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Aiming at the shortcomings of traditional vibrating screens with large vibration mass, a double eccentric cam self-synchronous vibrating screen is proposed. The motion differential equation of the vibrating screen system is derived by using Lagrange equation and the steady state solution is obtained. According to Hamilton principle, the synchronization condition of the vibration system is deduced, and the stability condition of the self-synchronization motion is obtained. The influencing factors of synchronization and stability are investigated by using numerical calculation and simulation analysis methods. The results show that stable self-synchronous motion of the vibration system is implemented when the synchronization and stability conditions are satisfied; the value of the stable phase difference of two cams varies in the range of (-1.5 rad, 0), and compared with the residual torque difference, the eccentricity of eccentric cams has a greater impact on the stable phase difference; additionally, a linear motion track of the vibrating screen is achieved. [ABSTRACT FROM AUTHOR]

Local high-accuracy velocity estimation is important for the ultrasound-based evaluation of regional myocardial function. The ultrasound phase difference at the center frequency of the transmitted signal has been conventionally used for velocity estimation. In the conventional method, spatial averaging is necessary owing to the frequency-dependent attenuation and interference of backscattered waves. Here, we propose a method for suppressing these effects using multifrequency phase differences. The resulting improvement in velocity estimation in the heart wall was validated by in vivo experiments. In the conventional method, the velocity waveform exhibits spike-like changes. The velocity waveform estimated using the proposed method did not exhibit such changes. Because the proposed method estimates myocardium velocity without spatial averaging, it can be used for measuring heart wall dynamics involving thickness changes. [ABSTRACT FROM AUTHOR]

For a dual-motor-driven elliptical vibrating screen, the driving frequencies of the two motors are studied in this paper and it exposes the significant influences of different driving frequencies on the vibration direction angle of the self-synchronous system. A dynamic model is established to demonstrate the new concepts and innovative ideas put forth in this paper. Simulink and prototype experiments are implemented to further study the influences of different driving frequencies on the phase angle and the vibration direction angle. The results of simulation and experiments shows that vibrating screen driven by the two motors can not only achieve a stable synchronization within a certain frequency range by changing the driving frequency of either of the two motors, but also the vibration direction angle significantly changes at similar but different driving frequencies. This is an important finding that has important significance for the future operations of dual-motor-driven vibrating screen in industry. The method developed in this study would be a valuable engineering tool which can be used in design and application of the screens and the screening operations. [ABSTRACT FROM AUTHOR]

Aiming at the poor precision problem in phase difference measurements with unknown frequencies in engineering practice, a new phase difference measurement method is proposed for Coriolis mass flowmeter based on correlation theories. Firstly, the signal frequency was estimated by using an adaptive notch filter, which was applied to filter the waves and determined the integer period of the sampling signals, and the non-integer period sampling signals needed to be extended. Then, the Hilbert transformation was conducted relative to the extended signals, and the correlation functions of these extended signals with the transformed signals can be computed. Finally, the formula of phase difference can be obtained by utilizing the sinusoidal function. Compared to traditional methods, such as the correlation method, the Hilbert transformation method, and sliding Goertzel algorithm, the proposed method is suitable for both integer period and non-integer period sampling signals, and its accuracy, real-time, and dynamic performance is superior. Simulation and experiment results validate the superiority and effectiveness of the proposed method.

Copyright of Journal of Harbin University of Science & Technology is the property of Journal of Harbin University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The rapid finger tap test is widely used in clinical assessment of dyskinesias in Parkinson’s disease. In clinical practice, doctors rely on their clinical experience and use the Parkinson’s Disease Uniform Rating Scale to make a brief judgment of symptoms. We propose a novel C-band microwave sensing method to evaluate finger tapping quantitatively and qualitatively in a non-contact way based on wireless channel information (WCI). The phase difference between adjacent antennas is used to calibrate the original random phase. Outlier filtering and smoothing filtering are used to process WCI waveforms. Based on the resulting signal, we define and extract a set of features related to the features described in UPDRS. Finally, the features are input into a support vector machine (SVM) to obtain results for patients with different severity. The results show that the proposed system can achieve an average accuracy of 99%. Compared with the amplitude, the average quantization accuracy of the phase difference on finger tapping is improved by 3%. In the future, the proposed system could assist doctors to quantify the movement disorders of patients, and it is very promising to be a candidate for clinical practice. [ABSTRACT FROM AUTHOR]

Due to economic development, many social infrastructures such as various large structures are being constructed around the world. Inspection and maintenance of social infrastructure such as huge bridges and tanks is one of the most important items in the world. In the present study, a new vibration actuator that extends the principle of operation invented by the authors was proposed and tested. New principle of operation for the actuator capable of reciprocating movement by controlling the phase of two vibration components has been considered. The principle of operation for the actuator was established by a very simple analysis. The experimental results indicate that reciprocating motion can be realized by controlling the phase of the vibration of the two vibration components. Experimental results reveal that this vibration actuator is able to pull a load mass of 190 g and the maximum efficiency of the actuator was about 12.5 % for the case with own-weight. The actuator was confirmed to be able to easily control the direction of movement with two-channel function generator and power amplifier. [ABSTRACT FROM AUTHOR]

Sleep disturbances are common complaints in patients with post-traumatic stress disorder (PTSD). To date, however, objective markers of PTSD during sleep remain elusive. Sleep spindles are distinctive bursts of brain oscillatory activity during non-rapid eye movement (NREM) sleep and have been implicated in sleep protection and sleep-dependent memory processes. In healthy sleep, spindles observed in electroencephalogram (EEG) data are highly synchronized across different regions of the scalp. Here, we aimed to investigate whether the spatiotemporal synchronization patterns between EEG channels during sleep spindles, as quantified by the phase-locking value (PLV) and the mean phase difference (MPD), are altered in PTSD. Using high-density (64-channel) EEG data recorded from 78 combat-exposed Veteran men (31 with PTSD and 47 without PTSD) during two consecutive nights of sleep, we examined group differences in the PLV and MPD for slow (10–13 Hz) and fast (13–16 Hz) spindles separately. To evaluate the reproducibility of our findings, we set apart the first 47 consecutive participants (18 with PTSD) for the initial discovery and reserved the remaining 31 participants (13 with PTSD) for replication analysis. In the discovery analysis, compared to the non-PTSD group, the PTSD group showed smaller MPDs during slow spindles between the frontal and centro-parietal channel pairs on both nights. We obtained reproducible results in the replication analysis in terms of statistical significance and effect size. The PLVs during slow or fast spindles did not significantly differ between groups. The reduced inter-channel phase difference during slow spindles in PTSD may reflect pathological changes in the underlying thalamocortical circuits. This novel finding, if independently validated, may prove useful in developing sleep-focused PTSD diagnostics and interventions.

A quantitative evaluation of the depth of field of optical systems is given. Results of the calculation of the distribution of the complex amplitude and intensity in a three-dimensional scattering pattern formed by the optical system for an on-axis point object are presented. The work was carried out as part of developing optical systems with an extended depth of field for a synthesized hologram of a point object located on a perpendicular constructed to the hologram center.

A complete collection of two-soliton bound states exhibiting ±π/2, 0, and π phase differences was realized in experiment in a mode-locked erbium-doped fiber laser with a graphene saturable absorber for the first time. The graphene mode-locker possesses modulation depth of about 6% and saturation fluency of about 300 μJ/cm2. By carefully adjusting the polarization controller in the laser cavity under appropriate pumping power, diverse soliton molecules with distinct temporal separations and different phase relationships were obtained. Our experimental findings provide clear evidence that stable soliton pairs with ±π/2, 0, and π phase differences can be tightly bounded in fiber lasers as intrinsic attractors, which is independent of cavity details such as the mode-locker we choose. In addition, our numerical simulations unravel the influence of nonlinear properties of a saturable absorber on bound states. It is found that mode-lockers with different modulation depth and/or saturation intensity play a role in interpulse separation and individual pulsewidth of generated soliton molecules while keeping the relative phases between bound solitons unchanged. This paper is instructive to explain current research works on bound states in fiber lasers with sorts of saturable absorbers and is of importance to understand the dissipative dynamics of soliton molecules.

This paper presents a novel structure for realizing a coupler with controllable power divisions, which is composed by two couplers and two phase shifters cascaded between them. This structure is applicable to constructing couplers with extremely-wide-range tunable power division, and the phase-difference performances can be predicted and controlled flexibly. In this paper, the rigorous design equations and methodologies are exhibited. For verification, two prototypes with rat-race and quadrature operations are fabricated and measured, and the measured results sufficiently confirm this topology to be effective and correct.

In this study, a three-dimensional simulation of a fish-like body swimming in a channel with non-slip walls was carried out to investigate the effects of kinematics on swimming performance. Self-propelled swimming in an inertial coordinate system was examined by using the direct forcing immersed boundary method. The fish body consisted of several rigid bodies and behaved analogously to a multi-segment robotic fish. The computational program was first validated by simulating fluid flow around a circular cylinder at Reynolds number (Re) =100 and Re = 1000, as well as around a settling particle. The results were compared with experimental and numerical results from past research in the area. A virtual parametric study of the tail-beat frequency, phase difference between neighboring body segments, and body amplitude was then conducted. The effect of the lateral and vertical distance between the model body and walls on swimming performance is also discussed. The results for the velocity and vorticity fields around the model body provided evidence for the mechanism of thrust generation and highlighted the effects of kinematics on swimming performance.

Two-dimensional numerical investigations have been carried out to study the temporal wake characteristics of laminar flow past two identical inline square cylinders performing transverse oscillations. Both the cylinders are forced to perform harmonic oscillations of same frequency and amplitude but with a phase difference. Computations are carried out using commercial software ANSYS Fluent 16.1 on a dynamically sliding mesh for fixed Reynolds number equal to 100. The oscillation frequency is varied from 0.4 to 1.6 times the frequency of vortex shedding behind a single stationary square cylinder. The amplitude of transverse oscillation is kept fixed equal to 0.4D (D = side of the cylinder). In addition, the effect of variation of inter-cylinder spacing has been investigated on wake interference which influences the modes of vortex shedding and resulting dynamic effects on the cylinders. Temporal signals as well as mean characteristics of lift and drag coefficients have been presented for different values of inter-cylinder spacing, phase difference between the two cylinders and frequency of oscillation.

In this paper, performance analysis of the cross-eye jamming effect under mechanical defects is dealt with. By using a numerical analysis-based approach, the performance analysis method proposed in this paper is closer to the not approximated empirical mean square difference (MSD) than the first-order Taylor approximation-based performance analysis method and the second-order Taylor approximation-based performance analysis method proposed in previous studies. In other words, the effects of amplitude ratio perturbation and phase difference perturbation on performance degradation are quantitatively analyzed. Note that the numerical integration is adopted to derive an analytic expression of the MSD.

Metal object detection (MOD) and detection of position (DoP) of pick‐up coils are increasingly critical to the commercialisation of the wireless power transfer system. In this study, a detection scheme based on phase‐detection, which can both realise the function of MOD and DoP, is newly introduced. The method is based on the principle that the presence of metal objects and pick‐up coils both affect the impedance phase of the detection coil loop. Comparing with the traditional detection methods, which is based on measuring the absolutely value of impedance in detection loop, the malfunction is avoided by adopting phase difference as the criterion of the existence of metal objects and pick‐up coils. An inexpensive and high‐precision sensing circuit is newly designed to acquire the phase difference accurately. Simulation models and experiments are conducted to verify the feasibility of the proposed detection scheme. The Δδ of the detection coil circuit with a coin placed reaches −5.17, while the Δδ of other detection coils without metal objects keeps zero. In the meantime, the position of the pick‐up coil is identified because the Δδ of these detection coils closer to the centre of the pick‐up coil varies more significantly while other coils vary slightly. [ABSTRACT FROM AUTHOR]

In this study, a class of wideband bandstop filters is proposed based on wideband 180° phase shifters. Different from traditional signal–interference-based bandstop filters, they make use of a 180° phase shifting in a wide operating band in principle. After numerical analysis of the phase responses of the two coupling-line paths, the optimal solutions for the largest 180° phase-shifting bandwidth or minimum impedance ratio can be obtained. Then, the wideband bandstop filter based on these two unique coupling lines is intensively analysed to reveal that three transmission zeros are generated in the stopband as the two paths have a 180° phase difference, thus exhibiting its wideband property. Moreover, by enlarging the impedance of the two paths, good out-of-band characteristics of the bandstop filter can be attained, while in-band performances are almost unchanged. Next, two types of bandstop filters with extended bandwidth are proposed by cascading an extra delay line for both paths, and they hold similar filtering characteristics as the aforementioned one. Finally, the design process and demonstration are provided. The measured results of the three fabricated filters show that Type-I, Type-II, and Type-III filters can satisfactorily obtain a 3 dB bandwidth of 108, 122, and 130% with 25, 14.7, and 11.6 dB rejection level, respectively. [ABSTRACT FROM AUTHOR]

Air-writing systems have recently been proposed as tools for human-machine interaction where instructions can be represented using letters or digits written in the air. Different technologies have been used to realize air-writing systems. In this article, we propose an air-writing system using acoustic waves. The proposed system consists of two components: a motion-tracking component and a text recognition component. For motion tracking, we utilize direction-of-arrival (DOA) information. An ultrasonic receiver array tracks the motion of a wearable ultrasonic transmitter by observing the change in the DOA of the signals. We propose a novel 2-D DOA estimation algorithm that can track the change in the direction of the transmitter using measured phase differences between the receiver array elements. The proposed phase-difference projection (PDP) algorithm can provide accurate tracking with a three-sensor receiver array. The motion-tracking information is passed next for text recognition. To this end, and in order to strike the desired balance between flexibility, processing speed, and accuracy, a training-free order-restricted matching (ORM) classifier is designed. The proposed air-writing system, which combines the proposed DOA estimation and text recognition algorithms, achieves a letter classification accuracy of 96.31%. The utility, processing time, and classification accuracy are compared with four training-free classifiers and two machine learning classifiers to demonstrate the efficiency of the proposed system. [ABSTRACT FROM AUTHOR]

A technique is proposed for the enhancement of gain and circularly polarised (CP) bandwidth of a singly‐fed CP dielectric resonator (DR) antenna. The specific geometry of DR is used to generate the orthogonal modes required for obtaining the CP response. The incremental harmonics of the fundamental and third‐order modes, TE11δ+1 and TE31δ+1, are generated by stacking of the similar DR layer topped with metallic patch after an air gap. This enhances the gain and CP bandwidth of the antenna maintaining the generated orthogonal modes with the required phase difference. The antenna with single DR layer provides the CP bandwidth of 13.56% and gain 4.04 dBic. After stacking, the antenna provides the measured CP bandwidth of 24.75% and 7.32 dBic stable gain over the passband. In addition, the antenna provides 92.87% radiation efficiency in the passband. [ABSTRACT FROM AUTHOR]

Understanding dynamic stability of a ship on a resonance frequency is important because comparatively smaller external forces and moments generate larger motions. The roll motion is most susceptible because of smaller restoring moments. Most studies related to the failure modes such as parametric roll and dead ship condition, identified by second generation of intact stability criteria (SGISC) are performed at a resonance frequency. However, the nature of resonance, where the model experiences an incremental roll motion, has not been well understood. In this study, nonlinear unsteady computational fluid dynamics (CFD) simulations were conducted to investigate the resonance phenomenon using a containership under a sinusoidal roll exciting moment. To capture the complexity of the phenomenon, simulations were conducted over a range of frequencies to cover the resonance frequency including lower and higher amplitudes. In addition to the resonance frequency, the phase shift between roll exciting moment and roll angle, as well as the phase difference between acceleration and roll angle, were found to have significant effects on the occurrence of resonance. [ABSTRACT FROM AUTHOR]

Under seismic loading, the soil layer is subjected to multidirectional cyclic shear stress with different amplitudes and frequencies because of the coupling of multiple shear waves and the soil element within a slope or behind a retaining wall is subjected to initial static shear stress before subjected to cyclic loading. Due to the complexity of seismic loading propagation, a phase difference exists between the initial static shear stress and cyclic shear stress. To investigate the influence of the phase difference and initial static shear stress on cyclic shear strain, cyclic modulus, and cyclic strength, a series of laboratory tests are performed on Wenzhou marine soft clay by multi-directional simple shear system, which can simulate the actual state better by controlling the horizontal cyclic stress in the x and y directions simultaneously. As the phase difference varies from 0° to 90°, the dynamic shear modulus increases and cyclic strain accumulation decreases with an increasing number of cycles. The shear strain increases with the initial shear stress. [ABSTRACT FROM AUTHOR]

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Convolutional neural networks (CNNs) and digital holographic interferometry (DHI) can be combined to improve the calculation efficiency and to simplify the procedures of many DHI applications. In DHI, for the measurements of concentration differences between liquid samples, two or more holograms are compared to find the difference phases among them, and then to estimate the concentration values. However, liquid samples with high concentration difference values are difficult to calculate using common phase unwrapping methods as they have high spatial frequencies. In this research, a new method to skip the phase unwrapping process in DHI, based on CNNs, is proposed. For this, images acquired by Guerrero-Mendez et al. (Metrology and Measurement Systems 24, 19–26, 2017) were used to train the CNN, and a multiple linear regression algorithm was fitted to estimate the concentration values for liquid samples. In addition, new images were recorded to evaluate the performance of the proposed method. The proposed method reached an accuracy of 0.0731%, and a precision of ±0.0645. The data demonstrated a high repeatability of 0.9986, with an operational range from 0.25 gL−1 to 1.5 gL−1. The proposed method was performed with liquid samples in a cylindrical glass. [ABSTRACT FROM AUTHOR]

The Floating nuclear power plant grid is composed of power generation, in-station power supply and external power delivery. To ensure the safety of the nuclear island, the in-station system adopts a special power supply mode, while the external power supply needs to be adapted to different types of external systems. Because of frequent single phase-ground faults and various fault forms, the fault line selection protection should be accurate, sensitive and adaptive. This paper presents a fault line selection method in cooperation with multi-mode grounding control. Based on the maximum united energy entropy ratio (MUEER), the optimal wavelet basis function and decomposition scale are adaptively chosen, while the fault line is selected by wavelet transform modulus maxima (WTMM). For high-impedance faults (HIFs), to enlarge the fault feature, the system grounding mode can be switched by the multi-mode grounding control. Based on the characteristic of HIFs, the fault line can be selected by comparing phase differences of zero-sequence current mutation and fault phase voltage mutation before and after the fault. Simulation results using MATLAB/Simulink show the effectiveness of the proposed method in solving the protection problems. [ABSTRACT FROM AUTHOR]

In order to verify that the vibration system driven by multi-eccentric rotors has multiple synchronous states, a model of three eccentric rotors horizontal installation of plane motion is established to study the coupling dynamic characteristics. Based on the average method of modified small parameters, the frequency capture equation is constructed to obtain the conditions of synchronous motion and vibration synchronization transmission. According to the synchronous conditions, the stability state of achieving synchronous motion is converted into the solution of balance equation of the synchronous torque. There are multiple solutions to the torque equation because of the non-linear characteristics of the vibration system driven by multi-eccentric rotors. Then the stability condition is used to estimate which of the solutions is stable. After substituting the parameters of the experimental machine into the above method, the curves of the phase difference and its stability coefficients of three eccentric rotors system are obtained numerically. Two experiments show that the selected synchronous state depends on the initial condition and external disturbance, and if the vibration synchronization transmission conditions are satisfied, three eccentric rotors can not only achieve vibration synchronization transmission of one motor with switching off the power but also that of two motors with switching off the power. [ABSTRACT FROM AUTHOR]

This article presents a new visual detection method with high precision, robustness, and processing rate to estimate the linear motor displacements. Subpixel level location is achieved by using the phase-difference matrix and a structured aperiodic fence stripe placed on the mover. Based on Fourier shifted properties, this subpixel method builds a linear relation between the mover's spatial displacements and the direct frequency-domain phase difference (not the phase correlation matrix) to calculate the translational shift in a series of stripe images; thereby, precisely determining the mover location of linear motor. Unlike the traditional phase correlation algorithm, the proposed method converts 2-D stripe images into 1-D signals via the projection technique and then uses the least squares method to linearly fit the phase difference slope, thereby acquiring subpixel shifts with less time complexity. Due to the motion parameter that is directly estimated from the phase difference, this method is also insensitive to the gray-scale change with certain anti-interference capability, thereby making it suitable for measuring the moving position of the mover. Experimental results show that the proposed vision-based detection method is efficient and applicable for real-time accurate positioning of linear motor, and the measuring root mean square error is about 0.05 mm. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Medical Equipment Journal is the property of Chinese Medical Equipment Journal Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper firstly investigates the frequency- and time-varying co-movement and causal relationship between crude oil prices (proxied by the West Texas Intermediate, Brent, Dubai and Nigerian Forcados spot oil prices) and geopolitical risks based on the wavelet analysis over the period of 1985–2016. Overall, our results demonstrate significant dynamic co-movement and causality in the varying time–frequency domains. We find high degree of co-movement between geopolitical risks and oil prices at high frequencies (in the short run) for the entire sample period; however, such a correlation does not exist at low frequencies (in the long run) for most of the sample period. We also find distinct patterns of causal relationships between geopolitical risks and oil prices across different benchmark markets. Results are robust when we control for global economic outlook. Our findings provide valuable implications for policy makers and oil market investors based on the dynamic relationship between geopolitical risks and oil prices. [ABSTRACT FROM AUTHOR]

In the integrated system of underwater single‐node detection and communication, active self‐interference cancellation requires high accuracy of time delay estimation. To solve this problem, this Letter proposes a high accuracy delay estimation method based on phase correction. Initially, the normalised frequency correction is calculated according to the phase difference and time delay of the signal. Then, the discrete spectrum is reconstructed, and the phase is obtained by the least square method. Finally, the time delay is estimated by the phase difference between the received signal and the reference signal. This method corrects the phase and frequency errors caused by the Fourier transform and improves the accuracy of time delay estimation. Simulation results confirm the efficacy of the proposed method and achieve the accuracy requirement of the active self‐interference cancellation. [ABSTRACT FROM AUTHOR]

In this Letter, a novel empty substrate‐integrated waveguide (ESIW) phase inverter (PI) applied in millimetre‐wave has been proposed. ESIW PI, based on the structural symmetry design, is made of four parts: top cover, middle layer, ESIW PCB, and bottom layer. Owing to the reversed‐phase transmission channel, the phase difference between the two outputs is absolutely equal to 180°. The simulation and measurement results are in a good agreement. In the entire Ka band, the return losses, insertion losses and amplitude imbalance of ESIW PI are better than 12.7, 2.66, and 0.64 dB ± 0.6 dB, respectively. Besides, the phase difference is within 180.5° ± 2.9° in the same frequency band. In addition, the input and output ports are located in the identical circuit plane, which is easy to integrate with other devices and components. [ABSTRACT FROM AUTHOR]

Displacer type pulse tube refrigerator has been the emphasis of research in refrigeration due to its high theoretical efficiency and wide refrigeration temperature range from 77 K to near room temperature. A pulse tube refrigerator with displacer as phase shifter was built and tested. According to the results, there is an optimum displacer rod diameter for getting high efficiency when the parameters of the mass-spring-damper system in displacers almost keep constant. The results also indicated that the cooling power 120 W was obtained at 178.8 K with the input power 684.6 W, which leaded to an efficiency of 11.2% of Carnot, about 25% higher when the inertance tube phase shifter was replaced by displacer. [ABSTRACT FROM AUTHOR]

The emerging orbital angular momentum (OAM) based wireless communication is expected to be a high spectrum-efficiency communication paradigm to solve the growing transmission data rate and limited bandwidth problem. Academic researchers mainly concentrate on the OAM-based line-of-sight (LoS) communications. However, there exist some surroundings around the transceiver in most practical wireless communication scenarios, thus forming multipath transmission. In this paper, a hybrid orthogonal division multiplexing (HODM) scheme by using OAM multiplexing and orthogonal frequency division multiplexing (OFDM) in conjunction is proposed to achieve high-capacity wireless communications in sparse multipath environments, where the scatterers are sparse. We first build the OAM-based wireless channel in a LoS path and several reflection paths combined sparse multipath environments. We concentrate on less than or equal to three-time reflection paths because of the severe energy attenuation. The phase difference among the channel amplitude gains of the LoS and reflection paths, which is caused by the reflection paths, makes it difficult to decompose the OAM signals. We propose the phase difference compensation to handle this problem and then calculate the corresponding capacity in radio vortex wireless communications. Numerical results illustrate that the capacity of wireless communications by using our proposed HODM scheme can be drastically increased in sparse multipath environments. [ABSTRACT FROM AUTHOR]

The high‐output triboelectric nanogenerator (TENG) is indispensable for its practical applications toward industrial products. However, the electricity loss in simple parallel connection among all units and the typically high crest factor output seriously hamper the practical applications of TENG. Here, a rectified TENG is reported in parallel structure to solve the problem of electricity loss in simple parallel connection. The rotational contact–separation structure with phase difference between rectified TENGs addresses high crest factor output and extends service life of rotational TENG simultaneously. The current crest factor is dramatically decreased to 1.31 in multiple rectifier multiple TENG in parallel (MRM‐TENG), while that of TENG in simple parallel is higher than 6. Meanwhile, the current output can retain up to ≈93% of its initial performance after 7 200 000 rotations under 2.00 r s−1 of 1000 h. Furthermore, the equivalent current can be in linear growth with low crest factor by making MRM‐TENG in parallel for distributed energy supply without electricity loss. This work may provide a new strategy for TENG in parallel to achieve a low crest factor output and long‐term cycling stability power generation in distributed energy harvesting for large‐scale power application. [ABSTRACT FROM AUTHOR]

The paper reports a 1 g shaking table test that was carried out on a reinforced soil wall with an objective to study the acceleration amplification in the backfill, and phase differences between dynamic responses of the reinforced and retained zones. Results of the study show that including the observed larger acceleration amplification in the upper half of the wall, and the phase difference between maximum lateral earth pressure and inertial load in the backfill in the analysis would lead to more accurate predictions of: (1) the wall response relative to predicted reinforcement load, (2) elevations of line of action for both the inertial and lateral earth forces in the backfill, and (3) wall deformations, as compared to pseudo-static methods of analysis. [ABSTRACT FROM AUTHOR]

To improve the calculation accuracy of the horizontal-to-vertical spectral ratio (HVSR) method, this study theoretically analyzed the influencing factors of Rayleigh wave polarizability. The phase difference of the horizontal component and the phase difference of the vertical component are found to play a key role in calculating the polarizability. The influence mechanism of the superposition of body waves and different Rayleigh waves on the polarizability of the Rayleigh wave is derived. The effects of the body wave, amplitude, frequency and Rayleigh wave superposition of different sources on the polarizability are verified by numerical simulation. The results show that the body wave significantly interferes with the polarizability of the Rayleigh wave. When a signal contains more than one set of Rayleigh waves, the superposition of the same-source Rayleigh waves does not affect the ratio. However, the superposition of Rayleigh waves from different sources significantly interferes with the calculation of the polarizability. This provides a technical method and a theoretical basis for accurately extracting the Rayleigh wave polarizability dispersion curve from a seismic record signal. This would help improve the detection accuracy of the HVSR method for ground pulse signals. [ABSTRACT FROM AUTHOR]

Steam generator water level control incorporates the system that controls the speed of the main water feed pump and the one that controls the degree to which the main water feed valve is open. Although these two control systems are set independently, they have a reciprocal influence. A key problem is that, in the actuator for the regulation of the two systems, the regulated variables tend to oscillate with a relatively large amplitude even under stable conditions. In this paper, a pervasive regulating resonance phenomenon is inspected and analyzed by means of simulating the real working conditions. And using a mathematical model of the main water feed flow, it reveals that the two factors which directly cause the regulation resonance phenomenon are the frequency characteristics of the control system and the phase difference. On the basis of this, three potential optimization schemes have been proposed: the optimization of the regulation parameters; changing the phase difference; and setting a regulation dead-band which can improve the stability of the control system. [ABSTRACT FROM AUTHOR]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To study the mechanism of periodic change of reflective rectangular metallic gratings' diffraction efficiencies, a dual secondary coherent light source array model was established based on the theory of Fabry-Perot resonator. It was assumed that when incident light falls on the grating surface, it transforms into two coherent sources on each grating period. One is on the upper surface of the grating, reflected by the metal surface; the other is at the entrance of the grating groove and propagates in the form of a fundamental mode λf Based on the above mentioned hypothesis, formulae for the phase difference ΔΦ of two sources and diffraction efficiency for the first and zero order with grating height h, were established. ΔΦ and h are linear relationships, the phase difference ΔΦ change due to the change of grating height h is the essencial cause of periodic changes of the diffraction efficiencies. When ΔΦ has a certain value, the energy is distributed only in the zero or the first order direction. The model does not only show the change regularity of each diffraction order's diffraction efficiency of reflective rectangular metallic grating, but it also shows the correlation of each diffraction order. It can help to predict diffraction performance of rectangular metallic gratings and to design gratings. [ABSTRACT FROM AUTHOR]

We developed a non-contact device that measures the volume of body fluids using microwave transmission. This device detects the phase difference between the radio waves that pass through the measurement target and the radio waves that do not pass through. When the radio waves pass through the water, the phase of the radio waves is delayed. The change in water volume cause phase differences, and our proposed device measures the relative temporal change of congestion without restraint. Deep vein thrombosis is caused by hypercoagulability, stagnation of blood flow, and vascular endothelial dysfunction. Remaining in a seated position for prolonged periods of time may cause deep vein thrombosis due to the stagnation of blood flow and may result in death. This device measures the volume of body fluids in the lower limbs. If venous congestion can be detected, we believe that the device will be developed as a new preventive measure for deep vein thrombosis. In this study, a subjectʼs lower leg was compressed with a cuff at a pressure of 60 mmHg for 5 min to induce venous congestion. We simultaneously measured the changes in phase difference and the changes in the outer diameter of the calf by our proposed device and a strain gauge. The results showed a strong correlation between the change in the phase difference and the change in the outer diameter of the calf. These findings suggest that the proposed device is able to measure the volume of body fluids without contact. Future work may explore the application of the device for measuring fluids in the lower body of individuals who sit for prolonged periods of time, including in e-sports. [ABSTRACT FROM AUTHOR]

Transmission of electromagnetic waves through nanometric multilayers (nanoresonators) including a main composite layer made of two alternating strips of low-absorbing dielectrics that is sandwiched between epsilon-near-zero (ENZ) or metallic spacer layers has been modeled. Analytical models are based on exact solutions of electromagnetic boundary problems. The spacers with the definite properties lead to extreme dependences of amplitude transmission coefficients on the system parameters and drastic increase in phase difference of the transmitted waves. These effects are most pronounced for subwavelength multilayer thicknesses due to multibeam interference features in the nanoresonator, and they can be amplified when the main layer and (or) the whole system thicknesses decrease. The investigated transmission features take place under variations of the system parameters such as anisotropy of the main layer materials, non-ideal realization of ENZ materials, oblique incidence of the exciting radiation (for small incidence angles). The obtained results can have applications in development of ultra-thin nanophotonics devices using phase transformation of transmitted waves. [ABSTRACT FROM AUTHOR]

Contact forces and skin deformation induced during tactile exploration have been investigated in the frequency domain to understand finger–material interaction. Their power spectra are one of the representative feature quantities that have been associated with the surface properties of materials. However, thus far, the phase information of these quantities has not been studied. Furthermore, most previous studies focused on uni-dimensional signals such as forces in either the normal or tangential directions. We investigated the phase differences between normal and shear forces induced during tactile exploration. The results showed that the phase differences between these two axial forces differ among materials and that they exhibit features different from their power spectra. These results indicate that the phase difference between two axial forces should be taken into account to understand the finger–material interactions during tactile exploration. [ABSTRACT FROM AUTHOR]

A sensorless control method based on the terminal voltage for doubly salient electro‐magnetic motor (DSEM) is researched here. The negative‐going zero‐crossing point (NGZCP) of the fundamental component of terminal voltage is detected to obtain the rotor position. Firstly, a fourth Butterworth filter is introduced to extract the fundamental component of the terminal voltage. The ratio of signal frequency to cut‐off frequency f/fc is optimised to acquire good filtering effect and good dynamic performance. Moreover, on this basis, the speed range is divided into several intervals to match the filters with different cut‐off frequencies. Secondly, the coordinate transformation is adopted to compensate for the phase difference between the NGZCPs of the extracted voltages with the ideal commutation points. The transformation angle is obtained by offline simulation and test. An 18 kW DSEM prototype is tested to verify the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

In this brief, a novel dual-band branch line coupler (BLC) for designing a dual-band Butler matrix (BM) has been proposed. To realize the proposed BLC, a unique dual-band impedance transformer (DBIT) with a derivation of closed-form design equations, capable of performing a dual-band operation for a traditional transmission line (TL) of any electrical length, has been proposed as well. The proposed BLC is different from the existing dual-band BLCs in terms of its phase difference between the output ports, which enables it to play a role equivalent to the combination of a dual-band equal power ±90° BLC and a dual-band ±45° / ±135° phase shifter. The circuit parameters analysis of the proposed BLC versus the frequency ratio has also been studied here. To verify the design method, a dual-band BLC has been designed using Keysight Technologies’ advanced design system (ADS), implemented on a Rogers 5870 for 1 GHz and 1.76 GHz operating frequencies, and then tested. [ABSTRACT FROM AUTHOR]

We present a system which uses a single spatial light modulator to control the spin angular momentum of multiple optical traps. These traps may be independently controlled both in terms of spatial location and in terms of their spin angular momentum content. The system relies on a spatial light modulator used in a "split-screen" configuration to generate beams of orthogonal polarisation states which are subsequently combined at a polarising beam splitter. Defining the phase difference between the beams with the spatial light modulator enables control of the polarisation state of the light. We demonstrate the functionality of the system by controlling the rotation and orientation of birefringent vaterite crystals within holographic optical tweezers.