Sources of sound in fluid flows

Some features of a flow that produce acoustic radiation, particularly when the flow is turbulent and interacting with solid surfaces such as turbine or compressor blades are discussed. Early theoretical ideas on the subject are reviewed and are shown to be inadequate at high Mach number. Some recent theoretical developments that form the basis of a description of sound generation by supersonic flows interacting with surfaces are described. At high frequencies the problem is treated as one of describing the surface-induced diffraction field of adjacent aerodynamic quadrupole sources. This approach has given rise to distinctly new features of the problem that seem to have bearing on the radiating properties of relatively large aerodynamic surfaces

System for interference signal nulling by polarization adjustment

A receiving system for automatically selecting a desired one of two approximately orthogonally polarized signals occupying the same bandwidth, is described. Received signals are provided by any orthomode antenna system at a pair of output ports, i.e., right hand and left hand circular polarizations or two linear polarizations. The received signals are then applied to the inputs of a hybrid junction to produce sum and difference signals. The resulting sum signal at one output port comprises components of the undesired one of two orthogonally polarized signals and is used to coherently detect and dynamically balance out the undesired signal components that are included at the difference signal port. The desired one of two orthogonally polarized signals is thereby provided at the difference port of the hybrid junction. Feedback loops are used to effect dynamic balancing

Multibeam-antenna feed system to isolate orthogonally polarized beams

System is polarization tracker and comprises variable polarizer, polarization control, and receiver servo loop. System simultaneously receives desired signal and undesired signal which are approximately orthogonal. They can be either paired as left and right circular polarizations or as cross-linear polarizations

Automatic water inventory, collecting, and dispensing unit

Two cylindrical tanks with piston bladders and associated components for automatic filling and emptying use liquid inventory readout devices in control of water flow. Unit provides for adaptive water collection, storage, and dispensation in weightlessness environment

Performance of PTFE-lined composite journal bearings

Plain cylindrical journal bearings consisting of aramid fiber reinforced epoxy outer shells and glass fiber reinforced PTFE lubricating liners were evaluated. All materials in these bearings are electrically nonconductive; thus eliminating the problem of galvanic corrosion sometimes encountered with metal bearings installed in dissimilar metal mountings. Friction and wear characteristics were determined for loads, temperatures, and oscillating conditions that are typical of current airframe bearing applications. Friction and wear characteristics were found to be compatible with most airframe bearing requirements from -23 C to 121 C. Contamination with MIL H-5606 hydraulic fluid increased wear of the PTFE liners at 121 C, but did not affect the structural integrity of the aramid/epoxy composite

Instrumentation design study for testing a hypersonic ramjet engine on the x-15 a-2. volume 3- conceptual design of measurement systems

Instrumentation for testing hypersonic ramjet engine on X-15A-2 aircraf

IRAS asteroid families

The Infrared Astronomical Satellite (IRAS) sampled the entire asteroid population at wavelengths from 12 to 100 microns during its 1983 all sky survey. The IRAS Minor Planet Survey (IMPS) includes updated results for more recently numbered as well as other additional asteroids with reliable orbital elements. Albedos and diameters were derived from the observed thermal emission and assumed absolute visual magnitudes and then entered into the IMPS database at the Infrared Processing and Analysis Center (IPAC) for members of the Themis, Eos, Koronis and Maria asteroid families and compared with their visual colors. The IMPS results for the small (down to about 20 km) asteroids within these major families confirm trends previously noted for their larger members. Each of these dynamical families which are defined by their similar proper elements appears to have homogeneous physical properties

‘Holding onto trauma?’ The prevalence and predictors of PTSD, anxiety, and depression in police officers working with victims of child abuse, rape, and sexual exploitation

Research into post-traumatic stress disorder (PTSD) and other common mental disorders (CMDs) in police officers is limited, with the majority of research predominately conducted outside the UK, and no study quantitively examining the role of social support in relation to the mental health of UK police officers working with victims of trauma. Therefore, this study aimed to examine the prevalence and predictors of PTSD and CMD in UK police officers who investigate rape, sexual exploitation, and child abuse, along with the potential protective role of social support. Participants were police officers (n = 353) within one police area, who completed self-report measures of PTSD, anxiety, depression, and social support. Results showed that 23% of officers had potentially clinical levels of PTSD, 26% had moderate to severe levels of anxiety and 35% had moderate to severe levels of depression. Female officers, those of constable rank, those working with victims of child abuse, and those with lowest levels of social support had poorer mental health. There was tentative evidence that social support statistically moderated the relationship between tenure and depression. These findings suggest the need for bespoke help for the sub-group of officers experiencing mental health problems and for further research into the potential protective role of social support