1,059 research outputs found
Fluidic low speed wind sensor research study Final report, Oct. 1968 - Oct. 1969
Cross flow and parallel flow concepts of fluidic wind speed sensor
Magnetism of 3d transition metal atoms on W(001): submonolayer films
We have investigated random submonolayer films of 3d transition metals on
W(001). The tight-binding linear muffin-tin orbital method combined with the
coherent potential approximation was employed to calculate the electronic
structure of the films. We have estimated local magnetic moments and the
stability of different magnetic structures, namely the ferromagnetic order, the
disordered local moments and the non-magnetic state, by comparing the total
energies of the corresponding systems. It has been found that the magnetic
moments of V and Cr decrease and eventually disappear with decreasing coverage.
On the other hand, Fe retains approximately the same magnetic moment throughout
the whole concentration range from a single impurity to the monolayer coverage.
Mn is an intermediate case between Cr and Fe since it is non-magnetic at very
low coverages and ferromagnetic otherwise.Comment: 5 pages, 3 figures in 6 files; presented at ICN&T 2006, Basel,
Switzerlan
Investigation of Copper Contamination and Corrosion Scale Mineralogy in Aging Drink Water Distributions Systems
Research has shown higher levels of copper appear in drinking water conveyed through relatively new copper piping systems; older piping systems typically deliver lower copper levels in their drinking water. This research contributes field data from a real drinking water distribution system, providing a better understanding of this phenomenon, as it relates to treatment considerations and compliance with the Lead and Copper Rule. Copper pipes and copper levels were sampled from drinking water taps of 16 buildings with pipes ranging in age from less than 1 to 48 years. Water samples from each building were collected before and following a 16-hour stagnation period. A piece of domestic cold water pipe was cut from each building and analyzed to determine the mineralogy of the copper scale present using x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) technologies. Results were compared to the predictions of the cupric hydroxide model, developed by the Environmental Protection Agency. The samples showed remarkable variation in scale appearance and mineralogy, demonstrating the diversity of pipe scales present within a single distribution system. A mix of highly soluble and relatively insoluble copper phases were identified in the real world scale. Both stable scales, such as malachite, and relatively instable solids, such as cupric hydroxide appear in pipes irrespective of age. In many samples cupric hydroxide and cuprite appeared on the surface of the scale while malachite was in the bulk. Copper cyanide was also identified in two pipe scales. XPS and XRD are shown to be complimentary techniques for characterizing complex scales made up of a mixture of amorphous and crystalline solids
Very low velocity flow sensor uses fluidic techniques
Parallel-flow wind sensor provides differential pressure output which is nearly linear and relatively insensitive to supply pressure over a wide range of wind velocities. Cross-flow wind sensor outputs are input to a fluidic amplifier to obtain high pressure output for low wind velocities without changing output characteristics
Correlated Doping in Semiconductors: The Role of Donors in III-V Diluted Magnetic Semiconductors
We investigate the compositional dependence of the total energy of the mixed
crystals (Ga,Mn)As co-doped with As, Sn, and Zn. Using the ab initio LMTO-CPA
method we find a correlation between the incorporation of acceptors (Mn, Zn)
and donors (Sn, antisite As). In particular, the formation energy of As_Ga is
reduced by approx. 0.1 eV in the presence of Mn, and vice versa. This leads to
the self-compensating behavior of (Ga,Mn)As.Comment: 8 pages, 2 figures, presented at the XXXI Int. School of
Semiconducting Compounds, Jaszowiec 2002, Polan
Spin-transfer torques in anti-ferromagnetic metals from first principles
In spite of the absence of a macroscopic magnetic moment, an anti-ferromagnet
is spin-polarized on an atomic scale. The electric current passing through a
conducting anti-ferromagnet is polarized as well, leading to spin-transfer
torques when the order parameter is textured, such as in anti-ferromagnetic
non-collinear spin valves and domain walls. We report a first principles study
on the electronic transport properties of anti-ferromagnetic systems. The
current-induced spin torques acting on the magnetic moments are comparable with
those in conventional ferromagnetic materials, leading to measurable angular
resistances and current-induced magnetization dynamics. In contrast to
ferromagnets, spin torques in anti-ferromagnets are very nonlocal. The torques
acting far away from the center of an anti-ferromagnetic domain wall should
facilitate current-induced domain wall motion.Comment: The paper has substantially been rewritten, 4 pages, 5 figure
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