Complex permeability of soft magnetic ferrite polyester resin composites at frequencies above 1 MHz

Composite soft magnetic materials consist of magnetic particles in a non-magnetic matrix. The properties of such materials can be modelled using effective medium theory. Measurements have been made of the complex permeability of composites produced using ferrite powder and polyester resin. The success of various effective medium expressions in predicting the variation of complex permeability with composition has been assessed

People's perceptions and classifications of sounds heard in urban parks : semantics, affect and restoration

Sounds have been broadly categorized by researchers into ‘human’, ‘nature’ and ‘mechanical’. It is less clear if the general public define and classify sounds in the same way and which factors influence their classification process. Establishing people’s classification and impression of urban park sounds helps identify their perception and experience of urban parks. This in turn aides the process of defining parks with reference to soundscapes, to produce an appreciated and potentially restorative place. This study involved urban park sounds, identified by park users, being presented in card sorts and survey items. Participants sorted the sounds into similar groups, in reference to a visited park. The terminology, factors involved and classification of the sounds was assessed using multidimensional scaling. Triangulation of the results suggests affect is a key factor in people’s classification process. Participants’ grouped sounds were labelled by affective terms more often than their perceived physical properties. Affective evaluations of each sound produced a similar classification structure as the card sort results. People’s classification structure also varied depending on how restorative they found their urban park. Furthermore schematic recollections played a part with many sounds being ‘expected’. Overall similarities and differences with ‘human’, ‘nature’ and ‘mechanical’ classifications were observed

Performance interface document for users of Tracking and Data Relay Satellite System (TDRSS) electromechanically steered antenna systems (EMSAS)

Satellites that use the NASA Tracking and Data Relay Satellite System (TDRSS) require antennas that are crucial for performing and achieving reliable TDRSS link performance at the desired data rate. Technical guidelines are presented to assist the prospective TDRSS medium-and high-data rate user in selecting and procuring a viable, steerable high-gain antenna system. Topics addressed include the antenna gain/transmitter power/data rate relationship; Earth power flux-density limitations; electromechanical requirements dictated by the small beam widths, desired angular coverage, and minimal torque disturbance to the spacecraft; weight and moment considerations; mechanical, electrical and thermal interfaces; design lifetime failure modes; and handling and storage. Proven designs are cited and space-qualified assemblies and components are identified