In this paper, a novel method to quantify the incubation of damage on piezoelectric crystal is presented. An intrinsic length scale parameter obtained from nonlocal field theory is used as a novel measure for quantification of damage precursor. Features such as amplitude decay, attenuation, frequency shifts and higher harmonics of guided waves are commonly-used damage features. Quantification of the ...

Da Det Norske Institutt for Kosmisk Fysikk ble del av Universitetet i Tromsø, opphørte Nordlysobservatoriet å eksistere som en formell enhet. Det som i dag omfattes av Nordlysobservatoriet, er dels en fortsettelse av den opprinnelige observasjonsvirksomheten til det gamle Nordlysobservatoriet - men også nye aktiviteter har kommet til - særlig innen feltene plasmafysikk og radiogeofysikk. I det ...

Among the basic cognitive skills of the biological brain in humans and other mammals, a fundamental one is the ability to recognize inexact patterns in a sequence of objects or events. Accelerating inexact string matching procedures is of utmost importance when dealing with practical applications where huge amounts of data must be processed in real time, as usual in bioinformatics or cybersecurity. ...

This article introduces the Rayleigh autoregressive moving average (RARMA) model, which is useful to interpret multiple different sets of remotely sensed data, from wind measurements to multitemporal synthetic aperture radar (SAR) sequences. The RARMA model is indeed suitable for continuous, asymmetric, and nonnegative signals observed over time. It describes the mean of Rayleigh-distributed ...

A two-dimensional scattering model based on the Finite Element Method (FEM) is built for simulating the microwave scattering of sea ice, which is a layered medium. The scattering problem solved by the FEM is formulated following a total- and scattered-field decomposition strategy. The model set-up is first validated with good agreements by comparing the results of the FEM with those of the small ...

One of the main challenges in conventional photoacoustic methods, is that thin biological samples typically have low optical absorption in the visible region. Therefore, it is often necessary to stain or label the sample with a color which provide sufficient absorption for the laser wavelength used in the scanning system. Unfortunately, the labeling often introduce unwanted properties to the biological ...

Remote sensing is a key instrument for monitoring sea ice surface properties over large areas. Synthetic Aperture Radar (SAR) as well as Real Aperture Radar (RAR) are two types of radars that are extensively used in this context and measure the backscatter of the surface that they illuminate. Backscattering of waves from rough surfaces is complicated and depends, among other things, on the roughness ...

Numerical simulations of reduced fluid models describing magnetized plasmas have previously been used to study the boundary of fusion plasmas extensively. A common approximation applied to these models is the so-called Boussinesq approximation. One of the requirements for the Boussinesq approximation to be applicable is that the background particle density is significantly higher than the fluctuations ...

Numerical studies of radial filament motions in the SOL of toroidally confined plasmas are studies. We use a two dimensional two-field model to characterize blob-like structures in the radial-poloidal domain. These structures are observed to achieve velocities in the order of the ion acoustic velocity in the SOL of tokamaks and other toroidal confinement devices. By numerical means we find a ...

Simuleringer av utbredelse av ultralydbølger i elastiske polymerer og i væsker ble utført med et kommersielt simuleringsverktøy, COMSOL Multiphysics, basert på endelig element metode. Simuleringer ble utført i en- og to-dimensjoner. Undersøkelser ble utført for å finne ut ved hvilke oppløsninger av tid og rom ga stabile simuleringer. For en to-dimensjonal modell basert på en elastisk ...