Search results for "frequency [modulation]"
showing 10 items of 569 documents
Regional frequency analysis of extreme rainfall in Sicily (Italy)
2018
Surface Cyclones in the ERA-40 Dataset (1958–2001). Part I: Novel Identification Method and Global Climatology
2006
Abstract A novel method is introduced to generate climatological frequency distributions of meteorological features from gridded datasets. The method is used here to derive a climatology of extratropical cyclones from sea level pressure (SLP) fields. A simple and classical conception of cyclones is adopted where a cyclone is identified as the finite area that surrounds a local SLP minimum and is enclosed by the outermost closed SLP contour. This cyclone identification procedure can be applied to individual time instants, and climatologies of cyclone frequency, fc, are obtained by simple time averaging. Therefore, unlike most other climatologies, the method is not based on the application of…
Artifacts and Errors in Cross-Spectrum Phase Noise Measurements : Invited lecture
2021
Inserting an attenuator between the oscillator under test and the phase noise analyzer, one expects that the white phase noise increases monotonically with the attenuation. By contrast, we observe that with some oscillators the white noise has sharp minimum for a given value of the attenuation, which clearly indicates problem. With other oscillators, it increases monotonically with the attenuation, but the values are not consistent with the thermal energy introduced by the attenuator. In both cases artifacts are present, which takes the form of a sharp notch in the spectrum, occurring where the white FM noise crosses the white PM noise. Such anomalous behavior is the tip of the iceberg, and…
On the Design of Probe Signals in Wireless Acoustic Sensor Networks Self-Positioning Algorithms
2018
A wireless acoustic sensor network comprises a distributed group of devices equipped with audio transducers. Typically, these devices can interoperate with each other using wireless links and perform collaborative audio signal processing. Ranging and self-positioning of the network nodes are examples of tasks that can be carried out collaboratively using acoustic signals. However, the environmental conditions can distort the emitted signals and complicate the ranging process. In this context, the selection of proper acoustic signals can facilitate the attainment of this goal and improve the localization accuracy. This letter deals with the design and evaluation of acoustic probe signals all…
Detection of steering direction using EEG recordings based on sample entropy and time-frequency analysis.
2016
Monitoring driver's intentions beforehand is an ambitious aim, which will bring a huge impact on the society by preventing traffic accidents. Hence, in this preliminary study we recorded high resolution electroencephalography (EEG) from 5 subjects while driving a car under real conditions along with an accelerometer which detects the onset of steering. Two sensor-level analyses, sample entropy and time-frequency analysis, have been implemented to observe the dynamics before the onset of steering. Thus, in order to classify the steering direction we applied a machine learning algorithm consisting of: dimensionality reduction and classification using principal-component-analysis (PCA) and sup…
Diffusion of Drone Journalism: the Case of Finland, 2011-2020
2020
This article details Finnish news organizations’ adoption of drones for journalistic purposes from 2011 to 2020. The theoretical starting point of the article is Rogers’ (1962) diffusion of innovations theory, which explains how new ideas and technologies spread in societies. The main empirical data for the study were derived from a phone survey conducted among the 80 most popular newspapers in Finland. The findings reveal that drone journalism in Finland has already diffused from a few pioneering organizations to a large number of newsrooms, including regional, mid-sized newspapers. Most of the newspapers are either using in-house drones, buying commissioned images, or using both strategie…
Low-complexity AoA and AoD Estimation in the Transformed Spatial Domain for Millimeter Wave MIMO Channels
2021
High-accuracy angle of arrival (AoA) and angle of departure (AoD) estimation is critical for cell search, stable communications and positioning in millimeter wave (mmWave) cellular systems. Moreover, the design of low-complexity AoA/AoD estimation algorithms is also of major importance in the deployment of practical systems to enable a fast and resource-efficient computation of beamforming weights. Parametric mmWave channel estimation allows to describe the channel matrix as a combination of direction-dependent signal paths, exploiting the sparse characteristics of mmWave channels. In this context, a fast Transformed Spatial Domain Channel Estimation (TSDCE) algorithm was recently proposed …
Emergence of statistically validated financial intraday lead-lag relationships
2014
According to the leading models in modern finance, the presence of intraday lead-lag relationships between financial assets is negligible in efficient markets. With the advance of technology, however, markets have become more sophisticated. To determine whether this has resulted in an improved market efficiency, we investigate whether statistically significant lagged correlation relationships exist in financial markets. We introduce a numerical method to statistically validate links in correlation-based networks, and employ our method to study lagged correlation networks of equity returns in financial markets. Crucially, our statistical validation of lead-lag relationships accounts for mult…
Accessing finite momentum excitations of the one-dimensional Bose-Hubbard model using superlattice modulation spectroscopy
2018
We investigate the response to superlattice modulation of a bosonic quantum gas confined to arrays of tubes emulating the one-dimensional Bose-Hubbard model. We demonstrate, using both time-dependent density matrix renormalization group and linear response theory, that such a superlattice modulation gives access to the excitation spectrum of the Bose-Hubbard model at finite momenta. Deep in the Mott-insulator, the response is characterized by a narrow energy absorption peak at a frequency approximately corresponding to the onsite interaction strength between bosons. This spectroscopic technique thus allows for an accurate measurement of the effective value of the interaction strength. On th…
Measuring High-Order Interactions in Rhythmic Processes Through Multivariate Spectral Information Decomposition
2021
Many complex systems in physics, biology and engineering are modeled as dynamical networks and described using multivariate time series analysis. Recent developments have shown that the emergent dynamics of a network system are significantly affected by interactions involving multiple network nodes which cannot be described using pairwise links. While these higher-order interactions can be probed using information-theoretic measures, a rigorous framework to describe them in the frequency domain is still lacking. This work presents an approach for the spectral decomposition of multivariate information measures, capable of identifying higher-order synergistic and redundant interactions betwee…