Sökning: "spatial frequency"

Visar resultat 11 - 15 av 329 avhandlingar innehållade orden spatial frequency.

1. 11. Uncertainty quantification for high frequency waves

   Författare :Gabriela Malenova; Olof Runborg; Fabio Nobile; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Mathematics; Matematik;

   Sammanfattning : We consider high frequency waves satisfying the scalar wave equation with highly oscillatory initial data represented by a short wavelength ε. The speed of propagation of the medium as well as the phase and amplitude of the initial data is assumed to be uncertain, described by a finite number of independent random variables with known probability distributions. LÄS MER

3. 12. Lake Dissolved Organic Matter Quantity and Quality : Variability across Temporal and Spatial Scales

   Författare :Roger André Müller; Gesa Weyhenmeyer; Emily Stanley; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; dissolved organic matter; organic carbon; CDOM; lakes; Biology with specialization in Limnology; Biologi med inriktning mot limnologi;

   Sammanfattning : Surface waters receive large amounts of dissolved organic matter (DOM) via runoff from land. The DOM is rich in organic carbon that serves as an energy source for the aquatic biota. During uptake of this energy, aquatic organisms mineralize organic carbon. LÄS MER

4. 13. Computational electromagnetics : software development and high frequency modeling of surface currents on perfect conductors

   Författare :Sandy Sefi; Jesper Oppelstrup; Francisco Saez de Adana; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; High frequency approximations; Maxwell’s equations; Method of Moments; Physical Optics; Geometrical Theory of Diffraction; Extraction Extrapolation; Numerical analysis; Numerisk analys;

   Sammanfattning : In high frequency computational electromagnetics, rigorous numerical methods be come unrealistic tools due to computational demand increasing with the frequency. Instead approximations to the solutions of the Maxwell equations can be employed to evaluate th electromagnetic fields. LÄS MER

5. 14. Spatial Resource Allocation in Massive MIMO Communications : From Cellular to Cell-Free

   Författare :Trinh Van Chien; Emil Björnson; Erik G. Larsson; David Gesbert; Linköpings universitet; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY;

   Sammanfattning : Massive MIMO (multiple-input multiple-output) is considered as an heir of the multi-user MIMO technology and it has gained lots of attention from both academia and industry since the last decade. By equipping base stations (BSs) with hundreds of antennas in a compact array or a distributed manner, this new technology can provide very large multiplexing gains by serving many users on the same time-frequency resources and thereby bring significant improvements in spectral efficiency (SE) and energy efficiency (EE) over the current wireless networks. LÄS MER

7. 15. Power Consumption and Joint Signal Processing in Fiber-Optical Communication

   Författare :Lars Lundberg; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; coherent detection; erbium-doped fiber amplifier; phase-tracking; optical amplifier; optical frequency comb; digital signal processing; carrier-recovery; spatial division multiplexing; power consumption; Fiber-optical communication; multicore fiber; Raman amplification; energy-efficiency;

   Sammanfattning : The power consumption of coherent fiber-optical communication systems is becoming increasingly important, for both environmental and economic reasons. The data traffic on the Internet is increasing at a faster pace than that at which optical network equipment is becoming more energy efficient, which means that the overall power consumption of the Internet is increasing. LÄS MER