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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Kontextuell helhet av 3D-printad träullsandwich - Från prefab till printning in-situ / Contextual entirety of 3D-printed wooden sandwich - From prefab to printing in-situ

Lundberg, Rasmus January 2019 (has links)
Projektet syftar till att föreslå en rimlig riktning för hur additiva produktionsmetoder, alltså tillverkningsmetoder som använder lager-på-lager-teknik, kan tänkas påverka arkitekturen, att försöka sätta sig in i teknikerna och komma fram till vilken riktning som upplevs mest givande eller gångbar. Hur ska man nyttja potentialen med den nya tekniken på ett bra sätt? Jag har försökt ta fram en produkt som nyttjar potentialen hos de additiva produktionsmetoderna och som upplevs tänkbar för fullskalig realisering i byggsektorn i en närliggande framtid. Produkten består av en metod för framställning av en sandwichkonstruktion med hög trähalt och troligen lång livslängd. Metoden minskar byggsektorns klimatbelastning och kan ge stora rumsliga kvaliteter och formgivningsmöjligheter. Jag har genom fysiska experiment och utforskande av olika digitala fabrikationsmetoder försökt att visualisera och identifiera möjligheter med dessa nya tekniska hjälpmedel. Genom praktiska tester har jag prövat mina föreställningar av hur dessa metoder kan användas på effektiva sätt. Projektet vidga-des från att initialt omfatta additiva produktionsmetoder till att senare under tillämpningsfasen även omfatta digitala hjälpmedel såsom fotogrammetri och verktyg för parametrisk design. Projektet har resulterat i ett tillvägagångsätt för printning av cellulosabaserade sandwichkonstruktioner i printade formverk av återvinningsbar biokomposit. / The project aims to propose a direction for how additive manufacturing methods can influence architecture, to study the techniques and find out which direction could be perceived as most rewarding or viable. How to use the potential of the new technology in a good way? I have tried to develop a product that utilizes the potential of the additive manufacturing methods and which is conceivable for full-scale realization in the construction sector in the near future. The product consists of a method for producing long lasting sandwich constructions with high wood content. The method reduces the building industry's climate impact and can provide great spatial qualities and design possibilities. Through physical experiments and exploration of various digital fabrication methods, I have tried to visualize and identify possibilities with these new technological aids. Through practical tests, I have tested my ideas of how these methods can be used effectively. The project was expanded from initially studying additive production methods to, later during the application phase, also include digital aids such as photogrammetry and tools for parametric design. The project has resulted in a strategy for printing cellulose-based sandwich constructions in printed molds of recyclable biocomposite.
122

Motorized tensioner systemfor prosthetic hands

Hardell, Felix, Tjomsland, Jonas January 2018 (has links)
Modern research in prosthetic devices and other assistivetechnologies are constantly pushing boundaries. Whilethe technology is impressive, it is still inaccessible for thegreater part of the people in need of it. Advanced devicesare often extremely expensive and require regularly maintenancefrom professionals. Enabling the Future is a globalnetwork of volunteers and was founded to face these problems.They design and 3D-print mechanical prosthetics forpeople in need all over the world.Most of the designs used by Enabling the Future are purelymechanical and do not implement motors. The purposeof this thesis was to take a new approach to the designand construction of low-cost motorized prosthetic hands.By distancing all the electronic components from the hand,including the motor, the project aimed to create a devicecompatible with all current designs of the Enabling the Futurecommunity.To conceptualize this approach a demonstrator was constructedand tested. It utilized a muscle sensor which allowedusers to control the hand by tightening their muscles.The distance between the electronic components andthe prosthetic hand measured approximately one and a halfmeters and still transfered enough force, from the motor tothe hand, to deliver an adequate grip strength. / Modern forskning inom protestillverkning och andrahandikapphjälpmedel gör kontinuerligt stora framsteg. Trotsatt tekniken är imponerade är den fortfarande otillgängligför den största del människor som behöver den. Avanceradehjälpmedel är ofta extremt dyra och kräver kontinuerligtunderhåll från yrkesverksamma. Enabling the Future,ett globalt nätverk av volontärer, grundades för att utmanadessa problem. De konstruerar och tillverkar 3D-skrivnamekaniska proteser för människor med behov över hela världen.De flesta konstruktioner som används av Enabling the Futureär helt mekaniska och använder inga motorer. Syftetmed detta kandidatexamensarbete var att med nya tillvägagångssättkonstruera en billig motoriserad handprotes.Genom att placera all elektronik på en distans från handen,inklusive motorn själv, var tanken att skapa ett systemsom är kompatibelt med de konstruktioner som Enablingthe Future använder.För att förverkliga detta konstruerades en prototyp somtestats. Prototypen använde sig av en muskelsensor somlät användaren kontrollera proteshanden genom att spännasin arm. Distansen mellan de elektriska komponenternaoch protesen var ungefär en och en halv meter, samtidigtsom tillräckligt stor kraft kunde transporteras för att stängahanden med ett tillräckligt grepp.
123

Optical Measurements of High-Viscosity Materials Using Variations of Laser Intensity Incident on a Semi-Rigid Vessel for use in Additive Manufacturing

Pote, Timothy Ryan 16 May 2017 (has links)
Additive manufacturing is a growing field dominated by printing processes that soften and re-solidify material, depositing this material layer by layer to form the printed shape. Increasingly, researchers are pursuing new materials to enable fabrication of a wider variety of associated capabilities. This includes fabrication with high-viscosity materials of many new classes of material compositions, such as doping for magnetic or electrically conducting polymers. These additives complicate the materials deposition process by requiring complex, non-linear calibration to synchronize these new candidate materials with the additive manufacturing software and hardware. In essence, additive manufacturing is highly dependent on identifying the delicate balance between materials properties, hardware, and software-which is currently realized via a time-consuming and costly iterative calibration process. This thesis is concerned with reducing this cost of calibration, in particular by providing a time-based metric based on material viscosity for material retraction at the conclusion of each extrusion. It presents a novel non-contact method of determining the material retraction rate (during reversal of extrusion), by measuring the variation in laser intensity resulting from the deformation of the material reservoir due to change in material pressure. Commercially available laser measurement systems cost more than $20,000 and are limited to 1 μm at a 300 ms (3 Hz) sampling rate. The experimental setup presented in this thesis costs less than $100 and is capable of taking measurements of 1 - 2 μm at a 0.535 ms (1870 Hz) sampling rate. For comparison, the stepper motor driving the material extruder operates at 0.667 ms (1500 Hz). Using this experimental setup, an inverse correlation is shown to exist between the viscosity of a material and the rate at which the material is retracted. Using this correlation and a simplified material analysis process, one can approximate the retraction time necessary to calibrate new materials, thereby significantly improving initial estimated calibration settings, and thus reducing the number of calibration iterations required to ready a new material for additive manufacturing. In addition, the insight provided into the material response can also be used as the basis for future research into minimizing the calibration process. / Master of Science
124

An improved distortion compensation approach for additive manufacturing using optically scanned data

Afazov, S., Semerdzhieva, E., Scrimieri, Daniele, Serjouei, A., Kairoshev, B., Derguti, F. 29 March 2021 (has links)
Yes / This paper presents an improved mathematical model for calculation of distortion vectors of two aligned surface meshes. The model shows better accuracy when benchmarked to an existing model with exceptional mathematical conditions, such as sharp corners and small radii. The model was implemented into a developed distortion compensation digital tool and applied to an industrial component. The component was made of Inconel 718 and produced by laser powder bed fusion 3D printing technology. The digital tool was utilised to compensate the original design geometry by pre-distortion of its original geometry using the developed mathematical model. The distortion of an industrial component was reduced from approximately ±400 µm to ±100 µm for a challenging thin structure subjected to buckling during the build process.
125

Novel Microwave Fluid Sensor for Complex Dielectric Parameter Measurement of Ethanol-Water Solution

Palandoken, M., Gocen, C., Khan, T., Zakaria, Z., Elfergani, I., Zemi, C., Rodriguez, J., Abd-Alhameed, Raed 15 May 2023 (has links)
Yes / In this paper, a 2.45 GHz band microwave sensor design is introduced to be utilized for the dielectric constant determination of ethanol-water solutions. The introduced microwave sensor is composed of two symmetrically positioned, directly coupled inter-connected split-ring resonators with a circular ring-shaped detection area in the middle region, into which a small amount of ethanol-water solution is dropped. The fabricated prototype of the microwave sensor has a total component size of 12 mm x 30 mm on Rogers RO4003 substrate. The sensor measurement performance is numerically evaluated and experimentally validated in good agreement. The introduced microwave sensor has the structural design novelty of possessing the main detection region in a form of a circular hollow where a disposable 3D printed fluid cup can be accommodated for multiple uses. The introduced microwave sensor has technical feasibility to be used as an ingredient identification device for the chemical solutions to figure out complex dielectric parameters of ethanol-water specimens with small, low-cost, reusable, easy-to-fabricate features as well as the determination of volume percentage concentration of ethanol content.
126

3D Printing of Zinc Anode for Zinc Ion Batteries

Amoko, Stephen Adot Oyo 12 1900 (has links)
Recently, 3D printing has received increasing attention for the fabrication and assembly of electrodes for batteries due to the freedom of creating structures in any shape or size, porosity, flexibility, stretchability, and chemistry. Particularly, zinc ion batteries (ZIBs) are favored due to high safety, cheap materials cost, and high volumetric capacity (5,849 mAh/cm3), however, rapid evaporation of Zn due to low melting temperature has limited its 3D printability via conventional laser-based additive manufacturing technique. Here, we develop a printable ink for the fabrication of flexible and 3D printed Zn anode with varied surface areas using the direct ink writing (DIW) method. Our 3D printed porous and high surface area Zn anode structures effectively suppressed the dendrite growth while providing high Zn ion diffusion towards the cathode to significantly enhance the performance of ZIB. By varying filament distancing and path, we 3D printed zinc anode structures with different active surface areas, surface area to volume ratio, porosity, flexible and multiple layer structures that can be incorporated on any device. Carbon in the composite improved conductivity, and mechanical stability of 3D printed zinc anode. Our 3D printed composite anodes allowed flexible designing of batteries surpassing conventional battery designs such as coin cells or pouch cells and can be used to design printed energy storage systems.
127

Imaging and Characterization of the Multi-scale Pore System of Microporous Carbonates

Hassan, Ahmed 11 1900 (has links)
Microporous carbonates host a significant portion of the remaining oil-in-place in the giant carbonate reservoirs of the Middle East. Improved understanding of petrophysical and multi-phase flow properties at the pore-scale is essential for the development of better oil recovery processes. These properties strongly depend on the 3D geometry and connectivity of the pore space. In this study, we harnessed the unique capabilities of fluorescence confocal laser scanning microscopy (CLSM) to capture both macroporosity and microporosity, down to 0.1 µm, to provide a more representative 3D representation of pore space compared to traditional methods. The experimental procedure developed was specifically designed to enable highresolution confocal 3D imaging of the pore space of carbonate systems. The protocol aims to render carbonates more "transparent" to CLSM by imaging etched epoxy pore casts of the sample and minimizing CLSM signal scattering. The resulting highquality 3D images of the multi-scale pore space allow more reliable petrophysical interpretation and prediction of transport properties. Additionally, we present a robust pore imaging approach that correlates 2D images produced by scanning electron microscopy (SEM) with the 3D models produced by CLSM that cover a range of scales, from millimeters in 3D to micrometers in 2D. For the first time, multi-color fluorescence confocal imaging was employed to characterize the geometric attributes of a porous medium. We foresee that the protocol developed in this study could be used as a standard protocol for obtaining high-quality 3D images of epoxy pore casts using confocal microscopy, and could contribute to improved characterization of micritic carbonate reservoirs and oil recovery methods. We also demonstrate the advantages of multi-scale and multi-color confocal images in realizing more accurate evaluations of petrophysical properties. Finally, we demonstrate that micro 3D printing (two-photon polymerization) can potentially be used to fabricate micromodels with sufficient resolution to capture the geometric attributes of micritic carbonates and that can replicate the inherent 3D interconnectivity between macro- and micro-pores.
128

3D Printed Self-Activated Carbon Electrodes for Supercapacitor Applications / Third Printed Self-Activated Carbon Electrodes for Supercapacitor Applications

Disi, Onome Aghogho 07 1900 (has links)
This study investigated a new approach to achieving high energy density supercapacitors (SCs) by using high surface area self-activated carbon from waste coffee grounds (WCGs) and modifying 3D printed electrodes' porous structure by varying infill density. The derived activated carbons' surface area, pore size, and pore volume were controlled by thermally treating the WCGs at different temperatures (1000˚C, 1100˚C, and 1200˚C) and post-treating with HCL to remove water-soluble ashes and contaminants that block activated carbon pores. Surface area characterization revealed that the carbon activated at 1000˚C had the highest surface of 1173.48 m2 g-1, and with the addition of HCL, the surface area increased to 1209.35 m2 g-1. This activated carbon was used for fabricating the electrodes based on the surface area and having both micropores and macropores, which are beneficial for charge storage. Direct ink writing (DIW) method was utilized for 3D printing SC electrodes and changing the electrode structure by increasing the infill densities at 30%, 50%, and 100%. Upon increasing the infill densities, the electrodes' mass increased linearly, porosity decreased, and the total surface area increased for the 30% and 50% infill electrodes but decreased for the 100% infill electrode. Cyclic voltammetry (CV) test on the assembled SC showed the highest specific capacitance and energy density of 5.81 F g-1 and 806.93 mWh kg-1 at 10 mV s-1, respectively, for the electrode printed at 50% infill density.
129

Additive Manufacturing Filled Polymer Composites for Environmental Contaminants: Material Extrusion Processing, Structure and Performance

Kennedy, Alan James 18 December 2023 (has links)
Research interest in Additive Manufacturing (AM) as an enabling technology for customizable parts is rapidly expanding. While much AM research focus is on high performance feedstocks and process optimization to obtain parts with improved mechanical properties, interest in the environmental applications of AM has recently increased. The lower cost and greater accessibility AM is leading to novel environmental research solutions in wastewater treatment and toxicity reduction by capitalizing on the increased affordability and accessibility of 3D printing (3DP) technologies for customizable, high surface area structures. The novelty and focus of this dissertation is exploration of Material Extrusion (MatEx) based Fused Filament Fabrication (FFF) of filled polymer composites as a disruptive technology enabler for deployable and retrievable structures in environmental media for adsorption, destruction and toxicity reduction of harmful chemicals. This dissertation addresses research questions that generally answer, "why AM for environmental applications?". The inherent layer-by-layer design provides larger surface area structures for interaction with contaminated media. Polylactic acid (PLA) was selected due to its green sources and biocompatibility relative to synthetic polymers and its wide processing window allowing shear thinning and "printability" despite the elevated viscosity and modulus of highly filled composites. The filler selected for contaminant adsorption was microporous zeolite, which has affinity for ammonia, radionuclides and Per- and Polyfluorinated Substances (PFAS). The filler selected for contaminant destruction was photocatalytic TiO2 nanoparticles which can degrade organic chemicals, harmful algal bloom toxins and PFAS. A preliminary research hurdle was overcome by demonstrating that immobilization of zeolite and TiO2 in a PLA binder matrix did not prevent adsorption or free radical release, respectively. The first major research objective involved investigation of high surface area printed PLA-zeolite geometries with different zeolite loadings and found that while ammonia was reduced, there were diminishing returns with increased loading in terms of mass standardized adsorptive performance due to insufficiently exposed zeolite. The research solution leveraged AM print process parameters to increase the macroporosity of the printed composite structure to create voids and channels allowing water infiltration and chemical adsorption to zeolite. Faster printing of larger roadways generated macrostructural voids that were maintained by extrusion at lower temperature for rapid solidification. The second research objective involved compounding different loadings and dispersion states of TiO2 in PLA to demonstrate immobilization of TiO2 closer to UV-light penetration water improves photocatalysis. Higher 32% w/w TiO2 loadings were heavily agglomerated and more difficult to print process due to high viscosity, rapid liquid-solid transition (G'>G") and particle network recovery during printer retractions, leading to nozzle clogging. Lower 20% w/w loading was more conducive to larger production printing due to lower viscosity, longer viscosity recovery times for retractions and thus generally a wider processing window. While altering twin screw processing parameters reduced TiO2 agglomerates in filaments, leading to increases in crystallinity (due to seeding effects and chain scission) and lower viscosity recovery, photocatalytic performance was not significantly improved. Evidence presented showed that larger particle agglomerates were more toward the inside of printed surfaces and thus less available to UV-light irradiation. This location of larger particles is supported by previous theoretical and empirical investigations showing larger particles migrate at a faster velocity away from the outer walls of confined extrudates within non-Newtonian flow fields due to normal forces, leaving more smaller particles toward outer surfaces. This research provided novel contributions to the environmental and AM research communities and pioneered a convergence of these fields into an interdisciplinary community of practice focused on better characterization and processing in environmental applications to improve structure-environmental property relationships. Future research should build on these findings to enhance performance through multi-functional materials that adsorb and destroy contaminants. The reactive surface area should be further increased through by high surface area designs and print parameter optimized porous structures providing a continuum of meso- to microporosity as confirmed by chemical flux and mass transfer studies for additional AM technologies (e.g., Direct Ink Write). / Doctor of Philosophy / Engineers and hobbies alike have great interest in Additive Manufacturing (AM), or 3D Printing, to customize parts and new designs. More recently, environmental scientists and engineers have turned to 3D printing to solve environmental problems due to the lower cost and user-friendliness of desktop machines. This research dissertation focuses on how 3D printing can allow for iterative improvements in customizable, high surface area structures to reduce chemical concentrations in water by either adsorbing or destroying the chemicals. Water is clearly a critical resource for ecosystems, recreation and drinking supplies as national security, human and ecosystem health are tied to clean water. This research addresses why 3D printing is interesting and effective for environmental solutions. Briefly the layer-by-layer design provides larger surface area structures for interaction with contaminated media. The common 3D printer feedstock Polylactic Acid (PLA) was selected since it is non-toxic and can be relatively easy to print even if modified by adding rigid filler particles for research. Micron-scale (zeolite) and nano-scale (Titanium Dioxide) particles were mixed with the polymer to make printable filaments to adsorb and destroy contaminants, respectively. This research demonstrated the proof-of-concept by removing ammonia, methylene blue dye and a harmful algal toxin from water. The materials produced are also applicable to both conventional organic pollutants and emerging contaminants of concern in the popular news such as Per- and Polyfluorinated Substances (PFAS), which were used as flame retardants and non-stick surfaces. This research ties the material properties of the experimental micro- and nano-composite filaments to how the materials extrude and solidify during 3D printing and how well the resulting printed structures work for reducing contaminant levels in water. Altering the parameters and conditions at which these materials are processed and 3D printed can significantly change their structure, density, porosity and distribution of particles and in turn increase effectiveness. The results provide new contributions to both the environmental and AM research communities and pioneers interdisciplinary collaborative ideas for these different subject matter experts to work together to better understand how handling and processing of these materials can improve their performance in environmental applications. New work should leverage the ideas and principles presented here to further improve performance, ease of production and scale-up of multifunctional material structures for multiple classes of chemicals that are of concern in surface and drinking water.
130

3D PRINTING TO CONTROL DRUG RELEASE FROM KERATIN HYDROGELS

Brodin, Erik W., V 17 July 2018 (has links)
No description available.

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