Missouri University of Science and Technology

About: Missouri University of Science and Technology is a education organization based out in Rolla, Missouri, United States. It is known for research contribution in the topics: Artificial neural network & Control theory. The organization has 9380 authors who have published 21161 publications receiving 462544 citations. The organization is also known as: Missouri S&T & University of Missouri–Rolla.

Novel variable step size nlms algorithms for echo cancellation

Abstract: In this paper we present two new variable step size (VSS) methods for adaptive filters. These VSS methods are so effective, they eliminate the need for a separate double-talk detection algorithm in echo cancellation applications. The key feature of both approaches is the introduction of a new near-end signal energy estimator (NESEE) that provides accurate and computationally efficient estimates even during double-talk and echo path change events. The first VSS algorithm applies the NESEE to the recently proposed Nonparametric VSS NLMS (NPVSS-NLMS) algorithm. The resulting algorithm has excellent convergence characteristics with an intrinsic immunity to double-talk. The second approach is somewhat more ad hoc. It is composed of a combination of an efficient echo path change detector and the NESEE. This VSS method also has excellent convergence, double talk immunity, and computational efficiency. Simulations demonstrate the efficacy of both proposed algorithms.

Densification and mechanical properties of TaC-based ceramics

Abstract: Densification of TaC was enhanced while the grain growth was suppressed by adding 1 or 2 wt% B4C, which allowed mechanical properties to be analyzed. A relative density of >98% was achieved for TaC with B4C additions by hot pressing at 2100 °C. By comparison, additive-free TaC could be hot pressed to only 94% relative density at 2300 °C. X-ray diffraction analysis identified TaB2 in TaC–B4C ceramics, indicating that a reaction occurred during hot pressing. Mechanical properties including Young's modulus, flexure strength, Vickers’ hardness, and fracture toughness were studied. The Griffith equation was used to calculate critical flaw sizes from measured properties. This analysis combined with observations of fracture surfaces identified surface flaws induced by machining and subsurface impurities picked up during milling as the critical flaws.

Practical Performance Analysis of Complex Switched-Capacitor Converters

Abstract: This paper introduces a new analysis technique for complex switched-capacitor (SC) converters. It uses conventional circuit analysis methods to derive state-space models of each switching mode. Steady-state performance is derived and expressed as an equivalent resistance. Whereas previous techniques have provided either the detailed performance of a simple SC converter or the limiting performance of a complex SC converter, this new method is flexible enough to provide detailed performance for any practical converter. Nonuniform component choices, asymmetric duty cycle, and other deviations from an ideal converter can be readily included. Dynamics can also be analyzed. The model has been validated through simulation techniques and experimental data collected from laboratory testing.

Substituent effects on the binding of phenols to cyclodextrins in aqueous solution

Abstract: Equilibrium constants and standard enthalpies have been measures calorimetrically for the formation of complexes of {alpha}- and {beta}-cyclodextrins with substituted phenols in aqueous solutions at 298.15 K. The study includes variation of the size and shape of the phenol, the size and degree of methylation of the cyclodextrin, and the effects of pH and ionic strength. Substituent effects were measured for p-chloro-, p-bromo-, p-methyl-, p-hydroxy-, p-nitro- and m-nitrophenols. The effects of ionization were studied with m- and p-nitrophenolate ions. The effects of methyl substitutions of {beta}-cyclodextrin were investigated with nitrophenol and nitrophenolate ions complexing with heptakis (2,6-di-O-methyl)-{beta}-cyclodextrin and heptakis (2,3,6-tri-O-methyl)-{beta}-cyclodextrin. All of the effects studied show a substantial amount of entropic-enthalpic compensation, such that free energy effects are relatively small in comparison to enthalpic and/or entropic effects, but there was no simple relationship between the standard enthalpies and entropies of complex formation. However, a linear relationship was observed between the enthalpy and entropy for the transfer of substituted phenols from the complex with {alpha}-cyclodextrin to the complex with {beta}-cyclodextrin. This relationship was independent of pH and ionic strength. In general, complex formation of a substituted phenol with {alpha}-cyclodextrin is more exothermic than with {beta}-cyclodextrin, but the entropy of complex formationmore » is also more negative.« less

High strain rate superplasticity in friction stir processed Al–Mg–Zr alloy

Abstract: Al–4Mg–1Zr extruded bar was subjected to friction stir processing (FSP), resulting in generation of a fine microstructure of 1.5 μm grain size. Superplastic deformation behavior of FSP Al–4Mg–1Zr alloy was investigated in strain rate range of 1×10−3 to 1 s−1 and temperature range of 350–550 °C and compared with that of as-rolled one. It is indicated that the FSP alloy exhibited significantly enhanced superplasticity at a high strain rate of 1×10−1 s−1, and a maximum elongation of 1280% was obtained at 525 °C and 1×10−1 s−1. Further, the FSP Al–4Mg–1Zr alloy exhibited excellent thermal stability at high temperature, and a large elongation of 1210% was observed at 550 °C and 1×10−1 s−1. Moreover, FSP resulted in a significant decrease in the flow stress in Al–4Mg–1Zr alloy. At a strain rate of 1×10−2 s−1, the flow stress (∼7 MPa) of FSP Al–4Mg–1Zr at 450 °C was comparable to that of as-rolled alloy at 550 °C.