Dissertations / Theses on the topic 'Layer-2 and Layer-3 handoff'
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Venkatachalaiah, Suresh, and suresh@catt rmit edu au. "Mobility prediction and Multicasting in Wireless Networks: Performance and Analysis." RMIT University. Electrical and Computer Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070301.130037.
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Handoff is a call handling mechanism that is invoked when a mobile node moves from one cell to another. Such movement may lead to degradation in performance for wireless networks as a result of packet losses. A promising technique proposed in this thesis is to apply multicasting techniques aided by mobility prediction in order to improve handoff performance. In this thesis, we present a method that uses a Grey model for mobility prediction and a fuzzy logic controller that has been fine-tuned using evolutionary algorithms in order to improve prediction accuracy. We also compare the self-tuning algorithm with two evolutionary algorithms in terms of accuracy and their convergence times. Our proposed method takes into account signal strengths from the base stations and predicts the signal strength of the next candidate base station in order to provide improved handover performance. The primary decision for mobility prediction is the accurate prediction of signal strengths obtained from the base stations and remove any unwanted errors in the prediction using suitable optimisation techniques. Furthermore, the model includes the procedures of fine-tuning the predicted data using fuzzy parameters. We also propose suitable multicasting algorithms to minimise the reservation of overall network resource requirements during handoff with the mobility prediction information. To be able to efficiently solve the problem, the situation is modelled using a multicast tree that is defined to maintain connectivity with the mobile node, whilst ensuring bandwidth guarantees and a minimum hop-count. In this approach, we have tried to solve the problem by balancing two objectives through putting a weight on each of two costs. We provide a detailed description of an algorithm to implement join and prune mechanisms, which will help to build an optimal multicast tree with QoS requirements during handoff as well as incorporating dynamic changes in the positions of mobile nodes. An analysis of how mobility prediction helps in the selection of potential Access Routers (AR) with QoS requirements - which affects the multicast group size and bandwidth cost of the multicast tree -- is presented. The proposed technique tries to minimise the number of multicast tree join and prune operations. Our results show that the expected size of the multicast group increases linearly with an increase in the number of selected destination AR's for multicast during handoff. We observe that the expected number of joins and prunes from the multicast tree increases with group size. A special simulation model was developed to demonstrate both homogeneous and heterogeneous handoff which is an emerging requirement for fourth generation mobile networks. The model incorporates our mobility prediction model for heterogeneous handoff between the Wireless LAN and a cellular network. The results presented in this thesis for mobility prediction, multicasting techniques and heterogeneous handoff include proposed algorithms and models which aid in the understanding, analysing and reducing of overheads during handoff.
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Mola, Guilo. "Interactions of Vertical Handoffs with 802.11b wireless LANs : Handoff Policy." Thesis, KTH, Mikroelektronik och Informationsteknik, IMIT, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-93067.
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Nomadic computing aims to be a leading short term revolution in the Internet, however to succeed in this the infrastructure, the protocols, the handoff mechanisms have to be designed and implemented to provide mobile computing with both reliability and transparency. A good deal of the work is addressed by mobile IP itself, but addressing wireless diversity is perhaps the most important next step. Many different wireless technologies are available; while one technology might provide wide coverage, another provides higher bandwidth, but can only be deployed locally, even uni-directional ad-hoc links can be used to carry IP traffic. To take full advantage of the potential infrastructure, a mobile device, with multiple network interfaces, should be able to dynamically switch from one link technology to another; hopefully totally transparently to the user. Moreover, having multiple interfaces allows the device to choose, each time a new connection is established, which interface to select to route the datagrams through, based on the type of service desired. In this thesis a possible solution is presented, involving both vertical handoff optimization and policy management. Our testing device is the the SmartBadge v4, provided with a GPRS link and a 802.11b WLAN interface.Nomadic Computing har för avsikt att revolutionera dagens Internet tillämpningar. För att lyckas måste dock infrastrukturen, IT protokollen och handoff procedurer utformas och implementeras med intentionen att förse mobilt dataöverföring med både driftsäkerhet och autonoma processer. En stor del av de nödvändiga förutsättningarna är tillgängliga tack vare Mobile IP, men mångfalden inom de befintliga Wireless teknologierna utgör fortfarande ett problem. Det stora antalet disponibla Wireless tekniker varierar från teknologierer som förser användaren med en stor täckningsgrad, till sådana som förser användaren med högre bandbredd, begränsad till lokala anv ändningområden. Även Uni-directional ad-hoc links kan läggas i denna lista av mångfald. För att förverkliga fördelarna med den tänkta infrastrukturen fullt ut måste den mobila enheten kunna utföra omkopplingar från den ena wireless teknologin till den andra, med syftet att vara osynlig för användaren. Utöver detta är det meningen att en apparat med många anslutningar ska kunna välja den anslutning som passar bäst, var gång en ny koppling ska göras, beroende på den tjänst som efterfrågas. Det här examensarbetet presenterar en möjlig lösning, som utnyttjar både Vertical Handoff optimering och Policy Management. Prototyp-enheten vi anv änder oss av för att genomföra undersökningen är Smart Badge v4, utrustad med GPRS och 802.11b Wireless LAN anslutningar.
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Holmgren, Carl. "Neocortical layer 2/3 microcircuits /." Stockholm, 2004. http://diss.kib.ki.se/2004/91-7140-092-3/.
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Bender, Kevin James. "Mechanisms of deprivation-induced map plasticity at layer 4 to layer 2/3 synapses in rat barrel cortex /." Diss., Connected to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2005. http://wwwlib.umi.com/cr/ucsd/fullcit?p3187822.
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Thesis (Ph. D.)--University of California, San Diego, 2005.Title from first page of PDF file (viewed January 11, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Wen, Jing. "Experience-dependent plasticity of layer 2/3 circuits in developing somatosensory neocortex." Research Showcase @ CMU, 2012. http://repository.cmu.edu/dissertations/121.
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Experience-dependent plasticity is the adaptability of brain circuits as a result of changes in neural activity, a phenomenon that has been proposed as the neural basis for important brain function in health and disease. The underlying mechanisms of experience-dependent plasticity can take different forms, depending on the organisms and brain areas under investigation. A better understanding of these mechanisms will help to interpret normal brain function as well as to guide therapies for neurological diseases. Mouse vibrissa system offers great experimental advantages to studying experience-dependent plasticity and the underlying molecular mechanisms at different levels.
Using sensory experience paradigms of unbalanced whisker activity, we find that sensory experience induces rapid synaptic strengthening at excitatory synapses converged onto single layer 2/3 pyramidal neurons, although the plasticity at these synapses displays remarkable input specificity. Furthermore, we discover that recently potentiated layer 4-2/3 excitatory synapses are labile and subject to activity-dependent weakening in vitro. Calcium-permeable AMPARs (CP-AMPARs) that are sometimes associated with synaptic strengthening are not essential for activity-induced synaptic weakening. Finally, we demonstrate that ongoing sensory experience triggers distinct phases of synaptic plasticity, which are tightly correlated with changes in NMDAR properties and function. Taken together, the results from this thesis show distinct manifestations and mechanisms of how sensory experience modulates synaptic properties and neuronal function that may provide insights into information processing and coding in the neocortex.
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Waindim, Mbu. "On Unsteadiness in 2-D and 3-D Shock Wave/Turbulent Boundary Layer Interactions." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1511734224701396.
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Cavallaro, Andrea. "Optimisation of CSD buffer layers for YBa(2)Cu(3)O(7) coated conductor development." Doctoral thesis, Universitat Autònoma de Barcelona, 2005. http://hdl.handle.net/10803/3218.
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Las cintas superconductoras de alta temperatura (HTS) han emergido como materiales prometedores para sus uso en el campo de l'energía puesto que permiten reducir a mitad el tamaño de los equipos de energía eléctrica respecto a los convencionales, reducir las pérdidas de energía, aumentar la eficacia en la generación, la transmisión y la distribución de la misma, y así la reducir el impacto ambiental.Sin embargo, diversamente de los conductores típicos, los materiales superconductores basados en óxido son frágiles, se dañado fácilmente y son así difíciles de procesar. Hasta ahora ha sido posible producir longitudes de un kilómetro de cables HTS de primera generación, para el uso en el trasporte de corriente eléctrica. Las cintas superconductoras de YBCO, por ejemplo, pueden soportar altas densidades de corrientes críticas y por esto representan un candidato prometedor en el trasporte de electricidad.
Uno del los substratos disponible para suportar el superconductor es un acero policristalino con una película epitaxial de YSZ en cima, YSZ(IBAD)/Stainless. El segundo que hemos utilizado es el NiO(SOE)/Ni(Rabit), una cinta de nickel previamente texturada por laminación y sucesivamente oxidata de manera controlada. Numerosas técnicas están disponible para la deposición de YBCO epitaxiale, nosotros elegimos el proceso más barato y industrialmente interesante: la técnica sol-gel. Para evitar la interacción entre el YBCO superconductor y el substrato epitaxial, evitando así la reducción de la corriente que el superconductor puede trasportar, es importante interponer un material inerte que transfiera su epitaxia al YBCO; este clase de películas se llaman capas tampón.
El objetivo principal de esta tesis ha sido optimizar el crecimiento de las capas tampón por técnica química y finalmente estudiar la deposición del YBCO por TFA sobres esas muestras optimizadas. Las capas de cerámica que hemos estudiados han sido: CeO2, BaZrO3, CaZrO3, SrZrO3, SrTiO3, BaCeO3 , y depositadas por el método químico: metal 2-4--diketone disuelto en ácido acético, o los metales isopropoxidos disuelto en metanol. Por depositar las soluciones precursoras hemos utilizado la técnica de spin coating. Controlando los diversos parámetros, velocidad, aceleración y la concentración de la solución obtuvimos películas homogéneas con diverso grosor. La fase de la cristalización se alcanza en un horno donde se controla l'atmósfera, la temperatura y la velocidad de calefacción. Durante esta investigación hemos adquirido un conocimiento total del acrecimiento de las películas delgada de MOD-CeO2. De una combinación de las análisis de TEM, de XRD y de RHEED observamos que el mecanismo de crecimiento tiene un comportamiento anómalo comparado con el otro materiales crecidos con la misma técnica.
En este proceso de síntesis de la ceria, la nucleation homogénea de hecho esta favorita debido al bajo valor de Tnuc./Tmel ceria (Tnuc./Tmel=0.21). Solamente los granos nucleados sobre el substrato resultan texturados. La dependencia del tamaño de grano con temperatura sigue una relación de tipo Arrhenius, características de un crecimiento 3D del grano. Los análisis de EELS revelaron una fracción significativa de C residual que adorna los límites de grano, es probable que el crecimiento del límite de grano se quede bloqueando debido estas impurezas.
Un proceso del recocido en aire a posteriores, ha demostrado la posibilidad de crecer las películas de CeO2 totalmente epitaxiales. Los análisis de EELS de tales muestras tratadas en oxígeno demuestran claramente que los límites de grano quedan limpios de las impurezas de C, desbloqueando así el crecimiento del grano. Después de un proceso largo de optimización de los parámetros de síntesis, podemos ahora controlar exactamente el crecimiento epitaxiale de la ceria. Se ha verificado que el óxido del cerio se puede crecer en YSZ(IBAD)/SS con solamente la orientación (00l). Para preservar la cinta del metal contra la oxidación, el proceso optimizado se ha adaptado a la deposición sobre substrato de acero inoxidable reduciendo la temperatura de síntesis a 900ºC.
Hemos optimizado también la preparación de SrTiO3(STO) y BaZrO3(BZO) sobre MgO y YSZ mono-cristales y en seguida también sobre YSZ(IBAD)/SS y NiO(SOE)/Ni.
La arquitectura más prometedora resultó ser STO/BZO/NiO(SOE)/Ni. Por ultimo depositamos YBCO por método TFA (Trifluoracéticetatos) sobre las capas tampones optimizadas. Una muestra de TFA-YBCO sobre CeO2/YSZ(IBAD)/SS preparada en aire a 900ºC en 8 h ha dato como resultado una densidad corriente crítica, Jc de 7 MA/cm2 a 5K, y 6·105A/cm2 a 77K. Estos valores están cerca de objectivo de un millón A/cm2 a 77K. Los experimentos sobre las capas tampón de BZO y de STO han demostrado la posibilidad de usar este sistema doble sobre NiO(SOE)/Ni como plantilla alternativa para el crecimiento de YBCO. Alcanzado una densidad de corriente crítica de Jc(5K) = 5·105A/cm2 con la mejor muestra de YBCO/STO/BZO/NiO(SOE)/Ni.
High-temperature superconducting (HTS) tapes have emerged as promising materials for superconducting power applications since they make possible electric power equipment that is half the size of conventional alternatives, with half energy losses, increasing the efficiency in the generation, transmission and distribution of the electric energy, and thus reducing the impact of power delivery on the environment.
However, unlike typical conductors, oxide based superconductor materials are brittle and easily damaged and thus they are difficult to process and handle, specially forming large and flexible wires.
Up to now it has been possible to produce kilometre lengths of the first generation of HTS wires for use in electrical transmission cables. YBCO coated conductors can support high critical current densities and is a promising candidate.
One of the substrate available is a polycrystalline metal substrate with an epitaxial YSZ film on it, the ion-beam assisted deposition YSZ(IBAD)/Stainless Steel. The second is the textured NiO(SOE)/Ni(Rabit).Numerous methods are available for epitaxial deposition of YBCO, including vacuum techniques but we choose the cheaper non vacuum sol-gel processes.
To avoid the interaction between the superconductor it is important to interpose a inert material that can transfer the epitaxy from the substrate to the YBCO, these kind of films are called buffer layers, avoiding than the reduction of the current that the superconductor can support.
The main aim of this thesis was optimising the buffer layer growth by chemical technique and finally studying the deposition of TFA-YBCO on those optimised templates.
The ceramic buffer layers studied:
CeO2 , BaZrO3 , CaZrO3, SrZrO3, SrTiO3,BaCeO3
The Sol-Gel system used was the Metal -diketone dissolved in Acid Acetic, or Metal isopropoxide dissolved in methanol.
The deposition step was performed by spin coating. Controlling the different parameters of rate and acceleration of the spinner and the precursor solution concentration we obtained homogenous films with different thickness. The crystallisation step is achieved in a furnace in a controlled atmosphere, temperature and heating rate.
Important knowledge on the MOD-CeO2 thin film growth has been acquired during this research. From a combination of TEM, XRD and RHEED analyses it was observed that its growth mechanism exhibits an anomalous behaviour compared with other CSD derived films. The homogeneous nucleation in fact is favoured in this MOD process due to the low Tnuc./Tmel value for ceria film (Tnuc./Tmel=0.21). Only grains nucleated on the substrate are textured as observed in XTEM images. The grain size dependence with temperature follows an Arrhenius relation:
The solution preparation and the deposition conditions for STO and BZO on MgO and YSZ have been also optimised. After several experiments of buffer deposition on YSZ(IBAD)/SS and NiO(SOE)/Ni technical metal substrates the most promising architecture resulted to be the STO/BZO/NiO(SOE)/Ni.
We have grown YBCO by the TFA(Trifluor Acetic Acid) method on the optimized buffer layers. A sample of TFA-YBCO on a CeO2/YSZ(IBAD)/SS template prepared in air at 900ºC for 8 h has shown a critical current density, Jc has a value of 7 MA/cm2 at 5K, and 6·105A/cm2 at 77K. These values are near the target of one million A/cm2 at 77K.
The experiments on BZO and STO buffer layers have demonstrated the possibility of using the double buffer on NiO(SOE)/Ni as an alternative template for YBCO deposition. A critical current density of Jc(5K)= 5·105A/cm2 has been achieved for the best sample of YBCO/STO/BZO/NiO(SOE)/Ni.
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Coll, Bau Mariona. "Chemical Solution Deposition of Oxide Buffer and Superconducting Layers for YBa(2)Cu(3)O(7) Coated Conductors." Doctoral thesis, Universitat Autònoma de Barcelona, 2007. http://hdl.handle.net/10803/3271.
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Nazarzadehmoafi, Maryam. "Electronic properties of metal-In 2 O 3 interfaces." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2017. http://dx.doi.org/10.18452/17771.
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Das Verhalten der elektronischen Eigenschaften von gespaltenen, aus der Schmelze gezüchteten In2O3-(111) Kristallen wurde bei Deposition von Edelmetallen, In und Sn mittels winkelaufgelöster Photoelektronen-Spektroskopie untersucht. Die Stöchiometrie, strukturelle Qualität und Kristall-Orientierung, die Oberflächenmorphologie und die Elektronenkonzentration wurden jeweils mittels energiedispersiver Röntgenspektroskopie, Laue-Beugung, Raster Tunnel-Mikroskopie (STM) und Hall-Effekt untersucht. Die Ähnlichkeit der fundamentalen und Oberflächen-Bandlücken kann auf das fast flache Verhalten der Bänder auf der gespaltenen Oberfläche der Kristalle zurückgeführt werden. Die Grenzflächen von Ag und Au/In2O3 zeigen Schottky-Verhalten, während ein ohmscher in Cu, In und Sn /In2O3-Kontakten beobachtet wurde. Aufgrund der Übereinstimmung zwischen optischen und Oberflächen-Bandlücken, der Bildung eines Gleichrichterkontaktes und des Auftretens der Oberflächenphotospannung auf der frischen Kristalloberfläche kann gefolgert werden, dass SEAL nicht eine intrinsische Eigenschaft der gespaltenen Oberfläche der untersuchten Kristalle ist. Des Weiteren wurden bei dicker Au- und Cu-Beschichtung von In2O3 bei Raumtemperatur Shockley-artige Oberflächenzustände beobachtet. Zusätzlich wurde die erste Phase des Wachstums von Cu und In auf In2O3 von der Ausbildung eines 2-dimensionalen Elektrongases (2DEG) begleitet, welches bei dickeren Schichten verschwand, die von dem auf reinen Oberflächen von dünnen In2O3- Filmen gemessenen 2DEG verschieden sind. Nach Messung der Austrittarbeit von In2O3 und den jeweils untersuchten Metallen in situ und unter Verwendung der Schottky-Mott-Regel trat außer bei Ag/In2O3 eine deutliche Abweichung auf. Die experimentellen Ergebnisse stimmen auch mit fortgeschrittenen Theorien, die auf dem Elektronegativitätskonzept und MIGS–Modellen basieren, nicht überein.The behavior of the electronic properties of as-cleaved melt-grown In2O3 (111) single crystals was studied upon noble metals, In and Sn deposition using angle-resolved photoemission spectroscopy. The stoichiometry, structural quality and crystal orientation, surface morphology, and the electron concentration were examined by energy dispersive X-ray spectroscopy, Laue diffraction, scanning tunneling microscopy (STM), and Hall-effect measurement, respectively. The similarity of the measured-fundamental and surface-band gaps reveals the nearly flat behavior of the bands at the as-cleaved surface of the crystals. Ag and Au/In2O3 interfaces show Schottky behavior, while an ohmic one was observed in Cu, In, and Sn/In2O3 contacts. From agreement of the bulk and surface band gaps, rectifying contact formation as well as the occurrence of photovoltage effect at the pristine surface of the crystals, it can be deduced that SEAL is not an intrinsic property of the as-cleaved surface of the studied crystals. Moreover, for thick Au and Cu overlayer regime at room temperature, Shockley-like surface states were observed. Additionally, the initial stage of Cu and In growth on In2O3 was accompanied by the formation of a two dimensional electron gas (2DEG) fading away for higher coverages which are not associated with the earlier-detected 2DEG at the surface of In2O3 thin films. The application of the Schottky-Mott rule, using in situ-measured work functions of In2O3 and the metals, showed a strong disagreement for all the interfaces except for Ag/In2O3. The experimental data also disagree with more advanced theories based on the electronegativity concept and metal-induced gap states models.
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Davu, Sandeep. "Connection Oriented Mobility Using Edge Point Interactivity." Kent State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=kent1206469405.
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Natarajan, Preethi. "Leveraging innovative transport layer services for improved application performance." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 155 p, 2009. http://proquest.umi.com/pqdweb?did=1674099761&sid=3&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Mohanty, Shantidev. "Architecture and Cross-Layer Mobility Management Protocols for Next-Generation Wireless Systems." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7586.
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As a result of rapid progress in research and development, today's wireless world exhibits several heterogeneous communication networks, such as cellular networks, satellite networks, wireless local area networks (WLAN), mobile ad hoc networks (MANET), and sensor networks. These networks are complementary to each other.
Hence, their integration can realize a unified wireless system that has the best features of the individual networks. This has spurred
much research interest in designing integrated next-generation of wireless systems (NGWS).
While existing wireless networks have been extensively studied individually, the integrated wireless system brings new challenges in architecture design, system management, and protocol design. The different wireless networks use different communication technologies
and are based on different networking paradigms. Therefore, it is challenging to integrate these networks such that their heterogeneities are hidden from each other and a harmonious
inter-operation among them is achieved. The objective of this research is to design a scalable, secure, and robust architecture
and to develop seamless mobility management protocols for NGWS.
More specifically, an architecture that integrates the heterogeneous wireless systems is first proposed for NGWS. Next, a cross-layer
(Layer 2 + 3) handoff management protocol is developed for NGWS. Afterward, analytical modeling is developed to investigate the
handoff performance of the existing mobility management protocols for different types of applications. Finally, a framework for
multi-layer mobility management is developed to support the seamless handoff support to all types of applications in NGWS.
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Brown, A. P. Y. "Intrinsic and visually-evoked properties of layer 2/3 neurons in mouse primary visual cortex and their dependence on sensory experience." Thesis, University College London (University of London), 2016. http://discovery.ucl.ac.uk/1475198/.
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Neurons in Primary Visual Cortex (V1) are known to respond strongly to visual stimuli. Studies of neuronal responses in V1, carried out first in cats, but later primates and other mammals, have demonstrated that bars of light at particular orientations evoke strong, reliable responses in terms of increased firing rate of action potentials. Tuning of neuronal responses to certain stimulus parameters, such as orientation but also spatial and temporal frequencies, as well as the apparent dichotomy between simple and complex responses, have given rise to a number of influential models not just of V1 function, but more generally in the field of cortical physiology and computer vision. Owing to its small size and the plethora of available molecular and genetic tools, the visual cortex of the mouse may be a more tractable model system than that of much larger animals. Recent studies of neuronal responses in mouse V1 have shown that these are broadly similar to those of primates and carnivores, although not identical in all aspects. My thesis aims firstly to characterise intrinsic and sensory-evoked properties in regularspiking, putative pyramidal neurons in L2/3 of the mouse visual cortex using whole-cell patch clamp recording in vivo . In addition, the anatomical connectivity of individual neurons is characterised using virus-assisted circuit mapping. The majority of these neurons are found to be simple cells. Orientation tuning (the degree to which neuronal responses are selective to stimuli of a preferred orientation) is found to be quite variable, even within this singular group of neurons. The potential roles of intrinsic diversity, functional connectivity, and sensory experience in setting the orientation tuning of a particular neuron are investigated. These findings provide an insight in to how diverse responses to sensory stimuli can be generated in an apparently homogenous group of neurons.
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Pancholi, Prasoon. "Influence of barrier layer on optical and electronic properties of quantum dot molecules." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 90 p, 2008. http://proquest.umi.com/pqdweb?did=1605158171&sid=3&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Tomorsky, Johanna. "Molecular Mechanisms of Laminar Circuit Formation in Visual Cortex." Thesis, University of Oregon, 2019. http://hdl.handle.net/1794/24539.
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The mammalian visual system develops to perform many complex tasks that allow us to perceive the natural world. These tasks rely on a dense network of synaptic connections transporting visual information both to and within visual cortex (V1). The laminar organization and functional properties of visual cortical neurons are largely conserved across mammals, and the mouse has been adopted as a model organism to study the development of this cortical circuit. Neurons in each cortical layer must find the correct synaptic partners for the optimal receipt, transfer, and processing of information. The molecular cues guiding the development of these connections, however, are largely unknown.
In this thesis, I identify and then examine the role of molecular factors important for synapse formation in layer 2/3 (L2/3) of visual cortex. L2/3 neurons are highly interconnected and fire selectively to a refined set of visual stimuli. The developmental refinement of these visual preferences has been shown to occur in the week following eye opening, corresponding with a period of intense synapse formation and dynamic gene expression in mouse V1. In Chapters II–IV, I use the TU-tagging technique to identify molecular factors enriched L2/3 neurons before and after eye opening and identify several candidate genes with potential functions in synapse formation.
In Chapter V, I examine the function of cell adhesion molecules nectin-1 and nectin-3, identified here as enriched in L2/3 visual cortex at eye opening, and previously shown to interact across synaptic junctions. I focus mainly on the effect of nectin-3 (having post-synaptic localization in hippocampus) on post-synaptic dendritic spine densities in developing L2/3 cortical neurons. I show that nectin-3 knockdown further increases spine densities after eye opening, while overexpressing a full length or truncated nectin-3 protein reduces spine densities. I conclude that nectin-3 may have a role in synapse formation following eye opening, and propose a mechanism describing the effects observed. Here, I describe a unique approach for understanding how cell-type specific connections are formed in visual cortex, beginning with the spatiotemporal examination gene expression and followed by the spatiotemporal manipulation of a single gene.
This dissertation includes previously published co-authored material.
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Symes, Andrew John. "A large-scale model of spatio-temporal patterns of excitation and inhibition evoked by the horizontal network in layer 2/3 of the visual cortex." Thesis, University of Plymouth, 2009. http://hdl.handle.net/10026.1/1999.
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Cortical processing of even the most elementary visual stimuli can result in the propagation of information over significant spatiotemporal scales. To fully understand the impact of such phenomena it is essential to consider the influence of both the neural circuitry beyond the immediate retinotopic location of the stimulus, including pre-cortical areas, and the temporal components of stimulus driven activity that may persist over significant periods. Two computational modelling studies have been performed to explore these phenomena and are reported in this thesis. I) The plexus of long and short range lateral connections is a prominent feature of the layer 2/3 microcircuit in primary visual cortex. Despite the scope for possible functionality, the interdependence of local and long range circuits is still unclear. Spatiotemporal patterns of activity appear to be shaped by the underlying connectivity architecture and strong inhibition. A modelling study has been conducted to capture population activity that has been observed in vitro using voltage sensitive dyes. The model demonstrates that the precise spatiotemporal spread of activity seen in the cortical slice results from long range connections that target specific orientation domains whilst distinct regions of suppressed activity are shown to arise from local isotropic axonal projections. Distal excitatory activity resulting from long range axons is shaped by local interneurons similarly targeted by such connections. It is shown that response latencies of distal excitation are strongly influenced by frequency dependent facilitation and low threshold characteristics of interneurons. Together, these results support hypotheses made following experimental observations in vitro and clearly illustrate the underlying mechanisms. However, predictions by the model suggest that in vivo conditions give rise to markedly different spatiotemporal activity. Furthermore, opposing data in the literature regarding inter-laminar connectivity give rise to profoundly different spatiotemporal patterns of activity in cortex. 2) The second computational modelling study considers simple moving stimuli. These stimuli are implicated in the 'motion streak' phenomenon whereby the movement of a visual feature can give rise to trajectory information that is not explicitly present. Published experimental data of an in vivo study in the cat has shown that a single small light square moving stimulus elicits activity in populations of neurons in primary visual cortex that are selective for orientations parallel to stimulus trajectory (Jancke 2000). In more recent, unpublished data, this work is extended to consider long term persistent cortical activity that is generated by similar stimuli. These data indicate that following initial cortical activation that appears to result directly from the stimulus, iso-orientation domains display persistent activity. Furthermore, initial activity is broadly tuned with respect to orientation whilst later activity is strongly selective for orientations that are parallel to the stimulus trajectory. Currently the generative processes involved have not been clearly defined. Hence the proposed thesis will contribute to a more complete understanding of the mechanisms responsible for such cortical representations of moving visual stimuli. More specifically this will be achieved by a large scale mean field model that will enable a thorough investigation of the anatomical and electrophysiological elements concerned with the observed spatiotemporal dynamic behaviour and will represent a significant region of cortex. In conjunction, an existing computational model of the retina will be integrated. In doing so this thesis will offer the notion that certain cortical representations are inextricably linked with earlier stages of the visual pathway. As such consideration of retinal processing is fundamental to the understanding cortical functions and failure to do so can only result in erroneous conclusions.
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Nguyen, Quoc The. "Protocols specification and validation for the movement of Grades 2 and 3 Bitstream data through the Virtual Channel Link Control layer of the return link of the CCSDS Principal Network (CPN)." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/43293.
Full textAbstract:
Specification of data communication protocols requirements requires a formal approach to ensure that the requirements are correctly and unambiguously specified. This research examines a proposed protocols specification for the movement of bitstream data through space segment by applying a formal definition technique known as the Language of Temporal Ordering System (LOTOS). Successful generation of the LOTOS specification to detail sequence of events and their internal structures in an implementation independent manner clarifies the requirements and provides a framework from which possible cases or events in each process can be tested.
In addition, a LOTOS software tool called HIPPO is used in the research. HIPPO identifies any deadlock that could happen in the protocols and allows sequence of events to be interactively simulated to ascertain of the specification consistency.Master of Science
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Chpoun, Amer. "Contribution a l'etude d'ecoulements hypersoniques (m=5) sur une rampe de compression en configuration 2-d et 3-d." Paris 6, 1988. http://www.theses.fr/1988PA06A005.
Full textAbstract:
Etude experimentale de l'influence de l'ecoulement transversal sur les distributions du flux thermique et de la pression parietale. Determination des grandeurs caracteristiques de la zone de decollement. Etude de l'apparition de la transition dans la zone du decollement en fonction du nombre de reynolds. Solution numerique pour la distribution de pression dans le cas de l'interaction laminaire
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Le, Bourlot Jacques. "Calcul de probabilites de transition d'intercombinaison entre les etats x **(1)sigma ::(g)**(+) et a **(3)pi ::(v) de c::(2) carbone moleculaire : application a l'equilibre de c::(2) dans les nuages interstellaires diffus." Paris 7, 1987. http://www.theses.fr/1987PA077128.
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Chpoun, Amer. "Contribution à l'étude d'écoulements hypersoniques (M=5) sur une rampe de compression en configuration 2-D et 3-D." Paris 6, 1988. http://www.theses.fr/1988PA066149.
Full textAbstract:
Etude expérimentale de l'influence de l'écoulement transversal sur les distributions du flux thermique et de la pression pariétale. Détermination des grandeurs caractéristiques de la zone de décollement. Etude de l'apparition de la transition dans la zone du décollement en fonction du nombre de Reynolds. Solution numérique pour la distribution de pression dans le cas de l'interaction laminaire
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Schäfer, Christian Martin. "Towards organic-inirganic hybrid thin films deposited by ALD/MLD." Master's thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/22267.
Full textAbstract:
Mestrado em QuímicaA técnica de deposição por camada atómica (ALD) permite a deposição de filmes finos em fase de vapor de alta qualidade com um controlo de espessura à nano-escala. No presente trabalho foi demonstrado a deposição de filmes finos de óxido de zinco (ZnO) por ALD de elevada uniformidade em diferentes substratos, incluído nano-estruturas como por exemplo, nanotubos de carbono. Demonstrou-se por difracção de raio-X que o processo de deposição do ZnO originou a formação da estrutura da hexagonal, na fase wurtzite, com uma taxa de crescimento por ciclo de 1.9 Å. A deposição de filmes finos de natureza inorgânica (e.g. óxidos metálicos) por ALD está bem estabelecida contrariamente à emergente deposição por camada molecular (MLD) de filmes finos puramente orgânicos. Actualmente, a combinação de ALD/MLD começa a ganhar importância na criação de estruturas híbridas do tipo orgânica-inorgânicas. Nomeadamente, através da selecção adequada dos precursores, é possível obter diferentes arquitecturas funcionais em forma de filme fino, incluindo nano-laminados, superestruturas e redes metalo-orgânicas (MOFs) nano-porosas. A deposição de MOFs por ALD/MLD surge como uma alternativa para superar as desvantagens dos métodos convencionais de deposição de filmes finos baseados em soluções. Este trabalho contempla também a revisão da literatura no que diz respeito à síntese de este tipo de filmes finos obtidos em fase de vapor. Procedeu-se à reprodução dos resultados da literatura tendo como objectivo a síntese de filmes finos híbridos orgânico-inorgânicos (e.g. MOFs). Numa primeira fase efectuou-se a transformação vapor-sólido de um filme de ZnO crescido por ALD por exposição ao vapor de 2-metilimidazol. Posteriormente usou-se um processo ALD/MLD com o propósito de depositar uma estrutura do tipo zeólito (ZIF-8) a partir da reacção do dietilzinco (DEZ) e o 2-metilimidazol. Finalmente realizou-se a síntese de dois sistemas de filmes finos híbridos com base no ácido tereftálico como precursor orgânico e os seguintes precursores organometálicos: DEZ e Eu(TMHD)3. Para o caso do sistema DEZ/TPA, a formação da ligação Zn-TP nos filmes híbridos, foi observada por espectroscopia de FTIR
Atomic layer deposition is a state-of-the-art vapor phase deposition method for the creation of high quality thin films with nanoscale thickness control. As demonstrated in this work by the deposition of ZnO with a home-built reactor, ALD enables uniform and conformal film deposition even on complex nanostructures like carbon nanotubes. Deposition of hexagonal wurtzite ZnO proven by GIXRD with a growth-per-cycle of 1.9 Å, determined from XRR thickness measurements, was demonstrated. While the ALD synthesis of inorganic thin films, such as metal oxides is widely established, the organic counterpart molecular layer deposition (MLD) is still emerging. Recently, combining ALD/MLD has attracted great interest for the creation of organic-inorganic hybrid structures. By choice and adaptation of suitable precursors a great versatility of functional thin film architectures is achievable, spanning from novel multilayer nanolaminates and superstructures for thermoelectrics, over luminescent lanthanide hybrid films for optical application to even crystalline, nanoporous metal-organic frameworks (MOFs) as low-κ dielectrics in microdevices. Especially in the field of MOFs, a clean and precise synthesis route by ALD/MLD is desirable for device implementation in order to overcome the drawbacks of conventional, solution-based thin film deposition techniques. In this work, recent advances towards these vapor-processed hybrids are reviewed. Then, the reproduction of literature results leading to the deposition of organic-inorganic hybrid thin films (e.g. MOFs) was studied. The feasibility of a vapor-solid transformation of a sacrificial ALD-grown ZnO film by exposure to 2-methylimidazole (HMIM) and a direct ALD/MLD method using HMIM and diethylzinc (DEZ) towards a zeolitic imidazole framework (ZIF-8) have been attempted. Finally, the synthesis of two different hybrid films was studied involving the organic precursor terephthalic acid (TPA) combined with the organometallic precursors DEZ or Eu(TMHD)3. In case of the DEZ/TPA system, the deposition of a hybrid thin film with Zn-terephthalate bondings was evidenced by FTIR spectroscopy.
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Pezzotti, Simone. "DFT-MD simulations and theoretical SFG spectroscopy to characterize H-Bonded networks at aqueous interfaces : from hydrophobic to hydrophilic environments Structural definition of the BIL and DL: a new universal methodology to rationalize non-linear χ(2)(ω) SFG signals at charged interfaces, including χ(3)(ω) contributions What the Diffuse Layer (DL) Reveals in Non-Linear SFG Spectroscopy 2D H-Bond Network as the Topmost Skin to the Air-Water Interface Combining ab-initio and classical molecular dynamics simulations to unravel the structure of the 2D-HB-network at the air-water interface 2D-HB-Network at the air-water interface: A structural and dynamical characterization by means of ab initio and classical molecular dynamics simulations Spectroscopic BIL-SFG Invariance Hides the Chaotropic Effect of Protons at the Air-Water Interface Molecular hydrophobicity at a macroscopically hydrophilic surface Graph theory for automatic structural recognition in molecular dynamics simulations DFT-MD of the (110)-Co3O4 cobalt oxide semiconductor in contact with liquid water, preliminary chemical and physical insights into the electrochemical environment." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLE008.
Full textAbstract:
Améliorer notre connaissance de la structure de l'eau dans l'environnement spécial offert par une interface est essentiel pour la compréhension de nombreux phénomènes naturels et applications technologiques. Pour révéler cette structure interfaciale de l'eau, des techniques capables de fournir des informations microscopiques, de manière sélective, pour cette couche interfaciale (BIL) sont nécessaires. Dans le présent travail de thèse, nous avons donc étudié les interfaces aqueuses au niveau moléculaire, en couplant la modélisation théorique à partir de simulations DFT-MD avec les spectroscopies SFG et THz-IR. En développant de nouveaux protocoles/outils d'investigation associant simulations DFT-MD et spectroscopie SFG, en particulier pour la rationalisation plus complexe des interfaces chargées, nous avons fourni une compréhension globale de l'effet des conditions interfaciales d'hydrophilicité, de pH, de force ionique sur le réseau des liaisons-H formé dans la couche interfaciale BIL, sur ses signatures spectroscopiques et sur son impact sur les propriétés physico-chimiques. Nous avons montré pour la première fois que, dans des conditions suffisamment hydrophobes, l'eau interfaciale crée des réseaux des liaisons-H bidimensionnels, révélé expérimentalement par les spectres THz-IR. Le réseau-2D dicte la dynamique de l'eau interfaciale, le potentiel de surface, l'acidité de surface, la tension superficielle et la thermodynamique d'hydratation des solutés hydrophobes. Cet "ordre horizontal" aux interfaces hydrophobes est opposé à "l'ordre verticale" obtenu aux interfaces hydrophiles. Nous avons aussi révélé comment les ions et les conditions de pH modifient ces arrangements structurauxImproving our knowledge on water H-Bonded networks formed in the special environment offered by an interface is pivotal for our understanding of many natural phenomena and technological applications. To reveal the interfacial water arrangement, techniques able to provide detailed microscopic information selectively for the interfacial layer are required. In the present thesis work, we have hence investigated aqueous interfaces at the molecular level, by coupling theoretical modeling from DFT-MD simulations with SFG & THz-IR spectroscopies. By developing new investigation protocols/tools, coupling DFT-MD simulations and SFG spectroscopy, in particular for the more complex rationalization of charged interfaces, we have provided a global comprehension of the effect of various interfacial conditions (hydrophilicity, pH, ionic strength) on the HB-Network formed in the interfacial layer (BIL), on its spectroscopic signatures and on its impact on physico-chemical properties. We have shown for the first time that, in sufficiently hydrophobic conditions, BIL interfacial water creates special 2-Dimensional HB-Networks, experimentally revealed by one specific THz-IR marker band. Such 2D-network dictates HBs and orientational dynamics of interfacial water, surface potential, surface acidity, water surface tension and thermodynamics of hydration of hydrophobic solutes. Such "horizontal ordering” of water at hydrophobic interfaces is found opposite to the “vertical ordering” of water at hydrophilic interfaces, while coexistence of the two orders leads to disordered interfacial water in intermediate hydrophilic/hydrophobic conditions. Both DFT-MD and SFG further revealed how ions & pH conditions alter these BIL-water orders
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Yu, Ming-Siou, and 余明修. "A Fast Pre-scanning Scheme for Layer-2 Handoff in IEEE 802.11 Wireless Networks." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/jhu49p.
Full textAbstract:
碩士國立東華大學
資訊工程學系
100
In the very first version of the IEEE 802.11 standards, only the Physical Layer and Data link layer are defined but no mechanism about the handoff process. In most implementations, the handoff mechanism is triggered when mobile nodes are out of range of the access points. As a result, problems, such as network disconnection, large amount of packet loss, and long-term packet delay are frequently incurred. To improve these problems, we propose a new Layer-2 handoff mechanism called Fast Pre-scanning Scheme for Layer-2 Handoff or FPSLH is short. The proposed mechanism adopts pre-scan process and packet buffer; the two designs can reduce the packet loss rate. Moreover, active scanning is substituted by passive scanning to reduce the packet delay caused by the long wait time of the active scanning mode. The proposed Layer-2 handoff mechanism is verified by simulations using NS-2. Not only did it efficiently decrease the End to End Delay time in the Layer-2 handoff mechanism, but it also has no packet loss during the whole stimulation process.
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Jan, Hsiao-Shun, and 詹孝順. "Layer 2 and Layer 3 Semi-Soft Handover Schemes in 802.11 Wireless LAN." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/45611276819777437666.
Full textAbstract:
碩士國立交通大學
電機資訊學院碩士在職專班
93
As WLAN gets more and more popular, many cities have been set up the dense wireless network. Therefore, WLAN have gradually joined to people’s life. One of the application is Voice Over WLAN. However, most of the application are using the structure of VoIP. Hence, it is very important and indispensability for WLAN industry to overcome how to keep the network stable and how to roam between two base stations or different networks. In this paper, we will bring up a kind of structure. That will help the wireless LAN company to solve the roaming problem. The wireless LAN module will solve the roaming in Layer2 and Layer3. First of all, we build up the connection by Semi-Soft in wireless LAN module that could help the message exchange in advance in Layer2 and Layer3 when the module starts roaming. In addition, we also create the NAT transformation in WLAN module. It could fix the up layer’s network IP and the application function does not need to change network IP for rebuilding network. Although we can use Semi-Soft to exchange the information in Layer 2 and Layer 3 beforehand, we just have one real hardware module. It means we just can connect only one AP at the same time. For this reason, when the packet cycle is less than 20ms, the roaming will have delay problem. Nevertheless, if we focus our application on VoIP which packet cycle more than 50ms, the idea is sufficient.
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Hsieh, Fu-Yia, and 謝復雅. "Cross-layer Handoff Scheme for IEEE 802.16e." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/g37xy3.
Full textAbstract:
碩士國立中央大學
通訊工程研究所
94
This paper is a research of cross-layer handoff scheme based on IEEE 802.16e. By combining the handoff message of 802.16e and Fast Mobile IPv6, this scheme can shorten the handoff delay time. In the following part of this paper, we simply describe how 802.16e works, and we explain the procedure of Mobile IPv6 and Fast Mobile IPv6. Furthermore, by analyzing the packets that 802.16e and Fast Mobile IPv6 brings out while handoff is processing, we explain how to use the cross-layer architecture to combine those messages from two different layers. In the final software simulation, the proposed cross-layer handoff scheme is compared with “Mobile IPv6 Fast Handoffs over IEEE 802.16e Networks” which is a draft on IETF. The results of the simulation show that this cross-layer handoff scheme is better than the draft on IETF in handoff delay time.
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Chen, Chia-Ling, and 陳嘉玲. "Smooth Handoff for Application Layer Mobility Management." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/wq2493.
Full textAbstract:
碩士靜宜大學
資訊管理學系研究所
92
Recent years have seen a tremendous amount of effort toward the development of Internet infrastructure and multimedia technology. Instant messaging communication is more and more popular. Session Initiation Protocol (SIP) is an application-layer control protocol that can establish real-time communications and support terminal, session, personal, and service mobility. If the User B moves during a session, it needs to register its new IP address with Registrar and send a re-INVITE to the communicating party User A. After receiving the re-INVITE message, User A transmit the subsequent packets to User B’s new location. User B can’t receive packets until they complete the handoff. Therefore, data in transit may be lost. In order to reduce the data loss, we use a general idea of REFER method to achieve smooth handoff that Old Proxy can buffer packets and redirect them to the current location of the User B. Simulation results indicate that the proposed smooth handoff is better than base SIP handoff.
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Tsai, Yueh-Feng, and 蔡岳峰. "The Implementation of TMS320DSC25Embedded System withNetwork Layer 2/3 Technology." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/12867968383554426599.
Full textAbstract:
碩士國立成功大學
工程科學系碩博士班
91
With a combination of Internet technology and embedded information appliance, people can get more real-time and important messages through the convenience and transparency of network and high mobility of embedded application. At the same time, with the coming of broadband generation, network transporting is playing an important role in the information appliance. With the advance in digital signal processing, digital multimedia products such like digital camera、digital video、web camera have great improvements on the quality and computing.TMS320DSC25 is a Texas Instrument''s solution for digital still camera that provides a greater design flexibility and speed. This thesis focuses on the design and implementation of network protocol and operation with PrKernel operating system in order to provide a complete multimedia application.
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Yang, Ming-Ta, and 楊明達. "Implementation of Cross-layer Fast-handoff Schemes for Inter-subnet Handoff in IEEE 802.11 WLANs." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/14520926252963248740.
Full textAbstract:
碩士國立中正大學
電機工程所
94
Internet is changing rapidly in terms of its size, the number of users and the technology that it uses. Up to date, there are many RTP/UDP applications using by people, like Voice over IP (VoIP). Because of the popularity of portable devices and wireless LANs based on IEEE 802.11 standard have become popular and widely used recently, the mobility in wireless network environment become more important. There are two important issues to be addressed in order to support real-time service across wireless networks. One is high transmission data rate; the other is low handoff delay latency. In this thesis, we propose a cross-layer fast-handoff scheme in order to provide seamless mobility support to the mobile hosts in IEEE 802.11 wireless networks. We modify enhanced Inter-Access Point Protocol (IAPP) to fit real-time traffic and extend the function of an IEEE 802.11 Access Point to co-operate for cross-layer considerations. The link-layer handoff latency, network-layer handoff latency and application-layer handoff latency have been improved by our proposed scheme.
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Wang, Jingyi. "Detailed morphological study of layer 2 and layer 3 pyramidal neurons in the anterior cingulate cortex of the rhesus monkey." Thesis, 2014. https://hdl.handle.net/2144/14689.
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The anterior cingulate cortex (ACC) can influence emotional and motivational states in primates by its dense connections with many neocortical and subcortical regions. Pyramidal neurons serve as the basic building blocks of these neocortical circuits, which have been extensively studied in other brain regions, but their morphological and electrophysiological properties in the primate ACC are not well understood. In this study, we used whole-cell patch clamp and high-resolution laser scanning confocal microscopy to reveal the general electrophysiological properties and detailed morphological features of layer 2 and 3 pyramidal neurons in ACC (area 24/32) of the rhesus monkey. Neurons from both layers had similar passive membrane properties and action potential properties. Morphologically, dendrites of layer 3 ACC neurons were more complex than those of layer 2 neurons, by having dendrites with longer total dendritic lengths, more branch points and dendritic segments, spanning larger convex hull volumes. This difference in total dendritic morphology was mainly due to the apical dendrites. In contrast, the basal dendrites displayed mostly similar features between the two groups of neurons. However, while apical dendrites extend to the same layer (layer 1), the basal dendrites of layer 3 extended into deeper layers than layer 2 because of the difference in soma-pia distance. Thus, basal dendrites of the two groups of neurons receive different laminar inputs. Analysis of spines showed that more spines were found in neurons of layer 3 apical dendritic arbors than layer 2 neurons. However, the apical spine densities were similar between neurons in the two layers. Thus, while higher spine number suggests that layer 3 neurons receive more excitatory input than layer 2 neurons, the similar spine density suggests similar spatial and temporal summation of these inputs. The combined effects of increased number of excitatory input and higher dendritic complexity in layer 3 than in layer 2 ACC neurons suggest the additional information received by layer 3 neurons, especially in the apical dendrites, might undergo more complex integration.
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Hsiao, Wei-Han, and 蕭煒翰. "Cross-Layer Partner-Based Fast Handoff Mechanism for IEEE 802.11 Wireless Networks." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/96143779879811722632.
Full textAbstract:
碩士國立中正大學
資訊工程所
94
In wireless/mobile networks, users freely and frequently change their access points, while they are communicating with other users. To support the mobility of mobile nodes, Mobile IPv6 (MIPv6) is used to inform the binding of its home address and current care-of-address (CoA) to its home agent. MIPv6 suffers a long delay latency and high packet losses because that MIPv6 not support the micromobility. Hierarchical Mobile IPv6 (HMIPv6) is proposed by providing micromobility and macromobility to reduce handoff latency by employing a hierarchical network structure. In this thesis, we propose a cross-layer partner-based fast handoff mechanism based on HMIPv6, called as PHMIPv6 protocol. Our PHMIPv6 protocol is a cross-layer, layer-2 + layer-3, approach. A new node, called partner node, is adopted in PHMIPv6 protocol. A new layer-2 trigger scheme used in PHMIPv6 protocol is to accurately predict the next AP (access point) and then to invite a possible partner node in the area of the next AP. With the aid of the partner node, CoA can be pre-acquired and DAD operation can be pre-executed by the partner node before the mobile node initialize the handoff request. By the way, PHMIPv6 protocol can significantly reduce the handoff delay time and packet losses. In the mathematical analysis, we verify that our PHMIPv6 protocol offers a better handoff latency than MIPv6, HMIPv6, and SHMIPv6. Finally, the experimental results also illustrate that PHMIPv6 protocol actually achieves the performance improvements in the handoff delay time, the packet loss rate, and the handoff delay jitter.
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Su, Ruey-Rong, and 蘇瑞榮. "A Study of Handoff and Cross Layer Resource Management in Wireless Networks." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/47uwcw.
Full textAbstract:
博士元智大學
資訊工程學系
105
Various wireless technologies are rapidly developed for the Next Generation Wireless access Networks (NGWN), such as WLAN, WiMAX, LTE, LTE-Advanced which are supposed to support universal multi-media service for mobile users. In the future, the mobile users are expected to communicate with each other in the Heterogeneous Wireless Network (HWN) with different modulation capability. In heterogeneous wireless networks, a mobile set may access the network from different services providers through various techniques such as handover, resource management, etc. The handover decision is based on multiple attributes and user preferences. Wireless networks support different handoff mechanisms, through which the mobile set can switch from one wireless network to another. Several call management strategies have been proposed to realize seamless handoff in heterogeneous networks; however, these decision-making methods appear arbitrary and, in some cases, even debatable. This study proposed using intelligent algorithm with multiple attributes and prediction-based risk-avoiding mechanism for handover decisions. The mobile set dynamically selects the optimal network and provides the user with high Quality of Service (QoS) and optimal resource allocation in heterogeneous networks. However, there are many challenges for HWN to provide a high QoS with different modulations, such as resource allocation, resource management, and scheduling. However, no WiMAX standards for optimal slot allocation have been defined. In this study, a new uplink bandwidth allocation scheme Grey Relational Analysis Knapsack Algorithm (GRAKA) which combines grey relational analysis with multiple attributes and the knapsack algorithms is proposed to improve resource utilization while satisfying the user’s requirements of throughput and fairness. In the past few years, the traditional architectures protocols are only optimized in each layer. Thus, the performance of analysis for cannot be optimized in the management about resource allocation for cross layers in the wireless network environment. The framework is designed which includes intelligent algorithms, Multiple Attributes Decision Making (MADM), prediction algorithms, cross layer resource allocation scheduling design, traffic classifier, resource management engine and QoS components to handle the cross layer architecture with multimedia service resource management and scheduling for supporting high QoS over heterogeneous wireless network in the 3GPP LTE networks. The intelligent scheduling algorithms are proposed to improve the system throughput and QoS. In this thesis, proposed algorithm significantly lowers call blocking times and lowers dropping rate with stable connections and allows higher quality of service. In this thesis, indicate that the proposed downlink resource management, HPWRR scheduling algorithm for six different traffic profiles particularly the integration of multicast traffic, and efficient scheduling of the traffic types. The simulation results show that the proposed schemes effectively reduce the average delay time of the specified traffic types and improve the quality of service and total throughput. In this thesis, indicate that the proposed uplink resource management, Grey Relational Analysis with Multiple Attributes and Knapsack Algorithm (GRAMAKA) performs best in terms of performance index which consists of throughput and fairness index.
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Yu, Chia-Feng, and 游家逢. "Fabrications and Properties ofPoly(3-hexylthiophene) / w-(2-Thienyl) Alkylphosphonic Acids / Titania Layer Heterojunction." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/85568229692928172954.
Full textAbstract:
碩士臺灣大學
高分子科學與工程學研究所
95
The heterojunction of organic solar cell is combined by two semiconductor materials which have different energy band gap. We can use the different electron affinities of these two materials to favor exciton separation, then to generate current. However, the incompatibility between organic and inorganic materials would cause voids in the face of the heterojunction. And it will block the electron transfer. So we developed a series of donor-accepter linkers which were applied into layer structure. The using of D-A Linkers has led to the synthesis of covalently linked donor-acceptor system. In our research, the D-A linker structure consists of three major parts : phosphonic acid, alkyl chain and thiophene ring. Poly (3-hexylthiophene) could thus link to TiO2 by introducing D-A linkers whose phosephonic acid anchored to TiO2, and thiophene ring initialized electrochemical polymerization of 3-hexylthiophene. The interfacial distance between donor and acceptor can be controlled by introducing alkyl spacers with different length that may cause different conditions of electrochemical polymerization. First, we use NMR spectrum to characterize the chemical structures of three different D-A linkers. After the linkers form the self-assembled monolayers on TiO2, we can measure the contact angle to realize the relationship with immersing time. And it indicated the adsorptions onto TiO2 to reach saturation are around one hour for all D-A linkers. Besides, the analysis of XPS spectra identified the bonding structure of all D-A linkers on TiO2 particles. And the use of TGA and UV-vis spectra calculated the content of linkers on the TiO2 particles. AFM images indicate the surface morphology of the self-assembled monolayers is similar to that of TiO2. In the electrochemical polymerization process, by the chronopotential method, the chronopotentiogram analysis showed the longer alkyl chain brings the bigger resistance. Also, the molecular weight measuring by GPC proved that the resistance resulting from alkyl chain blocked the polymerization on the self-assembled monolayers. However, from the AFM images of polymers, weather alkyl chain or resistance exist or not, it has no influence on the surface morphology of P3HT. Though the measurement from UV-vis and PL, although the different alkyl chain length caused the different molecular weight of P3HT, it didn’t affect the maximum of absorption wavelength and the emissions positions. We found out the P3HT propagating from linker-modified TiO2 substrates have higher quenching efficiency though the measurement of quantum yield. And the shorter length the alkyl chain is, the higher efficiency it results. As we believed, D-A linkers covalently linked TiO2 and conjugated polymers. This phenomenon avoided the generation of pin holes, and raised the considerable efficiency of the electron transfer between donor and acceptor.
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Meng-Hui, Ou. "Integration of Fast Intra-Network and Cross-layer Handoff (FINCH) with Ad Hoc Networks." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0016-1303200709283904.
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Ou, Meng-Hui, and 歐孟暉. "Integration of Fast Intra-Network and Cross-layer Handoff (FINCH) with Ad Hoc Networks." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/23172812854698841942.
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碩士國立清華大學
資訊工程學系
94
Mobile IP (MIP) has been proposed by the IETF as the mobility management protocol in IP networks. However, MIP might cause long handoff latency and high end-to-end delay. In order to minimize the inefficiency in MIP, micro-mobility management protocols have been proposed. However, most of them consider the mobility management at IP layer only. Unlike other proposals, earlier we have proposed Fast Intra-Network and Cross-layer Handoff (FINCH) which considers the mobility management at both link and IP layers. Because of the cross-layer design, the performance improvement is significant. Normally, micro-mobility management protocols are used in infrastructure networks, which provide Internet access through access points in the range of single wireless hop. Some protocols have been proposed to integrate micro-mobility management protocols with ad hoc networks, which extend the range to multiple hops away from an access point. In this thesis, we propose the integration of FINCH with two types of ad hoc routing protocols, Destination-Sequenced Distance-Vector (DSDV) and Ad-hoc On Demand Distance Vector (AODV). We also adapt the ad hoc routing protocols into the cross-layer design. The performance of our design is evaluated by extensive simulation. Results show that the cross-layer design outperforms those without crossing layer. The FINCH could be used with different ad hoc routing protocols. It is a trade-off between different performance metrics.
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Wu, Kun-Lin, and 吳昆霖. "A Cross-Layer Partner-Assisted Handoff Scheme for Hierarchical Mobile IPv6 in IEEE 802.16e Systems." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/99741974113626945520.
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碩士國立中正大學
資訊工程所
95
Mobility management, which supports seamless handoff and locality, is a key issue in the next generation wireless communication networks. Users get mobility capability and move around different kinds of subnets. Various enhanced wireless technologies, are proposed to support many kinds of internet services for mobile users. A new wireless technology, called WiMAX, has been specified in the IEEE 802.16e standard document, which provides higher bandwidth and larger coverage area than the IEEE 802.11 networks. In wireless IP network, Mobile IPv6 (MIPv6) provides the binding update message to update the mobile user’s IP information for supporting layer 3 mobility. Hierarchical Mobile IPv6 (HMIPv6) is proposed by employing a hierarchical network structure to reduce handoff latency of binding update procedures. However, HMIPv6 suffers large handoff delay and packet lost in macro mobility for mobile users. This thesis presents a cross-layer partner-assisted handoff mechanism based on HMIPv6, termed PHMIPv6 protocol. The PHMIPv6 protocol is a cross-layer, layer-2 and layer-3, approach. The partner station (PS), which is a new component with relay ability and adopted by our protocol, is an static mobile station (MS). With the aid of the PSs, care-of address (CoA) can be pre-acquired and DAD operation can be pre-executed by the PS before the MS initials the layer 2 handoff. The simulation results show that PHMIPv6 protocol actually achieves the performance improvements in the handoff delay time, the packet loss rate, and the handoff delay jitter.
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Fucke, Thomas [Verfasser]. "Biophysical characterization and simulation of neocortical layer 2/3 pyramidal neurons during postnatal development / presented by Thomas Fucke." 2008. http://d-nb.info/988473623/34.
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Chang, Ting-Hsuan Daniel, and 張珽瑄. "Comparison of Transmission at Synapses of Layers 2/3 Input onto Layer 5 Pyramidal and GABAergic Neurons in Rostral Agranular Insular Cortex." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/93585570272002491439.
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碩士國立臺灣大學
生命科學系
104
It has been shown that inhibition or lesion of the rostral agranular insular cortex (RAIC) results in analgesia, it suggests that RAIC tonically produces hyperalgesia signal. RAIC is a cortical area where nociceptive output originates, and it has been reported to activate in chronic pain perception. It’s believed that chronic pain is associated with the long-term change in synaptic plasticity. Moreover, the imbalance of excitatory and inhibitory (E/I) synaptic signaling in neural circuits is responsible to modulate synaptic plasticity in certain behavior disorders. In our lab, previous study had reported that the induction of chronic pain induced differential activation in pyramidal cells and GABAergic neurons in RAIC. We propose here that E/I imbalance in RAIC may contribute to the increased cortical output of nociceptive signal in chronic pain. To test this possibility, we compared synaptic transmission of layers 2/3 (L2/3) inputs onto layer 5 (L5) pyramidal cells (PC), which are the descending projection neurons, and onto local GABAergic interneurons (IntN) in RAIC. We performed dual-patch recording from a paired IntN-PC in layer 5, and elicited EPSC by putting an electrode in layer 2/3. We found functional connectivity in 34.2% of all recorded IntN-PC pairs. There was no significant difference in data sampled from IntN-PC pairs with and without functional connectivity, and all data were pooled. Our data showed no significant difference in paring-pulse ratio between transmission at L2/3-PC synapses and at L2/3-IntN synapses. L2/3-IntN seemed to have higher releasing probability than L2/3-PC synapse in quantum study. The ratio of NMDA and non-NMDA EPSCs component was larger at L2/3-PC synapses than at L2/3-IntN synapses. Furthermore, the rising and decay of EPSCs were much faster at L2/3-IntN synapse than at L2/3-PC synapse. We further examined the modulation of pERK on IntN-PC pairs by applying PKC activator Phorbol 12,13- diacetate (PDA). PDA enhanced the postsynaptic currents at L2/3-PC synapses and L2/3- IntN synapses. The further issue of chronic pain model is under studying.
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Szymanski, Michael P. "Endothelial cell layer subjected to flow mimicking the apex of an arterial bifurcation." 2007. http://proquest.umi.com/pqdweb?did=1320950661&sid=3&Fmt=2&clientId=39334&RQT=309&VName=PQD.
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Thesis (M.S.)--State University of New York at Buffalo, 2007.Title from PDF title page (viewed on Nov. 21, 2007) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Meng, Hui. Includes bibliographical references.
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Zhang, Yongxin. "Validation of the coupled NCEP mesoscale spectral model and an advanced land surface model over the Hawaiian Islands." Thesis, 2004. http://proquest.umi.com/pqdweb?index=1&did=813798361&SrchMode=1&sid=3&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1233779842&clientId=23440.
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