链间耦合对聚乙炔多链体系中电子极化子再激发态的影响

采用拓展紧束缚Su-Schrieffer-Heeger(SSH)模型,研究了链间耦合对反式聚乙炔多链体系中电子极化子再激发态的晶格位形、净电荷密度、局域能级波函数和态密度的影响.结果发现:对于两条链体系,当链间耦合很小(t⊥≤0.01 e V)时,注入到系统中的电子只会在第一条链上诱发产生一个晶格缺陷,形成电子极化子再激发态,这和单链体系是一致,而第二条链仍是二聚化基态.随着链间耦合的增大,第一条链上缺陷的局域度减少而第二条链上的缺陷局域度相应增加,直至两条链上的位形相同;对于多条链(5条链和6条链)体系,当耦合很小(t⊥≤0.05 e V)时,电子极化子再激发态也只会存在于一条链上,当链间耦合较强时,极化子再激发态会在链间层次性地扩展开来,并不会出现多条链位形相同;从两条链的能级图上可以看到随着链间耦合t⊥的增大,体系的带隙不断的增大和电子态密度显示的是完全吻合的,体系的导电性减弱.通过分析两条链体系在t⊥=0 e V和t⊥=0.1 e V的能级态密度,发现链间耦合越强,则中间局域能级的态密度越小,最后没有中间局域态.

孤子中的再激发研究

本文在准一维紧束缚近似下,研究了孤子中的再激发.得到S^0+hv(?)S~±+P^(?),S^0+hv(?)S^0+S^0+S^0,S^0+hv=K^(+(1/4))+K^(-(1/2)+K^(+(1/4)),S~±+hv(?)S^0+P~±,S^-+hv(?)K^0+K^(-1/2)+K^(-1/2).其中S^0,S~±和P~±分别代表中性孤子、带电孤子和带电极化子,K表示链中出现的扭结.

极化子、双极化子中的再激发研究

利用准一维紧束缚近似,理论上研究了极化子和双极化子中的再激发,分析了再激发态的物理性质。极化子激发后可能形成局域性更强的扭结、双极化子、激子态。双极化子激发后能够形成极化子、双极化子、双激子态。从中可以发现,有机聚合物中的载流子(极化子、双极化子)能够相互转换。电荷—自旋关系在光激发下能够发生变化。

新疆脱贫攻坚与乡村振兴战略衔接后脱贫群众的内生动力再激发

本文结合新疆深度贫困地区实际,仔细梳理脱贫群众内生动力再激发面临的挑战,在传统统扶志扶智基础上,探索提出强化村民参与村务、村干部问询质询和村小组绩效考核等措施,在党和政府的带领下,脱贫群众主动持续激发内生动力。

何首乌再激发药物性肝损伤的临床特征

我国人口基数庞大，临床药物种类繁多，人群不规范用药较为普遍，应用传统中药等较为随意，近年由此引起的药物性肝损伤（DILI）逐渐增加。药物再激发反应是指使用药物发生DILI后，再次使用该药物导致DILI的再次发生，是临床上诊断DILI的重要依据之一。

小议初一新生数学学习兴趣的再激发

兴趣是创新的源泉,可以激发学生的学习积极性。如何培养与激发初一新生的数学学习兴趣是新课标下的一个重要话题。

EBSD characterization of Al7075/graphene nanoplates/carbon nanotubes composites processed through post-deformation annealing

The effects of the post-deformation annealing on the microstructural evolution of hot rolled Al7075 matrix composites reinforced with CNTs and GNPs were investigated.The multi-pass hot rolling was applied on the stir cast samples.Annealing was then applied to the composites at 450℃ for 4 h.Microstructural evolution was examined by SEM,EDS,and EBSD techniques.EBSD data showed that the addition of 0.87 vol.%(GNPs+CNTs)significantly inhibited the occurrence of recrystallization.Also,in the composite with 0.96 vol.%CNTs,recrystallization was partially inhibited.Whereas,in composites with 0.92 vol.%of GNPs,the occurrence of recrystallization through particle stimulated nucleation(PSN)mechanism was significantly accelerated.The volume fraction of recrystallized grains depends significantly on the occurrence of PSN in the presence of reinforcements.The intensity and type of the main components of the texture as well as the FCC fibers depend on the type of reinforcement.

Role of particle stimulated nucleation in recrystallization of hot extruded Al 6061/SiC_p composites

Studies on texture and microstructure evolution in hot extruded Al 6061 aluminium alloy reinforced with uncoated and nickel coated SiC p were carried out by electron backscattered diffraction technique.Textures of both the alloy and its composite with nickel coated SiC p do exhibit strong β fiber with its axis parallel to the direction of extrusion.In addition to the dominant cube texture（001） 100,fully recrystallized grains with partially equiaxed structure have been observed in the alloy reinforced with uncoated SiC p.The recrystallization texture of this composite can be attributed to the particle stimulated nucleation（PSN） due to the presence of SiC p with size less than 5 μm.Under these conditions,the low value of Zener-Hollomon,Z（～1012s-1） confirms that PSN is one of the dominant mechanisms for recrystallization and is governed by formation of deformation zone rather than stored energy.

Correlating oriented grain number density of recrystallisation in particle-containing aluminium alloys

The recrystallized grain structure of Al-（Mn）-Fe-Si alloys after isothermal annealing was studied by electron backscatter diffraction（EBSD） technique. Statistical correlation suggests that the frequency of forming P-oriented（{011}？566？） grains at a particle larger than the critical diameter（about 1.1 μm） is about 2% when the effect of fine dispersoids and concurrent precipitation is negligible. The overall grain number density is correlated linearly with the number densities of P and Cube（{001}？100？） grains. The grain number densities of typical orientations（P, ND-rotated cube {001}？310？ and Cube） and the overall recrystallized grains increase as rolling strain increases, following a similar exponential law.

创设问题情境 激发学生思维

创设问题情境,激发学生思维,激疑,引发学生的学习动机,质疑,培养学生发现问题的能力,适度,提供学生积极思维的机会。引导学生主动探索,组织学生再创造活动,从而培养学生发现问题、提出问题、创造性地解决问题的能力。

含硫芴基的三苯胺多枝衍生物的光限幅特性

强双光子吸收有机分子在激光光限幅领域具有重要应用价值。通过测量纳秒脉冲下输入/输出光强的变化、纳秒/飞秒抽运下分子的双光子吸收以及单光子荧光衰减曲线,研究了一系列含硫芴基的三苯胺衍生物对纳秒激光的限幅特性与机制。结果表明,分子激发态寿命与激光脉宽在同一量级有助于激发态再吸收;具有长激发态寿命的多枝形分子其激发态再吸收更明显、表观双光子吸收截面显著增大,有利于提高分子的激光限幅效率。

Phonon Excitation and Energy Redistribution in Phonon Space for Energy Dissipation and Transport in Lattice Structure with Nonlinear Dispersion

We first propose fundamental solutions of wave propagation in dispersive chain subject to a localized initial perturbation in the displacement. Analytical solutions are obtained for both second order nonlinear dispersive chain and homogenous harmonic chain using stationary phase approximation. Solution is also compared with numerical results from molecular dynamics （MD） simulations. Locally dominant phonon modes （k-space） are introduced based on these solutions. These locally defined spatially and temporally varying phonon modes k（x, t） are critical to the concept of the local thermodynamic equilibrium （LTE）. Wave propagation accompanying with the nonequilibrium dynamics leads to the excitation of these locally defined phonon modes. It is found that the system energy is gradually redistributed among these excited phonons modes （k-space）. This redistribution process is only possible with nonlinear dispersion and requires a finite amount of time to achieve a steady state distribution. This time scale is dependent on the spatial distribution （or frequency content） of the initial perturbation and the dispersion relation. Sharper and more concentrated perturbation leads to a faster energy redistribution and dissipation. This energy redistribution generates localized phonons with various frequencies that can be important for phonon-phonon interaction and energy dissipation in nonlinear systems. Depending on the initial perturbation and temperature, the time scale associated with this energy distribution can be critical for energy dissipation compared to the Umklapp scattering process. Ballistic type of heat transport along the harmonic chain reveals that at any given position, the lowest mode （k = O） is excited first and gradually expanding to the highest mode （km^（x,t））, where km^（x,t） can only asymptotically approach the maximum mode kB of the first Brillouin zone （kmax（x,t） --~ kB）. NO energy distributed into modes with k_max（x,t） 〈 k 〈 k^B demonstrates that the local thermodynamic equilibrium cannot be established in harmonic chain. Energy is shown to be uniformly distributed in all available phonon modes k ≤ _max（x, t） at any position with heat transfer along the harmonic chain. The energy flux along the chain is shown to be a constant with time and proportional to the sound speed （ballistic transport）. Comparison with the Fourier＇s law leads to a time-dependent thermal conductivity that diverges with time.

Recycling alkali activated slag into artificial aggregate:Influence of particle size distribution of the starting material on granulation

Wet granulation is a potential method to develop artificial aggregates.In this paper,the granulation of recycled alkali-activated slag powders with different particle size(d_(50) ranging between 12.9-127.7μm)distributions were investigated in order to find how these affect on the engineering properties of the artificial aggregates.Blast furnace slag was added as co-binder in 10-30 wt.%during the granulation process and to enhance the properties,especially mechanical strength.The results show that the particle size of the raw material significantly affects the engineering properties of the produced aggregates,such as the crushing force(19-131.8 N),bulk density,water absorption,porosity and microstructure of the granules.The results show that granulation is a promising method to recycle alkali-activated materials as lightweight aggregates to replace natural aggregates.

Influence of extrusion ratio on microstructure and texture developments of high-temperature extruded AZ31 Mg alloy

Experiments were conducted to evaluate the effects of extrusion ratio on the microstructure and texture developments of AZ31 Mg alloy during forward extrusion. The forward extrusion was undertaken at 400℃ with extrusion ratios of 10, 18, and 25 after the alloy was homogenized at 410℃ for 12 h. Partially recrystallized microstructures were observed in all the extruded rods examined. The texture of the large elongated deformed grains appeared strongly centered at （1010） dominating the extrusion texture, while the recrystallized grains exhibited much more randomized texture. For the alloy with the largest ER （25）, coarse secondary recrystallized grains were found which presented a different texture component with （11 2 0） parallel to the ED. The occurrence of the coarse secondary recrystallized grains in the alloy with the largest ER might be attributed to that the large ER raised the die exit temperature during extrusion and thus promoted significantly grain growth after the extruded rod exited from extrusion die. The intensities of different texture components varied with ER because ER affected the contents of the deformed grains, DRX grains and coarse secondary recrystallized grains. In particular, the maximum intensity of fiber texture was decreased as ER increased due to the decrease of the large elongated deformed grains.