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71.
A. A. Zhukov G. K. Perkins J. V. Thomas A. D. Caplin H. Küpfer T. Wolf 《Journal of Low Temperature Physics》1996,105(5-6):1105-1110
Using vector magnetic moment measurements, in twinned YBa2Cu3Oy single crystals we observe a nearly reversible Mab component of the magnetisation with sharp peaks in the dependence of Mab on the magnetic field H and angle between c-axis and magnetic field. The association of these features with twin boundaries is supported by geometrical arguments and by comparison with detwinned samples. For a crystal with a single dominant direction of twin boundaries, the initial slope of the Mab(H) and Mab() dependences corresponds closely to ideal shielding of the transverse H component, as expected for the fully-locked vortex state. The peak position, which is related to the locking angle, shows a close to linear Hp
–1 vs dependence, which corresponds to a fixed value of HL, the locking field. The influence of twins vanishes above a trapping angle T which shows rather weak temperature and magnetic field dependences; at 60K and 1T these parameters are oHL=27mT and T 10 °. 相似文献
72.
Vladimir Z. Kresin Stuart A. Wolf Yu. N. Ovchinnikov 《Journal of Superconductivity》1996,9(3):329-333
The value of the critical temperature of the cuprates correlates with the doping level and is affected by the interplay of two competing factors: (1) the increase in carrier concentration, and (2) the pair-breaking effect of magnetic impurities. An analysis of the temperature dependence of the critical field leads to the conclusion that magnetic impurities are present even in a sample with the maximum observed value ofT
c.A new parameter, intrinsicT
c (T
cintr), which is its value in the absence of magnetic impurities, is introduced. The maximum value ofT
cintr, which corresponds to the maximum doping level, appears to be similar for different cuprates and to be equal to 160–170 K. This is the upper limit ofT
c in the cuprates. 相似文献
73.
During summer and autumn 2007, a 11 GHz microwave radiometer was deployed in an experimental tree plantation in Sardinilla, Panama. The opacity of the tree canopy was derived from incoming brightness temperatures received on the ground. A collocated eddy-covariance flux tower measured water vapor fluxes and meteorological variables above the canopy. In addition, xylem sapflow of trees was measured within the flux tower footprint. We observed considerable diurnal differences between measured canopy opacities and modeled theoretical opacities that were closely linked to xylem sapflow. It is speculated that dielectric changes in the leaves induced by the sapflow are causing the observed diurnal changes. In addition, canopy intercepted rain and dew formation also modulated the diurnal opacity cycle. With an enhanced canopy opacity model accounting for water deposited on the leaves, we quantified the influence of canopy stored water (i.e. intercepted water and dew) on the opacity. A time series of dew formation and rain interception was directly monitored during a period of two weeks. We found that during light rainfall up to 60% of the rain amount is intercepted by the canopy whereas during periods of intense rainfall only 4% were intercepted. On average, 0.17 mm of dew was formed during the night. Dew evaporation contributed 5% to the total water vapor flux measured above the canopy. 相似文献
74.
Multi-Modal Dialog Scene Detection Using Hidden Markov Models for Content-Based Multimedia Indexing 总被引:1,自引:1,他引:0
A class of audio-visual data (fiction entertainment: movies, TV series) is segmented into scenes, which contain dialogs, using a novel hidden Markov model-based (HMM) method. Each shot is classified using both audio track (via classification of speech, silence and music) and visual content (face and location information). The result of this shot-based classification is an audio-visual token to be used by the HMM state diagram to achieve scene analysis. After simulations with circular and left-to-right HMM topologies, it is observed that both are performing very good with multi-modal inputs. Moreover, for circular topology, the comparisons between different training and observation sets show that audio and face information together gives the most consistent results among different observation sets. 相似文献
75.
N. E. Alekseevskii G. Wolf V. I. Tsebro N. M. Dobrovolskii K. Bohmhammel S. Krautz 《Journal of Low Temperature Physics》1980,38(1-2):243-252
The heat capacity of molybdenum chalcogenides with different Sn/Ga content was measured at temperatures of T 60 K. The occurrence of two phases of the chalcogenides studied could clearly be seen for higher Ga concentrations. In the miscibility gap there coexists a superconducting phase (T
c= 12.5 K) SnGa0.25Mo5S6 with the ferromagnetic GaMo5S6 phase (T
curie = 19 K). As for the pure ternary compound GaMo5S6, a singularity of the heat capacity could also be observed in the range of the structural change (T = 45 K). All the singularities are discussed. 相似文献
76.
E. L. Wolf D. M. Burnell Z. G. Khim R. J. Noer 《Journal of Low Temperature Physics》1981,44(1-2):89-118
An extensive superconducting electron tunneling study of Ta, using both a proximity method and an optimized conventional spectroscopy, is reported. The results for Ta confirm the electron-phonon origin of superconductivity in this element, and provide slightly improved superconducting parameters: =0.73 and ph
* = 0.11. The results from the PET and optimized conventional methods are in substantial agreement, although the proximity method appears to provide somewhat better resolution of structure in the Eliashberg function 2
F(E).Operated for the U.S. Department of Energy by Iowa State University under contract No. W-7405-Eng-82. This research was supported by the Director for Energy Research, Office of Basic Energy Sciences, WPAS-KC-02-02-02. 相似文献
77.
The superconducting properties of YBa2Cu3O7-
y, (YBCO) depend strongly on the oxygen content, whereas the transition temperatureT
cremains relatively constant for oxygen content between 6.8 and 7.0 (the Plateau effect) this effect has attracted considerable attention [see, e.g., D. de Fontaineet al., Nature (London)
343, 544 (1990); H. Paulsenet al., Nature (London)
349, 594 (1991); J. Jorgensen,Phys. Today
44, No. 6, 34 (1991)]. In this letter we introduce a microscopic theory of this phenomenon. 相似文献
78.
Gietzelt M Schnabel S Wolf KH Büsching F Song B Rust S Marschollek M 《Computer methods and programs in biomedicine》2012,106(2):97-103
One of the key problems in accelerometry based gait analyses is that it may not be possible to attach an accelerometer to the lower trunk so that its axes are perfectly aligned to the axes of the subject. In this paper we will present an algorithm that was designed to virtually align the axes of the accelerometer to the axes of the subject during walking sections. This algorithm is based on a physically reasonable approach and built for measurements in unsupervised settings, where the test persons are applying the sensors by themselves. For evaluation purposes we conducted a study with 6 healthy subjects and measured their gait with a manually aligned and a skewed accelerometer attached to the subject's lower trunk. After applying the algorithm the intra-axis correlation of both sensors was on average 0.89±0.1 with a mean absolute error of 0.05g. We concluded that the algorithm was able to adjust the skewed sensor node virtually to the coordinate system of the subject. 相似文献
79.
Two dimensional simulations of non-cohesive granular matter in a biaxial shear tester are discussed. The effect of particle elasticity on the mechanical behavior is investigated using two complementary distinct element methods (DEM): Soft particle molecular dynamics simulations (Particle Flow Code, PFC) for elastic particles and contact dynamics simulations (CD) for the limit of perfectly rigid particles. As soon as the system dilates to form shear bands, it relaxes the elastic strains so that one finds the same stresses for rigid respectively elastic particles in steady state flow. The principal stresses in steady state flow are determined. They are proportional to each other, giving rise to an effective macroscopic friction coefficient which is about 10% smaller than the microscopic friction coefficient between the grains. 相似文献
80.
Comments on the paper by Mosig (IEEE Antennas and Propagation Magazine, vol.47, p.38-40, 2005 December). The paper by Mosig discussed acceleration of convergence of series. Without commenting on either the validity or efficiency of his method, the present author would like to draw attention to an existing method, published long ago by D. Shanks (1955). Briefly stated, this method takes a sequence and defines partial sums, which is described in this paper. 相似文献