Consistent description of nuclear charge radii and electric monopole transitions

A systematic study of energy spectra throughout the rare-earth region (even-even nuclei from $_{58}$Ce to $_{74}$W) is carried out in the framework of the interacting boson model (IBM), leading to an accurate description of the spherical-to-deformed shape transition in the different isotopic chains. The resulting IBM Hamiltonians are then used for the calculation of nuclear charge radii (including isotope and isomer shifts) and electric monopole transitions with consistent operators for the two observables. The main conclusion of this study is that an IBM description of charge radii and electric monopole transitions is possible for most of the nuclei considered but that it breaks down in the tungsten isotopes. It is suggested that this failure is related to hexadecapole deformation.Comment: 13 pages, 5 tables, 3 figures, accepted for publication in Physical Review

Higher-rank discrete symmetries in the IBM. I Octahedral shapes: general Hamiltonian

In the context of the interacting boson model with $s$, $d$ and $g$ bosons, the conditions for obtaining an intrinsic shape with octahedral symmetry are derived for a general Hamiltonian with up to two-body interactions.Comment: 19 pages, 2 figures, accepted for publication in Nuclear Physics

Perfomanse fotonaponskog sustava pumpanja pogonjenog jednofaznim indukcijskim motorom spojenim na fotonaponski generator

Solar energy is one of the most widely used renewable sources in the world. This explains the interest shown by researchers on the improvement of the quality and performances of this renewable source. The availability of low-cost solar cells increases the interest and needs in photovoltaic (PV) system applications following standard of living improvements. Nowadays, water pumping systems powered by solar-cell generators are one of the most important applications. In fact three phase induction motor fed by PVG is well known in literature, while the single phase induction motor for low power application used widely in domestic utility has never been investigated. In this paper the performances of a single phase induction motor (SPIM) connected to a photovoltaic generator (PVG) through an inverter are analyzed. Firstly, the mathematical model of the suggested structure is developed. Secondly, the concept of the Indirect Rotor-Field-Oriented Control (IRFOC) techniques is used to pilot the working of the single phase induction motor coupled with the centrifugal pump. Then, the chosen maximum power point tracking algorithm MPPT adjust pump operation to meet the desired water flow and pressure conditions. The proposed approach has the advantage no use the DC/DC converter, reduced size, low cost. This results in much higher overall system operating efficiencies. Finally, Simulation results show the effectiveness and feasibility of the suggested approach.Solarna energija je jedna od najkorištenijh oblika obnovljivih izvora energije u svijetu. To objašnjava interes istraživača za poboljšanjem kvalitete i performansi ovog obnovljivog izvora. Dostupnost jeftinih solarnih ćelija povećava interes i potrebu za aplikacijama fotonaponskih (PV) sustava prateći rast kvalitete životnih uvjeta. Danas, jedna od najvažnijih aplikacija je u sustavima za pumpanje vode. Zapravo, trofazni indukcijski motor kojeg pogoni PVG je dobro poznat u literaturi, dok jednofazni indukcijski motor koji se koristi u energetski nezahtjevnim sustavima kao što su kućanski aparati nikad nije istraživan. U ovom radu se analiziraju performanse jednofaznog indukcijskog motora (SPIM) spojenog na fotonaponski generator (PVG) pomoću invertera. Prvo je razvijen matematički model predloženog sustava. Potom je koncept indirektnog upravljanja orijentacijom-polja-rotora (IRFOC) korišten za upravljanje jednofaznim indukcijskim motorom spojenim s centrifugalnom pumpom. Zatim je iskorišten algoritam praćenja točke najveće snage (MPPT) za prilagodbu rada pumpe na zahtjevane protočne i tlačne uvjete. Predloženi pristup ima prednost korištenja DC/DC konvertera, smanjene veličine i niske cijene. Rezultat je mnogo veća efikasnost rada cjelokupnog sustava. Konačno, simulacijski rezultati pokazuju efektivnost i izvedivost predloženog pristupa

A new species for the vascular flora of Algeria: Cyperus eragrostis (Cyperaceae)

This study provides a definition and description of Cyperus eragrostis as a new alien species to Algeria and North African flora. This hemicryptophyte, native to the tropical parts of South America, is recorded for the first time in Jijel eco-complex wetlands in North-East Algeria. Applying the standard phytosociological method we studied the stands in which this alien species grows together with other hygrophilous and ruderal species. The present study improves the knowledge of the Algerian flora and completes the information about the distribution of C. eragrostis reported by the available international literature and public herbaria

Phase transitions in the sdgsdg interacting boson model

A geometric analysis of the $sdg$ interacting boson model is performed. A coherent-state is used in terms of three types of deformation: axial quadrupole ($\beta_2$), axial hexadecapole ($\beta_4$) and triaxial ($\gamma_2$). The phase-transitional structure is established for a schematic $sdg$ hamiltonian which is intermediate between four dynamical symmetries of U(15), namely the spherical ${\rm U}(5)\otimes{\rm U}(9)$, the (prolate and oblate) deformed ${\rm SU}_\pm(3)$ and the $\gamma_2$-soft SO(15) limits. For realistic choices of the hamiltonian parameters the resulting phase diagram has properties close to what is obtained in the $sd$ version of the model and, in particular, no transition towards a stable triaxial shape is found.Comment: 19 pages, 5 figures, submitted to J. Phys.

Correlating radii and electric monopole transitions of atomic nuclei

A systematic analysis of the spherical-to-deformed shape phase transition in even-even rare-earth nuclei from $_{58}$Ce to $_{74}$W is carried out in the framework of the interacting boson model. These results are then used to calculate nuclear radii and electric monopole (E0) transitions with the same effective operator. The influence of the hexadecapole degree of freedom ($g$ boson) on the correlation between radii and E0 transitions thus established, is discussed.Comment: 4 pages, 3 figures, accepted for publication in Phys. Rev. Letter

Discovery of the thallium, lead, bismuth, and polonium isotopes

Currently, forty-two thallium, forty-two lead, forty-one bismuth, and forty-two polonium isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.Comment: to be published in At. Data Nucl. Data Table

Application du modèle en couches à l'étude des états intrus de parité négative des noyaux sd moyennant la nouvelle interaction PSDPF

La structure nucléaire des noyaux de la couche sd a été bien étudiée expérimentalement à proximité de la ligne de stabilité et, plus récemment, l'intérêt a porté sur les noyaux riches en neutrons. Les états normaux de parité positive sont bien décrits à l'aide de l'interaction USD dans l'espace sd (espace 0 ) avec un coeur de 16O. Cette interaction a été récemment réajustée et les nouveaux Hamiltonians obtenus sont appelés USDA et USDB. Les spectres expérimentaux montrent l'existence, en plus des états normaux, d un ensemble d'états de parité négative nommé "états intrus", résultant de l'excitation d'un nucléon de la couche p vers sd, pour les noyaux près de 16O ou de la couche sd vers pf pour les noyaux proches de 40Ca. Au milieu de la couche sd il y a compétition entre les deux types d'excitations pour les intrus. Avant notre travail, il n existait pas de description unifiée des états de parité négative à travers toute la couche sd. Pour étudier les états intrus, nous avons élargi l'espace modèle de l'espace sd (coeur 16O) à l espace complet p-sd-pf (coeur 4He) appelé espace 1 . Cela nécessite la construction d'une nouvelle interaction compatible avec cette extension de l'espace modèle. Cette procédure est maintenant possible en raison de l'augmentation de la puissance de calcul. Nous avons ainsi mis au point pour la première fois une interaction 1 appelée PSDPF, qui comporte cinq parties distinctes: p, sd et pf en plus des termes croisés p-sd et sd-pf. Les trois interactions fixes pour p, sd et pf sont respectivement: CK, USDB et SDPF-NR, cette dernière contient également les éléments de matrice à deux corps sd-pf, l interaction p-sd est considérée comme étant l interaction PSDT. Nous avons modifié les contributions p-sd et sdpf pour reproduire l'évolution en énergie des états intrus de différents spins à travers toute la couche sd. Cette nouvelle interaction a été utilisée pour calculer les états intrus dans les noyaux sd avec N = Z et Z + 1. Les spectres en énergie des états + et dans tous les noyaux sd ont aussi été calculés. La comparaison expérience théorie montre un très bon accord et donne ainsi du crédit à notre nouvelle interaction proposée pour décrire les états intrus de la couche sd. Des états de parité ont été attribués certains niveaux de Jp inconnus. Les probabilités de transitions électromagnétiques réduites E2 et E3 des premiers états de parité + et , avec Jp = 2+ et 3 dans les noyaux pair pairs, ont été également calculées et les charges effectives pour les transitions E3 ont été étudiées pour la première fois.The nuclear structure of the sd shell nuclei has been well studied experimentally near the stability line and more recently the interest has been focused on the neutron rich nuclei. The normal positive parity states are well described using the USD interaction in the 0 sd shell space (0 space) with an 16O core. This interaction has recently been updated and the obtained new Hamiltonians are called USDA and USDB. The experimental spectra show the existence, in addition of the normal states, of a set of negative parity states named intruder states , resulting from the excitation of one nucleon from the p to the sd shell for nuclei near 16O or from the sd to the fp shell for nuclei close to 40Ca. In the middle of the sd shell there is a competition between the two types of excitations for the intruders. Before our work, no unified description of the negative parity states throughout the complete sd shell existed. To study the intruder states we must enlarge the model space from the sd space (16O core) to the full p sd pf space (4He core) which is named 1 space. This requires the construction of a new interaction compatible with this extended shell model space. Such a procedure is now possible due to the today increased computational power. We have thus developed for the first time a 1 interaction called PSDPF, which has five distinctive parts: p, sd and pf shells and cross p sd and sd pf shells. The fixed three interactions for the p, sd and pf shells are respectively: CK, USDB and SDPF NR, the latter one contains also the sd pf two body matrix elements, the p sd interaction is taken to be the PSDT interaction. We have modified the cross p sd and sd pf shells contributions to reproduce the energy evolution of the intruder states of different spins throughout the complete sd shell. This new interaction was used to calculate intruder states in the sd nuclei with N = Z and Z + 1. The energy spectra of + and states in all sd nuclei were also calculated. The comparison experience theory shows a very good agreement and gives thus credit to our new proposed interaction to describe the intruder states of the sd shell. States of parity were attributed to some unknown Jp levels. The reduced electromagnetic transitions probabilities E2 and E3 of the first states of parity + and , with Jp = 2+ and 3 in even even nuclei, were also calculated and the effective charges for the E3 transitions were studied for the first time.STRASBOURG-Sc. et Techniques (674822102) / SudocSTRASBOURG-Bib.Central Recherche (674822133) / SudocSudocFranceF