Numerical analysis of axisymmetric shells by one-dimensional continuum elements suitable for high frequency excitations

Axisymmetric shells are analyzed by means of one-dimensional continuum elements by using the analogy between the bending of shells and the bending of beams on elastic foundation. The mathematical model is formulated in the frequency domain. Because the solution of the governing equations of vibration of beams are exact, the spatial discretization only depends on geometrical or material considerations. For some kind of situations, for example, for high frequency excitations, this approach may be more convenient than other conventional ones such as the finite element method.

Numerical treatment of thick shells with holes

A Boundary Integral Equation Method (B.I.E.M.)formulation is presented. After a general situation of the method among other usual numerical ones, the possibilities of discretization are developed. As this is done only in the boundary the treatment of tridimensional problems is greatly simplified in comparison with other methods. Some results on a simple shell with holes are finally presented.

An algorithm for graphical computer results in shells

A Finite Element technique to interpolate general data (function values and its derivatives) has been developped. The technique can be considered as a generalized solution of the classical polynomial interpolation, because the condition for the interpolating function to be a polynomial is replaced by a minimizing condition of a given “smoothing” functional. In this way it is possible to find interpolating functions with a given level of continuity according to the class of finite elements used. Examples have been presented in order to assess the accuracy and efficiency of the procedure.

Application of global numerical procedures to the analysis of shells

Examples of global solutions of the shell equations are presented, such as the ones based on the well known Levy series expansion. Also discussed are some natural extensions of the Levy method as well as the inherent limitations of these methods concerning the shell model assumptions, boundary conditions and geometric regularity. Finally, some open additional design questions are noted mainly related to the simultaneous use in analysis of these global techniques and the local methods (like the finite elements) to finding the optimal shell shape, and to determining the reinforcement layout.

Design of Reinforcement in Concrete Shells: a unified Approach

The problem of design/verification of reinforcement in concrete shells is reviewed. Methods of analysis are classified, and the elastic-plastic approach is described in detail in the general case of shells subjected to both bending and membrane action. The procedure is then reduced to membrane shells (applicable also to concrete walls) and to pure bending, as in the case of plates. The procedure, which is based on previous research,generally requires the use of a desk-top computer.

Dynamic analysis of translational shells

In this paper a dynamic analysis of transnational shells is presented. The general linear shell theory is used in conjunction with additional shallow and curved plate approximations. In order to apply some type of extended Levy solution, the shell is assumed to be limited by a rectangular plan form, with two opposite edges simply supported (gable boundary conditions). First, the shells free vibrations are studied in the usual way, obtaining for each Fourier term the natural frequencies as solutions of a transcendental equation. However, solving these equations arises enormous computational difficulties. This paper deals specifically with this problem, trying to reduce its dimension by a discretization procedure. In the shell dynamic characteristics, namely the mass. The shell mass is lumped along a family of coordinate lines. Therefore, the natural frequencies for each harmonic term can be found from the solution of a typical matrix eigenvalues problem and standard numerical techniques can be applied. The shell response to forced vibrations, particularly to earthquake excitation, can be determined by using conventional procedure either in the time or in the frequency domain. Finally, extending the above procedure, any system of translational shells under dynamic loading can be studied. Then, by using matrix methods, a general computer program is written and applied to some illustrative examples. Numerical results has been obtained in two cases: circular cylindrical shell and box girder bridge.

Protein diagenesis in Patella shells: implications for amino acid racemisation dating

Se analiza la racemización de aminoácidos en proteínas inter e intracristalinas en conchas de Patella y su utilización como herramienta geocronológica, fundamentalmente empleadas en yacimientos arqueológicos.The inter- and intra-crystalline fractions of Patella vulgata limpets recovered from archaeological sites in Northern Spain (covering Neolithic, Mesolithic, Magdalenian, Solutrean, and Aurignacian periods) were examined for amino acid composition and racemisation over time. The calcitic apex and rim areas of the shells were found to probably be composed of similar proteins, as the D/L values and amino acids were comparable and varied in the same way with increasing age; however, the mineral structures present in these areas differed. The aragonitic intermediate part of the shell showed a distinctly different amino acid composition and mineral structure. The main protein leaching from the inter-crystalline fraction occurred within the first 6000 yr after the death of the organism. In contrast, the intra-crystalline fraction — comprised of a different protein composition than the inter-crystalline fraction — appeared to behave as a closed system for at least 34 ka, as reflected by the lack of a significant decrease in the amino acid content; however, changes in the amino acid percentages occurred during this period. The concentration of aspartic acid remained almost constant with age both in inter- and intra-crystalline proteins, and its contribution to the total amino acid content increased with age at the expense of other amino acids such as glutamic acid, serine, glycine and alanine. Temperature is thought to play a key role in the amino acid racemisation of P. vulgata and could explain why in the localities belonging to the Gravettian and Solutrean period, which formed during relatively cold conditions, D/L values were similar to those detected in shells from sites formed during the Magdalenian.

Dynamic analysis of translational shells

This paper presents a Levy-type solution for the natural frequencies of translational shells. A computer program in FORTRAN IV language corresponding to this solution is described. This direct solution is compared with some indirect solutions utilising Galerkin and Rayleigh methods. An extension to the study of forced vibrations is outlined.

A new set of relativistic screening constants for the screened hydrogenic model

AnewRelativisticScreenedHydrogenicModel has been developed to calculate atomic data needed to compute the optical and thermodynamic properties of high energy density plasmas. The model is based on anewset of universal screeningconstants, including nlj-splitting that has been obtained by fitting to a large database of ionization potentials and excitation energies. This database was built with energies compiled from the National Institute of Standards and Technology (NIST) database of experimental atomic energy levels, and energies calculated with the Flexible Atomic Code (FAC). The screeningconstants have been computed up to the 5p3/2 subshell using a Genetic Algorithm technique with an objective function designed to minimize both the relative error and the maximum error. To select the best set of screeningconstants some additional physical criteria has been applied, which are based on the reproduction of the filling order of the shells and on obtaining the best ground state configuration. A statistical error analysis has been performed to test the model, which indicated that approximately 88% of the data lie within a ±10% error interval. We validate the model by comparing the results with ionization energies, transition energies, and wave functions computed using sophisticated self-consistent codes and experimental data.

Coastal shapes. Geentic clasification 1973 - 2010

An analysis of a stretch of coastline shows multiple alterations through environmental climate actions. The narrow, fragile line displays singularities due to three basic causes. The first is the discontinuity in feed or localised loss of solid coastal material. Called massics, their simplest examples are deltas and undersea canyons. The second is due to a brusque change in the alignment of the shoreline’s edge, headlands, groins, harbour and defence works. Given the name of geometric singularities, their simplest uses are artificial beaches in the shelter of a straight groin or spits. The third is due to littoral dynamics, emerged or submerged obstacles which diffract and refract wave action, causing a change in the sea level’s super-elevation in breaker areas. Called dynamics, the simplest examples are salients, tombolos and shells. Discussion of the causes giving rise to variations in the coastline and formation of singularities is the raison d’être of investigation, using actual cases to check the suitability of the classification proposed, the tangential or differential action of waves on the coastal landscape in addition to possible simple, compound and complex shapes detected in nature, both in erosion and deposit processes

Valorización de subproductos agrícolas y forestales como sustratos de cultivo en el estado de Oaxaca (México)

El presente trabajo aborda el aprovechamiento de algunos subproductos agrícolas (bagazo de maguey y fibra de coco) y forestales (corteza de pino) en el Estado de Oaxaca (Sur de México). El objetivo principal se centra en localizar, cuantificar y caracterizar estos con vistas a su aplicación como sustratos o componentes de sustratos en cultivos ornamentales, forestales y hortícolas, y a su uso como enmiendas en cultivos tipo. Así mismo se persigue reducir el uso de la turba y la tierra de monte como sustratos mayoritarios en la actualidad. Para la localización de los subproductos se utilizaron los datos de los registros parcelarios de los productores de coco para la obtención de copra (generadores de fibra de coco) de la región costa y de los productores de mezcal (generadores del residuo de bagazo de maguey) de la región valles centrales, así como las ubicaciones de los aserraderos forestales en el Estado de Oaxaca. Se emplea un Sistema de Información Geográfica (SIG) con una cartografía digitalizada de los elementos del medio (clima, geología y suelo), de los cultivos generadores (bagazo de maguey, fibra de coco y corteza de pino), de la agricultura protegida como receptora (tomate) y de la agricultura extensiva con cultivos receptores de enmienda (café, hule, limón, mango, palma de coco y maguey). La producción anual de los residuos se cartografía y cuantifica con los siguientes resultados: bagazo de maguey 624.000 t, fibra de coco 86.000 m3 y 72.000 t de corteza de pino. Mediante el estudio de las características de los suelos de los cultivos receptores y de los requerimientos de materia orgánica de cada cultivo se calcularon las necesidades totales de materia orgánica para cada suelo. Los resultados de las cantidades globales para cada cultivo en todo el Estado muestran una necesidad total de 3.112.000 t de materia orgánica como enmienda. Con los datos obtenidos y a través de un algoritmo matemático se realiza una propuesta de localización de dos plantas de compostaje (de bagazo de maguey y fibra de coco) y cuatro plantas de compostaje de corteza de pino. Con el fin de conocer los subproductos a valorizar como sustrato o componente de sustrato se caracteriza su composición física‐química, siguiendo Normas UNE‐EN, y se analizan mediante Resonancia Magnética Nuclear (RMN). Para el acondicionamiento de bagazo de maguey y la corteza de pino se realizaron ensayos de compostaje. Al final de 241 días la temperatura y la humedad de ambos procesos se encontraban en los rangos recomendados, indicando que los materiales estaban estabilizados y con calidad para ser utilizados como sustrato o componente de sustrato. Para la fibra de coco se realizó el proceso de molienda en seco de conchas de coco provenientes de la comunidad de Río Grande Oaxaca (Principal zona productora de copra en Oaxaca). Posteriormente se emplean los materiales obtenidos como componentes para sustratos de cultivo. Se estudia el compost de bagazo de maguey y siete mezclas; el compost de corteza de pino y ocho mezclas y la fibra de coco con tres mezclas. Estos sustratos alternativos permiten obtener mezclas y reducir el uso de la tierra de monte, turba, arcilla expandida y vermiculita, siendo por tanto una alternativa sostenible para la producción en invernadero. Se elaboraron mezclas especificas para el cultivo de Lilium hibrido asiático y oriental (siete mezclas), sustratos eco‐compatibles para cultivo de tomate (nueve mezclas), para la producción de planta forestal (siete mezclas) y para la producción de plántula hortícola (ocho mezclas). Como resultados más destacados del bagazo de maguey, corteza de pino y las mezclas obtenidas se resume lo siguiente: el bagazo de maguey, con volúmenes crecientes de turba (20, 30, 50 y 60 %) y la corteza de pino, con volúmenes de turba 40 y 60%, presentan valores muy recomendados de porosidad, capacidad de aireación, capacidad de retención de humedad y equilibrio agua‐aire. Para la fibra de coco, la procedente de Río Grande presenta mejor valoración que la muestra comercial de fibra de coco de Morelos. Por último se llevó a cabo la evaluación agronómica de los sustratos‐mezclas, realizando cinco experimentos por separado, estudiando el desarrollo vegetal de cultivos tipo, que se concretan en los siguientes ensayos: 1. Producción de Lilium asiático y oriental en cama para flor de corte; 2. Producción de Lilium oriental en contenedor para flor de corte; 3. Producción de plántula forestal (Pinus greggii E y Pinus oaxacana M); 4. Producción de tomate (Solanum lycopersicum L) y 5. Producción de plántula de tomate en semillero (Solanum lycopersicum L). En relación a la producción de Lilium hibrido asiático en cama los sustratos corteza de pino (CPTU 80:20 v/v), corteza de pino + sustrato comercial (CPSC 80:20 v/v) y corteza de pino+turba+arcilla expandida+vermiculita (CPTAEV2 30:40:15:15 v/v) presentan los mejores resultados. Dichos sustratos también presentan adecuados resultados para Lilium hibrido oriental con excepción de la corteza de pino + turba (CPTU 80:20 v/v). En la producción de Lilium hibrido oriental en contenedor para flor de corte, además de los sustratos de CPSC y CPTAEV2, la mezcla de corteza de pino+turba+arcilla expandida+vermiculita (CPTAEV 70:20:5:5 v/v) manifestó una respuesta favorable. En el ensayo de producción de plántulas de Pinus greggii E y Pinus oaxacana Mirov, las mezclas con corteza de pino+turba+arcilla expandida+vermiculita (CPTAEV2 30:40:15:15 v/v) y bagazo de maguey turba+arcilla expandida+vermiculita (BMTAEV2 30:60:5:5 v/v) son una alternativa que permite disminuir el empleo de turba, arcilla expandida y vermiculita, en comparación con el sustrato testigo de turba+arcilla expandida+vermiculita (TAEV 60:30:10 v/v). En la producción de tomate (Solanum lycopersicum L) frente a la utilización actual del serrín sin compostar (SSC), las mezclas alternativas de bagazo de maguey+turba (BMT 70:30 v/v), fibra de coco de Río Grande (FCRG 100v/v) y corteza de pino+turba (CPT 70:30 v/v), presentaron los mejores resultados en rendimientos. Así mismo, en la producción de plántulas de tomate las dos mezclas alternativas de bagazo de maguey+turba+ arcilla expandida+vermiculita (BMTAEV5 50:30:10:10 v/v) y (BMTAEV6 40:40:10:10 v/v) presentaron mejores resultados que los obtenidos en la mezcla comercial (Sunshine 3), mayoritariamente utilizada en México en la producción de plántula de tomate y hortícola. ABSTRACT This paper addresses the use of some agricultural products (maguey bagasse and coconut fiber) and forestry (pine bark) in the State of Oaxaca (southern Mexico). The principal purpose is to locate, quantify and characterize these with the idea of applying them as substrates or substrate components in ornamental crops, forestry, horticultural, and their use as crop amendments. On the other hand, the reduction of peat and forest soil as main substrates is pursued. For the location of the products, registry parcel data from copra producers (coconut fiber generators) of the coastal region and mescal producers (maguey bagasse residue generators) of the central valleys region, as well as the locations of forest mills in the State of Oaxaca. A Geographic Information System (GIS) with digital mapping of environmental factors (climate, geology and soil), crop generators of residues (maguey bagasse, coconut and pine bark) receptors of amendments such as protected agriculture (tomato) and extensive agriculture crops (coffee, rubber, lemon, mango, coconut and agave). The annual production of waste is mapped and quantified with the following results: 624,000t maguey bagasse, coconut fiber 72,000 m3 and 86,000 t of pine bark. Through the study of receiving crops soils properties of and organic matter requirements of each crop, total needs of organic matter for each soil were estimated. The results of the total quantities for each crop across the state show a total of 3,112,000 t of organic matter needed as amendment. Using that data and a mathematical algorithm, the location of two composting plants (agave bagasse and coconut fiber) and four composting plants pine bark was proposed. In order to know the by‐products that were going to be used as substrates or substrate components, their physical‐chemical composition was analyzed following UNE‐EN technics. Furthermore they were analyzed by Nuclear Magnetic Resonance (NMR). For conditioning of maguey bagasse and pine bark, composting essays were conducted. At the end of 241 days the temperature and humidity of both processes were at the recommended ranges, indicating that the materials were stabilized and had reached the quality to be used as a substrate or substrate component. Coconut shells from the community of Rio Grande Oaxaca (Main copra producing area in Oaxaca) were put through a process of dry milling. Subsequently, the obtained materials were used as components for growing media. We studied the maguey bagasse compost and seven mixtures; the pine bark compost and eight blends and coconut fiber with three mixtures. These alternative substrates allow obtaining mixtures and reduce the use of forest soil, peat, vermiculite and expanded clay, making it a sustainable alternative for greenhouse production. Specific mixtures were prepared for growing Lillium, Asian and eastern hybrids (seven blends), eco‐compatible substrates for tomato (nine mixtures), for producing forest plant (seven mixtures) and for the production of horticultural seedlings (eight mixtures). Results from maguey bagasse, pine bark and mixtures obtained are summarized as follows: the maguey bagasse, with increasing volumes of peat (20, 30, 50 and 60%) and pine bark mixed with 40 and 60% peat by volume, have very recommended values of porosity, aeration capacity, water retention capacity and water‐air balance. Coconut fiber from Rio Grande had better quality than commercial coconut fiber from Morelos. Finally the agronomic evaluation of substrates‐mixtures was carried out conducting five experiments separately: 1. Production of Asiatic and Eastern Lilium in bed for cut flower, 2. Production of oriental Lillium in container for cut flower, 3.Production of forest seedlings (Pinus greggii E and Pinus oaxacana M), 4. Production of tomato (Solanum lycopersicum L) and 5. Tomato seedling production in seedbed (Solanum lycopersicum L). In relation to the production of hybrid Asian Lilium in bed, pine bark substrates (CPTU 80:20 v/v), pine bark + commercial substrate (CPSC 80:20 v/v) and pine bark + peat + expanded clay + vermiculite (CPTAEV2 30:40:15:15 v/v) showed the best results. Such substrates also have adequate results for Lilium Oriental hybrid except pine bark + peat (CPTU 80:20 v / v). In the production of Lilium oriental hybrid container for cut flower, besides the CPSC and CPTAEV2 substrates, the mixture of pine bark + peat + vermiculite expanded clay (CPTAEV 70:20:5:5 v / v) showed a favorable response. In the production of Pinus greggii E and Pinus oaxacana Mirov seedlings trial, mixtures with pine bark + peat + expanded clay + vermiculite (CPTAEV2 30:40:15:15 v/v) and maguey bagasse+ peat+ expanded clay + vermiculite (BMTAEV2 30:60:5:5 v / v) are an alternative which allows reducing the use of peat, vermiculite and expanded clay in comparison with the control substrate made of peat + expanded clay+ vermiculite (60:30 TAEV: 10 v/v). In the production of tomato (Solanum lycopersicum L), alternative mixes of maguey bagasse + peat (BMT 70:30 v/v), coconut fiber from Rio Grande (FCRG 100 v / v) and pine bark + peat (CPT 70:30 v / v) showed the best results in yields versus the current use of sawdust without compost (SSC). Likewise, in the production of tomato seedlings of the two alternative mixtures maguey bagasse + peat expanded clay + vermiculite (BMTAEV5 50:30:10:10 v/v) and (BMTAEV6 40:40:10:10 v/v) had better results than those obtained in the commercial mixture (Sunshine 3), mainly used in Mexico in tomato seedling production and horticulture.

Nonlinear response to ultrasound of encapsulated microbubbles

The acoustic backscatter of encapsulated gas-filled microbubbles immersed in a weak compressible liquid and irradiated by ultrasound fields of moderate to high pressure amplitudes is investigated theoretically. The problem is formulated by considering, for the viscoelastic shell of finite thickness, an isotropic hyperelastic neo-Hookean model for the elastic contribution in addition to a Newtonian viscous component. First and second harmonic scattering cross-sections have been evaluated and the quantitative influence of the driving pressure amplitude on the harmonic resonance frequencies for different initial equilibrium bubble sizes and for different encapsulating physical properties has been determined. Conditions for optimal second harmonic imaging have been also investigated and some regions in the parameters space where the second harmonic intensity is dominant over the fundamental have been identified. Results have been obtained for albumin, lipid and polymer encapsulating shells, respectively.

Theoretical Simulation of the A5 VEB Structure Pyrotechnique Shock Propagation

This paper presents some of the modelling criteria that have been used for the study of pyrotechnic shock propagation in the A5 VEB Structure, as well as the main conclusions from a mathematical model of the axymmetric effects in it. The separation of the lower stage of the ARIANE 5 Vehicle Equipment Bay (VEB)Structure is to be done using a pyrotechnic device. The wave propagation effects produced by the explosion have been analyzed with a computer program using as shape functions the analytical solution to the frequency response of a Timoshenko-Rayleigh beams and shells in that way the discretization can have elements as large as possible, depending on the material properties and boundary conditions. Moreover an enormous amount of possibilities in the treatment of concentrated masses, springs and dashpots, either with respect to a fixed reference or between nodes, is open for translational as well as rotational degrees of freedom.

Dynamic Studies of Shell and Spatial Structures

For the past 20 years, dynamic analysis of shells has been one of the most fascinating fields for research. Using the new light materials the building engineer soon discovered that the subsequent reduction of gravity forces produced not only the desired shape freedom but the appearance of ecologic loads as the first factor of design; loads which present strong random properties and marked dynamic influence. On the other hand, the technological advance in the aeronautical and astronautical field placed the engineers in front of shell structures of nonconventional shape and able to sustain substantialy dynamic loads. The response to the increasingly challenger problems of the last two decades has been very bright; new forms, new materials and new methods of analysis have arosen in the design of off-shore platforms, nuclear vessels, space crafts, etc. Thanks to the intensity of the lived years we have at our disposition a coherent and homogeneous amount of knowledge which enable us to face problems of inconceivable complexity when IASS was founded. The open minded approach to classical problems and the impact of the computer are, probably, important factors in the Renaissance we have enjoyed these years, and a good proof of this are the papers presented to the previous IASS meetings as well as that we are going to consider in this one. Particularly striking is the great number of papers based on a mathematical modeling in front of the meagerness of those treating laboratory experiments on physical models. The universal entering of the computer into almost every phase of our lifes, and the cost of physical models, are –may be- reasons for this lack of experimental methods. Nevertheless they continue offering useful results as are those obtained with the shaking-table in which the computer plays an essential role in the application of loads as well as in the instantaneous treatment of control data. Plates 1 and 2 record the papers presented under dynamic heading, 40% of them are from Japan in good correlation with the relevance that Japanese research has traditionally showed in this area. Also interesting is to find old friends as profesors Tanaka, Nishimura and Kostem who presented valuable papers in previous IASS conferences. As we see there are papers representative of all tendencies, even purely analytical! Better than discuss them in detail, which can be done after the authors presentation, I think we can comment in the general pattern of the dynamical approach are summarized in plate 3.

Effect of Sb incorporation on the electronic structure of InAs quantum dots

On the basis of optical characterization experiments and an eight band kp model, we have studied the effect of Sb incorporation on the electronic structure of InAs quantum dots (QDs). We have found that Sb incorporation in InAs QDs shifts the hole wave function to the center of the QD from the edges of the QD where it is otherwise pinned down by the effects of shear stress. The observed changes in the ground-state energy cannot merely be explained by a composition change upon Sb exposure but can be accounted for when the change in lateral size is taken into consideration. The Sb distribution inside the QDs produces distinctive changes in the density of states, particularly, in the separation between excitation shells. We find a 50% increase in the thermal escape activation energy compared with reference InAs quantum dots as well as an increment of the fundamental transition decay time with Sb incorporation. Furthermore, we find that Sb incorporation into quantum dots is strongly nonlinear with coverage, saturating at low doses. This suggests the existence of a solubility limit of the Sb incorporation into the quantum dots during growth.