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We study the effect of Josephson coupling between adjacent superconducting layers on the BCS energy spectrum. We find that the interference between the gap functions of two layers can lead to vanishing condensation energy for perpendicular momenta corresponding to the formation of standing waves. We therefore predict a conventional energy spectrum for large interlayer spacings, if the gap of the single layers has no nodes, and in all cases a gapless spectrum for small spacings. Within the experimental error, our numerical results account for the low-temperature dependence of the penetration depth reported in Nd1.85Ce0.15CuO4 and YBa2Cu3O6.9. 相似文献
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Identification of gaps in mangrove forests with airborne LIDAR 总被引:2,自引:0,他引:2
Mangrove forests change frequently due to disturbances from tropical storms, frost, lightning, and insects. It has been suggested that the death and regeneration of trees in small gaps due to lightning may play a critical role in mangrove forest turnover; however, the large-scale quantification of spatial pattern and areas of gaps is lacking for investigating this issue. Airborne light detection and ranging (LIDAR) technology provides an effective way for identifying gaps by remotely obtaining direct measurements of ground and canopy elevations. A method based on an alternative sequential filter and black top-hat mathematical morphological transformation was developed to extract gap features. Comparison of identified gap polygons with raw LIDAR measurements and field surveys shows that the proposed method successfully extracted gap features in mangrove forests in Everglades National Park. There are 400–500 lightning gaps per square kilometer in mangrove forests at the study sites. The distribution of gap sizes follows an exponential form and the area of gaps with sizes larger than 100 m2 account for 55–61% of the total area of gaps. The area of gaps in the mangrove forest in Everglades National Park is about 4–5% of the total forest area and the average gap formation rate is about 0.3% of the total forest area per year, indicating that lightning gaps play an important role in mangrove forest dynamics. 相似文献
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M. Liu Q. Fang G. He L.Q. Zhu S.S. Pan L.D. Zhang 《Materials Science in Semiconductor Processing》2006,9(6):876
High-k HfOxNy thin films have been grown by radio frequency (rf) reactive sputtering of metal Hf target in N2/Ar/O2 ambient at different substrate temperatures. The chemical compositions of the films have been investigated as a function of substrate temperature by X-ray photoelectron spectroscopy (XPS). XPS measurements showed that nitrogen concentration increases with an increase in substrate temperature. Room-temperature spectroscopic ellipsometry (SE) with photon energy 0.75–6.5 eV was used to investigate the optical properties of the films. SE results demonstrated that refractive index n increases with an increase in substrate temperature. Based on TL parameters which were obtained from the best fit results used in a simulation of the measured spectra, meanwhile, we conclude that the energy band gap (Eg) decreases with an increase in substrate temperature. 相似文献
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Sixiong Han Yasuaki Ichikawa 《International journal for numerical methods in engineering》1995,38(24):4081-4100
In this paper, a mathematical model is proposed for the problem of the scattering of plane waves in a three-dimensional cracked materials. Instead of obtaining closed-form solutions as in conventional theoretical analysis methods, this approach, called the Equivalent Nodal Force (ENF) method formulates the mechanical effects of cracks as an equivalent nodal force in a numerical procedure, and physically translates cracked material into an equivalent continuous one. Several mechanical relations between waves and cracks are evident from this method. Also the results of several numerical calculations are presented and these are compared with those obtained by the conventional methods. 相似文献
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The range of miscibility gap above 300 ℃ at low Cu side in Al-Cu-Zn ternary system was obtained by EPMA of the designed alloys and diffusion-couples treated for equilibrium. The results about the boundary trend of the α1 / (α1 α2 ) phase region was obtained. The α1 / (α1 α2 ) boundary moves towards the lower Zn side with the increase of Cu content. The results are opposite to traditional phase diagrams obtained by experiments, but consistent with recent thermodynamic calculations. 相似文献
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D. Clifton A. R. Mount G. M. Alder D. Jardine 《International Journal of Machine Tools and Manufacture》2002,42(11)
During the process of electrochemical machining the dependency of the inter-electrode gap with time and process parameters can be used to determine process characteristics and to define the shape of the workpiece surface relative to the tool surface. Defining process variables to map out the required gap-time function requires the use of time-consuming iterative trials. In-line monitoring of the gap would enable process control and tool to workpiece transfer characteristics to be achieved (for ideal conditions) without the requirement to generate such parameter maps. This work explores the use of ultrasound applied as a passive, non-intrusive, in-line gap measurement system for ECM. The accuracy of this technique was confirmed through correspondence between the generated gap-time and current time data and theoretical models applicable to ideal conditions. Gap measurements are also used to demonstrate and quantify the degree of departure from ideal behaviour for an In718/chloride system as the electrolyte flow rate is reduced from 16 to 4 l min−1. The monitoring of the gap size has also been shown to be effective when determining shape convergence under ideal conditions, for the example case of a 2D sinusoidal profile. 相似文献
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