Search results for "theory [gamma rays]"
showing 10 items of 976 documents
2D harmonic analysis of the cogging torque in synchronous permanent magnet machines
2004
Presents an approach to determine sources of cogging torque harmonics in permanent magnet electrical machines on the basis of variations of air‐gap magnetic flux density with time and space. The magnetic flux density is determined from the two‐dimensional (2D) finite element model and decomposed into the double Fourier series through the 2D fast Fourier transform (FFT). The real trigonometric form of the Fourier series is used for the purpose to identify those space and time harmonics of magnetic flux density whose involvement in the cogging torque is the greatest relative contribution. Carries out calculations for a symmetric permanent magnet brushless machine for several rotor eccentricit…
A simple unsynchronized two‐end algorithm for faults location and identification in electrical distribution systems
2012
PurposeThe purpose of this paper is to identify a new and simple two‐end algorithm for fault location identification and characterization, in electrical distribution systems.Design/methodology/approachThe developed diagnostic algorithm is based on a simple model of the network using a lumped parameters representation.FindingsTest results have proved the approach to be efficient, allowing a precise fault identification and location while not requiring synchronized measures from the two ends.Research limitations/implicationsThere is a need for measurement systems at all MV/LV substations.Practical implicationsApplicability with limited investments is not possible where metering systems are no…
Transmission line meshes for computational simulation of electromagnetic modes in the Earth's atmosphere
2007
PurposeTwo transmission line meshes to simulate electromagnetic waves in the Earth's atmosphere are developed, one with the link transmission lines connected in parallel and the other with connections in series.Design/methodology/approachThe equations describing propagation of waves through these parallel or series meshes are equivalent to the Maxwell equations for TEr or TMr modes in a spherical cavity with lossy dielectric material between the external conducting surfaces, respectively.FindingsThe transmission line meshes are used for a numerical study of the natural electromagnetic noise due to lightning discharges in the Earth‐ionosphere cavity.Originality/valueThe numerical algorithm f…
A computer‐aided instrument for pattern recognition of partial discharges
1998
In this paper a new computer‐aided digital system for partial discharge (PD) measurements is presented. The system is able to collect a great number of data, up to a pulse repetition rate of 100kHz, during the acquisition phase, thus allowing an off‐line analysis of PD data. After a description of the instrument, some experimental tests performed on epoxy specimens are here presented in terms of amplitude, phase and energy resolved histograms. Finally, emphasis is given to the very interesting use of the instrument for pattern recognition techniques in the discrimination and classification of discharges in HV components.
A Monte Carlo Method for the Auto-Evaluation of the Uncertainties in the Analog-to-Digital Conversion-Based Measurements
2004
This paper concerns with the measurement uncertainty estimation in the analog‐to‐digital conversion‐based instruments. By using an ad hoc developed software tool, the Monte Carlo method is applied in order to assess the uncertainties associated with the measurement results, overcoming the possible inapplicability of the pure theoretical approach prescribed in the ISO – “Guide to the Expression of Uncertainty in Measurement”. By implementing the software tool in the measurement instruments, the proposed approach can be utilized in order to make the instrument itself able to auto‐estimate the measurement uncertainties.
Field‐circuit analysis of construction modifications of a torus‐type PMDC motor
2003
This paper presents the field‐circuit analysis of a disc‐type torus DC motor with permanent magnets. Calculations of the magnetic field are carried out using the finite element method (FEM) in the 3D space. The integral quantities like the ripple‐cogging torque, back electromotive force, flux linkage, self and mutual inductances of the winding are analyzed. The electromagnetic torque is comparatively determined from the Maxwell stress tensor and co‐energy methods. Based on the 3D magnetic field calculations, the lumped‐parameter model of the tested motor is constructed, taking into account an electronic power converter as well. For comparison, various permanent magnet widths and teeth thick…
Turbulence model effect on heat exchange characteristics through the neutron beam window for European spallation source
2011
PurposeThe purpose of this paper is to compare k‐ω shear‐stress transport (SST) and large eddy simulation (LES) turbulence model application effect on numerical computation of flow pattern and heat exchange characteristics through the neutron beam window region for European spallation source setup model.Design/methodology/approachTransient hydrodynamic and thermal calculations with appropriate heat sources are performed using both turbulence models and typical discrepancies in flow and thermal patterns are discussed, as well as, simulation results are qualitatively compared with experimental data for heat transfer coefficient distribution α at the window surface.FindingsContribution of grea…
Las dificultades específicas de aprendizaje en el albor del siglo XXI
2012
El objetivo de este trabajo es acercar al lector la actualidad del debate sobre las dificultades específicas de aprendizaje. La barrera que impone la literatura científica en inglés hace que profesionales y estudiantes universitarios se pierdan los apasionantes avances sobre esta categoría diagnóstica que tan polémica trayectoria ha tenido desde su nacimiento formal. Presentamos las definiciones de las dificultades de aprendizaje que han estado vigentes hasta la primera década del siglo XXI, las nuevas definiciones y discutimos dos características de la historia de las definiciones en este campo. Concluimos con las exigencias que plantean las nuevas formulaciones. The purpose of this articl…
Los hábitos lectores en inglés de futuros maestros: Implicaciones didácticas
2014
Se presenta un estudio exploratorio y descriptivo sobre los hábitos lectores en inglés de estudiantes universitarios españoles para detectar cuáles son las áreas de atención prioritaria para poder seguir un Grado en inglés según el EEES. Se midió el nivel de inglés mediante el Oxford Online Placement Test. Se evaluaron los hábitos lectores y el tipo de materiales académicos que los estudiantes leen en inglés mediante un cuestionario. Gran parte de la muestra se encontraba en los niveles elementales e intermedios de dominio del inglés. Un porcentaje muy elevado de estudiantes declaró no tener el hábito de leer en inglés y leer solo materiales académicos obligatorios. Sin embargo, existe una …
Epigenomic k-mer dictionaries: shedding light on how sequence composition influences in vivo nucleosome positioning
2014
Abstract Motivation: Information-theoretic and compositional analysis of biological sequences, in terms of k-mer dictionaries, has a well established role in genomic and proteomic studies. Much less so in epigenomics, although the role of k-mers in chromatin organization and nucleosome positioning is particularly relevant. Fundamental questions concerning the informational content and compositional structure of nucleosome favouring and disfavoring sequences with respect to their basic building blocks still remain open. Results: We present the first analysis on the role of k-mers in the composition of nucleosome enriched and depleted genomic regions (NER and NDR for short) that is: (i) exhau…