Creep of Single Crystals of Nickel-Based Superalloys at Ultra-High Homologous Temperature

The creep behavior of single crystals of the nickel-based superalloy CMSX-4 was investigated at 1288 °C, which is the temperature of the hot isostatic pressing treatment applied to this superalloy in the industry. It was found that at this super-solvus temperature, where no γ′-strengthening occurs, the superalloy is very soft and rapidly deforms under stresses between 4 and 16 MPa. The creep resistance was found to be very anisotropic, e.g., the creep rate of [001] crystals was about 11 times higher than that of a [111] crystal. The specimens of different orientations also showed a very different necking behavior. The reduction of the cross-sectional area ψ of [001] crystals reached nearly 100 pct, while for a [111] crystal ψ?=?62 pct. The EBSD analysis of deformed specimens showed that despite such a large local strain the [001] crystals did not recrystallize, while a less deformed [111] crystal totally recrystallized within the necking zone. The recrystallization degree was found to be correlated with deformation behavior as well as with dwell time at high temperature. From the analysis of the obtained results (creep anisotropy, stress dependence of the creep rate, traces of shear deformation, and TEM observations), it was concluded that the main strain contribution resulted from 〈\( 0 1\bar{1} \)〉{111} octahedral slip.     

Oil consumption, CO2 emission and economic growth in MENA countries

This study examines the impact of oil consumption on the economic growth of the MENA countries during the period 1980–2009. The panel model is employed in this study. Based on the cointegration test results, it was found that CO₂ emission, and oil consumption has a long run relationship with economic growth. Moreover, there is also a bi-directional Granger causality between oil consumption, CO₂ emission and economic growth in both the short run and the long run. The results of this study show clearly that oil consumption plays an important role in the economic growth of the MENA countries.     

Sintering/shrinkage kinetics of metal injection molded copper brown body

The sintering shrinkage kinetics of metal injection molded copper brown parts was investigated at three different heating rates up to 1050 °C using a high temperature pushrod dilatometer. Non-isothermal and isothermal measurements were simultaneously used in the multivariate non-linear regression analysis to determine the kinetic reaction parameters. A four-step kinetic model was established using “Jander” diffusion equation. Using the rate control sintering, the temperature-time profile for the predefined shrinkage was achieved with respect to time saving. The temperature-time profile was confirmed by performing an experimental run in the production furnace. The metallographic analysis of the microstructure and determination of the sintered density revealed the validation of calculated temperature-time profile.     

Simulation of a pebble‐bed heat regenerator

A mathematical model to simulate the operational behaviour of a pebble‐bed heat regenerator has been developed, and an experimental study performed to test the model predictions. The model is based on finite heat balances for the solid and the fluid applied to a bed which is divided into several sections insulated from each other. Within each section, there is no radial or axial temperature gradient, i.e. the temperature of all the pebbles in a given section are the same. As the fluid stream flows through the idealized compartmented bed, there is heat exchange in each section between the pebbles and the fluid. The model, which is applicable both to the heating and cooling cycles, has been used to simulate the behaviour of a heat regenerator. To test the predictions of the model, experiments have been performed on a 7 ft by 8 in cylindrical column using a hot air stream of approximately 200°C at an average flow rate of 365 l min^‐1. A special technique, wherein a pebble is fixed to a thermocouple, was used to measure the temperature at different bed positions. Experimental conditions were such that interesting results have been generated. The model was able to predict with good accuracy all the unusual operational behaviour encountered. The deviations between the model and the experimental results can be explained by the fact that the model does not consider heat loss from the column wall. Copyright © 2000 John Wiley & Sons, Ltd.     

Characteristics of pulsed photo-stimulated luminescence and thermoluminescence for the identification of gamma irradiated poultry eggs

Pulsed photo-stimulated luminescence (PPSL) is a simple screening method that can be employed qualitatively at the spot for the detection of eggs treated with ionizing radiation.Due to the variations in the results during storage,the eggs of ostrich,duck,hen,and quail were irradiated to doses of 0,1,2,and 3 kGy.Most of the samples were incorrectly identified during storage after four months of irradiation.Thermoluminescence (TL) technique was also tried by using egg shells in order to confirm the irradiation treatment in eggs.TL glow curves were recorded between the temperatures 50℃to 400℃at the rate of 5°/s for all the control and irradiated samples.On the basis of integrated areas of first glow curves (TL1),the glow curve ratios (TL1/TL2) and the shapes of maxima of TL1, the irradiation treatment of all the eggs was confirmed.Furthermore,the presence of calcite and aragonite minerals that cause the TL signal in the egg shells were studied using X-ray diffraction spectrometry.     

Functional role of bioactive peptides with special reference to cheeses

Growing perception about diet in relation to health has extended the necessity to explore the biologically active components present in native foods. In this review, bioactive peptides released from cheeses that may have important physiological functions are discussed. Bioactive encrypted peptides can be generated from precursor milk proteins during food processing via enzymatic hydrolysis and fermentation. Generally, biofunctionalities of peptides are latent within precursor proteins. Bioactive peptides liberated from cheeses exhibit numerous potential therapeutic roles: for example, angiotensinogen‐converting enzyme (ACE) inhibition, antioxidant, anti‐thrombotic, anti‐microbial, anti‐cancer and anti‐inflammatory. This article critically focuses on the functional roles of bioactive peptides derived from different cheeses.     

Towards Probabilistic Formal Analysis of SATS-Simultaneously Moving Aircraft (SATS-SMA)

The objective of NASA’s Small Aircraft Transportation System (SATS) Concept of Operations (ConOps) is to facilitate high volume operation of advanced small aircraft operating in non-towered, non-radar airports. This system can provide improved and accessible air travel at a lower cost. Given the safety-critical nature of SATS, its analysis accuracy is extremely important. However, the commonly used analysis techniques, like pilot/computer simulation and traditional model checking, do not ascertain an error-free and complete verification of SATS due to the wide range of possibilities involved in SATS or the inability to capture the randomized and unpredictable aspects of the SATS ConOps environment in their models. Another limitation of these studies is that a limited speed range was used in the analysis. To overcome these limitations, we propose to formulate the SATS ConOps as a fully synchronous and probabilistic model, i.e., SATS-SMA, that supports simultaneously moving aircraft. The distinguishing features of our work include the preservation of safety of aircraft while providing a precise timing model, which is closer to reality compared to the previous hybrid analyses. Important insights related to the aircraft take-off and landing operations during the instrument meteorological conditions are also presented.     

Insulin elevates hippocampal GABA levels during ischemia. This is independent of its hypoglycemic effect

There are reports that insulin may protect neurons from the effects of ischemia. The mechanisms for this protection are not fully understood. We studied the extracellular levels of glutamate and GABA in insulin-treated animals exposed to transient forebrain ischemia under normoglycemic and hypoglycemic conditions. In vivo microdialysis technique was used to collect extracellular fluid from the CA1 region of the hippocampus. There was a significant increase in GABA levels in the two insulin-treated sub-groups compared with the controls. GABA levels were < 1 pmol/10 microliters in three 10 min collections prior to ischemia in all the groups. It increased from 11.1 +/- 3.5 pmol/10 microliters in the conrol group to 47 +/- 5 (P < 0.001) in the insulin-treated hypoglycemic group and up to 47.2 +/- 9.3+ (P < 0.005) in the insulin-treated normoglycemic group (two-way ANOVA with repeated measures). Ischemia resulted in an increase in the glutamate levels. The glutamate levels returned to baseline within 30 min of the insult. There were no significant differences in the glutamate levels in three groups. The increase in GABA concentrations in the extracellular space may result in the inhibition of CA1 pyramidal neurons. This may be a possible mechanism of neuronal protection in animals treated with insulin (with or without being hypoglycemic) during ischemia.