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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.
1

The effectiveness and acceptability of community speech and language therapy provision in pre-school children

Glogowska, Margaret January 2000 (has links)
No description available.
2

Queue lengths and delays at oversaturated traffic signal-controlled intersections

Shawaly, El-Sayed Abdel-Azim January 1985 (has links)
No description available.
3

Symptom Onset to First-Medical-Contact in ST-Segment Elevation Myocardial Infarction Patients

Balbaa, Amira January 2016 (has links)
ST-segment elevation myocardial infarctions (STEMI) make up approximately 25% to 40% of total myocardial infarction (MI) presentations. The total occlusion of the coronary artery that results in a STEMI makes timeliness to reperfusion crucial. Previously, the focus has been on decreasing door-to-balloon time (D2B). Although D2B time plays an important role in achieving timely treatment, it is only one component of the route from symptom onset to reperfusion. It has been shown that total ischemic time is a better predictor of clinical outcomes, including mortality and infarct time. Delays between symptom onset to first-medical-contact (FMC) consume the majority of total ischemic time, and remains one of the main reasons that patients do not receive timely care. Factors affecting symptom onset to FMC for STEMI patients receiving primary PCI as a method of reperfusion at the Aswan Heart Center (AHC) in Egypt and the Hamilton General Hospital (HGH) in Canada were examined using the prospectively collected data held in the STEMI registries at these sites and a modified version of the Response to Systems Questionnaire applied in Egypt. Exploring factors linked to early and late presentation in STEMI patients showed that delays were associated with gender, smoking, cardiac history, cardiogenic shock and mortality rate. Furthermore, the type and number of symptoms, presence and actions of bystanders, emotional response and the actions of the patients, as well as transportation time was shown to be different among delay groups. / Thesis / Master of Science (MSc)
4

On the modeling of time-varying delays

Shah, Chirag Laxmikant 30 September 2004 (has links)
This thesis is an effort to develop generalized dynamic models for systems with time-varying time delays. Unlike the simple time-delay model characterized by a transportation lag in the case of a fixed time delay, time-varying delays exhibit quite different characteristics, making the development of easy to use models a difficult endeavor. First an algorithm is developed to predict the actual input-output behavior when the input signal is directly fed into a device that characterizes the time-varying delay. Input-output behaviour generated with this algorithm serves as the truth model for subsequent approximate model development. Simulation results for different classes of delay and different inputs were obtained using the truth model. The input functions were limited to steps, ramps and sinusoids. This limited class of inputs and delays defines the scope of this thesis and the results are to be interpreted as such. The methodology adopted to identify the basic underpinnings of models was system identification where input-output data came from the truth model. Models for the aforementioned classes of inputs and delays were then derived using elementary system identification tools. These models were then carefully analyzed to extract trends by changing the delay parameter. A satisfactory trend was observed in the case of linearly varying time delay. A generalized model for the linearly varying time delay with step and polynomial inputs was developed. An attempt was also made at developing a generalized model for sinusoidally time-varying time delays. This study proposes a model for linearly time-varying time delay, whose structure is not surprisingly also dependent on the class of inputs. It is shown that the derived model reduces to the well known model in the case of a fixed delay.
5

On the modeling of time-varying delays

Shah, Chirag Laxmikant 30 September 2004 (has links)
This thesis is an effort to develop generalized dynamic models for systems with time-varying time delays. Unlike the simple time-delay model characterized by a transportation lag in the case of a fixed time delay, time-varying delays exhibit quite different characteristics, making the development of easy to use models a difficult endeavor. First an algorithm is developed to predict the actual input-output behavior when the input signal is directly fed into a device that characterizes the time-varying delay. Input-output behaviour generated with this algorithm serves as the truth model for subsequent approximate model development. Simulation results for different classes of delay and different inputs were obtained using the truth model. The input functions were limited to steps, ramps and sinusoids. This limited class of inputs and delays defines the scope of this thesis and the results are to be interpreted as such. The methodology adopted to identify the basic underpinnings of models was system identification where input-output data came from the truth model. Models for the aforementioned classes of inputs and delays were then derived using elementary system identification tools. These models were then carefully analyzed to extract trends by changing the delay parameter. A satisfactory trend was observed in the case of linearly varying time delay. A generalized model for the linearly varying time delay with step and polynomial inputs was developed. An attempt was also made at developing a generalized model for sinusoidally time-varying time delays. This study proposes a model for linearly time-varying time delay, whose structure is not surprisingly also dependent on the class of inputs. It is shown that the derived model reduces to the well known model in the case of a fixed delay.
6

Atidėtų mokėjimų įtaka rezervų įvertinimui / Pay delays infulence on reserves

Salatkaitė, Kristina 08 June 2005 (has links)
The pay delays influence on reserves are very important problem for insurance companies. We consider two particular examples of models that attempt to deal with pay delays in insurance, in this work. The first model provides one explanation for underwriting cycle; the second indicates the effects of delays. We were reckoned reserves by chain – ladder method, multiplicity method, and separation method. We had made pay delays modeling program with generated data; this program should made easier to estimate pay delays influence on reserves. We have done simulation with different damage distribution and come to some conclusion like: the insurance premium was enough for the insurance company, because the reserves were positive. There are no big differences in reserves results, calculated by different methods.
7

Implementation of algorithms for computing information propagation delays through sequences of fixed-priority periodic tasks

Tadakamalla, Vineet January 1900 (has links)
Master of Science / Department of Computing and Information Sciences / Rodney R. Howell / Nowadays, there is a rapid increase in the complexity of large automotive and control systems because of the integration of external software modules in them. Many of these systems are based on sampled-data control theory. And because of the different timing constraints of individual modules, each module has a different sampling rate. Typically, these systems operate with periodic task sequences and the information flows between the tasks. Generally the information propagates from tasks operating at one period to tasks operating at different periods. When this happens, unusually long information propagation delays can occur which can be disastrous because the system cannot respond to the changes until this delay has been elapsed. Although for arbitrary set of task sets the delays can be very long, Howell and Mizuno (2010) considers a set of task sequences with special constraints and some very useful bounds are derived for the worst case occurrences of them. Howell and Mizuno (2011) has laid out algorithms that compute the delays for certain special cases of task sequences considered in Howell and Mizuno (2010). The purpose of this project is to understand and implement the algorithms from Howell and Mizuno (2011). The implementation is done so that it avoids the manual computation of the delays and helps in better understanding the ideas presented in Howell and Mizuno (2011). The application can be tested against any valid input that meets our assumptions, and it constructs a schedule that exhibits the worst case behavior and from the schedule it computes the worst case information propagation delays.
8

Communication protocols, queuing and scheduling delay analysis in CANDU SCWR hydrogen co-generation model

Ahmed, Fayyaz 01 August 2011 (has links)
Industrial dynamical, Networked Control Systems (NCSs) are controlled over a communication network. We study a continuous-time CANada Deuterium Uranium-Super Critical Water Reactor (CANDU-SCWR) hydrogen plant and a discrete-time controller, sensor and actuator block, that are connected via a communication network, such as e.g. controller area network (CAN), Ethernet or wireless networks. Issues associated with NCSs are time-varying delays, timevarying sampling intervals and loss of data due to packet drop outs. Delays are also associated with software chosen, control system architecture and computation load. CANDU-SCWR hydrogen co-generation model reliability can be analyzed by dynamic flow graph methodology. We have analyzed the CANDU-SCWR feed water integration with the oxygen unit of copper chloride cycle and also conducted an analytical review of the current networked control system delays. / UOIT
9

Stability and Bifurcation Analysis on Delay Differential Equations

Lin, Xihui Unknown Date
No description available.
10

Stabiity for Systems with Unknown Time Delays

Gaudette, Darrell January 2013 (has links)
Time delays are of long-standing interest in the study of control systems since they appear in many practical control problems and tend to degrade overall system performance. In this thesis, we consider two distinct problems involving uncertain time delays. The first problem that we consider is the achievable delay margin problem, which is determining the longest delay for which stability can be maintained when using a linear time invariant (LTI) controller. This problem has been considered in continuous-time, where bounds (often tight) have been found for plants with non-zero right half plane poles. In this work, we consider the discrete-time case, where we prove that an LTI controller exists which stabilizes the plant and the plant with a one step delay if and only if the plant has no negative, real unstable poles. The second problem that we consider is stabilizing any continuous-time single-input single-output LTI plant with an arbitrarily large time delay and gain. To solve this problem, we propose a simple generalized hold whose resulting discretized system is amenable to adaptive control. Furthermore, by exploiting the structure of the resulting discretized system, we propose purpose built estimators for the unknown gain and delay, which allows us to not only provide bounded-input bounded-output (BIBO) closed-loop stability, but also guarantees the exponential decay of any plant initial conditions, robustness to un-modelled dynamics, and tolerance to occasional, possibly persistent, jumps in the gain and delay. Furthermore, for the case of a first order plant, a similar, but suitably modified controller is shown to tolerate continuous variation of the unknown delay while still providing BIBO closed-loop stability.

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