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Caresta, Mauro Mechanical & Manufacturing Engineering Faculty of Engineering UNSW. "Structural and acoustic responses of a submerged vessel." Publisher:University of New South Wales. Mechanical & Manufacturing Engineering, 2009. http://handle.unsw.edu.au/1959.4/44404.
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Excitation of the low frequency vibrational modes of a submerged vessel can generate significant radiated noise levels. Vibrational modes of a submarine hull are excited from the transmission of fluctuating forces through the shaft and thrust bearings due to the propeller rotating in an unsteady fluid. The focus of this work is to investigate the structural and acoustic responses of a submarine hull under axial excitation. The submarine hull is modelled as a cylindrical shell with internal bulkheads and ring stiffeners. The cylindrical shell is closed by truncated conical shells, which in turn are closed at each end using circular plates. The entire structure is submerged in a heavy fluid medium. The structural responses of the submerged vessel are calculated by solving the cylindrical shell equations of motion using a wave approach and the conical shell equations with a power series solution. The displacement normal to the surface of the structure in contact with the fluid medium was calculated by assembling the boundary/continuity matrix. The far field radiated sound pressure was then calculated by means of the Helmholtz integral. Results from the analytical model are compared with computational results from a fully coupled finite element/boundary element model. The individual and combined effects of the various influencing factors, corresponding to the ring stiffeners, bulkheads, conical end closures and fluid loading, on the structural and acoustic responses are characterised by examining the contribution by the circumferential modes. It is shown that equally spaced internal bulkheads generate a periodic structure thus creating a grouping effect for the higher circumferential modes, but do not have strong influence on the sound radiation. Stiffeners are found to have an important effect on both the dynamic and acoustic responses of the hull. The contribution of the conical end closures on the radiated sound pressure for the lowest circumferential mode numbers is also clearly observed. This work shows the importance of the bending modes when evaluating the sound pressure radiated by a submarine under harmonic excitation from the propulsion system.
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Mousa, A. I. "Finite element analysis of shell structure." Thesis, Cardiff University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.532180.
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Economides, George. "Investigations of open-shell open-shell Van der Waals complexes." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:e27330e0-2eaa-4181-af30-70e8b7a3a692.
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The question posed in this work is how one would model and predict the rotational spectrum of open-shell open-shell van der Waals complexes. There are two secondary questions that arise: the nature of radical-radical interactions in such systems and the modelling of the large amplitude motion of the constituent molecules. Four different systems were studied in this work, each providing part of the answer to the main question. Starting with the large amplitude motion, there are two theoretical approaches that may be adopted: to either model the whole complex as a semi-rigid molecule, or to perform quantum dynamical calculations. We recorded and analysed the rotational spectrum (using Fourier transform microwave spectroscopy) of the molecule of tertiary butyl acetate (TBAc) which exhibits a high degree of internal rotation; and of the weakly-bound complex between a neon atom and a nitrogen dioxide molecule (Ne-NO2). We used the semi-rigid approach for TBAc and the quantum dynamical approach for Ne-NO2. We also explored the compatibility of these two approaches. Moreover, we were able to predict and analyse the fine and hyperfine structure of the Ne-NO2 spectrum using spherical tensor operator algebra and the results of our dynamics calculations. To explore the nature of the interactions in an radical-radical van der Waals complex we calculated the PESs of the possible states that the complex may be formed in, when an oxygen and a nitrogen monoxide molecule meet on a plane using a number of high level ab initio methods. Finally, our conclusions were tested and applied when we performed the angular quantum dynamics to predict the rotational spectrum of the complex between an oxygen and a nitrogen dioxide molecule, and account for the effect of nuclear spin statistics in that system.
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Tanaka, Kaori. "Shell structure and classical orbits in mesoscopic systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ30172.pdf.
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Krämer, Tobias. "Electronic structure of open-shell transition metal complexes." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:1f4a1330-281d-4696-b3e6-62b76fb41d65.
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This thesis presents electronic structure calculations on problems related to the bonding in inorganic coordination compounds and clusters. A wide range of molecules with the ability to exist in different structural forms or electronic states has been selected and density functional theory is systematically applied in order to gain detailed insight into their characteristics and reactivity at the electronic level. First, we address the question of redox non-innocent behaviour of bipyridine in a series of 1st row transition metal complexes. Complexes of the type [M(2,2'-bipyridine)(mes)₂]<sup>0</sup> (M = Cr, Mn, Fe, Co, Ni; mes = 2,4,6-Me₃C6H₂) and their one-electron reduced forms have been explored. The results clearly show that the anions are best described as complexes of the monoanionic bipyridine radical (S<sub>bpy</sub> = 1/2), giving a rationale for the observed structural changes within the ligand. Likewise, we have identified dianionic bipyridine in both the complexes [Zn2(4,4'-bpy)(mes)₄]²<sup>−</sup> and [Fe(2,2'-bpy)₂]²<sup>−</sup>. In no case have we found evidence for significant metal-to-ligand backbonding. The subject of redox-noninnocence is further revisited in a comparative study of the two complexes [M(o-Clpap)₃] (M = Cr, Mo; o-Clpap = 2-[(2-chloro-phenyl)azo]-pyridine), and their associated electron transfer series. The results indicate that all electron transfer processes are primarily ligand-based, although in the case of the Mo analogue these are coupled to substantial electron density changes at the metal. The ability of pap to form radical anions finds a contrasting case in the di- nuclear Rh complex [Rh₂(μ-p-Clpap)₂ (cod)Cl₂], where the two ligand bridges act as acceptors of strong dπ∗ backbonding from a formally Rh<sup>–I</sup> centre. We then direct our attention to the endohedral Zintl clusters [Fe@Ge<sub>10</sub>]³<sup>−</sup> and [Mn@Pb<sub>12</sub>]³<sup>−</sup>, which reveal peculiar topologies. We have probed the electronic factors that influence their geometric preferences, and propose a model based on the shift of electron density from the endo- hedral metal to the cage to account for the observed geometries. Subsequently, we reassess the electronic structure of the xenophilic clusters Mn₂(thf)₄(Fe(CO)₄)₂ and [Mn(Mn(thf)₂)₃(Mn(CO)₄)₃]<sup>–</sup>. We conclude that these are best viewed as exchange coupled Mn<sup>II</sup> centres bridged by closed- shell carbonylate fragments. In the closing chapter the reduction of NO₂<sup>–</sup> to NO by the complex [Cu(tct)(NO₂)]<sup>+</sup> (tct = cis,cis-1,3,5-tris(cinnamylideneamino)cyclohexane) is studied, a process that mimics the enzyme-catalysed reaction. Two viable pathways for the reaction have been traced and key inter-mediates identified. Both direct release of NO or via decomposition of a Cu-NO complex are kinetically and thermodynamically feasible.
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Wang, Xiaoyan. "Investigation of 3D Shell Structure Nonwoven Processes and Products." Thesis, University of Manchester, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527410.
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Valdés, Vázquez Jesús Gerardo. "Nonlinear Analysis of Orthotropic Membrane and Shell Structures Including Fluid-Structure Interaction." Doctoral thesis, Universitat Politècnica de Catalunya, 2007. http://hdl.handle.net/10803/6866.
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Problemas de interacciónn fluido-estructura representan hoy en día un gran desafío en diferentes áreas de ingeniería y ciencias aplicadas. Dentro de las aplicaciones en ingeniería civil, el flujo del viento y los movimientos estructurales pueden ocasionar inestabilidades aeroelásticas en construcciones tales como puentes de gran luz, rascacielos y cubiertas estructurales ligeras. Por otro lado, aplicaciones en biomecánica están interesadas en el estudio de hemodinámica, por ejemplo: flujo sanguíneo en arterias, donde grandes deformaciones de las venas interactúan con fluidos.En la parte estructural de este trabajo, una nueva metodología para el análisis geométricamente no-lineal ortótropo de membranas y láminas sin grados de libertad de rotación es desarrollada basándose en la orientación de la fibra principal del material. Una consecuencia directa de la estrategia de orientación de fibras es la posibilidad de analizar membranas y láminas pretensadas cuya configuración inicial está fuera del plano. Por otra parte, ya que la teoría convencional de membranas permite que existan tensiones de compresión, un modelo de arrugado basado en la modificación de la ecuación constitutiva se presenta. El desarrollo estructural es modelado con elementos finitos provenientes de las ecuaciones de la elastodinámica.<br/>La parte de fluidos de este trabajo está gobernada por las ecuaciones de Navier-<br/>Stokes para flujos incompresibles, las cuales son modeladas por interpolaciones estabilizadas de elementos finitos. Ya que la solución monolítica de dichas ecuaciones tiene la desventaja que consumen mucho tiempo en la solución de grandes sistemas de ecuaciones, el método de pasos fraccionados se usa para aprovechar las ventajas computacionales que brinda gracias al desacoplamiento de la presión del campo de las velocidades. Además, el esquema α-generalizado para integración en el tiempo para fluidos es adaptado para que se use con la t´ecnica de los pasos fraccionados.<br/>El problema de interacción fluido-estructura es formulado como un sistema de tres campos: la estructura, el fluido y el movimiento de la malla. El movimiento del dominio del fluido es tomado en cuenta mediante la formulación arbitraria Lagrangiana-Euleriana, para la cual se usan dos estrategias de movimiento de malla.<br/>Para el acoplamiento entre el fluido y la estructura se usa un acoplamiento fuerte por bloques usando la técnica de Gauss-Seidel. Debido a que la interacción entre el fluido y la estructura es altamente no-lineal, se implementa el método de relajación basado en la técnica de Aitken, la cual acelera la convergencia del problema.<br/>Finalmente varios problemas se presentan en los diferentes campos, los cuales verifican la eficiencia de los algoritmos implementados.<br>Nowadays, fluid-structure interaction problems are a great challenge of different fields in engineering and applied sciences. In civil engineering applications, wind flow and structural motion may lead to aeroelastic instabilities on constructions such as long-span bridges, high-rise buildings and light-weight roof structures. On the other hand, biomechanical applications are interested in the study of hemodynamics, i.e. blood flow through large arteries, where large structural membrane deformations interact with incompressible fluids.<br/>In the structural part of this work, a new methodology for the analysis of geometrically nonlinear orthotropic membrane and rotation-free shell elements is developed based on the principal fiber orientation of the material. A direct consequence of the fiber orientation strategy is the possibility to analyze initially out-ofplane prestressed membrane and shell structures. Additionally, since conventional membrane theory allows compression stresses, a wrinkling algorithm based on modifying the constitutive equation is presented. The structure is modeled with finite elements emerging from the governing equations of elastodynamics.<br/>The fluid portion of this work is governed by the incompressible Navier-Stokes equations, which are modeled by stabilized equal-order interpolation finite elements.<br/>Since the monolithic solution for these equations has the disadvantage that take great computer effort to solve large algebraic system of equations, the fractional step methodology is used to take advantage of the computational efficiency given by the uncoupling of the pressure from the velocity field. In addition, the generalized-α time integration scheme for fluids is adapted to be used with the fractional step technique.<br/>The fluid-structure interaction problem is formulated as a three-field system: the structure, the fluid and the moving fluid mesh solver. Motion of the fluid domain is accounted for with the arbitrary Lagrangian-Eulerian formulation with two different mesh update strategies. The coupling between the fluid and the structure is performed with the strong coupling block Gauss-Seidel partitioned technique.<br/>Since the fluid-structure interaction problem is highly nonlinear, a relaxation technique based on Aitken's method is implemented in the strong coupling formulation to accelerate the convergence.<br/>Finally several example problems are presented in each field to verify the robustness and efficiency of the overall algorithm, many of them validated with reference solutions.
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Hu, Bin. "Stability analysis of linear thin shells." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7360/.
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Shell structure is widely used in engineering area. The purpose of this dissertation is to show the behavior of a thin shell under external load, especially for long cylindrical shell under compressive load, I analyzed not only for linear elastic problem and also for buckling problem, and by using finite element analysis it shows that the imperfection of a cylinder could affect the critical load which means the buckling capability of this cylinder.
For linear elastic problem, I compared the theoretical results with the results got from Straus7 and Abaqus, and the results are really close. For the buckling problem I did the same: compared the theoretical and Abaqus results, the error is less than 1%, but in reality, it’s not possible to reach the theoretical buckling capability due to the imperfection of the cylinder, so I put different imperfection for the cylinder in Abaqus, and found out that with the increasing of the percentage of imperfection, the buckling capability decreases, for example 10% imperfection could decrease 40% of the buckling capability, and the outcome meet the buckling behavior in reality.
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Dennis, Christopher Roger. "High resolution spectroscopy of open shell clusters." Thesis, University of Oxford, 1997. http://ora.ox.ac.uk/objects/uuid:43ac8ad5-724a-4a23-a03f-3eb78e6f4e72.
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The microwave spectrum of the open-shell van der Waals complex NO-HF has been recorded in the region 6-20GHz using a pulsed nozzle Fourier transform microwave spectrometer. This is the first observation of the microwave spectrum of a open-shell van der Waals complex between two molecules. The spectrum exhibits a rich hyperfine structure with the observation of intermolecular hyperfine interactions in an isolated system providing a sensitive probe of electron transfer in the complex. The spectrum consists of four fine structure transitions 5/2(e)-3/2(e), 3/2(e)-1/2(e), 5/2(f)-3/2(f), 3/2(f)-1/2(f) which have been fitted to a semi-rigid Hamiltonian developed to include the effects of the orbital and spin angular momenta of the unpaired electron on NO. A new treatment to account for the intermolecular hyperfine interaction was developed. The structure of the complex has been determined and is significantly bent with an angle of between 37 degrees and 49 degrees between the NO internuclear axis and the a-axis of the complex. The Renner-Teller parameter, epsilon 2, is very large and negative having the value of -10 449.32(4)GHz indicating that configuration with the unpaired electron in the plane of the complex is more stable. The analysis of the hyperfine interactions of the hydrogen and fluorine nuclei uses two constants for each nucleus, one for the spatial relationship between the magnetic moments of the unpaired electron and the nuclear magnetic moment and a Fermi-contact term. The Fermi-contact term for hydrogen is the first strong evidence of intermolecular charge transfer in an isolated van der Waals molecule.
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Gam, Ki Tak. "Structure-property relationship in core-shell rubber toughened epoxy nanocomposites." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/412.
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The structure-property relationships of epoxy nanocomposites with inorganic layer-structure nanofillers have been studied to obtain the fundamental understanding of the role of nanofillers and the physics of polymer nanocomposites in this dissertation. Several polymer nanocomposite systems with modified montmorillonite (MMT) or α-zirconium phosphate (ZrP) nanofillers were prepared with epoxy matrices of different ductility and properties. The successful nanofiller's exfoliations were confirmed with X-ray diffraction and transmision electronic microscopy (TEM). Dynamic mechanical analysis (DMA) on the prepared epoxy nanocomposites revealed the significant increase in rubbery plateau moduli of the epoxy nanocomposite systems above Tg, as high as 4.5 times, and tensile test results showed improved modulus by the nanofiller addition, while the fracture toughenss was not affected or slightly decreased by nanofillers. The brittle epoxy nanocomposite systems were toughened with core shell rubber (CSR) particles and showed remarkable increase in fracture toughness (KIC) value up to 270%. The CSR toughening is more effective at ductile matrices, and TEM observation indicates that major toughening mechanisms induced by the CSR addition involve a large scale CSR cavitation, followed by massive shear deformation of the matrix.
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Sonelius, Ulrika. "FISST - Fully Integrated Shell Structure : OPTIMIZATION OF AN AIRCRAFT FUSELAGE." Thesis, KTH, Lättkonstruktioner, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-164286.
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In order to reduce the costs of aircraft, the weight of the fuselage has to be reduced. This master thesis, collaboration between the Royal Institute of Technology and Airbus Group, aims to optimize a new aircraft fuselage under development. This new fuselage design, called FISST, consists of a sandwich panel to stiffen the structure instead of the stringers used in baseline fuselage. Apart from the goal of reducing the weight, the new design also has advantages during maintenance and repairing. During this project the FISST-concept has been optimized, by modeling using the Finite Element Method, in order to fulfill given requirements. The design has been evaluated for buckling, strains and displacements. Furthermore modeling methods have been validated in order to ensure that the results are accurate enough. This report shows that the FISST-concept fulfills the given requirements better than the baseline.
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Georgiadou, Anastasia. "Transfer Reactions Induced with 56Ni : Pairing and N=28 Shell Closure." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS294/document.
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La structure du noyau N = Z doublement magique 56Ni (N = 28, Z = 28) a été étudiée en mesurant les réactions de transfert á un et deux nucléons. Le transfert nous donne des informations sur deux aspects physiques différents: la fermeture de couche N=28 et l’intensité de l’appariement neutron-proton. Le nombre magique N=28 est particulier, car c’est le premier créé par le spin-orbit. La double magicité permet la détermination de la nature de particule indépendante des voisins N±1 par réaction de transfert d’un nucléon. De plus, en tant que noyau N=Z a couches fermeés, le 56Ni est un noyau clé pour l’étude de l’apparement np dans la plus grande couche accessible expérimentalement. L’apparement np se manifeste dans le canal isoscalaire (T=0) et isovecteur (T=1). L’intensité relative de chaque canal révèle la nature collective des états. L’expérience de ce travail a eu lieu au GANIL-Caen, en France, avec un faisceau radioactif de 56Ni á 30MeV / u produit par frag- mentation de 58Ni et purification avec le spectromètreLISE. Les mesures ont été effectuées en cinématique inverse sur des cibles CH2 et CD2. Les détecteurs MUST2 et TIARA ont été utilisés pour la détection de éjectiles légers et couvraient presque 4π. En outre, quatre détecteurs germanium d’EXOGAM ont été utilisés pour les coïncidences de particules-gamma afin d’identifier l’état peuplé du résidu de réaction. Pour étudier le gap de N=28, nous étudions la spectroscopie du 55Ni par les réactions de transfert de nucléons (d, t) et (p, d) sur le 56Ni. Le spectre en énergie d’excitation est déduit de la mesure des éjectiles légers seulement. Ensuite,les coincidences particule-gamma sont utilisées pour améliorer la résolution et identifier les principaux états peuplés. La comparaison des distributions angulaires ainsi obtenues avec des calculs DWBA permet d’extraire les facteurs spectroscopiques pour les états de particules et de trous ainsi peuplés. En ce qui concerne l’appariement np, nous avons analysé la réaction 56Ni(d,α)54Co qui réalise un transfert de paires neutron-proton. Un affaiblissement du canal T=0 á cause de l’effet du spin-orbite est attendu. La sélectivité en ∆T=0 de la réaction (d, α) permet d’étudier plus en détail le canal isoscalaire T = 0<br>The structure of the unstable doubly ma- gic nucleus 56Ni has been investigated by measuring one- and two-nucleon transfer reactions. Each trans- fer reaction provides information for two different physical aspects: the robustness of the N=28 shell gap and the strength of the neutron-proton pairing. 56Ni is a self-conjugate doubly magic nucleus with N=28 and Z=28. The magic number 28 is a peculiar shell closure created by spin-orbit splitting effects. The double magicity makes the determination of the single-particle nature of their N±1 neighbors by one-neutron transfer reaction of major interest to test both the robustness of shell closures as well as the evolution of particle and/or valence orbitals. Moreover 56Ni, as a N=Z nucleus with fully closed shells, is a key nucleus to investigate neutron-proton pairing in the largest shell accessible experimentally, the fp shell. Neutron-proton pairing can occur both in the isoscalar (T=0) and in the isovector (T=1) channels. The relative intensity of both channels reveals the collective nature of the states. The radioactive beam of 56Ni was produced at GANIL-Caen, France at 30 MeV/u by fragmentation of 58Ni and purification with the LISE spectrometer. The experimental set-up used, consists of the TIARA- MUST2-EXOGAM combination which provides an al- most 4π coverage and the ability to perform particle- γ coincidences. To probe the N=28 gap, we studied the spectroscopy of 55Ni through one-nucleon trans- fer reactions on 56Ni. The excitation energy spectrum is deduced by measuring the light ejectiles only, while particle-γ coincidences are used to improve the re- solution of the populated states and select the main ones. Comparison in between the extracted angular distributions and DWBA calculations allow the extraction of the spectroscopic strength of the hole- and particle- states populated by these one neutron pick- up reactions. As for neutron-proton pairing, a weakening of the strength is expected in the T=0 channel from previous results. The selectivity in ∆T=0 of the 56Ni(d,α)54Co reaction enables further investigation of the isoscalar channel contribution
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Hoteling, Nathan. "Structure of Fe isotopes at the limits of the (pf) shell." College Park, Md. : University of Maryland, 2008. http://hdl.handle.net/1903/8531.
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Thesis (Ph. D.)--University of Maryland, College Park, 2008.<br>Thesis research directed by: Dept. of Chemistry and Biochemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Lee, Seung Joon. "Nonlinear analysis of smart composite plate and shell structures." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/2218.
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Theoretical formulations, analytical solutions, and finite element solutions for laminated composite plate and shell structures with smart material laminae are presented in the study. A unified third-order shear deformation theory is formulated and used to study vibration/deflection suppression characteristics of plate and shell structures. The von K??rm??n type geometric nonlinearity is included in the formulation. Third-order shear deformation theory based on Donnell and Sanders nonlinear shell theories is chosen for the shell formulation. The smart material used in this study to achieve damping of transverse deflection is the Terfenol-D magnetostrictive material. A negative velocity feedback control is used to control the structural system with the constant control gain. The Navier solutions of laminated composite plates and shells of rectangular planeform are obtained for the simply supported boundary conditions using the linear theories. Displacement finite element models that account for the geometric nonlinearity and dynamic response are developed. The conforming element which has eight degrees of freedom per node is used to develop the finite element model. Newmark's time integration scheme is used to reduce the ordinary differential equations in time to algebraic equations. Newton-Raphson iteration scheme is used to solve the resulting nonlinear finite element equations. A number of parametric studies are carried out to understand the damping characteristics of laminated composites with embedded smart material layers.
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Nesvizhskii, Alexey I. "Theory and interpretation of L-shell x-ray absorption spectra /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/9738.
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Lei, Zhen. "Isogeometric shell analysis and optimization for structural dynamics." Thesis, Ecully, Ecole centrale de Lyon, 2015. http://www.theses.fr/2015ECDL0028/document.
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Cette thèse présente des travaux effectués dans le cadre de l'optimisation de forme de pièces mécaniques, sous critère dynamique, par approche isogéométrique. Pour réaliser une telle optimisation nous mettons en place dans un premier temps les éléments coque au travers des formulations Kirchhoff-Love puis Reissner-Minlin. Nous présentons une méthode permettant d'atteindre les vecteurs normaux aux fibres dans ces formulations au travers de l'utilisation d'une grille mixte de fonctions de base interpolantes, traditionnellement utilisées en éléments finis, et de fonction non interpolantes issues de la description isogéométrique des coques. Par la suite, nous détaillons une méthode pour le couplage de patch puis nous mettons en place la méthode de synthèse modale classique dans le cadre de structures en dynamique décrites par des éléments isogéometriques. Ce travail établit une base pour l'optimisation de forme sous critères dynamique de telles structures. Enfin, nous développons une méthode d'optimisation de forme basée sur le calcul du gradient de la fonction objectif envisagée. La sensibilité de conception est extraite de l'analyse de sensibilité au niveau même du maillage du modèle, qui est obtenue par l'analyse discrète de sensibilité. Des exemples d'application permettent de montrer la pertinence et l'exactitude des approches proposées<br>Isogeometric method is a promising method in bridging the gap between the computer aided design and computer aided analysis. No information is lost when transferring the design model to the analysis model. It is a great advantage over the traditional finite element method, where the analysis model is only an approximation of the design model. It is advantageous for structural optimization, the optimal structure obtained will be a design model. In this thesis, the research is focused on the fast three dimensional free shape optimization with isogeometric shell elements. The related research, the development of isogeometric shell elements, the patch coupling in isogeometric analysis, the modal synthesis with isogeometric elements are also studied. We proposed a series of mixed grid Reissner-Minlin shell formulations. It adopts both the interpolatory basis functions, which are from the traditional FEM, and the non-interpolatory basis functions, which are from IGA, to approximate the unknown elds. It gives a natural way to define the fiber vectors in IGA Reissner-Mindlin shell formulations, where the non-interpolatory nature of IGA basis functions causes complexity. It is also advantageous for applying the rotational boundary conditions. A modified reduce quadrature scheme was also proposed to improve the quadrature eficiency, at the same time, relieve the locking in the shell formulations. We gave a method for patch coupling in isogeometric analysis. It is used to connect the adjacent patches. The classical modal synthesis method, the fixed interface Craig-Bampton method, is also used as well as the isogeometric Kirchhoff-Love shell elements. The key problem is also the connection between adjacent patches. The modal synthesis method can largely reduce the time costs in analysis concerning structural dynamics. This part of work lays a foundation for the fast shape optimization of built-up structures, where the design variables are only relevant to certain substructures. We developed a fast shape optimization framework for three dimensional thin wall structure design. The thin wall structure is modelled with isogeometric Kirchhoff-Love shell elements. The analytical sensitivity analysis is the key focus, since the gradient base optimization is normally more fast. There are two models in most optimization problem, the design model and the analysis model. The design variables are defined in the design model, however the analytical sensitivity is normally obtained from the analysis model. Although it is possible to use the same model in analysis and design under isogeomeric framework, it might give either a highly distorted optimum structure or a unreliable structural response. We developed a sensitivity mapping scheme to resolve this problem. The design sensitivity is extracted from the analysis model mesh level sensitivity, which is obtained by the discrete analytical sensitivity analysis. It provides exibility for the design variable definition. The correctness of structure response is also ensured. The modal synthesis method is also used to further improve the optimization eficiency for the built-up structure optimization concerning structural dynamics criteria
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Ho, Yanfang. "Group theoretical analysis of in-shell interaction in atoms." Scholarly Commons, 1985. https://scholarlycommons.pacific.edu/uop_etds/487.
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A group theoretic approach to Layzer's 1/2 expansion method is explored. In part this builds on earlier work of Wulfman(2), of Moshinsky et al(l4), and of Sinanoglu, Herrick(lS), and Kellman (16) on second row atoms.
I investigate atoms with electrons in the 3s-3p-3d shell and find:
1. Wulfman's constant of motion accurately predicts configuration mixing for systems with two to eight electrons in the 3s-3p subshell.
2. The same constant of motion accurately predicts configuration mixing for systems with two electrons in the 3s-3p-3d shell.
3. It accurately predicts configuration mixing in systems of high angular momentum L and of high spin angular momentum S containing three electrons in the 3s-3p-3d shell, but gives less accurate results when L and S are both small.
I also show how effective nuclear charges may be calculated by a group theoretical approach. In addition I explore several new methods for expressing electron repulsion operators in terms of operators of the 80(4,2) dynamical group of one - electron atoms.
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Frankland, L. "Interpretation of fp-shell nuclei, '5'3Mn and '5'3Fe." Thesis, University of Brighton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367331.
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Van, Zyl Marilize. "Prediction of flow-induced vibration in shell-and-tube heat exchangers." Diss., University of Pretoria, 2004. http://hdl.handle.net/2263/28055.
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Please read the abstract (Summary) in the 00front part of this document<br>Dissertation (M Eng (Mechanical Engineering))--University of Pretoria, 2006.<br>Mechanical and Aeronautical Engineering<br>unrestricted
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Pramatarova, Radina. "The lamellar structure of the shell of Patella crenata a crystallographic study /." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=967134315.
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Thomas, Emmett E. Jr. "The Search For Structure in a Baptist Church." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/31004.
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First Baptist Church of Guilford in Columbia, MD is seeking a design for its fourth church due to its ever increasing membership. The needs of its members and surrounding community are however not limited to worship but also include the desire for commercial areas for business ventures, day care, and recreational facilities. These desires have the making of a â Super Churchâ which has become all too common in metropolitan areas.
The requirements of a growing church body requires the architect to have an understanding of the denomination, liturgy, and possess the design creativity to construct a structural envelope that is suitable for a religious building.
The purpose of this thesis is to explore alternative prototypical structural and architectural solutions in response to the building program created by the Architectural Committee and their design consultants.<br>Master of Architecture
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Ozsin, Gamzenur. "Production And Characterization Of Activated Carbon From Pistachio-nut Shell." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612892/index.pdf.
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In this study production and characterization of activated carbon from an agricultural waste, pistachio-nut shells, was investigated. To determine optimum production conditions by chemical activation method, effect of tempreature (300, 500, 700 and 900 oC) and effect of impregnation ratio (1:1, 2:1 and 3:1 as activation agent:sample) were investigated by applying two different methods (raw material activation and char activation) and with two different activation agents (phosphoric acid and potassium hydroxide).
To produce activated carbon, all the impregnated samples were heated to the final activation temperature under a continuous nitrogen flow (100 cm3/min) and at a heating rate of 10 oC/min and were held at that temperature for 1 hour.
Pore structures of activated carbons were determined by N2 adsorption and micro-mesopore analysis was made by &ldquo<br>Non-local Density Functional Theory&rdquo<br>and &ldquo<br>Monte Carlo Simulation&rdquo<br>method (NLDFT-Monte Carlo Simulation Method). BET surface areas of produced activated carbons were found from N2 adsorption data in the relative pressure range of 0.01 to 0.15.
BET surface areas of phosphoric acid activated carbons by raw material activation method were found between 880 and 1640 m2/g. The highest value of the BET surface area was obtained in the case of the activated carbon which was produced with an impregnation ratio of 3/1 (g H3PO4/g raw material), at an activation temperature of 500 oC. The repeatibility was also investigated on phosphoric acid activated carbons which were produced with conventional raw matererial activation method. Results showed that, both the BET surface area values and pore size distributions were consistent among themselves.
On the other hand char activation experiments with phosphoric acid produced activated carbons having lower BET surface areas than the ones obtained with raw material activation method by creating mesoporous structure. When the same char activation method was tried with potassium hydroxide, it was concluded that elevated temperatures could help in producing activated carbons with high BET surface areas by creating microporous structure.
Results also showed that properties of activated carbon such as ash content, slurry pH value, true density, elemental composition, methylene blue number and surface morphology were strongly affected by both production conditions and production method, as pore structure was affected considerably.
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Williams, Benjamin Parker. "Using Core-Shell Nanocatalysts to Unravel the Impact of Surface Structure on Catalytic Activity:." Thesis, Boston College, 2020. http://hdl.handle.net/2345/bc-ir:108918.
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Thesis advisor: Udayan Mohanty<br>The high surface area and atomic-level tunability offered by nanoparticles has defined their promise as heterogeneous catalysts. While initial studies began with nanoparticles of a single metal assuming thermodynamic shapes, modern work has focused on using nanoparticle composition and geometry to optimize nanocatalysts for a wide variety of reactions. Further optimization of these refined nanocatalysts remains difficult, however, as the factors that determine catalytic activity are intertwined and a fundamental understanding of each remains elusive. In this work, precise synthetic methods are used to tune a number of factors, including composition, strain, metal-to-metal charge transfer, atomic order, and surface faceting, and understand their impact on catalysis. The first chapter focuses on current achievements and challenges in the synthesis of intermetallic nanocatalysts, which offer long-range order that allows for total control of surface structure. A particular focus is given to the impact of the synthetic approach on the activity of the resulting nanoparticles. In the second chapter, multilayered Pd-(Ni-Pt)x nanoparticles serve as a controlled arena for the study of metallic mixing and order formation on the nanoscale. The third chapter controls the shell thickness of Au@PdPt core-alloyed shell nanoparticles on a nanometer scale to isolate strain at the nanoparticle surface. In the fourth chapter, the synthetic approaches of chapters two and three are applied to catalysis. In totality, the work presented here represents a brick in the foundation of understanding and exploiting structure-function relationships on the nanoscale, with an eye toward the rational design of tailored nanocatalysts<br>Thesis (PhD) — Boston College, 2020<br>Submitted to: Boston College. Graduate School of Arts and Sciences<br>Discipline: Chemistry
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Lam, Yek Wah. "Isospin symmetry breaking in sd shell nuclei." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14446/document.
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Dans cette thèse, nous avons développé une approche microscopique de la description des effets de la brisure de symétrie d’isospin dans les noyaux de la couche sd. Le travail est effectué dans le cadre du modèle en couches.Nous avons ajouté à un Hamiltonien nucléaire traditionnel, qui conserve l’isospin, l’interaction de Coulomb et le potentiel de type Yukawa d'échange de mésons pour modéliser les forces nucléaires dépendantes de la charge. La base de données sur les coefficients expérimentaux de l'équation des multiplets de masse isobariques (IMME) a été mise au point dans le cadre de cette thèse et a été utilisée pour ajuster les paramètres de l’hamiltonien. L'hamiltonien ainsi construit fournit une description théorique très précise du mélange d’isospin dans les états nucléaires. Nous montrons la pertinence de cette approche dans deux applications importantes : (i) le calcul des amplitudes d'émission de proton interdites par isospin, essentiels dans le cadre d’astrophysique nucléaire et (ii) le calcul de corrections (dues au mélange d'isospin) aux transitions bêta superpermises du type Fermi, cruciales pour les tests des symétries fondamentales du Modèle Standard de l’interaction électrofaible<br>In the thesis, we develop a microscopic approach to describe theisospin-symmetry breaking effects in sd-shell nuclei.The work is performed within the nuclear shell model.A realistic isospin-conserving Hamiltonian is supplementedby a charge-dependent part consisting of the Coulomb interaction andYukawa-type meson exchange potentials to model charge-dependent forces ofnuclear origin. The extended database of the experimental isobaric mass multiplet equation coefficients is compiled during the thesis work and is used in a fit of the Hamiltonian parameters.The constructed Hamiltonian provides an accurate theoretical description ofthe isospin mixing nuclear states. A specific behaviour of the IMME coefficients have been revealed.We present two important applications (i) calculations of isospin-forbiddenproton emission amplitudes, which is often of interest for nuclearastrophysics, and (ii) calculation on corrections to nuclear Fermi beta decay, which is crucial for the tests of fundamental symmetries of the weak interaction
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Lim, Zi-Yian. "Preparation, modification, and characterisation of Yolk-shell structure based catalysts for synthetic gas production." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/41666/.
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Hydrogen is an emerging energy carrier for oil refining and fuel cell applications. The development of an efficient and stable catalyst to produce hydrogen gas is required for industrial applications. However critical issues in the catalyst that lead to the deactivation of reactions include active metal particle growth and carbon fouling. Industrial catalysts that are frequently overwhelmed by such issues are substituted or re-treated, which is not time and cost efficient. Therefore, developing durable catalysts that are resistant to sintering and carbon fouling remains an area of interest. A novel and anti-agglomeration Ni@yolk-ZrO2 catalyst is first reported in this thesis. A specific study of the ZrO2 hollow shell showed that the varied porosity of the hollow shell contributed to the catalyst’s ability to inhibit the agglomeration of active Ni particles. The steam reforming of methane was selected as the probe study for this catalyst in this research. Before a thorough analysis of the Ni@yolk-ZrO2 catalyst was performed, the systematic synthesis of Ni@SiO2 was studied. The analysis showed that the Ni particle size can be controlled by tuning the synthesis temperature. Water-to-surfactant ratio in the microemulsion was shown to influence the morphology of the Ni@SiO2 particle. The tetraethyl orthosilicate (TEOS) amount added with fractionated dispensing and the amount of NiCl2 were found to have affected the size and morphology of the Ni@SiO2. For the Ni@yolk-ZrO2 sample, the catalyst was characterised by Transmission Electron Microscopy (TEM) and X-Ray Diffraction. TEM was used for morphology analysis, while X-ray Diffraction was performed for phase analysis and crystallite size measurements. Nitrogen adsorption-desorption isotherm was done to measure specific surface area, total pore volume, and the t-plot micropore volume of the samples. Reducibility analysis of the Nickel species of the Ni@yolk-ZrO2 catalyst was carried out using Temperature Programmed Reduction. The anti-agglomeration property of the Ni@yolk-ZrO2 was established from the TEM and X-ray Photoelectron Spectroscopy analysis. Results showed that the active Ni particles were inside the yolk-shell structured framework, which deterred Ni particles from moving onto the surface of the catalyst. Ni particles were found to be stabilised by the abundant volume of pores in the ZrO2 hollow shell. This result indicates that the Ni particles were anchored by the pores and remained stable during the steam reforming of methane. The Ni@yolk-ZrO2 catalyst was tested by varying the volumes of feed (GHSV) and the steam-to-carbon ratio. This catalyst was also subjected to a recyclability test and proved to be better than conventional impregnated Ni/ZrO2 catalysts. The Temperature Programmed Hydrogenation analysis also proofed that the yolk-shell structure framework inhibited higher order of carbon deposits on the Ni@yolk-ZrO2 catalyst. Varying the porosity of the ZrO2 hollow shell was found to affect the performance of the steam reforming of methane. This varied porosity can be achieved by varying the amount of surfactant during the synthesis of Ni@SiO2@ZrO2. X-ray Photoelectron Spectroscopy analysis results showed that the porosity of the ZrO2 hollow shell contributed to the moderately strong hydrothermal stability of the catalyst for the steam reforming of methane. The hollow shell of the ZrO2 was influenced by the instability of the SiO2. TEM analysis of used BrNi-4.8 catalysts showed that the yolk-shell structure framework of the catalyst collapsed. This result suggests that the shell has weak integrity, and proves that the SiO2 was not able to maintain the yolk-shell framework. The results also suggest that the varied porosity of the ZrO2 hollow shell influences the catalysts’ efficiency even though they share the same yolk-shell structure framework. This is likely due to the differences in the pores of each catalyst configuration, which directly affects the Nickel species involved in the catalytic reaction. Finally, it was demonstrated that the Ni@yolk-ZrO2 catalyst exhibits excellent catalytic performance in comparison to conventional catalysts for the steam reforming of methane. Catalytic activity remained stable and achieved a methane conversion of more than 90 % for 150 hours under operating conditions of GHSV of 50400 mL gcat-1h-1 and S/C = 2.5 at 750 oC.
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Cuhadar, Cigdem. "Production And Characterization Of Activated Carbon From Hazelnut Shell And Hazelnut Husk." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606430/index.pdf.
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In this study, the pore structures and surface areas of activated carbons produced from hazelnut shell and hazelnut husk by chemical activation technique using phosphoric acid (H3PO4), at relatively low temperatures (300, 400 and 500oC), were investigated. Raw materials were impregnated with different H3PO4 solutions of 30%, 40%, 50% and 60% by weight. To produce activated carbon, acid impregnated samples were heated<br>at a heating rate of 20 oC/min to the final carbonization temperature and held at that temperature for 2 hours.
The volume and surface areas of mesopores (2-50 nm) and BET surface areas of the samples were determined by N2 gas adsorption technique at -195.6oC. The pore volume and the area of the micropores with diameters less than 2 nm were determined by CO2 adsorption measurements at 0oC by the application of Dubinin Radushkevich equation.
N2 (BET) surface areas of the hazelnut shell and hazelnut husk based activated carbons were in the range of 242-596 m2/g and 705-1565 m2/g, respectively. CO2 (D-R) surface areas of the hazelnut shell and hazelnut husk based activated carbons were in the range of 433-576 m2/g and 376-724 m2/g, respectively.
The highest BET surface area was obtained as 596 m2/g among hazelnut shell based samples (HS 60.4<br>shell impregnated with 60 wt.% H3PO4, carbonized at 400 º<br>C) and as 1565 m2/g among hazelnut husk based samples (HH 40.4<br>husk impregnated with 40 wt.% H3PO4, carbonized at 400 º<br>C). Hazelnut shell based activated carbons were mainly microporous while hazelnut husk based ones were mesoporous.
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Burrows, Matthew. "Translationally Invariant Local Densities for Light Nuclei from No-Core-Shell-Model Calculations." Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1477569906766884.
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Vostinar, Marija. "Spectroscopy of 257,258Db in the vicinity of the N=152 deformed shell gap." Caen, 2015. http://www.theses.fr/2015CAEN2049.
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L’étude de la structure des noyaux autour de la fermeture de couche déformée N=152 offre des données capitales pour la compréhension de l’existence des éléments super lourds (Z>104). Des expériences récentes ont conduit à la détermination de l’amplitude et de la constance de cette fermeture de couche. Son influence sur des noyaux tels que le 255Lr et 256Rf a été étudiée. L’étude plus poussée sur l’évolution de la fermeture de couche déformée N=152 fournirait des informations précieuses quant à la formation des noyaux super lourds. A cette fin, les isotopes de 257Db et 258Db ont été produits et font l’objet de l’étude présentée dans ce manuscrit. Bien que ces deux noyaux aient déjà été étudiés précédemment, les données disponibles à l’heure actuelle sont limitées et ne permettent pas l’établissement d’un schéma de niveau complet. Le 257Db a été produit au GANIL par la réaction de fusion-évaporation 209Bi(50Ti,2n)257Db. Les deux états de longue durée de vie observés précédemment ont pu être confirmés, ainsi que les deux états isomériques du 253Lr. Le 258Db a été produit à GSI par la réaction de fusion-évaporation 209Bi(50Ti,1n)258Db. Une forte indication de l’existence de deux états dans le 258Db de durées de vie différentes a été observée. Une nouvelle transition γ dans le 250Md a été identifiée et son placement dans le schéma de niveau partiel proposé. La décroissance α du 258Rf a également été observée, suggérant un rapport de branchement plus faible que ce qui avait été mesurée auparavant<br>Investigations on the nuclear structure in the region around N=152 deformed shell gap provide an understanding of the existence of superheavy elements (Z>104). Recent experimental studies have lead to the determination of the size and the strength of this gap. Its influence was studied for nuclei like 255103Lr152 and 256104Rf152. Valuable information can be obtained by studying further the evolution of the N=152 deformed shell gap. To this purpose, the isotopes of 257105Db and 258105Db were produced and are the subject of this work. Even though these two isotopes were previously studied, the currently available data are limited and the level schemes are still not fully determined. 257Db was produced through the fusion-evaporation reaction 209Bi(50Ti,2n)257Db at GANIL. The two previously observed long lived states of 257Db were confirmed in this experiment, as well as the two isomeric states of 253Lr. 258Db was produced through the fusion-evaporation reaction 209Bi(50Ti,1n)258Db at GSI. A strong indication of the existence of two states in 258Db with different half lives was observed. A new γ-ray transition of 250Md was identified and its placement in the partial level scheme is proposed. The α decay of 258Rf was also observed, suggesting a smaller branching ratio than previously reported
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Baldock, Brandi. "Impact of Ligand Shell Architecture on Structure and Reactivity of DNA Aptamer-Linked Gold Nanoparticle Assemblies." Thesis, University of Oregon, 2016. http://hdl.handle.net/1794/20400.
Full textAbstract:
DNA-functionalized gold nanoparticles (DNA-NPs) have enormous potential as building blocks for materials due to their ability to specifically recognize and respond to target molecules and surfaces. The ability of DNA aptamers to adopt different conformations and bind either complementary DNA sequences or analyte molecules allows them to mediate nanoparticle assembly or disassembly, generating selective colorimetric responses.
Aptamer-mediated nanoparticle assembly and disassembly is sensitive to the nanoparticle ligand shell composition and structure, yet these topics have not been extensively explored. In this dissertation, a method for determining the ligand shell composition of DNA-NPs is described and a framework for understanding the impact of the DNA assembly arrangement and recognition strand density upon aptamer-mediated nanoparticle assembly and disassembly is developed. Design rules for creating sensors with desired properties are elucidated, leading to creation of sensors with improved detection limits and quantification ranges.
A technique was needed to determine the number of DNA strands of any base composition attached to gold nanoparticles (AuNPs) of any core size. A rapid, convenient and inexpensive method to quantify the number of label-free DNA strands attached to AuNPs was therefore developed. This technique was extended to determine two different DNA sequences bound to AuNPs using UV-visible and fluorescence spectroscopy. Based on the results of quantifying the ligand shells of DNA-NPs functionalized with two sequences, disulfide-terminated DNA non-specifically adsorbs and then rearranges to specifically bind the gold surface.
The position of the AuNPs and DNA strands within DNA-NP assemblies had a profound influence on their ability to assemble and sense adenosine. Assemblies designed for large inter-AuNP spacing were stable but unable to sense adenosine. Assemblies designed for short inter-AuNP spacing were unstable until the DNA ligand shell was diluted.
AuNPs functionalized with the fewest number of aptamers produced assemblies with the lowest detection limit and apparent disassociation constant and the largest analyte quantification range. Increasing the number of aptamer strands per AuNP increased the cooperativity of the AuNP disassembly response to adenosine.
This dissertation includes previously unpublished co-authored material.
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Bang, Won B. "Improving the strength of 3DP parts and development of controlled strength cellular structure investment casting shell." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38200.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996.<br>Includes bibliographical references (p. 79).<br>Three Dimensional Printing (3DP) is a rapid prototyping process that creates a three dimensional part directly from computer models by printing a sequence of two dimensional layers. In this research, the strength of 3DP parts were improved by using different "print styles" (the way binder is deposited on the powder bed in creating a 3DP part) for use in investment casting process. The print styles that were created optimized line to line interaction between the printed lines, binder overlap, and the amount of unprinted powder surrounding the printed features. The strength of the parts are measured in three different axes (X-fast, Y-slow, Z). The strength improved by factors of 2, 8, and 7 for the three different axes. A controlled strength cellular structure investment casting shell that enables the creation of a metal part without any stress related defects has been created. The ceramic shell has an open cell frame structure with thin inner shell where the metal casting is poured. The flexibility of the 3DP technology applied to controlled strength cellular structure investment casting shell will incorporate all the advantages of 3DP to investment casting (Sach 1992, ASME) as well as reduction in material consumption, controlled heat transfer, permeability, and of course controlled strength to eliminate stress related defects. The cellular structure ceramic mold is designed to withstand the pouring pressures of the molten metal and survive the handling during processing yet fail when the stresses from the contracting metal becomes excessive. The 3DP molds are usually 60% porous and cellular structure investment casting shells consist of only 35% of the 3DP material per volume. A controlled strength cellular structure investment casting shell is designed to fail when excessive stress is applied to the shell structure. The stress on the casting shell is caused by the shrinkage of the metal part. The controlled strength investment casting shell has an open cellular structure frame with a thin inner shell where the metal casting will form.<br>by Won B. Bang.<br>S.M.
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Zhang, Furui. "Mechanism and Interface Study of One-to-one Metal NP/Metal Organic Framework Core-shell Structure." Thesis, Boston College, 2017. http://hdl.handle.net/2345/bc-ir:107565.
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Thesis advisor: Chia-Kuang (Frank) Tsung<br>The core-shell hybrid structure is the simplest motif of two-component systems which consists of an inner core coated by an outer shell. Core-shell composite materials are attractive for their biomedical, electronic and catalytic applications in which interface between core and shell is critical for various functionalities. However, it is still challenging to study the exact role that interface plays during the formation of the core-shell structures and in the properties of the resulted materials. By studying the formation mechanism of a well interface controlled one-to-one metal nanoparticle (NP)@zeolite imidazolate framework-8 (ZIF-8) core-shell material, we found that the dissociation of capping agents on the NP surface results in direct contact between NP and ZIF-8, which is essential for the formation of core-shell structure. And the amount of capping agents on the NP surface has a significant effect to the crystallinity and stability of ZIF-8 coating shell. Guided by our understanding to the interface, one-to-one NP@UiO-66 core-shell structure has also been achieved for the first time. We believe that our research will help the development of rational design and synthesis of core-shell structures, particularly in those requiring good interface controls<br>Thesis (MS) — Boston College, 2017<br>Submitted to: Boston College. Graduate School of Arts and Sciences<br>Discipline: Chemistry
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Betancourt, Arturo. "Computational study of the heat transfer and fluid structure of a shell and tube heat exchanger." Thesis, Florida Atlantic University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10172609.
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<p> A common technique to improve the performance of shell and tube heat exchangers (STHE) is by redirecting the flow in the shell side with a series of baffles. A key aspect in this technique is to understand the interaction of the fluid dynamics and heat transfer. Computational fluid dynamics simulations and experiments were performed to analysis the 3-dimensional flow and heat transfer on the shell side of an STHE with and without baffles. Although, it was found that there was a small difference in the average exit temperature between the two cases, the heat transfer coefficient was locally enhanced in the baffled case due to flow structures. The flow in the unbaffled case was highly streamed, while for the baffled case the flow was a highly complex flow with vortex structures formed by the tip of the baffles, the tubes, and the interaction of flow with the shell wall.</p>
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"Optimization of shell structure acoustics." Thesis, 2010. http://hdl.handle.net/1911/62017.
Full textAbstract:
This thesis analyzes a mathematical model for shell structure acoustics, and develops and implements the adjoint equations for this model. The adjoint equations allow the computation of derivatives with respect to large parameter sets in shape optimization problems where the thickness and mid-surface of the shell are computed so as to generate a radiated sound field subject to broad-band design requirements.
The structure and acoustics are modeled, respectively, via the Naghdi shell equations, and thin boundary integral equations, with full coupling at the shell mid-surface. In this way, the three-dimensional structural-acoustic equations can be posed as a problem on the two-dimensional mid-surface of the shell. A wide variety of shapes can thus be explored without re-meshing, and the acoustic field can be computed anywhere in the exterior domain with little additional effort. The problem is discretized using triangular MITC shell elements and piecewise-linear Galerkin boundary elements, coupled with a simple one-to-one scheme.
Prior optimization work on coupled shell-acoustics problems has been focused on applications with design requirements over a small range of frequencies. These problems are amenable to a number of simplifying assumptions. In particular, it is often assumed that the structure is dense enough that the air pressure loading can be neglected, or that the structural motions can be expanded in a basis of low-frequency eigenmodes. Optimization of this kind can be done with reasonable success using a small number of shape parameters because simple modal analysis permits a reasonable knowledge of the parts of the design that will require modification. None of these assumptions are made in this thesis. By using adjoint equations, derivatives of the radiated field can be efficiently computed with respect to large numbers of shape parameters, allowing a much richer space of shapes, and thus, a broader range of design problems to be considered. The adjoint equation approach developed in this thesis is applied to the computation of optimal mid-surfaces and shell thicknesses, using a large shape parameter set, proportional in size to the number of degrees of freedom in the underlying finite element discretization.
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Chiang, Chii-Herng, and 蔣啟恆. "Dynamic Respona of Shell Structure." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/89397428358278071292.
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碩士<br>國立交通大學<br>土木工程研究所<br>77<br>The shell structures gain a great deal of attention due to its numerous practical applications such as the containment of nuclear power plant. The dynamic analyses of shell structures are thus very important especially in Taiwan which is located on an active earthquake region. In past, the dynamic responses of shell structures were almost calculated from direct integration method in time domain; and always encountered problems of huge memories occupying and large computational efforts. The purpose of this paper is to find an appropriate method that can avoid these problems. Instead of traditional time domain, frequency domain is applied in this research.
An 8 nodes isoparametric shell finite element is used to model the shell structure. Some important key nodes can be chosen, instead of total nodes, when using FRONTAL solver. First, the structural response datum are set up corresponding to unit-complex-exponential excitation function eiwt. Then the excitation applied is transformed into Fourier series in frequency domain by applying Fast-Fourier-Transforms (F.F.T.). The structural responses on those key nodes can be obtained by utilizing the interpolation technique. After a final inverse Fourier transformation, the responses versus the time history will be obtained.
From the verification, it is shown that the finite element model and F.F.T. program perform very good precision and convergency. Finally, a shell structure is presented to obtain its dynamic response due to certain ground excitation. It is shown that the analytical procedure subjected int his research provides a convenient way to solve the dynamic response of shell structure and does overcome the problems of memory and computing speed.
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沈孝邦. "Geometrically Nonlinear Analysis of Shell Structure." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/66506904559690638275.
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siman and 黃賜銘. "The structure of k-i shell model." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/42858948674616006472.
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碩士<br>中原大學<br>物理學系<br>88<br>While shell model(SM) calculating,it will get two big problems as such: 1. The dimensionsof elements of energe matrix are too large and it make the process of diagonalization not easy to program. 2. The parammeter of interaction of two bodies are too many and they are not easy to be determined. So I take both quasiorbital angular momentum k and quasiispin i basis(k-i) to set up nucleus' shell model to overcome the two large
difficulties.My paper illustratess the reason why While shell model(SM) calculating,it will get two big problems which The dimensionsof elements of matrix are too large and the parammeters are too many .Find the ways to overcome them.The stops of my paper read as such: 1.The SM' elementary theory. 2.Introduction of Fermion Dynamical Symmetry Model(FDSM). 3. The steps of the structure of k-i shell model. 4. The conclusions of my paper.
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Wu, Tong-Ching, and 吳東憬. "Vibration Analysis of Cone-type Shell Structure." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/12763223632869555808.
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碩士<br>國立交通大學<br>機械工程系<br>88<br>In this thesis, vibration characteristics of the conical shell structures are studied, especially the characteristics of concentric modes with circumferential wave numbers equaling to one. For given edge loads, modal characteristics and responses in frequency range from 1k Hz to 10k Hz are determined for different shell structures. The changes of the modal frequencies and mode shapes are presented with different conical angles, profiles, boundary conditions, and material constants.
In analyzing thicker conical shells, shear along the thickness direction is considered based on the first-order shear deformation. The finite element analysis of the shell structures is achieved using the commercial code MSC NASTRAN. Experiments have been performed to verify the accuracy of the theoretical predictions. The effects of material properties on the behaviors of the shell structures have also been studied. It has been found composite conical shells have different behaviors from the isotropic ones. Both theoretical and experimental results on isotropic and composite conical shells are given for comparison.
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Huang, Jing-Ting, and 黃敬庭. "Preparation of Polystyrene Nanoparticles with Core-shell Structure." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/x3v2u3.
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碩士<br>國立高雄應用科技大學<br>化學工程與材料工程系碩士在職專班<br>106<br>Core-shell polystyrene nano-spheres were successfull prepared by emulsion polymerization. In this system, styrene monomer, cross-linking agent divinyl-benzene, hydrophobic organic material isooctane and n-hexane were used as an oil phase. The water phase contains the deionized water, emulsifier, co-emulsifier and initiator (potassium persulfate; KPS).
Polymerization reactions for core-shell structure of polystyrene nano-spheres were conducted in an appropriate temperature. Sphere morphology was detected by FE-SEM. The particle size distribution was in the range of 100 to 200 nm. Core-shell structure was also observed by TEM. Effect of HLB values (hydrophile-lipophile babance) of emulsifiers on particle size was also investigated by a particle size analyser (PSA)
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Lee, Yu-Chun, and 李雨純. "Synthesis of monodispersed submicrospheres containing soft shell structure." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/07455515196832276246.
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碩士<br>國立中央大學<br>化學工程與材料工程研究所<br>99<br>Preparation of monodispersed P(MAA-co-St) /P(St-co-BMA) core-shell structure submicrospheres has been developed by two-step soap-free emulsion polymerization at boiling status. MAA and St were polymerized during a period
of time. Then BMA was introduced to the above reaction solution and polymerized. The conversion of the first step, the amount of monomer and chain transfer agent, and kinds of monomers at the second step were discussed. The
application of these monodispersed submicrospheres and dye-doped submicrospheres self-assembled to three dimensional photonic crystals (PCs) also have been discussed.
The results showed that P(MAA-co-St)/P(St-co-BMA) core/shell submicrospheres were easily prepared when the first step conversion was 80%. The weight ratios of core to shell were 0.6-2.0. There were two Tgs appeared in
the core/shell submicrospheres. The Tg of shell were decreased from 56.7 ℃ to 39 ℃ with increasing the content of BMA monomer. The Tg of shell were kept the same value when the chain transfer agent was introduced. Futhermore, the Tg of shell was decreased to 14.9 ℃ by adding BA monomer. The size and Cv of core/shell submicrospheres were 224-282 nm and less than 4%, respectively.
When the various sizes of monodispersed submicrospheres were self-assembled by capillarity driven, the structure colors in the whole range of the visible lights were observed. In UV-Vis spectra, the reflection of
self-assembled PCs of submicrospheres and dye-containing submicrospheres with the (111) planes in face-centered cubic (FCC) arrangement to confirm with the theoretical value calculated by Bragg’s law. Moreover, the structure color of dye-containing submicrospheres would be more brightly.
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Jyong-SianTsai and 蔡炯賢. "Fabrication and study of Core-Shell structure GaNnanowires." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/92137761873584761612.
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Lian, Tai Long, and 梁太隆. "Analysis of Shell Structure by Finite Element Method." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/63278849449255878776.
Full textAbstract:
碩士<br>國立成功大學<br>建築研究所<br>81<br>Shell Structure is one of most effecive structure
systems especially for long span roof structure.However
the analysis of the shell structure is complicated.In
general, it proceeded by using computer. The purpose of this
investigation is to analyze the response of shell structure.
Using the "sap90" computer program, several parameters that
affect the stress and displacement are discussed. That are
span of shell, height of shell, open ratio of shell and
thickness of shell. The effect of loading condition is also
investigated. During analysis, we assume that shall
structure are in elastic range. We also compare the "finite
element method" with "design method" and "approximate
method" which is widely used in engineer field, we
record the displacement of top-end,the normal stresses of
meridian plan and perpendicular to the meridians. In this
investigation, the response of shell show that 1. When span is
bigger which will increase top-end displacement and stress of
shell. 2. When rise is higher which will decrease top-end
displacement and stress of shell. 3. Deeper shell thickness
will increase top-end displacement and stress of shell. 4.
Bigger open ratio will decrease displacement and stress of
shell. 5. In three method''s comparison, we observe that
method by design manual is more conservative.
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Chang, Hsiao-Ching, and 張曉欽. "Stochastic Dynamic Analysis of a Geometrically Noninear Shell Structure." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/75818045296932527174.
Full textAbstract:
博士<br>國立中興大學<br>應用數學系<br>85<br>In this paper, a nonlinear displacement description is extended
to perform thedynamic analysis of a geometrically nonlinear
shell structure by using thefinite element method, which
improves the traditional restriction in smallincrements during
the deformation process. The present finite element schemeis
employed to investigate the natural frequency, also in
conjunction with theperturbation method to perform the
stochastic dynamic analysis of ageometrically nonlinear shell
structure.In early studies, the geometry and material properties
of the structures wereconsidered as deterministic despite the
fact that they intrinsically containuncertainty or randomness.
In this investigation, the statistical dynamicresponses of a
nonlinear shell structure with stochastic Young''s modulus
ofelasticity are investigated. In particular, the perturbation
technique ismainly used to deal with the corresponding nonlinear
stochastic field problem.Some results obtained by the
perturbation method are compared by the MonteCarlo simulation.
Meanwhile, the statistical responses of the
geometricallynonlinear shell structure which is subjected to a
nonstationary randomexcitation are also studied by using the
stochastic equivalent linearizationtechnique, and these
responses are checked by the Monte Carlo simulation aswell.
These statistically dynamical responses such as the mean value
ofdeflection, the standard deviation of the deflection, the
standard deviation ofthe velocity and the correlation
coefficient of the deflection and velocity arevery useful for
estimating the reliability of the structure.
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Chen, Fu-Jung, and 陳芙蓉. "CeO2@TiO2 Core-shell Structure and Its Photocatalytic Performance." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/94fb7m.
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Cheng, Cheng-Ching, and 鄭承晉. "Preparations and Photocatalysis Properties of InVO4 Core-shell Structure." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/3dnd5u.
Full textAbstract:
碩士<br>國立東華大學<br>材料科學與工程學系<br>106<br>In this study, we were used In2O3 and V2O5 to prepare InVO4 photocatalyst powder by solid state method. The decolorization was degraded by Cyanine N-5R acid dye solution, and the photocatalytic activity of the powder under illumination was measured. The experiment is divided into two different directions: different sintering temperatures and different raw material mole ratios. And observe whether the powder has different photocatalytic activity under visible light, and add PVP and PVA to try to reduce the agglomeration. XRD analysis shows that most of the raw materials react to InVO4-III when the sintering temperature is above 600oC. When sintering temperature lower than 600oC the powder retains V2O5 and In2O3. From the lower five sintering temperatures, it can be seen that the product produced two types of InVO4, namely InVO4-I and InVO4-III. The powder sintered at 500oC contains is more InVO4-I. When the sintering temperature is higher than 600oC, almost all InVO4-I is converted to InVO4-III.
Using UV-Vis. to observe the degradation results, it was found that the lower sintering temperature, the less complete the reaction. The more V2O5, the better the degradation effect. This is the result because V2O5 reacts with the dye to affect the measurement of UV-Vis. After cleaning the powder, changing the ratio of V2O5 and In2O3, adding PVP and PVA, it was found that the powder reacted at 650oC does not contain V2O5 and is most suitable for photocatalytic degradation of dyes.
Compared to sintering different proportions of powder at 650oC, It is found that the powder with the core-shell structure of In2O3 and V2O5 with a molar ratio of 1.5 to 1 has better degradation effect than the one with no core-shell structure of In2O3 and V2O5. The core-shell structure is helpful. Photocatalytic efficiency. The addition of PVP and PVA can reduce the phenomenon of agglomeration, but the effect of PVA is better. The best photocatalytic capacity parameter is In2O3: V2O5 = 1.5:1 mol% and PVA is sintered at 650oC for 12 hours.
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Wang, Ming-Zhe, and 王明哲. "Analysis of Vibration Characteristics for The Radial Shell Structure." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/48845517033508989943.
Full textAbstract:
碩士<br>國立屏東科技大學<br>機械工程系<br>93<br>This research takes the radial shells of two kinds of different materials to experiment the shell structure, makes use of the finite element analysis and the experimental modal analysis and carrys on the model identification and discussion. The ANSYS software is used to carry on the modal analysis and harmonic analysis to the shell structure of the radian first and then to get the modal parameters of the structure, which are the natural frequency and mode shapes. Then, the experimental modal analysis is started testing. The hammer is taked to impact structure as the input condition and the acceleration is measured from the structure as the output condition. Results are running through ME'Scope software to carry on the curve fitting. The natural frequency and the damping ratio from the experiment are obtained. The modal II
parameters that result from above two kinds of methods are used to carry on the comparison and identification, and then make sure the accuracy of the finite element model. Finally, the Taguchi optimization experiment method is used to carry on the optimization design to the shell of the radian. This is for the convenience of the method to be applied in the engineering in the future.
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Kuo, Pai-Chia, and 郭白嘉. "Preparation and Characteristic of ZnS-ZnO core-shell structure." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/a54ajg.
Full textAbstract:
碩士<br>國立交通大學<br>材料科學與工程系所<br>92<br>Nanomaterials have extraordinary functionality and strong potential for future development. Preparation methodology of nanomaterials have since been an important research field. In this work our emphasis lays
on the preparation of one dimensional core-shell structure. We use two different ways to fabricate ZnS-ZnO core-shell structure, namely hydrothermal method and atomic layer deposition method.
Wurtzite ZnS nanorods are obtained through hydrothermal processing for 6 hours under 200℃ using ethylenediamine of specific concentration as solvent. The diameter of the nanorods is smaller than 100 nm and the length of them is around several hundred of nanometers. Moreover, ZnS nanorods are also synthesized by codeposition under room temperature using ethylenediamine as solvent. These rods have a length from 500 to 2000 nm and a diameter from 20 to 150 nm. However, ZnS nanorods synthesized in this way contain un-decomposed ZnS 0.5en. Surfaces of the rods are oxidized by heating under 650℃ for 3 mins in an oxygen atmosphere. ZnS-ZnO core-shell structure is examined by XRD and SEM. The luminescence of core-shell structure is mainly in the visible region, with its PL peak at 490-500nm.
In the second part we use atomic layer chemical vapor deposition technique to deposit ZnO nanorod array in an anode aluminum oxide template. The optical properties is enhanced by reducing defect concentration through post-annealing processes. Resonance effects are observed, enhancing UV emission intensity. ZnS-ZnO core-shell nanotubes are obtained by the sulfurating the ZnO nanorod array using NaS solution. Transformation of ZnO to ZnS is proofed by XPS analysis. The optical properties of ZnS-ZnO core-shell structures have improved six times over ZnO nanorods. We assume the formation of ZnS, which diminishes defects and the quantum-sized effect may be the reason.
This research synthesized ZnO-ZnS one dimensional core-shell structure in two different ways, which both offer better optical properties than single material. This may have future potential for application in light emitting devices and flat panel display technology.
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"Nonlinear Analysis of Orthotropic Membrane and Shell Structures Including Fluid-Structure Interaction." Universitat Politècnica de Catalunya, 2007. http://www.tesisenxarxa.net/TDX-1126107-193535/.
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Berndt, Ingo [Verfasser]. "Structure of multi-temperature sensitive core shell microgels / Ingo Berndt." 2005. http://d-nb.info/978446917/34.
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Liang, Yi-Fan, and 梁藝礬. "The Plasmonic Induced Photocatalyst of Silica/Silver Core-Shell Structure." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/70050037844195790257.
Full textAbstract:
碩士<br>國立清華大學<br>材料科學工程學系<br>100<br>In this study, silica/silver core-shell nano-spheres with uniform diameter and morphology were successfully synthesized by a facile electroless plating method within a mild condition. With the help of glucose, the particle size of silver nanoparticles (AgNPs) deposited on silica spheres was well controlled in the range from 10 to 50 nm.
The morphology of the SiO2/Ag was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), while the lattice analysis were performed by X-ray diffraction (XRD) and high-resoluton TEM (HR-TEM). Furthermore, the binding energy and chemical shift were examined using X-ray photoelectron spectroscopy (XPS).
In the optical properties test, we found that when the diameter of AgNPs increased form10 to 50 nm, the surface plasmon resonance (SPR) absorption band shifted toward infra-red region and became broader gradually.
This result is very promising because the traditional TiO2 without doping other elements has to absorb UV-light to trigger the photocatalystic reaction. With the using of SiO2/Ag composite, we may efficiently change the solar energy to decompose the organic pollutants. It is not only a cost-effective route but also an energy-saving way to our environment.
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Chou, Tsung-Lin, and 周宗燐. "Dynamic response of cylindrical shell structure subjected to underwater explosion." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/14955163590060971142.
Full textAbstract:
碩士<br>國立臺灣大學<br>工程科學及海洋工程學研究所<br>93<br>The experimental and numerical studies of linear and nonlinear dynamic response of cylindrical shell structures with stiffener rings subjected to underwater explosion in a 4m×4m×4m water tank have been examined in this work. The dimensions of cylindrical structures are Length × Diameter × thickness = 90cm×30cm×1mm. Two models were examined:
- cylindrical shell structure with outside stiffener rings made of 1mm mild steel
- cylindrical shell structure with inside stiffener rings made of 1mm mild steel
The experiments of dynamic response of cylinder subjected to UNDEX were performed with different standoff distances, which were varied from 30cm to 190cm. The standoff from 50cm to 190cm were designed to observe the linear responses, and the standoff 30cm was used to observe the plastic failures of cylindrical structures.
The modified measured pressure data were used as incident pressure of shock wave.The numerical analysis for the same experimental model was performed forcomparison. The USA and LS/DYNA software systems were selected as analysis tools.
The accelerations and dynamic strains obtained from experiment and numerical analysis were compared.