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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.
21

Fused deposition modeling of API-loaded mesoporous magnesium carbonate

Abdelki, Andreas January 2020 (has links)
In this thesis, the incorporation of drug loaded mesoporous magnesium carbonate as an excipient for the additive manufacturing of oral tablets by fused deposition modeling was investigated. Cinnarizine, a BCS class II drug, was loaded into the pores of the mesoporous material via a soaking method, corresponding to a drug loading of 8.68 wt%. DSC measurements on the loaded material suggested that the drug was partially crystallized after incorporation, meanwhile the XRD diffractogram implied that the drug was in a state lacking long range order. The drug loaded material was combined with two pharmaceutical polymers, Aquasolve LG and Klucel ELF, and extruded into filaments with a single screw extruder. Filaments of Klucel ELF and drug loaded Upsalite (30:70 wt% ratio) were successfully implemented for the printing oral tablets, in contrast to the Aquasolve LG based filaments which were difficult to print due to thickness variations and non-uniform material distributions. The drug content obtained by TGA suggested drug loadings of 7.71 wt% and 2.23 wt% in the drug loaded Upsalite and tablets respectively. Dissolution studies using an USP II apparatus showed a slower API-release from the tablets in comparison to the crystalline drug, most probably due to slow diffusion of drug species through the polymeric matrix. For future studies, pharmaceutical polymers with higher aqueous solubility should be investigated in order to thoroughly examine the potential of utilizing the immediate release property of Upsalite.
22

Investigation on 3D-printing of homopolymer polypropylene

Shah, Nilay Gaurang 26 April 2023 (has links)
No description available.
23

Additive manufacturing : Optimization of process parameters for fused filament fabrication

Hayagrivan, Vishal January 2018 (has links)
An obstacle to the wide spread use of additive manufacturing (AM) is the difficulty in estimating the effects of process parameters on the mechanical properties of the manufactured part. The complex relationship between the geometry, parameters and mechanical properties makes it impractical to derive an analytical relationship and calls for the use of a numerical model. An approach to formulate a numerical model in developed in this thesis. The AM technique focused in this thesis is fused filament fabrication (FFF). A numerical model is developed by recreating FFF build process in a simulation environment. Machine instructions generated by a slicer to build a part is used to create a numerical model. The model acts as a basis to determine the effects of process parameters on the stiffness and the strength of a part. Determining the stiffness of the part is done by calculating the response of the model to a uniformly distributed load. The strength of the part depends on it's thermal history. The developed numerical model serves as a basis to implement models describing the relation between thermal history and strength. The developed model is suited to optimize FFF parameters as it encompass effects of all FFF parameters. A genetic algorithm is used to optimize the FFF parameters for minimum weight with a minimum stiffness constraint. / Ett hinder för att additiv tillverkning (AT), eller ”3D-printing”, ska få ett bredare genomslag är svårigheten att uppskatta effekterna av processparametrar på den tillverkade produktens mekaniska prestanda. Det komplexa förhållandet mellan geometri och processparametrar gör det opraktiskt och komplicerat att härleda analytiska uttryck för att förutsäga de mekaniska egenskaperna. Alternativet är att istället använda numeriska modeller. Huvudsyftet med denna avhandling har därför varit att utveckla en numerisk modell som kan användas för att förutsäga de mekaniska egenskaperna för detaljer tillverkade genom AT. AT-tekniken som avses är inriktad på Fused Filament Fabrication (FFF). En numerisk modell har utvecklats genom att återskapa FFF-byggprocessen i en simuleringsmiljö. Instruktioner (skriven i GCode) som används för att bygga en detalj genom FFF har här översatts till en numerisk FE-modell. Modellen används sen för att bestämma effekterna av processparametrar på styvheten och styrkan hos den tillverkade detaljen. I detta arbete har strukturstyvheten hos olika detaljer beräknats genom att utvärdera modellens svar för jämnt fördelade belastningsfall. Styrkan, vilket är starkt beroende på den tillverkade detaljens termiska historia, har inte utvärderats. Den utvecklade numeriska modellen kan dock fungera som underlag för implementering av modeller som beskriver relationen mellan termisk historia och styrka. Den utvecklade modellen är anpassad för optimering av FFF-parametrar då den omfattar effekterna av alla FFF-parametrar. En genetisk algoritm har använts i detta arbete för att optimera parametrarna med avseende på vikt för en given strukturstyvhet.
24

The OpenXO. 3D Printed Modular Exoskeleton Segment

Þorgerirsson, Árni Þór January 2023 (has links)
Exoskeletons are wearable devices that enhance or supplement the user’s natural abilities. They have been demonstrated to be efective in alleviating pain, reducing work related injuries, improving working conditions, and can play a pivotal role in improving recovery times and recovery outcomes. Commercial exoskeletons are expensive, specialised and not easily accessible to the average user. This thesis describes the design and manufacturing processes for the OpenXO, an open-source knee exoskeleton. The focus of the thesis is the design and manufacture of the exoskeleton drive system. It implements a cycloidal drive design. Additionally, a method of designing tapered crossed roller bearings was developed that allows for easy integration into elements of the drive system. The open source aspect is further supported by designing the OpenXO around commercially available additive manufacturing technologies. Rapid prototyping and iterative test-based design methods were used in conjunction with empirical testing and validation of both the design and manufacturing methods. Performance validations were conducted on an unpowered exoskeleton. The tests focus on ease of use and comfort. Validation on the exoskeleton and its components was performed at various stages during the design process. The resulting drive design was signifcantly lighter than commercially available solutions. The stator design implemented allows for press ft accuracy between the rotor and stator while allowing for smooth rotation. The fully assembled exoskeleton was tested by 5 individuals. All participants performed tasks to test the usability the exoskeleton in common day to day activities. The participants managed to perform several tasks with ease. However, the exoskeleton was prone to misalignment in specifc circumstances. Gait analysis on a user wearing the exoskeleton shows that the exoskeleton does infuence gait patterns. However, the user does not experience signifcant impact on their perceived range of motion. These tests do not demonstrate the efectiveness of the exoskeleton when it comes to powered assistance. Further work is needed to test and validate the powered assist functionality of the exoskeleton. / Eksoskeletonit ovat puettavia laitteita, jotka parantavat tai täydentävät käyttäjän luonnollisia kykyjä. Niiden on osoitettu olevan tehokkaita kipujen lievittämisessä, työtapaturmien vähentämisessä, työolosuhteiden parantamisessa ja niillä voi olla keskeinen rooli paranemisaikojen ja toipumistulosten parantamisessa. Kaupalliset eksoskeletonit ovat kalliita, erikoistuneita eivätkä tavallisen käyttäjän helposti saatavilla. Tämä opinnäytetyö kuvaa avoimen lähdekoodin polven eksoskeleton OpenXO:n suunnittelu-ja valmistusprosessit. Erityisesti painopiste on sykloidiseen käyttöjärjestelmään perustuvan ulkopuolisen tukirankajärjestelmän suunnittelussa ja valmistuksessa. Lisäksi kartiorullalaakereiden suunnittelumenetelmä kehitettiin siten, että se mahdollistaa helpon integroinnin käyttöjärjestelmän elementteihin. Avoimen lähdekoodin näkökulmaa tuetaan edelleen suunnittelemalla OpenXO kaupallisesti saatavilla olevien lisäaineiden valmistustekniikoiden ympärille. Nopeaa prototyyppiä ja iteratiivisia testipohjaisia suunnittelumenetelmiä käytettiin sekä suunnittelu-että valmistusmenetelmien empiirisen testauksen ja validoinnin yhteydessä. Suorituskyvyn validointi suoritettiin tehottomalla eksoskeletonilla 5 vapaaehtoisen poolissa. Testit suuntautuivat arjen yleisten toimintojen ympärille ja keskittyivät pääasiassa helppokäyttöisyyteen ja käyttömukavuuteen. Eksoskeleton ja sen komponenttien validointi suoritettiin suunnitteluprosessin eri vaiheissa. Tuloksena saatu käyttörakenne oli huomattavasti kevyempi kuin kaupallisesti saatavilla olevat ratkaisut. Toteutettu staattorin rakenne mahdollisti roottorin ja staattorin välisen puristussovituksen tarkkuuden säilyttäen samalla tasaisen pyörimisen. Osallistujat onnistuivat suorittamaan suurimman osan tehtävistä helposti. Eksoskeleton oli kuitenkin altis kohdistusvirheelle tietyissä olosuhteissa. Eksoskeletonia käyttävän käyttäjän kävelyanalyysi osoittaa, että ulkoinen luuranko vaikuttaa kävelykuvioihin, mutta käyttäjä ei koe merkittävää vaikutusta havaittuun liikerataan. Siitä huolimatta tarvitaan lisätyötä eksoskeletonin tehollisen aputoiminnon testaamiseksi ja validoimiseksi. / <p>Presentation conducted online via the Zoom video conferencing platform.</p>
25

The Ugly Side of the Beautiful Game - Hooliganism in French Football

Amado, Carlos Josue 11 November 2008 (has links) (PDF)
Football violence was a rare phenomenon in France until the nineteen eighties. Harsh economic times coupled with the challenges of unemployment brought a different type of fanatic to football stadia. To vent their frustration about the economic difficulties of their time, some fans found an easy scapegoat: the increasing number of African immigrants in France. These fans, known as hooligans, have become organized and can be found supporting most major French football clubs, disrupting what once was a relatively tranquil national pastime. This thesis traces their development in France, looks at what they borrowed from Italian and English fan groups, and suggests how their organization is now uniquely French.

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