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This research focuses on a desensitization method to develop a wide-range FBG sensor for extra-large strain monitoring, which is an essential requirement in large scale infrastructures or for some special occasions. Under appropriate hypotheses, the strain transfer distribution of wide-range FBG sensor based on the shear-lag theory is conducted to improve the accuracy of extra-large strain measurements. It is also discussed how the elastic modulus of adhesive layer affects the strain transfer rate. Two prototypes in different monitoring ranges are designed and fabricated by two layers of steel pipe encapsulation. The presented theoretical model is verified by experimental results. Moreover, it is demonstrated that experimentation in regards to the calibration of the wide-range FBG sensor, improved the amplification coefficient up to 2.08 times and 3.88 times, respectively. The static errors are both calculated and analyzed in this experiment. The wide-range FBG strain sensor shows favourable linearity and stability, which is an excellent property of sensors for extra-large strain monitoring.

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Biocement can be achieved through the microbially induced carbonate precipitation (MICP) process. Such a method can potentially be utilized as an eco-friendly method for civil and environmental engineering applications such as soil ground improvement and wind erosion control of surface soil. In this method, one key step is the effective production of ureolytic bacteria. In previous laboratory and field studies, the cultivation and production of the bacteria used for the MICP were usually expensive and time-consuming. The purpose of this study was to optimize the cultivation method of the ureolytic bacteria (Sporosarcina pasteurii), and soil stabilization tests were conducted to verify the effectiveness of the cultured bacteria used to strengthen soil against the wind-induced erosion. Bacterial cultivation methods were studied by investigating the effects of different cultivation media and conditions. Testing variables included the types and concentrations of nitrogen sources (urea or NH4Cl), pH values (7.5–9.5), cultivation conditions (batch or chemostat condition), and different carbon sources. It was found that, with the same amount of nitrogen source, the test with pure urea had the highest biomass yield, urease activity, and specific urease activity than the other tests with pure NH4Cl or both NH4Cl and urea. The use of urea as the nitrogen source in the media also led to an increase in pH, which was not found in the test with pure NH4Cl. As for the factor of urea concentration, the tests with a higher urea concentration had a higher biomass yield, urease activity, and pH. The factor of pH values also played an important role. The test with an 8.5 initial pH value had a higher biomass yield, urease activity, and specific urease activity than the tests with 7.5 and 9.5 initial pH values. In the chemostat condition, the ureolytic bacteria could be effectively produced with urease activity up to 7 mmol/L/min, as compared with around 12 mmol/L/min activity in the batch condition. Thus, the optimum nitrogen source, pH value, and cultivation condition for the cultivation of Sporosarcina pasteurii was urea, 8.5, and batch condition, respectively. In addition, when soybean milk powder or milk powder was used as the carbon source, the urease activity was around 2.5 mmol/L/min, which is also high enough to be used for biocement.

In order to obtain the cold flow structures inside a model scramjet combustor, direct-connected experiments have been conducted on the inlet Mach number of 2.0. The length to height ratio of the isolator is 6 and 8. The static pressure along the wall is measured with varied back pressure. The Schlieren technique is employed for visualizing the typical shock train structures in the model. The results indicate that the flowfield in the scramjet combustor is rather complicated because of shock wave/boundary layer interaction. The first shock of the normal shock train is bifurcated at the foot, while the subsequent shocks are seen to be of nearly normal shock. Each successive shock is weaker. The shock train moves towards the isolator entrance as back pressure increases. The position of the leading edge of shock train is sensitive to the pressure variation. The isolator of Liso/ h=8 can sustain pressure rise better than Liso/ h=6.

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