Search

Method of direct numerical simulation was used for the investigation of the local receptivity of a 2-D boundary layer of a flat plate to harmonic vortical disturbances in the freestream. Under the interaction of the vortical disturbances in the freestream and the roughness element on the wall, Tollmein-Schlichting (T-S) waves were generated and detected in the boundary layer, thus confirming that the wavelength conversion mechanism and the local receptivity exist. Numerical simulations were performed to obtain the relations between the amplitude of the generated T-S wave and the amplitude of freestream disturbance, the roughness height, and the width of rectangular roughness elements, which agree with those obtained from experiments. Then the range of validity of the linear receptivity formula, which was determined by these relations, also agrees with that determined by experimental results.

Parabolized stability equations (PSE) approach is used to investigate problems of secondary instability in supersonic boundary layers. The results show that the mechanism of secondary instability does work, whether the 2-D fundamental disturbance is of the first mode or second mode T-S wave. The variation of the growth rates of the 3-D sub-harmonic wave against its span-wise wave number and the amplitude of the 2-D fundamental wave is found to be similar to those found in incompressible boundary layers. But even as the amplitude of the 2-D wave is as large as the order 2%, the maximum growth rate of the 3-D sub-harmonic is still much smaller than the growth rate of the most unstable second mode 2-D T-S wave. Consequently, secondary instability is unlikely the main cause leading to transition in supersonic boundary layers.

A graph $G$ is called a cactus if each block of $G$ is either an edge or a cycle. Denote by $Cact(n;t)$ the set of connected cacti possessing $n$ vertices and $t$ cycles. In this paper, we show that there are some errors in [J. Du, G. Su, J. Tu, I. Gutman, The degree resistance distance of cacti, Discrete Appl. Math. 188 (2015) 16-24.], and we present some results which correct their mistakes. We also give the second-minimum and third-minimum degree resistance distances among graphs in $Cact(n;t)$, and characterize the corresponding extremal graphs as well., Comments and suggestions will be highly appreciated

Chinese higher education has entered the stage of popular education since 1999.Along with the entering into the stage of popularization of higher education, It is the common problems that improves the quality of education in the world. The young teacher teams in colleges and universities in our country expands constantly, the teaching ability of young teacher is related directly to the quality of education. From the current situation of the young teachers’ teaching ability and the factors which influence the teaching ability of young teachers, we presents the concept and implement scheme of the training of young teachers' teaching ability by teaching courseware.

The classical molecular dynamics simulation has been used to study the equation of state of gas H2, D2 and T2. It has also been investigated that the isotope mass affects on the accuracy of equation of state. Our calculated results show that the classical effect is principal and the isotope mass effects on the equation of state are obvious for the much light gases. At the same time, some useful theoretical data of equation of state for these gases have been provided. It is found that the classical simulation is still effective to the quantum gas. However, the quantum mechanics simulation and the improvement of intermolecular interaction potential are necessary if more accurate computational results are expected.

Mathematics experiments are applied in the course of complex analysis. By mathematical experiment, students can to chew the cud of theory, and mathematical software to calculate the results of validation, increase students' interest in learning and using math software ability to solve mathematical problems, improve the efficiency of problem solving. According to the constructivist learning theory,in accordance with teaching, programming, manual calculation, testify to teaching the process of reform.

To investigate mitochondrial factors associated with Leber hereditary optic neuropathy (LHON) through complete sequencing and analysis of the mitochondrial genome of Chinese patients with this disease.Two unrelated southern Chinese families with LHON and 10 matched healthy controls were recruited, and their entire mitochondrial DNA (mtDNA) was amplified and sequenced with the universal M13 primer. Then DNA sequence analysis and variation identification were perfomed by DNAssist and Chromas 2 software and compared with authoritative databases such as Mitomap.Mutational analysis of mtDNA in these two Chinese pedigrees revealed one common LHON-associated mutation, G11778A (Arg→His), in the MT-ND4 gene. In addition, there were two secondary mutations in Pedigree 1: C3497T (Ala→Val), and C3571T (Leu→Phe) in the MT-ND1 gene, which have not been reported; and two secondary mutations occurred in Pedigree 2: A10398G (Thr→Ala) in the MT-ND3 gene, and T14502C (Ile→Val) in the MT-ND6 gene. Three polymorphisms, A73G, G94A and A263G in the mtDNA control region, were also found.Our study confirmed that the known MT-ND4*G11778A mutation is the most significant cause of LHON. The C3497T and C3571T mutations in Pedigree 1 were also both at hot-spots of MT-ND1; they may affect the respiratory chain in coordination with the primary mutation G11778A. In Pedigree 2, the two secondary mutations A10398G of MT-ND3 and T14502C of MT-ND6 may influence mitochondrial respiratory complex I, leading to the mitochondrial respiratory chain dysfunction which results in optic atrophy together with G11778A. Therefore, not only the common primary LHON mutation is responsible for the visual atrophy, but other secondary mtDNA mutations should also be considered when giving genetic counseling.

This paper reports the process for fabricating Nb/Al-AlOx/Nb tunnel junction using rf-magnetron sputtering. The S-I-S sandwich structure is prepared without breaking vacuum. A detailed AES and XTEM analysis of the Nb/Al-AlOx/Nb sandwich structure shows the good quality of Al barrier. Typical l-V characteristic curves of tunnel junction are also given.