Initial Phase Difference Research Articles

Mixed Electric Field of Multi-Shaft Ship Based on Oxygen Mass Transfer Process under Turbulent Conditions

The theoretical basis for a multi-physics coupling modeling involving a turbulence flow field and a ship’s electric field was analyzed using the principles of electrochemistry and hydrodynamics. Considering the mass transfer of oxygen in the cathode reaction of electrochemical corrosion, the boundary element method was adopted to construct a corrosion electric field model for a multi-shaft ship under navigation. After dissecting the equivalent circuit resistance of the mechanical structure of a ship’s shaft, the initial phase difference of the equivalent resistance between different shafting systems of a multi-shaft ship was analyzed to reveal the regularity of variation of the ship corrosion mixed electric field, when the contact positions of the shaft grounding device were different. A ship model experiment was conducted to verify the correctness of the simulation model. As shown in the results, when the initial phase difference of two-shaft ship shafting equivalent resistance increased from 0° to 45°, 90°, 135°, and 180°, the amplitude of the ship’s mixed electric field varied by less than 3.7%, which was practically negligible. However, the amplitude of the ship’s shaft-rate electric field decreased by 8.30%, 25.4%, 50.2%, and 88.0%, respectively. Moreover, the minimum value of the shaft-rate electric field accounted for 4.11% of the maximum value. This significantly increased the difficulty of marine target detection based on electric field sensors.

Quantum phase measurement of two-qubit states in an open waveguide

We present a new method for quantum state tomography within a single-excitation subspace of two-qubit states in an open waveguide. The system under investigation consists of three qubits in an open waveguide, separated by a distance comparable to the wavelength of the electromagnetic field. We show that the modulation of the frequency of the central ancillary qubit allows us to obtain unambiguous information about the initial phase difference $\varphi_1-\varphi_3$ of the edge qubits via the measurement of the evolution of their probability amplitudes.

Radio-Frequency Intensity Interrogation for Temperature Measurement

In this letter, an optical-carrier microwave interferometer based on radio frequency Mach-Zehnder (RF-MZI) structure for temperature measurement is numerically investigated and experimentally demonstrated. The input RF signal travels along with the optical carrier to experience different phase differences caused by the applied temperature, leading to the intensity change of the RF signal. Thus, by tracking the RF intensity variation, the temperature can be recovered. Furthermore, the sensitivity affected by the power ratio between two arms of the RF-MZI is investigated for the first time. Results show that the sensing character is associated tightly with the selected initial phase difference. In the approximately linear region, the sensitivity can be enhanced ~2.79 times when the power ratio improved from 0.25 to 0.84.

The Role of a Mechanical Coupling in (Spontaneous) Interpersonal Synchronization: a Human Version of Huygens’ Clock Experiments

Abstract Interpersonal musical interaction typically relies on the mutual exchange of auditory and visual information. Inspired by the finding of Christiaan Huygens that two pendulum clocks spontaneously synchronize when hanging from a common, movable wooden beam, we explored the possible use of mechanical coupling as an alternative coupling modality between people to strengthen (spontaneous and instructed) joint (musical) synchronization. From a coupled oscillator viewpoint, we hypothesized that dyads standing on a common movable platform would cause bidirectional passive body motion (and corresponding proprioceptive, vestibular and somatosensory sensations), leading to enhanced interpersonal coordination and mutual entrainment. To test this hypothesis, we asked dyads to perform a musical synchronization–continuation task, while standing on a movable platform. Their rhythmic movements were compared under different conditions: mechanically coupled/decoupled platforms, and spontaneous/instructed synchronization. Additionally, we investigated the effects of performing an additional collaborative conversation task, and of initial tempo and phase differences in the instructed rhythms. The analysis was based on cross wavelet and synchrosqueezed transforms. The overall conclusion was that a mechanical coupling was effective in support of interpersonal synchronization, specifically when dyads were explicitly instructed to synchronize using the movable platform (instructed synchronization). On the other hand, results showed that mechanical coupling led only minimally to spontaneous interpersonal synchronization. The collaborative task and the initial phase and tempo have no strong effect. Although more research is required, possible applications can be found in the domains of music education, dance and music performance, sports, and well-being.

Effect of coupled platform pitch-surge motions on the aerodynamic characters of a horizontal floating offshore wind turbine

Floating offshore wind turbines (FOWTs) work in a complex natural environment. Under the coupling effect of wind and waves, the platform experiences a six-degree-of-freedom motion, which affects the performance of the wind turbine. In this paper, a computational fluid dynamic method is used to investigate the effect of platform pitch and surge motion coupled at the same frequency as well as at different frequencies with an initial phase difference on the aerodynamic characteristics of FOWTs. The results demonstrate that the platform pitch and surge motion coupling makes the wind turbine operation more unstable. The power and thrust fluctuations are the largest when the two motions are coupled in the same phase, which leads to a dramatic change in the aerodynamic performance of the wind turbine during operation, and can easily cause hazards such as blade fatigue damage. When the initial phase difference does not affect the coupling motion frequency, the effect on the instantaneous power is more significant than that on the instantaneous thrust. However, the effect on the average power and thrust values is weaker. When the initial phase difference leads to reverse coupling of the platform pitch and surge motions, the fluctuation of power and thrust is reduced, and the wind turbine operation is more stable and safer.

Multichannel Superposition of Grafted Perfect Vortex Beams.

Inspired by plant grafting, grafted vortex beams can be formed through grafting two or more helical phase profiles of optical vortex beams. Recently, grafted perfect vortex beams (GPVBs) have attracted much attention due to their unique optical properties and potential applications. However, the current method to generate and manipulate GPVBs requires a complex and bulky optical system, hindering further investigation and limiting its practical applications. Here, a compact metasurface approach for generating and manipulating GPVBs in multiple channels is proposed and demonstrated, which eliminates the need for such a complex optical setup. A single metasurface is utilized to realize various superpositions of GPVBs with different combinations of topological charges in four channels, leading to asymmetric singularity distributions. The positions of singularities in the superimposed beam can be further modulated by introducing an initial phase difference in the metasurface design. The work demonstrates a compact metasurface platform that performs a sophisticated optical task that is very challenging with conventional optics, opening opportunities for the investigation and applications of GPVBs in a wide range of emerging application areas, such as singular optics and quantum science.

Independent dual-single-sideband QPSK signal detection based on a single photodetector.

The two sidebands of the independent dual-single-sideband (dual-SSB) signal can carry different information to achieve higher spectral efficiency. However, the two sidebands of the independent dual-SSB vector signal are received independently. Generally, the receiver divides the signal into two channels. For each channel, we use an optical bandpass filter (OBPF) to select the left sideband (LSB) or right sideband (RSB), respectively. Then a photodetector (PD) is used for photoelectric conversion, followed by subsequent digital signal processing (DSP). To reduce the complexity and cost of the receiver, we propose a new independent dual-SSB vector signal detection scheme based on a single PD combined with conventional DSP. An electric bandpass filter (EBPF) filters out high-frequency components after photoelectric conversion, and then the signal is quadrature demodulated and processed by the DSP algorithm. The LSB and RSB are quadrature phase-shift keying (QPSK) modulated with an initial phase difference of π/4. Simulation results show that the proposed scheme performs better bit error rate (BER). For back-to-back (BTB) transmission, the BER of 2-Gbaud independent dual-SSB vector signal (1-Gbuad RSB and 1-Gbaud LSB) can reach the hard-decision forward error correction (HD-FEC) threshold of 3.8 × 10-3 when the input optical power into PD is -20 dBm. For 1-km and 2-km weak turbulence free-space optical (FSO) channel transmission, the BER of 2-Gbaud independent dual-SSB vector signal can reach the HD-FEC threshold when the input optical power into PD is -18.8 and -17 dBm, respectively. For 1-km weak turbulence FSO channel transmission, the BER of 4-, 8-, and 16-Gbuad independent dual-SSB vector signal can reach the HD-FEC threshold when the input optical power into PD is -17.8, -16, and -15 dBm, respectively.

Experimental generation and orbital angular momentum properties of focused field for vector vortex beams on Hybrid-order Poincaré sphere

Due to the anisotropic spatial polarization state and spiral phase distribution, the orbital angular momentum (OAM) of vector vortex beams (VVBs) has attracted increasingly attention in recent years. In this paper, the Hybrid-order Poincaré sphere VVBs are constructed by orthogonal left-handed (L-H) and right-handed (R-H) circularly polarized vortexes. The vector vortex light fields of different orders at the focal plane are collected and analyzed experimentally. Based on the vector diffraction integral theory, the effects of the topological charge and polarization order for VVBs, as well as the initial phase difference for L-H and R-H components on the OAM properties of focused field for the longitudinal component are investigated numerically. It is found that the OAM density distribution of the longitudinal component shows inner and outer two layers on the whole, and the layers mainly concentrate the corresponding L-H and R-H components respectively. Meanwhile, the signs of the topological charges for L-H and R-H components determine the positive and negative distributions of the inner and outer OAM density respectively. When the initial phase difference of L-H and R-H components ϕ0 changes in the range of 0–2π, the OAM density rotates the angle ϕ0/2 along the clockwise. However, the OAM of the longitudinal component does not change with ϕ0, and increases as the polarization order m increases when the topological charge of VVBs l>2. The results could be helpful to further explore the applications of the OAM for VVBs in the fields of optical detection and communication.

Field tests on model efficiency of twin vertical axis helical hydrokinetic turbines

Twin vertical axis helical hydrokinetic turbines (VAHHTs) are a type of renewable energy conversion device that can generate electricity from the kinetic energy of free flowing water. To optimize its hydrodynamic performance, a typical twin VAHHTs model with a NACA0020 blade profile, diameter (D) of 0.2 m, height (H) of 0.45 m, solidity ratio (σ) of 0.38, and enwinding ratio (ϖ) of 1.25 was tested. Based on the controllable open channel velocity, a test platform was built to study the effect of different rotational direction, spacing, inflow direction, and phase difference on the efficiency of twin VAHHTs. The results show that the torque measurement platform can accurately measure the torque (T), water velocity (V), and rotational speed (ω) simultaneously. When the rotational direction of the twin VAHHTs is not outward opposite (-+), the efficiency is more than 9.52% higher than that of a single VAHHT. The efficiency increases first, and then decreases with an increase of the spacing between the two turbines. The change of inflow direction angle has a large influence on the efficiency of the twin VAHHTs. The initial phase difference has little effect on the performance of the twin VAHHTs. The highest average efficiency of the twin VAHHTs is 0.2315, which is 10.24% higher than that of a single VAHHT. The results supplement the deficiencies of the measured data at high velocity and provide validation for the numerical calculation of the efficiency of twin VAHHTs.

Mechanism and Application of Blasting Technology Using Phase-Difference Vibration Mitigation on Adjacent Railway Tunnel

The blasting vibration velocity is a widely used controlling index for the safety assessment of tunnel structures. How to reduce the impact of blasting vibration on the operation of adjacent railway tunnels is worth studying. In this paper, the initial phase-difference of blasting using phase-difference shock absorption is derived from the propagation theory of the blasting stress wave. When the initial phase-difference is Δφi = ±(2n + 1)π (n = 1, 2, 3, …), the peak particle velocity (PPV) in the tunnel structure is decreased to the minimum. On the basis of blasting theory using phase-difference shock absorption, the blasting parameters were designed for the No. 2 drainage tunnel excavated which adjacent a railway tunnel from Guiyang to Changsha, and it carried out 4 times blasting tests. It was found that the PPV of the railway tunnel structure in X, Y, and Z directions reduced by 64.6%, 66.25%, and 81.26%, respectively, which compared with the conventional blasting with the same total quality. Meanwhile, the amount of overbreak and underbreak can be controlled within 5%. The results show that the effect of blasting technology using phase-difference vibration mitigation is obvious, which is able to match with the design requirements for the tunnel excavation contour. The blasting technology using phase-difference vibration mitigation can be achieved via controlling the blasting time interval accurately. Moreover, it is beneficial for enriching and developing the blasting vibration control technology.

Dual‐Beam Leaky‐Wave Radiations with Independent Controls of Amplitude, Angle, and Polarization Based on SSPP Waveguide

New dual‐beam leaky‐wave radiations based on spoof surface plasmon polariton (SSPP) waveguide, in which the amplitude, radiation, angle and polarization of each beam can be designed independently, is proposed. The proposed SSPP waveguide is made of a corrugated metallic strip with bilateral 45°‐tilted grooves, whose surface impedance is flexibly designed by changing the depth of grooves. To realize dual‐beam leaky‐wave radiations, the surface impedance of SSPP waveguide is modulated periodically based on the superposition theory of aperture fields. By simply adjusting the modulation factors, modulation periods, and initial phase differences of the modulated surface impedance, the amplitude, radiation angle, and polarization of each beam can be further controlled independently as well. The results have been validated by both numerical simulations and experimental measurements, which show good agreement with the theoretical predictions.

Coherent control of optical solitons interaction via external potential in electromagnetically induced transparency system

A scheme is proposed to realize coherent control of optical solitons propagation and interaction in a three level Λ type electromagnetically induced transparency (EIT) system with external potential. For single soliton propagation, we realize the transmission and trapping of optical soliton via external potential. For double solitons interaction, we realize the coherent control of attractive and repulsion interaction of two optical solitons, and design a XNOR logical operation. At last, for triple solitons incident case, we study the interaction properties of the three solitons depending on the initial phase difference, based on the coherent control of interaction between three solitons via external potential, we design a beam selector. The results obtained here are useful not only for the deep understanding of optical soliton interaction, but also for applications in all optical quantum information processing, etc.

Self-Trapping Phenomenon in an Exciton-Polariton System When the Lower Polariton Branch is Pumped by Two Laser Pulses with Close Frequencies

The dynamics of exciton-polariton states in a semiconductor microcavity is studied under pumping of the state corresponding to the lower polariton branch, taking into account single-mode and intermode elastic polariton-polariton interactions. In this case, pumping is carried out by two laser pulses with close frequencies. It is shown that at the initial phase difference equal to theta0=π/2, the regime of quantum self-trapping of exciton-polaritons is observed. Periodic and aperiodic modes of evolution of a system of quasiparticles are obtained. Keywords: exciton-polariton states, quantum self-trapping, periodic and apeiodic regimes.

Явление самозахвата в системе экситон-поляритонов при накачке нижней поляритонной ветви двумя лазерными импульсами с близкими частотами

The dynamics of exciton-polariton states in a semiconductor microcavity is studied under pumping of the state corresponding to the lower polariton branch, taking into account single-mode and intermode elastic polariton-polariton interactions. In this case, pumping is carried out by two laser pulses with close frequencies. It is shown that at the initial phase difference equal to θ_0=π⁄2, the regime of quantum self-trapping of exciton-polaritons is observed. Periodic and aperiodic modes of evolution of a system of quasiparticles are obtained.

Quantum oscillations between weakly coupled Bose–Einstein condensates: Evolution in a non-degenerate double well

In this paper, we discuss coherent atomic oscillations between two weakly coupled Bose–Einstein condensates that are energetically different. The weak link is notionally provided by a laser barrier in a (possibly asymmetric) multi-well trap or by Raman coupling between condensates in different hyperfine levels. The resultant boson Josephson junction dynamics is described by a double-well nonlinear Gross–Pitaevskii equation. On the basis of a new set of Jacobian elliptic function solutions, we describe the period of the oscillations as well as associated quantities and predict novel observable consequences of the interplay of the energy difference and initial phase difference between the two condensate populations.

Effect of initial phase on the Rayleigh–Taylor instability of a finite-thickness fluid shell

Rayleigh–Taylor instability (RTI) of finite-thickness shell plays an important role in deep understanding the characteristics of shell deformation and material mixing. The RTI of a finite-thickness fluid layer is studied analytically considering an arbitrary perturbation phase difference on the two interfaces of the shell. The third-order weakly nonlinear (WN) solutions for RTI are derived. It is found the main feature (bubble-spike structure) of the interface is not affected by phase difference. However, the positions of bubble and spike are sensitive to the initial phase difference, especially for a thin shell (kd < 1), which will be detrimental to the integrity of the shell. Furthermore, the larger phase difference results in much more serious RTI growth, significant shell deformation can be obtained in the WN stage for perturbations with large phase difference. Therefore, it should be considered in applications where the interface coupling and perturbation phase effects are important, such as inertial confinement fusion.

Wavelet-based multiresolution analysis of cavitation-induced loading instabilities under phase effect in a waterjet pump

As observed experimentally and numerically, the blade cavitation in a waterjet pump presents multi-temporal-spatial scales under the inlet guide vanes (IGVs) wake perturbations. Meanwhile, the phase effects on blade cavitation are specifically identified and confirmed to contribute to loadings and force spectrum instabilities. In light of this, the state-of-the-art multiresolution-proper orthogonal decomposition (MRPOD) and dynamic mode decomposition (MRDMD) are employed to separate the cavitating flow scales regarding to tonal- and broadband-spectrum (TS and BS respectively) to perform a space-time-frequency analysis. The results show that the surface cavitation on the adjacent blades globally evolves in a distinct way due to the phase difference between IGVs and rotor blades. As resolved by MRPOD, the TS oscillations are mainly arising around where cavitation dynamically develops, which is majorly attributable to the rotor-stator interference (RSI). The BS oscillations are in general emerging closing to hub regimes wherein usually deviate from the design operating point and perform more flow instabilities. Comparatively, the MRDMD identifies a frequency-jittering spectrum that slightly oscillates around the IGVs passing frequency, which is physically triggered by the cavitation-enhanced irregular loading impingements. The MRDMD relevant TS modes perform similar tendencies as MRPOD but alternatively oscillate with time around the leading edge due to the initial phase difference. The studies on pump cavitation dynamics accounting phase effects via multiresolution analysis (MRA) aim to gain a fundamental understanding of the cavitation-induced vibration to facilitate its control.

Dynamic behaviors of blade cavitation in a water jet pump with inlet guide vanes: Effects of inflow non-uniformity and unsteadiness

The waterjet pump cavities would unavoidably interact with inlet guide vanes (IGVs) wakes and thus to bring about dynamic loading impingements. This work jointly conducts experiments, numerical simulations, and time-frequency analysis to shed light on the dynamic behaviors of blade cavitation under the IGVs perturbations. As observed, the blade cavitation subjected to a lower incidence angle presents a highly dynamic pattern, which non-uniformly develops and globally performs a typical periodic cycle of generation, developing, and collapsing as each blade passes through the IGVs wake in sequence. At the same instant, the cavitation patterns on the adjacent blade would perform a distinctive tendency due to the initial phase difference. It is illuminated that the spatial-temporal incidence angle determined by inflow non-uniformity and unsteadiness majorly contribute to the uneven and intermittent development of blade cavitation. The cavitation evolutions and excited pressure and thrust deterministically oscillate with the IGVs passing frequency. The resultant cavity variations would additionally introduce broadband low-frequency thrust fluctuations that are interpreted as the non-uniform loading impacts on the blade surface. This work comparatively studies the dynamic behaviors of blade cavitation that are commonly encountered for a pump with inflow distortions, which aims to provide a fundamental understanding for cavitation dynamics in pumps.

Effects of phase difference between instability modes on boundary-layer transition

Phase effect on the modal interaction of flow instabilities is investigated for laminar-to-turbulent transition in a flat-plate boundary-layer flow. Primary and secondary three-dimensional (3-D) oblique waves at various initial phase differences between these two instability modes. Three numerical methods are used for a systematic approach for the entire transition process, i.e. before the onset of transition well into fully turbulent flow. Floquet analysis predicts the subharmonic resonance where a subharmonic mode locally resonates for a given basic flow composed of the steady laminar flow and the fundamental mode. Because Floquet analysis is limited to the resonating subharmonic mode, nonlinear parabolised stability equation analysis (PSE) is conducted with various phase shifts of the subharmonic mode with respect to the given fundamental mode. The application of PSE offers insights on the modal interaction affected by the phase difference up to the weakly nonlinear stage of transition. Large-eddy simulation (LES) is conducted for a complete transition to turbulent boundary layer because PSE becomes prohibitively expensive in the late nonlinear stage of transition. The modulation of the subharmonic resonance with the initial phase difference leads to a significant delay in the transition location up to $\Delta Re_{x, tr} \simeq 4\times 10^5$ as predicted by the current LES. Effects of the initial phase difference on the spatial evolution of the modal shape of the subharmonic mode are further investigated. The mechanism of the phase evolution is discussed, based on current numerical results and relevant literature data.

Optical vortex array with deformable hybrid Ferris structures

We proposed an optical vortex array (OVA) with deformable hybrid Ferris structures (DH-OVA). The DH-OVA was generated via the coaxial coherent superposition of two grafted elliptic perfect optical vortices (OVs) with different topological charges (TCs). The proposed DH-OVA exhibited the capacity of a free transformation from a circle to an ellipse except for the modulation of the number and sign of the unit OVs on the array. The OV distribution obeys the rule of uniform distribution of the area on the upper or lower half. By adjusting the initial phase difference, the orientation factor, and the direction of the grafted axis, a more complex OV motion and the entire hybrid rotation of the DH-OVA can be easily conducted according to the desired application. For instance, for the unidirectional and bidirectional motions of the OVs, regardless of whether they possessed the same or opposite signs, the entire rotation contained the unit OV’s motion. During the OV’s motion, the number of dark cores was not conserved, whereas the total TCs of the OVs were conserved on the DH-OVA. Results contrasted with the conventional wisdom on OVAs. Furthermore, the bidirectional motion of yeast particles via the DH-OVA was executed experimentally. This work provided a flexible DH-OVA, which will result in new potential applications in particle transfer, polarity particle sorting, and micro-particle manipulation.