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1
Hall, J. C. "Multi-layer network monitoring and analysis." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599865.
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A new passive monitoring architecture — Nprobe — is presented, based upon 'off the shelf components and which, by using clusters of probes, is scalable to keep pace with current high bandwidth networks without data loss. Monitored packets are fully captured, but are subject to the minimum processing in real time needed to identify and associate data of interest across the target set of protocols. Only this data is extracted and stored. The data reduction ratio thus achieved allows examination of a wider range of encapsulated protocols without straining the probe's storage capacity. Full analysis of the data harvested from the network is performed off-line. The activity of interest within each protocol is examined and is integrated across the range of protocols, allowing their interaction to be studied. The activity at higher levels informs study of the lower levels, and that at lower levels infers detail of the higher. A technique for dynamically modelling TCP connections is presented, which, by using data from both the transport and higher levels of the protocol stack, differentiates between the effects of network and end-process activity. The balance of the dissertation presents a study of Web traffic using Nprobe. Data collected from the IP, TCP, HTTP and HTML levels of the stack is integrated to identify the patterns of network activity involved in downloading whole Web pages: by using the links contained in HTML documents observed by the monitor, together with data extracted from the HTML headers of downloaded contained objects, the set of TCP connections used, and the way in which browsers use them, are studied as a whole. An analysis of the degree and distribution of delay is presented and contributes to the understanding of performance as perceived by the user. The effects of packet loss on whole page download times are examined, particularly those losses occurring early in the lifetime of connections before reliable estimations of round trip times are established. The implications of such early packet losses for pages downloads using persistent connections are also examined by simulations using the detailed data available.
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Weeks, Mark Alexander. "Plane-layer convection and magnetoconvection." Thesis, University of Exeter, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248180.
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Graham, William Richard. "Boundary-layer noise and vibration." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308331.
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Miller, Teresa S. "Turbulent boundary layer models for acoustic analysis." Diss., Wichita State University, 2011. http://hdl.handle.net/10057/3933.
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An analysis of the three types of turbulent boundary layer (TBL) models for acoustic analysis is presented because current preferred models over-predict TBL contributions to aircraft interior noise predictions. The mean square pressure is a measure of the total energy due to the pressure fluctuations beneath a turbulent boundary layer. The single point wall pressure spectrum sorts the energy into frequencies. The normalized wavenumber-frequency spectrum sorts the energy into wavenumbers. The pressure fluctuations beneath a turbulent boundary layer are found by solving the Poisson equation. In this work, the Poisson equation is solved both numerically and analytically using data from an LES/DES simulation. The numerical solution uses the point Gauss-Seidel method and has reasonable results. The analytical solution uses an eigenvalue expansion method that is less successful. The empirical mean square pressure models predict a relatively large spread in the pressure fluctuation values. It is difficult to draw any meaningful conclusions on which mean square pressure model is preferred when compared to data from the Spirit AeroSystems 6x6 duct. The single point wall pressure spectrum models are evaluated and the two more modern models of Smol’yakov and Goody seem to perform the best. These models are also compared to data from the Spirit AeroSystems 6x6 duct. The spectrum at low frequencies rolled off similar to the Goody model. This analysis indicates that the Goody model is the appropriate single point wall pressure spectrum model for aircraft applications. Important features of the normalized wavenumber-frequency spectrum models are presented and can be classified as either separable or non-separable. Separable models in the Corcos normalized wavenumber-frequency spectrum model class tend to over-predict the response for a range of cases. Both the non-separable Chase 1 and Smol’yakov-Tkachenko models appear to match the M.I.T. low noise, low turbulence wind tunnel data throughout the range of comparison. The Smol’yakov-Tkachenko model does not lend itself to straight forward Fourier transforms needed by the acoustic models. But the Chase 1 model can be converted from wavenumber-frequency spectrum to the cross spectrum, so it is the preferred model for aircraft applications. Therefore, the preferred turbulent boundary layer models for aircraft interior noise predictions are the single point wall pressure spectrum model of Goody and the normalized wavenumber-frequency spectrum model of Chase 1.Dissertation (Ph.D.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering
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Firing, Tia Helene. "Analysis of the Transport Layer Security protocol." Thesis, Norwegian University of Science and Technology, Department of Mathematical Sciences, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-10025.
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In this master thesis we have presented a security analysis of the TLS protocol with particular emphasis on the recently discovered renegotiation attack. From our security proof we get that the Handshake protocol with renegotiation, including the fix from IETF, is secure, and hence not vulnerable to the renegotiation attack anymore. We have also analysed the Handshake protocol with session resumption, and the Application data protocol together with the Record protocol. Both of these protocols were deemed secure as well. All the security proofs are based on the UC (Universal Composability) security framework.
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Eastwood, Brian S. Taylor Russell M. "Multiple layer image analysis for video microscopy." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2009. http://dc.lib.unc.edu/u?/etd,2813.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2009.Title from electronic title page (viewed Mar. 10, 2010). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Computer Science." Discipline: Computer Science; Department/School: Computer Science.
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Kunkel, Julian Martin. "Performance Analysis of the PVFS2 Persistency Layer." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:16-opus-63302.
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Tang, Wang-Rei 1975. "Design and analysis of double-layer grids." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80176.
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Ikin, John Bruce. "An experimental analysis of carrier layer flows." Thesis, University of Leeds, 2005. http://etheses.whiterose.ac.uk/3310/.
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This thesis is concerned with flows relating to the continuous coating of multiple layers on moving webs using the slide bead process. The lowermost layer is generally known as a carrier layer when the viscosity and flow rate are both small compared with the corresponding properties of the other layers. This study is predominantly experimental in nature and broad in scope as addressing issues relating to an industrial slide coating process used for the manufacture of photographic products and inkjet media. Novel specialist pieces of equipment have been designed and built for visualizing such flows as part of this work. The studies have been carried out using a pilot coating machine and ancillary flow control facilities currently owned by HARMAN technology Limited. The new techniques enable fresh insight into the interaction between the carrier layer and the surface properties of the substrate, including roughness, surface free energy, electric charge and porosity - an area of investigation that has hitherto been largely ignored. The behaviour of the bead when coating embossed webs showing a "stippled" finish is of particular interest when compared with apparently equally rough substrates of equivalent surface energy. Increasing slide angle is shown to be advantageous to expanding the coating window for difficult substrates. The results show that the widely perceived criteria for a carrier layer needs to be redefined when coating rough surfaces of low surface energy using this process. Charge assisted coating is shown likely to be superior to conventional slide bead coating for minimising waste due to streaks. The studies include the visualisation of flows at the slot exit and on the slide. The methods allow the profile of the interface as well as the free surface to be monitored and give new insight into two major unreported effects limiting the use of a thin low viscosity carrier layer. The scope also extends to the study of waves induced in the surface of wet multi-layer coatings when subjected to the impact of air from an impingement dryer - an area of considerable interest to the coating technologist yet largely ignored by the equipment supplier.
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Segura-Castillo, Luis. "Bi-layer diaphragm walls : experimental and numerical analysis." Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/134771.
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Leakage is a widespread problem associated with the construction of diaphragm walls whenever they are erected in water-bearing ground. The aim of the present research is to develop a new type of slurry wall: the bi-layer diaphragm wall (BL), which main objective is to tackle the aforementioned problem. The method to construct it is based on an existing solution: casting a second waterproof concrete layer against the diaphragm walls. In the BL technique, the second layer is made of steel fibre reinforced concrete (SFRC) sprayed over the conventional diaphragm wall (called Mono-Layer diaphragm wall (ML) in this thesis), including a waterproof admixture. The central idea is to maximize the functional attributes of the second layer, allowing it to play a structural role in addition to the waterproofing function.The proposed methodology is based on a combination of experimental works and numerical tools. A design method for the BL walls, which is based on an uncoupled structural-section model, is proposed. The method is later used to carry out different comparisons with ML walls and an exhaustive parametric analysis of the construction processes involved in the walls construction. The experimental campaign comprised test at two levels. At element level, the structural response of walls built in a real building located in Barcelona was studied and, at section level, the bond strength between concretes of cores extracted from the abovementioned walls was measured.The model at structural level, which is based on a finite element model, was contrasted with the results obtained in the experimental walls. The sectional analysis is taken from the specialized literature. With the complete structural-section model, the BL walls are analysed. The study shows that the main flexural resistance is provided by the first layer (the conventional diaphragm wall), providing the SFRC layer a secondary flexural resistance.For the geometrical ranges of the elements considered in the thesis (35 cm to 60 cm width first layer, and 10 cm width second layer) the increase in the cross-section ultimate bending resistance when it is strengthened by the SFRC layer is between 8% and 15%. This increase allows a reduction in the steel reinforcement of the first layer (up to 7.0% of the total flexural reinforcement) and, to some extent, it also collaborates with a displacement reduction (reducing up to 7.3% of the maximum displacements). It was also found that the spraying sequence is a crucial parameter to be able to take advantage of the SFRC collaboration, and specific indications are described.Good concrete to concrete bond strength was obtained for the extracted cores. The average shear strength value measured for each age (2, 6 and 35 days) was always above 1.0 MPa for the different cases. Beyond the local test performed, a monolithic behaviour was observed at element level in the experimental walls.A similar final material consumption was observed between the BL walls and the combined consideration of a ML wall and an external waterproof system. The consideration of the technology cost entails a higher construction cost for the BL technique. However, it is still an interesting option under particular circumstances, like space limitations or if continuous maintenance costs want to be avoided in the future.In general terms it can be said that the research herein presented lay the foundation for the development of the bi-layer diaphragm wall technique, which is a promising solution for the leakage problem of diaphragm walls. Nonetheless, more studies are needed to be able to fully use these types of walls as a standard technique, e.g. a detailed cost study and sustainability analysis, debonding risk, waterproofing capability and above all more full scale experimental cases.Un problema habitual en la construcción de pantallas continuas en terrenos con presencia de agua es la existencia de filtraciones. El objetivo de esta tesis busca resolver este problema mediante el desarrollo de un nuevo tipo de pantalla: la pantalla bi-capa (BL, por sus siglas en inglés). El método para construir estos muros se basa en una solución existente: realizar una segunda capa de hormigón impermeable sobre los muros pantalla. En las pantallas BL, la segunda capa se realiza con hormigón con fibras de acero (SFRC) proyectado sobre las pantallas convencionales (llamadas ML en esta tesis) e incluyendo a su vez una adición impermeabilizante. La idea central es maximizar las funciones de la segunda capa, asignándole un rol estructural, además de la función impermeabilizante. La metodología propuesta se basa en la combinación de trabajos experimentales y herramientas numéricas. Se propone un método de diseño para las pantallas BL basado en modelos estructura-sección desacoplados. Posteriormente se utiliza este método para realizar diferentes comparaciones con pantallas ML y un análisis paramétrico exhaustivo de distintos procesos constructivos involucrados en la construcción de las pantallas BL. La campaña experimental realizada comprende dos niveles: a nivel elemento, se estudió la respuesta estructural de pantallas construidas en un edificio real ubicado en Barcelona; a nivel seccional, se midió el nivel de adherencia entre ambas capas de hormigón mediante testigos extraídos de las pantallas antes mencionadas. El modelo a nivel estructural, basado en elementos finitos, se contrastó con los resultados experimentales obtenidos. El modelo seccional se tomó de la bibliografía estudiada. Con el modelo estructura-sección completo se analizaron las pantallas BL. El estudio muestra que la principal resistencia flexional es aportada por la primera capa (el muro pantalla convencional), siendo secundario el aporte de la capa de SFRC. Para el rango de elementos considerados en esta tesis (35 cm a 60 cm de espesor de primera capa y 10 cm de segunda), el incremento de la resistencia última a flexión cuando se considera el aporte de la capa de SFRC, está entre 8% y 15%. Este incremento permite una reducción en el acero de refuerzo de la primera capa de hasta un 7.0% del total del acero de flexión y, hasta cierto punto, también colabora con una reducción en los desplazamientos (alcanzando reducciones de hasta un 7.3% del desplazamiento máximo). Se observó también que la secuencia de proyección es un factor clave a la hora de aprovechar la colaboración extra aportada por la capa de SFRC. Indicaciones específicas se describen a este respecto. Se obtuvo una buena resistencia de adherencia entre hormigones para los testigos extraídos. La resistencia media medida a cada edad (2, 6, y 35 días) estuvo siempre, para los distintos casos, por encima de 1.0 MPa. Más allá de los ensayos puntuales, se observó un comportamiento monolítico a nivel elemento para las pantallas BL experimentales. Se obtuvo un consumo final de materiales similar entre pantallas BL y la consideración conjunta de una pantalla ML más un sistema impermeabilizante externo. Considerar los costos tecnológicos conlleva un costo constructivo mayor para las pantallas BL. Sin embargo, ésta es aún una opción interesante bajo consideraciones particulares, como limitaciones del espacio subterráneo interior o si se desean evitar costos continuos de mantenimiento. En términos generales, se puede decir que la investigación aquí presentada sienta las bases para el desarrollo de la técnica de muros pantalla bi-capa, la cual es una solución prometedora para el problema de las filtraciones en pantallas. No obstante, son necesarios más estudios para poder usar plenamente este tipo de pantallas de forma habitual, e.g. estudios de sostenibilidad detallados, evaluación del riesgo de desprendimiento de la segunda capa, capacidad impermeable y, sobre todo, más ensayos experimentales a escala real
11
Amidror, Isaac Amidror Itzhak Amidror Itzhak Amidror Itzhak. "Analysis of Moiré patterns in multi-layer superpositions /." [S.l.] : [s.n.], 1995. http://library.epfl.ch/theses/?nr=1341.
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Segura, Castillo Luís Emilio. "Bi-layer diaphragm walls : experimental and numerical analysis." Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/134771.
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Tesi per compendi de publicacionsLeakage is a widespread problem associated with the construction of diaphragm walls whenever they are erected in water-bearing ground. The aim of the present research is to develop a new type of slurry wall: the bi-layer diaphragm wall (BL), which main objective is to tackle the aforementioned problem. The method to construct it is based on an existing solution: casting a second waterproof concrete layer against the diaphragm walls. In the BL technique, the second layer is made of steel fibre reinforced concrete (SFRC) sprayed over the conventional diaphragm wall (called Mono-Layer diaphragm wall (ML) in this thesis), including a waterproof admixture. The central idea is to maximize the functional attributes of the second layer, allowing it to play a structural role in addition to the waterproofing function.The proposed methodology is based on a combination of experimental works and numerical tools. A design method for the BL walls, which is based on an uncoupled structural-section model, is proposed. The method is later used to carry out different comparisons with ML walls and an exhaustive parametric analysis of the construction processes involved in the walls construction. The experimental campaign comprised test at two levels. At element level, the structural response of walls built in a real building located in Barcelona was studied and, at section level, the bond strength between concretes of cores extracted from the abovementioned walls was measured.The model at structural level, which is based on a finite element model, was contrasted with the results obtained in the experimental walls. The sectional analysis is taken from the specialized literature. With the complete structural-section model, the BL walls are analysed. The study shows that the main flexural resistance is provided by the first layer (the conventional diaphragm wall), providing the SFRC layer a secondary flexural resistance.For the geometrical ranges of the elements considered in the thesis (35 cm to 60 cm width first layer, and 10 cm width second layer) the increase in the cross-section ultimate bending resistance when it is strengthened by the SFRC layer is between 8% and 15%. This increase allows a reduction in the steel reinforcement of the first layer (up to 7.0% of the total flexural reinforcement) and, to some extent, it also collaborates with a displacement reduction (reducing up to 7.3% of the maximum displacements). It was also found that the spraying sequence is a crucial parameter to be able to take advantage of the SFRC collaboration, and specific indications are described.Good concrete to concrete bond strength was obtained for the extracted cores. The average shear strength value measured for each age (2, 6 and 35 days) was always above 1.0 MPa for the different cases. Beyond the local test performed, a monolithic behaviour was observed at element level in the experimental walls.A similar final material consumption was observed between the BL walls and the combined consideration of a ML wall and an external waterproof system. The consideration of the technology cost entails a higher construction cost for the BL technique. However, it is still an interesting option under particular circumstances, like space limitations or if continuous maintenance costs want to be avoided in the future.In general terms it can be said that the research herein presented lay the foundation for the development of the bi-layer diaphragm wall technique, which is a promising solution for the leakage problem of diaphragm walls. Nonetheless, more studies are needed to be able to fully use these types of walls as a standard technique, e.g. a detailed cost study and sustainability analysis, debonding risk, waterproofing capability and above all more full scale experimental cases.
Un problema habitual en la construcción de pantallas continuas en terrenos con presencia de agua es la existencia de filtraciones. El objetivo de esta tesis busca resolver este problema mediante el desarrollo de un nuevo tipo de pantalla: la pantalla bi-capa (BL, por sus siglas en inglés). El método para construir estos muros se basa en una solución existente: realizar una segunda capa de hormigón impermeable sobre los muros pantalla. En las pantallas BL, la segunda capa se realiza con hormigón con fibras de acero (SFRC) proyectado sobre las pantallas convencionales (llamadas ML en esta tesis) e incluyendo a su vez una adición impermeabilizante. La idea central es maximizar las funciones de la segunda capa, asignándole un rol estructural, además de la función impermeabilizante. La metodología propuesta se basa en la combinación de trabajos experimentales y herramientas numéricas. Se propone un método de diseño para las pantallas BL basado en modelos estructura-sección desacoplados. Posteriormente se utiliza este método para realizar diferentes comparaciones con pantallas ML y un análisis paramétrico exhaustivo de distintos procesos constructivos involucrados en la construcción de las pantallas BL. La campaña experimental realizada comprende dos niveles: a nivel elemento, se estudió la respuesta estructural de pantallas construidas en un edificio real ubicado en Barcelona; a nivel seccional, se midió el nivel de adherencia entre ambas capas de hormigón mediante testigos extraídos de las pantallas antes mencionadas. El modelo a nivel estructural, basado en elementos finitos, se contrastó con los resultados experimentales obtenidos. El modelo seccional se tomó de la bibliografía estudiada. Con el modelo estructura-sección completo se analizaron las pantallas BL. El estudio muestra que la principal resistencia flexional es aportada por la primera capa (el muro pantalla convencional), siendo secundario el aporte de la capa de SFRC. Para el rango de elementos considerados en esta tesis (35 cm a 60 cm de espesor de primera capa y 10 cm de segunda), el incremento de la resistencia última a flexión cuando se considera el aporte de la capa de SFRC, está entre 8% y 15%. Este incremento permite una reducción en el acero de refuerzo de la primera capa de hasta un 7.0% del total del acero de flexión y, hasta cierto punto, también colabora con una reducción en los desplazamientos (alcanzando reducciones de hasta un 7.3% del desplazamiento máximo). Se observó también que la secuencia de proyección es un factor clave a la hora de aprovechar la colaboración extra aportada por la capa de SFRC. Indicaciones específicas se describen a este respecto. Se obtuvo una buena resistencia de adherencia entre hormigones para los testigos extraídos. La resistencia media medida a cada edad (2, 6, y 35 días) estuvo siempre, para los distintos casos, por encima de 1.0 MPa. Más allá de los ensayos puntuales, se observó un comportamiento monolítico a nivel elemento para las pantallas BL experimentales. Se obtuvo un consumo final de materiales similar entre pantallas BL y la consideración conjunta de una pantalla ML más un sistema impermeabilizante externo. Considerar los costos tecnológicos conlleva un costo constructivo mayor para las pantallas BL. Sin embargo, ésta es aún una opción interesante bajo consideraciones particulares, como limitaciones del espacio subterráneo interior o si se desean evitar costos continuos de mantenimiento. En términos generales, se puede decir que la investigación aquí presentada sienta las bases para el desarrollo de la técnica de muros pantalla bi-capa, la cual es una solución prometedora para el problema de las filtraciones en pantallas. No obstante, son necesarios más estudios para poder usar plenamente este tipo de pantallas de forma habitual, e.g. estudios de sostenibilidad detallados, evaluación del riesgo de desprendimiento de la segunda capa, capacidad impermeable y, sobre todo, más ensayos experimentales a escala real
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Perez-Suarez, D. "Multi-layer analysis of a coronal bright point." Thesis, Queen's University Belfast, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546410.
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Farhat, Ali Y. "Vibrational analysis of composite double layer skeletal structures." Thesis, University of Surrey, 1992. http://epubs.surrey.ac.uk/624/.
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Silva, Diogo Filipe Teixeira Cerqueira da. "Parameter analysis of the armour layer incoastal structures." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/13993.
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Mestrado em Engenharia CivilCoastal erosion is a serious problem that affects numerous countries and particularly Portugal. The sediment deficit, increasing urbanistic pressure and highly energetic coastal areas anticipate the necessity of large investments in shore protection structures. The design process of coastal structures is mainly dependent on empirical formulations, followed by tests on physical models to validate the design solutions. In these empirical formulations, the incorporation of several parameters in to coefficients, adds a level of subjectivity that is relevant on the results. This document intends to address the subjectivity problem through the analysis of the stability coefficient in the Hudson formula. In the original formula, this coefficient expresses the influence of a certain amount of parameters on the armour layer stability of coastal structures. However, there is an absence of recommended values that take into account some important parameters. By increasing the knowledge over the several parameters that influence the stability coefficient, a better accuracy can be achieved. The main focus is on the parameters considered by the Van der Meer formulations (permeability, storm duration, damage level and slope angle) and on the incidence angle in which the wave attacks the structure. A sensitivity analysis was performed for various parameters, in order to evaluate the influence of each parameter on the stability coefficient and final stability values. Using two study cases, a comparison was performed on the design stability coefficient and the coefficient that resulted from physical tests.
A erosão costeira é um problema grave que afecta muitos países do mundo e em particular, Portugal. O défice sedimentar e a crescente pressão urbanística, aliadas a um regime costeiro energético, anteveem a necessidade de avultados investimentos em estruturas de proteção costeira. O processo de dimensionamento de estruturas costeiras passa pela utilização de formulações empíricas, seguido de testes em modelo físico para validar as soluções. Nestas formulações, a incorporação de diversos aspectos em coeficientes, adiciona um nível de subjetividade relevante aos resultados. A intenção deste trabalho é abordar o problema da subjetividade pela análise do coeficiente de estabilidade, presente na fórmula de Hudson. Na fórmula original, este coeficiente exprime a influência de um certo número de parâmetros na estabilidade do manto de proteção de estruturas costeiras. No entanto, existe uma ausência de valores recomendados que tenham em conta alguns parâmetros importantes. Ao amentar o conhecimento sobre os diversos parâmetros que influenciam o coeficiente de estabilidade, é possível alcançar uma maior precisão. De entre os parâmetros que influenciam a estabilidade, o foco principal da análise é sobre os parâmetros considerados nas fórmulas de Van der Meer (permeabilidade, duração da tempestade, nível de dano e ângulo do talude da estrutura) e no ângulo de incidência da onda sobre a estrutura. Uma análise de sensibilidade foi feita para avaliar a influência de cada parâmetro no valor do coeficiente de estabilidade e na estabilidade final. Usando dois casos de estudo, foi feita uma comparação do coeficiente de estabilidade obtido na fase de projeto e o coeficiente que resulta dos testes em modelo físico.
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Scrobonia, David. "Rules Based Analysis Engine for Application Layer IDS." DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1773.
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Web application attack volume, complexity, and costs have risen as people, companies, and entire industries move online. Solutions implemented to defend web applications against malicious activity have traditionally been implemented at the network or host layer. While this is helpful for detecting some attacks, it does not provide the gran- ularity to see malicious behavior occurring at the application layer. The AppSensor project, an application level intrusion detection system (IDS), is an example of a tool that operates in this layer. AppSensor monitors users within the application by observing activity in suspicious areas not able to be seen by traditional network layer tools. This thesis aims to improve the state of web application security by supporting the development of the AppSensor project. Specifically, this thesis entails contributing a rules-based analysis engine to provide a new method for determining whether suspicious activity constitutes an attack. The rules-based method aggregates information from multiple sources into a logical rule to identify malicious activity, as opposed to relying on a single source of information. The rules-based analysis engine is designed to offer more flexible configuration for administrators and more accurate results than the incumbent analysis engine. Tests indicate that the new engine should not hamper the performance of AppSensor and use cases highlight how rules can be leveraged for more accurate results.
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Ryan, Shawn David. "Bifurcation and Boundary Layer Analysis for Graphene Sheets." University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1239646272.
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Affan, Amer. "Collapse of double-layer space grid structures." Thesis, University of Cambridge, 1987. https://www.repository.cam.ac.uk/handle/1810/250905.
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This dissertation is concerned with the behaviour of square-on-square double-layer space grids (DLSG's) and in particular their collapse mechanisms after initial buckling. A detailed review of the methods used for collapse analysis of these structures is conducted, which shows that their collapse can be of progressive nature. An outline of the remedies that have been suggested to make safe their collapse behaviour is given, and it traces the line for further study. The present investigation starts by describing the redundancy in these regular pin-jointed assemblies in terms of unit states of self-stress. This enables us to understand, by means of the extended Maxwell rule, how it is that mechanisms of collapse can occur when relatively few bars in the assembly have failed. The influence of boundary conditions on the mechanisms of collapse and its progressive nature is also investigated. This method of analysis is verified by detailed examination of several previously reported experimental results, and some conclusions can be drawn. The prestressing of statically indeterminate assemblies by means of lack-of-fit is investigated in the hope of changing their collapse characteristics. The unit state of self-stress has been used to explain a method for selecting the bars that can be shortened/lengthened in order to impose a prescribed state of self-stress, and the scope for achievable patterns of bar tensions has been described. A by-product of the investigation is an algorithm which calculates the required lack-of-fit to impose an initial state of self-stress which maximizes the load-carrying capacity of indeterminate trusses. Using the formulae derived for prestress, a statistical analysis is developed to estimate initial bar tensions due to random lack-of-fit in order to obtain a realistic estimate of the load-factor of an assembly before initial bar failure. Furthermore, we have argued and demonstrated how backlash at the bar-joint connection may have a beneficial effect in reducing substantially initial bar tensions due to the inevitable lack-of-fit on account of manufacturing errors of bars. An extensive experimental program has been conducted to verify the assumptions adopted and formulae derived in this dissertation.
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Giancecchi, Nicola. "Analysis and Implementation of the Messaging Layer Security Protocol." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18467/.
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The use of messaging services on smartphones has increased considerably in recent years, due to the growth in the availability of mobile devices and the evolution of communication technologies via Internet, factors that have effectively replaced the use of text messages.
This increase also concerned the use in the business environment, a context where the exchange of confidential information is more frequent and therefore the need to protect communication between two or more people. This is important not only on a security point of view, but also for personal privacy. The major global players have responded by implementing security measures within their services, such as end-to-end encryption and increasingly strict rules regarding the processing of personal data.
In this thesis we will illustrate Messaging Layer Security, shortened as MLS, a new protocol under development that guarantees security and efficiency in group conversations. When in a conversation between two clients, security can be ensured through end-to-end encryption and key exchange. The problem arises when multiple actors participate in the conversation asynchronously: in this case the computational effort is considerable, even more so considering the use of mobile devices with reduced battery capacity that does not guarantee the continuous presence of the online device.
The thesis will deal with both the architectural part, that is more general and traces the outline of the subject, and the protocol part, more technical and detailed. Finally, an implementation of MLS written in Rust and called Melissa will be illustrated, which provides all the basic functionalities indicated in the draft 05 version of the protocol.
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Sze, Kin Yip. "Analysis of line-source-fed single-layer microstrip reflectarrays." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ62669.pdf.
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Hall, David Kenneth. "Analysis of civil aircraft propulsors with boundary layer ingestion." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/97353.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 113-116).
This thesis describes (i) guidelines for propulsor sizing, and (ii) strategies for fan turbomachinery conceptual design, for a boundary layer ingesting (BLI) propulsion system for advanced civil transport aircraft. For the former, configuration performance analysis shows BLI yields a reduction in mechanical power required to propel a given aircraft. For the latter, fan turbomachinery design attributes are identified to mitigate the impact of BLI inlet distortion on propulsor performance. The propulsion system requirements are determined using a mechanical energy analysis, in which the performance of the airframe and propulsor are characterized in terms of sources and sinks of power. Using this framework, the propulsor can be sized based on the performance of the isolated airframe. Analysis of the power savings due to BLI (from reduction of viscous dissipation both in the aircraft wake and the propulsor jet) leads to scaling choices for the sizing of propulsor simulators for wind tunnel experiments to assess BLI benefit. Fan stage distortion response is assessed computationally for a range of turbomachinery design parameters and for distortions characteristic of BLI. The numerical results show the importance of three-dimensional flow redistribution upstream of the fan, and indicate that, for the parameters examined, non-axisymmetric fan stators have the largest effect on decreasing blade row velocity distortions and thus mitigating losses due to flow non-uniformity.
by David Kenneth Hall.
Ph. D.
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Romero, David Luis. "A comparative analysis of physical-layer rateless coding architectures." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90140.
Full textAbstract:
Thesis: S.M. in Electrical Engineering, Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.21
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 113-114).
An analysis of rateless codes implemented at the physical layer is developed. Our model takes into account two aspects of practical communication system design that are abstracted away in many existing works on the subject. In particular, our model assumes that : (1) practical error detection methods are used to determine when to terminate decoding; and (2) performance and reliability as observed at the transport layer are the metrics of interest. Within the context of these assumptions, we then evaluate two recently proposed high-performing rateless codes. Using our analysis to guide an empirical study, the process of selecting the best rateless code for a given set of system constraints is illustrated.
by David Luis Romero.
S.M. in Electrical Engineering
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Brynjell-Rahkola, Mattias. "Global stability analysis of three-dimensional boundary layer flows." Licentiate thesis, KTH, Stabilitet, Transition, Kontroll, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-175353.
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This thesis considers the stability and transition of incompressible boundary layers. In particular, the Falkner–Skan–Cooke boundary layer subject to a cylindrical surface roughness, and the Blasius boundary layer with applied localized suction are investigated. These flows are of great importance within the aviation industry, feature complex transition scenarios, and are strongly three-dimensional in nature. Consequently, no assumptions regarding homogeneity in any of the spatial directions are possible, and the stability of the flow is governed by an extensive three-dimensional eigenvalue problem. The stability of these flows is addressed by high-order direct numerical simulations using the spectral element method, in combination with a Krylov subspace projection method. Such techniques target the long-term behavior of the flow and can provide lower limits beyond which transition is unavoidable. The origin of the instabilities, as well as the mechanisms leading to transition in the aforementioned cases are studied and the findings are reported. Additionally, a novel method for computing the optimal forcing of a dynamical system is developed. This type of analysis provides valuable information about the frequencies and structures that cause the largest energy amplification in the system. The method is based on the inverse power method, and is discussed in the context of the one-dimensional Ginzburg–Landau equation and a two-dimensional flow case governed by the Navier–Stokes equations.QC 20151015
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Roberts, Ibiye Aseibichin. "Investigation of residual stresses in the laser melting of metal powders in additive layer manufacturing." Thesis, University of Wolverhampton, 2012. http://hdl.handle.net/2436/254913.
Full textAbstract:
Laser Melting (LM) is an Additive Layer Manufacturing (ALM) process used to produce three-dimensional parts from metal powders by fusing the material in a layerby- layer manner controlled by a CAD model. During LM, rapid temperature cycles and steep temperature gradients occur in the scanned layers. Temperature gradients induce thermal stresses which remain in the part upon completion of the process (i.e. residual stresses). These residual stresses can be detrimental to the functionality and structural integrity of the built parts. The work presented in this thesis developed a finite element model for the purpose of investigating the development of the thermal and residual stresses in the laser melting of metal powders. ANSYS Mechanical software was utilised in performing coupled thermal-structural field analyses. The temperature history was predicted by modelling the interaction of the moving laser heat source with the metal powders and base platform. An innovative ‘element birth and death’ technique was employed to simulate the addition of layers with time. Temperature dependent material properties and strain hardening effects were also considered. The temperature field results were then used for the structural field analysis to predict the residual stresses and displacements. Experiments involving laser melting Ti-6Al-4V powder on a steel platform were performed. Surface topography analyses using a laser scanning confocal microscope were carried out to validate the numerically predicted displacements against surface measurements. The results showed that the material strain hardening model had a direct effect on the accuracy of the predicted displacement results. Using the numerical model, parametric studies were carried out to investigate the effects of a number of process variables on the magnitude of the residual stresses in the built layers. The studies showed that: (i) the average residual stresses increased with the number of melted powder layers, (ii) increasing the chamber temperature to 300°C halved the longitudinal stresses. At 300°C, compressive stresses appeared on the Ti64 surface layer, (iii) reducing the raster length from 1 mm to 0.5 mm reduced the average longitudinal stress in the top layer by 51 MPa (0.04σy), (iv) reducing the laser scan speed from 1200 mm/s to 800 mm/s increased the longitudinal stress by 57 MPa (0.05σy) but reduced the transverse stress by 46 MPa (0.04σy).
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Sreedharan, Nair Shree Narayanan. "Impedance Measurement of Cells; Experiment and Analysis of Passivation Layer." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/46424.
Full textAbstract:
Biological cells like any other material do conduct electricity. Though they come across as insulators, the resistance to the flow of current, i.e. impedance, could be used to characterize the cell itself. In this aspect, the impedance of cells can be a promising tool to investigate the state of the cell.
A simple way of measuring the impedance would be a planar-microelectrode method. The cells are contained in culture medium while measurements are taken with micro-electrodes fabricated on top of a substrate. Since both the probe â tipsâ do not come in contact with the probed object, the impedance to be measured includes some components apart from that contributed by the cells.
There have been publications reporting the usage of impedance of a cell to determine changes in the state of cells due to healing, drug candidate testing, functional genomic studies and so on.
In this thesis, an effort has been made to measure the impedance of cells. Further, a component of the sensor, the passivation layer has been investigated for its contribution to the measured impedance in a quantitative manner.Master of Science
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Lim, Jong Il. "Transient finite element analysis of electric double layer using Nernst-Planck-Poisson equations with a modified stern layer." Texas A&M University, 2006. http://hdl.handle.net/1969.1/4703.
Full textAbstract:
Finite element analysis of electric double layer capacitors using a transient
nonlinear Nernst-Planck-Poisson (NPP) model and Nernst-Planck-Poisson-modified
Stern layer (NPPMS) model are presented in 1D and 2D. The NPP model provided
unrealistic ion concentrations for high electrode surface potential. The NPPMS model
uses a modified Stern layer to account for finite ion size, resulting in realistic ion
concentrations even at high surface potential.
The finite element solution algorithm uses the Newton-Raphson method to solve
the nonlinear problem and the alpha family approximation for time integration to solve
the NPP and NPPMS models for transient cases. Cubic Hermite elements are used for
interfacing the modified Stern and diffuse layers in 1D while serendipity elements are
used for the same in 2D. Effects of the surface potential and bulk molarity on the electric potential and ion
concentrations are studied. The ability of the models to predict energy storage capacity is
investigated and the predicted solutions from the 1D NPP and NPPMS models are
compared for various cases. It is observed that NPPMS model provided realistic and
correct results for low and high values of surface potential.
Furthermore, the 1D NPPMS model is extended into 2D. The pore structure on
the electrode surface, the electrode surface area and its geometry are important factors in
determining the performance of the electric double layer capacitor. Thus 2D models
containing a porous electrode are modeled and analyzed for understanding of the
behavior of the electric double layer capacitor. The effect of pore radius and pore depth
on the predicted electric potential, ion concentrations, surface charge density, surface
energy density, and charging time are discussed using the 2D Nernst-Planck-Poissonmodified
Stern layer (NPPMS) model.
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Harris, Brad G. "Analysis of lateral boundary effects on inner domain of COAMPS." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Sep%5FHarris.pdf.
Full textAbstract:
Thesis (M.S. in Meteorology and Physical Oceanography and M.S. in Applied Mathematics)--Naval Postgraduate School, Sept. 2004.Thesis advisor(s): Douglas K. Miller, Beny Neta. Includes bibliographical references (p. 83). Also available online.
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Belleschi, Marco. "Cross-layer optimization protocols in Ad-hoc networks: analysis and practical implementation of transport and network layers." Thesis, KTH, Reglerteknik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-105891.
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Ad-hoc wireless networks use multi-hop transmissions to communicate, without exploiting any infrastructure. Logical links create unreliable connections between nodes: the capacity of the channel can unpredictably change due to the presence of obstructions, interferences between nodes and stochastic phenomena such as fading. Moreover the medium is multi-access and resources are contended by different users. It is possible to notice that adjusting the power at the physical layer affects the interference perceived, which in turn modifies the resources availability, alters the queue length at the network layer and eventually influences the source rates at the transport layer. To this end, a lot of works have shown that a better understanding of inherent coupling between different layers in the networking stack is worth. Specifically, network performances can be increased if the traditionally separated network layers are jointly optimized. Network utility maximization has emerged as a powerful framework for studying such cross-layer issues and optimizing performances overall the network. In particular, we focus on distributed cross-layer algorithms that achieve a global optimum recurring to local information only. Although the literature is vast in this field, most of works remain as theory. We aim at clarifying the practical feasibility of such theoretical dissertations and what considerations are needed in order to establish a bridge between theory and practice. After analyzing different crosslayer methods, we focus on the work of Papandriopoulos et al.. We first discuss its theoretical benefits in an interference limited system such as CDMA, without accounting physical constraints of the network. In order to validate the performances in a more realistic scenario, we implement the algorithm of Papandriopoulos et al. in the NS-2 network simulator without breaking up the hierarchy of the standard ISO/OSI stack. We focus on modeling physical, data link, network and transport layer, underlining issues and possible solutions from a practical perspective. For instance, we propose a novel approach to calculate the congestion prices of the network. After discussing benefits and drawbacks of the underlying theory, we propose several results under many simulation scenarios and eventually a comparison with the standard protocol for wireless networks IEEE/802.11.
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Graffeo, Jeffrey K. "Mathematical modeling of adhesive layer cracks utilizing integral equations." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-05022009-040448/.
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Li, Pan. "Capacity analysis and cross-layer protocol design in wireless networks." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024777.
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Ware, John (John Welling). "An analysis of quadrotor flight in the urban canopy layer." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107056.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 105-113).
This thesis presents two distinct bodies of work concerning quadrotor flight in urban wind fields. The first attempts to characterize a quadrotor's ability to exploit urban wind fields for improved flight performance. A computational fluid dynamics model is used to obtain a wind field estimate given a 3D model of the environment and a prevailing wind estimate. Minimum-energy trajectories are then found through the environment using an empirically derived power consumption model for a specific quadrotor platform. It is shown in simulation that a minimum-energy planner aware of the wind field outperforms a naive, wind-unaware planner over metrics such as total energy consumption, time to goal, and failure rate. The second component of the work focuses on the development of an onboard wind sensor for quadrotors. Although it is not yet clear how to integrate these measurements into a global wind field estimate or use them in a planner, it is intuitive that on-board measurements could inform the local wind field estimate or validate the global one. Accordingly, an effort was made to integrate an existing microelectromechanical flow sensor into a quadrotor platform. Initial results from full-scale tests in the Wright Brothers wind tunnel at MIT demonstrate the the sensor's performance in flight and hover conditions.
by John Ware.
S.M.
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Merchant, Ali A. (Ali Abbas). "Design and analysis of supercritical airfoils with boundary layer suction." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10987.
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Mattingly, Brett T. (Brett Thomas). "Containment analysis incorporating boundary layer heat and mass transfer techniques." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/84749.
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Burich, Mariano Eduardo. "A cross layer analysis of harq protocols in wireless networks." Universidade Tecnológica Federal do Paraná, 2017. http://repositorio.utfpr.edu.br/jspui/handle/1/2570.
Full textAbstract:
Este trabalho estuda as potenciais melhorias na eficiência energética e vazão do método híbrido de requisição automática de retransmissão (Hybrid Automatic Retransmission Request, HARQ). A análise inclui as camadas física (PHY) e de acesso ao meio (MAC). É investigada a relação de compromisso gerada pelo HARQ, o qual demanda uma menor potência de transmissão para uma certa probabilidade de falha alvo ao custo de mais acessos ao canal. Uma vez que a competição para acesso ao canal na camada MAC é bastante custosa em termos de energia e atraso, os resultados mostram que a utilização do HARQ leva a uma grande melhoria de performance devido ao menor número de nós competidores – uma consequência da redução na potência de transmissão necessária. Contra-intuitivamente, esta análise leva à conclusão que retransmissões podem diminuir o atraso, melhorando a performance do sistema. Finalmente, são também investigados valores ótimos para o número de retransmissões permitidas, visando maximizar vazão ou/e eficiência energética.This work studies the potential improvements in terms of energy efficiency and throughput of a hybrid automatic retransmission request (HARQ) mechanism. The analysis includes both the physical (PHY) and medium access (MAC) layers. We investigate the trade-off provided by HARQ, which demands reduced transmit power for a given target outage probability at the cost of more accesses to the channel. Since the competition for channel access at the MAC layer is very expensive in terms of energy and delay, our results show that HARQ leads to great performance improvements due to the decrease in the number of contending nodes – a consequence of the reduced required transmit power. Counter-intuitively, our analysis leads to the conclusion that retransmissions may decrease the delay, improving the system performance. Finally, we investigate the optimum values for the number of allowed retransmissions in order to maximize either the throughput or the energy efficiency.
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Liang, Fang-Pei. "An inviscid stability analysis of unbounded supersonic mixing layer flows." Case Western Reserve University School of Graduate Studies / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=case1055355056.
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Hattori, Masanari. "Generalized slip-flow theory and its related Knudsen-layer analysis." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215508.
Full textAbstract:
The content of Chapter 1 is an author produced version of a paper published in Physics of Fluids. The final publication is available at AIP via http://dx.doi.org/10.1063/1.3691262. The content of Chapters 2 and 4 is an author produced version of papers published in Journal of Statistical Physics. The final publications are available at Springer via http://dx.doi.org/10.1007/s10955-012-0512-z and http://dx.doi.org/10.1007/s10955-015-1364-0, respectively.Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第19682号
工博第4137号
新制||工||1638(附属図書館)
32718
京都大学大学院工学研究科機械理工学専攻
(主査)教授 青木 一生, 教授 髙田 滋, 教授 稲室 隆二
学位規則第4条第1項該当
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Williamson, Matthew J. "Finite element analysis of hot-mix asphalt layer interface bonding." Diss., Kansas State University, 2015. http://hdl.handle.net/2097/19037.
Full textAbstract:
Doctor of PhilosophyDepartment of Civil Engineering
Mustaque A. Hossain
Tack coat is a thin layer of asphaltic material used to bind a newly-placed lift of hot-mix asphalt (HMA) pavement to a previously-placed lift or a new HMA overlay/inlay and existing pavement. The purpose of a tack coat is to ensure that a proper bond occurs so that traffic loads are carried by the entire HMA structure. Proper bonding exists when HMA layers act as a monolithic structure, transferring loads from one layer to the next. This depends on appropriate selection of tack coat material type and application rate, and is essential to prevent slippage failure and premature cracking in the wearing surface. This study focuses on development of a three-dimensional finite element (FE) model of HMA pavement structure in order to assess HMA interface bonding. The FE model was constructed using commercially available ABAQUS software to simulate an Accelerated Pavement Testing (APT) experiment conducted at the Civil Infrastructure Systems Laboratory (CISL) at Kansas State University. Mechanistic responses measured in the CISL experiment, such as localized longitudinal strain at the interface, were used to calibrate the FE model. Once calibrated, the model was used to predict mechanistic responses of the pavement structure by varying the tack coat property to reflect material characteristics of each application. The FE models successfully predicted longitudinal strains that corresponded to APT results.
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Bolourchi, M. "Inclusion of a layer of lead in infilled frame structure." Thesis, University of Surrey, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383465.
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Thim, Johan. "Simple Layer Potentials on Lipschitz Surfaces: An Asymptotic Approach." Doctoral thesis, Linköpings universitet, Tillämpad matematik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-16280.
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This work is devoted to the equation
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Sinha, Roy Arijit. "Analysis and control of boundary layer transition on a NACA 0008 wing profile." Thesis, KTH, Mekanik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-239931.
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The main aim of this thesis was to understand the mechanism behind the classical transition scenario inside the boundary layer over an airfoil and eventually attempting to control this transition utilizing passive devices for transition delay. The initial objective of analyzing the transition phenomenon based on TS wave disturbance growth was conducted at 90 Hz using LDV and CTA measurement techniques at two different angles of attack. This was combined with the studies performed on two other frequencies of 100 and 110 Hz, in order to witness its impact on the neutral stability curve behavior. The challenges faced in the next phase of the thesis while trying to control the transition location, was to understand and encompass the effect of adverse pressure gradient before setting up the passive control devices, which in this case was miniature vortex generators. Consequently, several attempts were made to optimize the parameters of the miniature vortex generators depending upon the streak strength and stability. Finally, for 90 Hz a configuration of miniature vortex generators have been found to successfully stabilize the TS wave disturbances below a certain forcing amplitude, which also led to transition delay.
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Yang, Chen-Chung, and 楊政中. "Performance analysis of Laser smoke layer dectector." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/36927375819771514809.
Full textAbstract:
碩士國立雲林科技大學
機械工程系碩士班
95
Fire damages always cast shadows on social events that people cannot forget. Besides claiming people’s lives, it’s more difficult to estimate for a great loss of treasure. According to the past statistics, the most fatal cause of building fires was dense smoke. It is because heavy smoke will bring about vision barriers, and then lead to much more difficulties in fleeing. As a result, the main purpose of this research is confer the performance test of smoke which laser smoke layer detectors bring. This research is mainly to test the voltage of smoke obscuration in different environment for judging if the external light do effect, and to change the voltage into the smoker layer obscuration ratio then estimate the eight- meter’s visibility of the emergency exit light when people are fleeing. How to use the smoke detector effectively to estimate the number of people who take refuge and flee is the main purpose of the research.
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Mahadevan, Pradeep. "Analysis of layer development and fusing for 3D laser printing." 2003. http://www.lib.ncsu.edu/theses/available/etd-05062003-080231/unrestricted/etd.pdf.
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魏中聖. "Numerical and Experimental Residual Stress Analysis on Laser Hardfacing Layer." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/79230260231513079005.
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博士國立中正大學
機械系
91
The hole-drilling method is applied extensively in the residual stress measurement. The integral hole-drilling method is further developed for improving the accuracy of the hole-drilling method especially for measuring residual stresses varying abruptly with depth. One of the important factors affecting the accuracy of stress values obtained from hole-drilling method is the calibration coefficients. A three-dimensional finite element model was established to determine and to improve the calibration coefficients for integral hole-drilling method. The calibration coefficients could be determined within one computation procedure with this model. The relationship between the calibration coefficients and plate thickness was investigated and the calibration coefficients determined in this work can be extended to measure residual stresses of either thin or thick plates. Experimental validation of the calibration coefficients for integral hole-drilling method based on the improved 3-D FE model was achieved using bending test of a cantilever beam. Experimental results of the bending test show a significant improvement of the accuracy of relieved stress calculation. Experimental results also show that significant error in the residual stress measurement could be induced if calibration coefficients were not chosen correctly for corresponding plate thickness. A transitional dimensionless thickness was proposed by examining the calculated relieved stresses obtained from the calibration coefficients for different plate thicknesses. The probability bounds of relieved stress corresponding to both cases were also calculated to reveal the improvement of the calibration coefficients obtained from 3-D model. Numerical simulation on the bending test was performed using a FEM model. The results show that the calculated residual stress value was strongly affected by the hole diameter used to evaluate the residual stress, and the error was attributed to the deviation of real hole geometry from an idealized model. Correction of the diameter was proposed to effectively reduce the error in the residual stress calculation. Integral hole-drilling method with improved calibration coefficients was applied to determine residual stresses at the interface of the clad layer for better accuracy. The transverse and longitudinal residual stress distributions near the interface between the clad layer and substrate is less uniform as that in the clad layer owing the phase transformation of the substrate and dissimilar properties between clad layer and substrate. The measured results at each hole depth increment revealed a good reproducibility of the integral hole-drilling method. Numerical analysis on the residual stress distribution of the laser clad layer was conducted considering the phase transformation of the substrate. A modified Goldak’s model was used to simulate the heat source and a reasonable shallow fusion zone was achieved. Thermo-metallurgical computation enables the quantitatively determination of phase proportion of the substrate after laser cladding. The resulted temperature history and the phase proportion were used to interpret the residual stress distribution obtained from integral hole-drilling method. The predicted residual stress distribution was consistent with the compared with the measured residual stresses in trends. With the help of numerical analysis, we had a better understanding on the development of the residual stresses in the laser clad layer.
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Lin, Guan-Yu, and 林冠宇. "Analysis of Ultrasonic Transducer Matching Layer." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/20115008474344750030.
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碩士國立臺灣大學
工程科學及海洋工程學研究所
102
The aim of this paper is to explore the sensitivity of ultrasonic transducer front matching layer using the piezoelectric wave equation and mason equivalent circuit as design conceptions. First, we introduce the structure of the ultrasonic piezoelectric transducer and the factors that impact the performance of the transducer. Through the wave equation, the impedance matrix of piezoelectric transducer is derived. In reproduction order to simplify the complex boundary condition on impedance matrix, using the concept of the acoustic energy transmitted to analyze the internal structure of the transducer. Then, the transfer matrix of transducer is derived. It can simulate acoustic signal transmission matrix transducer which are transferred by layers of the structure inner and outer to affect transducer transfer function. So, we can regard the transfer function as the sensitivity of transducer. This study found the tendency in different thickness of matching layer on impact of transfer function through the simulation. Using the pulse-echo system to measure the sensitivity of each transducer, and also find their tendency. The result shows the tendency of simulation is similar to experiment, but the peak value of sensitivity is not match. Also trying to improve the process to reproduce the different thickness of transducers and compare with each tendency. Finally, both are match.
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Fu, Chang-Chia, and 張家福. "Stress Analysis in the IMC Layer." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/65167993814702322249.
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碩士國立中山大學
機械工程學系研究所
88
The residual stress distribution, growth of Intermetallic Compound (IMC) layer and the equivalent strength in the Laser diode package are investigated in this thesis. The redistribution of residual stress in the solder layer is calculated by employing the MARC finite element package. The effects of residual stresses and IMC layer on the bonding strength of Laser diode under taken different thermal load cycles are studied. Numerical results are compared with the results measured experimentally. Results indicate the effect of residual stresses introduced in the solder solidification is so important in the stress analysis of a solder joint. The effects of different solder parameters, i.e, solder alloy, solder layer thickness and the number of thermal load cycles, are also analyzed in this work.. A better understanding about the solder bond strength is expected from this analysis.
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Nugraha, Brilian Tafjira, and Brilian Tafjira Nugraha. "Analysis of Layer Efficiency and Layer Reduction on Pre-trained CNN Models." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/2cvk37.
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碩士國立臺灣科技大學
電機工程系
106
Deep learning still encounters several issues like overfitting and oversize due to the use of a large number of layers. The huge size greatly constrains performance and portability of deep learning models in limited environments like embedded and IoT devices. In this study, we reported our analysis of activation and gradient output and weight in each layer of the pre-trained models of VGG-16 and custom AlexNet to measure the efficiency of its layers. The efficiencies are estimated by using our measurements and compared with the manual layer reduction to validate the most relevant method. The method for multiple layer reductions is used for validation. With this found approach, the time of one-layer reduction and re-training processes on both models can save up to 9 folds and 5 folds respectively without significant accuracy reduction.
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Tseng, Po-Kang, and 曾柏綱. "Analysis of Characteristics of Co-extrusion Multi-layer films with micron layer thickness." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/13367491956987210881.
Full textAbstract:
碩士國立交通大學
機械工程系所
102
Since single-layer polymer film do not meet the requirements of new applications of packaging and optical components, multi-layer polymer films are widely used. However, most current applications of multi-layer polymer films use a small number of layers but with increased thickness. Recent studies of nanomaterials show that multi-layer polymer films with layer thickness in micrometer and nanometer scale has become a new trend of technological development. This study investigated how of layer thickness, number of layers, and the interface between layers affect the mechanical characteristics and gas barrier ability while layer thickness does not change the thickness of multi-layer films, increasing the number of layers significantly decreases layer thickness to the micron scale. This study developed a new mold design that can separate and expand co-extruded polymer films by using a co-extrusion system that has been described previously. The mold enables repeated overlay of two polymer layers to reduce layer thickness and increase the number of layers. The specimen are then compared by optical microscope, and a gas permeability experiment is performed to determine the relationships among number of layers, layer thickness, and gas barrier ability in the multi-layer films. Finally, a gas permeability experiment is performed using size exclusion method to generalize the relationship between gas permeability, numbers of layers, and layer thickness, and to establish a numerical model of gas permeability. The experiments indicate that polypropylene is an effective water vapor barrier, and its oxygen barrier characteristics resemble those of polyamide. Overall, gas permeability revealed a strong correlation with the number of layers of multilayer films. The experimental results of this study provide a reference for further study of the functional mechanisms of polymer multilayer films.
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Lin, Jen-hsi, and 林仁喜. "Analysis of economic benefit of layer industry." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/19019944125665813690.
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碩士國立雲林科技大學
財務金融系碩士班
94
This thesis is basic on the production information of six-white layer species, to confer the cost recovering and break-even balance in different production cycle and layers strains within the traditional and automatic chicken house type. Furthermore, using three different prices of chicks, feed and table eggs to process sensitivity analysis, in order to know the condition of variant costs. On the other hand, use the sensitivity analysis of Break-even Analysis in CVP (Cost-Volume-Profit Analysis). To confer the variation of production profit and break-even point analysis within six layer strains, in order to improve the production cost and revenue value for layer farmers. The result show that, (1) To make decision of cost strategy in different production cycle, it’s not really suitable to be forced molting in every strain. But in different economic condition, as the CVP analysis, the first production cycle has better performance in BEP-week. This is also means that the cost recover of non- forced molting is sooner and the investment risk is less than forced molting. (2) Using CVP sensitivity analysis to compare the different strains, the high productivity strain can more raise the average income for every week. There is best weekly contribution margin in higher feed price as well as higher eggs price. This can speed up the cost recover of the production. Besides, to analyze the net productivity, the profit of IW strain is best. Therefore, this high productivity strain is the best choice for producers with low risk & high profit result. (3) To compare with traditional and automatic chicken house, the cost of depreciation and labor for weekly variant operating cost of automatic chicken house is less than traditional. But the weekly contribution margin of automatic chicken house is higher than traditional one, that the cost recover of automatic chicken house more quickly. (4) To integrated the comparison of the productivity under a limited resource, there are two species in the second production cycle and six strains in the first production cycle, within different prices of eggs, feed and chicks, the IW strain has the best contribution margin per unit. The average egg of every week production and totally egg capacity is most important factor of contribution margin per unit, this factor should be the most important consideration for decision makers. Hence, People would rather consider the best contribution per unit than the advantage of production period of strains. We hope this thesis can present the data of analysis result, to provide the reference indication of the production efficiency, in order to improve the competitiveness in layer industry. Key words: Layer, Strain, BEP, CVP, Egg, Chick price, Moltin
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Wang, I.-Kai, and 王奕凱. "Multi-layer Incremental Clustering for Malware Analysis." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/5a2czy.
Full textAbstract:
碩士國立中山大學
資訊管理學系研究所
104
The threat of malware is definitely the most important topic of internet security. As the growth of malware is faster ever and ever, the defense method of security must evolve. Unfortunately the IT expert only can start to deal with attack problem after the new malware have already invaded our system. The usual steps for malware attack issue is to collect the evidence first. Then the IT expert can analyze these evidence to find out the solution. At last, we need to improve our system in case that there will be another malware attack. In this paper, we propose a malware analysis system to accurately cluster new malware. We extract the significant feature from malware sample. For source code file, we extract the syntax string as the feature. For binary file, we transform the binary file to image file, and extract the matrix vector from the image as the feature. Then we adopt two different clustering algorithm, advanced incremental clustering and extended 1-NN, to cluster our malware sample. Finally, our system can offer a detailed report abou the malware family relationship. In our research, there are four experiments to verify our system. We compare the performance and accuracy about the two different clustering algorithm, and verify the system’s maturity with random sample analysis order. We also compare our system with Virustotal.com and Avira software, and the result confirms that our system can do better efficient clustering.
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JIANG, WEN-SHAN, and 江文山. "Analysis of laminar boundary layer under waves." Thesis, 1992. http://ndltd.ncl.edu.tw/handle/72040151112065662126.
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