885 research outputs found
Methods Development for Non-Destructive Measurement of Bond Strength in Adhesively Bonded Structures
While reasonably satisfactory methods exist for nondestructively determining t he presence or absence of an adhesive bond, no method exists for nondestructively determining the strength of what appears to be a good bond. Bonds that do not attain their full strength can be caused by a thin layer of contaminant , improper surface roughness, and a variety of other surface phenomena that are difficult to detect by conventional methods.l,2,3 One technique is to use an ultrasonic pulse to investigate the bond interface. Since the amplitude of the pulse reflected by t he bond interface is a f unction of the elastic properties of the bond, i t should be possible to correlate t he absolute ultrasonic reflectivity with t he bond strength
Frozen capillary waves on glass surfaces: an AFM study
Using atomic force microscopy on silica and float glass surfaces, we give
evidence that the roughness of melted glass surfaces can be quantitatively
accounted for by frozen capillary waves. In this framework the height spatial
correlations are shown to obey a logarithmic scaling law; the identification of
this behaviour allows to estimate the ratio where is the
Boltzmann constant, the interface tension and the temperature
corresponding to the ``freezing'' of the capillary waves. Variations of
interface tension and (to a lesser extent) temperatures of annealing treatments
are shown to be directly measurable from a statistical analysis of the
roughness spectrum of the glass surfaces
Scale-Free topologies and Activatory-Inhibitory interactions
A simple model of activatory-inhibitory interactions controlling the activity
of agents (substrates) through a "saturated response" dynamical rule in a
scale-free network is thoroughly studied. After discussing the most remarkable
dynamical features of the model, namely fragmentation and multistability, we
present a characterization of the temporal (periodic and chaotic) fluctuations
of the quasi-stasis asymptotic states of network activity. The double (both
structural and dynamical) source of entangled complexity of the system temporal
fluctuations, as an important partial aspect of the Correlation
Structure-Function problem, is further discussed to the light of the numerical
results, with a view on potential applications of these general results.Comment: Revtex style, 12 pages and 12 figures. Enlarged manuscript with major
revision and new results incorporated. To appear in Chaos (2006
Voltage security evaluation based on perturbation method
This is the post-print version of the final paper published in International Journal of Electrical Power & Energy Systems. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2009 Elsevier B.V.This paper proposes a new algorithm for estimating voltage security margin. The algorithm is based on the perturbation method and has significant computational efficiency. The proposed algorithm can be used for on-line voltage security evaluation. It has been validated using IEEE-14, IEEE-30 and IEEE-57 bus systems. Results from the tests show higher efficiency and smaller error margins compared to continuation power flow (CPF) method.
Voltage collapse is a serious threat to the security of stressed power systems; therefore, voltage security (VS) has become a major challenge for management of power systems. The motivation for this research is a direct consequence of the deregulation of electricity industries and markets worldwide
Entropy production in a mesoscopic chemical reaction system with oscillatory and excitable dynamics
Stochastic thermodynamics of chemical reaction systems has recently gained
much attention. In the present paper, we consider such an issue for a system
with both oscillatory and excitable dynamics, using catalytic oxidation of
carbon monoxide on the surface of platinum crystal as an example. Starting from
the chemical Langevin equations, we are able to calculate the stochastic
entropy production P along a random trajectory in the concentration state
space. Particular attention is paid to the dependence of the time averaged
entropy productionP on the system sizeN in a parameter region close to the
deterministic Hopf bifurcation.In the large system size (weak noise) limit, we
find that P N^{\beta} with {\beta}=0 or 1 when the system is below or abovethe
Hopf bifurcation, respectively. In the small system size (strong noise) limit,
P always increases linearly with N regardless of the bifurcation parameter.
More interestingly,P could even reach a maximum for some intermediate system
size in a parameter region where the corresponding deterministic system shows
steady state or small amplitude oscillation. The maximum value of P decreases
as the system parameter approaches the so-called CANARD point where the maximum
disappears.This phenomenon could be qualitativelyunderstood by partitioning the
total entropy production into the contributions of spikes and of small
amplitude oscillations.Comment: 13 pages, 6 figure
Asymptotic analysis of a secondary bifurcation of the one-dimensional Ginzburg-Landau equations of superconductivity
The bifurcation of asymmetric superconducting solutions from the normal solution is considered for the one-dimensional Ginzburg--Landau equations by the methods of formal asymptotics. The behavior of the bifurcating branch depends on the parameters d, the size of the superconducting slab, and , the Ginzburg--Landau parameter. The secondary bifurcation in which the asymmetric solution branches reconnect with the symmetric solution branch is studied for values of for which it is close to the primary bifurcation from the normal state. These values of form a curve in the -plane, which is determined. At one point on this curve, called the quintuple point, the primary bifurcations switch from being subcritical to supercritical, requiring a separate analysis. The results answer some of the conjectures of [A. Aftalion and W. C. Troy, Phys. D, 132 (1999), pp. 214--232]
Regular and quasi black hole solutions for spherically symmetric charged dust distributions in the Einstein-Maxwell theory
Static spherically symmetric distributions of electrically counterpoised dust
(ECD) are used to construct solutions to Einstein-Maxwell equations in
Majumdar--Papapetrou formalism. Unexpected bifurcating behaviour of solutions
with regard to source strength is found for localized, as well as for the
delta-function ECD distributions. Unified treatment of general ECD
distributions is accomplished and it is shown that for certain source strengths
one class of regular solutions approaches Minkowski spacetime, while the other
comes arbitrarily close to black hole solutions.Comment: LaTeX (IOP style) 17 pages, 10 figure
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