Using artificial intelligence to model heavy plate mill rolling

This research summary discusses the application of neural networks, evolutionary strategies, and other artificial intelligence techniques in the modeling and optimization of the models used for temperature, rolling force, and torque calculation in heavy plate milling.     

Mathematical analysis of viscometric (polymer) flow fields in capillaries: Taylor dispersion revisited

A general formulation for capillary flow of two miscible fluids – one a dilute plug of polymer fluid inserted into a fully developed Poiseuille flow of the other, a Newtonian stream – is examined for its long time behavior. Phenomenologically, the system evolves from an initial state, that of a plug within the boundaries of sharp, well defined fronts inside a Newtonian stream, to a more homogenized state in the very long time scale. This problem was addressed by G.I. Taylor but with regard to a system of two Newtonian fluids, leading to the well-known results commonly described as `Taylor axial dispersion'. In this paper, a general and systematic perturbation analysis is presented from which Taylor's result is recovered as a special case of a more general solution which applies to fluids incorporating elastic properties. In particular, the influence of viscoelasticity and (polymer) diffusivity on the observed pressure profile in the capillary conduit is examined. This effect is clearly separated out for small Peclet number flows using asymptotic and numerical analysis. The results identify the influence of fluid viscosity, elasticity, and diffusivity on the observed pressure profile and form the basis for the improved characterization of polymeric elasticity using capillaries – a finding that is of significant scientific and commercial interest. These results were obtained by the authors as a class of observations resulting from the perturbation analysis of forced-flow capillary devices in viscoelastic fluid property investigation.     

ANALYSIS AND PROCESSING OF LMF－COSTAS STEPPED FREQUENCY RADAR SIGNAL

Linear Modulated Frequency (LMF) Costas Stepped Frequency Radar (SFR) signal is introduced. Its ambiguity function is derived and analyzed in detail and its feasibility is validated in theory. The scheme of the proposed signal processing is also presented. The results of theoretic analysis and simulation show that, by using the proposed signal and increasing the bandwidth of the total stepped frequency, the ambiguity sidelobe is well suppressed and the range-velocity coupling in the stepped frequency radar is also greatly weakened.     

ACCELERATION AMBIGUITY FUNCTION OF RADAR SIGNALS AND ITS APPLICATION

High acceleration of radar targets is analyzed using Acceleration Ambiguity Function(AAF). The acceleration resolution based on AAF is defined. The AAF and acceleration resolution of rectangle pulse signal are derivated and the conclusion that its acceleration resolution is in inverse proportion with the square of its duration is drawn. In the end, these conclusions are applied to the parameter designing and performance evaluation for a certain type of pulse Doppler radar.     

Thermo-oxidative degradation of some polymer couples containing HNBR

Summary In this paper thermal behavior of some HNBR blends with CPE, PVC, CR and NBR at three temperatures, 150, 170 and 190°C is presented. Changes in characteristic IR bands, gel fraction, and chlorine content were assessed. Some mechanistic differences between the studied systems, regarding the involvement the depletion of chlorine and modification in gel content, were pointed out. Cyclization of nitrile structure was also observed by means of 2240 cm⁻¹ band ascribed to >C=NH. Kinetic considerations are presented. Received: 3 June 2002/Revised version: 14 November 2002/ Accepted 20 November 2002 Correspondence to Traian Zaharescu     

Rare-earth-enabled universal solders for microelectromechanical systems and optical packaging

In packaging of microelectromechanical systems (MEMS), optical, and electronic devices, there is a need to directly bond a wide variety of inorganic materials, such as oxides, nitrides, and semiconductors. Such applications involve hermetic-sealing components, three-dimensional MEMS assembly components as well as active semiconductor or optical components, dielectric layers, diffusion barriers, waveguides, and heat sinks. These materials are known to be very difficult to wet and bond with low melting-point solders. New Sn-Ag- or Au-Sn-based universal solders doped with a small amount of rare-earth (RE) elements have been developed, which now allow direct and powerful bonding onto the surfaces of various MEMS, optical, or electronic device materials. The microstructure, interface properties, and mechanical behavior of the bonds as well as the potential packaging applications of these new solder materials for MEMS and optical fiber devices are described. Various packaging-related structural, thermal, or electrical issues in MEMS are also discussed.     

Influence of fretting on the fatigue strength at the vise clamp-specimen interface

Fretting fatigue is one of the most important phenomena for inducing a significant reduction of fatigue strength and consequently, leading to unexpected failure accidents of the engineering structures even at very low stresses. In the present study, both plain and fretting fatigue tests with zero mean stress were carried out on two different types of steel, low-carbon steel and martensitic stainless steel, by means of a reversed bending fatigue testing machine. The drop in the fatigue strengths through fretting at vise clamp-specimen interface were significant for both tested steels. The fretting processes produced a reduction in fatigue strength of about 27% for low-carbon steel and 16% for martensitic stainless steel.