Search results for "FREQUENCY"
showing 10 items of 2158 documents
On the error sequences of M-ary FSK modulation schemes over Nakagami-m fading channels
2012
In this paper, we have studied some important statistical properties of error sequences of M-ary orthogonal frequency-shift keying (FSK) modulation schemes over Nakagami-m fading channels. We have derived the joint probability density function (PDF) of error sequences of arbitrary length. From the joint PDF, we have found an analytical solution for the autocorrelation function (ACF) of the error sequences. The correctness of the analytical expression for the ACF of error sequences has been confirmed by simulations, where the simulation results are obtained by using the sum-of-sinusoids principle. The derived joint PDF of error sequences is useful for the development of first-order and highe…
Analysis of Fresnel Zone Plates Focusing Dependence on Operating Frequency
2017
[EN] The focusing properties of Fresnel Zone Plates (FZPs) against frequency are analyzed in this work. It is shown that the FZP focal length depends almost linearly on the operating frequency. Focal depth and focal distortion are also considered, establishing a limit on the frequency span at which the operating frequency can be shifted. An underwater FZP ultrasound focusing system is demonstrated, and experimental results agree with the theoretical analysis and simulations.
Diagrammatic expansion for positive density-response spectra: Application to the electron gas
2015
In a recent paper [Phys. Rev. B 90, 115134 (2014)] we put forward a diagrammatic expansion for the self-energy which guarantees the positivity of the spectral function. In this work we extend the theory to the density response function. We write the generic diagram for the density-response spectrum as the sum of partitions. In a partition the original diagram is evaluated using time-ordered Green's functions (GF) on the left-half of the diagram, antitime-ordered GF on the right-half of the diagram and lesser or greater GF gluing the two halves. As there exist more than one way to cut a diagram in two halves, to every diagram corresponds more than one partition. We recognize that the most co…
G-protein-coupled receptor kinase 5 polymorphism and Takotsubo cardiomyopathy.
2015
BACKGROUND: Takotsubo cardiomyopathy (TTC) is an increasingly reported clinical syndrome that mimics acute myocardial infarction without obstructive coronary artery disease and is characterized by transient systolic dysfunction of the apical and/or mid-segments of the left ventricle. The syndrome mainly occurs in postmenopausal women with high adrenergic state conditions. Nowadays, the pathophysiology of TTC is not yet known and the possibility of a genetic predisposition is controversial. AIMS: The purpose of this study was to assess the genetic susceptibility to TTC through analysis of the L41Q polymorphism of the G-protein-coupled receptor kinase 5 (GRK5). METHODS AND RESULTS: In a cohor…
The Use of GAMLSS Framework for a Non-Stationary Frequency Analysis of Annual Runoff Data over a Mediterranean Area
2022
Climate change affects all the components of the hydrological cycle. Starting from precipitation distribution, climate alterations have direct effects on both surface water and groundwater in terms of their quantity and quality. These effects lead to modifications in water availability for agriculture, ecology and other social uses. Change in rainfall patterns also affects the runoff of natural rivers. For this reason, studying runoff data according to classical hydrological approaches, i.e., statistical inference methods that exploit stationary probability distributions, might result in missing important information relevant to climate change. From this point of view, a new approach has to…
A “Best Current Practice” for 3GPP-based cellular system security
2014
This paper is an attempt at formulating a Best Current Practice (BCP) for access security and a baseline for core network security in the 3GPP-based systems. This encompasses the 2G circuit-switched GSM system, the 2.5G packet-switched GPRS system, the 3G UMTS system and the 4G LTE/LTE-A system. The 3GPP have defined several security standards, but many measures are optional and there are several areas deliberately not covered by the 3GPP standards. The present document is therefore an attempt at pointing out the best available options and providing advice on how to achieve an overall system hardening, which is badly needed as the cellular systems have undoubtedly become one of the most cri…
Absence of spatial genetic structure in common dentex (Dentex dentex Linnaeus, 1758) in the Mediterranean Sea as evidenced by nuclear and mitochondri…
2018
International audience; The common dentex, Dentex dentex, is a fish species which inhabits marine environments in the Mediterranean and Northeast Atlantic regions. This is an important species from an ecological, economic and conservation perspective, however critical information on its population genetic structure is lacking. Most samples were obtained from the Mediterranean Sea (17 sites) with an emphasis around Corsica (5 sites), plus one Atlantic Ocean site. This provided an opportunity to examine genetic structuring at local and broader scales to provide science based data for the management of fishing stocks in the region. Two mitochondrial regions were examined (D-loop and COI) along…
Weak warning signals can persist in the absence of gene flow.
2019
Significance With our comprehensive set of field (model survival), laboratory (controlled learning, palatability, toxin analysis), and molecular data, we provide evidence that polymorphism can persist in an aposematic population, despite expectations of positive frequency-dependent selection. We show that this can happen if prey species carrying a strong signal can exploit predator learning to elicit broad avoidance of many signals, even if predators only have experience with a single signal. This could allow novel signals to be protected within a population of aposematic prey. Thus, under the expectations of broad generalization coupled with limited gene flow, weak aposematic signals can p…
WiWeHAR: Multimodal Human Activity Recognition Using Wi-Fi and Wearable Sensing Modalities
2020
Robust and accurate human activity recognition (HAR) systems are essential to many human-centric services within active assisted living and healthcare facilities. Traditional HAR systems mostly leverage a single sensing modality (e.g., either wearable, vision, or radio frequency sensing) combined with machine learning techniques to recognize human activities. Such unimodal HAR systems do not cope well with real-time changes in the environment. To overcome this limitation, new HAR systems that incorporate multiple sensing modalities are needed. Multiple diverse sensors can provide more accurate and complete information resulting in better recognition of the performed activities. This article…
A Machine Learning Approach for Fall Detection Based on the Instantaneous Doppler Frequency
2019
Modern societies are facing an ageing problem that is accompanied by increasing healthcare costs. A major share of this ever-increasing cost is due to fall-related injuries, which urges the development of fall detection systems. In this context, this paper paves the way for the development of radio-frequency-based fall detection systems, which do not require the user to wear any device and can detect falls without compromising the user's privacy. For the design of such systems, we present an activity simulator that generates the complex path gain of indoor channels in the presence of one person performing three different activities: slow fall, fast fall, and walking. We have developed a mac…