27,561 research outputs found
Saturation current spikes eliminated in saturable core transformers
Unsaturating composite magnetic core transformer, consisting of two separate parallel cores designed so impending core saturation causes signal generation, terminates high current spike in converter primary circuit. Simplified waveform, demonstrates transformer effectiveness in eliminating current spikes
Load insensitive electrical device
A class of power converters is described for supplying direct current at one voltage from a source at another voltage. It includes a simple passive circuit arrangement of solid-state switches, inductors, and capacitors by which the output voltage of the converter tends to remain constant in spite of changes in load. The switches are sensitive to the current flowing in the circuit and are employed to permit the charging of capacitance devices in accordance with the load requirements. Because solid-state switches (such as SCR's) may be used with relatively high voltage and because of the inherent efficiency of the invention that permits relatively high switching frequencies, power supplies built in accordance with the invention, together with their associated cabling, can be substantially lighter in weight for a given output power level and efficiency of operation than systems of the prior art
Saturation current protection apparatus for saturable core transformers Patent
Magnetic current regulator for saturable core transforme
Newtonian versus relativistic cosmology
We show how the relativistic matter and velocity power spectra behave in
different gauges. We construct a new gauge where both spectra coincide with
Newtonian theory on all scales. However, in this gauge there are geometric
quantities present which do not exist in Newtonian theory, for example the
local variation of the Hubble parameter. Comparing this quantity to second
order Newtonian quantities, we find that Newtonian theory is inaccurate on
scales larger than 10 Mpc. This stresses the importance of relativistic
corrections to Newtonian cosmological N-body simulations on these scales.Comment: 10 pages, 3 figures, accepted for publication in Physical Review D
(Sept. 2012
Scale dependence of cosmological backreaction
Due to the non-commutation of spatial averaging and temporal evolution,
inhomogeneities and anisotropies (cosmic structures) influence the evolution of
the averaged Universe via the cosmological backreaction mechanism. We study the
backreaction effect as a function of averaging scale in a perturbative approach
up to higher orders. We calculate the hierarchy of the critical scales, at
which 10% effects show up from averaging at different orders. The dominant
contribution comes from the averaged spatial curvature, observable up to scales
of 200 Mpc. The cosmic variance of the local Hubble rate is 10% (5%) for
spherical regions of radius 40 (60) Mpc. We compare our result to the one from
Newtonian cosmology and Hubble Space Telescope Key Project data.Comment: 6 pages, 2 figures; v3: substantial modifications, new figure
High aspect reactor vessel and method of use
An improved bio-reactor vessel and system useful for carrying out mammalian cell growth in suspension in a culture media are presented. The main goal of the invention is to grow and maintain cells under a homogeneous distribution under acceptable biochemical environment of gas partial pressures and nutrient levels without introducing direct agitation mechanisms or associated disruptive mechanical forces. The culture chamber rotates to maintain an even distribution of cells in suspension and minimizes the length of a gas diffusion path. The culture chamber design is presented and discussed
Determination of serum protein binding of 3H-ACTH using dextran gel filtration and desity gradient centrifugation
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