• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 617
  • 433
  • 114
  • 100
  • 53
  • 45
  • 41
  • 17
  • 12
  • 11
  • 11
  • 9
  • 8
  • 7
  • 7
  • Tagged with
  • 2000
  • 344
  • 315
  • 310
  • 239
  • 162
  • 117
  • 114
  • 91
  • 90
  • 87
  • 85
  • 85
  • 79
  • 78
  • 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.
541

Design, Fabrication and Evaluation of Nonconventional Optical Components

Li, Hui, Li January 2016 (has links)
No description available.
542

ASSOCIATIONS OF SNACK FOOD GROUP CONSUMPTION AND PATTERNS WITH WEIGHT STATUS AND DIET QUALITY AMONG ADOLESCENTS 12-19 YEARS IN THE UNITED STATES

Croce, Christina January 2020 (has links)
Purpose: Snacking is an important component of dietary intake yet remains understudied, particularly among adolescents who consume 25% of their daily calories from snacks. Previous research provides evidence that adolescents with overweight (OW) and obesity (OB) consume larger and more frequent snacks than adolescents with normal weight (NW). The objective of this study was to compare the food group composition of snacks by weight status as well as to identify snacking patterns and predictors among adolescents in the United States (US). Methods: Anthropometric, dietary, and demographic data from adolescents, 12-19 years old, in the 2005-2016 National Health and Nutrition Examination Survey were analyzed. The mean of the two days of dietary recall was used to measure dietary intake, which serves as a proxy for usual intake. Mean equivalents of the 37 food components present in individual snack foods reported by each adolescent across two days of intake were estimated using the Food Patterns Equivalents Database. Latent Class Analysis (LCA) was used to study the effect of mutually exclusive food component consumption groups. Multivariate logistic regression models were used to analyze membership in relation to dietary quality (Healthy Eating Index 2015 [HEI-2015] scores), weight status (BMI & BMI Z-score), selected snacking parameters (e.g., mean snack calories), and socio-demographic (e.g., race, gender) covariates. Results: Adolescents with two days of reliable dietary recall data and complete anthropometrics were included in the descriptive analysis (n = 6423). Adolescents with NW consumed greater energy, vegetable, whole grains, refined grains, dairy, and solid fat from snacks than adolescents with OW and OB (p < 0.05). LCA identified two main snacking patterns. The “Heavy Snackers” pattern was associated with higher consumption of each food component, total energy and snacking energy while the “Light Snackers” pattern was associated with lower consumption each food component, total energy and snacking energy. After adjustment for energy misreporting, OW or OB classification did not significantly increase the odds of being in either class while being classified with NW decreased the odds of being in the “Heavy Snacker” class. In addition, increasing BMI z-score and HEI-2015 total score increased and decreased the odds of being in the “Heavy Snackers” class respectively. The strongest predictors of a “Heavy Snacker” pattern were male gender, non-Hispanic white race, lower dietary quality, and increased snacking parameters, while female gender, all races except non-Hispanic white, better dietary quality, and decreased snacking parameters were strong predictors of a “Light Snacker” pattern. Conclusion: We can conclude that consuming less foods as snacks contributed positively to weight status and overall diet quality among US adolescents. Findings from this cross-sectional study remain consistent with snacking, diet quality, and weight status associations, but add to existing knowledge with the identification of snack consumption patterns. The dietary patterns derived may provide a useful basis for dietary interventions targeted at snacking among adolescents by recommending light snacking and low consumption of energy dense snack foods. Additional studies are needed to further understand what the main food pattern components are across gender and racial backgrounds and to confirm whether associations between snacking and weight status are due to food quality, quantity, or both. / Epidemiology
543

Effect of Multi-Component Excitation on the Sliding Response of Unanchored Components in Nuclear Facilities / Sliding Response Under Multi-Component Excitation

Arshad, Aamna 06 1900 (has links)
During an earthquake, unanchored equipment within a nuclear power plant facility can slide and interact with safety-critical systems and components. Previous studies on sliding have largely focused on the response due to unidirectional excitation, as computing the response of unanchored components in three dimensions can be complex and computationally expensive. As such, several prediction equations and a standardized approximate method as outlined in ASCE 4-16 have been developed to estimate the peak sliding displacement. This study investigates the effect of bidirectional horizontal interaction and the influence of vertical excitation on the sliding response of an unanchored object when the x, y, and z, components of earthquake excitation are applied simultaneously. The study also evaluates the approximate method detailed in ASCE 4-16. A suite of 40 floor acceleration histories obtained from response history analysis of a representative nuclear power plant facility are used as input for the sliding model. A wide range of friction coefficients is selected for analysis and the nonlinear sliding response of components is determined through the use of a Bouc-Wen type hysteretic model. Computed responses under uni-, bi- and tri-directional excitation reveal that the effect of bidirectional interaction and vertical excitation is greatest for sites with high shaking intensity. It is also concluded that the ASCE 4-16 approximate method is significantly overconservative in all cases. Additionally, the study expands the concept of multi-component excitation to intensity measures. Twelve intensity measures are selected and evaluated. It is found that most efficient intensity measures vary in efficiency depending on the coefficient of friction, and that the top intensity measures are not significantly affected by incorporating multiple components of excitation. / Thesis / Master of Applied Science (MASc) / Earthquakes can pose a huge risk to nuclear facilities. Unanchored objects within the facility may collide and interact with safety-critical equipment. Previous research on sliding behaviour lacks information on the response of an object subjected to earthquake excitation in both the horizontal plane and vertical direction simultaneously. Several prediction equations and an approximate method have been developed to estimate the sliding response as it becomes computationally expensive to solve. This research investigates the influence of simulatenous multi-component excitation on the sliding behaviour and evaluates the current standardized approximate method of estimating sliding displacement. Recommendations are given based on the friction coefficient between the object and the base. The research also explores which characteristics of earthquake ground motion (e.g. acceleration, velocity, energy) are most indicative of sliding behaviour.
544

Inheritance of Soluble Oligosaccharides in Soybean Seeds

Huhn, Melissa Rose 14 August 2003 (has links)
Sucrose, raffinose, and stachyose make up the majority of the carbohydrates in soybean seeds. While sucrose is a desirable component of soybean seeds, raffinose and stachyose are considered to be anutritive factors and eliminating or reducing them appears to be a beneficial endeavour. The major objective of this study was to determine the genetic mechanism controlling accumulation of soluble saccharides in soybean seeds. An experimental soybean line, V99-5089, with high sucrose (14.6%) content coupled with low amounts of raffinose (0.5%) and stachyose (0.4%) was the center of this study. Three populations were studied and segregation patterns were observed in F2:3 populations. All three sugars were extracted by an aqueous procedure and quantified by high pressure liquid chromatography (HPLC) using a NH2 column and refractive index (RI) detector. Segregation of seeds from F2:3 plants indicated a single, partially recessive gene reduced stachyose content of soybean seeds from about 4% to less than 1%. Estimates of genetic variability indicate the presence of sufficient additive variation in addition to the putative major gene to warrant selection. Raffinose and stachyose were positively correlated to each other and each was negatively correlated with sucrose while there was not a significant correlation between total sugar content and the amount of any of the individual sugars. Agronomic traits evaluated do not appear to be adversely effected by the reduction of stachyose content. Additionally, a negative relationship was observed between inorganic phosphorus and stachyose content of soybean seeds but a relationship was not observed between stachyose and phytate phosphorus or between inorganic phosphorus and phytate phosphorus. / Master of Science
545

OPTIMITZACIÓ DE MÈTODES MULTITÉCNICA PER A LA CARACTERITZACIÓ DE COMPONENTS ORGÀNICS I MORTERS DE CALÇ TRADICIONALS DE L'ANTIGUITAT. DESENVOLUPAMENT DE METODOLOGIES EXPERIMENTALS PER A LA SEVA CONSERVACIÓ I RESTAURACIÓ. APLICACIÓ A UN CAS D'ESTUDI: ELS ESTUCS DE LA PINTURA MURAL DE LA CULTURA MAIA (ANTIGA MESOAMÈRICA)

Guasch Ferré, Núria 03 March 2016 (has links)
[EN] The present research suggests, on one hand, optimizing a multi-technical method for the characterization of organic compounds and traditional lime mortars to use in monumental buildings of antiquity. To illustrate the effectiveness of this methodology it has been applied to a study case, the stucco from mural painting of Maya culture (Ancient Mesoamerica), which has been chosen by the need to continue studying the composition of preparation layers of these stuccos. There are two reasons for this choice: the first one is that knowledge of materials and of execution techniques of these surfaces is providing new data to understand the technological complexity of this culture; and the second one is based on the fact that just this type of research will allow us to know with certainty how these preparation layers were made and, this way, ensure the correct interventions of conservation and restoration. From these considerations, the study conducted establishes a methodological approach that comes from the specialized literature search of geographical and cultural context, the physical (geology and climatology) and biological environment (flora and vegetation) from Yucatan Peninsula (Mexico), getting theoretical knowledge necessary to deal with a detailed description and characterization of the raw materials from the geological environment that were used in the manufacture of the preparation layers from Maya mural painting. The method continues with the use of instrumental analysis techniques such as optical microscopy (OM), polarizing optical microscopy (POM), infrared Fourier transform spectroscopy (FT-IR), x-ray diffraction (XRD), scanning electron microscopy-x-ray microanalysis (SEM-EDX), x-ray microdiffraction (µ-XRD), transmission electron microscopy (TEM) and the optimization of instrumental techniques for analyzing organic compounds, such as gas chromatography/mass spectrometry (GC/MS). On the other hand, the current researches tend to reinforce the idea of incorporating organic components to the cementitious matrix of historical mortars. There is a debate about whether these additives modify the fresh mortar properties and if they also improve the hardened mortar properties. In this study is suggested the development of a method of making lime mortars with an application in the field of restoration, to provide adequate quality control over their constituents. To do this, it has been used an experimental research of air lime mortar paste to which cementitious matrix, two natural organic additives of vegetable origin in different proportions have been incorporated, so changes in its behavior related to the main rheological, hydraulics and physical-mechanical properties of the mortar can be assessed, as ecological and sustainable alternative to non-biodegradable and irreversible synthetic resins, and to ensure greater compatibility with the original materials. / [ES] La presente investigación propone, de un lado, la optimización de un método multitécnica para la caracterización de componentes orgánicos y morteros de cal tradicionales en construcciones monumentales de la antigüedad. Para ejemplificar la eficacia de esta metodología, se ha aplicado a un caso de estudio, los estucos de la pintura mural de la cultura maya (Antigua Mesoamérica), que ha sido elegido por la necesidad de seguir estudiando la composición de las capas de preparación de estos estucos. Existen dos motivos para esta elección: el primero es que el conocimiento de los materiales y de las técnicas de ejecución de estas superficies está aportando nuevos datos para comprender la complejidad tecnológica de esta cultura; y el segundo se basa en que tan sólo este tipo de investigaciones nos permitirán conocer con certeza como se realizaron estas capas de preparación y, de este modo, garantizar las correctas intervenciones de conservación-restauración. A partir de estas consideraciones, el estudio llevado a cabo establece un planteamiento metodológico que parte de la búsqueda de bibliografía especializada del contexto geográfico, del marco cultural, del medio físico (la geología y la climatología) y biológico (la flora y la vegetación) de la Península de Yucatán (México), consiguiendo el conocimiento teórico necesario para afrontar una descripción y caracterización ajustada de las materias primas del entorno geológico que se usaron en la manufactura de las capas de preparación de la pintura mural maya. El método continua con el aprovechamiento de técnicas instrumentales de análisis, como la microscopia óptica (MO), la microscopia óptica de luz polarizada (MOP), la espectroscopia infrarroja por transformada de Fourier (FT-IR), la difracción de rayos-x (DRX), la microscopia electrónica de barrido-microanálisis de rayos-x (SEM-EDX), la microdifracción de rayos-x (µ-DRX), la microscopía electrónica de transmisión (TEM) y la optimización de técnicas instrumentales avanzadas para el análisis de compuestos orgánicos, como la cromatografía de gases/espectrometría de masas (GC/MS). Por otro lado, las investigaciones actuales tienden a reforzar la idea de incorporar componentes orgánicos a la matriz cementante de los morteros históricos. Existe un debate sobre si estos aditivos modifican las propiedades del mortero fresco y si, además, mejoran las propiedades del mortero endurecido. En este estudio se propone la puesta a punto de un método de elaboración de morteros de cal normalizados de aplicación en el campo de la restauración, que permita un adecuado control de calidad sobre sus constituyentes. Para ello, se ha partido de la investigación experimental de morteros de cal aérea en pasta a los que se les ha incorporado en su matriz cementante dos aditivos orgánicos naturales de origen vegetal en proporciones variables, de modo que se puedan valorar las modificaciones de su comportamiento en relación a las principales propiedades reológicas, hídricas y físico-mecánicas del mortero, como alternativa ecológica y sostenible de las resinas sintéticas no biodegradables e irreversibles, y para asegurar una mayor compatibilidad con los materiales originales. / [CA] La present investigació proposa, per una banda, l'optimització d'un mètode multitècnica per a la caracterització de components orgànics i morters de calç tradicionals en construccions monumentals de l'antiguitat. Com exemplicació de l'eficàcia, aquesta metodologia s'ha aplicat a un cas d'estudi, els estucs de la pintura mural de la cultura maia (Antiga Mesoamèrica). L'elecció d'aquest cas d'estudi està motivada per la necessitat de seguir estudiant la composició de las capes de preparació d'aquests estucs. Existeixen dos motius per a això: el primer és que el coneixement dels materials i de les tècniques d'execució d'aquestes superfícies està aportant noves dades per a comprendre la complexitat tecnològica d'aquesta cultura i el segon és que, sols aquesta classe d'investigacions ens permetran conèixer amb certesa com foren realitzades aquestes capes de preparació, i en conseqüència, garantir correctes intervencions de conservació-restauració. A partir d'aquestes consideracions, l'estudi portat a terme estableix un plantejament metodològic que parteix de la recerca de bibliografia especialitzada, aconseguint un coneixement teòric, del context geogràfic, del marc cultural, del medi físic (la geologia i la climatologia) i biològic (la flora i la vegetació) de la Península de Yucatán (Mèxic), necessari per a afrontar la correcta descripció i caracterització de les matèries primeres de l'entorn geològic, utilitzades en la manufactura de las capes de preparació de la pintura mural maia i conseqüentment, per a la correcta interpretació dels estucs procedents dels assentaments arqueològics de les Terres Baixes Maies del Nord (Península de Yucatán, Mèxic) estudiats, mitjançant l'aprofitament de tècniques instrumentals d'anàlisis, com la microscòpia òptica (MO), la microscòpia òptica de llum polaritzada (MOP), l'espectroscòpia infraroja per transformada de Fourier (FT-IR), la difracció de raigs-x (DRX) i la microscòpia electrònica de rastreig-microanàlisis de raigs-x (SEM-EDX), la microdifracció de raigs-x (µ-DRX), la microscòpia electrònica de transmissió (TEM) i l'optimització de tècniques instrumentals avançades, per l'anàlisi de compostos orgànics, com la cromatografia de gasos/espectrometria de masses (GC/MS). Per altra banda, les investigacions actuals tendeixen a reforçar la idea d'incorporar components orgànics als morters històrics a la matriu cimentant. Existeix un debat sobre si aquests additius modifiquen les propietats del morter en estat fresc i si, a més a més, milloren les propietats del morter en estat endurit. En aquest estudi, es proposa la posada a punt d'un mètode d'elaboració de morters de calç normalitzats d'aplicació en el camp de la restauració, que permeti un adequat control de qualitat sobre els seus constituents, a partir de la investigació experimental de morters de calç aèria en pasta amb la incorporació de dos additius orgànics naturals d'origen vegetal, a la seva matriu cimentant, en proporcions variables, per tal de valorar les modificacions del seu comportament en relació a les principals propietats reològiques, hídriques i fisicomecàniques del morter, com alternativa ecològica i sostenible de les resines sintètiques no biodegradables i irreversibles, i per a assegurar una major compatibillitat amb els materials originals. / Guasch Ferré, N. (2016). OPTIMITZACIÓ DE MÈTODES MULTITÉCNICA PER A LA CARACTERITZACIÓ DE COMPONENTS ORGÀNICS I MORTERS DE CALÇ TRADICIONALS DE L'ANTIGUITAT. DESENVOLUPAMENT DE METODOLOGIES EXPERIMENTALS PER A LA SEVA CONSERVACIÓ I RESTAURACIÓ. APLICACIÓ A UN CAS D'ESTUDI: ELS ESTUCS DE LA PINTURA MURAL DE LA CULTURA MAIA (ANTIGA MESOAMÈRICA) [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/61385
546

Multimedia kiosk interface evaluation: an analysis of usage

Boggess, Howard P. 04 March 2009 (has links)
Although the Umultimedia computer kiosk" is a relatively new phenomenon, a great deal of academic research has been conducted on the programming of the systems. Little research has been conducted on the effectiveness of kiosk interface design, however, perhaps due to the lack of a formalized methodology for evaluation. This thesis presents one methodology for the evaluation of graphic components used in the interface of a computer kiosk designed for the United States Forest Service. There are many established conventions for multimedia interface design. Many graphic techniques, such as buttons that change colors and generate an audible click when pressed and "windows" on the screen used for displaying images or text, have become commonplace with the increasing popularity of video games, information kiosks, automated teller machines and automated point of sale systems. This thesis examines the usage patterns of the kiosk by analyzing the sequence of buttons pressed, determines search pattern preferences, the success of a non-standard button is evaluated, and sources of confusion or misunderstanding are identified. This study demonstrates the strengths and weaknesses of both the graphic components and the evaluation methodology, and it provides a foundation for the creation of a formalized approach for the evaluation of computer kiosk interfaces. / Master of Landscape Architecture
547

Biomass Estimation Using the Component Ratio Method for White Oak

DeYoung, Clara 26 August 2014 (has links)
With higher demands on biomass, the ability to accurately estimate the amount in a stand is more important now than ever before. Existing models currently in use by the Forest Inventory and Analysis (FIA) program of the United States Department of Agriculture (USDA) Forest Service include the Component Ratio Method (CRM). However, testing of the CRM models is needed to validate and calibrate them. The objective of this research was to test and develop a system of equations capable of producing consistent volume and biomass estimates for standing trees of commercially important hardwood species in the southeastern United States. Testing and comparing was done through use of new and legacy data to establish component ratios of trees and contrast these results to those from existing models. Specifically, analyses were completed for models of merchantable and whole stem volume, wood densities models and averages, and the component ratios for wood, bark, branches, and foliage. The existing models were then calibrated and adjusted. Results on accuracy and fitted results of updated models are reported, along with testing the effects of applying updated models over the state of Virginia. / Master of Science
548

Scheduling optimal maintenance times for a system based on component reliabilities

Rao, Naresh Krishna 04 May 2006 (has links)
This dissertation extends the work done on single component maintenance planning to a multi-component series system. An attempt is made to develop a function which represents the expected cost rate (cost per unit time) of any maintenance plan. Three increasingly complex cases are considered. The first and simplest case assumes that the component is restored to an “as good as new” condition after a maintenance operation. The second case assumes that an occasional imperfect maintenance Operation may occur. During this period of time, the failure rate of the component is higher. Hence, the likelihood of a failure is greater until the component is properly maintained in a subsequent maintenance operation. The final case assumes that there is some deterioration in the component behavior even after a maintenance operation. Therefore, it is necessary to replace the system at some point in time. Models for all three cases are developed. Based on these models, cost rate functions are constructed. The cost rate functions reflect the cost rates of maintaining a component at a particular time. In addition, the savings obtained through the simultaneous maintenance of components is also accounted for in the cost rate functions. A series of approximations are made in order to make the cost rate functions mathematically tractable. Finally, an algorithmic procedure for optimizing the cost rate functions for all three cases is given. / Ph. D.
549

Fabrication of 3D hybrid scaffold by combination technique of electrospinning-like and freeze-drying to create mechanotransduction signals and mimic extracellular matrix function of skin

Aghmiuni, A.I., Heidari Keshel, S., Sefat, Farshid, AkbarzadehKhiyavi, A. 21 February 2021 (has links)
Yes / Fabrication of extracellular matrix (ECM)-like scaffolds (in terms of structural-functional) is the main challenge in skin tissue engineering. Herein, inspired by macromolecular components of ECM, a novel hybrid scaffold suggested which includes silk/hyaluronan (SF/HA) bio-complex modified by PCP: [polyethylene glycol/chitosan/poly(ɛ-caprolactone)] copolymer containing collagen to differentiate human-adipose-derived stem cells into keratinocytes. In followed by, different weight ratios (wt%) of SF/HA (S1:100/0, S2:80/20, S3:50/50) were applied to study the role of SF/HA in the improvement of physicochemical and biological functions of scaffolds. Notably, the combination of electrospinning-like and freeze-drying methods was also utilized as a new method to create a coherent 3D-network. The results indicated this novel technique was led to ~8% improvement of the scaffold's ductility and ~17% decrease in mean pore diameter, compared to the freeze-drying method. Moreover, the increase of HA (>20wt%) increased porosity to 99%, however, higher tensile strength, modulus, and water absorption% were related to S2 (38.1, 0.32 MPa, 75.3%). More expression of keratinocytes along with growth pattern similar to skin was also observed on S2. This study showed control of HA content creates a microporous-environment with proper modulus and swelling%, although, the role of collagen/PCP as base biocomposite and fabrication technique was undeniable on the inductive signaling of cells. Such a scaffold can mimic skin properties and act as the growth factor through inducing keratinocytes differentiation.
550

A house for a boat

Monday, Nicholas 04 August 2008 (has links)
This thesis is the result of an exploration to develop an architectural series of modular units. It is my position that information regarding site and program are unnecessary when beginning an architectural project. This is clearly demonstrated through my process. In the beginning, these units were developed independently of any program or specific site information. After establishing a series of fundamental architectural ideas, they were used to address a specific program. / Master of Architecture

Page generated in 0.039 seconds