Abstract

The century old technology, the Bayer process remains the most economic means of obtaining alumina from bauxite till date. Worldwide alumina is produced from bauxite by Bayer Process which generates highly alkaline solid waste (pH 12 - 13.5) known as Red Mud. Around 70 million tonnes of red mud per annum is generated world wide of which ~ 4 million tonne of red mud is generated annually in India. Disposal of such a huge quantity of alkaline solid waste is creating a big environmental issue leading to its alternative usage / utilization methods. Several routes of using red mud in effective ways have been tried and extensive research is still going on to find the most suitable and economic way of utilizing the same. It is an iron-rich residue which also contains undigested alumina, titania and sodium aluminosilicates. Indian Red Mud mainly consists of Fe₂O₃ (35-55 wt %), Al₂O₃ (16-22 wt %), SiO₂ (4-16 wt %), Na₂O (3-6 wt %), TiO₂ (2-19 wt %), CaO (0.8-4.5 wt %) and other oxides in trace amount depending upon the mineralogy and process parameters used. Red mud is disposed as slurry having a high solid concentration of 30-60% and with a high ionic strength. It is disposed as dry or semi dry material in red mud pond or abandoned bauxite mines. The disposal of the red mud represents a major loss of valuable soda and has a high pH value as a result of the entrained soda.  The environmental concerns which are related to the disposal of red mud are its large quantity which consumes vast areas of land and its causticity. Problems associated with the disposal of red mud waste include its high pH (12-13), alkali seepage into underground water, safety in storage, and alkaline air borne dust impact on plant life. High iron content has also shown scope of metal / value added product recovery from the same. Many special adsorbent / compounds have been developed from red mud for pollution control purpose also. But these applications are not always economically viable because of source and surrounding conditions. So environmentally safe disposal has also been given importance; i.e. neutralization of red mud for safer disposal as well as amendment of red mud to support re-vegetation / vegetation cover in the plant and mine surrounding areas. At present, there is no viable process developed for utilising the bauxite residue, consequently this large quantity of waste material is required to be disposed economically and safely to the environment. In this paper, all different directions of red mud utilization are discussed. The paper also reviews the methods of neutralization for its safe disposal.

Abstract

Sound and reliable structural design demands high quality experimental data and rational analysis of the mechanical properties of the constituent materials of which the structural elements are made. Although several theoretical models and much experimental data on the behavior of fiber-reinforced concrete are available in the published literature, there is lot of scope for research and investigation in the area of the fiber-reinforced self-compacting concrete (FR-SCC) /6,7/. In the present technical note an attempt is made to report about the optimum value of fiber content to be used as a constituent material to improve mechanical properties of concrete significantly. It is also attempted to suggest and report about the optimum value of cement to be replaced by the corresponding value of fly-ash /2,3/ as a constituent material. This technical note presents the results of tests in compression, split tension and flexure of Steel Fiber-Reinforced Self-Compacting Concrete (SFR-SCC). Experimental tests /8,9/ were carried out on cubes, cylindrical specimens and prisms of plain and steel fiber-reinforced concrete. A fiber content of 0.5% and 1% by volume of concrete is used. Sophisticated digitized equipment as per the standard procedure is used for all the measurements. A critical comparative study SCC and SFR-SCC was carried out and reported in the form of tables, graphs and charts.

Abstract

The Ti6Al4V alloy is generally welded using gas tungsten arc welding (GTAW) technique, due to its easy availability and cheap equipment cost. The laser beam welding (LBW) technique is used in places where high quality and precision welds are preferred. Even though the GTAW technique is commercially cheaper, it has its inherent drawbacks like broad heat affected zone (HAZ) and associated metallurgical changes due to long duration of exposure to the welding arc. The laser beam welding produces a narrow heat affected zone (HAZ) and minimum welding defects, but its application is limited due to its high equipment cost.

In this investigation square butt joints were fabricated from 1.6 mm and 3 mm thick plates of Ti6Al4V alloy using laser beam welding process. The tensile strength, impact toughness, micro hardness, microstructure and the fractography of the weldments were studied to determine the effect of plate thickness on these mechanical properties and the mode of failure in laser beam welded joints. Even though the 3 mm thick plate exhibited high tensile strength, the notch strength ratio was less than unity, whereas the 1.6 mm thick plate showed lower tensile strength and higher notch strength ratio. This indicates that the 1.6 mm thick plate could be used in low strength applications and the 3 mm thick plates could be used in high strength static loads and low cycle load applications.

Abstract

This work presents the possibility to realize the self healing mechanisms for heterogeneous architectural metal/ceramic high temperature sandwich thermal barrier coating systems on the surfaces refractory metals by analogy of wound healing in the skin.

Abstract

A two-dimensional and three-dimensional computational study has been carried out respectively regarding aerodynamic forces affecting a symmetric spoiler, NACA0015 and a cambered spoiler, NACA2414. The negative lift (down force) and drag forces were predicted through the simulation of airflows over inverted rear-wings (spoilers) in different configurations namely; varying incidences i.e. angles of attack of the airfoils, two dimensional cross-section of the wings, and varying speeds of initial airflow.  The downforce increases as the angle of attack increases however, at high angle of attacks the rear-wing starts to stall which is  not a desired condition affecting  the vehicle stability. Furthermore, the camberness added to the airfoil increased the downforce, which contributes more to the stability concept of the automobile.

Abstract

In this paper, an image fusion technique in spatial domain using an image variance as a focus measure has been demonstrated and discussed. The image variance (IV) is used as a focus measure to measure the depth of field in the images. Then it is applied in the fusion process of fusing images in diverse focuses. The experiments were performed on a set of left and right focused images and the fused results were evaluated with various equal sub block sizes of the images.

Abstract

The quality of satellite images propagating through the atmosphere is affected by phenomena such as scattering and absorption of light, and turbulence, which degrade the image by blurring it and reducing its contrast. The Wiener filter, which corrects for turbulence blur, aerosol blur, and path radiance simultaneously, has been implemented in the digital restoration of remotely sensed imagery. Another filter for image restoration inverse filtering has also been implemented. Restoration improves both resolvable detail and contrast. Results of the filtering on simulation and realistic images are shown.  The remotely sensed image that is to be restored is subjected to one of the filters. The degradation is added in terms of PSNR (Picture-signal-to-noise-ratio). The resulting image after restoration is compared with original image and their performance has been evaluated in terms of CNR (Contrast-to-noise -ratio), RMS error per pixel, and Calculated PSNR. The enhancement technique has also been tested for first moon image sent by satellite mission CHANDRAYAAN [1].

Abstract

Flexural vibration of an infinite piezocomposite multilayer hollow cylinder made of piezoelectric layers of 6mm-class and an LEMV (LINEAR ELASTIC MATERIAL WITH VOIDS) layers is studied. The frequency equations are obtained for the traction free outer surface with continuity conditions at the interfaces. The frequency equations solved by using Muller’s method with VC++ programme. We can study about the attenuation effect and vibration characteristics. Numerical results are carried out for the inner hollow, middle and outer piezoelectric layers bonded by LEMV layers and the dispersion curves are compared with that of a similar model bonded by CFRP (CARBON FIBRE REINFORCED PLASTIC).

Abstract

Measurement of ultrasonic study gives information about physico-chemical behavior of solutions and liquid mixtures and molecular interactions of multicomponent liquid mixtures. In this paper the system for simulation, measurement and processing in graphical user interface implementation is presented. The received signal from the simulation is compared to that of an actual measurement in the time domain. The comparison of simulated, experimental data clearly shows that acoustic wave propagation can be modeled. The feasibility has been demonstrated in an ultrasound transducer setup for material property investigations. The results of simulation are compared to experimental measurements. Results obtained fit some much with those found in experiment and show the validity of the used model. The simulation tool therefore provides a way to predict the received signal before anything is built. Furthermore, the use of an ultrasonic simulation package allows for the development of the associated electronics to amplify and process the received ultrasonic signals. Such a virtual design and testing procedure not only can save us time and money, but also provide better understanding on design failures and allow us to modify designs more efficiently and economically.

Abstract

Multi-user detection in CDMA systems results in tremendous increase in capacity when compared to that provided by conventional detectors. Some sub-optimal but easily implementable multiuser detectors for Single Input Single Output (SISO) systems have already been researched. One such detector is the Successive Interference Cancellation (SIC) multiuser detector.

In this paper, we analyze the performance of a SIC multiuser detector with VBLAST to Multiple Input Multiple Output (MIMO) wireless systems using matlab tool box . The simulation results shows  the benefits of the SIC multiuser detector over the conventional detector for a few transmit-receive configurations. Further, the effect of thermal noise power on the performance of the SIC multiuser detector is simulated and the performance is analyzed.

Abstract

Cold upsetting experiments were carried out on sintered Fe-0.8%C-1.0%Si-0.8%Cu steel preforms in order to evaluate stress — strain, stress — densification and work hardening characteristics.  Powder preforms of 86% theoretical density and 0.40 of initial aspect ratio were prepared using a suitable die — set assembly on a 1MN capacity hydraulic press. Sintering was carried out in an electric muffle furnace for a period of 90 minutes at 11500C.  Each sintered compact was subjected to incremental compressive loading of 0.04MN under two different lubricating constraints namely nil/no and graphite lubricant till fracture appears at free surfaces.  The behavior of applied stresses with strain and densification exhibits a continuous enhancement but with three different modes of responses.  The first and third stage offers high resistance to deformation, whereas the second stage shows virtually steady state, deformation needed gradual increase in applied stresses but with high rate of densification. The instantaneous strain hardening exponent ni and strength co-efficient Ki of the aforementioned steel preforms were calculated and found to enhance continuously with the continuous enhancement of deformation and densification.