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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.
101

Micromechanical Numeric Investigation of Fiber Bonds in 3D Network Structures.

AZİZOĞLU, YAĞIZ January 2014 (has links)
In manufacturing of paper and paperboard, optimized fiber usage has crucial importance for process efficiency and profitability. Dry strength of paper is one of the important quality criteria, which can be improved by adding dry strength additive that affect fiber to fiber bonding. This study is using the micromechanical simulations which assist interpretation of the experimental results concerning the effect of strength additives. A finite element model for 3D dry fiber network was constructed to study the effect of bond strength, bond area and the number of bonds numerically on the strength of paper products. In the network, fibers’ geometrical properties such as wall thickness, diameter, length and curl were assigned according to fiber characterization of the pulp and SEM analyses of dry paper cross-section. The numerical network was created by depositing the fibers onto a flat surface which should mimic the handsheet-making procedure. In the FE model, each fiber was represented with a number of quadratic Timoshenko beam elements where fiber to fiber bonds were modelled by beam-to-beam contact. The contact model is represented by cohesive zone model, which needs bond strength and bond stiffness in normal and shear directions. To get a reasonable estimate of the bond stiffness, a detailed finite element model of a fiber bond was used. Additionally, the effect of different fiber and bond geometries on bond stiffness were examined by this model since the previous work [13] indicated that the bond stiffness can have a considerable effect on dry strength of paper. The network simulation results show that the effect of the strength additive comes through improving the bond strength primarily. Furthermore, with the considered sheet structure, both the fiber bond compliance and the number of bonds affect the stiffness of paper. Finally, the results of the analyses indicated that the AFM measurements of the fiber adhesion could not be used directly to relate the corresponding changes in the bond strength. The fiber bond simulation concluded that fiber wall thickness has the most significant effect on the fiber bond compliance. It was also affected by micro-fibril orientation angle, bond orientation and the degree of pressing.
102

Implementering och användning av digitala verktyg med fokus på nyttjande av 3D-modell i produktion / Implementation and usage of digital tools with focus on utilization of 3D models in production

Mohammed, Lina, Al Rifai, Rama January 2023 (has links)
Digitaliseringen inom byggbranschen har inte kommit långt i dess utveckling i jämförelse med andra branscher, men det finns en ökande insikt om att ökad digitalisering kan leda till betydande effektiviseringar. I detta arbete har fokus legat på att undersöka användningen av digitala verktyg, särskilt 3D-modellen, i produktionsskedet. Detta beror på att utvecklingen inom produktionen har varit relativt långsam jämfört med andra skeden. För närvarande används digitala verktyg och 3D-modellen främst i projekterings- och förvaltningsprocessen för att bland annat skapa digitala modeller, samordna olika discipliner och fungera som beräkningsverktyg. Trots framstegen kvarstår frågan om hur dessa verktyg, särskilt 3D-modellen, bör tillämpas och användas i produktionsskedet på ett mer omfattande sätt. Därför är målet med denna rapport att föreslå hur arbetssättet kan utvecklas inom produktionen för att öka användningen av 3Dmodellen och uppnå en mer effektiv arbetsprocess inom entreprenadföretag. Genom att utforska och identifiera de potentiella fördelarna med att använda 3D-modellen i produktionsskedet kan vi identifiera områden där den kan integreras på ett mer meningsfullt sätt. Rapporten undersöker eventuella hinder och brister i 3D-modellen som kan förhindra en bredare användning i produktionen. Genom att identifiera dessa kan det föreslås åtgärder och strategier för att övervinna dem och främja en mer omfattande användning av digitala verktyg samt 3D-modell i byggproduktionen. Metoden som har använts under studiens gång för att undersöka detta är både kvalitativ, som innefattar intervjuer, och kvantitativ i form av litteraturstudier. Intervjuerna genomfördes på fem arbetsledare som är verksamma på olika projekt på ett och samma större entreprenadföretag i Malmö. Litteraturstudier användes för att komplettera förståelsen och dra nytta av tidigare forskning. En viktig avgränsning i arbetet är att samtliga projekt är ungefär densamma i omfattning och storlek, detta för att bidra till ett mer tillförlitligt och jämförbart resultat. Resultatet av intervjuerna visar att arbetsledare nyttjar tillgång till digitala verktyg och 3Dmodell i produktion idag, dock till en begränsad omfattning. Det finns resurser för att använda sig av dem, men det finns inte en tydlig arbetsmetodik för det. Det finns dessutom diverse brister i 3D-modellen som gör det mindre tillförlitligt samt ökar svårigheten med att använda modellen. I det fallet faller arbetsledare och resterande arbetare tillbaka till att använda ritningar som komplement. Studiens slutsats är att det ligger en stor vikt vid att ha en tydlig presenterad arbetsmetod i början av ett projekt. Entreprenadföretagen bör ta fram arbetssätt som upplyser, demonstrerar samt utbildar samtliga arbetsledare om vilka funktioner 3D-modellen har, hur den kan effektivisera det vardagliga arbetet samt hur den kan nyttjas. Detta skulle bidra till mer motivation hos samtliga i produktionen samt ökad användning av de digitala verktygen. Dessutom påvisar studien vikten av en kontinuerligt uppdaterad 3D-modell samt ökad detaljhantering redan från projekteringen, som förutsättning för ökad användning av 3D-modell i produktion. / The digitalization of the construction industry has not advanced significantly compared to other industries, but there is a growing recognition that increased digitalization can lead to significant efficiency improvements. This study focuses on investigating the use of digital tools, particularly the 3D model, in the production phase. Therefore, the goal of this report is to propose ways to develop the workflow in production to increase the use of the 3D model and achieve a more efficient work process within construction companies. By exploring and identifying the potential benefits of using the 3D model in the production phase. The methodology employed in this study encompasses both qualitative aspects, such as interviews, and quantitative elements, through literature reviews. The interviews were conducted with five construction supervisors involved in different projects within a major construction company in Malmö. The interview findings indicate that construction supervisors currently utilize digital tools and the 3D model in production to a limited extent. While resources are available for their use, there is a lack of clear methodologies. Other challenges highlighted in the report include various deficiencies in the 3D model, which make it less reliable and increase the difficulty of its utilization. The study concludes that a significant emphasis should be placed on establishing a clearly presented workflow at the beginning of a project. Construction companies should develop approaches that inform, demonstrate, and educate all construction supervisors about the functionalities of the 3D model, how it can streamline daily work, and how it can be utilized. Furthermore, the study highlights the importance of maintaining an updated 3D model throughout the project and enhancing detail management from the design phase as a prerequisite for increased usage of the 3D model in production.
103

Kvalitetssäkrad arbetsprocess vid 3D-modellering av byggnader : Baserat på underlag från ritning och 3D-laserskanning / Quality assurance work process for 3D modeling of buildings : Based on data from drawing and 3D laser scanning

Fjärdsjö, Johnny, Muhabatt Zada, Nasir January 2014 (has links)
Tidigare vid ombyggnation, försäljning och förvaltning av byggnader som var uppförda innan 80-talet utgick fastighetsägarna från enkla handritade pappersritningar. Det är en svår utmaning att hålla ritningen uppdaterad till verkliga förhållanden d.v.s. relationsritning. För ca 25 år sedan (i början på 80-talet) byttes papper och penna ut mot avancerade ritprogram (CAD) för framtagning av ritningar. Idag används CAD i stort sett för all nyprojektering och de senaste åren har utvecklingen gått mot en större användning av 3D-underlag än tidigare 2D-ritningar. Den stora fördelen med att projektera i 3D är att en virtuell modell skapas av hela byggnaden för att få en bättre kontroll av ingående byggdelsobjekt och även att fel kan upptäckas i tidigare skeden än på byggarbetsplatsen. Genom att börja bygga en virtuell byggnad i 3D från första skedet och succesivt fylla den med mer relevant information i hela livscykeln får man en komplett informationsmodell. Ett av kraven som ställs på fastighetsägarna vid ombyggnation och förvaltning är att tillhandahålla korrekt information och uppdaterade ritningar. Det skall vara enkelt för entreprenören att avläsa ritningarna. I rapporten beskrivs en effektiviserad arbetsprocess, metoder, verktyg och användningsområden för framtagning av 3D-modeller. Detta arbete avser att leda fram till en metodbeskrivning som skall användas för erfarenhetsåterföring. Arbetet skall också vara ett underlag som skall användas för att beskriva tillvägagångsättet att modellera från äldre ritningar till 3D-modeller. Metodbeskrivningen kommer att förenkla förståelsen för modellering för både fastighetsägaren och inom företaget, samt höja kvalitén på arbetet med att skapa CAD-modeller från de olika underlag som används för modellering. / The use of hand drawn construction model was the only way of development, rebuilding, sales and real estate management before the 80’s. However, the challenge was to preserve the drawings and maintain its real condition. To make things work faster and easier the development of advanced drawing software (CAD) was introduced which replaced the traditional hand drawn designs. Today, CAD is used broadly for all new constructions with a great success rate. However, with the new advanced technology many engineers and construction companies are heavily using 3D models over 2D drawings. The major advantage of designing in 3D is a virtual model created of the entire building to get a better control of input construction items and the errors can be detected at earlier stages than at the construction sites. By modifying buildings in a virtual model in three dimensions yet at the first stage and gradually fill it with more relevant information throughout the life cycle of buildings to get a complete information model. One of the requirements from the property owners in the redevelopment and management is to provide accurate information and updated drawings. It should be simple for the contractor to read drawings. This report describes a streamlined work processes, methods, tools and applications for the production of 3D models. This work is intended to lead to a methodology and to be used as well as for passing on experience. This report will also be a base to describe the approach to model from older drawings into 3D models. The method description will simplify the understanding of model for both the property owners and for companies who creates 3D models. It will also increase the quality of the work to create CAD models from the different data used for modeling.
104

Development of a method to create subject specific cochlear models for electric hearing

Malherbe, Tiaan Krynauw 26 October 2011 (has links)
Cochlear implants are electronic devices intended for restoring hearing to the profoundly deaf. Unfortunately the degree of restored hearing varies greatly between subjects. To investigate some of the mechanisms that determine this variability, mathematical models of the auditory system are used. The level of detail that these models incorporate varies greatly. The present study describes the development of a method to create high detail, subject specific cochlea models. μ-CT scans and photomicrographs were used to obtain the morphology and histology of a specific guinea pig cochlea. A 3D model was constructed from this data and the finite element method was used to determine the potential distribution inside the cochlea. The potential distribution was calculated for different stimulus protocols applied to different modelled electrodes. A neuron model was then used to obtain neural excitation profiles. The modelled excitation profiles were compared to data from literature and it was found that this model is valid and can be used as a tool in electric hearing research. The model output was also compared to brainstem response data from the specific subject to assess the degree to which this model can predict brain stem data from a specific subject. Possible improvements to the model were also discussed. / Dissertation (MEng)--University of Pretoria, 2009. / Electrical, Electronic and Computer Engineering / unrestricted
105

The influence of torsional resistance of the deck on the dynamic response of a high-speed railway bridge : Case study: Ulla River Viaduct

Sanroman Cervero, Claudia January 2017 (has links)
Understanding how different parameters affect the dynamic response of high-speed railway bridges is crucial to selecting an efficient structural form. Despite existing numerous publications within this field, only few address the importance of torsional deformations. The main objective of this thesis is to investigate the influence of the torsional resistance of the deck on the dynamic response of an existing bridge. Ulla River Viaduct is presented as a case study, allowing to analyse some aspects of its design and what their alteration entails. To this end, 6 different 3D FE models are compared, 5 of which show a modification from the original configuration. In addition, several positions of the train are considered to contrast the effects when the torsional modes are excited. The performed dynamic calculations are based on the implicit direct integration procedure. The analysis of the case study demonstrates the benefit of closing the torsional circuit of the deck. The results also evidence the need of including torsional effects in its dynamic assessment when low values of torsional rigidity are considered. All this is not easy when simplified 2D or 3D beam models are used. As a final remark, the original design of the Ulla River Viaduct is found highly efficient from a dynamical point of view.
106

3D Geological Modelling of the Subsurface Adjacent to Cementa’s Quarry in Skövde, Sweden / Geologisk 3D modellering av närområdet till Cementas gruva i Skövde

Larsson, Minna January 2022 (has links)
Limestone is one of the main components of cement production. Limestone has been quarried in Skövde, Sweden, since the end of 19th century and Cementa AB has been operating the quarry since 1973. Aside from limestone, there are also Alum shale of Cambrian age, mudstones as well as bentonite layers of Ordovician age present in the quarry.  The production of cement evidently is important for Sweden’s infrastructure, and the quarry in Skövde is one of few known locations in the country with limestone with the right composition. Therefore, it is important to increase the knowledge regarding the character of the limestone to make accurate predictions for the future regarding the cement production. The geological knowledge of the area is already extensive; however, the aim of this thesis is to expand this knowledge further by constructing a 3D geological model. The data which has been used to construct the model are field observations, drill core data, chemical data, high-resolution pictures (photogrammetry) and resistivity measurements (field and samples). The resistivity measurements were done using the multiple gradient array, and apparent resistivity was inverted using Res2Dinv. The geological modelling was done using Leapfrog geo (© Seequent Systems, Incorporated). Two models have been proposed as a result of this project; one where high-grade limestone of lesser quality and whitestone has been regrouped with two other units (A) and one including all units (B). In the most recent drilling campaign, the nomenclature used to distinguish the units has been modified and does not differentiate high-grade limestone of lesser quality and whitestone from the rest. This affects coherence of the model and for this reason two models have been built. Both models show roughly flat lying units in the area of interest. Both low-grade limestone and lower waste stone units have consistent thickness in both models. The major difference between the models is how the high-grade limestone unit is modelled as a consequence of the additional units in model B. The result from the resistivity measurements shows unexpectedly low values, when compared to values from the literature as well as the measurements on hand samples from the quarry. The reason for these low values is still unclear, and therefore resistivity data has been used with caution. Considering this, it appears that resistivity measurements is not a suitable technique to characterize the subsurface in this particular area.  The models produced in this project provides information regarding thickness and extent of the units and overlying soil. As such, the new knowledge can be used to plan future prospecting campaigns, make projections, and estimates within current mining permits and evaluate how future mining can be conducted. / Kalksten är huvudkomponenten när det kommer till cementproduktion, vilken också behöver ha en specifik kemi för att vara lämplig att tillverka cement av. Kalksten av denna specifika kvalité har brutits i Skövde, Sverige, sedan slutet av 1800-talet. Cementproduktionen startade dock 1924 och Cementa köpte upp gruvan och fabriken 1973. I brottet finns förutom kalksten även alunskiffer, slamsten och bentonitlager. Vidare finns det två olika kvalitéer på kalkstenen, en med högt kalciumoxidvärde och en med lägre kalciumoxidvärde. Totalt representerar de formationer som finns i gruvan en 50 miljoner år lång historia av sedimentation. Cement utgör en grundläggande del för Sveriges infrastruktur, och brottet i Skövde är en av få platser i landet med en kalksten som har rätt kemi. Därmed är det viktigt att utöka kunskapen gällande karaktären på kalkstenslagren i och vid brottet för att kunna göra mer korrekta uppskattningar om Sveriges framtida cementproduktion. I dagsläget är kunskapen om geologin i och kring gruvan omfattande tack vare bland annat tidigare prospekteringskampanjer. Syftet med detta arbete är utöka den geologiska kunskapen ytterligare genom att konstruera en geologisk 3D modell. Denna geologiska 3D modell har skapats av data såsom borrhålsdata, resistivitetsmätningar samt drönarbilder för att bättre karakterisera de olika geologiska formationerna. På grund av att indelningen av de geologiska enheterna har varit olika mellan de tidigare prospekteringskampanjerna har två 3D modeller med olika upplösning skapats i stället för en. Modelleringen har fokuserats på ett område nordväst om nuvarande brytområde. Båda modellerna har sub-horisontella geologiska enheter inom intresseområdet. Vidare har modellerna liknande tjocklek och utbredning på enheterna i sin övre del, men skiljer sig åt längre ner. Detta på grund av att den ena modeller har flera enheter, vilket således även påverkar närliggande enheter. Dessa två modeller har utökat den geologiska kunskapen om området, till exempel de geologiska enheternas mäktighet och utbredning, samt hur mäktigt jordtäcket i området är. Denna nya kunskap kan användas för att planera och estimera hur brytning kan ske i framtiden. Det är dock viktigt att poängtera att det är modeller som skapats, vilka är antaganden av verkligheten.
107

Pro-oxidative and Pro-inflammatory Mechanisms of Brain Injury in Experimental Animal and 3D Cell Culture Model Systems

Cho, Hyung Joon 27 May 2015 (has links)
The pro-oxidative and pro-inflammatory mechanisms have been implicated in various human diseases including neurological and psychiatric disorders. However, there is only limited information available on the etiology in the progression of neurological damage to brain. The emergence of tissue engineering with the growing interest in mechanistic studies of brain injury now raises great opportunities to study complex physiological and pathophysiological process in vitro. Therefore, the prime goals of this study include: (1) Determination of the molecular and cellular mechanisms responsible for blast- and radiation-induced brain injuries and (2) Development of a three-dimensional (3D) model system in order to mimic in vivo-like microenvironments to further broaden our knowledge in pro-oxidative and pro-inflammatory mechanisms and their cellular responses within 3D constructs. In the first study, we demonstrated that blast exposure induced specific molecular and cellular alterations in pro-oxidative and pro-inflammatory environments in the brain and neuronal loss with adverse behavioral outcome. The results provide evidence that pro-oxidative and pro-inflammatory environments in the brain could play a potential role in blast-induced neuronal loss and behavioral deficits. In the second study, we investigated that fractionated whole-brain irradiation induced specific molecular and cellular alterations in pro-oxidative and pro-inflammatory environments in the brain along with elevation of reactive oxygen species (ROS)-generating protein (NOX-2) and microglial activation. Additionally, the contribution of NOX-2 in fractionated whole-brain radiation-induced oxidative stress was observed by dramatic amelioration of ROS generation after pharmacological inhibition of NOX-2. These results support that NOX-2 may play a pivotal role in fractionated whole-brain radiation-induced pro-oxidative and pro-inflammatory pathways in mouse brain. In the third study, we developed an in vitro 3D experimental model of brain inflammation by encapsulating microglia in collagen hydrogel with computational analysis of 3D constructs. The results indicated that our newly developed in vitro 3D model system provides a more physiologically relevant environment to mimic in vivo responses. In conclusion, these data may be beneficial in defining a cellular and molecular basis of pathophysiological mechanisms of brain injuries. Furthermore, it may provide new opportunities for preventive and therapeutic interventions for patients with brain injuries and associated neurological disorders. / Ph. D.
108

3D tombs modeling by simple tools

Aglan, Hassan 20 April 2016 (has links) (PDF)
New archaeological research was carried out between 2009 and 2011 by the Ministry of State for Antiquities (MSA) at central Dra’ Abu el-Naga. Joining the MSA excavation team in the field in 2009, the author has been studying the findings from this area since then. The excavation site is situated ca. 700 km south of Cairo, opposite the modern city of Luxor in Upper Egypt on the western side of the Nile. Dra\' Abu el-Naga is the modern name of the northern area of the extended necropolis. Central Dra’ Abu el-Naga lies to the north of the causeway of queen Hatshepsut and just south of the German and Spanish concessions, overlooking the valley where a temple of Amenhotep I was once erected. The tombs are situated just below the hilltop of the middle range of the Dra’ Abu el-Naga hills Review And to reach fulfill this main objective, it was proposed in 2013 to follow these research objectives: Consequently one main objective was the recording of architecture of the new discovered tombs and the reconstruction of the original context of the objects, which formed part of their burial equipment. The overlying aim of the research is: Preparing plans of all the new tombs, and also sections and 3D views of two of the tombs as they are very complicated. To place the new tombs in their archaeological context. 2D drawings can be tricky for some people to read, but 3D model views are a universal language that anyone can understand. By using SketchUp Pro to get owners, researchers heads in the same direction.
109

Byggnadsmodellers anpassning inför 3D-utskift & dess användning / Building model´s adjustments before 3D-printing & its use

Elander, Sofia, Bolmstad, Elin January 2016 (has links)
Syfte: Att utreda hur digitala 3D-modeller bör anpassas inför utskrift i en 3D-skrivare samt undersöka hur en sådan modell kan användas i byggprocessens olika skeden. Metod: En fallstudie genomförs med en befintlig digital 3D-modell som utgångspunkt där intervjuer och action research används som datainsamlingsmetoder. Empirin jämförs och analyseras med det teoretiska ramverket som tagits fram genom litteraturstudier. Resultat: En fysisk 3D-modell skulle kunna användas i flera skeden i byggprocessen, huvudsakligen i idéskedet, produktionsskedet och genomgående processen som ett kommunikationsverktyg och vid reklam/försäljning/presentation för ökad förstående. Inför utskrift bör alla byggnadsdelar vara solida, detaljer bör raderas beroende på skala och komponenter bör bestå av samma material. Konsekvenser: Då intervjuerna utförs med personer med varierande kunskap och erfarenhet är det viktigt att beakta det faktum att förslag på användningsområden eventuellt inte är genomförbara i praktiken då dessa är önskemål. Trots detta kan användning av fysiska 3D-modeller rekommenderas i flera av byggprocessens skeden för ökad förståelse och bättre kommunikation, vilket även styrks av det teoretiska ramverket. Gällande anpassningar av en digital modell krävs en digital 3D-model som utgångspunkt och viss vana av 3D-projektering. Begränsningar: Då denna studie är en fallstudie utförd på ett specifikt fall, kan kunskap och rekommendationer inte generaliseras statistiskt på andra typer av byggnader. Dock kan resultatet i denna studie implementeras på liknande projekt om små justeringar tillämpas. På grund av det faktum att studien är kvalitativ med ett begränsat antal respondenter finns möjlighet till ett annat resultat om utförandet skett med andra förutsättningar. Nyckelord: BIM-modell, fysisk byggnadsmodell, 3D-modell, 3D-skrivare, 3D- utskrift / Purpose: To investigate how digital 3D models should be adapted to enable 3D printing for use in the construction process in its various stages. Method: A case study is conducted with an existing digital 3D-model where interviews and action research is used as a data collection method. The empirical data are compared and analyzed with the theoretical framework developed through literature studies. Findings: A physical 3D model can be used at several stages in the construction process, mainly in idea development stages, the production stage and throughout the process as a communication tool and for advertising/sales/presentation for increased understanding. Prior to printing, all parts of the building should be solid, details should be erased depending on the scale used and components should consist of the same material. Implications: Based on interviews with people with varying knowledge and experience within the subject, it is important to take into consideration the fact that the proposals on the fields of use may not be enforceable in reality since they are requests. Despite this, the use of physical 3D models can be recommended in several construction phases of the process for greater understanding and better communication, which is corroborated by the theoretical framework. Adaptions of a digital model require a digital 3D model as a prerequisite and a certain experience of 3D design. Limitations: Since this study is a case study conducted in a specific case, knowledge and recommendations cannot be generalized statistically to other types of buildings. However, with small adjustments, this study can be implemented in similar projects. Due to the fact that the study is qualitative with a limited number of interviewees, there is a possibility of a different result if the execution occurred with other conditions. Keywords: BIM model, physical building model, 3D model, 3D printer, 3D printing
110

Etruscan rock-cut tombs and 3D modeling

Votroubeková, Tatiana January 2015 (has links)
This thesis examines Etruscan rock-cut tombs that are characteristic for inland southern Etruria and are dated from second quarter of the 6th century BC to the end of 3rd and beginning of the 2nd century BC. Thesis is focused on the architecture of the tombs, their typology, decoration, iconography and their architectural evolution. Main sites in Archaic period are necropoleis in San Giuliano, Blera, Tuscania and for Hellenistic period necropoleis in Norchia, Sovana and Castel d'Asso. Second part of thesis examines the potential of 3D recording, analysis, virtual reconstruction and virtual anastylosis for the study of the tomb façades through the case studies of the "Tomb of the Siren" from necropolis of Sovana and the "Doric Tombs" from necropolis of Norchia. Keywords Etruscans, Etruscan, rock-cut, rupestral, façade, necropolis, 3D modeling, multi-image photogrammetry, virtual reconstruction, virtual anastylosis

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