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STABILITY DOMAINS IN NONLINEAR POINT REACTOR DYNAMICSKendall, James Michael, 1944- January 1971 (has links)
No description available.
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NONLINEAR OSCILLATIONS AND STABILITY BOUNDS IN A NUCLEAR REACTOR WITH LINEAR REACTIVITY FEEDBACKYee, Samuel, 1924- January 1971 (has links)
No description available.
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On Invertibility of the Radon Transform and Compressive SensingAndersson, Joel January 2014 (has links)
This thesis contains three articles. The first two concern inversion andlocal injectivity of the weighted Radon transform in the plane. The thirdpaper concerns two of the key results from compressive sensing.In Paper A we prove an identity involving three singular double integrals.This is then used to prove an inversion formula for the weighted Radon transform,allowing all weight functions that have been considered previously.Paper B is devoted to stability estimates of the standard and weightedlocal Radon transform. The estimates will hold for functions that satisfy an apriori bound. When weights are involved they must solve a certain differentialequation and fulfill some regularity assumptions.In Paper C we present some new constant bounds. Firstly we presenta version of the theorem of uniform recovery of random sampling matrices,where explicit constants have not been presented before. Secondly we improvethe condition when the so-called restricted isometry property implies the nullspace property. / <p>QC 20140228</p>
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Development of health indicators for rough fescue grasslands in the southern interior of British ColumbiaLamagna, Sarah Frances 11 1900 (has links)
Grasslands throughout the world including those in British Columbia have been severely
reduced and altered by agricultural production and inappropriate livestock grazing practices.
Ongoing degradation of rangelands is a worldwide problem, currently affecting about 680
million hectares of rangelands.
Studies on development and application of criteria and indicators for forests and
grasslands are often lacking, or have been done on a limited number of sites with relatively
narrow ranges of climate and soil type. This study aims to (i) quantify the relationships among
soil/vegetation properties known to be affected by grazing to easily-assessed indicators, used in
the existing health assessment systems, that do not require laboratory analyses or time
consuming measurement, and (ii) to evaluate impacts of grazing on soil aggregate stability on the
rough fescue grasslands of the southern interior of British Columbia. During the growing
seasons of 2006 and 2007, soil and vegetation properties were measured on nine open grassland
sites with a potential natural plant community dominated by rough fescue (Festuca campestris
Rydb.) in the southern interior of British Columbia. Each site had at least one area excluded
from grazing and all units were classified into different seral stages according to the amount of
rough fescue present on the land.
Rough fescue cover was found to be a useful indicator of the presence of functioning
recovery mechanisms. Percent exposed mineral soil was found to be a sensitive indicator of the
degree of soil stability and watershed function, as well as an indicator of the integrity of nutrient
cycles and energy flows in rough fescue grasslands. Percent Junegrass cover was not as sensitive
an indicator as percent exposed mineral soil, but has general overall strength with many health
measures.. Only the 1-2 mm aggregate size class was closely related to most soil and vegetation
properties, showing that it is more sensitive than the other aggregate stability parameters to soil
and vegetation properties.
The results from this study can help rangeland managers and ranchers in determining the
rangeland health in their area as well as help researchers understand that only a certain number of
parameters need to be assessed.
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Combinatorial mechanicsAmiouny, Samir V. 08 1900 (has links)
No description available.
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Dissection of the telomere complex CST in Arabidopsis thalianaLeehy, Katherine 16 December 2013 (has links)
Telomeres are the ends of linear chromosomes tasked with preventing their recognition by the DNA damage machinery and providing a mechanism to solve the end replication problem. The telomeric DNA is mostly double-stranded, but it terminates in a 3’ protrusion termed the G-overhang. Telomeres utilize telomerase, a reverse transcriptase, to elongate the telomere, and thus, solve the end replication problem. Both the double strand region and the G-overhang are bound by specific proteins to facilitate the objectives of the telomere. First discovered in budding yeast, the CST (Cdc13(CTC1)/Stn1/Ten1) complex binds to the G-overhang and is important for both chromosome end protection and telomere replication. Work reported in this dissertation provided the first evidence that CST was present outside of yeast, which led to its subsequent identification in a number of vertebrates.
Here I present the identification and characterization of the three components of CST in Arabidopsis thaliana. Similar to yeast, Arabidopsis CST is required for telomere length maintenance, for preventing telomere recombination and chromosome end-to-end fusions. Mutations in the CST complex result in severe genomic instability and stem cells defects. My research also shows that CST and telomerase act synergistically to maintain telomere length. Together these data provide evidence for an essential role for CST in maintaining telomere integrity.
Unexpectedly, I discovered that the TEN1 component of CST may have a more complex role than other members of the heterotrimer. The majority of telomere-related functions we can assay using molecular and cytological approaches are shared by CTC1, STN1 and TEN1, though TEN1 has additional roles in maintaining genome stability, modulating telomerase activity and possibly non-telomeric functions in the chloroplast.
I also present genetic evidence that TEN1 and STN1 act in the same pathway for the maintenance of telomere length and chromosome end protection. Interestingly, however, disrupting the STN1/TEN1 interaction reveals a separation of STN1 function for chromosome end protection versus telomere length maintenance.
Finally, I describe the design and creation of a library of STN1 and TEN1 mutants that will be used to further characterize their functions and their interaction partners. By disrupting such interactions, it will be possible to elucidate the functional significance of these interactions, and thus, provide new insight into how CST functions in Arabidopsis.
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Itch E3 ubiquitin ligase regulates LATS1 tumour suppressor stabilityHo, King Ching 27 April 2011 (has links)
The Large Tumor Suppressor 1 (LATS1) is a serine/threonine kinase and tumor
suppressor found down-regulated in a broad spectrum of human cancers. It is a central
player of the emerging Hippo-LATS tumour suppressor pathway, which plays important
roles in cell proliferation, apoptosis, and stem cell differentiation. Despite the ample data
supporting a role of LATS1 in tumour suppression, how LATS1 is regulated at the
molecular level remains largely unknown. In this study, we have identified Itch, a HECT
class E3 ubiquitin ligase, as a novel binding partner of LATS1. Itch can complex with
LATS1 both in vitro and in vivo through the PPxY motifs of LATS1 and the WW
domains of Itch. Significantly, we found that over-expression of Itch promoted LATS1
degradation by polyubiquitination through the 26S proteasome pathway. On the other
hand, knockdown of endogenous Itch by shRNAs provoked stabilization of endogenous
LATS1 proteins. Finally, through several functional assays, we also revealed that change
of Itch abundance alone is sufficient for altering LATS1-mediated downstream signaling,
negative regulation of cell proliferation, and induction of apoptosis. Together, our study
identifies E3 ubiquitin ligase Itch as the first negative regulator of LATS1 and presents
for the first time a possibility of targeting LATS1/Itch interaction as a therapeutic strategy
in cancer. / Thesis (Master, Pathology & Molecular Medicine) -- Queen's University, 2011-04-26 22:25:46.008
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Stability, Performance, and Implementation Issues in Bilateral Teleoperation Control and Haptic Simulation SystemsHaddadi, Amir 03 January 2012 (has links)
Master-Slave teleoperation systems are designed to extend a human's manipulation capability to remote tasks. Recent applications of these systems are in robotic therapy, telesurgery, and medical simulators.
In practice, due to the uncertainties in the operator and environment dynamics, and time delay, stability and performance are compromised. Stability-based and performance-based controllers are introduced for these systems. A major class of the former controllers are based on the passivity theory and suffer from the assumed unbounded range of dynamics which is rather unrealistic. The latter class of controllers are mostly adaptive methods that are based on performance optimization.
The theme of this thesis is on the development of new stability analysis methods, control strategies, and implementation techniques for enhanced trade-off between stability and performance. I have developed a less conservative passivity-based robust stability method and introduced, for the first time, the notion of Bounded Impedance Absolute Stability. The method provides mathematical and visual aids to incorporate bounds of the passive environment impedance for less conservative guaranteed stability conditions, promising a better compromise between stability and performance.
I have extended the new method to include the dynamic range of the human operator for increased stability margins. I have also used the new method to develop a bilateral controller robust to time delays. Furthermore, I have investigated the effect of sampling position versus velocity for various sampling models to obtain less conservative coupled stability conditions for haptic simulation systems.
Estimates of the environment dynamics are required to include their variations. Therefore, I have proposed two new real-time parameter estimation methods for linear and nonlinear contacts and experimentally evaluated and compared them with the available techniques.
Finally, I have introduced needle insertion as a task in telerobotic systems to combine the expertise of the surgeon with robotic control. Here, the very first few steps needed to effectively control the targeting needles have been taken. I have developed a mechanics-based dynamic model for bevel-tip flexible needles inserted into soft tissues. Finite element models are used to estimate soft tissue deformation, while the mechanics-based model is used to predict needle deflections due to bevel-tip asymmetry. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2011-12-23 01:19:47.535
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TRANSIENT DROOP CONTROL STRATEGY FOR PARALLEL OPERATION OF DISTRIBUTED ENERGY RESOURCES IN AN ISLANDED MICROGRIDHassanzahraee, Mohammad 27 April 2012 (has links)
Future electric grid will evolve from the current centralized and radial model toward a more distributed one. In recent years, distributed generation (DG) units have been playing an important role in electric generation due to their promising advantages in reducing air pollution, improving power system efficiency, and relieving stress on power transmission and delivery systems. Despite the increased penetration of DG systems, the application of individual DG system always has its limitation such as high cost/W, limited capacity and reliability, and safety concerns. A better way to utilize the emerging potential of DG is to take a system approach viewing generation and associated loads as a subsystem called a “microgrid”.
Forming an electric island, the microgrid can work autonomously following a disturbance. In the islanded microgrid, micro sources are responsible for maintaining the voltage and the frequency of the microgrid system within their specified limits and sharing the load between the generators in a stable manner. However, a robust and stable operation of a microgrid depends on a robust control scheme of the microgrid sources.
The most common technique to control microgrid sources is based on conventional droop characteristics. Although the conventional frequency/voltage droop technique properly shares a common active load, the reactive power sharing accuracy can be strongly affected by system parameter and active power control. In addition, frequency variations of different sources in transient mode can cause poor active power sharing.
To override the above-mentioned problems, a novel frequency/voltage droop scheme is proposed in this thesis. The proposed scheme improves the performance of the microgrid in terms of power sharing and voltage regulation and smooths the system’s dynamic and transient responses.
This work has developed the modeling, control parameters design, and power-sharing control starting from a single voltage source inverter to a number of interconnected DG units forming a flexible microgrid. Specifically, this thesis presents:
• A control-oriented modeling based on active and reactive power analysis.
• A control synthesis based on enhanced droop control technique.
• A small signal stability study to give guidelines for properly adjusting the control system parameters according to the desired dynamic response. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2012-04-25 12:08:48.634
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Gain Analysis and Stability of Nonlinear Control SystemsZahedzadeh, Vahid Unknown Date
No description available.
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