Dissertations / Theses on the topic 'Layered'
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1
Wibom, Erika. "Layered space." Thesis, KTH, Arkitektur, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-281394.
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A thesis project that investigates layeredness in space in a museum for sketches on Djurgården in Stockholm. The thesis tries to explore spatial overlay, and how space can be created with the intention of achieving layered qualities. References of layered space have been gathered and investigated in order to further the analysis. The program of the sketch museum corresponds with the thesis question and is intended to act as another driving factor in the investigation.
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Suderman, Matthew. "Layered graph drawing." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86054.
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A layered graph drawing is a two-dimensional drawing of a combinatorial graph in which the vertices lie on a given set of horizontal lines. Such drawings are used in application domains such as software engineering, bioinformatics, and VLSI design. In addition to being layered, drawings in these applications may also satisfy other constraints, for example bounds on the number of edge crossings. The problems related to obtaining these drawings are almost always NP -hard, so, in this thesis, we investigate restricted versions of these problems in order to find efficient algorithmic solutions that can be used in practice.As a first very drastic restriction, we consider layered drawings that are planar. Even with this restriction, however, the resulting problems can still be NP -hard. In addition to proving one such hardness result, we do succeed in deriving efficient algorithms for two problems. In both cases, we correct previously published results that claimed extremely simple and efficient algorithmic solutions to these problems. Our solutions, though efficient as well, show that the truth about these problems is significantly more complex than the published results would suggest.
We also study non-planar layered drawings, particularly drawings obtained by crossing minimization and minimum planarization. Though the corresponding problems are NP -hard, they become tractable when the value to be minimized is upper-bounded by a constant. This approach to obtaining tractable problems is formalized in a theory called parameterized complexity, and the resulting tractable problems and algorithmic solutions are said to be fixed-parameter tractable ( FPT ). Though relatively new, this theory has attracted a rapidly growing body of theoretical results. Indeed, we derive original FPT algorithms with the best-known asymptotic running times for planarization in two layer drawings.
Because parameterized complexity is so new, little is known about its implications to the practice of graph drawing. Consequently, we have implemented a few FPT algorithms and compared them experimentally with previously implemented approaches, especially integer linear programming (ILP). Our experiments show that the performance of our FPT planarization algorithms are competitive with current ILP algorithms, but that, for crossing minimization, current ILP algorithms remain the clear winners.
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Chikan, Viktor. "Layered semiconductor nanoparticles /." Search for this dissertation online, 2002. http://wwwlib.umi.com/cr/ksu/main.
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Sturniolo, Rebecca Lynn. "A Layered Whole." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/93286.
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a series of sectional graphics are created to represent the architectural whole. this thesis is about how a three dimensional architecture is seen and perceived through use of two dimensional graphics. it is about understanding a finished work [the whole] by viewing its individual sectional layers [the parts]. a whole does not exist without its parts, just as architecture would not exist without section. in this case, the section is raised above all other things in order to see the potential of the whole.Master of Architecture
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Cai, Qingbo. "Layered Multicast Scheduling." Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1205436479.
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Al-Shahrani, Abdullah A. "Layered silicate nanocomposites." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492712.
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Over the past decade, nanomaterials have been the subject of enormous interest. Notable for their extremely small feature size, they have the potential for wide-ranging industrial applications. Using such materials combined with epoxy resin to synthesise nanocomposite is proposed to enhance the corrosion protection performance of the resin.
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Powell, Loreen Marie. "Elementary Educator's Experiences with Learning Object Repository Interfaces: Layered and Non-Layered." NSUWorks, 2007. http://nsuworks.nova.edu/gscis_etd/777.
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Learning object repositories (LORs) have the potential to improve education at the elementary school level. However, elementary educators are not effectively using LORs due to usability issues regarding their interface. The goal of this dissertation was to examine elementary educator experiences regarding a layered and non-layered interface.
This study was conducted over two academic quarters. A total of 49 elementary educators completed the study. Participants were divided into control and experimental groups. The groups were assigned a different LOR. Participants were asked to use the LOR and record their experiences of the LOR. Data were collected via a demographic survey, time diary, and interviews. Hypothesis 1, which examined the number of Learning Objects (LOs) incorporated into lesson plans between groups was tested using an Analysis of Variances (ANOV A); and a significant difference was found between groups. The experimental group had greater success in incorporating LORs into the lesson plans than the control group. Hypothesis 2, which examined the main effect of the number of times the LOR was used, the number of generated LOs, and the number of good quality LOs found between groups was tested using a Multiple Analysis of Variance (MANOVA); and a significant difference was found between groups. The experimental group had greater success than the control group. Additional ANOVAs were conducted to individually examine the number of times the LOR was used, the number of generated LOs, and the number of good quality LOs found between groups. No significant differences were found. Hypothesis 3, which examined the correlation between age, gender, experience, comfort level and skill level, and the number of LOs incorporated into lesson plans, was tested using an Intra Class Correlation (ICC); no significant difference was found between groups. Data gathered through interviews were analyzed using the constant comparison method. The qualitative findings supported the quantitative findings and helped to identify additional factors including time and limited LOR knowledge that are affecting the usage of the LORs.
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Chen, Jack Szu-Shen. "Distortion-free tolerance-based layer setup optimization for layered manufacturing." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/27268.
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Layer manufacturing has emerged as a highly versatile process to produce complex parts compared to conventional manufacturing processes, which are either too costly to implement or just downright not possible. However, this relatively new manufacturing process is characterized by a few outstanding issues that have kept the process from being widely applied. The most detrimental is the lack of a reliable method on a computational geometry level to predict the resulting part error. Layer setup with regard to the contour profile and thickness of each layer is often rendered to operator-deemed best. As a result, the manufactured part accuracy is not guaranteed and the build time is not easily optimized. Even with the availability of a scheme to predict the resulting finished part, optimal layer setup cannot be determined. Current practice generates the layer contours by simply intersecting a set of parallel planes through the computer model of the design part. The volumetric geometry of each layer is then constructed by extruding the layer contour by the layer thickness in the part building direction. This practice often leads to distorted part geometry due to the unidirectional bias of the extruded layers. Because of this, excessive layers are often employed to alleviate the effect of the part distortion. Such form of the distortion, referred to as systematic distortion, needs to be removed during layer setup. This thesis proposes methods to first remove the systematic distortion and then to determine the optimal layer setup based on a tolerance measure. A scheme to emulate the final polished part geometry is also presented. Case studies are performed in order to validate that the proposed method. The proposed scheme is shown to have significantly reduced the number of layers for constructing an LM part while satisfying a user specified error bound. Therefore, accuracy is better guaranteed due to the existence of error measure and control. Efficiency is greatly increased.
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Lee, V. "Layered stratified shear flows." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364874.
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Işık, Kıvanç Tanoğlu Metin. "Layered silicate/polypropylene nanocomposites/." [s.l.]: [s.n.], 2006. http://library.iyte.edu.tr/tezler/master/makinamuh/T000532.pdf.
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Lee, Kayi (Edmund Kayi) 1977. "Survivability in layered networks." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/63074.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 195-204).
In layered networks, a single failure at the lower (physical) layer may cause multiple failures at the upper (logical) layer. As a result, traditional schemes that protect against single failures may not be effective in layered networks. This thesis studies the problem of maximizing network survivability in the layered setting, with a focus on optimizing the embedding of the logical network onto the physical network. In the first part of the thesis, we start with an investigation of the fundamental properties of layered networks, and show that basic network connectivity structures, such as cuts, paths and spanning trees, exhibit fundamentally different characteristics from their single-layer counterparts. This leads to our development of a new crosslayer survivability metric that properly quantifies the resilience of the layered network against physical failures. Using this new metric, we design algorithms to embed the logical network onto the physical network based on multi-commodity flows, to maximize the cross-layer survivability. In the second part of the thesis, we extend our model to a random failure setting and study the cross-layer reliability of the networks, defined to be the probability that the upper layer network stays connected under the random failure events. We generalize the classical polynomial expression for network reliability to the layered setting. Using Monte-Carlo techniques, we develop efficient algorithms to compute an approximate polynomial expression for reliability, as a function of the link failure probability. The construction of the polynomial eliminates the need to resample when the cross-layer reliability under different link failure probabilities is assessed. Furthermore, the polynomial expression provides important insight into the connection between the link failure probability, the cross-layer reliability and the structure of a layered network. We show that in general the optimal embedding depends on the link failure probability, and characterize the properties of embeddings that maximize the reliability under different failure probability regimes. Based on these results, we propose new iterative approaches to improve the reliability of the layered networks. We demonstrate via extensive simulations that these new approaches result in embeddings with significantly higher reliability than existing algorithms.
by Kayi Lee.
Ph.D.
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Chisem, Ian. "Modified layered double hydroxides." Thesis, University of Cambridge, 1996. https://www.repository.cam.ac.uk/handle/1810/272599.
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Gibson-Robinson, Thomas. "Analysing layered security protocols." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:35c9e4e5-6540-4e1d-9fcc-a98f8f60c20a.
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Many security protocols are built as the composition of an application-layer protocol and a secure transport protocol, such as TLS. There are many approaches to proving the correctness of such protocols. One popular approach is verification by abstraction, in which the correctness of the application-layer protocol is proven under the assumption that the transport layer satisfies certain properties, such as confidentiality. Following this approach, we adapt the strand spaces model in order to analyse application-layer protocols that depend on an underlying secure transport layer, including unilaterally authenticating secure transport protocols, such as unilateral TLS. Further, we develop proof rules that enable us to prove the correctness of application-layer protocols that use either unilateral or bilateral secure transport protocols. We then illustrate these rules by proving the correctness of WebAuth, a single-sign-on protocol that makes extensive use of unilateral TLS. In this thesis we also present a full proof of the model's soundness. In particular, we prove that, subject to a suitable independence assumption, if there is an attack against the application-layer protocol when layered on top of a particular secure transport protocol, then there is an attack against the abstracted model of the application-layer protocol. In contrast to existing work in this area, the independence assumption consists of eight statically-checkable conditions, meaning that it can be checked statically, rather than having to consider all possible runs of the protocol. Lastly, we extend the model to allow protocols that consist of an arbitrary number of layers to be proven correct. In this case, we prove the correctness of the intermediate layers using the high-level strand spaces model, by abstracting away from the underlying transport-layers. Further, we extend the above soundness results in order to prove that the multi-layer approach is sound. We illustrate the effectiveness of our technique by proving the correctness of a couple of simple multi-layer protocols.
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Sainani, Varsha. "Hybrid Layered Intrusion Detection System." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_theses/44.
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The increasing number of network security related incidents has made it necessary for the organizations to actively protect their sensitive data with network intrusion detection systems (IDSs). Detecting intrusion in a distributed network from outside network segment as well as from inside is a difficult problem. IDSs are expected to analyze a large volume of data while not placing a significant added load on the monitoring systems and networks. This requires good data mining strategies which take less time and give accurate results. In this study, a novel hybrid layered multiagent-based intrusion detection system is created, particularly with the support of a multi-class supervised classification technique. In agent-based IDS, there is no central control and therefore no central point of failure. Agents can detect and take predefined actions against malicious activities, which can be detected with the help of data mining techniques. The proposed IDS shows superior performance compared to central sniffing IDS techniques, and saves network resources compared to other distributed IDSs with mobile agents that activate too many sniffers causing bottlenecks in the network. This is one of the major motivations to use a distributed model based on a multiagent platform along with a supervised classification technique. Applying multiagent technology to the management of network security is a challenging task since it requires the management on different time instances and has many interactions. To facilitate information exchange between different agents in the proposed hybrid layered multiagent architecture, a low cost and low response time agent communication protocol is developed to tackle the issues typically associated with a distributed multiagent system, such as poor system performance, excessive processing power requirement, and long delays. The bandwidth and response time performance of the proposed end-to-end system is investigated through the simulation of the proposed agent communication protocol on our private LAN testbed called Hierarchical Agent Network for Intrusion Detection Systems (HAN-IDS). The simulation results show that this system is efficient and extensible since it consumes negligible bandwidth with low cost and low response time on the network.
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Marcellini, Moreno. "Magnetic Ordering in Layered Magnets." Doctoral thesis, Uppsala universitet, Materialfysik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8604.
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The preparation of layered magnets needs the knowledge of growth techniques which are focused on the growth of Fe/V(001) superlattices. Such films have been structurally investigated by X-rays reflectivity and diffraction. The magnetic investigations have been carried out by magneto-optic Kerr effect (MOKE), Superconducting Quantum Interference Device (SQUID) magnetometry and polarized neutron reflectivity (PNR). This latter technique has been used in cooperation with the Institute Laue Langvin (Grenoble, France) and Ruhr Universität (Bochum, Germany). The cross-over in universality class is shown in a series of layered magnets where a δ-doping layer of Fe has been embedded between two layers of Pd showing that the magnetization depends on the effective magnetic thickness of the polarized Pd. A model for the cross-over has been developed in terms of magnetic excitations. The interlayer exchange coupling (IEC) mediated by a non-magnetic spacer has been reviewed focusing the attention on the recent theoretical and experimental works based on Fe/V(001) superlattices. The IEC can be tailored at will by reversibly alloying of the spacer with H: this has been proved in Fe/V(001) double layers showing that in the two dimensional limit, the universality class is not affected by the coupling. The magnetic order-disorder transitions in Fe/V(001) superlattices do not seem to belong to any universality class. A phenomenological model which accounts for the effective coupling at the boundaries has been developed. The influence of the inherent ordering temperatures of single magnetic layers has been investigated in Fe/V(001) superlattices proving that the weakest ferromagnetic layer affects the overall magnetic ordering. A new kind of layered magnet has been developed to increase the effect of the boundaries. PNR measurements show that the universality class depends on which length-scale is investigated.
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Kopp, Gail D. "Key factors and layered instruction." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0015/NQ54793.pdf.
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Mokaya, Robert. "Layered materials as selective adsorbents." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260454.
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Selkin, Peter Aaron. "Archean paleointensity from layered intrusions /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2003. http://wwwlib.umi.com/cr/ucsd/fullcit?p3100370.
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Seale, Sandra Hull. "Dynamic loads in layered halfspaces." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/70618.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.
Bibliography: leaves 209-213.
by Sandra Hull Seale.
Ph.D.
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Josepha, Elisha A. "Topochemical Manipulation of Layered Perovskites." ScholarWorks@UNO, 2011. http://scholarworks.uno.edu/td/464.
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Topochemical strategies, techniques that allow one to effectively manipulate the structures of nonmolecular solids once a crystal lattice is established, are effective in the low temperature (< 500 °C) modification of solid state structures, allowing the preparation of nonmolecular compounds not accessible by standard synthetic routes. Some of the techniques, ion exchange, intercalation/deintercalation, have proven to be excellent synthetic methods for preserving specific frameworks. The combination of these techniques can allow one to create a multistep approach that can be used to design new compounds with interesting properties.
As an expansion to the field of topotactic reactions, a multistep approach was developed towards the synthesis of the new compounds (A xM0.5Cly)LaNb2O7 (where A = Rb, Cs; M = Fe, Ni; x ≈ 1.5;y ≈ 1) at temperatures below 400oC. The first reaction step involved the ion exchange of the host materials (ALaNb2O7, A = Rb, Cs) to form the products M0.5LaNb2O7 (where M = Fe, Ni), a structure open to further chemistry. The next step involved reductive intercalation with Rb or Cs metal to form the air sensitive mixed-valence products with the nominal compositions, A1.5M0.5LaNb2O7. The last step involved the oxidative intercalation of chlorine using chlorine gas to obtain the final compounds. This multistep approach is a design to form mix-metal halide layers, specifically those with divalent cations, within layered perovskites, opening the doors to compounds that can have interesting properties.
This reaction series was also applied to the tantalate layered oxides, leading to the formation of the new compound Ni 0.5LaTa2O7 through ion exchange. The further multistep
topochemical manipulation of this new compound was not successful and was indicative of the difference in chemical behavior of the tantalates versus the niobates.
We have also investigated the oxidative intercalation of halogens into a series of Ruddlesden-Popper (R-P) ruthenate oxides with the formula Ae n+1RunO3n+1 (Ae = Ca, Sr; n = 1, 2, 3) using several sources of fluorine, chlorine, and bromine. A new method was developed to intercalate chlorine into layered systems; this new approach avoids the use of chlorine gas which is highly toxic. The new phase Sr3Ru2O7Cl0.7 was synthesized by the new method and further topotactic manipulations were explored. The chemistry was not limited to the n = 2 phase but was also applied to the n = 3 phase, Sr4Ru3O10.
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Dong, Jingwei. "Electron dynamics in layered materials." Thesis, Institut polytechnique de Paris, 2021. http://www.theses.fr/2021IPPAX019.
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Actuellement,les matériaux lamellaires suscitent un grand intérêt en raison de leurs propriétés électriques et optiques.On peut dire que le domaine de recherche des matériaux à basse dimensionnalité a été initié par la découverte du graphène et c’est rapidement élargi à d'autres matériaux comme les dichalcogénures de métaux de transition,le phosphore noir et le séléniure d'indium.Nos travaux portent sur la dynamique des états excités dans ces composés,ainsi que sur l'évolution de la structure des bandes lors d’un fort dopage de surface.Le manuscrit est organisé comme suit :Lechapitre1 est une introduction générale sur les matériaux lamellaires.En particulier,nous discutons des propriétés structurelles et électroniques des composés plus connus.Lechapitre2 décrit les principes de fonctionnement de la spectroscopique ultra-rapides et montre nombreuses applications sur des matériaux lamellaires.Nous attirons principalement l’attention sur la dynamique des électrons dans les cristaux semi-conducteurs ou avec onde de densité de charge.Lechapitre3 illustre la technique expérimentale que nous avons employée et l’enceinte dans lequel nous avons effectuées les mesures.La dynamique des électrons des matériaux lamellaires a été étudiée au moyen de la spectroscopie photoélectronique résolue en temps et en angle,qui est un outil puissant pour cartographier la structure des bandes électronique et pour suivre la dynamique des électrons photo-injectés via une source laser ultra-rapide. La discussion des données originales de notre travail débute dans lechapitre4.Les mesures TrARPES sur le phosphore noir suivent la distribution électronique dans la bande de conduction en fonction du délai temporale par rapport à l’instant de la photoexcitation.Nos données montrent qu'après thermalisation,les électrons photo-injectés ne produisent pas une diminution de bande d’énergie interdite,ni génèrent-ils une multiplication appréciable du nombre des porteurs.D'autre part,un élargissement Stark de la bande de valence est due à l’écrantage inhomogène d'un potentiel local autour de défauts chargés.Lechapitre5 présente les données ARPES résolues en temps sur une surface de phosphore noir dopée in situ par évaporation des métaux alcalins.Nous mesurons l'effondrement de la bande interdite dans la couche d'accumulation électronique avec une précision inédite et nous observons des états enterrés qui sont détectable à cause de la faible énergie de photons dans notre sonde.Ces états acquièrent une vitesse de bande étonnamment élevée quand la concentration de dopants augmente.Lechapitre6 montre la modification de la dynamique des porteurs chauds lors de la variation du dopage de surface de BP.Dans ce cas, l'analyse proposé est encore préliminaire et doit être complémenté par des calculs ab-initio.Lechapitre7 contient notre travail sur le composé ɛ-InSe.Comme dans le cas de phosphore noir, nous générons une couche d'accumulation de densité électronique variable à la surface du semi-conducteur.En variant le niveau de dopage à partir du limite semi-conducteur jusqu’au limite métallique,nous observons que l’écrantage quantique des phonons optiques longitudinaux n'est pas aussi efficace qu'il le serait dans un système strictement bidimensionnel.Ce résultat indique la présence d’un couplage à distance entre les états confinés à la surface et les phonons polaires du volume.Dans lechapitre8,nous étudions le 1T-TaS2.Ce matériau appartient aux systèmes d'ondes de CDW et a été largement étudié par plusieurs équipes de chercheurs.Dans le 1T-TaS2,la combinaison d'une distorsion structurelle avec des fortes corrélations électroniques conduit à un diagramme de phase complexe et fascinant.Nous reproduisons des données controversées qui ont été récemment publiées dans la littérature et qui identifient une nouvelle instabilité en proximité de la transition métal-isolant.Enfin,lechapitre9 résume les conclusions de nos résultats et aborde brièvement les orientations de recherche à venirCurrently,layered materials attract great interest due to their electrical and optical properties. Such crystals display an electronic band structure that strongly depends on the sample thickness.The large tunability of the electronic screening and gap size can be very attracting for the creation of heterostructures whose properties can be designed on demand. We can say that the research field of low dimensional materials has been boosted by the discovery of graphene and quickly has been enlarged to other materials as transition metal dichalcogenides,black phosphorous and Indium selenide.Our work will focus on the excited state dynamics in these compounds,as well as on the evolution of the band structure upon surface doping.The manuscript is organized as follow:Chapter1 provides a general introduction of layered materials.In particular,we discuss the structural and electronic properties of some relevant compounds.Chapter2 describes the principles of ultrafast spectroscopic methods and shows many applications to the case of the layered materials.We mainly focus our attention on the electron dynamics in semiconducting crystals and charge density waves systems. The electron dynamics of layered materials have been investigated by means of time-and angle-resolved photoelectron spectroscopy (TrARPES),which is a powerful tool to directly map the electronic band structure and to follow the dynamics of the electrons photoinjected via an ultrafast laser source.Chapter3 discusses the experimental technique of choice and the setup where we have been performed in the reported measurements.we begin the discussion of our original data in Chapter4.The TrARPES measurements of layered black phosphorus(BP) monitor the electronic distribution in the conduction and valence band as a function of delay time from photoexcitation.The data show that,after thermalization,the photo-injected electrons do not lead to sizable band gap renormalization,neither do they generate an appreciable amount of carrier multiplication.On the other hand,a Stark broadening of the valence band is ascribed to the inhomogeneous screening of a local potential around charge defects.Chapter5 shows time resolved ARPES data on a BP surface that is doped in-situ by means of alkali metals evaporation. We monitor the collapse of the band-gap in the accumulation layer with unmatched accuracy and we observe that the buried states detected by the low energy photons of our probing pulse acquire a surprisingly high band velocity at large dopants concentration.Chapter6 deals with the modification of hot carrier dynamics upon increasing the surface doping of BP.In this case the reported analysis is still preliminary and needs to be backed by ab-initio calculations.Chapter7 contains our work on layered ɛ-InSe.As in the case of BP,we generate an accumulation layer of varying electronic density on the surface of such semiconductor.By spanning the doping level from the semiconducting to the metallic limit,we observe that quantum screening of Longitudinal Optical phonons is not as efficient as it would be in a strictly bidimensional system,indicating a remote coupling of confined states to polar phonons of the bulk.Furthermore,we show that a 3D Fröhlich interaction with Thomas-Fermi screening can be used to mimic the effects of such a remote coupling at the ɛ-InSe surface.In Chapter8,we study the layered 1T-TaS2.This material belongs to the Charge density waves (CDW) systems and has been extensively investigated by several research groups.In 1T-TaS2,the combination of structural distortion with high electronic correlations leads to a complex and fascinating phase diagram.We could reproduce controversial data that have been recently published in the literature and that identify a new instability in proximity of the metal to-insulator transition.Finally,chapter9 summarizes the conclusions of our work and briefly discusses the perspectives of some future directions of research
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Zhao, Jingxian. "Studies of Layered Double Hydroxides." Thesis, University of North Texas, 1995. https://digital.library.unt.edu/ark:/67531/metadc332491/.
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This work concerns some synthetic processes and basic properties of layered double hydroxides (LDHs). A series of LDHs, a family of newly developed materials found to have many potential uses in industry, were investigated in relating to the origin of life on early Earth. In this work, I successfully intercalated some inorganic as well as organic species. Ammonium, accompanied with ferrocyanide ion, can enter the layered space. It was found there were two kin go f intercalated ferrocyanide species: one is that exchanged with anions and became a part of layered double hydroxide, while the other is suggested to be related to ammonium ferrocyanide neutral species. Formaldehyde, ethanolamine and formate can also be involved into LDHs. To improve the crystallinity, homogeneous precipitation method, which used Urea and Hexamine, was employed. The results reveal the success in the case by Urea but not in that by Hexamine. Annealing could also be used for this purpose. However, it needs to be preocessed in its mother liquor; no improvement on the crystallinity if the material has been washed before annealing.
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Wang, Rentong. "Failure mechanism of a brittle layered material." Columbus, Ohio : Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1086210643.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xii, 134 p.; also includes graphics. Includes abstract and vita. Advisor: Noriko Katsube, Dept. of Mechanical Engineering. Includes bibliographical references (p. 121-125).
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Reynolds, Kieran John. "Solution-processed layered inorganic materials as charge-injecting layers in polymer electronic devices." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619686.
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Vempati, Vamsi Krishna. "Texture Evolution In Materials With Layered Crystal Structures." Wright State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=wright1621942851365157.
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Thiesen, Michael Jerome. "A fast layered alternative to kriging." Thesis, Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/thiesen/TheisenM1207.pdf.
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Empirically gathered scientific data often comes in the form of scattered locations, each with an associated measurement. Visualizing scattered data is challenging because we need to estimate the measured values at many regularly spaced intervals in order to render the data to modern displays. Kriging is a common technique for visualizing scattered data that produces high quality output, but is often too slow for large data sets. In this thesis I present Layered Interpolation, an alternative to Kriging based on the idea of fitting fractal noise functions to scattered data. This technique produces output with quality that is comparable to Kriging, but with greatly reduced running time. Layered Interpolation's speed makes it an ideal choice for rendering large scattered data sets to modern high-resolution displays.
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Caliskan, Fatma. "Electromagnetic Analysis of Planar Layered Structures." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5116.
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ELECTROMAGNETIC ANALYSIS OF PLANAR LAYERED STRUCTURES
Fatma Caliskan
169 pages
Directed by Dr. Andrew F. Peterson
The electrical design of microelectronic devices and their packaging is complicated because of non-ideal attributes of the actual circuit realization. Electromagnetic modeling offers the possibility of accurately predicting the electrical performance of devices and reducing the cost associated with the design process. The proposed research concerns extensions of electromagnetic modeling techniques and their application to microelectronic package design. The method of moments (MoM) is utilized as a technique in modeling and analyzing these designs. Recently, an alternate approach called the locally corrected Nystrm method (LCN) has been applied to solve integral equations in electromagnetics. Recent research suggests that the LCN is well-suited for higher-order implementations and does not require cell-to-cell current continuity in the underlying representation. Thus it may offer advantages over the MoM, especially for problems involving complex 3-D structures. If cell-to-cell continuity is not required, nonconforming meshes may offer simpler geometrical modeling. In this proposal, we consider applying the above techniques to problems in package designs, which often involve multilayer structures, solid or perforated ground planes, embedded passive devices such as capacitors and spiral inductors, and interconnects in horizontal or vertical directions. Several examples will be used to illustrate the modeling.
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Forbes, Michael F. "Ultrasonic characterization of layered composite systems." Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/5633.
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Luong, Trân-Quân 1979. "Layered imagery in Chuck Close portraiture." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84057.
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This thesis explores layered imagery in the portraiture of Chuck Close. Portraits that exhibit qualities of layered imagery appear as an integrated whole from a distance, but as the observer approaches the canvas, the figure of the portrait disintegrates into atomic elements that stand on their own. We present a discussion of the perceptual principles that permit the effects of layered imagery, and apply these principles to the creation of systems that emulate Close's blobby and fingerprint styles. We discuss the textural aspects of his portraits that contribute to the effect of layered imagery, and detail methods to reproduce these effects. Finally, we present novel stylised renderings inspired by Close's artwork.
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Gabbianelli, Elena. "Layered periodic metafoundation for seismic isolation." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
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In the present thesis the dynamic response of two structures with different foundation, in particular the periodic foundation, are studied. Based on the parametric study of band of frequency gap two kind of periodic foundation are designed. In particular, the layered periodic foundation composed of several concrete and rubber layers, and the periodic foundation composed of concrete layers with interposed rubber blocks, are considered. To test the effectiveness of the isolation ability of these periodic foundations, the dynamic responses of a concrete frame and of a steel frame with the periodic foundations are evaluated and compared with the response of the structures without the metafoundation. First, the analyses are conducted in the frequency domain in order to be able to define the number of unit cell needed to reach the band gaps, previously defined for the infinite periodic foundation. Then, the analyses with sinusoidal waves, in the time domain, show that the waves cannot propagate in the periodic foundation without being attenuated when the frequencies of the seismic wave fall into the band gap of the periodic foundation. Finally, to illustrate the efficiency of these seismic isolation foundations, different ground motion are applied to the structures. The results show that the seismic responses of the structure with the periodic foundation are greatly attenuated as compared with those of the structure without periodic foundation.
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Becker, Lars-Ole 1973. "High performance epoxy-layered silicate nanocomposites." Monash University, School of Physics and Materials Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/5747.
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Li, Mingzheng. "Interfacial crack problems in layered materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0029/NQ38486.pdf.
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Gallant, Michael David. "Efficient and robust layered video coding." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq61091.pdf.
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Oliveira, Miguel Afonso Magano Hipolito De Jesus. "Electronic properties of layered semiconductor structures." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406392.
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Loader, Charlotte Bree. "Structural properties of multi-layered materials." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342222.
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Goddard, Paul. "Magnetotransport studies of layered metallic systems." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275491.
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Evans, John Simon Owen. "Structural studies on layered intercalation compounds." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386747.
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Bovey, J. "Modified layered silicates as acid catalysts." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596810.
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Three montmorillonites were modified by ion exchange, acid activation and pillaring. The acid activated clays were further pillared with Al, Ti, Zr or Cr polycations to produce pillared acid activated clays. Characterisation techniques included powder X-ray diffraction, FTIR spectroscopy, elemental analysis, N2 porosimetry and thermogravimetry. Characterisation revealed that the properties of the acid activated products were dependent upon the nature of the starting material and the conditions of activation. In turn, the properties of the pillared acid activated derivatives depended upon the particular and activated host and were generally intermediate between those of pillared raw clays and acid activated clays. In general, they possessed higher surface areas, pore volumes and acidities, wider pore size distributions and larger average pore diameters than their pillared raw counterparts. Variation of the pillaring cation revealed that the properties of the pillared acid activated materials depended on the pillar identity. Total surface areas and pore volumes of the Zr pillared materials were higher than those of the A1 pillared and Ti pillared counterparts. In general, Al pillared materials were the most microporous and Ti pillared materials were the most mesoporous. Three different methods reported in the literature were used to produce Ti pillared clays. Two of these methods led to products which did not appear to be pillared and which contained high amounts of precipitated anatase. A third method was successfully employed to produce Ti pillared acid activated clays and Ti pillared raw clays. The thermal stabilities of the products critically depended upon the identity of the host clay. Materials of maximal surface areas with large pore volumes were only formed upon calcination at 400 - 500oC. All the modifications of the original clays resulted in improved catalytic activity for a variety of acid catalysed reactions. In general, Al, Zr and Cr pillared acid activated clays were more active catalysts than their pillared raw counterparts. Ti pillared acid activated clays were, however, slightly less active than Ti pillared raw clays. The activities of the Ti pillared materials were comparable to those of the acid activated clays. In the one case examined, an overall order of activity existed which dependent on the identity of the pillaring cation such that Ti > Zr > Al ≥ Cr.
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Castle, R. C. "Stress sensing in layered ceramic structures." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597363.
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When a ceramic laminate consisting of alternate dielectric and conducting layers is loaded, the dimensions of the laminae will change, leading to a corresponding change in capacitance across the dielectric layers. The effect of mechanical strain on the capacitance of individual dielectric layers was studied by measuring the capacitance changes in the outer layer of Al2O3/Pt and TiO2/Pt laminates loaded in three point bending. Metal conducting layers were used in this work to provide a simple conductor at room temperature, which would be compatible with both ceramic materials. It is shown that in both materials systems the measured capacitance at zero load agrees well with the predicted values for a parallel plate capacitor, and that on loading the capacitance varies linearly with strain. The rate of change of capacitance with strain agrees well with values predicted from dimensional changes in the dielectric layer, and is observed to change sign when the sign of the strain is reversed. The change in capacitance is also observed when the laminates are unloaded and reloaded, and it is shown that the rate of change of capacitance is independent of the loading rate. The measured capacitance is found to be a sensitive function of the a.c. frequency used in the measurement circuit, and it is shown that this is due to the presence of inductance in the circuit which originates from the connecting wires. The rate of change of capacitance with strain is also found to vary significantly with the a.c. frequency. This results from a variation of inductance with strain which is thought to be due to the small movement of the connecting wires when the laminate to which they are attached is deflected in bending. This necessitates the use of low a.c. frequencies at which inductance effects are negligible. The temperature of the dielectric is also found to influence the measured capacitance significantly, and it is shown that in A12O3 this can be overcome by comparing the capacitance of the strained body with another at the same temperature under zero strain. However this technique cannot be used in TiO2 because of the large temperature coefficient of capacitance of this material.
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Adamson, Paul. "Synthesis and characterisation of layered oxychalcogenides." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531943.
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Kwok, Kwok-tung, and 郭國棟. "Hierarchical slice contours for layered manufacturing." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31224544.
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Drees, Jan Yvo. "Magnetism in layered Nickelates and Cobaltates." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-192533.
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Single layered perovskites with the chemical formula La2−xSrxTO4 (T = transition metal) exhibit a variety of intriguing ordering phenomena. The most outstanding is the occurrence of high temperature superconductivity in La2−xSrxCuO4, which can be considered as the prototype system for the more complex cuprates. Some cuprates show incommensurate static charge order at low temperatures [38–40]. For others it is believed that charges are dynamically correlated [39, 147, 259]. Such effects are difficult to measure if the charges fluctuate.
In contrast to the cuprate La2−xSrxCuO4 the isostructural nickelates and cobaltates remain insulating over a wide doping range [112, 134, 135, 138]. While incommensurate charge stripe order is long known for the nickelates, recently also evidence for charge stripes in cobaltates has been published [174].
Single crystal rods, with ≈10cm length and ≈0.8cm diameter, have been grown by the traveling solvent floating zone technique using an optical four mirror furnace. We investigated strontium doped nickelates in the range 0.15 ≤ x ≤ 0.22. In addition, also co-doped nickelates have been investigated. A large number of samples with different doping concentrations enabled us to systematically characterize the sample properties. Powder X-ray diffraction measurements were used to determine the lattice parameters. For the nickelates we could confirm the doping dependence of the lattice constants reported in literature [202].
The main interest for the cobaltate system was in the strontium doping range 1/3 ≤ x ≤ 1/2. It was previously reported that the ab-lattice parameter exhibits an anomalous peak around a Sr doping x ≈ 1/3 [140]. We could not confirm such an anomaly for our samples and, instead, we observe a strictly monotonic doping dependence of the lattice parameters which we attribute to the close to perfect stoichiometry of our samples.
Samples with the 214-layered perovskite structure can be synthesized over a wide range of oxygen off-stoichiometry. However, the oxygen content can have similarly strong influence on the sample properties as strontium doping. It is therefore essential for data interpretation to determine the oxygen off stoichiometry. EDX and WDX measurements were used to confirm the oxygen content in our nickelates to be nearly stoichiometric. The oxygen content determination of the cobaltates is somewhat more difficult. Thermogravimetry measurements in a flow of Ar/H2 confirmed a nearly stoichiometric oxygen content δ in La2−xSrxCoO4+δ for all samples.
We used neutron diffraction measurements to determine the magnetic order in our nickelate samples. In stripe ordered nickelates a small titanium co-doping of the order of 5% is suficcient to supress the incommensurate magnetism and restore antiferromagnetic order. Within the series of zinc co-doped nickelates three samples exhibit an incommensurability epsilon ≈ 1/8, indicating the stabilization of an intermediate stripe pattern with an eightfold unit cell. Compared to the epsilon ≈ 1/3 regime the correlation length is greatly reduced.
The magnon dispersion of two samples within the intermediate stripe phases with epsilon ≈ 1/8 and epsilon ≈ 1/4 has been measured with neutron spectroscopy. The observed dispersion neither resembles the one in the undoped nor the 1/3 strontium doped samples. Despite the amount of disorder in our co-doped nickelate materials there are no clear signs for the emergence of hourglass spectra which is most likely caused by a strong exchange interaction across the holes.
We investigated the charge and magnetic order in the incommensurate regime of La2−xSrxCoO4 with doping 0.33 ≤ x ≤ 0.5 by elastic neutron scattering and hard X-ray synchrotron measurements. In contrast to the established opinion that this phase is characterized by charge stripe order we were able to show that no charge stripes are present. Instead we found that checkerboard charge order, which is most stable at x = 1/2, persists to a much lower doping than previously thought. The absence of charge stripes is also in agreement with the dispersion of the top most Co-O bond stretching phonon mode. Charge order can induce an anomaly in this branch according to the modulation vector ~q. We observed a softening at ~q = (1/2 1/2 0), which is consistent with our expectations for a checkerboard charge ordered phase.
Inelastic neutron measurements revealed an additional high energy part of the hourglass dispersion which has not been reported so far. The entire lowenergy spin excitations that belong to the classical hour-glass dispersion are mostly in-plane excitations, the newly discovered high-energy magnon mode arises from out-of-plane excitations. The resemblance between the low energy excitations below the neck of the hourglass with the excitations in La1.5Sr0.5CoO4 and similarly between the high energy excitations with those observed in La2CoO4 suggests that the observed dispersion is not a single dispersion, but instead consists of two dispersions with distinct origin. In this model the low-energy dispersion arises mainly from magnetic excitations of hole doped regions and the high-energy part would be connected to magnetic excitations within the undoped islands.
The absence of charge stripe order in the insulating cobaltates in combination with an unmagnetic low spin state for Co+3 requires a different explanation for the presence of incommensurate magnetic order. We propose a picture on the basis of the ideal checkerboard charge order of the half doped reference system. Decreasing the strontium concentration requires the replacement of Co+3 by Co+2, effectively resulting in the competition between the antiferromagnetic order of the undoped and the antiferromagnetic order of the half doped compound. The induced frustration can be released by a twisting of magnetic moments away from their antiferromagnetic orientation, ultimately leading to the observed incommensurate magnetic order.
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Beale, Thomas ? W. "Orbital ordering in the layered manganites." Thesis, Durham University, 2006. http://etheses.dur.ac.uk/2741/.
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The interaction between the long range correlations of electrons and the encompassing crystal structure is a key aspect of solid state physics. This thesis studies the long range interactions of the 3D orbitals in the single and bilayered manganites. Orbital ordering and the omnipresent Jahu-Teller distortions appear at low temperatures ill these samples, accompanied by a real-space charge order. The results display different aspects of these long range order phenomena ill Lao.5Sr1.5nO4, Nd1_xSr1+xMn04 where 0.66 >x >0.8, and La2_2x:Sr1+2xMn207where 0.5 > x > 0.7 using different techniques of x-ray diffraction. High energy x-ray diffraction is optimised to detect structural aspects ill materials, and as Audi is sensitive to the Jalm-Teller distortions. Resonant scattering at the Mil к edge is used to study both the structural and the more specific charge and orbital ordering. Finally, soft x-ray resonant diffraction at the Mn L edge is used as a specialised technique for looking at the magnetic and orbital ordering. A small crystal field distortion irt always observed to be present ill the orbitally ordered materials, however the size of the distortion is very large in the single layer Lao.5Sr1.5MnO4aud very small ill the bilayer LaSr2Mn207. Despite this, orbital ordering is observed in both materials. Combining experimental data with theoretical models, suggests that integer charge ordering occurs oil the MnO6 octahedra in both materials within the orbitally ordered regime.
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Lazar, Laura [Verfasser]. "Fe/Pb layered systems / Laura Lazar." Bochum : Universitätsbibliothek, Ruhr-Universität Bochum, 2003. http://d-nb.info/116793296X/34.
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Ghandi, Mohammad Mahdi. "Layered video coding for wireless communications." Thesis, University of Essex, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426012.
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Barkshire, Ian Richard. "Quantitative Auger analysis of layered structures." Thesis, University of York, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306431.
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Smith, S. Alex. "Layered percolation on the complete graph." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1619405931&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Kaya, Elçin Dilek Tanoğlu Metin. "Development of layered silicate/epoxy nanocomposite/." [s.l.]: [s.n.], 2006. http://library.iyte.edu.tr/tezler/master/malzemebilimivemuh/T000538.pdf.
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Thesis (Master)--İzmir Institute Of Technology, İzmir, 2006.Keywords: epoxy resin, nanocomposites, clay, scanning electron microscope, mechanical properties. Includes bibliographical references (leaves. 93-98).
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Fisher, Henry Alexander. "Pharmaceutical applications of layered double hydroxides." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:f2a4490d-c3f6-4953-b994-06a5d191dc98.
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The principle aims of this thesis are to investigate the synthesis of layered double hydroxides (LDHs) for use as drug delivery systems, and to explore the potential of these compounds to provide solutions to typical pharmaceutical problems. In Chapter 1, background information on pharmaceutics and drug delivery is given. LDHs are introduced and their structure, synthesis and general applications described. The biomedical and pharmaceutical applications of LDHs are reviewed. Chapter 2 presents the intercalation of the GABAergic drugs gabapentin and pregabalin into an LDH using the coassembly method. The optimum conditions for the restacking process are investigated, an improved method of anhydrous restacking in ethanol at reduced temperatures is described, and a mechanism is suggested. The stabilising effect of LDH intercalation on the drug ions is measured. Chapter 3 explores the potential for LDHs to stabilise and deliver catecholamine drugs levodopa, carbidopa and methyldopa. The ability of a range of LDHs to intercalate and stabilise these drugs against racemisation and oxidative decomposition across a variety of conditions is reported. In Chapter 4, the potential for LDHs to deliver neutral hydrophobic and cationic drugs through the intercalation of cyclodextrin-drug inclusion complexes is investi- gated. A range of partially substituted anionic cyclodextrins are synthesised and intercalated into an LDH. Cyclodextrin-drug inclusion complexes are intercalated, their interlayer orientation is suggested and drug release measured. In Chapter 5, the potential of polymer-LDH composites for drug delivery is explored. A selection of drug intercalated LDHs from Chapters 2 and 3 are encapsulated in several enteric polymers typically used for drug delivery. The release profiles and stabilising effects of the composites are measured. Chapter 6 details the experimental procedures and analytical instruments used throughout this thesis. The Appendices contain supplementary characterisation and analytical data that are referred to in the main text.
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Morgan, Bo. "A substrate for accountable layered systems." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/91854.
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Thesis: Ph. D., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 193-196).
A system built on a layered reflective cognitive architecture presents many novel and difficult software engineering problems. Some of these problems can be ameliorated by erecting the system on a substrate that implicitly supports tracing the behavior of the system to the data and through the procedures that produced that behavior. Good traces make the system accountable; it enables the analysis of success and failure, and thus enhances the ability to learn from mistakes. This constructed substrate provides for general parallelism and concurrency, while supporting the automatic collection of audit trails for all processes, including the processes that analyze audit trails. My system natively supports a Lisp-like language. In such a language, as in machine language, a program is data that can be easily manipulated by a program, making it easier for a user or an automatic procedure to read, edit, and write programs as they are debugged. Constructed within this substrate is an implementation of the bottom four layers of an Emotion Machine cognitive architecture, including built-in reactive, learned reactive, deliberative, and reflective layers. A simple natural language planning language is presented for the deliberative control of a problem domain. Also, a number of deliberative planning algorithms are implemented in this natural planning language, allowing a recursive application of reflectively planned control. This recursion is demonstrated in a fifth super-reflective layer of planned control of the reflective planning layer, implying N reflective layers of planned control. Here, I build and demonstrate an example of reflective problem solving through the use of English plans in a block building problem domain. In my demonstration an AI model can learn from experience of success or failure. The Al not only learns about physical activities but also reflectively learns about thinking activities, refining and learning the utility of built-in knowledge. Procedurally traced memory can be used to assign credit to those thinking processes that are responsible for the failure, facilitating learning how to better plan for these types of problems in the future.
by Bo Morgan.
Ph. D.