Multi-scale modeling and simulation of crystallization during cooling in short fiber reinforced composites

To explore the crystallization during the cooling stage in short fiber reinforced composites, a multi-scale model in which macroscopic temperature and microscopic crystal morphology are related with each other is built up. According to this multi-scale model, the algorithm of coupling finite volume method with pixel coloring method is proposed. The finite volume method is used on the coarse grid to calculate the macroscopic temperature and the pixel coloring method is employed on the fine grid to capture the morphology of crystallization. Roles of cooling rate, initial temperature as well as the nucleation rate per unit fiber surface are investigated. To our knowledge this is the first time that a fully coupled multi-scale model and a multi-scale algorithm have been applied to the crystallization of short fiber reinforced composites.     

Optical transmittance enhancement and bandgap widening of ZnO:Al powders by W codoping

(Al, W)-codoped ZnO powders with a constant molar ratio of Zn:Al (99:1) and various molar ratios of W:Al (0–0.02) were synthesized by a sol–gel process and characterized by X-ray diffraction, field emission scanning electron microscopy, and UV–vis and luminescent spectrophotometry. The experiments indicated that the powders illustrated increased c-orientation and a decreased average particle size with increasing W content. The W doping also resulted in the enhancement of transmittance in the UV–vis light range and the widening of the bandgap. Optimal efficiency appeared at molar ratio of W:Al = 0.01. Moreover, the W doping led to the formation of a new emission center and the enhancement of the emissions in range of visible light.     

Tolerance specification and comparative analysis for computer-integrated dimensional inspection

Two important issues in the development of a computer-integrated dimensional inspection environment for manufactured parts are described, namely tolerance specification and comparative analysis. These two issues are related directly and therefore, should be addressed together. For supporting the computer-integrated dimensional inspection, a geometric dimensioning and tolerancing (GD&T) specification module and a comparative analysis module are developed and integrated with CATTA of the IBM CAD/CAM system. The proposed specification module supports ISO and ANSI geometric tolerances and allows multiple tolerance assignments on each single feature as well as on a group of same pattern features. Using this specification module, various tolerance information can be directly specified to the 3D CAD model of a part and can be used to support the subsequent planning and operation for manfacturing and inspection. The comparative analysis module is created to work with the GD&T module for constructing datum reference frames and comparing the actual measurement data with nominal design. After specifying all necessary tolerance information, using discrete measurement data from coordinate measuring machines (CMM), one can evaluate the dimensional quality of an actual feature through the comparative analysis module.     

Improvement in corrosion resistance of commercial pure titanium for the enhancement of its biocompatibility

A new surface modification protocol encompassing an anodization treatment has been developed to improve the surface properties of biomedical titanium. Anodization in presence of nickel sulfate is one of a good way to improve the resistance of commercial pure titanium (cp‐Ti) in phosphate saline buffer solution (PSB). The potentiostatic behavior of anodized titanium in sulfuric acid with nickel sulfate differed markedly from that of titanium anodized in sulfuric acid free from nickel sulfate. Polarization and electrochemical impedance spectroscopy (EIS) recorded an increase in the corrosion resistance of the passive film. Scanning electron microscopy (SEM) and energy diffraction X‐ray (EDX) analysis were used to investigate the morphology and structure of the anodized film in absence and in presence of nickel sulfate. On the other hand, sealed anodized titanium samples exposed to PSB for up to 3 days have been studied by EIS to obtain detailed information concerning the electrochemical properties of sealed anodized titanium. An equivalent circuit that reproduces the impedance results of porous cp‐Ti oxide (TiO₂) films is proposed. These observations indicate that anodization of cp‐Ti in presence of nickel sulfate and sealing the anodized film can serve as a simple low‐temperature method to enhance the corrosion resistance of cp‐Ti when used as an implant material.     

Preliminary investigation on strong magnetic field treated NiAl–Cr(Mo)–Hf near eutectic alloy

The Ni-33Al-28Cr-6Mo-0.3Hf near eutectic alloy was treated in a 10 T strong magnetic field at 1073 K and 1173 K for 1.5 h respectively. Microstructure examination reveals that after the strong magnetic field treatment, most Ni₂AlHf Heusler particles have changed into Hf solid solution, and moreover Hf solid solution and Heusler particles along eutectic cell boundaries distribute more uniformly. In addition, the eutectic cellular microstructure of the alloy with strong magnetic field treatment at 1173 K is changed greatly. The eutectic cell has an obvious disintegration and Cr(Mo) plates become coarsening and spheroidizing. The compression tests show that room temperature compressive ductility of the alloys with strong magnetic field treatment improves significantly, compared with the heat-treated alloy.     

Design of NPR DFT-Modulated Filter Banks via Iterative Updating Algorithm

In this paper, an efficient algorithm is proposed to design nearly-perfect-reconstruction (NPR) DFT-modulated filter banks. First, the perfect-reconstruction (PR) condition of the oversampled DFT-modulated filter banks in the frequency domain is transformed into a set of quadratic equations with respect to the prototype filter (PF) in the time domain. Second, the design problem is formulated as an unconstrained optimization problem that involves PR condition and stopband energy of the PF. With the gradient vector of the objective function, an efficient iterative algorithm is presented to design the PF, which is updated with linear matrix equations at each iteration. The algorithm is identified as a modified Newton’s method, and its convergence is proved. Numerical examples and comparison with many other existing methods are included to demonstrate the effectiveness of the proposed method.     

Validation of a UV Spectrophotometric Method for Determination of Proteolytic Activity of Enzymatic Detergents

Enzymatic detergents are widely used in health services. These products should be controlled to ensure their activity. In this paper, a UV spectrophotometric method for the determination of proteolytic activity in enzymatic detergents was validated. An artificial substrate (azocasein) was used to quantify the enzyme activity at 340 nm. The results showed that the method was satisfactory in respect to its specificity, linearity, precision, accuracy and robustness. This method fulfills both ICH’s and Brazilian criteria, demonstrating its suitability for routine analysis as well as its potential application for regulatory purposes.     

Investigation of Isotherm Polymer Adsorption in Porous Media

The injection of chemical solutions plays an important role in increasing the recovery factor of mature fields. Chemical flooding is considered as an attractive alternative to conventional waterflooding; it can improve the area sweep efficiency not only at the macroscale but also in the microscale by control mobility of displaced fluid. Adsorption of polymer in reservoir rock is an extremely important parameter for chemical flooding. Adsorption represents a loss of chemical agent from solution and, consequently, a net reduction in the surfactant–polymer slug. Therefore, the efficiency of polymer flooding is significantly diminished both technically and economically. However, numerical simulation of multicomponent adsorption is still limited and adsorption processes in a polymer–rock system have not yet been well developed, especially for highly heterogeneous reservoirs. In this article, adsorption was modeled by the Langmuir isotherm theory. The simulation results indicated that polymer adsorption strongly depends on polymer concentration, shear rate, pH, salt concentration, and reservoir heterogeneity. Effective control of such parameters can reduce the effect of polymer adsorption to minimize chemical loss and improve the economic efficiency of chemical flooding processes.