Amplitude Phase Research Articles

Improving near-field spatial uniformity of secondary sources for active noise control headrests

In an active noise control (ANC) headrest system, the near field uniformity of the secondary sound field affects the size of the generated quiet zone because the secondary sources are closer to the control zone than primary sources. In this study, a compound source with uniform near-field radiation is proposed to improve noise reduction performance of the ANC headrest system by using the sound pressure matching method. The compound source is driven with only one signal but consists of two loudspeaker units, whose amplitude ratio and phase difference are optimized with an ideal uniform target field and the secondary paths measured in the free field. In the paper, a numerical model in a diffuse sound field is developed first and the proposed compound source is demonstrated to be able to generate a larger quiet zone than a single loudspeaker. Then, the simulation results based on measured secondary paths and road noise data in a vehicle cabin are provided to show that the proposed compound source improves the average noise reduction of road noise by 2.0 dB in the 100–500 Hz frequency range compared to that with a single loudspeaker. Finally, it is shown that the proposed compound source is universally applicable and does not depend on specific application scenarios.

All-optical analog differential operation and information processing empowered by meta-devices

Abstract The burgeoning demand for high-performance computing, robust data processing, and rapid growth of big data necessitates the emergence of novel optical devices to efficiently execute demanding computational processes. The field of meta-devices, such as metamaterial or metasurface, has experienced unprecedented growth over the past two decades. By manipulating the amplitude, phase, polarization, and dispersion of light wavefronts in spatial, spectral, and temporal domains, viable solutions for the implementation of all-optical analog computation and information processing have been provided. In this review, we summarize the latest developments and emerging trends of computational meta-devices as innovative platforms for spatial optical analog differentiators and information processing. Based on the general concepts of spatial Fourier transform and Green’s function, we analyze the physical mechanisms of meta-devices in the application of amplitude differentiation, phase differentiation, and temporal differentiation and summarize their applications in image edge detection, image edge enhancement, and beam shaping. Finally, we explore the current challenges and potential solutions in optical analog differentiators and provide perspectives on future research directions and possible developments.

Causal evidence for increased theta and gamma phase consistency in a parieto-frontal network during the maintenance of visual attention.

Endogenous visuo-spatial attention is under the control of a fronto-parietal network of brain regions. One key node in this network, the intra-parietal sulcus (IPS), plays a crucial role in maintaining endogenous attention, but little is known about its ongoing physiology and network dynamics during different attentional states. Here, we investigated the reactivity of the left IPS in response to brain stimulation under different states of selective attention. We recorded electroencephalography (EEG) in response to single pulses of transcranial magnetic stimulation (TMS) of the IPS, while participants (N=44) viewed bilateral random-dot motion displays. Individual MRI-guided TMS pulses targeted the left IPS, while the left primary somatosensory cortex (S1) served as an active control site. In separate blocks of trials, participants were cued to attend covertly to the motion display in one hemifield (left or right) and to report brief coherent motion targets. The perceptual load of the task was manipulated by varying the degree of motion coherence of the targets. Excitability, variability and information content of the neural responses to TMS were assessed by analysing TMS-evoked potential (TEP) amplitude and inter-trial phase clustering (ITPC), and by performing multivariate decoding of attentional state. Results revealed that a left posterior region displayed reduced variability in the phase of theta and gamma oscillations following TMS of the IPS, but not of S1, when attention was directed contralaterally, rather than ipsilaterally to the stimulation site. A right frontal cluster also displayed reduced theta variability and increased amplitude of TEPs when attention was directed contralaterally rather than ipsilaterally, after TMS of the IPS but not S1. Reliable decoding of attentional state was achieved after TMS pulses of both S1 and IPS. Taken together, our findings suggest that endogenous control of visuo-spatial attention leads to changes in the intrinsic oscillatory properties of the IPS and its associated fronto-parietal network.

An Imaging Method for Marine Targets in Corner Reflector Jamming Scenario Based on Time–Frequency Analysis and Modified Clean Technique

In the corner reflector jamming scenario, the ship target and the corner reflector array have different degrees of defocusing in the synthetic aperture radar (SAR) image due to their complex motions, which is unfavorable to the subsequent target recognition. In this manuscript, we propose an imaging method for marine targets based on time–frequency analysis with the modified Clean technique. Firstly, the motion models of the ship target and the corner reflector array are established, and the characteristics of their Doppler parameter distribution are analyzed. Then, the Chirp Rate–Quadratic Chirp Rate Distribution (CR-QCRD) algorithm is utilized to estimate the Doppler parameters. To address the challenges posed by the aggregated scattering points of the ship target and the overlapping Doppler histories of the corner reflector array, the Clean technique is modified by short-time Fourier transform (STFT) filtering and amplitude–phase distortion correction using fractional Fourier transform (FrFT) filtering. This modification aims to improve the accuracy and efficiency of extracting scattering point components. Thirdly, in response to the poor universality of the traditional Clean iterative termination condition, the kurtosis of the residual signal spectrum amplitude is adopted as the new iterative termination condition. Compared with the existing imaging methods, the proposed method can adapt to the different Doppler distribution characteristics of the ship target and the corner reflector array, thus realizing better robustness in obtaining a well-focused target image. Finally, simulation experiments verify the effectiveness of the algorithm.

Design, Analysis, and Implementation of the Subdivision Interpolation Technique for the Grating Interferometric Micro-Displacement Sensor

A high-resolution grating interferometric micro-displacement sensor utilizing the subdivision interpolation technique is proposed and experimentally demonstrated. As the interference laser intensity varies sinusoidally with displacement, subdivision interpolation is a promising technique to achieve micro-displacement detection with a high resolution and linearity. However, interpolation errors occur due to the phase imbalance, offset error, and amplitude mismatch between the orthogonal signals. To address these issues, a subdivision interpolation circuit, along with 90-degree phase-shifter and high-precision DC bias-voltage techniques, converts an analog sinusoidal signal into standard incremental digital signals. This novel methodology ensures that its performance is least affected by the nonidealities induced by fabrication and assembly errors. Detailed design, analysis, and experimentation studies have been conducted to validate the proposed methodology. The experimental results demonstrate that the micro-displacement sensor based on grating interferometry achieved a displacement resolution of less than 1.9 nm, an accuracy of 99.8%, and a subdivision interpolation factor of 208. This research provides a significant guide for achieving high-precision grating interferometric displacement measurements.

Innovative solutions to the 2D nonlinear Schrödinger model in mathematical physics

We utilize a cohesive methodology to obtain some new solitary wave solutions for the (2 + 1)-dimensional nonlinear Schrödinger equation (2D-NLSE). The solutions provided herein are significant for elucidating physical phenomena in various domains, including optical fibers, plasma media, and ocean waves. Furthermore, scientific computing would be used to illustrate the physical interpretation of nonlinear waves. Our study examines how 2D-NLSE wave solutions affect physical model characteristics such as group velocity dispersion, nonlinearity, and linear coefficients. These variables functioned to control the amplitude and wave phase of the optical solitary waves during transmission. Finally, the strategy provided here is applicable to many nonlinear systems and new energy trends in natural science.

Influence of phase difference and amplitude ratio on Kelvin–Helmholtz instability with dual-mode interface perturbations

A two-component discrete Boltzmann method (DBM) is employed to study the compressible Kelvin–Helmholtz (KH) instability with dual-mode interface perturbations, consisting of a fundamental wave and a second harmonic. The phase difference is analyzed in two distinct ranges, and the amplitude ratio is studied by varying the amplitude of either the first or second harmonic. The global average density gradient and the global mixing degree are analyzed from a hydrodynamic non-equilibrium perspective. The thermodynamic non-equilibrium (TNE) intensity is probed as a thermodynamic non-equilibrium variable. The system is also explored from a geometric perspective, with a focus on the rotation of two vortices, the mixing layer width, and the non-equilibrium area. Physically, under the influence of shear velocity, the fluid interface becomes distorted and progressively elongated, resulting in the formation of two small vortex structures and an enhancement of the physical gradient. The two vortices then begin to interact and merge into a single large vortex with complex fluid structures. Consequently, the physical gradient decreases, and the local TNE intensity weakens. Subsequently, the material interface elongates further, increasing the non-equilibrium region and enhancing the local TNE intensity. Finally, the physical gradient decreases due to dissipation and/or diffusion, weakening the local TNE intensity.

Towards Optimizing the Downlink Transmit Power in UAV-Integrated IRS Wireless Systems

Air-to-ground interference poses a critical challenge in integrating unmanned aerial vehicles (UAVs) into cellular networks. In downlink scenarios, UAVs can withstand significant interference from co-channel base stations (BSs) due to the guaranteed line-of-sight (LoS) connection with ground users. Our research focuses on power optimization in BSs and applying green energy principles to pave the way for more sustainable and energy-efficient BSs within UAV-integrated wireless systems. To this end, this paper investigates a downlink UAV communication scenario in which the intelligent reflecting surface (IRS) is mounted on the UAV to practically nullify the interference originating from the co-channel BSs. We formulate the IRS beamforming matrix to reduce transmit power by optimizing passive beamforming for IRS elements, incorporating adjustments to phase shifts and amplitude coefficients while considering the positioning of the UAV. The proposed optimization problem is non-convex, and thus a successive convex approximation (SCA) method is adopted to convert all constraints to a quadratic approximation. Simulation results demonstrate that the proposed SCA algorithm provides an efficient transmit power minimization approach with low computational complexity for large IRS since it achieves close-to-optimal performance, and significantly outperforms conventional systems without IRS. In interference scenarios and with different numbers of IRS meta-atoms, the proposed algorithm achieves a power reduction of approximately 8 and 13 dBm, while maintaining the same required signal-to-interference-plus-noise ratio.

Correlation Coefficients of Complex Fuzzy Sets and Their Application

Complex fuzzy set (CFS) is an extension of the fuzzy set (FS) which can deal with ambiguity by allowing a complex-valued membership degree of an element of a universal set. A host of researchers studied the complex fuzzy sets in theoretical and practical due to their amplitude term and phase term membership degrees. At present, various applications of fuzzy correlation and correlation coefficients have emerged by numerous researchers. But most of the works are related to real fuzzy data. In this article, we introduce the concept of the correlation coefficient of the complex fuzzy sets and some of its related properties are described. Furthermore, an application of the correlation coefficient of the complex fuzzy sets in pattern recognition is illustrated. To show the reliability and validity of our technique, we explain a comparative study with the existing method. J. Bangladesh Math. Soc. 44.2 (2024) 028–038

APPLICATION OF INTERFEROMETRIC SYNTHETIC APERTURE RADAR DATA IN ASSESSING LAND SUBSIDENCE RESULTING FROM HUMAN FACTORS IN NINH BINH PROVINCE, VIETNAM

The method of Satellite Interferometric Synthetic Aperture Radar, based on analyzing the phase difference of radar complex images recorded from two different positions simultaneously observing a terrain area where the signals have the same amplitude, frequency, and wavelength but different phases, the deformation of the terrain surface in Ninh Binh province is analyzed and calculated. The preliminary results include the construction of a deformation map of the ground surface in the Ninh Binh province for the period 2020 - 2021, consisting of 78,077 points. The map shows areas that have been uplifted with values of 3 - 5 mm/year and >5 mm/year, particularly highlighting areas with significant subsidence velocities of <-10 mm/year (Kim Son and Yen Khanh districts), some areas with subsidence velocities ranging from -5 to -10 mm/year (Yen Nhan commune, Yen Mo district, Nam Binh ward, Ninh Phong district in Ninh Binh city), and subsidence values of 0 to -5 mm/year in the communes bordering between Nho Quan and Gia Vien districts. These results provide a basis for identifying the causes of terrain surface changes and proposing solutions to prevent and mitigate damages in Ninh Binh province; In-depth studies will continue.

Theta-Gamma Decoupling - A neurophysiological marker of impaired reward processing in Parkinson's disease.

Individuals with Parkinson's disease (PD) exhibit altered reward processing, reflected by a decreased amplitude of an event-related potential (ERP) marker called reward positivity (RewP). Most studies have used RewP to investigate reward behavior due to the high temporal resolution of EEG and its high sensitivity. However, traditional single-electrode ERP analyses often overlook the intricate dynamics of non-phase-locked oscillatory activity and the complex interactions within these neural oscillatory patterns. Studying oscillatory activity is crucial as it provides mechanistic insights into the functional, spatial, and temporal aspects of neuronal processing. To address this gap, we employed a data-driven approach to identify EEG-based markers associated with PD reward processing deficits. Using an openly available 64-channel EEG dataset of 28 age- and sex-matched PD and control participants during a reinforcement learning task, we conducted a comprehensive secondary analysis. First, we employed a cluster-based permutation method to extract ERP markers, finding a consistent decrease in reward positivity in PD, regardless of medication status. Additionally, through region of interest (ROI) analysis on time-frequency data, we identified specific oscillatory patterns during reward processing. PD patients exhibited attenuated theta power and increased gamma power compared to healthy controls (HC). Notably, within the PD group, those off medication showed anterior localization of high gamma power, while those on medication displayed higher posterior gamma power. Building upon these findings, we explored phase-amplitude coupling between theta phase and gamma amplitude measured by the modulation index. We observed a trend of decreased theta-gamma coupling in PD patients, with statistically significant differences between on and off medication conditions. These results highlight the potential role of theta-gamma coupling as a neuromodulatory target for improving goal-oriented behavior in PD. Our correlation analyses suggest that high gamma power is linked to longer disease duration, while reduced reward positivity and low theta-gamma coupling may serve as markers of the dopaminergic impact on reward processing. Thus, our study unveils the intricate time-frequency dynamics underlying reward processing deficits in PD, emphasizing the utility of a data-driven approach to elucidate neural mechanisms and to identify potential therapeutic targets.

A novel compact multifunctional coaxial to waveguide power combining transitions for X‐band applications

AbstractThis paper presents the design of novel compact multifunctional coaxial to waveguide power combining transition (PCT) for X‐band applications. For the proof of the proposed concept, 2‐way PCT operating over the entire X‐band (8.2–12.4 GHz) and 4‐way PCT operation from 9.5 to 10.8 GHz are designed, developed, and characterised. Two‐way PCT achieves a measured return loss better than 14 dB over the operating band, and the measured amplitude imbalance and phase imbalance are within 0.25 dB and 4°, respectively. Four‐way PCT achieves a measured return loss better than 15 dB over the operating band, and the measured amplitude imbalance and phase imbalance are within 1 dB and 10°, respectively. Furthermore, a 6‐way PCT is also designed, fabricated, and measured to demonstrate the scalability of the proposed concept. The 6‐way PCT achieves the measured return loss better than 15 dB from 9.9 to 10.475 GHz, and measured amplitude and phase imbalances are within 0.6 dB and 10°, respectively. The designed power combining transition is proposed to be used in X‐band applications like antenna array applications and power combining applications.

The Fine Structure of Coseismic Electromagnetic Response Based on Geomagnetic and Seismological Observations

This paper examines the response in geomagnetic field variations caused by the 2020–2023 earthquakes with magnitudes Mw ≥ 7.0 in the Aegean Sea and eastern Turkey. A detailed comparison of high-precision observations of the geomagnetic field and seismograms recorded at complex geophysical observatories within a radius of 3000 km from the epicenters was carried out. The joint analysis involves averaged 1-s data on the rate of change of the magnetic field and records from broadband seismic stations. Their characteristics are assessed in both time and frequency domains. The spectral characteristics of body and surface waves are separately compared with those of the geomagnetic signal. It is shown that the beginning of disturbance in the magnetic field at each observatory strictly coincides with the arrival of the P-wave and intensifies with the arrival of S-waves. The maximum geomagnetic disturbance is caused by surface waves. The amplitude of electromagnetic excitations is proportional to the amplitude of the parent seismic phases. Thus, the coseismic nature of the observed electromagnetic signal has been confirmed, suggesting its excitation in the Earth’s crust as seismic waves propagate.

Transcranial magneto-acoustic stimulation enhances motor function and modulates cortical excitability of motor cortex in a Parkinson's disease mouse model

Parkinson's disease (PD) is a neurodegenerative disorder characterized primarily by motor dysfunction. Transcranial magneto-acoustic stimulation (TMAS), an emerging non-invasive brain neuromodulation technology, is increasingly being applied in the treatment of brain diseases. However, the effects of TMAS on PD are unknown, which is not well studied. Here, we utilized TMAS on PD model mice induced by MPTP to investigate the underlying mechanism of therapy. Our study found that TMAS improved the behavioral performance of PD model mice, enhancing the motor function and motivation for movement. Besides, it inhibited the increased beta oscillations in the motor cortex, while also reducing gamma oscillations. Moreover, the abnormally exaggerated beta-broad gamma phase amplitude coupling (PAC) was decreased after TMAS, and there was a significant negative correlation between PAC and both distance traveled and mean speed during the open filed test. Additionally, the ongoing stimulation could provide neuroprotection, implying that TMAS could ameliorate the loss of dopaminergic neurons, with no damage observed in the brain tissue of mice. Our findings suggest that TMAS could provide a non-invasive tool for the treatment of Parkinson's disease and beta-broad gamma phase amplitude coupling could be employed as a biomarker for PD.

Amplitude–Phase Structure of the Sound Field in the Deep Sea

Amplitude–Phase Structure of the Sound Field in the Deep Sea

Effect of Ischemic Preconditioning on Endurance Running Performance in the Heat.

Ischemic preconditioning (IPC) is a strategy that may enhances endurance performance in thermoneutral environments. Exercising in the heat increases thermoregulatory and cardiovascular strain, decreasing endurance performance. The current study aimed to determine whether IPC administration improves endurance performance in the heat. In a randomized crossover design, 12 healthy subjects (V̇O2max: 54.4 ± 8.1 mL·kg-1·min-1) underwent either IPC administration (220 mmHg) or a sham treatment (20 mmHg), then completed a moderate-intensity 6-min running (EX1) and a high-intensity time-to-exhaustion running test (EX2) in a hot environment (35 °C, 50 % RH). Cardiac function, oxygen consumption (V̇O2), and core body temperature (TCORE) were measured. During EX2, IPC administration increased the total running time in the heat compared to the sham treatment (IPC: 416.4 ± 61.9 vs. sham 389.3 ± 40.7 s, P = 0.027). IPC administration also increased stroke volume (IPC: 150.4 ± 17.5 vs. sham: 128.2 ± 11.6 ml, P = 0.008) and cardiac output (IPC: 27.4 ± 1.7 vs. sham: 25.1 ± 2.2 ml min-1, P = 0.007) during 100% isotime of EX2. End-exercise V̇O2 (IPC: 3.72 ± 0.85 vs. sham: 3.54 ± 0.87 L·min-1, P = 0.017) and slow phase amplitude (IPC: 0.57 ± 0.17 vs. sham: 0.72 ± 0.22 L·min-1, P = 0.016) were improved. When compared with the baseline period, an increase in TCORE was less in the IPC condition during EX1 (IPC: 0.18 ± 0.06 vs. sham: 0.22 ± 0.08 °C, P = 0.005) and EX2 (IPC: 0.87 ± 0.10 vs. sham: 1.03 ± 0.10 °C, P < 0.001). IPC improves high-intensity endurance performance in the heat by 6.9 %. This performance benefit could be associated with improved cardiac and thermoregulatory function engendered by IPC administration.

Modulation of diurnal variation in rainfall associated with tropical cyclones over the East Asia–Western North Pacific region by environmental vertical wind shear

AbstractVertical wind shear (VWS), as an important dynamic factor influencing tropical cyclone rainfall (TCR), has a remarkable diurnal cycle of variation over the East Asia–western North Pacific region. The magnitude of tropical cyclone (TC)‐experienced VWS has enhanced amplitude but different phases over the South China Sea (SCS) and coastal East China (CEC) compared with that over the open ocean. Diurnal variation in TCR over the SCS shows statistically significant correlation with that of VWS. The convection concentrated in the downshear‐left quadrant strengthens markedly when VWS becomes large, thereby delaying the peak rainfall in the inner core of the TC and enhancing the amplitude of the diurnal cycle of TCR at ~09 local standard time. Over CEC, the diurnal signal of TCR is very weak but statistically significant in the downshear‐left and upshear‐right quadrants with opposite phase, illustrating the change in asymmetry of the spatial distribution of TCR induced by the large VWS diurnal cycle. The findings of this study could provide reference for improved forecasting of TCR on the fine temporal scale.

100 Gb/s/λ polarization multiplexing PON downlink based on simplified heterodyne coherent reception

In this work, we experimentally demonstrate a 100Gb/s/λ downstream transmission link for coherent passive optical networks (PONs) up to 50 km, achieving an optical power budget of 29 dB through polarization multiplexing (PolMux) of two 50 Gb/s channels using multiband carrierless amplitude phase modulation (multiCAP) and optical single side band (OSSB) modulation. Additionally, we introduce a separate PolMux 50 Gb/s link that presents an optical power budget of 38.7 dB. Both links have been achieved using a simplified polarization-demultiplexing heterodyne coherent receiver. The robustness of the system is experimentally evaluated by analyzing its response to various input states of polarization. The transmission has been accomplished using 10 GHz electrical bandwidth devices at both the transmission and receiving ends, thereby paving the way for low-cost 100G links suitable for applications such as PONs.

The Estimation of Power Losses in Composite Cores Excited by Harmonic Flux Density Waveforms

This paper presents a study of the empirical approach to the estimation of power losses in composite cores excited by harmonic flux density waveforms. Nowadays, magnetic cores operating in power electronic devices are excited by distorted (e.g., harmonic) flux density waveforms. Magnetic material properties are mostly determined for sinusoidal waveforms of the magnetic flux density. However, these properties can vary significantly in the case of harmonic excitations, which affects the devices’ efficiency. The effect of harmonic flux density waveform parameters (amplitude ratio and phase angle) on the level of power losses in soft magnetic composites is analyzed. A simple, empirical model of harmonic losses based on standardized measurements, i.e., carried out for sinusoidal flux density waveforms, is modified and validated. It is revealed that the empirical approach to estimating harmonic losses can be applied to magnetic composites with satisfactory modelling results.

Optical soliton noninteraction transmission in optical communication systems

The building of the national communication infrastructure and growing demand for data traffic both depend heavily on the advancement of optical soliton communication technology. In particular, by studying the interaction of optical solitons, some methods of controlling optical solitons can be explored to design more stable and efficient optical communication systems. In this paper, the interactions between optical solitons are studied based on the theory of generalized Schrödinger–Hirota equation. By studying the amplitude ratio, spacing and phase difference of the optical solitons, the interactions between the optical solitons occurring in the optical fiber transmission process are attenuated. The noninteraction transmission of optical solitons are realized with small spacing between them. The conclusions of this paper are not only of great significance for the in-depth understanding of the nature of optical soliton interactions, but also of great practical value for promoting the application of optical solitons in optical communications and other fields.