031057   FENIL A A, SIVAPRAGASAM M (Automotive and Aeronautical Engineering Dep, M S Ramaiah Univ of Applied Sciences, Bengaluru - 560 058, Email: sivapragasam.aae.et@msruas.ac.in) : Effect of leading-edge geometry on the aerodynamics and heat transfer in the stagnation region of uncooled turbine blades. Sadhana 2018, 43(11), 183.

The flow in the leading-edge stagnation region of uncooled turbine aerofoils is studied. The stagnation region is modelled based on the Hiemenz flow solution, following Holley and Langston (J. Turbomach. 130: 021001, 2008). These results are applied to the JT9D turbine blade and confirmed by computations. It is also shown that the heat transfer at the stagnation point is bounded by the Hiemenz flow and plane stagnation-point potential flow heat transfer solutions. The computations are further extended for a range of Reynolds numbers and freestream turbulence intensities. It is seen that for a wide range of these parameters considered in the present study and data collected from published literature, a majority of the data points are within these bounds. The leading-edge geometry of the JT9D turbine blade is modified with elliptical geometries. Blunter-leading-edge geometries have lower values of heat transfer at the stagnation region; however, their blade profile loss coefficients are higher. The off-design performance characteristics of the turbine blades are also computed. The results presented in this paper will be useful in designing leading-edge geometries for reduced heat transfer in the stagnation region of uncooled turbine blades.

16 illus, 36 ref

031059   GUPTA R K, CHANDRA A, GUPTA R K (Chemical Engineering Dep, Thapar Institute of Engineering and Technology, Patiala - 147 004, Email: avichiitk@yahoo.com) : Buoyancy-driven convective heat transfer from a semi-circular cylinder for various confinements. Sadhana 2018, 43(11), 182.

Buoyancy-driven convective heat transfer from a semi-circular cylinder for various confinements has been studied using numerical simulations for wide ranges of parameters, Reynolds numbers (1$\le$ Re $\le$ 50), Richardson numbers (0 $\le$ Ri $\le$ 2), Prandtl numbers (0.7 $\le$ Pr $\le$ 50) and confinement ratios (0.2 $\le$ $\mathrm{\beta }$ $\le$ 0.8). A hot semi-circular cylinder is symmetrically kept in a 2D rectangular confinement. The circular side of the cylinder faces the upstream flow and the fluid flows against gravity in the channel. The governing equations are numerically solved using FLUENT and the results obtained are presented in the form of isotherms, streamlines, pressure coefficients, drag coefficients, Nusselt numbers, etc. The highest value of pressure coefficient increases with blockage ratio for all cases. The drag coefficient decreases with Re and shows complex phenomena with change in Ri and blockage ratio of the channel. Pressure drag has contributed more as compared with viscous drag in all cases. The curved surface showed more heat transfer than the flat surface of the semi-circular cylinder. The value of $\mathrm{\beta }$ also has great influence at large value of Peclect numbers (= 2500). Overall average heat transfer in terms of average Nusselt number is a function of Ri, Re, Pr and $\mathrm{\beta }$.

13 illus, 3 tables, 30 ref

031080   SUGANTHI S T, DEVARAJ D, THILAGAR S H, RAMAR K (EEE Dep, Sri Shakthi Institute of Engineering and Technology, Coimbatore, Email: suganthi.sb@gmail.com) : Optimal generator rescheduling with distributed slack bus model for congestion management using improved teaching learning based optimization algorithm. Sadhana 2018, 43(11), 181.

This article proposes a new strategy for Congestion Management (CM) through Generation Rescheduling (GR) with Distributed Slack Bus (DSB) model using Improved Teaching Learning Based Optimization (ITLBO) algorithm. Most of the previous research mainly focuses on rescheduling the existing generators for CM and least concerned about the consequence of this rescheduling on the slack bus. As a result, the slack bus is supposed to carry the entire residual effect of all other generators which leads to increased Congestion Management Cost (CMC). This work proposes a distributed slack bus model for reducing the excess burden on the slack bus and a two-fold contribution is made to develop the proposed technique. First, is the selection of the participating generator for CM by means of Incremental Generator Sensitivity Factor (IGSF), which adopts the generator sensitivity as well as the bidding cost. Next, CM is formulated as an optimization problem with the objective function involving congestion management cost and solved using ITLBO algorithm, which incorporates the self-motivated learning concept with the basic TLBO operators. For evaluation, the standard IEEE 30-bus and IEEE 118-bus systems are used and the obtained results are compared with the other CM systems reported through literature.

8 illus, 12 tables, 20 ref

031049   ANAND M, LEE M Y, DIAMOND S L (Chemical Engineering Dep, Indian Institute of Technology Hyderabad, Sangareddy - 502 285, Email: anandm@iith.ac.in) : Combining data-driven neural networks of platelet signalling with large-scale ODE models of coagulation. Sadhana 2018, 43(11), 180.

Platelet signalling during blood coagulation is conveniently modelled using data-driven neural networks since mechanistic Ordinary Differential Equation (ODE)-based models, while available, are unwieldy due to the large number of equations. On the other hand, the extra-cellular protease cascade of reactions that occur during blood coagulation are conveniently modelled using mechanistic ODE-based models. It is essential to integrate platelet signalling with the extra-cellular reaction cascade to get a representative model for in-vitro coagulation. In this paper, a neural-network-based platelet calcium calculator is combined with a large-scale ODE model for thrombin production. The combined model is used to test the effect of platelet modulators on thrombin production during in-vitro coagulation. The model predictions generate two hypotheses on relative importance of platelet modulators: they need to be compared to experimental data to confirm the same. The novelty of the study lies in the combination of existing approaches to study coagulation, and in capturing the role of platelet modulators on thrombin production: excessively large number of equations are avoided, which would be the case in a purely ODE-based approach.

5 illus, 11 ref

031078   SHUKLA S, GILL S S, JATANA H S, NEHRU V, KAUR N (Electrical Engineering Dep, IIT Patna, Patna - 801 106, Email: satyam.pee17@iitp.ac.in) : Modelling and mitigation of single-event upset in CMOS voltage-controlled oscillator. Sadhana 2018, 43(11), 179.

Single-event effects (SEEs) have been the primary concern in study of radiation effects since late 1970s with the discovery of soft errors in terrestrial and space environments. The interaction of a single ionized particle with electronic devices leads to SEEs. In this paper, single-event upset (SEU) on CMOS devices in designing of a voltage-controlled oscillator (VCO) is analysed. Further, mitigation approaches of SEU are also discussed. To observe the impact of radiation, a VCO was designed in Cadence Virtuoso, and GDSII file of one ring oscillator stage was extracted to incorporate the same design in Silvaco MaskViews. With the help of layer map information file, masks were identified and used to design the CMOS inverter structure file for simulation of SEU condition. The input parameters for SEU simulation were evaluated from linear energy transfer (LET) graph of heavy ion under space conditions. The current profile of CMOS inverter was extracted under influence of a high-energy particle with the help of LET graph of that particle. This current profile was applied to different nodes of VCO and upset conditions were identified. Further, the impact of upset conditions on lock stage of phase-locked loop (PLL) is discussed. Results show that the SEU has significant impact on the logic state of inverters used in ring oscillator stage compared with current starving/biasing stage. The current profile of CMOS device has strong dependence on the energy of ion, its track, angle of incidence and the material. When angle of incidence is very less (7$°$-14$°$) the channel will be occupied by a funnel of charge and it leads to the maximum degradation of device. This work shows that a device operating at high frequency is more susceptible to SEU. Triple modular redundancy (TMR) and Radiation Hardened By Design (RHBD) can be used to mitigate SEU. TMR consumes more power and is less accurate compared with the RHBD approach.

10 illus, 1 table, 25 ref

031068   MO K H, LOH Z P, TAN C G, ALENGARAM U J, YAP S P (Civil Engineering Dep, Malaya Univ, 50603 Kuala Lumpur, Malaysia, Email: khmo@um.edu.my) : Behaviour of fibre-reinforced cementitious composite containing highvolume fly ash at elevated temperatures. Sadhana 2018, 43(11), 177.

This research describes the properties of acrylic fibre-reinforced cementitious composite containing high-volume fly ash. In this investigation, the fly ash content (30 % and 60 %) and the acrylic fibre dosage (0 %, 1 % and 2 %) were varied. Increased content of fly ash in the composite was found to be able to partially compensate the reduction in workability caused by the inclusion of fibres. On the other hand, although the use of fibres had minimal influence on the compressive strength, the fibres could significantly enhance the flexural strength of the composite, particularly in the composite containing higher fly ash content. At elevated temperatures, it was found that the inclusion of acrylic fibres was beneficial in the composite with higher fly ash content, as demonstrated by the increased strength retention and reduced spalling damage at elevated temperature.

7 illus, 2 tables, 27 ref

031073   PRADHAN V, KULKARNI A M, KHAPARDE S A (Electrical Engineering Dep, Indian Institute of Technology Bombay, Mumbai - 400 076, Email: vedanta.pradhan@gmail.com) : Computation of the controllable swing mode spectrum of FACTS and HVDC in large power systems. Sadhana 2018, 43(11), 176.

This paper presents computation of swing modes of a large power system that could be significantly affected by power swing damping controllers in FACTS or HVDC devices at a given location. Modal controllability is a suitable measure to isolate these modes for analysis. Computation of the controllable swing mode spectrum is useful, especially in situations where the controller structure and feedback signals are not frozen (e.g., at the planning stage). This paper proposes two important steps that allow us to map the problem of finding highly controllable swing modes to the problem of finding the swing modes that have high transfer function residues (for which efficient algorithms are available). The steps are: (a) normalization of the eigenvectors corresponding to different modes and (b) identification of specific feedback signals for each type of FACTS/ HVDC device such that the modal observability and modal controllability are tightly coupled. Once the mapping is done, a computationally efficient method like the Subspace Accelerated Dominant Pole Algorithm [16] (SADPA) can be adapted to find the highly controllable swing modes. The effectiveness of this approach is demonstrated by case studies of FACTS and HVDC devices in a 16-machine system and the Indian power grid.

8 illus, 8 tables, 25 ref

031058   GOPINATH S, PRAKASH A, AAHRTHY R, HARISH M B (CSIR - Structural Engineering Research Centre, Chennai - 600 113, Email: smithag@serc.res.in) : Investigations on the influence of matrix and textile on the response of textile reinforced concrete slabs under impact loading. Sadhana 2018, 43(11), 172.

Textile Reinforced Concrete (TRC) is gaining its popularity as a construction material. It is essential to investigate new materials to quantify its expected structural performance and integrity. The purposed study is to investigate the influence of material type and volume fraction of textile and type of matrix on the impact behaviour of textile reinforced concrete slabs. Both glass and basalt textiles were used in the investigations. Based on the investigations, it is concluded that the type of binder influences the impact resistance at first crack as well as the delamination possibility. Glass textile reinforced concrete slabs show more displacement and more residual capacity compared to basalt textile reinforced concrete slabs. With increased number of layers, the basalt textile reinforced concrete slabs exhibited decrease in impact resistance due to delamination. As energy level increases, glass textile reinforced slabs show increase in peak displacement whereas basalt textile reinforced concrete slabs show a decrease. The investigations reported will be useful for extending the knowledge of textile reinforced concrete for various impact resistant applications.

18 illus, 3 tables, 18 ref

031074   PRASAD V K, CHATTERJEE D, SINGH S P (CSIR-Central Mechanical Engineering Research Institute, Durgapur - 713 209, Email: d_chatterjee@cmeri.res.in) : Numerical simulation of gas-bubble formation through two submerged orifices. Sadhana 2018, 43(11), 171.

In this work, two-dimensional numerical simulations are carried out to analyse the dynamics of gasbubble formation at two adjacent orifices submerged in an immiscible Newtonian liquid under the condition of constant gas flow rate using finite-volume-based commercial CFD solver Ansys Fluent. Two conditions for the ambient liquid are considered: firstly the liquid is in quiet condition and secondly, it is also co-flowing with the gas stream. The full cycle from the bubble formation to its detachment and the corresponding dynamics are simulated using the volume of fluid (VOF) method, which is one of the efficient front capturing techniques of Eulerian family. The study includes: (i) time sequence profile of bubble formation to clearly represent the bubble growth, neck formation and bubble break-up at a given Weber number (We), Reynolds number (Re), Bond number (Bo) and liquid to gas mean velocity ratio (V_r); (ii) bubble growth history for different V_r and at constant Re, We and Bo; (iii) effect of orifice spacing on bubbling synchronicity and frequency at given V_r, We, Re and Bo and (iv) synchronous bubbling regime, bubble size and formation time determination, bubble coalescence phenomenon and technique for its inhibition.

9 illus, 3 tables, 36 ref

031075   RAZZAQUE A, JOSHI S, DHADED S, SAJJAN C, KONIN P, SUBASHANI T (Prosthodontics Dep, AME’s Dental Coll and Hospital, Raichur, Karnataka, Email: drshalinibn@gmail.com) : Occlusal vertical dimension: Effect on esthetic norms at smile. Indian J Dent Sci 2018, 10(4), 220-5.

The restorative and esthetic needs for the complete mouth rehabilitation patient frequently require an increase in occlusal vertical dimension (OVD), in whom there would be tooth loss or attrition in existing teeth, decreased OVD, or opposing teeth supraeruption. The effect of increasing OVD for restorative purpose and esthetic norms while smiling is not well understood; hence, the purpose of this study is to evaluate the effect of those norms at smile. Eighty patients (40 males and 40 females) were selected from the student population of AME’s Dental College, Raichur, between the age groups 21 and 30 years, and occlusal registrations of 2, 4, 6, and 8 mm in thickness for each individual were fabricated from the articulated casts. Posed smile images at OVD +0, +2, +4, +6, and +8 were taken with a digital single lens reflex (DSLR) camera and evaluated using AutoCAD software. In this study, it was found that with an increase in OVD, the interlabial gap height, incisal edge to lower lip distance, and display zone area were increased statistically significantly (P < 0.05) in both male and female patients, whereas the smile index was decreased significantly (P < 0.05). No significant changes were observed in the intercommissural width and incisal edge to the upper lip distance in both male and female patients. There is obvious effect of aesthetic norms such as the vertical distance between the incisal edge to upper lip, vertical distance between incisal edge–lower lips, interlabialgap height, intercommissural width, internal display zone area, and smile index in both male and female patients. The obtained values can serve as guide for esthetic rehabilitation of patients.

2 illus, 3 tables, 24 ref

031082   SWETHA V, JOSHI S, SAJJAN C, KONIN P, RAZZAQUE A, TIPPASHETTY S K (Prosthodontics Dep, A.M.E’s Dental Coll and Hospital, Raichur, Karnataka, Email: drshalinibn@gmail.com) : Effect on indigenous die spacer thickness at varied evaporation times. Indian J Dent Sci 2018, 10(4), 209-15.

The present study was conducted to compare the effect of evaporation at different time intervals on film thickness at various applications of indigenous die spacer (S) Surana Enterprises, Mangalore Dental Corporation, India and TRUFIT GEO. TAUB PROD. & FUSION CO. INC. Jersey City, N.J Die spacer on ultrarock KALABHAI, Karsan, India die stone (DI) and Resin modified gypsum SynaRock XR, DFS GmbH, Germany die stone (DII). A total of 200 samples were prepared for study, and each sample was used for specific number of die spacer application (1, 2, 3, 4, or 5) after its evaporation at specific interval of time (0 h, 2 h, 4 h, 8 h, or 24 h). The specimens so obtained were then sectioned and die spacer thickness was measured using a stereo microscope. One‑way analysis of variance was used for study parameters with 5 % level of significance followed by Tukey’s HSD post hoc test. The highest mean value of die spacer thickness of 32.85 ± 0.28 μm was for SynaRrock die stone sample with 5 applications of TRU-FIT die spacer after 24 hours of evaporation and least of 13.80 ± 0.02 μm for ultrarock die stone sample with 1 application of Surana die spacer after 0 hour of evapouration. There is a significant difference in all subgroups at various evaporation time intervals. Evaporation of volatile substances at various time intervals varies the thickness of die spacer and thus affects the casting relief. The indigenous die spacer and die stone can also be used effectively.

5 illus, 8 tables, 22 ref

031061   JUN-YOUNG CHO, TAE-HO AN, SHIN S Y, KIM H S, KIM Y S, SHIN H, BAE S-H, KIM M, HONG S-H, PARK C (Materials Science and Engineering Dep, Seoul National Univ, Seoul 08826, Korea, Email: pchan@snu.ac.kr) : Effects of sintering conditions on the microstructure and mechanical properties of SiC prepared using powders recovered from kerf loss sludge. Bull Mater Sci 2018, 41(6), 157.

The effects of sintering conditions on the microstructure and mechanical properties of the sintered SiC prepared using the SiC powder recovered from the kerf loss sludge were investigated. The recovered SiC powders were consolidated by spark plasma sintering (SPS) and conventional sintering methods. The effects of sintering temperature, time and methods (SPS and conventional sintering) on the phase, grain size and density of SiC were systematically studied. The Vickers hardness of spark plasma-sintered (SPSed) samples was higher than that of conventional sintered samples due to small grain size. When holding time was increased from 10 to 30 min, the grain size and relative density of SPSed samples were also increased, which lead to the almost constant Vickers hardness by competing effects of grain size and relative density. When holding time was over 30 min, no appreciable change of the relative density and grain size were observed, which can lead to similar values of Vickers hardness. SPS process can be used to make SiC with high density and hardness at relatively low temperature compared with the conventional sintering process.

6 illus, 1 table, 56 ref

031064   LANJEWAR M, GOHEL J V (Chemical Engineering Dep, Sardar Vallabhbhai National Institute of Technology, Surat 395007, Email: Jignasa.narsinhbhai@gmail.com) : Highly enhanced solar conversion efficiency of novel layer-by-layer PbS:Hg and CdS quantum dots-sensitized ZnO thin films prepared by sol–gel spin coating. Bull Mater Sci 2018, 41(6), 151.

Owing to superior optical properties, ZnO thin films have immense potential in solar cell preparation. ZnO thin films were prepared by sol–gel technology. However, this is prolonged technique and it necessitates a complex precursor solution. In the present work, ZnO thin films are prepared by sol–gel spin coating with simple precursor, zinc acetate. A very remarkable feature of the method is that polycrystalline, non-abrasive and translucent films were obtained. Additionally, novel PbS:Hg quantum dots (QDs) and CdS QDs are successfully synthesized. Moreover, both types of QDs are deposited layer-by-layer over pure ZnO and Ag:ZnO thin films. The films are characterized by X-ray diffraction, and crystallinity continuation is observed even after the addition of QDs layer. Presence of synthesized QDs over thin films is also confirmed. The films were also characterized by scanning electron microscopy (SEM) and UV–Vis spectroscopy. Uniform, dense and porous surface morphology is clearly revealed. Sensitized thin films show a huge decline in band gap and large enhancement in efficiency. Superior current density (10.87 mA cm⁻²) is achieved with PbS:Hg/CdS/Ag:ZnO, which leads to enhancement in overall solar conversion efficiency by 6.34 times.

8 illus, 1 table, 25 ref

031084   WANG H, ZHANG W, XU J, LIU G, XIE H, YANG L (Guilin Electronic Technology Univ, Guilin 541004, China, Email: wh65@guet.edu.cn) : Resistance-switching properties of Bi-doped SrTiO₃ films for non-volatile memory applications with different device structures. Bull Mater Sci 2018, 41(6), 149.

SrTiO₃ and Bi-doped SrTiO₃ films were fabricated with different device structures using the sol–gel method for non-volatile memory applications, and their resistance-switching behaviour, endurance and retention characteristics were investigated. SrTiO₃ and Sr_0.92Bi_0.08TiO₃ films grown on Si or Pt have the same phase structure, morphologies and grain size; however, the grain size of the Sr_0.92Bi_0.08TiO₃ films grown on Si is slightly larger than those of the SrTiO₃ films grown on Si and the Sr_0.92Bi_0.08TiO₃ films grown on Pt. The SrTiO₃ or Sr_0.92Bi_0.08TiO₃ films grown on Si or Pt all exhibit bipolar resistive-switching behaviour and follow the same conductive mechanism; however, the Ag/Sr_0.92Bi_0.08TiO₃/Si device possesses the highest RHRS/RLRS of 105 and the best endurance and retention characteristics. The doping of Bi is conducive to enhance the RHRS/RLRS of the SrTiO₃ films; meanwhile, the Si substrates help improve the endurance and retention characteristics of the Sr_0.92Bi_0.08TiO₃ films.

6 illus, 1 table, 37 ref

031071   PAUL S K, KUMAR S, TARAFDER S (Mechanical Engineering Dep, Indian Institute of Technology Patna, Patna 801106, Email: paulsurajit@yahoo.co.in) : Orientation-dependent crack-tip blunting and crack propagation in a single crystal BCC iron. Bull Mater Sci 2018, 41(6), 148.

Atomistic simulations of cracks with four different orientations in body-centered cubic single crystal iron are presented using molecular dynamics. Crystal orientation has considerable effect on the activation and evolution of crack propagation mechanisms. The results reveal that (a) crack-tip blunting depends on the crystallographic orientation, (b) continuous generation of dislocations form crack tip occurs for large crack-tip blunting, and (c) absence of deformation activities like dislocation generation, twin formation, etc. at the crack tip results in crack propagation in a brittle manner.

5 illus, 34 ref

031067   MANDAL S, TANNA H R, NATH A, SINGH R K, KUMAR A (ICAR-Central Institute of Agricultural Engineering, Bhopal- 462 038, Email: smandal2604@gmail.com) : Development of low cost portable biomass fired dryer for cardamom drying in hilly areas. J Environ Biol 2018, 39(6), 1021-6.

The aim of the present study was to develop a low cost portable biomass fired dryer for cardamom (Amomum subulatum Roxburgh) drying in hilly areas. A low-cost and portable biomass fired dryer was designed and evaluated for its suitability for drying large cardamom. The dryer was made in two halves containing the drying trays in upper half and the biomass burner in lower half. The upper half and lower half weighed 22 and 16 kg, respectively, making it light weight and portable. It was observed that large cardamom was dried from about 80 % initial moisture to 10 % final moisture content in 14 hrs for 20 kg loading and 19 hrs for 30 kg loading. It was also found that for drying of 20 and 30 kg fresh cardamom, 14 and 19.5 kg biomass was burnt and moisture driven away was 14.07 kg and 20.8 kg, respectively. Thus, the average fuel requirement for drying of per kg large cardamom was 0.67 kg. The cost of the dryer was found to be Rs. 8300 (USD 127.66) and cost of drying 100 kg cardamom was Rs. 245 (US $ 3.81). The developed cardamom dryer was found portable and low-cost. It consumed lesser fire wood than traditional bhatti system, required lesser drying time and delivered higher quality of dried products in terms of moisture content and colour values.

4 illus, 1 table, 25 ref

031066   LI J, FENG X-Y (Northwestern Polytechnical Univ, Xian 710 072, China, Email: 1402570898@qq.com) : Modeling of electric multipole moment in target scattering with system identification. Indian J Phys 2018, 92(12), 1561–9.

Based on the measurement of electromagnetic scattering data, the electromagnetic scattering system model of small-size targets, electrically large targets and a missile warhead of flat base are established by using the system identification method. Relations of their electric multipole moments with frequency and target size are obtained. The radiation field of electric multipole moments is almost the same as the scattered field of the corresponding target. This agreement shows the effectiveness of modeling of applying system identification to electromagnetic scattering as well as the validity of the obtained results. Target stealth method with electric multipole moments is proposed and calculations show that this new method may reduce the scattering cross-section of the target to - 30 dB up to - 50 dB. This stealth method has the characteristics of easy realization and a wide frequency band. It has explored a new approach for target stealth design.

13 illus, 22 ref

031052   CAVAS M (Mechatronics Engineering Dep, Firat Univ, Elazig, Turkey, Email: mcavas23@hotmail.com) : Improving the optical and electrical properties of NiO/n-Si photodiode by Li dopant. Indian J Phys 2018, 92(11), 1467–72.

In this study, Li-doped NiO solution was produced using a sol–gel spin coating technique. The manufactured solution was deposited onto the n-Si substrate to obtain a homogeneous thin film that could be used for photodiode production. Next, we measured the morphological, electrical, and optical parameters of the manufactured photodiode. First, the morphological properties of the thin film were studied by atomic force microscopy (AFM). Using AFM analysis software, the roughness and grain size of the thin film were estimated as 8.2–10 and 227–239 nm respectively. The optical transparency and the band gap of the Li-doped NiO thin film were studied. The optical measurements of the thin film were taken using a Shimadzu UV–Vis–NIR 3600 spectrophotometer. The transmittance of the thin film was 83.6 %, and the band gap was 3.57 eV. The current–voltage (I–V) characteristic of the photodiode was measured in the dark and under various intensities of illumination. We found that the current of the photodiode changed depending on the intensity of illumination. As the intensity of illumination increased, the current also increased, from 6.3 $\times$ 10^-7 to 3.36 $\times$ 10^-4 A. These data indicate that the photodiode is sensitive to illumination intensity and, therefore, could be used as an optical sensor. The barrier height and ideality factor of the photodiode were also determined using the thermionic emission model. The barrier height and ideality factor of the Al/n-Si/LiNiO/Au photodiode were 0.81 eV and 3.7 respectively. Also, the capacitance– voltage (C–V), the interface density (D_it), and the serial resistance of the photodiode were found to change with changing frequency. Taken together, these data show that the Li doping ratio improved the optical and electrical properties of NiO. Based on these findings, we propose that Li-doped NiO could be incorporated into optoelectronic devices, such as photodiodes and photosensors.

11 illus, 15 ref

031056   FATAHI-VAJARI A, AZIMZADEH Z (Mechanical Engineering Dep, Islamic Azad Univ, Shahryar, Iran, Email: alirezafatahi@shriau.ac.ir) : Analysis of nonlinear axial vibration of single-walled carbon nanotubes using Homotopy perturbation method. Indian J Phys 2018, 92(11), 1425–38.

This paper investigates the nonlinear axial vibration of single-walled carbon nanotubes (SWCNTs) based on Homotopy perturbation method (HPM). A second order partial differential equation that governs the nonlinear axial vibration for such nanotubes is derived using doublet mechanics (DM) theory. To obtain the nonlinear natural frequency in axial vibration mode, this nonlinear equation is solved using HPM. The influences of some commonly used boundary conditions, amplitude of vibration, changes in vibration modes and variations of the nanotubes geometrical parameters on the nonlinear axial vibration characteristics of SWCNTs are discussed. It was shown that unlike the linear one, the nonlinear natural frequency is dependent to maximum vibration amplitude. Increasing the maximum vibration amplitude decreases the natural frequency of vibration compared to the predictions of the linear models. However, with increase in tube length, the effect of the amplitude on the natural frequency decreases. It was also shown that the amount and variation of nonlinear natural frequency is more apparent in higher mode vibration and two clamped boundary conditions. To show the accuracy and capability of this method, the results obtained herein were compared with the fourth order Runge–Kuta numerical results and good agreement was observed. It is notable that the results generated herein are new and can be served as a benchmark for future works.

12 illus, 1 table, 48 ref

029686   NAIR A A, JAYARAJU M (Electronics and Communication Engineering Dep, Engineering Trivandrum Coll, Thiruvananthapuram - 695 016, Email: aparnayarphd@gmail.com) : Design and study on square lattice-based photonic crystal fibre under different air holes for supercontinuum generation. Pramana - J Phys 2018, 91(5), 66.

In this work, a comparative study is made on photonic crystal fibre (PCF) with circular and elliptical air holes in square lattice for supercontinuum generation. Using finite-element method analysis in COMSOL MULTIPHYSICS 4.3b software, numerical investigation on optical parameters such as dispersion, confinement loss, birefringence and nonlinearity has been carried out. Change in each optical parameter is observed by varying the radius of the circular air hole and the radius of the major axis of the elliptical air hole. The supercontinuum generation for the proposed PCF is also numerically simulated and studied under different power and pulse width.

11 illus, 40 ref

029684   LOLIYANA V D, PATEL P L (Civil Engineering Dep, Sardar Vallabhbhai National Institute of Technology, Surat - 395 007, Email: premlalpatel1966@gmail.com) : Performance evaluation and parameters sensitivity of a distributed hydrological model for a semi-arid catchment in India. J Earth Syst Sci 2018, 127(8), 117.

In present study, a distributed physics based hydrological model, MIKE SHE coupled with MIKE 11, is calibrated using multi-objective approach, i.e., minimization of error in prediction of stream flows and groundwater levels, using the data of eight years from 1991 to 1998 of Yerli sub-catchment (area = 15,881 km²) of upper Tapi basin in India. The sensitivity analyses of thirteen model parameters related with overland flow, unsaturated and saturated zones have been undertaken while simulating the runoff volume, peak runoff at catchment outlet and groundwater levels within the catchment with wide variations (± 50 %) in the model parameters. The calibrated model has also been validated for prediction of stream flow and groundwater levels within the Yerli sub-catchment for period 1999–2004. The simulated results revealed that calibrated model is able to simulate hydrographs satisfactorily for Yerli sub-catchment (NSE = 0.65–0.89, r = 0.80−0.95) at daily and monthly time scales. The ground water levels are predicted reasonably satisfactorily for the plain area (RMSE = 0.50–6.50 m) in the study area. The results of total water balance indicated that about 78 % of water is lost from the system through evapotranspiration, out of which about 3.5 % is contributed from the groundwater zone.

14 illus, 1 table, 39 ref

029682   GHODICHORE N, VINNARASI R, HANYA C T D, ROY S B (Civil Engineering Dep, Indian Institute of Technology, New Delhi -110 016, Email: dhanya@civil.iitd.ac.in) : Reliability of reanalyses products in simulating precipitation and temperature characteristics over India. J Earth Syst Sci 2018, 127(8), 115.

Various reanalyses have been utilized in numerous climate related researches around the globe, however, there exists considerable biasedness in these products, especially in precipitation and temperature data. The ability of these reanalysis products to simulate the precipitation and temperature patterns is observed to be satisfactory at global scale, while it differs significantly at regional scale, especially over regions of high spatio-temporal heterogeneity such as India. Therefore, it is essential to evaluate the applicability and robustness of reanalyses in climate related research. The annual and seasonal variability in spatiotemporal patterns and trends of precipitation and temperature data, with respect to the IMD gridded data over 34 yrs, are evaluated for six global reanalyses namely, NCEP/NCAR Reanalysis (NCEP R1), NCEP-DOE AMIP-2 Reanalysis (NCEP R2), Climate Forecast System Reanalysis (CFSR), ECMWF Interim Reanalysis (ERA-Interim), Modern Era Retrospective Analysis for Research and Application Land only model (MERRA-Land) and JMA 55-year Reanalysis (JRA-55). The ability of the reanalyses was tested based on several factors such as statistical and categorical indices, spells and trends, for annual and seasonal daily values. Several regional and seasonal differences were observed, particularly over high rainfall regions such as Western Ghats and northeastern India. MERRA-Land is found to give the best results for precipitation over India, which is attributed to the updated forcing data using gauge-based precipitation observations. Similarly, ERA-Interim and JRA-55 exhibit better performance for temperature than other datasets. All reanalyses failed to correctly reproduce the trends in IMD data, for both precipitation and temperature. These observations will provide a better perception on the reliability and applicability of reanalyses for climate and hydrological studies over India.

12 illus, 3 tables, 44 ref

029679   BAJARANGBALI R, MAJHI S (Electronics and Communication Engineering Dep, PES Institute of Technology - South Campus, Bangalore - 560100, Email: bajarangbali@iitg.ac.in) : Estimation of first and second order process model parameters. Proc Natl Acad Sci India A 2018, 88(4), 557–63.

In this paper, explicit expressions are proposed to estimate the unknown process model parameters during online and offline mode of operation. Mathematical expressions which are derived for second order system with time delay are generalized for second order overdamped, underdamped, critically damped, first order and unstable systems. The process information is extracted using relay with hysteresis which also reduces the effect of measurement noise. Under noisy environment as the process output is corrupted due to measurement noise, a closed loop denoising block is used to obtain noise free output. Validity of the presented method, with and without measurement noise, is demonstrated through simulation results which are compared with available methods in literature.

5 illus, 6 tables, 22 ref

029680   BANDIPALLY S, CHERIAN C, ARNEPALLI D N (Civil Engineering Dep, Indian Institute of Technology, Tamilnadu - 600 036, Email: arnepalli@iitm.ac.in) : Characterization of lime-treated bentonite using thermogravimetric analysis for assessing its short-term strength behaviour. Indian Geotech J 2018, 48(3), 393-404.

The recent research infers that the detailed characterization of lime-treated soils using analytical techniques enables better understanding of the complex soil–lime interaction mechanisms as well as the pivotal factors influencing the efficacy of lime treatment. In view of this, the present study focuses on evaluating the effects of lime treatment on the strength properties of sodium bentonite clay in terms of the variations in thermal characteristics derived by employing analytical thermogravimetric analysis. This technique is effectively used to monitor the consumption of free lime and evolution of new cementitious hydration products (viz., calcium silicate hydrate and calcium aluminate hydrate), as well as detrimental lime carbonation phenomenon occurring in the sodium bentonite-lime composite during short-term curing. Based on the comparative evaluation of untreated and limetreated sodium bentonite, variations in the weight loss corresponding to thermal decomposition of different chemical phases are estimated. The additional inferences from X-ray diffraction and Fourier transform infrared spectroscopy analyses substantiated the interpretations of thermogravimetric results regarding the lime stabilization mechanisms and consequent strength evolution in sodium bentonite-lime composites. Thus, the present study demonstrates that the comprehensive analysis of thermogravimetric results enables reliable interpretation of the soil–lime interaction mechanisms and the evolution of strength during curing.

10 illus, 2 tables, 64 ref

029687   PANDEY A, BHARGAV K S, KUMAR M, GUPTA N, PATEL N (Agril Engg Dep, R.V.S.K.V.V, Dewas - 455 001, Email: ksbhargav@rediffmail.com) : Evaluation of krishi vigyan kendratraining programme on mushroom cultivation. Plant Arch 2018, 18(2), 1655-8.

The present study was conducted in Dewas districts of Madhya Pradesh during the year 2013-14 to 2015-16 with the objective to work out the impact of mushroom trainings on knowledge and adoption. Training programme is generally conducted with a goal that the participants after being trained will translate the acquired knowledge and skill into action. Ninty trainees were imparted training on mushroom farming by conducting 5 vocational on campus training programmes. In order to evaluate these training programmes, the present study was undertaken to assess the gain in knowledge of the participants and adoption status of the enterprise of the mushroom to enhance the entrepreneurship in mushroom farming. It was showed from data that maximum number of the trainees belong to middle age group (61.11 %), having education up to middle (47.78 %) and primary (28.89 %). The maximum weighted number achieved 2.51 and minimum 1.82 by spawn production techniques and management of spent mushroom, respectively. Results revealed that most of the beneficiaries were found to be satisfied with the many aspects of training viz., training programs, course content and time and duration, facilities and overall use fullness of training.

3 tables, 7 ref

029688   PANDEY G, PANDEY V, PANDEY P R, THOMAS G (Molecular and Cellular Engineering Dep, Sam Higginbottom Univ of Agriculture, Allahabad, Email: georgethomas@shiats.edu.in) : Effect of extraction solvent temperature on betalain content, phenolic content, antioxidant activity and stability of beetroot (Beta vulgaris L.) powder under different storage conditions. Plant Arch 2018, 18(2), 1623-7.

Beetroot is a good source of natural food colorant because it contains significant amount of betalain pigment. The study target was to investigate the effect of temperature in the extraction of betalain, phenolic content and antioxidant activity as well as beetroot powder storage conditions. The extraction of betalain was performed with 5 pH and 50 % ethanol under different temperature combination (10, 20, 30, 40 and 50 °C). Further, the stability of beetroot powder during storage was analyzed by applying three different temperatures (10, 25 and 40 °C). At 30 °C, the maximum recovery of betacyanin (7.74 ± 0.38), betaxanthins (5.36 ± 0.31), total phenolic content (4.91 ± 0.66 mg/g) were obtained and at 40 °C, maximum antioxidant activity (6.91 ± 0.03 mM/g) was observed. The temperature of 10 °C was found optimum for storage of beetroot powder up to 5 weeks with minimum loss percentage and the storage results revealed that betaxanthins is more sensitive than betacyanins.

3 tables, 24 ref

028559   MANJUNATH G, VARDHAN R V, SALIAN A, JAGANNATHA R, KEDIA M, MANDAL S (Metallurgical and Materials Engineering Dep, National Institute of Technology Karnataka (NITK), Surathkal - 575 025, Email: smandal@nitk.edu.in) : Effect of annealing-temperature-assisted phase evolution on conductivity of solution combustion processed calcium vanadium oxide films. Bull Mater Sci 2018, 41(5), 126.

In this work, the effect of annealing temperature on the conductivity of solution-combustion-synthesized calcium vanadium oxide (CVO) films was studied. Conductivity was tailored by the appearance of the phases like CaVO₃, CaV₂O₅ and Ca₂V₂O₇ as a function of annealing temperature; CaVO₃ and CaV₂O₅ are responsible for high conductivity, whereas V⁵⁺ presence in Ca₂V₂O₇ contributes towards dielectric nature. Evolution of phases of CVO was identified through X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. A detailed conductivity measurement as a function of annealing temperature helps us to identify the decreasing trend of conductivity with increasing temperature up to 400^◦ C; beyond this it behaves like an insulator. There was a stable conductivity while aging the films in ambient for a few days. This study revealed safe application temperature domain of CVO, and a clear correlation of electrical conductivity with the in-depth structural–compositional–morphological study.

9 illus, 1 table, 41 ref

028552   JANA B, BHATTACHARYYA S, PATRA A (Materials Science Dep, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 32, Email: msap@iacs.res.in) : Perspective of dye-encapsulated conjugated polymer nanoparticles for potential applications. Bull Mater Sci 2018, 41(5), 122.

Design of highly luminescent nanomaterials is an emerging area of research for photonic and bio-photonic applications. Nowadays, dye-encapsulated polymer nanoparticles (PNPs) are found to be very promising alternative nextgeneration luminescent nanomaterials because of extraordinary brightness, easy synthesis, higher photo-stability and nontoxic behaviour. Herein, we have highlighted the dynamics of the fluorophore molecules inside PNPs. Furthermore, we discuss the fundamental correlation of particle brightness with the size of the PNPs as well as population of the dye molecules inside the PNPs. Considering the resonance energy transfer process, generation of white light by varying the dye concentration and singlet oxygen generation using photosensitizer dye have been described. Finally, we discuss the importance of hybrids of conjugated PNPs for potential light harvesting systems such as photovoltaic and optoelectronic applications.

5 illus, 61 ref

028549   GHOSH M, DATTA A (Spectroscopy Dep, Indian Association for the Cultivation of Science, Jadavpur - 700 032, Email: spad@iacs.res.in) : Pseudo-Jahn-Teller effects in two-dimensional silicene, germanene and stanene: A crystal orbital vibronic coupling density analysis. Bull Mater Sci 2018, 41(5), 117.

The presence of the pseudo-Jahn–Teller (PJT) effect has been investigated in the heavier analogues of graphene, namely silicene, germanene and stanene, by applying the orbital vibronic coupling density theory. In order to do so, we have made a vis-a-vis analogy with their respective planar, honeycomb molecular cluster models, namely hexasilabenzene (Si₆H₆), hexagermabenzene (Ge₆H₆) and hexastannabenzene (Sn₆H₆). One-to-one mapping of the occupied crystal orbitals and unoccupied crystal orbitals in two-dimensional (2D) Si, Ge and Sn systems to the occupied molecular orbitals and unoccupied molecular orbitals of the corresponding molecular units are used to identify PJT-active bands and compute the crystal orbital vibronic coupling density (c-OVCD) and crystal orbital vibronic coupling constants (c-OVCCs). c-OVCD and c-OVCC show the local picture of the PJT coupling in these 2D systems. This article exemplifies the fruitfulness of deciphering the structural aspects in materials based on orbitals of their corresponding simple molecular units—a reductionist quantum chemical approach to materials.

3 illus, 2 tables, 41 ref

028540   BHARDWAJ S, SHARMA R P (IIT Delhi, New Delhi - 110 016, Email: sshivanni@gmail.com) : Improving range of SPR tunability and extinction efficiency of spheroidal silver nanostructures in graphene environment. Bull Mater Sci 2018, 41(5), 123.

In photovoltaics, the materials having ability to manipulate the optical fields and coupling of energy flow inside the device play a crucial role. In this article, we report the role of graphene environment on spheroid-shaped Ag nanoparticles (NPs) with various shapes and sizes. This study confirms the tunability of surface plasmon resonances (SPRs) and an enhancement in extinction efficiency, derived numerically using discrete dipole approximation (DDA). We have chosen oblate- and prolate-shaped Ag NPs for the numerical experiment and analysed their optical signatures in terms of extinction efficiency and SPR tunability against the quasi-static approximation. The excitation of longitudinal and transversal resonances was also observed because of the asymmetric shape of Ag NPs. All optical responses have been analysed by varying the effective radii and aspect ratio of Ag NPs, and the thickness of graphene monolayer (from 0.1 to 0.5 nm). Tunability of longitudinal resonances has been observed in the 600–833 nm wavelength region, while for transversal resonances, the tunability is in the 450–505 nm wavelength range. The results represent the effect of graphene environment on the tunability of SPRs with enhanced extinction efficiency. This study could lead to the development of a photovoltaic device with wide range of tunability and enhanced efficiency.

4 illus, 32 ref

028539   BARAL M, RANJITHA A P, PRASAD S K (Centre for Nano and Soft Matter Sciences, Bengaluru - 560 013, Email: marlin.baral@cens.res.in) : Confinement of an antiferroelectric liquid crystal in a polymer nanonetwork: Thermal and dielectric behaviour. Bull Mater Sci 2018, 41(5), 135.

We report the thermal and dielectric investigations on a liquid crystal exhibiting an antiferroelectric phase and confined in a polymer network of sub-micron dimensions. Two different photo-polymerizable monomers have been employed for the purpose: one of them (HDDA) is bereft of any aromatic parts, while the other (RM82) contains aromatic as well as aliphatic units and, in fact, forms a liquid crystalline phase in its monomeric state. The polymerization, which is carried out in the presence of the liquid crystalline host, is expected to yield a nanosegregated structure for HDDA and blended structure for the RM82 case, the difference reflecting the morphologies of the networks, as evidenced by SEM images. Surprisingly, even a small concentration of the latter polymer added to the former variety has substantial influence on the morphology. The main work focusses on calorimetry and dielectric relaxation spectroscopy of the host liquid crystal confined in these nanonetworks created by the polymers, which can be considered to form virtual surfaces with a finite anchoring energy. We have investigated the in-phase and antiphase modes in the antiferroelectric phase, and the soft mode in the paraelectric phase preceding the antiferroelectric phase. The relaxation frequencies of all these modes are substantially influenced by the network, with the results showing certain surprises in cases containing both HDDA and RM82.

8 illus, 1 table, 28 ref

028538   BANDI S, HASTAK V, PESHWE D R, SRIVASTAV A K (Metallurgical and Materials Engineering Dep, Visvesvaraya National Institute of Technology, Nagpur - 440 010, Email: srivastav.ajeet.kumar@gmail.com) : In-situ TiO₂-rGO nanocomposites for CO gas sensing. Bull Mater Sci 2018, 41(5), 115.

TiO₂–reduced graphene oxide (rGO) nanocomposites were synthesized in-situ via hydrothermal route using graphene oxide (GO), TiCl₃ and ammonia solution. GO was prepared by the electrochemical exfoliation technique. The structure, phase conformation and morphology of TiO₂–rGO nanocomposite were characterized using X-ray diffraction, Fourier transform infra-red spectroscopy and scanning electron microscopy. Sensing behaviour of the TiO₂–rGO nanocomposite was examined under the 100 and 200 ppm of CO environment.

6 illus, 1 tables, 47 ref

028571   SAHIN Y, TING N S (Electrical–Electronics Engineering Dep, Bitlis Eren Univ, 13000 Bitlis, Turkey, Email: eee.yakupsahin@gmail.com) : Design, analysis and application of high set-up ZVT DC-DC converter with direct power transfer. Sadhana 2018, 43(10), 169.

In this paper, a new snubber cell for soft switched high set-up DC–DC converters is introduced. The main switch is turned on by zero-voltage transition and turned off by zero-voltage switching (ZVS). The main diode is turned on by ZVS and turned off by zero-current switching. Besides, all auxiliary semiconductor devices are soft switched. Any semiconductor device does not expose the additional current or voltage stress. The new snubber transfers some of the circulation energy to the output side when it ensures soft switching for main semiconductor devices. Thus, the current stress of auxiliary switch is significantly reduced. Besides, the total efficiency of converter is high due to the direct power transfer feature of new converter. A theoretical and mathematical analysis of the new converter is presented, and also verified with experimental set-up at 500 W and 100 kHz. Finally, the overall efficiency of new converter is 97.4 % at nominal output power.

7 illus, 2 tables, 32 ref

028564   PANDYA S N, MENGHANI J V (Mechanical Engineering Dep, S. V. National Institute of Technology, Surat - 395 007, Email: s.pandya@med.svnit.ac.in) : Developments of mathematical models for prediction of tensile properties of dissimilar AA6061-T6 to Cu welds prepared by friction stir welding process using Zn interlayer. Sadhana 2018, 43(10), 168.

Amount of intermetallics formed at the weld interface in dissimilar friction stir welding may be reduced by use of suitable interlayer materials such as Zn. In the present investigation, mathematical models have been developed for prediction of tensile properties of dissimilar AA6061-T6 to pure Cu welds prepared by friction stir welding process with Zn interlayer. Experiments were planned as per Box–Behnken design of response surface methodology. Three-factor, three-level Box–Behnken design with 15 runs was employed. Three process parameters: tool rotation speed (710, 1000 and 1400 rpm), tool travel speed (28, 56 and 80 mm/min) and tool pin offset (+0.5, +1.0 and +1.5 mm towards AA6061-T6 sheet) were considered. Lacks of fit for the developed models were assessed using analysis of variance (ANOVA). Validities of the developed models were checked by conducting confirmation runs. Predicted and experimental results of confirmation runs were found in reasonable agreements. Microstructural characterization revealed typical microstructure composed of intercalation of base metals. It was observed by X-ray diffraction analysis that use of Zn interlayer coupled with tool offset of +1.0 and +1.5 resulted in elimination of intermetallics of Al–Cu system at the weld interface, improving dissimilar weld quality.

17 illus,11 tables, 38 ref

028565   PATIDAR R, AGRAWAL S, PRATAP S (Mechanical Engineering Dep, Indian Institute of Information Technology, Jabalpur, Email: er.rakeshpatidar.sati@gmail.com) : Development of novel strategies for designing sustainable Indian agrifresh food supply chain. Sadhana 2018, 43(10), 167.

Traditional Indian agri-fresh food supply chain (AFSC) is unorganized and controlled by a large number of intermediaries, causing it to be unsustainable from the farmer (low profitability) to the customer (not getting quality product even after paying a high price). The purpose of this paper is to propose novel strategies for designing a sustainable Indian AFSC. Authors identify shortcomings as well as strengths, weaknesses, opportunities and threats (SWOT) of the Indian agriculture system through the literature survey. To improve overall performance of this chain, authors have developed eighty strategies by incorporating SWOT into TOWS (threat, opportunity, weakness and strength) matrix. They define four key objectives to mitigate the aforementioned problems. In this paper, twelve strategies are shortlisted from existing ones on the basis of fulfilling a maximum number of objectives. The shortlisting of strategies is further verified by evaluating strategies using performance measures (PMs) in sustainability dimensions, which revealed that the twelve chosen strategies dominate over other strategies. The shortlisted strategies are mainly focused on improving the economic dimension of AFSC by satisfying maximum number of objectives and PMs. The chosen strategies pledge for the optimum and most feasible ones to be recommended for managers/researchers towards redesigning the AFSC. The proposed viable strategies are expected to reform the conventional Indian AFSC by designing sustainable supply chain (SSC). The outcomes of this work will provide clear guidelines for researchers and policy makers to make sustainable agriculture.

7 tables, 72 ref

028560   MANU K V, DEY J, MATHEW J (Aerospace Engineering Dep, Indian Institute of Space Science and Technology, Trivandrum - 695 547, Email: manukv@iist.ac.in) : Boundary layer transition experiments with embedded streamwise vortices. Sadhana 2018, 43(10), 165.

Experiments were conducted with a counter-rotating, streamwise vortex pair embedded in flat plate boundary layers, in a low-turbulence wind tunnel, to understand the role of local separation on transition. Steady, streamwise vortices were generated downstream of gaps in spanwise-uniform, smooth hills (of height h) affixed to the plate, 175 mm from its leading edge. The flow between is directed away from the plate. At the four tunnel speeds 1.8–3.5 m/s considered, the Reynolds numbers based on displacement thickness at this location varied from 248 to 346. Small, medium and large gaps of 2, 4 and 8 mm, respectively, were set up; they were about a third to twice the boundary layer thickness (2=3\b=h\8=3). With the closest vortex pairs, transition was observed at all freestream speeds considered. With larger spacing, transition occurred at the highest speed only. The vortex pair caused the flow to separate in all but the largest-gap cases. Separation was steady and reattachment unsteady in all cases. Velocity fluctuations grew slightly upstream of re-attachment in transitional cases. No evidence was found for separation or re-attachment as a direct cause for transition; transition occurred even without separation. Instead, whenever transition was observed, its origin could be traced to instability of a streak of sufficient amplitude that had been created by the vortex pair. Streak instability appeared as fluctuations growing along its sides and spreading. Anomalous behaviour was also observed with moderate spacing, where transition did not occur in spite of flow separation and streak amplitudes in excess of known thresholds for streak instability.

10 illus, 1 table, 33 ref

028550   HEMADRI V, AGRAWAL A, BHANDARKAR U V (Mechanical Engineering Dep, Indian Institute of Technology Bombay, Powai, Mumbai 400076, Email: amit.agrawal@iitb.ac.in) : Determination of tangential momentum accommodation coefficient and slip coefficients for rarefied gas flow in a microchannel. Sadhana 2018, 43(10), 164.

This paper presents an experimental study of rarefied gas flow in a trapezoidal microchannel with a constant depth of 103 $\mu$m, top width of 1143 $\mu$m, bottom width of 998 lm and length of 2 cm. The aim of the study is to verify the upper limit of the validity of the second-order slip boundary condition to model rarefied gas flows. The slip coefficients and the tangential momentum accommodation coefficient (TMAC) are determined for three different gases, viz. argon, nitrogen and oxygen, and it is observed that they compare well to the literature values. The range of mean Knudsen number (Kn_m) investigated is 0.007–1.2. The non-dimensional mass flow rate exhibits the well-known Knudsen minimum in the transition regime (Kn_m $~$ 1). It is seen that the Navier–Stokes equation with a second-order boundary condition fits the data satisfactorily with a high value of correlation coefficient (r ²$>$99.95 %) in the entire range of Kn_m investigated. This work contributes by extending the range of Knudsen number studied in the context of validity of the second-order slip boundary condition.

5 illus, 2 tables, 28 ref

028573   SARKAR T, SUTRADHAR G (Jadavpur Univ, Kolkata - 700 032, Email: tannybesu@gmail.com) : Investigation on mechanical properties and wear behavior of Cu-alloyed austempered gray cast iron (AGI). Sadhana 2018, 43(10), 161.

The aim of this investigation is to assess the influence of austempering heat treatment on microstructure, mechanical properties, and wear behavior of copper alloyed AGI. Tensile and wear test samples are prepared from as-cast gray iron. Initially, samples are austenitized and then isothermally austempered at six different temperatures for the constant time period. The resulting microstructures are evaluated and characterized by means of a light microscope, scanning electron microscope (SEM) and X-ray diffraction analysis. The wear test is carried out using a ‘‘block-on-roller’’ type multi-tribotester machine. The mechanical properties and wear behavior of the AGI samples are also determined and discussed systematically. Results showed that the mechanical and wear properties of AGI are significantly enhanced in comparison with as-cast gray iron. The wear behavior of AGI samples may be correlated with microstructure and mechanical properties. The hardness, tensile strength, elongation and volume fraction of austenite act as independently in influencing the wear behavior.

16 illus, 1 table, 19 ref

028555   KUMAR A, GULATI V (Mechanical Engineering Dep, Guru Jambheshwar Science and Technology Univ, Hisar, Haryana 125001, Email: ajay.kumar30886@gmail.com) : Experimental investigations and optimization of forming force in incremental sheet forming. Sadhana 2018, 43(10), 159.

Incremental sheet forming process has been proved to be quiet suitable and economical for job and batch type production, which exempts expensive and complex tooling for sheet forming. Investigation of forming forces becomes important for selecting the appropriate hardware and optimal process parameters in order to assure perfection and precision of process. Moreover, lack of available knowledge regarding the process parameters makes the process limited for industrial applications. This research paper aims at finding out effects of different input factors on forming forces in single-point incremental forming (SPIF) process. For operation sustainability and hardware safety, it becomes critical to optimize forming forces for a given set of factors to form a particular shape. In this study, optimization of input factors has been performed to produce conical frustums with helical tool path using Taguchi analysis as design of experiment (DOE) and analysis of variance (ANOVA). The optimal experimental conditions for forming forces have been calculated as sheet thickness (0.8 mm), step size (0.2 mm), tool diameter (7.52 mm), tool shape (hemispherical), spindle speed (1000 rpm), feed rate (1000 mm/min) and wall angle (50°). Effects of tool shape and viscosity of lubricants have also been investigated. An intensive understanding of the mechanism of forming forces has been presented, which shows that force trend after peak values depends upon instant input factors that can be categorized as a safe, severe and crucial set of parameters.

12 illus, 9 tables, 23 ref

028583   YADAV N K, BALA A (Electrical Engineering Dep, DCR Science and Technology Univ, Murthal (Sonepat), Email: nareshyadhavdr@gmail.com) : Self-adaptiveness in particle swarm optimisation to enhance available transfer capability using thyristor-controlled series compensation (TCSC). Sadhana 2018, 43(9), 152.

Available transfer capability (ATC) is one of the challenging criteria under the functioning of the deregulated power system. The high demand for improving ATC is generally met using flexible alternating current transmission system (FACTS) devices in the power system. However, it suffers from serious crisis during determination of the optimal location and compensation stage of FACTS. The present study uses thyristor-controlled series compensation (TCSC) devices in order to compensate for the limitation of FACTS. Further, a novel self-adapted particle swarm optimisation (SAPSO) algorithm is proposed in this study for enhancing ATC. Experiments are carried on three benchmark bus systems such as IEEE 24, IEEE 30 and IEEE 57. Performance and statistical analyses are carried out by comparing the proposed SAPSO with the conventional PSO. Eventually, the study proves the effectiveness of the proposed method in case of ATC enhancement.

3 illus, 4 tables, 35 ref

028562   NANDY A, JOG G C (Mechanical Engineering Dep, Indian Institute of Technology Guwahati, Guwahati - 781 039, Email: arupn@iitg.ac.in) : A monolithic finite-element formulation for magnetohydrodynamics. Sadhana 2018, 43(9), 151.

This work develops a new monolithic strategy for magnetohydrodynamics based on a continuous velocity–pressure formulation. The magnetic field is interpolated in the same way as the velocity field, and the entire formulation is within a nodal finite-element framework. The velocity and pressure interpolations are chosen so that they satisfy the Babuska–Brezzi (BB) conditions. In most of the existing formulations, a stabilized formulation is used that requires a stabilization term, and some associated mesh-dependent parameters that need to be adjusted. In contrast, no such parameters need to be adjusted in the current formulation, making it more user-friendly and robust. Both transient and steady-state formulations are developed for two- and threedimensional geometries. An exact linearization of the monolithic strategy ensures that rapid (quadratic) convergence is achieved within each time (or load) step, while the stable nature of the interpolations used ensures that no instabilities arise in the solution. An existing analytical solution is corrected. The coarse mesh accuracy is shown to be better compared with other existing strategies in several benchmark problems, showing that the developed formulation is both robust and efficient.

14 illus, 2 tables, 33 ref

028541   CHAWARE P, SEWATKAR C M (Mechanical Engineering Dep, Engineering Pune (Affiliated to SPPU, Pune) Coll, Pune - 411 005, Email: cms.mech@coep.ac.in) : Effects of tangential and radial velocity on fluid flow and heat transfer for flow through a pipe with twisted tape insert-laminar flow. Sadhana 2018, 43(9), 150.

The present study reports the numerical analysis of fluid flow and heat transfer in a pipe with full length twisted tape insert. The investigation is carried out for five different twist ratios of 4, 5, 6, 8 and 10 at 100 $\le$ Re $\le$ 1000. The velocity field in terms of streamwise, tangential and radial velocity and temperature field are studied as a function of Reynolds number and twist ratio. The variation of friction factor and Nusselt number with Reynolds number for different twist ratios is also presented. The heat transfer enhancement due to insertion of twisted tape mainly comes from the tangential and radial components of velocities, which are regarded as secondary fluid motion. It is evident from the results that with increase in Reynolds number the axial convection increases. However, with the decrease in the twist ratio, the tangential and radial convection increases, leading to increased heat transfer. The secondary flow affects the thermal boundary layer inside the tube and increases the cross-flow mixing, which increases the heat transfer. The correlations for prediction of friction factor and Nusselt number based on the numerical data are also proposed.

14 illus, 1 table, 21 ref

028561   MUKHERJEE A, SENGUPTA A (Electrical Engineering Dep, Indian Institute of Engineering Sciences and Technology, Shibpur, Howrah 711103, Email: amukherjee966@gmail.com) : Delay-dependent stabilization of Lipschitz nonlinear systems. Sadhana 2018, 43(9), 148.

This work proposes an improvement over existing delay-dependent stabilization technique for linear systems having time-varying delays and norm-bounded uncertainties. The method is based on linear matrix inequalities (LMIs). Parameter tuning or iterative techniques are not required to get the required controller, if the proposed LMIs are satisfied. The method is also extended for systems having Lipschitz nonlinearities.

4 illus, 2 tables, 38 ref

028557   LAKSHMI K, RAO A R M (CSIR-Structural Engineering Research Centre, Chennai - 600 113, Email: lakshmik@serc.res.in) : Output-only damage localization technique using time series model. Sadhana 2018, 43(9), 147.

In this paper, we present a technique to detect the time instant and location of damage in civil structures using scalar time series models, by handling operational variability and measurement noise. The scalar Autoregressive (AR) and Autoregressive with exogenous inputs (ARX) models are used to obtain the time instant of damage and its spatial location. The spatial damage feature to locate the damage is obtained using a metric constructed from the probability density values of the prediction errors of AR–ARX model. The proposed method does not resort to any computationally expensive vector time series models to locate the damage and so highly preferable in smart wireless online continuous SHM schemes. Numerical simulation studies are carried out by using a simply supported beam model. The results of the studies indicate that the proposed technique is capable of identifying both the time instant and location of damage accurately using the proposed PDF based damage index. In order to validate the proposed technique with experimental results, the time-history data from the three-story bookshelf benchmark structure of EI-LANL is used. Finally, the laboratory experimental studies carried out on an RCC simply supported beam with inflicted damage are also presented. The experimental studies clearly indicate the effectiveness of the proposed damage index to detect the location of damage, by handling operational variability and measurement noise.

17 illus, 4 tables, 48 ref

028548   GHOSH A, SARMAH S P, JHA J K (Industrial and Systems Engineering Dep, Indian Institute of Technology Kharagpur, Kharagpur, Email: arindamiitan@gmail.com) : Collaborative model for a two-echelon supply chain with uncertain demand under carbon tax policy. Sadhana 2018, 43(9), 144.

Consideration of carbon policies while optimizing supply chain operations has become imperative as governments and regulatory bodies throughout the world have implemented different carbon policies to reduce emissions of greenhouse gasses, especially CO₂. ‘‘Carbon tax’’ is one of the major carbon policies, initiated by several governments to curtail emissions. In this study, we have considered this policy to optimize the total expected cost (TEC) of a two-echelon integrated supply chain with stochastic demand, where both backorders and lost sales are permitted. An unconstrained mixed integer non-linear programming (MINLP) problem is formulated and further solved to find the optimal production rate, order quantity, number of shipments and reorder point while minimizing the TEC. Emissions from all the major sources such as production, inventory and transportation have been taken into consideration. It is assumed that the emission from production is a function of production rate, and emission from transportation depends on payload and vehicle type. This study will help organizations to reduce cost and emissions, and regulatory bodies to decide proper tax rate on carbon emission.

8 illus, 6 tables, 45 ref

028537   BAHADOR M, KESHTKAR M M, ZARIEE A (Mechanical Engineering Dep, Islamic Azad Univ, Kerman, Iran, Email: mkeshtkar54@yahoo.com) : Numerical and experimental investigation on the breast cancer tumour parameters by inverse heat transfer method using genetic algorithm and image processing. Sadhana 2018, 43(9), 142.

This study presents numerical and experimental investigation on breast cancer tumour parameters by inverse heat transfer method using genetic algorithm (GA) and image processing (IP) to determine the depth and rate of heat generation of a breast cancer tumour. To simulate the problem, using the energy equation in a cylinder including a heater, the surface temperature distribution was obtained. Then, the temperature surface of the cylinder was analysed by the GA in MATLAB software to determine the depth and rate of heat generation of heater. The validity of the numerical method was evaluated using the IP from a laboratory sample. A thermal heater was placed inside a cylinder and was covered by a tissue similar to the human body tissue. According to the obtained results, it was determined that the results of the laboratory sample and the numerical method were in agreement with each other. Finally, these steps were applied on the thermal image of a patient’s cancer breast to determine the depth and rate of heat generation of the breast tumour. It is shown that the average computational error between numerical and experimental results in this method to determine the depth of the tumour is about 8–10 % and to determine the rate of tumour heat generation is about 0.01–1 %.

13 illus, 3 tables, 19 ref

028582   VARADHARAJAN R, KAMIN M, GANESH S, MATHEW J (Wageningen Research Center Univ, 6708 WE Wageningen, The Netherlands, Email: ramanathan.varadharajan@wur.nl) : On jet instability modes of a subsonic Hartmann whistle. Sadhana 2018, 43(9), 140.

Numerical experiments to understand the resonant acoustic response of a subsonic jet impinging on the mouth of a tube, known as the Hartmann whistle configuration, were performed as large-eddy simulations. The tube length was chosen so that its fundamental duct mode, for one end closed and one end open, would match the dominant mode in the exciting jet. When the tube mouth was placed in the path of a regular stream of vortex rings, formed by the instability of the jet’s bounding shear layer, a strong resonant, tonal response (whistling) was obtained. At three diameters from the jet, OASPL was 150–160 dB. A tube with a thicker lip generated a louder response. When the tube was held closer to the nozzle exit, the impinging unsteady shear layer could not provoke any significant resonance. The simulations reveal that the tonal response of a Hartmann whistle operating in subsonic mode is significant.

3 illus, 2 tables, 27 ref

028572   SANGMESH B, GOPALKRISHNA K, MANJUNATH S, KUMKAR M N, KUMAR G V (Visvesvaraya Technological Univ, Balagavi, Karnataka, Email: sangmesh.sangu293@gmail.com) : Heat transfer enhancement in a high power LED using heat sink with liquid pockets. J Sci Ind Res 2018, 77(10), 600-3.

This study presents an experimental investigation on two types of heat sinks, a novel Heat sink with liquid pockets (HSLP) and the other one being conventional heat sink. The heat transfer characteristics of the HSLP were investigated experimentally using passive cooling method. For this purpose, an experimental setup was built by drilling longitudinal holes in the base of heat sink. The holes were filled with De-ionized (DI) water to enhance heat transfer in high-power LED COBs. The junction temperature of the LED was measured, to measure increased heat transfer. The thermal performance of aluminium heat sink with liquid pockets was studied with parameters such as fill ratio, influence of liquid cooling and orientation effect. The performance of the HSLP was found to be better than conventional heat sink of same geometry due to its lower thermal resistance. The HSLP performs better than the conventional heat sink for 15°orintation, 100 vol. % with De-ionized water. Fluid channels filled with liquid in the heat sink have a noticeable effect on heat removal rate.

3 illus, 2 tables, 5 ref

028566   PHONGSAVATH A, PANNUCHAROENWONG N, BENJAPIYAPORN C (Automotive Engineering Dep, Thammasat Univ, Thailand 12120, Email: nattadon.pa@gmail.com) : Inlet water temperature reduction in ice production machine inlet water temperature reduction in ice production machine. J Sci Ind Res 2018, 77(10), 596-9.

This research proposes a performance improvement method of a tube ice production machine using the installation of a heat exchanger. At the end of an ice production process, there are cold rejected water from the defrost process. The cold rejected water are stored at the sump below the cooling tower. A prototype heat exchanger is submerged inside the sump. Incoming water for the next cycle was flown through the heat exchanger and are cooled before entering the cooling tower. The results showed that there are reduction in power consumption and the average production time reduced by 7.58 percent. As the system is more efficient, the machine’s production capacity is increased by 6 percent while being able to reach the payback period of the investment in less than five months.

3 illus, 3 tables, 6 ref

028576   SINGH P K, SHARMA K (Mechanical Engineering Dep, GLA Univ, Mathura, Email: kamal.sharma@gla.ac.in) : Molecular dynamics simulation of glass transition behavior of polymer based nanocomposites. J Sci Ind Res 2018, 77(10), 592-5.

Molecular Dynamics (MD) simulations were carried out to explore the effect of functionalization of graphene on the visco-elastic properties of epoxy based nanocomposites. Pristine graphene, graphene functionalized with amine (−NH₂) group and carboxyl (−COOH) group respectively involved in this research. The simulation result shows that glass transition temperature (T_g ) of the graphene epoxy based nanocomposites are higher than that of pure epoxy. The computational findings of T_g agrees well with the experimental results. Thus, the present MD simulation study can serve as good computational evidence for the existing experimental results on the T_g of graphene epoxy composites.

3 illus, 16 ref