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Biomechanical performance plays an important role in the long-term service of dental implants. Loosening and fatigue damage of the central screw are the most common problems. This research investigated the effect of the central screw taper angle on the loosening performance and fatigue characteristics of dental implants. Central screws with four taper angles, 30°, 60°, 90° and 180°, were processed and tested. The loosening performance of the screws under initial and postload conditions was compared. Then, the fatigue characteristics of dental implants was measured. Finally, the wear and fracture modes of the screws were observed. The damage locations were verified by finite element analysis (FEA). The results showed that the central screws with 30° taper had substantially better anti-loosening performance and less fretting wear. The central screws with 180° taper had a higher preload, resulting in a longer fatigue life. Furthermore, the fatigue fracture of the central screw occurred at the level of the first thread position, consistent with the FEA results. In the future clinical applications, central screws with a 30° taper angle may improve anti-loosening performance and prolong fatigue life by increasing the tightening torque.

The different pulsation of pressure between the upper and lower space of the shell in a rotary compressor used for refrigerator and air conditioner room could be a cause of the axial movement of the rotor. In this paper, the gas dynamics analysis of a rotary compressor was carried out. In order to analyze the mechanisms of the fluctuation of the axial force in rotor system and the functions of the gas force and the gas torque on the rotor system, a three-dimensional dynamic numerical model was built up by the method of CFD (computational fluid dynamics) and dynamic grid technique. The simulated results were compared by theoretical cycle and calorimeter performance experiment. Good agreement was found between the simulated results and experimental results for the rotary compressor system.

Micro-grinding is an important processing method in micro-manufacturing field. The influence factors of surface quality in micro-grinding are discussed in the article. The models of finite element analysis (FEA) in micro-grinding H62 with electroplated CBN micro-grinding tool were established. The influence of different grinding factors on the surface quality of the work-piece was discussed by FEA. Different grains sizes were considered to reveal the influence rules on surface roughness in grinding experiments. The results show that the surface roughness decreases with the decreasing of the feed speed and the increasing of the grinding speed. A better surface quality can be achieved with smaller grains sizes. The minimum surface roughness can reach 481nm in side grinding H62.

In order to improve the performance of the draft tube in hydraulic turbine, a multi–objective optimization method for the draft tube is developed by combining the design of experiment (DOE), the radial basis function (RBF) and the non–dominated sorting genetic algorithm (NSGA–II) in this paper. The geometrical design variables of the median section in the draft tube and the cross section in its exit diffuser are considered as design parameters in this optimization, which objective function is to maximize the pressure recovery factor (Cp) and minimize the energy loss coefficient (ζ). The limited numbers of design matrix required for the shape optimization of the draft tube is generated by optimal Latin hypercube (OLH) method of the DOE technique, of which performances are evaluated through computational fluid dynamic (CFD) numerical simulation. For reducing of the computational consumption, the approximate model is used based on the RBF. The Pareto optimal solutions are finally performed using the NSGA–II for obtaining the best geometrical parameters of the draft tube. The optimization result of the draft tube shows a marked performance improvement over the original, which verifies the theoretical validity and feasibility of the proposed method in this paper.

SnO2 and Cu-SnO2 thin films were fabricated by the sol-gel method. The influence of annealing temperature and copper addition on the morphology and microstructure of the films was studied using X-ray diffraction (XRD) and UV-Visible, respectively. The results show that the tetragonal rutile phase is evidenced by XRD with no other phases observed. The crystallinity of SnO2 and Cu-SnO2 thin films had been improved with the increasing annealing temperature. The grain size decreased after Cu doping. On theoretical, Pure and Cu-SnO2 were calculated by first-principles full potential linearized augmented plane wave ultra-soft pseudo-potential method to investigate band structure.

First, the basic principle of the DSMC method is introduced, which include simulating process, calculating of collision and key technique about simulation. Then a detailed process of simulation analysis to Disk-type Molecular Pumps extraction process based on DSMC method, is described, such as establishing geometric model, meshing, selection of collision model, boundary simulation, etc. At last, the ongoing work is pointed out .

Wurtzite Cu–Li codoped ZnO (Cu–Li:ZnO) films with Cu concentrations of 0–3 at.% were grown by sol–gel method. The conductivity, band gap and transparency of the Cu–Li:ZnO films decrease with increasing the Cu concentration due to the substitution of Cu for the Zn sites (Cu Zn ) and the interstitial Li atoms (Li i ). The Cu Zn defects generate a fully occupied impurity band above the valance band maximum (VBM), resulting in an upward shift of the VBM and a decrease of the band gap. The Cu Zn acceptors can compensate for the Li i donors and further form complex self-compensation defects [Cu Zn + Zn i ]. The carrier mobility of the Cu–Li:ZnO film is about 2–5 orders of magnitude lower than that of the intrinsic one due to the grain boundary and surface scattering.

In this paper TiN coating was prepared on stainless steel substrate using arc ion plating technique. The coating samples’ phases, surface morphology, micro-determination chemical composition, loss factor and damping ratio were tested. The phases of TiN coating were determined by X-ray diffraction (XRD) technique. The surface morphology and chemical composition of the TiN coating were analyzed by scanning electron microscope (SEM) and Energy Dispersive Spectrometer (EDS), respectively. The damping performance of the samples was measured by hammering activation according half power bandwidth method. The loss factor or damping ratio of samples were obtained according frequency response curve. The results showed that damping performance of samples was considerably improved by TiN coatings.

Plasma Optical Emission Spectroscopy was employed to investigate hysteresis process of reactive sputtering with high purity Zn target in the presence of Ar plus O2 plasma. An optimal working point was obtained through analyzing hysteretic curve in order to deposit high quality ZnO film. Scanning Electron Microscope was used to characterize effects of various O2 flow rate on surface crystal structure of samples. The SEM results indicate that the structure of ZnO film is strongly dependent on O2 flow rate at constant pressure and power. Specially, At 1.6 sccm O2 flow rate, the sample with best crystallite structure has been observed. Energy-dispersive X-ray Spectroscopy also demonstrates the relationship between the chemical compositions of ZnO films and O2 flow rate. The film to 1.6 sccm O2 shows the optimal atom ratio of Zn to O and the mass ratio of Zn to O. The water contact angle measurement also shows various O2 flow rate strongly affects wettability.