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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.
421

Women Recreating their Lives: Challenges and Resilience in Midlife

Rogers, Linda Peterson 28 April 2000 (has links)
This research explores how midlife women found the strength and resilience that enabled them to rebound and grow as they negotiated significant life challenges in their marriage, and with their children, parents, careers, and health. Using a family resilience framework grounded in systems theory with a feminist perspective, the researcher conducted in-depth interviews with 18 diverse women between the ages of 40 and 60 years in different regions of the United States. The phenomenological method of inquiry allowed the researcher to gather the experiences of midlife women in order to understand the protective processes of resilience for overcoming adversity. Three research questions guided this study: (1) How have women dealt with an adverse experience or challenging transition in their adult married life and where did the strength or resilience they needed to rise above it come from? (2) How did they use their resilience in challenging situations? (3) How did this challenging experience influence their marriage and how was the experience affected by their marriage? Results suggest that the participants' core beliefs facilitated how they made meaning of their struggle and influenced their response to their challenges. The themes they discussed fell into beliefs that were organized as affiliative values, facilitative beliefs and transcendent spiritual beliefs. These belief systems described how they made sense of their challenges. Themes related to the importance of connectedness and relationships also occurred frequently in the narratives of these midlife women as they developed resilience. As expected, marriage was important to the majority of the women as they discussed the importance of emotional support, but their sense of well-being was also greatly influenced by other close relationships in their communities with friends, family, children, and role models. Work and education emerged as significant themes in the women's appraisal of their challenges, beliefs, and connectedness as they described their sense of resilience. Resilience was fostered when these women made connections between their past, present, and future and integrated their experiences, their beliefs, relationships, and resources. / Ph. D.
422

The Development of Models to Identify Relationships Between First Costs of Green Building Strategies and Technologies and Life Cycle Costs for Public Green Facilities

Ahn, Yong Han 07 April 2010 (has links)
Public buildings and other public facilities are essential for the functioning and quality of life in modern societies, but they also frequently have a significant negative impact on the natural environment. Public agencies, with their large portfolios of facilities, have faced considerable challenges in recent years in minimizing their negative environmental impacts and energy consumption and coping with shortages of financial capital to invest in new facilities and operate and maintain existing ones, while still meeting their mission goals. These range from the need to provide a quality workplace for their staff to providing a public service and long term benefits to the public. The concept of green building has emerged as a set of objectives and practices designed to reduce negative environment impacts and other challenges while enhancing the functionality of built facilities. However, the prevailing belief related to implementing green building is that incorporating Green Building Strategies and Technologies (GBSTs) increases the initial cost of constructing a facility while potentially reducing its life cycle costs. Thus, this research deals with optimizing the design of individual facilities to balance the initial cost investment for GBSTs versus their potential Life Cycle Cost (LCC) savings without the need to conduct detailed life cycle cost analysis during the early capital planning and budget phases in public sector projects. The purpose of this study is to develop an approach for modeling the general relationship between investments in initial costs versus savings in LCCs involved in implementing green building strategies in public capital projects. To address the research question, this study developed multiple regression models to identify the relationships between GBSTs and their initial cost premiums, operating costs, and LCCs. The multiple regression models include dummy variables because this is a convenient way of applying a single regression equation to represent several nominal variables, which here consist of initial, operating, maintenance, and repair and replacement costs, and ordinal variables, which in this case are the GBST alternatives considered. These new regression models can be used to identify the relationship between GBST alternatives, initial cost premiums, annual operating costs and LCC in the earliest stage of a project, when public agencies are at the capital planning and budgeting stages of facility development, without necessarily needing to know the precise details of design and implementation for a particular building. In addition, this study also proposes and tests a method to generate all the necessary cost data based on building performance models and industry accepted standard cost data. This statistical approach can easily be extended to accommodate additional GBSTs that were not included in this study to identify the relationship between their initial cost premium and their potential LCC saving at the earliest stage of facility development. In addition, this approach will be a useful tool for other institutional facility owners who manage large facility portfolios with significant annual facility investments and over time should help them minimize the environmental impacts caused by their facilities. / Ph. D.
423

A life cycle cost based methodology for choosing among design alternatives

Brewer, Larry Arthur 27 April 2010 (has links)
A life cycle cost based methodology for choosing among mutually exclusive design alternatives is presented in this study. The methodology places emphasis on the iterative nature of the design process. That is, choosing among design alternatives involves the pairwise comparison of the current design iteration to a "baseline" design. An Equivalent Cost Function provides the cause-effect framework on which the methodology is based. In generating a design alternative, the designer alters design features (cause). These features manifest themselves as design dependent parameters (effect), and for each set of such values, optimal values of design variables are sought. This design development process occurs in the face of design independent parameters, with the final result being a value of equivalent life cycle cost. / Master of Science
424

Chloride Penetration Resistance and link to Service Life Design of Virginia Bridge Decks

Bales, Elizabeth Rose 19 June 2016 (has links)
Reinforced concrete (RC) bridge decks are exposed to chlorides from deicing salts. Chloride ingress in RC initiates corrosion of the reinforcing steel. The high costs of corrosion have sparked interest in service life design of bridge decks. This thesis characterized the exposure conditions of Virginia, including temperature and surface chloride concentration, as well as Virginia concrete mix properties, including initial chloride concentration and chloride migration coefficient. The service life estimations for a case study bridge in Virginia from three service life models were compared. The first model is based on the fib Bulletin 34 Model Code for Service Life Design, the second is a finite element solution of the fib Bulletin, and the third accounts for a time-, temperature-, moisture-, and concentration-dependent apparent diffusion coefficient. A sensitivity analysis was completed on the three models showing that the most important variables in these models are the aging coefficient and surface chloride concentration. Corresponding life cycle cost analyses were completed for plain and corrosion resistant reinforcing steel. This thesis showed that the error function solution underestimates chloride ingress. The life cycle cost analysis of plain and corrosion resistant reinforcing steels show that overestimation of service life leads to underestimation of life cycle costs. / Master of Science
425

Assessing the effect of design for producibility on repairable product life-cycle cost

Sowder, James Loyd 13 October 2010 (has links)
A life-cycle cost evaluation model is presented to assess the effect of design decisions (made in an attempt to induce higher degrees of producibility) upon a product's life-cycle cost. The model provides a measure of effectiveness in terms of an expected annual equivalent total system life-cycle cost for a deployed population of the product being evaluated. Parametric relationships are established between aspects of the product and the level to which the product is designed for producibility. These aspects include areas of cost arising during each phase of the product life cycle. The model limits the number of product design alternatives to three scenarios which are defined as a product designed to be highly, moderately, and less producible. The best of the three design alternatives is selected based upon the life-cycle costs calculated. / Master of Science
426

Design and Reconfiguration of Manufacturing Systems in Agile Manufacturing Environments

Daghestani, Shamil F. 20 April 1999 (has links)
Agile manufacturing has become a topic of great interest over the past several years. The entire domain of modeling and analyzing different types of agile manufacturing environments and systems, however, remain largely unexplored. The objective of this research is to provide fundamental insight into how manufacturing systems should be designed and reconfigured over time in order to cope with different agile manufacturing environments. To achieve this objective, three approaches are developed and integrated into one simulation-based model. The first approach is used to model different agile manufacturing environments. The second approach is used to define various ways in which manufacturing systems can be designed and reconfigured (i.e., design/reconfiguration strategies). The third comprises the cost and objective functions used to measure system performance when different design/reconfiguration strategies are used in different agile manufacturing environments. Based upon the assumptions adopted during this thesis, the experimental work performed suggests that despite the fact that agility incurs high costs, agile manufacturing systems are indeed necessary for certain manufacturing environments in which product life cycles are short yet demand per product type is high. Therefore, it is important in certain manufacturing environments to focus on reconfiguration in short periods of time, even at the expense of higher reconfiguration costs. / Master of Science
427

Biochar amendment as a tool for improving soil health and carbon sequestration in agro-ecosystems

Drew, Sophia Eliza 14 September 2022 (has links)
Conventional farming practices and land-use conversions drive carbon out of soil and into the atmosphere, where it contributes to climate change. Biochar, a soil amendment produced by pyrolyzing organic feedstocks under low-oxygen conditions, is a promising tool to restore soil carbon and draw down atmospheric carbon dioxide. Biochar has received considerable attention from scientists, growers, and environmentalists in the last 20 years, but there is still a gap between academic research and practical recommendations on biochar production and application that are relevant to small-scale growers. Here I present the results from two complementary studies that demonstrate the utility of local-scale biochar systems and provide some recommendations for those looking to work with biochar. The first study sought to determine the impact of biochar amendments on soil carbon and nutrient retention on three working farms across a variety of soil types, cropping systems, and climates in the United States. The effect of biochar amendment depended on initial soil characteristics and the properties of the biochar applied. Biochar amendments increased soil carbon in all three sites and increased soil nitrogen at two of the three. In this study pyrolysis conditions appeared to be as important as local soils and climate influences on the efficacy of biochar treatments. The second study was a life cycle assessment using SimaPro software to quantify the carbon balance and global warming potential of biochar produced from three local feedstocks (softwood, hardwood, and hay) applied to pasture soils in Southwest Virginia. Feedstock type, pyrolysis gas yield, and transportation distance significantly contributed to variation in the carbon balance of each agro-ecosystem. Biochar made from softwood lumber scraps performed best, with the highest net carbon storage and lowest global warming potential, followed by biochar made from hardwood scraps. Hay biochar performed worst, with positive carbon emissions (i.e., more carbon released than stored over its life cycle) in most scenarios tested, mainly because of its low biochar yield and the carbon emissions associated with agronomic production and transportation. Together these studies demonstrate the potential of local biochar systems to improve both soil health and carbon sequestration, and reinforce how important it is to know the characteristics of the soil and the production history and properties of the biochar being applied in order to meet soil health and carbon sequestration goals. / Master of Science / Conventional farming practices break down organic material in the soil, which decreases the capacity of soils to sustain crop growth and contributes to climate change as the soil releases carbon dioxide and other greenhouse gasses into the atmosphere. Biochar, or charcoal that is deliberately incorporated into soil, is gaining popularity among farmers, gardeners, and climate scientists for its ability to improve soil health and draw carbon out of the atmosphere to create stable long-term pools of carbon underground. Unfortunately, much of the research on biochar does not translate easily into recommendations for growers and land-managers to make and use biochar. Here I discuss the results from two studies examining the effect of biochar on soil health and carbon sequestration on local scales. In the first experiment I analyzed soil samples shared by farmers in New Mexico, Minnesota and Virginia who applied locally-sourced biochar to their soils. I found that the initial characteristics of the soil and of the biochar affected how the biochar application changed agriculturally-relevant soil properties. In general, biochar improved soil carbon and nitrogen levels, had mixed effects on soil pH depending on the biochar's pH, and had no effect on electrical conductivity (a measure of soil salinity). The second study was a life cycle assessment that quantified and compared greenhouse gas emissions of three different types of biochar, from feedstock harvest to biochar application to soil. I found that the type of feedstock used to make biochar, the amount of gas emitted during the conversion process, and the distance the feedstocks and biochar were transported all played a role in the overall carbon balance of the life cycle. The biochar made from softwood scraps performed best from a carbon storage perspective, followed by biochar made from hardwood. These two biochars tended to return more carbon to the soil than they emitted over their life cycle. The biochar made from hay performed worst, and emitted more carbon than it stored in most of the scenarios I tested. Together these studies show the potential of local biochar systems to improve both soil health and carbon sequestration and reinforce how important it is to be familiar with the soil and the production history and properties of the biochar being applied in order to meet soil health and carbon sequestration goals.
428

An Analysis of Scientific Learning in Growing Silkworms

Roberts, Odessa Hensley 08 1900 (has links)
The purpose of this study is to give the results of a science experiment in an elementary grade in raising silkworms. The purpose of the experiment was not to learn the laws and principles of science, but to determine whether the life cycle of the silkworm would create a greater interest in the field of science.
429

Sustainability assessment of active packaging incorporating nanomaterials

Zhang, Hai 16 November 2017 (has links)
Tesis por compendio / Packaging plays an important role in ensuring food safety and quality. The development antimicrobial packaging enables actively inhibiting/killing the spoilage microorganisms, and thus extending food product's shelf life. Generally, 50% shelf life extension is possible. The interest for using metallic nanoparticles in active packaging derives from its superior antimicrobial efficacy and no negative impact on the food sensory properties. In this thesis, the packaging material of concern is a PLA (Polylactic Acid) coated paper incorporating zinc oxide nanoparticles (ZnO NPs) in the coating layer. The material was characterized and its antimicrobial activity was evaluated. The SEM images show that the nanoparticles were homogenously distributed across the surface thanks to its surface modification. Antimicrobial assay indicates that the active material was effective in inactivating E. coli and S. aureus. Furthermore, E. coli was found to be more susceptible to this type of agent, showing 3.14 log reduction for 0.5 wt% agent loading in the PLA coating layer. This result was compared across the publications using the same agent for treating both Gram-positive and Gram-negative microorganisms. The discrepancy between the results can be explained by the fact that ZnO nanoparticles have multiple action mechanisms, and different antimicrobial testing methods may activate part of the action mechanisms. On the other hand, recyclability is regarded as an important attribute for paper-based packaging material, as it enables to conserve the resources and reduce the environmental impacts. Accordingly, when it comes to the nano-enabled paper packaging material, recyclability should be maintained. In this case, a recyclability test was carried out in a lab-scale paper recycling line. The protocol was based on a method adapted from the ATICELCA MC501-13, which enabled to recover over 99% of the solids material. The mass balance result indicates that 86%-91% zinc oxide nanoparticles ended up in the rejected material stream, mostly embedded within the polymer coating; whereas 7%-16% nanoparticles ended up in the accepted material stream. Besides, the tensile strength of the recycled handsheets suggests that the nano-enabled coating had no negative impacts on the recovered fibre quality. Active packaging plays a positive role in reducing food losses. If food and packaging are considered as a whole system, its overall environmental impact can be justified by incorporating the food loss reduction due to the application of active packaging. The LCA calculation shows that a breakeven point can be easily achieved for the case of red meat products of high environmental impact. / El envase juega un papel importante asegurando la seguridad y calidad de los alimentos. El desarrollo de envases activos, especialmente envase antimicrobiano, permite inhibir o matar los microorganismos causantes del deterioro de los alimentos, alargando por tanto su vida útil. De forma general es posible extender la vida útil de los alimentos en un 50%. El interés por el uso de nanopartículas metálicas en el envasado activo se deriva de su gran efectividad antimicrobiana sin causar un efecto negativo en sus propiedades sensoriales. En la presente tesis, se ha desarrollado un papel recubierto de PLA (ácido poliláctico) con nanopartículas de óxido de zinc (ZnO NPs) incorporadas en la capa de recubrimiento. Se ha caracterizado el material y se ha evaluado su capacidad antimicrobiana. Las imágenes obtenidas mediante SEM muestran que las nanopartículas fueron distribuidas a lo largo de la superficie gracias a su modificación. Los ensayos de efectividad antimicrobiana indicaron una actividad del material frente a E. coli y a S. aureus. Además, E. coli resultó ser más susceptible a este agente activo incorporado al 0.5 % en peso en el recubrimiento de PLA, mostrando una reducción de 3.14 log. Este resultado fue comparado con publicaciones donde se emplearon los mismos agentes activos para frente a microorganismos Gram-positivos y Gram-negativos. Las discrepancias encontradas entre los resultados pueden deberse a que las nanopartículas de ZnO tienen múltiples mecanismos de acción, y los diferentes métodos de ensayo poder estimular parte de estos mecanismos. Por otra parte, el reciclado juega un importante papel en la conservación de los recursos y en la reducción de los impactos medioambientales. Por tanto, cuando se trata de un material de envase de papel con sustancias de tamaño nano, el reciclado debe tratarse adecuadamente. El ensayo de reciclabilidad fue llevado a cabo a escala laboratorio en una línea de reciclado de papel. El protocolo de ensayo se basó en el método adaptado de ATICELCA MC501-13, permitiendo una recuperación del 99% de material sólidos. Los resultados del balance de materia indicaron que el 86%-91% de las nanopartículas de óxido de zinc llegaron al flujo de material de rechazo, principalmente mezclado en el recubrimiento polimérico. Además, los resultados de tracción de las láminas recicladas sugieren que el recubrimiento con partículas nano no tiene un efecto negativo sobre la calidad de la fibra recuperada. El envase activo juega un papel positivo en la reducción de los residuos alimentarios. Como resultado del uso del envase activo, considerando el envase y el alimento como un todo, el impacto ambiental sobre este sistema completo puede ser compensado por la reducción de pérdidas de alimentos. El cálculo LCA muestra que el punto de equilibrio se puede conseguir fácilmente en el caso de productos de carne roja de elevado impacto ambiental. / L'envàs té un paper prou important en la seguretat i la qualitat del aliments. El desenvolupament dels envasos actius, especialment l'envàs antimicrobià, el qual permeteix l'inhibició o mort dels microorganismes que produeixen el deteriorament dels aliments i, per tant, allargant la seua vida útil. De manera general, es possible l'allargament de la vida útil dels aliments en un 50%. L'interès per la utilització de nanopartícules metàl·liques en l'envasat actiu es deriva de la seua gran efectivitat antimicrobiana sense produir un efecte negatiu en les seus propietats sensorials. En aquesta present tesis, s'ha desenvolupat un paper recobert de PLA (àcid polilàctic) amb nanopartícules d'òxid de zinc (ZnO NPs) incorporades a la capa de recobriment. S'ha caracteritzat el material i s'ha avaluat la seua capacitat antimicrobiana. Les imatges obtingudes per mitjà del SEM mostren que les nanopartícules foren distribuïdes en tota la superfície gràcies a la seua modificació. Els assajos d'efectivitat antimicrobiana varen indicar una activitat del material front a E.coli i a S. aureus. A més, E. coli va resultar ser més susceptible a aquest agent actiu incorporat al 0.5 % en pes en el recobriment de PLA, mostrant una reducció de 3.14 log. Aquest resultat va ser comparat amb publicacions on es van emprar els mateixos agents actius front a microorganismes Gram-positiu i Gram-negatiu. Les discrepàncies trobades entre els resultats poden deure's a que les nanopartícules de ZnO tenen diversos mecanismes d'acció, i els diferents mètodes d'assaig poder estimular part d'aquestes mecanismes. Per altra banda, el reciclatge també té un paper important en la conservació dels recursos i en la reducció dels impactes mediambientals. Per tant, quan es tracta d'un material d'envàs de paper amb substàncies de la grandària 'nano', el reciclatge ha de tractar-se adequadament. El assaig de reciclabilitat va ser dut a terme a escala de laboratori en una línia de reciclatge de paper. El protocol de l'assaig es va basar en el mètode adaptat d'ATICELCA MC501-13, permetent una recuperació del 99% del material sòlid. Els resultats del balanç de matèria van indicar que el 86-91% de les nanopartícules d'òxid de zinc varen arribar al fluix material de rebuig, principalment mesclat en el recobriment polimèric. A més, els resultats de tracció de les làmines reciclades suggereixen que el recobriment amb nanopartícules nano no tenen un efecte negatiu sobre la qualitat de la fibra recuperada. L'envàs actiu juga un paper positiu en la reducció dels residus alimentaris. Com a resultat de l'ús de l'envàs actiu, considerant l'envàs i l'aliment com un tot conjunt, l'impacte ambiental sobre aquest sistema complet pot ser compensat per la reducció de pèrdues d'aliments. El càlcul LCA mostra que el punt d'equilibri es pot aconseguir fàcilment en el cas de productes de carn roja d'elevat impacte ambiental. / Zhang, H. (2016). Sustainability assessment of active packaging incorporating nanomaterials [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/75348 / Compendio
430

Strategic Life-Cycle Modeling and Simulation for Sustainable Product Innovation

Ny, Henrik January 2009 (has links)
Many specific methods and tools have been developed to deal with sustainability problems. However, without a unifying theory it is unclear how these relate to each other and how they can be used strategically. A Framework for Strategic Sustainable Development (FSSD) is being developed to cover this need for clarity and structure. It includes backcasting from a principled definition of sustainability as a key feature. The aim of this thesis is to study how this framework can guide the use and improvement of detailed methods and tools, in particular to support sustainable product innovation (SPI). First, a new strategic life-cycle management approach is presented, in which the selection of aspects to be considered are not based on typical down-stream impact categories, but on identified major violations of sustainability principles. Ideas of how this approach can inform various specific methods and tools are also presented, as a basis for an integrated “toolbox” for SPI. As part of such, a new “template” approach for sustainable product development (TSPD) is developed through a sustainability assessment case study of TVs. That study indicates that this approach can create a quick and strategically relevant overview of critical sustainability aspects of a product, as well as facilitate communication between top management, product developers and external stakeholders. Based on such an assessment, it is sometimes necessary to go deeper into details, including the use of specific engineering methods and tools. To facilitate a coordinated assessment of sustainability aspects and technical aspects, an introductory procedure for sustainability-driven design optimization is suggested trough a water jet cutting case study. Equally important, to get a breakthrough for SPI, it is essential to integrate sustainability aspects into the overall decision-making process at different levels in companies. An approach to assessing sustainability integration in strategic decision systems is therefore also developed through a case study involving several companies. Finally, the integration between the FSSD and general systems modeling and simulation (SMS) is discussed and tested in another water jet cutting case study. It is shown feasible to start with the FSSD to create lists of critical flows and practices, ideas of long term solutions and visions, and a first rough idea about prioritized early investments. After that, SMS can be applied to study the interrelationships between the listed items, in order to create more robust and refined analyses of the problems at hand, possible solutions and investment paths, while constantly coupling back to the sustainability principles and guidelines of the FSSD. This research shows that the combination of the FSSD with detailed methods and tools cohesively provides decision-makers with both a robust overview and, when needed, a more coordinated and effective detailed support. To utilize its full potential, this approach should now be integrated into decision processes, software and manuals for SPI.

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