Volume 66, Number 78, 2021
Theoretical, Mathematical, and Computational Physics
Quantum Entanglement and Quantum Steering of Two Bosonic Modes in Noisy Environments Marina Cuzminschi, Aurelian Isar Romanian Journal of Physics 66,
112 (2021)
We describe the behaviour of quantum entanglement and quantum steering of the Gaussian states of two bosonic modes, each one placed in its own noisy environment. The dynamics of the system is studied in the framework of the theory of open systems, based on completely positive quantum dynamical semigroups, using the KossakowskiLindblad master equation. The evolution of the quantum entanglement and quantum steering is described in terms of the covariance matrix formalism, by providing their dependence on the parameters characterising the system (squeezing between the modes, frequencies of the modes and their average photon numbers) and on the parameters of the noisy channels (temperatures, squeezing and phase of the environments). In particular, we make a comparison between quantum steering and quantum entanglement, and illustrate that entanglement is a necessary condition for the existence of the steering in the system.
Static Spherically Symmetric SpaceTime: Some Remarks Bijan Saha Romanian Journal of Physics 66,
113 (2021)
Within the scope of a spherically symmetric spacetime we study the role of different types of matter in the formation of different configurations with spherical symmetries. Here we have considered matter with barotropic equation of state, scalar field, electromagnetic field and an interacting system of scalar and electromagnetic field as the source. Corresponding field equations are solved exploiting harmonic coordinates. An easy to handle method is proposed which allows one to have an idea about the possible behavior of the metric functions once the components of the EMT of the source field is known.
Explicit Rational Solutions for TimeSpace Fractional Nonlinear Equation Describing the Propagation of Bidirectional Waves in LowPass Electrical Lines Fares Bekhouche, Marwan Alquran, Iryna Komashynska Romanian Journal of Physics 66,
114 (2021)
In this paper, the generalized Unified method is presented for finding explicit solutions for a nonlinear fractional equation. The proposed method is compared with all versions of (G′/G)expansion scheme and the connection between them is established. As for applications, we implement the Unified method to seek travelingwaves solutions to the nonlinear fractional model governing the propagation of bidirectional waves in lowpass electrical transmission lines. The obtained results confirmed the effectiveness of this method for solving nonlinear fractional applications and models.
An InversionFree Method for Computation of the Square Roots of Real Matrices Hooman Fatoorehchi, Randolph Rach Romanian Journal of Physics 66,
115 (2021)
An efficient method for computation of the square roots of real matrices is developed. Our method is based on the Adomian decomposition method and obviates the use of any matrix inversion as a significant advantage. Additionally, our method does not require any matrix factorization and only instead relies on the simple operations of addition and multiplication. We demonstrate the rapid convergence of our new approach in several numerical examples. Also, CPUtime analyses incorporating random matrices of large dimensions (n=10,000) shows the superiority of the proposed method over the previous Newtontype algorithms.
Analytical Solutions of the OneDimensional Schrödinger Equation with PositionDependent Mass Tiberiu Harko, Man Kwong Mak Romanian Journal of Physics 66,
116 (2021)
The study of the Schrödinger equation with the positiondependent effective mass has attracted a lot of attention, due to its applications in many fields of physics, including the properties of the semiconductors, semiconductor heterostructures, graded alloys, quantum liquids, Helium3 clusters, quantum wells, wires and dots etc. In the present work we obtain several classes of solutions of the onedimensional Schrödinger equation with positiondependent particle mass. As a first step the single particle Schrödinger equation with positiondependent mass is transformed into an equivalent Riccati type equation. By considering some integrability cases of the Riccati equation, seven classes of exact analytical solutions of the Schrödinger equation are obtained, with the particle mass function and the external potential satisfying some consistency conditions.
On the Dynamics of the Lyophobic Colloids M. Apostol, L. C. Cune Romanian Journal of Physics 66,
117 (2021)
According to the standard theory, a spatiallyextended (diffuse) double layer is assumed to occur in charged colloids (suspensions), leading to repulsive forces that might compensate, at relevant distances, the attractive molecular forces. It is shown in this paper that a surface double layer of atomic dimensions is present at the surface of neutral condensed bodies, which originates in the cohesion of the condensed matter. This surface double layer generates exponentially small forces, with a (negative) exponent of the order of the ratio of the distance to the mean distance between the atomic constituents. Such colloids may be termed neutral colloids. The forces generated by the surface double layer are too small to compensate the attractive molecular forces and to ensure the equilibrium at relevant distances. The surface doublelayer forces are calculated here explicitly for halfspaces and spheres, both in vacuum and in a material medium. The examination of the dynamics of the neutral colloids leads to the conclusion that, very likely, a (quasi) equilibrium may be attained for mean separation distances between the colloidal particles much larger than their plasma wavelength, where the molecular forces become, practically, ineffective. For charged colloids (charged, for instance, by electrolyte dissociation) the electric interaction of the ions and colloidal particles requires the application of the cohesion theory of electricallyinteracting particles, which may lead to particle stabilization, or even aggregation. The equilibrium mean separation distance is estimated here within this theory and the HardySchulzeOstwald law is obtained.
Atomic, Molecular, and Optical Physics
Spectrophotometric Techniques Used in the Prescreening Stage of Radiocarbon Dating Process M. M. Cozac (Manea), C. A. Simion, I. M. Stanciu, B. M. Stefan, D. G. Pacesila, S. Vasilca Romanian Journal of Physics 66,
202 (2021)
The characterization of samples by spectrophotometric methods, before radiocarbon dating using 1 MV HVEE Tandetron^{TM} accelerator, may offer additional information in establishing the age of museum materials being contaminated with preserving agents, and of archaeological materials contaminated with exogenous carbon in the postdepositional stage. Macromolecular structures can be determined using FTIR/FTRaman techniques. Old samples against modern ones may be compared, highlighting the impact of spectrophotometric methods results on radiocarbon dating estimates using AMS. The review of the possibilities of multidisciplinary analysis was done using some examples. The femtogram level reached in AMS measurements represents a strong reason to optimize the FTIR/FTRaman analyses, in a future research.
Nuclear Physics
Extensive Study of the Positive and Negative Parity Wobbling States for an OddMass Triaxial Nucleus I: Energy Spectrum R. Poenaru, A. A. Raduta Romanian Journal of Physics 66,
308 (2021)
A new interpretation of the wobbling structure in ^{163}Lu is developed. Four wobbling bands are experimentally known in this isotope, where three are wobbling phonon excitations TSD_{2,3,4}, and the ground state band, which is TSD_{1}. In this work, a particletriaxial rotor coupling is considered in a product space of singleparticle and collective core states. The singleparticle states describe a j=i_{13/2} proton, while the core states characterize the triaxial rotor and are either of positive parity, when the bands TSD_{1,2,3} are concerned or of negative parity for the TSD_{4} band. There are five free parameters, three moments of inertia, the strength of the particlecore interaction, and the $\gamma$ deformation. A very good description of all 62 experimental states is obtained, with a mean square error of about 80 keV. The newly obtained features evidenced in the present work enrich the knowledge about the wobbling properties of ^{163}Lu.
Condensed and Soft Matter Physics
Sulfur and Selenium Coincidence Doppler Broadening Signature Curves R. DomínguezReyes, A. RodríguezLópez Romanian Journal of Physics 66,
608 (2021)
High purity Sulfur and Selenium annealed samples have been studied by Coincidence Doppler Broadening spectroscopy. Their ratio curves with respect Aluminum, missing from literature, have been obtained. The position of the first maximum of each ratio curve distribution has been added to previously obtained data in order to analyze the tendencies that elements show as a function of atomic number Z. The obtained curves, signatures corresponding to pure elements, can be used as reference background knowledge to improve the understanding of previous and future Positron Annihilation Spectroscopy studies involving complex materials that contain Sulfur or Selenium as components.
Injection Photodiode Based on an Al–pSi–nZn_{85}Mg_{15}O–nZn_{65}Mg_{35}O–Ag Structure V. Morari, E. V. Rusu, V. Postolache, V. V. Ursaki, I. M. Tiginyanu, A. V.Rogachev, A. V. Semchenko Romanian Journal of Physics 66,
609 (2021)
A series of Zn_{1−x}Mg_{x}O thin films with the composition range x=0.00–0.60 has been prepared by aerosol spray pyrolysis deposition on Si or quartz substrates. The morphology, composition, crystals structure, and optical properties of the prepared films were studied by scanning electron microscopy (SEM), energy dispersive Xray analysis (EDX), Xray diffraction (XRD), and optical spectroscopy. It was found that the morphology of films is not significantly different for films with different compositions, while the compositions correspond to those preset in the spray solutions, and all the films are of wurtzite structure up to the x value of 0.6. The optical bandgap of films was determined from the absorption spectra, and the dependence of the bandgap on the Mg content was compared with previously reported data. A photodetector with a design composed of two Zn_{1−x}Mg_{x}O layers with different compositions was developed and characterized. It was found that the photodetector operates as injection photodiode with improved parameters as compared to a previous device with a single ZnMgO film prepared by spin coating.
Environmental and Earth Physics
Statistical Analysis of Morphological Parameters of Microbial Aggregates in the Activated Sludge from a Wastewater Treatment Plant for Improving Its Performances F. Aonofriesei, A. Bărbulescu, C.S. Dumitriu Romanian Journal of Physics 66,
809 (2021)
The morphological parameters of microbial aggregates are important for proper functioning of the activated sludge in wastewater treatment plants. Maintaining normal morphological and functional properties of activated sludge aggregates is necesary for this aim. Therefore, we carried out analysis of microscopic images of activated sludge under different nutritional conditions. Laboratory experiments revealed significant changes in size and shape of microbial aggregates during periods of deficiency in organic nutrients. Lack of nutrients has lead to the quantitative imbalance between filamentous bacteria and flocforming bacteria. The longer time the activated sludge was devoid of organic soluble matter, the greater were the alterations of perimeter and area of microbial aggregates. Thus, minimal amounts of soluble organics are required for a normal functioning of activated sludge aggregates.
Effects of soft soils on seismic ground motion in the Centre and Western Romania A. Coman, E. F. Manea, M. Radulian Romanian Journal of Physics 66,
810 (2021)
In this study, we investigate how the recorded seismic ground motion is influenced by the local/regional geological structure for sites located in the centre and western Romania. The HorizontaltoVertical Spectral Ratio (HVSR) technique was applied for 3.1–5.7 Mw events, to extract characteristics of the seismic wavefield and to evaluate the predominant frequency of resonance (f_{pred}). The amplitudes of the HVSR curves computed for the events located along the Carpathian arc are strongly reduced by backarc attenuation while no effects were observed for the others. The f_{pred} matches relatively well the fundamental frequency at sites deployed on a superficial layer of sediments while a migration to higher frequencies were observed for complex sedimentary structures.
Applied and Interdisciplinary Physics
Photophysical Properties of Au and Au@SiO_{2} Nanoparticledye Complexes in Mesoporous Silica Matrices for Theranostics Purposes K. Matveeva, A. Zyubin, A. Ognedyuk, E. Demishkevich, I. Kon, I. Samusev Romanian Journal of Physics 66,
907 (2021)
This paper summarizes a detailed study of plasmonenhanced/quenched fluorescence of gold nanoparticles (NPs) and rhodamine 6G (R6G) dye complexes. Spectral fluorescent properties of the complexes with/without SiO_{2} shell have been investigated. FDTD modeling of optical parameters has been carried out. Mesoporous silica nanoparticles (MSNs) have been added to the system in the case of Au@SiO_{2} NPs. The influence of SiO_{2} shells and MSNs on the photophysical properties of the complexes studied has been demonstrated.
A Novel Stealth Method Realized by the Structure of MultiLayered Film Laid on Perfect Electric Conductor at Microwave Frequency L. Zhao, N. Wang, T.T. Zhu Romanian Journal of Physics 66,
908 (2021)
In the paper, a novel transparent structure has been proposed based on epsilonnearzero (ENZ) medium laid on perfect electric conductor (PEC). As an example, the effective ENZ medium has been realized by the Cu/YIG/SiO_{2} multilayered film structures at microwave frequency. Then, the effective ENZ medium has been laid on PEC for constructing EM transparent structure. The results of calculation and simulation show that the EM transmittance of proposed structure is close to 100%, which reduces greatly the RCS of PEC. This work provides a novel concept of design for the development of new stealth materials.
