactively trains a malicious data generator network by steering the output of the global model toward a particular class. Experimental results on Fashion-MNIST, Cifar-10, and SVHN show that DFA, despite requiring fewer assumptions than existing attacks, achieves similar or even higher attack success rate than state-of-the-art untargeted attacks against various state-of-the-art defense mechanisms. Concretely, they can evade all considered defense mechanisms in at least 50% of the cases for CIFAR-10 and often reduce the accuracy by more than a factor of 2. Consequently, we design REFD, a defense specifically crafted to protect against data-free attacks. REFD leverages a reference dataset to detect updates that are biased or have a low confidence. It greatly improves upon existing defenses by filtering out the malicious updates and achieves high global model accuracy., Green 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., Data-Intensive Systems

Catalyzed by the popularity of blockchain technology, there has recently been a renewed interest in the design, implementation and evaluation of decentralized systems. Most of these systems are intended to be deployed at scale and in heterogeneous environments with real users and unpredictable workloads. Nevertheless, most research in this field evaluates such systems in controlled environments that poorly reflect the complex conditions of real-world environments. In this work, we argue that deployment is crucial to understanding decentralized mechanisms in a real-world environment and an enabler to building more robust and sustainable systems. We highlight the merits of deployment by comparing this approach with other experimental setups and show how our lab applied a deployment-first methodology. We then outline how we use Tribler, our peer-to-peer file-sharing application, to deploy and monitor decentralized mechanisms at scale. We illustrate the application of our methodology by describing a deployment trial in experimental tokenomics. Finally, we summarize four lessons learned from multiple deployment trials where we applied our methodology., Green 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., Data-Intensive Systems

In this work we present calibration approaches aimed at mitigating the measurement error in testbenches featuring multiple sensor-nodes and operating over-the-air. Such errors can arise from fluctuations in component responses and mechanical tolerances of the setup. The calibration approaches are detailed for the case of the Antenna Dome measurement setup previously presented by the authors.In the current implementation, the Antenna Dome employs multiple dual linearly-polarized scalar sensing nodes, to enable real-time 2D (theta and phi) radiation pattern acquisition. The variation of the electrical response among the different sensing elements as well as their position, with respect to the nominal one, due to the mechanical tolerances, introduce systematic error in the generated radiation patterns.Over-the-air procedures to linearize the power conversion asymmetry within the dually polarized nodes as well as the linearity response across them are described. Proposed approach provides a reduction of the angular dependent error within ±0.5 dB across the various nodes. Moreover, to minimize the impact of mechanical deviations an over-the-air method is described to transfer the sensor coordinates from the mechanical reference system to the antenna under test one., Green 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., Electronics

This article deals with the control design of a dual-spin projectile concept, characterized by highly nonlinear parameter-dependent and coupled dynamics, and subject to uncertainties and actuator saturations. An open-loop nonlinear model stemming from flight mechanics is first developed. It is subsequently linearized and decomposed into a linear parameter-varying system for the roll channel, and a quasi-linear parameter-varying system for the pitch/yaw channels. The obtained models are then used to design gain-scheduled H∞ baseline autopilots, which do not take the saturations into account. As a major contribution of this paper, the saturation nonlinearities are addressed in a second step through anti-windup augmentation. Three anti-windup schemes are proposed, which are evaluated and compared through time-domain simulations and integral quadratic constraints analysis. Finally, complete guided flight scenarios involving a wind disturbance, perturbed launch conditions, or aerodynamic uncertainties, are analyzed by means of nonlinear Monte Carlo simulations to evaluate the improvements brought by the proposed anti-windup compensators., Green 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., Control & Simulation

This thesis aims to solve the problem of designing the hardware for a wireless charging system to be used for keeping an autonomous robot swarm alive. Previous designs available to us lacked essential safety features and were very specific in their application. Current wireless charging specifications are also not sufficient to cater to the needs of these systems. Using a detailed analysis and clear requirements, this thesis describes the process of developing the hardware for such a system with flexibility and safety in mind., EE3L11, Electrical Engineering

Federated learning (FL) enables collaborative learning between parties, called clients, without sharing the original and potentially sensitive data. To ensure fast convergence in the presence of such heterogeneous clients, it is imperative to timely select clients who can effectively contribute to learning. A realistic but overlooked case of heterogeneous clients are Mavericks, who monopolize the possession of certain data types, e.g., children hospitals possess most of the data on pediatric cardiology. In this paper, we address the importance and tackle the challenges of Mavericks by exploring two types of client selection strategies. First, we show theoretically and through simulations that the common contribution-based approach, Shapley Value, underestimates the contribution of Mavericks and is hence not effective as a measure to select clients. Then, we propose FedEMD, an adaptive strategy with competitive overhead based on the Wasserstein distance, supported by a proven convergence bound. As FedEMD adapts the selection probability such that Mavericks are preferably selected when the model benefits from improvement on rare classes, it consistently ensures the fast convergence in the presence of different types of Mavericks. Compared to existing strategies, including Shapley Value-based ones, FedEMD improves the convergence speed of neural network classifiers with FedAvg aggregation by 26.9% and its performance is consistent across various levels of heterogeneity., Data-Intensive Systems

There is an ongoing trend of urbanisation, and cities are becoming more and more crowded. In 2014, 46\% of the population of the OECD countries lived in urban areas. Whereas the growth of cities was previously mainly an expansion, the growing population is now increasingly leading to densification. Since 2007, more than half of the constructed houses in the Netherlands has been placed within the existing built area. In the most recent period (2016 to 2018), the share even was 56 per cent. There is a controversy between the individual desire to have a car and the contrasting desire to remove cars from the outdoor space in inner cities. Moreover, land-use policies positively contribute to the environment by managing car use and improving accessibility. Identifying success and failure factors regarding the used strategy and implementation provides feedback to evaluate the strategy. The hub can combine different aspects of mobility, help remove cars from the streets, promote car-sharing and electric vehicles and therefore be an important part of the solution. However, the set-up and implementation of a mobility hub is a complex endeavour where many stakeholders are involved, and sound policy is crucial. In the structured search performed to identify success and failure factors of mobility hubs, an important finding was that the literature is heterogeneous. The gaps found between theory and practice concern the financial feasibility, the incentives for alternative transport, good relationships and clear responsibilities of stakeholders and attention for increasing the utilisation rates of transport modes. Concerning the barriers, competing goals of modal shift and EV adoption need attention, and again, stakeholder responsibilities were not completely clear., Transport, Infrastructure and Logistics

We introduce a new variant of Chubanov's method for solving linear homogeneous systems with positive variables. In the Basic Procedure we use a recently introduced cut in combination with Nemirovski's Mirror-Prox method. We show that the cut requires at most (Formula presented.) time, just as Chubanov's cut. In an earlier paper it was shown that the new cuts are at least as sharp as those of Chubanov. Our Modified Main Algorithm is in essence the same as Chubanov's Main Algorithm, except that it uses the new Basic Procedure as a subroutine. The new method has (Formula presented.) time complexity, where (Formula presented.) is a suitably defined condition number. As we show, a simplified version of the new Basic Procedure competes well with the Smooth Perceptron Scheme of Peña and Soheili and, when combined with Rescaling, also with two commercial codes for linear optimization., Optimization

Due to its high efficiency, routing based on greedy embeddings of rooted spanning trees is a promising approach for dynamic, large-scale networks with restricted topologies. Friend-to-friend (F2F) overlays, one key application of embedding-based routing, aim to prevent disclosure of their participants to malicious members by restricting exchange of messages to mutually trusted nodes. Since embeddings assign a unique integer vector to each node that encodes its position in a spanning tree of the overlay, attackers can infer network structure from knowledge about assigned vectors. As this information can be used to identify participants, an evaluation of the scale of leakage is needed. In this work, we analyze in detail which information malicious participants can infer from knowledge about assigned vectors. Also, we show that by monitoring packet trajectories, malicious participants cannot unambiguously infer links between nodes of unidentified participants. Using simulation, we find that the vector assignment procedure has a strong impact on the feasibility of inference. In F2F overlay networks, using vectors of randomly chosen numbers for routing decreases the mean number of discovered individuals by one order of magnitude compared to the popular approach of using child enumeration indexes as vector elements., Green 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., Data-Intensive Systems

One-third of the Dutch dike system consists of peat dikes. Drought causes these dikes to crack and fail more easily. Visual dike inspections are therefore inefficient, especially considering the increasing climate changes of the future. Research has shown that a fiber optic sensor cable (FOS), used in distributed temperature sensing (DTS), can help measure soil thermal responses, but the question remains whether it is also suitable as a replacement for visual inspections of dikes. This study helps to answer this question by coupling a finite element method (FEM) model with measured DTS information collected at Flood Proof Holland (Delft). In addition, (thermal) images are used to calibrate the FEM model. The measurement period was 20 summer days. The measured data consisted of webcam images, thermal images, and temperature time series of a FOS cable. The meteorological data was obtained via a weather station located in Rotterdam. The FEM model, calibrated and validated with the measured data, helped to find the thermal response of the system in situations of which no data was available, for example having various crack dimensions, cable positions or climatic conditions. The more distinguished the material properties of air and soil are (days with high water content and/or high radiation), the better the crack detection via DTS. After correction for the overestimation influence of radiation on the black FOS cable on sunny afternoons, the thermal response of the crack is corresponding to the air temperature more compared to the thermal response of grass. Crack detection via DTS turned out to be possible by x,T- and t,T-plots (diurnal temperature variation) and a regression plot with the daily peak-to-peak amplitude of the air temperature on the one hand and the daily peak-to-peak amplitude of the cable on the other. The advantage of the regression plot is that only one DTS thermal time series is needed to determine if the segment is most likely cracked or not. Further, Civil Engineering | Hydraulic Structures

What long ago started as a small fishing village, seeking refuge from the Romans, slowly evolved into the city of Venice that we know today. With its unique location came unique problems, most of which were related to the interplay between Venice and its lagoon. By severe measures in the past it has continued to withstand the test of time. In the decades to come, Venice, once again, has found itself in a difficult situation. Like has been done in the past, drastic measures are required to deal with the current and upcoming difficulties threatening the survival of Venice. These difficulties range from over-tourism to sea-level rise and the subsiding of the city. Acting like the Magistrato alle Acque acted in the past, extreme visions where laid out as possible solutions to these threats. A workshop week with focus on interdisciplinary design formed the basis for two extreme visions which are laid out in this report. With the aim of answering the main research question: How do flood defense systems influence the spatial aspects of the territory in the context of a high dynamic landscape in the Anthropocene? The plan for the Perfect Lagoon is one of these, which has focuses on tackling all of the current and upcoming problems were the emphasis lies on preserving and perfecting the lagoon using the building with nature philosophy, while also saving the city from drowning. Preservation is done by solving the sediment budget problems. Due to the constantly eroding system, salt marshes and land is slowly disappearing. In this plan, drastic actions will be taken to counteract the constant erosion as well as the effect that sea level rise will have on this unique estuary. Drastic measures like redirecting rivers and re-purposing the MOSE contribute towards this goal. After preservation comes restoration as one of the goals is to restore and increase ecological value, restoration of salt marshes and removal of negative influences like pollution. As a, Multidisciplinary Project, Architecture, Urbanism and Building Sciences

Routing based on greedy network embeddings enables efficient and privacypreserving routing in overlays where connectivity is restricted to mutually trusted nodes. In previous works, we proposed security enhancements to the embedding and routing procedures to protect against denial-of-service attacks by malicious overlay participants. In this work, we propose an improved timeout scheme to reduce the stabilization overhead of secure tree maintenance in response to node failures and malicious behavior. Furthermore, we present an attack-resistant packet replication scheme that leverages alternative paths discovered during routing, Distributed Systems

Lightning, the prevailing solution to Bitcoin's scalability issue, uses onion routing to hide senders and recipients of payments. Yet, the path between the sender and the recipient along which payments are routed is selected such that it is short, cost efficient, and fast. The low degree of randomness in the path selection entails that anonymity sets are small. However, quantifying the anonymity provided by Lightning is challenging due to the existence of multiple implementations that differ with regard to the path selection algorithm and exist in parallel within the network. In this paper, we propose a general method allowing a local internal attacker to determine sender and recipient anonymity sets. Based on an in-depth code review of three Lightning implementations, we analyze how an adversary can predict the sender and the recipient of a multi-hop transaction. Our simulations indicate that only one adversarial node on a payment path uniquely identifies at least one of sender and recipient for around 70% of the transactions observed by the adversary. Moreover, multiple colluding attackers can almost always identify sender and receiver uniquely., Distributed Systems

Microglia, the resident macrophages of the central nervous system, are key players in neuroinflammation and neurodegenerative diseases, such as Alzheimer’s and Parkinson’s. These cells represent promising cellular targets for therapeutic intervention, therefore a detailed cellular biological knowledge of microglia is of paramount importance. Current microglia in vitro cell culture models are limited in their ability to recapitulate in vivo microglia in terms of gene expression and cell morphology. There is growing evidence that mimicking the cellular environment of microglia in the central nervous system will contribute to a more physiologically accurate culture model. Three-dimensional geometries, and physical and biochemical cues similar to the brain’s extracellular matrix, are necessary to create a 3D biomimetic in vitro environment, as microglia cells can sense these environmental cues through mechanosensing. In this thesis, the effect of two-photon polymerized 2.5D and 3D microstructures on microglia morphology and phenotype was studied through quantitative and qualitative cell analysis. Also, an attempt was made to create in vitro ramified microglia that resemble in vivo microglia from a morphological point of view, by con-trolling the effective shear modulus through dimensional optimization of compliant micro-and nanopillars. It was found that culturing microglia especially on nanopillars enabled an increase of the ramified pheno-type and a more complex (i.e. more ramifications) cell morphology as compared to microglia cultured onflat fused silica substrates. Furthermore, we report that microglia cultured on 3D structures exhibit similarphenotypes observed in the 2D and 2.5D cultures, and were more resemblingin vivomicroglia in terms of3D cell morphology., Mechanical Engineering | Micro and Nano Engineering

Due to the much needed energy transition as agreed under the Paris climate agreement, it is expected that large amounts of variable renewable energy supply will be connected to the Dutch Transmission Network. Future social, economic and technological developments will determine both the amount of electrification as the central or decentral nature of the future supply of electricity. By investigating different reports with scenarios for 2030 and 2050, key uncertainties for the Extra High Voltage (EHV) network can be identified. As of now, no open source model of the Dutch EHV network is available for research. In this thesis a synthetic model of the Dutch EHV network is created from only publicly available data in DIgSILENT PowerFactory. The created synthetic model can be used as a tool to investigate future steady-state power flows considering the sensitivities of the topology, component parameters and different operational scenarios. Besides this, a method is created for generation of future scenarios in Python. Using this model and method, simulations were done to gain key insights into the Steady-State security of the future Dutch EHV Transmission Network. For the case study, it is investigated what the effect of future additions of variable renewable energy sources (VRES) and selected locations of 10 GW installed capacity of electrolysers would be on the Dutch EHV transmission network for 2030.

We consider nine elementary problems in optimization. We simply explore the conditions for optimality as known from the duality theory for convex optimization. This yields a quite straightforward solution method for each of these problems. The main contribution of this paper is that we show that even in the harder cases the solution needs only O(n) time., Accepted author manuscript, Discrete Mathematics and Optimization

IntroductionCardiovascular magnetic resonance imaging (CMR) is an imaging modality from which the structure, function, perfusion, and metabolism of the cardiovascular system can be evaluated, which is essential in acquired and congenital cardiovascular disease (CVD). CMR can improve the outcomes of CVD during long term follow-up. 4D Flow MRI is a three-dimensional time-resolved CMR technique that uses phase contrast sequences with three-directional velocity-encoding and allows evaluation of the blood flow. 4D Flow MRI data can be analyzed with particle tracing.Particle tracing is a technique that releases virtual particles in flow data (seeding) and traces the path the particles follow throughout the vasculature by integrating the flow data. The particle traces can subsequently be quantified with flow distribution analyses and visualized with pathlines. Important settings for particle tracing are the integration method, integration timestep and data interpolation method. The aim of this research is to investigate the effect of different particle tracing settings on the accuracy and computation time and provide a recommendation on the use of particle tracing in 4D Flow MRI data and which particle tracing settings to aim for.MethodsA particle tracing algorithm with a graphical user interface was developed for an existing inhouse developed 4D Flow post-processing workspace. Two 4D Flow MRI datasets from previous studies were acquired. One dataset was of a total cavopulmonary connection of a patient with Fontan circulation and the other was an intracardiac dataset of a healthy volunteer. Particle tracing with common settings and variations in integration method, integration timestep and data interpolation method was performed in both datasets and computation time, flow distributions (pulmonic distribution and four-component analysis), and number of particles that left the structure (missing particles fraction) and number of integration errors were quantified. The latter, Mechanical Engineering | BioMechanical Design

Acknowledged by the United Nations as part of their sustainable development goals, reduction of greenhouse gas emissions is paramount in preserving our planet for future generations. Electrication in the industrial sector is considered one of the energy transition pathways that can contribute to meeting the emission reduction targets of the Paris Agreement. An important barrier that needs to be overcome in order to fully adopt its potential is uncertainty and its risk to the implementation of different electrication alternatives. The absence of information that illustrates the effect of uncertainty on the performance of these alternatives decreases the stability of business cases and hinders the decision-making process. To filll a part of this knowledge gap, this research performed a case-study revolving around a mixed integer linear programming (MILP) model of an integrated chemical cluster in the Port of Rotterdam. The effect of the uncertain factors on the KPIs was analyzed using an exploratory modelling and analysis (EMA) approach. In addition, a key opportunity of the MILP model was utilized by changing the objective function to look at individual and collective actor optimization perspectives. This research implicates that EMA can be an effective approach to explore the effect of various uncertain factor on industrial systems undergoing electrication. Furthermore, when the goal is to perform a broad uncertainty analysis that allows for easy implementation of actor optimization perspectives while requiring only limited information about the uncertain factors in the form of sampling bandwidths, the combination of EMA and MILP can be a powerful tool.

Federated Learning is an emerging distributed collaborative learning paradigm adopted by many of today's applications, e.g., keyboard prediction and object recognition. Its core principle is to learn from large amount of users data while preserving data privacy by design as collaborative users only need to share the machine learning models and keep data locally. The main challenge for such systems is to provide incentives to users to contribute high-quality models trained from their local data. In this paper, we aim to answer how well incentives recognize (in)accurate local models from honest and malicious users, and perceive their impacts on the model accuracy of federated learning systems. We first present a thorough survey on two contrasting perspectives: incentive mechanisms to measure the contribution of local models by honest users, and malicious users to deliberately degrade the overall model. We conduct simulation experiments to empirically demonstrate if existing contribution measurement schemes can disclose low-quality models from malicious users. Our results show there exists a clear tradeoff among measurement schemes in terms of the computational efficiency and effectiveness to distill the impact of malicious participants. We conclude this paper by discussing the research directions to design resilient contribution incentives., Distributed Systems

Greedy embeddings on rooted spanning trees are the most promising solution to provide sufficiently scalable routing in dynamic networks with restricted topologies, for instance friend-to-friend overlays such as the Dark Freenet and payment channel networks such as Lightning. Yet, they are not deployed in practice, as electing a root and configuring addresses remains an unsolved problem in adverse environments. Indeed, faulty or malicious nodes might provide incorrect coordinates, prevent the network from stabilizing by simulating dynamics, or not start the assignment of coordinates in their subtree at all. All of the above attacks may result in an inability to route. To mitigate the above attacks, we design a novel embedding algorithm with an adapted distance metric that only relies on interconnections between benign subtrees for successful delivery. In other words, even if roots of (sub-)trees are malicious or faulty, the remaining nodes still receive coordinates and can communicate with nodes in their tree branch as well as other branches reachable via the neighborhood of their benign ancestors. Extensive simulations demonstrate that we thus facilitate efficient routing even when seemingly decisive parts of the network are under adversarial control., Distributed Systems

To reduce the CO2 emissions of the maritime industry, several alternative fuels are being researched to possibly achieve this goal. The absence of an infrastructure for alternative fuels in the current port environment is one of the barriers towards implementation of these high potential fuels. The goal of this thesis project was to create an optimization model which can provide more insight into the initial sizing, phased growth and corresponding cost of an infrastructure needed for maritime transport using different forms of alternative fuels. The corresponding main research question is: "How do the port refueling infrastructures of sodium borohydrate, liquid hydrogen and gaseous hydrogen compare to each other with respect to costs and supply chain set-up in terms of where, when, and at what sizes to build up the production, storage, distribution and refueling facilities?" To answer this research question a single-objective multi-period mathematical optimisation model (Mixed Integer Programming) has been created for the port refueling environment. The most important model innovations are the inclusion of a maritime refueling convention and the possibility to model less conventional alternative fuels such as sodium borohydrate (NaBH4). Furthermore, input for the model has been gathered from several sources. Next, some parameters of the model have been varied to research their effect on the total alternative fuel infrastructure. As a result it has been found that the gaseous hydrogen infrastructure is the cheapest with respect to facility capital costs and facility operating costs, but was the most expensive when looking at transportation of the fuel within the port. The liquefied hydrogen was the cheapest with respect to fuel transportation, but scored average on facility capital cost. Furthermore it is the most expensive infrastructure with respect to facility operating cost. The NaBH4-infrastructure is the most expensive infrastructure when looking at the facilit, Marine Technology

Payment channel networks like Bitcoin’s Lightning network are an auspicious approach for realizing high transaction throughput and almost-instant confirmations in blockchain networks. However, the ability to successfully conduct payments in such networks relies on the willingness of participants to lock collateral in the network. In Lightning, the key financial incentive to lock collateral are low fees for routing payments of other participants. While users can choose these fees, real-world data indicates that they mainly stick to default fees. By providing insights on beneficial choices for fees, we aim to incentivize users to lock more collateral and improve the effectiveness of the network. In this paper, we consider a node that given the network topology and the channel details establishes channels and chooses fees to maximize its financial gain. Our contributions are i) formalization of the optimization problem, ii) proving that the problem is NP-hard, and iii) designing and evaluating a greedy algorithm to approximate the optimal solution. In each step, our greedy algorithm establishes a channel that maximizes the increase to ’s total reward, which corresponds to maximizing the number of shortest paths passing through. Our simulation study leveraged real-world data sets to quantify the impact of our gain optimization and indicates that our strategy is at least a factor two better than other strategies., Coronavirus update: Authors whose travel is disrupted can arrange to give video presentations, Distributed Systems, Cyber Security

Current leader election algorithms fail in the presence of Sybil attacks, i.e., one malicious entity inserting many nodes, network dynamics, and restricted knowledge about the graph. However, social overlay networks, i.e., peer-to-peer networks with links corresponding to social relationships, face all of the above challenges. Social overlay networks naturally offer privacy, as they avoid connections with strangers, and furthermore prevent a Sybil attacker from controlling a large number of links in the graph. As recent ideas for scalable communication in such overlays rely heavily on attack resistant leader election, solving leader election for such overlays opens the door for decentralized, privacy-preserving, and secure communication at a large scale. In this work, we propose a novel leader election algorithm based on three-majority voting that utilizes timestamps and cryptographic signatures to detect leader faults in an attack resistant manner. We evaluate our algorithm with simulations on real-world as well as synthetic network topologies. Our results indicate that in networks whose degree sequence follows a power law, our leader election algorithm quickly achieves consensus for more than $80\%$ of all nodes. Furthermore, attackers are unlikely to become leaders as long as the number of connections they establish with honest nodes is low., Distributed Systems

Observations of barrier coasts around the world suggest that some systems do not conform to the O'Brien-Jarret law. Here we explain this by investigating how resonance and bottom friction affect the response of tidal inlets to variations in basin geometry. Therefore, we develop a morphodynamic barrier coast model that is based on the stability concept of Escoffier for the morphological evolution of the inlets, coupled with an idealized hydrodynamic model that describes the water motion in the outer sea, inlets, and arbitrarily shaped back-barrier basin. We find that the total tidal prism through all inlets is predominantly determined by the (cross-shore) width of the basin and identify three regimes for this. First, a linear regime for narrow basins (i.e., basin width (Formula presented.) tidal wavelength) where a larger basin leads to a linear increase in total tidal prism. Second, a resonant regime for basins with a width around the resonant condition in which the total tidal prism reaches a peak. This resonance condition is a quarter tidal wavelength for basins without friction, which shifts to narrower basins as friction becomes stronger, down to 0.15 tidal wavelength. Third, a dissipative regime for wide basins (i.e., the cross-shore basin dimension or basin width (Formula presented.) resonant condition) with sufficiently strong bottom friction in which the total tidal prism does not change for wider basins, because the tidal wave completely dissipates in the basin., Mathematical Physics

The master thesis is about testing the effectiveness of the Airport demand management strategies. Based on the problem of increasing pressure on airport capacity, due to the increase of the demand on flying. The goal is to find a system which supports planning of air traffic control by generating knowledge about the throughput of arrivals. A Discrete Event Simulation approach is used to simulate the behaviour of arrivals in case of capacity issues. The model uses random generated slot allocated schedules to test the effectiveness of several strategies. Eventually the result of the strategies is presented in an optimum ratio between delays and cancellations of the tested strategies. The main conclusion of the research is that the model is capable of testing the effectiveness of airport demand management strategies. It also provides knowledge on expected bottlenecks of the arrival operations by generating the average delay per hour and queue propagation for each strategy., Aerospace Engineering

Nodes in route-restricted overlays have an im-mutable set of neighbors, explicitly specified by their users. Pop-ular examples include payment networks such as the Lightningnetwork as well as social overlays such as the Dark Freenet.Routing algorithms are central to such overlays as they enablecommunication between nodes that are not directly connected.Recent results show that algorithms based on spanning treesare the most promising provably efficient choice. However, allsuggested solutions fail to address how distributed spanning treealgorithms can deal with active denial of service attacks bymalicious nodes.In this work, we design a novel self-stabilizing spanning treeconstruction algorithm that utilizes cryptographic signatures andprove that it reduces the set of nodes affected by active attacks.Our simulations substantiate this theoretical result withconcretevalues based on real-world data sets. In particular, our resultsindicate that our algorithm reduces the number of affectednodes by up to 74% compared to state-of-the-art attack-resistantspanning tree constructions, Distributed Systems

Purpose – The purpose of this paper is to explore the conceptualisation of the Smart Sustainable City (SSC) with new concepts of resilience thinking in relation to urgent societal challenges facing the built environment. The paper aims to identify novel methodologies for smart reuse of heritage sites with a pluralist past as integral to inclusive urban development. Design/methodology/approach – SSC concepts in the global literature are studied to define a new reference framework for integrated urban planning strategies in which cultural resilience and co-creation matter. This framework, augmented by UNESCO’s holistic recommendation on the Historic Urban Landscape (HUL), was tested in two investigative projects: the historic centre of South Africa’s capital Tshwane and the proximate former Westfort leprosy colony. Findings – The research confirms that SSC concepts need enlargement to become more inclusive in acknowledging “cultural diversity” of communities and engaging “chrono-diversity” of extant fabric. A paradigm shift in the discourse on integrated urban (re)development and adaptive reuse of built heritage is identified, influenced by resilience and sustainability thinking. Both projects show that different architectural intervention strategies are required to modulate built fabric and its emergent qualities and to unlock embedded cultural energy. Originality/value – Together with a critical review of SSC concepts and the HUL in relation to urban (re) development, this paper provides innovative methodologies on creative adaptation of urban heritage, reconciling “hard” and “soft” issues, tested in the highly resilient systems of Tshwane., Green 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., Heritage & Design, Heritage & Values, Heritage & Cultural Value

In this thesis, the implementation of a passive, chipless, frequency coded Radio-Frequency Identification (RFID) tag for bedload transport studies is proposed. The proposed tag will be deployed in the semi-arid Río Colorado river, Bolivia with the aim to develop quantitative sediment transport models that relate transport to grain size. The designed tag is an open-loop resonator with a fragment-loading structure, that has an op- timised configuration based on a Multiobjective Evolutionary Algorithm based on Decomposition combined with Enhanced Genetic Operators (MOEA/D-GO). The designed RFID tag can ideally reach a size of 4 by 4 millimetres with a maximum calculated reading range of 1.3 meters, and operates in the ultra wide band from 3 to 7 gigahertz. Numerous simulations on the tags were run to verify their properties. The tags proved to have a good directivity, quality factor and radio cross section on its resonant frequency. The tags could reach resonance frequencies as low as 2.9 gigahertz and quality factors as high as 130. The proof of concept on a Printed Circuit Board with an FR-4 substrate results in a tag of 6.4 by 3.4 millimetres. Unfortunately, these properties could not yet be verified by measuremen, Electrical Engineering | Electronic Instrumentation

Background: Aortic pulse wave velocity (PWV) is an indicator of aortic stiffness and is used as a predictor of adverse cardiovascular events. PWV can be non-invasively assessed using magnetic resonance imaging (MRI). PWV computation requires two components, the length of the aortic arch and the time taken for the systolic pressure wave to travel through the aortic arch. The aortic length is calculated using a multi-slice 3D scan and the transit time is computed using a 2D velocity encoded MRI (VE) scan. In this study we present and evaluate an automatic method to quantify the aortic pulse wave velocity using a large population-based cohort. Methods: For this study 212 subjects were retrospectively selected from a large multi-center heart-brain connection cohort. For each subject a multi-slice 3D scan of the aorta was acquired in an oblique-sagittal plane and a 2D VE scan acquired in a transverse plane cutting through the proximal ascending and descending aorta. PWV was calculated in three stages: (i) a multi-atlas-based segmentation method was developed to segment the aortic arch from the multi-slice 3D scan and subsequently estimate the length of the proximal aorta, (ii) an algorithm that delineates the proximal ascending and descending aorta from the time-resolved 2D VE scan and subsequently obtains the velocity-time flow curves was also developed, and (iii) automatic methods that can compute the transit time from the velocity-time flow curves were implemented and investigated. Finally the PWV was obtained by combining the aortic length and the transit time. Results: Quantitative evaluation with respect to the length of the aortic arch as well as the computed PWV were performend by comparing the results of the novel automatic method to those obtained manually. The mean absolute difference in aortic length obtained automatically as compared to those obtained manually was 3.3 ± 2.8 mm (p < 0.05), the manual inter-observer variability on a subset of 45 scans wa, Pattern Recognition and Bioinformatics

Vibrations are experienced as unwanted dynamic motions and the industry takes a lot of care to reduce these motions to improve comfort and to increase vehicle component durability. The properties of rubber, being generally soft while showing large inherent damping, makes the material a perfect choice to use in vibration isolators. To minimize vibrations the transfer path from vibrational source to the driver almost always includes a highly damped material like rubber. With the current trend of electrification in the automotive industry, higher order vibrations are becoming more pronounced. Although the produced sound is not of a high octave with respect to traditional combustion engines, they are experienced as unpleasant. Considering a large frequency range, the dynamic characterization of a rubber object is proven to be a difficult topic. In the search of improved rubber characterization new methods arise. The goal of this research is to provide a new approach for extracting material properties from the experimental impact method. Literature research is done on the rubber specific behaviour and how this affects the modelling approach. In the research itself both numerical and experimental characterization is used. Through impact testing the receptance of the rubber object is measured and by applying inverse substructuring the dynamic stiffness is obtained. The Finite Element model is used to directly obtain the dynamic stiffness. The numerical and experimental results are made comparable by applying the virtual point transformation method. With the finite element material model being the optimization variable, the numerical dynamic stiffness is optimized to match the experimental results. The rubber properties are obtained from the optimized material model. The presented inverse approach makes it possible to use the impact method for characterizing rubber material properties. It therefore broadens the abilities of impact testing used for rubber characterization. W

Het thema gedrag op de bedrijfsagenda doelt vaak op ongewenst gedrag. Wat het gewenste gedrag is, is vaak minder concreet. Een leidinggevende wenst dat zijn medewerkers veilig werken. Alleen, wat is veilig in de ogen van die leidinggevende? En is dit ook veilig in de beleving van de werkvloer? Hoe kun je als adviseur een rol spelen in een veranderproces naar gewenst gedrag? En wat is de relatie tussen adviseren en coachen? Met deze vragen gaan we middels een casus weer aan de slag., Safety and Security Science

Safety and Security Science

Safety and Security Science

There is evidence for a beneficial effect of aerobic exercise on cognition, but underlying mechanisms are unclear. In this study, we test the hypothesis that aerobic exercise increases cerebral blood flow (CBF) in patients with vascular cognitive impairment (VCI). This study is a multicenter single-blind randomized controlled trial among 80 patients with VCI. Most important inclusion criteria are a diagnosis of VCI with Mini-Mental State Examination ≥22 and Clinical Dementia Rating ≤0.5. Participants are randomized into an aerobic exercise group or a control group. The aerobic exercise program aims to improve cardiorespiratory fitness and takes 14 weeks, with a frequency of three times a week. Participants are provided with a bicycle ergometer at home. The control group receives two information meetings. Primary outcome measure is change in CBF. We expect this study to provide insight into the potential mechanism by which aerobic exercise improves hemodynamic status., ImPhys/Quantitative Imaging

Background: Hemodynamic balance in the heart-brain axis is increasingly recognized as a crucial factor in maintaining functional and structural integrity of the brain and thereby cognitive functioning. Patients with heart failure (HF), carotid occlusive disease (COD), and vascular cognitive impairment (VCI) present themselves with complaints attributed to specific parts of the heart-brain axis, but hemodynamic changes often go beyond the part of the axis for which they primarily seek medical advice. The Heart-Brain Study hypothesizes that the hemodynamic status of the heart and the brain is an important but underestimated cause of VCI. We investigate this by studying to what extent hemodynamic changes contribute to VCI and what the mechanisms involved are. Here, we provide an overview of the design and protocol. Methods: The Heart-Brain Study is a multicenter cohort study with a follow-up measurement after 2 years among 645 participants (175 VCI, 175 COD, 175 HF, and 120 controls). Enrollment criteria are the following: 1 of the 3 diseases diagnosed according to current guidelines, age ≥50 years, no magnetic resonance contraindications, ability to undergo cognitive testing, and independence in daily life. A core clinical dataset is collected including sociodemographic factors, cardiovascular risk factors, detailed neurologic, cardiac, and medical history, medication, and a physical examination. In addition, we perform standardized neuropsychological testing, cardiac, vascular and brain MRI, and blood sampling. In subsets of participants we assess Alz­heimer biomarkers in cerebrospinal fluid, and assess echocardiography and 24-hour blood pressure monitoring. Follow-up measurements after 2 years include neuropsychological testing, brain MRI, and blood samples for all participants. We use centralized state-of-the-art storage platforms for clinical and imaging data. Imaging data are processed centrally with automated standardized pipelines. Results and Conclusions: T, ImPhys/Quantitative Imaging

We deal with a recently proposed method of Chubanov [A polynomial projection algorithm for linear feasibility problems. Math. Program. 153 (2015), pp. 687–713] for solving linear homogeneous systems with positive variables. Some improvements of Chubanov's method and its analysis are presented. We propose a new and simple cut criterion and show that the cuts defined by the new criterion are at least as sharp as in [1]. The new cut criterion reduces the iteration bound for his Basic Procedure by a factor 5, without changing the order of its strongly polynomial complexity. Our Modified Main Algorithm is in essence the same as Chubanov's Main Algorithm, except that it uses our Modified Basic Procedure as a subroutine. It is shown that it has (Formula presented.) time complexity, just as in [1]. Some promising computational results are presented, in comparison with the optimization package Gurobi., Optimization

Purpose To evaluate viscous energy loss and the association with three-dimensional (3D) vortex ring formation in left ventricular (LV) blood flow during diastolic filling. Theory and Methods Thirty healthy volunteers were compared with 32 patients with corrected atrioventricular septal defect as unnatural mitral valve morphology and inflow are common in these patients. 4DFlow MRI was acquired from which 3D vortex ring formation was identified in LV blood flow at peak early (E)-filling and late (A)-filling and characterized by its presence/absence, orientation, and position from the lateral wall. Viscous energy loss was computed over E-filling, A-filling, and complete diastole using the Navier-Stokes energy equations. Results Compared with healthy volunteers, viscous energy loss was significantly elevated in patients with disturbed vortex ring formation as characterized by a significantly inclined orientation and/or position closer to the lateral wall. Highest viscous energy loss was found in patients without a ring-shaped vortex during E-filling (on average more than double compared with patients with ring-shape vortex, P < 0.003). Altered A-filling vortex ring formation was associated with significant increase in total viscous energy loss over diastole even in the presence of normal E-filling vortex ring. Conclusion Altered vortex ring formation during LV filling is associated with increased viscous energy loss. Magn Reson Med 77:794–805, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes., Pattern Recognition and Bioinformatics

Tijdens een adviesgesprek loopt de adviseur vaak onbewust in de valkuil van de opdrachtgever. Die biedt namelijk zíjn perspectief op het probleem. Op basis van de redenering waarmee het probleem werd gecreëerd. Wanneer de adviseur die overneemt, leidt dit onherroepelijk tot ‘als we steeds doen wat we altijd doen, dan krijgen we wat we altijd krijgen’, ofwel een zichzelf vervullende profetie. Hoe komt dat?, Safety and Security Science

Bij veel ongevallen is het leed achteraf voor medewerkers niet te overzien. Gebrek aan betrokkenheid, eenzijdige kijk op de situatie, onvoldoende passend advies en uiteindelijk geen duurzame oplossingen voor de toekomst. Hoe komt dit? Wat is de relatie tussen adviseren en de situatie rond een ongeval? Hoe herken je dit en wat kun je ermee? Met deze vragen gaan we middels een casus aan de slag., Safety and Security Science

In de tweede toetsronde op de primaire waterkeringen (2006) is ruim 33 kilometer van de Markermeerdijken tussen Amsterdam-Noord en Hoorn afgekeurd (IVW, 2006). Het overgrote deel van de dijken (90%) is afgekeurd op het faalmechanisme binnenwaartse stabiliteit. Daarnaast zijn de dijken op een gering aantal plekken niet hoog genoeg, niet stabiel aan de buitenzijde of voldoet de bekleding niet. Een potentiele oplossing is het verlagen van het Markermeerpeil door pompen. In dit rapport worden daarvoor de volgende vragen beantwoord: 1. In hoeverre kan met pompen op de Houtribdijk de hydraulische belasting (MHW) van het Markermeer significant verlaagd worden (met 30 tot 90 cm). a. Welke pompcapaciteit is nodig? b. Wat is het effect op de MHW? c. Wat zijn de kosten voor de pompen (gehele levenscyclus, inclusief o.a. beheer en onderhoud en energiekosten)? 2. Wat is het effect van een MHW-verlaging op het ontwerp van de Markermeerdijken? a. Kan daarmee een minder ingrijpend ontwerp worden gerealiseerd? b. Wat zijn de financiële baten (primair van de Markermeerdijken tussen Hoorn en Amsterdam, maar wellicht ook elders langs het Markermeer)., Hoogwaterbeschermingsprogramma

In this paper, a three-dimensional semi-idealized model for tidal motion in a tidal estuary of arbitrary shape and bathymetry is presented. This model aims at bridging the gap between idealized and complex models. The vertical profiles of the velocities are obtained analytically in terms of the first-order and the second-order partial derivatives of surface elevation, which itself follows from an elliptic partial differential equation. The surface elevation is computed numerically using the finite element method and its partial derivatives are obtained using various methods. The newly developed semi-idealized model allows for a systematic investigation of the influence of geometry and bathymetry on the tidal motion which was not possible in previously developed idealized models. The new model also retains the flexibility and computational efficiency of previous idealized models, essential for sensitivity analysis. As a first step, the accuracy of the semi-idealized model is investigated. To this end, an extensive comparison is made between the model results of the semi-idealized model and two other idealized models: a width-averaged model and a three-dimensional idealized model. Finally, the semi-idealized model is used to understand the influence of local geometrical effects on the tidal motion in the Ems estuary. The model shows that local convergence and meandering effects can have a significant influence on the tidal motion. Finally, the model is applied to the Ems estuary. The model results agree well with observations and results from a complex numerical model., Delft Institute of Applied Mathematics, Electrical Engineering, Mathematics and Computer Science

De zes hallen in de noordwestelijke hoek van Oostenburg in Amsterdam zijn eigendom van Woningbouwcorporatie Stadgenoot.1 Deze corporatie kocht in 2008 een groot deel van Oostenburg aan om dit gebied zelf te gaan ontwikkelen. De recente regelgeving heeft de mogelijkheden voor de corporaties beperkt. Stadgenoot zal nu het grootste deel van de aangekochte gronden en opstallen doorverkopen aan ontwikkelende partijen. De afdeling Monumenten en Archeologie van de gemeente Amsterdam heeft in juni 2014 voor een deel van de Werkspoorhallen een waardestelling gemaakt (zie bijlage 1). Deze waardestelling betreft de twee oudste hallen van het ensemble: Stelplaats 3 uit 1929 en de nagenoeg identieke uitbreiding uit 1939. Deze waardestelling biedt voldoende argumenten voor de aanwijzing van de twee hallen tot gemeentelijk monument, aldus de Commissie Welstand en Monumenten. Stadgenoot is bij de ontwikkelingen van plannen voor Oostenburg gaandeweg uitgegaan van sloop van de Werkspoorhallen, om ruimte te creëren voor de bouw van woningen en werkruimten. Het aanwijzen van de hallen tot gemeentelijk monument zou aanpassing van deze plannen noodzakelijk maken, hetgeen bovendien voor Stadgenoot forse negatieve gevolgen zou kunnen hebben voor de grondexploitatie van het plangebied. Mede op verzoek van het Stadsdeel Centrum Amsterdam heeft Stadgenoot zich goed beraden op een eventuele aanwijzing van de Werkspoorhallen tot gemeentelijk monument. De corporatie heeft in het najaar 2014 de sectie Heritage & Architecture van de Faculteit Bouwkunde van de Technische Universiteit Delft opdracht gegeven voor het schrijven van een ‘reflectie’ op de waardestelling. De rapport ‘De grote Werkspoorhallen op Oostenburg - Reflectie’ verscheen in januari 2015. De ‘reflectie’ stelt dat het voorstel voor de aanwijzing van de grote Werkspoorhallen tot gemeentelijk monument allereerst de aandacht vestigt op de grote cultuurhistorische waarden van het gehele gebied. Door de aandacht uitsluitend te richten op, Architectural Engineering +Technology, Architecture and The Built Environment

We present an improved version of an infeasible interior-point method for linear optimization published in 2006. In the earlier version each iteration consisted of one so-called feasibility step and a few---at most three---centering steps. In this paper each iteration consists of only a feasibility step, whereas the iteration bound improves the earlier bound by a factor $2\sqrt{2}$. The improvements are due to a new lemma that gives a much tighter upper bound for the proximity after the feasibility step., Software Computer Technology, Electrical Engineering, Mathematics and Computer Science

In this paper, we design a class of infeasible interior-point methods for linear optimization based on large neighborhood. The algorithm is inspired by a full-Newton step infeasible algorithm with a linear convergence rate in problem dimension that was recently proposed by the second author. Unfortunately, despite its good numerical behavior, the theoretical convergence rate of our algorithm is worse up to square root of problem dimension., Delft Institute of Applied Mathematics, Electrical Engineering, Mathematics and Computer Science

The section Heritage & Architecture of the Faculty of Architecture at Delft University of Technology deals with the built environment in terms of conservation, refurbishment and re-use. Reflecting the department philosophy, this book focuses on the durability and sustainability of existing buildings (heritage in a broad sense, from historic buildings to listed monuments), considered in terms of material and building techniques, form and function, and part of the wider context of sites and cities. At the basis stands the Heritage triangle: Design – Cultural value – Technology, Architecture Engineering and Technology, Architecture and The Built Environment

This paper explores an alternative method to determine extreme surge levels at the Dutch Coast. For this exploration, specific focus is on the extreme water level at Hoek van Holland, The Netherlands. The alternative method has been based on a joint probability model of the storm characteristics at the North Sea. The intent of this method is to provide a better physical and statistical insight into the effects of meteorological characteristics on surge levels and surge duration, especially for surges of more extreme storms currently not captured in existing water level measurement records. The meteorological part is an analytical parametrical model based on the Holland model for hurricanes, which results in time- and space-varying wind and pressure fields of North Sea storms. The wind and pressure forcing is then applied in the hydrodynamic model which numerically solves the nonlinear depth-averaged shallow water equations in a one-dimensional domain from the edge of the continental shelf between Scotland and Norway to Hoek van Holland. Validation against wind observations from historical storms at one location in the entire domain shows good results. Results of the calibrated surge level model are reasonable if peak surge levels are considered. The surge duration, however, is underestimated by the model. Next, the model has been applied to define extreme surge levels using Monte Carlo Analysis. Probability density distributions for the storm parameters based on historical data have been used as input. The computed surge level (including tide) with a statistical return period of 10,000 years appears to be close to the value from statistical extrapolation of surge levels. The output also indicates that the average duration of computed surges with a return period of 10,000 year is roughly two hours longer than the storm duration currently adopted., Hydraulic Engineering, Civil Engineering and Geosciences

In this paper, two alternative methods to the Inverse Kinematics problem are compared to traditional methods regarding computation time, accuracy, and convergence rate. The test domain is the arm of the NAO humanoid robot. The results show that FABRIK, a heuristic iterative approximation algorithm outperforms the two traditional methods, which are both based on the Jacobian inverse technique, on all aspects. An artificial neural network vastly outperforms all algorithms regarding computation time, but lacks accuracy. To demonstrate the practical applicability, FABRIK has been used enable a NAO humanoid robot to play tic-tac-toe.

The gait of humans is often assumed to be the most energy efficient way of walking. Srinivasan and Ruina [18] confirm this hypothesis using a simple model in which the human is a point mass with straight legs that can change in length during a step. Their results show that the inverted pendulum walk is the most energy efficient gait. The question is whether this result also holds for humanoid robots. This paper investigate what is the most energy efficient gait for a humanoid robot such as the Nao, and what the corresponding control policy is that needs to be implemented. To answer these questions, first, the model of Srinivasan and Ruina is adapted for humanoid robots, and is used to study the energy consumption of different gaits. The model assumes a gait with dynamic stability and assumes that the torque on the knee joint provides the main contribution to the energy consumption of a gait. The former assumption implies that no energy is needed to remain stable. The latter assumption is confirmed by an experiment with a humanoid robot, namely Nao. Based on experiments with this idealize model, a gait that minimizes the energy consumption is identified. A controller for the new gait is implemented and is evaluated on a Nao robot. In the future, this controller will be the basis of an intelligent controller that can adapt to varying circumstances.

In this paper a novel framework capable of both accurate predictions and classifications of dynamic images is introduced. The proposed technique makes of use of a novel combination of sparse coding, a feature extraction algorithm, and three-way weight tensor conditional restricted Boltzmann machines, a form of deep learning. Experiments performed on both the prediction and classification of various images show the efficiency, accuracy, and effectiveness of the proposed technique.