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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.
41

Krav och hinder med kalkylering i BIM / Requirements and obstacles with calculation in BIM

Knutsson, Josef, Al-Medana, Abir January 2015 (has links)
Syfte: BIM ger möjligheter till att utföra byggprojekt på ett effektivare sätt, genom att dela framtagen information mellan aktörer genom projektets alla delar. Denna rapport går igenom de krav och hinder som finns för att utföra effektiva BIM-kalkyleringar samt skillnader mellan dessa och traditionella kalkyleringar. Metod: Studien har besvarats genom intervjuer med projektörer och entreprenörer som arbetar med BIM i sin verksamhet, samt litteraturstudier av tidigare gjorda räkneexempel. Insamlad empiri har sedan jämförts med ett teoretiskt ramverk som skapats genom litteraturstudie av tidigare forskningsarbete inom ämnet. Resultat: I dagsläget finns det flera problem som måste lösas för att BIM- kalkyleringar ska bli effektiva. Det första problemet är osäkerheten kring det juridiska ansvaret, vem som är ansvarig och när. Det andra problemet är att BIM-modellerna inte uppfyller den kvalité som krävs för att ska den ska vara kalkylerbar. Det tredje är avsaknaden av en standardisering och gemensamt språk för BIM-modellen inom branschen. Konsekvenser: Det största problemet vid BIM-kalkyleringar är att BIM-modellen inte uppfyller kvalitetskravet som ställs på modellerna, detta kan delvis avlägsnas genom kommunikation mellan entreprenör och projektör vid en totalentreprenad eller att byggherren beställer en kalkylerbar BIM-modell av projektören vid en utförandeentreprenad. Utöver detta måste en standardisering utformas som den som finns för 2D-ritningar. Det juridiska ansvaret måste ses över, för att projektören ska känna sig säker att lämna ifrån sig BIM-modeller, varpå entreprenören ska kunna lita på levererade BIM-modeller. Begränsningar: Arbetet har begränsats till att fokusera på nybyggnation. / Purpose: BIM provides opportunities to perform projects more efficiently, by sharing information between designers, engineers and contractors. This report examines the requirements and the obstacles to perfume effective calculation within BIM. Differences between calculation within BIM and the traditional way are also examined. Method: The study has been answered through interviews with architects, structural engineers and contractors that work with BIM. A study of literature has also been used to get information from previous studies and examples of calculations. Collected empirical data were compared with a theoretical framework created by studies of previous research on the subject. Findings: In the current situation, there are several problems that must be solved in order to be able to do effective e calculation within BIM. The first problem is the uncertainty surrounding the legal responsibility, regarding who is responsible for the BIM model in certain situations. The second problem is that the BIM model does not meet the required quality to be calculable. The third problem is the lack of standardization and a common language of the BIM models within the industry. Implications: The main problem with calculations within in BIM is that, the BIM model does not meet the requirement of quality imposed on the model. This can partially be removed by communication between designers, engineers and contractors at a turnkey, or that the client orders a calculable BIM model from the designer. The legal responsibility must be reviewed in order to make projectors feel safe to deliver BIM models to the contractors, which the contractors need to have reliability on. Limitations: The work has been limited to focusing on new construction.
42

Localização de Gravidade 4D em Branas SUSY

Silva, Rodrigo César Fonseca da 01 March 2013 (has links)
Made available in DSpace on 2015-05-14T12:14:05Z (GMT). No. of bitstreams: 1 ArquivoTotal.pdf: 2327569 bytes, checksum: ca3439fab38cd32060e0c6840cfb183d (MD5) Previous issue date: 2013-03-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In the original Randall􀀀Sundrum model, the 5D gravity is coupled to a negative cosmological constant and a 3􀀀brane sourced by a delta function. The solution in such setup is a symmetric solution given in terms of two copies of AdS5 spaces patched together along the 3􀀀brane. Although in this setup the fifth dimension is infinite the volume of the 5D bulk space is infinite because the geometry is warped. As a consequence this allows having graviton zero mode responsible for 4D gravity on the brane. This is not necessarily true for spaces whose volume diverges, because no zero mode emerges anymore. We investigate the localization of metastable 4D gravity around a assymetric flat brane and a bent dilatonic brane, embedded into a 5D space, that exists only up to distances suficiently small compared to a crossover scale. Far from such scale, 5D effects causing deviations in Newtonian potential. In this thesis, we present a study on this effect considering the location of massive gravity on a asymmetric flat brane and non-BPS and BPS bent dilatonic 3􀀀brane solutions of a supergravity 5D. The parameters control the thickness of the membrane also control the crossover scale of the first case. In the other hand, the cosmological constant on the bent brane controls the size of the crossover scale in second case. For suficiently small positive cosmological constant, that is in accord with the present observations, the crossover scale becomes very large. Thus, as emphasized in Gregory-Rubakov-Sibiryakov (GRS) and Dvali-Gabadadze-Porrati (DGP) scenarios, we shall focus on the main beautiful characteristic of the 4D metastable gravity, that is the fact that where as gravity becomes four-dimensional for distances very much smaller than the crossover scale, it emerges as a 5D gravity for distances very much larger than such scale. In doing so, we will find the Newtonian potential induced by the gravity massive modes of a Schroedinger-like equation for the gravity fluctuations around the brane solutions. / No modelo de Randall􀀀Sundrum, a gravidade 5D está acoplada à uma constantecosmológica negativa e uma 3􀀀brana é originado por uma função delta. A solução nestaconfiguração é simétrica, e dada em termos de duas cópias de espaços AdS5 unidos ao longoda 3􀀀brana. Embora a quinta dimensão seja infinita, o volume formado pelo espaço maior5D é finito, pois a geometria é deformada e esta, permite termos um modo de zero grávitonresponsável pela gravidade 4D na brana. Isso não é necessário verdade para espaços cujovolume diverge, porque nenhum modo de zero emerge mais. Nós investigamos a localizaçãode gravidade 4D, metaestável, em torno de branas mergulhadas em um espaço 5D, que sóexiste até distâncias suficientemente pequenas em comparação com uma escala de crossover.Longe de tal escala, efeitos 5D desviam fortemente o potencial Newtoniano potencial. Nestatese, estudamos esse efeito, considerando a localização de gravidade em soluções tipo 3􀀀branaplana assimétrica, e 3􀀀branas curvas dilatônicas, não􀀀BPS e BPS, que se originam deuma supergravidade 5D. No primeiro caso, os parâmetros que controlam a largura da branaassimétrica também controlam o tamanho da escala de crossover. Por outro lado, a constantecosmológica (positiva) na brana curva dilatônica controla o tamanho da escala de crossoverno segundo caso. Para uma constante cosmológica suficiente pequena, que está de acordo comas observações atuais, a escala de crossover se torna muito grande. Tal como nos cenáriosde Gregory-Rubakov-Sibiryakov (GRS) e Dvali-Gabadadze-Porrati (DGP), nosso foco é ainteressante característica da gravidade é metaestável 4D, para distâncias muito menoresdo que a escala de crossover, que surge como uma gravidade 5D para distâncias muito muitomaior do que tal escala. Ao fazer isso, vamos encontrar o potencial Newtoniano induzido pelosmodos massivos de gravidade oriundos de uma equação tipo Schroedinger para as flutuaçõesda gravidade em torno das soluções tipo branas.
43

Interferometric Imaging and its Application to 4D Imaging

Sinha, Mrinal 03 1900 (has links)
This thesis describes new interferometric imaging methods for migration and waveform inversion. The key idea is to use reflection events from a known reference reflector to ”naturally redatum” the receivers and sources to the reference reflector. Here, ”natural redatuming” is a data-driven process where the redatuming Green’s functions are obtained from the data. Interferometric imaging eliminates the statics associated with the noisy overburden above the reference reflector. To mitigate the defocussing caused by overburden errors I first propose the use of interferometric least-squares migration (ILSM) to estimate the migration image. Here, a known reflector is used as the reference interface for ILSM, and the data are naturally redatumed to this reference interface before imaging. Numerical results on synthetic and field data show that ILSM can significantly reduce the defocussing artifacts in the migration image. Next, I develop a waveform tomography approach for inverting the velocity model by mitigating the velocity errors in the overburden. Unresolved velocity errors in the overburden velocity model can cause conventional full-waveform inversion to get stuck in a local minimum. To resolve this problem, I present interferometric full-waveform inversion (IFWI), where conventional waveform tomography is reformulated so a velocity model is found that minimizes the objective function with an interferometric crosscorrelogram misfit. Numerical examples show that IFWI, compared to FWI, computes a significantly more accurate velocity model in the presence of a nearsurface with unknown velocity anomalies. I use IFWI and ILSM for 4D imaging where seismic data are recorded at different times over the same reservoir. To eliminate the time-varying effects of the near surface both data sets are virtually redatumed to a common reference interface before migration. This largely eliminates the overburden-induced statics errors in both data sets. Results with synthetic and field data show that ILSM and IFWI can suppress the artifacts caused by non-repeatability in time-lapse surveys. This can lead to a much more accurate characterization of the movement of fluids over time. In turn, this information can be used to optimize the extraction of resources in enhanced oil recovery (EOR) operations.
44

Tvorba 3D modelu hradu Kumburk / Creation of 3D model of castle Kumburk

Andrle, Jan January 2014 (has links)
The subject of this thesis is the creation of documentation castle ruins Kumburk form of digital 3D model by photogrammetrical method using optical correlation. Text section describes the way of control establishing, measuring control points and photographic work. Furthermore, the text is dedicated to creating the 3D model itself, and testing its accuracy. Appendix contains the control documentation, testing the accuracy of the model and the 3D model in various formats.
45

Expanding the Organometallic Chemistry of 4d and 4f Arene Metal Complexes

Bamforth, Christopher 18 May 2022 (has links)
No description available.
46

Visualisering av dynamisk APD-plan med hjälp av interaktiv 4D-simulering

Shamoun, Rene January 2023 (has links)
Med tanke på att byggföretag bygger alltmer centralt i städerna, där det är tätare och merkompakt med hög trafik, blir en dynamisk arbetsplatsdispositionsplan (APD-plan) allt viktigare, avgörande och utmanande. Eftersom planering och konstruktion kan vara utmanandeatt implementera utan att hindra varandra eller personer som bor eller befinner sig i närheten av projektets område, kan visualiseringen vara en lösning som har potential att underlättaplaneringen och utformningen. Denna lösning använder BIM-modellering för att inkluderatiden utöver den traditionella tredimensionella modellen för att bygga en 4D-modell som är en drastisk utveckling över de tvådimensionella skisserna. Tidigare studier har visat möjligheten att visualisera med en 4D-modell för olika projekt, tillexempel en APD-plan eller en trappa i en byggnad. Men en studie (Thomasson & Guldbrand,2018) tillhandahåller inte en detaljerad beskrivning av visualiseringsmetoden, utan fokuserade stället på vilka program som kan användas och möjligheten att visualisera. Den andra studien (Kacprzyk & Kępa, 2014) presenterade en metod för att visualisera en del av en byggnad, men den fungerar över små delar enligt författarna. Vid större projekt kan programmen möta svårigheter och problem med lägre prestanda, så en annan metod krävs för större projekt. Denna studie utforskar hur tekniken kan anpassas för större projekt och hur teknikens funktioner kan utnyttjas. Metoden som används i studien inkluderar en fallstudie av böcker, artiklar och studier som är kopplade till byggprocessen, arbetsplatsdispositionsplan och mjukvarorna som används förvisualisering. Metoden inkluderar även skapandet av en prototyp som visas för experter och branschrepresentanter för att få återkoppling om vad som anses vara positivt och negativt, samt eventuella förbättringar. Utvärderingen av prototypen genom intervjuer visade att det finns både positiva och negativa resultat. Enligt respondenterna är fördelarna med prototypen eller sättet modellen skapas att den bidrar till en ökad förståelse av projektet, ökad säkerhet och besparing i tid och kostnader under arbetstiden och bebyggelsen. Dessutom kan modellen göras tillgänglig för allamedarbetare som arbetar på projektet. Å andra sidan inkluderar nackdelarna behovet av manuelluppdatering som görs av experten som jobbar med tekniken. Dessutom är det tidskrävande att bygga modellen som skulle visas för personalen. Metoden presenteras med utmaningar och svårigheter som kan påverka en effektiv visualisering av modellen. Dessutom krävs kunskap om tekniken tidsinvesteringar där bristande kunskap bidrar till ökad tidsåtgång för attv isualisera modellen.
47

3D Visualization of Highway Corridors: The I-77/81 Case Study near Wytheville, VA

Thota, Pramod Reddy 14 June 2002 (has links)
The application of Visualization and Simulation technologies to intuitively depict, analyze and execute transportation projects is gaining momentum, as advances in 3-Dimension (3D) Geographic Information Systems (GIS) technologies are rapidly progressing and there is an increased need for public acceptance of transportation projects. This thesis presents a visualization process framework that is applicable to highway corridor visualization, and the I-77/81 Relocation Study Visualization project is discussed along the lines of the visualization framework that has been developed. The changes in the roadway alignment and associated traffic volume and pattern changes will affect the town of Wytheville, both in terms of economy and community development. The goal of the project is to present these visualizations at public participation meetings. Visualizations that have been developed in 2D, 3D, 4D, and virtual reality, will be discussed along with their developmental life cycles and issues affecting their quality. / Master of Science
48

Scheduling and Control Strategies for the Departure Problem in Air Traffic Control

Bolender, Michael Alan January 2000 (has links)
No description available.
49

Large-Scale Simulations Using First and Second Order Adjoints with Applications in Data Assimilation

Zhang, Lin 23 July 2007 (has links)
In large-scale air quality simulations we are interested in the influence factors which cause changes of pollutants, and optimization methods which improve forecasts. The solutions to these problems can be achieved by incorporating adjoint models, which are efficient in computing the derivatives of a functional with respect to a large number of model parameters. In this research we employ first order adjoints in air quality simulations. Moreover, we explore theoretically the computation of second order adjoints for chemical transport models, and illustrate their feasibility in several aspects. We apply first order adjoints to sensitivity analysis and data assimilation. Through sensitivity analysis, we can discover the area that has the largest influence on changes of ozone concentrations at a receptor. For data assimilation with optimization methods which use first order adjoints, we assess their performance under different scenarios. The results indicate that the L-BFGS method is the most efficient. Compared with first order adjoints, second order adjoints have not been used to date in air quality simulation. To explore their utility, we show the construction of second order adjoints for chemical transport models and demonstrate several applications including sensitivity analysis, optimization, uncertainty quantification, and Hessian singular vectors. Since second order adjoints provide second order information in the form of Hessian-vector product instead of the entire Hessian matrix, it is possible to implement applications for large-scale models which require second order derivatives. Finally, we conclude that second order adjoints for chemical transport models are computationally feasible and effective. / Master of Science
50

Characterization of neurofluid flow using physics-guided enhancement of 4D flow MRI

Neal Minesh Patel (18429606) 24 April 2024 (has links)
<p dir="ltr">Cerebrospinal fluid (CSF) plays a diverse role within the skull including cushioning the brain, regulating intracranial pressure, and clearing metabolic waste via the glymphatic system. Disruptions in CSF flow have long been investigated for hydrocephalus-related diseases such as idiopathic normal pressure hydrocephalus (iNPH). Recently, changes in CSF flow have been implicated in neurodegenerative disorders such as Alzheimer’s disease (AD) and Parkinson’s disease. It remains difficult to obtain <i>in vivo </i>measurements of CSF flow which contribute to disease initiation, progression, and treatment. Three-directional phase-contrast MR imaging (4D flow MRI) has been used to measure CSF velocities within the cerebral ventricles. However, there remain challenges in balancing acquisition time, spatiotemporal resolution, and velocity-to-noise ratio. This is complicated by the low velocities and long relaxation times associated with CSF flow. Additionally, flow-derived metrics associated with cellular adaptations and transport rely on near-wall velocities which are poorly resolved and noisy. To address these challenges, we have applied physics-guided neural networks (PGNN) to super-resolve and denoise synthetic 4D flow MRI of CSF flow within the 3rd and 4th ventricles using novel physics-based loss functions. These loss functions are specifically designed to ensure that high-resolution estimations of flow fields are physically consistent and temporarily coherent. We apply these PGNN to various test cases including synthetically generated 4D flow MRI in the cerebral ventricles and vasculature, <i>in vitro</i> 4D flow MRI acquired at two resolutions in 3D printed phantoms of the 3rd and 4th ventricles, and in vivo 4D flow MRI in a healthy subject. Lastly, we apply these physics-guided networks to investigate blood flow through cerebral aneurysms. These techniques can empower larger studies investigating the coupling between arterial blood flow and CSF flow in conditions such as iNPH and AD.</p>

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