Search results for "Online"
showing 10 items of 4526 documents
Cross-Diffusion Driven Instability in a Predator-Prey System with Cross-Diffusion
2013
In this work we investigate the process of pattern formation induced by nonlinear diffusion in a reaction-diffusion system with Lotka-Volterra predator-prey kinetics. We show that the cross-diffusion term is responsible of the destabilizing mechanism that leads to the emergence of spatial patterns. Near marginal stability we perform a weakly nonlinear analysis to predict the amplitude and the form of the pattern, deriving the Stuart-Landau amplitude equations. Moreover, in a large portion of the subcritical zone, numerical simulations show the emergence of oscillating patterns, which cannot be predicted by the weakly nonlinear analysis. Finally when the pattern invades the domain as a trave…
Broadband telecom to mid-infrared supercontinuum generation in a dispersion-engineered silicon germanium waveguide.
2015
We demonstrate broadband supercontinuum generation (SCG) in a dispersion-engineered silicon-germanium waveguide. The 3 cm long waveguide is pumped by femtosecond pulses at 2.4 μm, and the generated supercontinuum extends from 1.45 to 2.79 μm (at the −30 dB point). The broadening is mainly driven by the generation of a dispersive wave in the 1.5–1.8 μm region and soliton fission. The SCG was modeled numerically, and excellent agreement with the experimental results was obtained.
<title>Second harmonic generation in selenium thin films</title>
2008
Results of second harmonic (SH) generation in amorphous and crystalline selenium films induced by titanium-sapphire femtosecond laser (wavelength λ - 800-1000 nm) are presented. It is found that the highest intensity of SH is provided by fundamental wave at wavelength 1000 nm and it reaches maximum in approximately 100 sec. The intensity of transmitted SH depends on film thickness while that of reflected does not.
<title>Second harmonic generation in selenium-metal structures</title>
2008
The article examines the processes of second harmonic generation (SHG) when selenium-metal (Cu) film structures are illuminated by femtosecond radiation (180 fs, 80 MHz) at wavelength 800 - 1000 nm. Selenium-copper structures were obtained by successive thermal evaporation of selenium and copper onto the glass substrate in vacuum. Microanalysis of the film composition was performed to determine amount of copper in thin films. The as-evaporated selenium-copper structures were crystallised by annealing in inert atmosphere at temperature 85°C. Just evaporated as well as annealed thin films were explored. The experiment was performed by confocal microscope [1] where the femtosecond radiation fr…
ON THE BOUSSINESQ HIERARCHY
2002
A new sequence of nonlinear evolution systems satisfying the zero curvature property is constructed, by using the invariant singularity analysis. All these systems are completely integrable and a pseudo-potential (linearization) is explicitly determined for each of them. The second system of the sequence is the Broer-Kaup system, which, as is well known, corresponds to the higher order Boussinesq approximation in describing shallow water waves.
Cross-diffusion driven instability for a nonlinear reaction-diffusion system
2008
In this work we investigate the possibility of the pattern formation for a system of two coupled reaction-diffusion equations. The nonlinear diffusion terms has been introduced to describe the tendency of two competing species to diffuse faster (than predicted by the usual linear diffusion) toward lower densities areas. The reaction terms are chosen of the Lotka-Volterra type in the competitive interaction case. The system is supplemented with the initial conditions and no-flux boundary conditions. Through a linear stability analysis we find the conditions which allow a homogeneous steady state (stable for the kinetics) to become unstable through a Turing mechanism. In particular, we show h…
Pattern Dystrophy of the Macula in a Case of Steinert Disease
2013
<b><i>Introduction:</i></b> Myotonic dystrophies are typically associated with ocular complications like ptosis, weakness of the ocular muscle and cataracts, but also with less recognized retinal changes. <b><i>Case Report:</i></b> A 41-year-old female with type 1 myotonic dystrophy complained of progressive vision loss. Slit lamp examination revealed the presence of typical bilateral polychromatic cataract with posterior subcapsular component. Dilated fundus examination was remarkable for bilateral macular depigmented changes. Multimodal imaging analysis of the macula suggested the presence of a butterfly-shaped pattern dystrophy. <b>&l…
HTTP-level e-commerce data based on server access logs for an online store
2020
Abstract Web server logs have been extensively used as a source of data on the characteristics of Web traffic and users’ navigational patterns. In particular, Web bot detection and online purchase prediction using methods from artificial intelligence (AI) are currently key areas of research. However, in reality, it is hard to obtain logs from actual online stores and there is no common dataset that can be used across different studies. Moreover, there is a lack of studies exploring Web traffic over a longer period of time, due to the unavailability of long-term data from server logs. The need to develop reliable models of Web traffic, Web user navigation, and e-customer behaviour calls for …
Application of neural network to predict purchases in online store
2016
A key ability of competitive online stores is effective prediction of customers’ purchase intentions as it makes it possible to apply personalized service strategy to convert visitors into buyers and increase sales conversion rates. Data mining and artificial intelligence techniques have proven to be successful in classification and prediction tasks in complex real-time systems, like e-commerce sites. In this paper we proposed a back-propagation neural network model aiming at predicting purchases in active user sessions in a Web store. The neural network training and evaluation was performed using a set of user sessions reconstructed from server log data. The proposed neural network was abl…
CN2-R: Faster CN2 with randomly generated complexes
2011
Among the rule induction algorithms, the classic CN2 is still one of the most popular ones; a great amount of enhancements and improvements to it is to witness this. Despite the growing computing capacities since the algorithm was proposed, one of the main issues is resource demand. The proposed modification, CN2-R, substitutes the star concept of the original algorithm with a technique of randomly generated complexes in order to substantially improve on running times without significant loss in accuracy.