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This work is a theoretical study of the speed at which the material of an impacted target is ejected during the formation of an impact crater. Our model, starting from the first principle of thermodynamics, can describes the speed of the ejecta recursing to considerations that include complex process in simple calculations. The fit of the model with observations shows that the many complex details implicit in an impact process could be included in some few parameters. Ejecta speed could be described independent of impactor parameters. The model is compared with subsonic and supersonic speed experiments showing coincidence in several cases. The model works with subsonic and supersonic impacts. We do not compare the model with hypersonic impacts (> 5 km/s), however, as the model derivation no depends on the impactor velocity it is likely that also work with this kind of impacts.
In [5] Graham and Rothschild consider a geometric Ramsey problem: finding the least n such that if all edges of the complete graph on the points {+1,-1}^n are 2-colored, there exist 4 coplanar points such that the 6 edges between them are monochromat
We have found weak long range antiferromagnetic order in the quasi-two-dimensional insulating oxide $ KCr_3(OD)_6(SO_4)_2$ which contains Cr$^{3+}$ S=3/2 ions on a kagom{e} lattice. In a sample with $approx$ 76% occupancy of the chromium sites the or
We study the magnetic excitations on top of the plateaux states recently discovered in spin-Peierls systems in a magnetic field. We show by means of extensive density matrix renormalization group (DMRG) computations and an analytic approach that one
We demonstrate suppression and enhancement of spontaneous parametric down- conversion via quantum interference with two weak fields from a local oscillator (LO). Pairs of LO photons are observed to upconvert with high efficiency for appropriate phase
Data from the New Horizons mission to Pluto show no craters on Sputnik Planum down to the detection limit (2 km for low resolution data, 625 m for high resolution data). The number of small Kuiper Belt Objects that should be impacting Pluto is known