23 research outputs found
Experimental Technique to Investigate Compliance of Fish Fin During Natural Swimming
No full textThe compliance of a fish fin and how it contributes to swimming has gained extensive attention in the biology and engineering research and design communities. Many studies have hypothesized that fish can actively control the stiffness of their fin rays and fins during swimming to optimize propulsion, but such active controls have not been confirmed through experiments with live fish during natural swimming. This is partly because there are no experimental devices or methodologies that can facilitate controlled experiments during natural swimming to investigate the compliance of the fish fins. It is proposed, through this research, that the compliance of a fish fin can be investigated by applying an external perturbation, like a vortex ring, to the fin while it is being used in locomotion and by measuring the displacement of the fin from its natural swimming motion. To that end, the goal of this thesis was to develop and validate a perturbation device (vortex generator) and a technique to investigate compliance of fins during natural swimming. Experiments were conducted to understand how the vortex formation, size and speed could be altered by tuning the design features on the vortex generator. The evaluation of the vortex generator, the development of the experimental protocol, and the investigation of compliance changes in a fish fin at different swimming speeds were done by conducting experiments with live bluegill sunfish at different steady-swimming speeds and with flexible foils of known flexural rigidities. The evaluation of the technique was conducted by building an engineered system with tunable compliance and estimating the compliance using the perturbation technique proposed herein. The results from the experiments showed that (a) the vortex generator was able to produce an adequate range of vortex rings that could be used to perturb the fins during natural swimming, (b) the fish at slower swimming speed responded similarly to a compliant foil, while the fish at higher swimming speeds responded similarly to a stiffer foil, suggesting a stiffer fin at higher swimming speeds, (c) we can successfully predict changes in the compliance of a system by comparing the maximum deflection and rate of deflection from the unperturbed state to the maximum deflection of a system. Perturbation of fins is a key technique to uncover not only compliance but also behavioral responses that cannot be understood through the study of normal locomotion alone. The outcomes of this research will continue to advance the understanding of fish swimming as fish continue to be one of the greatest inspirations for advanced underwater vehicles.Ph.D., Mechanical Engineering and Mechanics -- Drexel University, 201
Lhermitte′s Sign: The Current Status
No full textLhermitte′s sign was described by Marie and Chatelin and named after Jean Lhermitte. This sign is mostly described as an electric shock like condition by some patients of multiple sclerosis. This sensation occurs when the neck is moved in a wrong way or rather flexed. It can also travel down to the spine, arms, and legs, and sometimes the trunk. Demyelination and hyperexcitability are the main pathophysiological reasons depicted for the Lhermitte′s sign. Other causes for Lhermitte′s sign include transverse myelitis, behηet′s disease, trauma, etc. This article reviews the Lhermitte′s sign, its history, and its etiopathophysiology. Very few studies are available on Lermitte′s sign and more research need to be done on the same to ensure its sensitivity and specificity
Link Weight Tolerance: A study of betweenness centrality and data transmission in complex networks
No full textLinks play a significant role in the functioning of a complex network. The aim of this thesis is to study the links in a weighted network by introducing two new concepts. The link betweenness centrality of a link is defined as the fraction of shortest paths between all pairs of nodes in a graph that traverses that link. Although link betweenness is a widely known measure that characterizes the link, we introduce the concept, link weight tolerance, to understand the extent to which the weight of the link can be increased or decreased such that the shortest paths in the graph are unaffected, therefore the link betweenness of the links remain the same. We develop a method to generate the positive and negative tolerance of a link. We use examples to illustrate the algorithm and discuss the results. Prior to introducing this concept, in addition to surveying existing network theory measures, we also analyse the metric, betweenness centrality and describe the methods used to generate weighted and unweighted random graphs. To extend the concept of link betweenness, we introduce the second concept, link tension. Link tension provides the information related to the ability of the link to handle transmission of data and shows us the links that are important in a network.Electrical Engineering | Embedded System
A numerical study of cropland-atmosphere feedbacks by incorporating a crop growth module in the WRF model
No full textThis study investigates cropland-atmosphere feedbacks in the Midwestern United States. Growing crops impact local climate during the growing season by influencing heat, moisture and momentum exchange between the land and the atmosphere. These changes in turn affect the crop growth, thus completing a feedback loop. A computationally efficient modeling tool has been specifically developed to study these feedbacks. A vegetation module derived from a crop growth model SUCROS has been incorporated in the Weather Research Forecasting (WRF) model. This coupled model has the capability to explore cropland-atmosphere feedbacks at a high spatial resolution at mesoscale. Results from soybean fields in Nebraska and Illinois show that the crop growth depends directly on temperature, incoming shortwave radiation and precipitation. As the crops grow, they affect energy partitioning between sensible and latent heat leading to a change in the cloud cover and consequently changing incoming shortwave radiation, air temperature and precipitation. An increase in cloud cover reduces incoming shortwave radiation and hence photosynthesis, exerting a negative feedback. However, an increase in precipitation reduces water stress and promotes growth, resulting in a positive feedback. The net impact on crop growth is a nonlinear combination of these feedbacks.Item withdrawn by Mark Zulauf ([email protected]) on 2012-12-01T17:11:21Z
Item was in collections:
University of Illinois Theses & Dissertations (ID: 1)
No. of bitstreams: 2
Rastogi_Deeksha.docx: 7815489 bytes, checksum: d2785d15c37bf25b7aadf84904e5d7cf (MD5)
Rastogi_Deeksha.pdf: 7798911 bytes, checksum: 181440c8584a6a7d9c13a00121bf8b0a (MD5)Made available in DSpace on 2013-02-03T19:45:58Z (GMT). No. of bitstreams: 3
Deeksha_Rastogi.pdf: 7799436 bytes, checksum: abacff3b4ffed0bbbd192c7cf3e223e3 (MD5)
Rastogi_Deeksha.docx: 7815489 bytes, checksum: d2785d15c37bf25b7aadf84904e5d7cf (MD5)
license.txt: 4065 bytes, checksum: bb98bec824327f630b62a86729e0bb55 (MD5)Restriction data tranferred 2014-07-01T11:35:59-05:00
Original Data
Group with Access Administrator
Release Date: 2015-02-03 13:47:48 UTC
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemItem marked as restricted to the 'Administrator' Group (id=1) by Seth Robbins ([email protected]) on 2013-02-03T19:47:54Z
Item is restricted until 2015-02-03T19:47:48ZLimited Restriction Lifted for Item 42396 on 2015-02-03T11:00:31Z
Investigating undergraduate students' communication self-efficacy during an engineering design course
No full textInculcating a sense of stewardship and responsibility towards urban trees amongst citizens: Using i-tree technology as a means to facilitate active participation of local communities in urban forestry
No full textCities are in an urgent need to adapt to the impacts of climate change, particularly, high temperatures and heat stress. Urban Forests are the most effective means of climate adaptation. However, the multiple benefits of urban trees are highly undervalued in the urban contexts. This project focuses on positioning urban trees as effective agents in improving the overall liveability of cities. The premise of the project lies in the fuzzy front end of the innovation process where the i-Tree technology is being redeveloped for its effective adoption in Netherlands. The goal of the project is to synchronize the technical potential of i-Tree as a tool and communicate the benefits of trees to multiple stakeholders in the process.The overall design direction aims to address these problems through a series of interventions across the system of urban forestry. The concept introduces a public awareness campaign to bridge the knowledge gap between citizens and other stakeholders. The campaign is proposed to stretch over a duration of 10-11 months with several touchpoints along the way for citizens to get enthusiastic about the idea of maintaining and taking care of urban trees. The touchpoints aim to target events like Dutch Design week, Boomfeestdag (Tree Festival) and Springsnow festival. To make the awareness program desirable and interesting. A podcast series and a guide is developed called “How to befriend a Tree?”. A concept for the i-Tree Eco tool is proposed which communicates tree benefits in a way that is comprehensible by all the citizens. All the touch points lead the audience of the campaign to the digital platform of i-Tree Netherlands which helps people become caretakers of trees easily.Strategic Product Desig
Numerical Modelling of Power Transformers under Geomagnetically Induced Currents
No full textModelling of power transformers to predict and examine its performance in the presence of Geomagnetic Induced Currents (GICs) is of particular interest in research since these currents that are quasi-DC in nature drive the transformer into half-cycle saturation. During the half-cycle saturation, the increased leakage flux and harmonics have undesirable effects on the windings and the structural components of the transformer, which can possibly lead to their permanent damage. This prompts the need to perform a precautionary study of the transformer validating its robustness when subject to GICs. This thesis proposes a method to model the transformer and its electromagnetic (EM) behaviour under GICs that combines the accuracy of Finite Element Modelling (FEM) with the speed of Magnetic Equivalent Modelling (MEM) to produce a fast-computing yet detailed modelling method using simulation tools, COMSOL and MATLAB Simulink, respectively. The transformer under study in this thesis is a single-phase 280MVA, 500/230kV auto transformer designed by Royal Smit Transformers. It was first modelled using FEM in COMSOL, providing details of the equivalent 2D axisymmetric geometry of the core and the windings and the material properties to each component. The model was then computed and validated against factory measurements done by Royal SMIT for the transformer when not subjected to GICs. After which, the model was run for the condition in which the transformer is subject to a GIC. The main problem of failure of the model to converge before reaching steady-state condition under GIC was overcome after optimizing the solver settings of the FEM software. The difference in the EM behaviour of the transformer with and without GIC were studied. After ensuring that the FEM model was robust and accurately represents the transformer under GIC as well, the time-consuming part of computing the FEM model till it reached steady-state under GIC was then made to be taken care of by a MEM model developed in Simulink. Induced flux versus magnetizing current characteristics of the transformer were obtained from the FEM model, and fed to the MEM model, which only took a few seconds to run. The magnetizing current waveform obtained for a few cycles after reaching steady-state under GIC was then transferred to the FEM model, which could finally compute - for those values of magnetizing current - the detailed EM effects of GICs on the transformer, spatially. An important EM study needing the spatial distribution of the EM properties within the transformer is the calculation of eddy current losses in the windings. In this thesis, a method that only considers the envelope of the set of windings as opposed to modelling every strand to calculate their losses is developed using an analytical formula found in literature. This is validated against the losses calculated by Royal SMIT as well as the FEM software for a detailed model of the windings. The timesaving method to study the EM behaviour of transformers subject to GIC proposed in this thesis accurately models the transformer in the saturation region that should enable conducting EM studies furthermore to winding loss calculation with ease.Electrical Engineering | Electrical Power Engineerin
Artistic rendering in computer graphics
No full textArtistic Rendering in Computer Graphics is an advancing area under image processing domain. It is used to generate artistic images from photographs. Artistic Rendering is also called Non-Photorealistic Rendering (NPR) because it produces images which are more art based and not true to life, possessing no resemblance to photographs which are true to life. NPR finds applications in many areas such as painterly rendering of images, designing games graphics, cartoon animation, oil paintings, and colored pencil drawings. As part of the project, the author designed and developed a software called as “PhotoMagine” which takes an image as input, applies various artistic effects to it and outputs the images produced as a result of adding each of the effects. The software was designed to exhibit an interactive and user friendly Graphical User Interface with important functionalities such as history box to keep track of the algorithms applied by the user over a particular image. The author further contributed to the project by implementing and incorporating important functionalities such undo and redo effects to enable user to be able to undo/redo a particular effect at any time. The amount of time taken by various effects to apply to the input image was also computed as part of the software and displayed on the interface. The algorithms related to artistic rendering were therefore studied by the author and included as part of the software to carry out several experiments. The detailed description of the phases in the software development life cycle, ranging from requirements analysis, designing of the graphical user interface, implementation and testing of algorithms is described as part of the report.Bachelor of Engineering (Computer Engineering
Measuring undergraduate students' self-efficacy in engineering design in a project-based design course
No full textEvaluation of a Snake Jaw Robot to Teach Integrated Biology, Mathematics, and Engineering
No full text
