Axial ratio of an antenna illuminated by an imperfectly circularly polarized source

A method for determining the axial ratio of an antenna illuminated by an imperfectly circularly polarized source is described. This method requires measurements of the right- and left-handed amplitude components and their relative phases for both the receiving and transmitting (or source) antennas. From these measured data and, of course, the theory of power transfer between the source and receiving antennas, an algorithm is derived for the actual axial ratio of the receiving antenna. Illustrative results showing the effects of the phase angle are presented.     

Synthesis and characterization of local clay–titanium dioxide core–shell extender pigments

A simple chemical technique has been used to prepare core–shell extender pigments based on Nigerian indigenous clays as core and titanium dioxide as shell. The prepared core–shell extender pigments were characterized using X-ray fluorescence and scanning electron microscopy. The physico-chemical properties of these extender pigments were also evaluated according to ASTM measurements. The study showed that the prepared core–shell pigments were nontoxic and environmentally friendly. They are of low cost and can be incorporated in semi-gloss paints, paper, rubber, and plastic composites without much effect on the volume. The characteristics of these pigments showed that they combine the properties of both their precursors, and have the potential to overcome their disadvantages, e.g., low hiding power of clays and photochemical activity of titanium dioxide.     

Road-surface properties affecting rates of energy dissipation from vehicles

The rates of energy that moving vehicles dissipate to road surfaces as well as noise emissions and their propensities for pitting (and hence their repair costs per year) all depend upon the structural properties of these surfaces. Thus, to increase the strength of bituminous concrete (i.e. a typical flexible road-surface) has been one of the major recent aims in highway engineering. The present study explored techniques that will increase these strength properties by modifying the material, using rubber latex, through rubberization and hence, improve the strength of the flexible trafficked surface when in contact with vehicles. At the optimal design asphalt (i.e. bitumen) content of 4.68%, the successive addition of various percentages of the rubber latex produced a design value of 1.65% rubber content, which increased the stability of the roadway from 1595 to 2639 N (i.e. an 65.5% increase) and the density from 2447 to 2520.8 kg/m³ (i.e. a 3.02% increase). This shows that the addition of rubber latex to bituminous concrete (a flexible road-surface) increased sustainability and the strength (in terms of stability and density). Similarly, the air voids and voids in the mineral aggregate (VMA) were reduced by introducing latex from 4.22% to 3.45% (i.e. a 17.06% reduction) and 16.25% to 13.43% (i.e. an 17.4% reduction), respectively. Whereas, the reduction in voidage volume added strength to the bituminous concrete by increasing its stability and density, the reduction in VMA had no positive impact on the strength properties of the flexible road-surface.     

Porosity and permeametry at sub-atmospheric pressures

The Carman-Kozeny equation is applicable in the viscous flow regime but, as the powder becomes finer, this equation fails. The controlling factor is the ratio of the hydraulic diameter to the mean free path of gas molecules (r_H/λ) and, as this approaches unity, “slip flow” occurs. This effect increases with (a) increasing fineness, i.e. r_H reduced, (b) decreasing porosity, i.e. r_H reduced, and (c) decreasing pressure, i.e. λ increased. In order to account for the enhanced flow arising as a result of this failure, a second term is introduced into the equation and this includes an unknown “constant” (δK₀/K), the coefficient of slip. It was considered probable that this so-called constant was a function of (r_H/λ), and an attempt was made to investigate this relationship.     

Developing alternative design concepts in VR environments using volumetric self-organizing feature maps

The conceptual design process has not benefited from conventional computer-aided design (CAD) technology to the same degree as embodiment design because the creative activities associated with developing and communicating alternative solutions, with minimal detail, is far less formulaic in its implementation. Any CAD system that seeks to support and enhance conceptual design must, therefore, enable natural and haptic modes of human–computer interaction. A computational framework for economically representing deformable solid objects for conceptual design is described in this paper. The physics-based deformation model consists of a set of point masses, connected by a series of springs and dampers, which undergo movement through the influence of external and internal forces. The location of each mass point corresponds to a node on a 3D mesh defined by a volumetric self-organizing feature map (VSOFM). A reference mesh is first created by fitting the exterior nodes of the VSOFM to sampled data from the surface of a primitive shape, such as a cube, and then redistributing the interior nodes to reflect evenly spaced hexahedral elements. Material properties are introduced to the mesh by assigning a mass value to individual nodes and spring coefficients to the nodal connections. Several illustrations involving the redesign of an ergonomic writing pen is used to demonstrate how the proposed virtual reality-based modeling system will permit the industrial designer to interactively change the shape and function of a design concept.     

Advances in gas permeability measurements

The Carman-Arnell equation relates the rate of flow of a fluid through a packed bed to the pressure drop across the bed. This equation is the basis for surface area determination by permeametry. It is found that the surface area measured at sub-atmospheric pressure varies with the bed porosity, so a porosity was selected where the rate of change was at a minimum. The study suggests that, at reduced pressures, the gas flow rate is a linear function of the mean pressure.     

Jet penetration and liquid splash in submerged gas injection

Jet penetration, bubble dispersion, and liquid splash were studied in the nitrogen-water system. Among the effects evaluated were those due to lance design, nozzle dimensions, gas driving pressure, and liquid density. In side-nozzle injection, penetration is found to increase with jet force number,N, given by the product of the gas driving pressure and the nozzle diameter. In top-submerged injection, horizontal and vertical penetrations increase with the horizontal and vertical components, respectively, of the jet force number. Liquid splash is greater in the side-nozzle injection than in top-submerged multiple-orifice injection, and appears to decrease as the number of orifices increases.     

Studies on the alcoholysis of some seed oils

The effects of time and temperature on the alcoholysis of rubber seed, melon seed, linseed, and soyabean oils have been studied. The following temperatures were investigated: 200, 220, 245, and 260°C. Litharge (PbO) was used as the alcoholysis catalyst. The optimum alcoholysis temperature was found to be 245 ± 2 °C for each of the oils. At lower alcoholysis temperatures (<245°C), there is the preferential alcoholysis of seed oils derived from unsaturated acid; and the general alcoholysis rates were found to be in the following order: linseed oil ≈ rubber seed oil ≥ soyabean oil ≈ melon seed oil. The alcohol‐solubility of the oils is generally observed to begin at 42–45% conversion of oils to monoglycerides. The α‐monoglyceride contents of the alcoholysis mixtures of rubber seed and linseed oils were generally similar at methanol tolerance, and higher than those of melon seed and soyabean oils. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1826–1832, 2000     

Microneedles from fish scale biopolymer

This article reports on microneedles produced from biopolymer films extracted from fish scales of tilapia (Oreochromiss sp.) using micromolding technique. Evaluation of the properties of polypeptide films prepared from the fish scales gave refractive index (1.34), protein concentration (78%), ash content (1.6%) at (22%) moisture content. The microneedles successfully inserted into artificial skin models and imaging using digital camera showed microneedles remained intact when inserted and when removed from the skin model. Microneedles also successfully inserted into porcine skin and were shown to dissolve gradually at 0 s, 60 s, 120 s, and 180 s after insertion. Microneedles containing methylene blue as model drug were also produced and successfully pierced porcine skin. 3D finite element (FEM) simulations were performed using the measured mechanical properties of the biopolymer films (Young's modulus 0.23 N/mm² and tensile strength 1.8105 N/mm²) to evaluate the stress distribution on various dimensions of the fish scale derived microneedles and hence, their ability to withstand force necessary to pierce the skin without fracture. Results from mechanical analysis using FEM showed that microneedles with tip radius between 10 and 100 μm could withstand up to 0.12 N of force per microneedle without fracture, which is indicated when the stress at the tip of the microneedle exceeds the ultimate stress of the material of fabrication. Using skin insertion tests and finite element simulations, this study provides evidence that microneedles fabricated from fish scale biopolymer can effectively pierce and degrade into skin and therefore are good candidate for transdermal applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40377.