Channel Response Research Articles

Image Contour Detection Based on Visual Pathway Information Transfer Mechanism

Based on the coding mechanism and interactive features of visual information in the visual pathway, a new method of image contour detection is proposed. Firstly, simulating the visual adaptation characteristics of retinal ganglion cells, an adaptation & sensitization regulation model (ASR) based on the adaptation-sensitization characteristics is proposed, which introduces a sinusoidal function curve modulated by amplitude, frequency and initial phase to dynamically adjusted color channel response information and enhance the response of color edges. Secondly, the color antagonism characteristic is introduced to process the color edge responses, and the obtained primary contour responses is fed forward to the dorsal pathway across regions. Then, the coding characteristics of the “angle” information in the V2 region are simulated, and a double receptive fields model (DRFM) is constructed to compensate for the missing detailed contours in the generation of primary contour responses. Finally, a new double stream information fusion model (DSIF) is proposed, which simulates the dorsal overall contour information flow by the across-region response weighted fusion mechanism, and introduces the multi-directional fretting to simulate the fine-tuning characteristics of ventral detail features simultaneously, extracting the significant contours by weighted fusion of dorsal and ventral information streams. In this paper, the natural images in BSDS500 and NYUD datasets are used as experimental data, and the average optimal F-score of the proposed method is 0.72 and 0.69, respectively. The results show that the proposed method has better results in texture suppression and significant contour extraction than the comparison method.

First experimental evaluation of a high-resolution deep silicon photon-counting sensor.

Current photon-counting computed tomography detectors are limited to a pixel size of around 0.3 to 0.5mm due to excessive charge sharing degrading the dose efficiency and energy resolution as the pixels become smaller. In this work, we present measurements of a prototype photon-counting detector that leverages the charge sharing to reach a theoretical sub-pixel resolution in the order of . The goal of the study is to validate our Monte-Carlo simulation using measurements, enabling further development. We measure the channel response at the MAX IV Lab, in the DanMAX beamline, with a 35keV photon beam, and compare the measurements with a 2D Monte Carlo simulation combined with a charge transport model. Only a few channels on the prototype are connected to keep the number of wire bonds low. The measurements agree generally well with the simulations with the beam close to the electrodes but diverge as the beam is moved further away. The induced charge cloud signals also seem to increase linearly as the beam is moved away from the electrodes. The agreement between measurements and simulations indicates that the Monte-Carlo simulation can accurately model the channel response of the detector with the photon interactions close to the electrodes, which indicates that the unconnected electrodes introduce unwanted effects that need to be further explored. With the same Monte-Carlo simulation previously indicating a resolution of around with similar geometry, the results are promising that an ultra-high resolution detector is not far in the future.

The use of OFDM signals in pseudorandom tuning of the operating frequency technology (FHSS)

The paper investigates the ways of organizing FHSS communication system using OFDM signals under the conditions of the measured parameters of the channel used. It is assumed that "protective gaps" are not used in the structure of the group signal FHSS technology. A variant of the formation of the OFDM symbol structure with a "test combination" is considered, the knowledge of which allows the regularization method to solve the problem of estimating the samples of the impulse response of the communication channel with memory. In this case, estimates are obtained from solving a system of algebraic equations, the order of which is determined by the size of the channel memory. To solve the problem of demodulating the signal from the "working package" of the OFDM symbol, estimates of the envelope counts of this part of the OFDM symbol are formed, according to which decisions on the transmitted discrete symbols are recorded at the output of the FFT calculation unit. Data on computer modeling of the problems under consideration are presented, the results of which confirm the possibility of using the proposed solutions for special purpose networks.

Software-architectural configuration of the multifunctional audio digital signal processor module for signal mediatesting of audio devices

Objectives. The aim of this study is to develop and analyze parameters for a multifunctional audio module based on the ADAU1701 audio digital signal processor in the SigmaStudio environment. This will be used for testing audio devices in the following modes: routing of balanced and unbalanced audio channels according to the differential scheme Di-Box/R Di-Box; spatiotemporal and dynamic audio processing; three-band monochannel cross-separation with independent equalization; and correction of the frequency response of the audio channel with tracking notch auto-suppression of electro-acoustic positive feedback in a given spectral band.Methods. Visual-graphical architectural programming of audio modules in the SigmaStudio and Flowstone, as well as algorithms for real-time signal audio measurements and analysis of experimental data in the REW and Soundcard Oscilloscope are used.Results. The characteristics of the Di-Box/R Di-Box circuit were studied, in order to estimate the effect of differential signal conversion on the signal-to-noise ratio in the audio signal path. The characteristics of the reverberation and saturation submodules were established. Furthermore, the effect of equalization modes on the frequency response correction of a studio audio monitor was determined. The paper also studied the effect of an audio compressor on the dynamic range and the level of the output signal. The experimental results of the submodule for compensating the frequency response of an audio monitor using matched filtering were established, and the spectral characteristics of the submodule for automatic suppression of electro-acoustic positive feedback were obtained.Conclusions. The software architecture of a multifunctional audio module based on the ADAU1701 audio digital signal processor for testing and debugging media devices in a given spectral-dynamic and spectral-temporal ranges was designed. Balanced routing allows the effect of noise induced into the audio channel to be reduced 20-fold, thus enabling calibration of pickup audio devices. The audio signal processing submodule provides: compression response in the dynamic range from −27 to 18.6 dB with the possibility of equalization parameterization in the range of 0.04–18 kHz; reverberation response in the range from 0.5–3000 ms; audio-channel cross-division into 3 with the ability to adjust the amplitude-frequency response in the dynamic range from −30 to 30 dB. The auto-correction submodule of the amplitude-frequency response allows the dynamic nonuniformity of the amplitude-frequency response to be reduced by 40 dB. The auto-suppression submodule of electro-acoustic positive feedback provides notch formant suppression up to −100 dB with an input dynamic range from −50 to 80 dB.

CRGAN-based turbo code interleaver for underwater acoustic communications

This paper proposes a channel response generative adversarial network (CRGAN)-based turbo code interleaver that estimates a channel response and interleaver indices at a transmitter by using a sound speed profile (SSP) and the ocean environments without feedback from a receiver. The interleaver indices are designed to allocate important bits from the turbo code to subcarriers with great channel gains, which reduces them from being affected by deep fading. Computer simulations and practical ocean experiments demonstrate that the proposed method estimates the channel response with low mean squared errors (MSEs) and improves bit error rate (BER) performances compared with the conventional method.

A Lightweight and Efficient Key Generation Scheme From OFDM Subcarriers’ Channel Responses

A Lightweight and Efficient Key Generation Scheme From OFDM Subcarriers’ Channel Responses

Modeling of IC Buffers from Channel Responses via Machine Learning Kernel Regression

Modeling of IC Buffers from Channel Responses via Machine Learning Kernel Regression

Frequency Domain UWB Channel Characterization and Modeling in Indoor Static Environment

In this article, distance and frequency‐dependent indoor wireless channel characterization and modeling are presented in C, X, and Ku bands at the line of sight (LOS) and nonline of sight (nLOS) scenarios. Complex frequency responses of the indoor radio channel are measured using the frequency‐domain approach. The terminal and measurement setup dependencies of the propagation channel are deconvoluted using closed‐form expressions devised from a two‐port network model approach of the antenna transreceiver system. Subsequently, terminal independent frequency‐domain channel transfer functions (CTFs) and time‐domain channel impulse responses (CIRs) are derived for accurate statistical analysis of large‐ and small‐scale fading parameters of the propagation channel. A distance‐dependent statistical pathloss model is proposed. Successively, a frequency domain channel model using the fifth‐order autoregressive process is proposed. Subsequently, the existence of the multiple clusters in the environment is analyzed by the poles of the transfer functions of the model. Models are validated in both time and frequency domains by comparing the computer‐simulated synthetic model data with the empirical channel responses. The measurement data and the model data are seen to be in good agreement.

Stabilization responses of an infinite porous flow channel containing ferrofluids

This paper investigates the effect of a magnetic field on the stability of two interfacial waves propagating between three infinite layers of viscous fluids. The flow propagates saturated in porous media so that liquids have distinct physical properties and are immiscible. The principal purpose of this study is to examine the impact of the porosity outcome and fluid viscosity on the growth rate in the existence of a magnetic field. In the horizontal axis direction. Fluid stability results from the amplitude of the waves and the extent to which they are affected by the interference between magnetic features and the effect of the media's porosity. The stability conditions are realized theoretically in which stability diagrams are achieved. The influence of the various quantities of the problem on the interface stability is thoroughly evaluated.

Decoding time-resolved neural representations of orientation ensemble perception.

The visual system can compute summary statistics of several visual elements at a glance. Numerous studies have shown that an ensemble of different visual features can be perceived over 50-200 ms; however, the time point at which the visual system forms an accurate ensemble representation associated with an individual's perception remains unclear. This is mainly because most previous studies have not fully addressed time-resolved neural representations that occur during ensemble perception, particularly lacking quantification of the representational strength of ensembles and their correlation with behavior. Here, we conducted orientation ensemble discrimination tasks and electroencephalogram (EEG) recordings to decode orientation representations over time while human observers discriminated an average of multiple orientations. We modeled EEG signals as a linear sum of hypothetical orientation channel responses and inverted this model to quantify the representational strength of orientation ensemble. Our analysis using this inverted encoding model revealed stronger representations of the average orientation over 400-700 ms. We also correlated the orientation representation estimated from EEG signals with the perceived average orientation reported in the ensemble discrimination task with adjustment methods. We found that the estimated orientation at approximately 600-700 ms significantly correlated with the individual differences in perceived average orientation. These results suggest that although ensembles can be quickly and roughly computed, the visual system may gradually compute an orientation ensemble over several hundred milliseconds to achieve a more accurate ensemble representation.

Foreground Capture Feature Pyramid Network-Oriented Object Detection in Complex Backgrounds.

Feature pyramids are widely adopted in visual detection models for capturing multiscale features of objects. However, the utilization of feature pyramids in practical object detection tasks is prone to complex background interference, resulting in suboptimal capture of discriminative multiscale foreground semantic features. In this article, a foreground capture feature pyramid network (FCFPN) for multiscale object detection is proposed, to address the problem of inadequate feature learning in complex backgrounds. FCFPN consists of a foreground dual attention (FDA) module and a pathway aggregation (PA) structure. Specifically, the FDA mechanism activates top-down foreground channel responses and lateral spatial foreground location features, so that channel and spatial foreground features are adequately captured. Then, the PA module adaptively learns the fusion weights of multiscale features at different levels of the feature pyramid, which enhances the complementarity of semantic information between different levels of the foreground feature maps. Since the fusion weights are learned adaptively based on different pyramid levels, the detection model accordingly retains the gained information of feature sizes and suppresses the conflicting information. The evaluations on public datasets and the self-built complex background dataset demonstrate that the detection average precision (AP) and the feature learning performance of the proposed method are superior compared with other FPNs, which proves the effectiveness of the proposed FCFPN.

Role of bradykinin and prostaglandin EP4 receptors in regulating TRPV1 channel sensitization in rat dorsal root ganglion neurons.

Transient receptor potential vanilloid type-1 (TRPV1) channels play key roles in chronic pain conditions and are modulated by different inflammatory mediators to elicit heat sensitisation. Bradykinin is a 9-amino acid peptide chain that promotes inflammation. The aim of present study is to investigate how bradykinin and prostaglandin receptors (EP3 and EP4 ) modulate the sensitisation of TRPV1-mediated responses. Calcium imaging studies of rat dorsal root ganglion (DRG) neurons were employed to investigate the desensitizing responses of TRPV1 ion channels by capsaicin, and the re-sensitization of TRPV1 by bradykinin, then to explore the role EP3 and EP4 receptors in mediating these bradykinin-dependent effects. Immunocytochemistry was used to study the co-expression and distribution of EP4, TRPV1, COX-1 and B2 in rat DRG neurons. Desensitization was seen upon repeated capsaicin application, we show that bradykinin-mediated sensitization of capsaicin-evoked calcium responses in rat DRG neurons occurs is dependent on COX-1 activity and utilizes a pathway that involves EP4 but not EP3 receptors. Immunocytochemical techniques revealed that EP4, TRPV1, COX-1 and B2 proteins are expressed mainly in small diameter (<1000 μm2 ) cell bodies of rat DRG neurons which are typically nociceptors. The present study provides suggestive evidence for a potential signalling pathway through which bradykinin may regulate TRPV1 ion channel function via EP4 receptors. In addition to confirming existing knowledge, the anatomical distribution and colocalization of these proteins in DRG neurons as revealed by this study offer valuable insight.

Spectrum-based channel attention cooperating with time continuity encoding in transformer for EEG emotion analysis

Recently, electroencephalogram (EEG) emotion analysis has attracted increasing attention in many fields, such as neuroscience and brain-computer fusion. Due to the spatial channel difference and time continuity of emotional responses, it is necessary to capture relevant properties from EEG signals. In this paper, spectrum-based spatial channel attention is developed to reveal the emotional responses of different electrode channels located in different cerebral cortex regions. In addition, a time continuity encoding mechanism is developed to encode the temporal relations of time series signals in the transformer. In our model, the spectrum-based spatial channel attention cooperates with the time continuity encoding mechanism to fully utilize the spectral, spatial and temporal features of EEG signals (SST-Emo). Extensive experiments with different window sizes (1 s and 3 s) are carried out on DEAP for both binary and multiclass classification tasks. The accuracies are 96.28 %, 95.25 %, 95.52 %, 95.83 % and 93.88 % for 1 s window-size on arousal, valence, dominance, liking and 5-class, respectively. For 3 s window-size, the accuracies are 96.13 %, 95.74 %, 95.23 %, 95.7 % and 95.83 %, respectively. The results show that SST-Emo is superior to the state-of-the-art methods, which indicates that SST-Emo is able to extract more discriminative emotional representations.

Dynamic asymmetric mechanical responsive carbon nanotube fiber for ionic logic gate

Inspired by biological ion channels, numerous artificial asymmetric ion channels have been synthesized to facilitate the fabrication of ionic circuits. Nevertheless, the creation of biomimetic asymmetric ion channels necessitates expensive scientific apparatus and intricate material processing procedures, which constrains its advancement within the realm of ionic devices. In this study, we have devised dynamic asymmetric ion channels with mechanical responsiveness by combining polymers of varying elastic modulus along the longitudinal axis of carbon nanotube fiber (CNTF). The ion rectification can be modulated via the disparate response of CNTF-based ion channels to mechanical stress. We have effectively employed these asymmetric ion channels with mechanical sensitivity in the design of a logic gate device, achieving logic operations such as “AND” and “OR”. The conception of these dynamic asymmetric ion channels with mechanical sensitivity offers a straightforward, cost-effective, and versatile approach for generating ion channels, highlighting their potential application in intricate, highly integrated ionic circuits.

Shrinking Desert Channel Response to Increasing Human Interferences and Changing Natural Factors in the Upper Yellow River

Many rivers are tightly coupled and intersected with aeolian sand dunes, whose geomorphological evolution involves not only fluvial processes but also aeolian processes that pose a new challenge to fluvial geomorphological studies. However, due to few field studies, our overall understanding of the desert channel geomorphic process is limited. In this paper, we present an outstanding example of desert river channel evolution regulated by aeolian–fluvial interactions in the Ulan Buh Desert of the Yellow River, based on a long time series data set (1966–2019) of channel cross-sections. The results indicate that the lateral addition of aeolian sand, the water–sediment relationship and human interference have a significant role at different periods of channel evolution. Before 1986, higher discharge, lower sediment content and greater intensity of aeolian activity caused aeolian–fluvial interactions and a relative scouring and silting balance in the channel, with little human activity. From 1986 to 2000, an increase in large reservoir operation, vegetation coverage and floodplain farming, coupled with water–sediment relationship variation, caused rapid deposition and shrinkage of the river channel. From 2000 to 2014, the channel kept a slight scouring state. With Haibowan reservoir operation beginning in 2014, the talweg experienced rapid scouring and undercut rebound. However, an expanding and stable floodplain accelerated sedimentation on the floodplain and weakened river lateral erosion, indicating that the channel has shown a shrinkage trend. Meanwhile, wavelet analysis results indicate that human interferences and aeolian activities have no significant role in the periodical characteristics of the channel’s longitudinal erosion and deposition. Therefore, on the whole, increasing human interferences and decreasing wind dynamics have driven this desert wandering channel to be stable, and to gradually form a new balance between erosion and sedimentation.

Channel change during catastrophic flood: Example of Storm Alex in the Vésubie and Roya valleys

Documenting and interpreting channel responses to catastrophic floods help understanding how rapid fluvial metamorphosis can propagate in a catchment under sediment cascading effects. The recent example of the October 2020 Storm Alex in SE France (∼500 mm of rain in 24 h) provides a unique opportunity to investigate major geomorphic responses along 70 km of two confined alpine valleys (Vésubie and Roya) and to link them to sediment wave initiation and propagation. GIS-based analysis of remote sensing data (high-resolution ortho-imagery and airborne LiDAR data) acquired before and after the flood allowed combining channel changes with sediment erosion and deposition along a 35-km reach of the Vésubie, including the most impacted portions of the valley. In the Roya, the analysis was restricted to 2D morphological changes reconstructed with the sequence of ortho-imagery. Archives of aerial imagery were also used to integrate the storm impact in the historical trajectory of the rivers. The reconstruction of geomorphic responses shows a quasi-continuous fluvial metamorphosis along the investigated stream networks, with dramatic active channel widening and aggradation, having no antecedent analogs during the last 70 years in both valleys. The different glacial imprints between the two valleys are considered a key factor explaining the exacerbated channel response in the Vésubie, where a braided channel emerged along a 35-km river length. Many evidences strongly support that the fuelling effect of alluvial storage is a key element of the sediment cascade at the origin of the braided channel formation. This regional case study allows us to discuss the critical role of floodplain and terrace erosion in the formation of the post-flood braided channel, and to compare the geomorphic impact of the storm with similar reported cases in the literature.

Nocistatin and Products of Its Proteolysis Are Dual Modulators of Type 3 Acid-Sensing Ion Channels (ASIC3) with Algesic and Analgesic Properties.

The neuropeptide nocistatin (NS) is expressed by the nervous system cells and neutrophils as a part of a precursor protein and can undergo stepwise limited proteolysis. Previously, it was shown that rat NS (rNS) is able to activate acid-sensing ion channels (ASICs) and that this effect correlates with the acidic nature of NS. Here, we investigated changes in the properties of rNS in the course of its proteolytic degradation by comparing the effects of the full-size rNS and its two cleavage fragments on the rat isoform 3 ASICs (ASIC3) expressed in X. laevis oocytes and pain perception in mice. The rNS acted as both positive and negative modulator by lowering the steady-state desensitization of ASIC3 at pH 6.8-7.0 and reducing the channel's response to stimuli at pH 6.0-6.9, respectively. The truncated rNSΔ21 peptide lacking 21 amino acid residues from the N-terminus retained the positive modulatory activity, while the C-terminal pentapeptide (rNSΔ30) acted only as a negative ASIC3 modulator. The effects of the studied peptides were confirmed in animal tests: rNS and rNSΔ21 induced a pain-related behavior, whereas rNSΔ30 showed the analgesic effect. Therefore, we have shown that the mode of rNS action changes during its stepwise degradation, from an algesic molecule through a pain enhancer to a pain reliever (rNSΔ30 pentapeptide), which can be considered as a promising drug candidate.

Beta-Barrel Channel Response to High Electric Fields: Functional Gating or Reversible Denaturation?

Ion channels exhibit gating behavior, fluctuating between open and closed states, with the transmembrane voltage serving as one of the essential regulators of this process. Voltage gating is a fundamental functional aspect underlying the regulation of ion-selective, mostly α-helical, channels primarily found in excitable cell membranes. In contrast, there exists another group of larger, and less selective, β-barrel channels of a different origin, which are not directly associated with cell excitability. Remarkably, these channels can also undergo closing, or “gating”, induced by sufficiently strong electric fields. Once the field is removed, the channels reopen, preserving a memory of the gating process. In this study, we explored the hypothesis that the voltage-induced closure of the β-barrel channels can be seen as a form of reversible protein denaturation by the high electric fields applied in model membranes experiments—typically exceeding twenty million volts per meter—rather than a manifestation of functional gating. Here, we focused on the bacterial outer membrane channel OmpF reconstituted into planar lipid bilayers and analyzed various characteristics of the closing-opening process that support this idea. Specifically, we considered the nearly symmetric response to voltages of both polarities, the presence of multiple closed states, the stabilization of the open conformation in channel clusters, the long-term gating memory, and the Hofmeister effects in closing kinetics. Furthermore, we contemplate the evolutionary aspect of the phenomenon, proposing that the field-induced denaturation of membrane proteins might have served as a starting point for their development into amazing molecular machines such as voltage-gated channels of nerve and muscle cells.

Effects of sediment transport on flood hazards: Lessons learned and remaining challenges

Sediment transport (bedload and suspension) plays a relevant role in the morphological response of river channels to large floods. Sediment load controls erosion and aggradation patterns during high flows, drives the migration of macroforms and contributes to the definition of thresholds for bank erosion and channel instability. Given this influence on channel morphology, it is clear that sediment transport influences both the channel geometry and water stage reached during floods and should therefore be considered in flood hazard analysis. So far, however, legislation on flood hazard and flood management plans still continues to typically disregard sediment transport. This is due mainly to the paucity of available data on sediment transport and the lack of standardized approaches for its integration into flood hazard analysis. The present work, which aims to provide some guidance on how to advance in this issue, has undertaken a bibliometric study and thorough review of the published scientific literature that had previously addressed the implications of sediment transport on flood hazards assessment. This review showed that: i) most studies on the influence of sediment transport on flood risk have focused on mountain streams, as they are highly sensitive systems to changes in sediment supply; ii) research has also focused on explaining historical changes in channel-conveyance capacity and flood frequency based on long-term trends in sediment supply; and iii) recent developments in hydrodynamic and morphodynamic numerical models provide opportunities to explicitly incorporate sediment transport in flood hazard analysis. However, despite the recent advances, we have identified important challenges and discussed needs to better consider sediment transport in flood hazards at different spatial and temporal scales.

Divalent Aptamer-Functionalized Nanochannels for Facile Detection of Cancer Cell-Derived Exosomes.

Exosomes are considered potential biomarkers for early screening and accurate non-invasive diagnosis of cancer, so development of innovatively facile approaches for the detection of cancer cell-derived exosomes has become increasingly important. Herein, we propose a facile electrochemical biosensor based on divalent aptamer-functionalized nanochannels for highly efficient detection of cancer cell-derived exosomes. The aptamer against transmembrane receptor protein CD63 and the aptamer targeting membrane protein EpCAM are simultaneously immobilized on the nanochannels to construct the divalent aptamer-functionalized nanochannels. Thus, the target exosomes can be recognized and selectively captured by the functionalized nanochannels in a divalent collaborative manner. The combined exosomes overlay the ion channel effectively and hinder the ionic flow through the nanochannels, resulting in an evidently varied ionic transport behavior corresponding to the abundance of exosomes. The divalent aptamer-functionalized nanochannels can substantially promote the binding stability and enhance the detection specificity, while the sensitivity of detection is improved greatly by virtue of the amplified response of array channels synergized with the electrochemical technique. Therefore, the developed biosensor provides a highly specific, sensitive, and accurate approach for the detection of cancer cell-derived exosomes, which may hold great potential for application in early clinical cancer diagnosis.