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981.
982.
在电灯发明之后的100多年里,照明技术的不断发展使白炽灯和荧光灯面临着严重的威胁.特别是发光二极管技术的逐步成熟,引发了照明光源的一场技术革命.不仅仅是红绿灯,在大型屏幕显示、室内照明、汽车车灯、广告标志等所有需要光亮的地方,发光二极管都将取代传统的照明设备,成为未来的重要光源. 相似文献
983.
The conservation of transgenic materials is very important, paticularly for their potential future use in crop development. In this study, transgenic callus cultures of 'Newhall' navel orange (Citrus sinensis Osbeck) were cryopreserved by a vitrification method. Transgenic calluses survived cryopreservation and recovered under normal culture conditions. The results of PCR (Polymerase Chain Reaction) amplification, Southern blotting and SSCP (Single-Strand Conformation Polymorphism) assay showed that the GUS gene was still maintained in the genome of callus cultures recovered from cryopreservation. X-Gluc staining further indicated GUS gene expression in callus cultures recovered from cryopreservation. 相似文献
984.
The effects of <sup>60</sup>Co γ-ray irradiation on the DC characteristics of enhancement-mode AlGaN/GaN high-electron-mobility transistors 下载免费PDF全文
The effects of 60Co γ-ray irradiation on the DC characteristics of AlGaN/GaN enhancement-mode high-electron-mobility transistors (E-mode HEMTs) are investigated. The results show that having been irradiated by 60Co γ-rays at a dose of 3 Mrad (Si), the E-mode HEMT reduces its saturation drain current and maximal transconductance by 6% and 5%, respectively, and significantly increases both forward and reverse gate currents, while its threshold voltage is affected only slightly. The obvious performance degradation of E-mode AlGaN/GaN HEMTs is consistent with the creation of electronegative surface state charges in the source-gate spacer and gate-drain spacer after being irradiated. 相似文献
985.
We propose a novel method for multiple-image encryption using a phase retrieve algorithm and intermodulation in the Fourier domain. All plaintexts to be encoded are first encoded separately into a phase-only function in the Fourier domain with the help of the phase retrieve algorithm. Then these phase-only functions serve mutually as the second encryption keys to be intermodulated into a single image. As a result, all plaintexts can be extracted from the ciphertext without any cross-talk and the encrypted capacity is nearly unlimited. The feasibility and effectiveness of the proposed method are demonstrated by numerical results. 相似文献
986.
Finite Difference/Element Method for a Two-Dimensional Modified Fractional Diffusion Equation 下载免费PDF全文
We present the finite difference/element method for a
two-dimensional modified fractional diffusion equation. The analysis
is carried out first for the time semi-discrete scheme, and then for
the full discrete scheme. The time discretization is based on the
$L1$-approximation for the fractional derivative terms and the
second-order backward differentiation formula for the classical
first order derivative term. We use finite element method for the
spatial approximation in full discrete scheme. We show that both the
semi-discrete and full discrete schemes are unconditionally stable
and convergent. Moreover, the optimal convergence rate is obtained.
Finally, some numerical examples are tested in the case of one and
two space dimensions and the numerical results confirm our
theoretical analysis. 相似文献
987.
By use of a laser diode as a pump source, a self-Q-switched laser from a Cr, Nd:YAG crystal is demonstrated. The output Q-switched traces are very stable, the threshold pump power is 3.5 W, the pulse duration is 50 ns, and the slope efficiency is as high as 20%. In addition, the pulse width remains constant while the pulse repetition rate varies with pump power. 相似文献
988.
989.
We extend our previous treatment of a mixed ionic electronic conductor membrane, consisting of a porous cathode and anode separated by a thin non-porous layer, to the case where mass transport of molecules in the porous electrodes can be the rate-limiting step. The linearized transport equations for the ion-hole pairs in the solid and of the gas molecules in the pores are characterized by the length scales LP = √Ld(1 − φ)/Sτs and Lg = 2Lp√[τsφ/τ(1 − φ)][Dgcg/DIEci] respectively, where Ld = DIE/K is the length scale that determines the transition from diffusion limited to surface exchange limited transport in the non-porous electrodes, K is the surface exchange coefficient, DIE and Dg are the diffusion coefficients of the ion-hole pairs and of the molecules, ci and cg are the concentrations of the ions and molecules, S is the pore surface area per unit volume, φ the porosity and τs and τ the tortuosities of the solid and pore phases respectively. When Lg Lp, which is the case treated previously, the rate-limiting step in the transport is ionic diffusion and surface exchange. Enhancements in oxygen ion current of two orders in magnitude, over non-porous electrodes, are in principle achievable with porous perovskite MIEC having surface area s = 106 cm−1. When Lg Lp the rate-limiting step is mass transport in the pores and the enhancement in ion current is substantially reduced. 相似文献
990.