001105   ZOLGHADRI M, SABER-SAMANDARI S, AHMADI S, ALAMARA K (Amirkabir Univ, Tehran 1591634653, Iran, Email: saeedss@aut.ac.ir) : Synthesis and characterization of porous cytocompatible scaffolds from polyvinyl alcohol–chitosan. Bull Mater Sci 2019, 42(1), 35.

In this study, novel porous cytocompatible scaffolds with a 3D nanocomposite structure were synthesized by using nanoclay particles embedded into a biopolymer blend composed of polyvinyl alcohol (PVA) and chitosan (CS). According to the results, the Fourier transform infrared spectrum confirmed the presence of nanoclay, PVA and CS in the scaffold structure. X-ray diffraction outcomes showed the enhancement of crystalline zone in the synthesized 3D scaffolds by increasing the nanoclay content. Scanning electron microscopy (SEM) images revealed the highly porous interconnected microstructure of the scaffolds. Also, the energy-dispersive X-ray spectra verified the presence of nanoclay, PVA and CS in the sample with the highest nanoclay content. According to mechanical properties and porosity of the synthesized 3D scaffolds, compressive strength (i.e., 3.5 ± 0.2 MPa), elastic modulus (1.42 ± 0.02 GPa) and porosity (75–82 %) of the sample with the highest nanoclay content was in the range of mechanical properties and porosity of a natural trabecular bone tissue. The swelling of samples in a phosphate-buffered saline solution was less than the swelling in water. In addition, increasing the content of nanoclay decreases the percentage of swelling. Outcomes of cell culture experiments confirmed that the synthesized 3D scaffolds were not toxic and the cell attachment SEM images showed a sufficient attachment of the cell to the interconnected porous structure of the sample. Results suggest that the synthesized 3D scaffold in this study possesses proper microstructure properties and no cytotoxicity to be replaced with natural bone tissues.

7 illus, 1 table, 42 ref

001069   RAVINDRAN R S E, THOMAS P, RENGANATHAN S (ECE Dep, KLEF (Deemed to be Univ), Vaddeswaram, Guntur - 522 502, Email: ravindran.ernest@kluniversity.in) : Effect on dielectric, structural and thermal behaviour of CaCu₃Ti₄O₁₂ in a Nylon 11 matrix. Bull Mater Sci 2019, 42(1), 28.

This paper discusses the probability of obtaining high-dielectric permittivity from ceramic–polymer composites by mixing higher dielectric material, CaCu₃Ti₄O₁₂ (CCTO) in a Nylon 11 matrix by the melt-mixing method. The volume percentage of addition of CCTO micro-particles was from 0 to 20 vol %. The dielectric, structural morphology and thermal properties of the composites were analysed using an impedance analyser, a scanning electron microscope, a differential scanning calorimeter and a thermogravimetric analyser, respectively. The permittivity of 50 vol % of the composite is 12, which is increased to that of virgin Nylon 11 of 5.8. Different theoretical models were employed to rationalize the dielectric behaviour of the composite and found to be accurate with that of the experimental data. The thermal behaviour of the composites was good after the addition of CCTO micro-particles into it. It provides the means to employ the ceramic– polymer composites at low temperature with less permittivity and loss.

10 illus, 32 ref

001033   MAHAJAN V, BHARJ R S, BHARJ J (Mechanical Engineering Dep, Dr. B.R. Ambedkar National Institute of Technology, Jalandhar, Punjab 144011, Email: vishalm.me.14@nitj.ac.in) : Role of nano-carbon additives in lead-acid batteries: A review. Bull Mater Sci 2019, 42(1), 21.

Development in lead (Pb)-acid batteries (LABs) is an important area of research. The improvement in this electrochemical device is imperative as it can open several new fronts of technological advancement in different sectors like automobile, telecommunications, renewable energy, etc. Since the rapid failure of a LAB due to Pb sulphation under partial-state-of-charging, electrode grid corrosion and water loss are some major obstructions in its advancement. The doping of various carbon forms into the negative active material of an electrode has been suggested to be effective at improving the storage capacity and cyclic life of LABs by suppressing irreversible sulphation. This report is an attempt to focus on different theories related to the working mechanism of carbon and to summarize the investigation results observed by various researchers regarding the significant role of nano-carbon additives in LABs. On the basis of that, we tried to compare their performance along with the discussion on the best possible additive.

12 illus, 1 table, 94 ref

001085   SINGH V, SIVARAMAIAH G, SINGH N, PATHAK M S, RAO J L, SINGH P K, NAGPURE A S (Chemical Engineering Dep, Konkuk Univ, Seoul 143701, Korea, Email: vijayjiin2006@yahoo.com) : Ultraviolet B emission from a Gd³⁺-doped BaAl₂O₄ powder phosphor. Bull Mater Sci 2019, 42(1), 19.

A BaAl₂O₄:Gd³⁺ phosphor was successfully prepared using a combustion technique. An X-ray diffraction pattern was used to characterize the resultant phosphor, and the photoluminescence (PL) of the prepared BaAl₂O₄:Gd³⁺ was studied. Under a 273-nm excitation, the main emission peak of the phosphor is located at 314 nm, and this is attributed to the ⁶P_7/2 →⁸S_7/2 transition of Gd³⁺. Electron paramagnetic resonance (EPR) spectrum appears to be U-shaped, and lines are evident at geff $~$ 2.14, 4.56 and 6.75. The PL and EPR analyses indicate the presence of Gd as Gd³⁺ in this sample.

3 illus, 75 ref

001100   WU C Y, HSIAO R C, HSU C H, HSIEH T H, KAO J Y, HSU C Y (Mechanical Engineering Dep, Lunghwa Univ of Science and Technology, Taoyuan 33306, Taiwan, Email: cyhsu@mail.lhu.edu.tw) : Microstructure and mechanical performance of (AlCrNbSiTiV)N films coated by reactive magnetron sputtering. Bull Mater Sci 2019, 42(1), 17.

(AlCrNbSiTiV)N films are prepared on cermet cutter tool substrates using direct current reactive magnetron sputtering with a high-entropy alloy target. The use of a grey based Taguchi method to determine the deposition parameters of (AlCrNbSiTiV)N films has been studied by considering multiple performance characteristics. Taguchi quality design concept with an L₉ (3⁴) orthogonal array, signal-to-noise ratio and analysis of variance are used to determine the performance characteristics of the deposition process. The effect of various deposition parameters of (AlCrNbSiTiV)N films on the chemical composition, the microstructure, the morphology, the mechanical performance and cutting performance of the coated cutter in dry machining is determined. The experimental results show a cutter that is coated with (AlCrNbSiTiV)N exhibits less surface roughness (for workpiece) and flank wear (for cutter), so coated cutter tools have a much longer tool life than the uncoated tools. Transmission electron microscopy patterns confirm that the (AlCrNbSiTiV)N films have a polycrystalline face-centred cubic structure. In the confirmation runs, using grey relational analysis, there are improvements of 3.7 % in surface roughness, 69.6 % in flank wear and 3.2 % in elastic recovery. The Rockwell adhesion test categorizes the coatings as class HF1.

7 illus, 9 tables, 26 ref

001030   LIU X, LIU Z, LIU G, WANG W, LI J (Nanjing Univ of Aeronautics and Astronautics, Nanjing 210016, People’s Republic of China, Email: liuzili@nuaa.edu.cn) : First-principles study of solid solution strengthening in Mg–X (X=Al, Er) alloys. Bull Mater Sci 2019, 42(1), 16.

To study the solid solution strengthening effect on magnesium (Mg)–X (X = Al, Er) alloys, supercell models of Mg, Mg₃₅Er and Mg₃₅Al are established to perform the first-principles pseudopotential plane wave calculations based on density functional theory. The calculated cohesive energy of Mg₃₅Er is lower than that of Mg₃₅Al. This indicates that Mg₃₅Er has better structural stability than Mg₃₅Al. The bulk modulus, Young’s modulus and shear modulus of the solid solutions increases simultaneously when Al and Er are doped into the Mg matrix. Moreover, the solid solution strengthening of Er is much higher than the Al containing alloy. The order of toughness of the three solutions from the highest to the lowest is Mg, Mg₃₅Er and Mg₃₅Al, while the order of increasing elastic anisotropy is in the reverse order. The number of bonding electrons of Mg₃₅Er in the low-energy region of the Fermi level is much higher than that of Mg₃₅Al, and the density of states of Mg₃₅Er at the Fermi level is higher than that of Mg₃₅Al. Compared with Al atoms, Er atoms share more electric charges with Mg atoms, which leads to an increasingly uniform charge distribution around Er atoms.

6 illus, 4 tables, 31 ref

001071   ROOPA T S, MURTHY H N N, SWATHI H S, ANGADI G, HARISH D V N (Mechanical Engineering Dep, R V Coll of Engineering, Bangalore - 560 059, Karnataka, Email: hnmdatta@yahoo.com) : Synthesis and characterization of spin-coated clay/PVDF thin films. Bull Mater Sci 2019, 42(1), 15.

This paper reports the fabrication of Cloisite-15A (C-15A)-dispersed polyvinylidene fluoride (PVDF) nanocomposite thin films by spin coating and their characterization for sensor applications. The effects of nanoclay, duration of ultrasonication and spinning speed on the morphology and properties of thin films were studied. The influence of these parameters on the amount of β-phase was analysed using Fourier transform infrared (FTIR) and X-ray diffraction (XRD) techniques. The influence of C-15A on the morphology and surface quality of thin films was analysed by scanning electron microscopy (SEM). Piezoelectric coefficient was measured at 110 Hz and 0.25 N. Contact angle was measured to assess the hydrophobicity of thin films. The β-phase of 82.97 % was obtained in the specimens with 5 wt % C-15A, processed at 500 rpm and spun for 35 min. The piezoelectricity of the specimens increased from −18 to −25 pC N⁻¹. Experiments were conducted as per L₁₆ orthogonal array.

5 illus, 3 tables, 39 ref

001019   KANNAN P K, CHAUDHARI S, DEY S R (Materials Science and Metallurgical Engineering Dep, Indian Institute of Technology Hyderabad, Kandi, Sangareddy - 502 285, Email: suhash@iith.ac.in) : Impact of sulphurization environment on formation of Cu₂ZnSnS₄ films using electron beam evaporated stacked metallic precursors. Bull Mater Sci 2019, 42(1), 11.

The superiority of copper zinc tin sulphide (Cu₂ZnSnS₄; CZTS) over the existing absorber layer materials is inevitable owing to its cheap, non-toxic and earth abundant constituents with high absorption coefficient value. In the present study, CZTS films are prepared by sulphurizing electron beam deposited precursors of glass/Cu/Zn/Sn/Cu and glass/Cu/Sn/Zn/Cu stacking sequences in two different environments i.e., elemental S powder and 5 % H₂S + N₂ gas at different ramping rates. The effect of sulphurization environment and sulphurization ramping rate on the formation of CZTS is investigated using X-ray diffraction and Raman spectroscopy. The morphology and composition of the films are analysed respectively using field emission gun scanning electron microscopy and energy dispersive X-ray spectroscopy. It is observed that films prepared in elemental S powder at a low ramping rate exhibit better crystallinity with less impurity phases. The presence of ZnS is observed in all the films, while the presence of SnS is observed in films prepared with H₂S gas alone, thus concluding that sulphurization in the presence of elemental S powder at a low ramping rate is highly favourable for CZTS film formation. CZTS films with minor ZnS impurity with a bandgap of 1.48 eV is successfully fabricated by using a glass/Cu/Zn/Sn/Cu precursor stack.

8 illus, 1 table, 44 ref

001012   GÜLER O, GÜLER S H, TASKIN M (Metalurgical and Material Engineering Dep, Mersin Univ, Mersin, Turkey, Email: oguler@mersin.edu.tr) : The production of graphene–boron nitride nanosheet heterostructures via liquid phase exfoliation assisted by a milling process. Bull Mater Sci 2019, 42(1), 7.

Graphene–boron nitride (BN) nanosheet heterostructures have become one of the highly interesting matters in recent times owing to their advantages. In this study, the liquid phase exfoliation method was preferred for production of graphene–BN nanosheet heterostructures. However, a pre-milling process was applied to starting materials, instead of the classical liquid phase exfoliation method previously used in the literature. Hexagonal graphite (h-G) and h-BN mixtures were milled for 50 h and the milled powders were subjected to the liquid phase exfoliation process. As a result of the examinations, it was observed that graphene–BN nanosheet heterostructures were successfully synthesized. The widths of the synthesized nanosheets were 300–500 nm and nanosheets were multi-layers. It was seen that a large part of the powder mixture were occurred at high amorphization during the ball milling process. According to X-ray diffraction (XRD) peaks, the amorphization ratio was almost 90 %. But, almost all of amorphous structures were removed during acid mixing and the thermal process. But, amorphous structures still existed in samples. In addition, the ball milling process damaged the sheets and defects formed. Despite all these disadvantages, the milling process carried out in this study provided formation of thinner and larger sheets compared with previous similar studies.

7 illus, 26 ref

001020   KARABULUT A (Electrical and Electronics Engineering Dep, Sinop Univ, Sinop 57000, Turkey, Email: akerimkara@gmail.com) : Barrier height modification in Au/Ti/n-GaAs devices with a HfO₂ interfacial layer formed by atomic layer deposition. Bull Mater Sci 2019, 42(1), 5.

X-ray photoelectron spectroscopy has been carried out to characterize the surface of the hafnia (HfO₂) thin films grown on n-GaAs wafer by atomic layer deposition, and the surface morphology of the HfO₂ layer on GaAs has been analysed using atomic force microscopy. The barrier height (BH) values of 1.03 and 0.93 eV (300 K) for the Au/Ti/HfO₂/nGaAs structures with 3- and 5-nm HfO₂ interfacial layers, respectively, have been obtained from the I –V characteristics of the devices, which are higher than the value of 0.77 eV (300 K) for the Au/Ti/n-GaAs diode fabricated by us. Therefore, it can be said that the HfO₂ thin layer at the metal/GaAs interface can also be used for BH modification as a gate insulator in GaAs metal-oxide semiconductor (MOS) capacitors and MOS field-effect transistors. The ideality factor values have been calculated as 1.028 and 2.72 eV at 400 and 60 K; and as 1.04 and 2.58 eV at 400 and 60 K for the metal–insulating layer–semiconductor (MIS) devices with 3- and 5-nm interfacial layers, respectively. The bias-dependent BH values have been calculated for the devices by both Norde’s method and Gaussian distribution (GD) of BHs at each sample temperature. At 320 K, the $\mathrm{\varphi }$_b(V) value at 0.70 V for a 3-nm MIS diode is about 1.08 eV from the $\mathrm{\varphi }$_b(V) vs. V curve determined by the GD, and about 0.99 eV at 0.58 V for a 5-nm MIS diode. It has been seen that these bias-dependent BH values are in close agreement with those obtained by Norde’s method for the same bias voltage values.

15 illus, 2 tables, 65 ref

001000   DEB P, DEOGHARE A B (Mechanical Engineering Dep, National Institute of Technology Silchar, Assam - 788 010, Email: payeldebmech13@gmail.com) : Effect of pretreatment processes on physicochemical properties of hydroxyapatite synthesized from Puntius conchonius fish scales. Bull Mater Sci 2019, 42(1), 3.

The current study emphasizes on the novel idea of synthesizing hydroxyapatite (HAp) from Puntius conchonius fish scales’ bio-waste and study the effect of acid, alkali and acid–alkali pretreatments on its physicochemical properties. Material characterization is carried out to study the physicochemical properties of the synthesized HAp using Fouriertransform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDX) and transmission electron microscopy (TEM) analysis. FTIR and XRD plots show peaks corresponding to natural bone apatite which confirms the formation of HAp. TG analysis shows a maximum weight loss of 2.28 % indicating high thermal stability of HAp beyond 800$°$C. SEM micrographs illustrate highly porous morphology with interconnected pores. EDX analysis of the HAp exhibits close proximity of the calcium/phosphorous (Ca/P) ratio to natural bone apatite. TEM micrographs show the formation of polycrystalline HAp particles with size ranging from 38 ± 1.54 to 219 ± 5.88 nm. A comparative study on the physicochemical properties of HAp synthesized using three different pretreatment processes is performed. Results reveal that HAp synthesized from acid-treated fish scales show highest yield percentage, better thermal stability and highly porous morphology with a particle size of 38 ± 1.54 nm. Thus, HAp synthesized from acid-treated fish scales can be a promising candidate for the development of porous bone scaffolds.

6 illus, 2 tables, 25 ref

001022   KARRI B R T, GUPTA N (Electrical and Electronics Engineering Dep, Birla Institute of Technology and Science, Pilani, Rajasthan - 333 031, Email: baburaviteja.k@pilani.bits-pilani.ac.in) : Hybrid bilayer gate dielectric-based organic thin film transistors. Bull Mater Sci 2019, 42(1), 2.

Organic thin film transistors (OTFTs) are key building blocks for flexible, low cost electronics systems. They provide a viable alternative for silicon-based electronics with added advantages of low cost and flexibility. However, few issues like high-operating voltage, low-switching speed, high-leakage current and reliability are still a challenge. The overall performance of an OTFT depends on organic semiconductors and gate dielectric interface. In this paper, we review the current status and trends in the choice of dielectric layer for OTFTs. As a starting point, the performance parameters of an OTFT and their dependence on the dielectric layer are briefly discussed. A variety of dielectric materials which includes high-k inorganic, organic, surface coated inorganics and nanocomposites are also presented. The advantages and drawbacks of each of these materials are discussed in detail. We reviewed the latest developments in the dielectric materials especially, self-assembled monolayers (SAMs), hybrid bilayers and nanocomposites. SAM-based OTFTs offer several advantages but shift in the threshold voltage remains a concern. Nanocomposites are a latest addition to the dielectric materials, which offer advantages like solution processing and improved dielectric constant but have a rough surface. A hybrid bilayer that incorporates the inorganic dielectric as a base layer and a thin polymer layer over it to improve the surface properties offers several desirable characteristics over the other choices. Hence, we propose that hybrid bilayer gate dielectrics shall play a pivotal role in improving the OTFT performance.

5 illus, 5 tables, 131 ref

001089   SURESH S, GOWD G H, KUMAR M L S D (Mechanical Engineering Dep, Jawaharlal Nehru Technological Univ, Ananthapuramu, Andhra Pradesh, Email: sonagirisuresh@gmail.com) : Experimental investigation on mechanical properties of Al 7075/Al₂O₃/Mg NMMC’s by stir casting method. Sadhana 2019, 44(2), 51.

There is an increasing demand for light-weight, affordable and rapidly processed products as a result of their significant level of superiority these days. In the present research, the effect of mechanical stir casting on 7075 based lightweight aluminium alloy established together with nano-Al₂O₃ with average particle size (20–30) nanometre and wt.% of (1.0, 2.0,3.0, and 4.0) has been studied. Several scientists exposed that nonconsistent distribution of nanoparticles possessing high porosity in the matrix. Electric stir casting could protect against the difficulties encountered with mechanical stir casting. By infusing Al₂O₃ particulates right into aluminium alloy the aluminium 7075/1 % Wt. Al₂O₃ is giving area to nanocomposite. By including 1 %, micro magnesium powder improved the wettability of the reinforcement. Optical microscope, SEM, studies carried out for the evaluation of composites. SEM micrographs reported that the nanoparticles were consistently distributed throughout the matrix and the active grain microstructure studies were preformed. The hardness, tensile strength, and impact results of Al7075/1 % Wt. Al₂O₃ nanocomposites have been improved as compared with the Al7075 base alloy.

11 illus, 5 tables, 19 ref

000990   BHUTANGE S P, LATKAR M V, CHAKRABARTI T (Civil Engineering Dep, Visvesvaraya National Institute of Technology (VNIT), Nagpur - 440 010, Email: snigdhabhutange12@gmail.com) : Role of biocementation to improve mechanical properties of mortar. Sadhana 2019, 44(2), 50.

Biocementation or Microbially Induced Calcium Carbonate Precipitation (MICCP) is a naturally occurring green technique which involves the deposition of calcium carbonate by peculiar action of ureolytic bacteria, which improves the mechanical properties of cementitious materials. These bacteria require a protein source, a vitamin source and a carbon source for optimum growth. Urea and calcium source are necessary to carry out the ureolysis reaction to get CaCO₃ depositions which fill the voids within the cementitious materials thereby improving their mechanical properties. To make the process economical, it is necessary to find out optimum concentrations of the various chemicals and ingredients used in the process. Present study aims at finding out the best possible combination of urea and protein source to carry out the MICCP process successfully. There was 22.44 % increase in compressive strength and 16.62 % reduction in the water absorption of experimental mortar cubes at 28 days of curing with the optimum combination of urea and protein source concentrations.

4 illus, 6 tables, 24 ref

001036   MANCHANDA M, GAMBHIR D (Electronics and Communications Engineering Dep, Amity School of Engineering and Technology, Bijwasan, New Delhi, Email: meenumanchanda73@gmail.com) : Multifocus image fusion based on waveatom transform. Sadhana 2019, 44(2), 49.

Multifocus image fusion has emerged as a challenging research area due to the availability of various image-capturing devices. The optical lenses that are widely utilized in image-capturing devices have limited ‘depth-of-focus’ and, therefore, only the objects that lie within a particular depth remain ‘in-focus’, whereas all the other objects go ‘out-of-focus’. In order to obtain an image where all the objects are well focused, multifocus image fusion method based on waveatom transform is proposed. The core idea is to decompose all input images using waveatom transform and perform fusion of resultant waveatom coefficients. The waveatom coefficients with higher visibility, corresponding to sharper image intensities, are used to perform the process of image fusion. Finally, the fused image is obtained by performing inverse waveatom transform. The performance of the proposed method is demonstrated by performing fusion on different sets of multifocus images and comparing the results of the proposed method to the results of existing image fusion methods.

14 illus, 7 tables, 26 ref

000987   BARHATTE A, DALE M, GHONGADE R (Electronics and Telecommunication Dep, AISSMS-Institute of Information Technology, Pune, Maharashtra - 411 001, Email: alka.barhatte@mitpune.edu.in) : Cardiac events detection using curvelet transform. Sadhana 2019, 44(2), 47.

Cardiac event detection is one of the essential steps in cardiac signal processing, analysis and disease diagnosis. Complete morphology of cardiac waves (P–QRS–T) extracted from the location of R-peak is helpful for feature extraction of many applications related to cardiac diseases classification. Therefore cardiac event detection is a prerequisite for reliable cardiac disease diagnosis, and hence it should be robust and timeefficient so that it can be used for real-time signal processing. This work proposes a novel method for R-peak detection using curvelet transform (CT). It demonstrates the use of curvelet energy with an adaptive threshold to estimate the boundaries around R-peak. The exact R-peak locations are then detected from the input signal with the predefined estimated boundaries. The proposed method is evaluated and analysed with all 48 records from the MIT-BIH arrhythmia database. The experimental analysis result yields an average sensitivity of 99.62 %, average positive productivity of 99.74 % and average detection error rate of 0.6 %. The results obtained have higher than or comparable indices to those in literature. Thus, the proposed system yields high accuracy, low complexity and high processing speed.

7 illus, 3 tables, 30 ref

001015   JIANG T, YE H, REN G, ZHANG J, LI Y, WANG J, WU H, ZHANG C, HUANG G, KE B, ET aL (Wuhan Univ of Technology, Wuhan 430070, Hubei Province, People’s Republic of China, Email: yehaiwang369@hotmail.com) : Crack initiation and propagation in coalbed gas reservoir during hydraulic fracturing. Sadhana 2019, 44(2), 43.

The crack initiation and propagation calculation model during hydraulic fracturing in a coalbed methane reservoir with interlayers is established in this paper. The influence of coal elasticity modulus and fracturing fluid displacement on the fracture geometry are studied. Results show that the fracture initiation begins at the perforation interval. Stress inhomogeneity is detrimental for the formation of multiple cracks for the extension of the fracturing area. The cracks at the boundary have changed from less developed to more developed with increasing horizontal stress coefficient. The coal elasticity modulus and fracturing fluid displacement both play a determinative effect on fracture geometry. The study provides a reference basis for implementing hydraulic fracturing of low permeability coal seams with interlayers.

10 illus, 3 tables, 19 ref

001055   PANSARE S R, NAIK S S (Mechanical Engineering Dep, Veermata Jijabai Technological Institute, Mumbai - 400 019, Email: ssnaik@me.vjti.ac.in) : Detection of inclined edge crack in prismatic beam using static deflection measurements. Sadhana 2019, 44(2), 42.

The effectiveness of a static deflection method for detection of an inclined edge crack in a prismatic cantilever beam is presented in this paper. A rotational spring is used to represent the flexibility due to the inclined crack. Two values of static deflections are needed for detection of crack location and rotational spring stiffness. The spring is positioned at the crack tip. Twenty-one mild steel specimens with various crack inclinations, locations and depths are used for experimentation. The experimental results confirm that the static deflection measurements can be used to predict the crack location of an inclined edge crack with acceptable accuracy.

9 illus, 1 table, 24 ref

001023   KAUR C, KUMAR R (Electronics and Computer Engineering Dep, Thapar Univ, Patiala - 147 004, Email: lpu_chandan@yahoo.co.in) : Mean centred clustering: Improving melody classification using time- and frequency-domain supervised clustering. Sadhana 2019, 44(2), 40.

This paper reports a new approach for clustering melodies in audio music collections of both western as well as Indian background and its application to genre classification. A simple yet effective new classification technique called mean centred clustering (MCC) is discussed. The proposed technique maximizes the distance between different clusters and reduces the spread of data in individual clusters. The use of MCC as a preprocessing technique for conventional classifiers like artificial neural network (ANN) and support vector machine (SVM) is also demonstrated. It is observed that the MCC-based classifier outperforms the classifiers based on conventional techniques such as Principal Component Analysis (PCA) and discrete cosine transform (DCT). Extensive simulation results obtained on different data sets of western genre (ISMIR) and classical Indian ragas are used to validate the efficiency of proposed MCC-based clustering algorithm and ANN/SVM classifiers based on MCC. As an additional endeavour, the performance of MCC on preprocessed data from PCA and DCT is studied. Based on simulation results, it is concluded that the application of MCC on DCT coefficients resulted in the highest overall classification success rate over different architectures of the classifiers.

9 illus, 9 tables, 33 ref

000985   ARULMURUGAN B, MODI K, SANJAY A P, YASHWANT P A, RICKWITH N, MOHAN C G, SUBRAMANI P, AGILAN M, MANIKANDAN M, ARIVAZHAGAN N (Vellore Institute of Technology, Vellore, Tamil Nadu, Email: enggarul@gmail.com) : Effect of post-weld heat treatment on the microstructure and tensile properties of electron-beam-welded 21st century nickel-based super alloy 686. Sadhana 2019, 44(2), 38.

This work examines the influence of post-weld heat treatment (PWHT) on the fusion zone microstructure, and mechanical properties of electron beam (EB)-welded alloy 686. Comparative studies have been made on weld microstructure and tensile properties of the weldments both in as-welded and post-welded heat-treated conditions. PWHT consists of direct aging (DA/480 $°$C for 3 h) and solution treatment (ST, 980 $°$C for 1 h) followed by ageing and finally, homogenizing treatment (HT, 1200 $°$C for 1 h) followed by DA and ST. The secondary topologically closed packed (TCP) phases formation, their distribution and microsegregation characteristics are studied with the aid of scanning electron microscope (SEM) analysis. Energy-dispersive X-ray spectroscopy (EDS) is also performed to estimate the microsegregation of alloying elements in the dendritic core and interdendritic regions of the weldments. The result shows that there is no significant change in the microstructure of DA and solution-treated sample as compared to the as-welded sample. The microstructure of HT sample was entirely different from those of as-welded and other HT samples. The SEM/EDS analysis illustrates the presence of secondary TCP phases (r, P and l) in the as-weld, DA and ST condition, whereas HT weldments did not show the presence of TCP phases. Tensile test results show higher tensile strength in ST condition whereas homogenization samples show higher ductility compared with others.

8 illus, 7 tables, 25 ref

000999   DAS S, HARI V S S P K, KUMAR A, NARAYANAN G (Electrical and Electronics Engineering Dep, National Institute of Technology, Goa - 403 401, Email: soumitradas81@gmail.com) : Analysis of generalized continual-clamp and split-clamp PWM schemes for induction motor drive. Sadhana 2019, 44(2), 36.

Continual-clamp pulse width modulation (CCPWM) clamps each phase of a three-phase inverter to one of the two dc buses continually for 60$°$ duration in each half of the fundamental cycle. Split-clamp pulse width modulation (SCPWM) divides the 60$°$ clamping interval into two sub-intervals, which are not necessarily equal, and falling in two different quarter cycles. Whether continual clamp or split clamp, the positioning of the clamping interval in case of CCPWM, and the ratio of splitting the clamping interval in SCPWM – all influence the waveform quality of the inverter output. This paper derives analytically closed-form expressions for the total RMS harmonic distortion factor and torque ripple factor pertaining to CCPWM with any arbitrary position of the clamping interval (i.e., generalized CCPWM) and also corresponding to SCPWM with any arbitrary ratio of splitting of the clamping interval (i.e., generalized SCPWM). The analytical results are well supported by experimental results on 3-hp and 5-hp induction motor drives.

16 illus, 3 tables, 37 ref

001094   VEREKAR P K, ARAKERI J H (Mechanical Engineering Dep, Indian Institute of Science, Bangalore - 560 012, Email: jaywant@mecheng.iisc.ernet.in) : Three-dimensional flow separations on a rolling sphere. Sadhana 2019, 44(2), 35.

Experiments are conducted to study the flow separations on a sphere rolling on an inclined plane submerged in water. These experiments are performed at Reynolds numbers Re between 1350 and 1550. The experiments show that the flow separations on the surface of a rolling sphere can be organized into four distinct regions: (i) region of primary separation-I on the front upper sphere and extending below the poles, (ii) region of viscous blockage at the crevice surrounding the point of contact and shear layer separation ahead and at the sides of the viscous blockage, (iii) region of primary separation-II on the rear lower sphere and (iv) secondary separations on the rear upper sphere surface. The ratio of the width of the viscous blockage to the diameter of the sphere is found to be 0.4. Primary separation-I surface is symmetrical about the equatorial plane of the rolling sphere. Primary separation-II from the rear lower sphere surface is asymmetrical about the equator and eddies are shed alternately on either side of the equator from this separation surface. These lower eddies are energetic and dominate the dynamics of the wake. The upper eddy shedding from the primary separation-I surface and the lower eddy shedding from the primary separation-II surface are synchronized.

18 illus, 23 ref

001096   VIJAY B T, MALARKODI B (Electronics and Communication Engineering Dep, National Institute of Technology, Tiruchirappalli - 620 015, Email: bt.vvts@gmail.com) : High-efficiency WLANs for dense deployment scenarios. Sadhana 2019, 44(2), 33.

In this article, we review the latest technical attributes such as orthogonal frequency division multiple access (OFDMA), multi-user MIMO (MU-MIMO) and enhanced clear channel assessment (CCA) for better spatial reuse used in the 802.11ax amendment to the 802.11 standard that leads to PHY and MAC enhancements for high-density scenarios of access points (APs). IEEE 802.11ax, also referred to as highefficiency wireless local area network (WLAN) (HEW), provides mechanisms to thoroughly utilize the unlicensed spectrum bands (2.4 and 5 GHz) and strengthen the user experience. The functional requirements of HEW are stressed on interactive video transmission latency and access efficiency to meet quality of service (QoS) requirements. Finally, we investigate three configurations—MU-MIMO, OFDMA and combination of both or mixed mode—for 4-user AP transmission schemes in 802.11ax. The performance of the MU schemes varies with packet size and operating SNR. OFDMA is more efficient than MU-MIMO at low SNRs for all packet sizes, which means 5th percentile stations (STAs) can get desired throughput.

12 illus, 6 tables, 25 ref

001018   KAMALI C, OZGER E (CSIR-National Aerospace Laboratory, Bangalore - 560 017, Email: ckamali@nal.res.in) : Limitations of Flight Path Reconstruction techniques. Sadhana 2019, 44(2), 32.

The Flight Path Reconstruction (FPR) techniques are performed to verify the data compatibility check and post-flight. This is often achieved by calibrating the onboard sensors such as inertial and airdata sensors. In this paper, the limitations of FPR techniques in terms of Maximum Likelihood Estimation (MLE) and Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF) have been reported. To demonstrate the FPR and sensor calibration, kinematic trajectory simulations with wind box type maneuvers have been performed. It is also shown as how a kinematic simulation is valid for the studies carried out in this work.

13 illus, 4 tables, 15 ref

001088   SONI A, TIWARI S (Mechanical Engineering Dep, Indian Institute of Technology, Chennai - 600 036, Email: shaligt@iitm.ac.in) : Three-dimensional numerical study on aerodynamics of non-flapping bird flight. Sadhana 2019, 44(2), 31.

Numerical investigations have been carried out to study aerodynamics of non-flapping characteristics of bird flight. Commercial software ANSYS Fluent 16.1 has been used for three-dimensional computations by considering four types of wing models. At first, square prisms with built-in side flaps are considered and the effects of Reynolds number (Re), angle of attack and dihedral angle on flow characteristics have been investigated. Thereafter, flow past actual bird wing has been considered for wings of owl, seagull, teal and bat. Role of shear layer formation at mid-span of wings has been illustrated with the help of streamline plots for different values of Re. In addition, pulsating flow is imposed on inlet velocity and the responses are obtained in form of force coefficients, phase portraits, time-dependent signals and their spectra.

17 illus, 1 table, 27 ref

001040   MANUPATI V K, PANIGRAHI S, AHSAN M, LAHIRI S, CHANDRA A, THAKKAR J J, PUTNIK G, VARELA M L R (Mechanical Engineering Dep, NIT Warangal, Warangal, Telangana, Email: manupati.vijay@nitw.ac.in) : Estimation of manufacturing systems degradation rate for residual life prediction through dynamic workload adjustment. Sadhana 2019, 44(2), 30.

Complex systems in a work cell often consist of multiple units to process the manufacturing functions effectively for achieving the desired objectives. All manufacturing work cells are familiar with many unforeseeable events, for instance machine down time and scheduled maintenance. In fact, every configuration naturally exhibits some level of redundancy during those unpredictable events that may fail a small portion of units. In this work, using the remaining units and by raising the workloads on these units, up to the level of their capacities, we tried to fulfil the requirement of products. To procure the requirement, dynamic workload adjustment strategy has been suggested on two important configurations such as parallel and hybrid, by actively controlling its degradation path and failure times. During its operation, at each decision-making point, termed as decision epoch, the examination of the real-time condition monitoring data has been carried out for upgrading the posterior distribution. Using this updated distribution as the root of all operations, the residual life distribution of every concerned unit is calculated, for a particular workload. Subsequently, the establishment of an optimization scheme, i.e., an optimization framework, has been carried out with the help of the predicted residual life to eliminate the unit failures, for individual units, coinciding with each other. Eventually, with various scenarios, simulation has been carried out on the proposed methodology to assess the rate of degradation of various units. The validation of the approach’s effectiveness has been shown by the simulation results on two different configurations having different scenarios.

16 illus, 5 tables, 37 ref

001016   JIMENEZ-FERNANDEZ V M, VALDES-ORTEGA E, MARTINEZMELCHOR J A, VAZQUEZ-LEAL H, FILOBELLO-NINO U A, CARRILLO-RAMON N (Veracruzana Univ, Veracruz, Mexico, Email: vicjimenez@uv.mx) : A new representation of polygonal curves based on piecewise-linear functions with potential application in shape identification. Sadhana 2019, 44(2), 29.

In this paper, a new representation of polygonal curves is proposed. The motivation behind this proposal is to find a descriptive model with potential application in shape identification. In particular, our work addresses the problem of identifying the shape of a given polygonal curve from a set of different ones. In accordance with the proposed representation, a curve is originally described as a series of consecutive points whose connection by straight lines sketches its characteristic shape. In order to define a proper identification scheme, each series of points is mapped to a one-dimensional piecewise-linear function that assigns to each point its corresponding angle. Depending on the case under study, this assignation is performed by following two possible alternatives: (i) in the case where the shape to be identified exactly corresponds with one of the previously stored ones, a sorted sequence beginning from the minimum value of angle and ending with the maximum one is considered, and (ii) in the case where the shape to be identified is similar to one of the previously stored ones, the assignation is performed by following the sequence of points as they appear in the polygonal curve (without sorting). Under this scheme of representation, by a cyclic comparative process between the computed functions, after several steps it is decided whether the graph of any input piecewise-linear function matches the polygonal curve to be recognized within a certain tolerance. In particular, in the case of the identification of two equal shapes, this proposal exploits the well-known principle of similarity geometry, which allows a polygon to be recognized independently of scale, translation and rotation. In order to validate this representation, a comparative analysis between two different shape identification methods (Fourier descriptors and canonical representation) and the piecewise-linear proposal is performed.

13 illus, 2 tables, 24 ref

001065   RAJA S P (Computer Science and Engineering Dep, Vel Tech Rangarajan Dr. Sagunthala R&D Institute of Science and Tech, Chennai - 600 062, Email: avemariaraja@gmail.com) : Joint medical image compression–encryption in the cloud using multiscale transform-based image compression encoding techniques. Sadhana 2019, 44(2), 28.

The recent years have witnessed rapid strides in the use of cloud computing and its countless applications. A cloud can contain massive volumes of multimedia data in the form of images, video and audio. Cloud computing platforms confront challenges in terms of data confidentiality, message integrity, user authentication and compression. Multimedia data needs plenty of storage capacity. Consequently, there is a need for multimedia data compression to reduce data size. Compression techniques are quite reliable, offering benefits to organizations dealing with metasized data in the cloud. Compressing large quanta of data leads to superior utilization of cloud storage. Compression techniques can compress data used for storage and transmission, yet compression alone is inadequate because multimedia data shared should, of necessity, be secure. Therefore, both multimedia compression and security are mandatory in the cloud. The chief goal of this paper is to propose a new framework, comprising multiscale transforms, public key cryptography and appropriate encoding techniques, that performs joint medical image compression and image encryption in the cloud. Multiscale transforms play a lead role in image compression, and the ones discussed in this paper include wavelet, bandelet, curvelet, ridgelet and contourlet transforms. Wavelet transforms offer robust localization both in terms of time and frequency domains. Bandelet transforms offer natural images geometric regularity to help improve the efficiency of representation. Curvelet transforms handle curve discontinuities well, with ridgelet transforms being the core idea behind curvelets. Contourlet transforms capture smooth contours and edges at any orientation. The Rivest-Shamir-Adleman (RSA) algorithm is used to encrypt images to provide maximum security when they are being transferred. Encoding techniques involved in this paper comprise the Embedded Zerotree Wavelet (EZW), Set Partitioning in Hierarchical Trees (SPIHT), Wavelet Difference Reduction (WDR), and Adaptively Scanned Wavelet Difference Reduction (ASWDR). Performance parameters such as peak signal to noise ratio (PSNR), mean square error (MSE), image quality index and structural similarity index (SSIM) are used for evaluation. It is justified that the proposed framework compresses images securely in the cloud.

5 illus, 1 table, 42 ref

001097   VISHNU VENUGOPAL T, DE A K (Mechanical Engineering Dep, Indian Institute of Technology, Guwahati - 781 039, Email: akd@iitg.ac.in) : Flow periodicity and convection modes in rotating Rayleigh–Be´nard convection at low Rayleigh numbers. Sadhana 2019, 44(2), 27.

A three-dimensional numerical study on rotating Rayleigh–Be´nard convection of water in a cylindrical container with a specific aspect ratio is performed in the present work. The simulations are carried out at four different Rayleigh numbers (3 X10⁴; 5 X 10⁴; 7 X 10⁴ and 10⁵) and a fixed Prandtl number (Pr = 7) for a range of rotation rates. Flow structures and their evolution with the addition of rotation to the system are studied in detail. Emphasis is given on the analysis of wall mode and bulk mode convection that appear at different rotation rates. The changes in heat transfer and stability of the system are also investigated. Heat transfer rate is measured by calculating the average Nusselt number at the hot wall. The results show that rotation primarily has an inhibiting effect on heat transfer. For Ra$\le$7 10⁴ the decrease in heat transfer is negligible at lower rotation rates, while it declines steeply for higher rotation rates. At Ra = 10⁵ a small increase in Nusselt number is obtained at low rotation rates before it drops at higher rotation rates. Numerous probes placed at different points within the flow domain are used to investigate the flow regimes and convection modes. The flow initially remains steady at low rotation rates and transforms to a periodic stage with bulk-modedominated convection at moderate rotation rates. Further increase in rotation gives a wall mode convection accompanied by a drastic drop in heat transfer rate before finally approaching a static conductive stage. The dual role of rotation on the stability of Rayleigh–Benard convection is clearly identified in the present study. At moderate rotation rates, the rotation force destabilizes the system to reach a periodic flow whereas extremely large rotation rate stabilizes it.

19 illus, 5 tables, 30 ref

001017   JOTHI T J S, SRINIVASAN K (Mechanical Engineering Dep, National Institute of Technology Calicut, Calicut - 673 601, Email: tjsjothi@nitc.ac.in) : Shock structures of underexpanded non-circular slot jets. Sadhana 2019, 44(1), 25.

Flow visualization studies using shadowgraph technique are carried out to investigate the shock evolution from non-circular slot jets at various under-expansion levels. The non-circular topologies considered are triangular, square and elliptic, and the circular jet is taken as the baseline case for the study. These jets are underexpanded in the pressure ratio (R) range of 2–6 corresponding to a fully expanded jet Mach number up to 1.85. Results indicate that the shock cell structures of non-circular jets strongly depend upon the initial shape of the topology. The shock structures of triangular jet have additional secondary oblique shocks that are distinct from those of other non-circular jets. Mach disk is almost absent in a shock cell structure of triangular jet, which is unlike the case of other jets used in the study. The study suggests that square jet undergoes faster diffusion process compared with the triangular jet. Axis-switching phenomenon is predicted for the elliptical jet at a distance of 3–7 equivalent diameters.

12 illus, 29 ref

001084   SINGH T S, JAIN A K (Electrical Engineering Dep, Indian Institute of Technology Delhi, New Delhi - 110 016, Email: sumeet.nitw@gmail.com) : Voltage minimization control of vector controlled interior permanent magnet motor. Sadhana 2019, 44(1), 24.

Maximum Torque Per Voltage trajectory has been utilized only during field weakening operation of Interior Permanent Magnet (IPM) motor. In this paper, the voltage minimization control from zero-speed is proposed. Voltage minimization results in maximum torque per voltage control of IPM motor. The control implementation is also simple in comparison to current minimization, as the operation is always along the current-limit locus irrespective of operation in field-weakening. Voltage minimization technique minimizes the core losses whereas current minimization would minimize the copper losses. The mathematical model of IPM motor following voltage minimization is derived and the solution to the 4^th order quartic equations is obtained using Ferrari’s method. The solution obtained is utilized to develop a look-up table for vector control of IPM motor. A comparative analysis of voltage minimization and current minimization is established which is supported by simulation results and demonstrated by detailed experimental results.

12 illus, 34 ref

001047   NAIK B K, MUTHUKUMAR P (Mechanical Engineering Dep, Indian Institute of Technology Guwahati, Guwahati - 781 039, Email: pmkumariitg@gmail.com) : Performance assessment of evacuated U-tube solar collector: A numerical study. Sadhana 2019, 44(1), 23.

This paper presents a finite element method based three-dimensional thermal model for predicting the performance of evacuated U-tube solar collector. Numerically predicted working fluid outlet temperature is compared with the experimental data available in the literature and a good agreement is observed between them. The influence of average solar irradiance on efficiency and useful heat gain rate of the solar collector is studied for two different evacuated tube configurations. Employing water and air as working fluid, copper, aluminium and brass as U-tube material, and graphite, magnesium oxide and aluminium oxide as filler material and the performance of the evacuated tube solar collector is investigated in detail.

13 illus, 5 tables, 13 ref

001048   NARENDER G, RAMJEE E, PRASAD N E (Mechanical Engineering Dep, Vignan Institute of Technology and Science, Hyderabad - 508 284, Email: narenderr_g@yahoo.co.in) : In-plane anisotropy and tensile deformation behaviour of aluminium alloy AA 2014 forge plates. Sadhana 2019, 44(1), 22.

Plastic flow behaviour and fracture mechanism of aluminium alloy AA 2014 forged plates under tensile loading conditions are investigated and the results obtained are presented and discussed in the present study. The effects of heat treatment (namely, solution treatment and artificial ageing) on micro-structural homogeneity, tensile behaviour and nature of fracture were studied using hardness, tensile, optical and scanning electron microscopy methods. Experimental engineering stress–engineering strain and true stress–true strain data of the aluminium alloy AA 2014 in different ageing conditions have been analysed using Hollomon, Ludwik and Ludwigson plastic flow relationships. The alloy is found to exhibit moderate degree of in-plane anisotropy and anisotropic index. Further, the alloy in both solution-treated and aged conditions exhibits three different stages of strain-hardening rate and the highest strain-hardening rate occurs at regions of lower strain both in solution-treated and peak-aged conditions. It is also observed that the longitudinal specimen (L parallel to forging direction) exhibits higher strain hardening, while the specimen with T orientation exhibits lowest strain-hardening rates both in solution-treated and aged conditions. The alloy under study in all the heat treatment conditions exhibits ductile fracture mechanism with higher density of uniformly distributed macro- and micro-dimples.

13 illus, 7 tables, 34 ref

001061   PRANESH C, SIVAPRAGASAM M, DESHPANDE M D, NARAHARI H K (Automotive and Aeronautical Engineering Dep, M S Ramaiah Univ of Applied Sciences, Bengaluru - 560058, Email: sivapragasam.aae.et@msruas.ac.in) : Negative lift characteristics of NACA 0012 aerofoil at low Reynolds numbers. Sadhana 2019, 44(1), 21.

Numerical investigations on the flow over NACA 0012 aerofoil are carried out to provide better understanding of the unusual lift characteristics exhibited by this aerofoil at low Reynolds numbers. Computations are carried out at Re = 10,000–100,000, for different values of angles of attack and freestream turbulence intensity. There exists a narrow range of these parameters where the net circulation around this symmetrical aerofoil is negative, leading to the generation of negative lift at positive angles of attack. Different flow regimes are identified and physical explanations are given for this unusual behaviour of negative lift, and the influence of different flow parameters is discussed.

7 illus, 1 table, 10 ref

000993   CHANDRAN K, SAHA A K, MOHAPATRA P K (Mechanical Engineering Dep, Indian Institute of Technology, Kanpur- 208 016, Email: aksaha@iitk.ac.in) : Simulation of free surface flows with non-hydrostatic pressure distribution. Sadhana 2019, 44(1), 20.

In this work, a free surface flow simulator is developed in which Navier–Stokes equations using Marker and Cell (MAC) method in the framework of finite difference methodology have been solved. The free surface is tracked by the volume of fluid (VOF) method. The numerical code without free-surface is validated against the flow past a square cylinder. Three different free surface flows, i.e., dam break flow, two-dimensional cavity filling and undular bore, are studied to demonstrate the efficacy of the developed numerical model to simulate free surface flow. The numerical model used in the present work involves tracking of free surface of a single fluid in a two-fluid system. The parameters which can affect the interface orientation of the fluid is given as boundary condition at the interface. The inherent advantage of such numerical models is its ability to track free surface for high density and viscosity ratio fluids like air–water. The numerical model used in the present work is capable of solving such high density ratio two-fluid systems for which the effects due to surface tension are negligible. Results from all the problems are compared with earlier results available in literature.

11 illus, 5 tables, 34 ref

001049   NARWANE G K, MILLO J-V, KRISHNA S N, RAMESH S (Homi Bhabha National Institute, Mumbai - 400 094, Email: ganeshk@cse.iitb.ac.in) : Design variability verification in software product lines. Sadhana 2019, 44(1), 18.

This paper proposes a novel notion called variability verification applicable to Software Product Lines (SPL). Variability is central to SPL and we have observed that variability is expressed differently at different levels of abstraction in the development flow of SPL. A natural problem in this context is the conformance of variability information expressed at different levels. Design variability verification, in particular, checks whether the variability expressed at the design level conforms to that at the requirement level. Unlike many existing approaches to SPL modelling, our work does not assume a single global view of variation points, even within the same level of abstraction. In our view, an SPL is a concurrent composition of features, where each feature exhibits independent variability. This enables incremental addition of variability. The procedure is compositional in the sense that the verification of an entire SPL consisting of multiple features is reduced to the verification of the individual features. Feature level verification essentially involves standard model checking while, in the second step, a Quantified Boolean Formula (QBF) is synthesized and solved. The method has been implemented and demonstrated in a tool SPL Engine for Design Verification (SPLEnD) on a couple of fairly large case studies. SPLEnD uses SPIN tool for the feature level conformance, while the state-of-the-art QBF solver CirQit is used for the SPL level conformance. SPLEnD easily handles the evolution of SPL by addition of new features and modification of existing features. Experimental results with SPLEnD look very promising.

24 illus, 43 ref

001086   SINHA R S, MUKHOPADHYAY A K (Mining Machinery Engineering Dep, Indian Institute of Technology (Indian School of Mines), Dhanbad - 826 004, Email: ravishankarism0181@gmail.com) : Failure rate analysis of jaw crusher: A case study. Sadhana 2019, 44(1), 17.

Failure of crusher components has considerable influence on the productivity of a crushing plant. In order to improve performance and operational reliability, its critical components are needed to be identified to make replacement in time before any catastrophic failure happens. Though traditional maintenance practices exist in crushing plants, a methodical analysis of failure trend is imperative to improve operational reliability of this critical equipment. The present paper deals with failure analysis of rock crusher and its critical components using total time on test (TTT)-plot and other statistical tools. TTT-plot has proven to be a useful tool in reliability analysis.

6 illus, 8 tables, 15 ref

001082   SINGH J, CHAUHAN A (Panjab Univ, Chandigarh - 160 014, Email: drchauhan98@gmail.com) : A review of microstructure, mechanical properties and wear behavior of hybrid aluminium matrix composites fabricated via stir casting route. Sadhana 2019, 44(1), 16.

This article focuses on the mechanical and wear properties of the Al-based hybrid composites fabricated by stir casting route. A wide range of literature has been consulted in this regard and it has been revealed that processing conditions can be tailored to obtain homogeneous structure of the Al-composites. The addition of ceramic particles has been found to be essential to provide requisite strength and hardness to these composites. Also, use of agro/industrial waste materials such as fly ash, red mud and rice husk ash as a complementary reinforcement reduces the density of the hybrid composites without compromising the mechanical properties. The literature review also indicates that addition of soft reinforcements along with hard reinforcements reduces the brittleness of the hybrid composites. Moreover, the presence of solid lubricants like graphite significantly improves the wear resistance of these materials. It has been noticed that incorporation of solid lubricants also helps in the formation of a protective tribolayer at the interface thereby reducing the wear rate and plastic deformation of these composites. In overall, study concludes that Al-based hybrid composites have great promise to serve as a substitute to the ceramic reinforced composites and the unreinforced Al-alloys in various automotive applications requiring low cost, high strength-to-weight ratio and superior wear resistance.

16 illus, 1 table, 61 ref

001092   VASWANI A, SHRIVASTAVA S (Mechanical Engineering Dep, BITS Pilani, Pilani - 333 031, Email: sharad_shrivastava@pilani.bits-pilani.ac.in) : CAD modeling and finite elemental design of indigenous knee brace. Sadhana 2019, 44(1), 14.

Walking problems aggravate with the advent of old age. One of the treatments for the walking problems is the use of knee brace. This paper reviews the existing designs of knee braces, assesses their merits and demerits and proposes an efficient, cost-effective, light-weight and attractive design of knee brace for Indian population. This paper models design of knee brace and analyzes stress shielding capacity of the knee brace using Finite elemental analysis. This paper discusses how this knee brace can overcome difficulties faced by other knee braces in market.

6 illus, 2 tables, 16 ref

001051   NEMATI M, MATIN R K (Mathematics Dep, Islamic Azad Univ, Karaj, Iran, Email: rkmatin@kiau.ac.ir) : A data envelopment analysis approach for resource allocation with undesirable outputs: An application to home appliance production companies. Sadhana 2019, 44(1), 11.

Traditional data envelopment analysis (DEA) models use all multiple inputs and outputs to estimate efficiency scores of decision-making units (DMUs). Each unit may consist of several subunits in cases such as manufacturing systems, and each subunit may produce both desirable and undesirable outputs. Providing information about the proportion of resources for each subunit could assist managers in making better decisions for increasing the efficiency of production systems. The current study proposes a new approach for resource allocation and efficiency estimation of production units by considering partial impacts among inputs and outputs in the DEA framework. A weak disposable technology is used in these evaluations, and an empirical application of the proposed approach for obtaining performance of home appliances production companies is provided for illustration purposes.

3 illus, 7 tables, 31 ref

001090   USTKOYUNCU N (Electrical and Electronics Engineering Dep, Erciyes Univ, 38039 Kayseri, Turkey, Email: nurettinu@erciyes.edu.tr) : Application of an in-wheel direct drive motor based on switched reluctance motors for low-power electric vehicles. Sadhana 2019, 44(1), 10.

This paper presents application of a switched reluctance motor with exterior rotor as an in-wheel direct drive motor for low-power electric vehicles (EVs). A prototype system is realized for experimental studies. Both analytical method and finite-element analysis (FEA) are used in this research to obtain characteristics of the motor. The results of the FEA and analytical calculations are presented, and compared to experimental results. The obtained test and simulation results show that the proposed system is suitable for lowpower and low-cost EVs.

13 illus, 1 table, 14 ref

001045   MORADI M M, AVAL H J, JAMAATI R (Materials Engineering Dep, Babol Noshirvani Univ of Technology, Babol 47148-71167, Iran, Email: h.jamshidi@nit.ac.ir) : Effect of tool pin geometry and weld pass number on microstructural, natural aging and mechanical behaviour of SiC-incorporated dissimilar friction-stir-welded aluminium alloys. Sadhana 2019, 44(1), 9.

The aim of this investigation was to study the effect of tool pin geometry and pass number on mechanical and microstructural behaviour of SiC-incorporated dissimilar friction stir welding of 6-mm-thick plates of AA6061-T6 and AA2024-T351. Two tool pin geometries, square and triangle frustum, were used. It was found that the weld made by square frustum pin and two passes with rotation in the same direction produces more homogenized and finer distribution of SiC particles. Also, the grain size of stir zone in the weld made by two passes is finer than that made by one pass. The weld made by triangle frustum pin shows higher thermomechanically affected zone hardness, natural aging kinetics and tensile strength than the others.

8 illus, 3 tables, 23 ref

001050   NAYAK A S, BHALE D, VIJAYAN R, DINGH D K, RAWAT V S (Laser and Plasma Technology Div, Bhabha Atomic Research Centre, Mumbai - 400 085, Email: anilsn@barc.gov.in) : Development of an auto-synchronization technique for improving the power stability of copper vapour laser oscillator and amplifier configuration. Sadhana 2019, 44(1), 8.

A technique to synchronize multiple copper vapour laser (CVL) systems in master oscillator power amplifier configuration to obtain long-duration power stability is discussed in this manuscript. The technique utilizes optoelectronic interconversion of the current pulses of CVL oscillator and amplifiers units as a feedback signal. The signal processing of the current pulses was performed using a monostable multivibrator, R–S flipflop and passive low pass filter. The DC voltage generated corresponding to the quantum of temporal mismatch between the oscillator and the amplifier modules is sampled, averaged and compared to the set point voltage using a Programmable Logic Controller. The timing signal of the respective amplifiers could be accordingly adjusted to synchronize with the CVL oscillator optical pulses to obtain long-duration power stability.

10 illus, 6 ref

000983   ANNETTE J R, BANU A (Computer Science Engineering Dep, Saveetha Institute of Medical and Technical Sciences, Chennai - 602 105, Email: rubysubash2010@gmail.com) : Ranking cloud render farm services for a multi criteria recommender system. Sadhana 2019, 44(1), 7.

Recommender systems that recommend ideal services or items to the online users are a very useful tool for both the users and the businesses. Usually for recommending services, multiple attributes of the services are evaluated and these types of recommender systems that evaluate multiple attributes are called multi criteria recommender systems. In these types of multi criteria recommender systems the ranking of services plays a major role. This work is focused on ranking the cloud render farm services which are of the PaaS (Platform-as-aService) type of cloud services that provide the entire platform for the animators to render the files using the cloud resources. This work identifies the Quality of Service (QoS) attributes that are important for the animators for selecting a cloud render farm service. The QoS values of four different real time cloud render farm services were collected by conducting real time experiments using the files of the ‘‘Big Buck Bunny’’, an open-source animated film project and were ranked using three Multi-Criteria Decision Making (MCDM) methods, namely the AHP (Analytical Hierarchical Process), TOPSIS (Technique for Order Preference by Similarity to the Ideal Solution) and SAW (Simple Additive Weighting). The analysis of the ranks obtained using the three different MCDM methods provide many useful insights and conclusions.

7 illus, 11 tables, 41 ref

001056   PAUL M N, TIWARI S (Mechanical Engineering Dep, Indian Institute of Technology, Chennai - 600 036, Email: shaligt@iitm.ac.in) : Effect of downstream cylinder rotation on wake dynamics of two inline circular cylinders. Sadhana 2019, 44(1), 5.

Two-dimensional numerical investigations have been carried out to study flow past two inline circular cylinders with stationary upstream and rotating downstream cylinder. Computations are performed using commercial software ANSYS Fluent 16.0 for a fixed Reynolds number (Re) of 150 to study wake characteristics unsteady laminar flow. Optimal values of spacing between cylinders and downstream cylinder rotation speed have been identified, confirming the suitability of such an arrangement for drag reduction and flow control. Steady and unsteady features of the wake have been examined with the help of vorticity contours, lift and drag coefficients, their signals and spectra. Interesting phenomena that include multiple transitions in the temporal behavior of the flow and appearance of circulation zone, its development, stabilization, and transformation have been elaborated in this study.

16 illus, 2 tables, 25 ref

001034   MALATHI D, GOMATHI M (Electronics and Communication Engineering Dep, Kongu Engineering Coll, Perundurai - 638 060, Email: malathid2001@gmail.com) : Design of inductively degenerated common source RF CMOS low noise amplifier. Sadhana 2019, 44(1), 4.

The Low Noise Amplifier (LNA) is the first stage in RF CMOS receivers. The Common Gate (CG) LNA and Inductively Degenerated Common Source (CS) LNA are one of the widely used topologies for realizing RF CMOS receivers. The present work emphasizes a simple and exhaustive search procedure for the synthesis and analysis of CMOS CG and Inductively Degenerated CS LNA circuits. The width (W), gate source voltage (V_gs) and drain source voltage (V_ds) of the transistors constitute the design space in the circuit design. The design first involves the use of a circuit simulator (HSPICE) to obtain the small signal parameters of the circuit for various W, V_gs, and V_dsof the transistors and then to generate a Look-Up Table (LUT) for all design points using the obtained values. This LUT is used to meet the target performance specifications along with appropriate analytical expressions derived from the circuit in a numerical simulator (MATLAB). This will enable one to explore the whole design space quickly and fastly for arriving at the optimal values for the device dimensions, bias voltages and bias currents of the two LNA circuits. The design methodology is demonstrated by designing CG and Inductively Degenerated CS LNA circuits using 90 nm CMOS technology library in which Inductively Degenerated CS LNA gets high gain and low noise figure than CG LNA.

9 illus, 3 tables, 13 ref

001044   MOHANTY S D, MAHAPATRA S S, MOHANTY R C (Mechanical Engineering Dep, Centurion Univ of Technology and Management, Bhubaneswar, Odisha, Email: saumyadarsan@gmail.com) : PCA based hybrid Taguchi philosophy for optimization of multiple responses in EDM. Sadhana 2019, 44(1), 2.

The present study is aimed at a multi-response optimization problem by applying Principal Component Analysis (PCA) combined with Taguchi method. The investigation has been carried out through a case study in Electric Discharge Machining (EDM) of D2 steel by using copper, brass and Direct Metal Laser Sintered (DMLS) electrode produced by direct metal laser sintering using Directmetal20. The research work has been carried out to evaluate the best parametric combination which could fulfill multiple responses like lower Tool Wear Rate (TWR), higher Material Removal Rate (MRR) and lower Surface Roughness (R_a). Unlike the use of single-objective optimization problem in traditional Taguchi method, a hybrid Taguchi method has been developed in combination with PCA to solve multi-objective problem. Taguchi method assumes that the quality characteristics should be uncorrelated or independent which is not always fulfilled in actual condition. PCA is applied to remove response correlation and to calculate independent (uncorrelated) quality indices known as principal components. These principal components combined with weighted principal component analysis (WPCA) are used to calculate overall quality index denoted as Multi-response Performance Index (MPI). This investigation combines WPCA and Taguchi method for forecasting optimal setting. The predicted result by this method was validated through confirmatory test proving the efficacy of the process. Out of five input process parameters considered, tool electrode has been found to be the most significant factors through the Analysis of Variance (ANOVA).

2 illus, 9 tables, 29 ref

000997   DAS R, BAISHYA S (Electronics and Communication Engineering Dep, National Institute of Technology Silchar, Assam - 788 010, Email: rajashree18das@gmail.com) : Dual-material gate dual-stacked gate dielectrics gate-source overlap tri-gate germanium FinFET: Analysis and application. Indian J Phys 2019, 93(2), 197–205.

This study proposes a novel dual-material-gate dual-stacked-gate dielectrics gate–source overlap Ge FinFET and compares its characteristics with conventional FinFET. The proposed device shows very less leakage current (I_OFF) ($~$ 10^-17 A), significant on drain current ($~$ I_ON) ($~$ 10^-4 A), very high ratio of I_ON to I_OFF (I_ON/I_OFF) ($~$ 10¹³) and less subthreshold swing of (SS) (71 mV/dec). This study presents the effect of different dielectrics, oxide thicknesses (t_ox) and back-gate voltages (V_GB) on transfer characteristics of the proposed device. The effect of channel concentration on I_ON/ I_OFF, threshold voltage (V_th), transconductance (g_m) and SS is also investigated. The effect of overlap length (L_ov) on analog parameter, gate–source capacitance (C_gs), is also analyzed. Moreover, the effect of fin thickness (T_fin) on V_th and SS is also studied. The height of the BOX plays an important role in reducing I_OFF. Moreover, with emphasis on digital application, by using the proposed device a digital inverter circuit is implemented, and this study investigates the characteristics using mixed-mode simulation.

12 illus, 22 ref

000982   ALANI I A M, AHMAD B A, AHMED M H M, LATIFF A A, AL-MASOODI A H H, LOKMAN M Q, HARUN S W (Electrical Engineering Dep, Malaya Univ, Kuala Lumpur-50603, Malaysia, Email: swharun@um.edu.my) : Nanosecond mode-locked erbium doped fiber laser based on zinc oxide thin film saturable absorber. Indian J Phys 2019, 93(1), 93–9.

In this paper, we report a nanosecond mode locked erbium doped fiber laser (EDFL) using zinc oxide (ZnO) nanoparticles as a saturable absorber (SA) for the first time. Due to its excellent optical properties, in particular a high nonlinear optical response and fast recovery time, ZnO nanoparticles can be used as a saturable absorber device for pulsed laser generation. For easy integration into the laser cavity, the ZnO nanoparticles were imbedded into a polymer film using a seeding solution technique. 400 ns mode locked pulse train was successfully obtained at a relatively low threshold pump power of 45.4 mW. The output laser operates at the fundamental frequency of 1 MHz with a center wavelength of 1558.34 nm. The highest pulse energy and peak power achieved by the laser are estimated at 11.6 nJ and 27.3 mW respectively at the maximum available pump power of 142 mW. The results show that the SA derived from ZnO nanoparticles is capable of producing nanosecond mode locked EDFL for possible applications that require high pulse energy and medium output power.

10 illus, 1 table, 42 ref

001104   ZHANG C-L, LIU W-W (Information Engineering Dep, Yango Univ, Fuzhou- 350 015, China, Email: mzhangchunling@163.com) : Generation of W state by combining adiabatic passage and quantum Zeno techniques. Indian J Phys 2019, 93(1), 67–73.

We propose a scheme to prepare W state for three atoms in a cavity via adiabatic passage and quantum Zeno dynamics. Appropriate Rabi frequencies of the classical fields are selected to realize the present scheme. Numerical analysis is showed, which indicates that the scheme is robust against the floating of the pulse delay and laser intensity, and the atomic spontaneous radiation and the cavity decay are efficiently suppressed by engineering adiabatic passage. Moreover, the scheme is more achievable in experiment than other existing schemes. Based on the current experimental technology, this scheme for generation of high-fidelity W state for three atoms can be achieved.

8 illus, 55 ref