In shallow-water areas,the marine magnetotelluric(MT)method faces a challenge in the investigation of seabed conductivity structures due to electrical and magnetic noises induced by ocean waves,which seriously contami...In shallow-water areas,the marine magnetotelluric(MT)method faces a challenge in the investigation of seabed conductivity structures due to electrical and magnetic noises induced by ocean waves,which seriously contaminate MT data.Ocean waves can affect electric and magnetic fields to different extents.In general,their influence on magnetic fields is considerably greater than that on electric fields.In this paper,a complex adaptive filter is adopted to reduce wave-induced magnetic noises in the frequency domain.The processing results of synthetic and measured MT data indicate that the proposed method can effectively reduce wave-induced magnetic noises and provide reliable apparent resistivity and phase data.展开更多
<span style="font-family:Verdana;">In Nigeria, most welding activities are carried out by road side welders, majority of this welders are ignorant of weld residual stress and its adverse effect on weld...<span style="font-family:Verdana;">In Nigeria, most welding activities are carried out by road side welders, majority of this welders are ignorant of weld residual stress and its adverse effect on weldment. Residual stress (RS) measuring device </span><span style="font-family:Verdana;">is</span><span style="font-family:Verdana;"> vital in the measurement of inherent stresses in material. The aim of this research was to employ proof of principle in analyzing the weld residual stresses in a material. This was achieved by measuring samples with magnetic residual stress device and then subjecting the weld samples to mechanical tensile test with hope that materials with more residual stresses fail first. Finally the result from both procedures w</span><span style="font-family:Verdana;">as</span><span style="font-family:Verdana;"> compared to establish </span><span style="font-family:Verdana;">a </span><span style="font-family:Verdana;">relationship</span><span style="font-family:""><span style="font-family:Verdana;">. Four (4) pieces of mild steel coupons measuring 100 × 40 × 3 mm were welded, producing two specimens, A</span><sub><span style="font-family:Verdana;">11</span></sub><span style="font-family:Verdana;"> and B</span><sub><span style="font-family:Verdana;">11</span></sub><span style="font-family:Verdana;"> of 200 × 40 × 3 mm</span></span><span style="font-family:Verdana;">,</span><span style="font-family:""><span style="font-family:Verdana;"> respectively. The specimens were measured using the Magnetic device developed and 37 signals were obtained per specimen, thereafter, the welded specimens were subjected to tensile testing and results analyzed. From the results obtained, Specimen A</span><sub><span style="font-family:Verdana;">11</span></sub><span style="font-family:Verdana;"> was observed to have the highest signal peak at the weld zone with RS signal of 20.3983 mV compared to B</span><sub><span style="font-family:Verdana;">11</span></sub><span style="font-family:Verdana;"> with 19.358 mV. While under tensile loading, it took 1.63 kN to cause failure to specimen A</span><sub><span style="font-family:Verdana;">11</span></sub><span style="font-family:Verdana;"> and 8.65 kN for specimen B</span><sub><span style="font-family:Verdana;">11</span></sub><span style="font-family:Verdana;">. From this simple experiment, it implies that the Magnetic RS device was able to mimic the behavior of residual stress and also predicted that A</span><sub><span style="font-family:Verdana;">11</span></sub><span style="font-family:Verdana;"> would fail first.展开更多
Effect of ball scribing on magnetic Barkhausen noise (MBN) of conventional grain-oriented (CGO) and high- permeability grain-oriented (HGO) electrical steel was investigated. The results showed that after ball s...Effect of ball scribing on magnetic Barkhausen noise (MBN) of conventional grain-oriented (CGO) and high- permeability grain-oriented (HGO) electrical steel was investigated. The results showed that after ball scribing, root mean square of MBN (MBNrms) of CGO electrical steel increased 9.8% with 4 mm scribing spacing at 1.2 T, and that of HGO electrical steel apparently decreased 17.3% with 16 mm scribing spacing at 1.2 T. Through the formation and development of free magnetic poles and secondary magnetic domains due to compressive stress, primary magnetic domain space of grain-oriented electrical steel becomes smaller, which reflects as a variation of MBN in the macroscopic magnetic properties. Through correlation formula derivation of MBNrms and equilibrium distance between domain walls, effect of domain refinement on grain-oriented electrical steel was also interpreted, and optimum equilibrium distance between domain walls was determined.展开更多
Nuclear magnetic resonance gyroscopes (NMRGs) are a kind of rotation-speed sensor that senses the angular velocity by measuring a frequency shift in the Larmor pre- cession of the nuclear spin in a constant magnetic...Nuclear magnetic resonance gyroscopes (NMRGs) are a kind of rotation-speed sensor that senses the angular velocity by measuring a frequency shift in the Larmor pre- cession of the nuclear spin in a constant magnetic field.展开更多
基金supported by the National Natural Science Foundation of China(Nos.91958210 and 41904075)。
文摘In shallow-water areas,the marine magnetotelluric(MT)method faces a challenge in the investigation of seabed conductivity structures due to electrical and magnetic noises induced by ocean waves,which seriously contaminate MT data.Ocean waves can affect electric and magnetic fields to different extents.In general,their influence on magnetic fields is considerably greater than that on electric fields.In this paper,a complex adaptive filter is adopted to reduce wave-induced magnetic noises in the frequency domain.The processing results of synthetic and measured MT data indicate that the proposed method can effectively reduce wave-induced magnetic noises and provide reliable apparent resistivity and phase data.
文摘<span style="font-family:Verdana;">In Nigeria, most welding activities are carried out by road side welders, majority of this welders are ignorant of weld residual stress and its adverse effect on weldment. Residual stress (RS) measuring device </span><span style="font-family:Verdana;">is</span><span style="font-family:Verdana;"> vital in the measurement of inherent stresses in material. The aim of this research was to employ proof of principle in analyzing the weld residual stresses in a material. This was achieved by measuring samples with magnetic residual stress device and then subjecting the weld samples to mechanical tensile test with hope that materials with more residual stresses fail first. Finally the result from both procedures w</span><span style="font-family:Verdana;">as</span><span style="font-family:Verdana;"> compared to establish </span><span style="font-family:Verdana;">a </span><span style="font-family:Verdana;">relationship</span><span style="font-family:""><span style="font-family:Verdana;">. Four (4) pieces of mild steel coupons measuring 100 × 40 × 3 mm were welded, producing two specimens, A</span><sub><span style="font-family:Verdana;">11</span></sub><span style="font-family:Verdana;"> and B</span><sub><span style="font-family:Verdana;">11</span></sub><span style="font-family:Verdana;"> of 200 × 40 × 3 mm</span></span><span style="font-family:Verdana;">,</span><span style="font-family:""><span style="font-family:Verdana;"> respectively. The specimens were measured using the Magnetic device developed and 37 signals were obtained per specimen, thereafter, the welded specimens were subjected to tensile testing and results analyzed. From the results obtained, Specimen A</span><sub><span style="font-family:Verdana;">11</span></sub><span style="font-family:Verdana;"> was observed to have the highest signal peak at the weld zone with RS signal of 20.3983 mV compared to B</span><sub><span style="font-family:Verdana;">11</span></sub><span style="font-family:Verdana;"> with 19.358 mV. While under tensile loading, it took 1.63 kN to cause failure to specimen A</span><sub><span style="font-family:Verdana;">11</span></sub><span style="font-family:Verdana;"> and 8.65 kN for specimen B</span><sub><span style="font-family:Verdana;">11</span></sub><span style="font-family:Verdana;">. From this simple experiment, it implies that the Magnetic RS device was able to mimic the behavior of residual stress and also predicted that A</span><sub><span style="font-family:Verdana;">11</span></sub><span style="font-family:Verdana;"> would fail first.
基金The financial support of the National Natural Science Foundation of China(Nos.51174057 and 51274062)the National High Technology Research and Development Program (No.2012AA03A503)
文摘Effect of ball scribing on magnetic Barkhausen noise (MBN) of conventional grain-oriented (CGO) and high- permeability grain-oriented (HGO) electrical steel was investigated. The results showed that after ball scribing, root mean square of MBN (MBNrms) of CGO electrical steel increased 9.8% with 4 mm scribing spacing at 1.2 T, and that of HGO electrical steel apparently decreased 17.3% with 16 mm scribing spacing at 1.2 T. Through the formation and development of free magnetic poles and secondary magnetic domains due to compressive stress, primary magnetic domain space of grain-oriented electrical steel becomes smaller, which reflects as a variation of MBN in the macroscopic magnetic properties. Through correlation formula derivation of MBNrms and equilibrium distance between domain walls, effect of domain refinement on grain-oriented electrical steel was also interpreted, and optimum equilibrium distance between domain walls was determined.
基金supported by the National Natural Science Foundation of China(Nos.61673041,61673041,and 61227902)the National High Technology Research and Development Program 863(No.2014AA123401)
文摘Nuclear magnetic resonance gyroscopes (NMRGs) are a kind of rotation-speed sensor that senses the angular velocity by measuring a frequency shift in the Larmor pre- cession of the nuclear spin in a constant magnetic field.