512 research outputs found
An efficient representation for kernels in the 2d dynamics displacement discontinuity method for cracked elastic materials
The displacement discontinuity method is a rather standard approach to study cracks in elastic materials. This is in fact a certain technique to construct the system of Boundary Integral Equations (BIE), or equivalently, Boundary Element Methods (BEM). In the static case this typically results in explicit expressions for the kernels of respective BIE, both in 2d and 3d problems. In the work the authors give efficient representations for such kernels in explicit form
Reconstruction of Crack Cluster in the Rectangular Domain by Ultrasonic Waves
In the present article we study the reconstruction problem for clusters of linear cracks inside a rectangular domain. The parameters to be reconstructed are the number of cracks and the size and slope of each defect. The scanning is performed by a single ultrasonic transducer placed at a certain boundary point. The input data, used for the reconstruction algorithm, is taken as measured oscillation amplitudes over an array of chosen boundary points. The proposed numerical algorithm is tested on some examples with multiple clusters of cracks whose position and geometry are known a priori
ABIOTIC DEGRADATION OF IODOSULFURON-METHYL-ESTER IN AQUEOUS SOLUTION
The abiotic degradation of iodosulfuron-methyl-ester was investigated under both alkaline and acidic
pH conditions in the dark, and results showed it to be a rather stable molecule in neutral or slightly
alkaline environments. Photochemical reactions were studied using a high-pressure mercury arc lamp,
and results showed that direct phototransformation is possible under normal environmental conditions
(ì > 290 nm). High-performance liquid chromatography (HPLC-UV and HPLC-MS) analyses were
used to identify the degradates and to study the kinetics of photodecomposition and hydrolysis. Five
main products of iodosulfuron-methyl-ester degradation were tentatively identified, and one of them
(4-methoxy-6-methyl-1,3,5-triazin-2-amine) was confirmed using an authentic standard. Among the
phototransformation mechanisms, photosubstitution of the iodide atom by a hydroxyl group,
photodissociation of the N-S bond, and photoassisted hydrolysis were observed. The quantum
efficiencies (multiwavelength quantum yield) of the photodegradation under different conditions were
determined, and values of 0.054 ( 0.02 (pH 9.6), 0.08 ( 0.02 (pH 7), and 0.044 ( 0.008 (pH 5.3)
were obtained
Higher Derivative Corrections to Locally Black Brane Metrics
In this paper we generalize the construction of locally boosted black brane
space time to higher derivative gravities. We consider the Gauss-Bonnet term
(with coefficient ) as a toy example. We find the solution to the
corrected Einstein equations to first order in the boundary
derivative expansion. This allows us to find the corrections to the
boundary stress tensor in the presence of the Gauss-Bonnet term in the bulk
action. We therefore obtain the ratio of shear viscosity to entropy which
agrees with other methods of computation in the literature.Comment: 0+17 page
Degradation of lansoprazole and omeprazole in the aquatic environment
Lansoprazole and omeprazole degrade in water leading to sulfides, benzimidazolones and a red complex material.
Degradation is accelerated in acid medium and by solar simulator irradiation. Benzimidazoles, dianilines and pyridines
have also been identified
Higher Derivative Gravity, Causality and Positivity of Energy in a UV complete QFT
In this note we discuss the relation between the constraints imposed by
causality in the bulk of and the condition of positivity of the energy
measured in ideal calorimeters in a collider experiment in the dual CFT. We
first extend the analysis in the literature and recover all bounds imposed by
causality of the boundary theory in the bulk dynamics for all polarizations of
the graviton and the gauge boson field. These results translate to specific
bounds for the ratio of central charges in the dual CFT, already
found by analyzing the energy one point function. Then, we generalize this
discussion and we study shock wave backgrounds in which we make manifest the
relation between causality in the bulk and the three point function in the dual
field theory. We remark that particular care has to be given to the
exponentiation procedure of the three point function when solving the classical
equations of motion in the higher gravity theory, as it is not clear that every
theory will present causality problems. Finally, we present a field theoretic
argument explaining the positivity of energy condition in any UV complete QFT.Comment: 31 pages, 3 figures; v2: references adde
On multiple crack identification by ultrasonic scanning
The present work develops an approach which reduces operator equations arising in the engineering problems to the problem of minimizing the discrepancy functional. For this minimization, an algorithm of random global search is proposed, which is allied to some genetic algorithms. The efficiency of the method is demonstrated by the solving problem of simultaneous identification of several linear cracks forming an array in an elastic medium by using the circular Ultrasonic scanning
Multiple algebraisations of an elliptic Calogero-Sutherland model
Recently, Gomez-Ullate et al. (1) have studied a particular N-particle
quantum problem with an elliptic function potential supplemented by an external
field. They have shown that the Hamiltonian operator preserves a finite
dimensional space of functions and as such is quasi exactly solvable (QES). In
this paper we show that other types of invariant function spaces exist, which
are in close relation to the algebraic properties of the elliptic functions.
Accordingly, series of new algebraic eigenfunctions can be constructed.Comment: 9 Revtex pages, 3 PS-figures; Summary, abstract and conclusions
extende
Horizons and the Thermal Harmonic Oscillator
We show that two-dimensional anti-de Sitter spacetime (AdS_2) can be put in
correspondence, holographically, both with the harmonic oscillator and the free
particle. When AdS_2 has an horizon the corresponding mechanical system is a
thermal harmonic oscillator at temperature given by the Hawking temperature of
the horizon.Comment: Content changed, title slightly modifie
Central Executive Dysfunction and Deferred Prefrontal Processing in Veterans with Gulf War Illness.
Gulf War Illness is associated with toxic exposure to cholinergic disruptive chemicals. The cholinergic system has been shown to mediate the central executive of working memory (WM). The current work proposes that impairment of the cholinergic system in Gulf War Illness patients (GWIPs) leads to behavioral and neural deficits of the central executive of WM. A large sample of GWIPs and matched controls (MCs) underwent functional magnetic resonance imaging during a varied-load working memory task. Compared to MCs, GWIPs showed a greater decline in performance as WM-demand increased. Functional imaging suggested that GWIPs evinced separate processing strategies, deferring prefrontal cortex activity from encoding to retrieval for high demand conditions. Greater activity during high-demand encoding predicted greater WM performance. Behavioral data suggest that WM executive strategies are impaired in GWIPs. Functional data further support this hypothesis and suggest that GWIPs utilize less effective strategies during high-demand WM
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