388 research outputs found
Effect of one variant of Ti3Ni4 particles on stress-induced martensitic transformations in <111>-oriented Ti49.2Ni50.8 single crystals
In the present study the effects of stress-assisted aging of the Ti49.2Ni50.8 single crystals oriented along [11] direction on the stress-induced B2-R-B19' thermoelastic martensitic transformations and superelasticity are investigated. It is experimentally established that aging at 823 K for 1h under compression stress of 150 MPa along [11] direction leads to the precipitation of one crystallographic variant of Ti3Ni4 particles of 350(±30) nm in size. Precipitation the single variant of Ti3Ni4 particle results in an appearance of homogeneous long-range internal stress field || ≈ 65 MPa, that defines the main features of stress-induced B2-R-B19' transformation and determines the increase in the characteristic temperatures of martensitic transformation and the existence of two-way shape memory effect
Energetics in Condensate Star and Wormholes
It is known that the total gravitational energy in localized sources having
static spherical symmetry and satisfying energy conditions is negative
(attractive gravity). A natural query is how the gravitational energy behaves
under circumstances where energy conditions are violated. To answer this, the
known expression for the gravitational energy is suitably modified to account
for situations like the ones occurring in wormhole spacetime. It is then
exemplified that in many cases the modified expression yields desirable
answers. The implications are discussed.Comment: 16 pages, 1 figure, references added, To appear in PR
Evolution of the double neutron star merging rate and the cosmological origin of gamma-ray burst sources
Evolution of the coalescence rate of double neutron stars (NS) and neutron
star -- black hole (BH) binaries are computed for model galaxies with different
star formation rates. Assuming gamma-ray bursts (GRB) to originate from NS+NS
or NS+BH merging in distant galaxies, theoretical logN--logS distributions and
tests of gamma-ray bursts (GRB) are calculated for the first time
taking the computed merging rates into account. We use a flat cosmological
model (Omega=1) with different values of the cosmological constant Lambda and
under various assumptions about the star formation history in galaxies. The
calculated source evolution predicts a 5-10 times increase of the source
statistics at count rates 3-10 times lower than the exising BATSE sensitivity
limit. The most important parameter in fitting the 2nd BATSE catalogue is the
initial redshift of star formation, which is found to be z_*=2-5 depending on a
poorly determined average spectral index of GRB.Comment: 13 pages, compressed uuencoded postscript, 6 figures. This paper has
been accepted for publication in the Astrophysical Journal part
INTEGRAL observations of SS433, a supercritically accreting microquasar with hard spectrum
Observations of SS433 by INTEGRAL carried out in March -- May 2003 are
presented. SS433 is evidently detected on the INTEGRAL images of the
corresponding sky region in the energy bands 25-50 and 50-100 keV. The
precessional variability of the hard X-ray flux is clearly seen. The X-ray
eclipse caused by the binary orbital motion is also detected. A possible origin
of the hard continuum is briefly discussed.Comment: 5 pages, 6 figures. Accepted to A&A INTEGRAL special volum
INTEGRAL Observations of SS433: Analysis of Precessional and Orbital X-ray Periodicities
Hard X-ray INT observations of SS 433 carried out during 2003-2005 years with
an analysis of precessional and orbital variability is presented. The width of
X-ray eclipse in the 25-50 keV range at the precessional phase
(accretion disk is open to observer) is higher than that in the Ginga 18.4-27.6
keV range. This fact suggests existance the presence of hot extended corona
around the supercritical accretion disk. Spectrum of hard X-rays in the range
10-200 keV does not change with the precessional phase which also suggests that
hard X-ray flux is generated in the hot extended corona around the accretion
disk. The parameters of this hot corona are: kT=23-25 keV, \tau = 1.8-2.8. Mass
ratio estimated from the analysis of the ingress part of the eclipse light
curve is in the range q=m_x/m_v=0.3-0.5.Comment: 5 pages, 10 figure
Influence of High-Current Pulsed Electron Beam Surface Treatment on Tribological Characteristics of Non-Equimolar Al-Co-Cr-Fe-Ni High-Entropy Alloy
In this study wire-arc additively manufactured high-entropy alloy Al-Co-Cr-Fe-Ni system was subjected to high-current electron beam surface treatment at different energy density of an electron beam. The tribological characteristics such as wear rate and coefficient of friction were studied.This research was funded by Russian Science Foundation (project 20-19-00452)
Digital receivers for low-frequency radio telescopes UTR-2, URAN, GURT
This paper describes digital radio astronomical receivers used for decameter
and meter wavelength observations. This paper describes digital radio
astronomical receivers used for decameter and meter wavelength observations.
Since 1998, digital receivers performing on-the-fly dynamic spectrum
calculations or waveform data recording without data loss have been used at the
UTR-2 radio telescope, the URAN VLBI system, and the GURT new generation radio
telescope. Here we detail these receivers developed for operation in the strong
interference environment that prevails in the decameter wavelength range. Data
collected with these receivers allowed us to discover numerous radio
astronomical objects and phenomena at low frequencies, a summary of which is
also presented.Comment: 24 pages, 15 figure
Statics, metastable states and barriers in protein folding: A replica variational approach
Protein folding is analyzed using a replica variational formalism to
investigate some free energy landscape characteristics relevant for dynamics. A
random contact interaction model that satisfies the minimum frustration
principle is used to describe the coil-globule transition (characterized by
T_CG), glass transitions (by T_A and T_K) and folding transition (by T_F).
Trapping on the free energy landscape is characterized by two characteristic
temperatures, one dynamic, T_A the other static, T_K (T_A> T_K), which are
similar to those found in mean field theories of the Potts glass. 1)Above T_A,
the free energy landscape is monotonous and polymer is melted both dynamically
and statically. 2)Between T_A and T_K, the melted phase is still dominant
thermodynamically, but frozen metastable states, exponentially large in number,
appear. 3)A few lowest minima become thermodynamically dominant below T_K,
where the polymer is totally frozen. In the temperature range between T_A and
T_K, barriers between metastable states are shown to grow with decreasing
temperature suggesting super-Arrhenius behavior in a sufficiently large system.
Due to evolutionary constraints on fast folding, the folding temperature T_F is
expected to be higher than T_K, but may or may not be higher than T_A. Diverse
scenarios of the folding kinetics are discussed based on phase diagrams that
take into account the dynamical transition, as well as the static ones.Comment: 41 pages, LaTeX, 9 EPS figure
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