Volume 71, Number 4, 2019
 
THEORETICAL, MATHEMATICAL, AND COMPUTATIONAL PHYSICS
 
Photon dynamics in the gravitational field in 4D and its 5D extension
D.YU. TSIPENYUK, V. B. BELAYEV
Rom. Rep. Phys. 71, 109 (2019)
Abstract. Extended space model (ESM) is a generalization of the special theory of relativity at a 5-dimensional space, and more specifically at (1+4)-dimensional space. Rotations in extended space correspond to the motion of a particle in gravity field in the embedded four-dimensional space-time. The possibility of a transition from the components of the 5-momentum of a particle in extended flat space to the components of a 4-momentum in an arbitrary 4-dimensional space by means of rotations is considered. Variational principle of the stationary energy integral of photon allows us to determine its dynamics. We consider variation of energy of the light-like particle in the pseudo-Riemann space-time, find Lagrangian, canonical momenta and forces. We study how (TS)-rotation in ESM agrees with photon dynamics in the Schwarzschild field. Equations of the critical curve are obtained by the nonzero energy integral variation in accordance with principles of the calculus of variations in mechanics. This method is compared with the Fermat's principle and geodesics principle. Energy and momentum of the particle transferred to the gravity field is defined. The produced equations are solved for the metrics of Schwarzschild and Goedel. The gravitation mass of the photon is found in central gravity field in the Newtonian limit.
Article no. 109: PDF 
Rogue wave structure and formation mechanism in the coupled nonlinear Schrödinger equations
ZAIDONG LI, HONGCHEN WEI, PENGBIN HE
Rom. Rep. Phys. 71, 110 (2019)
Abstract. By using the method of Darboux transformation, we solve the coupled nonlinear Schrödinger equations and obtain different types of exact rogue wave solutions. By adjusting the parameters of the dynamical model, we get a variety of rogue wave structures, namely bright, dark, and eye-shaped rogue waves. Also, their key characteristics are discussed in detail. We find that the non-uniform exchange rate of energy between the rogue wave and the continuous wave background can be adequately used to describe the formation mechanism of rogue waves in the coupled nonlinear Schrödinger equations.
Article no. 110: PDF 
 
ATOMIC, MOLECULAR, AND NUCLEAR PHYSICS
 
Resonant coupling of the electron cloud with the nucleus in heavy atoms
M. APOSTOL
Rom. Rep. Phys. 71, 210 (2019)
Abstract. The paper envisages the interaction of the laser radiation with the atomic nucleus in heavy atoms. Within a linearized Thomas-Fermi theory we show that the electron cloud in heavy atoms exhibits giant dipolar vibrations as eigenmodes with a frequency in the range 15 ZeV, where Z is the atomic number. These eigenmodes screen to a large extent the electric field of the optical-laser radiation (within the dipolar approximation). At the same time, there may appear a resonant coupling of these modes with the nucleus, which increases considerably the strength of the internal electric field acting upon the electrons and the nucleus. We estimate the effect of this electric field on the atom ionization and the emission rate of nucleons from nucleus and find that, although the nucleon emission rate may be enhanced appreciably, the nucleon emission process is, in fact, stopped by the faster ionization rate, which spoils the resonance regime.
Article no. 210: PDF 
Determination of the 60Co source activity by using the sum-peak method
S. ILIE, C. A. UR, O. SIMA, G. SULIMAN, A. PAPPALARDO
Rom. Rep. Phys. 71, 211 (2019)
Abstract. The sum-peak method is one of the methods used for absolute activity measurement of radionuclides emitting gamma-ray photons in coincidence. This method is based on the use of acquired pulse-height distribution data only, without knowledge of the detector efficiencies. In this paper it is shown that by using Monte Carlo techniques for angular correlation corrections, pile-up peaks for corrections of accidental coincidences, low-level discriminator corrections, the activity of the 60Co source can be measured with accuracy and reproducibility below 5% by using spectral data only.
Article no. 211: PDF 
Cosmic ray measurements using WILLI-air setup
A. BALACEANU, N.V. ZAMFIR, A. GHERGHEL-LASCU, B. MITRICA, M. NICULESCU-OGLINZANU, A. SAFTOIU, D. STANCA, T. MOSU, D. DUMITRIU, C. VANCEA, M. DOBRE
Rom. Rep. Phys. 71, 212 (2019)
Abstract. The Weak Ionization Lead Lepton Interaction for Air-shower Investigations in Romania (WILLI-AIR) experiment aims to investigate the secondary charged particles produced in the interactions of cosmic rays with atmosphere nuclei, focusing on the low energy region of the primary incident particles spectrum, up to 1015 eV. With 24 field detector stations, forming the AIR array, and a 20 layers electromagnetic calorimeter, named WILLI, the experiment is focusing on determinations of the muon flux and the muon charge ratio measured only in Extensive Air Showers. Each field station uses two pieces of plastic scintillator as sensitive volume, read-out individually by one photo-multiplier. The experiment covers a 1600 m2 area, being correlated with the energy range of the investigated primary particles. Combining the information from the AIR array and the WILLI determinations, the muon charge ratio in Extensive Air Showers is determined.
Article no. 212: PDF 
Decay properties of superheavy nuclei Z = 118 - 122 and N = 182 - 186
C.I. ANGHEL, I. SILISTEANU, M. ZADEHRAFI
Rom. Rep. Phys. 71, 213 (2019)
Abstract. The α-decay and spontaneous fission half-lives of yet-unaccessible superheavy elements are estimated with the formulas derived from the energy-lifetime systematics of both the data and calculated decay properties for the Z = 104 - 118 known nuclei. The trend of decay properties in the region of studied nuclei indicates as a possible center of the island of stability at the spherical closed shells Z = 120 and N = 184. The dominant decay mode in this region of nuclei is the spontaneous fission and not α-decay. Our predictions for decay properties are compared with the ones given by empirical and model approximations.
Article no. 213: PDF 
 
OPTICS AND PHOTONICS, PLASMA, LASER AND BEAM PHYSICS
 
Nonlinear conical diffraction in superhoneycomb lattice induced in a photorefractive crystal
YIQING TIAN, HUA ZHONG, MILIVOJ R. BELIC, YANPENG ZHANG, FULI LI, YIQI ZHANG
Rom. Rep. Phys. 71, 412 (2019)
Abstract. We report nonlinear conical diffraction in the superhoneycomb lattice, which is an edge-centered honeycomb lattice, induced in a photorefractive crystal. This system is of special interest, as it represents a hybrid fermionic-bosonic physical system. When nonlinearity is imposed, conical diffraction from a fermionic Dirac cone will change from circular diffraction rings, formed by small hexagons, into a triangular arrangement of hexagons. But from the bosonic Dirac cone, conical diffraction changes into elliptic diffraction rings of different inner symmetries, with the outer ring intensity damped.
Article no. 412: PDF 
Surface oxidation and enhanced hydrophilization of polyamide fiber surface after he / ar atmospheric pressure plasma exposure
A. V. NASTUTA, G. POPA
Rom. Rep. Phys. 71, 413 (2019)
Abstract. Due to their bulk and surface properties the polymeric fibers are used for various applications as surgery, textile industry and many others. In the present paper the surface modification, wettability and chemical composition of polyamide 6 fibers, after direct atmospheric dielectric barrier discharge treatment, in helium and argon, are studied. The contact angle method, atomic force microscopy technique and X-ray photoelectrons spectroscopy were used to investigate plasma induced modifications of polyamide surface. Increased hydrophilic properties of plasma-treated surfaces were proofed by static water contact angle measurement, with values up to 70% lower than pristine polymer. It was found that the surface roughness increases up to 3 times after helium plasma treatment and 2 times after argon plasma treatment, for up to 7 days. Surface oxidation, after plasma exposure, was observed through X-ray photoelectrons spectroscopy. These experimental findings, proven by the good correlation of the obtained results from both plasma diagnosis and polymeric surface characterization, underline the usage of plasma sources for polymeric surface processing.
Article no. 413: PDF 
Tailoring sp2/sp3 ratio in diamond-like carbon films via deposition parameters in a high voltage anodic vacuum plasma
M. BADULESCU, A. ANGHEL, C. C. SURDU-BOB, C. LOGOFATU, C. LUCULESCU
Rom. Rep. Phys. 71, 414 (2019)
Abstract. Tailoring sp2/sp3 ratio in diamond-like carbon thin films offers new surface engineering solutions for the continuously increasing devices requirements in various fields. We report here the control of sp2/sp3 carbon content using the high voltage anodic plasma in vacuum. Correlation of data obtained by visible Raman Spectroscopy and XPS spectra of our DLC films with deposition parameters showed an increase in sp3 bonding of about 10% when decreasing the discharge voltage from 600 V to 200 V or increasing the anode-substrate distance from 15 cm to 36 cm.
Article no. 414: PDF 
 
CONDENSED AND SOFT MATTER PHYSICS
New hybrid MWCNT/Co-Fe-B nanoparticles composite material for applications in microwave domain
A. GHEMES, G. ABABEI, G. STOIAN, N. LUPU, H. CHIRIAC
Rom. Rep. Phys. 71, 508 (2019)
Abstract. A new hybrid composite material based on multiwalled carbon nanotubes (MWCNTs) and soft magnetic Co-Fe-B nanoparticles for applications in microwave domain is proposed. MWCNTs with length of about 300 μm have been synthesized by chloride mediated chemical vapor deposition method. Co-Fe-B nanoparticles with diameters of about 30 nm were prepared by chemical reduction method. The electromagnetic shielding characteristics of the composite material was investigated by determination of the microwave shielding effectiveness in the 1 GHz to 8 GHz frequency range. The new material showed high shielding effectiveness in broadband frequency range.
Article no. 508: PDF 
Electrical capacitors based on magnetorheological elastomers: effects of the static and pulsating magnetic field on electrical properties
L.M. CIRTINA, I. BICA, L. CHIRIGIU, D. CIRTINA
Rom. Rep. Phys. 71, 509 (2019)
Abstract. Magnetorheological elastomers (MRE) based on iron microparticles and silicone rubber are used as dielectric materials for fabrication of electrical capacitors. We show that the electrical properties of the capacitors are sensibly influenced by external magnetic and electric fields. We present and describe the experimental setup used for preparation of MRE and capacitors. The physical mechanisms leading to the observed effects are explained by using the model of dipolar approximation.
Article no. 509: PDF 
 
BIOPHYSICS AND MEDICAL PHYSICS
NMR characterization of bone collagen used for 14C dating of osteological material
O. GAZA, M. ENACHESCU, C.S. TUTA, C.STAVARACHE, H. IOVU
Rom. Rep. Phys. 71, 604 (2019)
Abstract. The degree of conservation of collagen used for radiocarbon dating was determined by evaluating the percentage of broken collagen chains as a result of its degradation caused by improper storage conditions. This paper proposes a method for determining the amino acid content of fragments that are lost through the Amicon Ultra Filter 30 kDa filter used for collagen extraction to date osteological material. For this purpose, the 13C-NMR spectra obtained from the analysis of collagen extracted from four bones of different ages were used.
Article no. 604: PDF 
 
ENVIRONMENTAL AND EARTH PHYSICS
Statistical analysis and classification of the water parameters of Beas river (India)
ALINA BARBULESCU, ANITA DANI
Rom. Rep. Phys. 71, 716 (2019)
Abstract. Historical secondary data for Beas River (India) were used to study the water parameters for a period of eight years at 23 hydrological stations. Similarity tests have been conducted for each parameter to examine the fluctuations at the stations and per years. An aggregated indicator of water quality (WA) was computed using the mean value of each parameter and two classification techniques were used for the analysis of river water quality data. Two-step clustering proved to be an appropriate technique to create three profiles of all data collected from the stations of Beas River for each year. C&RT technique was used to classify all stations based on the WA indicator. The approach can be employed for any data for taking documented decision about preservation and amelioration the water quality of different rivers.
Article no. 716: PDF 
Radon concentrations and gamma radiation activity measurements of Mugla, Turkey
M.G. ERDOGAN, B. AKKUS, L. AMON SUSAM, N. HAFIZOGLU ALKAN, A. ERTOPRAK,Y. OKTEM, F.C. OZTURK
Rom. Rep. Phys. 71, 717 (2019)
Abstract. In the present study, the indoor radon activity concentrations in air were measured by using the LR-115 solid state nuclear track detectors in 25 dwellings (chosen as 9 old and 16 new) in Mugla, Turkey. The indoor radon activity concentration values for old dwellings vary from 160.37 to 367.54 Bq/m3 and for new dwellings from 79.83 to 347.41 Bq/m3. Moreover, the gamma-ray activity measurements of 238U, 232Th, 40K, and 137Cs vary from 5.6 to 72.6 Bq/kg, 2.26 to 38.03 Bq/kg, 79.54 to 867.48 Bg/kg, and 0 to 1.42 Bq/kg, respectively. Most of the activity and effective dose values were within the limits of United Nations Scientific Committee on the Effects of Atomic Radiations (UNSCEAR) reports. In addition, a comparison between Mugla and other cities specified in the literature was also given.
Article no. 717: PDF 
Dispersion model for low wind and atmospheric calm - Part II: evaluation experiment at a nuclear power plant in Romania
VASILE CUCULEANU, ALEXANDRU LUPU, GEORGIANA GRIGORAS, ION POPESCU, ALEXANDRU TOMA
Rom. Rep. Phys. 71, 718 (2019)
Abstract. An evaluation experiment was conducted around the Cernavoda nuclear power plant in Romania using as tracer tritium released into the atmosphere by the plant stack. Measured values of tritium concentrations in air samples were obtained by using the liquid scintillation method. The ConDefa model is evaluated against the measured concentrations. It is shown that the model can provide reliable estimates of tritium concentrations, particularly for those higher than the local background.
Article no. 718: PDF 
 
PHYSICS EDUCATION
Experimental analysis of Doppler effect using the rotating sound emitting source
T. NEMES, S. ILIC, LJ. BUDINSKI-PETKOVIC, M. VESELINOVIC
Rom. Rep. Phys. 71, 904 (2019)
Abstract. While the principle to observe the Doppler Effect with a rotating source is known and very simple, there are no existing commercial apparatus for lab- oratory exercise. The full realization of the apparatus and an easy procedure to study Doppler Effect in the laboratory practice is described through a paper.
Article no. 904: PDF 
Educational laboratory system based on electrochemical devices
S. DINU, B. DOBRICA, S. VOINEA
Rom. Rep. Phys. 71, 905 (2019)
Abstract. Fossil fuel crisis and issues of greenhouse gas emissions led to the development of renewable energy sources. To create a right mentality among young people for using renewable energy sources, it is important to understand how devices produce green energy. The most efficient device that converts chemical energy into electricity is the fuel cell. We have created a computerized educational laboratory system, consisting of three types of combustion cells: H2/O2, ethanol and magnesium with salt water. This system is monitored by an Arduino microprocessor. The proposed automatic educational laboratory is a simple and agreeable mode to learn fundamental physics concepts.
Article no. 905: PDF 
Education and training tradition at IFIN-HH in radon measurement and evaluation of radiological impact
MARIA SAHAGIA, GABRIEL STANESCU, AURELIAN LUCA, ANDREI ANTOHE, MARIAN ROMEO CALIN, ILEANA RADULESCU
Rom. Rep. Phys. 71, 906 (2019)
Abstract. This paper presents the work carried out in Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH) for the measurement of indoor and outdoor 222Rn concentration as a historical development and as present situation, focused on the assurance of its metrological chain, from primary standardization, up to in field measurement. These activities are in tight connection with the activity of education and training for staff involved in exposure to naturally occurring radioactive materials (NORMs), especially radon, and for those involved in the measurement of radon concentrations in field. Two types of training actions will be presented: the courses organized for people working in uranium industry and public health and the course prepared and presented within the ANNETTE EU Project, Horizon 2020 Research and Innovation Programme.
Article no. 906: PDF 

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