2. Articole

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Author: search.filters.author.Paladi, FlorentinEnd date: 2019

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    CINETICA TRANZIŢIILOR DE FAZĂ DIRIJATĂ CU PARAMETRII DE CONTROL
    (CEP USM, 2013-09-26) Gubceac, Ghenadii; Șveț, Aliona; Paladi, Florentin
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    SIMULAREA SISTEMELOR FIZICE COMPLEXE ÎN BAZA MODELELOR ABM
    (CEP USM, 2013-09-26) Guţu, Roman; Căpăţână, Gheorghe; Paladi, Florentin
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    ȘCOALA DOCTORALĂ – ELEMENT-CHEIE ÎN ORGANIZAREA ȘTIINŢEI MODERNE
    (Academia de Ştiinţe a Moldovei, 2011) Paladi, Florentin
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    VIBRONIC INTERACTION IN TETRAMERIC CLUSTERS WITH TWO-ELECTRON TRANSFER: MAGNETIC PROPERTIES
    (American Scientific Publishers, 2009) Boldyrev, S. I.; Paladi, Florentin
    The influence of vibronic interactions on the magnetic properties of the tetrameric square-planar mixed-valence d0-d0-d1-d1 cluster with two-electron transfer is investigated. The dynamic vibronic problem has been solved taking into account the Heisenberg and double exchange. It was shown that the double exchange and vibronic coupling leads to two types of pseudo-Jahn-Teller problems: (1An1+1Ad1+1B1+1B2+1E) ⊗ (b2+e) and (3B2+3A2+3En+3Ed) ⊗ (b2+e). The dependence of magnetic properties on vibronic interaction was studied. All peculiarities of magnetic moments take place in the case of intermediate vibronic coupling. The results show that the vibronic interaction essentially affects the magnetic properties of the system, such as for the tetrameric tetrahedral cluster with one extra electron.
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    CONTRIBUŢII LA TEORIA RELAXĂRII STĂRILOR METASTABILE ÎN LICHIDE SUBRĂCITE ŞI STICLE
    (CEP USM, 2009) Paladi, Florentin
    The theory of phase transitions in supercooled liquids and glasses based on the cluster concept, and taken into accountthe recent discovery of the generation and extinction of crystal nuclei in supercooled liquids at very low temperatures,has been developed. In particular, the generation and extinction of nuclei was found at low temperatures in supercooled liquids of o-benzylphenol, salol and 2,2’-dihydroxybenzophenone, and was brought a new concept of irreversible structural relaxation in supercooled liquids and glasses. The practical value of this research is determined by the importance of understanding the connection between physical properties, microscopic structure of the substance and macroscopicconditions of materials processing, which is vital to produce new materials with advanced technological properties. However, the results allow to formulate the essence of a new research development in the study of complex cluster systems bymethods of statistical physics, numerical calculation and computer modeling.
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    EQUILIBRIUM STATES OF THERMODYNAMIC SYSTEMS IN A SMALL VICINITY OF THE EQUILIBRIUM VALUES OF PARAMETERS: BIFURCATION, STABILITY AND SENSITIVITY ANALYSES
    (Elsevier, 2019) Barsuk, Alexandr A.; Paladi, Florentin
    The dynamic behavior of thermodynamic systems described by a single order parameter and several control parameters is studied in a small neighborhood of ordinary and bifurcation equilibrium values of the system parameters. Using the general methods of investigating the branching (bifurcations) of solutions for nonlinear equations, we performed an exhaustive analysis of the order parameter dependences on the control parameters in a small vicinity of the equilibrium values of parameters, including the stability analysis of the equilibrium states, and the asymptotic behavior of the order parameter dependences on the control parameters (bifurcation diagrams). Relations between the infinitesimal quantities of order parameters and the control of dynamical systems are given, and the formulae for the order parameter sensitivity are presented depending on the variations in the control parameters. In addition, we carried out specific calculations with respect to the thermodynamic systems described by one order parameter and several control parameters in the Landau-type kinetic potential. The peculiarities of the anomalous generation and extinction phenomenon of crystal nuclei at very low temperatures in non-equilibrium supercooled liquids are also presented.
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    MEASURING HETEROGENEITY IN STOCHASTIC MODELS
    (CEP USM, 2007) Paladi, Florentin; Doţenco, Denis; Gamurari, Visarion
    Un model teoretic care descrie interacţiunea într-o populaţie eterogenă de agenţi a fost dezvoltat şi analizat în cadrul discuţiilor recente despre decalajul dintre modelele computaţionale ABM şi modelele analitice stocastice [1]. A fost demonstrat că acest model probabilistic descrie exact rezultatul previzibil al simulărilor computaţionale care trebuie săfie suficient de lungi pentru a echilibra starea sistemului. Acest rezultat depinde de distribuţia stărilor în sistem şi este definit atât cu ajutorul valorii medii, cât şi al coeficientului de variaţie pentru payoff. Ultima mărime este independentă de scara valorilor şi denotă cât de inegale sunt distribuţiile în sistem, iar, prin urmare, şi nivelul de eterogenitate al modelului nostru stocastic. Rezultatele obţinute sunt raportate pentru valoarea medie şi coeficientul de variaţie pentru payoff, calculate pentru modelul prezentat în [1]. În lucrare nu este specificată o formă funcţională particulară pentru a evita alegeri arbitrare, în cazul unui sistem format din patruzeci agenţi cu 1221759 distribuţii posibile în şase clustere după trei stări diferite.
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    THERMAL AND DIELECTRIC STUDIES OF 2,2’-DIHYDROXYBENZOPHENONE
    (Akadémiai Kiadó, 2005) Tomitaka, S.; Mizukami, M.; Paladi, Florentin; Oguni, M.
    Thermal and dielectric properties of 2,2’-dihydroxybenzophenone were studied in relation with the potential progress of crystal nucleation and growth below the ordinary glass transition temperature, Tgα. Differential scanning calorimetry was carried out in a range 100-350 K. The α glass transition was found to occur at Tgα=239 K. Crystallization and fusion were observed to take place when the sample was cooled down to 103 K, but not observed when cooled to 203 K. Crystal nucleation was interpreted as having happened during annealing for a short time at 103 K which is much below the Tgα. Heat capacities were measured in a range 7-350 K by an intermittent heating method with an adiabatic calorimeter. The temperature, enthalpy and entropy of fusion were determined to be 334.46 K, 20.07 kJ mol-1 and 60.01 J K-1mol-1, respectively. Crystal growth was found to proceed even at 220 K below the Tgα, but no glass transition was detected below 220 K. Dielectric losses were measured in a temperature range of 100-250 K and a frequency range of 30Hz-10 kHz. β-Relaxation process was found dielectrically with the activation energy of 22.6 kJ mol-1, and the corresponding glass transition was expected to occur at 76.9 K. It is discussed, based on the “structurally ordered clusters aggregation” model for supercooled liquids and glasses, that the β process is potentially attributed to the crystal nucleation progressing at 103 K.
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    PROIECTAREA FORMELOR PENTRU INTRODUCEREA DOCUMENTELOR ÎN SISTEMUL INFORMATIC „E-ADMITEREA”LA USM
    (CEP USM, 2016) Eni, Natalia; Ciobu, Victor; Paladi, Florentin