Modeling blue stragglers in young clusters

A grid of binary evolution models are calculated for the study of a blue straggler （BS） population in intermediate age （log Age = 7.85 - 8.95） star clusters. The BS formation via mass transfer and merging is studied systematically using our models. Both Case A and B close binary evolutionary tracks are calculated for a large range of parameters. The results show that BSs formed via Case B are generally bluer and even more luminous than those produced by Case A. Furthermore, the larger range in orbital separations of Case B models provides a probability of producing more BSs than in Case A. Based on the grid of models, several Monte-Carlo simulations of BS populations in the clusters in the age range are carded out. The results show that BSs formed via different channels populate different areas in the color magnitude diagram （CMD）. The locations of BSs in CMD for a number of clusters are compared to our simulations as well. In order to investigate the influence of mass transfer efficiency in the models and simulations, a set of models is also calculated by implementing a constant mass transfer efficiency,β=0.5, during Roche lobe overflow （Case A binary evolution excluded）. The result shows BSs can be formed via mass transfer at any given age in both cases. However, the distributions of the BS populations on CMD are different.

Preparation &Microscopic Characterization of Non-Chrome Chemical Conversion Film in Aluminum Surface

A chromium-free environmental protection aluminum surface treatment technology was developed by theoretical analysis and a large number of experiments. Add zirconium ions and cerium ions to the treatment solution, besides adding fluoride, aluminum and hydrogen peroxide, etc. According to the orthogonal test obtained a non-chromate film-formation process of environmental friendly aluminum. The characterization methods including SEM, XPS and XRD were applied to study and analyze the morphology, composition, phase, and corrosion resistance of phosphate film, then discussed the film-forming reaction mechanism. Results showed that chemical conversion film formed on the aluminum surface was uniform, compact and stronger anti-corrosion could replace the traditional, more toxic chromate conversion film.

Thermal Analysis of Turbine Blades with Thermal Barrier Coatings Using Virtual Wall Thickness Method

Avirtual wall thicknessmethod is developed to simulate the temperature field of turbine bladeswith thermal barrier coatings(TBCs),to simplify the modeling process and improve the calculation efficiency.The results show that the virtualwall thickness method can improve themesh quality by 20%,reduce the number ofmeshes by 76.7%and save the calculation time by 35.5%,compared with the traditional real wall thickness method.The average calculation error of the two methods is between 0.21%and 0.93%.Furthermore,the temperature at the blade leading edge is the highest and the average temperature of the blade pressure surface is higher than that of the suction surface under a certain service condition.The blade surface temperature presents a high temperature at both ends and a low temperature in themiddle height when the temperature of incoming gas is uniformand constant.The thermal insulation effect of TBCs is the worst near the air film hole,and the best at the blade leading edge.According to the calculated temperature field of the substrate-coating system,the highest thermal insulation temperature of the TC layer is 172.01 K,and the thermal insulation proportions of TC,TGO and BC are 93.55%,1.54%and 4.91%,respectively.

Construction and Genetic Analysis of Murine Hepatitis Virus Strain A59 Nsp16 Temperature Sensitive Mutant and the Revertant Virus

Coronaviruses (CoVs) are generally associated with respiratory and enteric infections and have long been recognized as important pathogens of livestock and companion animals. Mouse hepatitis virus (MHV) is a widely studied model system for Coronavirus replication and pathogenesis. In this study,we created a MHV-A59 temperature sensitive (ts) mutant Wu"-ts18(cd) using the recombinant vaccinia reverse genetics system. Virus replication assay in 17C1-1 cells showed the plaque phenotype and replication characterization of constructed Wu"-ts18(cd) were indistinguishable from the reported ts mutant Wu"-ts18. Then we cultured the ts mutant Wu"-ts18(cd) at non-permissive temperature 39.5°C,which "forced" the ts recombinant virus to use second-site mutation to revert from a ts to a non-ts phenotype. Sequence analysis showed most of the revertants had the same single amino acid mutation at Nsp16 position 43. The single amino acid mutation at Nsp16 position 76 or position 130 could also revert the ts mutant Wu"-ts18 (cd) to non-ts phenotype,an additional independent mutation in Nsp13 position 115 played an important role on plaque size. The results provided us with genetic information on the functional determinants of Nsp16. This allowed us to build up a more reasonable model of CoVs replication-transcription complex.

FURTHER STUDIES ON STROH-TYPE FORMALISMS FOR ANISOTROPIC PLATES WITH BENDING-EXTENSION COUPLING

Stroh-type formalisms for anisotropic thin plates in literature axe reviewed and discussed, and two kinds of hybrid Stroh-type formalisms axe compared. It is seen that the two Stroh-type formalisms are essentially equivalent. With simple transfer relations, they can be expressed each other. In addition, with properly defined notation systems, the two Stroh-type formalisms can also be written in unified forms, which will be convenient in applications.

Comparative study on microstructure evolution and failure mechanisms of ordinary and refurbished EB-PVD TBC under cyclic oxidation

Refurbishment of thermal barrier coating(TBC)has become a valuable technique to prolong the service life of high-temperature components.This study investigates the effect of the refurbishment process(coating removal and recoating)on the microstructure evolution and physical properties of TBC,including oxidation characteristics,element diffusion behavior,and crack failure mechanisms.The results showed that a certain amount of interdiffusion zone(IDZ)with Cr-rich would be retained in DD6 superalloy substrate after coating removal.The microstructure of the refurbished specimens showed equiaxedβ-NiAl phases,while the ordinary specimens have elongated grain shapes with a high aspect ratio.Moreover,mixed oxides in the refurbished TBC specimens were earlier observed during cyclic oxidation,with a greater thickness compared to ordinary TBC,due to the influence of BC layer phase sizes.The growth mechanism of thermally grown oxide(TGO-Al_(2)O_(3)layer)in the refurbished TBC specimens was also different,resulting from the different mechanisms of mixed oxides growth.Furthermore,under cyclic oxidation with water quenching at 1100℃,the cracks in the refurbished specimen tend to occur in the mixed oxides layer,while the cracks in the ordinary specimen occur in the top coat(TC)layer,attributing to the earlier and thicker mixed oxides layer formed in refurbished specimens.

THREE-DIMENSIONAL MODELING FOR THIN PLATE-LIKE STRUCTURES INCLUDING SURFACE EFFECTS BY USING STATE SPACE METHOD

A three-dimensional （3-D） approach based on the state space method is proposed to study size-dependent mechanical properties of ultra-thin plate-like elastic structures considering surface effects. The structure is modeled as a laminate composed of a bulk bounded with upper and bottom surface layers, which are allowed to have different material properties from the bulk layer. State equations, including the surface properties of the structure, can be established on the basis of 3-D fundamental elasticity to analyze the size-dependent static characteristics of the thin plate-like structure. Compared with two-dimensional plate theories based size-dependent models for thin film structures in literature, the present 3-D approach is exact, which can provide benchmark results to assess the accuracy of 2-D plate theories and various numerical approaches. To show the feasibility of the proposed approach, a 3-D analytical solution for a simply supported plate-like thin structure including surface layers is derived. An algorithm is proposed for the calculation of the state equations obtained to ensure that the numerical results can reveal the surface effects clearly even for extremely thin surface layers. Numerical examples are carried out to exhibit the surface effects and some discussions are provided based on the results obtained.

Ionic Electroactive Polymers Used in Bionic Robots： A Review

Ionic electroactive polymers （IEAPs） are a category of intelligent soft materials exhibiting large displacement under electric excitation, based on inner ion or solvent transport. Due to their unique advantages such as flexibility, low driving voltage, large bending displacement and aquatic-environment adaptability, IEAPs have been documented as very promising actuators for the applications in bionic robots. This review presents an analysis to the current research status of IEAPs exploited in bionic robots. According to the specific bionic parts, those robots are divided into four classes： imitation of fins, limbs, joints and trunks. Their dimension, weight, voltage amplitude, frequency and maximum speed were summarized to show the optimum design range. The results show that the approach velocity of the current robots were higher （〉 35 mm· s-1） when the robot weighted 60 g - 180 g and the body was 90 mm - 130 mm long. For voltage from 1 V - 3 V and frequencies from 0.7 Hz - 1.2 Hz, the speed was relatively higher （〉 35 mm·s-1）.To some extent, the maximum speed decreases when the area of the IEAP material used in bionic robot increases. For underwater circumstances, IEAP materials are most suitable for designing bionic robots swimming with Body and/or Caudal Fin （BCF）. This review provides important guidance for the design of lEAP bionic robots.