Academic literature on the topic 'Roll fronts'
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Journal articles on the topic "Roll fronts"
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Aizhulov, Daniar, Madina Tungatarova, and Aidarkhan Kaltayev. "Streamlines Based Stochastic Methods and Reactive Transport Simulation Applied to Resource Estimation of Roll-Front Uranium Deposits Exploited by In-Situ Leaching." Minerals 12, no. 10 (September 25, 2022): 1209. http://dx.doi.org/10.3390/min12101209.
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Roll-front uranium deposits are ore mineralizations that occur in sandstones or arkoses downstream from redox fronts or reduced/oxidized geochemical barriers. They are often bounded above and below by impermeable shaly/muddy layers making them ideal for in-situ leaching exploitation. Several stochastic simulations were previously investigated either to characterize the ore grade distribution within roll-front type deposits, or for describing geological processes involved in their formation. This work suggests some modifications/improvements of conventional geostatistical algorithms for honoring hydrodynamic constraints that govern fluid flows in ore bearing layers. In particular, instead of using the classical Euclidian or curvilinear (for Sgrid) distance for computing the variogram, it is proposed to calculate the variogram accounting for the time of flight (TOF) of water particles down the streamlines together with available well data. Non-deterministic streamline-based methods seem to provide more accurate interpolation results and resource estimation compared to a traditional geostatistical approach when applied to roll-front deposits.
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Walter, Fabian, Zhen Zhang, Jordan Aaron, Brian McArdell, and Christoph Graf. "Seismic Measurements of Roll Waves in Debris Flows." E3S Web of Conferences 415 (2023): 03031. http://dx.doi.org/10.1051/e3sconf/202341503031.
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Accurate debris-flow modelling depends on the ability to simulate surging and pulsing behaviour. However, our understanding of these phenomena is starved of observational constraints. Here we propose the use of seismic measurements, which resolve the arrival of coarse-grained roll wave fronts in debris flows at Illgraben, Switzerland. Roll waves likely play a key role in flow pulses but are typically only observed with point measurements like depth gauges. We compare in-torrent force plate measurements with near-torrent seismic records and discuss how these data can test existing roll wave theories.
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HIGGINS, P. "FOSSILS TO FERTILIZER: TAPHONOMIC IMPLICATIONS OF URANIUM ROLL FRONTS." PALAIOS 22, no. 5 (September 1, 2007): 577–82. http://dx.doi.org/10.2110/palo.2005.p05-140r.
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Ng, Chiu-On, and Chiang C. Mei. "Roll waves on a shallow layer of mud modelled as a power-law fluid." Journal of Fluid Mechanics 263 (March 25, 1994): 151–84. http://dx.doi.org/10.1017/s0022112094004064.
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We give a theory of permanent roll waves on a shallow layer of fluid mud which is modelled as a power-law fluid. Based on the long-wave approximation, Kármán's momentum integral method is applied to derive the averaged continuity and the momentum equations. Linearized instability analysis of a uniform flow shows that the growth rate of unstable disturbances increases monotonically with the wavenumber, and therefore is insufficient to suggest a preferred wavelength for the roll wave. Nonlinear roll waves are obtained next as periodic shocks connected by smooth profiles with depth increasing monotonically from the rear to the front. Among all wavelengths only those longer than a certain threshold correspond to positive energy loss across the shock, and are physically acceptable. This threshold also implies a minimum discharge, viewed in the moving system, for the roll wave to exist. These facts suggest that a roll wave developed spontaneously from infinitesimal disturbances should have the shortest wavelength corresponding to zero dissipation across the shock, though finite dissipation elsewhere. The discontinuity at the wave front is a mathematical shortcoming needing a local requirement. Predictions for the spontaneously developed roll waves in a Newtonian case are compared with available experimental data. Longer roll waves, with dissipation at the discontinuous fronts, cannot be maintained if the uniform flow is linearly stable, when the fluid is slightly non-Newtonian. However, when the fluid is highly non-Newtonian, very long roll waves may still exist even if the corresponding uniform flow is stable to infinitesimal disturbances. Numerical results are presented for the phase speed, wave height and wavenumber, and wave profiles for a representative value of the flow index of fluid mud.
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DOELMAN, ARJEN, BJÖRN SANDSTEDE, ARND SCHEEL, and GUIDO SCHNEIDER. "Propagation of hexagonal patterns near onset." European Journal of Applied Mathematics 14, no. 1 (February 2003): 85–110. http://dx.doi.org/10.1017/s095679250200503x.
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For a pattern-forming system with two unbounded spatial directions that is near the onset to instability, we prove the existence of modulated fronts that connect (i) stable hexagons with the unstable trivial pattern, (ii) stable hexagons with unstable roll solutions, (iii) stable hexagons with unstable hexagons, and (iv) stable roll solutions with unstable hexagons. Our approach is based on spatial dynamics, bifurcation theory, and geometric singular perturbation theory.
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Schmidt, Christoph W., and Robert A. Goler. "Nonlinear Waves ahead of Fronts in the Great Australian Bight." Monthly Weather Review 138, no. 9 (September 1, 2010): 3474–97. http://dx.doi.org/10.1175/2010mwr3232.1.
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Abstract This study investigates nonlinear waves ahead of cold fronts in the Great Australian Bight, south of the Australian continent. These waves often form a series of roll clouds on their crests analogous to the “morning glory,” which is observed around the Gulf of Carpentaria in northeastern Australia. High-resolution visible satellite imagery from NASA’s polar-orbiting Aqua and Terra satellites between 23 October 2004 and 29 February 2008 is used to determine how frequently these cloud lines occur ahead of cold fronts. A total of 14 cases are identified with the most cases occurring in summer and none occurring in winter. The authors hypothesize that the summer maximum is due to a combination of lower cloud amounts associated with summertime cold fronts, and a stronger maritime stable layer, which is produced as hot continental air, is advected offshore. Three cloud line events are modeled using the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5, version 3.6). In each case the low-level divergence field reveals convergence lines, which coincide with the cloud lines as identified on the satellite images. In two cases vertical cross sections of virtual potential temperature and horizontal and vertical velocity through the disturbances show a cold front advancing into a stratified environment leading to wave production at the leading edge of the cold air mass. Modeled maximal upward velocities range between 0.8 and 2.5 m s−1. Surface pressure jumps of about 1 hPa associated with the propagating waves occur in each case, which coincides with that predicted by simple bore theory. In two cases the front moves at supercritical speed (i.e., the frontal speed is larger than the speed of the fastest mode of small-amplitude long waves). In the third case the front does not propagate and the nonlinear waves produced become stationary as well.
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Skyllingstad, Eric D., and Roger M. Samelson. "Instability Processes in Simulated Finite-Width Ocean Fronts." Journal of Physical Oceanography 50, no. 9 (September 1, 2020): 2781–96. http://dx.doi.org/10.1175/jpo-d-20-0030.1.
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AbstractA simple, isolated front is modeled using a turbulence resolving, large-eddy simulation (LES) to examine the generation of instabilities and inertial oscillations by surface fluxes. Both surface cooling and surface wind stress are considered. Coherent roll instabilities with 200–300-m horizontal scale form rapidly within the front after the onset of surface forcing. With weak surface cooling and no wind, the roll axis aligns with the front, yielding results that are equivalent to previous constant gradient symmetric instability cases. After ~1 day, the symmetric modes transform into baroclinic mixed modes with an off-axis orientation. Traditional baroclinic instability develops by day 2 and thereafter dominates the overall circulation. Addition of destabilizing wind forcing produces a similar behavior, but with off-axis symmetric-Ekman shear modes at the onset of instability. In all cases, imbalance of the geostrophic shear by vertical mixing leads to an inertial oscillation in the frontal currents. Analysis of the energy budget indicates an exchange between kinetic energy linked to the inertial currents and potential energy associated with restratification as the front oscillates in response to the vertically sheared inertial current. Inertial kinetic energy decreases from enhanced mixed layer turbulence dissipation and vertical propagation of inertial wave energy into the pycnocline.
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Carver, Steve, Dave Sear, and Eric Valentine. "An Observation of roll waves in a supraglacial meltwater channel, Harlech Gletscher, East Greenland." Journal of Glaciology 40, no. 134 (1994): 75–78. http://dx.doi.org/10.3189/s0022143000003816.
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AbstractObservations of pulsating flow conditions in a supraglacier meltwater channel on Harlech Gletscher, East Greenland, are reported. Waves of water with turbulent wave fronts and smooth recessive limbs were observed passing downstream at regular intervals of 6-7 s. Peak channel discharge was estimated at 0.5-1.0 m3 s−1, in between which discharge was zero. It is suggested that the phenomenon as observed was due to the formation of roll waves in response to channel morphology and prevalent discharge conditions. Measurements of channel morphology are given together with calculations of critical flow conditions, supporting the hypothesis of roll waves in a natural ice channel. A brief introduction to roll waves and the theory regarding their formation is included.
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Carver, Steve, Dave Sear, and Eric Valentine. "An Observation of roll waves in a supraglacial meltwater channel, Harlech Gletscher, East Greenland." Journal of Glaciology 40, no. 134 (1994): 75–78. http://dx.doi.org/10.1017/s0022143000003816.
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Abstract Observations of pulsating flow conditions in a supraglacier meltwater channel on Harlech Gletscher, East Greenland, are reported. Waves of water with turbulent wave fronts and smooth recessive limbs were observed passing downstream at regular intervals of 6-7 s. Peak channel discharge was estimated at 0.5-1.0 m3 s−1, in between which discharge was zero. It is suggested that the phenomenon as observed was due to the formation of roll waves in response to channel morphology and prevalent discharge conditions. Measurements of channel morphology are given together with calculations of critical flow conditions, supporting the hypothesis of roll waves in a natural ice channel. A brief introduction to roll waves and the theory regarding their formation is included.
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Hamayotsu, Kikue, and Ronnie Nataatmadja. "Indonesia in 2015." Asian Survey 56, no. 1 (January 2016): 129–37. http://dx.doi.org/10.1525/as.2016.56.1.129.
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The new Indonesian president, Joko Widodo (“Jokowi”), has faced formidable challenges on a number of fronts in his first year in office. Although Jokowi has managed to roll out his pet projects for the poor, management of competing partisan and personal interests as well as the economy and religious conflict continues to be a challenge. Overall, the new government’s contribution to democratic reforms has been modest thus far.
Dissertations / Theses on the topic "Roll fronts"
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Langanay, Jean. "Quantification des incertitudes d'une exploitation d'un gisement d'uranium par Récupération In Situ." Electronic Thesis or Diss., Université Paris sciences et lettres, 2021. http://www.theses.fr/2021UPSLM035.
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La Lixiviation In-Situ d’uranium, ou In-Situ Recovery (ISR), est basée sur la lixiviation directe des minéraux uranifères au coeur du gisement par une solution minière injectée. Les résultats des écoulements et des réactions chimiques dans le réservoir sont difficiles à prédire en raison des incertitudes géochimiques, pétrophysiques et géologiques. Les codes de simulation de transport réactif utilisés pour modéliser l’ISR sont particulièrement sensibles à la distribution spatiale des propriétés physiques et chimiques dans le dépôt. Ainsi, la modélisation géostatistique est utilisée pour représenter l’incertitude de la répartition spatiale des propriétés géologiques. On peut représenter cette incertitude par un grand nombre de réalisations du modèle géostatistique. La propagation directe des incertitudes géologiques est difficile à résoudre en contexte industriel en raison du temps CPU nécessaire pour effectuer une simulation de l’ISR. Les travaux réalisés dans cette thèse présentent différents moyens de propager l’incertitude géologique en incertitude sur la production d’uranium avec un coût en temps de calcul réduit. On utilise pour cela la méthode de réduction de scénarios, qui permet de propager parcimonieusement l’incertitude. Un sous-ensemble de simulations géostatistiques est sélectionné pour approximer la variabilité d’un ensemble plus large. La sélection est obtenue en utilisant un proxy de la simulation de transport réactif. La principale contribution de ce travail est la construction de différents proxys pour approximer la lixiviation de l’uranium. Ils permettent de reproduire la dissimilarité des réalisations en terme de production d’uranium. Ensuite, les simulations de l’ISR effectuées dans les réalisations géostatistiques sélectionnées donnent une approximation de la variabilité de production d’uranium de l’ensemble des réalisations. Cette approximation est enfin utilisée pour quantifier les incertitudes de la production d’uranium sur des cas réels. Finalement, la propagation de l’incertitude de production de l’échelle du bloc de production à l’échelle de la mine est développée. Par ailleurs, un travail exploratoire a été mené dans le but d’utiliser des modèles de substitution du solveur de la chimie pour accélérer les simulations de transport réactifUranium In Situ Recovery (ISR) is based on the direct leaching of the uranium ore in the deposit by a mining solution. Fluid flow and geochemical reaction in the reservoir are difficult to predict due to geological, petrophysical and geochemical uncertainties. The reactive transport simulation code used to model ISR is very sensitive to the spatial distribution of the physical and chemical properties of the deposit. Geostatistical models are used to represent the uncertainty of the spatial distribution of geological properties. The direct propagation of geological uncertainties by multiple ISR mining simulations is intractable in an industrial context. This work presents a way to propagate geological uncertainties into uranium production uncertainties at a reduced computational cost, thanks to a scenario reduction method. A subset of geostatistical simulations is built to approximate the variability of a larger set. The selection is obtained using a proxy of reactive transport simulation. The main contribution of this work is the development of different proxys to approximate the uranium leaching. They allow the discrimination of geostatistical realizations in terms of potential uranium production.Then, the ISR simulation carried out with the selected geostatistical realizations gives an approximation of the uranium production variability over the whole set of geostatistical simulations. This approximation is then used to quantify the uncertainties on the uranium production. The proposed approach is assessed on real case studies. Finally, the propagation of the uranium production uncertainty, assessed by the scenario reduction method, on mining operation planning is developped. Furthermore, an exploratory work about the use of statistical meta-models as chemistry solvers is also presented
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Pons, Tony. "Caractérisation des oxy-hydroxydes de fer et des éléments associés (S, Se, As, Mo, V, Zr) dans les environnements redox favorables aux gisements d’uranium." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112197/document.
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Ce travail présente une étude multi-échelle et multi-technique sur la caractérisation des oxy-hydroxydes de fer dans trois types de gisements d’uranium et leur encaissant. Le choix des sites d’études s’est porté sur un gisement de type roll front : Zoovch Ovoo dans le bassin crétacé de East Gobi (Mongolie) ; un autre de type tectono-lithologique : Akola/Ebba dans le bassin de Tim Mersoï (Niger) et enfin un type discordance protérozoïque : Kiggavik en bordure du bassin du Thelon (Canada). Une nouvelle approche a été mise en œuvre pour caractériser les oxy-hydroxydes de fer sur échantillons macroscopiques : la spectroscopie infrarouge de terrain en utilisant le spectromètre ASD TerraSpec®. À partir d’indices originaux calculés sur les spectres, il a été possible à la fois de caractériser les oxy-hydroxydes de fer ; seules l’hématite et la goethite ont été identifiées dans les parties oxydées des différents fronts uranifères, et de visualiser les différentes zonations d’altération le long des fronts redox. De plus, la partie visible du spectre a été utilisée pour quantifier la couleur des échantillons à travers les paramètres des systèmes ITS (Intensité – Teinte – Saturation) et de Munsell. L’étude des paramètres de couleurs a permis d’identifier une teinte spécifique pour les échantillons minéralisés étudiés : un mélange de jaune et de rouge (2,5 à 10 YR en notation de Munsell). A l’échelle des cristaux, les oxy-hydroxydes de fer ont été caractérisés par la spectroscopie micro-Raman. Cette étude a permis de mettre en évidence une différence de cristallinité des cristaux d’hématite dans les différents gisements. D’un point de vue morphologique, les cristaux de goethite du gisement de Zoovch Ovoo, seul oxy-hydroxyde de fer authigène décrit dans ce front, sont maclés en forme d’étoile à six branches, ce qui témoigne d’une cristallisation de basse température, comparé aux gisements du Niger et de Kiggavik. Cette cristallisation est principalement contrôlée par la disponibilité des ions Feᴵᴵᴵ dans le fluide, libérés par la dissolution de la pyrite en milieu oxydant et le pH. D’un point de vue chimique, les oxy-hydroxydes de fer enregistrent le passage du fluide uranifère de part leur teneur eu uranium. Et d’autre part la composition en éléments en trace qui marque la typologie du gisement, par exemple de la teneur en zirconium dans les oxy-hydroxydes de fer provenant du gisement du Niger, source d’origine volcanique. Cette typicité de la mobilité du zirconium est particulièrement bien exprimée dans les fronts uranifères d’Ebba par la précipitation de cristaux authigènes de zircon contemporains de la pechblende. Les données minéralogiques et géochimiques obtenues dans ce travail sur le gisement de Zoovch Ovoo permettent de proposer un modèle original pour sa formation : l’uranium n’a pas précipité massivement en amont du front puisqu’il n’y a pas d’auréole d’irradiation observable en cathodoluminescence dans les minéraux détritiques dans la zone oxydée. L’uranium a précipité lorsque l’eau oxydante a rencontré un faciès sédimentaire ayant un pouvoir réducteur assez fort pour permettre la réduction de l’uranium. La précipitation a lieu dans un endroit particulier de la formation : un paléo-lac où la matière organique et la pyrite sont abondantesThis work presents a multi-scale and a multi-technical study for the characterization of iron oxi-hydroxides in three uranium-type deposits and host rock. The choice of sites has focused on a roll front deposit: Zoovch Ovoo in a Cretaceous basin of East Gobi (Mongolia); a tectonic-lithological type: Akola/Ebba in Tim Mersoï basin (Niger) and a Proterozoic unconformity type: Kiggavik in Thelon basin (Canada). A new approach has been implemented to characterize the iron oxi-hydroxides on macroscopic samples: field infrared spectroscopy using the ASD TerraSpec® spectrometer. From the original indexes calculated on the spectra, it was possible both to characterize the iron oxi-hydroxides; only hematite and goethite were identified in the different parts of oxidized uranium fronts, and visualize the alteration zonation along the redox front. In addition, the visible part of spectrum was used to quantify the color of samples through the IHS system parameters (Intensity – Hue – Saturation) and the Munsell system. The color setting of the study identified a specific hue for mineralized samples studied: a mixture of yellow and red (2.5 to 10YR in Munsell notation). At the crystals scale, the iron-hydroxides were characterized by µ-Raman spectroscopy. The study highlighted a difference in crystallinity of hematite crystals in different fields. From a morphological point of view, the crystals of goethite in the Zoovch Ovoo deposit, is only authigenic iron oxi-hydroxides described in this uranium front, are twinned in the form of six-pointed star, reflecting a low crystallization temperature, compared to Niger and Kiggavik deposits. This crystallization is mainly controlled by the availability of Feᴵᴵᴵ ions in the fluid, released by pyrite dissolution in an oxidizing environment and pH. From a chemical point of view, iron oxi-hydroxides record the fluid passage owing their uranium content. Secondly, the composition in trace elements marks the type of deposit, for example zirconium content in oxi-hydroxides from Niger deposit, volcanic source. This typical mobility of zirconium is particularly expressed in the uranium front in Ebba deposit by the precipitation of authigenic crystals of zircon contemporary of pitchblende. The mineralogical and geochemical data obtained in this work on the Zoovch Ovoo deposit (Mongolia) allow us to propose an original model for its formation: uranium did not precipitate massively in upstream edge of front, because not radiation halo is visible in cathodoluminescence in detrital minerals in the oxidized area. Uranium precipitated when the oxidizing water met with sedimentary facies having a fairly strong reducing power to allow uranium reduction. The precipitation occurs in a particular location of the formation: paleo-lake where organic matter and pyrite are abundant
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Rallakis, Dimitrios. "Le système métallogénique et le piège redox dans le gisement d’uranium de type roll-front de Zoovch-Ovoo, Mongolie. Rôle des porteurs du carbone et du soufre." Thesis, Université de Lorraine, 2019. http://www.theses.fr/2019LORR0079.
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L'objectif de la thèse concerne l'analyse du système matières organiques (carbone)-uranium-sulfure qui contrôle la formation du gisement d'uranium de type de roll-front au Zoovch Ovoo (Mongolie). La formation Cénomanienne du Sainshand est constituée de sédiments continentaux silicoclastiques déposés dans des milieux fluvio-lacustres. Le système global est en début de diagénèse et n'a pas été affecté par un enfouissement significatif, estimé à moins de 600 m pour une température maximale de 40°C. Le réservoir se caractérise par des sables non consolidés et des argiles silteuses. Parfois, certains lits de grès d’épaisseur décimétriques sont cimentés par des carbonates et disposés au sein de faciès silicoclastiques non consolidés. L’étude systématique des grès à ciment carbonaté a révélé la présence exclusive de dolomite. Quatre types de dolomite différents ont été reconnus. Tous ont été formés par des eaux d'origine météorique et présentent des caractéristiques isotopiques (C, O) semblables. Ils sont génétiquement liés les uns aux autres, avec de possibles épisodes de recristallisation impliquant une réincorporation progressivement moindre des éléments en traces comme les terres rares et le manganèse. Le premier type de dolomite est contrôlé par les conditions de sédimentation, tandis que les trois suivants sont contrôlés par diagenèse. Le troisième type de dolomite n'a été trouvé que dans des échantillons ayant été affectés par le roll-front alors que le quatrième est postérieur aux porteurs d'uranium. La matière organique détritique est très abondante et joue un rôle majeur dans le piégeage de l’uranium aux côtés de la pyrite. L'étude en pétrographie organique a montré que toute est d'origine végétale supérieure et immature, comme l'ont montré les mesures de réflectance de la vitrinite (<0,4%). Elle est exclusivement présente sous forme de particules détritiques et sa distribution est donc régie par l’évolution des conditions de dépôt sédimentaires. Huit générations de pyrite ont été identifiées sur la base textures et des associations minérales, avec trois types majeurs : les pyrites framboidales en sphérolites isolés, les surcroissances automorphes, et les pyrites de remplacement (épigénie). L'étude isotopique du δ34S de la pyrite a montré qu’une grande parties des pyrites s‘est formée par bio-réduction des sulfates. Les porteurs de l’uranium sont la pechblende et dans une moindre mesure la phospho-coffinite. La pechblende cimente et remplace la matière organique mais aussi les pyrites automorphes corrodées ce qui indique que l’enrichissement ou l’introduction massive de l’uranium s’est produit assez tardivement. La matière organique a piégé l’uranium de manière diffuse à des fortes concentrations, sous une forme minéralogique non accessible au MEB. Il peut s’agir de nanophases de pechblende de taille inférieure à la centaine de nanomètres. Pour expliquer ces concentrations, une préconcentration ne peut pas être totalement exclue ou un processus de diffusion piégeage lors du stade de minéralisation. La considération de l’ensemble des données indique que l’aquifère principal a été le siège probable d’activité microbienne subcontinue, qui est attestée par la formation à différentes stades de l’histoire du bassin de pyrites dont les caractéristiques isotopiques indiquent des processus complexes de fractionnement. La présence de matière organique en quantité significative et des pyrites peut expliquer l’efficacité du piège redox pour la réduction de l’uranium. Le modèle métallogénique présenté est celui d’un système mixte où un processus de type roll-front lié aux caractéristiques sédimentologiques de cette zone se superpose à un piège redox particulier dont la chimie C-S-U est assistée par les bactériesThe objective of the PhD thesis concerns the analysis of the processes governing the carbon-uranium-sulfide system in the aquifers of the roll-front type Zoovch Ovoo uranium-deposit (Mongolia). The Cenomanian Sainshand Formation hosting the ore deposit contains reservoirs made of silicoclastic sediments deposited in fluvio-lacustrine settings mostly characterized by unconsolidated silty clays and sands ranging from arenite to sub-arkose. Occasionally some decimetres thick sandstone beds are dolomite cemented. Four different dolomite fabrics are recognized and classified according to their crystal boundaries and geochemistry. Isotopic analysis indicates that they were formed from meteoric waters with the carbon source being probably the detrital material itself issued from basement rock erosion. Dolomites are genetically related to each other with possible recrystallization episodes that are indicated by gradual depletion in REE and Mn. The first dolomite type was depositionally controlled, while the next three parageneses are diagenetic. The third dolomite type is found only in samples that have experienced roll-front waters, whereas the fourth post-dates uranium formation. As a result the dolomite cements paragenetic evolution is used as reference to document the whole burial history of the deposit. Organic matter particles, pyrite and uranium are very intimately related. Organic matter present in clay, silt and sand is always represented by poorly preserved detrital elements of higher plant origin and is very immature (peat stage; vitrinite reflectance <0.4%). At the scale of the sedimentary particles, organic matter complexes U(VI). However, despite a systematic association to UO2, it cannot be considered as directly involved in the reduction mechanism of uranium because of the low burial temperatures (max 50°C) and hence very limited diagenesis. Nevertheless, the investigation reveals that organic matter is the most important element in the U trapping process. Indeed, it acts as a substrate sustaining and focusing bacterial activity into specific sedimentary layers. In turn the microbial communities catalyze the reduction of sulfur, iron and especially uranium leading to two major consequences: 1) the precipitation of UO2 onto organic matter particles and 2) the formation of pyrite which acts as an additional reducer for U(VI). It appears that the uranium ore deposit at Zoovch Ovoo is primarily controlled by the distribution of the detrital organic matter in the sedimentary system as well as by the permeability network allowing the input of S, U and micro-organisms. The rather shallow aquifers probably underwent a nearly continuous bacterial activity which is responsible of many chemical features and processes controlling the U and sulfide precipitation. However, main uranium deposition events occur since the beginning of exhumation when enhanced fluid movement sustains roll-front activity. The latter displaces and combines the ingredients of the biochemical trap, allowing progressive enrichment in uranium through time
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Graham, Robert M. "The role of Southern Ocean fronts in the global climate system." Doctoral thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-108736.
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The location of fronts has a direct influence on both the physical and biological processes in the Southern Ocean. However, until recently fronts have been poorly resolved by available data and climate models. In this thesis we utilise a combination of high resolution satellite data, model output and ARGO data to improve our basic understanding of fronts. A method is derived whereby fronts are identified as local maxima in sea surface height gradients. In this way fronts are defined locally as jets, rather than continuous-circumpolar water mass boundaries. A new climatology of Southern Ocean fronts is presented. This climatology reveals a new interpretation of the Subtropical Front. The currents associated with the Subtropical Front correspond to the western boundary current extensions from each basin, and we name these the Dynamical Subtropical Front. Previous studies have instead suggested that the Subtropical Front is a continuous feature across the Southern Ocean associated with the super gyre boundary. A comprehensive assessment of the relationship between front locations and wind stress is conducted. Firstly, the response of fronts to a southward shift in the westerly winds is tested using output from a 100 year climate change simulation on a high resolution coupled model. It is shown that there was no change in the location of fronts within the Antarctic Circumpolar Current as a result of a 1.3° southward shift in the westerly winds. Secondly, it is shown that the climatological position of the Subtropical Front is 5-10° north of the zero wind stress curl line, despite many studies assuming that the location of the Subtropical Front is determined by the zero wind stress curl. Finally, we show that the nutrient supply at ocean fronts is primarily due to horizontal advection and not upwelling. Nutrients from coastal regions are entrained into western boundary currents and advected into the Southern Ocean along the Dynamical Subtropical Front.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted.
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Nathwani, Falguni. "Fronto-striatal circuitry : role in behaviour and cognition." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619737.
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Bonnetti, Christophe. "La genèse des gisements de type roll front dans le bassin d'Erlian, Chine." Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0282/document.
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Le bassin d'Erlian localisé au NE de la Chine s'est développé au cours de l'extension continentale de la fin du Mésozoïque en Asie de l'Est. Le socle sur lequel il repose correspond à la partie orientale de la ceinture orogénique centre asiatique. Les granites indosiniens (236.8±5.8 Ma) étudiés, proviennent d'une série magmatique calco-alcaline fortement potassique dérivée de la fusion partielle d'un manteau enrichi (143Nd/144Ndi faible; epsilon Nd(t) négatif) et correspondent à des sources majeures d'U. Les systèmes fluviatiles en tresse qui dominent au cours de l'épisode post-rift du bassin, sont des environnements favorables au dépôt des sables réduits qui constituent les pièges pour les minéralisations U. Les sédiments post-rifts contiennent des concentrations syn-sédimentaires significatives en U, principalement adsorbé aux minéraux argileux. Celles-ci sont ensuite redistribuées quasi in situ au cours de l'évolution diagénétique des sédiments, s'exprimant sous forme de coffinite et de pechblende (e.g. Nuheting). La MO contenue dans ces sédiments est d'origine continentale et correspond à un kérogène de type IV immature. Enfin, le gisement roll front de Bayinwula se caractérise par un modèle biogénique. Dans la zone à pyrite, la MO est dégradée par des bactéries sulfato-réductrices. La production de H2S contribue à la dissolution des oxydes de fer/titane qui sont progressivement remplacés par la pyrite (de même que la MO), caractérisée par une signature delta 34S très négative. L'U porté par ces oxydes et la MO est libéré et peut alors être lessivé par les fluides oxydants. Le H2S produit favorise la réduction de l'U qui précipite au front sous forme de coffinite et de ningyoiteThe Erlian Basin located in NE China developed during the late Mesozoic continental extension in eastern Asia. This basin lies on a basement corresponding to the eastern part of the Central Asia Orogenic Belt. Indosinian magmatism (236.8±5.8 Ma) is widely represented by high-K calcalkaline granites derived from an enriched mantle (low 143Nd/144Ndi; negative epsilon Nd(t)) and correspond to major U sources. Braided fluvial systems of post-rift sediments of the Erlian Basin correspond to favorable sedimentary conditions for the genesis of permeable and reduced sandstones. Post-rift sediments contain significant synsedimentary U concentrations, mainly adsorbed on clay minerals. These pre-concentrations are redistributed in situ, during the diagenetic evolution, and mineralized as coffinite and pitchblende replacing pyrite or pyritized OM (e.g. Nuheting). The OM occurring within these sediments is mainly terrigenous and corresponds to kerogens of type IV, thermally immature. Finally, the roll front-type Bayinwula deposit is characterized by a biogenic model involving reactions between OM, U-rich Fe/Ti oxides and sulfate-reducing bacteria. In the pyrite zone, the OM is degraded by bacteria and replaced by pyrite. H2S production contributes in the dissolution of Fe/Ti oxides that are progressively epigenized into pyrite, characterized by strongly negative values of delta 34S. U concentrations from Fe/Ti oxides and OM are liberated and can be leached by oxygenated groundwater. H2S creates a reducing barrier contributing in the reduction of uranium that precipitates at the redox front as coffinite and ningyoite
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Raosa, Andrea Natalia. "Analisi sperimentale della formazione e propagazione di treni d'onda a fronte ripido (roll waves)." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amslaurea.unibo.it/710/.
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Cooper, Ian Michael. "The role of surface and diffusive processes on potential vorticity in atmospheric fronts." Thesis, University of Reading, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306836.
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Andersen, Jordan Turner. "Movement Characteristics of Front Crawl Swimming at Sprint Pace and Middle-Distance Pace: Establishing Demands on the Torso Muscles." Thesis, The University of Sydney, 2019. http://hdl.handle.net/2123/20906.
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Dry-land training of the torso muscles is common in swimming programs; however, the role of the torso muscles in front crawl is unclear. The purpose of this thesis was to establish demands on the torso muscles in front crawl from analysis of kinematic data and torso muscle activity during sprint and middle-distance swimming. In the first two studies, 3D kinematic data were analysed from swimmers swimming at sprint and 400m pace. In Study 1, the range of hip roll decreased while shoulder roll range was similar as swimming speed increased. These differences produced greater range and velocity of torso twist as swimming speed increased, indicating higher demands on the torso muscles at sprint than at 400m pace. In Study 2, Fourier analysis was used to decompose angular momentum signals to determine the impact of the flutter kick on longitudinal body rotation. The third harmonic frequency, representing effects from the flutter kick, was greater in lower limb than in upper limb angular momentum at both paces, indicating a reduction in the rotation transferred from the lower to upper limbs. This reduction was more pronounced at sprint than at 400m pace. In Study 3, 3D kinematic data and surface EMG data from internal oblique, external oblique, rectus abdominis, and lumbar and thoracic erector spinae were collected from swimmers swimming at sprint and 400m pace. Torso twist angle did not relate to EMG data and no relationships between muscle activity and torso twist acceleration could be detected. Findings from this study indicate that the torso muscles may play a greater role in stability and posture than they do in producing torso twist in front crawl. Guidelines were developed to improve dry-land training specificity for swimmers: (1) increase torso muscle demands as swimming speed increases, (2) use the torso muscles to provide stability during lower limbs movements, and (3) challenge the torso muscles to maintain torso posture while moving the upper and lower limbs.
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Schomers, Malte [Verfasser]. "Establishing action-perception circuits as a neural basis for meaning-carrying linguistic symbols – the role of frontal speech motor areas and fronto-temporal connectivity / Malte R. Schomers." Berlin : Freie Universität Berlin, 2017. http://d-nb.info/1128150646/34.
Full textBooks on the topic "Roll fronts"
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author, Murog Igorʹ, ed. S fronta boevogo na front politekhnicheskiĭ: Rolʹ frontovikov v sudʹbe Ri︠a︡zanskogo Politekha. Ri︠a︡zanʹ: IP Zhukov V. I︠U︡., 2020.
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1948-, Clarence-Smith W. G., ed. Cocoa pioneer fronts since 1800: The role of smallholders, planters, and merchants. New York: St. Martin's Press, 1996.
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Widgery, David. Beating time: Riot 'n' race 'n' rock 'n' roll. London: Chatto and Windus, 1986.
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The unquiet western front: Britain's role in literature and history. Cambridge: Cambridge University Press, 2002.
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Saich, Tony. The origins of the first United Front in China: The role of Sneevliet (alias Maring). Leiden: E.J. Brill, 1991.
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Inc, Joint Commission Resources, ed. Front line of defense: The role of nurses in preventing sentinel events. 2nd ed. Oakbrook Terrace, IL: Joint Commission Resources, 2007.
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Pizer, Christine M. On the front line: The county government role in health service delivery. Washington, D.C. (440 First St., NW, Washington 20001): National Association of Counties Research Foundation/County Health Policy Project, 1994.
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Barha, Kāḥsāy. Ethiopia: democratization and unity: The role of the Tigray People's Liberation Front. Münster: Monsenstein und Vannerdat, 2005.
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Henniker, Tony. Rolls-Royce on the front line: The life and times of a service engineer. Derby: Rolls-Royce Heritage Trust, 2000.
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Serazetdinov, B. U. Rybnyĭ front i ego rolʹ v smi︠a︡gchenii prodovolʹstvennoĭ problemy v SSSR, 1941-1945 gg. Moskva: Institut rossiĭskoĭ istorii RAN, 2010.
Find full textBook chapters on the topic "Roll fronts"
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Dorlac, Warren C., and Carlos J. Rodriguez. "The Homefront: Role 4 and 5 Care." In Front Line Surgery, 677–97. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-56780-8_39.
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Rugh, William A. "Defense Department Communications: Changing Role." In Front Line Public Diplomacy, 181–99. New York: Palgrave Macmillan US, 2014. http://dx.doi.org/10.1057/9781137444158_12.
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Vallenilla, Nikita Harwich. "The Eastern Venezuela Pioneer Front, 1830s–1930s: The Role of the Corsican Trade Network." In Cocoa Pioneer Fronts since 1800, 23–44. London: Palgrave Macmillan UK, 1996. http://dx.doi.org/10.1007/978-1-349-24901-5_2.
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Deckard, Nathan A., Bradley F. Marple, and Pete S. Batra. "The Role of Fungus in Diseases of the Frontal Sinus." In The Frontal Sinus, 149–67. Berlin, Heidelberg: Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-48523-1_11.
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"Front Matter." In Roll-to-Roll Manufacturing, i—xiii. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2018. http://dx.doi.org/10.1002/9781119163824.fmatter.
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"Front Matter." In Roll With It, i—iv. Duke University Press, 2013. http://dx.doi.org/10.2307/j.ctv11smkp3.1.
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"Front Matter." In Roll-to-Roll Vacuum Deposition of Barrier Coatings, i—xv. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2015. http://dx.doi.org/10.1002/9781118946183.fmatter.
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"Front Matter." In See How We Roll, i—iv. Duke University Press, 2021. http://dx.doi.org/10.2307/j.ctv1wdvx78.1.
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"Front Matter." In Männer: Rolle vorwärts, Rolle rückwärts, 2–4. Verlag Barbara Budrich, 2009. http://dx.doi.org/10.2307/j.ctvdf0206.1.
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Smith, Virginia F. "Mountain Interval." In A Scientific Companion to Robert Frost, 45–66. Liverpool University Press, 2018. http://dx.doi.org/10.3828/liverpool/9781942954484.003.0004.
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In early 1915, the Frost family made a hurried departure from England as the war in Europe escalated. Although they successfully escaped the ravages of World War I, at the time the most mechanized conflict in history, the Frosts returned to a country undergoing its own rapid and irreversible changes at the hands of technology. In the collection Mountain Interval, published in 1916, Frost depicts the violence of technology toward humans in poems such as “Out, Out –“ and “The Vanishing Red,” but most of the violence is reserved for plants and animals, both domestic and wild. He also addresses the role of technology in society, especially the telephone, and starts to move from observational to theoretical descriptions of astronomical objects. This chapter begins with an alternative interpretation of the natural setting in one of Frost’s most popular poems, “The Road Not Taken.”
Conference papers on the topic "Roll fronts"
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Mousavi Bideleh, Seyed Milad, and Viktor Berbyuk. "Multiobjective Optimization of a Railway Vehicle Dampers Using Genetic Algorithm." In ASME 2013 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/detc2013-12988.
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Ride comfort, safety, wear and vehicle speed are the most important factors in evaluating the efficiency of railway transportation. In order to decrease the track access charges it is often desirable to run the vehicle at maximum allowed speed, while keeping an admissible amount of wear in system. This usually deteriorates the ride comfort and safety level during the operation. Therefore, an optimization problem to find a tradeoff value for vehicle speed and design parameters is inevitable. Since, ride comfort, safety and wear values are sensitive to primary and secondary suspensions’ damping parameters it is desirable to find the optimum values of such design variables. In this regard, the multiobjective optimization of railway vehicle dampers is considered to increase the cost-efficiency of railway operation. One car vehicle model with 26 degrees of freedom (DOF) along with a set of initial states, design parameters and operational conditions is explored here. All bodies are assumed to be rigid. Vehicle carbody and bogie frames supposed to have the full set of DOF in space. While, only lateral and yaw motions are considered for each wheelset. It is also assumed that wheelset roll angle is a function of the lateral displacement. Primary and secondary suspensions compromised of parallel linear springs and dampers in longitudinal, vertical and lateral directions which connect wheelsets to bogie frames, and bogie frames to carbody, respectively. Lagrange formalism is employed to obtain the system’s equations of motion. The nonlinear heuristic theory is chosen to relate creepages and the corresponding creep contact forces. The dynamic response of the system is obtained for different operational scenarios including ideal and imperfect tangent and curved tracks. Series-based functions are chosen to approximate the harmonic lateral track irregularities. Accelerations at carbody level, shift forces and wear number are used to evaluate the ride comfort, safety and wear, respectively. MATLAB genetic algorithm optimization routine is applied to perform the optimization. The Pareto sets and Pareto fronts obtained from this study provide the vectors of optimal design parameters corresponding to maximum admissible vehicle speed and guarantee the best tradeoff values for safety and comfort with threshold on wear for each operational scenario. Analysis of the obtained results gives insight into multiobjective optimized dynamic response of a railway vehicle and useful hints for designing adaptive bogie systems with the possibility to switch between optimal damping parameters value and provide the best operational efficiency.
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Browne, Alan L., Nancy L. Johnson, and Mark E. Botkin. "Composite Crash Box: Roll Wrap Fabrication and Dynamic Axial Crush Performance." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-41143.
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A feature of many vehicles is a bolt-on, replaceable front end clip designed to protect the remaining structure in 0° to 30° frontal and offset crashes up to 15 km/hr (ECE-R42, European Danner (AZT), Allianze, VDS, or Thatcham Tests). The principle energy absorbing elements in such front clips are called crash or crush boxes. These are hollow cross section often tubular structures located between the bumper and the front ends of the lower rails. Previous studies of the dynamic axial crush response of carbon fiber reinforced composite tubes suggested that both the mass of the crash box and the amount of overhang of the front end clip could be reduced by switching from a metal to a carbon fiber reinforced composite crash box. The axial dimension of the crash box could theoretically be reduced because of the 20% reduction in stack-up exhibited by composite compared to metal tubular structures. The mass could theoretically be reduced because of the higher energy dissipation capability per unit mass of the carbon fiber composite and the shorter length that would be required. The initiative summarized in this paper was the roll wrapping portion of a one year program intended to prove out these benefits. Specifically, it encompassed the design, roll wrapping fabrication, and dynamic axial crush testing of a carbon fiber composite version of the crash box for a mid-size vehicle. All project goals were met. As first steps crush performance of the baseline Al crash box was determined and requirements were established for the geometry and crush force of the composite crash box, the needed crush force being 70 kN. To achieve the desired crush force levels while reducing mass by 20% compared to Al requires an SEA (specific energy absorption) on the order of 45. Crash box specimens manufactured with the roll wrapping process spanned a wide range of fiber architectures which were chosen based on findings of earlier crush tests of composite tubular specimens. Dynamic axial crush tests were then conducted on these specimens. Through these tests we were successful in identifying combinations of fiber type, fiber architecture, and tube wall thickness that simultaneously satisfied the multiple targets of high crush force, low stack-up (high crush efficiency), and reduced mass.
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Zhao, Qishen, Nan Hong, Dongmei Chen, and Wei Li. "Controlling Peeling Front Geometry in a Roll-to-Roll Thin Film Transfer Process." In ASME 2020 15th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/msec2020-8507.
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Abstract Mechanical peeling is becoming an important manufacturing process in areas such as transfer printing and two-dimensional (2D) materials fabrication. Existing research has demonstrated the potential of successful peeling in small-scale by hand or with a robotic system. However, to scale up the manufacturing process, a roll-to-roll continuous system is needed. It is generally understood that the peeling front characteristics, including peeling angles, speed, and tension, are critical to the quality of the peeling process. In a roll-to-roll setting, controlling these characteristics becomes challenging since there are fewer degrees of freedom in the control design, and the complex relationship among the process parameters. In this study, a system model of a roll-to-roll peeling process is developed and a feedback controller to maintain the desired system performance is proposed. The control method is demonstrated with both numerical simulation and experimental results. It is shown that with the proposed control scheme, desired peeling front geometry can be achieved.
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STAAL, JEROEN, BARIS CAGLAR, and VÉRONIQUE MICHAUD. "RADICAL INDUCED CATIONIC FRONTAL POLYMERIZATION FOR RAPID OUT-OF-AUTOCLAVE PROCESSING OF CARBON FIBER REINFORCED POLYMERS." In Proceedings for the American Society for Composites-Thirty Seventh Technical Conference. Destech Publications, Inc., 2022. http://dx.doi.org/10.12783/asc37/36384.
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Radical induced cationic frontal polymerization (RICFP) is considered as a promising method for processing of fiber reinforced polymers (FRPs). Optimization of the local heat flow is required to pave the way for its adaptation to an industrial processing method. In this work we present an overview on the role of the mold design on the frontal polymerization characteristics and resulting chemical properties. Mold properties were found of significant influence on the front characteristics. Highly insulating molds allowed for the highest front temperatures and velocities while consequent delayed cooling is suggested beneficial for the monomer conversion in neat polymer and FRP systems. An optimized mold configuration was subsequently used for FRP production, allowing for self-sustaining RICFP in FRPs with fiber volume fractions (Vfs) up to 45.8%. A processing window was moreover defined relating the Vf and required heat generation to the potential formation of a self-sustaining or supported front.
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Zhang, SongAn, Qing Zhou, and Yong Xia. "Influence of Wheels on Frontal Crash Response of Small Lightweight Electric Vehicle." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-50699.
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For vehicle frontal crash, the front wheels may affect impact load transfer and load path, and to some extent, the tire deformation may contribute to crash energy absorption. The effects would be especially prominent when it comes to the cases of micro car, offset crash and electric car. For a micro or small car, the front compartment space is small and the wheels are relatively large, and so the wheel’s role on transferring impact load to the A-pillar and the rocker is more significant and the energy absorbed by the tire deformation contributes to a relatively large portion. Moreover, in the case of an offset or small overlap collision, the wheel impacted is apparently engaged at a deeper level than that in full frontal crash. For an electric car when its electric motor is positioned in the rear of the car, the front compartment does not have space-taking engine and so the structural deformation and space use are more affected by the wheels. In this paper, by finite element simulations using a small lightweight electric vehicle (SLEV) model, the above-mentioned aspects are studied. The model has no complex components, and therefore is suitable for parametric study. The influence of the front wheels on the impact load transfer and the energy absorbed by the tire deformation are analyzed. Also front crash results of SLEV are compared with Yaris to show how front wheels affect load path in crash. The results show that the influence of wheels on frontal crash response of small lightweight electric vehicles should not be ignored and should be an integral part of crash safety design.
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He, Longting, and Chung Law. "The role of hydrodynamic instability in detonation fronts." In 37th Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1999. http://dx.doi.org/10.2514/6.1999-971.
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Feng, Zhengkun, and Henri Champliaud. "Modeling and Simulation of Mecano-Welding Process for Cylinders." In ASME 2012 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/detc2012-70337.
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Pyramidal three-roll bending is widely used in manufacture due to its simple configuration and advantage for thick plate roll bending. However, there remain two planar zones near the front and rear ends of the bent shape. A mecano-welding process which provides improved circularity of the bent shape is proposed in this paper. This process includes three sub-processes: the first sub-process is the roll bending from a plate with cylindrical rolls; the second sub-process is the gas metal arc-welding process used to join the gap of the bent tubular section; the third sub-process is the rerun roll bending of the welded shape. Results of the numerical simulation of the first two sub-processes under the well-known ANSYS and ANSYS/LS-DYNA environment are reported. The bent shape after the first roll bending, the distributions of the temperature and residual stress after the welding are illustrated and discussed.
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Feng, Zhengkun, and Henri Champliaud. "Numerical Simulation of Mecano-Welding Process for Cylinder Manufacturing." In ASME 2012 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/pvp2012-78071.
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Pyramidal three-roll bending has the advantage of simple configuration and is widely used in manufacture. However, the bent shape has two planar zones near the front and rear ends. This paper proposes the modeling of the mecano-welding process which provides improved circularity of the bent shape. This process includes three sub-processes: the first sub-process is the roll bending from a plate with cylindrical rolls, the second sub-process which is the gas metal arc-welding process used to join the gap of the bent tubular section, and the third sub-process is the rerun roll bending of the welded shape. Results of the simulation of the first two sub-processes under the well-known ANSYS and ANSYS/LS-DYNA environment are reported. The bent shape after the first roll bending, the distributions of the temperature and residual stress after the welding are illustrated.
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"Front cover." In 2015 Conference on Raising Awareness for the Societal and Environmental Role of Engineering and (Re)Training Engineers for Participatory Design (Engineering4Society). IEEE, 2015. http://dx.doi.org/10.1109/engineering4society.2015.7177888.
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Kamiya, Kensaku. "Role of electric field curvature in the formation of edge transport barrier." In FRONT-RUNNERS’ SYMPOSIUM ON PLASMA PHYSICS IN HONOR OF PROFESSORS KIMITAKA ITOH AND SANAE-I. ITOH. Author(s), 2018. http://dx.doi.org/10.1063/1.5048714.
Full textReports on the topic "Roll fronts"
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Bru Muñoz, María. The forgotten lender: the role of multilateral lenders in sovereign debt and default. Madrid: Banco de España, January 2023. http://dx.doi.org/10.53479/25026.
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The role of multilateral lenders in sovereign default has been traditionally overlooked by the literature. However, these creditors represent a significant share of lending to emerging markets and feature very distinct characteristics, such as lower interest rates and seniority. By including these creditors in a traditional DSGE model of sovereign default, I reproduce the high debt levels found in the data while maintaining default probabilities within realistic values. Additionally, I am able to analyze the role of multilateral debt in emerging economies. Multilateral loans complement private financing and reduce the incompleteness of international financial markets. Also, multilateral funding acts as an insurance mechanism in bad times, providing countries with some degree of consumption smoothing, opposite to the role of front-loading consumption fulfilled by private financing.
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Lin, Yuh-Lang, Michael L. Kaplan, and Steven E. Koch. A New Theory for Diabatically-Induced Along-Stream Jet/Front Formation and Its Role in Severe Weather. Fort Belvoir, VA: Defense Technical Information Center, April 1998. http://dx.doi.org/10.21236/ada345552.
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Näslund-Hadley, Emma, Michelle Koussa, and Juan Manuel Hernández. Skills for Life: Stress and Brain Development in Early Childhood. Inter-American Development Bank, April 2021. http://dx.doi.org/10.18235/0003205.
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Learning to cope with disappointments and overcoming obstacles is part of growing up. By conquering some challenges, children develop resilience. Such normal stressors may include initiating a new activity or separation from parents during preschool hours. However, when the challenges in early childhood are intensified by important stressors happening outside their own lives, they may start to worry about the safety of themselves and their families. This may cause chronic stress, which interferes with their emotional, cognitive, and social development. In developing country contexts, it is especially hard to capture promptly the effects of stressors related to the COVID-19 pandemic on childrens cognitive and socioemotional development. In this note, we draw on the literature on the effect of stress on brain development and examine data from a recent survey of households with young children carried out in four Latin American countries to offer suggestions for policy responses. We suggest that early childhood and education systems play a decisive role in assessing and addressing childrens mental health needs. In the absence of forceful policy responses on multiple fronts, the mental health outcomes may become lasting.
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Miller, Eric T. Achievements and Challenges of Trade Capacity Building: A Practitioner's Analysis of the CAFTA Process and its Lessons for the Multilateral System. Inter-American Development Bank, October 2005. http://dx.doi.org/10.18235/0011013.
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In policy circles and intellectual centers throughout the world, there is considerable debate on how to make globalization "work" for smaller, poorer, and otherwise disadvantaged countries. The challenges and potential solutions have manifested themselves in a myriad of ways, from the declarations of the Monterrey Summit on Trade and Development to policy papers on reform of the "global financial architecture". On the trade front, the World Trade Organization (WTO) launched the Doha Development Agenda in Qatar in November 2001, which sought, among other things, to give the challenges of capacity and "systemic fairness" a central role in the policy discussion. Differing levels of trade capacity and the attendant consequences have also become issues in various regional trade initiatives, particularly in the Americas. Developing countries are quite correct in pointing out that the quantity of non-reimbursable resources relative the countries¿ needs is presently very small. The great challenge in the years ahead is to find efficient ways to close this gap. Undoubtedly, the institutional and governmental partners that have participated as donors in the IF and CAFTA processes will have an important role to play.
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Lever, James, Emily Asenath-Smith, Susan Taylor, and Austin Lines. Assessing the mechanisms thought to govern ice and snow friction and their interplay with substrate brittle behavior. Engineer Research and Development Center (U.S.), December 2021. http://dx.doi.org/10.21079/1168142742.
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Sliding friction on ice and snow is characteristically low at temperatures common on Earth’s surface. This slipperiness underlies efficient sleds, winter sports, and the need for specialized tires. Friction can also play micro-mechanical role affecting ice compressive and crushing strengths. Researchers have proposed several mechanisms thought to govern ice and snow friction, but directly validating the underlying mechanics has been difficult. This may be changing, as instruments capable of micro-scale measurements and imaging are now being brought to bear on friction studies. Nevertheless, given the broad regimes of practical interest (interaction length, temperature, speed, pressure, slider properties, etc.), it may be unrealistic to expect that a single mechanism accounts for why ice and snow are slippery. Because bulk ice, and the ice grains that constitute snow, are solids near their melting point at terrestrial temperatures, most research has focused on whether a lubricating water film forms at the interface with a slider. However, ice is extremely brittle, and dry-contact abrasion and wear at the front of sliders could prevent or delay a transition to lubricated contact. Also, water is a poor lubricant, and lubricating films thick enough to separate surface asperities may not form for many systems of interest. This article aims to assess our knowledge of the mechanics underlying ice and snow friction.
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O’Brien, Tom, Deanna Matsumoto, Diana Sanchez, Caitlin Mace, Elizabeth Warren, Eleni Hala, and Tyler Reeb. Southern California Regional Workforce Development Needs Assessment for the Transportation and Supply Chain Industry Sectors. Mineta Transportation Institute, October 2020. http://dx.doi.org/10.31979/mti.2020.1921.
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COVID-19 brought the public’s attention to the critical value of transportation and supply chain workers as lifelines to access food and other supplies. This report examines essential job skills required of the middle-skill workforce (workers with more than a high school degree, but less than a four-year college degree). Many of these middle-skill transportation and supply chain jobs are what the Federal Reserve Bank defines as “opportunity occupations” -- jobs that pay above median wages and can be accessible to those without a four-year college degree. This report lays out the complex landscape of selected technological disruptions of the supply chain to understand the new workforce needs of these middle-skill workers, followed by competencies identified by industry. With workplace social distancing policies, logistics organizations now rely heavily on data management and analysis for their operations. All rungs of employees, including warehouse workers and truck drivers, require digital skills to use mobile devices, sensors, and dashboards, among other applications. Workforce training requires a focus on data, problem solving, connectivity, and collaboration. Industry partners identified key workforce competencies required in digital literacy, data management, front/back office jobs, and in operations and maintenance. Education and training providers identified strategies to effectively develop workforce development programs. This report concludes with an exploration of the role of Institutes of Higher Education in delivering effective workforce education and training programs that reimagine how to frame programs to be customizable, easily accessible, and relevant.
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Gregow, Hilppa, Antti Mäkelä, Heikki Tuomenvirta, Sirkku Juhola, Janina Käyhkö, Adriaan Perrels, Eeva Kuntsi-Reunanen, et al. Ilmastonmuutokseen sopeutumisen ohjauskeinot, kustannukset ja alueelliset ulottuvuudet. Suomen ilmastopaneeli, 2021. http://dx.doi.org/10.31885/9789527457047.
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The new EU strategy on adaptation to climate change highlights the urgency of adaptation measures while bringing forth adaptation as vitally important as a response to climate change as mitigation. In order to provide information on how adaptation to climate change has been promoted in Finland and what calls for attention next, we have compiled a comprehensive information package focusing on the following themes: adaptation policy, impacts of climate change including economic impacts, regional adaptation strategies, climate and flood risks in regions and sea areas, and the availability of scientific data. This report consists of two parts. Part 1 of the report examines the work carried out on adaptation in Finland and internationally since 2005, emphasising the directions and priorities of recent research results. The possibilities of adaptation governance are examined through examples, such as how adaptations steering is organised in of the United Kingdom. We also examine other examples and describe the Canadian Climate Change Adaptation Platform (CCAP) model. We apply current information to describe the economic impacts of climate change and highlight the related needs for further information. With regard to regional climate strategy work, we examine the status of adaptation plans by region and the status of the Sámi in national adaptation work. In part 2 of the report, we have collected information on the temporal and local impacts of climate change and compiled extensive tables on changes in weather, climate and marine factors for each of Finland's current regions, the autonomous Åland Islands and five sea areas, the eastern Gulf of Finland, the western Gulf of Finland, the Archipelago Sea, the Bothnian Sea and the Bay of Bothnia. As regards changes in weather and climate factors, the changes already observed in 1991-2020 are examined compared to 1981-2010 and future changes until 2050 are described. For weather and climate factors, we examine average temperature, precipitation, thermal season duration, highest and lowest temperatures per day, the number of frost days, the depth and prevalence of snow, the intensity of heavy rainfall, relative humidity, wind speed, and the amount of frost per season (winter, spring, summer, autumn). Flood risks, i.e. water system floods, run-off water floods and sea water floods, are discussed from the perspective of catchment areas by region. The impacts of floods on the sea in terms of pollution are also assessed by sea area, especially for coastal areas. With regard to marine change factors, we examine surface temperature, salinity, medium water level, sea flood risk, waves, and sea ice. We also describe combined risks towards sea areas. With this report, we demonstrate what is known about climate change adaptation, what is not, and what calls for particular attention. The results can be utilised to strengthen Finland's climate policy so that the implementation of climate change adaptation is strengthened alongside climate change mitigation efforts. In practice, the report serves the reform of the National Climate Change Adaptation Plan and the development of steering measures for adaptation to climate change both nationally and regionally. Due to its scale, the report also serves e.g. the United Nations’ aim of protecting marine life in the Baltic Sea and the national implementation of the EU strategy for adaptation to climate change. As a whole, the implementation of adaptation policy in Finland must be speeded up swiftly in order to achieve the objectives set and ensure sufficient progress in adaptation in different sectors. The development of binding regulation and the systematic evaluation, monitoring and support of voluntary measures play a key role.
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Yatsymirska, Mariya. Мова війни і «контрнаступальна» лексика у стислих медійних текстах. Ivan Franko National University of Lviv, March 2023. http://dx.doi.org/10.30970/vjo.2023.52-53.11742.
Full textAbstract:
The article examines the language of the russian-ukrainian war of the 21st century based on the materials of compressed media texts; the role of political narratives and psychological-emotional markers in the creation of new lexemes is clarified; the verbal expression of forecasts of ukrainian and foreign analysts regarding the course of hostilities on the territory of Ukraine is shown. Compressed media texts reflect the main meanings of the language of the russian-ukrainian war in relation to the surrounding world. First of all, the media vocabulary was supplemented with neologisms – aggressive and sad: “rashism”, “denazification”, “katsapstan”, “orks”, “rusnia”, “kremlins”, “parebrik”, “in the swamps”, “nuclear dictator”, “putinism”, “two hundred” and others. Numerals acquired new expressive and evaluative meanings: “200s” (dead), “300s” (wounded), “400s” (russian military personnel who filed reports for termination of the contract), “500s” (hopelessly drunk russian soldiers, alcoholics who are unable to perform combat tasks). The language of war intensified the slogans of the struggle for state independence and people’s freedom. The scope of the greeting “Glory to Ukraine! – Glory to Heroes!”. New official holidays have appeared in the history of Ukraine since 2014: “Heroes of the Heavenly Hundred” Day (February 20), “Ukrainian Volunteer Day” (March 14), “Defenders and Defenders of Ukraine Day” (October 14), “Volunteer Day” (5 December). As you know, the professional holiday of the military is the Day of the Armed Forces of Ukraine” (December 6). A special style is characteristic of media texts on military topics: “Iron Force of Ukraine” (Iron Force of Ukraine), “digitize the Army” (for effective simulation of military operations); “grain corridor” (export of Ukrainian grain to African and European countries); “don’t let Ukraine lose” (the position of the Allies at the first stage of the war), “Ukraine must win!” (the position of the Allies in the second stage of the war); “in the Russian-Ukrainian war, the thinking of the 19th century collided with the thinking of the 21st century”, “a politician is a person who understands time” (Grigori Yavlinskyy, Russian oppositionist); “aggressive neutrality” (about Turkey’s position); “in Russia”, “there, in the swamps” (in Russia), “weak, inadequate evil” (about Russia), “behind the fence”; “a great reset of the world order”; “technology of military creativity”; “they are not Russian and not Ukrainian, they are Soviet”, “people without mentality”, “in Ukraine and without Ukraine” (Vitaly Portnikov about a separate category of Russian-speaking citizens in Ukraine); “information bed of Ukraine” (about combat operations on the front line; “when a descendant asks me what I did in those terrifying moments, I will know what to answer. At the very least, I did not stand aside” (opinion of a Ukrainian fighter). Compressed in media texts is implemented in the headline, note, infographic, chronicle, digest, help, caption for photos, blitz poll, interview, short articles, caricature, visual text, commercial, etc. Researchers add “nominative-representative text (business card text, titles of sections, pages, names of presenters, etc.) to concise media texts for a functional and pragmatic purpose.” accent text (quote, key idea); text-navigator (content, news feed, indication of movement or time); chronotope”. A specific linguistic phenomenon known as “language compression” is widespread in media texts. Language compression is the art of minimization; attention is focused on the main, the most essential, everything secondary is filtered out. Compression uses words succinctly and sparingly to convey the meaning as much as possible. For example, the headline “Racism. What is the essence of the new ideology of the Russian occupiers?”. The note briefly explains the meaning of this concept and explains the difference from “nazism” and “fascism”. Key words: compressed media text, language compression, language of war, emotional markers, expressive neologisms, political journalism.
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Aas, Randi Wågø, Mikkel Magnus Thørrisen, Hildegunn Sagvaag, Lise Haveraaen, and Åsa Sjøgren. Alkoholbruk og alkoholkultur i en transportbedrift: En case-rapport fra forskningsprosjektet WIRUS. University of Stavanger, 2016. http://dx.doi.org/10.31265/usps.212.
Full textAbstract:
Nesten ni av ti arbeidstakere drikker alkohol. Dette blir ofte forklart med alle de positive aspektene bruk av alkohol har i sosiale sammenhenger. En kartlegging utført av Statistisk sentralbyrå viser imidlertid at 17 prosent av befolkningen har et drikkemønster som kan betegnes som risikofylt (Halkjelsvik & Storvoll, 2014). Økt alkoholkonsum, herunder også arbeidsrelatert alkoholkonsum, henger blant annet sammen med økt tilgjengelighet til alkohol (Frøyland, 2005). Alkoholkonsum på et risikofylt nivå er forbundet med sosiale, medisinske, jobbrelaterte og økonomiske problemstillinger (Babor, Higgins-Biddle, Saunders & Monteiro, 2001). Det er vanskelig å gi et klart svar på hvor grensen for risikofylt drikking går. Grenseverdier på 14 alkoholenheter1 pr. uke for kvinner og 21 enheter pr. uke for menn har blitt foreslått (Fauske, 1993). Babor mfl. (2001) har fremhevet at såkalt "lavrisikodrikking" innebærer maksimalt 20 gram alkohol pr. dag maksimalt 5 dager i uken. Det amerikanske National Institute on Alcohol Abuse and Alcoholism (2016) understreker at grenseverdien for risikodrikking går ved 7 enheter pr. uke (og maksimalt 3 enheter på én dag) for kvinner og ved 14 enheter pr. uke (og maksimalt 4 enheter på én dag) for menn. Likevel vil slike grenseverdier alltid være kulturspesifikke og individuelle. I Norge har man funnet det hensiktsmessig å operere med verdier på 8 alkoholenheter pr. uke for kvinner og 13 enheter pr. uke for menn (Nesvåg & Lie, 2004). Forskning har vist at det er behov for å kartlegge mer enn bare antall alkoholenheter over tid for å vite noe om reell risikodrikking. Eksempelvis vil forhold som hvor mye en drikker ved hver situasjon kunne medføre mer negative konsekvenser for sykefravær enn hvor mye en typisk drikker over en gitt periode (Bacharach, Bamberger & Biron, 2010). Dette kan forklares ved at helsekonsekvenser av høyt gjennomsnittsforbruk først viser seg over tid, mens episoder med stordrikking (såkalt binge-drikking der en drikker store mengder alkohol ved én og samme anledning, ofte målt som >6 enheter) gjerne medfører midlertidige funksjonsnedsettelser (eksempelvis "fyllesyke") som kan resultere i sykefravær (Bacharach mfl., 2010; Salonsalmi, Laaksonen, Lahlema & Rahkonen, 2009) eller sykenærvær, dvs. å være på jobben uten å kunne yte som normalt. Individuelle forskjeller vil også spille en rolle med hensyn til hva som er risikofylt drikking. Det er individuelt hvor mye en tåler, og andre aspekter ved livsstilen, for eksempel om en er fysisk aktiv, vil kunne påvirke hvor mye en kan drikke før negative konsekvenser inntreffer. For enkelte grupper vil ethvert alkoholinntak kunne betraktes som risikofylt. Dette gjelder for eksempel: (1) personer som skal kjøre bil eller håndtere maskiner/verktøy, (2) personer som bruker medisiner som interagerer med alkohol, (3) personer som har en medisinsk tilstand som kan forverres av alkohol, og (4) personer som er gravide (National Institute on Alcohol Abuse and Alcoholism, 2016). I Norge drikkes det lite i direkte arbeidssituasjoner, men alkoholbruk relatert til arbeidssammenhenger hevdes å være utbredt (Frøyland, 2005). Sammenkomster som inkluderer alkohol foregår da utenfor primærarbeidstiden, men i regi av arbeidsplassen, kunder/klienter eller på initiativ fra kollegaer. Bruk av alkohol skjer dermed i gråsoner mellom arbeid og fritid. Nesvåg (2005) fant at 23 prosent av det samlede alkoholkonsumet blant et utvalg ansatte i privat norsk næringsliv var arbeidsrelatert. Flere studier har pekt på at ansatte, både på ledernivå og medarbeidernivå, har positive forventninger til jobbrelatert alkoholbruk, herunder forventninger om at alkohol er en effektiv strategi for å mestre arbeidsbelastninger og at alkohol bidrar til å skape gode fellesskap og sosiale relasjoner (Cooper, Russell & Frone, 1990; Henderson, Hutcheson & Davies, 1996). Normer og forventninger utvikles og formes i relasjonelt samspill, blant annet på arbeidsplassen (Kjærheim, Mykletun, Aasland, Haldorsen & Andersen, 1995) og disse normene og forventningene påvirker ansattes alkoholvaner (Ames & Janes, 1992). Ansattes alkoholnormer og –forventninger kan således betraktes som uttrykk for en felles kultur på arbeidsplassen, som i større eller mindre grad kan gjenspeiles i de ansattes alkoholbruk. Tradisjonelt sett har det vært gruppen med store alkoholproblemer som har fått tilbud og oppmerksomhet gjennom arbeidsplassens helse-, miljø- og sikkerhetsarbeid. Her har man i de senere årene sett en endring i retning av økt fokus på den betydelig større gruppen som drikker risikofylt. Dette er bakgrunnen for prosjektet WIRUS, som er finansiert av Helsedirektoratet. I prosjektet deltar blant annet en privat transportbedrift. Denne rapporten er en presentasjon av denne bedriftens resultater fra fire av temaene som inngår i WIRUS-studien: (1) alkoholbruk, (2) arbeidsrelaterte alkoholnormer, (3) forventninger til alkoholbruk, og (4) situasjoner tilknyttet den aktuelle bedriften der ansatte eksponeres for alkohol.
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Thørrisen, Mikkel Magnus, Hildegunn Sagvaag, Lisebet Skeie Skarpaas, Lise Haveraaen, and Randi Wågø Aas. Alkoholbruk og alkoholkultur i et offentlig myndighetsorgan: En case-rapport fra forskningsprosjektet WIRUS. University of Stavanger, June 2016. http://dx.doi.org/10.31265/usps.214.
Full textAbstract:
Nesten ni av ti arbeidstakere drikker alkohol. Dette blir ofte forklart med alle de positive aspektene bruk av alkohol har i sosiale sammenhenger. En kartlegging utført av Statistisk sentralbyrå viser imidlertid at 17 prosent av befolkningen har et drikkemønster som kan betegnes som risikofylt (Halkjelsvik & Storvoll, 2014). Økt alkoholkonsum, herunder også arbeidsrelatert alkoholkonsum, henger blant annet sammen med økt tilgjengelighet til alkohol (Frøyland, 2005). Alkoholkonsum på et risikofylt nivå er forbundet med sosiale, medisinske, jobbrelaterte og økonomiske problemstillinger (Babor, Higgins-Biddle, Saunders & Monteiro, 2001). Det er vanskelig å gi et klart svar på hvor grensen for risikofylt drikking går. Grenseverdier på 14 alkoholenheter[1] pr. uke for kvinner og 21 enheter pr. uke for menn har blitt foreslått (Fauske, 1993). Babor mfl. (2001) har fremhevet at såkalt "lavrisikodrikking" innebærer maksimalt 20 gram alkohol pr. dag maksimalt 5 dager i uken. Det amerikanske National Institute on Alcohol Abuse and Alcoholism (2016) understreker at grenseverdien for risikodrikking går ved 7 enheter pr. uke (og maksimalt 3 enheter på én dag) for kvinner og ved 14 enheter pr. uke (og maksimalt 4 enheter på én dag) for menn. Likevel vil slike grenseverdier alltid være kulturspesifikke og individuelle. I Norge har man funnet det hensiktsmessig å operere med verdier på 8 alkoholenheter pr. uke for kvinner og 13 enheter pr. uke for menn (Nesvåg & Lie, 2004). Forskning har vist at det er behov for å kartlegge mer enn bare antall alkoholenheter over tid for å vite noe om reell risikodrikking. Eksempelvis vil forhold som hvor mye en drikker ved hver situasjon kunne medføre mer negative konsekvenser for sykefravær enn hvor mye en typisk drikker over en gitt periode (Bacharach, Bamberger & Biron, 2010). Dette kan forklares ved at helsekonsekvenser av høyt gjennomsnittsforbruk først viser seg over tid, mens episoder med stordrikking (såkalt binge-drikking der en drikker store mengder alkohol ved én og samme anledning) gjerne medfører midlertidige funksjonsnedsettelser (eksempelvis "fyllesyke") som kan resultere i sykefravær (Bacharach mfl., 2010; Salonsalmi, Laaksonen, Lahlema & Rahkonen, 2009) eller sykenærvær, dvs. å være på jobben uten å kunne yte som normalt. Individuelle forskjeller vil også spille en rolle med hensyn til hva som er risikofylt drikking. Det er individuelt hvor mye en tåler, og andre aspekter ved livsstilen, for eksempel om en er fysisk aktiv, vil kunne påvirke hvor mye en kan drikke før negative konsekvenser inntreffer. For enkelte grupper vil ethvert alkoholinntak kunne betraktes som risikofylt. Dette gjelder for eksempel: (1) personer som skal kjøre bil eller håndtere maskiner/verktøy, (2) personer som bruker medisiner som interagerer med alkohol, (3) personer som har en medisinsk tilstand som kan forverres av alkohol, og (4) personer som er gravide (National Institute on Alcohol Abuse and Alcoholism, 2016). I Norge drikkes det lite i direkte arbeidssituasjoner, men alkoholbruk relatert til arbeidssammenhenger hevdes å være utbredt (Frøyland, 2005). Sammenkomster som inkluderer alkohol foregår da utenfor primærarbeidstiden, men i regi av arbeidsplassen, kunder/klienter eller på initiativ fra kollegaer. Bruk av alkohol skjer dermed i gråsoner mellom arbeid og fritid. Nesvåg (2005) fant at 23 prosent av det samlede alkoholkonsumet blant et utvalg ansatte i privat norsk næringsliv var arbeidsrelatert. Flere studier har pekt på at ansatte, både på ledernivå og medarbeidernivå, har positive forventninger til jobbrelatert alkoholbruk, herunder forventninger om at alkohol er en effektiv strategi for å mestre arbeidsbelastninger og at alkohol bidrar til å skape gode fellesskap og sosiale relasjoner (Cooper, Russell & Frone, 1990; Henderson, Hutcheson & Davies, 1996). Normer og forventninger utvikles og formes i relasjonelt samspill, blant annet på arbeidsplassen (Kjærheim, Mykletun, Aasland, Haldorsen & Andersen, 1995) og disse normene og forventningene påvirker ansattes alkoholvaner (Ames & Janes, 1992). Ansattes alkoholnormer og –forventninger kan således betraktes som uttrykk for en felles kultur på arbeidsplassen, som i større eller mindre grad kan gjenspeiles i de ansattes alkoholbruk. Tradisjonelt sett har det vært gruppen med store alkoholproblemer som har fått tilbud og oppmerksomhet gjennom arbeidsplassens helse-, miljø- og sikkerhetsarbeid. Her har man i de senere årene sett en endring i retning av økt fokus på den betydelig større gruppen som drikker risikofylt. Dette er bakgrunnen for prosjektet WIRUS, som er finansiert av Helsedirektoratet. I prosjektet deltar blant annet et offentlig forvaltningsorgan. Denne rapporten er en presentasjon av denne bedriftens resultater fra fire av områdene som inngår i WIRUS-studien: (1) alkoholbruk, (2) arbeidsrelaterte alkoholnormer, (3) forventninger til alkoholbruk, og (4) situasjoner tilknyttet den aktuelle bedriften der ansatte eksponeres for alkohol.