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Modeling the effect of prior austenite grain size on bainite formation kinetics
No full textWhile experiments show that refining the prior austenite grain size can either accelerate or decelerate bainite formation in steels, kinetic models based on the successive nucleation of bainitic ferrite subunits can only predict an acceleration. In this work we develop a physically-based model for bainite kinetics assuming a displacive growth mechanism which is able to reproduce both faster and slower bainite formation kinetics induced by austenite grain refinement. A theoretical analysis of the model and comparison against published experimental data show that slower kinetics for smaller grains is favored as the difference between the activation energy for grain boundary and autocatalytic nucleation of bainite increases, and as the austenite grain refinement results in finer bainite sub-units. We also theoretically analyze the density of initially present potential nucleation sites for bainite and show that the values of density used in other published bainite nucleation models are mostly underestimated. After using physically consistent values for the density of potential nucleation sites, we were able to calculate the apparent lengthening rate of bainite sheaves which were in line with experimentally measured lengthening rates.Team Maria Santofimia NavarroTeam Erik Offerma
Extending SymbolicPlanners with forward propagation landmark extraction
No full textThe Fast Downward planning system is currently mainly used for solving classical problems. Another alternative to Fast Downward is SymbolicPlanners, which sacrifices speed for generality and extensibility. SymbolicPlanners is missing landmark based planners and landmark extraction algorithms. The research question we are trying to answer in this research paper is: What design choices can be made to adapt the forward propagation extraction algorithm into SymbolicPlanners? The forward propagation landmark generation design choices are discussed and implemented in SymbolicPlanners. The runtime performance of the implementation is only about two times slower than the Fast Downward implementation. Another aspect of the implementation is the incorrect amount of landmarks generated in complex problems caused by limitation in the relaxed planning graph from SymbolicPlanners.CSE3000 Research ProjectComputer Science and Engineerin
Dynamic loadability of cables in grids connected to offshore wind farms
No full textAbstract:As grids become more and more saturated due to addition of more renewable energy sources in the system, the power demand keeps on increasing. This puts a pressure on the electrical utilities especially the power cables transferring power from one voltage level to another. Therefore, prior investigation into the effect of dynamic loading of such power cables is required before implementing the system in the physical grid.One such saturated system is the implementation of offshore wind farm cables and the utilities connected to it.The objective of this study was to check the effect of the dynamic nature of power flow through the connected cable system. In order to get a quantified result the degradation of the cable is measured in terms of the lifetime consumption of the cables under different loading schemes.The offshore grid connection from Ijmuiden ver area in the North sea operated by Tennet has been identified as a case study for explaining the results. The offshore platforms are connected to the converter station with the help of 3-core 66kV HVAC cables. The connection from the converter station to the onshore grid is with the help of 2 525kV 1-core HVDC cables. The setup has been modelled with the help of two separate models for both the AC and DC cable sross-sections respectively. The models were developed in MATLAB (analytical) and Comsol Multiphysics5.0 (numerical) to check the effect of dynamic loading of the cables with the help of different current vs. time profiles. The temperature variation with time was checked for the two cable systems.The parameters of soil thermal resistivity and the burial depth were varied from (0.2[W/mK],1200[mm]) to (0.36[W/mK],1500[mm]).For the AC cable, it was observed that the lifetime consumption increases on changing the soil thermal conductivity and burial depth from 0.36[W/mK],1500[mm] to 0.2[W/mK],1200[mm]. The percentage lifetime consumption is dependent on the time duration for which the cable has been overloaded with a current value greater than the steady state value of 310[A] corresponding to 90◦C. The worst case change between the two cases was observed as going from 0.4439% to 0.5295% per year.Thus, showing that prior investigation is needed before loading the cable with a certain current profile under a given scenario.For the AC case, on overloading the cable with a current value about 1.2 times the normal value, the maximum percentage lifetime consumption observed was 0.6208%. For the DC cable, the lifetime consumption was measured in terms of the time to failure of the insulation. This parameter is a function of the radial thickness of the insulation from the conductor screen to the insulation. The time to failure increases as one moves away from the conductor screen. Greater insulation deterioration was found to happen with the burial depth and soil thermal conductivity being (1200[mm],0.2[W/mK]) as compared to the case (1500[mm],0.36[W/mK]).A reversal in thetrend of time to failure was observed when the cable was overloaded with a current value of 1.2 times the normal current. The worst case mean value of time to failure observed was 39.68[y] for the normal case.Electrical Engineering | Sustainable Energy Technolog
What are the types of projects that Scratch users create?: How do different types of features relate to the project type?
No full textScratch is a block-based programming language. It is designed to be simple and syntax error avoidant. This makes Scratch an accessible platform for cultivating coding skills. Many young learners are taught about different programming skills using various project types as examples. For instance, games are used as an engagement tool, and various games can motivate new learners to make their own. This influx of new published projects are manually classified into different types by using tags in the project descriptions. However, this manual classification only happens when the user adds the appropriate tags. This calls for an extension of that feature, which could help classify all projects published on the Scratch website. This has the goal of improving the browsing process, especially for new projects. To address this gap, in this initial iteration we leverage the fact that there are likely similarities, or even various project type defining features that would help improve the accuracy of classification through machine learning. Filling this gap also opens the possibility of automatic classification, depending on the accuracy of the results. Within this study, various machine learning models were tested with quantifiable project features as input data. The accuracy scores were compared to draw conclusions on how well various features extracted from Scratch projects performed for classification.CSE3000 Research ProjectComputer Science and Engineerin
Re-evaluating the Full Landmark Extraction Algorithm: A Performance Analysis of FULL
No full textLandmarks are propositions or actions that must be true at some point in every valid solution plan [16]. Using landmarks, planners can develop solutions more efficiently. Different algorithms exist to extract landmarks from a planning problem. The one used in this study is FULL [13], a landmark extraction algorithm by Marzal et al. from 2011.In this research, the performance of the FULL algorithm is analysed by comparing the total number of landmarks found to two other landmark extraction algorithms, namely forward propagation by Zhu and Givan [22] and backward propagation by Porteous et al. [16].The original FULL algorithm is slightly modified, by removing orderings and disjunctive landmark extraction. FULL is implemented using Julia and was run on five different domains from the International Planning Competitions. All of these domains are logical and 15 problems were randomly selected from them.FULL managed to extract more landmarks in two out of the five domains, Grid and Logistics, compared to the two aforementioned algorithms. In the three other domains, FULL matched the number of landmarks found by the best out of the two. The two domains where FULL performed well, were both transportation domains and this is where FULL's performance excels.Runtime was not an issue when extracting landmarks in four of the five domains. Freecell consistently exceeded the timeout put in place, likely due to a bug.Furthermore, a higher number of landmarks is also a desired outcome due to its use in planners, either as heuristics or intermediary goals.CSE3000 Research ProjectComputer Science and Engineerin
Can we extract a relevant, available, and self-contained core of the Maven ecosystem?: Extracting the pillars of the community, and their dependencies.
No full textThe Maven ecosystem, with an emphasis on Maven Central, contains a plethora of toy-projects. This paper addresses this problem by formulating a core containing the pillars of the Maven ecosystem, such that it can be exploited for research concerning li- brary quality. The construction of said core is done by analyzing the availability, relevance and depen- dencies of packages in the Maven ecosystem. It involves answering questions regarding the distri- bution of library usages, the dependencies of popu- lar libraries and the effect of a usage threshold fil- tering mechanism. We found the popular libraries to be utilized to an incredible extend, while their less popular counterparts are seldom, if ever, used. Delving into the creation of a core reveals its non- trivial nature, requiring intricate knowledge of the Maven dependency mechanism and its accompany- ing tools to construct. This paper explores the com- plexities, nuances and considerations involved.CSE3000 Research ProjectComputer Science and Engineerin
Pedestrian Interaction Modelling: Leveraging Trajectory Prediction for Belief Representation
No full textAutonomy in traffic (e.g., autonomous vehicles) could potentially benefit mobility, safety, accessibility and sustainability. However, the realisation of these advancements is highly dependent on how effective these autonomous vehicles interact with vulnerable road users such as pedestrians. Before we can understand how pedestrians will interact with autonomous vehicles, it is essential to understand how pedestrians interact among themselves in interactive traffic scenarios. Previous studies have focused on describing these scenarios with probabilistic trajectory prediction methods such as TrajFlow. However, these approaches often fall short in capturing the nuances of mutual interactions. Simple interaction models have been proposed that can describe these interactions, but neglect the influence of another person's intentions. To address this issue, in existing work the Communication-Enabled-Interaction (CEI) framework was proposed that describes interactions by modelling communication and a belief of another person's intentions. The idea of using beliefs in interaction modelling is based on the concept that people have a general but uncertain idea about the plans of other people. These beliefs are one of the fundamental aspects of the CEI framework and must therefore contain valuable information about possible decisions. That is why this study investigates the use of the probabilistic trajectory prediction method TrajFlow for the belief construction of the CEI framework. TrajFlow is trained on the belief-based Forking Paths dataset, integrated into the CEI framework, and tested in four simulated pedestrian interaction scenarios. The analysis shows that the framework is able to simulate plausible interaction behaviour, dealing with conflicting goals and trajectories in multiple simulations. By doing so, this study takes a positive step towards modelling pedestrian interactions and contributes to the broader goal of realising the benefits linked to autonomy in traffic.Mechanical Engineering | Vehicle Engineering | Cognitive Robotic
Examining the Efficacy of Persuasive eHealth Applications in Facilitating Smoking Cessation: An Analysis of Competency Based Activities
No full textTo assist smokers in potentially quitting their habit, this paper investigates digital eHealth applications. Based on a dataset provided by research into an eHealth application, it aims to determine if persuasive activities can convince users of the usefulness of competencies determined to assist in quitting smoking. A thematic analysis was used on the participant's qualitative responses to the activities. Using this and the quantitative data derived, insights into the efficacy of persuasion were determined. It was determined that engagement with the optional qualitative aspect of the data produced similar utility perspectives on the competencies to those who did not comment. It was noted that the general perspective of the competencies rose after completing the activity, however not to a significant degree. Additionally, no notable correlations between age, gender or educational level and increased perception of the competency arose. Several interesting remarks from participants were analysed to offer considerations for any future research in this field.CSE3000 Research ProjectUnderstanding and Modeling Human Behavior in Quitting SmokingComputer Science and Engineerin
The future of waste collection in Amsterdam: Exploring the trade-offs between different water-based waste collection systems in the canal area of Amsterdam
No full textHeavy traffic in the city of Amsterdam has damaged the 17th-century bridges and quays over the past years. To prevent further damage and expand the lifespan of both existing and renovated structures, a maximum axle load of 7,5 tonnes is mandated in the city centre. Currently, the municipal waste collection department has a permanent exemption from this regulation due to the absence of an alternative method to collect the city's waste. One promising solution involves re-utilising the city's waterways and employing vessels to transport waste out of the city. Two pilots involving water-based waste transport have been conducted in the city and were found to be a working proof of concept. It is, however, not known what a water-based collection system for the whole centre should look like to service the city and preserve the quays and bridges. This thesis aims to assess the trade-offs between three conceptual water-based waste collection systems (WCSs) to guide the direction for designing a suitable WCS for the city. The three concepts examined concepts differ in the scale of the transshipment locations (the point where waste is transferred from land to water), categorised as WCSs with small- medium- and large-scale transshipment locations. The study focuses on the trade-offs between WCSs within and between the domains of social acceptance and technical feasibility. This thesis consists of two main parts, in the first part the three water-based conceptual WCSs were defined using a design workshop. During the workshop, six employees of the municipality used different exercises to generate ideas on how waste could be collected using the waterways and to turn these ideas into conceptual designs. In the second part of this thesis, these three conceptual WCSs were studied using a case study. The units of analysis in each of the WCSs were the social acceptance and the technical feasibility. To evaluate the technical feasibility of each of the WCSs, expert interviews with specialists in vessels, waterways, quay walls and assets were conducted. The social acceptance of the three WCSs was studied using a survey administered to potential users of these systems. They were asked to choose between various WCSs based on walking distance, their general preferences, their preferences in specific situations and their concerns regarding these systems. Parallel to the survey, potential user interviews were conducted to gain deeper insights into respondents' reasons for preferences or aversions to specific WCSs. The results from the expert interviews were summarised and presented in a table to provide an overview of the feasibility of the three WCSs. Survey results were depicted through graphs illustrating respondents' choices, while potential user interviews were analysed thematically, supported by quotes from the interviews. WCS with large- and medium-scale transshipment locations were both found to be potentially feasible from a technical perspective, whereas the small-scale option was deemed unlikely to be feasible. The survey indicated that the majority of the respondents had a preference for self-disposal in containers close to their homes as opposed to having their waste collected at a self-scheduled time, requiring them to be present at home to hand over the waste to the pickup service. Additionally, respondents preferred disposal facilities not too close to their homes or within their direct line of sight. Insights from potential user interviews revealed that participants favouring self-disposal valued flexibility, while on the other hand, those preferring self-scheduled pick-up appointments believed this WCS would address the litter issue in the city. In conclusion, a key trade-off identified was between providing residents with their most preferred waste disposal method through numerous disposal locations versus the technical challenges, if not impossibility, of realizing such a large number of locations. Based on this, the municipality was recommended to conduct further research on WCSs with large- and medium-scale transshipment locations, alongside implementing pilot projects to test these systems in a real-world setting.Management of Technology (MoT
Four-dimensional computational ultrasound imaging of brain hemodynamics
No full textFour-dimensional ultrasound imaging of complex biological systems such as the brain is technically challenging because of the spatiotemporal sampling requirements. We present computational ultrasound imaging (cUSi), an imaging method that uses complex ultrasound fields that can be generated with simple hardware and a physical wave prediction model to alleviate the sampling constraints. cUSi allows for high-resolution four-dimensional imaging of brain hemodynamics in awake and anesthetized mice.Computer EngineeringSignal Processing System