Effects Of Phase Delay Research Articles

Exploring the effects of phase delay on propeller noise: an experimental study in tandem configuration

Noise cancellation is a revolutionary control strategy, so effective that it has been integrated into high-end headphones. Implementing this approach on drones may seem challenging, but at the same time, it is highly appealing. The idea is to use some rotors, which constitute the main noise source, as a secondary pressure wave to eliminate the noise emitted by the entire propulsion system by inducing destructive interference among the individual sources. Implementing this kind of technology requires a significant understanding of the interaction mechanism of pressure waves emitted by the blades. The associated signature is not sinusoidal and exhibits strong directivity. This article will clearly demonstrate the potential of this approach by focusing attention not only on the effects but also on the nature of the interference mechanism. This finding is pivotal for the design of an active noise control system.

Nonlinear standing waves for assessing material nonlinearity in thin samples

The second harmonic generation (SHG) technique offers a quantitative damage parameter known as the acoustic nonlinearity parameter (β) capable of detecting the change in the inherent material nonlinearity. However, current SHG methods, in particular, those used for measuring β in construction materials, have an unresolved issue in their application due to limited sample sizes. The restricted sample dimensions lead to the generation of boundary-reflected waves, which hinder the selective detection of propagating waves and thus the precise evaluation of material nonlinearity through β. Furthermore, the use of large samples limits the compatibility of the SHG method with other characterization modalities, such as mechanical tests, X-ray diffraction, and computerized tomography. To address this issue, this paper introduces a new SHG method that is based on the use of nonlinear standing waves – the dominant longitudinal standing waves in a forced-free configuration. The corrections for phase delay and attenuation effect of each reflected wave are made, enabling accurate measurements of β in thin samples with no requirement in the thickness-wavelength ratio. The measured β is then employed to quantify the microstructural modification in cement paste induced by thermal damage, validating the proposed method as a promising tool for quantifying microstructural changes in materials.

Micropolar viscoelastic nanostructures subjected to laser-induced heat flux using the modified higher-order thermoelasticity model incorporating phase delay effects

Micropolar viscoelastic nanostructures subjected to laser-induced heat flux using the modified higher-order thermoelasticity model incorporating phase delay effects

Co‐designed radome with parasitic patches for the profile reduction and gain enhancement of antennas

AbstractTraditional radome adversely influences the antenna performance besides protecting the antenna from the outside environment. In this work, one co‐design of a millimeter‐wave antenna and radome using parasitic patches is presented, featuring a low profile and high gain. First, the basic influence of radome on patch antenna is investigated on a transparent and low‐loss material cyclic olefin copolymer. Then, the electromagnetic interaction between the patches and the antenna is investigated in detail to reduce the adverse effect of field reflection and phase delay. One prototype of the co‐designed radome and antenna was fabricated for demonstration. The measured results show that the entire profile of the co‐designed radome and antenna is significantly reduced from traditional 0.5–0.2 λg and the gain is enhanced by 2.4 dB.

Nonlinearity-Induced Asymmetric Synchronization Region in Micromechanical Oscillators.

Synchronization in microstructures is a widely explored domain due to its diverse dynamic traits and promising practical applications. Within synchronization analysis, the synchronization bandwidth serves as a pivotal metric. While current research predominantly focuses on symmetric evaluations of synchronization bandwidth, the investigation into potential asymmetries within nonlinear oscillators remains unexplored, carrying implications for sensor application performance. This paper conducts a comprehensive exploration employing straight and arch beams capable of demonstrating linear, hardening, and softening characteristics to thoroughly scrutinize potential asymmetry within the synchronization region. Through the introduction of weak harmonic forces to induce synchronization within the oscillator, we observe distinct asymmetry within its synchronization range. Additionally, we present a robust theoretical model capable of fully capturing the linear, hardening, and softening traits of resonators synchronized to external perturbation. Further investigation into the effects of feedback strength and phase delay on synchronization region asymmetry, conducted through analytical and experimental approaches, reveals a consistent alignment between theoretical predictions and experimental outcomes. These findings hold promise in providing crucial technical insights to enhance resonator performance and broaden the application landscape of MEMS (Micro-Electro-Mechanical Systems) technology.

Enhancement of synchronization bandwidth in an arch beam

Synchronization in microstructures has been widely investigated because of its rich dynamics and promising applications. Most investigations are devoted to revealing the basic features or enhancing the application performance in oscillator with hardening nonlinearity. However, few theoretical and experimental studies have been conducted on synchronization with softening nonlinearity, which easily occurs in imperfect manufacturing. In this paper, we built up a phase feedback loop with an arch beam that exhibits softening effect subjected to a synchronization perturbation. Theoretical analysis and experimental verification are applied to explore the effects of the feedback phase delay and nonlinearity on the synchronization bandwidth. The optimal phase delay for best synchronization bandwidth is determined and the significant enhancement of nonlinearity on the synchronization bandwidth is observed. An practical approach of manipulating the nonlinearity strength is proposed by tuning the ratio of the applied ac voltage VAC to DC voltage VDC. The presented foundings provide novel strategies to enhance the synchronization bandwidth in nonlinear oscillator with softening effects.

Spontaneous object recognition in capuchin monkeys: assessing the effects of sex, familiarization phase and retention delay.

The spontaneous object recognition (SOR) task is a versatile and widely used memory test that was only recently established in nonhuman primates (marmosets). Here, we extended these initial findings by assessing the performance of adult capuchin monkeys on the SOR task and three potentially intervening task parameters-object familiarization phase, retention delay and sex. In Experiment 1, after an initial 10-min familiarization period with two identical objects and a pre-established retention delay (0.5, 6 or 24h), the capuchins preferentially explored a new rather than the familiar object during a 10-min test trial, regardless of delay length. In Experiment 2, the capuchins were again exposed to two identical objects (but now for 10 or 20 min), then a 30-min retention delay and a 10-min test trial. An exploratory preference for the new over the familiar item was not affected by the length of the familiarization interval, possibly because overall exploration remained the same. However, the amount of initial object exploration was not related to task performance, and both males and females performed similarly on the SOR task with a 10-min familiarization, 30-min delay and 10-min test trial. Therefore, male and female capuchins recognize objects on the SOR task after both short and long delays, whereas a twofold increase in the familiarization phase does not affect task performance. The results also provide further support for the use of incidental learning paradigms to assess recognition memory in nonhuman primates.

Wide controllable range for the local surface plasmon resonance of Cu NWs

This work demonstrated the wide controllable range of local surface plasmon resonance (LSPR) for Cu nanowires (Cu NWs). The LSPR of Cu nanospheres (Cu NSs) and Cu NWs were calculated by the finite-difference time-domain (FDTD). As the diameter was increased from 75 to 300 nm, the extinction peak of Cu NSs could be mediated from 582 to 599 nm, whereas the extinction peaks for the Cu NWs could be shifted from 568 to 627 nm. This contrast is derived from the anisotropy and enhanced phase delay effect of Cu NWs. In attempts to verify this viewpoint, pure Cu NSs and Cu NWs with controllable diameter were prepared by hydrothermal method. And their LSPR spectrum results are well consistent with the simulation. Moreover, it is simulated that the spacing for NS would alter on LSPR peak for Cu NS. However, the arrangement of Cu NWs shows a negligible influence on their LSPR spectrum. As another anisotropic nanostructure, the LSPR spectrum of Cu nanoplates was investigated. And the experimental results could not be inconsistent well with the simulation, which is derived from the stacking effect of the nanoplates. Considering it is difficult to achieve the arrangement for nanostructures orderly, Cu NWs with negligible stacking effect would be a promising optical material that could apply in real application.

Hybrid ray-tracing/Fourier optics method to analyze multilayer diffractive optical elements.

The performance (paraxial phase delay) of conventional diffractive optical elements is generally analyzed using the analytical scalar theory of diffraction, based on thin-element approximation (TEA). However, the high thickness of multilayer diffractive optical elements (MLDOEs) means that TEA yields inaccurate results. To address this, we tested a method based on ray-tracing simulations in mid-wave and long-wave infrared wave bands and for multiple f-numbers, together with the effect of MLDOE phase delay on a collimated on-axis beam with an angular spectrum method. Thus, we accurately generate optical figures of merit (point spread function along the optical axis, Strehl ratio at the "best" focal plane, and chromatic focal shift) and, by using a finite-difference time-domain method as a reference solution, demonstrate it as a valuable tool to describe and quantify the longitudinal chromatic aberration of MLDOEs.

Local Plasmon Phase Delay Effect in Plasmon–Exciton Coupling

AbstractManipulating plasmon–exciton coupling is a pivotal desire for many potential applications. Here, it is found that the plasmonic phase delay can modulate the interference‐induced asymmetrical spectrum line shape of the plasmon–exciton coupling system considerably. The phase effect in a hybrid system consisting of monolayer WSe2 and an individual gold nanorod is demonstrated. The phase delay can modulate the relative intensities of the coupling modes but not the splitting energy, effective in both weak and strong coupling regimes. There is an excellent agreement between the numerical calculations and the experimental results. The findings reveal that the local phase delay can act as an effective way to manipulate plasmon−exciton coupling properties at the nanoscale.

Mitigating Atmospheric Effects in InSAR Stacking Based on Ensemble Forecasting with a Numerical Weather Prediction Model

The interferometric synthetic aperture radar (InSAR) technique is widely utilized to measure ground-surface displacement. One of the main limitations of the measurements is the atmospheric phase delay effects. For satellites with shorter wavelengths, the atmospheric delay mainly consists of the tropospheric delay influenced by temperature, pressure, and water vapor. Tropospheric delay can be calculated using numerical weather prediction (NWP) model at the same moment as synthetic aperture radar (SAR) acquisition. Scientific researchers mainly use ensemble forecasting to produce better forecasts and analyze the uncertainties caused by physic parameterizations. In this study, we simulated the relevant meteorological parameters using the ensemble scheme of the stochastic physic perturbation tendency (SPPT) based on the weather research forecasting (WRF) model, which is one of the most broadly used NWP models. We selected an area in Foshan, Guangdong Province, in the southeast of China, and calculated the corresponding atmospheric delay. InSAR images were computed through data from the Sentinel-1A satellite and mitigated by the ensemble mean of the WRF-SPPT results. The WRF-SPPT method improves the mitigating effect more than WRF simulation without ensemble forecasting. The atmospherically corrected InSAR phases were used in the stacking process to estimate the linear deformation rate in the experimental area. The root mean square errors (RMSE) of the deformation rate without correction, with WRF-only correction, and with WRF-SPPT correction were calculated, indicating that ensemble forecasting can significantly reduce the atmospheric delay in stacking. In addition, the ensemble forecasting based on a combination of initial uncertainties and stochastic physic perturbation tendencies showed better correction performance compared with the ensemble forecasting generated by a set of perturbed initial conditions without considering the model’s uncertainties.

Acting law of in-hole initiation position on distribution of blast vibration field

In rock drilling and blasting, the in-hole initiation position determines the propagation direction of the explosive detonation wave, and thereby affects the distribution of blast vibration field (BVF). In this study, the acting mechanism of the initiation position was investigated via the comprehensive analysis of the distribution of the detonation products, the explosion energy as well as BVF of the cylindrical charge. Then, the distribution law of BVF under different initiation positions was analyzed using the Heelan’s short-column-solution based superposition model of an extended charge. At last, the acting effect of the initiation position on the distribution of BVF was demonstrated by the onsite blasting experiment. Results indicate that the acting mechanism of the initiation position lies in the axial non-uniform distribution of the explosive energy and the phase delay effect of the superposition of BVF. The in-hole initiation position has the adjustment effect on the distribution of BVF, due to which, the blast vibration amplitude is strengthened at the forward direction of the detonation wave. It needs to be pointed that the non-uniformity of the distribution of BVF is under some control of the explosive length and the explosive velocity of detonation. For the common initiation modes, the field test results indicate that the ground peak particle velocities under the bottom are larger than those under the top and mid-point initiations, and the top initiation is the smallest. Besides, the blast vibration differences becomes more obvious as the blast-hole depth increases, but the vibration difference gradually vanishes with distance.

Phase delay effect of nonsequential double ionization of Ar atoms in a 45°cross-linearly-polarized two-color laser field

We theoretically investigate the nonsequential double ionization (NSDI) of Ar atoms by a three-dimensional (3D) classical ensemble method in a 45∘ cross-linearly-polarized two-color (CTC) laser field. Our results show that the phase delay of the synthesized two-color laser field can influence the NSDI process. By tracing the classical trajectories of the NSDI process, we find that the single-recollision (SR) and the double-recollision (DR) both occur. Whether the recollision processes happen once or twice, the NSDI predominantly experience the recollision-induced excitation with subsequent ionization (RESI) channel. And the phase delay of the CTC pulse could influence the probability of the double ionization and the energy transfer in NSDI process. This provides a method to obtain the information about the dynamics of the recollision process.

Effects of both the drive- and sense-mode circuit phase delay on MEMS gyroscope performance and real-time suppression of the residual fluctuation phase error

This work analyses circuit phase delay for carrier-modulation MEMS capacitive gyroscopes. The temperature-dependent circuit phase delay is a major source of gyroscope output drift, which deteriorates the gyroscope bias instability (BI) and angle random walk (ARW). Effects of both drive-mode and sense-mode circuit phase delay on gyroscope performance when using different signal extraction architectures are analyzed in detail. The online suppression method which combines the so-called modified double sideband (MDSB) extraction architecture in the gyroscope drive mode and closed-loop force-rebalance loop in the sense mode can eliminate the impact of residual fluctuation error of circuit phase delay in real time. When drive-mode circuit phase delay equivalently varies from −20° to 20°, using MDSB decreases the fluctuation of the open-loop zero-rate output (ZRO) by 70% compared to using double sideband (DSB) and by 99.7% with respect to using single sideband (SSB). Meanwhile, improvement for the closed-loop ZRO using MDSB is 92.48% and 94% compared to cases using DSB and SSB, respectively. Furthermore, when the equivalent circuit phase delay of the sense-mode alters from −20° to 20°, ZRO variation for the gyroscope with force rebalanced sense loop and quadrature stiffness nulling loop decreases by 80% in contrast to the case with open loop, which demonstrates the effectiveness of online suppression for circuit phase delay of both the drive-mode and sense-mode. Using the online suppression method, the gyroscope has achieved a BI of 0.16° h−1 and ARW of 0.011° (√h)−1. Furthermore, using the MDSB in the drive mode obtains the best stability compared to using the DSB and SSB as the temperature changes.

A monolithic missile radome with improved radiation patterns for application in frequency modulated continuous wave radar

In this letter, a monolithic missile radome for application in frequency modulated continuous wave radar (FMCWR) at missile warhead is proposed with improved radiation performance. The radome is cone-shaped and two patch antenna subarrays for transmission and reception are placed off the central line of radome. To address the issues of radiation distortion caused by radome, an improved radome with variable thickness is proposed. Theoretical analysis is conducted to reveal the working principle, which demonstrates that proper condition of radome thickness can minimize the adverse effects of field reflection and phase delay on radiation patterns. By further optimizing the radome thickness through simulation, the ripple variation of main beam is mitigated and radiation patterns become more symmetric. Simulated and measured results show that the radiation performance of the antenna with proposed radome has been significantly improved as compared with that of the antenna with uniform thickness radome (UTR).

Focusing characteristics of optical vortex passing through a Fresnel zone plate

The focusing characteristics of Fresnel zone plate (FZP) on vortex beams at 1550 nm are investigated. Employing the Fresnel diffraction integral, the diffraction characteristics on different circular structures are calculated. Many calculations and measurements of the transmission light field-phase distribution demonstrate that the focusing characteristics of the vortex beam through FZP are similar to Gaussian beam. The effect of radius-dependent phase delay on the focus position is verified. At the same time, it is proved that the topological charge has nothing to do with the major focal position and the FZP will not change the topological charge of the incident vortex beam.

DSP techniques for protein coding region identification based on background noise and nonlinear phase delay reduction from period-3 spectrum using zero phased anti-notch filter and Savitzky-Golay (S-G) filter

Short time discrete Fourier transform (STDFT) and anti-notch filters (ANF) are perhaps the most common DSP tools that uses the period-3 feature of protein coding sequences to discriminate between protein-coding regions and noncoding regions. However, the performance of these techniques is still limited due to the background noise present in their period-3 spectrum. The drawback with existing de-noising techniques is that it also distorts the period-3 feature besides noise suppression. In this article, the Savitzky-Golay (SG) filter is used to suppress the background noise from period-3 spectrum. A zero phased anti-notch filter (ZANF) is also used to overcome the effect of nonlinear phase delay from the period-3 spectrum of ANF. It is obtained that the combined use of ZANF and SG filters increases the prediction accuracy of conventional ANF by around 19% -26%.

DSP techniques for protein coding region identification based on background noise and nonlinear phase delay reduction from period-3 spectrum using zero phased anti-notch filter and Savitzky-Golay (S-G) filter

Short time discrete Fourier transform (STDFT) and anti-notch filters (ANF) are perhaps the most common DSP tools that uses the period-3 feature of protein coding sequences to discriminate between protein-coding regions and noncoding regions. However, the performance of these techniques is still limited due to the background noise present in their period-3 spectrum. The drawback with existing de-noising techniques is that it also distorts the period-3 feature besides noise suppression. In this article, the Savitzky-Golay (SG) filter is used to suppress the background noise from period-3 spectrum. A zero phased anti-notch filter (ZANF) is also used to overcome the effect of nonlinear phase delay from the period-3 spectrum of ANF. It is obtained that the combined use of ZANF and SG filters increases the prediction accuracy of conventional ANF by around 19% -26%.

A hula-hooping-like nonlinear buckled elastic string electromagnetic energy harvester for omnidirectional broadband excitations

This paper reports a hula-hooping-like nonlinear buckled elastic string electromagnetic energy harvester for wideband vibration energy harvesting. The harvester is comprised of a magnetic rotor attached at the middle of a clamped-clamped buckled elastic string and a stator with an embedding coil array. Attributed to the geometric nonlinear characteristic of the elastic string, the harvester can convert the reciprocate vibration in arbitrary in-plane direction to a hula-hooping-like curvilinear translation plane motion. A hardening nonlinear wideband voltage response was demonstrated by sweep excitation from 5\\,∼\\,23 Hz. The output peak power for a single coil can reach 1.12 mW at a 5 ms−2 excitation. To overcome the phase delay effects between the voltages of three spatially distributed coils, they were rectified separately and connected serially or parallelly to provide the final output. An open circuit peak voltage of 0.53 V was obtained from the serial connection at a 4 ms−2 up-sweep excitation, under which a 100μF capacitor was successfully charged to 0.35 V within 120 s. The omnidirectional energy scavenging performance of the harvester was further validated experimentally, suggesting its great promise for practical vibration energy harvesting.

Theory of birefringence correction for polarization-controlled CARS.

Polarization-controlled coherent Raman spectroscopy is used as a high-throughput method to characterize the anisotropic nature of a molecular system, such as the molecular orientation distribution. However, optical birefringence originating from the molecular anisotropy can cause the observed Raman spectrum to be significantly distorted, making it extremely challenging to obtain quantitative information from polarization Raman measurements. Here, the birefringence effect on the signal intensity and the spectral shape of a polarization-controlled coherent anti-Stokes Raman scattering (CARS) is theoretically described using a uniaxially symmetrical model system. Due to the complexity, the effect of phase delay in the incident lights is not considered but only that of the generated CARS signal is considered. A new analytical method is presented to eliminate the birefringence contribution from polarization-controlled CARS data by analyzing polarization intensity profiles and retrieving the resonant Raman susceptibility spectra. This method is tested with two sets of polarization-controlled CARS data simulated with various combinations of symmetries of multiple underlying Raman modes. The analysis result clearly demonstrates that the effect of birefringence can be corrected for polarization-controlled CARS data and the symmetry tensor elements of all underlying Raman modes can be quantitatively characterized.