• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 232
  • 53
  • 44
  • 19
  • 19
  • 19
  • 19
  • 19
  • 19
  • 18
  • 8
  • 5
  • 5
  • 5
  • 5
  • Tagged with
  • 436
  • 436
  • 75
  • 67
  • 55
  • 47
  • 45
  • 43
  • 38
  • 35
  • 32
  • 31
  • 30
  • 27
  • 25
  • 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.
391

Contribuição da análise térmica no desenvolvimento de formulações de batons / Contribution of thermal analysis in the development of lipstick formulations

Floripes Ferreira de Oliveira 27 February 2003 (has links)
Este trabalho consiste na caracterização química, física e termoanalítica de algumas amostras de batons e dos componentes de suas formulações. O estudo termoanalítico foi desenvolvido a partir das técnicas TG/OTG sob atmosfera dinâmica de ar ou enriquecida com O2 e por DSC sob atmosfera dinâmica de N2, com razão de aquecimento de 10°C min-1 em ambos os casos. Os testes de estabilidade com exposição das amostras a 4, 25 e 43°C e à luz solar indireta permitiram avaliar as propriedades organolépticas, físicas e térmicas. Os resultados da análise de ponto de fusão obtidos pelo método convencional foram comparados àqueles encontrados por ensaios de DSC. A estabilidade térmica foi determinada pela exposição a 43°C em estufa convencional e a partir da técnica de TG no estudo da cinética de decomposição, utilizando-se os métodos dinâmico e isotérmico. Foi realizada a predição do prazo de validade de 2,4 anos para uma amostra específica de batom foi determinada por meio do estudo cinético pelo método isotérmico, aplicando-se a equação de Arrhenius. A performance de três diferentes antioxidantes quanto à estabilidade térmica de uma amostra de batom foi avaliada, verificando-se, melhor comportamento da mistura de tocoferáis aplicada a 1%. / This work consists of the chemical, physical and thermoanalytical characterization of some samples of lipsticks and the components of their formulation. The thermoanalytical study was developed by means of TG/DTG techniques under dynamic air atmosphere or air enriched with O2 and by DSC in dynamic nitrogen atmosphere, with heating rate of 10°C min-1 in both cases. The stability tests with the submitled samples at 4, 25, 43°C and sunlight allowed to evaluate the organoleptic, physical and thermal properties. The analytical results of melting point obtained from conventional methods were compared to the ones measured by DSC. The thermal stability was determined by exposition at 43°C in a conventional stove and by TG technique in the study of decomposition\'s kinetic, using dynamic and isothermal methods. A shelf-life prediction of 2.4 years for a specific sample of Iipstick was determined by means of a kinetic study, using an isothermal method and applying Arrhenius\' equation. The performance of three different antioxidants concerning the thermal stability of a Iipstick sample was evaluated, the tocopherol mix showed the better performance when applied at 1%.
392

Técnica para controlar o comprimento de onda da dispersão zero de uma fibra microestruturada / Technique to control the zero¿dispersion wavelength of a microstructured optical fiber

Ramos Gonzales, Roddy Elky 22 August 2018 (has links)
Orientador: Hugo Enrique Hernández Figueroa / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-22T14:17:05Z (GMT). No. of bitstreams: 1 RamosGonzales_RoddyElky_D.pdf: 101751842 bytes, checksum: 8dc15b7e91881cfef8e1c24fa619f3ca (MD5) Previous issue date: 2013 / Resumo: Propor uma técnica eficiente para controlar o Comprimento de Onda da Dispersão Zero (ZDW - Zero Dispersion Wavelength) de uma Fibra Óptica Microestruturada (MOF - Microstructured Optical Fiber). Esta técnica baseia-se na variação do índice de refração linear e na variação da espessura de um filme fino que cobre as superfícies interiores dos buracos da MOF. Foi utilizado um código potente e preciso baseado na formulação do Método dos Elementos Finitos (FEM - Finite Element Method) totalmente vetorial em conjunto com Camadas Perfeitamente Casadas (PMLs - Perfectly Matched Layers). E demonstrado um deslocamento Maximo do ZDW de 570 nm. Este filme fino pode ser incluído durante ou apos a fabricação da MOF, isso significa que a Dispersão Zero (ZD - Zero Dispersion) da fibra pode ser adaptada conforme a necessidade / Abstract: An efficient technique to control the zero-dispersion wavelength (ZDW) of a microstructured optical fiber (MOF) is proposed and numerically demonstrated in this work. This technique is based on the variation of the linear refractive index and the thickness of a thin film covering the microstructured optical fiber holes' inner surfaces. A powerful and accurate code based on a full-vector finite-element method formulation in conjunction with perfectly matched layers was used. A maximum of 570-nm zero-dispersion wavelength displacement is demonstrated. This thin film can be included after the microstructured optical fiber has been fabricated, and that means the zero dispersion of such fiber can be tailored as needed / Doutorado / Telecomunicações e Telemática / Doutor em Engenharia Elétrica
393

Método de medição de alinhamento de suspensão veicular não intrusivo baseado em visão computacional / Not intrusive method for the measurement of alignment angles of vehicular suspension based on computer vision

Mingoto Junior, Carlos Roberto 21 August 2018 (has links)
Orientador: Paulo Roberto Gardel Kurka / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-21T02:23:47Z (GMT). No. of bitstreams: 1 MingotoJunior_CarlosRoberto_D.pdf: 4676498 bytes, checksum: f396cb633ba04f6ff1589cea747bb133 (MD5) Previous issue date: 2012 / Resumo: O presente projeto de pesquisa aplica técnicas de visão estereoscópica computacional no desenvolvimento da configuração de um equipamento de medição de ângulos de alinhamento de suspensão veicular, usando câmeras de vídeo de baixo custo. Atualmente, a maioria dos dispositivos de medição de ângulos de alinhamento de suspensão de veículos baseia-se no uso de componentes eletromecânicos, como pêndulos resistivos, inclinômetros capacitivos, dispositivos opto-mecânicos (espelhos e raio de luz monocromática de baixa intensidade). Com a sequência aqui estabelecida dos fundamentos algébricos e técnicas de visão computacional, realizam-se estudos de viabilidade científica e proposta de construção de um equipamento de verificação de ângulos de alinhamento veicular. São apresentados testes virtuais e reais, ilustrativos da potencialidade operacional do equipamento / Abstract: This research project uses stereoscopic computer vision techniques to develop a system to measure alignment angles of vehicular suspensions, using low cost cameras. Currently, most of the devices intended to measure vehicular suspension angles are based on the use of electromechanical components, such as resistive pendulums, capacitive inclinometers or opticmechanical devices (mirrors and projection of beams of monochromatic light of low intensity). Fundaments of linear algebra and computer vision techniques, lead to studies of feasibility and practical implementation of a system used to measure vehicular suspension alignment angles. Virtual and real measurements are carried out to illustrate the operative potential of such a system / Doutorado / Mecanica dos Sólidos e Projeto Mecanico / Doutor em Engenharia Mecânica
394

Metodologia para medição de tensões em virabrequins utilizando ESPI / Stress measurements in crankshafts using ESPI

Matsusaki, Eduardo Hiroshi 18 August 2018 (has links)
Orientador: Auteliano Antunes dos Santos Júnior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-18T19:03:51Z (GMT). No. of bitstreams: 1 Matsusaki_EduardoHiroshi_M.pdf: 16938577 bytes, checksum: 51152fe274507619364344f4ec28e4b9 (MD5) Previous issue date: 2009 / Resumo: Tensões mecânicas estão entre as principais causas de falhas de componentes estruturais. A medição de tais tensões pode ser feita com técnicas que relacionam alguma variável física a tensão existente. Técnicas destrutivas podem ser usadas para tal finalidade, mas apenas no controle de qualidade. Entre as técnicas não destrutivas destacam-se os Raios X, a difração de Nêutrons e a acustoelasticidade. Uma das técnicas mais promissoras envolve a Interferometria a Laser. Segundo essa técnica, a interferência entre feixes de luz permite a identificação de pontos da superfície e estes, quando deslocados sob a aplicação de esforços, possibilitam o cálculo das deformações e tensões. Este trabalho apresenta a aplicação da técnica de Interferometria Eletrônica entre Padrões de Speckles - ESPI para a medição de tensões em virabrequins. O estudo consistiu em uma revisão teórica do método; no estudo dos fatores que influenciam o resultado da medição; na validação da técnica para a medição de tensões, através da comparação com resultados do MEF e da extensometria; na aplicação da técnica para a medição cm chapa entalhada e no emprego desta para a medição de tensões em virabrequins. O estudo permitiu também a ajustagem ótima dos parâmetros que influenciem a medição. Os resultados obtidos mostraram que o método é promissor quanto ao seu emprego generalizado; que a resolução obtida é adequada para o emprego na medição nos componentes analisados e que o método tem limitações importantes, que devem ser avaliadas para cada aplicação / Abstract: Mechanical stresses are among the main causes of failure of structural components. The measurement of such stresses can be made with techniques that relate some physical variable with the stress. Destructive techniques can be used for this purpose, but only in quality control. Non-destructive methods such as the X rays, the neutron diffraction and acoustoelasticity, are among the most used techniques. One of the most promising techniques applies Laser Interferometry. In this technique, the interference between light beams identifies points on the surface and these, when displaced under external forces, enable the calculation of the deformations and of the stresses. This paper presents the employ of the Electronic Speckle Pattern Interferometry technique for measuring stresses in crankshafts. It consisted of a theoretical review of the method; the study of the factors that would compromise the measuring results; a validation of the technique to measure stresses, by comparing MEF with strain gauges results; using the technique to take measures in a entailed plate and in the stresses measurements of crankshafts. This work also allowed the optimum adjustment for the parameters inducing the measurements. The obtained results showed a promising method for its general use; showed too that the resolution obtained is proper to the use in parts analyzed and that the method has important limitations that should be analyzed in every situation / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica
395

Qualidade das mudas clonais de dois híbridos de eucalipto em função do manejo hídrico /

Garcia, Rodolfo D'Aloia, 1984- January 2011 (has links)
Orientador: Magali Ribeiro da Silva / Banca: João Carlos Cury Saad / Banca: Jane Luisa Wadas Lopes / Resumo: No Brasil observa-se que o cultivo do eucalipto contribui expressivamente na economia nacional, isso se dá em decorrência de elevadas taxas de produtividade das florestas existentes no território nacional. Analisando então, uma floresta produtiva se inicia através de mudas com boa qualidade morfológicas e resistentes às adversidades fisiológicas apresentadas pelo meio, para se definir como sendo de boa qualidade uma série de fatores são considerados essenciais no processo de produção desta muda, e o manejo hídrico é um fator primordial a ser analisado. Os estudos sobre manejo hídrico em viveiros de produção são escassos e desatualizados em decorrência das diversas descobertas no âmbito clonal de produção de mudas. Neste sentido o trabalho teve por objetivo verificar a influência da lâmina e a frequência de irrigação, aplicadas as mudas de Eucalyptus grandis vs. Eucalyptus urophylla em ambiente controlado, com o foco final na formação de uma muda de melhor qualidade para as mais diversas necessidades do mercado florestal. O experimento foi conduzido no Viveiro do Departamento de Recursos Naturais/Setor de Ciências Florestais, na Fazenda Experimental Lageado, pertencente à Faculdade de Ciências Agronômicas (FCA) da UNESP, no município de Botucatu - SP. O trabalho constituiu-se de dois experimentos sendo um com o clone 144 (mais resistente ao déficit hídrico) e o outro com o clone 103 (mais suscetível ao déficit hídrico). O substrato utilizado foi o produto comercial denominado Carolina Soil Florestal®. O delineamento estatístico foi um fatorial (3x2) inteiramente casualizado constituído dos seguintes fatores: 2 frequências de irrigação (2 e 5 vezes ao dia) e 3 lâminas brutas de irrigação (8, 12 e 16 mm). O experimento foi composto por 06 tratamentos, cada qual composto por... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In Brazil we found that each passing day the national economy depends on the cultivation of eucalyptus. Thus a productive forest comes from a good quality seedlings. This study aimed to investigate the influence of intensity and frequency of irrigation applied to seedlings of Eucalyptus grandis vs. Eucalyptus urophylla in a controlled environment with a focus on the formation of a final change to better quality, both in nursery and field workers. The experiment was conducted in the Nursery Department of Natural Resources / Division of Forest Science at the Experimental Farm Lageado belonging to the Faculdade de Ciências Agronômicas (FCA) of UNESP, Botucatu - SP. The substrate used was a commercial product called Carolina Forest Soil. The design was a factorial (3x2x2) randomized consists of the following factors: 3 intensity of irrigation (8, 12 and 16 mm), two irrigation frequencies (2 and 5 x day), two hybrid clones of Eucalyptus grandis vs. Eucalyptus urophylla. The experiment consisted of 12 treatments, each treatment with 04 replications, each consisting of 48 plants (24 plants useful per plate), totaling 96 plants per treatment. The seedling were evaluated as: aerial part height (H); diameter of collect (DC); aerial part... (Complete abstract click electronic access below) / Mestre
396

Clinician Trust in Predictive Clinical Decision Support for In-Hospital Deterioration

Schwartz, Jessica January 2021 (has links)
Background The landscape of clinical decision support systems (CDSSs) is evolving to include increasingly sophisticated data-driven methods, such as machine learning, to provide clinicians with predictions about patients’ risk for negative outcomes or their likely responses to treatments (predictive CDSSs). However, trust in predictive CDSSs has shown to challenge clinician adoption of these tools, precluding the ability to positively impact patient outcomes. This is particularly salient in the hospital setting where clinician time is scarce, and predictive CDSSs have the potential to decrease preventable mortality. Many have advised that clinicians should be involved in the development, implementation, and evaluation of predictive CDSSs to increase translation from development to adoption. Yet, little is known about the prevalence of clinician involvement or the factors that influence clinicians’ trust in predictive CDSSs for the hospital setting. The specific aims of this dissertation were: (a) to survey the literature on predictive CDSSs for the hospital setting to describe the prevalence and methods of clinician involvement throughout stages of system design, (b) to identify and characterize factors that influence clinicians’ trust in predictive CDSSs for in-hospital deterioration, and (c) to explore the use of a trust conceptual framework for incorporating clinician expertise into machine learning model development for predicting rapid response activation among hospitalized non-ICU patients using electronic health record (EHR) data. Methods To address the first aim (presented in Chapter Two), a scoping review was conducted to summarize the state of the science of clinician (nurse, physician, physician assistant, nurse practitioner) involvement in predictive CDSS design, with a specific focus on systems using machine learning methods with EHR data for in-hospital decision-making. To address the second aim (presented in Chapter Three), semi-structured interviews with nurses and prescribing providers (i.e., physicians, physicians assistants, nurse practitioners) were conducted and analyzed inductively and deductively (using the Human-Computer Trust conceptual framework) to identify factors that influence trust in predictive CDSSs, using an implemented predictive CDSS for in-hospital deterioration as a grounding example. Finally, to address the third aim (presented in Chapter Four), clinician expertise was elicited in the form of model specifications (requirements, insights, preferences) for facilitating factors shown to influence trust in predictive CDSSs, as guided by the Human-Computer Trust conceptual framework. Specifications included: (a) importance ranking of input features, (b) preference for a more sensitive or specific model, (c) acceptable false positive and negative rates, and (d) prediction lead time. Specifications informed development and evaluation of machine learning models predicting rapid response activation using retrospective EHR data. Results The scoping review identified 80 studies. Seventy-six studies described developing a machine learning model for a predictive CDSS, 28% of which described involving clinicians during development. Clinician involvement during development was categorized as: (a) determining clinical relevance/correctness, (b) feature selection, (c) data preprocessing, and (d) serving as a gold standard. Only five studies described implemented predictive CDSSs and no studies described systems in routine use. The qualitative investigation with 17 clinicians (9 prescribing providers, 8 nurses) confirmed that the Human-Computer Trust concepts of perceived understandability and perceived technical competence are factors that influence hospital clinicians’ trust in predictive CDSSs and further characterized these factors (i.e., themes). This study also identified three additional themes influencing trust: (a) actionability, (b) evidence, and (c) equitability, and found that clinicians’ needs for explanations of machine learning models and the impact of discordant predictions may vary according to the extent to which clinicians rely on the predictive CDSS for decision-making. Only two of 28 categories/sub-categories and one theme emerged uniquely to nurses or prescribing providers. Finally, the third study elicited model specifications from fifteen total clinicians. Not all clinicians answered all questions. Vital sign frequency was ranked the most important feature category on average (n = 8 clinicians), the most frequently preferred prediction lead time was shift-change/8-12 hours (n = 9 clinicians), most preferred a more specific than sensitive model (71%; n = 7 clinicians), the average acceptable false positive rate was 42% (n = 9 clinicians), the average acceptable false negative rate was 29% (n = 6 clinicians). These specifications informed development and testing of four machine learning classification models (ridge regression, decision trees, random forest, and XGBoost). 249,676 patient admissions from 2015–2018 at a large northeastern hospital system were modeled to predict whether or not patients would have a rapid response within the 12-hour shift. The random forest classifier met clinician’s average acceptable false positive (27.7%) and negative rates (28.9%) and was marginally more specific (72.2%) than sensitive (71.1%) on a holdout test set. Conclusions Studies do not routinely report clinician involvement in model development of predictive CDSSs for the hospital setting and publications on implementation considerably lag those on development. Nurses and prescribing providers described largely shared experiences of trust in predictive CDSSs. Clinicians’ reliance on the predictive CDSS for decision-making within the target clinical workflow should be considered when aiming to facilitate trust. Incorporating clinician expertise into model development for the purpose of facilitating trust is feasible. Future research is needed on the impact of clinician involvement on trust, clinicians’ personal attributes that influence trust, and explanation design. Increased education for clinicians about predictive CDSSs is recommended.
397

Thermo-Mechanical Selective Laser Assisted Die Transfer

Miller, Ross Alan January 2011 (has links)
Laser Induced Forward Transfer (LIFT) techniques show promise as a disruptive technology which will enable the placement of components smaller than what conventional pick-and-place techniques are capable of today. Limitations of current die-attach techniques are presented and discussed and present the opportunity for a new placement method. This study introduces the Thermo-Mechanical Selective Laser Assisted Die Transfer (tmSLADT) process and is an application of the unique blistering behavior of a dynamic releasing layer when irradiated by low energy focused UV laser pulses. The potential of tmSLADT as the next generation LIFT technique is demonstrated by the "touchless" transfer of 65 μm thick silicon tiles between two substrates spaced 195 μm apart. Additionally, the advantages of an enclosed blister-actuator mechanism over previously studied ablative and thermal releasing techniques are discussed. Finally, experimental results studying transfer precision indicate this non optimized die transfer process compares with, and may exceed, the placement precision of current assembly techniques. / Defense Microelectronics Activity (DMEA) under agreement number H94003-09-2-0905
398

Innovative Duplex Filter for Hydraulic Applications

Mössinger, Klaus January 2016 (has links)
For decades, duplex filters have been put to use virtually unmodified. Technologies, handling and use of materials show enormous potential for improvement. Filter element emoval/replacement is performed according to a complex process sequence. With the newly developed Duplex Filter, the market demands concerning simple filter element removal/replacement, as well as weight and pressure loss reduction are fully met.
399

Machine Learning Algorithms for Efficient Acquisition and Ethical Use of Personal Information in Decision Making

Tkachenko, Yegor January 2022 (has links)
Across three chapters of this doctoral dissertation, I explore how machine learning algorithms can be used to efficiently acquire personal information and responsibly use it in decision making, in marketing and beyond. In the first chapter, I show that machine learning on consumer facial images can reveal a variety of personal information. I provide evidence that such information can be profitably used by marketers. I also investigate the mechanism behind how facial images reveal personal information. In the second chapter, I propose a new self-supervised deep reinforcement learning approach to question prioritization and questionnaire shortening and show it is competitive against benchmark methods. I use the proposed method to show that typical consumer data sets can be reconstructed well based on relatively small select subsets of their columns. The reconstruction quality grows logarithmically in the relative size of the column subset, implying diminishing returns on measurement. Thus, many long questionnaires could be shortened with minimal information loss, increasing the consumer research efficiency and enabling previously impossible multi-scale omnibus studies. In the third chapter, I present a method to speed up ranking under constraints for live ethical content recommendations by predicting, rather than finding exactly, the solution to the underlying time-intensive optimization problem. The approach enables solving larger-than-previously-reported constrained content-ranking problems in real time, within 50 milliseconds, as required to avoid the perception of latency by the users. The approach could also help speed up general assignment and matching tasks.
400

Extending Technology Roadmap through Fuzzy Cognitive Map-based Scenarios: The Case of the Wind Energy Sector of Pakistan

Amer, Muhammad 09 May 2013 (has links)
In this modern era, energy is a key element required for sustainable development and prosperity of a society. Pakistan is an energy deficient country facing problems due to the shortage of over 4000 MW of electricity. The national energy sector is heavily dependent on imported fossil-fuel resources. The energy crisis is negatively affecting all economic and business activities, and it is widely recognized as a severe obstacle to growth and poverty reduction in the country. Establishment of wind farms can help to overcome the energy crisis. In this research, a national level wind energy roadmap is developed through scenario planning. Multiple future scenarios are developed using the fuzzy cognitive maps (FCM) approach. This research has extended technology roadmapping through FCM-based scenario analysis. Building scenarios with FCM is a very new approach, and for the first time FCM-based scenarios are developed for the wind energy sector of Pakistan. Based on these multiple scenarios, a technology roadmap has been developed. This research approach is applied to the wind energy sector of Pakistan as a case study. This approach has been used to establish objectives and national targets of the roadmap. Then in a systematic way, critical roadmap barriers are identified against each scenario, and appropriate action items have been proposed to overcome barriers and promote deployment of wind energy projects in Pakistan. The objectives and targets of the roadmap have been translated into action items. The technology roadmap has four layers: strategic objectives, targets, barriers, and action items. Expert panels have been utilized to develop scenarios and technology roadmaps. Validation of this research is also carried out using experts. This new approach has helped to develop a robust roadmap and enabled anticipation of a wide range of possible future outcomes. This research fills an important gap by combining scenario planning and technology roadmapping techniques in future studies, and it has enhanced flexibility of the developed roadmap. Moreover, for the first time multiple and plausible FCM-based scenarios are developed, which combine the benefits of both qualitative and quantitative analysis. Moreover, the technology roadmap for the wind energy sector of Pakistan is developed with a comprehensive study of practical obstacles and barriers towards deployment of wind energy technology. The research findings suggest that policy, financial, economic, lack of competition with conventional power plants, and technical are the most critical barriers towards deployment of wind energy projects in the country. Appropriate action items required to overcome the roadmap barriers against each scenario are also proposed in the developed roadmap. The experts also assigned responsibilities for the key roadmap action items to the major stakeholders.

Page generated in 0.1748 seconds