As a major indicator in marine life research and geochemistry, the in-situ monitoring of dissolved oxygen has become increasingly important in the assessment of marine ecosystem. It has been proved that fluorescence quenching may result in shorter fluorescence lifetime. Based on it, this paper proposes an in-situ dissolved oxygen monitoring system of high precision and low power consumption applicable to long-term monitoring of complex marine environment. Using phase detecting method, an AC analog amplification channel on Precision photoelectric detection, and used digital phase detection method and three order integral average method to detect the phase offset. The ultralow-power microcontroller was used to control system. The experiments results show that the system has high stability, high precision(0.02mg/L), quick response time(≤40s), low power consumption(peak current ≤10mA), strong anti interference ability.

In this article, research on hydration mechanism of 50% Portland cement–50% fly ash(FA) systems has been carried out with TAM AIR Isothermal Calorimete (TA) and 29Si nuclear magnetic resonance(NMR) spectroscopy. The research was including hydration heat liberation behavior and nanostructure of C-S-H gel in hydrated cement systems. The addition of fly ash could observably reduce the total hydration heat and the mean chain length (MCL) of C-S-H gel was found to be and respectively for 7-day-old and 28-day-old.

In this article, through the measurements on neat cement paste strength and heat of hydration at the early stage and using several analytical methods including XRD and SEM, effect of large amount of fly ash on the hydration process and cement's hardening mechanism of portland cement was studied when water to binder ratio is 0.35 and fly ash content is between 20% and 50%.The research outcomes find that the pozzolanic activities of fly ash are not good at the early stage.The more the content of fly ash was, the bigger the effect on strength would be.

Aggregate is the main contribution to shield the radiation in the radiation shielding concrete. Based on the fact that the heavy element barium has excellent γ-rays shielding function, sludge with the high content of barium has been made into aggregate with low dissolution rate and high strength by calcination at high temperature; the existing forms of element barium after it was melted inside the aggregate have been analyzed by using XRD and SEM techniques; the linear attenuation coefficients have been measured among the functional aggregates, basalt and barite. The results have showed that the radiation shielding capacity of functional aggregate has been improved substantially compared with the basalt, however, it is equal to barite.