The origin and rapid diversification of flowering plants has puzzled evolutionary biologists, dating back to Charles Darwin. Since that time a number of key life history and morphological traits have been proposed as developmental correlates of the extraordinary diversity and ecological success of angiosperms. Here, I identify several innovations that were fundamental to the evolutionary labili...

We experimentally studied the propagation of coupled fluid stress waves and tube flexural waves generated through projectile impact along the axis of a water-filled tube. We tested mild steel tubes, 38–40 mm inner diameter and wall thicknesses of 0.8 mm, 6.4 mm, and 12.7 mm. A steel impactor was accelerated using an air cannon and struck a polycarbonate buffer placed on top of the water surface...

Polarization of low-lying excitonic bands in finite-size semiconducting single-walled carbon nanotubes (SWNTs) is studied by using quantum-chemical methodologies. Our calculations elucidate properties of cross-polarized excitons, which lead to the transverse optical absorption of nanotubes and presumably couple to intermediate-frequency modes recently observed in resonance Raman excitation spec...

A fully-coupled, finite-element method is used to investigate the steady flow of a viscous fluid through a thin-walled, elastic tube mounted between two rigid tubes. The steady, three-dimensional, Navier–Stokes equations are solved simultaneously with the equations of geometrically-non-linear, Kirchhoff–Love shell theory. If the transmural (internal minus external) pressure acting on the tube i...

This paper provides analytic solutions for the dynamics of a pressurized elastoplastic thin-walled tube at small strains. The closed-form expressions stress and displacement fields are derived within framework thin cylindrical shell theory. Three dynamic load-processes considered: an increasing-constant internal pressure, rectangular triangular pulse loads. It is found that, depending on extern...

Crash-dynamics research has always concentrated significantly in the safety, survivability of passengers a car crash. To identify capability energy absorption crash box, thin-walled structure will be modeled and simulated by ABAQUS software. Investigate influence material, cross-sectional, thickness factors on capacity tube, using MCDM – Multi-Criteria Decision-Making to get best option testing...

we report the enhanced capacitance of the multi-walled carbon nanotubes (mwcnts) after a chemical unzipping process in concentrated sulfuric acid (h2so4) and potassium permanganate (kmno4). the effects of the test duration and temperature were investigated on the unzipping process of the mwcnts to synthesize the graphene oxide nanoribbons. the sem and tem studies were carried out on untreated a...

To maximize the controllable energy absorption of corrugation troughs as observed in the single sided corrugated (SSC) tube, we proposed and tested a new structure design, i.e., double-sided corrugated (DSC) tube made of Al 6060-T6 aluminum alloy or CF1263 carbon/epoxy composite. Finite element models were developed to test the mechanical advantage of the DSC tube in comparison with both SSC an...

The unique electronic properties of single-walled carbon nanotubes (SWNTs) make them promising candidates for next generation electronics, particularly in systems that demand high frequency (e.g., radio frequency, RF) operation. Transistors that incorporate perfectly aligned, parallel arrays of SWNTs avoid the practical limitations of devices that use individual tubes, and they also enable comp...

We studied the impact of wall strain and surrounding pressure on the onset of airflow limitation in a thin-walled "floppy" tube model. A vacuum source-generated steady-state (baseline) airflow (0-350 ml/s) through a thin-walled latex tube (length 80 mm, wall thickness 0.23 mm) enclosed within a rigid, sealed, air-filled, cylindrical chamber while upstream minus downstream pressure, chamber pres...