Journal Articles
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Item Oxide bifilms in aluminium alloy castings - A review(2011) Gopalan, R.; Prabhu, K.N.Aluminium alloy castings are most widely used in automobile industry because of their light weight, better castability and improved properties. The liquid aluminium surface easily oxidises during melting, transferring and pouring operation which may entrain oxide films into the casting. Research work has shown that the entrainment of this surface film and formation of bifilms in castings appear to be the source of most of the casting defects leading to a significant reduction in the mechanical properties of aluminium alloy castings. In this paper, the phenomenon of formation of oxide bifilms in aluminium alloy castings, effect of these bifilms on casting properties and their assessment techniques are discussed. For enhancing the quality of casting, research should focus towards development of process techniques for healing of bifilms in liquid metal during solidification. © 2011 Institute of Materials, Minerals and Mining.Item Reactive wetting, evolution of interfacial and bulk IMCs and their effect on mechanical properties of eutectic Sn-Cu solder alloy(2011) Satyanarayan, S.; Prabhu, K.N.Lead free solders are increasingly being used in electronic applications. Eutectic Sn-Cu solder alloy is one of the most favored lead free alloys used for soldering in electronic applications. It is inexpensive and principally used in wave soldering. Wetting of liquid solder on a substrate is a case of reactive wetting and is accompanied by the formation of intermetallic compounds (IMCs) at the interface. Wettability of Sn-0.7Cu solder on metallic substrates is significantly affected by the temperature and the type of flux. The wettability and microstructural evolution of IMCs at the Sn-0.7Cu solder/substrate interfaces are reviewed in the present paper. The reliability of solder joints in electronic packaging is controlled by the type and morphology of interfacial IMCs formed between Sn-0.7Cu solder and substrates. The formation and growth mechanisms of interfacial IMCs are highlighted. Mechanical behavior of bulk solder alloy and solder joint interfaces are analyzed. The characteristics of the IMCs which have marked effect on the mechanical properties and fracture behavior as well as reliability of solder joints of the alloy are discussed. An attempt has also been made to discuss the effect of cooling rate and strain rate on shear strength, tensile properties and creep resistance of the solder alloy. It is recommended that future work should focus on evolving a standard procedure involving sequential assessment of wetting behavior, evolution of IMCs and mechanical properties. © 2011 Elsevier B.V.Item Preparation, characterization and performance study of poly(isobutylene- alt-maleic anhydride) [PIAM] and polysulfone [PSf] composite membranes before and after alkali treatment(2011) Padaki, M.; Isloor, A.M.; Belavadi, G.; Prabhu, K.N.Recently, nanofiltration (NF) membranes have been drawing much attention in the field of filtration and the purification process of water/industrial effluents, because of their energy efficiency and low cost. Although reverse osmosis (RO) membranes are widely used in present desalination units, NF membranes are considered as "future membranes" for desalination, because of the low operating pressure. In the present paper, we hereby report the synthesis of a new composite NF membranes of poly(isobutylene-alt-maleic anhydride) (PIAM) with polysulfone, using a diffusion-induced phase separation (DIPS) method. The anhydride groups were converted to acid group by alkaline treatment. Newly prepared composite membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) studies. The membranes were tested for salt rejection and water swelling. The resulted NF membranes exhibited significantly enhanced water permeability while retaining high salt rejection. The flux and rejection rate of the NF membrane to Na2SO4 (500 ppm) reached to 11.73 L/(m2 h) and 49% rejection under 1 MPa and also 70:30 composition of the membrane showed 54% water swelling; contact angle measurement, ion exchange capacity, and water uptake of the membrane were recorded. © 2011 American Chemical Society.Item A Critical Review of Construction, Analysis and Behaviour of Stone Columns(Kluwer Academic Publishers, 2013) Dheerendra Babu, M.R.; Nayak, S.; Shivashankar, R.Stone columns have been used as an effective technique for improving the engineering behaviour of soft clayey grounds and loose silt deposits. The soil improvement via stone columns are achieved from accelerating the consolidation of weak soil due to shortened drainage path, increasing the load carrying capacity and/or settlement reduction due to inclusion of stronger granular material. This paper discusses the techniques, methods of construction of stone columns, mechanisms of stone column behaviour under load and associated design philosophies along with some practical findings from recent research programs. © 2012 Springer Science+Business Media B.V.Item Optimization of deposition conditions for bright zn-fe coatings and its characterization1(2011) Bhata, R.; Bhat, U.; Hegdea, A.C.Sulfate bath having ZnSO4 ̇ 7H2O, Fe 2(SO4)3 ̇ H2O and thiamine hydrochloride (THC) and cit- ric acid (CA) in combination, represented as (THC + CA) was optimized for deposition of bright Zn-Fe alloy coating on mild steel. Bath constituents and operating parameters were optimized by standard Hull cell method, for peak performance of the coating against corrosion. The effect of current density (c.d.), pH and temperature on deposit characters, such as corrosion resistance, hardness and glossiness were studied and dis- cussed. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods were used to assess the corrosion behaviors. Surface morphology, and composition of the coatings were examined using Scanning Electron Microscopy (SEM), interfaced with EDXA facility, respectively. The Zn-Fe alloy, with intense peaks corresponding to Zn(100) and Zn(101) phases, showed highest corrosion resistance, evi- denced by X-ray diffraction (XRD) study. A new and cheap sulfate bath, for bright Zn-Fe alloy coating on mild steel has been proposed, and results are discussed. © Pleiades Publishing, Ltd., 2011.Item Gamma radiation shielding characteristics of concrete mixes-the state of art(2013) Santhoshkumar, M.; Narasimhan, M.C.; Karkera, B.In this paper, initially the interaction of gamma radiation with materials in general and concrete in particular are discussed. The state-of-art attempts made in different parts of the world, in improving the gamma radiation shielding properties by incorporating alternate/additional ingredients in concrete mixes are discussed. Such incorporation may be in terms of changes in any of the binder, coarse or fine aggregate components of the concrete mixes. The usage of materials such as mineral admixtures, high density solid wastes and fibres is also reported. The possible use of other mineral materials in concrete mixes for enhanced shielding performance against gamma radiation in nuclear installations is brought out. A brief review of the mix design parameters controlling shielding performance of concrete mixes is also cited. An attempt has been made to compare the shielding performances of different concretes by comparing their linear attenuation co-efficient values (μ) reported in the literature. In view of the exponential surge in γ-ray sources in nuclear industry this review is relevant to save the planet earth from an impending global disaster as well as introducing radiation in industries, food preservation, nuclear medicine and many other such applications. © 2013 CAFET-INNOVA TECHNICAL SOCIETY.Item Review on non-conventional machining of shape memory alloys(Nonferrous Metals Society of China B12 Fuxing Road Beijing 100814, 2014) Manjaiah, M.; Narendranath, S.; Basavarajappa, S.Shape memory alloys (SMAs) are the developing advanced materials due to their versatile specific properties such as pseudoelasticity, shape memory effect (SME), biocompatibility, high specific strength, high corrosion resistance, high wear resistance and high anti-fatigue property. Therefore, the SMAs are used in many applications such as aerospace, medical and automobile. However, the conventional machining of SMAs causes serious tool wear, time consuming and less dimensional deformity due to severe strain hardening and pseudoelasticity. These materials can be machined using non-conventional methods such as laser machining, water jet machining (WJM) and electrochemical machining (ECM), but these processes are limited to complexity and mechanical properties of the component. Electrical discharge machining (EDM) and wire EDM (WEDM) show high capability to machine SMAs of complex shapes with precise dimensions. The aim of this work is to present the consolidated references on the machining of SMAs using EDM and WEDM and subsequently identify the research gaps. In support to these research gaps, this work has also evolved the future research directions. © 2014 The Nonferrous Metals Society of China.Item Integrated adaptive reach setting of distance relaying scheme in series compensated lines(School of Electrical Engineering and Informatics, 2010) Srivani Iyengar, S.G.; Vittal, K.P.The protection of series compensated lines is considered to be one of the most difficult tasks. The paper reviews the series compensated line protection challenges initially and presents state of art solution to improve the distance relay performance. The work describes the development and evaluation of an integrated adaptive distance protection scheme. Development of the adaptive scheme is in the specific area of incorporating the adaptive feature like adaptive reach setting of the relay as the compensation level changes in the series compensated lines, for optimum dependability and security of the protection system. The relay adapts its characteristics according to the informations received from the communication unit. Upon extensive testing on different data set of fault cases with fault resistance and varying percentage compensation level and fault location, performance of the developed method ensures that the proposed scheme overcomes the overreach/underreach problem of the distance relay in series compensated lines and is found to be quite promising.Item Halophilic bacteria and their compatible solutes -osmoregulation and potential applications(2011) Shivanand, P.; Mugeraya, G.Halophilic bacteria grow over an extended range of salt concentrations. Their metabolic patterns are distinct compared to their terrestrial counterparts and obligate halophiles. The possibility of rapid adjustment to changes in the external salt concentration makes them potential candidates for bioprocessing. Halophilic bacteria produce enzymes, metabolites, solutes, exopolysaccharides and pigments which have high commercial value. However, compared to the obligate halophilic archaea, they have been less studied with only a few reports available on designing the production processes. Compatible solutes are the highly soluble, low-molecular weight organic compounds that make halophilic bacteria versatile in their adaptation to salinity. Halophilic bacteria either take in the solutes from the medium or synthesize them de novo. Compatible solutes include amino acids, carbohydrates or their derivatives, sugars and polyols. In addition to their stabilizing effects, they offer a multitude of physiological and potential biotechnological applications ranging from stabilizers of biomolecules, stress-protective agents to therapeutic agents and cosmetic actives. Exploring the significant applications of compatible solutes could be an attractive proposition towards commercialization. Moreover, it would enlighten the bases of adaptations of moderately halophilic bacteria.Item Hydrological impacts of afforestation - A review of research in India(Springer Nature, 2014) Venkatesh, B.; Lakshman, N.; Purandara, B.K.We review the current status of experimental studies in India to understand the linkages between afforestation and hydrology. This discipline deals with the use and management of water, social awareness of environmental problems, and ecosystem limitations on provision of watershed services by river basins in the mountain regions of India. Our review begins with examination of experimental works in tropical countries and proceeds to discussion of initiatives of Indian research institutes and Government organizations towards establishing experimental watersheds to understand the impacts of land cover changes on hydrologic regimes in the Indian sub-continent. This is followed by the review of the experimental work carried out by various authors to assess the impact of land cover changes on major water balance components such as, runoff, groundwater, evapotranspiration and sediment yield. The spatial scales of these experiments have been limited to small watersheds or field plots. This paper also describes impacts of human interventions (such as plantations of exotic forest species to restore degraded landscapes) on the water balance components in diverse hydro-geo-environmental conditions in the Indian sub-continent. We focus on identifying the research areas which require immediate attention to develop tools to assist planners and policy makers in assessing and managing the water resources in these complex environments. The review is largely based on research results reported during the last 20 to 30 years. © 2014 Northeast Forestry University and Springer-Verlag Berlin Heidelberg.