This paper compares the estimated electromagnetic forces due to short circuits in power transformers using two computational models. The first model is based on approximate analytical expressions of the electromagneti...This paper compares the estimated electromagnetic forces due to short circuits in power transformers using two computational models. The first model is based on approximate analytical expressions of the electromagnetic lbrces as they have been compiled in earlier versions of the IEC standard 60076-5. The second model is based on a finite element model of the transformer using the software FEMM （Finite Element Method Magnetics）. The paper shows how valid the analytical model is for design purposes. Results have been obtained and compared from both models in a number of actual power distribution transformers. It is possible to conclude that the analytical formulation provides satisfactory results for the design of power transformers compared to detailed finite element models. A tool has been designed for this purpose and the main features of it will be described in the paper.展开更多
Removal of milling marks at the root fillet of titanium alloy blade is a tough work because of the interference between the polishing tool and the workpiece.A polishing method based on elastic magnetic tool was propos...Removal of milling marks at the root fillet of titanium alloy blade is a tough work because of the interference between the polishing tool and the workpiece.A polishing method based on elastic magnetic tool was proposed.The software ANSYS Maxwell was used to simulate the effect of different pole orientation arrangements on the magnetic field distribution.A comparison of polishing effect was made between elastic and inelastic magnetic pole carriers.The processing parameters of the elastic magnetic tool polishing for the blade root were optimized by orthogonal experiment(Taguchi)method.Results show that compared with the inelastic magnetic polishing tool,the elastic magnetic polishing tool with polyurethane as the pole carrier can effectively improve the surface quality of the polished workpiece.Under the optimal processing parameters(rotational speed=900 r/min,feeding rate=6 mm/min,machining gap=1.5 mm and abrasive size=10‒14μm),the original milling marks at the blade root are effectively removed and the average surface roughness Ra is dropped from 0.95μm to 0.12μm,which verifies the feasibility of the elastic magnetic polishing tool in the surface finishing of the titanium alloy blade root.展开更多
Magnetic nanoparticles have emerged as a powerful tool for magnetic resonance imaging, biodetection, drug delivery, and hyperthermia. This review focuses on the biological detection of magnetic nanoparticles as well a...Magnetic nanoparticles have emerged as a powerful tool for magnetic resonance imaging, biodetection, drug delivery, and hyperthermia. This review focuses on the biological detection of magnetic nanoparticles as well as their physicochemical properties. Substantial progress in the sensitivity of detection has been made by developing variety of methods. Five applications of magnetic nanoparticles in biological detection are discussed in this review: magnetic separation, magnetic sensing, magnetic manipulation, magnetic catalysis, and signal enhancer for surface plasmon resonance(SPR). Finally, some future trends and perspectives in these research areas are outlined.展开更多
文摘This paper compares the estimated electromagnetic forces due to short circuits in power transformers using two computational models. The first model is based on approximate analytical expressions of the electromagnetic lbrces as they have been compiled in earlier versions of the IEC standard 60076-5. The second model is based on a finite element model of the transformer using the software FEMM （Finite Element Method Magnetics）. The paper shows how valid the analytical model is for design purposes. Results have been obtained and compared from both models in a number of actual power distribution transformers. It is possible to conclude that the analytical formulation provides satisfactory results for the design of power transformers compared to detailed finite element models. A tool has been designed for this purpose and the main features of it will be described in the paper.
基金Joint Funds of the National Natural Science Foundation of China(U20A20293)。
文摘Removal of milling marks at the root fillet of titanium alloy blade is a tough work because of the interference between the polishing tool and the workpiece.A polishing method based on elastic magnetic tool was proposed.The software ANSYS Maxwell was used to simulate the effect of different pole orientation arrangements on the magnetic field distribution.A comparison of polishing effect was made between elastic and inelastic magnetic pole carriers.The processing parameters of the elastic magnetic tool polishing for the blade root were optimized by orthogonal experiment(Taguchi)method.Results show that compared with the inelastic magnetic polishing tool,the elastic magnetic polishing tool with polyurethane as the pole carrier can effectively improve the surface quality of the polished workpiece.Under the optimal processing parameters(rotational speed=900 r/min,feeding rate=6 mm/min,machining gap=1.5 mm and abrasive size=10‒14μm),the original milling marks at the blade root are effectively removed and the average surface roughness Ra is dropped from 0.95μm to 0.12μm,which verifies the feasibility of the elastic magnetic polishing tool in the surface finishing of the titanium alloy blade root.
基金supported by the National Natural Science Foundation of China(2014M561073,51173139)the Program for Young Outstanding Scientists of Institute of Chemistry,and the Chinese Academy of Science(Y41Z011)
文摘Magnetic nanoparticles have emerged as a powerful tool for magnetic resonance imaging, biodetection, drug delivery, and hyperthermia. This review focuses on the biological detection of magnetic nanoparticles as well as their physicochemical properties. Substantial progress in the sensitivity of detection has been made by developing variety of methods. Five applications of magnetic nanoparticles in biological detection are discussed in this review: magnetic separation, magnetic sensing, magnetic manipulation, magnetic catalysis, and signal enhancer for surface plasmon resonance(SPR). Finally, some future trends and perspectives in these research areas are outlined.
