Articoli di riviste: "Hydrostatic models"

1

Hasegawa, Tatsuhiko. "Hydrostatic models of Bok globules". Astrophysics and Space Science 119, n. 1 (gennaio 1986): 151–54. http://dx.doi.org/10.1007/bf00648835.

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White, A. A., B. J. Hoskins, I. Roulstone e A. Staniforth. "Consistent approximate models of the global atmosphere: shallow, deep, hydrostatic, quasi-hydrostatic and non-hydrostatic". Quarterly Journal of the Royal Meteorological Society 131, n. 609 (1 luglio 2005): 2081–107. http://dx.doi.org/10.1256/qj.04.49.

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3

Gibbon, J. D., e D. D. Holm. "Extreme events in solutions of hydrostatic and non-hydrostatic climate models". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 369, n. 1939 (28 marzo 2011): 1156–79. http://dx.doi.org/10.1098/rsta.2010.0244.

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Initially, this paper reviews the mathematical issues surrounding hydrostatic primitive equations (HPEs) and non-hydrostatic primitive equations (NPEs) that have been used extensively in numerical weather prediction and climate modelling. A new impetus has been provided by a recent proof of the existence and uniqueness of solutions of viscous HPEs on a cylinder with Neumann-like boundary conditions on the top and bottom. In contrast, the regularity of solutions of NPEs remains an open question. With this HPE regularity result in mind, the second issue examined in this paper is whether extreme events are allowed to arise spontaneously in their solutions. Such events could include, for example, the sudden appearance and disappearance of locally intense fronts that do not involve deep convection. Analytical methods are used to show that for viscous HPEs, the creation of small-scale structures is allowed locally in space and time at sizes that scale inversely with the Reynolds number.

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Deupree, Robert G. "Multidimensional Hydrodynamic and Hydrostatic Stellar Models". Symposium - International Astronomical Union 215 (2004): 378–87. http://dx.doi.org/10.1017/s0074180900195919.

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Results for multidimensional stellar model simulations of both 2D and 3D hydrodynamic models and 2D stellar evolution sequences are presented. Simulations of the highly superadiabatic region of the solar convective region provide a good example of the current status and limitations of explicit 3D finite difference methods in stellar problems. Such simulations cannot be used for stellar cores, where the motion is expected to be well subsonic. The results of some 2D fully implcit hydrodynamic simulations of convective cores and shells are given for models with and without rotation, and their effects examined through fully 2D stellar evolution sequences. One effect of moderate to rapid rotation in convective cores is to alter the convective flow pattern so that convective eddies tend to line up parallel to the rotation axis. Rotation also appears to modestly reduce the amount of convective core overshooting, at least for intermediate mass models.

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Duffy, Dean G. "Hydrostatic Adjustment in Nonhydrostatic, Compressible Mesoscale Models". Monthly Weather Review 125, n. 12 (dicembre 1997): 3357–67. http://dx.doi.org/10.1175/1520-0493(1997)125<3357:haincm>2.0.co;2.

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6

Ascasibar, Y., A. C. Obreja e A. I. Díaz. "Hydrostatic photoionization models of the Orion Bar". Monthly Notices of the Royal Astronomical Society 416, n. 2 (11 luglio 2011): 1546–55. http://dx.doi.org/10.1111/j.1365-2966.2011.19151.x.

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7

Zingale, M., L. J. Dursi, J. ZuHone, A. C. Calder, B. Fryxell, T. Plewa, J. W. Truran et al. "Mapping Initial Hydrostatic Models in Godunov Codes". Astrophysical Journal Supplement Series 143, n. 2 (dicembre 2002): 539–65. http://dx.doi.org/10.1086/342754.

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8

Guerra, Jorge E., e Paul A. Ullrich. "A high-order staggered finite-element vertical discretization for non-hydrostatic atmospheric models". Geoscientific Model Development 9, n. 5 (1 giugno 2016): 2007–29. http://dx.doi.org/10.5194/gmd-9-2007-2016.

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Abstract. Atmospheric modeling systems require economical methods to solve the non-hydrostatic Euler equations. Two major differences between hydrostatic models and a full non-hydrostatic description lies in the vertical velocity tendency and numerical stiffness associated with sound waves. In this work we introduce a new arbitrary-order vertical discretization entitled the staggered nodal finite-element method (SNFEM). Our method uses a generalized discrete derivative that consistently combines the discontinuous Galerkin and spectral element methods on a staggered grid. Our combined method leverages the accurate wave propagation and conservation properties of spectral elements with staggered methods that eliminate stationary (2Δx) modes. Furthermore, high-order accuracy also eliminates the need for a reference state to maintain hydrostatic balance. In this work we demonstrate the use of high vertical order as a means of improving simulation quality at relatively coarse resolution. We choose a test case suite that spans the range of atmospheric flows from predominantly hydrostatic to nonlinear in the large-eddy regime. Our results show that there is a distinct benefit in using the high-order vertical coordinate at low resolutions with the same robust properties as the low-order alternative.

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Savoulides, N., K. S. Breuer, S. Jacobson e F. F. Ehrich. "Low-Order Models for Very Short Hybrid Gas Bearings". Journal of Tribology 123, n. 2 (16 giugno 2000): 368–75. http://dx.doi.org/10.1115/1.1308000.

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A low-order model was created to analyze a small-scale gas bearing with a diameter of 4.1 mm, designed to spin at 2.4 million rpm. Due to microfabrication constraints, the bearing lies outside the standard operating space and stable operation is a challenge. The model is constructed by reference to Newton’s second law for the rotor and employs stiffness and damping coefficients predicted by other models. At any operating point it is able to predict (1) whether the journal can sustain stable operation, and (2) the whirling frequency of the journal. Analysis shows that the best way to operate the bearing is in a hybrid mode where the bearing relies on hydrostatics at low speeds and hydrodynamics at high speeds. However, in transitioning from hydrostatic to hydrodynamic operation, the model shows that the bearing is prone to instability problems and great care must be taken in scheduling the bearing pressurization system in the course of accelerating through low and intermediate rotational speeds.

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Kållberg, P., e A. Montani. "A case study carried out with two different NWP systems". Natural Hazards and Earth System Sciences 6, n. 5 (4 settembre 2006): 755–60. http://dx.doi.org/10.5194/nhess-6-755-2006.

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Abstract. A model intercomparison between two atmospheric models, the non–hydrostatic Lokal Modell (LM) and the hydrostatic HIgh Resolution Limited Area Model (HIRLAM) is carried out for a one-week period, including a case of cyclogeneis leading to heavy precipitation over Northern Italy. The two models, very different in terms of data-assimilation and numerics, provide different results in terms of forecasts of surface fields. Opposite diurnal biases for the two models are found in terms of screen level temperatures. HIRLAM wind speed forecasts are too strong, while LM precipitation forecasts have larger extremes. The intercomparison exercise identifies some systematic differences in the weather products generated by the two systems and sheds some light on the biases of the two numerical weather prediction systems.

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11

Seroussi, H., M. Morlighem, E. Larour, E. Rignot e A. Khazendar. "Hydrostatic grounding line parameterization in ice sheet models". Cryosphere 8, n. 6 (17 novembre 2014): 2075–87. http://dx.doi.org/10.5194/tc-8-2075-2014.

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Abstract. Modeling of grounding line migration is essential to accurately simulate the behavior of marine ice sheets and investigate their stability. Here, we assess the sensitivity of numerical models to the parameterization of the grounding line position. We run the MISMIP3D benchmark experiments using the Ice Sheet System Model (ISSM) and a two-dimensional shelfy-stream approximation (SSA) model with different mesh resolutions and different sub-element parameterizations of grounding line position. Results show that different grounding line parameterizations lead to different steady state grounding line positions as well as different retreat/advance rates. Our simulations explain why some vertically depth-averaged model simulations deviate significantly from the vast majority of simulations based on SSA in the MISMIP3D benchmark. The results reveal that differences between simulations performed with and without sub-element parameterization are as large as those performed with different approximations of the stress balance equations in this configuration. They also demonstrate that the reversibility test is passed at relatively coarse resolution while much finer resolutions are needed to accurately capture the steady-state grounding line position. We conclude that fixed grid SSA models that do not employ such a parameterization should be avoided, as they do not provide accurate estimates of grounding line dynamics, even at high spatial resolution. For models that include sub-element grounding line parameterization, in the MISMIP3D configuration, a mesh resolution finer than 2 km should be employed.

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Seroussi, H., M. Morlighem, E. Larour, E. Rignot e A. Khazendar. "Hydrostatic grounding line parameterization in ice sheet models". Cryosphere Discussions 8, n. 3 (24 giugno 2014): 3335–65. http://dx.doi.org/10.5194/tcd-8-3335-2014.

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Abstract. Modeling of grounding line migration is essential to simulate accurately the behavior of marine ice sheets and investigate their stability. Here, we assess the sensitivity of numerical models to the parameterization of the grounding line position. We run the MISMIP3D benchmark experiments using a two-dimensional shelfy-stream approximation (SSA) model with different mesh resolutions and different sub-element parameterizations of grounding line position. Results show that different grounding line parameterizations lead to different steady state grounding line positions as well as different retreat/advance rates. Our simulations explain why some vertically depth-averaged model simulations exhibited behaviors similar to full-Stokes models in the MISMIP3D benchmark, while the vast majority of simulations based on SSA showed results deviating significantly from full-Stokes results. The results reveal that differences between simulations performed with and without sub-element parameterization are as large as those performed with different approximations of the stress balance equations and that the reversibility test can be passed at much lower resolutions than the steady-state grounding line position. We conclude that fixed grid models that do not employ such a parameterization should be avoided, as they do not provide accurate estimates of grounding line dynamics, even at high spatial resolution. For models that include sub-element grounding line parameterization, a mesh resolution lower than 2 km should be employed.

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van Putten, T., A. L. Watts, C. R. D'Angelo, M. G. Baring e C. Kouveliotou. "Models of hydrostatic magnetar atmospheres at high luminosities". Monthly Notices of the Royal Astronomical Society 434, n. 2 (12 luglio 2013): 1398–410. http://dx.doi.org/10.1093/mnras/stt1093.

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14

Keilegavlen, Eirik, e Jarle Berntsen. "Non-hydrostatic pressure in σ-coordinate ocean models". Ocean Modelling 28, n. 4 (gennaio 2009): 240–49. http://dx.doi.org/10.1016/j.ocemod.2009.02.006.

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15

Carroll, John J., Luis R-Mendez-Nu�ez e Saffet Tanrikulu. "Accurate pressure gradient calculations in hydrostatic atmospheric models". Boundary-Layer Meteorology 41, n. 1-4 (1987): 149–69. http://dx.doi.org/10.1007/bf00120437.

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16

Rõõm, Rein, Pedro M. A. Miranda e Alan J. Thorpe. "Filtered non-hydrostatic models in pressure-related coordinates". Quarterly Journal of the Royal Meteorological Society 127, n. 574 (aprile 2001): 1277–92. http://dx.doi.org/10.1002/qj.49712757408.

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17

Wedi, Nils P., e Piotr K. Smolarkiewicz. "A framework for testing global non-hydrostatic models". Quarterly Journal of the Royal Meteorological Society 135, n. 639 (gennaio 2009): 469–84. http://dx.doi.org/10.1002/qj.377.

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18

Fernández-Nieto, E. D., J. Garres-Díaz e P. Vigneaux. "Multilayer models for hydrostatic Herschel-Bulkley viscoplastic flows". Computers & Mathematics with Applications 139 (giugno 2023): 99–117. http://dx.doi.org/10.1016/j.camwa.2023.03.018.

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19

Jourdon, Anthony, e Dave A. May. "An efficient partial-differential-equation-based method to compute pressure boundary conditions in regional geodynamic models". Solid Earth 13, n. 6 (29 giugno 2022): 1107–25. http://dx.doi.org/10.5194/se-13-1107-2022.

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Abstract. Modelling the pressure in the Earth's interior is a common problem in Earth sciences. In this study we propose a method based on the conservation of the momentum of a fluid by using a hydrostatic scenario or a uniformly moving fluid to approximate the pressure. This results in a partial differential equation (PDE) that can be solved using classical numerical methods. In hydrostatic cases, the computed pressure is the lithostatic pressure. In non-hydrostatic cases, we show that this PDE-based approach better approximates the total pressure than the classical 1D depth-integrated approach. To illustrate the performance of this PDE-based formulation we present several hydrostatic and non-hydrostatic 2D models in which we compute the lithostatic pressure or an approximation of the total pressure, respectively. Moreover, we also present a 3D rift model that uses that approximated pressure as a time-dependent boundary condition to simulate far-field normal stresses. This model shows a high degree of non-cylindrical deformation, resulting from the stress boundary condition, that is accommodated by strike-slip shear zones. We compare the result of this numerical model with a traditional rift model employing free-slip boundary conditions to demonstrate the first-order implications of considering “open” boundary conditions in 3D thermo-mechanical rift models.

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Kuell, Volker, e Andreas Bott. "A hybrid convection scheme for use in non-hydrostatic numerical weather prediction models". Meteorologische Zeitschrift 17, n. 6 (9 dicembre 2008): 775–83. http://dx.doi.org/10.1127/0941-2948/2008/0342.

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21

Xu, Xiao Qiu, Jun Peng Shao, Xiao Dong Yang, Yan Qin Zhang, Xiao Dong Yu e Bing Wei Gao. "Simulation on Multi-Oil-Cavity and Multi-Oil-Pad Hydrostatic Bearings". Applied Mechanics and Materials 274 (gennaio 2013): 274–77. http://dx.doi.org/10.4028/www.scientific.net/amm.274.274.

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Taking multi-oil-cavity and multi-oil-pad hydrostatic bearings as studied projects, firstly make brief instructions for structure characteristics and working principal of hydraulic system; Then, build three-dimensional models of multi-oil-cavity and multi-oil-pad hydrostatic bearings respectively. Adopting finite volume method, oil film mesh is generated by universal finite analysis software CFD; then, carry on numerical simulations for pressure distribution and temperature distribution of the two studied hydrostatic thrust bearing under various viscosity, and make comparative analysis for difference between the two studied hydrostatic thrust bearing. Based on the analysis of numerical simulation results, the conclusions whether oil-return groove is set for hydrostatic bearing could be received. Simulation results reveal truly the influence of setting oil-return groove or not on hydrostatic thrust bearing, and improve structure design for hydrostatic thrust bearing.

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Okahata, Go, Shigeki Okuyama e Akinori Yui. "Numerical Study on Constant-Flow Hydrostatic Water Bearing for a Machine-Tool Table". Advanced Materials Research 325 (agosto 2011): 357–62. http://dx.doi.org/10.4028/www.scientific.net/amr.325.357.

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Precision machine tools using hydrostatic water bearings are superior to those using hydrostatic oil bearings in terms of environmental protection, worker’s safety, and cost. As for hydrostatic water bearings, a constant-flow type is more suitable than a constant-pressure type. However, the hydrostatic water bearings applied for machine tools are few cases, and there are only a few reports concerning the constant-flow bearings. In this study, sustaining force of the constant-flow hydrostatic water bearing pad is computed numerically by using ANSYS FLUENT. Then the solutions evaluated by the simple analytical models, which were proposed previously, are examined by comparing them with the numerical result. Additionally, an improved analytical model is proposed.

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23

Poniatowski, L. G., J. O. Sundqvist, N. D. Kee, S. P. Owocki, P. Marchant, L. Decin, A. de Koter, L. Mahy e H. Sana. "Dynamically inflated wind models of classical Wolf-Rayet stars". Astronomy & Astrophysics 647 (marzo 2021): A151. http://dx.doi.org/10.1051/0004-6361/202039595.

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Context. Vigorous mass loss in the classical Wolf-Rayet (WR) phase is important for the late evolution and final fate of massive stars. Aims. We develop spherically symmetric time-dependent and steady-state hydrodynamical models of the radiation-driven wind outflows and associated mass loss from classical WR stars. Methods. The simulations are based on combining the opacities typically used in static stellar structure and evolution models with a simple parametrised form for the enhanced line opacity expected within a supersonic outflow. Results. Our simulations reveal high mass-loss rates initiated in deep and hot, optically thick layers around T ≈ 200 kK. The resulting velocity structure is non-monotonic and can be separated into three phases: (i) an initial acceleration to supersonic speeds (caused by the static opacity), (ii) stagnation and even deceleration, and (iii) an outer region of rapid re-acceleration (by line opacity). The characteristic structures seen in converged steady-state simulations agree well with the outflow properties of our time-dependent models. Conclusions. By directly comparing our dynamic simulations to corresponding hydrostatic models, we explicitly demonstrate that the need to invoke extra energy transport in convectively inefficient regions of stellar structure and evolution models, in order to prevent drastic inflation of static WR envelopes, is merely an artefact of enforcing a hydrostatic outer boundary. Moreover, the dynamically inflated inner regions of our simulations provide a natural explanation for the often-found mismatch between predicted hydrostatic WR radii and those inferred from spectroscopy; by extrapolating a monotonic β-type velocity law from the observable supersonic regions to the invisible hydrostatic core, spectroscopic models likely overestimate the core radius by a factor of a few. Finally, we contrast our simulations with alternative recent WR wind models based on co-moving frame (CMF) radiative transfer to compute the radiation force. Since CMF transfer currently cannot handle non-monotonic velocity fields, the characteristic deceleration regions found here are avoided in such simulations by invoking an ad hoc very high degree of clumping.

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Jang, Jihyeon, e Song-You Hong. "Comparison of Simulated Precipitation over East Asia in Two Regional Models with Hydrostatic and Nonhydrostatic Dynamical Cores". Monthly Weather Review 144, n. 10 (ottobre 2016): 3579–90. http://dx.doi.org/10.1175/mwr-d-15-0428.1.

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This study examines the characteristics of a nonhydrostatic dynamical core compared to a corresponding hydrostatic dynamical core in the Regional Model Program (RMP) of the Global/Regional Integrated Model system (GRIMs), a spectral model for regional forecasts, focusing on simulated precipitation over Korea. This kind of comparison is also executed in the Weather Research and Forecasting (WRF) finite-difference model with the same physics package used in the RMP. Overall, it is found that the nonhydrostatic dynamical core experiment accurately reproduces the heavy rainfall near Seoul, South Korea, on a 3-km grid, relative to the results from the hydrostatic dynamical core in both models. However, the characteristics of nonhydrostatic effects on the simulated precipitation differ between the RMP and WRF Model. The RMP with the nonhydrostatic dynamical core improves the local maximum, which is exaggerated in the hydrostatic simulation. The hydrostatic simulation of the WRF Model displaces the major precipitation area toward the mountainous region along the east coast of the peninsula, which is shifted into the observed area in the nonhydrostatic simulation. In the simulation of a summer monsoonal rainfall, these nonhydrostatic effects are negligible in the RMP, but the simulated monsoonal rainfall is still influenced by the dynamical core in the WRF Model even at a 27-km grid spacing. One of the reasons for the smaller dynamical core effect in the RMP seems to be the relatively strong horizontal diffusion, resulting in a smaller grid size of the hydrostatic limit.

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Jiang, Gui Yun, Yong Qin Wang e Xin Chun Yan. "Study on Throttle Methods for Hydrostatic Bearing". Applied Mechanics and Materials 373-375 (agosto 2013): 2119–23. http://dx.doi.org/10.4028/www.scientific.net/amm.373-375.2119.

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In hydrostatic bearing, the applied load is carried through the compensatory effect of restrictors. Different throttle methods will bring different oil film rigidity and carrying capacity. There are mainly four types restrictors such as capillary,orifice,slide valve and film feedback restrictors. The mathematical models of carrying capacity and oil film rigidity of the hydrostatic bearings throttled by the restrictors mentioned above were presented. The oil film rigidity of hydrostatic bearings throttled by different restrictors were analyzed. Reynolds equation was provided and the numerical solution model was constructed. The pressure fields show the static performances of hydrostatic bearing with different restrictors.

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Klein, Rupert, e Tommaso Benacchio. "A Doubly Blended Model for Multiscale Atmospheric Dynamics". Journal of the Atmospheric Sciences 73, n. 3 (11 febbraio 2016): 1179–86. http://dx.doi.org/10.1175/jas-d-15-0323.1.

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Abstract The compressible flow equations for a moist, multicomponent fluid constitute the most comprehensive description of atmospheric dynamics used in meteorological practice. Yet, compressibility effects are often considered weak and acoustic waves outright unimportant in the atmosphere, except possibly for Lamb waves on very large scales. This has led to the development of “soundproof” models, which suppress sound waves entirely and provide good approximations for small-scale to mesoscale motions. Most global flow models are based instead on the hydrostatic primitive equations that only suppress vertically propagating acoustic modes and are applicable to relatively large-scale motions. Generalized models have been proposed that combine the advantages of the hydrostatic primitive and the soundproof equation sets. In this note, the authors reveal close relationships between the compressible, pseudoincompressible (soundproof), hydrostatic primitive, and the Arakawa and Konor unified model equations by introducing a continuous two-parameter (i.e., “doubly blended”) family of models that defaults to either of these limiting cases for particular parameter constellations.

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Behrens, Bernd Arno, Thomas Hagen, Andreas Klassen, Julian Knigge, Jens Mielke e Insa Pfeiffer. "Forging of Aluminium Components under a Superimposed Hydrostatic Pressure to Induce Local Strain Hardening". Advanced Materials Research 137 (ottobre 2010): 191–217. http://dx.doi.org/10.4028/www.scientific.net/amr.137.191.

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A promising approach to handling low ductile aluminium alloys in a forming process is forming under superimposed hydrostatic pressure. The influence of superimposed hydrostatic pressure on the flow stress as well as on the formability for various hydrostatic pressures and temperatures was analysed [15, 3, and 7]. By increasing the formability of the workpiece, larger local plastic strains could be achieved. The results reveal highly increased formability at superimposed pressure of 85 MPa for workpieces from thermosetting alloy AlSi1MgMn (EN AW 6082) in comparison to those from self-hardening alloy AlMg4.5Mn0.7 (EN AW 5083). As a general tendency, the self-hardening alloys show a lower increase in formability when forged under superimposed pressure. But additionally, a charge-dependent influence of macro- and micro defects on the crack resistance was detected for alloy AlMg4.5Mn0.7. By evaluating damage models in finite element models the damage occurring in cold forming processes under superimposed hydrostatic pressure was predicted.

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Lu, Huaiqing, e Zhuxin Tian. "Investigation of the Static Performance of Hydrostatic Thrust Bearings Considering Non-Gaussian Surface Topography". Lubricants 11, n. 6 (20 giugno 2023): 267. http://dx.doi.org/10.3390/lubricants11060267.

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The dynamic and static characteristics of hydrostatic thrust bearings are significantly affected by the bearing surface topography. Previous studies on hydrostatic thrust bearings have focused on Gaussian distribution models of bearing surface topography. However, based on actual measurements, the non-Gaussianity of the distribution characteristics of bearing surface topography is clear. To accurately characterize the non-Gaussian distribution of bearing surface topography, the traditional probability density function of Gaussian distribution was modified by introducing Edgeworth expansion. The non-Gaussian surface was then reflected by two parameters: kurtosis and skewness. This had an effect on the static characteristics of hydrostatic thrust bearings with both circumferential and radial surface topographies. The comparison between the Gaussian distribution results and those of the non-Gaussian model showed that errors between the two models could reach more than 10%. Therefore, it is important to take into account the non-Gaussianity of bearing surface when discussing static characteristics of hydrostatic thrust bearings considering the surface topography.

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Hammond, Lloyd, e Raphael Grzebieta. "The Requirement for Hydrostatic Initialisation in LS-DYNA/USA Finite Element Models". Shock and Vibration 7, n. 2 (2000): 57–65. http://dx.doi.org/10.1155/2000/972928.

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The LS-DYNA/USA (Underwater Shock Analysis) coupled finite element codes are being investigated as a tool for predicting the local response of compliant plate structures subjected to far-field underwater explosion.It had previously been observed in LS-DYNA/USA models that extraneous pressure build-ups emanating from the DAA (doubly asymptotic approximation) boundaries may occur in the surrounding fluid region of the model, which inevitably lead to erroneous modelling of fluid-structure interaction and inaccurate structural responses. These instabilities typically result in divergence of the solution and eventually premature termination of the simulation. After a comprehensive investigation, it was found that the instabilities did not arise if the finite element model was hydrostatically initialised before conducting the LS-DYNA/USA simulation.The purpose of this study is to investigate the need for achieving hydrostatic equilibrium prior to the modelling of the shock wave propagation through the fluid-structure media. The method for achieving static equilibrium with the current version of the LS-DYNA/USA software is presented. The example simulations presented show that the hydrostatic initialisation procedure is effective in removing instabilities occurring at the DAA-fluid boundary, associated with the USA ambient hydrostatic pressure condition.

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Bai, Yefei, e Kwok Fai Cheung. "Dispersion and kinematics of multi-layer non-hydrostatic models". Ocean Modelling 92 (agosto 2015): 11–27. http://dx.doi.org/10.1016/j.ocemod.2015.05.005.

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Sigut, T. A. A., M. A. McGill e C. E. Jones. "BE STAR DISK MODELS IN CONSISTENT VERTICAL HYDROSTATIC EQUILIBRIUM". Astrophysical Journal 699, n. 2 (26 giugno 2009): 1973–81. http://dx.doi.org/10.1088/0004-637x/699/2/1973.

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Bourchtein, Andrei, Ludmila Bourchtein e Vladimir Kadychnikov. "Correctness of the vertical discretization in hydrostatic atmospheric models". Quarterly Journal of the Royal Meteorological Society 135, n. 638 (28 novembre 2008): 263–76. http://dx.doi.org/10.1002/qj.336.

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Lucas, Carine, Madalina Petcu e Antoine Rousseau. "Quasi-hydrostatic primitive equations for ocean global circulation models". Chinese Annals of Mathematics, Series B 31, n. 6 (22 ottobre 2010): 939–52. http://dx.doi.org/10.1007/s11401-010-0611-6.

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Shi, Fengyan, Gangfeng Ma, James T. Kirby e Tian-Jian Tom Hsu. "APPLICATION OF A TVD SOLVER IN A SUITE OF COASTAL ENGINEERING MODELS". Coastal Engineering Proceedings 1, n. 33 (15 dicembre 2012): 31. http://dx.doi.org/10.9753/icce.v33.currents.31.

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This paper describes the recent developments in a suite of coastal engineering models using Godunov-type shock-capturing schemes. The developments include a depth-integrated, wave resolving Boussinesq model, a hydrostatic, wave-averaged circulation model, and a fully 3-D non-hydrostatic model in a surface-following $\sigma$ coordinate formulation. The models implemented with the shock-capturing TVD scheme show robust performances in modeling breaking waves, nearshore circulation and coastal inundation. In this paper, we present model equations in a conservative form, MUSCLE-TVD numerical scheme and model applications. We also point out some problems caused by the TVD scheme in the recent model applications.

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Taqieddin, Ziad N., e George Z. Voyiadjis. "Studying the effect of a hydrostatic stress/strain reduction factor on damage mechanics of concrete materials". Journal of the Mechanical Behavior of Materials 22, n. 5-6 (1 dicembre 2013): 149–59. http://dx.doi.org/10.1515/jmbm-2013-0022.

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AbstractIn the non-linear finite element analysis (NFEA) of concrete materials, continuum damage mechanics (CDM) provides a powerful framework for the derivation of constitutive models capable of describing the mechanical behavior of such materials. The internal state variables of CDM can be introduced to the elastic analysis of concrete to form elastic-damage models (no inelastic strains), or to the elastic-plastic analysis in order to form coupled/uncoupled elastic-plastic-damage models. Experimental evidence that is well documented in literature shows that the susceptibility of concrete to damage and failure is distinguished under deviatoric loading from that corresponding to hydrostatic loading. A reduction factor is usually introduced into a CDM model to reduce the susceptibility of concrete to hydrostatic stresses/strains. In this work, the effect of a hydrostatic stress/strain reduction factor on the performances of two NFEA concrete models will be studied. These two (independently published) models did not provide any results showing such effect. One of these two models is an elastic-damage model, whereas the other is an uncoupled elastic-plastic-damage model. Simulations and comparisons are carried out between the performances of the two models under uniaxial tensile and compressive loading conditions. Simulations are also provided for the uncoupled elastic-plastic-damage model under the following additional loading conditions: biaxial tension and biaxial compression, uniaxial cyclic loading, and varying ratios of triaxial compressive loadings. These simulations clearly show the effect of the reduction factor on the numerically depicted behaviors of concrete materials. To have rational comparisons, the hydrostatic stress reduction factor applied to each model is chosen to be a function of the internal state variables common to both models. Therefore, once the two models are calibrated to simulate the experimental behaviors, their corresponding reduction factors are readily available at every increment of the iterative NFEA procedures.

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36

Ettori, S., V. Ghirardini, D. Eckert, E. Pointecouteau, F. Gastaldello, M. Sereno, M. Gaspari, S. Ghizzardi, M. Roncarelli e M. Rossetti. "Hydrostatic mass profiles in X-COP galaxy clusters". Astronomy & Astrophysics 621 (gennaio 2019): A39. http://dx.doi.org/10.1051/0004-6361/201833323.

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Aims. We present the reconstruction of hydrostatic mass profiles in 13 X-ray luminous galaxy clusters that have been mapped in their X-ray and Sunyaev–Zeldovich (SZ) signals out to R200 for the XMM-Newton Cluster Outskirts Project (X-COP). Methods. Using profiles of the gas temperature, density, and pressure that have been spatially resolved out to median values of 0.9R500, 1.8R500, and 2.3R500, respectively, we are able to recover the hydrostatic gravitating mass profile with several methods and using different mass models. Results. The hydrostatic masses are recovered with a relative (statistical) median error of 3% at R500 and 6% at R200. By using several different methods to solve the equation of the hydrostatic equilibrium, we evaluate some of the systematic uncertainties to be of the order of 5% at both R500 and R200. A Navarro-Frenk-White profile provides the best-fit in 9 cases out of 13; the remaining 4 cases do not show a statistically significant tension with it. The distribution of the mass concentration follows the correlations with the total mass predicted from numerical simulations with a scatter of 0.18 dex, with an intrinsic scatter on the hydrostatic masses of 0.15 dex. We compare them with the estimates of the total gravitational mass obtained through X-ray scaling relations applied to YX, gas fraction, and YSZ, and from weak lensing and galaxy dynamics techniques, and measure a substantial agreement with the results from scaling laws, from WL at both R500 and R200 (with differences below 15%), from cluster velocity dispersions. Instead, we find a significant tension with the caustic masses that tend to underestimate the hydrostatic masses by 40% at R200. We also compare these measurements with predictions from alternative models to the cold dark matter, like the emergent gravity and MOND scenarios, confirming that the latter underestimates hydrostatic masses by 40% at R1000, with a decreasing tension as the radius increases, and reaches ∼15% at R200, whereas the former reproduces M500 within 10%, but overestimates M200 by about 20%. Conclusions. The unprecedented accuracy of these hydrostatic mass profiles out to R200 allows us to assess the level of systematic errors in the hydrostatic mass reconstruction method, to evaluate the intrinsic scatter in the NFW c − M relation, and to robustly quantify differences among different mass models, different mass proxies, and different gravity scenarios.

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Liu, Lei, Xu Guang Wang, Yi Yang e Guo Hua Wang. "Experimental Method Study on Emulsion Explosives under Hydrostatic Pressure in Models Blasting". Advanced Materials Research 524-527 (maggio 2012): 569–74. http://dx.doi.org/10.4028/www.scientific.net/amr.524-527.569.

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Study on compression resistance of emulsion explosives can provide a theoretical basis for underwater blasting and deep-hole basting and development of emulsion explosives. Environment of deep water charge is simulated by a change of pressure of the micro-explosive device .The micro-explosive device was put in the reserved drill hole of mortar test block and applied rating pressure to explode, through fractal theory G-G-S lumpiness distribution function, which was used to date processing to study the fallen extent of explosion capability of emulsion explosives under hydrostatic pressure. The practice has shown that this is an effective new experimental method to study the fallen extent of explosion capability of emulsion explosives under hydrostatic through blasting effects.

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38

Nakano, Masuo, Akiyoshi Wada, Masahiro Sawada, Hiromasa Yoshimura, Ryo Onishi, Shintaro Kawahara, Wataru Sasaki et al. "Global 7 km mesh nonhydrostatic Model Intercomparison Project for improving TYphoon forecast (TYMIP-G7): experimental design and preliminary results". Geoscientific Model Development 10, n. 3 (31 marzo 2017): 1363–81. http://dx.doi.org/10.5194/gmd-10-1363-2017.

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Abstract. Recent advances in high-performance computers facilitate operational numerical weather prediction by global hydrostatic atmospheric models with horizontal resolutions of ∼ 10 km. Given further advances in such computers and the fact that the hydrostatic balance approximation becomes invalid for spatial scales < 10 km, the development of global nonhydrostatic models with high accuracy is urgently required. The Global 7 km mesh nonhydrostatic Model Intercomparison Project for improving TYphoon forecast (TYMIP-G7) is designed to understand and statistically quantify the advantages of high-resolution nonhydrostatic global atmospheric models to improve tropical cyclone (TC) prediction. A total of 137 sets of 5-day simulations using three next-generation nonhydrostatic global models with horizontal resolutions of 7 km and a conventional hydrostatic global model with a horizontal resolution of 20 km were run on the Earth Simulator. The three 7 km mesh nonhydrostatic models are the nonhydrostatic global spectral atmospheric Double Fourier Series Model (DFSM), the Multi-Scale Simulator for the Geoenvironment (MSSG) and the Nonhydrostatic ICosahedral Atmospheric Model (NICAM). The 20 km mesh hydrostatic model is the operational Global Spectral Model (GSM) of the Japan Meteorological Agency. Compared with the 20 km mesh GSM, the 7 km mesh models reduce systematic errors in the TC track, intensity and wind radii predictions. The benefits of the multi-model ensemble method were confirmed for the 7 km mesh nonhydrostatic global models. While the three 7 km mesh models reproduce the typical axisymmetric mean inner-core structure, including the primary and secondary circulations, the simulated TC structures and their intensities in each case are very different for each model. In addition, the simulated track is not consistently better than that of the 20 km mesh GSM. These results suggest that the development of more sophisticated initialization techniques and model physics is needed to further improve the TC prediction.

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NIMURA, Masaki, Koji KAWASAKI, Tomokazu MURAKAMI, Shinya SHIMOKAWA, Satoshi IIZUKA e Shuzo NISHIDA. "APPLICABILITY OF HYDROSTATIC / NON-HYDROSTATIC MODELS OF TSUNAMI SIMULATOR “T-STOC” TO STORM SURGE -INDUCED INANDATION ANALYSIS". Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 76, n. 2 (2020): I_115—I_120. http://dx.doi.org/10.2208/kaigan.76.2_i_115.

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Hu, Jiang, e Suhua Wu. "Statistical modeling for deformation analysis of concrete arch dams with influential horizontal cracks". Structural Health Monitoring 18, n. 2 (10 marzo 2018): 546–62. http://dx.doi.org/10.1177/1475921718760309.

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Several concrete dams all over the world exhibit severe cracks. It is very important to investigate the influence of cracks on the long-term behavior of dam structures to ensure safe operation. The interpretation of measured dam displacements is usually based on statistical hydrostatic-seasonal-time and hydrostatic-thermal-time models. The main purpose of this article is to present a statistical hydrostatic-thermal-crack-time model to interpret displacements of concrete arch dams with influential horizontal cracks. The hydrostatic-thermal-crack-time model is applied to analyze the Chencun dam, an arch–gravity dam with a large-scale horizontal crack on the downstream face. The crack stretches horizontally across most of the dam blocks. Its crack mouth opening displacement had been continually increasing even after reinforcement treatment, accompanied by abnormal deformation characteristics of the arch–cantilever system. A three-dimensional finite element model, containing the pre-existing crack using special gap elements, is built to reproduce the structural response, assess the contribution of the crack on the registered movements, and obtain the relationship between the crack mouth opening displacement and the dam crest displacement. Based on this, the hydrostatic-thermal-CMOD-time model considering crack mouth opening displacement is developed. Compared with the traditional models, the hydrostatic-thermal-crack-time model is expected to provide a better fit accuracy. The results also show that the crack and the corresponding reinforcement measure have a significant effect on the deformation behavior of the dam. This can provide some useful indications for concrete structures with similar problems.

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Gao, Junyuan, Xiurong Sun, Leon C. Moore, Thomas W. White, Peter R. Brink e Richard T. Mathias. "Lens intracellular hydrostatic pressure is generated by the circulation of sodium and modulated by gap junction coupling". Journal of General Physiology 137, n. 6 (30 maggio 2011): 507–20. http://dx.doi.org/10.1085/jgp.201010538.

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We recently modeled fluid flow through gap junction channels coupling the pigmented and nonpigmented layers of the ciliary body. The model suggested the channels could transport the secretion of aqueous humor, but flow would be driven by hydrostatic pressure rather than osmosis. The pressure required to drive fluid through a single layer of gap junctions might be just a few mmHg and difficult to measure. In the lens, however, there is a circulation of Na+ that may be coupled to intracellular fluid flow. Based on this hypothesis, the fluid would cross hundreds of layers of gap junctions, and this might require a large hydrostatic gradient. Therefore, we measured hydrostatic pressure as a function of distance from the center of the lens using an intracellular microelectrode-based pressure-sensing system. In wild-type mouse lenses, intracellular pressure varied from ∼330 mmHg at the center to zero at the surface. We have several knockout/knock-in mouse models with differing levels of expression of gap junction channels coupling lens fiber cells. Intracellular hydrostatic pressure in lenses from these mouse models varied inversely with the number of channels. When the lens’ circulation of Na+ was either blocked or reduced, intracellular hydrostatic pressure in central fiber cells was either eliminated or reduced proportionally. These data are consistent with our hypotheses: fluid circulates through the lens; the intracellular leg of fluid circulation is through gap junction channels and is driven by hydrostatic pressure; and the fluid flow is generated by membrane transport of sodium.

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Socie, D. "Multiaxial Fatigue Damage Models". Journal of Engineering Materials and Technology 109, n. 4 (1 ottobre 1987): 293–98. http://dx.doi.org/10.1115/1.3225980.

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Two multiaxial fatigue damage models are proposed: a shear strain model for failures that are primarily mode II crack growth and a tensile strain model for failures that are primarily mode I crack growth. The failure mode is shown to be dependent on material, strain range and hydrostatic stress state. Tests to support these models were conducted with Inconel 718, SAE 1045, and AISI Type 304 stainless steel tubular specimens in strain control. Both proportional and non-proportional loading histories were considered. It is shown that the additional cyclic hardening that accompanies out of phase loading cannot be neglected in the fatigue damage model.

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Scholz, M. "Mira model photospheres". Symposium - International Astronomical Union 122 (1987): 385–86. http://dx.doi.org/10.1017/s0074180900156815.

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The temperature stratifications and the emitted fluxes of Mira model photospheres based upon the extended density distribution of a pulsation model differ substantially from those of conventional model photospheres based upon a hydrostatic density distribution. Hence, the interpretation of Mira spectra by means of hydrostatic models is inadequate, and the spectral characteristics of Miras may deviate significantly from those of non-Miras.

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Nazir, I., e M. Azam. "Stability of generalized polytropic models". International Journal of Geometric Methods in Modern Physics 16, n. 04 (aprile 2019): 1950056. http://dx.doi.org/10.1142/s0219887819500567.

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In this paper, we have investigated the stability of a spherically symmetric object with charged anisotropic matter by using the concept of cracking. The cracking is a very intuitive technique to check the stability which is based on the analysis of the radial forces that appear on the system due to perturbations taking it out of its equilibrium state. For this, we have applied and studied the effect of local density perturbations to the hydrostatic equilibrium equation and on all the physical parameters with generalized polytropic equation of state. It is found that some of the generalized polytropic models exhibit cracking.

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Berntsen, Jarle, Jiuxing Xing e Guttorm Alendal. "Assessment of non-hydrostatic ocean models using laboratory scale problems". Continental Shelf Research 26, n. 12-13 (agosto 2006): 1433–47. http://dx.doi.org/10.1016/j.csr.2006.02.014.

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Lei, Yuan, Shadi Rajabi, Ryan M. Pedrigi, Darryl R. Overby, A. Thomas Read e C. Ross Ethier. "In Vitro Models for Glaucoma Research: Effects of Hydrostatic Pressure". Investigative Opthalmology & Visual Science 52, n. 9 (11 agosto 2011): 6329. http://dx.doi.org/10.1167/iovs.11-7836.

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Zhang, Di, Jiming Guo, Ming Chen, Junbo Shi e Lv Zhou. "Quantitative assessment of meteorological and tropospheric Zenith Hydrostatic Delay models". Advances in Space Research 58, n. 6 (settembre 2016): 1033–43. http://dx.doi.org/10.1016/j.asr.2016.05.055.

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Mahdavian, S. M. "A Thermal Hydrodynamic Lubrication Analysis for Hydrostatic Extrusion of a Work Hardening Metal". Journal of Tribology 108, n. 3 (1 luglio 1986): 368–71. http://dx.doi.org/10.1115/1.3261206.

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The thermal hydrodynamic lubrication theory is extended to hydrostatic extrusion of a strain hardening metal. The effects of viscous heating in both inlet and work zones, and surface temperature of work zones are included. The results are compared with previous theoretical models. It indicates that thermal strain hardening effects play an important role in determining hydrostatic extrusion for high reduction of area and high strength metals.

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Kaup, Magdalena, Wojciech Jurczak e Janusz Kaup. "Design Methodology of Strength Verification of Platform During Load Out of the Arkutun Dagi SE-Topside 43.800 MT". Polish Maritime Research 23, n. 4 (1 dicembre 2016): 117–28. http://dx.doi.org/10.1515/pomr-2016-0078.

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Abstract This paper presents the methodology of strength verification during load out of the heavy cargo, in this case Arkutun Dagi SE-Topside platform. General methodology of making calculation models and load algorithms has been presented. Paper shows results of verification of global shear forces and bending moments using self-developed algorithms to modify centre of gravity, fill tanks and hydrostatically balance a 3D finite element model with commercial hydrostatic code. The NAPA and ANSYS codes were used to calculate hydrostatic pressures and to apply to 3D-FE models and to carry out strength calculation of barge construction.

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Lemanis, Robert, Stefan Zachow e René Hoffmann. "Comparative cephalopod shell strength and the role of septum morphology on stress distribution". PeerJ 4 (13 settembre 2016): e2434. http://dx.doi.org/10.7717/peerj.2434.

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The evolution of complexly folded septa in ammonoids has long been a controversial topic. Explanations of the function of these folded septa can be divided into physiological and mechanical hypotheses with the mechanical functions tending to find widespread support. The complexity of the cephalopod shell has made it difficult to directly test the mechanical properties of these structures without oversimplification of the septal morphology or extraction of a small sub-domain. However, the power of modern finite element analysis now permits direct testing of mechanical hypothesis on complete, empirical models of the shells taken from computed tomographic data. Here we compare, for the first time using empirical models, the capability of the shells of extantNautilus pompilius,Spirula spirula, and the extinct ammoniteCadocerassp. to withstand hydrostatic pressure and point loads. Results show hydrostatic pressure imparts highest stress on the final septum with the rest of the shell showing minimal compression.S. spirulashows the lowest stress under hydrostatic pressure whileN. pompiliusshows the highest stress.Cadocerassp. shows the development of high stress along the attachment of the septal saddles with the shell wall. Stress due to point loads decreases when the point force is directed along the suture as opposed to the unsupported chamber wall.Cadocerassp. shows the greatest decrease in stress between the point loads compared to all other models. Greater amplitude of septal flutes corresponds with greater stress due to hydrostatic pressure; however, greater amplitude decreases the stress magnitude of point loads directed along the suture. In our models, sutural complexity does not predict greater resistance to hydrostatic pressure but it does seem to increase resistance to point loads, such as would be from predators. This result permits discussion of palaeoecological reconstructions on the basis of septal morphology. We further suggest that the ratio used to characterize septal morphology in the septal strength index and in calculations of tensile strength of nacre are likely insufficient. A better understanding of the material properties of cephalopod nacre may allow the estimation of maximum depth limits of shelled cephalopods through finite element analysis.

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