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In large caliber gun system, the high speed, high temperature and high pressure gas produced by propellant combustion will cause serious erosion damage to the inner wall of barrel, which will lead to continuous decline of gun performance and termination of the maximum life of barrel. The theories and methods of gun barrel life prediction mainly involve thermodynamics, chemistry, material and machinery science and so on. This paper mainly introduces the main mechanism of gun erosion and the calculation model of gun erosion which involves the numerical solution in internal ballistic combustion process, the heat transfer and erosion calculation of gun barrel. In view of the accurate calculation of parameters such as the temperature of gunpowder gas can more accurately reflect the erosion of inner wall of gun barrel, this paper summarizes the calculation methods of the temperature, thermal physical property parameters and convective heat transfer coefficient of high temperature and high pressure gas in gun barrel. In order to determine the erosion wear quantity and study the effect of heat input on the erosion process of inner wall of gun, erosion experiments are usually required. At present, the common erosion experiments mainly include the measurement of erosion quantity with semi-closed explosive device and the change of surface characteristics of gun steel target with laser pulse heating. By analyzing the criterion of barrel life, the establishment method of barrel life prediction model is studied deeply, and the main barrel life prediction model is introduced, which is convenient to guide engineering application.

A magnetic shielding system combining three-axis active magnetic shielding and a high-Tc superconducting ring (TASR) was developed. The active shield mainly responds to DC field while the ring operates for shielding AC fields below 1 kHz. In this study, the system’s shielding effects were evaluated experimentally, and the results suggest that this system can effectively shield the interference of static and low-frequency magnetic fields to ensure the operation of high-precision magnetic sensors. The shielding factor reached 99.9% for geomagnetic field (DC, 38 500 nT), which exceeded 98% for about 10 000 nT AC magnetic field at 30–1000 Hz. Then, magnetic non-destructive testing of the circuit was performed in this TASR shielding system. The images clearly showed the magnetic field distribution in different kinds of circuits that could be inverted to current density information, indicating that the shielding system can detect circuit defects and has great application potential in integrated circuit diagnosis.

The expression for the radial moments r n c of the nuclear charge density has been discussed under the plane wave Born approximation method recently, which is significant to investigate the nuclear surface thickness and neutron distribution radius. In this paper, we extend the studies of extracting second-order moment r 2 c and fourth-order moment r 4 c from the Coulomb form factors |F C(q)|2 by the distorted wave Born approximation (DWBA) at the small momentum transfer q region. Based on the relativistic mean-field calculations, the DWBA form factors F C D W ( q ) are expanded into q 4, where the corresponding charge distributions are corrected by the contributions of neutron and spin–orbit densities. In the small q region, it is found that the experimental |F C(q)|2 can be well reproduced by considering the contributions of the r 4 c at the small q region. Through further analyzing the second-order and fourth-order expansion coefficients of the F C D W ( q ) , the relationship between the expansion coefficients and proton number Z is obtained. By the relationship, we extract the r 2 c and r 4 c from the limited experimental data of form factors at the small q region. Within the permissible range of error, the extracted r n c are consistent with the experimental data in this paper.

Numerical simulations of pre-cracked concrete subjected to dynamic impact compressive stress wave are carried out via DRFPA (Dynamic Realistic Failure Process Analysis). This code is validated firstly by comparing experimental results. Then, the initiation, propagation and coalescence of wing cracks and secondary cracks are numerically investigated by varying elastic modulus, uniaxial compressive strength, and homogeneity index of some phases (bond and aggregate) of concrete. The numerically simulated concrete failure mode (tension/shear failure) and its development in both quasi-coplanar plane and concrete bridge are analyzed and discussed. Numerical results show that the tension failure occurs firstly whereas shear failure occurs shortly thereafter with continuous dynamic loadings and its reflected wave. Meanwhile, the evolution of wing cracks and secondary cracks are numerically investigated. In addition, the effect of elastic modulus, uniaxial compressive strength, and homogeneity index of concrete phases on the crack evolutions are also studied.

The disc-seal single screw pump (DSSP) used in the field of oily sludge transport has a huge advantage. However, there is no research on the leakage characteristics of the DSSP at present, which makes its application limited. Therefore, the mathematical calculation model of leakage amount of each leakage channel was established in this paper according to the geometric model of the leakage channel. By using this mathematical model, the influence rule of working parameters on the leakage characteristics was analyzed. The results show that the total leakage amount per unit time of the DSSP varies periodically with the rotation of the screw, and the total leakage per unit time of the DSSP will increase with the increase of outlet pressure and screw rotation velocity. When the dynamic viscosity coefficient of the medium increases, the corresponding leakage will be reduced, in which the transmission medium dynamic viscosity is the main factor affecting the total leakage of the DSSP. The study of the leakage characteristics of the DSSP can provide a theoretical basis for the optimal design of its structure in the future.

Single screw compressor (SSC) is a type of rotary compressor with excellent performance. However, under high temperature conditions, the hot deformation of the screw rotor and the star wheel cause the change of the gap of the meshing pairs, which seriously degrades the compressor performance. In order to solve the problem of the gap variation of the meshing pairs, a new hot-state machining method is proposed to study the deformation characteristics of the screw rotor in the hot-state machining process, which provides some reference data for the pre-deformation of the rotor in the machining process. Numerical calculation model of thermal machining process for screw rotor was established by using finite element method. With the validated model, the deformation characteristics in the process of hot working were studied by changing the number of heating holes, diameter of heating holes and temperature of heating holes. Results show that screw rotor deformation will increase with the increase of heat source temperature and diameter, and the deformation distribution of the screw rotor is not significantly affected by the heat source temperature and diameter, but will be more uniform with the increase of heat source quantity. The research work in this paper can provide theoretical basis for hot machining of screw rotor for SSC.

The influence of triaxial deformation γ on the purely collective form of wobbling motion in even–even nuclei is discussed based on the triaxial rotor model. It is found that the harmonic approximation is realized well when the value γ = 30° is adopted for the properties of energy spectra and electric quadrupole transition probabilities, while this approximation gets worse when γ gradually deviates from 30°. Recent data from a Coulomb excitation experiment, namely 3 1 + and 2 2 + for 110Ru, are studied and might be suggested as the bandhead of the wobbling bands. In addition, two types of angular momentum geometries for wobbling motion, stemming from different γ values, are exhibited by the azimuthal plots.

A new and explicit approach is proposed for accurately simulating pseudo-elastic hysteresis loops of any shape in shape-memory alloys (SMAs). For this purpose, new finite strain elastoplastic J2-flow equations are established for modeling finite strain behavior of SMAs. A stress-strain loop of any given shape in each uniaxial loading-unloading cycle is derived exactly from these equations. Then, a new technique is further introduced toward integrating usual piecewise linear splines into a single smooth interpolating function in a unified form. With the proposed equations and technique, test data for SMA hysteresis loops of any shape may be automatically fitted with high accuracy based on a single-parameter identification.

A unified and explicit approach is proposed for accurately characterizing a complex hardening-softening behavior of metals with a tension-compression strength asymmetry. The proposed approach provides an explicit determining of the yield strength as plastic work function and contains the following three procedures: (i) a mode invariant is introduced to express the yield strength as a sum of two uncoupled parts for the tension and the compression case; (ii) a new expression for the plastic work is derived explicitly in terms of the uniaxial stress-strain function and, then, the yield strength function can be determined jointly from the just-mentioned two functions with the axial strain as parametric variable; and, finally, (iii) the axial stress-strain function is presented for representing the hardening-softening features. With these procedures, test data over the entire hardening-softening range can be fitted independently for the tension and the compression cases by directly treating the uniaxial stress-strain function. As such, tedious trial-and-error procedures are bypassed in identifying numerous unknown parameters. Numerical examples show that accurate simulations may be achieved with the proposed approach.

This article presents a direct and efficient algorithm for simulating high-cycle fatigue failure effects within the framework of a recently proposed elastoplastic model, in which fatigue failure effects of metals are incorporated as inherent constitutive features. Toward bypassing very time-consuming procedures in conducting numerical integrations of the elastoplastic rate equations for extremely large number of loading cycles, from the new model it is possible to derive an explicit expression for the fatigue life directly in terms of the stress amplitude. Numerical examples show that the new algorithm thus established is much more efficient than usual direct numerical procedures and that is particularly the case in simulating fatigue failure effects with very high cycle number.

Hydrogenated microcrystalline silicon-germanium (μc-Si1-xGex: H) films were fabricated by plasma-enhanced chemical vapor deposition. The influence of hydrogen dilution on the optoelectronic and crystal structural properties of μc-Si1-xGex: H films were investigated upon alloy composition. Under the relatively low hydrogen dilution condition, the Si atoms of films are easier to crystallize than the Ge atoms, and the dark and photo-conductivity decreased with the Ge concentration because of the reduced crystalline volume fraction of the Si atoms (X Si-Si ) and the increased Ge dangling bond density. However, under higher hydrogen dilution condition, crystallization of the Si atoms decreased while crystallization of the Ge atoms increased with Ge incorporation, and the optoelectronic properties were strongly influenced by the defect density and crystallization of Ge atoms in films.

Full and accurate characterization of metal hardening-softening effects till failure is carried out with a new explicit approach. To this purpose, a new expression for the plastic work is presented explicitly in terms of the uniaxial stress-strain function of any given form. Accordingly, the yield strength as function of the plastic work can be determined jointly from the above functions with the axial logarithmic strain as parametric variable. Using the proposed approach, any test data obtained within the entire stress-strain range with hardening and softening portions up to failure can be fitted by directly treating a suitable form of the uniaxial stress-strain function. This allows one to bypass usual tedious trial-and-error numerical procedures in dealing with nonlinear elastoplastic rate equations for identifying numerous unknown parameters. Accurate simulation results are shown with numerical examples.

The candidate chiral doublet bands in 98Tc with configuration πg9/2 ⊗ νh11/2 are studied theoretically for the first time via the triaxial particle rotor model. The main properties of the doublet bands including the energy spectra and electromagnetic transitions are calculated for different triaxiality parameter γ, and the data in 98Tc can be well described by the calculations with γ = 38°. Based on the analysis of angular momentum components, it is found that the chiral rotational geometry in 98Tc deviates from the ideal chiral picture.

We report a reconstruction method, called a back-projection filtered (BPF) algorithm, for fan beam differential phase contrast computed tomography (DPC-CT) with equidistant geometrical configuration. This work comprises a numerical study of the algorithm and its experimental verification with a three-grating interferometer and an x-ray tube source. The numerical simulation and experimental results demonstrate that the proposed method can deal with several classes of truncated datasets. It could be of interest in future medical phase contrast imaging applications.

The current work envisages the use of Remote sensing,Geography information systems and Global positioning systems literature analysis of precipitation, field investigation and laboratory analysis to perform a comprehensive investigation on the present situation of wetland resources of Pingshan Wetland in Hebei Province. The results showed that there were 5 types of wetlands, including the riverine wetland, flood plain, reservoir and pond, water-conveyance canal, and paddy field, with a total area of 162.61 km2. There were 311 species of wetland higher plants in Pingshan County, including 10 species of bryophytes, 296 angiosperm species, 5 species of ferns, and 81 phytoplankton species. There were 186 wetland birds, 35 species of fish, 5 species of amphibians, 14 species of reptiles, and 19 species of mammals in Pingshan County. In view of the present situation and the threat of wetland in Pingshan County, certain suggestions have been proposed to strengthen the protection and utilization of the wetland.

The criteria for chiral doublet bands based on one particle and one hole coupled to a triaxial rotor have been summarized. Two representative cases in $A\sim100$ odd-odd nuclei, nearly degenerate $\Delta I =1$ doublet bands in $^{104}$Rh and $^{106}$Rh are checked against these chiral criteria. It is shown that $^{106}$Rh possesses better chiral geometry than $^{104}$Rh, although the energy near degeneracy is achieved in $^{104}$Rh in comparison with the constant energy separation of doublet bands in $^{106}$Rh.

Excited states of 123I were populated via the 116Cd(14N, α3n) reaction at 65 MeV. The resultant γ-rays were detected using standard γ-ray spectroscopic techniques with the NORDBALL detector array. Two previously known positive-parity ΔI = 2 sequences have been extended up to 31/2+ and 41/2+. In addition, a number of ΔI = 1 transitions linking the two ΔI = 2 sequences have been observed. It is suggested that both ΔI = 2 sequences are based on a common configuration. This ΔI = 1 band is proposed to be built predominantly on the g7/2[404]7/2+ oblate configuration, based on the energy-level spectra, B(M1)/B(E2) ratios and the theoretical predictions from the particle-rotor model. The previously identified ΔI = 1 rotational band built on the prolate g9/2[404]9/2+ orbital has also been extended to higher spins. Another previously identified but weakly populated ΔI = 1 band is confirmed and is proposed to be built on the d5/2[413]5/2+ configuration with the ground state of 123I as the bandhead.

Undoped and Ce-doped Ba0.5Sr0.5TiO3 (BST) thin films were prepared by pulsed-laser deposition onto a Nb-doped SrTiO3 (STON) substrate. The Ce concentration, ranging from 0.5 to 1.0 at.%, was found to have a strong influence on the electric properties of films at room temperature. We find that, with a positively biased Pt electrode, the leakage current controlled by BST/STON interface can be described by a space-charge-limited-current model. When the Pt electrode is negatively biased, the leakage current controlled by the BST/Pt interface can be explained by the Schottky emission mechanism. In both cases the Ce-doped BST thin films exhibited a lower leakage current (1.2 × 10 −4 and 5.0 × 10 −5 versus 3.4 × 10 −2 Ac m −2 at 450 kV cm −1 ;4 .0 × 10 −4 and 4.0 × 10 −5 versus 6.2 × 10 −3 Ac m −2 at −450 kV cm −1 ) than undoped BST films. The reduction of the leakage current is ascribed to the effect of acceptor Ce 3+ doping, determined by x-ray photoelectron spectroscopy measurement. (Some figures in this article are in colour only in the electronic version)

Since the first successful running of the people-carrying high temperature superconducting (HTS) Maglev test vehicle on 31 December 2000, about 27 000 people have taken it, and the accumulated running distance is about 400 km. The levitation force of the onboard HTS equipment is measured periodically, and new experimental results measured on 5 March 2003 show that the performance of the onboard HTS Maglev equipment is almost the same as that of two years ago. Experimental results indicate that the long-term stability of the HTS Maglev vehicle is good. This further proves the feasibility of the HTS Maglev vehicle for practical transportation. It is worth mentioning that all the results are measured at a low speed; however, investigations of the dynamic performance of the HTS Maglev vehicle at high speed are necessary for practical application. Research on the dynamic performance of the HTS Maglev vehicle is ongoing.

The two key parameters for levitation performance over a permanent magnet (PM) guideway are the levitation force and the stiffness of the high temperature superconductor (HTS) YBaCuO bulk. Their distributions along a lateral displacement (LD) were measured in zero-field-cooling (ZFC) and in field-cooling (FC) conditions. There are two cases of applied magnetic field for a single HTS bulk: symmetrical or unsymmetrical about the bulk axis. Although the levitation force has a linear relationship with the applied field in the symmetrical case, such a linear relationship disappears once the applied field becomes unsymmetrical. Furthermore, the levitation stiffness is measured in FC, and they still change more drastically than the levitation force in ZFC. In particular, the levitation stiffness has a linear relationship with the associated levitation force, whether the applied field is symmetrical or unsymmetrical. Its lateral distribution at a gap of 20 mm in FC agrees with the levitation force distribution at a gap of 10 mm in ZFC.

A single-crystalline Si/SiO2/poly-WSix/Sub-Si structure has been successfully fabricated by a new method incorporating a standard smart-cut® technique and a high temperature reaction between tungsten and silicon. Annealing at 800–1100 °C does not only strengthen the bonding of the wafers but also induces solid phase reaction of deposited tungsten and silicon. A poly-crystalline WSix (1 < x < 2) layer with a tetragonal structure is formed below the buried oxide layer. Cross section images of TEM show three steep interfaces of the four layers. It is found that increasing the annealing temperature is in favour of decreasing the sheet resistance of tungsten silicide and improving the crystal quality of the top silicon layer. However, a spreading resistance profile measurement shows that annealing under high temperature (≥1000 °C) will induce diffusion of tungsten into the Si substrate which is confirmed by the EDX results and the reason is presented.

In this paper, we report optical studies of nitrogen doped ZnSe epilayers grown by molecular beam epitaxy. Photoluminescence spectra of the donor-acceptor pair region at different temperatures and different carrier concentrations show that two donors are present in the samples, residual shallow donors with activation energy 26 meV and deep donors with activation energy of 46 meV previously assigned to a VSe-Zn-NSe complex. In the exciton region we observe a new emission at 2.765 eV and the intensity increases when the epilayer is compensated by the deep donor. We therefore propose that this transition is related to a deep donor bound exciton. Excitation power dependent photoluminescence measurements show the presence of two deep transitions separated by 23 meV at low excitation intensities which we propose are due to deep donor-acceptor pairs.

In this paper we demonstrate, for the first time, that photovoltage spectroscopy (PVS) with an aqueous electrolyte/semiconductor contact can be extended to the wavelength range of 1-2 mu m by using an optical fibre which comes directly into contact with the semiconductor, thus avoiding the strong absorption by the electrolyte which occurs in this spectral range. This technique is illustrated for lattice-matched In1-xGaxAs grown on InP having a bandgap of 0.74 eV corresponding to lambda g=1.67 mu m. Thus, carrier and composition depth profiling can be carried out on ternary and quaternary alloys used for 1.3 mu m and 1.5 mu m optoelectronic devices.

In this paper, we extend our previous work of classical over barrier ionization (COBI) model to study the multipleionization and mean charge state of noble gases colliding with heavy ions at energies close to the Bragg peak region ranging up to some hundreds of keV/amu. The method we report is in good agreement with experimental data and offers the advantage of very small computation time. Therefore, this model will be extremely helpful to be included in numerical codes to calculate the charge state distribution in plasma.

The authors report the use of an electrochemical iodine cell to dope epitaxial ZnSe grown by molecular beam epitaxy over a range of carrier concentrations from 1016 to 1019 cm-3. The doping levels throughout the layers have been measured by electrochemical CV profiling and staircase doping structures have been used to calibrate the doping level in terms of the cell flux. Photoluminescence and Hall data confirm the growth of well-behaved n-type ZnSe.

Epitaxial La0.8Ca0.2MnO3 (LCMO) thin films with varied thicknesses were successfully grown on 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) substrates with pulsed-laser deposition. Due to a large lattice mismatch between LCMO and PMN-PT, in-plane tensile strain was introduced into the LCMO layers. The tensile strain could be controlled by varying the layer thickness of LCMO. It was found that the in-plane tensile strain in LCMO layers could enhance the electroresistance (ER) effect significantly. A maximum value of ER ((R10??A?R1?mA)/R10??A?100%) was found to be ~80% in a 10?nm thick LCMO film that suffered a 2.21% in-plane tensile strain. The mechanism for the impact of strain on the ER effect is discussed within the framework of the electron-lattice coupling and the phase separation scenario.

Accurate measurement of specific absorption rate (SAR) is essential for quantifying the power dissipation of magnetic nanoparticle suspensions in alternating magnetic fields, which have applications in cancer hyperthermia. Current SAR measurement setups usually comprise a coil surrounding a container holding the sample fluid. The temperature rise of the magnetic fluid is recorded once the field is turned on and SAR is determined from the initial slope of the temperature as a function of time. However several factors, including volume of the fluid sample, thermal properties of the container, positioning of the temperature sensor and non-uniformities in the magnetic field induced by the sample and coil geometry, may influence the reported SAR. To illustrate these effects theoretical and experimental investigations are carried out. The results show that the SAR measured on samples of relatively small volume may be subjected to errors associated with conductive heat losses to the container holding the sample. Numerical simulations also show that the fluid experiences internal convection during heating, which dictates the positioning of the temperature sensor. Moreover, the heat generation is shown to depend on sample geometry because this has an effect on the magnetic flux passing through the sample. Since SAR is proportional to squared field strength, small differences in the magnetic field may result in large differences in SAR. The findings reported here are also relevant to the measurement of power dissipation in capacitively coupled, radio-frequency heating of metallic nanoparticles.

We have deposited La0.8Ca0.2MnO3 (LCMO) thin films onto a 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) single-crystal substrate to construct field effect devices and investigated the electric-field–induced strain and polarization effects on the structure, magnetic, and transport properties of LCMO films. LCMO not only exhibits the usual insulator-metal transition associated with the onset of ferromagnetic state, but also a lower-temperature metal-insulator transition due to charge/orbital order. Especially, the latter transition can be modulated reversely and continuously by electric fields, leading to a large electroresistance in LCMO films (ΔR/R(0) of ~70% at 50 K). Such phenomenon could be explained based on the coactions of the piezoelectric effect and the ferroelectric-field polarization effect, which could ultimately tailor the strain and density of charge carriers in LCMO films.

The spatial pulse profile makes experimental values of Two-and three photon absorption (TPA and 3PA) coefficient deviate from its true value. We report an approach taking account of the influence of pump laser pulse profile on the nonlinear absorption coefficients (NAC) in Z-scan technique. We developed a new approach in which the factor (f factor) introduced to describe the influence coming from the spatial profile of laser on two and three photon absorption coefficient. The approximation of the approach is also estimated quantitatively. With Gaussian beams the numerically related results show that, compared with NAC based on the way dealing with the pulse in usual Z-scan, the relative differences of 2-photon and 3-photon absorption coefficients obtained based on the traditional one are less than 4.2% and 16.7%. The results suggest that the factor may become useful and simple parameters in dealing with the NAC deviation resulting from the pump laser pulse envelopes for the purpose of shortcutting the Z-scan datum process.

The secular equation of medium coating were obtained by considering the particularity of THz, which had some reference value in designing of THz waveguides. The attenuation of medium coating metal hallow waveguides were theoretically calculated, the conclusion is that the power loss is less than the metal waveguides. Also we obtained the mode characters and attenuation in metal waveguides, and we noted that there exists an absorption peak. And we studied the affection of shape and size on propagation and got some useful conclusion. The split rectangular waveguide (SRW) is suitable for THz transmission which is confirmed by experiment. Our secular equation can be considered to be a theoretically discussion on it.

Thrust measurements were performed on a coil made of YBa2Cu3O7-d coated conductor acting as the excitation system of a single-sided linear synchronous motor. The superconducting coil was a single pancake in the shape of a racetrack with 100 turns, the width and effective lengths were 42 mm and 84 mm, respectively. The stator was made of conventional copper wire. At 77 K and a gap of 10 mm, with an operating direct current of I_DC=30 A for the superconducting coil and alternating current of I_AC=9 A for the stator coils, thrust of 24 N was achieved. With addition of an iron core, thrust was increased by 49%. With addition of an iron back plate, thrust was increased by 70%., Comment: 9 pages, 4 figures

In order to improve the performance of the present high temperature superconducting (HTS) maglev vehicle system, the maglev performance of single- and double-layer bulk high temperature superconductors (HTSC) was investigated above a permanent magnet guideway (PMG). It is found that the maglev performance of a double-layer bulk HTSC is not a simple addition of each layer's levitation and guidance force. Moreover, the applied magnetic field at the position of the upper layer bulk HTSC is not completely shielded by the lower layer bulk HTSC either. 53.5% of the levitation force and 27.5% of the guidance force of the upper layer bulk HTSC are excited in the double-layer bulk HTSC arrangement in the applied field-cooling condition and working gap, bringing a corresponding improvement of 16.9% and 8.8% to the conventional single-layer bulk HTSC. The present research implies that the cost performance of upper layer bulk HTSC is a little low for the whole HTS maglev system.

In order to improve the cost performance of the present high-Tc superconducting (HTS) Maglev vehicle system for practical application, the multi-pole permanent magnet guideway (PMG) concept was introduced. A well-known double-pole Halbach PMG was chosen as a representative of multi-pole PMGs to compare with traditional monopole PMGs from the point of view of levitation efficiency and cost. Experimental results show that YBCO bulks above the double-pole Halbach PMG can exhibit better load capability and guidance performance as well as dynamics stability at the applied working height between the bulk HTSC and the PMG due to a more reasonable magnetic field distribution at the working range of bulk HTSC. Furthermore, the double-pole PMG configuration can play a more important role in improving guidance performance due to the potential-well field configuration. By comparing with former 'century' PMGs, the double-pole Halbach PMG shows another remarkable advantage in reducing the cost of levitation. As another necessary issue, magnetic field homogeneity and the corresponding magnetic drag force of a double-pole Halbach PMG has been considered by experiment in spite of the above highlights. Synthetically, the multi-pole Halbach PMG design is concluded to be one important choice for future HTS Maglev vehicle applications because of its high efficiency and low cost.

A magnetic levitation vehicle using bulk high-Tc superconductors (HTSC) is considered as a promising transportation type thanks to its lateral inherent stability, but previous studies have found that the levitation force (LF) decays due to lateral movement. In this paper, a pre-load method is presented to reduce the LF decay, and the experimental results indicate that this method is very applicable in supressing this decay in spite of the applied field and material property of the bulk HTSC, and this effect can be ascribed to the reduction of the hysteresis loss in the bulk HTSC, i.e. more trapped magnetic flux after the pre-load case. In the end, experimental results indicate that the Halbach PMG has an advantage to reduce the cost of the PMG, but its rate of LF decay is also larger due to lateral movement

A linear dynamic model is established for the stable rotor-spun composite yarn spinning process. Approximate oscillating frequencies in the vertical and horizontal directions are obtained. By suitable choice of certain processing parameters, the mixture construction after the convergent point can be optimally matched. The presented study is expected to provide a general pathway to understand the motion of the rotor-spun composite yarn spinning process.

The bulk high temperature superconductors (HTSCs) with unique flux-pinning property have been applied to fabricate two superconducting axial bearings for an energy storage flywheel model. The two superconducting axial bearings are respectively fixed at two ends of the vertical rotational shaft, whose stator is composed of seven melt-textured YBa2Cu3O7-x (YBCO) bulks with diameter of 30 mm, height of 18 mm and rotor is made of three cylindrical axial-magnetized NdFeB permanent magnets (PM) by superposition with diameter of 63 mm, height of 27 mm. The experimental results show the total levitation and lateral force produced by the two superconducting bearings are enough to levitate and stabilize the 2.4 kg rotational shaft. When the two YBCO stators were both field cooled to the liquid nitrogen temperature at respective axial distances above or below the PM rotor, the shaft could be automatically levitated between the two stators without any contact. In the case of a driving motor, it can be stably rotated along the central axis besides the resonance frequency. This double-superconducting axial bearing system can be used to demonstrate the flux-pinning property of bulk HTSC for stable levitation and suspension and the principle of superconducting flywheel energy storage system to visitors.

We report the results of the electrical resistivity and Seebeck coefficient as well as thermal conductivity measurements on the stoichiometric CaAl(2)Si(2) and non-stoichiometric CaAl(1.75)Si(2.25), CaAl(1.9)Si(2.1), CaAl(2.1)Si(1.9), and CaAl(2.25)Si(1.75) compounds in the temperature range 10-300 K. It has been found that the magnitude of electrical resistivity decreases for the non-stoichiometric samples, attributed to the shift of Fermi energy from the dip of the density of states as a consequence of the changed Si/Al content. In addition, a systematic change in the magnitude of Seebeck coefficient as a function of Al/Si concentration has been observed. The results have been associated with the effect of hole/electron doping on the Fermi level density of states. A detailed analysis of the electrical resistivity and Seebeck coefficient suggests the presence of two types of charge carrier and the temperature dependent changes in their mobility. From the thermal conductivity results, we correlated the extent of disorder and Al/Si ratio with various thermal scattering mechanisms in the investigated temperature range.