High-pass Signals Research Articles

DPGCL: Dual pass filtering based graph contrastive learning

Graph Contrastive Learning (GCL), which learns node or graph representation from supervision signals derived from the graph data itself, has recently attracted extensive research attention and achieved great success. Remarkably, most of the existing GCL encoders essentially perform low-frequency filtering on graph, which however limits their expressive power on heterophilous graphs where dissimilar nodes tend to be connected. This raises an interesting question: can high frequency be informative for GCL? In this work, we experimentally study the influence of high-frequency signals on GCL and find that adding some high-frequency signals in contrasting is beneficial for improving GCL performance. That motivates us to design a more general GCL framework beyond low-pass filtering, which simultaneously performs low-pass and high-pass signal contrasts, so as to capture both low and high-frequency information in general graphs. Furthermore, to enable the representation learning to be aware of neighbor diversity in heterophilic graphs, we propose a novel graph contrastive loss, termed Adap-infoNCE, which can automatically decide the weights of negative samples based on feature representations of neighboring nodes. Here two types of neighbors are considered, i.e., spatial neighbors and featural neighbors, whose effectiveness is verified using empirical study on synthetic datasets. Extensive experiments demonstrate that our method brings significant and consistent improvements over the base GCL approach and exceeds multiple state-of-the-art results on several unsupervised benchmarks, even surpassing the performance of supervised benchmarks.

Structure-based graph convolutional networks with frequency filter

• We design a latent space to correlate the underlying nodes for obtaining structured and meaningful messages. • We elaborate a structured adaptive frequency GNN by ingeniously combining the latent space nodes. • Comprehensively aggregating the vital components of neighbor nodes and underlying nodes. • We outperform the state-of-the-art methods significantly in terms of accuracy and computational efficiency Message-passing neural networks (MPNNs) have attracted a lot interesting in academia and industry and have been applied to various graph analytical problems of real-world applications and achieved prominent successes. For the most of current works on MPNNs, they mainly focus on two categories: spectral-based and spatial-based methods. The former seeks to distill useful information (e.g. low-pass and high-pass signals) and the later designs structural schemes. However, it is not enough to only utilize one of them. We tackle this drawback by proposing an efficient and elegant method of taking advantage of the structural graph neural network (GNN) for advanced spectral-based information filtering. Through the learnable frequency components and global virtual neighbor nodes, the proposed scheme is elaborated to obtain informative and structured messages of neighbor nodes and latent space correlational nodes. Experimental results show that our method outperforms the state-of-the-art performance in a series of datasets of graph tasks.

A Simple Laptop-based Phonocardiography System: A Novel and Inexpensive Instrument for Research and Clinical Use

Background: Cardiac auscultation is a frequent first step in diagnosing heart disorders. However, the lack of dependability of ordinary auscultation in the hands of inexperienced clinicians remains a problem. Objective: We sought to develop an inexpensive system for digital cardiac auscultation (digital phonocardiography) using a Windows laptop computer, freely downloadable software and an inexpensive USB microphone. Description: The system, based on the free open-source Audacity software package, offers advanced features such as phonocardiogram storage and retrieval, low-pass and high-pass waveform filtering and variable-speed signal playback with pitch preservation. Results: Sample results for both raw and digitally filtered phonocardiograms are provided. Conclusion: An innovative laptop-based phonocardiogram system offering advanced features can be easily produced at minimal cost.

A note on measurement accuracy and thermal stability of filter polychromators for Thomson scattering diagnostics

This note is devoted to a filter polychromator combining built-in optical, data acquisition and processing subsystems designed for electron temperature and density measurements in fusion plasma by Thomson scattering (TS). Special attention is paid to assessing the accuracy of TS signals measured in the polychromator spectral channels. The potential for estimating TS error caused by background emission is demonstrated using high-pass signal. The recent polychromator tests have shown APD gain stabilization better than ±0.5% over the ambient temperature range from 17.5 °C to 35 °C

Analytical model for signal and gain modulation on thulium-doped fiber amplifiers in S and near-C bands including amplified spontaneous emission: signal power analysis

Multiple transition levels covering S and near-C bands (1460 to 1565 nm) of thulium-doped fiber amplifiers (TDFAs) allows them as potential alternative to erbium-doped fiber amplifiers (EDFAs) hence getting employed in dense wavelength division multiplexing (DWDM) in optical fiber communication. We present overmodulation gain dynamics (OGD) on TDFAs using the EDFA’s Bononi and Rusch (1998) model. The paper portrays overmodulation of digital optical communication signal, of which amplitude was modulated by low-frequency (∼100 kHz), for line-surveillance and management control of optical information in DWDM TDFA systems. Signal-to-signal and signal-to-amplified spontaneous emission (ASE) transfer functions were derived to predict the system’s performance under high input signal power conditions and its variation on input modulation indices. Difference of −10.3 dB (0.093 W) in output signal gain was observed at 1490 nm signal wavelength with ASE. Output modulation index of 15% having high pass signal characteristics as of a lead compensator was observed with the applied signal frequency sweep. Overmodulation sensitivity for various levels of input signal power demonstrates undesirable 30% increment in the output modulation index at 8 dBm and 1490 nm signal wavelength, respectively, at corner frequency.

An injection molding method to prepare chitosan-zinc composite material for novel biodegradable flexible implant devices

ABSTRACTNovel biodegradable flexible implant materials require precise fabrication and novel design on top of the biocompatibility and biodegradability. By injection modeling technic, the thin and well-designed circuits can be precisely manufactured. Therefore, it emerged as an attractive method toward the research of advanced implant. In this study, a simple two-step method, natural precipitation and galvanization, was introduced to prepare a chitosan-zinc composite for conducting circuit and electrodes fabrications. The chitosan–zinc composite is biocompatible and biodegradable. The unique bond between chitosan and zinc solves the conventional unstable connection problem and secures the structural stability of our products. To optimize this processing, the effect of composition and galvanization time on viscosity and ohm resistance were investigated. The high structural stability, good shear-thinning characteristics, and fine high pass signal transferring ability were verified by viscosity test, scanning electronic microscopy (SEM) and electronic impedance spectroscopy (EIS), separately.

On the determinacy problem for measures

We study the general moment problem for measures on the real line, with polynomials replaced by more general spaces of entire functions. As a particular case, we describe measures that are uniquely determined by a restriction of their Fourier transform to a finite interval. We apply our results to prove an extension of a theorem by Eremenko and Novikov on the frequency of oscillations of measures with a spectral gap (high-pass signals) near infinity.

Interaural level differences and sound source localization for bilateral cochlear implant patients.

The aims of this study were (i) to determine the magnitude of the interaural level differences (ILDs) that remain after cochlear implant (CI) signal processing and (ii) to relate the ILDs to the pattern of errors for sound source localization on the horizontal plane. The listeners were 16 bilateral CI patients fitted with MED-EL CIs and 34 normal-hearing listeners. The stimuli were wideband, high-pass, and low-pass noise signals. ILDs were calculated by passing signals, filtered by head-related transfer functions (HRTFs) to a Matlab simulation of MED-EL signal processing. For the wideband signal and high-pass signals, maximum ILDs of 15 to 17 dB in the input signal were reduced to 3 to 4 dB after CI signal processing. For the low-pass signal, ILDs were reduced to 1 to 2 dB. For wideband and high-pass signals, the largest ILDs for ±15 degree speaker locations were between 0.4 and 0.7 dB; for the ±30 degree speaker locations between 0.9 and 1.3 dB; for the 45 degree speaker locations between 2.4 and 2.9 dB; for the ±60 degree speaker locations, between 3.2 and 4.1 dB; and for the ±75 degree speaker locations between 2.7 and 3.4 dB. All of the CI patients in all the stimulus conditions showed poorer localization than the normal-hearing listeners. Localization accuracy for the CI patients was best for the wideband and high-pass signals and was poorest for the low-pass signal. Localization accuracy was related to the magnitude of the ILD cues available to the normal-hearing listeners and CI patients. The pattern of localization errors for the CI patients was related to the magnitude of the ILD differences among loudspeaker locations. The error patterns for the wideband and high-pass signals, suggest that, for the conditions of this experiment, patients, on an average, sorted signals on the horizontal plane into four sectors-on each side of the midline, one sector including 0, 15, and possibly 30 degree speaker locations, and a sector from 45 degree speaker locations to 75 degree speaker locations. The resolution within a sector was relatively poor.

Continuous-time delta-sigma modulator using vector filter in feedback path to reduce effect of clock jitter and excess loop delay

In this paper, we propose a novel delta-sigma modulator (DSM) that reduces the effects of clock jitter and excess loop delay by using a vector filter in the feedback path. The vector filter divides the input signal into a high-frequency part and a low-frequency part. The low-pass signal is placed in the path to the first-stage digital-to-analog converter for reducing the effects of the clock jitter, and the high-pass signal is placed in the feedback path to the last integrator in order to compensate for the excess loop delay. The DSM using the vector filter in the feedback path (DSM-VF) is verified using MATLAB/Simulink. Further, a clock jitter (0.1 %) in DSM-VF leads to an improvement in the signal-to-noise-ratio (SNR) to 22.5 dB as compared to the SNR of a conventional CTDSM. Moreover, the SNR deterioration caused by the excess loop delay is improved.

다기능성 나노자성복합소재 기술동향

Recently, it has been developed for Eco-environment, Super light, Multi-functional nano materials. As needed mobile parts in Smart phone or TV, computer, information communication for high pass signal, multi-function, Magnetic thin film materials have been developed. As last, magnetic powder, sintered and sputtering parts were thick and low purity than electroplating layer, low pass signal and noise were resulted, vibrated TV screen. Because chemical complex temperature was high and ununiform surface layer, it has been very difficult for data pass in High Frequency (GHz) area. Large capacity data pass is used to GHz. Above GHz, signal pass velocity is dependent on Skin Effect of surface layer. If surface layer is thick or ununiform, attachment is poor, low pass signal and cross talk, noise are produced and leaked. It has been reported technical trend of Electrochemically plating and Surface treatment of Metal, Polymer, Ceramic etc. by dispersion/complex for Multi functional nano-magnetic material in this paper.

HEADPHONE SURROUND USING ARTIFICIAL REVERBERATION

A surround experience for headphones can be created using various techniques and tools. The described techniques and tools can be applied separately or in combination. For example, a surround experience can be created by splitting input audio channel signals into high-pass and low-pass signals. The low-pass signals can undergo cross-mixing and artificial reverberation. The artificial reverberation can apply different delay profiles to the low-pass audio signals. The high-pass and low-pass audio signals can be combined to generate output audio channel signals. A surround experience can be crated using a system comprising an input module, a crossover module, a channel cross-mixing module, a reverberation module, and an adder module.

Reliability and Frequency Response of Excitatory Signals Transmitted to Different Types of Retinal Ganglion Cell

The same visual stimulus evokes a different pattern of neural signals each time the stimulus is presented. Because this unreliability reduces visual performance, it is important to understand how it arises from neural circuitry. We asked whether different types of ganglion cell receive excitatory signals with different reliability and frequency content and, if so, how retinal circuitry contributes to these differences. If transmitter release is governed by Poisson statistics, the SNR of the postsynaptic currents (ratio of signal power to noise power) should grow linearly with quantal rate (qr), a prediction that we confirmed experimentally. Yet ganglion cells of the same type receive quanta at different rates. Thus to obtain a measure of reliability independent of quantal rate, we calculated the ratio SNR/qr, and found this measure to be type-specific. We also found type-specific differences in the frequency content of postsynaptic currents, although types whose dendrites branched at nearby levels of the inner plexiform layer (IPL) had similar frequency content. As a result, there was an orderly distribution of frequency response through the depth of the IPL, with alternating layers of broadband and high-pass signals. Different types of bipolar cell end at different depths of the IPL and provide excitatory synapses to ganglion cell dendrites there. Thus these findings indicate that a bipolar cell synapse conveys signals whose temporal message and reliability (SNR/qr) are determined by neuronal type. The final SNR of postsynaptic currents is set by the dendritic membrane area of a ganglion cell, which sets the numbers of bipolar cell synapses and thus the rate at which it receives quanta [SNR = qr x (SNR/qr)].

Random Sampling Estimates of Fourier Transforms: Antithetical Stratified Monte Carlo

We estimate the Fourier transform of continuous-time signals on the basis of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> discrete-time nonuniform observations. We introduce a class of antithetical stratified random sampling schemes and we obtain the performance of the corresponding estimates. We show that when the underlying function <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> ) has a continuous second-order derivative, the rate of mean square convergence is 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> , which is considerably faster that the rate of 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> for stratified sampling and the rate of 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> for standard Monte Carlo integration. In addition, we establish joint asymptotic normality for the real and imaginary parts of the estimate and give an explicit expression for the asymptotic covariance matrix. The theoretical results are illustrated by examples for low-pass and high-pass signals.

Semi-Invariant Reversible Mapping from Color to Gray

This paper proposes a reversible algorithm to convert color images to gray images while keeping chroma and spatial resolution. The original method of Braun and de Queiroz [Ref. 5] had theoretical problems such as deterioration in both chroma and spatial resolution. The authors describe a solution for these problems by devising a color embedding technique. A semi-invariant algorithm for chroma and spatial resolution can be realized by replacing a subband of the luminance component with the quantized high-pass luminance and chrominance signals. Experimental results show that the proposed algorithm can recover vivid color images from the textured gray images of the original color images, while keeping spatial resolution. Furthermore, the ability of color recovery from coded gray images is evaluated from the point of view of image coding using JPEG and JPEG2000.

Efficient coding of high frequency signal information in a signal using a linear/non-linear prediction model based on a low pass baseband

An efficient coding scheme with higher audio bandwidth and/or better audio quality at lower bitrates, wherein the scheme eliminates long-term and short-term frequency domain correlation in a signal via frequency domain predictors. The coding scheme compresses information consisting of coded low frequency components as well as a parametric representation for the high frequency components based on a non-linear model. Additionally, by working on the frequency domain representations of the signal (such as the MDCT representation which is naturally available to a PAC encoder and decoder), low pass and high pass signal components are easily obtained by windowing the appropriate ranges of frequencies in the signal. Furthermore, the power functions of the signal are replaced by corresponding convolution functions of the same order.

A comparative study of chaotic and white noise signals in digital watermarking

Digital watermarking is an ever increasing and important discipline, especially in the modern electronically-driven world. Watermarking aims to embed a piece of information into digital documents which their owner can use to prove that the document is theirs, at a later stage. In this paper, performance analysis of watermarking schemes is performed on white noise sequences and chaotic sequences for the purpose of watermark generation. Pseudorandom sequences are compared with chaotic sequences generated from the chaotic skew tent map. In particular, analysis is performed on highpass signals generated from both these watermark generation schemes, along with analysis on lowpass watermarks and white noise watermarks. This analysis focuses on the watermarked images after they have been subjected to common image distortion attacks. It is shown that signals generated from highpass chaotic signals have superior performance than highpass noise signals, in the presence of such attacks. It is also shown that watermarks generated from lowpass chaotic signals have superior performance over the other signal types analysed.

Representation of Auditory Signals in the M-Cell: Role of Electrical Synapses

The teleost Mauthner (M-) cell mediates a sound-evoked escape behavior. A major component of the auditory input is transmitted by large myelinated club endings of the posterior VIIIth nerve. Paradoxically, although nerve stimulations revealed these afferents have mixed electrical and glutamatergic synapses on the M-cell's distal lateral dendrite, paired pre- and postsynaptic recordings indicated most individual connections are chemically silent. To determine the sensory information encoded and the relative contributions of these two transmission modes, M-cell responses to acoustic stimuli in air were recorded intracellularly. Excitatory postsynaptic potentials (EPSPs) evoked by both short 100- to 900-Hz "pips" and longer-lasting amplitude- and frequency-modulated sounds were dominated by fast, repetitive EPSPs superimposed on an underlying slow depolarization. Fast EPSPs 1) have kinetics comparable to presynaptic action potentials, 2) are maximal on the distal lateral dendrite, and 3) are insensitive to GluR antagonists. They presumably are coupling potentials, and power spectral analysis indicated they constitute a high-pass signal that accurately tracks sound frequency and amplitude. The spatial profile of the slow EPSP suggests both proximal and distal dendritic sources, a result supported by predictions of a multicompartmental model and the effects of AMPAR antagonists, which preferentially reduced the proximal component. Thus a second class of afferents generates a portion of the slow EPSP that, with sound stimuli, demonstrate that the dominant mode of transmission at LMCE synapses is electrical. The slow EPSP is a dynamic, low-pass representation of stimulus strength. Accordingly, amplitude and phase information, which are segregated in other systems, are faithfully represented in the M-cell.

Extracting star formation histories from medium-resolution galaxy spectra

We adapt an existing data compression algorithm, moped, to the extraction of median-likelihood star formation histories from medium-resolution galaxy spectra. By focusing on the high-pass components of galaxy spectra, we minimize potential uncertainties arising from the spectrophotometric calibration and intrinsic attenuation by dust. We validate our approach using model high-pass spectra of galaxies with different star formation histories covering the wavelength range 3650–8500 Å at a resolving power of ∼2000. We show that the method can recover the full star formation histories of these models, without prior knowledge of the metallicity, to within an accuracy that depends sensitively on the signal-to-noise ratio. The investigation of the sensitivity of the flux at each wavelength to the mass fraction of stars of different ages allows us to identify new age-sensitive features in galaxy spectra. We also highlight a fundamental limitation in the recovery of the star formation histories of galaxies for which the optical signatures of intermediate-age stars are masked by those of younger and older stars. As an example of application, we use this method to derive average star formation histories from the highest-quality spectra of typical (in terms of their stellar mass), morphologically identified early- and late-type galaxies in the Early Data Release (EDR) of the Sloan Digital Sky Survey (SDSS). We find that, in agreement with the common expectation, early-type galaxies must have formed most of their stars over 8 Gyr ago, although a small fraction of the total stellar mass of these galaxies may be accounted for by stars with ages down to 4 Gyr. In contrast, late-type galaxies appear to have formed stars at a roughly constant rate. We also investigate the constraints set by the high-pass signal in the stacked spectra of a magnitude-limited sample of 20 623 SDSS-EDR galaxies on the global star formation history of the Universe and its distribution among galaxies in different mass ranges. We confirm that the stellar populations in the most massive galaxies today appear to have formed on average earlier than those in the least massive galaxies. Our results do not support the recent suggestion of a statistically significant peak in the star formation activity of the Universe at redshifts below unity, although such a peak is not ruled out.

Removal of α-Stable Noise in Frequency Modulated Signals Using Robust DFT Forms

A task of filtering (denoising) of high-pass signals corrupted by heavy tail (α-stable) noise is considered. For this purpose, several techniques based on the robust DFT forms have been proposed recently. In this paper we study various approaches for design of the robust DFT and compare their performance for frequency-modulated (FM) signals. In particular, we consider the DFT estimates based on the linear combination of order statistics (L-estimate), myriad, Wilcoxon and Hodges-Lehman estimates. Possible strategies for selection of parameters in these robust estimation schemes are studied. Moreover, a new hard-switching adaptive robust estimate is proposed and tested.

Nonexpansive pyramid for image coding using a nonlinear filterbank

A nonexpansive pyramidal decomposition is proposed for low-complexity image coding. The image is decomposed through a nonlinear filterbank into low- and highpass signals and the recursion of the filterbank over the lowpass signal generates a pyramid resembling that of the octave wavelet transform. The structure itself guarantees perfect reconstruction and we have chosen nonlinear filters for performance reasons. The transformed samples are grouped into square blocks and used to replace the discrete cosine transform (DCT) in the Joint Photographic Expert Group (JPEG) coder. The proposed coder has some advantages over the DCT-based JPEG: computation is greatly reduced, image edges are better encoded, blocking is eliminated, and it allows lossless coding.