Degradation of effective carrier-power-to-noise densityratio based on code trackingspectral sensitivitycoefficient for GNSS radio frequencycompatibilityin C band

The frequency band between 5 010 MHz and 5 030 MHz allocated as C band has been used as a candidate in the global navigation satellite systems （GNSS） along with more and more naviga- tion services in L band. The potential benefits and technical requirements of C band for satellite navi- gation have been analyzed before. However the degradation of effective carrier-power-to-noise densi- ty ratio（ A （C/No ）eu） based on code tracking spectral sensitivity coefficient（ CT_SSC ） as a compati- bility assessment methodology for potential GNSS radio frequency compatibility in C-Band has not been discussed clearly. So the compatibility of the signals in the C band between BeiDou （BD） B1 C and GPS L1C, L1C/A, Galileo E1Os as the interoperability or classical signals in L band is analyzed. Simulation results reveal the interference degree between BD III B1C and GPS L1C/A, L1C, Galileo E1OS. The results can also reveal that the multiplexed binary offset carrier （MBOC） and binary phase shift keying （BPSK） modulation is not appropriate for C band.

Research on Decalcification Degradation Process of Cement Stone

An accelerated laboratory method（saturated ammonium nitrate solution immersion method） was used to analyze the degradation of cement decalcification process. By studying the changes of intensity, volume, elastic modulus, quality, p H value, the Ca/Si, and mineral phase, it could be found that the first cement decalcification degradation process was the decalcification of calcium hydroxide, and then CSH gel, AFm, etc. The secondary ettringite deposition happened and the decalcification degradation depth was proportional to the square root of time. Moreover, the corresponding strength of cement would be gradually reduced, cement rock volume shrinkage occurred, p H values decreased, the surface elastic modulus decreased down to a certain level, and slightly changed and the Ca/Si was 3.1 from the beginning and lasted down to 1.3.

Advances in Medical Magnesium Alloy Surface Modification for Corrosion Resistance Improvement

Since the magnesium and magnesium alloys have good load transmission,exceptional biosafety,unique biodegradability,etc,they have significant application possibilities in the field of medical implantation.Furthermore,excellent corrosion resistance is one of the paramount prerequisites for magnesium and magnesium alloys as medical implants.However,magnesium alloys exhibit poor corrosion resistance,leading to rapid degradation in physiological environments due to high corrosion rates.This premature degradation,before completing their intended service life,compromises their structural integrity,severely limiting their clinical applications.Surface modification treatment of magnesium alloy to improve corrosion resistance has become a research hotspot of medical magnesium alloy.This study primarily focused on the research advancements in the corrosion resistance enhancement of medical magnesium alloys.The developmental trajectory and characteristics of medical magnesium alloys were outlined.Additionally,surface modification techniques such as micro-arc oxidation and ion implantation,as well as microstructure and properties of magnesium alloy surfaces after surface modification were reviewed.The formation mechanisms of various coatings were discussed,and their structures and properties were analyzed.The impact of coatings on the degradation rate of magnesium alloys was elucidated,aiming to identify key issues and potential solutions in the implementation and application of surface modification for medical magnesium alloys.Recommendations were also provided,presenting the research directions for surface modification of medical magnesium alloys.