001328   BHATTACHARYA A, ROY B, CHOWDHURY S K, BHATTACHARJEE A K (Electronics and Communication Engineering Dep, National Institute of Technology, Durgapur - 713 209) : Compact printed hexagonal ultra wideband monopole antenna with band-notch characteristics. Indian J Pure Appl Phys 2019, 57(4), 272-7.

This article presents a compact, printed hexagonal monopole, ultra wideband antenna along with band-notch characteristics. The proposed monopole antenna consists of a printed hexagonal radiating element and a defected ground structure. Printed round-slot geometry and defected ground structure play a vital role in achieving the ultra wide bandwidth. Band-notch characteristics for eliminating the interference arising from the existing WLAN (5.15 – 5.825 GHz) band has been incorporated in the antenna frequency response by the insertion of C-shaped stubs near the feeding segment. The antenna shows a decent gain of ≥ 3.0 dBi throughout the entire bandwidth except at the notched frequency band. Measured results agree well with the simulated values.

12 illus, 15 ref

001342   JOYA M R, BARBA-ORTEGA J, RABA A M (Fisica Dep, Nacional de Colombia Univ, Bogotá, Colombia) : Vibrational Raman modes and particle size analysis of cupric oxide with calcination temperature. Indian J Pure Appl Phys 2019, 57(4), 268-71.

In this work a study of the effect of the synthesis conditions on the vibratory and particle size properties in the cupric oxide (CuO) has been presented. The synthesis has been carried out by the polymeric precursor method without modifying the PH in the process, this being a low cost method. The samples obtained have been subjected to several calcination temperatures, 450 °C, 550 °C, 650 °C and 800 °C. In particle analysis by X-ray, scanning electron microscopy (SEM) and statistical it has been observed that for very low or very high calcination temperatures the particle size increases, finding 650 °C as the best calcination temperature. In the Raman spectra, the Ag and Bg vibration have been presented in the samples, with the peaks being narrower for the temperature of 450 °C.

4 illus, 1 table, 12 ref

001356   NAGANATHAPPA M, CHAUDHARI A (Physics Dep, Government Vidarbha Institute of Science & Humanities, Amravati - 444 604) : Theoretical and experimental study of dimethyl sulfoxide and N-substituted DMSO. Indian J Pure Appl Phys 2019, 57(4), 261-7.

Infrared spectrum of dimethylsulfoxide (DMSO) has been studied using quantum chemical calculations and FTIR spectroscopy. Theoretical infrared and electronic absorption spectra for the ions of DMSO, DMSO in water solvent and nitrogen substituted DMSO (N-DMSO) have also been obtained using second order Møller-Plesset and 6-311++g(d,p) basis set. The IEFPCM model has been used to study the solvation effect for DMSO. The geometrical parameters and dipole moments for the neutral DMSO have been compared with the available experimental determinations. Calculated vibrational frequencies have been compared with the experimental frequencies for the DMSO obtained using FTIR spectrometer. Rotational and centrifugal distortional constants for these molecules have been reported. The electronic absorption spectra of DMSO, its ions, and N-DMSO have been obtained using time dependent density functional theory (TDDFT) approach. Almost all the vibrational modes in the vibrational spectrum of DMSO anion are intense whereas fewer intense modes have been observed in the vibrational spectra of DMSO, its cation, DMSO in water solvent and N-DMSO. The most intense mode is different for DMSO, its ions and N-DMSO. The S=O stretching mode is the most intense mode for DMSO as well as DMSO in water solvent and it is red shifted by 62 cm^-1 in latter than the former.

3 illus, 4 tables, 27 ref

001354   MANIMARAN S, SAMBATHKUMAR K, RAJKAMAL N, VENKATACHALAPATHY M, CHANDRASEKARAN K (Physics Dep, A A Government Arts Coll, Villupuram - 605 602) : Spectroscopic (FT-IR, FT-Raman and NMR) and NBO analysis of 3, 4-dimethylanisole by density functional method. Indian J Pure Appl Phys 2019, 57(4), 236-49.

Combined experimental and theoretical studies have been conducted on the molecular structure and vibrational, spectra of 3, 4-dimethyl anisole (DMA). The FT-IR and FT-Raman spectra of DMA have been recorded in the solid phase. The molecular geometry and vibrational frequencies of DMA in the ground state have been calculated by using the ab-initio Hartree-Fock (HF) and density functional methods (B3LYP) invoking 6-31+G (d,p) basis set. The optimized geometric bond lengths and bond angles obtained by HF method shows best agreement with the experimental values. Comparison of the observed fundamental vibrational frequencies of DMA with calculated results by HF and density functional methods indicates that B3LYP is superior to the scaled HF approach for molecular vibrational problems. The difference between the observed and scaled wave number values of most of the fundamental is very small. The thermodynamic functions and atomic change of the title compound has also been performed at HF/B3LYP/6-31+G(d,p) level of theories. A detailed interpretation of the FT-IR, FT-Raman, NMR spectra of DMA has also been reported. The theoretical spectrograms for infrared and Raman spectra of the title molecule have been constructed. The thermodynamic function of the title compound has also been performed at HF/6-31+G (d,p) and B3LYP/6-31+G (d,p) level of theories. Natural bond orbital analysis has been carried out to explain the change transfer or delocalization of change due to the intra-molecular interactions. Energy of the highest occupied molecular (HOMO) orbital and lowest unoccupied (LUMO) molecular orbital have been predicted.

6 illus, 9 tables, 28 ref

001377   UNIYAL M, BHATT S C, KASHYAP S (Physics Dep, H N B Garwal Univ, Srinagar (Garwal) - 246174) : Preparation and ultrasonic study of sodium potassium tantalate (Na_1-xK_xTaO₃) mixed system. Indian J Pure Appl Phys 2019, 57(3), 212-6.

Ultrasonic velocity of the piezoelectric ceramic pellets of ferroelectric material Na_1-xK_xTaO₃ (X=0, 0.2, 0.3, 0.4, 0.5, 0.6 and 1.0) have been investigated at temperature 32 ºC and frequency 5 MHz with the help of ultrasonic c-scan system developed at NPL, New Delhi. The samples have been prepared by the conventional solid-state reaction method and sintering process.

3 illus, 3 tables, 29 ref

001368   SHARMA R P, PAUL A (JECRC Univ, Jaipur - 303 905) : Transient natural convection magnetohydrodynamic motion over an exponentially accelerated vertical porous plate with heat source. Indian J Pure Appl Phys 2019, 57(3), 205-11.

Effects of heat source on the magnetohydrodynamic (MHD) one-dimensional flow past a vertical surface have been analyzed. Thermal radiation effect is present. The Laplace transformation procedure reduces the involved governing PDEs into the ODEs and hence closed form solutions have been obtained. The effect of permeability parameter (k), heat source parameter (Q), thermal radiation (R), suction parameter (γ), magnetic field parameter (M) have been analyzed on the velocity and temperature distributions, Skin friction coefficient (τ) and Nusselt number (Nu). The convergence of the obtained solutions has been seen through graphical results. Effects of skin friction (τ) and the Nusselt number (Nu) for different parameters have also been analyzed.

14 illus, 20 ref

001373   SURESH G, SAHADEVAN K, SAMBATHKUMAR K, KUMARESAN P (Physics Dep, Agignar Anna Government Arts Coll, Villupuram - 605 602) : Significance of HOMO and LUMO studies on dye doped glycene lithium sulphate (GLS) crystals for non-linear optical applications. Indian J Pure Appl Phys 2019, 57(3), 196-204.

The ideal material that could have potential applications in non-linear optical (NLO) devices should possess the combination of large non-linear figure of merit for frequency conversion, high laser damage threshold, fast optical response time, wide phase matchable angle, architectural flexibility for molecular design and morphology, optical transparency and high mechanical strength. The stability of glycene lithium sulphate (GLS) single crystal has been improved by doping organic dyes. The structural, chemical, optical, mechanical and non-linear optical properties of the dye doped crystals have been analyzed with the characterization studies such as powder XRD, FT-IR, UV-Visible and SHG measurements, respectively. NMR, HOMO and LUMO energies have been performed by time dependent density functional theory (TD-DFT) approach. The Mulliken charge analysis indicates that the sulphur atoms of the benzene ring and the OH group attached to the ring are the main reactive centers of glycene lithium sulphate. And the temperature dependence of the thermodynamic properties of constant pressure (C_p), entropy (S) and enthalpy change (ΔH0→T) for glycene lithium sulphate have also been determined.

11 illus, 6 tables, 28 ref

001364   SENTHILKUMAR P, GANESH T, VINOTH K, SYLVESTER M M, KARUNAKARAN D J S A, HUDGE P, KUMBHARKHANE A C (Physics Dep, Bharathidasan Univ, Thanjavur - 613 005) : Dielectric relaxation and molecular interaction investigation of glycolic acid-water mixture using time domain reflectometry. Indian J Pure Appl Phys 2019, 57(3), 180-7.

The complex spectra of glycolic acid (GA) and water mixture have been measured by time domain reflectometry (TDR) in the frequency range 10 MHz to 30 GHz at various temperatures for entire concentration. Dielectric relaxation time (τ), static dielectric constant (ɛ₀) and dielectric permittivity at low frequency (ɛʹ) and at optical frequency (ɛʺ) have been determined from measured complex spectra (ɛ*) using non-linear square fit method. Conductivity, Kirkwood and effective Kirkwood correlation factor of mixture calculated from the determined dielectric parameters have been used to find the alignment of dipoles between molecules. Thermodynamic parameters enthalpy, entropy and Gibb’s free energy have been determined which enable the direction of reaction. Excess permittivity of glycolic acid-water mixture has also been determined which confirms the molecular interaction. Macroscopic parameters such as density and viscosity of mixture have been determined at room temperature. FTIR spectral characterization concedes the solute-solvent interaction.

9 illus, 1 table, 44 ref

001345   KHAVALE S V, LOKHANDE B J (Solapur Univ, Solapur, Maharashtra) : Optimizations of preparative parameters in potentiodynamic synthesis of cobalt oxide thin films: Capacitive approach. Indian J Pure Appl Phys 2019, 57(3), 166-74.

The present article reports synthesis of Co₃O₄ thin films by facile potentiodynamic-electrodeposition technique using variations in the preparative parameters such as ingredient, solution concentration and deposition time. The prepared samples were analysed using XRD, FE-SEM, TEM, cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. Crystallographic study shows polycrystalline face centered cubic spinel structure of the deposit. Cyclic voltammogram reveals pseudocapacitive behavior. The calculated highest value of specific capacitance at the scan rate 5 mV/s was 237.68 F/gin 1 M KOH, within the potential window -0.92 to 0.45 V versus Ag/AgCl. The calculated maximum value of specific energy, specific power and columbic efficiency from chronopotentiometry were 4.91 Wh/kg, 28.69 kW/kg and 94.78 %, respectively. The internal resistance observed using electrochemical impedance spectroscopy was~ 3.55 Ω.

11 illus, 1 table, 43 ref

001370   SINGH S, SINGH D, SINGH M (CSIR-National Physical Laboratory, New Delhi - 110012) : Synthesis of nanostructured thin films for resolution and diffraction/ camera length calibration of transmission electron microscopes. Indian J Pure Appl Phys 2019, 57(3), 157-65.

Transmission electron microscope (TEM) is one of the highly sophisticated, sensitive and accurate tool for carrying out microstructural detailed investigations of the materials in terms of their crystallographic structure, lattice imaging, phase identification, variety of defects present, particle size and shape analysis, etc., at the nano scale level. The accuracy and efficiency of electron microscope depends upon the magnification and resolution of the instrument. Evaporated films of gold, magnesium oxide, and thallium chloride make excellent calibrating substances since they have d (interplaner spacing) values accurately determined by x-ray diffraction. In the present investigations, preliminary studies on thermally evaporated thin films of high purity tin and silver deposited on KCl substrate and carbon coated Ni/Cu TEM grids under high vacuum conditions (of the order of 10^-6 torr) have been undertaken. These films have been characterized for particle shape, size, lattice imaging by using TEM, high resolution transmission electron microscope (HRTEM) and selected area electron diffraction (SAED) pattern. The deposition process of nanoparticles has precisely been monitored to get high quality, stable and with repeatable and uniform sized particles. The aim of the study is to optimise the synthesis parameters to deposit uniformly distributed nano size gold particles using thermal evaporation technique which will be further used as a standard sample for the calibration of camera length and resolution of TEM.

10 illus, 2 tables, 12 ref

001382   ZHONG J, MA D, REN J, YAO L (Nanjing Univ of Science and Technology, Nanjing 210094, China, Email: zhongjianlin@njust.edu.cn) : Lubrication performance analysis of sealing structures in rodless open cylinders. Sadhana 2019, 44(4), 96.

As the lubrication performance of sealing structures in rodless open cylinders varies with sliding velocity, the concept of a critical velocity is proposed based on the aforementioned characteristics and the lubrication performance of sealing structure is analysed. A finite-element model of sealing structure is established and the oil film load under dynamic lubrication condition is obtained. A two-dimensional theoretical model of lubrication performance in sealing structure is established based on the proposed critical velocity. The influence on critical velocity of parameters including pre-compression, geometry size and microscopic morphology is analysed. Considering surface microscopic morphology, generation of heat by friction, heat flux distribution and other factors, a three-dimensional numerical model of lubrication performance of sealing structure is established to reveal the influence of texture mechanism on lubrication performance. As concluded, with the increase of pre-compression, the lip angle and the temperature of lubrication oil, the critical velocity increases. The three-dimensional microscopic morphology of seal ring is found to pose obvious influence on critical velocity, and the isotropic microscopic morphology tends to form total lubrication under the same conditions.

16 illus, 2 tables, 26 ref

001325   ATES A (Selcuk Univ, Konya, Turkey, Email: aates@selcuk.edu.tr) : Transient conjugated heat transfer in thick walled pipes with axially periodic surface temperature in downstream region. Sadhana 2019, 44(4), 82.

Thermal entrance region transient conjugate heat transfer is investigated involving fluid axial heat conduction for laminar pipe flows. Constant outer wall temperature boundary condition is assumed in the upstream region of a thick walled, two regional pipe. In the downstream region, the outer wall temperature is considered changing spatially in a periodical manner. The problem is solved numerically by a finite difference method. A parametric analysis is conducted in order to determine the effects of Peclet number, wall thickness ratio, wall-to-fluid thermal conductivity ratio, wall-to-fluid thermal diffusivity ratio and axial frequency on heat transfer characteristics. It is seen that, the results are highly dependent on the parameter values and the most effective ones are the Peclet number and the wall thickness ratio. It is observed that heat is transferred towards upstream due to the axial conduction in the wall and in the fluid and with increasing values for high axial frequency.

17 illus, 2 tables, 34 ref

001367   SHARMA A, AMARNATH M, KANKAR P K (Indian Institute of Technology, Indore - 453 552, Madhya Pradesh, Email: pavankankar@gmail.com) : Nonlinear dynamic analysis of defective rolling element bearing using Higuchi’s fractal dimension. Sadhana 2019, 44(4), 76.

In the present study, localized surface defects are modelled in inner race and outer race, and nonlinear dynamic behaviour of the system has been observed and quantified using Higuchi’s fractal dimensions. The Hertzian contact among the rollers and races, clearance and nonlinear damping are considered as sources of nonlinearity. Dynamic responses show system behaviour as periodic, quasi-periodic and chaotic at different rotor speeds. The onset of chaotic motion is identified using Poincare´ maps and Higuchi’s fractal dimensions. The system shows low peak-to-peak amplitude of vibration responses at higher speeds in the presence of defects. Results also indicate that Higuchi’s fractal dimensions can be effectively used as a diagnostic tool for health monitoring.

11 illus, 4 tables, 44 ref

001335   DHOLEY S (Mathematics Dep, M.U.C. Women’s Coll, Burdwan - 713 104, West Bengal, Email: sdholey@gmail.com) : Unsteady hydromagnetic flow and heat transfer of a viscous fluid near a suddenly accelerated flat surface. Sadhana 2019, 44(3), 68.

The unsteady boundary layer flow and heat transfer near a suddenly accelerated flat surface in an unbounded mass of hydromagnetic viscous fluid with the combined influence of the magnetic field, viscous dissipation, internal heat generation/absorption and thermal radiation have been investigated. A new similarity transformation is recommended, which transforms the hydromagnetic boundary layer equations into a set of non-linear ordinary differential equations. These equations are then solved numerically using the finite-difference method for some values of the governing parameters that involve unsteadiness parameter $\mathrm{\beta }$, heat source/ sink parameter $\mathrm{\lambda }$, Eckert number E, magnetic interaction parameter M, radiation parameter N and Prandtl number Pr. The influence of these parameters on the velocity as well as the temperature field is investigated in detail. In particular, the impact of viscous dissipation (measured through E), which is a strong function of constant reference temperature T_ref , on the temperature field has been investigated in different situations. This entails considering the value of T_ref as positive or negative depending on whether the surface temperature is higher or lower than the fluid temperature. The analysis reveals that there exists a critical value of E depending upon the values of the other physical parameters for which the surface heat flux vanishes. Below this critical value, heat flows either from the surface to the fluid or from the fluid to the surface depending on whether T_ref > or < 0.

11 illus, 22 ref

001353   MANABENDRA M D, MATHUR J S, VENGADESAN S (Applied Mechanics Dep, Indian Institute of Technology Madras, Chennai - 600 036, Tamil Nadu, Email: vengades@iitm.ac.in) : Recurrence studies of insect-sized flapping wings in inclined-stroke plane under gusty conditions. Sadhana 2019, 44(3), 67.

Global recurrence plots (GRPs) and windowed recurrence quantification analysis (WRQA) are two recurrence paradigms which find wide applications to detect the onset of instability in a dynamic system. The present work reports the attempt to employ these recurrence paradigms to assess the effect of frontal gust on the force patterns of an insect-sized flapping wing in the inclined-stroke plane. Horizontal and vertical forces generated by the flapping wing in the presence of gusts of the form u_G/u_w = u_$\infty$/u_w + (u_g/u_w) sin (2$\mathrm{\pi }$t f_g/f_w) were numerically estimated in the 2D reference frame for Re = 150. Nine gusts with combinations of the ratio of gust frequency to wing’s flapping frequency, f_g/f_w = 0.1, 0.5 and 1 and ratio of gust velocity amplitude to root mean square averaged flapping velocity, u_g/u_w = 0.1, 0.5 and 1 were considered. Recurrence studies of the forces were carried out to find out the gusty condition, which would trigger an onset of unstable behaviour. Studies indicated a possible onset of instability in the force patterns for gust with f_g/f_w = 0.1 and u_g/u_w = 1. The onset of unstable behaviour was prominently captured by WRQA of the vertical force coefficient based on determinism (DET) and laminarity (LAM) series.

21 illus, 6 tables, 60 ref

001362   RAO T G, MURTHY J V R, RAO G S B (Basic Sciences and Humanities Dep, Gudlavalleru Engineering Coll, Gudlavallru - 521 356, Andhra Pradesh, Email: govind.tangudu@gmail.com) : Longitudinal oscillations of a circular cylinder in a micro-polar fluid: Case of resonance. Sadhana 2019, 44(3), 66.

The problem of the longitudinal oscillations of a circular cylinder along its axis of symmetry in an incompressible micro-polar fluid and the flow generated due to these oscillations in the fluid is considered. The Stokes flow is considered by neglecting nonlinear convective terms in the equations of motion on the assumption that the flow is so slow that oscillations’ Reynolds number is less than unity. Here we get a rare, but distinct special case referred to as resonance in which material constants are interrelated in a particular way. In nonresonance case, all material constants are independent and are not related. The solution in this case cannot be obtained as limiting case of a non-resonance problem. The velocity and micro-rotation components of the flow for the case of resonance and non-resonance are obtained. The skin friction acting on the cylinder is evaluated and the effect of physical parameters like micro-polarity and couple stress parameter on the skin friction due to oscillations is shown through graphs.

8 illus, 11 ref

001331   CHEN B, ZHANG L, LUO Q, ZHANG Q (Chongqing Univ, Chongqing 400044, People’s Republic of China, Email: 20153201011@cqu.edu.cn) : The thermodynamic analysis of an electrically supercharged Miller Cycle gasoline engine with early intake valve closing. Sadhana 2019, 44(3), 65.

Electric superchargers are able to improve the thermodynamic process of gasoline engines by selfadapting running state to dominate intake air in all operation conditions. This paper proposes a novel approach for electrically supercharged Miller Cycle with early intake valve closing based on thermodynamics to settle the fuel economy problem of gasoline engines at low load operations by taking advantages of the domination of electric superchargers to intake air. Electrically supercharged Miller Cycle with early intake valve closing was realized by matching an electric supercharger, redesigning the inlet cam, and setting the intake valves closing before bottom dead center while keeping intake valves opening constant. An over-expanded engine cycle is attempted to be used to promote thermal efficiency by increasing geometric compression ratio, in addition to maintaining the effective compression ratio. Here, it has been attempted to systematically analyze the law of the energy losses of the electrically supercharged Miller Cycle gasoline engine with early intake valve closing using a reliable thermodynamic model from the perspective of heat engine. The results indicate that electrically supercharged Miller Cycle with early intake valve closing could improve the thermal efficiency of gasoline engines by significantly decreasing the pumping and exhaust losses.

11 illus, 1 table, 32 ref

001334   DESHMUKH A A, SINGH D, RAY K P (Electronics and Telecommunication Dep, Dwarkadas J Sanghvi Coll of Engineering, Mumbai - 400 056, Email: amitdeshmukh76@gmail.com) : Modified designs of broadband E-shape microstrip antennas. Sadhana 2019, 44(3), 64.

Wideband designs of rectangular microstrip antennas embedded with three rectangular slots are proposed. These slots modify resonance frequencies of patch’s TM₁₀, TM₀₂ and TM₁₁ mode, to give bandwidth of more than 500 MHz (50 %). Further, pair of slots cut variations of rectangular patch with three slots is proposed. Additional pair of slots tune the next higher order TM₁₂ mode frequency with respect to modified lower order resonant modes, resulting in further increase in bandwidth of more than 600 MHz (>55 %). Increased bandwidth obtained in the proposed designs is more than that obtained from equivalent E-shape and U-slot cut patches. As compared with $\mathrm{\psi }$-shape patch antenna, the proposed configurations yield wider bandwidth with 38 % reduction in patch size.

13 illus, 2 tables, 15 ref

001379   VISHNU S B, KUZHIVELI B T (National Institute of Technology Calicut, Calicut - 673 601, Email: vishnusb90@gmail.com) : Effect of micro- and elevated gravity condition on the evolution of stratification and self-pressurization in a cryogenic propellant tank. Sadhana 2019, 44(3), 63.

An efficient way of handling and storing cryogenic propellant is required for future space exploration. In rocketry applications, propellants are stored at subcooled conditions in foam-insulated tanks. Any kind of heat infiltration may lead to stratification and self-pressurization of the tank. The supply of warm propellant beyond the cavitation limit to a turbo-pump is dangerous and hence additional propellant has to be loaded, which affects the payload capacity. The evolution of stratification during lift-off and accelerated conditions and coast phase will be different from those during normal ambient conditions. During lift-off the gravity value can reach up to 6 g and microgravity ($\mathrm{\mu }$g) conditions at the coast phase. Hence, accurate prediction of the state of propellant at all stage is required for the successful mission planning. A multiphase axis-symmetric CFD model is developed, which can simultaneously account for heat transfer from the ambient and heat exchanges within the fluids during different gravity conditions. The results show that the self-pressurisation in microgravity condition is due to phase change rather than thermal stratification. The flow velocity will be maximum during lift-off and accelerated condition. Hence, greater self-pressurisation happens during the initial period and reduction in pressure rise rate is noticed later, which is due to turbulence of the fluid.

9 illus, 1 table, 13 ref

001366   SHARMA A K, JOSHI A S (Advanced Lasers and Optics Div, Raja Ramanna Centre for Advanced Technology, Indore - 452 013, Email: aksharma@rrcat.gov.in) : On the estimation of absolute grating groove density and inter-grating groove density errors of laser pulse compression gratings. Sadhana 2019, 44(3), 59.

In this paper, experimental studies on estimation of absolute groove density of gratings and intergrating groove density errors are reported with typical detector limited accuracies of ± 0.23 lines mm^-1 and ± 0.005 lines mm^-1 , respectively at groove density of ~1740 lines mm^-1 of holographic laser pulse compression gratings. A simple single detector based optical set-up with fixed optical elements to avoid mechanical eccentric errors, if any, due to goniometric movement of a rotatory stage, has been proposed to estimate absolute groove density of gratings. A modified Fizeau or a modified Michelson interferometer based optical set-up has been used to estimate inter-grating groove density errors of gratings. Various gratings from different manufacturers were examined for their absolute groove densities and inter-grating groove density errors.

4 illus, 16 ref

001327   BASU R, SORNADURAI D, AMIRTHAPANDIAN S, DHARA S (Surface and Nanoscience Div, Homi Bhabha National Institute, Kalpakkam - 603102, Email: dhara@igcar.gov.in) : Unique identification of phonon modes using polarized Raman studies of SnO(001) crystals. Bull Mater Sci 2019, 42(2), 83.

Stannous oxide (SnO), an exclusive p-type oxide semiconductor in the oxide family, is a source of renewed interest because of its ability to be an excellent anode material. So far, there are very few reports on the vibrational properties of SnO and controversy remains in the assignment of vibrational modes. Textured single crystals of SnO were synthesized by a one-step solvothermal method. The as-synthesized SnO crystals have a wide (001) plane, as confirmed by high resolution transmission electron microscopy images. Raman spectroscopy is used for the identification of phase as well as crystalline orientation. Moreover, a unique assignment of phonon modes in SnO is also performed using polarized Raman spectroscopic studies for different orientations around c-axis of the crystal with the incident electric field vector. Thus, a novel methodology of phonon assignment is adopted with a minimum amount of data collection for a diatomic molecule having a tetragonal symmetry with a number of symmetry elements.

4 illus, 23 ref

001320   ABD-ELRAHMAN M I, BAKIER Y M, ABU-SEHLY A A, HAFIZ M M (Physics Dep, Assiut Univ, Assiut 71516, Egypt, Email: mostafaia11@yahoo.com) : Glass transition and crystallization kinetics of a new chalcogenide-alkali metal Se₈₀Te₈(NaCl)₁₂ alloy. Bull Mater Sci 2019, 42(2), 81.

A new chalcogenide-alkali metal alloy of Se₈₀Te₈(NaCl)₁₂ has been prepared by a melt-quench technique. The crystallized phases due to the thermal annealing are observed by X-ray diffraction of the powdered sample. The glass transition and kinetics of crystallization in the Se₈₀Te₈(NaCl)₁₂ alloy are studied using the differential scanning calorimetric technique under non-isothermal conditions. The activation energy of the glass transition is evaluated by Kissinger and Mahadevan methods. The crystallization activation energy (E_c) is calculated by isoconversion Friedman methods. The decrease of E_c with increasing crystallization conversion is attributed to the complex mechanism of the crystallization process. Based on the shape of the characteristic kinetic function, the crystallization growth is found to be a three-dimensional growth from the bulk nuclei. The results show that the conditions of the Sestak–Berggren model are satisfied for describing the crystallization process of the studied Se₈₀Te₈(NaCl)₁₂ alloy. The parameters M and N involved in this model are calculated and related to the crystallization process.

10 illus, 3 tables, 28 ref

001376   TANNARANA M, SOLANKI G K, PATEL K D, PATHAK V M, PATANIYA P (Physics Dep, Sardar Patel Univ, Anand - 388 120, Email: mohittanna6@gmail.com) : Effect of off-stoichiometry on properties of tin selenide crystals. Bull Mater Sci 2019, 42(2), 79.

The tin selenide crystals with different proportions of Sn and Se were grown by a direct vapour-transport technique. The layer by layer growth of crystals from the vapour phase was promoted by screw dislocation mechanism. The powder X-ray diffraction (XRD) shows good crystallinity of grown compound. The XRD patterns of grown compounds are well-indexed to orthorhombic structure. In the off-stoichiometric compound, evidence of SnSe₂ secondary phase is observed due to excess of selenium. The morphological investigations were carried out using a Carl Zeiss optical microscope. The electron diffraction was also recorded from tiny flakes using a transmission electron microscope. The electrical resistivity both parallel and perpendicular to the c-axis was measured in the temperature range of 303–490 K and activation energy was also calculated using Arrhenius relation. The electrical study depicts the extrinsic semiconducting nature of grown compositions.

4 illus, 2 tables, 21 ref

001365   SHAHDAN D, FLAIFEL M H, CHEN R S, AHMAD S, HASSAN A (Physics Dep, The National Univ of Malaysia, Selangor, Malaysia, Email: rueyshanchen@hotmail.com) : Role of sonication time on thermal behaviour and dynamic mechanical analysis of NiZn ferrite incorporated PLA/LNR nanocomposite. Bull Mater Sci 2019, 42(2), 78.

The investigation on thermal properties of polylactic acid/liquid natural rubber (PLA/LNR) blend embedded with nickel zinc (NiZn) ferrite nanoparticles at various loading (1–5 wt %) and treated with different ultrasonication time (1–2 h) is the main core of this study. The novel NiZn nanocomposite based on the matrix of PLA:LNR with a ratio of 90:10 was fabricated via melt blending technique with the aids of ultrasonication. The effects of nanofiller loading and ultrasonic treatment on nanocomposite were examined by scanning electron microscopy, differential scanning calorimetry and dynamic mechanical analyser. The results revealed that the thermal properties of PLA/LNR matrix have improved with incorporation of nanoparticles in which improvement was observed until an optimum level at 4 wt % NiZn ferrite within 1 h of ultrasonic treatment. The optimum ultrasonication for 1 h is believed to be sufficient to promote a good dispersion of NiZn ferrite nanoparticles within the PLA/LNR and in order to enhance the thermal stability, which makes it potentially to be used in electronic applications.

5 illus, 1 table, 28 ref

001378   VERMA H, RAO B K, VERMA M L, CHAUHAN J (Applied Physics Dep, FET-SSGI Shri Shankaracharya Technical Campus, Bhilai - 490 020, Email: b.keshav26@gmail.com) : First principles study of breaking energy and mechanical strength of Kevlar-29. Bull Mater Sci 2019, 42(2), 76.

The first principles study is performed for the mechanical strength of Kevlar-29, and is based on density functional theory. The bond strength is investigated relative to the displacement of central nitrogen atom along X, Y and Z directions, respectively. The structural property analysis explains the asymmetric nature. A higher bond breaking energy is observed during compression along Z direction and vice versa for elongation. It is an insulator of forbidden energy gap which increases while compression and reduces during elongation. Crystal orbital overlap population reveals the higher strength of anti-bonding orbitals. It is mechanically stronger along the Z-axis and weaker along the Y -axis.

6 illus, 3 tables, 34 ref

001360   PHUOC L H, THO D D, DUNG N T, HIEN V X, VUONG D D, CHIEN N D (Hanoi Univ of Science and Technology, Hanoi 112 400, Vietnam, Email: tho.doduc@hust.edu.vn) : Enhancement of ethanol-sensing properties of ZnO nanoplates by UV illumination. Bull Mater Sci 2019, 42(2), 72.

ZnO nanoplates with hexagonal wurtzite structure were synthesized by hydrothermal treatment. The average dimension and average thickness of the plates were ∼200 × 400 and 40 nm, respectively. ZnO nanoplates were deposited on Pt-interdigitated electrodes for the fabrication of gas-sensing devices. The ethanol-sensing properties of the devices were investigated in the dark vs. ultraviolet (UV) illumination. Under the UV illumination, the optimal operating temperature of the devices can be reduced from 237 to 164 ^◦C and the response of the device was increased from 2.8 to 8.5 towards 1500 ppm ethanol vapour.

6 illus, 1 table, 27 ref

001352   MAJUMDER T, MONDAL S P (Physics Dep, National Institute of Technology, Agartala - 799 046, Email: suvraphy@gmail.com) : Graphene quantum dots as a green photosensitizer with carbon-doped ZnO nanorods for quantum-dot-sensitized solar cell applications. Bull Mater Sci 2019, 42(2), 65.

Graphene quantum dots (GQDs), N-doped GQDs (NGQDs) and S, N co-doped GQDs (SNGQDs) were synthesized using hydrothermal methods. All GQDs were attached with carbon-doped ZnO nanorods (C-ZnO NRs) grown on fluorine-doped tin oxide (FTO)-coated glass substrates, for the fabrication of metal-free eco-friendly quantum-dotsensitized solar cells (QDSSCs). SNGQD-decorated nanorod-based solar cells demonstrated maximum open circuit voltage (VOC ∼ 360 mV), short circuit current (JSC ∼ 1.84 mA cm⁻²) and power conversion efficiency ( η ∼ 0.293 %) compared to other devices.

4 illus, 1 table, 18 ref

001321   ABDULLAH O G H, HANNA R R, SALMAN Y A K (Physics Dep, Sulaimani Univ, Sulaimani, Iraq, Email: omed.abdullah@univsul.edu.iq) : Structural and electrical conductivity of CH:MC bio-poly-blend films: Optimize the perfect composition of the blend system. Bull Mater Sci 2019, 42(2), 64.

In this study, solid polymer blend films based on chitosan (CH) and methylcellulose (MC) were prepared in various compositions by the solution cast technique. The features of structure and complexation of the blend polymer films were studied using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analysis. The shift of FTIR peaks of the amino groups of CH and the hydroxyl groups of MC reveals the formation of interchain hydrogen-bonding between CH and MC chains in blend films. From the XRD pattern, the semi-crystalline structure of CH was depressed with the addition of MC and shows the CH:MC blend system with ratio 75:25 has the minimum degree of crystallinity. The highest room temperature conductivity was found to be 0.05×10⁻⁶ S cm⁻¹ for 75CH:25MC blend polymer composition. The dc conductivity exhibits Arrhenius-type behaviour with temperature. The drastic increase in conductivity up to 37.92 × 10⁻⁶ S cm⁻¹ at 373 K, can be explained by free volume model. The highest value of electrical conductivity for all prepared samples was associated with the minimum value of activation energy.

7 illus, 62 ref

001344   KHARRAT A B J, HLIL E K, BOUJELBEN W (Sfax Univ, 3000 Sfax, BP 1171, Tunisia, Email: benjaziaaida@gmail.com) : Prediction of magnetic and magnetocaloric properties in Pr_0.8−xBi_xSr_0.2MnO₃ (x = 0, 0.05 and 0.1) manganites. Bull Mater Sci 2019, 42(2), 62.

In this work, we have investigated the magnetic and magnetocaloric properties of Pr_0.8−xBi_xSr_0.2MnO₃ (x = 0, 0.05 and 0.1) polycrystalline manganites prepared by sol–gel route on the basis of a phenomenological model. Temperature dependence of magnetization indicates that all our samples exhibit a second order paramagnetic to ferromagnetic transition with a decrease in temperature. A correlation between experimental results and theoretical analysis based on a phenomenological model is investigated. The magnetic and magnetocaloric measurements are well simulated by this model. Under a magnetic applied field of 5 T, the theoretical absolute values of the maximum of magnetic entropy change $∆$S_Max are found to be equal to 5.33, 3.33 and 2.97 J kg⁻¹ K⁻¹ for x = 0, 0.05 and 0.1 respectively. The relative cooling power and the specific heat capacity values are also estimated. The predicted results permit us to conclude that our compounds may be promising candidates for magnetic refrigeration at low temperatures.

10 illus, 3 tables, 31 ref

001322   AKHTAR N, RAFIQUE H M, ATIQ S, ASLAM S, RAZAQ A, SALEEM M (Physics Dep, Punjab Univ, Lahore 54590, Pakistan, Email: naadiaakhtar@gmail.com) : Structural, morphological and dielectric traits of Zr_1−xCa_xTiO₄(x = 0, 0.05, 0.10, 0.15 and 0.2) ceramics. Bull Mater Sci 2019, 42(2), 58.

The influence of Ca doping on structural, morphological and dielectric characteristics of Zr_1−xCa_xTiO₄ (x = 0, 0.05, 0.10, 0.15 and 0.2) ceramics has been planned in this effort. Un-doped and Ca-doped ZrTiO₄ (ZT) have been synthesized through a sol–gel auto-combustion approach. The orthorhombic phase of ZT and Ca-doped ZT is confirmed through X-ray diffraction patterns. The variation in structural morphology and particle size due to Ca incorporation in ZT has further been revealed by field emission scanning electron microscopy. The investigation showed that the size of the particle gradually reduced from 0.5 to 0.125 μm with the increase of Ca content. It was confirmed from Fourier transform infrared spectroscopy that organic content was not found in the prepared samples. Dielectric constant, dielectric loss factor and tangent loss reduce with the increase in frequency and increase in Ca content. These dielectric parameters show independency at a higher frequency. The modulus plots confirmed that the capacitive parts were relatively independent of the frequency, whereas ac conductivity exhibited frequency dependent behaviour i.e., an increase with Ca concentration and with increasing frequency. The impedance plots revealed the resistance dominance due to the grain boundary effect.

6 illus, 2 tables, 35 ref

001351   MAHBOOB S, RIZWANA, PRASAD G, KUMAR G S (Physics Dep, Osmania Univ, Hyderabad - 500 007, Email: mahboob1978@yahoo.com) : Simulation of dielectric and resonance and anti-resonance data using modified Lorentz equation (T and ω simultaneously) of relaxor ferroelectric and piezoelectric ceramics. Bull Mater Sci 2019, 42(2), 56.

Dielectric data of new [Ba(Nd_xTi_1−2xNb_x )O₃]_0.30[Na_0.5Bi_0.5TiO₃]_0.70 (x = 0.075) relaxor ceramic was modelled using a new modified Lorentz equation (T and ω simultaneously) as proposed by us. The activation energy for thermally activated orientation of dipoles and relaxation times were estimated. Dielectric resonance and anti-resonance data as a function of temperature and angular frequency of other piezoelectric compound [Ba(Nd_0.1Ti_0.8Nb_0.1)O₃]_0.35 [(Na_0.5Bi_0.5)TiO₃]_0.65 was also modelled using the modified Lorentz equation as proposed by us. It is shown that using this equation, it is possible to obtain the polarizability, piezoelectric charge constant, piezoelectric voltage constant and activation energy for resonance and anti-resonance.

5 illus, 6 tables, 16 ref

001343   KARIMZADEH A, ALIOFKHAZRAEI M, ROUHAGHDAM A S (Materials Engineering Dep, Tarbiat Modares Univ, Tehran 1411713116, Iran, Email: maliofkh@gmail.com) : Study on wear and corrosion properties of functionally graded nickel–cobalt–(Al₂O₃) coatings produced by pulse electrodeposition. Bull Mater Sci 2019, 42(2), 53.

Functionally graded nickel–cobalt coatings with/without alumina nanoparticles were pulse electrodeposited on a carbon steel substrate by a continuous decrease in duty cycle from 95 to 10 % at different frequencies of 100, 500 and 1000 Hz. The effect of pulse parameters on the nanoparticle content, chemical composition, microstructure, corrosion properties and tribological behaviour of coatings was studied. Energy-dispersive X-ray spectroscopy analysis showed that the amount of cobalt is gradually reduced and the content of alumina nanoparticles is increased from the substrate/coating interface to the surface. Based on the electrochemical studies in 3.5 wt % NaCl, the nanocomposite coatings gain the highest corrosion resistance at the lowest frequency. Also, the hardness of coatings gradually increased. Evaluation of the tribological behaviour of coatings by a pin-on-disk wear test showed that the nanoparticles have a positive effect on wear resistance and improve it by increasing frequency.

11 illus, 3 tables, 67 ref

001363   REDDY B J, VICKRAMAN P, JUSTIN A S (Physics Dep, The Gandhigram Rural Institute-DU, Gandhigram - 624 302) : A facile synthesis of novel α-ZnMoO₄ microspheres as electrode material for supercapacitor applications. Bull Mater Sci 2019, 42(2), 52.

A mixed metal oxide, α-ZnMoO₄ is prepared in a simple, lucid and facile synthesis route as an active material for supercapacitor applications. The structural and morphological information is provided by X-ray diffraction, Fourier transform infrared, Raman and scanning electron microscopy data. The as-prepared α-ZnMoO₄ microspheres are subjected to cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy studies to examine its electrochemical behaviour in 2 M KOH aqueous electrolyte. Zinc molybdate microspheres have demonstrated very good electrochemical performance with 234.75 F g⁻¹ at 0.5 A g⁻¹ with good specific capacitance retention (82 %) for sustained 1600 charge/discharge cycles.

6 illus, 30 ref

001338   GULLU H H, YILDIZ D E, SÜRÜCÜ O B, TERLEMEZOGLU M, PARLAK M (Physics Dep, Hitit Univ, Corum, Turkey, Email: desrayildiz@gmail.com) : Temperature dependence of electrical properties in In/Cu₂ZnSnTe₄/Si/Ag diodes. Bull Mater Sci 2019, 42(2), 45.

Cu₂ZnSnTe₄ (CZTTe) thin films with In metal contact were deposited by thermal evaporation on monocrystalline n-type Si wafers with Ag ohmic contact to investigate the device characteristics of an In/CZTTe/Si/Ag diode. The variation in electrical characteristics of the diode was analysed by carrying out current–voltage (I –V) measurements in the temperature range of 220–360 K. The forward bias I –V behaviour was modelled according to the thermionic emission (TE) theory to obtain main diode parameters. In addition, the experimental data were detailed by taking into account the presence of an interfacial layer and possible dominant current transport mechanisms were studied under analysis of ideality factor, n. Strong effects of temperature were observed on zero-bias barrier height ($\mathrm{\phi }$_B0) and n values due to barrier height inhomogeneity at the interface. The anomaly observed in the analysis of TE was modelled by Gaussian distribution (GD) of barrier heights with 0.844 eV mean barrier height and 0.132 V standard deviation. According to the Tung’s theoretical approach, a linear correlation between $\mathrm{\phi }$_B0 and n cannot be satisfied, and thus the modified Richardson plot was used to determine Richardson constant (A^∗). As a result, A^∗ was calculated approximately as 120.6 A cm⁻² K⁻² very close to the theoretical value for n-Si. In addition, the effects of series resistance (R_s) by estimating from Cheng’s function and density of surface states (N_ss) by taking the bias dependence of effective barrier height, were discussed.

11 illus, 1 table, 35 ref

001372   SONI M (Chemistry Dep, DAV Coll, Abohar, Punjab) : A review on the measurement of optical activity by using a Polarimeter. J Pharmacogn Phytochem 2019, 8(2), 358-60.

The plane polarized light passing through the solutions of some organic and inorganic compounds caused polarized light to rotate. This property is known as optical activity. The amount and direction of rotation can be determined with a Polarimeter. The present work gives the earlier, current developmental status and design considerations of existing optical activity measurements, instruments, analysis and techniques for automation. The above said areas are covered in the review. The intention of the present work is to develop the future research work in the field of polarimetry.

1 illus, 18 ref

001347   KUMAR R, KUMAR P (Chemistry Dep, Malaviya National Institute of Technology Jaipur, Jaipur - 302 017, Email: pradeep.chy@mnit.ac.in) : Effect of anharmonicity on energy relaxation of a dissipative quantum oscillator. J Chem Sci 2019, 131(3), 23.

The effect of anharmonicity on the energy relaxation of excited state has been studied by means of a dissipative oscillator. The present study also sheds light on the recent femtosecond stimulated Raman spectroscopy results of Kovalenko et al. (J. Chem. Phys. 139 011101 2013) on optical cooling of trans-stilbene. It has been shown that anharmonicity plays a crucial role in explaining the time-dependent frequency shift as well as the time evolution of bandwidth of ν_C=C mode of trans-stilbene in excited state, found in experiment.

5 illus, 3 tables, 37 ref

001329   CHAKRABORTY A K, UDDIN M S, SHARIFF M A, LATIF S A, RASHID M A, KHANDAKER M U (Institute of Nuclear Science and Technology, Dhaka, Bangladesh, Email: animeshbd@yahoo.com) : Efficiency calibration of γ-ray detector for extended sources. Pramana – J Phys 2019, 92(4), 67.

Precise identification and quantification of radioisotope in a sample largely depend on the accuracy of the full-energy peak efficiency of the detector. It is generally observed that the efficiency for a given energy of point-like sources is not the same as the extended source. However, number of correction factors such as detector geometry, photon attenuation, coincidence-summing, etc. may reduce such a difference in efficiency regardless of sources, or they should be considered in the measurement of extended samples. In connection to this, the variation of absolute photopeak efficiency of a high-purity germanium (HPGe) detector with the distances from the surface of the detector as well as with the γ-ray energies were investigated using γ-ray standard point sources. We present a method to determine the loss of efficiencies in radioactivity measurement of the thin extended radioactive disc samples in comparison to point source.

4 illus, 1 table, 24 ref

001355   MUTUK H (Physics Dep, Ondokuz Mayis Univ, Samsun, Turkey, Email: halilmutuk@gmail.com) : Asymptotic iteration and variational methods for Gaussian potential. Pramana – J Phys 2019, 92(4), 66.

In this paper we studied the approximate solutions of radial Schrödinger equation with the attractive Gaussian potential. We used asymptotic iteration method and variational method to obtain energy eigenvalues for any n and l quantum numbers. Our results are in good agreement with the other studies.

2 tables, 20 ref

001349   LI H, LI X (Huaqiao Univ, Fujian, People’s Republic of China, Email: lihongmin@hqu.edu.cn) : On the integrability of some two-component Camassa–Holm-type systems. Pramana – J Phys 2019, 92(4), 65.

Some two-component Camassa–Holm-type systems are proposed. These systems are shown to be integrable with Lax pairs and bi-Hamiltonian structures. We construct dual hierarchies of these two-component Camassa–Holm-type systems via the tri-Hamiltonian duality method, and derive spectral problems of these dual hierarchies.

26 ref

001383   ZOU W-K, LI N-W, HAN C, LIU D-D (Xuzhou Univ of Technology, Xuzhou, China, Email: zouweike@126.com) : Quantum quench dynamics of the one-dimensional Ising model in transverse field. Pramana – J Phys 2019, 92(4), 61.

The quantum quench dynamics of the one-dimensional Ising model in transverse field is investigated using the quantum renormalisation group method. The analytic expression of concurrence C(t) is obtained, where the initial state is a superposition state which is constructed from the eigenstates of pure Ising system. The effect of parameter a in the period and range of concurrence are exhibited respectively in the vicinity of the critical point, which show scaling behaviour. When effective magnetic field g is big enough, the maximum limit value is 1.0. However, the minimum value is different, which is also dependent on the evolved time t.

5 illus, 30 ref

001333   DAMODARAKURUP S, SOORAT R, VUDAYAGIRI A (Physics Dep, Government Coll Kanjiramkulam, Thiruvananthapuram - 695 524, Email: sajeevphy@gmail.com) : Long-time dynamics of a vertical-cavity surface-emitting laser under optical feedback. Pramana – J Phys 2019, 92(4), 59.

External optical feedback in vertical-cavity surface-emitting laser (VCSEL) is found to influence its output intensity. We studied the effect of the amount of total output polarisation feedback and polarisation-selective feedback on the output intensities of a VCSEL for a low-resolution sampling and for long temporal duration. A 40 μs resolution time-series correlation analysis is performed for different feedback conditions and the characteristic dynamics is investigated. We found a correlated fluctuation in VCSEL output for a moderate amount of total feedback and polarised feedback. The period of such fluctuations is found to be reduced from total feedback to the polarised feedback of the system.

12 illus, 37 ref

001350   LIU Y, XU X, XU Z, FENG Y, LOU X (Northwest Institute of Nuclear Technology, Xi’an 710024, China, Email: liuyang@nint.ac.cn) : The impact of surface plasma on the total emission charge from PZST cathode induced by nanosecond electric pulse. Pramana – J Phys 2019, 92(4), 58.

Electron emission from antiferroelectric (Pb_0.99Nb_0.02)[(Zr_0.80Sn_0.20)_0.952Ti_0.048]_0.98O₃ cathode has been investigated. The PZST cathode can maintain a metastable ferroelectric phase by the application of a highenough field, thus implying three possibly pulse-loading configurations for electron emission measurements. The fact that emission charge is larger than the non-compensated charge indicates that the surface plasma contributes to the total emission charge. Furthermore, χ_i (i = A, B, C), characterising the contribution of surface plasma to the total emission charge, was defined. It was found that the emission charge increases almost linearly with χ_i . Our results are of great importance for a better understanding of electron emission in antiferroelectric/ferroelectric cathodes.

6 illus, 27 ref

001339   HAYAT T, MUHAMMAD K, KHAN M I, ALSAEDI A (Mathematics Dep, Quaid-I-Azam Univ, Islamabad 45320, Pakistan, Email: mikhan@math.qau.edu.pk) : Theoretical investigation of chemically reactive flow of water-based carbon nanotubes (single-walled and multiple walled) with melting heat transfer. Pramana – J Phys 2019, 92(4), 57.

This study reports the chemically reacting flow of carbon nanotubes (CNTs) over a stretchable curved sheet. The flow is initialised due to a stretched surface. A heat source is present. Water is considered as the base liquid. The vital interest of this work is that heat phenomenon is studied via melting heat transfer. Xue relation of nanoliquid is implemented to explain the properties of both single- and multiwall CNTs. Mathematical systems (partial differential equations) for the flow field are obtained. Appropriate transformations are utilised in order to transform partial differential systems into nonlinear ordinary differential systems. Further, these systems are solved numerically. Variations in flow, temperature, concentration, skin friction coefficient and Nusselt number via the involved influential variables are illustrated graphically.

16 illus, 1 table, 49 ref

001361   RANE R, JOSHI A, AKKIREDDY S, MUKHERJEE S (Institute for Plasma Research, Ahmedabad - 382 428, Email: ramu@ipr.res.in) : Comparative study of discharge characteristics and associated film growth for post-cathode and inverted cylindrical magnetron sputtering. Pramana – J Phys 2019, 92(4), 55.

In this study, an experimental investigation of a DC cylindrical magnetron discharge for argon gas in post-cathode (i.e. direct) and hollow-cathode (i.e. inverted) configurations was carried out. The discharge properties at different externally applied magnetic fields and operating pressures were measured and compared for both the configurations. The discharge current (I)–voltage (V) characteristics obey I ∝ Vⁿ, where the value of n is in the range of 3–8. The discharge current increases linearly with the magnetic field in the post-cathode configuration, whereas it saturates at higher magnetic fields in the case of inverted configuration. Measurement of plasma potential indicated a considerable anode fall in the inverted magnetron configuration, whereas a negligible anode fall and strong cathode fall were observed in the case of post-cathode configuration. The plasma density and electron temperature, measured using a double Langmuir probe, were observed to be higher in the inverted magnetron configuration. The plasma density was found to be maximum at around 3–4 cm away from the respective inner electrode in both the configurations. A clear change in surface morphology of copper thin film was observed in the case of inverted magnetron configuration, which might be due to the extra ionisation near the anode owing to the anode fall.

11 illus, 22 ref

001357   NASSERI M M (Institute of Nuclear Science and Technology (AEOI), Tehran, Iran, Email: mnasseri@aeoi.org.ir) : Determination of molybdenum target parameters for transmission X-ray tube: A Geant4 simulation study. Pramana – J Phys 2019, 92(4), 54.

Carbon nanotube-based transmission X-ray tubes are widely used in different applications including mammography and X-ray fluorescence (XRF) experiment. Molybdenum (Mo) is one of the suitable target materials for this type of tube. In this paper, we used a well-known simulator, Geant4, to achieve some of the parameters of the Mo target. The optimum thickness for maximum production of usable X-ray from Mo target was obtained when it was exposed to the electron beam with an energy of 50 keV. In addition, according to the results, hemisphere geometry was recommended for the target at least for XRF application. By increasing target thickness, Mo acts as a filter resulting in limited X-ray energy. For estimating the target’s temperature generation, the amount of deposited energy was also evaluated.

8 illus, 24 ref

001346   KHORRAM-HOSSEINI S A, ZARRINKAMAR S, PANAHI H (Basic Sciences Dep, Islamic Azad Univ, Garmsar, Iran, Email: zarrinkamar.s@gmail.com) : Minimal length Schrödinger equation via factorisation approach. Pramana – J Phys 2019, 92(4), 53.

The fourth-order modified Schrödinger equation due to the generalised uncertainty principle is considered in one dimension with a box problem. The factorisation of fourth-order self-adjoint differential equations is then discussed and thereby the wave functions and energy spectra of the modified Schrödinger equation are derived.

24 ref

001358   OUANNAS A, KHENNAOUI A-A, ZEHROUR O, BENDOUKHA S, GRASSI G, PHAM V-T (Ton Duc Thang Univ, Ho Chi Minh City, Vietnam, Email: phamvietthanh@tdtu.edu.vn) : Synchronisation of integer-order and fractional-order discrete-time chaotic systems. Pramana – J Phys 2019, 92(4), 52.

This paper studies the synchronisation of integer- and fractional-order discrete-time chaotic systems with different dimensions. Control laws are proposed for the full-state hybrid projective synchronisation (FSHPS) of a master–slave pair, where the difference equations of the master have an integer order while those of the slave have a fractional order. Moreover, inverse FSHPS laws are proposed for a fractional-order master and an integer-order slave. The Lyapunov stability theory of integer-order maps and the stability theory of linear fractional-order maps are utilised to establish the asymptotic stability of the zero equilibrium corresponding to the synchronisation error system. Numerical results are presented to verify the findings of the study.

6 illus, 39 ref

001324   ANDRIYAS T (Allahabad Univ, Allahabad - 211 002, Email: tushar.andriyas@aggiemail.usu.edu) : Comparison of substorm onsets during different levels of interplanetary magnetic field B_z. Pramana – J Phys 2019, 92(4), 51.

The magnetospheric response during the substorm events to solar wind driving, as determined by the level and sign of the interplanetary magnetic field (IMF) B_z, is analysed. Using the superposed epoch analysis, solar wind and geomagnetic conditions under three levels of B_z are characterised, i.e. northward or BZN (B_z > 0 nT, 75 events), very weak or BZ0 (B_z ∼ 0 nT, 78 events) and southward or BZS (B_z < 0 nT, 80 events). No northward turning is observed during BZS, while northward turning occurs 20 and 50 min prior to onset, during the BZN and BZ0 classes, respectively. IMF has a strong duskward component and the solar wind speed is also the fastest during BZN onsets. Auroral activity, as measured by the AL index, takes a longer time to decay to preonset values during BZ0 and BZS onsets compared to the BZN onsets. The level of IMF B_z does not seem to influence the oval thickness in the noon sector. The oval is the thinnest during BZ0 events in all the sectors. The rate of auroral widening in the dawn sector is found to be evidently slower than in the dusk sector during the BZS group.

4 illus, 26 ref

001348   KUNDU M (Institute for Plasma Research, Gandhinagar - 382 428, Email: mkundu@ipr.res.in) : Beyond the conventional collisional absorption of laser light in under-dense plasma: A particle-in-cell simulation study. Pramana – J Phys 2019, 92(4), 50.

Collisional absorption of laser light in an under-dense plasma is studied by particle-in-cell (PIC) simulation with Monte Carlo binary Coulomb collisions between charge particles. For a given plasma thickness of a few times the wavelength of 800 nm laser, fractional absorption (α) of the laser light due to Coulomb collisions (mainly between electrons and ions) is calculated at different electron temperature T_e with a total velocity v = (v_th² + v₀²/2)^1/2 dependent Coulomb logarithm ln (v), where v_th and v₀ are thermal and ponderomotive velocity of an electron. In the low-temperature regime (T_e <$~$15 eV), it is found that α increases with increasing laser intensity I₀ up to a maximum corresponding to an intensity I_c, and then it drops (approximately) obeying the conventional scaling of α ∝ I₀^−3/2 when I₀ > I_c. Such a non-conventional increase of α with I₀ in the lowintensity regime was demonstrated earlier in experiments, and recently explained by classical and quantum models [Phys. Plasmas 21, 13302 (2014); Phys. Rev. E 91, 043102 (2015)]. Here, for the first time, we report this nonconventional collisional laser absorption by PIC simulation, thus bridging the gap between models, simulations, and experimental findings. Moreover, electron energy distributions naturally emanating during the laser interaction (in PIC simulations) are found to be anisotropic and non-Maxwellian in nature, leading to some deviations from the earlier analytical predictions.

4 illus, 58 ref

001326   BANSAL S, AGGARWAL M (I.K. Gujral Punjab Technical Univ, Kapurthala - 144 601, Email: sonabansal34@gmail.com) : Non-planar electron-acoustic waves with hybrid Cairns–Tsallis distribution. Pramana – J Phys 2019, 92(4), 49.

Non-planar electron-acoustic waves having Cairns–Tsallis distributed hot electrons are investigated under multiple temperature electrons model in unmagnetised plasma. In this model, Korteweg–de Vries (KdV) equation is obtained in the cylindrical/spherical coordinates. On the basis of the solutions of KdV equation, variation of solitary wave features (amplitude, velocity and width) with different plasma parameters are analysed. Dispersion and nonlinear coefficients obtained depend on the particle density α, non-extensive parameter q, electron temperature ratio θ and non-thermal parameter γ . Combined effect of all these plasma parameters significantly changes the properties of the solitary waves in non-planar geometry. It is observed that increasing the number of non-thermal electrons in the medium increases the amplitude, velocity as well as width of the non-planar waves whereas with the increase in temperature, the velocity of waves decreases and this impact is dominant in spherical waves. This two-parameter (γ , q) distribution model (C–T) is applicable to a wide range of observed plasmas, i.e. auroral region and magnetosphere of the Earth.

4 illus, 43 ref