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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1281

Closed-Loop Tracking System Provides Reference for Data Collection Exercises

Wallace, Keith, Weinberg, Patrick 10 1900 (has links)
International Telemetering Conference Proceedings / October 26-29, 1992 / Town and Country Hotel and Convention Center, San Diego, California / A computational system was developed to support data collection for advanced airborne technology research. Basic research is conducted using a variety of sensing devices for collection of flight characteristics data from aircraft. To maximize control over as many variables as possible during research activities, a controlled aircraft tracking environment is needed to provide reference data for real-time operation and post-mission analysis. The solution to this requirement is realized with the ACMI Interface System (ACINTS). The ACINTS extracts real-time tracking data from a closed-loop telemetered tracking array, reprocesses needed parameters, provides reference data (positioning and control commands) to the sensor device, and records aircraft kinematics for later correlation with other collected data.
1282

Breaking and non-breaking solitary wave impact pressures on a cylinder over a 3-D bathymetry

Bisgard, Charlie. 01 1900 (has links)
ter have most of their energy held in the region of the water column near to the surface. Tsunamis are extremely long waves with long periods that can range from five minutes to several hours. Due to their very long wavelengths, tsunamis travel at the shallow water wave celerity which is equal to the square root of the gravitational acceleration times the water depth. The speed of a tsunami in the open ocean can reach in excess of 500 miles per hour. Tsunamis are also characterized by low wave height when moving through oceanic depths and are often hard to recognize when seen out in the deep ocean. As tsunamis approach the coastal region, they are affected by the rapid decrease in water depth. / US Navy (USN) author.
1283

AR modeling of coherence in time delay and Doppler estimation

Lee, Jun 12 1900 (has links)
Approved for public release; distribution is unlimited / The estimation of time delay and Doppler difference of a signal arriving at two physically separated sensors is investigated in this thesis. Usually, modified cross power spectrum coupled with Doppler compensation is used to detect a common, passive signal received at two separated sensors. Another successful approach uses the cross coherence to achieve this goal. This thesis modifies these two techniques to model the Doppler difference via an autoregressive (AR) technique. Analytical results are derived and experimentally verified via a computer simulation. Performance at high and low signal to noise ratios (SNRs) is examined. / http://archive.org/details/armodelingofcohe00leej / Captain, Korea Air Force
1284

Performance Analysis of Service in Heterogeneous Operational Environments

Konduru, Prathisrihas Reddy January 2016 (has links)
Context. In recent years there is a rapid increase in demand for cloud services, as cloud computing has become a flexible platform for hosting micro services over the Internet.~Micro services are the core elements of service oriented architecture (SOA) that facilitate the deployment of distributed software systems.  Objectives. This thesis work aims at developing a typical service architecture to facilitate the deployment of compute and I/O intensive services. The thesis work also aims at evaluating the service times of these services when their respective sub services are deployed in heterogeneous environments with various loads. Methods. The thesis work has been carried out using an experimental test bed in order to evaluate the performance. The transport level performance metric called Response time is measured. It is the time taken by the server to serve the request sent by the client. Experiments have been conducted based on the objectives that are to be achieved. Results. The results obtained from the experimentation contain the average service times of a service when it is deployed on both virtual and non-virtual environments. The virtual environment is provided by Docker containers. They also include the variation in the position of their sub services. Conclusions. From results, it can be concluded that the total service times obtained are less in the case of non-virtual environment when compared to container environment.
1285

Improving SLAM on a TOF Camera by Exploiting Planar Surfaces

Bondemark, Richard January 2016 (has links)
Simultaneous localization and mapping (SLAM) is the problem of mapping your surroundings while simultaneously localizing yourself in the map. It is an important and active area of research for robotics. In this master thesis two approaches are attempted to reduce the drift which appears over time in SLAM algorithms. The first approach tries 3 different motion models for the camera. Two of the models exploit the a priori knowledge that the camera is mounted on a trolley. These two methods are shown to improve the results. The second approach attempts to reduce the drift by reducing noise in the point cloud data used for mapping. This is done by finding planar surfaces in the point clouds. Median filtering is used as an alternative to compare the result for noise reduction. The planes estimation approach is also shown to reduce the drift, while the median estimation makes it worse. / Simultaneous localization and mapping (SLAM) är problemet att kartlägga sin omgivning samtidigt som man lokaliserar sig själv i kartan. Det är ett viktigt och aktivt forskningsområde inom robotik. I det här exjobbet testas två tillvägagångssätt för att minska felet i kameraposition och orientering som uppstår över tiden i SLAM-lösningar. Det första tillvägagångssättet testar 3 olika rörelsemodeller för kameran. Två av modellerna utnyttjar vetskapen om att kameran sitter monterad på en vagn. Dessa två metoder förbättrar resultatet för SLAM-algoritmen. Det andra tillväggagångssättet försöker minska felet genom att reducera bruset i punktmolnsdatan som används i kartläggningen. Det görs genom att hitta plana ytor i punktmolnen. Medianfiltrering används som en alternativ lösning för att jämföra hur bra planestimeringen står sig. Planestimeringen visar sig också minska felet i lösningen, medan medianfiltreringen endast försämrar resultatet.
1286

The Time Is at Hand: The Development of Spatial Representations of Time in Children’s Speech and Gesture

Stites, Lauren 15 December 2016 (has links)
Children achieve increasingly complex language milestones initially in gesture before they do so in speech. In this study, we ask whether gesture continues to be part of the language-learning process as children develop more abstract language skills, namely metaphors. More specifically, we focus on spatial metaphors for time and ask whether developmental changes in children’s production of such metaphors in speech also become evident in gesture and what cognitive and linguistic factors contribute to these changes. To answer these questions, we analyzed the speech and gestures produced by three groups of children (ages 3-4, 5-6, and 7-8)—all learning English as first language—as they talked about past and future events, along with adult native speakers of English. Here we asked how early we see change in the orientation (sagittal vs. lateral), directionality (left-to-right, right-to-left, backward, or forward) and congruency with speech (lateral gestures with Time-RP language and sagittal gestures with Ego-RP language). Further, we asked how comprehension of metaphors for time and literacy level would influence these changes. We found developmental changes in the orientation, directionality, and congruency of children’s gestures about time. We found that children’s gestures about time change in orientation (sagittal vs. lateral), in that children increase their use of lateral gestures with age and that this increase is influenced by their literacy level. Further, the directionality (left-to-right, right-to-left, forward, backward) of children’s gestures changes with age. For sagittal gestures we found that children that understood metaphor for time were more likely to produce sagittal gestures that placed the past behind and the future ahead. For lateral gestures, we found that children with higher levels of literacy were more likely to use lateral gestures that place the past to the left and the future to the right. Finally the congruency of children’s gesture with their speech changed. The older children were more likely to pair lateral gestures with Time-RP language than Ego-RP language.
1287

Analysis methods for single molecule fluorescence spectroscopy

Gryte, Kristofer January 2012 (has links)
This thesis describes signal analysis methods for single-molecule fluorescence data. The primary factor motivating method development is the need to distinguish single-molecule FRET fluctuations due to conformational dynamics from fluctuations due to distance-independent FRET changes. Single-molecule Förster resonance energy transfer (FRET) promises a distinct advantage compared to alternative biochemical methods in its potential to relate biomolecular structure to function. Standard measurements assume that the mean transfer efficiency between two fluorescent probes, a donor and an acceptor, corresponds to the mean donor-acceptor distance, thus providing structural information. Accordingly, measurement analysis assumes that mean transfer efficiency fluctuations entail mean donor-acceptor distance fluctuations. Detecting such fluctuations is important in resolving molecular dynamics, as molecular function often necessitates structural changes. A problem arises, however, in that factors other than donor-acceptor distance changes may induce mean transfer efficiency fluctuations. We refer to these factors as distance-independent FRET changes. We present analysis methods to detect distance-independent photophysical dynamics and to determine their correlation with distance-dependent FRET dynamics. First, we review a theory of photon statistics and show how we can use the theory to detect FRET fluctuations. Second, we extend the theory to alternating laser excitation (ALEx) measurements and demonstrate how fluorophore stoichiometry, a measure of fluorophore brightness, reports on distance-independent photophysical dynamics. Next, we provide a measure to determine the extent to which stoichiometry fluctuations account for FRET dynamics. Finally, we use a framework similar to the preceding along with recent advances in the theory of total internal reflection fluorescence (TIRF) microscopy FRET measurements to detect TIRF FRET fluctuations which occur on a timescale faster than the measurement temporal resolution. We validate our methods with simulations and demonstrate their utility in delineating RNA polymerase open complex conformational dynamics.
1288

Disruption of the aluminosilicate lattice by acid fluoride solutions

Semmens, Barrie January 1965 (has links)
TThe disruption of the aluminosilioate crystal lattice by aqueous fluoride solutions has been studied, The effect of reaction time, fluoride concentration, pH, and temperature on the reaction have been investigated« The stoichiometric exchange of hydroxyls by fluoride ions in kaolinite and muscovite at pH 7 below? was extremely doubtful., Disruption of the aluminosil ate crystallattice was thought t o be the predominant reaction over the acid pH range• Fluoride ions were found t react preferentially with the aluminium in the cry s tallattice to form AlP especially at the high e r temperature w
1289

Minimum description length, regularisation and multi-modal data

Van der Rest, John C. January 1995 (has links)
Conventional feed forward Neural Networks have used the sum-of-squares cost function for training. A new cost function is presented here with a description length interpretation based on Rissanen's Minimum Description Length principle. It is a heuristic that has a rough interpretation as the number of data points fit by the model. Not concerned with finding optimal descriptions, the cost function prefers to form minimum descriptions in a naive way for computational convenience. The cost function is called the Naive Description Length cost function. Finding minimum description models will be shown to be closely related to the identification of clusters in the data. As a consequence the minimum of this cost function approximates the most probable mode of the data rather than the sum-of-squares cost function that approximates the mean. The new cost function is shown to provide information about the structure of the data. This is done by inspecting the dependence of the error to the amount of regularisation. This structure provides a method of selecting regularisation parameters as an alternative or supplement to Bayesian methods. The new cost function is tested on a number of multi-valued problems such as a simple inverse kinematics problem. It is also tested on a number of classification and regression problems. The mode-seeking property of this cost function is shown to improve prediction in time series problems. Description length principles are used in a similar fashion to derive a regulariser to control network complexity.
1290

Approximating differentiable relationships between delay embedded dynamical systems with radial basis functions

Potts, Michael Alan Sherred January 1996 (has links)
This thesis is about the study of relationships between experimental dynamical systems. The basic approach is to fit radial basis function maps between time delay embeddings of manifolds. We have shown that under certain conditions these maps are generically diffeomorphisms, and can be analysed to determine whether or not the manifolds in question are diffeomorphically related to each other. If not, a study of the distribution of errors may provide information about the lack of equivalence between the two. The method has applications wherever two or more sensors are used to measure a single system, or where a single sensor can respond on more than one time scale: their respective time series can be tested to determine whether or not they are coupled, and to what degree. One application which we have explored is the determination of a minimum embedding dimension for dynamical system reconstruction. In this special case the diffeomorphism in question is closely related to the predictor for the time series itself. Linear transformations of delay embedded manifolds can also be shown to have nonlinear inverses under the right conditions, and we have used radial basis functions to approximate these inverse maps in a variety of contexts. This method is particularly useful when the linear transformation corresponds to the delay embedding of a finite impulse response filtered time series. One application of fitting an inverse to this linear map is the detection of periodic orbits in chaotic attractors, using suitably tuned filters. This method has also been used to separate signals with known bandwidths from deterministic noise, by tuning a filter to stop the signal and then recovering the chaos with the nonlinear inverse. The method may have applications to the cancellation of noise generated by mechanical or electrical systems. In the course of this research a sophisticated piece of software has been developed. The program allows the construction of a hierarchy of delay embeddings from scalar and multi-valued time series. The embedded objects can be analysed graphically, and radial basis function maps can be fitted between them asynchronously, in parallel, on a multi-processor machine. In addition to a graphical user interface, the program can be driven by a batch mode command language, incorporating the concept of parallel and sequential instruction groups and enabling complex sequences of experiments to be performed in parallel in a resource-efficient manner.

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