Academic literature on the topic 'Tilted Linear Smoother'
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Journal articles on the topic "Tilted Linear Smoother"
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Ivers, D. J. "Tilted incompressible Coriolis modes in spheroids." Journal of Fluid Mechanics 833 (November 2, 2017): 131–63. http://dx.doi.org/10.1017/jfm.2017.669.
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The incompressible flow of a uniform fluid, which fills a rigid spheroid rotating about an arbitrary axis fixed in an inertial frame, is dominated at small Rossby and Ekman numbers by the rotation through the Coriolis force. The effects of rotation on the flow can be found by treating the Coriolis force modified by a pressure gradient as a skew-symmetric bounded linear operator $\boldsymbol{{\mathcal{C}}}$ acting on smooth inviscid incompressible flows in the spheroid. It is shown that the space of incompressible polynomial flows of degree $N$ or less in the spheroid is invariant under $\boldsymbol{{\mathcal{C}}}$ for any $N$. The skew symmetry of $\boldsymbol{{\mathcal{C}}}$ implies the Coriolis operator $\boldsymbol{{\mathcal{C}}}$ is non-defective for such flows with an orthogonal set of eigenmodes (inertial and geostrophic modes) which form a basis for the finite-dimensional space of spheroidal polynomial flows. The eigenmodes are tilted if the rotation axis is not aligned with the symmetry axis of the spheroid. The non-defective property of $\boldsymbol{{\mathcal{C}}}$ enables enumeration of the modes and proof of their completeness using the Weierstrass polynomial approximation theorem. The fundamental tool, which is required to establish invariance of spheroidal polynomial flows under $\boldsymbol{{\mathcal{C}}}$ and completeness of the Coriolis modes, is that the solution of the polynomial Poisson–Neumann problem, i.e. Poisson’s equation with Neumann boundary condition and polynomial data, in a spheroid is a polynomial. The Coriolis modes of degree one and all geostrophic modes are explicitly constructed. Only the modes of degree one have non-zero angular momentum in the boundary frame.
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Deng, Hongping, and Gordon I. Ogilvie. "Non-linear behaviour of warped discs around a central object with a quadrupole moment." Monthly Notices of the Royal Astronomical Society 512, no. 4 (March 30, 2022): 6078–92. http://dx.doi.org/10.1093/mnras/stac858.
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ABSTRACT The non-linear behaviour of low-viscosity warped discs is poorly understood. We verified a non-linear bending-wave theory, in which fluid columns undergo affine transformations, with direct 3D hydrodynamical simulations. We employed a second-order Godunov-type scheme, meshless finite mass (MFM), and also the smoothed particle hydrodynamics (SPH) method, with up to 128 million particles. For moderate non-linearity, MFM maintains well the steady non-linear warp predicted by the affine model for a tilted inviscid disc around a central object with a quadrupole moment. However, numerical dissipation in SPH is so severe that even a low-amplitude non-linear warp degrades at a resolution where MFM performs well. A low-amplitude arbitrary warp tends to evolve towards a non-linear steady state. However, no such state exists in our thin disc with an angular semithickness H/R = 0.02 when the outer tilt angle is beyond about 14°. The warp breaks tenuously and reconnects in adiabatic simulations, or breaks into distinct annuli in isothermal simulations. The breaking radius lies close to the location with the most extreme non-linear deformation. Parametric instability is captured only in our highest resolution simulation, leading to ring structures that may serve as incubators for planets around binaries.
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Sedyowati, Laksni, and Eko Indah Susanti. "Effects of Concrete Block Pavement on Flow Retardation Factor." Journal of Applied Engineering Sciences 7, no. 1 (May 1, 2017): 28–36. http://dx.doi.org/10.1515/jaes-2017-0004.
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AbstractSurface roughness has an important role in retarding the runoff velocity. The increase in paving blocks usage, particularly in urban areas, can change the surface roughness of the land. This study investigated the effects of four types of concrete block pavements (CBPs) in retarding the surface runoff velocity. Three design parameters based on CBP properties that considerably influenced the flow retardation were promoted. They were opening ratio (Or), void ratio (Vr) and straight channel ratio (Sr). A tilted plot equipped with a rainfall simulator was used to investigate the influence of surface slope and rainfall intensity to the flow on various CBPs. A modified dye tracing method in view was performed to monitor the surface flow velocity under various rainfall intensities. Flow retardation coefficient (Frd) were calculated based on velocity data on smooth pavement and on CBPs layer measured under the same slope and rainfall intensity. The results showed that flow retardation coefficient increased with an increase in openings ratio, rainfall intensity and surface slope. The relationship between flow retardation coefficient and all design parameters was expressed by a linear regression function. A further study is required to increase the accuracy of the model by modifying the regression function and increasing the variation of design parameters.
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Nandakumar, K., and H. J. Weinitschke. "A bifurcation study of mixed-convection heat transfer in horizontal ducts." Journal of Fluid Mechanics 231 (October 1991): 157–87. http://dx.doi.org/10.1017/s002211209100335x.
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The bifurcation structure of two-dimensional, pressure-driven flows through a horizontal, rectangular duet that is heated with a uniform flux in the axial direction and a uniform temperature around the periphery is examined. The solution structure of the flow in a square duct is determined for Grashof numbers (Gr) in the range of 0 to 106 using an arclength continuation scheme. The structure is much more complicated than reported earlier by Nandakumar, Masliyah & Law (1985). The primary branch with two limit points and a hysteresis behaviour between the two-and four-cell flow structure that was computed by Nandakumar et al. is confirmed. An additional symmetric solution branch, which is disconnected from the primary branch (or rather connected via an asymmetric solution branch), is found. This has a two-cell flow structure at one end, a four-cell flow structure at the other, and three limit points are located on the path. Two asymmetric solution branches emanating from symmetry-breaking bifurcation points are also found for a square duct. Thus a much richer solution structure is found with up to five solutions over certain ranges of Or. A determination of linear stability indicates that all two-dimensional solutions develop some form of unstable mode by the time Gr is increased to about 220000. In particular, the four-cell becomes unstable to asymmetric perturbations. The paths of the singular points are tracked with respect to variation in the aspect ratio using the fold-following algorithm. Transcritical points are found at aspect ratios of 1.408 and 1.456 respectively for Prandtl numbers Pr = 0.73 and 5. Above these aspect ratios the four-cell solution is no longer on the primary branch. Some of the fold curves are connected in such a way as to form a tilted cusp. When the channel cross-section is tilted even slightly (1°) with respect to the gravity vector, the bifurcation points unfold and the two-cell solution evolves smoothly as the Grashof number is increased. The four-cell solutions then become genuinely disconnected from the primary branch. The uniqueness range in Grashof number increases with increasing tilt, decreasing aspect ratio and decreasing Prandtl number.
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Xue, Jiao, Hanming Gu, and Chengguo Cai. "Model-based amplitude versus offset and azimuth inversion for estimating fracture parameters and fluid content." GEOPHYSICS 82, no. 2 (March 1, 2017): M1—M17. http://dx.doi.org/10.1190/geo2016-0196.1.
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The normal-to-shear fracture compliance ratio is commonly used as a fluid indicator. In the seismic frequency range, the fluid indicator lies between the values for isolated fluid-filled fractures and dry fractures, and it is not easy to discriminate the fluid content. Assuming that the fracture surfaces are smooth, we use [Formula: see text], with [Formula: see text] and [Formula: see text] representing the normal fracture weakness of the saturated and dry rock, to indicate fluid types, and to define a fluid influencing factor. The fluid influencing factor is sensitive to the fluid properties, the aspect ratio of the fractures, and the frequency. Conventionally, the amplitude versus offset and azimuth (AVOA) inversion is formulated in terms of the contrasts of the fracture weaknesses across the interface, assuming that the fractures are vertical with the same symmetry axis. We consider fractures with arbitrary azimuths, and develop a method to estimate fracture parameters from wide-azimuth seismic data. The proposed AVOA inversion algorithm is tested on real 3D prestack seismic data from the Tarim Basin, China, and the inverted fracture density show good agreement with well log data, except that there are some discrepancies for one of the fractured reservoir sections. The discrepancies can be ascribed to neglect of the dip angle for the tilted fractures and the conjugate fracture sets, and to the validity of the linear-slip model. The fractured reservoirs are expected to be liquid saturated, under the assumption of smooth fractures. Overall, the inverted fracture density and fluid influencing factor can be potentially used for better well planning in fractured reservoirs and quantitatively estimating the fluid effects.
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Dranyaev, S. B., M. N. Chatkin, and S. M. Koryavin. "Modeling the operation of a screw L-shaped knife of a tiller." Traktory i sel hozmashiny 84, no. 7 (July 15, 2017): 13–19. http://dx.doi.org/10.17816/0321-4443-66315.
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During the operation, standard L-shaped knives are exposed to various loads. The shape of the L-shaped knife blades does not meet the requirement of performing sliding cutting, which leads to an increase in the energy intensity of milling the soil. To ensure optimal cutting conditions without weed-covering and knife blocking, it is necessary that in any section of the blade (in the plane of rotation) the angle of its setting у (cutting) is constant. Therefore, the blade of the knife should be made on a screw line, which will ensure its smooth entry and sliding cutting when moving in the soil. The purpose of the study is to improve the quality and reduce the energy consumption of soil cultivation by selecting a rational angle for installing the blade and optimizing the parameters of the screwed L-shaped cutter blades. To study the work and the loading process of the screw L-shaped cutter knife, the finite element method was used from the APM FEM application library of the KOMPAS-3D system. The design of the knife was broken into elements to show their movements and deformations through the displacements of the boundary points (knots) of the element, then the nodal displacements, deformations and stresses were determined. In the course of the study, the dependence of the values of linear displacements and stress values was studied depending on the angle of installation of the knife blade (у = 35° ... 60°). The results of the study showed that as the angle of the blade was increased to у = 60 °, the total linear displacements decreased by 18 % reaching 0,6978 mm, compared to у = 35 ° (0,8455 mm) at a maximum load of 2000 N. The knife with an installation angle у = 60° has safety factor values higher than a knife with у = 35° for all load stages (500, 1000, 1500 and 2000 N). The screw knife with a large installation angle is most suitable for milling soil with slip, which is typical for sod processing. As a result of the research it was proposed to use knives with a screw working surface for milling the soil with high quality.
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TEMPELMANN, DAVID, ARDESHIR HANIFI, and DAN S. HENNINGSON. "Spatial optimal growth in three-dimensional boundary layers." Journal of Fluid Mechanics 646 (March 8, 2010): 5–37. http://dx.doi.org/10.1017/s0022112009993260.
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A parabolized set of linear equations is derived, which, in combination with the proposed solution procedure, allows for the study of both non-modal and modal disturbance growth in three-dimensional boundary layers. The method is applicable to disturbance waves whose lines of constant phase are closely aligned with the external streamline. Moreover, strongly growing disturbances may fall outside the scope of application. These equations are used in conjunction with a variational approach to compute optimal disturbances in Falkner–Skan–Cooke boundary layers subject to adverse and favourable pressure gradients. The disturbances associated with maximum energy growth initially take the form of streamwise vortices which are tilted against the mean crossflow shear. While travelling downstream these vortical structures rise into an upright position and evolve into bent streaks. The physical mechanism responsible for non-modal growth in three-dimensional boundary layers is therefore identified as a combination of the lift-up effect and the Orr mechanism. Optimal disturbances smoothly evolve into crossflow modes when entering the supercritical domain of the flow. Non-modal growth is thus found to initiate modal instabilities in three-dimensional boundary layers. Optimal growth is first studied for stationary disturbances. Influences of parameters such as sweep angle, spanwise wavenumber and position of inception are studied, and the initial optimal amplification of stationary crossflow modes because of non-modal growth is investigated. Finally, general disturbances are considered, and envelopes yielding the maximum growth at each position are computed. In general, substantial growth is already found upstream of the first neutral point. The computations show that at supercritical conditions, maximum growth of optimal disturbances in accelerated boundary layers can exceed the growth predicted for modal instabilities by several orders of magnitude.
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Rabinovich, Michael, Ziv Kizner, and Glenn Flierl. "Barotropic annular flows, vortices and waves on a beta cone." Journal of Fluid Mechanics 875 (July 18, 2019): 225–53. http://dx.doi.org/10.1017/jfm.2019.494.
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We consider two-dimensional quasi-geostrophic annular flows around a circular island with a radial offshore bottom slope. Since the conical bottom topography causes a certain beta effect, by analogy with the conventional beta plane we term our model a beta cone. Our focus is on the flows with zero total circulation, which are composed of two concentric rings of uniform potential vorticity (PV) attached to the island. The linear stability of such flows on a beta cone was investigated in a previous publication of ours. In the present paper, we study numerically the nonlinear evolution of weakly viscous flows, whose parameters are fitted so as to guarantee the highest instability of the azimuthal mode $m=1,\ldots ,6$. We study the production of vortices and Rossby waves due to the instability, consider the effect of waves on the emerging vortices and the interaction between the vortices. As in the flat-bottom case, at $m\geqslant 2$, the instability at weak bottom slopes normally leads to the emission of $m$ dipoles. However, a fundamental difference between the flat-bottom and beta-cone cases is observed in the trajectories of the dipoles as the latter recede from the island. When the flow is initially counterclockwise, the conical beta effect may force the dipoles to make a complete turn, come back to the island and rearrange in new couples that again leave the island and return. This quasi-periodic process gradually fades due to filamentation, wave radiation and viscous dissipation. Another possible outcome is symmetrical settling of $m$ dipoles in a circular orbit around the island, in which they move counterclockwise. This behaviour is reminiscent of the adaptation of strongly tilted beta-plane modons (dipoles) to the eastward movement. If the initial flow is clockwise, the emerged dipoles usually disintegrate, but sometimes, the orbital arrangement is possible. At a moderate slope, the evolution of an unstable flow, which is initially clockwise, may end up in the formation of a counterclockwise flow. At steeper slopes, a clockwise flow may transform into a quasi-stationary vortex multipole. When the slope is sufficiently steep, the topographic Rossby waves developing outside of the PV rings can smooth away the instability crests and troughs at the outer edge of the main flow, thus preventing the vortex production but allowing the formation of a new quasi-stationary pattern, a doubly connected coherent PV structure possessing $m$-fold symmetry. Such an $m$-fold pattern can be steady only if it rotates counterclockwise, otherwise it radiates Rossby waves and transforms eventually into a circularly symmetric flow.
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Rota, Franco. "Some Quot schemes in tilted hearts and moduli spaces of stable pairs." International Journal of Mathematics 32, no. 13 (October 18, 2021). http://dx.doi.org/10.1142/s0129167x21500981.
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For a smooth projective variety [Formula: see text], we study analogs of Quot schemes using hearts of non-standard [Formula: see text]-structures of [Formula: see text]. The technical framework uses families of [Formula: see text]-structures as studied in A. Bayer, M. Lahoz, E. Macrì, H. Nuer, A. Perry and P. Stellari, Stability conditions in families, preprint (2019), arXiv:1902.08184. We provide several examples and suggest possible directions of further investigation, as we reinterpret moduli spaces of stable pairs, in the sense of M. Thaddeus, Stable pairs, linear systems and the Verlinde formula, Invent. Math. 117(2) (1994) 317–353; D. Huybrechts and M. Lehn, Stable pairs on curves and surfaces, J. Algebraic Geom. 4(1) (1995) 67–104, as instances of Quot schemes.
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Imbol Nkwinkwa Njouodo, Arielle Stela, Mathieu Rouault, Noel Keenlyside, and Shunya Koseki. "Impact of the Agulhas Current on southern Africa precipitation: a modelling study." Journal of Climate, September 30, 2021, 1–50. http://dx.doi.org/10.1175/jcli-d-20-0627.1.
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AbstractThe Agulhas Current (AC) creates a sharp temperature gradient with the surrounding ocean, leading to a large turbulent flux of moisture from ocean to atmosphere. We use two simulations of the Weather Research and Forecasting (WRF) model to show the seasonal impact of the warm core of the AC on southern Africa precipitation. In one simulation the sea surface temperature (SST) of the AC is similar to satellite observations, while the second uses satellite SST observations spatially smoothed to reduce the temperature of the core of the AC by ~1.5°C. We show that decreasing the SST of the AC reduces the precipitation of the wettest seasons (austral summer and autumn) inland. Over the ocean, reducing the SST reduces precipitation, low-level wind convergence, SST and SLP Laplacian above the AC in all seasons, consistent with the pressure adjustment mechanism. Moreover, winter precipitation above the Current may be also related to increased latent flux. In summer and autumn, the AC SST reduction is also associated with decreased precipitation further inland (more than 1.5 mm/day), caused by an atmospheric circulation that decreases the horizontal moisture flux from the AC to South Africa. The reduction is also associated with higher geopotential height extending from the surface east and over the AC to the mid-troposphere over southeastern Africa. The westward tilted geopotential height is consistent with the linear response to shallow diabatic heating in midlatitudes. An identical mechanism occurs in spring but is weaker. Winter rainfall response is confined above the AC.
Book chapters on the topic "Tilted Linear Smoother"
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Rouai-Abidi, Besma, Sangkyu Kang, and Mongi Abidi. "A Fully Automated Active Shape Model for Segmentation and Tracking of Unknown Objects in a Cluttered Environment." In Advances in Image and Video Segmentation, 161–87. IGI Global, 2006. http://dx.doi.org/10.4018/978-1-59140-753-9.ch008.
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The segmentation of shapes is automated using a new objective function to deform and move a contour toward the actual shape. New profile modeling and optimization criterion to automatically find corresponding points are also applied for segmentation and tracking of people in cluttered backgrounds. The proposed framework utilizes a Pan-Tilt-Zoom (PTZ) camera and automatically performs the initial target acquisition through motion and color-based segmentation. Successful results are presented for within and between frame segmentation and tracking. This algorithm presents a major extension to the state of the art and the original active shape model (ASM) which was designed for known objects in smooth non-changing backgrounds and where the landmark points need to be manually picked off-line. This is a fully automated, real time ASM that deals with changing backgrounds and does not require prior knowledge of the object to be segmented and tracked.
Conference papers on the topic "Tilted Linear Smoother"
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Anandalakshmi, R., and Tanmay Basak. "Heat Flow Visualization for Natural Convection in Rhombic Enclosures: Bejan’s Heatline Approach." In ASME/JSME 2011 8th Thermal Engineering Joint Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajtec2011-44531.
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The phenomena of natural convection within a rhombic enclosure filled with air (Pr = 0.71) for (a) isothermally (case 1) and (b) non-isothermally (case 2) heated bottom walls with various aspect-ratios has been studied numerically. In all the cases, top horizontal wall is maintained adiabatic and side walls are maintained cold. Galerkin finite element method with penalty parameter is used to solve non-linear coupled partial differential equations for flow and temperature fields. Poisson equation of streamfunction and heatfunction is also solved using Galerkin method. Simulations are carried out over a range of Rayleigh numbers and numerical results are presented in terms of streamfunction, heatfunction and temperature contours. Streamlines are useful to visualize the fluid flow whereas heatlines are used to study the heat energy distribution within the rhombic cavity. Heatlines are further used to visualize the trajectories of heat flow and zones of high thermal mixing. At lower Ra, heatlines are smooth circular arcs with low magnitude streamfunctions and heatfunctions and thus the heat transfer is conduction dominant. Asymmetric flow is observed for all the cases due to geometrical asymmetry. As Ra increases, buoyant force starts dominating and the magnitudes of streamfunctions and heatfunctions are found to be greater due to enhanced convection effect. Heatlines are distorted greatly showing complex heat distribution inside the cavity. It is observed that primary heat circulation cell is larger for greater tilt angles and thus thermal mixing is high. Heat transfer rates are also studied via local and average Nusselt numbers as functions of Ra and Pr on bottom, left and right walls. Various quantitative and qualitative features of Nusselt numbers have also been explained based on heatlines.
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Holt, Rob, Fatima Al Darmaki, Jose Rodriguez Gonzalez, Paul F. Anderson, and Steve Adiletta. "Lessons Learnt Reprocessing a Noisy Onshore 3D Seismic Survey." In Abu Dhabi International Petroleum Exhibition & Conference. SPE, 2021. http://dx.doi.org/10.2118/207965-ms.
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Abstract An 1,100 km2 400-fold seismic survey was acquired over some of the largest sand dunes in UAE in 2007. Large sand dunes generate many challenges for seismic processing due to the irregular data acquisition, large statics caused by the significant difference between the sand and sabkha velocities, and a massive amount of reverberation noise that hides the signal in the data. Occidental and ADNOC Sour Gas reprocessed this survey from January 2019 to August 2020 to overcome the challenges of the strong sand dune noise. For the first time, it was processed through prestack depth migration (PSDM). The primary objectives of the reprocessing project were to get an accurate PSDM volume that tied all of the available well control data; and to derive as accurate seismic amplitudes as possible over the target reservoir interval from near to far offsets to enable elastic inversion for reservoir porosity and net-thickness prediction. Whilst the reprocessing project achieved the project objectives and generated good subsurface images, it did not run as smoothly as hoped, despite being processed by one of the premier multinational processing companies. The extremely large sand dunes, which are present across most of the survey area, created major imaging problems. Key technical lessons learnt during reprocessing included: (1) CRS errors occurred sporadically during acquisition, requiring correction; (2) the sand curve (Liner, 2008) worked well for sand dune static corrections for this data set; (3) near surface statics changed whilst the survey was acquired by up to 6 ms - each shot station needed to be corrected for these statics changes because the shot stations were acquired twice with a symmetric split recording spread; and (4) the contractor's standard post-migration processing sequence (gather flattening, radon, noise attenuation, stack) did not work well for this very noisy data set. Next time we work with similar data and require a high quality result, we know to double the estimated project timeline as every step in the processing sequence takes much longer than expected when the signal-to-noise ratio of the data is very low. The novelty of this work was that we obtained large improvements in the seismic stack by applying offline gather conditioning before calculating trim statics to optimally flatten the very noisy migrated offset vector tile (OVT) gathers, prior to running the final noise attenuation and stacking workflows. Without this offline gather conditioning, the trim statics workflow mostly aligned the noise and damaged the stack.