• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 25
  • 23
  • 5
  • 4
  • 4
  • 2
  • 1
  • 1
  • Tagged with
  • 84
  • 18
  • 16
  • 9
  • 9
  • 8
  • 8
  • 8
  • 8
  • 7
  • 7
  • 7
  • 6
  • 6
  • 6
  • 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.
61

Stepped care for depression : a systematic review and feasibility study

Hill, Jacqueline Janet January 2016 (has links)
Background. Stepped care is widely implemented as a means to organise depression treatment. However, it is unclear how this system and the system it was designed to replace – long-term intensive psychotherapy for all – compare. Aim. To further the development and evaluation of stepped care. Specifically, assess the clinical effectiveness of stepped care and prepare for a fully-powered evaluation of stepped care vs. high-intensity psychotherapy alone for depressed adults. Design. A systematic review and mixed methods feasibility study encompassing a pilot randomised controlled trial and semi-structured interviews. Results of the systematic review. Fourteen randomised controlled trials involving 4580 participants were included. Relative to controls, there was significantly greater improvement in depression for adults treated with stepped care (d=0.34 at six months; 95% CI 0.20 to 0.48). The quality of included studies was good and there was little evidence of publication bias. All comparisons were with usual care. Results of the feasibility study. 66 patients were recruited to the pilot trial. The recruitment rate was 2.9% and follow-up data was obtained from 90.9% of participants. A third of stepped care patients stepped up to high-intensity therapy. Patients improved in both groups: the mean reduction in depressive symptoms was 13.4 in the stepped care group and 13.6 in the high-intensity therapy alone group. Recruitment methods were appropriate to patients and therapists but only somewhat appropriate to IAPT staff. Although the stepped care intervention was broadly acceptable to therapists, patient experience varied and some patients who demonstrated a low level of self-efficacy declined any therapy or dropped out of treatment. Conclusions. The effectiveness of stepped care compared with long-term intensive psychological therapy for all has not yet been established. A fully-powered trial of stepped care vs. high-intensity therapy alone is feasible although pilot trial methods and procedures should be modified to improve recruitment and acceptability.
62

Patient-initiated Strategies for Self-management of Depression and Low Mood: Understanding Theory and Changing Behaviour

Philip, Grandia January 2014 (has links)
Background: Depression is a major health concern and self-management of depressive symptoms using patient-initiated strategies has the potential to reduce the burden of this condition. A better understanding of behaviour change related to these patient-initiated strategies is needed. Method: This randomized controlled trial study used an online survey and Knowledge Translation and Transfer theory-based educational intervention to examine the Theory of Planned Behavior model in the context of nine patient-initiated strategies for the self-management of depression and low mood. Results: Perceived Behavioural Control was identified as the single greatest predictor of Intentions to engage in strategies. Attitudes predicted Intentions to a lesser degree. Subjective Norms were not identified as unique predictors. Theory of Planned Behavior antecedent variables together explained over one third of the variance in Intentions. Intentions to engage in patient-initiated strategies were shown, in some cases, to significantly predict actual engagement in strategies. Level of depressive symptoms did not meaningfully impact any of the antecedent variables or Intentions. Results also suggest that an educational intervention based on Knowledge Translation and Knowledge Transfer principles significantly improved both Attitudes and Subjective Norms – Physician towards patient-initiated strategies. Perceived Behavioural Control and Intentions were not improved as a result of the educational intervention. Theoretical Conclusions: Findings suggest that the Theory of Planned Behavior functions well in the context of patient-initiated strategies for depression and low mood. Perceived Behavioural Control was identified as the greatest predictor of Intentions to engage in patient-initiated strategies. Results also suggest mood difficulties are not captured by the model’s antecedent variables but instead should be included as an additional variable in this model. The findings of the current study support an integrated model of Knowledge Translation and Transfer and Theory of Planned Behavior. Practical Conclusions: The current study’s findings provide a better understanding of behaviour change in the context of patient-initiated strategies and will help guide interventions aimed at improving engagement in these behaviours. Findings also provide support and recommendations for the use of Knowledge Translation and Transfer theory-based educational interventions to improve self-management of depression and low mood.
63

Épuration en eaux courantes : évaluation et modélisation de la capacité d'oxygénation dans les cascades et les chutes d'eau / Purification in running water : evaluation and modeling of oxygenation capacity of stepped cascades and waterfalls

Khdhiri, Hatem 03 December 2014 (has links)
Ce travail s’inscrit dans le cadre global de la restauration des cours d’eau pollués par une intensification des mécanismes d’autoépuration, en particulier la dégradation de la matière organique et de l’azote. L’objectif principal de cette étude est d’évaluer et modéliser la capacité de transfert d’oxygène air-eau par les principaux ouvrages hydrauliques à savoir les cascades en marches d’escalier et les chutes d’eau. Les expériences d’aération menées dans un pilote de laboratoire modulable, servant à la fois de cascade et de chute d’eau, ont permis d’évaluer le potentiel d’aération de ces structures, ainsi que d’étudier les effets des paramètres géométriques et opératoires. En première approche, une corrélation semi-empirique globale de calcul d’efficacité d’aération dans les cascades, avec un large spectre de validité, a été élaborée, en fonction du débit, nombre de marches et pente de la cascade, sur la base de nos mesures expérimentales et des données collectées dans les publications. La même démarche a été suivie pour élaborer une corrélation semi-empirique permettant une estimation de l’efficacité d’aération dans les chutes d’eau en fonction de la hauteur de chute, le niveau d’eau en aval et le débit d’écoulement. Afin de rendre compte des caractéristiques du phénomène de transfert dans les cascades d’eau (aire interfaciale d’échange air-eau et volume d’eau), des expériences de traçage ont été associées aux expériences d’aération ce qui a permis de mesurer le volume d’eau et de corréler le coefficient de transfert volumique d’oxygène kLa avec les différents paramètres intervenant dans les mécanismes d’aération. L’aire spécifique interfaciale a été simulée numériquement via l’approche VOF en fonction des conditions opératoires et géométriques. Une équation prédictive de calcul du coefficient de transfert du film liquide kL en fonction des paramètres d’influence a été obtenue à l’issu de l’ensemble des simulations et des mesures d’aération expérimentales / This work represents a part of polluted watercourses restoration by intensification of self-purification mechanisms essentially the degradation of organic matter and nitrogen. The main objective is to evaluate and model the air-water oxygen transfer by major hydraulic structures, namely stepped cascades and waterfalls. Aeration experiments conducted in a geometrically adjustable laboratory pilot, serving as stepped cascade and waterfall were used to assess the aeration potential of these structures as well as to study the geometrical an operating parameters effects. In a first approach, a global semi-empirical correlation for aeration efficiency calculation in stepped cascades, valid for a wide range of parameters, was developed, depending on water discharge, number of steps and chute slope, basing on our experimental measurements and data collected in publications. The same procedure was followed for developing a semi-empirical correlation to estimate the aeration efficiency of waterfalls in terms of the chute height, downstream water level and flowrate. In order to take into account the oxygen transfer phenomenon characteristics in stepped cascade (water volume and air-water exchange interfacial area), tracer experiments were associated with aeration experiments to allow measuring water volume and correlating the volume oxygen transfer coefficient kLa with the various parameters involved in the aeration mechanism. The interfacial specific area was numerically simulated using VOF approach depending on operating and geometrical parameters. A predictive equation for liquid film transfer coefficient kL calculation based on the parameters of influence was issued from both the simulations and experimental aeration measures
64

New multi-standard dual-wideband and quad-wideband asymmetric step impedance resonator filters with wide stop band restriction

Al-Yasir, Yasir I.A., Tu, Yuxiang X., Ojaroudi Parchin, Naser, Abdulkhaleq, Ahmed M., Kosha , Jamal S.M., Ullah, Atta, Abd-Alhameed, Raed, Noras, James M. 28 September 2023 (has links)
Yes / New multi-standard wide band filters with compact sizes are designed for wireless communication devices. The proposed structures realize dual-wideband and quad-wideband characteristics by using a new skew-symmetrical coupled pair of asymmetric stepped impedance resonators, combined with other structures. The first and second dual-wideband filters realize fractional bandwidths (FBW) of 43.2%/31.9% at the central frequencies (CF) of 1.875/1.63 GHz, and second bandwidths of 580 MHz/1.75 GHz at CF of 5.52/4.46 GHz, respectively. The proposed quad-band filter realizes its first/second/third/fourth pass bands at CF 2.13/5.25/7.685/9.31 GHz with FBW of 46.0%/11.4%/4.6%and 5.4%, respectively. The wide pass bands are attributed to the mutual coupling of the modified ASIR resonators and their bandwidths are controllable by tuning relative parameters while the wide stop band performance is optimized by the novel interdigital cross coupled line structure and parallel uncoupled microstrip line structure. Moreover, the quad band is generated by introducing the novel defected rectangle structure. These multi-standard filters are simulated, fabricated and measured, and measured results agree well with both simulated results and theory predictions. The good in-band and out-of-band performances, the miniaturized sizes and simple structures of the proposed filters make them very promising for applications in future multi-standard wireless communication. / Horizon 2020 Framework Programme(European Union), Grant/Award Number:H2020-MSCA-ITN-2016 SECRET-722 424
65

Escoamento deslizante sobre turbilhões em descarregadores em degraus de largura constante e convergentes, usando o método Hidrodinâmica Suavizada de Partículas / Skimming flow over stepped spillways with non-converging and converging sidewalls using Smoothed Particles Hydrodynamics Method

Juliana Dorn Nóbrega 23 November 2018 (has links)
O método Hidrodinâmica Suavizada de Partículas (em inglês: Smoothed Particle Hydrodynamics - SPH) foi utilizado para o desenvolvimento de um estudo numérico envolvendo descarregadores lisos e descarregadores em degraus (considerando escoamento deslizante sobre turbilhões), com paredes laterais paralelas e paredes convergentes, usando o software DualSPHysics. Muitas vezes é conveniente utilizar a construção de descarregadores com maior largura na crista, e menor largura do descarregador, para adaptação das limitações físicas locais. O estreitamento do descarregador de forma gradual até atingir a largura da seção de jusante é feito por meio de paredes laterais convergentes, que por sua vez induzem à formação de ondas estacionárias laterais, e consequentemente aumento da altura do escoamento junto às paredes. Existem poucos estudos na literatura sobre esse tema, justificando o estudo numérico desenvolvido neste trabalho. O modelo numérico foi desenvolvido com base em um modelo físico do Laboratório de Hidráulica e Recursos Hídricos do Instituto Superior Técnico, Portugal, sendo os resultados experimentais obtidos em estudos anteriores. A instalação experimental é composta por um descarregador com declividade de fundo de 26,6º, e ângulo das paredes de 0º; 9,9º e 19,3º em relação ao plano vertical. As simulações foram realizadas em duas ou três dimensões, conforme a condição de largura constante ou convergente. Os resultados foram comparados com dados experimentais em termos de alturas do escoamento na parede e no eixo do descarregador, perfis de velocidade na região não-aerada do escoamento, e largura da onda estacionária lateral. Para as simulações tridimensionais, também foram elaborados gráficos de isolinhas para a altura do escoamento, podendo-se observar a extensão das ondas estacionárias laterais conforme a condição de superfície lisa ou em degraus, e a elevação de água junto às paredes. Em geral, houve boa aproximação entre dados numéricos e experimentais, verificando-se a aplicabilidade do método SPH para simular o escoamento deslizante sobre turbilhões em estruturas em degraus, ou estruturas convencionais de paramento liso. / A numerical study using the Smoothed Particle Hydrodynamics method (SPH) was developed for smooth and stepped spillways (for skimming flow regime), with converging and non-converging sidewalls, using the software DualSPHysics. In numerous situations, it is convenient to built spillways with longer width at the crest and narrower width at the downstream end of the spillway, depending on the site constrains. The gradual narrowing of the spillway width is usually made through converging sidewalls, which induce the formation of shockwaves, leading to higher flow depths along the sidewalls. Few studies in the literature were carried out in this research topic to date, justifying the numerical study developed in this project. The numerical model was based on a physical model assembled at the Hydraulic and Water Resources Laboratory of the Instituto Superior Técnico, Portugal, using experimental data obtained in previous studies. The experimental setup was composed by a spillway with slope of 26.6º, and angles of converging sidewalls of 0º, 9.9º, and 19.3º in relation to the vertical plane. Two-dimensional or three-dimensional simulations were carried out according to the condition of constant width or converging walls. The results were compared with experimental data, related to the flow depths at the centerline and sidewall of the spillway, the velocity profiles on the non-aerated region, and the lateral standing wave width. Regarding the three-dimensional simulations, contours of the flow depth were also represented, to visualize the extent and height of the sidewall shockwaves, according to the smoothed or stepped face. In general, a good agreement was obtained between numerical and experimental results, which confirms the ability of the SHP method to simulate the skimming flow over stepped spillways, or the flow on more conventional, smooth spillway chutes.
66

Escoamento deslizante sobre turbilhões em descarregadores em degraus de largura constante e convergentes, usando o método Hidrodinâmica Suavizada de Partículas / Skimming flow over stepped spillways with non-converging and converging sidewalls using Smoothed Particles Hydrodynamics Method

Nóbrega, Juliana Dorn 23 November 2018 (has links)
O método Hidrodinâmica Suavizada de Partículas (em inglês: Smoothed Particle Hydrodynamics - SPH) foi utilizado para o desenvolvimento de um estudo numérico envolvendo descarregadores lisos e descarregadores em degraus (considerando escoamento deslizante sobre turbilhões), com paredes laterais paralelas e paredes convergentes, usando o software DualSPHysics. Muitas vezes é conveniente utilizar a construção de descarregadores com maior largura na crista, e menor largura do descarregador, para adaptação das limitações físicas locais. O estreitamento do descarregador de forma gradual até atingir a largura da seção de jusante é feito por meio de paredes laterais convergentes, que por sua vez induzem à formação de ondas estacionárias laterais, e consequentemente aumento da altura do escoamento junto às paredes. Existem poucos estudos na literatura sobre esse tema, justificando o estudo numérico desenvolvido neste trabalho. O modelo numérico foi desenvolvido com base em um modelo físico do Laboratório de Hidráulica e Recursos Hídricos do Instituto Superior Técnico, Portugal, sendo os resultados experimentais obtidos em estudos anteriores. A instalação experimental é composta por um descarregador com declividade de fundo de 26,6º, e ângulo das paredes de 0º; 9,9º e 19,3º em relação ao plano vertical. As simulações foram realizadas em duas ou três dimensões, conforme a condição de largura constante ou convergente. Os resultados foram comparados com dados experimentais em termos de alturas do escoamento na parede e no eixo do descarregador, perfis de velocidade na região não-aerada do escoamento, e largura da onda estacionária lateral. Para as simulações tridimensionais, também foram elaborados gráficos de isolinhas para a altura do escoamento, podendo-se observar a extensão das ondas estacionárias laterais conforme a condição de superfície lisa ou em degraus, e a elevação de água junto às paredes. Em geral, houve boa aproximação entre dados numéricos e experimentais, verificando-se a aplicabilidade do método SPH para simular o escoamento deslizante sobre turbilhões em estruturas em degraus, ou estruturas convencionais de paramento liso. / A numerical study using the Smoothed Particle Hydrodynamics method (SPH) was developed for smooth and stepped spillways (for skimming flow regime), with converging and non-converging sidewalls, using the software DualSPHysics. In numerous situations, it is convenient to built spillways with longer width at the crest and narrower width at the downstream end of the spillway, depending on the site constrains. The gradual narrowing of the spillway width is usually made through converging sidewalls, which induce the formation of shockwaves, leading to higher flow depths along the sidewalls. Few studies in the literature were carried out in this research topic to date, justifying the numerical study developed in this project. The numerical model was based on a physical model assembled at the Hydraulic and Water Resources Laboratory of the Instituto Superior Técnico, Portugal, using experimental data obtained in previous studies. The experimental setup was composed by a spillway with slope of 26.6º, and angles of converging sidewalls of 0º, 9.9º, and 19.3º in relation to the vertical plane. Two-dimensional or three-dimensional simulations were carried out according to the condition of constant width or converging walls. The results were compared with experimental data, related to the flow depths at the centerline and sidewall of the spillway, the velocity profiles on the non-aerated region, and the lateral standing wave width. Regarding the three-dimensional simulations, contours of the flow depth were also represented, to visualize the extent and height of the sidewall shockwaves, according to the smoothed or stepped face. In general, a good agreement was obtained between numerical and experimental results, which confirms the ability of the SHP method to simulate the skimming flow over stepped spillways, or the flow on more conventional, smooth spillway chutes.
67

Quantum-size effects in the electronic structure of novel self-organized systems with reduced dimensionality

Varykhalov, Andrei January 2005 (has links)
The Thesis is focused on the properties of self-organized nanostructures. Atomic and electronic properties of different systems have been investigated using methods of electron diffraction, scanning tunneling microscopy and photoelectron spectroscopy. Implementation of the STM technique (including design, construction, and tuning of the UHV experimental set-up) has been done in the framework of present work. This time-consuming work is reported to greater detail in the experimental part of this Thesis. <br><br> The scientific part starts from the study of quantum-size effects in the electronic structure of a two-dimensional Ag film on the supporting substrate Ni(111). Distinct quantum well states in the sp-band of Ag were observed in photoelectron spectra. Analysis of thickness- and angle-dependent photoemission supplies novel information on the properties of the interface. For the first time the Ni(111) relative band gap was indirectly probed in the ground-state through the electronic structure of quantum well states in the adlayer. This is particularly important for Ni where valence electrons are strongly correlated. Comparison of the experiment with calculations performed in the formalism of the extended phase accumulation model gives the substrate gap which is fully consistent with the one obtained by ab-initio LDA calculations. It is, however, in controversy to the band structure of Ni measured directly by photoemission. These results lend credit to the simplest view of photoemission from Ni, assigning early observed contradictions between theory and experiments to electron correlation effects in the final state of photoemission. <br><br> Further, nanosystems of lower dimensionality have been studied. Stepped surfaces W(331) and W(551) were used as one-dimensional model systems and as templates for self-organization of Au nanoclusters. Photon energy dependent photoemission revealed a surface resonance which was never observed before on W(110) which is the base plane of the terrace microsurfaces. The dispersion E(k) of this state measured on stepped W(331) and W(551) with angle-resolved photoelectron spectroscopy is modified by a strong umklapp effect. It appears as two parabolas shifted symmetrically relative to the microsurface normal by half of the Brillouin zone of the step superlattice. The reported results are very important for understanding of the electronic properties of low-dimensional nanostructures. <br><br> It was also established that W(331) and W(551) can serve as templates for self-organization of metallic nanostructures. A combined study of electronic and atomic properties of sub-monolayer amounts of gold deposited on these templates have shown that if the substrate is slightly pre-oxidized and the temperature is elevated, then Au can alloy with the first monolayer of W. As a result, a nanostructure of uniform clusters of a surface alloy is produced all over the steps. Such clusters feature a novel sp-band in the vicinity of the Fermi level, which appears split into constant energy levels due to effects of lateral quantization. <br><br> The last and main part of this work is devoted to large-scale reconstructions on surfaces and nanostructures self-assembled on top. The two-dimensional surface carbide W(110)/C-R(15x3) has been extensively investigated. Photoemission studies of quantum size effects in the electronic structure of this reconstruction, combined with an investigation of its surface geometry, lead to an advanced structural model of the carbide overlayer. <br><br> It was discovered that W(110)/C-R(15x3) can control self-organization of adlayers into nanostructures with extremely different electronic and structural properties. Thus, it was established that at elevated temperature the R(15x3) superstructure controls the self-assembly of sub-monolayer amounts of Au into nm-wide nanostripes. Based on the results of core level photoemission, the R(15x3)-induced surface alloying which takes place between Au and W can be claimed as driving force of self-organization. The observed stripes exhibit a characteristic one-dimensional electronic structure with laterally quantized d-bands. Obviously, these are very important for applications, since dimensions of electronic devices have already stepped into the nm-range, where quantum-size phenomena must undoubtedly be considered. <br><br> Moreover, formation of perfectly uniform molecular clusters of C<sub>60</sub> was demonstrated and described in terms of the van der Waals formalism. It is the first experimental observation of two-dimensional fullerene nanoclusters with "magic numbers". Calculations of the cluster potentials using the static approach have revealed characteristic minima in the interaction energy. They are achieved for 4 and 7 molecules per cluster. The obtained "magic numbers" and the corresponding cluster structures are fully consistent with the results of the STM measurements. / Die aktuelle Doktorarbeit ist auf die Eigenschaften von selbst-organisierten Nanostrukturen fokussiert. Die strukturellen und elektronischen Eigenschaften von verschiedenen Systemen wurden mit den Methoden Elektronenbeugung, Rastertunnelmikroskopie und Photoelektronenspektroskopie untersucht. Insbesondere wurde die fuer die Rastertunnelmikroskopie in situ praeparierter Proben eingesetzte Apparatur im Rahmen dieser Arbeit konstruiert und aufgebaut. Einzelheiten hierzu sind im experimentellen Kapitel zu finden. <br><br> Der wissenschftliche Teil beginnt mit Untersuchungen von Quantentrogeffekten in der elektronischen Struktur einer Ag-Schicht auf Ni(111)-Substrat. Charakteristische Quantentrogzustaende im Ag-sp-Band wurden in Photoelektronenspektren beobachtet. Die Analyse von schichtdicken- und winkelabhaengiger Photoemission hat neue und wesentliche Informationen ueber die Eigenschaften des Ag/Ni-Systems geliefert. Insbesondere konnte zum ersten Mal eine relative Bandluecke im Ni-Substrat durch das Verhalten der Quantentrogzustaende indirekt vermessen werden. Das ist fuer Ni besonders wichtig, weil es sich bei Ni um ein stark korreliertes Elektronensystem handelt. Die Ergebnisse wurden mit Rechnungen auf der Basis des erweiterten Phasenmodelles verglichen. Der Vergleich ergibt eine Bandluecke, die sehr gut mit ab-initio-Rechnungen auf Basis der lokalen Elektronendichte-Naehrung uebereinstimmen. Dennoch widersprechen die Daten der Ni-Bandstruktur, die direkt mit Photoemission gemessen wird. Diese Kontroverse zeigt deutlich, dass der Unterschied zwischen Theorie und Experiment Korrelationeffekten im Endzustand der Photoemission zugeordnet werden kann. <br><br> Des weiteren wurden Nanosysteme von noch niedrigerer Dimensionalitaet untersucht. Gestufte Oberflaechen W(331) und W(551) wurden als eindimensionale Modellsysteme fuer die Selbstorganisation von Au-Nanoclustern benutzt. Photonenenergieabhaengige Photoemission hat eine neue Oberflaechen-resonanz aufgedeckt, die auf der Basisebene der Terrassen dieser Systeme auftritt. Die Dispersion E(k) von diesem Zustand, die mit winkelaufgeloester Photoemission vermessen wurde, zeigt deutlich die Einwirkung von Umklapp-Effekten. Diese zeigen sich als zwei Parabeln, die relativ zu der Terrassennormale symmetrisch um die Haelfte der Oberflaechen-Brillouinzone verschoben sind. Die erzielten Ergebnisse sind sehr wichtig fuer das Verstaendnis der elektronischen Eigenschaften von eindimensionalen Nanostrukturen. <br><br> Ausserdem wurde gezeigt, dass W(331) und W(551) als Vorlage fuer selbstorganisierte metallische Nanostrukturen dienen koennen. Eine kombinierte Untersuchung von strukturellen und elektronischen Eigenschaften von unter-monolagen Mengen von Au auf diesen Substraten wurde durchgefuehrt. Es hat sich gezeigt, dass Au mit dem Substrat an der Oberflaeche legieren kann, wenn die Oberflaeche ein wenig oxidiert und die Temperatur erhoert ist. Als Folge formiert sich auf den Stufen eine Nanostruktur von gleichen (aber nicht regelmaessig verteilten) Nanoclustern aus dieser Au-W Legierung. Diese Oberflaechenlegierung bildet ein neuartiges sp-Band in der Naehe der Fermi-Kante. Zudem spaltet dieser neue elektronische Zustand in konstante Energieniveaus auf. Das beobachtete Phaenomen wird als laterale Quantisierung interpretiert. <br><br> Das letzte Kapitel dieser Doktorarbeit bildet auch den Hauptteil. Es handelt von Selbstorganisierungsphaenomenen auf einer Oberflaechenrekonstruktion und den Eigenschaften von so hergestellten Nanostrukturen. Das zweidimensionale Oberflaechen-Karbid W(110)/C-R(15x3) wurde intensiv untersucht. Beobachtete Quantentrogeffekte in der Photoemission in Kombination mit den Ergebnissen der Rastertunnelmikroskopuntersuchungen fuehren zu einem verbesserten Strukturmodell fuer das Oberflaechenkarbid. <br><br> Es wurde auch gezeigt, dass W(110)/C-R(15x3) die Selbstorganisierung von Nanostrukturen mit sehr verschiedenen elektronischen und strukturellen Eigenschaften steuern kann. Es wurde gefunden, dass bei erhoehter Temperatur die R(15x3)-Ueberstruktur die Bildung von Nanostreifen aus unter-monolagiger Au Bedeckung, von denen jede 1 nm breit ist, kontrolliert. Die hergestellten Nanostreifen besitzen eine charakteristische eindimensionale elektronische Struktur mit lateral quantisierten d-Baendern. Basierend auf der Photoemission von Rumpfniveaus wird eine Kohlenstoff-induzierte Oberflaechenlegierung zwischen Au und W als Grund fuer die beobachtete Organisierung vorgeschlagen. Solche Phaenomene sind sehr wichtig fuer Anwendungen, seit die Mikroelektronik in den nm-Massstab eingetreten ist, in welchem mit Quantentrogeffekten zu rechnen ist. <br><br> Zusaetzlich wurde die Bildung von perfekt uniformen molekularen Nanoclustern von C<sub>60</sub> auf W(110)/C-R(15x3) demonstriert. Dieses Phaenomen kann im van-der-Waals Formalismus beschrieben werden. Die berichteten Ergebnisse sind eine erstmalige experimentelle Beobachtung von zweidimensionalen Fulleren-Nanoclustern mit "magischen Zahlen". Berechnungen der Clusterpotentiale in der statischen Naeherung im Girifalco-Modell zeigen Minima der Wechselwirkungsenergie fuer Cluster aus 4 und 7 C<sub>60</sub>-Molekuelen. Diese "magischen Zahlen" sowie die entsprechenden Clusterkonfigurationen sind vollkommen konsistent mit den Ergebnissen des STM-Experiments.
68

Microwave filters with high stop-band performance and low-loss hybrid developement

U-yen, Kongpop 17 November 2006 (has links)
This dissertation contains two significant investigations. One is the development of the broadband microwave bandpass filters with high out-of-band performance. The other is the development of low-loss hybrids. These researches are parts of the National Aeronautic and Space Administrator (NASA)s mission to explore the universe. The former is focused on the techniques used in microstrip line bandpass filter design that help achieving both low in-band insertion loss and high out-of-band attenuation level. Moreover, these filters achieve very broadband out-of-band attenuation bandwidth. These techniques are related to the improvement of stepped impedance resonators, coupling between resonators and effective methods to allocate transmission zeros to suppress filters out-of-band spurious responses. The later is focused on the techniques used in planar magic-T designs such that the developed magic-T obtains high isolation between port E (difference port) and port H (sum port). Moreover, it obtains low-loss and broadband characteristics. These techniques are related to the development of the low-loss broadband microstrip-toslotline (MS-to-SL transition and the magic-T with a highly symmetric structure. The theoretical analysis and experimental measurements have been performed. The experimental results of both the filter and magic-T researches show significant improvement over their prior state-of-the-art designs by number of magnitude. The designs also reduce fabrication complexity.
69

Automated Planning and Scheduling for Industrial Construction Processes

Hu, Di Unknown Date
No description available.
70

Suspension dewatering: characterisation and optimisation

Usher, Shane Patrick Unknown Date (has links) (PDF)
The alumina industry produces a significant quantity of bauxite residue suspension (red mud) that must be washed and dewatered in trains of thickeners and residue disposal areas to recover valuable alumina and sodium hydroxide. The Australian Alumina Industry have come together to sponsor a project to address waste minimisation and environmental impact issues collectively through the optimisation of dewatering in their washer trains and residue disposal areas. The project aims to maximise thickener underflow and tailings dam solids concentrations. (For complete abstract open document)

Page generated in 0.3634 seconds