• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 10
  • 2
  • 1
  • Tagged with
  • 198
  • 198
  • 198
  • 26
  • 16
  • 13
  • 11
  • 11
  • 10
  • 10
  • 10
  • 9
  • 9
  • 8
  • 8
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The application of data clustering algorithms in packet pair/stream dispersion probing of wired and wired-cum-wireless networks

Hosseinpour, Mehri January 2012 (has links)
This thesis reports a study of network probing algorithms to wired and wireless Ethernet networks. H begins with a literature survey of Ethernet and related technology, and existing research on bandwidth probing. The OPtimized Network Engineering Tool (OPNET) was used to implement a network probing testbed, through the development of packet pair/stream modules. Its performance was validated using a baseline scenario (two workstations communicating directly on a wired or wireless channel) and it was shown how two different probe packet sizes allowed link parameters (bandwidth and the inter-packet gap) to be obtained from the packet pair measurements and compared with their known values. More tests were carried out using larger networks of nodes carrying cross-traffic, giving rise to multimodal dispersion distributions which could be automatically classified using data-clustering algorithms. Further studies used the ProbeSim simulation software, which allowed network and data classification processes were brought together in a common simulation framework The probe packet dispersion data were classified dynamically during operation, and a closed¬loop algorithm was used to adjust parameters for optimum measurement. The results were accurate for simple wired scenarios, but the technique was shown to be unsuitable for heterogeneous wired-cum-wireless topologies with mixed cross-traffic.
2

Programming support for CSCW : using X windows

Winnett, Maria E. January 1995 (has links)
This thesis presents a model for programming support for synchronous, distributed CSCW (Computer Supported Co-operative Work). Synchronous, distributed CSCW aims to allow groups of people separated, by distance to work together in real time as if they were at the same location. The model proposed in the thesis allows an application program to be constructed using user interface components known as “shared widgets”. A shared widget displays underlying application data on multiple screens and processes input from multiple users distributed over a network. The distribution of data to and from the users and the underlying network communication is hidden from the application program within the shared widget. The model describes a shared widget as comprising a single “Artefact” and a number of “Views.” The Artefact contains the underlying data and the actions that can be performed on it. A View is the presentation of the Artefact on a user's screen. Shared widgets contain a View for each user in the group. Each user can provide input to the Artefact via their own View, and any change made to the Artefact is reflected synchronously in all the Views. The Artefact can also impose a floor control policy to restrict input to a particular user or group of users, by checking each input event against a known floor control value. The model differs from previous approaches to programming support for CSCW in that the distributed nature of the users is hidden from the application programmer within the shared widgets. As a result, the application programmer does not have to be concerned with the processing of input events or the distribution of output to multiple users. The hiding of these implementation details within the shared widgets allows the CSCW application to be constructed in a similar way to a single-user application. An implementation of the shared widget model, using X Windows, is also described in the thesis. Experimental results and observations are given and used to suggest future directions for further research.
3

Motion segmentation of semantic objects in video sequences

Thirde, David J. January 2007 (has links)
The extraction of meaningful objects from video sequences is becoming increasingly important in many multimedia applications such as video compression or video post-production. The goal of this thesis is to review, evaluate and build upon the wealth of recent work on the problem of video object segmentation in the context of probabilistic techniques for generic video object segmentation. Methods are suggested that solve this problem using formal probabilistic learning techniques, this allows principled justification of methods applied to the problem of segmenting video objects. By applying a simple, but effective, evaluation methodology the impact of all aspects of the video object segmentation process are quantitatively analysed. This research focuses on the application of feature spaces and probabilistic models for video object segmentation are investigated. Subsequently, an efficient region-based approach to object segmentation is described along with an evaluation of mechanisms for updating such a representation. Finally, a hierarchical Bayesian framework is proposed to allow efficient implementation and comparison of combined region-level and object-level representational schemes.
4

Object modelling of temporal changes in Geographical Information Systems

Adamu, Abdul T. January 2003 (has links)
Changes in current temporally enabled GIS systems, thàt have been successfully implemented, are based on the snapshot approach which consist of sequences of discrete images. This approach does not allow either the pattern of changes to be shown or the complexities within the changes to be examined. Also the existing GIS database models cannot represent effectively the history of geographical phenomena. The aim of this research is to develop an object-oriented GIS model (OOGIS) that will represent detailed changes of geographical objects and track the evolution of objects. The detailed changes include spatial, thematic, temporal, events and processes that are involved in the changes. Those have been addressed, but not implemented, by a number of previous GIS projects. Object tracking and evolution includes not only attributes changes to homogenous objects, but also major changes that lead to transforming/destroying existing objects and creating new ones. This will allow the pattern of changes of - geographical phenomena to be examined by tracking the evolution of geographical objects. The OOGIS model was designed using an object-oriented visual modelling tool and was implemented using an object-oriented programming environment (OOPE), an object-oriented database system (OODBS). The visual modelling tool for designing the OOGIS model was Unified Modelling Language (UML), OOPE for implementing the OOGIS model was Microsoft Visual C++ and the OODBS was Objectivity/DB. The prototype of the investigation has been successfully implemented using a Case Study of Royal Borough of Kingston-Upon-Thames, in the United Kingdom. This research is addressing in particular the deficiencies in two existing GIS models that are related to this work. The fust model, the triad model, represents the spatial, thematic and temporal but fails to represent events and processes connected to the changes. The second model, the event-oriented model, though it represents the events (or processes) related to the changes, it stores the changes as attributes of the object. This model is.limited to temporal stable (static) changes and can not be applied to the evolution of geographical phenomena or changes that involve several objects sharing common . .propertíes and temporal relationships. Moreover, the model does not take into account the evolution (e.g. splitting, transformation etc) of a specific object which can involve more than changes to its attributes. Both models are not able to tackle, for instance, in situation when an object such as a park is disappearing to make way for new objects (i.e. roads and new buildings) or in situation where an agriculture piece of land becomes an industrial lot or village becomes a city. In this work the construction of a new approach which overcomes these deficiencies is presented. Also the approach take into account associations and relationships between objects such as inheritance which would be reflected in the object oriented database. For example a road can be regarded a base class from which other classes can be derived such as motorways, streets, dual roads etc which might reflect the evolution of objects ,in non-homogenous ways. The object versioning technique in this work will allow the versions of a geographical object to be related, thereby creating temporal relationships between them. It requires less data storage, since only the changes are recorded. The association between the versions allows continuous forward and backward movement within the versions, and promotes optimum query mechanisms.
5

An energy expert advisor and decision support system for aluminium melting and casting

Yoberd, Belmond January 1994 (has links)
The aim of this project was to develop and implement an expert advisor system to provide information for selecting and scheduling several items of small foundry plants using electric resistance bale-out furnaces, to optimise metal use and reduce energy costs. This involved study in formulating the procedures and developing a “foundry user friendly” expert system for giving advice to unskilled operatives in what was a complex multi- variable process. This system (FOES) included investigation and development of an advising system on the casting of a large numbers of different objects cast under different operating conditions and electricity tariffs. Knowledge elicitation techniques were developed and used during the complicated knowledge election process. Since this research programme intended to look at the complete process of melting, holding and pouring of the aluminium alloy, complex electricity tariffs were incorporated into the expert system in order to accurately calculate the energy cost of each process. A sub-section of the FOES system (DAD) could advise the unskilled foundry operative identify and eliminate the seven most common aluminium alloy casting defect by using a novel technique of incorporating actual defect photographs which were digitally scanned into the system.
6

An integrated modelling framework for the design and construction of distributed messaging systems

Makoond, Bippin Lall January 2008 (has links)
Having evolved to gain the capabilities of a computer and the inherent characteristic of mobility, mobile phones have transcended into the realm of the Internet, forcing mobile telecommunication to experience the phenomenon of IP Convergence. Within the wide spectrum of mobile services, the messaging business has shown the most promising candidate to exploiting the Internet due to its adaptability and growing popularity. However, mobile operators have to change the way they traditionally handle the message logistics, transforming their technologies while adhering to aspects of quality of service. To keep up with the growth in messaging, in the UK alone reaching to 52 billion in 2007, and with the increased complexity of the messages, there is an urgent need to move away from traditional monolithic architectures and to adopt distributed and autonomous systems. The aim of this thesis is to propose and validate the implementation of a new distributed messaging infrastructure that will sustain the dynamics of the mobile market by providing innovative technological resolutions to the common problem of quality modelling, communication, evolution and resource management, within mobile Telecoms. To design such systems, requires techniques, not only found in classical software engineering, but also in the scientific methods, statistics and economics, thus the emergence of an apparent problem of combining these tools in a logical and meaningful manner. To address this problem, we propose a new blended modelling approach which is at the heart of the research process model. We formulate a Class of problems that categorises problem attributes into an information system and assess each requirement against a quality model. To ensure that quality is imprinted in the design of the distributed messaging system, we formulate dynamic models and simulation methods to measure the QoS capabilities of the system, particular in terms of communication and distributed resource management. The outcomes of extensive simulation enabled the design of predictive models to build a system for capacity. A major contribution of this work relates to the problem of integrating the aspect of evolution within the communication model. We propose a new multi-criteria decision making mechanism called the BipRyt algorithm, which essentially preserve the quality model of the system as it tends to grow in size and evolve in complexity. The decision making I process is based on the availability of computational resources, associated rules of usage and defined rules for a group of users or the system as a whole. The algorithm allows for local and global optimisation of resources during the system life cycle while managing conflicts among the rules, such as racing condition and resource starvation. Another important contribution relates to the process of organizing and managing nodes over distributed shared memory. We design the communication model in the shape of a grid architecture, which empowers the concept of single point management of the system (without being a single point of failure), using the same discipline of managing an information system. The distributed shared memory is implemented over the concept of RDMA, where the system runs at very high performance and low latency, while preserving requirements such as high availability and horizontal scalability. A working prototype of the grid architecture is presented, which compares different network technologies against a set of quality metrics for validation purposes.
7

Sketch-based skeleton-driven 2D animation and motion capture

Pan, Junjun January 2009 (has links)
This research is concerned with the development of a set of novel sketch-based skeleton-driven 2D animation techniques, which allow the user to produce realistic 2D character animation efficiently. The technique consists of three parts: sketch-based skeleton-driven 2D animation production, 2D motion capture and a cartoon animation filter. For 2D animation production, the traditional way is drawing the key-frames by experienced animators manually. It is a laborious and time-consuming process. With the proposed techniques, the user only inputs one image ofa character and sketches a skeleton for each subsequent key-frame. The system then deforms the character according to the sketches and produces animation automatically. To perform 2D shape deformation, a variable-length needle model is developed, which divides the deformation into two stages: skeleton driven deformation and nonlinear deformation in joint areas. This approach preserves the local geometric features and global area during animation. Compared with existing 2D shape deformation algorithms, it reduces the computation complexity while still yielding plausible deformation results. To capture the motion of a character from exiting 2D image sequences, a 2D motion capture technique is presented. Since this technique is skeleton-driven, the motion of a 2D character is captured by tracking the joint positions. Using both geometric and visual features, this problem can be solved by ptimization, which prevents self-occlusion and feature disappearance. After tracking, the motion data are retargeted to a new character using the deformation algorithm proposed in the first part. This facilitates the reuse of the characteristics of motion contained in existing moving images, making the process of cartoon generation easy for artists and novices alike. Subsequent to the 2D animation production and motion capture,"Cartoon Animation Filter" is implemented and applied. Following the animation principles, this filter processes two types of cartoon input: a single frame of a cartoon character and motion capture data from an image sequence. It adds anticipation and follow-through to the motion with related squash and stretch effect.
8

3D digital relief generation

Wang, Meili January 2011 (has links)
This thesis investigates a framework for generating reliefs. Relief is a special kind of sculptured artwork consisting of shapes carved on a surface so as to stand out from the surrounding background. Traditional relief creation is done by hand and is therefore a laborious process. In addition, hand-made reliefs are hard to modify. Contrasted with this, digital relief can offer more flexibility as well as a less laborious alternative and can be easily adjusted. This thesis reviews existing work and offers a framework to tackle the problem of generating three types of reliefs: bas reliefs, high reliefs and sunken reliefs. Considerably enhanced by incorporating gradient operations, an efficient bas relief generation method has been proposed, based on 2D images. An improvement of bas relief and high relief generation method based on 3D models has been provided as well, that employs mesh representation to process the model. This thesis is innovative in describing and evaluating sunken relief generation techniques. Two types of sunken reliefs have been generated: one is created with pure engraved lines, and the other is generated with smooth height transition between lines. The latter one is more complex to implement, and includes three elements: a line drawing image provides a input for contour lines; a rendered Lambertian image shares the same light direction of the relief and sets the visual cues and a depth image conveys the height information. These three elements have been combined to generate final sunken reliefs. It is the first time in computer graphics that a method for digital sunken relief generation has been proposed. The main contribution of this thesis is to have proposed a systematic framework to generate all three types of reliefs. Results of this work can potentially provide references for craftsman, and this work could be beneficial for relief creation in the fields of both entertainment and manufacturing.
9

Adaptive motion synthesis and motor invariant theory

Liu, Fangde January 2012 (has links)
Generating natural-looking motion for virtual characters is a challenging research topic. It becomes even harder when adapting synthesized motion to interact with the environment. Current methods are tedious to use, computationally expensive and fail to capture natural looking features. These difficulties seem to suggest that artificial control techniques are inferior to their natural counterparts. Recent advances in biology research point to a new motor control principle: utilizing the natural dynamics. The interaction of body and environment forms some patterns, which work as primary elements for the motion repertoire: Motion Primitives. These elements serve as templates, tweaked by the neural system to satisfy environmental constraints or motion purposes. Complex motions are synthesized by connecting motion primitives together, just like connecting alphabets to form sentences. Based on such ideas, this thesis proposes a new dynamic motion synthesis method. A key contribution is the insight into dynamic reason behind motion primitives: template motions are stable and energy efficient. When synthesizing motions from templates, valuable properties like stability and efficiency should be perfectly preserved. The mathematical formalization of this idea is the Motor Invariant Theory and the preserved properties are motor invariant In the process of conceptualization, newmathematical tools are introduced to the research topic. The Invariant Theory, especially mathematical concepts of equivalence and symmetry, plays a crucial role. Motion adaptation is mathematically modelled as topological conjugacy: a transformation which maintains the topology and results in an analogous system. The Neural Oscillator and Symmetry Preserving Transformations are proposed for their computational efficiency. Even without reference motion data, this approach produces natural looking motion in real-time. Also the new motor invariant theory might shed light on the long time perception problem in biological research.
10

Constrained parameterization with applications to graphics and image processing

Yu, Hongchuan January 2012 (has links)
Surface parameterization is to establish a transformation that maps the points on a surface to a specified parametric domain. It has been widely applied to computer graphics and image processing fields. The challenging issue is that the usual positional constraints always result in triangle flipping in parameterizations (also called foldovers). Additionally, distortion is inevitable in parameterizations. Thus the rigid constraint is always taken into account. In general, the constraints are application-dependent. This thesis thus focuses on the various constraints depended on applications and investigates the foldover-free constrained parameterization approaches individually. Such constraints usually include, simple positional constraints, tradeoff of positional constraints and rigid constraint, and rigid constraint. From the perspective of applications, we aim at the foldover-free parameterization methods with positional constraints, the as-rigid-as-possible parameterization with positional constraints, and the well-shaped well-spaced pre-processing procedure for low-distortion parameterizations in this thesis. The first contribution of this thesis is the development of a RBF-based re-parameterization algorithm for the application of the foldover-free constrained texture mapping. The basic idea is to split the usual parameterization procedure into two steps, 2D parameterization with the constraints of convex boundaries and 2D re-parameterization with the interior positional constraints. Moreover, we further extend the 2D re-parameterization approach with the interior positional constraints to high dimensional datasets, such as, volume data and polyhedrons. The second contribution is the development of a vector field based deformation algorithm for 2D mesh deformation and image warping. Many presented deformation approaches are used to employ the basis functions (including our proposed RBF-based re-parameterization algorithm here). The main problem is that such algorithms have infinite support, that is, any local deformation always leads to small changes over the whole domain. Our presented vector field based algorithm can effectively carry on the local deformation while reducing distortion as much as possible. The third contribution is the development of a pre-processing for surface parameterization. Except the developable surfaces, the current parameterization approaches inevitably incur large distortion. To reduce distortion, we proposed a pre-processing procedure in this thesis, including mesh partition and mesh smoothing. As a result, the resulting meshes are partitioned into a set of small patches with rectangle-like boundaries. Moreover, they are well-shaped and well-spaced. This pre-processing procedure can evidently improve the quality of meshes for low-distortion parameterizations.

Page generated in 0.1048 seconds