208 research outputs found
CONTACT DURABILITY ОF SAMPLES AND DURABILITY OF BEARINGS ALTER DIFFERENT METHODS OF PROCESSING
The results of studies of contact endurance of samples and bench tests of bearings after various methods of hardening treatment are presented. It is shown that as the intensity of hardening treatment increases, estimated by the integral value of residual stresses, the contact endurance of samples increases monotonically. However, tests on sam¬ples not detect a negative influence of distortion of the rings due to technological residual stresses on the durability of bearings. The dependence of bearing life on the deformation of rings has an optimum at which to determine the permissible deformation and the corresponding processing modes
Experimental studies of light-wave phase shift by polymer dispersed liquid crystal films
Polymermethacrylate (PMMA) and polyvinyl butyral (PVB) thin films with
the dispersed liquid crystal droplets are prepared by the described technique. The
measurements of light wave polarization-independent phase shift induced by the electric
field are displayed. It was been shown that the phase shift in polymethylmethacrylate
films can approach five radians at the applied electric field about 10 V/μm
The Nuclear Response in Delta-Isobar Region in the (He,t) Reaction
The excitation of a -isobar in a finite nucleus in charge--exchange
(He,t) reaction is discussed in terms of a nuclear response function. The
medium effects modifying a - and a pion propagation were considered for
a finite size nucleus. The Glauber approach has been used for distortion of a
He and a triton in the initial and the final states. The effects
determining the peak positions and its width are discussed. Large displacement
width for the - h excitations and considerable contribution of
coherent pion production were found for the reaction on C.Comment: 29 pages including 8 figures, IU/NTC 92-3
SPECTRAL CHARACTERISTICS STUDY OF PHASE-SHIFTED FIBER BRAGG GRATINGS UNDER PRESSURE APPLIED PERPENDICULAR TO FIBER AXIS
Subject of Research.The paper presents the study of effect that occurs when pressure is applied to the phase-shifted fiber Bragg gratings perpendicular to the fiber axis. Method. Fiber Bragg gratings inscription was performed using Talbot interferometer, and the introduction of a phase shift – by means of the electrical discharge of an arc fusion splicer. The excimer laser system was used as a radiation source. The change in the reflection spectra at different pressures on the optical fiber is measured. Main Results. Fiber Bragg gratings with a phase shift are obtained by the procedure that excludes the use of high-precision instruments during the phase-shift introduction step. Experiment results are given showing up the distance dependence between the local minima in the reflection spectrum of fiber Bragg grating with a phase shift on the applied mass arising as a result of the induced birefringence. It is shown that the change in spectral characteristics is related to the birefringence effect owing to stresses inside the fiber. As a result, the second local minimum appears in reflectance band. Practical Relevance. Research results can be used in creation of a sensing element of a fiber optic pressure sensor. This study demonstrates the application possibilities of Bragg gratings with a phase shift as sensing elements in fib
The anapole moment and nucleon weak interactions
From the recent measurement of parity nonconservation (PNC) in the Cs atom we
have extracted the constant of the nuclear spin dependent electron-nucleon PNC
interaction, ; the anapole moment constant, ; the strength of the PNC proton-nucleus potential, ; the -meson-nucleon interaction constant,
; and the strength of the neutron-nucleus potential, .Comment: Uses RevTex, 12 pages. We have added an explanation of the effect of
finite nuclear siz
Nuclear Magnetic Quadrupole Moments in Single Particle Approximation
A static magnetic quadrupole moment of a nucleus, induced by T- and P-odd
nucleon-nucleon interaction, is investigated in the single-particle
approximation. Models are considered allowing for analytical solution. The
problem is also treated numerically in a Woods-Saxon potential with spin-orbit
interaction. The stability of results is discussed.Comment: LATEX, 9 pages, 1 postscript figure available upon request from
"[email protected]". BINP 94-4
Renormalization of the P- and T-odd nuclear potentials by the strong interaction and enhancement of P-odd effective field
Approximate analytical formulas for the self-consistent renormalization of
P,T-odd and P-odd weak nuclear potentials by the residual nucleon-nucleon
strong interaction are derived. The contact spin-flip nucleon-nucleon
interaction reduces the constant of the P,T-odd potential 1.5 times for the
proton and 1.8 times for the neutron. Renormalization of the P-odd potential is
caused by the velocity dependent spin-flip component of the strong interaction.
In the standard variant of -exchange, the conventional strength
values lead to anomalous enhancement of the P-odd potential. Moreover, the
-meson exchange contribution seems to be large enough to generate an
instability (pole) in the nuclear response to a weak potential.Comment: 5 pages, Revtex3, no figure
No Sommerfeld resummation factor in e+e- -> ppbar ?
The Sommerfeld rescattering formula is compared to the e+e- -> ppbar BaBar
data at threshold and above. While there is the expected Coulomb enhancement at
threshold, two unexpected outcomes have been found: |G^p (4M_p^2)|= 1, like for
a pointlike fermion, and moreover data show that the resummation factor in the
Sommerfeld formula is not needed. Other e+e- -> baryon-antibaryon cross
sections show a similar behavior near threshold.Comment: 9 pages, 6 figure
Current-induced highly dissipative domains in high Tc thin films
We have investigated the resistive response of high Tc thin films submitted
to a high density of current. For this purpose, current pulses were applied
into bridges made of Nd(1.15)Ba(1.85)Cu3O7 and Bi2Sr2CaCu2O8. By recording the
time dependent voltage, we observe that at a certain critical current j*, a
highly dissipative domain develops somewhere along the bridge. The successive
formation of these domains produces stepped I-V characteristics. We present
evidences that these domains are not regions with a temperature above Tc, as
for hot spots. In fact this phenomenon appears to be analog to the nucleation
of phase-slip centers observed in conventional superconductors near Tc, but
here in contrast they appear in a wide temperature range. Under some
conditions, these domains will propagate and destroy the superconductivity
within the whole sample. We have measured the temperature dependence of j* and
found a similar behavior in the two investigated compounds. This temperature
dependence is just the one expected for the depairing current, but the
amplitude is about 100 times smaller.Comment: 9 pages, 9 figures, Revtex, to appear in Phys. Rev.
Further evidence for a variable fine-structure constant from Keck/HIRES QSO absorption spectra
[Abridged] We previously presented evidence for a varying fine-structure
constant, alpha, in two independent samples of Keck/HIRES QSO spectra. Here we
present a detailed many-multiplet analysis of a third Keck/HIRES sample
containing 78 absorption systems. We also re-analyse the previous samples,
providing a total of 128 absorption systems over the redshift range
0.2<z_abs<3.7. All three samples separately yield consistent, significant
values of da/a. The analyses of low- and high-z systems rely on different
ions/transitions with very different dependencies on alpha, yet they also give
consistent results. We identify additional random errors in 22 high-z systems
characterized by transitions with a large dynamic range in apparent optical
depth. Increasing the statistical errors on da/a for these systems gives our
fiducial result, a weighted mean da/a=(-0.543+/-0.116)x10^-5, representing
4.7-sigma evidence for a smaller weighted mean alpha in the absorption clouds.
Assuming that da/a=0 at z_abs=0, the data marginally prefer a linear increase
in alpha with time: dota/a=(6.40+/-1.35)x10^-16 yr^-1. The two-point
correlation function for alpha is consistent with zero over 0.2-13 Gpc comoving
scales and the angular distribution of da/a shows no significant dipolar
anisotropy. We therefore have no evidence for spatial variations in da/a. We
extend our previous searches for possible systematic errors, identifying
atmospheric dispersion and isotopic structure effects as potentially the most
significant. However, overall, known systematic errors do not explain the
results. Future many-multiplet analyses of QSO spectra from different
telescopes and spectrographs will provide a now crucial check on our Keck/HIRES
results.Comment: 31 pages, 25 figures (29 EPS files), 8 tables. Accepted by MNRAS.
Colour versions of Figs. 6, 8 & 10 and text version of Table 3 available at
http://www.ast.cam.ac.uk/~mim/pub.htm
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