• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 14
  • 3
  • 1
  • 1
  • Tagged with
  • 27
  • 27
  • 6
  • 6
  • 5
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • 3
  • 3
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Außentemperatur, Jahreszeit und individuelle Trajektorien beeinflussen den Blutdruck von Kindern, Jugendlichen und jungen Erwachsenen.

Miersch, André 19 May 2014 (has links) (PDF)
Background: Seasonal fluctuations in outdoor temperature have been shown to affect blood pressure in adults. We have asked whether or not there is either a seasonal variation or an influence of outdoor temperature on blood pressure measurements in children and adolescents in middle Europe. Methods: Blood pressure was routinely measured in healthy and sick children and adolescents in outpatient clinics and during hospitalisation in a total of 6714 subjects (3,497 boys/3,237 girls), age 3 to 21 years, with a median of 10.6 years. Results: Cross-sectional analysis showed a significant seasonal variation in blood pressure measurements. The mean increase of systolic and diastolic blood pressure was 4.45/2.42 mmHg during winter. A significant correlation between average outdoor temperatures and systolic blood pressure was found (ρ=-0.074 p<0.001). However, the effect was only detectable at an average temperature below 0° C/32° F and above 10° C/50° F. For each degree Celsius increase in average outdoor temperature, the systolic blood pressure fell by 0.12 mmHg. Conclusion: Blood pressure measurements in children and adolescents, even in a temperate climate, are influenced by temperature and seasonal variation. Considering seasonal variations in blood pressure could be of clinical interest. / Background: High blood pressure is a major risk factor for cardiovascular disease. Blood pressure tracking could help to identify individuals with potential hypertension. Therefore, we have asked whether or not tracking was of predictive value for the development of hypertension in early life. Methods: Blood pressure was routinely measured in 13,261children and adolescents in outpatient clinics as well as during hospitalization. In a sub-analysis 568 individuals with normotensive and elevated blood pressure were compared after three follow-up periods (two, four and six years) and 2,157 normotensive individuals were compared in a paired t-test. Results: The follow-up analysis showed a significant tracking effect. However, the Pearson correlation coefficients of the systolic and diastolic blood pressure SDS decreased over time. Upon the follow-up after six years 35.6% of the children and adolescents with elevated blood pressure values remained in the elevated range group. Of the children within the normotensive blood pressure range 80.4% remained normotensive after six years. Children with normotensive blood pressure showed a stronger tracking than those who had had one hypertensive blood pressure reading. Children with high body weight gain left their SDS track to higher blood pressure values. Conclusion: Blood pressure tracking in children and adolescents is moderate. We conclude that the predictive power of a single hypertensive blood pressure measurement during a single visit is rather small, and thus repetitive measurements across several consecutive visits are necessary.
22

Etude expérimentale de l'aéroélasticité d'une plaque oscillante impactée par une batterie de jets turbulents / Experimental Approach to the Aeroelastic Behaviour of an Oscillating Plate Impinged by Arrays of Turbulent Jets

Nyirumulinga, Yohann 26 April 2011 (has links)
Les instabilités aéroélastiques de bandes d’acier constituent aujourd’hui l’un des problèmes majeurs dans les sections de refroidissement par jets impactants des lignes de recuit continues.En effet, le traitement thermique des nouveaux aciers nécessite de très fortes pentes de température impliquant constamment des augmentations de vitesse de soufflage susceptibles de mettre en jeu des instabilités aéroélastiques. Des flottements ainsi que des divergences de bande ont déjà été constatées et identifiées. Ces deux instabilités impliquent dans la plupart des cas des chocs entre la bande et les buses de soufflage ce qui engendre des défauts de surface sur la bande.Un banc d’essai a été conçu et fabriqué dans le but d’analyser ces instabilités et d’anticiper leur apparition. A partir d’observations, la dynamique structurelle de la bande a été simplifiée à un mode de rotation rigide. Le banc comporte une plaque oscillante en mouvement forcé.Celle-ci est impactée par un dispositif de plusieurs jets axisymétriques turbulents ayant une disposition identique à celle des tours industrielles. Les efforts aérodynamiques stationnaires et instationnaires agissant sur la plaque sont mesurés au moyen de capteurs de pression.L’impact de plusieurs jets en interaction crée de très importants gradients de pression sur la plaque il est donc nécessaire que la grille de prises de pression soit très fine pour que l’estimation des efforts aérodynamiques soit correcte. La plaque est donc instrumentée de 91capteurs de pression sur une surface de 18 cm². Elle peut également être translatée dans les ois directions de l’espace, ce qui permet d’obtenir la distribution des efforts instationnaires ainsi que des coefficients aéroélastiques sur une grande surface de plaque et à différentes distances d’impact.Les mesures de pression stationnaires ont permis d’établir les courbes d’évolution des efforts d’impact des jets sur la plaque en fonction de la distance jet-plaque ainsi que de la géométrie des buses. Les résultats ont permis de déterminer la stabilité statique de la plaque en mouvement de pompage. Les mesures de vitesses des jets libres ont été effectuées paranémométrie à fil chaud et ont permis de déterminer leurs propriétés statistiques.Les mesures de coefficients aéroélastiques sur la plaque en rotation ont été effectuées surune seule géométrie de soufflage, pour différentes vitesses réduites. Les résultats mettent en évidence l’importance des effets de bords sur la stabilité de plaque. Des méthodes de post traitements ont proposées afin d’extrapoler les résultats à différentes largeurs de bande. Ils sont confrontés aux travaux de Regardin et al. (réf. [1]) et mettent en évidence des désaccords avec le cas réel. Des suggestions sont apportées afin d’améliorer la représentativité du banc vis-à-vis des bandes industrielles. / Aeroelastic instabilities of steel strips impinged by arrays of cooling gas jets have becomeone of the main issues in cooling sections of continuous annealing lines. Indeed, the new steeltreatments require very high temperature variation rates which involve increases in jetvelocities that are likely to onset some aeroelastic instabilities. Strip flutter and divergencehave already been observed and identified. These two aeroelastic instabilities imply a strongrisk of contact with the blowing boxes, which can seriously blemish the strip.An experimental test rig was designed and built in order to analyze and predict of theseinstabilities. From observations, the strip’s structural dynamics was simulated by a rigidrotation mode. The rig included a forced oscillating plate which is impinged by an array ofaxisymmetric jets having the exact industrial geometry. The plate was instrumented withpressure sensors to measure the steady and unsteady surface pressures. The impingement ofinteracting jets creates very large pressure gradients on the plate and therefore a tight mesh ofpressure taps (91 over an 18cm² jet impingement surface) was necessary to allow a goodestimation of the aerodynamic loads The plate could also be moved in the three coordinatedirections as to obtain surface mappings of the unsteady jet forces and aeroelastic coefficientscan be obtained over a wide area and different jet-to-plate distances.The variation of the impinging aerodynamic forces was established as a function of the jetto-plate distance for different nozzle geometries. These results were used to determine the jetstatic stability in plunging motion. Velocity and turbulence measurements in free jets werecarried out using hot wire anemometry in order to determine their statistical properties.Aeroelastic coefficient measurements were carried out on the oscillating plate with onlyone nozzle geometry and different reduced velocities. Results show that the plate’s stability ismainly dependent on the boundary effects. Post processing methods are suggested in order toapply the results to larger plates. Results are compared to the data of Regardin et al. (réf. [1])and emphasize some discrepancies with respect to the real case. Finally some improvementsto the test-rig are suggested for it to be more representative of the industrial situation.
23

Analysis of thermal effects in circumferential groove journal bearings with reference to the divergent zone / Analyse des effets thermiques dans les paliers hydrodynamiques avec une rainure circonférentielle en tenant compte de la zone divergente

Cristea, Alex Florian 12 December 2012 (has links)
Ce travail porte sur l'étude des effets thermiques dans un palier hydrodynamique, alimentée par une rainure circonférentielle (CGJB) sous charge statique, en tenant compte des phénomènes de rupture de film dans la zone divergente. La recherche expérimentale a été réalisée à l'Université de Poitiers ; elle a permis une détermination minutieuse des champs de pression et de température sur la portée située à l’avant d’un CGJB et dans la section médiane de sa rainure. Ces mesures sous un régime stationnaire sont originales par rapport celles existantes, quel que le type de palier, de par le grand nombre de points de mesure, 180 pour la pression et 144 pour la température, l'instrumentation de haute précision, la large plage de conditions d'exploitation (pression spécifique variant de 0,125 à 2 MPa et vitesse linéaire de l’arbre allant de 5,25 à 21 m/s). Des études du régime transitoire de démarrage au régime stationnaire établi ont été effectuées pour de faibles charges. Des expériences effectuées à l'Université "Politehnica" de Bucarest ont montré une bonne corrélation entre la perte de portance, anti-portance et la rupture du film sur un patin Rayleigh (RSP), ce qui est essentiel pour l'évaluation des phénomènes de rupture dans les paliers. Quelques modèles théoriques ont été utilisés pour évaluer les risques de serrage au démarrage qui est une instabilité thermoélastique catastrophique. Les principaux résultats sont l’obtention d’une base fiable de données expérimentales permettant le développement des modèles théoriques avancés et l’infirmation d’une répartition de pression constante dans la zone divergente et de pression et température constantes dans la rainure d'alime / The main objective of the thesis is to study the thermal effects in steadily loaded circumferential groove journal bearings (CGJBs), including cavitation phenomena occurring in the divergent zone of such bearings. Experimental research conducted at University of Poitiers – Institut Pprime – France enabled a thorough determination of film pressure and temperature fields for the front land of a CGJB plus its mid-groove section, and several performance parameters. Measurements of film pressure and temperature fields under steady-state regime surpassed existing works, regardless of journal bearing design, through: sheer number of land measurement locations, 180 for pressure and for 144 temperature; high precision state of art instrumentation; broad range of operating conditions, 0.125 … 2 MPa specific bearing pressure and 5.25 … 21 m/s shaft speeds. Transient start-up to steady-statestabilization regimes have been investigated at low loads. Experiments at University "Politehnica" of Bucharest – Romania showed a correlation between the downforce thrust and film rupture for a Rayleigh step pin (RSP), important in evaluating divergent zone cavitation phenomena. Theoretical research consisted in developing simple models for evaluating CGJBs performance in steady-state and transient start-up regimes. Several theoretical models were employed for assessing start-up seizure, catastrophic transient thermoelastic instability and damage risk. The major result is a reliable experimental data collection that: enables development of advanced theoretical models; disprove flat film pressure distributions in divergent zones, and constant pressure and temperature in the bearing supply groov
24

Spectroscopie de luminescence et Raman de matériaux moléculaires cristallins et modélisation par la théorie de la fonctionnelle de la densité

Bélanger Desmarais, Nicolas 08 1900 (has links)
No description available.
25

Synthesis and Characterization of Transition Metal Complexes as well as their Application in the Formation of Metal-based Materials and the Investigation of their (Spectro)Electrochemical Behavior

Preuß, Andrea 30 July 2020 (has links)
This Ph.D. thesis concentrates on the synthesis and characterization of tailor-made metal-based precursors and their application in the metal-organic chemical vapor deposition (MOCVD), combustion chemical vapor deposition (CCVD) and in the spin-coating process. Therefore, different complexes containing copper, ruthenium, palladium and gold were synthesized and investigated concerning their thermal properties, especially their decomposition behavior and volatility. Copper(II) and palladium(II) β-ketoiminates were synthesized and used in MOCVD or spin-coating deposition experiments for the formation of metal and metal oxide materials. Ruthenium complexes of type Ru(CO)2(PEt3)2(O2CR)2 (R = Me, Et, iPr, tBu, CH2OMe, CF3) were investigated concerning their physical characteristics depending on the different carboxylates. While primarily focusing on the thermal decomposition behavior, VT IR (variable temperature infrared) spectroscopy, TG-MS (thermogravimetry-mass-spectrometry) studies and DFT (density-functional theory) calculations were carried out to gain a deeper inside into the degradation of the respective complexes, whereby it was possible to propose decomposition mechanisms. Furthermore, from these results it was possible to propose decomposition mechanisms. Gold carboxylates of type [AuO2CCH2OMe(PR’3)] (R’ = Et, nBu) were synthesized and characterized for the use as precursors within CCVD processes to generate Au and SiOx:Au materials. The deposits were used as heterogeneous catalyst in the reduction of 4-nitrophenol. The deposition behavior of zinc diolate towards zinc oxide layer formation was studied by MOCVD experiments, whereby an influence on the crystallinity of the received films was observed depending on the deposition conditions. The second part of this dissertation focuses on the synthesis of polyaromatic hydrocarbons (napthalene, phenanthrene and pyrene) functionalized with Fc (Fc = Fe(η5-C5H4)(η5-C5H5)) units as redox-active group. Thereby, the main emphasis was on the investigation of the charge transfer properties between the ferrocenyl entities through the π-conjugated bridges. The charge transfer behavior was affected by the substituents or substitution pattern at the aryls resulting in more or less intense intervalence charge transfer (IVCT) excitations of the respective compounds. In order to explore the interaction between the Fc-functionalized arenes and SWCNTs (single-walled carbon nanotubes), these molecules were studied by single-crystal X-ray diffraction analysis and DFT calculations. Moreover, disentangling experiments of SWCNTs with a Fc-functionalized pyrene led to the formation of a novel nanoconjugation, whereby the electrochemical response of the ferrocenyl entities is still present. / Die vorliegende Arbeit befasst sich mit der Synthese und Charakterisierung von maßgeschneiderten Übergangsmetall-basierten Precursoren und deren Anwendung in der metallorganischen chemischen Gasphasenabscheidung (MOCVD), in der Flammenbeschichtung (CCVD), oder in der Rotationsbeschichtung. Dafür wurden Kupfer-, Ruthenium-, Palladium- und Gold-haltige Komplexe hergestellt und bezüglich ihrer thermischen Eigenschaften, insbesondere das Zersetzungsverhalten und die Flüchtigkeit, charakterisiert. Cu(II)- und Pd(II)-β-Ketoiminate wurden synthetisiert und in der MOCVD oder in der Rotationsbeschichtung genutzt, um metallische und metalloxidische Materialien abzuscheiden. Ruthenium Komplexe des Typs Ru(CO)2(PEt3)2(O2CR)2 (R = Me, Et, iPr, tBu, CH2OMe, CF3) wurden hinsichtlich ihrer physikalischen Eigenschaften in Abhängigkeit der verschiedenen Substituenten der Carboxylate untersucht. Dabei lag der Fokus im Besonderen auf der thermischen Zersetzungen, welche mittels VT IR (variable Temperatur-Infrarot) Spektroskopie, TG-MS (Thermogravimetrie-Massenspektrometrie) Untersuchungen und DFT (Dichtefunktionaltheorie) Berechnungen genauer beleuchtet wurden. Dabei war es anhand der erhaltenen Ergebnisse möglich Zersetzungsmechanismen zu formulieren. Weiterhin wurden Goldcarboxylate der Art [AuO2CCH2OMe(PR’3)] (R’ = Et, nBu) synthetisiert und in der CCVD untersucht, um Au und SiOx:Au Materialien herzustellen, welche im Weiteren als heterogene Katalysatoren für die Reduktion von 4-Nitrophenol genutzt wurden. Das Abscheideverhalten von Zinkdiolaten in der MOCVD zur Erzeugung von dünnen Zinkoxidfilmen wurde beispielsweise in Hinblick des Einflusses auf die Kristallinität der Filme untersucht. Im zweiten Teil der Dissertation wird die Synthese von Fc-funktionalisierten (Fc = Fe(η5-C5H4)(η5-C5H5)) polyaromatischen Kohlenwasserstoffen (Naphthalen, Phenanthren, Pyren) diskutiert. Der Schwerpunkt lag dabei auf der Untersuchung des Elektrontransferverhaltens zwischen den Redox-aktiven Gruppen in Abhängigkeit der Substituenten und des Substitutionsmusters der π-konjugierten Brücke. Diese Verbindungen wurden mittels Röntgeneinkristallstrukturanalyse und DFT-Berechnungen untersucht um festzustellen, ob eine Wechselwirkung zwischen den Fcfunktionalisierten Arenen und SWCNTs (einwandige Kohlenstoffnanoröhren) möglich ist. Entbündelungsversuche von SWCNTs in Anwesenheit eines Fc-funktionalisierten Pyrens lieferten ein neuartiges Hybridsystem, welches Fc-basierte Redoxprozesse zeigte.
26

Außentemperatur, Jahreszeit und individuelle Trajektorien beeinflussen den Blutdruck von Kindern, Jugendlichen und jungen Erwachsenen.

Miersch, André 26 March 2014 (has links)
Background: Seasonal fluctuations in outdoor temperature have been shown to affect blood pressure in adults. We have asked whether or not there is either a seasonal variation or an influence of outdoor temperature on blood pressure measurements in children and adolescents in middle Europe. Methods: Blood pressure was routinely measured in healthy and sick children and adolescents in outpatient clinics and during hospitalisation in a total of 6714 subjects (3,497 boys/3,237 girls), age 3 to 21 years, with a median of 10.6 years. Results: Cross-sectional analysis showed a significant seasonal variation in blood pressure measurements. The mean increase of systolic and diastolic blood pressure was 4.45/2.42 mmHg during winter. A significant correlation between average outdoor temperatures and systolic blood pressure was found (ρ=-0.074 p<0.001). However, the effect was only detectable at an average temperature below 0° C/32° F and above 10° C/50° F. For each degree Celsius increase in average outdoor temperature, the systolic blood pressure fell by 0.12 mmHg. Conclusion: Blood pressure measurements in children and adolescents, even in a temperate climate, are influenced by temperature and seasonal variation. Considering seasonal variations in blood pressure could be of clinical interest.:Inhaltsverzeichnis......................................................................i Widmung .................................................................................. iii Bibliographische Beschreibung ................................................. iv I. Abkürzungen ......................................................................... i 1. Einführung ........................................................................... 1 1.1. Bedeutung von Blutdruckmessungen im Allgemeinen ................................................................................................. 1 1.2. Bedeutung und Durchführung von Blutdruckmessungen bei Kindern und Jugendlichen ................................................................................................ 2 1.3. Tracking ................................................................................................ 4 1.4. Innere und äußere Einflussfaktoren des Blutdrucks ................................................................................................ 5 1.5. Zweck der Studie ................................................................................................ 7 2. Publikationsmanuskript ................................................................................................ 10 2. 1. Influence of seasonal variation on blood pressure measurements in children, adolescents and young adults ................................................................................................ 10 Abstract .................................................................................. 11 Introduction ................................................................................................ 12 Subjects and methods ................................................................................................ 13 Results .................................................................................... 15 Discussion ................................................................................................ 18 Conclusion ................................................................................................ 21 Acknowledgements ................................................................................................ 22 References............................................................................... 23 Tables ..................................................................................... 27 Figure legends ................................................................................................ 29 Figures ................................................................................... 30 2.2. Blood pressure tracking in children and adolescents ....... 33 Abstract .................................................................................. 34 Inhaltsverzeichnis Subjects and methods ................................................................................................ 35 Results .................................................................................... 39 Discussion ................................................................................................. 42 Conclusion ................................................................................................. 44 Acknowledgements ................................................................................................. 45 References................................................................................ 46 Legends to figures .................................................................................................. 53 Figures ...................................................................................... 55 3. Zusammenfassung der Arbeit ................................................................................................... 62 4. Literaturverzeichnis ............................................................... 68 II. Erklärung über die eigenständige Abfassung der Arbeit ........ ii III. Lebenslauf ............................................................................ iii IV. Danksagung .................................................................................................... iv / Background: High blood pressure is a major risk factor for cardiovascular disease. Blood pressure tracking could help to identify individuals with potential hypertension. Therefore, we have asked whether or not tracking was of predictive value for the development of hypertension in early life. Methods: Blood pressure was routinely measured in 13,261children and adolescents in outpatient clinics as well as during hospitalization. In a sub-analysis 568 individuals with normotensive and elevated blood pressure were compared after three follow-up periods (two, four and six years) and 2,157 normotensive individuals were compared in a paired t-test. Results: The follow-up analysis showed a significant tracking effect. However, the Pearson correlation coefficients of the systolic and diastolic blood pressure SDS decreased over time. Upon the follow-up after six years 35.6% of the children and adolescents with elevated blood pressure values remained in the elevated range group. Of the children within the normotensive blood pressure range 80.4% remained normotensive after six years. Children with normotensive blood pressure showed a stronger tracking than those who had had one hypertensive blood pressure reading. Children with high body weight gain left their SDS track to higher blood pressure values. Conclusion: Blood pressure tracking in children and adolescents is moderate. We conclude that the predictive power of a single hypertensive blood pressure measurement during a single visit is rather small, and thus repetitive measurements across several consecutive visits are necessary.:Inhaltsverzeichnis......................................................................i Widmung .................................................................................. iii Bibliographische Beschreibung ................................................. iv I. Abkürzungen ......................................................................... i 1. Einführung ........................................................................... 1 1.1. Bedeutung von Blutdruckmessungen im Allgemeinen ................................................................................................. 1 1.2. Bedeutung und Durchführung von Blutdruckmessungen bei Kindern und Jugendlichen ................................................................................................ 2 1.3. Tracking ................................................................................................ 4 1.4. Innere und äußere Einflussfaktoren des Blutdrucks ................................................................................................ 5 1.5. Zweck der Studie ................................................................................................ 7 2. Publikationsmanuskript ................................................................................................ 10 2. 1. Influence of seasonal variation on blood pressure measurements in children, adolescents and young adults ................................................................................................ 10 Abstract .................................................................................. 11 Introduction ................................................................................................ 12 Subjects and methods ................................................................................................ 13 Results .................................................................................... 15 Discussion ................................................................................................ 18 Conclusion ................................................................................................ 21 Acknowledgements ................................................................................................ 22 References............................................................................... 23 Tables ..................................................................................... 27 Figure legends ................................................................................................ 29 Figures ................................................................................... 30 2.2. Blood pressure tracking in children and adolescents ....... 33 Abstract .................................................................................. 34 Inhaltsverzeichnis Subjects and methods ................................................................................................ 35 Results .................................................................................... 39 Discussion ................................................................................................. 42 Conclusion ................................................................................................. 44 Acknowledgements ................................................................................................. 45 References................................................................................ 46 Legends to figures .................................................................................................. 53 Figures ...................................................................................... 55 3. Zusammenfassung der Arbeit ................................................................................................... 62 4. Literaturverzeichnis ............................................................... 68 II. Erklärung über die eigenständige Abfassung der Arbeit ........ ii III. Lebenslauf ............................................................................ iii IV. Danksagung .................................................................................................... iv
27

Thermal Snail : Design and Performance Evaluation of a Non-Electronic Autonomous Vehiclefor Harnessing Thermal Expansion of Volatile Fluid for Movement

Chen, Xin, Velin, Benjamin January 2024 (has links)
No description available.

Page generated in 0.1049 seconds