Levitation Performance Study of Bulk HTSC over Monopole PMG Consider Different Cross-Section Configuration with 3D-Modeling Numerical Method

Magnetic levitation force of bulk high temperature superconductors (HTSCs) above monopole permanent magnet guideway (PMG) is simulated using finite element method (FEM). The models are formulated by H-formulation and resolving codes is developed using Finite Element Program Generator (FEPG). The E–J power law is used to describe the electrical field vs. current density nonlinear characteristic of HTSC. By the method, the levitation performance is studied consider different cross-section configure of the monopole PMG. The simulation results show that the maximum levitation force (MLF) of the bulk HTSC will increase when the height/width of the PMG rises while fixing the width/height of the monopole PMG cross-section. The increasing trends to slow when the absolute differential value of the height and the width of the PMG cross-section become larger and larger. For a certain cross-section area of the monopole PMG, the economical levitation cost may be achieved while the ratio of height to width of the cross-section changes between 0.475 and 0.525.     

3D-Modeling Numerical Solution of Guidance Force of HTSC Bulk Above Permanent Magnetic Guideway

This paper presents a 3D-modeling numerical method to simulate the electromagnetic behavior of high-temperature superconductors (HTSC) while the bulk departs from the center line of the guideway. In this paper, for a typical superconducting levitation style with a bulk superconductor suspended above a permanent magnet guideway (PMG), the guidance characteristics of the system were investigated computationally followed by experimental work. Based on the proposed 3D-modeling numerical solutions of electromagnetic behavior of a HTS bulk sample, we used the grid multiplexing technology in which the meshing nodes inside the HTS bulk represent the centers of pinning to simulate flux pinning of HTS bulk. The resolved code of the 3D-modeling of high-temperature maglev was developed with the FORTRAN language. Comparisons between the experimental and numerical results indicated the effectiveness of the method utilized in the paper.     

The Influence on Levitation Force of the Bulk HTSC Above a Permanent Magnet Guideway Operating Dive-Lift Movement with Different Angles

In practical applications, the operating of accelerating or decelerating inevitably happens in the high temperature superconducting (HTS) Maglev train. For the further research of the Maglev properties of bulk high temperature superconductor (HTSC) above a permanent magnet guideway (PMG), by moving a fixed vertical distance, this paper studies the influence on levitation force of the bulk HTSC operating dive-lift movement with different angles. Results show that with the angle increasing, the maximal levitation force decreases when the levitation gap is about 10?mm and the hysteresis is increasing. The hysteresis reaches the largest at first time of back and forth movement, and with the operating times increasing; the hysteresis is almost the same case in the following times of back and forth movements.     

Influence of Maglev Force Relaxation on Hysteresis of Bulk HTSC Above the NdFeB Guideway at Different Lateral Displacements

After the maglev force (both levitation and guidance forces) relaxation property of a high-temperature superconductor (HTS) above a permanent-magnet guideway (PMG) was studied experimentally, the HTS bulk was horizontally moved in the lateral direction with different displacements above the permanent-magnet guideway. Both levitation and guidance force curves with lateral displacement were obtained by a SCML-2 measurement system synchronously. It was found that the levitation force hysteresis after relaxation was reduced compared to the case without relaxation, while the guidance force hysteresis curve almost did not change. This study provided a scientific analysis for the practical application of the bulk HTS.     

Correlations Between Magnetic Flux and Levitation Force of HTS Bulk Above a Permanent Magnet Guideway

In order to clarify the correlations between magnetic flux and levitation force of the high-temperature superconducting (HTS) bulk, we measured the magnetic flux density on bottom and top surfaces of a bulk superconductor while vertically moving above a permanent magnet guideway (PMG). The levitation force of the bulk superconductor was measured simultaneously. In this study, the HTS bulk was moved down and up for three times between field-cooling position and working position above the PMG, followed by a relaxation measurement of 300 s at the minimum height position. During the whole processes, the magnetic flux density and levitation force of the bulk superconductor were recorded and collected by a multipoint magnetic field measurement platform and a self-developed maglev measurement system, respectively. The magnetic flux density on the bottom surface reflected the induced field in the superconductor bulk, while on the top, it reveals the penetrated magnetic flux. The results show that the magnetic flux density and levitation force of the bulk superconductor are in direct correlation from the viewpoint of inner supercurrent. In general, this work is instructive for understanding the connection of the magnetic flux density, the inner current density and the levitation behavior of HTS bulk employed in a maglev system. Meanwhile, this magnetic flux density measurement method has enriched present experimental evaluation methods of maglev system.     

Influence of AC External Magnetic Field on the Levitation Force Relaxation of HTS Bulk Above NdFeB Guideway

In the present High-Temperature Superconducting (HTS) maglev vehicle system, the air gaps between the adjacent permanent magnets make the magnetic fields above the NdFeB guideway non-uniform. So one is required to study the characteristics of levitation force of the HTS bulk influenced by non-uniform fields. In this paper, we have studied the characteristics of the levitation force relaxation by an experiment in which the AC external magnetic field generated by an electromagnet is used to simulate the time-varying external magnetic field caused by the inhomogeneity of the NdFeB guideway. From the experiment results, it is found that the levitation force is attenuated with the application of the AC external magnetic field, and the decay is increased with the amplitude of the AC magnetic field, but the decay is almost independent of the frequency of the AC magnetic field.     

Levitation Force Relaxation of HTS Bulk above NdFeB Guideways at Different Approaching Speeds

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.      

Influence of Thickness on the Levitation Force of High-Tc Bulk over a Permanent Magnetic Guideway with Numerical Method

Levitation forces of a high temperature superconductor (HTS) bulk with a different thickness over a permanent magnet railway (PMR) is studied mathematically. Several cylindrical models of HTS bulk with a diameter of 30 mm and a different thickness over a PMR are researched by the magnetic field vector method (H-method). A 3D-modeling numerical method using finite element method (FEM) is used to simulate the electromagnetic behavior of the models. The thickness of the HTS bulk increases with 1 mm from 4 mm to 15 mm. The simulation results show that the thickness of the HTS bulk and the minigap between the bottom surface of the bulk and the top surface of the PMR have much influence on the levitation forces. With a certain applied magnetic field, there is a certain thickness value of the bulk, which means the levitation force will not increase obviously with the increase of the thickness while the thickness larges the value.     

Numerical Evaluation of Levitation Force Oscillation of HTS Bulk Exposed to AC Magnetic Field over NdFeB Guideway

The levitation force of the YBCO bulk over an NdFeB guideway used in the high-temperature superconducting (HTS) maglev vehicle system is oscillated by the application of the AC external magnetic field. In our previous work, we interpreted that the oscillation is due to the shielding current fluctuation caused by fluctuant external magnetic field. In this paper, based on the Bean model, an analytical model is adopted to evaluate the levitation force. Comparing with the experimental results, the calculated results show good matching. The model can reveal the oscillation characteristics of the levitation force of HTS bulk which is being exposed to AC external magnetic field. Therefore, the levitation force oscillation of the HTS bulk in the maglev vehicle system can be evaluated by this numerical method.     

Relationship of the Levitation Force Between Single and Multiple YBCO Bulks Above a Permanent Magnet Guideway Operating Dive-Lift Movement with Different Angles

In practical applications, the acceleration and deceleration motions inevitably happen in the operation of high temperature superconducting (HTS) maglev trains. For further research of the maglev properties of YBaCuO bulk above a permanent magnet guideway (PMG), by moving a fixed vertical distance, this paper studies the relationship of the levitation force between single and multiple YBCO bulks above a PMG operating dive-lift movement with different angles. Experimental results show that the maximal levitation force increment of two bulks than one bulk is smaller than the maximal levitation force increment of three bulks than two bulks. With the degree decreasing, the maximal levitation force increment of three bulks is bigger than the maximal levitation force increment of two bulks and one bulk, and the hysteresis loop of the levitation force of the three-bulk arrangement is getting smaller.     

Effect of Na-dopant on the Levitation Force of Single Domain YBCO Bulk Superconductors Fabricated by TSMTG Process

Na-doped single domain YBa_2−x Na _x Cu₃O_7−δ (YBCO, x=0.05, 0.1, 0.15, 0.2, 0.25, 0.3) bulk superconductors were prepared by a modified melt textured process and the effect of Na substitution on the levitation force of YBCO bulks have been investigated. The maximum levitation forces (MLF) are much different for samples with a different Na element content. It is found that the optimum Na element content in YBCO for the strong MLF is around x=0.2. It is also found that the addition of Na could reduce and increase the ATH of the YBCO platelet while x less than 0.1 and larger than 0.1, some of adjacent platelet grains are well intergrown each other in the sample with x=0.2 comparing to the other samples and the influence of the Na addition on the Y211 particle size is not obvious.     

Measurement Method to Evaluate the Practical Levitation Force of Onboard Bulk Superconductor in the High-Temperature Superconducting Maglev Vehicle System

As the basic parameter in the design of high-temperature superconducting (HTS) magnet levitation (maglev) vehicle system, the levitation force data are usually obtained by experiments, so a reliable measurement method is needed to know the practical levitation force of onboard bulk superconductor. Considering in the actual operation the vehicle will experience some small vertical or lateral movements, especially during the passenger going on or off the vehicle, the usual measurement method for levitation force, in which force with gap and force relaxation are measured, cannot be able to predict the levitation force change due to the vertical or lateral movements. So a measurement method is presented regarding effects of force with gap, relaxation, vertical and lateral movements. Compared with a former measurement method, the presented method may support more reliable levitation force data for the HTS maglev vehicle design.     

Effect of Y 2 Ba4CuBiO y Nanoparticles Doping on the Levitation Force of Single-Domain YBCO Bulk Superconductor by Top-Seeded Infiltration Process

The top-seeded infiltration and growth process (TSIG) is a very effective method for the preparation of YBa₂Cu₃O_7?x (YBCO) bulk superconductors. In this paper, single-domain YBCO bulk superconductors with different ratio of nanoscale Y₂Ba₄CuBiO _y (YBi2411) inclusions have been fabricated by TSIG process. The growth morphology, microstructure and levitation force of the YBCO bulks have been investigated. The amount of nanoscale YBi2411 added to Y₂BaCuO₅ (Y211) is in the range from 0.5 wt.% to 5 wt.%. It is found that the optimum proportion is obtained in the sample with 3.0 wt.% YBi2411 addition. The results are very helpful for the fabrication of high-quality single-domain YBCO bulk superconductors.     

Magnetic Forces Simulation of Bulk HTS over Permanent Magnetic Railway with Numerical Method

Magnetic levitation forces of bulk high temperature superconductor (HTS) above two types permanent magnet railway (PMR) is simulated using finite element method (FEM). The models are formulated by H-formulation and resolving codes is developed using Finite Element Program Generator (FEPG). The E-J power law is used to describe the electrical field vs. current density nonlinear characteristic of HTS. The applied magnetic fields induced by the PMR are calculated by the standard analysis method with the equivalent surface current model. By the method, the calculation formulation of magnetic fields generated by Halbach PMR and symmetrical PMR is derived respectively. The simulation results show that the finite element dynamic mesh rebuilding problem of HTS magnetic levitation transportation system comprised of bulk HTS and PMR can be easily avoided by the methods.     

Effect of Y2Ba4CuNbO y Additions on the Levitation Force of Single Domain YBCO Bulk Superconductor by the Top-Seeded Infiltration and Growth Process

The top-seeded infiltration and growth process (TSIG) is an important method for the preparation of YBa₂Cu₃O_7?x (YBCO) bulk superconductors. In this paper, single domain YBCO bulk superconductors with different content of nanoscale Y₂Ba₄CuNbO _y (YNb2411) inclusions have been fabricated by TSIG process. The growth morphology, microstructure and levitation force of the YBCO bulks have been investigated. It is found that the levitation force is increasing from 16.2?N to 20.9?N with the increasing of YNb2411 additions from 0?wt% to 2?wt%, and decreasing from 20.9?N to 14.0?N with the increasing of YNb2411 additions from 2?wt% to 5?wt%. The largest levitation force is obtained in the sample with 2?wt% YNb2411 addition. This is closely related with the addition content of YNb2411 nanoparticles and its distribution in the samples.     

Investigation of Heat Transfer of Bulk and Thin-Film PbInTe Samples by the Method of Dynamic Gratings

Journal of Engineering Physics and Thermophysics - Measurements of the thermal diffusivity of thin and bulk indium-doped lead telluride have been taken using a modified method of dynamic gratings....     

三维物探中区域反问题的数值模拟

物理探测中通过测试数据Эu/Эn|ЭΩ=g来确定区域的形状是一个具有挑战性的问题。给出三维情况下的算法和数值模拟，并给出三维的算例，图形和表格，以表明算法的可行性和有效性。     

Numerical and Experimental Investigation of Bearing Capacity for Compressed Stiffened Composite Panel with Different Stringer Section Geometries

Applied Composite Materials - In this paper, the bearing capacity of the compressed stiffened composite panel with I and T stringer section is detailly-investigated. The finite element simulation...     

溶胶–凝胶法制备不同形态的半透明羟基磷灰石陶瓷

为探索制备不同形态半透明羟基磷灰石(T-HA)陶瓷的方法, 采用微米级HA粉体为原料, 甲壳素为粘结剂, 用溶胶–凝胶法制备出球状和纤维状的陶瓷初坯, 然后进行常压烧结得到纯HA陶瓷, 最后经过热等静压烧结得到T-HA陶瓷。溶胶–凝胶法赋形简单, 制备出的球状T-HA陶瓷的球形度良好, 纤维状T-HA陶瓷的纵横比高, 其致密度为99.1%, 平均晶粒尺寸为2.2 μm。其中球状半透明HA陶瓷的抗压强度为10.2 MPa, 高于常规烧结得到的球状致密和多孔HA陶瓷(分别为8.9和4.7 MPa)。仿生矿化和细胞培养的结果显示半透明HA陶瓷具有良好的生物相容性。     

熔盐法制备片状钛酸铋粉体的研究

采用NaCl-KCl熔盐法制备了生长各向异性的片状Bi4Ti3O12粉体.研究了预烧温度及熔盐含量对粉体形貌及显微结构的影响.结果表明,750℃预烧所得Bi4Ti3O12粉体为单一的钙钛矿型结构,随熔盐含量的增加,Bi4Ti3O12粉粒的尺寸及生长的各向异性程度均有所增大,预烧温度的增加也促进了粉粒的生长,获得明显生长各向异性的钛酸铋粉体的最佳预烧温度为950～1000℃.