301 |
Hydromorfologický průzkum a identifikace referenčních stavů řeky Jizery / Hydromorphological survey and identification of reference status of the Jizera RiverTomšová, Zuzana January 2015 (has links)
Long-term and intensive human use of watercourses has led to their considerable degradation. Recently, there has been an effort to improve the ecological status of aquatic ecosystems, based on studies of hydromorphological characteristics of natural watercourses and identification of reference conditions. The aim of this thesis was the hydromorphological survey and an identification of reference conditions of the Jizera River. The selection of sites suitable for identification of reference status was based on pre-set criteria determined on remote sensing data, which eliminated significant anthropogenic impacts on the channel and floodplain. The survey using River Habitat Survey (Environmental Agency, 2003), Hydroecological Monitoring (Langhammer et al., 2014) and REFCON (Šmerousová a Matoušková, 2014a) methods was conducted in selected sites. Sites where hydromorphological conditions correspond with very good class, according to Hydroecological Monitoring, were used for identification of the type-specific reference conditions. Physico-chemical characteristics according to ČSN 757221 (1998) and Rosendorf et al. (2011) and the biological quality element macroinvertebrates according to Opatřilová et al. (2011) were also evaluated. Physico-chemical characteristics reached class I - II (ČSN, 1998) and...
|
302 |
Random Walks in Dirichlet Environments with Bounded JumpsDaniel J Slonim (12431562) 19 April 2022 (has links)
<p>This thesis studies non-nearest-neighbor random walks in random environments (RWRE) on the integers and on the d-dimensional integer lattic that are drawn in an i.i.d. way according to a Dirichlet distribution. We complete a characterization of recurrence and transience in a given direction for random walks in Dirichlet environments (RWDE) by proving directional recurrence in the case where the Dirichlet parameters are balanced and the annealed drift is zero. As a step toward this, we prove a 0-1 law for directional transience of i.i.d. RWRE on the 2-dimensional integer lattice with bounded jumps. Such a 0-1 law was proven by Zerner and Merkl for nearest-neighbor RWRE in 2001, and Zerner gave a simpler proof in 2007. We modify the latter argument to allow for bounded jumps. We then characterize ballisticity, or nonzero liiting velocity, of transienct RWDE on the integers. It turns out that ballisticity is controlled by two parameters, kappa0 and kappa1. The parameter kappa0, which controls finite traps, is known to characterize ballisticity for nearest-neighbor RWDE on the d-dimensional integer lattice for dimension d at least 3, where transient walks are ballistic if and only if kappa0 is greater than 1. The parameter kappa1, which controls large-scale backtracking, is known to characterize ballisticity for nearest-neighbor RWDE on the one-dimensional integer lattice, where transient walks are ballistic if and only if the absolute value of kappa1 is greater than 1. We show that in our model, transient walks are ballistic if and only if both parameters are greater than 1. Our characterization is thus a mixture of known characterizations of ballisticity for nearest-neighbor one-dimensional and higher-dimensional cases. We also prove more detailed theorems that help us better understand the phenomena affecting ballisticity.</p>
|
303 |
Role of αPhe-291 Residue in the Phosphate-Binding Subdomain of Catalytic Sites of Escherichia Coli ATP SynthaseBrudecki, Laura, Grindstaff, Johnny J., Ahmad, Zulfiqar 15 March 2008 (has links)
The role of αPhe-291 residue in phosphate binding by Escherichia coli F1F0-ATP synthase was examined. X-ray structures of bovine mitochondrial enzyme suggest that this residue resides in close proximity to the conserved βR246 residue. Herein, we show that mutations αF291D and αF291E in E. coli reduce the ATPase activity of F1F0 membranes by 350-fold. Yet, significant oxidative phosphorylation activity is retained. In contrast to wild-type, ATPase activities of mutants were not inhibited by MgADP-azide, MgADP-fluoroaluminate, or MgADP-fluoroscandium. Whereas, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) inhibited wild-type ATPase essentially completely, ATPase in mutants was inhibited maximally by ∼75%, although reaction still occurred at residue βTyr-297, proximal to αPhe-291 in the phosphate-binding pocket. Inhibition characteristics supported the conclusion that NBD-Cl reacts in βE (empty) catalytic sites, as shown previously by X-ray structure analysis. Phosphate protected against NBD-Cl inhibition in wild-type but not in mutants. In addition, our data suggest that the interaction of αPhe-291 with phosphate during ATP hydrolysis or synthesis may be distinct.
|
304 |
Learning with Recurrent Neural Networks / Lernen mit Rekurrenten Neuronalen NetzenHammer, Barbara 15 September 2000 (has links)
This thesis examines so called folding neural networks as a mechanism for machine learning. Folding networks form a
generalization of partial recurrent neural networks such that they are able to deal with tree structured inputs instead of
simple linear lists. In particular, they can handle classical formulas - they were proposed originally for this purpose. After
a short explanation of the neural architecture we show that folding networks are well suited as a learning mechanism in
principle. This includes three parts: the proof of their universal approximation ability, the aspect of information theoretical
learnability, and the examination of the complexity of training.
Approximation ability: It is shown that any measurable function can be approximated in probability. Explicit bounds on
the number of neurons result if only a finite number of points is dealt with. These bounds are new results in the case of
simple recurrent networks, too. Several restrictions occur if a function is to be approximated in the maximum norm.
Afterwards, we consider briefly the topic of computability. It is shown that a sigmoidal recurrent neural network can
compute any mapping in exponential time. However, if the computation is subject to noise almost the capability of tree
automata arises.
Information theoretical learnability: This part contains several contributions to distribution dependent learnability: The
notation of PAC and PUAC learnability, consistent PAC/ PUAC learnability, and scale sensitive versions are considered.
We find equivalent characterizations of these terms and examine their respective relation answering in particular an open
question posed by Vidyasagar. It is shown at which level learnability only because of an encoding trick is possible. Two
approaches from the literature which can guarantee distribution dependent learnability if the VC dimension of the concept
class is infinite are generalized to function classes: The function class is stratified according to the input space or
according to a so-called luckiness function which depends on the output of the learning algorithm and the concrete
training data.
Afterwards, the VC, pseudo-, and fat shattering dimension of folding networks are estimated: We improve some lower
bounds for recurrent networks and derive new lower bounds for the pseudodimension and lower and upper bounds for
folding networks in general. As a consequence, folding architectures are not distribution independent learnable.
Distribution dependent learnability can be guaranteed. Explicit bounds on the number of examples which guarantee valid
generalization can be derived using the two approaches mentioned above. We examine in which cases these bounds are
polynomial. Furthermore, we construct an explicit example for a learning scenario where an exponential number of
examples is necessary.
Complexity: It is shown that training a fixed folding architecture with perceptron activation function is polynomial.
Afterwards, a decision problem, the so-called loading problem, which is correlated to neural network training is examined.
For standard multilayer feed-forward networks the following situations turn out to be NP-hard: Concerning the
perceptron activation function, a classical result from the literature, the NP-hardness for varying input dimension, is
generalized to arbitrary multilayer architectures. Additionally, NP-hardness can be found if the input dimension is fixed
but the number of neurons may vary in at least two hidden layers. Furthermore, the NP-hardness is examined if the
number of patterns and number of hidden neurons are correlated. We finish with a generalization of the classical NP
result as mentioned above to the sigmoidal activation function which is used in practical applications.
|
305 |
Entwicklung und Evaluation eines elektronischen Systems zur Unterstützung der Informationsverarbeitung in pflegerischen DienstübergabenFlemming, Daniel 16 December 2015 (has links)
Pflegerische Dienstübergaben in Einrichtungen des Gesundheitswesens stellen für die Patientensicherheit und die kontinuierliche Versorgung von Patienten zentrale, aber gefährdete Kommunikationsszenarien dar. Die Akteure übergeben dabei nicht nur relevante Detailinformationen, sondern insbesondere auch die Verantwortung über die Versorgung des einzelnen Patienten. Zu diesem Zweck verständigen sie sich auf ein gemeinsames Bild oder mentales Modell zu dem klinischen Fall und dessen Versorgung. Es sind somit neben den kommunikativen insbesondere auch kognitive Prozesse in Dienstübergaben von Bedeutung.
Vor diesem Hintergrund zielt die vorliegende Arbeit darauf ab, mithilfe eines neuartigen Ansatzes in Form einer kognitiven Karte des klinischen Falls innerhalb einer erweiterten Elektronischen Patientenakte die menschliche Informationsverarbeitung in Dienstübergaben zu unterstützen. Die kognitive Karte soll sowohl die frühen kognitiven Prozesse wie Aufmerksamkeit und Wahrnehmung, als auch die nachfolgenden kognitiven Prozesse wie Entscheiden und Planen fördern.
Die Arbeit beschreibt die Anforderungsanalyse, die Systementwicklung und eine erste initiale Evaluation der Gebrauchstauglichkeit und der kognitiven Unterstützung des entwickelten Prototypens zur Darstellung kognitiver Karten im Rahmen von pflegerischen Dienstübergaben.
|
306 |
Evaluation der Qualität von Epikutantestungen im Rahmen des Hautarztverfahrens / Evaluation of the quality of patch testing as part of the dermatologist's procedureMentzel, Franziska 20 April 2017 (has links)
Epikutantestungen stellen einen wesentlichen Eckpfeiler in der berufsdermatologischen Diagnostik dar. Im Forschungsprojekt EVA_Haut wurden im Rahmen des Hautarztverfahrens durchgeführte Epikutantestungen erstmals im Sinne einer Qualitätsprüfung systematisch analysiert. Ziel war es die leitliniengerechte Durchführung unter den besonderen Rahmenbedingungen des ambulanten Hautarztverfahrens zu überprüfen. Wesentliche Beurteilungskriterien sind die Indikationsstellung, Durchführung, leitliniengerechte Dokumentation und die Auswahl und der Umfang der Testungen in Abhängigkeit vom vorliegenden Beruf sowie die Beurteilung der klinischen und beruflichen Relevanz bei vorliegender Sensibilisierung.
Mittels bundesweiter randomisierter Quotenstichprobe (N=1600) anteilig bezogen auf alle UV-Träger wurden ca. 10 % der jährlichen BK-5101-Verdachtsmeldungen analysiert (Rekrutierungszeitraum 4. Quartal 2007). Es konnten N=1543 Fälle ausgewertet werden. Die Hautarztberichte, die im einjährigen Nachbeobachtungszeitraum erstattet worden sind, wurden anonymisiert durch ABD-zertifizierte Gutachter mittels eines Gutachterfragebogens evaluiert.
In N=1135 Fällen wurde eine Epikutantestung durchgeführt. Getestet wurde in fast 90% der Fälle im Zusammenhang mit dem Erstbericht, im Sinne einer zeitnahen diagnostischen Abklärung der beim Versicherten vorliegenden Hauterkrankung. Es erfolgte in 86,7% (n=995) eine leitliniengerechte Dokumentation. Die Hauptkritikpunkte in den übrigen 13,3% (n=147) waren fehlende Angaben zum Zeitpunkt der Testpflasterabnahme bzw. Ablesezeitpunkten, nicht standardisierte Formen der Dokumentation der Testreaktionen sowie unvollständige/nicht nachvollziehbare Angaben zu getesteten Allergenen und Konzentrationen. In den analysierten Fällen wurde die Forderung, nicht unter floriden Hautveränderungen zu testen, überwiegend berücksichtigt. Das berufliche Spektrum wurde in etwas mehr als 40% der Fälle, in denen eine Epikutantestung erfolgte, abgedeckt, in 40% wurde es als unvollständig eingestuft, in knapp 10% als zu umfangreich. Bei dokumentierter Sensibilisierung (N=706) erfolgte in der Mehrheit der Fälle (63,5%; n=448) keine Beurteilung der klinischen und beruflichen Relevanz. Die Ergebnisse der Arbeit zeigen, dass die Empfehlungen zur Durchführung von Epikutantestungen im Rahmen des Hautarztverfahrens durch die niedergelassenen Kollegen überwiegend berücksichtigt werden. Die Formulare F6050 und F6052 sind gute Instrumente zur Erfassung der berufsdermatologisch-allergologisch relevanten Informationen zur Indikationsstellung und Umfang einer ECT. Deutliches Verbesserungspotential besteht in der Auswahl der Allergene zur Abbildung des beruflichen Spektrums und in der Beurteilung der klinischen und beruflichen Relevanz, z.B. durch eine dezidierte Abfrage der Relevanz im Hautarztbericht. Angestoßen durch die Ergebnisse dieser Studie ist dies jüngst durch die gesetzliche Unfallversicherung umgesetzt worden (01.01.2016).
|
307 |
On irreducible, infinite, non-affine coxeter groupsQi, Dongwen 30 July 2007 (has links)
No description available.
|
308 |
Synthesis and Characterization of Multiblock Copolymers for Proton Exchange Membrane Fuel Cells (PEMFC)Wang, Hang 25 January 2007 (has links)
Nanophase-separated hydrophilic-hydrophobic multiblock copolymers are promising proton exchange membrane (PEM) materials due to their ability to form various morphological structures which enhance transport.
Four arylene chlorides monomers (2,5-Dichlorobenzophenone and its derivatives) were first successfully synthesized from aluminum chloride-catalyzed, Friedel-Crafts acylation of benzene and various aromatic compounds with 2,5-dichlorobenzoyl chloride. These monomers were then polymerized via Ni (0)-catalyzed coupling reaction to form various high molecular weight substituted poly(2,5-benzophenone)s. Great care must be taken to achieve anhydrous and inert conditions during the reaction.
A series of poly(2,5-benzophenone) activated aryl fluoride telechelic oligomers with different block molecular weights were then successfully synthesized by Ni (0)- catalyzed coupling of 2,5-dichloro-benzophenone and the end-capping agent 4-chloro-4'-fluorobenzophenone or 4-chlorophenly-4′-fluorophenyl sulfone. The molecular weights of these oligomers were readily controlled by altering the amount of end-capping agent. These telechelic oligomers (hydrophobic) were then copolymerized with phenoxide terminated disulfonated poly (arylene ether sulfone)s (hydrophilic) by nucleophilic aromatic substitution to form novel hydrophilic-hydrophobic multiblock copolymers.
A series of novel multiblock copolymers with number average block lengths ranging from 3,000 to 10,000 g/mol were successfully synthesized. Two separate Tgs were observed via DSC in the transparent multiblock copolymer films when each block length was longer than 6,000 g/mol (6k). Tapping mode atomic force microscopy (AFM) also showed clear nanophase separation between the hydrophilic and hydrophobic domains and the influence of block length, as one increased from 6k to 10k. Transparent and creasable films were solvent-cast and exhibited good proton conductivity and low water uptake.
These PAES-PBP multiblock copolymers also showed much less relative humidity (RH) dependence than random sulfonated aromatic copolymers BPSH 35 in proton conductivity, with values that were almost the same as Nafion with decreasing RHs. This phenomenon lies in the fact that this multiblock copolymer possesses a unique co-continuous nanophase separated morphology, as confirmed by AFM and DSC data. Since this unique co-continuous morphology (interconnected channels and networks) dramatically facilitates the proton transport (increase the diffusion coefficient of water), improved proton conductivity under partially hydrated conditions becomes feasible. These multiblock copolymers are therefore considered to be very promising candidates for high temperature proton exchange membranes in fuel cells. / Ph. D.
|
309 |
Critical Erosion/Corrosion Piping Wall Thicknesses Under Static and Fatigue Stress Conditions According to ASME GuidelinesComeau, Christian R. 08 October 2001 (has links)
The purpose of this project was to show the updated procedures and to make additions to the computer program called Tmin designed by E. I. DuPont De Nemours and Company. This program is used as a screening tool for determining the largest of the minimum pipe-wall thicknesses in a piping system.
This project involved several additions that will be released in the next version of the Tmin computer program. The first major additions to be implemented are four alternating Stress-to-Number of cycles curves: Aluminum 1100, Aluminum 3003-0, Aluminum 6061-T6, and Nickel 200. In addition, procedures of the ASME for fatigue curve analysis and implementation of fatigue data were investigated. These four stress-to-number of cycles (S-N) fatigue curves were added to Tmin's internal Microsoft Access® database. Next, a 2-D vertical piping span configuration was incorporated. Finally, DuPont required a Microsoft Word® document output of the pipe-wall thickness data including the piping span model information. Other user-friendly additions were included.
Since this computer program was to be American Society of Mechanical Engineers (ASME) compliant, a study of the ASME Pressure Vessel and Piping standards and codes was made to determine how pipe-wall thickness calculations were to be processed. The 2-D vertical piping span calculation procedures were investigated. Once the 2-D vertical piping span analysis was complete, the largest pipe-wall thickness value calculated were passed to a Microsoft Word® document. The last implementation is the inclusion of help files. Help file button additions in all input boxes allowed for the user to know exactly what was needed before a data entry was made. / Master of Science
|
310 |
Méthode de génération de colonnes pour les problèmes de conception de réseaux avec coûts d’ajout de capacitéEl Filali, Souhaïla 05 1900 (has links)
Les problèmes de conception de réseaux ont reçu un intérêt particulier et ont été largement étudiés de par leurs nombreuses applications dans différents domaines, tels que les transports et les télécommunications.
Nous nous intéressons dans ce mémoire au problème de conception de réseaux avec coûts d’ajout de capacité. Il s’agit d’installer un ensemble d’équipements sur un réseau en vue de satisfaire la demande, tout en respectant les contraintes de capacité, chaque arc pouvant admettre plusieurs équipements. L’objectif est de minimiser les coûts variables de transport des produits et les coûts fixes d’installation ou d’augmentation de capacité des équipements.
La méthode que nous envisageons pour résoudre ce problème est basée sur les techniques utilisées en programmation linéaire en nombres entiers, notamment celles de génération de colonnes et de coupes. Ces méthodes sont introduites dans un algorithme général de branch-and-bound basé sur la relaxation linéaire.
Nous avons testé notre méthode sur quatre groupes d’instances de tailles différentes, et nous l’avons comparée à CPLEX, qui constitue un des meilleurs solveurs permettant de résoudre des problèmes d’optimisation, ainsi qu’à une méthode existante dans la littérature combinant des méthodes exactes et heuristiques. Notre méthode a été plus performante que ces deux méthodes, notamment pour les instances de très grandes tailles. / Network design problems received a particular interest and have been widely studied because of their many applications in different areas, such as logistics and telecommunications.
We focus in this work on the multicommodity capacitated network design problem with capacity expansion costs. It consists in opening a set of facilities on a network in order to meet the demand of some commodities, while respecting the capacity constraints. Each arc can admit several facilities. The objective is to minimize the commodities transportation costs, and the fixed costs of opening or increasing the capacity of the facilities.
The method we are using to solve this problem is based on techniques used in integer programming, including column generation and cutting-plane methods. These methods are introduced into a general branch-and-bound algorithm, based on linear relaxation.
We test our method on four groups of instances of different sizes, and we compare it with CPLEX, which is one of the best solvers available for optimization problems. We compare it also with an existing method in the literature, combining exact and heuristic methods.
Numerical results show that our method was able to outperform both methods, especially when tested on large scale instances.
|
Page generated in 0.0862 seconds