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This study has developed an improved real-time kinematic (RTK) algorithm by adding the double-differenced (DD) observations between L1 and L2 frequencies. It also introduces new biases between the frequencies to recover the integer of the DD ambiguities. The validations show that the new bias between the frequencies is stable and can be estimated as a constant in the same reference period. Compared with the standard RTK method, the new RTK model increased the observation number. The availability and reliability is thus greatly improved, especially in environmental conditions unsuitable for observation, and in which the observed satellite number is small. [ABSTRACT FROM AUTHOR]

This study proposes an approach to facilitate real-time fast point positioning of the BeiDou Navigation Satellite System (BDS) based on regional augmentation information. We term this as the precise positioning based on augmentation information (BPP) approach. The coordinates of the reference stations were highly constrained to extract the augmentation information, which contained not only the satellite orbit clock error correlated with the satellite running state, but also included the atmosphere error and unmodeled error, which are correlated with the spatial and temporal states. Based on these mixed augmentation corrections, a precise point positioning (PPP) model could be used for the coordinates estimation of the user stations, and the float ambiguity could be easily fixed for the single-difference between satellites. Thus, this technique provided a quick and high-precision positioning service. Three different datasets with small, medium, and large baselines (0.6 km, 30 km and 136 km) were used to validate the feasibility and effectiveness of the proposed BPP method. The validations showed that using the BPP model, 1–2 cm positioning service can be provided in a 100 km wide area after just 2 s of initialization. Thus, as the proposed approach not only capitalized on both PPP and RTK but also provided consistent application, it can be used for area augmentation positioning. [ABSTRACT FROM AUTHOR]

A new type heat treatment process comprising super-high temperature pretreatment and austempering treatment (S&A treatment) was used to process carbidic austempered ductile iron (CADI). The results showed that the netlike eutectic carbides were significantly reduced after super-high temperature pretreatment. Due to the increase in supercooling during super-high temperature pretreatment cooling, the inter-laminar spacing of pearlite was reduced from 300 nm to 100 nm. When the ductile iron with superfine pearlite was reheated, a large amount of Fe 3 C particles were retained inside the prior austenite grains. After austempering, a superfine ausferrite matrix with a length of 1–3 μm and a thickness of 50 nm was obtained. The main reason for this refinement is the increased number of nucleation-sites for the austenite grains and the retardation-effect of Cr on their growth. TEM results indicated that a possible orientation relationship between bainitic ferrite with a cubic lattice and precipitated Fe 3 C particles with a orthorhombic lattice is (01 1 ¯) α-Fe //(210) Fe3C , and their boundaries are coherent boundaries. The CADI obtained by S&A treatment has an impact toughness 120% higher than the traditional CADI without sacrificing hardness, and has excellent wear resistance under high wear load. Unlabelled Image • The impact toughness of CADI is significantly improved by super-high temperature pretreatment and austempering treatment. • The CADI obtained by S&A treatment has excellent wear resistance under high wear load. • With the rise of reheating temperature, the pearlite decreases gradually, and the precipitated particles are retained. • A superfine ausferrite matrix with a length of 1-3 μm and a thickness of 50 ± 10 nm is obtained. • The boundaries between bainitic ferrite and precipitated particles are coherent boundaries. [ABSTRACT FROM AUTHOR]