• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 44
  • 26
  • 10
  • 5
  • 5
  • 5
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 103
  • 40
  • 34
  • 23
  • 19
  • 17
  • 16
  • 16
  • 15
  • 15
  • 14
  • 14
  • 14
  • 12
  • 12
  • 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.
11

Degradação da resina de troca iônica utilizando o reagente de Fenton / Degradation of ion spent resin using the Fentons reagent

Leandro Goulart de Araujo 15 August 2013 (has links)
O método mais comum de tratamento da resina de troca iônica radioativa é a imobilização em cimento, que reduz a liberação de radionuclídeos para o meio ambiente. Apesar de eficiente, esse método é custoso, pois a quantidade final de rejeito gerada é elevada, já que a capacidade de carga de imobilização é baixa. Este trabalho tem como objetivo desenvolver um método de degradação das resinas provenientes do reator de pesquisa nuclear do Instituto de Pesquisas Energéticas e Nucleares, utilizando o Processo Oxidativo Avançado (POA) com reagentes de Fenton. Isso permitiria uma incorporação maior no cimento. Três formas da resina foram avaliadas: catiônica, aniônica, e uma mistura de ambas as resinas. As reações foram realizadas variando a concentração do catalisador (25, 50, 100 e 150 mM), do volume de peróxido de hidrogênio (320 a 460 mL), e de três temperaturas diferentes, 50, 60 e 70 °C. A solução de catalisador mais eficiente foi a de concentração de 50 mM e volume de 330 mL de peróxido, degradando aproximadamente 98% da quantidade de resina. A temperatura mais eficiente foi a de 60 º C. / The most common method for spent radioactive ion exchange resin treatment is its immobilization in cement, which reduces the radionuclides release into the environment. Although this method is efficient, it increases considerably the final volume of the waste due to the low incorporation capacity. The objective of this work was to develop a degradation method of spent resins arising from the nuclear research reactor located at the Nuclear and Energy Research Institute (IPEN-CNEN/SP), using an Advanced Oxidation Process (AOP) with Fentons reagents. This method would allow a higher incorporation in cement. Three different resins were evaluated: cationic, anionic and a mixture of both resins. The reactions were conducted varying the catalyst concentration (25, 50, 100 and 150 mM), the volume of hydrogen peroxide (320 to 460 mL), and three different temperatures, 50, 60 and 70 ºC. Degradation of about 98% was achieved using a 50 mM catalyst solution and 330 mL of hydrogen peroxide solution. The most efficient temperature was 60ºC.
12

Processos oxidativos avançados assistidos por microondas aplicados na remoção de pesticidas em meio aquoso / Microwave-assisted advanced oxidation processes applied to removal of pesticides in aqueous medium

Barros, Francisco Cláudio de Freitas January 2014 (has links)
BARROS, Francisco Cláudio de Freitas. Processos oxidativos avançados assistidos por microondas aplicados na remoção de pesticidas em meio aquoso. 2014. 90 f. Tese (Doutorado em química)- Universidade Federal do Ceará, Fortaleza-CE, 2014. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-05-31T19:26:07Z No. of bitstreams: 1 2014_tese_fcfbarros.pdf: 2270924 bytes, checksum: 0233401fd5169501903fef16491b9d07 (MD5) / Approved for entry into archive by José Jairo Viana de Sousa (jairo@ufc.br) on 2016-05-31T23:15:36Z (GMT) No. of bitstreams: 1 2014_tese_fcfbarros.pdf: 2270924 bytes, checksum: 0233401fd5169501903fef16491b9d07 (MD5) / Made available in DSpace on 2016-05-31T23:15:36Z (GMT). No. of bitstreams: 1 2014_tese_fcfbarros.pdf: 2270924 bytes, checksum: 0233401fd5169501903fef16491b9d07 (MD5) Previous issue date: 2014 / The use of pesticides in crop protection has contributed to a massive increase in global food production. However, pesticides have generated a growing concern about your environmental risks. Advanced oxidation processes (AOP) have proved a particularly useful alternative to degrade organic compounds in aqueous medium, converting them into low toxic substances or nontoxic substances. In this work, was evaluated the removal efficiency of the chlorpyrifos pesticide in continuous and batch AOP systems involving microwave radiation, ultraviolet radiation, hydrogen peroxide and titanium dioxide. The MO/UV/H2O2/TiO2 batch system was efficient in the chlorpyrifos removal (100%) using 10% H2O2 solution for most of the microwave power conditions and treatment time. Fractional factorial design was applied to the pesticides treatment in AOP batch system to indicate the optimum values of the parameters: pH, pesticide concentration, oxidizing agent concentration, treatment time, and microwave power. The study of AOP continuous system showed that in 1-hour treatment of 500 mg.L-1 of chlorpyrifos, in alkaline medium, performed a pesticide removal of 87% at 10 ml.min-1 flow rate. Chromatographic analysis of samples treated in AOP continuous system suggests a partial mineralization of the pesticide. / A utilização de pesticidas na proteção de culturas tem contribuído com um aumento maciço na produção mundial de alimentos. Mas apesar de seus efeitos benéficos, os efeitos negativos dos agrotóxicos têm gerado uma crescente preocupação em relação ao risco de contaminação ambiental. Os processos oxidativos avançados (AOP) têm se mostrado uma alternativa particularmente útil para degradar compostos orgânicos em meio aquoso, convertendo-os em substâncias de pouca ou nenhuma toxidade. Ao longo de nosso estudo, foi avaliada a eficiência de remoção do pesticida clorpirifós em sistemas contínuos e descontínuos (batelada) de processos oxidativos avançados envolvendo radiação de microondas, radiação ultravioleta, peróxido de hidrogênio e dióxido de titânio, com resultados promissores. O sistema MO/UV/H2O2/TiO2 de POA descontínuo foi o mais eficiente na remoção de clorpirifós, com 100% de remoção de pesticida em amostras com 10% de H2O2 em quase todas as potências de microondas e tempo de tratamento avaliados. Estudos de planejamento fatorial fracionado aplicado ao tratamento de pesticidas em sistema de POA descontínuo apontaram as condições ótimas de trabalho para os seguintes parâmetros: pH, concentração de pesticida, concentração de agente oxidante, tempo e potência de microondas. O estudo de POA em sistema contínuo mostrou que, ao final de 1 hora, o tratamento de uma amostra de 500 mg.L-1 de clorpirifós em meio alcalino, alcançou uma remoção de 87% do pesticida com velocidade de fluxo de amostra de 10 mL.min-1. Análises cromatográficas das amostras tratadas em POA descontínuo sugerem uma mineralização parcial do pesticida.
13

Implementacion de Context-Aware Aspects en Reflex y Evaluación en una Aplicación Context-Aware

Herrera Ordenes, Alexis January 2007 (has links)
El objetivo general de este trabajo consiste en extender el framework Reflex para soportar context-aware aspects. Este nuevo framework permitirá integrar sensores de contexto implementados con WildCAT para el desarrollo de una aplicación modelo que requiera aspectos context-aware.
14

Implementation of Emerging Technologies: Treatment Capability of Peracetic Acid and Ultraviolet Irradiation

January 2017 (has links)
abstract: Advanced oxidation processes (AOP’s) are water/wastewater treatment processes simultaneously providing disinfection and potential oxidation of contaminants that may cause long-term adverse health effects in humans. One AOP involves injecting peracetic acid (PAA) upstream of an ultraviolet (UV) irradiation reactor. Two studies were conducted, one in pilot-scale field conditions and another under laboratory conditions. A pilot-scale NeoTech UV reactor (rated for 375 GPM) was used in the pilot study, where a smaller version of this unit was used in the laboratory study (20 to 35 GPM). The pilot study analyzed coliform disinfection and also monitored water quality parameters including UV transmittance (UVT), pH and chlorine residual. Pilot study UV experiments indicate the unit is effectively treating flow streams (>6 logs total coliforms) twice the 95% UVT unit capacity (750 GPM or 17 mJ/cm2 UV Dose). The results were inconclusive on PAA/UV inactivation due to high data variability and field operation conditions creating low inlet concentrations.Escherichia coli (E. coli) bacteria and the enterobacteria phage P22—a surrogate for enteric viruses—were analyzed. UV inactivated >7.9 and 4 logs of E. coli and P22 respectively at a 16.8 mJ/cm2 UV dose in test water containing a significant organics concentration. When PAA doses of 0.25 and 0.5 mg/L were injected upstream of UV at approximately the same UV Dose, the average E.coli log inactivation increased to >8.9 and >9 logs respectively, but P22 inactivation decreased to 2.9 and 3.0 logs, respectively. A bench-scale study with PAA was also conducted for 5, 10 and 30 minutes of contact time, where 0.25 and 0.5 mg/L had <1 log inactivation of E. coli and P22 after 30 minutes of contact time. In addition, degradation of the chemical N-Nitrosodimethylamine (NDMA) in tap water was analyzed, where UV degraded NDMA by 48 to 97% for 4 and 0.5 GPM flowrates, respectively. Adding 0.5 mg/L PAA upstream of UV did not significantly improve NDMA degradation. The results under laboratory conditions indicate that PAA/UV have synergy in the inactivation of bacteria, but decrease virus inactivation. In addition, the pilot study demonstrates the applicability of the technology for full scale operation. / Dissertation/Thesis / Masters Thesis Civil and Environmental Engineering 2017
15

Processos oxidativos avanÃados assistidos por microondas aplicados na remoÃÃo de pesticidas em meio aquoso / Microwave-assisted advanced oxidation processes applied to removal of pesticides in aqueous medium

Francisco ClÃudio de Freitas Barros 20 February 2014 (has links)
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / A utilizaÃÃo de pesticidas na proteÃÃo de culturas tem contribuÃdo com um aumento maciÃo na produÃÃo mundial de alimentos. Mas apesar de seus efeitos benÃficos, os efeitos negativos dos agrotÃxicos tÃm gerado uma crescente preocupaÃÃo em relaÃÃo ao risco de contaminaÃÃo ambiental. Os processos oxidativos avanÃados (AOP) tÃm se mostrado uma alternativa particularmente Ãtil para degradar compostos orgÃnicos em meio aquoso, convertendo-os em substÃncias de pouca ou nenhuma toxidade. Ao longo de nosso estudo, foi avaliada a eficiÃncia de remoÃÃo do pesticida clorpirifÃs em sistemas contÃnuos e descontÃnuos (batelada) de processos oxidativos avanÃados envolvendo radiaÃÃo de microondas, radiaÃÃo ultravioleta, perÃxido de hidrogÃnio e diÃxido de titÃnio, com resultados promissores. O sistema MO/UV/H2O2/TiO2 de POA descontÃnuo foi o mais eficiente na remoÃÃo de clorpirifÃs, com 100% de remoÃÃo de pesticida em amostras com 10% de H2O2 em quase todas as potÃncias de microondas e tempo de tratamento avaliados. Estudos de planejamento fatorial fracionado aplicado ao tratamento de pesticidas em sistema de POA descontÃnuo apontaram as condiÃÃes Ãtimas de trabalho para os seguintes parÃmetros: pH, concentraÃÃo de pesticida, concentraÃÃo de agente oxidante, tempo e potÃncia de microondas. O estudo de POA em sistema contÃnuo mostrou que, ao final de 1 hora, o tratamento de uma amostra de 500 mg.L-1 de clorpirifÃs em meio alcalino, alcanÃou uma remoÃÃo de 87% do pesticida com velocidade de fluxo de amostra de 10 mL.min-1. AnÃlises cromatogrÃficas das amostras tratadas em POA descontÃnuo sugerem uma mineralizaÃÃo parcial do pesticida. / The use of pesticides in crop protection has contributed to a massive increase in global food production. However, pesticides have generated a growing concern about your environmental risks. Advanced oxidation processes (AOP) have proved a particularly useful alternative to degrade organic compounds in aqueous medium, converting them into low toxic substances or nontoxic substances. In this work, was evaluated the removal efficiency of the chlorpyrifos pesticide in continuous and batch AOP systems involving microwave radiation, ultraviolet radiation, hydrogen peroxide and titanium dioxide. The MO/UV/H2O2/TiO2 batch system was efficient in the chlorpyrifos removal (100%) using 10% H2O2 solution for most of the microwave power conditions and treatment time. Fractional factorial design was applied to the pesticides treatment in AOP batch system to indicate the optimum values of the parameters: pH, pesticide concentration, oxidizing agent concentration, treatment time, and microwave power. The study of AOP continuous system showed that in 1-hour treatment of 500 mg.L-1 of chlorpyrifos, in alkaline medium, performed a pesticide removal of 87% at 10 ml.min-1 flow rate. Chromatographic analysis of samples treated in AOP continuous system suggests a partial mineralization of the pesticide.
16

RemoÃÃo do AgrotÃxico Organofosforado ClorpirifÃs usando Processo Oxidativo AvanÃado / Removal of Organophosphorus Pesticides Chlorpyrifos using advanced oxidation processes

Andrà Gadelha de Oliveira 10 February 2011 (has links)
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / O presente trabalho estudou o uso de processo oxidativo avanÃado para a remoÃÃo do agrotÃxico organofosforado clorpirifÃs. Para tanto, sistema de reator em escala laboratorial e escala piloto foram estudados. Na primeira etapa, em escala laboratorial, foram realizados estudos dos parÃmetros temperatura, pH e dosagem do perÃxido de hidrogÃnio, concentraÃÃo do agrotÃxico e efeito inibitÃrio de Ãnions. Os resultados indicaram que uma temperatura de 45 oC propicia melhor remoÃÃo do agrotÃxico usando apenas a radiaÃÃo UV, contudo, para o sistema combinado UV/H2O2, a temperatura nÃo afetou o rendimento do processo. A influÃncia do pH foi estudada para os sistemas H2O2 e UV/H2O2 e foi verificado que o pH nÃo influenciou na eficiÃncia do sistema UV/H2O2, entretanto, em pH 10 ocorreu um melhor rendimento para o sistema H2O2 na remoÃÃo do agrotÃxico. Entre as dosagens de perÃxido de hidrogÃnio estudadas, a de 1,5g/L foi a mais eficiente na remoÃÃo do agrotÃxico. O efeito inibitÃrio dos Ãnions, cloreto, nitrato, sulfato e carbonato nÃo se mostrou efetivo na remoÃÃo do agrotÃxico durante 480 minutos, contudo, o Ãnion bicarbonato provocou em 60 minutos a total conversÃo do clorpirifÃs em um composto desconhecido. A segunda etapa foi realizada no reator de escala piloto e foram estudados trÃs vazÃes, 1,5; 2,0 e 3,0 L/min. As concentraÃÃes residuais do agrotÃxico ao final de 480 minutos de experimento para os trÃs vazÃes foram 0,30; 0,43 e 0,5 mg/L, respectivamente. A remoÃÃo de turbidez e cor foram eficientes para as vazÃes estudadas, em contraste com a remoÃÃo de DQO. / This study investigated to advanced oxidation process (POA) for removal of organophosphorus pesticide chlorpyrifos. Reactor system, in laboratory and pilot scale, have been studied. In the first stage, in laboratory scale, were performed studies of the parameters temperature, pH, dosage of hydrogen peroxide, pesticide concentration and inhibitory effects of anions. The results indicated that a temperature of 45 oC showed a better pesticide removal using only UV radiation, however, for the system UV/H2O2, the temperature did not affect the process. The pH effect was studied for H2O2 and UV/H2O2 systems and was observed that pH did not affect the efficiency of the system UV/H2O2. In addition, at pH 10 a better performance for the system H2O2 on the removal of pesticide was observed. Hydrogen peroxide dosage also was studied, and 1,5g/L dosage was most efficient in the pesticide removal. The inhibitory effect of the anions, such as chloride, nitrate, sulfate and bicarbonate was not significantive in the pesticide removal at a time of 480 minutes. In contrast, presence of carbonate anion at 60 minutes, there was a total transformation of chlorpyrifos in an unknown compound. The second stage was conducted on a pilot scale, and flow rate were studied (1.5; 2.0 and 3.0 L/min). The final concentration of pesticide at 480 minutes, for the three flow, were 0.30; 0.43 and 0.5 mg/L, respectively. The turbidity and color removal was efficient for all flows studied, in contrast with the DQO removal.
17

Disinfection of biological agents in the field using a mobile advanced oxidation process

Mudd, Shannon, Mud January 1900 (has links)
Master of Science / Department of Biological & Agricultural Engineering / Stacy L. Hutchinson / As an alternative to traditional disinfection methods, the use of an advanced oxidation process (AOP) was investigated for exercise in theatre to expediate water usability. The system utilized for this study was a mobile combination of UV irradiation and ozonation, which provided multiple mechanisms for treatment without the addition of chemicals. As a compact and transportable apparatus, the proposed unit would treat water for secondary purposes including vehicle washing, equipment cleaning, and other demands not involving consumption or personal hygiene. Several varying dilutions of hog farm lagoon water and military vehicle wash water were combined with microbial concentrations up to 9.10E+04 mpn/mL. The inoculant tested was Escherichia coli for frequency of occurrence and similarities to microbes of bioterrorism. The overall results for the AOP treatment do not indicate a connection between inactivation and suspended solids, but there does exist a significant relationship to contact time as indicated by changes in the flow rate. The experimental data showed a correlation to increased inactivation with lower flow rates. Although inactivation was not complete, the once through flow system could be adjusted to recirculate water for additional treatment. Due to time constraints additional testing was not possible, but the benefit could be examined in future research. The relationship of TSS to inactivation was not evident as inactivation occurred in similar distributions whether suspended solids were elevated or reduced.
18

Simplifying development of secure software : Aspects and Agile methods

Boström, Gustav January 2006 (has links)
Reducing the complexity of building secure software systems is an important goal as increased complexity can lead to more security flaws. This thesis aims at helping to reduce this complexity by investigating new programming techniques and software development methods for implementing secure software. We provide case studies on the use and effects of applying Aspect-oriented software development to Confidentiality, Access Control and Quality of Service implementation. We also investigate how eXtreme Programming can be used for simplifying the secure software development process by comparing it to the security engineering standards Common Criteria and the Systems Security Engineering Capability Maturity Model. We also explore the relationship between Aspect-oriented programming and Agile software development methods, such as eXtreme Programming. / QC 20101130
19

Space Health Effects Informed Through Application of the Adverse Outcome Pathway Framework

Kozbenko, Tatiana 19 December 2022 (has links)
The scientific evidence required to make policy decisions that protect human health can be challenging to organize. Primary research is often silo-ed between different agency repositories, the pace of publication is unflagging and wide-spread interdisciplinary collaboration can be logistically difficult. Since 2012, the Organisation for Economic Co-operation and Development (OECD) adverse outcome pathway (AOP) framework has provided solutions for some of the challenges of supplying relevant and accessible scientific data for evidence-based decision-making. Development of AOPs is guided by a crowd-sourced approach in which progressions of adverse outcomes (AO) are distilled into pathways containing only the essential key events (KEs) and the causal key event relationships (KERs) that connect them. The framework has widely been adopted in the toxicology community and more recently projects have applied it to the radiation safety field. Presently, a collaborative effort aims to further expand the use of AOPs through creating a network linking exposure to the space exposome with resulting human health outcomes. The network contains four adverse non-cancer outcomes for which participants of future long-range space missions will be at risk. The work of this thesis has contributed to the construction of the space-health AOP network by accomplishing two main objectives. The first was the creation of a novel protocol for collecting a weight of evidence (WOE) that included the benefits of scoping review and artificial intelligence (AI) tools for literature screening. The scoping review WOE collection strategy was then deployed for collecting data across all four outcomes in the space-health network. The second objective was to identify KEs and KERs and summarize the WOE linking space exposure to one of the four AOs: vascular remodeling. In addition to summarizing the pathway, we have also highlighted important modulating factors and knowledge gaps in the WOE. This thesis work contributes to the future of the AOP framework by formulating a new development protocol and employing it in a novel regulatory context. Using the new protocol, this thesis has furthered biological understanding of the effects of space exposure on the cardiovascular system by collating mechanistic information across scientific disciplines to identify KEs and KERs in occurrence of vascular remodeling.
20

Investigation of Color Removal by Chemical Oxidation for Three Reactive Textile Dyes and Spent Textile Dye Wastewater

Edwards, Jessica Corinne 22 August 2000 (has links)
This research investigated the efficacy of chlorine dioxide (ClO₂), ultraviolet (UV) irradiation, UV in combination with chlorine dioxide (UV/ClO₂), and UV in combination with hydrogen peroxide (UV/H₂O₂) for decolorizing three reactive azo dyes (sultan red, indigo blue and cypress green) and treated textile-manufacturing wastewater. The objective was to determine the best treatment for reducing color to the Virginia Pollutant Discharge Elimination System (VPDES) permit level of 300 American Dye Manufacturers Institute (ADMI) units. The effects of the three chemical oxidation treatments provided color reduction for all three dyes. The results suggested UV/H₂O₂ and UV/ClO₂2 treatments provided maximum color reduction of the red and blue dyes, and UV/H₂O₂ was the most effective for maximum reduction of the green dye. A research goal was to provide predictive models of the wastewater effluent for the treatment processes, including the UV exposure time required to reach the 300 ADMI permit value and the effective ClO₂ dose necessary to achieve the 300 units. The results of the investigations regarding the effluent indicated that UV/H₂O₂ and UV/ClO₂ (5 mg/L) provided reduction to 300 units in less than 10 minutes UV exposure when the initial effluent color was less than 500 ADMI units. Without the addition of oxidant, contact times longer than 10 minutes were required for UV to decolorize these effluents to 300 ADMI units. Chlorine dioxide dosages between 10 and 30 mg/L both with and without UV irradiation achieved the same results. / Master of Science

Page generated in 0.0237 seconds