Letteratura scientifica selezionata sul tema "Solvant durable"
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Articoli di riviste sul tema "Solvant durable"
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Wu, Yunxuan, Jie Li, Yangfu Jin e Mi Zhou. "Binary solvent systems for durable self-adhesive conductive hydrogels". Journal of Polymer Engineering 40, n. 3 (25 febbraio 2020): 221–30. http://dx.doi.org/10.1515/polyeng-2019-0304.
Testo completoAbstract (sommario):
AbstractConductive hydrogels without adhesiveness and durability characteristics face great challenges in practical applications, such as inconvenient use, unstable contact voltage, and difficult to store. Herein, we present sodium polyacrylate (PAANa) hydrogels with binary solvent systems composed of water and an alcohol [ethylene glycol (EG), glycerol (GLY), or poly(ethylene glycol) (PEG)] as solvent instead of traditional water to research their self-adhesiveness, durability, conductivity, and mechanical properties. PAANa hydrogels exhibited higher self-adhesive properties and durability after alcohol content increased, and GLY/water hydrogels showed the best self-adhesive and stable properties. With more alcohols added, the weaker conductivity became, and EG/water hydrogels showed the highest conductivity. It was observed the long carbon chain length of alcohol could help improve the rheological properties of hydrogels. Thus, PEG/water hydrogels had the highest storage modulus, loss modulus, and consistency. The results demonstrated that the GLY/water binary solvent could provide good self-adhesiveness and durability, but EG/water and PEG/water showed better conductivity and mechanical properties, respectively. Therefore, our work may provide novel physical insights into the long-term usage of self-adhesive conductive hydrogels to practical requirements.
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Sreekantan, Srimala, Ang Xue Yong, Norfatehah Basiron, Fauziah Ahmad e Fatimah De’nan. "Effect of Solvent on Superhydrophobicity Behavior of Tiles Coated with Epoxy/PDMS/SS". Polymers 14, n. 12 (14 giugno 2022): 2406. http://dx.doi.org/10.3390/polym14122406.
Testo completoAbstract (sommario):
Superhydrophobic coatings are widely applied in various applications due to their water-repelling characteristics. However, producing a durable superhydrophobic coating with less harmful low surface materials and solvents remains a challenge. Therefore, the aim of this work is to study the effects of three different solvents in preparing a durable and less toxic superhydrophobic coating containing polydimethylsiloxane (PDMS), silica solution (SS), and epoxy resin (DGEBA). A simple sol-gel method was used to prepare a superhydrophobic coating, and a spray-coating technique was employed to apply the superhydrophobic coating on tile substrates. The coated tile substrates were characterized for water contact angle (WCA) and tilting angle (TA) measurements, Field-Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM), and Fourier Transform Infrared Spectroscopy (FTIR). Among 3 types of solvent (acetone, hexane, and isopropanol), a tile sample coated with isopropanol-added solution acquires the highest water contact angle of 152 ± 2° with a tilting angle of 7 ± 2° and a surface roughness of 21.80 nm after UV curing for 24 h. The peel off test showed very good adherence of the isopropanol-added solution coating on tiles. A mechanism for reactions that occur in the best optimized solvent is proposed.
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Brown, Philip S., e Bharat Bhushan. "Durable superoleophobic polypropylene surfaces". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, n. 2073 (6 agosto 2016): 20160193. http://dx.doi.org/10.1098/rsta.2016.0193.
Testo completoAbstract (sommario):
Polypropylene (PP) is a popular plastic material used in consumer packaging. It would be desirable if such plastic containers were liquid repellent and not so easily fouled by their contents. Existing examples of superoleophobic surfaces typically rely on poorly adhered coatings or delicate surface structures, resulting in poor mechanical durability. Here, we report a facile method for creating superoleophobic PP surfaces via incorporation of nanoparticles (NPs) into the polymer surface. A solvent–NP–PP mixture was spin coated at high temperature to achieve the necessary roughness. Such surfaces were further functionalized with fluorosilane to result in a durable, super-repellent surface. They were also found to exhibit some repellency towards shampoos. This method of incorporating NPs into polymer surfaces could also prove useful in improving the anti-bacterial, mechanical and liquid-repellent properties of plastic devices. This article is part of the themed issue ‘Bioinspired hierarchically structured surfaces for green science’.
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Poggiali, Lisa. "Solving Refugees' Problems or Solving the Problem of Refugees?" Politikon: The IAPSS Journal of Political Science 10 (1 novembre 2005): 51–61. http://dx.doi.org/10.22151/politikon.10.4.
Testo completoAbstract (sommario):
In the following paper I argue that in our contemporary global political climate - which is characterized by gross power differentials between the global North and South - the "international humanitarian regime" conceptualizes refugees as a "problem" to be "solved". It is through this conceptualization that repatriation has become the preferred "durable solution" to refugees' plight. Rather than solving refugees' problems, however, I contend that repatriation today serves to solve the problem of refugees. As such, I argue that repatriation is not only far from a durable solution, but far from a solution at all. I suggest that if we wish to truly help refugees find durable solutions to their problems we must first interrogate the unequal global power dynamics that produce refugee situations.
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Pan, Shuaijun, Rui Guo e Weijian Xu. "Durable superoleophobic fabric surfaces with counterintuitive superwettability for polar solvents". AIChE Journal 60, n. 8 (18 giugno 2014): 2752–56. http://dx.doi.org/10.1002/aic.14517.
Testo completo
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Lu, Tian-Dan, Liu-Lin Zhao, Wai Fen Yong, Qian Wang, Lei Duan e Shi-Peng Sun. "Highly solvent-durable thin-film molecular sieve membranes with insoluble polyimide nanofibrous substrate". Chemical Engineering Journal 409 (aprile 2021): 128206. http://dx.doi.org/10.1016/j.cej.2020.128206.
Testo completo
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De Sloovere, Dries, Danny E. P. Vanpoucke, Andreas Paulus, Bjorn Joos, Lavinia Calvi, Thomas Vranken, Gunter Reekmans et al. "Deep Eutectic Solvents as Nonflammable Electrolytes for Durable Sodium‐Ion Batteries". Advanced Energy and Sustainability Research 3, n. 3 (12 gennaio 2022): 2100159. http://dx.doi.org/10.1002/aesr.202100159.
Testo completo
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De Sloovere, Dries, Danny E. P. Vanpoucke, Andreas Paulus, Bjorn Joos, Lavinia Calvi, Thomas Vranken, Gunter Reekmans et al. "Deep Eutectic Solvents as Nonflammable Electrolytes for Durable Sodium‐Ion Batteries". Advanced Energy and Sustainability Research 3, n. 3 (marzo 2022): 2270007. http://dx.doi.org/10.1002/aesr.202270007.
Testo completo
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Šutka, Andris, Linda Mežule, Viktorija Denisova, Jochen Meier-Haack, Akshay Kulkarni, Sanda Bitina, Krisjanis Smits e Svetlana Vihodceva. "Straightforward Approach for Preparing Durable Antibacterial ZnO Nanoparticle Coatings on Flexible Substrates". Molecules 27, n. 22 (8 novembre 2022): 7672. http://dx.doi.org/10.3390/molecules27227672.
Testo completoAbstract (sommario):
Flexible antibacterial materials have gained utmost importance in protection from the distribution of bacteria and viruses due to the exceptional variety of applications. Herein, we demonstrate a readily scalable and rapid single-step approach for producing durable ZnO nanoparticle antibacterial coating on flexible polymer substrates at room temperature. Substrates used are polystyrene, poly(ethylene-co-vinyl acetate) copolymer, poly(methyl methacrylate), polypropylene, high density polyethylene and a commercial acrylate type adhesive tape. The deposition was achieved by a spin-coating process using a slurry of ZnO nanoparticles in toluene. A stable modification layer was obtained when toluene was a solvent for the polymer substrates, namely polystyrene and poly(ethylene-co-vinyl acetate). These coatings show high antibacterial efficiency causing >5 log decrease in the viable counts of Gram-negative bacteria Escherichia. coli and Gram-positive bacteria Staphylococcus aureus in 120 min. Even after tapping these coated surfaces 500 times, the antibacterial properties remained unchanged, showing that the coating obtained by the presented method is very robust. In contrast to the above findings, the coatings are unstable when toluene is not a solvent for the substrate.
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Yang, Guang, Michelle Lehmann, Ethan Self e Tomonori Saito. "(Invited) Innovating Sustainable, Cost-Effective, and Durable Redox Flow Battery Membranes". ECS Meeting Abstracts MA2024-01, n. 3 (9 agosto 2024): 527. http://dx.doi.org/10.1149/ma2024-013527mtgabs.
Testo completoAbstract (sommario):
In the quest to integrate renewable energy sources like solar and wind into the electric grid efficiently, the development of long-duration energy storage (LDES) systems is paramount. The U.S. Department of Energy's Long Duration Storage Shot initiative is at the forefront of this endeavor, aiming to reduce the costs of grid-scale energy storage by 90% for systems with over 10 hours of operation. A key player in this mission is the non-aqueous redox flow battery (RFB), known for its use of earth-abundant materials and potential to meet these cost-reduction goals. However, the commercial viability of RFBs hinges on the development of high-performance, cost-effective membranes, which are crucial for their functionality and affordability. These membranes' ionic conductivity is vital for the power density of RFBs, while their ion selectivity and solvent uptake greatly influence the batteries' cycle life. Our team has made groundbreaking advancements in membrane technology for non-aqueous flow batteries. We've addressed the challenge of balancing ionic conductivity with mechanical strength in polymer electrolytes. Our findings reveal that enhanced solvent uptake while boosting membrane ionic conductivity, can compromise mechanical integrity. To counter this, we've employed two strategies: selective plasticization of the ion-conductive block in block copolymers and reinforcing the membrane's mechanical strength through hydrogen and ionic bonds with an inorganic scaffold. Significantly, we've also reduced the crossover of redox-active species in our membrane designs, notably decreasing polysulfide species crossover in a Na metal – polysulfide hybrid flow battery. This has led to improved capacity retention, Coulombic efficiency, and extended cycle life compared to traditional porous membranes. Our latest innovations include the development of hydrocarbon single-ion conductors, demonstrating enhanced conductivity and stability. We've also introduced crosslinking chemistry to control solvent uptake more effectively, thus improving ionic conductivity while preserving mechanical strength. Lastly, our pioneering tape casting method for producing ceramic-polymer composite membranes represents a major leap in scalable membrane production, paving the way for the practical application of non-aqueous redox flow batteries in long-duration energy storage. Acknowledgment This research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) and is sponsored by the U.S. Department of Energy through the Energy Storage Program in the Office of Electricity. We acknowledge Dr. Jagjit Nanda SLAC National Accelerator Laboratory for the fruitful discussions.
Tesi sul tema "Solvant durable"
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Chagnoleau, Jean-Baptiste. "Extraction de composés naturels à l'aide de solvants durables : expérience et modélisation". Electronic Thesis or Diss., Université Côte d'Azur, 2024. http://www.theses.fr/2024COAZ5023.
Testo completoAbstract (sommario):
Les extraits naturels de plantes sont des ingrédients précieux pour un large éventail d'applications, notamment dans les industries cosmétiques ou pharmaceutiques ou dans les industries des parfums ou alimentaires. Mais l'extraction de ces composés naturels reste majoritairement réalisée à l'aide de solvants organiques volatils (COV) et de procédés ayant des impacts environnementaux importants. Dans le contexte récent de la chimie verte et de l'éco-extraction, des solvants alternatifs durables ont été développés pour remplacer les COV. Parmi ces solvants, les solvants biosourcés (BioSol), les solvants eutectiques profonds (DES) et les liquides ioniques (IL) ont fait l'objet d'intenses études au cours des deux dernières décennies. Néanmoins, les développements actuels des techniques d'extraction végétale reposent majoritairement sur des essais expérimentaux, ce qui limite le nombre de conditions et de solvants d'extraction pouvant être évalués. Pour remédier à cette limitation, plusieurs outils de modélisation ont été développés pour prédire les propriétés des solvants et soutenir le choix des solvants. Dans le chapitre I, la durabilité des solvants alternatifs sera discutée et des outils permettant de prédire les propriétés des solvants seront introduits.Dans le contexte de l'économie circulaire et du recyclage des déchets, les sous-produits sont désormais considérés comme une source alternative de composés naturels. Dans le chapitre II de ce travail, la valorisation des kiwis rejetés est proposée par l'extraction de composés bioactifs à l'aide de solvants durables à savoir des solvants eutectiques profonds (DES). Les résultats montrent que les extraits d'écorces de kiwi obtenus avec des DES à base d'acides carboxyliques présentent une activité antioxydante améliorée par rapport aux solvants conventionnels.Dans le domaine des industries de la parfumerie ou de l'agroalimentaire, les techniques d'extractions actuellement utilisées présentent plusieurs inconvénients. Dans le chapitre III de ce travail, des techniques alternatives ont été étudiées pour proposer de nouveaux ingrédients parfumés obtenus à l'aide de solvants durables. Des extraits de feuilles et de fruits de poivre rose (Schinus molle L.) ont été obtenus par extraction solide-liquide et hydrodistillation dans des solutions aqueuses de DES ou d'IL, tandis que les extraits de pétales de Rosa centifolia ont été obtenus par extraction solide-liquide dans des BioSol, DES et IL.Après extraction des plantes, les extraits naturels obtenus sont des mélanges chimiques complexes. Certaines applications nécessitant l'utilisation de composés purs, plusieurs techniques de séparation ont été développées. La chromatographie de partage centrifuge (CPC) est une technique de séparation utilisant les deux phases d'un système biphasique comme phase mobile et stationnaire pour effectuer des séparations chromatographiques préparatives. La possibilité d'utiliser des solvants durables et en particulier le DES pour former des systèmes biphasiques pour le CPC a été peu étudiée. Dans le chapitre IV de ce travail, le développement de systèmes biphasiques contenant du DES ont été étudiés comme systèmes potentiels de séparation des composés naturels. Enfin, le potentiel du modèle COSMO-RS dans la conception de systèmes biphasiques pour la séparation de composés naturels a été étudié. Les résultats démontrent que COSMO-RS prédit dans la plupart des cas les courbes binodales des systèmes biphasiques et les coefficients de partage des composés naturels avec une bonne précision. Ainsi, ces résultats indiquent que COSMO-RS peut être un outil puissant dans la conception de systèmes de séparation et de purification.Dans l'ensemble, ces travaux donnent un aperçu du potentiel de divers solvants durables pour l'extraction et la séparation de composés naturelsNatural plant extracts are valuable ingredients for a wide range of applications, particularly in the cosmetic or pharmaceutical industries or in the perfume or food industries. But the extraction of these natural compounds remains mainly carried out using volatile organic solvents (VOCs) and processes with significant environmental impacts. In the recent context of green chemistry and eco-extraction, sustainable alternative solvents have been developed to replace VOCs. Among these solvents, biobased solvents (BioSol), deep eutectic solvents (DES) and ionic liquids (ILs) have been the subject of intense studies over the last two decades. However, current developments in plant extraction techniques are mainly based on experimental trials, which limits the number of extraction conditions and solvents that can be evaluated. To address this limitation, several modeling tools have been developed to predict solvent properties and support solvent choice. In Chapter I, the sustainability of alternative solvents will be discussed and tools to predict solvent properties will be introduced.In the context of the circular economy and waste recycling, by-products are now considered as an alternative source of natural compounds. In chapter II of this work, the valorization of rejected kiwifruit is proposed by the extraction of bioactive compounds using sustainable solvents, namely deep eutectic solvents (DES). The results show that kiwi peel extracts obtained with carboxylic acid-based DES exhibit improved antioxidant activity compared to conventional solvents.In the field of perfumery or food industries, the extraction techniques currently used have several drawbacks. In chapter III of this work, alternative techniques were studied to propose new fragrance ingredients obtained using sustainable solvents. Extracts of leaves and fruits of pink pepper (Schinus molecular L.) were obtained by solid-liquid extraction and hydrodistillation in aqueous solutions of DES or IL, while extracts of petals of Rosa centifolia were obtained by solid-liquid extraction in BioSol, DES and IL.After extraction from the plants, the natural extracts obtained are complex chemical mixtures. Certain applications requiring the use of pure compounds, several separation techniques have been developed. Centrifugal partition chromatography (CPC) is a separation technique using the two phases of a biphasic system as mobile and stationary phase to perform preparative chromatographic separations. The possibility of using sustainable solvents and in particular DES to form biphasic systems for CPC has been little studied. In Chapter IV of this work, the development of biphasic systems containing DES were investigated as potential systems for separating natural compounds. Finally, the potential of the COSMO-RS model in the design of two-phase systems for the separation of natural compounds was investigated. The results demonstrate that COSMO-RS predicts in most cases the binodal curves of biphasic systems and the partition coefficients of natural compounds with good accuracy. Thus, these results indicate that COSMO-RS can be a powerful tool in the design of separation and purification systems.Overall, this work provides insight into the potential of various sustainable solvents for the extraction and separation of natural compounds
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Garg, Garima. "Solvants ioniques biosourcés et CO2 supercritique : conception des processus durables pour la synthèse de molécules cibles (BISCO2)". Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0085.
Testo completoAbstract (sommario):
Cette thèse représente un projet multidisciplinaire qui explore des aspects allant de l'ingénierie des solvants à la catalyse à l'aide de nanoparticules métalliques. Dans le cadre de ce projet, l’ingénierie des solvants a été appliquée à des solvants eutectiques profonds (SEP) biosourcés synthétisés à partir de tosylalaninate de choline et de glycérol afin diminuer leur viscosité en utilisant différentes quantités de dioxyde de carbone. Les rotors moléculaires ont été utilisés comme méthode innovante pour mesurer la viscosité, évitant ainsi l’utilisation d’une instrumentation coûteuse et donnant accès à la microviscosité du système. De plus, ce système a été appliqué à la synthèse de nanoparticules de palladium, jouant également un rôle de stabilisants, qui ont été entièrement caractérisées. Les nanoparticules de palladium bien dispersées ont été ensuite utilisées pour l'hydrogénation catalytique de liaisons C-C insaturées, de groupes nitro et carbonyle. Le CO2 dans ses états sub- ou supercritique a été utilisé pour améliorer l'efficacité des nanoparticules de palladium dans les réactions d'hydrogénation catalytique et subséquemment pour l'extraction du produit après la réaction de catalyse. Ce travail représente an effort pour intensifier un procédé dehydrogénation dans un milieu très visqueux, non volatile, biodégradable, biosourcé et non-toxique en utilisant du CO2 1) pour améliorer le transfert de matière et 2) pour extraire les produits de la réaction du milieu réactionnelThis Thesis represents a multi-disciplinary project where aspects going from solvent engineering to catalysis using metal-based nanoparticles, are explored. In this project, solvent engineering has been applied to bio-based deep eutectic solvents (DES) synthesized from choline tosylalaninate and glycerol in an effort to decrease the solvent viscosity by using different amounts of carbon dioxide. In this context, molecular rotors were used as an innovative method to measure the viscosity, avoiding the use of expensive instrumentation and giving the possibility to access to the microviscosity of the system. Furthermore, DES have been applied for the synthesis of palladium nanoparticles, also acting as stabilizers, which were fully characterized. The as-prepared palladium nanoparticles were then used for catalytic hydrogenations of unsaturated C-C bonds, and nitro and carbonyl groups. Sub and supercritical CO2 conditions have been applied to improve the efficiency of the palladium nanocatalysts in hydrogenation reactions and afterwards for the extraction of organic products. This work represents an effort to intensify a hydrogenation process in a highly viscous, non-volatile, biodegradable, and non-toxic DES by using CO2 in order to decrease mass transfer limitations and to extract products from the reaction media
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Fournier, Antoine. "Développement de procédés écoresponsables pour la synthèse de solvants et d'organocatalyseurs biosourcés". Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCK046/document.
Testo completoAbstract (sommario):
Les oxazolidinones sont des composés prometteurs pour des applications industrielles, mais aucune méthode ne convient à ce jour pour les produire à large échelle, à cause de l'utilisation de réactifs et de catalyseurs métalliques nocifs pour la santé et l'environnement. Une nouvelle méthode de synthèse de ces composés a donc été élaborée en utilisant des aminoalcools et du carbonate de diéthyle. Cette réaction est catalysée par un hydrogénocarbonate d'imidazolium biosourcé qui est produit par voie électrochimique afin de réduire son impact sur l'environnement.Cette méthode de synthèse d'oxazolidinones a ensuite été appliquée à la synthèse d'une oxazolidinone biosourcée. Pour cela, la synthèse d'un aminoalcool a été réalisée, et sa structure a été établie à partir de réactifs pouvant être issus de ressources renouvelables. La voie de synthèse a fait l'objet de modifications pour permettre la production de l'aminoalcool à plus grande échelle dans des conditions plus sûres.La seconde thématique de ces travaux porte sur les liquides ioniques, des sels liquides très peu volatils, couramment utilisés comme solvants. Ces composés sont généralement chers, ainsi, plutôt que de les éliminer à la fin de leur utilisation, il est plus intéressant de les recycler. Mais leur faible volatilité empêche leur recyclage par distillation, contrairement aux solvants organiques usuels. Il a ainsi été développé une première méthode électrochimique, économe en énergie, qui permet le recyclage de liquides ioniques biosourcés par la formation d'un hydrogénocarbonate d'imidazolium intermédiaire. Cette méthode a été comparée à d'autres procédés de recyclage grâce à une étude préliminaire du cycle de vie.Mots clés : oxazolidinone, aminoalcool, imidazolium, liquide ionique, biosourcé, recyclage, électrochimie, développement durable, écoconception, cycle de vieOxazolidinones are promising compounds for industrial applications, but nowadays there is not convenient method to produce them on large scale, because of the use of reactants and metallic catalysts harmful for health and environment. A new synthesis method of these compounds was thus elaborated using aminoalcohols and diethyl carbonate. This reaction is catalysed by a biobased imidazolium hydrogen carbonate which is produced by an electrochemical pathway in order to reduce its impact on the environment.This oxazolidinones synthesis method was then applied to the synthesis of a biobased oxazolidinone. To achieve this, an aminoalcohol synthesis was realised, and its structure was established from reactants that can come from renewable resources. The synthesis pathway was the object of modifications to permit the production of the aminoalcohol on a larger scale in safer conditions.The second thematic of these works is based on ionic liquids, very low volatile liquid salts, commonly used as solvents. These compounds are usually expensive, so, rather than to eliminate them at the end of their use, it is more interesting to recycle them. But their low volatility prevents their recycling by distillation, unlike common organic solvents. So, a first electrochemical method was developed, low energy consuming, permitting the recycling of biobased ionic liquids by the formation of an imidazolium hydrogen carbonate as intermediate. This method was compared with other recycling processes through a preliminary life cycle study.Keywords: oxazolidinone, aminoalcohol, imidazolium, ionic liquid, biobased, recycling, electrochemistry, sustainable development, eco-design, life cycle
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Estager, Julien. "Méthodes d'activation non conventionnelles et solvants propres pour une chimie durable : synthèse et valorisation organique des liquides ioniques". Chambéry, 2007. http://www.theses.fr/2007CHAMS048.
Testo completoAbstract (sommario):
L'étude des liquides ioniques a connu un essor considérable au cours de ces dernières années. En effet, en plus de leur faible volatilité, de leur non inflammabilité et de leur caractère non explosif, ils présentent une grande stabilité thermique et une forte aptitude à solvater, à la fois des composés organiques et inorganiques. Ces propriétés physico-chimiques originales en font des solvants de choix pour une chimie organique respectueuse de l'environnement dans l'optique du développement durable. Les objectifs de ce travail de Doctorat sont la synthèse et la valorisation de ces composés en profitant notamment de certaines de leurs qualités intrinsèques autorisant l'utilisation de méthodes d'activation dites non-conventionnelles comme les ultrasons ou l'irradiation par micro-ondes généralement rattachées à la chimie du développement durable. Après avoir détaillé les différentes propriétés des liquides ioniques, le premier chapitre de ce manuscrit de thèse décrit comment des phénomènes physiques comme des ondes ultrasonores ou micro-ondes peuvent influencer la réactivité chimique de manière différente par rapport à un chauffage thermique classique. Dans ces travaux de doctorat, l'utilisation des ultrasons pour la synthèse des liquides ioniques de seconde génération en une étape est ainsi étudiée; une forte diminution du temps de réaction est observée pour la plupart des liquides ioniques choisis. L'emploi combiné de la sonochimie et de l'irradiation par micro-ondes permet d'accélérer encore plus la cinétique de ces synthèses en mettant en commun les différents effets physiques et chimiques des ultrasons avec le chauffage homogène et rapide généré par les micro-ondes. A la fin de cette étude, des liquides ioniques de seconde génération sont ainsi obtenus avec de bons rendements et une cinétique de l'ordre de quelques minutes, comparées aux quelques 48-72h Emma nécessaires sous chauffage thermique classique. Bien que leur utilisation se limite souvent à un simple rôle de solvant, les liquides ioniques possèdent des propriétés en terme de réactivité qui peuvent aussi être mises à profit notamment en catalyse. Au cours de cette étude, ils ont été utilisés comme catalyseurs pour la réaction de condensation benzoïne, que ce soit sous irradiation ultrasonore ou sous irradiation micro-ondes. Les résultats obtenus ont montré de bonnes conversions et le liquide ionique a été recyclé sous certaines conditions. La réaction de cyclisation de Pictet-Spengler, souvent utilisée pour la synthèse d'hétérocycles bio-actifs, a été catalysée par différents liquides ioniques notamment de seconde génération. Ces sels incorporant des anions halogénures de métaux sont connus pour posséder une forte acidité. Sur cette observation, des liquides ioniques à tâche spécifique acide ont été utilisés pour la synthèse de 1-phényl-tetrahydro-β-carbolines via la réaction de Pictet-SpenglerThese last years, RTILs have become a very attractive alternative to conventional solvents. Because of their negligible vapor pressure, they are used as green solvents. In addition, their wide liquid range, tunable polarity or good solvating ability make them very interesting in organic synthesis. Finally, their non flammability and non explosive character make them good candidates to replace traditional molecular solvents in term of green chemistry. The objectives of this PhD thesis are the synthesis and the valuable use of these compounds by taking advantage of some of their remarkable properties with the use of non conventional activation methods such as microwave and / or ultrasound irradiation. The nature and properties of ionic liquids are described along the first chapter of this work and then the physical effects that lead to sonochemistry and chemistry effects under microwave irradiation are also discussed. The second chapter of this thesis described the advantage of non traditional activation methods for improving the synthesis of second generation ionic liquids. By using, ultrasonic irradiation, different families of nitrogen-bearing ionic liquids are obtained in a solvent-free or in aqueous medium, which gives a greener touch to the overall process. Aiming to overcome some limitations of this method, a new activation method using simultaneous ultrasound/microwave irradiation has been shown to lead to good yields in second generation ionic liquid in a kinetic of only few minutes. Then, the synthesis of benzion via benzoin condensation reaction has been studied with various ionic liquids as catalysts. Microwave activation and ultrasonic irradiation have been tested and good yields in benzoin have been observed whereas the recycling of the ionic catalyst was shown to be possible in specific conditions. Finally, different ionic liquids have been chosen to catalyse the electrophilic cyclisation of Pictet-Spengler, a classical synthetic method to reach bioactive molecules. Various acidic ionic compounds, including task specific ionic liquids have been tested and good conversion in tetrahydro-β-carbolines have been obtained with the most suited ionic catalyst
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Drillaud, Nicolas. "Agro-ressources et photo-régulation : vers la synthèse de nouveaux chromophores appliquée au domaine du développement durable". Compiègne, 2012. http://www.theses.fr/2012COMP2050.
Testo completoAbstract (sommario):
De nos jours, il existe une forte demande pour que le secteur de la chimie devienne plus éco-compatible. L’un des enjeux majeurs de la chimie verte est de remplacer, dans les réactions organiques, les solvants qui sont généralement très toxiques par des solvants moins nocifs comme l’eau. Néanmoins, la faible solubilité des composés organiques en milieu aqueux ne permet pas l’obtention de bons rendements réactionnels. Afin de pallier ce problème, l’ajout de tensioactifs au milieu réactionnel a été envisagé. Leur organisation sous forme d’agrégats va permettre de solubiliser des composés organiques dans l’eau. Les tensioactifs vont alors jouer le rôle de chimio-réacteurs. Cependant, il est parfois difficile d’extraire les produits en fin de réaction, ce qui entraîne également une difficulté pour le recyclage du milieu réactionnel. Pour résoudre ce problème, nous avons envisagé de synthétiser un tensioactif comportant un chromophore de type azobenzène. En effet ces composés ont la propriété de s’isomériser de façon réversible de leur forme trans à leur forme cis lorsqu’ils sont irradiés à une longueur d’onde spécifique. Nous avons mis au point la synthèse de l’un de ces tensioactifs. Ces propriétés physico-chimiques de tensioactivité et de photo-régulation ont été par la suite mises en évidence. Son rôle de chimio-réacteur pour la synthèse organique a été évalué et son emploi permet d’augmenter le rendement réactionnel. De plus, ses propriétés photochromiques permettent de faciliter l’extraction des produits en fin de réaction ainsi que son recyclageThe field of chemistry has witnessed a huge development since the 20th century. Nowadays, this field really needs to become more eco-friendly. One of the major challenges in green chemistry is to replace organic solvents with less hazardous solvents such as water. However, organic compounds are not very soluble in water, which involves a poor yield of organic reactions. To solve this problem, the use of surfactants has been considered. Indeed, those products organized themselves to form micelles, which allows the solubilization of organic compounds and play the part of chimio-reactors. Nevertheless, it can be difficult to extract the products at the end of the reaction, which will make the recycling of the reactional media less efficient. The solution we consider is to synthesize a new surfactant containing an azobenzene as chromophore. Actually, those compounds have the properties to isomerize themselves from their trans forms to their cis forms. This process is reversible. One of these surfactants was synthesized. Its physico-chemicals properties of tensioactivity and photo-regulation have been proved. The use of this surfactant as chimio-reactor for the organic synthesis has been assessed. We were able to show that its employ allows the increase of the yield of the reaction. Moreover, its photochromism properties permit to make the extraction of the products- at the end of the reaction- and also the recycling easier
6
Michelon, Carina. "EFICÁCIA DA ATIVAÇÃO ULTRASSÔNICA PASSIVA DO SOLVENTE NA REMOÇÃO DE MATERIAL OBTURADOR DURANTE O RETRATAMENTO ENDODÔNTICO ANÁLISE POR MICROTOMOGRAFIA COMPUTADORIZADA". Universidade Federal de Santa Maria, 2013. http://repositorio.ufsm.br/handle/1/6106.
Testo completoAbstract (sommario):
Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorThe removal of pre-existing root canal filling is basic requirement for endodontic retreatment in order to reveal necrotic tissue debris and bacteria which may be responsible for periapical inflammation and by the treatment failure. The aim of this study was to evaluate the efficacy of passive ultrasonic activation (PUA) with use of organic solvent as an assistant method in removal of filling material during endodontic retreatment and determine a protocol for its utilization, using high-resolution micro-Computed Tomography (micro-CT). Thirty curved mesial roots of mandibular molars with isthmus area were instrumented and filled with gutta-percha and EndoFill (Dentsply-Maillefer, Ballaigues, Switzerland) through Tagger s hybrid technique. After 30 days, the filling material was removed with the ProTaper Retreatment rotary system (Dentsply-Maillefer, Ballaigues, Switzerland) and the root canals were prepared with the F1-F4 ProTaper instruments (Dentsply-Maillefer, Ballaigues, Switzerland). The specimens will be randomized into two groups according to the final irrigation protocol. In the Manual Group, the root canals were irrigated and agitated manually with Orange Oil solvent (Citrol, Biodinâmica, Ibiporã, Brazil), 2,5% Sodium Hypochlorite (NaOCl) (Biodinâmica, Ibiporã, Brazil) and 17% Ethylenediaminetetraacetic Acid (EDTA) (Biodinâmica, Ibiporã, Brazil). In the PUA Group, the specimens were submitted to PUA with Orange Oil solvent, 2,5% NaOCl and 17% EDTA. High-resolution micro-CT scans was used to select the sample, analyze the root filling and measure the volume of the remaining root filling material after each stage of the retreatment. The volume of remaining filling material was established and transformed into percentage in relation to total volume of filling material. The dates were statistically analyzed with a significance level set at α = 0.05. The Mann Whitney test was used to compare the percentage of remaining filling material between groups, for canal thirds in each retreatment step. The Friedman test was used to verify differences among root filling material and the successive retreatment stages at each canal segment in same group. The differences amongst the coronal, middle and apical third in the each group were analyzed with Friedman test. The Dunn test was performed as the post-hoc multiple comparison method. No significant differences between groups when rotary instrumentation (Stage 1) was considered (P > 0.05). None of the irrigation protocols removed completely the remains of the root canal filling. The use of Manual e PUA protocols decreases statistically the amount of remaining filling material compared to Stage 1 (P = 0.000). In the PUA Group, the root canals showed significantly less percentage remaining filling material compared with Manual Group, for all thirds (P < 0.05). The PUA protocol left similar amount of filling material among the apical, middle and cervical thirds (P > 0.05). None of the irrigation protocols tested was able to completely remove all gutta-percha/sealer from the curved canals and with isthmus area. However, the results of this study suggest that in root canals with complex anatomy that require endodontic retreatment, the PUA with orange oil, NaOCl and EDTA can be a great aid in the removal of the remaining root filling material left after removal of the bulk of filling material.
A remoção do material obturador pré-existente é um requisito fundamental para a realização do retratamento endodôntico a fim de revelar restos de tecido necrótico e bactérias que podem ser responsáveis pela inflamação periapical e pela falha do tratamento. O objetivo deste estudo foi avaliar a eficácia da Ativação Ultrassônica Passiva (AUP) com uso de solvente orgânico, como um método auxiliar na remoção do material obturador durante o retratamento endodôntico e determinar um protocolo para sua utilização, através da Microtomografia Computadorizada (micro-CT). Trinta raízes mesiais curvas e com istmo de dentes molares inferiores foram instrumentadas e obturadas com guta percha e cimento EndoFill (Dentsply-Maillefer, Ballaigues, Suíça) através da técnica híbrida de Tagger. Após 30 dias, o material obturador foi removido com o sistema rotatório de desobturação ProTaper Retratamento (Dentsply-Maillefer, Ballaigues, Suíça) e o canal repreparado com os instrumentos F1-F4 do sistema rotatório ProTaper Universal (Dentsply-Maillefer, Ballaigues, Suíça). Os espécimes foram aleatoriamente divididos em dois grupos (n=15) de acordo com o protocolo de irrigação final. No Grupo Manual, os canais radiculares foram irrigados e agitados manualmente com solvente a base de Óleo de Laranja (Citrol, Biodinâmica, Ibiporã, Brasil), Hipoclorito de Sódio (NaOCl) 2,5% (Citrol, Biodinâmica, Ibiporã, Brasil) e Ácido Etilenodiaminotetracético (EDTA) 17% (Citrol, Biodinâmica, Ibiporã, Brasil) . No Grupo AUP, os espécimes foram submetidos à AUP com Óleo de Laranja, NaOCl 2,5% e EDTA 17%. A seleção da amostra, a análise da obturação e a mensuração do volume de material obturador remanescente após cada estágio do retratamento foram realizadas através da micro-CT. O volume de material obturador remanescente foi estabelecido e transformado em porcentagem em relação ao volume total de material obturador. Os dados foram submetidos à análise estatística com nível de significância fixado em α = 0.05. O teste de Mann Whitney foi usado para comparar a porcentagem de material obturador remanescente entre os grupos, em cada fase do retratamento. O teste de Friedman foi usado para analisar diferenças entre o volume da obturação e os estágios do retratamento dentro de um mesmo grupo. Diferenças entre os terços cervical, médio e apical dentro do mesmo grupo foram analisadas com o teste de Friedman. O teste de Dunn foi usado como post hoc para múltiplas comparações. Não houve diferença estatisticamente significante entre os grupos quando a instrumentação rotatória (Estágio 1) foi considerada (P > 0.05). Nenhum dos protocolos de irrigação removeu completamente os remanescentes de material obturador em todos os espécimes. Tanto o protocolo da AUP quanto o Manual diminuíram a quantidade de remanescente de guta percha e cimento em relação ao Estágio 1 (P = 0.001). No grupo AUP, os canais radiculares mostraram significantemente menos porcentagem de remanescentes de material obturador que o grupo Manual, para todos os terços (P < 0.05). O protocolo da AUP deixou quantidade similar de material remanescente em todos os terços do canal radicular (P > 0.05). Nenhum dos protocolos de irrigação testados foi capaz de remover completamente a guta percha/cimento de canais radiculares curvos e com área de istmo. Contudo, os resultados obtidos neste estudo sugerem que em canais radiculares com anatomia complexa que necessitam de retratamento endodôntico, a AUP com óleo de laranja, NaOCl e EDTA pode ser um grande auxiliar na remoção dos remanescentes de material obturador deixados após a desobturação do canal radicular.
7
Heintz, Juliette. "Systemic approach and decision process for sustainability in chemical engineering : Application to computer aided product design". Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0087/document.
Testo completoAbstract (sommario):
Dans un contexte de prise en compte croissante des enjeux environnementaux, l'industrie de la chimie et des procédés se retrouve confrontée à des problématiques de substitution de molécules. Les méthodes de formulation inverse, qui consistent en la recherche assistée par ordinateur de molécules satisfaisant un ensemble de contraintes, répondent de manière efficace à ces problématiques. A partir de l'analyse systémique des usages et fonctionnalités nécessaires dans ce contexte, nous développons un outil logiciel de formulation inverse mettant en oeuvre un algorithme génétique. Celui-ci est capable d'explorer un espace de solutions plus vaste en considérant les mélanges et non les molécules seules. Par ailleurs, il propose une définition des problèmes très flexible qui permet la recherche efficiente de molécules issues de filières renouvelables. En s'appuyant sur l'ingénierie système et l'ingénierie d'entreprise, nous proposons un processus formel de prise de décision pour la substitution de produit dans un contexte industriel. Ce processus de décision multi-critères englobe les phases de définition des exigences, de génération de solutions alternatives, de sélection de la meilleure alternative et de mise en oeuvre du produit. Il utilise une approche dirigée par les modèles et des techniques de prises de décision qui garantissent un alignement opérationnel en complément de l'alignement stratégique. A travers un cas d'étude, nous montrons comment l'utilisation conjointe de notre outil de recherche par formulation inverse et de notre processus de décision permet une démarche environnementale de substitution de produit à la fois efficiente et conforme à la réalité de l'entrepriseIn a context where environmental issues are increasingly taken into account, the chemical related industry faces situations imposing a chemical product substitution. Computer aided molecular design methods, which consist in finding molecules satisfying a set of constraints, are well adapted to these situations. Using a systemic analysis of the needs and uses linked to this context, we develop a computer aided product design tool implementing a genetic algorithm. It is able to explore a wider solution space thanks to a flexible molecular framework. Besides, by allowing a very flexible setting of the problem to be solved, it enables the search of molecules sourced from renewable resources. Based on concepts from system and enterprise engineering, we formalize a decision making process dedicated to the product substitution in an industrial context. This multi-criteria decision process includes the phases of the requirements definition, of the generation of alternative solutions, of the selection of the best alternative and of the product application. It uses a model driven approach and decision making techniques that guaranty an operational alignment in addition to the strategic alignment across the chemical enterprise. Through a case study, we expose how the combination of our computer aided product design tool and our decision making process enables an environmentally compliant approach of product substitution which is both efficient and in adequacy with enterprise context
8
Mangin, Floriane. "Synthèses de nouveaux tensioactifs éco-compatibles : étude de synthèses catalytiques et radicalaires en milieu micellaire". Thesis, Compiègne, 2015. http://www.theses.fr/2015COMP2224/document.
Testo completoAbstract (sommario):
Basé sur les concepts de développement durable et de chimie verte, l’une des alternatives envisagées par les chimistes, pour une chimie plus propre, est de substituer les solvants organiques, pouvant être dangereux et toxiques, par des solvants plus verts. L’eau est un bon candidat pour cette substitution car c’est le solvant le moins cher dans nos contrées, et le plus sûr : il est non-toxique, ininflammable et non explosif. Afin de palier la faible solubilité de la majeure partie des composés organiques dans l’eau, les tensioactifs peuven têtre utilisés afin d’améliorer les rendements réactionnels. Les milieux ainsi obtenus sont difficilement recyclables car ils nécessitent une forte dilution afin de casser les agrégats et de récupérer les produits. C’est pourquoi, l’utilisation de tensioactifs photo-régulables est une bonne alternative car il est possible d’organiser/désorganiser les agrégats par irradiation lumineuse et ainsi récupérer les composés organiques en fin de réaction tout en recyclant le milieu réactionnel. Pour cela, nous avons synthétisé trois tensioactifs possédant une fonction azobenzène(anionique, cationique, non ionique), afin de les tester en catalyse micellaire. Certains de ces tensioactifs, après en avoir déterminé leurs propriétés physico-chimiques (cmc et spectre UV-Visible) ont été testés dans une réaction pallado-catalysée : la substitution allylique de Tsuji-Trost. Nous avons réussi à démontrer l’intérêt d’utiliser un tensioactif photo-régulable par rapport aux tensioactifs commerciaux en terme de rendement et de recyclabilité. D’autre part, la décarboxylation de Barton, décrite pour la première fois en 1983, permet la formation d’alcanes à partir d’acides carboxyliques en utilisant un dérivé d’étain comme donneur d’hydrogène. Depuis lors, cette réaction a toujours été utilisée comme étape clé en synthèse totale de composés naturels et en solvants organiques. De plus, cette réaction est historiquement réalisée par activation conventionnelle, thermique ou par irradiation ultra-violette. C’est pourquoi, nous avons décidé d’étudier cette décarboxylation radicalaire dans l’eau, en présence de tensioactifs et en utilisant des modes d’activation non conventionnels : les micro-ondes et les ultrasons. De plus, en lieu et place d’étain, nous avons préféré l’utilisation de N-phénylmaléimide, déjà connu et étudié comme piège à radicaux, afin d’obtenir des maléimides substitués par des chaînes carbonées. Les rendements obtenus en milieux micellaires se sont avérés être aussi bons, voire meilleurs qu’en solvants organiquesBased on concepts of sustainable development and green chemistry, one of the alternatives envisioned by chemists is to substitute organic solvents, which can be dangerous and toxic, for greener solvents. Water is the best candidate for this substitution because it is thesafest and cheapest solvent in our countries : this solvent is non-toxic, non-flammable and inexplosive. In order to overcome the low solubility of most of organic compounds in water, surfactants can be used to improve the reaction yields. Media thus obtained are difficult to recycle because they require high dilution in order to break aggregates and recover products. Therefore, using photo-switchable surfactants is a good alternative because they can organize/disorganize by light irradiation. Organic compounds could be recovered after reactions and the recyclability of the medium can be improved. For this purpose, we synthesized three surfactants having an azobenzene moiety (anionic,cationic, nonionic), to test them in micellar catalysis. Some of these surfactants, after determining their physicochemical properties (CMCs and UV-visible spectra) were studied in a pallado-catalyzed reaction, the allylic substitution of Tsuji-Trost. We have successfully demonstrated the value of using a photo-switchable surfactant compared to commercialones in terms of yields and recyclability. In other hand, Barton decarboxylation, described for the first time in 1983, permits the formation of alkanes from carboxylic acids, using tin derivatives as hydrogen donors. Since then, this reaction has always been used as a key step in total synthesis of natural compounds in organic solvents. In addition, historically, this reaction was carried out by conventional activation (heat or ultraviolet light). Therefore, we decided to study this radical decarboxylation in water, in the presence of surfactants and using unconventional activation modes : microwave and ultrasound. Moreover, instead of tin, we preferred the use of N-phenylmaleimide, already known and studied as a radical trap, to obtain maleimides substituted by carbon chains. Yields obtained in micellar media were found tobe at least as good as in organic solvents
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Martins, Beatriz Lopes. "Implementação de melhorias para reduzir as rejeições durante o fabrico de embalagens de vidro". Master's thesis, 2019. http://hdl.handle.net/10316/97245.
Testo completoAbstract (sommario):
Dissertação de Mestrado em Engenharia e Gestão Industrial apresentada à Faculdade de Ciências e TecnologiaA presente dissertação surge na sequência da implementação de um projeto de melhoria contínua, numa fábrica de produção de embalagens de vidro. Este projeto surgiu a partir da necessidade de redução do número de rejeições verificadas, que originam o chamado “Stock especial”, o qual tem vindo a assumir um valor crescente ao longo dos anos. O objetivo máximo é então atingir uma produção sem defeitos. E, paralelamente, pretende-se conseguir monitorizar e analisar diariamente os dados relativos às rejeições verificadas e à fiabilidade das máquinas de inspeção automática. Numa primeira abordagem, é explicado o processo produtivo do vidro, bem como os processos de reescolha e de inspeção automática, processos sobre os quais irá incidir o âmbito deste projeto.O trabalho de pesquisa centrou-se na assunção da relevância que as não conformidades representam para a qualidade a garantir ao longo dos processos produtivos e daí serem consideradas como problemas que requerem uma resolução através da aplicação de um conjunto de ferramentas disponíveis. Foram desenvolvidas e implementadas ações de melhoria, discutidas nas sessões de trabalho realizadas com base, quer nos resultados obtidos no ano anterior, quer no acompanhamento dos dados relativos às rejeições das produções a decorrer durante o desenvolvimento do projeto, através da criação de um indicador de performance atualizado diariamente e disponibilizado aos colaboradores.As ações de melhoria executadas abrangem diferentes fases do processo, e são aplicadas tanto num contexto teórico, ao nível procedimental e de instrução, como prático, por exemplo, através das ferramentas a utilizar e das manutenções programadas a executar.Após uma análise aos resultados conseguidos, é estabelecida uma relação com as ações tomadas, de forma a perceber, para cada causa apontada, quais devem ser generalizadas e quais deveriam ter sido abordadas de forma diferente.
The present dissertation follows the implementation of a continuous improvement project in a glass containers production plant. This project arose from the need to reduce the number of rejections, which originate the so-called “Special stock”, which has assumed an increasing value over the years. The ultimate goal is to achieve a faultless production. At the same time, it is intended to be able to monitor and analyse daily the verified rejection data and the reliability of the automatic inspection machines.In a first approach, the glass production process is explained as well as the processes of resorting and automatic inspection, processes that will affect the scope of this project.The research work focused on the assumption of the relevance that the nonconformities represent for the quality to be assured throughout the productive processes and for this reason are considered as problems that require a resolution through the application of a set of available tools.Improvement actions were developed and implemented, discussed in the work sessions carried out, based on both the results obtained in the previous year and the monitoring of the data related to the rejections of the productions during the development of the project, through the creation of an indicator of performance updated daily and made available to employees.The improvement actions carried out cover different stages of the process and are applied in a theoretical context, at procedural and instructional level, as well as practical, for example, through the tools to be used and the scheduled maintenance to be performed. After an analysis of the results achieved, a connection is established with the actions taken, in order to realize, for each cause, which actions should be generalized, and which should have been a different approach.
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Ferreira, Mariana Xavier Cardoso. "A resolução participada de problemas relativos à organização do espaço e dos materiais experienciados durante o tempo de trabalho na área da casa". Master's thesis, 2017. http://hdl.handle.net/1822/57381.
Testo completoAbstract (sommario):
Relatório de estágio de mestrado em Educação Pré-EscolarO presente relatório de estágio, construído no âmbito da unidade curricular Estágio (inserida no plano de estudos do Mestrado em Educação Pré-Escolar), reporta-se à conceção, desenvolvimento e avaliação de um projeto de intervenção pedagógica supervisionada que decorreu numa sala de jardim de infância relativa a um grupo de vinte e cinco crianças com idades compreendidas, a oito de novembro de dois mil e dezasseis, entre os quatro anos e nove meses e os cinco anos e dez meses. Tendo em consideração as variáveis situacionais observadas, delineou-se como principal finalidade promover situações favoráveis à resolução, por parte das crianças, de problemas relativos à organização do espaço e dos materiais por si experienciados durante o tempo de trabalho na área da casa. Durante este percurso de resolução, estruturalmente documentado tendo em consideração etapas consideradas caracterizadoras do mesmo - a problematização, a delineação de um plano, a execução do plano e a avaliação -, num contexto aproximado ao da investigação-ação, procurou-se perceber qual o impacto educativo da intervenção pedagógica desenvolvida. Esta investigação, neste caso, de caráter qualitativo, ancorou-se em registos escritos e em imagens, os quais foram possibilitados graças à observação e ao registo vídeo, áudio e fotográfico. Esta informação, depois de organizada e de os seus significados essenciais serem sintetizados, permitiu concluir que, contrariamente ao verificado antes da efetivação deste projeto, os planos das crianças se revelaram mais detalhados, não sendo caracterizados por uma certa relutância relativamente à especificação dos materiais que intencionavam utilizar. Verificou-se ainda que durante o tempo de trabalho as crianças tiveram facilidade em encontrar os materiais que desejavam e levaram a cabo os seus planos, não revelando dúvidas quanto ao local e modo de arrumação dos materiais. Indiciou também que o facto de este ter sido um processo de resolução levado a cabo por um grupo de crianças ativamente implicado nele teve consideráveis repercussões no que se refere, entre outros aspetos, à sensação de bem-estar, à apropriação da utilização do espaço e da localização de cada material - a qual constitui a base de uma progressiva autonomia -, ao desenvolvimento de competências de resolução de problemas, da autoconfiança, do sentido de pertença e da consciência de si como aprendente - componentes que integram o desenvolvimento da área transversal formação pessoal e social. Neste sentido, salienta-se a importância da reflexão permanentemente sobre esta decisiva dimensão pedagógica - o espaço -, não desvalorizando, também neste âmbito, a participação das crianças: sujeitos e agentes do processo educativo.
The present practicum report, written in the scope of the practicum curricular unit (inserted in the study plan of the Master's in Pre-School Education), reports the conception, development and evaluation of a supervised pedagogical intervention project which occurred in a kindergarten room with a group of twenty-five children between four years and nine months and five years and ten months of age on the eighth of November, two thousand and sixteen. Considering the situational variabilities observed, the goal was to promote situations favourable to the solving of problems related to the organization of the space and the materials experienced over the work time at the house area by the children. During this problem solving process, structurally documented considering its characterizing steps — problematization, the definition of a plan, the execution of the plan and the evaluation -, in a context approximate to that of action research, we tried to understand the educative impact of the developed pedagogical intervention. This research, of qualitative character, anchored itself in written records and images, which were taken through observation, video, audio and photographic record. This information, once organized and its essential meanings synthesized, allowed to conclude that, contrary to what was verified before the implementation of this project, the plans of the children revealed themselves more detailed, not being characterized by a certain reluctance in specifying the materials they intended to use. Moreover, it was verified that the children could easily find the materials they wished for and that the work time proceeded as they had planned, not presenting doubts in relation to the place and mode of arranging the materials. It was also indicted that the fact that this solving process was performed by a group of children actively implicated in it had considerable repercussions in relation to, amongst other aspects, the feeling of well-being; the appropriation of the utilization of the space and the location of each material — which constitutes the basis for a progressive autonomy —; the development of problem solving competences, self-confidence, the sense of ownership and the consciousness of oneself as learner - components which integrate the development of the transversal area of personal and social formation. Thus, the importance of permanent reflexion about this decisive pedagogical dimension - space - is emphasized. It is, nonetheless, crucial not to depreciate, also in this sense, the participation of the children: subjects and agents of the educative process.
Libri sul tema "Solvant durable"
1
Manuel, Agosin, a cura di. Solving the riddle of globalization and development. New York: Routledge, 2006.
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2
1957-, Morse Stephen, a cura di. Resilient participation: Saving the human project? Abingdon, Oxon: Earthscan, 2012.
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3
Bloom, David, Manuel Agosin, George Chapelier e Jagdish Saigal. Solving the Riddle of Globalization and Development. Taylor & Francis Group, 2006.
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4
Bloom, David, Manuel Agosin, George Chapelier e Jagdish Saigal. Solving the Riddle of Globalization and Development. Taylor & Francis Group, 2006.
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5
Bloom, David, Manuel Agosin, George Chapelier e Jagdish Saigal. Solving the Riddle of Globalization and Development. Taylor & Francis Group, 2006.
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(Foreword), Jonathan Lash, a cura di. Eco-Pioneers: Practical Visionaries Solving Today's Environmental Problems. The MIT Press, 1998.
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Eco-pioneers: Practical visionaries solving today's environmental problems. Cambridge, Mass: MIT Press, 1997.
Cerca il testo completoCapitoli di libri sul tema "Solvant durable"
1
Dobrocky, Tomas, e Àlex Rovira. "Problem Solving Disorders of CSF". In IDKD Springer Series, 13–27. Cham: Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-50675-8_2.
Testo completoAbstract (sommario):
AbstractSpontaneous Intracranial Hypotension (SIH)Spontaneous intracranial hypotension (SIH) is a debilitating medical condition, which is perpetuated by the continuous loss of cerebrospinal fluid (CSF) at the level of the spine, and is the top differential diagnosis for patients presenting with orthostatic headache. Neuroimaging plays a crucial role in the diagnostic work-up and monitoring SIH, as it provides objective data in the face of various clinical symptoms and very often a normal opening pressure on lumbar puncture. Brain MRI frequently demonstrates typical signs of CSF depletion and includes homogenous dural enhancement, venous distention, subdural collections, and brain sagging. Three types of CSF leaks may be distinguished: (1) ventral dural leaks due to microspurs, (2) leaking spinal nerve root cysts, (3) or direct CSF venous fistula. The quest for the leak may be the fabled search for the needle in the haystack, scrutinizing the entire spine for a dural breach often the size of pin. The main role of spine imaging is the correct classification and precise localization of CSF leaks. Precise localization of the CSF leak site is crucial to successful treatment, which is generally a targeted percutaneous epidural patch or surgical closure when conservative measures fail to provide long-term relief.Obstructive Hydrocephalus. Communicating Hydrocephalus. Normal Pressure HydrocephalusModern imaging techniques play an essential role for understanding of the anatomy of the cerebrospinal fluid (CSF) spaces and ventricular system, as well as the hydrodynamics of CSF flow, and consequently in the assessment of the different types of hydrocephalus. Obstructive (non-communicating) hydrocephalus is a complex disorder resulting from an obstruction/blockage of the CSF circulation along one or more of the narrow apertures connecting the ventricles, being the most common type of hydrocephalus in children and young adults. On the other hand, communicating hydrocephalus is defined as a cerebrospinal fluid flow circulation abnormality outside the ventricular system that produces an increase in the ventricular size. Most cases are secondary to obstruction of CSF flow between the basal cisterns and brain convexity and include common conditions such as subarachnoid hemorrhage and meningitis (infectious and neoplastic). In a subset of communicating hydrocephalus, no CSF obstruction can be demonstrated as occurs in normal pressure hydrocephalus (NPH), a complex entity with poorly understood cerebrospinal fluid dynamics. Neuroradiology plays an essential role in the diagnosis of hydrocephalus, and in distinguishing this condition from other causes of ventriculomegaly.
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Cook, E. K., M. Brown-Augustine, E. Creel e S. Raj. "Greener Solutions to Achieve Durable Water Repellency Without Using PFASs". In Toward a PFAS-free Future, 154–88. Royal Society of Chemistry, 2023. http://dx.doi.org/10.1039/bk9781837671410-00154.
Testo completoAbstract (sommario):
This chapter explores achieving durable water repellent (DWR) coatings on textiles without the use of perfluoroalkyl and polyfluoroalkyl substances (PFASs). This was a challenge posed by W. L. Gore and Associates to the Greener Solutions Course project team at the University of California (UC) Berkeley. Ideally, a non-PFAS DWR coating would be highly hydrophobic to achieve dynamic water repellency; exhibit oil-repelling (oleophobic) properties for self-cleaning and insulation; and be durable, washable, and aesthetically pleasing to consumers. Inspiration for non-fluorinated, bio-inspired solutions was drawn from the natural hydrophobic mechanism of micro- and nano-hierarchical structuring of the lotus leaf as well as other organisms. The project team performed a literature review specific for hierarchical structuring using low hazard fibers and solvents, resulting in numerous potential alternatives. The two most promising solutions were silica nanosols and blow spinning, which showed the best hydrophobicity, potential for oleophobicity, and applicability to textiles. This chapter also highlights the mechanics of water- and oil-repellency of the possible DWR alternatives, potential hazards, and recommendations made by the project team based on these findings.
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Efraín Deras, José, Alberto Cortés e Guillermo Funes. "The Role of the Central American Bank for Economic Integration in Regional Integration and Development". In Regional Development Banks in the World Economy, 116–30. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198861089.003.0006.
Testo completoAbstract (sommario):
The Central American Bank of Economic Integration (CABEI) is one of the few modern regional institutions that has proved to be durable in the Central American context, despite the many hurdles the Bank has had to jump since its creation. Accumulated knowledge and the relationships with its main stakeholders have allowed it to develop strengths and to create an efficient and solvent entity in providing medium- and long-term finance to promote regional integration, and the economic and social development of the isthmus. The partners’ commitment and the Bank’s status achieved in international capital markets have turned the CABEI into the main regional development bank source of financing in the region and a strategic development institution for the future of the region. The underlying strength of CABEI lies in its balance sheet in terms of liquidity, capitalization, the quality of its assets, and the capacity to generate income—thus the support of its shareholders who are also beneficiaries as clients.
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Forestal, Jennifer. "Digital Technologies and the Problem of Democracy". In Designing for Democracy, 1–30. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780197568750.003.0001.
Testo completoAbstract (sommario):
This chapter introduces the book’s argument and approach. It argues that participatory democracy—understood as a method of collective problem-solving—is well suited for understanding the democratic implications of digital technologies. The chapter then explains why the book takes the methodological approach of examining the democratic effects of digital technologies through the lens of the built environment. Ultimately, the reason is one of power: the built environment exerts considerable power over us, shaping our behavior in often-invisible ways. Insofar as democracy requires citizen participation in the decisions that shape their lives, they require a built environment that affords the opportunity to engage in the requisite democratic affordances—specifically, the practices of recognition, attachment, and experimentalism. In order to facilitate these affordances, democratic environments must have three characteristics: (1) boundaries, to facilitate recognition; (2) durable spaces, to cultivate attachment; and (3) flexible spaces, to provide opportunities and resources for experimental habits.
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Kumar, Sunil, Digvijay Pandey, Sunil Kumar, Abhishek Dwivedi, Abhishek Kumar Mishra e Mohit Singh Chauhan. "Predictive Modeling of Supply Chain Disruptions in the COVID-19 Pandemic Using Advanced Machine Learning Approaches". In Advances in Logistics, Operations, and Management Science, 124–36. IGI Global, 2024. http://dx.doi.org/10.4018/979-8-3693-1347-3.ch009.
Testo completoAbstract (sommario):
In light of the COVID-19 pandemic, this research examines supply chain disruptions critically, highlighting their devastating effect on businesses like as drugs and perishable food. The report emphasizes the need of durable supply networks, encouraging firms to invest in strong risk mitigation measures and cutting-edge technology to maintain continuity and adaptation in an ever-changing business environment. Deep learning and machine learning approaches have emerged as critical tools for solving these supply chain difficulties. Decision trees, random forests, k-nearest neighbors, and support vector machines (SVM) have all been shown to be effective in mitigating supply chain issues, with SVM achieving an impressive accuracy rate of 96.6%. Furthermore, the random forest model has a respectable accuracy of 95.00%. Notably, the study discovers that the gated recurrent unit architecture outperforms the long short-term memory design, with an accuracy rate of 98.01%. This investigation provides useful insights for the difficulties confronting contemporary supply networks.
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Cruz Romo, Lesly Jhanela, e Stephanie Geraldine Rosero Achicanoy. "Evaluación del extracto obtenido de la cáscara de papaya y su posible uso como colorante alimentario." In Sostenibilidad de procesos desde la economía circular en el contexto de la pospandemia covid-19, 26–44. Editorial UNIMAR, 2022. http://dx.doi.org/10.31948/editorialunimar.163.c4.
Testo completoAbstract (sommario):
La cáscara de papaya es un residuo orgánico que se genera durante todo el año en grandes cantidades, causando efectos negativos sobre el medioambiente. Por otra parte, la industria alimentaria emplea colorantes sintéticos que pueden ser perjudiciales para la salud de las personas, por ejemplo, el colorante número 5 (tartrazina). Por lo tanto, la presente investigación propone una solución para ambas problemáticas, la obtención de un colorante natural con propiedades nutraceúticas a partir de este residuo, que pueda ser usado como aditivo en la industria alimentaria. La obtención del colorante se realizó mediante la extracción asistida por ultrasonido, en donde se usó etanol en concentraciones de 60, 75 y 90 % y a temperaturas de 20 y 40 °C; seguidamente, se realizó la cuantificación de polifenoles mediante el método de UV-vis. Finalmente, se concluyó que la mejor extracción fue por ultrasonido durante 60 minutos, a una concentración de solvente de 60 % y temperatura de 20 °C, con una cantidad de polifenoles de 1268,35 ± 21,01, expresados en mg de ácido gálico por cada 100 gramos de muestra; asimismo, se observó que el extracto obtenido puede ser una buena alternativa a un colorante sintético.
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Levitt, Roberta, e Joseph Piro. "Game-Changer". In Gamification, 807–25. IGI Global, 2015. http://dx.doi.org/10.4018/978-1-4666-8200-9.ch040.
Testo completoAbstract (sommario):
Technology integration and Information and Communication Technology (ICT)-based education have enhanced the teaching and learning process by introducing a range of web-based instructional resources for classroom practitioners to deepen and extend instruction. One of the most durable of these resources has been the WebQuest. Introduced around the mid-1990s, it involves an inquiry-centered activity in which some or all of the information learners interact with comes from digital artifacts located on the Internet. WebQuests still retain much of their popularity and educational relevance and have shown remarkable staying power. Because of this, recontextualizing the WebQuest and situating it within the modern-day trend of the “gamification” of instructional design is examined, together with how the WebQuest can promote solid academic gain by placing students inside a learning space patterned after a multi-user virtual environment. This structure includes emphasis on teamwork and socially responsible problem-solving, intense task immersion, task game flow and scalability, and reward cycles. The authors also discuss how including an upgraded WebQuest informed by Common Core Grade-Specific Learning Standards in pre-service education curriculum can advance multiple facets of teacher education with candidates who are acquiring, learning, applying, and integrating pedagogical, technological, and content-area skills. Further, the authors offer suggestions for new directions in the use of web-based resources in 21st century education enterprise.
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Khuntia, Rashmita, Manoj Kumar Banjare e Prashant Mundeja. "BASICS OF IONIC LIQUIDS AND ITS APPLICATION". In Futuristic Trends in Chemical Material Sciences & Nano Technology Volume 3 Book 6, 212–26. Iterative International Publishers, Selfypage Developers Pvt Ltd, 2024. http://dx.doi.org/10.58532/v3bjcs6p2ch7.
Testo completoAbstract (sommario):
Ionic liquids (ILs) can be treated in chemical synthesis, biocatalytic transformations, electrochemical, and analytical device designs, biosensors constructions, and food-related separation processes. Imidazole-based ILs are generally used as extraction solvents and in food analysis. Based on this context, this book chapter focuses on the characteristics, synthesis, generations, and main applications of ILs in different areas such as Metallurgy, separations, biochemistry, the food industry, and drug delivery systems. This chapter also includes physicochemical, and toxicological, and also discusses ILs composed of ions based on natural products. Future outlooks on the subject and the major technological challenges and advantages of using these attractive liquids are also discussed. As we know in our day-to-day lives the demand for drugs in society is being to increases. With these new trends getting new challenges to design new drugs. To meet this requirement in society many pharmaceutical companies are introducing new drugs with poor solubility which shows no proper diagnosis and indicates the birth of another health issue in the human body our research groups are trying to solve the problem by introducing and adding ionic liquids in the drugs to the enhance of proper solubility of drugs in the human body. Here we have discussed the preparation and advanced types of biodegradable Ionic liquids (BDILs), Task-special Ionic liquids(TSILs), and Room-Temperature Ionic liquids(RTILs) which are very useful in society. This molten solution can be categorized as sustainable, durable, active substance in the pharmaceutical field, and reliable. It can be treated as a good catalyst and, a better quality enhancer in the medical field.
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SOARES, S. J. L., P. B. V. SILVA e D. S. RIBEIRO. "Betalaínas: extração e estabilidade – breve revisão". In A indústria de alimentos e a economia circular: alimentando uma nova consciência. Agron Food Academy, 2021. http://dx.doi.org/10.53934/9786599539640-11.
Testo completoAbstract (sommario):
A cor é um dos atributos mais perceptíveis nos alimentos, de forma a desempenhar papel relevante no sucesso de um produto alimentício no mercado. A busca por colorir alimentos de forma a torná-los atraentes levou a indústria a desenvolver uma gama de corantes sintéticos, estes por sua vez são conhecidos atualmente por causarem danos à saúde do consumidor. Com isso, frente a preocupação do consumidor, as indústrias estão buscando cada vez mais obter corantes de forma natural, uma vez que o uso de corantes naturais tem a ele atrelado benefícios à saúde. Dentro das classes de pigmentos naturais com potencial para uso como corante alimentício, encontram-se as betalaínas, pigmentos nitrogenados, solúveis em água, responsáveis pela coloração brilhante de algumas plantas, podendo ser classificadas em betacianinas (vermelho-violeta) e betaxantinas (amarelo). As betalaínas podem ser obtidas a partir de plantas pertencentes à ordem Caryophyllales e fungos superiores dos gêneros Amanita e Hygrophorus. A extração de betalaínas é comumente realizada por meio da maceração ou moagem da fonte primária (planta crua ou cultura celular), em algum solvente. As betalaínas apresentam-se instáveis a diversos fatores intrínsecos e extrínsecos, que devem ser controlados tanto durante a extração, como após. Sendo assim, esta revisão visa fornecer uma visão geral sobre as betalaínas, formas de extração e estabilidade, de modo a conhecer melhor as condições de obtenção das mesmas.
Atti di convegni sul tema "Solvant durable"
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Weliweriya, Nandana, Tra Huynh e Eleanor C. Sayre. "Standing fast: Translation among durable representations using evanescent representations in upper-division problem solving". In 2017 Physics Education Research Conference. American Association of Physics Teachers, 2018. http://dx.doi.org/10.1119/perc.2017.pr.103.
Testo completo
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Yoon, Heonjun, Byeng D. Youn e Heung S. Kim. "Analysis of Electromechanical Performance of Energy Harvesting Skin Based on the Kirchhoff Plate Theory". In ASME 2014 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/detc2014-35433.
Testo completoAbstract (sommario):
As a compact and durable design concept, energy harvesting skin (EH skin), which consists of piezoelectric patches directly attached onto the surface of a vibrating structure as one embodiment, has been recently proposed. This study aims at developing an electromechanically-coupled analytical model of the EH skin so as to understand its electromechanical behavior and get physical insights about important design considerations. Based on the Kirchhoff plate theory, the Hamilton’s principle is used to derive the differential equations of motion. The Rayleigh-Ritz method is implemented to calculate the natural frequency and the corresponding mode shapes of the EH skin. The electrical circuit equation is derived by substituting the piezoelectric constitutive relation into Gauss’s law. Finally, the steady-state output voltage is obtained by solving the differential equations of motion and electrical circuit equation simultaneously. The results of the analytical model are verified by comparing those of the finite element analysis (FEA) in a hierarchical manner.
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Bogdanovich, Alexander, e Naveen Rastogi. "3-D Variational Analysis of Bonded Composite Plates". In ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-0623.
Testo completoAbstract (sommario):
Abstract Analysis and design of strong and durable joints of composite structural parts is recognized as primarily important problem. Most common analytical techniques for bonded, bolted, riveted and other typical joints are based on 2-D shell/plate theories which allow one to obtain reasonable results only in the zones away from the sites of high stress/strain gradients. Accordingly, these theories may provide not only quantitatively inaccurate, but even qualitatively wrong results in the zones of sharp stress/strain variation, even in the case of relatively thin adherends. High shear and peel stress concentration (possibly, even singularity) may occur along these lines causing delaminations, subsequent loss of hermeticity and destruction of the joint. Analysis of this problem shows that complete and accurate solution can be only obtained in 3-D elasticity formulation. A general methodology and some preliminary results of solving 3-D problems of bonded plates are presented in this paper. Numerical results reveal high concentration of the in-plane normal stress and transverse normal and shear stresses along the edge lines of the joint.
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ANA, MARCIO DE FREITAS SANTA. "FORMAÇÃO DE MEMBRANA PROTÔNICA COM NANOCOMPÓSITOS SULFONADOS DE PS / PEEK / ARGILA MMT E AGENTE INTERFACIAL MB APLICADAS A CÉLULA COMBUSTÍVEL TIPO PEM". In Brazilian Congress. brazco, 2020. http://dx.doi.org/10.51162/brc.dev2020-00022.
Testo completoAbstract (sommario):
Este artigo visa a utilizacao de fontes energeticas sustentaveis tendo como foco a preservacao dos recursos naturais, visando atender a demanda energetica com o minimo de danos ao Meio Ambiente com a obtencao de Nanocompositos a partir da conjugacao dos polimeros comerciais sulfonados PS (poliestireno) PEEK (poli-eter- cetona) com o reforco da argila sulfonada para que a membrana tenha as caracteristicas necessarias para ser aplicadas na PEMFC. A justificativa desta proposta esta baseada na investigacao de que a sulfonacao previa tanto das bases polimericas quanto da argila mineral (Montmorilonita-MMT), utilizados para preparar o nanocomposito pode ser uma alternativa para se conjugar as propriedades que tanto se almeja encontrar nas membranas, isto e, elevada permeabilidade protonica e resistencias termica e mecanica. Em termos economicos, a justificativa esta vinculada a necessidade de reduzir custos de producao e ao mesmo tempo obter membranas com elevadas condutividade e resistencias termicas e mecanicas em linhas gerais, a proposta do artigo tem o objetivo preparar blendas polimericas de alto desempenho baseadas em PEEK e PS com adicao de agente compatibilizante durante o preparo da solucao polimerica de mostrar o desenvolvimento de uma materia-prima alternativa para substituir a membrana utilizada comercialmente. Garantindo a homogeneidade e analisar a confiabilidade das membranas do tipo PEM para utilizacao em celulas combustiveis, baseadas em PEKK E PS com adicao de agente compatibilizante durante o preparo da solucao polimerica, garantindo a homogeneidade, uma vez que requisitos de durabilidade e custo passaram a ser fundamentais a esta tecnologia. A metodologia proposta para o preparo da mistura polimerica foi solubilizar os polimeros SPEEK (poli (eter-eter-cetona) sulfonado), SPS (Poliestireno sulfonado) e 22298-CN - MB (Agente Interfacial) no solvente DMF (Dimetilformamida) em sistema fechado acoplado a um condensador de refluxo, para evitar a evaporacao do solvente, e promover a mistura das bases polimericas e do agente compatibilizante MB no teor de 3 % em peso em relacao a mistura. Os resultados preliminares do grupo de pesquisa indicaram que a mistura sPS/sPEEK apresentou boas caracteristicas protonicas e termicas ,
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Konak, Fatih, e Hakan Turan. "Was the Turkish Financial Crisis in 2001 Caused by External or Internal Factors?" In International Conference on Eurasian Economies. Eurasian Economists Association, 2013. http://dx.doi.org/10.36880/c04.00724.
Testo completoAbstract (sommario):
There has been much discussion on the issue of whether financial crisis are caused by external factors or internal factors. This research has attempted to demonstrate what were the real reasons whether internal or external factors, behind the Turkish financial crisis in 2001. The crucial question that demands an answer is ‘which one of them overwhelmingly triggered the crisis. It was argued that before the crisis occurred, the Turkey economy had been affected by some unfavourable external shocks such as, rise in crude oil prices which increased the current account deficit; however, it can be seriously solved by employing correct finance technique that using long-term capital and direct investment instead of short-term capital. Therefore, external factors effects on the economy can be eliminated by right monetary policy, which means they were not the key factors. On the other hand, there were many internal factors behind the crisis such as fragile finance and banking system, ruling out dis-inflation negative effects and seasonal factors and so on. It could be advocated that these factors led the Turkish economy into uncertain situation and they had central part in the crisis because, when the last global financial crisis was occurred in 2008, although all unexpected external factors were soared, the Turkish economy was less affected, because the Turkish economy has been become more durable by solving the internal triggering factors.
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Ojovan, Michael I., Pavel P. Poluektov e Vladimir A. Kascheev. "Self-Disposal Option for Heat-Generating Waste". In ASME 2011 14th International Conference on Environmental Remediation and Radioactive Waste Management. ASMEDC, 2011. http://dx.doi.org/10.1115/icem2011-59182.
Testo completoAbstract (sommario):
Self-descending heat generating capsules can be used for disposal of dangerous radioactive wastes in extremely deep layers of the Earth preventing any release of radionuclides into the biosphere. Self-disposal option for heat-generating radioactive waste such as spent fuel, high level reprocessing waste or spent sealed radioactive sources, known also as rock melting concept, was considered in the 70s as a viable alternative disposal option by both Department of Energy in the USA and Atomic Industry Ministry in the USSR. Self-disposal is currently reconsidered as a potential alternative route to existing options for solving the nuclear waste problem and is associated with the renaissance of nuclear industry. Self-disposal option utilises the heat generated by decaying radionuclides of radioactive waste inside a heavy and durable capsule to melt the rock on its way down. As the heat from radionuclides within the capsule partly melts the enclosing rock, the relatively low viscosity and density of the silicate melt allow the capsule to be displaced upwards past the heavier capsule as it sinks. Eventually the melt cools and solidifies (e.g. vitrifies or crystallizes), sealing the route along which the capsule passed. Descending or self-disposal continues until enough heat is generated by radionuclides to provide partial melting of surrounding rock. Estimates show that extreme depths of several tens and up to hundred km can be reached by capsules which could never be achieved by other techniques. Self-disposal does not require complex and expensive disposal facilities and provides a minimal footprint used only at operational stage. It has also an extremely high non-proliferation character and degree of safety. Utilisation of heat generated by relatively short-lived radionuclides diminishes the environmental uncertainties of self-disposal and increases the safety of this concept. Self-sinking heat-generating capsules could be launched from the bottom of the sea as well as from intermediate-depth or deep boreholes. Self-disposal can also be used with a novel purpose — to penetrate into the very deep Earth’s layers beneath the Moho’s discontinuity and to explore Earth interior.
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SOUZA, EWERTON SILVA VIEIRA DE, CIBELE DANTAS PEIXOTO, DIANA CARLA SECUNDO DA LUZ, GABRIEL DE FIGUEIREDO BEZERRA COSTA, KARLA SUSANNA CORREIA CAVALCANTI DE ALBUQUERQUE, MAIARA ALVES DA SILVA, MARIA LETICIA DE FREITAS BASILIO e MATHEUS SANTOS DE MACEDO. "USO DO RESÍDUO DO PAPEL GERADO PELA UFRN NA FABRICAÇÃO DE TIJOLOS - DESENVOLVIMENTO DE UMA METODOLOGIA". In Brazilian Congress. brazco, 2020. http://dx.doi.org/10.51162/brc.dev2020-00018.
Testo completoAbstract (sommario):
A crescente producao de residuos solidos e, cada vez mais, uma adversidade decorrente do consumo desenfreado que marca a contemporaneidade. A tomada de solucoes que reduzam o impacto social, economico e ambiental e, gradativamente, tratada como uma urgencia em todas as areas. Para tanto, a construcao civil e aberta a inovacoes que possibilitem a diminuicao dos custos e o aumento da produtividade. Assim sendo, aliando um cenario em que o papel representa cerca de 70% do material recolhido e passivel de reciclagem no Campus Central da UFRN, pensou-se em desenvolver um tijolo macico de papel que possibilitasse um reaproveitamento desse insumo na instituicao, alem de contribuir para uma melhor destinacao do residuo solido. A partir de pesquisa da bibliografia disponivel sobre tijolos ecologicos de papel e dos dados coletados durante as praticas desenvolvidas nos Laboratorios de Materiais de Construcao Civil e Materiais Ceramicos da UFRN, este trabalho visa analisar o processo produtivo das etapas da fabricacao do tijolo e propoe um metodo para sistematiza-lo. Como resultado da sua aplicacao, aqui proposto, foi possivel promover, por exemplo, a economia dos materiais, a otimizacao no uso dos instrumentos disponiveis e a definicao de alguns parametros como tamanho das tiras de papel, proporcao entre solvente e soluto, formas de prensagem e tecnicas de secagem, quando comparado com outros metodos existentes para fabricacao de tijolos similares.,
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Musrati, Firas, Ali Elmozwagi, Ayoub Sherik, M. Ben Abdalla, S. Sadeg, Ziyad Aoun e Seraj Bosnina. "Field Reactivation Using Innovative and Long-Term High-Alloy Coiled-Tubing Gas Lift System in Highly Corrosive Mediterranean Offshore Field, Libya". In SPE Conference at Oman Petroleum & Energy Show. SPE, 2024. http://dx.doi.org/10.2118/218574-ms.
Testo completoAbstract (sommario):
Abstract An offshore Libya mature oil field with a large gas cap underlies a massive aquifer located in the Mediterranean Sea. It is a naturally fractured carbonate reservoir producing an extremely corrosive crude – naturally- from [SD3][AS4]14 monobore horizontal oil wells and one gas observation well drilled across gas cap. The field suffers from increased water cut and major crossflows across perforated intervals. In previous years, all systematic and maintenance shutdowns, including those caused by force-majeure due to security and political instability in the country, were feasibly overcome by naturally restarting the field. However, recently with the increased water cut, a greater volume of water flooding into the oil-producing zones would make it impossible to reactivate the field without use of artificial lift systems. Installing any artificial lift means in a monobore completion in the depleted field would require a large investment that would make the installation uneconomical. Hence, all future planned shutdowns would be at risk without making a big investment or developing an innovative solution. Developing such a solution meant solving a complex problem in short time that demanded attention to detail, critical thinking, and creative problem-solving, using the already available operational structure to restart the field safely. N2 kickoff was initially performed to reactivate the field without success due to the large N2 quantities required to produce all flooded water into oil zones which takes from a week to few months of lifting, in additional to the logistical challenges and involved cost. A rigless electrical submersible pump does not meet the required flow rates of more than 3,000 BLPD to stop the dynamic crossflow and hence, the reactivation would not be successful. The field was already producing 46 MMscf/D of gas, most of which was burnt out. It was proposed to use part of that wasted gas or to divert the gas production of the only gas well and inject the gas through temporarily installed coiled tubing as a single gas injection point at a predefined depth to offload the flooded water and reestablish the previous production figures. In 2017, 2 wells out of 14 producing wells suffered from liquid loading and were successfully revived using conventional carbon steel single-point coiled tubing gas lift system (CTGL). In 2022, all wells in the field were affected by increasing water cut. The field went on a complete shutdown and all wells required reactivation using the CTGL technique. However, the issues that were faced in the 2017 CTGL operation would be more challenging and complex due to the greater number of wells. These challenges included corrosion pitting, upstream pressure decline (the gas well's wellhead pressure) and lifting time and efficiency with more than 1 month required per well. The greater number of wells would increase CT cost, and the increasing water cut would increase lifting time per well, which would reduce production efficiency and increase corrosion rate. Additionally, because of the urgent timeline requirement for the execution, the single injection point design was extremely critical and had to work within the specifications of the available injection pressure, required flow rates of greater than 4000 BOPD, and available CT reels in country to reactivate all wells. A small error on chosen the injection point would compromise the entire reactivation process. Because this is a sour field, two categories of CT material were required to achieve a durable CT string with acceptable pitting based on a corrosion test. Carbon steel was chosen for a 2- to 3-week lifting period and chrome for a lifting period greater than 4 weeks. This innovative solution uses the already existing platform structure to deliver a green solution. Using the only gas well as a source of gas and pressure, the reinjected gas method aligns with green business objectives with a reduction of up to 80% less CO2 compared to the other possible long-term solutions available to the project.
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Лежнев, Д. В. "THE STRUCTURE OF PINE PHYTOCOENOSIS IN THE MOSCOW REGION UNDER CLIMATIC IMPACT". In Лесные экосистемы в условиях изменения климата: биологическая продуктивность и дистанционный мониторинг. Crossref, 2023. http://dx.doi.org/10.25686/foreco.2023.10.66.007.
Testo completoAbstract (sommario):
В статье изложены результаты исследования строения сосновых фитоценозов в условиях изменения климата. Изучение строения сосновых сообществ имеет важное значение для понимания различных эколого-биологических аспектов их формирования. При решении задач многоцелевого использования лесных экосистем необходима тщательная оценка строения древостоев. В условиях климатической трансформации актуальным становится изучение строения древостоев, так как оно характеризует жизненное состояние насаждений и по нему можно выявить протекающие сукцессии в фитоценозе. Целью исследования стало изучение закономерностей строения сосновых древостоев для определения тенденций развития экосистем под влиянием климатических трансформаций. Объектом исследования послужили 28 постоянных пробных площадей в сосновых лесах разного класса возраста, расположенных на территории г. Москвы и Московской области. Рассчитанные коэффициенты вариации находятся в диапазоне от 15,5 до 31,4 %, что характеризует изменчивость диаметров деревьев как среднюю. На исследуемых пробных площадях под действием факторов внешней среды происходит изменение рядов распределения в сторону асимметричных и эксцессивных кривых. На примере отдельных пробных площадей рассмотрено распределение деревьев по ступеням толщины. Строение сосновых древостоев носит ярко выраженное многовершинное распределение, которое обусловлено наличием различных пород разного возраста, составляющих древостой. Отмечена тенденция по закономерному изреживанию сосны с увеличением её возраста. По результатам исследования обоснован вывод, что сосновые насаждения в условиях Московского региона отличаются достаточно высокой долговечностью. Сосновые фитоценозы в данных условиях способны сохранять устойчивость в возрасте более 180 лет. The article presents the results of a study of the structure of pine phytocenoses in the conditions of climate change. The study of the structure of the pine stands is important for understanding various ecological and biological aspects of their formation. When solving the problems of multi-purpose use of forest ecosystems, a thorough assessment of the structure of stands is necessary. In the conditions of climatic impact, the study of the structure of stands becomes relevant, since it characterizes the vital state of stands and it is possible to identify the ongoing successions in the phytocenosis. The purpose of the study was to study the regularities of the structure of pine stands to determine the trends of ecosystem development under the influence of climatic transformation. The object of the study was 28 permanent observation plots in pine forests of different age classes located on the territory of Moscow and the Moscow region. The calculated coefficients of variation range from 15.5% to 31.4%, which characterizes the variability of tree diameters as average. On the permanent observation plots under study, under the influence of environmental factors, the distribution series change towards asymmetric and excessive curves. The distribution of trees by thickness steps is considered on the example of individual permanent observation plots. The structure of pine stands has a pronounced multi-vertex distribution, which is due to the presence of different breeds of different ages that make up the stand. There is a tendency for the natural thinning of pine with an increase in its age. According to the results of the study, it is noted that pine stands are quite durable in the conditions of the Moscow region. Pine phytocenoses in these conditions are able to maintain stability at the age of more than 180 years.
10
López Mejía, Juan, Jesús Diego Tuero-O'Donnell Zulaica e Saúl David Bertel Hoyos. "Una posible aplicación de la física eléctrica en la ingeniería civil". In Ingeniería para transformar territorios. Asociación Colombiana de Facultades de Ingeniería - ACOFI, 2023. http://dx.doi.org/10.26507/paper.2844.
Testo completoAbstract (sommario):
Desde el año 2020, los autores de esta experiencia han venido adaptando la asignatura de Física Eléctrica, ubicada en el segundo semestre de la carrera de Ingeniería Civil (Universidad Pontificia Bolivariana, seccional Montería), a las necesidades propias de esa rama de ingeniería, siguiendo las sugerencias dadas desde el departamento de ciencias básicas de orientar las asignaturas hacia la práctica profesional. Para ello, teniendo en cuenta que el pénsum de Ingeniería Civil no incorpora más temas de electricidad en su carrera, y que la asignatura sufrió una reducción en contenidos y horarios desde ese año, se propuso ajustar la carta descriptiva del curso y centrarse en los temas más prácticos de la electrostática y electrodinámica, que fueran necesarios para que los estudiantes pudieran entender y poner en práctica una aplicación de la electricidad en el mundo de la Ingeniería Civil. Dicha aplicación fue la caracterización de suelos mediante la técnica de los sondeos eléctricos verticales, que se estudia durante las últimas cinco semanas del curso. La experiencia se enmarca dentro del modelo pedagógico de la universidad, pensándose desde las necesidades e intereses de los estudiantes, en el contexto de un currículo integrador, que potencia el papel activo de los mismos, mediante una relación abierta entre sus contenidos. Además, en cuanto a las intencionalidades formativas, la experiencia contribuye al principio de interdisciplinariedad, al integrar varios objetos con los que el estudiante se enfrentará en distintas asignaturas de la carrera, encaminándose también al entendimiento de situaciones y problemas propios de su profesión o relacionados con ella. A nivel procedimental y concretando los principales recursos teóricos en torno a los cuales gira la experiencia, se tomó como referente y punto de partida la norma RA6-014 divulgada por las empresas públicas de Medellín (EPM). Básicamente, los contenidos teóricos en los que se enfoca la asignatura son: Repaso a los fundamentos de electricidad e introducción a las técnicas geofísicas eléctricas; resistividad eléctrica en elementos naturales; factores de los que depende; técnicas para medir la resistividad eléctrica, según el método de los sondeos eléctricos verticales: disposiciones de Schlumberger y Wenner; interpretación de las curvas de resistividad aparente; modelos de suelos homogéneos: criterios de identificación; modelos de suelos no homogéneos: uso de gráficas normalizadas para dos capas; normativas en electricidad; manejo de la aplicación informática IPI2win. Hasta la fecha, se han realizado un total de 15 cursos, con 490 estudiantes beneficiados, encontrándose una respuesta positiva en los participantes, con incremento del interés y participación en las clases. Para el futuro próximo, se espera contar con la llegada de una empresa externa que realice una práctica de exhibición y capacitación docente de esta técnica, que solvente las dificultades encontradas, al no contar con el equipo idóneo para implementarla en el campus de la universidad.
Rapporti di organizzazioni sul tema "Solvant durable"
1
Beverinotti, Javier. Prioridades de desarrollo y determinantes del crecimiento en Costa Rica. Inter-American Development Bank, febbraio 2016. http://dx.doi.org/10.18235/0010092.
Testo completoAbstract (sommario):
Costa Rica es un país que históricamente se ha caracterizado por sus indicadores socioeconómicos favorables y por sus reformas sociales. Por el lado del crecimiento económico, la economía ha crecido a tasas promedio de más del 5% durante las últimas cinco décadas. En el plano social, luego que los niveles de pobreza alcanzaran el 50% durante la crisis del 80, los mismos se redujeron al 20% y se mantienen en ese nivel desde hace ya dos décadas. Junto con el alto nivel de crecimiento, Costa Rica ha tenido importantes logros macroeconómicos que se reflejan en una inflación bajo control, un déficit de cuenta corriente financiado por IED, y un sistema financiero solvente. Sin embargo, desde 2009 el déficit fiscal ha venido aumentado hasta alcanzar un 5,9% del PIB en 2015; explicado principalmente porque los ingresos totales no han aumentado al mismo ritmo que el gasto total. El objetivo de este documento es identificar los principales desafíos para el desarrollo y el crecimiento sostenible. Para ello, se hará un análisis de las áreas con mayores potenciales para lograr estos objetivos y se analizarán los determinantes del crecimiento durante las últimas décadas. En el primer capítulo, se describe la situación macroeconómica del país. El capítulo dos hace una reseña del crecimiento del país en el tiempo, enumera las determinantes del crecimiento y hace una síntesis de las principales restricciones que el país enfrenta para su futuro desarrollo. Finalmente, el capítulo tres presenta recomendaciones con un enfoque social integral de políticas para algunas de las áreas identificadas en los capítulos anteriores.