Subdivision Shell Elements with Anisotropic Growth

A thin shell finite element approach based on Loop's subdivision surfaces is proposed, capable of dealing with large deformations and anisotropic growth. To this end, the Kirchhoff-Love theory of thin shells is derived and extended to allow for arbitrary in-plane growth. The simplicity and computational efficiency of the subdivision thin shell elements is outstanding, which is demonstrated on a few standard loading benchmarks. With this powerful tool at hand, we demonstrate the broad range of possible applications by numerical solution of several growth scenarios, ranging from the uniform growth of a sphere, to boundary instabilities induced by large anisotropic growth. Finally, it is shown that the problem of a slowly and uniformly growing sheet confined in a fixed hollow sphere is equivalent to the inverse process where a sheet of fixed size is slowly crumpled in a shrinking hollow sphere in the frictionless, quasi-static, elastic limit.Comment: 20 pages, 12 figures, 1 tabl

Novel Discretization Schemes for the Numerical Simulation of Membrane Dynamics

Motivated by the demands of simulating flapping wings of Micro Air Vehicles, novel numerical methods were developed and evaluated for the dynamic simulation of membranes. For linear membranes, a mixed-form time-continuous Galerkin method was employed using trilinear space-time elements, and the entire space-time domain was discretized and solved simultaneously. For geometrically nonlinear membranes, the model incorporated two new schemes that were independently developed and evaluated. Time marching was performed using quintic Hermite polynomials uniquely determined by end-point jerk constraints. The single-step, implicit scheme was significantly more accurate than the most common Newmark schemes. For a simple harmonic oscillator, the scheme was found to be symplectic, frequency-preserving, and conditionally stable. Time step size was limited by accuracy requirements rather than stability. The spatial discretization scheme employed a staggered grid, grouping of nonlinear terms, and polygon shape functions in a strong-form point collocation formulation. Validation against existing experimental data showed the method to be accurate until hyperelastic effects dominate

Response variation of Chladni patterns on vibrating elastic plate under electro-mechanical oscillation

Fine grain particles such as sugar, sand, salt etc. form Chladni patterns on the surface of a thin plate subjected to acoustic excitation. This principle has found its relevance in many scientific and engineering applications where the displacement or response of components under the influence of vibration is vital. This study presents an alternative method of determining the modal shapes on vibrating plate in addition to other existing methods like the experimental method by Ernst Chladni. Three (3) finite element solvers namely: CATIA 2017 version, ANSYS R15.0 2017 version and HYPERMESH 2016 version were employed in the modelling process of the 0.40 mm x 0.40 mm plate and simulation of corresponding mode shapes (Chladni patterns) as well as the modal frequencies using Finite Element Method (FEM). Result of modal frequency obtained from the experimental analysis agreed with the FEM simulated, with HYPERMESH generated results being the closest to the experimental values. It was observed that the modal frequencies obtained from the FEM and experimental approach increased as the excitation time increased. ANSYS R15.0 and HYPERMESH software clearly represented the modal lines and mode shapes for each frequency which CATIA software was somewhat limited. This study has shown that FEM is an effective tool that can save time and energy invested in acoustic experiments in determining modal frequencies and patterns.Keywords: Vibration, Chladni patterns, Modal frequency, Thin plate, Experimental analysi

Growth of nanostructured zinc oxide on flexible conductive substrate: a review

In this paper, a review on the structural and morphological of nanostructured zinc oxide (ZnO) fabricated on flexible conductive substrate, mainly indium tin oxide coated on polyethylene terephthalate (ITO/PET) via various fabrication method is reported. Besides fabrication method, the effect of fabrication condition such as immersion time of ZnO-ITO/PET via hydrothermal method, concentration of modification material of precursor solution via sol-gel method, value of applied cathodic voltage and value of current densities via electrochemical deposition are also discussed. XRD analysis showed that the growth of ZnO-ITO/PET are preferred on (002) or (101) planes. SEM analysis revealed various type of nanostructured ZnO when prepared by sol-gel, spin coating, HWT and hydrothermal method, highlighting ZnO nanorods as the main morphology of ZnO�ITO/PET. The diameter of ZnO nanorods ranges from 10 nm to 830 nm

Real-time implementation of the shamisen using finite difference schemes

The shamisen is a Japanese three-stringed lute. It is a chordophone that has the front of the body covered by a tensioned membrane which greatly contributes to the distinct sound of the instrument. Although the shamisen is a traditional Japanese instrument, it is a rare instrument in the rest of the world, making it mostly inaccessible by the majority of artists. To our knowledge, no physically modelled synthesizer of the shamisen is available, forcing producers and musicians to use samples. The objective of this paper is to make the shamisen’s distinct sound more accessible to digital music artists. The real-time implementation of the shamisen physical model is presented along with the derivation of solution using the finite-difference timedomain (FDTD) methods. The digital instrument sounds mostly as intended, though lacking the shamisen’s distinct buzzing sound requiring further development

NASA Tech Briefs, November 1988

Topics covered include: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

Large scale atomistic simulations of complex IV reveal novel protein-lipid interactions

In mitochondria and many bacteria, the electron transport chain produces energy from foodstuff as a part of cell respiration. Complex IV, also known as Cytochrome c Oxidase, is the last protein complex in the electron transport chain. It couples electron transport with the transfer of protons across the inner mitochondrial membrane (or the cell membrane in bacteria). The pumped protons produce a proton-motive force, which drives adenosine triphosphate synthase to generate adenosine triphosphate molecules used as energy currency in many cellular functions. Dysfunction of complex IV may cause myopathies and other mitochondrial malfunctions, and therefore it is important to understand how this enzyme functions and is regulated. The work performed in this Thesis provides novel insights into the intricate function of the enzyme and reveals the importance of lipid-protein interactions that turn out to be critical in the enzyme function. These insights provide new ways to better understand how cardiolipin as a key lipid in mitochondrial membranes participates in proton uptake pathways, and whether cardiolipin also has an important role in complex IV dimerization. Six large-scale atomistic molecular dynamics simulations of complex IV were performed, including simulations of the dimeric as well as the monomeric complex IV. In each simulation, the membrane consisted of three kinds of primary lipids found in the inner mitochondrial membrane. All the simulations were two to three microseconds long, therefore representing the current state-of-the-art in membrane-protein simulations in this context. The simulation data show that the dimeric complex IV is stable. The data also reveal that there are fewer protein-protein ion pairs between complex IV monomers in the presence of cardiolipins at the interface, however cardiolipin could also function as glue forming charge-charge interactions with both of the monomers. Cardiolipin-complex IV interactions seem to have more significance compared to other lipid-complex IV interactions, favoring the earlier proposals that cardiolipins are possibly involved in proton uptake. The monomeric complex IV was observed to tilt 5-10 degrees with respect to the initial position of the protein and membrane normal, while for the dimeric complex IV no tilt was observed. The difference in tilt might work as a free energy barrier in dimerization. It is also suggested that cardiolipins between the monomers could reduce the possible free energy barrier in dimerization. Understanding of these microscopic aspects by means of molecular dynamics simulations may open up new avenues to target mitochondrial dysfunctions