Investigation of ship hydroelasticity     

Ivo  &#x;ime  Stipe 《Ocean Engineering》2008,35(5-6):523-535

The importance of hydroelastic analysis of large and flexible container ships of today is pointed out. A methodology for investigation of this challenging phenomenon is drawn up and a mathematical model is worked out. It includes definition of ship geometry, mass distribution, structure stiffness, and combines ship hydrostatics, hydrodynamics, wave load, ship motion and vibrations. Based on the presented theory, a computer program is developed and applied for hydroelastic analysis of a flexible segmented barge for which model test results of motion and distortion in waves have been available. A correlation analysis of numerical simulation and measured response shows quite good agreement of the transfer functions for heave, pitch, roll, vertical and horizontal bending and torsion. The tool checked in such a way can be further used for reliable hydroelastic analysis of ship-like structures.  相似文献   

Time-domain calculation of moored ship motions in nonlinear waves     

Wim van der Molen  Ivo Wenneker 《Coastal Engineering》2008

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Slow growth and early sexual maturity: Bane and boon for the red coral Corallium rubrum     

Ivo Gallmetzer  Alexandra Haselmair  Branko Velimirov 《Estuarine, Coastal and Shelf Science》2010

This study investigates the size, age and growth of Corallium rubrum which is a key species of the only large reef-like structure in the Mediterranean Sea, the coralligéne. Two populations were studied in the Ligurian Sea at a depth between 36 and 42 m. Basal diameter, colony height and numbers of branches of 230 colonies were measured, and age and growth rates were assessed from 25 colonies. Mean growth rate was 0.2 mm yr⁻¹ of basal diameter growth, corresponding to a mean annual total branch length increase of 5 mm. These results point to a coral growth much slower than assumed in many earlier studies. Additionally, age and size at first reproduction were analysed. Male colonies were shown to become sexually mature at a minimum age of six years (1.2 mm of basal diameter), while female colonies reached maturity when at least 10 years old (2 mm of basal diameter). We further discuss the implications of slow growth and early sexual maturity for red coral management and conservation.  相似文献   

Application of infrared thermography for mapping open fractures in deep-seated rockslides and unstable cliffs     

Ivo Baroň  David Bečkovský  Lumír Míča 《Landslides》2014,11(1):15-27

We present a new approach for mapping open cracks and tension fractures within rock slope instabilities and rock cliffs, which resides in high-resolution ground-based and airborne infrared thermography (IRT). The method is restricted to cold seasons, and its utility is demonstrated through three examples from the Flysch Belt of the Outer West Carpathians (rockslides at Kopce Hill and Mt. Kněhyně) and from the Northern Calcareous Alps (deep-seated gravitational slope deformations in Gschliefgraben/Mt. Traunstein). The approach is based on a contrast between temperatures deep within the rock mass, which at a depth of few meters represent local mean annual values, and winter-time temperatures of the ground surface. In winter, warmer, buoyant air from depth rises to the ground surface through open cracks and joints, and the temperature contrast can be detected by IRT. Our test survey was conducted in the beginning of February 2012, in order to achieve the best contrast between temperatures around open tension cracks and the adjacent ground. For temperature sensing, we used a FLIR B360 thermal camera; for airborne surveys in the ambient air, temperatures at the time of our surveys ranged from approximately ?19 to ?7 °C. IRT results conclusively revealed the presence of open cracks, loosened rock zones, and pseudo-karst caves over a distance sometimes greater than 1 km. The IRT approach proved useful for rapidly assessing the distribution of open cracks and tension fractures, key information required for assessing rockfall and rockslide hazard.  相似文献   

Near-infrared template spectra of normal galaxies: k-corrections, galaxy models and stellar populations   总被引：2，自引：0，他引：2  

F. Mannucci  F. Basile  B.M. Poggianti  A. Cimatti  E. Daddi  L. Pozzetti  L. Vanzi 《Monthly notices of the Royal Astronomical Society》2001,326(2):745-758

We have observed 28 local galaxies in the wavelength range between 1 and 2.4 μm in order to define template spectra of the normal galaxies along the Hubble sequence. Five galaxies per morphological type were observed in most cases, and the resulting rms spread of the normalized spectra of each class, including both intrinsic differences and observational uncertainties, is about 1 per cent in K , 2 per cent in H and 3 per cent in J . Many absorption features can be accurately measured. The target galaxies and the spectroscopic aperture (7×53 arcsec²) were chosen to be similar to those used by Kinney et al. to define template UV and optical spectra. The two data sets are matched in order to build representative spectra between 0.1 and 2.4 μm. The continuum shape of the optical spectra and the relative normalization of the near-IR ones were set to fit the average effective colours of the galaxies of the various Hubble classes. The resulting spectra are used to compute the k -corrections of the normal galaxies in the near-IR bands, and to check the predictions of various spectral synthesis models: while the shape of the continuum is generally well predicted, large discrepancies are found in the absorption lines. Among the other possible applications, here we also show how these spectra can be used to place constraints on the dominant stellar population in local galaxies. Spectra and k -corrections are publicly available and can be downloaded from the web site http://www.arcetri.astro.it/~filippo/spectra .  相似文献   

Discovery of A New Class of Pulsating Stars: Gravity-mode Pulsators among Subdwarf B Stars     

Elizabeth M. Green  Keith Callerame  Ivo R. Seitenzahl  Brooke A. White  Elaina A. Hyde  Melissa Giovanni  Mike Reed  Gilles Fontaine  Roy Østensen 《Astrophysics and Space Science》2003,284(1):65-68

During the course of an ongoing CCD monitoring program to investigate low-level light variations in subdwarf B (sdB) stars, weserendipitously discovered a new class of multimode pulsators withperiods of the order of an hour. These periods are a factor of tenlonger than those of previously known multimode sdB pulsators (EC14026 stars), implying the new pulsations are due to gravity modes rather than pressure modes. The iron opacity instability that drives the short period EC 14026 stars is effective in hot sdB's. Thelong period pulsators are found only among cooler sdB stars, wherethey are surprisingly common. The mechanism responsible for excitingthe deeper g-modes in cool sdB's is currently unknown, but thetemperature and gravity range in which these stars occur must be animportant clue. We present the first observational results for thisnew class of pulsating sdB stars, and discuss some possible implications.  相似文献   

Report on a recent deep-seated landslide at G��rov�� Mt., Czech Republic, triggered by a heavy rainfall: The G��rov�� Mt., Outer West Carpathians; Czech Republic     

Ivo Baro��  Tom��? ?eh��nek  Ji?�� Vo?mik  V��t��zslav Musel  Lucie Kondrov�� 《Landslides》2011,8(3):355-361

A large deep-seated landslide, triggered by a heavy rainfall, activated early in the morning on May 19, 2010 along the SW slope of Gírová Mt., NE Czech Republic. The landslide occurred within a zone of pre-existing deep-seated gravitational deformation, and it was accompanied with pronounced ground liquefying in the central and lower portion of the sliding mass. The precipitation that triggered the landslide was about 244.6 mm that fell between May 15th and 18th with an average of 61 mm/day. No properties or lives were lost. However, the landslide provided a good case study on triggering factors and process of liquefaction at mountain slopes in the E Czech Republic and adjacent areas.  相似文献   

Numerical investigation of undrained cavity expansion in fine-grained soils     

Abid Ali  Thomas Meier  Ivo Herle 《Acta Geotechnica》2011,6(1):31-40

Based on the spherical cavity expansion (SCE) problem, Cudmani and Osinov (Can Geotech J 38:622–638, 2001), Osinov and Cudmani (Int J Numer Anal Method Geomech 25:473–495, 2001) developed a semi-empirical method of interpretation of CPT for coarse-grained soils (sand, gravel) using a hypoplastic constitutive model. Using a material-independent shape factor, the cone penetration resistance was related to the limit pressure required to expand a spherical cavity. The shape factor was observed to be a function of the soil state only, in particular the pressure-dependent relative density. This paper presents an analogous interpretation technique for CPT in fine-grained soils using the shape factor concept, Cavity Expansion approach, and a hypoplastic constitutive model. Relations for the shape factor and the limit pressure have been proposed based on the parameters affecting these quantities. A validation of the proposed interpretation technique with experimental results has also been performed.  相似文献   

A Boussinesq-type wave driver for a morphodynamical model to predict short-term morphology     

Ivo Wenneker  Ap van Dongeren  Jamie Lescinski  Dano Roelvink  Mart Borsboom 《Coastal Engineering》2011

The prediction of near-shore morphology on the time scale of a storm event and the length scale of a few surf zone widths is an active area of research. Intense wave breaking drives offshore-directed currents (undertow) carrying sediment seawards, resulting in offshore bar migration. In contrast, higher order nonlinear properties, such as wave asymmetry (velocity skewness) and velocity asymmetry, are drivers for shoreward transport. These wave processes are included in phase-resolving models such as Boussinesq-type wave models (e.g., TRITON). Short-wave averaging in the wave model yields wave-induced forces (e.g., radiation stress gradients) and a wave asymmetry term. The wave-induced forces are used in a hydrostatic model (e.g., Delft3D flow module) to drive the current and undertow, resulting in a 3D velocity profile. The wave model and hydrostatic model are coupled online with a morphodynamic model (e.g., Delft3D morphology module). The latter computes, based on the 3D flow profile and the wave asymmetry term, the sediment transport and performs the bathymetry updates. The updates are transferred directly back to the hydrodynamic models. The coupling of the wave model TRITON and the Delft3D modules is validated by comparing against extensive laboratory data sets (LIP and Boers) and a field case (Duck94), and show a good performance for the hydrodynamics and a reasonable/fair performance for the bar movements.  相似文献   

Modelling floodplain sedimentation using particle tracking     

Ivo Thonon  Kor de Jong  Marcel van der Perk  Hans Middelkoop 《水文研究》2007,21(11):1402-1412

Both climate change and river rehabilitation projects induce changes in floodplain sedimentation. Notably along the lower River Rhine, the sediment deposition patterns and rates are subject to change. To assess the magnitude of these changes, we developed the MoCSED model, a floodplain sedimentation model within a geographical information system for the lower Rhine River. We based MoCSED on the ‘method of characteristics’ (MoC), a particle tracking method that minimizes numerical dispersion. We implemented the MoCSED model in the PCRaster dynamic modelling language. The model input comprises initial suspended sediment concentrations, water levels, flow velocities, and longitudinal and transverse dispersivities. We used a combination of the Krone and Chen concepts to calculate the subsequent sedimentation (SED routine). We compared the model results with sediment trap data for the Bemmel floodplain along the Dutch Waal River during the 2003 inundation. This comparison showed that MoCSED was able to simulate the pattern of sediment deposition. In addition, the model proved to be an improvement in comparison with a conventional raster‐based floodplain sedimentation model for the lower River Rhine. In future, MoCSED may serve well to study the impact of a changing discharge regime due to climate change and floodplain rehabilitation plans on deposition of sediments. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献