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Communication technology have advanced quickly since the COVID-19 epidemic started, providing consumers with additional benefits and conveniences. Concerns over the privacy and confidentiality of this data have grown in importance as initiatives that promote the use of audio and video to enhance interpersonal interactions become more common. In the context of the Internet of Things (IoT), audio communications security is essential in the biomedical domain. Sensitive medical data may be compromised in these connections, which include exchanges between patients and doctors and broadcasts of vital signs. To protect patient privacy and reduce cybersecurity threats, strong security measures such as data encryption must be put in place. Our study attempts to address these issues in this environment. Comparative examination of the Chacha20, Salsa20, and Camellia encryption algorithms enabled us to ascertain that Chacha20 performs exceptionally well when it comes to audio file decryption and encryption speed. The results of our trials attest to this encryption method’s astounding effectiveness and efficacy. We have also used the noise reduction technique, which is frequently used in audio security to enhance the quality of recordings and make it easier to identify significant information in audio signals. Then, Fourier transform technique, which is also used to analyze audio files and can be used to identify changes, extract hidden information, and authenticate audio files. By doing this, the audio files security and integrity are strengthened. [ABSTRACT FROM AUTHOR]

The instrument's sound quality assessment is an arduous task to be performed computationally. This work aims to compare high quality sound characteristics among instruments. The impulse response of the guitar is recording in the time domain and, by means of the Fourier and Continuous Wavelet Transforms the characteristics among high quality guitars, in the frequency domain, are shown. To discriminate high quality, through experimentation, the criteria are: 1) tuning of notes, sound projection and definition of notes; 2) sound balance at all frequencies and timbre. Comparison of the frequency response (intensity, density, shape, range) gives a good intuition regarding sound quality of the instruments that shares similar characteristics, according to the criteria defined. Note that, among the high-quality classical guitars, it is not possible to define what is better sound-wise due to the fact that high quality instruments are hearing-perceptual defined, therefore, depends on the criteria of the musician. [ABSTRACT FROM AUTHOR]

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The use of brain-machine interfaces in people who has suffered a cerebrovascular accident could help the rehabilitation process through the cognitive involvement of the patient. These interfaces translate the brain waves into commands to control the movement of an assistant mechanical device. However, the control of these devices should be more stable and achieve a higher accuracy. This work studies if algorithms, such as Stockwell or Hilbert-Huang transform, can improve the control of these devices, and if a personalization by subject or electrode configuration is desirable. Besides, through the analysis of five volunteers is determined that the motor intention can not be detected only by data acquired previously to the movement using desynchronized/synchronized related events. Therefore, it is needed to extend the time processing to the two seconds after the movement starting.

En este trabajo se presenta un método de diferencias finitas escalonado para analizar y simular la generación y el comportamiento de ondas sonoras en el interior de un tubo. Luego, se describe un tratamiento numérico especial de las condiciones de frontera que modelan fenómenos de reflexión y transmisión a partir del concepto de impedancia acústica. Mediante un muestreo exhaustivo de frecuencias y la transformada rápida de Fourier (FFT), se realiza un análisis modal cuando el aire en el interior del tubo es sometido a perturbaciones armónicas y aleatorias. Por último, se analiza el comportamiento del factor de calidad del sistema acústico y se confirma su carácter exponencial, así como su dependencia de la impedancia acústica. Los resultados muestran la utilidad del método en la simulación de fenómenos acústicos como reflexión, transmisión, disipación de ondas sonoras y resonancia en dominios acotados. El método propuesto permite analizar casos generales como la dispersión de ondas sonoras no armónicas.

In this paper we present the solution of the stationary Schrödinger equation in the coordinates and momentum representations for three simple problems: the linear potential, the harmonic oscillator and the Dirac delta potential. We verify through explicit calculation that the wave functions obtained in each representation are connected through the Fourier transform, showing that both solutions constitute two complementary representations of the same quantum state. From a pedagogical point of view, this shows that both solutions contain information of equal theoretical value and constitute two complementary representations. [ABSTRACT FROM AUTHOR]

This article aims to present for the video version or not, in a clear and objective way to use the teaching language that is being used for teaching musical guidance and practice to play guitar. It is a great increase in the use of mobile devices and its use in the education approach. The proposal of this article is the development of a mobile application for the Android operating system, which is intended to conduct a self-directed study on this subject. The audio recording will be used in the Fourier Transform, thus determining the frequency of musical notes played by the user. [ABSTRACT FROM AUTHOR]

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En este artículo se presenta una evaluación de descriptores espacio frecuencia y técnicas de análisis de texturas para la clasificación de textiles. La metodología de trabajo consta de tres etapas fundamentales: la caracterización, la clasificación y la validación. En la etapa de caracterización se utilizan descriptores como la Transformada Wavelet, la Transformada de Fourier, un método de caracterización de textura del estado del arte como lo es segmentación fractal para el análisis de texturas (SFTA) y la adaptación de la transformada corta de Fourier en espacio. Para la etapa de clasificación se analiza el uso de tres métodos del estado del arte, como lo son las Redes Neuronales Artificiales (RNA), Máquinas de Soporte Vectorial (SVM) y el Proceso Gaussiano (GP), a estos dos últimos se les incluyeron el uso de kernels lineales, Gaussianos y polinomiales. Para validar el método se construye una base de datos anotada con diez tipos de telas, con un total de 1.000 fotos, a las cuales se les aplica el proceso caracterización y clasificación por medio de un experimento Montecarlo. En esta etapa se generan configuraciones aleatorias de entrenamiento (70 %) y prueba (30 %), obteniendo el desempeño de cada modelo de clasificación. Por último, se obtiene la matriz de confusión y se determinan los porcentajes de acierto de cada experimento, adicionalmente se realiza un análisis de tiempos para cada uno de los algoritmos, tanto a nivel de descriptor como a nivel de clasificador, con el fin de determinar la configuración que mejores prestaciones presenta y su costo computacional.

Nesse trabalho, a equação diferencial linear que representa a corrente elétrica em um circuito simples do tipo resistor-indutor (RL) com uma voltagem E(t)=E_0 exp(-at^2) é resolvida detalhadamente usando a transformada de Fourier e a integração complexa. Devido à natureza exponencial da força de voltagem, não foi possível obter a solução analítica por meio de funções elementares, mas tal dificuldade pode ser contornada por meio da análise complexa. Uma solução numérica com o método de série de Taylor mostrou boa concordância com a solução explícita obtida.

Neste artigo, pertencente à pesquisa sobre a elaboração de um modelo para a análise da música eletroacústica mista a partir de descritores de áudio, realizamos a análise de Ressonâncias (2015) para piano e sons eletrônicos de Jônatas Manzolli. Como fundamentação teórica, apresentamos uma abordagem sobre as Séries e a Transformada de Fourier, operação que serve de base para os processamentos eletroacústicos empregados na composição e para as análises realizadas a partir dos descritores. As hipóteses a serem verificadas dizem respeito à maleabilidade dos processamentos eletroacústicos empregados na peça, que podem fornecer resultados distintos em interpretações diferentes, além da existência de uma tendência de maior similaridade espectral no processo composicional realizado, em que o nível de variação entre duas interpretações é maior nas seções iniciais e menor nas seções finais. Como metodologia, analisamos as características espectrais dos sons compostos em suporte fixo e comparamos o timbre produzido (amálgama dos sons instrumentais e eletroacústicos) em duas interpretações diferentes, a partir dos dados obtidos nas análises. Concluímos discutindo dois aspectos: (1) sobre o nível de maleabilidade sonora atingido pelo compositor na estruturação do processo criativo, e (2) a análise desenvolvida aponta para a impossibilidade da notação musical tradicional de representar a completude dos resultados sonoros emergentes, que decorrem da interação entre os sons instrumentais e eletroacústicos. Ou seja, o modelo de análise estudado justifica a sua aplicabilidade no contexto da música eletroacústica mista atual, principalmente quando foca a fusão dinâmica da parte instrumental com o suporte fixo e/ou com o tratamento em tempo real.

La tomografía computarizada (TC) es un gran avance tecnológico utilizado en medicina para diagnósticar enfermedades. La misma técnica es usada en otras áreas, tales como química aeroespacial, radioastronomia, etc. El principal objetivo de la TC es reconstruir la parte interna de un objeto sin tener la necesidad de abrirlo, dicho procedimiento es conocido como un ensayo no destructivo. Para lograr este propósito, la TC usa la atenución que sufren los rayos X al atravesar por el objeto con dicha información, se reconstruye la parte interna del objeto, es decir la TC se trata de un problema inverso. En este artículo se utiliza con la transformada de Fourier para la reconstrucción de la parte interna, para ello se parte directamente de un modelo continuo, representando la densidad en el punto (x, y) de una sección considerada, con una función p = p(x, y); y aunque no se requiera que p sea continua, el método de Fourier es más eficiente y se conseguirá un mejor resultado cuanto más regular sea p.

Este artículo presenta cómo obtener la fase de la impedancia eléctrica a partir del análisis de señales transitorias, usando transformada de Fourier y Transformada Wavelet. Tradicionalmente, la transforma de Fourier ha sido utilizada para estos análisis, sin embargo, la transformada de Fourier está principalmente orientada al análisis de señales periódicas y no al análisis de señales transitorias. Por lo tanto, en este artículo se propone un nuevo método basado en la transformada Wavelet, el cual utiliza como wavelet madre, la Morlet modificada que es una adecuación de la Morlet compleja tradicional, con el fin de obtener una mejor representación de la fase en el dominio de la frecuencia. Tal mejoramiento se valida tomando como referencia los resultados obtenidos por el software “MATLAB” a partir de la impedancia de un circuito RLC en respuesta al impulso de la señal de voltaje, logrando mejorar las limitaciones de la transformada de Fourier para el análisis de este tipo de señales. El estudio realizado se ha dividido en dos partes, la primera parte incluye lo realizado de manera teórica y mediante simulación, la segunda parte consiste en presentar los resultados experimentales de un caso real validando el método desarrollado. Para ambos casos se utilizaron los mismos dos métodos matemáticos, donde se muestra la potencialidad de la transformada Wavelet para el análisis de transitorios en la obtención de la impedancia eléctrica ante la transformada de Fourier.

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The second-order partial differential equation associated with the problem of pricing continuous arithmetic Asian options is presented, together with the application of the Fourier transform on the terms of the resulting equation after a series of variable changes. An analytical solution is obtained for the value of this type of options. [ABSTRACT FROM AUTHOR]

Copyright of Ciencia e Ingenieria Neogranadina is the property of Ciencia e Ingenieria Neogranadina and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Se propone desarrollar, calibrar y validar un modelo matemático que pronostique la demanda real de agua potable en Quito con horizontes de corto, mediano y largo plazos, considerando las principales variables que actúan en el suministro de agua. Se supone que la demanda de agua potable en Quito puede ser pronosticada ya que su fluctuación y crecimiento están definidos en gran parte por variables meteorológicas, urbanísticas o de ordenamiento territorial, demográficas, económicas, sociales y la autocorrelación propia de la demanda. El modelo de pronóstico de la demanda de agua corresponde al estudio y análisis de una serie temporal o vector X1 de 2557 datos de caudales medios diarios (litros/seg.) entregados por la Planta de Tratamiento de Agua Potable de Bellavista, PTAP de Quito, desde enero 2007 hasta diciembre 2013. Para el análisis de la serie temporal o vector X1 se utilizan varias herramientas estadísticas y la transformada rápida de Fourier que nos ayuda a determinar las periodicidades del fenómeno. Se concluye obteniendo explícitamente la función de pronóstico de agua potable buscada. La validación de la función de demanda obtenida se la hará en la segunda etapa de la investigación, usando los datos que van desde el inicio de 2014 hasta el año 2016.

En el presente trabajo se muestra la comparación realizada del método de Perfilometría por Transformada de Fourier. Utilizando en primer lugar laTrasformada de Fourier Unidimensional y posteriormente la Transformada de Fourier Bidimensional, ambas propuestas son utilizadas para la digitalización de objetos, teniendo variaciones principalmente en la etapa del filtrado de la frecuencia espacial, así como la forma de aplicar dicho filtro a la escena capturada. Se presentan los resultados de tres objetos analizados, el primero es un objeto virtual, con el cual se compara el funcionamiento de ambos métodos, posteriormente se realiza la comparación de dos objetos reales; en todos los resultados se utiliza el desdoblamiento de fase sencillo para su representación 3D, y a partir de los mismos se concluye que el método con la Transformada de Fourier Bidimensional obtiene mejores resultados ya que al realizar un análisis cualitativo estos presentan menores discontinuidades.

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In this study, a model for obtaining the AC magnetic susceptibility of La2/3Ca1/3MnO3 manganites was proposed. The samples were composed of a combination of Mn4+ and Mn3+ ions that influence the material stoichiometry. The model is based on the Hamiltonian, including the Heisenberg interaction and the Zeeman effect. For determining AC susceptibility, a timedependent external magnetic field h(t) was applied to the sample. Several mathematical tools, such as Fourier transforms, were required for performing the simulations. The study was conducted for various angular frequencies and temperatures. The simulations were obtained using a graphic interface that allowed the online monitoring of the results. According to the results, the AC susceptibility decreases not only with the temperature, but also with the frequency. [ABSTRACT FROM AUTHOR]

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Esse trabalho apresenta uma análise matemática dos sinais de vibrações causadas pela implosão de bolhas de vapor d’agua presentes no escoamento em grandes dutos de água. Deste modo, o objetivo deste estudo foi identificar a duração e a frequência destas vibrações, que são importantes para estudos sobre o fenômeno de implosão de bolhas pelas suas consequências. A metodologia constou de técnicas de análise de sinais como a medição do sinal original por transformadas de Fourier e do espectro de potência para distinguir frequências dos pulsos de picos de ruídos. Assim, foi usado o espectrograma do sinal para definir a localização temporal, utilizando-se outros parâmetros, de forma a aumentar sua resolução temporal. Para a determinação da localização temporal dos pulsos foi construído um filtro passa-baixa em torno de cada uma das frequências determinadas, na transformada de Fourier do sinal. Concluímos que somando todas as componentes filtradas do sinal obtemos uma aproximação do sinal original sem ruídos.

In this work, a method which seeks to locate a radial-color mark attached to the object using the high sensitivity of the phase to determine the position spatial and angular with subpixel resolution due to movement of an object in a 2D scene is presented. The reference pattern is formed by a regular distribution with radially symmetrical of color-RGB fringes. The reconstruction of the absolute phase associated to the fringes allows the location the precise center of the mark and it finds position of the object with sub-pixel resolution. The reconstruction of absolute phase associated with the fringes using the phase shifting technique at three-frame and a development phase algorithm is calculated. A transformation of coordinates and a least squares adjustment is realized giving a function for to extract the center of the reference pattern. Experimental results of measurements of position, displacement and orientation with subpixel resolution is presented, as well as the description of the process for system optimization. [ABSTRACT FROM AUTHOR]

Nowadays, new genomic databases (DNA sequences) are available to the whole scientist community for its analysis. The bioinformatics has developed algorithms to extract information and features of the sequences. However, the bioinformatics algorithms have restrictions. An alternative is the use of digital signal processing (DSP) tools adapted to genomic sequences (genomic signal processing - GSP). This work analyzes the first four statistics moments (mean, standard deviation, skewness and kurtosis) and other two moments (median and variance) of the frequency spectra of 15 regulatory regions (RRs) in ENCODE database with the main objective of studying the statistics differences and frequency features. The selected database is mapped. Then, the FFT is calculated to these genomic signals and finally the statistic moments implemented. The results show a three-group behavior in the RRs with the mean, median and kurtosis. The deviations standard and the variance do not show important behavior. Finally, the skewness shows a homogeneous behavior with the lack of atypical values in some RRs. These observations support the idea of the presence of periodicities in a sequence that may be related or may determine the biological function that a sequence may perform. [ABSTRACT FROM AUTHOR]

Copyright of Revista Andaluza de Medicina del Deporte is the property of Centro Andaluza de Medicina del Deporte and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper we use the Fourier Transform to study a theorem of elliptic regularity for solution weak of the equation ...

En este trabajo se muestra que, a partir de un interferograma, es posible calcular el error de la forma cóncava para una superficie pulida ópticamente que será usada como espejo en un telescopio reflector. En el Laboratorio de Óptica de la PUCP, se ha implementado un interferómetro Twyman- Green donde se adquieren imágenes de la superficie, superpuestas con franjas de interferencia que se denominan interferogramas. Para realizar el cálculo se utilizan algoritmos de evaluación de la fase basados en la transformada de Fourier que permite reconstruir las imágenes procesadas para obtener la información de la forma de la superficie y su desviación respecto de su forma ideal cóncava. Fueron evaluadas las imágenes de los interferogramas de una misma superficie para diferentes frecuencias de franjas; en cada caso, una sola imagen permite determinar el error superficial, sin tener contacto con la superficie.

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Copyright of Revista Española de Medicina Nuclear e Imagen Molecular is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a mathematical analysis of the signal waves of the vibration caused by the implosion of water bubbles during the fluid flow in water ducts of greater size. Therefore, the main purpose of this study was to identify the duration and the frequency of such vibrations, which are important for the study of the phenomenon of bubble implosion due to its consequences. The methodology consisted of using signal analysis techniques like the analysis of the original signal by Fourier transform and the power spectrum to distinguish the frequency of the pulses of noise peaks. The signal spectrogram helped to define the temporal location, by using different parameters, raising its temporal resolution. For the temporal determination of pulses it was used a low-pass filter around every determined frequency in Fourier transform. We concluded that summing up all signal filtered components resulted in an approximation of the original signal without noises. [ABSTRACT FROM AUTHOR]

The results of the design, implementation and evaluation of a semi-anechoic chamber to guarantee reliability in data acquisition for diagnosis of mechanical systems are presented. Noise analysis is one of the predictive maintenance techniques that detect faults based on the monitoring of characteristic parameters of proper functioning of a system. To do this, the characteristics of insulating and absorbent material were determined, and their arrangement inside the chamber. The evaluation was performed using the analysis of acoustic signals emitted by a source (internal combustion Diesel engine) under its normal and failure operation. These signals were acquired using a sound level meter and analyzed in the frequency domain using fast Fourier transform. [ABSTRACT FROM AUTHOR]