Enhanced Mechanical Properties and Corrosion Behavior of Biodegradable Mg-Zn/HA Composite

Metallurgical and Materials Transactions A - Magnesium (Mg) and its alloys have shown potential for use in the biomedical industry due to their excellent biological performance and biodegradability...     

Some Investigations on Friction Stir Processed Zone of AZ91 Alloy

In this study, AZ91 based hybrid nanocomposite was fabricated using mixture of TiC and alumina by friction stir processing (FSP). FSP of AZ91 was conducted with as well as without particle addition and under different cooling conditions. Distribution of nano TiC and Al₂O₃ particles in the Mg matrix was studied using SEM. Grain size analysis of the as-cast and FSP AZ91/(TiC?+?Al₂O₃) composite was done using optical microscopy. The performance of the fabricated nanocomposite was investigated using microhardness, bulk hardness and scratch tests. Microhardness testing was done at 50?gf load and bulk hardness at 5?Kgf load. Scratch test was performed at 2 and 5?N normal load values on a universal tribometer using Rockwell indentor. AZ91/(TiC?+?Al₂O₃) composite exhibited improved mechanical properties.     

Decarburization as a tool to explore parallels between solid-solid and liquid-solid transformations: Fe-C-Mn-Si steels

The study of single-interface transformations under controlled conditions offers insights into the similarities and distinctions between solidification and solid-solid transformations. In this contribution, we consider some parallels between the formation of a layer of ferrite on an originally austenitic steel bar and the growth of the columnar zone in the solidification of an alloy ingot. The necessary conditions for solid-solid interfacial breakdown of a decarburization front are explored and the evidence to date reviewed. The response of some Fe-C-Mn-Si steels to controlled decarburization is considered, and we present a first report of the morphological instability of a ferrite/austenite decarburization interface, and compare it with the interfacial breakdown in the solid-liquid interface. The instability is tentatively ascribed to the effects of grain-boundary nucleation and/or grain-boundary diffusion of alloying elements in austenite. Other similarities (and differences) between the growth of a ferrite layer on an alloy steel and the development of the columnar zone of an ingot are discussed.     

Particle engulfment and pushing by solidifying interfaces: Part 1. Ground experiments

Directional solidification experiments have been carried out to determine the pushing/engulfment transition for two different metal/particle systems. The systems chosen were aluminum/zirconia particles and zinc/zirconia particles. Pure metals (99.999 pct A1 and 99.95 pct Zn) and spherical particles (500 μm in diameter) were used. The particles were nonreactive with the matrices within the temperature range of interest. The experiments were conducted so as to ensure a planar solid/liquid (SL) interface during solidification. Particle location before and after processing was evaluated by X-ray transmission microscopy (XTM) for the Al/ZrO₂ samples. All samples were characterized by optical metallography after processing. A clear methodology for the experiment evaluation was developed to unambiguously interpret the occurrence of the pushing/engulfment transition (PET). It was found that the critical velocity for engulfment ranges from 1.9 to 2.4 μm/s for Al/ZrO₂ and from 1.9 to 2.9 μm/s for Zn/ZrO₂.     

Simulation of cooling of liquid Al–33 wt.% Cu droplet impinging on a metallic substrate and its experimental validation

In the present work a model for heat transfer during collision of a falling liquid Al–33 wt.% Cu droplet on a 304 stainless steel substrate has been developed on a FLUENT 6.3.16 platform. The model simultaneously takes into account the fluid flow and heat transfer in the liquid droplet and the surrounding gas, and the heat transfer in the substrate. The liquid–gas interface was tracked using the volume of fluid method and the contact resistance between Al–33 wt.% Cu and the substrate was taken into account. The comprehensive model correctly predicted the total spread in the droplet. As per the predicted transient thermal field, the solidification front speed oscillated along the radius of the spread droplet. Based on the estimated front speeds at these locations and Jackson–Hunt plot for Al–33 wt.% Cu, the variation of interlamellar spacing along the radial direction was found. It matched well with the variation of the experimentally measured interlamellar spacing at different locations along the radius.     

Reusable Dry Adhesive: Aluminium-Aluminium Bonding by Self-Vulcanisable Blend Based on Carboxylated Nitrile Rubber and Chlorobutyl Rubber

A self-vulcanisable blend of chlorobutyl rubber and carboxylated nitrile rubber can be used as an adhesive for aluminium-aluminium bonding. The peel strength depends on the state of cure of the adhesive, testing temperature and carboxyl content of the carboxylated nitrile rubber. At moulding times below 15 minutes, the adhesive was found to be reusable after repeated post-peel mouldings.     

SELECTIVE FLAT PLATE COLLECTORS FOR SOLAR DRYERS

ABSTRACT

Five different selective surfaces coated with oxides of nickel, manganese, chromiUm, lead, am iron on galvanized iron substrate by electro-deposition or chemical method were studied for properties such as absorptivity, emissivity, temperature rise of the surface and stagnation air temperature. The properties of the surfaces which may change due to weather conditions were predicted by: subjecting the collector surfaces to accelerated tests. The best among them was found to be black nickel, followed by manganese, chromium, lead, and iron oxides. Black nickel and manganese surfaces were included in the solar drying system and their drying air temperatures recorded. With selective surfaces, a temperature rise between 250to 4sOC was observed depending on the surface (either manganese oxide or nickel oxide)., Hence high mo~sture content food crops can be dried in less than half the time using selective surface     

Carboxymethylation of Cassia tora gum

The preparation of carboxymethyl (CM)–Cassia tora gum (CTG) with monochloroacetic acid and sodium hydroxide was investigated under different reaction conditions. The carboxymethylation reaction was studied with respect to the degree of substitution of CM–CTG. The variables studied were the concentration of reactants, methanol–water ratio (solvent), reaction time, and reaction temperature. Carboxymethylation of CTG increased its solubility in cold water and the stability of its paste to microorganisms. Regardless of the degree of substitution of these products, their aqueous solutions were characterized by non‐Newtonian pseudoplastic behavior. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3216–3219, 2003     

Kinetics of structure II gas hydrate formation for propane and ethane using an in-situ particle size analyzer and a Raman spectrometer

The kinetics of structure II gas hydrates, formed from pure propane and a mixture of propane and ethane, were investigated and intrinsic rate constants were regressed from the experimental data. The experiments were conducted in a semi-batch stirred tank reactor equipped with an in-situ particle size analyzer and connected to an external Raman spectrometer. Experiments were conducted with pure propane at temperatures ranging from 274 to 276 K and pressures ranging from 0.39 to 0.43 MPa. The intrinsic rate constant for ethane in structure II was subsequently regressed from experimental data on the formation of hydrates formed from an equimolar mixture of propane and ethane at 274 K and 0.35 MPa. Raman spectroscopy was used to verify that ethane was present only in the large sII cavity.     

Visual data mining for crowd anomaly detection using artificial bacteria colony

This paper presents a novel method for global anomaly detection in crowded scenes. The optical flow of frames is used to extract the foreground of areas with people motions in the crowd in the form of layers. The optical flow between two frames generates one layer. The proposed method applies the metaheuristic of artificial bacteria colony as a robust algorithm to optimize the extracted layers. Artificial bacteria cover all regions of interest that have high movement between frames. The artificial bacteria colony adapts quickly to the most varied scenarios. Moreover, the algorithm has low sensibility to noise and to sudden changes in video lighting as captured by optical flow. The bacteria population of the colonies, its food storage and the colony’s centroid position regarding each optical flow layer, are used as input to train a Kohonen’s neural network. Once trained the network is able to detect specific events based on behavior patterns similarity, as produced by the bacteria colony during such events. Experiments are conducted on available public dataset. The achieved results show that the proposed method captures the dynamics of the crowd behavior successfully, revealing that the proposed scheme outperforms the available state-of-the-art algorithms for global anomaly detection.