To see the other types of publications on this topic, follow the link: Eavesdropping on the graph state.
Dissertations / Theses on the topic 'Eavesdropping on the graph state'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Eavesdropping on the graph state.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Lawrence, Alan Christopher. "Optimizing compilation with the value state dependence graph." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611873.
Full text
2
Li, Wei. "An approach to graph-based modeling of network exploitations." Diss., Mississippi State : Mississippi State University, 2005. http://sun.library.msstate.edu/ETD-db/ETD-browse/browse.
Full text
3
Meana, Richard William Piper. "Approximate Sub-Graph Isomorphism For Watermarking Finite State Machine Hardware." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4728.
Full textAbstract:
We present a method of mitigating theft of sequential circuit Intellectual Property hardware designs through means of watermarking. Hardware watermarking can be performed by selectively embedding a watermark in the state encoding of the Finite State Machine. This form of watermarking can be achieved by matching a directed graph representation of the watermark with a sub-graph in state transition graph representation of the FSM. We experiment with three approaches: a brute force method that provides a proof of concept, a greedy algorithm that provides excellent runtime with a drawback of sub-optimal results, and finally a simulated annealing method that provides near optimal solutions with runtimes that meet our performance goals. The simulated annealing approach when applied on a ten benchmarks chosen from IWLS 93 benchmark suite, provides watermarking results with edge overhead of less than 6% on average with runtimes not exceeding five minutes.
4
Steenken, Dominik [Verfasser]. "Verification of infinite-state graph transformation systems via abstraction / Dominik Steenken." Paderborn : Universitätsbibliothek, 2015. http://d-nb.info/106989933X/34.
Full text
5
Stanier, James. "Removing and restoring control flow with the Value State Dependence Graph." Thesis, University of Sussex, 2012. http://sro.sussex.ac.uk/id/eprint/7576/.
Full textAbstract:
This thesis studies the practicality of compiling with only data flow information. Specifically, we focus on the challenges that arise when using the Value State Dependence Graph (VSDG) as an intermediate representation (IR). We perform a detailed survey of IRs in the literature in order to discover trends over time, and we classify them by their features in a taxonomy. We see how the VSDG fits into the IR landscape, and look at the divide between academia and the 'real world' in terms of compiler technology. Since most data flow IRs cannot be constructed for irreducible programs, we perform an empirical study of irreducibility in current versions of open source software, and then compare them with older versions of the same software. We also study machine-generated C code from a variety of different software tools. We show that irreducibility is no longer a problem, and is becoming less so with time. We then address the problem of constructing the VSDG. Since previous approaches in the literature have been poorly documented or ignored altogether, we give our approach to constructing the VSDG from a common IR: the Control Flow Graph. We show how our approach is independent of the source and target language, how it is able to handle unstructured control flow, and how it is able to transform irreducible programs on the fly. Once the VSDG is constructed, we implement Lawrence's proceduralisation algorithm in order to encode an evaluation strategy whilst translating the program into a parallel representation: the Program Dependence Graph. From here, we implement scheduling and then code generation using the LLVM compiler. We compare our compiler framework against several existing compilers, and show how removing control flow with the VSDG and then restoring it later can produce high quality code. We also examine specific situations where the VSDG can put pressure on existing code generators. Our results show that the VSDG represents a radically different, yet practical, approach to compilation.
6
Zhou, Rong. "Memory-efficient graph search applied to multiple sequence alignment." Diss., Mississippi State : Mississippi State University, 2005. http://library.msstate.edu/etd/show.asp?etd=etd-06282005-015428.
Full text
7
Lei, Jiansheng. "Using graph theory to resolve state estimator issues faced by deregulated power systems." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1292.
Full text
8
El, Musleh Mohammad. "Transformation of UML State Machine Diagram into Graph Database to Generate Test Cases." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-426060.
Full textAbstract:
The manual approach in software testing is considered as expensive, error-prone, and time-consuming activity since it depends highly on the test engineers. As well, the process of software testing requires proper planning and resources to design the test cases. For this reason, any approach that can be used to enhance or automate the current testing process is necessary. This thesis introduces an approach to transform the Unified Modeling Language (UML) behavioral state machines diagram into a graph database inside Neo4j, a graph database software. Moreover, a framework is proposed that fetches test data from the graph database. Based on the similarity between the state machine notation and the nodes and edges (with properties) in graph databases, a set ofrules for representation is presented in this thesis. Along with a framework based on GRANDstack (full-stack framework), the framework should use the pre-built graph database together with other technologies to generate test cases from the inserted requirements specification. A proof-of-concept is implemented to demonstrate the proposed framework. By using a dedicated schema, the fetched data is matched with the expected results. The results prove that the transformation method and the proposed framework have a good potential to be developed and evaluated with a realistic test from the industry practice. Keywords: requirement, test data, UML, state machine diagram, black-box testing, test case generation, Neo4j, GraphQL API
9
Black, Chelsea Lynn. "Resting-State Functional Brain Networks in Bipolar Spectrum Disorder: A Graph Theoretical Investigation." Diss., Temple University Libraries, 2016. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/393135.
Full textAbstract:
PsychologyPh.D.
Neurobiological theories of bipolar spectrum disorder (BSD) propose that the emotional dysregulation characteristic of BSD stems from disrupted prefrontal control over subcortical limbic structures (Strakowski et al., 2012; Depue & Iacono, 1989). However, existing neuroimaging research on functional connectivity between frontal and limbic brain regions remains inconclusive, and is unable to adequately characterize global functional network dynamics. Graph theoretical analysis provides a framework for understanding the local and global connections of the brain and comparing these connections between groups (Sporns et al., 2004). The purpose of this study was to investigate resting state functional connectivity in individuals at low and high risk for BSD based on moderate versus high reward sensitivity, both with and without a BSD diagnosis, using graph theoretical network analysis. Results demonstrated decreased connectivity in a cognitive control region (dorsolateral prefrontal cortex), but increased connectivity of a brain region involved in the detection and processing of reward (bilateral orbitofrontal cortex), among participants at high risk for BSD. Participants with BSD showed increased inter-module connectivity of the dorsal anterior cingulate cortex (ACC). Reward sensitivity was associated with decreased global and local efficiency, and interacted with BSD risk group status to predict inter-module connectivity. Findings are discussed in relation to neurobiological theories of BSD.
Temple University--Theses
10
Schäfer, Alexander. "Identifying Changes of Functional Brain Networks using Graph Theory." Doctoral thesis, Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-166041.
Full textAbstract:
This thesis gives an overview on how to estimate changes in functional brain networks using graph theoretical measures. It explains the assessment and definition of functional brain networks derived from fMRI data. More explicitly, this thesis provides examples and newly developed methods on the measurement and visualization of changes due to pathology, external electrical stimulation or ongoing internal thought processes. These changes can occur on long as well as on short time scales and might be a key to understanding brain pathologies and their development. Furthermore, this thesis describes new methods to investigate and visualize these changes on both time scales and provides a more complete picture of the brain as a dynamic and constantly changing network.
11
Lampka, Kai. "A symbolic approach to the state graph based analysis of high-level Markov reward models." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=985513926.
Full text
12
Thompson, Barrett Michael. "An analysis of the state space graph for integer permutation with application to local search." Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/25027.
Full text
13
Rossi, Magi Lorenzo. "Graph-based analysis of brain resting-state fMRI data in nocturnal frontal lobe epileptic patients." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8332/.
Full textAbstract:
Il lavoro che ho sviluppato presso l'unità di RM funzionale del Policlinico S.Orsola-Malpighi, DIBINEM, è incentrato sull'analisi dati di resting state - functional Magnetic Resonance Imaging (rs-fMRI) mediante l'utilizzo della graph theory, con lo scopo di valutare eventuali differenze in termini di connettività cerebrale funzionale tra un campione di pazienti affetti da Nocturnal Frontal Lobe Epilepsy (NFLE) ed uno di controlli sani.
L'epilessia frontale notturna è una peculiare forma di epilessia caratterizzata da crisi che si verificano quasi esclusivamente durante il sonno notturno. Queste sono contraddistinte da comportamenti motori, prevalentemente distonici, spesso complessi, e talora a semiologia bizzarra.
L'fMRI è una metodica di neuroimaging avanzata che permette di misurare indirettamente l'attività neuronale. Tutti i soggetti sono stati studiati in condizioni di resting-state, ossia di veglia rilassata.
In particolare mi sono occupato di analizzare i dati fMRI con un approccio innovativo in campo clinico-neurologico, rappresentato dalla graph theory. I grafi sono definiti come strutture matematiche costituite da nodi e links, che trovano applicazione in molti campi di studio per la modellizzazione di strutture di diverso tipo.
La costruzione di un grafo cerebrale per ogni partecipante allo studio ha rappresentato la parte centrale di questo lavoro. L'obiettivo è stato quello di definire le connessioni funzionali tra le diverse aree del cervello mediante l'utilizzo di un network. Il processo di modellizzazione ha permesso di valutare i grafi neurali mediante il calcolo di parametri topologici che ne caratterizzano struttura ed organizzazione.
Le misure calcolate in questa analisi preliminare non hanno evidenziato differenze nelle proprietà globali tra i grafi dei pazienti e quelli dei controlli. Alterazioni locali sono state invece riscontrate nei pazienti, rispetto ai controlli, in aree della sostanza grigia profonda, del sistema limbico e delle regioni frontali, le quali rientrano tra quelle ipotizzate essere coinvolte nella fisiopatologia di questa peculiare forma di epilessia.
14
FRANCH, Daniel Kudlowiez. "Dynamical system modeling with probabilistic finite state automata." Universidade Federal de Pernambuco, 2017. https://repositorio.ufpe.br/handle/123456789/25448.
Full textAbstract:
Submitted by Fernanda Rodrigues de Lima (fernanda.rlima@ufpe.br) on 2018-08-02T22:51:47Z
No. of bitstreams: 2
license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5)
DISSERTAÇÃO Daniel Kudlowiez Franch.pdf: 1140156 bytes, checksum: c02b1b4ca33f8165be5960ba5a212730 (MD5)Approved for entry into archive by Alice Araujo (alice.caraujo@ufpe.br) on 2018-08-07T21:11:31Z (GMT) No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Daniel Kudlowiez Franch.pdf: 1140156 bytes, checksum: c02b1b4ca33f8165be5960ba5a212730 (MD5)
Made available in DSpace on 2018-08-07T21:11:31Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Daniel Kudlowiez Franch.pdf: 1140156 bytes, checksum: c02b1b4ca33f8165be5960ba5a212730 (MD5) Previous issue date: 2017-03-10
FACEPE
Discrete dynamical systems are widely used in a variety of scientific and engineering applications, such as electrical circuits, machine learning, meteorology and neurobiology. Modeling these systems involves performing statistical analysis of the system output to estimate the parameters of a model so it can behave similarly to the original system. These models can be used for simulation, performance analysis, fault detection, among other applications. The current work presents two new algorithms to model discrete dynamical systems from two categories (synchronizable and non-synchronizable) using Probabilistic Finite State Automata (PFSA) by analyzing discrete symbolic sequences generated by the original system and applying statistical methods and inference, machine learning algorithms and graph minimization techniques to obtain compact, precise and efficient PFSA models. Their performance and time complexity are compared with other algorithms present in literature that aim to achieve the same goal by applying the algorithms to a series of common examples.
Sistemas dinâmicos discretos são amplamente usados em uma variedade de aplicações cientifícas e de engenharia, por exemplo, circuitos elétricos, aprendizado de máquina, meteorologia e neurobiologia. O modelamento destes sistemas envolve realizar uma análise estatística de sequências de saída do sistema para estimar parâmetros de um modelo para que este se comporte de maneira similar ao sistema original. Esses modelos podem ser usados para simulação, referência ou detecção de falhas. Este trabalho apresenta dois novos algoritmos para modelar sistemas dinâmicos discretos de duas categorias (sincronizáveis e não-sincronizáveis) por meio de Autômatos Finitos Probabilísticos (PFSA, Probabilistic Finite State Automata) analisando sequências geradas pelo sistema original e aplicando métodos estatísticos, algoritmos de aprendizado de máquina e técnicas de minimização de grafos para obter modelos PFSA compactos e eficientes. Sua performance e complexidade temporal são comparadas com algoritmos presentes na literatura que buscam atingir o mesmo objetivo aplicando os algoritmos a uma série de exemplos.
15
Soto, Manuel. "Unmanned aerial vehicle real-time guidance system via state space heuristic search." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2007. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
Full text
16
Balasubramanian, Suman. "On the Erdős-Sòs conjecture and the Cayley Isomorphism Problem." Diss., Mississippi State : Mississippi State University, 2009. http://library.msstate.edu/etd/show.asp?etd=etd-07102009-113145.
Full text
17
Bodily, Ty Alvin. "A Graph Theoretical Analysis of Functional Brain Networks Related to Memory and Healthy Aging." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7567.
Full textAbstract:
The cognitive decline associated with healthy aging begins in early adulthood and is important to understand as a precursor of and relative to mild cognitive impairment and Alzheimer disease. Anatomical atrophy, functional compensation, and network reorganization have been observed in populations of older adults. In the current study, we examine functional network correlates of memory performance on the Wechsler Memory Scale IV and the Mnemonic Discrimination Task (MST). We report a lack of association between global graph theory metrics and age or memory performance. In addition, we observed a positive association between lure discrimination scores from the MST and right hippocampus centrality. Upon further investigation, we confirmed that old subjects with poor memory performance had lower right hippocampus centrality scores than young subjects with high average memory performance. These novel results connect the role of the hippocampus in global brain network information flow to cognitive function and have implications for better characterizing and predicting memory decline in aging.
18
Shankar, Anita. "Resting-state Graph Theory Metrics Predict Processing Speed and Correlate with Disease Burden in Relapsing-Remitting Multiple Sclerosis." The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1618447775667055.
Full text
19
Vasudevan, Dilip Prasad. "Automatic test pattern generation for asynchronous circuits." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/7670.
Full textAbstract:
The testability of integrated circuits becomes worse with transistor dimensions reaching nanometer scales. Testing, the process of ensuring that circuits are fabricated without defects, becomes inevitably part of the design process; a technique called design for test (DFT). Asynchronous circuits have a number of desirable properties making them suitable for the challenges posed by modern technologies, but are severely limited by the unavailability of EDA tools for DFT and automatic test-pattern generation (ATPG). This thesis is motivated towards developing test generation methodologies for asynchronous circuits. In total four methods were developed which are aimed at two different fault models: stuck-at faults at the basic logic gate level and transistor-level faults. The methods were evaluated using a set of benchmark circuits and compared favorably to previously published work. First, ABALLAST is a partial-scan DFT method adapting the well-known BALLAST technique for asynchronous circuits where balanced structures are used to guide the selection of the state-holding elements that will be scanned. The test inputs are automatically provided by a novel test pattern generator, which uses time frame unrolling to deal with the remaining, non-scanned sequential C-elements. The second method, called AGLOB, uses algorithms from strongly-connected components in graph graph theory as a method for finding the optimal position of breaking the loops in the asynchronous circuit and adding scan registers. The corresponding ATPG method converts cyclic circuits into acyclic for which standard tools can provide test patterns. These patterns are then automatically converted for use in the original cyclic circuits. The third method, ASCP, employs a new cycle enumeration method to find the loops present in a circuit. Enumerated cycles are then processed using an efficient set covering heuristic to select the scan elements for the circuit to be tested.Applying these methods to the benchmark circuits shows an improvement in fault coverage compared to previous work, which, for some circuits, was substantial. As no single method consistently outperforms the others in all benchmarks, they are all valuable as a designer’s suite of tools for testing. Moreover, since they are all scan-based, they are compatible and thus can be simultaneously used in different parts of a larger circuit. In the final method, ATRANTE, the main motivation of developing ATPG is supplemented by transistor level test generation. It is developed for asynchronous circuits designed using a State Transition Graph (STG) as their specification. The transistor-level circuit faults are efficiently mapped onto faults that modify the original STG. For each potential STG fault, the ATPG tool provides a sequence of test vectors that expose the difference in behavior to the output ports. The fault coverage obtained was 52-72 % higher than the coverage obtained using the gate level tests. Overall, four different design for test (DFT) methods for automatic test pattern generation (ATPG) for asynchronous circuits at both gate and transistor level were introduced in this thesis. A circuit extraction method for representing the asynchronous circuits at a higher level of abstraction was also implemented. Developing new methods for the test generation of asynchronous circuits in this thesis facilitates the test generation for asynchronous designs using the CAD tools available for testing the synchronous designs. Lessons learned and the research questions raised due to this work will impact the future work to probe the possibilities of developing robust CAD tools for testing the future asynchronous designs.
20
Pitts, Christine Maria. "A Dynamic Network Study on How Consolidating State Governance Models Relates to Legislator Voting Patterns." Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23766.
Full textAbstract:
In 2011, Oregon was one of many states in the U.S. consolidating their education governance around an early learning, K-12, and postsecondary hub. This study uses legislator-voting data to investigate the relationship between this consolidated model and endogenous policy formulation processes. This study employs a separable temporal exponential random graph model (STERGM) to investigate how an education governance shift toward consolidated authority relates to bipartisan outcomes for education-related bills over time. Oregon legislator voting networks were analyzed for cohesion, centrality, and community detection measures, as well as by legislator attributes (e.g. gender, party, and title) to test the association they had on the likelihood of forming ties with other legislators. Finally, to study the relationship of bipartisanship with legislators’ likelihood to vote commonly, I added the legislators’ political party attributes within dyads to analyze the association that having different political parties had on legislators’ common votes. The results highlight evidence of legislator networks that were very dense at each time point included in the study, with a high likelihood of forming ties. However, when Oregon shifted to centralized education governance model their legislator networks became more distributed and cohesive when compared to other years included in the longitudinal study. It is possible that such a shift prompted collaboration among legislators resulting in mutuality that increased the likelihood for underrepresented groups of legislators (e.g. females and republicans) to vote commonly with their colleagues. Aligned with previous research, this study found that centralized governing bodies reinforced by political legislation provided collaborative initiatives for the legislative community. Attending to bipartisan voting patterns dynamically through a governance shift is a valuable investigation that will provide nuanced inferences about education governance and policymaking for states making similar consolidated governance shifts in the future.
21
Clad, François. "Disruption-free routing convergence : computing minimal link-state update sequences." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAD012/document.
Full textAbstract:
Avec le développement des applications temps-réel sur Internet, telles que la télévision, la voix sur IP et les jeux en ligne, les fournisseurs d'accès à Internet doivent faire face à des contraintes de plus en plus fortes quant aux performances de leurs services. Cependant, après chaque changement topologique, les protocoles de routage à état des liens, utilisés dans les réseaux de cœur de ces opérateurs, entrent dans une période de convergence durant laquelle des boucles de routage peuvent apparaître. Ce phénomène dégrade les performances du réseau (latence, congestions, pertes de paquets) et peut durer plusieurs secondes. Dans le cadre de cette thèse, nous proposons de nouvelles solutions permettant de prévenir ces perturbations dans le cas de reconfigurations sur un lien ou un routeur. Notre approche a pour particularité de ne reposer que sur les mécanismes de base des protocoles de routage à état des liens, et d’être ainsi déployable de manière incrémentale dans n’importe quel réseau. Intuitivement, il s’agit de contrôler implicitement l’ordre de mise à jour des routeurs, à travers une modification progressive du poids d’un sous-ensemble de liens. Par exemple, l’augmentation du poids d’un lien aura pour effet de forcer les routeurs les plus éloignés de ce composant à se mettre à jour avant les routeurs plus proches. En adaptant finement l’amplitude de tels changements, il est alors possible de répartir la mise à jour de routeurs potentiellement impliqués dans une boucle sur plusieurs étapes. Cette opération peut ensuite être répétée jusqu’à ce que le composant ne soit plus utilisé pour acheminer des données dans le réseau, permettant un retrait sans impact sur le routageThe use of real time media or mission critical applications over IP networks is making strong pressure on service providers to operate disruption free networks. However, after any topological change, link-state Interior Gateway Protocols (IGPs), such as IS-IS or OSPF, enter a convergence phase during which transient forwarding loops may occur. Such loops increase the network latency and cause packet losses for several seconds. In this thesis, we propose and evaluate innovative solutions to prevent these perturbations in case a planned modification on a link or a router. Our approach only relies on core functionalities of link-state routing protocols, thus being incrementally deployable in any network. Intuitively, it consists in implicitly controlling the routers update order through successive IGP weight reconfigurations on a subset of links. For example, progressively increasing the weight of a link forces farthest routers to update their routes first, before closest ones. Hence, finely tuning such changes may allow to spread the update of routers potentially implied in a loop across multiple steps. This operation can be repeated until the component to be removed is no longer used to forward traffic in the network, thus allowing its removal with no impact on the routing decisions
22
Hart, Michael Gavin. "Network approaches to understanding the functional effects of focal brain lesions." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274018.
Full textAbstract:
Complex network models of functional connectivity have emerged as a paradigm shift in brain mapping over the past decade. Despite significant attention within the neuroimaging and cognitive neuroscience communities, these approaches have hitherto not been extensively explored in neurosurgery. The aim of this thesis is to investigate how the field of connectomics can contribute to understanding the effects of focal brain lesions and to functional brain mapping in neurosurgery. This datasets for this thesis include a clinical population with focal brain tumours and a cohort focused on healthy adolescent brain development. Multiple network analyses of increasing complexity are performed based upon resting state functional MRI. In patients with focal brain tumours, the full complement of resting state networks were apparent, while also suggesting putative patterns of network plasticity. Connectome analysis was able to identify potential signatures of node robustness and connections at risk that could be used to individually plan surgery. Focal lesions induced the formation of new hubs while down regulating previously established hubs. Overall these data are consistent with a dynamic rather than a static response to the presence of focal lesions. Adolescent brain development demonstrated discrete dynamics with distinct gender specific and age-gender interactions. Network architecture also became more robust, particularly to random removal of nodes and edges. Overall these data provide evidence for the early vulnerability rather than enhanced plasticity of brain networks. In summary, this thesis presents a combined analysis of pathological and healthy development datasets focused on understanding the functional effects of focal brain lesions at a network level. The coda serves as an introduction to a forthcoming study, known as Connectomics and Electrical Stimulation for Augmenting Resection (CAESAR), which is an evolution of the results and methods herein.
23
García-García, Isabel, María Ángeles Jurado, Maite Garolera, Idoia Marqués-Iturria, Annette Horstmann, Bàrbara Segura, Roser Pueyo, et al. "Functional network centrality in obesity: a resting-state and task fMRI study." Psychiatry research (2015) 233, 3, S. 331-338, 2015. https://ul.qucosa.de/id/qucosa%3A14785.
Full textAbstract:
Obesity is associated with structural and functional alterations in brain areas that are often functionally distinct and anatomically distant. This suggests that obesity is associated with differences in functional connectivity of regions distributed across the brain. However, studies addressing whole brain functional connectivity in obesity remain scarce. Here, we compared voxel-wise degree centrality and eigenvector centrality between participants with obesity (n=20) and normal-weight controls (n=21). We analyzed resting state and task-related fMRI data acquired from the same individuals. Relative to normal-weight controls, participants with obesity exhibited reduced degree centrality in the right middle frontal gyrus in the resting-state condition. During the task fMRI condition, obese participants exhibited less degree centrality in the left middle frontal gyrus and the lateral occipital cortex along with reduced eigenvector centrality in the lateral occipital cortex and occipital pole. Our results highlight the central role of the middle frontal gyrus in the pathophysiology of obesity, a structure involved in several brain circuits signaling attention, executive functions and motor functions. Additionally, our analysis suggests the existence of task-dependent reduced centrality in occipital areas; regions with a role in perceptual processes and that are profoundly modulated by attention.
24
Lu, Qifeng. "Bivariate Best First Searches to Process Category Based Queries in a Graph for Trip Planning Applications in Transportation." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/26444.
Full textAbstract:
With the technological advancement in computer science, Geographic Information Science
(GIScience), and transportation, more and more complex path finding queries including category
based queries are proposed and studied across diverse disciplines. A category based query, such
as Optimal Sequenced Routing (OSR) queries and Trip Planning Queries (TPQ), asks for a
minimum-cost path that traverses a set of categories with or without a predefined order in a
graph. Due to the extensive computing time required to process these complex queries in a large scale environment, efficient algorithms are highly desirable whenever processing time is a
consideration. In Artificial Intelligence (AI), a best first search is an informed heuristic path
finding algorithm that uses domain knowledge as heuristics to expedite the search process.
Traditional best first searches are single-variate in terms of the number of variables to describe a state, and thus not appropriate to process these queries in a graph. In this dissertation, 1) two new types of category based queries, Category Sequence Traversal Query (CSTQ) and Optimal Sequence Traversal Query (OSTQ), are proposed; 2) the existing single-variate best first searches are extended to multivariate best first searches in terms of the state specified, and a class of new concepts--state graph, sub state graph, sub state graph space, local heuristic, local admissibility, local consistency, global heuristic, global admissibility, and global consistency--is
introduced into best first searches; 3) two bivariate best first search algorithms, C* and O*, are developed to process CSTQ and OSTQ in a graph, respectively; 4) for each of C* and O*,
theorems on optimality and optimal efficiency in a sub state graph space are developed and
identified; 5) a family of algorithms including C*-P, C-Dijkstra, O*-MST, O*-SCDMST, O*-
Dijkstra, and O*-Greedy is identified, and case studies are performed on path finding in
transportation networks, and/or fully connected graphs, either directed or undirected; and 6) O*-
SCDMST is adopted to efficiently retrieve optimal solutions for OSTQ using network distance
metric in a large transportation network.Ph. D.
25
Saksena, Mayank. "Verifying Absence of ∞ Loops in Parameterized Protocols." Doctoral thesis, Uppsala University, Department of Information Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8605.
Full textAbstract:
The complex behavior of computer systems offers many challenges for formal verification. The analysis quickly becomes difficult as the number of participating processes increases.
A parameterized system is a family of systems parameterized on a number n, typically representing the number of participating processes. The uniform verification problem — to check whether a property holds for each instance — is an infinite-state problem. The automated analysis of parameterized and infinite-state systems has been the subject of research over the last 15–20 years. Much of the work has focused on safety properties. Progress in verification of liveness properties has been slow, as it is more difficult in general.
In this thesis, we consider verification of parameterized and infinite-state systems, with an emphasis on liveness, in the verification framework called regular model checking (RMC). In RMC, states are represented as words, sets of states as regular expressions, and the transition relation as a regular relation.
We extend the automata-theoretic approach to RMC. We define a specification logic sufficiently strong to specify systems representable using RMC, and linear temporal logic properties of such systems, and provide an automatic translation from a specification into an analyzable model.
We develop acceleration techniques for RMC which allow more uniform and automatic verification than before, with greater power. Using these techniques, we succeed to verify safety and liveness properties of parameterized protocols from the literature.
We present a novel reachability based verification method for verification of liveness, in a general setting. We implement the method for RMC, with promising results.
Finally, we develop a framework for the verification of dynamic networks based on graph transformation, which generalizes the systems representable in RMC. In this framework we verify the latest version of the DYMO routing protocol, currently being considered for standardization by the IETF.
26
Kebdani, Mohamed. "Modélisation dynamique basée sur l'approche bond graph d'une boucle fluide diphasique à pompage mécanique avec validation expérimentale." Thesis, Ecole centrale de Lille, 2016. http://www.theses.fr/2016ECLI0009/document.
Full textAbstract:
Cette thèse s’inscrit dans le cadre du projet FUI THERMOFLUIDE-RT impliquant des Grands Groupes (Zodiac DS, Safran Hispano, MBDA), des PME (Atmostat, ADR, ControlSys) et cinq laboratoires (CRIStAL, LML Arts et Métiers Paris Tech, LEGI Grenoble, LMT ENS Cachan, CEA-Liten Grenoble). Le but est d’étudier un nouveau système de refroidissement de l’électronique. La technologie retenue est celle d’une boucle fluide diphasique à pompage mécanique (BFDPM). La thèse traite la modélisation dynamique et la validation expérimentale des composants de la boucle. Ceci permet de prévoir l’efficacité du système à partir de ses paramètres d’entrée, d’analyser les problèmes de régimes transitoires, et de proposer un outil de dimensionnement. La méthodologie bond graph est retenue à cause du caractère multi-physique des composants. D’abord, la problématique de base et le contexte sont présentés. Ceci permet d’introduire la solution retenue, celle des BFDPM. Les objectifs de la thèse sont décrits. Ensuite, une description du banc expérimental développé au cours de cette thèse est proposée. Les trois chapitres suivant sont consacrés à l’étude théorique et expérimentale des équipements de la boucle. Chacun de ces chapitres commence par l’état de l’art sur les travaux de modélisation et les corrélations des coefficients d’échange et des pertes de charge. Une seconde partie décrit les phénomènes et les équations. Une troisième partie est réservée à la validation des modèles. Un dernier chapitre récapitule les travaux de couplage des modèles dynamiques validés séparément. En conclusion, un récapitulatif des contributions est effectué. Des perspectives à court et moyen terme sont proposéesThis thesis is part of the collaborative project FUI THERMOFLUIDE-RT involving major groups (Zodiac DS, Safran Hispano, and MBDA), SMEs (Atmostat Alcen, ADR, AER, ControlSys) and five laboratories (CRIStAL Ecole Centrale de Lille, LML Arts et Métiers Paris Tech, LEGI Grenoble, LMT ENS Cachan, CEA-Liten Grenoble). The main purpose is to study a new electronic cooling system. The technology chosen consists of a two-phase fluid loop mechanically pumped (TPLMP). The thesis deals with the dynamic modeling and experimental validation of the cooling components. The developed dynamic model allows to predict the efficiency of the cooling loop, to conduct the study of transitional regimes, and provides an original tool dedicated to design the loop components. The bond graph methodology is adopted because of the multi physics character of the studied components. First, the basic issues and the industrial context are presented. This allows to introduce the chosen solution (TPLMP). The objectives of the thesis are described. Then, a description of the rig test is proposed. The following three chapters are devoted to a theoretical and experimental study of the loop equipment. Each chapter begins with a state of the art on modeling and correlations of the heat exchange coefficients and losses. A second part of the chapter describes phenomena and equations. A third part is dedicated to the experimental validation. A final chapter presents the coupling works of dynamic models validated separately. Finally, a summary of all contributions is made. Prospects for future developments in short and medium term are proposed
27
Ambrazas, Nerijus. "Pasiekiamų būsenų grafo sudarymo sudėtingumo tyrimas." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2008. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2008~D_20080811_154652-52373.
Full textAbstract:
Darbe nagrinėjamas realiojo laiko sistemų, specifikuotų agregatiniu metodu, verifikavimo uždavinys. Sprendžiant šį uždavinį, naudojama pasiekiamų būsenų grafo sudarymo metodika, leidžianti įvertinti laiko intervalus, kuriais įvyksta sistemoje apibrėžti įvykiai. Darbe nagrinėjami pasiekiamų būsenų grafo sudarymo algoritmai ir pateikta prototipinėse programose naudojama duomenų struktūra. Suformuluoti ir įrodyti teiginiai apie pasiekiamų būsenų grafo sudarymo algoritmo sudėtingumą (maksimalaus vienos būsenos galimų perėjimų skaičiaus; grafo viršūnių skaičiaus augimo priklausomybės nuo įvykių skaičiaus; maksimalaus įvykių skaičiaus elgsenoje laiko intervale; maksimalaus viršūnių skaičiaus laiko intervale.) Pateikta trijų testinių sistemų grafų automatizuoto sudarymo analizė. Parodyta, kad Simplekso optimizavimo procedūra laiko momentų palyginimui gali būti naudojama tik atskirais atvejais.The work deals with a verification task of real time system specified by aggregate method. While solving the task, a technique for creation a reachable state graph is used. The technique permits to evaluate intervals of time when the defined system events occur. Reachable state graph creation algorithms are analysed in the work. A data structure used in prototype software is presented in the work too. Assertions about a complexity of algorithm for reachable state graph creation are formulated and proved. These assertions concern maximum number of transitions from single state, dependency of number of graph verteles growth on a number of events, maximum number of events in a behaviour during time interval, and maximum number of vertexes during time interval. Analysis of automated creation of graphs for three test systems is presented. It is shown that Simplex optimisation procedure for comparison of time intervals can be used only in certain cases.
28
Aronsson, Peter. "Automatic Parallelization of Simulation Code from Equation Based Simulation Languages." Licentiate thesis, Linköping University, Linköping University, PELAB - Programming Environment Laboratory, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5720.
Full textAbstract:
Modern state-of-the-art equation based object oriented modeling languages such as Modelica have enabled easy modeling of large and complex physical systems. When such complex models are to be simulated, simulation tools typically perform a number of optimizations on the underlying set of equations in the modeled system, with the goal of gaining better simulation performance by decreasing the equation system size and complexity. The tools then typically generate efficient code to obtain fast execution of the simulations. However, with increasing complexity of modeled systems the number of equations and variables are increasing. Therefore, to be able to simulate these large complex systems in an efficient way parallel computing can be exploited.
This thesis presents the work of building an automatic parallelization tool that produces an efficient parallel version of the simulation code by building a data dependency graph (task graph) from the simulation code and applying efficient scheduling and clustering algorithms on the task graph. Various scheduling and clustering algorithms, adapted for the requirements from this type of simulation code, have been implemented and evaluated. The scheduling and clustering algorithms presented and evaluated can also be used for functional dataflow languages in general, since the algorithms work on a task graph with dataflow edges between nodes.
Results are given in form of speedup measurements and task graph statistics produced by the tool. The conclusion drawn is that some of the algorithms investigated and adapted in this work give reasonable measured speedup results for some specific Modelica models, e.g. a model of a thermofluid pipe gave a speedup of about 2.5 on 8 processors in a PC-cluster. However, future work lies in finding a good algorithm that works well in general.
Report code: LiU-Tek-Lic-2002:06.
29
Otčeskich, Olga. "Paskirstytųjų sistemų agregatinių specifikacijų validavimas analizuojant būsenų pasiekiamumą." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2005. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2005~D_20050517_183614-75526.
Full textAbstract:
The problem of analyzing concurrent systems has been investigated by many researchers, and several solutions have been proposed. Among the proposed techniques, reachability analysis—systematic enumeration of reachable states in a finite-state model—is attractive because it is conceptually simple and relatively straightforward to automate and can be used in conjunction with model-checking procedures to check for application-specific as well as general properties. The system validation problem considered here is the problem of verifying that the original specification is itself logically consistent. If, for instance, the specification has a design error, an implementation is expected to pass a conformance test if it contains the same error. A validation for the logical consistency of the system, however, must reveal the design error. An automated analysis of all reachable states in a distributed system can be used to trace obscure logical errors that would be very hard to find manually. This type of validation is traditionally performed by the symbolic execution of a finite state machine model of the system studied. The author presents an overview of the existing validation techniques and methods. Specified and analyzed systems are presented as reachable state graph. The implementation of the aggregate specifications validation system is also presented.
30
Atchuthan, Dinesh. "Towards new sensing capabilities for legged locomotion using real-time state estimation with low-cost IMUs." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30316/document.
Full textAbstract:
L'estimation en robotique est un sujet important affecté par les compromis entre certains critères majeurs parmi lesquels nous pouvons citer le temps de calcul et la précision. L'importance de ces deux critères dépend de l'application. Si le temps de calcul n'est pas important pour les méthodes hors ligne, il devient critique lorsque l'application doit s'exécuter en temps réel. De même, les exigences de précision dépendent des applications. Les estimateurs EKF sont largement utilisés pour satisfaire les contraintes en temps réel tout en obtenant une estimation avec des précisions acceptables. Les centrales inertielles (Inertial Measurement Unit - IMU) demeurent des capteurs répandus dnas les problèmes d'estimation de trajectoire. Ces capteurs ont par ailleurs la particularité de fournir des données à une fréquence élevée. La principale contribution de cette thèses est une présentation claire de la méthode de préintégration donnant lieu à une meilleure utilisation des centrales inertielles. Nous appliquons cette méthode aux problèmes d'estimation dans les cas de la navigation piétonne et celle des robots humanoïdes. Nous souhaitons par ailleurs montrer que l'estimation en temps réel à l'aide d'une centrale inertielle à faible coût est possible avec des méthodes d'optimisation tout en formulant les problèmes à l'aide d'un modèle graphique bien que ces méthodes soient réputées pour leurs coûts élevés en terme de calculs. Nous étudions également la calibration des centrales inertielles, une étape qui demeure critique pour leurs utilisations. Les travaux réalisés au cours de cette thèse ont été pensés en gardant comme perspective à moyen terme le SLAM visuel-inertiel. De plus, ce travail aborde une autre question concernant les robots à jambes. Contrairement à leur architecture habituelle, pourrions-nous utiliser plusieurs centrales inertielles à faible coût sur le robot pour obtenir des informations précieuses sur le mouvement en cours d'exécution ?Estimation in robotics is an important subject affected by trade-offs between some major critera from which we can cite the computation time and the accuracy. The importance of these two criteria are application-dependent. If the computation time is not important for off-line methods, it becomes critical when the application has to run on real-time. Similarly, accuracy requirements are dependant on the applications. EKF estimators are widely used to satisfy real-time constraints while achieving acceptable accuracies. One sensor widely used in trajectory estimation problems remains the inertial measurement units (IMUs) providing data at a high rate. The main contribution of this thesis is a clear presentation of the preintegration theory yielding in a better use IMUs. We apply this method for estimation problems in both pedestrian and humanoid robots navigation to show that real-time estimation using a low- cost IMU is possible with smoothing methods while formulating the problems with a factor graph. We also investigate the calibration of the IMUs as it is a critical part of those sensors. All the development made during this thesis was thought with a visual-inertial SLAM background as a mid-term perspective. Firthermore, this work tries to rise another question when it comes to legged robots. In opposition to their usual architecture, could we use multiple low- cost IMUs on the robot to get valuable information about the motion being executed?
31
Решетицький, Олександр Вікторович. "Інтегрована система відображення стану мережевої інфраструктури в режимі реального часу." Master's thesis, КПІ ім. Ігоря Сікорського, 2019. https://ela.kpi.ua/handle/123456789/32398.
Full textAbstract:
Об’єктом дослідження є складна мережева інфраструктура.
Метою даної магістерської дисертації є розробка програмної системи відображення
стану мережевої інфраструктури.
Система використовує мову програмування Go для серверної частини, графову базу даних ArangoDB для збереження графу стану мережі, чергу повідомлень RabbitMQ для комунікації між сервісами-стрімерами та сервісом nvt-composer, реляційну базу даних PostgreSQL для збереження конфігурації, мову TypeScript для клієнтської частини та протокол WebSocket для забезпечення взаємодії між клієнтом та сервером в режимі реального часу.
Розроблена система використовує гнучку модель конфігурації для відображення елементів графу та надає можливість легкої інтеграції з існуючими системами моніторингу мереж.Object of the research is a complex network infrastructure. Purpose of master's thesis is to develop software system for displaying state of network infrastructure. System uses Go as server-side programming language, graph database ArangoDB for storing network state graph, message queue RabbitMQ for communication between streaming services and nvt-composer service, relational database PostgreSQL for storing configuration, TypeScript as client-side programming language and WebSocket protocol to provide real-time client-server interaction. Developed system uses flexible configuration model for displaying graph elements and provides ease of integration with existing network monitoring systems.
32
Wibling, Oskar. "Creating Correct Network Protocols." Doctoral thesis, Uppsala universitet, Avdelningen för datorteknik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9361.
Full textAbstract:
Network protocol construction is a complex and error prone task. The challenges originate both from the inherent complexity of developing correct program code and from the distributed nature of networked systems. Protocol errors can have devastating consequences. Even so, methods for ensuring protocol correctness are currently only used to a limited extent. A central reason for this is that they are often complex and expensive to employ. In this thesis, we develop methods to perform network protocol testing and verification, with the goal to make the techniques more accessible and readily adoptable. We examine how to formulate correctness requirements for ad hoc routing protocols used to set up forwarding paths in wireless networks. Model checking is a way to verify such requirements automatically. We investigate scalability of finite-state model checking, in terms of network size and topological complexity, and devise a manual abstraction technique to improve scalability. A methodology combining simulations, emulations, and real world experiments is developed for analyzing the performance of wireless protocol implementations. The technique is applied in a comparison of the ad hoc routing protocols AODV, DSR, and OLSR. Discrepancies between simulations and real world behavior are identified; these are due to absence of realistic radio propagation and mobility models in simulation. The issues are mainly related to how the protocols sense their network surroundings and we identify improvements to these capabilities. Finally, we develop a methodology and a tool for automatic verification of safety properties of infinite-state network protocols, modeled as graph transformation systems extended with negative application conditions. The verification uses symbolic backward reachability analysis. By introducing abstractions in the form of summary nodes, the method is extended to protocols with recursive data structures. Our tool automatically verifies correct routing of the DYMO ad hoc routing protocol and several nontrivial heap manipulating programs.
33
Krivoūsas, Tomas. "Verifikavimo algoritmų panaudojimas analizuojant formalių PLA specifikacijų teisingumą." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2008. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2008~D_20080811_151721-05181.
Full textAbstract:
Formalios specifikacijos – tai matematinis programinės ar techninės įrangos aprašymas, kurį galima naudoti sistemos realizacijai. Formalių specifikacijų naudojimas dar negarantuoja specifikacijos teisingumo. Tam naudojami formalaus verifikavimo metodai. Šiame dokumente aptariami formalių specifikacijų validavimo metodai. Du populiaraiausi formalių specifikacijų validavimo metodai yra pasiekiamų būsenų grafo analizė bei invarianto tikrinimas. Pasiekiamų būsenų grafo analizę sudaro pasiekiamų būsenų grafo generavimas ir analizė. Grafo analizės metu ieškoma aklaviečių, uždarų ciklų, nepasiekiamų būsenų, atliekamas būsenų koordinačių apribojimų tikrinimas bei invarianto tikrinimas. Tradiciniai pasiekiamų būsenų grafo sudarymo algoritmai grafo sudarymui naudoja sistemos būsenų eilę. Kiekviena išanalizuota būsena įrašoma į pasiekiamų būsenų grafą. Dokumente aptariamas lygiagretaus programavimo naudojimas būsenų grafo generavimui, kuris analizuoja ir generuoja sistemos būsenas naudodamas lygiagrečias gijas. Eksperimentų su vienkanale aptarnavimo sistema metu nustatyta, kad lygiagretaus algoritmo naudojimas šio uždavinio metu leidžia pagerinti sistemos veikimą iki 35%, priklausomai nuo būsenų skaičiaus.Arguably the most important task in creation of software is user requirement specification. Accurate requirement specification allows avoidance of errors in late stages of software development. This is extremely important in critical systems, where even vague error can cause great financial losses or even human victims. One of the methods used for precise user requirement specification is use of formal specifications. Formal specification is a mathematical method for describing of software or hardware, which might be suitable for system realization. Nevertheless, the construction of formal specifications does not guarantee the correctness of specification. For this reason formal specification validation is necessary. In this paper methods of formal specification validation are discussed. Two most popular methods of formal specification validation are reachable state graph analysis and invariant checking. Reachable state graph analysis consists of graph generation and graph analysis. Graphs can be analyzed for dead-ends, closed loops, state reach ability checking, coordinate restriction checking or invariant checking. Traditional reachable graph generation algorithm uses unanalyzed states queue to produce reachable state graph. Each step single state is analyzed and depending on results new vertex or edge is added to state graph. An improvement to the algorithm to consider is usage of parallel programming to process multiple states simultaneously. This allows increasing the... [to full text]
34
Karlaftis, Vasileios Misak. "Structural and functional brain plasticity for statistical learning." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/278790.
Full textAbstract:
Extracting structure from initially incomprehensible streams of events is fundamental to a range of human abilities: from navigating in a new environment to learning a language. These skills rely on our ability to extract spatial and temporal regularities, often with minimal explicit feedback, that is known as statistical learning. Despite the importance of statistical learning for making perceptual decisions, we know surprisingly little about the brain circuits and how they change when learning temporal regularities. In my thesis, I combine behavioural measurements, Diffusion Tensor Imaging (DTI) and resting-state fMRI (rs-fMRI) to investigate the structural and functional circuits that are involved in statistical learning of temporal structures. In particular, I compare structural connectivity as measured by DTI and functional connectivity as measured by rs-fMRI before vs. after training to investigate learning-dependent changes in human brain pathways. Further, I combine the two imaging modalities using graph theory and regression analyses to identify key predictors of individual learning performance. Using a prediction task in the context of sequence learning without explicit feedback, I demonstrate that individuals adapt to the environment’s statistics as they change over time from simple repetition to probabilistic combinations. Importantly, I show that learning of temporal structures relates to decision strategy that varies among individuals between two prototypical distributions: matching the exact sequence statistics or selecting the most probable outcome in a given context (i.e. maximising). Further, combining DTI and rs-fMRI, I show that learning-dependent plasticity in dissociable cortico-striatal circuits relates to decision strategy. In particular, matching relates to connectivity between visual cortex, hippocampus and caudate, while maximisation relates to connectivity between frontal and motor cortices and striatum. These findings have potential translational applications, as alternate brain routes may be re-trained to support learning ability when specific pathways (e.g. memory-related circuits) are compromised by age or disease.
35
Маслова, Зоя Іванівна, Зоя Ивановна Маслова, Zoia Ivanivna Maslova, Тетяна Володимирівна Лаврик, Татьяна Владимировна Лаврик, and Tetiana Volodymyrivna Lavryk. "Software implementation of calculating the value of a logical expression in compilers." Thesis, Sumy State University, 2016. http://essuir.sumdu.edu.ua/handle/123456789/46996.
Full textAbstract:
This paper describes an algorithm to optimize a process of determining the value of a logical expression. This algorithm is based on the principles of the algebra of logic, graphs and automata theory. Fast calculation of a logical expression is achieved by a reduction in the number of operations. The program is a multi-functional simulator.
36
Angus, Simon Douglas Economics Australian School of Business UNSW. "Economic networks: communication, cooperation & complexity." Awarded by:University of New South Wales. Economics, 2007. http://handle.unsw.edu.au/1959.4/27005.
Full textAbstract:
This thesis is concerned with the analysis of economic network formation. There are three novel sections to this thesis (Chapters 5, 6 and 8). In the first, the non-cooperative communication network formation model of Bala and Goyal (2000) (BG) is re-assessed under conditions of no inertia. It is found that the Strict Nash circle (or wheel) structure is still the equilibrium outcome for n = 3 under no inertia. However, a counter-example for n = 4 shows that with no inertia infinite cycles are possible, and hence the system does not converge. In fact, cycles are found to quickly dominate outcomes for n > 4 and further numerical simulations of conditions approximating no inertia (probability of updating > 0.8 to 1) indicate that cycles account for a dramatic slowing of convergence times. These results, together with the experimental evidence of Falk and Kosfeld (2003) (FK) motivate the second contribution of this thesis. A novel artificial agent model is constructed that allows for a vast strategy space (including the Best Response) and permits agents to learn from each other as was indicated by the FK results. After calibration, this model replicates many of the FK experimental results and finds that an externality exploiting ratio of benefits and costs (rather than the difference) combined with a simple altruism score is a good proxy for the human objective function. Furthermore, the inequity aversion results of FK are found to arise as an emergent property of the system. The third novel section of this thesis turns to the nature of network formation in a trust-based context. A modified Iterated Prisoners' Dilemma (IPD) model is developed which enables agents to play an additional and costly network forming action. Initially, canonical analytical results are obtained despite this modification under uniform (non-local) interactions. However, as agent network decisions are 'turned on' persistent cooperation is observed. Furthermore, in contrast to the vast majority of non-local, or static network models in the literature, it is found that a-periodic, complex dynamics result for the system in the long-run. Subsequent analysis of this regime indicates that the network dynamics have fingerprints of self-organized criticality (SOC). Whilst evidence for SOC is found in many physical systems, such dynamics have been seldom, if ever, reported in the strategic interaction literature.
37
Termenon, Conde Maite. "Analyse par graphes de la connectivité fonctionnelle de repos par IRM : vers de nouveaux biomarqueurs de la récupération fonctionnelle dans l'AVC." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAS023/document.
Full text
38
Nielsen, Jerel Bendt. "Robust Visual-Inertial Navigation and Control of Fixed-Wing and Multirotor Aircraft." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7584.
Full textAbstract:
With the increased performance and reduced cost of cameras, the robotics community has taken great interest in estimation and control algorithms that fuse camera data with other sensor data.In response to this interest, this dissertation investigates the algorithms needed for robust guidance, navigation, and control of fixed-wing and multirotor aircraft applied to target estimation and circumnavigation.This work begins with the development of a method to estimate target position relative to static landmarks, deriving and using a state-of-the-art EKF that estimates static landmarks in its state.Following this estimator, improvements are made to a nonlinear observer solving part of the SLAM problem.These improvements include a moving origin process to keep the coordinate origin within the camera field of view and a sliding window iteration algorithm to drastically improve convergence speed of the observer.Next, observers to directly estimate relative target position are created with a circumnavigation guidance law for a multirotor aircraft.Taking a look at fixed-wing aircraft, a state-dependent LQR controller with inputs based on vector fields is developed, in addition to an EKF derived from error state and Lie group theory to estimate aircraft state and inertial wind velocity.The robustness of this controller/estimator combination is demonstrated through Monte Carlo simulations.Next, the accuracy, robustness, and consistency of a state-of-the-art EKF are improved for multirotors by augmenting the filter with a drag coefficient, partial updates, and keyframe resets.Monte Carlo simulations demonstrate the improved accuracy and consistency of the augmented filter.Lastly, a visual-inertial EKF using image coordinates is derived, as well as an offline calibration tool to estimate the transforms needed for accurate, visual-inertial estimation algorithms.The imaged-based EKF and calibrator are also shown to be robust under various conditions through numerical simulation.
39
Malagurski, Brigitta. "Signatures neurales de l'abolition et de la récupération de conscience à partir du coma." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30039/document.
Full textAbstract:
Les objectifs de cette thèse étaient de caractériser les corrélats neuronaux fonctionnels et structurels de l'abolition de la conscience observés pendant le coma et d'identifier les signatures neuronales précoces de la récupération neurologique à partir de cet état. Pour atteindre ce but, nous avons étudié des patients cérébrolésés, recrutés au stade aigu du coma, à l'aide de l'IRM fonctionnelle au repos et IRM structurale. Nos résultats indiquent une réorganisation topologique globale du cerveau des patients, reflétée par une dédifférenciation et une réduction de la résilience des réseaux fonctionnels au repos d'ordre élevé. Ces anomalies sont accompagnées d'une perte de connexions fronto-pariétales à longue distance. Au niveau régional, nous avons observé un schéma complexe de diminution et d'augmentation de la densité de connexion fonctionnelle entre le cortex postéromédial et le cortex préfrontal médial : régions précédemment décrites pour avoir un rôle critique dans la conscience. De manière intéressante, ces modifications de densité de connexion étaient significativement liées à la récupération des patients trois mois après le coma. Enfin, l'analyse multimodale a permis de démontrer une association significative entre la connectivité fonctionnelle et l'intégrité structurelle cérébrales antéro-postérieure, fournissant des informations importantes sur le lien structure/fonction au décours de ces troubles acquis de la conscienceThe aim of the present thesis was to characterize the functional and structural neural correlates of acute consciousness abolition induced by severe brain injury and identify early neural signatures of long-term neurological recovery. To do so, we studied brain-injured patients, recruited in the acute stage of coma, using resting-state functional and structural MRI. Our findings indicated a global topological brain reorganization in coma patients, reflected in dedifferentiated and less resilient high-order resting-state functional networks, paralleled with a loss of long-range fronto-parietal connections. On a regional level, we found a complex pattern of voxel-wise decrease and increase in functional connection density between the posteromedial cortex and the medial prefrontal cortex, regions previously described to have a critical role in conscious processing. These connection density patterns seemed to permit outcome prediction in patients, assessed three months post-coma. Furthermore, the multi-modal MRI analysis demonstrated a significant association between antero-posterior functional connectivity and structural integrity, providing further insights into the pathological underpinning of conscious processing
40
Self, Joel P. "On-the-Fly Dynamic Dead Variable Analysis." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/886.
Full textAbstract:
State explosion in model checking continues to be the primary obstacle to widespread use of software model checking. The large input ranges of variables used in software is the main cause of state explosion. As software grows in size and complexity the problem only becomes worse. As such, model checking research into data abstraction as a way of mitigating state explosion has become more and more important. Data abstractions aim to reduce the effect of large input ranges. This work focuses on a static program analysis technique called dead variable analysis. The goal of dead variable analysis is to discover variable assignments that are not used. When applied to model checking, this allows us to ignore the entire input range of dead variables and thus reduce the size of the explored state space. Prior research into dead variable analysis for model checking does not make full use of dynamic run-time information that is present during model checking. We present an algorithm for intraprocedural dead variable analysis that uses dynamic run-time information to find more dead variables on-the-fly and further reduce the size of the explored state space. We introduce a definition for the maximal state space reduction possible through an on-the-fly dead variable analysis and then show that our algorithm produces a maximal reduction in the absence of non-determinism.
41
YAMIN, MUHAMMAD ABUBAKAR. "Investigating Brain Functional Networks in a Riemannian Framework." Doctoral thesis, Università degli studi di Genova, 2021. http://hdl.handle.net/11567/1040663.
Full textAbstract:
The brain is a complex system of several interconnected components which can be categorized at different Spatio-temporal levels, evaluate the physical connections and the corresponding functionalities. To study brain connectivity at the macroscale, Magnetic Resonance Imaging (MRI) technique in all the different modalities has been exemplified to be an important tool. In particular, functional MRI (fMRI) enables to record the brain activity either at rest or in different conditions of cognitive task and assist in mapping the functional connectivity of the brain.
The information of brain functional connectivity extracted from fMRI images can be defined using a graph representation, i.e. a mathematical object consisting of nodes, the brain regions, and edges, the link between regions. With this representation, novel insights have emerged about understanding brain connectivity and providing evidence that the brain networks are not randomly linked. Indeed, the brain network represents a small-world structure, with several different properties of segregation and integration that are accountable for specific functions and mental conditions. Moreover, network analysis enables to recognize and analyze patterns of brain functional connectivity characterizing a group of subjects.
In recent decades, many developments have been made to understand the functioning of the human brain and many issues, related to the biological and the methodological perspective, are still need to be addressed. For example, sub-modular brain organization is still under debate, since it is necessary to understand how the brain is functionally organized. At the same time a comprehensive organization of functional connectivity is mostly unknown and also the dynamical reorganization of functional connectivity is appearing as a new frontier for analyzing brain dynamics. Moreover, the recognition of functional connectivity patterns in patients affected by mental disorders is still a challenging task, making plausible the development of new tools to solve them.
Indeed, in this dissertation, we proposed novel methodological approaches to answer some of these biological and neuroscientific questions. We have investigated methods for analyzing and detecting heritability in twin's task-induced functional connectivity profiles. in this approach we are proposing a geodesic metric-based method for the estimation of similarity between functional connectivity, taking into account the manifold related properties of symmetric and positive definite matrices.
Moreover, we also proposed a computational framework for classification and discrimination of brain connectivity graphs between healthy and pathological subjects affected by mental disorder, using geodesic metric-based clustering of brain graphs on manifold space. Within the same framework, we also propose an approach based on the dictionary learning method to encode the high dimensional connectivity data into a vectorial representation which is useful for classification and determining regions of brain graphs responsible for this segregation. We also propose an effective way to analyze the dynamical functional connectivity, building a similarity representation of fMRI dynamic functional connectivity states, exploiting modular properties of graph laplacians, geodesic clustering, and manifold learning.
42
Gonzalez, Vieyra Joel Abraham. "Estimation et Contrôle des Systèmes Dynamiques à Entrées Inconnues et Energies Renouvelables." Thesis, Ecole centrale de Lille, 2019. http://www.theses.fr/2019ECLI0012/document.
Full textAbstract:
De nos jours, les processus industriels se doivent d’être efficaces, en particulier au niveau de leur production et/ou consommation énergétique.Ce travail vise à améliorer l’efficacité des processus en analysant l’influence des perturbations sur leur comportement, de la phase de conception à la synthèse des contrôleurs/observateurs, ceci dans une approche intégrée.Le problème du Rejet de Perturbation est introduit ainsi que différents types de contrôles permettant d’atténuer et/ou rejeter ces perturbations. Le système de Barre de Torsion est présenté. Une loi de commande basée sur le concept d’état dérivé est présentée et ensuite validée avec comme application le rejet de perturbation. Il est nécessaire d’estimer les grandeurs physiques utilisées dans les différentes expressions de loi de commande. Un observateur à entrées inconnues basé sur la représentation bond graph est rappelé et ensuite étendu au cas multi-variable. C’est la première contribution théorique de ce travail de recherche.Nous comparons ensuite l’efficacité de différentes techniques de commandes pour le rejet de perturbation par simulation sur le système barre de torsion et analysons ainsi l’efficacité de la technique proposée. Une extension théorique au problème du découplage entrée-sortie nous permet de généraliser le problème du rejet de perturbation dans une même démarche intégrée d’analyse et de synthèse. Enfin, ces techniques sont exploitées et analysées sur le système réel. Nous validons ainsi expérimentalement nos résultats.Un modèle très simplifié de centrale hydroélectrique est développé afin d’appliquer les résultats de nos travaux. Un modèle bond graph simplifié est validé par simulationNowadays, industrial processes must be efficient, particularly at the production level and/or energy consumption.This research work aims at improving the process efficiency by analysing the influences of disturbances on their behaviour, from the conception phase to the synthesis of controller/observer, in an integrated approach.The disturbance rejection problem is first introduced as well as different control laws allowing attenuate/reject these disturbances. A control law based on the concept of derivative state variable is presented and validated while applied as disturbance rejection.In order to reject the disturbance, different physical variables must be estimated, such as state variables, derivative state variables as disturbance variables. An unknown input observer based on the bond graph representation is recalled and extended in the multivariable case. It is the first theoretical contribution of this work.We thus compare the efficiency of different so-called «modern control laws» for the disturbance rejection problems by simulation with the Torsion-Bar system example. We analyse the efficiency of our approach. One extension to the Input-Output decoupling problem allows us to extend the disturbance rejection problem to other control law type in an integrated approach. At least, these techniques are applied on the real Torsion-Bar system and compared. We validate our approach.Since this work aims at analysing and developing efficient control laws for industrial processes, a simplified model of a hydroelectric plant is developed, in order to apply our results. A simplified bond graph model is validated with simulations
43
Faivre, Anthony. "Etude de la réorganisation de la connectivité cérébrale au repos dans la sclérose en plaques." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM5022/document.
Full textAbstract:
L'IRMf de repos qui repose sur l'étude des fluctuations du signal BOLD chez un sujet au repos, pourrait permettre d'explorer les mécanismes du handicap dans la Sclérose En Plaques (SEP). En utilisant l'IRMf de repos, ce travail a eu pour objectif de caractériser la réorganisation fonctionnelle des patients atteints de SEP et ses liens avec leur handicap.Nous avons d'abord réalisé une étude combinant IRMf de repos et d'activation au stade précoce de la SEP et montré l'existence d'une corrélation entre la plasticité fonctionnelle du système moteur des patients au repos et durant la tâche. Nous avons ensuite montré l'existence d'une augmentation diffuse du niveau de connectivité fonctionnelle des patients présentant une SEP débutante, corrélée à leurs performances. Dans la 3ème partie, nous avons objectivé l'existence d'un déclin dynamique de la topologie fonctionnelle corrélée à la progression du handicap grâce à une étude longitudinale utilisant la théorie des graphes. Enfin, nous avons démontré que le gain fonctionnel obtenu par la rééducation chez les patients SEP était corrélé à une augmentation de connectivité fonctionnelle du réseau cérébral par défaut et central exécutif et de densité de substance grise dans le cortex frontal.Nos travaux montrent l'existence d'une réorganisation cérébrale fonctionnelle complexe et dynamique dans la SEP qui pourrait correspondre à des phénomènes compensatoires, dont le déclin avec l'évolution de la maladie participe à la progression du handicap. Ils démontrent l'intérêt de l'IRMf de repos pour la compréhension des substrats anatomo-fonctionnels du handicap dans la SEP et comme potentiel instrument futur d'évaluation thérapeutiqueResting-state fMRI (rs-fMRI) may provide important clue concerning disability in multiple sclerosis (MS) by exploring the spontaneous BOLD fluctuations at rest in the whole brain. The aim of this work is to depict the functional reorganization of resting-state networks in MS patients and to assess its potential relationships with disability.In the first part, we performed an fMRI protocol combining a rs-fMRI and task-associated fMRI during a motor task, in a group of early MS patients. This study evidenced a direct association between reorganization of connectivity at rest and during activation in the motor system of patients. In the second rs-fMRI study, we evidenced an increased of the global level of connectivity in most of the rs-networks, strongly associated with the level of disability of patients. In the third part, we evidenced in a 2-year longitudinal study using graph theoretical approach that MS patients exhibited a dynamical alteration of functional brain topology that significantly correlated with disability progression. In the last part, we evidenced that the transient clinical improvement following physical rehabilitation in MS patients is associated with reversible plasticity mechanisms located in the default mode network, the central executive network and in the left fronto-orbital cortex. These works evidence that MS patients exhibit a complex and dynamical functional reorganization of rs-networks, significantly associated with disability progression. This PhD thesis confirms that rs-fMRI is a relevant biomarker of pathophysiology leading to disability in MS and represents a promising tool for therapeutic assessment of MS patients in the future
44
Макаришкін, Денис Анатолійович, and Denys Makaryshkin. "Методи функціональної діагностики та технічного обслуговування промислових автоматизованих систем." Master's thesis, Тернопільський національний технічний університет ім. І. Пулюя, Факультет прикладних інформаційних технологій та електроінженерії, Кафедра автоматизації технологічних процесів і виробництв, 2021. http://elartu.tntu.edu.ua/handle/lib/36754.
Full textAbstract:
Робота виконана на кафедрі автоматизації технологічних процесів і виробництв факультету прикладних інформаційних технологій та електроінженерії Тернопільського національного технічного університету імені Івана Пулюя Міністерства освіти і науки України. Захист відбудеться «24» грудня 2021р. о 9.00год. на засіданні екзаменаційної комісії №22 у Тернопільському національному технічному університеті імені Івана Пулюя.У кваліфікаційній роботі на здобуття освітнього ступеня магістр розглянуто питання розробки методів підвищення функціональної надійності безпечності автоматизованих систем керування технологічним обладнанням. Запропоновано удосконалений метод підвищення функціональної надійності безпечності автоматизованих систем керування. В результаті дослідження запропоновано розробку системи АСУ ТП, яка застосовує теорію графів до управління обладнанням для шиття та склеювання килимових виробів. Визначення завдання підвищення надійності та безпеки обладнання, що потребує належного аналізу графу станів та переходів обладнання, та модернізації його відповідно до вимог надійності та безпеки. У виконанні цих двох завдань є протиріччя, оскільки для підвищення безпеки необхідно ввести додаткові вузли та модулі, що знизить надійність, і навпаки. Розроблено схемо-технічні рішення пристрою керування технологічним обладнанням пришивання і проклеювання бахроми до килимового виробу. Поєднуючи характеристики діаграми стану та діаграми переходу, з метою підвищення надійності та безпеки обладнання запропоновано пристрій керування АСУ ТП. Показано що середній час відновлення обладнання в разі аналізу непрацездатних умов і без аналізу становить 1,5 години та – 8,07 години вдповідно. Запропоновано вдосконалення стратегії функціональної діагностики, в якій рекомендується враховувати сучасні виробничі умови.
In the qualification work for the master's degree the question of development of methods of increase of functional reliability of safety of automated control systems of technological equipment is considered. An improved method for increasing the functional reliability of automated control systems is proposed. As a result of the research, the development of the ACS TP system is proposed, which applies graph theory to the control of equipment for sewing and gluing carpet products. Defining the task of improving the reliability and safety of equipment that requires proper analysis of the graph of states and transitions of equipment, and its modernization in accordance with the requirements of reliability and safety. There are contradictions in these two tasks, as additional nodes and modules need to be introduced to increase security, which will reduce reliability, and vice versa. Schematic and technical solutions of the control device for technological equipment for sewing and gluing fringe to carpet products have been developed. Combining the characteristics of the state diagram and the transition diagram, in order to increase the reliability and safety of the equipment, the control device of the ACS TP is proposed. It is shown that the average recovery time of equipment in the case of analysis of inoperable conditions and without analysis is 1.5 hours and - 8.07 hours, respectively. It is proposed to improve the strategy of functional diagnostics, which recommends taking into account modern production conditions.
РЕФЕРАТ 2 ЗМІСТ 8 ВСТУП 10 1 АНАЛІТИЧНА ЧАСТИНА 12 1.1 Аналіз стану питання за літературними та іншими джерелами 12 1.2 Актуальність виконання роботи 14 1.3 Методи вирішення поставленої задачі 15 1.4 Висновки та постановка задач на кваліфікаційну роботу магістра 16 2 ТЕХНОЛОГІЧНА ЧАСТИНА. 17 2.1 Характеристика виробу та його призначення 17 2.1.1 Аналіз умов роботи виробу, матеріалу та його властивостей 17 2.1.2 Аналіз конструктивних особливостей виробу та технологічних особливостей його роботи 18 2.1.3 Розробка та аналіз технічного завдання на розробку виробу 20 2.2 Розробка технологічного процесу подвійного пришивання та проклеювання бахроми до килимових виробів 23 2.3 Висновки до розділу 2 24 3 НАУКОВО-ДОСЛІДНА ЧАСТИНА 25 3.1 Характеристика об’єкту та предмету дослідження 25 3.2 Розробка графу системи автоматичного керування машини пришивання і проклеювання 27 3.3 Удосконалення графу системи автоматичного керування машини пришивання і проклеювання 30 3.5 Висновки по розділу 3 35 4 КОНСТРУКТОРСЬКА ЧАСТИНА 36 4.1 Розробка схеми електричної структурної 36 4.2 Схема електрична принципова 40 4.2.1 Вхід силової мережі змінного струму ~380В, 50Гц 40 4.2.2 Блок живлення 43 4.2.3 Реле безпеки 44 4.2.4 Промисловий контролер 46 4.2.5 Частотний перетворювач 50 4.2.6 Панель оператора 52 4.3 Висновки по розділу 4 54 5 СПЕЦІАЛЬНА ЧАСТИНА 55 5.1Розробка блок схеми алгоритму керування пристроєм 55 5.2 Аналіз надійності приладу 57 5.3 Стратегія функціональної діагностики 61 5.4 Висновки по розділу 5 63 6 ОХОРОНА ПРАЦІ ТА БЕЗПЕКА В НАДЗВИЧАЙНИХ СИТУАЦІЯХ 64 6.1 Вступ 64 6.2 Створення сприятливих санітарно-гігієнічних умов праці на об'єкті, що проектується 65 6.3 Планування і фінансування заходів щодо охорони праці 68 6.2 Розрахунок захисного заземлення 73 ПЕРЕЛІК ПОСИЛАНЬ 81
45
Wheeler, David Orton. "Relative Navigation of Micro Air Vehicles in GPS-Degraded Environments." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6609.
Full textAbstract:
Most micro air vehicles rely heavily on reliable GPS measurements for proper estimation and control, and therefore struggle in GPS-degraded environments. When GPS is not available, the global position and heading of the vehicle is unobservable. This dissertation establishes the theoretical and practical advantages of a relative navigation framework for MAV navigation in GPS-degraded environments. This dissertation explores how the consistency, accuracy, and stability of current navigation approaches degrade during prolonged GPS dropout and in the presence of heading uncertainty. Relative navigation (RN) is presented as an alternative approach that maintains observability by working with respect to a local coordinate frame. RN is compared with several current estimation approaches in a simulation environment and in hardware experiments. While still subject to global drift, RN is shown to produce consistent state estimates and stable control. Estimating relative states requires unique modifications to current estimation approaches. This dissertation further provides a tutorial exposition of the relative multiplicative extended Kalman filter, presenting how to properly ensure observable state estimation while maintaining consistency. The filter is derived using both inertial and body-fixed state definitions and dynamics. Finally, this dissertation presents a series of prolonged flight tests, demonstrating the effectiveness of the relative navigation approach for autonomous GPS-degraded MAV navigation in varied, unknown environments. The system is shown to utilize a variety of vision sensors, work indoors and outdoors, run in real-time with onboard processing, and not require special tuning for particular sensors or environments. Despite leveraging off-the-shelf sensors and algorithms, the flight tests demonstrate stable front-end performance with low drift. The flight tests also demonstrate the onboard generation of a globally consistent, metric, and localized map by identifying and incorporating loop-closure constraints and intermittent GPS measurements. With this map, mission objectives are shown to be autonomously completed.
46
Cheng, Sibo. "Error covariance specification and localization in data assimilation with industrial application Background error covariance iterative updating with invariant observation measures for data assimilation A graph clustering approach to localization for adaptive covariance tuning in data assimilation based on state-observation mapping Error covariance tuning in variational data assimilation: application to an operating hydrological model." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPAST067.
Full textAbstract:
Les méthodes d’assimilation de données et plus particulièrement les méthodes variationnelles sont mises à profit dans le domaine industriel pour deux grands types d’applications que sont la reconstruction de champ physique et le recalage de paramètres. Une des difficultés de mise en œuvre des algorithmes d’assimilation est que la structure de matrices de covariance d’erreurs, surtout celle d’ébauche, n’est souvent pas ou mal connue. Dans cette thèse, on s’intéresse à la spécification et la localisation de matrices de covariance dans des systèmes multivariés et multidimensionels, et dans un cadre industriel. Dans un premier temps, on cherche à adapter/améliorer notre connaissance sur les covariances d’analyse à l’aide d’un processus itératif. Dans ce but nous avons développé deux nouvelles méthodes itératives pour la construction de matrices de covariance d’erreur d’ébauche. L’efficacité de ces méthodes est montrée numériquement en expériences jumelles avec des erreurs indépendantes ou relatives aux états vrais. On propose ensuite un nouveau concept de localisation pour le diagnostic et l’amélioration des covariances des erreurs. Au lieu de s’appuyer sur une distance spatiale, cette localisation est établie exclusivement à partir de liens entre les variables d’état et les observations. Finalement, on applique une combinaison de ces nouvelles approches et de méthodes plus classiques existantes, pour un modèle hydrologique multivarié développé à EDF. L’assimilation de données est mise en œuvre pour corriger la quantité de précipitation observée afin d’obtenir une meilleure prévision du débit d’une rivière en un point donnéData assimilation techniques are widely applied in industrial problems of field reconstruction or parameter identification. The error covariance matrices, especially the background matrix in data assimilation are often difficult to specify. In this thesis, we are interested in the specification and localization of covariance matrices in multivariate and multidimensional systems in an industrial context. We propose to improve the covariance specification by iterative processes. Hence, we developed two new iterative methods for background matrix recognition. The power of these methods is demonstrated numerically in twin experiments with independent errors or relative to true states. We then propose a new concept of localization and applied it for error covariance tuning. Instead of relying on spatial distance, this localization is established purely on links between state variables and observations. Finally, we apply these new approaches, together with other classical methods for comparison, to a multivariate hydrological model. Variational assimilation is implemented to correct the observed precipitation in order to obtain a better river flow forecast
47
Oujamaa, Lydia. "Evolution topologique des hubs dans l'état de conscience altérée post-traumatique : un marqueur de récupération fonctionnelle." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALS013.
Full textAbstract:
Ce travail doctoral s’inscrit dans le champ de la recherche translationnelle. Nous avonsvoulu explorer la plasticité cérébrale post-lésionnelle qui sous-tend la restauration de la conscience après un coma traumatique. L’étude de la connectivité fonctionnelle de repos, c’est à dire de la corrélation temporelle du signal BOLD (blood oxygenationlevel dependent) entre régions cérébrales, a été appliquée à une cohorte de 36 patients traumatisés crâniens graves sortant de réanimation. A cette date, les patients pouvaient se trouver en état de conscience altérée ou être conscients. Nous avons réalisé une étude transversale et longitudinale : une 1ère IRM fonctionnelle en condition de veille de repos était réalisée à la sortie des soins intensifs et une seconde après un séjour de un moisen rééducation post-réanimation. Ainsi, à l’aide de la méthode des graphes, nous avons exploré l’intérêt diagnostique et pronostique de la connectivité fonctionnelle lors de la réémergence de la conscience après coma traumatique.Nous avons centré notre analyse sur un index de perturbation des hubs qui traduitla redistribution des connexions fonctionnelles dans le graphe. Les hubs du réseau cérébral,qui physiologiquement concentrent le plus de connexions, ont été caractérisésavec plusieurs métriques d’intégration, de ségrégation et de centralité dans le transfertd’information.Nos résultats suggèrent qu’une perturbation de la topologie des hubs fonctionnels estobjectivement "cartographiable" et qu’elle est corrélée à l’évolution neurologique cliniqueaprès agression cérébrale. En effet, notre étude a montré que, chez le traumatisé crâniengrave adulte, ce marqueur de perturbation fonctionnelle du réseau cérébral est sensible,dans une analyse de groupe, à l’état de conscience (patients conscients vs en état deconscience altérée) et à sa restauration au cours du temps. L’index de perturbation deshubs est également sensible à une autre dimension clinique : la prédiction du handicap neurologique à 6 mois post-coma.La computation des données de connectivité en une méta-donnée, l’index de perturbationdes hubs de l’ensemble du réseau cérébral, permet d’aller plus loin qu’un modèle descriptif de la plasticité cérébrale après coma (d’altération ou de restitution de connectivité dans un ou plusieurs réseaux). Ainsi, la restitution de la capacité du cerveau à traiterde l’information locale dans les hubs fonctionnels serait nécessaire à la ré-émergence de la conscience après coma traumatique. Ce résultat est original car dans la littérature actuelle, basée sur les théories de l’espace de travail global et de l’intégration de l’information,l’atteinte traumatique cérébrale est modélisée comme une altération de laconnectivité à longue distance et donc de l’intégration fonctionnelle.Cette étude pilote était un pré-requis pour évaluer à l’avenir cet index de perturbation fonctionnelle cérébrale à l’échelle individuelle et objectiver la réponse thérapeutique(psychostimulants, électrostimulation cérébrale....) de patients en état de conscience altéréeThis work takes part in the field of translational research. Our aim was to explore thepost-lesional brain plasticity necessary to recover consciousness after a traumatic coma.The study of resting state functional connectivity, meaning the temporal correlation ofBOLD signal (blood oxygenation level dependent) between remote cerebral areas, wasapplied to severe traumatic brain injured (sTBI) patients.Using graph method, we explored the diagnosis and prognosis value of resting statefunctional connectivity during recovery of consciousness after a traumatic coma.Thirty six sTBI patients were studied in a cross sectional and a longitudinal design.We recorded a resting state functional MRI sequence while sTBI patients were eitherconscious or in altered state of consciousness when discharged from intensive care unit(ICU). A second fMRI was recorded after one month spent in a post-ICU rehabilitationunit.Our analysis focused on a hub disruption index (HDI) which expresses the reallocationof functional connections inside the graph. In the brain network, the hubs, which are definedas highly connected to the brain network in healthy subjects, have been characterizedwith integration, segregation and centrality metrics for information transfer.Our results suggest that the topological disruption of functional hubs is an objectivemapping of the brain network changes that correlates with post-TBI neurological recovery.Indeed, in our group analysis, the hub disruption index of the post TBI brainnetwork was sensitive to the state of consciousness and to its recovery during a onemonth follow-up. This index was also relevant to predict the level of disability 6 monthsafter injury.The computation of connectivity data in a metadata, the hub disruption index ofthe brain network, enhances the classical approach describing the post-traumatic brainplasticity as a loss and recovery of connectivity in one or several cortical networks. Therecovery of the brain network ability to compute local information in the functionalhubs could be necessary to recover consciousness after a traumatic coma. This resultis original as the recent litterature, based on the information integration theory andthe global workspace theory of consciousness, is considering severe TBI as a long rangeconnectivity disruption inducing a functional integration impairment.This pilot study was necessary prior to the assessment of the HDI on a single-subjectlevel and to quantifie the response of brain injured patients with disorder of consciousnessto several therapeutic options (psychostimulant drugs, electrical stimulation..)
48
Jackson, James Scott. "Enabling Autonomous Operation of Micro Aerial Vehicles Through GPS to GPS-Denied Transitions." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8709.
Full textAbstract:
Micro aerial vehicles and other autonomous systems have the potential to truly transform life as we know it, however much of the potential of autonomous systems remains unrealized because reliable navigation is still an unsolved problem with significant challenges. This dissertation presents solutions to many aspects of autonomous navigation. First, it presents ROSflight, a software and hardware architure that allows for rapid prototyping and experimentation of autonomy algorithms on MAVs with lightweight, efficient flight control. Next, this dissertation presents improvments to the state-of-the-art in optimal control of quadrotors by utilizing the error-state formulation frequently utilized in state estimation. It is shown that performing optimal control directly over the error-state results in a vastly more computationally efficient system than competing methods while also dealing with the non-vector rotation components of the state in a principled way. In addition, real-time robust flight planning is considered with a method to navigate cluttered, potentially unknown scenarios with real-time obstacle avoidance. Robust state estimation is a critical component to reliable operation, and this dissertation focuses on improving the robustness of visual-inertial state estimation in a filtering framework by extending the state-of-the-art to include better modeling and sensor fusion. Further, this dissertation takes concepts from the visual-inertial estimation community and applies it to tightly-coupled GNSS, visual-inertial state estimation. This method is shown to demonstrate significantly more reliable state estimation than visual-inertial or GNSS-inertial state estimation alone in a hardware experiment through a GNSS-GNSS denied transition flying under a building and back out into open sky. Finally, this dissertation explores a novel method to combine measurements from multiple agents into a coherent map. Traditional approaches to this problem attempt to solve for the position of multiple agents at specific times in their trajectories. This dissertation instead attempts to solve this problem in a relative context, resulting in a much more robust approach that is able to handle much greater intial error than traditional approaches.
49
Ellingson, Gary James. "Cooperative Navigation of Fixed-Wing Micro Air Vehicles in GPS-Denied Environments." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8706.
Full textAbstract:
Micro air vehicles have recently gained popularity due to their potential as autonomous systems. Their future impact, however, will depend in part on how well they can navigate in GPS-denied and GPS-degraded environments. In response to this need, this dissertation investigates a potential solution for GPS-denied operations called relative navigation. The method utilizes keyframe-to-keyframe odometry estimates and their covariances in a global back end that represents the global state as a pose graph. The back end is able to effectively represent nonlinear uncertainties and incorporate opportunistic global constraints. The GPS-denied research community has, for the most part, neglected to consider fixed-wing aircraft. This dissertation enables fixed-wing aircraft to utilize relative navigation by accounting for their sensing requirements. The development of an odometry-like, front-end, EKF-based estimator that utilizes only a monocular camera and an inertial measurement unit is presented. The filter uses the measurement model of the multi-state-constraint Kalman filter and regularly performs relative resets in coordination with keyframe declarations. In addition to the front-end development, a method is provided to account for front-end velocity bias in the back-end optimization. Finally a method is presented for enabling multiple vehicles to improve navigational accuracy by cooperatively sharing information. Modifications to the relative navigation architecture are presented that enable decentralized, cooperative operations amidst temporary communication dropouts. The proposed framework also includes the ability to incorporate inter-vehicle measurements and utilizes a new concept called the coordinated reset, which is necessary for optimizing the cooperative odometry and improving localization. Each contribution is demonstrated through simulation and/or hardware flight testing. Simulation and Monte-Carlo testing is used to show the expected quality of the results. Hardware flight-test results show the front-end estimator performance, several back-end optimization examples, and cooperative GPS-denied operations.
50
Gour, Natalina. "Réorganisation des systèmes anatomo-fonctionnels et de la topologie cérébrale entre les formes à début précoce et tardif de maladie d'Alzheimer. : Approche comportementale et en IRMf de repos." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM5069.
Full textAbstract:
Les fonctions cognitives reposent sur la communication dynamique de régions cérébrales interconnectées. Dans la maladie d’Alzheimer (MA), les travaux antérieurs suggèrent que le processus neuropathologique cible de façon précoce un ou plusieurs systèmes anatomo-fonctionnels spécifiques. La dysfonction du réseau par défaut a été objectivée de façon consistante. Cependant, ses relations avec les symptômes cliniques et avec l’atteinte des régions du lobe temporal interne qui lui sont fonctionnellement connectées restent à clarifier. L’IRM fonctionnelle de repos est une technique pertinente pour caractériser in vivo chez l’Homme la connectivité cérébrale.Par une approche des systèmes neuraux, ce travail de thèse a pour objectif de caractériser la réorganisation fonctionnelle neuronale dans la MA, ses corrélats cliniques, ainsi que l’influence de l’âge de début des symptômes. Par le recueil et l’analyse des données neuropsychologiques, en IRMf de repos et en IRM structurale, acquises chez des sujets avec des troubles de la mémoire et avec une forme mnésique légère de MA, notre travail apporte des éclairages : i) sur l’implication du réseau temporal antérieur dans la mémoire déclarative décontextualisée et ses modifications dans le cours de la MA ; ii) sur les similitudes et spécificités des systèmes anatomo-fonctionnels ciblés dans les deux formes cliniques distinctes - à début précoce et tardif - de la MA ; iii) sur la réorganisation de l’organisation topologique cérébrale dans son ensemble de ces deux formes de la maladieCognitive functions rely on the dynamic interplay of connected brain regions. Previous studies suggest that in Alzheimer disease (AD), early pathological changes target one or several specific anatomo-functional networks. Dysfunction of the default mode network is a consistent finding. However, its relationship with clinical symptoms and interconnected medial temporal regions remains to be clarified. Resting state functional MRI (fMRI) is an emerging method aimed at characterizing in vivo brain connectivity in the Human.Using a neural system approach, the aim of this thesis was to characterize neuronal functional reorganization in AD, its clinical correlates, and to determine the influence of age at onset. Neuropsychological data, structural and fMRI were obtained in subjects with early memory impairment and mild “amnestic” AD. This work provides new insights into : i) the functional role of the anterior temporal network in context-free declarative memory and its changes throughout the course of AD; ii) the common and specific features in targeted anatomo-functional networks between early and late onset AD ; iii) the reorganization of whole brain topological properties in the two forms of the disease