Search results for "harmonic"
showing 10 items of 984 documents
A sharp estimate for Neumann eigenvalues of the Laplace-Beltrami operator for domains in a hemisphere
2018
Here, we prove an isoperimetric inequality for the harmonic mean of the first [Formula: see text] non-trivial Neumann eigenvalues of the Laplace–Beltrami operator for domains contained in a hemisphere of [Formula: see text].
Flat bands, Dirac cones, and atom dynamics in an optical lattice
2010
We study atoms trapped with a harmonic confinement in an optical lattice characterized by a flat band and Dirac cones. We show that such an optical lattice can be constructed which can be accurately described with the tight binding or Hubbard models. In the case of fermions the release of the harmonic confinement removes fast atoms occupying the Dirac cones while those occupying the flat band remain immobile. Using exact diagonalization and dynamics we demonstrate that a similar strong occupation of the flat band does not happen in bosonic case and furthermore that the mean field model is not capable for describing the dynamics of the boson cloud.
Investigation about selective harmonic elimination in unbalanced multilevel inverters
2022
In this paper 5 and 7 levels cascaded H-bridges inverters are considered, feeding by unequal dc voltage sources. The effect of these unbalancing operation is examined concerning harmonic analysis and total harmonic distortion of the output voltages. The system of equations, obtained by the expansion in the Fourier series of phase output voltage, is solved by applying a method of graphic solution that allows obtaining the switching angles able to eliminate the lower order harmonics.
High-Order Harmonics Generation in Atomic and Molecular Zinc Plasmas
2021
We demonstrate the variations of single harmonic resonance enhancement during high-order harmonics generation in zinc-containing atomic and molecular species at the conditions of single-color and two-color pumps of laser-induced plasmas by applying different laser sources. We show how selenides of this metal notably modify the enhancement of single (9th, 15th or 16th) harmonic compared with purely atomic zinc plasmas. The variations of single harmonic enhancement are demonstrated using fixed (806 nm) and tunable (1280–1440 nm) radiation.
Nonlinear Disorder Mapping Through Three-Wave Mixing
2010
We implement a simple and powerful approach to characterize the domain distribution in the bulk of quadratic ferroelectric crystals via far-field second-harmonic spectroscopy. The approach is demonstrated in a lithium tantalate sample with periodic electric field poling and random mark-to-space ratio.
A novel improved matlab-based software for the electric and magnetic analysis and design of rotating electrical machines
2015
The aim of this paper is to present a software for the analysis and design of windings of rotating electrical machines, considering both the electric and the magnetic specifications on the machine. The considered machines are induction motors (IM) and PM synchronous motors (PMSM). The software accounts for the case of buried magnets (IPMSM), but with some limits, because the calculations require a much more detailed analysis regarding the magnetic circuit. However, this initial limitation of the software, that will be removed in a later version, does not constitute a major limitation as confirmed by the examples presented in this paper.
Current status on the adoption of high energy devices in Italy. An Italian Society for Endoscopic Surgery and New Technologies (SICE) national survey
2021
Background: In the past three decades, different High Energy Devices (HED) have been introduced in surgical practice to improve the efficiency of surgical procedures. HED allow vessel sealing, coagulation and transection as well as an efficient tissue dissection. This survey was designed to verify the current status on the adoption of HED in Italy. Methods: A survey was conducted across Italian general surgery units. The questionnaire was composed of three sections (general information, elective surgery, emergency surgery) including 44 questions. Only one member per each surgery unit was allowed to complete the questionnaire. For elective procedures, the survey included questions on thyroid…
Verbesserte Orts- und Kontrastauflösung in der Ultraschalldiagnostik durch Nutzung Harmonischer Frequenzen
2001
Background: The aim of new techniques in head and neck sonography is to increase the sensitivity and the specificity of the examination, With tissue harmonic imaging (THI) and contrast harmonic imaging (CHI) new techniques are available which allow increased contrast and resolution in head and neck sonography as well as a better detection of small blood vessels. Methods: We studied whether these techniques improve sonographic detection of head and neck lymph nodes and primary tumours of the upper aerodigestive tract. Results: The results indicate that THI allows a better detection of cervical lymph nodes. Furthermore, intranodal structures and the borders of the lymph node can be better det…
Third-harmonic generation in optical microfibers
2012
We explain the relatively easy, wideband, THG conversion that we observe experimentally in silica glass microfibers by the tapering geometry. As a challenging perspective, we compare THG effective efficiencies in silica and tellurite glasses.
Quadrature domains for the Helmholtz equation with applications to non-scattering phenomena
2022
In this paper, we introduce quadrature domains for the Helmholtz equation. We show existence results for such domains and implement the so-called partial balayage procedure. We also give an application to inverse scattering problems, and show that there are non-scattering domains for the Helmholtz equation at any positive frequency that have inward cusps.