972 research outputs found
The determination of the thermal properties of unconsolidated materials
Heat transfer in a composite cylindrical region is considered. An approximate analytical solution of the direct problem is obtained. It is shown that, beginning at the instant t > t , the relative error of the solution obtained does not exceed 1%. On the basis of this, algorithms are constructed which enable inverse problems to be solved effectively. Examples of the use of the algorithms to determine the thermal properties of unconsolidated materials are presented. © 2012 Springer Science+Business Media, Inc
Freezing and melting of 3D complex plasma structures under microgravity conditions driven by neutral gas pressure manipulation
Freezing and melting of large three-dimensional complex plasmas under
microgravity conditions is investigated. The neutral gas pressure is used as a
control parameter to trigger the phase changes: Complex plasma freezes (melts)
by decreasing (increasing) the pressure. Evolution of complex plasma structural
properties upon pressure variation is studied. Theoretical estimates allow us
to identify main factors responsible for the observed behavior.Comment: Phys. Rev. Lett. (in press); 4 pages, 4 figure
A search for J^{PC}=1^{-+} exotic mesons in the pi- pi- pi+ and pi- pi0 pi0 systems
A partial wave analysis (PWA) of the pi-pi-pi+ and pi-pi0pi0 systems produced
in the reaction pi- p -> (3pi)-p at 18 GeV/c was carried out using an isobar
model assumption. This analysis is based on 3.0M pi-pi0pi0 events and 2.6M
pi-pi-pi+ events and shows production of the a2(1320), pi2(1670) and \pi(1800)
mesons. An earlier analysis of 250K pi-pi-pi+ events from the same experiment
showed possible evidence for a J^{PC}=1^{-+}$ exotic meson with a mass of 1.6
GeV/c^2 decaying into rho pi. In this analysis of a higher statistics sample of
the (3pi)- system in two charged modes we find no evidence of an exotic meson.Comment: 4 pages, 5 figures, added comment about the negative reflectivity
exotic wave
Fluid-solid phase transitions in 3D complex plasmas under microgravity conditions
Phase behavior of large three-dimensional complex plasma systems under
microgravity conditions onboard the International Space Station is
investigated. The neutral gas pressure is used as a control parameter to
trigger phase changes. Detailed analysis of structural properties and
evaluation of three different melting/freezing indicators reveal that complex
plasmas can exhibit melting by increasing the gas pressure. Theoretical
estimates of complex plasma parameters allow us to identify main factors
responsible for the observed behavior. The location of phase states of the
investigated systems on a relevant equilibrium phase diagram is estimated.
Important differences between the melting process of 3D complex plasmas under
microgravity conditions and that of flat 2D complex plasma crystals in ground
based experiments are discussed.Comment: 13 pages, 10 figures; submitted to Phys. Rev.
Phenomena in Complex (Dusty) Plasma Studied under Microgravity Conditions
Complex (dusty) plasmas are composed of weakly ionized gas and charged microparticles and represent the plasma state of soft matter. The investigations which are not available on ground have been per-formed onboard the International Space Station (ISS) with the help of the “Plasma Crystal-3 Plus” (PK-3 Plus) laboratory. A number of interesting phenomena has been observed. The phase transition from iso-tropic plasma into electrorheological plasma was initiated. The crystal-liquid phase transition was ob-tained in large 3D isotropic dusty plasma. The slow compression of the dust particle subsystem has been investigated
Dust density waves in a dc flowing complex plasma with discharge polarity reversal
We report on the observation of the self-excited dust density waves in the dc
discharge complex plasma. The experiments were performed under microgravity
conditions in the Plasmakristall-4 facility on board the International Space
Station. In the experiment, the microparticle cloud was first trapped in an
inductively coupled plasma, then released to drift for some seconds in a dc
discharge with constant current. After that the discharge polarity was
reversed. DC plasma containing a drifting microparticle cloud was found to be
strongly non-uniform in terms of microparticle drift velocity and plasma
emission in accord with [Zobnin et.al., Phys. Plasmas 25, 033702 (2018)]. In
addition to that, non-uniformity in the self-excited wave pattern was observed:
In the front edge of the microparticle cloud (defined as head), the waves had
larger phase velocity than in the rear edge (defined as tail). Also, after the
polarity reversal, the wave pattern exhibited several bifurcations: Between
each of the two old wave crests, a new wave crest has formed. These
bifurcations, however, occurred only in the head of the microparticle cloud. We
show that spatial variations of electric field inside the drifting cloud play
an important role in the formation of the wave pattern. Comparison of the
theoretical estimations and measurements demonstrate the significant impact of
the electric field on the phase velocity of the wave. The same theoretical
approach applied to the instability growth rate, showed agreement between
estimated and measured values.Comment: 7 pages, 4 figure
Observation of exotic meson production in the reaction at 18 GeV/c
An amplitude analysis of an exclusive sample of 5765 events from the reaction
at 18 GeV/c is described. The
production is dominated by natural parity exchange and by
three partial waves: those with and . A
mass-dependent analysis of the partial-wave amplitudes indicates the production
of the meson as well as the meson, observed for the
first time decaying to . The dominant, exotic
(non- partial wave is shown to be resonant with a mass of
GeV/c^2 and a width of GeV/c^2 . This exotic state, the , is produced with a
dependence which is different from that of the meson, indicating
differences between the production mechanisms for the two states.Comment: 5 pages with 4 figure
Partial-wave analysis of the eta pi+ pi- system produced in the reaction pi-p --> eta pi+ pi- n at 18 GeV/c
A partial-wave analysis of 9082 eta pi+ pi- n events produced in the reaction
pi- p --> eta pi+ pi- n at 18.3 GeV/c has been carried out using data from
experiment 852 at Brookhaven National Laboratory. The data are dominated by
J^{PC} = 0^{-+} partial waves consistent with observation of the eta(1295) and
the eta(1440). The mass and width of the eta(1295) were determined to be 1282
+- 5 MeV and 66 +- 13 Mev respectively while the eta(1440) was observed with a
mass of 1404 +- 6 MeV and width of 80 +- 21 MeV. Other partial waves of
importance include the 1++ and the 1+- waves. Results of the partial wave
analysis are combined with results of other experiments to estimate f1(1285)
branching fractions. These values are considerably different from current
values determined without the aid of amplitude analyses.Comment: 22 pages, 8 figure
A partial wave analysis of the system produced in charge exchange collisions
A partial wave analysis of the of the system produced in the
charge exchange reaction: at an incident momentum of
is presented as a function of invariant mass,
, and momentum transfer squared, , from the incident
to the outgoing system.Comment: 24 pages total,8 pages text, 14 figures, 1 table. Submitted to Phys
Rev
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