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1
Lam, Patrick Ph D. Massachusetts Institute of Technology. "The Hob system for verifying software design properties." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38688.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 157-164).
This dissertation introduces novel techniques for verifying that programs conform to their designs. My Hob system, as described in this dissertation, allows developers to statically ensure that implementations preserve certain specified properties. Hob verifies heap-based properties that can express important aspects of a program's design. The key insight behind my approach is that Hob can establish detailed software design properties--properties that lie beyond the reach of extant static analysis techniques due to scalability or precision issues-by focusing the verification task. In particular, the Hob approach applies scalable static analysis techniques to the majority of the modules of a program and very precise, unscalable, static analysis or automated theorem proving techniques to certain specific modules of that program: those that require the precision that such analyses can deliver. The use of assume/guarantee reasoning allows the analysis engine to harness the strengths of both scalable and precise static analysis techniques to analyze large programs (which would otherwise require scalable, imprecise analyses) with sufficient precision to establish detailed data structure consistency properties, e.g. heap shape properties.
(cont.) A set-based specification language enables the different analysis techniques to cooperate in verifying the specified design properties. My preliminary results show that it is possible to successfully verify detailed design-level properties of benchmark applications: I have used the Hob system to verify user-relevant properties of a water molecule simulator, a web server, and a minesweeper game. These properties constrain the behaviour of the program by stating that selected sets of objects are always equal or disjoint throughout the program's execution.
by Patrick Lam.
Ph.D.
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Irwin, Gary M. "Interactive 3-D computer-aided design of external spur gears cut by a hob." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/90943.
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An interactive program is presented which enhances the design of external spur gears cut by a hob. The program code calculates the geometry of an involute spur gear with trochoidal fillets and then uses the Graphical Kernel System (GKS), CADAM, and MOVIE.BYU to represent and display the gear. GKS, an international standard, is used to represent the gear in two dimensions; while the CAD/CAM system CADAM and the software package MOVIE.BYU accurately create wireframe geometric design models in three dimensions. Examples of the input parameters needed and each of the software packages in use are shown and explained.M.S.
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Lima, João Expedito de. "Monitoramento do corte de dentes de engrenagem com ferramenta hob via corrente eletrica do motor da maquina." [s.n.], 1995. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263032.
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Orientador: Anselmo Eduardo DinizDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-07-20T15:01:22Z (GMT). No. of bitstreams: 1 Lima_JoaoExpeditode_M.pdf: 15304918 bytes, checksum: c10372069969cacd953522f774836459 (MD5) Previous issue date: 1995
Resumo: Este trabalho trata do monitoramento da corrente elétrica do motor da máquina ferramenta à nível de chão de fábrica, aplicado no corte de dentes de engrenagem com cortador HOB, com objetivo de verificar a existência ou não de alguma relação entre o desgaste do cortador e a corrente consumida pelo motor da máquina. Havendo essa relação estudar a viabilidade de se determinar o momento de troca do cortador a partir de análise dos parâmentros elétricos. Esse trabalho foi dividido em duas etapas: -) Monitoramento de uma máquina cortadora de engrenagem convencional. -) Monitoramento de uma máquina cortadora de engrenagem CNC. Os resultados provaram qua a corrente elétrica é um bom parâmetro no auxílio da determinação do momento de fim da vida da ferramenta, principalmente quando a máquina CNC é usada
Abstract: This work is about the monitoring of the electrical current of the machine tool motor in production floor, used in cutting of gear teeth with HOB tools, aiming to verify the relationship between the cutter wear and electrical current. Based on this, the purpose is to check the feasibility of determining the moment to replace the tool using the value of the motor electrical current. This work was carried out in two difIerents machines: -) Convencional gear cutting machine tool. -) CNC gear cutting machine tool. The results proved that the electrical current is a good parameter to help the determination of the moment of the end of tool life, manly when the CNC machine is used.
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
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Buogo, Rafaela Priscila Fernandes. "Desgaste de Fresa Caracol na usinagem de engrenagens." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2010. http://hdl.handle.net/10183/29052.
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Um dos métodos de fabricação de engrenagem em grande escala é baseado na usinagem por ferramentas de corte denominadas Cortador Hob ou Fresa Caracol. Esse método permite agilidade e precisão. A máquina e a ferramenta destinadas a esse processo são para aplicação específica na fabricação de dentados em engrenagens e eixos, fazendo-se necessário portanto um aprofundamento na otimização, melhor utilização dessas ferramentas. A não substituição da ferramenta no momento correto implica em dois problemas: ou ela poder ser trocada antes do término da vida ou ela pode ser usada em excesso e formar o chamado desgaste excessivo, o que reduz o número de afiações do cortador. O ponto a ser estudado o qual se trata essa dissertação é poder estimar a quantidade de peças a ser produzida com cada uma dessas ferramentas. Entretanto, sabe-se que uma mesma ferramenta pode ser aplicada a diversos tipos de peças, com variação de diâmetro e espessura, o que caracteriza a complexibilidade desse processo. Para isso foram coletados dados de usinagem e de desgaste da ferramenta em função das dimensões do par peça/ferramenta. Depois foram determinada curva padrão de desgaste em relação ao par peça/ferramenta e a partir dessa curva padrão, determinar a vida dos cortadores em quantidade de peças a serem fabricadas. Em seguida, os testes realizados puderam comprovar a efetividade dessa correlação.The method of manufacture of gear on a large scale is based on process that use cutting tools, called Hob or “Caracol”. This method allows the speed and accuracy. The machine and tool designed for this process are specific for application in the manufacture of toothed gears and shafts. This making it necessary insight into the optimization of these tools. Failure to replace the tool at the right time involves two problems: or it can be exchanged before the end of life, or it can be overused and form the so-called excessive wear, which reduces the number of cutter sharpenings. The point of study from which it comes this work is to determine the quantity of parts to be produced with each of these tools, it know that the same tool can be applied to various types of pieces, ranging in diameter and thickness, which characterizes the complexity of this process. Therefore data about machining tool wear depending on the size of the pair part / tool were plotted collected. After that, standard curves of wear in relation to the pair part / tool and by this standard curve, to determine the life of the cutters in quantities of parts to be manufactured. Soon after, the tests performed could proved the effectiveness of this correlation.
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Trautmann, Christina. "Investigation of the use of biogas in a gas hob - and the feasibility of upgrading it on a household scale." Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/11679.
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Incldes abstract.Includes bibliographical references.
The production and use of biogas on a household scale is becoming more common. The biogas is mainly used for lighting and cooking. Since some households may already be using sophisticated gas appliances prior to investing in an anaerobic digester and might not wish to downgrade to relatively simple and robust biogas appliances, a need to investigate the compatibility of biogas with a standard household appliance was identified. A gas hob was chosen.
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Rérych, Pavel. "Optimalizace výroby součásti na hlubokotažném lisu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-402503.
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The diploma thesis present technology production of draining outlet. This is a rectangular deep drawn part, where basic shape is formed in two towing operations now. The used material is an austenitic stainless steel 17 240 with thickness 1 mm. According to the entry documentation the production technology was not change – current technology (it means drawing without thinning the wall) is most suitable. Based on technological and control calculations two-operations production was determined, which will take place in the united conventional instrument. The hydraulic press with marking Dieffenbacher PO250, which has a magnetic tool clamping, per stroke will perform here both operations. The payback was calculated for yearlong production 50 000 pieces after 0,8 years. The proposed production will make the current production more efficient including economic benefits.
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Chen, Quanjun Computer Science & Engineering Faculty of Engineering UNSW. "Analysis and application of hop count in multi-hop wireless ad-hoc networks." Awarded By:University of New South Wales. Computer Science & Engineering, 2009. http://handle.unsw.edu.au/1959.4/44769.
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Hop count, i.e., the number of wireless hops a packet has to go through to reach the destination, is a fundamental metric in multi-hop wireless ad-hoc networks. Network performance, such as throughput, end-to-end delay, energy consumption, and so on, depends critically on hop count. Previous work on modeling hop count is limited in making unrealistic simplifying assumptions either at the physical or network, or both layers of the communication protocol stack. A key contribution of this thesis is to present an analytical model to derive the probability distribution of hop count under realistic assumptions at both physical and network layers. Specifically, the model considers a log-normal shadowing radio propagation capable of accommodating the random signal fading observed in most wireless communication environments, and the widely used geographic routing at the network layer. Validation of the model is achieved by a comprehensive set of simulation experiments including a trace driven simulation of a real-word vehicular ad-hoc network. The model reveals that the presence of randomness in radio propagation reduces the required number of hops to reach a given destination significantly. To demonstrate the utility of the proposed hop count model, the thesis proposes three new applications which address some of the key challenges in multi-hop wireless networks. The first application derives the per-node packet forwarding load in multi-hop wireless sensor networks and reveals that the nodes in the vicinity of the base station has a significantly less forwarding load than previously thought under simplifying radio propagation and routing assumptions. The second application demonstrates that using hop count as a measure of distance traveled by a data packet, geocasting can be achieved in multi-hop wireless networks in situations when some of the network nodes do not have access to reliable location information. Finally, the proposed hop count model is used to evaluate the performance of the third application which demonstrates that the overhead of geographic routing can be reduced significantly by embracing a position update philosophy which adapts to the mobility and communication patterns of the underlying ad-hoc network.
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Pandey, Manoj Kumar. "A Hop-by-Hop Architecture for Multicast Transport in Ad Hoc Wireless Networks." Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd3119.pdf.
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Wang, Zhenyu. "Channel modelling for urban multi-hop/ad hoc networks." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435742.
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Di, Felice Marco <1980>. "Cross-layer optimizations in multi-hop ad hoc networks." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/915/.
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Unlike traditional wireless networks, characterized by the presence of last-mile, static and
reliable infrastructures, Mobile ad Hoc Networks (MANETs) are dynamically formed by
collections of mobile and static terminals that exchange data by enabling each other's
communication. Supporting multi-hop communication in a MANET is a challenging
research area because it requires cooperation between different protocol layers (MAC,
routing, transport). In particular, MAC and routing protocols could be considered
mutually cooperative protocol layers. When a route is established, the exposed and
hidden terminal problems at MAC layer may decrease the end-to-end performance
proportionally with the length of each route. Conversely, the contention at MAC layer
may cause a routing protocol to respond by initiating new routes queries and routing table
updates.
Multi-hop communication may also benefit the presence of pseudo-centralized virtual
infrastructures obtained by grouping nodes into clusters. Clustering structures may
facilitate the spatial reuse of resources by increasing the system capacity: at the same
time, the clustering hierarchy may be used to coordinate transmissions events inside the
network and to support intra-cluster routing schemes. Again, MAC and clustering
protocols could be considered mutually cooperative protocol layers: the clustering
scheme could support MAC layer coordination among nodes, by shifting the distributed
MAC paradigm towards a pseudo-centralized MAC paradigm. On the other hand, the
system benefits of the clustering scheme could be emphasized by the pseudo-centralized
MAC layer with the support for differentiated access priorities and controlled contention.
In this thesis, we propose cross-layer solutions involving joint design of MAC, clustering
and routing protocols in MANETs.
As main contribution, we study and analyze the integration of MAC and clustering
schemes to support multi-hop communication in large-scale ad hoc networks. A novel
clustering protocol, named Availability Clustering (AC), is defined under general nodes'
heterogeneity assumptions in terms of connectivity, available energy and relative
mobility. On this basis, we design and analyze a distributed and adaptive MAC protocol,
named Differentiated Distributed Coordination Function (DDCF), whose focus is to
implement adaptive access differentiation based on the node roles, which have been
assigned by the upper-layer's clustering scheme. We extensively simulate the proposed
clustering scheme by showing its effectiveness in dominating the network dynamics,
under some stressing mobility models and different mobility rates. Based on these results,
we propose a possible application of the cross-layer MAC+Clustering scheme to support
the fast propagation of alert messages in a vehicular environment.
At the same time, we investigate the integration of MAC and routing protocols in large
scale multi-hop ad-hoc networks. A novel multipath routing scheme is proposed, by
extending the AOMDV protocol with a novel load-balancing approach to concurrently
distribute the traffic among the multiple paths. We also study the composition effect of a
IEEE 802.11-based enhanced MAC forwarding mechanism called Fast Forward (FF),
used to reduce the effects of self-contention among frames at the MAC layer. The
protocol framework is modelled and extensively simulated for a large set of metrics and
scenarios.
For both the schemes, the simulation results reveal the benefits of the cross-layer
MAC+routing and MAC+clustering approaches over single-layer solutions.
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Alves, Alícia Viviana Prata. "Filmes de colagénio eletricamente estimulados para crescimento de tecidos." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14909.
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Mestrado em Materiais e Dispositivos BiomédicosAo longo dos últimos anos tem- se tornado evidente que em alguns casos os biomateriais devem ser mais do que meros suportes temporários para o crescimento de novos tecidos, podendo intervir ativamente no processo de regeneração. O facto de o fenómeno piezoelétrico estar associado à reparação óssea, foi uma das principais motivações para a procura de materiais com características piezoelétricas, como potenciais indutores da regeneração de tecidos. Deste modo, os materiais piezoelétricos têm captado, nos últimos anos, a atenção dos investigadores, para a medicina regenerativa. O objetivo deste trabalho foi a preparação, caracterização e investigação do efeito da polarização dos filmes de colagénio tipo I na morfologia e adesão das células hOB e MG-63. O colagénio tipo I foi o material piezoelétrico escolhido para a realização deste trabalho, uma vez que, para além de ser a principal proteína constituinte do organismo humano, se pensa que as suas propriedades piezoelétricas estejam envolvidas na autorreparação óssea. Foram preparados filmes de colagénio tipo I pelo método de drop-casting tendo sido posteriormente polarizados a 40 ºC pelo método da descarga de Corona, carregando desta forma os filmes positiva e negativamente. Para uma melhor análise dos filmes obtidos foram realizadas primeiramente caracterizações aos filmes relativamente à sua morfologia, estrutura, rugosidade e comportamento térmico, tendo posteriormente sido analisados filmes sem submissão à polarização e filmes polarizados, relativamente à sua molhabilidade e composição estrutural com o principal objetivo de analisar se existe alguma alteração induzida pela polarização dos mesmos. Estes estudos foram seguidos dos estudos celulares preliminares por recurso a duas linhas celulares: as hOB que são células osteoblásticas humanas e as MG-63, uma linha tumoral proveniente de osteossarcomas. Os filmes de colagénio, com uma espessura aproximada de 2 μm, revelam rugosidades micrométricas, geralmente favoráveis às atividades celulares, com rugosidades médias de 111 ± 20 nm. A análise térmica evidencia um pico endotérmico largo aos aproximadamente 62 ºC, indicando a existência de moléculas com estabilidades/ comportamentos térmicos diferentes. As medidas de ângulos de contacto revelaram que todas as superfícies analisadas se encontram no domínio hidrofílicos, tendo-se no entanto registado melhorias na molhabilidade dos filmes de colagénio submetidos à polarização. A análise da composição estrutural através da Espectroscopia de Infravermelho com Transformada de Fourier (FTIR) mostrou a presença das bandas típicas para o colagénio tipo I, tendo sido detetada a amida A, I,II e III, para todos os grupos de filmes analisados. Nos estudos celulares preliminares realizados verificou-se que para ambas as linhas celulares (hOB e MG-63), as células em contacto com as superfícies polarizadas apresentam um maior número de filamentos de F-actina bem orientados, o que indica a existência de uma forte interação das células com este tipo de superfície. As contagens celulares apontam para uma preferência das hOB relativamente aos filmes de colagénio (-), enquanto que, não foram detetadas diferenças significativas na adesão celular para nenhum dos grupos de filmes analisados para o caso da linha celular MG-63.
Over the past few years it has become apparent that in some cases the biomaterials should be more than temporary supports for the growth of new tissues and must intervene actively during the regeneration process. The discovery of piezoelectricity and their involvement on the repair process in biological tissues, such us, skin, tendon and bone, has led to the idea of using unique materials, such as materials that exhibit surface charges, as potential inducers for regenerative medicine. The aim of this study lays on the preparation, characterization and subsequent analysis of the influence that polarization of type I collagen films has on cell morphology and adhesion. Type I collagen is the piezoelectric material selected for this work because besides being the most abundant protein in the body that plays a fundamental role in tissues and organs formation, it is thought that the piezoelectric properties of this protein could be related to the ability of bone self-repair. For this purpose collagen films were prepared by dop-casting method and subsequently macroscopically polarized at 40 ° C by Corona poling. In that way there were produced negatively and positively charged films. For a better understanding of the obtained films there were done characterizations regarding their morphology, structure, roughness and thermal behavior. Subsequently polarized and non-polarized films were analyzed in relation to their wettability and chemical composition with the main goal to detect possible changes induced by polarization. Preliminary cellular studies were conducted with two cell lines: a human osteoblastic cell type (hOB) and an osteosarcoma cell line (MG-63). The obtained collagen films have a thickness of approximately 2 μm. The surface roughness measurements of the films show a micrometric roughness that generally is promising for cellular activities. The average roughness that was obtained is around 111 ± 20 nm. Thermal analyses show a broad endotherm peak at approximately 62 ° C representing a variability of molecules with different thermal stabilities. The contact angle measurements have shown that all analyzed surfaces are in the hydrophilic domain. However it was shown a significant improvement of the wettability for the polarized collagen films. Results of Fourier Transform InfraRed Spectroscopy (FTIR) analyses indicate the presence of the typical peaks for collagen type I FTIR spectra. It was detected the characteristic bands of amide A, I, II and III for all analyzed film groups. In preliminary cellular studies it was found that for both cell lines (hOB and MG-63) the cells in contact with the polarized surfaces spread with cytoskeletal rearrangements of actin filaments being observed through the formation of stress fibers, which indicates the existence of a strong interaction between the cell and the charged surfaces. The cell counting indicates that the hOB cells prefer the negatively charged collagen films (-) while for the cell line MG-63 no significant differences were detected in cell adhesion between any of the analyzed films groups.
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Westin, Ola. "TCP Performance in Wireless Mobile Multi-hop Ad Hoc Networks." Thesis, KTH, Mikroelektronik och Informationsteknik, IMIT, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-93070.
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There are many issues that limit the performance of wireless mobile multi-hop ad hoc networks (MANETs). One of them is that TCP is not well adapted to networks where routes can change or disappear often. In this paper the behaviour of a standard TCP implementation is studied in situations typical for MANETs and compared to the behaviour of a partial implementation of a ATCP, a TCP modification that is intended to increase performance in MANETs. Simulations with simple scenarios show that TCP easily creates a full network load which causes send failures and decreased throughput performance. In some cases the partial ATCP implementation increases throughput but more often it causes an increased amount of duplicate retransmissions. In these scenarios it is unlikely that even a complete ATCP implementation would increase throughput performance. A few modifications to ATCP and TCP are analysed. Especially a limit of the congestion window size shows a large throughput increase. The results are inconclusive, the simulations are too simple to show if the results are applicable in more complex scenarios. It is not clear if ATCP actually is useful in a MANET.Många faktorer begränsar prestandan i trådlösa mobila multi-hopp ad hoc-nätverk (MANET:er). En av dem är att TCP inte är anpassat till nätverk där rutter ofta kan förändras eller försvinna. I den här rapporten studeras hur en vanlig TCP-implementation uppför sig i typiska MANET-situationer. Detta beteende jämförs mot en partiell implementation av ATCP, en TCPmodifiering som är tänkt att öka prestanda i MANET:er. Simuleringar med enkla scenarier visar att TCP lätt genererar en full nätverkslast vilket orsakar misslyckade sändningar och en minskad genomströmningsprestanda. I vissa fall ökar den partiella ATCP-implementationen genomströmningen, men oftare ger den en ökad mängd onödiga omsändningar. I dessa scenarier är det inte troligt att ens en komplett ATCP-implementation skulle öka genomströmningsprestanda. Några mindre förändringar av ATCP och TCP analyseras. Särskilt ger en begränsning av stockningsfönstret en stor ökning av genomströmningen. Resultaten är ofullständiga. Simuleringarna är för enkla för att kunna visa om om resultaten är tillämpliga i mer komplexa scenarier. Det är inte klarlagt ifall ATCP verkligen är användbart i ett MANET.
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Al, Mojamed Mohammad. "A one hop overlay system for mobile ad hoc networks." Thesis, University of Stirling, 2016. http://hdl.handle.net/1893/24320.
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Peer-to-Peer (P2P) overlays were initially proposed for use with wired networks. However, the very rapid proliferation of wireless communication technology has prompted a need for adoption of P2P systems in mobile networks too. There are many common characteristics between P2P overlay networks and Mobile Ad-hoc Networks (MANET). Self-organization, decentralization, a dynamic nature and changing topology are the most commonly shared features. Furthermore, when used together, the two approaches complement each other. P2P overlays provide data storage/retrieval functionality and MANET provides wireless connectivity between clients without depending on any pre-existing infrastructure. P2P overlay networks can be deployed over MANET to address content discovery issues. However, previous research has shown that deploying P2P systems straight over MANET does not exhibit satisfactory performance. Bandwidth limitation, limited resources and node mobility are some of the key constraints. This thesis proposes a novel approach, OneHopOverlay4MANET, to exploit the synergies between MANET and P2P overlays through cross-layering. It combines Distributed Hash Table (DHT) based structured P2P overlays with MANET underlay routing protocols to achieve one logical hop between any pair of overlay nodes. OneHopOverlay4MANET constructs a cross-layer channel to permit direct exchange of routing information between the Application layer, where the overlay operates, and the MANET underlay layer. Consequently, underlay routing information can be shared and used by the overlay. Thus, OneHopOverlay4MANET reduces the typical management traffic when deploying traditional P2P systems over MANET. Moreover, as a result of building one hop overlay, OneHopOverlay4MANET can eliminate the mismatching issue between overlay and underlay and hence resolve key lookups in a short time, enhancing the performance of the overlay. v In this thesis, we present OneHopOverlay4MANET and evaluate its performance when combined with different underlay routing protocols. OneHopOverlay4MANET has been combined with two proactive underlays (OLSR and BATMAN) and with three reactive underlay routing protocols (DSR, AODV and DYMO). In addition, the performance of the proposed system over OLSR has been compared to two recent structured P2P over MANET systems (MA-SP2P and E-SP2P) that adopted OLSR as the routing protocol. The results show that better performance can be achieved using OneHopOverlay4MANET.
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Xu, Lei. "Potential single-occupancy vehicle demand for the Katy Freeway and Northwest Freeway high-occupancy vehicle lanes." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4358.
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Since the 1960âÂÂs, high-occupancy vehicle (HOV) lanes have been successfully used as a
travel demand management technique. In recent years, there has been a growing interest
in the use of high-occupancy toll (HOT) lanes as an alternative to HOV lanes to help
manage the increasing demand for travel. HOT lanes combine pricing and vehicle
occupancy restrictions to optimize the demand for HOV lanes. As two of the four HOT
lanes in the world, the HOT lane facilities in Houston, Texas received relatively low
patronage after operating for over 6 years on the Katy Freeway and over 4 years on the
Northwest Freeway. There existed an opportunity to increase the usage of these HOT
lanes by allowing single-occupancy vehicle (SOV) travelers to use the lanes, for an
appropriate toll. The potential SOV demand for HOV lane use during the off-peak
periods from the Katy Freeway and Northwest Freeway general-purpose lane (GPL)
travelers was estimated in this study by using the data collected from a 2003 survey of
travelers on the Katy and Northwest Freeway GPLs who were not enrolled in
QuickRide. Based on survey results, more travelers would choose to drive on the HOT lanes
as SOV travelers during the off-peak periods when the facilities provided higher travel
time savings and charged lower tolls. Two important factors influencing travelersâ use
of the HOV lanes were their value of travel time savings (VTTS) and penalty for
changing travel schedule (VPCS). It was found that respondents had VTTS
approximately 43 percent of their hourly wage rate and VPCS approximately 3 percent
of their hourly wage rate. Combining this information with current travel time savings
and available capacity on the HOV lanes, it was found that approximately 2000 SOV
travelers per day would pay an average toll of $2.25 to use the HOV lanes during the
off-peak periods.
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Zhang, Xin. "Network Formation and Routing for Multi-hop Wireless Ad-Hoc Networks." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11470.
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An energy-aware on-demand Bluetooth scatternet formation and routing protocol taking into
account network architecture and traffic pattern is proposed. The scatternet formation protocol is able to cope with multiple sources initiating
traffic simultaneously as well as prolong network lifetime. A modified Inquiry scheme using extended ID packet is introduced for fast device discovery and power efficient propagation of route request messages with low delay. A mechanism employing POLL packets in Page processes is proposed to transfer scatternet formation and route reply information without extra overhead. In addition, the energy aware forwarding nodes selection scheme is based on local information and results in more uniform network resource utilization and improved network lifetime. Simulation results show that this protocol can provide scatternet formation
with reasonable delay and with good load balance which results in prolonged network lifetime for Bluetooth-based wireless sensor networks.
In this research, a metric-based scatternet formation algorithm for the Bluetooth-based sensor motes is presented. It optimizes the Bluetooth network formation from the hop distance
and link quality perspectives. In addition, a smart repair mechanism is proposed to deal with link/node failure and recover the network connectivity promptly with low overhead. The experiments with the Intel Mote platform demonstrate the effectiveness of the optimizations.
This research also investigates the scalability of ad hoc routing protocols in very large-scale wireless ad hoc networks. A comprehensive
simulation study is conducted of the performance of an on-demand routing protocol on a very large-scale, with as many as 50,000 nodes in the network. The scalability analysis is addressed based on various network sizes, node density, traffic load, and mobility. The reasons for packet loss are analyzed and categorized at each network layer. Based on the observations, we observe the effect of the parameter selection and try to exhaust the scalability boundary
of the on-demand routing protocol for wireless ad hoc networks.
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Rajendran, Venkatesh. "Medium access control protocols for multi-hop wireless ad hoc networks /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2006. http://uclibs.org/PID/11984.
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Antic, Filip S. "Capactiy of single-hop communication links in wireless ad hoc networks." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/33100.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (leaves 67-68).
This thesis defines the capacity of single-hop communication links in wireless ad hoc networks as the transferable data rate over that link determined by the Shannon limit and by the fixed modulation scheme and bit error rate. The resulting capacity formulas are derived under the assumption of r-3.8 path loss and uniform, but random, distribution of users. Rank of the link R is defined and included in the capacity formulas. After defining link capacity, the improvement of capacity is studied when different network components are implemented. These include successive interference cancellation (SIC), and multiple antenna arrays at the transmitting and the receiving end of the link. These strategies are then compared in terms of the dB improvement of capacity that they provide. Network parameter NP is defined in order to characterize spatial reuse in the network, and optimal network parameter is determined for maximizing link capacity in the process of dividing the network single frequency channel into equally sized subchannels.
by Filip S. Antic.
M.Eng.
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Zhao, Xiwei. "Foundational Forensic Techniques for Cellular and Ad Hoc Multi-hop Networks." FIU Digital Commons, 2008. http://digitalcommons.fiu.edu/etd/23.
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The Internet has become an integral part of our nation's critical socio-economic infrastructure. With its heightened use and growing complexity however, organizations are at greater risk of cyber crimes. To aid in the investigation of crimes committed on or via the Internet, a network forensics analysis tool pulls together needed digital evidence. It provides a platform for performing deep network analysis by capturing, recording and analyzing network events to find out the source of a security attack or other information security incidents. Existing network forensics work has been mostly focused on the Internet and fixed networks. But the exponential growth and use of wireless technologies, coupled with their unprecedented characteristics, necessitates the development of new network forensic analysis tools. This dissertation fostered the emergence of a new research field in cellular and ad-hoc network forensics. It was one of the first works to identify this problem and offer fundamental techniques and tools that laid the groundwork for future research. In particular, it introduced novel methods to record network incidents and report logged incidents. For recording incidents, location is considered essential to documenting network incidents. However, in network topology spaces, location cannot be measured due to absence of a 'distance metric'. Therefore, a novel solution was proposed to label locations of nodes within network topology spaces, and then to authenticate the identity of nodes in ad hoc environments. For reporting logged incidents, a novel technique based on Distributed Hash Tables (DHT) was adopted. Although the direct use of DHTs for reporting logged incidents would result in an uncontrollably recursive traffic, a new mechanism was introduced that overcome this recursive process. These logging and reporting techniques aided forensics over cellular and ad-hoc networks, which in turn increased their ability to track and trace attacks to their source. These techniques were a starting point for further research and development that would result in equipping future ad hoc networks with forensic components to complement existing security mechanisms.
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Qin, Xiaoqi. "On Throughput Maximization in a Multi-hop MIMO Ad Hoc Network." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23160.
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In recent years, there has been a growing research interest in throughput optimization problems in a multi-hop wireless network. MIMO (multiple-input multiple-output), as an advanced physical layer technology, has been employed in multi-hop wireless networks to increase throughput with a given bandwidth or transmit power. It exploits the use of multiple antennas at the transmitter and receiver to increase spectral efficiency by leveraging its spatial multiplexing (SM) and interference cancellation (IC) capabilities. Instead of carrying complex manipulations on matrices, degree-of-freedom(DoF) based MIMO models, which require only simple computations, are widely used in networking research to exploit MIMO\'s SM and IC capabilities.In this thesis, we employ a new DoF model, which can ensure feasible solution and achieve
a higher DoF region than previous DoF-based models. Based on this model, we study the DoF scheduling for a multi-hop MIMO network. Specifically, we aim to maximize the minimum rate among all sessions in the network. Some researches have been done based on this model to solve throughput optimization problems with the assumption that the route of each session is given priori. Although the fixed routing decreases the size of the problem, it also limits the performance of the network to a great extent.
The goal of this thesis is to employ this new model to solve the throughput maximization
problem by jointly considering flow routing, scheduling, and DoF allocation for SM and IC. We
formulate it as a mixed integer linear program (MILP), which cannot be solved efficiently by
commercial softwares even for moderate sized networks. Thus, we develop an efficient polynomial time algorithm by customizing the sequential fixing framework. Through simulation results, we show that this algorithm can efficiently provide near-optimal solutions for networks with different sizes.
Master of Science
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Oehlsen, Golaleh [Verfasser]. "Stochastic Geometric Distances in Multi-Hop Wireless Ad Hoc Networks / Golaleh Oehlsen." München : Verlag Dr. Hut, 2012. http://d-nb.info/1020299436/34.
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Viswanath, Kumar. "Adaptive integrated approach to group communications in multi-hop ad-hoc networks /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2005. http://uclibs.org/PID/11984.
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Lu, Yu Ming. "Routing strategies for capacity enhancement in multi-hop wireless ad hoc networks." Thesis, University of York, 2007. http://etheses.whiterose.ac.uk/11080/.
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This thesis examines a Distributed Interference Impact Probing (DIIP) strategy for Wireless Ad hoc Networks (WANETs), using a novel cross-layer Minimum Impact Routing (MIR) protocol. Perfonnance is judged in tenns of interference reduction ratio, efficiency, and system and user capacity, which are calculated based on the measurement of Disturbed Nodes (DN). A large number of routing algorithms have been proposed with distinctive features aimed to overcome WANET's fundamental challenges, such as routing over a dynamic topology, scheduling broadcast signals using dynamic Media Access Control (MAC), and constraints on network scalability. However, the scalability problem ofWANET cannot simply adapt the frequency reuse mechanism designed for traditional stationary cellular networks due to the relay burden, and there is no single comprehensive algorithm proposed for it. DIIP enhances system and user capacity using a cross layer routing algorithm, MIR, using feedback from DIIP to balance transmit power in order to control hop length, which consequently changes the number of relays along the path. This maximizes the number of simultaneous transmitting nodes, and minimizes the interference impact, i.e. measured in tenns of 'disturbed nodes'. The perfonnance of MIR is examined compared with simple shortest-path routing. A WANET simulation model is configured to simulate both routing algorithms under multiple scenarios. The analysis has shown that once the transmitting range of a node changes, the total number of disturbed nodes along a path changes accordingly, hence the system and user capacity varies with interference impact variation. By carefully selecting a suitable link length, the neighbouring node density can be adjusted to reduce the total number of DN, and thereby allowing a higher spatial reuse ratio. In this case the system capacity can increase significantly as the number of nodes increases. In contrast, if the link length is chosen regardless ofthe negative impact of interference, capacity decreases. In addition, MIR diverts traffic from congested areas, such as the central part of a network or bottleneck points.
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Suthaputchakun, Chakkaphong. "Multi-hop broadcast protocols for emergency message dissemination in vehicular ad hoc networks." Thesis, University of Surrey, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608349.
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Emergency Message (EM) dissemination in Vehicular Ad hoc Networks (VANETs) has attracted significant attention in Intelligent Transportation System (ITS) in recent years. Such dissemination mechanisms mostly rely on licensed Dedicated Short Range Communications (DSRC) systems such as IEEE 802.11p and IEEE PI609.1-4 standards. By timely broadcasting of emergency messages (EMs), drivers can avoid potentially dangerous accidents and experience a safer driving environment. As the result, a concern of the number of accidents is also reduced. Thus, an efficient broadcast protocol is required in this scenario. In this thesis, designs of robust broadcast protocols are considered for Emergency Message Dissemination in VANETs. It presents four innovative contributions. Firstly, a literature review as well as challenges and issues of the protocols designed for EM dissemination application are presented. Secondly, Priority-based Routing Protocol (PRP) and its reliability enhancement (PRP-RE) have been proposed as broadcast protocols for different types of EM disseminations, providing; 1) fully distributed broadcast protocol; 2) different Quality of Services (QoS) for different types of EMs: 3) maximum message dissemination distance per hop; and 4) high communication reliability. Thirdly, a more efficient and robust multi-hop broadcast protocol for time-critical EM disseminations is proposed as Trinary Partitioned Black-Burst based Broadcast Protocol (3P3B). A mini-DIPS in MAC sub-layer is introduced to give the time-critical EMs the highest priority access to the communication channel compared to other EMs. In addition, a trinary partitioning is designed to iteratively partition the communication area into small sectors, allowing only the furthest possible vehicle to perform EM forwarding. Therefore. 3P3B can increase dissemination speed and reduce contention period jitter. The performance evaluation results demonstrate that 3P3B outperforms benchmarks of the existing broadcast protocols in VANETs in terms of average message dissemination speed, message progress, communication delay, and packet delivery ratio. Finally, 3P3B-DTN is proposed based on an enhancement of 3P3B to deal with communications in a disruptive network with an introduction of EM store, carry, and forward to maximize packet delivery ratio while minimizing end-to-end delay. The performance evaluation results show that 3P3BDTN achieves higher packet delivery ratio than 3P3B even when the network is disrupted with a trade-off of higher end-to-end delay and overhead for those EMs, which would be lost otherwise.
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Seddik, Alaa Agoulmine Nazim. "TCP performance study and enhancements within wireless multi-hop ad hoc network environments." S. l. : S. n, 2009. http://www.biblio.univ-evry.fr/theses/2009/2009EVRY0006.pdf.
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Seddik, Alaa. "TCP performance study and enhancements within wireless multi-hop ad hoc network environments." Thesis, Evry-Val d'Essonne, 2009. http://www.theses.fr/2009EVRY0006/document.
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Les réseaux ad hoc diffèrent des réseaux filaires par la multitude de perturbation auxquels ils sont sujets. Alors qu’une rupture de lien est un événement plutôt rare sur des réseaux filaires, et généralement imputable à l’état physique du matériel intermédiaire, cet événement est courant avec les communications radio. Ceci est lié à la qualité du signal reçu de l’autre extrémité ou à la configuration de l’environnement. Les perturbations causées par l’environnement ne mènent pas seulement à une rupture d’un lien, elles peuvent avoir un impact sur la réception des données. La volatilité des liens est typique dans les réseaux sans fil alors pour les réseaux filaires ce problème est inexistant. TCP, qui est prévu pour assurer la transmission fiable des données, n’a été conçu qu’en tenant compte des contraintes des réseaux filaires. Ainsi, certains événements dans la transmission de données sans fil peuvent être mal interprétés et engendrer une mauvaise réaction de TCP. Pour améliorer la performance de TCP dans les réseaux ad hoc, l’objectif de cette thèse est double. Dans un premier temps, une étude complète des performances de TCP dans les réseaux ad hoc est dressée. Celle-ci concerne à la fois les débits atteignables et aussi la consommation d’énergie induite par l’utilisation de ce protocole de transport dans un réseau ad hoc. Cette étude permet d’identifier les points d’amélioration de TCP pour qu’il soit utilisable dans les réseaux ad hoc. Dans un second temps, nous proposons une nouvelle variante de TCP, appelée TCP-WELCOME, dont l’objectif est de traiter de façon adéquate les différents types de perte de paquets sur un réseau ad hoc et optimiser la performance de TCPWireless ad hoc networks are different from wired networks by the multitude of data packet loss situations they are subjected to. This is due to the characteristics of wireless channel that might obstruct the proper reception of data packet at the destination end. In some case, these vulnerabilities of wireless channel can result in a complete link failure. Although link failure is of low probability in wired networks, it is rather common in wireless networks. The volatility of communication channel is a typical problem with wireless links, which is not the case with wired cables. TCP is a transport protocol that aims at ensuring high reliability and guarantying reception of data packets. However, TCP was designed for wired networks to address congestion, which is the main cause for data packet loss in wired networks. Therefore, other types of data packet loss encountered in wireless networks are prone to misinterpretation by TCP, which will lead to TCP performance degradation within the network. To overcome the performance limitation of TCP when used within ad hoc networks, the aim of this thesis is twofold. First, a complete performance study of TCP over ad hoc networks is achieved. This evaluation concerns two performance metrics: the achievable throughput and the energy consumption of TCP within ad hoc networks. This study allows identifying the potential room of improvement to enhance TCP efficiency in ad hoc networks. Second, we propose a new TCP variant, TCP-WELCOME that optimizes the performance of TCP in ad hoc networks through its ability to distinguish among, and efficiently deal with, different data packet loss situations, within ad hoc networks
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Mahdi, Rafid, and Pontus Tobiasson. "An experimental verification of single-frequency networks in multi-hop ad hoc networks." Thesis, Mittuniversitetet, Avdelningen för informations- och kommunikationssystem, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-27968.
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A multi-hop ad hoc network requires no infrastructure, like base stations or routers to function. This means that it can quickly be deployed and in movement, making it ideal for scenarios like natural disasters or battlefield communication. A single-frequency network (SFN) is the idea that transmitters can cooperate to send the same signals simultaneously over the same frequency channel, such that the signals are amplified. It was previously proposed that SFNs could be created in multi-hop ad hoc networks. According to simulations, this could improve the energy consumption, signal reachability, and data transfer rate. As this has only been simulated, the purpose of this project is to experimentally verify that SFN is attainable in a multi-hop ad hoc network, and to assess what the difficulties are of an actual implementation. The method involved synchronizing the transmission of two devices operating under the 802.11a standard. A multi-hop ad hoc network was created by changing the settings of the network interface cards. The devices used were mainly laptops and transmissions were monitored in Wireshark. The laptops were forced to send on one frequency channel to make interference possible, and identical packets were sent. Experiments were made to assess whether SFN was attained. The packet loss rate and distance were used to evaluate the results. The results suggest that a synchronized transmission off by less than 2 μs was attained. However, the error of these measurements were neither known nor approximable. This meant it was hard to know when a SFN was formed. The results indicate that SFN was attained, as the packet loss rate decreased significantly when employed. The effectiveness of SFN was hard to assess because the results were not comparable with the simulation values. The difficulty of an actual implementation is deemed to be the synchronization of transmissions.
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Chum, Geoffrey Linus. "Potential shift from transit to single occupancy vehicle due to adaptation of a high occupancy vehicle lane to a high occupancy toll lane." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2469.
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Krause, Wolfram O. "Wireless communication networks : structure and dynamics of wireless multi-hop ad hoc communication networks /." Lichtenberg (Odenw.) : Harland media, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=015507583&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Raghunathan, Arun Roppel Thaddeus A. "Ad-hoc and multi-hop wireless sensor networks for activity capture in cooperative robotics." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Summer/Theses/RAGHUNATHAN_ARUN_24.pdf.
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SAYADI, Afef. "Medium access protocol (MAC) design for wireless multi-hop ad hoc and sensor networks." Phd thesis, Institut National des Télécommunications, 2013. http://tel.archives-ouvertes.fr/tel-00997665.
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Wireless multi-hop ad hoc and sensor networks provide a promising solution to ensure ubiquitous connectivity for the Future Internet. Good network connectivity requires designing a reliable Medium Access Control (MAC) protocol, which is a challenging task in the ad hoc and sensor environments. The broadcast and shared nature of the wireless channel renders the bandwidth resources limited and expose the transmissions to relatively high collisions and loss rates. The necessity to provide guaranteed Quality of Service (QoS) to the upper layers triggered the design of conflict-free MAC protocols. The TDMA synchronization constraint is basically behind the rush of MAC protocol design based on a fixed frame size. This design shows inflexibility towards network variations and creates a network dimensioning issue that leads to a famine risk in case the network is under-dimensioned, and to a waste of resources, otherwise. Moreover, the alternative dynamic protocols provide more adaptive solutions to network topology variations at the expense of a fair access to the channel. Alongside with the efficient channel usage and the fair medium access, reducing the energy consumption represents another challenge for ad hoc and sensor networks. Solutions like node activity scheduling tend to increase the network lifetime while fulfilling the application requirements in terms of throughput and delay, for instance. Our contributions, named OSTR and S-OSTR, address the shortcomings of the medium access control protocol design in the challenging environment of wireless multi-hop ad hoc and sensor networks, respectively. For OSTR the idea consists in adopting a dynamic TDMA frame size that increases slot-by-slot according to the nodes arrival/departure to/from the network, and aiming to achieve a minimum frame size. For this end, OSTR couples three major attributes: (1) performing slot-by-slot frame size increase, (2) providing a spatial reuse scheme that favors the reuse of the same slot if possible, (3) and ensuring an on-demand frame size increase only according to the node requirements in terms of throughput. To tackle different frame sizes co-existence in the network, OSTR brings a cooperative solution that consists in fixing an appointment, a date when the frame size in the network is increased. Concerning S-OSTR, it is an amendment of OSTR for wireless sensor networks. It brings the idea of a dynamic active period, since it deploys a dynamic frame size that is built slot-by-slot according to nodes arrival to the network. S-OSTR enforces the slot-by-slot frame size increase by a node activity scheduling to prolong the inactivity period in the network, and hence prolong the overall network lifetime for wireless sensor networks. Our contributions are both based on the new dynamic TDMA frame size increase that consists in increasing the frame size slot-by-slot aiming to achieve a shorter frame size, and hence improve the channel utilization, and reduce the energy consumption. The performance analysis of OSTR and S-OSTR shows that they present good potentials to support QoS requirements, to provide energy-efficiency, to ensure fair medium access, to accommodate network topology changes and finally, to enhance robustness against scalability. The impact of this new TDMA frame size increase technique on the medium access control protocol performance is highlighted through multiple simulations of OSTR and S-OSTR. Multiple comparative studies are also handled to point out the effectiveness of this new technique and the soundness of our contributions
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Sayadi, Afef. "Medium access protocol (MAC) design for wireless multi-hop ad hoc and sensor networks." Thesis, Evry, Institut national des télécommunications, 2013. http://www.theses.fr/2013TELE0002/document.
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Les réseaux sans fil multi-sauts ad hoc et les réseaux de capteurs présentent une solution prometteuse pour assurer une connectivité quasi-permanente dans l'Internet du Futur. Cette connectivité, néanmoins, nécessite la conception d'un protocole d'accès au canal radio fiable, ce qui défi les caractéristiques hostiles et instables des réseaux ad hoc et des réseaux de capteurs. Cet environnement, en effet, est caractérisé par la rareté des ressources radio disponibles, la perte de la bande passante due aux collisions et aux interférences. La nécessité de garantir une meilleure qualité de service aux couches applicatives a promu la conception des protocoles MAC basés sur la technique d'accès TDMA. Essayant de contourner la contrainte d’une fine synchronisation horloge imposée par ce type de protocoles, les recherches se sont orientées vers une conception de protocoles MAC basés sur la technique TDMA dont la taille de la trame est fixe. Cependant, cette conception présente deux principaux inconvénients: d'une part elle procure une inflexibilité quant à la variation de la topologie du réseau suite aux mouvements des nœuds. D'une autre part, elle soulève un problème de dimensionnement : si la taille de la trame est surdimensionnée par rapport au nombre de nœuds présents dans le réseau, des slots non alloués apparaissent induisant la perte de la bande passante. Toutefois, si la taille de la trame est sous-dimensionnée, un risque de famine surgit. Les protocoles MAC basés sur la technique TDMA à taille de trame dynamique présentent une alternative, qui réussit à augmenter le débit au détriment d’une non-équité entre les nœuds dans le réseau. Outre l'utilisation optimale et équitable de la bande passante disponible, la réduction de la consommation d'énergie constitue un autre défi majeur pour les réseaux ad hoc et les réseaux de capteurs. Dans ce travail, deux contributions nommées OSTR et S-OSTR, sont conçues pour améliorer le débit, l'équité et la réduction de la consommation d'énergie dans l'environnement des réseaux ad hoc et des réseaux de capteurs. L'idée motrice d'OSTR consiste à augmenter la taille de la trame TDMA dynamiquement de manière à aboutir à une taille de trame réduite. Dans ce but, OSTR met en place une augmentation à la demande de la taille de la trame. Cette augmentation est établie slot par slot. OSTR se base sur une réutilisation spatiale des times slots ; i.e. un même slot peut être utilisé au même moment par plusieurs nœuds dans le réseau. Afin de prévenir les collisions dues à la coexistence de plusieurs tailles de trames au même temps dans le réseau, OSTR déploie une solution coopérative qui consiste à fixer un rendez-vous au moment duquel la taille de la trame est augmentée simultanément par tous les nœuds dans le réseau. S-OSTR constitue une adaptation du protocole OSTR à l'environnement des réseaux de capteurs. S-OSTR vise à augmenter la durée de vie du réseau. Il déploie ainsi une période d'activité dynamique qui consiste en une trame TDMA augmentant slot-par-slot. S-OSTR effectue également un ordonnancement des activités des nœuds afin de prolonger la période d'inactivité, et par suite prolonger la durée de vie du réseau. Nos deux contributions se basent sur une nouvelle technique d'augmentation dynamique de la taille de la trame TDMA qui consiste à augmenter la taille slot-par-slot. Cette technique permet d'atteindre une taille réduite, et par conséquent d’améliorer l'utilisation de la bande passante et de minimiser la consommation de l'énergie dans le réseau. L'analyse des performances d'OSTR et de S-OSTR souligne leurs potentiels pour s'adapter aux exigences des applications en termes de QoS, pour assurer un accès équitable au canal radio, pour réduire la consommation de l'énergie et pour s'adapter aux différents changements de la topologie du réseauWireless multi-hop ad hoc and sensor networks provide a promising solution to ensure ubiquitous connectivity for the Future Internet. Good network connectivity requires designing a reliable Medium Access Control (MAC) protocol, which is a challenging task in the ad hoc and sensor environments. The broadcast and shared nature of the wireless channel renders the bandwidth resources limited and expose the transmissions to relatively high collisions and loss rates. The necessity to provide guaranteed Quality of Service (QoS) to the upper layers triggered the design of conflict-free MAC protocols. The TDMA synchronization constraint is basically behind the rush of MAC protocol design based on a fixed frame size. This design shows inflexibility towards network variations and creates a network dimensioning issue that leads to a famine risk in case the network is under-dimensioned, and to a waste of resources, otherwise. Moreover, the alternative dynamic protocols provide more adaptive solutions to network topology variations at the expense of a fair access to the channel. Alongside with the efficient channel usage and the fair medium access, reducing the energy consumption represents another challenge for ad hoc and sensor networks. Solutions like node activity scheduling tend to increase the network lifetime while fulfilling the application requirements in terms of throughput and delay, for instance. Our contributions, named OSTR and S-OSTR, address the shortcomings of the medium access control protocol design in the challenging environment of wireless multi-hop ad hoc and sensor networks, respectively. For OSTR the idea consists in adopting a dynamic TDMA frame size that increases slot-by-slot according to the nodes arrival/departure to/from the network, and aiming to achieve a minimum frame size. For this end, OSTR couples three major attributes: (1) performing slot-by-slot frame size increase, (2) providing a spatial reuse scheme that favors the reuse of the same slot if possible, (3) and ensuring an on-demand frame size increase only according to the node requirements in terms of throughput. To tackle different frame sizes co-existence in the network, OSTR brings a cooperative solution that consists in fixing an appointment, a date when the frame size in the network is increased. Concerning S-OSTR, it is an amendment of OSTR for wireless sensor networks. It brings the idea of a dynamic active period, since it deploys a dynamic frame size that is built slot-by-slot according to nodes arrival to the network. S-OSTR enforces the slot-by-slot frame size increase by a node activity scheduling to prolong the inactivity period in the network, and hence prolong the overall network lifetime for wireless sensor networks. Our contributions are both based on the new dynamic TDMA frame size increase that consists in increasing the frame size slot-by-slot aiming to achieve a shorter frame size, and hence improve the channel utilization, and reduce the energy consumption. The performance analysis of OSTR and S-OSTR shows that they present good potentials to support QoS requirements, to provide energy-efficiency, to ensure fair medium access, to accommodate network topology changes and finally, to enhance robustness against scalability. The impact of this new TDMA frame size increase technique on the medium access control protocol performance is highlighted through multiple simulations of OSTR and S-OSTR. Multiple comparative studies are also handled to point out the effectiveness of this new technique and the soundness of our contributions
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Zhao, Rui. "Mesh distributed coordination function for efficient wireless Mesh networks supporting QoS /." Aachen : Mainz, 2007. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016149899&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Heinemann, Andreas. "Collaboration in Opportunistic Networks." Phd thesis, Saarbrücken VDM Verlag Dr. Müller, 2007. http://tuprints.ulb.tu-darmstadt.de/834/1/heinemann07-diss.pdf.
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Motivation. With the increasing integration of wireless short-range communication technologies (Bluetooth, 802.11b WiFi) into mobile devices, novel applications for spontaneous communication, interaction and collaboration are possible. We distinguish between active and passive collaboration. The devices help users become aware of each other and stimulate face-to-face conversation (active collaboration). Also, autonomous device communication for sharing information without user interaction is possible, i.e., devices pass information to other devices in their vicinity (passive collaboration). Both, active and passive collaboration requires a user to specify what kind of information he offers and what kind of information he is interested in. Object of Research: Opportunistic Networks. Spontaneous communication of mobile devices leads to so-called opportunistic networks, a new and promising evolution in mobile ad-hoc networking. They are formed by mobile devices which communicate with each other while users are in close proximity. There are two prominent characteristics present in opportunistic networks: 1) A user provides his personal device as a network node. 2) Users are a priori unknown to each other. Objectives. Due to the fact that a user dedicates his personal device as a node to the opportunistic network and interacts with other users unknown to him, collaboration raises questions concerning two important human aspects: user privacy and incentives. The users’ privacy is at risk, since passive collaboration applications may expose personal information about a user. Furthermore, some form of incentive is needed to encourage a user to share his personal device resources with others. Both issues, user privacy and incentives, need to be taken into account in order to increase the user acceptability of opportunistic network applications. These aspects have not been addressed together with the technical tasks in prior opportunistic network research. Scientific Contribution and Evaluation. This thesis investigates opportunistic networks in their entirety, i.e., our technical design decisions are appropriate for user privacy preservation and incentive schemes. In summary, the proposed concepts comprise system components, a node architecture, a system model and a simple one-hop communication paradigm for opportunistic network applications. One focus of this work is a profile-based data dissemination mechanism. A formal model for this mechanism will be presented. On top of that, we show how to preserve the privacy of a user by avoiding static and thus linkable data and an incentive scheme that is suitable for opportunistic network applications. The evaluation of this work is twofold. We implemented two prototypes on off-the-shelf hardware to show the technical feasibility of our opportunistic network concepts. Also, the prototypes were used to carry out a number of runtime measurements. Then, we developed a novel two-step simulation method for opportunistic data dissemination. The simulation combines real world user traces with artificial user mobility models, in order to model user movements more realistically. We investigate our opportunistic data dissemination process under various settings, including different communication ranges and user behavior patterns. Our results depict, within the limits of our model and assumptions, a good performance of the data dissemination process.
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Lee, Tsung Han. "An investigation into cross-layer design for energy conservation in multi-hop and ad-hoc wireless networks." Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484974.
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Energy is a critical resource in the design of Ad-hoc and multi-hop wireless networks, since wireless devices are often powered by batteries which provide a finite amount of energy. Hence, there is a need to reduce the energy demands of the components that make up a wireless network, ~d in particular the IEEE 802.11 network interface. Ad-hoc wireless networks are currently receiving a significant amount of interest. Some of this interest may be attributed to the distributed nature ofIEEE 802.11's DCF, which allows for instant deployment and routing of packets around nodes in ad-hoc multi-hop wireless networks. In the IEEE 802.11 DCF, the wireless channel needs t.o be shared efficiently among contending nodes, and considerable research efforts are being dedicated to improving the energy consumption in these networks. In this thesis several aspects of energy consumption and the efficient utilization of limited energy resources of IEEE 802.11-based communication systems are explored. The studies provide para!11eters that are used to determine the energy consumption of the network interface for various modes of operation, modulation schemes, .transmission rates and different radio link qualities. A new metric, the energy consumed to transmit one payload bit successfully, is employed to determine meaningful power consumption. Three new approaches for conserving the energy consumed by a wireless network interface are presented. The first technique uses a novel dynamic contention window control scheme to improve the performance and energy efficiency of IEEE 802.11 DCF (Distributed Coordinated Function) wireless networks. This al,lows a transmitter to dynamically vary the contention window size in ad-hoc wireless networks to reduce the energy induced by retransmissions caused by packet collisions. The second technique uses a rate adaptation scheme that varies transmission power in order to reduce the energy consumed by retransmissions caused by transmission errors in the radio channel. The third technique involves energy conservation for routing in ad-hoc and multi-hop networks, whkh uses a cross-layer framework and operates in the PHY, MAC and Network layers. With this technique, dynamic power control is used to produce an efficient protocol design for multi-hop wireless networks in the physical layer, and a cross-layer routing algorithm is' used to provide a balance between energy-efficient transmission and a fair distribution of energy consumption across the nodes involved in a route. A cross-layer design for power-efficient wireless communication is then proposed which is based on these energy conservation techniques. This is the first time that the routing protocol, topology control, rate adaptation and dynamic contention window control for the MAC, have been considered to work in an integrated manner. This research also explicitly considers the physical link quality ofcommunication as an indication of the achievable reduction in energy consumption by ~sing the cross-layer framework design for ad-hoc and multi-hop wireless networks. The performance of the cross-layer design is evaluated through theoretical analysis as well}s extensive simulation, and the results show that the power-efficient cross-layer design is both effective and efficient.
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Sims, Yelana. ""Can't Teach an Old Hoe New Tricks"| An Analysis of Instagram Comments on Black Women in Hip-Hop." Thesis, The George Washington University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10745995.
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This study is an analysis of comments left on the Instagram posts of Black female celebrities, particularly those within Hip-Hop. This analysis put the comments in conversation with Patricia Hill-Collins’s theory of the new racism as well as previous scholarship concerning the jezebel stereotype and imagery. Previous research concerning the jezebel stereotype, including Hill-Collins’s work Black Sexual Politics, limit their analysis to traditional mass media outlets, including television, news, film, and music. This study was intended to interrogate social media’s function as a form of mass media and to analyze how the jezebel stereotype can be seen in interactions therein. A data set of 800 comments, 200 each from four subjects, was created and coded using a grounded theory approach. It was found that all four subjects of the study were associated with the jezebel stereotype, but the commenters’ responses to the individual women were markedly different along axes of motherhood, class, and status within Hip-Hop. Two significant code families were created through grouping codes together according to place and method of occurrence: Bodily Motherhood and Othering & Affiliation. Within Bodily Motherhood, it was found that pregnancy and motherhood are not only antitheses to the jezebel stereotype, but the subject must be forced back into the jezebel status through regulation of the physical body as well as pejorative acknowledgement of motherhood. The second code family of Othering and Affiliating speaks to the commenters’ acknowledgement of subjectivity for some of the women, but not all, as well as how the commenters attempted to Affiliate themselves with two of the subjects even though they were relegated to jezebel status. Through these results, this study determined that social media and the interactions within are indicative of the new racism described by Hill-Collins even though they do not function within a traditional mass media platform; the results also show that the jezebel stereotype and those who participate in its evolution work constantly and consistently at all points of a woman’s life to relegate her to such status. Through engaging with how the jezebel stereotype, an example of intersectional oppression, functions in current day society, we hope to open possibilities of scholarly thought and actionable change. By acknowledging the methods through which women are successfully fighting or owning the public’s perception of them as jezebel, we acknowledge that Black women are neither passive participants in their lives nor passive victims of a racism that attacks their body and attempts to steal their agency.
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Scofield, Dan. "Hop-by-hop transport control for multi-hop wireless networks /." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1812.pdf.
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Scofield, Daniel N. "Hop-by-Hop Transport Control for Multi-Hop Wireless Networks." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/889.
Full textAbstract:
TCP can perform poorly in multi-hop wireless networks due to problems with contention and poor feedback from end-to-end control algorithms. This thesis explores the design of a hop-by-hop transport protocol (HxH). By allowing intermediate nodes to actively participate, the protocol can respond more quickly to changing network conditions and exploit the unique characteristics of wireless networks. Results indicate that hop-by-hop transport can achieve throughput rates that are double those of TCP, depending on the speed of the wireless links.
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梁立奇. "Profile Error Analysis of Gear Hob Resharpened by Hob Resharpener." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/82399229700400368389.
Full textAbstract:
碩士國立中正大學
機械系
89
Hob is widely used in gear manufacturing. The precision and cutting edge sharpness of hob are maintained by correct and accurate re-sharpening. The hob sharpener and the cutting edge flute of hob are mathematically modeled in the thesis. The machine settings of hob sharpener and the profile of the grinding wheel can be determined by the proposed mathematical model. Assume the geometry of cutting edge flute of hob are known, we use the equations of flute to derive the machine settings of hob sharpener and the geometry of the grinding wheel. Singularity of the ground flute was studied to avoid undesired undercutting. Sensitivity analysis of machine settings is also studied to identify the accuracy requirement of each machine setting. Based on the results of this thesis, a hob sharpener was designed by Luren co. and three hob sharpening machines has been manufactured in MIRL/ITRI. The accuracy of the machine based on the proposed mathematical model was acceptable.
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Huang, Sheng-Kai, and 黃聖凱. "STUDY ON THE FLANK CORRECTION OF HOB FLUTES BASED ON THE HOB SHARPENING MACHINE." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/vwyv66.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
98
Based on the theory of gearing and differential geometry, we develop a mathematical model for the cutting face of hob based on the universal-type hob sharpening machine. Apply the proposed mathematical model, the axial profile of the grinding wheel can be derived, and it also can simulate the motion for the grinding wheel sharpening the cutting face of hob. This manufacturing process is the profile grinding method. It is well-known that the axial profiles of wheels for grinding different helical angles of hob flutes are not the same in this process. Therefore, the main purpose of the thesis is to investigate whether the same wheel profile can be use to sharpen the cutting faces with a range of helical angles to satisfy the demand of hob precision or not. Another purpose is to establish the mathematical model for the cutting face of hobs based on the six-axis CNC hob sharpening machine and its correction method for reducing the manufacturing errors. Based on the structure of CNC hob sharpening machine of Luren Precision Co., Ltd, the coordinate systems of the six-axis CNC hob sharpening machine are established at first. The six-axis movement for resharpening the cutting face of hob can be obtained by way of the conversion from a universal machine to a six-axis machine. And then, the mathematical model for the cutting face of hob is derived based on the six-axis CNC hob sharpening machine. Based on the mathematical model of the hob cutting face, the sensitivity matrix of six-axis machine settings is established. According to this sensitivity matrix and the given flank errors of hob cutting face, the corrections for six-axis machine settings can be calculated by the linear regression. The corrections of machine settings can be applied to regrind the work-piece for reducing the manufacturing errors. In this thesis, all results are obtained by the computer simulation.
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Lin, Guan-Hau, and 林冠豪. "The study of gear cutter measurement using involute hob." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/08984045480595555225.
Full textAbstract:
碩士國立中正大學
機械工程學系暨研究所
103
Gear measurement has always being one of important skills for improving gear accuracy. The coordinate measuring machine is the most commonly used and also is the best way for inspecting gear accuracy. Generally, Klingeknberg’s measuring machine of series P and Leitz’s pmmc are the most common used machine for measuring gear cutter. However, gear cutter measurement belongs to a specific measuration method, so it needed to purchase additional mold and positioned with an object. This paper used involute hob which is the most commonly used machining tool as the object of study. This paper aims at inspecting measurement error of hob and constructing its path plan. The author references gear cutter standard and observes Klingelnberg’s measuring machine to measure the path of hob. Through writing the code such as path plan measurement of profile and lead, the author put the measuring probe moving along the direction of helix on the hob blade side till the probe leaveing to the cutting edge. Thus, the author can get the actual measurement data through path measurement. In order to examine the validity of measuring path and the error accuracy standards of gear hob, the author set up mathematical of gear cutting edge. In order to set up the measurement path of gear hob, the author proceeds error comparison between actual measurement data and mathematical method, evaluating error precision, and outputting through report model for reference. Keywords:Iinvolute Hob,Coordinate Measuring Machine,Gear
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Ya-Yen, Chang, and 張雅雁. "Haydn Sonata in C-Major (Hob. XVI: 50)Analysis and Interpretation." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/29566989700576031936.
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Lee, Ying-hui, and 李盈慧. "The Interpretation of Haydn piano sonata in C major Hob. XVI：50." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/99110277628520440796.
Full textAbstract:
碩士東吳大學
音樂學系
98
Haydn’s piano sonata play an important role in the development of keyboard works, is also one of the most representative form in his works. In 1775, Haydn wrote keyboard sonata for the first time and finished the last three sonata in 1796. From his music texture and harmony with thin to heavy, we can see the obvious relationship between the development of piano to Haydn’s composition. In 1791, Haydn’s London journeys have a deep influence to his composition, particularly in the second journey he contacts the Piano and fascinated by it, the piano sonata Hob.XVI：50 is the wok of this period. Haydn used the variation’s technique at this sonata: at the first movement he uses the single subject with different tunes and figures; at the second movement the single subject enriched by gorgeous trills; at the third movement the subject vary from the motive. In this thesis I discuss the time of the classical period, the musician’s composition environment, and the development of the sonata form, Finally I attempt to find out the most appropriate interpretation performance for this work.
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"Multi-Axes CNC Turn-Mill-Hob Machining Center and Its applications in biomedical engineering." 2012. http://library.cuhk.edu.hk/record=b5549559.
Full textAbstract:
随着对减小零件尺寸和增加其复杂性和准确性的日益增加的需求，传统机床已经不能有效的加工微型元件了。一个典型的例子是牙科种植体（生物医学设备）和和用于机械手表机芯的齿轮轴。由于这些零件的复杂几何形状和严格的公差要求，市面上只有很少一部分机床有能力加工它们。我们设计的多轴数控“车削-铣削-滚齿加工中心对加工精密复杂工程零件是非常有效的。此机器为8轴机床，除了执行加工的8轴外，还有一个自动上料机构和一个自动收集机构,可以实现自动上料，加工，收集等整条生产线的运作。运用电子齿轮技术以保证精密滚齿功能；运用先进控制技术（深层交叉耦合技术）以保证多轴的同步控制，实现加工的高效，高精度，并且容易使用。另外，为了保障机床精度，我们研发了多轴数控机床几何误差的软件补偿技术。根据实验测试，此加工中心的车削精度为0.003毫米，铣削精度为0.005毫米，滚齿误差小于0.0075毫米。众多的生物医学零件是轴不对称零件。虽然这些零件可以用传统的数控加工方法进行加工，但是效率极低且成本高。而基于我们加工中心的新型铣削方法可以有效、高精度的加工这些零件。这种方法是运用极坐标的插值原理，比利用笛卡尔直角坐标系加工的原理更加优越，特别是当需要一个线性轴和旋转轴插值生成曲线时。为了方便使用这个极坐标插值模块，我们开发了一系列特殊的极坐标加工G代码。整个开发的程序模块最终融入我们多轴数控“车削-铣削-滚齿“加工中心。
另外一个重要的发现是运用滚齿方法加工轴对称和轴不对称零件。从滚齿方法被发明出来的这100年中，其一直是最有效的加工齿轮的方式。它的高效是由于多个刀齿同时切削工件。现在，滚齿是一种标准的加工方式并且每天运用这种方法加工几百万个零件。但是，没有人用这种方法加工轴不对称零件。经过仔细研究滚齿原来，可以得出以下观点：一）齿轮的齿形是与滚刀的齿形一样的；二）齿轮轮廓是由工件和滚刀的相对位置确定的。把滚刀设计和控制工件和滚刀的相对位置结合起来，我们发现运用滚齿的方法是可以加工各种轴对称和非对称部分，例如：星形零件和多边形零件。特别是，该方法可以有效的加工不断变化的轴不对称零件。最后，我们比较其的加工效率和传统的铣削加工，结果验证运用这种方法的加工时间远小于采用铣削方法。
我们设计的加工中心和新型加工方法在生物医学工程有很多的应有。牙科种植体就是一个典型的例子。具权威机构统计，约有10%的人会在一生中选用种植牙技术对牙齿进行修复。但是不幸的是，没有人研究个性化种植体。目前，市面上的种植体并不能精确的适合病人牙根情况，完成特殊口腔环境的牙齿修复。所以，对个性化种植体的研究是迫切并具有市场效益的。关于个性化种植体研制的一个难点是其的制造。个性化种植体之所以难加工是由于它的复杂形状及所用材料（钛）。但是，我们设计的多轴数控“车削-铣削-滚齿“加工中心和基于此机床的新型加工方法可以有效、高精度的加工此种植体。
With the ever increasing demand for reduced size and increased complexity and accuracy, traditional machine tools have become ineffective for machining miniature components. A typical example is the dental implant and the other is the pinion used mechanical watch movement. With complex geometry and tight tolerance, few machine tools are capable of making these parts. We designed and built a CNC Turn-Mill-Hob Machining Center that is capable of machining various complex miniature parts. The machining center has 8 axes, an automatic bar feeder, an automatic part collection tray, and a custom-made CNC controller. In particularly, the CNC controller gives not only higher accuracy but also ease of use. In addition, to improve the accuracy, a software based volumetric error compensation system is implemented. Based on the experiment testing, the machining error is ± 4 μm for turning, ± 7 μm for milling, and the maximum profile error is less than ± 7.5 μm for gear hobbing.
Many biomedical parts are axial asymmetric parts. While these parts can be machined using conventional CNC machining methods, the efficiency is low and the cost is high. We proposed a new CNC machining method based on polar coordinate interpolation, which is better than the Cartesian coordinate interpolation when rotational axes are involved. To facilitate the use the polar coordinate interpolation module, a special G code is developed. This module is integrated into our CNC Turn-Mill-Hob Machining Center.
Another important development is the use of hobbing method for machining axial symmetric / asymmetric parts. Invented some 100 years ago, hobbing is the most efficient method for machining gears. Its efficiency lies on multiple teeth simultaneous cutting. Presently, gear hobbing is a standard manufacturing process making millions of gears every day. Though, no one has used it for machining axial asymmetrical parts. After carefully examining the gear hobbing, it is found that the profile of the gear tooth is determined by a combination of the profile of the hob tooth and the relative position and motion between the hob and the workpiece. Therefore, by tuning the hob tooth profile and controlling the relative position and motion between the hob and the workpiece, it is possible to machine various axial symmetrical and asymmetrical parts, such as a start, a hexagon and etc. This method is efficient to machine continuously changed axial asymmetrical parts. This is validated by means of experiments. The experiments also indicate that the new method is much more efficient than the conventional milling method.
Our machining center and new machining methods have many practical applications. Dental implant is a typical example. It is estimated that 10% of the people will need dental implants in their life time. Presently, there are a number of brands in the market, though these implants may not fit for patients who have special oral conditions. In this case, custom-made implants are necessary. The key problem of the custom-made dental implant is manufacturing. Our multi-axes CNC Turn-Mill-Hob Machining Center and the new machining method can effectively machine the custom-made dental implants. Moreover, the efficient is good.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Chen, Xianshuai.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2012.
Includes bibliographical references (leaves 116-127).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract also in Chinese.
Abstract --- p.I
摘要 --- p.III
Acknowledgement --- p.V
Table of Contents --- p.VI
List of Tables --- p.VIII
List of Figures --- p.IX
Acronym --- p.XIII
Chapter Chapter 1: --- Introduction --- p.1
Chapter 1.1 --- Background --- p.1
Chapter 1.2 --- Overall Literature Review --- p.3
Chapter 1.3 --- Objectives --- p.17
Chapter Chapter 2: --- The Multi-Axes CNC Turn-Mill-Hob Machining Center --- p.18
Chapter 2.1 --- A Brief Review --- p.18
Chapter 2.2 --- The Design and Prototype --- p.20
Chapter 2.3 --- The CNC Controller --- p.26
Chapter 2.4 --- The Calibration --- p.32
Chapter 2.5 --- Cutting Tests --- p.35
Chapter 2.6 --- Summary --- p.43
Chapter Chapter 3: --- Hobbing Gears and Axial Asymmetric Parts --- p.45
Chapter 3.1 --- A Brief Review --- p.45
Chapter 3.2 --- The Theory --- p.47
Chapter 3.3 --- Computer Simulation --- p.54
Chapter 3.4 --- Cutting Tests --- p.68
Chapter 3.5 --- Summary --- p.78
Chapter Chapter 4: --- Millining Axial Asymmetric Parts --- p.80
Chapter 4.1 --- A Brief Review --- p.80
Chapter 4.2 --- The Theory --- p.81
Chapter 4.3 --- Cutting Tests --- p.89
Chapter 4.4 --- Summary --- p.94
Chapter Chapter 5: --- Machining Dental Implants --- p.95
Chapter 5.1 --- A Brief Review --- p.95
Chapter 5.2 --- The Database of Custom-made Dental Implant --- p.98
Chapter 5.3 --- The Design and FEA --- p.103
Chapter 5.4 --- Cutting Tests --- p.108
Chapter 5.5 --- Summary --- p.110
Chapter Chapter 6: --- Concluding Remarks and Future Work --- p.111
Chapter 6.1 --- Concluding Remarks --- p.111
Chapter 6.2 --- Future Work --- p.113
Bibliography --- p.116
Publication Record --- p.127
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Tsai, Feng-Ying, and 蔡鋒穎. "Stress Analysis of Shaving Cutter with Relief Portion and Design of the Generating Hob Cutter." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/7686yb.
Full textAbstract:
碩士國立虎尾科技大學
動力機械工程研究所
94
The main objectives in this thesis are studying the design of protuberance hob cutter and the generated shaving cutter. The protuberance hob cutter proposed is used to manufacture the relief portion of the shaving cutter. In the design of hob cutter, the choose of parameters is the most difficult process in the design. Here, the principle of coordinate transformation, the theory of differential geometry, and the theory of gearing are used to determine the complete profile of the shaving cutter. Two different methods of optimun, i.e., global search method and optimum subroutine in Matlab software, are applied to determine the optimum parameters of the hob cutter satisfying the objective function, geometry constraint of throat width, and the constraint of serration depth. The CATIA software is then used to construct the solid modeling of the shaving cutter. By applying the mathematical model of the shaving cutter derived, the solid modeling is then transformed into the FEM model for the 3-D stress analysis with different load and element type. The contact surface topology method is also used to determine the shaved contact pattern. The stress analysis is then proceeded. This information for the stress analysis can help us to modify the design of shaving cutter and offer better design information for correcting the concave phenomenon in the tooth profile.
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曾冠智. "Establishment of mathematical Model of Hob and the Analysis of the cutted tooth profile errors." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/47447997370241367217.
Full textAbstract:
碩士國立中正大學
機械系
91
Hobs have been widely used for manufacturing a variety of gears. This technique is also one of the most efficient and economic procedures for gear industry. Besides the parameters of the hobbing machine, the manufacturing accuracy of the hob greatly effects the precision of the tool in the process of hobbing. This study aims to set up mathematical model to simulate the hobbing surface of the tool with the relieved and resharped cutting edge. And vanes the machine settings to discuss the influence on the tool, also finds on the settings of hobbing machine after the sharpness of hob.
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Chang, Shi-Jie, and 張仕杰. "An Analysis and Interpretation of FranzJoseph Haydn《Cello Concerto No.1 in C Major, Hob. Vll :1》." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/v6pz67.
Full textAbstract:
碩士國立臺北教育大學
音樂學系碩士班
106
Haydn (Franz Joseph Haydn,1732-1809) was born in the end of 18th century. This is a moderate generation, the form is not as large and complex as Baroque music, nor the personal dreams, pain, ideals and vision in romantic nineteenth century. People in this era is focus on the melody, main tonality of the music, because they thought that the purpose of music is to entertain each other together. Haydn is a representative composer of this era, so as his own bold and vigilant personality. He loves to have adventure but not as rebel as Mozart(Wolfgang Amadeus Mozart,1756－1791). The way Haydn composed is also keeping to the working routine, stable but not rush. This deeply earned him respect and love from the people, and the music taste of the people in those days. You can feel the light and brisk music that Haydn wrote in his symphonies, chamber music, Mass and the two great oratorios. And no matter how long the earlier works were written, the way and the style never changes. He had written more than 120 symphonies over his life, especially when he hold a post in Paul Anton Esterhazy Orchestra for thirty years. He always experiment every composing possibilities in the music. Eventually, he had composed a series of great symphonies that people loved and established the form and the structure of the symphony. This earned him the title of “Father of the Symphony”
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Lin, Geng-Ching, and 林庚慶. "Stress Analysis of the ZK-Type Worm Gear Set Generated by Oversize Hob Cutters with Asymmetric Tooth Profiles." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/58417287927865975840.
Full textAbstract:
碩士明新科技大學
精密機電工程研究所
97
The worm gear set is one of the cross axes transmission mechanisms. Worm gear set can conquer the tooth undercutting problem, which occurs due to the small number of teeth of conventional gear sets with some special modules. Therefore, worm gear set can provide high gear ratios that spur and helical gear set could not offer. Besides, the worm gear set has a larger contact ratio which enables its loading capability. In this research, mathematical model of a worm gear set is developed based on the theory of gearing and the technique of computer aided design. The worm is generated by an asymmetrical grinding wheel. The mathematical model of the asymmetric ZK-type worm surfaces can be obtained by simulation of the generation mechanism of the grinding wheel and worm. With the design of an oversize worm type hob cutter, the mathematical model of the worm gear surfaces can be obtained according to the oversize hob cutter and worm gear hobbing mechanism. The equation of meshing between the oversize hob cutter and the produced worm gear surfaces is also studied. Based on the developed mathematical models of the worm and worm gear, the finite element stress analysis of the worm gear set is performed. Analysis results of the asymmetric ZK-type worm gear set are compared with those of conventional symmetric ZK-type worm gear set. The analysis results are most helpful to the designer and manufacturer of the worm gear set. Key words：Worm and worm gear set, ZK-type, Oversize hob cutter, Asymmetric tooth profile, Stress analysis.
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LIN, JIUN-JI, and 林俊吉. "The Effect of Gear Hob Setting and Processing Parameters on The Gear Dry Cutting Accuracy and Tool Life." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/pb7p79.
Full textAbstract:
碩士國立虎尾科技大學
動力機械工程系機械與機電工程碩士班
106
The dry hobbing process is the most representative method in gear manufacture, which has grown rapidly recently. However, the studies on the reduced diameter of the tool after re-sharpening, with a changed meshing lead angle, and the accuracy of the generated gear were not found in the research of dry hobbing. Therefore, experiments and analysis will be performed on the input lead angle of the hob cutter in the machine setting, due to the reduced diameter after re-sharpening in this study. The experimental study can improve the precision of hobbing tool design and machining. Moreover, introducing the concept of correcting lead angle to the gear manufacturing industry is helpful to the industry. It is also found that the modification of tool lead angle input in the machine can improve gear cutting accuracy and tool life through the experimental study in this study. The design and analysis of experiments was applied to find out the optimum machining parameters for hobbing process. Compared with the previous methods that only rely on operators' experience, the optimum method saves blind test time and improves hobbing technology and efficiency.
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Chen, Pei-Chun, and 陳姵君. "Performance Issues and Analytical Interpretation on Variations Hob. XVII:6 by Haydn and Variations Op. 34 by Beethoven." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/80325740506130854801.
Full textAbstract:
碩士中國文化大學
音樂學系西洋音樂組
101
Variation as musical form was applied early and also common in musical works. The form of variation was established in the 16th century, later mainly in variation of ground bass in the Baroque period (for example, in chaconne and passacaglia) and in theme and variations of the Classical period. Variations of the Romantic and later period were freer in compositional skills. There are representative works of variation in each period, to which they are unique in style. Variation with its abundance in categories and forms plays an important role in the western music history. Variation in F minor Hob.XVII:6 by Haydn and Variation in F major, op.34 by Beethoven are the main issues of this thesis. Firstly, the historical evolution and the categories of variation will be introduced, followed by discussion on the two works, both of which belong to the main variation form in the Classical period--theme and variation, focusing on the different variational techniques and structural usages. The discourse will then start with introduction to the composers’ lives and continue with formal analyses on the works and suggestions for performance interpretation. This thesis includes five chapters. Chapter One is the preface, Chapter Two is the introduction of variation, Chapter Three is the study of Variation in F minor, Hob.XVII:6 by Haydn, Chapter Four is the study of Variation in F major, op.34 by Beethoven, and the final chapter is the conclusion.
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Larouche, Sarah-Ann. "Vers une typologie du premier mouvement de sonate chez Joseph Haydn (1732-1809) : une analyse des 52 premiers mouvements Hob. XVI." Thesis, 2020. http://hdl.handle.net/1866/25207.
Full textAbstract:
Bien qu’une vaste littérature musicologique porte sur Joseph Haydn (1732-1809), aucune ne comprend une étude exhaustive de l’ensemble de ses sonates pour clavier, incluant les premières oeuvres composées dans la décennie 1750.
La présente recherche se propose de combler en partie cette lacune par le biais d’une analyse des 52 premiers mouvements Hoboken (Hob.) XVI. Basée sur des outils empruntés principalement à William E. Caplin, Brian Alegant et Don McLean, cette étude constitue un premier pas vers une typologie du premier mouvement de sonate chez Haydn, permettant par le fait même de refléter l’évolution de la forme sonate, en mutation tout au long de la vie créative du compositeur.
Dans un premier temps, une série d’analyse capliniennes permet d’effectuer un survol des différentes formes qui composent le corpus à l’étude afin d’en dégager certains procédés spécifiques, nommément l’exploitation de techniques formelles à des fins de développement thématique, ainsi que l’emploi marqué d’ambiguïtés formelles et fonctionnelles.
Dans un second temps, une analyse de la disposition du matériau suggère une conception du premier mouvement en forme sonate basée sur le développement thématique d’un nombre réduit d’idées musicales, dont la répétition est compensée par plusieurs procédés dont les principaux sont la variation structurelle dans la section de réexposition et l’emploi de différentes fonctions formelles à chaque itération.
Prises dans leur ensemble, ces analyses démontrent que l’ensemble des premiers mouvements de sonate pour clavier Hob. XVI sont liées par une certaine imprévisibilité créée spécifiquement au moyen de la réutilisation thématique et des fonctions formelles.Although there is a vast musicological literature on Joseph Haydn (1732-1809), none includes an exhaustive study of all his keyboard sonatas, including the first works composed in the 1750s. The present research aims to fill this gap through an analysis of the 52 first movements of the keyboard sonatas Hoboken (Hob.) XVI. This study constitutes a first step towards a typology of Haydn’s sonata first movement, thereby making it possible to look at the evolution of the sonata form, under development throughout the composer's creative life. Initially, a first series of Caplinian analysis allows an overview of the different forms that make up the corpus under study in order to identify certain specific procedures, namely the use of formal techniques for thematic development purposes as well as the marked use of formal and functional ambiguities. Secondly, an analysis of the arrangement of the material suggests the conception of the sonata form’s first movement to be based on the thematic development of a reduced number of ideas, the repetition of which is compensated for by several processes, the main ones of which are structural variation in the recapitulation section as well as the use of various formal functions for each iteration. Taken as a whole, these analysis show that the 52 first movements Hob. XVI are linked by the expression of a certain unpredictability caused specifically by thematic restatement and the use of various formal functions.