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Operators of quantum theory of Dirac's free field

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Chinese Physics C 2024年第12期48卷 73-106页

作者： ion i.cotaescu West University of Timişoara V.Pârvan Ave.4RO-300223 TimişoaraRomania

The Pryce(e)spin and position operators of the quantum theory of Dirac's free field were re-defined and studied recently with the help of a new spin symmetry and suitable spectral representations[***.J.C 82,1073(2022)].This approach is generalized here,associating a pair of integral operators acting directly on particle and antiparticle wave spinors in momentum representation to any integral operator in configuration representation,acting on mode *** framework allows an effective quantization procedure,giving a large set of one-particle operators with physical meaning as the spin and orbital parts of the isometry generators,the Pauli-Lubanski and position operators,or other spin-type operators proposed to *** attention is paid to the operators that mix the particle and antiparticle sectors whose off-diagonal associated operators have oscillating terms producing *** principal operators of this type,including the usual coordinate operator,are derived here for the first *** an application,it is shown that an apparatus measuring these new observables may prepare and detect oneparticle wave packets moving uniformly without Zitterbewegung or spin dynamics,spreading in time normally as any other relativistic or even non-relativistic wave packet.

关键词： Dirac theory integral operators Pryce's operators integral representations canonical quantization propagation

Kinemaitcs in spatially flat FLRW spacetimes

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Chinese Physics C 2021年第10期45卷 92-101页

作者： ion i.Cotäescu West University of Timiäoara

The kinematics on spatially flat FLRW spacetimes is presented for the first time in local charts with physical coordinates,i.e.,the cosmic time and proper Cartesian space coordinates of Painlevé-*** is shown that there exists a conserved momentum that determines the form of the covariant four-momentum on geodesics in terms of physical ***,with the help of this conserved momentum,the peculiar momentum can be defined,thus separating the peculiar and recessional motions without *** is shown that the energy and peculiar momentum satisfy the mass-shell condition of special relativity while the recessional momentum does not produce *** this framework,the measurements of the kinetic quantities along geodesics performed by different observers are analyzed,pointing out an energy loss of the massive particles similar to that producing the photon *** examples of the kinematics on the de Sitter expanding universe and a new Milne-type spacetime are extensively analyzed.

关键词： FLRW specetime peculiar momentum recessional momentum conserved quantities energy loss redshift de Sitter expanding universe Milne-type universe

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

Modeling net-charge fluctuations in heavy-ion collisions at the LHC

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Chinese Physics C 2025年第1期49卷 281-289页

作者： G.O.Ambaryan A.S.Chernyshov G.Kh.Eyyubova V.L.Korotkikh i.P.Lokhtin S.V.Petrushanko A.M.Snigirev E.E.Zabrodin Physics Department Lomonosov Moscow State UniversityRU-119991 MoscowRussia Skobeltsyn institute of Nuclear Physics Lomonosov Moscow State UniversityRU-119991 MoscowRussia Bogoliubov Laboratory of Theoretical Physics Joint Institute for Nuclear ResearchRU-141980 DubnaRussia Department of Physics University of OsloN-0316 OsloNorway

Analysis of Pb+Pb data for net-charge fluctuations at LHC energies using the HYDJET++model is *** strongly intensive quantities D and Σ were used to remove the effects related to system volume *** employed two versions of HYDJET++for the *** first one is the standard or default version,whereas the second one is a modification that takes into account explicit event-by-event conservation of the electric net-charge of produced *** inclusion of the canonical net-charge conservation in the model allows for better description of the experimental data obtained by the ALiCE and CMS Collaborations.A comparison with calculations from other models is also presented.

关键词： relativistic heavy-ion collisions net-charge fluctuations strongly intensive variables canonical charge conservation

Mechanical properties of a Gum-type Ti–Nb–Zr–Fe–O alloy

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international Journal of Minerals,Metallurgy and Materials 2017年第8期24卷 909-917页

作者： Anna Nocivin ion Cinca Doina Raducanu Vasile Danut Cojocaru ion Alexandru Popovici Faculty of Mechanical Industrial and Maritime Engineering Ovidius University of Constanta Faculty of Materials Science and Engineering Politehnica University of Bucharest Carol Davila University of Medicine and Pharmacy

A new Gum-type alloy(Ti–Nb–Zr–Fe–O) in which Fe is used instead of Ta was subjected to a particular thermomechanical processing scheme to assess whether its mechanical characteristics(fine ?-grains with high strength and low modulus) render it suitable as a biomedical implant material. After a homogenization treatment followed by cold-rolling with 50% reduction, the specimens were subjected to one of three different recrystallization treatments at 1073, 1173, and 1273 K. The structural and mechanical properties of all of the treated specimens were analyzed. The mechanical characterization included tensile tests, microhardness determinations, and fractography by scanning electron microscopy. The possible deformation mechanisms were discussed using the Bo – Md diagram. By correlating all of the experimental results, we concluded that the most promising processing variant corresponds to recrystallization at 1073 K, which can provide suitable mechanical characteristics for this type of alloys: high yield and ultimate tensile strengths(1038 and 1083 MPa, respectively), a low modulus of elasticity(62 GPa), and fine crystalline grain size(approximately 50 ?m).

关键词： biomaterials mechanical properties Gum-type alloy thermomechanical processing tensile test

Sharp large deviation results for sums of independent random variables

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Science China Mathematics 2015年第9期58卷 1939-1958页

作者： FAN XieQuan GRAMA ion LiU QuanSheng Regularity Team Institut National de Recherche en Informatique et en Automatique Laboratoire de Mathmatiques Appliques aux Systèmes Ecole Centrale Paris-Grande Voie des Vignes Laboratoire de Mathmatiques de Bretagne Atlantique UMR 6205 University Bretagne-Sud School of Mathematics and Computing Science Changsha University of Science and Technology

We show sharp bounds for probabilities of large deviations for sums of independent random variables satisfying Bernstein's condition. One such bound is very close to the tail of the standard Gaussian law in certain case; other bounds improve the inequalities of Bennett and Hoeffding by adding missing factors in the spirit of Talagrand(1995). We also complete Talagrand's inequality by giving a lower bound of the same form, leading to an equality. As a consequence, we obtain large deviation expansions similar to those of Cram′er(1938),Bahadur-Rao(1960) and Sakhanenko(1991). We also show that our bound can be used to improve a recent inequality of Pinelis(2014).

关键词： Bernstein’s inequality sharp large deviations Cramér large deviations expansion of BahadurRao sums of independent random variabl

Growing and aging of hematopoietic stem cells

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World Journal of Stem Cells 2021年第6期13卷 594-604页

作者： ion Udroiu Antonella Sgura Department of Science Roma Tre UniversityRome 00146Italy

in the hematopoietic system, a small number of stem cells produce a progeny ofseveral distinct lineages. During ontogeny, they arise in the aorta-gonadmesonephrosregion of the embryo and the placenta, afterwards colonise the liverand finally the bone marrow. After this fetal phase of rapid expansion, thenumber of hematopoietic stem cells continues to grow, in order to sustain theincreasing blood volume of the developing newborn, and eventually reaches asteady-state. The kinetics of this growth are mirrored by the rates of telomereshortening in leukocytes. During adulthood, hematopoietic stem cells undergo avery small number of cell divisions. Nonetheless, they are subjected to aging,eventually reducing their potential to produce differentiated progeny. The causalrelationships between telomere shortening, DNA damage, epigenetic changes,and aging have still to be elucidated.

关键词： Bone marrow Fetus Growth and development Hematopoietic stem cells Leukemia Liver

Performance enhancement of cantilever piezoelectric energy harvesters by sizing analysis

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international Journal of Smart and Nano Materials 2020年第2期11卷 93-116页

作者： Peyman Hajheidari ion Stiharu Rama Bhat Department of Mechanical Industrial and Aerospace Engineering(MIAE)University of ConcordiaMontrealQuébecCanada

This paper presents the results of the performance of piezoelectric cantilever beams in relation to their *** total produced power represents the main indicator of performance of a piezoelectric harvesting system while the area of the beams stays *** design is an important aspect in any industry,mainly in the *** this study,the effects of non-uniformity on the efficiency and power output are *** element method(FEM)with the application of superconvergent element(SCE)is adopted here to solve the *** is observed that the trapezoidal geometry(converging beam)provides a higher output power while the efficiency ***,in order to prove that the power enhancement is achievable while the amount of piezoelectric material consumed is constant the new configuration is *** the configuration,an array of uniform beams connected in series is used instead of one single rectangular *** proposed setting generates an output power of 1.817mWat a resonant frequency of 284.6 Hz when excited by an input acceleration of 1 *** only challenge is the fundamental frequency difference which ismet with the application of proof mass and thinner substrate and piezoelectric layers.

关键词： Piezoelectric energy harvester superconvergent element tapered beam performance enhancement sizing

Berry-Esseen bounds and moderate deviations for the norm, entries and spectral radius of products of positive random matrices

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Science China Mathematics 2024年第3期67卷 627-646页

作者： Hui Xiao ion Grama Quansheng Liu institut fur Mathematik und Angewandte informatik Universitat HildesheimHildesheim 31141Germany Academy of Mathematics and Systems Science Chinese Academy of SciencesBeijing 100190China LMBA Universite Bretagne SudCNRS UMR 6205Vannes F-56000France

Let(g_(n))_(n≥1) be a sequence of independent and identically distributed positive random d×d matrices and consider the matrix product G_(n)=g_(n)…g_*** suitable conditions,we establish the Berry-Esseen bounds on the rate of convergence in the central limit theorem and Cramer-type moderate deviation expansions,for any matrix norm ‖G_(n)‖ of G_(n),its entries G_(n)^(i,j) and its spectral radius ρ(G_(n)).Extended versions of their joint law with the direction of the random walk G_(n)x are also established,where x is a starting point in the unit sphere of R~d.

关键词： Berry-Esseen bound Cramér-type moderate deviation product of random matrices operator norm entry spectral radius