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Optical Fiber Current Transformer (FOCT) is susceptible to various types of noise, which leads to a decrease in its measurement accuracy, especially when the primary current is small. Improving its signal-to-noise ratio is one of the key technologies of FOCT. This article comprehensively analyzes FOCT's optical signal noise, signal detection noise and noise sources introduced by the external environment, and gives the calculation method of FOCT SNR. The influence of different noise sources on the signal-to-noise ratio is simulated through theory, and the FOCT signal-to-noise ratio optimization design plan is proposed. It is pointed out that the receiver optical power can be increased, increasing the number of sensitive optical fibers of the sensor head and selecting the appropriate closed-loop feedback phase modulation bias operating point method can effectively improve the signal-to-noise ratio and has been verified by experiments. Based on this design FOCT prototype, rated current of 600 A when meet GB / T 20840.8-2007 predetermined 0.2S level requirements, and the SNR is 30.2dB at 1% rated current, the ratio error is less than 0.61%, the phase error is less than 12.39′.

Estimation of ultimate bearing capacity (UBC) of pre-stressed high-strength concrete (PHC) pipe pile is critical for optimizing pile design and construction. In this study, a standard penetration test (SPT), static cone penetration test (CPT) and static load test (SLT) were carried out to assess, determine and compare the UBC of the PHC pipe pile embedded in saturated sandy layers at different depths. The UBC was calculated with three methods including the JGJ94-2008 method, Meyerhof method and Schmertmann method based on in-situ blow count (N) of SPT (SPT-N) which was higher than the values recommended in survey report regardless of pile length. The average UBC values calculated with cone-tip resistance and sleeve friction from CPTs was also higher than the value recommended in the survey report. Moreover, the actual UBC values directly obtained by load-displacement curves from SLTs were in line with the calculated values based on in-situ SPTs and CPTs, but approximately twice as high as the values recommended in the survey report regardless of pile length. For the SPT method, the application of bentonite mud in saturated sand layers is critical for the assessment of pile capacity in the survey phase, CPTs can provide reliable results regardless of soil characteristics and groundwater if the soil layer can be penetrated, and SLTs are necessary to accurately determine the UBC in complex stratum.

In this paper, a mathematical model for describing the solid-fluid transformation of ice water is put forward based on the special geometry cases. The correctness of the obtained model is verified through comparison with numerical analysis and experiments. The good agreement indicates that the obtained model is available for the study of the solid-fluid transformation of ice water. The theory derived in this paper lays a foundation for the research of solid-fluid transformation phenomena of other materials and may have important applications in engineering areas such as rheology, creep, and instability of materials.

In order to meet the high-speed response requirements of DC fiber-optic current transformer (FOCT) in flexible DC transmission engineering, the step response characteristics of DC FOCT and its dynamic performance improvement methods are studied. The discrete mathematical model of DC FOCT is established and analyzed by simulation. The key parameters affecting the step response characteristics of DC FOCT are transit time, forward channel gain, filter order, and communication delay. A step response test platform for DC FOCT is built, and the step response characteristics of DC FOCT are tested. The experimental results are consistent with the simulation analysis. It is shown by experimental results that the step response rise time of the DC FOCT is less than 40μs after parameter optimization, meeting the relevant application requirements.

Under investigation in this paper is a higher-order nonlinear Schrodinger equation which can describe the propagation of ultrashort pulse in the inhomogeneous optical fiber. Lax pair and conservation laws are constructed from which the integrability of the equation can be verified. Nonautonomous breathers and rogue waves for the equation are derived based on the Darboux transformation (DT) and generalized DT, respectively. Influence of the group-velocity dispersion, third- and forth-order dispersion and gain or loss coefficient on the propagation and interaction of the nonautonomous breathers and rogue waves, is also discussed specifically. There exist two types of nonautonomous breathers. Expressions of the quasi-periods for the two types of nonautonomous breathers are given and the effects of coefficients on the quasi-periods are also discussed. Gain or loss coefficient affects the background for the nonautonomous breather, while third-order dispersion has an influence on the trajectory of the nonautonomous breather. Group-velocity dispersion affects the range of the nonautonomous rogue wave. In addition, group-velocity dispersion also produces a skew angle and the skew angle rotates in the clockwise direction with the increase of group-velocity dispersion. When forth-order dispersion coefficient is taken as a linear function of distance, the structure of rogue wave pair can be formed. The separation and relative locations for the two constituents of rogue wave pair are affected by the coefficients of the linear function.

Soil conditioning is of great significance for tunneling in soft ground with earth pressure balance shield (EPBS) machines, which leads to safe, highly efficient, and high-quality tunneling. To study the effects of soil conditioning on properties of a clay-sand-gravel mixed soil encountered in an EPBS tunneling project in Beijing, a series of geotechnical test methods was carried out based on laboratory test in this paper. The decay behaviors of foam particles generated by the Waring-Blender method were studied first using the image particle analysis system, and then the feasibility of soil conditioning on the mixed soil was qualitatively and quantitatively assessed through the mixing test, slump test, and friction coefficient test. The preliminary test results indicate that drainage of water in liquid film plays an important role in the decay of foam microstructure. The viscosity and flowability of the conditioned soil were modified dramatically by using various amount of water and foam, and a suitable state meeting the requirement of EPBS machines was obtained. The net power and mixing time, which reflects the interaction between the blending rods and tested soils, as well as the slump value, providing the overall indication for liquidity of the conditioned soils, and friction coefficient, reflecting the friction between steel and tested soils, were used to provide insight into the variation in viscosity and flowability of the tested soils.

When machining Inconel 718, tool wear is a serious problem, which affects the quality of workpiece. In order to analyze the wear mechanism in dry machining Inconel 718 with cemented carbide tool, the wear morphology of tool was observed by CCD and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometer in this paper. The results showed that at low cutting speed, the formation and shedding of the built-up-edge caused severe cutting tool breakage. When the cutting speed reached 40 m/min, the tool material fell off from the tool substrate in the form of wear debris, which was the main reason for tool wear. In addition, the elements diffusion between the tool and the workpiece and oxidation reaction accelerated the formation and falling off of wear debris. According to the tool wear mechanism, a tool wear prediction model was established. In machining Inconel 718, the excellent experimental agreement have been obtained in the prediction of wear in cemented carbide tool.

In order to investigate the effect of fissure and temperature on deep-seated rock, uniaxial compression experiments were conducted on rock-like material with different fissure angle at different temperatures. We investigated the influence of fissure angle and temperature on strength and the influence of fissure on failure mode of the rock. Also, we simulated the uniaxial compression experiment of rock-like material with ABAQUS. The results of experiments and simulations confirmed that the strength of rock-like material decreased with increasing temperatures and the strength decreased first then increased with increased fissure angle. The crack initiation started from the tips of the pre-existing fissure and we could speculate via the simulation that the reason of the crack initiation was stress concentration on fissure tips.

The effect of a commercially available compound probiotics product containing Bacillus subtilis YB-1 (50%) and Bacillus cereus YB-2 (50%) fed to sea cucumbers, Apostichopus japonicus (Selenka) on challenge infections and non-specific immune responses was assessed. Sea cucumbers (were randomly allocated into nine aquariums at a density of 30 sea cucumbers per tank and triplicate groups) were fed diets containing 0 (control), 107 and 1010 cfu (g diet)−1 of the probiotics mixture for 32 days. The growth factors and immunological parameters were measured. In addition, the effects on resistance against Vibrio alginolyticus infection were also evaluated. The results indicate that all the immunological parameters (phagocytic activity, superoxide anion production, lysozyme activity, catalase activity and phenoloxidase activity) measured and the growth rate of sea cucumbers fed 1010 cfu of the probiotics mixture were significantly (P 0.05), Bacillus sp. levels were significantly elevated in sea cucumbers fed the probiotics mixture (P