Volume 65, Number 910, 2020
Theoretical, Mathematical, and Computational Physics
Geometric Quantum Discord of Two Bosonic Modes in a Squeezed Thermal Bath Alina Dobre, Aurelian Isar Romanian Journal of Physics 65,
120 (2020)
We describe the time evolution of the geometric quantum discord for a system composed of two bosonic modes in interaction with a squeezed thermal bath. We work in the framework of the theory of open quantum systems, based on completely positive dynamical semigroups, using the geometric quantification of the total nonclassical correlations for Gaussian states. We use the Hellinger measure for the geometric quantum discord, taking initial squeezed thermal states, and we show that discord decays asymptotically in time.
Restoration of the Reduced TimeReversal Symmetry: Six Forms of Metamatter Ion I. Geru Romanian Journal of Physics 65,
121 (2020)
There are described six incomplete timereversal operators, under the action of which only one or two angular momentum projection operators change the sign. The incomplete time reversal operators, along with the conventional timereversal one, are part of discrete generalized symmetry groups of 8th and 16th orders. These groups are Abelian for integer values of the angular momentum $J$, whereas for halfinteger $J$ they are nonAbelian. When the $\mathbf{T}$symmetry is reduced to one of six incomplete time reversal symmetries, it can be restored involving six types of metaparticles. The conclusion about existence of metaparticles follows from the grouptheoretical analysis. Because there are six types of metaparticles corresponding to each particle in the Universe, it means that there are six possible metauniverses besides the Universe and the Antiuniverse.
Numerical Analysis of Nanofluid Cooling Efficiency of Hot Multishaped Cylinder in Vertical Porous Channel Ridha Djebali Romanian Journal of Physics 65,
122 (2020)
In this study a mesoscopic numerical analysis of mixed convection and nanofluid cooling efficiency is conducted for a heat exchanger. The later is composed of porous vertical channel crossed by shaped cylinder designing a solar concentrator. Various shape forms of the concentrator are tested and the effect of the fluid and the porous medium parameters are analyzed. The horizontal elongated elliptical shape was found to be the most efficient. Results are mainly presented using response surfaces of the Nusselt number as a function of influencing factors. The conducted optimization for the use of porous matrix inside the channel as well as the determination of optimal factors values will augment the heat transfer between the heat exchanger and the flowing nanofluid. Correlations are given for broad ranges of problem factors.
Pulse Amplification and Damping in Lossy Nonlinear Transmission Lines A. Nkongho Achere, Alain M. Dikande, B. Z. Essimbi Romanian Journal of Physics 65,
123 (2020)
A model of nonlinear electrical transmission line, which mimics a ladder circuit periodically loaded with Schottky varactors having a resistance in their shunt branches and connected to voltageterminal modules, is considered from both analytical and numerical standpoints. Analytical treatment of the problem, following the multiplescale expansion and the adiabatic perturbation theory involving a perturbed Kortewegde Vries equation, establishes that pulseshaped electrical solitons can propagate in the nonlinear transmission line while experiencing amplification due to the voltage terminals, but also a damping caused by the resistance. Direct numerical simulations of the line equations provide evidence of a dominant damping effect due to the resistance, over pulse amplification due to the voltage terminal. Numerical simulations bring out a novel process namely a possible disintegration of the single pulse into two or more pulses upon propagation in the nonlinear transmission line, resulting from the competition between amplification and damping.
Nuclear Physics
The Influence of the Form of Nucleon Form Factors on the Calculation of Tensor Deuteron Polarizations $t_{2i}$ V.I. Zhaba Romanian Journal of Physics 65,
306 (2020)
The main features of the estimation of the nucleon form factors are analysed. Tensor deuteron polarizations $t_{2i}(p)$ were obtained for the nucleonnucleon potential Reid93 when using different theoretical models or approximations of experimental data for nucleon form factors. Calculated set of tensor deuteron polarizations $t_{2i}$ was compared with the experimental data for the leading modern collaborations and reviews. The best model for describing theoretical values in comparison with the experimental data is the choice of nucleon form factors by the modiﬁed dipole fit 2 or the relativistic harmonic oscillator model. The found positions of the zero for tensor polarizations $t_{20}$ and $t_{21}$ were compared with the corresponding theoretical values for other potentials and with experimental data. Experimental studies in certain momentum range are insufficient and therefore require further refinements or new measurements. Perspectives for further use of the obtained values are discussed.
Lasers, Plasmas, and Beam Physics
Intensifying of Selective Nitrogen Plasma Species Using Rectangular Hollow Cathode in 2 MHz RFDC Plasma J.M. Windajanti, D.J.D.H. Santjojo, M.A. Pamungkas, A. Abdurrouf Romanian Journal of Physics 65,
502 (2020)
The nitrogen glow discharge occurring inside a rectangular hollow cathode cavity has been investigated. The RF plasma ignited at a frequency about 2 MHz with a voltage of 150 V and then the DC bias of –500 V applied independently to attract the positive ions to the cathode plate. The hollow cathode was used to enhance the intensity of plasma as well as to control the plasma species. The emission spectra of the discharge were analyzed using optical emission spectroscopy at a wavelength range of 200 to 900 nm. The results show the high intensity lines of N$_2^+$ according to the First Negative System with the strongest peak at 391.4 nm of the (0,0) transition of $B^2 \Sigma_{u}^{+} \to X^2 \Sigma_{g}^{+}$ and the lines of N$_2^*$ correspond to the Second Positive System with the strongest peak at 337.1 nm of the (0,0) transition of $C^3 \Pi_u \to B^3 \Pi_g$. In this system, the maximum intensity of N$_2$ and N$_2^+$ species increases by 67.0% and 50.3%, respectively. The hollow gap size affects the increase of plasma species type. The intensity of N$_2^+$ species will increase higher in the use of a 1.5 cm rectangular hollow cathode, while the N$_2$ species will be more dominant in a gap size of 1.0 cm.
Condensed and Soft Matter Physics
Thermodynamic and Structural Properties of HCP Metals and Binary Alloys G. S. Agunbiade, F. MatthewOjelabi, T. H. Akande , A. I. Ogundare, O. O. Awe Romanian Journal of Physics 65,
611 (2020)
The modified embeddedatom method, MEAM for hcp Mg & Ti metals and alloys have been designed. The monovacancy formation, migration and activation energies in the hcp out plane were computed and reasonably agree with available data from experiments. The divacancy formation and binding energies of the first nearestneighbour were reported. The computed value for the binding energy is positive, an indication of stability. The five independent elastic constants in hcp metals were determined and they all correlate with the experimental values. Finally, the enthalpy of solution for Mg$^H$Ti$^G$ and Mg$^G$Ti$^H$ binary alloys were considered. The values are positive but data from experiment are unavailable. For a better comparism, data from experiment are seriously needed.
Behaviors of 10%NiYSZ Thin Films on Different Substrates for Reference Oxygen Electrode Sensor Rovena Veronica Pascu Romanian Journal of Physics 65,
612 (2020)
Thin films of 10% Ni: YSZ where grown on Si (100) and Pt/Si (100) substrates by Pulsed Laser Deposition (PLD). It was reported optical and structural characterization methods like Xray Diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscope (SEM) and Variable Angle Spectroscopic Ellipsometry (VASE). XRD spectra were influenced by the nature of substrate that was also confirmed in VASE analyses of roughness and refractive index. Optical properties are characterized by the refractive index values of 10%Ni: YSZ measured by VASE. Temperature and frequency dependent dielectric properties are coordinated with the conduction mechanism.
Collective Excitations in Biased Bilayer Graphene: Temperature Effects Nguyen van Men, Nguyen Quoc Khanh, and Dong Thi Kim Phuong Romanian Journal of Physics 65,
613 (2020)
We have studied the temperature effect on collective excitations in biased bilayer graphene within randomphase approximation. From the zeros of dynamical dielectric function we have found one weakly damped plasmon mode. For a given electrostatic potential bias, at low (high) temperature $T$ the plasmon frequency changes slightly (increases remarkably) with $T$. We have also studied the effects of potential bias and carrier density on the plasmon frequency.
Biophysics and Medical Physics
Calcium Interaction with Native and Mutant ASIC1a Channels Addressed by Computational Methods L.L. Ghica, M. Mernea, R. Niculae, D.F. Mihailescu Romanian Journal of Physics 65,
707 (2020)
Ca$^{2+}$ changes the pH dependency of acid sensing ion channels 1a (ASIC1a) activation. To explain this mechanism, we computationally investigated the interaction between Ca$^{2+}$ and ASIC1a channels, both native and mutant, bearing mutations that render it insensitive to Ca$^{2+}$, at three pH values associated with different channel activation states.
Environmental and Earth Physics
Occurrence, Toxicological Risks of Heavy Metals and Possible Agricultural Consequences of Sewage Sludge from Urban Treatment Plants Narcis Mihai Tanase, Ion V. Popescu, Cristiana Radulescu, Ioan Alin Bucurica, Ioana Daniela Dulama, Sofia Teodorescu, Raluca Maria Stirbescu, Georgian Alin Barboiu Romanian Journal of Physics 65,
812 (2020)
All water treatment plants (WWTPs) produce waste/residue known as sewage sludge (SS) during the purification of raw water. Typically, treatment procedures involve coagulation, flocculation, sedimentation, and filtration processes for removing colloidal as well as suspended solids from wastewater, then it follows chemical and biological processes. In this study, the sewage sludge resulted from urban WWTP is investigated for physicochemical characteristics. Withal, this article aims to determine the elemental composition of SS samples, in order to identify the major percentage of chemical components present in the sludge. Different analytical techniques such as Inductive Coupled Plasma – Mass Spectrometry (ICP–MS), Attenuated Total Reflectance – Fourier Transform Infrared Spectroscopy (ATRFTIR) and Raman spectrometry were used to obtain the first information about collected samples. Silica, alumina, ferric oxide and lime constitute the main constituents of analyzed samples. Some heavy metals are also found in the sewage sludge. It is required to explore a suitable option for developing sustainable sludge management strategies under stringent environmental norms. Based on the characteristics, the sewage sludge can be used in agriculture or in the manufacture of cement and cementitious materials, as a substitute for building materials, providing a safe disposal way. In this respect, one of the goals of this paper is to point whether sewage sludge from urban WWTP can be used in agriculture, according to Council Directive 86/278 / EEC Protection of the environment, and in particular of the soil, when sewage sludge is used in agriculture.
Influence of Active Cosmic Factors on the Dynamics of Natural Infrasound in the Earth's Atmosphere V. Koshovyy, O. Ivantyshyn, V. Mezentsev, B. Rusyn, M. Kalinichenko Romanian Journal of Physics 65,
813 (2020)
Hypothesis about the extended interpretation of the term “geoefficiency” of active space factors is considered. A stable correlation between the dynamics of the average monthly values of atmospheric infrasound, the entry of galactic cosmic rays into the Earth’s atmosphere and International sunspot number has been experimentally confirmed and quantified.
Investigations of the Seismic Site Response for Safer Urban Environment B. F. Apostol, S. F. Balan, A. Tiganescu Romanian Journal of Physics 65,
814 (2020)
The seismic response and local seismic effects are analysed in terms of spectral accelerations, peak ground acceleration (PGA) and site’s oscillation periods for city of Bucharest. By means of these parameters we may characterize the seismic hazard generated over the city area by Vrancea intermediatedepth seismic source. A data set consisting of the available seismic recordings is used for the last strong Vrancea earthquakes $(M_w > 6.4)$. Also, the geological description and interpretation of data contained in detailed geological maps is employed as the main and most basic information necessary to perform such an investigation. The existence of downhole data complements the geological information. The necessity of defining a dominant periodvalue range corresponding to seismic movements for each site is highlighted, by comparing some terrain characteristics induced by strong events (acceleration, response spectra, oscillating period of the superficial soil deposit) and their changes related to the magnitude of the earthquake. Despite the fact that seismic effects may not be characterized entirely by critical values in the range of the nonlinear effects, the particular geological features of the Romanian capital Bucharest may induce various amplifications, as a response to major earthquakes. These data about soil deposits behaviour could be used as input data for seismic risk mitigation. They provide an important contribution, in a very effective way, to getting solutions toward a safer seismic design.
