Search

We investigate the molecular-beam-epitaxy growth of highly relaxed Si0.45Ge0.55 films with very low dislocation densities. By using the Si3N4 film as the mask material, the Si0.45Ge0.55 film can be grown on a compositionally stepwise graded SiGe buffer layer in 3 μm×3 μm windows on a Si (001) substrate. Raman scattering spectroscopy measurement shows that more than 90% strain of the Si0.45Ge0.55 film is relaxed, and almost neither misfit dislocation lines nor etch pits of thread dislocations could be observed when the sample is etched by the modified Schimmel etchant. We suggest that the results can be explained by influence of the edge-induced strain relaxation of the epitaxial film and the edge-induced stress of the mask material.

This article makes new interpretation of impacts of ecotourism from the perspective of biological environment, and points out negative impacts of ecotourism on biological environment, which are water attractions, soil and vegetation, as well as wildlife. On this basis, a detailed analysis of the negative impacts is made to reveal deep-rooted causes, and finally the tentative protective countermeasures to solve the problems are put forward: cultivation of environmental protection awareness, implementation of relevant legislation and regulation as well as limiting numbers within the carrying capacity of biological environment.

As a prosperous technology for ending-phase Internet access, Worldwide interoperability for Microwave Access (WiMAX) appeals concentration throughout the world since there are some places where wired infrastructures are not available. However, Call Admission Control (CAC) is critical to control different traffic loads and prevent the network from being blocked in WiMAX environment. In our paper, a novel bandwidth allocation scheme for IEEE 802.16 in WiMAX networks is proposed to balance various loads conditions. We develop a thorough set of simulation platform according to the WiMAX criteria. Results show that our presented idea could effectively improve blocking probability and increase bandwidth utility to some extent.

The static partitioning algorithm and assigning were generally researched respectively, which has largely resulted in the deficiency in the workload balance of the static partitioning. A new partitioning scheme of parallel VHDL simulation is presented in the paper. Partitioning and assigning both are processed just before the simulation in the scheme, and are included in the running phase. Because of this, it strictly requests that the time complexity of partitioning algorithm is minimum. A new static partitioning algorithm, fan-out right partitioning algorithm, which has a lower time complexity and good performance, is presented in the paper. The experiment result shows that the performance of parallel VHDL simulation is improved with this scheme and partitioning algorithm

By using compositionally graded SiGe films as virtual substrates, tensile strained Si films with the strain of 1.5% and the threading dislocation density less than 1.0 × 105 cm−2 are successfully grown in micron size windows by molecular beam epitaxy (MBE). The thickness of the virtual substrates was only 330nm. On the surface of the s-Si films no cross-hatched lines resulting from misfit dislocations could be observed. We attribute these results to the edge-induced strain relaxation of the epitaxial films in windows, and the patterned virtual substrates with compositionally graded SiGe films.