The NLR/NGTE joint programme on the measurement of attenuation and impedance in acoustic flow duct facilities.

The National Aerospace Laboratory NLR in the Netherlands and the National Gas Turbine Establishment NOTE operate similar acoustic flow duct facilities but with differences in their respective approaches to the measurement of attenuation and impedance of duct linings. A joint exercise was arranged with the object of comparing methods and results,...

Dissemination of ERS-a low bitrate data and the use od L-band receiving stations

The dissemination of ERS-1 real-time thematic products via the Global Telecommunication System, the ECS satellite telecom system or the Eiuronet packet switching network is analysed and evaluated against the use of direct-receive L-band stations as used for NOAA weather image reception.

Trends in airline avionics

Modern avionics are an integral part of the aircraft. They provide the functions of communication, navigation, energy management, identification, weather, terrain, and collision avoidance, the presentation of flight and warning data as well as aircraft guidance and stabilization. New developments in micro-electronics and display technology...

Computer aided EMC analysis: A review of available tools

A review is given of methods for the analysis of intrasystem electromagnetic compatibility. Emphasis is placed on pocket calculator programs and on the SEMCAP computer program. Taking into account the applications at NLR, we conclude that both tools can be very useful for such an analysis. As far as antenna-to-antenna coupling is considered, the...

Image data security in the concept of the agricultural real time imaging satellite system (artiss)

The study on image data security is directed to the requirement for exclusive access to satellite imagery in the concept of the Agricultiiral Real Time Imaging Satellite System (ARTISS). The security assessment indicates that user survey requests are handled confidentially and it shows the access vulnerability of the transmission of image data...

Reflection and Transmission Characteristics of Porous Rubble-Mound Breakwaters

This report presents the results of a study of the reflection and transmission characteristics of porous rubble-mound breakwaters. An attempt was made at making the procedures entirely self-contained by introducing empirical relationships for the hydraulic characteristics of the porous material and by establishing experimentally an empirical...

Calculation of acoustic modes in an infinite duct with shear flow and sound absorbing walls

The sound field in an infinitely long duct with shear flow and sound absorbing walls, but with the sound source unspecified, is analysed into its constituents, the acoustic duct modes. The equations, wave numbers, and various properties of the modes are discussed. Some calculated results are used to show the effects of shear flow and absorbing...

Wave transmission through rock structures

Application of the energy method leads to a theoretical expression of the coefficient of transmission through a prismatic structure, constructed from rocks of uniform size, for long waves traversing the structure. When the dissipation in the voids is due partly to turbulent forces, the transmissions are expressed by a power formula . The formula...