共查询到20条相似文献,搜索用时 125 毫秒
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空间微重力环境下几乎无对流和沉降,可为晶体生长提供一个相对稳定和均一的理想环境,易于得到尺寸较大的高质量单晶。但是,空间结晶实验成功率低,费用昂贵,实验机会受限。因此,研发各种空间微重力环境地基模拟技术具有重要意义。目前可用于晶体生长的地基无容器悬浮技术主要有空气动力悬浮、静电悬浮、电磁悬浮、液体界面悬浮、超声悬浮和磁场悬浮技术等。这些地基模拟技术可实现晶体的无容器悬浮生长,避免器壁对晶体生长的不良影响,提高晶体质量,为解决X射线单晶衍射技术中的瓶颈问题提供新途径,还可为在地基进行结晶动力学和机理研究提供简单易行的方法。从技术原理、优势、缺陷及在结晶(特别是蛋白质结晶)中的应用4个方面对这些技术逐一进行了介绍和评述。重点介绍了液体界面悬浮、超声悬浮和磁场悬浮技术这3种用于蛋白质晶体生长的较为成熟的地基无容器悬浮技术。 相似文献
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为实现均匀辐照,ICF靶的无接触支撑是关键。提出用近场声悬浮对ICF靶进行无接触支撑,对悬浮ICF靶丸类微球的压电换能器和悬浮系统进行了初步设计,换能器发射端采用了凹球面结构,利用ANSYS软件对发射端的凹球面结构进行了优化。并构建了近场声悬浮测试系统,对不同直径的钢球在不同工作电压下进行了悬浮实验。实验结果表明:当发射端凹球面直径与钢球直径接近或相等时,悬浮效果是最好的,并且用气动的方式可以实现悬浮钢球的非接触驱动。当工作电压为600V时,钢球的悬浮高度为50μm,扰动振幅为3μm,这说明ICF靶近场声悬浮是可行的。 相似文献
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本工作针对一种新型的电容式力平衡加速度计-微型静电悬浮Z向加速度进行了计算机模拟。模拟中的Z向加速度计拟采用微机械加工技术在硅片上制作,利用静电悬浮原理平衡质量块,感应加速度并输出信号。计算机模拟分析了加速度计的悬浮特性,稳定特性,响应特性。对C-F转换电路的输出特性也进行了分析,该电路可用CMOS工艺集成在加速度传感器的周围。模拟结果表明该加速度计的悬浮特性,稳定特性,响应特性。对C-F转换电路 相似文献
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静电悬浮条件下的材料典型热物理性质测量 总被引:1,自引:0,他引:1
随着对材料研究的逐渐深入,材料制备和材料分析的方法越来越重要,并且一些材料重要的物理性质是开展相关研究的基础。由于一些材料熔点高、难熔化,同时,传统手段无法避免容器壁的污染,或者无法在真空条件下进行试验避免气体的污染,或者由于实验性质原因只能测量特定的材料,这些方法很难测量材料在高温下过热过冷阶段的热物理性质。系统介绍了静电悬浮技术,这是一种新型的实现深过冷的方式,可以达到高温下对材料热物理性质进行测量的目的。静电悬浮技术使样品在两极板间悬浮,在悬浮的状态下采用激光对样品进行加热,使材料达到高温熔化,同时进行热物性的测量。对比了几种实现测量典型热物理性质的方法,了解静电悬浮的优势,并详细地介绍了静电悬浮技术对材料的熔体密度、热膨胀系数、表面张力和粘度系数以及比热的测量。 相似文献
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M. K. Alqadi F. Y. Alzoubi H. M. Al-khateeb N. Y. Ayoub 《Journal of Superconductivity and Novel Magnetism》2008,21(7):415-419
Levitation force between a small superconducting cylinder in the mixed state and a magnetic ring was calculated using the
critical state model. The dependence of the levitation force on the size of the superconductor as well as the magnet was investigated.
The finite size effect of the superconductor is included by demagnetizing factor approximation. The stiffness for the levitating
system was calculated. The position of the maximum levitation force depends on the size of the superconductor and the magnet.
Trend of the calculated force is in agreement with the experimental results.
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Some levitation tests using superconducting coils on superconducting sheets are reported.These tests are used to provide preliminary data for the design of a levitation system for a gravitational antenna. Levitation tests on a small 60 kg bar are also reported. An empirical relation which enables displacement to be predicted as a function of the geometrical size, the weight, and the number of Ampere-turns of the coils is obtained from these tests. 相似文献
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Levitation technologies are used in containerless processing of materials, as microscale manipulators and reactors, and in the study of single drops and particles. Presented here is a method for controlling the amount and polarity of charge on a levitating drop. The method uses single-axis acoustic levitation to trap and levitate a single, initially neutral drop with a diameter between 400 microm and 2 mm. This drop is then charged in a controllable manner using discrete packets of charge in the form of charged drops produced by a piezoelectric drop-on-demand dispenser equipped with a charging electrode. The magnitude of the charge on the dispensed drops can be adjusted by varying the voltage applied to the charging electrode. The polarity of the charge on the added drops can be changed allowing removal of charge from the trapped drop (by neutralization) and polarity reversal. The maximum amount of added charge is limited by repulsion of like charges between the drops in the trap. This charging scheme can aid in micromanipulation and the study of charged drops and particles using levitation. 相似文献
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《低温学》2016
In order to simulate vibration around working points in practical operation of superconducting levitation system, magnet in a simple superconductor-magnet system are conducted reciprocating motions around static height in this study. Two YBCO cylindrical samples with different grain orientations are used to investigate the effect of reciprocating motions of magnet on superconducting magnetic force. The c-axis of sample S1 is perpendicular to the top surface while sample S2 is parallel to the top surface. The initial cooling processes for the superconductors include zero-field-cooled (ZFC) and filed-cooled (FC). Compared to the levitation force before reciprocating motions, the ZFC levitation force at static height becomes smaller after reciprocating while the FC force presents opposite phenomenon. It is found that levitation force at static height tends to be stable after several times of reciprocating under ZFC and FC conditions and its time-decay phenomenon is suppressed in some extent, which is meaningful for the practical application of superconducting levitation system. Based on vortex dynamic, some physical discussions are presented to the experimental results. 相似文献
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W.M Yang L ZhouY Feng P.X ZhangC.P Zhang Z.M YuX.D Tang R NicolskyR Andrade Jr. 《低温学》2002,42(10):589-592
The levitation forces of samples with different grain size have been directly investigated and identified in well-textured YBCO bulks. A single-domain YBCO bulk of ∅30 mm was prepared by a top seeded melt growth process, then divided into two, three and four parts to acquire the levitation forces of samples with different grain size but with completely the same grain orientation. The maximum levitation force for the single-domain sample is about 1.68, 2.05 and 2.4 times higher than that of the samples with two, three, and four grain domains. It is directly confirmed that the levitation force of a single-domain YBCO bulk is much superior than that of samples with multiple domains. It is found that the levitation force is inversely proportional to the total length of grain boundaries of the corresponding sample. 相似文献
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Yujie Qin Yiyun Lu Suyu Wang Jiasu Wang 《Journal of Superconductivity and Novel Magnetism》2009,22(5):511-516
The zero-field cooling levitation force relaxation of the YBCO bulk above two types of NdFeB guideways, which were used in
the high-temperature superconducting maglev vehicle system, was studied experimentally when the bulk moved towards the guideways
at different speeds. In this experiment, a sample with the diameter of 50 mm and thickness of 15 mm was used; the time range
in the relaxation measurements was from 0 s to 200 s. As a result, a nearly linear logarithmic decay of the levitation forces
with time was observed. It was found that the influence of the approaching speeds on the levitation force relaxation is different,
and that the levitation force decay is closely related to the guideway structures. Based on the monopole peak PMG, the approaching
speeds will influence more the levitation force decay than the multipole Halbach. So the maglev vehicle above mutipole Halbach
structure PMG will work more stably than that above the monopole peak PMG.
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《Advanced Powder Technology》2022,33(3):103497
Separation and transportation of powders are important processes in various technological applications. Although mechanical, chemical, or electrical methods can provide possible solutions, operational or environmental constraints may require alternative methods. Spreading and levitation of clusters (aggregates) of fluorinated fumed silica nanoparticles placed under atmospheric pressure on a hot plate is reported. The powder spreading in the chamber continued until the temperature-dependent saturation value of the spot radius, which grew linearly with the temperature. Open space experiments clearly demonstrated levitation of the powder clouds. Qualitative physical analysis of the observed phenomena is suggested. The effect of levitation is explained by the lifting thermo-phoretic force emerging in the Knudsen layer of air. The levitation of the powder under atmospheric pressure becomes possible due to the combination of low adhesion of the fluorinated fumed silica clusters to the substrate, low density of the particles and clusters, and their high specific surface area. 相似文献
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Zhang Jie Zhou Chuande Zheng Fuzhong Lu Shuhua Feng Miao Tang Yike 《Particulate Science and Technology》2019,37(6):737-745
Traveling-wave electric curtain (EC) has been developed for potential application in particle removal/shield on solar panels and other surfaces. Levitation and transport of a particle in a traveling-wave electric field were simulated. Results show that levitation directions/angles and levitation trajectories differ because of the difference in starting positions and starting times. The particles in the two positive acceleration regions are levitated in opposite directions, and the particles distributed on the dielectric surface are levitated and transported successively rather than simultaneously. Movement trajectories are complex and affected by various factors. In the current paper, movement trajectories are modeled to analyze which motion modes are advantageous or disadvantageous to particle removal. This process is beneficial to elucidate the mechanism of particle removal and provide a guidance for movement control by designing appropriate operating parameters. 相似文献
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Qingyong He Jiasu Wang Suyu Wang 《Journal of Superconductivity and Novel Magnetism》2009,22(4):409-415
The loading capacity of the high temperature superconducting (HTS) maglev vehicle is closely relative to the maglev characteristics
of the HTS bulk under the load. The investigation of the characteristics is necessary for the application of the HTS maglev
vehicle. In our previous work, it was found that the levitation force relaxation increased with the increase of the reloading.
In this paper, in terms of a HTS maglev system composed of the permanent magnetic guideway (PMG) and a HTS YBCO bulk, the
levitation force relaxation under different loads is investigated by the numerical calculation and the experiment. It is found
that the normalized relaxation rate of the levitation force increased with the increase of the load. The influence of the
load on the current density distribution is also discussed in this paper. This work might be helpful for the research of the
loading capacity of the HTS maglev vehicle.
相似文献
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H. M. Al-Khateeb M. K. Alqadi F. Y. Alzoubi N. Y. Ayoub 《Journal of Superconductivity and Novel Magnetism》2008,21(2):93-96
Based on the Meissner effect and the image method, we studied the interaction between a magnetic point dipole and a superconducting
sphere. We obtained analytical expressions for the interaction energy and the levitation force when the dipole is in an arbitrary
orientation. Our calculations show the validity of using the image method for a antisymmetrical superconducting sphere-magnet
system. Results show that the energy and the force are maxima when the magnetic dipole is perpendicular to the surface of
superconductor and minima when it is tangent to the surface. Furthermore, the force acting on the tip of a magnetic force
microscope above a superconducting sphere was derived as a generalization of the levitation force acts on a point dipole.
相似文献