59 research outputs found
Neural network utilization for evaluation of the steel material properties
The aim of this work is to develop and test a new method for identification of material properties of the steel. This work deals with application of the small punch test for evaluation of material degradation of power station in the ČEZ company (main Czech energetic company) within the project TE01020068 “Centre of research and experimental development of reliable energy production, work package 8: Research and development of new testing methods for evaluation of material properties”. The main effort is here an improvement of empirical correlation of selected steel materials used in power industry for manufacturing of the critical components (rotors, steam-pipes, etc.). The effort here is on the utilization of the finite element method (FEM) and the neural network (NN) for evaluation of mechanical properties (Young modulus of elasticity, yield stress, tensile strength) of the selected material, based on SPT results only
Space-time versus particle-hole symmetry in quantum Enskog equations
The non-local scattering-in and -out integrals of the Enskog equation have
reversed displacements of colliding particles reflecting that the -in and -out
processes are conjugated by the space and time inversions. Generalisations of
the Enskog equation to Fermi liquid systems are hindered by a request of the
particle-hole symmetry which contradicts the reversed displacements. We resolve
this problem with the help of the optical theorem. It is found that space-time
and particle-hole symmetry can only be fulfilled simultaneously for the
Bruckner-type of internal Pauli-blocking while the Feynman-Galitskii form
allows only for particle-hole symmetry but not for space-time symmetry due to a
stimulated emission of Bosons
Non-instant collisions and two concepts of quasiparticle
The kinetic theory recently implemented in heavy ion reactions combines a
non-local and non-instant picture of binary collisions with quasiparticle
features. We show that the non-instant description is compatible with the
spectral concept of quasiparticles while the commonly used variational concept
is consistent only with instant collisions. The rearrangement energy, by which
the variational concept surpasses the spectral one, is shown to be covered by a
medium effect on non-instant collisions.Comment: PRE 59,1 rap. com
Nonlinear relaxation field in charged systems under high electric fields
The influence of an external electric field on the current in charged systems
is investigated. The results from the classical hierarchy of density matrices
are compared with the results from the quantum kinetic theory. The kinetic
theory yields a systematic treatment of the nonlinear current beyond linear
response. To this end the dynamically screened and field-dependent
Lenard-Balescu equation is integrated analytically and the nonlinear relaxation
field is calculated. The classical linear response result known as Debye -
Onsager relaxation effect is only obtained if asymmetric screening is assumed.
Considering the kinetic equation of one specie the other species have to be
screened dynamically while the screening with the same specie itself has to be
performed statically. Different other approximations are discussed and
compared.Comment: language correction
Anomalous radial expansion in central heavy-ion reactions
The expansion velocity profile in central heavy-ion reactions in the Fermi
energy domain is examined. The radial expansion is non-hubblean and in the
surface region it scales proportional to a higher exponent () of
the radius. The anomalous expansion velocity profile is accompanied by a power
law nucleon density profile in the surface region. Both these features of
central heavy-ion reactions disappear at higher energies, and the system
follows a uniform Hubble expansion ()
Effects of impurity scattering on electron-phonon resonances in semiconductor superlattice high-field transport
A non-equilibrium Green's function method is applied to model high-field
quantum transport and electron-phonon resonances in semiconductor
superlattices. The field-dependent density of states for elastic (impurity)
scattering is found non-perturbatively in an approach which can be applied to
both high and low electric fields. I-V curves, and specifically electron-phonon
resonances, are calculated by treating the inelastic (LO phonon) scattering
perturbatively. Calculations show how strong impurity scattering suppresses the
electron-phonon resonance peaks in I-V curves, and their detailed sensitivity
to the size, strength and concentration of impurities.Comment: 7 figures, 1 tabl
A phase 2 study of ibrutinib in combination with bortezomib and dexamethasone in patients with relapsed/refractory multiple myeloma
Objective: We evaluated ibrutinib, a once-daily inhibitor of Bruton's tyrosine kinase, combined with bortezomib and dexamethasone in patients with relapsed or relapsed/refractory multiple myeloma who had received 1-3 prior therapies. Methods: This was a phase 2, single-arm, open-label, multicentre study (NCT02902965). The primary endpoint was progression-free survival (PFS). Results: Seventy-six patients were enrolled; 74 received ≥1 dose of study treatment. After median follow-up of 19.6 months, median PFS was 8.5 months (95% CI: 6.2-10.8); median overall survival was not reached. Overall response rate was 57% (95% CI: 45-68), and median duration of response was 9.5 months (95% CI: 6.9-10.6). Grade 3/4 AEs occurred in 73% of patients and fatal AEs occurred in 15% of patients. Incidence of major haemorrhage was 5%; one patient died from cerebral haemorrhage. After an observed increased incidence of serious (42%) and fatal (11%) infections, enrolment was suspended to implement risk-minimisation measures. The safety profile was otherwise consistent with known safety profiles of the individual drugs. Conclusion: Ibrutinib combined with bortezomib and dexamethasone elicited clinical responses. However, efficacy assessments conducted at potential restart of enrolment indicated that the targeted PFS could not be reached with additional patient enrolment, and the study was terminated
Quantum dynamics and thermalization for out-of-equilibrium phi^4-theory
The quantum time evolution of \phi^4-field theory for a spatially homogeneous
system in 2+1 space-time dimensions is investigated numerically for
out-of-equilibrium initial conditions on the basis of the Kadanoff-Baym
equations including the tadpole and sunset self-energies. Whereas the tadpole
self-energy yields a dynamical mass, the sunset self-energy is responsible for
dissipation and an equilibration of the system. In particular we address the
dynamics of the spectral (`off-shell') distributions of the excited quantum
modes and the different phases in the approach to equilibrium described by
Kubo-Martin-Schwinger relations for thermal equilibrium states. The
investigation explicitly demonstrates that the only translation invariant
solutions representing the stationary fixed points of the coupled equation of
motions are those of full thermal equilibrium. They agree with those extracted
from the time integration of the Kadanoff-Baym equations in the long time
limit. Furthermore, a detailed comparison of the full quantum dynamics to more
approximate and simple schemes like that of a standard kinetic (on-shell)
Boltzmann equation is performed. Our analysis shows that the consistent
inclusion of the dynamical spectral function has a significant impact on
relaxation phenomena. The different time scales, that are involved in the
dynamical quantum evolution towards a complete thermalized state, are discussed
in detail. We find that far off-shell 1 3 processes are responsible for
chemical equilibration, which is missed in the Boltzmann limit. Finally, we
address briefly the case of (bare) massless fields. For sufficiently large
couplings we observe the onset of Bose condensation, where our scheme
within symmetric \phi^4-theory breaks down.Comment: 77 pages, 26 figure
Quantum kinetics and thermalization in a particle bath model
We study the dynamics of relaxation and thermalization in an exactly solvable
model of a particle interacting with a harmonic oscillator bath. Our goal is to
understand the effects of non-Markovian processes on the relaxational dynamics
and to compare the exact evolution of the distribution function with
approximate Markovian and Non-Markovian quantum kinetics. There are two
different cases that are studied in detail: i) a quasiparticle (resonance) when
the renormalized frequency of the particle is above the frequency threshold of
the bath and ii) a stable renormalized `particle' state below this threshold.
The time evolution of the occupation number for the particle is evaluated
exactly using different approaches that yield to complementary insights. The
exact solution allows us to investigate the concept of the formation time of a
quasiparticle and to study the difference between the relaxation of the
distribution of bare particles and that of quasiparticles. We derive a
non-Markovian quantum kinetic equation which resums the perturbative series and
includes off-shell effects. A Markovian approximation that includes off-shell
contributions and the usual Boltzmann equation (energy conserving) are obtained
from the quantum kinetic equation in the limit of wide separation of time
scales upon different coarse-graining assumptions. The relaxational dynamics
predicted by the non-Markovian, Markovian and Boltzmann approximations are
compared to the exact result. The Boltzmann approach is seen to fail in the
case of wide resonances and when threshold and renormalization effects are
important.Comment: 39 pages, RevTex, 14 figures (13 eps figures
Chaotic scattering on surfaces and collisional damping of collective modes
The damping of hot giant dipole resonances is investigated. The contribution
of surface scattering is compared with the contribution from interparticle
collisions. A unified response function is presented which includes surface
damping as well as collisional damping. The surface damping enters the response
via the Lyapunov exponent and the collisional damping via the relaxation time.
The former is calculated for different shape deformations of quadrupole and
octupole type. The surface as well as the collisional contribution each
reproduce almost the experimental value, therefore we propose a proper
weighting between both contributions related to their relative occurrence due
to collision frequencies between particles and of particles with the surface.
We find that for low and high temperatures the collisional contribution
dominates whereas the surface damping is dominant around the temperatures
of the centroid energy.Comment: PRC su
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