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Lamia, B., L. C. Molano, C. Viacroze, A. Cuvelier e J. F. Muir. "Pertinence d’un indice composite échocardiographique pour améliorer le dépistage de l’hypertension pulmonaire". Revue des Maladies Respiratoires 31 (gennaio 2014): A26. http://dx.doi.org/10.1016/j.rmr.2013.10.070.
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Sjahriza, Ahmad, Zainal Alim Mas’ud e Komar Sutirah. "Mechanical and Barrier Properties of PVP-Carbon Dot Nanocomposite Films". Jurnal Kimia Terapan Indonesia 20, n. 2 (28 gennaio 2019): 49–56. http://dx.doi.org/10.14203/jkti.v20i2.392.
Abstract (sommario):
This research reported carbon dot were synthesized form citric acid and urea through a single step microwave process and Poly Vinyl Pirrolidone (PVP) films composited by carbon dot were prepared. The effects of different composition carbon dots on mechanical strength of films and water vapour barrier were evaluated. Highest mechanical yielded composite film were analyzed their thermal stability. Average of carbon dot diameter was found 90.61 nm and polydispersity indice 0.396. Different composition carbon dot exhibit significant improvement in tensile strength and modulus. Water permeablity of films varieate with content of carbon dot. The presence of carbon dot had a negligible effect on Tg of film and show melting process.
3
Gaujoux-Viala, Cécile, Gaël Mouterde, Athan Baillet, Pascal Claudepierre, Bruno Fautrel, Alain Cantagrel, Philippe Gaudin et al. "Évaluation de l’activité de la polyarthrite rhumatoïde, quel indice composite faut-il utiliser ?" Revue du Rhumatisme 76 (dicembre 2009): S3—S10. http://dx.doi.org/10.1016/s1169-8330(09)72764-4.
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Bouffard1, Léandre, e Micheline Dubé. "L’inégalité de revenus : un « virus » qui affecte la santé mentale et le bonheur". Mosaïque 38, n. 2 (21 marzo 2014): 215–33. http://dx.doi.org/10.7202/1023997ar.
Abstract (sommario):
L’objectif du présent texte est de démontrer les effets de l’inégalité de revenus sur la santé mentale et le bonheur dans les pays riches. La première section fait état du niveau élevé d’inégalité de revenus aux États-Unis et, à un degré moindre, dans les autres pays riches. Les résultats présentés dans la seconde partie font voir des corrélations positives de l’inégalité de revenus avec la maladie mentale, avec un indice de consommation de drogues et avec un indice composite de 10 problèmes psychosociaux. De plus, il existe une corrélation négative entre l’inégalité de revenus et un indice de bien-être des enfants mis au point par l’UNICEF. La troisième partie aborde l’association négative élevée entre l’inégalité de revenus et le bonheur, concrétisée ici par la satisfaction de vivre, dans les pays riches. De nombreux arguments appuient l’idée de la causalité selon laquelle l’inégalité de revenus est une source importante des problèmes psychosociaux, comme un « virus » qui affecte le bien-être de toute la population. Enfin, les praticiens des sciences humaines sont invités à s’impliquer dans l’élaboration des politiques sociales, dans les efforts d’éducation pour contrer les coûts de l’inégalité et dans des programmes susceptibles de favoriser une santé mentale « florissante ».
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Jonnaert, Philippe, e Dany Laveault. "Évaluation de la familiarité de la tâche : quelle confiance accorder à la perception de l’élève?" Articles 20, n. 2 (10 ottobre 2007): 271–91. http://dx.doi.org/10.7202/031710ar.
Abstract (sommario):
Résumé Notre étude s'inscrit dans le courant des recherches sur la perception de la tâche par rélève. Plus spécifiquement, nous avons cherché à déterminer si les élèves d'une même classe sont capables d'autoévaluer avec fidélité la familiarité d'une tâche qui leur est proposée. Les résultats obtenus confirment que les élèves s'entendent entre eux pour juger de la familiarité d'une situation didactique et que les indicateurs sur lesquels ils se prononcent sont suffisamment homogènes pour permettre le calcul d'un indice composite, le facteur K.
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Guillaumin, Cyriac. "Zones monétaires optimales et (a)symétrie des chocs en Asie". Économie appliquée 61, n. 2 (2008): 121–51. http://dx.doi.org/10.3406/ecoap.2008.1880.
Abstract (sommario):
L’objectif de cette étude est de montrer si l’Asie présente les caractéristiques d’une zone monétaire optimale (ZMO). Pour cela nous procédons de deux manières. (1) Nous construisons un indice composite de ZMO. (2) Nous analysons la volatilité des taux de change réels afin de définir la nature des chocs. Au vu de l’équation estimée, l’Asie remplirait les conditions d’une ZMO. La volatilité des taux de change réels fait, quant à elle, apparaître des chocs asymétriques. Nous montrons aussi que ces deux méthodes sont sujettes à discussion et qu’elles doivent être utilisées avec précaution.
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Lucic, Nicolas, e Jean-François Hoarau. "Le statut politique des petites économies insulaires a-t-il une influence sur leurs performances de développement ?" Mondes en développement 204, n. 4 (4 gennaio 2024): 17–34. http://dx.doi.org/10.3917/med.204.0017.
Abstract (sommario):
L’objectif de cet article est de comparer les performances macroéconomiques de développement d’un ensemble de 80 petits territoires insulaires à l’aune de leur statut politique et du degré de souveraineté atteint. Nous construisons quatre profils institutionnels (intégration complète, autonomie, souveraineté limitée et souveraineté totale) à partir d’un indice composite modifié de souveraineté proposé par Alberti et Goujon (2020). Ensuite, nous réalisons des tests de comparaison de moyenne sur 26 critères. Au final, nous trouvons que les dépendances insulaires autonomes sont plus économiquement développées, socialement avancées et matures sur le plan démographique que les autres groupes institutionnels. Classification JEL : O11, O57, P51
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Wister, Andrew, Theodore Cosco, Barbara Mitchell, Verena Menec e Ian Fyffe. "Development and Concurrent Validity of a Composite Social Isolation Index for Older Adults Using the CLSA". Canadian Journal on Aging / La Revue canadienne du vieillissement 38, n. 02 (11 gennaio 2019): 180–92. http://dx.doi.org/10.1017/s0714980818000612.
Abstract (sommario):
RÉSUMÉL’isolement social a retenu l’attention des chercheurs, en particulier dans la recherche concernant les personnes âgées, étant donné les corrélations établies avec la mortalité et le risque de mauvaise santé physique ou mentale. Toutefois, les mesures utilisées jusqu’à maintenant pour l’isolement social ont grandement varié et manquent souvent de clarté conceptuelle. La présente étude s’appuie sur un cadre conceptuel de classification des mesures d’isolement social et explique l’élaboration et la validation d’un indice composite d’isolement social (ELCV-SII) qui a été créé en utilisant les données de l’Étude longitudinale canadienne sur le vieillissement (ELCV). L’échantillon de l’ELCV incluait 21 491 Canadiens âgés de 65 ans ou plus (âge moyen : 72,9 ans; à 53,5 % de sexe féminin) retrouvés dans les données de base des cohortes de suivi et de la cohorte globale de l’ELCV (n = 51 338). Le CLSA-SII a été élaboré en utilisant une méthodologie standard, qui a été suivie pour la création d’autres mesures, dont la résilience à la multimorbidité et les indices de vieillissement efficaces. Les associations entre l’ELCV-SII et quatre variables clés (échelle de satisfaction de vie, dépression, santé mentale perçue et santé perçue) ont été évaluées par des analyses de régression, en tenant compte de l’âge, du sexe, du revenu et de la scolarité. Les associations entre l’indice CLSA-SII et les quatre variables d’intérêt ont donné lieu à des associations modérées statistiquement significatives conformes à la tendance prévue, qui concordent avec les recherches antérieures, ce qui démontre une bonne validité convergente pour l’ELCV-SII.
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Carbonara, Pierluigi, Teresa Silecchia, Maria Spedicato, Alessandra Acrivulis e Giuseppe Lembo. "A GEOSTATISTICAL APPROACH TO THE ASSESSMENT OF THE SPATIAL DISTRIBUTION OF PARAPENAEUS LONGIROSTRIS (LUCAS, 1846) IN THE CENTRAL-SOUTHERN TYRRHENIAN SEA". Crustaceana 72, n. 9 (1999): 1093–108. http://dx.doi.org/10.1163/156854099504040.
Abstract (sommario):
AbstractThe spatial distribution of the abundance indices of the deep-water rose shrimp Parapenaeus longirostris was investigated applying geostatistical techniques on data collected in the central southern Tyrrhenian Sea from bottom trawl surveys carried out in the autumn since 1994. Experimental variograms (auto and cross) were constructed on the variable "abundance index", expressed in kg/km2, and those variogram models best describing the spatial continuity were detected and validated by the jackknife technique. The spatial structure of the "abundance index", exhibiting a similar pattern throughout the surveys, was described by a spherical model and characterized by a spatial continuity at a small scale level in the whole area. The linear geostatistical approach was applied by different kriging techniques and the estimates extended to the spatio-temporal dimension, in this case adopting the co-regionalized models and applying the cokriging technique. This method applied to the spatial dimension (abundance index and depth). Also, linking the spatial and temporal dimension of the abundance indices, measured in two different years, contributed to represent a more accurate picture of the abundance distribution, and allowed the detection of a temporal persistence of the localization of areas with higher abundance, reducing the standard deviation of the estimation error. This information, if coupled with an analysis of the geographical allocation of the fishing effort, could be of importance in stock assessment, allowing some variant application of the composite surplus production models. La distribution spatiale des indices d'abondance de la crevette rose d'eau profonde Parapenaeus longirostris a ete etudiee en appliquant les techniques de la geostatistique aux donnees collectees dans le centre-sud de la mer Tyrrhenienne au cours des campagnes de chalutage demersal realisees pendant l'automne, depuis 1994. Les variogrammes experimentaux (auto et cross) ont ete construits sur la variable "indice d'abondance", exprimee en kg/km2, et les modeles de variogramme decrivants le mieux la continuite spatiale ont ete determines et valides par la technique du "jackknife". La structure spatiale de l'indice d'abondance a presente le meme aspect pour tous les echantillonages; elle a ete decrite au moyen d'un modele spherique et caracterisee par une continuite spatiale a petite echelle dans toute la zone. La geostatistique lineaire a ete appliquee en utilisant differentes techniques du krigeage, et les estimations ont ete etendues a la dimension spatio-temporelle en appliquant les modeles coregionalises et la technique du cokrigeage. Cette methode, appliquee soit dans la dimension spatiale (indice d'abondance et profondeur), soit dans la dimension spatio-temporelle en considerant l'indice d'abondance echantillonne en deux annees differentes, a contribue a representer une image plus precise de la distribution de l'abondance, et a permis de detecter une persistance temporelle de la localisation des aires a plus grande abondance, en reduisant l'ecart type de l'erreur d'estimation. Cette information, avec l'analyse de l'allocation geografique de l'effort de peche, pourrait etre importante dans l'evaluation des stocks, en permettant l'application, avec quelques variantes, des modeles composites de production.
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Garnier, P., B. Tran, V. Salomon e V. Drouvot. "P4-1 - Élaboration d’un indice composite des activités de lutte contre les infections nosocomiales dans les établissements de santé : ICALIN". Revue d'Épidémiologie et de Santé Publique 54 (agosto 2006): 73. http://dx.doi.org/10.1016/s0398-7620(06)76903-6.
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Noreau, Luc, Patrick Fougeyrollas, Julie Tremblay, Serge Dumont e Myreille St-Onge. "Les facteurs personnels et environnementaux associés à l’appauvrissement des personnes ayant des incapacités : utilisation d’un indice composite : « revenu x participation sociale »". Santé, Société et Solidarité 4, n. 2 (2005): 165–80. http://dx.doi.org/10.3406/oss.2005.1068.
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Simard, Majella. "La géographie des disparités économiques au sein des localités du Canada atlantique : une étude comparative au cours de la période 1981–2006". Études, n. 27 (15 dicembre 2016): 83–117. http://dx.doi.org/10.7202/1038349ar.
Abstract (sommario):
En dépit de ses nombreux éléments de similitude liés notamment à la faiblesse de l’armature urbaine, à une économie fortement orientée vers la mise en valeur des ressources et à une démographie qui peine à se renouveler, le Canada atlantique se présente comme un milieu fort hétérogène. Cette diversité entraîne des niveaux différents de développement selon les endroits. Bien que, de façon générale, les disparités économiques aient eu tendance à s’atténuer au cours des 25 dernières années, il n’en demeure pas moins que plusieurs localités sont aux prises avec des problèmes aigus d’emploi et de faibles niveaux de revenu. Le but de cet article est de dégager l’évolution des disparités économiques au sein des quatre provinces atlantiques entre 1981 et 2006. L’analyse, qui porte sur les 752 subdivisions de recensement de ce territoire, est effectuée à partir de quatre variables clés dans l’étude des disparités. Celles-ci sont examinées en considérant diverses catégories de milieux, établies en fonction de leur taille démographique. Un indice composite conduit à la construction de typologies permettant de mettre en évidence différents niveaux d’évolution.
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Sweeney-Magee, Molly, Carolyn Gotay, Mohammad Ehsanul Karim, Jennifer Telford e Trevor Dummer. "Tendances et déterminants de l’adhésion aux recommandations en matière de prévention primaire et secondaire du cancer colorectal dans le cadre du BC Generations Project". Promotion de la santé et prévention des maladies chroniques au Canada 42, n. 2 (febbraio 2022): 89–104. http://dx.doi.org/10.24095/hpcdp.42.2.04f.
Abstract (sommario):
Introduction L’adhésion aux recommandations en matière de prévention du cancer peut grandement réduire le risque de cancer colorectal. Cette étude porte sur les tendances et les déterminants de l’adhésion à ces recommandations par les participants (n = 26 074) au début d’une étude de cohorte en Colombie‑Britannique (Canada). Méthodologie Nous avons mesuré l’adhésion à cinq comportements de prévention primaire du cancer colorectal tirés des recommandations émises par la Société canadienne du cancer et le Fonds mondial de recherche contre le cancer (absence de tabagisme, indice de masse corporelle (IMC), activité physique, consommation d’alcool et consommation de fruits et légumes) et nous avons établi un score composite reposant sur la somme des mesures. La définition de l’adhésion aux comportements de prévention secondaire est fondée sur les recommandations du Groupe d’étude canadien sur les soins de santé préventifs pour le dépistage du cancer colorectal. Résultats L’adhésion aux lignes directrices en matière de prévention primaire variait entre 94,8 % (absence de tabagisme) à 44,2 % (IMC santé). Le score composite médian était de 4. Les scores composites supérieurs ont été associés au fait d’être une femme, d’être marié(e) et d’avoir un niveau de scolarité plus élevé. Le taux d’adhésion au dépistage du cancer colorectal était de 62,4 %. Un âge avancé, la présence de maladies chroniques, le fait d’avoir subi un examen médical récemment et le fait de faire partie d’un ménage à revenu élevé étaient associés à une probabilité accrue d’adhésion au dépistage. Conclusion L’adhésion à certains comportements de prévention du cancer colorectal s’est révélée élevée, ce qui concorde avec les constatations selon lesquelles la Colombie-Britannique affiche des taux faibles pour de nombreux comportements risqués pour la santé. Cependant, on a constaté une agglomération de plus faible adhésion aux comportements de prévention les uns avec les autres et en présence d’autres facteurs de risque. L’adhésion au dépistage s’est révélée élevée, mais varie en fonction de certains facteurs sociodémographiques et sanitaires. Les travaux futurs devraient porter sur des interventions ciblées visant à améliorer l’adhésion des individus faisant partie des groupes dont le statut socioéconomique et l’état de santé sont les plus précaires. Il faut également mieux comprendre les obstacles à l’accès et à la participation au dépistage du cancer colorectal, qui persistent même au sein du système de santé public canadien.
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Guataquí, Juan Carlos, Nohora Forero e Andrés Felipe García. "¿A quiénes afecta el desempleo? Análisis de la tasa de incidencia en Colombia". Lecturas de Economía, n. 70 (11 settembre 2009): 109–36. http://dx.doi.org/10.17533/udea.le.n70a2257.
Abstract (sommario):
La tasa de incidencia representa un indicador compuesto que tiene en cuenta el volumen de desempleados y su persistencia (duración). Su análisis permite caracterizar de forma más completa a quienes tienen una mayor probabilidad de entrar o permanecer en el desempleo. En este estudio encontramos que en Colombia existen diferencias significativas derivadas del análisis de la tasa de desempleo y de la tasa de incidencia; lo cual sugiere que detrás de la duración del desempleo se encuentran importantes elementos que se deben considerar en el análisis de la tipología del desempleo y la formulación de políticas encaminadas a enfrentarla. Palabras Clave: tasa de desempleo, búsqueda de empleo, duración del desempleo, incidencia. Clasificación JEL: J21, J64. Abstract: The incidence rate represents a composite indicator that takes account of both thenumber of unemployed people and the average duration of employment. The analysis of this rate allows to portrait a more complete profile of those individuals who are more likely to either become unemployed or stay in such a situation. We find significant differences in the analysis of the unemployment rate and the incidence rate in Colombia, which suggests the importance of addressing certain elements underlying unemployment duration when appraising unemployment typology and policies aimed to overcome it. Keywords: unemployment rate, job search, unemployment duration, unemployment incidence. JEL Classification: J21, J64. Résumé: Le taux d'incidence est un indice composite qui tient en compte le nombre de chômeurs et sa permanence au chômage (la durée). Son analyse permet de caractériser de manière plus complète ceux qui ont une plus grande probabilité d'entrer au chômage ou rester dans cette situation. Dans cette étude nous trouvons que, pour le cas colombien, il existe des différences significatives dérivées de l'analyse du taux de chômage et du taux d'incidence. Ces différences indiquent que, derrière la notion de durée du chômage, il existe des éléments importants qui doivent être considérés dans l'analyse de la typologie du chômage et dans la formulation des politiques économiques. Mots clé: taux de chômage, recherche d'emploi, durée du chômage, incidence. Classification JEL: J21, J64.
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Singha, Amar S., Balbir S. Kaith e Aishwarya J. Khanna. "Synthesis and characterization of Cannabis indica fiber reinforced composites". BioResources 6, n. 2 (25 aprile 2011): 2101–17. http://dx.doi.org/10.15376/biores.6.2.2101-2117.
Abstract (sommario):
This paper reports on the synthesis of Cannabis indica fiber-reinforced composites using Urea-Resorcinol-Formaldehyde (URF) as a novel matrix through compression molding technique. The polycondensation between urea, resorcinol, and formaldehyde in different molar ratios was applied to the synthesis of the URF polymer matrix. A thermosetting matrix based composite, reinforced with lignocellulose from Cannabis indica with different fiber loadings 10, 20, 30, 40, and 50% by weight, was obtained. The mechanical properties of randomly oriented intimately mixed fiber particle reinforced composites were determined. Effects of fiber loadings on mechanical properties such as tensile, compressive, flexural strength, and wear resistance were evaluated. Results showed that mechanical properties of URF resin matrix increased considerably when reinforced with particles of Cannabis indica fiber. Thermal (TGA/DTA/DTG) and morphological studies (SEM) of the resin, fiber and polymer composite thus synthesized were carried out.
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Dolbin, Igor V., Gusein M. Magomedov e Georgii V. Kozlov. "The Influence of Phases Division Surface in Nanocomposites Polymer/2D-Nanofiller on their Reinforcement Degree - The Percolation Model". Key Engineering Materials 869 (ottobre 2020): 516–23. http://dx.doi.org/10.4028/www.scientific.net/kem.869.516.
Abstract (sommario):
The simple percolation model, in which critical indices are defined by the form of a reinforcing component of nanostructured composite structure, was proposed for the description of reinforcement degree for nanostructured composites polymer/2D-nanofiller. The indicated critical indices are close by absolute values to standard percolation indices. The form of reinforcing component controls the type of nanostructured composite. It has been shown that reinforcement degree of these nanomaterials is independent on modulus of elasticity of nanofiller, but is defined by its structure (aggregation level), created in polymer matrix. The percolation indices of a percolation model, which are due to the form of reinforcing component and nanocomposite type, are defined by its main characteristic – the fraction of phases division surface in overall sample volume and are the basic factor, controlling reinforcement degree of nanostructured composites.
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Schmeling, M., A. Meyer-Filho, M. A. C. Andrada e L. N. Baratieri. "Chromatic Influence of Value Resin Composites". Operative Dentistry 35, n. 1 (1 gennaio 2010): 44–49. http://dx.doi.org/10.2341/09-44-l.
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Roodman, David. "Composite indices". Journal of Economic Inequality 9, n. 3 (9 agosto 2011): 483–84. http://dx.doi.org/10.1007/s10888-011-9197-9.
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Sosa, Edward D., Erica S. Worthy e Thomas K. Darlington. "Microwave Assisted Manufacturing and Repair of Carbon Reinforced Nanocomposites". Journal of Composites 2016 (13 ottobre 2016): 1–9. http://dx.doi.org/10.1155/2016/7058649.
Abstract (sommario):
We report a composite capable of advanced manufacturing and damage repair. Microwave energy is used to induce thermal reversible polymerization of the matrix allowing for microwave assisted composite welding and repair. Composites can be bonded together in just a few minutes through microwave welding. Lap shear testing demonstrates that microwave welded composites exhibit 40% bond strength relative to composites bonded with epoxy resin. Double cantilever beam testing shows 60% recovery in delamination strength after microwave assisted composite repair. The interfacial adhesion and composite repair after microwave exposure are examined by X-ray computed tomography. The microwave processing is shown to be reproducible and consistent. The ability to perform scalable manufacturing is demonstrated by the construction of a large structure from smaller components.
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Kouadio Daouda, SOMAN, NDOUNIAMA ONIONGUI Van-Brentano e HACHEMI Bentahar. "Développement financier : cas des pays de la zone UEMOA (Burkina Faso, Côte d’Ivoire et Mali)". International Journal of Financial Accountability, Economics, Management, and Auditing (IJFAEMA) 3, n. 4 (29 luglio 2021): 489–99. http://dx.doi.org/10.52502/ijfaema.v3i4.117.
Abstract (sommario):
L’objet de ce papier est de connaître quel est le pays qui a le niveau de développement financier le plus élevé sur la période allant de 1975 à 2020. Pour se faire, nous avons utilisé l’analyse en composantes principales (ACP) afin d’avoir l’indice composite de chaque pays. Après comparaison des différents indices composites via l’ACP, les résultats montrent avec évidence que, pour le cas du Mali, la première valeur propre indique que la première composante principale explique plus de 71,509% de l’inertie totale (et plus de 74,564% respectivement 89,234%) pour la Côte d’Ivoire et le Burkina Faso. Par-là, nous pouvons dire que le Burkina Faso a le niveau de développement financier le plus élevé.
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Zhang, Peng, Qing-fu Li, Juan Wang, Yan Shi e Yi-feng Ling. "Effect of PVA fiber on durability of cementitious composite containing nano-SiO2". Nanotechnology Reviews 8, n. 1 (26 ottobre 2019): 116–27. http://dx.doi.org/10.1515/ntrev-2019-0011.
Abstract (sommario):
Abstract In the current investigation, the influence of polyvinyl alcohol (PVA) fibers on flowability and durability of cementitious composite containing fly ash and nano-SiO2 was evaluated. PVA fibers were added into the composite at a volume fraction of 0.3%, 0.6%, 0.9%, and 1.2%. The flowability of the fresh cementitious composite was assessed using slump flow. The durability of cementitious composite includes carbonation resistance, permeability resistance, cracking resistance as well as freezing-thawing resistance, which were evaluated by the depth of carbonation, the water permeability height, cracking resistance ratio of the specimens, and relative dynamic elastic modulus of samples after freeze-thaw cycles, respectively. The results indicated that addition of PVA fibers had a little disadvantageous influence on flowability of cementitious composite, and the flowability of the fresh mixtures decreased with increases in PVA fiber content. Incorporation of PVA fibers significantly improved the durability of cementitious composites regardless of addition of nano-particles. When the fiber content was less than 1.2%, the durability indices of permeability resistance and cracking resistance increased with fiber content. However, the durability indices of carbonation resistance and freezing-thawing resistance began to decrease as the fiber dosage increased from 0.9% to 1.2%. The fiber reinforced cementitious composite exhibited better durability due to addition of nano-SiO2 particles. Nano-SiO2 particle improves microscopic structure of fiber reinforced cementitious composites, and the nano-particles are beneficial for PVA fibers to play the role of reinforcement in cementitious composites.
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Refaat, Eman, e Ali Hadi. "Constructing composite indices". International Journal of Sociology and Social Policy 38, n. 1/2 (12 marzo 2018): 58–86. http://dx.doi.org/10.1108/ijssp-12-2016-0135.
Abstract (sommario):
Purpose The purpose of this paper is to construct, for the first time, composite index for Egypt that measures the economic and social rights fulfillment (ESRF) based on socioeconomic surveys at the household/individual levels. Design/methodology/approach The paper highlights some of the statistical debatable issues about composite indices and focuses mainly on six of them. Those issues are indicators selection, handling missing data, identification of and dealing with outliers, scale of measurement, computing the margin of error, weights assigned for indicators and domains and aggregation method. Handling these problematic issues gave rise to a rigorous index. Findings The quality of economic and social rights fulfillment index (ESRFI) is judged by its bootstrap standard error. Based on these margin of errors, confidence intervals can be computed and rigorous comparisons across all disaggregation levels of the ESRFI can be made. The results shows that the overall index is accurate and representative in measuring the ESRF in Egypt. Comparisons between rural and urban regions indices show that the rural areas are always worse than the urban areas in all levels of dimensions, especially for the Right to Education and Adequate Housing. Research limitations/implications The ESRFI is not very current because it is based on the 2010 Egyptian Household Conditions Observatory Survey (EHCOS), which is the latest published version of the survey with complete variables for the index data. When the next EHCOS becomes available, an updated ESRFI can be easily and quickly constructed. Practical implications The ESRFI could strengthen policy formulation that takes into account ESRF, especially by highlighting the situation in different regions and disaggregation levels. Social implications The proposed ESRFI would strengthen policy formulation that takes into account ESRF, especially by highlighting the situation in different regions and different disaggregation levels. Originality/value The paper emphasizes the importance of recognizing and handling of the six problematic issues that arise when constructing composite indices. The paper presents the first ESRFI for Egypt and demonstrates the rigor of its construction.
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El Fallahi, Fadwa, Abdelmajid Ibenrissoul e Youssef Bouazizi. "The effect of a company’s innovation and its leader’s personal characteristics on corporate environmental sustainability within the Moroccan context". Revue Management & Innovation N° 9, n. 3 (26 marzo 2024): 61–80. http://dx.doi.org/10.3917/rmi.209.0061.
Abstract (sommario):
Dans un contexte de préoccupations environnementales croissantes, le lien entre l’innovation et la performance environnementale suscite une attention importante à la fois dans les milieux académiques et commerciaux. Des études récentes mettent en avant le rôle essentiel de l’innovation dans la résolution des défis environnementaux. Cependant, une analyse approfondie des preuves empiriques révèle une relation complexe. Cette étude vise à explorer la connexion entre l’innovation des modèles d’entreprise, la durabilité environnementale des entreprises et les caractéristiques personnelles des dirigeants. En introduisant le concept d’un effet médiateur, nous cherchons à mieux comprendre les mécanismes sous-jacents qui relient l’innovation à la performance environnementale, allant au-delà des traits organisationnels généralement analysés. Pour ce faire, nous avons utilisé une analyse économétrique, en employant spécifiquement la méthode des moindres carrés ordinaires. De plus, nous avons développé un indice composite pour évaluer les niveaux de durabilité environnementale des entreprises. Le jeu de données de cette étude comprend les réponses de 452 participants valides parmi les 1 096 entreprises inter-sectorielles marocaines interrogées lors de l’enquête annuelle de la Banque mondiale en 2019-2020. Nos résultats de recherche suggèrent que les entreprises dotées de modèles d’entreprise innovants ont une plus grande propension à aborder les préoccupations liées à la durabilité environnementale. De plus, les caractéristiques personnelles des dirigeants jouent un rôle partiel de médiation dans cette relation. Cet article éclaire l’impact distinct de diverses formes d’innovation sur la performance environnementale, en mettant particulièrement l’accent sur le contexte économique en évolution du Maroc et le paysage politique environnemental, où l’engagement environnemental reste modeste. De plus, il a le potentiel de stimuler des initiatives pratiques visant au développement de réglementations nationales et de pratiques axées sur la préservation de l’environnement.
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Sethuraman, Balu, Sampath Pavayee Subramani, Sathish Kumar Palaniappan, Bhuvaneshwaran Mylsamy e Karthik Aruchamy. "Experimental investigation on dynamic mechanical and thermal characteristics of Coccinia Indica fiber reinforced polyester composites". Journal of Engineered Fibers and Fabrics 15 (gennaio 2020): 155892502090583. http://dx.doi.org/10.1177/1558925020905831.
Abstract (sommario):
Due to superior material properties of fiber reinforced composites, they are utilized in many structural fabrications. Even though many studies have been reported about various fiber reinforced composites, it is indeed to find more eco-friendly composites for modern applications. So, developing the new fiber reinforced composites and revealing its mechanical properties are vital. In this examination, the natural fiber reinforced polymer matrix composite was prepared by compression molding method. The natural fiber named as Coccinia Indica was used to fabricate the fiber reinforced composites. The impact of different fiber length on dynamic mechanical properties like loss modulus, storage modulus, and loss of weight in fiber reinforced composites was predicted using dynamic mechanical analysis and thermogravimetric analysis. The outcomes revealed that fiber length of 30 mm shows better values in storage modulus and nominal loss modulus owing to higher interfacial bonding among fiber and matrix. However, in other fiber lengths, the storage modulus depicts poor result and high loss modulus is due to inefficient stress transfer.
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Stelea, Lucia, Ioan Filip, Gabriela Lisa, Mariana Ichim, Mioara Drobotă, Costică Sava e Augustin Mureșan. "Characterisation of Hemp Fibres Reinforced Composites Using Thermoplastic Polymers as Matrices". Polymers 14, n. 3 (25 gennaio 2022): 481. http://dx.doi.org/10.3390/polym14030481.
Abstract (sommario):
Hemp fibres used as a reinforcing agent and three polymeric matrices (polypropylene, bicomponent, recycled polyester) were used to obtain composite materials by needle punching and heat pressing. The influence of the hemp/matrix ratio and the nature of the matrix on the properties of the composites were analysed. The obtained composites were characterised by physical–mechanical indices, thermal analysis (thermogravimetry (TG), differential thermogravimetry (DTG) and Differential Scanning Calorimetry (DSC)), Fourier Transform Infrared Spectroscopy (FTIR-ATR) analysis, Scanning Electron Microscopy (SEM) and Chromatic measurements. The mechanical properties of composites are influenced by both the hemp/matrix ratio and the nature of the matrix. The thermal stability of composites decreased as the amount of hemp increased (for the same mass losses, the decomposition temperature decreased significantly for composites containing a quantity of hemp greater than 50%). Regarding the nature of the matrix, for the same mass loss, the highest decomposition temperature was presented by the composites containing recycled polyester as matrix, and the lowest one was presented by composites containing polypropylene fibres as matrix. The FTIR and SEM analyses highlight the changes that occurred in the structure of the composite, changes determined both by the amount of hemp in the composite and by the nature of the matrix.
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Dorairajan, Mukundan, Vikram Srinivas, Vasanthakumari Raju e Gayathri Raghavan. "Temperature Dependent Electrical Properties of Green Synthesized Silver Nanoparticles-Polyaniline Composite". Advanced Materials Research 938 (giugno 2014): 230–35. http://dx.doi.org/10.4028/www.scientific.net/amr.938.230.
Abstract (sommario):
Polyaniline (PANI) Nanocomposites are potential materials for actuators, EMI shielding, Fuel cells and components in non volatile memory. Silver nanoparticles have wide range of applications such as catalysis, microelectronics, biotechnology and silver-oxide batteries. This work reports the effect of thermal alteration [lowhigh temperatur on the electrical conductivity of green synthesized silver (Ag) nanoparticles-polyaniline composite. A simple low cost green synthesis using Azadirachta indica [Neem] extract is employed for synthesis of silver nanoparticles; Polyaniline is prepared by redox polymerization of aniline using ammonium per sulphate. The silver nanoparticles are incorporated into Polyaniline during polymerization. PANI and PANI-Ag composites are characterized by FTIR, UV-Vis, TGA, XRD, TEM and DC conductivity. The DC conductivity and UV-Vis spectral response were recorded for the samples at low temperatures [263K, 273K, and 283 and high temperatures [353K, 433K, and 533. The effect of thermal alteration showed a significant change in both conductivity and UV-Vis spectral response. UV-visible spectra show the transition occurring in PANI Emeraldine salt phase to Pernigraniline with increase in temperature. TGA analysis confirms the improved thermal stability for PANI-Ag composite. The mechanism of electrical conductivity with temperature in the system is investigated and reported. Thus, this work deals with an approach to analyze the electrical behavior of green synthesized silver nanoparticles composited with a conducting polymer. The results show that these composites can be suitable for temperature dependent semiconductors, bio sensors and catalytic reactions.
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Swain, Priyadarshi Tapas Ranjan, e Sandhyarani Biswas. "Influence of fiber surface treatments on physico-mechanical behaviour of jute/epoxy composites impregnated with aluminium oxide filler". Journal of Composite Materials 51, n. 28 (23 febbraio 2017): 3909–22. http://dx.doi.org/10.1177/0021998317695420.
Abstract (sommario):
The present paper discovers the effect of ceramic filler inclusion on physico-mechanical and water absorption behaviour of untreated and chemically treated (alkali and benzoyl chloride treated) bi-directional jute natural-fiber-reinforced epoxy composites. In practice, the major drawbacks of using natural fibers are their high degree of moisture absorption and poor dimensional stability. Currently, chemical treatments are able to induce fiber modifications that increase their resistance when utilized in composite products. Jute fibers were subjected to various chemical modifications to improve the interfacial bonding with the matrix. In this study, an analysis has been carried out to make pre-treated jute fiber (10, 20, 30 and 40 wt.%) and different filler content (5 and 10 wt.%) with epoxy-based composites. A comparative study of all the untreated jute/aluminium oxide based hybrid composites with chemically treated jute/aluminium oxide based hybrid composites was carried out. The investigational result reveals that chemically treated composites considerably improved the mechanical properties of the composite. The maximum water absorption resistance and strength properties were found with benzoyl chloride-treated fiber-reinforced composite. Lastly, the surface morphology of fractured surfaces after tensile and flexural testing is studied using scanning electron microscope.
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Mohd Ghazali, Aruan Efendy, e Kim L. Pickering. "The effect of fibre surface treatment and coupling agents to improve the performance of natural fibres in PLA composites". Journal of Polymer Engineering 41, n. 10 (7 ottobre 2021): 842–53. http://dx.doi.org/10.1515/polyeng-2021-0120.
Abstract (sommario):
Abstract This paper describes work carried out to assess the effect of fibre treatments and coupling agent on the mechanical performance of PLA composites reinforced with 20 wt% fibre. The chemically-treated harakeke and hemp fibres used to produce fibre mats. Maleic anhydride (MA) grafted PLA (MA-g-PLA) was used as a coupling agent. Composites with fibre treated with silane and dicumyl peroxide (DCP) and composites using MA-g-PLA were characterised by swelling testing, scanning electron microscopy (SEM), tensile testing, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). It was found that the interfacial bonding for composites with fibres treated using silane and peroxide and composites coupled with MA-g-PLA noticeably improved supported by lower swelling indices, higher tensile strengths and lower tan δ compared to those composites with fibres treated using alkali only, with the highest tensile strength of about 11% higher obtained from composites treated with MA-g-PLA followed by silane and then peroxide. However, using silane, peroxide and MA-g-PLA as additional composite treatments increased significantly the composite failure strain by up 11, 19 and 30%, respectively for harakeke composites and by 13, 24 and 30%, respectively for hemp composites.
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Abdul Khalil, H. P. S., M. M. Marliana e Turki Alshammari. "Material properties of epoxy-reinforced biocomposites with lignin from empty fruit bunch as curing agent". BioResources 6, n. 4 (29 ottobre 2011): 5206–23. http://dx.doi.org/10.15376/biores.6.4.5206-5223.
Abstract (sommario):
Lignin was obtained from black liquor samples from soda-AQ pulping of oil palm empty fruit bunch (EFB) fiber. Oil palm EFB reinforced epoxy composite samples with varying lignin content of 15, 20, 25, and 30% as curing agent were prepared. The chemical structures of lignin were characterized by FT-IR, and CHN analysis. FT-IR and CHN analysis confirmed structural changes of epoxy resin after use of EFB-lignin as curing agent in epoxy resin. Thermal analysis of composites was carried out by thermogravimetric analysis (TGA). The TGA graphs showed that crosslinking of epoxy and lignin as curing agent may induce relatively high-chain rigidity in the polymer and may result in an enhanced thermal stability of the EFB/lignin-epoxy composite systems. The mechanical properties (tensile, flexural, and impact behavior) and physical properties (water absorption) of the composite samples were evaluated. Mechanical properties of epoxy composites cured with 25% lignin were found to be higher than that of the composite prepared from a commercial curing agent. Scanning electron micrographs showing tensile fracture of the composites showed evidence of good fiber–matrix interaction, induced by the curing agent.
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Dougados, Maxime, Julien Lucas, Emilie Desfleurs, Cédric Lukas, Alain Saraux, Anne Tournadre, Adeline Ruyssen-Witrand, Daniel Wendling, Philippe Goupille e Pascal Claudepierre. "Impact of disease activity outcome measures reporting in the medical records of patients with axial spondyloarthritis on the retention rates of biological treatment: the example of secukinumab use in daily practice in France". RMD Open 8, n. 1 (marzo 2022): e002106. http://dx.doi.org/10.1136/rmdopen-2021-002106.
Abstract (sommario):
ObjectivesTo estimate the frequency of reporting composite indices evaluating axial spondyloarthritis (axSpA) disease activity in daily practice and to assess its impact on the secukinumab (SEC) retention rate.MethodsStudy design: Retrospective, multicentre. Data collected: (1) Recommended composite indices: Bath Ankylosing Spondyltitis Disease Activity Index (BASDAI) +C reactive protein or Ankylosing Spondylitis Disease Activity Score (ASDAS) at the time of initiation of SEC and at least once during the first year of follow-up; (2) Drug retention rate: percentage of patients still on SEC over time according to whether at least one recommended composite index had been optimally reported.ResultsA recommended composite index has been collected in 22% of the 906 enrolled axSpA patients. The percentage of patients still on treatment after 1, 2 and 3 years of follow-up was greater in those for whom at least one composite index had been optimally reported (respectively, 64% (57–71) vs 57% (54–61), 55% (48–62) vs 41% (38–45) and 52% (44–59) vs 38% (34–42), log rank test, p=0.016) with a lower risk of SEC discontinuation for these patients (HR: 0.70 (95% CI 0.5 to 0.88), Cox model, p=0.003).ConclusionThis study suggests that reporting of recommended composites indices for monitoring axSpA might be associated with higher retention rates of biological therapies.
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Sayyar, Mohammad, Anagi M. Balachandra e Parviz Soroushian. "Energy absorption capacity of pseudoelastic fiber-reinforced composites". Science and Engineering of Composite Materials 21, n. 2 (1 marzo 2014): 173–79. http://dx.doi.org/10.1515/secm-2013-0021.
Abstract (sommario):
AbstractPseudoelastic fiber-reinforced metal matrix composite with enhanced ductility and energy absorption capacity was developed. This composite system relies on the distributed nature of large pseudoelastic strains to mitigate localization of inelastic deformation and failure, and thus mobilizes a major fraction of volume for effective energy absorption. The pseudoelastic fibers were made of Ni-Ti-Cr alloy used in conjunction with two different matrices, aluminum and copper. Tension and pull-out tests were performed to evaluate the ductility and energy absorption capacity of control and pseudoelastic fiber-reinforced composites. Experimental results confirmed the ability of pseudoelastic fibers to induce distributed inelastic deformation within metal matrix composites for realizing major gains in ductility and energy absorption capacity.
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Alameri, A., I. Gutman, V. R. Kulli, A. Ayache e M. Alsharafi. "Chemical Applications on General Zagreb Indices of Composite Graphs". international journal of mathematics and computer research 12, n. 03 (31 marzo 2024): 4114–18. http://dx.doi.org/10.47191/ijmcr/v12i3.06.
Abstract (sommario):
A topological index is a quantity computed from the molecular graph, that finds application in chemistry, material science, computer science, and biological application-driven fields. Recently, the general Zagreb indices were studied, and methods for their calculation for composite graphs were established. In the present paper, we provide examples for chemical applications of these methods, computing the first and second general Zagreb indices of several composite molecular species, in particular of biphenyl, naphthalene, biphenylene, and bicoronylene. In this paper, we compute the Nirmala index and its corresponding exponential of chloroquine, hydroxychloroquine and remdesivir. Also we determine the inverse Nirmal indices of chloroquine, hydroxychloroquine and remdesivir.
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Shamsuri, Ahmad Adlie, e Siti Nurul Ain Md Jamil. "Application of Quaternary Ammonium Compounds as Compatibilizers for Polymer Blends and Polymer Composites—A Concise Review". Applied Sciences 11, n. 7 (2 aprile 2021): 3167. http://dx.doi.org/10.3390/app11073167.
Abstract (sommario):
A wide variety of quaternary ammonium compounds (QACs) have escalated the attraction of researchers to explore the application of QACs. The compounds have frequently been synthesized through alkylation or quaternization of tertiary amines with alkyl halides. Recently, QACs have been applied to compatibilize polymer blends and polymer composites in improving their thermo-mechanical properties. This concise review concentrates on the application of two types of QACs as compatibilizers for polymer blends and polymer composites. The types of QACs that were effectively applied in the blends and composites are quaternary ammonium surfactants (QASs) and quaternary ammonium ionic liquids (QAILs). They have been chosen for the discussion because of their unique chemical structure which can interact with the polymer blend and composite components. The influence of QASs and QAILs on the thermo-mechanical properties of the polymer blends and polymer composites is also described. This review could be helpful for the polymer blend and polymer composite researchers and induce more novel ideas in this research area.
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Adams, L. A., E. R. Essien e E. E. Kaufmann. "Mechanical and bioactivity assessment of wollastonite/PVA composite synthesized from bentonite clay". Cerâmica 65, n. 374 (giugno 2019): 246–51. http://dx.doi.org/10.1590/0366-69132019653742584.
Abstract (sommario):
Abstract Glass/polymer composites can mimic the natural structure of bone by possessing a fiber-matrix configuration which provides appropriate physical and biological properties. Wollastonite ceramics are known for their promising bioactivity and biocompatibility when applied in bone regeneration. Polyvinyl alcohol (PVA) has various attractive properties including biocompatibility and degradability which may be exploited as a polymer matrix in composites for biomedical applications. Therefore, a cost-effective method of preparing wollastonite/PVA composites is desirable by starting from bentonite clay as a silica source for the glass, instead of traditional alkoxysilanes. The composite prepared was characterized by mechanical testing, scanning electron microscopy, X-ray diffractometry and Fourier-transform infrared spectroscopy to evaluate its compressive strength, morphology, phase composition and bioactivity, respectively. Results obtained revealed for the composite a compressive strength of 0.3 MPa, the ability to induce apatite on its surface when immersed in a simulated body fluid for 7 days and desirable controlled degradation. Hence, this method can be up-scaled for preparation of wollastonite/PVA composite commercially for possible use in bone regeneration.
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Hemdan, Bahaa A., Ahmed Mostafa, Marwa M. Elbatanony, Amal M. El-Feky, Tsvetelina Paunova-Krasteva, Stoyanka Stoitsova, Mohamed Azab El-Liethy, Gamila E. El-Taweel e Mobarak Abu Mraheil. "Bioactive Azadirachta indica and Melia azedarach leaves extracts with anti-SARS-CoV-2 and antibacterial activities". PLOS ONE 18, n. 3 (8 marzo 2023): e0282729. http://dx.doi.org/10.1371/journal.pone.0282729.
Abstract (sommario):
The leaves of Azadirachta indica L. and Melia azedarach L., belonging to Meliaceae family, have been shown to have medicinal benefits and are extensively employed in traditional folk medicine. Herein, HPLC analysis of the ethyl acetate fraction of the total methanolic extract emphasized the enrichment of both A. indica L., and M. azedarach L. leaves extracts with phenolic and flavonoids composites, respectively. Besides, 4 limonoids and 2 flavonoids were isolated using column chromatography. By assessing the in vitro antiviral activities of both total leaves extracts against Severe Acute Respiratory Syndrome Corona virus 2 (SARS-CoV-2), it was found that A. indica L. and M. azedarach L. have robust anti-SARS-CoV-2 activities at low half-maximal inhibitory concentrations (IC50) of 8.451 and 6.922 μg/mL, respectively. Due to the high safety of A. indica L. and M. azedarach L. extracts with half-maximal cytotoxic concentrations (CC50) of 446.2 and 351.4 μg/ml, respectively, both displayed extraordinary selectivity indices (SI>50). A. indica L. and M. azedarach L. leaves extracts could induce antibacterial activities against both Gram-negative and positive bacterial strains. The minimal inhibitory concentrations of A. indica L. and M. azedarach L. leaves extracts varied from 25 to 100 mg/mL within 30 min contact time towards the tested bacteria. Our findings confirm the broad-spectrum medicinal value of A. indica L. and M. azedarach L. leaves extracts. Finally, additional in vivo investigations are highly recommended to confirm the anti-COVID-19 and antimicrobial activities of both plant extracts.
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Kang, Hyoseop, Ki Hoon Kim, Geon Su Kim, Hyeseong Lee, Ji-un Jang e Seong Yun Kim. "Synergistic enhancement in electrical conductivity of polymer composites simultaneously filled with multi-walled carbon nanotube and pitch-based carbon fiber via one-step solvent-free fabrication". Functional Composites and Structures 4, n. 1 (1 marzo 2022): 015008. http://dx.doi.org/10.1088/2631-6331/ac5d26.
Abstract (sommario):
Abstract Recently, studies have been reported to synergistically improve the electrical conductivity of polymer composites by simultaneously incorporating hybrid fillers, but systematic studies on filler loading and ratio are still scarce. In this study, a one-step process was proposed to induce the incorporation of uniformly dispersed fillers with a high content, and synergistic improvement in the electrical conductivity of polymer composites was studied by applying two types of carbon fillers: nano-sized multi-walled carbon nanotube (MWCNT) and micro-sized pitch-based carbon fiber (PCF). Based on the proposed process, it was possible to fabricate a polymer composite in which the filler was uniformly dispersed within 40 wt%. The electrical conductivity of the composite containing up to 10 wt% MWCNT which was the percolation plateau content and 30 wt% PCF was 3940 S m−1, showing the maximum performance. This result was improved by 595% and 586%, respectively, compared to the electrical conductivity of the composite containing only 40 wt% MWCNT or PCF. These findings can contribute to expanding the application of conductive composites in the fields of antistatic or electromagnetic interference shielding by providing insight into the optimal design of hybrid filler systems to improve the electrical conductivity of composites.
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Zhao, Jian, Wei Li, Xin Dong e Jiying Chen. "Material Properties of Strontium Doped Bioactive Glasses/Hydroxyapatite Composite and Its Mechanism of Promoting Bone Repair". Journal of Biomaterials and Tissue Engineering 11, n. 12 (1 dicembre 2021): 2313–20. http://dx.doi.org/10.1166/jbt.2021.2853.
Abstract (sommario):
Based on bioactive glasses (BG) of 58S, sol–gel method is used to prepare strontium oxide substituted bioactive glasses (SrO-BG) with different strontium content. SrO-BG and nano hydroxyapatite (HAp) composite materials were synthesized using precipitation method. The phase composition and morphologies of the prepared materials were examined by x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The dissolution and bio-mineralization of SrO-BG and SrO-BG/HAp composites in SBF are investigated by immersion method. The effects of secretion components of macrophages regulated by strontium doped SrO-BG/HAp composites on the osteogenic differentiation (OD) of bone marrow mesenchymal stem cells (BMSCs) are analyzed. The results demonstrate that the SrO-BG can inhibit the dissolution of BG. Different proportions of SrO-BG/HAp composites show good ability to induce HAp in SBF. The bio-mineralization ability of SrO-BG/HAp composites increases with the increase of SrO-BG content. The results of dissolution behavior and bio-mineralization of SrO-BG/HAp composite show that the dissolution rate of each ion can be controlled by adjusting the content of SrO-BG in the composite, and then the degradation rate can effectively be controlled. The results of in vitro experiments show that SrO-BG/HAp composites with 2%, 5% and 8% strontium content are more effective in promoting M2 polarization of macrophages than SrO-BG/HAp composites with 0% strontium content. Among them, 5% strontium doped SrO-BG/HAp has the strongest effect on M2 polarization of macrophages, and the secretion of macrophages regulated by 5% strontium doped SrO-BG/HAp composite is more conducive to bone repair.
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Lalunio-Manikan, Marilyn, Aldrin P. Bonto e Carmelo Miguel H. Ebreo. "Nanosilver Immobilized in Carbonaceous Particles Derived from Hydrothermal Carbonization of Eleusine indica Leaf Extract". Trends in Sciences 18, n. 23 (15 novembre 2021): 681. http://dx.doi.org/10.48048/tis.2021.681.
Abstract (sommario):
In this study, for the first time, hydrothermal treatment of Eleusine indica leaf extract and silver nitrate produced nanosilver immobilized in hydrothermal carbon synthesized at different reaction times (RT) - 6, 12, 24 and 48 h. The surface morphology of nanosilver hydrochar (AgNP@hydrochar) composites was studied using SEM, while their chemical functionalities were investigated using FT-IR, UV-Vis, XRF and EDX spectroscopy. The AgNP@hydrochar were observed to be agglomerated spherical particles with size ranges from 128 to 171 nm. Varying C=O and C=C IR absorption peaks at different RT suggested that the plant extract reduced Ag+ into Ag0 in solution. Elemental analysis using EDX showed that Ag is dominant in the composite (84.07 %) supported by the Ag spatial distribution as demonstrated by the EDX elemental mapping.
HIGHLIGHTS
For the first time, hydrothermal treatment of Eleusine indica leaf extract with silver nitrate resulted in nanosilver trapped in hydrothermal carbon
HTC process of E. indica extract produced composite having agglomerated spherical particles
EDX elemental mapping showed an abundant silver in the synthesized composite
GRAPHICAL ABSTRACT
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Yan, Hui, Liang Wang, Xiaoming Wang, Botao Jiang, Hongcan Liu, Binbin Wang, Liangshun Luo, Yanqing Su, Jingjie Guo e Hengzhi Fu. "Effects of Melt Hydrogenation on the Microstructure Evolution and Hot Deformation Behavior of TiBw/Ti-6Al-4V Composites". Materials 16, n. 6 (21 marzo 2023): 2496. http://dx.doi.org/10.3390/ma16062496.
Abstract (sommario):
In this study, Ti-6Al-4V matrix composites reinforced with TiB ceramic whiskers were in situ synthesized and hydrogenated using the melt hydrogenation technique (MHT). The effects of MHT on the microstructure evolution and hot compression behavior of the composites were investigated by optical microscopy (OM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). Hot compression tests were performed at strain rates of 0.1/s, 0.01/s, and 0.001/s and temperatures of 800 °C, 850 °C, and 900 °C; the hot workability of composites significantly improved after hydrogenation, for example, the 900 °C peak flow stress of hydrogenated composites (43 MPa) decreased by 53.76% compared with that of unhydrogenated ones (93 MPa) at a strain rate of 0.01/s. Microstructural observations show that MHT can effectively facilitate the dispersion of TiB whiskers and induce the α/β lath refinement of the matrix in our as-cast hydrogenated composite. During hot compression, MHT effectively promoted the as-cast composite microstructure refinement, accelerated the dynamic recrystallization (DRX) generation, and reduced the stress concentration at the interface between the reinforcement and matrix; in turn, the hydrogenated composites presented low peak stress during hot compression.
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Sultana, S., HP Nur, T. Saha e M. Saha. "Fabrication of raw and oxidized saw dust reinforced low density polyethylene (LDPE) composites and investigation of their physico-mechanical properties". Bangladesh Journal of Scientific and Industrial Research 47, n. 4 (6 marzo 2013): 365–72. http://dx.doi.org/10.3329/bjsir.v47i4.14065.
Abstract (sommario):
In this research work, cellulosic waste mango (Mangifera indica) saw dust used as the reinforcing material with low density polyethylene (LDPE). A number of samples of saw dust reinforced low density polyethylene (LDPE) composites were prepared by compression moulding technique. In order to improve the mechanical properties of saw dust-LDPE composites, unbleached raw saw dust fibers were modified by oxidation using sodium hypochlorite. FT-IR spectroscopic and scanning electron micrograph (SEM) analyses were done and the results showed the evidence of positive oxidation reaction. The effects of oxidized saw dust on the performance of oxidized saw dust reinforced LDPE composites were studied comparing with the raw saw dust-LDPE composites. The effects of fiber content on the physico-mechanical properties of composites were also studied by preparing the composites with different percentage of fiber loading (from 7.5 wt% to 30 wt%) for each type of composite. Mechanical properties such as tensile strength, tensile modulus, elongation at break, flexural strength, flexural modulus of the resulting composite were measured. Better results were obtained from oxidized saw dust-LDPE composites. Scanning electron micrograph and water absorption tests were carried out for all composites and improved results were found for oxidized saw dust-LDPE composites. Bangladesh J. Sci. Ind. Res. 47(4), 365-372, 2012 DOI: http://dx.doi.org/10.3329/bjsir.v47i4.14065
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Liu, Ting-Yu, Peng Zhang, Qing-Fu Li, Shao-Wei Hu e Yi-Feng Ling. "Durability Assessment of PVA Fiber-Reinforced Cementitious Composite Containing Nano-SiO2 Using Adaptive Neuro-Fuzzy Inference System". Crystals 10, n. 5 (28 aprile 2020): 347. http://dx.doi.org/10.3390/cryst10050347.
Abstract (sommario):
In this study, the durability of polyvinyl alcohol fiber-reinforced cementitious composite containing nano-SiO2 was evaluated using the adaptive neuro-fuzzy inference system (ANFIS). According to the structural characteristics of the cementitious composite material and some related standards, the classification criteria for the evaluation indices of cementitious composite materials were clarified, and a corresponding structural framework of durability assessment was constructed. Based on the hypothesis testing principle, the required test data capacity was determined under a certain degree of accuracy, and durability experimental data and expert evaluation results were simulated according to statistical principles to ensure that there were sufficient datasets for ANFIS training. Using an environmental factor submodule as an example, 14 sets of actual test data were used to verify that the ANFIS can quickly and effectively mimic the expert evaluation reasoning process to evaluate the durability of cementitious composites. Compared with other studies related to the durability of cementitious composites, a systematic evaluation system for the durability of concrete was established. We used a polyvinyl alcohol fiber-reinforced cementitious composite containing nano-SiO2 to conduct a comprehensive evaluation of cementitious composites. Compared with the traditional expert evaluation method, the durability evaluation system based on the ANFIS learned expert experience, stored the expert experience in fuzzy rules, and eliminated the subjectivity of expert evaluation, thereby making the evaluation more objective and scientific.
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Fischer, Liudmila, Ke Ran, Christina Schmidt, Kerstin Neuhaus, Stefan Baumann, Patrick Behr, Joachim Mayer et al. "Role of Fe/Co Ratio in Dual Phase Ce0.8Gd0.2O2−δ–Fe3−xCoxO4 Composites for Oxygen Separation". Membranes 13, n. 5 (29 aprile 2023): 482. http://dx.doi.org/10.3390/membranes13050482.
Abstract (sommario):
Dual-phase membranes are increasingly attracting attention as a solution for developing stable oxygen permeation membranes. Ce0.8Gd0.2O2−δ–Fe3−xCoxO4 (CGO-F(3−x)CxO) composites are one group of promising candidates. This study aims to understand the effect of the Fe/Co-ratio, i.e., x = 0, 1, 2, and 3 in Fe3−xCoxO4, on microstructure evolution and performance of the composite. The samples were prepared using the solid-state reactive sintering method (SSRS) to induce phase interactions, which determines the final composite microstructure. The Fe/Co ratio in the spinel structure was found to be a crucial factor in determining phase evolution, microstructure, and permeation of the material. Microstructure analysis showed that all iron-free composites had a dual-phase structure after sintering. In contrast, iron-containing composites formed additional phases with a spinel or garnet structure which likely contributed to electronic conductivity. The presence of both cations resulted in better performance than that of pure iron or cobalt oxides. This demonstrated that both types of cations were necessary to form a composite structure, which then allowed sufficient percolation of robust electronic and ionic conducting pathways. The maximum oxygen flux is jO2 = 0.16 and 0.11 mL/cm2·s at 1000 °C and 850 °C, respectively, of the 85CGO-FC2O composite, which is comparable oxygen permeation flux reported previously.
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Zhang, Hong Yan, Hai Quan Wang, Lin Tong Wang e Yi Min Feng. "Electrical Conducting Properties of Unsaturated Polyester/Graphite Nanosheet Composite under Electric Field". Advanced Materials Research 455-456 (gennaio 2012): 520–23. http://dx.doi.org/10.4028/www.scientific.net/amr.455-456.520.
Abstract (sommario):
Unsaturated polyester resin/Graphite nanosheet composites were prepared using in situ polymerization under AC electric field which was applied during composite curing to induce orientation of graphite nanosheets. Scanning electron microscopy (SEM) has been applied to demonstrate the orientation of graphite nanosheets As a result, the percolation threshold was decreased to 0.25 wt% due to the orientation of the graphite nanosheets.
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Xiao, Huigang, Min Liu e Jinbao Jiang. "Effect of aligning conductive particles on the piezoresistivity of composites". Sensor Review 35, n. 1 (19 gennaio 2015): 43–50. http://dx.doi.org/10.1108/sr-08-2013-722.
Abstract (sommario):
Purpose – The purpose of this paper is to study the effect of alignment of conductive particles on the piezoresistivity of composite based on a theoretical model. The piezoresistivity of composite is associated with the characteristics of conductive network formed by the conductive particles distributed in the composite, which can be changed through aligning the conductive particles. Design/methodology/approach – The orientations of the tunnel resistors formed by each two adjacent conductive particles are dependent on the aligned level of the conductive particles, and different orientations induce different deformations for a tunnel resistor under external strain, which determines the piezoresistivity of the composites. To investigate the resistance behavior of composites with various characteristics of conductive networks, a piezoresistivity model is developed in this paper by considering the aligned level of conductive particles. Findings – The results obtained from the proposed piezoresistivity model indicate that the sensitivity and stability of composites can be enhanced through aligning the conductive particles. Also, the piezoresistivity of composites filled with randomly distributed conductive particles is isotropic, and it turns to be anisotropic when the conductive particles are aligned. Originality/value – The change and its mechanism of the piezoresistivity upon the aligned level of conductive particles have been pointed out in this paper based on the proposed model. The achievement of this paper will help the people understand, predict and optimize the piezoresistivity of composites, and provide a new approach to design a strain sensor based on the piezoresistivity.
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Chaochanchaikul, Kantima, Krishnan Jayaraman, Vichai Rosarpitak e Narongrit Sombatsompop. "Influence of lignin content on photodegradation in wood/HDPE composites under UV weathering". BioResources 7, n. 1 (3 novembre 2011): 38–55. http://dx.doi.org/10.15376/biores.7.1.38-55.
Abstract (sommario):
The aim of this work was to examine the influence the lignin component of wood on the photodegradation of high-density polyethylene (HDPE) in wood/HDPE (WPE) composites. The neat HDPE and wood/HDPE composites were prepared using a twin screw extruder followed by an injection moulder. The lignin content was varied from 0 to 29 %wt. of wood by the addition of delignified wood pulp into wood flour. The results suggested that the photodegradation of HDPE in WPE composites was accelerated by the presence of lignin; the chromophoric groups in the lignin enhanced UV adsorption onto the WPE composite surface. The carbonyl and vinyl indices, color, percentage crystallinity, and the melting temperature increased when the lignin contents were increased. The color fading in WPE composites resulted from photobleaching of lignin. In addition, the presence of lignin led to the development ofl cracks in WPE composites, especially at high lignin contents. For the effect of UV weathering time, the carbonyl and vinyl indices, discoloration, and percentage crystallinity increased as a function of UV weathering times, whereas the melting temperature of HDPE in both neat HDPE and WPE composites and water absorption of specimens decreased; the wood index in WPE composites increased during the initial UV weathering times and then decreased at 720 h weathering time.
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Damansabz, Reza, e Fathollah Taheri-Behrooz. "Actuation of a carbon/epoxy beam using shape memory alloy wires". Journal of Intelligent Material Systems and Structures 30, n. 2 (21 novembre 2018): 186–97. http://dx.doi.org/10.1177/1045389x18810807.
Abstract (sommario):
Shape memory effect of NiTi wires is utilized to design various smart composite structures. In these systems, smart wires can induce strains in the host structure by their inherent shape memory effect and phase transformation at elevated temperatures. This article presents an experimental and numerical study on the actuation capability of shape memory alloy wires embedded in the carbon/epoxy composite. In the experimental part, hybrid shape memory alloy/carbon/epoxy composite specimens are fabricated and examined to measure induced strains in the host structure by the phase transformation of the shape memory alloy wires. Hybrid composite specimens were clamped at one end, and the shape memory alloy wires were activated using electrical resistive heating. Numerical simulations were carried out using ABAQUS software to simulate the actual thermomechanical behavior of the hybrid composite specimens. A three-dimensional finite element model based on cohesive zone modeling is used to predict interfacial debonding in hybrid composite plates. The results of the parametric study suggest that by increasing Young’s modulus of the host composites, the amount of the induced strain decreases rapidly. However, for Young’s moduli more than 20 GPa, the induced strain will stay almost constant. Moreover, it was confirmed that increasing the shape memory alloy pre-strain without controlling the actuation temperature may result in the reduction of induced strain in the host composites.
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Roman, Alexandra, Emöke Páll, Mărioara Moldovan, Darian Rusu, Olga Şoriţău, Dana Feştilă e Mihaela Lupşe. "Cytotoxicity of Experimental Resin Composites on Mesenchymal Stem Cells Isolated from Two Oral Sources". Microscopy and Microanalysis 22, n. 5 (9 settembre 2016): 1018–33. http://dx.doi.org/10.1017/s1431927616011624.
Abstract (sommario):
AbstractResin composite materials that are used to restore tooth cervical lesions associated with gingival recessions can hamper healing after root coverage surgeries. This study evaluates the in vitro cytotoxic effect of five resin composites (two commercial and three experimental) on oral mesenchymal stem cells (MSCs) and the persistence of stemness properties in high passage MSCs. Sorption and solubility tests were made for all materials. MSCs were isolated from re-entry palatal and periodontal granulation tissues and were characterized and cultured on composite discs. Cytotoxicity of the materials was evaluated by the Alamar Blue viability test, by Paul Karl Horan (PKH) labeling, and by immunocytochemical staining for actin. Water and saliva sorption and solubility data revealed that two of the experimental materials behaved comparable with the marketed resin composites. The Alamar Blue viability test shows that both cell lines grew well on composite discs that seemed to induce no apparent toxic effects. No signs of disruption of cytoskeleton organization was seen. Experimental resin composites can be recommended for further investigation for obtaining approval for use. The standard minimal criteria were fulfilled for high passage MSCs. Palatal tissue regains its regenerative properties in terms of MSC presence in the re-entry area after 6 months of healing.
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Kaczmarek, Halina, Marta Chylińska, Bogusław Królikowski, Ewa Klimiec, Dagmara Bajer e Jolanta Kowalonek. "Influence of glass beads filler and orientation process on piezoelectric properties of polyethylene composites". Journal of Materials Science: Materials in Electronics 30, n. 24 (15 novembre 2019): 21032–47. http://dx.doi.org/10.1007/s10854-019-02473-9.
Abstract (sommario):
AbstractThe effect of silica filler (in the form of glass beads) on polyethylene composite properties has been studied. Conditions for obtaining polyethylene-based composites in the extrusion process were developed. Two types of such composites were prepared: non-oriented and oriented in the uniaxial stretching process in a ratio of 3:1. The morphology, microstructure (including crystallinity degree), mechanical resistance, and thermal stability of the obtained composites containing 2.5–10% of the filler were analyzed by the scanning electron microscopy connected with energy dispersive X-ray analysis, X-ray diffraction, differential scanning calorimetry, thermogravimetry methods, and tensile tests. In order to induce piezoelectric effect, the samples were charged with a direct current of 100 V/μm at 85 °C. The piezoelectric properties of the polyethylene composites were determined by the measurement of charge and voltage of current generated during action of stress up to 120 kPa. Piezoelectric coefficients, d33 and g33, versus applied stress were determined and the stability of electrets stored during 2–5 months was tested too. The best piezoelectric properties were found for medium-density polyethylene composite containing 5% of glass beads.
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Rana, Ashvinder K., Vijay Kumar Thakur e Amar S. Singha. "Towards the use of acrylic acid graft-copolymerized plant biofiber in sustainable fortified composites: Manufacturing and characterization". e-Polymers 21, n. 1 (1 gennaio 2021): 881–96. http://dx.doi.org/10.1515/epoly-2021-0080.
Abstract (sommario):
Abstract In this study, the impact of particle form of the Cannabis indica plant biofibers and the fiber’s surface tailoring on the physical, thermal, dielectric, and mechanical properties of unsaturated polyester composite specimens manufactured utilizing nonconventional materials were investigated. The mechanical properties such as compressive, flexural, and tensile strengths of the composite specimens were noticed to increase after functionalization of biofiber with acrylic acid and maximum enhancement was found at 20% of biofiber sacking. The physical characterization was concentrated on the assurance of the dielectric constant, dielectric strength, dielectric loss, moisture absorption, chemical resistance, percentage of swelling, limiting oxygen index, and biodegradation of polymer composites under red soil. An increase in dielectric strength from 28 to 29 kV, limiting oxygen index values from 19% to 23%, and moisture/water absorption behavior was noted for resulted bio-composites after surface tailoring of biofiber. To assess the deterioration of the polymeric materials with the temperature, differential scanning calorimetric and the thermogravimetric tests were carried out and enhancement in thermal stability was noted after fortification of polyester composites with functionalized biofiber.
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Zheng, Hang, Ruixiang Zhang, Qin Xu, Xiangqing Kong, Wanting Sun, Ying Fu, Muhong Wu e Kaihui Liu. "Fabrication of Cu/Al/Cu Laminated Composites Reinforced with Graphene by Hot Pressing and Evaluation of Their Electrical Conductivity". Materials 16, n. 2 (9 gennaio 2023): 622. http://dx.doi.org/10.3390/ma16020622.
Abstract (sommario):
Metal laminated composites are widely used in industrial and commercial applications due to their excellent overall performance. In this study, the copper/graphene-aluminum-copper/graphene (Cu/Gr-Al-Cu/Gr) laminated composites were prepared by ingenious hot pressing design. Raman, optical microscope (OM), scanning electron microscope (SEM), van der Pauw (vdP), and X-Ray Diffractometer (XRD) were used to investigate the graphene status, interface bonding, diffusion layer thickness, electrical conductivity, Miller indices and secondary phases, respectively. The results demonstrate that the Cu-Al interfaces in the Cu/Gr-Al-Cu/Gr composites were free of pores, cracks and other defects and bonded well. The number of graphene layers was varied by regulating the thickness of the Cu/Gr layer, with the Cu/Gr foils fabricated by chemical vapor deposition (CVD). The electrical conductivity of the composite was significantly improved by the induced high-quality interfaces Cu/Gr structure. The increased number of graphene layers is beneficial for enhancing the electrical conductivity of the Cu/Gr-Al-Cu/Gr composite, and the highest conductivity improved by 20.5% compared to that of raw Al.