Influence of Controller’s Parameters on Static Bifurcation of Magnetic-Liquid Double Suspension Bearing

Magnetic-Liquid Double Suspension Bearing (MLDSB) is composed of an electromagnetic supporting and a hydrostatic supporting system. Due to greater supporting capacity and static stiffness, it is appropriate for occasions of middle speed, overloading, and frequent starting. Because of the complicated structure of the supporting system, the probability and degree of static bifurcation of MLDSB can be increased by the coupling of hydrostatic force and electromagnetism force, and then the supporting capacity and operation stability are reduced. As the key part of MLDSB, the controller makes an important impact on its supporting capacity, operation stability, and reliability. Firstly, the mathematical model of MLDSB is established in the paper. Secondly, the static bifurcation point of MLDSB is determined, and the influence of parameters of the controller on singular point characteristics is analyzed. Finally, the influence of parameters of the controller on phase trajectories and basin of attraction is analyzed. The result showed that the pitchfork bifurcation will occur as proportional feedback coefficient Kp increases, and the static bifurcation point is Kp = −60.55. When Kp < −60.55, the supporting system only has one stable node (0, 0). When Kp > −60.55, the supporting system has one unstable saddle (0, 0) and two stable non-null focuses or nodes. The shape of the basin of attraction changed greatly as Kp increases from −60.55 to 30, while the outline of the basin of attraction is basically fixed as Kp increases from 30 to 80. Differential feedback coefficient Kd has no effect on the static bifurcation of MLDSB. The rotor phase trajectory obtained from theoretical simulation and experimental tests are basically consistent, and the error is due to the leakage and damping effect of the hydrostatic system within the allowable range of the engineering. The research in the paper can provide theoretical reference for static bifurcation analysis of MLDSB.

Simulating the Negative Jet Feedback Mechanism in Common Envelope Jet Supernovae

We use the stellar evolution code MESA to study the negative jet feedback mechanism in common envelope jet supernovae (CEJSNe), in which a neutron star (NS) launches jets in the envelope of a red supergiant (RSG). We find that the feedback reduces the mass accretion rate to be χ j ≃ 0.04–0.3 times the mass accretion rate without the operation of jets. We mimic the effect of the jets on the RSG envelope by depositing the energy that the jets carry into the envelope zones outside the NS orbit. The energy deposition inflates the envelope, therefore reducing the density in the NS vicinity, which in turn reduces the mass accretion rate in a negative feedback cycle. In calculating the above values for the negative jet feedback coefficient (the further reduction in the accretion rate) χ j, we adopt the canonical ratio of jet power to actual accretion power of 0.1, and the results of numerical simulations that show the actual mass accretion rate to be a fraction of 0.1–0.5 of the Bondi–Hoyle–Lyttleton mass accretion rate.

Effective suppression of mode distortion induced by stimulated Raman scattering in high-power fiber amplifiers

Mode distortion induced by stimulated Raman scattering (SRS) has become a new obstacle for the further development of high-power fiber lasers with high beam quality. Here, an approach for effective suppression of the SRS-induced mode distortion in high-power fiber amplifiers has been demonstrated experimentally by adjusting the seed power (output power of seed source) and forward feedback coefficient of the rear port in the seed source. It is shown that the threshold power of the SRS-induced mode distortion can be increased significantly by reducing the seed power or the forward feedback coefficient. Moreover, it has also been found that the threshold power is extremely sensitive to the forward feedback power value from the rear port. The influence of the seed power on the threshold power can be attributed to the fact that the seed power plays an important role in the effective length of the gain fiber in the amplifier. The influence of the forward feedback coefficient on the threshold power can be attributed to the enhanced SRS configuration because the end surface of the rear port together with the fiber in the amplifier constitutes a half-opening cavity. This suppression approach will be very helpful to further develop the high-power fiber amplifiers with high beam quality.

Optimizing Single-Shot Coherent Power-Spectrum Scattering Imaging Adaptively by Tuning Feedback Coefficient for Practical Exposure Conditions

With only one piece of the power-spectrum pattern, the single-shot coherent power-spectrum imaging can provide a clear object image for real-time applications even if the object is hidden by opaque scattering media, in which the feedback coefficient β value for the reconstruction with least retrievals and fastest speed has to be pre-estimated through time-consuming iterative loops. Here we report a method for estimating the optimal β value from the captured raw power-spectrum images adaptively to optimize the single-shot coherent power-spectrum imaging for practical exposure conditions. The results demonstrate that, based on exposure level analysis of the captured raw power-spectrum images even of underexposure, moderate exposure, and overexposure cases, the β value could be quickly determined with a compact expression for the algorithm to achieve clear reconstruction output efficiently. The proposed method helps to push ahead of the coherent diffractive imaging devices for real-time imaging through turbid mediums in Artificial Intelligence (AI), driving assistance, and flight assistance applications.

PROCEDURE OF ASSESSING CREDIBILITY TO THE EXPERT IN TERMS OF THE PROBLEM OF AGE CATEGORIZATION OF WEB CONTENT

Currently the solution of a set of tasks is impossible without using expert procedures. At the same time, some of them require the involvement of the great number of experts, increasing the probability of human factor errors, fabrication and falsification of expert assessments. There has been suggested the method of obtaining the quantitative assessment of the degree of trust to experts, which allows to improve the quality and accuracy of the expert procedures. The developed method helps to consider both the established reputation of the expert and his reaction in the course of the expertise. The description and examples of calculations of key indicators involved in the formation of the expert's feedback coefficient (in applying one of the most common expert methods - a survey), such as: duration of filling/answering a question, time difference between answers to the related questions, availability of incorrect answers to trap questions. The adequacy of the method has been confirmed by the results of the computational experiment conducted in a group of 20 experts solving the problem of web resource age categorization. The developed method is amenable to further algorithmization and can be applied in decision support systems for various purposes.

Synchronization of Non-Linear Dynamic Systems Under the Conditions of Noise Action in the Channel

Areas of optimal amplitudes and minimal spectral unevenness of Rucklidge chaotic signals with better correlation abilities are demonstrated in the present research. A model of chaotic synchronization and information transmission system is implemented. The effect of the synchronization feedback coefficient and signal-to-noise ratio on the systems noise immunity is shown.