Polygonal Columns Research Articles

Elastic Bifurcation, Postbuckling Behavior, and Collapse of Thin-Walled Regular Polygonal Columns

Elastic Bifurcation, Postbuckling Behavior, and Collapse of Thin-Walled Regular Polygonal Columns

The Decoration of the Columns and Pillars from the Henket-ankh of Thutmose III (Western Thebes)

The Temple of Millions of Years of Thutmose III called Henket-ankh, located on the West Bank of Thebes, was probably an important and impressive monument of which very little remains nowadays. Previous work at the site, which started already in the first half of the nineteenth century, contributed greatly to the understanding and identification of this complex. The Spanish-Egyptian project that resumed the archaeological works at the site in 2008 improved our knowledge about the temple architectural and decorative features. This paper will focus on the characteristics and decoration of the vertical architectural elements with support function, that is to say columns and pillars, may have had in this temple. The fragments and blocks examined and the few architectural elements preserved in situ have allowed ascertaining of the existence in the temple of polygonal columns with sixteen sides, squared pillars, some of which were of Osiride type, and circular columns that were most likely crowned by Hathoric capitals.

Effects of intra/inter-molecular potential parameters, length and grafting density of side-chains on the self-assembling behavior of poly(3′-alkylthiophene)s in the ordered state

The self-assembling behavior of conjugated regioregular poly(3′-alkylthiophene) (P3AT) polymers with various grafting density and length of alkyl side-chains are systematically examined by the coarse-grained molecular dynamics (CGMD) simulations. The effective CG interaction potentials are determined by taking into account the atomistic structural details from all-atom (AA) MD through the mapping route between the AAMD and CGMD data via the Iterative Boltzmann Inversion (IBI) methods. Except the non-bonded interaction potential between two thiophenes is modified by simply calculating the potential energy curve for them in a trans-orientation. With the dihedral angle constraint, two types of the grafted side-chains, which are located on both sides (anti-) and the same side (syn-) of the backbones, are modeled at GD = 100%, 33% and 50%, 25%, respectively. For densely grafted side-chains, such as when GD = 100% and 50%, the strong π–π attraction between the thiophene rings plays the most dominant role on the self-assembling behavior of P3AT molecules. Thus, we observe the formation of single-walled and double-walled lamellae, which however become more twisted with increasing the length of side-chains at GD = 100% and 50%, respectively. This is not surprising as longer flexible alkyl side-chains cause the backbone thiophene rings to suffer a larger distortion degree. When the grafting density is reduced significantly, not only the π–π attraction between the thiophene rings can induce the ordered packing of main-chains, but also the significant space between the side-chains can facilitate the interdigitation and aggregation of side-chains. Accordingly, for the poly(3′-nonylthiophene), poly(3′-dodecylthiophene), and poly(3′-pentadecylthiophene) molecules with 25% grafting density, we predict the formation of polygonal columns, which are formed by the packing of main-chains parallel to the column axes and the aggregation of the side-chains within the columns. When the side-chain length is increased further, these aggregated long side-chains can no longer be constrained within the polygonal minor-domains. Instead, double-walled lamellae become the most stable phase for P3AT molecules with 25% GD.

One‐Step Hydrothermal Synthesis of Carboxyl‐Functionalized Upconversion Phosphors for Bioapplications

In this paper, we report a facile one-step hydrothermal method to synthesize phase-, size-, and shape-controlled carboxyl-functionalized rare-earth fluorescence upconversion phosphors by using a small-molecule binary acid, such as malonic acid, oxalic acid, succinic acid, or tartaric acid as capping agent. The crystals, from nano- to microstructures with diverse shapes that include nanospheres, microrods, hexagonal prisms, microtubes, microdisks, polygonal columns, and hexagonal tablets, can be obtained with different reaction times, reaction temperatures, molar ratios of capping agent to sodium hydroxide, and by varying the binary acids. Fourier transform infrared, thermogravimetric analysis, and upconversion luminescence spectra measurements indicate that the synthesized NaYF(4):Yb/Er products with hydrophilic carboxyl-functionalized surface offer efficient upconversion luminescent performance. Furthermore, the antibody/secondary antibody conjugation can be realized by the carboxyl-functionalized surfaces of the upconversion phosphors, thus indicating the potential bioapplications of these kinds of materials.

Experimental and numerical investigation on crush resistance of polygonal columns and angle elements

Energy absorption characteristics of regular polygonal columns and rhombic columns under quasi-static axial compression are investigated by using an INSTRON materials testing machine. The influence of central angle on deformation mode and mean crushing force of angle elements is studied. Numerical investigations are also carried out to study the crush resistance of polygonal columns and angle elements under quasi-static and dynamic axial compression. The numerical predicted crushing force and deformation mode of the polygonal columns are found to be in good agreement with the experimental results. In addition, based on the experiment observations, some discussion about the deformation mechanism of energy absorption is presented.

Origin and evolution of polygonal cracks in hydrous sulphate sands, White Sands National Monument, New Mexico

AbstractThe nucleation and propagation of polygonal cracks in hydrous sulphate dunes at White Sands National Monument, New Mexico, are affected by water availability, transport through the sand and exchange with the atmosphere. These gypsum sands are cohesive enough to crack due to capillary forces and gypsum cements formed during evaporation. Surface cracks form five‐sided polygons with a variety of triple‐junction angles. Cracks extend down to variable depths and polygons increase in size with depth, showing a maturation similar to experimentally produced polygonal columns in drying corn starch. Results from two years of monitoring crack geometries, temperature and humidity demonstrate that cracks form when water is lost to the atmosphere through the transport of water vapour. Subsurface relative humidity below 5 to 10 cm is almost always maintained at 100% by the evaporation and condensation of water in thin films on grains. The amplitude of daily temperature and thus absolute humidity changes decreases with depth, consistent with lower evaporation and condensation rates with increasing depth. Changes in absolute humidity and the contrast between humidity in pore spaces versus the overlying atmosphere result in significant water loss from the dunes except during times of precipitation and frost/dew condensation. This water loss allows cracks to nucleate and propagate into the dunes. This study hypothesizes that crack tips propagate into sand to the depth at which thin films of water on grains are drying, and that this depth varies from the surface of the dune during precipitation events to depths greater than 45 cm when dunes are drier.

Crushing analysis of polygonal columns and angle elements

Abstract Energy absorption characteristics of regular polygonal columns and angle elements under dynamic axial compression are investigated by using non-linear explicit finite element code LS-DYNA. The influence of central angle on deformation mode and mean crushing force of angle elements is studied. Based on two types of deformation mechanisms known by experiments, two types of initial indentation triggers are introduced. By assuming appropriate boundary condition on the edges, a simplified finite element model is adopted in the analysis of angle elements and validated by comparing with full polygonal column model. Numerical investigations are also carried out to study the influence of angle on angle elements with three and four panels by using the simplified model. Several useful conclusions are drawn about the axial crushing of polygonal columns and angle elements and can be used to guide the design of crashworthiness structures. In addition, a comparison is conducted between the numerical results and theoretical predictions of the mean forces of some special angle elements. Good agreement is obtained.

Magma flow and thermal contraction fabric in tabular intrusions inferred from AMS analysis. A case study in a late-Variscan folded sill of the Albarracín Massif (southeastern Iberian Chain, Spain)

The effects of different petrological processes on the rock fabric of a folded sill from the Albarracin Massif (southeastern Iberian Chain, Spain) were studied by means of the anisotropy of magnetic susceptibility (AMS) technique. The most outstanding feature of the sill at outcrop-scale is a network of joints linked to thermal contraction, which define polygonal columns. The analysis of the magnetic fabric, taking the orientation of sill walls and column axes as a reference and using the ‘restored’ directional data corresponding to the whole of K3 susceptibility axes, has revealed magnetic fabrics related to two processes: (a) magma flow with a SW-trending flow vector characterized by a curved geometry of the magma foliations and (b) thermal contraction coeval to lava cooling. Early magnetite crystals, grown in a relatively high viscosity calc-alkaline magma, are the main carriers involved in the AMS fabric. Passive rotation of the early magnetic mineralogy within a medium-viscosity magma explains the magnetic fabric linked to both magma flow and near-solidus thermal contraction of the magma. Late-Variscan folding of the sill produced the rigid-body reorientation of the magnetic fabric.

Cylindrical Columnar Joints in Precambrian Mafic Dikes, Bighorn Mountains, Wyoming

The rare occurrence of cylindrical columnar jointing has been noted in Precambrian mafic dikes in the Bighorn Mountains, Wyoming. The cylindrical columns occur at random locations along the length of several steeply dipping dikes which range from 50 to 100 feet in thickness. They are circular or elliptical in cross section, 3 to 10 feet in diameter, and continuous across the width of the dikes. These columns contrast markedly with polygonal columns that have been secondarily rounded due to spheroidal weathering. Like polygonal columnar jointing, the cylindrical columns have their long axes oriented normal to the outer dike walls and are probably primary features formed by shrinkage attendant on cooling inward from the walls.