Strangeness Enhancement and Canonical Suppression

We demonstrate the essential role of canonical suppression in strangeness enhancement. The pattern of enhancement of strange and multistrange baryons observed by the WA97 collaboration can be understood on this basis. Besides, it is shown that in canonical approach strangeness enhancement is a decreasing function of collision energy. It is the largest at $\sqrt{s}=8.7$ GeV where the enhancement of $\Omega,\Xi$ and $\Lambda$ is of the order of 100, 20 and 3 respectively.We demonstrate the essential role of canonical suppression in strangeness enhancement. The pattern of enhancement of strange and multistrange baryons observed by the WA97 collaboration can be understood on this basis. Besides, it is shown that in canonical approach strangeness enhancement is a decreasing function of collision energy. It is the largest at $\sqrt{s}=8.7$ GeV where the enhancement of $\Omega,\Xi$ and $\Lambda$ is of the order of 100, 20 and 3 respectively.We demonstrate the essential role of canonical suppression in strangeness enhancement. The pattern of enhancement of strange and multistrange baryons observed by the WA97 collaboration can be understood on this basis. Besides, it is shown that in canonical approach strangeness enhancement is a decreasing function of collision energy. It is the largest at $\sqrt{s}=8.7$ GeV where the enhancement of $\Omega,\Xi$ and $\Lambda$ is of the order of 100, 20 and 3 respectively

Formation and Evolution of the Quark-Gluon Plasma

Imposing an equilibrium between the thermal pressure of deconfined quarks and gluons and the dynamical compression pressure exercised by in-flowing nuclear matter, we study the initial thermal conditions reached in a quark-gluon plasma fireball formed in a relativistic heavy ion collision. We show that entropy is produced primarily in the pre-equilibrium stage of the reaction. We test our approach, comparing our results with the S-W/Pb collision results at 200 GeV A and find a surprising degree of agreement assuming about 50% stopping. We apply our method to a determination of the conditions in collisions of Au-Au at 11 GeV A and Pb-Pb at 157 GeV A, assuming full stopping of momentum, energy and baryon number. Our detailed results directly determine the spectral shape and abundance of (strange) hadrons and electromagnetic probes (photons, dileptons) produced in the collision, and we explore specific experimental consequences.Comment: Replaced for bad printing on US paper. 16 pages, LaTeX, 3 postscript figure

Strange anti-baryons - QGP versus HG

We study quark-gluon plasma (QGP) and hadronic gas (HG) models of the central fireball presumed to be the source of abundantly produced strange (anti-)baryons in S -> W collisions at 200 GeV A. We consider how multi-strange (anti-)baryon multiplicities depend on strangeness conservation and compare the HG and QGP fireball scenarios. We argue that the total particle multiplicity emerging from the central rapidity region as well as the variation of production rates with changes in the beam energy allows to distinguish between the two reaction scenarios.Comment: 10 pages, LaTeX, 4 postscript figures, Published in Dallas HEP (1992) 983-99

Hadronic Signatures of Deconfinement in relativistic nuclear collisions

We describe the remarkable accomplishments of the current heavy ion Pb--Pb collision experiments involving strange particle production, carried out at 158A GeV at CERN--SPS. These experimental results, together with the earlier 200A GeV S-induced reactions, imply that, at central rapidity, a novel mechanism of strangeness production arises, accompanied by excess entropy formation. We argue that: These results are consistent with the formation of a space-time localized, highly excited, dense state of matter; The freeze-out properties of strange hadrons are suggestive of the formation of a color-deconfined, thermally and nearly chemically equilibrated phase, which provides at present the only comprehensive framework to describe all experimental data; The matter fireball is undergoing a transverse expansion with nearly the velocity of sound of relativistic matter; longitudinal expansion is not in the scaling regime. We present a first analysis of the recent Pb-Pb results and discuss several alternative reaction scenarios. We evaluate quantitatively strangeness production in the deconfined quark-gluon phase and obtain yields in agreement with the experimental observations made in 200A GeV S--W and 158A GeV Pb-Pb interactions. We also present a qualitative discussion of J/Psi results consistent with our understanding of strange particle results.Comment: 26 pages, LaTeX, 9 postscript figures, Submitted to Acta Physica Polonica

ANFIS control of a shunt active filter based with a five-level NPC inverter to improve power quality

© 2021 The Author(s). This is an open access article under the CC BY-SA license (https://creativecommons.org/licenses/by-sa/4.0/).This paper addresses the problem of power quality, and the degradation of the current waveform in the distribution network which results directly from the proliferation of the nonlinear loads. We propose to use a five-level Neutral Point Clamped (NPC) inverter topology for the implementation of the shunt active filter (SAPF). The aim of the SAPF is to inject harmonic currents in phase opposition at the connection point. The identification of harmonics is based on the pq method. A neuro-fuzzy controller based on ANFIS (Adaptive Neuro Fuzzy Inference System) is designed for the SAPF. The simulation study is carried out using MATLAB/Simulink and the results show a significant improvement in the quality of energy and a reduction in Total Harmonic Distortion (THD) in accordance with IEC standard, IEEE-519, IEC 61000, EN 50160.Peer reviewe

Canonical Description of Strangeness Enhancement from p-A to Pb-Pb Collisions

We consider the production of strange particles in Pb-Pb and p-A collisions at the SPS energy reported by the WA97 experiment. We show that the observed enhancement of strange baryon and antibaryon yields in Pb-Pb collisions relative to p-Be and p-Pb can be explained in terms of the statistical model formulated in canonical ensemble with respect to strangeness conservation. The importance and the role of strangeness under saturation is also discussed.Comment: 8 pages, 3 figure

Hot hadronic matter and strange anti-baryons

We demonstrate that both quark-gluon plasma (QGP) and hadronic gas (HG) models of the central fireball created in S -> W collisions at 200 GeV A are possible sources of the recently observed strange (anti-) baryons. From the theoretical point of view, the HG interpretation we attempt remains more obscure because of the high fireball temperature required. The thermal properties of the fireball as determined by the particle ratios, are natural for the QGP state. We show that the total particle multiplicity emerging from the central rapidity region allows to distinguish between the two scenarios.Comment: 10 pages, LaTeX, 1 postscript figure

Strange Antibaryons from QGP

We study as function of the collision energy and stopping the thermal conditions reached in a quark-gluon plasma fireball formed in a relativistic heavy ion collision. We explore strange particle yields for the current round of Pb-Pb and Au-Au experiments.Comment: 4 pages, LaTeX, 3 postscript figures, Presented at Quark Matter 1995, Montere

EFFET DE LA VIBRATION TRANSVERSE SOUS CHARGE THERMIQUE DANS L’ETUDE DES NANOMATERIAUX

Le comportement mécanique de (CNTs) a été exploré par des expériences: simulations de la dynamique moléculaire (MD). et la mécanique élastique continue.Actuellement il y a quelques difficultés rencontrées dans la conduite des expériences sur les (CNTs) en raison des dimensions de nanomètre. On rapporte dans la littérature que la mécanique de milieu continu peut servir de méthode alternative pour étudier CNTs au lieu de MD et expériences. Ces dernières années, beaucoup de modèles du milieu élastique continu ont été développés tel le modèle de poutre, le modèle cylindrique de coque et les modèles de l'espace tridimensionnel (ferme) pour étudier la flexion, ainsi que les comportements en vibration des (CNTs). En cet communication, basé sur la théorie nonlocal d'élasticité , le modèle de poutre est développé pour l’étude de la propagation des ondes dans les nanotubes de carbone (DWNTs) inclus dans un milieu élastique (matrice de polymère), qui explique l'effet thermique en formulation. Les effets du milieu élastique et les forces élastiques de Van der Waals entre les tubes intérieurs et externes sont pris en compte. Dans des calculs d'exemple, les propriétés mécaniques des nanotubes de carbone et de la matrice de polymère, respectivement, sont prises comme fonctions de changement de température. Des expressions explicites sont dérivées pour des fréquences normales et des rapports d'amplitude associés de l'intérieur aux tubes externes pour le cas de DWNTs simplement soutenu, et les influences du changement de température et de l’effet de petit échelle de longueur sur eux sont étudiées. L’équation du mouvement de vibration transverse est donnée par le modèle de poutre d’Euler. Dans des calculs d'exemple, les propriétés mécaniques des nanotubes de carbone et de la matrice de polymère, respectivement, sont traitées comme fonctions de température. Des courbes illustrent les variations de fréquences sont présentés