Optimization of Continuous Casting Using Simulation

This paper describes the development and use of an integrated system of metamodels and simulation experiments for managing quality in a continuous casting system. A systematic procedure was developed to satisfy the necessary process conditions connected to one or more process parameters. The values of these parameters are to be determined such that all the process conditions are satisfied simultaneously to ensure that the product will have the desired quality. This procedure utilizes a set of metamodels, simulation experiments, and an index called the “undesirability index” for quality, which establishes a functional relationship between the input variables or process parameters and the quality criteria. This system, when applied to the data pertaining to a case, demonstrated that the methodology developed could be used to effectively manage product quality.     

Oxidation behavior of the TiNi shape memory alloy with a laser surface melted layer

The isothermal oxidation behavior of TiNi specimens with or without laser surface melted (LSM) layers in pure oxygen over the temperature range of 600—800°C was studied. Characterization of the specimens after oxidation was conducted using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The oxidation resistance of the LSM specimens has been improved significantly. The formation of a compact oxide layer on the LSM specimens contributes to good oxidation resistance.     

Multiobjective differential evolution (MODE) for optimization of adiabatic styrene reactor

In this paper, a novel algorithm is proposed for solving multiobjective optimization problems. The proposed algorithm, multiobjective differential evolution (MODE), is applied to optimize industrial adiabatic styrene reactor considering productivity, selectivity and yield as the main objectives. Five combinations of the objectives are considered. Pareto set (a set of equally good solutions) obtained for all the cases is compared with results reported using non-dominated sorting genetic algorithm (NSGA). The results show that all objectives besides profit can be improved compared to those reported using NSGA and current operating conditions. The Pareto optimal front provides wide-ranging optimal operating conditions and an appropriate operating point can be selected based on the requirements of the user.     

Classification of run-length encoded binary data

In classification of binary featured data, distance computation is carried out by considering each feature. We represent the given binary data as run-length encoded data. This would lead to a compact or compressed representation of data. Further, we propose an algorithm to directly compute the Manhattan distance between two such binary encoded patterns. We show that classification of data in such compressed form would improve the computation time by a factor of 5 on large handwritten data. The scheme is useful in large data clustering and classification which depend on distance measures.     

The influence of parameters of chemical synthesis on the optical properties of CdS nanocrystals

A systematic analysis is presented on the influence of parameters of synthesis on the formation and optical properties of CdS nanocrystals prepared using dimethyl formamide as solvent and stabilizing agent. The parameters considered are the molar ratios of cadmium to sulfur, initial concentration of Cd²⁺ and S²⁻ at a fixed molar ratio and atmospheric conditions. Optical absorption and photoluminescence measurements were carried out during the synthesis to monitor the changes in optical properties. The results clearly indicate that the nanocrystals size could be tuned by varying the molar ratio of the starting materials. Ambient conditions are found to play a vital role on the stability and optical properties of the nanocrystals whereas the concentration of the starting materials had little influence on the optical absorption and luminescence properties. These results are expected to help in developing a better understanding of the mechanisms of solution growth and size stabilization of semiconductor nanocrystals during chemical synthesis.     

Intergranular corrosion damage evaluation through laser scattering technique

AISI type 316 austenitic stainless steel in sensitized condition was subjected to ASTM A262 practice A test (electrolytic etching in 10% ammonium persulphate at 1 A/cm²) for various durations from 10 s to 90 s. The different degrees of intergranular corrosion attack produced on these tested specimens were evaluated by laser scattering technique using a 1 mW He-Ne laser. The scattering intensity pattern of the laser beam incident on the specimen was acquired using a CCD camera and transferred to a computer for further analysis. The specular intensity of the scattering pattern and its full width at half maximum (FWHM) was calculated. The results indicated that the specular intensity decreased and the FWHM increased as the degree of IGC attack increased. A good correlation was found between the extent of IGC with the laser scattering parameters.     

Emission spectroscopy analysis for the non-destructive evaluation of the health of thermal barrier coatings

Lithium oxide was selected as an emission spectroscopic marker in yttria stabilized zirconia (YSZ) thermal barrier coatings (TBCs). The spectral response of excited lithium atoms from dip-coated YSZ containing 5, 3, 1, and 0.3 wt.% lithium oxide and plasma-sprayed YSZ containing 1 wt% lithium oxide was examined under an oxy-acetylene flame. Results showed that the intensity of lithium emission spectrum is a function of the concentration of lithium oxide in the YSZ, the flame temperature, and the degree of TBC degradation. It indicates that an emission spectroscopy can be used to monitor the degradation of TBCs.     

Microstructural Evolution during Transient Plastic Phase Processing of Titanium Carbide-Titanium Boride Composites

Transient plastic phase processing is a form of reactive hot pressing for fabricating fully dense ceramic-ceramic composites at relative low homologous temperatures. In this study, this technique has been used on two powder mixtures—4:1 Ti/B₄C and 1:1 TiC_0.5/TiB₂, which are equivalent in terms of elemental compositions—to produce fully dense titanium carbide-titanium boride composites. The composites formed in each case are comprised of the same final phases—TiC_x, TiB₂, and Ti₃B₄, in roughly the same volume fractions—but exhibit distinctly different grain morphologies. Ti₃B₄ phase nucleates and grows as platelets for the 4:1 Ti/B₄C starting composition but as equiaxed grains for the 1:1 TiC_0.5/TiB₂ composition. TiB has been identified as an intermediate phase in the "platelet" composition and appears to be important to the development of the Ti₃B₄ platelets. X-ray diffractometry and scanning electron microscopy results indicate that the evolution of the microstructure is governed by the diffusion of boron and carbon, rather than titanium. In addition, the faster diffusion of carbon, relative to boron, is instrumental in the microstructural evolution of the platelet composite. The produced composites possess >99% density and good mechanical properties. The higher strength and toughness of the platelet composite are believed to be due to the platelet morphology of the Ti₃B₄ phase.