Search for dissertations about: "directivity"

Showing result 1 - 5 of 30 swedish dissertations containing the word directivity.

  2. 1. On the Directivity of Railway Noise Sources

    Author : Xuetao Zhang; Chalmers tekniska högskola; []
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; railway traction noise; railway rolling noise; line source; railway aerodynamic noise; moving source; equivalent source line; De-Dopplerization; sound emission time; sound immission time; directivity; the Doppler factor;

    Abstract : This dissertation deals with the directivity of railway noise. The directivity of railway noise is of particular importance when we have high-rise buildings close to the track, tunnel openings, partial barriers, or when we calculate the maximum sound pressure level during a pass-by based on the sound power level of the different sub-sources of a train. READ MORE

  4. 2. Applicable directivity description of railway noise sources

    Author : Xuetao Zhang; Chalmers tekniska högskola; []
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; directivity; the Doppler factor; scattered fluid sound; railway noise; perpendicular dipole pair;

    Abstract : For a sound source, directivity is an important parameter to specify. This parameter also reflects the physical feature of the sound generation mechanism. For example, turbulence sound is of quadrupole directivity whilst fluid-structure interaction often induces a sound of dipole characteristic. READ MORE

  5. 3. Antenna Limitations and Q-factor Trade-off between Parameters, Steps towards Optimal Antenna Design

    Author : Shuai Shi; Lars Jonsson; Ala Sharaiha; KTH; []
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Antenna limitation; Q-factor; directivity; radiation pattern; current optimization; Electrical Engineering; Elektro- och systemteknik;

    Abstract : Sub-wavelength antennas have become ubiquitous in essential devices, such as mobile phones, sensors, Internet of things (IoT) and machine to machine (M2M) communication devices. Such antennas are often embedded as a small part of the device chassis or their circuit-boards. READ MORE

  6. 4. Source analysis of multiplet earthquakes (two case studies in Iran)

    Author : Samar Amini; Roland Roberts; Björn Lund; Zaher Hossein Shomali; Kuvvet Atakan; Uppsala universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Multiplet earthquakes; slip inversion; Coulomb stress; rupture directivity;

    Abstract : Multiplet earthquakes are large earthquakes of similar magnitude which occur close in time in the same limited geographical area. They are not common but they considerably increase the potential hazard in the area in which they occur. READ MORE

  7. 5. Topology optimization for acoustic wave propagation problems

    Author : Eddie Wadbro; Martin Berggren; Uppsala universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Scientific Computing; Beräkningsvetenskap;

    Abstract : The aim of this study is to develop numerical techniques for the analysis and optimization of acoustic horns for time harmonic wave propagation. An acoustic horn may be viewed as an impedance transformer, designed to give an impedance matching between the feeding waveguide and the surrounding air. READ MORE