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GRAIL: Checking Transaction Isolation Violations with Graph Queries
No full textDistributed databases are surging in popularity with the growing need for performance and fault tolerance. However, implementing transaction isolation models on distributed databases is more challenging due to their sharding and replication. As a result, they can produce executions that violate their claimed isolation guarantees. In this work, we propose a novel isolation model-agnostic approach that utilizes graph databases to efficiently detect isolation violations expressed as anti-patterns in transactional dependency graphs. To illustrate our approach, we introduce the GRAIL framework, implemented on top of the popular ArangoDB and Neo4j graph databases. GRAIL combines soundness guarantees and high performance with understandable, detailed counter-examples.Software Engineerin
Regional divergent evolution of vegetation greenness and climatic drivers in the Sahel-Sudan-Guinea region: nonlinearity and explainable machine learning
No full textIntroduction: The vegetation dynamics of the Sahel-Sudan-Guinea region in Africa, one of the largest transition zones between arid and humid zones, is of great significance for understanding regional ecosystem changes. However, a time-unvarying trend based on linear assumption challenges the overall understanding of vegetation greenness evolution and of tracking a complex ecosystem response to climate in the Sahel-Sudan-Guinea region. Methods: This study first applied the ensemble empirical mode decomposition (EEMD) method to detect the time-varying trends in vegetation greenness based on normalized difference vegetation index (NDVI) data in the region during 2001–2020, and then identified the dominant climatic drivers of NDVI trends by employing explainable machine learning framework. Results: The study revealed an overall vegetation greening but a significant nonlinear spatio-temporal evolution characteristic over the region. Trend reversals, i.e., browning-to-greening and greening-to-browning, were dominant in approximately 60% of the study area. The browning-to-greening reversal was primarily observed in the southern Sahel, Congo Basin north of the Equator, and East Africa, with a breakpoint around 2008, while the greening-to-browning reversal was mainly observed in West Africa, with a breakpoint around 2011. The sustained greening primarily took place in northern Sahel, Central African Republic and South Sudan; while sustained browning clustered in central West Africa and Uganda, mainly in agricultural lands. Furthermore, the combination of Random Forest (RF) algorithm and the SHapley Additive exPlanations (SHAP) method could robustly model and reveal the relationships between the observed trends in NDVI and in climatic variables, also detected by applying EEMD. The results suggested that air temperature and precipitation were the most important climatic drivers controlling the NDVI trends across the Sahel-Sudan-Guinea region. The NDVI trends were more likely to have negative correlations with solar radiation and vapor pressure deficit in arid areas, while they could have positive correlations in humid areas. The study also found that large-scale climate changes induced by sea surface temperature (SST) anomalies had strong relationships with trend reversals in vegetation greenness at a sub-continental scale. These findings advanced the understanding of the impacts of climatic drivers on vegetation greenness evolution in the Sahel-Sudan-Guinea region.Optical and Laser Remote Sensin
Design Roadmapping: Guidebook for Future Foresight Techniques
No full textDESIGN ROADMAPPING is for anyone interested in design, strategy and innovations and its wonderful combination that can be found in a design roadmap - For those who dare to create a future vision, frame the time pacing and map the pathways towards it.This guidebook teaches how to create a roadmap. It outlines the origins, design theories and research findings. Strategic designers, innovation managers and professors share their roadmapping experiences, views and achievements, including those from companies such as Canon, Peerby, Ferrari, Philips, Victoria State Library. By design roadmapping you devise creative responses to future strategic challenges. Guided by future foresight techniques, to uncover new trends, scout for new technologies and map the values and ideas on the roadmap. Through strong visualization, a design roadmap supports anorganizational mindset on value innovations.TU Delft OPEN TextbookDesIgning Value in Ecosystem
Random hyperbolic graphs in d+1 dimensions
No full textWe consider random hyperbolic graphs in hyperbolic spaces of any dimension d+1≥2. We present a rescaling of model parameters that casts the random hyperbolic graph model of any dimension to a unified mathematical framework, leaving the degree distribution invariant with respect to the dimension. Unlike the degree distribution, clustering does depend on the dimension, decreasing to 0 at d→∞. We analyze all of the other limiting regimes of the model, and we release a software package that generates random hyperbolic graphs and their limits in hyperbolic spaces of any dimension.Network Architectures and Service
Designing the future role of human operators in an autonomous bus system: A case study on Autonomous Airside Operations in Schiphol Airport
No full textThis thesis aims to design the future roles of human operators in an autonomous bus system in Autonomous Airside Operations at Schiphol Airport. The research was conducted in collaboration with Delft University of Technology and Royal Schiphol Group, focusing specifically on the implementation of autonomous buses for passenger transportation between terminals and aircraft.The study employs a human-centered design approach since the successful integration of technology relies not only on its technical capabilities but also on human operators, who will work in and interact with an autonomous bus system. By placing humans at the center of the design process, a valuable future human operator role is created, that contributes to the successful implementation of an autonomous bus system in AAO.To emphathize with the current bus operations, context studies at Schiphol Airport are conducted with 3 key roles in the current bus operation. Additionally, 11 expert interviews were conducted to gather different perspectives on the future human operator role in AAO. The context research revealed 4 current operator responsibilities besides driving-related tasks. Additionally, based on the expert interviews, 5 future human operator responsibilities in an Autonomous Airside Operations are identified. Combinations between current and future responsibilities resulted in the design of 4 potential future scenarios, each with a different future human operator role. The study provides 4 human operator roles in potential future scenarios where human operators remain crucial in an autonomous bus system, which is: (1) the role of the safety driver to enable autonomous driving as an addition to manual operations; (2) the role of host/hostess or fleet coordinator to provide onboard assistance; (3) the role of the (de)boarding assistant to ensure a safe boarding and deboarding procedure; and (4) the role of the rescuer to immediately operate in case of an emergency. These scenarios are further developed into animation videos, which serve as speculative design artifacts to envision, reflect, and discuss potential future scenarios. Strategic Product Desig
Opto-electrical modelling and roadmap for 2T monolithic Perovskite/CIGS tandem solar cells
No full textTwo terminal (2T) perovskite/copper-indium-gallium-selenide (CIGS) tandem solar cells combine high conversion efficiency with lightweight flexible substrates which can decrease manufacturing and installation costs. In order to improve the power conversion efficiency of these tandem solar cells, the use of advanced simulation tools is crucial to estimate the loss mechanisms. In this regard, most of the available simulation works on tandem solar cells are oriented to minimize optical losses and assuming simplifications for the electrical simulations in particular in the top and bottom cell interconnection at the so-called tunnel recombination junction (TRJ) neglecting the inner physics of the complete tandem device. Therefore, the effect of charge exchange mechanism between top and bottom soler cells on the external parameters of a tandem devices is not fully understood yet. In this work, we present an experimentally validated opto-electrical model based on the fundamental semiconductor equations for the study of loss mechanisms of a reference perovskite/CIGS solar cell. Different from other numerical works, because our simulation platform includes the fundamental working mechanisms of the layers comprising the TRJ, we can properly calculate the losses related to it. We firstly present the calibration and validation of our opto-electrical model with respect to three fabricated reference solar cells: top cell only, bottom cell only and tandem device. Then, we use the calibrated model to evaluate main loss mechanisms affecting the baseline tandem device. Finally, we use the model to propose a roadmap for the optimization of monolithic perovskite/CIGS tandem solar cells.Photovoltaic Materials and DevicesEthics & Philosophy of Technolog
Investigating the Role of Executive Intrafirm Alumni Networks in Top Management Fraud: Multilevel Study in China's Construction Industry
No full textTo explore factors that influence the likelihood of committing fraud in the construction industry, this study concentrated on senior executives and tested whether some characteristics at the individual and firm levels have impacts on the likelihood of fraud committed by top management. Based on social network theory, this study first proposes that intrafirm alumni networks may increase the probability of senior executives engaging in corrupt behavior. Then the study explored whether the effect of executives' alumni networks on their wrongdoings is influenced by external and internal corporate governance measures. To verify the hypotheses, this study collected data on 2,017 senior executives from 118 construction companies in China from 2013 to 2021. Because of the multilevel structure of the data, hierarchical linear modeling was used. The results show that alumni networks have a significant positive effect on top management fraud. The effect is weakened by external auditing, altered by board independence, and strengthened by the size of the board of directors and the size of the supervisory board. This multilevel research contributes to advancing the understanding of managers' fraudulent behavior within an organization and extends the literature on social networks and corporate governance in the construction industry.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.Design & Construction Managemen
Shaping spaces, shifting perspectives: Luzia Hartsuyker's focus on gender inclusive designs
No full textLuzia Hartsuyker-Curjel emerges as a significant figure in Dutch architectural history, reshaping urban living discourse in the post-war era. This study explores her focus on gender-inclusive design, intersecting with transformative societal shifts and architectural innovations. Through case studies and socio-cultural analysis, it investigates the prevailing context during Hartsuyker-Curjel’s emphasis on gender-inclusive designs in the 1980s. Grounded in historical frameworks and supported by literature, the research reveals the dynamic interplay between societal perceptions of gender roles and architectural works. Hartsuyker-Curjel’s projects, the Geindriedorp and Borssenburgplein developments, exemplify her commitment to inclusivity and innovation. The ‘Burgerziekenhuis voor Vrouwen’ project stands as a testament to community-driven initiatives promoting gender equality. This thesis raises questions about the appearance of underrepresentation of the BVV project in professional discourse, urging further investigation into systemic biases within the architectural profession. Overall, Hartsuyker-Curjel’s work invites reflection on architecture’s broader role in shaping societal values and fostering diversity, serving as a catalyst for creating more humane and sustainable built environments.AR2A011Architectural History ThesisArchitecture, Urbanism and Building Science
Experimental Study of Flat Plate Drag Reduction by Air Lubrication
No full textDrag reduction in ships is a key approach to decreasing their energy consumption. Besides saving fuel costs, it also decreases greenhouse gas emissions. One of the most promising techniques for drag reduction in ships is air lubrication, which reduces drag due to friction. Despite its great potential, application of air lubrication in the maritime industry is limited, owing to a lack of understanding of its underlying physical phenomena and stability issues.The present work aims to experimentally study drag reduction on a flat plate resulting from air lubrication at a representative free-stream velocity of 2.5 m/s over a set of increasing air injection rates covering all the three air layer regimes (BDR, TALDR, ALDR) and assess its dependence on air morphology in terms of the plate’s non-wetted area. The experiments were conducted at the Multi-Phase Flow Tunnel located at the Ship Hydromechanics group of TU Delft.To achieve this, first, a custom force balance comprising a spring system was designed to facilitate the measurement of the total drag acting on the plate by means of a load cell. Drag measurements in single-phase flow were conducted on a conventional flat plate to obtain a reference dataset and validate the drag measurement system. An uncertainty analysis was performed to quantify the measurement accuracy. Then, single-phase and dual-phase experiments were conducted on another plate of similar dimensions fitted with additional parts necessary for the generation of air lubrication. For the quantification of the plate’s non-wetted area in dual phase flow, these experiments were accompanied by image capture with cameras positioned vertically below the plate. The recorded images were processed using a binary approach to distinguish regions under the plate covered with water and air. Finally, the non-wetted area ratio of the plate was computed based on these processed images. Uncertainty in both drag reduction and the non-wetted area ratio was also determined beforeanalysing the results.Results from the present work indicate a positive linear correlation between drag reduction and the associated non-wetted area ratio achieved in BDR and ALDR. However, this correlation varies in slope per air layer regime, possibly due to the physical phenomena governing the regime. Thus, further investigation into the underlying physical phenomena governing each regime could shed light on the reason(s) for different slopes in thecorrelation. To improve the current work, estimation of the non-wetted area ratio in the TALDR regime may be carried out to increase the resolution of the correlation found. Moreover, the non-wetted area resulting from the thickness of the air layer may also be studied to define the non-wetted area ratio of the plate more accurately.Marine Technology | Ship Hydromechanic
Application of Axiomatic Design in Engineering: Designing a Smart Medical Cast: Increasing Robustness by Decreasing Information
No full textBy applying Axiomatic Design, a Smart Medical Cast was developed to provide patients, who are suffering from forearm fractures, with a personalized healing process. The device monitors the overall healing status and three complications, which are: Muscle Atrophy, Compartment Syndrome, and Deep Vein Thrombosis. In the conceptual phase, desk research has been performed to find biomarkers that correlate with the monitored processes. Per biomarker, a measuring principle has been designed and these combined formed the design of the smart medical cast. Following the design phase, two tests were performed on healthy individuals to measure the robustness in a real application. The first test focused on correctly measuring the biomarkers and further specifying the sensor specifications. For the second test, a new prototype was used to determine correlations between the measured data and the monitored process and the impact of application during the casting process. The test results show that the measuring system can measure the biomarkers within the expected range, except for bone density. No significant impact on the casting process was measured. The Smart Medical Cast has only been evaluated in situations without a fracture, the next step will be to test the measurables in an environment with a fracture.Medical Instruments & Bio-Inspired Technolog
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