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[Objective] In order to explore the relationship between the windbreak direction and the prevailing wind erosion direction in the black soil region of Northeast China. [Methods] The basic characteristics of the windbreak in the study area were obtained by remote sensing interpretation and field survey, and the angle of intersection between the windbreak direction and the prevailing wind erosion direction, that is, the wind direction declination angle, was calculated and analyzed by combining the wind speed and wind direction data of 43 meteorological stations in the study area. [Results] The westerly wind in Mengdong black soil sub-region accounted for a large proportion, the wind direction was more concentrated, the prevailing wind erosion direction dominance was strong, the wind direction in the Songnen black soil sub-region was scattered, and the prevailing wind erosion direction dominance was weak. Average windbreak density Songnen black soil sub-area > Mengdong black soil sub-region; The windbreak direction accounted for the largest proportion in the Songnen black soil sub-area was the N-S trend windbreak direction, and there was no obvious regularity in the Mengdong black soil sub-region. In the study area, the proportion of wind declination angle 30° was 70.40%, and the wind protection effect was poor. [Conclusion] The direction of a large number of windbreak in the study area is oblique to the prevailing wind erosion direction, and the protective effect is poor. The results of this study have important reference value for understanding the density and trend of existing windbreak belts, and for further construction and transformation of windbreak.

In the case of sequential mining with single wing arrangement in coal mine working face, the drilling along the working face is easily affected by the support stress of adjacent working faces, leading to drilling failure. At present, research on borehole protection focuses on enhancing the strength of the borehole itself, without proposing solutions to the fundamental factors that affect borehole stability. In order to solve the above problems, a hydraulic fracturing weakening roof borehole protection technology has been proposed. By using hydraulic fracturing to weaken the roof, the peak mining support stress acting on adjacent coal working faces is reduced, and the transmission of high support stress to the surrounding coal bodies in the bedding boreholes is blocked. The entire process of screening is carried out in the bedding boreholes to ensure that the gas escaping from the coal body can enter the bedding boreholes. Numerical simulation is used to analyze the changes in vertical stress and plastic zone of the coal body around the borehole before and after hydraulic fracturing weakening the roof. The results show that by weakening the roof through hydraulic fracturing, the peak vertical stress of the coal body around the borehole decreases from 21.2 MPa to 9.1 MPa, and the plastic zone range of the coal body decreases from 19 m to 11 m. According to the numerical simulation results, hydraulic fracturing parameters are determined and tested on site. The results show that after using hydraulic fracturing weakening roof borehole protection technology, the average volume fraction of gas extraction from boreholes increases from 3.6% to 14.1%. The average mixed flow rate of gas extraction decreases from 1.28 m3/min to 0.464 m3/min. There is no occurrence of coal oxidation and CO production in a large area of bedding boreholes. Therefore, hydraulic fracturing weakening roof borehole protection technology can effectively avoid drilling failure and gas leakage, improve drilling and extraction efficiency, and ensure drilling and extraction safety.

The hydrodynamic performance of propeller is mostly studied in calm water, but the propeller working behind ship is often affected by waves. According to the literature, there is relatively little research on hydrodynamic performance of propeller in waves at present. In view of this, RANS solver based on OpenFOAM is used to calculate and analyze the influence of waves on the thrust and torque of propeller. The results show that time history curves of thrust and torque oscillate under the influence of waves. The disturbance of free surface and the oscillation amplitude of time history curves increase with the decrease of immersion depth and advance coefficient. Compared with the calm water condition, the average thrust and torque of propeller in waves are reduced when the immersion depth and advance coefficient are the same. The computational results are in good agreement with the experimental data.

A new fuel technology named REMIX (REgenerated MIXture of uranium and plutonium oxides) based on the spent nuclear fuel of light water reactors and fast reactors has come into being in the pursuit of closed fuel cycle in many countries. It was first raised in Russia as a possible way to reduce spent nuclear fuel storage. In traditional spent nuclear fuel reprocessing progress, uranium and plutonium are separated after the codecontamination cycle. For REMIX fuel, the uranium and plutonium nuclides from spent nuclear fuel can be used together without a further separation, which brings the benefits in natural uranium consumption reduction and nuclear non-proliferation. This article aims at validating the feasibility of 5 recycles and analyzing the radiation and decay heat characteristics of spent REMIX fuel. The CMS code package was used in core calculation, and the spent nuclear fuel characteristics were calculated through the SNF program in the package. A typical M310 reactor core was chosen as the target reactor in this article, 30% REMIX FA (fuel assembly) loading fuel management for 5 REMIX recycles was primarily researched, in which enriched uranium was added to the reprocessed fuel of uranium and plutonium. The REMIX core, which contains 30% (48 of 157) REMIX FA, meets equilibrium after three cycles while the REMIX FA from the former recycles can be completely replaced by the new REMIX FA manufactured in the next recycles at the same time. The spent REMIX fuel was gathered and mixed with fresh fuel after a 5-year cooling. The radiation and decay heat characteristics of the cooled spent nuclear fuel were analyzed, which helps the design of radiation shielding during separating the dissolved fuel rods and manufacturing new FA. The results show that the 30% REMIX FA loading fuel management plan can be used in the M310 core without changing the basic neutronics and safety design of the reactor. The feasibility of 5 recycles was proved. Although the spent nuclear fuel may be recycled more than 5 times, the nuclides in the spent nuclear fuel of 5th recycle has already made it hard to be reprocessed and used. The radioactivity and heat release rate of the spent nuclear fuel increase with the recycling times, which contributes to the cost increasing of the spent nuclear fuel reprocessing and FA manufacturing. It is also a factor that decreases the economy of further recycling. The gamma power of the spent nuclear fuel reduces due to the reduction of 134Cs and 137Bam in the spent nuclear fuel, which means that the existing MOX FA manufacturing progress can handle the spent REMIX fuel without extra gamma shielding. The results of this article can help the further research of REMIX fuel on the M310 reactor core.