132571 research outputs found
Sort by
A new approach for fast field calculation in electrostatic electron lens design and optimization
No full textIn electron optics, calculation of the electric field plays a major role in all computations and simulations. Accurate field calculation methods such as the finite element method (FEM), boundary element method and finite difference method, have been used for years. However, such methods are computationally very expensive and make the computer simulation challenging or even infeasible when trying to apply automated design of electrostatic lens systems with many free parameters. Hence, for years, electron optics scientists have been searching for a fast and accurate method of field calculation to tackle the aforementioned problem in the design and optimization of electrostatic electron lens systems. This paper presents a novel method for fast electric field calculation in electrostatic electron lens systems with reasonably high accuracy to enable the electron-optical designers to design and optimize an electrostatic lens system with many free parameters in a reasonably short time. The essence of the method is to express the off-axis potential in an axially symmetrical coordinate system in terms of derivatives of the axial potential up to the fourth order, and equate this to the potential of the electrode at that axial position. Doing this for a limited number of axial positions, we get a set of equations that can be solved to obtain the axial potential, necessary for calculating the lens properties. We name this method the fourth-order electrode method because we take the axial derivatives up to the fourth order. To solve the equations, a quintic spline approximation of the axial potential is calculated by solving three sets of linear equations simultaneously. The sets of equations are extracted from the Laplace equation and the fundamental equations that describe a quintic spline. The accuracy and speed of this method is compared with other field calculation methods, such as the FEM and second order electrode method (SOEM). The new field calculation method is implemented in design/optimization of electrostatic lens systems by using a genetic algorithm based optimization program for electrostatic lens systems developed by the authors. The effectiveness of this new field calculation method in optimizing optical parameters of electrostatic lens systems is compared with FEM and SOEM and the results are presented. It should be noted that the formulation is derived for general axis symmetrical electrostatic electron lens systems, however the examples shown in this paper are with cylindrical electrodes due to the simplicity of the implementation in the software.ImPhys/Hagen groupHigh Voltage Technology GroupImPhys/Hoogenboom grou
Recovery of microbial biomass and purification performance after scraping of full-scale slow sand filters
No full textSlow sand filters (SSFs) are widely used in drinking water production to improve microbial safety and biological stability of water. Full-scale SSFs are maintained by scraping the biomass-rich top layers of sand. The period of downtime required for filter recovery after scraping is a major challenge due to limited knowledge of the re-stabilisation of purification processes. This study examined the recovery of microbial biomass, and removal of dissolved organic carbon (DOC) and ammonium (NH4+) in water phase and/or on sand along the depth of a scraped full-scale SSF. Scraping reduced microbial biomass on sand in the top layers, while the main prokaryotic taxa remained unaltered. Cellular ATP (cATP) and intact cell counts (ICC) in water sampled from the top layers increased, indicating a temporary disruption in functionality for 37 days. However, stable concentrations of cATP and ICC and similar microbial community composition in the effluent after scraping revealed that deeper layer biofilms offset any scraping effect. Consistent DOC and NH4+ removal after scraping showed that deeper layers effectively performed the role of the top layer. These findings highlight the resilience and robustness of microbial communities in mature full-scale SSFs and their contribution to water treatment efficiency after disturbances caused by scraping.Sanitary Engineerin
Exploring the Possibilities for Collaboration among Dutch mobile Network Operators for C-ITS ready 5G Networks
No full textDutch road transportation networks are increasingly facing challenges regarding congestion, safety and environmental pollution. These challenges are intensified by increased urbanization and a growing need for connectivity . In the past, the remedy to most of these challenges laid in expanding the physical infrastructure through new asphalt. Nowadays, information and communication technologies increasingly play a role in infrastructure management by utilizing the available infrastructure more efficiently. With that, Cooperative Intelligent Transport Systems (C-ITS), presents a new beacon of hope. Through C-ITS, vehicles and infrastructure components are connected to realize a safe and efficient flow of traffic. However, the realization and implementation of C-ITS is hindered by legal, technological, economic and organizational challenges that need resolving. One of the main challenges is the absence of a sufficing robust network infrastructure that facilitates the data transmission across devices and road users. Mobile Network Operators (MNOs), are believed to occupy a central role in the future, designing, building and operating these network infrastructures. However, MNOs are already facing challenges in making current 5G network business models profitable. New large investments already loom for MNOs to serve C-ITS, however, without profitable business models, further investments can be pushed to the future which can cause further delay of the deployment of C-ITS. Therefore this thesis aimed to identify conditions and potential forms of collaboration among Dutch MNOs for C-ITS ready networks. A literature review identified potential collaborative forms between private competing companies and provided an initial overview of conditions that can stimulate collaboration. Subsequent interview with stakeholders from the Dutch mobile network operator domain further refined these conditions and identified potential forms of collaboration that potentially can deliver viable collaborative efforts: knowledge sharing, joint R&D and passive network sharing. The research indicated that the creation of a shared vision across both the public and private domain is crucial to get an institutional environment that supports collaboration. On top of that, a sense of ‘needing each other’ needs to emerge between MNO’s in the form of individually unattainable profits. Although, regulation can also act as a pushing mechanism towards collaboration, it can’t force the creation of such networks. The realization of profitable business models is thus crucial for MNOs to build the networks. Further problems in collaboration come from severe distrust among MNOs who also have collaborative experiences which resulted in conflicts and opportunistic behavior. A public body can act as an independent ‘referee’ to mitigate these potential conflicts in future collaborative efforts. With that, a lot of challenges still need to be overcome to realize collaboration between MNOs which makes that collaborative efforts are unlikely to succeed in the near future.Complex Systems Engineering and Management (CoSEM
Response of Late-Eocene warmth to incipient glaciation on Antarctica
No full textThe Eocene-Oligocene Transition is marked by a sudden δ18O excursion occurring in two distinct phases: a precursor event at 34.15±0.04 Ma and the Earliest Oligocene oxygen Isotope Step at 33.65±0.04 Ma. These events signal a shift from the warm Late-Eocene greenhouse climate to cooler conditions, with temperature decreases of 3-5 °C, and the emergence of the first continent-wide Antarctic Ice Sheet (AIS). Despite clear evidence from proxy data, general circulation models (GCMs) struggle to replicate this Antarctic transition accurately, failing to capture the shift from warm, ice-free to cold, glaciated conditions. Even with unrealistically low pCO2 levels, Late-Eocene Antarctic summers in GCMs remain too warm and moist for snow or ice to survive. This study evaluates CESM1.0.5 simulations conducted by Baatsen et al. (2020), using a 38 Ma geo- and topographical reconstruction, considering different radiative (4 pre-industrial carbon levels (PIC) and 2 PIC) and orbital (present-day insolation and low Antarctic summer insolation) forcings. The climate is found to be highly seasonal, characterised by hot and wet summers and cold and dry winters. While reduced radiative and summer insolation forcing weaken this seasonality, the persistent atmospheric circulation still impedes ice sheet growth by limiting summer snow survival. For that reason, a new simulation is conducted with regional, moderately-sized ice sheets imposed on the continent, in order to investigate their stability and their influence on the atmospheric circulation. These ice sheets demonstrate self-sustaining and even expansion potential under 2 PIC and low summer insolation conditions. However, correlating resulting temperature and precipitation patterns with proxy data proves challenging, given the absence of terrestrial proxies. Extended simulations with coupled GCM-ISM models are therefore recommended, allowing for more dynamic atmosphere-ice-ocean-vegetation feedback mechanisms and dynamic radiative and orbital forcing.Environmental Fluid Mechanic
A Graph-Neural-Network Approach for Reconstructing Temporal Networks
No full textReconstructing a minimum reticulation network from phylogenetic trees is used in evolutionary studies. In this thesis, we focus on finding temporal networks using cherry-picking sequences for binary trees with all taxa. Finding such a minimum reticulation temporal network is NP-hard.We introduce an algorithm to find a minimum reticulation network with a running time of O(2^n poly(n,t)). In addition, this study explores potential enhancements to the algorithm through the utilisation of branch and bound.Additionally, we introduce a similar algorithm to determine the existence of a temporal phylogenetic network. This algorithm is improved upon by integrating a new concept called cherry growing. This leads to a notable speed-up in performance.Furthermore, we examine the application of Graph Neural Networks (GNN) in heuristics to find a cherry-picking sequence which can be used to construct a network. This is done by classifying leaves into good, which leads to optimal solutions, and bad leaves. To assess this, two types of data were employed: one simulating evolutionary models and the other employing a fully random approach. The best-performing GNN model has a 97.4% accuracy for evolution-based data and a 79.1% accuracy for random-based data.The GNN models are implemented as predictors in two classes of heuristics. The first generates a cherry-picking sequence by repeatedly picking leaves. The second class of heuristics is based on a tree search heuristic. This tree-search-based heuristic outperforms the cherry-picking-based heuristic. Furthermore, the GNN heuristics outperform their random variant, even for problems substantially larger than the GNN was trained on.We also examine the use of GNN in predicting the existence of a phylogenetic temporal network given a set of trees. The best-performing GNN found for this problem has an accuracy of 80.3%.https://github.com/fonemillion/MEP CodeApplied Mathematic
Research on Urban Heritage Values based on the UNESCO Historic Urban Landscape (HUL) Approach: The case study of Suzhou
No full textAs far as a historic city is concerned, a city is a dynamic complex which consists of many different interrelated and interactive elements. It is unreasonable to assess urban heritage by using a single value category. The evaluation of urban heritage values needs to develop a theoretical framework to represent the relationships between different elements. In view of the above issues, there is so far still a lack of systematic study on urban heritage values in Chinese academic circles. Therefore, it is necessary to construct the value system of urban heritage by adopting a scientific method.This study aims to build up an integrated value system to facilitate the identification of urban heritage values, so that the complexity of urban heritage values is revealed through connections of different elements. The research work includes theoretical construction and a case study. First, the HUL is interpreted as a method of spatialtemporal scale by discussing the philosophical framework of HUL. Based on this finding, the gap between HUL at the operational level and the heritage value theories is filled. Second, as a case study, the analysis of the ancient city Suzhou is a verification of the value system of urban heritage in the practical sense. It also proves that the constructed value system is reasonable and achievable for urban conservation in the Chinese context.History, Form & Aesthetic
Cultural Intelligence as a Skill Taught in an Entrepreneurial Education setting: Proposal for improvements of a cultural intelligence learning programme as part of the Minor in International Entrepreneurship and Development at TU Delft
No full textThis thesis examines the integration of Cultural Intelligence (CQ) in entrepreneurial education, specifically in the Minor in International Entrepreneurship and Development program at TU Delft. It identifies a significant gap in the current curriculum regarding CQ training, crucial for navigating the culturally diverse landscape of global business. Through an analysis of existing frameworks, interviews with students and professionals, and curriculum evaluation, the thesis highlights the shortcomings in preparing students for international entrepreneurship. It proposes curriculum enhancements focusing on experiential learning and reflection to foster cultural understanding and adaptability. These recommendations aim to equip students with the necessary skills to succeed in a multicultural entrepreneurial environment, making the program more comprehensive and globally relevant.Management of Technology (MoT
Activating business models for condominium renovations: Identification of viable business models for Integrated Home Renovation Services for condominiums in the Netherlands and Flanders D2.2
No full textThe need for energy efficient buildings has become increasingly important in climate change mitigation. Almost 75% of the building stock in Europe is energy inefficient. Residential buildings are responsible for 27% of the total energy consumption in Europe. Integrated home renovation services (IHRS) have emerged as a potential solution to accelerate highly energy-efficient renovations for homeowners’ associations (HOAs). The question arises: How can the business models of current IHRS accelerate highly energy-efficient renovations by HOAs? This report explores the current state of IHRS in Europe with a focus on the viewpoint of the Netherlands and Flanders. The methods used are desk research, questionnaires and interviews. Five business models (BMs) of CondoReno project partners were analyzed, to support their development strategies within the regional context. This report compares IHRS BMs and brings knowledge about the operation of IHRS. The results show that the BMs of the project partners share some similarities and differ in other aspects. Regarding the similarities, all five providers share the value of offering customized energy renovation packages, also in terms of customer segments, by addressing the specific needs of HOAs. They slightly differ regarding the channels used, customer relationships, key resources, key activities and key partners. They differ in revenue/value streams and cost structure, owing to context-specific aspects of the type of organization. As such, this study informs stakeholders about the development of effective and targeted IHRS initiatives in the EU.Real Estate Managemen
Are civilizations destined to collapse?: Lessons from the Mediterranean Bronze Age
No full textAs the world faces multiple crises, lessons from humanity's past can potentially suggest ways to decrease disruptions and increase societal resilience. From 1200 to 1100 BCE, several advanced societies in the Eastern Mediterranean suffered dramatic collapse. Though the causes of the Late Bronze Age Collapse are still debated, contributing factors may include a “perfect storm” of multiple stressors: social and economic upheaval, earthquake clusters, climate change, and others. We examined how collapse might have propagated through the societies’ connections by modeling the Eastern Mediterranean Late Bronze Age trade and socio-political networks. Our model shows that the Late Bronze Age societies made a robust network, where any single node's collapse was insufficient to catalyze the regional collapse that historically transpired. However, modeled scenarios indicate that some paired node disruptions could cause cascading failure within the network. Subsequently, a holistic understanding of the region's network incentive structures and feedback loops can help societies anticipate compounding risk conditions that might lead to widespread collapse and allow them to take appropriate actions to mitigate or adapt societal dependencies. Such network analyses may be able to provide insight as to how we can prevent a collapse of socio-political, economic and trade networks similar to what occurred at the end of the Late Bronze Age. Though such data-intensive analytics were unavailable to these Bronze Age regions, modern society may be able to leverage historical lessons in order to foster improved robustness and resilience to compounding threats. Our work shows that civilization collapses are preventable; we are not necessarily destined to collapse.Network Architectures and Service
The Hotel—Single Women's Segment: Her Hotel
No full textHer Hotel is a Single Women’s hotel segment that supports women to live freely and confidently. It is part of The Hotel, a collective project that studies the hotel, both as a building type and as a place of hospitality, through a collection of fourteen individual contributions inside one skyscraper. The project imagines hospitality as a realm of exchange that condenses the diversity of the city through an assortment of guests, staff, and the broader public. The hotel is a function of temporality and hospitality. The study questions the requirements for an architecture of hospitality to welcome, host, and entertain. As an architecture of temporality—an architecture that is dynamic and ever-changing, embodying a sense of transience and constant activity—the hotel allows for experimentation, while anticipating adaptation to meet the changing demands of its temporary residents. The hotel, as type, is understood beyond its curated front. It is, instead, a place of anonymity and exchange, of served and serving, a place characterized by short stays in a lasting structure.The skyscraper, as a formal and monumental object, appears to contrast the hotel’s temporality. In its autonomy, the skyscraper is a landmark in the skyline. Located in Midtown Manhattan—on the former site of Hotel Pennsylvania and adjacent to Penn Station—this project is a reflection on the metropolis of New York City. The Hotel consists of the design of the skyscraper as landmark—The Metropolitan—and the hotel as tenant—One Hotel. Collective propositions:1. The Hotel embraces the frenetic energy of New York City while opposing its outward expansion. 2. The Metropolitan will outlast One Hotel.3. One Hotel accommodates fourteen types of guests, and its staff.4. One Hotel shares accommodation, amenities, systems, and services with a 24/7 cycle.5. The Hotel sets a standard for an architecture of hospitality.Single Women’s segment Segment Propositions:1. The Single Women’s segment supports women as they face safety concerns, difficulty navigating New York City, and an increasing cost of living.2. Elevated high in the skyscraper, the segment’s private floors are connected to the vertical city of the skyscraper through program and public spaces designed for women.3. The Single Women’s segment caters to solo travelers and career-focused women through a kind of new domesticity, accommodations for a variety of budgets, and protection within a secure boundary.4. The Single Women’s segment advocates for women across One Hotel, through safety measures, caregiving spaces, and hotel programming that empowers.5. The Single Women’s segment is a place for social exchange among women.http://thehotel.theberlage.nlThe Berlage Post-MSc in Architecture and Urban Desig