Sökning: "frequency transform"

Visar resultat 1 - 5 av 106 avhandlingar innehållade orden frequency transform.

  1. 1. Optical Frequency Comb Fourier Transform Spectroscopy

    Författare :Alexandra C. Johansson; Aleksandra Foltynowicz; Ove Axner; Jürgen Röpcke; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Optical frequency comb spectroscopy; Fourier transform; molecular absorption dispersion; fysik; Physics;

    Sammanfattning : Fourier transform spectroscopy (FTS) based on optical frequency combs is an excellent spectroscopic tool as it provides broadband molecular spectra with high spectral resolution and an absolutely calibrated frequency scale. Moreover, the equidistant comb mode structure enables efficient coupling of the comb to enhancement cavities, yielding high detection sensitivity. LÄS MER

  3. 2. Fourier transform and Vernier spectroscopy using optical frequency combs

    Författare :Amir Khodabakhsh; Aleksandra Foltynowicz; Ove Axner; Frans Harren; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; optical frequency comb spectroscopy; molecular absorption; resonant cavity; Fourier transform spectroscopy; Vernier spectroscopy; fysik; Physics;

    Sammanfattning : Optical frequency comb spectroscopy (OFCS) combines two previously exclusive features, i.e., wide optical bandwidth and high spectral resolution, enabling precise measurements of entire molecular bands and simultaneous monitoring of multiple gas species in a short measurement time. LÄS MER

  4. 3. The Texture-Transform : An Operator for Texture Detection and Discrimination

    Författare :Alireza Tavakoli Targhi; Jan-Olof Eklundh; Arnold Smeulders; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Computer science; Datalogi;

    Sammanfattning : In this thesis we present contributions related to texture detection and discrimination to be used for analyzing real world images. Many computer vision applications can benefit from a fast and low dimensional texture descriptor. LÄS MER

  5. 4. Precision molecular spectroscopy in the near- and mid-infrared using frequency comb-based Fourier transform spectrometers

    Författare :Adrian Hjältén; Aleksandra Foltynowicz; Ove Axner; Adam Fleisher; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; optical frequency comb; molecular spectroscopy; Fourier transform spectrometer; high resolution; mid-infrared; line list; double-resonance spectroscopy; difference frequency generation; fysik; Physics;

    Sammanfattning : Absorption spectroscopy is a powerful scientific tool for non-invasive and remote sensing applications ranging from atmospheric monitoring to astrophysics. In spectroscopic detection schemes it is necessary to have spectral models for any molecular species to be detected or quantified. LÄS MER

  7. 5. High resolution time-frequency representations

    Författare :Isabella Reinhold; Statistical Signal Processing Group; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; time-frequency analysis; non-stationary signals; multi-component signals; IF estimation; reassignment;

    Sammanfattning : Non-stationary signals are very common in nature, e.g. sound waves such as human speech, bird song and music. It is usually meaningful to describe a signal in terms of time and frequency. LÄS MER