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991.
The g factors g // and g ⊥ of the ground Γ6(2 T 2) and excited Γ4,5(2 E), Γ6(2 E) states for trigonal Cu2+ centres in ZnO crystals are calculated from three theoretical methods, the complete diagonalization (of the energy matrix) method, the second-order perturbation method (PTM-I) and the simplified second-order perturbation method (PTM-II, this method was described in an earlier paper). These methods are based on the cluster approach in which the spin-orbit coupling parameters ζ, ζ′ and the orbital reduction factors k, k′ are calculated from a semi-empirical molecular orbital method. The crystal-field parameters used in the calculations are obtained from the superposition model and so the defect structure of Cu2+ centres in ZnO can be acquired. The calculated g factors from the three methods are in reasonable agreement with the experimental values and the defect structure of Cu2+ centres in ZnO is acquired. It appears that in some cases the approximate PTM can be applied in the studies of g factors of various states. The conditions that the PTM are ineffective are discussed. 相似文献
992.
利用惠普实验室荷控和磁控两种忆阻器模型设计了一个五阶混沌电路. 数值仿真结果表明该电路在参数变化情况下能产生Hopf分岔和反倍周期分岔两种分岔行为,并能产生双涡卷、单涡卷、周期态等不同相轨道. 为了验证电路的混沌行为,利用基本元器件设计了惠普实验室荷控和磁控忆阻器模拟器,并将其应用到对所设计电路中进行Pspice仿真,电路仿真结果验证了理论分析的正确性.
关键词:
混沌电路
HP忆阻器
模拟器
Pspice仿真 相似文献
993.
单载波时域均衡在长时延扩展水声信道中计算量大,并对接收机参数的选择较为敏感,可靠性低,而正交频分复用信号峰均功率比高、对频率偏移敏感. 针对这些问题,提出基于扩频码的单载波块传输高速率水声通信方法和基于T/4分数间隔迭代频域均衡的接收机算法. 该接收机利用已知扩频码进行信道估计以及对由多普勒偏移引起的旋转相位进行估计,并通过一种低复杂度迭代频域均衡算法改善系统性能. 开展了湖上实验研究,结果表明在浅水1.8 km距离且复杂多径干扰条件下,利用BPSK/QPSK调制可实现10-2–10-4的误码率并达到1500–3000 bit/s的有效数据率.
关键词:
水声通信
单载波
频域均衡
迭代处理 相似文献
994.
In this paper, a microring resonator with two embedded microring (MRTEM) has been presented and studied theoretically. Transfer matrix method (TMM) has been used to simulate MRTEM and analyze the relations between add/drop spectrum and embedded microring arrangements. Three kinds of embedded microring arrangements have been proposed and analyzed by TMM. The theoretical and simulation results show that the Q factor of our structure is higher than that of traditional microring structure and the spectrum of MRTEM is independent on embedded arrangements. 相似文献
995.
A type of high birefringence dual-core photonic crystal fibers (DC-PCFs) with a central row of elliptical air holes have been proposed. The transverse electric field vector distributions of the two modes are evaluated, the birefringence or coupling length with the different parameters is numerically analyzed based on finite-element method. The numerical results show values for the birefringence of 8.247 × 10−3 (for wavelength, λ = 1.5 μm and lattice length, Λ = 1.3 μm), and for the coupling lengths about 3.1 mm and 2.6 mm (λ = 1.5 μm and Λ = 1.5 μm) to modes of x and y polarized, respectively. With the increasing of the air-filling fraction in proposed DC-PCF, the coupling length becomes longer and the birefringence becomes higher. 相似文献
996.
Previous studies have revealed that dislocation structures in metals with medium-to-high stacking fault energy, depend on the grain orientation and therefore on the slip systems. In the present work, the dislocations in eight slip-plane-aligned geometrically necessary boundaries (GNBs) in three grains of near 45° ND rotated cube orientation in lightly rolled pure aluminium are characterized in great detail using transmission electron microscopy. Dislocations with all six Burgers vectors of the ½?1?1?0? type expected for fcc crystals were observed but dislocations from the four slip systems expected active dominate. The dislocations predicted inactive are primarily attributed to dislocation reactions in the boundary. Two main types of dislocation networks in the boundaries were identified: (1) a hexagonal network of the three dislocations in the slip plane with which the boundary was aligned; two of these come from the active slip systems, the third is attributed to dislocation reactions (2) a network of three dislocations from both of the active slip planes; two of these react to form Lomer locks. The results indicate a systematic boundary formation process for the GNBs. Redundant dislocations are not observed in significant densities. 相似文献
997.
Single photon pulse ranging system with extremely high sensitivity has been widely used in distance measurement and 3D imaging. To analyze the factors that affect the measurement precision and accuracy will help to improve system performance. According to system structure and principle, we mainly discussed the following factors: laser intensity, pulse width, detection efficiency and time jitter. A simulation model based on Monte Carlo stochastic method was constructed in this paper, and we get the specific influence of factors on measurement precision and accuracy by simulation. Finally, we set up laboratory experiment system and took effective experiments on ranging precision and accuracy. 相似文献
998.
Chang Wen Minghou Xu Dunxi Yu Changdong Sheng Hongwei Wu Ping’an Zhang Yu Qiao Hong Yao 《Proceedings of the Combustion Institute》2013,34(2):2383-2392
The formation of PM10 (particles less than or equal to 10 μm in aerodynamic diameter) during char combustion in both air-firing and oxy-firing was investigated. Three Chinese coals of different ranks (i.e., DT bituminous coal, CF lignite, and YQ anthracite) were devolatilized at 1300 °C in N2 and CO2 atmosphere, respectively, in a drop tube furnace (DTF). The resulting N2-chars and CO2-chars were burned at 1300 °C in both air-firing (O2/N2 = 21/79) and oxy-firing (O2/CO2 = 21/79). The effects of char properties and combustion conditions on PM10 formation during char combustion were studied. It was found that the formation modes and particle size distribution of PM10 from char combustion whether in air-firing or in oxy-firing were similar to those from pulverized coal combustion. The significant amounts of PM0.5 (particles less than or equal to 0.5 μm in aerodynamic diameter) generated from combustion of various chars suggested that the mineral matter left in the chars after coal devolatilization still had great contributions to the formation of ultrafine particles even during the char combustion stage. The concentration of PM10 from char combustion in oxy-firing was generally less than that in air-firing. The properties of the CO2-chars were different from those of the N2-chars, which was likely due to gasification reactions coal particles experienced during devolatilization in CO2 atmosphere. Regardless of the combustion modes, PM10 formation in combustion of N2-char and CO2-char from the same coal was found to be significantly dependent on char properties. The difference in the PM10 formation behavior between the N2-char and CO2-char was coal-type dependent. 相似文献
999.
M. Ahmad E. Ahmed Yuewei Zhang N.R. Khalid Jianfeng Xu M. Ullah Zhanglian Hong 《Current Applied Physics》2013,13(4):697-704
Novel Al-doped ZnO (AZO) photocatalysts with different Al concentrations (0.5–6.0 mol%) were prepared through a facile combustion method and followed by calcination at 500 °C for 3 h. The obtained nanopowders were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM) combined with EDX, transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy and photoluminescence spectroscopy. The XRD patterns of AZO nanopowders were assigned to wurtzite structure of ZnO with the smallest crystallite size about 11 nm consistent with the results from TEM. The doping of Al in ZnO crystal structure successfully suppressed the growth of ZnO nanoparticles confirmed by XRD patterns. The absorption spectra analysis showed that the optical band gap energy (Eg) for the AZO nanopowders were in the range of 3.12–3.21 eV and decreased with increasing of Al dopant. The photocatalytic activities of the samples were evaluated by photocatalytic degradation of methyl orange under visible light (λ ≥ 420 nm) and sunlight irradiation. The results showed that the AZO photocatalyst doped with 4.0 mol% Al exhibited five times enhanced photocatalytic activity compared to pure ZnO. The enhanced photocatalytic activity could be attributed to extended visible light absorption, inhibition of the electron–hole pair's recombination and enhanced adsorptivity of MO dye molecule on the surface of AZO nanopowders. 相似文献
1000.
关于Lagrange内插过程的“1/2”平均 总被引:1,自引:0,他引:1
本文研究了以Chebyshev多项式的零点为插值节点的Lagrange插值过程“1/2”平均算子,给出了点态收敛阶,并重新证明了A.F.Timan定理。 相似文献