Search results for "frequency [modulation]"
showing 10 items of 569 documents
Fatigue life under non-Gaussian random loading from various models
2004
Fatigue test results on the 10HNAP steel under constant amplitude and random loading with non-Gaussian probability distribution function, zero mean value and wide-band frequency spectrum have been used to compare the life time estimation of the models proposed by Bannantine, Fatemi–Socie, Socie, Wang–Brown, Morel and Łagoda–Macha. Except the Morel proposal which accumulates damage step by step with a proper ethodology, all the other models use a cycle counting method. The rainflow algorithm is used to extract cycles from random histories of damage parameters in time domain. In the last model, where a strain energy density parameter is employed, additionally spectral method is evaluated for …
A novel frequency domain method for predicting fatigue crack growth under wide band random loading
2007
This work deals with the evaluation of the fatigue crack growth rate of structural components subjected to uniaxial Gaussian stationary wide band random loading. In detail, a new frequency domain method that allows the user to estimate the expected crack growth rate directly from the PSD data is proposed. Using a stochastic mean function properly, introduced and described by simple closed form relationships implemented by systematic numerical simulations of a high number of wide band random processes, the proposed method permits to avoid the onerous time domain simulations and provides in general crack growth rate predictions in a good accordance with the so-called time domain method. Pract…
Static and dynamic policies with RFID for the scheduling of retrieval and storage warehouse operations
2013
Warehouses are essential components of logistics and supply chains. The performance of warehouse operations significantly affects the efficiency of the whole chain it belongs to. Radio frequency identification (RFID) is an emerging technology capable of providing real-time information about the location and properties of tagged object(s), such as people, equipment or products. The objective of this article is threefold, to propose and compare different offline and online policies for the scheduling of warehouse operations, to design a tool that allows the decision maker to compare policies and environments without putting them into practice, and to study the benefits that can be obtained if…
Sparsity-aware narrowband interference mitigation and subcarriers selection in OFDM-based cognitive radio networks
2016
In this paper, the performance of an orthogonal frequency division multiplexing overlay cognitive radio network with subcarrier selection schemes is investigated. We propose three subcarrier selection techniques that reduce the level of interference at the primary base station based on collected channel state information from the different network nodes. Approximated outage probability expressions are also derived and verified by simulations for the different studied techniques. In addition, we propose and investigate a new approach for asynchronous narrowband interference (NBI) estimation and mitigation in cognitive radio networks. The proposed approach does not require prior knowledge of …
A Sparsity-Aware Approach for NBI Estimation and Mitigation in Large Cognitive Radio Networks
2016
Underlay cognitive networks should follow strict interference thresholds to operate in parallel with primary networks. This constraint limits their transmission power and eventually the coverage area. Therefore, in this paper, we first design a new approach for asynchronous narrow-band interference (NBI) estimation and mitigation in orthogonal frequency-division multiplexing cognitive radio networks that does not require prior knowledge of the NBI characteristics. Our proposed approach allows the primary user to exploit the sparsity of the secondary users' interference signal to recover it and cancel it based on sparse signal recovery theory. We also propose two subcarrier selection schemes…
Comparative evaluation of pulse width modulation techniques on effective DC link voltage utilization of grid connected inverter
2016
In this paper, comparison between two different Pulse Width Modulation (PWM) techniques employed for three phase voltage source inverter (VSI) is discussed. The three phase voltage source inverter is basic topology used to supply a grid. In this paper we have design a LC filter between the inverter and the grid in order to stabilize the output voltage. The filter gives sinusoidal three phase voltage at the output of the inverter with almost zero/less harmonic distortion. A suitable PWM technique is employed to obtain the required output voltage in the line side of the inverter. The PWM generation techniques used mainly based on sinusoidal based Pulse Width Modulation (SPWM) and Space Vector…
Low stiffness variation in structural systems: identification and localization
2008
When a very low damage occurs, the undamaged structural response totally overlaps the damaged one either in time domain or in frequency domain; on the other hand, by considering some characteristics of the analytical signal, such as the phase, it has been possible to develop a damage identification procedure that allows the identification and localization of damage even if the structure experiences multiple damages at the same time. This procedure is also robust with respect to the presence of measuring noise. In order to assess the validity of the proposed damage identification procedure, numerical applications on single degree of freedom and 2 DOF and 4 DOF are presented using data record…
Geometry-Based Modeling of Wideband Industrial Indoor Radio Propagation Channels
2015
In this paper, we present a geometrical scattering model for a typical class of industrial indoor environments. The proposed industrial reference model takes into account scattering components arising from metallic structures and the surrounding walls of the investigated environment. Starting from the geometrical scattering model, we derive the analytical expressions of the probability density function (PDF) of the angle of arrival (AoA), PDF of the time of arrival (ToA), and the autocorrelation function (ACF) in the frequency domain. The obtained results reveal a large difference between industrial channels and other home and office environments. The theoretical results of the reference mo…
Enhanced LMMSE equalizer for high-speed single frequency network in HSDPA
2011
Currently, considerable interest has been shown in the research and standardization communities in multicell transmission schemes for HSPA, with a number of possible schemes under discussion that include Multiflow, Fast Cell Switching (FCS) and High-Speed Single Frequency Network (HS-SFN). In particular, HS-SFN is a promising technique that not only combines received energy from participating cells, but also reduces intercell interference with low UE complexity. In principle, HS-SFN can be implemented with a small modification to an LMMSE receiver at the UE. This paper introduces a more advanced LMMSE equalizer for High-Speed Single Frequency Network in HSDPA that achieves further performan…
Multiresolution wavelet-based approach to identification of modal parameters of a vehicle full-scale crash test
2012
In this work estimation of vehicle modal parameters was achieved by application of a wavelet-based method. The time-frequency analysis, which comprises those techniques that study a signal in both the time and frequency domains simultaneously, using Morlet wavelet properties are applied to the measured acceleration pulse of the colliding vehicle. Determination of the ridge of the wavelet coefficients matrix makes it possible to identify the frequency components of the recorded crash pulse. Subsequently, by using the estimated natural frequency of the system, the values of damping factor for a given mode shape are assessed. In this work there are concerned both: the major frequencies of the …