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131.
Using the finite element method, this paper investigates lateral
stress-induced propagation characteristics in a photonic crystal
fibre of hexagonal symmetry. The results of simulation show the
strong stress dependence of effective index of the fundamental
guided mode, phase modal birefringence and confinement loss. It also
finds that the contribution of the geometrical effect that is
related only to deformation of the photonic crystal fibre and the
stress-related contribution to phase modal birefringence and
confinement loss are entirely different. Furthermore,
polarization-dependent stress sensitivity of confinement loss is
proposed in this paper. 相似文献
132.
Element-free Galerkin (EFG) method for a kind of two-dimensional linear hyperbolic equation 下载免费PDF全文
The present paper deals with the numerical solution of
a two-dimensional linear hyperbolic equation by using the element-free
Galerkin (EFG) method which is based on the moving least-square
approximation for the test and trial functions. A variational method
is used to obtain the discrete equations, and the essential boundary
conditions are enforced by the penalty method. Compared with
numerical methods based on mesh, the EFG method for hyperbolic
problems needs only the scattered nodes instead of meshing the
domain of the problem. It neither requires any element connectivity
nor suffers much degradation in accuracy when nodal arrangements are
very irregular. The effectiveness of the EFG method for two-dimensional
hyperbolic problems is investigated by two numerical examples in
this paper. 相似文献
133.
The influence of strain-reducing layer on strain distribution and ground state energy levels of GaN/AlN quantum dot 下载免费PDF全文
This article deals with the strain distributions around GaN/AlN
quantum dots by using the finite element method. Special attention
is paid to the influence of Al0.2Ga0.8N strain-reducing
layer on strain distribution and electronic structure. The numerical
results show that the horizontal and the vertical strain components
are reinforced in the GaN quantum dot due to the presence of the
strain-reducing layer, but the hydrostatic strain in the quantum dot
is not influenced. According to the deformation potential theory, we
study the band edge modifications and the piezoelectric effects.
The result demonstrates that with the increase of the strain reducing layer,
the transition energy between the ground state electron and the heavy hole
increases. This result is consistent with the emission wavelength
blue shift phenomenon observed in the experiment and confirms that the
wavelength shifts toward the short wavelength range is realizable by
adjusting the structure-dependent parameters of GaN/AlN quantum dot. 相似文献
134.
野生和人工栽培漆树液多糖的分子结构与生物活性 总被引:4,自引:0,他引:4
从湖北毛坝野生(大木)和人工栽培(小木)漆树液中分离纯化出酸性杂多糖D-LP和X-LP,化学降解和光谱分析表明两种多糖均含有D-Gal、D-GlcA、L-Ara和L-Rha,其摩尔比分别为77:18.3:3.7:1和63.7:13.3:3.9:1.两种漆多糖都是以β(1→3)D-Gal为主链的高度支化酸性杂多糖.D-LP支化度较高,分支点在Gal的C6和C4位;而X-LP仅有部分主链D-Gal的C6位发生支化.小鼠腹腔注射试验表明,两种漆多糖均具有明显的免疫抑制作用,同时由野生漆树液提取的D-LP显示出比X-LP更高的免疫抑制功能和升白细胞活性功能. 相似文献
135.
合成了新的O-(硫杂蒽酮-[2]-基)-氧乙酸及其稀土配合物.通过元素分析,IR,1H NMR,UV,DTA-TG和13C NMR谱对其结构进行了表征.研究表明:配体羧羰基脱质子后与金属离子配位,2位氧原子也与金属离子配位,配合物中含有一定量的配位水,配合物为非电解质类型.同时,研究了O-(硫杂蒽酮-[2]-基)-氧乙酸稀土配合物对质粒DNA的切割作用.结果表明:铕的配合物对DNA的切割较明显,且当配合物浓度增加时,质粒DNA的超螺旋构型逐渐减少,而缺刻、开环型构型逐渐增多.在相同条件下,Eu(Ⅲ)离子对质粒pBR322DNA几乎没有切割作用;配体O-(硫杂蒽酮-[2]-基)-氧乙酸对质粒pBR322DNA也有切割作用,但配合物EuL3对质粒pBR322DNA的切割作用明显强于配体,表明稀土离子Eu(Ⅲ)与配体生成配合物后有较好的协同切割作用. 相似文献
136.
137.
138.
We present equilibrium composition maps in InGaAs/GaAs conic strained quantum dots, using the finite element method and quadratic programming optimization method. The axis-symmetric model is adopted. We compare the steep islands with the shallow islands and determine the influence of entropie energy. The difference of equilibrium composition maps between the single dot and the quantum dot stacks is also discussed. 相似文献
139.
分析了量子点盖层生长过程中隔层厚度对应变分布的影响,指出隔层材料的纵向晶格常数与量子点材料的纵向晶格常数对应变分布具有重要意义.定性说明了应变因素在隔离层生长过程中对量子点高度塌陷产生的影响.讨论了当隔离层顶面与量子点高度持平后,增加盖层厚度对应变分布的影响.基于变形势理论,讨论了上述几何参数的变化对发光波长的影响,并与实验结果进行了对比.结果表明,在量子点加盖过程中,应变因素对其形貌和发光特性具有重要作用,以应变工程为基础的发射波长调控是拓展量子点波长发射范围的有效途径.
关键词:
应变工程
半导体量子点
隔离层
盖层 相似文献
140.
Surface diffusion of Si,Ge and C adatoms on Si (001) substrate studied the molecular dynamics simulation 下载免费PDF全文
Depositions of Si, Ge and C atoms onto a preliminary Si (001) substrate at different temperatures are investigated by using the molecular dynamics method. The mechanism of atomic self-assembling occurring locally on the flat terraces between steps is suggested. Diffusion and arrangement patterns of adatoms at different temperatures are observed. At 900 K, the deposited atoms are more likely to form dimers in the perpendicular [110] direction due to the more favourable movement along the perpendicular [110] direction. C adatoms are more likely to break or reconstruct the dimers on the substrate surface and have larger diffusion distances than Ge and Si adatoms. Exchange between C adatoms and substrate atoms are obvious and the epitaxial thickness is small. Total potential energies of adatoms and substrate atoms involved in the simulation cell are computed. When a newly arrived adatom reaches the stable position, the potential energy of the system will decrease and the curves turns into a ladder-like shape. It is found that C adatoms can lead to more reduction of the system energy and the potential energy of the system will increase as temperature increases. 相似文献