Colorimetric properties of wool dyed with natural dyes after treatment with ammonia

An evaluation has been carried out of the effect of ammonia on the colouristic properties of wool dyed with a range of natural dyes containing anthraquinone, naphthaquinone, flavone and tannin structures. It was found in all cases that after-treatment with ammonia caused a decrease in the lightness ( L *) values. The reasons for this are discussed, as is the fact that the colour change is not reversible on subsequent treatment with acid.     

Fatigue life improvements of the AISI 304 stainless steel ground surfaces by wire brushing

The surface and subsurface integrity of metallic ground components is usually characterized by an induced tensile residual stress, which has a detrimental effect on the fatigue life of these components. In particular, it tends to accelerate the initiation and growth of the fatigue cracks. In this investigation, to deliberately generate compressive residual stresses into the ground surfaces of the AISI 304 stainless steel (SS), wire brushing was applied. It was found that under the experimental conditions selected in this investigation, while the surface roughness was slightly improved by the brushing process, the surface residual stress shifted from a tensile stress (σ_‖=+450 MPa) to a compressive stress (σ_‖=−435 MPa). On the other hand, the work-hardened deformation layer was almost two times deeper after wire brushing. Concerning the fatigue life, an improvement of 26% in terms of endurance limit at 2×10⁶ cycles was realized. Scanning electron microscope (SEM) observations of the fatigue fracture location and size were carried out to explain the fatigue life improvement. It was found that the enhancement of the fatigue strength could be correlated with the distribution and location of the fatigue fracture nucleation sites. Concerning the ground surfaces, it was seen that the fatigue cracks initiated at the bottom of the grinding grooves and were particularly long (150–200 μm). However, the fatigue cracks at the brushed surfaces were shorter (20–40 μm) and appeared to initiate sideways to the plowed material caused by the wire brushing. The results of the wire-brushed surface characterization have shown that significant advantages can be realized regarding surface integrity by the application of this low-cost process compared to shot peening.     

Flexural Strengthening of Reinforced Concrete Flanged Beams with Composite Laminates

Bonding composite laminates to the tension face can effectively increase the flexural strength of the reinforced-concrete flanged beams. In comparison to rectangular concrete beams, the flange provides a larger area of concrete to resist compression stresses, and considering the role of the composite in resisting tensile stresses, its addition to flanged beams can efficiently upgrade the flexural capacity. Failure of the strengthened beam may result from crushing of concrete or rupture of the plate; however, the beam must be properly detailed to avoid local shear failure at the plate cut-off point. In this paper, equations required for strengthening of the flanged beams for gravity loads will be presented. The equations have been developed based on load and resistance factor design, and have been verified through a comparison with available experimental results. Close agreement with the experimental results indicates the accuracy of the equations. Terms, definitions, and notations compatible to ordinary reinforced-concrete design codes have been used to facilitate the application of the equations.     

Characterization and identification of rejection mechanisms in nanofiltration membranes using extended Nernst–Planck model

Nanofiltration (NF) membranes have found increasing applications especially in water and wastewater treatment. In order to predict and optimize the performance of NF membranes, the membranes need to be characterized properly in terms of their structural parameters such as pore radius (r _p) and effective thickness (Δx/A _k) as well as the effective charge density (X _d). In this work, three cellulose acetate NF membranes were fabricated to different properties and were characterized using a model based on the extended Nernst–Planck equation. The results show that the variations of r _p, Δx/A _k and X _d are quite distinct between the three membranes. The membranes were found to have r _p>1.2 nm and high X _d. Thus the rejection mechanism depends very much on the Donnan effect rather than the steric effect. The high rejection of several negatively charged organics and salts confirmed this finding. Apart from being effective, this method of characterization offers a cheaper alternative in understanding NF membranes. Electronic Publication     

Studies of polymer-cellulose blends prepared from solution

The conditions under which cellulose-cellulose triacetate (CTA) and cellulose-poly(acrylonitrile) (PAN) blends can be prepared from solution, are described in this paper. These two systems form transparent films when the blend contains less than 50% PAN or 60% CTA. Young's modulus, tensile strength, and elongation at rupture were measured for these blends. These values usually are between those of the corresponding homopolymers, except for the blend containing 10% polymer (PAN or CTA) which has a tensile strength value larger than that of cellulose. This result seems to indicate a certain level of compatibility for this blend. However, x-ray measurements indicate the presence of two crystal structures for these systems, suggesting that compatibility does not exist at the molecular level, in the crystalline fraction of the samples.     

Linear stability analysis and experimental verification of stratified air–water flow in a horizontal bend

Stratified flow in gas–liquid systems is a basic flow configuration which occurs frequently in industries due to the large density differential between the phases that helps to sustain stable stratification for relatively wide ranges of flow rates. The study on stability of stratified flow and the development of transitional criteria to various flow patterns have been very actively pursued for straight pipes, resulting in a broad understanding of the underlying mechanisms. Beside straight pipes, pipelines contain other fittings, which pose abrupt changes to the flow direction, and hence their impact on the flow stability needs to be ascertained.This study attempts to extend the linear stability analysis of stratified flows in a straight pipe to a horizontal bend. A model for the effect of a horizontal elbow on the transition from stratified to non-stratified patterns using the two-fluid approach is presented. The Inviscid Kelvin–Helmholtz (IKH) and Viscous Kelvin–Helmholtz (VKH) stability criteria for stratified flow transition are derived.Experiments are carried out using air and water in a 0.05 m diameter horizontal pipe work containing an intermediate bend of 0.5 m radius of curvature and the flow pattern observed in the bend is compared with the stability theory. The results show that the IKH and VKH stability criteria for stratified flow in a bend have identical forms as their counterparts in an inclined straight pipe, except that the tilt of the liquid lump in the bend which depends on the liquid velocity replaces the inclination angle for a straight pipe. The stable region is over-predicted by the IKH criterion while the VKH criterion shows good agreement for transition from stratified to slug flow if the liquid surface gradient is taken into account in the solution of the flow parameters under fully developed conditions.The work presented in this paper is of tremendous help to oil production engineers who need to know and control the flow regime transitions in order to avoid problems associated during production. These problems are mainly due to the generation of slug flow which leads to severe unwanted jigging.     

Error Detection Enhancement in COTS Superscalar Processors with Performance Monitoring Features

Increasing use of commercial off-the-shelf (COTS) superscalar processors in industrial, embedded, and real-time systems necessitates the development of error detection mechanisms for such systems. This paper presents an error detection scheme called Committed Instructions Counting (CIC) to increase error detection in such systems. The scheme uses internal Performance Monitoring features and an external watchdog processor (WDP). The Performance Monitoring features enable counting the number of committed instructions in a program. The scheme is experimentally evaluated on a 32-bit Pentium® processor using software implemented fault injection (SWIFI). A total of 8181 errors were injected into the Pentium® processor. The results show that the error detection coverage varies between 90.92 and 98.41%, for different workloads. To verify the experimental results an analytical evaluation of the coverage is also performed.     

A frame-based approach for wideband correlation-inversion of lossless scatterers

Presented here is an ultra-wideband-correlation-based scheme for imaging and inversion of an unknown weak and lossless scatterer embedded in a known background medium. The scheme uses an excitation and reception of ultra wideband/short-pulsed fields by an array of transducers located outside the imaging domain. The scatterer image is formed by cross correlating (in the short-pulsed domain or via spectral integration in the ultra wideband domain) the numerically/ analytically back-propagated, measured, and scattered data set with the forward-propagation excitations. It is shown that in the ultra wideband domain, the forward-backward propagation functions form a frame set in a finite Hilbert space. Within the weak scattering assumption (Born approximation) the scatterer's image and object function (velocity profile) are related via the corresponding frame operator. Therefore, an exact inversion scheme of the frame operator is readily available to yield the object function via an iterative scheme or using the dual frame set. Numerical examples that demonstrate the performance of the imaging and inversion schemes for scatterers with various velocity profiles are presented. It is shown that the scatterer image is generally of poor resolution. However, on inversion, a high-quality velocity profile is obtained that captures the scatterer fine details.