An inertial decomposition and related range results

With quasicommutative n-square complex matrices A₁,…,A_s and s-square hermitian G=(g_ij), relationships are given between the image $\text{Σ}{}^{\mathrm{s}}{}_{\mathrm{i,j=1}}\text{g}{}_{\mathrm{ij}}\text{A}{}_{\mathrm{i}}\text{HA}{}^1{}_{\mathrm{j}}$ of a linear transformation on $\text{H}$_n being positive definite and the action of H on generalized inertial decompositions of $\text{C}$ⁿ.     

The determination of cationic surfactants in the presence of anionic surfactant in biodegradation test liquors

A method is described for the determination of cationic surfactants in biodegradation test liquors and effluents containing anionic surfactant and other components which interfere with existing colorimetric procedures. The cationic surfactant is concentrated by evaporation of the aqueous sample and separated from the resulting residue by solvent extraction as an ion-association compound. The extract is treated under non-aqueous conditions on Bio-Rad AG 1-X2 resin in the chloride form to remove interfering anionic components. The isolated cationic surfactant is determined colorimetrically as its disulphine blue ion-association compound, extractable into chloroform. The recovery of added cationic surfactants from biodegradation test liquors is generally better than 95 %, and concentrations in the range 0.1–10 mg l^-1 can be determined. The method is suitable for biodegradability test studies where control liquors are available, e.g. OECD Screen and Confirmatory tests. In environmental samples, materials other than cationic surfactant may respond to disulphine blue and these limit severely the application of the procedure.     

The stability of two stratified ”power-law“ liquids in couette flow

Consideration is given to the stability of the flow of two ”power-law“ liquids between two infinite parallel planes when one of the planes moves with constant velocity in its own plane. It is found that the ratios of the power-law parameters for each layer have a dramatic effect and can be chosen to destabilize the flow.     

The relationship between membrane surface pore characteristics and flux for ultrafiltration membranes

Surface porosities of Amicon XM100A and XM300 membranes have been measured by electron microscopy and found to be less than 1 per cent. From the measured pore size distributions it is deduced that 50 per cent of the solvent flow is through 20 to 25 per cent of the pores.The conventional model for concentration polarisation in ultrafiltration (UF), which assumes a homogeneously permeable membrane surface, has been modified to account for regions of differing permeability. An effective free area correction factor (≤ 1.0) has been introduced to allow for the effect of membrane surface properties on gel-polarised UF flux.Ultrafiltration experiments with protein solutions and membranes with a range of water fluxes confirm that gel-polarised UF flux is dependent on membrane permeability and surface properties. Effective free area correction factors vary from about 0.4 to 1.0 with values < 1.0 obtained for membranes with water fluxes typically < 150 1/m² hr at 100 kPaSupport for the effective free area concept in UF is provided by an analogy between a gel-polarised UF membrane and a composite reverse osmosis membrane. In both cases the magnitude of the upper ‘controlling’ resistance may be influenced by the pore size and spacing of the lower supporting structure.     

Commercial road vehicle noise

A survey of the characteristics of the noise emitted by commercial vehicles has been made. The most important single parameter determining the noise of a modern diesel-engined vehicle is the engine speed. All of the other parameters such as load, road speed, etc., have only a secondary effect.The sources of noise on the vehicle are reviewed and it is shown how the characteristics of these sources determine the overall noise characteristics of the vehicle. It has been found that a simple model of the vehicle as a number of coincident point sources predicts the overall noise characteristics of the vehicle to ±2 dB(A). It is shown that there are two extremes of behaviour, the rolling noise controlled vehicle and the power unit noise controlled vehicle; the engine is currently the controlling noise source.Tyre noise has been investigated in some detail as comparatively little has been published previously on this source. Empirical relationships between the tyre noise and speed, tyre size and road surface roughness are given. It is concluded that tyre noise is generated by impacting between elements of the tyre tread and elements of the road surface.Modifications have been made to the engine, exhaust, intake and cooling fan of a 9 ton, 6 litre diesel engined truck which have reduced its ISO test noise level from 88 dB(A) to 80 dB(A). However, it is concluded that 80 dB(A) commercial vehicles are not yet feasible for production. In particular insufficient is known about cooling fan design.Finally cab noise has been investigated and it has been found to originate from the same source as the exterior noise, power unit airborne noise. Therefore any modifications to the power unit to reduce exterior noise will have a similar effect on interior noise. This is confirmed by the vehicle modifications mentioned above which reduced the maximum cab noise from 87 dB(A) to 79 dB(A).