• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1286
  • 766
  • 183
  • 158
  • 147
  • 104
  • 47
  • 21
  • 20
  • 19
  • 16
  • 12
  • 11
  • 9
  • 9
  • Tagged with
  • 3266
  • 387
  • 341
  • 286
  • 270
  • 226
  • 223
  • 215
  • 207
  • 201
  • 191
  • 191
  • 181
  • 170
  • 169
  • 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.
311

Energy-Efficient Time-Based Encoders and Digital Signal Processors in Continuous Time

Patil, Sharvil Pradeep January 2017 (has links)
Continuous-time (CT) data conversion and continuous-time digital signal processing (DSP) are an interesting alternative to conventional methods of signal conversion and processing. This alternative proposes time-based encoding that may not suffer from aliasing; shows superior spectral properties (e.g. no quantization noise floor); and enables time-based, event-driven, flexible signal processing using digital circuits, thus scaling well with technology. Despite these interesting features, this approach has so far been limited by the CT encoder, due to both its relatively poor energy efficiency and the constraints it imposes on the subsequent CT DSP. In this thesis, we present three principles that address these limitations and help improve the CT ADC/DSP system. First, an adaptive-resolution encoding scheme that achieves first-order reconstruction with simple circuitry is proposed. It is shown that for certain signals, the scheme can significantly reduce the number of samples generated per unit of time for a given accuracy compared to schemes based on zero-order-hold reconstruction, thus promising to lead to low dynamic power dissipation at the system level. Presented next is a novel time-based CT ADC architecture, and associated encoding scheme, that allows a compact, energy-efficient circuit implementation, and achieves first-order quantization error spectral shaping. The design of a test chip, implemented in a 0.65-V 28-nm FDSOI process, that includes this CT ADC and a 10-tap programmable FIR CT DSP to process its output is described. The system achieves 32 dB – 42 dB SNDR over a 10 MHz – 50 MHz bandwidth, occupies 0.093 mm2, and dissipates 15 µW–163 µW as the input amplitude goes from zero to full scale. Finally, an investigation into the possibility of CT encoding using voltage-controlled oscillators is undertaken, and it leads to a CT ADC/DSP system architecture composed primarily of asynchronous digital delays. The latter makes the system highly digital and technology-scaling-friendly and, hence, is particularly attractive from the point of view of technology migration. The design of a test chip, where this delay-based CT ADC/DSP system architecture is used to implement a 16-tap programmable FIR filter, in a 1.2-V 28-nm FDSOI process, is described. Simulations show that the system will achieve a 33 dB – 40 dB SNDR over a 600 MHz bandwidth, while dissipating 4 mW.
312

A recuperação no processo de ensino - aprendizagem: legislação e discurso de professores. / Revision classes in the process of learning: legislation and discourse of state school teachers of São Paulo.

Marcia Josefina Norcia 05 August 2008 (has links)
Trata-se de uma pesquisa teórica e de campo, com o objetivo de analisar as práticas de recuperação que foram implantadas nas escolas estaduais paulistas, como resultado da opção pelo regime de progressão continuada e da organização do ensino fundamental em ciclos a partir de 1998. O objetivo central de nosso trabalho foi o de caracterizar a concepção das práticas de recuperação na Lei de Diretrizes e Bases nº 9394/96 e como as mesmas foram regulamentadas no Estado de São Paulo, por meio do Conselho Estadual de Educação de São Paulo e da Secretaria da Educação do Estado de São Paulo. Não obstante, as práticas de recuperação se vinculam sempre a um posicionamento político e a uma opção por determinados valores e princípios que norteiam a avaliação escolar. Longe de representar um aspecto apenas técnico do cotidiano escolar, a avaliação envolve esferas muito mais amplas e complexas, já que se apóia em orientações legais (legislação federal e estadual) que, por sua vez, espelham fundamentações teóricas que lhes apontam diretrizes. O desenvolvimento deste trabalho de pesquisa acompanhou um período de sucessivas transformações em relação ao sistema de avaliação e às práticas de recuperação nas escolas de 1ª a 4ª série da rede pública estadual de São Paulo. Embora a Lei nº 9394/96 continue a representar a orientação legal mais ampla para as práticas de recuperação em nível federal, o Parecer CEE/SP nº 67/98, a Resolução SE 05/98 e a Resolução SE 06/08 (alterada pela Resolução 26/08) representam indicadores legais estaduais paulistas sobre as práticas de recuperação que revelam aspectos vitais para o entendimento do sistema de recuperação que tem vigorado em nossas escolas. Além da análise da legislação federal e estadual que apóia as atividades de recuperação nas escolas estaduais, aplicamos um questionário a trinta professores da rede pública estadual de São Paulo sobre as práticas de recuperação no regime de progressão continuada. O conjunto de dados obtidos permitiu concluir que a maioria dos professores considera que houve mudanças significativas na organização da escolarização em ciclos, principalmente porque afasta o fantasma da repetência (63%), mas 37% se declararam contra a recuperação no sistema de ciclos por considerar que não há respaldo suficiente aos professores para trabalhar com as práticas de recuperação e que o tempo que antecede a recuperação ao final de ciclo é longo demais (quatro anos). / It is a theorical and field-work research, which has the aim to annalyse the revision classes that were implanted in the public schools of the State of São Paulo as result of the option for the continuous promotion and the new organization of primary school that happened in 1998. The central objective of this work was the characterization of the conception of the revision classes in Leis de Diretrizes e Bases (LDB -Guidelines and Bases Act of Education)-, Law n. 9394/96 and how it was regulated in the State of São Paulo, by the Conselho Estadual de Educação de São Paulo (CNE - Brazilian Council for Education) and by the Secretaria da Educação do Estado de São Paulo (State Secretariat of Education of São Paulo). Nevertheless, the practice of revision classes are always linked to a political position and to an option for some values and principles that structure the educational evaluation. The intention is not only represent the technical aspect; the educational evaluation involves more complexes questions because of the fact that is based in legal orientation (federal and state legislation) that revels theorycal fundaments of the guidelines. The development of this research followed a period of transformations in the relation of education evaluation system and the revision classes in the 1st to 4th grades in the public schools of the state of São Paulo. Although the Law nº 9394/96 continues to represent a broaden legal orientation to the revision in the federal level, the resolutions Parecer CEE/SP nº 67/98, a Resolução SE 05/98 e a Resolução SE 06/08 (modified by Resolução 26/08) represent state legal indicators about the revision classes, which revels vital aspects for the understanding of revision classes system existent in our schools. Besides the analyze of the federal and state legislation that supports the revision activities in the state schools, we collected data of 30 teachers using a questionnaire about the revision classes in the universe of continuous promotion. The data we have obtained permitted conclude that the large majority of teachers consider that it had important changes in the organization in cycles. It hides the ghost of repeater (63%), but 37% declare themselves against the revision classes in the system of cycles owing to the fact that there is no sufficient base for the teachers to work with the repetition practice and that the time that occurs before the recuperation in the end of the cycle is too long (four years).
313

Dynamic generalisation of continuous action spaces in reinforcement learning : a neurally inspired approach

Smith, Andrew James January 2002 (has links)
This thesis is about the dynamic generalisation of continuous action spaces in reinforcement learning problems. The standard Reinforcement Learning (RL) account provides a principled and comprehensive means of optimising a scalar reward signal in a Markov Decision Process. However, the theory itself does not directly address the imperative issue of generalisation which naturally arises as a consequence of large or continuous state and action spaces. A current thrust of research is aimed at fusing the generalisation capabilities of supervised (and unsupervised) learning techniques with the RL theory. An example par excellence is Tesauro’s TD-Gammon. Although much effort has gone into researching ways to represent and generalise over the input space, much less attention has been paid to the action space. This thesis first considers the motivation for learning real-valued actions, and then proposes a set of key properties desirable in any candidate algorithm addressing generalisation of both input and action spaces. These properties include: Provision of adaptive and online generalisation, adherence to the standard theory with a central focus on estimating expected reward, provision for real-valued states and actions, and full support for a real-valued discounted reward signal. Of particular interest are issues pertaining to robustness in non-stationary environments, scalability, and efficiency for real-time learning in applications such as robotics. Since exploring the action space is discovered to be a potentially costly process, the system should also be flexible enough to enable maximum reuse of learned actions. A new approach is proposed which succeeds for the first time in addressing all of the key issues identified. The algorithm, which is based on the ubiquitous self-organising map, is analysed and compared with other techniques including those based on the backpropagation algorithm. The investigation uncovers some important implications of the differences between these two particular approaches with respect to RL. In particular, the distributed representation of the multi-layer perceptron is judged to be something of a double-edged sword offering more sophisticated and more scalable generalising power, but potentially causing problems in dynamic or non-equiprobable environments, and tasks involving a highly varying input-output mapping. The thesis concludes that the self-organising map can be used in conjunction with current RL theory to provide real-time dynamic representation and generalisation of continuous action spaces. The proposed model is shown to be reliable in non-stationary, unpredictable and noisy environments and judged to be unique in addressing and satisfying a number of desirable properties identified as important to a large class of RL problems.
314

Passive eruption patterns in first molars

Hoelscher, Benjamin Charles 01 May 2011 (has links)
OBJECTIVE: The purpose of this study is to determine the eruption patterns of maxillary and mandibular first molars from the first occlusal contacts to adulthood. Previous studies have failed to obtain measurements into adulthood or have not been longitudinal in design. By using a measurement during the subjects' adulthood, a better estimate of the changes that occur between the tooth and the gingival margin throughout growth and aging can be obtained. METHODS: The material for this research project was obtained from the Meredith Facial Growth Study from the University of Iowa Orthodontics Department. Records from a set of 64 subjects (35 males and 29 females) were used. Each of these patients had intraoral models taken throughout adolescence into adulthood. A final model was available for each subject in their twenties. Twenty-eight subjects had final records available in their forties (14 males and 14 females). Measurements were recorded for the maxillary first molars (Teeth 3 and 14), and the mandibular first molars (Teeth 19 and 30). Measurements were taken at eleven time points for all sixty-four subjects starting at year 8 and yearly until age 18 with a final measurement taken on a model from the patient's twenties. A subset of twenty-eight subjects contained measurements in their forties. Bitewing Radiographs were also used to measure changes in alveolar bone height at 12, 20, and 40. RESULTS AND CONCUSIONS: Alveolar bone heights and their changes over time measured from the CEJ indicate that the sample population had a stable periodontium. Crown heights at age 20 and 40 were significantly greater than age 11. At age 40, crown heights were significantly greater than age 20. Teeth continue to erupt into a patient's forties in the absence of bone loss and attrition.
315

Numerical modeling of porosity and macrosegregation in continuous casting of steel

Du, Pengfei 01 May 2013 (has links)
The continuous casting process is a widely used technique in modern steel plants. However, it is a complicated process that is not well understood. The objective of this research is to model the porosity and macrosegregation due to shrinkage related effects and solid deformation in the continuous casting of steel. Solid phase movements due to bulging and variable roll gap are modeled with a simple algebraic equation based on assumed slab surface deflection. A simplified single domain fluid flow model is derived to predict the pressure field. When liquid pressure drops to zero, porosity starts to form. The distribution of porosity is calculated using the porosity equation which is based on the mass conservation. A macrosegregation model based on the species conservation is derived. With the relative velocity calculated from the pressure results and the solid velocity, macrosegregation is obtained. Since the solid phase velocity is not zero and mixture density is not assumed to be constant, porosity and macrosegregation due to both solid deformation and shrinkage effects are incorporated. In order to validate the model, the pressure field of a three-dimensional pure metal solidification system is simulated. The results show the feasibility of the proposed model to predict the fluid flow. The porosity and macrosegregation prediction for different casting conditions are performed. The results confirm the necessity of including solid phase deformation in the prediction of porosity and centerline macrosegregation. The results also reveal the relations between different operating conditions (such as degree of bulging, soft reduction, and casting speed) and the porosity/macrosegregation defects in the final product.
316

Continuous Disclosure for Australian Listed Companies

Coffey, Josephine Margaret January 2002 (has links)
ABSTRACT This thesis investigates the legal and theoretical basis of continuous disclosure regulation in Australia as it applies to listed companies. An empirical study is undertaken to further investigate the operation of the legislation. As part of the Enhanced Disclosure regime, the continuous disclosure provision was effective from 5 September 1994 as s1001A of the Corporations Law, now the Corporations Act 2001 (Cth). This statutory provision is replaced by s674, inserted by Schedule 2 to the Financial Services Reform Act 2001 (Cth), and effective from 11 March 2002. The provision reinforces Australian Stock Exchange (ASX) listing rule 3.1. The rule requires a listed disclosing entity to notify ASX immediately of information that would be expected to have a �material effect� on the share price of the company. However, the disclosure requirement is weakened by a number of specific exemptions or �carve-outs� to listing rule 3.1. If a reasonable person would not expect the information to be disclosed, and if the confidentiality of the information is maintained, then disclosure is not mandatory in special circumstances. This study analyses 427 query notices, issued by ASX to listed companies from July 1995 to April 1996. The queries request information concerning unexplained movements in a company�s share price or a failure to comply with the listing rules. An analysis of the companies� replies to these notices provides a profile of the type of company that is likely to be queried. The study also attempts to evaluate the extent to which these companies have relied on the �carve-outs� as an exemption to the regulation.
317

Revision of Lacquer Range

Klasson, Martin January 2010 (has links)
<p>Detta examensarbete utfördes på lack- och tryckavdelningen på företaget</p><p>Emballator Ulricehamns Bleck med målet att undersöka om det fanns brister och</p><p>slöserier i det befintliga lacksortimentet.</p><p>Efter en noggrann nulägesanalys som inkluderade bland annat genomgång av</p><p>applicerbara datablad, arbetsplatsintroduktion och studiebesök hos en av</p><p>företagets lackleverantörer genomfördes arbetet utan missöden. Nulägesanalysen</p><p>resulterade i en översikt av dagens lacksortiment och efter det fortsatte arbetet</p><p>med att ta fram en egenskapsmatris innehållande samtliga lacker i sortimentet.</p><p>Efter att de lacker som föll inom författarens specifikation för dubbletter</p><p>identifierats togs ett antal rekommendationer för hur företaget bör agera för att ha</p><p>ett uppdaterat sortiment fram. Förutom detta har författaren tagit fram ett förslag</p><p>på hur företaget skall testa sina insideslacker för att i framtiden ha möjligheten att</p><p>undersöka om några av dessa kan tas ut ur sortimentet.</p> / <p>This degree project was performed in the coating and printing department at</p><p>Emballator Ulricehamns Bleck. The task was to investigate if any waste and</p><p>improvement opportunities in the lacquer range at Emballator Ulricehamns Bleck</p><p>exist.</p><p>A thorough analysis of the current situation including a review of applicable data,</p><p>work place introduction and a visit to one of the company´s suppliers was made.</p><p>This gave a good understanding of the current status. The result of the analysis</p><p>was an overview of the lacquer range that helped the author to compile a</p><p>characteristic matrix including all the products in the lacquer range. Following</p><p>this the author identified products that could be specified as duplicates.</p><p>Furthermore the degree project has resulted in 5 recommendations regarding</p><p>future work with the design of the lacquer range. The last part of the project</p><p>resulted in an analysis of today’s test schedule and a suggestion how to modify it</p><p>for future needs.</p>
318

Ständiga förbättringar och praktisk problemlösning : en explorativ studie på Saab Automobile AB

Sefton, Martin January 2009 (has links)
<p>Continuous improvement is one of five principles in General Motors – Global Manufacturing System (GM-GMS). GM-GMS has been used by Saab Automobile AB since 2003 and is a central component for realisation of GM’s vision. Internal audits have discovered problems with one of the tools, practical problem solving (PPS), which needs to be improved. The department manufacturing of press and body (PK) wants to survey the problems and initiate a process of improvement. The purpose of this thesis work is to develop a foundation for future re-designs of the PPS process. Employees have been interviewed and observed in order to explore possible difference theoretical and practical problem solving with PPS. The result of the investigation shows 4 different and interrelated problem categories. 1. Information transfer, PPS hand over to product quality engineers (PQE) department cause problem when general assemblies (GA) are excluded from the improvement work. General assemblies do not get any feedback information from (PQE) about planed countermeasures. 2. Problem solving, team leaders has difficulties with identifying the true problem. Using “five-why” during the analysis work causes problem, since team leaders do not have the knowledge of how to use the tool in a proper way. 3. Documentation of PPS, the content in the PPS-form is a problem according to team leaders. Lack of knowledge and understanding of how to use the PPS-document leads to incomplete and incorrect analysis. 4. Coordination of involved people, support and help are missing from the management and quality engineer according team leaders. PPS from Global Costumer Audit are imposing time stress according to team leaders. Recommendations for further work is to investigate the opportunities with a web based PPS and process to improve information transfer and documentation of PPS. A second recommendation is to train and coach team leaders in problem solving and improve coordination of involved people and skills in problem solving.</p>
319

Delta-sigma modulators employing continuous-time circuits and mismatch-shaped DACs

Zhang, Bo 03 April 1996 (has links)
Delta-sigma modulators are currently a very popular technique for making high-resolution analog-to-digital and digital-to-analog converters. These oversampled data converters have several advantages over conventional Nyquist-rate converters, including an insensitivity to many analog component imperfections, a simpler antialiasing filter and reduced accuracy requirements in the sample and hold. Though the initial uses of delta-sigma modulators were in the audio field, the development of bandpass modulators opened up the application range to radar systems, digital communication systems and instruments which convert IF, or even RF, analog signals directly to digital form. This thesis presents a method used to analyze and synthesize continuous-time delta-sigma modulators for given specifications. A fourth-order prototype continuous-time bandpass delta-sigma modulator employing g[subscript m]-LC resonator structure is demonstrated on a PCB board and measurement results corroborate the theory. To allow the construction of very high performance delta-sigma modulators, this thesis presents an architecture for a multibit DAC constructed from unit elements which shapes element mismatches. Theoretical analysis and simulation shows that this architecture greatly increases the noise attenuation in the band-of-interest and facilitates the use of multibit quantization in delta-sigma modulators. The methods presented in this thesis will allow high-frequency wideband bandpass delta-sigma modulators to be constructed. / Graduation date: 1996
320

CQ-Buddy: Harnessing Peers For Distributed Continuous Query Processing

Ng, Wee Siong, Shu, Yanfeng, Tok, Wee Hyong 01 1900 (has links)
In this paper, we present the design and evaluation of CQ-Buddy, a peer-to-peer (p2p) continuous query (CQ) processing system that is distributed, and highly-scalable. CQ-Buddy exploits the differences in capabilities (processing and memory) of peers and load-balances the tasks across powerful and weak peers. Our main contributions are as follows: First, CQ-Buddy introduces the notion of pervasive continuous queries to tackle the frequent disconnected problems common in a peer-to-peer environment. Second, CQ-Buddy allows for inter-sharing and intra-sharing in the processing of continuous queries amongst peers. Third, CQ-Buddy peers perform query-centric load balancing for overloaded data source providers by acting as proxies. We have conducted extensive studies to evaluate CQ-Buddy’s performance. Our results show that CQ-Buddy is highly scalable, and is able to process continuous queries in an effective and efficient manner. / Singapore-MIT Alliance (SMA)

Page generated in 0.054 seconds