3,266 research outputs found
Minimal energy control of a nanoelectromechanical memory element
The Pontryagin minimal energy control approach has been applied to minimise the switching energy in a nanoelectromechanical memory system and to characterise global stability of the oscillatory states of the bistable memory element. A comparison of two previously experimentally determined pulse-type control signals with Pontryagin control function has been performed, and the superiority of the Pontryagin approach with regard to power consumption has been demonstrated. An analysis of global stability shows how values of minimal energy can be utilized in order to specify equally stable states
Mixtures of Bose gases confined in concentrically coupled annular traps
A two-component Bose-Einstein condensate confined in an axially-symmetric
potential with two local minima, resembling two concentric annular traps, is
investigated. The system shows a number of quantum phase transitions that
result from the competition between phase coexistence, and radial/azimuthal
phase separation. The ground-state phase diagram, as well as the rotational
properties, including the (meta)stability of currents in this system, are
analysed.Comment: 6 pages, 5 figures, minor revision
Patterned superhydrophobic paper for microfluidic devices obtained by writing and printing
Published online: 26 July 2013This work outlines inexpensive patterning
methodologies to create open-air microfluidic paperbased
devices. A phase-separation methodology was
used to obtain biomimetic superhydrophobic paper,
hierarchically composed by micro and nano topographies.
Writing and printing are simple actions that can
be used to pattern flat superhydrophobic paper with
more wettable channels. In particular, inkjet printing
permits controlling the wettability of the surface by
changing the darkness of the printed regions. The
difference between capillary forces provides the
possibility to control and drive liquid flows through
the open path lines, just by titling the piece of paper.
Additionally, maintaining a continuous flow, it is
possible to direct the liquid at different volumetric
rates in a horizontal position along non-linear channel
paths printed/written over the surface
Enron And Continental Vending: A Comparison
We have all heard it said that if we don’t learn from history, we are condemned to repeat it. It appears that we, as the accounting profession, failed to learn from the Continental Vending case that occurred about four decades ago and thus repeated our mistakes in the Enron case. First, we will give a brief review of the basics of the Continental Vending case since few of us seem to remember it
Molecular dynamics in polymeric systems
It is well known that the properties of polymeric materials depend strongly upon their chemical structure. Other more specific factors that may be related to the chemical structure also determine the macroscopic behaviour of such materials, namely the relative position of the different segments of the polymeric chain, the molecular architecture (molecular weight distribution, branching, copoly-mer organisation, cross-linking extent, etc.), the crystalline environment and the pressure/temperature conditions. All these factors have a common impact in the material: they are strongly correlated to the mobility on the molecular level. That is why a huge amount of work has been devoted to the study of translational/rota-tional mobility that occurs within the polymeric chains. This review is intended to provide a brief survey on such kinds of mobilities, how they can be studied and what are their main characteristics. Examples on systems studied in our groups will be provided, obtained by dielectric and mechanical spectroscopies and differential scanning calorimetry. It will be mainly focused on molecular motions that occur in the solid phase (i.e., to temperatures up to the rubbery plateau). The dynamics in blends or copolymers will be avoided here, as they would deserve a special dis-cussion in their own context. Special attention will be paid to the glass transition and the mobility that occurs below and above it. The dynamics that are observed in peculiar systems, such as semi-crystalline or liquid crystalline polymers, will be addressed
Randomly Diluted e_g Orbital-Ordered Systems
Dilution effects on the long-range ordered state of the doubly degenerate
orbital are investigated. Quenched impurities without the orbital degree
of freedom are introduced in the orbital model where the long-range order is
realized by the order-from-disorder mechanism. It is shown by the Monte-Carlo
simulation and the cluster-expansion method that a decrease in the orbital
ordering temperature by dilution is remarkable in comparison with that in the
randomly diluted spin models. Tiltings of orbitals around impurity cause this
unique dilution effects on the orbital systems. The present theory provides a
new view point for the recent experiments in KCuZnF.Comment: 4 pages, 4 figure
Plagiarism Deterrence in CS1 Through Keystroke Data
Recent work in computing education has explored the idea of analyzing and grading using the process of writing a computer program rather than just the final submitted code. We build on this idea by investigating the effect on plagiarism when the process of coding, in the form of keystroke logs, is submitted for grading in addition to the final code. We report results from two terms of a university CS1 course in which students submitted keystroke logs. We find that when students are required to submit a log of keystrokes together with their written code they are less likely to plagiarize. In this paper we explore issues of implementation, adoption, deterrence, anxiety, and privacy. Our keystroke logging software is available in the form of an IDE plugin in a public plugin repository
Drug release of pH/temperature-responsive calcium alginate/poly(N-isopropylacrylamide) semi IPN beads
A series of semi-interpenetrating, polymer
network (semi-IPN), hydrogel beads, composed of calcium
alginate (Ca-alginate) and poly(N-isopropylacrylamide)
(PNIPAAM), were prepared for a pH/temperature-sensitive
drug delivery study. The equilibrium swelling showed the
independent pH- and thermo- responsive nature of the
developed materials. At pH¼2.1, the release amount of
indomethacin incorporated into these beads was about 10%
within 400 min, while this value approached to 95% at
pH¼7.4. The release rate of the drug was higher at 37 8Cthan
that at 25 8C and increased slightly with increasing
PNIPAAM content. These results suggest that the Caalginate/
PNIPAAM beads have the potential to be used as
an effective pH/temperature sustainable delivery system of
bioactive agents
Towards bioinspired superhydrophobic poly(L-lactic acid) surfaces using phase inversion-based methods
The water repellency and self-cleaning ability of many biological surfaces has inspired many
fundamental and practical studies related to the development of synthetic superhydrophobic
surfaces. However, the investigation of such substrates made of biodegradable polymers has
been scarce. Simple approaches based on a single step, performed at room temperature (and
pressure), were implemented to obtain superhydrophobic poly(L-lactic acid) (PLLA) surfaces
via phase inversion-based methods, without addition of low-surface-energy compounds. Water
contact angles above 150â—¦ were obtained using some processing conditions. In such cases
scanning electronic microscopy micrographs of such surfaces revealed a clear rough texture
composed by leafy clusters with micro-nano binary structures. Such materials could be used in
specific environmental and biomedical applications, namely in implantable materials or in
antibacterial or antithrombogenic surfaces
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