In this paper the dual reciprocity boundary element method is employed to solve nonlinear differential equation del(2) u + u + epsilon u(3) = b. Results obtained in an example have a good agreement with those by FEM a...In this paper the dual reciprocity boundary element method is employed to solve nonlinear differential equation del(2) u + u + epsilon u(3) = b. Results obtained in an example have a good agreement with those by FEM and show the applicability and simplicity of dual reciprocity method (DRM) in solving nonlinear differential equations.展开更多
The misch-metal （MM） partially substituted Nd-Fe-B sintered magnets were fabricated by the dual alloy method, and the crystal structure, microstructure, and magnetic properties were analyzed comprehensively. X-ray d...The misch-metal （MM） partially substituted Nd-Fe-B sintered magnets were fabricated by the dual alloy method, and the crystal structure, microstructure, and magnetic properties were analyzed comprehensively. X-ray diffraction （XRD） reveals that the increasing content of the MM has an inconsiderable effect on the crystallographic alignment of the magnets. Grains of the two main phases are uniformly distributed, and slightly deteriorate on the grain boundary. Due to the diffusion between the adjacent grains, the MM substituted Nd-Fe-B magnets contain three types of components with different Ce/La concentrations. Moreover, the first-order reversal curve （FORC） diagram is introduced to analyze the magnetization reversal process, coercivity mechanism, and distribution of reversal field in magnetic samples. The analysis indicates that there are two major reversal components, corresponding to the two different main phases. The domain nucleation and growth are determined to be the leading mechanism in controlling the magnetization reversal processes of the magnets sintered by the dual alloy method.展开更多
It is usually difficult to measure acoustic velocities through a casing, especially when the casing is poorly bonded with formation. An acoustic logging technique using the dual source of opposite polarity is proposed...It is usually difficult to measure acoustic velocities through a casing, especially when the casing is poorly bonded with formation. An acoustic logging technique using the dual source of opposite polarity is proposed to enhance the Signal to Noise Ratio of the formation signal and to reduce the casing wave in the data acquisition process. In what follows, a theoret- ical modeling is used to caculate the wavefroms of cased wells. And then, a scaled experiment was conducted in the 1：10 scaled experimental well using the proposed technique in the poorly- bonded condition. The results show that this technique can effectively suppress the casing wave and enhance the formation wave, even in the poorly-bonded condition. By analyzing the measured wavefroms, the amplitude of casing wave is reduced to 12% compared to the conventional one-source technique, and the compressional wave velocity can be easily obtained by using this technique. Both the theoretical modeling and experiment results demonstrate the feasibility of the proposed technique. This study establishes the theoretical and experimental foundation for the cased-hole, dual source of opposite polarity, acoustic logging tool development.展开更多
文摘In this paper the dual reciprocity boundary element method is employed to solve nonlinear differential equation del(2) u + u + epsilon u(3) = b. Results obtained in an example have a good agreement with those by FEM and show the applicability and simplicity of dual reciprocity method (DRM) in solving nonlinear differential equations.
基金Project supported by the National Natural Science Foundation of China(Grant No.51590880)the National Key Research and Development Program of China(Grant Nos.2014CB643702 and 2016YFB0700903)+1 种基金Key Research Program of the Chinese Academy of Sciences of Chinathe Inner Mongolia Science and Technology Major Project of China 2016
文摘The misch-metal （MM） partially substituted Nd-Fe-B sintered magnets were fabricated by the dual alloy method, and the crystal structure, microstructure, and magnetic properties were analyzed comprehensively. X-ray diffraction （XRD） reveals that the increasing content of the MM has an inconsiderable effect on the crystallographic alignment of the magnets. Grains of the two main phases are uniformly distributed, and slightly deteriorate on the grain boundary. Due to the diffusion between the adjacent grains, the MM substituted Nd-Fe-B magnets contain three types of components with different Ce/La concentrations. Moreover, the first-order reversal curve （FORC） diagram is introduced to analyze the magnetization reversal process, coercivity mechanism, and distribution of reversal field in magnetic samples. The analysis indicates that there are two major reversal components, corresponding to the two different main phases. The domain nucleation and growth are determined to be the leading mechanism in controlling the magnetization reversal processes of the magnets sintered by the dual alloy method.
基金supported by the National Natural Science Foundation for the Youth of China(41204070)
文摘It is usually difficult to measure acoustic velocities through a casing, especially when the casing is poorly bonded with formation. An acoustic logging technique using the dual source of opposite polarity is proposed to enhance the Signal to Noise Ratio of the formation signal and to reduce the casing wave in the data acquisition process. In what follows, a theoret- ical modeling is used to caculate the wavefroms of cased wells. And then, a scaled experiment was conducted in the 1：10 scaled experimental well using the proposed technique in the poorly- bonded condition. The results show that this technique can effectively suppress the casing wave and enhance the formation wave, even in the poorly-bonded condition. By analyzing the measured wavefroms, the amplitude of casing wave is reduced to 12% compared to the conventional one-source technique, and the compressional wave velocity can be easily obtained by using this technique. Both the theoretical modeling and experiment results demonstrate the feasibility of the proposed technique. This study establishes the theoretical and experimental foundation for the cased-hole, dual source of opposite polarity, acoustic logging tool development.
