Based on large numbers of experiments, together with some theoretic support such as equations related to the experiment, thermodynamic principles and so on, one useful and reasonable self-protecting boron formulation ...Based on large numbers of experiments, together with some theoretic support such as equations related to the experiment, thermodynamic principles and so on, one useful and reasonable self-protecting boron formulation is got to reinforce the muzzle shunt rail gun rail. The preliminary friction and abrasion test results show that the formulation is acceptable and the abrasion resistance of the steel rail enhances to some extent after the surface reinforcement.展开更多
In order to solve the problem that the traditional space jamming countermeasure cannot deal with the mainlobe self-protecting jammings,a polarization-space joint mainlobe jamming countermeasure technique based on divi...In order to solve the problem that the traditional space jamming countermeasure cannot deal with the mainlobe self-protecting jammings,a polarization-space joint mainlobe jamming countermeasure technique based on divided dimensions is proposed.Specifically,the digital beam of each row and column is firstly formed by using dual polarization digital receiving in multi-channel.Then,the polarization-space joint cancellation in both azimuth and elevation dimensions is carried out based on the polarization-space joint difference between the target echo and the jamming,as well as the divided dimension feature of the row and column beams.Finally,the sum and difference beams of the full array in the elevation or azimuth dimension are formed by the beams after jamming cancelling,and the monopulse angle measurement is further employed to obtain target angles.The effectiveness of the proposed technique is verified by simulations,indicating that the self-protecting jamming and multiple mainlobe following jammings can be both cancelled simultaneously with the angle measurement unchanged.展开更多
A kind of self-protective flux cored wire has been developed for joining 960 MPa high strength steel. Weld metal containing different aluminium elements contents was obtained by changing the content of aluminum powder...A kind of self-protective flux cored wire has been developed for joining 960 MPa high strength steel. Weld metal containing different aluminium elements contents was obtained by changing the content of aluminum powder in the composition of the flux core. The strength and toughness of weld metal were tested by tensile test and impact test at different temperatures, and the influence mechanism of aluminium element on the microstructure and mechanical properties of weld metal was analyzed by means of metallographic microstructure observation and scanning electron microscope observation. The results show that aluminium element content on impact ductility of weld metal of 960 MPa high strength steel is great, but the influence on tensile strength and elongation of weld metal is little. With increasing aluminium element contents of weld metal, the impact energy of weld metal increases at first and then decreases, the best aluminium element content of weld metal is 0.2 wt.%. Aluminium oxide is easy to be formed in weld metal with low aluminium element contents, and the aluminium oxide can easily become nucleation particle for acicular ferrite. It is conducive to formation more acicular ferrite and will improve impact absorbing energy of weld metal. Aluminium nitride will easily formed in weld metal with high aluminium element content, and the coarse ferrite microstructure appears in weld metal and reduces impact energy of weld metal.展开更多
Among the factors which restrict the large-scale utilization of magnesium-based hydride as a hydrogen storage medium,the high operating temperature,slow kinetics,and air stability in particular are key obstacles.In th...Among the factors which restrict the large-scale utilization of magnesium-based hydride as a hydrogen storage medium,the high operating temperature,slow kinetics,and air stability in particular are key obstacles.In this work,a novel method,namely hydriding combustion synthesis plus short-term mechanical milling followed by air exposure,was proposed to synthesize air stable and autocatalytic magnesium nickel hydride(Mg2NiH4),which shows excellent hydrogen absorption/desorption kinetics,capacity retention and oxidation resistance.The short-term-milled Mg2NiH4 can desorb 2.97 wt.%hydrogen within 500 s at 230℃.Even after exposure under air atmosphere for 67 days,it can still desorb 2.88 wt.%hydrogen within 500 s at 230℃.The experimental and theoretical results both indicated that the surface of as-milled Mg2NiH4 was easy to be oxidized under air atmosphere.However,the in-situ formed Ni during air exposure of Mg2NiH4 improved the hydrogen desorption kinetics,and the formed surface passivation layer maintained the hydrogen storage capacity and avoided further poisoning,which we called autocatalytic and self-protective effect.Such a novel dual effect modified the reaction activity and oxidation resistance of the air-exposed Mg2NiH4.Our findings provide useful insights into the design and preparation of air stable metal-based hydride for large-scale utilization and long-term storage.展开更多
文摘Based on large numbers of experiments, together with some theoretic support such as equations related to the experiment, thermodynamic principles and so on, one useful and reasonable self-protecting boron formulation is got to reinforce the muzzle shunt rail gun rail. The preliminary friction and abrasion test results show that the formulation is acceptable and the abrasion resistance of the steel rail enhances to some extent after the surface reinforcement.
文摘In order to solve the problem that the traditional space jamming countermeasure cannot deal with the mainlobe self-protecting jammings,a polarization-space joint mainlobe jamming countermeasure technique based on divided dimensions is proposed.Specifically,the digital beam of each row and column is firstly formed by using dual polarization digital receiving in multi-channel.Then,the polarization-space joint cancellation in both azimuth and elevation dimensions is carried out based on the polarization-space joint difference between the target echo and the jamming,as well as the divided dimension feature of the row and column beams.Finally,the sum and difference beams of the full array in the elevation or azimuth dimension are formed by the beams after jamming cancelling,and the monopulse angle measurement is further employed to obtain target angles.The effectiveness of the proposed technique is verified by simulations,indicating that the self-protecting jamming and multiple mainlobe following jammings can be both cancelled simultaneously with the angle measurement unchanged.
基金Project was supported by the 2019 Scientific Research Foundation of Liaoning Provincial Education Department (Grant No. LJJF201902)Special Research Foundation of Liaoning Equipment Manufacture College of Vocational and Technology (Grant No.2018YYYJ-5)。
文摘A kind of self-protective flux cored wire has been developed for joining 960 MPa high strength steel. Weld metal containing different aluminium elements contents was obtained by changing the content of aluminum powder in the composition of the flux core. The strength and toughness of weld metal were tested by tensile test and impact test at different temperatures, and the influence mechanism of aluminium element on the microstructure and mechanical properties of weld metal was analyzed by means of metallographic microstructure observation and scanning electron microscope observation. The results show that aluminium element content on impact ductility of weld metal of 960 MPa high strength steel is great, but the influence on tensile strength and elongation of weld metal is little. With increasing aluminium element contents of weld metal, the impact energy of weld metal increases at first and then decreases, the best aluminium element content of weld metal is 0.2 wt.%. Aluminium oxide is easy to be formed in weld metal with low aluminium element contents, and the aluminium oxide can easily become nucleation particle for acicular ferrite. It is conducive to formation more acicular ferrite and will improve impact absorbing energy of weld metal. Aluminium nitride will easily formed in weld metal with high aluminium element content, and the coarse ferrite microstructure appears in weld metal and reduces impact energy of weld metal.
基金the National Natural Science Foundation of China(Nos.51771092,52071177,and 21975125)Six Talent Peaks Project in Jiangsu Province(No.2018-XNY-020)the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions.
文摘Among the factors which restrict the large-scale utilization of magnesium-based hydride as a hydrogen storage medium,the high operating temperature,slow kinetics,and air stability in particular are key obstacles.In this work,a novel method,namely hydriding combustion synthesis plus short-term mechanical milling followed by air exposure,was proposed to synthesize air stable and autocatalytic magnesium nickel hydride(Mg2NiH4),which shows excellent hydrogen absorption/desorption kinetics,capacity retention and oxidation resistance.The short-term-milled Mg2NiH4 can desorb 2.97 wt.%hydrogen within 500 s at 230℃.Even after exposure under air atmosphere for 67 days,it can still desorb 2.88 wt.%hydrogen within 500 s at 230℃.The experimental and theoretical results both indicated that the surface of as-milled Mg2NiH4 was easy to be oxidized under air atmosphere.However,the in-situ formed Ni during air exposure of Mg2NiH4 improved the hydrogen desorption kinetics,and the formed surface passivation layer maintained the hydrogen storage capacity and avoided further poisoning,which we called autocatalytic and self-protective effect.Such a novel dual effect modified the reaction activity and oxidation resistance of the air-exposed Mg2NiH4.Our findings provide useful insights into the design and preparation of air stable metal-based hydride for large-scale utilization and long-term storage.
