The proposition that use of twin inverted pulses could provide enhancement to radar is tested in ... more The proposition that use of twin inverted pulses could provide enhancement to radar is tested in the laboratory. A total of six targets are tested. Two are simple representative targets: an aluminium plate (a linear scatterer) and a dipole with a diode across its feedpoint (a nonlinear scatterer). Others are practical targets: a rusty bench clamp and several mobile phones of different models. Twin Inverted Pulse Radar (TWIPR) is shown to discriminate between target types. Depending on the model of the mobile phone, TWIPR can indicates whether it is switched on, switched off or whether it contains a valid SIM card.
Dolphin-Inspired Target Detection for Sonar and Radar
Archives of Acoustics, 2015
ABSTRACT Gas bubbles in the ocean are produced by breaking waves, rainfall, methane seeps, exsolu... more ABSTRACT Gas bubbles in the ocean are produced by breaking waves, rainfall, methane seeps, exsolution, and a range of biological processes including decomposition, photosynthesis, respiration and digestion. However one biological process that produces particularly dense clouds of large bubbles, is bubble netting. This is practiced by several species of cetacean. Given their propensity to use acoustics, and the powerful acoustical attenuation and scattering that bubbles can cause, the relationship between sound and bub-ble nets is intriguing. It has been postulated that humpback whales produce ‘walls of sound’ at audio frequencies in their bubble nets, trapping prey. Dolphins, on the other hand, use high frequency acous-tics for echolocation. This begs the question of whether, in producing bubble nets, they are generating echolocation clutter that potentially helps prey avoid detection (as their bubble nets would do with man-made sonar), or whether they have developed sonar techniques to detect prey within such bubble nets and distinguish it from clutter. Possible sonar schemes that could detect targets in bubble clouds are proposed, and shown to work both in the laboratory and at sea. Following this, similar radar schemes are proposed for the detection of buried explosives and catastrophe victims, and successful laboratory tests are undertaken.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2003
Fast neutron radiography is a non-destructive testing technique with a variety of industrial appl... more Fast neutron radiography is a non-destructive testing technique with a variety of industrial applications and the capability for element sensitive imaging for contraband and explosives detection.
A Cyclostationary Analysis Applied to Detection and Diagnosis of Faults in Helicopter Gearboxes
Lecture Notes in Computer Science, 2008
In several cases the vibration signals generated by rotating machines can be modeled as cyclostat... more In several cases the vibration signals generated by rotating machines can be modeled as cyclostationary processes. A cyclostationary process is defined as a non-stationary process which has a periodic time variation in some of its statistics, and which can be characterized in terms of its order of periodicity. This study is focused on the use of cyclic spectral analysis, as
The profound effect of bubbles on the propagation of sound and ultrasound through liquids and tis... more The profound effect of bubbles on the propagation of sound and ultrasound through liquids and tissue has meant that understanding of this process is key to a wealth of applications. These range from cases where that interaction is exploited (such as in the use of biomedical contrast agents) to circumstances where the potency of the effect massively hinders our capabilities (for example, the operation of sonar in coastal waters). The two diagnostic examples given above are revealing. The fact that in biomedicine the bubbles are exploited, whilst in the oceanic case they are problematic, stems from the readiness with which the biomedical field has embraced the concept of bubble nonlinearity, compared to the response of the sonar community, which relies upon linear propagation models. This is not because of differences in the abilities of the workers in the two fields, but rather for two more subtle reasons: first, the bubble size distribution for contrast agents is so well-known and wellconstrained that researchers in the field need rely on little more than single-bubble models. This compares to the oceanic case, where the distribution of bubble radii will often span four orders of magnitude, will change dramatically over the course of a single measurement, and is often unknown. Indeed, the usual course in ocean acoustics is to appeal to historical datasets (often taken in vastly different environments, such as surf zone and deep water, with a wide range of windspeeds, fetch and air/sea temperatures etc.). These data provide some sort of estimate against which, for any given bubble size, it is hoped that the actual bubble number density does not vary by more than one order of magnitude. Second, the task in ocean acoustics would be to minimize the contribution of the bubbles to the detected signal and enhance the scatter from some other target. This undertaking is vastly more complicated than the task with biomedical ultrasonic contrast agents, which is to maximize the scatter from the bubble as opposed to the tissue. However there are intelligent creatures with a lifetime of experience of working in ocean acoustics, and generations in which to evolve techniques for coping with bubbly ocean water. This paper addresses the question of what physics would allow the cetaceans to do in bubbly ocean water in order to exploit the peculiar propagation conditions there. This question is particularly apt given that there are indeed instances where cetaceans generate bubbles in the water in order to facilitate their hunting. The question of whether cetaceans do indeed exploit the available physics is beyond the scope of this paper. However in discovering what techniques the physics would allow them to exploit, the opportunity opens up for humans to exploit the same techniques in order to enhance sonar in bubbly ocean water, and to enhance the exploitation of ultrasonic contrast agents.
The theoretical modeling of ultrasonic propagation in cancellous bone is pertinent to improving t... more The theoretical modeling of ultrasonic propagation in cancellous bone is pertinent to improving the ultrasonic diagnosis of osteoporosis. First, this paper reviews applications of Biot’s theory to this problem. Next, a new approach is presented, based on an idealization of cancellous bone as a periodic array of bone-marrow layers. Schoenberg’s theory is applied to this model to predict wave properties.
THE EFFECT OF WATER QUALITY ON THE DAMPING OF BUBBLES
... 1 Hz at a resonance of 3 kHz and < 4 Hz at a resonance of 10 kHz for damping values given ... more ... 1 Hz at a resonance of 3 kHz and < 4 Hz at a resonance of 10 kHz for damping values given byDevin's theory. ... В 8. К 8ЮЗ Hydrophone V MHz Receiver , & Transmitter Rising Bubble Ring Transducer Needle Air feed PC Aquisition Random Noise Generator Barr & Stroud ...
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