132571 research outputs found
Sort by
Empowering Meru Farmers: Design and development of a context-adapted manual groundnut thresher for smallholder farmers in the Meru Region, Kenya
No full textIn a collaborative effort spanning between the Netherlands and Kenya, this project aimed to enhance the livelihoods of smallholder farmers in the Meru region by designing a manual groundnut thresher. Recognising the importance of cultural context, I embarked on a journey guided by a cultural anthropological research approach, placing a strong emphasis on co-creation and iterative prototyping to ensure the tool’s effectiveness and usability. Through research, several challenges faced by smallholder farmers in Meru were uncovered. Handpicking groundnuts is labour-intensive and time-consuming, limiting productivity and income generation. Additionally, there is a lack of tools available to aid in the harvest of groundnuts, and the options found in other regions, such as Asia, were prohibitively expensive or unsafe. This project fostered a collaborative environment where stakeholders from diverse backgrounds actively participated in the design process. Farmers, engineers, and students from a local technical institute worked together to co-create solutions tailored to the specific needs and preferences of the community. This inclusive approach ensured that the final product addressed the real challenges faced by farmers on the ground. Prototyping played a prominent role in refining the design concepts and iterating towards the final prototype. We experimented with various mechanisms and configurations to optimise the thresher’s performance and usability. Continuous feedback loops enabled us to make iterative improvements, ensuring that the final product met the standards of quality and functionality. After multiple iterations and rigorous testing, we developed a working final prototype: the Manual Groundnut Harvester. This innovative tool streamlines the harvesting process, reducing the time and labour required to thresh groundnuts. Its design allows for easy operation by farmers of all skill levels, empowering them to increase their productivity and income. Additionally, the thresher’s cultural sensitivity ensures seamless integration into the local farming practices, further enhancing its adoption and impact. Looking ahead, the project holds promising prospects for the future. The Manual Groundnut Harvester and its redesign have the potential to significantly improve groundnut farming in Meru, offering a sustainable solution to enhance productivity and livelihoods. Moreover, the collaborative approach serves as a model for future design projects, emphasising the importance of co-creation and cultural sensitivity in addressing complex socio-economic challenges. In conclusion, this journey to design and develop the Manual Groundnut Harvester exemplifies the power of inclusive design and collaborative innovation. By leveraging local knowledge, expertise, and resources, we have created a solution that not only improves agricultural practices but also fosters economic empowerment and community resilience in the Meru region.Integrated Product Desig
Instability in strongly stratified plane Couette flow with application to supercritical fluids
No full textThis paper addresses the stability of plane Couette flow in the presence of strong density and viscosity stratifications. It demonstrates the existence of a generalised inflection point that satisfies the generalised Fjørtoft criterion of instability when a minimum of kinematic viscosity is present in the base flow. The characteristic scales associated with this minimum are identified as the primary controlling parameters of the associated instability, regardless of the type of stratification. To support this finding, analytical stability models are derived in the long-wave approximation using piecewise linear base flows. Numerical stability calculations are carried out to validate these models and to provide further information on the production of disturbance vorticity. All instabilities are interpreted as arising from the interaction between two vorticity waves. Depending on the type of stratification, these two waves are produced by different physical mechanisms. When both strong density and viscosity stratifications are present, we show that they result from the concurrent action of shear and inertial baroclinic effects. The stability models developed for simple fluid models ultimately shed light on a recently observed unstable mode in supercritical fluids (Ren et al., J. Fluid Mech., vol. 871, 2019, pp. 831–864), providing a quantitative prediction of the stability diagram and identifying the dominant mechanisms at play. Furthermore, our study suggests that the minimum of kinematic viscosity reached at the Widom line in these fluids is the leading cause of their instability. The existence of similar instabilities in different fluids and flows (e.g. miscible fluids) is finally discussed.Energy Technolog
Multi-scale study of rejuvenation mechanism and evaluation method for aged bitumen recycling
No full textThe increasing popularity of sustainable asphalt pavement stems from its advantageous attributes, such as cost-saving, environmental protection, and reductions in energy and material consumption. Although there is a desire to maximize the reuse of reclaimed asphalt (RA) waste materials in road construction, this is hindered by the poor performance of aged bitumen. In response, rejuvenation technology has been developed to restore the cohesive and adhesive properties of aged binders. To effectively select appropriate rejuvenators for aged bitumen derived from diverse RA sources and showing varying chemo-mechanical properties, it is crucial to establish an evaluation method that can assess and differentiate the rejuvenation efficiency of different rejuvenator-aged bitumen blends. Furthermore, it is essential to gain a fundamental understanding of the underlying mechanisms responsible for the variations.This dissertation aims to develop a comprehensive and multi-scale approach for assessing the rejuvenation efficiency and mechanisms of various rejuvenator-aged bitumen blends. The combination of molecular dynamics (MD) simulations prediction and experimental validation is throughout the whole thesis to evaluate the compatibility potential and diffusive capacity of rejuvenators within aged bitumen, as well as their rejuvenation effectiveness in the chemo-thermodynamic-rheological performance. Additionally, the intermolecular interactions occurring between the rejuvenator and aged bitumen molecules are visualized and quantified by MD simulations.The accurate construction of molecular models for aged bitumen is crucial for investigating the fundamental effects of aging on bitumen behavior at the molecular scale. To accomplish this, the long-term aging influence on the chemical characteristics of bitumen was assessed through Saturate, Aromatic, Resin, and Asphaltene (SARA) fractionation, Fourier Transform Infrared Spectroscopy (FTIR) test and element analysis method. The chemical information obtained served as a foundation for determining the molecular structures of bitumen models. Various thermodynamic parameters of both virgin and aged bitumen were predicted to fundamentally evaluate the aging effect on bitumen properties. Lastly, functional group and SARA-based long-term aging reaction kinetics models were proposed to anticipate the chemical characteristics of aged bitumen with different aging degrees, thereby establishing the corresponding molecular models without the need for additional experimental procedures.Simultaneously, novel average and multi-component molecular models for various rejuvenators (bio-oil BO, engine-oil EO, naphthenic-oil NO, aromatic-oil AO) were established. The average models were based on the average chemical characteristics, such as functional group distribution, element component, and average molecular weight. On the other hand, multi-component models were derived from molecular component distribution in rejuvenators through Gas Chromatography-Mass spectrometry (GC-MS) analysis. Both models were validated by comparing MD outputs with experimental results. It was found that the average models provided more accurate predictions regarding the glass transition temperatures, especially for the aromatic-oil. Additionally, a range of thermodynamic parameters for the rejuvenators were predicted and compared. Finally, the average structures of rejuvenators were adopted to construct subsequent molecular models of rejuvenated binders.The consideration of compatibility between the rejuvenator and aged bitumen is crucial due to the potential phase separation. In this thesis, different thermodynamic parameters, such as solubility parameter difference Δδ, Flory-Huggins parameter\chi, and mixing free energy ΔGm were predicted and calculated using MD simulations for various rejuvenated bitumen systems. The predicted compatibility ranking for four rejuvenators was AO > BO > NO > EO, aligned with the experimentally measured thermal stability results. Moreover, separation index (SI) parameters based on rheological and chemical indices were available to assess the thermal stability of rejuvenated bitumen.Furthermore, a comprehensive investigation was implemented to explore the effects of rejuvenator type, temperature, and aging degree of bitumen on the diffusion behavior of rejuvenators in aged binders at multiple scales. The molecular dynamics (MD) simulation method was employed to detect the molecular-level diffusion characteristics of rejuvenators and predict their diffusion coefficient (D) parameters. At the atomic scale, it was observed that there was a mutual but partial interfacial diffusion feature between rejuvenators and aged bitumen molecules. Meanwhile, the concentration distribution of rejuvenator molecules in aged bitumen was well described by Fick's Second Law. The calculated D values for the four rejuvenators ranged from 10-11 to 10-10 m2/s, and the diffusive capacities followed the order of BO > EO > NO > AO. To verify the MD simulation outputs, diffusion tests and dynamic shear rheometer (DSR) characterizations were conducted. The experimental results regarding the magnitude and order of the D values were in good agreement with the MD simulation findings. Lastly, it was observed that an increased aging degree of bitumen had a negative impact on the molecular diffusivity of BO, EO, and NO rejuvenators, whereas the D value of AO molecules enlarged as the aging level deepened.A series of measurements were conducted to estimate the combined effects of rejuvenator type/dosage and aging degree of bitumen on the rheological properties of rejuvenated bitumen. Importantly, several critical indicators were identified that effectively assess and differentiate the rejuvenation efficiency of different rejuvenators on aged bitumen performance. In terms of high-temperature performance, parameters rutting failure temperature (RFT) and zero-shear viscosity (ZSV) from the linear viscoelastic (LVE) and flow tests were found to be useful. Additionally, parameters R3.2, Jnr0.1 or Jnr3.2, and Jnrslope were recommended for estimating the elastic performance, creep potential, and stress sensitivity of rejuvenated bitumen. Among these, the RFT parameter played a crucial role in evaluating and distinguishing the rejuvenation effectiveness of various rejuvenators on the high-temperature performance of aged bitumen. For the low-temperature relaxation property, parameters τ50s, t25%, and A were proposed as critical indicators. Regarding fatigue life improvement, BO demonstrated the highest rejuvenation effectiveness, followed by EO, NO, and AO rejuvenators. The fatigue failure temperature (FFT) parameter was identified as an effective indicator for fatigue performance evaluation in LVE tests. In linear amplitude sweep (LAS) tests, the fatigue life (Nf5), peak strain (ɛsr), and elastic modulus (E) parameters were optimized as effective fatigue indicators. Nonetheless, crack width (C) results were consistent with conclusions drawn from LVE and LAS tests. Particularly, the crack width C500 parameter showed strong correlations with other critical fatigue indicators, and its prediction could be achieved using correlation equations without the need for time-consuming TS tests.At the atomic-level evaluation, several key thermodynamic properties of variable rejuvenated bitumen models were outputted by molecular dynamics (MD) simulation. The rejuvenation effectiveness of different rejuvenators on the thermodynamic indices of aged bitumen was estimated and compared. Importantly, the potential connections between these essential nanoscale parameters and critical macroscale indicators in terms of high-and-low temperature performance and fatigue behaviors of rejuvenated binders were explored. It was revealed that the addition of rejuvenators inherently catalysed a restoration of density and cohesive energy density (CED) values toward those of virgin bitumen. A suite of indicators, including UVEP, UWEK, EN, UVET, UNED, and ECT, are introduced as critical energetic parameters, each reflecting rejuvenator efficacy on atomic-level energetic features, except for specific cases involving aromatic-oil rejuvenated binders. Meanwhile, it is recommended to predict the relaxation properties of different rejuvenated bitumen by the fractional free volume parameter from MD simulation. The surface free energy (γ) emerges as a dependable index for assessing the rejuvenation efficacy of the cohesive cracking potential of aged bitumen. In summary, a multiscale evaluation framework of rejuvenated bitumen was proposed and developed in this dissertation, together with a full understanding of the difference in rejuvenation efficiency and mechanism between various rejuvenators on chemo-thermodynamic-rheological performance restoration of aged bitumen. The outcomes of this thesis would be beneficial to promoting the formation of classification standards of rejuvenator additives, development of advanced multifunctional rejuvenators, and improvement of all-round evaluation method on rejuvenated binder.Pavement Engineerin
An adaptive network model for AI-assisted monitoring and management of neonatal respiratory distress
No full textThis article presents the use of second-order adaptive network models of hospital teams consisting of doctors and nurses, interacting together. A variety of scenarios are modelled and simulated, in relation with respiratory distress of a neonate, along with the integration of an AI-Coach for monitoring and support of such teams and of organizational learning. The research highlights the benefits of introducing a virtual AI-Coach in a hospital setting. The practical application setting revolves around a medical team responsible for managing neonates with respiratory distress. In this setting an AI-Coach act as an additional team member, to ensure correct execution of medical procedure. Through simulation experiments, the adaptive network models demonstrate that the AI-Coach not only aids in maintaining correct medical procedure execution but also facilitates organizational learning, leading to significant improvements in procedure adherence and error reduction during neonatal care.Safety and Security Scienc
Distributed Multi-Agent Pathfinding
No full textMulti-agent path finding (MAPF) is the task of finding non-conflicting paths for multiple agents that operate in a environment with shared resources. Finding an optimal solution quickly becomes intractable for many applications and consequently suboptimal methods are also explored extensively in literature. This work presents the Decentralized Optimization (DECOP) algorithm: a novel receding horizon control algorithm that exploits insights from MAPF research as well as decentralized control. In the proposed framework, each travelling agent communicates with agents in its proximity to solve a local MAPF problem that considers only a selected tractable number of agents. Inter-agent cooperation and conflict free operation are induced through applying a common local optimization policy during parallel local optimization and through a subsequent path reservation scheme based on random priorities. Inter-agent communication consists of sharing respective route alternatives from which additional information with regard to an agents' entanglement can be inferred which can also be included in the local optimization cost function.Comparative results with other decentralized algorithms show that the DECOP algorithm yields competitive results while guaranteeing conflict free operations, with limited required communication and without the need of any training time. Among many degrees of freedom to be explored further, including information about the entanglements of an agent's route alternatives in the common policy for local optimization yields an increase in performance and suggests an increased extent of induced cooperation.Mechanical Engineering | Systems and Contro
Crashworthiness Assessment of the Flying-V Under Complex Crash Scenarios with Partially Detailed Structures
No full textThis research delves into aircraft crashworthiness, focusing on the innovative Flying-V configuration, aiming to improve safety in unconventional designs. Challenges arise due to the Flying-V's unique V-shaped fuselage, complicating traditional crashworthiness assessments. To address this, the study proposes modelling approaches, particularly for the central part of the fuselage lacking detailed structural information.Various modelling approaches are explored, building on a finite element model of the Flying-V developed in previous work. Drop tests validate optimal section designs, emphasizing a minimum vertical impact velocity. Spatial variations in Dynamic Response Index (DRI) and Severity Index (SEV) prompt nuanced studies on impact scenarios and potential passenger side loads.As the analysis progresses, extending the computational domain becomes crucial for reliability. Insights into weight distribution imbalances and challenges with corrective measures emerge from analyses of extended fuselage sections. Spatial fluctuations in DRIs and SEVs underscore the need for a balanced approach between computational efficiency and result realism.A newly introduced modelling technique leveraging moments of inertia is implemented, yielding realistic results for straightforward scenarios and reducing simulation time significantly. Further analysis explores intricate landing scenarios, highlighting differences between full and reduced models, particularly at elevated pitch angles.Recognizing the limitations of simplified methodologies, a submodelling technique is proposed for extreme crash scenarios, effectively capturing engine section dynamics with reduced computational time.While reduced modelling techniques show promise, the study underscores the need for a comprehensive finite element method representation of the Flying-V, recommending successive simulations with a coarse overall mesh followed by submodelling for detailed assessment of critical regions.Flying-VAerospace Engineerin
Dynamic Adaptive Policy Pathways for flood risk management in Galveston Bay: Making informed flood defence decisions for an uncertain future
No full textMaking decisions when future conditions are uncertain is a challenging endeavor. This thesis develops a framework to analyse flood risk and create Dynamic Adaptive Policy Pathways, which can provide insights in the behaviour of flood risk protection measures in many future scenarios. The pathways are used to identify robust measures, dead ends and compare measures. The framework is applied to a case study in the Galveston Bay area.Civil Engineering | Hydraulic Engineering | Hydraulic Structures and Flood Ris
A Novel Smart Wearable: for Parkinson’s Disease
No full textIn the dynamic realm of medical technology, innovation to improve the lives of those with chronic conditions like Parkinson's Disease (PD) is paramount. This graduation report represents the culmination of a project aiming to address prevalent symptoms in individuals with PD. Client and Objective: The project aims to develop a concept product for Dopple B.V., a Dutch tech company specializing in head-worn audio smart wearables, seeking to expand into the medical market. The focus is on utilizing their existing product line to create a solution. Scope: The project focuses on creating a smart wearable audio device equipped with modern technology to alleviate symptoms of PD, particularly "freeze of gait & festination." Symptoms: Freeze of gait (FoG) refers to a sudden inability to move forward despite intending to walk, significantly impacting mobility and increasing fall risk. Festination involves a rapid, short-stepped gait, leading to balance issues and difficulties in movement control. User Testing: Tests conducted with PD clients showed promising results in evaluating the effectiveness of feedback mechanisms. Product Features: The "Dopple Earbuds" utilize advanced technology such as smartphone integration, neural networks, and Bluetooth data transmission. Beyond addressing FoG and festination, they offer a range of functionalities including object detection, heart rhythm monitoring, fall detection, posture correction, and more. Design: The Dopple Earbuds are designed with considerations for aesthetics, ergonomics, and materials, tailored to the needs of elderly users. The involvement of neural networks necessitates careful management of memory, battery consumption, and data flow. Collaboration: The project involved collaboration with healthcare professionals, Dopple engineers, and coaching, aiming to pioneer novel solutions in medical technology beyond traditional pharmaceutical approaches. In summary, this project represents a significant step forward in leveraging technology to improve the quality of life for individuals with PD, showcasing the potential of medical assistance technology in complementing existing treatments.Integrated Product Design | Medisig
The use of green H2 and sustainable carburization to Fe3C for the direct reduction of iron ore pellets
No full textSteel manufacturing is a carbon intensive process, that is responsible for approximately 7% of the total global CO2 emissions. Therefore, TATA Steel IJmuiden aims to lower its carbon emissions. One way to bring down emissions, is to replace the existing blast furnace (BF) CO reduction process with the H2-based direct reduction of iron ore (DRI). The two most widely applied H2-DRI processes around the world are the low pressure MIDREX, abbreviated as MLP, and medium pressure HYL-Energiron, abbreviated as EMP. Since TATA Steel IJmuiden wants to study the switch from BF to H2-DRI steelmaking, it is relevant to gain insight into which gas phase reactions are dominant for both processes, into the direct reduction process itself and into the behaviour of the carburization reactions that improve the steel quality. In the gas phase reactions, it was seen that for the MLP process in situ reforming of natural gas can be a viable option before switching to a 100% H2 process. This may prove to be worthwhile in the early stages of H2-DRI steel production, when green H2 is still scarce and expensive. For EMP, internal reforming seems less of a possibility due to the high reaction rate for the reverse water gas-shift. When comparing both MLP and EMP, reaction rates are generally higher for EMP than for MLP and hence smaller reactor volumes are required for the EMP process to acquire the same amount of output. Direct reduction with H2 has a higher reaction rate than reduction with CO, while for the carburization reactions methane cracking was found to be the dominant reaction. Techno-economic scenarios for 100% H2-based DRI in which green H2 is imported are only feasible when H2-prices fall below €1.80/kg. Meanwhile, a scenario with an on-site electrolyzer powered by grey grid electricity only proves to be worthwhile for electricity prices lower than €20/MWh. The most promising techno-economic scenario, which includes an on-site electrolyzer and the construction of a wind farm just off the coast from the TATA Steel IJmuiden site, assumes an electricity price of €40/MWh.Electrical Engineering | Sustainable Energy Technolog
Manufacturing Laminate-Free PV Modules at Large Scale
No full textAs photovoltaic (PV) technology enters the terawatt era, reliability, sustainability, and circularity in the solar industry can no longer be optional considerations for manufacturing solar modules. Despite two decades of intense solar manufacturing, the PV industry still predominantly operates within a linear economic structure, characterized by energy-intensive production and limited sustainability practices. One significant challenge associated with crystalline PV modules is the encapsulation process, which occurs within costly and unwieldy laminator machines. While laminating PV modules offers long-term stability and performance, it also imposes significant limitations on the disassembly, repairability, and recyclability of valuable PV module materials. The development of sustainable PV designs and manufacturing processes is crucial for transitioning to a circular economy. In response to this problem, Biosphere Solar, a startup company based in Delft, is developing a novel solar module design that eliminates the need for lamination. Their focus is on creating an easily disassembled solar module to facilitate repair, reuse, and ultimately achieving full recyclability with low-energy input. It is crucial to recognize that transitioning to non-laminated modules presents challenges in manufacturing. This thesis aims to identify and address barriers encountered in manufacturing laminate-free PV modules compared to traditional PV panels. First, becoming acquainted with laminated PV lines provided insights into the challenges to be encountered. The analysis of the laminate-free product primarily examines the module components, and materials diverging from laminated panels, such as adhesives, solder pastes, fillers, and edge sealants, assessing their trade-offs and configurations in terms of manufacturability. The product analysis has facilitated the definition of a manufacturing process flow, which is constructed based on assembly operations that both align with and diverge from standard PV manufacturing practices. This is complemented by an exploration of non-standardized processing methods, considering the associated boundary conditions in the assembly. The main challenges encountered include the metal paste dispensing, low-temperature soldering, and fluid filling processes, with multiple units installed and a necessity for a specific design tailored to this application. This study demonstrates competitiveness with respect to laminate PV line scales, particularly evident in larger-scale operations. Technically, a 30% reduction in energy consumption for machinery and up to 50% factory area savings can be achieved. The electrical consumption of the laminator(s) alone, for production volumes up to 300MW, can range between 20% and 50%, with a footprint share of up to 10% of the total manufacturing space. Economically, capital costs also demonstrate promise and have the potential to outperform laminated PV modules, especially in a highly automated setup line. Savings between 20-30% for equipment costs and up to 50% for building infrastructure costs are achievable. Nevertheless, the main factors offsetting these mitigated capital costs are the operational expenses associated with the bill of materials and the manpower required to produce this specific product. These material expenses can be up to 4-5 times higher than for a laminated panel, and up to twice the investment in manufacturing labour. This assessment lays the foundation for future research leveraging the trade-offs explored to refine choices and achieve optimal results.Electrical Engineering | Sustainable Energy Technolog
Data sources:
Access Repository Dashboard
Do you manage Open Research Online? Become a CORE Member to access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard! 👇