Uso de la técnica SPH para el estudio de la interacción entre olas y estructuras

[ES] Se muestra la potencialidad del método SPH (Smoothed Particle Hydrodynamics) para el tratamiento de la interacción entre olas y estructuras. En particular, se estudia el proceso de rebase de una ola sobre una estructura horizontal paralela a la superficie del agua en reposo mediante una versión bidimensional del código y la colisión de una ola solitaria con una estructura vertical delgada mediante una versión tridimensional. En ambos casos se muestra cómo el modelo reproduce tanto cualitativa como cuantitativamente diferentes experimentos de laboratorio.Gómez Gesteira, M.; Dalrymple, R.; Crespo, A.; Cerqueiro, D. (2004). Uso de la técnica SPH para el estudio de la interacción entre olas y estructuras. Ingeniería del agua. 11(2):147-170. https://doi.org/10.4995/ia.2004.2525OJS147170112Baarholm, R.J., 2001. Theoretical and Experimental Studies of Wave Impact underneath Decks of Offshore Platforms.Batchelor, G. K., 1974. Introduction to fluid dynamics. Cambridge University Press. U.K.Benz, W., 1989. Smooth particle hydrodynamics: A review. Numerical Modeling of Stellar Pulsation: Problems and Prospects, (Proceedings of NATO Workshop, Les Arcs, France).Benz, W. and Asphaug, E., 1993. Explicit 3D continuum fracture modeling with smoothed particle hydrodynamics. Proceedings of Twenty- fourth Lunar and Planetary Science Conference. Lunar and Planetary Institute, 99- 100.Benz, W. and Asphaug, E., 1994. Impact simulations with fracture. I. Methods and tests. Icarus 107, 98-116.Benz, W. and Asphaug, E., 1995. Simulations of brittle solids using smoothed particle hydrodynamics. Comp. Phys. Comm., 87, 253- 265.Bonet, J. and Kulasegaram, S., 2000. Corrections and stabilization of Smooth Particle Hydrodynamics methods with applications in metal forming simulations. Intl. J. Num. Meth. Engrng., 47, 1189-1214.Buchner, B. and Cozijn, J.L., 1997. An investigation into the numerical simulation of green water. MARIN, February 1997.Buchner, B.a and van Ballegoyen, G., 1997a. Joint Industry Project: F(P)SO Green Water Loading. MARIN, May 1997. Volume A2: Technical Report.Buchner, B. and van Ballegoyen, G., 1997b. Joint Industry Project: F(P)SO Green Water Loading. MARIN, May 1997. Volume A3: Scale effect tests.Buchner, B. and van Ballegoyen, G., 1997c. Joint Industry Project: F(P)SO Green Water Loading. MARIN, May 1997. Volume C9: Buchner, B. and van Ballegoyen, G., 1997d. Joint Industry Project: F(P)SO Green Water Loading. MARIN, December 1997. Volume A1: Discussion Report.Cerqueiro, D., Zou, S, Gómez-Gesteira, M, and Dalrymple, R.A. 2004. Boundary conditions generated by static particles in SPH methods. Submitted J. Comput. Phys.Chen, S., Johnson, D.B., Raad, P.E., and Fadda, D., 1997. The Surface Marker and Micro Cell Method. International Journal for Numerical Methods in Fluids, 25, 749-778.Cox, D. T. and Ortega, J. A., 2002. Laboratory observations of green water overtopping a fixed deck. Ocean Engnrg. 29, 1827-1840.Cummins, S. J. and Rudman, M., 1999. An SPH projection meted. J. Comp. Phys. 152, 584-607.Dalrymple, R.A. and Knio, O., 2000. SPH Modelling of Water Waves. Proc. Coastal Dynamics, Lund, 779-787Dalrymple, R. A., Knio, O., Cox, D. T., Gomez-Gesteira, M. and Zou, S., 2002. Using a Lagrangian particle method for deck overtopping. Proc. Waves 2001, ASCE. 1083- 1091.Durisen, R. H., Gingold, R. A. and Boss, A. P., 1986. Dynamic Fission Instabilities in Rapidly Rotating n=3/2 Polytropes: A Comparison of Results from Finite-difference and Smoothed Particle Hydrodynamics Codes. Astron. J. 305, 281- 308.Evrard A.E., 1988. Beyond N-body: 3D cosmological gas dynamics. Mon. Not. R. Astr. Soc., 235, 911- 934.Faber, J.A and Manor, J.B., 2001. Post Newtonian SPH Calculations of Binary Neutron Star Coalescence. II. Mass- ratio, equation of state and spin. Physical Review D (63), 044012 (1-16)Faber, J.A and Rasio, F.A., 2000. Post Newtonian SPH Calculations of Binary Neutron Stars Coalescence. Method and First Results. Physical Review D (62) 064012 (1-23)Faltinsen, O.M., Greco, M. and Landrini, M., 2001. Green water loading on a FPSO. JOMAE Special Issue.Fontaine, E., 2000. On the use of smoothed particle hydrodynamics to model extreme waves and their interaction with structures. Proc. Rogue Waves 2000, Brest, France. www.ifremer.fr/metocean/conferences/wk.htmlGingold, A. and Monaghan, J. J., 1977. Smoothed Particle Hydrodynamics: theory and application to non-spherical stars. Mon. Not. R. Astr. Soc. 181, 375-389.Gómez-Gesteira, M. and Dalrymple, R., 2004. Using a 3D SPH method for wave impact on a tall structure. J. Wtrwy. Port, Coastal and Ocean Engrg.130(2), 63-69Gómez-Gesteira, M., Cerqueiro, D., Crespo, C. and Dalrymple, R.A. 2004. Green water overtopping analyzed with a SPH model. To appear in Ocean Engineering.Gotoh, H. and Sakai, T., 1999. Lagrangian simulation of breaking waves using particle meted. Coastal Eng. J. 41(3&4), 303-326.Gotoh, H. and Fredsoe, J., 2000. Lagrangian two- phase flow model of the settling behavior of fine sediment dumped into water. In Coastal Engineering 2000, 3906-3919.Gotoh, H., Shibahara, T. and Sakai, T., 2001. Sub- particlescale turbulence model for the MPS method- lagrangian flow model for hydraulic engineering. Computational Fluid Dybanics Journal 9(4) 339- 347.Gotoh, H., Sakai, T and Hayashi, M., 2002. J. Of Hydroscience and Hydraulic Engineering 20(1) 95-102.Greco, M., 2001. A Two-Dimensional Study of Green-Water Loading. Ph. D. Thesis.Johnson, G.R,. Stryk, R.A. and Beissel S.R., 1996. SPH for high velocity impact computations. Comput. Methods Applo. Mech. Eng ., 139, 347- 373.Habe, A., 1989. In Status Rep. Super Computing Japan, ed. T. Nakamura, M. Nagasawa. National Lab. High Energy Phys.Health & Safety Executive. 2001. Analysis of green water susceptibility of FPSO/FSU's on UKCS. HSE Books, Sudbury.Herant, M. and Benz, W., 1991. Hydrodynamical instabilities and mixing in SN 1987A - Two-dimensional simulations of the first 3 months. Astrophysical Journal, 370, 81-84Hsu, T., -J, Sakakiyama, T. and Liu, P.L.-F., 2002. A numerical model for waves and turbulence flow in front of a composite breakwater. Coastal Emgrg., 46, 25-50.Lahy, N., 1989. A particle method for relativistic fluid mechanics. MSc. Thesis. Monash Univ.Libersky, L.D. and Petscheck, A.G., 1991. Smoothed particle hydrodynamics with strength oif materials. Proceedings of the Next Free Lagrange Conference, Vol. 395, Trease, H, Fritts, J and Crowley, W (eds.), Springer- Verlag, 248- 257.Libersky, L.D. and Petscheck, A.G., 1993. High strain Lagrangian hydrodynamics- a three- dimensional SPH code for dynamic material response. J. Comput. Phys. 109, 67- 75.Liu, G.R., 2003. Mesh Free Methods. Moving Beyond the Finite Element Method. CRC Press.Lucy, L., 1977. A numerical approach to the testing of the fission hypothesis. Astron. J. 82(12), 1013-1024.Monaghan, J.J., 1989. On the problem of penetration in particle methods. J. Comp. Phys. 82, 1-15.Monaghan, J.J., 1992. Smoothed particle hydrodynamics. Ann. Rev. Astron. Appl. 30, 543- 574.Monaghan, J.J., 1994. Simulating free surface flows with SPH. J. Comp. Phys. 110, 399- 406.Monaghan, J.J., 1996. Gravity Currents and Solitary Waves. Physica D.98, 523-533.Monaghan, J.J., Cas, R.F., Kos, A., Hallworth, M., 1999. Gravity currents descending a ramp in a stratified tank. J. Fluid Mech. 379, 39-70.Monaghan, J.J.and Kos, A., 1999. Solitary waves on a Cretan beach. J. Wtrwy. Port, Coastal and Ocean Engrg. 125, 145-154.Monaghan, J.J., 2000. SPH without tensile instability. J. Comp. Phys. 159, 290-311.Monaghan, J.J., Kos, A., 2000. Scott Russell's wave generator. Phys. Fluids 12, 622-630.Monaghan, J. J. and Latanzio, J.C. 1985. A refined method for astrophysical problems. Astron. Astrophys, 149, 135- 143.Monaghan, J. J. and Latanzio, J.C., 1991.A simulation of the collapse and fragmentation of cooling molecular clouds. Astrophysical Journal, 375, 177-189.Nagasawa, M., Nakamura, T., Miyama, S. M., 1988. Three-dimensional hydrodynamical simulations of type II supernova - Mixing and fragmentation of ejecta Publ. Astron. Soc. Jpn. 40, 691-708.Peskin, C. S., 1977. Numerical analysis of blood flow in the heart. Journal Computational Physics 25, 220- 252.Phillips, G.J. and Monaghan, J.J., 1985. A Numerical Method for Three-dimensional simulations of Collapsing, Isothermal, Magnetic Gas Clouds. Mon. Not. R. Astr. Soc., 216, 883-895Raad, P. http://engr.smu.edu/waves/project.htmlRandles, P.W. and Libersky, L.D., 1996. Smoothed Particle Hydrodynamics - some recent improvementsand applications. Comput. Methods Appl. Mech. Eng., 138, 375- 408.Sakakiyama, T. and Liu, P.L.-F., 2001. Laboratory esperiments for wave motions and turbulence flows in front of a breakwater. Coastal Engrg., 44, 117-139.Shapiro P.R., Martel H., Villumsen J.V., and Owen J.M., 1996. Adaptive Smoothed Particle Hydrodynamics, with Application to Cosmology: Methodology. Astrophysical Journal Supplement 103, .269- 330Stellingwerf, R. F. and Peterkin, R. E., 1990. Smooth particle magnetohydrodynamics. Tech. Rep. MRC/ABQ-R-1248. Albuquerque: Mission Res. Corp.Swelgle, K.S. and Attaway, S.W., 1995. On the feasibility of using smoothed particle hydrodynamics for underwater explotion calculation. Comput- Mech., 17, 151- 168.Trulsen, K., Spjelkavik, B. and Mehlum, E., 2002. Green water computed with a spline-based collocation method for potential flow. Intl. J. Appld. Mech. Engrg. 7(1), 107-123.Wang, Z., Jensen, J. J., Xia, J., 1998. On the Effect of Green Water on Deck on the Wave Bending Moment. Proceedings of the Seventh International Symposium on Practical Design of Ships and Mobile Units, The Hagu

The genetic architecture of the human cerebral cortex

INTRODUCTION The cerebral cortex underlies our complex cognitive capabilities. Variations in human cortical surface area and thickness are associated with neurological, psychological, and behavioral traits and can be measured in vivo by magnetic resonance imaging (MRI). Studies in model organisms have identified genes that influence cortical structure, but little is known about common genetic variants that affect human cortical structure. RATIONALE To identify genetic variants associated with human cortical structure at both global and regional levels, we conducted a genome-wide association meta-analysis of brain MRI data from 51,665 individuals across 60 cohorts. We analyzed the surface area and average thickness of the whole cortex and 34 cortical regions with known functional specializations. RESULTS We identified 306 nominally genome-wide significant loci (P < 5 × 10−8) associated with cortical structure in a discovery sample of 33,992 participants of European ancestry. Of the 299 loci for which replication data were available, 241 loci influencing surface area and 14 influencing thickness remained significant after replication, with 199 loci passing multiple testing correction (P < 8.3 × 10−10; 187 influencing surface area and 12 influencing thickness). Common genetic variants explained 34% (SE = 3%) of the variation in total surface area and 26% (SE = 2%) in average thickness; surface area and thickness showed a negative genetic correlation (rG = −0.32, SE = 0.05, P = 6.5 × 10−12), which suggests that genetic influences have opposing effects on surface area and thickness. Bioinformatic analyses showed that total surface area is influenced by genetic variants that alter gene regulatory activity in neural progenitor cells during fetal development. By contrast, average thickness is influenced by active regulatory elements in adult brain samples, which may reflect processes that occur after mid-fetal development, such as myelination, branching, or pruning. When considered together, these results support the radial unit hypothesis that different developmental mechanisms promote surface area expansion and increases in thickness. To identify specific genetic influences on individual cortical regions, we controlled for global measures (total surface area or average thickness) in the regional analyses. After multiple testing correction, we identified 175 loci that influence regional surface area and 10 that influence regional thickness. Loci that affect regional surface area cluster near genes involved in the Wnt signaling pathway, which is known to influence areal identity. We observed significant positive genetic correlations and evidence of bidirectional causation of total surface area with both general cognitive functioning and educational attainment. We found additional positive genetic correlations between total surface area and Parkinson’s disease but did not find evidence of causation. Negative genetic correlations were evident between total surface area and insomnia, attention deficit hyperactivity disorder, depressive symptoms, major depressive disorder, and neuroticism. CONCLUSION This large-scale collaborative work enhances our understanding of the genetic architecture of the human cerebral cortex and its regional patterning. The highly polygenic architecture of the cortex suggests that distinct genes are involved in the development of specific cortical areas. Moreover, we find evidence that brain structure is a key phenotype along the causal pathway that leads from genetic variation to differences in general cognitive function

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Wave Propagation in Shallow Water

The propagation of waves from offshore to onshore is a difficult problem due to the mathematical complexities of the governing equations and the degree of uncertainty of the bathymetry over which the waves must travel. In this lecture, the various methods of transforming offshore wave trains to shallow water are discussed. First, single wave trains will be covered and then the shoaling of spectra will be introduced. Various wave transformation methods, such as ray tracing and parabollic modelling, are covered.ICCE 199

Water wave models and wave forces with shear currents

Water wave modeIs, incorporating shear currents, are developed for linear and nonlinear waves. The first model assumes a constant vorticity over the depth of the fluid; the case for a wave propagating on a linear shear current. For greater generality, a second model is presented which assumes that the fluid is composed of two layers, each with a different, but constant, vorticity. The nonlinear solutions require the use of a numerical perturbation procedure. The last wave model, using a finite difference approach, generates waves propagating on arbitrary vorticity distributions. Examples of the effect of the vorticity on the waves are presented. Further, the use of two of these models in the analysis of actual measured wave data is shown. Wave force measurement programs conducted for the purposes of obtaining drag and inertia coefficients on structures are affected by the presence of currents, and the biases introduced into these coefficients by neglecting the currents are investigated via small amplitude wave theory. Further, an approximate procedure for de termining currents for measured wave force data is presented, as weIl as some results from Wave Project 11 dàta, which were obtained during Hurricane Carla in the Gulf of Mexico.KWP-collectio

Assessing the role of a mammalian frugivorous species on seed germination potential depends on study design: A case study using wild samango monkeys

Frugivory and seed dispersal contribute to the maintenance and regeneration of plant communities through transportation of seeds and enhancing germination through seed processing mechanisms. The effects of mammalian frugivore seed processing mechanisms on seed germination are generally well studied and the potential benefits include disinhibition (pulp removal), scarification (gut passage) and fertilisation (from faecal matrix). Nevertheless, our review found that there is bias in the comparative treatments included in seed dispersal studies through exclusion of entire fruit control groups and the fertiliser effect. In this study, we aimed to address such bias by using ecologically relevant experiments to investigate the influence of seed processing mechanisms on germination probability and latency of selected locally abundant fleshy-fruiting plant species, common in the diet of samango monkeys (Cercopithecus albogularis schwarzi), who are seed-spitters (disinhibition) and seed-swallowers (gut-passage and fertiliser effects). We designed experiments to isolate the cumulative effects of seed processing mechanisms and tested the effects of five treatments and one control treatment (entire fruit). We further assessed if exclusion of ecologically relevant seed treatments or relevant controls would affect our interpretation of the impact of the disperser on seed germination. Comparing gut passage and disinhibition indicated negative effects, whereas comparing gut passage and entire fruit controls indicated neutral effects in one species. Compared with gut passage alone, the fertiliser effects indicated positive or neutral benefits on germination probability. Our study demonstrated that the impacts of mammalian frugivores on germination may be under- or over-estimated in ecological literature where relevant treatments and meaningful controls are excluded