Search results for "approximation"
showing 10 items of 818 documents
Theoretical study of neutrino scattering off the stable even Mo isotopes at low and intermediate energies
2011
A systematic study of the cross sections of neutral-current neutrino scattering off the stable even Mo isotopes (mass number A = 92, 94, 96, 98, 100), at low and intermediate neutrino energies (E(nu) <= 130 MeV), is presented and discussed. The required wave functions for the initial (ground state) and all accessible final nuclear states are constructed in the context of the quasi-particle random-phase approximation (QRPA) and tested against data on the low-lying energy spectra of the isotopes in question. The individual contributions coming from the polar-vector and axial-vector components of the hadronic current for the coherent and incoherent channels of each isotope are investigated. Th…
Analytical solutions of magnetohydrodynamical problems on a flow of conducting fluid in the entrance region of channels in a strong magnetic field šķ…
2014
Darbā iegūti analītiskie atrisinājumi magnetohidrodinamiskiem (MHD) uzdevumiem par elektrovadoša šķidruma plūsmu plakanā un cilindriskā kanālā stiprā magnētiskā laukā gadījumiem, kad šķidrums ietek kanālos caur galīga platuma spraugu vai caur galīga rādiusa atveri kanāla sānu malā. Pamatojoties uz iegūtajiem atrisinājumiem, veikta plūsmas ātruma lauka skaitliskā analīze. Iegūti uzdevumu asimptotiskie atrisinājumi lieliem Hartmana skaitļiem. Turklāt darbā pētīta pilna spiediena spēka šķidruma ieplūdes apgabalā atkarība no funkcijas veida, ar kuru ir uzdots ātruma robežnosacījums. Pētījums veikts analītiski, risinot divas hidrodinamiskas problēmas un divas MHD problēmas par viskoza šķidruma i…
Quantitative Runge Approximation and Inverse Problems
2017
In this short note we provide a quantitative version of the classical Runge approximation property for second order elliptic operators. This relies on quantitative unique continuation results and duality arguments. We show that these estimates are essentially optimal. As a model application we provide a new proof of the result from \cite{F07}, \cite{AK12} on stability for the Calder\'on problem with local data.
High-energy resummation effects in the production of Mueller-Navelet dijet at the LHC
2016
We study the production of two forward jets with a large interval of rapidity at hadron colliders, which was proposed by Mueller and Navelet as a possible test of the high energy dynamics of QCD, within a complete next-to-leading logarithm framework. We show that using the Brodsky-Lepage-Mackenzie procedure to fix the renormalization scale leads to a very good description of the recent CMS data at the LHC for the azimuthal correlations of the jets. We show that the inclusion of next-to-leading order corrections to the jet vertex significantly reduces the importance of energy-momentum non-conservation which is inherent to the BFKL approach, for an asymmetric jet configuration. Finally, we ar…
System identification via optimised wavelet-based neural networks
2003
Nonlinear system identification by means of wavelet-based neural networks (WBNNs) is presented. An iterative method is proposed, based on a way of combining genetic algorithms (GAs) and least-square techniques with the aim of avoiding redundancy in the representation of the function. GAs are used for optimal selection of the structure of the WBNN and the parameters of the transfer function of its neurones. Least-square techniques are used to update the weights of the net. The basic criterion of the method is the addition of a new neurone, at a generic step, to the already constructed WBNN so that no modification to the parameters of its neurones is required. Simulation experiments and compa…
Complex dynamics, hidden attractors and continuous approximation of a fractional-order hyperchaotic PWC system
2018
In this paper, a continuous approximation to studying a class of PWC systems of fractionalorder is presented. Some known results of set-valued analysis and differential inclusions are utilized. The example of a hyperchaotic PWC system of fractional order is analyzed. It is found that without equilibria, the system has hidden attractors.
Low-rank approximation based non-negative multi-way array decomposition on event-related potentials
2014
Non-negative tensor factorization (NTF) has been successfully applied to analyze event-related potentials (ERPs), and shown superiority in terms of capturing multi-domain features. However, the time-frequency representation of ERPs by higher-order tensors are usually large-scale, which prevents the popularity of most tensor factorization algorithms. To overcome this issue, we introduce a non-negative canonical polyadic decomposition (NCPD) based on low-rank approximation (LRA) and hierarchical alternating least square (HALS) techniques. We applied NCPD (LRAHALS and benchmark HALS) and CPD to extract multi-domain features of a visual ERP. The features and components extracted by LRAHALS NCPD…
Suppression of phase ambiguity in digital holography by using partial coherence or specimen rotation
2008
In this paper we present two approaches for extracting the surface profile as well as obtaining 3D imaging of near field objects by usage of partial coherence and digital holography. In the first approach a light source with given temporal partial coherence is used to illuminate a near field object. The reflected light is interfered with the reference source. By computing the local contrast of the generated fringes one may estimate the 3D topography and the profile of the object. This approach extracts the 3D information from a single image, and its accuracy does not depend on triangulation angle like in fringe projection methods. The second approach is tomography based. There we illuminate…
Optical analysis to predict outcomes after implantation of a double intraocular lens magnification device.
2007
Purpose To analyze the effect of different optical parameters of the eye on the outcomes of implantation of a double intraocular lens (IOL) magnification device in patients with low vision. Setting Fundacion Oftalmologica del Mediterraneo, Valencia, Spain. Methods The eye's refraction and magnification before and after surgery were evaluated using a theoretical eye model based on paraxial optics approximation. Four parameters on which refraction and magnification are dependent were evaluated: anterior chamber depth (ACD), axial length (AL), mean keratometry (Km), and the distance between the 2 implanted IOLs. The 4 variables were analyzed separately in the first stage. Next, different combi…
Biomechanical and histological evaluation of abdominal wall compliance with intraperitoneal onlay mesh implants in rabbits: A comparison of six diffe…
2012
Abstract Background An ideal prosthetic mesh for incisional hernia repair should mimic the anisotropic compliance of the abdominal wall, and at lower loads should exhibit higher distensibility without impairment of safety at higher loads. This study evaluated the biomechanical properties of six meshes in a rabbit model. Methods New Zealand white rabbits were used for this study. Two meshes of the same brand (Ethicon Physiomesh™, Bard Composix ® L/P, Gore Dualmesh ® , Bard Sepramesh ® , Ethicon Proceed ® or Parietex™ Composite) were implanted into each animal for assessment of intra-abdominal hernia repair, with a total of ten meshes per group. Twelve weeks after implantation, the abdominal …