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Articles 1 - 7 of 7

Full-Text Articles in Engineering Science and Materials

Step Growth And Meandering In A Precursor-Mediated Epitaxy With Anisotropic Attachment Kinetics And Terrace Diffusion, Mikhail Khenner Dec 2014

Step Growth And Meandering In A Precursor-Mediated Epitaxy With Anisotropic Attachment Kinetics And Terrace Diffusion, Mikhail Khenner

Mikhail Khenner

Step meandering instability in a Burton-Cabrera-Frank (BCF)-type model for the growth of an isolated, atomically high step on a crystal surface is analyzed. It is assumed that the growth is sustained by the molecular precursors deposition on a terrace and their decomposition into atomic constituents; both processes are explicitly modeled. A strongly nonlinear evolution PDE for the shape of the step is derived in the long-wave limit and without assuming smallness of the amplitude; this equation may be transformed into a convective Cahn-Hilliard-type PDE for the step slope. Meandering is studied as a function of the precursors diffusivity and ...


Electromigration-Driven Evolution Of The Surface Morphology And Composition For A Bi-Component Solid Film, Mikhail Khenner, Mahdi Bandegi Dec 2014

Electromigration-Driven Evolution Of The Surface Morphology And Composition For A Bi-Component Solid Film, Mikhail Khenner, Mahdi Bandegi

Mikhail Khenner

A two PDEs-based model is developed for studies of a morphological and compositional evolution of a thermodynamically stable alloy surface in a strong electric field, assuming different and anisotropic diffusional mobilities of the two atomic components. The linear stability analysis of a planar surface and the computations of morphology coarsening are performed. It is shown that the conditions for instability and the characteristic wavelength and growth rate differ from their counterparts in a single-component film. Computational parametric analyses reveal the sensitivity of the scaling exponents to the electric field strength and to the magnitude of anisotropies difference.


Crack Nucleation In A Peridynamic Solid, S. Silling, O. Weckner, E. Askari, Florin Bobaru Jul 2013

Crack Nucleation In A Peridynamic Solid, S. Silling, O. Weckner, E. Askari, Florin Bobaru

Florin Bobaru Ph.D.

A condition for the emergence of a discontinuity in an elastic peridynamic body is proposed, resulting in a material stability condition for crack nucleation. The condition is derived by determining whether a small discontinuity in displacement, superposed on a possibly large deformation, grows over time. Stability is shown to be determined by the sign of the eigenvalues of a tensor field that depends only on the linearized material properties. This condition for nucleation of a discontinuity in displacement can be interpreted in terms of the dynamic stability of plane waves with very short wavelength. A numerical example illustrates that cracks ...


Use Of A Single Multiplexed Cmos Oscillator As Direct Frequency Read-Out For An Array Of Eight Aln Contour-Mode Nems Resonant Sensors, Matteo Rinaldi, Chiara Zuniga, Brandon Duick, Gianluca Piazza Feb 2013

Use Of A Single Multiplexed Cmos Oscillator As Direct Frequency Read-Out For An Array Of Eight Aln Contour-Mode Nems Resonant Sensors, Matteo Rinaldi, Chiara Zuniga, Brandon Duick, Gianluca Piazza

Matteo Rinaldi

This paper reports on the first demonstration of a single multiplexed CMOS oscillator circuit employed as direct frequency readout for an array of 8 nanoscaled aluminum nitride Contour-Mode Resonant Sensors (CMR-S). In this first prototype 8 thin-film (250 nm) AlN CMR-S operating at 186 MHz were fabricated on the same chip and simultaneously wire-bonded to a Pierce-like oscillator circuit (fabricated in the ON Semiconductor 0.5 µm CMOS process) by means of 8 CMOS transmission gates addressed via a 3 bit on-chip decoder. The 8 CMR-S were simultaneously exposed to different concentrations of methanol (0.1–1% of the saturated ...


Green Scheduling For Radiant Systems In Buildings, Truong Nghiem, Madhur Behl, George Pappas, Rahul Mangharam Oct 2012

Green Scheduling For Radiant Systems In Buildings, Truong Nghiem, Madhur Behl, George Pappas, Rahul Mangharam

Rahul Mangharam

In this report we look at the problem of peak power reduction for buildings with electric radiant floor heating systems. Uncoordinated operation of a multi-zone radiant floor heating system can result in temporally correlated electricity demand surges or peaks in the building’s electricity consumption. As peak power prices are 200-400 times that of the nominal rate, this uncoordinated activity can result in high electricity costs and expensive system operation. We have previously presented green scheduling as an approach for reducing the aggregate peak power consumption in buildings while ensuring that indoor thermal comfort is always maintained. This report extends ...


Salmon Fibrin Supports An Increased Number Of Sprouts And Decreased Degradation While Maintaining Sprout Length Relative To Human Fibrin In An In Vitro Angiogenesis Model, Alisha Sarang-Sieminski, Keith Gooch Apr 2012

Salmon Fibrin Supports An Increased Number Of Sprouts And Decreased Degradation While Maintaining Sprout Length Relative To Human Fibrin In An In Vitro Angiogenesis Model, Alisha Sarang-Sieminski, Keith Gooch

Alisha L. Sarang-Sieminski

Salmon-derived fibrin has been proposed as a preferred alternative to human or bovine fibrin because of its reduced potential for disease transmission. Here we evaluate salmon fibrin as an alternative ECM support for therapeutic angiogenesis applications, such as vascularizing engineered tissues. Human umbilical vein endothelial cells (HUVEC) seeded on gelatin beads and suspended in either salmon or human fibrin sprouted and formed capillary-like structures. Sprout length was generally increased with the addition of bFGF and VEGF and further increased with the addition of phorbol myristate acetate (PMA). The number of sprouts per bead was increased 61-188% in salmon fibrin relative ...


Biomimetic Actuators: Where Technology And Cell Biology Merge [Review Article], Michael Knoblauch, Winfried Peters Nov 2004

Biomimetic Actuators: Where Technology And Cell Biology Merge [Review Article], Michael Knoblauch, Winfried Peters

Winfried S. Peters

The structural and functional analysis of biological macromolecules has reached a level of resolution that allows mechanistic interpretations of molecular action, giving rise to the view of enzymes as molecular machines. This machine analogy is not merely metaphorical, as bio-analogous molecular machines actually are being used as motors in the fields of nanotechnology and robotics. As the borderline between molecular cell biology and technology blurs, developments in the engineering and material sciences become increasingly instructive sources of models and concepts for biologists. In this review, we provide a – necessarily selective – summary of recent progress in the usage of biological and ...