20 research outputs found
Analysis of financial indices by means of the windowed Fourier transform
The goal of this study is to analyze the dynamical
properties of financial data series from nineteen worldwide
stock market indices (SMI) during the period 1995–2009.
SMI reveal a complex behavior that can be explored since it
is available a considerable volume of data. In this paper is
applied the window Fourier transform and methods of fractional
calculus. The results reveal classification patterns typical
of fractional order systems
Power law analysis of financial index dynamics
Power law PL and fractional calculus are two faces of phenomena with long memory behavior.
This paper applies PL description to analyze different periods of the business cycle. With such
purpose the evolution of ten important stock market indices DAX, Dow Jones, NASDAQ, Nikkei,
NYSE, S&P500, SSEC, HSI, TWII, and BSE over time is studied. An evolutionary algorithm is
used for the fitting of the PL parameters. It is observed that the PL curve fitting constitutes a good
tool for revealing the signal main characteristics leading to the emergence of the global financial
dynamic evolution
Analysis of stock market indices through multidimensional scaling
We propose a graphical method to visualize possible time-varying correlations between fifteen
stock market values. The method is useful for observing stable or emerging clusters of
stock markets with similar behaviour. The graphs, originated from applying multidimensional
scaling techniques (MDS), may also guide the construction of multivariate econometric
models
Analysis of stock market indices with multidimensional scaling and wavelets
Stock market indices SMIs are important measures of financial and economical performance.
Considerable research efforts during the last years demonstrated that these signals have a chaotic
nature and require sophisticated mathematical tools for analyzing their characteristics. Classical
methods, such as the Fourier transform, reveal considerable limitations in discriminating different
periods of time. This paper studies the dynamics of SMI by combining the wavelet transform
and the multidimensional scaling MDS . Six continuous wavelets are tested for analyzing the
information content of the stock signals. In a first phase, the real Shannon wavelet is adopted for
performing the evaluation of the SMI dynamics, while their comparison is visualized by means of
the MDS. In a second phase, the other wavelets are also tested, and the corresponding MDS plots
are analyzed
Analysis of financial data series using fractional Fourier transform and multidimensional scaling
The goal of this study is the analysis of
the dynamical properties of financial data series from
worldwide stock market indexes during the period
2000–2009. We analyze, under a regional criterium,
ten main indexes at a daily time horizon. The methods
and algorithms that have been explored for the
description of dynamical phenomena become an effective
background in the analysis of economical data.
We start by applying the classical concepts of signal
analysis, fractional Fourier transform, and methods of
fractional calculus. In a second phase we adopt the
multidimensional scaling approach. Stock market indexes
are examples of complex interacting systems for
which a huge amount of data exists. Therefore, these
indexes, viewed from a different perspectives, lead to
new classification patterns
Heart rate variability behavior in athletes after a sports concussion: A systematic review
Objective
This systematic review aims to investigate the adaptations of the autonomic nervous system (ANS) after a concussion by measuring HRV in athletes over the age of 16 after injury.
Methods
This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). Web of Science, Pubmed, SCOPUS, and Sport Discus were searched using predefined search terms to identify relevant original cross-sectional, longitudinal, and cohort epidemiological studies published before December 2021.
Results
After screening 1737 potential articles, four studies met the inclusion criteria. Studies included participants with concussion (n = 63) and healthy control athletes (n = 140) who practised different sports. Two studies describe a decrease in HRV following a sports concussion, and one proposed that the resolution of symptoms does not necessarily reflect ANS recovery. Lastly, one study concluded that submaximal exercise induces alteration in ANS, not seen in rest after an injury.
Conclusions
In the frequency domain, a decrease in high frequency power and an increase of low frequency/high frequency ratio is expected, as the activity of the sympathetic nervous system increases, and the parasympathetic nervous system decreases after injury. In the frequency domain, heart rate variability (HRV) may help monitor the activity of ANS evaluating signals of somatic tissue distress and early identification of other types of musculoskeletal injuries. Further research should investigate the relationship between HRV and other musculoskeletal injuries.info:eu-repo/semantics/publishedVersio
Identifying economic periods and crisis with the multidimensional scaling
This paper applied MDS and Fourier transform
to analyze different periods of the business cycle.
With such purpose, four important stock market
indexes (Dow Jones, Nasdaq, NYSE, S&P500) were
studied over time. The analysis under the lens of the
Fourier transform showed that the indexes have characteristics
similar to those of fractional noise. By the
other side, the analysis under the MDS lens identified
patterns in the stock markets specific to each economic
expansion period. Although the identification
of patterns characteristic to each expansion period is
interesting to practitioners (even if only in a posteriori
fashion), further research should explore the meaning
of such regularities and target to find a method to estimate
future crisis
Manual de Procedimentos de Trabalho de Campo em Pomares de Cajueiro na Guiné-Bissau
O projeto TCP/GBS/3081 “Apoio à luta contra doenças e
pragas do cajueiro na Guiné-Bissau” é uma iniciativa da delegação
da FAO na Guiné-Bissau, que conta com a colaboração e apoio
técnico-científico dos parceiros portugueses da Universidade de
Lisboa, em particular do cE3c (Centre for Ecology, Evolution and
Environmental Changes / Faculdade de Ciências) e o LEAF (Linking
Landscape, Environment, Agriculture and Food / Instituto Superior
de Agronomia).
Este projeto tem como objetivo geral identificar os inimigos do
cajueiro na Guiné-Bissau, determinar a sua incidência, severidade,
e impacto na produtividade dos pomares, com o objetivo final de
propor medidas de mitigação e disseminação contra as principais
doenças, pragas e parasitas do cajueiro identificados no paísinfo:eu-repo/semantics/publishedVersio