Cone-shaped Shell Research Articles

Effect of porosity on the nonlinear free vibrational behavior of two-directional functionally graded porous cone-shaped shells resting on elastic substrates

The present article describes an analytical approach to investigate the nonlinear free vibrational behavior of a two-directional functionally graded porous (TDFGP) cone-shaped shell resting on elastic substrates. A mixture model with the power-law distribution functions is utilized to obtain the TDFGP shell’s mechanical properties. In addition, it is assumed that the internal porosities in the matrix materials can be dispersed into two independent patterns, either even or uneven porosity distribution. The field displacement in the TDFGP shell is approximated using first-order shear deformation theory. Hamilton’s principle and von Karman’s large deformation assumptions give a dynamic model for the TDFGP shell. The Galerkin decomposition method is employed to discretize the governing partial differential equations into time-dependent ordinary differential equations. The harmonic balance method is used to analytically solve the final time-dependent equations and acquire the nonlinear frequency response of the TDFGP shell. Research has been conducted on porosity, gradient indexes, elastic substrates, boundary conditions, and geometric ratios through parametric studies to investigate the outcomes and their applicability to real-world issues.

Nonlinear Forced Vibration Analysis of Two-Directional Functionally Graded Truncated Conical Shells

It is crucial to comprehend the nonlinear vibration behavior of sophisticated engineering constructions to aid in the examination, creation and production procedures. The primary objective of this study, therefore, is to focus on exploring the nonlinear forced vibrational characteristics of two-directional functionally graded (TDFG) cone-shaped shell for the first time. To accomplish this, the motion equations of the TDFG cone-shaped shell are derived based upon the framework of first-order shear deformation theory (FSDT) in conjunction with von Kármán assumption. TDFG cone-shaped shell models have mechanical properties that can change smoothly and continuously across the thickness and length of the shell, following a power law distribution pattern. To discretize the partial differential equations and transform them into ordinary differential equations, the Galerkin approach was used and ultimately, these equations were solved using the multiple time scales method. The accuracy and effectiveness of this analytical model are indicated through comparison with existing solutions. Finally, some comprehensive parametric investigations are carried out to gain insight into the impacts of several factors on the nonlinear behavior of the shell, highlighting the significant influence of transverse and longitudinal gradient indices on the nonlinear frequency response, which is not considered before. The new insights gained from this research could serve as valuable benchmark outcomes as well as contribute to a more comprehensive understanding of the nonlinear vibrations in future analysis and design processes.

Nonlinear Inflatable Actuators for Distributed Control in Soft Robots.

As soft robotic systems grow in complexity and functionality, the size and stiffness of the needed control hardware severely limits their application potential. Alternatively, functionality can be embodied within actuator characteristics, drastically reducing the amount of peripherals. Functions such as memory, computation, and energy storage then result from the intrinsic mechanical behavior of precisely designed structures. Here, actuators are introduced with tunable characteristics to generate complex actuation sequences from a single input. Intricate sequences are made possible by harnessing hysteron characteristics encoded in the buckling of a cone-shaped shell incorporated in the actuator design. A large variety of such characteristics are generated by varying the actuator geometry. This dependency is mapped and used for creating a tool to determine the actuator geometry that yields a desired characteristic. Using this tool, a system with six actuators is created that plays the final movement of Beethoven's Ninth Symphony with a single pressure supply.

Localization and functions of native and eGFP-tagged capsid proteins in HIV-1 particles.

In infectious HIV-1 particles, the capsid protein (CA) forms a cone-shaped shell called the capsid, which encases the viral ribonucleoprotein complex (vRNP). Following cellular entry, the capsid is disassembled through a poorly understood process referred to as uncoating, which is required to release the reverse transcribed HIV-1 genome for integration into host chromatin. Whereas single virus imaging using indirect CA labeling techniques suggested uncoating to occur in the cytoplasm or at the nuclear pore, a recent study using eGFP-tagged CA reported uncoating in the nucleus. To delineate the HIV-1 uncoating site, we investigated the mechanism of eGFP-tagged CA incorporation into capsids and the utility of this fluorescent marker for visualizing HIV-1 uncoating. We find that virion incorporated eGFP-tagged CA is effectively excluded from the capsid shell, and that a subset of the tagged CA is vRNP associated. These results thus imply that eGFP-tagged CA is not a direct marker for capsid uncoating. We further show that native CA co-immunoprecipitates with vRNP components, providing a basis for retention of eGFP-tagged and untagged CA by sub-viral complexes in the nucleus. Moreover, we find that functional viral replication complexes become accessible to integrase-interacting host factors at the nuclear pore, leading to inhibition of infection and demonstrating capsid permeabilization prior to nuclear import. Finally, we find that HIV-1 cores containing a mixture of wild-type and mutant CA interact differently with cytoplasmic versus nuclear pools of the CA-binding host cofactor CPSF6. Our results suggest that capsid remodeling (including a loss of capsid integrity) is the predominant pathway for HIV-1 nuclear entry and provide new insights into the mechanism of CA retention in the nucleus via interaction with vRNP components.

Mollusks and Medicine

When you read about the relationship of science and the arts, you most often are presented with accounts of how the arts have been used to reflect science or scientific thought. In other words, the science comes before the art. Examples include paintings of surgeons in the operating theater, anatomists studying a human cadaver, the grand entrances of historic hospitals and libraries, even the works of science illustrators. But once in a while the opposite happens, where the art precedes the science, where natural elements, beloved for their beauty, serve as the inspiration or foundation for scientific discovery. Such is the case for the seashells of the world and the mollusks that produce these external skeletons from chemical elements found in the oceans. One family of mollusks, the cone snails, produces a cone-shaped shell that is among the most beautiful and sought after seashells. As pieces of art on their own, the shells of the cone snails can fetch large sums of money, even by today's standards. In the 18th century, one such seashell, that of the Conus gloriamaris (glory of the sea cone) (Fig. 1), was valued at an amount comparable to Johannes Vermeer's Woman in Blue Reading a Letter (1), now a priceless part of the collection of the Rijksmuseum Amsterdam. The natural beauty of cone snails also provides a story of how collecting seashells ultimately led to scientific discovery, specifically a novel pain medicine. Fig. 1. Conus gloriamaris. ©Reproduced with permission from Bruno Mathe—www.zonatus.com. The discovery of ziconotide (Prialt®), a unique non-opioid analgesic that is an N-type calcium channel blocker, has its roots …

The Effect of Volume Fraction of Single-Walled Carbon Nanotubes on Natural Frequencies of Polymer Composite Cone-Shaped Shell Made from Poly(Methyl Methacrylate)

In this paper, the effect of volume fraction of single-walled carbon nanotubes on natural frequencies of polymer composite cone-shaped shells made from Poly(Methyl Methacrylate) (PMMA) is studied. In order to determine the characterization of materials reinforced with nanoparticles, the molecular dynamics and mixture rule has been used. The motion equations of composite shell based on the classical thin shells theory using Hamilton’s principle are obtained. Then, using the Ritz method, approximate analytical solution of the natural frequency is presented. Results indicate that the nanotubes have a noticeable effect on the natural frequencies.

Mineral and Matrix Components of the Operculum and Shell of the Barnacle Balanus amphitrite: Calcite Crystal Growth in a Hydrogel

Sessile barnacles produce two types of mineralized exoskeletons: a cone-shaped shell and an operculum that is used to seal the shell opening. The mineral of both types is calcite. We show that the calcite crystals of the shell and the operculum (specifically the scutum) of the sessile barnacle Balanus amphitrite both fracture with conchoidal cleavage, have surfaces decorated with small rhombohedral shaped calcite crystals, and are poorly oriented. The scutum calcite is significantly more disordered at the atomic level than the shell calcite. We also show that a major component of the intercrystalline organic matrix of the shell and scutum is a nonproteinaceous sulfate-rich polymer that behaves as a hydrogel, and that the intracrystalline matrix contains highly acidic proteins. The crystal properties and microstructure are consistent with the calcite crystals forming in a hydrogel-like environment. The barnacle shell and operculum have many unique properties indicating that the crystal growth conditions are well controlled and possibly adapted to fulfill mechanical functions, which enable the barnacle to survive in the high energy environment of the intertidal zone.