To see the other types of publications on this topic, follow the link: Multilayered systems.
Dissertations / Theses on the topic 'Multilayered systems'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Multilayered systems.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Udo-Chijioke, Onyinyechi. "Aquasomes : multilayered nanoparticular drug delivery systems." Thesis, Aston University, 2016. http://publications.aston.ac.uk/33399/.
Full textAbstract:
Nanoparticulate delivery systems have been widely used in recent decades, available in a wide variety of structures, for targeted drug delivery. They provide controlled and prolonged release for drugs, peptides and biopharmaceuticals. Ceramic nanoparticles are one of the various nanocarriers, which have been employed in local targeted delivery, most commonly in the area of orthopaedic drug delivery to enhance treatment therapies. This thesis therefore focused on the development of aquasomes, a ceramic nanoparticulate carrier system, for the delivery of proteins, growth factors and antibiotics for its potential application in bone regeneration in fracture healing. The suitability of non-aqueous silicone elastomer gels (NASEGs) as a topical/transdermal delivery system for proteins as well as protein-loaded aquasomes was also investigated. Through process optimisation, a suitable lyophilisation method was developed and used for the preparation of bioactive aquasome formulations of growth factors, bone morphogenetic protein (BMP-2), vascular endothelial growth factor (VEGF-121), and antibiotic, gentamicin. Physical characterisation of aquasomes using zeta potential and optimisation of preliminary aquasome formulations were optimised by utilising smaller nanocore sizes. In addition, scanning electron microscopy (SEM), confocal microscopy analysis and entrapment efficiency studies were performed to ascertain the drug loading efficiency of the different aquasome formulations. BMP-2 loading aquasomes exhibited an entrapment efficiency of 98.9% Protein loading on aquasomes yielded a higher negative zeta potential in comparison to blank nanocores. Confocal microscopy images elucidated the behaviour of nanocore particles showing agglomeration of nanocores and the presence of fluorescent drug adsorbed onto nanocores. The bioactivity of the aquasome formulations were analysed via in vitro cell culture model assays and microbiological assays. BMP-2-loaded aquasomes were investigated for enhanced osteogenic proliferation and differentiation effects on osteoblast-like cells, MG63 cells. The enhanced osteogenic effect of HUVECs in co-culture with these cells was also examined. In addition, the committed differentiation of ATMSCs into osteoblasts induced by their exposure to BMP-2 -loaded aquasomes was also investigated. Results exhibited the enhanced osteogenic differentiation effect, analysed by alkaline phosphatase (ALP) secretion (a major biochemical marker of osteoblastic differentiation) from MG63 cells was dependent on the protein loading onto the aquasome formulation. However, differentiation of ATMSCs cultured in osteogenic medium was significantly higher than ATMSCs exposed to BMP-2 or VEGF-121 treatments. Gentamicin-loaded aquasomes were investigated for their antimicrobial activity against Staphylococcus aureus, a major pathogen popularly implicated in cases of osteomyelitis. Results showed that gentamicin released from aquasomes exhibited excellent bactericidal activity against bacterial cultures without any reproduction of bacteria in 24 hours. In conclusion, the aquasome formulations were able to offer controlled release of bioactive antimicrobials and growth factors over a prolonged duration. The amount of bio-actives released was dependent on the loading of the bio-actives in the fabrication process of aquasome formulations. However, minute (ng/μg) amounts of adsorbed growth factor/drug were observed in comparison to the loading (high ng/mg) within the duration of study. It can be inferred these aquasomes can be employed in the sustained local and targeted delivery of antimicrobials and growth factors in orthopaedic treatments for enhanced fracture healing. However, the loading of bio-actives onto aquasome formulations may need to be optimised to increase the amount of bio-actives released to elicit more pronounced pharmacological effects.
2
ZHANG, GUOJUN. "CRYSTALLINE POLYMERS IN MULTILAYERED FILMS AND BLEND SYSTEMS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1404923073.
Full text
3
Ji, Shanzuo. "BIO-INSPIRED POLYMER LENS SYSTEMS FROM MULTILAYERED FILMS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1441292644.
Full text
4
Aram, Michael, and Gustaf Neumann. "Multilayered analysis of co-development of business information systems." Springer London, 2015. http://dx.doi.org/10.1186/s13174-015-0030-8.
Full textAbstract:
Business information systems (BIS) comprise technological (e.g. programs), informational (e.g. content) and social artifacts (e.g. collaboration structures). Typically, such systems are constantly and collectively developed (co-developed) further by a variety of individuals within the organization. By recognizing these varying types of actors (concerning their goals, technical expertise and language means) and their predominantly developed artifact type, one can distinguish two types of subsystems: technical subsystems wherein the development of the system behavior is conducted by software developers; and business subsystems dominated by end-users developing informational artifacts. So far, co-development structures within and between these subsystems are not well understood, especially the aspect that - potentially driven by appropriate measures such as the provision of domain-specific languages - co-development might shift between these subsystems.
This paper presents an approach for characterizing the co-development of real-world BIS with respect to direct participation from different kinds of contributors. This multilayered approach allows us to analyze the co-development with programming languages, domain-specific languages and end-user tools. The approach is suited to assess the direct participation of individuals from different subsystems in the development of evolving BIS. We focus on the intersection of these subsystems, present appropriate metrics and a multilayered analysis scheme. Contributions to artifacts are analyzed using social network analysis to detect structural properties of continuous co-development.
The application to Learn@WU, a real-world BIS, demonstrates how end-user enabling technologies have shifted the co-development effort of the system from a small group of developers to a several orders of magnitude larger group of contributors. We observed an increase of direct participation over time on both informational and executable artifacts, while the number of technical experts was more or less constant.
Our approach may act as a trigger for the application and further development of rigorous instruments for assessing co-development of BIS. (authors' abstract)
5
Kim, Yong-Jun. "Application of polymer/metal multi-layer processing techniques to microelectromechanical systems." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/14987.
Full text
6
Pahirathan, Selvarajah. "Magneto-optical properties of multilayered systems and enhancement of the polar Kerr effect." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318781.
Full text
7
Salamone, Sam. "Densification of and constitutive laws for ceramic matrix composites and multilayered systems /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/10585.
Full text
8
Hamza, Mukhail. "A Quantitative Study of Multilayered Market Systems and Small and Medium-Sized Enterprises." ScholarWorks, 2015. https://scholarworks.waldenu.edu/dissertations/1782.
Full textAbstract:
Small and medium-sized enterprises (SMEs) account for approximately 50% of the world's gross domestic product. However, these economic agents suffer from inadequate access to liquid funds to finance their operations. The liquidity gap has led to early bankruptcy and liquidation, stagnant growth and development, and fewer employment opportunities. The problem under study was the effect of funding limitations on SMEs' business operations and growth. The purpose was to examine the impact of multilayered capital systems as alternative funding for SME growth. This study was informed by Gilbrat's law and the theory of financial exclusion. The research questions addressed the use of a multilayered capital market as a substitute for the conventional methods of funding for SMEs. A survey instrument was used to collect data using a stratified random sample of 54 small-scale business owners and finance professionals. These participants were identified from U.S. Census Bureau data between 2009 and 2014 across the information technology, service, and manufacturing sectors. Multiple regressions and correlation analyses were used to analyze the data. The results showed that age, credit score, average turnover, and total assets have significant impacts on obtaining funding, especially total assets. Moreover, results showed that growth rates correlated with funding from multilayered capital systems. This study contributes positively to social change by highlighting alternative means of funding SMEs, leading to reduced dependency on government, less crime through gainful employment, and improved corporate social responsibility due to better interactions among community members
9
Parra, Martinez Juan Pablo. "On multilayered system dynamics and waves in anisotropic poroelastic media." Doctoral thesis, KTH, VinnExcellence Center for ECO2 Vehicle design, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-195801.
Full textAbstract:
The mechanical and acoustic anisotropy of media is a governing factor in the behaviour of multilayered systems including such media. The understanding of the mechanisms conditioning the dynamic behaviour of multilayered systems is of paramount importance. In particular, the intrinsic anisotropy of poroelastic media presents a potential for the optimal design of systems for multifunctional performances. Indeed, these multilayered systems are bound by stiffness, thermal and acoustic performance constraints in simultaneously. A plane wave method is presented to study the influence of material orientation in the dynamic behaviour of multilayered systems composed of anisotropic poroelastic media. The method is applied to a system composed of an anisotropic open-celled melamine foam core in between two metal sheets. This particular multilayered configuration allows to shed light on phenomena intrinsic to layers composed of anisotropic poroelastic materials, such as the frequency shift of the fundamental resonance of the panel, or the compression-shear coupling effects taking place in the poroelastic core layers. The latter phenomena is of particular importance, as it is evidenced on the unconventional polarisation of waves in anisotropic poroelastic media. Finally, the method is adapted to the optimisation of multilayered systems for acoustic performance. the design variables are consequently the core material orientations with respect to the global coordinate system. The solutions to the optimisation problem are analysed in terms of dynamic behaviour, thus allowing to correlate acoustic performance of the overall structure, and the response of each individual layer.QC 20161110
10
Fromell, Karin. "Nanoscale Reaction Systems." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8249.
Full text
11
Handjis, Petros. "Northern Rhodes sedimentary sequence : a methodology for the hydrogeological assessment of multilayered aquifer systems on the basis of well information." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441536.
Full text
12
Kazanavičius, Vygintas. "Realaus laiko neardančiosios kontrolės signalų apdorojimo sistema." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2005. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2005~D_20050524_145734-54296.
Full textAbstract:
The employment of real time NDT systems has been spread widely last years. It is very important to control in real-time layer thicknesses of multi-layered materials during manufacturing process. In this work multi-layer thickness measurement digital signal processing methods are evaluated. Presented real-time nondestructive testing system and signal propagation model is a background for measurement algorithm analysis and development. In this work multi-layer thickness measurement problem is addressed with a different approach, by applying correlation functions on parts of the ultrasonic signal, thus reducing the overall computational complexity.
13
Chouquet, Caroline. "Élaboration et caractérisation de revêtements type "Diamond-Like Carbon" déposés par un procédé chimique en phase vapeur assisté par un plasma basse fréquence." Thesis, Vandoeuvre-les-Nancy, INPL, 2008. http://www.theses.fr/2008INPL096N/document.
Full textAbstract:
Ce travail de thèse concerne l’étude de différents revêtements type « Diamond-Like Carbon » élaborés par un procédé CVD assisté par un plasma basse fréquence (40 kHz). Deux revêtements de référence sont d’abord étudiés : des couches de carbone amorphe hydrogéné (a-C:H) et des couches de carbure de silicium amorphe hydrogéné (a-SiC:H). L’évolution de leurs propriétés mécaniques (dureté, module d’Young) et tribologiques (frottement, usure) est décrite en fonction des paramètres du procédé et corrélée à leur microstructure. Les résultats obtenus pour ces deux couches de référence sont ensuite exploités pour proposer deux systèmes complémentaires : des revêtements a-C:H dopées et des systèmes multicouche a-C:H/a-SiC:H. Ces deux solutions présentent des contraintes résiduelles réduites par rapport à un revêtement a-C:H monocouche ce qui permet d’envisager une augmentation importante des épaisseurs de dépôt tout en conservant des propriétés mécaniques et tribologiques intéressantes. Enfin, en vue d’une application industrielle de ces revêtements sur des pièces de moteur par exemple, l’optimisation de leur adhérence par insertion de sous-couches adaptées ainsi que de leurs performances tribologiques en conditions lubrifiées par l’intermédiaire de texturation de surface est alors envisagéeHydrogenated amorphous carbon films (a-C:H) and hydrogenated silicon carbide films (a-SiC:H) are deposited by low frequency (40 kHz) plasma enhanced chemical vapour deposition (LF PECVD). Structural, mechanical and tribological properties of those single layers have been first studied in relation with process parameters. Then those results have been used to study two other systems. The first one corresponds to silicon doped a-C:H thin films and the second one to multilayered coatings consisting in a stack of a-C:H and a-SiC:H layers. Those coatings offer potential advantages such as lower residual stress level comparing to that of a-C:H stress level which gives the opportunity to deposit thicker films, and also attractive mechanical and tribological properties. Moreover, in case of applications like car engine parts for example, adhesion and tribological properties under lubrication have to be improved. Solutions as incorporating underlayer or texturing surface are thus also investigated in this study
14
Phongphanphanee, Chai. "Multilayer mobile communication systems." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324001.
Full text
15
Jara, Olivares Angelica Yuliana. "Biocompatible nanostructured multilayer systems." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT222/document.
Full textAbstract:
Le domaine des couches minces fait l’objet d’un grand nombre d’études en raison du vaste champ d’applications. La modification de surfaces par des revêtements sous forme de couches minces a ainsi été étudiée dans le domaine biomédical afin d’améliorer les propriétés de bioactivité et biocompatibilité des matériaux. Des couches minces monocouches, Ta et TaN, ainsi que bi-couches, TaN/Ta, ont été déposées sur des substrats de verre, d’acier, SS316LVM, et de titane par pulvérisation cathodique. La caractérisation des couches par diffraction des rayons X (XRD and GIXRD) a montré que la nature du substrat a une forte influence sur la nature de la phase, Ta, formée. La formation de la phase ordonnée, Ta-a, est obtenue sur le substrat acier alors que la phase désordonnée métastable, Ta-b, se forme sur le substrat titane. Quant à la phase TaN, elle cristallise sous la forme cubique de type NaCl (Fm3m) sur les différents substrats mais présente une orientation préférentielle selon le plan (200) dans le cas du substrat verre. L’étude de la composition chimique par XPS a montré que les couches sont également constituées de phases oxydes, telles que TaxOy et TaOxNy, en raison de la forte affinité du tantale avec l’oxygène. Les observations en microscopie électronique à balayage ont mis en évidence une croissance colonnaire des couches avec une microstructure de surface dite de type « chou-fleur ». Cette microstructure est caractéristique du procédé de pulvérisation cathodique et correspond à la microstructure dite de zone I prédite par le modèle de Thornton, dérivé du modèle de Movchan and Demchishin. Des méthodes biomimétiques ont été utilisées afin d’évaluer la bioactivité des couches minces étudiées. Dans ce but, les échantillons ont été immergés dans un fluide biologique (SBF, Simulated Body Fluid) afin de promouvoir le dépôt de phosphate de calcium. Après étude de fluides de compositions différentes, le fluide SBF 1.5, enrichi en ions Ca2 + and PO43-, a été choisi. Les analyses par XRD, FTIR et XPS ont mis en évidence la formation en surface d’une couche cristalline d’hydroxyapatite quelle que soit la nature des sous-couches, Ta, TaN ou TaN/Ta, après immersion de trois semaines. Le mécanisme de dépôt d’hydroxyapatite implique la formation de liaisons Ta-OH par hydratation de la couche passive d’oxyde de tantale présente en surface.Pour étudier les propriétés de biocompatibilité, les échantillons ont été placés en milieux de culture contenant des ostéoblastes. Tous les matériaux observés présentent une adhésion des cellules en surface avec la formation de filipodia. L’un des principaux problèmes des implants osseux est la formation en surface d’un biofilm du à la colonisation de bactéries. Des essais en milieu bactériologique ont donc été réalisés avec des bactéries de type Pseudomonas Aeruginosa, agents pathogènes très fréquemment observés lors d’opérations chirurgicales. Ces essais expérimentaux ont permis de déterminer la réaction des différents matériaux étudiés au contact de ces bactéries. Il s’est avéré que l’adjonction de couches de tantale permet de réduire fortement la formation de bio-films en comparaison avec des couches de titane, qui présentent une croissance importante de bio-films à base de P. aeruginosa.Des films minces de silice ont également été étudiés en tant qu’agents bactéricides. Ces études ont montré l’absence de colonies microbiennes et l’absence de la formation de bio-films en surfaceThin films have been the subject of intense study in materials because they offer multiple applications of great interest. Various surfaces have been modified with thin films or coatings to study how to improve their bioactivity and biocompatibility properties to form a biomaterial. Thin films of Ta, TaN and Ta/TaN were deposited on glass substrates, metallic substrates, SS316LVM and Ti, by RF Sputtering technique. By High angle XRD and GIXRD it was found that the nature of the substrate has a strong influence on the Ta phase formed. Formation of ordered α-Ta phase was obtained on SS316LVM, but the disordered metastable β-Ta phase was formed on Ti and on TaN substrates. While TaN crystallizes in the cubic phase (Fm3m) NaCl type on metallic substrates but shows a preferential orientation in the (200) plane on the glass substrate. The chemical analysis of the surfaces by XPS reveals that in the surfaces of the deposited layers are several oxidized chemical species such as Ta2O5, TaOxNy TaxOy due to Ta is a very reactive metal and is readily oxidized even at low partial pressures as for our synthesis conditions. Characterization by Scanning Electron Microscopy reveals that the microstructure of the films was homogeneous with small clusters size and a cauliflower type, also the films exhibit the typical columnar growth for films deposited by PVD techniques, following the growth of zone I described by the model developed by Movchan and Demchisin and Thornton. Biomimetic method was used to evaluate the bioactivity in all surfaces which involves immersing the thin films in simulated body fluid (SBF) to promote the deposition of calcium phosphates, two concentrations were used to assess qualitatively which could deposit the stoichiometric calcium phosphate hydroxyapatite and make it more efficiently. The SBF 1.5 enriched in Ca2 + and PO43- ions was chosen. A new layer was deposited upon the surfaces and it was determined by XRD, FTIR and XPS that crystalline Hydroxyapatite phase was formed, so that all our surfaces have the ability to form apatite spontaneously after an immersion period of three weeks. The mechanism of deposition of HAp involves the formation of small amounts of Ta-OH groups by a hydration of the tantalum oxide passive layer on its surface. To study biocompatibility properties, films were placed in cell culture containing osteoblasts, all surfaces exhibit cell adhesion and formation of filipodia. Whereas one of the main problems of bone implants is biofilm formation caused by bacterial colonization, tests were made with the bacterium Pseudomonas Aeruginosa, which is a major human opportunistic pathogens in surgical procedures, causing infections in soft tissue, bones, among others. This assay allowed us to know how the different surfaces react when exposed to this bacteria, Titanium had greater growth of P. aeruginosa and biofilm formation in all periods of study, while Ta surfaces showed the lowest activity of biofilm formation. Mesoporous silica thin films where used as bactericidal agents, and it was found by MEB that no microbial colonization or biofilm formation occur on these surfaces
16
Rajaram, Srinath. "Multilayer Nanomagnetic Systems for Information Processing." Scholar Commons, 2014. http://scholarcommons.usf.edu/etd/5109.
Full textAbstract:
The Spin-Transfer Torque Magnetoresistive Random Access Memory (STT-MRAM) has opened new doors as an emerging technology with high potential to replace traditional CMOS-based memory technology. This has come true due to the density, speed and non- volatility that have been demonstrated. The STT-MRAM uses Magnetic Tunnel Junction (MTJ) elements as non-volatile memory storage devices because of the recent discovery of spin-torque phenomenon for switching the magnetization states. The magnetization of the free layer in STT-MRAM can be switched from logic "1" to logic "0" by the use of a spin-transfer torque. However, the STT-MRAMs have till now only been used as universal memory. As a result, STT-MRAMs are not yet commercially used as computing elements, though they have the potential to be used as Logic-In-Memory computation applications.
In order to advance this STT-MRAM technology for computation, we have used different MRAM devices that are available as memory elements with different geometries, to use it as computing elements. This dissertation presents design and implementation of such devices using different multilayer magnetic material stacks for computation. Currently, the design of STT-MRAMs is limited to only memory architectures, and there have been no proposals on the viability of STT-MRAMs as computational devices. In the present work, we have developed a design, which could be implemented for universal logic computation. We have utilized the majority gate architecture, which uses the magneto-static interaction between the freelayers of the multilayer nanomagnets, to perform computation.
Furthermore, the present work demonstrates the study of dipolar interaction between nanomagnetic disks, where we observed multiple magnetization states for a nanomagnetic disk with respect to its interaction energy with its neighboring nanomagnets. This was achieved by implementing a single layer nanomagnetic disk with critical dimension selected from the phase plot of single domain state (SDS) and vortex state (VS). In addition, we found that when the interaction energy between the nanomagnetic disks with critical dimension decreases (increase in center-to-center distance) the magnetization state of the nanomagnetic disks changes from single domain state to vortex state within the same dimension. We were able to observe this effect due to interaction between the neighboring nanomagnets.
Finally, we have presented the design and implementation of a Spin-Torque driven Re- configurable Array of Nanomagnets (STRAN) that could perform Boolean and non-Boolean computation. The nanomagnets are located at every intersection of a very large crossbar array structure. We have placed these nanomagnets in such a way that the ferromagnetic free layers couple with each other. The reconfigurable array design consists of an in-plane (IP) free layer and a fixed polarizer [magnetized out-of-plane (OP)]. The cells that need to be deselected from the array are taken to a non-computing oscillating state.
17
Walz, Andrew R. "A multilayer network approach to quantifying biologically-derived systematic risk in biomedical finance." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107356.
Full textAbstract:
Thesis: S.M. in Engineering and Management, Massachusetts Institute of Technology, School of Engineering, System Design and Management Program, Engineering and Management Program, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 100-106).
Sharply rising disease prevalence and associated healthcare costs are placing an increasingly significant economic burden on society. Biomedical research and industry have struggled to adequately address this challenge, as evidenced by the stagnation and even decline of new therapeutics development success rates. Recent work in the MIT Laboratory for Financial Engineering has explored the potential of using financial engineering in the form of biomedical "megafunds" to help tackle this problem. New methods will be needed to better assess systematic financial risks for these therapeutic project portfolios. This primarily methodological thesis seeks to explore the opportunity to leverage multilayer network models as tools to help measure this risk, specifically the biologically-derived component of risk resulting from project correlations generated through the underlying biological networks. Historical examples of coupling between drug development projects are used to motivate a framework in which project correlations emerge from a combination of indication and target similarity. This framework motivates the construction of a multilayer network model, drawing upon multiple systems biology databases for its construction and using a sample of FDA orphan designations as a representative project set. Using shortest path distance and Random Walk with Restart (RWR) relevance, indication and target similarity between projects are quantitatively evaluated. Comparing average sales correlations to the log of average RWR relevance for classes of compounds reveals notable relationships between correlation and network similarity. This relationship is shown to be stronger for the case of disease relevance (R2 = 0.99) than for target relevance (R2 = 0.93). A potential approach is finally described for integrating biological network similarity with financial models useful for portfolio analysis, and implications on portfolio selection are discussed through synthetic construction of hypothetical orphan drug portfolios..
by Andrew R. Walz.
S.M. in Engineering and Management
18
KRISHT, MUHAMMED HUSSEIN, and MUHAMMED HUSSEIN KRISHT. "LPCVD TUNGSTEN MULTILAYER METALLIZATION FOR VLSI SYSTEMS." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/187983.
Full textAbstract:
Advances in microlithography, dry etching, scaling of devices, ion-implantation, process control, and computer aid design brought the integrated circuit technology into the era of VLSI circuits. Those circuits are characterized by high packing density, improved performance, complex circuits, and large chip sizes. Interconnects and their spacing dominate the chip area of VLSI circuits and they degrade the circuit performance through the unacceptable high time delays. Multilayer metallization enables shorter interconnects, ease of design and yet higher packing density for VLSI circuits. It was shown in this dissertation that, tungsten films deposited in a cold-wall LPCVD reactor offer viable solution to the problems of VLSI multilayer interconnects. Experiments showed that LPCVD tungsten films have good uniformity, high purity, low resistivity, low stress-good adherence and are readily patterned into high resolution lines. Moreover, a multilayer interconnect system consisting of three layers of tungsten metallization followed by a fourth layer of aluminum metallization has been designed, fabricated and tested. The interlevel dielectric used to separate the metal layers was CVD phosphorus doped silicon dioxide. Low ohmic contacts were achieved for heavily doped silicon. Also, low resistance tungsten-tungsten intermetallic contacts were obtained. In addition to excellent step coverage, high electromigration resistance of interconnects was realized. Finally, CMOS devices and logic gates were successfully fabricated and tested using tungsten multilayer metallization schemes.
19
Chung, David. "Development of system level integration of compact RF components on multilayer liquid crystal polymer (LCP)." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42763.
Full textAbstract:
A system packaging level approach on liquid crystal polymer (LCP) was proposed for low cost, lightweight, and compact wireless communication systems. Via technology was explored for V-band W-band transitions and an active cooling system that are essential for compact multilayer integration. RF MEMS switches were fabricated and integrated at the component level to enable multi-functional devices with optimal performance. A pattern reconfigurable antenna for MIMO applications and 3D phase shifters for phased array antennas that use RF MEMS switches were presented. In addition, a lightweight expandable array was designed and measured with up to 256 elements on multilayer LCP integrated at the system level. Furthermore, a 60 GHz multilayer transceiver front end device with simultaneous transmit and receive was designed and measured for low cost 60 GHz applications. The wide variety of multilayer LCP applications integrated at the system level shows a promising future for the next generation low cost lightweight wireless communication systems.
20
Kyselov, Mykola. "Phenomenological theories of magnetic multilayers and related systems." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-63594.
Full textAbstract:
In this thesis multidomain states in magnetically ordered systems with competing long-range and short range interactions are under consideration. In particular, in antiferromagnetically coupled multilayers with perpendicular anisotropy unusual multidomain textures can be stabilized due to a close competition between long-range demagnetization fields and short-range interlayer exchange coupling. These spatially inhomogeneous magnetic textures of regular multidomain configurations and irregular networks of topological defects as well as complex magnetization reversal processes are described in the frame of the phenomenological theory of magnetic domains. Using a modified model of stripe domains it is theoretically shown that the competition between dipolar coupling and antiferromagnetic interlayer exchange coupling causes an instability of ferromagnetically ordered multidomain states and results in three possible ground states: ferromagnetic multidomain state, antiferromagnetic homogeneous and antiferromagnetic multidomain states. The presented theory allows qualitatively to define the area of existence for each of these states depending on geometrical and material parameters of multilayers. In antiferromagnetically coupled superlattices with perpendicular anisotropy an applied magnetic bias field stabilizes specific multidomain states, so-called metamagnetic domains. A phenomenological theory developed in this thesis allows to derive the equilibrium sizes of metamagnetic stripe and bubble domains as functions of the antiferromagnetic exchange, the magnetic bias field, and the geometrical parameters of the multilayer. The magnetic phase diagram includes three different types of metamagnetic domain states,
namely multidomains in the surface layer and in internal layers, and also mixed multidomain states may arise. Qualitative and quantitative analysis of step-like magnetization reversal shows a good agreement between the theory and experiment. Analytical equations have been derived for the stray field components of these multidomain states in perpendicular multilayer systems. In particular, closed expressions for stray fields in the case of ferromagnetic and antiferromagnetic stripes are presented. The theoretical approach provides a basis for the analysis of magnetic force microscopy (MFM) images from this class of nanomagnetic systems. Peculiarities of the MFM contrast have been calculated for realistic tip models. These characteristic features in the MFM signals can be employed for the investigations of the different multidomain modes. The methods developed for stripe-like magnetic domains are employed to calculate magnetization processes in twinned microstructures of ferromagnetic shape-memory materials. The remarkable phenomenon of giant magnetic field induced strain transformations in such ferromagnetic shape memory alloys as Ni-Mn-Ga, Ni-Mn-Al, or Fe-Pd arises as an interplay of two physical effects: (i) A martensitic transition creating competing phases, i.e. crystallographic
domains or variants, which are crystallographically equivalent but have different orientation. (ii) High uniaxial magnetocrystalline anisotropy that pins the magnetization vectors along certain directions of these martensite variants. Then, an applied magnetic field can drive a microstructural transformation by which the martensitic twins, i.e. the different crystallographic domains, are redistributed in the martensitic state. Within the phenomenological (micromagnetic) theory the equilibrium parameters of multivariant stripe patterns have been derived as functions of the applied field for an extended single-crystalline plate. The calculated magnetic phase diagram allows to give a detailed description of the magnetic field-driven martensitic twin rearrangement in single crystals of magnetic shape-memory alloys. The analysis reveals the crucial role of preformed twins and of the dipolar stray-field energy for the magnetic-field driven transformation process in magnetic shape-memory materials. This work has been done in close collaboration with a group of experimentalists from Institute of Metallic Materials of IFW Dresden, Germany and San Jose Research Center of
Hitachi Global Storage Technologies, United States. Comparisons between theoretical and experimental data from this cooperation are presented throughout this thesis as vital part of my work on these different subjects.
21
Yu, Xiaoju, Min Liang, and Corey Shemelya. "3D Printable Multilayer RF Integrated System." International Foundation for Telemetering, 2015. http://hdl.handle.net/10150/596450.
Full textAbstract:
ITC/USA 2015 Conference Proceedings / The Fifty-First Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2015 / Bally's Hotel & Convention Center, Las Vegas, NVIn this work, a 3D-printable multilayer phased array system is designed to demonstrate the applicability of additive manufacturing technique combining dielectric and conductor processes at room temperature for RF systems. Phased array systems normally include feeding networks, antennas, and active components such as switches, phase shifters and amplifiers. To make the integrated system compact, the array system here uses multilayer structure that can fully utilize the 3D space. The vertical interconnections between layers are carefully designed to reduce the loss between layers. Simulated results show good impedance matching and high-directive scanning beam. This multilayer phased array will finally be 3D printed by integrating thermal / ultrasound wire mesh embedding method (for metal) and fused-deposition-modeling technique (for dielectric).
22
Zhaojiang, Li. "Hardness characteristics in electrodeposited Cu/Ni multilayer systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0020/MQ52687.pdf.
Full text
23
Naumovich, Anna. "Efficient numerical methods for the Biot poroelasticity system in multilayered domains." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=984262660.
Full text
24
Chinnakavanam, Sundararaj Sharath Kumar. "Development of a Multilayered Association Polymer System for Sequential Drug Delivery." UKnowledge, 2013. http://uknowledge.uky.edu/cbme_etds/13.
Full textAbstract:
As all the physiological processes in our body are controlled by multiple biomolecules, comprehensive treatment of certain disease conditions may be more effectively achieved by administration of more than one type of drug. Thus, the primary objective of this research was to develop a multilayered, polymer-based system for sequential delivery of multiple drugs. This particular device was designed aimed at the treatment of periodontitis, a highly prevalent oral inflammatory disease that affects 90% of the world population. This condition is caused by bacterial biofilm on the teeth, resulting in a chronic inflammatory response that leads to loss of alveolar bone and, ultimately, the tooth. Current treatment methods for periodontitis address specific parts of the disease, with no individual treatment serving as a complete therapy.
The polymers used for the fabrication of this multilayered device consists of cellulose acetate phthalate (CAP) complexed with Pluronic F-127 (P). After evaluating morphology of the resulting CAPP system, in vitro release of small molecule drugs and a model protein was studied from both single and multilayered devices. Drug release from single-layered CAPP films followed zero-order kinetics related to surface erosion property of the association polymer. Release studies from multilayered CAPP devices showed the possibility of achieving intermittent release of one type of drug as well as sequential release of more than one type of drug. Mathematical modeling accurately predicted the release profiles for both single layer and multilayered devices. After the initial characterization of the CAPP system, the device was specifically modified to achieve sequential release of drugs aimed at the treatment of periodontitis. The four types of drugs used were metronidazole, ketoprofen, doxycycline, and simvastatin to eliminate infection, inhibit inflammation, prevent tissue destruction, and aid bone regeneration, respectively. To obtain different erosion times and achieve appropriate release profiles specific to the disease condition, the device was modified by increasing the number of layers or by inclusion of a slower eroding polymer layer. In all the cases, the device was able to release the four different drugs in the designed temporal sequence. Analysis of antibiotic and anti-inflammatory bioactivity showed that drugs released from the devices retained 100% bioactivity.
Following extensive studies on the in vitro sequential drug release from these devices, the in vivo drug release profiles were investigated. The CAPP devices with different release rates and dosage formulations were implanted in a rat calvarial onlay model, and the in vivo drug release and erosion was compared with in vitro results. In vivo studies showed sequential release of drugs comparable to those measured in vitro, with some difference in drug release rates observed. The present CAPP association polymer-based multilayer devices can be used for localized, sequential delivery of multiple drugs for the possible treatment of complex disease conditions, and perhaps for tissue engineering applications, that require delivery of more than one type of biomolecule.
25
Khariwala, Devang. "STRUCTURE-PROPERTY RELATIONSHIPS IN MULTILAYERED POLYMERIC SYSTEM AND OLEFINIC BLOCK COPOLYMERS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1288290405.
Full text
26
Qian, Haijun. "High temperature wetting and multilayer adsorption in oxide systems." Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1219855598/.
Full text
27
Wasley, Thomas J. "Digitally driven microfabrication of 3D multilayer embedded electronic systems." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/23237.
Full textAbstract:
The integration of multiple digitally driven processes is seen as the solution to many of the current limitations arising from standalone Additive Manufacturing (AM) techniques. A technique has been developed to digitally fabricate fully functioning electronics using a unique combination of AM technologies. This has been achieved by interleaving bottom-up Stereolithography (SL) with Direct Writing (DW) of conductor materials alongside mid-process development (optimising the substrate surface quality), dispensing of interconnects, component placement and thermal curing stages. The resulting process enables the low-temperature production of bespoke three-dimensional, fully packaged and assembled multi-layer embedded electronic circuitry. Two different Digital Light Processing (DLP) Stereolithography systems were developed applying different projection orientations to fabricate electronic substrates by selective photopolymerisation. The bottom up projection orientation produced higher quality more planar surfaces and demonstrated both a theoretical and practical feature resolution of 110 μm. A top down projection method was also developed however a uniform exposure of UV light and planar substrate surface of high quality could not be achieved. The most advantageous combination of three post processing techniques to optimise the substrate surface quality for subsequent conductor deposition was determined and defined as a mid-processing procedure. These techniques included ultrasonic agitation in solvent, thermal baking and additional ultraviolet exposure. SEM and surface analysis showed that a sequence including ultrasonic agitation in D-Limonene with additional UV exposure was optimal. DW of a silver conductive epoxy was used to print conductors on the photopolymer surface using a Musashi dispensing system that applies a pneumatic pressure to a loaded syringe mounted on a 3-axis print head and is controlled through CAD generated machine code. The dispensing behaviour of two isotropic conductive adhesives was characterised through three different nozzle sizes for the production of conductor traces as small as 170 μm wide and 40 μm high. Additionally, the high resolution dispensing of a viscous isotropic conductive adhesive (ICA) also led to a novel deposition approach for producing three dimensional, z-axis connections in the form of high freestanding pillars with an aspect ratio of 3.68 (height of 2mm and diameter of 550μm). Three conductive adhesive curing regimes were applied to printed samples to determine the effect of curing temperature and time on the resulting material resistivity. A temperature of 80 °C for 3 hours resulted in the lowest resistivity while displaying no substrate degradation. ii Compatibility with surface mount technology enabled components including resistors, capacitors and chip packages to be placed directly onto the silver adhesive contact pads before low-temperature thermal curing and embedding within additional layers of photopolymer. Packaging of components as small as 0603 surface mount devices (SMDs) was demonstrated via this process. After embedding of the circuitry in a thick layer of photopolymer using the bottom up Stereolithography apparatus, analysis of the adhesive strength at the boundary between the base substrate and embedding layer was conducted showing that loads up to 1500 N could be applied perpendicular to the embedding plane. A high degree of planarization was also found during evaluation of the embedding stage that resulted in an excellent surface finish on which to deposit subsequent layers. This complete procedure could be repeated numerous times to fabricate multilayer electronic devices. This hybrid process was also adapted to conduct flip-chip packaging of bare die with 195 μm wide bond pads. The SL/DW process combination was used to create conductive trenches in the substrate surface that were filled with isotropic conductive adhesive (ICA) to create conductive pathways. Additional experimentation with the dispensing parameters led to consistent 150 μm ICA bumps at a 457 μm pitch. A flip-chip bonding force of 0.08 N resulted in a contact resistance of 2.3 Ω at a standoff height of ~80 μm. Flip-chips with greater standoff heights of 160 μm were also successfully underfilled with liquid photopolymer using the SL embedding technique, while the same process on chips with 80 μm standoff height was unsuccessful. Finally the approaches were combined to fabricate single, double and triple layer circuit demonstrators; pyramid shaped electronic packages with internal multilayer electronics; fully packaged and underfilled flip-chip bare die and; a microfluidic device facilitating UV catalysis. This new paradigm in manufacturing supports rapid iterative product development and mass customisation of electronics for a specific application and, allows the generation of more dimensionally complex products with increased functionality.
28
Magogodi, Steven Mothibakgomo. "Hydrogen storage capacity of the Ti-Pd multilayer systems." University of the Western Cape, 2020. http://hdl.handle.net/11394/7711.
Full textAbstract:
>Magister Scientiae - MScHydrogen has high energy density and it is regarded as the future energy carrier. Hydrogen can be stored as a gas in high-pressure cylinders, as a liquid in cryogenic tanks and as a solid in metal hydrides. The storage of hydrogen in gas and liquid form has many limitations. Light metal hydrides show high energy density and are a promising and more practical mode of hydrogen storage. In particular, titanium and its alloys are promising metal hydrides for hydrogen storage due to their high affinity to hydrogen. The aim of this study is to investigate the effect of thermal annealing on hydrogen storage capacity of Ti-Pd multilayer systems. Ti-Pd multilayer films were prepared on CP-Ti (commercial pure Ti) and Ti6Al4V substrates using an electron beam evaporator equipped with a thickness monitor. The sequential deposition of layers Pd(50nm)/Ti(25nm)/Pd(50nm) was done at a constant deposition rate of 0.6 Å/s. The first batch of samples were thermally annealed at 550 °C in vacuum for two hours, the second batch of samples were annealed at 550 oC under H2(15%)/Ar(85%) gas mixture for two hours and the third series of samples was annealed under pure H2 gas at 550 oC for one hour. SEM showed relatively homogeneous and smooth topography of surfaces in as-deposited samples, while a rough textured surface was observed in both samples annealed under vacuum and under H2/Ar gas mixture. The samples annealed under pure H2 gas did not show any sign of crystallites grow but instead a relatively smooth surface with sign of etching. XRD revealed structural transformation as evidenced by the presence of PdTi2 phase in samples annealed under vacuum; in samples annealed under the gas mixture Pd2Ti was noted in addition to TiH2 and TiO2. While the TiH2 phase is an indication of hydrogen absorption, the TiPd2 phase suggests intermixing of the deposited layers and the presence of TiO2 is evidence of oxidation. The samples annealed under pure H2 gas showed only TiH2 with no trace of structural transformation. RBS confirmed the intermixing of layers in the samples annealed under vacuum and H2(15%)/Ar(85%) gas mixture, while samples annealed under pure H2 gas did not show any intermixing of layers. ERDA revealed an average H content of ~ 3.5 at.% in CP-Ti and ~6.2 at.% in Ti6Al4V for samples annealed under H2(15%)/Ar(85%) gas mixture. We recorded an hydrogen content of ~19.5 at.% in CP-Ti annealed under pure H2 while ~25.5 at.% was found in Ti6Al4V annealed under the same conditions. When the thickness of the Pd catalyst layers was increased to 100 nm (i.e. Pd (100 nm)/Ti (25 nm)/Pd (100 nm)), only ~ 12.5 at.% and 11.2 at. % hydrogen content was recorded in samples prepared on CP-Ti and Ti6Al4V alloy respectively, both annealed under pure hydrogen for one hour as above.
29
Papaefthymiou, Evangelos. "Systems of nonlinear PDEs arising in multilayer channel flows." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24974.
Full textAbstract:
This thesis presents analysis and computations of systems of nonlinear partial differential equations (PDEs) modelling the dynamics of three stratified immiscible viscous layers flowing inside a channel with parallel walls inclined to the horizontal. The three layers are separated by two fluid-fluid interfaces that are free to evolve spatiotemporally and nonlinearly when the flow becomes unstable. The determination of the flow involves solution of the Navier-Stokes in domains that are changing due to the evolution of the interfaces whose position must be determined as part of the solution, providing a hard nonlinear moving boundary problem. Long-wave approximation and a weakly nonlinear analysis of the Navier-stokes equations along with the associated boundary conditions, leads to reduced systems of nonlinear PDEs that in general form are systems of coupled Kuramoto- Sivashinsky equations. These physically derived coupled systems are mathematically rich due to the rather generic presence of coupled nonlinearities that undergo hyperbolic-elliptic transitions, along with high order dissipation. Analysis and numerical computations of the resulting coupled PDEs is presented in order to understand the stability of multilayer channel flows and explore and quantify the different types of underlying nonlinear phenomena that are crucial in applications. Importantly, it is found that multilayer flows can be unstable even at zero Reynolds numbers, in contrast to single interface problems. Furthermore, the thesis investigates the dynamical behaviour of the zero viscosity limits of the derived systems in order to verify their physical relevance as reduced models. Strong evidence of the existence of the zero viscosity limit is provided for mixed hyperbolic-elliptic type systems whose global existence is an open and challenging mathematical problem. Finally, a novel sufficient condition is derived for the occurrence of hyperbolic-elliptic transitions in general conservation laws of mixed type; the condition is demonstrated for several physical systems that have been studied in the literature.
30
Wübben, Dirk [Verfasser]. "Effiziente Detektionsverfahren für Multilayer-MIMO-Systeme / Dirk Wübben." Aachen : Shaker, 2006. http://d-nb.info/1186587377/34.
Full text
31
Laschewsky, André, H. Ringsdorf, and J. Schneider. "Oriented supramolecular systems-polymeric monolayers and multilayers from prepolymerized amphiphiles." Universität Potsdam, 1986. http://opus.kobv.de/ubp/volltexte/2008/1713/.
Full textAbstract:
Oriented polymeric membranes were originally prepared by polymerization or polycondensation of preoriented monomers. The introduction of hydrophilic spacer groups into the polymeric amphiphiles allowed the formation of highly ordered systems (monolayers, liposomes, multilayers) from prepolymerized amphiphiles: due to the partial decoupling of the different mobilities and orientation tendencies of the polymer chain and the amphiphilic side groups, these polymers are able to self-organize. In monolayer experiments the high order of these membranes could be demonstrated by their surface pressure area-diagrams. In addition the combination of order and mobility of these spacer groups containing polymeric amphiphiles allowed the formation of Langmuir-Blodgett-multilyers with a high layer correlation. Thus, disturbancies in highly oriented layers can be avoided normally taking place during the polymerization reaction (e.g. contractions) or oriented monomeric layers.
32
Weisbach, Tobias, Jens Sumpf, and Christian Bumm. "Thermoplastic Multilayer Slide-Foil." Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-231676.
Full textAbstract:
The training of movement procedures to increase the skills of athletes is a fundamental part of competitive sports. A realistic training, supported by technical equipment provides athletes a better success of training and is requested by trainers and training centers all over the world. Especially in winter sports, like luge or bob, a realistic training simulation is not always possible and demands adaptations of specific training procedures. As a part of this article, a new multilayer slide-foil will be presented, which allows athletes an even more realistic training. For this purpose the structure and production process of the foil composite will be shown, as well as results of the tribological behaviour of the foilDas Training von Bewegungsabläufen, zur Steigerung von Fähigkeiten, ist ein fundamentaler Bestandteil im Leistungssport. Ein realistisches Training, unterstützt durch technische Systeme, ermöglicht es Athleten optimale Trainingserfolge zu erzielen und wird dementsprechend von Trainern und Leistungszentren überall auf der Welt gewünscht. Insbesondere in Wintersportarten, wie z. B. Rennrodeln oder Bobfahren, kann dies allerdings nur bedingt realisiert werden und erfordert oftmals Abstriche bei der Trainingsgestaltung. Im Rahmen dieses Beitrags wird daher eine mehrschichtige Verbundfolie vorgestellt, welche den Athleten ein realistischeres Training ermöglichen soll. Hierzu werden zum einen der Aufbau und die Herstellung des Folienverbundes erläutert sowie tribologische Untersuchungsergebnisse präsentiert
33
Mecif, Lilia. "Polyelectrolyte multilayer self assembly system for cell encapsulation." Thesis, University of Nottingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.523601.
Full text
34
Ullah, Saeed. "Optical control and detection of spin coherence in multilayer systems." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-10052017-163058/.
Full textAbstract:
Since a decade, spintronics and related physics have attracted considerable attention due to the massive research conducted in these areas. The main reason for growing interest in these fields is the expectation to use the electrons spin instead of or in addition to the charge for the applications in spin-based electronics, quantum information, and quantum computation. A prime concern for these spins to be possible candidates for carrying information is the ability to coherently control them on the time scales much faster than the decoherence times. This thesis reports on the spin dynamics in two-dimensional electron gases hosted in artificially grown III-V semiconductor quantum wells. Here we present a series of experiments utilizing the techniques to optically control the spin polarization triggered by either optical or electrical methods i.e. well known pump-probe technique and current-induced spin polarization. We investigated the spin coherence in high mobility dense two-dimensional electron gas confined in GaAs/AlGaAs double and triple quantum wells, and, it\'s dephasing on the experimental parameters like applied magnetic field, optical power, pump-probe delay and excitation wavelength. We have also studied the large spin relaxation anisotropy and the influence of sample temperature on the long-lived spin coherence in triple quantum well structure. The anisotropy was studied as a function sample temperature, pump-probe delay time, and excitation power, where, the coherent spin dynamics was measured in a broad range of temperature from 5 K up to 250 K using time-resolved Kerr rotation and resonant spin amplification. Additionally, the influence of Al concentration on the spin dynamics of AlGaAs/AlAs QWs was studied. Where, the composition engineering in the studied structures allows tuning of the spin dephasing time and electron g-factor. Finally, we studied the macroscopic transverse drift of long current-induced spin coherence using non-local Kerr rotation measurements, based on the optical resonant amplification of the electrically-induced polarization. Significant spatial variation of the electron g-factor and the coherence times in the nanosecond scale transported away half-millimeter distances in a direction transverse to the applied electric field was observed.Há uma década, a spintrônica e outras áreas relacionadas vêm atraindo considerável atenção, devido a enorme quantidade de pesquisa conduzidas por elas. A principal razão para o crescente interesse neste campo é a expectativa da aplicação do controle do spin do elétron no lugar ou em adição à carga, em dispositivos eletrônicos e informação e computação quânticas. A possibilidade destes spins carregarem informação depende, primeiramente, da habilidade de controlá-los coerentemente, em uma escala de tempo muito mais rápida do que o tempo de decoerência. Esta tese trata da dinâmica de spins em gases de elétrons bidimensionais, em poços quânticos de semicondutores III-V, crescidos artificialmente. Nós apresentamos uma série de experimentos, utilizando técnicas para o controle ótico da polarização de spin, desencadeadas por métodos óticos ou eletrônicos, ou seja, técnicas conhecidas de bombeio e prova e polarização de spin induzida por corrente. Nós investigamos a coerência de spin em gases bidimensionais, confinados em poços quânticos duplos e triplos de GaAs/AlGaAs e a dependência da defasagem com parâmetros experimentais, como campo magnético externo, potência ótica, tempo entre os pulsos de bombeio e prova e comprimento de onda da excitação. Também estudamos a grande anisotropia de relaxação de spin como função da temperatura da amostra, potência de excitação e defasagem entre bombeio e prova, medidos para uma vasta gama de temperatura, entre 5K e 250K, usando Rotação de Kerr com Resolução Temporal (TRKR) e Amplificação Ressonante de Spin (RSA). Além disso estudamos a influência da concentração de Al na dinâmica dos poços de AlGaAs/AlAs, para o qual a engenharia da composição da estrutura permite sintonizar o tempo de defasagem de spin e o fator $ g $ do elétron. Por fim, estudamos a deriva transversal macroscópica da longa coerência de spin induzida por corrente, através de medidas de Rotação de Kerr não-locais, baseadas na amplificação ressonante ótica da polarização eletricamente induzida. Observamos uma variação espacial significante do fator $ g $ e do tempo de vida da coerência, na escala de nanosegundos, deslocada distâncias de meio milímetro na direção transversa ao campo magnético aplicado.
35
Zhou, Yijun. "Polymer-Ceramic Composites for Conformal Multilayer Antenna and RF Systems." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1245240041.
Full text
36
Souza, Claudio Roberto Lima de. "STRUCTURE-PROPERTY RELATIONSHIPS IN HIGH BARRIER MULTILAYER FILM/FOAM SYSTEMS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1605692744465504.
Full text
37
Li, Zhenpeng. "Information Programming by Scaling of Polymeric Layered Systems." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case154834158541737.
Full text
38
Currie, Christa Anne. "Capillary and Microchip Electrophoresis Systems for Pharmaceutical Analysis." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1242998601.
Full text
39
Hettich, Mike [Verfasser]. "Investigation of Multilayer Systems by Coherent Acoustic Phonon Spectroscopy / Mike Hettich." München : Verlag Dr. Hut, 2014. http://d-nb.info/1055863508/34.
Full text
40
Rongzhi, Huang. "MULTILAYER CO-EXTRUSION AND TWIN-SCREW COMPOUNDING OF POLYMERIC ELASTOMER SYSTEMS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1404864078.
Full text
41
Gu, Erdan. "Studies in thin film systems and X-ray multilayer film design." Thesis, University of Aberdeen, 1992. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU547604.
Full textAbstract:
The design and optimization of soft X-ray multilayer film mirrors have been studied using optical theory. Our investigations show that the reflectivity of multilayer films is sensitive to their modulation wavelength and that their reflectivity can be improved by structural optimization. A new design method has been developed which can be used to increase the bandwidth and to change the shape of the reflectivity curves of multilayer film mirrors. Detailed studies of the formation and structure of practical vacuum deposited erbium(Er) thin film systems are presented. It was found that the phase and structure of these deposited films are strongly influenced by deposition conditions and film thickness. On the basis of these studies, very high purity low thicknesss erbium films (&'60 300 AA) with h.c.p. structure have be grown for the first time. The preferred orientation of crystallites and its dependence on deposition conditions in these erbium films are also investigated in detail. We have prepared Er/C multilayer films using the ultra high vacuum electron beam evaporation technique. The compositional periodic structure and intra-layer structure of these multilayer films have been studied using X-ray diffraction. The diffusion and short-range order formation occurring at the interfaces and within layers of C-Er thin-film systems and Er/C multilayer films were investigated by extended X-ray absorption fine structure technique (EXAFS).
42
Al-Shargabi, Asma Abdulghani Qassem. "A multilayer framework for quality of context in context-aware systems." Thesis, De Montfort University, 2015. http://hdl.handle.net/2086/11149.
Full textAbstract:
Context-aware systems use context information to decide what adaptation actions to perform in response to changes in their environment. Depending on applications, context information includes physical context (e.g. temperature and location), user context (e.g. user preferences and user activity), and ICT context (e.g. device capabilities and battery power). Sensors are the main mean of capturing context. Unfortunately, sensed context data are commonly prone to imperfection due to the technical limitations of sensors, their availability, dysfunction, and the highly dynamic nature of environment. Consequently, sensed context data might be imprecise, erroneous, conflicting, or simply missing. To limit the impact of context imperfection on the behavior of a context-aware system, a notion of Quality of Context (QoC) is used to measure quality of any information that is used as context information. Adaptation is performed only if the context data used in the decision-making has an appropriate quality level. This thesis conducts a novel framework for QoC in context-aware systems, which is called MCFQoC (Multilayered-Context Framework for Quality of Context). The main innovative features of our framework, MCFQoC, include: (1) a new definition that generalizes the notion of QoC to encompass sensed context as well as user profiled context; (2) a novel multilayer context model, that distinguishes between three context abstractions: context situation, context object, and context element in descending order. A context element represents a single value and many context elements can be compound into a context object. Many context objects in turn form a context situation; (3) a novel model of QoC parameters which extends the existing parameters with new quality parameter and explicitly distributes the quality parameters across the three layers of context abstraction; (4) a novel algorithm, RCCAR (Resolving Context Conflicts Using Association Rules), which has been developed to resolve conflicts in context data using the Association Rules (AR) technique; (5) a novel mechanism to define QoC policy by assigning weights to QoC parameters using a multi-criteria decision-making technique called Analytical Hierarchy Process (AHP); (6) and finally, a novel quality control algorithm called IPQP (Integrating Prediction with Quality of context Parameters for Context Quality Control) for handling context conflicts, context missing values, and context erroneous values. IPQP is extension of RCCAR. Our framework, MCFQoC, has been implemented in MatLab and evaluated using a case study of a flood forecast system. Results show that the framework is expressive and modular, thanks to the multilayer context model and also to the notion QoC policy which enables us to assign weights for QoC’s parameters depending on quality requirements of each specific application. This flexibility makes it easy to apply our approach to a wider type of context-aware applications. As a part of MCFQoC framework, IPQP algorithm has been successfully tested and evaluated for QoC control using a variety of scenarios. The algorithm RCCAR has been tested and evaluated either individually and as a part of MCFQoC framework with a significant performance concerning resolving context conflicts. In addition, RCCAR has achieved a good success comparing to traditional prediction methods such as moving average (MA), weighted moving average, exponential smoothing, doubled exponential smoothing, and autoregressive moving average (ARMA).
43
Kalogirou, Anna. "Nonlinear dynamics of surfactant-laden multilayer shear flows and related systems." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/25067.
Full textAbstract:
The nonlinear stability of two-fluid shear flows in the presence of inertia and/or an insoluble surfactant at the interface is studied in this thesis. Asymptotic analysis in the limit of a thin lower layer is performed and a system of coupled weakly nonlinear evolution equations is derived. The system describes the spatiotemporal evolution of the interface and its local surfactant concentration. It contains a nonlocal term which arises by appropriately matching solutions of the linearised Navier-Stokes equations in the thicker layer to the thin layer solution. The problem corresponding to two-dimensional flows is first solved numerically, by implementing highly accurate linearly implicit schemes in time with spectral discretisations in space. Numerical experiments for asymptotically small and finite Reynolds numbers indicate that the solutions are mostly nonlinear travelling waves or time-periodic waves. As the length of the system increases, the dynamics become more complex and include quasi-periodic and chaotic fluctuations. The stability in three-dimensions of the nonlinear travelling waves observed in two-dimensional flows is also examined. The model derived is also shown to be appropriate in describing interfacial wave structures arising in two-fluid Couette flow experiments. A related two-dimensional dissipative-dispersive partial differential equation is considered in the second part of the thesis. The PDE is similar to the surfactant-free version of the interfacial evolution equation derived in the previous part. A generalisation of that equation with a nonlinearity written in a gradient form provides the well-known two-dimensional Kuramoto-Sivashinsky equation (2D KSE). The 2D KSE has received attention with respect to its mathematical analysis, but numerical solutions are obtained for the first time here. For relatively small domain sizes the solutions are steady states or travelling waves and as the domain becomes increasingly larger, solutions are trapped into a chaotic attractor which is characterised by energy equipartition and symmetry of the energy spectrum.
44
Pasqual, Michael C. "Multilayer network modeling of change propagation for engineering change management." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62481.
Full textAbstract:
Thesis (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 141-143).
Engineering change management is a critical and challenging process within product development. One pervasive source of difficulty for this process is the phenomenon of change propagation, by which a change to one part or element of a design requires additional changes throughout the product. Research efforts to understand and manage change propagation have largely drawn on network analysis. This thesis builds upon past research by introducing a multilayer network model that incorporates three proposed layers, or domains, that contribute to change propagation: namely, the product layer, change layer, and social layer. Each layer contains a distinct network of nodes and intralayer edges, but also connects to the other two layers through inter-layer dependencies. The model facilitates extensive quantitative analysis of change propagation using a repository of single-layer, double-layer, and triple-layer tools and metrics. A case study of a large technical program, which managed over 41,000 change requests in eight years, is employed to demonstrate the practical utility of the model. Most significantly, the case study explores the program's social layer and discovers a real-world correspondence between an engineer's organizational role and the propagation effects of his or her work, as measured by the newly proposed Engineer Change Propagation Index (Engineer-CPI). The case study also reveals that parent-child propagation often spanned more than one, but never more than three, system interfaces, thus confirming the possibility of indirect propagation. Finally, the study finds that propagation always stopped after five, and rarely more than four, generations of descendants. In all, the multilayer network model's holistic approach has significant policy implications for engineering change management in industry.
by Michael C. Pasqual.
S.M.
S.M.in Technology and Policy
45
Sule, Mary-Jane. "Trusted cloud computing modelling with distributed end-user attestable multilayer security." Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/12893.
Full textAbstract:
As cloud computing continues to gain popularity and its economies of scale continue to improve, stakeholders want to minimise the security risk, protect their data and other resources while maximising the gains of using any cloud resources and its application. It is predicted that by the end of 2017, bulk of spending on any IT infrastructure would be on cloud infrastructure and services as many critical applications – power, medical, finance among others continue to be migrated onto cloud platforms. For these sectors, the security challenges of cloud adoption continue to be of a great concern even with its benefits. The ability to trust and measure security levels of any cloud platform is paramount in the complete adoption and use of cloud computing in many mission critical sectors. In-depth study and analysis of the trustworthiness of various cloud based platforms/systems are often limited by the complex and dynamic nature of cloud and often do not correctly foresee or practically determine the varying trust relationship between and across the cloud layers, components (schedulers), algorithms and applications especially at a large scale. Tradition security and privacy controls continue to be implemented on cloud but due to its fluid and dynamic nature, research work in the area of end-user attestable trust evaluation of the cloud platform is limited. Most of the current simulation tools do not cater for modelling of Trust on scalable multi-layer cloud deployments (including workflow and infrastructure).Even as these tools continue to be implemented none has been used to cater for all the layers of the cloud platform. This research presents a deployment of trusted computing applied in cloud computing suited for mission critical applications. It attempts to simplify the integration of trusted platform module based integrity measurement into cloud infrastructure. Using Eucalyptus cloud software on server-grade hardware, a trusted community cloud platform was deployed on the Brunel Network as presented in Chapter 3. Security is enhanced by the integration of an end-user accessible TPM integrity measurement and verification process; this guarantees trusted ownership and integrity of the uploaded data and provides additional level of trust for the cloud platform. This research further presents a technique which allows data owners to first secure their data offline by inserting colour drops into the data using steganography. The colour drops are used to detect unauthorised modifications, verify data owner in the event the copyright of the data is in dispute and identify the path through which it was tampered with. This process ensures integrity and confidentiality of the resources. This thesis also presents a trust model using fuzzy logic which was simulated using Simulink in Matlab and subsequently evaluated on an experimental platform deployed on the Brunel network. Using this model, end-users can determine the trust values for a cloud platform or service, as well as, classify and compare various cloud platforms. The results obtained suggest that the outputs of this research work can improve end-user confidence when selecting or consuming cloud resources with enhanced data integrity and protection.
46
Sennerfors, Therese. "Interfacial Behaviour of Polyelectrolyte-Nanoparticle Systems." Doctoral thesis, KTH, Chemistry, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3310.
Full text
47
Rühl, Maximilian. "Prozessmodellierung von Reaktiv-Multischicht-Systemen (RMS)." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-198818.
Full textAbstract:
The focus of this work is the theoretical and experimentell descreption of so-called Reactive Multilayer Systems (RMS). The RMS consist of at least two mostly metallic materials, which can exothermic response with each other. Using magnetron sputter deposition (MSD) several hundred to thousands alternating layers are produced. The periodic thickness varies between 10-150 nm and the total thickness between 10-100 µ m . The exotermic reaction is effected by an activation energy, e.g. with an electric spark. In this case a phase transition of the RMS materials, which are in a metastable equilibrium, will take place. This released energy in the shape of heat, which actvates the reaction in the neighboring areas. It forms a self-sustaining thermal wave through the RMS foil. In this case the amount of energy is present, that a solder on the RMS or the joining samples or even the material itself can be melted. Therefore the RMS can be used as a heat source for joining two components. The major advantage of this technology is the very low heat input in the bonding components, due to the milliseconds of the reaction. Thus the components are heated only superfical and there is no structural damage. Thus a very low-stress joining is possible.
Furthermore is guaranteed, because of the metallic materials, a very high electrical and thermal conductivity. For the theoretical characterization of the physical and chemical processes within the RMS FEM-Simulations of the absolut temperature and the propagation velocity are preformed. In order to calculate the tmeperature ditribution in the components a new method will presented. It is thus possible to calculate the temperature penetration of the components to determine potential thermal barrier layer-thickness and the meltig time. Thus parameters for the specific joint problem such as period thickness, etc. of the RMS are derived. Modelling the heat transport after joining with RMS it is possible to derive a corralation between the thermal conductivity and shear strength. To quantify the theoretical results and to require certain parameters for the calculations experiments were preformed. The RMS will be investigated experimentally in terms of their enthalpy H , propagation velocity v , nascent temperature, melting time t schmelz , interdiffusion zone w , phase transition and its use as inovative heat source for joining components. The experimental results are compared with the theortical and complet this work.
48
Großmann, Martin [Verfasser]. "Characterization of interface adhesion and acoustic attenuation in multilayer systems / Martin Großmann." Konstanz : Bibliothek der Universität Konstanz, 2017. http://d-nb.info/1144858666/34.
Full text
49
Ji, Ran. "Development and characterisation of nano-multilayer CrAlSiN coating systems for cutting tools." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4254/.
Full textAbstract:
Two types of CrAlSiN nano-multilayer coating were designed and synthesised on AISI M2 high speed steel. Selected coatings were also deposited on pre-nitrided M2 substrate to investigate the effect of duplex treatment. A series of type I CrAlSiN coatings, which have sharp interfaces between individual nano-layers, were designed with varying bilayer thickness. An fcc and an hcp phase were identified for all type I coatings, and it has been found that the bilayer thickness has a significant influence on the orientation of both phases, which in turn affects their mechanical properties. Type II CrAlSiN coatings, with blurred interfaces, were synthesised with a medium bilayer thickness. Due to the insignificant difference in composition between neighbouring nano-layers, only one fcc phase was found in type II CrAlSiN coating. The wear resistance of the new nano-multilayer CrAlSiN coating is about 10 times higher than CrN when tested at room and elevated temperatures. This could be attributed to high H/E ratio and good oxidation resistance conferred by the nano-multilayer structure and multi-component composition. It is also found that duplex treatment can improve the wear resistance of nano-multilayer coating by two orders of magnitude due to the improved load bearing capacity of the coating system.
50
Hatton, Hilary J. "Magnetic and structural studies of nanoscale multilayer and granular alloy systems of Ag and FeCo." Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286916.
Full text