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The BeiDou Navigation Satellite System (BDS) is a constantly-updated huge system with tightly-coupled space and ground segments and long construction period. Faced with the multiple challenges of highly complicated key technical scheme, high-intensity satellite deployment and launching tasks, and high difficulty in system stable operation, BDS has very high demands for the system's test and verification. This paper analyzes the test and verification tasks of BDS including system design and verification, space and ground segment integration, and simulation operation, and proposes the system architecture of the ground test and verification bed which equivalent to the full-system, full-scale and full-elements BDS. The bed is featured with synchronized work of the software and hardware platforms, equivalent operation of the simulation and real systems, and remote connection between the test bed and system segments, and solves the problems of multi-system simulation modeling, high-dynamic simulation as well as software and hardware synchronized simulation; realizes the whole process verification of the BDS design, deployment and operation, and also realizes the test and verification of the BDS new technical schemes such as inter-satellite links, BDS satellite autonomous integrity monitoring, and precise orbit determination. The bed for BDS is the only test and verification system in the field of satellite navigation that can realize all-states system simulation, and synchronized iterative evolution and operation with the real system, and can serve as important reference for the verification work of other space missions.

A detailed description of BDS-3 including constellation design, different types of services, signal structure, coordinate and time frame, mechanics of orbit determination and time synchronous is provided. A RNSS service performance assessment parameters list is provided. It consists of parameters about time and coordinate frame, signal quality, signal in space accuracy and service performance. Tracking data is collected from stations globally distributed, and performance of BDS-3 initial service is assessed. From results, ratio bias of signal component effective power is less than 0.25 dB, S curve bias is less than 0.3 ns, position dilution of precision (PDOP) availability of current constellation is better than 85% at global level, signal-in-space ranging error is 0.48 m(RMS), signal-in-space availability reached 99.78%, signal-in-space continuity reached 99.99%, UTC offset error is 19.1 ns. All of them fulfill the design specification and requirements of BDS open service performance standard. Compared to BDS-2 satellites, current BDS-3 constellation realized global coverage and achieved a better performance in signal-in-space error, signal-in-space availability and signal-in-space continuity.

Background: A number of studies have been conducted to explore the association of XRCC1 polymorphisms with Breast cancer (BC) risk in Asians, but the results have been inconsistent. We therefore performed the present meta-analysis to explore the relationship in detail. Materials and Methods: Reported studies were searched from 1990 to October 15, 2014 in PubMed and Wan fang Med Online. We performed a meta-analysis of 13 published case-control studies fitting our eligibility criteria. These studies involved XRCC1 Arg399Gln polymorphisms in 4984 BC cases and 5744 controls in dominant (ArgArg vs. GlnGln+ArgGln), recessive (ArgGln+ArgArg vs. GlnGln), and co-dominant (ArgArg vs. GlnGln) inheritance models. The total odds Ratio (OR) and 95% CI were calculated and analyzed by Review Manager 5.2 and STATE 12. Results: Overall, significantly increased BC risk was observed in any genetic model (dominant model: odds ration [OR] = 1.31, 95% confidence interval [CI] = [1.08, 1.58]; recessive model: OR = 0.63, 95% CI = [0.50, 0.81]; codominant model: OR = 2.52, 95% CI: [1.38, 4.60]) when all eligible studies were pooled into the meta-analysis. In further stratified analyses, no association was found between Arg399Gln polymorphism and BC risk in Chinese fewer than three hereditary models. Conclusions: Our results suggest that the XRCC1 Arg399Gln polymorphism may be associated with increased Breast cancer risk among Asians, except Chinese population.