Relevant bibliographies by topics / Composition gradient

Academic literature on the topic 'Composition gradient'

Author: Grafiati
Published: 7 July 2024

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Contents

  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers
  6. Reports

Journal articles on the topic "Composition gradient":

1

Vazan, Allona, Ravit Helled, and Tristan Guillot. "Jupiter’s evolution with primordial composition gradients." Astronomy & Astrophysics 610 (February 2018): L14. http://dx.doi.org/10.1051/0004-6361/201732522.

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Recent formation and structure models of Jupiter suggest that the planet can have composition gradients and not be fully convective (adiabatic). This possibility directly affects our understanding of Jupiter’s bulk composition and origin. In this Letter we present Jupiter’s evolution with a primordial structure consisting of a relatively steep heavy-element gradient of 40 M⊕. We show that for a primordial structure with composition gradients, most of the mixing occurs in the outer part of the gradient during the early evolution (several 107 yr), leading to an adiabatic outer envelope (60% of Jupiter’s mass). We find that the composition gradient in the deep interior persists, suggesting that ~40% of Jupiter’s mass can be non-adiabatic with a higher temperature than the one derived from Jupiter’s atmospheric properties. The region that can potentially develop layered convection in Jupiter today is estimated to be limited to ~10% of the mass.
2

Wei Zhang and Wai-Kuen Cham. "Gradient-Directed Multiexposure Composition." IEEE Transactions on Image Processing 21, no. 4 (April 2012): 2318–23. http://dx.doi.org/10.1109/tip.2011.2170079.

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Campos-Cerqueira, Marconi, and T. Mitchell Aide. "Changes in the acoustic structure and composition along a tropical elevational gradient." Journal of Ecoacoustics 1, no. 1 (December 6, 2017): 1. http://dx.doi.org/10.22261/jea.pnco7i.

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Elevational gradients influence the distribution and composition of animal species and can provide useful information for the development of conservation strategies in the context of climate change. Despite an increase in studies of species diversity along elevational gradients, there is still a lack of information about community responses to environmental gradients, in part because of the logistical limitations of sampling multiple taxa simultaneously. One solution is to use passive acoustic monitoring (PAM) to acquire and analyze information from different animal taxa simultaneously along an entire elevational gradient. To improve our understanding of how environmental gradients influence patterns of animal communities and to test the relationship between soundscapes and animal composition we investigated how variation in bird and anuran composition affect the acoustic structure and composition of the soundscapes along an elevation gradient. We used PAM deploying portable acoustic recorders along three elevational transects in the Luquillo Mountains (LM), Puerto Rico. We found that elevation plays a major role in structuring the acoustic community and that the soundscape composition reflected the same patterns of anuran and bird distribution and composition along the elevational gradient. This study shows how different animal taxa respond to environmental gradients and provide strong evidence for the use of soundscapes as a tool to describe and compare species distribution and composition across large spatial scales.
4

Bresnahan, Brady L., and David L. Poerschke. "High-Throughput Multi-Principal Element Alloy Exploration Using a Novel Composition Gradient Sintering Technique." Metals 14, no. 5 (May 9, 2024): 558. http://dx.doi.org/10.3390/met14050558.

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This work demonstrates the capabilities and advantages of a novel sintering technique to fabricate bulk composition gradient materials. Pressure distribution calculations were used to compare several tooling geometries for use with current-activated, pressure-assisted densification or spark plasma sintering to densify a gradient along the long dimension of the specimen. The selected rectangular tooling design retains a low aspect ratio to ensure a uniform pressure distribution during consolidation by using a side loading configuration to form the gradient along the longest dimension. Composition gradients of NixCu1−x, MoxNb1−x, and MoNbTaWHfx (x from 0 to 1) were fabricated with the tooling. The microstructure, composition, and crystal structure were characterized along the gradient in the as-sintered condition and after annealing to partially homogenize the layers. The successful fabrication of a composition gradient in a difficult-to-process material like the refractory multi-principal element alloy system MoNbTaWHfx shows the utility of this approach for high-throughput screening of large material composition spaces.
5

Garnett, D. R., and G. A. Shields. "The composition gradient across M81." Astrophysical Journal 317 (June 1987): 82. http://dx.doi.org/10.1086/165257.

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Li, Qiang, and Ming Qing Wu. "Based on the Gradient Source Representation of Functionally Gradient Materials." Applied Mechanics and Materials 496-500 (January 2014): 80–83. http://dx.doi.org/10.4028/www.scientific.net/amm.496-500.80.

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In the process of functionally gradient material entity modeling, in order to meet the design requirements, one needs to constantly change coefficient of material composition equation. In order to facilitate visual design of functionally graded material entities within the distribution, the method based on gradient material source be adopted to directly change the coefficient of material composition functions, and according to the coefficient of material composition equation function image to choose material composition functions. Homogenous approaching gradient is used, the feasibility of change of gradient direction transformatio is proved.
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Pero, Edgardo J. I., Paola A. Rueda Martín, and María C. Reynaga. "Species and genus richness and assemblage composition of stream caddisflies (Insecta: Trichoptera) vary with latitude in mountain rainforest of Argentina." Marine and Freshwater Research 70, no. 5 (2019): 687. http://dx.doi.org/10.1071/mf18209.

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Evidence found in results of studies of latitudinal gradients of benthic macroinvertebrate diversity is variable. This study analysed how species and genus richness and the composition of caddisfly assemblages (Insecta: Trichoptera) vary in Argentinean mountain forest through a latitudinal gradient from 22 to 28°S. Qualitative and quantitative data from 20 stream sites were compared. Assemblage richness and composition were analysed by comparing linear regressions, rank–abundance (RA) curves and non-metric multidimensional scaling (nMDS). Taxonomic richness increased from high to low latitude. RA curves showed changes in assemblage composition and structure across the latitudinal gradient. The nMDS revealed that the composition of the assemblages also changed along the latitudinal gradient. The patterns are similar to those observed in plants and vertebrates from the study region. The results are of particular note because a latitudinal gradient of aquatic insect diversity has rarely been observed in a narrow range.
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Prata, Eduardo Magalhães Borges, Aloysio De Pádua Teixeira, Carlos Alfredo Joly, and Marco Antonio Assis. "The role of climate on floristic composition in a latitudinal gradient in the Brazilian Atlantic Forest." Plant Ecology and Evolution 151, no. 3 (November 28, 2018): 303–13. http://dx.doi.org/10.5091/plecevo.2018.1407.

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Background and aims – Latitudinal gradients have an important influence on species distribution reflecting the effects of environmental factors such as temperature, rainfall, soil, and geographical distance. In the southeastern Brazilian Atlantic Forest, the role of climatic variables in the floristic composition is better known for altitudinal gradients of the Serra do Mar Mountains rather than for the latitudinal gradient. Here, we investigated the effects of mean annual temperature and rainfall on tree species distribution and composition in a latitudinal gradient in the Atlantic forest.Methods – We calculated each species frequency of occurrence and the latitudinal range. We used multivariate analyses (direct ordination, Hierarchical Clustering followed by Indicator Species analysis and NMDS) to investigate variation in floristic composition, and regression analyses to evaluate mean annual temperatures and rainfall effects on tree species composition along the latitudinal gradient (21°S to 28°S).Key results – A total of 789 species were registered, of which a majority (646 species) were present in less than 20% of the sampled areas, and only four species (0.5%) were present in more than 80% of the sampled areas. Only ten species (1.3%) reached the maximum latitudinal range (~6°). We found a strong correlation between variation in floristic composition and the spatial position in the latitudinal gradient. The cluster analyses detected two main floristic groups, one composed by the forests from Rio de Janeiro (21°S to 23°S) and the second by the forests from São Paulo, Paraná and Santa Catarina States (23°S to 28°S). The multiple regression analysis revealed a strong effect of the climatic variables on the variation of the floristic composition along the latitudinal gradient (r2 = 0.81, P < 0.001), where 62.82% of the variation were explained by mean annual temperature, 8.27% by annual rainfall and 10.45% by both variables together.Conclusions – The restricted distribution of most species may be explained by variations in mean annual temperature and annual rainfall along the latitudinal gradient. For instance, the decreasing mean annual temperature along the coast and the occurrence of frosts at higher latitudes may limit the southward distribution of some species while the lower annual rainfall (with marked seasonality) in the north of the gradient may limit the northward distribution of other species. Although mean annual temperature explained most of the variation in species composition along the latitudinal gradient, the abrupt variation in annual rainfall may explain the high floristic dissimilarity detected in the north of the gradient.
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Xu, C., S. E. Barnes, T. Wu, D. A. Fischer, D. M. DeLongchamp, J. D. Batteas, and K. L. Beers. "Solution and Surface Composition Gradients via Microfluidic Confinement: Fabrication of a Statistical-Copolymer-Brush Composition Gradient." Advanced Materials 18, no. 11 (June 6, 2006): 1427–30. http://dx.doi.org/10.1002/adma.200502341.

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Manaila, R., A. Devenyi, D. Biro, L. David, P. B. Barna, and A. Kovacs. "Multilayer TiAlN coatings with composition gradient." Surface and Coatings Technology 151-152 (March 2002): 21–25. http://dx.doi.org/10.1016/s0257-8972(01)01633-4.

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You might also be interested in the extended bibliographies on the topic 'Composition gradient' for particular source types:
Journal articles Dissertations / Theses Books

Dissertations / Theses on the topic "Composition gradient":

1

Benrabah, Imed-Eddine. "Développement d’alliages métalliques à gradient de composition pour l’exploration combinatoire des microstructures." Thesis, Université Grenoble Alpes, 2021. http://www.theses.fr/2021GRALI005.

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La transformation de l'austénite en ferrite dans les aciers présente un intérêt considérable pour le contrôle des propriétés finales des aciers, en particulier des aciers à haute résistance (AHSS) tels que l'acier dual phase (DP). Malgré les efforts considérables déployés pour comprendre les mécanismes qui contrôlent la cinétique de formation de la ferrite, le rôle des éléments substitutionnels pendant la croissance de la ferrite et leur interaction avec l'interface de migration α/γ restent peu clair. Plusieurs modèles ont été développés pour décrire la cinétique de croissance de la ferrite dans les systèmes ternaires et les systèmes d’ordre supérieur. Les modèles ‘solute drag’ ont été utilisés avec succès pour prédire la cinétique de transformation pour plusieurs solutés et à de nombreuses compositions et températures dans les systèmes ternaires. Cependant, l'extension de ce modèle aux systèmes d'ordre supérieur a mis en évidence un comportement complexe de l'interaction entre les différents éléments interstitiels et substitutionnels à l'interface. La validation des modèles développés nécessite une étude expérimentale de l'effet de la composition et de la température sur la cinétique de croissance. L'objectif de cette contribution est de présenter une méthodologie combinatoire à haut débit complète pour accélérer l'étude l’effet de la concentration des solutés sur la transformation austénite-ferrite. Il convient toutefois de noter que cette nouvelle méthodologie pourrait être utilisée pour étudier toute autre transformation de phase dans tout autre alliage métallique. L'essence de la méthodologie est de fabriquer des matériaux avec des gradients de composition macroscopiques, et d'effectuer des expériences in situ de diffraction des rayons X à haute énergie, résolues dans le temps et dans l'espace, pour enregistrer la cinétique de transformation de phases austénite-ferrite en de nombreux points de l'espace de composition. Des couples de diffusion contenant des gradients de soluté à l'échelle millimétrique et une teneur en carbone presque constante ont été générés en utilisant la présente méthodologie et utilisés pour étudier la cinétique de croissance de la ferrite à des températures intercritiques en utilisant des expériences in situ de diffraction des rayons X à haute énergie. Pendant 4 jours d'expériences, plus de 1500 cinétiques ont été mesurées pour différentes compositions et à différentes températures. Cet ensemble de données d'une taille sans précédent a été utilisé pour valider une version modifiée du modèle ‘three-jump solute drag’ pour les systèmes ternaires et quaternaires. Les calculs du modèle correspondent parfaitement à la cinétique de transformation expérimentale à toutes les températures étudiées et sur presque toutes les plages de composition étudiées de Si, Cr, Mn, Ni et Mo, contrairement aux résultats des modèles de para-équilibre (PE) et de partitionnement négligeable à l'équilibre local (LENP). En outre, il a été démontré que l'étalonnage des paramètres thermodynamiques dans les systèmes ternaires reste valable dans les systèmes quaternaires, ouvrant la voie à la modélisation de la transformation dans les systèmes d'ordre supérieur
The transformation of austenite into ferrite in steels is of considerable interest in controlling the final properties of steels, in particular Advanced High-Strength Steels (AHSS) such as Dual Phase (DP) steel. Despite tremendous efforts in understanding the mechanisms controlling ferrite formation, the role of substitutional elements during ferrite growth and their interaction with the migrating α/γ interface remain unclear. Several models have been developed to describe ferrite growth kinetics in ternary and higher systems. The solute drag based models have been successfully used to predict kinetics for multiple substitutional solutes, compositions and temperatures in ternary systems. However, the extension of this model to higher order systems highlighted a complex behavior of the interaction between the different interstitial and substitutional elements at the interface. Validation of the developed models requires an experimental study of the effect of both composition and temperature on growth kinetics. The aim of this contribution is to present a complete combinatorial high-throughput methodology to accelerate the investigation of the dependency of ferrite growth kinetics on substitutional composition in alloy steels. It is noteworthy, however, that this new methodology could be used to study any other phase transformation in any other metallic alloy. The essence of the methodology is to fabricate materials with macroscopic composition gradients, and to perform time- and space-resolved in situ high-energy X-ray diffraction experiments to gather the austenite-to-ferrite phase transformation kinetics in many points of the compositional space. Diffusion couples containing millimeter-scale solute gradients and an almost constant carbon content were generated using the present methodology and used to study ferrite growth kinetics at inter-critical temperatures using in-situ high-energy X-ray diffraction experiments. During 4 days of experiments, more than 1500 kinetics were gathered for different compositions and at different temperatures. This dataset of unprecedented size was used validate a modified version of the three-jump solute drag model for both ternary and quaternary systems. The model calculations matched experimental transformation kinetics at all investigated temperatures and over almost all the investigated composition ranges of Si, Cr, Mn, Ni, and Mo, contrary to results from para-equilibrium (PE) and local equilibrium negligible partitioning (LENP) models. Additionally, it was demonstrated that the calibration of thermodynamic parameters in ternary systems held true in quaternary systems, paving the way towards modeling of the transformation in higher-order systems
2

Villaret, Flore. "Développement d’une jonction austéno-martensitique à gradient de composition chimique par fabrication additive." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI104.

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Ces travaux de thèse concernent la problématique des liaisons bimétalliques acier austénitique/acier martensitique. Cette action de recherche se focalise sur une liaison acier austénitique 316L (X2 CrNiMo 18-12-02) / acier martensitique Fe-9Cr-1Mo (X10 CrMo 9-1). L’objectif est de comprendre la problématique métallurgique liée à l’assemblage de ces deux types de nuance et d’évaluer les possibilités de réaliser par métallurgie des poudres et par fabrication additive des transitions aciers austénitiques/aciers martensitiques. Une soudure obtenue par faisceau d’électrons sert de liaison de référence pour cette étude qui se focalise sur l’intérêt de la métallurgie des poudres pour réaliser une transition entre deux aciers. Des matériaux à gradient de composition chimique ont été consolidés par CIC et par SPS et montrent de très bonnes propriétés mécaniques et une excellente jonction entre les deux types de nuances. Par fabrication additive (DED-LB ou PBF-LB), nous obtenons aussi de très bonnes liaisons entre les deux aciers mais les microstructures sont beaucoup plus complexes. On observe curieusement que plus la vitesse de refroidissement du procédé est importante et plus la présence de ferrite dans l’acier martensitique est importante. Différents calculs basés sur la germination et la croissance de la phase austénitique ont permis de proposer un scénario cohérent pour expliquer les fractions de phases présentes dans les matériaux. La zone de transition entre les deux aciers présente, elle, de fortes variations de duretés. Ces variations sont expliquées par les changements de composition chimique, entrainant des modifications dans les températures de changement de phases, et les cycles thermiques particuliers vus lors de la fabrication. D’un point de vue technologique, les matériaux obtenus par fabrication additive présentent en traction des performances très semblables à ce que l’on obtient par soudage par faisceau d’électrons. Il est montré que la fabrication additive permet aussi de piloter le gradient de composition entre un acier martensitique et un acier austénitique
This PhD work concerns the problem of bimetallic austenitic/martensitic steel connections. This research action focuses on a 316L austenitic steel (X2 CrNiMo 18-12-02) / Fe-9Cr-1Mo (X10 CrMo 9-1) martensitic steel connection. The objective is to understand the metallurgical problems related to the assembly of these two steels and to evaluate the possibilities of using powder metallurgy and additive manufacturing to produce austenitic/martensitic steel transitions. A weld obtained by electron beam is used as a reference for this study which focuses on the interest of powder metallurgy to achieve a transition between two steels. Materials with a chemical composition gradient have been consolidated by HIP and SPS and show very good mechanical properties and an excellent junction between the two steels. By additive manufacturing (DED-LB or PBF-LB), we also obtain very good bonds between the two steels, but the microstructures are much more complex. Curiously, we observe that the higher the cooling rate, the higher the ferrite fraction in the martensitic steel. Different calculations based on the nucleation and growth of the austenitic phase have made it possible to propose a coherent scenario to explain the phase fractions present in the materials. The transition zone between the two steels shows strong variations in hardness. These variations are explained by changes in chemical composition, leading to modifications in phase change temperatures, and the particular thermal cycles seen during building. From a technological point of view, materials obtained by additive manufacturing have tensile performances very similar to those obtained by electron beam welding. It is shown that additive manufacturing also makes it possible to control the composition gradient between a martensitic and an austenitic steel
3

Jouenne, Stephane. "Structuration et renforcement du polystyrene par des copolymeres styrene/butadiene a gradient de composition." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2005. http://tel.archives-ouvertes.fr/tel-00012106.

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Cette étude porte sur le renforcement du polystyrène qui a un comportement fragile à température ambiante. Le mélange avec un copolymère styrène/butadiène à gradient de composition permet d'obtenir un matériau nanostructuré plus tenace, qui conserve sa transparence. Ces copolymères de type polystyrène-b-(polybutadiène-grad-polystyrène)-b-polystyrène (noté S1-(B/S)grad-S2) sont synthétisés en deux étapes par voie anionique. L'asymétrie entre les blocs S1 et S2 et le gradient de composition ont une influence déterminante sur la structuration et les propriétés, en pur ou en mélange. Des synthèses modèles avec mesures de conversion ont permis de déterminer les rapports de réactivité de la synthèse et d'évaluer l'asymétrie et la forme du gradient composition. L'asymétrie est responsable d'un décalage du diagramme de phase vers des compositions plus riches en styrène. Par une modélisation des propriétés mécaniques aux faibles déformations, il est montré que le bloc gradient a pour effet d'élargir l'interphase et augmenter le volume de phase molle. Sous cisaillement, le mélange avec différents polystyrènes de haute masse donne des matériaux nanostructurés transparents malgré l'immiscibilité vérifiée de ces systèmes. La viscosité élevée de la matrice permet de disperser finement le copolymère. Le système est piégé dans un état hors équilibre lors du refroidissement. En traction, les mélanges présentent une augmentation nette de l'élongation à la rupture pour une fraction critique de copolymère qui dépend de l'architecture de ce dernier. Une courbe universelle est obtenue lorsque les propriétés mécaniques sont présentées
4

Furimsky, Anna M. "Characterization of the lipid composition of washed and percoll gradient centrifuged epididymal mouse sperm." Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/9396.

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Capacitation is an important yet poorly understood process during which the fluidity of the sperm membrane increases to prepare sperm for the acrosome reaction (AR) and subsequent sperm-egg binding. While cholesterol efflux may be partially responsible for this increase, modification of lipid components, such as remodeling of specific phospholipid (PL) bound unsaturated fatty acyl chains, may also be involved, since no change in the cholesterol:PL molar ratio following capacitation in mouse has been previously described. In this study, lipid classes (cholesterol, PL, sulfogalactosylglycerolipid (SGG), diacylglycerol and triacylglycerol) were quantified and the fatty acyl chain compositions of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were characterized in washed non-capacitated (WS), washed capacitated (WCS), and Percoll gradient centrifuged (PGC) capacitated (PGCS) epididymal mouse sperm. Fatty acid methyl esters were generated from PC and PE by acid methanolysis and their identity was analyzed by gas chromatography. (Abstract shortened by UMI.)
5

Coppin, Ross Mark. "Ecklonia maxima kelp forests along a thermal gradient: community composition and recovery from disturbance." University of the Western Cape, 2017. http://hdl.handle.net/11394/6163.

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Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv & Cons Biol)
Climate change will influence species distributions, survival and ecosystem functioning, mostly through changes in sea surface temperatures and storm disturbance. Species are expected to shift poleward in response to ocean warming, which will increase species interaction strength, and cause tropicalisation of temperate ecosystems. Furthermore, if storm frequency and magnitude increases, this could have detrimental effects for species already on their thermal limits. One such group of coastal species is kelp. Kelp are ecosystem engineers that rely on cool-temperate water for survival, and which support an array of fauna and flora. Kelp-based ecosystems are also highly productive, and provide important inorganic input into coastal food webs, largely through detritus. Temperature and disturbance have been shown to be important drivers of kelp ecosystems globally, and we expect that local changes in these drivers may affect kelp ecosystem composition and functioning along the south-western Cape coastline where they form extensive habitats.
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Jouenne, Stéphane. "Structuration et renforcement du polystyrène par des copolymères styrène / butadiène à gradient de composition." Paris 6, 2005. http://www.theses.fr/2005PA066315.

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Hutton, Jacob Matthew. "DIET COMPOSITION EXPLAINS REDUCTIONS IN STREAM SALAMANDER OCCUPANCY AND ABUNDANCE ALONG A CONDUCTIVITY GRADIENT." UKnowledge, 2018. https://uknowledge.uky.edu/forestry_etds/40.

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Changes in land use such as mountaintop removal mining with valley fills (MTR/VF) affect chemical, physical, and hydrological properties of headwater streams. Although numerous stream taxa have experienced significant declines from MTR/VF, stream salamanders appear to be particularly sensitive. Yet, the specific mechanism(s) responsible for the population declines has eluded researchers. We sampled salamander assemblages across a continuous specific conductivity (SC) gradient in southeastern Kentucky and estimated occupancy rates and abundance estimates along this gradient. We also examined the diet of larval and adult salamanders to determine if autochthony (A/T prey), total prey volume, and body condition is influenced by SC. As SC increased, occupancy and abundance declined consistently among all salamander species and life stages. Diet composition explained the declines; for example, larval salamanders experienced a 12−fold decline in autochthony, a 4.2−fold decline in total prey volume, and a rapid decline in body condition as SC increased. Our results indicate that SC indirectly affects stream salamander populations by eliminating an adequate availability of aquatic prey for salamanders, which in turn lead may lead to reduced population persistence in streams with elevated SC.
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Simões, Catarina Cordeiro. "Species richness and composition of butterfly assemblages (Lepidoptera:Rhopalocera) along the altitudinal gradient of Serra da Estrela." Master's thesis, Universidade de Évora, 2016. http://hdl.handle.net/10174/20707.

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Os gradientes altitudinais são importantes modelos em ecologia pois permitem, numa escala reduzida, estudar a influência da variação de diversas variáveis ambientais nos padrões de biodiversidade existentes. Estes padrões são influenciados por diversos factores, desde variáveis climáticas às relacionadas com a perturbação humana. Nesta tese é estudada a variação na composição das comunidades de borboletas ao longo do gradiente altitudinal na Serra da Estrela e são testadas duas hipóteses sobre os padrões de riqueza específica ao longo do gradiente altitudinal: a regra de Rapoport e o “Mid Domain Effect” (MDE). Foram assinaladas 70 espécies de borboletas neste estudo e constatou-se que a variação na riqueza de espécies de borboletas apresenta um padrão “mid peak” apoiando o MDE. Verificou-se também que as comunidades de borboletas do mesmo nível altitudinal são mais semelhantes entre si independentemente da vertente em que se encontram e são também mais semelhantes com as comunidades dos níveis altitudinais adjacentes. Finalmente, a análise da distribuição de algumas espécies ameaçadas de borboletas torna evidente a necessidade de realização de mais estudos sobre a biologia da conservação deste grupo de animais em Portugal; Abstract: Altitudinal gradients are important ecological models because they allow us to study the influence of diverse environmental variables in the existing biodiversity patterns. These patterns are influenced by various factors, from climatic variables to variables related to human disturbance. In this thesis we studied the variations in the composition of the butterfly assemblages along the altitudinal gradient of Serra da Estrela and we tested two hypotheses regarding the species richness patterns along the altitudinal gradient: Rapoport’s rule and the Mid Domain Effect (MDE). In this study 70 butterfly species were marked recorded and it was observed that the butterfly species richness presents a mid-peak pattern supporting the MDE. It was also noted that the butterfly assemblages in the same altitudinal level show more similarity within themselves regardless of the slope they are found in, and are also more similar to the assemblages present in the adjacent altitudinal levels. Finally, the distribution of some threatened butterfly species was analyzed and it became evident the need to do more studies regarding the conservation biology of this animal group in Portugal.
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Hasan, Md Nazmul. "Microstructure and mechanical properties of a CrMnFeCoNi high-entropy alloy with gradient structures." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23036.

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High-entropy alloys (HEAs) that demonstrate excellent mechanical properties over steel-based alloys are not exempt from the common dilemma of strength–ductility trade-off, which limits their potential applications. One way to improve the property of CrMnFeCoNi HEA is by using the rotationally accelerated shot peening technique to introduce a gradient structure. Two gradient profiles—a thin gradient layer with an undeformed core and a fully deformed structure—are introduced by adjusting the processing parameters. The effects of these gradient profiles on mechanical properties and microstructural evolution at various loading conditions and temperatures are systematically explored. In this thesis, various mechanical tests are performed to investigate the effect of the gradient structure on mechanical properties such as tensile properties at room and cryogenic temperatures, compression at different strain rates and dynamic compression at high strain rates. Material characterisations are performed using various electron microscopic techniques to build a structure–property relationship and investigate microstructural evolution.
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Dahlø, Eva Sofie. "Variation in chemical composition and genetic differentiation among bilberry (Vaccinium myrtillus L.) populations on a latitudinal gradient." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for biologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-12795.

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Bilberry (Vaccinium myrtillus) is native to Europe and North America and constitutes an important nutritional resource for both humans and animals. Over the years, a series of chemical analyses have revealed several health-beneficial compounds in bilberry, and with the current demand of the berries mainly covered by Sweden and Eastern Europe, there has become an increasing desire to cultivate bilberry in Norway. In order for such cultivation to be successful an increased knowledge about bilberry is seen as essential and thus several studies have investigated the chemical composition of the berry. However, the underlying genetic diversity and the variation between populations in biochemical compounds remain to be thoroughly investigated. Therefore, the aim of present study was to investigate the differences in biochemical composition between populations of bilberry distributed on a latitudinal gradient, and estimate the level of genetic variation within and among the populations. This in order to examine whether biochemical composition was reflected by observed levels of genetic variation.Bilberries from four Norwegian populations at three regions differing in latitude were analysed for content of total phenolics (TPH), total anthocyanins (ACY) and antioxidant activity (FRAP). Furthermore, metabolic profiling was performed by gas chromatography-mass spectrometry (GC-MS) to reveal biochemical differences between the populations in content of sugars, acids and some simple phenolics. Multivariate statistics were performed and revealed a clustering of samples from the two locations in Mid-Norway, and a clustering of the northern with the southern population. In addition, there were found significant differences in some of the compounds between the populations.Genetic analyses using four microsatellites were carried out to examine whether metabolic differences between populations were reflected by genetic differentiation. Despite the significant differences between populations in the concentrations of some metabolites no significant genetic differentiation was found. Thus, it seems that the variation in biochemical compounds discovered among populations could be environmentally induced differences on a similar genetic background. However, due to the limited number of working microsatellites and the fact that these molecular markers are neutral, there is still a possibility that the genetic differences causing compound concentrations to differ could be so minor as to remain undetected. Hence, further studies utilizing more microsatellite markers or new state-of-the-art molecular techniques are needed to determine whether this result holds and is valid also for genetic variation in coding parts of the genome.
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Books on the topic "Composition gradient":

1

Kennen, Jonathan G. Relation of environmental characteristics to the composition of aquatic assemblages along a gradient of urban land use in New Jersey, 1996-98. West Trenton, N.J: U.S. Dept. of the Interior, U.S. Geological Survey, 2002.

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Kennen, Jonathan G. Relation of environmental characteristics to the composition of aquatic assemblages along a gradient of urban land use in New Jersey, 1996-98. West Trenton, N.J: U.S. Dept. of the Interior, U.S. Geological Survey, 2002.

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1942-, Tchudi Stephen, and NCTE Committee on Alternatives to Grading Student Writing., eds. Alternatives to grading student writing. Urbana, Ill: National Council of Teachers of English, 1997.

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Speck, Bruce W. Grading student writing: An annotated bibliography. Westport, Conn: Greenwood Press, 1998.

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Bakkestuen, V. Vegetation composition, gradients and environment relationships of birch forest in six references areas in Norway. Oslo, Norway: Natural History Museum, University of Oslo, 2010.

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1939-, Zak Frances, and Weaver Christopher C. 1962-, eds. The theory and practice of grading writing: Problems and possibilities. Albany: State University of New York Press, 1998.

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Bratcher, Suzanne. Evaluating children's writing: A handbook of grading choices for classroom teachers. 2nd ed. Mahwah, N.J: L. Erlbaum, 2004.

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Libby, Allison, Bryant Lizbeth, and Hourigan Maureen M. 1942-, eds. Grading in the post-process classroom: From theory to practice. Portsmouth, NH: Boynton/Cook-Heinemann, 1997.

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United States. National Aeronautics and Space Administration., ed. Acoustic propagation in a thermally stratified atmosphere: Final report. Salt Lake City, Utah: Mechanical and Industrial Engineering Dept., University of Utah, 1987.

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Center, Langley Research, ed. Acoustic propagation in a thermally stratified atmosphere. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1988.

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Book chapters on the topic "Composition gradient":

1

Steinhausen, Ralf, and Horst Beige. "Composition Gradient Actuators." In Piezoelectric and Acoustic Materials for Transducer Applications, 289–304. Boston, MA: Springer US, 2008. http://dx.doi.org/10.1007/978-0-387-76540-2_14.

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Some, Daniel. "Composition-Gradient Multiangle Light Scattering." In Encyclopedia of Biophysics, 336–43. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-16712-6_770.

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Gupta, Jugal K., Kirill Efimenko, Daniel A. Fischer, Jan Genzer, and Nicholas L. Abbott. "Orientational Anchoring of Liquid Crystals on Surfaces Presenting Continuous Gradients in Composition." In Soft Matter Gradient Surfaces, 109–28. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2012. http://dx.doi.org/10.1002/9781118166086.ch5.

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Basak, Pratyay, Pedro Zapata, Keith Reed, Ismael Gomez, and J. Carson Meredith. "Continuous Infusion Microchannel Approach to Generate Composition Gradients from Viscous Polymer Solutions." In Soft Matter Gradient Surfaces, 129–43. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2012. http://dx.doi.org/10.1002/9781118166086.ch6.

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Glöckner, Gottfried. "Separation of Copolymers by Composition through Gradient High-Performance Liquid Chromatography." In Gradient HPLC of Copolymers and Chromatographic Cross-Fractionation, 113–47. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-75799-0_9.

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Ghorai, Mrinmoy, Soumitra Samanta, and Bhabatosh Chanda. "Scale-Invariant Image Inpainting Using Gradient-Based Image Composition." In Computer Vision, Graphics, and Image Processing, 97–108. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-68124-5_9.

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Minton, Allen P. "Detection and Quantitative Characterization of Macromolecular Heteroassociations via Composition Gradient Sedimentation Equilibrium." In Analytical Ultracentrifugation, 523–32. Tokyo: Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-55985-6_26.

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Parihar, Rityuj Singh, and Neha Verma. "The Development of Cemented Carbide with Cobalt Composition Gradient by Powder Metallurgy Method." In Lecture Notes in Mechanical Engineering, 969–76. Singapore: Springer Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-7787-8_77.

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Trifonova, I. S. "Phytoplankton composition and biomass structure in relation to trophic gradient in some temperate and subarctic lakes of north-western Russia and the Prebaltic." In Phytoplankton and Trophic Gradients, 99–108. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-017-2668-9_8.

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Ahmad, Zeeshan, Murtaza Hussain, Muhammad Iqbal, Shah Khalid, Habib Ahmad, and Shujaul Mulk Khan. "Weed Vegetation in Maize Crop of the Shahbaz Garhi, District Mardan; Gradient of Diversity and Species Composition." In Biodiversity, Conservation and Sustainability in Asia, 657–79. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-73943-0_36.

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Conference papers on the topic "Composition gradient":

1

Livchits, Vladislav Ya. "Structure and Composition of Grin Glasses for Ion Exchange." In Gradient-Index Optical Imaging Systems. Washington, D.C.: Optica Publishing Group, 1994. http://dx.doi.org/10.1364/giois.1994.pd2.

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Miceli, Joseph J., and Denis P. Naughton. "A Model for Gradient Formation in Polycrystalline Germanium - Silicon Alloy Crystals via Czochralski Crystal Growing." In Gradient-Index Optical Imaging Systems. Washington, D.C.: Optica Publishing Group, 1987. http://dx.doi.org/10.1364/giois.1987.thd5.

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A mathematical model has been developed that describes the silicon composition gradient produced in germanium-silicon alloy crystals which have been formed via Czochralski crystal growing. This model is based on the naturally occuring segregation effect of silicon in germanium. In addition the refractive index of the alloy is described in terms of its relation to the band gap energy, which is itself dependent on the silicon concentration. A relationship between refractive index and the silicon compositon of the alloy is then derived.
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Jones, Steven M. "Gradient composition sol-gel materials." In Symposium on Integrated Optoelectronics, edited by Bruce S. Dunn, Edward J. A. Pope, Helmut K. Schmidt, and Masayuki Yamane. SPIE, 2000. http://dx.doi.org/10.1117/12.384345.

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Houde-Walter, S. N. "Glass structure and ion exchange." In Gradient-Index Optical Imaging Systems. Washington, D.C.: Optica Publishing Group, 1994. http://dx.doi.org/10.1364/giois.1994.gtue1.

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Measurable degradation in the image quality of radial and spherical gradient lenses can be caused by what might seem to be excruciatingly small perturbations from ideal gradient-index profiles. These are controlled by a number of empirically determined fabrication parameters that include glass composition, salt melt composition, thermal history, applied electric field and multiple diffusion steps.
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Zhang, Wei, and Wai-Kuen Cham. "Gradient-directed composition of multi-exposure images." In 2010 IEEE Conference on Computer Vision and Pattern Recognition (CVPR). IEEE, 2010. http://dx.doi.org/10.1109/cvpr.2010.5540168.

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Kilinc, Muhammed, Alireza Jalouli, Peijian Wang, Christian Neureuter, Hao Zeng, and Tim Thomay. "2D Gradient Composition Alloys: Excitonic and Dielectric Properties." In CLEO: Applications and Technology. Washington, D.C.: OSA, 2020. http://dx.doi.org/10.1364/cleo_at.2020.jw2d.19.

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Ghazanfari, Amir, and Ming C. Leu. "Composition Optimization for Functionally Gradient Parts Considering Manufacturing Constraints." In ASME 2014 International Manufacturing Science and Engineering Conference collocated with the JSME 2014 International Conference on Materials and Processing and the 42nd North American Manufacturing Research Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/msec2014-3960.

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Being able to design and fabricate parts made of Functionally Gradient Materials (FGMs) with optimum properties is of prime importance. Very limited research has been carried out thus far regarding the optimization of composition of different constituent materials throughout the part. In this paper, a technique is introduced to maximize the stiffness of parts made of FGM by determining the material composition for each small element inside the part. To demonstrate the effectiveness of this technique, two examples are examined. In the first one, a two dimensional cantilever beam made of two materials is considered and a Sequential Approximate Optimization method is used to determine the optimum composition of materials for the beam so that the global stiffness is maximized. The only applied force on the beam is a nodal force acting at the tip. One of the constituent materials is stiffer and heavier than the other material. The optimization constraint is the total mass of the beam predetermined by the engineer. The problem is how to distribute materials throughout the beam so as to have the maximum stiffness. The second example is a simply supported beam under a uniform pressure. The same methodology is employed for this example to maximize the stiffness of the beam. The results show a considerable increase in the stiffness of the beams after optimization as compared to the beams with uniformly distributed materials. Additive Manufacturing (AM) methods that are capable of fabricating the designed parts and their constraints are also discussed.
8

Shaikh, J. A., K. Murata, H. Kuramata, and H. K. Mogensen. "Impact of a Vertical Temperature Gradient on H2S Gradient in Sour, Near-Critical Reservoir Fluids." In SPE Conference at Oman Petroleum & Energy Show. SPE, 2024. http://dx.doi.org/10.2118/218801-ms.

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Abstract An equation of state model is presented, developed for an H2S-rich field, where the fluid type changes smoothly from gas to oil through a zone with a critical fluid and not through a classical gas-oil contact with a discontinuity in fluid properties. For use in connection with compositional reservoir simulation studies, a depth gradient model has been developed that provides a good representation of the compositional variation with depth, including the depth where the fluid type changes from gas to oil. The depth gradient model considers the influence of both gravity and the vertical temperature gradient on the distribution of the individual components in the fluid column. A depth gradient model that only considers gravity and ignores the temperature gradient will simulate an increasing H2S concentration with depth, while the fluid samples show that the H2S concentration decreases with increasing depth. When the effect of the temperature gradient is included, a good match is obtained of the development of fluid composition, saturation point and GOR with depth.
9

Suzuki, Ryosuke, Masaaki Matsubara, Takumi Maruyama, Kenji Sakamoto, and Kazuyuki Arakawa. "Experimental Investigation of Manufacturing Possibility of Multilayered Ni-ZrO2 System Functionally Graded Material by Powder Injection Molding." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-66233.

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Manufacturing possibility was experimentally investigated for a bulk multilayered Ni-ZrO2 system functionally graded material (FGM) by powder injection molding. Ni-ZrO2 system FGMs with various composition gradients and layer numbers were manufactured from compounds used in powder injection molding methods. Compounds with various chemical compositions were obtained by kneading Ni and ZrO2 powders with a polymeric binder. A compound was filled into a mold and heated to the softening temperature of binder. A compact was obtained by compressing at the softening temperature. Some compacts were stacked in the mold and compressed at the softening temperature again. The multilayered compact was heated to near the melting point of Ni. The FGM with little flaws was obtained for high composition gradient in ZrO2 rich side. However, calculated maximum thermal stress of the FGM was higher than that of the linear composition gradient. The maximum thermal stress was compressive stress and occurred in ZrO2 rich side. The compressive strength of a ceramics is higher than that of the tensile strength. Thus, the thermal compressive stress in ZrO2 rich side would be effective to manufacture a bulk multilayered Ni-ZrO2 system FGM by powder injection molding.
10

Dong, Changsheng, Minlin Zhong, Wenjin Liu, Minxing Ma, and Hongjun Zhang. "Laser deposition of Ti6Al4V-316L composition gradient structure: Challenge on intermetallics." In ICALEO® 2009: 28th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing. Laser Institute of America, 2009. http://dx.doi.org/10.2351/1.5061595.

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Reports on the topic "Composition gradient":

1

Smith, G. P. Structure and Composition of Vegetation on Longleaf Plantation Sites Compared to Natural Stands Occurring Along an Environmental Gradient at the Savannah River Site. Office of Scientific and Technical Information (OSTI), October 2000. http://dx.doi.org/10.2172/807720.

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Smith, Sean, Phillip van Mantgem, and Dennis Odion. Vegetation community monitoring: Species composition and biophysical gradients in Klamath Network parks. National Park Service, March 2021. http://dx.doi.org/10.36967/nrr-2284769.

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Burton R. Patterson. Effect of Casting Conditions and Composition on Microstructural Gradients in Roll Cast Aluminum Alloys. Office of Scientific and Technical Information (OSTI), May 2008. http://dx.doi.org/10.2172/927781.

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Wells, Aaron, Tracy Christopherson, Gerald Frost, Matthew Macander, Susan Ives, Robert McNown, and Erin Johnson. Ecological land survey and soils inventory for Katmai National Park and Preserve, 2016–2017. National Park Service, September 2021. http://dx.doi.org/10.36967/nrr-2287466.

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This study was conducted to inventory, classify, and map soils and vegetation within the ecosystems of Katmai National Park and Preserve (KATM) using an ecological land survey (ELS) approach. The ecosystem classes identified in the ELS effort were mapped across the park, using an archive of Geo-graphic Information System (GIS) and Remote Sensing (RS) datasets pertaining to land cover, topography, surficial geology, and glacial history. The description and mapping of the landform-vegetation-soil relationships identified in the ELS work provides tools to support the design and implementation of future field- and RS-based studies, facilitates further analysis and contextualization of existing data, and will help inform natural resource management decisions. We collected information on the geomorphic, topographic, hydrologic, pedologic, and vegetation characteristics of ecosystems using a dataset of 724 field plots, of which 407 were sampled by ABR, Inc.—Environmental Research and Services (ABR) staff in 2016–2017, and 317 were from existing, ancillary datasets. ABR field plots were located along transects that were selected using a gradient-direct sampling scheme (Austin and Heligers 1989) to collect data for the range of ecological conditions present within KATM, and to provide the data needed to interpret ecosystem and soils development. The field plot dataset encompassed all of the major environmental gradients and landscape histories present in KATM. Individual state-factors (e.g., soil pH, slope aspect) and other ecosystem components (e.g., geomorphic unit, vegetation species composition and structure) were measured or categorized using standard classification systems developed for Alaska. We described and analyzed the hierarchical relationships among the ecosystem components to classify 92 Plot Ecotypes (local-scale ecosystems) that best partitioned the variation in soils, vegetation, and disturbance properties observed at the field plots. From the 92 Plot Ecotypes, we developed classifications of Map Ecotypes and Disturbance Landscapes that could be mapped across the park. Additionally, using an existing surficial geology map for KATM, we developed a map of Generalized Soil Texture by aggregating similar surficial geology classes into a reduced set of classes representing the predominant soil textures in each. We then intersected the Ecotype map with the General-ized Soil Texture Map in a GIS and aggregated combinations of Map Ecotypes with similar soils to derive and map Soil Landscapes and Soil Great Groups. The classification of Great Groups captures information on the soil as a whole, as opposed to the subgroup classification which focuses on the properties of specific horizons (Soil Survey Staff 1999). Of the 724 plots included in the Ecotype analysis, sufficient soils data for classifying soil subgroups was available for 467 plots. Soils from 8 orders of soil taxonomy were encountered during the field sampling: Alfisols (<1% of the mapped area), Andisols (3%), Entisols (45%), Gelisols (<1%), Histosols (12%), Inceptisols (22%), Mollisols (<1%), and Spodosols (16%). Within these 8 Soil Orders, field plots corresponded to a total of 74 Soil Subgroups, the most common of which were Typic Cryaquents, Typic Cryorthents, Histic Cryaquepts, Vitrandic Cryorthents, and Typic Cryofluvents.
5

Weihs, Timothy, and Michael Falk. Final Report for DOE Award: DE-SC0019217: Experimental and Computational Studies of Crystal Nucleation in Composition Gradients. Office of Scientific and Technical Information (OSTI), May 2024. http://dx.doi.org/10.2172/2349115.

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Marley, M. S., and G. Glatzmaier. The role of composition gradients in the evolution of uranus and neptune. Progress report, 1 January 1994--1 September 1994. Office of Scientific and Technical Information (OSTI), December 1994. http://dx.doi.org/10.2172/82333.

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Isom, Shelby. Compositional and Physical Gradients in the Magmas of the Devine Canyon Tuff, Eastern Oregon: Constraints for Evolution Models of Voluminous High-silica Rhyolites. Portland State University Library, January 2000. http://dx.doi.org/10.15760/etd.5773.

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Knotek-Smith, Heather, and Catherine Thomas. Microbial dynamics of a fluidized bed bioreactor treating perchlorate in groundwater. Engineer Research and Development Center (U.S.), September 2022. http://dx.doi.org/10.21079/11681/45403.

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Optimization of operation and performance of the groundwater treatment system regarding perchlorate removal at Longhorn Army Ammunition Plant (LHAAP) is dependent on specific conditions within the reactor and the larger groundwater treatment process. This study evaluated the microbial community compositions within the plant during periods of adequate perchlorate degradation, sub-adequate perchlorate degradation, and non-operating conditions. Factors affecting the performance of the LHAAP ground water treatment system (GWTS) perchlorate de-grading fluidized bed reactor (FBR) are identified and discussed. Isolation of the FBR from naturally occurring microbial populations in the groundwater was the most significant factor reducing system effectiveness. The microbial population within the FBR is highly susceptible to system upsets, which leads to declining diversity within the reactor. As designed, the system operates for extended periods without the desired perchlorate removal without intervention such as a seed inoculant. A range of modifications and the operation of the system are identified to increase the effectiveness of perchlorate removal at LHAAP.
9

Lahav, Ori, Albert Heber, and David Broday. Elimination of emissions of ammonia and hydrogen sulfide from confined animal and feeding operations (CAFO) using an adsorption/liquid-redox process with biological regeneration. United States Department of Agriculture, March 2008. http://dx.doi.org/10.32747/2008.7695589.bard.

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The project was originally aimed at investigating and developing new efficient methods for cost effective removal of ammonia (NH₃) and hydrogen sulfide (H₂S) from Concentrated Animal Feeding Operations (CAFO), in particular broiler and laying houses (NH₃) and hog houses (H₂S). In both cases, the principal idea was to design and operate a dedicated air collection system that would be used for the treatment of the gases, and that would work independently from the general ventilation system. The advantages envisaged: (1) if collected at a point close to the source of generation, pollutants would arrive at the treatment system at higher concentrations; (2) the air in the vicinity of the animals would be cleaner, a fact that would promote animal growth rates; and (3) collection efficiency would be improved and adverse environmental impact reduced. For practical reasons, the project was divided in two: one effort concentrated on NH₃₍g₎ removal from chicken houses and another on H₂S₍g₎ removal from hog houses. NH₃₍g₎ removal: a novel approach was developed to reduce ammonia emissions from CAFOs in general, and poultry houses in particular. Air sucked by the dedicated air capturing system from close to the litter was shown to have NH₃₍g₎ concentrations an order of magnitude higher than at the vents of the ventilation system. The NH₃₍g₎ rich waste air was conveyed to an acidic (0<pH<~5) bubble column reactor where NH₃ was converted to NH₄⁺. The reactor operated in batch mode, starting at pH 0 and was switched to a new acidic absorption solution just before NH₃₍g₎ breakthrough occurred, at pH ~5. Experiments with a wide range of NH₃₍g₎ concentrations showed that the absorption efficiency was practically 100% throughout the process as long as the face velocity was below 4 cm/s. The potential advantages of the method include high absorption efficiency, lower NH₃₍g₎ concentrations in the vicinity of the birds, generation of a valuable product and the separation between the ventilation and ammonia treatment systems. A small scale pilot operation conducted for 5 weeks in a broiler house showed the approach to be technically feasible. H₂S₍g₎ removal: The main goal of this part was to develop a specific treatment process for minimizing H₂S₍g₎ emissions from hog houses. The proposed process consists of three units: In the 1ˢᵗ H₂S₍g₎ is absorbed into an acidic (pH<2) ferric iron solution and oxidized by Fe(III) to S⁰ in a bubble column reactor. In parallel, Fe(III) is reduced to Fe(II). In the 2ⁿᵈ unit Fe(II) is bio-oxidized back to Fe(III) by Acidithiobacillus ferrooxidans (AF).In the 3ʳᵈ unit S⁰ is separated from solution in a gravity settler. The work focused on three sub-processes: the kinetics of H₂S absorption into a ferric solution at low pH, the kinetics of Fe²⁺ oxidation by AF and the factors that affect ferric iron precipitation (a main obstacle for a continuous operation of the process) under the operational conditions. H₂S removal efficiency was found higher at a higher Fe(III) concentration and also higher for higher H₂S₍g₎ concentrations and lower flow rates of the treated air. The rate limiting step of the H₂S reactive absorption was found to be the chemical reaction rather than the transition from gas to liquid phase. H₂S₍g₎ removal efficiency of >95% was recorded with Fe(III) concentration of 9 g/L using typical AFO air compositions. The 2ⁿᵈ part of the work focused on kinetics of Fe(II) oxidation by AF. A new lab technique was developed for determining the kinetic equation and kinetic parameters (KS, Kₚ and mₘₐₓ) for the bacteria. The 3ʳᵈ part focused on iron oxide precipitation under the operational conditions. It was found that at lower pH (1.5) jarosite accumulation is slower and that the performance of the AF at this pH was sufficient for successive operation of the proposed process at the H₂S fluxes predicted from AFOs. A laboratory-scale test was carried out at Purdue University on the use of the integrated system for simultaneous hydrogen sulfide removal from a H₂S bubble column filled with ferric sulfate solution and biological regeneration of ferric ions in a packed column immobilized with enriched AFbacteria. Results demonstrated the technical feasibility of the integrated system for H₂S removal and simultaneous biological regeneration of Fe(III) for potential continuous treatment of H₂S released from CAFO. NH₃ and H₂S gradient measurements at egg layer and swine barns were conducted in winter and summer at Purdue. Results showed high potential to concentrate NH₃ and H₂S in hog buildings, and NH₃ in layer houses. H₂S emissions from layer houses were too low for a significant gradient. An NH₃ capturing system was designed and tested in a 100-chicken broiler room. Five bell-type collecting devices were installed over the litter to collect NH₃ emissions. While the air extraction system moved only 10% of the total room ventilation airflow rate, the fraction of total ammonia removed was 18%, because of the higher concentration air taken from near the litter. The system demonstrated the potential to reduce emissions from broiler facilities and to concentrate the NH₃ effluent for use in an emission control system. In summary, the project laid a solid foundation for the implementation of both processes, and also resulted in a significant scientific contribution related to AF kinetic studies and ferrous analytical measurements.
10

Singhvi, Punit, Javier García Mainieri, Hasan Ozer, and Brajendra Sharma. Rheology-Chemical Based Procedure to Evaluate Additives/Modifiers Used in Asphalt Binders for Performance Enhancements: Phase 2. Illinois Center for Transportation, June 2021. http://dx.doi.org/10.36501/0197-9191/21-020.

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The increased use of softer binders in Illinois over the past decade is primarily attributed to the increased use of recycled materials in asphalt pavement construction. The shift in demand of using PG 58-28 over PG 64-22 has resulted in potential alternative methods to produce softer binders more economically using proprietary products. However, there are challenges in using these proprietary products for asphalt modification because of uncertainty in their long-term performance and significant variability in binder chemistry. The current SuperPave performance grading specification for asphalt binders is insufficient in differentiating binders produced from these modifiers. Therefore, the objective of this study is to evaluate the performance of various softener-type asphalt binder modifiers using a wide array of rheological and chemistry tests for their integration into the Illinois Department of Transportation’s material specifications. The small-strain rheological tests and their parameters allowed for consistent grouping of modified binders and can be used as surrogates to identify performing and nonperforming asphalt binders. A new parameter, Δ|G*|peak τ, was developed from the linear amplitude sweep test and showed potential to discriminate binders based on their large-strain behavior. Chemistry-based parameters were shown to track aging and formulation changes. The modifier sources were identified using fingerprint testing and were manifested in the modified binder chemical and compositional characteristics. The two sources of base binders blended with the modifiers governed the aging rate of the modified binders. Mixture performance testing using the Illinois Flexibility Index Test and the Hamburg Wheel-Track Test were consistent with the rheological and chemical findings, except for the glycol amine-based modified binder, which showed the worst cracking performance with the lowest flexibility index among the studied modifiers. This was contrary to its superior rheological performance, which may be attributed to lower thermal stability, resulting in high mass loss during mixing. According to the characterization of field-aged binders, laboratory aging of two pressurized aging vessel cycles or more may represent realistic field aging of 10 to 15 years at the pavement surface and is able to distinguish modified binders. Therefore, an extended aging method of two pressurized aging vessel cycles was recommended for modified binders. Two different testing suites were recommended for product approval protocol with preliminary thresholds for acceptable performance validated with field-aged data.

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