The dynamics of gravity currents are believed to be strongly influenced by dissipation due to turbulence and mixing between the current and the surrounding ambient fluid. This paper describes new theory and experiments on gravity currents produced by lock exchange which suggest that dissipation is unimportant when the Reynolds number is sufficiently high. Although there is mixing, the amount of energy dissipated is small, reducing the current speed by a few percent from the energy-conserving value. Benjamin (J. Fluid Mech. vol. 31, 1968, p. 209) suggests that dissipation is an essential ingredient in gravity current dynamics. We show that dissipation is not important at high Reynolds number, and provide an alternative theory that predicts the current speed and depth based on energy-conserving flow that is in good agreement with experiments. We predict that in a deep ambient the front Froude number is 1, rather than the previously accepted value of √ 2. New experiments are reported for this case that support the new theoretical value.

Abstract-The three-year Line of Sight/Beyond Line of Sight (LOS/BLOS) electro-thermal chemical (ETC) launcher program, funded by US Army ARDEC, Picatinny Arsenal, is a comprehensive effort to advance ETC launcher technologies. The program includes development of ETC plasma injectors for 120 mm M829A2s, build of a 100 kJ pulsed power supply small and robust enough to be realistically integrated into a combat vehicle, improvement of power connections to the gun to allow electromagnetic field containment and automated connection to the round, and tests of the completed ETC system with various chemical propellants and electrical energy levels.As part of the LOS/BLOS program, a new, coaxial version of BAE Systems' Basepad plasma injector has been developed and tested successfully in XM36, XM291, and M256 cannons. The Basepad's coaxial design effectively insulates the gun breech, thus preventing any part of the gun from being part of the high voltage discharge circuit. A compact electro-thermal ignition pulsed power supply (ETIPPS) has been designed, built, and tested. Including its own high-voltage charger, actuation circuitry, safety systems, and peripherals, ETIPPS' low weight and volume make it easily small enough for vehicle integration, as was demonstrated in a concurrent effort that included ETC firings from a combat vehicle.Test firings, currently ongoing, have validated the system architecture and performance and continue to supply data on performance at different temperatures, electrical energy levels, propellant loading, and propellant type. These tests demonstrate many of the benefits of ETC launchers, including: improved accuracy from precision ignition; maximum performance Report Documentation PageForm Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

Freud was the first to invite his patients to lie down on a couch, facilitating the closing of the eyes. If the mere fact of closing the eyes favors access to unconscious materials, it should also favor primary process mentation. Primary process is an associative mode of thought based on superficial similarities including phonology, while secondary process mentation in language is primarily concerned with meaning. Fifty-two participants were given French Word Lists with phonological choices (P) corresponding to primary processes, while semantic choices (S) represent secondary processes when they are in mutual competition (PS). For example, participants were given a first word, such as, e.g. cale (to hold), and then had to choose between lac (P; lake) and fixe (S; fix), which alternative was most similar to the first word, cale. Two control lists, SN and PN, where the other choice is unrelated (N for nothing), verify that the subjects are equally capable of recognizing the phonological and semantics similarity. Results show an (near 10% increase in P choices in PS when participants close their eyes, while results on PN and SN were unchanged. The mere fact of closing the eyes induces a modest increase in primary process mentation. Based on the literature, the eyes closed (EC) condition is linked to increased alpha synchronization, which is thought to induce an inward mental shift. This research contributes to validating the psychoanalytic technique consisting on inviting patients to lie down on a couch and invite them to close their eyes.