Response of A356 to warm rotary forming and subsequent T6 heat treatment

The through-process microstructural effects in A356 subjected to rotary forming at elevated temperatures have been investigated. Macro and micro-hardness testing have been used extensively to track changes in the material from the as-cast state to as-formed, and T6 heat treated. Targeted thermal treatments have been used to isolate the effects of mechanical deformation through comparative measurements. These measurements include macro and micro hardness measurements, Energy-dispersive X-ray analysis and examination of eutectic-Si particle size and morphology. The results indicate that the as-cast material is stable up to approximately 144{\deg}C, with the rotary formed material exhibiting decreased macrohardness in-line with the time spent at elevated temperature. Post heat treatment, there was a significant decrease in hardness with increased levels of deformation. Results indicate that precipitation hardening is not appreciably affected by rotary forming, and the principal cause for the drop in hardness with deformation is due to the condition of Al-Si eutectic phase.Comment: 26 pages, 13 figure

Analysis and modelling of a rotary forming process for cast aluminum alloy A356

Spinning of a common aluminum automotive casting alloy A356 (Al-7Si-0.3 Mg) at elevated temperatures has been investigated experimentally with a novel industrial-scale apparatus. This has permitted the implementation of a fully coupled thermomechanical finite element model aimed at quantifying the processing history (stress, strain, strain-rate and temperature) and predicting the final geometry. The geometric predictions of this model have been compared directly to the geometry of the workpieces obtained experimentally. This study is novel in regards to both the size and shape of the component as well as the constitutive material representation employed. The model predictions are in reasonable agreement with experimental results for small deformations, but errors increase for large deformation conditions. The model has also enabled the characterization of the mechanical state which leads to a common spinning defect. Suggestions for improving the accuracy and robustness of the model to provide a predictive tool for industry are discussed

Isolation and characterisation of two chymotrypsins from Allocyttus niger (black oreo dory) viscera

Two serine proteases from the viscera of deep-sea fish, black oreo dory (Allocyttus niger),were purified by hydrophobic, affinity, and cation exchange chromatography. They were designated as chymotrypsins on the basis of substrate specificity and susceptibility to inhibitors. The pH optima of chymotrypsin I and II were 8.6 and 10, respectively. Chymotrypsin II retained a remarkable 80% activity at pH 12.5. Thermal stability of both enzymes was enhanced in the presence of calcium ions. Both chymotrypsins were inhibited by high concentrations of substrate Suc-AAPF-NA

Supersymmetric lepton flavour violation in a linear collider: the role of charginos

The occurrence of a significant amount of supersymmetric lepton flavour violation at laboratory energies, through $\tilde\nu_\mu - \tilde\nu_\tau$ mixing, has become a realistic possibility in the wake of the super-Kamiokande atmospheric neutrino result. This effect can be observed in an e+e- linear collider with the distinct final state tau+mu+ jets+E_T. We show that the pair production of charginos can make an important contribution to this process and has to be taken into account in addition to that of sneutrinos or charged sleptons. Some case studies are presented with CM energies of 500 and 800 GeV and integrated luminosities of 50, 500 and 1000 fb-1.Comment: 15 pages, latex, including 2 figure

MODELING OF AGRICULTURAL SYSTEMS

The authors present an overview of agricultural systems models. Beginning with why systems are modeled and for what purposes, the paper examines types of agricultural systems and associated model types. The broad categories range from pictorial (iconic) models to descriptive analogue models to symbolic (usually mathematical) models. The uses of optimization versus non-optimizing mechanistic models are reviewed, as are the scale and aggregation challenges associated with scaling up from the plant cell to the landscape or from a farm enterprise to a world market supply-demand equilibrium Recent modeling developments include the integration of formerly stand-alone biophysical simulation models, increasingly with a unifying spatial database and often for the purpose of supporting management decisions. Current modeling innovations are estimating and incorporating environmental values and other system interactions. At the community and regional scale, sociological and economic models of rural community structure are being developed to evaluate long-term community viability. The information revolution is bringing new challenges in delivering agricultural systems models over the internet, as well as integrating decision support systems with the new precision agriculture technologies.Farm Management,

Trade deficits: causes and consequences

According to conventional wisdom, trade balances reflect a country's competitive strength-the lower the trade deficit, the stronger the country's industries and the higher its rate of economic growth. In this article, David Gould and Roy Ruffin review the history of the conventional wisdom and empirically examine whether large overall trade deficits or bilateral trade imbalances are associated with lower rates of economic growth. They find that, once the fundamental determinants of growth have been accounted for, trade imbalances have little effect on rates of economic growth.Deficit financing ; Free trade