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1
Cheng, Chuen-kei Joseph y 鄭傳基. "Path perception from optic flow". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B4961759X.
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Perceiving the path we are travelling on is important for successful navigation. Relative motion between the world and the observer generates optical flow on the retinae (retinal flow). Gibson (1950) pointed out that when travelling on a straight path with no eye, head, or body rotation, retinal flow is radial and the stationary point indicates the instantaneous direction of travelling, or heading, of the observer. The straight path can then be recovered as it coincides with heading.
Nevertheless, it is rarely the case that people travel with no rotation. Instead, they normally look at different points of interest when they are navigating. The result of changing one's gaze or rotating one's head is the addition of a rotational component, which is a laminar flow, to the flow field. The rotational component shifts the stationary point from heading and makes heading perception difficult. Extensive research has been conducted on how the human visual system removes the rotational component of the retinal flow and how extra-retinal information, such as efferent copies of eye muscle commands, may contribute to this process.
The paths on which people travel are not always straight, but often curved. When a path is curved, it no longer coincides with heading. In this case, heading is the tangent of the path. Researchers have proposed theories to explain how curved paths are perceived. Each of them requires different visual information and gaze conditions (e.g., fixating on a target or gazing along the heading direction). They can be categorized by whether or not path perception depends on heading perception.
The goal of this thesis is to systematically examine different theories of path perception and determine how humans perceive curved paths. Study 1 examined different path perception theories by comparing human path perception performance in various gaze conditions and with the availability of various optic flow information. Study 2 investigated whether path perception depends on heading perception. Study 3 examined the contribution of reference objects to path perception. Study 4 investigated how extra-retinal informationcontribute to path perception.
The experiments that I present here show that (a) when there is no extra-retinal information, path perception is accurate only when one's gaze is along heading such that the rotation in the flow field is equal to path rotation; (b) when one's gaze is not along heading such that the rotation in the flow field is not equal to path rotation, path perception is inaccurate. Adding more visual information, such as acceleration, dense flow field, and/ or reference objects does not improve the accuracy; (c) eye movement signals support accurate path perception only in the natural case of self-motion in which body orientation is aligned with heading such that eye movement signals help to stabilize heading in the body-centric coordinate system.published_or_final_version
Psychology
Doctoral
Doctor of Philosophy
2
Gough, William Dennis. "Automated Flow Path Design Optimization Using Mesh Morphing". BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2843.
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The use of CAD models and CFD analysis has become an essential part of fluid flow design. To reduce the time spent determining a design, optimization frameworks have been implemented to automate the process. Mesh morphing has been implemented within these frameworks to further reduce the time needed. While optimization methods have been developed to optimize a fluid flow path, the optimum design needs to be recreated in a CAD model. A method has been developed which eliminates the need to recreate the optimal results in CAD. This is accomplished by using mesh morphing, CAD and CFD together in an optimization framework. The method developed has been implemented with a significant time savings over the use of a traditional meshing optimization framework.
3
Shukla, Ankur. "Image Based Flow Path Recognition for Chromatography Equipment". Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-392105.
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The advancement in computer vision field with the help of deep learning methods is significant. The increase in computational resources, have lead researchers developing solutions that could help them in achieving high accuracy in image segmentation tasks. We performed segmentation of different types of objects in the chromatography instruments used in GE Healthcare, Uppsala. In this thesis project, we investigated methods in Computer vision and deep learning to segment out the different type of objects in instrument image. For a machine to automatically learn the features directly from instrument image, a deep convolutional neural network was implemented based on a recently developed existing architecture. The dataset was collected and preprocessed before using it with the neural network model. The model was trained with two different architecture Unet and Segnet developed for image segmentation. Both the used architecture is efficient and suitable for semantic segmentation tasks. Among different components to segment out in the instrument, there was a thin pipe. Unet was able to achieve good results while segmenting thin pipes with fewer data as well. Results show that Unet can act as a suitable architecture for segmenting different objects in an instrument even if we have only 100 images. Further advances can be done to improve the performance of the model by generating a better mask of the model and finding a way to collect more data for training the model.
4
Ryu, Seungkyu. "Modeling Transportation Planning Applications via Path Flow Estimator". DigitalCommons@USU, 2015. https://digitalcommons.usu.edu/etd/4225.
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The Path Flow Estimator (PEE) concept was originally developed to estimate path flows (hence origin-destination flows) and link flows for a whole road network (given some counts at selected roads). It is now further developed as an alternative for modeling different transportation planning applications: (1) a bicycle network analysis tool for non-motorized transportation planning, (2) a multi-class traffic assignment model for freight planning, and (3) a simplified travel demand forecasting framework for small community planning.
The first application of the redeveloped PFE is to develop a two-stage bicycle traffic assignment model for estimating/predicting bicycle volumes on a transportation network. The first stage considers key criteria (e.g., distance related attributes, safety related attributes, air quality related attributes etc.) to generate a set of non-dominated (or efficient) paths, while the second stage adopts several traffic assignment methods to determine the flow allocations to the network. This two-stage approach can be used as a stand-alone bicycle traffic assignment to the transportation network given a bicycle origin-destination (O-D) matrix. The second application aims to enhance the realism of traffic assignment models for freight planning by incorporating different modeling considerations into the multi-class traffic assignment problem. These modeling considerations involve developing both model formulation and customized solution algorithm, which in turn involve asymmetric interactions among different vehicle types (i.e., cars versus trucks), a path-size logit (PSL) model (for accounting random perceptions of network conditions with explicit consideration of route overlapping), and various traffic restrictions imposed either individually or together to multiple vehicle types in a transportation network. In the third application, a simplified planning framework is developed to perform planning applications in small communities where limited planning resources hinder the development and application of a full four-step model. Two versions (i.e., base year and future year) of the PFE are proposed to address the specific transportation planning issues and needs of small communities.
These new PFE developments for planning applications are tested with different realistic transportation networks. The results suggest that the new PFE applications proposed in this dissertation provide an alternative to the traditional four-step travel demand forecasting model that can be used as a stand-alone application with better modeling capability and fewer resources.
5
SoÌlyom, PeÌter. "The effect of flow path geometry on landscape evolution". Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422439.
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Jackson, George Andrew. "Multiple path ultrasonic flow measurement techniques : theory and practice". Thesis, University of Liverpool, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.232944.
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Jhunjhunwala, Manish. "Multiphase flow and control of fluid path in microsystems". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/37456.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2005.Includes bibliographical references.
Miniaturized chemical-systems are expected to have advantages of handling, portability, cost, speed, reproducibility and safety. Control of fluid path in small channels between processes in a chemical/biological network is crucial for connecting process elements. We show complete separation of individual phases (phase routing) from two-phase gas-liquid and liquid-liquid (aqueous-organic) mixtures on microscale. To provide for robust interfacing of operations in a network, we demonstrate this ability over a wide range of two-phase flow conditions, including transient ones. Enabled by the technique for complete separation of individual phases from two-phase mixtures, we show mixing of liquids by introduction of a passive gas-phase and demonstrate integration of mixing, reaction and phase separation on a single platform. Additionally, we use the principles developed for phase routing to design microfluidic valves that do not rely on elastic deformation of material. Such valves can be used in a variety of chemical environments, where polymer-based deformable materials would fail.
(cont.) We show a concept for realization of logic-gates on microscale using appropriate connections for these valves, paving the way for design of automation and computational control directly into microfluidic analysis without use of electronics. Further, we use the phase separation concept for sampling liquid from gas-liquid and liquid-liquid mixtures. Such sampling ability, when coupled with a suitable analysis system, can be used for retrieving process information (example mass-transfer coefficients, chemical kinetics) from multiphase-processes. We provide evidence of this through estimation of mass-transfer coefficients in a model oxygen-water system and show at least an order-of-magnitude improvement over macroscale systems. Controlled definition of fluid path enabled by laminar flow on microscale is used in a large number of applications. We examine the role of gravity in determining flow path of fluids in a microchannel. We demonstrate density-gradient-driven flows leading to complete reorientation of fluids in the gravitational field.
(cont.) We provide estimates of the time and velocity scales for different parameter ranges through two-dimensional and three-dimensional finite-element models, in agreement with experimental observations. We believe this thesis addresses a number of both: system and fundamental issues, advancing applications and understanding of microfluidic networks.
by Manish Jhunjhunwala.
Ph.D.
8
Poletto, Massimiliano Antonio. "Path splitting--a technique for improving data flow analysis". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/35028.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (p. 83-87).
by Massimiliano Antonio Poletto.
M.Eng.
9
Chen, Ying Chih. "Visualizing Load Path in Perforated Shear Walls". Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7609.
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Shear walls are the primary lateral load resisting elements in bearing wall systems used in masonry construction. Horizontal loads due to wind or earthquake are transferred to vertical walls by diaphragms that are rigid such as concrete floor slabs or flexible such as wood floors. With rigid diaphragms, loads are apportioned to the supporting walls based on their relative rigidity. Walls with openings accommodating doors and windows (“perforated walls”) have reduced rigidity that can be determined using available hand calculation methods. These methods primarily focus on analysis procedures, not on the visualization of the load path that is critically important in structural engineering practice.
The analogy of springs in series or parallel is used to determine the equivalent stiffness of elastic systems in structural dynamics. This thesis uses this analogy to develop a method that can help visualize load flow in perforated shear walls connected to rigid diaphragms. Rigidities are calculated using existing methods and combined as springs in series or parallel to represent a perforated wall. Loads taken by the wall segments correspond to the electrical current flowing through this imaginary “circuit”. To help visualize the load path, the line drawing representation of springs in series or parallel and the applied lateral load are deliberately oriented in the vertical direction. The application of the analogy is illustrated by several numerical examples of varying complexity taken from text books. Finite element solutions are included in the comparisons to provide a measure of the relative accuracy of hand calculation methods.
The analogy can be extended to refine existing hand calculation methods though this increases computational effort. It improves accuracy but only for cases where the aspect ratio of the wall segments is such that shear effects are dominant.
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Kaya, Mustafa. "Path Optimization Of Flapping Airfoils Based On Unsteady Viscous Flow Solutions". Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12609349/index.pdf.
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The flapping path of a single airfoil and dual airfoils in a biplane configuration is optimized for maximum thrust and/or propulsive efficiency. Unsteady, low speed viscous flows are computed using a Navier-Stokes solver in a parallel computing environment. A gradient based algorithm and Response Surface Methodology (RSM) are employed for optimization. The evaluation of gradient vector components and the design of experiments for RSM, which require unsteady solutions, are also carried out in parallel. Parallel computations are performed using Parallel Virtual Machine (PVM) library. First, a single airfoil undergoing a combined sinusoidal or non-sinusoidal pitching and plunging motion is studied. The non-sinusoidal flapping motion is described using an elliptic curve or Non-Uniform Rational B-Splines
(NURBS). It is shown that the thrust generation may significantly
be increased in comparison to the sinusoidal flapping motion. For
a high thrust, the airfoil stays at high effective angle of attack
values during the upstroke and the downstroke, and the effective pitching occurs at minimum and maximum plunge positions. Secondly, the optimization of sinusoidal and non-sinusoidal flapping paths of dual airfoils is considered. Moving and deforming overset grids are used for computations. The deforming overset grids remove the restrictions on the flapping motion, and improve the optimization results obtained earlier. At low flapping frequencies, an airfoil in a biplane configuration produces more thrust than a single airfoil. Yet, at high frequencies the airfoil in biplane configuration produces less thrust at a significantly lower efficiency than the single airfoil.
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Sanders, Johnny Ray. "Understanding the material flow path of the friction stir weld process". Master's thesis, Mississippi State : Mississippi State University, 2005. http://library.msstate.edu/etd/show.asp?etd=etd-11102005-142957.
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Bakkalbasi, Omer. "Flow path network design and layout configuration for material delivery systems". Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/25617.
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Mishra, Shashank. "Developing Novel Computational Fluid Dynamics Technique for Incompressible Flow and Flow Path Design of Novel Centrifugal Compressor". University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1460731437.
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Sawyer, Frederick Emile. "Coupled mixing-cell and mass balance flow path models of the White River Flow System, Nevada, USA". abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1467765.
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Pirbhai, Shafiq. "Using mobile agents and maximum path flow algorithms to maximize network utilization". Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/27165.
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The purpose of this thesis is to show how the use of one or more of the shortest augmenting path (polynomial time) algorithms are used to maximize the bandwidth usage and minimize the cost and latency in Multiprotocol Label Switched (MPLS) networks. The thesis will also show how providers that offer services such as Virtual Private Networks (VPNs) based on Border Gateway Protocol (BGP) and MPLS, or Virtual Private LAN Services (VPLS) can use such an algorithm to offer premium services to higher paying customers.
This thesis extends the problem of adaptive routing in communications networks:
It focuses on maximizing the bandwidth usage in a MPLS network by using a modified augmenting path algorithm. The algorithm is influenced by Resource Reservation Protocol (RSVP) to reserve traffic flows on routers. The algorithm proposed is inspired by previous research in the area of indirect communication among agents through modifications induced in their environment or simply known as stigmergy. The agents implement the Edmonds Karp Algorithm rather than the pheromone tables in stigmergy. By using a mobile agents approach, the Augmenting Path Algorithm is adapted to find the maximum flow through a network.
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AGARKAR, KEDAR GIRISH. "FLOW PATH DESIGN AND RELIABILITY OF AUTOMATED GUIDED VEHICLES IN MATERIAL HANDLING". University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1089661534.
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Agarkar, Kedar G. "Flow path design and reliability of automated guided vehicles in material building". Cincinnati, Ohio : University of Cincinnati, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1089661534.
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Geng, Xi. "The signature of a rough path : uniqueness". Thesis, University of Oxford, 2015. http://ora.ox.ac.uk/objects/uuid:f15c0439-2b30-4738-9eab-0dffd86bed69.
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The main contribution of the present thesis is in two aspects. The first one, which is the heart of the thesis, is to explore the fundamental relation between rough paths and their signatures. Our main goal is to give a geometric characterization of the kernel of the signature map in different situations. In Chapter Two, we start by establishing a general fact that a continuous Jordan curve on a Riemannian manifold can be arbitrarily well approximated by piecewise minimizing geodesic interpolations which are again Jordan. This result enables us to prove a generalized version of Green’s theorem for planar Jordan curves with finite p-variation 1 ≤ p < 2, and to prove that two such Jordan curves have the same signature if and only if they are equal up to reparametrization. In Chapter Three, we investigate the problem for general weakly geometric rough paths. In particular, we show that a weakly geometric rough path has trivial signature if and only if it is tree-like in the sense we will define later on. In Chapter Four, we study the problem in the probabilistic setting. In particular, we show that for a class of stochastic processes, with probability one the sample paths are determined by their signatures up to reparametrization. A fundamental example is Gaussian processes including fractional Brownian motion with Hurst parameter H > 1/4, the Ornstein-Uhlenbeck process and the Brownian bridge. The second one is an application of rough path theory to the study of nonlinear diffusions on manifolds under the framework of nonlinear expectations. In Chapter Five, we begin by studying the geometric rough path nature of G-Brownian motion. This enables us to introduce rough differential equations driven by G-Brownian motion from a pathwise point of view. Next we establish the fundamental relation between rough (pathwise theory) and stochastic (L2-theory) differential equations driven by G-Brownian motion. This is a crucial point of understanding nonlinear diffusions and their generating heat flows on manifolds from an intrinsic point of view. Finally, from the pathwise point of view we construct G-Brownian motion on a compact Riemannian manifold and establish its generating heat flow for a class of G-functions under orthogonal invariance. As an independent interest, we also develop the Euler-Maruyama scheme for stochastic differential equations driven by G-Brownian motion.
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Wright, Steven Douglas. "A linear programming approach to path flow estimation in SCOOT controlled road networks". Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337371.
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Rivera, Grant. "Mapping Traffic Flow for Telemetry System Planning". International Foundation for Telemetering, 2010. http://hdl.handle.net/10150/605957.
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ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, CaliforniaTelemetry receivers must typically be located so that obstacles do not block the signal path. This can be challenging in geometrically complex indoor environments, such as factories, health care facilities, or offices. An accurate method for estimating the paths followed by typical telemetry transmitters in these environments can assist in system planning. It may be acceptable to provide marginal coverage to areas which are rarely visited, or areas which transmitters quickly transit. This paper discusses the use of the ant colony optimization and its application to the telemetry system planning problem.
21
Chen, Ming-Te Mark. "Flow path design of a class of material handling systems for robustness and reliability". Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/25381.
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Huber, Florian M. [Verfasser]. "Impact of kinetics and flow path heterogeneity on nanoparticle/radionuclide migration / Florian Mathias Huber". Berlin : Freie Universität Berlin, 2012. http://d-nb.info/1026695147/34.
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Williams, Matthew. "Investigation of machine vision and path planning methods for use in an autonomous unmanned air vehicle". Thesis, Bangor University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367393.
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Dubé, Denis. "Flight path of pollinators foraging on impatiens : decision rules and their implications for gene flow". Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61990.
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Angella, Giuliano. "Strain path, flow stress and microstructure evolution of an austenitic stainless steel at high temperature". Thesis, University of Sheffield, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251254.
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Wei, Quantum Jichi. "Time-optimal path planning in uncertain flow fields using stochastic dynamically orthogonal level set equations". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98749.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 53-54).
Path-planning has many applications, ranging from self-driving cars to flying drones, and to our daily commute to work. Path-planning for autonomous underwater vehicles presents an interesting problem: the ocean flow is dynamic and unsteady. Additionally, we may not have perfect knowledge of the ocean flow. Our goal is to develop a rigorous and computationally efficient methodology to perform path-planning in uncertain flow fields. We obtain new stochastic Dynamically Orthogonal (DO) Level Set equations to account for uncertainty in the flow field. We first review existing path-planning work: time-optimal path planning using the level set method, and energy-optimal path planning using stochastic DO level set equations. We build on these methods by treating the velocity field as a stochastic variable and deriving new stochastic DO level set equations. We use the new DO equations to simulate a simple canonical flow, the stochastic highway. We verify that our results are correct by comparing to corresponding Monte Carlo results. We explore novel methods of visualizing the results of the equations. Finally we apply our methodology to an idealized ocean simulation using Double-Gyre flows.
by Quantum Jichi Wei.
S.B.
27
Rodgers, Paul John. "Natural tracers as tools for upscaling hydrological flow path understanding in two mesoscale Scottish catchments". Thesis, University of Aberdeen, 2004. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU188552.
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Natural geochemical and isotopic tracers were used to assess and model hydrological processes in two mesoscale (>200km2) catchments in the Scottish highlands, the Feshie and Feugh, in order to upscale understanding from the traditional headwater catchment scale (<10km2). Gran alkalinity was used as a geochemical tracer to distinguish acidic, organically enriched soil water from more alkaline groundwater. Spatial variations in alkalinity reflected the influence of different hydrological sources at the sub-catchment and catchment-wide scale, whereas temporal alkalinity variation at different flows over the hydrological year and over shorter event timescales provided information on the influence of hydrological flow paths. The well-defined relationship between alkalinity and flow meant that two-component end member mixing analysis could be used to quantify the influence of these hydrological flow paths and sources over a range of scales and contrasting catchment characteristics. These techniques were then used to examine more specific groundwater-surface water interactions in the River Feshie's extensive braided section. These interactions were seen to exert a significant and dynamic impact on the hydrochemistry of main stem surface flows and as a result, the hydrological and hydroecological functioning of the catchment as a whole. Stable isotope (18O) variations were also employed as a natural tracer to further investigate hydrological flow paths and provide preliminary catchment residence time estimates. These estimates indicated the relative dominance of catchment characteristics over the more general influence of scale in determining the age sources of catchment runoff. This represented one of the first such assessments of stable isotopic tracers for investigating catchment hydrology other than at the headwater scale. The natural tracer approach therefore provided considerable insight into mesoscale catchment hydrological functioning that would not have been feasible through more conventional small-scale hydrometric investigation. This has direct utility for the sustainable management of such catchment systems as well as highlighting the potential for applying such tracer investigations in order to help structure and validate more accurate hydrological models.
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Hammer, Christian. "Information flow control for Java a comprehensive approach based on path conditions in dependence graphs". Karlsruhe Univ-Verl. Karlsruhe, 2009. http://d-nb.info/996983112/04.
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Beddiaf, Salah. "Continuous steepest descent path for traversing non-convex regions". Thesis, University of Hertfordshire, 2016. http://hdl.handle.net/2299/17175.
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In this thesis, we investigate methods of finding a local minimum for unconstrained problems of non-convex functions with n variables, by following the solution curve of a system of ordinary differential equations. The motivation for this was the fact that existing methods (e.g. those based on Newton methods with line search) sometimes terminate at a non-stationary point when applied to functions f(x) that do not a have positive-definite Hessian (i.e. ∇²f → 0) for all x. Even when methods terminate at a stationary point it could be a saddle or maximum rather than a minimum. The only method which makes intuitive sense in non-convex region is the trust region approach where we seek a step which minimises a quadratic model subject to a restriction on the two-norm of the step size. This gives a well-defined search direction but at the expense of a costly evaluation. The algorithms derived in this thesis are gradient based methods which require systems of equations to be solved at each step but which do not use a line search in the usual sense. Progress along the Continuous Steepest Descent Path (CSDP) is governed both by the decrease in the function value and measures of accuracy of a local quadratic model. Numerical results on specially constructed test problems and a number of standard test problems from CUTEr [38] show that the approaches we have considered are more promising when compared with routines in the optimization tool box of MATLAB [46], namely the trust region method and the quasi-Newton method. In particular, they perform well in comparison with the, superficially similar, gradient-flow method proposed by Behrman [7].
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Leitao, Joao Paulo Correia. "Enhancement of digital elevation models and overland flow path delineation methods for advanced urban flood modelling". Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508782.
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The objective of this thesis is to improve existing and develop new DEM enhancement methods and DEM-based overland flow delineation methods in order to generate reliable overland flow networks. These networks can be used in conjunction with existing urban drainage modelling methodologies in order to improve surface flooding simulation results. The objective has been achieved by: developing new methods to merge DEMs; evaluating nad improving available DEM enhancement methods; improving methods to solve DEM flat area problems, and developing novel methods to improve overland flow path delineation. All improvements and new developments have been adapted to the specific characteristics of high-resolution DEMs and urban catchments. The experimental work undertaken in Lisbon, together with two case-studies in the UK, was used to validate the concepts proposed in this thesis. It is concluded that DEM enhancement methods can be used to improve DEMs for overland flow delineation, thereby enhancing the reliability of urban flood modelling. The advanced flow path delineation methods developed here produce more reliable results than conventional overland flow path delineation methods. The hydraulic simulation results obtained confirm the advantages of applying 1D/1D modelling to simulate urban flood events. However, the findings show that the use of these methods needs to be preceded by a thorough analysis and quantification of Dem surface characteristics, and by a detailed calibration and validation procedure. Independent testing carried out by UKWIR has proved the adequacy and reliability of the developed methodology in full scale flood risk mapping applications.
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Chobot, Anthony T. (Anthony Thomas) 1972. "Modeling the evolution of trace species in the post-combustor flow path of gas turbine engines". Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/87125.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 215-218).
by Anthony T. Chobot, III.
S.M.
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Ren, Hui. "Exam of the Relationship of Traffic Flow, Density and Speed with RADAR Data". University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535382803620171.
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MARTINS, R. S. "Numerical Simulations Of Installation Effects Caused By Upstream Elbows On Single-path Transit-time Ultrasonic Flare Flow Meters". Universidade Federal do Espírito Santo, 2012. http://repositorio.ufes.br/handle/10/4169.
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Previous issue date: 2012-05-23A indústria de petróleo e gás requer medições de vazão com baixa incerteza, uma vez que são estabelecidas por lei. Contudo, curvas e outros obstáculos são comumente encontrados nesse cenário, o que pode afetar a qualidade da medição de vazão em função de perturbações no escoamento, tais como swirl e assimetrias no peril de velocidades. Medidores de vazão por ultrassom de um canal são frequentemente utilizados em instalações de gás de queimadores, apesar de serem sensíveis a tais perturbações. O presente trabalho usa códigos comerciais de CFD para obter o escoamento à jusante de instalações com uma curva e duas curvas, visando a investigar a magnitude e o comportamento de tais efeitos na medição de vazão. Integração numérica é utilizada para diversos arranjos de caminho acústico, simulando medidores de vazão por ultrassom de um canal em várias condições para avaliar o desvio do fator de correção em escoamentos perturbados. Números de Reynolds de 1 x 104 a 2 x 106 são considerados. Ângulos de montagem dos transdutores de 0° a 180° são testados e posições axiais até 80D à jusante do obstáculo são avaliadas. Os resultados indicam que medidores de vazão por ultrassom são sensíveis aos efeitos de acidente de linha. O desvio do fator de correção mostra-se, em geral, consideravelmente maior que 2% em distâncias menores que 20D, conforme recomendado por alguns fabricantes e por leis. Não obstante, tais desvios podem atingir 0,01% em algumas configurações específicas, o que sugere que a medição de vazão por ultrassom pode ser melhorada pelo rearranjo do aparato em posição angular favorável e, principalmente, pela implementação de funções específicas para fatores de correção em condições perturbadas.
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Morrey, Nicola. "Enacting product-service business models : the role of lean thinking". Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/13591.
Texto completoResumen
As competitively tendering for work is becoming increasingly difficult, and with profit margins reducing, UK construction companies are looking to differentiate their offering to clients. Safely delivering on time, within budget and to the required quality standard is no longer a differentiator in a market where clients are demanding increased value, building information modelling and life cycle provision. Construction companies are therefore looking to extend their activities into business consulting, financing and operational services, which will provide new sources of revenue in addition to their core production activities. This holistic service should provide solutions that meet their client s business needs, not just their building needs, ultimately resulting in long-standing relationships that over time yield a more predictable, long-term return. Over half of the top 20 UK construction companies, by turnover, have stated their intent to provide solutions to their clients - the case study organisation in which this research has been carried out is one of those companies. Part of a group of companies, the case study company, Shepherd Construction Ltd (SCL), has a vision to deliver integrated solutions to their clients, with the ultimate aim being that companies across the group can pool their expertise and deliver a service offering unique to the industry. Existing literature states the characteristics that integrated solutions providers need to possess, and proposes models for how an organisation needs to structure itself to deliver a service. However, the applicability of these models to SCL was unknown, and along with current literature on how to enact the transition pathway being vague, highlighted an area for investigation. Since the aim of integrated solutions provision is the delivery of a service to the client that adds value, it was proposed that lean thinking could provide a means of enacting the P-S transition: the starting point for lean thinking is value (Womack & Jones, 2003). Lean thinking principles (Womack & Jones, 2003) state that value needs to flow through the value stream the series of actions that transform inputs into the completed output raising the further proposition that flow is required through the stages of the integrated solutions lifecycle (the value stream) in order to successfully deliver all aspects of the client s value proposition, i.e. the desired solution. As a long established main-contractor, or product provider, SCL s challenge to transition from products-to-services was set against a backdrop of inconsistent performance and loss of continuity of service at crucial pinch-points in the delivery process. The action research carried out therefore sought to understand these problems and develop practices based on lean thinking that could be implemented in the company to enable consistent delivery of integrated solutions, i.e. enable the products-to-service transition, and in doing so provide the basis for the wider group vision. An abductive approach was taken to the research strategy; the experiences of the participants involved in the changes prompted by the action research process were used to inform the development of new theories and practices, and evaluate them once implemented. The methods used for collecting data and accounting for the experiences of people in the company included observation, both participant and non-participant, semi-structured interviews and analysis of company records. The research findings show that lean thinking has a role to play in enabling an organisation to transition from the provision of products to services. Standard processes and tools, based on lean thinking and developed through the action research framework, are shown to be the basis for consistent and repeatable performance within the phases of the integrated solutions lifecycle. Flow of information through and between phases of the lifecycle is then shown to be essential to ensuring the client s value proposition is realised and information is not lost during the transitions between lifecycle phases. The operational framework for service delivery , one of the practices developed, itself a form of standardised work, draws on lean thinking to provide a structured, yet flexible, means of developing a plan for service delivery that is focused on the client and ensuring the client s definition of value flows through the integrated solutions value stream and is therefore continually understood, and ultimately delivered, by the whole team as the project progresses. The practices developed through the research the standard company management system, operational framework for service delivery , service delivery plan and maturity assessment are shown to have improved consistency and company performance, and to have contributed to improved customer satisfaction (the ultimate aim of delivering a service) such that the company is starting to be perceived in the marketplace as an integrated solutions provider. This research also contributes to existing theory by evidencing that the transition pathway from products-to-services isn t as smooth as current literature portrays. In trying to implement current models in a construction setting, the products-to-service transition has been problematised and deficiencies in existing characteristics and models identified. Along with showing that lean thinking provides a theoretical framework for enacting the products-to-service transition, the hybrid model of the integrated solutions lifecycle developed, along with the maturity assessment, provide new theoretical insights, such as the need for feedback loops between all phases of the lifecycle.
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Agbenowosi, Newland Komla. "GIS based optimal design of sewer networks and pump stations". Thesis, Virginia Tech, 1995. http://hdl.handle.net/10919/43184.
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In the planning and design of sewer networks, most of the decisions are spatially dependent because of the right of way considerations and the desire to have flow by gravity. This research addresses the application of combined optimization-geographic information system (GIS) technology in the design process. The program developed for the design uses selected manhole locations to generate the candidate potential sewer networks. The design area is delineated into subwatersheds for determining the locations for lift stations when gravity flow is not possible. Flows from upstream subwatersheds are transported to the downstream subwatersheds via a force main. The path and destination of each force main in the system is determined by applying the Dijkstra's shortest path algorithm to select the least cost path from a set of potential paths. This method seeks to minimize the total dynamic head. A modified length is used to represent the length of each link or force main segment. The modified length is the physical length of the link (representing the friction loss) plus an equivalent length (representing the static head). The least cost path for the force main is the path with the least total modified length. The design approach is applied to two areas in the town of Blacksburg, Virginia. The resulting network and the force main paths are discussed.
Master of Science
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Kong, Jiantao. "Trusted data path protecting shared data in virtualized distributed systems". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33820.
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When sharing data across multiple sites, service applications should not be trusted automatically. Services that are suspected of faulty, erroneous, or malicious behaviors, or that run on systems that may be compromised, should not be able to gain access to protected data or entrusted with the same data access rights as others. This thesis proposes a context flow model that controls the information flow in a distributed system. Each service application along with its surrounding context in a distributed system is treated as a controllable principal. This thesis defines a trust-based access control model that controls the information exchange between these principals. An online monitoring framework is used to evaluate the trustworthiness of the service applications and the underlining systems. An external communication interception runtime framework enforces trust-based access control transparently for the entire system.
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Liu, Qingyu. "Delay-Aware Multi-Path Routing in a Multi-Hop Network: Algorithms and Applications". Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/90405.
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Delay is known to be a critical performance metric for various real-world routing applications including multimedia communication and freight delivery. Provisioning delay-minimal (or at least delay-bounded) routing services for all traffic of an application is highly important. As a basic paradigm of networking, multi-path routing has been proven to be able to obtain lower delay performance than the single-path routing, since traffic congestions can be avoided. However, to our best knowledge, (i) many of existing delay-aware multi-path routing studies only consider the aggregate traffic delay. Considering that even the solution achieving the optimal aggregate traffic delay has a possibly unbounded delay performance for certain individual traffic unit, those studies may be insufficient in practice; besides, (ii) most existing studies which optimize or bound delays of all traffic are best-effort, where the achieved solutions have no theoretical performance guarantee.
In this dissertation, we study four delay-aware multi-path routing problems, with the delay performances of all traffic taken into account. Three of them are in communication and one of them is in transportation. Note that our study differ from all related ones as we are the first to study the four fundamental problems to our best knowledge. Although we prove that our studied problems are all NP-hard, we design approximation algorithms with theoretical performance guarantee for solving each of them. To be specific, we claim the following contributions.
Minimize maximum delay and average delay. First, we consider a single-unicast setting where in a multi-hop network a sender requires to use multiple paths to stream a flow at a fixed rate to a receiver. Two important delay metrics are the average sender-to-receiver delay and the maximum sender-to-receiver delay. Existing results say that the two delay metrics of a flow cannot be both within bounded-ratio gaps to the optimal. In comparison, we design three different flow solutions, each of which can minimize the two delay metrics simultaneously within a $(1/epsilon)$-ratio gap to the optimal, at a cost of only delivering $(1-epsilon)$-fraction of the flow, for any user-defined $epsilonin(0,1)$. The gap $(1/epsilon)$ is proven to be at least near-tight, and we further show that our solutions can be extended to the multiple-unicast setting.
Minimize Age-of-Information (AoI). Second, we consider a single-unicast setting where in a multi-hop network a sender requires to use multiple paths to periodically send a batch of data to a receiver. We study a newly proposed delay-sensitive networking performance metric, AoI, defined as the elapsed time since the generation of the last received data. We consider the problem of minimizing AoI subject to throughput requirements, which we prove is NP-hard. We note that our AoI problem differs from existing ones in that we are the first to consider the batch generation of data and multi-path communication. We develop both an optimal algorithm with a pseudo-polynomial time complexity and an approximation framework with a polynomial time complexity. Our framework can build upon any polynomial-time $alpha$-approximation algorithm of the maximum delay minimization problem, to construct an $(alpha+c)$-approximate solution for minimizing AoI. Here $c$ is a constant dependent on throughput requirements.
Maximize network utility. Third, we consider a multiple-unicast setting where in a multi-hop network there exist many network users. Each user requires a sender to use multiple paths to stream a flow to a receiver, incurring an utility that is a function of the experienced maximum delay or the achieved throughput. Our objective is to maximize the aggregate utility of all users under throughput requirements and maximum delay constraints. We observe that it is NP-complete either to construct an optimal solution under relaxed maximum delay constraints or relaxed throughput requirements, or to figure out a feasible solution with all constraints satisfied. Hence it is non-trivial even to obtain approximate solutions satisfying relaxed constraints in a polynomial time. We develop a polynomial-time approximation algorithm. Our algorithm obtains solutions with constant approximation ratios under realistic conditions, at the cost of violating constraints by up to constant-ratios.
Minimize fuel consumption for a heavy truck to timely fulfill multiple transportation tasks. Finally, we consider a common truck operation scenario where a truck is driving in a national highway network to fulfill multiple transportation tasks in order. We study an NP-hard timely eco-routing problem of minimizing total fuel consumption under task pickup and delivery time window constraints. We note that optimizing task execution times is a new challenging design space for saving fuel in our multi-task setting, and it differentiates our study from existing ones under the single-task setting. We design a fast and efficient heuristic. We characterize conditions under which the solution of our heuristic must be optimal, and further prove its optimality gap in case the conditions are not met. We simulate a heavy-duty truck driving across the US national highway system, and empirically observe that the fuel consumption achieved by our heuristic can be $22%$ less than that achieved by the fastest-/shortest- path baselines. Furthermore, the fuel saving of our heuristic as compared to the baselines is robust to the number of tasks.Doctor of Philosophy
We consider a network modeled as a directed graph, where it takes time for data to traverse each link in the network. It models many critical applications both in the communication area and in the transportation field. For example, both the European education network and the US national highway network can be modeled as directed graphs. We consider a scenario where a source node is required to send multiple (a set of) data packets to a destination node through the network as fast as possible, possibly using multiple source-to-destination paths. In this dissertation we study four problems all of which try to figure out routing solutions to send the set of data packets, with an objective of minimizing experienced travel time or subject to travel time constraints. Although all of our four problems are NP-hard, we design approximation algorithms to solve them and obtain solutions with theoretically bounded gaps as compared to the optimal. The first three problems are in the communication area, and the last problem is in the transportation field. We claim the following specific contributions. Minimize maximum delay and average delay. First, we consider the setting of simultaneously minimizing the average travel time and the worst (largest) travel time of sending the set of data packets from source to destination. Existing results say that the two metrics of travel time cannot be minimized to be both within bounded-ratio gaps to the optimal. As a comparison, we design three different routing solutions, each of which can minimize the two metrics of travel time simultaneously within a constant bounded ratio-gap to the optimal, but at a cost of only delivering a portion of the data. Minimize Age-of-Information (AoI). Second, we consider the problem of minimizing a newly proposed travel-time-sensitive performance metric, i.e., AoI, which is the elapsed time since the generation of the last received data. Our AoI study differs from existing ones in that we are the first to consider a set of data and multi-path routing. We develop both an optimal algorithm with a pseudo-polynomial time complexity and an approximation framework with a polynomial time complexity. Maximize network utility. Third, we consider a more general setting with multiple source destination pairs. Each source incurs a utility that is a function of the experienced travel time or the achieved throughput to send data to its destination. Our objective is to maximize the aggregate utility under throughput requirements and travel time constraints. We develop a polynomial-time approximation algorithm, at the cost of violating constraints by up to constant-ratios. It is non-trivial to design such algorithms, as we prove that it is NPcomplete either to construct an optimal solution under relaxed delay constraints or relaxed throughput requirements, or to figure out a feasible solution with all constraints satisfied. Minimize fuel consumption for a heavy truck to timely fulfill multiple transportation tasks. Finally, we consider a truck and multiple transportation tasks in order, where each task requires the truck to pick up cargoes at a source timely, and deliver them to a destination timely. The need of coordinating task execution times is a new challenging design space for saving fuel in our multi-task setting, and it differentiates our study from existing ones under the single-task setting. We design an efficient heuristic. We characterize conditions under which the solution of our heuristic must be optimal, and further prove its performance gap as compared to the optimal in case the conditions are not met.
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Pagliazzi, Marco. "Time domain, near-infrared diffuse optical methods for path length resolved, non-invasive measurement of deep-tissue blood flow". Doctoral thesis, Universitat Politècnica de Catalunya, 2019. http://hdl.handle.net/10803/667682.
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The non-invasive and, often, continuous measurement of the hemodynamics of the body, and for the main purposes of this thesis, the brain, is desired because both the instantaneous values and their changes over time constantly adapt to the conditions affecting the body and its environment. They are altered in pathological situations and in response to increased function. It is desirable for these measurements to be continuous, reliable, minimally invasive, and relatively inexpensive. In recent years, optical techniques that, by using diffusing and deep-reaching (up to few centimeters) light at skin-safe levels of intensity, combine the aforementioned characteristics, have increasingly become used in clinical and research settings. However, to date there is, on one side the need to expand the number and scope of translational studies, and, on the other, to address shortcomings like the contamination of signals from unwanted tissue volumes (partial volume effects). A further important goal is to increase the depth of penetration of light without affecting the non-invasive nature of diffuse optics.
My PhD was aimed at several aspects of this problem; (i) the development of new, more advanced methods, i.e. the time/pathlength resolved, to improve the differentiation between superficial and deeper tissues layers, (ii) the exploration of new application areas, i.e. to characterize the microvascular status of bones, to study the functional response of the baby brain, and (iii) to improve the quality control of the systems , i.e. by introducing a long shelf-life dynamic phantom.
In conceptual order, first I introduce long shelf-life reference standards for diffuse correlation spectroscopy. Secondly, I describe the use of an existing hybrid time domain and diffuse correlation spectroscopy system to monitor the changes that some pathological conditions, in this case osteoporosis and human immunodeficiency virus infection, may have on many aspects of the human bone tissue that are currently not easy to measure (i.e. invasively assessed) by conventional techniques. Thirdly, I describe the development of a novel time domain optical technique that intimately combines, introducing many previously unmet advancements, the two previously cited optical spectroscopy techniques. For the first time I was able to produce a time domain device and protocol that can monitor the blood flow in vivo in the head and muscles of healthy humans. Lastly, I describe a device and method that I have used to monitor changes in blood flow in healthy human infants of three to five months of age, for the first time in this age bracket, as a marker of activation following visual stimulation.
Overall, this work pushes the limit of the technology that makes use of diffuse light to minimally invasively, continuously, and reliably monitor endogenous markers of pathological and physiological processes in the human body.La medición no invasiva y, a menudo, continua de la hemodinámica del cuerpo, y para los propósitos principales de esta tesis, del cerebro, es conveniente porque tanto los valores instantáneos como sus variaciones en el tiempo se adaptan constantemente a las condiciones que afectan el cuerpo humano y su entorno. Estas suelen alterarse en situaciones patológicas o como respuesta a una mayor función. Es deseable que estas mediciones sean continuas, confiables, mínimamente invasivas y relativamente asequibles. En los últimos años, las técnicas ópticas que, mediante el uso de luz difusa para medir los tejidos en profundidad (hasta unos pocos centímetros) mediante niveles de intensidad que son seguros para la piel, combinan las características arriba mencionadas, se han utilizado cada vez más tanto en entornos clínicos como de investigación. Sin embargo, al día de hoy hay, por un lado, la necesidad de ampliar el número y el ámbito de los estudios translacionales y, por el otro, de suplir a las deficiencias como por ejemplo la contaminación de volúmenes de tejido no deseados (efectos de volumen parcial). Otro objetivo importante es aumentar la profundidad de penetración de la luz sin afectar la naturaleza no invasiva de la óptica difusa. Mi doctorado está destinado a mejorar varios aspectos de este problema; (i) el desarrollo de nuevos métodos más avanzados, es decir, el método resuelto en el tiempo/trayectoria de los fotones, para mejorar la diferenciación entre los tejidos superficiales y profundos, (ii) la exploración de nuevas áreas de aplicación, es decir, para caracterizar el estado microvascular de los huesos, para estudiar la respuesta funcional del cerebro en los niños, y (iii) para mejorar el control de calidad de los sistemas, es decir, mediante la introducción de un phantom dinámico de larga vida útil. En orden conceptual, primero voy a introducir estándares de referencia de larga vida útil para la espectroscopia de correlación difusa (DCS). En segundo lugar, voy a describir el uso de un sistema híbrido espectroscopia tiempo-resuelta (TRS) con DCS ya existente para monitorizar los cambios que algunas condiciones patológicas, en este caso la osteoporosis y la infección por el virus de la inmunodeficiencia humana, pueden comportar para muchos aspectos del tejido óseo humano que actualmente no se pueden medir con facilidad (es decir, se van evaluado de forma invasiva) mediante técnicas convencionales. En tercer lugar, voy a describir el desarrollo de una novedosa técnica óptica en el dominio temporal que combina íntimamente, introduciendo muchos avances previamente no cumplidos, TRS y DCS. Por primera vez pude producir un dispositivo y un protocolo tiempo-resueltos para medir el flujo de la sangre en la cabeza y en los músculos de seres humanos sanos. Por último, en esta tesis voy a describir un dispositivo y un método que he usado para monitorear los cambios en el flujo sanguíneo como marcadores de activación del cerebro debida a estímulos visivos en bebés entre tres y cinco meses de edad. En general, este trabajo amplia los limites de la tecnología que hace uso de la luz difusa para monitorizar, de forma mínimamente invasiva, continua y confiable los marcadores endógenos de procesos patológicos y fisiológicos en el cuerpo humano.
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Gagne, Anton. "Effects of Asymmetry and Other Non-Standard Excitations on Structural Dynamic Forced Response Analysis of Turbomachinery Flow-Path Components". Thesis, KTH, Kraft- och värmeteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-154623.
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A recent paper explored a potential deficiency in the single frequency harmonic response structural dynamic analysis approach typically used to assess a resonant condition in turbomachinery flow path components. This deficiency is prevalent in supersonic flow conditions when non-adjacent stages are present. The previous investigation demonstrated other excitation sources present in complex or supersonic flows could be missed using the typical analysis approach, in some cases leading to large under-prediction of structural response when compared with a baseline transient analysis. This paper presents the results of a follow on study, in which the inclusion of these effects in dynamic analyses is investigated. A representative rotor was created and analyzed for forced response characteristics when individual and combined unsteady content was present. A simple shell and beam 2D model was used to study the forced response behavior using transient and harmonic analyses. The results showed a significant contribution from non-integer forcing as well as from certain integer order forcing. A 3D model was also created for future analysis but did not display the sideband characteristics similar to flow seen in the previous investigation.
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Oskarsson, Andreas. "Efficient transformation from general flow into a specific test case in an automated testing environment". Thesis, Blekinge Tekniska Högskola, Institutionen för programvaruteknik och datavetenskap, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-3718.
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SIMON is an automated testing application developed by WM-Data Consulting in Växjö, Sweden. Previously the test cases, called BIFs, run by SIMON to test the applications under test has been written manually in a very time consuming manner offering no protection against errors in the structure or misspellings. This thesis investigates a replacement to the manual method when creating the BIFs; my own developed application called the BIF-Editor. The usage of the BIF-Editor guaranteed correct syntax and structure and made the creation of the BIFs faster, but did it increase the quality of the BIFs? So to evaluate the BIF-Editor, the quality regarding path coverage of BIFs manually created was compared with BIFs created during the same elapsed time using the BIF-Editor. This evaluation showed that the usage of the BIF-Editor increased the quality of the BIFs by making the creation safer, but primarily faster which enabled the user to produce more BIFs than previously possible resulting in a raised path cover.
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Meadows, Crystal. "Determining Impediments to Gene Flow in a Natural Population of Cornus florida L. Cornaceae, Using Integrative Landscape Genetic Techniques". VCU Scholars Compass, 2011. http://scholarscompass.vcu.edu/etd/184.
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This study examined the impact intervening environment has on gene flow in the insect pollinated understory tree, Cornus florida L., by combining GIS and landscape genetic techniques (Least Cost Path Analysis, Circuit Theory, and Conditional Genetic Distance). Traditional population genetic analysis indicated pair-wise relatedness was significantly correlated to distance (Pearson; r = -0.312, P < 0.001) suggesting a spatial component to offspring relatedness. Dispersal throughout the study site was non-random, exhibiting a high degree of pollen pool structure due to restricted gene flow (Two-Generation Analysis; Φft = 0.161, P = 0.001). Forest structure was quantified in GIS layers representing coniferous canopies, mixed hardwood canopies, C. florida canopies, open understory (roads), and open understory/canopy due to tree removal. Of these layers, landscape isolation for the roads layer provided the best-fit model for describing genetic differentiation among sampled pollen pools (Mantel; r = 0.542, P = 0.001). These data also suggest that improved biological inferences can be gained by examining a range of landscape isolation models.
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Hammer, Christian [Verfasser] y G. [Akademischer Betreuer] Snelting. "Information flow control for java : a comprehensive approach based on path conditions in dependence Graphs / Christian Hammer ; Betreuer: G. Snelting". Karlsruhe : KIT Scientific Publishing, 2009. http://d-nb.info/1185493255/34.
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Yam, Chi Kin 1980. "Validation of modeling methodology and investigation of mass addition effects on evolution of trace species in post-combustor flow path". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/82791.
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Gardner, Christopher Brent. "Rock-Derived Micronutrient Transport across Landscape Units: Hydrologic Flow Path Analysis and Catchment-Scale Transport in the Tropics and Small Mountainous Rivers". The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1449157172.
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Jazayeri, Noushabadi Mahmoud Reza. "Characterisation of relationships between fracture network and flow-path network in fractured and karstic Reservoirs : Numerical modelling and field investigation (Lez aquifer, Southern France)". Montpellier 2, 2009. http://www.theses.fr/2009MON20206.
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Bien que le comportement et la modélisation des écoulements dans les réservoirs fracturés constituent une problématique de recherche abordée depuis le milieu des années soixante, la caractérisation des réservoirs fracturés soulève encore de nombreuses incertitudes. Dans le contexte du développement et de l'exploitation des réservoirs fracturés, le problème principal le plus souvent cité comprend la définition des propriétés du réseau de fractures qui détermine le réseau d'écoulement ainsi que les modalités de l'écoulements inter-porosité. L'essai de puits est l'un des outils le plus utilisé pour caractériser les propriétés géométriques et hydrodynamiques des réservoirs fracturés sur la base de solution analytique simple. La considération d'une solution analytique de type double porosité pour l'interprétation de l'essai de puits permet ainsi de renseigner le coefficient d'échange inter-porosité, ainsi que le rapport entre les propriétés hydrodynamiques des fractures et celles du réservoir. Ces informations, qui concernent un réservoir fracturé donné, sont généralement issues de l'interprétation, à l'échelle régionale, de la réponse hydrodynamique obtenue sur quelques puits seulement. Néanmoins, tous les puits d'observation n'ont pas la même réponse hydrodynamique à un essai de puits ; ceci pose la question de l'impact de la localisation du puits de pompage et du piézomètre sur la détermination des propriétés hydrodynamiques du réservoir lors de l'interprétation de l'essai de puits. Pour évaluer les différents effets liés à l'emplacement du puits de pompage sur la réponses hydrodynamique, une série d'essais de puits a été simulée dans des réseaux de fractures synthétiques et leur réponse hydrodynamique a été interprétée à l'aide d'un modèle de type double porosité L'impact de la localisation du puits de pompage et des propriété géométriques du réservoir fracturé, telles que l'espacement et la longueur des fractures, sur le comportement des écoulements et la valeur du coefficient d'échange inter-porosité est examiné dans le premier chapitre. Dans le deuxième chapitre, la relation entre réseau de fractures et réseau d'écoulement est examinée dans le cas d'un aquifère fracturé et karstique (aquifère du Lez), en considérant le comportement hydrodynamique à l'échelle locale et le comportement hydrodynamique à l'échelle régionale. De cette façon, sont appréhendés les paramètres principaux qui conditionnent le réseau d'écoulement préférentiel, et ses liens avec le réseau de fractures. Différentes propriétés géométriques, telles que la densité, l'orientation, et la longueur des fractures sont déterminées à différentes échelles : échelle du puits, échelle locale (site expérimental), et échelle régionale (aquifère). A cette fin, différentes techniques d'acquisition (imagerie de puits, mesures à l'affleurement, photographie aérienne) sont utilisées pour caractériser la fracturation. Des mesures géophysique réalisées à l'échelle locale (site expérimental) permettent d'obtenir des cartes de résistivité 2D et 3D qui illustrent la grande hétérogénéité du site, caractéristique des réservoirs fracturés. L'investigation du réseau d'écoulement est réalisée au moyen de diagraphies de puits, de tests d'interférences et de tests d'impulsions, à l'échelle locale et à l'échelle régionale. Ces différents outils nous renseignent sur la connectivité des différents puits avec le réseau d'écoulement ainsi que sur les propriété hydrodynamiques de différentes zones du réservoir fracturé. Dans le troisième chapitre, un modèle hydrogéologique conceptuel est proposé à l'échelle locale et à l'échelle régionale. Ces modèles servent de fondement à deux modèles numériques 2D basé pour voir si la geomodélisation numérique et les résultats de simulation d'écoulements de fluides confirment notre hypothèse intégrée dans les modèles conceptuelsAlthough the specific flow behaviour of fractured reservoirs has been identified and modelled since relatively long time, there are still lots of problem concerning the fractured reservoir characterisation. The main problem, often cited in the context of the development and exploitation of fractured reservoirs, is the difficulty in defining the fracture network properties that impact the flow path-network and the inter-porosity flow transfer between the fracture continuum and matrix continuum. Well test is one of the tools that are used for the characterisation of geometrical and hydrodynamic properties of fractured reservoir, such as inter-porosity flow exchange coefficient, fracture storativity to whole reservoir storativity ratio, and reservoir permeability. But all these information applied to characterise a fractured reservoir at regional scale are inferred from only a few boreholes. One may thus wonder if all observation boreholes have the same hydrodynamic response to a well test. In order to answer this question a series of numerical well tests are conducted in synthetic fracture networks to evaluate the effect of the pumping well location on the dual porosity pressure responses. The impact of geometrical parameters, such as fracture spacing and mean length, on fluid flow behaviour and inter-porosity exchange coefficient are investigated for different pumping well location in the first chapter. Well test simulations in the synthetic fractured reservoirs, with a non uniform distribution pattern, highlight the dependency of the measured inter-porosity flow exchange coefficient to the pumping test location. The mean fracture length (which controls connectivity) is assessed to be the main geometrical parameter which influences the reservoir hydrodynamic response during well test. In the second chapter, the relationship between fracture network and flow-path network are investigated in a real fractured and karstic carbonate aquifer (Lez aquifer, southern France). A multi-disciplinary case study, which aims to assess the main parameters which affect the preferential flow-path network, is thus performed. It comprises geological, geophysical and hydrodynamic data acquisition and interpretations. The collection of geometrical parameters such as fracture density, orientation, length is done at different scales (borehole, field site, aquifer). Applying different data acquisition techniques such as borehole image, outcrop observation and aerial photography are claimed to characterise the fracture network. In this experimental part, it is shown that geological and geophysical data such as fracture data acquisition, borehole imagery (OTV), reservoir electrical resistivity imaging are the minimum requested data for characterizing the fracture network of a given reservoir. Investigation of flow-path network is done through conducting a series of well logging, interference tests and pulse tests at two scales. This step gives some clarifications about the quality of connectivity and conductivity of fractures at different zones. Then, we assess the relationship between fracture network and flow-path network by integrating all geological, geophysical and hydrodynamic data. It is shown that conducting well test series at two different scales within the same fractured and karstic reservoir allow verifying the scale dependency of permeability within a same system; it also shows that other important factors than the scale of observation affect these permeability variations. Combination of all data (geological, geophysical and hydrodynamic) illustrates that the borehole connectivity to the flow-path network and water table level during well test operation are the parameters which mainly control the permeability value estimation, whatever the scale of observation. Finally, in the third chapter, we define the hydrogeological conceptual models at local and regional scales. Then a simple 2D numerical model based on the hydrogeological conceptual model at each scale is proposed and the numerical geomodelling and fluid flow simulation are compared to the observed hydrodynamic behaviour in the site. Results of fluid flow simulation in the numerical models at local and regional scales confirm our hypothesis about effect of borehole location and its connectivity with the flow-path network on the recorded hydrodynamic responses at borehole
46
Thakur, Aditya. "Comprehensive Path-sensitive Data-flow Analysis". Thesis, 2008. https://etd.iisc.ac.in/handle/2005/836.
Texto completoResumen
Data-flow analysis is an integral part of any aggressive optimizing compiler. We propose a framework for improving the precision of data-flow analysis in the presence of complex control-flow. We initially perform data-flow analysis to determine those control-flow merges which cause the loss in data-flow analysis precision. The control-flow graph of the program is then restructured such that performing data-flow analysis on the resulting restructured graph gives more precise results. The proposed framework is both simple, involving the familiar notion of product automata, and also general, since it is applicable to any forward or backward data-flow analysis. Apart from proving that our restructuring process is correct, we also show that restructuring is effective in that it necessarily leads to more optimization opportunities.
Furthermore, the framework handles the trade-off between the increase in data-flow precision and the code size increase inherent in the restructuring. We show that determining an optimal restructuring is NP-hard, and propose and evaluate a greedy heuristic.
The framework has been implemented in the Scale research compiler, and instantiated for the specific problems of Constant Propagation and Liveness analysis. On the SPECINT 2000 benchmark suite we observe an average speedup of 4% in the running times over Wegman-Zadeck conditional constant propagation algorithm and 2% over a purely path profile guided approach for Constant Propagation. For the problem of Liveness analysis, we see an average speedup of 0.8% in the running times over the baseline implementation.
47
Thakur, Aditya. "Comprehensive Path-sensitive Data-flow Analysis". Thesis, 2008. http://hdl.handle.net/2005/836.
Texto completoResumen
Data-flow analysis is an integral part of any aggressive optimizing compiler. We propose a framework for improving the precision of data-flow analysis in the presence of complex control-flow. We initially perform data-flow analysis to determine those control-flow merges which cause the loss in data-flow analysis precision. The control-flow graph of the program is then restructured such that performing data-flow analysis on the resulting restructured graph gives more precise results. The proposed framework is both simple, involving the familiar notion of product automata, and also general, since it is applicable to any forward or backward data-flow analysis. Apart from proving that our restructuring process is correct, we also show that restructuring is effective in that it necessarily leads to more optimization opportunities.
Furthermore, the framework handles the trade-off between the increase in data-flow precision and the code size increase inherent in the restructuring. We show that determining an optimal restructuring is NP-hard, and propose and evaluate a greedy heuristic.
The framework has been implemented in the Scale research compiler, and instantiated for the specific problems of Constant Propagation and Liveness analysis. On the SPECINT 2000 benchmark suite we observe an average speedup of 4% in the running times over Wegman-Zadeck conditional constant propagation algorithm and 2% over a purely path profile guided approach for Constant Propagation. For the problem of Liveness analysis, we see an average speedup of 0.8% in the running times over the baseline implementation.
48
Lin, Hung-I. y 林宏奕. "Investigation of preferential flow path in fractured rocks". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/92938235396383384381.
Texto completoResumen
博士國立成功大學
資源工程學系碩博士班
97
The hydraulic properties of single fracture and fracture networks were discussed in this research to explain the influence of effective fractures, and how to separate preferential flow path from original fracture networks. First, seven hydraulic aperture modes were applied to confer the applicable addition of fractures. Then the fracture outcrops were used in estimating the hydraulic conductivity and groundwater seepage into tunnel. Finally, the estimation of representative elementary volume, REV, and method of preferential flow path separation were built in this research. Joint roughness and mechanical aperture are the major parameters in hydraulic aperture estimation. There were six target modulus based on the elevation of fracture wall used to the standard joint roughness coefficient curve. Result shows roughness average and root-mean-square roughness were useful in roughness evaluation. In addition, seven approaches to evaluate hydraulic aperture in single fracture were compared to interpret the application conditions. Results indicate that the ratio of the mean aperture to its standard deviation of fracture wall is the most significant factor. When this ratio is lager than 8, the parallel plate model is suitable. If the ratio is between 3 and 8, the approach was chosen by the roughness characteristic of fracture wall. In case of the ratio is smaller than 3, numerical simulation is the best approach in hydraulic aperture estimation. Parameters of fractures are the basic components of hydraulic models in fractured rocks. However, the outcrops of fractures on the hydraulic boundary are the actual passages of inflow and outflow in fractured rocks and tunnel wall. The computer code, TUNFLOW, which is based on the discrete fracture model is applied to estimate the hydraulic conductivity and outcrops of simulated cases in this research. Results show that the preferential path exists in partial fracture net. Density and trace length of fractures are the major factors to amount of the effective outcrops, which are the outcrops that groundwater passed. There is a fairly relation between seepage and outcrops on the tunnel wall. This result could be used in estimating the groundwater surge with number of outcrops, and result in the case of Syueshan tunnel is very close to the record in-situ. The void fractures of fracture network are the principal reason in the difference of hydraulic property between continuum and discrete approaches. The representative elementary volume, REV, was calculated by the computer code, TUNFLOW, in this research. The distribution of percolation factors shows the similar results. Then the particle tracing was applied to separate preferential flow path. The cumulative frequency of each node is equal to the probability of groundwater passed. This approach could help to display the path of preferential flow, so that it would be a useful method in interrelated research.
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Tsai, Yih-Jin y 蔡易縉. "AIR SPARGING TRACER TEST TO INVESTIGATE THE FLOW PATH". Thesis, 2001. http://ndltd.ncl.edu.tw/handle/24436570458909694327.
Texto completoResumen
博士國立成功大學
資源工程研究所
89
Air sparging is frequently used for groundwater remediation. The efficiency of field remediation is greatly dependent on the flow path and radius of influence of the injected air. The thesis presents a useful method for investigating the flow path of the injected air, estimating the radius of influence, and assisting the design of well spacing of sparging wells. The method applies both tracer and modeling approach. A field test using helium as a tracer was conducted on an air sparging pilot. A 3-dimensional, 3-phase compositional model was utilized to simulate the air sparging process at the pilot. The model was first calibrated with the tracer concentrations observed in the field test at various locations between the air sparging well and the soil vapor extraction well. The input data of the model were based on the soil borings, slug tests, air injection tests, and air extraction tests. Modifications of permeability and porosity were made based on field observations and conditions. The calibrated model was then used to predict the flow path of the injected air and to simulate the water and gas saturation distributions in the aquifer. The steady-state gas saturation distribution was found useful for estimating the radius of influence of air sparging and for designing the well spacing of sparging well. The radius of influence of the injected air was estimated around 2.5 meter based on the 10% gas saturation map.
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Chiang, Chia-Sheng y 江家昇. "Heat Sinks Shape Design Techniques Based on Flow Path". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/84134149402953199858.
Texto completoResumen
碩士國立臺灣科技大學
機械工程系
91
This research aims first to establish the analysis capabilities on AMD Athlon XP heat sinks by using the commercial FEM package, ANSYS. A good comparison between the experimental data and the numerical results was obtained. Many different inlet/outlet location combinations in the same design space were defined, and the proposed method is then used to design the heat dissipation fins based on air flow patterns. By using identical fin materials, the air flow based techniques can automatically create curvilinear fins that will minimize the maximum temperature of the fins. To test the effectiveness of the proposed air flow based method, for each inlet/outlet conditions, the straight line fins of the optimum angle orientation is obtained and the performance is compared to the curvilinear fins obtained by using the proposed air flow based method. Experiments show that the air flow based method can be used to create curvilinear fins with improved heat dissipation capabilities.