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A novel upconversion nanoprobe for detecting ascorbic acid is developed, and the photostability of dye-sensitized UCNPs is greatly enhanced.

International audience; Thermal effect will greatly affect the engineering performance of high-temperature superconductors (HTSs) due to its strong dependence of electromagnetic parameters upon the local temperature. To advance the understanding of such thermal effects, a validated 3-D strong-coupled electromagnetic-thermal model for HTS bulk was established in commercial finite-element software COMSOL, which ensures the easy access and universality of the model. Jc(B,T) was employed to reflect both magnetic field and thermal field dependences of HTS in this model. In addition, the thermal transient equation and convective boundary condition were employed with experimentally measured HTS thermal conductivity and heat capacity to describe the thermal flux exchange between HTS and cryogenic medium. As an example of application, the established electromagnetic-thermal model was tailored to study the dynamic characteristics of a linear HTS magnetic levitation (maglev) bearing. The methodologies to numerically study the dynamic response of the linear HTS maglev bearing under free vibration state and typical operating excitations, e.g., earthquake, track irregularity, and crosswind, were put forward in this article. The influences of field cooling height, preload, and ambient temperature, were also studied, and promising methods to improve the system stability were put forward according to the obtained conclusions. The above-mentioned results are reasonable and keep in concert with former experimental and theoretical studies. Moreover, some results which are inaccessible in the 2-D models, for instance, the thermal field distribution inside HTS bulk, can also be obtained due to the versatility of the 3-D model. To conclude, the established HTS electromagnetic-thermal model could serve as a flexible and extensible simulation tool to study various applications of HTS bulk. Besides the application in linear HTS maglev bearing, which was systematically studied in this article, other potential applications such as thermal analysis of HTS bulk in pulse magnetization process, HTS bulkbased electrical machines, can also be expected in future work.

The linear superconducting magnetic bearing (SMB) discussed in this article consists of a high-temperature superconducting bulk of YBaCuO and a permanent magnet rail to provide the excitation magnetic field. The dynamics of SMB is vital to engineering applications; however, previous experimental and theoretical explorations on dynamic behaviors of linear SMB only provide qualitative analysis, because of limited experimental conditions and approximated analytical models. Furthermore, the pulsed and harmonic excitations have not been taken into account in the published numerical works on the dynamics of linear SMB. In this article, a two-dimensional (2-D) model of the linear SMB was introduced and coupled with the 2-D motion second-order equations with respect to time, to simulate the dynamic behaviors in the vertical and lateral directions. Under the external excitations, the displacements in time and frequency domains, phase trajectories, and motion trajectories are presented in the vertical and lateral directions to discuss the effects of pulsed and harmonic forces on the dynamic characteristics of linear SMB. It turns out that the 2-D model with ease of implementation can provide a utile tool for analyzing the dynamics of linear SMB, and the numerical results, inaccessible through simplified analytical models, provide the quantitative dynamic characteristics and principles for applications of linear SMB.

A new lignan, arborlignan A, along with five known substances, neoechinulin A, 4-hydroxy-3,5-dimethoxybenzaldehyde, 3,3′-dimethoxy-4,4′-dihydroxystilbene, β-hydroxypropiovanillone, and coniferyl aldehyde, are isolated from Schefflera arboricola. Their structures are elucidated by mass spectrometry and nuclear magnetic resonance spectroscopy experiments and by comparison with literature data. These compounds are isolated from the genus Schefflera for the first time.

This study aimed to determine the effectiveness of comprehensive rehabilitation for patients with aneurysmal subarachnoid hemorrhage (aSAH) and to explore the factors influencing the prognosis of rehabilitation. This was a retrospective study. Twenty-five patients with aSAH were treated with physical therapy, occupational therapy, speech therapy, cognitive therapy, music therapy, Chinese acupuncture, hyperbaric oxygen, and transcranial magnetic stimulation. The general data of all patients were collected, and the functional scores at admission were compared with those at discharge. The Mini Mental State Examination, Fugl-Meyer Assessment Scale (FMAS) for motor and balance assessment, Holden Functional Ambulation Classification (FAC), modified Rankin Scale, National Institute of Health Stroke Scale, Modified Barthel Index for activities of daily living (ADL), and Glasgow Outcome Scale were significantly improved among 25 patients with aSAH after 1 month of comprehensive rehabilitation training. Hydrocephalus was an independent factor of the ability to perform ADLs (odds ratio, 0.29; 95% confidence interval, 2.03. 3.15; p = 0.000). The improvement of ADLs in aSAH patients was not related to sex, surgical method, aneurysm location, age, or smoking status. Comprehensive and professional rehabilitation is effective for the cognition, movement, walking, ADLs, and functional prognosis of patients with aSAH, while early hydrocephalus may be a risk factor for poor ADLs.

Fast radio bursts (FRBs) are extremely strong radio flares lasting several milliseconds, most of which come from unidentified objects at a cosmological distance. They can be apparently repeating or not. In this paper, we analyzed 18 repeaters and 12 non-repeating FRBs observed in the frequency bands of 400-800 MHz from CHIME. We investigated the distributions of FRB isotropic-equivalent radio luminosity, considering the K correction. Statistically, the luminosity distribution can be better fitted by Gaussian form than by power-law. Based on the above results, together with the observed FRB event rate, pulse duration, and radio luminosity, FRB origin models are evaluated and constrained such that the gamma-ray bursts (GRBs) may be excluded for the non-repeaters while magnetars or neutron stars (NSs) emitting the supergiant pulses are preferred for the repeaters. We also found the necessity of a small FRB emission beaming solid angle (about 0.1 sr) from magnetars that should be considered, and/or the FRB association with soft gamma-ray repeaters (SGRs) may lie at a low probability of about 10%. Finally, we discussed the uncertainty of FRB luminosity caused by the estimation of the distance that is inferred by the simple relation between the redshift and dispersion measure (DM)., 12 pages, 2 figures, 2 tables. Accepted in Research in Astronomy and Astrophysics (RAA)

The properties of the young pulsars and their relations to the supernova remnants (SNRs) have been the interesting topics. At present, 383 SNRs in the Milky Way galaxy have been published, which are associated with 64 radio pulsars and 46 pulsars with high energy emissions. However, we noticed that 630 young radio pulsars with spin periods of less than half a second have been not yet observed the SNRs surrounding or nearby them, which arises a question of that could the two types of young radio pulsars with/without SNRs hold distinctive characteristics? Here, we employ the statistical tests on the two groups of young radio pulsars with (52) and without (630) SNRs to reveal if they share different origins. Kolmogorov-Smirnov (K-S) and Mann-Whitney-Wilcoxon (M-W-W) tests indicate that the two samples have the different distributions with parameters of spin period ($P$), derivative of spin period ($\dot P$), surface magnetic field strength ($B$), and energy loss rate ($\dot E$). Meanwhile, the cumulative number ratio between the pulsars with and without SNRs at the different spindown ages decreases significantly after $\rm10-20\,Kyr$. So we propose that the existence of the two types of supernovae (SNe), corresponding to their SNR lifetimes, which can be roughly ascribed to the low-energy and high-energy SNe. Furthermore, the low-energy SNe may be formed from the $\rm8-12\,M_{\odot}$ progenitor, e.g., possibly experiencing the electron capture, while the main sequence stars of $\rm12-25\,M_{\odot}$ may produce the high-energy SNe probably by the iron core collapse., Comment: 8 pages, 10 figures, 3 tables. Published in MNRAS

Based on the detected spin periods ( $P$ ) and inferred magnetic field strengths ( $B$ ) by the cyclotron resonance scattering features, we analyze the $B-P$ properties of Be/X-ray Pulsars (BeXPs). We find that the $P$ distribution of BeXPs exhibits a bimodal feature separated at $P\sim 40$ s, where the average spin period of the BeXPs with $P>40$ s ( $\langle P\rangle \sim 267$ s) is larger than that of the sources with $P

Fast Radio Bursts (FRBs) are the short, strong radio pulses lasting several milliseconds. They are subsequently identified, for the most part, as emanating from unknown objects at cosmological distances. At present, over one hundred FRBs have been verified, classified into two groups: repeating bursts (20 samples) and apparently non-repeating bursts (91 samples). Their origins, however, are still hotly debated. Here,we investigate the statistical classifications for the two groups of samples to see if the non-repeating and repeating FRBs have different origins by employing Anderson-Darling (A-D) test and Mann-Whitney-Wilcoxon (M-W-W) test. Firstly, by taking the pulse width as a statistical variant, we found that the repeating samples do not follow the Gaussian statistics (may belong to a chi-square distribution), although the overall data and non-repeating group do follow the Gaussian. Meanwhile, to investigate the statistical differences between the two groups, we turn to M-W-W test and notice that the two distributions have different origins. Secondly, we consider the FRB radio luminosity as a statistical variant, and find that both groups of samples can be regarded as the Gaussian distributions under the A-D test, although they have different origins according to M-W-W tests. Therefore, statistically, we can conclude that our classifications of both repeaters and non-repeaters are plausible, that the two FRB classes have different origins, or each has experienced distinctive phases or been subject to its own physical processes., Comment: 7 pages, 5 figures, 3 tables. Accepted for publication in MNRAS

Polysaccharides, common components of natural products extensively studied as dietary supplements and functional foods, have been found to have various activities. In the present study, a water-soluble polysaccharide, namely GBSP3a, was isolated and purified from G. biloba sarcotesta. The anti-inflammatory activity of GBSP3a in lipopolysaccharide (LPS)-induced RAW264.7 macrophages and the potential underlying molecular mechanisms were then assessed. RESULTS GBSP3a exerted its anti-inflammatory effect by remarkably inhibiting the secretion of pro-inflammatory mediators and cytokines, including nitric oxide (NO), prostaglandin E2 (PGE2), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1? (IL-1?) in LPS-stimulated RAW264.7 macrophages. Excessive mRNA and protein expression levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were dose-dependently inhibited by GBSP3a in LPS-stimulated RAW264.7 cells. Further research suggested that the anti-inflammatory effect of GBSP3a can be attributed to the modulation of the NF-?B and MAPK signaling pathways. CONCLUSION GBSP3a exhibits anti-inflammatory activity and exerts its anti-inflammatory effect probably through suppressing both NF-?B and MAPK signaling pathway, indicating that GBSP3a could be used for the development of anti-inflammatory agent or nutraceuticals. ? 2018 Society of Chemical Industry

In this work, we experimentally investigated the dynamic responses of stacked coated conductor tapes that were levitated over an Nd-Fe-B magnet guideway. The experiments were carried out on a recently designed test rig that can simultaneously measure the acceleration and levitation force during a vibration process. We applied three typical excitations, viz., unloading, free fall, and pulsed excitation. The attenuation coefficient and damping ratio of such stack-based maglev system were analyzed by means of free vibration attenuation method. Last, the dynamic response of mechanical components of the stack-based maglev on pulsed excitation was visualized clearly. Results obtained by this study tell us that the damping ratio is relative to the intensity of external disturbance, which means a weak excitation will cause a small damping ratio and a longer convergence time; however, a larger damping ratio and a faster convergence of vibration will be presented when a stronger stimulation is imposed on. This phenomenon could be contributed by the metal components of the stack, and is promising in practical application, particularly, in construction of HTS maglev where a large damping ratio is required.

Addressing the impact of quantization error in analog-to-digital converter (ADC) for signal processing, a Discrete Fourier Transform (DFT) based method for the generation of dithering signals is presented. Effective in reducing quantization error, the dithering signal generated using the method is not only independent of the input signal but also can improve the performance of the ADC. To illustrate the advantages of the dithering signal reconstructed using the method, three kinds of typical dithering effects, namely, Triangular Distribution Dithering, Gaussian Distribution Dithering and Uniform Distribution Dithering on the quantization error in an ADC are considered. The properties of three practical dithering signals are investigated. It is shown that while these typical dithering may be useful they are some potential problems. The dithering signals reconstructed using the DFT based generation scheme is shown to contribute significantly to reducing quantization error. Numerical experiments and theoretical analyses demonstrate that the DFT based dithering reconstruction can obtain prominent performance for ADC in comparison to typical dithering signals.

Multiseeded YBaCuO bulk crystallized by melt growth process is usually employed as the levitated magnet in high-temperature superconducting (HTS) maglev system. However, to the state of art, the intergrain supercurrent between different domains in the multiseeded bulk superconductor is much harder to simulate than the intragrain supercurrent in the single-seeded bulk, hindering the numerical study of multiseeded bulks. In this paper, we first discussed how to simulate the electromagnetic response of multiseeded bulk superconductor levitated above permanent magnetic guideway (PMG) through treating the multiseeded bulk as magnetically coupling but electric uncoupling domains, discriminating from assuming it as a single-seeded bulk superconductor. This model was validated through experiments of a three-seeded bulk levitated at different positions above a Halbach-derived PMG, comparing with a single-seeded bulk with the same geometrical dimensions. To realize a heavy-load HTS maglev system that can carry over a ton per meter length of levitation constituent, we introduced the feasible paths to increase the load, increasing the volumes of superconductors and PMs. We also optimized the selective configurations of the HTS maglev system by the genetic algorithm to reduce the total cost. The final summarized rules for designing the heavy-load HTS maglev system applied multiseeded bulk superconductors and Halbach-derived PMGs are deemed important to industrial-level application.

The paper introduces a new method to produce large sized Al-B4C-Al2O3np composites, which combines ball milling to prepare Al2O3np/Al mixed powder and semi-solid casting to contribute the injection of Al2O3np/Al mixed powder into the melt. The deformation performance of Al2O3np and micro-Al through ball milling with different Al/Al2O3np ratios, different milling time and different balls were studied respectively. It was revealed that micro-Al particles were milled from twisted and crimpled foil pieces to shuttles with Al2O3np embedded on it through 4h milling with 10mm balls. And we consider it as the best bonding between Al2O3np and micro-Al we could attain. And a plate of 25kg of Al-B4C-Al2O3np composite was fabricated successfully with the injection of the Al2O3np/Al mixed powder. Spherical Al2O3np of 300nm and needle-like TiB2 with 200nm in radius and 800nm-4μm in length were found in SEM photographs. Tensile properties of Al-B4C-Al2O3np composites were tested at room temperature and high temperature. It was showed higher mechanical properties than Al-B4C composites at room temperature and elevated temperature. Particularly, a 40% increase of UTS of Al-15wt.% B4C-1wt.%Al2O3np at 350°C was observed.

We devised a linear induction motor (LIM) that uses the close-ended coated superconductor coils as the secondary to explore the potential solutions of enhancing the thrust performance at large clearance, which is generally required for the linear propulsion of transit systems. In this proposal, the coated superconductor coils are embedded into a ferromagnetic yoke whose function is to guide and concentrate the travelling fields generated by the three-phase conventional stator. To make a preliminary study before the laboratory demonstration, we built a numerical model of this proposal by resorting to the finite-element software of MagNet, a recognized professional tool to simulate the electrical machines in the scientific community. Through a treatment of the power law, the developed numerical model has included the nonlinear constitutive law of superconductor, which is currently thought to be difficult in the MagNet environment. This general treatment takes a step forward toward the use of the professional software to perform complex simulations of the superconducting machines. Based on the numerical model, we carried out a set of transient studies on the proposed LIM to observe the distributions of travelling flux, the starting characteristics, and the time evolutions of thrust and speed. The achieved results clearly display that the proposed LIM has advantages over the conventional type and could be thereby regarded as a candidate for developing high thrust linear LIM with large clearance.

The evolution of neutron star (NS) magnetic field (B-field) has long been an important topic, which is still not yet settled down. Here, we analyze the NS B-fields inferred by the cyclotron resonance scattering features (CRSFs) for the high mass X-ray binaries (HMXBs) and by the magnetic dipole model for the spin-down pulsars. We find that the B-fields of both the 32 NSHMXBs and 28 young pulsars with the supernova remnants follow the log-normal distributions, with the average values of 3.4 * 10^12 G and 4.1 * 10^12 G respectively, which are further verified to come from the same continuous distribution by the statistical tests. These results declaim that the two methods of measuring NS B-fields are reliable for the above two groups of samples. In addition, since the NS-HMXBs have experienced the spin-down phase as the normal pulsars without accretion and then the spin-up phase by accretion, their ages should be about million years (Myrs). Our statistical facts imply that the B-fields of NS-HMXBs have little decayed in their non-accretion spin-down phases of ~ Myrs, as well as in their accretion phases of ~ 0.1Myrs., 8 pages, 2 figures, 4 tables, accepted by Astrophysics and Space Science

The superconducting levitation realized by immersing the high-temperature superconductors (HTSs) into nonuniform magnetic field is deemed promising in a wide range of industrial applications such as maglev transportation and kinetic energy storage. Using a well-established electromagnetic model to mathematically describe the HTS, we have developed an efficient scheme that is capable of intelligently and globally optimizing the permanent magnet guideway (PMG) with single or multiple HTSs levitated above for the maglev transportation applications. With maximizing the levitation force as the principal objective, we optimized the dimensions of a Halbach-derived PMG to observe how the field, current and force distribute inside the HTSs when the optimized situation is achieved. Using a pristine PMG as a reference, we have analyzed the critical issues for enhancing the levitation force through comparing the field, current and force distributions between the optimized and pristine PMGs. It was also found that the optimized dimensions of the PMG are highly dependent upon the levitated HTS. Moreover, the guidance force is not always contradictory to the levitation force and may also be enhanced when the levitation force is prescribed to be the principle objective, depending on the configuration of levitation system and lateral displacement.

Using a well-established theoretical model to calculate the levitation behavior of multiple high-temperature superconductors, the levitation capability of multiseeded Y-Ba-Cu-O blocks over two promising permanent-magnet guideways (PMGs) was evaluated and its dependence on the number of seeds was clearly displayed. The multiseeded Y-Ba-Cu-O blocks are ideally supposed to be composed of a set of single domains that are magnetically coupled but electrically insulated, which means we only consider the intragrain current. This assumption is a prerequisite for avoiding the complexity of assessing the morphology of the intergrain current, which is actually weaker than the intragrain current due to the unsolved obstacles in material process such as the weak link of grain boundary that impedes the current transfer across the grains. The insights attained by this numerical study, being inaccessible from experiments, tell us that, given the width of the Y-Ba-Cu-O block, the levitation force is found to be mostly degraded as the number of the seeds increases or the width of each seed decreases, whereas the lateral force exhibits a more complex behavior.

Optimization is essential to reduce the cost of high-temperature superconducting (HTS) maglev systems composed of a permanent magnetic guideway (PMG) and an HTS unit and thus promote their application. In this paper, the geometrical shape of a Halbach-derived PMG is optimized via an intelligent genetic algorithm to devise a more cost-effective system. We compute the levitation force of the HTS unit above the PMG with self-made finite-element codes, using the Kim-Bean current-voltage relationship in the governing equation of the 2-D model of HTS maglev system. Then, we introduce how the genetic algorithm is coupled with this 2-D model. Taking the levitation force of the HTS unit at a vertical distance above the PMG as the objective function, considering some practical geometry and cost constraints, we optimized a kind of Halbach-derived PMG. This optimization approach can provide a more general rule for the future design of the HTS Maglev system.

Two new anthracene derivatives were synthesized as emitter for low power triplet-triplet annihilation upconversion. Compared with anthracene, the emitter exhibits high quantum yields up to 85%. Pd (II) tetraphenylporphyrin which was selected as the sensitizer with the existence of BBA in DMF, We find a pretty high efficiency (Φuc=21.9%) of the upconversion fluorescence at 532nm with a low excitation power density of 0.5w/cm2.With the comparison of Anthracene, BBA and BTPA systems, quantum yield of the emitter is very important to the improving of the efficiency of upconversion.

Exploring the structure-property relationships is a fundamental but significant work for the design of new molecular. Rationaly designing of electrochromic materials that can switch rapidly and durably requires sophisticated understanding of the correlations between molecular structure and the performance. This work presents four electro-polymerizable metallosupramolecular coordinations self-assembled from triphenylamine-based terpyridine ligands and metal ions (Fe2+, Ru2+). The polymerized metal complexes can exhibit reversible change of the metal-to-ligand charge transfer (MLCT) absorption intensity. Along with the increase of voltage, the intensity of MLCT absorption peaks gradually reduced to disappear. Structure/performance correlations in electrochromic performance, especially the influence of different ligands and metal ions upon the coloration efficiency have been discussed.

A practically realizable magnetic hose, constructed by wrapping a ferromagnetic cylinder with an alternating superconductor–ferromagnet (SC–FM) heterostructure, was developed and its capability to transfer the static magnetic fields, e.g., generated by a Nd–Fe–B magnet, is examined. A diverse dependence of the transfer efficiency on the diameter of the inner cylinder was found in the magnetic hose demonstrators and the underlying cause was clarified by finite-element simulations. Transfer efficiency of over 50% in terms of a moderate field was achieved in the best demonstrator of this study, even with a thin sheet having only moderate magnetism to embody the FM in the heterostructure. This work links a theoretically derived model with physical reality and also conceives solutions to form a magnetic circuit with minimum leakage or to create a magnetically shielded space, both of which are promising for use in most electromagnetic devices.

We investigated the pulsar radio luminosity (L), emission efficiency (ratio of radio luminosity to its spin-down power E ˙ ), and death line in the magnetic field (B) versus spin period (P) diagram. We found that the dependence of pulsar radio luminosity on its spin-down power ( L − E ˙ ) is very weak, shown as L ∼ E ˙ 0.06 , which deduces an equivalent inverse correlation between emission efficiency and spin-down power as ξ ∼ E ˙ − 0.94 . Furthermore, we examined the distributions of radio luminosity of millisecond and normal pulsars and found that for the similar spin-down powers, the radio luminosity of millisecond pulsars is about one order of magnitude lower than that of the normal pulsars. The analysis of pulsar radio flux suggests that these correlations are not due to a selective effect but are intrinsic to the pulsar radio emission physics. Their radio radiations may be dominated by the different radiation mechanisms. The cut-off phenomenon of currently observed radio pulsars in B – P diagram is usually referred as the “pulsar death line”, which corresponds to E ˙ ≈ 10 30 erg s−1 and is obtained by the cut-off voltage of electron acceleration gap in the polar cap model of pulsar proposed by Ruderman and Sutherland. Observationally, this death line can be inferred by the actual observed pulsar flux S ≥ 1mJy and 1 kpc distance, together with the maximum radio emission efficiency of 1%. However, the observation data show that the 37 pulsars pass over the death line, including the recently observed two pulsars with long periods of 23.5 s and 12.1 s, which violate the prediction of the polar cap model. At present, the actual observed pulsar flux can reach 0.01mJy by FAST telescope. This will arise the observational limit of spin-down power of pulsars as low as E ˙ ≈ 10 28 erg s−1. This means that the new death line is downward shifted two orders of magnitude, which might be favorably referred as the “observational limit–line”. Accordingly, the pulsar theoretical model for the cut-off voltage of gap should be heavily modified.

The purpose of this study was to compare the efficacy of repetitive transcranial magnetic stimulation (rTMS) applied at different frequencies to the contra-lesional hemisphere to optimize the treatment of post-stroke non-fluent aphasia.Patients with post-stroke non-fluent aphasia were divided randomly into four groups: a high-frequency rTMS (HF-rTMS) group (10 Hz), a low-frequency rTMS (LF-rTMS) group (1 Hz), a sham stimulation group, and a control group. All groups received the standard treatment (consisting of drug therapy, conventional physical exercises, and speech training); in the HF-rTMS and LF-rTMS, this was supplemented with magnetic stimulation that targeted the mirror area within the right hemispheric Broca's area. Patients' language ability was assessed prior to, immediately after, and at 2 months post-treatment by the Chinese version of the Western Aphasia Battery (WAB).When measured immediately post-treatment, as well as at 2 months post-treatment, the LF-rTMS group exhibited a more marked improvement than the HF-rTMS group in spontaneous speech, auditory comprehension, and aphasia quotients (AQ). Compared to the control group, the HF-rTMS cohort exhibited significant improvement at 2-months post-treatment in repetition and AQ.LF-rTMS and HF-rTMS are both beneficial to the recovery of linguistic function in patients with post-stroke non-fluent aphasia. LF-rTMS produced immediate benefits that persisted long-term, while HF-rTMS only produced long-term benefits. In addition, the benefits produced with LF-rTMS were more marked than those produced by HF-rTMS.

In this paper, high magnetic fields generated by HTS magnet, instead of permanent magnet, was adopted to enhance the levitation property of HTS bulk on the fact that levitation force is positively related to the magnetic field strength. Based on the generally-accepted H-formulation, a validated 2-D axisymmetric finite element model was established to study and predict the levitation performances of HTS bulk in high magnetic fields. The fishtail effect Jc(|B|,T) dependence, which is closer to reality demonstrating unique magnetic dependence of HTS critical current in high magnetic fields, was employed to improve the effectiveness of numerical model. The results indicate that the levitation force could be greatly improved by taking magnetic field close to the peak field of fishtail effect Jc(|B|,T) curve. This work could serve as a vital method to predict the levitation performance of HTS bulk in high magnetic fields and a guide concerning how to choose external field in balance of performance and cost in future applications.

International audience; Three superconducting stacks made of 120 REBCO coated conductor tapes were each fabricated and assembled to obtain several REBCO modules. Their levitation responses over two different permanent magnet (PM) guideways were investigated by experiment and finite element simulation. For the experiment, a test rig was developed that can measure the force in the three directions for any given relative movement between the REBCO stacks and the PM guideway. For the finite element simulation, a 2D H-formulation was adopted. To treat the high aspect ratio of REBCO tapes, an anisotropic homogenization technique was used. The agreement between the measurements and the simulations is good, thus validating the modeling methodology. It was observed from the experiment and simulation results that the perpendicular field contributes to the levitation force whereas the parallel field is responsible for the guidance force, as a result of the existence of anisotropy on the local magnetic stimulation. Based on that, promising REBCO modules including both longitudinal and transverse arrangements of REBCO stacks were proposed and tested, in terms of providing a significant levitation force with the lateral stability preserved. Moreover, a pre-load process able to suppress the relaxation of the levitation force was put forward. To conclude, this study outlines explicit principles to obtain an appropriate layout of coated conductor stacks that could be effective for practical magnetic levitation operation.

Owing to instinctive self-stable levitation characteristics, high-temperature superconducting (HTS) maglev using bulk high-temperature superconductors attracts more and more attention from scientists and engineers around the world. In this paper, the levitation force relaxation and guidance force characteristics of a Y–Ba–Cu–O levitation unit with different eccentric distances (EDs) off the center of the permanent magnet guideway were experimentally investigated under field-cooling (FC) conditions. Experimental results indicate that the levitation force slightly increases at small EDs firstly, but degrades with further increasing of EDs. However, the maximum guidance force and its stiffness exhibit enhancement in moderate ED range. The results demonstrate that a properly designed initial FC eccentric distance is important for the practical applications of HTS maglev according to specific requirements like running in curve lines.

t was theoretically and experimentally proved that High Temperature Superconducting (HTS) Maglev had huge potential employment in rail transportation and high speed launch system. This had attracted great research interests in practical engineering. The optimization design was one of the most important works in the application of the HTS Maglev. As the NdFeB permanent magnet and HTS materials prices increased constantly, the design optimization of the permanent guideway (PMG) of HTS maglev became one of the indispensable works to decrease the cost of the application. This paper first reviewed four types of PMGs used by the HTS Maglev, then disucssed their structures and magnetic fields. Finally, the optimization methods of these four PMGs were compared. It was suggested that with better optimization methods, the levitation performance within a limit cost got better. That would be helpful to the future numerical optimization of the PMG of the HTS maglev.

For a high-Tc superconducting (HTS) maglev system with large force requirements, the use of magnetized bulk high-Tc superconductor magnets (MBSCMs) is a good candidate because of its strong flux pinning ability and corresponding high trapped flux. Different from the rare-earth permanent magnet (PM), the trapped flux of a MBSCM is sustained by the supercurrent produced by a magnetizing process, so the trapped flux is sensitive to variations of the supercurrent. The lateral displacement of a MBSCM above a PM guideway (PMG) will provide disturbance of the applied field and then alter the supercurrent as a process of remagnetization. Different magnetization histories will bring different remagnetization characteristics and consequently diverse levitation performances for a MBSCM during the lateral displacements. When the MBSCMs are applied into the HTS maglev system, the influence of lateral displacements on levitation performance should be taken into consideration. This article investigates the remagnetization characteristics of a MBSCM when it is subject to the lateral displacements above a PMG with different trapped magnetic flux and opposite magnetization polarities. Relevant analyses about the internal supercurrent configuration based on the critical state model are also included to better understand the remagnetization characteristic of a MBSCM.

A magnetized bulk high-Tc superconductor (HTSC) magnet is a good candidate to improve the levitation performance of the high-Tc superconducting (HTS) maglev system. Compared with the unmagnetized bulk HTSC, the magnetized bulk HTSC magnet can supply stronger levitation or guidance force above a permanent magnet guideway (PMG). Different from the permanent magnet, the magnetic field of a magnetized bulk HTSC magnet is sustained by the induced superconducting current produced during the magnetizing process. Given that the induced superconducting current within the magnetized bulk HTSC magnet is very sensitive to the magnetic field, the levitation performance of the magnetized bulk HTSC magnet is directly related to its own trapped field and the magnetic field of the PMG. This article discusses the influence of trapped and external magnetic fields on the levitation performance of a magnetized bulk HTSC magnet by experiments, and the Critical State Model is used to analyze the test results. The analyses and conclusions of this article are useful for the application of magnetized bulk HTSC magnet in practical HTS maglev systems.

This paper is devoted to numerically investigate the structural effect of the permanent magnet guideway (PMG) on the dynamic characteristics of a levitated high temperature superconductor (HTS). Being different from the existing results of this subject, this work considers the magnetic stimulation with translational symmetry (being not axisymmetric) and the geometry of the PMG to provide the external field has been economically optimized by a self-developed intelligent scheme, which makes our studies be closer to the practical situation. We introduce a 2-D finite-element model of generalized magnetic vector potential to theoretically describe and numerically solve the electromagnetic behavior of HTS over the PMG. A second-order dynamic equation is applied to characterize the vertical vibration of the levitated HTS subject to external disturbance, and it couples the electromagnetic model via the levitation force. We studied three typical configurations of PMG, all of which have been regarded as candidates in the development of the HTS maglev transit.

By using the method of in-situ X-ray diffraction and profile analysis, the variation of grain size and microstrain of the cold-rolled Sic w /Al composite at high temperature was measured, and the recrystallization behaviorof the composite was investigated. Test results showed that the activation energy of grain growth after recrystallization and recovery at higher temperature of matrix in composite is close to the activation energy for self-diffusion of pure Al. It was verified that the recovery phenomenon was accompanied with the grain growth, and the whiskers cannot affect the grain growth and recovery of matrix in composite at higher temperature.

The lanthanide superoxide complexes Tp2Sm(η2-O2) (1) (Tp=hydrotris-(pyrazolyl)borate), Tp2Yb(η2-O2) (2) and Tp*2Yb(η2-O2) (3) [Tp*=hydrotris(3,5-dimethylpyrazolyl)borate], have been synthesized by the reactions of Tp2Sm, Tp2Yb and Tp*2Yb with dioxygen in toluene at −75°C, respectively. The reaction of Tp*2Sm with a half equivalent of pyridine N-oxide in THF yields complex [Tp*2Sm]2(μ-η2:η2-O2)·2THF (4). The addition of hexane to the mother liquid, which was generated after the separation of complex 4, yields crystals of [Tp*Pz*2-Sm(μ3-O)(BOH)]2·2THF (5) (Pz*=3,5-dimethylpyrazolyl) structurally characterized by X-ray diffraction. Meanwhile 3,5-dimethylpyrazole resulted from the cleaved Tp* was also detected. Complex 5 is a seven-coordinated dimeric molecule with a pseudo-octahedral coordination geometry and crystallizes in the triclinic space group P1 (no. 2) with a=13.458(4) A, b=13.740(5) A, c=10.198(3) A, α=105.88(3)°, β=107.99(2)°, γ=86.85(3)°, Z=1. The samarium to nitrogen distances range from 2.516(5) to 2.624(5) A. The samarium to oxygen distances are 2.249(4)–2.324(4) A. The complex contains two Tp*, four Pz*, two samarium atoms and two bridged oxygen atoms.

Objective: To investigate the related genes in lung cancer tissues associated with residential high radon exposure. Methods: Differentially expressed gene fragments in lung cancer and normal lung tissues were discovered by differential display and reverse Northern blot hybridization method. The fragments positive in lung cancer and negative in normal lung tissue were determined. Results: Seven differential displayed fragments were sequenced. One of them named NA7 is 95% homologous with AI208667 in EAT of Genbank. Another fragment named NG2 is up to 98% homologous with five fragments. The remained one CA1 may be a new gene fragment. Conclusion: 3 gene fragments were discovered from lung cancer and normal lung tissues of high radon exposure resident.

Objective: A method for separating mRNAs by means of the polymerase chain reaction (differential display mRNA), and identifying the genes related to radiationinduced lung cancer was introduced. Methods: The RNAs were isolated from two pairs of samples, SV40-immortalized human fetal tracheal fibroblast cell (SHTF) versus αSHTF cell (transformed SHTF cell induced by r162p articles) and lung cancer tissue versus normal lung tissue obtained from one miner, and amplified by RTPCR. The differential expressed gene fragments were displayed by autoradiograph or silver nitrate stain. Results: The differential display mRNA method was established using both cell and tissue samples. The bands stained by silver nitrate were clearer than those on X-ray film. The rate of reamplification of differentially expressed gene fragments stained by silver nitrate is 80%, higher than that by autoradiograph, 50%. Conclusion: Differential display mRNA method was established successfully on both cell and tissue samples. The modified method for staining band increased the rate of reamplification and established the basis for confirming relative genes.

To meet the requirement of improved water quality, the economic water treatment process could be achieved by systematic coagulant selection and optimization of coagulation process. The experimental results show that the new coagulant developed has significantly improved the water quality, with marked modification of the particle size distribution feature after sediment and improved filtration efficiency. The organic removal ability, as shown by low TOC and UV254 in the finished water, is also significantly improved and also verified by using resin absorption characterization method. The TTHMFP for the source water is 20.98 microg/L and 11.01 microg/L for the traditional process. By using the new coagulant the TTHMFP is further decreased to 6.40 microg/L. With application of the new coagulant, the treatment costs are significantly decreased with further improved and simplified treatment process.

The magnetized bulk high- superconductor (MBSCM) can provide dramatic improvements towards the levitation performance of HTS Maglev systems if sufficient and suitable magnetic excitation methods are employed. In the field-cooling excitation mode, the demagnetization process greatly influences the levitation performance of the MBSCM in some special operation modes. A difference in the levitation performance was observed from experimental tests under different demagnetization field strengths and rates. Simulation based on finite element method was used to calculate the temperature rise within the MBSCM during the studied demagnetization process. With experimental results and analyses, an optimal demagnetization process for the MBSCM for engineering applications was derived.