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Mach 4.5 tests in a conventional trans-supersonic wind tunnel are often accompanied by the air liquefaction phenomenon, resulting in the low reliability of test data. The Mach 4.5 nozzle developed in a hypersonic wind tunnel is able to heat airflow and provide more accurate test data. At present, China does not have the capability to test the Mach 4.5 nozzle in the 0.5-meter hypersonic wind tunnel. This gap may be filled by developing the Mach 4.5 nozzle in the hypersonic wind tunnel. The axisymmetric nozzle profile was calculated by the inviscid flow calculation method, and the boundary layer was modified by the Sivells-Payne method. Then, the numerical simulation was carried out, and the simulation results prove that the nozzle profile thus calculated meets the design requirements of the Mach number. For its structural design, a three-section design method is adopted to ensure the continuity and smoothness of the inner surface so as to better calibrate the flow field. Standard model tests were also carried out. The test results show that the velocity field of the Mach 4.5 nozzle we developed meets technical requirements. The standard model test data provide data reliable support for the development of aircraft.

ObjectiveTo explore the variation rules and health risks of trihalomethane in regional drinking water， and to provide evidence for the innovative water processing technology and the optimization of drinking water quality.MethodsBased on regional drinking water sanitation monitoring， non-parametric rank sum test was used to analyze the effects of residual trihalomethane production in different periods and with disinfection methods. The United States environmental protection agency （USEPA） classic "four-step" health risk assessment model was used to evaluate the carcinogenic risk and non-carcinogenic risk of trihalomethane through drinking water exposure.ResultsThe yield of trichloromethane in wet season was 6.3 μg·L-1， which was higher than that in dry season. Compared with chlorination pretreatment， ozone pretreatment reduced the content of bromomethane dichloromethane. Compared to liquid chlorine disinfection， sodium hypochlorite treatment incresed the levels of trichloromethane and bromomethane chloride. Although the total carcinogenic and non-carcinogenic risks of trihalomethane in drinking water in the region were at safe levels， they were above the acceptable limits occasionally. The highest carcinogenic risk of trihalomethane were dichlorobromomethane and chlorodibromomethane，and the highest non-carcinogenic risk was trichloromethane. The health risk of children was 1.2 times higher than that for adults.ConclusionThe production of residual trihalomethane in drinking water in this area is relatively low， which is less harmful to the health of adults and children. Monitoring， including other disinfection byproducts， should continue and appropriate disinfection techniques for drinking water should be explored.

In order to solve the problem of low audit efficiency due to the use of power exponent, bilinear mapping, point hash mapping and other expensive operations in the existing certificateless cloud auditing scheme, an efficient certificateless cloud auditing scheme was designed in this paper. In the key generation stage, combined with the certificateless signature technology, the user's public and private keys were generated by the key generating center (KGC) in cooperation with the user, so that the strong dependence of auditing system security on KGC security was avoided. Consequently, the shortcomings of complex public key certificate management under the public key infrastructure (PKI) system and the inherent key escrow issues under the identity-based cloud audit scheme were solved. In the data preprocessing stage, the data was encrypted and divided into blocks. Therefore, the data content privacy was protected and the calculation and communication overhead of the scheme was reduced. In the data dynamic update stage, the virtual index data structure was used to realize the insertion, deletion and modification of data blocks. As a result, the extra computational overhead caused by label recalculation was avoided. In the data auditing stage, the task of users to verify the integrity evidence was replaced by a third party auditor (TPA), which reduces the user's computational burden. In the section of security analysis, it was proved that the substitution attack from the cloud was resisted, the privacy protection was achieved, and the forgery attacks by two types of adversaries were resisted. In the performance analysis part, numerical analysis and comparison of the proposed scheme with the existing schemes were carried out on the JPBC library. The experiments show that the proposed scheme significantly reduces the computational cost. [ABSTRACT FROM AUTHOR]

Cu2O sensitized ZnO nanorod array films were prepared on transparent conductive glass (FTO) by electrochemical deposition method. The microstructure, surface morphologies and photoelectric properties of Cu2O sensitized ZnO films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray energy spectrum (EDS) and electrochemical workstation (CHI601C). The results show that electrochemical deposition of Cu2O nanocrystals can be formed heterojunction with the ZnO nanorods and improve the photoelectric conversion efficiency of ZnO thin films. The photoelectric conversion efficiency of Cu2O sensitized ZnO nanorod films is the highest when the deposition time of Cu2O is 5 min. [ABSTRACT FROM AUTHOR]

Objective: To investigate celluar toxicity and antibacterial property of nano-silver coating modified denture base and to provide a theortical basis for clinical application., Method: The samples were divided into coating group and denture base group. Samples in coating groups were treated with silver ion sputtering and were further divided into the 10, 20, 40, 60, 80, 100 s subgroups according to their sputtering time. Surface microstructure of samples in coating groups and denture base group were observed by scanning electron microscopy (SEM), and composition of material surface were determined with energy dispersive spectrum (EDS) analysis. Methyl thiazolyl terazolium (MTT) method was used to analysis L929 cells proliferation rate and cell toxicity grade while the coating groups (n = 6) and group test specimens (n = 6), negative control (polyethylene, PE) (n = 6) and positive control group (PVC-org.Sn) (n = 6) were co-cultured with L929 cells. The antibacterial properties of coating groups were investigated by using the bacterial membrane adhering method with Streptococcus mutans and Candida albicans., Results: SEM observation showed that the surface of control group specimens were smooth, whereas dense and uniform distributed nano silver particles were visible on the surface of coating group specimens. The silver particles were round, and the diameter size was 10 nm. MTT assay showed that after being co-cultured with specimens in control group, L929 cell had higher proliferation rate than 100% at 24, 48, 72 h, and cytotoxicity were graded 0. The membrane adhering method results showed that all of bacterial colonies were found in control group, but without anything at the coating groups., Conclusions: Deposition of nano silver on the denture base surface by ion sputtering method is a viable method. There's no cytotoxicity of series Ag-coating material. Nano-silver modified denture base material benefits L929 cell surface proliferation and has antibacterial action.

Objective: To determinate adenine, guanine, hypoxanthine, xanthine and uric acid simultaneously in meat, a reversed-phase high performance liquid chromatography (HPLC) was developed., Methods: The meat were hydrolyzed with perchloric acid 10% (v/v) in boiling water for 60 mm. After the hydrolysate was adjusted to pH 4, centrifuge , and filtrated with a 0.45 mirom membrane, the supernatants were separated on an Agilent ZORBAX Eclipse XDB-C18 column (250 mm x 4.6 mm i.d., 5 microm) at 25 degrees C with a mobile phase of 7 x 10(-3) mol/L KH2PO4-H3P04(pH 4.0) ,a flow rate of 1.0 ml/ mm, and UV detection at 254 nm., Results: Each component in the corresponding concentration range showed a good linear relation with its peak area, correlation coefficient r > 0.9999, recovery was 90.0%-107. 5%, RSD was 1.7%-13.3%. In addition to containing four kinds of purines, there was quite amount of uric acid (about 133.7 -86.2 pug/g) in the mentioned meat. The ratio of uric acid to total purine and uric acid was about 7%. The content of total purine in chicken was (1759.3 +/- 64.6) microg/g higher than in rabbit, mutton, pork and beef (1440-1000 microg/g)., Conclusion: The validated method is simple, rapid, accurate and reliable to the determination of purines and uric acid in meat.

Objective: To observe the micromorphological characteristic of bacterial biofilm on mucosa of chronic rhinosinusitis (CRS)., Method: Mucosa samples of middle turbinate were obtained from 4 patients of CRS during ESS. The size of each sample was about 4 mm x 4 mm. The samples were fixed in 4% paraformaldehyde for 24 hours, then fixed in 1% osmium tetroxide for 2 hours, graded dehydration with ethanol, dried with carbon dioxide and sputter coated with gold. The ultrastructure of these samples was observed by scanning electron microscope., Result: Bacterial biofilms were found on samples in all 4 patients. The biofilms were mainly formed on the surface of cilia. The bacterial flagella and cilia were intertwined. The biofilms could be found in a lot kinds of bacterial infections or mixed infections which were caused by multiple bacteria and fungi., Conclusion: Bacterial biofilm could be formed on ciliated epithelia.