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61.
We study controllable self-shifting Bloch modes in anisotropic hexagonal photonic lattices. The shifting results from a deformed band structure due to deformation of the index distribution in each unit cell. By reconfiguration of the index profile of the unit cell, the direction in which the Bloch modes move can be controlled. Our theoretical predictions are experimentally demonstrated in hexagonal lattices optically induced in an anisotropic nonlinear crystal. 相似文献
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64.
超声流量测量系统中,严重影响时间差检测的准确度和稳定性的“零点误差”和“温度漂移”问题可以通过对测量系统互易性的改善加以改进。本文通过对测量系统等效电路模型的分析阐述了系统互易的成立条件,并提出了一种通过对激励和接收电路等效阻抗进行对称性设计提高测量系统互易性的测量电路。这一电路设计易于在仪表中实现,其中换能器的负载阻抗能够根据需要灵活设定。在实际测量管道上进行的实验证明,使用这样的电路设计进行流量测量,能够大幅降低零点误差并抑制温度漂移,使得流量测量结果更加准确稳定。 相似文献
65.
Dynamic Fracture Toughness and Failure Mechanisms of ZnO Whiskers Secondary Reinforced Composites 下载免费PDF全文
Quasi-static and dynamic fracture properties and damage mechanism of glass fiber polymer composites embeaaea with different mass percentages of ZnO whiskers are investigated by using an Instron Testing machine and a Split- Hopkinson pressure bar. According to the experimental results and linear fracture mechanics, the quasi-static fracture toughness Kic and the dynamic fracture toughness Kid under various impact velocities of specimens are obtained. Fracture mechanism is investigated by fractography analysis with a scanning electron microscope. The experimental results show that the mass percentage of ZnOw has little influence on the quasi-static fracture toughness, but a little influence on the dynamic fracture toughness and time of initial fracture point of specimens by the reason of various fracture mechanisms. 相似文献
66.
Liquid scintillators are widely used as the neutrino target in neutrino experiments.The absorption and emission of different components of a ternary liquid scintillator (Linear Alkyl Benzene (LAB) as the solvent,2,5-diphenyloxazole (PPO) as the fluor and p-bis-(o-methylstyryl)-benzene (bis-MSB) as wavelength shifter) are studied.It is shown that the absorption of this liquid scintillator is dominant by LAB and PPO at wavelengths less than 349 nm,and the absorption by bis-MSB becomes prevalent at the wavelength larger than 349 nm.The fluorescence quantum yields,which are the key parameters to model the absorption and re-emission processes in large liquid scintillation detectors,are measured. 相似文献
67.
C.H. Lin S.Y. Chen N.J. Ho D. Gan P. Shen 《Journal of Physics and Chemistry of Solids》2009,70(12):1505-1510
The α-Cr2O3 single-crystal nanocondensates were fabricated by pulsed laser ablation in air and characterized by analytical electron microscopy regarding shape-dependent local internal stress of the anisotropic crystal. The nanocondensates formed predominantly as rhombohedra with well-developed surfaces and occasionally hexagonal plate with thin edges and blunt corners. Such nanocondensates showed Raman shift for the CrO6 polyhedra, indicating a local compressive stress up to ca. 4 GPa on the average. Careful analysis of the lattice fringes revealed a local compressive stress (0.5% strain) at the thin edge of the hexagonal plates and a local tensile stress (0.3–1.0% strain) near the relaxed , , and (0 0 0 1) surfaces of truncated rhombohedra. The combined effects of nanosize, capillarity force at sharp edge, and specific surface relaxation account for the retention of a local internal compressive stress built up in an anisotropic crystal during a very rapid heating–cooling process. 相似文献
68.
Qian C Fu R Gor'kov P Brey WW Cross TA Gan Z 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,196(1):96-99
Polarization Inversion Spin Exchange at Magic Angle (PISEMA) is a powerful experiment for determining peptide orientation in uniformly aligned samples such as planar membranes. In this paper, we present (14)N-PISEMA experiment which correlates (14)N quadrupolar coupling and (14)N-(1)H dipolar coupling. (14)N-PISEMA enables the use of (14)N quadrupolar coupling tensor as an ultra sensitive probe for peptide orientation and can be carried out without the need of isotope enrichment. The experiment is based on selective spin-exchange between a proton and a single-quantum transition of (14)N spins. The spin-exchange dynamics is described and the experiment is demonstrated with a natural abundant N-acetyl valine crystal sample. 相似文献
69.
水下复杂壳体结构在多源激励下的振动及声辐射特性研究 总被引:3,自引:0,他引:3
为了综合评估水下复杂壳体结构在多源激励下的振动与声辐射特性,专门设计了一个多舱段复杂壳体模型,分别进行了单台设备激励、多台设备激励的壳体振动与声辐射试验。试验结果表明,多源激励下的结构响应和辐射声场可以近似为单源激励下结构响应和辐射声场的非相干叠加。通过对激励源与结构响应、辐射声场之间传递关系的理论分析,讨论了以单源激励响应非相干叠加合成得到多源激励响应的合理性和误差。研究结果对复杂壳体结构在实际激励下的振动与噪声预报具有重要价值。 相似文献
70.
Ivan Hung Julien Trbosc Gina L. Hoatson Robert L. Vold Jean-Paul Amoureux Zhehong Gan 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,201(1):81-86
The multiple-quantum magic-angle spinning (MQMAS) and satellite-transition magic-angle spinning (STMAS) experiments refocus second-order quadrupolar broadening of half-integer quadrupolar spins in the form of two-dimensional experiments. Isotropic shearing is usually applied along the indirect dimension of the 2D spectra such that an isotropic projection free of anisotropic quadrupolar broadening can be obtained. An alternative shear transformation by a factor equal to the coherence level (quantum number) selected during the evolution period is proposed. Such a transformation eliminates chemical shift along the indirect dimension leaving only the second-order quadrupolar-induced shift and anisotropic broadening, and is expected to be particularly useful for disordered systems. This transformation, dubbed Q-shearing, can help avoid aliasing problems due to large chemical shift ranges and spinning sidebands. It can also be used as an intermediate step to the isotropic representation for expanding the spectral window of rotor-synchronized experiments. 相似文献