Adaptive noise reduction using numerically stable fast recursive least squares algorithm

This paper is concerned with adaptive noise reduction based on the fast recursive least squares (FRLS) algorithm. It is well known that the fast recursive least squares (FRLS) algorithm suffers from numerical instability when operating under the effects of finite precision arithmetic. Several numerical solutions of stabilization were proposed in the case of stationary signals. In this work a new version of a numerically stable FRLS algorithm (NS‐FRLS) is proposed. The stability characteristics of this new stabilized algorithm are analysed. The analysis is based on a linear model for the errors in the states of the adaptive filter. Experimental results confirm the merits of adaptive filtering with the NS‐FRLS algorithm over optimum filtering using the solution provided by Wiener–Hopf equations. Copyright © 2006 John Wiley & Sons, Ltd.     

Processing, microstructure, properties and wear behavior of in situ synthesized TiB2 and TiC thick films on steel substrates

TiB₂ and TiC reinforced Fe matrix thick films (2 mm thickness) were produced through the synthesis reaction from Ti, C and FeB powders with varying porosity on the steel substrates. Powder technology was used as a processing method. The films and the substrates were sintered in a single step. TiB₂, TiC and Fe were detected in the films by X-ray diffraction analysis. The fact that no other reaction product was detected revealed the thermal stability of TiB₂ and TiC. The formation of secondary reaction products was inhibited during the reactive sintering. The films showed maximum strength of 163-466 MPa when sintered separately at 1350 °C. The strength of the films varied with their porosity. The films showed considerable bonding strength with the steel substrates. The delamination of the films from the steel substrates was observed at stress values from 454-781 MPa. The microstructure, fracture and delaminated surface morphologies were studied. The wear resistance against hardened high speed steel was studied in reciprocating sliding tests. The wear mechanisms were discussed by means of microscopical observation on the worn surfaces.     

The effect of ammonium sulphate—decabromobiphenyl oxide on the flammability of polyester/cotton blend

A 87.5:12.5 polyester/cotton blended fabric was treated with various concentrations of ammonium sulphate and decabromobiphenyl oxide (DBBO) as well as mixtures of the two additives. The flammability of the resulting systems was determined by the limiting oxygen index (LOI) method and their thermal decomposition by thermogravimetry. Ammonium sulphate was particularly less effective as a flame retardant than the DBBO. Decabromobiphenyl oxide acts in the gas phase to retard the flammability of the polyester while the inorganic salt acts in the condensed phase to decrease that of the cotton. A mechanism for the interaction of ammonium sulphate with cotton was suggested. When a mixture of the two additives containing a high percentage of the bromo-compound was used a significant increase in the LOI values was observed compared to one having the same total loading but containing a higher percentage of ammonium sulphate. This may be attributed to the stabilizing effect of the released ammonia on the intermediate species formed after the liberation of the bromine radicals from the DBBO.     

Assessment of a method for measuring serum thyroxine by radioimmunoassay, with use of polyethylene glycol precipitation

We assessed the efficacy of a new thyroxine radioimmunoassay kit (Abott) in which polyethylene glycol is used to separate bound from free hormone. Mean serum thyroxine was 88 +/- 15 (+/-SD) microgram/liter for 96 normal persons. Results for hypothyroid and hyperthyroid persons were clearly separated from those for normal individuals. Women taking oral contraceptive preparations showed variable increases in their serum thyroxine values. The coefficient of variation ranged from 1 to 3% within assay and from 5.4 to 11% among different assays. Excellent parallelism was demonstrated between thyroxine values estimated by this method and those obtained either by competitive protein binding or by a separate radioimmunoassay for the hormone.     

The preparation of thiophenes. III. From aromatic compounds and carbon disulphide

The high-temperature, vapour-phase reaction of carbon disulphide with 2-isopropyl-phenol and with o-methylbenzyl alcohol in the presence of various catalysts gave high yields of 3-methylbenzo[b]furan and dihydrobenzo[c]thiophene, respectively.     

The preparation of thiophenes. II. From C5-C7-molecules and carbon disulphide

Substituted thiophenes have been obtained in high yields by passing C₅-C₇-molecules and carbon disulphide (CS₂) over a promoted chromium-aluminium oxide catalyst (Girdler G41)¹ in the vapour phase at 500°C. Both the scope and mechanism of these reactions have been studied using an alkane and a number of alcohols and ketones, and the reaction products have been identified. The reaction of pentan-₂-ol with ¹³C-carbon disulphide (¹³CS₂) has been carried out to study the incorporation of the carbon atom of the CS₂ into the thiophene ring.     

The structural properties of Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Sb<Subscript>40−<Emphasis Type="Italic">x</Emphasis></Subscript> Se<Subscript>60</Subscript> system

High purity glasses with an average coordination number N_c in the Ge_xSb_40–xSe₆₀ ternary system between 2.4 and 2.7, were prepared under vacuum with x = 0, 10, 20 and 30. X-ray diffraction (XRD) as, well as the Differential Scanning Calorimetry (DSC) studies were carried out to identify the amorphous and polycrystalline structure for the Ge-Sb-Se system. The dependence of properties such as the mean atomic volume V_a, the glass transition temperature T_g and the number of topological constraints N_con were studied as a function of N_c, in the light of recent model proposed for covalent random network. The occurrence of this dependence in addition to those due to topological effects leads to the conclusion that the effects of chemical ordering and the effect, which have topological origin, coexist in this system. To understand the effect of N_c on the glass-forming capability, the number of lone-pair electrons, (N_cs–N_c)/2, and the efficiency of the structural modification were calculated and discussed in relation to topological consideration. This then renders support to Phillipstheoretical model.     

Liquid distribution and redistribution in packed columns—II. Experimental

The theory of liquid redistribution in packed columns under the influence of a potential when the boundary conditions have been set by differences in permeability between the wall and bulk regions, has been tested in experiment. Liquid distribution in a packed column 0.3 m in diameter and 1.5 m long has been measured for $\text{1}\text{2}$, 1 and 1$\text{1}\text{2}$ in. Raschig rings both with and without gas flow. The trend of experimental points was found to be in general agreement with the theoretical relationship when there was no gas flow. For gas flow conditions in the loading region there was close agreement between experimental and theory.The experimental estimates of the permeability ratio are analysed for the range of experimental conditions.