226 research outputs found
GPU-accelerated depth map generation for X-ray simulations of complex CAD geometries
No full textInteractive x-ray simulations of complex computer-aided design (CAD) models can provide valuable insights for better interpretation of the defect signatures such as porosity from x-ray CT images. Generating the depth map along a particular direction for the given CAD geometry is the most compute-intensive step in x-ray simulations. We have developed a GPU-accelerated method for real-time generation of depth maps of complex CAD geometries. We preprocess complex components designed using commercial CAD systems using a custom CAD module and convert them into a fine user-defined surface tessellation. Our CAD module can be used by different simulators as well as handle complex geometries, including those that arise from complex castings and composite structures. We then make use of a parallel algorithm that runs on a graphics processing unit (GPU) to convert the finely-tessellated CAD model to a voxelized representation. The voxelized representation can enable heterogeneous modeling of the volume enclosed by the CAD model by assigning heterogeneous material properties in specific regions. The depth maps are generated from this voxelized representation with the help of a GPU-accelerated ray-casting algorithm. The GPU-accelerated ray-casting method enables interactive (> 60 frames-per-second) generation of the depth maps of complex CAD geometries. This enables arbitrarily rotation and slicing of the CAD model, leading to better interpretation of the x-ray images by the user. In addition, the depth maps can be used to aid directly in CT reconstruction algorithms.This proceeding may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This proceeding appeared in Grandin, Robert J., Gavin Young, Stephen D. Holland, and Adarsh Krishnamurthy. "GPU-accelerated depth map generation for X-ray simulations of complex CAD geometries." In AIP Conference Proceedings, vol. 1949, no. 1, p. 190002. AIP Publishing LLC, 2018, and may be found at
DOI: 10.1063/1.5031636.
Copyright 2018 Author(s).
Posted with permission
Incorporation of composite defects from ultrasonic NDE into CAD and FE models
No full textFiber-reinforced composites are widely used in aerospace industry due to their combined properties of high strength and low weight. However, owing to their complex structure, it is difficult to assess the impact of manufacturing defects and service damage on their residual life. While, ultrasonic testing (UT) is the preferred NDE method to identify the presence of defects in composites, there are no reasonable ways to model the damage and evaluate the structural integrity of composites. We have developed an automated framework to incorporate flaws and known composite damage automatically into a finite element analysis (FEA) model of composites, ultimately aiding in accessing the residual life of composites and make informed decisions regarding repairs. The framework can be used to generate a layer-by-layer 3D structural CAD model of the composite laminates replicating their manufacturing process. Outlines of structural defects, such as delaminations, are automatically detected from UT of the laminate and are incorporated into the CAD model between the appropriate layers. In addition, the framework allows for direct structural analysis of the resulting 3D CAD models with defects by automatically applying the appropriate boundary conditions. In this paper, we show a working proof-of-concept for the composite model builder with capabilities of incorporating delaminations between laminate layers and automatically preparing the CAD model for structural analysis using a FEA software.This proceeding may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This proceeding appeared in Bingol, Onur Rauf, Bryan Schiefelbein, Robert J. Grandin, Stephen D. Holland, and Adarsh Krishnamurthy. "Incorporation of composite defects from ultrasonic NDE into CAD and FE models." AIP Conference Proceedings 1806, no. 1, (2017): 150004. , and may be found at DOI: 10.1063/1.4974728. Posted with permission.</p
Optogenetic control of developmental signaling pathways
No full textHow a complex multicellular organism forms from a single cell is a question that defies simplistic understanding. Yet, embryonic developmental programs use a surprisingly small set of signaling pathways to pattern the embryonic tissue into germ layers from which the various tissues and organs emerge. A hallmark of embryonic development is that these recurring developmental signaling pathways are carefully orchestrated in space and time to facilitate proper development. Understanding the spatiotemporal intricacies of these pathways necessitates tools which enable their perturbation in precisely defined spatiotemporal patterns. Optogenetics uses light-induced conformational changes to enable or disable protein-protein interactions, thereby permitting control of signal transduction at the flip of a switch. Consequently, light is emerging as a powerful tool to study embryonic development owing to its rapid, reversible and residue-free application, which empowers the researcher with excellent spatial and temporal control of signaling. Here, I first review recent accomplishments in optical microscopy and optogenetics which highlight the dual roles of light in visualizing as well as perturbing cellular microenvironments and processes. Second, I present an optogenetic approach to control the mitogen-activated protein kinase (MAPK) pathway which we successfully applied in both neuroblasts and frog embryos. Third, I demonstrate an optogenetic approach to control the Wnt signaling pathway in mammalian cells and frog embryos. Finally, I propose and provide working proof for a generalizable optogenetic platform to control those developmental signaling pathways, the activities of which involve the homo-association of plasma membrane-localized receptor tyrosine kinases.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-12-01The student, Vishnu Vardhan Krishnamurthy, accepted the attached license on 2019-11-27 at 10:27.The student, Vishnu Vardhan Krishnamurthy, submitted this Dissertation for approval on 2019-11-27 at 10:29.This Dissertation was approved for publication on 2019-12-04 at 10:19.DSpace SAF Submission Ingestion Package generated from Vireo submission #14554 on 2020-02-28 at 17:36:14Made available in DSpace on 2020-03-02T22:38:43Z (GMT). No. of bitstreams: 3
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Mesoscopic Heat engines beyond the Limits of Thermodynamics
No full textDespite the central role that Equilibrium thermodynamics has played in our understanding of many body systems, the underlying theoretical construct is strictly correct only in the ‘Thermodynamic Limit’. On the other hand, biological micromotors that function in a regime where this limit is violated are known to perform with a superior efficiency even in the absence of temperature differences. In this thesis, we discuss the design and operation of heat engines that successively defy the three conditions involved in this limit viz. quasi-static limit, macroscopic limit and equilibrium limit and explore the consequences of this on their performance. While all macroscopic engines that surpass the quasi-static limit are known to compromise efficiency for power, we demonstrate that by further breaching the macroscopic limit and using a Gaussian colored noise, such a trade-off might not even be necessary. Our results indicate that for engines with low degrees of freedom, in the presence of a colored Gaussian noise, even the quasi-static efficiency can be exceeded at finite times. We examined the operation of heat engines beyond the equilibrium and macroscopic limits by introducing motile bacteria into the surrounding bath. Under the influence of the active noise due to the bacterial motion, we observed that the performance increased by orders of magnitude surpassing even the equilibrium quasi-static efficiency at infinite temperature difference. Finally, we demonstrated that generating macroscopic motion by grouping engines that trespass the limits of thermodynamics, can further result in even better performance and tunability. Our results highlight that the major constraints imposed by equilibrium and finite time thermodynamics can be relaxed by employing a bottom-up architecture and calls for rethinking the fundamentals of the approaches to engine desig
Investigation of the effects of polymicrobial infection on the induction of otitis media
No full textBacterial otitis media (OM) is a well known paediatric condition predominantly caused by Streptococcus pneumoniae, nontypeable Haemophilus influenzae and Moraxella catarrhalis. The polymicrobial etiology and the mechanisms and pathogenesis of the disease caused by single bacterium, synergistic bacterial-viral interactions, and inflammatory processes have been studied using different animal models. The complexities associated with polymicrobial OM, mechanisms of host-bacterial relationships, inflammatory responses, and microbial interactions would be better understood in an experimental model comprising of the predominant bacteria involved. These issues were explored in this thesis in the context of investigating the effects of polybacterial infection on the incidence and severity of OM. An experimental polymicrobial infection murine (BALB/c) model was established involving different combinations of the above mentioned bacteria along with a respiratory virus (Sendai). This model was used to demonstrate for the first time that the presence of M. catarrhalis as a co-colonising agent of the nasopharynx significantly exacerbates pneumococcal OM. Another significant finding was that the inflammatory response generated, was due to the synergistic bacterial-viral infection and not by the respiratory virus alone (Chapter 2). This model was next used to show that the incidence of lower respiratory and middle ear infections caused by M. catarrhalis and NTHi was not affected by bacterial dosage and pre-colonisation of the nasopharynx (Chapter 3 & 4 respectively). In contrast, pre-viral infection and increased bacterial numbers facilitated greater incidence of pneumococcal OM and lower respiratory tract infections (Chapter 3). The incidence of pneumococcal OM was also evident in the presence of a precoloniser (M. catarrhalis) in the nasopharynx (Chapter 4). The impact of the polymicrobial environment in the nasopharynx on the incidence of OM could be better understood with real-time monitoring of infection progression by biophotonic imaging. Following intranasal infection, co-colonisation patterns and its effect on OM of luminescent NTHi and S. pneumoniae were measured (Chapter 5). The data not only showed rapid ascension of S. pneumoniae when pre-infected with M. catarrhalis and coinfected with NTHi and M. catarrhalis, but also showed the ability of bacteria to colonise different niches. The factors associated with microbial interactions, including adherence, with the host were identified using in vitro cell cultures as a model because of their ease of manipulation and cost-effectiveness (Chapters 6 and 7). This was performed using the above mentioned bacterial combinations and adenovirus on lung (A549) and bronchial (BEAS 2B) epithelial cell lines. When infected alone, adherence of M. catarrhalis and S. pneumoniae to adenovirus-infected BEAS-2B cells was greater than virus-infected A549 cells, but was reduced on BEAS-2B cells in a co-infection with M. catarrhalis and S. pneumoniae. In contrast, this co-infection increased the adherence to virus-infected A549 cells (Chapter 6). This observation supports the findings of the in vivo studies (Chapter 2) indicating a positive association between these two bacteria to cause infections. The pulmonary burden caused by bacterial products could be different in the various respiratory compartments, as seen with different adherence levels to epithelial cells, suggesting the possibility of different cytokine responses. This was demonstrated for IL-6, with significant differences in the release of IL-6 by BEAS 2B and A549 cells in response to bacterial infection, and a synergistic effect of M. catarrhalis and S. pneumoniae, and, S. pneumoniae and NTHi co-infections on IL-6 production (Chapter 7). The overall finding of this thesis was that the nasopharyngeal M. catarrhalis infection not only predisposes pneumococcal otitis media, but also promotes pneumococcal colonisation at a site distal from its initial inoculation site. Furthermore, this association also enhanced the adherence to alveolar epithelial cells releasing high levels of the inflammatory cytokine IL-6. This finding contributes to better understanding of the early onset of OM observed evidently at an alarming rate, particularly in Australian Aboriginal children, and will assist strategies to for preventing and managing infections. -- Abstract
Crystalline And Glassy States In Hard Sphere Colloids : Density Functional And Simulational Studies
No full textGraphene coatings for protection against microbiologically induced corrosion
No full textDecember 2014School of EngineeringThe success/failure of coating techniques is not purely dictated by their ability to protect the surface, but also by the ease of coating application onto any given surface. Chapter 4 explains the methods by which high quality graphene can be used to protect surfaces that are not conducive to graphene growth and the problems associated with the current transfer techniques. A Raman Spectroscopy based surface mapping is performed to understand the defect peak intensities across the surface and the reasons for coating failure when using the state-of-the-art transfer techniques is discussed.Microbiologically induced corrosion (MIC) is a special form of electrochemical corrosion where micro-organisms affect the local environmental conditions at the metal-electrolyte interface by forming a stable biofilm. The biofilm introduces localized concentration cells, which accelerate the electrochemical corrosion rates. MIC has been found to affect many industrial systems such as sewage waste water pipes, heat exchangers, ships, underwater pipes etc. It has been traditionally eradicated by physical, biochemical and surface protection methods. The cleaning methods and the biocidal deliveries are required periodically and don't provide a permanent solution to the problem. Further, the use of biocides has been harshly criticized by environmentalists due to safety concerns associated with their usage. Surface based coatings have their own drawback of rapid degradation under harsh microbial environments. This has led to the exploration of thin, robust, inert, conformal passivation coatings for the protection of metallic surfaces from microbiologically induced corrosion.Chapter 1 introduces the basics of microbiologically induced corrosion and graphene. A comprehensive review of literature is used to discuss the role of micro-organisms, their impact on corrosion and their eradication. The conflicting results behind the use of graphene as a coating material are evaluated using the available literature and its future as an effective MIC resistant coating is then discussed.Graphene is a 2D arrangement of carbon atoms in a hexagonal honeycomb lattice. The carbon atoms are bonded to one another by sp2 hybridization and each layer of the carbon ring arrangement spans to a thickness of less than a nm. Due to its unique 2D arrangement of carbon atoms, graphene exhibits interesting in-plane and out of plane properties that have led to it being considered as the material for the future. Its excellent thermal, mechanical, electrical and optical properties are being explored in great depth to understand and realize potential applications in various technological realms. Early studies have shown the ability of bulk and monolayer graphene to protect metallic surfaces from air oxidation and solution based galvanic corrosion processes for short periods. However, the role of graphene in resisting MIC is yet to be determined, particularly over the long time spans characteristic of this form of corrosion.Chapter 2 is a study of the effectiveness of graphene based coatings for passivating metal surfaces against microbial induced corrosion. The effectiveness of graphene is evaluated against a bare metal electrode and a regular carbon based electrode using Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), Spectrophotometry and Scanning Electron Microscopy (SEM). Results indicate 3-orders-of-magnitude lower corrosion currents in the graphene coated electrode and about two orders of magnitude higher impedance to interfacial electrochemical reactions.After establishing the superiority of graphene over bare metal electrode, further studies were conducted to compare its performance over other state of the art polymer coatings such as parylene and polyurethane. This study is discussed in detail in Chapter 3. Quantitatively, graphene outperforms the polymer coated electrodes by offering close to two orders of magnitude higher MIC resistance, while qualitatively, optical images indicate severe oxidation in both the polymer coated metal structures. The chapter is concluded with discussions on the unparalleled corrosion resistance provided by graphene based coatings.Ph
Prospective: A Data-Driven Technique to Predict Web Service Response Time Percentiles
No full textDelivering fast response times for user transactions is a critical requirement for Web services. Often, a Web service has Service Level Agreements (SLA) with its users that quantify how quickly the service has to respond to a user transaction. Typically, SLAs stipulate requirements for Web service response time percentiles, e.g., a specified target for the 95th percentile of response time. Violating SLAs can have adverse consequences for a Web service operator. Consequently, operators require systematic techniques to predict Web service response time percentiles. Existing prediction techniques are very time consuming since they often involve manual construction of queuing or machine learning models. To address this problem, we propose Prospective, a data-driven approach for predicting Web service response time percentiles. Given a specification for workload expected at the Web service over a planning horizon, Prospective uses historical data to offer predictions for response time percentiles of interest. At the core of Prospective is a lightweight simulator that uses collaborative filtering to estimate response time behaviour of the service based on behaviour observed historically. Results show that Prospective significantly outperforms other baseline techniques for a wide variety of workloads. In particular, the technique provides accurate estimates even for workload scenarios not directly observed in the historical data. We also show that Prospective can provide a Web service operator with accurate estimates of the types and numbers of Web service instances needed to avoid SLA violations.Library OA Fun
Making sense of ‘new age data sets’: researching from afar
No full textThis chapter considers the central role of uncertainty for cognition and action in construction project organising with a focus on how project practitioners think about the future. It takes a cognitive approach to uncertainty in the context of a broader information processing approach to decision-making in organisations. The chapter’s main concern is the failure of this approach to connect cognition through to action. The chapter presents the UnCoCoH (Un-Certain Complex Complicated Hidden) model as a tool to assist in recognising the transition from individual cognition to collective action. It also highlights the role of narratives for stabilising uncertainty through this transition. This provides a foundation for working towards the development of a projectivity perspective in construction project organising and advancing a research agenda for this program of research.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.Integral Design & Managemen
Wire arc additive manufactured AWS ER100S-G steel: Very high cycle fatigue characterization
No full textThis paper presents a comprehensive study on the very high cycle fatigue (VHCF) characterization of a wire arc additive manufactured (WAAM) AWS ER100S-G steel. The demand for highperformance materials with superior fatigue properties has grown exponentially. However, the VHCF behavior of large-format WAAM'd structures remains relatively unexplored. In this study, a series of VHCF tests were conducted under fully reversed cyclic loading conditions to investigate the extended fatigue life (performance) of the WAAM ER100S-G steel. The VHCF properties, relative to conventional fatigue employing a servohydraulic testing system, of the WAAM ER100S-G steel were evaluated by analyzing the stress-life (S-N) curves, fatigue crack initiation, and propagation behavior, in a statistical framework, and the fracture surfaces. The results revealed the controlling mechanisms of VHCF failure of the WAAM ER100S-G steel and the fatigue response of the material beyond the conventional fatigue limit of 107 cycles. The findings provide valuable insights into the influence of WAAM-induced defects/microstructure on the extended fatigue performance of WAAM ER100S-G steel, which can aid in optimizing fatigue and durability design guidelines for additive manufacturing applications in high-cycle and very highcycle fatigue domains
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