Small Phase Differences Research Articles

Adaptive neuro-fuzzy inference control for active stabilizer bars based on multiple data sources.

In this research, we propose using active stabilizer bars to prevent rollover when steering. An intelligent control solution, the adaptive neuro-fuzzy inference system (ANFIS), is established in this article to control the performance of the active anti-roll systems. In contrast to the previously published studies, the intelligent algorithm designed in this research has many outstanding advantages, such as generating a large impact force, a fast response time, a small phase difference, and high convergence ability. The data used to train ANFIS are carefully selected and combined from the previous studies. The initial simulation observes that the roll angle decreases significantly from 8.15° to 6.87° when the ANFIS algorithm is applied to regulate the anti-roll bars. In contrast, the roll angles for the proportional-integral-derivative (PID) and passive (Mechanical) situations are respectively recorded at 7.08° and 7.80°. The reduction of the vertical force at wheels is also solved when the ANFIS algorithm is applied instead of other methods. This value increases sharply from 671.06 N (without bars) to 3030.40 N (ANFIS control), while it only reaches 2544.27 N (PID control) and 1428.83 N (mechanical bars), according to the research findings. If the vehicle does not have the anti-roll bars, a rollover occurs in the second case when the vehicle steers at v3 (80 km/h) and v4 (90 km/h). In contrast, the interaction between the wheels and the road is well maintained when the automobile is equipped with active bars controlled by the ANFIS solution. This is demonstrated by the minimum vertical force value in the rear wheel, which reaches 2687.33 and 2447.33 N, respectively, for the abovementioned conditions. In general, the vehicle's rolling stability can be well guaranteed in all moving situations when using the ANFIS controller for the anti-roll system in the vehicle.

Numerical investigation on the energy extraction characteristics of parallel multi foils arranged in columns

Abstract The oscillating foil is a focus device in the clean energy utilization field. The presence of an oscillating foil structure within the flow field significantly impacts the energy extraction capabilities of the system. In this paper, three types of parallel multi-foil structures arranged in columns are proposed. The energy extraction characteristics of diverse multi-foil structures under various oscillation conditions are analyzed numerically. The flow field structure and the impact of parallel multi foils on the aerodynamic characteristics are investigated. Results demonstrate that the multi-foil structure with a phase difference of 180° achieves the highest level of energy extraction performance, and the maximal mean power coefficient achieves 0.894, which is 11.03% higher than that of the structure with a smaller phase difference. The size of the trailing edge vortex under the structure with a phase difference of 180° is significantly larger, leading to an obvious fluctuation in the aerodynamic lift.

Research on Leakage Current Waveform Spectrum Characteristics of Artificial Pollution Composite Insulator

In order to know about the change features of leakage current during the pollution flashover process of composite insulators, the study of the pollution flashover test on composite insulator under the pollutional condition is presented in the artificial fog cabinet. The characteristics of leakage current waveforms in time-domain and frequency-domain are measured and analyzed during the test. The analysis results show that there is a strong correlation among the fundamental harmonic, the third harmonic and fifth harmonic. The characteristics of leakage current spectrum are represented by the maximum value of leakage current (Im), total harmonic distortion (THD), and phase difference of fundamental leakage current (θ). During a near-flash event, the leakage current exhibits high amplitude, low harmonic content, and small phase difference between the fundamental leakage current and voltage. The research findings provide a basis for establishing a pollution flash warning system based on leakage current characteristic quantities.

Anomalous Resistivity and Electron Heating by Lower Hybrid Drift Waves during Magnetic Reconnection with a Guide Field.

The lower hybrid drift wave (LHDW) has been a candidate for anomalous resistivity and electron heating inside the electron diffusion region of magnetic reconnection. In a laboratory reconnection layer with a finite guide field, quasielectrostatic LHDW (ES-LHDW) propagating along the direction nearly perpendicular to the local magnetic field is excited in the electron diffusion region. ES-LHDW generates large density fluctuations (δn_{e}, about 25% of the mean density) that are correlated with fluctuations in the out-of-plane electric field (δE_{Y}, about twice larger than the mean reconnection electric field). With a small phase difference (∼30°) between two fluctuating quantities, the anomalous resistivity associated with the observed ES-LHDW is twice larger than the classical resistivity and accounts for 20% of the mean reconnection electric field. After we verify the linear relationship between δn_{e} and δE_{Y}, anomalous electron heating by LHDW is estimated by a quasilinear analysis. The estimated electron heating is about 2.6±0.3 MW/m^{3}, which exceeds the classical Ohmic heating of about 2.0±0.2 MW/m^{3}. This LHDW-driven heating is consistent with the observed trend of higher electron temperatures when the wave amplitude is larger. Presented results provide the first direct estimate of anomalous resistivity and electron heating power by LHDW, which demonstrates the importance of wave-particle interactions in magnetic reconnection.

White dwarf–white dwarf collisions in AGN discs via close encounters

ABSTRACT White dwarfs (WDs) in active galactic nucleus (AGN) discs might migrate to the inner radii of the discs and form restricted three-body systems with two WDs moving around the central supermassive black hole (SMBH) in close orbits. These systems could be dynamically unstable, which can lead to very close encounters or direct collisions. In this work, we use N-body simulations to study the evolution of such systems with different initial orbital separation p, relative orbital inclination Δi, and SMBH mass M. It is found that close encounters of WDs occur mainly at $1.1R_{\rm H} \lesssim p \lesssim 2\sqrt{3}R_{\rm H}$, where RH is the mutual Hill radius. For p < 1.1RH, the majority of WDs move in horseshoe or tadpole orbits, and only few of them with small initial orbital phase difference undergo close encounters. For p = 3.0RH, WD–WD collisions occur in most of the samples within a time 105P1, and considerable collisions occur within a time t < 62P1 for small orbital radii, where P1 is the orbital period. The peak of the closest separation distribution increases and the WD–WD collision fraction decreases with an increase in relative inclination. The closest separation distribution is similar in cases with different SMBH mass, but the WD–WD collision fraction decreases as the mass of SMBHs increases. According to our estimation, the event rate of cosmic WD–WD collisions in AGN discs is about 300 Gpc−3 yr−1, roughly 1 per cent of that of observed Type Ia supernovae. The corresponding electromagnetic emission signals can be observed through large surveys of AGNs.

Wideband Filtering Rat-Race Coupler with Shared Triple-Mode Resonator

In this paper, a filtering rat-race coupler (FRC) is presented, which features the merits of a wideband filtering response, good impedance matching at both input and output ports, good isolation, high-frequency selectivity, small in-band phase difference error, a wide stopband, and small size. It was composed of two leading triple-mode resonators, one core section, and two λ/2 open-circuited transmission lines (TLs). The core section consisted of three λ/4 TLs and one λ/4 short-circuited parallel coupled line (CL). The leading triple-mode resonator consisted of one λ/4 short-circuited stub and two λ/4 TLs. By loading the triple-mode resonator as the shared component and combining it with the core section, a wideband filtering response with four transmission poles could be achieved. In addition, two transmission zeros were generated by loading the λ/2 open-circuited TLs to the output ports of the FRC. The working principles of the proposed FRC are analyzed, and equations are derived with parametric analysis. For demonstration, a prototype operating at the center frequency of 1.4 GHz was designed, fabricated, and measured. Measurement results show that a fractional bandwidth of more than 60% was achieved under the criteria of 10 dB return loss and 20 dB isolation. In this bandwidth, the amplitude imbalances and phase difference errors were less than 1 dB and 10°, respectively. Additionally, it also exhibited high selectivity and a wide stopband.

Numerical Investigation on Torsional Mode Self-Excited Vibration of Guide Vane in a Reversible Pump-Turbine during Pump Mode’s Starting Up

In reversible pump-turbines, guide vane vibrations are considered to have potentially severe consequences of noise and structural damage. Unstable torsional mode self-excited vibrations of guide vanes have been reported at small guide vane openings during transient operations involving pump flow, such as pump starting and closing processes. In this study, coupling simulations were carried out under different operating conditions based on the unsteady computational fluid dynamics (CFD) method with a single-degree-of-freedom (1DOF) oscillator. The results show that the operating conditions, including the initial opening angle and the pressure difference between the runner side and the stay vane side, significantly affect the instability of guide vane torsional mode self-excited vibration. Energy-based analysis indicates that the positive cumulative work done by total hydraulic torque is responsible for unstable torsional mode self-excited vibration. Furthermore, the relatively small phase difference between total hydraulic torque and guide vane angular velocity, and the positive feedback between vibration amplitude and energy accumulation, are considered to be the root causes that eventually induce unstable self-excited vibrations under the operating conditions of small opening angles and high pressure differences.

Higher-order gap resonance and heave response of two side-by-side barges under Stokes and cnoidal waves

Coupled piston-mode fluid response and the heave motion of two identical barges in side-by-side configuration is studied under finite-depth and shallow-water waves using a two-dimensional fully nonlinear numerical wave tank. To understand possible critical responses of the gap flow and the floating barge, regular-wave conditions which are able to excite up to 5th-order nonlinear gap resonance and also the resonant heave motion of the barge are considered. In shallow-water waves, high-frequency oscillations, featured by secondary peaks in the time histories, are observed for both wave elevation in the gap and the heave motion of the barge. The shallow-water wave-induced 4th- or 5th-order gap resonance can be equally crucial as the 1st- and 2nd-order resonances due to finite-depth waves. At higher-order gap resonance, the higher-harmonic heave motion of the barge is negligibly small, in contrast to the gap-flow response. Compared with fixed barges, the free-heave motion of an upstream barge tends to increase the wave elevation in the gap in most of the resonant conditions, except at 1st-order gap resonance where the gap response is greatly reduced. When the resonant heave motion of a floating barge, either located upstream or downstream, is excited, significant barge motion is observed. However, the relative motion between the gap flow and the floating barge is seen to be very small, ascribed by small phase difference between the two. The present study suggests that the effects of heave motion and water-depth should be carefully considered in the design of side-by-side marine operations, and hiding the small bunkering ships behind the large receiving ships is regarded as a preferred arrangement during the bunkering operations in offshore and coastal environments.

Multi‐Ion Oscillitons—Origin of Coherent Magnetospheric EMIC Waves

AbstractThe recent spacecraft observations by MMS and Van Allen Probes associated with electromagnetic ion cyclotron (EMIC) waves in the Earth magnetosphere emphasize the important role of multi‐ion plasma composition for generation and characteristics of these emissions. We show that main properties of the coherent EMIC waves can be explained with the concept of “multi‐ion oscillitons” (Sauer et al., 2001, https://doi.org/10.1029/2001GL013047). In a plasma with two types of ions of different masses (e.g., protons and oxygen ions), oscillitons arise from the exchange of momentum and energy between the two ion components, with the electromagnetic field acting as a mediator. At frequencies near cross‐over frequencies of different wave modes in the multi‐ion plasma the nonlinear resonance which strongly amplifies the seed unstable mode can be excited. A small phase difference in oscillations of different ion species leads to a nonlinear wave beating and generation of wave packets. The “resonance” frequency is characterized by a local maximum of the phase velocity and the coincidence of phase and group velocity. It is suggested that the oscillitons are triggered by the instability due to the proton temperature anisotropy and may survive outside the source region for long distances. The generation of coherent waves by oscillitons is of a general nature and may contribute to understand the manifold of phenomena in other space plasma environments in which the dynamics of minor ion admixtures cannot be neglected. The concept of oscillitons can also be applied to the momentum exchange between particle groups of the same mass, but different temperature.

Millimeter-Wave Multi-Band Reconfigurable Differential Power Divider for 5G Communication

A differential four-way power divider for 24 to 30 GHz and a frequency reconfigurable differential four-way power divider for 24 to 30 GHz and 37 to 43.5 GHz are presented. The differential structure provides sound virtual grounds in a multiple-channel chip. Both circuits have a four-way Wilkinson power divider (WPD) configuration based on lumped elements that provide small chip sizes. The first one has a small core chip area of 0.09 mm², a small insertion loss of 0.93 to 1.94 dB, and the port-to-port isolation of 19.1 to 25.6 dB from 24 to 30 GHz. It has a small amplitude and phase differences at four outputs. The second one allows frequency-reconfigurable operation by switching inductances and capacitances to cover widely separated frequency bands (5G NR n257-n261 bands). In addition, switched capacitors (SCs) are inserted to resonate out the parasitic series inductances in isolation resistors at both bands of 24-30 GHz and 37-43.5 GHz. It has a core chip area of 0.168 mm², insertion losses of 1.65-1.89 dB at 24 to 30 GHz and 2.04-2.70 dB at 37 to 43.5 GHz, respectively. The port-to-port isolations are 23.4-37.6 dB at 24 to 30 GHz and 22.6-28.4 dB at 37 to 43.5 GHz.

Unequal Power Divider Based on Inverted Microstrip Gap Waveguide and Its Application for Low Sidelobe Slot Array Antenna at 39 GHz

This article presents a novel unequal power divider based on an inverted microstrip gap waveguide. This new geometry can achieve a large power ratio of the two output ports and a small phase difference less than 5°. Based on this novel geometry, a few distinctive unequal power dividers with different output power ratios were proposed for designing a low sidelobe array antenna at 39 GHz. To verify the design, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$16\times 16$ </tex-math></inline-formula> antenna array was designed and measured. The measurement results indicate that the entire array antenna achieves a −10 dB impedance bandwidth of 18.5% (in the range of 35.9–43.2 GHz), a gain greater than 29 dBi from 37.5 to 41.8 GHz, and an antenna efficiency greater than 50% over the entire operating frequency band. Based on the application of the newly invented distribution network, the proposed array antenna is below −23 dB on both the E- and H-planes at 37–42 GHz. Furthermore, the radiation pattern of the entire array complies with the European Telecommunications Standards Institute (ETSI)-Class II standard for all azimuth angles.

Research on Leakage Current Waveform Spectrum Characteristics of Artificial Pollution Porcelain Insulator

The surface discharge development processes of polluted porcelain insulators for power transmission lines are tightly related with the development of leakage current (LC), the characteristics of LC, the insulating condition, and discharge intensity of the insulator surface have an important significance for revealing the contamination discharge state of insulators. In order to analyze the LC characteristics of porcelain insulators in the process of pollution flashover, artificial pollution flashover tests on porcelain insulators were conducted in the artificial fog cabinet, and the characteristics of LC waveforms in time-domain and frequency-domain were simultaneously measured and analyzed during the tests. The results indicated that the amplitude of LC, fundamental harmonic, the third harmonic, and fifth harmonic had a strong correlation, the maximum of LC(Im), the rate of total harmonics (THD), and the phase difference of fundamental harmonic (θ) were used for the representation of the characteristics of the LC waveform. The LC has the characteristics of high amplitude, low proportion harmonic, and small phase difference between the fundamental harmonic and voltage before the flashover occurrence. The test results provide effective reference for porcelain insulators in pollution flashover forecasting.

Design and analysis of low-insertion-loss G-band CMOS four-way Wilkinson power dividers and dual balun

We present the design and analysis of G-band CMOS Wilkinson power dividers and dual balun for G-band communication and imaging systems. Miniature spiral and U-shaped four-way Wilkinson power dividers, which are based on three two-way Wilkinson power dividers, are designed and implemented. Miniature spiral dual balun, which is equivalent to an upper balun and a lower balun in parallel, is also designed and implemented for comparison. These devices are planar and symmetrical, and their main structure is implemented by the 2.34-µm-thick topmost metal to minimize the resistive loss. This leads to low insertion loss, and small amplitude imbalance (AI) magnitude and phase difference (PD) deviation. For instance, the spiral four-way Wilkinson power divider occupies 0.033 mm2 chip area and achieves S11 of − 11.4 dB, S21 of − 6.271 dB, S31 of − 6.445 dB, S41 of − 6.676 dB, and S51 of − 6.111 dB at 180 GHz, one of the smallest chip areas and lowest insertion losses for four-way power dividers with similar operation frequency. The corresponding AI magnitude and PD deviation are 0.565 dB and 3.2°, respectively. Moreover, the spiral dual balun occupies 0.026 mm2 chip area and achieves S11 of − 10.6 dB, S21 of − 7.549 dB, S31 of − 7.1 dB, S41 of − 7.598 dB, and S51 of − 7.352 dB at 180 GHz. The corresponding AI magnitude and PD deviation are 0.498 dB and 5.7°, respectively. The prominent results of the spiral and U-shaped four-way Wilkinson power dividers, and the spiral dual balun indicate that they are suitable for power division/combination in G-band systems.

A Variable Power Divider Employing Magic-T and Variable Phase Shifter

In this letter, a novel variable power divider, which provides wide-range variable power division, is proposed. The proposed power divider consists of a magic-T, variable phase shifter, and 90° delay line. The operating principle of the proposed circuit is theoretically discussed, and a 5-GHz band prototype using a planar magic-T is designed and experimentally evaluated. The measured power division range is more than 14 dB with a small phase difference variation of less than 15°. The concept and feasibility of the proposed variable power divider are experimentally confirmed.

A time-dependent dynamic model for ball passage vibration analysis of recirculation ball screw mechanism

Ball passage vibration arising during recirculation of rolling elements is a limitation of high-precision performance associated with ball screw. A relatively deep understanding of this phenomenon when rolling balls leave load area and enter circulation channel has been achieved by now. However, few mechanical models are established for calculation of rolling ball contact deformation and force inside nut while moving by taking into account transient phase at import and export of circulation channel. In this work, we present a general time-dependent dynamic model for description of ball motion and axial periodic micro fluctuation within ball screw subjected to external load. The numerical simulation is employed to deal with equation of motion including segmented restoring force function. Effects of applied load, preload and screw rotational speed on dynamic response are discussed theoretically. Reduced vibration amplitude may be realized by small ball diameter and phase difference between ball groupings. Proposed model is experimentally illustrated.

Effect of double-excitation ultrasonic elliptical vibration turning trajectory on surface morphology

To explore the formation law and influence factors of three-dimensional geometry in axial turning surface, the turning experiment of 7075 aluminum alloy was carried out by using double excitation three-dimensional ultrasonic elliptical vibration method. Based on the theory of turning kinematics, the tool tip trajectory model of three-dimensional ultrasonic elliptical vibration turning (3D-UEVT) was established, and the related mechanism in surface residual height, surface topography formation characteristics, and turning transmission was given. Through single factor simulation and turning test, the influence of spindle speed, feed speed, amplitude, and phase difference on the surface microstructure and roughness of workpiece was analyzed contrastively. The results show that, compared with the traditional turning, the double excitation ellipse assisted turning can affect the surface topography and quality of the workpiece by causing the dynamic change of the cutting angle of the tool tip and the residual height of the material. Combined with the analysis of simulation and experimental results, it is found that the ideal microstructure and roughness can be obtained with low speed, slow feed, small amplitude, and small phase difference. Meanwhile, the tool workpiece separation characteristics, surface topography, roughness, and surface defect level can be effectively improved under the three-dimensional ultrasonic elliptical assisted vibration.

History of Development of the Methods and Interference Devices for Measuring a Small Optical Phase Difference (Review)

Interferometry methods, which are applied for measuring quite small phase differences in fundamental and applied problems, are considered. It is shown that first improvements of the interferometric methods for measuring small phase differences to detect various physical phenomena in the second half of the 19th century and in the early 20th century were made by H. Fizeau, A.A. Michelson, E.W. Morley, Lord Rayleigh, D.C. Miller, and G. Sagnac. It is also shown that the most sensitive method of modulation interferometry was developed in 1949–1952 by Soviet radiophysicists A.A. Andronov, I.L. Bershtein, and G.S. Gorelik. Note that the method of modulation interferometry could be implemented even in 1914 using a photocell with external photoelectric effect or in 1923 using a photocell with internal photoelectric effect (photodiode). However, professional opticians used conventional methods of measuring a small phase difference at that time, and radiophysics only began to develop as science. It is shown that the methods of electric and photoelectric harmonic analysis developed in the late 19th century and in the beginning of the 20th century could be successfully applied in interferometry; however, they have been almost completely forgotten by the time of their possible practical application.

История развития методов и интерференционных приборов для измерения малой разности оптических фаз (обзор)

Methods of interferometry, which are used to measure very small phase differences, are considered. in fundamental and applied problems. It is shown that the first improvements in interferometric methods for measuring small phase differences for recording various physical phenomena in the second half of the XIX - early XX centuries. carried out by I.A. Fizeau, A.A. Michelson, E. Morley, Lord Rayleigh, D.C. Miller and J.M. Sagnac. It was also shown that the most sensitive method of modulation interferometry was created in the period 1949-1952. Soviet radiophysicists A.A. Andronov, I.L. Berstein and G.S. Gorelik. It is noted that the modulation interferometry method could be implemented even in 1914 with a photocell on an external photoelectric effect, or in 1923 with a photocell on internal photoelectric effect (photodiode). However, then professional opticians used traditional methods for measuring small phase differences, and radiophysics as a science was just beginning its formation. It is shown that the methods of electrical and photoelectric harmonic analysis developed in late XIX - early XX centuries could find successful application in interferometry, but by that time, when they could find practical use, they were almost completely forgotten.

Exploration of swimming performance for a biomimetic multi-joint robotic fish with a compliant passive joint

In this paper, a novel compliant joint with two identical torsion springs is proposed for a biomimetic multi-joint robotic fish, which enables imitatation of the swimming behavior of live fish. More importantly, a dynamic model based on the Lagrangian dynamic method is developed to explore the compliant passive mechanism. In the dynamic modeling, a simplified Morrison equation is utilized to analyze the hydrodynamic forces. Further, the parameter identification technique is employed to estimate numerous hydrodynamic parameters. The extensive experimental data with different situations match well with the simulation results, which verifies the effectiveness of the obtained dynamic model. Finally, motivated by the requirement for performance optimization, we firstly take advantage of a dynamic model to investigate the effect of joint stiffness and control parameters on the swimming speed and energy efficiency of a biomimetic multi-joint robotic fish. The results reveal that phase difference plays a primary role in improving efficiency and the compliant joint presents a more significant role in performance improvement when a smaller phase difference is given. Namely, at the largest actuation frequency, the maximum improvement of energy efficiency is obtained and surprisingly approximates 89%. Additionally, the maximum improvement in maximum swimming speed is about 0.19 body lengths per second. These findings demonstrate the potential of compliance in optimizing joint design and locomotion control for better performance.

Realization of a Compact and High-Performance Power Divider Using Parallel RC Isolation Network

In this brief, the design methodology of high- performance lumped-distributed Wilkinson power divider with extremely small chip area is proposed. A parallel capacitor is included at the input port (port 1) to compensate the imaginary part of the input admittance for input matching. A parallel RC network is connected between the output ports (ports 2 and 3) to attain perfect input matching and isolation of the output ports in the odd- and the even-mode excitations. Dual spiral structure with transmission line length of about λ/10 and symmetrical layout is adopted to achieve miniature area and small amplitude imbalance (AI) and phase difference (PD). At 33 GHz, the prototyped power divider achieves S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> of -17.8 dB, S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sub> and S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">33</sub> of -22.7 dB, S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">32</sub> of -34.7 dB, S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> of -4.1 dB, and S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sub> of -4.07 dB. The corresponding AI is -0.03 dB and PD is -0.08°. The chip area is only 1.2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , one of the smallest normalized chip area ever reported for millimeter-wave (mm-wave) power dividers. The superb results of the power divider indicate that it is suitable for power division/combination in mm-wave transceivers.