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The operation of the SuperKEKB has been ongoing since 2016. The vacuum systems of the main ring (MR) which consists of a 7-GeV electron ring (HER) and a 4-GeV positron ring (LER), the damping ring (DR) for 1.1 GeV positrons in the middle of the injector linac have been working well as a whole. As of June 2022, the maximum stored beam currents of MR are 1.46 and 1.14 A for the LER and the HER, respectively, and approximately 30 mA for the DR. The pressure increase per unit beam current is steadily decreasing and the new vacuum components developed for the SuperKEKB have been working as expected. No significant electron cloud effect has been observed in the LER after installing solenoids in drift spaces in 2017 which apply magnetic fields in the beam direction. The recent pressure behavior of the LER with increased beam current is explained by considering thermal gas desorption induced by the beam as well as photon-stimulated gas desorption. Currently, the beam lifetime is primarily limited by the Touschek effect rather than the vacuum pressure, and their degrees of contribution are evaluated. The challenges associated with high beam currents, such as damage to beam-collimator heads and excess heating of beam pipes at wiggler sections have become more apparent as beam currents are increased. The status of the SuperKEKB vacuum system and the experiences during the past 6 years of operation are presented here.

The binary offset carrier (BOC) proposed for the global navigation satellite systems (GNSS) will enhance navigation performance and spectrum compatibility. However, the acquisition process is made more complex, due to the ambiguity in the autocorrelation function (ACF) of BOC. This paper proposes an unambiguous acquisition technique for the new cosine phased BOC (cosine-BOC) modulated signals, which will most likely be used in both European Galileo system and Chinese Compass system. The test criterion employed in this technique is based on a synthesized correlation function which completely removes major positive side peaks while keeping the sharp main peak using the concept of simultaneous perturbation stochastic approximation (SPSA). Theoretical analysis and simulation results indicate that the proposed technique completely removes the ambiguity threat in acquisition process with some performance degradation. This technique is also suitable for arbitrary order cosine-BOC signals.

A novel tracking method in the phased antenna array with a single-channel receiver for the moving signal source is presented in this paper. And the problems of the direction-of-arrival track and beamforming in the array system are converted to the power maximization of received signal in the free-interference conditions, which is different from the existing algorithms that maximize the signal to interference and noise ratio. The proposed tracking method reaches the global optimum rather than local by injecting the extra noise terms into the gradient estimation. The antenna beam can be steered to coincide with the direction of the moving source fast and accurately by perturbing the output of the phase shifters during motion, due to the high efficiency and easy implementation of the proposed beamforming algorithm based on the simultaneous perturbation stochastic approximation (SPSA). Computer simulations verify that the proposed tracking scheme is robust and effective.

A new type of composite concrete which can be called corundum-rubble concrete (CRC) was presented to improve the resistance of protective structure to the projectile impact. Comparative experiments were conducted between CRC and reinforced concrete, and a modified Taylor model was proposed to predict the penetration depth of CRC targets. Experimental results show that CRC is much higher than reinforced concrete in both strength and hardness and shows excellent resistance to the 0.125 m-diameter projectile impact. Theoretical analyses demonstrated that the modified Taylor model’s predicted results were in good agreement with the measured values.

Global Navigation Satellite Systems (GNSS) positioning accuracy indoor and urban canyons environments are greatly affected by multipath due to distortions in its autocorrelation function. In this paper, a cross-correlation function between the received sine phased Binary Offset Carrier (sine-BOC) modulation signal and the local signal is studied firstly, and a new multipath mitigation method based on cross-correlation function for sine-BOC signal is proposed. This method is implemented to create a cross-correlation function by designing the modulated symbols of the local signal. The theoretical analysis and simulation results indicate that the proposed method exhibits better multipath mitigation performance compared with the traditional Double Delta Correlator (DDC) techniques, especially the medium/long delay multipath signals, and it is also convenient and flexible to implement by using only one correlator, which is the case of low-cost mass-market receivers.

A novel method to de-noise microelectromechanical system (MEMS) inertial sensors by cascaded integration of singular spectrum analysis (SSA) and independent component analysis (ICA) is proposed to improve the attitude accuracy for low-cost attitude estimation. The low-frequency vibration noise and acceleration disturbance induce large errors to attitude estimation since MEMS accelerometers provide attitude measurement for sensor fusion by measuring the gravity vector. It is proposed to remove the low-frequency vibration noise by SSA and to mitigate the acceleration disturbance by ICA. SSA can effectively separate the trend and periodic vibration noise and ICA can effectively extract the acceleration disturbance with the help of turning rate measured by the yaw gyro. The proposed technique was tested on real road experiments showing significant improvement of attitude accuracy. [ABSTRACT FROM AUTHOR]

In the presence of large pointing error, an iterative worst-case performance optimisation based robust beamformer is proposed in a new perspective. Based on the relationship between the optimal weight vector and the steering vector (SV) of the Capon beamformer, the proposed approach can update the estimated desired SV through iterative computations with a small uncertainty set, and does not need any reformulation of the optimisation problem. Simulation results show that the proposed iterative approach outperforms the beamformers with large uncertainty set in the presence of large pointing error. [ABSTRACT FROM AUTHOR]

For the vehicle-mounted phased-array antenna in the mobile satellite receiver, a novel beamforming algorithm based on improved simultaneous perturbation stochastic approximation (SPSA) is developed. It estimates the gradient of the received signal power in the assured direction rather than fully isotropic by adding a fit searching direction. Besides the SPSA beamforming algorithm's merit, the proposed method can track the target satellite quickly, accurately and steadily in the single-channel receiver. Computer simulations verify that the proposed algorithm is indeed robust and effective. [ABSTRACT FROM AUTHOR]