Ultra-high sensitivity microwave-photonic sapphire fiber Fabry-Perot interferometry based on the Vernier effect.

The wavelength of microwave is longer than that of lightwave, causing the interferometric optical path difference induced by the measurand changes to be relatively smaller than that of microwave, which results in the lower sensitivity of sapphire fiber Fabry-Perot interferometer (FPI) sensor in microwave band. To improve sensitivity, a parallel FPI sensing system is constructed, in which a section of sapphire fiber connected to a single-mode transmission fiber is used as a sensing FPI, and a single-mode fiber (SMF) with a slightly different optical path from a sensing FPI is utilized as a reference FPI. By connecting two FPIs in parallel, Vernier effect is formed to improve sensitivity. The influence of relationship between the optical path difference of the reference FPI and the sensing FPI on the sensitivity amplification factor is analyzed based on the microwave interference spectrum of the parallel FPI. A section of sapphire fiber with the length of 8 cm is used as temperature sensor to construct high-temperature sensing system. The results demonstrate that the temperature sensitivity reaches about 2338.68kHz/°C, which is approximately 130 times higher than that of the sensing FPI alone. Furthermore, when the difference of optical path between the sensing FPI and the reference FPI is kept constant while the sensing FPI is unchanged, the amplification factor of the temperature sensitivity is approximately 2.64 times higher with longer length of the reference FPI compared to the situation with shorter length of the reference FPI.

Hydrochemical assessments and driving forces of groundwater quality and potential health risks of sulfate in a coalfield, northern Ordos Basin, China.

Groundwater is the primary water source in coalfields under arid and semiarid climates. However, the problem of excessive concentrations of sulfate, which is a constant component in coalfields, and its potential health risks are often neglected in Northwest, China. To determine the groundwater quality, health threats, and driving forces of sulfate in coal mine groundwater, this study performed hydrochemical and isotopic analyses of 61 groundwater samples from a typical coalfield in northwestern China. We found that phreatic groundwater had lower total dissolved solid (TDS) and freshwater hydrochemical types (mainly Ca-HCO3 and Ca-Na + K-HCO3 types). In contrast, confined groundwater showed saline affinity (Na + K-SO4 type) and high TDS values, and the quality was unacceptable for drinking, with EWQI values larger than 100, which could be attributed to its high SO42- concentration. In addition, confined groundwater was also unsuitable for irrigation with high values of electric conductivity (EC), sodium absorption ratio (SAR), and Na%. Combining with isotopic analysis (δD, δ18Owater, δ34S and δ18Osulfate), the sulfate of confined and phreatic groundwater was controlled by gypsum dissolution and irrigation activities. As for public human health, SO42- poses potential non-carcinogenic risks to various populations, especially children. Therefore, the impact of geogenic and anthropogenic factors should be paid attention to, including the reduction of the use of sulfur-containing fertilizers and discharge of sulfur-containing sewage; and the water treatment should be carried out. Importantly, there is a need to adopt a strategy of water supply from multiple sources to ensure human health.

Silicone Rubber Fabry-Perot Pressure Sensor Based on a Spherical Optical Fiber End Face.

To improve the fringe contrast and the sensitivity of Fabry-Perot (FP) pressure sensors, a silicone rubber FP pressure sensor based on a spherical optical fiber end face is proposed. The ratio of silicone rubber ingredients and the diameter and thickness of silicone rubber diaphragm were optimized by a simulation based on experimental tests that analyzed elastic parameters, and the influence of the radius of a spherical optical fiber and the initial cavity length of the sensor on the fringe contrast was investigated and optimized. Pressure sensor samples were fabricated for pressure test and temperature cross-influence test. Gas pressure experimental results within a pressure range of 0~40 kPa show the average sensitivity of the sensor is -154.56 nm/kPa and repeatability error is less than 0.71%. Long-term pressure experimental results show it has good repeatability and stability. Temperature experimental results show its temperature cross-sensitivity is 0.143 kPa/°C. The good performance of the proposed FP pressure sensor will expand its applications in biochemical applications, especially in human body pressure monitoring.

The public goods game with shared punishment cost in well-mixed and structured populations.

Both experimental and theoretical studies have shown that punishment plays an important role in promoting cooperation. Various forms of punishment are proposed to explain why costly punishment could be maintained in the population and stabilize cooperation. Here we consider an altruistic behavior that cooperators perform cooperation and punishment simultaneously and share the punishment cost. We investigate the role of punishment cost shared among cooperators in the evolution of cooperation in public goods game. We show that the punishment can promote and stabilize cooperation when the penalty imposed on defectors is large enough compared to the punishment cost incurred by cooperators in well-mixed populations. In structured populations, cooperation could emerge under lower fine threshold and coexist with defection. However, as the penalty increases, cooperation will have a larger basin of attraction in the well-mixed population than that in the structured population. Our analytical and simulated results indicate that punishment indeed can effectively promote the evolution of cooperation. We also find that population structure can promote the coexistence of cooperation and defection but not always be beneficial to cooperation.