Volume 69, Number 3, 2017
 
THEORETICAL, MATHEMATICAL, AND COMPUTATIONAL PHYSICS
 
Rational solutions to a system of coupled partial differential equations
HAO CHEN, WENWEN CHEN
Rom. Rep. Phys. 69, 111 (2017)
Abstract. Two types of high-order rational solutions to a system of coupled partial differential equations, namely general high-order rogue wave solutions and W-shaped soliton solutions, are derived via the Hirota bilinear method. These rational solutions are given in terms of determinants whose matrix elements have plain algebraic expressions. It is shown that the general N-th order rogue waves contain N-1 free irreducible complex parameters. The N-th order W-shaped rational solitons consist of N parallel W-shaped line waves.
Article no. 111: PDF 
 
New solutions of Dodd-Bullough-Mikhailov equation by using an improved tanh-method
RADU CONSTANTINESCU
Rom. Rep. Phys. 69, 112 (2017)
Abstract. In this paper an improved tanh-method and the symbolic Maple computations are applied to the Dodd-Bullough-Mikhailov (DBM) equation in order to construct in an unitary way several multiple travelling wave solutions. The main idea of this method is to take a full advantage of Riccati equation and consequently to provide a guideline able to classify the various types of solutions accordingly to the values of some parameters. Multiple soliton-like solutions as well as others under trigonometric function forms or under rational forms are discussed. This method may as well successfully solve other nonlinear partial differential equations.
Article no. 112: PDF 
 
New rheological models within local fractional derivative
XIAO-JUN YANG, FENG GAO, H.M. SRIVASTAVA
Rom. Rep. Phys. 69, 113 (2017)
Abstract. In this article, two local fractional rheological models via spring and dash pot elements in the one-dimensional case are proposed for the first time. The creep and relaxation behaviors of the fractal Maxwell fluid and Kelvin-Voigt solid are discussed. The constitutive relationships of the fractal mechanical elements are formulated by using local fractional calculus. The viscoelastic characteristics of the real materials are efficiently demonstrated and illustrated with the fractal charts.
Article no. 113: PDF 
 
Rogue waves of the (3+1)-dimensional potential Yu-Toda-Sasa-Fukuyama equation
WEI LIU
Rom. Rep. Phys. 69, 114 (2017)
Abstract. General high-order rogue waves of the (3+1)-dimensional potential Yu-Toda-Sasa-Fukuyama equation are derived by employing the bilinear method. These rogue wave solutions are given in terms of determinants whose matrix elements have simple algebraic expressions. It is shown that fundamental rogue waves in the (x, z) plane are line rogue waves, which arise from the constant background with a line profile and then disappear into the constant background again. The typical dynamics in other planes have also been illustrated by three dimensional plots. It is also shown that high-order rogue waves in the (x, z) plane are parallel line rogue waves, which also arise from the constant background and then decay back to it. Besides, dynamical behaviours of these high-order rogue waves in the (x, y) and (x, t) planes are also illustrated.
Article no. 114: PDF 
 
 
ATOMIC, MOLECULAR, AND NUCLEAR PHYSICS
 
Sub-natural-width N-resonances observed in large frequency interval
A. KRASTEVA, S. GATEVA, A. SARGSYAN, D. SARKISYAN, S. CARTALEVA
Rom. Rep. Phys. 69, 202 (2017)
Abstract. Sub-natural-width N-type resonance prepared in Λ-system on the D2 line of Cs atoms is measured by two, couple and probe monomode laser beams. The probe light is scanned over very large spectral interval of more than 40 GHz. Fixing the couple frequency within this interval provides observation of enhanced-absorption SNW N-resonance at various frequencies, as well as N-resonance couple with equal sign and well-known frequency difference, or even couple with reversed signs.
Article no. 202: PDF 
 
Determination half-life of heavy nuclei using Fermi gas model
A. ATTARZADEH, M.J. TAHMASEBI BIRGANI, S.MOHAMMADI, P.PARVARESH
Rom. Rep. Phys. 69, 203 (2017)
Abstract. Calculations on the α-decay half-lives of heavy nuclei are performed through Fermi gas model. The Wood Saxon potential is employed to calculate half-lives through a Coulomb barrier. The present study is initially restricted to even-even nuclei in the heavy mass region with N>126. Then the study is extended to the heaviest nuclei including super heavy elements. The main consideration in this model is V0b2 = 100 MeV, where b is the force range between two nucleons which represents the attractive well, and -V0 is depth. The calculated α-decay half lives are found to be in good agreement with the experimental data for heavy nuclei with approximately spherical shape. The results are independent from deformation parameters for super heavy nuclei.
Article no. 203: PDF 
 
 
OPTICS AND PHOTONICS, PLASMAS, LASER AND BEAM PHYSICS
 
Advances by using computers and last generation optics devices in experiments and demonstrations
ANNA CONSORTINI
Rom. Rep. Phys. 69, 410 (2017)
Abstract. In Optics, as well as in other disciplines, use of computers and sophisticated apparatuses is now common, both for collecting and elaborating data and for demonstrations of basic experiments and training of students. Both advantages and disadvantages arise from the use of these complex apparatuses. In general, the advantages are enormous. Here we will consider a number of examples, including a negative one, which received large resonance in the international community in recent years.
Article no. 410: PDF 
 
Operating the HIPIMS discharge with ultra-short pulses: a solution to overcome the deposition rate limitation
I.-L. VELICU, I. MIHAILA, G. POPA
Rom. Rep. Phys. 69, 411 (2017)
Abstract. This study presents results on the influence of pulse duration in HiPIMS discharge on the sputtering mechanisms, target-to-substrate particles transport, and deposition rate. A copper disk-shaped target was sputtered in argon atmosphere, increasing the pulse duration from 3 μs to 50 μs and adjusting the pulsing frequency in order to keep a constant average power of 100 W. Voltage and current waveforms, time-resolved fast imaging, time resolved-optical emission spectroscopy, time evolution of the ion flux towards the substrate, and energy-resolved mass spectrometry were used in order to investigate the plasma composition and its change in front of the target. Increasing the pulse duration, the sputtering mechanism is gradually transformed from dominant gas sputtering to self-sputtering driven mode and the deposition rate decreases.
Article no. 411: PDF 
 
 
CONDENSED AND SOFT MATTER PHYSICS
 
Steady-state photoconductivity of amorphous (As4S3Se3)1-xSnx and GexAsxSe1-2x thin films
O. IASENIUC, M. IOVU
Rom. Rep. Phys. 69, 505 (2017)
Abstract. In the present paper the experimental results on steady-state photoconductivity of amorphous (As4S3Se3)1-xSnx and GexAsxSe1-2x thin films are presented and discussed. It was shown, that the spectral distribution of the stationary photoconductivity for both glass systems depends on the composition and polarity of the illuminated electrode. The experimental results are discussed in framework of the multiple trapping models for amorphous materials, with exponential distribution of the localized states in the band gap. The contact phenomenon appears at the interface between a metal electrode and an amorphous layer, what also is considered to be responsible for the peculiar features of photoelectric properties of investigated materials.
Article no. 505: PDF 
 
Temperature influence on the capacitance-voltage hysteresis of transparent a-IGZO/PZT/FTO MFS-heterostructure
L.M. TRINCA, C. BESLEAGA, V. STANCU, R. RADU, A. IUGA, A.G. BONI, A.C. GALCA, L. PINTILIE
Rom. Rep. Phys. 69, 506 (2017)
Abstract. Capacitance-voltage (C-V) hysteresis of metal-ferroelectric-semiconductor (MFS) structure based on a-In2GaZnO5.5 and Pb0,2Zr0.8TiO3 layers are recorded in the 350-470 K range. The structure is grown on FTO/glass to obtain a transparent MFS. The memory functionality of the heterostructure is proved through C-V and P-V characteristics. The memory window is dependent on the temperature, the largest value of 2.5 V being obtained at 470 K, where the contribution of the ferroelectric-semiconductor interface defect states is minimized. The direction of C-V hysteresis is clockwise at 350 K, and it turns counterclockwise at higher temperatures where the ferroelectric polarization has the main contribution.
Article no. 506: PDF 
 
Near-infrared energy bandgap bismuth oxide thin films and their in-depth morpho-structural and optical analysis
S. CONDURACHE-BOTA, N. TIGAU, M. PRAISLER, G. PRODAN, R. GAVRILA
Rom. Rep. Phys. 69, 507 (2017)
Abstract. This paper presents the results of the analysis of bismuth oxide thin films prepared by thermal evaporation in vacuum of pure bismuth onto heated glass substrates (from room temperature till 200 oC), followed by thermal oxidation in air. The crystalline structure and the grain size distribution were analyzed by means of transmission electron microscopy and the results were related to the optical properties of the films. The refractive index of the films varies around 2.0 and the energy bandgap (the Wemple-Didomenico model) varies around 1.5 eV, in the near-infrared, making such films useful for thermal energy capture.
Article no. 507: PDF 
 
 
BIOPHYSICS AND MEDICAL PHYSICS
 
Cellular differentiation exacerbates radiation sensitivity in vitro in a human dopaminergic neuronal model
M. TEMELIE, C. MUSTACIOSU, M.L. FLONTA, D. SAVU
Rom. Rep. Phys. 69, 611 (2017)
Abstract. UV radiations are well known cellular stressors. Following exposure to genotoxic factors the cells respond by molecular mechanisms aimed to repair the damages, block the proliferation or trigger cell death. Our study investigates how neuronal differentiation interferes with repair processes following UV-induced genotoxic stress, in a model of dopaminergic neurons (SH-SY5Y). Our work proved a higher level of DNA damage induced by UVC radiation in the dose range of 0.358-2.150 mJ/cm2 in differentiated cells compared to the proliferative variants. Cellular viability decreases proportionally with the irradiation dose and post-exposure time and correlates with an increased apoptosis through caspase 3/7 activation. These effects were enhanced in differentiated cells in which we have seen increased DNA damage, incomplete repair, exacerbated viability loss and apoptosis induction.
Article no. 611: PDF 
 
 
ENVIRONMENTAL AND EARTH PHYSICS
 
Radiological risk assessment of workers for radioactive liquid effluents transfer
A. STOCHIOIU, C. TUCA, R. DEJU, F. MIHAI
Rom. Rep. Phys. 69, 707 (2017)
Abstract. The paper aims to assess the radiological risk of workers involved in liquid waste transfer operations resulted from decommissioning process of a nuclear reactor, considering both normal and abnormal risk scenarios. The sources for liquid effluents are an underground buffer tank (source 1) and four spent fuel storage ponds (source 2). In normal working condition is calculated the effective dose based on the activity concentrations measured for liquid effluents and specific dose coefficients. The total personal equivalent dose Hp(10) received by a worker from source 1 is about 13.16 μSv and for source 2 is 185.04 μSv, 198.20 μSv from both of them (67 transfer operations). In parallel the dose ambient equivalent H*(10) measurements was performed for source 2 using an environment thermo-luminescent system, resulting in a value of 3.8 μSv in good agreement with evaluation from activity, considering both operational quantities as being equivalent. In abnormal situation the workers are exposed during clean-up operations. Supposing that a single incident of contamination occurs, beta dose rates are highest for accidental discharges of liquid from the pond 3-0.70 μSv/h - and underground buffer tank -0.16 μSv/h - due to the concentration of activity 3.21E+08 Bq and 7.29E+07 respectively
Article no. 707: PDF 
 
Magnetic environmental pollution: experimental simulation of engineered magnetic nanoparticles impact on Zea Mays vegetal embryos
M. RACUCIU, H. OLOSUTEAN
Rom. Rep. Phys. 69, 708 (2017)
Abstract. The engineered nanoparticles release into the environment raises important ecological worldwide problems. To evaluate the effects of the magnetic nanoparticles on Zea mays vegetal embryos, we have accomplished experimental studies focused on the cell proliferation in the root tips tissue during the seeds germination under the influence of magnetic nanoparticles (MNPs) coated with different layers. Mitotic division process appears to be stimulated than controls and chromosomal aberrations occurred under MNPs presence. The experimental results have been comparatively analysed by means a statistically soft in order to obtain mathematical models to describe the MNPs influence on mitotic index and aberrations index.
Article no. 708: PDF 
 
Monitoring of radon and air ionization in a seismic area
VICTORIN-EMILIAN TOADER, IREN-ADELINA MOLDOVAN, ALEXANDRU MARMUREANU, PUSHAN KR DUTTA, RALUCA PARTHENIU, EDUARD NASTASE
Rom. Rep. Phys. 69, 709 (2017)
Abstract. Our multidisciplinary network (AeroSolSys) located in Vrancea (Curvature Carpathian Mountains) includes radon concentration monitoring in five stations. We focus on lithosphere and near surface low atmosphere phenomena using real-time information about seismicity, +/- ions, clouds, solar radiation, temperature (air, ground), humidity, atmospheric pressure, wind speed and direction, telluric currents, variations of the local magnetic field, infrasound, variations of the atmospheric electrostatic field, variations in the earth crust with inclinometers, electromagnetic activity, CO2 concentration, ULF radio wave propagation, seismo-acoustic emission, animal behavior. The main purpose is to inform the authorities about risk situation and update hazard scenarios. The radon concentration monitoring is continuously with 1 hour or 3 hours sample rate in locations near to faults in an active seismic zone characterized by intermediate depth earthquakes. Trigger algorithms include standard deviation, mean and derivative methods. We correlate radon concentration measurements with humidity, temperature and atmospheric pressure from the same equipment. In few stations we have meteorological information, too. Sometime the radon concentration has very high variations (maxim 4535 Bq/m3 from 106 Bq/m3) in short time (1-2 days) without being accompanied by an important earthquake. Generally the cause is the high humidity that could be generated by tectonic stress. Correlation with seismicity needs information from minimum 6 month in our case. For 10605 hours, 618 earthquakes with maxim magnitude 4.9 R, we have got radon average 38 Bq/m3 and exposure 408111 Bqh/m3 in one station. In two cases we have correlation between seismicity and radon concentration. In other one we recorded high variation because the location was in an area with multiple faults and a river. Radon can be a seismic precursor but only in a multidisciplinary network. A pair of ions counters (positive and negative) work together in few stations. The anomalies for short or long period of time should be correlated with local environment factors (e.g. humidity).
Article no. 709: PDF 
 
 
APPLIED AND INTERDISCIPLINARY PHYSICS
 
3D digitization of an antique decorative textile artifact using photogrammetry
L.M. ANGHELUTA, R. RADVAN
Rom. Rep. Phys. 69, 801 (2017)
Abstract. This paper describes a project aimed to demonstrate the great potential of photogrammetry in realizing a detailed 3D digital model of an old Romanian traditional decorative textile piece, from a valuable collection, for 3D printing purposes. The challenge was to record with high precision the planar textile surface and then process the digital replica to the level of a printable 3D object. For the purpose of this experiment close range photogrammetry was employed. Within this paper we are going into every detail of the processing, online publishing and 3D printing stages and discuss each aspect that can influence the final results.
Article no. 801: PDF 
 
 
PHYSICS EDUCATION
 
On elementary derivation of Green's function of wave equation
A.E. RASTEGIN
Rom. Rep. Phys. 69, 903 (2017)
Abstract. Green's functions are typically derived with the use of mathematics with which undergraduate students are not familiar. Educational programs may be organized so that the wave equation is learned before the course of mathematical physics. Meanwhile, the technique of using Green's functions can be introduced at undergraduate level. In this paper, a simple approach to derivation of Green's function of the wave equation is proposed. It demands no more than usual reasons typical for studies of Poisson's equation. One starts with the divergence theorem and the Laplacian expressed in spherical coordinates. The proposed approach is illustrated with a lot of examples. They are connected with Huygens' principle and Euler's analysis of the vibrating string problem.
Article no. 903: PDF 
 
Coin toss modeling
R.C. STEFAN, T.O. CHECHE
Rom. Rep. Phys. 69, 904 (2017)
Abstract. The torque-free motion of rigid body in gravitational field is analyzed. The coin lands on a soft surface (such as the palm of the hand) that allows no bouncing. The model assumes the coin as a rigid bodywith constant angular momentum vector in the body frame, and no air resistance. Unbiased probabilities of heads and tails are obtained for various initial conditions accessible to a usual person.
Article no. 904: PDF 
 

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