A new modified Reynolds equation for ultrathin film gas lubrication

A new modified Reynolds equation for solving the ultrathin film gas lubrication is proposed to overcome the complicated and time-consuming difficulties of solving the linearized Boltzmann equation. The model equation is based on modified high-order slip-flow velocity distribution with three adjustable coefficients, which are corrected according to the Boltzmann model. The results are compared to those obtained using other kinds of currently employed modified Reynolds equations. It shows that the present model produces a closer approximation to that of the exact Boltzmann model than do other models, in a wider range of inverse Knudsen number. In addition, the newly derived equation is widely applicable to practical use     

An Average Flow Model for Couple Stress Fluids

The interactions of surface roughness and flow rheology of couple stress fluids on thin film lubrication problems are modeled. The generalized average Reynolds equation as well as the flow factors is derived. The effects of couple stress parameters (l), the standard derivation of surface roughness ( _i ), the Peklenik number ( _i), and the roughness orientation angle ( _i) on the flow factors ( ^p _ij , ^s _ij) are discussed. In results, the related Reynolds-type equations and flow factors for Newtonian fluids, power-law non-Newtonian fluids, mixtures of Newtonian and power-law non-Newtonian fluids, and couple stress fluids are tabulated.     

Elastohydrodynamic lubrication of circular contacts at pure squeeze motion with non-Newtonian lubricants

In this study a numerical method for general applications with non-Newtonian fluids is developed to investigate the pure squeeze motion in an isothermal elastohydrodynamic lubricated spherical conjunction under constant load conditions. The coupled transient modified Reynolds, the elasticity deformation, and the load equilibrium equations are solved simultaneously. Computer simulation is carried out to investigate the effects of flow rheology and operations on the relationship between the pressure and film thickness distributions. The simulation results reveal that the larger the flow index (n), the larger the film thickness and the smaller the maximum central pressure. This results in larger time needed to obtain maximum central pressure. In addition, the elastic deformation is more significant for the lower flow index. Therefore, the smaller the flow index becomes, the greater the difference between the hydrodynamic lubrication (HL) solution and elastohydrodynamic lubrication (EHL) solution becomes.     

Micro-abrasion of Y-TZP in tea

The objective of this work is to investigate the micro-abrasion of Y-TZP in tea. This material is a candidate replacement in dental restoration and to date there has been very little work carried out to investigate the wear behaviour in oral cavity conditions. Various additions such as milk and sugar, which affect the solution viscosity and pH, were assessed as part of this work and the results were compared to the performance of the material in aqueous conditions. Wear maps were generated showing the change in wear rate as a function of applied load and exposure time.     

Phase Formation of Zinc Titanate Precursor Powders Prepared by a Hydrothermal Process in Various pH Environments

For the precursor, powders were calcined at 773 K (500 °C) for 1 hour. The anatase TiO₂ and ZnO appear as the predominant and minor phases, respectively, when the precursor powders are obtained at pH 5. The phases of Zn₂Ti₃O₈, anatase TiO₂, and ZnO coexist for the precursor powders obtained at pH 7. In addition, the Zn₂Ti₃O₈ and ZnO are the predominant and minor phases, respectively, for the precursor powders obtained at pH 9.     

三峡四期蓄水清库工程“最后一爆”——涪陵白涛旧乌江大桥拆除爆破

随着三峡水库175m蓄水,标高只有185m的涪陵白涛旧乌江大桥已不能满足通航要求,因此,该大桥的爆破是三峡清库工作至关重要的一环。涪陵白涛旧乌江大桥的成功爆破,为三峡四期蓄水清库工程扫清了最后一道障碍。文章详细论述了涪陵白涛乌江大桥爆破拆除工程中各种情况和爆破参数,为该类情况下的爆破拆除提供了经验。     

On the construction of wear maps for Y-TZP dental ceramics in aqueous environments: pH, exposure time and impact angle effects

The object of this work was to evaluate the particulate erosion performance of Y-TZP (Yttria Tetragonal Zirconia Polycrystalline), used in the construction of artificial teeth, at various pH values, impact angles and exposure times. The results showed that the highest degradation recorded was in acidic environments. However, the incubation time to high wastage was also affected by impact angle and exposure time. Wear maps were constructed, based on the results, identifying wastage regimes for the material as a function of the exposure conditions. In addition, a wear map was generated based on the observed phase transformations for the material.     

Coupled effects of surface roughness and flow rheology on elastohydrodynamic lubrication

The coupled effects of surface roughness and flow rheology on elastohydrodynamic lubrication (EHL) circular contact problems are analyzed and discussed. The averaged type Reynolds equation utilizing the average flow model on the interactions between couple stress fluids and surface roughness, the elastic deformation equation, the viscosity–pressure and density–pressure relations equations, and the force balance equation are solved numerically by the multilevel multi-integration (MLMI) algorithm to calculate the pressure distributions and film thickness shapes. The results show that the transverse type roughness and standard deviation of composite roughness enhance the pressure and film thickness in the central contact region. Moreover, the longer the characteristic length of the couple stress fluids is, the smaller the pressure distribution is in the central contact region and the greater the film thickness is in all regions.     

Synthesis of zinc oxide nanocrystalline powders for cosmetic applications

The synthesis of zinc oxide (ZnO) nanocrystalline powders for cosmetic applications by a coprecipitation process has been investigated. When the Zn(OH)₂ precipitates are calcined at 373 K for 10 min, the crystalline phases comprise the major phase of Zn(OH)₂ and the minor phase of ZnO. XRD pattern shows that only ZnO is present and no other phase is detected when the Zn(OH)₂ precipitates calcined at 413 K for 10 min. The nanocrystallite size of ZnO increases slightly from 32.3 to 44.3 nm when the calcination temperature increases from 413 to 873 K. The activation energy of ZnO nanocrystallite growth is 2.02 kJ/mol, which reveals that the nanocrystalline ZnO is easily grown at low temperature. The UV transmission of ZnO nanocrystallites in the wavelength range from 290 to 375 nm is about 35%, indicating that the ZnO nanocrystallites have an excellent UV-absorbing capability.