• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 46
  • 11
  • 9
  • 6
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 110
  • 110
  • 18
  • 18
  • 16
  • 15
  • 13
  • 13
  • 12
  • 12
  • 12
  • 11
  • 11
  • 10
  • 10
  • 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.
71

Effects of Environmental Factors on Construction of Soil-Cement Pavement Layers

Michener, John E. 24 September 2008 (has links)
The specific objectives of this research were to quantify the effects of certain environmental factors on the relative strength loss of soil-cement subjected to compaction delay and to develop a numerical tool that can be easily used by engineers and contractors for determining a maximum compaction delay time for a given project. These objectives were addressed through extensive laboratory work and statistical analyses. The laboratory work involved testing an aggregate base material and a subgrade soil, each treated with two levels of cement. Environmental factors included in the experimentation were wind speed, temperature, and relative humidity, and three levels of each were evaluated in combination with varying compaction delay times. The primary response variables in this research were relative compaction and relative strength. The findings indicate that relative strength is sensitive to variability among the selected independent variables within the ranges investigated in this research, while relative compaction is not. Inferring relative strength from relative compaction is therefore not a reliable approach on soil-cement projects. Consistent with theory, higher wind speed, higher air temperature, lower relative humidity, and higher compaction delay time generally result in lower relative strength. With the nomographs developed in this research, the maximum delay time permitted for compaction of either a base or subgrade material similar to those tested in this research can be determined. Knowing in advance how much time is available for working the soil-cement will help contractors schedule their activities more appropriately and ultimately produce higher quality roads. When acceptable compaction delays are not obtainable due to adverse environmental conditions, a contractor may consider using set retarder, mixing at water contents above OMC, or constructing at night as possible solutions for achieving target relative strength values.
72

Non-target Effects of Genetically Modified Trees

Blomberg, Patrik January 2007 (has links)
To date, few studies have focused on the effects of genetically modified trees (GM trees) on the environment. One concern with GM trees is that they may have unanticipated effects on non-target organisms, i.e. effects on organisms that are not direct targets of the genetically modified trait. The main objective of this thesis was to study potential non-target effects from the interaction between GM trees and natural enemies, including phytopathogens and herbivorous insects. To study this I used a system consisting of GM trees featuring changes in growth-related characteristics, and naturally occurring enemies. The GM trees used were the aspen hybrids Populus tremula x tremuloides: one unmodified wild type clone T89 (control) and transgenic lines with altered expression of gibberellin (GA 20-oxidase), sucrose (SPS) or pectin (PME); and Populus tremula x alba: one unmodified wild type clone INRA 717-1-B4 (control) and lines modified to suppress the activity of the enzymes in the lignin biosynthetic pathway, i.e. CAD, COMT, CCR or CCoAOMT. The natural enemies used were the parasitic phytopathogens Melampsora pinitorqua, M. populnea and Venturia tremulae, and the herbivorous leaf-beetle Phratora vitellinae. To address this question inoculation experiments, feeding preference experiments, analyses of secondary chemistry and field inventories were performed. The results of the studies showed that the GM trees significantly affected the interaction with the natural enemies, both in the laboratory as well as in the field. For instance, both M. pinitorqua and V. tremulae showed an altered disease incidence on the GM trees of P. tremula x tremuloides compared to the unmodified wild type T89, where all tested transgenic lines exhibited altered susceptibility to the pathogens. However, there were also differences in aggressiveness to the aspens depending on pathogen population. The results from the field inventory showed that lines within all tested transgenic construct, COMT, CAD, CCoAOMT and CCR of P. tremula x alba differed significantly from the wild type INRA 717-1-B4 in susceptibility to M. populnea. In addition, the susceptibility to the rust also differed significantly between lines carrying the same transgenic constructs. Furthermore, we found that overexpression of SPS in P. tremula x tremuloides, unintentionally induced changes in plant secondary chemistry, where the GM-line SPS33A exhibited the largest deviation from the wild type T89 in contents of plant phenolics and nitrogen, and that these changes coincide with a concurrent decrease in herbivory by P. vitellinae on this line. I argue that the altered interactions are the result of physiological changes in the trees. They can originate from direct effects i.e. altered expression of the modified trait, indirect effects of the genetic modification process e.g. pleiotropy, or effects from the transformation process e.g. position effects, to which the tested natural enemies respond. The result stresses the importance of further research on the causes and mechanisms responsible for the altered interaction between GM trees and non-target organisms, as well as evaluating the potential environmental effects of cultivation of GM trees in the field. Such research will require collaboration between researchers from different disciplines, such as plant ecology and physiology, functional genomics, proteomics and metabolomics.
73

Development of an Environment-Accident Index : A planning tool to protect the environment in case of a chemical spill / Utveckling av Miljöolycksindex : Ett planeringsverktyg för att skydda miljön i händelse av kemikalieolycka

Scott Andersson, Åsa January 2004 (has links)
The increasing mass and complexity of chemicals being produced and transported has resulted in more rigorous demands on both authorities as well as chemical-handling industries to assess the risks involved. The Environment-Accident Index (EAI), has been proposed as a planning tool created as an equation in which chemical properties (variables describing the chemical involved) are combined with site-specific properties (variables describing the accident site). The EAI is intended to facilitate assessment of the environmental effects related to chemical accident scenarios and hence assist the organisation of preventative programs. The main objective of the work described in this thesis was to evaluate, develop and improve the proposed EAI. The steps involved in the development process included I) evaluation of the feasibility of the EAI approach, II) selection of a representative and diverse set of chemical accidents to be used in the development III) the use of questionnaires and expert judgements to develop response values for environmental effects of a chemical accident, and IV) to create a new EAI model using multivariate modelling (PLS). The EAI approach proved to be useful in the work to protect the environment in case of a chemical accident. A representative set of accidents was selected by means of statistical multivariate design (PCA) based on assembled data related to a set of 55 chemical accidents. The selection generated a set of accidents representing a diverse spectrum of chemical accident scenarios. To develop a measure of environmental effects of the chemical accidents i.e. responses, an expert panel was asked to judge their environmental effects (such as effects on animal life in the aquatic or terrestrial environment). The results showed that the judgements give a rough estimate of environmental effects that could be used as responses in the development of the EAI. The developed responses were then related to the chemical and site-specific properties to create a new EAI model. This resulted in a PLS-based EAI connected to a new classification scale. The advantages of the new EAI are that it can be calculated without the use of tables; it can estimate the effects for all included responses, and make a rough classification of chemical accidents according to the new classification scale. Finally, the new EAI is a more stable model than the previously proposed EAI, and it is founded on a valid base of accident scenarios, making its use for a variety of chemicals and situations more reliable since it covers a broader spectrum of accident scenarios. The new EAI can be expressed as a regression model to facilitate calculation of the index for people that do not have access to PLS. The highest priorities for further refining the new EAI in the future are: external validation of the EAI; further refinement of the formula’s structure; adjustment of the new classification scale; and real-life evaluation of the EAI.
74

Åkers Sweden AB - Outbound Logistics : Reduction of Environmental Effects / Åkers Sweden AB - Utgående Distribution : Reducering av miljöpåverkan

Gustafsson, Anders, Larsson, Carina, Sundström, Henric January 2009 (has links)
Summary Environmental issues have become increasingly more important the last decade. It is of great importance to reduce emissions of green house gases (GHG) and the transport sector contributes to a large part of GHG emissions. The transport sector is the only sector that actually has increased the emissions during the last decade. This is a result of a growing economy and an increased demand of both carriages of passengers as well as freight transports. To reduce GHG emissions there is a need of smart, effective logistics solutions and new technologies. This thesis will contain a review of Åkers Sweden AB’s outbound logistics of rolls. The aim of this thesis is to identify environmental improvements without increasing further costs. A questionnaire for environmental evaluation of transport suppliers will also be developed in this thesis. Initial question formulations of this thesis are:   1. What are the environmental effects of the different modes of freight transports that are used in the case of Åkers Sweden AB? Are there any environmental improvements possible to establish without increasing costs? 2. How can distributors be evaluated regarding environmental effects?   Emissions and energy use of Åkers Sweden AB’s transports is calculated with the calculation model NTMcalc version 1.9.9. This model is developed by the Network for Transport and Environment (NTM). Examined modes of transport are road, rail and sea transports. Both theory and result in this thesis demonstrate that rail transports should be preferred to road transports from an environmental point of view. A disadvantage of rail transports is longer transport time in most cases. Longer transport time contribute to higher capital cost of goods during transit. Another disadvantage is that rail transports are limited between terminals or that customers have an industrial railway track. That leads to an increased need of reloading and handling costs. Potential alternative with less impact on the environment has been developed. This involves less impact than current alternative. The new alternative will decrease freight costs by 37 %. However, an increased capital cost by 84 % has been identified due to additional transportation time that is required for the alternative suggested. Transport costs are poorly connected to the real cost on the society. Governments throughout the world need to encourage transport buyers to choose more environmentally adapted alternatives by using management control measures. Also, a questionnaire for environmental evaluation of transport suppliers has been developed. It contains questions of the environmental organisation of the company, how they work with education of staff and reporting of environmental effects. / Sammanfattning Under senare tid har miljöfrågor fått en alltmer framträdande roll i samhällsdebatten. Det är av största vikt att reducera alla utsläpp av växthusgaser och transportsektorn står för en betydande del av dessa. Transportsektorn är den enda samhällssektorn som ökat utsläppen av växthusgaser under senare år. Detta till följd av en växande ekonomi och ett ökat behov av både person- och frakttransporter. För att reducera utsläppen krävs smarta, effektiva lösningar och ny teknologi. Detta examensarbete kommer att innehålla en fördjupning av Åkers Sweden AB:s utgående distribution av valsar. Målet är att försöka hitta en distributionslösning som är mer miljövänlig än nuvarande alternativ, men samtidigt inte dyrare. Även ett förslag till miljöbedömning av transportleverantörer kommer att utvecklas i detta examensarbete. Detta arbete syftar att svara på följande frågeställningar:   1. Vilken miljöpåverkan har de olika typer av frakttransporter som används av Åkers Sweden AB? Kan ett mer miljövänligt alternativ utvecklas utan att kostnaderna ökar? 2. Hur kan transportleverantörer utvärderas ur ett miljöperspektiv?   Utsläpp och energiförbrukning vid Åkers Sweden AB:s transporter beräknades med hjälp av kalkylverktyget NTMcalc version 1.9.9. Denna modell är utvecklad av Nätverket för Transporter och Miljön (NTM). De transportslag som undersöks är väg- sjö- och järnvägstransporter. Både teori och resultat i denna rapport visar att järnvägstransport bör föredras ur ett miljöperspektiv framför vägtransport. Nackdelen med järnvägstransporter är att de oftast har en längre transporttid under framförallt kortare transporter. En längre transporttid ger högre kapitalbindning i produkter under transport. En annan nackdel är att järnvägstransporter är bundna mellan terminaler eller är beroende av att kunden har industrispår. Därmed krävs omlastning vilket leder till att hanteringskostnader ökar. I detta examensarbete har ett mer miljövänligt alternativ har utvecklats. Detta alternativ har en betydligt mindre miljöpåverkan än i nuvarande situation. Fraktkostnaden minskar med 37 % i det nya alternativet. Eftersom transporttiden ökar, stiger kapitalkostnaden för det nya alternativet med 84 %. Transportkostnader speglar sällan den totala kostnaden de har för samhället. Regeringar runt om i världen behöver med hjälp av ekonomiska styrmedel uppmuntra transportköpare att välja ett miljövänligare alternativ. Ett formulär för miljöbedömning av transportleverantörer har även utvecklats. Detta innehåller frågor kring hur företaget arbetar med miljöorganisation, utbildning av personal och rapportering av miljöpåverkan.
75

Institutionalized Environments and Information Security Management: Learning from Y2K

Hassebroek, Pamela Burns 02 July 2007 (has links)
The successful elimination of the Y2K vulnerability from the information technology (IT) systems of a large, complex critical sector organization provided a model to study how organizations contend with problems affecting the security of electronically stored and transmitted information, and how context influences their solutions. This dissertation proposed that the institutionalized environments of sub-unit business areas influenced compliance solutions during the Year 2000 Program process at Delta Air Lines, Inc. The investigation applied rival organization theories. A comparative case study method was employed to explain the Y2K compliance solutions of four business areas as embedded sub-cases. Data for the study were the Delta Year 2000 Program archive, and personal interviews with individuals related to the Delta Year 2000 Program. Data analysis revealed characteristics of both the institutional and the rational-contingency models. Case results showed that: * A positive relationship among entities in the sectoral environment benefited the air transportation field in addressing the Y2K problem. In this cooperative setting, addressing common issues in one place helped a vast network of related organizations. Recognizing that all were stakeholders made it work. * Business area decisions were influenced by the institutionalized environments of their respective fields. * The Year 2000 Program team lacked awareness that the Y2K bug was an information security issue. * In the process of eliminating the Y2K bug from the Delta systems, new vulnerabilities were introduced. While tradeoffs are always required among security, functionality, and efficiency within the IT structures and systems of the present time, this negative effect might have been anticipated; but it was not. * The success of this complex, short-term project at Delta underscored the importance of leadership, understanding of IT, vision, motivation, IT skills, understanding of assets, and appropriate strategy. The Delta case study contributes to the fields of information security and organization studies. Results have implications for policymaking and for future research in the field of information security.
76

Diel Mediated Populus balsamifera Transcriptome Components Test the Impacts of Artificial Nighttime Lighting

Skaf, Joseph 27 November 2012 (has links)
Artificial nighttime lighting (ANL) is known to adversely affect animals, but little is known what the consequences are to plants. Two genotypes of Populus balsamifera, a common urban tree, were used to investigate how ANL impacts plants. While the two genotypes varied in their physiological sensitivity to ANL, poorer levels of net leaf carbon assimilation compared to control samples suggested that ANL perturbed the perception of time of day for these plants. Gene set analysis on a subset of PopGenExpress microarray samples identified time of day specific processes in P. balsamifera, and a set of candidate ANL-sensitive genes were identified from these. Transcript measurements from the two genotypes revealed that ANL affects plants at the molecular level, for the diel cycling of the putative ANL-sensitive genes was perturbed. Together, these results suggest that ANL affects plants at the physiological and molecular level by perturbing their perception of time of day.
77

Diel Mediated Populus balsamifera Transcriptome Components Test the Impacts of Artificial Nighttime Lighting

Skaf, Joseph 27 November 2012 (has links)
Artificial nighttime lighting (ANL) is known to adversely affect animals, but little is known what the consequences are to plants. Two genotypes of Populus balsamifera, a common urban tree, were used to investigate how ANL impacts plants. While the two genotypes varied in their physiological sensitivity to ANL, poorer levels of net leaf carbon assimilation compared to control samples suggested that ANL perturbed the perception of time of day for these plants. Gene set analysis on a subset of PopGenExpress microarray samples identified time of day specific processes in P. balsamifera, and a set of candidate ANL-sensitive genes were identified from these. Transcript measurements from the two genotypes revealed that ANL affects plants at the molecular level, for the diel cycling of the putative ANL-sensitive genes was perturbed. Together, these results suggest that ANL affects plants at the physiological and molecular level by perturbing their perception of time of day.
78

Variation in wild stocks of the freshwater prawn Macrobrachium australiense (Holthuis, 1950): Environmental influence on external morphology.

Dimmock, Amanda January 2004 (has links)
Macrobrachium australiense is a common freshwater prawn found throughout most of eastern and inland Australia. Debate has been ongoing on the systematics of this species due to high morphological variation: past studies have relied on external morphology assessments to describe genetic relationships between populations. An individual's morphological phenotype results however, from an interplay of genetic factors, environmental, and interactions between genes and the environment. The current study examined the strength of genetic constraint on morphological traits in this species. Examination of over 1000 M. australiense museum specimens collected from across the species' extensive natural range, documented high phenotypic variation with no regional pattern of variation. Within regions, 88% of variation in morphological traits in mature males and juveniles was present between local rivers. Therefore, morphological variation is not structured at the regional level. If there is a strong genetic base to morphological variation then populations in a single river system must be evolving essentially in isolation. More intensive sampling within a single river system demonstrated high morphological variation in 600 M. australiense individuals from 18 populations within a geographically connected system. Populations separated by as little as 1km showed significant morphological differences in 50% of mature male traits. If morphological variation is primarily genetically based, then populations within a river system were evolving independently at a very fine spatial scale. This hypothesis was tested by breeding morphologically divergent populations of M. australiense in a controlled environment to isolate genetic influences on morphological variation. Low heritability for morphological traits in five divergent populations raised under identical environments established that there is no strict genetic control on morphological variation in these M. australiense populations. Morphologically homogenous offspring resulted from wild parents that had exhibited significant differences at 73% of traits examined. Therefore, the fundamental assumption that morphological variation in M. australiense is dictated by strict genetic control is not supported in these representative populations. Moreover, significant variation in 41% of morphological traits was produced by raising a single population at different environmental temperatures (28oC and 22 oC). A single homogenous stock of M. australiense should not produce morphologically divergent offspring if genetic factors are the major influence of phenotypic expression. Crossing of pure line divergent stocks resulted in hybrid offspring with significant differences in 50% of female morphological traits, whereas male offspring varied for only 31% of morphological traits. This result suggests that female morphological expression is affected more strongly by genetic factors than male offspring in this trial. The growth and maturation of external morphological traits during development in M. australiense is under limited genetic constraint, especially in the later phases of growth. Only 17% of traits varied between juvenile stocks in the last three months of development when individuals were exposed to identical environmental conditions. Maturation size was homogenous, except for females in the absence of maturing males in divergent stocks exposed to identical environmental conditions. Females were much larger in size and shape of morphological traits in the absence of mature males in the population. Thus environmental factors strongly influence phenotypic expression of external morphology in M. australiense. Past problems with the taxonomy of this species are therefore understandable as many important traits used in systematics appear to be under limited genetic control. Past evolutionary studies based on morphological diversity in this species therefore may be unreliable as the traits used to identify divergent forms may not provide a true reflection of genetic divergence.
79

Conceito de embarcações adaptadas à via aplicado à navegação fluvial no Brasil. / Waterway adapted ships concept applied on Brazilian inland navigation.

Carlos Daher Padovezi 03 October 2003 (has links)
É elaborada uma proposta de procedimentos de projetos de comboios fluviais adaptados às condições existentes das vias navegáveis, a partir de uma visão ampliada da necessidade de obtenção de menores custos de transporte, com níveis adequados de segurança e de respeito ao meio ambiente. Uma análise das inter-relações técnicas entre hidrovias e embarcações, assim como dos condicionantes e implicações do conceito de embarcações adaptadas às vias navegáveis, orientou a elaboração do modelo. Este foi estruturado em módulos, com o objetivo de reproduzir, um a um, os fatores mais importantes que influenciam a eficiência, a segurança e o nível de interferência ambiental do transporte de cargas por comboios. Um programa computacional foi desenvolvido como instrumento de aplicação do modelo, consolidando os procedimentos propostos para a escolha das melhores alternativas de projeto e de operação de comboios. Resultados experimentais com comboios em escala real e com modelos em tanques de provas, foram utilizados para validação dos procedimentos adotados. Dados de acidentes com comboios em várias hidrovias do mundo foram utilizados como bases para avaliações de risco. O modelo foi aplicado aos casos de transportes de soja pela hidrovia Tietê-Paraná e pelo rio Araguaia, exemplificando as formas de análise e de escolha das alternativas de soluções de projeto. Ao final, os resultados obtidos comprovaram a utilidade da adoção de um enfoque mais abrangente do processo de projeto de comboios fluviais. / It is proposed a procedure model for design of barges push-tow adapted to waterway actual conditions, with the purpose of minimize transportation costs but always making verifications of navigation safety and ambient interferences levels. An analysis of inter-relations on inland waterways and cargo ships and, also, detailed conditionings and implications of waterway adapted ships concept, was used for model elaboration. It was structured in blocks to reproduce, one to one, the most important factors that modify efficiency, safety and environmental interference levels of barges push-tow cargo transportation. A computational program was developed to consolidate the proposed model and to apply procedures to choose best design and operational alternatives. Results of full scale and towing tank tests with push-tows were used to verify the mathematical and semi-empirical models. Barges push-tows accidents data from waterways of the world was used as risk model basis. To evaluate its effectiveness, the model was applied to bulk grain transportation cases by Tietê-Paraná waterway and by Araguaia river. The results shows that the special emphasis on three factors (efficiency, safety and ambient) improves the quality of barges push-tow design process.
80

Influências socioeconômicas do extrativismo e da silvicultura nos municípios de Formosa da Serra Negra e Sítio Novo - MA / Socioeconomic influences of the forest exploratation and silviculture in development from the municipal districts form Formosa da Serra Negra and Sitio Novo - MA

Aurélio Oliveira dos Santos 10 December 2015 (has links)
A região sudoeste do estado do Maranhão teve um crescimento econômico expressivo após os anos 1990 com a chegada de grandes indústrias. A passagem por esta região da Ferrovia dos Carajás, pela qual a Companhia Vale do Rio Doce transporta o minério da Serra dos Carajás para o porto de Itaqui localizado na capital Maranhense, fez com que inicialmente indústrias siderúrgicas se instalassem na cidade de Açailândia que fica às margens da mencionada ferrovia; e por último no ano de 2013 uma grande fábrica de papel e celulose fosse inaugurada na cidade de Imperatriz. Esses empreendimentos impactaram na economia de vários municípios do entorno destas duas cidades, pois muitas áreas de terras até então utilizadas na agropecuária foram adquiridas e plantadas com eucalipto para suprir carvão e celulose, duas matérias primas essenciais a estas indústrias. Por estas razões, este estudo busca compreender as influências socioeconômicas do extrativismo e da silvicultura nos municípios de Formosa da Serra Negra e Sítio Novo MA, dois recortes tipicamente rurais da região maranhense das serras que foram alcançados por estas modalidades de extrativismo a partir do ano 2000. Trata-se de uma pesquisa bibliográfica e documental com abordagem qualitativa na qual com o uso do método comparativo se fez análises de indicadores socioeconômicos como: população, PIB, produção extrativista, IDHM, IDM e Índice de Gini destes dois municípios, buscando identificar ocorrência de desenvolvimento nesses locais, usando como parâmetro os municípios de Açailândia e Imperatriz, Grajaú que é sede da Região das Serras e o próprio estado do Maranhão. Os resultados demonstraram que ocorreram avanços econômicos em ambos os municípios, apesar de não ficar evidente o grau de influência das atividades extrativistas e de silvicultura nesse processo. Entretanto, nos aspectos socioambientais elas se apresentaram como um sistema insustentável, altamente predatório do meio ambiente e danoso às condições de saúde e vida das pessoas que residem nas proximidades desses empreendimentos nos dois municípios. / The southwest region of Maranhão State had a significant economic growth after the 1990s with the arrival of large industries. The passage through this region of the Carajás Railroad, in which the Companhia Vale do Rio Doce transports ore from Serra dos Carajás to the harbor of Itaqui located in Maranhão capital, made initially ironworks install themselves in the city of Açailândia which is to margins of said rail; and finally in 2013 a large pulp and paper factory was inaugurated in the city of Imperatriz. These enterprises impacted the economy of several municipal districts around these two cities, as many areas of land previously used for agriculture were purchased and planted with eucalyptus to supply coal and cellulose, two essential raw materials to these industries. For these reasons this study aims to understand the socioeconomic influences of the extractive and forestry in the cities of `Formosa da Serra Negra and `Sítio Novo; two typically rural clippings of Maranhão region of saws that have been achieved by these methods of extraction from 2000. This is a bibliographic and documental research with a qualitative approach in which using the comparative method was made socioeconomic indicators analyzes such as population, GDP, extractive production, IDHM, IDM and the Gini index of these two municipalities in order to identify occurrence development in these locations, using as as parameter the municipalities of Açailândia and Imperatriz, Grajaú that hosts the Region of the Sierras and the state of Maranhão. The results demonstrated economic advances have occurred in both municipalities, though not become apparent the degree of influence of extractive and forestry activities in these proceedings; however in social and environmental aspects they presented themselves as an unsustainable system, highly predatory of the environment and harmful to health and living conditions of the people residing in the vicinity of these enterprises in the two counties.

Page generated in 0.0975 seconds