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KAHAN'S INTEGRATOR AND THE FREE RIGID BODYDYNAMICS

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Journal of Computational Mathematics 1999年第2期17卷 221-224页

作者： Mircea Puta(Department of Mathematics, west university of timisoara, B-dul. V.Pdrvan, 1900timisoara, Romania European university Dragan, 1800 Lugoj, Romania)loan Casu(Department of Mathematics, west university of timisoara, B-dul. V. Parvan, 1900Timisoar west university of timisoara 罗马尼亚

Kahan's integrator for the free rigid body dynamics is described and some ofits properties are pointed out.

关键词： Kahan's integrator Free rigid body

First order QED processes in a spatially flat FLRW space-time with a Milne-type scale factor

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Chinese Physics C 2020年第5期44卷 140-149页

作者： Ion ICotaescu Diana Popescu west university of timisoara V.Parvan Ave.4RO-300223 TimisoaraRomania

The quantum electrodynamics(QED)in a spatially flat(1+3)-dimensional Friedmann-Lema?tre-Robertson-Walker(FLRW)space-time with a Milne-type scale factor is outlined focusing on the amplitudes of the allowed processes in the first order *** definition of the transition rates is reconsidered such that an appropriate angular behavior of the probability for creation of an electron-positron pair from a photon is obtained,which has a similar rate as the creation of a photon and an electron-positron pair from *** is shown that these processes are allowed only in the first order perturbations,since the photon emission or absorption by an electron or positron are forbidden.

关键词： spatially flat FLRW space-time Milne-type scale factor first order amplitudes transition rates

Flat limit of the de Sitter QFT in the rest frame vacuum

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Chinese Physics C 2021年第1期45卷 97-108页

作者： Ion I.Cotaescu west university of timisoara V.Parvan Ave.4RO-300223 TimisoaraRomania

The problem of the flat limits of the scalar and spinor fields on the de Sitter expanding universe is considered in the traditional adiabatic vacuum and in the new rest frame vacuum we proposed recently,in which the frequencies are separated in the rest frames as in special *** is shown that only in the rest frame vacuum can the Minkowskian flat limit be reached naturally fbr any momentum,whereas in the adiabatic vacuum,this limit remains undefined in rest frames in which the momentum *** important role is played by the phases of the fundamental solutions in the rest frame vacuum,which must be regularized to obtain the desired Minkowskian flat *** procedure fixes the phases of the scalar mode functions and Dirac spinors,resulting in their definitive expressions derived *** physical consequenee is that,in the rest frame vacuum,the flat limits of the oneparticle operators are simply the corresponding operators of special relativity.

关键词： de Sitter space-time Klein-Gordon field Dirac field flat limit approximation method phase regularization

Access control and surveillance in a smart home

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High-Confidence Computing 2022年第1期2卷 38-46页

作者： Cristina Stolojescu-Crisan Calin Crisan Bogdan-Petru Butunoi Department of Communications Politehnica University of TimisoaraTimisoaraRomania SafeFleet Telematics TimisoaraRomania Department of Computer Science West University of TimisoaraTimișoaraRomania

In the past years smart homes solutions have become more and more popular with the introduction of a high number of both Internet of Things(IoT)applications and smart *** automation and security systems market is in a continuous growth,traditional security systems are evolving fast,and more and more people choose Smart home *** this paper,we propose two IoT based systems in the context of Smart homes:qToggle for multiple home automation,and MotionEyeOS,a video surveillance OS for single-board *** qToggle devices are based on ESP8266/ESP8285 chips or on Raspberry Pi boards and smart sensors,while MotionEye uses Raspberry Pi boards.

关键词： Access control Internet of things Security Smart homes Video surveillance

Scattering of massless fermions by Schwarzschild and Reissner-Nordstrm black holes

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Chinese Physics C 2017年第12期41卷 4-10页

作者： Ciprian A.Sporea west university of timisoara V. Parvan Ave. 4 RO-300223 Timisoara Romania

We study the scattering of massless Dirac fermions by Schwarzschild and Reissner-Nordstrm black holes. This is done by applying partial wave analysis to the scattering modes obtained after solving the massless Dirac equation in the asymptotic regions of the two black hole geometries. We successfully obtain analytic phase shifts, with the help of which the scattering cross section is computed. The glory and spiral scattering phenomena are shown to be present, as in the case of massive fermion scattering by black holes.

关键词： black holes scattering massless fermions

Gazeau–Klauder coherent states examined from the viewpoint of diagonal ordering operation technique

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Chinese Physics B 2016年第7期25卷 114-123页

作者： Dusan Popov Romeo Negrea Miodrag Popov Politehnica university timisoara Department of Physical Foundations of Engineering 300223 Timisoara Romania Politehnica university of timisoara Department of Mathematics 300006 Timisoara Romania politehnica university timisoara Department of Architecture and Urban Planning 300223 Timisoara Romania

In this paper we investigate the Gazeau–Klauder coherent states using a newly introduced diagonal ordering operation technique, in order to examine some of the properties of these coherent states. The results coincide with those obtained from other purely algebraic methods, but the calculations are greatly simplified. We apply the general theory to two cases of Gazeau–Klauder coherent states： pseudoharmonic as well as the Morse oscillators.

关键词： coherent states operator technique density operator

Perovskite type lanthanum manganite：Morpho-structural analysis and electrical investigations

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Journal of Rare Earths 2018年第5期36卷 499-504页

作者： Paula Sfirloaga Maria Poienar Iosif Malaescu Antoanetta Lungu Paulina Vlazan Institute for Research and Development in Electrochemistry and Condensed Matter P. Andronescu Street No.1 300224 Timisoara Romania west university of timisoara Vasile Parvan 4 300223 Romania

Perovskite-type oxides of LaMnO3 were synthesized by means of the sol-gel method, in the presence of citric acid as gelling agent. The precursors used were Mn（NO3）2·H2O, La2O3, and NaOH,mixed in the stoichiometric ratio to obtain perovskite materials. The obtained gel was heat-treated at 400, 600 and 800 ℃ respectively, for 6 h. X-ray diffraction and FT-IR spectroscopy were used to analyze the phase transformation as a function of temperature, and the Rietveld refinement was used in order to characterize the materials obtained structurally. The average crystallite size of the products was calculated from XRD data and the average particle size was measured from the TEM micrographs. At 600 ℃, the synthesized compound is well-crystallized, showcases a perovskite structure（Pm-3m space group）, and exhibits uniform and homogeneous hexagonally-shaped particles, with sizes in the 20-50 nm *** impedance measurements in the 20-2 × 10^6 Hz frequency range were carried out at different temperatures（26-115 ℃）, and the electrical conduction mechanism is discussed.

关键词： Rare earths Sol-gel method Physico-chemical properties Electrical investigations

MnFe2O4 nanoparticles as new catalyst for oxidative degradation of phenol by peroxydisulfate

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Journal of Environmental Sciences 2017年第3期29卷 269-277页

作者： Marcela Stoia Cornelia Muntean Bogdan Militaru Faculty of Industrial Chemistry and Environmental Engineering Politehnica University TimisoaraR0-300223 TimisoaraRomania Research Institute for Renewable Energy Politehnica University TimisoaraRO-300006TimisoaraRomania

Manganese ferrite nanopowder was prepared by thermal decomposition at 400℃ of the gel synthesized from manganese and iron nitrates and polyvinyl alcohol. X-ray diffractometry evidenced that manganese ferrite was formed as single crystalline phase at this temperature. Scanning electron microscope images evidenced the formation of very fine spherical particles （d 〈 11 nm） of manganese ferrite, with specific surface area of 147 m2/g. The powder obtained at 400℃ was used as a catalyst for the oxidative degradation of phenol in aqueous solutions, in the presence of potassium peroxydisulfate as oxidant. High phenol removal efficiencies above 90% were reached at： pH 3-3.5, phenol initial concentration around 50 mg/L, peroxydisulfate：phenol mass ratio 10：1, and catalyst dose 3 g/L. Total organic carbon measurements showed that the degradation of phenol goes, under these conditions, to mineralization in an extent of 60%.

关键词： Manganese ferriteNanoparticlesPhenolPeroxydisulfateCatalytic oxidation

Evaluation of the effective thermal conductivity of composite polymers by considering the filler size distribution law

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Journal of Zhejiang university-Science A(Applied Physics & Engineering) 2009年第5期10卷 704-709页

作者： Sorin HOLOTESCU Floriana D. STOIAN Department of Thermal Machines Technology and Transportation "Politehnica" University of TimisoaraTimisoara RO-300222 Romania

We present an empirical model for the effective thermal conductivity (ETC) of a polymer composite that includes dependency on the filler size distribution-chosen as the Rosin-Rammler distribution. The ETC is determined based on certain hypotheses that connect the behavior of a real composite material A, to that of a model composite material B, filled with mono-dimensional filler. The application of these hypotheses to the Maxwell model for ETC is presented. The validation of the new model and its characteristic equation was carried out using experimental data from the reference. The comparison showed that by using the size distribution law a very good fit between the equation of the new model (the size distribution model for the ETC) and the reference experimental results is obtained, even for high volume fractions, up to about 50%.

关键词： Effective thermal conductivity (ETC) Filler size distribution Equivalent volume fraction Composite polymer