Journal articles on the topic 'Composites variables et anisotropes'
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Ducret, D., R. El Guerjouma, M. Dubuget, and J. C. Baboux. "Caractérisation ultrasonore de l’élasticité et de l’endommagement anisotropes des matériaux composites." Matériaux & Techniques 88, no. 9-10 (2000): 3–7. http://dx.doi.org/10.1051/mattech/200088090003.
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Gavarri, J. R., P. Boher, and A. W. Hewat. "Monoxyde PbOα(II): Élasticité et vibrations anisotropes; modélisation; constantes élastiques." Journal of Solid State Chemistry 58, no. 1 (June 1985): 87–97. http://dx.doi.org/10.1016/0022-4596(85)90271-3.
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Hall, Richard B. "A Thermodynamic Framework for Viscoplasticity Based on Overstress (VBO)." Journal of Engineering Materials and Technology 127, no. 4 (March 28, 2005): 369–73. http://dx.doi.org/10.1115/1.1924562.
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A thermodynamic framework is presented for the theory of Viscoplasticity Based on Overstress (VBO) developed by Krempl and co-workers (Krempl, E., and Ho, K., 2001, in Lemaitre Handbook of Materials Behavior Models, Academic Press, New York, pp. 336–348; 2000, in Time Dependent and Nonlinear Effects in Polymers and Composites, ASTM STP 1357, Schapery, R. A., and Sun, C. T., eds., ASTM, West Conshohocken, PA, pp. 118–137; Cernocky, E. P., and Krempl, E., 1979, Int. J. Non-Linear Mech., 14, pp. 183–203; Gomaa et al., 2004, Int. J. Solids Struct., 41, pp. 3607–3624), for anisotropic materials and small deformations. A Caratheodory-based approach is applied to demonstrate the existence of entropy and absolute temperature, as previously described by Hall (2000, Compos. Sci. Technol., 60, pp. 2581–2599). The present framework indicates that the stress rate-dependent term in the established growth law for the equilibrium stress cannot contribute to the dissipation, and is therefore referred to here as the elastic equilibrium stress rate. A new temperature rate-dependent term is obtained for the same growth law, which is also required to be dissipationless. These terms are therefore identified with dissipationless changes of the stored energy and∕or entropy. In general, the traditional, and thermodynamically justified, forms for the potential functions that arise in the present nonequilibrium treatment lead to dissipationless contributions from internal variable growth law terms that are linear in the rates of the controllable variables. Similar indications, without first establishing entropy and absolute temperature existence, were noted in the modeling of Lehmann (1984, in The Constitutive Law in Thermoplasticity, T. Lehmann, ed., Springer, New York).
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Chater, R., J. R. Gavarri, and A. W. Hewat. "Évolution structurale sous pression de NiSb2O4: Compressibilités anisotropes et ordre magnetique." Journal of Solid State Chemistry 67, no. 1 (March 1987): 98–103. http://dx.doi.org/10.1016/0022-4596(87)90344-6.
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Chater, R., and J. R. Gavarri. "Evolution structure entre 2 et 300 K de l'oxyde MnSb2O4: Proprie´te´se´lastiques et magne´tiques anisotropes." Journal of Solid State Chemistry 59, no. 1 (August 1985): 123–31. http://dx.doi.org/10.1016/0022-4596(85)90359-7.
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Chater, R., J. R. Gavarri, and A. Hewat. "Structures isomorphes MeX2O4—Evolution structurale entre 2 K et 300 K de l'antimonite FeSb2O4: Elasticité et ordre magnétique anisotropes." Journal of Solid State Chemistry 60, no. 1 (November 1985): 78–86. http://dx.doi.org/10.1016/0022-4596(85)90166-5.
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Djibril, Oumar. "Examen de la Dette Extérieure Publique D’un Pays à Revenu Intermédiaire par une Approche D’indicateur de Sutenabilité: le cas de la Côte d’Ivoire." European Scientific Journal, ESJ 18, no. 28 (September 30, 2022): 94. http://dx.doi.org/10.19044/esj.2022.v18n28p94.
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Cette étude examine la soutenabilité de la dette extérieure de la Côte d’Ivoire, pays à revenu intermédiaire avant et après son élection à l’IPPTE[1] en 2012, date cruciale de son histoire par l’approche de l’Indicateur de Soutenabilité de la Dette (ISD). Les résultats de l’étude montrent que son niveau d’endettement extérieur pose un problème de soutenabilité avant la période de l’atteinte du point d’achèvement mais relativement moins après. Le recours à la mesure de l’ISD fondé sur des variables socioéconomiques composites permet de conclure que la Côte d’Ivoire s’appauvrit empiriquement au plan socio-économique en dépit de son taux d’endettement s’inscrivant dans les normes de l’UEMOA (<70% du PIB). La dette extérieure étant insoutenable, sa bonne gestion et le recours régulier aux opérations d’emprunts obligataires et l’exploitation des avantages comparatifs sont à encourager.
[1] Initiative Pays pauvres très endettés (IPPTE) ; solution qui a pour objectif de rendre la dette extérieure des pays pauvres soutenable. Elle est lancée par les Institutions de Bretton Woods depuis 1996.
This paper examines alternatively the sustainability of Ivorian external indebtedness through HIPCs issue before and after the year 2012, a key date of Côte d’Ivoire’s history. The study takes into account social and economic variables instead of economic indicators only used by international financial institutions (IFI) and other studies. With reference to debt sustainability indicator (DSI) analysis focused on economic and also social variables provided, this study outlines the state of highly indebted poor country in terms of lack of social infrastructures before the initiative and after. Therefore, after the achievement point, the result remains relatively the same. As a matter of fact, these findings justify the poorest state of Côte d’Ivoire: the external debt is therefore unsustainable. From our findings, good external debt management, the regular using of financial bonds market and exploiting comparative advantages are encouraged.
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Koadri, Zainate, Azzedine Benyahia, Nadir Deghfel, Kamel Belmokre, Brahim Nouibat, and Ali Redjem. "Étude de l’effet du temps de traitement alcalin de fibres palmier sur le comportement mécanique des matériaux à base d’argile rouge de la région de M’sila." Matériaux & Techniques 107, no. 4 (2019): 404. http://dx.doi.org/10.1051/mattech/2019031.
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Ce travail s’inscrit dans le développement de matériaux locaux, telle que la fibre végétale (fibre de palmier) et l’argile rouge du sud Algérien, largement utilisées dans la préparation des briques, comme matériaux de construction rurale. Les fibres végétales possèdent des propriétés très intéressantes, elles sont : renouvelables, biodégradables et le rapport coût/légèreté faible. Leurs propriétés mécaniques sont très importantes. Cependant, le problème prédominant dans ce type de matériaux composites est la faible adhésion de l’interface matrice-fibre, attribuée probablement, à la nature de la surface et au caractère hydrophobe des fibres naturelles, conduisant ainsi, à des propriétés mécaniques faibles pour le composite envisagé. Le but de cette étude consiste à traiter la fibre de palmier par une solution basique d’hydroxyde de sodium (NaOH 4 % [m/v]) durant des périodes variables : 3, 7, 24 et 48 heures, afin d’améliorer l’adhésion interfaciale. Les résultats obtenus à partir des essais réalisés sur le composite renforcé par les fibres de palmier traitées durant 7 h ont montré une nette augmentation quant à la résistance, à la flexion et à la compression ; cette croissance est respectivement de l’ordre de 57 et 60 %, comparativement au composite renforcé par les fibres non traitées. On peut déduire que les fibres de palmier peuvent être considérées comme l’un des matériaux appropriés pour le renforcement de l’argile.
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Shange, Musawenkosi G., Nduduzo L. Khumalo, Samson M. Mohomane, and Tshwafo E. Motaung. "Factors Affecting Silica/Cellulose Nanocomposite Prepared via the Sol–Gel Technique: A Review." Materials 17, no. 9 (April 23, 2024): 1937. http://dx.doi.org/10.3390/ma17091937.
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Cellulose/silica nanocomposites, synthesised through the sol–gel technique, have garnered significant attention for their unique properties and diverse applications. The distinctive characteristics of these nanocomposites are influenced by a range of factors, including the cellulose-to-silica ratio, precursor concentration, pH, catalysts, solvent selection, temperature, processing techniques, and agitation. These variables play a pivotal role in determining the nanocomposites’ structure, morphology, and mechanical properties, facilitating tailoring for specific applications. Studies by Raabe et al. and Barud et al. demonstrated well-deposited silica nanoparticles within the interstitial spaces of cellulosic fibres, achieved through TEOS precursor hydrolysis and the subsequent condensation of hydroxyl groups on the cellulose fibre surface. The introduction of TEOS established a robust affinity between the inorganic filler and the polymer matrix, emphasising the substantial impact of TEOS concentration on the size and morphology of silica nanoparticles in the final composites. The successful functionalisation of cellulose fibres with the TEOS precursor via the sol–gel method was reported, resulting in reduced water uptake and enhanced mechanical strength due to the strong chemical interaction between silica and cellulose. In research conducted by Feng et al., the silica/cellulose composite exhibited reduced weight loss compared to the pristine cellulose matrix, with the integration of silica leading to an elevated temperature of composite degradation. Additionally, Ahmad et al. investigated the effects of silica addition to cellulose acetate (CA) and polyethylene glycol membranes, noting an increase in Young’s modulus, tensile strength, and elongation at break with silica incorporation. However, concentrations exceeding 4% (w/v) resulted in significant phase separations, leading to a decline in mechanical properties.
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Atallah, Eyad, Lance F. Bosart, and Anantha R. Aiyyer. "Precipitation Distribution Associated with Landfalling Tropical Cyclones over the Eastern United States." Monthly Weather Review 135, no. 6 (June 1, 2007): 2185–206. http://dx.doi.org/10.1175/mwr3382.1.
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Abstract Tropical cyclones (TCs) making landfall over the United States are examined by separating those associated with precipitation predominantly left of their tracks from those with the same to the right of their tracks. Composites of atmospheric variables for these two TC categories are performed and analyzed using potential vorticity (PV) and quasigeostrophic (QG) frameworks. Dynamical signatures are retrieved from these composites to help understand the evolution of precipitation in these storms. Results indicate that a left of track precipitation distribution (e.g., Floyd 1999) is characteristic of TCs undergoing extratropical transition (ET). In these cases, a positively tilted midlatitude trough approaches the TC from the northwest, shifting precipitation to the north-northwest of the TC. Potential vorticity redistribution through diabatic heating leads to enhanced ridging over and downstream of the TC, resulting in an increase in the cyclonic advection of vorticity by the thermal wind over the transitioning TC. A right of track precipitation distribution is characteristic of TCs interacting with a downstream ridge (e.g., David 1979). When the downstream ridge amplifies in response to TC-induced diabatic heating ahead of a weak midlatitude trough, the PV gradient between the TC and the downstream ridge is accentuated, producing a region of enhanced positive PV advection (and cyclonic vorticity advection by the thermal wind) over the TC. The diabatic enhancement of the downstream ridge is instrumental in the redistribution of precipitation about the transitioning TCs in both cases and poses a significant forecast challenge.
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Duveiller, Gregory, Federico Filipponi, Sophia Walther, Philipp Köhler, Christian Frankenberg, Luis Guanter, and Alessandro Cescatti. "A spatially downscaled sun-induced fluorescence global product for enhanced monitoring of vegetation productivity." Earth System Science Data 12, no. 2 (May 13, 2020): 1101–16. http://dx.doi.org/10.5194/essd-12-1101-2020.
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Abstract. Sun-induced chlorophyll fluorescence (SIF) retrieved from satellite spectrometers can be a highly valuable proxy for photosynthesis. The SIF signal is very small and notoriously difficult to measure, requiring sub-nanometre spectral-resolution measurements, which to date are only available from atmospheric spectrometers sampling at low spatial resolution. For example, the widely used SIF dataset derived from the GOME-2 mission is typically provided in 0.5∘ composites. This paper presents a new SIF dataset based on GOME-2 satellite observations with an enhanced spatial resolution of 0.05∘ and an 8 d time step covering the period 2007–2018. It leverages on a proven methodology that relies on using a light-use efficiency (LUE) modelling approach to establish a semi-empirical relationship between SIF and various explanatory variables derived from remote sensing at higher spatial resolution. An optimal set of explanatory variables is selected based on an independent validation with OCO-2 SIF observations, which are only sparsely available but have a high accuracy and spatial resolution. After bias correction, the resulting downscaled SIF data show high spatio-temporal agreement with the first SIF retrievals from the new TROPOMI mission, opening the path towards establishing a surrogate archive for this promising new dataset. We foresee this new SIF dataset becoming a valuable asset for Earth system science in general and for monitoring vegetation productivity in particular. The dataset is available at https://doi.org/10.2905/21935FFC-B797-4BEE-94DA-8FEC85B3F9E1 (Duveiller et al., 2019).
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Tutum, Cem C., Ismet Baran, and Jesper Hattel. "Utilizing Multiple Objectives for the Optimization of the Pultrusion Process Based on a Thermo-Chemical Simulation." Key Engineering Materials 554-557 (June 2013): 2165–74. http://dx.doi.org/10.4028/www.scientific.net/kem.554-557.2165.
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Pultrusion is one of the most effective manufacturing processes for producing composites with constant cross-sectional profiles. This obviously makes it more attractive for both researchers and practitioners to investigate the optimum process parameters, i.e. pulling speed, power and dimensions of the heating platens, length and width of the heating die, design of the resin injection chamber, etc., to provide better understanding of the process, consequently to improve the efficiency of the process as well the product quality. Numerous simulation approaches have been presented until now. However, optimization studies had been limited with either experimental cases or determining only one objective to improve one aspect of the performance of the process. This objective is either augmented by other process related criteria or subjected to constraints which might have had the same importance of being treated as objectives. In essence, these approaches convert a true multi-objective optimization problem (MOP) into a single-objective optimization problem (SOP). This transformation obviously results in only one optimum solution and it does not support the efforts to get more out of an optimization study, such as relations between variables and objectives or constraints. In this study, an MOP considering thermo-chemical aspects of the pultrusion process (e.g. cure degree, temperatures), in which the pulling speed is maximized and the heating power is minimized simultaneously (without defining any preference between them), has been formulated. An evolutionary multi-objective optimization (EMO) algorithm, non-dominated sorting genetic algorithm (NSGA-II [Deb et al., 2002]), has been used to solve this MOP in an ideal way where the outcome is the set of multiple solutions (i.e. Pareto-optimal solutions) and each solution is theoretically an optimal solution corresponding to a particular trade-off among objectives. Following the solution process, in other words obtaining the Pareto-optimal front, a further postprocessing study has been performed to unveil some common principles existing between the variables, the objectives and the constraints either along the whole front or in some portion of it. These relationships will reveal a design philosophy not only for the improvement of the process efficiency, but also a methodology to design a pultrusion die for different operating conditions.
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Ayeni, A. O., M. Adegbenro, O. E. Dick, E. S. Oyedokun, I. O. Olasehinde, and J. O. Agbede. "Performance, haemato-biochemical indices and antioxidants status of broiler chickens fed diets supplemented with avocado-bamboo composite leaf mix." Nigerian Journal of Animal Production 49, no. 1 (February 25, 2022): 293–303. http://dx.doi.org/10.51791/njap.v49i1.3428.
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Phytogenic feed additives have been suggested to augment nutrient utilization in the gastrointestinal tract by enhancing production of digestive secretions and enzymatic activity. Such effects on gastrointestinal morphology have been postulated to increase the nutrient digestibility in poultry. However, research on avocado—bamboo composite mix on broiler chickens are limited, this thus forms the focus of this study.A six week feeding trial was conducted to evaluate the growth, haemato-biochemical indices and antioxidants status of broiler chickens fed varying levels of composite leaf mix (CLM). The avocado and bamboo leaves used were manually harvested, air-dried and milled to produce leaf meal. The two leaf meals were then mixed in ratio 1:1 to form the CLM. The CLM was included in broiler basal diets at 0, 4, 8 and 12g/kg levels designated diets I – IV, respectively. Ninety six day-old Cobb broiler chicks were randomly allotted to four treatments of three replicates with eight chicks each. At the end of the feeding trial, the result revealed that average final weight of chicken fed diets II (2533.33±66.67g) and III (2406.55±30.59g) were similar but higher than those fed the control (2216.67±29.83g). The same pattern was observed for total weight gain. The feed conversion ratio (FCR) was not affected although birds fed diet II had the best FCR (2.08±0.06).No significant (P>0.05) difference was observed in all the haematological indices save mean cell volume and mean cell haemoglobin which was highest in birds fed 4g/kg CLM supplemented diet (149.87±24.73fL and 49.95±8.25 pg/cell, respectively) as compared to 111.32±16.56fL and 37.12±5.55pg/cell in those supplemented 12g/kg CLM. The same pattern was repeated in percentage lymph .Among the serum biochemistry parameters measured, only Aspartate transaminase was affected and highest in birds fed diet supplemented with 4g/kg CLM (102.52±5.88µ/L) and lowest in those fed 12g/kg CLM (99.33±5.13µ/L). The superoxide dismutase, catalase and Glutathione peroxidase increased with increased CLM supplementation. The growth, haematological, serum biochemical and antioxidant parameters obtained from this study suggested that the CLM has no adverse effect on the health status of broiler chickens but on the other hand improved the growth, blood serum and serum antioxidant profiles.
Des additifs alimentaires phytogéniques ont été suggérés pour augmenter l'utilisation des nutriments dans le tractus gastro-intestinal en améliorant la production de sécrétions digestives et l'activité enzymatique. De tels effets sur la morphologie gastro-intestinale ontété postulés pour augmenter la digestibilité des nutriments chez la volaille. Cependant, les recherches sur le mélange composite avocat-bambou sur les poulets de chair sont limitées, c'est donc l'objet de cette étude. Un essai d'alimentation de six semaines a été mené pour évaluer la croissance, les indices hémato-biochimiques et le statut en antioxydants de poulets à griller nourris à des niveaux variables de mélange de feuilles composites (MFC). Les feuilles d'avocat et de bambou utilisées ont été récoltées manuellement, séchées à l'air et broyées pour produire de la farine de feuilles. Les deux farines de feuilles ont ensuite été mélangées dans un rapport 1:1 pour former le MFC. Le MFC a été inclus dans les régimes de base des poulets de chair à des niveaux de 0, 4, 8 et 12 g/kg désignés régimes I à IV, respectivement. Quatre-vingt-seize poussins de chair Cobb âgés d'un jour ont été répartis au hasard dans quatre traitements de trois répétitions avec huit poussins chacun. À la fin de l'essai d'alimentation, le résultat a révélé que le poids final moyen des poulets nourris avec les régimes II (2533,33 ± 66,67 g) et III (2406,55 ± 30,59 g) était similaire mais supérieur à celui des poulets nourris avec le témoin (2216,67 ± 29,83 g). La même tendance a été observée pour le gain de poids total. Le taux de conversion alimentaire (TCA) n'a pas été affecté bien que les oiseaux nourris avec le régime II aient eu le meilleur TCA (2,08 ± 0,06). Aucune différence significative (P>0,05) n'a été observée dans tous les indices hématologiques, sauf le volume cellulaire moyen et l'hémoglobine cellulaire moyenne qui le plus élevé chez les oiseaux nourris avec 4 g/kg de régime supplémenté en MFC (149,87 ± 24,73 fLet 49,95 ± 8,25 pg/cellule, respectivement) par rapport à 111,32 ± 16,56 fLet 37,12 ± 5,55 pg/cellule chez ceux supplémentés en 12 g/kg de MFC. Le même schéma a été répété en pourcentage de lymphe. Parmi les paramètres biochimiques sériques mesurés, seule l'aspartate transaminase était affectée et la plus élevée chez les oiseaux nourris avec un régime supplémenté de 4 g/kg de MFC (102,52 ± 5,88 µ/L) et la plus faible chez ceux nourris avec 12 g/kg de MFC (99,33 ± 5,13 µ/L). La superoxyde dismutase, la catalase et la glutathion peroxydase ont augmenté avec l'augmentation de la supplémentation en MFC. Les paramètres de croissance, hématologiques, biochimiques sériques et antioxydants obtenus à partir de cette étude suggèrent que le MFC n'a pas d'effet néfaste sur l'état de santé des poulets de chair mais améliore en revanche les profils de croissance, de sérum sanguin et d'antioxydants sériques.
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Klein, François, Nerilie J. Abram, Mark A. J. Curran, Hugues Goosse, Sentia Goursaud, Valérie Masson-Delmotte, Andrew Moy, et al. "Assessing the robustness of Antarctic temperature reconstructions over the past 2 millennia using pseudoproxy and data assimilation experiments." Climate of the Past 15, no. 2 (April 5, 2019): 661–84. http://dx.doi.org/10.5194/cp-15-661-2019.
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Abstract. The Antarctic temperature changes over the past millennia remain more uncertain than in many other continental regions. This has several origins: (1) the number of high-resolution ice cores is small, in particular on the East Antarctic plateau and in some coastal areas in East Antarctica; (2) the short and spatially sparse instrumental records limit the calibration period for reconstructions and the assessment of the methodologies; (3) the link between isotope records from ice cores and local climate is usually complex and dependent on the spatial scales and timescales investigated. Here, we use climate model results, pseudoproxy experiments and data assimilation experiments to assess the potential for reconstructing the Antarctic temperature over the last 2 millennia based on a new database of stable oxygen isotopes in ice cores compiled in the framework of Antarctica2k (Stenni et al., 2017). The well-known covariance between δ18O and temperature is reproduced in the two isotope-enabled models used (ECHAM5/MPI-OM and ECHAM5-wiso), but is generally weak over the different Antarctic regions, limiting the skill of the reconstructions. Furthermore, the strength of the link displays large variations over the past millennium, further affecting the potential skill of temperature reconstructions based on statistical methods which rely on the assumption that the last decades are a good estimate for longer temperature reconstructions. Using a data assimilation technique allows, in theory, for changes in the δ18O–temperature link through time and space to be taken into account. Pseudoproxy experiments confirm the benefits of using data assimilation methods instead of statistical methods that provide reconstructions with unrealistic variances in some Antarctic subregions. They also confirm that the relatively weak link between both variables leads to a limited potential for reconstructing temperature based on δ18O. However, the reconstruction skill is higher and more uniform among reconstruction methods when the reconstruction target is the Antarctic as a whole rather than smaller Antarctic subregions. This consistency between the methods at the large scale is also observed when reconstructing temperature based on the real δ18O regional composites of Stenni et al. (2017). In this case, temperature reconstructions based on data assimilation confirm the long-term cooling over Antarctica during the last millennium, and the later onset of anthropogenic warming compared with the simulations without data assimilation, which is especially visible in West Antarctica. Data assimilation also allows for models and direct observations to be reconciled by reproducing the east–west contrast in the recent temperature trends. This recent warming pattern is likely mostly driven by internal variability given the large spread of individual Paleoclimate Modelling Intercomparison Project (PMIP)/Coupled Model Intercomparison Project (CMIP) model realizations in simulating it. As in the pseudoproxy framework, the reconstruction methods perform differently at the subregional scale, especially in terms of the variance of the time series produced. While the potential benefits of using a data assimilation method instead of a statistical method have been highlighted in a pseudoproxy framework, the instrumental series are too short to confirm this in a realistic setup.
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Kenney, Lauren E., Jared Tanner, Samuel J. Crowley, Thomas H. Mareci, Francesca V. Lopez, Adrianna M. Ratajska, Katie Rodriguez, et al. "22 Cognitive Reserve's Relationship to Brain Burden in Parkinson's Disease Without Dementia." Journal of the International Neuropsychological Society 29, s1 (November 2023): 539–40. http://dx.doi.org/10.1017/s1355617723006938.
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Objective:Individuals with Parkinson's disease (PD) have varying trajectories of cognitive decline. One reason for this heterogeneity may be "cognitive reserve": where higher education/IQ/current mental engagement compensates for increasing brain burden (Stern et al., 2020). With few exceptions, most studies examining cognitive reserve in PD fail to include brain metrics. This study's goal was to examine whether cognitive reserve moderated the relationship between neuroimaging indices of brain burden (diffusion free water fraction and T2-weighted white matter changes) and two commonly impaired domains in PD: executive function and memory. We hypothesized cognitive reserve would mitigate the relationship between higher brain burden and worse cognitive performance.Participants and Methods:Participants included 108 individuals with PD without dementia (age mean=67.9±6.3, education mean=16.6±2.5) who were prospectively recruited for two NIH-funded projects at the University of Florida. All received neuropsychological measures of executive function (Trails B, Stroop, Letter Fluency) and memory (delayed recall: Hopkin's Verbal Learning Test-Revised, WMS-III Logical Memory). Domain specific z-score composites were created using data from age/education matched non-PD peer controls (N=62). For the Cognitive Reserve (CR) proxy, a z-score composite included years of education, WASI-II Vocabulary, and Wechsler Test of Adult Reading. At the time of testing, participants completed multiple MRI scans (T1-weighted, diffusion, Fluid Attenuated Inversion Recovery) from which the following were extracted: 1) whole-brain free water within the white matter (a measure of microstructural integrity and neuroinflammation), 2) white matter hyperintensities/white matter total volume (WMH/WMV), and bilaterally-averaged edge weights of white matter connectivity between 3) dorsolateral prefrontal cortex and caudate and 4) entorhinal cortex and hippocampi. Separate linear regressions for each brain metric used executive function and memory composites as dependent variables; predictors were age, CR proxy, respective brain metric, and a residual centered interaction term (brain metric*CR proxy). Identical models were run in dichotomized short and long disease duration groups (median split=6 years).Results:In all models, a lower CR proxy significantly predicted worse executive function (WMH/WMV: beta=0.49, free water: beta=0.54, frontal edge weight: beta=0.49, p's<0.001) and memory (WMH/WMV: beta=0.42, free water: beta=0.35, temporal edge weight: beta=0.39, p's <0.01). For neuroimaging metrics, higher free water significantly predicted worse executive function (beta=-0.39, p=0.002) but not memory. No other brain metrics were significant predictors of either domain. Accounting for PD duration, higher free water predicted worse executive function for those with both short (beta=-0.49, p=0.04) and long disease duration (beta=-0.48, p=0.02). Specifically in those with long disease duration, higher free water (beta=-0.57 p=0.02) and lower edge weights between entorhinal cortex and hippocampi (beta=0.30, p=0.03) predicted worse memory. Overall, no models contained significant interactions between the CR proxy and any brain metric.Conclusions:Results replicate previous work showing that a cognitive reserve proxy relates to cognition. However, cognitive reserve did not moderate brain burden's relationship to cognition. Across the sample, greater neuroinflammation was associated with worse executive function. For those with longer disease duration, higher neuroinflammation and lower medial temporal white matter connectivity related to worse memory. Future work should examine other brain burden metrics to determine whether/how cognitive reserve influences the cognitive trajectory of PD.
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Gowtham, G. K., H. Somashekarappa, and R. Somashekar. "Third-order nonlinearity and functional data analysis of ADP-doped PVA/PVP polymer composites." International Journal of Modern Physics B, June 17, 2023. http://dx.doi.org/10.1142/s021797922450231x.
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The structural dependence of nonlinear optical properties associated with ADP-doped PVA/PVP polymer composites is discussed in this work. Polymer composites are fabricated using the solution casting method. X-ray diffraction (XRD) was used to perform structural analysis on these samples whose average crystallite size increases with an increase in dopant concentration. Results from UV–Vis–NIR spectra show that the samples are transparent in the IR region. The Z-scan technique was established by following the method described by Sheik-Bahae et al. The shape of the open aperture plot suggests that the samples exhibit two-photon absorption. The NLO properties such as nonlinear absorption coefficient ([Formula: see text], two-photon absorption cross-section ([Formula: see text] and the imaginary part of third-order nonlinear susceptibility [Formula: see text] were investigated at 1064 nm and these values were found to be in the order of [Formula: see text][Formula: see text]W/cm, [Formula: see text][Formula: see text]cm4/GW and [Formula: see text][Formula: see text]esu, respectively. The open aperture Z-scan method yielded optical limiting data, from which the optical limiting threshold was calculated to be in the order of [Formula: see text][Formula: see text]W/m2. Functional data analysis uses a suitable basis representation to assess the functional correlation between global and local variables.
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R., Ranjith, and S. Nalin Vimalkumar. "Integrated MOORA-ELECTRE approach for solving multi-criteria decision problem." World Journal of Engineering ahead-of-print, ahead-of-print (June 7, 2021). http://dx.doi.org/10.1108/wje-12-2020-0656.
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Purpose The most difficult tasks in the design and development of products for diverse engineering applications were the selection of suitable materials. Choice of inappropriate process variables leads to poor performance, which increases the cost of the product. The selection of the best option of available alternatives is important to improve the performance and productivity of the manufacturing enterprises. Design/methodology/approach The paper aims to develop Hybrid Multi-Criteria Decision Making (HMCDM) by integrating two potential optimization techniques Elimination Et Choix Traduisant la REalité and multi-objective optimization on the basis of ratio analysis. The weight of the criteria was calculated using the critic weight method. Findings The efficiency and flexibility of the proposed HMCDM technique were illustrated and validated by two examples. In the first case, the best electrode material among the five available alternatives was selected for the electrical discharge machining of AZ91/B4Cp magnesium composites. In the second case, the optimum weight percentage of composites providing the best tribological properties was chosen. Originality/value It was noted that the HMCDM methodology was quite simple to comprehend, easy to apply and provided reliable rankings of the material alternatives. The proposed hybrid algorithm is suitable for product optimization as well as design optimization.
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Amaral, Rafaela de Oliveira, Armando Lopes Moreno, Wallison Angelim Medeiros, and Guilherme Aris Parsekian. "Residual mechanical resistance of concrete blocks and laying mortars after high temperatures." Fire and Materials, December 13, 2023. http://dx.doi.org/10.1002/fam.3186.
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AbstractThis paper reports an experimental campaign to evaluate the residual mechanical resistance after high temperatures of two structural masonry components: block and mortar. Residual compressive strength and deformation modulus of four different hollow concrete blocks and two different mortar mixes after heating at high temperatures are investigated. The test method used was the one recommended by RILEM TC 200 for mortars and an adaptation of the same method proposed by Medeiros et al. suitable for the geometry of hollow blocks. Despite the sharp drop in the deformation modulus after heating blocks and mortar, no different behaviours are observed in the deformability of the materials caused by the variables studied. The same cannot be said in relation to the variation of the residual compressive strength of the blocks, which is affected by the variables: initial nominal compressive strength and width of the concrete block. Regarding laying mortars, the results confirmed the small influence of compressive strength on the evolution of residual mechanical strength. The data and analyses reported here on the residual mechanical properties of hollow concrete blocks produced from a concrete mixture of very dry consistency, vibro‐pressed and with normal weight aggregates are relevant, since the data found in the literature generally refer to the wet cast concrete material and in cylindrical bodies.
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Nambirajan, J., D. Vinoth Kumar, and D. Chakkravarthy. "MYOCARDIAL PERFORMANCE INDEX AS AN ECHOCARDIOGRAPHIC PREDICTOR OF EARLY HEART FAILURE IN ACUTE ST ELEVATION MYOCARDIAL INFARCTION." INTERNATIONAL JOURNAL OF SCIENTIFIC RESEARCH, September 1, 2022, 65–66. http://dx.doi.org/10.36106/ijsr/1201969.
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Myocardial infarction causes variable degrees of left ventricular (LV) systolic and diastolic dysfunctions. The ejection fraction (EF) and transmitral ow are the frequently used method for evaluating the systolic and diastolic functions respectively with considerable limitations. The MPI is a single independent parameter, capable of estimating both systolic and diastolic performance combined and lacks such limitations. We enrolled 100 patients presented with a rst acute STEMI who have undergone Thrombolysis. Echocardiography was done within 24 h of chest pain with measurement of MPI. The LV MPI was calculated as (isovolumic contraction time ''ICT” + relaxation time ''IRT”)/Ejection time ''ET”. simultaneously, clinical and echocardiographic variables were analyzed and CHF was dened as Killip class >=II. Results: Early in-hospital HF occurred in 38 of patients (38%). Ejection fraction was found to have a highly signicant negative correlation with the development of in-hospital HF (p = .0001), while MPI was found to have a highly signicant positive correlation (p = .0001). Acut-off point of MPI > 0.72 showed a very high specicity (93.6%) and sensitivity (77.3%) for identifying patients with HF. On the other hand, a cut-off point of EF <=32% has shown 93.4% specicity and 57.5% sensitivity for HF prediction. Conclusions: The MPI might be a strong predictor of in-hospital HF after acute ST elevation M