Towards optimization of the osmotic drying process of alumina-gelatin objects: Regression analysis and verification

In this study, further analysis of the osmotic drying process was conducted to identify the optimum combination of parameters for drying rectangular alumina-gelatin beams. This study was designed to determine the effect of three variables related to the osmotic drying process (osmotic pressure, molecular weight, and immersion time) on the interaction between the liquid desiccant and the submerged alumina-gelatin samples. The water loss from the alumina-gelatin samples was positively correlated with the molecular weight, osmotic pressure, and immersion time. Up to 40% by weight of the initial water content was removed during the osmotic drying process. The samples also experienced solids gain due to the counterflow of solute from the liquid desiccant. The least amount of solids gain resulted from drying for the shortest immersion time at low osmotic pressure and high molecular weight. Evidence of possible interactions between variables was noted for the sintered density metric. Statistical methods were used to form regression equations for the measured responses (water loss, solids gain, bulk density). A verification experiment was conducted to compare the experimental outcomes to the predicted outcomes. The responses were simultaneously optimized to identify the combination of variable settings required to meet specified goals. In order to maximize water loss, minimize solids gain, and maximize bulk density, the ceramic-gelatin object should be immersed for approximately 60?min in an aqueous solution of 100,000?g/mol poly(ethylene oxide) at an osmotic pressure of 2.50?MPa. These values are valid for the range of parameter settings tested and the sample fabrication and drying methods used.     

Failure modes of fibre reinforced composites: The effects of strain rate and fibre content

The many aspects of high speed response of fibre reinforced composite materials have received the attention of a large number of investigators. Nevertheless, the understanding of the mechanisms governing failure under high speed loadings remain largely unknown. The effect of rate and fibre content on failure mechanisms was investigated by viewing fractured surfaces of tensile specimens using a scanning electron microscope (SEM). Tensile tests were conducted on a woven glass/epoxy laminate at increasing rates of strain. A second laminate (with random continuous glass reinforcement) was tested in tension at varying fibre volume fractions in order to ascertain the relationship between fibre content and failure mechanisms. The results suggest a brittle tensile failure in fibres of the woven laminate. In addition, the matrix was observed to play a greater role in the failure process as speed was increased, resulting in increased matrix damage and bunch fibre pull-out. The results also indicated that increasing the fibre volume fraction increased the likelihood of a matrix dominated failure mode.     

The effects of infrastructure and policy on e-business in Latin America and Sub-Saharan Africa

This study investigates experts' assessments of the pertinent factors affecting e-business in developing countries from a theory-based national infrastructure perspective. We surveyed experts (business people, academicians, and officials of governmental and non-governmental organizations) in e-business in Latin America (LA) and Sub-Saharan Africa (SSA). Our partial least squares analysis shows that experts believed that policies targeted specifically toward e-business are important in affecting e-business capabilities and in obtaining value from e-business, more so than non-specific general information and communication technologies (ICT) policies, which are not significantly influential. ICT infrastructure generally affects e-business capabilities, though this was not found to be the case in Brazil. Experts believed that national government institutions positively affect e-business value in SSA, but not in LA. Experts did not believe that commercial infrastructure significantly affects e-business value. This study theoretically and empirically distinguishes between two different dimensions of e-business outcomes: specific capabilities and value derived from e-business. It operationalizes the effects of national government institutions and commercial infrastructure on e-business outcomes and empirically tests for their effects. The study provides empirical support for conceptual arguments for the need of ICT policies specific to the needs of e-business.     

Chemoecological role of mammalian urine in host location by tsetse,Glossina spp. (Diptera: Glossinidae)

Trap catch size was used to investigate whetherGlossina pallidipes andG. longipennis could distinguish between the urine of the African buffalo, cattle, and waterbuck at Nguruman in southwest Kenya. NG2G traps baited with aged urine of these bovids caught significantly more of each tsetse than did the controls. The mean catch of either tsetse species in traps baited with aged urine of buffalo and cattle (tsetse hosts) and waterbuck (a nonhost) did not differ significantly. Aged urine from both tsetse hosts (buffalo and cattle) and the nonhost (waterbuck) was found to contain 4-cresol and 3-n-propylphenol in about the same ratio. However, the aged urine from other tsetse hosts (bushpig and warthog) lacked 3-n-propylphenol. Cattle urine had to be aged outside the soil to produce statistically significant increases in the trap catch ofG. pallidipes. Furthermore, patches of soil on which fresh urine of cattle was deposited, and in which it was aged, failed to effect a significant increase in the trap catch of eitherG. austeni, G. brevipalpis, orG. pallidipes as Gazi, southeast Kenya. The likelihood of tsetse either differentiating its hosts from nonhosts or locating favored hosts by the urine scent appears remote under natural conditions. It is more likely that the chemical signals critical for host location by the tsetse emanate from skin glands rather than volatilize from the urine of mammals.     

Trends in reinforced composite design for ionizing radiation shielding applications: a review

This review explored recent developments in reinforced composite design and applications for improved radiation shielding and high percentage attenuation. Radiation energy moves as a wave. Thus unguarded exposure to high-energy radiation is inimical to the human tissue and the overall health standing of individuals which may result in cancer, tumour, skin burns and cardiovascular diseases. Radiation energy is conventionally contained using lead-based shields. However, recent literature has faulted the continued use of lead citing drawbacks such as high toxicity, poisoning, lack of chemical stability, heaviness and hazardous after life handling. Consequently, the trending research evidence has shown mass deviation towards the use of reinforced polymer composite as an alternative to lead due to their light weight, low cost, high resilience, good mechanical tenacity and interesting electrical properties. The present review therefore summarizes the criteria for ionizing radiation shielding material design, mechanism of radiation energy shielding, beam penetration in composite shielding materials, theoretical shielding parameters in the design of radiation protective materials, scheme of reinforced composite material selection for shielding purposes and various control variables in the design of composite for ionizing radiation shielding. In addition, an attempt was made to highlight gaps in research and draw future scope for further studies. It is expected that this review will give some guidance to the future exploration in the design and application of reinforced composite with respect to ionizing radiation shielding processes.

     

Improvement by oxidising agents of the baking performance of pure and composite flours from nigerian-grown wheats (Lee X and Inia 66)

The feasibility of improving the bread-baking performance of two varieties of Nigerian-grown wheat (Lee X and Inia 66) in pure and composite flour, using the oxidising agents potassium bromate and ascorbic acid was studied. Composite flour was prepared by mixing pre-cooked bambara bean (Voandzeia subterranean) flour at levels between 0 and 50% with each of commercial (control), Lee X and Inia 66 wheat flour. Physical and sensory evaluations showed that the performance of straight Lee X and Inia 66 flours was inferior to that of the commercial flour. The commercial flour showed better tolerance to blending with bambara flour, producing acceptable loaves at up to 20% substitution with bean flour; Lee X and Inia 66 could not tolerate blending beyond 15% and 5% levels, respectively. Physical properties and baking performance of the Lee X and Inia 66 flours were improved by treatment with various levels of the oxidising agents KBrO₃, ascorbic acid and KBrO₃/ascorbic acid combinations. Lee X flour was more responsive to the treatments than Inia 66. Concentrations of 25 mg kg^?1 KBrO₃ and 80 mg kg^?1 ascorbic acid singly were found to improve Lee X flours adequately, but a combination of the two agents at a level of 25/60 mg kg^?1 KBrO₃/ascorbic acid was optimal. When treated with the optimal level of improver combination, Lee X flour performed as well as the commercial flour; and treated Lee X composite flours containing up to 30% pre-cooked bambara flour were found to produce loaves not significantly different from 100% commercial wheat bread (P≤0.05).     

Preliminary assessment of the ultra violet curing of composites manufactured by the resin infusion between double flexible tooling process

This study evaluates the feasibility of designing and incorporating a cure on demand system into the resin infusion between double flexible tooling (RIDFT) process, using ultraviolet (UV) light for the curing of composite laminates. This work set out to develop a process for the RIDFT that would eliminate or reduce the inflexibility in the current production process, resulting in shortened production cycle times. UV cured laminates were produced at a fraction of the time required for catalyst cured laminates. Mechanical and rheological tests were performed on each of the UV cured laminates produced. The results were referenced against those obtained for laminates produced using a catalyst curing system to determine their overall quality. Experimental results from the tensile and rheological tests inferred that the UV cured laminates yielded material properties that were comparable and in a few instances slightly better than that of thermally cured laminates. POLYM. COMPOS., 27:417–424, 2006. © 2006 Society of Plastics Engineers     

Fracture Toughness Enhancement for Alumina Systems: A Review

Investigations have been carried out to determine ways of tailoring ceramic materials in order that one or more toughening mechanisms are activated in service. Microstructural manipulations, as well as composite formulations involving metallic, intermetallics, and ceramic phases have been used with ceramic matrices. Macrostructurally, laminated structures and functional gradient materials (FGMs) have also been formulated to enhance mechanical properties. Although significant improvements in material properties have been reported, ceramics are still below their projected positions on the materials map. This article presents a review of research activities pursuant to improving fracture toughness of alumina matrix systems and the enhancements achieved.