Electroconvective instability in a fluid layer

Electroconvective instabilities in fluid laye

Electrohydrodynamic charge relaxation and interfacial perpendicular field instability

Electrohydrodynamic charge relaxation and interfacial perpendicular-field instabilit

An electrohydrodynamically induced spatially period cellular Stokes-flow

Spatially periodic, time invariant electric field used to create spatially periodic cellular flow by action of electric shear stress in region of fluid-fluid interfac

Uncovering the Secrets of Statistics as Evidence in Business Valuations

Trials over the value of a business involve data, in large amounts, which must be presented in an understandable and impactful way. Statistics, when used properly, allow us to detect patterns or test theories we could not comprehend from a sea of numbers. But these shortcuts can be misused to create the appearance of accuracy, either through the expert’s failure to understand statistics or desire to deceive. This article explains, in simple terms, how to avoid these traps and spot a good statistic from a bad one

The experimental use of polytetrafluorethylene as an implant material

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The influence of alkaline phosphatase, calcium glycerophosphate and alginate on the repair of bone

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Liquid Oxygen/Liquid Methane Test Results of the RS-18 Lunar Ascent Engine at Simulated Altitude Conditions at NASA White Sands Test Facility

Tests were conducted with the RS-18 rocket engine using liquid oxygen (LO2) and liquid methane (LCH4) propellants under simulated altitude conditions at NASA Johnson Space Center White Sands Test Facility (WSTF). This project is part of NASA's Propulsion and Cryogenics Advanced Development (PCAD) project. "Green" propellants, such as LO2/LCH4, offer savings in both performance and safety over equivalently sized hypergolic propulsion systems in spacecraft applications such as ascent engines or service module engines. Altitude simulation was achieved using the WSTF Large Altitude Simulation System, which provided altitude conditions equivalent up to ~122,000 ft (~37 km). For specific impulse calculations, engine thrust and propellant mass flow rates were measured. LO2 flow ranged from 5.9 - 9.5 lbm/sec (2.7 - 4.3 kg/sec), and LCH4 flow varied from 3.0 - 4.4 lbm/sec (1.4 - 2.0 kg/sec) during the RS-18 hot-fire test series. Propellant flow rate was measured using a coriolis mass-flow meter and compared with a serial turbine-style flow meter. Results showed a significant performance measurement difference during ignition startup due to two-phase flow effects. Subsequent cold-flow testing demonstrated that the propellant manifolds must be adequately flushed in order for the coriolis flow meters to give accurate data. The coriolis flow meters were later shown to provide accurate steady-state data, but the turbine flow meter data should be used in transient phases of operation. Thrust was measured using three load cells in parallel, which also provides the capability to calculate thrust vector alignment. Ignition was demonstrated using a gaseous oxygen/methane spark torch igniter. Test objectives for the RS-18 project are 1) conduct a shakedown of the test stand for LO2/methane lunar ascent engines, 2) obtain vacuum ignition data for the torch and pyrotechnic igniters, and 3) obtain nozzle kinetics data to anchor two-dimensional kinetics codes. All of these objectives were met with the RS-18 data and additional testing data from subsequent LO2/methane test programs in 2009 which included the first simulated-altitude pyrotechnic ignition demonstration of LO2/methane