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A new high-T_c (HT_c) rf SQUID working at around 1.3GHz has been developed to avoid electromagnetic interference such as growing mobile communication jamming. This new system works in a frequency range from 1.23 to 1.42GHz (centred at 1.3GHz), which is not occupied by commercial communication. The sensor used in the 1.3GHz rf SQUID is made of a HT_c coplanar superconducting resonator and a large-area HT_c superconducting film concentrator. We have achieved in the 1.3GHz HT_c rf SQUID system a minimal flux noise of 2.5×10^{-5}Φ_0/\sqrt{Hz} and a magnetic field sensitivity of 38fT/\sqrt{Hz} in white noise range, respectively. The effective area of the concentrator fabricated on a 15×15mm^2 substrate is 1.35mm^2. It is shown that the 1.3GHz rf SQUID system has a high field sensitivity. Design and implementation of 1.3GHz HT_c rf SQUID offers a promising direction of rf SQUID development for higher working frequency ranges. 相似文献
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A new high-T_c (HT_c) rf SQUID working at around 1.3GHz has been developed to avoid electromagnetic interference such as growing mobile communication jamming. This new system works in a frequency range from 1.23 to 1.42GHz (centred at 1.3GHz), which is not occupied by commercial communication. The sensor used in the 1.3GHz rf SQUID is made of a HT_c coplanar superconducting resonator and a large-area HT_c superconducting film concentrator. We have achieved in the 1.3GHz HT_c rf SQUID system a minimal flux noise of 2.5×10^{-5}Φ_0/\sqrt{Hz} and a magnetic field sensitivity of 38fT/\sqrt{Hz} in white noise range, respectively. The effective area of the concentrator fabricated on a 15×15mm^2 substrate is 1.35mm^2. It is shown that the 1.3GHz rf SQUID system has a high field sensitivity. Design and implementation of 1.3GHz HT_c rf SQUID offers a promising direction of rf SQUID development for higher working frequency ranges. 相似文献
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本文研究了一种自建的低成本简易磁屏蔽室及其操控条件,提出了能被高温超导rf SQUID仪器所接受的简易磁屏蔽室,并且运用由该磁屏蔽室和rf SQUID梯度计所构成的组合系统测量了微弱的生物磁信号.研究结果表明,该磁屏蔽室能够有效降低电磁干扰,确保SQUID长时稳定工作,基于该磁屏蔽室的复合MCG测量系统具备捕捉微弱生物磁信号的能力,且所得信号具有可接受的信噪比.这将使得开发一种低造价的实用高温超导MCG测量系统成为现实. 相似文献
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Simulation of dielectric resonator for a high-To radio frequency superconducting quantum interference device
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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. 相似文献
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Simulation of dielectric resonator for a high-T_c radio frequency superconducting quantum interference device
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Nowadays,the high-critical-temperature radio frequency superconducting quantum interference device (high-T c rf SQUID) is usually coupled to a dielectric resonator that is a standard 10 × 10 × 1 mm 3 SrTiO 3 (STO) substrate with a YBa 2 Cu 3 O 7-δ (YBCO) thin-film flux focuser deposited on it.Recently,we have simulated a dielectric resonator for the high-T c 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-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-T c rf SQUID.Therefore,we think the ANSOFT HFSS can be very helpful for investigating the characteristics of dielectric resonators for high-T c rf SQUIDs. 相似文献
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We have studied the basic characteristics of a radio frequency superconducting quantum interference device (rf SQUID) involving two Josephson junctions connected in series, the case for the widely used grain boundary junction (GBJ) rf SQUID. It is found that the SQUID properties are determined mainly by the weaker junction when the critical current of the weaker junction is much lower than that of the other junction. Otherwise, the effect of the other junction is not negligible. We also find that only when the hysteresis parameter β is less than 1-α, where α is the critical current ratio of the two junctions, will the SQUID operate in the nonhysteretic mode. 相似文献
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Mizrach A 《Ultrasonics》2000,38(1-8):717-722
A nondestructive ultrasonic measurement system was developed for the assessment of some transmission parameters which might have quantitative relations with the maturity, firmness and other quality-related properties of avocado and mango fruits. The system utilizes a set of low-frequency probes arranged to measure the ultrasonic signal transmitted and received over a short distance across the peel. The attenuation of the ultrasonic waves, transmitted through the peel and the attached fruit tissue, changes as a result of the progressive ripening and softening of the fruit during the fruiting season and in the course of storage. The present study quantitatively addressed the linkage between the ultrasonic attenuation and the physiological parameters of the flesh of the fruits. Results were obtained in the time and frequency domain, and the data set was analyzed statistically to identify the relations between the major physiological indices and the ultrasonic parameters. Quantitative relations were developed to describe the linkage between ultrasonic parameters and the maturity, firmness and other quality-related properties in mango and avocado fruits. 相似文献
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为了解决图像信号源卡与高速图像记录器实际测试过程中出现的误码较多、图像显示效果不佳等问题,给出了系统组成及原理,并在对发送与接收时序及误码出现原因加以细致分析后,提出了时钟相移与降频等方法对发送端的时序进行优化设计。通过实验对比优化前与优化后发送端的波形图以及数据校验结果,证明了优化后的数据传输更加稳定可靠,大大减少了误码的出现,提高了图像数据的准确率与可靠性。因此该优化方法切实有效,并且对其他高速同步数据的发送与接收具有一定的参考价值。 相似文献
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不同比例有机无机肥配施土壤腐殖质组分的光谱学特征 总被引:3,自引:0,他引:3
以16年长期定位试验为基础,探讨不同比例有机无机肥配施对土壤腐殖质特征的影响。通过分离纯化腐殖质中的胡敏酸(HA)和富里酸(FA)组分,并利用元素分析、红外光谱和核磁共振研究分析了F1(70%化肥+30%有机肥)、F2(50%有机肥+50%化肥)和F3(100%有机肥)三种施肥方式下的HA和FA含量及结构变化。结果表明,F3对于提升HA和FA含量的效果优于F1和F2处理,说明有机肥的施用量越高,土壤腐殖质组分的含量就越高。元素分析表明,不同配比的有机无机肥对HA和FA各元素含量及原子比影响不同。F2和F3都提高了HA的缩合度,降低了氧化度和极性,其中F3的效果更加明显;有机肥的施用还能促进HA中含氮化合物的形成,并且在F2中的效果最好;有机肥的施用同样提高了FA的缩合度而降低了氧化度和极性并促进了含氮化合物的形成,尤其在F2处理中尤为明显。腐殖质红外光谱分析表明,与F1相比,F2和F3提高了HA中脂肪族化合物、碳水化合物物质的含量,FA的羧基基团、脂肪基团含量也增加,且在F3处理中表现最为显著;F2处理则降低了HA中脂肪烃物质的含量,FA中的碳水化合物则达到最高。13C核磁共振波谱分析显示,在三种处理中,有机肥的施用提高了HA和FA的脂化度而降低其芳化度,其中F2处理中HA官能团变化更加显著,FA在F3处理中则变化更加明显。综上所述,有机肥显著提高了土壤腐殖质组分含量,并且提高了HA和FA的脂化度降低其芳化度,但是不同用量有机肥下HA和FA的形成机制不同。 相似文献
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Surface chemistry of nanodiamonds 总被引:2,自引:0,他引:2
I. I. Kulakova 《Physics of the Solid State》2004,46(4):636-643
The experimental data available in the literature and the results obtained by the author in research into the structure of nanodiamonds and the physicochemical and chemical properties of their surface are generalized. An account is given of the problems concerning the chemical state and modification of the nanodiamond surface in gaseous and liquid media and the infiuence of modification on the sorption and catalytic properties of nanodiamonds, their compactibility, and sintering. The similarity and difference in the behavior of nanodiamonds and diamond macrocrystals in oxidation processes are discussed. The activation energies of oxidation of nanodiamonds by different reagents are determined in the absence and presence of catalysts. 相似文献
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We study the interaction with bulk and surface modes of electrons emitted in the proximity of a solid surface. We analyze the modifications in the energy loss, and in bulk and surface plasmon excitations, taking into account the effects due to the sudden creation of the electron and residual atomic hole, and the finite distance to the surface. The process is described using the dielectric function formulation and the specular reflection model. We derive expressions for the electrostatic potential in the medium and in vacuum, which include all the terms due to bulk and surface modes. The effect of each term in the energy loss rate and in the average number of plasmon excitations is discussed. The results illustrate in detail the different spatial dependences of the electron and ion interactions with the bulk and surface perturbations, through the relevant range of distances for studies of electron emission in the proximity of solid surfaces. 相似文献
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通过对Φ42 mm和Φ82 mm口径非球面光学零件精密铣磨成型过程的加工特点和加工误差因素的分析,在工艺中引入刀具与工件变形、刀具半径误差等因素,结合经典Hertz接触理论建立了刀具与工件变形量及刀具半径误差和补偿理论模型,并且应用在精密铣磨成型过程中,通过实验,Φ42 mm口径非球面光学零件经一次精密铣磨成型后元件面形精度PV值为1.91μm,RMS值达到0.288μm;Φ82 mm口径非球面光学零件经一次精密铣磨成型后元件面形精度PV值为1.60μm,RMS值达到0.385μm,完全满足加工精度要求,加工时间节省了50%以上。实验验证了理论分析及误差补偿方法的正确性,实现了精密光学非球面元件的快速精密铣磨成型加工。 相似文献
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A. A. Bush K. E. Kamentsev V. F. Meshcheryakov Y. K. Fetisov D. V. Chashin L. Y. Fetisov 《Technical Physics》2009,54(9):1314-1320
The forward and inverse magnetoelectric (ME) effects are experimentally studied in a two-layer planar structure containing
mechanically coupled Galfenol and PZT plates. The process of production of polycrystalline Galfenol plates and their magnetic
and magnetostriction characteristics are described. For the forward ME conversion, the dependences of the amplitude of the
voltage generated by the structure on the magnitude and orientation of a dc magnetic field and the frequency and amplitude
of a modulating magnetic field are measured. For the inverse ME conversion, the dependences of the amplitude of the change
in the magnetic induction of the structure on the dc magnetic field and the frequency of an ac electric field applied to the
structure are measured. The efficiencies of the forward and inverse ME conversion are estimated for the case of low-frequency
field modulation and under conditions of the resonance excitation of bending and longitudinal mechanical vibrations in the
structure. 相似文献
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大学物理演示实验作为大学物理实验的重要组成部分,逐渐被越来越多的高校重视。本文介绍了大学物理演示实验的作用与特点、大学物理演示实验仪器的DIY制作及大学物理演示实验DIY的实践与探索。本文认为大学物理演示实验对于提高学生大学物理成绩、实验操作能力及在对学生的培养中都具有重要的地位与作用。 相似文献