• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 902
  • 582
  • 184
  • 96
  • 46
  • 42
  • 18
  • 18
  • 12
  • 11
  • 8
  • 8
  • 7
  • 7
  • 6
  • Tagged with
  • 2327
  • 775
  • 323
  • 322
  • 311
  • 235
  • 177
  • 148
  • 144
  • 140
  • 140
  • 135
  • 133
  • 123
  • 119
  • 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.
661

Groundwater impact assessment and protection

Eliasson, Åse January 2001 (has links)
<p>In the recent decades, therehave been frequent conflicts between groundwater waterresources and environmentally hazardous activities. Newmethodologies for aiding decision-making in groundwater impactassessment and protection areneeded and in which issues ofincreased awareness, better understanding of the groundwaterresources processes, and validation of predictive mathematicalmodels are addressed.</p><p>A framework fordecision–aid, based on predictive simulations that a)predicts the environmental impacts b) provides the totaleconomical value c) visualises the impacts and the groundwaterproperties and d) describes the uncertainties in the results isproposed herein. The framework can be applied in environmentalimpact assessments, strategic environmental assessments andprotection and management of water resources. The results ofthe model are used as feedback for determining new scenarios,depending on the required uncertainties, and if the plannedactivity is sustainable, and/or fulfils the legislative andpolicy measures. This framework is applied to a particular casestudy, Nybroåsen, in the south-eastern part of Sweden,where the highway E22 is constructed through the importantglaciofluvial esker aquifer, passing the protection zone of thewater supply for the Kalmar municipality.</p><p>The impacts from the new highwayand the existing road have been predicted by two-dimensionalphysically based time-variant flow and solute groundwatermodelling. The results, breakthrough curves of contaminantconcentration in wells and maps of concentration distributions,as well as travel times, flow paths, and capture zones forwells determined by particle tracking have been presented.</p><p>The constructed model of theNybroåsen study area was calibrated by comparing observedand simulated groundwater levels for 15 observation wells forten years of measurements. The model has been evaluated bothgraphically and numerically and the calibration target wasfulfilled for 13 of the 15 observation wells. The model workincludes investigations of the catchment information, a waterbalance study, simulation of the groundwater recharge,consideration of the unsaturated zone by a numerical columnsimulation, and sensitivity analysis.</p><p>From the sensitivity analysis ofthe flow and transport parameters, it has been shown that theuncertainties are mainly due to the hydraulic conductivity.Comparison of the derived conductivity from the steady-stateautomatic calibration and the time-variant calibration showedthat there are major differences in the derived parameters,which illustrates the importance of a time dependentcalibration over both wet and dry periods and in more than onepoint in the area of interest of the model predictions.</p><p>In addition, a multi-criteriadecision analysis has been carried out for four roadalternatives (including the new highway E22) and the existingroad in the case study concerned. The multi-criteria decisionaid is applied as an illustration of how it can be used in thestudy area to identify a) interest groups of actors and theirconcerns b) ranking of alternative road scenarios according toactors’preferences and c) coalition groups of actors<i>i.e.</i>groups that have similar views with regard to theroad alternatives.</p><p><b>Keywords:</b>Physically-based groundwater modelling,contamination, flow and solute transport, glaciofluvialdeposits, Nybroåsen, Sweden, and multi-criteriadecision-aid.</p>
662

Traffic-Related Metals in Soil and Sediment in Mauritius / Trafikrelaterade metaller i jord och sediment på Mauritius

Petersson, Liselott January 2005 (has links)
<p>Trafik utgör en stor föroreningskälla av tungmetaller i vägnära jordar och särskilt är det koppar (Cu), bly (Pb) och zink (Zn) som associeras med fordonstrafik. I ett historiskt perspektiv härrör blyutsläpp främst från bränsleförbränning, medan kopparemissioner (i första hand från slitage av bromsbelägg) och zinkutsläpp (från däck) från trafik står för så mycket som hälften av det urbana utsläppet av koppar och zink till omgivningen.</p><p>Koppar-, bly- och zinkkoncentrationer i vägnära jord och sediment undersöktes inom avrinningsområdet för Grand River North West i Mauritius. Eftersom totalmetall utgör en dålig indikator på den mängd metall som finns potentiellt tillgänglig för biota användes extraktion med hjälp av 0.5 M HCl tillsammans med totalkoncentrationer.</p><p>Den rumsliga variationen längsmed transekt vinkelrätt mot vägar undersöktes liksom variationen med djupet. Observerade kopparkoncentrationer var jämförbara med bakgrundsnivåer. Till skillnad från Cu var koncentrationer av Pb och Zn förhöjda i den omedelbara närheten till vägar med relativt stor trafikintensitet, men halterna minskade snabbt med avståndet. Resultat från platserna för jordreferenser visar på storskalig förorening av Pb på ön. Uppmätta kopparkoncentrationer kunde inte knytas till trafikens påverkan.</p><p>Vid regn kan metaller som finns i förorenat vägdamm och förorenad jord övergå till löslig form, eller sköljas bort i partikulär form, och transporteras till närliggande vattendrag. I Mauritius är det här av speciell vikt eftersom flodsediment till slut kommer att deponeras i de känsliga kustområdena som omger ön. Dock tyder inte resultaten på förhöjda metallhalter i sediment nära de studerade vägarna.</p><p>Även om erhållna resultat av Cu inte visar på någon förhöjning och zonen med hög förorening av Pb och Zn är relativt smal, är det angeläget att följa utvecklingen eftersom antalet fordon växer snabbt i Mauritius, vilket kan förändra dagens situation och ge upphov till större miljöpåverkan. För att undvika eventuella ekologiska skador är det därför av stor vikt att i fortsättningen övervaka situationen längs landets vägar.</p> / <p>Traffic has been identified as a significant heavy metal polluter of roadside soils, and copper (Cu), lead (Pb) and zinc (Zn) in particular are associated with road travel. In a historic perspective, the Pb contribution from anthropogenic sources to nature has predominantly been a result of fuel combustion. There are indications that Cu (mainly through braking system) and Zn (emissions from tires) released from traffic give rise to as much as half of the total urban contribution of copper and zinc to the environment.</p><p>Concentrations of Cu, Pb and Zn in roadside soils and sediment have been determined at selected roads within the Grand River North West watershed in Mauritius. As total metal concentrations are not a suitable indicator of the metal concentrations that are potentially available to biota, metals extractable in 0.5 M HCl have been determined along with total concentrations. The spatial variation in metal concentration along soil transects perpendicular to roads were investigated, as was the variation with depth.</p><p>Observed Pb and Zn concentrations exhibited elevated levels in topsoil in the immediate vicinity of roads with relatively large traffic densities, but the decrease in concentration with distance was rapid. Results from soil reference sites pointed to a large scale Pb pollution on the island. In comparison, observed Cu concentrations could not be assigned any influence from traffic at the selected study sites.</p><p>In the event of rain, metals contained in polluted road dust and soil may be released into soluble form, or flushed from roadways as particulate matter, and transported to nearby water courses. In Mauritius, this is of particular importance as sediment in rivers eventually may be deposited in the sensitive coastal areas of the island. However, results do not indicate that there were any elevated levels of heavy metals in sediment close to roads that were investigated in this study.</p><p>Although Cu concentrations in roadside soils did not show any enrichment and the zone of elevated Pb and Zn concentrations was not wide, there is a concern that the continuing rapid increase in the number of vehicles in Mauritius will change the situation, possibly resulting in greater impact on the surrounding environment. Hence, in order to avoid any ecological damage, it is desirable to continue monitoring the situation along highways in the country.</p>
663

Etude expérimentale du comportement des aérosols et de leurs dépôts dans un élévateur à godets : impact sur la contamination croisée en alimentation animale

Leloup, Marine 25 May 2012 (has links) (PDF)
La problématique des contaminations croisées (transfert inter-lots de micro-ingrédients : additifs et/ou produits médicamenteux) dans le secteur de l'alimentation animale est entrée, depuis quelques décennies, au cœur des préoccupations de la profession. Ce phénomène se décompose en 2 phases : le dépôt de particules par un lot de fabrication et sa récupération par le/les lot(s) suivant(s). Plusieurs études expérimentales, ont incriminé l'élévateur à godets post-mélangeur dans l'augmentation du niveau de contamination d'une ligne de fabrication. Cet appareil de manutention achemine verticalement des mélanges pulvérulents de diverses matières premières, pouvant contenir, en particulier, des additifs ou des produits médicamenteux. L'objectif de ces travaux est de comprendre dans quelles mesures cet appareil est source de transfert inter-lots, et quels paramètres liés au procédé entrent en jeu. Plusieurs outils ont été mis en place et la réalisation d'un plan d'expériences a permis de mettre en lumière l'impact de certains facteurs sur la contamination croisée :d'une part, le mode de vidange (lié à la vitesse de la sangle) en tête de l'élévateur et l'angle de la bavette de jetée agissent sur la quantité de micro-ingrédient déposée lors du passage d'un lot, et d'autre part, l'espace autour des godets, modifie la capacité du lot suivant à collecter les reliquats.Ces informations définissent une position optimale des paramètres de l'élévateur qui, sur pilote, réduit le niveau de contaminations croisées de 9 à 7 %. Enfin, des observations des champs de vitesses pendant la jetée du produit ont apporté de éléments de compréhension sur mouvements d'air et d'aérosols à l'origine des contaminations.
664

Hazard analysis and critical control point system for home prepared foods as a basis for adult education in urban Guayaquil, Ecuador

Morales R., Maria F. 23 August 1993 (has links)
The Hazard Analysis and Critical Control Point (HACCP) system for studying the food preparation process was conducted in four households in an environmentally poor urban neighborhood of Guayaquil, Ecuador. The analysis consisted of observing all of the steps in the food preparation process, measuring food temperatures at each step, and collecting food and water samples. Food and water samples were tested for total aerobic microorganisms, molds and yeast, total coliforms, and fecal coliforms. Temperatures reached during the cooking process were high enough to kill vegetative forms of foodborne pathogens; however, heat-resistant spores could have survived. Leftover food was held at room temperature for long periods of time which allowed multiplication of vegetative forms from spores or from contaminated food utensils. Leftover food was eaten either cold or reheated to warm temperatures. Water samples were taken from water delivery trucks and from each family. Water was identified as one of the main hazards in food preparation. None of the water samples met the criteria of the Ecuadorean National Institute of Standards for human consumption. Fecal samples were taken from children in the families, and were analyzed for parasites. Parasites were found in all of the samples. After critical control points were identified, appropriate interventions were taken to improve safety at each step. Based on these HACCP observations, a food and water safety program was designed and taught to five mothers attending a Guayaquil Child Care Center. The program included a lesson on each of four topics: food and water safety, parasites, care during diarrhea with emphasis on oral rehydration therapy and the introduction of solid food, and nutrition. A control mother was identified for each group. Diarrhea occurred in children of both groups but none of the children was hospitalized. With the exception of nutrition concepts, the knowledge about food and water safety concepts, parasites and care during diarrhea were well understood by both groups. This was reflected in positive changes in families' behavior toward using improved food and water sanitation practices as observed during a visit to each family which followed the HACCP study and the educational program. / Graduation date: 1994
665

Applications of grazing-angle reflection absorption Fourier transform infrared spectroscopy to the analysis of surface contamination

Hamilton, Michelle LoAnn January 2007 (has links)
Cleaning validation of pharmaceutical manufacturing equipment is required by legislation. Generally, wet chemical techniques are employed using swabbing and/or rinse sampling methods. These are generally either selective and time consuming, or less selective and give results in a shorter period. The infrared reflection absorption spectroscopy (IRRAS) technique explored here attempts to deliver accurate, selective surface contamination information in real time to complement current methods and reduce down-time. The IRRAS instrument used in this research is a Fourier transform infrared (FTIR) spectrometer coupled by an IR fibre-optic cable to a grazing-angle sampling head with a fixed incidence angle of 80°. The introduced flexibility permits collection of in situ spectra from contaminated surfaces. Calibration models are developed using the multivariate, linear partial least squares (PLS) statistical method. The research focuses on sodium dodecyl sulfate (SDS), a model cleaning agent, on metal (aluminium and stainless steel) and dielectric (glass, EPDM and silicone) surfaces. The effects of surface finish are investigated for SDS on stainless steel. Calibrations for SDS and paracetamol in the presence of each other on glass surfaces are examined, as well as a common industrial cleaner (P3 cosa® PUR80) on polished stainless steel. For the calibration sets in this thesis, RMSECV values were < 0.41 µg cm⁻², corresponding to conservative surface residues detection limits of better than ~0.86 µg cm⁻². However, RMSECV values depend on the calibration loading range, and the detection limits were typically ~0.2 µg cm⁻² for loading ranges 0-2.5 µg cm⁻². These are below visual detection limits, generally taken to be 1-4 µg cm⁻², depending on the analyte and substrate. This shows that IRRAS is a viable method for the real-time detection and quantification of surface contamination by surfactants and active pharmaceutical ingredients on metals and dielectrics.
666

The Role of Community Participation Mechanisms in the Search for Social and Environmental Justice in Vieques, Puerto Rico

Richardson, Belinda Lian 05 1900 (has links)
This paper assesses the continued community participation mechanisms, especially the Restoration Advisory Board, and the role of these mechanisms in the environmental cleanup of post U.S. military training operations in the current colonial situation of the Puerto Rican island municipality of Vieques. Today the community has many informal and formal mechanisms of organization meant to address the social, economic, health and environmental problems resulting from the Navy's presence on the island. These mechanisms are the cornerstone of the community's search for social and environmental justice. This paper provides a brief history of the Navy's presence on Vieques, the evolution of community participation mechanisms and an analysis of how these mechanisms allow the community to interact with public, private and government institutions involved in the cleanup. The research is centered around interviews with community members to discern whether they feel these mechanisms are effective in properly addressing community concerns. The case study of Vieques could also have international implications for the future of foreign military bases and toxic waste disposal around the world. Analysis of the effectiveness of community participation mechanisms could help marginalized communities deal with developed countries on issues that may concern human health and environmental risks as a result of the developed countries' activities. The analysis of community participation mechanisms can be used as a guide for Vieques and other communities around the world trying to achieve social, economic and environmental justice.
667

METABOLISM OF 2,2, - BIS (P-CHLOROPHENYL)-1, 1-DICHLOROETHYLENE (DDE) BY THE BOVINE.

MOHAMMAD, KASSIM HASSAN. January 1984 (has links)
Twelve lactating Holstein dairy cows were randomly divided into four groups of three animals each. Group A served as the control, group B was dosed at 0.05ppm/day of DDE (2,2-bis(P-chlorophenyl-1, 1-dichloroethylene), cows in group C were dosed at 0.1ppm DDE/day, while group D cows were dosed at 1.0ppm DDE/day. DDE was administered in a residue free peanut oil solution for 32-consecutive days. Milk samples were taken daily during the 32 day dosing period and for an additional 32 days after the dosing period. Quantitative analysis of DDE residue in milk fat was determined by using a Tracor MT-220 gas chromatograph with a Tritium electron capture detector. The average increase in DDE milk fat concentration during the dosing period was directly related to intake levels. DDE was the only organochlorine compound detected in the milk fat. The general slope and shape of the curves of milk fat DDE levels were similar for all treatments. The levels of DDE increased rapidly after the onset of dosing. After 15 days of dosing and throughout the remaining 17 days of the dosing period, milk fat DDE increased at a relatively slow rate. The level of milk fat DDE declined rapidly as soon as the DDE residue source was withdrawn. At the end of the 32-day post-dosing period, one cow from each group was slaughtered and samples were taken from muscles, brain, lung, lymph, spleen, kidney fat, heart, gonad, placenta, udder, and kidney for DDE analysis. Considerable DDE was found in the muscle, lymph, kidney fat, and udder tissues.
668

Removal of charged aerosols

Tripathi, Sachchida Nand January 2000 (has links)
No description available.
669

Development of EPSILON : a gamma ray imaging system for the nuclear industry

Durrant, Paul Timothy January 1999 (has links)
No description available.
670

Large scale entrance surface dose survey and organ dose measurements during diagnostic radiology using the Harshaw 5500 and 6600 TLD systems

Broadhead, Dawn January 2001 (has links)
No description available.

Page generated in 0.0979 seconds