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The highly stable propagation characteristics of VLF transmissions make them an ideal source of world-wide navigation data. The arrival phase of a VLF signal is continuously compared with a local standard. The change in the phase difference between the received signal and the local standard is converted to relative motion with respect to the VLF transmitter. Very low frequency transmissions form the...
Two prototype solid-state switching devices and a multiplexer system were designed, fabricated, and successfully tested to demonstrate the use of solid-state devices under hydrostatic pressure cycling to 13,500 psi. The two switching devices were designed to use 24-Vdc voltages in controlling the application of 120-Vdc supply voltages, with a steady-state current of 10 A and surge currents of 100...
The effects of high pressure on the performance of active semiconductor devices are determined by both the number of times the device is exposed to the pressure and the duration of this exposure. The damage that results from either or both types of exposure is of three types; (1) structural damage, (2) physical device damage and (3) chemical damage. The anticipated effects of each damage category...
A self-recording thermistor buoy system was developed at the SACLANT ASW Research Centre to registe the variability of temperature in the upper ocean. The system consists of 20 thermistors spaced on a vertical cable between the sea surface and 250 m. The thermistors are incorporated into parallel RC circuits which, when electronically triggered, produce a pulse train wherein the individual pulse arrival...
Viable concepts of ELF transmitter arrays (SANGUINE) involve an orthogonal grid tens of miles on a side, composed of roughly parallel antenna lines in each direction, buried about 6 feet deep. Multiple, buried transmitter stations are included at, or near, antenna intersections.
A mathematical simulation technique was developed which predicts the dynamic response of a single scoped mooring line holding a buoy in deep water. The buoy was subjected to typical ocean wave forces. The basic partial differential equations were obtained by considering the conservation of mass and momentum in the normal and tangential directions of a small element of the line. These partial differential...
This paper discusses the development of a unique portable underwater light which is rugged, shock-resistant, and is suitable for continuous use in air or underwater. The light is designed for general area illumination either underwater or on the surface. The light assembly consists of a 10,000 lumen tungsten-halogen lamp, a heat treated globe, a heat-sinked fixture, and a cable reel with appropriate...
A microwave radar capable of yielding spectral decompositions of large wave properties such as slope or orbital velocity is currently being built for installation over looking the Chesapeake Bay. The principle of this radar, the simple embodiment which is actually being built, and a description of the wave properties one might hope to measure with this radar are all discussed.
A real time dereverberator was tested in an attempt to eliminate multiples on marine reflection seismograms. The whole system consists of a4 \times 30-m sectional array, a slacking winch used to stop the array during the recording period, a 1000-in3airgun with a pulse shaper, four programmed gain amplifiers, a time varying mixer, a time varying bandpass filter and a real-time correlator and dereverberation...
The intent of this paper is to suggest areas where beneficial changes might be made in the display of underwater scenes. Presently, the turbidity of the water medium produces a rapid scene-brightness fall -off that carries over into the system's display. In addition to this problem, the second-generation viewing systems (range gate and synchronous scan) possess spatial peculiarities that appear as...
Multiple reflections in the water column often make the detection of deep seismic reflectors in oceanographic exploration very difficult. A novel method of modelling the unwanted feedback generating these multiples is introduced. This model formulates the removal of the multiples as a system identification problem, and the maximum likelihood method of statistics is used to derive an algorithm for...
In recent years several radar techniques have evolved which allow the remote measurement of certain parameters important in the description of sea state. At MF and HF, monostatic and bistatic configurations employing satellites, ships, islands, and/or land based stations can measure the ocean waveheight spectrum with several frequencies via first-order Bragg scatter. At high HF and VHF, the ocean...
During 1964, RCA developed the H/I conductivity measurement technique as the most appropriate method of determining the effective earth conductivity for the siting of an ELF transmitting system. In the fall of 1964 and the summer of 1965 and 1966, measurements by this technique were carried out at 43 different locations in Northern Wisconsin and Northeast Minnesota. Most of these locations were in...
Radio waves of frequency below about 1 kHz propagate around the earth-ionosphere cavity with very little attenuation. These waves also can propagate useful distances down into the ocean. They are attractive therefore, for providing long-range communication to submarines from a single site. By considering the various components of the communication channel in turn, the paper develops the design principles...
This paper examines the influence of correlated wavefronts and directional noise (anisotropic background) on the performance of conventional and adaptive beamforming schemes used with linear arrays in the ocean environment.
The latest information on the capillary portion of the ocean wave spectrum confirms the growth of such spectral components with wind speed to high values. The numerous radar return theories all seem to indicate that the radar acts as a "filter" that causes the signal to respond to ocean wave components near the "Bragg wavelength." Since these components are the ones that grow with...
An optically pumped rubidium 87 vapor magnetometer is described which measures the earth's magnetic field to one part in3frac{1}{2}million. The sensitivity is about .01 gamma in the earth's field of 52,000\lambda(0.52 oersteds). Rubidium 87 is preferred to rubidium 85 because the nuclear spin is 3/2 rather than 5/2. Thus the magnetometer described can "lock on" to a single hyperfine absorption...
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