Effect of sulphuric acid on concrete with iron ore tailings

Researches into the uses of waste materials are increasingly being explored to meet up society’s needs and global protection for sustainable, safe and economic development. This paper assessed concrete with iron ore tailings (IOT) exposed to dilute sulphuric acid. Iron ore tailings are the materials left-over after separating the valuable fraction from the uneconomic fraction of an ore. To study the effect of sulphuric acid, concrete of 100 mm cube with a different mix ratios containing IOT were prepared and cured for 28 days in water. The cubes were later immersed into dilute sulphuric acid at a concentration of 5%. The compressive strength of concrete at 7, 28 and 90 days of water curing were determined. Mass loss and strength reduction due to sulphuric effect were evaluated at 7, 28 and 90 days respectively. XRD microstructure of concrete specimens was analysed. Test results indicated that the IOT could be used in concrete as sand replacement since the concrete with IOT has similar trend in compressive strength loss and mass loss to sulphuric acid attack compared to control specimen. The mineralogical crystal failure patterns due to the sulphuric acid in terms X-ray diffraction analysis are the same for control and IOT concrete

Benchmark notch test for life prediction

Aircraft gas turbine engine components are subjected to severe stress, temperature, and environmental conditions. Economic and reliabilty demands have prompted inordinate effort in development of analytic methods to predict stresses and strains in aircraft engines. There remains, however, the need to check or verify these analytical methodologies against actual experimental data measurements. The laser interferometric strain displacement gage was recognized as having the potential to accomplish this task and was employed in this program. The actual strains incurred at the root of a discontinuity in cyclically loaded test samples subjected to inelastic deformation at high temperature where creep deformation readily occur were measured. The steady-state, cyclic stress-strain response at the root of the discontinuity in the tested samples was analyzed for comparison with the measured results. A comprehensive set of local notch root strain measurements for a variety of load patterns in an Inconel 718 notch specimen at 649 C (1200 F) was obtained and documented using the laser interferometric strain displacement gage

Phase Segregation Dynamics in Particle Systems with Long Range Interactions I: Macroscopic Limits

We present and discuss the derivation of a nonlinear non-local integro-differential equation for the macroscopic time evolution of the conserved order parameter of a binary alloy undergoing phase segregation. Our model is a d-dimensional lattice gas evolving via Kawasaki exchange dynamics, i.e. a (Poisson) nearest-neighbor exchange process, reversible with respect to the Gibbs measure for a Hamiltonian which includes both short range (local) and long range (nonlocal) interactions. A rigorous derivation is presented in the case in which there is no local interaction. In a subsequent paper (part II), we discuss the phase segregation phenomena in the model. In particular we argue that the phase boundary evolutions, arising as sharp interface limits of the family of equations derived in this paper, are the same as the ones obtained from the corresponding limits for the Cahn-Hilliard equation.Comment: amstex with macros (included in the file), tex twice, 20 page

The Relationship between Mold Exposure and Allergic Response in Post-Katrina New Orleans

Objectives. The study's objective was to examine the relation between mold/dampness exposure and mold sensitization among residents of Greater New Orleans following Hurricane Katrina. Methods. Patients were recruited from the Allergy Clinic of a major medical facility. Any patient receiving a skin prick test for one of 24 molds between December 1, 2005 and December 31, 2008 was eligible for the study. Exposure was assessed using standardized questionnaires. Positive mold reactivity was defined as a wheal diameter >3 mm to any mold genera. Results. Approximately 57% of participants tested positive to any indoor allergen, 10% to any mold. Over half of respondents had significant home damage, 34% reported dampness/mold in their home, half engaged in renovation, and one-third lived in a home undergoing renovation. Despite extensive exposure, and multiple measures of exposure, we found no relationship between mold/dampness exposure and sensitivity to mold allergens. Conclusions. These results along with results of earlier research indicate no excess risk of adverse respiratory effects for residents living in New Orleans after the devastation of Hurricane Katrina

Gravitational Instantons from Minimal Surfaces

Physical properties of gravitational instantons which are derivable from minimal surfaces in 3-dimensional Euclidean space are examined using the Newman-Penrose formalism for Euclidean signature. The gravitational instanton that corresponds to the helicoid minimal surface is investigated in detail. This is a metric of Bianchi Type $VII_0$, or E(2) which admits a hidden symmetry due to the existence of a quadratic Killing tensor. It leads to a complete separation of variables in the Hamilton-Jacobi equation for geodesics, as well as in Laplace's equation for a massless scalar field. The scalar Green function can be obtained in closed form which enables us to calculate the vacuum fluctuations of a massless scalar field in the background of this instanton.Comment: One figure available by fax upon request. Abstract missing in original submission. Submitted to Classical and Quantum Gravit

Nanofluid-based Nanocarbons An Investigation of Thermal Conductivity Performance

This paper presents a study of thermal conductivity performance, using a nanofluid-based nanocarbon formulate, with three different types of nanocarbons. NC300, NC200, and commercial carbon nanotube (CNT)were used together with Sodium Dodecyl Sulphate (SDS) as a dispersant, and deionized water as a solvent. A weighted ratio of the nanocarbons (0.4 - 1.0wt%) was set-up and the thermal conductivity was measured at 6°C, 25°C, and 45°C using a KD2 Pro thermal properties analyser. The results showed that NC300 with 1wt% of nanocarbons at 45°C gave the highest improvement of almost 30%, compared to deionized water. Meanwhile, the best nanofluid, based on prepared nanocarbons (NC200) and commercial CNT, showed improvement of more than 9% and 12%, respectively, with the addition of 0.6wt% nanocarbons at 45°C. Morphology analysis using electron microscopy, revealed the structural properties of the nanocarbons. NC300 showed a loose CNT with an average diameter of 70-150nm. NC200 are supported by nanocarbons with an average diameter of 10- 30nm. Meanwhile, the commercial CNT showed a similar characteristic to that of NC300. Even though NC200 had the smallest diameter of all nanocarbons, (which should provide the highest surface area), the larger sizes of the activated carbons, as a nanocarbon support, are expected to reduce thermal conductivity performance

Feed-Forward Chains of Recurrent Attractor Neural Networks Near Saturation

We perform a stationary state replica analysis for a layered network of Ising spin neurons, with recurrent Hebbian interactions within each layer, in combination with strictly feed-forward Hebbian interactions between successive layers. This model interpolates between the fully recurrent and symmetric attractor network studied by Amit el al, and the strictly feed-forward attractor network studied by Domany et al. Due to the absence of detailed balance, it is as yet solvable only in the zero temperature limit. The built-in competition between two qualitatively different modes of operation, feed-forward (ergodic within layers) versus recurrent (non- ergodic within layers), is found to induce interesting phase transitions.Comment: 14 pages LaTex with 4 postscript figures submitted to J. Phys.