Effect of temperature and hold time on internal hardening behavior of a near α titanium alloy under cyclic deformation

In the present work, the study of dynamic strain aging (DSA) in near α titanium alloy Timetal 834 is reported in terms of internal hardening variables (kinematic and isotropic hardening variable). Total strain controlled low cycle fatigue tests have been conducted in air at 300 °C and from 400 °C to 500 °C at a temperature interval of 25 °C at nominal strain rates of 6.67 × 10⁻³ s⁻¹. The alloy exhibits gradual cyclic softening till failure at 300 °C, whereas, it exhibits initial cyclic softening followed by marked cyclic hardening from 400 °C to 500 °C. The cyclic hardening is attributed to DSA phenomena, resulting due to increase in isotropic stress component. The observed maximum peak stress ratio, lower fatigue life and minimum half-life plastic strain range at 450 °C indicates the maximum effect of DSA at that temperature. The fatigue life of tensile and compressive hold at 450 °C was observed to be inferior as compared to pure fatigue tests.     

Fatigue crack growth behaviour of nickel based superalloys at ambient temperature

The present investigation deals with the study of fatigue crack growth rate (FCGR) behaviour of conventional IN 718 (Ni-0.02%C-19.0%Cr-19.35%Fe-3.0%Mo-5.10%Nb-0.50%Al-1.00%Ti-0.0033%B, all in wt%) and modified IN 718 (Ni-0.02%C-19.04%Cr-19.31%Fe-3.04%Mo-4.73%Nb-1.01%Al-1.16%Ti-0.0033%B, all in wt%) alloys at ambient temperature. Modified IN 718 alloy exhibits enhanced crack growth resistance due to roughness induced crack closure as compared to conventional IN 718 alloy.     

Challenges in developing an integrated catchment management model

Directives and policies increasingly call for more integrated management of land and water. Frameworks such as integrated catchment management may address these calls, and yet their implementation requires decisions to be taken under conditions of extreme complexity and uncertainty. This paper summarises a participatory framework through which decision‐makers, experts and system modellers can collaboratively develop an integrated model to support such decisions. A feasibility study showed the potential of the framework. An operational version of the model, able to analyse the effects of 50 management options on 20 indicators, is estimated to require in the order of 225 man‐months from system modellers, alongside substantial inputs from stakeholders. The significant technical challenges confronting such an exercise may be overshadowed by the institutional challenges, including the fundamental question of whether organisations are truly committed. However, the reward for overcoming such challenges is the opportunity to achieve genuine improvements in the social, economic and environmental quality of our catchments.     

Atomistic analyses of the effect of temperature and morphology on mechanical strength of Si–C–N and Si–C–O nanocomposites

3-D molecular dynamics (MD) analyses of SiC–Si₃N₄ nanocomposite deformation and SiCO nanocomposite deformation are performed at 300 K, 900 K, and 1500 K. In SiC–Si₃N₄ nanocomposites, distribution of second phase SiC particles, volume fraction of atoms in GBs, and GB thickness play an important role in temperature dependent mechanical behavior. The deformation mechanism is a trade-off between the stress concentration caused by SiC particles and Si₃N₄–Si₃N₄ GB sliding. The temperature increase tends to work in favor of GB sliding leading to softening of structures. However, microstructural strength increases with increase in temperature when GBs are absent. In the case of SiCO nanocomposites, findings indicate that temperature change dependent amorphization of nanodomains, the nanodomain wall placement, the nanodomain wall thickness, and nanodomain size are important factors that directly affect the extent of crystallinity and the strength against mechanical deformation.     

Thermally-stimulated spontaneous currents from metal-iodine doped polyvinyl pyrrolidone-metal system

A study of the spontaneous response currents from the metal-iodine doped polyvinyl pyrrolidone-metal (MPM) systems, on thermal stimulation at a constant rate, has been made with similar (Al-Al, Ag-Ag and Au-Au) and dissimilar (Al-Cu/Ag/Ni/PbZn) electrode systems. Thermograms of spontaneous current emission of iodine-doped PVP films exhibit two maxima around 90 ± 10°C and 130–160°C in the first heating run, whereas with the second heating run a single peak is found around 140–170°C. The magnitude and direction of current depend on the choice and combination of electrode materials. The position of the current peak in the thermal spectrum shifts with different heating run. A temperature dependence of open-circuit voltage (OCV) is also reported and it was found that OCV varied linearly with the difference in electrode work functions. The active centres of PVP are the carbonyl group of double-bond tertiary nitrogen atom (> N-C=O), and thus the charge transfer complexes are formed with iodine in PVP. The spontaneously-generated current is discussed in terms of weak complex formation with the water molecules and the liberation of different types of charges.     

Thermally stimulated current and electrical conduction in metal (1)-ethyl cellulose-metal (1)/(2) systems

Depolarization current characteristics of solution grown pure ethyl cellulose (EC) films of about 20μm thickness have been studied as a function of electrode materials at constant poling field (5 × 10⁴ V/cm) and poling temperature 40°C. Thermally stimulated current (TSC) thermograms of EC consists of two well resolved peaks (located at 60°C and 140°C) for Al-Al system, which are attributed to the deorientation of strongly attached ethoxy groups of glycosidal units and diffusion of space charges either at electrodes or due to their thermal release at higher temperatures from the defect levels. For dissimilar electrode combinations (Al-Ag/Cu/Au/Sn/Pb), an indication of peak of lower magnitude at around (50–70°C) alongwith a higher temperature peak (140–155°C), have been observed. TSC parameters are found to change with the choice of electrode material. The dependence of dark current at 40°C in metal-ethyl cellulose-metal systems on applied voltage in the range (2·0–5·0) × 10⁴V/cm has also been studied. The results of current-voltage measurement on EC have been interpreted to show that the Schottky-Richardson mechanism is the controlling transport mechanism. Zero field current density extrapolated fromI-E ^1/2 plots are found to vary with metal work function.     

Influence of Interfacial LSMO Nanoparticles/Layer on the Vortex Pinning Properties of YBCO Thin Film

YBa₂Cu₃O_7?δ (YBCO) thin films have been deposited on bare and La_0.67Sr_0.33MnO₃ (LSMO) modified single crystal SrTiO₃ (STO) substrates. The effect of randomly distributed ferromagnetic LSMO nanoparticles and a complete LSMO layer, present at STO/YBCO interface, on the superconducting properties of YBCO thin films has been investigated by temperature dependent magnetization studies. The YBCO thin film on LSMO nanoparticles decorated STO substrate shows significant improvement in the critical current density and pinning force density as compared to the YBCO thin film deposited on bare STO substrate and this improvement is more significant at higher applied magnetic field. However, the LSMO/YBCO bilayer showed the improved flux pinning properties only up to a magnetic field of 1.5 T above which it deteriorates. In the case of LSMO/YBCO bilayer, the underlying LSMO layer gives rise to magnetic inhomogeneities due to domain structure, which leads to improved flux pinning properties limited to lower field. However, in the case of LSMO nanoparticles decorated substrate, the presence of LSMO nanoparticles at YBCO/STO interface seems to introduce magnetic inhomogeneities as well as structural defects, which might be acting as correlated pinning sites leading to improved flux pinning properties of the YBCO thin film over a wide range of applied magnetic field.     

Intel 870: a building block for cost-effective, scalable servers

Architects based the Intel 870 system architecture on the scalability port, a coherent system interconnect. The system's building-block approach lets a single chip set support a wide range of server segments.     

Web-log-driven business activity monitoring

Business process transformation defines a new level of business optimization that manifests as a range of industry-specific initiatives that bring processes, people, and information together to optimize efficiency. This new optimization level is possible because the Web has assumed the role of a common infrastructure. To examine how BPT can optimize an organization's processes, we describe a corporate initiative that was developed within IBM's supply chain organization to transform the import compliance process that supports the company's global logistics. The initiative sought to give IBM greater awareness of regulatory compliance exceptions - information critical to the corporation and its importing partners.