5,061 research outputs found
Spectra of Urea and Thiourea in the 3µ Region
Observations are reported on the polarized infrared spectra of single crystals of urea and thiourea in the 3µ region. Complex structures accompanying the N [Single Bond] H fundamentals appear, at least in considerable part, to be attributable to combinations and overtones of fundamentals in the neighborhood of 1650 cm^—1
A search for outflows from X-ray bright points in coronal holes
Properties of X-ray bright points using two of the instruments on Solar Maximum Mission were investigated. The mass outflows from magnetic regions were modeled using a two dimensional MHD code. It was concluded that mass can be detected from X-ray bright points provided that the magnetic topology is favorable
Ionic charge distributions of energetic particles from solar flares
The effects which solar flare X-rays have on the charge states of solar cosmic rays is determined quantitatively. Rather than to characterize the charge distribution by temperature alone, it is proposed that the X-ray flux at the acceleration site also is used. The effects of flare X-rays are modeled mathematically
Underground coal mine instrumentation and test
The need to evaluate mechanical performance of mine tools and to obtain test performance data from candidate systems dictate that an engineering data recording system be built. Because of the wide range of test parameters which would be evaluated, a general purpose data gathering system was designed and assembled to permit maximum versatility. A primary objective of this program was to provide a specific operating evaluation of a longwall mining machine vibration response under normal operating conditions. A number of mines were visited and a candidate for test evaluation was selected, based upon management cooperation, machine suitability, and mine conditions. Actual mine testing took place in a West Virginia mine
Development of biaxial test fixture includes cryogenic application
Test fixture has the capability of producing biaxial stress fields in test specimens to the point of failure. It determines biaxial stress by dividing the applied load by the net cross section. With modification it can evaluate materials, design concepts, and production hardware at cryogenic temperatures
Effect of Engine Operating Conditions on the Vaporization of Safety Fuels
Tests were conducted with the N.A.C.A. combustion apparatus to determine the effect of compression ratio and engine temperature on the vaporization of a hydrogenated "safety fuel" during the compression stroke under conditions similar to those in a spark-ignition engine. The effects of fuel boiling temperature on vaporization using gasoline, safety fuel, and Diesel fuel oil was also investigated. The results show that increasing the compression ratio has little effect on the rate of fuel vaporization, but that increasing the air temperature by increasing the engine temperature increases the rate of fuel vaporization. The results also show that the vaporized fuel forms a homogeneous mixture with the air more rapidly that does the atomized fuel spray
Quantum Cosmology and Conformal Invariance
According to Belinsky, Khalatnikov and Lifshitz, gravity near a space-like
singularity reduces to a set of decoupled one-dimensional mechanical models at
each point in space. We point out that these models fall into a class of
conformal mechanical models first introduced by de Alfaro, Fubini and Furlan
(DFF). The deformation used by DFF to render the spectrum discrete corresponds
to a negative cosmological constant. The wave function of the universe is the
zero-energy eigenmode of the Hamiltonian, also known as the spherical vector of
the representation of the conformal group SO(1,2). A new class of conformal
quantum mechanical models is constructed, based on the quantization of
nilpotent coadjoint orbits, where the conformal group is enhanced to an ADE
non-compact group for which the spherical vector is known.Comment: 4 pages, latex2e, uses revtex
Current Induced Order Parameter Dynamics: Microscopic Theory Applied to Co/Cu/Co spin valves
Transport currents can alter alter order parameter dynamics and change steady
states in superconductors, in ferromagnets, and in hybrid systems. In this
article we present a scheme for fully microscopic evaluation of order parameter
dynamics that is intended for application to nanoscale systems. The approach
relies on time-dependent mean-field-theory, on an adiabatic approximation, and
on the use of non-equilibrium Greens function (NEGF) theory to calculate the
influence of a bias voltage across a system on its steady-state density matrix.
We apply this scheme to examine the spin-transfer torques which drive
magnetization dynamics in Co/Cu/Co spin-valve structures. Our microscopic
torques are peaked near Co/Cu interfaces, in agreement with most previous
pictures, but suprisingly act mainly on Co transition metal -orbitals rather
than on -orbitals as generally supposed.Comment: 9 pages, 5 figure
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