Shell Structure

An Al-6.3Li-0.07Sc-0.02Yb (at.%) alloy is subjected to a double-aging treatment to create nanoscale precipitates, which are studied by atom-probe tomography and transmission electron microscopy. After homogenization and quenching, Yb atoms form clusters exhibiting L1 2-like order. A first aging step at 325°C leads to a doubling of microhardness as a result of the formation of coherent precipitates with an Al 3 Yb-rich core and an Al 3 Sc-rich shell. The core and shell both exhibit the L1 2 structure and both contain a large concentration of Li, which substitutes for up to 50% of the Sc or Yb atoms at their sublattice positions. These core/single-shell precipitates provide excellent resistance to overaging at 325°C. Subsequent aging at 170°C increases the microhardness by an additional 30%, through precipitation of a metastable d 0-Al 3 Li second shell on the core/single-shell precipitates, thereby forming a chemically and structurally complex core/double-shell structure. The metastable d 0-Al 3 Li phase is observed to form exclusively on pre-existing core/shell precipitates.

ZrO 2 hollow microspheres with the average diameter of about 500 nm and the shell thickness of about 50 nm were synthesized by a facile technique using carbon spheres as templates. The corresponding ZrO 2 hollow microspheres were obtained by calcining the precursors of C-Zr(OH) 4 core-shell heterostructures, which were synthesized with the precipitation of ZrCl 4 solution with aqueous ammonia on the surface of colloid carbons. SEM, XRD, TGA and BET were used to characterize the composition, morphology, size and crystal structure of synthesized products. The effects of ultrasonic dispersion and separation process on the hollow spheres were studied, and the surfactant PEG-1000 was added to tune the shell structure of synthesized ZrO 2 hollow spheres.

We prepared SiO 2 @Ag core-shell nanospheres: silver nanoparticles ($4 ± 2 nm in diameter) coated silica nanospheres ($50 ± 10 nm in diameter). The preparation route is a modification of the Stöber method, and involves the preparation of homogeneous silica spheres at room temperature, combined with the deposition of silver nanoparticles from Ag + in solution, by using water/ethanol mixtures, tetraethylorthosilicate as Si source and silver nitrate as Ag source in a single-pot wet chemical route without an added coupling agent or surface modification, which leads to the formation of core@shell homogeneous nanospheres. We present the preparation and characterization of the SiO 2 @Ag core-shell nanospheres and also of bare silica spheres in the absence of silver, and propose a reaction mechanism for the formation of the core-shell structure.

Manufacturing of complex-shaped bimetals utilizing two-color powder injection molding (2C-PIM) and three-dimensional printing (3DP) processes, which basically involve sintering of a powder/binder mixture, has been attracted a great interest. This article addresses sintering of biocompatible Co-Cr-Mo alloy for manufacturing stepwise porosity-graded composite structures. Such composite structures provide strength at the core and a porous layer for the tissue growth. To evaluate the process, two grades of gas atomized Co-Cr-Mo powder with an average particle size of 19 and 63 m were used. Isothermal and non-isothermal sintering behavior of the loose powders under hydrogen and argon atmospheres, which is a simulated condition of 2C-PIM and 3DP processes after de-binding, was studied. Microstructural characteristics of the sintered specimens were evaluated. It was found that an intermediate sintering temperature of 1280 • C in argon can be used for manufacturing of the porosity-graded composite layers, i.e., a relatively dense core (5% porosity) with a porous layer (33% porosity) can be produced. A hip-joint with a core/shell structure was produced as a case study.

During the manipulation of hen eggs from the farm to the consumer due to action of external forces and weak mechanical strength of shell, the eggs break. The goal of egg producers is to reduce losses when breaking eggs during the production and placement, and thus increase revenues. Each egg can be damaged by external forces whose values are greater than maximum strength of the egg shell. Direct and indirect methods are used to determine the quality of eggs and shell strength. By direct methods, strength of the shell can be determined on the basis of puncture force measurements, impact forces, quasi-static compression forces and free fall forces on a known surface. In our research, a device was constructed for the realization of experiment and a direct method for determining strength of eggs was applied on the basis of measured breaking force of the shell. The device for measuring strength of eggs by the direct method of puncture eggshell was constructed and applied at the Faculty o...

A powerful method to study carbon nanotubes (CNTs) grown in patterned substrates for potential interconnects applications is transmission electron microscopy (TEM). However, high-quality TEM samples are necessary for such a study. Here, TEM specimen preparation by focused ion beam (FIB) has been used to obtain lamellae of patterned samples containing CNTs grown inside contact holes. A dualcap Pt protection layer and an extensive 5 kV cleaning procedure are applied in order to preserve the CNTs and avoid deterioration during milling. TEM results show that the inner shell structure of the carbon nanotubes has been preserved, which proves that focused ion beam is a useful technique to prepare TEM samples of CNT interconnects.

As one of requirements of human life is health and hygiene, so, some places should be forecasted for these affairs to being true. Hygiene and health will be divided to physical and mental branches which researchers states that if mental health is provided, physical health can be easily available and finally, human can easily take his course during treatment which obtain healthy life. It finally causes creating great works and massive movements in human life. One characteristics of a good medicinal center is easy and rapid access, so that patients can have access to these centers with minimum time. This access is defined from the place where the patient resides to the interior spaces of medical centers, and many factors affect the quality of this path. On factor is the human view of form, how to create a different form by designing an external shell and embedding the original structure under this shell so that it can be developed and expanded at the same time, and at the same time be inviting, so that clients and users move towards these centers and walk indoors comfortably and away from double stress. Doing studies and data collection and information evaluation is of the basics of designing and requires a full research design. The present study is to provide a comprehensive cognitive understanding of all those involved in architectural design for hospital building and patients. Besides, studying and collecting all available written and verbal references, principles and optimized guidelines of designing an efficient hospital were extracted in order to meet medicinal and psychological needs of patients.

In this paper a numerical approach of a time-dependent fluid-structure coupling for membrane and thin shell structures with large displacements is presented. The frame algorithm is partitioned, yet fully implicit because of a predictor-corrector scheme being applied to the structural displacements within each time step. In order to reach a high modularity, two powerful codesFone of them highly adapted to flow simulation and the other one to structural dynamicsFrun simultaneously and exchange fluid loads and displacements within each fluidstructure iteration. The finite volume based CFD code is able to compute three-dimensional, incompressible, turbulent flows. The structural simulations are performed using a finite element program including algorithms for geometrically and physically non-linear problems.

The surface of the shell of the pelagic Antarctic gastropod, Limacina helicina antarctica forma antarctica, was smooth, with riblike structures also observed. The larger specimen, with six to seven whorls, had visible ribs on its most outer whorl. The shell thickness of L. helicina antarctica forma antarctica was very thin, approximately 5e7 mm, on an individual with a shell diameter of 1.4 mm. Shell microstructure, as examined by SEM, was composed mostly of a crossed-lamellar structure. Shell thickness of the dominant benthic bivalve Laternula elliptica, was approximately 99e132 mm on an individual of shell length 19 mm. It was composed of two calcareous layers, including a thick outer homogeneous or granular layer and a thin nacreous inner layer. The characteristics of shell structure are discussed with reference to previous results, and in terms of adaptation to Antarctic waters.

Aqueous acrylic-polyurethane hybrid emulsions were prepared by semibatch emulsion polymerization of a mixture of acrylic monomers (butyl acrylate, methyl methacrylate, and acrylic acid) in the presence of polyurethane dispersion. Equivalent physical blends were prepared by mixing acrylic emulsion and polyurethane dispersion. The weight ratio between acrylic and polyurethane components varied to obtain different emulsion properties, microphase structure, and mechanical film properties of hybrid emulsions and physical blends. Particle size and molecular mass measurements, scanning electron microscopy, glass transition temperature, and rheological measurements performed characterization of the latex system. The mechanical properties were investigated by measuring tensile strength and Koenig hardness of dried films. The experimental results indicate better acrylic-polyurethane compatibility in hybrid emulsions than in physical blends, resulting in improved chemical and mechanical properties.

This paper presents a combined shape and reinforcement layout optimization method of shell structures. The approach described in this work is applied to optimize simultaneously the geometry of the shell mid-plane as well as the layout of surface stiffeners on the shell. This formulation involves a variable ground structure, since the shape of the shell surface is modified in the course of the process. Here we shall consider a global structural design criterion, namely the compliance of the structure, following basically the classical problem of distributing a limited amount of material in the most favourable way. The solution to the problem is based on a finite element discretization of the design domain. The material within each of the elements is modelled by a second-rank layered Mindlin plate microstructure. By a simple modification, this type of microstructure can be used to find the optimum distribution of stiffeners on shell structures. The effective stiffness properties are computed analytically through a “smear-out” procedure. The proposed method has been implemented into a general optimization software called Odessy and satisfactorily applied to the solution of some numerical examples, which are illustrated at the end of the paper.

A Kirchhoff-Love shell element is developed on the basis of the isogeometric approach . NURBS as basis functions for analysis have proven to be very efficient and offer the great feature of exact geometric representation. For a Kirchhoff-Love shell element they additionally have the significant advantage that the necessary continuities between elements are easily achieved. The element is formulated geometrically nonlinear. It is discretized by displacement degrees of freedom only. Aspects related to rotational degrees of freedom are handled by the displacement control variables, too. A NURBS-based CAD program is used to model shell structures built up from NURBS and isogeometric analysis is performed on the same model without meshing. Different examples show the performance of this method and its applicability for the integration of design and analysis.

Acrylic-polyurethane hybrid emulsions were prepared by converting amphiphilic acrylic-polyurethane graft copolymers previously synthesized in nonaqueous media by grafting vinyl monomers to partially vinyl-endblocked polyurethanes to aqueous emulsions. These emulsions were ...

Actions of a wider geopolitical, social, economic and creative milieu had as their consequence, creation of the Belgrade Fair. Politically bipolar but multicultural global system during the PostWar period, served as an impetus in the discovery of the archetypal Belgrade Fair while using the model of a world fair. The urban concept of the Belgrade Fair outreaches the framework and needs of normal fairs, and a delay in construction and changes to the development programme of New Belgrade, in the period between 1950-1954, resulted in the fair taking a role of an attractive urban zone-new urban centre. Extensive research has confirmed that the influence of world fairs makes them unique public manifestations of economic and geopolitical importance. The paradigm of growth and creation of world fairs, as well as the processes which predated this industrial era phenomenon can, to a certain extent, be considered as a model according to which the concept of new urban centre in Belgrade was established, thus establishing economic, cultural and general social standards of the new socialist society. This phenomenon can be considered through a number of manifestations following the Fair's opening-sport, cultural, political events for the development of a new national consciousness. 1961 being of specific importance due to the first congress of non-aligned movement taking place and, thus, marking the formal creation and future development of this organization. On this occasion all delegations visited the Fair, which definitively established the new imperial framework of socialist Yugoslavia in the world.

Beogradski sajam je nastao kao fenomen delovanja šireg geopolitičkog, društvenog, ekonomskog i stvaralačkog prostora. Politički bipolarno ali multikulturalno svetsko ureñenje u posleratnom periodu bilo je inicijacija za pronalaženje arhetipa nastanka Beogradskog sajma primenom modela svetske izložbe. Urbanistički koncept Beogradskog sajma prevazilazi okvire i potrebe sajmišta, preuzimajući ulogu privlačne gradske zone – novog gradskog centra, usled zastoja u izgradnji i promene programskog osnova Novog Beograda u periodu 1950-1954. Godine. Tokom šireg istraživanja utvrñen je uticaj svetskih izložbi kao najizrazitijih javnih manifestacija privrednog i geopolitičkog značaja. Paradigma razvoja i nastanak svetskih izložbi, kao i procesi koji su prethodili ovom fenomenu industrijske ere mogu se u odreñenoj meri posmatrati kao model po kome je koncept novog gradskog centra u Beogradu postavljen, uspostavljajući tržišne, kulturne i opšte društvene standarde novog socijalističkog društva. Ovaj fenomen se može sagledati kroz niz manifestacija nakon otvaranja sajma – sportskog, kulturnog, političkog sadržaja za razvoj svesti nove nacije, dok 1961. godina ima poseban značaj kada je održan prvi samit pokreta nesvrstanosti koji je obeležio formalno nastajanje i dalji razvoj ove organizacije. Ovom prilikom sve delegacije su posetile sajam, čime je definitivno uspostavljen novi imperijalni okvir socijalističke Jugoslavije u svetu.

This paper presents advancements in mycelium construction, demonstrated through a large-scale monolithic mycelium vault structure. In the burgeoning field of bio-materials, mycelium has emerged as a potentially viable building material because it is naturally occurring, demands little energy for its production, is lightweight, and completely biodegradable. Whereas, previous architecture-scale mycelium constructions used component-based techniques, this paper presents novel research on grown-in-place and self-supporting monolithic mycelium structures, achieved using techniques resembling common practices for cast-in-place concrete.

When the visual presence of materials decreases, the maximal transparency creates astounding beauty. In order to enhance transparency, clearer and lighter structures should be used. Although glass is extremely noteworthy as a transparent load bearing material, the structural use of glass is still unfamiliar to architects. Since the advancement in architecture requires knowledge about the path of developments, this study was conducted in order to discern the potential of improvement in glass structures as a result of scientific and technological advances. Through analysis of existing challenges and opportunities, this study aims to investigate the possibility of constructing completely transparent buildings in the near future. The findings indicate that improvements in the field of materials, selection of appropriate forms, the advent of innovative techniques, plus fine-tuning the existing technologies can improve structural efficiency, safety, durability, and transparency of glass buildings, so that the imagination of modern architecture can be realized.

Morphological (including ultrastructural) and developmental characters utilized in recent literature are critically reviewed as the basis to reassess the phylogenetic relationships of gastropods. The purpose of this paper is to provide a framework of characters for future studies and a testable phylogenetic hypothesis. This is one of the first attempts to use such characters to assess the relationships of all major clades using parsimony methods. The analysis uses 117 characters and includes 40 taxa, predominantly 'prosobranchs'. Five outgroup taxa are included, representing four conchiferan groups and Polyplacophora. Of the 117 characters reviewed and included in the analyses, nine are shell characters (four of these are shell structure), two opercular, two muscular, four ctenidial, 12 renopericardial and 24 reproductive (including 17 based on sperm and spermatogenesis), 27 of the digestive system, 32 of the nervous system and sense organs; the remainder are developmental (3) and of the foot and hypobranchial gland. In the initial analysis the data set included a mixture of binary and multistate characters with all characters unordered. These data were also analysed after scaling so that each character had equal weight. A third data set was constructed in which all characters were coded as binary characters. These analyses resulted in some implausible character transformations, mainly involving the regaining of lost pallial structures. Additional analyses were run on all three sets of data after removing five characters showing the most unlikely transformations. These analyses resulted in generally similar topologies. The robustness of the clades was tested using clade decay. The adaptive radiation of gastropods and their life history traits are briefly described and discussed and the terminology for simultaneous hermaphroditism refined. A scenario for the evolution of torsion equated with the fossil record is proposed and the effects of torsion and coiling on gastropods are discussed along with asymmetry imposed by limpet-shaped body forms. It is suggested that the first gastropods were ultradextral. The idea that heterochrony has played a major part in gastropod evolution is developed and discussed, particularly the paedomorphic stamp imposed on the apogastropods. The veliger larvae of caenogastropods and heterobranchs are contrasted and found to differ in many respects. The evolution of planktotrophy within gastropods is discussed. Recent phylogenetic hypotheses for gastropods based on molecular data are generally in broad agreement with the present results. On the basis of our analyses we discuss the major monophyletic groups within gastropods. Gastropods appear to be a monophyletic clade, and divide into two primary groups, the Eogastropoda (incorporating the patellogastropods and their (probably sinistrally coiled) ancestors and the Orthogastropoda -the Correspondence to W.F. Ponder. remainder of the gastropods. Orthogastropoda comprises several well defined clades. The vetigastropod clade encompasses most of the groups previously included in the paraphyletic Archaeogastropoda (fissurellids, trochoideans, scissurelloideans, halioroideans pleurotomarioideans) as well as lepetodriloidean and lepetelloidean limpets and seguenzids. The location of the hot vent taxa Peltospiridae and Neomphalidae varies with each analysis, probably because there is a lack of ultrastructural data for these taxa and parallelism in many characters. They either form a paraphyletic or monophyletic group at or near the base of the vetigastropods or a clade with the neritopsines and cocculinoideans. The neritopsines (Neritoidea etc.) consistently form a clade with the cocculinoidean limpets, but their position on the tree also differs depending on the data set used and (in the case of the scaled data) whether or not the full suite of characters is used. They are either the sister to the rest of the orthogastropods or to the apogastropods. Caenogastropods [Mesogastropoda ( + architaenioglossan groups) + Neogastropoda] are consistently monophyletic as are the heterobranchs ('Heterostropha' + Opisthobranchia + Pulmonata). The caenogastropods and heterobranchs also form a clade in all the analyses and the name Apogastropoda is redefined to encompass this group. New taxa are proposed, Sorbeoconcha for the caenogastropods exclusive of the architaenioglossan taxa, and Hypsogastropoda for the 'higher caenogastropods' -the Sorbeoconcha exclusive of the Cerithioidea and Campaniloidea.

Nuclear Astrophysics as a broad and diverse field of study can be viewed as a magnifier of the impact of microscopic processes on the evolution of macroscopic events. One of the primary goals in Nuclear Astrophysics is the understanding of the nucleosynthesis processes that take place in the cosmos and the simulation of the correlated stellar and explosive burning scenarios. These simulations are strongly dependent on the input from Nuclear Physics which sets the time scale for all stellar dynamic processes-from giga-years of stellar evolution to milli-seconds of stellar explosions-and provides the basis for most of the signatures that we have for the interpretation of these events-from stellar luminosities, elemental and isotopic abundances to neutrino flux from distant supernovae.

This paper presents a state of the art review on geometrically nonlinear analysis of shell structures that is limited to the co-rotational approach and to flat triangular shell finite elements. These shell elements are built up from flat triangular membranes and plates. We propose an element comprised of the constant strain triangle (CST) membrane element and the discrete Kirchhoff (DKT) plate element and describe its formulation while stressing two main issues: the derivation of the geometric stiffness matrix and the isolation of the rigid body motion from the total deformations. We further use it to solve a broad class of problems from the literature to validate its use. c 2006 by CIMNE, Barcelona (Spain).

In this paper we review the state of the art in an emerging new technology: embedded ultrasonic non-destructive evaluation (NDE). Embedded ultrasonic NDE permits active structural health monitoring, i.e. the on-demand interrogation of the structure to determine its current state of structural health. The enabling element of embedded ultrasonic NDE is the piezoelectric wafer active sensor (PWAS). We begin by reviewing the guided wave theory in plate, tube, and shell structures, with special attention to Lamb waves. The mechanisms of Lamb wave excitation and detection with embeddable PWAS transducers is presented. It is shown analytically and verified experimentally that Lamb wave mode tuning can be achieved by the judicious combination of PWAS dimensions, frequency value, and Lamb mode characteristics. Subsequently, we address in turn the use of pitch-catch, pulse-echo, and phased array ultrasonic methods for Lambwave damage detection. In each case, the conventional ultrasonic NDE results are contrasted with embedded NDE results. Detection of cracks, disbonds, delaminations, and diffuse damage in metallic and composite structures are exemplified. Other techniques, such as the time reversal method and the migration technique, are also presented. The paper ends with conclusions and suggestions for further work.

Combustion of appropriate precursor sprays in a flame spray pyrolysis (FSP) process is a highly promising and versatile technique for the rapid and scalable synthesis of nanostuctural materials with engineered functionalities. The technique was initially derived from the fundamentals of the wellestablished vapour-fed flame aerosols reactors that was widely practised for the manufacturing of simple commodity powders such as pigmentary titania, fumed silica, alumina, and even optical fibers. In the last 10 years however, FSP knowledge and technology was developed substantially and a wide range of new and complex products have been synthesised, attracting major industries in a diverse field of applications. Key innovations in FSP reactor engineering and precursor chemistry have enabled flexible designs of nanostructured loosely-agglomerated powders and particulate films of pure or mixed oxides and even pure metals and alloys. Unique material morphologies such as core-shell structures and nanorods are possible using this essentially one step and continuous FSP process. Finally, research challenges are discussed and an outlook on the next generation of engineered combustion-made materials is given.

The observational point of departure in this paper is that infinitivals (in Dutch and German) have no tense. Apparent counterexamples to this claim can be shown to involve aspect/Aktionsarten rather than tense. There is consequently no reason to posit any of the functional shell structure associated with tense. Hence, the infinitival markers (zu, te) may be assumed to be in (or close to) the VP. This is in accordance with the observation that these infinitival markers are always directly adjacent to the verb, which makes them similar to the verbal participial prefix ge-. A Minimalist account of zu/te, which is similar but not identical to ge-, is proposed. The question is then raised how zu (originally a true local-allative preposition) could have become a verbal prefix, and relevant diachronic data are adduced. Finally it is shown that a functionalist, or 'cognitivist', theory of grammaticalization like Haspelmath's misses the point in a number of ways. A more formalist theory of 'grammaticalizing reanalysis' is proposed as a better alternative.

Magnetite nanoparticles were prepared by coprecipitation of Fe 2' and Fe 3' with NH 4 OH, and then, amino silane was coated onto the surface of the magnetite nanoparticles. Transmission electronic microscopy shows the average size of 7.5 nm in diameter. Powder X-ray diffraction and electronic diffraction measurements show the spinel structure for the magnetite nanoparticles. FT Á/IR spectra indicate that amino silane molecules have been bound onto the surface of the magnetite nanoparticles by FeÃ/OÃ/Si chemical bonds. Energy dispersive X-ray spectroscopy (SEM Á/EDS) indicates atomic ratio of 96.75:3.25 for Fe:Si, implying a nearly monolayer coating of amino silane on the magnetite particle surface according to a rough calculation. By an enzyme-linked assay, it was proved that the amino silane-coated magnetite nanoparticles could significantly improve the protein immobilization. #

This paper focuses on the dynamic behavior of functionally graded conical, cylindrical shells and annular plates. The last two structures are obtained as special cases of the conical shell formulation. The first-order shear deformation theory (FSDT) is used to analyze the above moderately thick structural elements. The treatment is developed within the theory of linear elasticity, when materials are assumed to be isotropic and inhomogeneous through the thickness direction. The two-constituent functionally graded shell consists of ceramic and metal that are graded through the thickness, from one surface of the shell to the other. Two different power-law distributions are considered for the ceramic volume fraction. The homogeneous isotropic material is inferred as a special case of functionally graded materials (FGM). The governing equations of motion, expressed as functions of five kinematic parameters, are discretized by means of the generalized differential quadrature (GDQ) method. The discretization of the system leads to a standard linear eigenvalue problem, where two independent variables are involved without using the Fourier modal expansion methodology. For the homogeneous isotropic special case, numerical solutions are compared with the ones obtained using commercial programs such as Abaqus, Ansys, Nastran, Straus, Pro/Mechanica. Very good agreement is observed. Furthermore, the convergence rate of natural frequencies is shown to be very fast and the stability of the numerical methodology is very good. Different typologies of non-uniform grid point distributions are considered. Finally, for the functionally graded material case numerical results illustrate the influence of the power-law exponent and of the power-law distribution choice on the mechanical behavior of shell structures.

A new plane-stress triangular element is derived using the free formulation of Bergan and Nyg~rd. The triangle possesses nine degrees of freedom: six corner translations and three corner normal rotations. The element is coordinate-invariant and passes the patch test for any geometry. Two free parameters in the formulation may be adjusted to optimize the behavior for in-plane bending patterns. With the recommended parameter choices the element performance is sigmficantly better than that of the constant-strain triangle. Because of the presence of the rotational freedoms, this new element appears especially suitable as membrane component of a fiat triangular element for modelling general shell structures.

The study of ornaments made of marine shells has remarkable importance for understanding prehistoric societies. They tell us about fashion, aesthetic and cultural affinities of the individuals and social groups, as well as ancient networks of communication and exchange. The number of marine shell items known from the Neolithic period of North Macedonia is relatively low. Albeit few, they vary in ornament type, with beads, bangles and pendants represented, and the kind of shell used as raw material, as they are made of shells of bivalves, gastropods, and scaphopods. Of special importance is a find of 157 shell beads, presumably from a single string, discovered in 1958 in an anthropomorphic vessel at the site of Vršnik in Ovče pole. It was the recognition of this find, and the fact that it was originally poorly described, and later almost completely forgotten, that initiated this study. The majority of beads are tubular and made of shells of two mollusks with very different shell morp...

With the combination of the enhanced assumed strain (EAS) and assumed natural strain (ANS) techniques in the removal of shear and volumetric locking, the solid-shell formulation requires a minimum set of enhanced modes, and this results in a competitive approach when compared with other fully EAS solid elements in terms of computational costs. Moreover, the latter reportedly suffers difficulties when dealing with very thin plate and shell structures due to the severe transverse shear locking. The paper presents an alternative solid-shell formulation, in which the ANS technique is applied to the upper and lower surfaces instead of at the mid-surface of the solid-shell element as previously adopted. The numerical results show the accuracy and efficiency of the proposed technique.

This paper presents a study of a special type of tape springs, that are both longitudinally and transversely curved, as required for the ribs of a novel deployable re#ector. It is shown that, although curved tape springs have much in common with straight tape springs, there is an important di!erence for equal-sense folds with small rotation angles. Thus, it is shown that full deployment of the re#ector cannot be guaranteed if equal-sense folds are used when packaging it. : S 0 0 2 0 -7 4 0 3 ( 9 9 ) 0 0 0 5 6 -9

The calibration methods are applied to define the optimal code format according to some target safety levels. The calibration procedure can be seen as a specific optimization process where the control variables are the partial factors of the code. Different methods are available in the literature, but the choice of an appropriate method is not usually an easy task. Each method can be shown to have a better performance for a particular kind of problems. The scope of this paper is to underline the advantages and disadvantages of the classical methods, to define their domain of validity and to propose new efficient methods. In our approach, the accuracy is balanced with time efficiency by the mean of iterative scheme using approximate methods. The presented ideas are clarified by four numerical examples of parabolic performance function, column buckling, stability of submarine shells and structural elements.

Metode yang dipakai dalam perencanaan struktur cangkang ini berdasarkan teori-teori struktur cangkang dari buku acuan teori Pelat dan Cangkang yang ditulis oleh Timoschenko, Schodeck maupun teori-teori yang didapat dari buku acuan yang membahas tentang struktur cangkang lainya, dalam perencanaan struktur cangkang ini perhitungan dan syarat-syarat yang digunakan berdasarakan SNI-2847-2002 tentang Komponen Struktur Cangkang dan Pelat Lipat Pasal 21. Gambar 5.1. Denah atap kubah (Shell Structure)

This study is focused on the preparation, characterization, and determination of thermal properties of microencapsulated docosane with polymethylmethacrylate (PMMA) as phase change material for thermal energy storage. Microencapsulation of docosane has been carried out by emulsion polymerization. The microencapsulated phase change material (MEPCM) was characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Thermal properties and thermal stability of MEPCM were measured by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). DSC analysis indicated that the docosane in the microcapsules melts at 41.0 1C and crystallizes at 40.6 1C. It has latent heats of 54.6 and À48.7 J/g for melting and crystallization, respectively. TGA showed that the MEPCM degraded in three distinguishable steps and had good chemical stability. Accelerated thermal cycling tests also indicated that the MEPCM had good thermal reliability. Based on all these results, it can be concluded that the microencapsulated docosane as MEPCMs have good potential for thermal energy storage purposes such as solar space heating applications.

The effects of base-isolation on the seismic response of cylindrical vertical flexible liquid storage tanks subjected to horizontal seismic ground motion are presented in this paper. The whole system consists of two main parts: the baseisolation component, and the fluid-structure interaction subsystem. Dynamic analysis of liquid storage tank is achieved through the use of finite shell elements for the structure and internal boundary elements for the liquid region. The boundary element equations are employed to obtain an equivalent liquid mass matrix which is then coupled with the shell structure mass matrix, resulting in the coupled equations of motion. Finally, the coupled equations of motion are connected with the base-isolation system to observe the whole system behavior. A bilinear hysteretic element is used to illustrate the base-isolation system. The analysis is performed in the time domain in which, hydrodynamic interaction is taken into account. It is shown that the seismic response of the isolated tank could be significantly reduced compared with the fixed-foundation tanks. Parametric studies are carried out to study the effects of different system parameters on the effectiveness of the base-isolation system. These parameters are the tank geometry aspect ratio (height to radius), the flexibility of the isolation system, the liquid surface displacement variations, and the tank wall flexibility. It is observed that the seismic isolation is more effective in slender tanks in comparison with broad tanks. Furthermore, it is shown that the isolation efficiency is partially more significant in rigid tanks. It is also noticeable that flexible isolators considerably reduce the seismic response in comparison with stiff isolators. Despite the foregoing advantages, liquid surface displacement increases due to seismic isolation, especially in slender tanks. r

Gallery 400, University of Illinois at Chicago, January 19 – March 3, 2018. Curated by Alexander Eisenschmidt, with research and models provided by UNAM in Mexico City and Candela scholar Juan Ignacio del Cueto Ruiz-Funs; a collaboration between the University of Illinois at Chicago (UIC) and the Universidad Nacional Autónoma de México (UNAM).

This exhibition highlights the work of Félix Candela through photographs, models, and plans. In addition, it seeks to shed light on his time as a professor at the School of Architecture at the University of Illinois at Chicago (UIC) from 1971-1978, a period in Candela’s life that we know very little about.
Candela exiled to Mexico at the end of the Spanish Civil War in 1939, where he lived for thirty years and established his career as an architect. In the 1950s, ten years into his practice in Mexico, Candela debuted his experimental signature shell structures by designing a continuous curved surface of minimal thickness. His designs evolved as feats of architectural engineering, using hyperbolic paraboloid geometry to create numerous reinforced concrete shells. These curved and cantilevered forms were not only structural advancements but also brought new textural and atmospheric qualities to the collective spaces they shelter. Such structures include the Pavilion of Cosmic Rays at UNAM, Mexico City (1951); the Chapel Lomas de Cuernavaca, Cuernavaca (1958); Los Manantiales Restaurant, Xochimilco (1958); and the Palace of Sports for the 1968 Olympic Games in Mexico City.
In Chicago’s built environment, parallels to Candela’s work can be seen in the experiments with concrete architecture of the 1960s, including Walter Netsch’s UIC Campus and Bertrand Goldberg’s Marina City. Recently, formal influences of his innovations can be found in works by Zaha Hadid’s Heydar Aliyev Ali (Azerbaijan, 2013), FOA’s Yokohama Terminal (Japan, 2002), and UNstudio’s Burnham Pavilion (Chicago, 2009).

Program:
Jan. 20, 2pm Curator Talk
Jan. 27, 3pm, “Creating Candela’s Cascarones,” a workshop by UIC Arquitectos and lead by UIC faculty Antonio Torres
Feb. 13, 3pm, “A People’s Tour: Architecture & Activism at UIC,” a campus walking tour, organized by the Latino Cultural Center at UIC
Feb. 17, 3pm, “Luminous Intensity: Growing up with Fire and Dancing in the Spring,” performance by Emilio Rojas
Feb. 24, 1pm, “Shells, Surfaces, and Public Life,” a workshop with Paola Aguirre Serrano and Mejay Gula

Press:
Patrick Sisson, “Felix Candela, the Architect Who Showcased Concrete’s Curves: A New Exhibition Explores the Engineer, Architect, and Contractor Who Turned Everyday Material into Spectacular Shapes,” Curbed, January 25, 2018.
Amanda Pimenta, “Las estructuras de Félix Candela mostradas a través de fotografías, maquetas y planos,” ArchDaily, January 31, 2018.
Amanda Pimenta, “Felix Candela’s Concrete Shells Through Photographs, Architectural Models, and Plans,” ArchDaily, February 4, 2018.
Hope Daley, “The Curved Concrete of Experimental Architect Félix Candela on Display in Chicago,” Archinect, February 1, 2018.
John Hill, “Candela in Chicago,” A Daily Dose of Architecture, February 1, 2018.
“Félix Candela’s Concrete Shells,” Bustler, February 1, 2018.
Pablo Cuesta, “Las conchas de hormigón de Félix Candela: una arquitectura diseñada para México y Chicago,” Metalocus, February 4, 2018.
“Felix Candela’s Concrete Shells at Gallery 400, Chicago,” Blouin Art Info, February 7 , 2018.
KT Hawbaker, “Engineering Memory between Chicago, Mexico,” Chicago Tribune, February 23, 2018.
Claire Voor, “The Curving Concrete Poetry of a Daring Experimental Architect,” Hyperallergic, February 27, 2018.

We present a simple methodology to design isotropic triangular shell finite elements based on the Mixed Interpolation of Tensorial Components (MITC) approach. Several mixed-interpolated isotropic triangular shell finite elements are proposed. We perform well-established numerical tests and show the performance of the new elements.

A consistent formulation of the geometrically linear shell theory with drilling rotations is obtained by the consistent linearization of the geometrically non-linear shell theory considered in Parts I and I1 of this work. It was also shown that the same formulation can be recovered by linearizing the governing variational principle for the three-dimensional geometrically non-linear continuum with independent rotation field. In the finite element implementation of the presented shell theory, relying on the modified method of incompatible modes, we were able to construct a four-node shell element which delivers a very high-level performance. In order to simplify finite element implementation, a shallow reference configuration is assumed over each shell finite element. This approach does not impair the element performance for the present four-node element. The results obtained herein match those obtained with the state-of-the-art implementations based on the classical shell theory, over the complete set of standard benchmark problems.

We examine the effect of cluster size on the interaction of Ar55-Ar2057 with intense extreme ultraviolet (XUV) pulses, using a model we developed earlier that includes ionization via collisional excitation as an intermediate step. We find that the dynamics of these irradiated clusters is dominated by collisions. Larger clusters are more highly collisional, produce higher charge states, and do so more rapidly than smaller clusters. Higher charge states produced via collisions are found to reduce the overall photon absorption, since charge states of Ar 2+ and higher are no longer photo-accessible. We call this mechanism collisionally reduced photoabsorption, and it decreases the effective cluster photoabsorption cross-section by more than 30% for Ar55 and 45% Ar2057. An investigation of the shell structure soon after the laser interaction shows an almost uniformly charged core with a modestly charged outer shell which evolves to a highly charged outer shell through collisions. This leads to the explosion of the outer positive shell and a slow expansion of the core, as was observed in mixed clusters at shorter wavelength . The time evolution of the electron kinetic energy distribution begins as a (mostly) Maxwellian distribution. Larger clusters initially have higher temperature, but are overtaken by smaller temperature after the laser pulse. The electron velocity distribution of large clusters quickly become isotropic while smaller clusters retain the inherent anisotropy created by photoionization. Lastly, the total electron kinetic energy distribution is integrated over the spacial profile of the laser and the log-normal distribution of cluster size for comparison with a recent experiment , and good agreement is found.

This paper presents a unified formulation for the modelling of doubly curved composite shell structures. Via this approach, higher-order, zig-zag, layer-wise and mixed theories can be easily formulated. Classical theories, such as Love’s and Mindlin’s models, can be obtained as particular cases. The governing differential equations of the static linear problem are derived in a compact general form, tackling the difficulties due to the higher than classical terms. These equations are solved via a Navier-type, closed form solution. Shells are subjected to distributed and localised loadings. Displacement and stress fields are investigated. Thin and moderately thick as well as shallow and deep shells are accounted for. Several stacking sequences are considered. Conclusions are drawn with respect to the accuracy of the theories for the considered loadings, lay-outs and geometrical parameters. The importance of the refined shell models for describing accurately the three-dimensional stress state is outlined. The proposed results might be useful as benchmark for the validation of new shell theories and finite elements.

Hard/soft CoFe 2 O 4 /ZnFe 2 O 4 and soft/hard ZnFe 2 O 4 /CoFe 2 O 4 core/shell nanoparticles were prepared by combining high-temperature thermolysis of metal oxide precursors with seed-mediated growth. Magnetic properties of the core/shell nanoparticles were compared to those of individual CoFe 2 O 4 and ZnFe 2 O 4 nanoparticles of similar size prepared by the same method. The structure of the core/shell materials was established using a combination of X-ray and neutron powder diffraction, and transmission electron microscopy. Further evidence for core/shell structure was obtained from magnetic measurements using a SQUID magnetometer. Magnetization measurements as a function of temperature reveal that the core/shell nanoparticles display a single blocking temperature suggesting that the spins of the hard CoFe 2 O 4 and the soft ZnFe 2 O 4 are strongly coupled and respond jointly to changes of temperature and magnetic field. The blocking temperature increases according to the relative amount of hard magnetic material (CoFe 2 O 4 ) in the nanoparticles in the range of 46-150 K. Magnetic measurements on the nanoparticles as pressed powders and as dispersions in paraffin wax indicate that interparticle interactions significantly influence magnetization and coercivity of the particles, and these must be taken into account before the magnetization behavior of the core/shell structures can be interpreted in terms of coupling between the soft and hard magnetic materials.