77 research outputs found
Two-phonon structures for beta-decay theory
The -decay rates of Ca have been studied within a microscopic
model, which is based on the Skyrme interaction T45 to construct
single-particle and phonon spaces. We observe a redistribution of the
Gamow-Teller strength due to the phonon-phonon coupling, considered in the
model. For Sc, the spin-parity of the ground state is found to be .
We predict that the half-life of Ca is 0.3 ms, while the total
probability of the emission is 6.1%. Additionally, the random
matrix theory has been applied to analyse the statistical properties of the
spectrum populated in the -decay to elucidate the obtained
results.Comment: 4 pages, 1 figure, proceedings of International Conference on Nuclear
Structure and Related Topics (NSRT18), June 3-9 2018, Burgas, Bulgari
Design and optimization of squirrel cage geometries in aircraft engines toward robust whole engine dynamics
In this work, an coupled end-to-end approach for the optimization of the rotor dynamic behavior of a dual-spool aircraft engine along with fatigue life optimization of squirrel cages (SQC) is presented. A realistic model to simulate the rotor dynamics is created, where the high-pressure (HP) rotor is supported by two squirrel cages. The aim of this work is to find a robust rotor dynamics design by shifting a critical speed to higher rotational speed, and at the same time improving the squirrel cage design with respect to fatigue life.
Fully automatized coupled analysis process chain is implemented, allowing to compute the influence of the SQCs geometry variation onto the full rotor dynamics and structural performance of the SQC. Two global optimization techniques are employed to explore the SQCs design space and find optimal 3D geometries, using the aforementioned coupled process.
Optimization results are compared and discussed in detail, indicating the importance of the numerical optimization to improve fatigue life of the squirrel cage. It is shown that optimized and non-optimized SQC designs, both fulfilling rotor dynamics goals, can have significantly different performance regarding their fatigue life. Moreover, the advantage of the coupled process is illustrated, allowing to find superior SQC designs by considering both disciplines simultaneously in comparison with a sequential (uncoupled) approach, when the target elastic properties of an SQC, selected only based on the rotor dynamics requirements, may lead to sub-optimal fatigue life
Influence of 2p-2h configurations on beta-decay rates
The effects of the phonon-phonon coupling on the beta-decay rates of
neutron-rich nuclei are studied in a microscopic model based on Skyrme-type
interactions. The approach uses a finite-rank separable approximation of the
Skyrme-type particle-hole (p-h) residual interaction. Very large
two-quasiparticle spaces can thus be treated. A redistribution of the
Gamow-Teller (G-T) strength is found due to the tensor correlations and the
2p-2h fragmentation of G-T states. As a result, the beta-decay half-lives are
decreased significantly. Using the Skyrme interaction SGII together with a
volume-type pairing interaction we illustrate this reduction effect by
comparing with available experimental data for the Ni isotopes and neutron-rich
N=50 isotones. We give predictions for 76Fe and 80Ni in comparison with the
case of the doubly-magic nucleus 78Ni which is an important waiting point in
the r-process.Comment: 8 pages, 6 figures, accepted for publication in Physical Review
Mathematical modelling of the thermal and hydraulic behaviour of plate heat exchanger in the fouling conditions
The mathematical model of Plate Heat Exchanger (PHE) subjected to fouling is proposed. It is represented by the system of ordinary differential equations. The model is accounting for the distribution of process parameters along the PHE channel that allows predicting fouling development in time at different locations along the channel length. The development of the fouling deposit is accounted with the fouling model presented by the equation in dimensionless form. The relative influence of different terms is characterized by empirical coefficients which can be identified with the data of monitoring the PHE thermal and hydraulic performance. The model allows also the prediction of pressure drop variation in PHE with the development of fouling deposition layer and respective reduction in channels cross-section area. The application of the model and its accuracy is demonstrated with two case studies considering the monitoring of PHEs thermal and hydraulic performance in the industry at sugar factory and in District Heating system
Fine structure of the isoscalar giant monopole resonance in Ni, Zr, Sn and Pb
Over the past two decades high energy-resolution inelastic proton scattering
studies were used to gain an understanding of the origin of fine structure
observed in the isoscalar giant quadrupole resonance (ISGQR) and the isovector
giant dipole resonance (IVGDR). Recently, the isoscalar giant monopole
resonance (ISGMR) in Ni, Zr, Sn and Pb was
studied at the iThemba Laboratory for Accelerator Based Sciences (iThemba LABS)
by means of inelastic -particle scattering at very forward scattering
angles (including ). The good energy resolution of the measurement
revealed significant fine structure of the ISGMR.~To extract scales by means of
wavelet analysis characterizing the observed fine structure of the ISGMR in
order to investigate the role of different mechanisms contributing to its decay
width. Characteristic energy scales are extracted from the fine structure using
continuous wavelet transforms. The experimental energy scales are compared to
different theoretical approaches performed in the framework of quasiparticle
random phase approximation (QRPA) and beyond-QRPA including complex
configurations using both non-relativistic and relativistic density functional
theory. All models highlight the role of Landau fragmentation for the damping
of the ISGMR especially in the medium-mass region. Models which include the
coupling between one particle-one hole (1p-1h) and two particle-two hole
(2p-2h) configurations modify the strength distributions and wavelet scales
indicating the importance of the spreading width. The effect becomes more
pronounced with increasing mass number. Wavelet scales remain a sensitive
measure of the interplay between Landau fragmentation and the spreading width
in the description of the fine structure of giant resonances.Comment: 13 pages,7 figures, regular articl
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HE-LHC: The High-Energy Large Hadron Collider: Future Circular Collider Conceptual Design Report Volume 4
Abstract: In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km tunnel infrastructure, as well as the physics opportunities of these two colliders, and a high-energy LHC, based on FCC-hh technology. This document constitutes the third volume of the FCC Conceptual Design Report, devoted to the hadron collider FCC-hh. It summarizes the FCC-hh physics discovery opportunities, presents the FCC-hh accelerator design, performance reach, and staged operation plan, discusses the underlying technologies, the civil engineering and technical infrastructure, and also sketches a possible implementation. Combining ingredients from the Large Hadron Collider (LHC), the high-luminosity LHC upgrade and adding novel technologies and approaches, the FCC-hh design aims at significantly extending the energy frontier to 100 TeV. Its unprecedented centre-of-mass collision energy will make the FCC-hh a unique instrument to explore physics beyond the Standard Model, offering great direct sensitivity to new physics and discoveries
HE-LHC: The High-Energy Large Hadron Collider – Future Circular Collider Conceptual Design Report Volume 4
In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km tunnel infrastructure, as well as the physics opportunities of these two colliders, and a high-energy LHC, based on FCC-hh technology. This document constitutes the third volume of the FCC Conceptual Design Report, devoted to the hadron collider FCC-hh. It summarizes the FCC-hh physics discovery opportunities, presents the FCC-hh accelerator design, performance reach, and staged operation plan, discusses the underlying technologies, the civil engineering and technical infrastructure, and also sketches a possible implementation. Combining ingredients from the Large Hadron Collider (LHC), the high-luminosity LHC upgrade and adding novel technologies and approaches, the FCC-hh design aims at significantly extending the energy frontier to 100 TeV. Its unprecedented centre-of-mass collision energy will make the FCC-hh a unique instrument to explore physics beyond the Standard Model, offering great direct sensitivity to new physics and discoveries
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