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Cylindrical Shells (cylindrical + shell)
Selected AbstractsSurvey of Theoretical Work for the Proposed HEDgeHOB Experimental Schemes: HIHEX and LAPLASCONTRIBUTIONS TO PLASMA PHYSICS, Issue 4-5 2007N. A. Tahir Abstract This paper presents a review of the theoretical work that has resulted in a scientific proposal on studies of High-Energy-Density (HED) states in matter using intense beams of energetic heavy ions that will be available at the future Facility for Antiprotons and Ion Research (FAIR) at Darmstadt [W.F. Henning, Nucl. Inst. Meth B 24 (2003) 725-729]. The proposal is named HEDgeHOB that stands for High Energy Density Matter Generated by Heavy Ion Beams. Two experimental schemes have been worked out for the HEDgeHOB experimental proposal, namely, HIHEX and LAPLAS. The first scheme allows for studies of HED states by isochoric and uniform heating of matter by an intense heavy ion beam that is followed by isentropic expansion of the heated material. Numerical simulations have shown that using the beam parameters that will be available at the FAIR, one can access all the interesting physical states of HED matter including an expanded hot liquid state, twophase liquid-gas region, critical point parameters and strongly coupled plasmas for all the materials of interest. The second scheme involves a low-entropy compression of a test material like hydrogen that is enclosed in a cylindrical shell of a high-Z material like gold or lead. The target can be driven by a hollow or a circular beam. This compression scheme relies on multiple shock reflection between the hydrogen-gold (lead) boundary and the cylinder axis. The hydrodynamic stability of the LAPLAS target has also been analyzed that shows that the implosion is completely stable to Rayleigh-Taylor and Richtmyer-Meshkov instabilities. LAPLAS implosion using a hollow beam is suitable for studying the problem of hydrogen metallization whereas the one employing a circular focal spot leads to physical conditions that are expected to exist in the interiors of the giant planets. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Meshfree simulation of failure modes in thin cylinders subjected to combined loads of internal pressure and localized heatINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 8 2008Dong Qian Abstract This paper focuses on the non-linear responses in thin cylindrical structures subjected to combined mechanical and thermal loads. The coupling effects of mechanical deformation and temperature in the material are considered through the development of a thermo-elasto-viscoplastic constitutive model at finite strain. A meshfree Galerkin approach is used to discretize the weak forms of the energy and momentum equations. Due to the different time scales involved in thermal conduction and failure development, an explicit,implicit time integration scheme is developed to link the time scale differences between the two key mechanisms. We apply the developed approach to the analysis of the failure of cylindrical shell subjected to both heat sources and internal pressure. The numerical results show four different failure modes: dynamic fragmentation, single crack with branch, thermally induced cracks and cracks due to the combined effects of pressure and temperature. These results illustrate the important roles of thermal and mechanical loads with different time scales. Copyright © 2008 John Wiley & Sons, Ltd. [source] On the classical shell model underlying bilinear degenerated shell finite elementsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 4 2001Mika MalinenArticle first published online: 2 AUG 200 Abstract We study the shell models arising in the numerical modelling of shells by bilinear degenerated shell finite elements. The numerical model of a cylindrical shell obtained by using flat shell elements is given an equivalent formulation based on a classical two-dimensional shell model. We use the connection between the models to explain how a parametric error amplification difficulty or locking is avoided by some elements. Copyright © 2001 John Wiley & Sons, Ltd. [source] Cylindrical metamaterial-based subwavelength antennaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2009Aycan Erentok Abstract A subwavelength monopole antenna radiating in the presence of a truncated cylindrical shell, which has a capped top face and is made of a negative permittivity metamaterial, is analyzed numerically by a method of moments for the volume-surface integral equation on the one hand, and a finite element method on the other hand. It is shown that a center-fed truncated cylinder, in contrast to an infinite cylinder, provides subwavelength resonances, thus suggesting the possibility of having a subwavelength antenna system. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1496,1500, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24386 [source] On the investigation of shell buckling due to random geometrical imperfections implemented using Karhunen,Loève expansionsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2008K. J. Craig Abstract For the accurate prediction of the collapse behaviour of thin cylindrical shells, it is accepted that geometrical and other imperfections in material properties and loading have to be accounted for in the simulation. There are different methods of incorporating imperfections, depending on the availability of accurate imperfection data. The current paper uses a spectral decomposition of geometrical uncertainty (Karhunen,Loève expansions). To specify the covariance of the required random field, two methods are used. First, available experimentally measured imperfection fields are used as input for a principal component analysis based on pattern recognition literature, thereby reducing the cost of the eigenanalysis. Second, the covariance function is specified analytically and the resulting Friedholm integral equation of the second kind is solved using a wavelet-Galerkin approach. Experimentally determined correlation lengths are used as input for the analytical covariance functions. The above procedure enables the generation of imperfection fields for applications where the geometry is slightly modified from the original measured geometry. For example, 100 shells are perturbed with the resulting random fields obtained from both methods, and the results in the form of temporal normal forces during buckling, as simulated using LS-DYNA®, as well as the statistics of a Monte Carlo analysis of the 100 shells in each case are presented. Although numerically determined mean values of the limit load of the current and another numerical study differ from the experimental results due to the omission of imperfections other than geometrical, the coefficients of variation are shown to be in close agreement. Copyright © 2007 John Wiley & Sons, Ltd. [source] Swelling effect on the dynamic behaviour of composite cylindrical shells conveying fluidINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 4 2006M. H. Toorani Abstract This paper presents a semi-analytical investigation of a fluid,structure system. Both isotropic and composite cylindrical shells filled with or subjected to a flowing fluid have been considered in this study. The structure may be uniform or non-uniform in the circumferential direction. The hybrid finite element approach, shearable shell theory and velocity potential flow theory have been combined to establish the dynamic equations of the coupled system. The set of matrices describing their relative contributions to equilibrium is determined by exact analytical integration of the equilibrium equations. The linear potential flow theory is applied to describe the fluid effects that lead to the inertial, centrifugal and Coriolis forces. The axisymmetric, beam-like and shell modes of vibrations in both cases of uniform and non-uniform cylindrical shells are investigated. Fluid elastic stability of a structure subjected to a flowing fluid is also studied. This theory yields the high and the low eigenvalues and eigenmodes with comparably high accuracy. Reasonable agreement is found with other theories and experiments. Copyright © 2005 John Wiley & Sons, Ltd. [source] Vibrations of thin cylindrical shells with a periodic structurePROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2008Barbara Tomczyk Free vibrations of thin linear,elastic Kirchhoff,Love cylindrical shells, having a periodic structure along one direction tangent to the shell midsurface, is considered. In order to take into account the effect of the periodicity cell size in this problem, a new averaged non,asymptotic model of such shells, proposed by Tomczyk (2006), is applied. The new additional higher,order free vibration frequencies dependent on the microstructure size will be derived and discussed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Development of multilayered cell-hydrogel composites using an acoustic focusing techniqueBIOTECHNOLOGY PROGRESS, Issue 2 2010Jason P. Mazzoccoli Abstract Multilayered composites, composed of mammalian cells arranged in a hydrogel, have been prepared using an acoustic focusing technique. Acoustic focusing is a simple, nonchemical technique that allows for the fast arrangement of cells in matrices where the control of cell geometry is beneficial. Breast cancer cells (MDA-MB231) were dispersed in a 30 wt % solution of poly(ethylene glycol) diacrylate (PEGDA) of molecular weight 400 at a density of 5 × 106 cells/mL of PEGDA solution. An ultrasonic field was used to organize the cells before polymerization of PEGDA. Disk-shaped hydrogel composites, typically 1 cm in diameter and 2-mm thick were prepared based on a PEGDA solution volume of 130 ,L. At an acoustic frequency of 2.32 MHz, composites having cells positioned within concentric cylindrical shells interspersed with zones of cell-free hydrogel were produced. The cells were located in annuli approximately 80-,m thick and about 300 ,m apart. The structure and viability of the cells within these constructs were studied using a fluorescent LIVE/DEAD assay. The viability of the cells was on the order of 50%. For the conditions used in this study, cell death was primarily attributed to exposure of cells to the PEGDA solution prior to polymerization, rather than adverse effects of polymerization or the sound field itself. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] | ||||||||||