Investigation on design method of curved compression surface of inlet on scramjet

Suppose that curved compression surface of inlet consists of segments. Two curved surfaces formed by equal compression angles of the micro-element segments and a slight increase in the compression angle of the micro-element segments are designed respectively. The numerical simulation method is used to compare the performance of two curved surfaces with the reference three-wedge compression surface. Select NASA classic test data, in order to determine the turbulence model and calculation method chosen by the numerical simulation Fluent software. The results show: the configuration of the segment compression angle deeply affects compression efficiency of the curved surface compression system. Pressure gradient distribution on the compression surface with constant compression angles segments is nearly constant along the incoming flow direction, and the curved compression surface easily resist the separation of the boundary layer compared to three-wedges compression surface. The approximate calculation method of the bending shock profile is given.

Entropy Analysis for Cilia-Generated Motion of Cu-Blood Flow of Nanofluid in an Annulus

In this study, a novel model of entropy generation effects measured in the Cu-blood flow of a nanofluid under the effect of ciliary-oriented motion is proposed. The effects of viscous dissipation are also taken into account. The physical model was composed with the incorporation of a low Reynolds number and long-wavelength phenomena. The exact solutions for the axial velocity, temperature and pressure gradient distribution were achieved successfully. Key findings are presented through a strategy of plotting the significant factors affecting the physical quantities of the stream. It was found that the heat absorption parameter and Brownian motion accounted for the large thermal transfer rate, while the effect of entropy was minimal compared to these factors in the center of the flow but increased on the walls in the case of Cu-blood flow. It can also be added that a more intense flow gave rise to the entropy effects. This study may be helpful in medical science as cilia play vital roles, which include cell migration and external fluid transport, in human tissues and some key organs. Moreover, the considered annulus-shaped geometry gives vital readings that are used in medical equipment such as endoscopes.

Micro-structural and compositional study: ε-Fe2O3 crystals in the Hare’s Fur Jian Ware

The Jian kilns in the present-day Jianyang county of Fujian province are well-known as their thick and lustrous black-glazed porcelain production. The hare’s fur (HF) glazed Jian wares characterized by radial fur-like strips, as one of the most typical representatives of black-glazed tea bowls, are originated from phase separation of glaze melt and crystallization of iron oxides. In this work, various techniques were performed on the yellowish-brown HF samples, including portable energy-dispersive X-ray fluorescence (PXRF), synchrotron X-ray absorption near-edge spectroscopy (XANES), optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy (RS). The objective of this study was to well understand the microstructure characteristics and chemical compositions of glaze patterns. Results showed that the main constituents of the ceramic glaze were alumina (10.61-16.43 wt.%), silica (62.20-77.07 wt.%), calcium (3.85-6.97 wt.%) and iron oxide (4.10-8.35 wt.%). The studies evidenced that the presence of metastable epsilon-hematite crystals (ε-Fe2O3) formed on the brownish yellow glazed surface. Microstructural analysis revealed that there were three types of crystal structures in the glaze surface, one consisted of well-grown leaf-like or dendritic-like structure with highly ordered branches at micrometers scales, one was comprised of flower-like clusters accompanied by branches radiating from the center, petals growing along the branches and needles on both sides of the petals, and the last embraced a honeycomb structure tightly packed with plentiful spherical or irregular-shaped particles. In addition, ε-Fe2O3 crystals in the cross-section of glaze showed a gradient distribution.

LAMOST medium-resolution spectral survey of Galactic nebulae (LAMOST-MRS-N): subtraction of geocoronal Hα emission

We introduce a method of subtracting geocoronal Hα emissions from the spectra of LAMOST medium-resolution spectral survey of Galactic nebulae (LAMOST-MRS-N). The flux ratios of the Hα sky line to the adjacent OH λ6554 single line do not show a pattern or gradient distribution in a plate. More interestingly, the ratio is well correlated to solar altitude, which is the angle of the Sun relative to the Earthʼs horizon. It is found that the ratio decreases from 0.8 to 0.2 with the decreasing solar altitude from –17 to –73 degree. Based on this relation, which is described by a linear function, we can construct the Hα sky component and subtract it from the science spectrum. This method has been applied to the LAMOST-MRS-N data, and the contamination level of the Hα sky to nebula is reduced from 40% to less than 10%. The new generated spectra will significantly improve the accuracy of the classifications and the measurements of physical parameters of Galactic nebulae.

Effect of Pouring Temperature on Microstructures and Mechanical Properties of 7085 Ingot Casting by Finite Element Analysis

The microstructure and mechanical properties of the 7085 ingot casting was tested by OM, SEM and EDS, the fatigue damage was observed in the driving test process, the temperature gradient distribution was adjusted observably by using the FEM simulation analysis. By adjusting the pouring temperature, many micro shrinkage metallurgical defects were eliminated, the tensile strength, yield strength and elongation were raised to 498MPa, 362MPa and 7.4% at the T6 heat treatment state.

A field experiment on surface wave isolation by partially embedded periodic pile barriers

The bandgap characteristics of periodic structures show a great application prospect in seismic isolation and vibration mitigation. A T-shaped partially embedded periodic pile barrier is designed and studied based on the Bloch’s theorem. The proposed structure is fabricated and tested in field experiment to validate the simulation and the isolation performance. Good agreements are observed between the measured and the corresponding simulated results which present effective isolation for surface waves. The influences of the embedded length in the soil and the arrangement of the pile are investigated. The results show that the embedded length is the key parameter affecting the vibration attenuation. The smaller the embedded length, the lower the frequency of attenuation zone, and thanks to the embedded length; the proposed barrier exhibits better performances than the fully embedded and non-embedded barriers in maximum bandgap width, tunability, and feasibility in engineering. Gradient distribution of the embedded length leads to a wider frequency range of attenuation.