Dissertations / Theses on the topic 'Spatial and geometric constraints'
To see the other types of publications on this topic, follow the link: Spatial and geometric constraints.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Spatial and geometric constraints.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Senger, Fabrice. "Dynamique du cytosquelette et polarité cellulaire." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAV089/document.
Abstract:
Une cellule reçoit et intègre une multitude de signaux physiques et biochimiques. Elle est capable de sentir et de répondre à ces signaux de sorte que ses fonctions s’accordent avec son environnement. Si l’intégration de ces signaux est hautement régulée par des voies de signalisation et de rétroaction, certaines étapes semblent résulter de processus d’auto-organisation géométrique et mécanique du réseau d’actine. Il est capable de s’auto-assembler et d’adopter différentes architectures. Celles-ci sont autant de modules qui coexistent dans la cellule avec une claire ségrégation spatiale et fonctionnelle. Notamment, le cytosquelette d’actine participe à l’intégration des signaux encodés par la matrice extracellulaire. Cette intégration suppose entre autre, une régulation des forces de tension entre la cellule et son environnement impliquant le cytosquelette d’actine, les adhésions cellulaire et la matrice. Afin d’explorer ces mécanismes, nous avons eu recours à des techniques avancées de micropatterning, de mesure de force de traction cellulaire et de microdissection laser. Nous avons ainsi montré en réprimant l’expression de l’ alpha-actinine, une des principales protéines de réticulation du cytosquelette d’actine, que la connectivité du réseau d’actine était essentielle à l’intégration des signaux émanant de la matrice extracellulaire. Elle participe à l’évaluation de la rigidité de la matrice et au mécanisme de migration dirigé haptotactique. Elle participe donc potentiellement aux mécanismes de différentiation cellulaire et au maintien de la polarité cellulaire. Dans le même esprit nous avons pris part à une étude portant sur l’organisation et la maturation des adhésions cellulaires, en participant à la caractérisation d’une protéine d’adhésion Kank2. Nous avons ainsi pu démontrer le rôle essentiel de cette protéine dans le phénomène de rigidity sensing. L’ensemble de l’étude ayant montré l’implication de cette protéine dans le processus de maturation des adhésions cellulaires et de mécano-transductionCells sense and integrate a wealth of mechanical and biochemical signals. Signal integration is part of a process, which ensures that cellular functions are in accordance with the extracellular environment. While these processes are highly regulated by biochemical and mechanical signalling and feedback loops, some of the fundamental processes appear to rely on actin cytoskeleton autoassembly giving raise to modules with defined geometrical and mechanical properties. Thus the actin cytoskeleton is a modular architecture, and the modules co-exist within the cell with spatial and functional specificity. The actin cytoskeleton, notably, is involved in cell/matrice signalling. This interaction relies mainly on mechanical signalling involving the actin cytoskeleton, cell/matrix adhesions and the extracellular matrix. To characterize these mechanisms we took advantage of advanced micropatterning techniques, traction force measurements and laser microdissection. By downregulating the expression of α-actinin, one of the main actin crosslinking proteins, we demonstrated that actin cytoskeleton connectivity is essential for proper integration of cell/matrix signalling. Connectivity is essential for rigidity sensing and haptotaxis by ensuring balanced force distribution through the whole cell. Therefore connectivity might be crucial for cell differentiation processes and cellular polarity. Further, in the context of a collaborative project, we have contributed to the characterization of a novel cell adhesion protein, namely, Kank2. We showed, by traction force measurements, that this protein is essential for rigidity sensing. Globally this study demonstrated the implication of Kank2 in cell adhesion maturation and mecanotransduction
2
Alborzi, Houman. "Geometric issues in spatial indexing." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/4057.
Abstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Computer Science. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
3
Ralley, Richard. "Spatial constraints on attention." Thesis, University of Hertfordshire, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302301.
4
Dai, Xiangyuan. "Spatial queries based on non-spatial constraints." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B38436395.
5
Dai, Xiangyuan, and 戴祥元. "Spatial queries based on non-spatial constraints." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B38436395.
6
Coulter, Stewart. "Representation of geometric constraints in parametric synthesis." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/17982.
7
Ma'ani-Hessari, Nason J. "Design of quadruplex DNA through geometric constraints." Thesis, University of Ulster, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551558.
Abstract:
This thesis is concerned with the rational design of a group of DNA higher order architectures known as quadruplex DNA. Quadruplex DNA is comprised of a stem of stacking guanine tetrads linked by loops comprised of single stranded DNA. Due to the different combinations of loop types possible, it has great structural diversity and has potential nanotechnological and biological applications. Currently, only a few loop combinations, or topologies are known. Those that have been determined experimentally were not explicitly designed. Using a geometric formalism, the sum of currently available knowledge on quadruplex folding was used to create a set of parameters for the design of novel quadruplex architectures. We present the proof of principle for rational design of said structures, through making the novel topology (-pd+l) and the (G:C:G:C) tetrad- containing topology -(Ppp). We apply this principle to interpret thermal difference spectra signatures of a number of designed quadruplexes. Finally, we show that such novel quadruplexes can be used as building blocks for nanowires. This thesis therefore describes the proof of principle of design, means to expediate design, and an example application of design, of quadruplex nucleic acids. Through achieving these three aims, we present the feasibility of designing novel quadruplexes to be used as nanotechnological or medical devices.
8
Wilczkowiak, Marta. "3D modelling from images using geometric constraints." Grenoble INPG, 2004. http://www.theses.fr/2004INPG0034.
9
Phipps, Richard L. "Some Geometric Constraints on Ring-Width Trend." Tree-Ring Society, 2005. http://hdl.handle.net/10150/262639.
Abstract:
Simulations of tree rings from trees of undisturbed forest sites are used to describe natural, long-term width trends. Ring-width trends of canopy-sized white oak are simulated from regressions of BAI (ring area) data of real trees. Examples are given of a tree from a typical re-growth forest in Illinois and of a more slowly growing tree from an old-growth forest in Kentucky. The long-term width trend was simulated as being toward constant ring width regardless of growth rate of the tree. Conditions by which either increasing or decreasing ring-width trends could be simulated from the same linear BAI trend are examined. I conclude that curvilinear width trends, either increasing or decreasing, represent width adjustments to changes in growth rate (BAI trend) after which the width trend stabilizes to a near-constant value. Interpretation of ring-width trends of trees from undisturbed stands may be useful in assessing stand disturbance history.
10
Dodwell, Timothy J. "Multilayered folding with constraints." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.549892.
Abstract:
In the deformation of layered materials such as geological strata, or stacks of paper, mechanical properties compete with the geometry of layering. Smooth, rounded corners lead to voids between layers, while close packing leads to geometrically induced curvature singularities. When creation of voids is penalized by external pressure, the system trades off these competing effects, leading to various accommodating formations. Three two dimensional energy based nonlinear models are presented to describe the formation of voids at areas of intense geological folding. For each model the layers are assumed to be flexible elastic beams under hard unilateral contact constraint; which are solved as quasi-static obstacle problems with a free boundary. In each case an application of Kuhn-Tucker theory leads to representation as a nonlinear fourth order differential equation. Firstly a single layered model for voiding is presented. An elastic layer is forced into a V-shaped singularity by a uniform overburden pressure, where the fourth order free boundary problem is shown to have a unique, convex, symmetric solution. Drawing parallels with the Kuhn-Tucker theory, virtual work and ideas of duality, the physical significance of this differential equation is emphasised. Finally, appropriate scaling of either the potential energy or the differential equation shows the solutions scale to a single parametric group, for which the size of the void scales inversely with the ratio of overburden pressure to bending stiffness of the layer. Common to structural geology, one or several especially thick layers can dominate the deformation process. As a result, the remaining weak layers must accommodate into the geometry imposed by these competent layers. The second model, extends the first by introducing a plastic hinge to replicate the geometry imposed by the competent layer, and also axial springs to resist the slip over the limbs. The equilibrium equations for the system are investigated using the mathematical techniques developed for the first model. Under rigid loading the system may snap from an initially flat state to a convex voiding solution, as seen in the first model. However, if resistance to slip is high, the slightest imperfection causes the system to jump to a convoluted up-buckled solution, following a de-stiffened path to a point of self contact. These solutions have similarities with the delamination of carbon fibre composites. Finally, we extend the two single layered models to a simple multilayered model, which describes the periodic formation of voids in a chevron fold. The model shows that in the limit of high overburden pressures solutions form voids every layer, producing straight limbs punctured by sharp corners. This analysis shows good agreement when compared with recent experiments. This work provides the basis for future work on the buckling of thin multilayer assemblies in which voids may develop, and emphasizes the importance of the intricate nonlinear constraints of layers fitting together in multilayered folds.
11
Pennington, Sandra Lynn. "Automatic geometric modeling of spatial mechanism links." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/91056.
Abstract:
This thesis introduces GENMOD, a collection of subroutines which allow automatic geometric modeling of 3-D models for spatial links or linkages given a minimum amount of information as input. The subroutines utilize the CADCD (CADAM, Inc.) geometry interface software to enter 3-D data directly into the CAD/CAM database. Wire-frame and surface models are produced. Input is accepted from user created files with a standardized format allowing the GENMOD subroutines to be implemented regardless of the synthesis and analysis routines used. The realistic visualization of a mechanism during the synthesis and analysis process can help the mechanism designer to eliminate unacceptable linkage configurations in the early design stages thereby saving time and money. A complete description of the subroutines is provided in addition to sample graphic output.M.S.
12
Wang, Boyang, and Boyang Wang. "Secure Geometric Search on Encrypted Spatial Data." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625567.
Abstract:
Spatial data (e.g., points) have extensive applications in practice, such as spatial databases, Location-Based Services, spatial computing, social analyses, computational geometry, graph design, medical imaging, etc. Geometric queries, such as geometric range queries (i.e., finding points inside a geometric range) and nearest neighbor queries (i.e., finding the closest point to a given point), are fundamental primitives to analyze and retrieve information over spatial data. For example, a medical researcher can query a spatial dataset to collect information about patients in a certain geometric area to predict whether there will be a dangerous outbreak of a particular disease (e.g., Ebola or Zika).
With the dramatic increase on the scale and size of data, many companies and organizations are outsourcing significant amounts of data, including significant amounts of spatial data, to public cloud data services in order to minimize data storage and query processing costs. For instance, major companies and organizations, such as Yelp, Foursquare and NASA, are using Amazon Web Services as their public cloud data services, which can save billions of dollars per year for those companies and organizations. However, due to the existence of attackers (e.g., a curious administrator or a hacker) on remote servers, users are worried about the leakage of their private data while storing and querying those data on public clouds.
Searchable Encryption (SE) is an innovative technique to protect the data privacy of users on public clouds without losing search functionalities on the server side. Specifically, a user can encrypt its data with SE before outsourcing data to a public server, and this public server is able to search encrypted data without decryption. Many SE schemes have been proposed to support simple queries, such as keyword search. Unfortunately, how to efficiently and securely support geometric queries over encrypted spatial data remains open.
In this dissertation, to protect the privacy of spatial data in public clouds while still maintaining search functions without decryption, we propose a set of new SE solutions to support geometric queries, including geometric range queries and nearest neighbor queries, over encrypted spatial data. The major contributions of this dissertation focus on two aspects. First, we enrich search functionalities by designing new solutions to carry out secure fundamental geometric search queries, which were not supported in previous works. Second, we minimize the performance gap between theory and practice by building novel schemes to perform geometric queries with highly efficient search time and updates over large-scale encrypted spatial data.
Specifically, we first design a scheme supporting circular range queries (i.e., retrieving points inside a circle) over encrypted spatial data. Instead of directly evaluating compute-then-compare operations, which are inefficient over encrypted data, we use a set of concentric circles to represent a circular range query, and then verify whether a data point is on any of those concentric circles by securely evaluating inner products over encrypted data.
Next, to enrich search functionalities, we propose a new scheme, which can support arbitrary geometric range queries, such as circles, triangles and polygons in general, over encrypted spatial data. By leveraging the properties of Bloom filters, we convert a geometric range search problem to a membership testing problem, which can be securely evaluated with inner products. Moving a step forward, we also build another new scheme, which not only supports arbitrary geometric range queries and sub-linear search time but also enables highly efficient updates.
Finally, we address the problem of secure nearest neighbor search on encrypted large-scale datasets. Specifically, we modify the algorithm of nearest neighbor search in advanced tree structures (e.g., R-trees) by simplifying operations, where evaluating comparisons alone on encrypted data is sufficient to efficiently and correctly find nearest neighbors over datasets with millions of tuples.
13
Khan, Muhammad Nazar. "Discriminative Dictionary Learning with Spatial Constraints." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5657.
Abstract:
In this thesis, we investigate the use of dictionary learning for discriminative tasks on natural images. Our contributions can be summarized as follows: 1) We introduce discriminative deviation based learning to achieve principled handling of the reconstruction-discrimination tradeoff that is inherent to discriminative dictionary learning. 2) Since natural images obey a strong smoothness prior, we show how spatial smoothness constraints can be incorporated into the learning formulation by embedding dictionary learning into Conditional Random Field (CRF) learning. We demonstrate that such smoothness constraints can lead to state-of-the-art performance for pixel-classification tasks. 3) Finally, we lay down the foundations of super-latent learning. By treating sparse codes on a CRF as latent variables, dictionary learning can also be performed via the Latent (Structural) SVM formulation for jointly learning a classifier over the sparse codes. The dictionary is treated as a super-latent variable that generates the latent variables.Ph.D.
Doctorate
Computer Science
Engineering and Computer Science
Computer Science
14
Sturz, Bradley R. Katz Jeffrey S. "Geometric rule learning by pigeons." Auburn, Ala., 2007. http://repo.lib.auburn.edu/2006%20Fall/Dissertations/STURZ_BRADLEY_52.pdf.
15
Crum-Lindqvist, Anne. "Geometric and extra-geometric spatial conceptualisation : a cross-linguistic and non-verbal perspective." Thesis, University of Plymouth, 2008. http://hdl.handle.net/10026.1/2875.
Abstract:
Almost all past empirical work exploring the Functional Geometric Framework (FGF) proposed by Coventry and Garrod (2004) for spatial language use has been based on a single language - English. Therefore the extent to which the framework applies across languages has not been established. The current thesis investigated whether geometric and extra-geometric factors affect production and comprehension of spatial language across three languages; English, Finnish and Spanish. Eight cross-linguistic appropriateness rating studies identified similarities and differences in the factors that underlie our verbal conceptualisation of space across three classes of spatial relations/terms: 1) topological relations (e.g., in/on), 2) vertical axis projective terms (e.g., above/below), and 3) horizontal axis projective terms (e.g., in front of/behind) and their Finnish and Spanish counterparts. There was support for the FGF crosslinguistically, and many of the results were in line with what has been previously discovered in research on English, although extra-geometric factors, such as conceptual knowledge and dynamic kinematic-routines, were revealed to often have different weightings in different languages. Given the importance of extra-geometric factors across languages, the second part of the thesis asks whether extra-geometric factors also influence (non-linguistic) memory for spatial object relations. This question was addressed by two non-verbal spatial memory experiments which revealed that this was the case in some circumstances. Horizontal shifts in position by a potentially horizontally mobile object were more accurately remembered in specific conditions, i.e. when the located object was positioned along the diagonal axes of the reference object rather than cardinal axes, and when the movement was against the direction of expected movement of the located object. However, location memory for vertical shifts of position, was not affected in such a way by potentially vertically mobile objects in any circumstances. In the closing chapter of the thesis the generalisability of the FGF for crosslinguistic and non-linguistic relations is discussed.
16
Latham, Richard Samuel. "Combinatorial algorithms for the analysis and satisfaction of geometric constraints." Thesis, Brunel University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336642.
17
GRITAI, ALEXEI. "MULTI-VIEW GEOMETRIC CONSTRAINTS FOR HUMAN ACTION RECOGNITION AND TRACKING." Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4032.
Abstract:
Human actions are the essence of a human life and a natural product of the human mind. Analysis of human activities by a machine has attracted the attention of many researchers. This analysis is very important in a variety of domains including surveillance, video retrieval, human-computer interaction, athlete performance investigation, etc. This dissertation makes three major contributions to automatic analysis of human actions. First, we conjecture that the relationship between body joints of two actors in the same posture can be described by a 3D rigid transformation. This transformation simultaneously captures different poses and various sizes and proportions. As a consequence of this conjecture, we show that there exists a fundamental matrix between the imaged positions of the body joints of two actors, if they are in the same posture. Second, we propose a novel projection model for cameras moving at a constant velocity in 3D space, \emph cameras, and derive the Galilean fundamental matrix and apply it to human action recognition. Third, we propose a novel use for the invariant ratio of areas under an affine transformation and utilizing the epipolar geometry between two cameras for 2D model-based tracking of human body joints. In the first part of the thesis, we propose an approach to match human actions using semantic correspondences between human bodies. These correspondences are used to provide geometric constraints between multiple anatomical landmarks ( e.g. hands, shoulders, and feet) to match actions observed from different viewpoints and performed at different rates by actors of differing anthropometric proportions. The fact that the human body has approximate anthropometric proportion allows for innovative use of the machinery of epipolar geometry to provide constraints for analyzing actions performed by people of different anthropometric sizes, while ensuring that changes in viewpoint do not affect matching. A novel measure in terms of rank of matrix constructed only from image measurements of the locations of anatomical landmarks is proposed to ensure that similar actions are accurately recognized. Finally, we describe how dynamic time warping can be used in conjunction with the proposed measure to match actions in the presence of nonlinear time warps. We demonstrate the versatility of our algorithm in a number of challenging sequences and applications including action synchronization , odd one out, following the leader, analyzing periodicity etc. Next, we extend the conventional model of image projection to video captured by a camera moving at constant velocity. We term such moving camera Galilean camera. To that end, we derive the spacetime projection and develop the corresponding epipolar geometry between two Galilean cameras. Both perspective imaging and linear pushbroom imaging form specializations of the proposed model and we show how six different ``fundamental" matrices including the classic fundamental matrix, the Linear Pushbroom (LP) fundamental matrix, and a fundamental matrix relating Epipolar Plane Images (EPIs) are related and can be directly recovered from a Galilean fundamental matrix. We provide linear algorithms for estimating the parameters of the the mapping between videos in the case of planar scenes. For applying fundamental matrix between Galilean cameras to human action recognition, we propose a measure that has two important properties. First property makes it possible to recognize similar actions, if their execution rates are linearly related. Second property allows recognizing actions in video captured by Galilean cameras. Thus, the proposed algorithm guarantees that actions can be correctly matched despite changes in view, execution rate, anthropometric proportions of the actor, and even if the camera moves with constant velocity. Finally, we also propose a novel 2D model based approach for tracking human body parts during articulated motion. The human body is modeled as a 2D stick figure of thirteen body joints and an action is considered as a sequence of these stick figures. Given the locations of these joints in every frame of a model video and the first frame of a test video, the joint locations are automatically estimated throughout the test video using two geometric constraints. First, invariance of the ratio of areas under an affine transformation is used for initial estimation of the joint locations in the test video. Second, the epipolar geometry between the two cameras is used to refine these estimates. Using these estimated joint locations, the tracking algorithm determines the exact location of each landmark in the test video using the foreground silhouettes. The novelty of the proposed approach lies in the geometric formulation of human action models, the combination of the two geometric constraints for body joints prediction, and the handling of deviations in anthropometry of individuals, viewpoints, execution rate, and style of performing action. The proposed approach does not require extensive training and can easily adapt to a wide variety of articulated actions.Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Computer Science PhD
18
Stein, Gideon P. (Gideon Pascal). "Geometric and photometric constraints : motion and structure from three views." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9959.
Abstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.Includes bibliographical references (p. 165-171).
by Gideon P. Stein.
Ph.D.
19
Lawver, Jordan D. "Robust Feature Tracking in Image Sequences Using View Geometric Constraints." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1365611706.
20
Atalay-Satoglu, Fatma Betul. "Spatial decompositions for geometric interpolation and efficient rendering." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1812.
Abstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2004.Thesis research directed by: Computer Science. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
21
Ng, Ee Sin. "Image feature matching using pairwise spatial constraints." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610418.
22
Seth, Abhishek. "Combining physical constraints with geometric constraint-based modeling for virtual assembly." [Ames, Iowa : Iowa State University], 2007.
23
KAIMAL, VINOD GOPALKRISHNA. "A NEURAL METHOD OF COMPUTING OPTICAL FLOW BASED ON GEOMETRIC CONSTRAINTS." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1037632137.
24
TRINH, DUC CUONG. "Geometric Perspective on Kinematics and Singularities of Spatial Mechanisms." Doctoral thesis, Università degli studi di Genova, 2018. http://hdl.handle.net/11567/928948.
Abstract:
This doctoral dissertation deals with the kinematics and singularity analyses of serial
and parallel manipulators with multiple working modes. The inverse kinematics of
6R architectures with non-spherical wrists were solved using simple geometric considerations;
the problem was reduced to the solution of a trigonometric equation in one
variable, the sixth joint angle. The direct kinematic analysis of the parallel manipulator,
namely the Exechon, was conducted; it involves using a standard numerical tool to
solve the system of equations in platform’s angle variables. Both kinematics analyses
took advantage of the standard numerical solver to obtain the solutions. The singularities
of the Exechon were studied with the geometrical interpretation. By using the
theory of reciprocal screws, the input-output velocity equations were introduced. This
led to the investigation of the Jacobian matrices, which is an essential part when working
with any manipulator. A method for obtaining the singularity loci and the numerical
example was provided. The formulations presented in this dissertation are general and
effective enough to be applicable for many other similar architectures.
25
Richards, Lynn Valerie. "Children's production of locative expressions in English : the influence of geometric and extra-geometric factors." Thesis, University of Plymouth, 2001. http://hdl.handle.net/10026.1/456.
Abstract:
The research in this thesis examines the influence that both geometric and extrageometric factors have on children's spatial language production. Over the years it has widely been assumed that spatial prepositions identif' where objects are in the world (geometric factors) and that this is reflected in the semantic representations of these words. More recently, researchers investigating the lexical semantics of spatial prepositions have begun to question this assumption by demonstrating that what objects are and how they are interacting can also affect the way we describe where they are in the world (extra-geometric factors). Following on from research conducted with adults that has demonstrated the importance of both of these factors on spatial language, the main aim of this thesis was to ascertain for the first time whether these factors also influenced children's spatial language production, and if so, when they became important in children's development of spatial expressions. Additionally, due to the paucity of research investigating the production of spatial terms, the Experiments reported in this theis set out to redress the balance. The research in this thesis demonstrated for the first time that both geometric and extra geometric factors influence the production of children's spatial expressions from an early age. In doing so, however, the Experiments reported here were not necessarily revealing as to the nature of the semantic representation of spatial terms, rather they highlighted a different issue; how people make distinctions during a verbal interaction. Evidence is presented that suggests a level of agreement between people regarding the nonconventional use of words. In order to distinguish between functional and non-functional situations, both adults and children used different types of spatial terms to locate an object even when they had a limited number of words in their lexicon. An approach to the whole process of prepositional production is suggested rather than concentrating on what is represented in an individual's lexicon.
26
Mäs, Stephan. "On the Consistency of Spatial Semantic Integrity Constraints." Neubiberg Universitätsbibliothek der Universität der Bundeswehr, 2010. http://d-nb.info/1000831663/34.
27
Otto, Michael. "Spatial Constraints and Topology in Urban Road Networks." Master's thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-202967.
Abstract:
Spatial and topological features of urban road networks have been observed variously in the past. No previous study, however, has investigated and compared an extensive data set from cities all over the world regarding their network properties. In this work, re-spectively 20 large cities from 5 continents and Germany are analyzed. In the process, node degree, link length, shortest paths, detour index as well as measures for rectangu-larity are used to characterize and to differentiate the networks. While most networks properties are quite diverse from continent to continent, the detour index as a measure of efficiency shows remarkable similarities and homogeneity over all regions, independ-ent of their spatial network structure. It is shown that in some cities this efficiency is mainly sustained by a subnetwork of major roads, while in others it relies on a balance between minor and major roads. Rectangularity in all regions is shown to be predomi-nant in the structure of minor road subnetworks, while it is shown that this feature is not trivially connected to the node degreeRäumliche und topografische Eigenschaften urbaner Straßennetzwerke sind in der Ver-gangenheit vielfältig untersucht wurden. Keine der bisherigen Studien hat jedoch eine umfassende Anzahl weltweiter Städte auf ihre Netzwerkeigenschaften untersucht. In dieser Arbeit werden jeweils 20 Großstädte aus 5 Kontinenten analysiert. Knotengrad, Kantenlängen, kürzeste Pfade, Detour Index sowie die Rechtwinkligkeit werden schritt-weise untersucht, um die Netzwerke zu charakterisieren und voneinander zu differen-zieren. Während die meisten Netzwerkmaße große Unterscheide von Kontinent zu Kon-tinent aufweisen, lassen sich beim Detour Index, welcher ein Maß für die Effizienz im Netzwerk dient, bemerkenswerte Gemeinsamkeiten in allen Regionen unabhängig von der räumlichen Netzwerkstruktur feststellen. Es wird gezeigt, dass die Effizienz in eini-gen Städten hauptsächlich durch ein Teilnetz von Hauptstraßen getragen wird, während sie anderswo auf einer Balance zwischen Haupt- und Nebenstraßen beruht. Vor allem in der Struktur von Nebenstraßennetzwerken kann Rechtwinkligkeit festgestellt werden, während gleichzeitig wird, dass letztere in keinem trivialen Zusammenhang mit dem Knotengrad steht
28
Keller, Matthew R. "Effects of time constraints on social spatial memory." Click here for download, 2009. http://proquest.umi.com/pqdweb?did=1707435841&sid=1&Fmt=2&clientId=3260&RQT=309&VName=PQD.
29
Cocke, Matthew. "Natural constraints on Euclidean motions." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367122.
30
Chen, Jin. "The use of multiple cameras and geometric constraints for 3-D measurement." Thesis, City University London, 1995. http://openaccess.city.ac.uk/7542/.
Abstract:
This thesis addresses some of the problems involved in the automation of 3-D photogrammetric measurement using multiple camera viewpoints. The primary research discussed in this thesis concerns the automatic solution of the correspondence problem. This and associated research has led to the development of an automated photograrnmetric measuring system which combines the techniques from both machine vision and photogrammetry. Such a system is likely to contribute greatly to the accessibility of 3-D measurement to non-photogrammetrists who will generally have little knowledge and expertise of photogrammetry. A matching method, which is called the 3-D matching method, is developed in the thesis. This method is based on a 3-D intersection and "epipolar plane", as opposed to the 2-D intersection of the epipolar line method. The method is shown to provide a robust and flexible procedure,especially where camera orientation parameters are not well known. The theory of the method is derived and discussed. It is further developed by combination with a bundle adjustment process to iteratively improve the estimated camera orientations and to gradually introduce legitimate matched target images from multiple cameras. The 3-D target matching method is also optimised using a 3-D space constrained search technique. A globally consistent search is developed in which pseudo target images are defined to overcome problems due to occlusion. Hypothesis based heuristic algorithms are developed to optimise the matching process. This method of solving target correspondences is thoroughly tested and evaluated by simulation and by its use in practical applications. The characteristics of the components necessary for a photogrammetric measuring system are investigated. These include sources of illumination, targets, sensors, lenses, and framegrabbers. Methods are introduced for analysis of their characteristics. CCD cameras are calibrated using both plumb line and self calibration methods. These methods provide an estimation of some of the sources of error, which influence the performance of the system as a whole. The design of an automated photogrammetric measuring system with a number of novel features is discussed and a prototype system is developed for use in a constrained environment. The precision, accuracy, reliability, speed, and flexibility of the developed system are explored in a number of laboratory and experimental applications. Trials show that with further development the system could have commercial value and be used to provide a solution suitable for photogrammetrists and trained operators in a wide range of applications.
31
Ros, Lluís. "A kinematic-geometric approach to spatial interpretation of line drawings." Doctoral thesis, Universitat Politècnica de Catalunya, 2000. http://hdl.handle.net/10803/5932.
Abstract:
This Thesis contributes with new algorithms for line drawing interpretation. A line drawing is a 2D diagram of vertices and straight edges aiming to depict a polyhedral 3D scene. Given one such drawing we usually want to first test whether it is a correct projection. If it is, then we wish to reconstruct all possible scenes it can depict. Otherwise, we attempt to correct the drawing so that it becomes reconstractable.Traditionally, the Machine Vision approach to these problems has been mainly algebraic. Although computer scientists have discovered graphical techniques like the reciprocal diagrams, these have not been fully exploited or sometimes left apart, arguing that they only provide necessary conditions for realizability. However, a careful investigation of related areas of Geometry reveals the existence of complete and purely geometric tools that, using just pencil and straightedge, are able to decide the correctness of certain families of drawings. A first goal of this Thesis has been to select one such tool, the so-called cross-section diagram, and extend its validity to a broader class of drawings; namely, those of polyhedral surfaces generated by scenes of opaque polyhedra.
At present, however, no general realizability test using pencil and straightedge alone has been devised for general drawings so that relying on algebraic methods seems unavoidable. A second goal of the Thesis has been to exploit a known mapping between spatial polyhedra and the instantaneous motions of an articulated mechanism. Based on this mapping, we give a concise realizability test that outperforms the most popular algebraic approach known so far, due to Sugihara: it is faster, numerically stable, straightforwardly implementable in floating-point arithmetic and yields a linear parameterization of all possible reconstructions of the drawing. Additionally, this gives a model of the Necker reversal phenomenon and, in some cases, it allows obtaining all concavity/convexity patterns of the edges, neither resorting to consistent labelling techniques, nor consulting junction dictionaries.
A correction module is usually necessary, since drawings with a general geometry are seldom correct. In practice, for example, if a drawing is got from a hand-made sketch or by filtering a real image, the coordinates of its vertices will seldom lie in the right places, and reconstruction will not be possible. The third goal of the Thesis has been to efficiently solve this problem. To this end, we have devised the first algorithm for line drawing correction that allows the simultaneous movement of all the vertices. This yields better solutions than existing approaches, which only allowed the displacement of a subset of the vertices, or failed to correct some combinatorial structures. Moreover, we have provided a second correction strategy that keeps the vertices fixed but alters the combinatorial structure.
The developed techniques find applications in the design of new man-machine interfaces for solid modeling, since they allow the reconstruction of 3D shapes from rough hand-made sketches.
32
Krainer, Thomas, and Bert-Wolfgang Schulze. "Long-time asymptotics with geometric singularities in the spatial variables." Universität Potsdam, 2000. http://opus.kobv.de/ubp/volltexte/2008/2582/.
Abstract:
Content:
Introduction
1 Anisotropic operators in a cylinder with a conical base
1.1 Manifolds with conical singularities and opertors of Fuchs type
1.2 Typical operators and symbol structures
2 Weighted wedge Sobolev spaces and edge asymptotics
2.1 Discrete edge asymptotics
2.2 Continuos edge asymptotics with discrete limit at infinity
2.3 Calculus with operator valued symbols
3 Corner asymptotics at infinity
3.1 The structure of singular functions
3.2 Operators with trace and potential conditions
3.3 Asymptotics and (anisotropic) elliptic regularity
33
Keil, Mitchel J. "Automatic generation of interference-free geometric models of spatial mechanisms." Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-08252008-162631/.
34
Ros, Giralt Lluís. "A kinematic-geometric approach to spatial interpretation of line drawings." Doctoral thesis, Universitat Politècnica de Catalunya, 2000. http://hdl.handle.net/10803/5932.
Abstract:
This Thesis contributes with new algorithms for line drawing interpretation. A line drawing is a 2D diagram of vertices and straight edges aiming to depict a polyhedral 3D scene. Given one such drawing we usually want to first test whether it is a correct projection. If it is, then we wish to reconstruct all possible scenes it can depict. Otherwise, we attempt to correct the drawing so that it becomes reconstractable.Traditionally, the Machine Vision approach to these problems has been mainly algebraic. Although computer scientists have discovered graphical techniques like the reciprocal diagrams, these have not been fully exploited or sometimes left apart, arguing that they only provide necessary conditions for realizability. However, a careful investigation of related areas of Geometry reveals the existence of complete and purely geometric tools that, using just pencil and straightedge, are able to decide the correctness of certain families of drawings. A first goal of this Thesis has been to select one such tool, the so-called cross-section diagram, and extend its validity to a broader class of drawings; namely, those of polyhedral surfaces generated by scenes of opaque polyhedra.At present, however, no general realizability test using pencil and straightedge alone has been devised for general drawings so that relying on algebraic methods seems unavoidable. A second goal of the Thesis has been to exploit a known mapping between spatial polyhedra and the instantaneous motions of an articulated mechanism. Based on this mapping, we give a concise realizability test that outperforms the most popular algebraic approach known so far, due to Sugihara: it is faster, numerically stable, straightforwardly implementable in floating-point arithmetic and yields a linear parameterization of all possible reconstructions of the drawing. Additionally, this gives a model of the Necker reversal phenomenon and, in some cases, it allows obtaining all concavity/convexity patterns of the edges, neither resorting to consistent labelling techniques, nor consulting junction dictionaries.A correction module is usually necessary, since drawings with a general geometry are seldom correct. In practice, for example, if a drawing is got from a hand-made sketch or by filtering a real image, the coordinates of its vertices will seldom lie in the right places, and reconstruction will not be possible. The third goal of the Thesis has been to efficiently solve this problem. To this end, we have devised the first algorithm for line drawing correction that allows the simultaneous movement of all the vertices. This yields better solutions than existing approaches, which only allowed the displacement of a subset of the vertices, or failed to correct some combinatorial structures. Moreover, we have provided a second correction strategy that keeps the vertices fixed but alters the combinatorial structure.The developed techniques find applications in the design of new man-machine interfaces for solid modeling, since they allow the reconstruction of 3D shapes from rough hand-made sketches.
35
McInnes, Lynsey. "Spatial and temporal signatures of ecological constraints on diversity." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/7081.
Abstract:
Broad-scale diversity patterns are the outcome of ecological and evolutionary processes that permit different numbers of species to coexist in a region. Many studies have focused on understanding the factors that allow a region to contain more species or a clade to diversify more rapidly. In this thesis, I shift focus to instead explore the constraints that prevent biodiversity increasing unbounded, using a combination of phylogenetic and biogeographical approaches across a range of temporal and spatial scales. In chapter two, I investigate conservatism (i.e., the tendency for more closely related species to be more similar) in the extremes of climate tolerated by a species, assessing the hypothesis that tightly-conserved tolerances are influential in determining the range extents of the species. By using global data from two vertebrate classes and a range of climatic variables, I assess the taxonomic generality of this hypothesis and identify the most strongly conserved variables. In chapters three and four, I develop novel macroecological analyses of factors that may limit the extent of geographic ranges and apply them to Afrotropical birds (chapter three) and all continental mammals (chapter four). Chapter five assesses how the spatial distribution of range limits can be used to compare species’ relative abilities to occupy available landscape. In chapter six, I present new methods to detect signals of past changes to diversity limits in phylogenies, using simulations to explore the power of phylogenies to reveal such patterns of diversity-dependent cladogenesis. In addition to the main research chapters, I append a synthetic review, of which I am joint first author, exploring the evolutionary underpinnings of large-scale species-area relationships. This thesis builds links between the macroecology of species’ distributions with the dynamics of clades over macroevolutionary timescales to determine how geography, phylogeny and history interact in the generation and maintenance of large-scale biodiversity.
36
MEDEIROS, VIVIAN SUZANO. "DETERMINATION OF THE OPTIMAL TRAJECTORIES ON RACE TRACKS WITH DYNAMIC AND GEOMETRIC CONSTRAINTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=25685@1.
Abstract:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
O presente projeto de pesquisa objetiva desenvolver um procedimento para determinação de trajetórias ótimas em pistas de corrida baseado em técnicas de otimização, considerando os limites geométricos da pista e as características dinâmicas do veículo. O veículo será representado por meio de um modelo simplificado de partícula orientada, mas que inclui as capacidades de tração, frenagem e aceleração normal típicas de um veículo terrestre de competição. Primeiramente, é determinada a trajetória de tempo mínimo para uma curva de 90 graus por meio da análise geométrica do problema e em seguida, é obtida a solução analítica geral para aplicação a qualquer ângulo. Em seguida, técnicas de otimização com restrição são empregadas de forma a obter a curva de menor tempo que concatena as trajetórias ótimas individuais de cada curva, previamente determinadas. São estudadas, ainda, as características dinâmicas de algumas curvas polinomiais para inferir aquela que melhor pode ser aplicada no processo de concatenação. A trajetória de menor tempo da pista de corrida obtida pelo procedimento de concatenação é apresentada e é feita uma análise das vantagens e desvantagens do método proposto. Como alternativa, é apresentada uma visão geral do problema de controle ótimo e é formulada a modelagem completa do problema de trajetória de mínimo tempo utilizando esta abordagem, incluindo as restrições dinâmicas do veículo e as restrições geométricas da pista. Algumas técnicas possíveis para solução do problema de controle ótimo são sugeridas.
This work proposes a new procedure to determine the optimal trajectory on race tracks based on constrained optimization techniques, where the constraints are defined by means of the dynamic characteristics of the vehicle and the geometrical limits of the track. The vehicle is represented by an oriented particle with the capabilities of traction, braking and normal acceleration, which are typical in a competition vehicle. First, the minimum-time trajectory for a 90-degree curve is obtained through a geometrical analysis of the problem. The solution is then expanded to be applied to all angles. Starting from the individual minimum-time trajectory for each curve of the track, constrained optimization techniques are employed in order to obtain the shorter curve that concatenates these individual optimal trajectories. The dynamic characteristics of some polynomial curves are analyzed to infer the one that can best be applied in the concatenation process. The minimum-time trajectory for the race track obtained by the concatenation procedure is presented and the advantages and disadvantages of the proposed method are discussed. Alternatively, an overview of the optimal control problem is presented and a complete model of the minimum-time trajectory problem is developed using this approach, including the dynamic constraints of the vehicle and the geometric constraints of the track. Some possible methods for the solution of the optimal control problem are suggested.
37
Fleming, Alan Duncan. "Analysis of uncertainties and geometric tolerances in assemblies of parts." Thesis, University of Edinburgh, 1988. http://hdl.handle.net/1842/6626.
Abstract:
Computer models of the geometry of the real world have a tendency to assume that the shapes and positions of objects can be described exactly. However, real surfaces are subject to irregularities such as bumps and undulations and so do not have perfect, mathematically definable forms. Engineers recognise this fact and so assign tolerance specifications to their designs. This thesis develops a representation of geometric tolerance and uncertainty in assemblies of rigid parts. Geometric tolerances are defined by tolerance zones which are regions in which the real surface must lie. Parts in an assembly can slop about and so their positions are uncertain. Toleranced parts and assemblies of toleranced parts are represented by networks of tolerance zones and datums. Each arc in the network represents a relationship implied by the tolerance specification or by a contact between the parts. It is shown how all geometric constraints can be converted to an algebraic form. Useful results can be obtained from the network of tolerance zones and datums. For example it is possible to determine whether the parts of an assembly can be guaranteed to fit together. It is also possible to determine the maximum slop that could occur in the assembly assuming that the parts satisfy the tolerance specification. Two applications of this work are (1) tolerance checking during design and (2) analysis of uncertainty build-up in a robot assembly plan. I n the former, a designer could check a proposed tolerance specification to make sure that certain design requirements are satisfied. In the latter, knowledge of manufacturing tolerances of parts being manipulated can be used to determine the constraints on the positions of the parts when they are in contact with other parts.
38
Bass, Henry Morgan. "Automatic modification of part geometries subject to manufacturing constraints using fuzzy logic." Thesis, Virginia Tech, 1996. http://hdl.handle.net/10919/45086.
Abstract:
There is frequently a need for algorithms capable of automatic modification of geometric models in response to manufacturing process constraints. Designers typically initiate product models using ideal, exact geometry; however, several non-traditional manufacturing processes frequently require slight modifications to the ideal model to accommodate various manufacturing process constraints. These modifications can be difficult, complex, and tedious to compute. For instance, metal-ceramic brazing requires adjustments to the part geometry
primarily to accommodate thermal expansion and to allow for the insertion of a narrow braze-filler gap. These adjustments depend on the particular geometry, material properties, and processing parameters. Any modification to these product model parameters necessitates extensive recomputation to reestablish a manufacturable part geometry.
This thesis demonstrates in part the integration of geometry into the overall product model by having the non-geometric parts of the product model provide feedback to the geometry by means of automatically modifying its shape. The methodology is demonstrated in a prototype model which introduces the concept of auxiliary geometric structures. In particular, the auxiliary geometric structures provide a mapping between the designer's intent and the part geometry
described in the solid model. The designer's intent is represented in a rule base for metal-ceramic brazing that is controlled by fuzzy logic. This rule base aids the user in quantifying and generating from the auxiliary geometric structures the geometric modifications needed to conform with a complex set of rules derived from both analytic and empirical work in metal-ceramic brazingMaster of Science
39
GLIDER, PEGGY. "THE EMERGENCE OF CHILDREN'S SPATIAL ABILITIES: A QUESTION OF GEOMETRIC PRECISION." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183953.
Abstract:
This research investigated the precision with which spatial information can be maintained in memory and reproduced as well as factors which may effect these emerging abilities. To study this, ten males and ten females in each of first, third, fifth, and seventh grades participated in three drawing tasks under two conditions (match and recall). The tasks involved the presentation of a 4" straight line or a 2" x 2" right angle drawn on an 8" white disc. Subjects were asked to draw a line exactly the same size and in the same place (static), after an imagined rotation, or after an imagined bending or unbending of the line (transformation) on an 1" white disc. Several mixed design analyses of variance with repeated measures on the task variables were run. First graders made significantly more errors than all other subjects. Third and fifth graders differed little and both performed significantly less accurately than seventh graders. Performance on the rotation task and the transformation task did not differ significantly with performance on both yielding more error than performance on the static task. The match condition generally proved easier than the recall condition, straight lines led to less error than bent lines, and orientation information was more accurately preserved than metric information. The requirements of the task, i.e., no change, change in position, or a change in form, interacted with both the stimulus type and the type of information preserved. Grade level also interacted significantly with task and stimulus type. When determining how spatial abilities emerge and the accuracy with which spatial information can be dealt, task demands, stimulus characteristics, and type of information being measured must be considered along with the developmental changes.
40
Matos, Ralha Maria Elfrida Ramos de. "A study of spatial abilities in university students." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277622.
41
Guo, Jiulin. "Geometric and spatial heterogeneity in natural fracture systems formed during 3D strain." Thesis, Durham University, 2009. http://etheses.dur.ac.uk/2172/.
Abstract:
The geometric and spatial heterogeneity in fracture systems of natural fault zones reflect complex strain patterns and exert substantial influences on host rock properties. It has been recognized that general 3D strains will produce diffuse fracture orientation patterns and characteristic kinematics, which are proposed to vary towards the fault core. The bootstrapping methods and spatial correlation analysis [(semi-) variograms] were adopted to investigate the geometric and spatial hetero-geneity in fracture orientations collected systematically with reference to their spatial locations from three distinct fault zones. This relatively rigorous approach revealed that fracture orientation patterns display systematic spatial variations and high spatial correlations traversing fault zones. Factors related to the presence of pre-existing structures and lithologies can modify strains, creating complex fracture patterns and kinematics at different scales and spatial locations. The results suggest that spatially heterogenous fracture networks in subsurface can be highly connected as channels or barriers and will, in anyways, affect the fluid flow path in aquifers.
42
Wong, Kok Cheong. "Representation, feature extraction and geometric constraints for recognising 3D objects from a single perspective view." Thesis, University of Surrey, 1992. http://epubs.surrey.ac.uk/843449/.
Abstract:
This dissertation considers the problem of modelling, feature extraction and recognizing 3D objects from a single perspective view. A solid modelling system based on generalized cylinder is presented. A new algorithm is proposed for grouping 2D line segments into intermediate token features to be used as geometric cues for indexing into the model database and for generating hypotheses for polyhedral objects. A polyhedral object recognition system using a hypothesis and verification paradigm has been proposed and developed. In the modelling system, generalized cylinders are used as geometric primitives for representing objects. The analysis of generalized cylinders is presented. A number of useful expressions and properties of the contour generators of straight homogeneous generalized cylinders are derived under perspective projection. Right and oblique straight homogeneous generalized cylinders with circular and abitrary cross-section are discussed. A novel algorithm for extracting geometric features such as triples of connected edges, triangle- pairings, image trihedral vertices and closed polygons is implemented. Both heuristic and physical rules are utilised to control the combinatorial explosion of the feature grouping process. Physical rules are used to reject closed polygons which are incompatible with a single planar surface hypothesis. Experiments are demonstrated on real data and many features which could reasonably be due to spatial physical properties of the objects are idenified. Only a few spurious features are accidently detected. These irrelevant features are then pruned away in the hypothesis generation and verification process modules of the proposed recognition system. A polyhedral object recognition system based on a single perspective image is developed. A hypothesis and verification paradigm based on the use of local geometric features of objects is presented. In the framework, two high-level geometric primitives, namely triangle-pair and quadrilateral are employed as key features for model invocation and hypothesis generation. Two geometric constraints, namely distance and angle constraints are proposed and integrated into the recognition system. Many model and scene correspondences are pruned away in the early stage of the matching process using the two geometric constraints. As a by-product of the hypothesis generation the relative pose of the 3D objects expressed in camera frame is recovered. A verification process for performing a detailed check on the model-to-scene correspondences is developed. Detailed experimental results are performed to confirm the feasibility and robustness of the recognition system. An intuitive mathematical formulation is proposed for the interpretation of the geometric relationships of a triple of spatial edges and their perspective projection forming image lines. No restriction is imposed on the configuration of the triple of spatial edges. An eighth-degree polynomial equation explicitly defined by the space angles between the corresponding three spatial edges measured with respect to an object centered coordinate system is derived. The crux of this representation is that the angular attributes of pairs of spatial edges are object-independent. An effective hypothesis generation scheme is proposed which can take advantage of the commonality of this novel representation. It avoids replicating the same recognition module for every occurrence of the same triple feature in the same generic triple group. The groups are distinguished by the angles between the constituent model edges and do not involve any length metric property. Generally, a relatively small number of defined generic triple groups are employed to describe a wide range of polyhedral object models. Particular closed form solutions are derived for specific but common configurations of edges such as rectangular bar end and orthogonal triple. The practical significance and generality of our result are multifold. Extensive experiments are performed to verify the plausibility of employing connected triple edges and trihedral vertices as key features in the paradigm of hypothesis-generation and Hough-clustering approaches to object recognition. It is demonstrated that the accuracy of the estimated pose of objects is adequate. Finally, outstanding problems identified and possible solutions to these problems are discussed. Future research directions are proposed.
43
Changizi, Navid. "FRAME TOPOLOGY OPTIMIZATION WITH STANDARD CROSS SECTIONS: ACCOUNTING FOR BUCKLING, STRESS CONSTRAINTS AND GEOMETRIC VARIABILITY." Cleveland State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=csu1470847100.
44
Tongtoe, Samruam. "Failure Prediction of Spatial Wood Structures: Geometric and Material Nonlinear Finite Element Analysis." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30557.
Abstract:
The purpose of this study is to investigate spatial wood structures, trace their response on equilibrium paths, identify failure modes, and predict the ultimate load. The finite element models of this study are based on the Crafts Pavilion dome (Triax) in Raleigh, North Carolina, and the Church of the Nazarene dome (Varax) in Corvallis, Oregon. Modeling considerations include 3-d beam finite elements, transverse isotropy, torsional warping, beam-decking connectors, beam-beam connectors, geometric and material nonlinearities, and the discretization of pressure loads.
The primary objective of this study is to test the hypothesis that the beam-decking connectors (B-D connectors) form the weakest link of the dome. The beam-decking connectors are represented by nonlinear springs which model the load slip behavior of nails between the beam and the decking.
The secondary objective of this study is to develop models that are sufficiently simple to use in engineering practice.Ph. D.
45
Smyser, Eileen Marie. "The effects of The Geometric Supposers : spatial ability, van Hiele levels, and achievement /." Connect to resource, 1994. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1234541992.
46
Zhang, Hao-Chen. "Mobility and kinematics of some spatial four-bar mechanisms with additional constraints." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56991.
Abstract:
Mobility and kinematics of a folding cube are introduced. This cube is shown to be an array of 12 parallel, symmetric 1-dof 4-bar linkages.The cube is composed of 8 corner tripods and 12 edge rods. There is a hinge at the end of each edge rod connected to an adjacent corner tripod leg. Motion is obtained by each tripod screwing inward about an axis along the cube space diagonal. Two different foldings are described by adjacent tripods screwing in the same, isorotation, or in the opposite, counter-rotation, hand.
Folding motion and direct and inverse kinematics are derived. Results are easily obtained in closed form not only for the folding cube but also for the underlying general four-bar kernel mechanism where crank and follower are of different radii and axes are skewed. Singularity and joint combinations analyses are presented along with other angular relationships among mechanism components.
The folding cube can be adapted as a robotic manipulator component which promises to be stiff, light and simple. This component mechanism appears to be a member of a family of similar, parallel mechanisms where the 4-bar kernel axes are coplanar. Family architecture appears to be based on the 5 platonic solids. The folding rectangle and the folding tetrahedron are introduced as two members of the family.
47
Galanidi, Maria. "Spatial considerations and environmental constraints on benthic prey resources for common scoter." Thesis, Bangor University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443651.
48
Doktor, Eugeniusz. "Organizing the execution of transportation tasks under spatial, temporal and other constraints." Thesis, University of Strathclyde, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260543.
49
Cabral, Mariza Castanheira de Moura da Costa. "Effects of spatial constraints on channel network topology : implications for geomorphological inference /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/10147.
50
Jørgensen, Carl-Johan. "Scheduling activities under spatial and temporal constraints to populate virtual urban environments." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S033/document.
Abstract:
Les modèles de simulation de foules visent généralement à produire des foules visuellement crédibles avec l'intention d'insuffler de la vie à des environnements virtuels. Notre travail se concentre sur la génération de comportements statistiquement cohérents qui peuvent être utilisés pour piloter des modèles de simulation de foules sur de longues périodes de temps, jusqu'à plusieurs jours. Dans les foules réelles, les comportements des individus dépendent principalement de l'activité qu'ils ont l'intention d'effectuer. La façon d’ordonnancer cette activité repose sur l'interaction étroite qui existe entre l'environnement, les contraintes spatiales et temporelles associées à l'activité et les caractéristiques personnelles des individus. Par rapport à l'état de l'art, notre modèle gérer mieux cette interaction. Nos principales contributions se situent dans le domaine de l'ordonnancement d'activités et de la planification de chemin. Dans un premier temps, nous proposons un processus d'ordonnancement d'activités individuelles et son extension aux activités coopératives. Basé sur les descriptions de l'environnement, des activités désirées et des caractéristiques des agents, ces processus génèrent une séquence de la tâche pour chaque agent. Des lieux où ces tâches doivent être effectuées sont sélectionnés et un timing relâché est produit. Cet ordonnancement est compatible avec les contraintes spatiales et temporelles liées à l'environnement et à l'activité prévue par l'agent et par d'autres agents en coopération. Il prend également en compte les caractéristiques personnelles des agents, induisant de la diversité dans les ordonnancements produits. Nous montrons que notre modèle produit des comportements statistiquement cohérents avec ceux produits par des personnes dans les mêmes situations. Dans un second temps, nous proposons un processus de planification de chemins hiérarchique. Il repose sur un processus d'analyse de l'environnement automatique qui produit une représentation hiérarchique sémantiquement cohérente des villes virtuelles. La nature hiérarchique de cette représentation est utilisée pour modéliser différents niveaux de prise de décisions. Un chemin grossier est d'abord calculé, puis raffiné pendant la navigation lorsque de l'information pertinente est disponible, permettant ainsi à l'agent d'adapter son chemin à des événements inattendus. Le modèle proposé gère des décisions rationnelles à long terme guidant la navigation des agents dans les villes virtuelles. Il prend en compte la forte relation entre le temps, l'espace et l'activité pour produire les comportements des agents plus crédibles de. Il peut être utilisé pour peupler facilement des villes virtuelles avec des foules au sein desquelles des phénomènes observables émergent de l'activité individuelleCrowd simulation models usually aim at producing visually credible crowds with the intent of giving life to virtual environments. Our work focusses on generating statistically consistent behaviours that can be used to pilot crowd simulation models over long periods of time, up to multiple days. In real crowds, people's behaviours mainly depend on the activities they intend to perform. The way this activity is scheduled rely on the close interaction between the environment, space and time constraints associated with the activity and personal characteristics of individuals. Compared to the state of the art, our model better handle this interaction. Our main contributions lie in the domain of activity scheduling and path planning. First, we propose an individual activity scheduling process and its extension to cooperative activity scheduling. Based on descriptions of the environment, of intended activities and of agents' characteristics, these processes generate a task schedule for each agent. Locations where the tasks should be performed are selected and a relaxed agenda is produced. This task schedule is compatible with spatial and temporal constraints associated with the environment and with the intended activity of the agent and of other cooperating agents. It also takes into account the agents personal characteristics, inducing diversity in produced schedules. We show that our model produces schedules statistically coherent with the ones produced by humans in the same situations. Second, we propose a hierarchical path-planning process. It relies on an automatic environment analysis process that produces a semantically coherent hierarchical representation of virtual cities. The hierarchical nature of this representation is used to model different levels of decision making related to path planning. A coarse path is first computed, then refined during navigation when relevant information is available. It enable the agent to seamlessly adapt its path to unexpected events. The proposed model handles long term rational decisions driving the navigation of agents in virtual cities. It considers the strong relationship between time, space and activity to produce more credible agents' behaviours. It can be used to easily populate virtual cities in which observable crowd phenomena emerge from individual activities