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61.
We have developed a kinematical theory for the asteroidal belt and Kirkwood gaps from the point of view of stellar dynamics.
We have generated the potential that would produce these gaps and have made a spectral analysis study. We have shown that
these gaps could be due to spiral tubes of matter in the ecliptic plane as a consequence of differential rotation and spatial
interference of density waves. We have also shown that this mechanism could account for depletion of matter from this region. 相似文献
62.
The geometric structures, infrared spectra and hydrogen bond binding energies of the various hydrogen‐bonded Res?‐water complexes in states S0 and S1 have been calculated using the density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) methods, respectively. Based on the changes of the hydrogen bond lengths and binding energies as well as the spectral shifts of the vibrational mode of the hydroxyl groups, it is demonstrated that hydrogen bonds HB‐II, HB‐III and HB‐IV are strengthened while hydrogen bond HB‐I is weakened in the four singly hydrogen‐bonded Res?‐Water complexes upon photoexcitation. When the four hydrogen bonds are formed simultaneously between one resorufin anion and four water molecules in the Res?‐4Water complex, all the hydrogen bonds are weakened in both the ground and excited states compared with those in the corresponding singly hydrogen‐bonded Res?‐Water complexes. Furthermore, in complex Res?‐4Water, hydrogen bonds HB‐II and HB‐IV are strengthened while hydrogen bonds HB‐I and HB‐III are weakened after the electronic excitation. The hydrogen bond strengthening and weakening in the various hydrogen‐bonded Res?‐water complexes should be due to the redistribution of the charges among the four heteroatoms (O1‐3 and N1) within the resorufin molecule upon the optical excitation. 相似文献
63.
位错是金属塑性变形普遍形式,对其可动位错演化特性与规律探寻并充分利用,将在金属强韧化提升中有着潜在基础前瞻性研究价值.本文基于分子动力学法对金属Al塑性变形的可动位错迁演特性展开研究,洞悉纳米压痕诱导的可动位错与孪晶界面间作用规律,揭示出金属强化微观机制,并分析单层孪晶界高度与多层孪晶界层间距对可动位错迁演、位错密度、硬度、黏着效应的影响.研究发现:高速变形下的金属非晶产生和密排六方结构的出现会协同主导Al基塑性变形,而孪晶界会阻碍可动位错滑移、诱导可动位错缠绕及交滑移产生,在金属承载提升中扮演了位错墙和诱导位错胞形成的微观作用.通过在孪晶界形成钉扎位错和限制位错迁移,在受限域形成高密度局域可动位错,显著强化了金属硬度和韧性,降低了卸载时黏附于探针表面的原子数.结果表明:Al基受载会诱导上表面局部非接触区原子失配斑出现;单层孪晶界高度离基底上表面距离减小时,位错缠绕和交滑移作用越明显,抗黏着效应也随之下降;载荷持续增加会诱驱孪晶界成为位错萌生处与发射源,并伴随塑性环的繁衍增殖. 相似文献
64.
65.
A modified spatially extended Tang-Othmer Ca2+ model is used to study intracellular Ca2+ spiral waves numerically.It is found that,as a local stimulation,the local agonist-binding on the cell membrane,which enhances the local concentration of the messenger molecule inositol 1,4,5-trisphosphate(IP 3),can influence the dynamics of the spiral waves.1) Strong enough stimuli can change the spiral wave from a meandering to a rigidly rotating one.2) On the other hand,strong enough stimuli can suppress the spiral wave from the system.It provides the theoretical clue for controlling the spiral waves by stimulating the cell membrane. 相似文献
66.
为了提高对等离子体内界面区域的诊断精度,研究了利用螺旋型波带片实现边缘增强成像的技术。制作了用于可见光波段的一阶螺旋型波带片,最外环宽度3μm。利用螺旋型波带片对振幅式物体进行了边缘增强成像,实验获得了成像物体内边界区域的清晰图像,界面区域的成像强度得到很大增强。通过实验测量发现,当物距在菲涅耳衍射区域内时,螺旋型波带片也能够获取较好的成像质量,表明螺旋型波带片具有较大的视场角,能够对大尺度物体进行边缘成像。基于螺旋型波带片的边缘增强成像可以弥补传统成像方式对界面区域成像的不足,提高对等离子体内界面区域的诊断能力。 相似文献
67.
采用螺旋线和折叠线技术相结合的方法,设计了一种基于水介质高功率脉冲调制器。该调制器采用了两个开关,通过控制两个开关的导通时刻,可以在两个负载上得到脉冲长度相等的两个脉冲。对该种折叠型传输线的波过程进行了详细分析,给出了过渡段部分阻抗等参数对负载电压的影响;用Pspice电路软件对脉冲形成线的充电电压和二极管电压、电流进行了模拟;最后利用高压同轴电缆,对该种类型调制器进行了低压情况下的验证实验,实验结果与理论分析、模拟研究一致。此种类型的调制器具有结构紧凑、可同时输出两个脉冲的优点。 相似文献
68.
Multi-mode spiral wave and its breakup in 1-d and 2-d coupled oscillatory media is studied here by theoretic analysis and numerical simulations. The analysis in 1-d system shows that the dispersion relation curve could be nonmonotonic depending on the coupling strength. It may also lead to the coexistence of different wave numbers within one system. Direct numerical observations in 1-d and 2-d systems conform to the prediction of dispersion relation analysis. Our findings indicate that the wave grouping can also be observed in oscillatory media without tip meandering and waves with negative group velocity can occur without inhomogeneity. 相似文献
69.
70.
We fabricate 2D–3D photonic crystal heterostructures based on the silicon [001]-diamond:1 square spiral geometry using glancing angle deposition. We compare the normal incidence reflection properties of the fabricated 2D–3D heterostructures to simulated spectra generated using finite-difference time-domain calculations. Reflection peaks are observed, resulting from the presence of a photonic band gap, and defect modes are created by the 2D layer. Deterioration of the reflectance peaks with increased number of vertical spiral periods is observed. A series of square spiral structures are fabricated with a varying number of vertical periods to quantify the degradation of reflection peaks. At normal light incidence, a maximum reflection peak is observed from the film with three vertical periods. Beyond three spiral rotations, deterioration of the substrate-plane periodicity causes scattering losses. 相似文献