Search results for "Amplitude"
showing 10 items of 1169 documents
Photo-thermal modulation of surface plasmon polariton propagation at telecommunication wavelengths
2013
International audience; We report on photo-thermal modulation of thin film surface plasmon polaritons (SPP) excited at telecom wavelengths and traveling at a gold/air interface. By operating a modulated continuous-wave or a Q-switched nanosecond pump laser, we investigate the photo-thermally induced modulation of SPP propagation mediated by the temperature-dependent ohmic losses in the gold film. We use a fiber-to-fiber characterization set-up to measure accurately the modulation depth of the SPP signal under photo-thermal excitation. On the basis of these measurements, we extract the thermo-plasmonic coefficient of the SPP mode defined as the temperature derivative of the SPP damping const…
Molecular alignment echoes probe collision-induced rotational-speed changes
2020
International audience; We show that the decays with pressure of the rotational alignment echoes induced in N 2 O-He gas mixtures by two ultrashort laser pulses with various delays show detailed information about collision-induced changes of the rotational speed of the molecules. Measurements and classical calculations consistently demonstrate that collisions reduce the echo amplitude all the more efficiently when the echo appears late. We quantitatively explain this behavior by the filamentation of the classical rotational phase space induced by the first pulse and the narrowing of the filaments with time. The above mentioned variation of the echo decay then reflects the ability of collisi…
Phase-Noise and Amplitude-Noise Measurement of DACs and DDSs
2019
This article proposes a method for the measurement of Phase Noise (PN, or PM noise) and Amplitude Noise (AN, or AM noise) of Digital-to-Analog Converters (DAC) and Direct Digital Synthesizers (DDS) based on modulation-index amplification. The carrier is first reduced by a controlled amount (30-40 dB) by adding a reference signal of nearly equal amplitude and opposite in phase. Then, residual carrier and noise sidebands are amplified and sent to a conventional PN analyzer. The main virtues of our method are: (i) the noise specs of the PN analyzer are relaxed by a factor equal to the carrier suppression ratio; and, (ii) the capability to measure the AN using a PN analyzer, with no need for th…
Physical activity accumulation along the intensity spectrum differs between children and adults
2021
Purpose Detailed exploration of physical activity accumulation with fine grading along the intensity spectrum has indicated the potential pragmatic utility of such an approach. However, it is currently unclear what sorts of accumulation patterns along particular intensity bands are found in the children and adult populations. Therefore, we conducted a comparison of activity accumulation in specific intensity bands between four distinct populations: children, adults with sedentary lifestyles, habitual joggers, habitual marathon runners. Methods Free-living waist-worn accelerometry records from 28 children aged 7 to 11, and 61 adults aged 25 to 35 were analysed. Activity intensity was evaluat…
Maksimālo un minimālo gaisa temperatūru diennakts svārstību amplitūdas un to ilglaicīgās izmaiņas Latvijā 1951. - 2016. gads
2019
Bakalaura darba tēma ir “Maksimālās un minimālās gaisa temperatūru svārstību amplitūdas un to ilglaicīgās izmaiņas Latvijā 1951.-2016.gads”. Tika ievākti un analizēti dati no 18 Latvijas meteoroloģiskajām stacijām, kas ļauj izvērtēt iegūtās likumsakarības atšķirīgos fizioģeogrāfiskos novietojumos esošu meteoroloģisko staciju ilggadīgos novērojumus. Bakalaura darba mērķis ir izvērtēt maksimālo un minimālo gaisa temperatūru diennakts svārstību amplitūdas un to izmaiņas atšķirīgos fizioģeogrāfiskos novietojumos Latvijā laika posmā no 1951.-2016. gadam. Darba gaitā 18 novērojumu stacijas tika iedalītas divās grupās -piekrastes un kontinentālās novērojumu stacijās. Iegūtie rezultāti liecina, ka …
Abnormal textures identification based on digital Hilbert optics methods: fundamental transforms and models
2018
The article presents the abnormal textures identification technology based on structural and statistical models of amplitude-phase images (APIm)– multidimensional data arrays (semantic models) and statistical correlation analysis methods using the generalized discrete Hilbert transforms (DHT)– 2D Hilbert (Foucault) isotropic (HTI), anisotropic (HTA) and total transforms – AP-analysis (APA) to calculate the APIm. The identified fragments of textures are obtained as examples of experimental observation of real mammograms contains areas of pathological tissues. The DHT based information technology as conceptual chart description is discussed and illustrated with DHO domain images. As additiona…
Contribution of observed multi frequency spectrum of Alfvén waves to coronal heating
2019
Context. Whilst there are observational indications that transverse magnetohydrodynamic (MHD) waves carry enough energy to maintain the thermal structure of the solar corona, it is not clear whether such energy can be efficiently and effectively converted into heating. Phase-mixing of Alfvén waves is considered a candidate mechanism, as it can develop transverse gradient where magnetic energy can be converted into thermal energy. However, phase-mixing is a process that crucially depends on the amplitude and period of the transverse oscillations, and only recently have we obtained a complete measurement of the power spectrum for transverse oscillations in the corona. Aims. We aim to investig…
Extended Depth-of-Field 3-D Display and Visualization by Combination of Amplitude-Modulated Microlenses and Deconvolution Tools
2005
One of the main challenges in 3-D display and visualization is to overcome its limited depth of field. Such limitation is due to the fast deterioration of lateral resolution for out-of-focus object positions. Here we propose a new method to significantly extend the depth of field. The method is based on the combined benefits of a proper amplitude modulation of the microlenses, and the application of deconvolution tools. Numerical tests are presented to verify the theoretical analysis.
Depth sensing using coherence mapping
2010
A method for depth sensing based on sensing the visibility associated with the coherence function of a laser source is presented. The setup is based on an electronic speckle pattern interferometric (ESPI) setup, where the object depth is encoded into the amplitude of the interference pattern without the need for depth scanning. After performing phase-shifting method, the object three-dimensional (3-D) shape is reconstructed by means as a range image from the visibility of the image set of interferograms and where each gray level represents a given object depth. Experimental results validate the proposed approach for reflective diffuse objects at different measurement distances.
Statistical properties of the capacity of Rice channels with MRC and EGC
2009
In this paper, we have studied the statistical properties of the capacity of Rice channels for both maximal ratio combining (MRC) and equal gain combining (EGC) schemes. We have analyzed the effect of the number of diversity branches and the amplitude of the line-of-sight (LOS) components in the diversity branches on the statistics of the channel capacity. Specifically, we have derived analytical expressions for the probability density function (PDF), cumulative distribution function (CDF), level-crossing rate (LCR), and average duration of fades (ADF) of the capacity of Rice channels when using MRC and EGC. It is observed that if the number of diversity branches or the amplitude of the LOS…