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Recently, reconfigurable intelligent surface (RIS) has attracted continuous attention in wireless communications. Because the normal incidence condition of electromagnetic waves cannot always be satisfied in practical applications, the angular insensitivity in RISs has become an important issue. The angular sensitivity in RISs may lead to the failure of RIS-assisted wireless communication networks that rely on the reciprocity of wireless channels. In this work, an angle-insensitive 3-bit RIS meta-atom is proposed. By introducing metallic vias in the substrate of programmable meta-atoms, the interference induced by multiple reflections in the multilayered structure is restrained, and the decoupling between adjacent meta-atoms makes the metasurface insensitive to the incident angle. Hence the angular insensitivity can be achieved. An RIS is fabricated using the proposed angleinsensitive programmable meta-atom with metallic vias, which is capable of maintaining stable phase and amplitude responses at oblique incidences. Both simulated and measured results show stable angle performance. A maximum of 3150 phase range and eight digital coding states with 450 stable interval are obtained for wide incidence angles from 00 to 600. Finally, numerical simulations and experimental results of anomalous reflections are performed to verify the angular reciprocity of the proposed RIS, which is important in wireless communications.

The semi-Z-source inverter with least switch count (only two switches) eliminates the leakage current due to the doubly grounded structure. However, the main disadvantage is the high voltage stresses of the switches (the sum of double PV output voltages and the amplitude grid voltage). This paper proposed an improved inverter based on the SZSI. It inherits the advantage of the less leakage current and owns other merit of lower switch voltage stresses. Besides, the operation of the proposed inverter is bimodal and only two switches operate at high frequency in each mode. Firstly, the circuit structure and the operation principle are introduced in detail. Then, the grid current controllers in both modes are designed. Two comparisons are investigated for better clarification of the pros and cons of the proposed inverter. Finally, experimental results, obtained with a 500-W laboratory prototype are presented to validate its performance.

BACKGROUND AND OBJECTIVES Bilateral subthalamic nucleus deep brain stimulation (STN DBS) in Parkinson's disease (PD) can have detrimental effects on eye movement inhibitory control. To investigate this detrimental effect of bilateral STN DBS, we examined the effects of manipulating STN DBS amplitude on inhibitory control during the antisaccade task. The prosaccade error rate during the antisaccade task, that is, directional errors, was indicative of impaired inhibitory control. We hypothesized that as stimulation amplitude increased, the prosaccade error rate would increase. MATERIALS AND METHODS Ten participants with bilateral STN DBS completed the antisaccade task on six different stimulation amplitudes (including zero amplitude) after a 12-hour overnight withdrawal from antiparkinsonian medication. RESULTS We found that the prosaccade error rate increased as stimulation amplitude increased (p

A two-dimensional axisymmetric model, employing a dynamic mesh and user-defined functions, is used to numerically simulate the transient multiphase flow field produced by an underwater gun. Furthermore, a visualized shooting experiment platform with a high-speed camera is built to observe the evolution process of such a multiphase flow field. The simulated phase distribution diagram is agreed well with the shadow photo of the experiment, indicating that the numerical model is reasonable. Further examinations of the multiphase flow fields by using the submerged and sealed launch methods show that use of the sealed launch can significantly improve the interior ballistic performance of an underwater gun. In the cases by using these two types of underwater launch methods, the displacement of the projectile within the range of the muzzle flow field meets the exponential law over time. Moreover, a not fully developed bottle-shaped shock wave is formed when t = 0.4 ms, but this bottle-shaped shock wave expands more rapidly for the sealed launch. In addition, the amplitude of pressure oscillation for the sealed launch is larger than that of the submerged launch, but the pressure oscillation of the sealed launch lasts shorter.

The three-dimensional computational fluid dynamics (3D-CFD) of a pulsating flow applied to the fluid catalytic cracking (FCC) reaction was investigated in the riser of a circulating fluidized bed reactor. The kinetic parameters of the FCC and coke burning reactions for predicting the reactant conversion and product yield percentages were applied. To increase the reactant conversion level and product yield, the effect of the pulsating flow operating parameters was considered using a 2k statistical experimental design with four factors (amplitude, frequency, types of the waveform, and amplitude ratio). The 3D-CFD simulation was successfully validated from the experimental literature data. The frequency and type of the waveform were found to be the significant operating parameters. The expression of the fitted regression model and response surface contour were derived and revealed that the pulsating flow provides a higher reactant conversion level and product yield percentages compared to a non-pulsating or steady flow.

Thermoacoustics is about conversion between thermal and acoustical energies to provide alternative green technology for power cycle and cooling system. The oscillatory flow across porous structure inside the system is playing the role of energy conversion between the acoustic wave and the surface of the porous structure. Better understanding of fluid dynamics of oscillatory flow inside thermoacoustic system is therefore important for the thermoacoustic based energy conversion system. This paper presents the ‘entrance’ and ‘exit’ effects of the oscillatory flow within a parallel-plate structure that is placed inside a standing-wave thermoacoustic environment. Two-dimensional SST k-ω CFD models which were validated using experimental data and theoretical predictions were used for this investigation. Two different operating frequencies of 14.2 Hz and 23.6 Hz were studied for flow with five different amplitudes that were represented using drive ratios of 0.3%, 0.83%, 1.5%, 2.1% and 3%. These correspond to cases with Reynolds numbers between 5936 and 62926. Due to the cyclic nature of the flow, a region defined as an ‘exit’ region was observed in addition to the usual ‘entrance’ region and the fully developed region for flow inside a channel. The change of shape of velocity profiles from the ‘m’ shape profile, to the ‘slug-like’ profile and ‘parabolic-like’ profile was discussed in relation to the ‘entrance’ and ‘exit’ effects on flow inside the channel. The ‘entrance’ and ‘exit’ effects become bigger as drive ratio increases. The effect of ‘entrance’ and ‘exit’ are slightly reducing as frequency increases from 14.2 Hz to 23.6 Hz. This may be related to the shorter travel distance of fluid as the frequency increases. The results shown in this paper suggest that the flow within a 200 mm parallel-plate structure should be treated as developing flow especially for flow with low resonance frequency at drive ratio higher than 1%.

The bifurcation structure of the oscillations of ultrasound contrast agents (UCAs) was studied as a function of the driving pressure for excitation frequencies that were determined using the UCAs pressure-dependent resonances $$(f_\mathrm{s})$$ . It was shown that when excited by the $$(f_\mathrm{s})$$ , the UCA can undergo a saddle-node bifurcation (SNB) to higher amplitude oscillations. The driving pressure at which the SNB occurs is controllable and depends on the $$(f_\mathrm{s})$$ magnitude. Utilizing the appropriate $$(f_\mathrm{s})$$ , the scattering cross section of the UCAs can significantly be enhanced (e.g., $$\sim $$ ninefold) while at the same time avoiding potential UCA destruction (by limiting the radial expansion ratio $$

Multi-element array photoelectric detector is the core devices to form a photoelectric detection target with a large field of view. This photoelectric detection target brings about the problem of uneven detection sensitivity distribution in the detection screen. To improve the uneven detection sensitivity of this photoelectric detection target, this paper analyzes the distribution law of the uneven detection sensitivity of the photoelectric detection target using the multi-element array photoelectric detector, dissects the main factors affecting the detection sensitivity according to the photoelectric detection principle, establishes the calculation model of detection sensitivity of the photoelectric detection target in the different detection areas and proposes a method to improve the detection sensitivity by compensating the gain of each unit photoelectric detector. The analysis of simulation and experimental results show that the proposed method of photoelectric detection target can effectively improve the output signal amplitude of the projectile under the certain detection distance, in particular, the output signal amplitude of the projectile is significantly increased when the projectile passes through the detection blind area. The experimental results are consistent with the simulation results, which verify the effectiveness of the proposed improvement method.

We propose and demonstrate an overall non-mechanical spectrally steered laser rangefinder using the dispersion-tuned swept laser (DTSL) and a passive diffractive element. The DTSL has no mechanical moving parts, making it possible to achieve an inertial-free high wavelength sweeping speed. The inherent intensity-modulation characteristic of the DTSL allows the modulation phase-shift method to be applied, similar to that used for an amplitude-modulated continuous-wave (AMCW) rangefinder. Since the pulse repetition rate of the DTSL is chirped, standard signal processing techniques for AMCW are not applicable. In this paper, we propose a novel chirped amplitude-modulated phase-shift (CAMPS) method with a signal processing technique to obtain the phase-shift information from a chirped amplitude-modulated signal. As a proof of concept, we demonstrated the CAMPS LiDAR with an axial ranging resolution of ~50 m at a scanning speed of 10 kHz.

Although pulse charging strategy has many advantages, it is still controversial. The paradox is that it prolongs the charging time to eliminate the polarization voltage by the pulse interval, and the AC component in pulse current will increase the ohmic losses. In this paper, an optimal charging strategy with complementary pulse current of Lithium-ion is proposed to address and alleviate these issues. For the pulse frequency, the optimization can be achieved through the electrochemical impedance spectroscopy (EIS) analysis to reduce the battery’s AC impedance. For the pulse amplitude, based on the battery’s internal resistance characteristics, minimize the ohmic losses to obtain the optimal amplitude. For the pulse duty cycle, it is adjusted to achieve state of charge (SOC) balancing in the early charging stage, and battery’s terminal voltage balancing in the later stage. Based on the optimized charging strategy, a pulse charger concept is proposed, which can flexibly control the pulse charging currents and use complementary pulses to completely eliminate the prolonged charging time caused by the pulse interval. In the end, an experimental platform for pulse charger of lithium-ion batteries is designed, and the theoretical analysis is verified by the comparative experiments.

In order to study the propagation laws of acoustic wave of coal samples from the Upper Permian Xuanwei Formation in the east of Yunnan Province, China, under saturated water and dry conditions, the basic physical parameters, acoustic parameters and anisotropic parameters were obtained through the experiments. Based on FFT and wavelet analysis theory, the spectral characteristics of coal samples under different conditions were studied. The results show that physical parameters of coal samples in different directions have different values, that is, the anisotropy of coal samples is obvious. When the coal samples are saturated with water, the acoustic velocities and the attenuation coefficient increase, whereas the dominant frequency decreases. The signal amplitude of the frequency domain significantly decreases, that is, the internal structure of coal samples is damaged. The P-wave velocity and S-wave velocity increase with the increase of the confining pressure, whereas the anisotropy parameters decrease with the increase of the confining pressure. Overall, this study provides the basis to understand basic acoustic information and anisotropy characteristics of coal samples.

This article presents a cross-domain model that defines and sets the acoustic signal generation process due to the fast dose deposition induced by a proton beam penetrating an energy absorber. The proposed model reduces the complex iono-acoustic energy transformation process to a simple impulse-response of a linear-time-invariant (LTI) system and is validated by comparing LTI output simulation results (in both time and frequency domain) with experimental acoustic signals emitted by a physical proton beam at 20 MeV and 70-120-ns pulse time width. Thanks to the intrinsic simplicity of the system, it is possible to predict and estimate the effective acoustic power at the sensor and the resultant beam range measurement precision. More importantly, the information coming from LTI simulations provides well-defined methodologies that allow to increase acoustic signal amplitude from +3 up to +9 dB and to improve the measurement precision of the beam range localization (up to +/ - 0.3 mm versus +/ - 0.6 mm state of the art for 200-MeV energy and 75-mGy total dose).

We report the characterization of an achromatic focusing metasurface at oblique incident angles. We show that in addition to the inherent off-axis aberrations that occurs due to the hyperbolic phase profile of the metasurface, the focusing performance is significantly degraded due to the meta-atoms' angular dispersion. To obtain insights into how the angular and spectral bandwidth of meta-atoms relate to the metasurface focusing performance, point-dipole models are used which incorporate different aspect's of the meta-atoms' angular response. It is emphasized that despite the meta-atoms being designed under the assumption that they support a single dipolar resonance, other resonances exist within the meta-atom geometry and become stronger at oblique incidence. These resonances disturb the designed phase and amplitude responses, resulting in lower focusing efficiency at higher incident angles. The modelling of higher order modes leads to good agreement with the experimental measurements, confirming that angular dispersion of the meta-atoms is the dominant mechanism in determining off-axis aberrations.

In this paper, a low sidelobe-level (SLL) circularly-polarized (CP) leaky-wave antenna with A-shaped elements is proposed based on substrate integrated image guide (SIIG). The A-shaped CP radiating element consists of a horizontal LP structure and a vertical LP structure. The horizontal LP wave and the vertical LP wave can be excited by a pair of inclined transversal metal strip patches and a longitudinal metal strip patch respectively. Their phases are orthogonal and amplitudes can be controlled to be equal by adjusting the tilted angle of the horizontal LP structure and the length of the vertical LP structure. Moreover, the longitudinal metal strip patch is modified to the V-shaped strip patch, which can realize the field cancellation, thereby achieving the boresight radiation for such a leaky-wave antenna. Furthermore, a low SLL is realized by controlling the aperture-field distribution to obtain the desired amplitude distribution and the relatively small axial ratio (AR). In addition, because of the short waveguide wavelength of the SIIG, this feed line can be used to achieve the small interelement spacing and element size, thereby realizing the short length of the array. The measured peak gain of this antenna is 12.3 dBi and the SLL is 19.1 dB.

In this paper, a new approach to time series classification is proposed. It transforms the scalar time series into a two-dimensional space of amplitude (time series values) and a change of amplitude (increment). Subsequently, it uses this representation to plot the data. One figure is produced for each time series. In consequence, the time series classification problem is converted into the visual pattern recognition problem. This transformation allows applying a wide range of algorithms for standard pattern recognition – in this domain, there are more options to choose from than in the domain of time series classification. In this paper, we demonstrated the high effectiveness of the new method in a series of experiments on publicly available time series. We compare our results with several state-of-the-art approaches dedicated to time series classification. The new method is robust and stable. It works for time series of differing lengths and is easy to extend and alter. Even with a baseline variant presented in an empirical study in this paper, it achieves a satisfying classification accuracy. Furthermore, the proposed conversion of raw time series into images that are subjected to feature extraction opens the possibility to apply standard clustering algorithms.

This article presents a 2.4-4-GHz wideband 7-bit switch-type phase shifter (STPS) with a switch driver. Three switch-type phase shifting topologies are employed for the design of the phase shifter (PS), including the switched L/C structure, T-type structure, and high-/low-pass network. For minimizing the phase and amplitude deviations, an improved T-type structure with a switched filter structure has been proposed to boost the performance of the PS. Besides, a phase compensation cell also has been adapted to further decrease the phase error of the STPS. Based on the topology choice of each cell and the amplitude compensation among cells, a systematic design method is developed to extend the bandwidth of the PS. The proposed 7-bit STPS was implemented in the 0.5-μm GaAs pHEMT process. The measured root-mean-square (rms) phase error of the proposed STPS is less than 3.1° from 2.4 to 4 GHz and less than 1.5° at 2.8-3.7 GHz. The average insertion loss (IL) is 4.5-4.9 dB with an rms amplitude error of less than 0.34 dB. IP $_{{1,dB}}$ is about 30 dBm. To the best of our knowledge, this PS achieves the highest resolution and the lowest rms amplitude error among the published GaAs/GaN PSs over a similar frequency band. The IL, bandwidth, and rms phase error of the proposed PS also show good performance.

In this paper, a novel structure of the high-order-mode cavity fed sequentially rotated patch antenna array is proposed for diverse polarizations. The diverse polarizations, including right hand circular polarization(RHCP), left hand circular polarization(LHCP), -45∘ linear polarization(LP), 0∘ LP, 45∘ LP, and 90∘ LP, are achieved based on the current distribution on the patches and different electric field modes in the high-order-mode cavity by adjusting the phase and amplitude of the two orthogonal feeding ports. Furthermore, from the electric field distribution in the high-order-mode cavity with different feeding schemes, arbitrary polarizations were analyzed and obtained. An 8×8 dual-circularly polarized(dual-CP) antenna is demonstrated. Good agreement between the simulated and measured results is obtained, validating the design. The experimental results show that the impedance bandwidths(

This paper proposes the wideband circularly polarized (CP) phased array antenna system for wide axial ratio scanning. For mobile satellite communication, the low profile CP antenna with a wide axial ratio scanning region in wide frequency bandwidth is necessary, but the antenna with the required axial ratio performance is rarely reported. In this paper, the proposed CP phased array antenna system with an axial ratio control scheme has a wide axial ratio scanning region in the wide frequency bandwidth. In the proposed axial ratio control scheme, the amplitude and phase of the received signals are controlled to compensate for the difference between dual polarizations. The proposed antenna system is designed at 5.8 GHz and has a fractional frequency bandwidth of 20%. In a simulation, the axial ratio is under 1 dB at the elevation scanning region from -60∘ to 60∘ at every 360∘ azimuth angle in the operating frequency bandwidth. For validation, the 1x8 CP phased array antenna system was implemented. The measured axial ratio is under 2 dB at the elevation scanning region from -57∘ to 57∘ in the operating frequency bandwidth.

This article presents a physics-based inversion technique for reliable characterization of droplets deposited by a liquid metal jetting additive manufacturing system, using an in-situ millimeter wave diagnostic. The overall approach is demonstrated in a custom droplet-on-demand liquid metal jetting system with effective droplet diameters ranging from 0.8 to 1.7 mm. The inversion results demonstrate that this approach can provide information about the droplet size and lift-off distance between the droplet and the diagnostic by monitoring the amplitude and phase of the reflection coefficient at the input port.

In the current work we have used the deep learning based long short-term memory model to predict the strength and peak time of solar cycle 25 by employing the monthly smoothed sunspot number data obtained from WDC-SILSO, Royal Observatory of Belgium, Brussels. We have used the stacked LSTM forecasting model to predict the upcoming cycle 25. From our analysis it has been shown that our proposed model is capable of capturing long term dependencies as well as trend within the data. For cycle 20 and 21 the error difference between predicted as well as observed peak value is 2.3 and 0.7 respectively while the peak prediction error is 1.47% and 0.30%. The RMSE of the model for cycle 20 and 21 is 3.97 and 4.34 respectively. For cycle 22, the AE and RE is 4.6 and 2.16% while the RMSE of the model for this case is 4.50. The predicted peak amplitude of solar cycle 23 and 24 from our proposed model has a relative error of 1.75% and 1.99% respectively from the observed value while the RMSE is 3.4 for cycle 23 and 4.2 for cycle 24. Our projected prediction of cycle 25 using the proposed LSTM model, says that it will be stronger than cycle 24 and weaker than cycle 23. The solar cycle 25 will peak with an amplitude of sunspot number at 171.9 ± 3.4 and will be 47 % stronger than cycle 24. The solar cycle 25 will reach its peak in August 2023 ± 2 months.

We study the impact of redundant via placement on Fraunhofer interference patterns in superconductor-insulator-superconductor Josephson junctions with thin counter electrodes. By varying the number and location of contact vias to the counter electrode in otherwise equivalent junctions and studying the magnetic field dependence of the critical current, we observe a variety of unconventional features in the interference patterns, including a lifting of critical current minima and differences in node positions and side lobe amplitudes. We attribute these features to local changes in the Josephson phase gradient arising from the non-uniform magnetic thickness resulting from the vias. Our findings highlight the significant role that contact vias on thin counter electrodes play in the response of Josephson junctions to applied magnetic fields.

Using QHD model, the quantum effects (QEs) on parametric amplification of acoustical phonons in semiconductor magneto-plasmas have been investigated. Assuming that the origin of nonlinear interaction lies in nonlinear induced current density of the medium (arising due to density perturbations of the medium) in the presence of pump field, expressions have been obtained for second-order susceptibility of the medium and hence the threshold pump amplitudes (with and without QEs) and as well as parametric gain coefficients (with and without QEs). Numerical analysis has been made for n-InSb-CO2 laser system. The dependence of these parameters on acoustic wave number, external magnetic field, and doping concentration has been explored. It has been found that the Bohm potential in the electron dynamics reduces the threshold pump amplitude for the onset of parametric amplification four times whereas enhances the parametric gain coefficient approximately fourteen times. The analysis provides the detailed information of quantum effects semiconductor magneto-plasmas and establishes the technological potentiality of semiconductor magneto-plasmas as the hosts for fabrication of efficient parametric amplifiers.

During the solar eclipse, the perturbation of ionospheric D layer changes the characteristics of the Earth's Ionospheric Waveguide (EIWG) on which the very low frequency (VLF, 3-30 kHz) wave propagation depends. Therefore, the amplitude and phase of the VLF signal transmitted through the waveguide will be abnormal. In this article, based on the VLF transmitter signals observed in Suizhou (31.57°N, 113.32°E) during the total solar eclipse on December 26, 2019 and the days before and after, the variation characteristics of VLF transmitter signals along the north-south propagation path are analyzed in detail. Responses of the amplitude and phase of the signal during the solar eclipse are closely related to the solar obscuring rate. There is a positive correlation between the signal fluctuation and the solar obscuring rate, and the peak time of the two has a delay of ~5 min. By adopting the amplitude and phase of the observed signals and performing the Long Wavelength Propagation Capability (LWPC) propagation simulations, the electron density of the ionosphere over the propagation path is calculated. The results show that the electron density profile above the path during the solar eclipse changes significantly. The electron density decreases with a maximum drop of ~53.5% at the 70 km height, and the reflection height of the signal increases correspondingly. The obtained results are useful to better understand the propagation characteristics of VLF transmitter waves and the corresponding response features of the ionospheric D layer to solar radiation flux variations, especially during the solar eclipse.

Due to the constraints of natural environments, acquired prestack seismic data is usually not complete, which seriously affects subsequent seismic data processing. With the progress of deep learning, many neural networks with different structures have been applied to missing seismic data interpolation. Among them, U-net can efficiently interpolate the regularly and irregularly missing seismic traces with small gap. While for consecutively missing seismic traces with big gap, the interpolation results for low amplitude missing components need to be further improved. In this letter, we analyze the variation of interpolation results for consecutively missing seismic traces during the traditional U-net training process, and find that U-net tends to only interpolate the high amplitude missing components. Meanwhile, due to the distribution difference between low and high amplitude seismic data, one U-net model is insufficient to interpolate both high and low amplitude missing components with a wide amplitude range. To improve the interpolation results of single U-net, we propose a multistage training process to train multiple U-net models. Each U-net model focuses on interpolating different missing components with a small amplitude range. In this way, more accurate interpolation results for low amplitude missing components can be obtained. Comparison experiments conducted on synthetic and field seismic data show that, under the same number of training epochs, the proposed training process can produce more accurate interpolation results comparing with traditional single U-net.

Objectives Subperception spinal cord stimulation (SCS) is described mostly utilizing waveforms that require high energy. However, the necessity of these waveforms for effective subperception has not been established. We aimed to explore whether effective subperception pain relief can be achieved using frequencies below 1 kHz. Materials and methods Thirty chronic pain patients implanted with SCS were enrolled as part of a multicenter, real-world, consecutive, observational case series. An effective stimulation location was determined using a novel electric field shape designed to preferentially modulate dorsal horn elements. Subsequently, programs at lower frequencies (600, 400, 200, 100, 50, and 10 Hz) were provided with pulse-width and amplitude adjusted to optimize response. Results All tested frequencies (1 kHz down to 10 Hz) provided effective subperception relief, yielding a mean of 66-72% reduction in back, leg, and overall pain. It was found that to maintain analgesia, as frequency was decreased, the electrical or "neural" dose had to be adjusted according to parameter relationships described herein. With the reduction of frequency, we observed a net reduction of charge-per-second, which enabled energy savings of 74% (200 Hz) and 97% (10 Hz) relative to 1 kHz. Furthermore, pain reduction was sustained out to one year, with 85% of patients reporting a preference for frequencies of 400 Hz or below. Conclusions We have derived an electric field configuration and, along with previous learnings in the kHz range, a set of neural dosing parameter relationships (10-10,000 Hz), which enable the expansion of effective subperception SCS to low frequency and achieve major energy savings.

Mirrored aperture synthesis (MAS) has been proposed as a novel interferometry to achieve higher spatial resolution in passive microwave remote sensing. The phase and amplitude errors for MAS are a crucial problem that has yet to be analyzed. In this letter, a model for the phase and amplitude errors is established. A correction method based on an external source is proposed to correct the phase and amplitude errors. An analysis of the position of the external source is performed by computing its impact on the radiometric accuracy of a reference scene. The imaginary parts of the cross correlations for MAS are analyzed for the first time. Simulations and experiments are carried out to demonstrate the effectiveness of the correction method.

We demonstrate a broadband near-100%-efficiency ultrathin metasurface operating at microwave and millimeter-wave frequencies. We develop and employ two orthogonally polarized metallic gratings to form a Fabry-Perot cavity and incorporate a subwavelength metallic double-split-ring resonator at the center of each unit cell. It allows arbitrary amplitude-phase combinations with no coupling between amplitude and phase or between transmitted and reflected waves, leading to the design of an ultrathin but highly efficient broadband metasurface with multiple functionalities. Furthermore, the proposed metasurface can generate diffractive beams with different orders and vortex beams with different orbital angular momentum (OAM) modes in reflection and transmission spaces simultaneously. Both numerical and experimental results verify that the proposed metasurface has superior performance to its counterparts that are based solely on phase control. The proposed metasurface presents a lightweight, low-cost, and easily deployable flat device for microwave and millimeter-wave applications.

Background: The aim of this study was to investigate whether blood pressure (BP) circadian rhythm in African Americans differed from that in European Americans. We further examined the genetic and/or environmental sources of variances of the BP circadian rhythm parameters and the extent to which they depend on ethnicity or sex. Method: Quantification of BP circadian rhythm was obtained using Fourier transformation from the ambulatory BP monitoring data of 760 individuals (mean age, 17.2 +/- 3.3; 322 twin pairs and 116 singletons; 351 African Americans). Results: BP circadian rhythm showed a clear difference by ethnic group with African Americans having a lower amplitude (P = 1.5e-08), a lower percentage rhythm (P = 2.8e-11), a higher MESOR (P = 2.5e-05) and being more likely not to display circadian rhythm (P = 0.002) or not in phase (P = 0.003). Familial aggregation was identified for amplitude, percentage rhythm and acrophase with genetic factors and common environmental factors together accounting for 23 to 33% of the total variance of these BP circadian rhythm parameters. Unique environmental factors were the largest contributor explaining up to 67--77% of the total variance of these parameters. No sex or ethnicity difference in the variance components of BP circadian rhythm was observed. Conclusion: This study suggests that ethnic differences in BP circadian rhythm already exist in youth with African Americans having a dampened circadian rhythm and better BP circadian rhythm may be achieved by changes in environmental factors.

Background: The character motion of 3D animation production is difficult, and to solve this problem, motion-pose capture technology is very effective. The workload of character motion control is reduced by this technique and the animation development is improved. It is used in virtual training grounds and real-time tracking of the motion. The complete contour features cannot be efficiently acquired by the 3D visual motion technique. The 3D visual motion amplitude tracking method in sports is studied in order to improve the training quality of athletes effectively. However, when the current method is used for motion amplitude tracking, the markers in the adjacent monocular sequence motion amplitude images cannot be calculated. Methodology: At this point, there is a problem of a large tracking error of 3D visual motion amplitude. To this end, a 3D amplitude tracking method in sports based on inverse kinematics is proposed. This method locates the marker points that appear in the adjacent monocular sequence motion range and merges it with the rotation angle method to predict the position of the motion range in the image. Results: The motion amplitude is obtained, and 3D visual motion amplitude is outside the optimization area; this has been used as a basis to complete the tracking of the 3D visual motion amplitude in sports. Conclusion: Experimental simulation performed in MATLAB proves the high tracking accuracy of the proposed method.

Introduction Direction-aware mapping algorithms improve the accuracy of voltage mapping by measuring the maximal voltage amplitude recorded in the direction of wavefront propagation. While beneficial for stationary catheters, its utility for roving catheters collecting electrograms at multiple angles is unknown. Objective To compare the directional dependency of bipolar voltage amplitude between stationary and roving catheters. Methods In 10 swine, a transcaval ablation line with gap was created. The gap was mapped using an array catheter (Optrell™, Biosense Webster). In step 1, the array was kept stationary over the gap, and 4 voltage maps were created during activation of the gap from superior, inferior, septal, and lateral directions. In step 2, 4 additional maps were created, however the catheter was allowed to move with points acquired at multiple angles. In step 3, the gap was re-mapped, however bipoles were computed using a direction-aware mapping algorithm. Results In a stationary catheter position, bipolar voltage distribution was influenced by the direction of activation with maximal differences obtained between orthogonal directions 32% (13-53%). However, roving the catheter produced similar bipolar voltage maps irrespective of the direction of activation 11% (5-18%). A direction-aware mapping algorithm was beneficial for reducing the directional dependency of voltage maps created by stationary catheters but not by roving catheters. Conclusions The directional dependency of bipolar voltage amplitude is greatest when the catheter is stationary. However, when the catheter is allowed to rove and collect electrograms at multiple angles as occurs clinically, the directional dependency of bipolar voltage is minimal. This article is protected by copyright. All rights reserved.

The modulation bandwidth (fBW) is a critical figure-of-merit for wireless communication applications of spin torque nano-oscillators (STNOs) as it determines the maximum data rate. Although both theory and previous experiments have shown that fBW in STNOs is governed by the amplitude relaxation frequency fp, we here demonstrate, using single-shot time-resolved measurements of a magnetic tunnel junction based STNO, that it can be many times larger under strong modulation. The behavior is qualitatively reproduced in macrospin simulations. Our results show that fBW of STNOs is not as limiting a factor for future wireless applications as previously believed.

Objective The purpose of this study was to determine better- ear listening effect on spatial separation with the N1–P2 complex. Methods Twenty individuals with normal hearing participated in this study. The speech stimulus /ba/ was presented in front of the participant (0°). Continuous Speech Noise (5 dB signal-to-noise ratio) was presented either in front of the participant (0°), left-side (-90°), or right-side (+90°). N1- P2 complex has been recorded in quiet and three noisy conditions. Results There was a remarkable effect of noise direction on N1, P2 latencies. When the noise was separated from the stimulus, N1 and P2 latency increased in terms of when noise was co-located with the stimulus. There was no statistically significant difference in N1-P2 amplitudes between the stimulus-only and co-located condition. N1-P2 amplitude was increased when the noise came from the sides, according to the stimulus-only and co-located conditions. Conclusion These findings demonstrate that the latency shifts on N1-P2 complex explain cortical mechanisms of spatial separation in better-ear listening.

Model predictive control has been considered as a potential alternative method in electrical drives. High reliable predictive model design is a research hotspot. To further improve the performance, a robust continuous model predictive speed and current control for PMSM with an adaptive integral sliding-mode approach are put forward. The prediction model is directly derived from the integral slinging-mode surface. By using the self-regulation method control and the amplitude of the sliding-mode function, an adaptive integral sliding-mode predictive control (AISMPC) is designed. The proposed strategy solves the chattering problem of sliding-mode control and improves the dynamics of the system. AISMPC has been carried out on a digital signal processing hardware system. The experimental results validate the excellent tracking performance of the proposed strategy.

The annual periodic deformation of Earth’s surface can be obtained indirectly using existing models. However, model reliability is affected by numerous uncertain factors such as indirect observation, inversion algorithms, and other factors. In this study, a model of annual vertical surface displacements of mainland China is built based on the direct observation of deformation by 234 continuous Global Positioning System (GPS) stations and unified data processing using the multisurface function method (referred to as the GPS model). The GPS model shows that the weighted root mean square (WRMS) is reduced for 97% of the GPS stations after applying the model correction. The average, maximum, and minimum reductions in the WRMS are 11.6%, 37.2%, and −3.6%, respectively. The slope of the fit lines are 0.40 and 0.61 for the GPS/SLM and GPS/GRACE annual periodic amplitudes, respectively, while a slope of 0.79 for GPS/GPS model from this paper, showing the advantage of GPS model in the representing of surface displacement. Additionally, the GPS model can accurately reflect the detailed motion characteristics of mainland China, particularly in areas between large and small hydrological changes. The difference between models and GPS observation in mainland China may be related to the leakage errors in the GRACE data processing and large uncertainty in the land water storage in SLM, indicating that GPS model may provide more realistic load estimates in mainland China. The GPS model can accurately describe the annual signal, which will be extremely important for practical applications and geoscience research in the future.

Investigating the fatigue performance of high-strength bolt is essential to prevent related accidents. An axial-tensile fatigue test under a stress ratio of 0.5 was performed on 21 specimens of high-strength bolts to investigate the constant-amplitude fatigue performance of grade 8.8 M24 high-strength bolts. Based on experimental results, S–N curves were obtained through regression analysis, and fractographic analysis was conducted on typical specimens. Moreover, the results were compared with the existing fatigue experimental results and standards. Further, a finite element model was established to analyze the stress distribution of the bolts. It was found that the fatigue strength of the high-strength bolt at 2 × 106 cycles under a stress ratio of 0.5 was 89.76 MPa, which is 1.60 to 1.87 times greater than the values specified in the current standards. Through the comparison of the fatigue tests under stress ratios of 0.3, 0.5, and 0.8, the fatigue strength decreased as the stress ratio increased. Additionally, two main fatigue failure modes were found, with most bolts fracturing at the root of the first loaded thread; this is confirmed by the stress concentration location obtained from finite element analysis. The fracture morphology of the bolts exhibited a single-point fatigue source and possessed obvious fatigue fracture characteristics. It was concluded that the area of the fatigue propagation region was basically inversely proportional to stress ratio.

Structural behavior of RC structures under explosive loads is an emerging field of research especially RC columns since the damage of RC columns can lead to progressive collapse. Most research works investigated and concentrated on the behavior of RC columns when exposed to far-field detonations (FFD). A limited study is available on the effects of near-field detonation (NFD) and close-in detonation (CID) on the behavior of RC columns. Hence, the main purpose of the current research is to investigate the influence of different types of detonation scenarios on the dynamic behavior of RC columns. The influences of extreme loading conditions on the columns are defined by using Lagrangian analyses in LS-DYNA. Validation of the numerical model is implemented by comparing the numerical analysis results with UFC 3–340-02 Standard. It is shown that the model yields a reliable prediction of damage on all RC columns. Intensive studies are performed to evaluate the influences of various scaled distances on the dynamic behavior of the columns. The results demonstrated that when the columns are subjected to CID explosions, they undergo the maximum pressure and the columns fail due to severe impulsive regime loading. The results revealed that when the scaled distance is in the CID range, the peak blast load increases but the duration of the positive phase of the blast wave decreases resulting in higher amplitude, lower-duration shock pulse and when the scaled distance is in the FFD range, the peak blast load decreases but the duration of the positive phase blast wave increases resulting in lower amplitude, longer-duration shock pulse. Also, the results show that increasing the scaled distance in RC columns subjected to NFD and FFD detonations resulted in a further decrease in the peak deflection histories and damage degree of RC columns in comparison to CID explosions. The current investigation and the outcomes can be utilized for evaluation of the effect of an explosion on the RC columns.

In this paper, we propose a novel circularly polarized (CP) dipole antenna fed by modified quadrature hybrid couplers (QHCs). In a conventional CP antenna, such as a sequentially rotated structure, the electrical length of the line connecting the radiating elements changes as the frequency changes. This characteristic produces a narrow axial ratio (AR) bandwidth and changes the radiation patterns of the array antenna at different frequencies. A modified QHC with minimal variation in the phase and amplitude difference between the output ports over a wide frequency range is used to achieve wide AR bandwidth and stable radiation patterns. The -10 dB impedance bandwidth of the proposed antenna is 4.1-7.6 GHz (58.3%), and the 3-dB AR bandwidth is 4.8-7.4 GHz (43.3%). The maximum gain is 4.4 dBic, and the 3-dB gain bandwidth is 5.0-7.5 GHz (40.0%). The antenna size is 21.0 × 21.0 × 0.2032 mm3 (0.42 × 0.42 × 0.004 λo 3 at 6 GHz).

A novel method to enhance the high frequency gain of a wideband Fabry-Perot (FP) antenna by using a truncated field correcting structure (TFCS) is proposed. The TFCS is formed by laminated dual-layer dielectric substrates and acts as the high-frequency operating band phase and amplitude correcting structure of the FP antenna for the radiated field. This method not only has a small effect on the operating bandwidth of the antenna, but also has a positive effect on improving the gain over the low-frequency operating band. The simulation and experimental results verify that the TFCS can effectively enhance the gain within the high-frequency operating band, and expand the 3-dB gain bandwidth of the FP antenna. The measured results show that the proposed antenna has a 10-dB return loss bandwidth of 8.49-12.34 GHz (37.0%), a 3-dB gain bandwidth of 8.48-11.82 GHz (32.9%), and a maximum gain of 17.73 dBi. The 3-dB gain bandwidth of the FP antenna is extended from 28.8% to 32.9% after loading with the TFCS, and the maximum gain enhancement within the high frequency operating band is increased by 3.48 dB at 11.58 GHz.

AIM: To assess changed spontaneous brain activity in hyperthyroid exophthalmos (HE) patients by the amplitude of the low-frequency fluctuation (ALFF) method, and to analyze the correlation between brain activity and ALFF values in these patients. METHODS: Totally 18 HE and 18 hyperthyroid non-exophthalmos (HNE) patients were enrolled. The participants were tested by resting-state functional magnetic resonance imaging, and receiver operating characteristic (ROC) curves were generated to classify the ALFF values of the study population. Pearson’s correlation analysis was utilized to evaluate the relationship between the ALFF values obtained from different brain areas and clinical manifestations. RESULTS: Contrary to HNE patients, we observed lower ALFF values in the left calcarine fissure and surrounding cortex (LCFSC) in HE patients. In the ROC curve analysis of the LCFSC, the area under the curve reflected a high degree of accuracy. In addition, there was positive correlation between mean ALFF values of the LCFSC and the best-corrected visual acuity of the affected eyes. CONCLUSION: The study displays abnormal brain activity in LCFSC in patients with HE, which might suggest pathological mechanism of visual impairment of HE patients.

The improvement of the energy utilization rate of a hydraulic vibration-excitation system is critical to the research and development of hydraulic vibration equipment. In this paper, a hydraulic vibration-excitation system controlled by a new type of shock rotary vibrator is proposed. A system model considering the pipeline effect was established for the hydraulic shock phenomenon. In addition, the model was compared with the one that does not consider the pipeline effect. The effectiveness of the proposed model was verified experimentally. Finally, the shock phenomenon during the process of switching the working state of the vibrator and the influence of certain important parameters of the system on the vibration output were investigated based on the proposed model. The results showed that (1) the hydraulic shock phenomenon occurred when the working state of the hydraulic vibrator was switched and (2) the hydraulic shock wave could effectively improve the excitation force of the system. The excitation force increased with an increase in the oil supply pressure, spindle speed, and load. However, it was negatively correlated with the spring stiffness. The amplitude of the vibration waveform output was positively correlated with the oil supply pressure and negatively correlated with the spindle speed and load. The amplitude first increased and then decreased as the stiffness of the vibration spring increased. The only influence of the precompressed length of the spring on the system output was its alteration of the vibration center of the system output vibration.

The high sensitivity of Lorentz sensors comes from its narrowband resonant characteristics marked by rapid slope change of slope of its phase spectrum, a phenomenon known as Anomalous dispersion. Unlike conventional microwave resonant sensors which have a resonant amplitude, the Lorentz sensors also have unique signature in its phase spectra which adds a second degrees of freedom in detection and removes ambiguity in the identification of the resonant frequency. We demonstrate two sensing applications in which ultra-high sensitivity is required. In particular, we show that by exploiting the high electric field regions in Lorentz resonators detection of low density gaseous water states (steam) and sub-wavelength sized biomaterials is possible. The material sensing is performed by characterizing the resonant shifts in the frequency range of 1 to 2 GHz. Depending on the gaseous state concentrations, the dielectric constant of the detected steam lies between 1.04 and 1.6 GHz. The Lorentz resonator is shown to distinguish accurately between different sub-wavelength samples derived from different parts of chicken. We anticipate that the proposed sensor can be used in biosensing of cancerous cells and in detecting low-permittivity poisonous gaseous matter such as clear smoke, carbon mono oxide, methane and nitrogen.

Due to the popularity of JPEG format images in recent years, JPEG images will inevitably involve image editing operation. Thus, some tramped images will leave tracks of Non-aligned double JPEG ( NA-DJPEG ) compression. By detecting the presence of NA-DJPEG compression, one can verify whether a given JPEG image has been tampered with. However, only few methods can identify NA-DJPEG compressed images in the case that the primary quality factor is greater than the secondary quality factor. To address this challenging task, this article proposes a novel feature extraction scheme based optimized pixel difference ( OPD ), which is a new measure for blocking artifacts. Firstly, three color channels (RGB) of a reconstructed image generated by decompressing a given JPEG color image are mapped into spherical coordinates to calculate amplitude and two angles (azimuth and zenith). Then, 16 histograms of OPD along the horizontal and vertical directions are calculated in the amplitude and two angles, respectively. Finally, a set of features formed by arranging the bin values of these histograms is used for binary classification. Experiments demonstrate the effectiveness of the proposed method, and the results show that it significantly outperforms the existing typical methods in the mentioned task.

Sapphire possesses chemically inert and high hardness. Therefore, it is difficult to get idea material removal rate (MRR) and low surface roughness through chemical mechanical polishing (CMP). Ultr...

This work provides a novel approach that combines computational fluid dynamics (CFD) with computational solid mechanics (CSM) to dynamically simulate the fully coupled hydroelastic interaction between nonlinear ocean waves and a submerged-horizontal-plate breakwater (SHPB). Based on a systematic series of simulations, it is shown that the wave damping performance of an SHPB can be evidently improved by an appropriate extent of deformation, which can be achieved through the design of its bending stiffness by varying elasticity and/or aspect ratio. The wave attenuation effect is found to be maximized when an SHPB has a deformation amplitude close to the incident wave amplitude. By accounting for the hydroelastic effect through the fully coupled CFD+CSM approach, this work presents a new computational technique that supports the design of deformable offshore and coastal structures.

The acoustic nonlinearity parameter of skeletal muscles changes with their contractions and has the potential to be utilized for exoskeleton control. In our previous work, a system comprising a wearable ultrasound probe was developed to estimate the acoustic nonlinearity parameter in vivo by measuring amplitudes of second-harmonic ultrasound. The estimating accuracy was found to be significantly affected by the corruption between echoes due to the limited axial resolution of ultrasound. As both frequency components of the single echo and the extent of corruption are unknown, a method based on a bi-directional deconvolution is proposed in this paper to decompose corrupted echoes, and integrated into the measuring system. Eight subjects were recruited for the in vivo measurement of the biceps brachii acoustic nonlinearity parameter, thickness, and elbow torque. Linear regression between the elbow torque and (1) the estimated acoustic nonlinearity parameter, (2) the thickness demonstrated the correlations, with average coefficients of determinations ( $R^{2}$ ) of 0.861 and 0.633 respectively. This work paves a way for estimating the acoustic nonlinearity parameter of skeletal muscles in vivo .

The Chinese lunar spacecraft Chang’E-3 (CE3) was launched on December 1, 2013, and it kept transmitting differential one-way range (DOR) signals during the whole mission. Differential phase delays calculated from those DOR signals are examined. An interesting phenomenon is that differential phase delays of different frequency pairs change in similar patterns before CE3′s landing on the Moon, whereas they change differently after the landing. Moreover, differential phase delays and signals’ power experience sudden and large-amplitude variations from time to time. Our analysis shows that, before the landing, signal reflection mainly happened on the spacecraft surface while CE3 was moving in space. Thus, the delay of reflected signals was a few nanoseconds with amplitude variation much larger than 0.12 ns, causing differential phase delays to vary in similar patterns. However, after CE3′s landing, reflected signals from lunar surface were received by ground stations when CE3 was sitting still on the Moon. Accordingly, the delay of reflected signals was more than 20 ns and with amplitude variation within a few tens of picoseconds, causing differential phase delays to change in different patterns. Further investigation reveals that those sudden, large-amplitude variations in differential phase delays and signals’ power were caused by CE3 maneuvers and onboard device movements.

In this study, the Gravity Recovery and Climate Experiment (GRACE) satellite observations, combining 71 continuous Global Positioning System (CGPS) data, are used to detect surface vertical loading deformation of the Amazon Basin during 2002–2020. The results show that the maximal annual amplitude of the surface mass changes derived by GRACE is more than 80 cm in terms of the equivalent water height (EWH) in the Amazon Basin. Most part of Amazon experiences mass gain, especially the Amazon River, while there is little mass loss in the northern and eastern parts. Through the Pearson correlation analysis, the monthly de-trended time series of GPS-observed vertical deformation and GRACE-derived mass loading are in good agreement with an average correlation coefficient of about 0.75 throughout the Amazon region. The common seasonal signals of GPS vertical displacements and GRACE/GFO loading deformations are extracted using the stack averaging. The two kinds of common seasonal signals show a good consistency, and together indicate approximate 20 mm peak-to-peak seasonal amplitude. Strong annual variations are identified both in the monthly GPS and GRACE/GFO data by the wavelet analysis. However, the time-frequency spectrum of GPS has more signal details and more significant semi-annual variations than that of GRACE/GFO. These results may contribute to the understanding of secular crustal vertical deformation in the Amazon Basin.

Nonlinear materials can exhibit bistability, namely support different possible outputs for the same input, depending on the excitation history. This property can find direct application to photonic memory devices, the vast majority of which operate by changing the amplitude of the incoming signals. In this work, we study impedance metasurfaces producing hysteresis responses with respect to impinging beam angle by keeping a fixed intensity profile; accordingly, the considered setups remember the history of illumination incidence. The reported findings may open new unexplored avenues toward the design of photonic systems supporting a wide range of fixed-power memory functionalities from switching and sensing to information storage and data writing.