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Owing to the existence of non-line-of-sight (NLOS) signals in global navigation satellite system (GNSS) challenged environment, the real-time kinematic (RTK) position precision is seriously damaged. In order to improve the position accuracy, the authors propose a robust positioning method which tackles this problem by detecting the NLOS through a decision tree and estimating the double-differenced multipath errors in real time. The NLOS detection performance of the proposed method is 95.64%. The field experiment shows that the ambiguity fixing rate has improved by 43% in the instantaneous mode, and the 3D position accuracy is about 81.77% higher better than that of normal RTK method which is implemented by using RTKLIB software. [ABSTRACT FROM AUTHOR]

In time synchronisation systems, the code phase of the spread spectrum signal is an important characteristic that can provide users with high‐precision and unambiguous observation results. However, digital code phase discriminators have limited sampling frequencies that distort the signal correlation peak and generates a zero‐bias code‐phase estimate. In this Letter, the authors evaluate and analyse the zero‐phase deviations of digital code phases. An optimal correlation interval design method, based on a code phase discriminator that can effectively suppress the zero‐crossing deviation, is also proposed. The simulation results show that the proposed algorithm can reduce the deviation of 96.5% and effectively improve the measurement accuracy of the code phase. [ABSTRACT FROM AUTHOR]

ZK60–RE alloys were made by melting ZK60 alloy and cerium-rich rare earth (RE) metal in an electric furnace. The content of RE is 0, 0.5, 1, 1.5, 2, 3 wt.% RE, respectively. The influence of RE on microstructure and tensile mechanical properties of ZK60 magnesium alloys was studied. The results showed that cerium-rich misch metal (MM) had an obvious effect of reducing the grain size of the as-extruded ZK60 alloys. The ultimate and yield strengths of extruded ZK60–RE alloys were improved by the addition of RE. The ultimate and yield strength increased with increasing RE content in the range investigated. It is also found that the ultimate strength and yield strength decrease with increasing extrusion temperature. The improvement of tensile properties of ZK60–RE alloys was due to the extrusion texture and the fine microstructure induced by RE additions. [Copyright &y& Elsevier]

Adaptive antenna arrays are widely used to protect Global Navigation Satellite System (GNSS) receivers from interference. However, conventional blind anti-jamming array processing methods can cause satellite signal attenuation, which reduces signal tracking precision and measurement accuracy. To alleviate this problem, this paper proposes the noncoherent channel combining method for GNSS signal tracking with an adaptive antenna array. A two-stage processing architecture is applied in the proposed method, where the first stage implements interference suppression, and the second stage achieves noncoherent channel combining. The proposed method has the advantage of blind characteristics that can be implemented without any other auxiliary information. It also reveals a unified processing architecture for anti-jamming array processing methods. Thus, a detailed comparison and analysis of the proposed method with several typical blind anti-jamming methods is performed. Simulation results demonstrate the effectiveness of the proposed method and its superiority over existing methods in terms of tracking performance. [ABSTRACT FROM AUTHOR]

Spoofing interference poses a significant challenge to the Global Navigation Satellite System (GNSS). To effectively combat intermediate spoofing signals, this paper presents an enhanced spoofing detection method based on abnormal energy of the quadrature (Q) channel correlators. The detailed principle of this detection method is introduced based on the received signal model under spoofing attack. The normalization parameter used in this method was the estimation of the noise floor. The performance of the proposed Q energy detector is validated through simulations, the Texas Spoofing Test Battery dataset and field tests. The results demonstrate that the proposed detector significantly enhances detection performance compared to signal quality monitoring methods, particularly in overpowered scenarios and dynamic scenarios. By increasing the detection probability in the presence of spoofing signals and decreasing the false alarm probability in the absence of spoofing signals, the proposed detector can better meet the requirements of practical applications. [ABSTRACT FROM AUTHOR]

Effects of Zn and RE additions on the solidification behavior of Mg–9Al alloy were studied. Zinc (Zn) and rare earths (RE) elements were added to a maximum quantity of 1.2 and 1.6wt.%, respectively. Cooling curves were obtained under commercial production conditions. Hot tearing susceptibility was investigated using crack-ring molds. Microstructure was analyzed by metallographic examination and electron probe micro-analysis. Zinc additions decreased the end-solidifying temperature, promoted the precipitation of Mg17Al12 in grain boundaries and increased the hot-tearing susceptibility coefficient (HSC). Al4RE phase precipitation slowed down the temperature decrease at the initial stage of solidification. RE additions had little effect on HSC of Mg–9Al with low or no Zn content, while when Zn content was exceeded 0.8 wt.%, RE additions decreased HSC of Mg–9Al alloys distinctly. [Copyright &y& Elsevier]

In situ composites of Zn–27Al–6.3Mg–3.7Si alloy have been fabricated by centrifugal casting using the heated permanent mold. This kind of composites is consisted of three layers: inner layer segregates lots of blocky primary Mg2Si and a little blocky primary Si, middle layer does not contain primary Mg2Si and primary Si, outer layer contains a little primary Mg2Si and primary Si. The position, quantity and distribution of primary Mg2Si and primary Si are determined by solidification velocity under the effect of centrifugal force and their floating velocity inward. The inner and outer layer contained primary Mg2Si and primary Si exhibit much higher hardness and wear resistance than the middle layer. [Copyright &y& Elsevier]