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Delay-Dependent Robust Stability Analysis and Stabilization for Uncertain Systems with Time-Varying DelayChen, Jun-Shen 04 September 2010 (has links)
This thesis concerns delay-dependent robust stability analysis and stabilization for time-delay system with uncertainties. By choosing new Lyapunov-Krasovskii functional and using methods which can reduce conservativeness of stability condition in the literature, new delay-dependent sufficient stability conditions are obtained in terms of linear matrix inequality. It is shown that the new stability conditions can provide less conservative results than some existing ones. Furthermore, the new stability conditions are also used to design the state feedback controllers. Finally, numerical examples are given to show the derived results and compared with results in the literature.
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Time series study of urban rainfall suppression during clean-up periodsGeng, Jun 15 May 2009 (has links)
The effect on urban rainfall of pollution aerosols is studied both by data analysis
and computational simulation. Our study examines data for urban areas undergoing
decadal clean-up. We compare the annual precipitation between polluted sites and
relatively clean sites through the time range before and during their clean-up periods to
see how the air quality may affect the precipitation amount. By comparing the annual
precipitation amount between two polluted sites with different elevations we demonstrate
the role that elevation may play in rainfall suppression. Based on the data we collected,
we built a model to analyze the relationship between air pollution aerosols and
precipitation. Finally, we used a model of time dependent condensational aerosol growth
to numerically study the relationship of air pollution aerosols and precipitation amount.
Based on these results, we found a negative relationship of precipitation amount and air
pollution amount; also, the simulation results clearly demonstrated that too many air
pollution particles will deplete the water vapor and suppress further growth of condensation nuclei (CN) toward cloud condensation nuclei (CNN). This study
supported the theoretical explanation on why air pollution could suppress urban rainfall.
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Determination of fluid viscosities from biconical annular geometries: Experimental and modeling studiesRondon, Nolys Javier 15 May 2009 (has links)
Knowledge of viscosity of flow streams is essential for the design and operation of
production facilities, drilling operations and reservoir engineering calculations. The
determination of the viscosity of a reservoir fluid at downhole conditions still remains a
complex task due to the difficulty of designing a tool capable of measuring accurate
rheological information under harsh operational conditions. This dissertation presents
the evaluation of the performance of a novel device designed to measure the viscosity of
a fluid at downhole conditions.
The design investigated in this study addresses several limitations encountered in
previous designs. The prototype was calibrated and tested with fluids with viscosities
ranging from 1 to 28 cp under temperatures ranging from 100 to 160oF. Viscosity
measurements were validated with independent measurements using a Brookfield
viscometer. We proposed a mathematical model to describe the performance of the
device for Power-law fluids. This model describes the response of the device as a function of the rheology of the fluid and the physical dimensions of the device.
Experimental data suggests the validity of the model to predict the response of the
device under expected operating conditions. This model can be used to calculate optimal
dimensions of the device for customized target applications.
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Coordinated Multi-Agent Motion Planning Under Realistic ConstraintsMaithripala, Diyogu Hennadige Asanka 15 May 2009 (has links)
Considered is a class of cooperative control problems that has a special affine characterization.
Included in this class of multi-agent problems are the so called radar
deception problem, formation keeping and formation reconfiguration. An intrinsic geometric
formulation of the associated constraints unifies this class of problems and it
is the first time such a generalization has been presented. Based on this geometric formulation,
a real-time motion planning algorithm is proposed to generate dynamically
feasible reference trajectories for the class. The proposed approach explicitly considers
actuator and operating constraints of the individual agents and constrained dynamics
are derived intrinsically for the multi-agent system which makes these constraints
transparent. Deriving the constrained dynamics eliminates the need for nonlinear
programming to account for the system constraints, making the approach amenable
to real-time control. Explicit consideration of actuator and operating limitations and
nonholonomic constraints in the design of the reference trajectories addresses the important
issue of dynamic feasibility. The motion planning algorithm developed here
is verified through simulations for the radar deception, rigid formation keeping and
formation reconfiguration problems.
A key objective of this study is to advocate a change in paradigm in the approach
to formation control by addressing the key issues of dynamic feasibility and
computational complexity. The other important contributions of this study are: Unifying formulation of constrained dynamics for a class of problems in formation control
through the intrinsic geometry of their nonholonomic and holonomic constraints; Deriving
these constrained dynamics in any choice of frame that can even be coordinate
free; Explicit consideration of actuator and operating limits in formation control to
design dynamically feasible reference trajectories and Developing a real-time, distributed,
scalable motion planning algorithm applicable to a class of autonomous
multi-agent systems in formation control.
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Real-Time Task Scheduling under Thermal ConstraintsAhn, Youngwoo 2010 August 1900 (has links)
As the speed of integrated circuits increases, so does their power consumption.
Most of this power is turned into heat, which must be dissipated effectively in order
for the circuit to avoid thermal damage. Thermal control therefore has emerged as an
important issue in design and management of circuits and systems. Dynamic speed
scaling, where the input power is temporarily reduced by appropriately slowing down
the circuit, is one of the major techniques to manage power so as to maintain safe
temperature levels.
In this study, we focus on thermally-constrained hard real-time systems, where
timing guarantees must be met without exceeding safe temperature levels within the
microprocessor. Speed scaling mechanisms provided in many of today’s processors
provide opportunities to temporarily increase the processor speed beyond levels that
would be safe over extended time periods. This dissertation addresses the problem
of safely controlling the processor speed when scheduling mixed workloads with both
hard-real-time periodic tasks and non-real-time, but latency-sensitive, aperiodic jobs.
We first introduce the Transient Overclocking Server, which safely reduces the
response time of aperiodic jobs in the presence of hard real-time periodic tasks and
thermal constraints. We then propose a design-time (off-line) execution-budget allocation
scheme for the application of the Transient Overclocking Server. We show
that there is an optimal budget allocation which depends on the temporal character istics of the aperiodic workload. In order to provide a quantitative framework for the
allocation of budget during system design, we present a queuing model and validate
the model with results from a discrete-event simulator.
Next, we describe an on-line thermally-aware transient overclocking method to
reduce the response time of aperiodic jobs efficiently at run-time. We describe a modified
Slack-Stealing algorithm to consider the thermal constraints of systems together
with the deadline constraints of periodic tasks. With the thermal model and temperature
data provided by embedded thermal sensors, we compute slack for aperiodic
workload at run-time that satisfies both thermal and temporal constraints. We show
that the proposed Thermally-Aware Slack-Stealing algorithm minimizes the response
times of aperiodic jobs while guaranteeing both the thermal safety of the system and
the schedulability of the real-time tasks. The two proposed speed control algorithms
are examples of so-called proactive schemes, since they rely on a prediction of the
thermal trajectory to control the temperature before safe levels are exceeded.
In practice, the effectiveness of proactive speed control for the thermal management
of a system relies on the accuracy of the thermal model that underlies the
prediction of the effects of speed scaling and task execution on the temperature of
the processor. Due to variances in the manufacturing of the circuit and of the environment
it is to operate, an accurate thermal model can be gathered at deployment
time only. The absence of power data makes a straightforward derivation of a model
impossible.
We, therefore, study and describe a methodology to infer efficiently the thermal
model based on the monitoring of system temperatures and number of instructions
used for task executions.
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Development of a Real-Time PCR Assay to Detect Legionella Species and Chlamydia pneumoniae from Clinical Specimens of Patients with Community-acquired Pneumonia in VGHKSKuo, Chia-chou 02 August 2005 (has links)
Abstract
Legionella species and Chlamydia pneumoniae are a common cause of community-acquired pneumonia and occasional cause of hospital-acquired pneumonia. Significant mortality rates among the elderly and patients with severe underlying disease may occur as a result of infection with those pathogen. Diagnostic delay may also result in increased mortality. Therefore, nucleic acid amplification assays have been shown to be useful for the detection of Legionella.spp and Chlamydia pneumoniae. The genes that encode 16S ribosomal subunits and the macrophage infectivity potentiator (MIP) gene have been shown to contain signature sequences that are useful for the identification of L. pneumophila and a variety of other Legionella species. The pst-1 fragment is useful for identification of Chlamydia pneumoniae. Here we try to test clinical specimens by Real-time PCR assays to detect L.pneumophila and other Legionella species in the same tube, and detect Chlamydia pneumoniae by SYBR Green 1 reagent. By this method, these amplicons of 16S ribosomal subunits gene and MIP gene can be discriminated by different melting curve dependent on different Tm values. In this study, we detected more 5 and 6 patients in Legionella species and Chlamydia pneumoniae than conventional diagnostic tools. Hence, the Real-time PCR also demonstrated that it¡¦s a rapid and high sensitivity method in diagnosis of legionnaires¡¦ disease. In this study, it also demonstrated that Real-time PCR is effective in prediction of atypical pathogen infection.
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The Relationship Between Physical Activity Levels And Time Management Skills Among Selected University StudentsDincay, Hulya 01 June 2008 (has links) (PDF)
The purpose of this study was to explore the relationship between the physical activity levels and the time management practices of selected university students, and to identify the differences between physical activity levels and time management practices in terms of gender. The subjects of this study were 128 male (55,9%) and 101 female (44,1%) university students from six universities in istanbul, Turkey which were selected on a volunteer basis. The Physical Activity Assessment Questionnaire (PAAQ) and the Time Management Questionnaire (TMQ) were used to gather data. The data were analyzed by employing a Statistical Package for Social Statistics. Both descriptive and inferential statistics were used to analyze the data. The level .05 of significance was selected.
There was significant correlation between total hours spend in a week and time planning, and negative correlation between time wasters. There was significant correlation between total MET spend in an hour and time attitudes, between total MET intensities and time attitudes. According to Chi-squared analysis gender difference is dependent of the PA levels in terms of &ldquo / sport MET&rdquo / and &ldquo / total MET&rdquo / intensities. Multivariate analysis of variance (MANOVA) indicated a significant main effect. Subsequent unvaried analysis indicated differences in Time Management in terms of gender.
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The LM Test for a VAR Model with Time Trend-The Cointegration Analysis on Money Demand Function in TaiwanLu, Su-Lien 02 July 2001 (has links)
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Architecture for Web Server with Push CapabilityTsai, Ching-Shin 20 July 2001 (has links)
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Study of Taipower Load Characteristics and Its Impact to the System Fault Critical Clearing TimeChen, Yi-Kuang 29 June 2003 (has links)
A systematic procedure is proposed in this thesis to study the effect of temperature change to the power system load demand by using the typical load patterns of customer classes. The billing data of all service customers are retrieved to derive the daily load profile of the selected Taipower district. To verify the accuracy of the estimated load composition, the simulation results are compared to the actual load profile collected by the SCADA system. The sensitivity analysis of load demand with respect to the temperature change for each customer class is performed by statistic regression according to the actual customer power consumption and temperature data. With temperature rise, the load contribution by each customer class is updated by the corresponding temperature sensitivity and integrated together to form the new load profile of the service district.
To investigate the effect of customer load characteristics to system stability, the equivalent circuit of Taipower 345 KV network is created. With the integration of the load composition by load survey study and temperature sensitivity of customer load, the load demand of each load bus is derived. For fault contingency of system buses, the transient stability analysis has performed to determine the critical clearing time under different temperature conditions.
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