An investigation of the fatigue and fracture behavior of mn-containing gamma titanium aluminides

The fatigue and fracture mechanisms in Ti-48Al-xMn (x = 1.4 to 2.0 at. pct) gamma-based titanium aluminide alloys are elucidated. Unlike most gamma alloys, which fail predominantly by transgranular fracture at room temperature, fracture in ternary Ti-48Al-xMn alloys is shown to occur mainly by intergranular failure. The incidence of intergranular failure increased with increasing annealing duration and temperature. Intergranular fracture is shown to occur as a result of the segregation of Mn to equiaxed and interlamellar boundaries. Annealing either above or below the eutectoid temperature results in the precipitation of α₂ particles. The reduction in the strength and toughness of ternary Mn-containing alloys is attributed to the combined effects of segregation and α₂ precipitation. A micromechanics framework is presented for the assessment of twin toughening mechanisms under monotonie and cyclic loading. Formerly Staff Scientist with General Electric Research and Development, Schenectady, NY 12301 Formerly Undergraduate Student, Department of Materials Science and Engineering, The Ohio State University     

BSSM Measurement Lecture 1986 Measurement in engineering—a gas industry view

Without reliable measurement, engineering as we know it would not be possible. Our lives would be totally different as a result. The gas industry in the UK is no exception. As a major supplier of energy, it depends on measurement in many forms over a wide range of applications. Some examples are described covering early forms of gas metering to new developments in the rapidly expanding field of optics.     

The gamma subunit of the Na,K-ATPase induces cation channel activity

The gamma subunit of the Na,K-ATPase is a hydrophobic protein of approximately 10 kDa. The gamma subunit was expressed in Sf-9 insect cells and Xenopus oocytes to ascertain its role in Na,K-ATPase function. Immunoblotting has shown that the gamma subunit is expressed in Sf-9 cells infected with recombinant baculovirus containing the cDNA for the human gamma subunit. Confocal microscopy demonstrates that the gamma subunit can be delivered to the plasma membrane of Sf-9 cells independently of the other Na,K-ATPase subunits and that gamma colocalizes with alpha1 when these proteins are coexpressed. When Sf-9 cells were coinfected with alpha1 and gamma, antibodies to the gamma subunit were able to coimmunoprecipitate the alpha1 subunit, suggesting that gamma is able to associate with alpha1. The gamma subunit is a member of a family of single-pass transmembrane proteins that induces ion fluxes in Xenopus oocytes. Evidence that the gamma subunit is a functional component was supported by experiments showing gamma-induced cation channel activity when expressed in oocytes and increases in Na+ and K+ uptake when expressed in Sf-9 cells.     

Migration from plasticized films into foods. 2. Migration of di-(2-ethylhexyl)adipate from PVC films used for retail food packaging

A UK survey of di-(2-ethylhexyl)adipate (DEHA) levels in retail foods (83 samples) wrapped in plasticized PVC film has been carried out, examining a wide range of different food types obtained from retail and take-away outlets. Foodstuffs analysed included fresh meat and poultry, ready-cooked poultry, cheese, fruit, vegetables and baked goods such as cakes, bread rolls and sandwiches. Analysis by stable isotope dilution GC/MS showed DEHA levels ranging from 1.0 to 72.8 mg/kg in uncooked meat and poultry, 9.4 to 48.6 mg/kg in cooked chicken portions, 27.8 to 135.0 mg/kg in cheese, less than 2.0 mg/kg in fruit and vegetables and 11 to 212 mg/kg in baked goods and sandwiches. The level of DEHA migration correlated with the extent of contact between the film and exposed fatty portions of the food, whether that was the mayonnaise filling of a sandwich or the surface fat from a joint of uncooked meat. The level of DEHA in meat exposed to plasticized film was not reduced significantly by volatilization or chemical transformation on subsequent cooking by grilling or frying.     

Simulation of square-cup deep-drawing with various friction and material models

Two constitutive models of the blank proposed by Estrin and Robinson, and two friction models: the non-linear pressure-dependent model and a quasi-steady-state sliding model; have been used in the finite-element simulation of a prismatic-cup deep-drawing process. These simulations are compared with the results obtained for the J₂ elastic-plastic material model and the classical Coulomb friction model. The deep drawing processes for Estrin's and Robinson's models are formulated as a fully coupled thermo-mechanical process.     

Ambiguity in the Operator's Sense

Ambiguity is a central problem for operators working in dynamic, high‐risk environments. Operators must decide on a course of action before knowing with certainty how the system will respond. Though ambiguity is expected, how it presents is unexpected. We reduce ambiguity when we can give meaning to information and events through use of context, responsiveness of the system, and when we can view events from a higher level. Preparation and training for routine operations helps identify potential ambiguities before events begin. The experienced operator engages the situation relying on real‐time experience to learn what works through action, thus further reducing ambiguity.     

Multifactor interactions and the air traffic controller: the interaction of situation awareness and workload in association with automation

Air traffic controllers must maintain a consistently high level of human performance in order to maintain flight safety and efficiency. In current control environments, performance-influencing factors such as workload, fatigue and situation awareness can co-occur and interact to affect performance. However, multifactor influences and the association with performance are under-researched. This study utilised a high-fidelity, human-in-the-loop, en route air traffic control simulation to investigate the relationship between workload, situation awareness and controller performance. The current study aimed to replicate Edwards et al.’s (in: Proceedings of the 4th AHFE international conference, 21–25th July, San Francisco, USA, 2012) previous finding that factors known to be associated with controller performance do co-vary and can interact, which is associated with a compound influence on performance. In addition, the current study aimed to extend Edwards et al.’s (2012) study by engaging retired controllers as participants and comparing multifactor relationships across four levels of automation. Results suggest that workload and situation awareness may interact to produce a compound (as opposed to cumulative) impact on controller performance. In addition, the effect of the interaction on performance may be dependent on the context and level of automation. Findings have implications for human–automation teaming in air traffic control, and the potential prediction of performance-influencing situations, supporting controller performance in the operational environment.     

Effect of tannic acid concentration on development of the western treehole mosquito,Aedes sierrensis (Diptera: Culicidae)

Populations ofAedes sierrensis (Ludlow) completed development in tannic acid solutions over a wide concentration range (i.e., 0–1.0 g/liter) in artificial microcosms exposed to field conditions. The most notable effects of high tannic acid concentration were to slow larval developmental rates and to reduce numbers of adults produced; adult size and sex ratio were minimally affected. Vector potential of the western treehole mosquito is discussed in terms of tannin concentration.