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Search Results: 1 - 10 of 130398 matches for " V. Perina "
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Classification of Jaw Bone Cysts and Necrosis via the Processing of Orthopantomograms
J. Mikulka,E. Gescheidtova,M. Kabrda,V. Perina
Radioengineering , 2013,
Abstract: The authors analyze the design of a method for automatized evaluation of parameters in orthopantomographic images capturing pathological tissues developed in human jaw bones. The main problem affecting the applied medical diagnostic procedures consists in low repeatability of the performed evaluation. This condition is caused by two aspects, namely subjective approach of the involved medical specialists and the related exclusion of image processing instruments from the evaluation scheme. The paper contains a description of the utilized database containing images of cystic jaw bones; this description is further complemented with appropriate schematic repre sentation. Moreover, the authors present the results of fast automatized segmentation realized via the live-wire method and compare the obtained data with the results provided by other segmentation techniques. The shape parameters and the basic statistical quantities related to the distribution of intensities in the segmented areas are selected. The evaluation results are provided in the final section of the study; the authors correlate these values with the subjective assessment carried out by radiologists. Interestingly, the paper also comprises a discussion presenting the possibility of using selected parameters or their combinations to execute automatic classification of cysts and osteonecrosis. In this context, a comparison of various classifiers is performed, including the Decision Tree, Naive Bayes, Neural Network, k-NN, SVM, and LDA classifica tion tools. Within this comparison, the highest degree of accuracy (85% on the average) can be attributed to the Decision Tree, Naive Bayes, and Neural Network classifiers
1/N-expansion and nonclassical state generation in higher-order anharmonic oscillators
Kirill N. Alekseev,Natasha V. Alekseeva,Jan Perina
Physics , 1998,
Abstract: Paper is withdrawn
Quantum-classical correspondence and nonclassical states generation in dissipative quantum optical systems
Kirill N. Alekseev,Natasha V. Alekseeva,Jan Perina
Physics , 1999, DOI: 10.1134/1.559142
Abstract: We develop a semiclassical method for the determination of the nonlinear dynamics of dissipative quantum optical systems in the limit of large number of photons N, based on the 1/N-expansion and the quantum-classical correspondence. The method has been used to tackle two problems: to study the dynamics of nonclassical state generation in higher-order anharmonic dissipative oscillators and to establish the difference between the quantum and classical dynamics of the second-harmonic generation in a self-pulsing regime. In addressing the first problem, we have obtained an explicit time dependence of the squeezing and the Fano factor for an arbitrary degree of anharmonism in the short-time approximation. For the second problem, we have established analytically a characteristic time scale when the quantum dynamics differs insignificantly from the classical one.
Statistics of light in Raman and Brillouin nonlinear couplers
J. Perina, Jr.,J. Perina
Physics , 1999, DOI: 10.1088/1355-5111/9/3/013
Abstract: Statistical properties of optical fields in nonlinear couplers composed of two waveguides in which Raman or Brillouin processes (with classical pumping) are in operation and which are mutually connected through the Stokes and/or anti-Stokes linear interactions are investigated within the framework of generalized superposition of coherent fields and quantum noise. Heisenberg equations describing the couplers are solved both analytically under special conditions and numerically in general cases. Regimes for nonclassical properties of optical fields, such as sub-Poissonian photon-number statistics, negative reduced moments of integrated intensity and squeezing of quadrature fluctuations are discussed for the cases of single and compound fields. General results are compared with those from short-length approximation.
Dispersion in Femtosecond Entangled Two-Photon Interference
J. Perina, Jr.,A. V. Sergienko,B. M. Jost,B. E. A. Saleh,M. C. Teich
Physics , 1998, DOI: 10.1103/PhysRevA.59.2359
Abstract: We theoretically investigate the quantum interference of entangled two-photon states generated in a nonlinear crystal pumped by femtosecond optical pulses. Interference patterns generated by the polarization analog of the Hong-Ou-Mandel interferometer are studied. Attention is devoted to the effects of the pump-pulse profile (pulse duration and chirp) and the second-order dispersion in both the nonlinear crystal and the interferometer's optical elements. Dispersion causes the interference pattern to have an asymmetric shape. Dispersion cancellation occurs in some cases.
The extended structure of the dwarf irregular galaxy Sagittarius
G. Beccari,M. Bellazzini,F. Fraternali,G. Battaglia,S. Perina,A. Sollima,T. A. Oosterloo,V. Testa,S. Galleti
Physics , 2014, DOI: 10.1051/0004-6361/201424411
Abstract: We present a detailed study of the stellar and HI structure of the dwarf irregular galaxy Sagittarius. We use new deep and wide field photometry to trace the surface brightness profile of the galaxy out to ~5.0' (corresponding to ~1600 pc) and down to $\mu_V\simeq 30.0$ mag/arcsec$^2$, thus showing that the stellar body of the galaxy is much more extended than previously believed, and it is similarly (or more) extended than the overall HI distribution. The whole major-axis profile is consistent with a pure exponential, with a scale radius of $\simeq 340$ pc. The surface density maps reveal that the distribution of old and intermediate-age stars is smooth and remarkably flattened out to its edges, while the associated HI has a much rounder shape, is off-centred and presents multiple density maxima and a significant hole. No clear sign of systemic rotation is detectable in the complex HI velocity field. No metallicity gradient is detected in the old and intermediate age population of the galaxy, and we confirm that this population has a much more extended distribution than young stars (age$\lt 1$ Gyr).
Invitado especial Seguridad territorial vs. Seguridad democrática Notas sobre la controversia colombo-ecuatoriana
Rubén M. Perina
AD-minister , 2008,
Abstract: .
Aquisi o lexical no desenvolvimento normal e alterado de linguagem: um estudo experimental
Juliana Perina Gandara
Revista da Sociedade Brasileira de Fonoaudiologia , 2008, DOI: 10.1590/s1516-80342008000200018
Abstract:
Interplay of creation, propagation, and relaxation of an excitation in a dimer
J. Perina, Jr.
Physics , 1999,
Abstract: Interplay of simultaneous creation, annihilation, propagation, and relaxation of an excitation in molecular condensates interacting with an ultrashort quantum optical pulse is studied in general and specialized to a dimer. A microscopic model appropriate for such systems (with strong exciton-phonon coupling) is presented. It also incorporates effects of (quantum) noise in the optical field. A variety of new features in the initial stage of excitation dynamics (when it is being created) is revealed; a strong influence of the coherent excitation propagation on the processes of excitation creation and annihilation in a molecule strongly interacting with phonons is the most remarkable one.
Quantum properties of counter-propagating two-photon states generated in a planar waveguide
Jan Perina Jr
Physics , 2007, DOI: 10.1103/PhysRevA.77.013803
Abstract: A nonlinear planar waveguide pumped by a beam orthogonal to its surface may serve as a versatile source of photon pairs. Changing pump-pulse duration, pump-beam transverse width, and angular decomposition of pump-beam frequencies characteristics of a photon pair including spectral widths of signal and idler fields, their time durations as well as degree of entanglement of two fields can be changed significantly. Using the measured spectral widths of the down-converted fields and width of a coincidence-count dip in a Hong-Ou-Mandel interferometer entropy of entanglement can be determined.
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