Analysis of the International Geomagnetic Reference Field (IGRF) 1900-2000 showsthat the Earth’s main magnetic field has changed dramatically during the 20th century: its dipole moment has decreased by 6.5% since 190...Analysis of the International Geomagnetic Reference Field (IGRF) 1900-2000 showsthat the Earth’s main magnetic field has changed dramatically during the 20th century: its dipole moment has decreased by 6.5% since 1900, the strengths of its quadrupole and octupole have increased by 95% and 74%, respectively, four major planetary-scale magnetic anomalies on the Earth’s surface have enhanced by 21%-56%, and the magnetic center has shifted 200 km towards the Pacific Ocean. These time-variation features are similar to the behavior before a geomagnetic polarity reversal.展开更多
The method of natural orthogonal components (NOC) is used to analyze the earth抯 main magnetic field IGRF 1900—2000, and the NOC model of the field is established. The first step of the analysis is to calculate eigen...The method of natural orthogonal components (NOC) is used to analyze the earth抯 main magnetic field IGRF 1900—2000, and the NOC model of the field is established. The first step of the analysis is to calculate eigen modes of the field from the Gauss coefficients of IGRF 1900—2000. Then the magnetic field for each epoch is expanded in a series at the basic function set constructed by the eigen modes, and the intensity coefficients of the eigen modes are calculated. Test of the convergency and stability of the NOC model shows that the model has very short series and much rapid convergency in comparison with the conventional spherical harmonic models of IGRF. Comparison of the eigen modes obtained from different IGRF model groups indicates that the low-degree eigen modes are rather stable, while the high-degree modes show a relatively large variability. The physical meaning of the eigen modes in the NOC model is discussed, and an interesting relationship is found between the spatial structure of the main field and its secular variation.展开更多
Under over 50 years' development, Chinese rare earth magnetic industry developed into the global AINiCo, ferrite permanent magnets and NdFeB magnets manufacturing center, and average consumption of magnets per per...Under over 50 years' development, Chinese rare earth magnetic industry developed into the global AINiCo, ferrite permanent magnets and NdFeB magnets manufacturing center, and average consumption of magnets per person in China increased to 1.026 tons in 2003 from 0.217 ton in 1990. Although China has been the large producing country of rare earth permanent magnetic materials, to be the strongest one, there are many problems to solve. Main Problems Faced By Chinese Permanent Magnet展开更多
The rotating circular plate is widely used in mechanical engineering, meanwhile the plates are often in the electromagnetic field in modern industry with complex loads. In order to study the resonance of a rotating ci...The rotating circular plate is widely used in mechanical engineering, meanwhile the plates are often in the electromagnetic field in modern industry with complex loads. In order to study the resonance of a rotating circular plate under static loads in magnetic field, the nonlinear vibration equation about the spinning circular plate is derived according to Hamilton principle. The algebraic expression of the initial deflection and the magneto elastic forced disturbance differential equation are obtained through the application of Galerkin integral method. By mean of modified Multiple scale method, the strongly nonlinear amplitude-frequency response equation in steady state is established. The amplitude frequency characteristic curve and the relationship curve of amplitude changing with the static loads and the excitation force of the plate are obtained according to the numerical calculation. The influence of magnetic induction intensity, the speed of rotation and the static loads on the amplitude and the nonlinear characteristics of the spinning plate are analyzed. The proposed research provides the theory reference for the research of nonlinear resonance of rotating plates in engineering.展开更多
In order to reduce the starting wind speed of the wind wheel and improve the efficiency of the wind wheel, this paper proposes a new type of composite magnetic circuit permanent magnet generator, which changes the rel...In order to reduce the starting wind speed of the wind wheel and improve the efficiency of the wind wheel, this paper proposes a new type of composite magnetic circuit permanent magnet generator, which changes the relationship between the magnetic induction intensity and the air gap by changing the structure of the main magnetic circuit. The structure greatly improves the air gap sensitivity of the generator, which makes the structural design of the permanent magnet generator easier to implement. Finally, the effectiveness and feasibility of the method are verified by simulation.展开更多
Wall thickness is always a key index for boiler tube inspection in power plant,in order to improve the inspection efficiency and accuracy,a new method fusing the magnetic and ultrasonic technique was proposed.The magn...Wall thickness is always a key index for boiler tube inspection in power plant,in order to improve the inspection efficiency and accuracy,a new method fusing the magnetic and ultrasonic technique was proposed.The magnetic technique was used to do full inspection and locate the flaws,and the ultrasonic was employed to implement further quantitative inspection accu- rately.After comparing the precision of the polynomial,exponential and logarithmic function,the polynomial model was selected to fit the relations between the wall thickness and the peak value of magnetic signals,and the data measured by ultrasonic thickness meter was used to calibrate the model parameters online,the defect depth can be sized quickly.The experimental results demon- grate that the model used in this system has better accuracy than the statistics relation model clearly,and it is also suitable for defect evaluation real-time.Moreover,it is unnecessary to have much more experimental data for the curve fitting technology,so it has better practicability than the other methods.展开更多
The electro-magnetic (EM) and acoustic emission (AE) in the fracture process of both dry and wet rock samples including gabbro, granite, sandstone and marble are studied in the experiment in the laboratory under uniax...The electro-magnetic (EM) and acoustic emission (AE) in the fracture process of both dry and wet rock samples including gabbro, granite, sandstone and marble are studied in the experiment in the laboratory under uniaxial pressure. Signals during the test are detected in ultralow frequency band. The experimental results may be outlined as follows: original waveforms of the electro-magnetic radiation (EMR) and AE in the range of 0-20 kHz frequencies are obtained; the EMR's intensity in fracture process is related to some factors as rock type, content of water, fracture intensity of rocks, loading rates and fracture state etc.; the EMR'S rate is proportional to that of AE during fracture statistically. About 70% of maximum values of EMR rate and AE rate are corresponded with each other; furthermore, the EM signals (EMS) are generally more developed and longer duration than AE signals; the principal energy of EMS detected by copper coin antenna as sensor in power spectra are distributed in frequencies lower than 6 kHz and otherwise those detected by EMinduction coil are at about 10 kHz, and in contrast the major energies of AE are in frequencies less than3 kHz; another notable phenomenon is that distinct electro-magnetic signals are detected before AE occurrence. Since EMR and AE signals obtained in the process of rock fracture are better corresponded to eachother, therefore it'S reasonable to propose that the EMR anormalies observed prior to some earthquakes aremainly produced by fractures of rock in source region, as for the EMS occurred before AE may be related topiezoelectric and piezomagnetic effects.展开更多
There was elaborated a method for calculating magnetic fields of the Solar System planets. It is based on the quantum theory of electroconductivity of metals and semiconductors. The latter helps to calculate thermoele...There was elaborated a method for calculating magnetic fields of the Solar System planets. It is based on the quantum theory of electroconductivity of metals and semiconductors. The latter helps to calculate thermoelectrical processes, always taking place in the bowels of “hot” planets. Main elements of those processes are planetary temperature gradients, thermo electromotive force and radially directed thermoelectrical currents, which are associated with Seebeck effect. Thermo electromotive force causes directional movement of planetary thermoelectrical currents both in metal cores and other conductive shells of planets. Those currents are big and they generate magnetic fields of proportional intensity. The capacities of the calculation method were tested while finding the reason why the Jupiter magnetic field is such complicated. As a result it was specified that the source of the main magnetic field of a planet is its metal core and the source of an additional magnetic field is the layer of liquid metal hydrogen. There was also found the third source of a local magnetic field of low intensity along the circular zone of the equatorial region. The conclusion that the Jupiter’s main magnetic field has a polarity opposite to the Earth’s one.展开更多
The design and manufacture of the main drift chamber（MDC） and the electro-magnetic calorimeter are most important issues in Beijing electron-positron collider upgraded projects. The whole mass of electro-magnetic ca...The design and manufacture of the main drift chamber（MDC） and the electro-magnetic calorimeter are most important issues in Beijing electron-positron collider upgraded projects. The whole mass of electro-magnetic calorimeter （EMC） in BESIII is 40 t, thus high stiffness, strength and dynamical properties are required for the design of entire structural of electro-magnetic calorimeter. Based on numerical technique, the strength and the dynamical properties of EMC are analyzed, which provide theoretical reference for the design of entire structural of EMC. The MDC is composed of the elements with 28 680 pre-stressed high-sensitive wires and during the assembly the wires are stringed layer by layer. The stretching forces of the wires vary continuously and couple with each other in the whole process. The modeling technique with high precision （especially ＂element birth and death＂） is carefully used to study the stress state during the process of assembly. So the variations of the stretching force of the wire are investigated, and several design schemes are evaluated and optimized. The research results have been adopted in the Beijing electron-positron collider＇s new project directly.展开更多
Steering control of a capsule robot in curve environment by magnetic navigation is not yet solved completely.A petal-shaped capsule robot with less steering resistance based on multiple wedge effects is presented,and ...Steering control of a capsule robot in curve environment by magnetic navigation is not yet solved completely.A petal-shaped capsule robot with less steering resistance based on multiple wedge effects is presented,and an optimization method with two processes for determining the orientation of a pre-applied universal magnetic spin vector is proposed.To realize quick and non-contact steering swimming,a fuzzy comprehensive evaluation method for optimizing the steering driving angle is presented based on two evaluation indexes including the average steering speed and the average steering trajectory deviation,achieving the initial optimal orientation of a universal magnetic spin vector.To further reduce robotic magnetic vibration,a main target method for optimizing its final orientation,which is used for fine adjustment,is employed under the constrains of the magnetic moments.Swimming experimental results in curve pipe verified the effectiveness of the optimization method,which can be effectively used to realize non-contact steering swimming of the petal-shaped robot and reduce its vibration.展开更多
文摘Analysis of the International Geomagnetic Reference Field (IGRF) 1900-2000 showsthat the Earth’s main magnetic field has changed dramatically during the 20th century: its dipole moment has decreased by 6.5% since 1900, the strengths of its quadrupole and octupole have increased by 95% and 74%, respectively, four major planetary-scale magnetic anomalies on the Earth’s surface have enhanced by 21%-56%, and the magnetic center has shifted 200 km towards the Pacific Ocean. These time-variation features are similar to the behavior before a geomagnetic polarity reversal.
基金the National Natural Science Foundation of China(Grant Nos.49734140, 49974014).
文摘The method of natural orthogonal components (NOC) is used to analyze the earth抯 main magnetic field IGRF 1900—2000, and the NOC model of the field is established. The first step of the analysis is to calculate eigen modes of the field from the Gauss coefficients of IGRF 1900—2000. Then the magnetic field for each epoch is expanded in a series at the basic function set constructed by the eigen modes, and the intensity coefficients of the eigen modes are calculated. Test of the convergency and stability of the NOC model shows that the model has very short series and much rapid convergency in comparison with the conventional spherical harmonic models of IGRF. Comparison of the eigen modes obtained from different IGRF model groups indicates that the low-degree eigen modes are rather stable, while the high-degree modes show a relatively large variability. The physical meaning of the eigen modes in the NOC model is discussed, and an interesting relationship is found between the spatial structure of the main field and its secular variation.
文摘Under over 50 years' development, Chinese rare earth magnetic industry developed into the global AINiCo, ferrite permanent magnets and NdFeB magnets manufacturing center, and average consumption of magnets per person in China increased to 1.026 tons in 2003 from 0.217 ton in 1990. Although China has been the large producing country of rare earth permanent magnetic materials, to be the strongest one, there are many problems to solve. Main Problems Faced By Chinese Permanent Magnet
基金Supported by National Natural Science Foundation of China(Grant No11472239)Hebei Provincial Natural Science Foundation of China(Grant No.A2015203023)Key Project of Science and Technology Research of Higher Education of Hebei Province of China(Grant No.ZD20131055)
文摘The rotating circular plate is widely used in mechanical engineering, meanwhile the plates are often in the electromagnetic field in modern industry with complex loads. In order to study the resonance of a rotating circular plate under static loads in magnetic field, the nonlinear vibration equation about the spinning circular plate is derived according to Hamilton principle. The algebraic expression of the initial deflection and the magneto elastic forced disturbance differential equation are obtained through the application of Galerkin integral method. By mean of modified Multiple scale method, the strongly nonlinear amplitude-frequency response equation in steady state is established. The amplitude frequency characteristic curve and the relationship curve of amplitude changing with the static loads and the excitation force of the plate are obtained according to the numerical calculation. The influence of magnetic induction intensity, the speed of rotation and the static loads on the amplitude and the nonlinear characteristics of the spinning plate are analyzed. The proposed research provides the theory reference for the research of nonlinear resonance of rotating plates in engineering.
文摘In order to reduce the starting wind speed of the wind wheel and improve the efficiency of the wind wheel, this paper proposes a new type of composite magnetic circuit permanent magnet generator, which changes the relationship between the magnetic induction intensity and the air gap by changing the structure of the main magnetic circuit. The structure greatly improves the air gap sensitivity of the generator, which makes the structural design of the permanent magnet generator easier to implement. Finally, the effectiveness and feasibility of the method are verified by simulation.
基金Project(No.20045006071-27)supported by the Youth Chengguang Project of Science and Technology of Wuhan City of Chinathe Open Foundation of Hubei Key Laboratory of Modern Manufacture Quality Engineering(No.LMQ2005B07).
文摘Wall thickness is always a key index for boiler tube inspection in power plant,in order to improve the inspection efficiency and accuracy,a new method fusing the magnetic and ultrasonic technique was proposed.The magnetic technique was used to do full inspection and locate the flaws,and the ultrasonic was employed to implement further quantitative inspection accu- rately.After comparing the precision of the polynomial,exponential and logarithmic function,the polynomial model was selected to fit the relations between the wall thickness and the peak value of magnetic signals,and the data measured by ultrasonic thickness meter was used to calibrate the model parameters online,the defect depth can be sized quickly.The experimental results demon- grate that the model used in this system has better accuracy than the statistics relation model clearly,and it is also suitable for defect evaluation real-time.Moreover,it is unnecessary to have much more experimental data for the curve fitting technology,so it has better practicability than the other methods.
文摘The electro-magnetic (EM) and acoustic emission (AE) in the fracture process of both dry and wet rock samples including gabbro, granite, sandstone and marble are studied in the experiment in the laboratory under uniaxial pressure. Signals during the test are detected in ultralow frequency band. The experimental results may be outlined as follows: original waveforms of the electro-magnetic radiation (EMR) and AE in the range of 0-20 kHz frequencies are obtained; the EMR's intensity in fracture process is related to some factors as rock type, content of water, fracture intensity of rocks, loading rates and fracture state etc.; the EMR'S rate is proportional to that of AE during fracture statistically. About 70% of maximum values of EMR rate and AE rate are corresponded with each other; furthermore, the EM signals (EMS) are generally more developed and longer duration than AE signals; the principal energy of EMS detected by copper coin antenna as sensor in power spectra are distributed in frequencies lower than 6 kHz and otherwise those detected by EMinduction coil are at about 10 kHz, and in contrast the major energies of AE are in frequencies less than3 kHz; another notable phenomenon is that distinct electro-magnetic signals are detected before AE occurrence. Since EMR and AE signals obtained in the process of rock fracture are better corresponded to eachother, therefore it'S reasonable to propose that the EMR anormalies observed prior to some earthquakes aremainly produced by fractures of rock in source region, as for the EMS occurred before AE may be related topiezoelectric and piezomagnetic effects.
文摘There was elaborated a method for calculating magnetic fields of the Solar System planets. It is based on the quantum theory of electroconductivity of metals and semiconductors. The latter helps to calculate thermoelectrical processes, always taking place in the bowels of “hot” planets. Main elements of those processes are planetary temperature gradients, thermo electromotive force and radially directed thermoelectrical currents, which are associated with Seebeck effect. Thermo electromotive force causes directional movement of planetary thermoelectrical currents both in metal cores and other conductive shells of planets. Those currents are big and they generate magnetic fields of proportional intensity. The capacities of the calculation method were tested while finding the reason why the Jupiter magnetic field is such complicated. As a result it was specified that the source of the main magnetic field of a planet is its metal core and the source of an additional magnetic field is the layer of liquid metal hydrogen. There was also found the third source of a local magnetic field of low intensity along the circular zone of the equatorial region. The conclusion that the Jupiter’s main magnetic field has a polarity opposite to the Earth’s one.
基金Selected from Proceedings of the 7th International Conference on Frontiers of DesignManufacturing(ICFDM'2006)This projects is supported by National Natural Science Fund for Distinguished Young Scholars of China(No.59825117)National Natural Science Foundation of China(No.50175060).
文摘The design and manufacture of the main drift chamber（MDC） and the electro-magnetic calorimeter are most important issues in Beijing electron-positron collider upgraded projects. The whole mass of electro-magnetic calorimeter （EMC） in BESIII is 40 t, thus high stiffness, strength and dynamical properties are required for the design of entire structural of electro-magnetic calorimeter. Based on numerical technique, the strength and the dynamical properties of EMC are analyzed, which provide theoretical reference for the design of entire structural of EMC. The MDC is composed of the elements with 28 680 pre-stressed high-sensitive wires and during the assembly the wires are stringed layer by layer. The stretching forces of the wires vary continuously and couple with each other in the whole process. The modeling technique with high precision （especially ＂element birth and death＂） is carefully used to study the stress state during the process of assembly. So the variations of the stretching force of the wire are investigated, and several design schemes are evaluated and optimized. The research results have been adopted in the Beijing electron-positron collider＇s new project directly.
基金Supported by National Natural Science Foundation of China(Grant Nos.60875064,61175102,51277018)
文摘Steering control of a capsule robot in curve environment by magnetic navigation is not yet solved completely.A petal-shaped capsule robot with less steering resistance based on multiple wedge effects is presented,and an optimization method with two processes for determining the orientation of a pre-applied universal magnetic spin vector is proposed.To realize quick and non-contact steering swimming,a fuzzy comprehensive evaluation method for optimizing the steering driving angle is presented based on two evaluation indexes including the average steering speed and the average steering trajectory deviation,achieving the initial optimal orientation of a universal magnetic spin vector.To further reduce robotic magnetic vibration,a main target method for optimizing its final orientation,which is used for fine adjustment,is employed under the constrains of the magnetic moments.Swimming experimental results in curve pipe verified the effectiveness of the optimization method,which can be effectively used to realize non-contact steering swimming of the petal-shaped robot and reduce its vibration.
