Phase Difference Research Articles

Effect of Electrode Distance and Size on Electrocorticographic Recordings in Human Sensorimotor Cortex.

Subdural electrocorticography (ECoG) is a valuable technique for neuroscientific research and for emerging neurotechnological clinical applications. As ECoG grids accommodate increasing numbers of electrodes and higher densities with new manufacturing methods, the question arises at what point the benefit of higher density ECoG is outweighed by spatial oversampling. To clarify the optimal spacing between ECoG electrodes, in the current study we evaluate how ECoG grid density relates to the amount of non-shared neurophysiological information between electrode pairs, focusing on the sensorimotor cortex. We simultaneously recorded high-density (HD, 3mm pitch) and ultra-high-density (UHD, 0.9mm pitch) ECoG, obtained intraoperatively from six participants. We developed a new metric, the normalized differential root mean square (ndRMS), to quantify the information that is not shared between electrode pairs. The ndRMS increases with inter-electrode center-to-center distance up to 15mm, after which it plateaus. We observed differences in ndRMS between frequency bands, which we interpret in terms of oscillations in frequencies below 32Hz with phase differences between pairs, versus (un)correlated signal fluctuations in the frequency range above 64Hz. The finding that UHD recordings yield significantly higher ndRMS than HD recordings is attributed to the amount of tissue sampled by each electrode. These results suggest that ECoG densities with submillimeter electrode distances are likely justified.

Examining the upper frequency limit of dynamic cerebral autoregulation: Considerations across the cardiac cycle during eucapnia.

There are differences within the literature regarding the upper frequency cut-off point of the dynamic cerebral autoregulation (CA) high-pass filter. The projection pursuit regression approach has demonstrated that the upper frequency limit is ∼0.07Hz, whereas another approach [transfer function analysis (TFA) phase approaching zero] indicated a theoretical upper frequency limit for the high-pass filter of 0.24Hz. We investigated how these limits accurately represent the CA upper frequency limit, in addition to extending earlier findings with respect to biological sexes and across the cardiac cycle. Sixteen participants (nine females and seven males) performed repeated squat-stand manoeuvres at frequencies of 0.05, 0.10, 0.15, 0.20 and 0.25Hz, with insonation of the middle and posterior cerebral arteries. Linear regression modelling with adjustment for sex and order of squat completion was used to compared TFA gain and phase with 0.25Hz (above the theoretical limit of CA). The upper frequency limit of CA with TFA gain was within the range of 0.05-0.10Hz, whereas TFA phase was within the range of 0.20-0.25Hz, and consistent between vessels, between sexes and across the cardiac cycle. Females displayed greater middle cerebral artery gain compared with males (all P<0.047), and no phase differences were present (all P>0.072). Although sex-specific differences were present for specific TFA metrics at a given frequency, the upper frequency limit of autoregulation was similar between cerebral conduit vessels, cardiac cycle phase and biological sex. Future work is warranted to determine whether an upper frequency limit exists with respect to hysteresis analyses.

Unsteady Flow Structure of Rotating Instability in a 1.5-Stage Axial Compressor

Abstract Unsteady flow structure of the rotating instability (RI) in a 1.5-stage axial compressor is investigated through experimental and numerical analyses. In the tested compressor, the total pressure rise of the rotor stagnates at a certain flow coefficient before it increases again towards lower flow rate in a case involving a wide tip clearance. The RI appears beyond this stagnant point as the compressor is throttled. The RI indicates a gentle hump in the frequency spectra of wall pressure or the flow velocity near the tip in a range approximately 20 to 40% of the blade-passing frequency. As the flow rate decreases, the mode order of the RI increases, in contrast to more commonly reported tendency, while the propagation velocity remains constant. These features are well captured by DES of the half-annulus model. At its onset, RI is formed by the collision of the tip leakage vortex onto the pressure surface of the adjacent blade and subsequent vortex segmentation. This vortex structure spans two blade passages and propagates in the direction opposite to the rotor rotation. As the compressor is throttled, RI becomes more dominated by the circumferential propagation of vortex breakdown of tip leakage vortices, which occur simultaneously among neighboring passages with slight phase differences. The mechanism is discussed in relation to the temporal change in the blade tip loading. The frequency of vortex shedding increases with the reduction in flow rate and thus the increase in the number of RI disturbances.

Dynamic tunable nonreciprocal single-photon scattering mediated by a giant atom assisted with a time-modulated cavity

Nonreciprocal single-photon scattering in a one-dimensional waveguide coupled to a giant two-level atom assisted with a time-modulated single-mode cavity is investigated. The analytic expressions of the single-photon scattering amplitudes are derived by using an effective Floquet Hamiltonian in real space. The scattering characteristics are discussed detail in both the Markovian and the non-Markovian regimes, and the corresponding conditions for achieving perfect nonreciprocal single-photon transmission are obtained. In the Markovian regime, a frequency-tunable single-photon diode with an ideal transmission contrast ratio can be realized by adjusting the frequency of the cavity mode, the local coupling phase difference, and the accumulated phase between the two coupling points. Furthermore, the influence of the intrinsic energy dissipations on the photon transport is discussed in detail. It is found that the dissipations of the cavity and the giant atom affect discriminatively the nonreciprocal single-photon scattering process. In the non-Markovian regime, the influence of the non-Markovian retarded effect induced by the time delay on the nonreciprocal single-photon scattering is discussed in detail. The results reveal that, although the retarded effect leads to a complex nonreciprocal scattering spectrum, dynamic tunable perfect nonreciprocal transmission with more abundant physical phenomena suitable for photons with different frequencies within a larger range can also be achieved. Such a nonreciprocal single-photon device can be used as an elementary unit for various quantum information processing and may have potential applications in quantum network engineering.

Phase-modulation-induced reconfigurable rotating photonic lattices in atomic vapors.

We propose a method to prepare optically induced rotating hexagonal and honey-comb photonic lattices by employing the phase modulated three-beam interference in atomic vapors with electromagnetically induced transparency. The phase differences among the three beams are dynamically elaborated to synthesize the circular motion (in transverse dimensions) of waveguides in the photonic lattices. Further, we verify this model experimentally in the case of low-speed modulation. A weak Gaussian probe field is sent into the constructed helical photonic lattices to image their structures under electromagnetically induced transparency (EIT). The motion trajectories of the sites on the discretized output patterns exhibit repeated circles, advocating the formation of rotating lattices. By introducing phase modulations to involved beams, we provide a continent way for producing transverse motions in waveguide arrays with reconfigurability in rotational direction, radius, and speed. This work looks forward to promising applications in topological photonics with great popularity.

Comparable Theta Phase Coding Dynamics Along the Transverse Axis of CA1.

Topographical projection patterns from the entorhinal cortex to area CA1 of the hippocampus have led to a hypothesis that proximal CA1 (pCA1, closer to CA2) is spatially more selective than distal CA1 (dCA1, closer to the subiculum). While earlier studies have shown evidence supporting this hypothesis, we recently showed that this difference does not hold true under all experimental conditions. In a complex environment with distinct local texture cues on a circular track and global visual cues, pCA1 and dCA1 display comparable spatial selectivity. Correlated with the spatial selectivity differences, the earlier studies also showed differences in theta phase coding dynamics between pCA1 and dCA1 neurons. Here we show that there are no differences in theta phase coding dynamics between neurons in these two regions under the experimental conditions where pCA1 and dCA1 neurons are equally spatially selective. These findings challenge the established notion of dCA1 being inherently less spatially selective and theta modulated than pCA1 and suggest further experiments to understand theta-mediated activation of the CA1 sub-networks to represent space.

Phase shift in optical fiber induced by mechanical stress

This work refers to the vibration optimization of a fiber optic interferometer whose detection performance may be compromised due to external mechanical or acoustic excitations. In such an interferometer, the optical path is split into two arms, with one significantly longer than the other. Optimizing the interferometer involves minimizing the phase difference of light caused by mechanical deformations, particularly in the long arm, resulting from unintended external excitations. Extending previous works from Hocker, who considered isotropic compression and longitudinal stress, we also investigate an additional mechanical load on the fiber: torsional stress. All these different loads will be compared to determine which one induces the most significant phase shift. Ultimately, incorporating protection into the equations will lead to a more realistic model. This approach will allow us to identify the most suitable protective materials to achieve a fiber optic interferometer resilient to external constraints.

Space- and frequency-division multiplexing in photonic second-order topological insulators

Higher-order topological insulators, originally proposed in quantum condensed matters, have provided a new avenue for localizing and transmitting light in photonic devices. Nontrivial band topology in crystals with certain symmetries can host robust topological edge states and lower dimensional topological corner states (TCS), making them a promising platform for photonics applications. Here, we have designed several types of TCS with only two specific C6v-symmetric photonic crystals with various seamless splicing boundaries, where all the supposed TCS with diverse electromagnetic characteristics are visualized via numerical simulations and experimental measurements. More interestingly, we have observed that those TCS overlapping in spectral and spatial space tend to interweaved, inducing spectrum division. Meanwhile, the equivalent corners appear to have TCS with a phase difference, which is critical for directional activation of pseudospin dependence. Our findings demonstrate that coupled TCS with phase difference at different nanocavities can be selectively excited by a chiral source, which indicates that the TCS at this time have pseudospin-dependent properties. We further design a specific splicing structure to prevent coupling between adjacent TCS. This work provides a flexible approach for space- and frequency-division multiplexing in photonic devices.

Simulation study of abdominal hemorrhage based on magnetic induction tomography.

Abdominal hemorrhage is an important clinical disease that can be life-threatening in severe cases. Therefore, timely detection and treatment of abdominal hemorrhage is crucial for the health and safety of patients. Magnetic induction tomography is a non-invasive, nonradioactive, and non-contact electromagnetic imaging technology with potential application value for disease screening and continuous monitoring. In this paper, a simulation model of electrical impedance distribution close to the real human abdominal tissue was constructed, and based on this model, the magnetic induction tomography simulation method of internal bleeding was studied by the finite element numerical method, and the comparison was verified by phantom experiments. The eddy current density distribution inside the abdominal tissue and the magnetic induction phase data at the tissue boundary are solved, and sensitivity analysis of phase differences caused by changes in the radius and position of bleeding volume was conducted, and three sensitivity indicators were proposed. Both the simulation and phantom experiment show that when there are six types of tissues with different conductivity in the abdomen, the radius of bleeding increases from 10 to 30mm, and the radius phase difference sensitivity index Ar increases approximately linearly monotonically. Its radius transformation sensitivity Kr is 3.0961 × 10-5°/cm. When the position of the bleeding volume changes, the sensitivity index Ax of the x-axis displacement phase difference shows a quasilinear monotonic decrease, and the x-axis displacement sensitivity Kx is -6.3744 × 10-6°/cm. The y-axis displacement phase difference sensitivity Ay index shows a quasilinear relationship and monotonically increases, with a y-axis displacement sensitivity Ky of 5.2870 × 10-4°/cm. The results indicate that the phase difference sensitivity before and after the occurrence of bleeding can be used as a quantitative monitoring indicator to monitor the occurrence and trend of intra-abdominal hemorrhage, laying the foundation for the preliminary screening and continuous monitoring of abdominal hemorrhage diseases using magnetic induction imaging.

Levonorgestrel 52 mg intrauterine device placement without uterine sounding: A feasibility study

ObjectivesTo evaluate feasibility of levonorgestrel 52 mg intrauterine device (IUD) placement without uterine sounding. Study designWe performed a three-phase feasibility study from February 2023-May 2024. In phase one, participants had levonorgestrel 52 mg IUD placement with sounding. In the experimental phases, placement occurred without sounding and with (phase two) or without (phase three) concurrent transabdominal sonography and participants had 3-month follow-up. We defined feasibility as successful IUD placement without uterine sounding based on ultrasound confirmation. We measured total instrumentation time from the sound or inserter touching the cervix to inserter removal. Participants reported maximal pain experienced using a 100-mm Visual Analog Scale when the inserter was removed. We calculated a sample size of 30 per phase so that if there was one failed placement, the lower 95% confidence interval of the successful placement rate would be no less than 90.0%. ResultsSuccessful placement without sounding occurred in 30(100%) participants in phase two and 28(93.3%) in phase three. Median instrumentation was longest in phase one (49.5 [interquartile range (IQR) 42.3–55.0] seconds) compared to phases two (16.0 [IQR12.0–28.0] seconds, p < 0.0001) and three (25.0 [IQR 18.5–32.2] seconds, p < 0.0001). Participants’ median placement pain was 21.0 (IQR 10.3–32.8) mm in phase one with no difference in phase two (25.5 [IQR 14.3–47.0] mm, p = 0.35), but was higher in phase three (36.0 [IQR 22.8, 61.0] mm, p = 0.01). ConclusionsLevonorgestrel 52 mg IUD placement without sounding is feasible with concurrent sonography. Placement without sounding results in shorter instrumentation time but does not decrease maximum placement pain.

A semi-analytical prediction model for fluid elastic instability in the streamwise direction of a normal triangular tube array

Fluid elastic instability (FEI) is widely regarded as the most destructive mechanism of flow-induced vibration. Numerous failures of heat exchanger tubes have been attributed to this phenomenon. This paper focuses on a normal triangular tube array and develops a semi-analytical time-domain solving model to address FEI in the streamwise direction. Utilizing computational fluid dynamics simulations and image processing techniques, a comprehensive set of tube-in-channel model parameters is derived, including the area perturbation amplitude, phase difference, mean area along the flow channel, and steady-state term of flow velocity. Tube motion in the streamwise direction generates a disturbance distinct from that caused by transverse flow, leading to revisions in the expressions of relevant model parameters. Furthermore, variations in these parameters across different positions and velocities are quantitatively analyzed through function fitting, yielding specific mathematical formulas. Ultimately, the derived tube-in-channel model parameters applicable to streamwise FEI are validated against experimental data, affirming the model's accuracy.

Study on the characteristics of fluid exciting force on impeller of high-speed centrifugal pump under the condition of poiseuille inflow

Abstract The paper adopted the turbulence model of Wall-Model Large Eddy Simulation with improved algebraic form (WMLES S-Omega) to carry out the study on the fluid exciting force on impeller of high-speed centrifugal pump under the conditions of Poiseuille inflow and uniform inflow. The external characteristics and the vibration displacement of the shaft of high-speed centrifugal pump are tested. The results indicated that it is the high matching that the test and numerical external data of high-speed centrifugal pump under the condition of Poiseuille inflow. The test results of vibration displacement of shaft match the fluid exciting force better in terms of waveform and phase difference under the condition of Poiseuille inflow. The contribution degree of force and torque from the shroud inner surface in the X and Y direction is 76.3%, 80.7%, 79.5% and 85% of the resultant force and torque, and its force from the inner and outer surfaces of shroud and hub in the Z direction is 94.3%, and its torque from blades’ surfaces in the Z direction is 98.3%. The study results can provide some theoretical support for the research of fluid exciting force and hydraulic optimization design of centrifugal pump.

High precision phase difference calculation based on adaptive mixed-radix All-phase FFT for Tokamak plasma electron density measurement

In many Tokamak devices, laser interferometers, such as HCN, DCN, CO2, etc, are employed to measure the plasma electron density by calculating the phase difference between the reference signal and the detector signal. This paper proposes an adaptive All-phase fast Fourier transform (Ap-FFT) method in the electronic density of the plasma. And analyze the reasons why the multi-frequency measurement phase is inaccurate. The proposed method can reduce the accuracy of phase calculation by adjusting the conversion length and mixed-radix to reduce the spectrum leakage and grid effect. At the same time, the experimental data verifies the correctness of the calculation results of this method, and it shows that the measurement uncertainty of the method is 10% higher than the 1024-point Ap-FFT, and 15% higher than the 1024-point FFT. This method can be effectively applied to the measurement of the electronic density of an ionic plasma for plasma and provides a valuable reference for other phase detection systems and equipment.

The mechanism of aerodynamic performance enhancement of flapping wings with spanwise active deformation

The single stiffness makes the micro-air vehicles (MAVs) only to show excellent flight performance in a specific flow field environment. The MAVs should have the ability to actively deform to adapt to different application scenarios. This study investigates the effects of spanwise active deformation amplitude (ψmax), phase difference (φP), and Strouhal number (St) on the aerodynamic loads and vortex of a wing through numerical simulations. Under the condition of Re= 1000, numerical simulations were conducted on a rectangular wing with an aspect ratio of 4 during the flapping process. The study reveals that moderate spanwise deformation can increase the thrust of the wing and improve propulsion efficiency (ηP). Within the study's scope, the thrust coefficient increases monotonically and linearly with the deformation, but the propulsion efficiency improves only within a limited parameter range. By observing the vortex under different spanwise deformations and monitoring the forces at different positions of the wing, it was found that active deformation can enhance the strength of the leading-edge vortex (LEV) and the wingtip vortex (TV), thereby enhancing the generation of thrust. The results also indicate that the enhancement of LEV is achieved through the coupling between LEV and secondary vortex. At different Strouhal numbers, improvements in ηP can only be achieved through the combined effects of increased vortex strength and optimal vortex residence time. Additionally, it was observed that at lower St, TV can switch from contributing thrust to causing drag.

Pelvic floor muscle electrical coupling in chronic pelvic pain: Insights into pathophysiology and botulinum toxin treatment effects

This study aimed to assess the electrical coupling between both pelvic floor muscle (PFM) sides (two-sided coupling) and within individual PFM sides (one-sided coupling) in chronic pelvic pain (CPP) before and after botulinum neurotoxin type A (BoNT/A) treatment. Surface electromyographic (sEMG) signals were recorded from the left and right PFM of 24 patients (P) with CPP before and after being treated with BoNT/A (Weeks 0,8,12,24). Recordings were also made in 24 healthy women (H). PFM two-sided and one-sided coupling was evaluated during contractions by the cross-correlation (CC) and the imaginary part of coherency (iCOH) of their sEMG signals. Significant differences between their values were assessed comparing P(0) vs. P(8,12,24) and H vs. P(0,8,12,24). This study showed that PFM two-sided coupling is similar across groups before treatment, while PFM one-sided coupling on the patients’ most painful side is deranged before and also after BoNT/A treatment: amplitude coupling is lower (<CC) and phase difference is greater (>iCOH) than healthy women’s. This could be justified by altered neuromotor control strategies developed as an adaptation to muscle pain, structural and electrical changes in PFM, and alterations in their innervation pattern, which may influence the onset, perpetuation, or recurrence of CPP after treatment.

Synchronization analysis of a four-motor excitation with torsion spring coupling vibrating system

In oil drilling processes, vibrating screen is a crucial solid control equipment for separating harmful solid-phase particles. However, the conventional utilization of either dual-motor or triple-motor is inadequate demanding the excitation force of large vibrating equipment. Moreover, self-synchronization in zero phase is difficult to achieve in multiple motors system. To avoid cancellation of the excitation force caused by the phase inconsistency of multiple motors, the adoption of a four-motor excitation with torsion spring coupling system is proposed this work. Initially, the mathematical model of the vibrating system is formulated through the Lagrange's equation. Subsequently, the steady-state solution is determined using Laplace transform. Then the conditions and characteristics in stable equilibrium state are elucidated employing the small parameter averaging method. Ultimately, the reliability and applicability of the theoretical results are substantiated through numerical simulations. The findings reveal that with the increase of the torsion spring stiffness, the phase difference between the motors connected by torsion springs (MCTSs) is exponentially decreased, and desired zero-phase synchronization in engineering is eventually achieved. Furthermore, the present study uncovers two distinct synchronization mechanisms in the torsion spring coupling system: mechanical controlled synchronization between MCTSs is inevitably achieved, while the self-synchronization between motors unconnected by torsion springs (MUTSs) is limited by the synchronization conditions. The study provides valuable insights for designing mechanical controlled synchronization and self-synchronization vibrating machines.

Polarization-maintaining fiber based macehead shaped interferometric sensor for accurate measurement of refractive index and temperature

A macehead-shaped bent polarization-maintaining fiber-based interferometric sensing structure called MBPIS is described and experimentally demonstrated for precise temperature and refractive index measurement. The sensor’s working principle is explained by simulating the spatial distribution of the field intensity in straight and bending PANDA fibers. A maximum extinction ratio (∼21 dBm) for the interference dip wavelength (1527.825 nm) in the sensor’s output spectrum was optimized by manipulating the birefringence of propagating fiber modes by adjusting PMF’s bending diameter from 17 to 11 mm. The phase difference changes between these fiber modes due to temperature and RI-induced birefringence cause a shift in the interference spectrum. The sensor’s highest RI sensitivity has been seen at −259.32 nm/RIU for a wide range of analytes from 1.3333 to 1.3579. In contrast, the highest temperature sensitivities evaluated for the temperature range of 0 ∼ 100 ℃ are −220 pm/℃ and −0.139 dBm/℃, respectively.

Quantum Accelerometry Based on a Geometric Phase

A conceptual model of a promising quantum accelerometer based on a two-mode atomic Bose–Einstein condensate has been proposed. Acceleration generates a specific difference in geometric phases between the condensate modes, which shifts the interference pattern of matter waves. The modes have ring configurations, in the plane of which the measured acceleration vector lies. The homogeneity of the potentials of the ring configurations is interrupted by additional localized potentials generated by defects. Under the variation of the parameters of appropriately located defects with a certain structure, the wavefunctions of the condensate modes acquire geometric phases that differ in the presence of acceleration. Calculations performed for ring configurations of the condensate of 87Rb atoms with a radius of 0.25 mm has showed that the proposed scheme can detect a microgravity of ~10–6–10–7g.

Atomic-scale revelation of Cu diffusion mechanism in high-performance Pr-doped 2:17-type SmCo magnets

The coercivity of 2:17-type SmCo magnets is mainly determined by the gradient distribution of Cu within the cell boundary phase. However, the fundamental migratory behavior and driving force causing such Cu distribution remains unclear. In this work, the phenomenon of Cu enrichment at the lamellar/intracellular interface is reported at the atomic scale, and a new Cu diffusion mechanism of 2:17-type SmCo magnets is proposed via combining microstructure characterization with first-principles calculation. Our study indicates that Cu will migrate from the intracellular phase to the lamellar/intracellular phase interface following the migration of twin boundary, and then diffuses further along the lamellar phase interface to the cell boundary, achieving the expected Cu-rich cell boundary structure. Doping Pr results in a reduction of Cu substitution energy in the lamellar phase, leading to a decreased driving force during the subsequent Cu diffusion. As a result, the Cu does not completely diffuse into the cell boundary phase there is Cu enrichment at the interface between lamellar and intracellular phases. The Cu concentration of the cell boundaries could be increased in 2:17-type SmCo magnets by reasonable designing the substitution energy difference of intracellular phase, lamellar phase and cell boundary phase that promote Cu diffusion to cell boundary. Our study sheds light on the control of Cu segregation in magnets and a new strategy for enhancing the magnetic performance of 2:17-type SmCo magnets.

Dynamic simulation of differential accumulation history of deep marine oil and gas in superimposed basin: A case study of Lower Paleozoic petroleum system of Tahe Oilfield, Tarim Basin, NW China

According to the complex differential accumulation history of deep marine oil and gas in superposition basins, the Lower Paleozoic petroleum system in Tahe Oilfield of Tarim Basin is selected as a typical case, and the process of hydrocarbon generation and expulsion, migration and accumulation, adjustment and transformation of deep oil and gas is restored by means of reservoine-forming dynamics simulation. The thermal evolution history of the Lower Cambrian source rocks in Tahe Oilfield reflects the obvious differences in hydrocarbon generation and expulsion process and intensity in different tectonic zones, which is the main reason controlling the differences in deep oil and gas phases. The complex transport system composed of strike-slip fault and unconformity, etc. controlled early migration and accumulation and late adjustment of deep oil and gas, while the Middle Cambrian gypsum-salt rock in inner carbonate platform prevented vertical migration and accumulation of deep oil and gas, resulting in an obvious “fault-controlled” feature of deep oil and gas, in which the low potential area superimposed by the NE-strike-slip fault zone and deep oil and gas migration was conducive to accumulation, and it is mainly beaded along the strike-slip fault zone in the northeast direction. The dynamic simulation of reservoir formation reveals that the spatio-temporal configuration of “source-fault-fracture-gypsum-preservation” controls the differential accumulation of deep oil and gas in Tahe Oilfield. The Ordovician has experienced the accumulation history of multiple periods of charging, vertical migration and accumulation, and lateral adjustment and transformation, and deep oil and gas have always been in the dynamic equilibrium of migration, accumulation and escape. The statistics of residual oil and gas show that the deep stratum of Tahe Oilfield still has exploration and development potential in the Ordovician Yingshan Formation and Penglaiba Formation, and the Middle and Upper Cambrian ultra-deep stratum has a certain oil and gas resource prospect. This study provides a reference for the dynamic quantitative evaluation of deep oil and gas in the Tarim Basin, and also provides a reference for the study of reservoir formation and evolution in carbonate reservoir of paleo-craton basin.