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排序方式: 共有4034条查询结果,搜索用时 31 毫秒
911.
H.S. Shin M.J. Dedicatoria 《Physica C: Superconductivity and its Applications》2010,470(20):1329-1333
In the case of 2G coated conductor (CC) tapes, it has been reported that thin–thick CC tapes with IBAD substrate showed a superior electromechanical property even at smaller bending radius compared with the cases of 1G BSCCO tapes. Considering the application of CC tapes it is significant to evaluate the transport property under operating environment, because CC tapes might experience a change in operating pressure that can affect its current carrying capacity due to temperature variation and deformation. This study was focused on the Ic degradation behavior in bent CC tapes under pressurized liquid nitrogen. Differently processed YBCO and SmBCO CC tapes with IBAD substrate are used as samples. The bending strain characteristics at elevated pressure levels were evaluated by using the ρ-shaped sample holder which can induce different bending strain values at pressured state. Depressurization and thermal cycling were performed to check the reversibility of Ic in CC tapes. Vacuuming tests were also carried out to investigate the characteristics of Ic at different LN2 temperature levels. 相似文献
912.
A. Toda T. Arai S. Ochiai H. Okuda H. Matsubayashi M. Sugano K. Osamura W. Prusseit 《Physica C: Superconductivity and its Applications》2010,470(20):1346-1349
The coated conductors are subjected to mechanical and electromagnetic stresses in preparation and service. When the stress is high, the coated layer is damaged, resulting in loss of superconducting property. The present work was carried out to reveal the influence of tensile damage on V–I curve, critical current and n-value of DyBa2Cu3O7−δ coated conductor. The changes of the V–I curve, critical current and n-value with increasing applied tensile strain were measured experimentally. The features of the shift of the V–I curve to the lower current range and increase in its curvature, and accordingly the decrease in critical current and n-value, with increasing applied strain, were detected. For analysis of the experimental results, the model of Fang et al, which treats with the voltage generation due to the current shunting under existent crack, was applied. The experimentally observed features were described satisfactorily. 相似文献
913.
Y. Ding Y. Sun X.D. Wang H.C. Wang Z.X. Shi Z.A. Ren J. Yang W. Lu 《Physica C: Superconductivity and its Applications》2010,470(22):2051-2056
Polycrystalline NdFeAsO0.88F0.12 superconductors prepared by high pressure (HP) and ambient pressure (AP) methods were comparatively studied by magnetization and transport measurements. Upper critical field Hc2, irreversibility field Hirr and the anisotropy parameter Γ were estimated from resistance transition curves. The broadening of transition width was observed, and was ascribed to both Hc2 anisotropy and superconductivity inhomogeneity of samples. Magnetic hysteresis loops (MHLs) in low fields were measured to detect the trace of weak-link behavior. The reclosed hysteresis loops in low fields indicate that there are weak links in both samples. Magnetization critical current density Jcm were derived from MHLs. Sample HP shows higher Jcm than sample AP. Direct transport I–V measurements show that the transport critical current density Jct are very low but persist up to 9 T, suggesting intrinsic strong-link existing in both samples. 相似文献
914.
S.A. Lajevardi 《Applied Surface Science》2010,256(22):6775-1156
The aim of this study is to investigate the effects of pulse electrodeposition parameters on the properties of nickel-titania composite coatings electrodeposited from a nickel Watts type bath. The effects of average current density, frequency and duty cycle on the surface morphology, crystal size, preferred orientation of the deposits and the amount of embedded nano-TiO2 particles in the composite coatings were investigated. The results represented the optimum amount of average current density (e.g., 4 A dm−2) for obtaining the highest volume percentage of the incorporated titania particles and subsequently the maximum microhardness. Moreover, by increasing the frequency up to 10 Hz while reducing the duty cycle to 10% at constant peak current density, the volume percentage of particles increased to about 7% which is almost twice as much the volume percentage as deposited particles in direct current method. According to the results the composite coating exhibited obviously [1 0 0] + [2 1 1] as preferred orientation at low pulse frequency and the diffraction intensity of the [2 1 1] fiber orientation is increased, probably due to the pH increase adjacent to the electrolyte/cathode interface at higher frequencies. Also, it has been found that by reduction in the duty cycle, more titania particles were incorporated in the composite coatings and this promoted the nickel crystals growth on [1 0 0] planes and consequently the coatings preferred orientation changed from the [2 1 1] to [1 0 0] + [2 1 1] planes. 相似文献
915.
N. M. Bogdanovich D. I. Bronin G. K. Vdovin I. Yu. Yaroslavtsev B. L. Kuzin 《Russian Journal of Electrochemistry》2009,45(4):456-464
The sintering features, electroconductivity, and electrochemical characteristics of bilayer electrodes with functional composite
layers based on La(Sr)MnO3 (LSM) and La(Sr)Fe(Co)O3 with LSM collector layer and Bi(Y)O1.5 (YDB) electrolyte additive in contact with Ce (Sm)O2(SDC), La(Sr)Ga(Mg)O3, and Zr(Sc)O2 electrolytes were studied. YDB additive to the electrode collector layer was shown to produce a positive effect to the properties
of the studied electrode systems. The maximum electrochemical activity and electroconductivity was observed for the electrodes
with 5 wt % of YDB electrolyte additive in the collector layer. Thus, electroconductivity of electrodes is almost doubled
and 100 mV cathode overvoltage current density is increased by 30% at the temperatures of 800 to 900°C and up to 10-fold at
650 to 700°C. The collector layer sintering temperature of bilayer electrodes can be reduced from 1150 to 1000°C without loss
of electrochemical activity. The service life tests (about 1200 h) of composite electrodes with LSM2-SDC functional layer
and 90% LSM2 + 10% YDB collector layer in contact with SDC electrolyte showed the time dependences of polarization resistance
tending to saturation and described with damped exponent.
Original Russian Text ? N.M. Bogdanovich, D.I. Bronin, G.K. Vdovin, I.Yu. Yaroslavtsev, B.L. Kuzin, 2009, published in Elektrokhimiya,
2009, Vol. 45, No. 4, pp. 486–494. 相似文献
916.
The homogeneous catalytic oxidation of coenzyme nicotinamide adenine dinucleotide (NADH) with dopamine at a thiolactic acid modified gold spherical electrode of radius 0.0128 cm has been studied in aqueous phosphate media (pH 7.0) using linear sweep voltammetry and chronopotentiometry with power time and exponential time currents. We have proved that, under the conditions of this study, the steady state is reached, in such a way that the expressions for the I?E and dI/dE?E responses are simplified and become independent of time and the electrochemical technique employed. Therefore, the experimental I?E and dI/dE?E curves obtained in chronopotentiometry and linear sweep voltammetry are practically superimposable and, from easy expressions for the peak parameters of the dI/dE?E curves deduced in this paper, values of the chemical and electrochemical rate constants have been obtained. 相似文献
917.
Chandrasekar M. S. Shanmugasigamani Srinivasan Malathy Pushpavanam 《Journal of Solid State Electrochemistry》2009,13(5):781-789
Zinc–cobalt (Zn–Co) and zinc–nickel (Zn–Ni) alloy electrodeposits each prepared from acid and alkaline formulations were compared
for their properties. Compared to alkaline baths, acid baths offer higher metal percent of the alloying element and higher
current efficiency. In alkaline baths, the variation of metal percent in deposit with current density is less significant,
but that of current efficiency with current density is more. Electrolyte pH does not change significantly in alkaline solutions
compared to acid solutions. X-ray diffraction evaluation of Zn–Co deposits from both electrolytes indicated their presence
in the η-phase, while Zn–Ni shows pure γ-phase for deposits obtained from alkaline solutions and the existence of γ-phase
with traces of η-phase of zinc for deposits obtained from the acid electrolytes. Scanning electron microscope examination
shows finer grain structure for deposits obtained from alkaline solutions, and atomic force microscope studies confirm their
nanostructure with reduced surface roughness. Deposits obtained from the alkaline baths exhibited higher corrosion resistance
probably due to their nanostructure. 相似文献
918.
Shan He Yanbin Lu Liyan Jiang Bin Wu Feiying Zhang Yuanjiang Pan 《Journal of separation science》2009,32(14):2339-2345
Preparative high‐speed counter‐current chromatography (HSCCC) was successfully applied to the isolation and purification of three stilbene oligomers from Vitis chunganeniss using stepwise elution with a pair of two‐phase solvent systems composed of n‐hexane–ethyl acetate–methanol–water at (2:5:2:5, v/v) and (1:2:1:2, v/v). The preparative HSCCC separation was performed on 800 mg of crude sample yielding hopeaphenol (21.1 mg), amurensin G (37.2 mg) and vitisin A (95.6 mg) in a one‐step separation, with purities over 95% as determined by HPLC. The structures of these three compounds were identified by MS, 1H NMR and 13C NMR. In addition, their antioxidant activities were screened by DPPH assay, where vitisin A showed strong antioxidant activity. Further EPR experiments with spin‐trapping technique demonstrated that vitisin A is a potent and selective singlet oxygen quencher, which may be used in singlet oxygen‐mediated diseases as a pharmacological agent. 相似文献
919.
Pratim Sengupta Uri Wilensky 《International Journal of Computers for Mathematical Learning》2009,14(1):21-50
Electricity is regarded as one of the most challenging topics for students of all ages. Several researchers have suggested
that na?ve misconceptions about electricity stem from a deep incommensurability (Slotta and Chi 2006; Chi 2005) or incompatibility (Chi et al.
1994) between na?ve and expert knowledge structures. In this paper we argue that adopting an emergent levels-based perspective
as proposed by Wilensky and Resnick (1999), allows us to reconceive commonly noted misconceptions in electricity as behavioral evidences of “slippage between levels,”
i.e., these misconceptions appear when otherwise productive knowledge elements are sometimes activated inappropriately due
to certain macro-level phenomenological cues only. We then introduce NIELS (NetLogo Investigations In Electromagnetism), a
curriculum of emergent multi-agent-based computational models. NIELS models represent phenomena such as electric current and
resistance as emergent from simple, body-syntonic interactions between electrons and other charges in a circuit. We discuss results from a pilot
implementation of NIELS in an undergraduate physics course, that highlight the ability of an emergent levels-based approach
to provide students with a deep, expert-like understanding of the relevant phenomena by bootstrapping, rather than discarding their existing repertoire of intuitive knowledge.
相似文献
Pratim SenguptaEmail: |
920.
Ultrasound changes its intensity and speed when propagating through a liquid or a suspension containing particles. In addition it generates a weak electric signal by altering the motion of ions and charged particles. Hence acoustic and electroacoustic measurements provide information about the properties of suspended particles and molecules. Here we present both acoustic and electroacoustic results on blood suspensions and protein solutions, relevant to life sciences. For blood cells a strong increase in acoustic attenuation with volume fraction is found, from which the speed of sound in an erythrocyte is found to be about 1900 m/s, assuming the attenuation is due to scattering only. A similar value of 1700 m/s is found from the increase in sound speed of the dispersion with concentration. Electroacoustic measurements on bovine serum albumin (BSA) yield a charge of about seven elementary charges per BSA molecule. These results show the power and usefulness of acoustic and electroacoustic measurement techniques for biological systems. 相似文献