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Soil microbial biomass nitrogen (MBN) contains the largest proportion of biologically active nitrogen (N) in soil, and is considered as a crucial participant in soil N cycling. Agronomic management practices such as crop rotation and mono-cropping systems, dramatically affect MBN in agroecosystems. However, the influence of crop rotation and mono-cropping in agroecosystems on MBN remains unclear. A meta-analysis based on 203 published studies was conducted to quantify the effect of crop rotation and mono-cropping systems on MBN under synthetic N fertilizer application. The analysis showed that crop rotation significantly stimulated the response ratio (RR) of MBN to N fertilization and this parameter reached the highest levels in upland-fallow rotations. Upland mono-cropping did not change the RR of MBN to N application, however, the RR of MBN to N application in paddy mono-cropping increased. The difference between crop rotation and mono-cropping systems appeared to be due to the various cropping management scenarios, and the pattern, rate and duration of N addition. Crop rotation systems led to a more positive effect on soil total N (TN) and a smaller reduction in soil pH than mono-cropping systems. The RR of MBN to N application was positively correlated with the RR of mineral N only in crop rotation systems and with the RR of soil pH only in mono-cropping systems. Combining the results of Random Forest (RF) model and structural equation model showed that the predominant driving factors of MBN changes in crop rotation systems were soil mineral N and TN, while in mono-cropping systems the main driving factor was soil pH. Overall, our study indicates that crop rotation can be an effective way to enhance MBN by improving soil N resources, which promote the resistance of MBN to low pH induced by intensive synthetic N fertilizer application.

The fine-grained heat-affected zone (FGHAZ) specimens for P92 steel weld were produced by welding thermal simulator, then the simulated specimens were aged at 923 K for 0∼5000 h. The Laves phase parameters of FGHAZ were measured using SEM-back-scattered electron, and a two-dimensional (2D) precipitate/matrix model was used to calculate the stress-strain concentration at Laves phase/matrix interface by ANSYS. The results indicate that the maximum precipitated quantity of Laves phase in both FGHAZ and base metal (BM) is around 1.0%; however, the time to the saturated value is about 500 h shorter in the FGHAZ than in the BM, meanwhile. In fact, the differences in precipitation and coarsening of Laves phase between the FGHAZ and BM are closely correlated to the grain size. Furthermore, the matrix of FGHAZ is softened due to its polygonal sub-grains with low dislocation densities replacing the martensitic lath structure. The concentration of stress-strain at the Laves phase/matrix interface is larger in the FGHAZ than in BM, resulting from its softened matrix and coarser Laves phase, which contributes to the formation of creep voids on grain boundaries. Among these two factors, the softening of matrix has more significant influence on the formation of creep voids over the coarsening of Laves phase.

In order to facilitate studying real-time mooring force of offshore cage, based on the combination of ZigBee and GPRS technologies, the secondary development was conducted, the detection system of mooring force was designed. It was mainly designed the overall system solution and integrate the system hardware architecture, the development of the software programs of analog-data acquisition, ZigBee networking, remote data transmission and the server were designed. The system test results show that the data could be effectively transmitted between the terminals and server. This system is small in size and low power consuming which can be used as a remote detection tool of mooring force in process when studying on offsore cage aquaculture.

Poor compression in the strain clamp often makes the strands overheat and fracture. There exists a certain gap between conductors and the strain clamp if the strain clamp is compressed poorly. The ashes, oxide, corrosion and abrasion tend to gather and scale in the gap, forming scale layers of high resistivity. As the exposure time increases, the layers expand and thicken, which causes the worsening of conductive properties of current and heat, and leads to abnormal temperature elevation, the degradation of microstructure and properties and strands fracture at last. In consideration of this kind of strands fracture phenomenon and through FEM, non-uniform temperature field influenced by scale layer in the clamp has been analyzed and the quantitative relationship between the scale layer, peak temperature and current has been obtained. The results of material experiments show that the strands vary from each other in the roundness of shear lips. Serious erosion is found on the surface of outer Al (aluminum) strands attaching to the clamp, while there is almost no erosion mark on the surface attaching to inner Al strands. Erosion spots in Al strands surface attaching to the scale layer are the deepest, and each erosion pit is large and some of which have even developed into plaques. The interacting deterioration of scale and temperature causes the Al strands attaching to the scale layer to fail and then led to fracture-temperature domino effect of other strands. The longitudinal fibrous microstructure of steel strands disappeared as the temperature rose. The plasticity of strands increased after recovery and recrystallization. The rapid degradation of mechanics properties resulted in the drop accident of conductors.

Fretting damage generates under the breeze vibration condition. Fretting wear under various pitch diameter ratio at the ACSR strand interface has been studied by FEM method with the LGJ-25/4 ACSR taken as an example. The contact mechanics parameter distribution laws at the strand interface have been obtained. It shows that the peak of von Mises stress, contact pressure, contact state and shear stress at the contact spot decrease as the pitch diameter ratio increases. And the width of yield area also decreases as the pitch diameter ratio increases.