Compression of unmagnetized Nd_(2)Fe_(14)B permanent magnets is executed by using shock waves with different pressures in a one-stage light gas gun system.The microstructure,crystal structure,and magnetic properties o...Compression of unmagnetized Nd_(2)Fe_(14)B permanent magnets is executed by using shock waves with different pressures in a one-stage light gas gun system.The microstructure,crystal structure,and magnetic properties of the magnets are examined with scanning electronic microscopy,x-ray diffraction,hysteresis loop instruments,and a vibrating sample magnetometer,respectively.The NdFeB magnets display a demagnetization phenomenon after shock wave compression.The coercivity dropped from about 21.4kOe to 3.2kOe.The critical pressure of irreversible demagnetization of NdFeB magnets should be less than 4.92GPa.The coercivity of the NdFeB magnets compressed by shock waves could be recovered after annealing at 900℃and 520℃for 2h,sequentially.The chaotic orientation of Nd_(2)Fe_(14)B grains in the compressed magnets is the source of demagnetization。展开更多
为了有效比较由美国空间研究中心(Center of Space Research,CSR)、德国地学中心(Helmholtz-Centre Potsdam-German Research Centre for Geosciences,GFZ)和美国喷气推进实验室(Jet Propulsion Laboratory,JPL)机构提供的3种GRACE-FO R...为了有效比较由美国空间研究中心(Center of Space Research,CSR)、德国地学中心(Helmholtz-Centre Potsdam-German Research Centre for Geosciences,GFZ)和美国喷气推进实验室(Jet Propulsion Laboratory,JPL)机构提供的3种GRACE-FO RL06时变重力场模型精度,分别从模型阶方差、C_(20)项精度、全球和局部陆地水储量变化反演等角度对3种模型进行了详尽的阐述。结果表明:JPL的RL06模型阶方差要大于其他2个机构发布的结果;而在C_(20)项精度方面,CSR和JPL发布的数据更接近于卫星激光测距(Satellite Laser Ranging,SLR);通过对比这3种模型反演的陆地水储量变化结果与全球陆面数据同化系统(Global Land Data Assimilation system,GLDAS)水文模型的反演结果,发现3种模型与GLDAS模型的结果符合度都比较高,从局部反演结果来看,在3种模型中CSR与GLDAS模型的符合度较高。展开更多
基金Supported by the National High-Technology Research and Development Program of China under Grant No 2011AA03A401the National Basic Research Program of China under Grant No 2010CB934601the National Natural Science Foundation of China under Grant Nos 51171049 and 11072036.
文摘Compression of unmagnetized Nd_(2)Fe_(14)B permanent magnets is executed by using shock waves with different pressures in a one-stage light gas gun system.The microstructure,crystal structure,and magnetic properties of the magnets are examined with scanning electronic microscopy,x-ray diffraction,hysteresis loop instruments,and a vibrating sample magnetometer,respectively.The NdFeB magnets display a demagnetization phenomenon after shock wave compression.The coercivity dropped from about 21.4kOe to 3.2kOe.The critical pressure of irreversible demagnetization of NdFeB magnets should be less than 4.92GPa.The coercivity of the NdFeB magnets compressed by shock waves could be recovered after annealing at 900℃and 520℃for 2h,sequentially.The chaotic orientation of Nd_(2)Fe_(14)B grains in the compressed magnets is the source of demagnetization。
文摘为了有效比较由美国空间研究中心(Center of Space Research,CSR)、德国地学中心(Helmholtz-Centre Potsdam-German Research Centre for Geosciences,GFZ)和美国喷气推进实验室(Jet Propulsion Laboratory,JPL)机构提供的3种GRACE-FO RL06时变重力场模型精度,分别从模型阶方差、C_(20)项精度、全球和局部陆地水储量变化反演等角度对3种模型进行了详尽的阐述。结果表明:JPL的RL06模型阶方差要大于其他2个机构发布的结果;而在C_(20)项精度方面,CSR和JPL发布的数据更接近于卫星激光测距(Satellite Laser Ranging,SLR);通过对比这3种模型反演的陆地水储量变化结果与全球陆面数据同化系统(Global Land Data Assimilation system,GLDAS)水文模型的反演结果,发现3种模型与GLDAS模型的结果符合度都比较高,从局部反演结果来看,在3种模型中CSR与GLDAS模型的符合度较高。
