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1
Skinner, Gregory H. "Two-dimensional auto-regressive modeling." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26310.
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Pimental-Lopez, Jose. "Modeling two-dimensional infiltration from furrows." Diss., The University of Arizona, 2002. http://hdl.handle.net/10150/279977.
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Numerical simulations were performed to study two-dimensional infiltration from furrows. The simulations were carried out using the models SWMS_2D, HYDRUS-2D and HYDRUS-1D. The first model was used to evaluate the individual effect of soil and furrow parameters on cumulative infiltration and deep seepage. Cumulative infiltration was found to be more sensitive to saturated hydraulic conductivity, wetted perimeter and furrow spacing than the other parameters for relatively long times, while cumulative deep seepage was more sensitive to the same parameters except to the furrow spacing. It was verified that two-dimensional cumulative infiltration can be approximated using one-dimensional models, for example HYDRUS-1D, by combining the vertical and horizontal infiltrations. The two-dimensional cumulative infiltration is underpredicted by no more than 35% using this calculation. When steady state is reached the steady infiltration rate may be linearly related to the depth of the furrow. As a result, steady infiltration rate is dependent only on type of soil, water depth in the furrow and furrow width. Broocks-Corey soil hydraulic parameters were matched to the van Genuchten parameters by four different procedures. The method based on matching sorptivities produced the closest results to the van Genuchten solution for one- and two-dimensional cumulative infiltration. However, cumulative deep seepage was not accurately simulated. The SCS infiltration parameters were also matched but using an inverse problem methodology. The parameters obtained described cumulative infiltration reasonably well.
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Gräf, Michael. "Two-Dimensional Analytical Modeling of Tunnel-FETs." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/450516.
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Basat en un mecanisme de transport de corrent de banda a banda, el túnel-FET és capaç de superar la limitació de pendent sub-llindar física del MOSFET de 60 mV /dec. Per tant, s'ha convertit en un dels dispositius més prometedors per ser el successor del MOSFET clàssic en els últims anys.
Aquesta tesi descriu tots els passos necessaris per modelar analíticament un Túnel-FET de doble porta. El model inclou una solució electrostàtica de dues dimensions en totes les regions del dispositiu, el que permet fins i tot simulacions hetero-unió del dispositiu. Per a un comportament més realista del dispositiu, cal tenir en compte el rendiment del dispositiu que limita els perfils de dopatge de forma Gaussiana en les unions del canal. Les expressions per a les probabilitats de túnel de banda a banda i les de Trap-Assisted-Tunneling (TAT) són executades per un enfocament WKB quasi bidimensional. El corrent del dispositiu es calcula mitjançant la teoria de transmissió de Landauer. El model és vàlid per a dispositius de canal curt i les estàncies estan ben comparades amb les dades de simulació TCAD Sentaurus i amb les medicions proporcionades.
S'introdueix un modelo general per les flactuacions del dopant aleatoria, que prediu les influencies característiques del dispositiu en el corrent de sortida i el voltatge llindar. El model s'aplica al MOSFET, així com a dispositius TFET.Basado en un mecanismo de transporte de corriente banda a banda, el Tunnel-FET es capaz de superar la limitación de pendiente sub-umbral física del MOSFET de 60 mV/dec. Por lo tanto, esto lo convierte en uno de los dispositivos más prometedores para ser el sucesor del MOSFET clásico en los últimos años. Esta tesis describe todos los pasos necesarios para modelar analíticamente un Tunnel-FET de doble puerta. El modelo incluye una solución electrostática bidimensional en todas las regiones del dispositivo, lo que permite incluso simulaciones de hetero-unión del dispositivo. Para un comportamiento más realista del dispositivo se tiene en cuenta el rendimiento del dispositivo que limita los perfiles de dopaje de forma Gaussiana en las uniones del canal. Las expresiones para las probabilidades de túnel de banda a banda y de Trap-Assisted-Tunneling (TAT) se implementan mediante un enfoque de WKB cuasi bidimensional. La corriente del dispositivo se calcula mediante la teoría de transmisión de Landauer. El modelo es válido para dispositivos de canal corto y las estancias están bien comparadas con los datos de simulación TCAD Sentaurus y con las mediciones proporcionadas. Se introduce un modelo general para las fluctuaciones del dopado aleatorio, que predice las influencias características del dispositivo en la corriente de salida y el voltaje umbral. El modelo se aplica al MOSFET, así como a los dispositivos TFET.
Based on a band-to-band current transport mechanism, the Tunnel-FET is able to overcome the physical subthreshold slope limitation of the MOSFET of 60 mV/dec. Therefore, it has become one of the most promising devices to be the successor of the classical MOSFET in the last few years. This thesis describes all necessary steps to analytically model a double-gate Tunnel-FET. The model includes a two-dimensional electrostatic solution in all device regions, which enables even hetero-junction device simulations. Device performance limiting Gaussian-shaped doping profiles at the channel junctions are taken into account for a realistic device behavior. Expressions for the band-to-band and trap-assisted-tunneling probabilities are implemented by a quasi two-dimensional WKB approach. The device current is calculated based on Landauer's transmission theory. The model is valid for short-channel devices and stays is good agreement with the TCAD Sentaurus simulation data and with the provided measurements. A general model for random-dopant-fluctuations is introduced, which predicts characteristic device influences on the output current and threshold voltage. The model is applied to MOSFET, as well as TFET devices.
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Seto, Haruki. "Two-Dimensional Transport Modeling of Tokamak Plasmas." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188588.
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Gonzalez, Ninel S. "Two-dimensional modeling of the Red River Floodway." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0004/MQ45048.pdf.
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Esmond, Micah Jeshurun. "Two-dimensional, Hydrodynamic Modeling of Electrothermal Plasma Discharges." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/81447.
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A two-dimensional, time-dependent model and code have been developed to model electrothermal (ET) plasma discharges. ET plasma discharges are capillary discharges that draw tens of kA of electric current. The current heats the plasma, and the plasma radiates energy to the capillary walls. The capillary walls ablate by melting and vaporizing and by sublimation. The newly developed model and code is called the Three-fluid, 2D Electrothermal Plasma Flow Simulator (THOR). THOR simulates the electron, ion, and neutral species as separate fluids coupled through interaction terms. The two-dimensional modeling capabilities made available in this new code represent a tool for the exploration and analysis of the physics involved in ET plasma discharges that has never before been available.
Previous simulation models of ET plasma discharges have relied primarily on a 1D description of the plasma. These models have often had to include a tunable correction factor to account for the vapor shield layer - a layer of cold ablated vapor separating the plasma core from the ablating surface and limiting the radiation heat flux to the capillary wall. Some studies have incorporated a 2D description of the plasma boundary layer and shown that the effects of a vapor shield layer can be modeled using this 2D description. However, these 2D modeling abilities have not been extended to the simulation of pulsed ET plasma discharges. The development of a fully-2D and time-dependent simulation model of an entire ET plasma source has enabled the investigation of the 2D development of the vapor shield layer and direct comparison with experiments. In addition, this model has provided novel insight into the inherently 2D nature of the internal flow characteristics involved within the plasma channel in an ET plasma discharge. The model is also able to capture the effects of inter-species interactions.
This work focuses on the development of the THOR model. The model has been implemented using C++ and takes advantage of modern supercomputing resources. The THOR model couples the 2D hydrodynamics and the interactions of the plasma species through joule heating, ionization, recombination, and elastic collisions. The analysis of simulation results focuses on emergent internal flow characteristics, direct simulation of the vapor shield layer, and the investigation of source geometry effects on simulated plasma parameters. The effect of elastic collisions between electrons and heavy species are shown to affect internal flow characteristics and cause the development of back-flow inside the ET plasma source. The development of the vapor shield layer has been captured using the diffusion approximation for radiation heat transfer within the ET plasma source with simulated results matching experimental measurements. The relationship between source radius and peak current density inside ET plasma discharges has also been explored, and the transition away from the ablation-controlled operation of ET plasma discharges has been observed.Ph. D.
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Ng, Karen Pei-Tak. "Two-dimensional hydraulic-habitat modeling of a rehabilitated river." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99003.
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The application of a 2D hydraulic-habitat model, River2D, to simulate flows and fish habitat areas in a reach of the Nicolet River (Quebec, Canada) containing two sets of double-wing rock current deflectors to enhance fish habitat was examined. Depth-averaged velocity in the reach was determined using one or two measurement points in the vertical under the assumption that the profile was logarithmic; however, the presence of boulders and obstructions disturbed the profile, making it difficult to characterize using only two measurement points. The sensitivity of the simulation results to roughness characterization, topographic scale, mesh refinement, and boundary conditions was evaluated. The simulated and observed depths had correlation coefficients of 0.93 to 0.97, while the velocity correlation coefficients were 0.56 to 0.67. Qualitatively, the model accurately predicted the flow patterns, e.g. the recirculation zones downstream of the deflectors. Habitat suitability curves for brown trout, taken from literature, were used in the habitat model. Simulated discharges from 0.74 m3/s to 1.94 m3/s were critical minimum flows for suitable spawning brown trout habitat. The model was adequate for qualitatively simulating flow and habitat in this reach, however, the complex flow conditions may be better represented by a 3D model.
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Killingstad, Marc W. "Two-dimensional numerical modeling of enhanced in situ denitrification." Master's thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-01202010-020321/.
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Olds, Shana D. "Modeling and LQR Control of a Two-Dimensional Airfoil." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/36668.
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In this paper we develop a mathematical model of a two-dimensional aeroelastic airfoil. This model is used to design a flutter suppression controller. Flutter is a vibration in a wing caused by airstream energy being absorbed by the lifting surface. Flutter increases with increasing speed. For simplicity, we consider a flat plate in a two-dimensional flow. The model is developed in the frequency domain and then transformed into the time domain. The uncontrolled model is numerically simulated using MATLAB. Linear Quadratic Regulator (LQR) theory is used to design a state feedback controller. The LQR control scheme consists of using a full state feedback controller of the form u=-Kx, where K is a control gain matrix. The goal is to use LQR theory to supress flutter and to maintain stability of the closed loop system.Master of Science
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Gross, Matthew L. "Two-Dimensional Modeling of AP/HTPB Utilizing a Vorticity Formulation and One-Dimensional Modeling of AP and ADN." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2077.pdf.
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Tsay, Michael Meng-Tsuan. "Two-dimensional numerical modeling of Radio-Frequency ion engine discharge." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62713.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 106-109).
Small satellites are gaining popularity in the space industry and reduction in spacecraft size requires scaling down its propulsion system. Low-power electric propulsion poses a unique challenge due to various scaling penalties. Of high-performance plasma thrusters, the radio-frequency ion engine is most likely to succeed in scaling as it does not require an externally applied magnetic field and is structurally simple to construct. As part of a design package an original two-dimensional simulation code for radio-frequency ion engine discharge is developed. The code models the inductive plasma with fluid assumption and resolves the electromagnetic wave in the time domain. Major physical effects considered include magnetic field diffusion and coupling, plasma current induction and ambipolar plasma diffusion. The discharge simulation is benchmarked with data from an experimental thruster. It shows excellent performance in predicting the load power and the internal power loss of the plasma. Predictability of anode current depends on the operating power but is generally adequate. Optimum skin depth on the order of half of chamber radius is suggested by the simulation. The code also demonstrates excellent scaling ability as it successfully predicts the performance of a smaller thruster with errors less than 10%. Using the code a brief optimization study was conducted and the results suggest the maximum thrust efficiency does not necessarily occur at the same frequency that maximizes the power coupling efficiency of the matching circuit.
by Michael Meng-Tsuan Tsay.
Ph.D.
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Fife, John Michael. "Two-dimensional hybrid particle-in-cell modeling of Hall thrusters." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11568.
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Jung, Gang Seob. "Multiscale modeling of two-dimensional materials : structures, properties, and designs." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123228.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 257-274).
Multiscale modeling undertakes to describe a system with multiple models at different scales. In principle, quantum mechanics provides sufficient information. However, the development of a scaled-up model, e.g., molecular dynamics, from quantum mechanics, should be validated against the experiments. Two-dimensional (2D) materials provide excellent platforms to verify theoretical models by directly comparing atomic structures and properties with advanced transmission electron microscopy (TEM) techniques due to their high crystallinity and thin nature. In this thesis, molecular dynamics (MD) models have been developed for the 2D transition metal dichalcogenides (TMDs) such as MoS₂, WS₂, MoSe₂, and WSe₂ from density functional theory (DFT) by focusing on their nonlinearity and failure strains. The structures, crack-tip behaviors, and fracture patterns from the models are directly compared with atomic level in-situ TEM images.
The models have revealed atomic scale mechanisms on the crack-tip behaviors in the single crystals such as roles of sulfur vacancies, geometric interlocking frictions, and the directions of crack propagation. The models have been further validated with more complicated structures from grain boundaries in the WS₂ bilayer and lateral heterostructures, e.g., MoS₂-WSe₂ by the images from ADF-STEM. Also, a method for generation of grain boundary has been proposed for well-stitched grain boundaries based on experimentally observed dislocations and defects. The models and methods have been utilized to understand the chemical reactions for MoS₂ channel growth in WSe₂ and fracture toughness of polycrystalline graphene. Finally, the validated models and methods are utilized to predict the atomic structures of 2D materials with three-dimensional (3D) surfaces, e.g., triply periodic minimal surfaces (TPMS) and corrugated surfaces with non-zero Gaussian curvatures.
The mechanics, failure behaviors, and thermal properties of TPMS graphene are systematically studied from the predicted structures. A recent experiment shows the predicted scaling laws of Young's modulus and strengths agree well with the measurements.
"Funded by the MIT Presidential Fellowship (Edward H. Linde), AFOSR (DOD-MURI, Grant No. FA9550-15-1-0514), ONR (Grant No. N00014- 16-1-233), NSF (Grant No. CMMI-1300649), and NIH (Grant No. U01EB014976; 5U01EB016422)"--Page 8
by Gang Seob Jung.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering
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Lindau, Jules Washington. "Multidimensional dynamic compression system modeling." Diss., This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-02132009-171914/.
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Baykal, Cuneyt. "Two-dimensional Depth-averaged Beach Evolution Modelling." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614148/index.pdf.
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In this study, a two-dimensional depth-averaged beach evolution numerical model is developed to study the medium and long term nearshore sea bottom evolution due to non-cohesive sediment transport under the action of wind waves only over the arbitrary land and sea topographies around existing coastal structures and formations. The developed beach evolution numerical model is composed of four sub-models: a nearshore spectral wave transformation model based on energy balance equation including random wave breaking and diffraction terms to compute the nearshore wave characteristics, a nearshore wave-induced circulation model based on the non-linear shallow water equations to compute the nearshore depth averaged wave-induced current velocities and mean water level changes, a sediment transport model to compute the local total sediment transport rates occurring under the action of wind waves and a bottom evolution model to compute the bed level changes in time due to gradients of sediment transport rates in cross-shore and longshore directions. The governing partial differential equations are solved utilizing finite difference schemes. The developed models are applied successfully to several theoretical and conceptual benchmark cases and an extensive data set of laboratory and field measurements. As an alternative approach to be used in beach evolution problems, a distributed total sediment load formula is proposed based on the assumption that the local total sediment transport rates across the surf zone are proportional to the product of the rate of dissipation of wave energies due to wave breaking and wave-induced current velocities. The proposed distribute load approach is validated with the available laboratory and field measurements.
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Esfahani, Samineh R. "Two-Dimensional Computer Model of Human Atrial Ablation." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3093.
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A finite-element model of a two-dimensional slice of human atrial tissue for the study of the electrograms and propagation of action potentials is presented. Action potential propagation is described by a reaction-diffusion model coupled with the complex Courtemanche et al. atrial cell model. The effects of recording electrode size and location on electrograms are presented. Action potential propagation as a result of atrial fibrillation ablation therapy is also modeled by defining a lesion area with decreased electrical conductivity. The effect of electrical conductivity and geometry of the lesion was also studied. It is shown that the success rate of atrial fibrillation ablation therapy is primarily correlated with the creation of continuous ablation lines and also the formation of fibrous tissue.
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Khanal, Anish. "Two Dimensional Hydrodynamic Numerical Simulation of Flow Around Chevrons." OpenSIUC, 2012. https://opensiuc.lib.siu.edu/theses/799.
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A chevron is a U-shaped rock structure constructed for improving navigation conditions by diverting majority of flow towards main channel. The objective of this study is to improve understanding of how chevrons affect channel flow. For this study, a two-dimensional numerical hydrodynamic model of a two-km-long reach of the Mississippi River was developed; three chevrons have been constructed in the modeled reach. The model was calibrated by adjusting Manning's n to match predicted and observed water surface elevations (WSELs). The model was validated using measured WSEL and velocity data from two events: a low-flow discharge (4,500 m3/s) and high-flow discharge (14,000 m3/s). At reach scale the model performed well in predicting WSELs. Average difference between model prediction and observed WSEL was 0.23 m in low-flow condition and 0.05 in high flow condition. Root mean square of errors (RMSEs) and mean absolute errors (MAEs) were used to measure the degree of agreement between predicted and measured velocities. At the reach scale there was reasonable agreement between predicted and observed velocities (RMSE = 0.416 m/s and 0.425 m/s, respectively, for low-flow and high-flow conditions). Local differences between predicted and observed velocities were up to 1.5 m/s; this is attributed to uncertainties in the velocity measurements. The model's sensitivity of to changes in Manning's n, eddy viscosity and bathymetry were also analyzed. The sensitivity analysis showed that there are specific areas (e.g., near the banks of the river) which are sensitive to changes in Manning's n. This indicates that spatial distribution of Manning's n is required to increase the accuracy in the model's predictions of velocity. Model was found to be stable in a specific range of eddy viscosity values. Eddy viscosity had little effect on velocity predictions but was important for model stability (i.e., the model was stable only for a range of eddy viscosity values). Reach scale changes in bathymetry had minor impacts on RMSE and MAE. However, local changes in channel bathymetry resulted in differences in velocity predictions as much as ±0.4 m/s.
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Dorsel, Daniel S. "Spring Hollow Reservoir: Application of a two-dimensional water quality model." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36889.
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The BETTER water quality model, created by TVA, was used to model the temperature and dissolved oxygen (DO) in Spring Hollow Reservoir. The water balance consisted of pump discharge from the Roanoke River, runoff, releases at the dam, leakage, and storage. The geometry of the reservoir was represented by four columns and a variable number of five-foot layers. Through a sensitivity analysis, the parameters that influenced temperature and DO the most were determined. Temperature was then calibrated to a subset of the 19-month simulation period by systematically varying the most sensitive parameters. DO was calibrated to the entire simulation period due to the young age of the reservoir and the inconsistent inflow rates and timing. The verification process showed that the model reasonably reproduced the seasonal temperature patterns. By varying the sediment oxygen demand temporally and spatially, the model depicted the gradual hypolimnetic oxygen depletion in the reservoir. The model results suggest that the inflow organics and subsequent settling and accumulation are key factors in the DO depletion rate. Therefore, to enhance water quality conditions in the reservoir, a monitoring system in the Roanoke River should be installed with filling carried out when water quality in the river is optimal. For future modeling purposes, this research indicated that the model was very sensitivity to meteorological data, especially in determining temperature. Thus, a weather station located at the reservoir would permit collection of more accurate meteorological data, leading to greater confidence in the interpretation of the model predictions.Master of Science
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Searles, Shawn 1966 Carleton University Dissertation Engineering Electrical. ""A study and modeling of two dimensional effects in bipolar transistors"." Ottawa.:, 1989.
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Brauner, J. Steven. "Two-dimensional modeling of in situ bioremediation using sequential electron acceptors." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-07212009-040537/.
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Krishnan, Anantha Raman. "Signal Processing for Two-Dimensional Magnetic Recording." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202984.
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With magnetic storage devices already achieving storage densities of up to 400 Gigabits per square inch (Gb/in2), the state of the art is rapidly approaching theoretical limits (dictated by thermal stability concerns). Hence, there is an eort in the industry to develop alternative magnetic storage technologies. Two-dimensional magnetic recording (TDMR) is one such candidate technology. In contrast to other technologies(e.g. heat-assisted magnetic recording [1], bit-patterned media [2]) which rely on signicant changes being made to the recording medium, TDMR relies on the use of traditional recording media, while relying on signal processing to make improvements in the recording density. Though advantageous due to the fact that no drastic re-engineering of media is required, there are signicant challenges that need to be addressed in order to make TDMR a viable candidate for next-generation recordingsystems.The main challenges involved in TDMR arise due to (i) the small bit-area, along with an aggressive write/read process, which leads to a large amount of noise, and (ii) the two-dimensional nature of the recording process { so far not encountered in today's systems. Thus, a gamut of 2D signal processing algorithms need be developed for the compensation of errors occurring due to the aggressive write/read processes. In this dissertation, we present some of the work done with regard to the signal processing tasks involved in TDMR. In particular, we describe our work on (i) channel modelling, (ii) detection strategies, and (iii) error-correction coding strategies targetted at TDMR.
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Haile, Sosina Shimeles. "VS2DRT: Variably saturated two dimensional reactive transport modeling in the vadose zone." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-107821.
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Contaminate transport in vadose is a huge concern since the vadose zone is the main passage way for ground water recharge. Understanding this process is crucial in order to prevent contamination, protect and rehabilitate ground water resources. Reactive transport models are instrumental for such purposes and there are numerous solute transport simulation programs for both ground water and vadose zone but most of this models are limited to simple Linear, Langmuir and Freundlich sorption models and first order decay and fail to simulate more complex geochemical reactions that are common in the vadose zone such as cation exchange, surface complexation, redox reaction and biodegradation. So it is necessary to enhance capabilities of solute transport models by incorporating well tested hydrogeochemical models like PHREEQC in to them to be able closely approximate the geochemical transport process in the subsurface.
In this PhD research a new reactive transport model called VS2DRT was created by coupling existing public domain solute and heat transport models VS2DT, VS2DH with hydro-chemical model PHREEQC using non-iterative operator splitting technique. VS2DRT was compiled using MinGW compiler using tools like autotools and automake. A graphical user interface was also created using QT creator and Argus ONE numerical development tools. The new model was tested for one dimensional conservative Cl transport, surface complexation, cation exchange, dissolution of calcite and gypsum, heat and solute transport as well as for two dimensional cation exchange cases. Their results were compared with VS2DT, VS2DH, HP1 and HP2 models and the results are in good agreement.
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Larson, Gregg D. "Two-dimensional modeling of a proposed auxilliary ionization scheme for thermionic converters." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/15964.
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ARAUJO, TEREZA DENYSE PEREIRA DE. "ELASTO-PLASTIC ADAPTATIVE ANALYSIS FOR MODELING FRACTURE PROCESSES OF TWO-DIMENSIONAL STRUCTURES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1999. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1885@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORA análise de problemas mecânicos e estruturais, pelo método dos elementos finitos,requer do analista certa experiência na discretização do modelo para minimizar os erros das soluções. A geração da malha é uma tarefa árdua, que torna- se ainda mais difícil quando trincas estão presentes no modelo. Em um modelo discreto, cada vez que a trinca propaga, a geometria do modelo muda e a malha deve ser atualizada. Neste trabalho é apresentado um sistema gráfico interativo, para modelagem bidimensional de problemas de fraturamento estrutural. O sistema permite introduzir trincas em qualquer posição no modelo, regenerando sua malha e executando um processo auto-adaptativo de elementos finitos. Este sistema pode ser usado para problemas mecânicos, com ou sem trincas, elásticos lineares ou elastoplásticos. O processo auto-adaptativo está baseado em estimadores de erro a posteriori, com refinamento do tipo h. Três tipos de estimadores estão disponíveis. O primeiro, baseado na norma de energia, é aplicado na análise de problemas elásticos lineares. O segundo e o terceiro, baseados em tensão efetiva e na razão do trabalho plástico, respectivamente, são aplicados na análise de problemas elastoplásticos. A geração da malha está baseada em técnicas de enumeração espacial recursiva, que consiste de uma partição em árvore binária (binary tree) para as curvas do contorno, incluindo as curvas das trincas, e uma partição em árvore quaternária (quadtree) para a geração da malha no domínio. O sistema integra diferentes ferramentas: um modelador geométrico que cria a geometria do modelo, um pré-processador que gera a malha e aplica os atributos, um módulo de análise numérica que avalia a resposta de elementos finitos e um módulo, chamado de módulo adaptativo, que faz o gerenciamento do processo adaptativo das malhas e que também é um pós-processador que auxilia na visualização dos resultados, inclusive dos parâmetros de fratura. No processo adaptativo não linear, uma interpolação das variáveis de solução é realizada entre malhas para que a análise incremental da plasticidade continue. O critério deA análise de problemas mecânicos e estruturais, pelo método dos elementos finitos, requer do analista certa experiência na discretização do modelo para minimizar os erros das soluções. A geração da malha é uma tarefa árdua, que torna-se ainda mais difícil quando trincas estão presentes no modelo. Em um modelo discreto, cada vez que a trinca propaga, a geometria do modelo muda e a malha deve ser atualizada. Neste trabalho é apresentado um sistema gráfico interativo, para modelagem bidimensional de problemas de fraturamento estrutural. O sistema permite introduzir trincas em qualquer posição no modelo, regenerando sua malha e executando um processo auto-adaptativo de elementos finitos. Este sistema pode ser usado para problemas mecânicos, com ou sem trincas, elásticos lineares ou elastoplásticos. O processo auto-adaptativo está baseado em estimadores de erro a posteriori, com refinamento do tipo h. Três tipos de estimadores estão disponíveis. O primeiro, baseado na norma de energia, é aplicado na análise de problemas elásticos lineares. O segundo e o terceiro, baseados em tensão efetiva e na razão do trabalho plástico, respectivamente, são aplicados na análise de problemas elastoplásticos. A geração da malha está baseada em técnicas de enumeração espacial recursiva, que consiste de uma partição em árvore binária (binary tree) para as curvas do contorno, incluindo as curvas das trincas, e uma partição em árvore quaternária (quadtree) para a geração da malha no domínio. O sistema integra diferentes ferramentas: um modelador geométrico que cria a geometria do modelo, um pré-processador que gera a malha e aplica os atributos, um módulo de análise numérica que avalia a resposta de elementos finitos e um m
The numerical analysis of structural and mechanical problems by the finite element method requires, by the analyst, some knowledge and experience on mesh refinement. Mesh generation is a difficult task, especially when the model contains cracks. As the crack propagates in the discret model, the geometry of the model changes and the mesh must be updated. This work presents an interactive graphics system for modeling fracture processes of two-dimensional structures. This system may consider any number of cracks that can be inserted in the model at any position, with automatic and adaptive finite element mesh generation. The system can be used for linear and elastic-plastic mechanical problems, with and without cracks. The self-adaptive process is based on an h-type refinement, with an a posteriori error estimation. Three types of error estimators are available. The first, which is based on the energy norm, is used for elastic- linear analysis. The second and the third, which are based on effective stress and on ratio of plastic work, respectively, are used for elastic-plastic analysis. Mesh generation is based on spatial decomposition techniques, which consists on a binary tree partition of boundary curves, including crack curves, and on a quadtree partition for the domain refinement. The system incorporates the following components: a geometric modeler to create the model geometry, a pre- processor that generates the initial mesh and applies model attributes, a numerical analysis module that evaluates the finite element response, and a module, called the adaptive module, that manages the adaptive process of mesh generation. The latter module also incorporates post-processing features that assist in the visualization of analysis results, including fracture parameters. In the non- linear adaptive process for incremental plasticity analysis, it is used a technique for interpolating analysis variables across distinct meshes. The von Mises yielding criterion, with isotropic hardening, is used. Some examples are presented to evaluate the methods for computing fracture analysis parameters and the performance of the adaptive process.
El análisis de problemas mecánicos y extructurales, por el método de los elementos finitos, requiere del analista cierta experiencia en la discretización del modelo para minimizar el error de la solución. La generación de la malla es una tarea árdua, que resulta todavía más difícil cuando grietas están presentes en el modelo. En un modelo discreto, cada vez que la grietas se propaga, la geometría del modelo muda y se debe actualizar la malla. En este trabajo se presenta un sistema gráfico interactivo, para modelaje bidimensional de problemas de fractura extructural. El sistema permite introducir grietas en cualquier posición en el modelo, regenerando su malla y ejecutando un proceso autoadaptativo de elementos finitos. Este sistema puede ser usado en problemas mecánicos, con o sin grietas, elásticos lineales o elastoplásticos. EL proceso autoadaptativo está basado en estimadores a posteriori del error, con refinamientodel tipo h. Tres tipos de estimadores están disponibles. El primeiro, basado en la norma de energía, se aplica en el análisis de problemas elásticos lineales. El segundo y el tercero, basados en tensión efectiva y en la razón del trabajo plástico, respectivamente, se aplican en el análisis de problemas elastoplásticos. La generación de la malla está basada en técnicas de enumeración espacial recursiva, que consiste de una partición en árbol binaria (binary tree) para las curvas del contorno, incluyendo las curvas de las grietas, y una partición en árbol cuaternaria (quadtree) para la generación de la malla en el dominio. El sistema integra diferentes herramientas: un modelador geométrico que crea la geometría del modelo, un préprocesador que genera la malla y aplica los atributos, un módulo de análisis numérico que evalúa la resposta de elementos finitos y un módulo, llamado de módulo adaptativo, que se encarga de gerenciar el proceso adaptativo de las mallas y que también constituye un posprocesador que auxilia en la visualización de los resultados, incluso de los parámetros de fractura. En el proceso adaptativo no lineal, la interpolación de las variables de solución se realiza entre mallas para que el análisis incremental de la plasticidad continue. Se presentan ejemplos que permiten evaluar los métodos de cálculo de los parámetros de fractura y el desempeño del proceso adaptativo.
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McGinnis, Daniel Frank. "Two-Dimensional Lake and Reservoir Modeling: Natural and Plume-Induced Mixing Mechanisms." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/29395.
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Lakes and reservoirs exhibit a number of mixing and transport mechanisms. Understanding the transport is crucial to understanding and predicting constituent and density structures. Transport in waterbodies can be natural, such as seiche-induced boundary mixing or advectively-driven inflows. Hypolimnetic oxygenation using bubble-plumes also leads to enhanced mixing. Whether natural or plume-induced, increased mixing will alter the waterbody properties. Conversely, the density structure affects the behavior of plumes as well as inflowing and outflowing water. For example, stratification resulting from impounding a river can result in nutrient and suspended solids retention. Similarly, operation of plumes can induce mixing in the hypolimnion, resulting in warming, increased nutrient transport, and resuspension of settled particles.
Modeling is extremely useful in determining the effects of dams on water quality constituents, enhanced transport, and the performance of mitigation techniques, such as hypolimnetic oxygenation. In this work, a variety of modeling techniques are used to evaluate natural and man-made mixing mechanisms. These include simple temperature and mass budgets, a two-dimensional lake model, and a two-phase plume model.
A bubble-plume and plume-enhanced mixing was studied in Lake Hallwil. It was found that the plume-lake interaction was much more complex then previously expected, and knowledge of the seiche- and plume-enhanced near-field was necessary to accurately model the plume performance. A two-dimensional lake model was then coupled with a linear-plume model to accurately predict not only the plume performance, but also the plume-enhanced mixing in Spring Hollow Reservoir. The same two-dimensional lake model, used in conjunction with data analysis, demonstrated that the Iron Gate I Reservoir was not a significant sink for suspended solids, with only the large, adjacent side bay (Orsova Bay) thought to be the permanent sink. Furthermore, significant stratification did not develop, preventing substantial primary productivity. While the impoundment did change the water quality characteristics, the extent is much less than previously expected. The modeling methods presented here and the coupled plume-reservoir model should be useful tools for the design, modeling and greater understanding of bubble-plumes and other transport-related phenomena in lakes and reservoirs.Ph. D.
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Alzahrani, Abdulaziz S. "Application of Two-Dimensional Hydraulic Modeling in Riverine Systems Using HEC-RAS." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1493135117254329.
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Shao, Zhiyu S. "TWO-DIMENSIONAL HYDRODYNAMIC MODELING OF TWO-PHASE FLOW FOR UNDERSTANDING GEYSER PHENOMENA IN URBAN STORMWATER SYSTEM." UKnowledge, 2013. http://uknowledge.uky.edu/ce_etds/5.
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During intense rain events a stormwater system can fill rapidly and undergo a transition from open channel flow to pressurized flow. This transition can create large discrete pockets of trapped air in the system. These pockets are pressurized in the horizontal reaches of the system and then are released through vertical vents. In extreme cases, the transition and release of air pockets can create a geyser feature.
The current models are inadequate for simulating mixed flows with complicated air-water interactions, such as geysers. Additionally, the simulation of air escaping in the vertical dropshaft is greatly simplified, or completely ignored, in the existing models.
In this work a two-phase numerical model solving the Navier-Stokes equations is developed to investigate the key factors that form geysers. A projection method is used to solve the Navier-Stokes Equation. An advanced two-phase flow model, Volume of Fluid (VOF), is implemented in the Navier-Stokes solver to capture and advance the interface.
This model has been validated with standard two-phase flow test problems that involve significant interface topology changes, air entrainment and violent free surface motion. The results demonstrate the capability of handling complicated two-phase interactions. The numerical results are compared with experimental data and theoretical solutions. The comparisons consistently show satisfactory performance of the model.
The model is applied to a real stormwater system and accurately simulates the pressurization process in a horizontal channel. The two-phase model is applied to simulate air pockets rising and release motion in a vertical riser. The numerical model demonstrates the dominant factors that contribute to geyser formation, including air pocket size, pressurization of main pipe and surcharged state in the vertical riser. It captures the key dynamics of two-phase flow in the vertical riser, consistent with experimental results, suggesting that the code has an excellent potential of extending its use to practical applications.
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Pelton, Robert John. "One-Dimensional Radial Flow Turbomachinery Performance Modeling." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2192.pdf.
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Bitter, Jamin J. "One-Dimensional Performance Modeling of Centrifugal Flow Vaned Diffusers." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1711.pdf.
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Schwarz, Mike. "Two-dimensional analytical predictive modeling of schottky barrier soi and multi-gate mosfets." Doctoral thesis, Universitat Rovira i Virgili, 2012. http://hdl.handle.net/10803/108995.
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En esta tesis se analiza el comportamiento físico de los principales mecanismos de transporte en dispositivos Schottky barrier (Double-Gate) MOSFET nanométricos, y se presentan nuevos modelos compactos apropiads. Se desarrollaron soluciones analíticas completamente bidimensionales de la electrostàtica de estos dispositivos con ayuda de la técnica de mapeado conforme Schwarz-Christoffel. Basándose en estas soluciones electrostáticas analíticas, se desarrolló un método analítico de cálculo de las corrientes. El modelo se comparó y validó con simulaciones numéricas obtenidas mediante TCAD Sentaurus para longitudes de canal de hasta 22 nm, y con medidas experimentales de dispositivos SB-UTB-MOSFET con segregación de dopantes y longitud de canal de 80 nm. Se obtuvo una muy buena concordancia entre las predicciones del modelo compacto por un lado, y las simulaciones TCAD y medidas experimentales por otro.
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De, Abreu Pedro Felipe. "Modeling the thermal performance of windows using a two-dimensional finite volume model." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21338.pdf.
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Khatami, Seyed Mehrdad. "Read Channel Modeling, Detection, Capacity Estimation and Two-Dimensional Modulation Codes for TDMR." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/577306.
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Magnetic recording systems have reached a point where the grain size can no longer be reduced due to energy stability constraints. As a new magnetic recording paradigm, two-dimensional magnetic recording (TDMR) relies on sophisticated signal processing and coding algorithms, a much less expensive alternative to radically altering the media or the read/write head as required for the other technologies. Due to 1) the significant reduction of grains per bit, and 2) the aggressive shingled writing, TDMR faces several formidable challenges. Firstly, severe interference is introduced in both down-track and cross-track directions due to the read/write head dimensions. Secondly, reduction in the number of grains per bit results in variations of bit boundaries which consequently lead to data-dependent jitter noise. Moreover, the bit to grain ratio reduction will cause some bits not to be properly magnetized or to be overwritten which introduces write errors to the system. The nature of write and read processes in TDMR necessitates that the information storage be viewed as a two-dimensional (2D) system. The challenges in TDMR signal processing are 1) an accurate read channel model, 2) mitigating the effect of inter-track interference (ITI) and inter-symbol interference (ISI) by using an equalizer, 3) developing 2D modulation/error correcting codes matching the TDMR channel model, 4) design of truly 2D detectors, and 5) computing the lower bounds on capacity of TDMR channel. The work is concerned with several objectives in regard to the challenges in TDMR systems. 1. TDMR Channel Modeling: As one of the challenges of the project, the 2D Microcell model is introduced as a read channel model for TDMR. This model captures the data-dependent properties of the media noise and it is well suited in regard to detector design. In line with what has been already done in TDMR channel models, improvements can be made to tune the 2D Microcell model for different bit to grain densities. Furthermore, the 2D Microcell model can be modified to take into account dependency between adjacent microtrack borders positions. This assumption will lead to more accurate model in term of closeness to the Voronoi model. 2. Detector Design: The need for 2D detection is not unique to TDMR systems. However, it is still largely an open problem to develop detectors that are close to optimal maximum likelihood (ML) detection for the 2D case. As one of the important blocks of the TDMR system, the generalized belief propagation (GBP) detector is developed and introduced as a near ML detector. Furthermore, this detector is tuned to improve the performance for the TDMR channel model. 3. Channel Capacity Estimation: Two dimensional magnetic recording (TDMR) is a new paradigm in data storage which envisions densities up to 10 Tb/in² as a result of drastically reducing bit to grain ratio. In order to reach this goal aggressive write (shingled writing) and read process are used in TDMR. Kavcic et al. proposed a simple magnetic grain model called the granular tiling model which captures the essence of read/write process in TDMR. Capacity bounds for this model indicate that 0.6 user bit per grain densities are possible, however, previous attempt to reach capacities are not close to the channel capacity. We provide a truly two-dimensional detection scheme for the granular tiling model based on generalized belief propagation (GBP). Factor graph interpretation of the detection problem is provided and formulated in this section. Then, GBP is employed to compute marginal a posteriori probabilities for the constructed factor graph. Simulation results show huge improvements in detection. A lower bound on the mutual information rate (MIR) is also derived for this model based on GBP detector. Moreover, for the Voronoi channel model, the MIR is estimated for the case of constrained and unconstrained input. 4. Modulation Codes: Constrained codes also known as modulation codes are a key component in the digital magnetic recording systems. The constrained code forbids particular input data patterns which lead to some of the dominant error events or higher media noise. The goal of the dissertation in regard to modulation codes is to construct a 2D modulation code for the TDMR channel which improves the overall performance of the TDMR system. Furthermore, we implement an algorithm to estimate the capacity of the 2D modulation codes based on generalized belief propagation (GBP) algorithm. The capacity is also calculated in presence of white and colored noise which is the case for TDMR channel. 5. Joint Detection and Decoding Schemes: In data recording systems, a concatenated approach toward the constrained code and error-correcting code (ECC) is typically used and the decoding is done independently. We show the improvement in combining the decoding of the constrained code and the ECC using GBP algorithm. We consider the performance of a combined modulation constraints and the ECC on a binary-input additive white Gaussian noise (AWGN) channel (BIAWGNC) and also over one-dimensional (1D) and 2D ISI channels. We will show that combining the detection, demodulation and decoding results in a superior performance compared to concatenated schemes.
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Holmes, Kenneth L. "Two-dimensional modeling of aluminum gallium nitride/gallium nitride high electron mobility transistor." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02Jun%5FHolmes.pdf.
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Baird, Eric S. "Hydrodynamic and thermal modeling of two-dimensional microdroplet arrays for digitized heat transfer." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3315772.
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Jacobs, Richard A. (Richard Alberto). "Two-dimensional modeling of the removal of contaminants from soils by electric fields." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11494.
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Barrows, Richard James. "Two Dimensional Finite Element Modeling of Swift Delta Soil Nail Wall by "ABAQUS"." PDXScholar, 1994. https://pdxscholar.library.pdx.edu/open_access_etds/4741.
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Soil nail walls are a form of mechanical earth stabilization for cut situations. They consist of the introduction of passive inclusions (nails) into soil cut lifts. These nailed lifts are then tied together with a structural facing (usually shotcrete) . The wall lifts are constructed incrementally from the top of cut down. Soil nail walls are being recognized as having potential for large cost savings over other alternatives. The increasing need to provide high capacity roadways in restricted rights of way under structures such as bridges will require increasing use of techniques such as combined soil nail and piling walls. The Swift Delta Soil Nail wall required installing nails between some of the existing pipe piling on the Oregon Slough Bridge. This raised questions of whether the piling would undergo internal stress changes due to the nail wall construction. Thus, it was considered necessary to understand the soil nail wall structure interaction in relation to the existing pile supported abutment. The purpose of this study was to investigate the Swift Delta Wall using finite element (FE) modeling techniques. Valuable data were available from the instrumentation of the swift Delta Wall. These data were compared with the results of the FE modeling. This study attempts to answer the following two questions: 1. Is there potential for the introduction of new bending stresses to the existing piling? 2. Is the soil nail wall system influenced by the presence of the piling? A general purpose FE code called ABAQUS was used to perform both linear and non-linear analyses. The analyses showed that the piling definitely underwent some stress changes. In addition they also indicated that piling influence resulted in lower nail stresses. Comparison of measured data to predicted behavior showed good agreement in wall face deflection but inconsistent agreement in nail stresses. This demonstrated the difficulty of modeling a soil nail due to the many variables resulting from nail installation.
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Myrland, Johanna. "Two-dimensional hydraulic modeling for flood assessment of the Rio Rocha, Cochabamba, Bolivia." Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-229921.
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Historically humans have settled in river valleys, which has made flooding a natural hazard for human communities. This is also the situation in the valley of Cochabamba, which is frequently affected by floods. Therefore it is of high relevance to assess and manage the flood risk in order to reduce the impact in the affected areas. For this purpose hydraulic simulations were performed with the two-dimensional model Iber. The study area includes 17 kilometers of the main river, Rio Rocha, and its tributaries. The data used in the project was elevation data of high resolution and computed hydrographs. Field work and sensitivity analysis were performed to evaluate the result. The model was used to describe the dynamics of the Rio Rocha and its tributaries during flooding, such as flow path and water levels. The simulations showed that flooding mainly occurs in the tributaries and at eleven other sites without a clear riverbank. Most of the area affected by flooding is agricultural land, but also residential areas and infrastructure were also at risk. The flood duration shown to be longest for agricultural land, which can lead to major crop damage due to anoxic condition. Even though a smaller part of the affected area is residential land, the urbanization in this area is predicted to increase and more land may be settled in the near future.This thesis, along with other studies, highlights the importance of high resolution mesh to perform a hydraulic simulation with a two-dimensional model and the need of data to validate the result.
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Owen, Charles Blake. "Two Dimensional Friction Stir Welding Model with Experimental Validation." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1200.pdf.
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Gu, Hongmei. "Structure Based, Two-dimensional, Anisotropic, Transient Heat Conduction model for Wood." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/28938.
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The importance of precise values for the parameters used in heat and mass transfer models has been demonstrated by many research studies. Thermal conductivity values used in previous models are usually empirical and fluctuate. Theoretical analysis and estimations of wood thermal conductivities in the radial and tangential directions were conducted with the geometric models built up from the macro- and micro-structure observations. Theoretically, thermal conductivity in the radial direction is about 1.5 to 2.5 times of the tangential direction for softwood species with moisture content (MC) below Fiber Saturation Point (FSP). When MC is over the FSP, tangential radial thermal conductivity both increase dramatically and are linear function of MC. The two thermal conductivity values are close with a ratio of near one estimated by the model for MC above the FPS. In hardwood species, radial thermal conductivity estimated by the model is 1.5 times of the tangential thermal conductivity. Validation tests for model estimations of thermal conductivities in the radial and tangential directions for three wood species showed the reliability of the geometric models developed in this project. Correlations between the wood thermal conductivity and structure parameters, such as latewood percentage and cell wall percentage, were examined. Linear relationships for the thermal conductivity and average temperature in wood were established in both radial and tangential directions of three wood species.
A two-dimensional transient heat conduction model was developed utilizing thermal conductivity values derived from geometric models. The anisotropic material property affect on heat transport in radial and tangential directions was discussed using an assumed situation. The simulation run showed slightly faster heat flow in the radial direction than in the tangential direction due to higher thermal conductivity in the radial direction. Validation tests on practical wood blocks showed the 2D model with the use of theoretical thermal conductivity values can predict good temperature distribution in wood during the heating process. However, in the practical wood samples with curved rings on the cross section, no significant difference was found in the two transverse directions.
Mathematica software was introduced in this study for the intense and complicated math calculations and model programming. Mathematica was found to be a powerful technique for solving sophisticated math problems. It had abundant and flexible plotting options for providing optimized presentations for the results. These advantages make Mathematica popular for engineering modeling research.Ph. D.
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Dolzhenko, Egor. "Modeling State Transitions with Automata." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4468.
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Models based on various types of automata are ubiquitous in modern science. These models allow reasoning about deep theoretical questions and provide a basis for the development of efficient algorithms to solve related computational problems. This work discusses several types of automata used in such models, including cellular automata and mandatory results automata.
The first part of this work is dedicated to cellular automata. These automata form an important class of discrete dynamical systems widely used to model physical, biological, and chemical processes. Here we discuss a way to study the dynamics of one-dimensional cellular automata through the theory of two-dimensional picture languages. The connection between cellular automata and picture languages stems from the fact that the set of all space-time diagrams of a cellular automaton defines a picture language. We will discuss a hierarchy of cellular automata based on the complexity of the picture languages that they define. In addition to this, we present a characterization of cellular automata that can be described by finite-state transducers.
The second part of this work presents a theory of runtime enforcement based on mech- anism models called Mandatory Results Automata (MRAs). MRAs can monitor and trans- form security-relevant actions and their results. Because previous work could not model general security monitors transforming results, MRAs capture realistic behaviors outside the scope of previous models. MRAs also have a simple but realistic operational seman- tics that makes it straightforward to define concrete MRAs. Moreover, the definitions of policies and enforcement with MRAs are significantly simpler and more expressive than those of previous models. Putting all these features together, we argue that MRAs make good general models of (synchronous) runtime mechanisms, upon which a theory of run- time enforcement can be based. We develop some enforceability theory by characterizing the policies deterministic and nondeterministic MRAs enforce.
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Struble, John D. "Micro-scale planar and two-dimensional modeling of two phase composites with imperfect bonding between matrix and inclusion." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17345.
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Obregon, Oliver. "Evaluating Climate Change Effects in Two Contrasting Reservoirs Using Two-Dimensional Water Quality and Hydrodynamic Models." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3094.
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I analyzed and compared impacts from global climate change (GCC) and land use change to Deer Creek (United States) a temperate reservoir and Aguamilpa (Mexico), a tropical reservoir by using calibrated CE-QUAL-W2 (W2) water quality and hydrodynamic models based on field data over an extended time period. I evaluated and compared the sensitivity to predicted GCC and land use changes. I individually evaluated changes to air temperature (TAIR), inflow rates (Q), and nutrient loads (PO4-P and NO3-NO2-N) followed by analysis of worst case scenarios. I developed analysis methods using indexes to represent the total reservoir change calculated using the total parameter mass (i.e., algae, dissolved oxygen, total dissolved solids) normalized by the reservoir volume to eliminate apparent mass changes due to volume changes. These indexes have units of average concentrations, but are better thought of as a global reservoir index or normalized concentration. These indexes allow analysis of the total reservoir and not just specific zones. Total normalized algal concentrations were impacted more by changes in nutrient inflows (land use) in both reservoirs than to changes in TAIR and Q. For Deer Creek, PO4-P changes significantly increased normalized algal concentrations in the reservoir and in dam releases when PO4-P inflow was increased by 50%. Aguamilpa was more sensitive to NO3-NO2-N changes, exhibiting significant increases in normalized algal concentration for the +50% NO3-NO2-N simulation. Both reservoirs showed small changes to normalized algal concentration for the +3ºC TAIR simulation with the largest changes occurring during warm seasons. However, Deer Creek exhibited decreased total algal levels when TAIR was increased by 3ºC while Aguamilpa showed increased total algal levels with the 3ºC increase in TAIR. These contrasting trends, a decrease in Deer Creek and an increase in Aguamilpa, were produced by algae succession processes. Changes in Q affected normalized algal concentration in both reservoirs in different ways. In Aguamilpa, total algal levels increased under dry conditions while Deer Creek showed little general change associated with flow changes. Worst case scenario simulations, which included changing more than one parameter, showed that GCC changes can cause large impacts if they occur simultaneously with high nutrient loadings. These results begin to show how GCC could impact reservoirs and how these impacts compare to potential impacts from land use change. The results show that both temperate and tropical reservoirs are impacted by GCC but are more sensitive to nutrients. The methods, plots, and tools developed in this study can assist water managers in evaluating and studying GCC and land use changes effects in reservoirs worldwide.
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Griffin, Patrick D. "Two-dimensional modeling of a chemically reacting boundary layer flow in a catalytic reactor." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0014866.
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Tuesday, Andrew J. "Modeling Atomic Defects in a Two-Dimensional Lennard-Jones Lattice Using Molecular Dynamics Simulations." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1334579948.
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Xiao, Ying. "A Two-dimensional Stochastic Model for Prediction of Localized Corrosion." Ohio University / OhioLINK, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1108481091.
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Hacarlioglu, Pelin. "Experimental and Modeling Studies of the Methane Steam Reforming Reaction at High Pressure in a Ceramic Membrane Reactor." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/29580.
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This dissertation describes the preparation of a novel inorganic membrane for hydrogen permeation and its application in a membrane reactor for the study of the methane steam reforming reaction. The investigations include both experimental studies of the membrane permeation mechanism and theoretical modeling of mass transfer through the membrane and simulation of the membrane reactor with 1-D and 2-D models.
A hydrothermally stable and hydrogen selective membrane composed of silica and alumina was successfully prepared on a macroporous alumina support by chemical vapor deposition in an inert atmosphere at high temperature. Before the deposition of the silica-alumina composite, multiple graded layers of alumina were coated on the alumina support with a mean pore size of 100 nm by the sequential application of three boehmite sols with gradually decreasing sol particle sizes of 630, 200 and 40 nm, respectively. The resulting supported composite alumina-silica membrane had high permeability for hydrogen in the order of 10-7 mol m-2 s-1 Pa-1 at 873 K with a H2 /CH4 selectivity of 940 and exhibited much higher stability to water vapor at the high temperature of 873 K. In addition, the same unusual permeance order of Heï¼ H2ï¼ Ne previously observed for the pure silica membrane was also observed for the alumina-silica membrane, indicating that the silica structure did not change much after introduction of the alumina. The permeation of hydrogen and helium through vitreous glass and silica membranes was modeled using ab initio density functional calculations. Comparison of the calculated activation energies to those reported for vitreous glass (20â 40 kJ mol -1) indicated the presence of 5- and 6-membered siloxane rings, consistent with the accepted structure of glass as a disordered form of cristobalite.
The experimental studies of the steam reforming of methane were examined at various temperatures (773-923 K) and pressures (1-20 atm) with a commercial Ni/MgAl2O4 catalyst in a hydrogen selective silica-alumina membrane reactor and compared with a packed bed reactor. One-dimensional and two-dimensional modeling of the membrane rector and the packed bed reactor were performed at the same conditions and their performances were compared with the values obtained in the experimental study. Improved methane conversions and hydrogen yields were obtained in the membrane reactor compared to the packed bed reactor at all temperatures and pressures. From the two modeling studies, it was also found out that the two-dimensional model performed better in the membrane reactor case especially at higher pressures.Ph. D.
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Costa, Paula Dornhofer Paro 1978. "Two-dimensional expressive speech animation = Animação 2D de fala expressiva." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260903.
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Orientador: José Mario De MartinoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: O desenvolvimento da tecnologia de animação facial busca atender uma demanda crescente por aplicações envolvendo assistentes, vendedores, tutores e apresentadores de notícias virtuais; personagens realistas de videogames, agentes sociais e ferramentas para experimentos científicos em psicologia e ciências comportamentais. Um aspecto relevante e desafiador no desenvolvimento de cabeças falantes, ou "talking heads", é a reprodução realista dos movimentos articulatórios da fala combinados aos elementos de comunicação não-verbal e de expressão de emoções. Este trabalho presenta uma metodologia de síntese de animação facial baseada em imagens, ou animação facial 2D, que permite a reprodução de uma ampla gama de estados emocionais de fala expressiva, além de suportar a modulação de movimentos da cabeça e o controle de elementos faciais tais como o piscar de olhos e o arqueamento de sobrancelhas. A síntese da animação utiliza uma base de imagens-protótipo que são processadas para obtenção dos quadros-chave da animação. Os pesos utilizados para a combinação das imagens-protótipo são derivados de um modelo estatístico de aparência e formas, construído a partir de um conjunto de imagens de treinamento extraídas de um corpus audiovisual de uma face real. A síntese das poses-chave é guiada pela transcrição fonética temporizada da fala a ser animada e pela informação do estado emocional almejado. As poses-chave representam visemas dependentes de contexto fonético que implicitamente modelam os efeitos da coarticulação na fala visual. A transição entre poses-chave adjacentes é realizada por um algoritmo de metamorfose não-linear entre imagens. As animações sintetizadas aplicando-se a metodologia proposta foram avaliadas por meio de avaliação perceptual de reconhecimento de emoções. Dentre as contribuições deste trabalho encontra-se a construção de uma base de dados de vídeo e captura de movimento para fala expressiva em português do Brasil
Abstract: The facial animation technology experiences an increasing demand for applications involving virtual assistants, sellers, tutors and newscasters; lifelike game characters, social agents, and tools for scientific experiments in psychology and behavioral sciences. A relevant and challenging aspect of the development of talking heads is the realistic reproduction of the speech articulatory movements combined with the elements of non-verbal communication and the expression of emotions. This work presents an image-based, or 2D, facial animation synthesis methodology that allows the reproduction of a wide range of expressive speech emotional states and also supports the modulation of head movements and the control of face elements, like the blinking of the eyes and the raising of the eyebrows. The synthesis of the animation uses a database of prototype images which are combined to produce animation keyframes. The weights used for combining the prototype images are derived from a statistical active appearance model (AAM), which is built from a set of sample images extracted from an audio-visual corpus of a real face. The generation of the animation keyframes is driven by the timed phonetic transcription of the speech to be animated and the desired emotional state. The keyposes consist of expressive context-dependent visemes that implicitly model the speech coarticulation effects. The transition between adjacent keyposes is performed through a non-linear image morphing algorithm. To evaluate the synthesized animations, a perceptual evaluation based on the recognition of emotions was performed. Among the contributions of the work is also the building of a database of expressive speech video and motion capture data for Brazilian Portuguese
Doutorado
Engenharia de Computação
Doutora em Engenharia Elétrica
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Mollier, Stéphane. "Two-dimensional macroscopic models for large scale traffic networks." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALT005.
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Les fréquentes congestions que connaissent les réseaux routiers des grandes métropoles mondiales ont de lourdes conséquences économiques et environnementales. La compréhension et la modélisation dynamique des mécanismes à l'origine de ces congestions permettent d'en prédire l'évolution et donc d'améliorer l'efficacité des politiques de régulations utilisées par les opérateurs du réseau.La modélisation des réseaux routiers a commencé par le cas d'une route isolée puis a été étendue à des réseaux urbains. Ce changement d'échelle présente de nombreuses difficultés en matière de temps de calcul, de calibrage et de scénarisation, ce qui a incité la communauté scientifique à s'intéresser à des modèles agrégés, décrivant une représentation simplifiée de la réalité. Un de ces modèles vise à représenter de denses réseaux urbains par une équation aux dérivées partielles continue dans le plan. Ainsi, les véhicules sont représentés par une densité bi-dimensionnelle et leurs trajectoires sont décrites comme des directions de flux.L'objectif de la thèse est de développer cette approche et de proposer des méthodes pour son calibrage et sa validation. Les contributions correspondent à trois extensions successives du modèle. Tout d'abord, un simple modèle bi-dimensionnel est proposé pour le cas de réseaux homogènes --avec des limitations de vitesse et des concentrations de routes similaires en tout point-- et dans lesquels une direction de propagation privilégiée existe. Une méthode de comparaison avec un microsimulateur est présentée. Ensuite, le modèle est étendu au cas de réseaux hétérogènes --avec des limitations de vitesse et des concentrations de routes variables-- mais toujours avec une direction privilégiée. Ces dépendances spatiales permettent de décrire les phénomènes d'engorgement existant dans les réseaux routiers. Enfin, un modèle constitué de plusieurs couches, chacune représentant une direction de flux différente, est étudié. La complexité de la modélisation réside dans la formulation des interactions entre les différentes directions. Ce type de modèle n'est pas toujours hyperbolique ce qui impacte sa stabilitéCongestion in traffic networks is a common issue in big cities and has considerable economic and environmental impacts. Traffic policies and real-time network management can reduce congestion using prediction of dynamical modeling. Initially, researchers studied traffic flow on a single road and then, they extended it to a network of roads. However, large-scale networks present challenges in terms of computation time and parameters' calibration. This led the researchers to focus on aggregated models and to look for a good balance between accuracy and practicality.One of the approaches describes traffic evolution with a continuous partial differential equation on a 2D-plane. Vehicles are represented by a two-dimensional density and their propagation is described by the flow direction. The thesis aims to develop these models and devises methods for their calibration and their validation. The contributions follow three extensions of the model.First, a simple model in two-dimensional space to describe a homogeneous network with a preferred direction of flow propagation is considered. A homogeneous network has the same speed limits and a similar concentration of roads everywhere. A method for validation using GPS probes from microsimulation is provided. Then, a space-dependent extension to describe a heterogeneous network with a preferred direction of flow propagation is presented. A heterogeneous network has different speed limits and a variable concentration of roads. Such networks are of interest because they can show how bottleneck affects traffic dynamics. Finally, the case of multiple directions of flow is considered using multiple layers of density, each layer representing a different flow direction. Due to the interaction between layers, these models are not always hyperbolic which can impact their stability
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Zang, Di [Verfasser]. "Signal modeling for two-dimensional image structures and scale-space based image analysis / Di Zang." Kiel : Universitätsbibliothek Kiel, 2009. http://d-nb.info/1019866292/34.
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Boykov, Nikolay D. "Two-dimensional gravity modeling of the Rattlesnake Springs watershed, Carlsbad Caverns National Park, New Mexico." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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