Добірка наукової літератури з теми "Shape preferred orientation"

The preferred orientation of MnS inclusions in hot-rolled steel was studied by electron diffraction. Specimens of resulfurized steel were examined after casting and after hot rolling to true strains of 0.5, 1.0 and 1.5. After rolling, the orientations of the inclusions tended toward an ideal 〈100〉 {001}. Only a moderate correlation between the final inclusion shape and orientation was found.

The classification of pyrrhotite fabrics proposed by Lusk and Ostwald identifies E-type pyrrhotite, which has no dimensional or crystallographic preferred orientation and an equant grain shape, and F-type pyrrhotite, which has a distinct dimensional and crystallographic preferred orientation and flattened, elongate grain shapes. The results of an analysis of pyrrhotite fabrics studied for Ducktown, Tennessee, do not conform with this classification. The data suggest that the three parameters, crystallographic orientation, dimensional orientation, and grain shape, are independent. Therefore, the E- and F-type classification of pyrrhotite fabrics appears not to have universal applicability.

Although gravitropism forces trees to grow vertically, stems have shown to prefer specific orientations. Apart from wind deforming the tree shape, lateral light can result in prevailing inclination directions. In recent years a species dependent interaction between gravitropism and phototropism, resulting in trunks leaning down-slope, has been confirmed, but a terrestrial investigation of such factors is limited to small scale surveys. ALS offers the opportunity to investigate trees remotely. This study shall clarify whether ALS detected tree trunks can be used to identify prevailing trunk inclinations. In particular, the effect of topography, wind, soil properties and scan direction are investigated empirically using linear regression models. 299.000 significantly inclined stems were investigated. Species-specific prevailing trunk orientations could be observed. About 58% of the inclination and 19% of the orientation could be explained by the linear models, while the tree species, tree height, aspect and slope could be identified as significant factors. The models indicate that deciduous trees tend to lean down-slope, while conifers tend to lean leeward. This study has shown that ALS is suitable to investigate the trunk orientation on larger scales. It provides empirical evidence for the effect of phototropism and wind on the trunk orientation.

Iron crystals were deposited by thermally activated chemical vapor deposition with imposition of magnetic field. In this study, the deposition was conducted by imposing a magnetic field up to 3.5 T in a temperature range between 0.48 and 0.51 of TmFe (melting point of iron), which is below the Curie point of iron (0.58 TmFe). The microstructures and crystal orientations of the deposits were investigated. In the deposition process, island-shaped crystals were formed on a scale of several microns; then a film was grown by their coalescence. As the magnetic field magnitude increased, population of the island-shaped crystals having a cubic shape increased. Simultaneously, their ω-scanned (200) profile became sharper. Their degree of (100) preferred orientation was dependent on the magnetic field up to 3.5 T, which is usually high enough for the saturated magnetization of iron crystals. However, when the substrate was placed parallel to the magnetic field, (100) preferred orientation was not observed for the island-shaped crystals. A large and bimodal ω-scanned (110) profile having sharp peaks was obtained when the substrate was inclined 45° to the field. Preferred (100) orientation was not obtained from the iron films, for which two reasons were pointed out. The first is the secondary grown crystals on the island-shaped crystals having different orientations, and the second is the observed zone III grain structure of the films, where grain boundary migration occurred.

The magmatic processes involved in building the plutonic section of the oceanic crust at fast-spreading centers remain debated. At this stage, no intact section of this important lithospheric layer, known as seismic layer 3, has been drilled. Yet, Ocean Drilling Program Hole 1256D, located on the eastern flank of the East Pacific Rise, provides unparalleled opportunities to investigate the mode of emplacement and fabric development of the two uppermost gabbro bodies in this crust. Although inferences made from a drill core remain limited due to the intrinsically linear nature of observations, the samples recently recovered hold potential clues on fabric-forming processes and the magma convection in such small intrusions. Gabbro 1 forms a 52 m-thick body intruded in the texturally granoblastic altered zone of the sheeted dike complex. Gabbro 2, situated below gabbro 1, is only 24 m-thick. Both gabbro bodies lack a macroscopically visible fabric and were, until this study, considered structurally isotropic. We use digital image analysis of petrographic thin-sections and the intercept method (Launeau and Robin, 1996) to determine the shape-preferred orientation of plagioclase phenocrysts in 3-D. Thirty-three sets of three mutually perpendicular thin-sections were prepared and analyzed in this manner. The mode of plagioclase grains ranges from 15 to 20% in the upper interval of gabbro 1, 13 to 36% in the lower interval of gabbro 1, and 9 to 28% in gabbro 2. These values refer to the mode of euhedral to subhedral grains only and do not reflect the total mode of plagioclase in the rock. The two gabbros display a weakly anisotropic shape-preferred orientation characterized by an average shape ratio > 1.050. The aspect ratio indicates plagioclase fabric strength deviation from a perfectly anisotropic distributed population. The aspect ratio in the upper interval of gabbro 1 ranges from 1.068 to 1.153. The aspect ratio in the lower interval of gabbro 1 ranges from 1.074 to 1.183. The aspect ratio in gabbro 2 ranges from 1.056 to 1.220. The fabric of these gabbros also displays broad consistency between nearby specimens. Lineation plunges in the upper interval of Gabbro 1 range from 1° to 36°. Lineations plunge in the lower interval of gabbro 1 range from 0° to 44°. Lineations in gabbro 2 plunge from 6° to 69°. In general, the symmetry of plutonic fabrics provides clues on the nature of magmatic fabric-forming processes. Prolate fabrics support magmatic flow while oblate fabrics rather suggest gravitational settling of crystals. Fabrics in gabbro 1 and gabbro 2 are both prolate and oblate. Fabric in the upper interval of gabbro 1 is more prolate than oblate whereas the lower interval of gabbro 1 and gabbro 2 have even distributions of fabric ellipsoids. Detailed observations of petrographic thin-sections reveal several microstructures suggestive of brittle and plastic deformation in plagioclase grains. Microstructures indicative of plastic deformation include kink-banding, mechanical twinning, and undulose extinction. Microstructures indicative of brittle deformation include submagmatically-fractured laths. These subtle features appear in at least one crystal per thin-section analyzed. With the exception of mechanical twins, shipboard scientists of Expeditions 312 and 335 have not documented these microstructures. Numerical calculations reveal that for both gabbro bodies the Rayleigh Number ranges between 1015 and 1018, depending primarily on the kinematic viscosity of the magmas and temperature change across the intrusions. These values indicate that turbulent flow (Rayleigh number > 106) occurred during emplacement. This type of flow may provide an explanation for the variability of aspect ratio and the variability in linear crystal fabric.

L’étude de la microstructure des roches est indispensable pour nos enjeux contemporains et futurs en matière d'énergie, d’ingénierie et de construction. D’autre part, cette étude permet de caractériser les processus de déformation géologique ayant conduit à l’état actuel des unités lithologiques. Les roches clastiques à grain fin, communément appelées "shales" en anglais, représentent environ deux-tiers de l’ensemble des roches sédimentaires. Les données 3D relatives aux grains de silt ou clastes inclus dans la matrice argileuse et poreuse de ce type de roche sont peu fréquentes. Ces données sont pourtant cruciales pour comprendre les propriétés anisotropes à l’échelle macroscopique mais aussi pour évaluer l’état de déformation de la matrice rocheuse. Mieux connaitre la microstructure de ces roches permettrait d’être prédictif quant à leurs propriétés mécaniques ou physiques indispensables pour les applications du secteur de l’énergie par exemple. La tomographie à rayons X (XCT) est une technique non destructive permettant d’obtenir une image 3D de la microstructure d'un objet. Une caractérisation géométrique directe des constituants des roches clastiques à grain fin est envisageable grâce à cette technique. Sur la base d'images XCT, cette thèse vise d’abord à développer des aspects méthodologiques pour étudier la fabrique de forme 3D des clastes ainsi que leur distribution spatiale. Ces aspects sont élaborés à partir de la méthode des moments d’inertie qui est appliquée sur les grains segmentés des images 3D numériques. Nous présentons ensuite des applications sur des roches à grain fin possédant une fabrique sédimentaire et sur des roches à grain fin déformées présentant une fabrique d’origine tectonique. Le premier volet applicatif de la thèse s’intéresse à une même unité lithologique ayant enregistrée différentes quantités de déformation. Des échantillons du bassin sud-pyrénéen et des échantillons issus d’un affleurement historique dans les Appalaches centrales ont été collectés. Nous apportons de nouvelles données sur l’évolution de la forme 3D des grains et des pores à l’échelle micrométrique et sur leur agencement dans la matrice rocheuse en fonction de la déformation. Les données obtenues permettent de discuter des mécanismes de déformation à l’échelle du grain des différentes phases minéralogiques. Cependant, la petite taille des échantillons imagés par XCT (≤ 2 mm de diamètre) soulève la question de la représentativité de ces analyses. Sur le chantier sud-pyrénéen, certains échantillons sont étudiés de manière plus approfondie pour vérifier l’homogénéité des résultats. Nous y montrons que les données XCT complètent les mesures indirectes pétrophysiques en permettant de décrire et de localiser les sous-fabriques intégrées dans une mesure globale de la fabrique. Les limites apparaissent lorsque la dimension caractéristique des structures de déformation avoisine la taille de l'échantillon imagé par XCT. Dans le second volet applicatif, des échantillons provenant de systèmes turbiditiques du bassin sud-pyrénéen sont analysés. Ces systèmes, lorsque déformés en tectonique compressive, présentent l’avantage d’enregistrer la même quantité de raccourcissement différemment exprimée dans les unités lithologiques qui les constituent. Les résultats obtenus à partir de la forme des clastes sont comparés à nos mesures magnétiques globales de la fabrique et montrent une bonne cohérence. La méthodologie présentée dans ce travail peut s’étendre à d'autres types de milieux poreux et granulaires pour une meilleure compréhension de l'influence de l'anisotropie structurale sur leurs propriétés macroscopiques et leur comportement mécanique
The study of the microstructure of rocks is essential for our contemporary and future challenges in energy, engineering and construction. Furthermore, this study allows us to characterize the geological deformation processes that led to the current state of geological formations. Fine-grained clastic rocks, commonly called "shales", represent about two-thirds of all sedimentary rocks. 3D data concerning silt-sized grains or clasts embedded in the porous clay-rich matrix of this type of rock are relatively scarce despite the fact that these data are crucial to understand the anisotropic properties of these rocks at the macroscale but also to evaluate the deformation state of the rock matrix. A better understanding of the microstructure of these rocks would allow us to predict their mechanical or physical properties, which are essential for applications in the energy sector, among others. X-ray computed tomography (XCT) is a non-destructive technique providing a 3D image of the microstructure of any object. A direct geometric characterization of the constituents of fine-grained clastic rocks is possible with this technique. Based on XCT images, this thesis aims first to develop methodological aspects to study the 3D shape fabric of silt particles and their spatial distribution. The moments of inertia of segmented grains from 3D digital images are used for this development. We then present applications on fine-grained rocks with a sedimentary fabric and on deformed fine-grained rocks with a tectonic fabric. The first application part of the thesis focuses on the same lithologic unit having experienced different amounts of deformation. Samples from the South Pyrenean Basin and samples from a historical outcrop in the Central Appalachians were collected. We provide new data on the evolution of the 3D shape of grains and pores at the micrometer scale and their arrangement in the rock matrix with respect to the deformation intensity. The obtained data allow discussing the deformation mechanisms at the grain scale of the different mineralogical phases. However, the limited size of the imaged samples by means of XCT (≤ 2 mm diameter) raises the question of the representativeness of these analyses. On the South Pyrenean site, some samples are studied in more detail to evaluate the homogeneity of the results. We show that the XCT data complement the indirect petrophysical measurements by providing access to localized sub-fabrics that are integrated in a bulk measurement of the rock fabric. The limits are reached when the characteristic length of the deformation structures are on the order of the sample size imaged by XCT. In the second application part, samples from turbiditic systems of the South Pyrenean basin are analyzed. These systems, when deformed in compressive tectonic settings, record the same amount of shortening differently expressed in the various siliciclastic matrices. The results obtained from the shape data of the clasts are compared to our bulk magnetic fabric measurements and show a good consistency. The methodology presented in this work can be extended to other types of porous and granular media for a better understanding of the influence of fabric anisotropy on their macroscopic properties and mechanical behavior

Le comportement rhéologique de suspensions magmatiques synthétiques hydratées a été expérimentalement étudié en déformation coaxiale et en torsion à haute température et haute pression à l'aide d'une presse de type Paterson. Les résultats obtenus illustrent l'influence de la fraction cristalline et de la forme des cristaux sur la rhéologie et le développement des Orientations Préférentielles de Forme (OPF) des particules au sein des suspensions magmatiques. La formation d'une charpente cristalline, associée à une forte hausse de la viscosité, intervient pour des fractions solides comprises entre fs = 0,20 et 0,38 en relation avec le développement de fabriques de type pénétratif. En augmentant la fraction solide (fs = 0,50), le développement d'une fabrique pénétrative, couplé à des bandes de cisaillement bordées de gradients de déformation, engendre un adoucissement de la réponse rhéologique et une hausse moins importante de la viscosité. Pour fs = 0,58, des bandes de cisaillement de type cassant sans gradient de déformation, recoupant une suspension non déformée, apparaissent et contrôlent le fort adoucissement de la réponse rhéologique. La viscosité de la suspension n'augmente plus alors que légèrement. Au-delà de cette fraction cristalline, les suspensions étudiées montrent une forte réduction de la taille et du rapport de forme des cristaux se traduisant par une stabilisation de la réponse rhéologique en fonction de la déformation. Aucune OPF n'a pu être déterminée et une quasistabilisation de la viscosité est observée (comportement mécanique de solide). Toutes les suspensions étudiées se caractérisent par un comportement rhéologique non-Newtonien de type rhéofluidifiant. La dépendance entre le comportement rhéologique des suspensions magmatiques et le développement des microstructures doit être intégrée dans la modélisation de la mécanique des suspensions magmatiques.

Partitioning of finite strains in different domains within the limb and hinge regions of a fold can be used to understand the deformation processes operative during fold formation. Samples taken from the limb and hinge regions of a gently plunging, asymmetric, tight, mesoscale fold in the Erwin formation of the Blue Ridge in North Carolina were analyzed to determine the deformation mechanisms and strains associated with the folding event. Rf/phi grain shape fabric analysis was conducted for each sample and used to calculate the orientation and magnitude of the final grain shape fabric ellipsoids. Flexural folding and passive-shear folding models predict that the highest finite strains will be recorded in the hinge of a fold. The highest grain shape magnitudes recorded in the North Carolina fold, however, lie along the overturned fold limb. The final geometry of many folds indicates that hinge plane migration processes are active during compressive deformation events. Numeric, conceptual, and analogue based studies have demonstrated the migration of fold hinges during deformation. However, documentation of these processes in field based studies is rare and limited to techniques that are frequently site specific. Methods proven successful in natural studies include the analysis of superposed folding; the migration of earlier hinge-related features such as fractures, cleavage planes, and boudinaged bedding planes; and the kinematic analysis of syntectonic pressure shadows. The magnitude and orientation of the grain shape ellipsoids calculated for the North Carolina fold indicate that rocks in the overturned limb were once located in the hinge of the fold. Subsequent noncoaxial deformation processes operative during folding resulted in the migration of the hinge to its present orientation and position. This relationship indicates that it is possible to use strain/shape fabric analysis as a test for hinge migration in folds, and that this technique may be more generally applicable in natural settings than previously proposed tests.
Master of Science

A trama de magmas graníticos alojados na crosta intermediária e superior pode-se originar pela ação de forças de corpo (ascensionais, convectivas) e/ou tectônicas. Diferentes mecanismos podem concorrer para a formação de tramas, embora a interação entre a deformação magmática e a tectônica regional seja um dos mecanismos fundamentais, notadamente nos granitos alojados em faixas orogênicas. No Domínio Apiaí da Faixa Ribeira (SP - PR), os batólitos graníticos alongados têm sido historicamente classificados como sintectônicos, ou seja, colocados durante o desenvolvimento de um arco magmático continental neoproterozóico. Os plútons menores, de forma circular a ovalada, geralmente discordantes e com típica coloração avermelhada, são considerados pós-tectônicos ou alojados após a colisão continental entre os diferentes blocos litosféricos que formaram a Faixa Ribeira. Essa classificação esquemática tem sido baseada em geoquímica e geocronologia dos granitos. Este trabalho identificou e mapeou a trama interna dos plútons sin-tectônicos (Ribeirão Branco) e pós-tectônicos (Capão Bonito e Sguário) utilizando a anisotropia de suscetibilidade magnética (ASM), de forma a inserí-los propriamente nos modelos de classificação tectônica, cujas premissas básicas são de natureza estrutural. Os granitos porfiríticos (Ribeirão Branco e Itaóca) possuem uma elevada suscetibilidade magnética (k 10-2 SI), a qual é menor (k 5 x 10-3 SI) nos granitos vermelhos (Capão Bonito e Sguário). A suscetibilidade dos granitos porfiríticos é proveniente de óxidos ferromagnéticos, notadamente magnetita pobre em Ti, que encontra-se frequentemente associada com titanita, biotita e anfibólio. Nos granitos vermelhos a suscetibilidade é gerada por magnetita, variavelmente oxidada (maghemita) e Ti-hematita (hemo-ilmenita), havendo também significativa contribuição da fração paramagnética (biotita cloritizada) à suscetibilidade total nas rochas, quando k < 10-3 SI. O grau de anisotropia magnética (P) tanto nos granitos porfiríticos como nos vermelhos é variável, porém tipicamente maior nos porfiríticos (P = 1,14, dp. 0,08), se comparado aos vermelhos (P = 1,07, dp. 0,05). A maior anisotropia de suscetibilidade no plúton Ribeirão Branco é atribuída a uma incipiente foliação detectada em vários setores do granito, que contrasta com a microestrutura aparentemente isótropa dos granitos vermelhos. O estudo da trama de silicatos no granito porfirítico Itaóca e no granito Capão Bonito mostrou que os eixos principais de anisotropia de suscetibilidade magnética e da orientação preferencial de forma (OPF) de feldspato e de biotita, são correspondentes, porém, comumente oblíquos. Essa obliquidade entre eixos é atribuída às características físicas próprias (forma, tamanho e anisotropia) dos minerais marcadores da trama. O estudo combinado da ASM e da OPF revelou ainda que P tende a crescer com a intensidade da orientação preferencial de silicatos, o que permitiu identificar os domínios de maior deformação magmática e correlacioná-los com a estrutura regional. A trama magnética do granito Ribeirão Branco organiza-se em coerência com uma tectônica regional transcorrente sinistral. Na margem ocidental deste granito, contudo, a orientação da trama é diferente do restante do maciço, tendo sido aparentemente afetada pela intrusão do granito Sguário. A trama magnética do Ribeirão Branco contrasta com a do plúton Itaóca, este último exibindo um padrão concêntrico que antecedeu ao desenvolvimento da deformação transcorrente regional. Zircões do Itaóca forneceram uma idade U-Pb (SHRIMP) concordante de 623 ± 10 Ma, atribuída à cristalização deste plúton. Dados da literatura indicam que o granito Capão Bonito é aproximadamente 15 Ma mais jovem que os batólitos de granito porfirítico. O Capão Bonito, entretanto, apresenta uma trama muito bem organizada, típica de intrusões sin-tectônicas, destacando-se excelente alinhamento da lineação magnética. No granito Sguário, o arranjo da trama é tipicamente helicoidal e, junto com a estrutura do Capão Bonito, podem ter sido organizadas em resposta a uma deformação transcorrente E-W destral. Este evento tardio estaria associado à reativação da zona de cisalhamento Ribeira, que afetou a borda sul do granito Itaóca e que contém uma componente extensional. A deformação transtensiva E-W, que favoreceu a injeção dos granitos vermelhos no Domínio Apiaí, sucederia a um evento tectonomagmático principal, que teria sido responsável pela colocação e deformação dos batólitos de granito porfirítico. A intrusão dos grandes corpos graníticos ocorreu em torno de 615 Ma e foi relacionada à convergência crustal e estiramento subparalelo à Faixa Ribeira, com a deformação localizada notadamente nas estruturas transcorrentes de direção NE-SW.
The fabric of granitic magmas emplaced in the middle and upper crustal levels can be caused by the stress action during the ascension and convection of plutons and/or tectonic strain. Several mechanisms can contribute for the previous thing, nevertheless the interaction between the distortions and tectonic is the domineering one, principally in granites located in orogenic belts. In the Apiaí domain of the Ribeira belt (SP-PR) the elongated granitic batholiths have been historically classified like syn-tectonic and them was emplaced during the development of a neoproterozoic continental magmatic arch. Small Plutons with subcircular to oval forms generally discordant with regard to the disposition of the regional structures and that in turn possess feldspars of reddish typical colour, had been considered pos-tectonic, and therefore, emplaced after the collision that joined the different litho-tectonic units that constitute the Ribeira orogenic belt. This schematic classification of these granites relicts on geochemistry and geochronology data. In this study was identified and recorded in map the internal fabric of the syn-tectonic Ribeirão Branco granite and of the pos-tectonic Capão Bonito and Sguário granites using the anisotropy of magnetic susceptibility (AMS) with the aim of inserting them appropriately in the models of tectonic classification whose basic premises are of structural nature. The porphyritic Ribeirão Branco and Itaóca granites have a high magnetic susceptibility (k = 10-2 SI), which is minor than (k = 5 x 10-3 SI) in the red granites (Capão Bonito, Sguário). In the first ones the poor Ti magnetite is the main source of susceptibility, commonly associated to titanite, biotite and amphibole. In the red granites, the susceptibility is provided by magnetite variability rusty (maghemite) and Ti - hematite (hemo-ilmenite), in addition to the significant contribution of biotite altered by hydrothermal processes. The grade of anisotropy rise (P) in the porphyritic granites (P = 1,14 SD. 0,08) and this is bigger than in the red ones (P = 1,07, SD. 0,05). In the Ribeirão Branco pluton, the high value of P is attributed to an incipient foliation detected in several sectors, which contrasts with the microstructure seemingly isotropic of the red granites. The study of the fabrics of silicates in the porphyritic granites Ribeirão Branco and Itaóca revealed that the orientations of the main axes of AMS and of shape preferred orientation (SPO) of feldspar and mafic silicates (biotite + amphibole) are congruent, nevertheless some obliquities occur. Those obliquities are attributed to the influence of the proper characteristics (form, size, anisotropy) of the marker minerals of the respective sub fabrics. In the same way, the above-mentioned study of silicates fabric demonstrated that P tends to grow up with the intensity of the SPO of silicates, which allowed to identify domains with major magmatic distortion into de granitic bodies and to correlate them with the regional structure. In general, the magnetic fabric of the Ribeirão Branco granite is organized coherently with the tectonic regional sinestral strike-slip shear zones; nevertheless, in the western sector the orientation of the magnetic fabric was likely modified by the accommodation of the Sguário granite. In the Itaóca granite, the organization of the magnetic fabric is different if compared with fabrics of the previous pluton. In Itaóca granite was recorded a fabric with a concentric organization in 623 ± 10Ma. (MSWD 0,31), according to the concordant U-Pb (SHRIMP) age in zircons obtained for the crystallization of the granite, that seems to be occurred before the strain related with the activation of the regional strike-slip shear zones. Geochronology data of the literature indicates that the Capão Bonito granite is approximately 15 Ma. younger than the batholiths of porphyritic granite. The Capão Bonito granite has an organized fabric typical of syn-tectonic intrusions that has an excellent alignment of the magnetic lineation. In the granite Sguário, the fabric has a spiral organization, in the same way as recorded in Capão Bonito, like response to a strain associated with to a small strike-slip shear zone with W-E direction. This event would be related to the reactivation of the Ribeira strike-slip shear zone, which affected the south sector of the Itaóca granite, with the participation of an extensional component. The W-E transtensive deformation that favoured the injection of the red granites in the Apiaí Domain likely was subsequent to a main tetonomagmatic event and this should have been the responsible by the emplacement and strain in the porphyritic granites. The intrusion of the big granitic bodies ~ 615 Ma. and could be it related to the convergence between crustal blocks and to the consequent stretching sub parallel of the Ribeira belt, in which the distortion was located remarkably in the strike-slip shear zones with NE-SW direction.

This book explores how work, television, and waged labor come to have meaning in our everyday lives. However, it is not an analysis of workplace sitcoms or quality dramas. Instead, it explores the forgotten history of how American private sector workplaces used television in the twentieth century. It traces how, at the hands of employers, television physically and psychically managed workers and attempted to make work meaningful under the sign of capitalism. It also shows how the so-called domestic medium helped businesses shape labor relations and information architectures foundational to the twinned rise of the technologically mediated corporation and a globalizing information economy. Among other things, business and industry built extensive private television networks to distribute live and taped programming, leased satellite time for global “meetings” and program distribution, created complex closed-circuit television (CCTV) data search and retrieval systems, encouraged the use of videotape for worker self-evaluation, used videocassettes for training distributed workforces, and wired cantinas for employee entertainment. Television at work describes the myriad ways the medium served business’ attempts to shape employees’ relationships to their labor and the workplace in order to secure industrial efficiency, support corporate expansion, and inculcate preferred ideological orientations. By uncovering industrial television as a prolific sphere of media practice—one that continually sought to reshape the technology’s cultural meanings, affordances, and uses—Television at Work positions the medium at the heart of Post-Fordist experiments into reconfiguring the American workplace and advancing understandings of labor that increasingly revolved around dehumanized technological systems and information flows.

Practical tools that can be useful in tectonic studies are briefly examined in this chapter. Field geologists will find some of these tools to be theoretical and conceptual (e.g., tensors), while a few, such as the universal stage (mounted on an optical microscope), are rarely used in the 21st century. It was routinely employed in the previous century, particularly in crystallography, before the advent of modern (but costly) techniques that use X-rays, neutrons or secondary electrons, which will be also discussed. A good handling of orientation data on 2D-projections (Schmidt or Wulff nets) continues to be very practical and of regular use to geologists. The chapter will end with brief introduction to digital imagery and magnetic studies (Anisotropy of Magnetic Susceptibility, AMS) that help to define shape preferred orientations (SPOs) in rocks, and with gravity techniques that are also commonly in practice in geological studies.

ABSTRACT The ~11-km-wide, Paleoproterozoic Dhala impact structure in north-central India comprises voluminous exposures of impact melt breccia. These outcrops are discontinuously spread over a length of ~6 km in a semicircular pattern along the northern, inner limit of the monomict breccia ring around the central elevated area. This study of the magnetic fabrics of impact breccias and target rocks from the Dhala impact structure identified a weak preferred magnetic orientation for pre-impact crystalline target rocks. The pre- and synimpact rocks from Dhala have magnetite and ilmenite as common magnetic phases. The distributions of magnetic vectors are random for most impact melt breccia samples, but some do indicate a preferred orientation. Our anisotropy of magnetic susceptibility (AMS) data demonstrate that the shape of susceptibility ellipsoids for the target rocks varies from prolate to oblate, and most impact melt breccia samples display both shapes, with a slight bias toward the oblate geometry. The average value for the corrected degree of anisotropy of impact melt rock (P′ = 1.009) is lower than that for the target rocks (P′ = 1.091). The present study also shows that both impact melt breccia and target rock samples of the Dhala structure have undergone minor postimpact alteration, and have similar compositions in terms of magnetic phases and high viscosity. Fine-grained iron oxide or hydroxide is the main alteration phase in impact melt rocks. Impact melt rocks gave a narrow range of mean magnetic susceptibility (Km) and P′ values, in contrast to the target rock samples, which gave Km = 0.05–12.9 × 10−3 standard international units (SI) and P′ = 1.036–1.283. This suggests similar viscosity of the source magma, and limited difference in the degrees of recorded deformation. Between Pagra and Maniar villages, the Km value of impact melt breccias gradually decreases in a clockwise direction, with a maximum value observed near Pagra (Km = 1.67 × 10−3 SI). The poor grouping of magnetic fabrics for most impact melt rock samples implies local turbulence in rapidly cooled impact melt at the front of the melt flow immediately after the impact. The mean K1 for most impact melt samples suggests subhorizontal (&lt;5°) flow in various directions. The average value of Km for the target rocks (4.41 × 10−3 SI) is much higher compared to the value for melt breccias (1.09 × 10−3 SI). The results of this study suggest that the melt breccias were likely part of a sheet-like body of sizeable extent. Our magnetic fabric data are also supported by earlier core drilling information from ~70 locations, with coring depths reaching to −500 m. Our extensive field observations combined with available widespread subsurface data imply that the impact melt sheet could have covered as much as 12 km2 in the Dhala structure, with an estimated minimum melt volume of ~2.4 km3.

A magma is a two-phase material made of crystals immersed in a silicate melt, which displays a high viscosity contrast between the liquid and the solid fractions. A specific rheological behaviour is therefore expected from such a material, particularly as a function of the volume ratio between phases. Emplacement of magma to shallower levels of earth’s crust results in crystallization. As a consequence, crystal percentage increases and volume ratio between phases changes. Different structures at both the mesoscopic (field) and microscopic scales develop, which are characteristic of a particular crystal fraction. These aspects, and how shape preferred orientations (shape fabrics) develop in magmas, are discussed in this chapter. Rheological aspects of magma systems are presented, illustrated by significant microstructural features observed in granites. Our focus will then concern the construction mode of magmatic fabrics. Examples will demonstrate that, with the help of microstructures and sometimes of near-field gravity data distribution, emplacement modes of plutons are rather simple to analyse. Finally, mafic rocks will be considered at the end of chapter through case studies concerning, principally, the Skaergaard complex and gabbros from the oceanic crust.

Thin film shape memory alloys are a promising material for use in micro-scale devices for actuation and sensing due to their strong actuating force, substantial displacements, and large surface to volume ratios. NiTi, in particular, has been of great interest due to its biocompatibility and corrosion resistance. Effort has been directed toward adjusting the microstructure of as-deposited films in order to modify their shape memory properties for specific applications. The anisotropy of the shape memory and superelastic effects suggests that inducing preferred orientations could allow for optimization of shape memory properties. Limited work, however, has been performed on adjusting the crystallographic texture of these films. In this study, thin film NiTi samples are processed using excimer laser crystallization and the effect on the overall preferred orientation is analyzed through the use of electron backscatter diffraction and x-ray diffraction. A 3-dimensional Monte Carlo grain growth model is developed to characterize textures formed through surface energy induced abnormal grain growth during solidification. Furthermore, a scaling factor between Monte Carlo steps and real time is determined to aid in the prediction of texture changes during laser crystallization in the partial melting regime.

We study the capillary-induced interactions and configuration of spherical and non-spherical Janus particles adsorbed at flat liquid-fluid interfaces. For Janus spheres, the equilibrium orientation results in each hemisphere being exposed to its more favored fluid. However, experimental observations suggest that some of these particles may take a tilted orientation at the interface, giving rise to a deformed interface. On the other hand, Janus ellipsoids with a large aspect ratio or a small difference in the wettability of the two regions tend to tilt even at equilibrium. The overlap of deformed menisci results in energetic interactions between neighboring particles. We numerically calculate the interface shape around the particles by minimizing the total surface energy of the system comprising of the interface and particle-fluid regions. We quantify these interactions through evaluation of capillary energy variation as a function of the orientation and separation distance between the particles. We find that Janus spheres with similar orientations undergo a relative realignment in the interface plane in order to minimize the capillary energy. In case of ellipsoidal particles, the particles assemble in a preferred side-by-side configuration. We evaluate the role of anisotropy and degree of amphiphilicity on the inter-particle force and the capillary torque. The results can be used to predict the migration and oriented assembly of Janus particles with various geometrical and surface properties at liquid-fluid interfaces.

The controlled synthesis of nanostructured particles with uniform size, shape, composition, and preferred orientation is a formidable task. Some conventional techniques have been demonstrated with limited success; however, reproducible processing schemes for heterogeneous multifunctional materials are still not satisfactory. To realize the advantageous technical applications of nanostructured materials, self-assembly or self-organizing methods are currently under investigation. Our results show that the matrix or template used for directed growth of nanoparticles (Fe, Ni) significantly affects the resultant mechanical properties of the multilayered structure. For example, a crystalline material like TiN, which grows epitaxially on silicon, results in embedded epitaxial nanoparticles. Conversely, an amorphous template like Al2O3 results in polycrystalline magnetic particles. In this work, we will discuss the effect of matrix type, specifically yttria stabilized zirconia (YSZ), on the orientation of nanoparticle assemblies. The resultant mechanical and magnetic properties of the multilayer structures will be discussed in the oral presentation.

The microstructure of magnetic shape memory alloys (MSMAs) is comprised of tetragonal martensite variants, each with their preferred internal magnetization orientation. In the presence of an external magnetic field, the martensite variants tend to reorient so that the preferred internal magnetization aligns with the external magnetic field. As a result, MSMAs exhibit the shape memory effect when there is a magnetic field in the vicinity of a material point. Furthermore, the tetragonal nature of the martensite variants allows for a compressive stress to cause variant reorientation. This paper studies the magneto-mechanical behavior of MSMAs under various load paths, including complex loading conditions where both the applied magnetic field and compressive stress vary simultaneously. Typically, MSMAs have been studied experimentally and modeled mathematically with either axial compressive stress or transverse magnetic field varying and the other remaining constant. For each load case, the mathematical models are calibrated with a set of experimental data that mimics those to be predicted. Model parameters have been found to be quite different when the calibration was performed with experimental results from different load cases. This work investigates if current models, namely the Kiefer and Lagoudasmodel or the Waldauer et al. model, are capable of predicting both of the typical loading configurations mentioned above with a single calibration. Furthermore, this work uses the Waldauer et al. model to simulate more complex loading, where an MSMA element is subject to simultaneously varying stress and field; this type of loading might occur if an actuator is being designed to displace a variable load over a controlled distance.

Magnetorheological elastomers (MREs) are a re-emerging class of smart materials whose novel behavior stems from their response to magnetic fields. Historically comprised of soft-magnetic carbonyl (spherical) iron particles embedded in highly compliant matrix materials, MRE research has focused on their apparent change in shear modulus (in excess of 60%) under a magnetic field. Recent work by the authors has departed from the experimental and theoretical focus on MREs made from soft-magnetic particles (S-MREs) to investigate MREs having hard-magnetic particle inclusions (H-MREs). While H-MRE materials do not perform well in dynamic shear stiffness applications when compared to the traditional S-MREs, H-MREs provide remotely powered, fully reversible actuation capabilities that S-MREs are unable to achieve. In addition, in the same dynamic shear stiffness applications these H-MREs provide a measure of active control of which S-MREs are also incapable. This work examines the role that particle magnetization, developed due to shape anisotropy, plays in the actuation response S-MREs in contrast to H-MREs. H-MRE response is predicated on the response of the hard-magnetic particles to the external magnetic field and to neighboring particles. Since hard-magnetic particles have an internal preferred magnetic orientation, they are able to generate torques at the particle level, T = M × B, where T is the torque density, M is the magnetization, and B is the local magnetic flux density. In contrast, soft-magnetic particles may develop an induced magnetization when exposed to an external field if the particles exhibit shape anisotropy. This induced magnetization is also capable of producing torque at the particle level, however, spherical particles like those historically used in MREs are geometrically isotropic and therefore do not develop induced magnetization either and consequently the widely studied MREs comprised of soft-magnetic spherical particles generate no torque at the particle level. Shape anisotropy further complicates the mechanical response by inducing Eshelby-type shape-dependent effects on the mechanical stresses developed local to the particle. These effects vary the local particle rotation, resulting from a given macroscopic loading, and in turn affect the local magnetic field by changing the particle’s magnetization axis with respect to the external field. The result is a material system whose elastomagnetic response depends on particle shape and orientation as well as on particle magnetization. In previous works the authors used barium hexaferrite (a hard magnetic material) and carbonyl iron powders to generate MRE materials having varying particle alignment and magnetization permutations. These materials were examined in cantilever bending modes to assess and differentiate their abilities as bending actuators. In this work, finite element studies mirroring the bending tests are performed to determine the role of particle/magnetization anisotropy on the behavior. Results show strong dependence on particle shape anisotropy.

In this paper a micro-mechanical model that incorporates single crystal constitutive relationships is used for studying the pseudoelastic response of polycrystalline shape memory alloy beams subjected to bending. In the micro-mechanical framework, the stress-free transformation strains of all the 24 correspondence variant pairs (CVPs) obtained from the crystallographic data of NiTi are used, and the overall transformation strain is obtained by defining a set of martensitic volume fractions corresponding to active CVPs during a phase transformation. A three-dimensional finite element model is used and a polycrystalline beam is modeled based on Voronoi tessellations. The effect of crystallographic texture and the tension-compression asymmetry on the bending response of superelastic beams is studied. The results of texture measurements are used to assign appropriate crystal orientations to the grains in the model. By considering various combinations of crystal orientations, the effect of preferred crystallographic texture on the bending response is studied. The size effect is also studied by considering two polycrystal structures with different number of grains.