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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
281

Consumable Process Development for Chemical Mechanical Planarization of Bit Patterned Media for Magnetic Storage Fabrication

Bonivel, Joseph T., Jr. 25 October 2010 (has links)
As the superparamagnetic limit is reached, the magnetic storage industry looks to circumvent the barrier by implementing patterned media (PM) as a viable means to store and access data. Chemical mechanical polishing (CMP) is a semiconductor fabrication technique used to planarize surfaces and is investigated as a method to ensure that the PM is polished to surface roughness parameters that allow the magnetic read/write head to move seamlessly across the PM. Results from this research have implications in feasibility studies of utilizing CMP as the main planarization technique for PM fabrication. Benchmark data on the output parameters of the CMP process, for bit patterned media (BPM), based on the machine process parameters, pad properties, and slurry characteristics are optimized. The research was conducted in a systematic manner in which the optimized parameters for each phase are utilized in future phases. The optimum results from each of the phases provide an overall optimum characterization for BPM CMP. Results on the CMP machine input parameters indicate that for optimal surface roughness and material removal, low polish pressures and high velocities should be used on the BPM. Pad characteristics were monitored by non destructive technique and results indicate much faster deterioration of all pad characteristics versus polish time of BPM when compared to IC CMP. The optimum pad for PM polishing was the IC 1400 dual layer Suba V pad with a shore hardness of 57, and a k-groove pattern. The final phase of polishing evaluated the slurry polishing properties and novel nanodiamond (ND) slurry was created and benchmarked on BPM. The resulting CMP output parameters were monitored and neither the ND slurry nor the thermally responsive polymer slurry performed better than the commercially available Cabot iCue slurry for MRR or surface roughness. Research results indicate CMP is a feasible planarization technique for PM fabrication, but successful implementation of CMP for planarizing PM must address the high initial start up cost, increase in the number of replacement pads, and increase in polishing time to reach the required surface roughness for magnetic storage devices.
282

Automatisierte Konfiguration des Antriebsstrangs bei der Projektierung dieselelektrischer Schienenfahrzeuge

Siegel, Ronny 25 August 2015 (has links) (PDF)
Die vorliegende Arbeit verfolgt als Ziel Algorithmen zur anwendungsbezogenen Komponen-tenauswahl und Antriebskonfiguration dieselelektrischer Schienenfahrzeuge zu entwickeln und umzusetzen. Aus modellierten Einzelkomponenten werden automatisiert virtuelle Antriebsstränge generiert, anhand einer vorgebbaren Transportaufgabe simulationstechnisch bewertet und miteinander verglichen. Aus den Berechnungsergebnissen kann die für die vorgegebenen Randbedingungen am besten geeignete Antriebskonfiguration ermittelt werden. Zum Verifizieren der Ergebnisse wurden messtechnische Untersuchungen durch-geführt.
283

Towards a scalable design of video content distribution over the internet

Ryu, Mungyung 21 September 2015 (has links)
We are witnessing a proliferation of video in the Internet; YouTube is the most bandwidth intensive service of today’s Internet. It accounts for 20 - 35% of the Internet traffic with 35 hours of videos uploaded every minute and more than 700 billion playbacks in 2010. Netflix, a web service that streams premium contents such as TV series, shows, and movies, consumes 30% of the network bandwidth in North America at peak time. Recently, leveraging the content distribution networks (CDNs), a new paradigm for video streaming on the Internet has emerged, namely, Adaptive HTTP Streaming (AHS). AHS has become the industry standard for video streaming over the Internet adopted by broadcast networks as well as VoD services such as YouTube, Netflix, Hulu, etc. In the 90’s and early 2000’s, Internet-based video streaming for high-bitrate video was challenging due to hardware limitations. In that era, to cover the hardware limitations, every software component of a video server needed to be carefully optimized to support the real-time guarantees for jitter-free video delivery. However, most of the software solutions have become less important with the remarkable hardware improvements over the past two decades. There is 100× speedup in CPU speeds; RAM capacity has increased by 1,000×; hard disk drive (HDD) capacity has grown by 10,000×. Today, CPU is no longer a bottleneck for video streaming. On the other hand, storage bandwidth and network bandwidth are still serious bottlenecks for large scale on-demand video streaming. In this dissertation, we aim at a scalable video content distribution system that addresses both storage bottleneck and network bottleneck. The first part of the dissertation pertains to the storage system on the server side: A multi-tiered storage system that exploits a flash memory solid-state drive (SSD) can meet the bandwidth needs in a much more cost- effective way than a traditional two-tier storage system. We first identify the challenges in architecting such a system given the performance quirks of flash-based SSDs, and the lim- itations of state-of-the-art multi-tiered storage systems for video streaming. Armed with the knowledge of these challenges, we show how to construct such a storage system and implement a real web server with multi-tiered storage, evaluate the system with AHS work- loads, and demonstrate significant performance gains while reducing the TCO. The second part of the dissertation pertains to the network system on the client side: Integrating peer- to-peer (P2P) technology with the client-server paradigm results in a much more scalable video content distribution system. AHS is a paradigm for client-driven video streaming; its philosophy matches well with that of P2P video streaming. An adaptation mechanism is the most important component of AHS that determines overall video streaming quality and user experience. We show a throughput-smoothing-based adaptation mechanism that is designed for a client-server architecture does not work well for a P2P architecture. We pro- vide a buffer-based adaptation mechanism, evaluate our solution with OMNeT++/INET simulator, and demonstrate significant performance gains.
284

Switched reluctance machine electromagnetic design and optimization

Dang, Jie 21 September 2015 (has links)
The objective of this dissertation is to study the switched reluctance machine (SRM) electromagnetic design and optimization. The research of electric machines is mostly driven by the motivation for higher efficiency and lower cost. The demands for high-performance electric machines also come from the development of emerging industries, such as electric vehicles (EV), hybrid electric vehicles (HEV), renewable energy conversion, energy storage and precision manufacturing. The additional requirements for those applications include volume, weight, speed, torque, reliability, fault tolerance capability, etc. The focus of the research effort is on the high speed and high torque applications, where the SRM stands out compared to other types of machines. The conventional design method significantly depends on the designer’s experience, which uses equivalent magnetic circuit models, and therefore the SRM design is not well developed. A novel SRM electromagnetic design and optimization method is developed, which uses the current-fed FEA simulation as the SRM performance estimation tool. This method serves as the main innovation of this research work. First, the proposed method is applicable to any SRM topologies and dimension, and no detailed modeling of a specific SRM configuration is required in advance. Therefore, an automated SRM design and optimization approach is developed. Secondly, great accuracy of the SRM electromagnetic analysis, e.g. flux density, torque, and current calculation, is achieved by using FEA simulation instead of simplified magnetic circuit approximations. This contribution is particularly significant when considering the poor accuracy of conventional SRM analytical analysis methods, where several assumptions and approximations are used. Lastly, the proposed design method takes the typical SRM control strategy into account, where the excitation current profile is characterized as a trapezoid. This method adapts the flux linkage of the first FEA simulation result to specify the excitation current profile for the second FEA simulation, so the calculated SRM performance in FEA simulation agrees with the measurement on a practical machine. The proposed SRM design and optimization method is used for a 12/8 SRM rotor design and for a complete 4/2 SRM design. These design examples validate the applicability of the proposed method to different SRM configurations and dimensions. Detailed design steps are presented for both design cases, and the selection of the parametric design variables are also discussed. The optimization results are demonstrated using multi-dimension diagrams, where the optimal design with the highest torque can be easily identified. The FEA simulation results are compared to the experimental results of a fabricated SRM prototype, and good agreement is found. In addition, a new rotor configuration with a flux bridge is proposed for an ultra high speed SRM design. The primary motivation of this rotor topology is to reduce the windgae losses and the acoustic noise at a high speed of 50,000 rpm. However, care must be taken for the flux bridge design, and the impact of different flux bridge thicknesses to the SRM performance is studied. Meanwhile, the manufacturing difficulties and the mechanical stresses should also be considered when fabricating the flux-bridge rotor. As a result, two SRM prototypes are built, and the two rotors are one without a flux bridge and one with a flux bridge. The prototypes are tested at different speeds (10,000 rpm, 20,000 rpm and 50,000 rpm) respectively, and the experimental results show good agreement with the FEA simulation results.
285

Investigating the Relationship among Drive for Thinness, Life Event Stressors, and Harm Avoidance in Predicting Eating Disorder Symptomatology: A Prospective Analysis

Woods, Amanda Michelle 12 June 2006 (has links)
The current study sought to prospectively explore the potential main effects and interactive relations among drive for thinness, life event stress, and harm avoidance in the prediction of disordered eating in an ethnically diverse sample of women (N = 58). During the initial and follow-up assessments, standardized questionnaires were utilized to assess drive for thinness, life event stress, and a harm avoidant temperament. Additionally, semi-structured diagnostic interviews were administered to assess disordered eating. Results revealed a significant interaction between drive for thinness and life event stress in the prediction of eating pathology. Neither the two-way life event stress x harm avoidance interaction nor the three-way drive for thinness x life event stress x harm avoidance interaction were significant predictors of eating pathology. These findings suggest that the previously suggested relation between drive for thinness and pathological eating is dependent upon the degree of life event stress experienced.
286

A multidimensional perspective on the role of behavior in evolution

Munoz, Martha Monica 23 October 2014 (has links)
Behavior determines how organisms interact with their environment, and has long been posited as a pacemaker for evolution. The classical view is that novel behaviors expose organisms to new selective pressures, in turn "driving" evolution. Behavior can also restrain evolutionary change. Some behaviors, such as thermoregulation, help organisms maintain a constant selective environment, thus "inhibiting" evolution. This thesis seeks to understand the role of behavior in influencing the evolutionary process. In the first part, I test the hypothesis that the same behavior can simultaneously impede and impel evolution in different traits. I focus on the lizard, Anolis cybotes, from the Caribbean island of Hispaniola. Through a replicated field experiment I show that behavioral flexibility allows these lizards to maintain a constant body temperature in markedly different thermal habitats. I determine that this similarity in body temperatures is associated with physiological stasis, as the preferred temperature and heat tolerance are nearly identical among populations. I demonstrate that the behavioral change allowing lizards to maintain a constant body temperature involves a perch switch. Finally, I demonstrate that this shift in structural habitat use from trees at low elevation to rocks at high elevation in turn impels morphological evolution in traits associated with rock use, and that these traits are likely genetically based. Thus, a perch switch to rocks at high elevation is simultaneously impeding physiological evolution, whilst impelling morphological evolution. In the second part of my study, I asked whether rates of evolution differ among physiological traits, and how thermoregulation influences these rates. I found that cold tolerance evolves significantly faster than heat tolerance in the cybotoid anoles, a clade of anoles that contains A. cybotes and its relatives. I demonstrate that thermal variation is considerably greater during the day than at night and, at high elevation, nighttime temperatures are so cold that they would incapacitate most lizards. In the absence of thermal refuges and behavioral buffering, lizards at high elevation have no choice but to adapt their physiology. Thus, the ability to thermoregulate during, but not at night, likely influences differences in rates of evolution between heat and cold tolerance.
287

Δομή και λειτουργία ηλεκτρικού κινητήριου συστήματος χαρτοποιητικής μηχανής με καταγραφή και αποθήκευση κρίσιμων λειτουργικών μεγεθών

Τριάντης, Περικλής 03 July 2009 (has links)
Στην παρούσα διπλωματική εργασία γίνεται περιγραφή του ηλεκτρικού κινητήριου συστήματος της Πατραϊκής Χαρτοποιίας αποτελούμενο από κινητήρες συνεχούς ρεύματος για την παραγωγή χαρτιού "tissue". Επίσης παρουσιάζεται η σχεδίαση συστήματος καταγραφής βλαβών σε περιστρεφόμενες μηχανές μέσω της ανάλυσης φάσματος κραδασμών στο πλαίσιο της εφαρμοσμένης μεθόδου παρακολούθησης κραδασμών της προβλεπτικής συντήρησης. / In the current diploma thesis takes place a description of the electric motor drive system of Patraikh Xartopoiia which consist of direct current machines for the production of tissue type paper. Furthermore the design of damage recording system in rotating motors through vibration analysis is presented in the line of vibration monitoring applied method.
288

Nietzsche et le problème de Socrate

Diotte, Etienne 10 1900 (has links)
Ce mémoire a pour but d’élucider l’analyse et l’évaluation nietzschéennes du sens et de la portée de la figure de Socrate dans les cultures antique et moderne. Pour ce faire, nous nous pencherons d’abord sur la question de l’identité de Socrate, ce qui permettra d’introduire une distinction centrale à l’analyse de Nietzsche, soit celle entre la doctrine et la personnalité du célèbre Athénien. En effet, Nietzsche isole la personnalité de Socrate, qu’il circonscrit à partir des notions d’instinct, de pulsion et d’affect, de sa doctrine, qu’il appelle le socratisme et qu’il définit à partir de l’équation socratique raison = vertu = bonheur. Ensuite, nous développerons les trois éléments sur lesquels il s’appuie pour expliquer que Socrate ait pu séduire les Grecs, soit le fait qu’il fut un grand érotique, qu’il introduisit une nouvelle forme de joute à Athènes et qu’il apparut comme étant un médecin pour ses contemporains. Cette question des raisons permettant d’expliquer que Socrate ait pu séduire les Grecs est déterminante pour Nietzsche, puisque c’est de là qu’il est amené à se demander qui est ce Socrate et quel a été son véritable impact sur la culture, soit les deux questions qui sont au cœur de ce qu’il appelle « le problème de Socrate ». Enfin, nous nous pencherons sur le diagnostic que le philosophe allemand pose sur le célèbre Athénien ainsi que sur son évaluation de l’impact du socratisme sur les cultures antique et moderne, après quoi nous présenterons l’inversion des valeurs que Nietzsche tente d’opérer dans sa propre culture. Nous verrons alors qu’il cherche entre autres par cette inversion des valeurs à nous libérer du socratisme, car il est d’avis que cette doctrine dévalorise toute forme d’agir puisant ses motifs dans ce qui relève de l’inconscient et survalorise une morale luttant contre les pulsions dominantes en nous. / The purpose of this thesis is to investigate Nietzsche’s analysis and assessment of the meaning and the impact of Socrates’ character on the classical and modern culture. To that effect, I will emphasize the question of Socrates’ identity, in order to introduce the crucial issue in Nietzsche’s analysis, namely the distinction between Socrates’ doctrine and his character. Nietzsche isolated Socrates’ character – which he defined through the categories of instinct, drive, and affect – from his doctrine, which he labelled socratism and defined through the Socratic equation reason = virtue = happiness. This thesis explores the three core elements Nietzsche used to explain how Socrates was able to seduce the Greeks: not only was Socrates a very erotic figure, he also introduced a new form of debate to Athens, and was considered an eminent physician by his contemporaries. Socrates’ appeal to the Greek is of fundamental importance to Nietzsche, since it prompted him to question Socrates’ inherent character, and his true impact on Athenian culture. It thus forms the crux of what he called “the problem of Socrates.” Nietzsche’s understanding of socratism as well as its impact on classical and modern culture allows him to revaluate all values within his own culture. To that effect, I reveal Nietzsche’s critiques of socratism – in particular, his belief that society needed to be liberated from socratism, since it denies all agency to individuals. Given that it was strongly motivated by the unconscious, socratism, according to Nietzsche, overemphasizes a certain morality in the struggle against our dominant impulses.
289

Streetcar strip to neighbourhood centre: the characteristics of good neighbourhood shopping streets examined in the context of Commercial Drive and West 41st Avenue

Scott, Lisa M. 11 1900 (has links)
Good neighbourhood shopping streets have long been significant in their ability to provide goods and services within walking distance of neighbourhood residents, to create a rich public realm, and to foster a sense of community. Far removed from their past as streetcar strips, the neighbourhood shopping street is once again being looked at as an important element of the urban environment. The purpose of this thesis is to determine the characteristics of good neighbourhood shopping streets and to examine these characteristics in the context of two Vancouver case studies—Commercial Drive and West 41st Avenue. Based on a review of planning, urban design, and landscape architecture literature, the fundamental principles of good neighbourhood shopping streets are revealed. Specifically, a good neighbourhood shopping street is accessible, comfortable, sociable, a place, adaptable, beautiful, and diverse. Flowing from these principles, and the means to them, are the characteristics of good neighbourhood shopping streets—buildings that relate to the street, good walking facilities, pedestrian amenities, traffic management, street activity, neighbourhood goods and services, maintenance, supportive neighbourhood context, and supportive government. The research suggests that real-life neighbourhood shopping streets rarely have all the characteristics that the literature holds as ideal. Rather, some characteristics— buildings that relate to the street, street activity, neighbourhood goods and services, a supportive neighbourhood context, and supportive government—appear as fundamental to good neighbourhood shopping streets but are exhibited to varying degrees. More specifically, the case studies help illustrate what particular elements are either essential or helpful, creating a checklist that other streets can benefit from.
290

Maitinama iš autonominio šaltinio tiesiaeigė elektros pavara / Linear electric drive powered from renewable source

Ryškevič, Andrej 10 June 2004 (has links)
The final master thesis investigates work of linear electric drive, powered by alternative energy source. There is analyzed influence of solar cell inner resistance for asynchronous drive work. There are analyzed principle or solar cell work and made it mathematical model it Matlab software package. Using this model there were made UI characteristics of solar cell working under different irradiance and temperature levels. In this work there is described simplified algorithm of calculation of linear asynchronous drive. Using this algorithm and Matlab software package there where calculated and modeled linear asynchronous drive and its dynamic speed and force characteristics. A result of this work is a dependence of linear asynchronous drive force from inner solar cell resistance.

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