In order to eliminate the influence of the large-amplitude magnetic field noise that has complicated magnetocardio- graphic studies since October 2009, we have performed high-accuracy measurement of the environmental ...In order to eliminate the influence of the large-amplitude magnetic field noise that has complicated magnetocardio- graphic studies since October 2009, we have performed high-accuracy measurement of the environmental magnetic field noise in the vicinity of Beijing Subway Line 4 using a three-component height Tc radio frequency （rf） superconducting quantum interference device （SQUID）. By analysing the spatial form and other characteristics of the time and the fre- quency domains and by calculating the circumferential magnetic field distribution based on a duel-end feeding system model, we reach the following conclusions： （i） the main source of magnetic field noise is the magnetic field generated by thel subway trains, and （ii） the magnetic field interference results mainly from the imbalance between traction current and return rail current that is caused by the leakage current.展开更多
The electromagnetic field of a human heart system is a bioelectromagnetic field. Electrocardiography （ECG） and magnetocardiography （MCG） are both carriers of electromagnetic information about the cardiac system, a...The electromagnetic field of a human heart system is a bioelectromagnetic field. Electrocardiography （ECG） and magnetocardiography （MCG） are both carriers of electromagnetic information about the cardiac system, and they are nonstationary signals. In this study, ECG and MCG data from healthy subjects are acquired; the MCG data are captured using a high-Tc radio frequency superconducting quantum interference device （HTc rf SQUIDs） and the QRS complexes in these data are analysed by the evolutionary spectrum analysis method. The results show that the quality factor Q and the central frequency fz of the QRS complex evolutionary spectrum are the characteristic parameters （CHPs） of ECG and MCG in the time-frequency domain. The confidence intervals of the mean values of the CHPs are estimated by the Student t distribution method in mathematical statistics. We believe that there are threshold ranges of the mean values of Q and fz for healthy subjects. We have postulated the following criterion： if the mean values of CHPs are in the proper ranges, the cardiac system is in a normal condition and it possesses the capability of homeostasis. In contrast, if the mean values of the CHPs do not lie in the proper ranges, the homeostasis of the cardiac system is lacking and some cardiac disease may follow. The results and procedure of MCG CHPs in the study afford a technological route for the application of HTc rf SQUIDs in cardiology.展开更多
Nowadays, the high-critical-temperature radio frequency superconducting quantum interference device （high-Tc rf SQUID） is usually coupled to a dielectric resonator that is a standard 10× 10×1 mm^3 SrTiO3 ...Nowadays, the high-critical-temperature radio frequency superconducting quantum interference device （high-Tc rf SQUID） is usually coupled to a dielectric resonator that is a standard 10× 10×1 mm^3 SrTiO3 （STO） substrate with a YBa2Cu3O7-δ （YBCO） thin-film flux focuser deposited on it. Recently, we have simulated a dielectric resonator for the high-Tc rf SQUID by using the ANSOFT High Frequency Structure Simulator （ANSOFT HFSS）. We simulate the resonant frequency and the quality factor of our dielectric resonator when it is unloaded or matches a 50-Ω impedance. The simulation results are quite close to the practical measurements. Our study shows that ANSOFT HFSS is quite suitable for simulating the dielectric resonator used for the high-Tc rf SQUID. Therefore, we think the ANSOFT HFSS can be very helpful for investigating the characteristics of dielectric resonators for high-Tc rf SQUIDs.展开更多
The ground state of a two-dimensional square superconducting πring array has been investigated. The circulating currents of the π ring array will spontaneously magnetize to the ＇antiferromagnetic＇ arrangement wit...The ground state of a two-dimensional square superconducting πring array has been investigated. The circulating currents of the π ring array will spontaneously magnetize to the ＇antiferromagnetic＇ arrangement with directions of the nearest-neighbouring currents circulating oppositely in the absence of an external magnetic field. It is found that the external magnetic field could destroy the anti-parallel configuration effectively. The external magnetic field needed to destroy the anti-parallel configuration is related to the superconducting π ring＇s inductance parameter β= 2πLIc/Ф0. For a small β the anti-parallel configuration, which is the lowest-energy ground state of the system, will be fully destroyed and changed to the configuration that the circulating currents have the same direction and parallel to the external magnetic field when the magnetic flux reaches Ф0/4 in each ring. Moreover, the magnetic field needed to destroy the anti-parallel configuration will be very small when β is large enough.展开更多
Laser light can induce many effects on the vicinity of the sample surface due to the proximity effects,such as the field enhancement at the surface of a small conducting particle;plasma exchange effect between the met...Laser light can induce many effects on the vicinity of the sample surface due to the proximity effects,such as the field enhancement at the surface of a small conducting particle;plasma exchange effect between the metallic tip and substrate surface.We have observed a new optical tip-sample interaction:laser induced force as the results of light pressure in the near-field region.Under the side illumination of a laser light,an additional attractive force was observed between a dielectric tip and various samples of C60,optical glass,YBa_(2)Cu_(3)O_(7-d)(YBCO)thin film.No such effect was observed in metallic samples.This optical binding force is due to the multiple scattering of light between two close objects.The results are in good agreement with the recent theoretical calculation.The effects of the optical refraction index,thermal expansion of probe tip due to laser radiation are discussed.展开更多
The structural,magnetic and superconducting properties of the Tl_(2)Ba_(2)(Ca_(1-x)Mg_(x))_(2)Cu_(3)O_(y)system with x=0,0.05,0.1,0.15,0.2,0.3,0.4,0.5 were studied.Replacement of calcium by magnesium depresses Tc from...The structural,magnetic and superconducting properties of the Tl_(2)Ba_(2)(Ca_(1-x)Mg_(x))_(2)Cu_(3)O_(y)system with x=0,0.05,0.1,0.15,0.2,0.3,0.4,0.5 were studied.Replacement of calcium by magnesium depresses Tc from 116.3K(x=0)to 93.3K(x=0.5).The critical current also decreases with increasing x.展开更多
基金supported by the State Key Development Program for Basic Research of China (Grant Nos. 2006CB601007 and 2011CBA00106)the National Natural Science Foundation of China (Grant No. 10674006)the National High Technology Research and Development Program of China (Grant Nos. 2007AA03Z238 and 2007AA03Z213)
文摘In order to eliminate the influence of the large-amplitude magnetic field noise that has complicated magnetocardio- graphic studies since October 2009, we have performed high-accuracy measurement of the environmental magnetic field noise in the vicinity of Beijing Subway Line 4 using a three-component height Tc radio frequency （rf） superconducting quantum interference device （SQUID）. By analysing the spatial form and other characteristics of the time and the fre- quency domains and by calculating the circumferential magnetic field distribution based on a duel-end feeding system model, we reach the following conclusions： （i） the main source of magnetic field noise is the magnetic field generated by thel subway trains, and （ii） the magnetic field interference results mainly from the imbalance between traction current and return rail current that is caused by the leakage current.
基金supported by the National Natural Science Foundation of China (Grant No. 607710003)
文摘The electromagnetic field of a human heart system is a bioelectromagnetic field. Electrocardiography （ECG） and magnetocardiography （MCG） are both carriers of electromagnetic information about the cardiac system, and they are nonstationary signals. In this study, ECG and MCG data from healthy subjects are acquired; the MCG data are captured using a high-Tc radio frequency superconducting quantum interference device （HTc rf SQUIDs） and the QRS complexes in these data are analysed by the evolutionary spectrum analysis method. The results show that the quality factor Q and the central frequency fz of the QRS complex evolutionary spectrum are the characteristic parameters （CHPs） of ECG and MCG in the time-frequency domain. The confidence intervals of the mean values of the CHPs are estimated by the Student t distribution method in mathematical statistics. We believe that there are threshold ranges of the mean values of Q and fz for healthy subjects. We have postulated the following criterion： if the mean values of CHPs are in the proper ranges, the cardiac system is in a normal condition and it possesses the capability of homeostasis. In contrast, if the mean values of the CHPs do not lie in the proper ranges, the homeostasis of the cardiac system is lacking and some cardiac disease may follow. The results and procedure of MCG CHPs in the study afford a technological route for the application of HTc rf SQUIDs in cardiology.
基金Project supported by the National Basic Research Program of China (Grant No.2006CB601007)the National Natural Science Foundation of China (Grant No.10674006)+1 种基金the National High Technology Research and Development Program of China (Grant No.2007AA03Z238)the Foundation of the State Key Laboratory of Information Control Technology for Communication System,China (Grant No.9140C1304010803)
文摘Nowadays, the high-critical-temperature radio frequency superconducting quantum interference device （high-Tc rf SQUID） is usually coupled to a dielectric resonator that is a standard 10× 10×1 mm^3 SrTiO3 （STO） substrate with a YBa2Cu3O7-δ （YBCO） thin-film flux focuser deposited on it. Recently, we have simulated a dielectric resonator for the high-Tc rf SQUID by using the ANSOFT High Frequency Structure Simulator （ANSOFT HFSS）. We simulate the resonant frequency and the quality factor of our dielectric resonator when it is unloaded or matches a 50-Ω impedance. The simulation results are quite close to the practical measurements. Our study shows that ANSOFT HFSS is quite suitable for simulating the dielectric resonator used for the high-Tc rf SQUID. Therefore, we think the ANSOFT HFSS can be very helpful for investigating the characteristics of dielectric resonators for high-Tc rf SQUIDs.
文摘The ground state of a two-dimensional square superconducting πring array has been investigated. The circulating currents of the π ring array will spontaneously magnetize to the ＇antiferromagnetic＇ arrangement with directions of the nearest-neighbouring currents circulating oppositely in the absence of an external magnetic field. It is found that the external magnetic field could destroy the anti-parallel configuration effectively. The external magnetic field needed to destroy the anti-parallel configuration is related to the superconducting π ring＇s inductance parameter β= 2πLIc/Ф0. For a small β the anti-parallel configuration, which is the lowest-energy ground state of the system, will be fully destroyed and changed to the configuration that the circulating currents have the same direction and parallel to the external magnetic field when the magnetic flux reaches Ф0/4 in each ring. Moreover, the magnetic field needed to destroy the anti-parallel configuration will be very small when β is large enough.
基金Supported by the National Natural Science Foundation of China under Grant No.19674004。
文摘Laser light can induce many effects on the vicinity of the sample surface due to the proximity effects,such as the field enhancement at the surface of a small conducting particle;plasma exchange effect between the metallic tip and substrate surface.We have observed a new optical tip-sample interaction:laser induced force as the results of light pressure in the near-field region.Under the side illumination of a laser light,an additional attractive force was observed between a dielectric tip and various samples of C60,optical glass,YBa_(2)Cu_(3)O_(7-d)(YBCO)thin film.No such effect was observed in metallic samples.This optical binding force is due to the multiple scattering of light between two close objects.The results are in good agreement with the recent theoretical calculation.The effects of the optical refraction index,thermal expansion of probe tip due to laser radiation are discussed.
文摘The structural,magnetic and superconducting properties of the Tl_(2)Ba_(2)(Ca_(1-x)Mg_(x))_(2)Cu_(3)O_(y)system with x=0,0.05,0.1,0.15,0.2,0.3,0.4,0.5 were studied.Replacement of calcium by magnesium depresses Tc from 116.3K(x=0)to 93.3K(x=0.5).The critical current also decreases with increasing x.
