Search results for "numerical [methods]"
showing 10 items of 500 documents
Advanced Techniques for Design and Manufacturing in Marine Engineering
2022
Modern engineering design processes are driven by the extensive use of numerical simulations, and naval architecture as well as ocean engineering are no exception. Structural design or fluid dynamic performance evaluation can only be carried out by means of several dedicated pieces of software. Classical naval design methodology can take advantage of the integration of these pieces of software, giving rise to more robust design in terms of shape, structural and hydrodynamic performances, and manufacturing processes. This Special Issue (SI) on “Advanced Techniques for Design and Manufacturing in Marine Engineering”, published in the Journal of Marine Science and Engineering, aimed to invite …
Looking More Closely at the Rabinovich-Fabrikant System
2016
Recently, we looked more closely into the Rabinovich–Fabrikant system, after a decade of study [Danca & Chen, 2004], discovering some new characteristics such as cycling chaos, transient chaos, chaotic hidden attractors and a new kind of saddle-like attractor. In addition to extensive and accurate numerical analysis, on the assumptive existence of heteroclinic orbits, we provide a few of their approximations.
Influence of Skin Depth on Convective Heat Transfer in Induction Heating
2017
International audience; We investigate convection driven by induction heating of a horizontal fluid layer using direct numerical simulations (DNS). This problem is of particular interest in the context of nuclear severe accident mastering. In a real severe accident, the molten core is subjected to homogeneous internal sources resulting from nuclear disintegrations. This situation is mimicked in the laboratory using induction heating as the internal source. In induction heating, however, heat sources are localized in the skin layer. Consequently, this concentration of heat may modify the flow and wall heat transfer compared to the case of homogeneous internal sources. DNS are carried out for…
Influence of growth parameters and melt convection on the solid-liquid interface during RF-floating zone crystal growth of intermetallic compounds
2001
Abstract The influence of growth parameters and melt convection on the solid–liquid interface of the intermetallic compound Ni3Si grown by the RF-floating zone technique was investigated experimentally as well as numerically. Numerical simulations showed that the heat transfer is strongly influenced by the electromagnetically driven and Marangoni convections whereas both the buoyancy and feed rotation have a negligible effect. It was found experimentally that the inductor design, the rod diameter and the length of the molten zone influence the solid–liquid interface shape significantly. The electromagnetically driven convection increases dramatically with increasing zone length due to the r…
Enhancement of the Lifetime of Metastable States in Er-Doped Si Nanocrystals by External Colored Noise
2015
The changes in the lifetime of a metastable energy level in Er-doped Si nanocrystals in the presence of an external source of colored noise are analyzed for different values of noise intensity and correlation time. Exciton dynamics is simulated by a set of phenomenological rate equations which take into account all the possible phenomena inherent in the energy states of Si nanocrystals and Er^{3+} ions in the host material of Si oxide. Electronic deexcitation is studied by examining the decay of the initial population of the Er atoms in the first excitation level 4I_{13/2} through fluorescence and cooperative energy transfer upconversion. Our results show that the deexcitation process of th…
Set Descriptors for Visual Evaluation of Human Corneal Endothelia
2001
Images of corneal endothelium obtained from specular microscopy are of great importance in the evaluation of the corneal endothelium status. Several commercial tools provide some numerical descriptors to characterize these images in terms of cell density, hexagonality, and some descriptive statistics of the cell areas. However, it is a too simple analysis that only detects severe abnormal endothelia with many irregular and large cells. Detection of subtle abnormalities needs a more refined analysis. This paper proposes a shape-size descriptor based on some modified versions of the geometric covariogram. This descriptor is presented as a valid alternative to the classical analysis that provi…
Non-circular rotating beams and CMB experiments
2002
This paper is concerned with small angular scale experiments for the observation of cosmic microwave background anisotropies. In the absence of beam, the effects of partial coverage and pixelisation are disentangled and analyzed (using simulations). Then, appropriate maps involving the CMB signal plus the synchrotron and dust emissions from the Milky Way are simulated, and an asymmetric beam --which turns following different strategies-- is used to smooth the simulated maps. An associated circular beam is defined to estimate the deviations in the angular power spectrum produced by beam asymmetry without rotation and, afterwards, the deviations due to beam rotation are calculated. For a cert…
A classification of European skulls from three time periods.
1987
We analyze the taxonomic structure of European populations at three time periods, the Early Middle Ages, the Late Middle Ages and the Recent Period. The data consist of sample means for 10 cranial variables based on 137, 108, and 183 samples for the three periods. Clustering by standard numerical taxonomic procedures reveals that the data are represented only poorly as hierarchic classifications. The clusters form significant and moderately strong associations with an arrangement of the samples by regions (geography) and by language family. Whereas during the early period, language family showed a stronger association with clusters based on cranial morphology, in the recent populations thes…
An improved immersed boundary method for curvilinear grids
2009
Abstract In the present paper we propose an extension of the direct-forcing immersed boundary technique, recently developed and employed by Verzicco and co-authors [Fadlun EA, Verzicco R, Orlandi P, Mohd-Yusof J. Combined immersed-boundary finite-difference methods for three-dimensional complex flow simulations. J Comput Phys 2000;161:35–60; Verzicco R, Fatica M, Iaccarino G, Moin P, Khalighi B. Large eddy simulation of a road vehicle with drag-reduction devices. AIAA J 2002;40(12):2447–55; Cristallo A, Verzicco R. Combined immersed boundary/large-eddy-simulations of incompressible three-dimensional complex flows. Flow Turbul Combust 2006;77(1–4):3–26.] and successively improved by Balaras …
Taxonomic study of sucrose-positive Aeromonas jandaei-like isolates from faeces, water and eels: emendation of A. jandaei Carnahan et al. 1992
2003
Fourteen sucrose-positive Aeromonas jandaei-like isolates from fresh water and reared European eels were subjected to a polyphasic study to determine their taxonomic position. Numerical taxonomy was used to analyse phenotypic data obtained for these isolates and 43 type and reference strains representative of recognized Aeromonas species. The A. jandaei cluster (phenon 1) was defined at 81.6 % similarity (S(J)); this included the A. jandaei-like isolates, the sucrose-positive strain Aeromonas veronii biogroup sobria CECT 4910 and nearly all A. jandaei reference strains used in the study. Four other reference strains of A. veronii biogroup sobria and the type strain of Aeromonas ichthiosmia …