Search results for "Frequency domain"
showing 10 items of 141 documents
Rotational Raman spectroscopy of ethylene using a femtosecond time-resolved pump-probe technique.
2005
154309; Femtosecond Raman-induced polarization spectroscopy (RIPS) was conducted at low pressure (250 mb at 295 K and 400 mb at 373 K) in ethylene. The temporal signal, resulting from the beating between pure rotational coherences, was measured with a heterodyne detection. The temporal traces were converted to the frequency domain using a Fourier transformation and then analyzed thanks to the D2hTDS software (http://www.u-bourgogne.fr/LPUB/shTDS.html) dedicated to X2Y4 molecules with D2h symmetry. The effective Hamiltonian was expanded up to order 2, allowing the determination of five parameters with an rms of 0.017 cm(-1). Special care was taken in the precise modeling of intensities, taki…
Monitoring of the action of drugs in melanoma cells by dynamic laser speckle
2014
Abstract. This work presents the development of a protocol based on the dynamic laser speckle designed tomonitor the reaction of cancer cells of line MEL-RC08 to the application of the drug Colcemid in two differentconcentrations: 0.2 and 0.4 μg∕mL. The protocol was designed using the forward scattering approach with anHe-Ne laser of 632.8 nm illuminating the samples, a control, and two variations of Colcemid, being monitoredalong 8 h. The data were analyzed numerically in the time and in the frequency domain, and the results pre-sented the ability of the technique to monitor the action of the drug, particularly Colcemid (0.4 μg∕mL). © 2014Society of Photo-Optical Instrumentation Engineers …
Wavelet-based efficient simulation of electromagnetic transients in a lightning protection system
2003
In this paper, a wavelet-based efficient simulation of electromagnetic transients in a lightning protection systems (LPS) is presented. The analysis of electromagnetic transients is carried out by employing the thin-wire electric field integral equation in frequency domain. In order to easily handle the boundary conditions of the integral equation, semiorthogonal compactly supported spline wavelets, constructed for the bounded interval [0,1], have been taken into account in expanding the unknown longitudinal currents. The integral equation is then solved by means of the Galerkin method. As a preprocessing stage, a discrete wavelet transform is used in order to efficiently compress the Fouri…
Stochastic response determination of structural systems modeled via dependent coordinates: a frequency domain treatment based on generalized modal an…
2019
Generalized independent coordinates are typically utilized within an analytical dynamics framework to model the motion of structural and mechanical engineering systems. Nevertheless, for complex systems, such as multi-body structures, an explicit formulation of the equations of motion by utilizing generalized, independent, coordinates can be a daunting task. In this regard, employing a set of redundant coordinates can facilitate the formulation of the governing dynamics equations. In this setting, however, standard response analysis techniques cannot be applied in a straightforward manner. For instance, defining and determining a transfer function within a frequency domain response analysis…
Discrete frequency models for inventory management – an introduction
2001
Abstract The paper deals with the problem of devising a periodic replenishment policy when orders must be periodic, but only a given, discrete set of order frequencies can be used. The multi-item, instantaneous replenishment case with known demand is studied. In particular, staggering policies somehow arranging replenishments not to come at the same time instants are considered. The paper is composed of three parts: first, a taxonomy of several versions of the discrete frequency problem is proposed, according to different elements; in the second part, a general mixed integer programming model is proposed which is able to capture the peculiarities of the whole spectrum of this kind of proble…
CNN based Gearbox Fault Diagnosis and Interpretation of Learning Features
2021
Machine learning based fault diagnosis schemes have been intensively proposed to deal with faults diagnosis of rotating machineries such as gearboxes, bearings, and electric motors. However, most of the machine learning algorithms used in fault diagnosis are pattern recognition tools, which can classify given data into two or more classes. The underlined physical phenomena in fault diagnosis are not directly interpretable in machine learning schemes, thus it is usually called black/gray box models. In this study, convolutional neural networks (CNN) machine learning algorithm is proposed to classify gearbox faults, and the learning features of the CNN filters are visualized to understand the…
An Advanced Numerical Model in Solving Thin-Wire Integral Equations by Using Semi-Orthogonal Compactly Supported Spline Wavelets
2003
Abstract—In this paper, the semi-orthogonal compactly sup- ported spline wavelets are used as basis functions for the efficient solution of the thin-wire electric field integral equation (EFIE) in frequency domain. The method of moments (MoM) is used via the Galerkin procedure. Conventional MoM directly applied to the EFIE, leads to dense matrix which often becomes computation- ally intractable when large-scale problems are approached. To overcome these difficulties, wavelets can be used as a basis set so obtaining the generation of a sparse matrix; this is due to the local supports and the vanishing moments properties of the wavelets. In the paper, this technique is applied to analyze elec…
Evaluation of time domain electromagnetic fields radiated by constant velocity moving particles traveling along an arbitrarily shaped cross-section w…
2012
[1] A technique for the accurate computation of the time domain electromagnetic fields radiated by a charged distribution traveling along an arbitrarily shaped waveguide region is presented. Based on the transformation (by means of the standard Fourier analysis) of the time-varying current density of the analyzed problem to the frequency domain, the resulting equivalent current is further convolved with the dyadic electric and magnetic Green’s functions. Moreover, we show that only the evaluation of the transverse magnetic modes of the structure is required for the calculation of fields radiated by particles traveling in the axial direction. Finally, frequency domain electric and magnetic f…
A simulation model for electromagnetic transients in lightning protection systems
2002
This paper deals with the evaluation of electromagnetic transients in a lightning protection system (LPS). A field approach is used, based on the numerical solution of a modified version of the thin-wire electric field integral equation in the frequency domain. Time profiles of interesting electromagnetic quantities are computed by using a discrete fast Fourier transform algorithm. The model takes into account coupling effects among aerial parts and ground electrodes in order to correctly estimate the quantities which can determine electromagnetic hazard inside the LPS; transient touch and step voltages can be easily evaluated also taking into account the human body presence on the soil sur…
An Investigation of the Cutting Process for Chip Breaking Monitoring in Turning of Steels
1998
This paper presents some results of an experimental study on chip breaking monitoring when turning steels with chip forming inserts. In the first part of this study the recognition of chip forms by means of cutting force analysis in the frequency domain is described. Generally, the present work is concerned with the use of the interface control factor for determining the transition from unacceptable chip forms to the chip breaking. For this purpose experiments under approximately orthogonal machining conditions including measuring the shear strain, the cutting energy and the average interface temperature are carried out. The obtained results confirmed that the initiation of acceptable chip …