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991.
When the activation function possesses multilevel property, the Hopfield neural network has some novel dynamical behaviors, and it is worthwhile to study. First, some properties about the activation function are obtained, on this foundation, some theoretical analysis about the quasi-equilibrium points has been made. From local and global view, some theorems about the boundedness are presented. Finally, two theorems about the first derivative of trajectory with respect to time are found, the first theorem indicates that the trajectory cannot keep increasing or decreasing for time t > t0, the second theorem is about the complete stability of the trajectory. 相似文献
992.
P.A. Hu Y.Q. Liu L. Fu L.C. Cao D.B. Zhu 《Applied Physics A: Materials Science & Processing》2005,80(7):1413-1417
Inorganic fullerene-like (IF) nanotubes constructed from layered metal chalcogenides are of particular significance because of their excellent physical properties and potential application in wide fields. But very few previous studies were focused on the IF nanotubes of layered III-VI semiconductor. Therefore we investigate the preparation, structure and photoluminescence (PL) properties of GaS nanotube (an important III-VI semiconductor IF nanotube). A simple method is introduced to prepare GaS multi-walled nanotubes for the first time by annealing the natural lamellar precursor in Ar. The reaction temperature is crucial for the formation of nanotube. A suitable temperature range is 500–850 °C. Bulk quantities of GaS nanotubes with diameters of 30–150 nm and lengths up to ten micrometers were produced. Some of these nanotubes show corrugated and interlinked structure and form many segments, demonstrating a bamboo-like structure. As compared to bulk materials, the obvious distinction of the products in PL spectra at liquid nitrogen temperature of 77 K was due to the structure variety. PACS 61.46.+w; 81.07.De; 81.16.Be 相似文献
993.
994.
采用sol-gel法制备了Zn2 掺杂的锐钛矿相纳米TiO2薄膜电极.通过光电流作用谱和电流-电位(I-U)曲线研究了掺杂不同浓度Zn2 的TiO2薄膜电极的光电特性.由光电流作用谱可知,Zn2 的掺杂可显著影响薄膜电极的光电流大小,且掺杂的最佳浓度与薄膜晶粒尺度有关.在320nm单色光照射下,掺杂浓度(摩尔浓度)为0.1%的薄膜电极光电流最大,与未掺杂的本征薄膜电极相比增幅达40%.I-U曲线表明,光照下,随电极电位由正到负逐渐降低,不同掺杂浓度的TiO2薄膜电极中均出现了阳极电流向阴极电流转换的现象,且Zn2 掺杂浓度可影响电极阳极电流的初始电位.另外,无光照的暗态下,各薄膜在负电位区域观察到了相似的随电位降低而迅速增大的阴极暗电流. 相似文献
995.
Qingping Dou Haitao Ma Gang Jia Zhanguo Chen Kun Cao Tiechen Zhang 《Optics & Laser Technology》2007,39(3):647-651
The cubic boron nitride (cBN) is a kind of artificial electro-optic (EO) crystal, and we have not found any relative reports so far. Because the artificial synthetic cBN wafers are very small and hard, the wafers cannot be cut into rectangular slabs. The polarizer-sample-λ/4 retardation plate (compensator)-analyzer (PSCA) transverse EO modulator has to be adjusted to the minute irregular octahedron of cBN wafers. When the applied voltage is along [1 1 1] direction of the wafer, due to refraction, the angle between the incident beam direction and the (1 1 1) plane (top or bottom plane) of the wafer should be 25.4°, and the angle between the polarization direction of the polarizer and the plane of incidence should be 50.8° by calculation, respectively. The half-wave voltage of the cBN sample was obtained for the first time, by means of detection of the output optic signals from the modulator with and without an applied electric field on the sample, respectively. Furthermore, the linear EO coefficient was obtained, . The analysis of the experimental resulting error was carried out. 相似文献
996.
We report a quantum dot microcavity laser with a cw sub-microW lasing threshold, where a significant reduction of the lasing threshold is observed when a single quantum dot (QD) state is aligned with a cavity mode. The quality factor exceeds 15,000 before the system lases. When no QD states are resonant, below threshold the cavity mode initially degrades with increasing pump power, after which saturation occurs and then the cavity mode recovers. We associate the initial cavity mode spoiling with QD state broadening that occurs with increasing pump power. 相似文献
997.
Experimental investigation ofd Nd:YAG monolithic nonplanar ring lasers operated at 1123 nm wavelength is presented. Stable single-frequency 1123 nm laser output has been obtained with successful suppression of the strong 1064 nm radiation. Single-frequency output power of 1.25 W is demonstrated with a pump power of 3.98 W at 808 nm, which gives a slope efficiency of 39%. The laser frequency tuning range is over 3 GHz, and the average tuning rate with temperature is -2.6 GHz/ degrees C. A strong iodine absorption line can be covered within the laser frequency tuning range. 相似文献
998.
A new scheme for single attosecond pulse generation from asymmetric molecules with a multicycle laser pulse is proposed. It is shown that both even and odd harmonics are generated from the asymmetric molecules, and the attosecond pulses are produced every full cycle of the driving laser field rather than each half-cycle. By filtering the harmonics in the cutoff of the spectrum, a single attosecond pulse can be obtained with a multicycle laser pulse with a duration of 2 times longer than the few-cycle pulse conventionally used. 相似文献
999.
Acta Mathematicae Applicatae Sinica, English Series - In this paper, we investigate the global solution and the structures of interaction between two dimensional non-selfsimilar shock wave and... 相似文献
1000.
本文针对带非线性源项的Riesz回火分数阶扩散方程,利用预估校正方法离散时间偏导数,并用修正的二阶Lubich回火差分算子逼近Riesz空间回火的分数阶偏导数,构造出一类新的数值格式.给出了数值格式在一定条件下的稳定性与收敛性分析,且该格式的时间与空间收敛阶均为二阶.数值试验表明数值方法是有效的. 相似文献