To achieve high microwave permeability in wide-band for the micron-thick magnetic films,[Fe-Fe_(20)Ni_(80)/Cr]_(n) multilayer structure was proposed by co-sputtering Fe and FeNi to form the magnetic layers and Cr to f...To achieve high microwave permeability in wide-band for the micron-thick magnetic films,[Fe-Fe_(20)Ni_(80)/Cr]_(n) multilayer structure was proposed by co-sputtering Fe and FeNi to form the magnetic layers and Cr to form the interlayers.The multilayer structure contributes to the high permeability by reducing the coercivity and diminishing out-of-plane magnetization.The maximum imaginary permeability of[Fe-Fe_(20)Ni_(80)/Cr]_(n) multilayer film reaches a large value of 800 at 0.52 GHz even though its overall thickness exceeds 1μm.Besides,the magnetic resonance frequency of the multilayer film can be modulated from 0.52 to 1.35 GHz by adjusting the sputtering power of Fe from 0 to 86 W,and its bandwidth for μ’’>200(Δf) is as large as 2.0 GHz.The desirable broad Δf of magnetic permeability,which can be well fitted by the Landau-Lifshitz-Gilbert equations,is due to dual magnetic resonances originated from double magnetic phases of Fe and FeNi that are of different saturation magnetization.The micron-thick multilayer films with high permeability in extended waveband are promising candidate for electromagnetic noise suppression application.展开更多
Simultaneous observations at Zhongshan Station, Antarctica, during May 1-7, 1998 are presented to show the responses of the polar ionosphere to the April/May 1998 solar events. One of the main geo-effects of the solar...Simultaneous observations at Zhongshan Station, Antarctica, during May 1-7, 1998 are presented to show the responses of the polar ionosphere to the April/May 1998 solar events. One of the main geo-effects of the solar events resulted in the major magnetic storm on May 4. At the storm onset on May 2 the ionosphere F2 layer abruptly increased in altitude, the geomagnetic H-component started negative deviation and the spectral amplitude of the ULF wave intensified. Both large isolated riometer absorption and large negative deviation of the geomagnetic H-component occurred at about 0639UT. There was a time lag of about one hour and ten minutes between the storm onset and the IMF southward turning, as measured by the WIND satellite. The polar ionosphere was highly disturbed, as shown by frequent large deviations of the geomagnetic H-component, large riometer absorption events and strong ULF waves in all the courses of the storm. The absorption increased greatly causing the digisonde to be blackout most of the time. However, the data still showed a substantial decrease in the F2 electron density and oscillation of the F2 layer peak height with an amplitude exceeding 200 km.展开更多
AIM： To assess Magnetic resonance colonography with fat enema as a method for detection of colorectal neoplasm.METHODS： Consecutive twenty-two patients underwent MR colonography with fat enema before colonoscopy. Tl...AIM： To assess Magnetic resonance colonography with fat enema as a method for detection of colorectal neoplasm.METHODS： Consecutive twenty-two patients underwent MR colonography with fat enema before colonoscopy. Tl-weighted three-dimensional fast spoiled gradient- echo with inversion recovery sequence was acquired with the patient in the supine position before and 75 s after Gadopentetate Dimelumine administration. Where by, pre and post MR coronal images were obtained with a single breath hold for about 20 s to cover the entire colon. The quality of MR colonographs and patients＇ tolerance to fat contrast medium was investigated. Colorectal neoplasms identified by MR colonography were compared with those identified on colonoscopy and sensitivity of detecting the lesions was calculated accordingly.RESULTS： MR colonography with fat enema was well tolerated without sedation and analgesia. 120 out of 132 （90.9%） colonic segments were well distended and only 1 （0.8%） colonic segment was poor distension. After contrast enhancement scan, mean contrast-to-noise ratio （CNR） value between the normal colonic wall and lumen was 18.5 ± 2.9 while mean CNR value between colorectal neoplasm and lumen was 20.2± 3.1. By Magnetic resonance colonography, 26 of 35 neoplasms （sensitivity 74.3%） were detected. However, sensitivity of MRC was 95.5% （21 of 22） for neoplasm larger than 10 mm and 55.6% （5 of 9） for 5-10 mm neoplasm.CONCLUSION： MR colonography with fat enema and Tl-weighted three-dimensional fast spoiled gradientecho with inversion recovery sequence is feasible in detecting colorectal neoplasm larger than 10 mm.展开更多
In order to eliminate noise interference of metal magnetic memory signal in early diagnosis of stress concentration zones and metal defects, the empirical mode decomposition method combined with the magnetic field gra...In order to eliminate noise interference of metal magnetic memory signal in early diagnosis of stress concentration zones and metal defects, the empirical mode decomposition method combined with the magnetic field gradient characteristic was proposed. A compressive force periodically acting upon a casing pipe led to appreciable deformation, and magnetic signals were measured by a magnetic indicator TSC-1M-4. The raw magnetic memory signal was first decomposed into different intrinsic mode functions and a residue, and the magnetic field gradient distribution of the subsequent reconstructed signal was obtained. The experimental results show that the gradient around 350 mm represents the maximum value ignoring the marginal effect, and there is a good correlation between the real maximum field gradient and the stress concentration zone. The wavelet transform associated with envelop analysis also exhibits this gradient characteristic, indicating that the proposed method is effective for early identifying critical zones.展开更多
基金Funded by the Young Top-notch Talent Cultivation Program of Hubei Provincethe Fundamental Research Funds for the Central Universities(WUT:2021IVA116 and WUT:2021CG015)。
文摘To achieve high microwave permeability in wide-band for the micron-thick magnetic films,[Fe-Fe_(20)Ni_(80)/Cr]_(n) multilayer structure was proposed by co-sputtering Fe and FeNi to form the magnetic layers and Cr to form the interlayers.The multilayer structure contributes to the high permeability by reducing the coercivity and diminishing out-of-plane magnetization.The maximum imaginary permeability of[Fe-Fe_(20)Ni_(80)/Cr]_(n) multilayer film reaches a large value of 800 at 0.52 GHz even though its overall thickness exceeds 1μm.Besides,the magnetic resonance frequency of the multilayer film can be modulated from 0.52 to 1.35 GHz by adjusting the sputtering power of Fe from 0 to 86 W,and its bandwidth for μ’’>200(Δf) is as large as 2.0 GHz.The desirable broad Δf of magnetic permeability,which can be well fitted by the Landau-Lifshitz-Gilbert equations,is due to dual magnetic resonances originated from double magnetic phases of Fe and FeNi that are of different saturation magnetization.The micron-thick multilayer films with high permeability in extended waveband are promising candidate for electromagnetic noise suppression application.
基金the National Natural Science Foundation of China (Grant Nos. 49634160, 40074038) the Major Scientific Project of the Chinese Academy of Sciences (655951-1-305).
文摘Simultaneous observations at Zhongshan Station, Antarctica, during May 1-7, 1998 are presented to show the responses of the polar ionosphere to the April/May 1998 solar events. One of the main geo-effects of the solar events resulted in the major magnetic storm on May 4. At the storm onset on May 2 the ionosphere F2 layer abruptly increased in altitude, the geomagnetic H-component started negative deviation and the spectral amplitude of the ULF wave intensified. Both large isolated riometer absorption and large negative deviation of the geomagnetic H-component occurred at about 0639UT. There was a time lag of about one hour and ten minutes between the storm onset and the IMF southward turning, as measured by the WIND satellite. The polar ionosphere was highly disturbed, as shown by frequent large deviations of the geomagnetic H-component, large riometer absorption events and strong ULF waves in all the courses of the storm. The absorption increased greatly causing the digisonde to be blackout most of the time. However, the data still showed a substantial decrease in the F2 electron density and oscillation of the F2 layer peak height with an amplitude exceeding 200 km.
基金Supported by the Developing Research Programs of Science Technology Commission Foundation of Shanghai,No.34958038
文摘AIM： To assess Magnetic resonance colonography with fat enema as a method for detection of colorectal neoplasm.METHODS： Consecutive twenty-two patients underwent MR colonography with fat enema before colonoscopy. Tl-weighted three-dimensional fast spoiled gradient- echo with inversion recovery sequence was acquired with the patient in the supine position before and 75 s after Gadopentetate Dimelumine administration. Where by, pre and post MR coronal images were obtained with a single breath hold for about 20 s to cover the entire colon. The quality of MR colonographs and patients＇ tolerance to fat contrast medium was investigated. Colorectal neoplasms identified by MR colonography were compared with those identified on colonoscopy and sensitivity of detecting the lesions was calculated accordingly.RESULTS： MR colonography with fat enema was well tolerated without sedation and analgesia. 120 out of 132 （90.9%） colonic segments were well distended and only 1 （0.8%） colonic segment was poor distension. After contrast enhancement scan, mean contrast-to-noise ratio （CNR） value between the normal colonic wall and lumen was 18.5 ± 2.9 while mean CNR value between colorectal neoplasm and lumen was 20.2± 3.1. By Magnetic resonance colonography, 26 of 35 neoplasms （sensitivity 74.3%） were detected. However, sensitivity of MRC was 95.5% （21 of 22） for neoplasm larger than 10 mm and 55.6% （5 of 9） for 5-10 mm neoplasm.CONCLUSION： MR colonography with fat enema and Tl-weighted three-dimensional fast spoiled gradientecho with inversion recovery sequence is feasible in detecting colorectal neoplasm larger than 10 mm.
基金Project(10772061) supported by the National Natural Science Foundation of ChinaProject(A200907) supported by the Natural Science Foundation of Heilongjiang Province, China Project(20092322120001) supported by the PhD Programs Foundations of Ministry of Education of China
文摘In order to eliminate noise interference of metal magnetic memory signal in early diagnosis of stress concentration zones and metal defects, the empirical mode decomposition method combined with the magnetic field gradient characteristic was proposed. A compressive force periodically acting upon a casing pipe led to appreciable deformation, and magnetic signals were measured by a magnetic indicator TSC-1M-4. The raw magnetic memory signal was first decomposed into different intrinsic mode functions and a residue, and the magnetic field gradient distribution of the subsequent reconstructed signal was obtained. The experimental results show that the gradient around 350 mm represents the maximum value ignoring the marginal effect, and there is a good correlation between the real maximum field gradient and the stress concentration zone. The wavelet transform associated with envelop analysis also exhibits this gradient characteristic, indicating that the proposed method is effective for early identifying critical zones.
