027553   MA P-C, CHEN G-B, LI X-W, ZHAN Y-B (Physics Dep, Huaiyin Normal Univ, Huaian- 223 300, Email: pengchengma007@126.com) : Deterministic assisted cloning of an unknown single-particle four-dimensional quantum state. Pramana- J Phys 2018, 91(1), 6.

In this paper, we present a scheme which can produce a perfect copy of an unknown single-particle four-dimensional quantum state with assistance from a state preparer. Two stages were included in this scheme. The first stage requires the usual teleportation, after Alice’s (the state sender) generalised Bell state measurement. Bob (the state receiver) can get the original state with unit probability. In the second stage, after having received Victor’s (the state preparer) classical message, and using the rest resource of the teleportation process, the perfect copy of an original unknown state can be produced in Alice’s place. To realise the scheme, several novel sets of measuring basis were introduced. It must be pointed out that, in the present scheme, the total success probability for assisted cloning of a perfect copy of the unknown state can reach 1.

1 table, 28 ref

027586   SANTHOSH K P, KRISHNAN S, JOSEPH J G (Kannur Univ, Payyanur- 670 327, Email: drkpsanthosh@gmail.com) : All possible tripartitions of ²³⁶U isotope in collinear configuration. Pramana- J Phys 2018, 91(1), 5.

Using the recently proposed unified ternary fission model (UTFM), the tripartition of ²³⁶U isotope was studied for all possible fragmentations, in which the interacting potential barrier is taken as the sum of the Coulomb and proximity potentials with fragments in collinear configuration. The highest yield is obtained for the fragmentation ⁴⁸Ca + ⁵⁸Ti + ¹³⁰Sn and next highest yield is found for ⁵⁸Cr + ⁴⁶Ar + ¹³²Sn, which stress the importance of doubly magic or near doubly magic nuclei in the tripartition of ²³⁶U isotope. The formation of ⁶⁸Ni and ⁷⁰Ni as the edge fragments linking the doubly magic nucleus ¹³²Sn by the isotope of Si is in good agreement with experimental and theoretical studies, in the collinear cluster tripartition of ²³⁶U isotope which reveals the reliability of our model (UTFM) in ternary fission.

7 illus, 1 table, 44 ref

027537   EZHILARASU P M, INBAVALLI M, MURALI K, THAMILMARAN K (Bharathidasan Univ, Tiruchirappalli- 620 024, Email: maran.cnld@gmail.com) : Strange non-chaotic attractors in a state controlled-cellular neural network-based quasiperiodically forced MLC circuit. Pramana- J Phys 2018, 91(1), 4.

In this paper, we report the dynamical transitions to strange non-chaotic attractors in a quasiperiodically forced state controlled-cellular neural network (SC-CNN)-based MLC circuit via two different mechanisms, namely the Heagy–Hammel route and the gradual fractalisation route. These transitions were observed through numerical simulations and hardware experiments and confirmed using statistical tools, such as maximal Lyapunov exponent spectrum and its variance and singular continuous spectral analysis. We find that there is a remarkable agreement of the results from both numerical simulations as well as from hardware experiments.

19 illus, 1 table, 54 ref

027552   LIU Y-L, LIANG J, LI X, XIAO N, YUAN X-G (Research Institute of System Engineering, Beijing- 100 077, China, Email: huapofeixue@sina.com) : Tunable microwave generation based on frequency quadrupling. Pramana- J Phys 2018, 91(1), 3.

To generate linearly chirped microwave signals with large frequency tunable range, a photonic approach is proposed. A dual-output dual-parallel Mach–Zehnder modulator followed by a polarisation beam combiner and an optical filter are utilised to generate orthogonally polarised ± second-order optical sidebands. A polarisation modulator is employed to achieve phase modulation of the two wavelengths. The balanced detection is applied to suppress the distortion and background noise. The central frequency of the generated signal is four times that of the local oscillator frequency. Simulation results show that a linear pulse is produced with time-bandwidth as well as a compression ratio for the pulse of 11 and 9.3 respectively. Moreover, a peak-to-side lobe ratio of 7.4 dB is generated. The system has both good reconfigurability and tunability, and its frequency can be continuously adjusted from about 10 GHz to as much as 50 GHz in principle.

9 illus, 21 ref

027570   POORVASHA S, LAKSHMI B (VIT Univ, Chennai- 600 127, Email: lakshmi.b@vit.ac.in) : Influence of structural and doping parameter variations on Si and Si_1-x Ge_x double gate tunnel FETs: An analysis for RF performance enhancement. Pramana- J Phys 2018, 91(1), 2.

This paper deals with the effect of structural and doping parameter variations on RF parameters for Si and Si_1−xGe_x -based double gate (DG) tunnel FETs (TFETs). For the first time, asymmetric gate oxide is introduced in the gate-drain overlap and compared with that of DG TFETs. The DC parameter subthreshold swing (SS) and RF parameter metrics, unity gain cut-off frequency (f_t) and maximum oscillation frequency (f_max) are extracted by varying structural parameters, gate length (L_g), gate oxide thickness (t_ox), channel thickness (t_ch), doping parameters, channel doping (N_ch), drain doping (N_d) and source doping (N_s) in and around their nominal value. For a channel thickness of 15 nm, a very less SS of 8 mV/dec is achieved in Si_1−xGe_x -based DG TFETs with gate-drain overlap. Variations of gate oxide thickness offer better RF performance enhancement for Si-based asymmetric gate oxide devices. This could be achieved because of the higher tunnelling rate of electrons occurring at the source side of asymmetric gate oxide devices.

18 illus, 2 tables, 27 ref

027580   RENTHLEI L, RAMAKRISHNA S A, WANARE H (Physics Dep, Indian Institute of Technology, Kanpur- 208 016, Email: fela@iitk.ac.in) : Cloaks for suppression or enhancement of scattering of diffuse photon density waves. Pramana- J Phys 2018, 91(1), 1.

Enhancement of wave-like characteristics of heavily damped diffuse photon density waves in a random medium by amplification can induce strongly localised resonances. These resonances can be used to either suppress or enhance scattering from an inhomogeneity in the random medium by cloaking the inhomogeneous region by a shell of random medium with the correct levels of absorption or amplification. A spherical core–shell structure consisting of a shell of a random amplifying medium is shown to enhance or suppress specific resonant modes. A shell with an absorbing random medium is also shown to suppress scattering which can also be used for cloaking the core region.

6 illus, 35 ref

026283   CHAUDHURI S, SAHOO S (KIIT Deemed Univ, Bhubaneswar- 751 024, Email: sumanta.chaudhurifme@kiit.ac.in) : Effect of the aspect ratio on the flow characteristics of magnetohydrodynamic (MHD) third grade fluid flow through a rectangular channel. Sadhana 2018, 43(7), 106.

The magnetohydrodynamic (MHD) flow of a third grade fluid through a rectangular channel, considering the effect of aspect ratio, has been investigated. The flow considered is steady, laminar, incompressible and hydro-dynamically fully developed. The equation, describing the flow, is a highly non-linear partial differential equation (PDE) with remote possibility of having an exact solution and even numerical solution also is very difficult to obtain. A combination of the homotopy perturbation method (HPM) and integral method (IM) has been employed to solve the non-linear PDE which is scarce in open literature. The results of the present study are compared with the results obtained by the least square method (LSM) of the MHD third grade fluid flow through a rectangular channel, without the effect of aspect ratio and are found to be in close agreement. The results indicate that the flow field is significantly affected by the aspect ratio which should be considered for practical applications. In all the available literatures of the third grade fluid flow, the aspect ratio effect is neglected and this simplifying assumption reduces the highly complicated non-linear PDE to a nonlinear ordinary differential equation (ODE). The novelty of the subject work lies in the inclusion of the effects of aspect ratio in the governing equation describing the flow of a third grade fluid through a channel and solving this by a combined analytical method (HPM and IM). Further, the effects of the Hartmann number and nonNewtonian third grade fluid parameter on the flow filed are discussed.

6 illus, 17 ref

026282   BOUZEKRAOUI Y, BENTAYEB F, ASMI H, BONUTTI F (Physics Dep, Mohammed V Univ, Morocco, Email: youssef0fsr@gmail.com) : Comparison of image quality of different radionuclides Technetium-99m, Samarium-153, and Iodine-123. Indian J Nucl Med 2018, 33(3), 201-4.

The choice of the radionuclide has a key role in nuclear medicine which appearing the lowest scatter fraction. In addition, the presence of penetrated and scattered photons from collimator in single‑photon emission computed tomography images degrades resolution and contrast. Thus, image quality depends on sensitivity and resolution of the collimator–detector system. The goal of this study was to compare the image quality that can be achieved by three radionuclides: technetium‑99 m (Tc‑99 m), iodine‑123 (I‑123), and samarium‑153 (Sm‑153). Tc‑99 m and Sm‑153 were imaged with low‑energy high resolution (LEHR) collimator, while I‑123 was imaged with medium‑energy (ME) collimator. We modeled the Siemens Symbia Medical system using Monte Carlo simulation code SIMIND. The imaging characteristics of each radionuclide were investigated by simulated data: point spread function, sensitivity (Cps/MBq) and geometric, penetration and scattering distribution. Tc‑99 m and Sm‑153 give best and results with LEHR collimator for spatial resolution (full width at half maximum [FWHM] = 3.19 mm; full width at tenth maximum [FWTM] = 6.73 mm) and (FWHM = 3.22 mm; FWTM = 7.39 mm), respectively. Whereas, I‑123 provided with ME collimator a lower resolution (FWHM = 4.89 mm; FWTM = 9.89 mm). The sensitivity recorded by Tc‑99 m, Sm‑153, and I‑153 were (31.21 Cps/MBq), (10.16 Cps/MBq), and (51.22 Cps/MBq), respectively. Tc‑99 m and Sm‑153 give the best and generally similar imaging properties with LEHR. For I‑123, the ME collimator helps lowering the influence of high‑energy gamma rays.

4 illus, 4 tables, 18 ref

026275   MADHAVAN NAMPOOTHIRI S, SABU SEBASTIAN M, SAJITH KUMAR P C (DRDO-Naval Physical and Oceanographic Laboratory, Cochin- 682 021, Email: madhavan@npol.drdo.in) : Implementation of Peltier cooling in hermetically sealed electronic packaging unit for sub-sea vessel. Def Sci J 2018, 68(3), 326-32.

This paper presents the methodology adopted for implementation of Peltier cooling in hermetically sealed electronic packaging units used in sub-sea vessels. In sub-sea vessels, sonar front-end electronics is packaged in hermetically sealed electronic packaging units. The thermal design of the unit is a highly challenging task considering the heat dissipation of 300 W from the electronics, non-availability of chilled air for cooling and IP68 sealing requirements. Cooling fans cannot be integrated, since these units are to be placed in acoustically sensitive pressure capsule area of the subsea vessel. The electronic cooling in this unit is achieved using conduction cooling with external fins. To enhance the cooling, suitable Peltier cooling (Thermo-electric cooling or TEC) module is selected and implemented with the system. Computational fluid dynamic analysis of the unit is carried-out to study the air-flow and thermal performances with Peltier cooler. The unit is realised and the estimated temperatures validated by experimental temperature measurements on the realised unit. The measured temperatures are within the safe operating limits of the electronic components and hence the cooling design of the unit is satisfactory. It is also observed that maximum temperature reduction has occurred at 1.5 A current and card edge temperature of Printed circuit board lowered by 9.28 °C by implementing Peltier cooling.

12 illus, 2 tables, 15 ref

026274   MITTAL G, PATHAK N P (DRDO-Defence Electronics Applications Laboratory, Dehradun – 248 001, Email: gauravmittal.drdo@gmail.com) : Design, analysis and characterisation of spoof surface plasmon polaritons based wideband bandpass filter at microwave frequency. Def Sci J 2018, 68(3), 300-6.

This paper presents the wideband bandpass filter (BPF) in the microwave frequency domain. The realisation approach is based on spoof surface plasmon polaritons (SSPPs) phenomenon using plasmonic metamaterial. A novel unit cell is designed for filter design using an LC resonator concept. Then SSPPs BPF is realised using an optimised mode converter and five unit cells. This paper includes a brief design detail of the proposed novel unit cell. The passband of BPF is achieved at approximately 1.20 - 5.80 GHz, 3 dB bandwidth is tentatively 4.60 GHz and the insertion loss is less than 2 dB approximately over the passband. The overall dimension of fabricated filter is (90 x 45) mm. A basic schematic of transmission line representation is also proposed to evaluate the BPF structure.

11 illus, 30 ref

026273   MOORTHY Y K, PILLAI S S, SHINY G (Mar Baselios Coll of Engineering and Technology, Trivandrum – 695 015, Email: yamunakmoorthy@gmail.com) : Energy-efficient multiple relay selection in cognitive radio network. Def Sci J 2018, 68(3), 295-9.

Cognitive radios play very important role in military applications due to their capability to adapt intelligently according to the prevailing environmental conditions. Relays form the main communication enablers in infrastructureless networks. In this paper, relay selection for increasing the energy efficiency of a cognitive radio network is considered. The proposed approach considers the multiple - relay selection scheme with strict outage probability constraints. Energy maximisation is posed as an optimisation problem, the solution to which shows that relay selection under outage constraints is different from the one without such a constraint. It can be observed from the simulations that energy efficiency and outage behaviour follows trade-off relations. Moreover, the original Branch and Bound algorithm has been re-designed for faster convergence. It has also been demonstrated that when strict outage constraints are imposed, the optimal number of relays selected will be more in comparison to the case where there is no outage consideration.

5 illus, 1 table, 17 ref

026272   AMIT, RAWAL D S, SHARMA S, KAPOOR S, LIASHRAM R, CHAUBEY R K, VINAYAK S, SHARMA R K (DRDO-Solid State Physics Laboratory, Delhi - 110 054, Email: ds_rawal@sspl.drdo.in) : Design and fabrication of multi-finger field plate for enhancement of AlGaN/GaN HEMT breakdown voltage. Def Sci J 2018, 68(3), 290-4.

The design and fabrication of gate/source connected multi-finger field plate structures using TCAD ATLAS simulation software is presented. The designed field plate structures are fabricated on indigenous AlGaN/GaN HEMT devices. AlGaN/GaN HEMT devices with field plate structures exhibit about three times improvement in breakdown voltage of device and are in close agreement with the simulation results. Integration of field plates in device have resulted in higher VDS (drain to source voltage) operation and improvement in output power of AlGaN/GaN HEMT devices. Incorporation of field plates also decrease the reverse leakage current of HEMT devices.

7 illus, 15 ref

026271   SOGUNURU A, VIKRAM P, VARUGHESE S (DRDO-Centre for Airborne Systems, Bengaluru - 560 037, Email: annapurna@cabs.drdo.in) : Thermal design, analysis and packaging of an airborne multi-output power supply unit. Def Sci J 2018, 68(3), 235-40.

Design of airborne multi-output power supply unit (MOPS) is restricted by space, weight and predefined geometry of air flow path. The unit is cooled by ram air and hence, exposed to the extreme external thermal environment that changes typically from +55 °C to -40 °C, from ground to cruising altitude within a few minutes. Hence the design should meet the thermal requirements of the electronics inside the packaging adequately, for both the positive and negative extremities of the temperature, so that device limiting temperatures are not exceeded. At the same time, it must accommodate the necessary circuitry. Details of the thermal and mechanical design and performance of the MOPS unit at various altitudes, hot spot location, flow requirements and optimal heat sink design are presented in this paper.

10 illus, 5 tables, 10 ref

026281   YIGITEROL F, GULLU H H, YILDIZ E D (Physics Dep, Hitit Univ, 19030 Çorum, Turkey, Email: desrayildiz@hitit.edu.tr) : Influence of Si₃N₄ layer on the electrical properties of Au/n-4H SiC diodes. Bull Mater Sci 2018, 41(3), 66.

In this study, the effect of Si₃N₄ insulator layer on the electrical characteristics of Au/n-4H SiC diode was investigated. The current–voltage (I−V), capacitance–voltage (C−V) and conductance–voltage (G/w−V) measurements were carried out at room temperature condition. Under thermionic emission model, electrical parameters as zero-bias barrier height ($\phi$Bo), ideality factor (n), interface states (D_it), and series (R_s) and shunt (R_sh) resistances were estimated from forward bias I−V analyses. The values of n and $\phi$Bo were about 1.305 and 0.796 eV for metal–semiconductor (MS) rectifying diode, and 3.142 and 0.713 eV for metal–insulator–semiconductor (MIS) diode with the insertion of Si₃N₄ layer, respectively. Since the values of n were greater than the unity, the fabricated diodes showed non-ideal I−V behaviour. The energy distribution profile of D_it of the diodes was calculated by taking into account of the bias dependence of the effective barrier height ($\phi$_e) and R_s. The obtained D_it values with R_s are almost one order of magnitude lower than those without R_s for two diodes. According to Cheung’s model, R_s were calculated and these values were found in increasing behaviour with the contribution of Si₃N₄ insulator layer. In addition, the J_R−V plot behaviours with linear dependence between ln(J_R) vs. V^0.5 indicated that the dominant conduction mechanism in the reverse bias region was Schottky effect for both MS and MIS diodes. In the room temperature C−V measurements, different from the results of MIS diode, the values of C for MS diode was observed in decreasing behaviour from ideality with crossing the certain forward bias voltage point (∼2.5 V). The decrease in the negative capacitance corresponds to the increase of G/w.

12 illus, 1 table, 63 ref

026280   SANGEETHA K, THAMOTHARAN S, BABU R R, KUMAR S M (SASTRA Deemed Univ, Tirumalaisamudram, Thanjavur 613 401, Email: sangeetha.proj@gmail.com) : Linear and nonlinear optical properties of 4-nitrobenzoic acid (4-NBA) single crystals. Bull Mater Sci 2018, 41(3), 73.

4-Nitrobenzoic acid (4-NBA) single crystals were studied for their linear and nonlinear optical properties. The crystals were grown by slow solvent evaporation method at room temperature. The structure and functional groups were confirmed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopic studies. The 4-NBA crystal has an optical absorption at 263 nm and a wide transparency window for the visible light. Theoretical predictions for the measured optical absorption and charge transfer mechanism in 4-NBA were explained with HOMO and LUMO illustrations. The crystal is found to be birefringent and has produced an optical quality interference pattern. The optic plane of the crystal is observed along 100 direction. The crystal exhibits nonlinear optical effects viz. reverse saturable absorption and selfdefocussing of laser beam. Considerable nonlinear refraction (n₂) and nonlinear absorption (β) coefficients and third-order nonlinear optical susceptibility (χ⁽³⁾ ) were determined using Z-scan technique.

10 illus, 3 tables, 28 ref

026279   LEBBAD A, KERKACHE L, LAYADI A, LEROY F, ALSHEHRI B, DOGHECHE E (Physique Dep, Ferhat Abbas Univ, Sétif- 19000, Algeria, Email: kerkachelaid@yahoo.fr) : Surface morphology, structural and electrical properties of RF-sputtered ITO thin films on Si substrates. Bull Mater Sci 2018, 41(3), 74.

Series of indium tin oxide (ITO) thin films were deposited onto Si(100) substrate by RF sputtering. The film thickness ranges from 61 to 768 nm. X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) experiments were performed to study the structure and the surface morphology of these films. The electrical properties were obtained by a Hall effect measurement system; the electrical resistivity ρ, the carrier concentration n and the mobility μ were measured. Annealing experiments were carried out in the air at 400 $°$C for 60 min. The different physical parameters were investigated as a function of thickness before and after annealing. The effects of power and deposition rate were also addressed. We noted that the behaviour of some parameters with thickness is different before and after annealing. All these results are discussed and correlated in this article. Also, the results of the present ITO/Si system were compared to those of the ITO/glass, we have previously published.

7 illus, 2 tables, 30 ref

026278   LAPA H E, KOKCE A, OZDEMIR A F, USLU I, ATINDAL S (Physics Dep, Suleyman Demirel Univ, Isparta- 32260, Turkey, Email: farukozdemir@sdu.edu.tr) : A comparative study on dielectric behaviours of Au/(Zn-doped PVA)/n-4H-SiC (MPS) structures with different interlayer thicknesses using impedance spectroscopy methods. Bull Mater Sci 2018, 41(3), 82.

Three different thicknesses (50, 150 and 500 nm) Zn-doped polyvinyl alcohol (PVA) was deposited on n-4HSiC wafer as interlayer by electrospinning method and so, Au/(Zn-doped PVA)/n-4H-SiC metal–polymer–semiconductor structures were fabricated. The thickness effect of Zn-doped PVA on the dielectric constant (ε ), dielectric loss (ε), losstangent (tan δ), real and imaginary parts of electric modulus (M and M) and ac electrical conductivity (σ_ac) of them were analysed and compared using experimental capacitance (C) and conductance (G/ω) data in the frequency range of 1–500 kHz at room temperature. According to these results, the values of ε and ε decrease with increasing frequency almost exponentially, σ_ac increases especially, at high frequencies. The M and M values were obtained from the ε and ε data and the M and M vs. f plots were drawn for these structures. While the values of ε , ε and tan δ increase with increasing interlayer thickness, the values of M and M decrease with increasing interlayer thickness. The double logarithmic σ_ac vs. f plots for each structure have two distinct linear regimes with different slopes, which correspond to low and high frequencies, respectively, and it is prominent that there exist two different conduction mechanisms. Obtained results were found as a strong function of frequency and interlayer thickness.

4 illus, 36 ref

026277   SEKHAR K C, HAMEED A, SATHE V G, CHARY M N, SHAREEFUDDIN M D (Physics Dep, Osmania Univ, Hyderabad- 500 007, Email: chandu_07u@yahoo.co.in) : Physical, optical and structural studies of copper-doped lead oxychloro borate glasses. Bull Mater Sci 2018, 41(3), 79.

Bluish coloured glasses are obtained from the composition PbCl₂–PbO–B₂O₃ doped with Cu²⁺ ions. Basic physical properties and spectroscopic studies (optical absorption, electron paramagnetic resonance, Fourier transform infrared and Raman spectroscopies) were carried out on these samples. The increase in PbCl₂ content resulted in the decrease in density and increase in molar volume. At optical frequencies, band gaps and Urbach energies were evaluated and their variation is explained. Spin-Hamiltonian parameters (SHP) obtained from the EPR spectra suggest that the ligand environment around Cu²⁺ is tetragonally distorted octahedral sites and the orbital d_x2−y2 is the ground state. The characteristics broad bands in the optical absorption spectra are assigned to the ²B_1g → ²B_2g transition. The bonding coefficient values were evaluated using optical data and SHP. FTIR studies suggested that the glass structure is built up of BO₃ and BO₄ units. The presence of diborate, pyroborate, pentaborate groups, etc. in the glass network was confirmed from Raman spectra.

9 illus, 3 tables, 41 ref

026276   RANI K J, RADHA M, RADHIKA K (ECE Dep, GIST, Nellore) : PAPR reduction for OFDM based massive MIMO systems using selected mapping technique. Asian J Sci Technol 2018, 9(5), 8095-8.

The problem of peak-to-average power ratio (PAPR) reduction in orthogonal frequency-division multiplexing (OFDM) based massive multiple-input multiple-output (MIMO) downlink systems is considered. OFDM consist of large number of independent subcarriers, as a result of which the amplitude of such a signal can have high peak values. The peak to average power ratio of a transmitted signal is one of main challenges in OFDM or MIMO-OFDM. Understanding the effects of PAPR on OFDM and MIMO-OFDM systems is critical when determining what techniques to use improve system performance. Selective-Mapping (SLM) scheme which does not require the transmission of side information and can reduce the PAPR in OFDM system is proposed. SLM is a distortion less technique that can reduce PAPR efficiently without increase in power requirement and incurring data rate loss. Simulation results show that the system can achieve significant reduction in PAPR and satisfactory bit error rate performance over AWGN channels.

5 illus, 8 ref

025124   NANDAKUMAR H, SUBRAMANIA A K, SRIVASTAVA S (Physics Dep, Sri Sathya Sai Institute of Higher Learning, Anantapur - 515 134, Email: hari@radiosai.org) : Sub-4-micron full-field optical coherence tomography on a budget. Sadhana 2018, 43(6), 97.

We evaluate the construction and performance of an ultra-low-cost full-field optical coherence tomography (FF-OCT) instrument, also known as an optical coherence microscope. Although the cost of construction of the instrument from off-the-shelf parts is at least ten times lower than those of commercial products, sub-4-micron axial and lateral resolutions are obtained, albeit at the cost of higher acquisition times. Standard test samples are imaged and the performance of the instrument is evaluated. The device is found to be useful in measuring length, dispersion and group refractive index as well. Suggestions for bettering performance are discussed.

7 illus, 28 ref

025123   SENTHILKUMAR G, PANCHAPAKESAN N R (Indian Institute of Technology, Chennai - 600 036, Email: gsk.mach23@gmail.com) : Effect of flapping kinematics on aerodynamic force of a flapping two-dimensional at plate. Sadhana 2018, 43(5), 72.

Potential applications of flapping-wing micro-aerial vehicles (MAVs) have prompted enthusiasm among the engineers and researchers to understand the flow physics associated with flapping flight. An incompressible Navier–Stokes solver that is capable of handling flapping flight kind of moving boundary problem is developed. Arbitrary Lagrangian–Eulerian (ALE) method is used to handle the moving boundaries of the problem. The solver is validated with the results of problems like inline oscillation of a circular cylinder in still fluid and a flat plate rapidly accelerating at constant angle of attack. Numerical simulations of flapping flat plate mimicking the kinematics of those like insect wings are simulated, and the unsteady fluid dynamic phenomena that enhance the aerodynamic force are studied. The solution methodology provides the velocity field and pressure field details, which are used to derive the force coefficients and the vorticity field. Time history of force coefficients and vortical structures gives insight into the unsteady mechanism associated with the unsteady aerodynamic force production. The scope of the work is to develop a computational fluid dynamic (CFD) solver with the ALE method that is capable of handling moving boundary problems, and to understand the flow physics associated with the flapping-wing aerofoil kinematics and flow parameters on aerodynamic forces. Results show that delayed stall, wing–wake interaction and rotational effect are the important unsteady mechanisms that enhance the aerodynamic forces. Major contribution to the lift force is due to the presence of leading edge vortex in delayed stall mechanism.

13 illus, 4 tables, 15 ref

025122   ZHANG P (Yangtze Normal Univ, China, Email: zhangp007@foxmail.com) : Monte Carlo simulation of secondary electron images for gold nanorods on the silicon substrate. Pramana - J Phys 2018, 90(6), 0081.

Recently, gold nanorods (Au NRs) have attracted much attention because at a particular photoelectricity the gold nanorods present a characteristic which is different from other types of Au nanomaterials with various shapes. Accurate measurement of aspect ratios does provide very high value of optical property for Au NRs. Monte Carlo (MC) simulation is thought of as the most accurate tool to perform size measurement through extracting structure parameters from the simulated scanning electron microscopy (SEM) image which best matches the experimental one. In this article, a series of MC-simulated secondary electron (SE) images have been taken for Au NRs on a silicon substrate. However, it has already been observed that the two ends of Au NRs in the experimental SEM image is brighter than that of the middle part. It seriously affects the accuracy of size measurement for Au NRs. The purpose of this work is to understand the mechanism underlying this phenomenon through a series of systematical analysis. It was found that the cetyltrimethylammonium bromide (CTAB) which covers the Au NRs indeed can alter the contrast of Au NRs compared to that without CTAB covering. However, SEs emitting from CTAB are not the reason for the abnormal brightness at the two ends of NRs. This work reveals that the charging effect might be the leading cause for this phenomenon.

9 illus, 22 ref

025121   GOYAL M, GUPTA B R K (Physics Dep, GLA Univ, Mathura - 281 406, Email: monika.goyal@gla.ac.in) : Shape, size and temperature dependency of thermal expansion, lattice parameter and bulk modulus in nanomaterials. Pramana - J Phys 2018, 90(6), 0080.

A theoretical model is described here for studying the effect of temperature on nanomaterials. The thermodynamic equation of state (EoS) proposed by Goyal and Gupta in High Temp.-High Press. 45, 163 (2016); Oriental J. Chem. 32(4), 2193 (2016), is extended in the present study using Qi and Wang model [Mater. Chem. Phys. 88, 280 (2004)]. The thermal expansion coefficient is expressed in terms of shape and size and used to obtain the isobaric EoS of nanomaterials for the change in volume V/V0V/V0. The variation in V/V0V/V0 with temperature is estimated for spherical nanoparticles, nanowires and nanofilms. It is found that the volume thermal expansivity decreases as size of the nanomaterial increases, whereas V/V0V/V0 increases with temperature across nanomaterials of different sizes. The lattice parameter variation with temperature is studied in Zn nanowires, Se and Ag nanoparticles. It is found that lattice constant increases with increase in temperature. Also, bulk modulus is found to increase with temperature in nanomaterials. The results obtained from the present model are compared with the available experimental data. A good consistency between the compared results confirms the suitability of the present model for studying thermal properties of the nanomaterials.

4 illus, 1 table, 29 ref

025120   JOSHI G, G RAVI, MUKHERJEE S (Nirma Univ, Ahmedabad- 382 481, Email: jgareema@gmail.com) : A new linear plasma device for the study of plasma waves in the electron magnetohydrodynamics regime. Pramana - J Phys 2018, 90(6), 0079.

A new, user-friendly, linear plasma device has been developed in our laboratory where a quiescent (Δn/n≈1%Δn/n≈1%), low temperature (1–10 eV), pulsed (3–10 ms) plasma can be produced over a large uniform region of 30–40 cm diameter and 40 cm length. Salient features of the device include the flexibility of tuning the plasma density in the range of 10101010 to 1012cm−31012cm−3 and capability of scanning the plasma and field parameters in two dimensions with a precision of < 1 mm. The plasma is produced by a multifilamentary cathode and external magnetic field by Helmholtz coils, both designed and constructed in-house. The plasma parameters can be measured by Langmuir probes and electromagnetic field parameters by miniature magnetic probes and Rogowski coils. The plasma produced is uniform and essentially unbounded for performing experiments on waves and turbulence. The whole device can be operated single-handedly by undergraduate or graduate students. The device can be opened, serviced, new antennas/probes installed and ready for operation in a matter of hours. Some results on the excitation of electromagnetic structures in the context of electron magnetohydrodynamics (EMHD) are also presented to demonstrate the suitability of the device for carrying out such experiments. 

14 illus, 1 table, 19 ref

025119   REDDY A N K, HASHEMI M, KHONINA S N (Samara National Research Univ, Russia, Email: naarereddy@ssau.ru; naarereddy@gmail.com) : Apodization of two-dimensional pupils with aberrations. Pramana - J Phys 2018, 90(6), 0077.

The technique proposed to enhance the resolution of the point spread function (PSF) of an optical system underneath defocussing and spherical aberrations. The method of approach is based on the amplitude and phasemaskinginaringapertureformodifyingthelightintensitydistributionintheGaussianfocalplane(YD =0) and in the defocussed planes (YD = π and YD = 2π). The width of the annulus modifies the distribution of the light intensity in the side lobes of the resultant PSF. In the presence of an asymmetry in the phase of the annulus, the Hanning amplitude apodizer [cos(πβρ)] employed in the pupil function can modify the spatial distribution of light in the maximum defocussed plane (YD =2π), results in PSF with improved resolution.

6 illus, 3 tables, 27 ref

025118   TIRANDAZ H, MOLLAEE A K (Hakim Sabzevari Univ, Iran, Email: tirandaz@hsu.ac.ir) : On synchronisation of a class of complex chaotic systems with complex unknown parameters via integral sliding mode control. Pramana - J Phys 2018, 90(6), 0076.

Chaotic systems demonstrate complex behaviour in their state variables and their parameters, which generate some challenges and consequences. This paper presents a new synchronisation scheme based on integral sliding mode control (ISMC) method on a class of complex chaotic systems with complex unknown parameters. Synchronisation between corresponding states of a class of complex chaotic systems and also convergence of the errors of the system parameters to zero point are studied. The designed feedback control vector and complex unknown parameter vector are analytically achieved based on the Lyapunov stability theory. Moreover, the effectiveness of the proposed methodology is verified by synchronisation of the Chen complex system and the Lorenz complex systems as the leader and the follower chaotic systems, respectively. In conclusion, some numerical simulations related to the synchronisation methodology is given to illustrate the effectiveness of the theoretical discussions.

4 illus, 33 ref

025117   BHATT K, RANI C, VAID M, KAPOOR A, KUMAR P, KUMAR S, SHRIWASTAWA S, SHARMA S, SINGH R, TRIPATHI C C (Kurukshetra Univ, Kurukshetra - 136 119, Email: kapilbhattuiet@gmail.com) : A comparative study of graphene and graphite-based field effect transistor on flexible substrate. Pramana - J Phys 2018, 90(6), 0075.

In the present era, there has been a great demand of cost-effective, biodegradable, flexible and wearable electronics which may open the gate to many applications like flexible displays, RFID tags, health monitoring devices, etc. Due to the versatile nature of plastic substrates, they have been extensively used in packaging, printing, etc. However, the fabrication of electronic devices requires specially prepared substrates with high quality surfaces, chemical compositions and solutions to the related fabrication issues along with its non-biodegradable nature. Therefore, in this report, a cost-effective, biodegradable cellulose paper as an alternative dielectric substrate material for the fabrication of flexible field effect transistor (FET) is presented. The graphite and liquid phase exfoliated graphene have been used as the material for the realisation of source, drain and channel on cellulose paper substrate for its comparative analysis. The mobility of fabricated FETs was calculated to be 83cm²/Vs83cm²/Vs (holes) and 33cm²/Vs33cm²/Vs (electrons) for graphite FET and 100cm²/Vs100cm²/Vs (holes) and 52cm²/Vs52cm²/Vs (electrons) for graphene FET, respectively. The output characteristic of the device demonstrates the linear behaviour and a comprehensive increase in conductance as a function of gate voltages. The fabricated FETs may be used for strain sensing, health care monitoring devices, human motion detection, etc.

6 illus, 1 table, 31 ref

025116   REVATHY J S, ANOOJA J, KRISHNAVENI R B, GANGADATHAN M P, VARIER K M (Physics Dep, Univ Coll, Thiruvananthapuram- 695034) : Effective atomic numbers in some food materials and medicines for γ-ray attenuation using 137Cs γ-ray. Pramana - J Phys 2018, 90(6), 0072.

A light-weight multichannel analyser (MCA)-based γ-ray spectrometer, developed earlier at the Inter University Accelerator Centre, New Delhi, has been used as part of the PG curriculum, to determine the effective atomic numbers for γ attenuation of 137Cs γ-ray in different types of samples. The samples used are mixtures of graphite, aluminum and selenium powders in different proportions, commercial and home-made edible powders, fruit and vegetable juices as well as certain allopathic and ayurvedic medications. A narrow beam good geometry set-up has been used in the experiments. The measured attenuation coefficients have been used to extract effective atomic numbers in the samples. The results are consistent with XCOM values wherever available. The present results suggest that the γ attenuation technique can be used as an effective non-destructive method for finding adulteration of food materials.

3 illus, 7 tables, 9 ref

025115   LI Y, LIU J G (Beijing Univ of Posts and Telecommunications, China, Email: 395625298@qq.com) : Multiple periodic-soliton solutions of the (3+1)-dimensional generalised shallow water equation. Pramana - J Phys 2018, 90(6), 0071.

Based on the extended variable-coefficient homogeneous balance method and two new ansätz functions, we construct auto-Bäcklund transformation and multiple periodic-soliton solutions of (3+1)(3+1)-dimensional generalised shallow water equations. Completely new periodic-soliton solutions including periodic cross-kink wave, periodic two-solitary wave and breather type of two-solitary wave are obtained. In addition, cross-kink three-soliton and cross-kink four-soliton solutions are derived. Furthermore, propagation characteristics and interactions of the obtained solutions are discussed and illustrated in figures.

12 illus, 37 ref

025113   KOMATHIRAJ K, SHARMA R (Physics Dep, P.D. Women’s Coll, Jalpaiguri - 735 101, Email: rsharma@associates.iucaa.in) : A family of solutions to the Einstein-Maxwell system of equations describing relativistic charged fluid spheres. Pramana - J Phys 2018, 90(5), 0068.

In this paper, we present a formalism to generate a family of interior solutions to the Einstein–Maxwell system of equations for a spherically symmetric relativistic charged fluid sphere matched to the exterior Reissner– Nordström space–time. By reducing the Einstein–Maxwell system to a recurrence relation with variable rational coefficients, we show that it is possible to obtain closed-form solutions for a specific range of model parameters. A large class of solutions obtained previously are shown to be contained in our general class of solutions. We also analyse the physical viability of our new class of solutions.

6 illus, 45 ref

025112   HAMMAMY M N E, ATTIA A (Physics Dep, Damanhur Univ, Egypt, Email: marwa1374@yahoo.com) : 16C-elastic scattering examined using several models at different energies. Pramana - J Phys 2018, 90(5), 0066.

In the present paper, the first results concerning the theoretical analysis of the 16C p reaction by investigating two elastic scattering angular distributions measured at high energy compared to low energy for this system are reported. Several models for the real part of the nuclear potential are tested within the optical model formalism. The imaginary potential has a Woods–Saxon shape with three free parameters. Two types of density distribution and three different cluster structures for 16C are assumed in the analysis. The results are compared with each other as well as with the experimental data to give evidence of the importance of these studied items.

8 illus, 5 tables, 32 ref

025111   ZHANG S, ZENG Y, LI Z, WANG M, XIONG L (Xiangtan Univ, China, Email: yichengz@xtu.edu.cn) : A novel grid multiwing chaotic system with only non-hyperbolic equilibria. Pramana - J Phys 2018, 90(5), 0063.

The structure of the chaotic attractor of a system is mainly determined by the nonlinear functions in system equations. By using a new saw-tooth wave function and a new stair function, a novel complex grid multiwing chaotic system which belongs to non-Shil’nikov chaotic system with non-hyperbolic equilibrium points is proposed in this paper. It is particularly interesting that the complex grid multiwing attractors are generated by increasing the number of non-hyperbolic equilibrium points, which are different from the traditional methods of realising multiwing attractors by adding the index-2 saddle-focus equilibrium points in double-wing chaotic systems. The basic dynamical properties of the new system, such as dissipativity, phase portraits, the stability of the equilibria, the time-domain waveform, power spectrum, bifurcation diagram, Lyapunov exponents, and so on, are investigated by theoretical analysis and numerical simulations. Furthermore, the corresponding electronic circuit is designed and simulated on the Multisim platform. The Multisim simulation results and the hardware experimental results are in good agreement with the numerical simulations of the same system on Matlab platform, which verify the feasibility of this new grid multiwing chaotic system.

14 illus, 34 ref

025110   MANJUNATHA H C , SOWMYA N (Physics Dep, Government Coll for Women, Kolar- 563 101, Email: manjunathhc@rediffmail.com) : Parametrisation of the experimental fusion-fission cross-sections. Pramana - J Phys 2018, 90(5), 0062.

We have presented non-linear analytical formula for fusion–fission cross-sections. This is achieved by analysing many fusion–fission experiments of the compound nuclei of atomic number range 23 Z 146 available in literature. Our parametrised formula can reproduce the fusion–fission cross-sections which agree well with the experiments. Our parametrisations depend on the charges and masses of the compound nuclei and fission fragments only. These results can be used as a guideline for estimating the fusion–fission cross-sections in those cases where measurements do not exist and also for studying new nuclei which are not yet explored.

8 illus, 3 tables, 76 ref

025109   MAHMOUD A, AHMED M, MAHMOUD S W Z (Physics Dep, Minia Univ, Egypt, Email: alaa.abutaleb@lira.bsu.edu.eg) : Optimum parameters controlling distortion and noise of semiconductor laser under analog multichannel modulation. Pramana - J Phys 2018, 90(5), 61.

This paper presents a comprehensive modelling and simulation study on the optimum parameters that control the distortion and noise of semiconductor lasers (SLs) subject to multichannel modulation for use in analog cable television (CATV) fibre links. The study is based on numerical integration of the rate equation model of the semiconductor laser. The parameters comprise the modulation index per channel (m/ch), number of loaded channels (N) and fibre length (LF ). The signal distortions include the composite second-order (CSO) and composite triple beat (CTB) distortions. The noise is assessed in terms of the relative intensity noise (RIN) and carrier-to-noise ratio (CNR). In order to achieve acceptable CNR values for SL, m/ch should be less than 7.5 and 2 % when loading 12 and 80 channels, respectively. For the CATV fibre link with LF 10 km, the increase in the number of channels from 12 to 80 corresponds to lowering the optimum value of m/ch from 7 to 1 %. The increase of LF to 50 km limits the optimum value of m/ch between 1.4 and 1 %, which corresponds to loading between 12 and 17 channels only.

8 illus, 1 table, 33 ref

025108   RAEEI M A, DAHER M S E (Physics Dep, Damascus Univ, Syria, Email: eldaherm@scs-net.org) : Analytical static structure factor for a two-component system interacting via Van der Waals potential. Pramana - J Phys 2018, 90(5), 60.

In this work, we derive analytical solutions for static structure factor for homogeneous and isotropic solution composed of two components interacting with each other via simple van der Waals potential which is inversely proportional to the sixth power of the distance between the two components. We assume that the first component is the solvent and the second component is the dissolved material which has low concentration or density in comparison to the concentration of the solvent, i.e. dilute solution, which is common for macromolecular fluids. The presented solution is obtained using direct and inverse Fourier transforms in solving Ornstein–Zernike equations (OZE) for multicomponent systems. We calculated isothermal compressibilities as a function of concentration and comparison with other simulation and theoretical results are presented. We believe that the presented solution can be useful in studying biomolecular fluids and other soft matter fluids.

3 illus, 1 table, 18 ref

025107   VOHRA R, SAWHNEY R S (Guru Nanak Dev Univ, Amritsar- 143 001, Email: rajanvohraece.rsh@gndu.ac.in) : Envisaging quantum transport phenomenon in a muddled base pair of DNA. Pramana - J Phys 2018, 90(5), 0058.

The effect of muddled base pair on electron transfer through a deoxyribonucleic acid (DNA) molecule connected to the gold electrodes has been elucidated using tight binding model. The effect of hydrogen and nitrogen bonds on the resistance of the base pair has been minutely observed. Using the semiempirical extended Huckel approach within NEGF regime, we have determined the current and conductance vs. bias voltage for disordered base pairs of DNA made of thymine (T) and adenine (A). The asymmetrical behaviour amid five times depreciation in the current characteristics has been observed for deviated Au–AT base pair–Au devices. An interesting revelation is that the conductance of the intrinsic AT base pair configuration attains dramatically high values with the symmetrical zig-zag pattern of current, which clearly indicates the transformation of the bond length within the strands of base pair when compared with other samples. A thorough investigation of the transmission coefficients T (E) and HOMO–LUMO gap reveals the misalignment of the strands in base pairs of DNA. The observed results present an insight to extend this work to build biosensing devices to predict the abnormality with the DNA.

7 illus, 4 tables, 37 ref

025106   ANITHA A, ARULMOZHI M (Physics Dep, Jayaraj Annapackiam Coll for Women (Autonomous), Periyakulam, Theni District - 625 601, Email: arulpkm@yahoo.co.in) : Exciton binding energy in a pyramidal quantum dot. Pramana - J Phys 2018, 90(5), 0057.

The effects of spatially dependent effective mass, non-parabolicity of the conduction band and dielectric screening function on exciton binding energy in a pyramid-shaped quantum dot of GaAs have been investigated by variational method as a function of base width of the pyramid. We have assumed that the pyramid has a square base with area a a and height of the pyramid H a/2. The trial wave function of the exciton has been chosen according to the even mirror boundary condition, i.e. the wave function of the exciton at the boundary could be non-zero. The results show that (i) the non-parabolicity of the conduction band affects the light hole (lh) and heavy hole (hh) excitons to be more bound than that with parabolicity of the conduction band, (ii) the dielectric screening function (DSF) affects the lh and hh excitons to be more bound than that without the DSF and (iii) the spatially dependent effective mass (SDEM) affects the lh and hh excitons to be less bound than that without the SDEM. The combined effects of DSF and SDEM on exciton binding energy have also been calculated. The results are compared with those available in the literature.

8 illus, 23 ref

025105   FENG L, LIU H, KAPTEYN H J, FENG A Y (Liaoning Univ of Technology, China, Email: attophys1101@gmail.com) : XUV pulse effect on signal modulations of harmonic spectra from H₂+ and T₂+. Pramana - J Phys 2018, 90(5), 0056.

The effects of signal modulations on the molecular high-order harmonic generations in H₂+ and T₂+ have been theoretically investigated. It is found that with the introduction of the XUV pulse, due to the absorption of the extra XUV photons in the recombination process, multiplateaus on the harmonic spectra, separated by the XUV photon energy can be found. Moreover, this multiplateau structure is insensitive to the wavelength of the XUV pulse. In shorter pulse duration, the intensities of the multiplateaus from H₂+ are higher than those from T₂+ ; while in longer pulse duration, the opposite results can be found. Finally, by changing the delay time of the XUV pulse, the signal modulations (including the amplitude and the frequency modulations) of the multiplateaus can be controlled.

9 illus, 50 ref

025104   ATULKAR R, MANSOORI A A, KHAN P A, PUROHIT P K (Electronics Dep, Barkatullah Univ, Bhopal- 462 026, Email: roshniatulkar@gmail.com) : Solar cycle variation and its impact on critical frequency of F layer. Indian J Radio Space Phys 2018, 47(1-2), 20-9.

The ionosphere exhibits the variability over different time scales. In the present paper we present the long term solar activity variations of mid latitude ionosphere. To accomplish this study we have considered a famous Australian station namely Hobart (42.88 °S , 147.32 °E), which falls in the mid latitudinal region. The variability has been examined over the previous three solar cycles i.e, 21, 22 and 23 solar cycles. To characterize the long term variability of the solar activity we have used four indices namely sunspot number (Rz), solar radio flux (F 10.7cm), Mg II core to wing ratio and solar flare index. Similarly, for ionospheric variability we have the critical frequency of F2 layer (foF2). From our study, we found that the long term changes in the solar activity indices which are closely and synchronously reflected in the ionospheric foF2. To quantify the magnitude of association between the long term solar activity variations and the ionsopehric variations we have performed the single regression analysis and computed the correlation coefficients between the two types of indicies, and found that there exists an extremely strong correlation between the two types of indices for all the three solar cycles. Hence, it has been concluded that the ionospheric foF2 is strongly influenced by solar activity with an 11-year variability.

12 illus, 1 table, 27 ref

025103   JAYESHLAL G S, SATYANARAYANA M, MOTTY G S, DHAMAN R K, MAHADEVAN PILLAI V P (Optoelectronics Dep, Kerala Univ, Thiruvananthapuram - 695 581, Email: jayeshlalgs@gmail.com) : Correlation analysis of lidar derived optical parameters for investigations on thin cirrus features at a tropical station Gadanki (13.5 ⁰N and 79.2 ⁰E), India. Indian J Radio Space Phys 2018, 47(1-2), 9-19.

The optical characterization of thin cirrus clouds is very important to understand its radiative effects. The optical parameters of cirrus clouds namely extinction ($\mathrm{\sigma }$), Optical depth () and Linear depolarization ratio (LDR), have been derived from lidar data, obtained from a ground based polarization lidar at a tropical station, Gadanki (13.5 ºN and 79.2 ºE), India. The range dependent Lidar ratio (LR) has been derived by using an in-house developed iterative method. The present study makes an effort to understand the correlation between different optical parameters, and to get an insight in to the structure, composition and stability of the topical cirrus clouds. The variation of LR values with LDR gives an idea about the nature of aerosol content present within the cloud. It has been observed that there is a negative correlation between LDR and LR with a second degree polynomial fit for thin cirrus cloud conditions. The correlation between ice water content (IWC) derived directly from extinction value and LDR has been found to be positive and it has been used to establish cloud phase accurately instead of from the LDR value itself. From the time series observation it has been also found that the extinction and hence the IWC increases due to the growth of cirrus particle.

11 illus, 44 ref

025102   RAO S S, SHARMA S, PANDEY R (Physics Dep, MLS Univ, Udaipur - 313 001, Email: ssraophy116@gmail.com) : Study of night time TEC depletion over Indian region. Indian J Radio Space Phys 2018, 47(1-2), 5-8.

Observations of night time total electron content depletions recorded over the Indian stations, Udaipur and Bengaluru, are presented. Udaipur is located near the crest of the equatorial ionization anomaly and Bengaluru is the near equatorial station. New features like location of plasma bubble over equator, north-west drift of the plasma bubble and time duration of sustainability of plasma bubble that produced depletion over low latitudes are being reported.

6 illus, 17 ref

025101   GUNDIMEDA A, MISHRA M, AHMAD R, SRIVASTAVA R, DWIVEDI U K, GUPTA G (CSIR-NPL Campus, New Delhi - 110 060, Email: govind@nplindia.org) : Influence of active layer thickness on electrical properties of P3HT/n-Si based hybrid heterostructure. Indian J Pure Appl Phys 2018, 56(6), 468-74.

In the present study, we analyze the effect of active (organic) layer thickness on the optical and electrical properties of poly 3-hexylthiophene/n-silicon hybrid hetero-structure. The organic/inorganic sandwiched heterojunction have been prepared via spin-coating of poly 3-hexylthiophene film onto an oxide passivated Si substrate at room temperature. The device structure has been fabricated via depositing silver and aluminum contacts on Poly 3-hexylthiophene and n-silicon layers, respectively. The optical and electrical properties of the fabricated heterostructures have been examined by varying the active layer thickness from 50 to 120 nm. Photoluminescence measurements displayed a sharp intense peak at 578 nm corresponding to characteristic poly 3-hexylthiophene band-to-band transition. Enhancement in forward current and reduction in leakage current was observed with increased active layer thickness. It has been observed that employing an active layer thickness of 100 nm, the device produces enhanced forward currents with low leakage currents which leads to the formation of high quality heterojunction and demonstrates better performance of the device.

4 illus, 1 table, 40 ref

025100   HAMMAMI N E, BOUANZ M, TOUMI A (Physique Dep, Carthage Univ, Tunisia, Email: adel.toumi@fst.rnu.tn) : Acoustical and thermodynamic study of binary mixture cyclohexane-methanol using ultrasonic interferometer at different temperatures. Indian J Pure Appl Phys 2018, 56(6), 461-7.

The ultrasonic velocity (U) mass density (ρ) and shear viscosity (η) of the binary liquid mixtures of cyclohexane- methanol have been determined experimentally in the single-phase region and over the whole composition range at temperature range (T = 321.15 to 325.15 K). The experimental measurements of these properties have been carried out at atmospheric pressure, for a constant frequency 2 MHz. From these experimental data values, various acoustic and thermodynamic parameters namely adiabatic compressibility (βs), acoustic impedance (Z), intermolecular free length (L_f), relaxation time (τ), molar volume (V_m), free volume (V_f), internal pressure (π_i), attenuation (α/f^₂), Gibb’s energy (ΔG), and cohesive energy (CE) have been calculated. Also their excess values have been calculated. All these parameters and their excess values have been interpreted in terms of molecular interaction such as dipole-dipole and dipole induced dipole interactions through hydrogen bonding between components of binary liquid mixture.

9 illus, 3 tables, 40 ref

025099   RAWAT S, SHARMA J, SHARMA S (Jawaharlal Nehru Univ, New Delhi - 110 067, Email: shatendra@gmail.com) : Hydrothermal synthesis and characterization of nickel doped potassium titanate. Indian J Pure Appl Phys 2018, 56(6), 453-60.

The potassium titanate nanowires doped with nickel using nickel chloride as dopant are synthesized by hydrothermal method. These synthesized structures are then characterized by XRD, SEM and TEM and the dopant concentrations are estimated by EDS. The XRD characterization of samples shows that the product formed is mainly K₂Ti₆O₁₃. The nanowires/fibres of the K₂Ti₆O₁₃ are formed having length up to 20 microns and thickness of about 20 nm. The TEM imaging confirms the formation of uniform internal structures of all nanowires however the inner structure of nickel doped samples are denser in comparison to the undoped samples. The annealing of synthesized nanowires at temperatures in the range of 600-1000 ^$\circ$C modifies their crystal structure. The EDS results have shown that the measured Ni doping concentration in all samples is about four times higher than the expected values. Therefore the possibility of chemical bonding or trapping of nickel atoms in the structure cannot be ruled out. The UV-Vis and Raman spectra of the doped samples are compared with that of un-doped samples. In present work, the use of nickel chloride as dopant in potassium titanate using hydrothermal method is reported for the first time.

10 illus, 1 table, 57 ref

025098   JERUSHA E, KIRUPAVATHY S S, SHALINI S (Physics Dep, Velammal Engineering Coll, Chennai - 600 066, Email: shahilkirupavathy@yahoo.co.in) : Influence of L-Lysine as dopant in ammonium tetroxalate dihydrate- spectral, optical, thermal, mechanical and dielectric properties. Indian J Pure Appl Phys 2018, 56(6), 444-52.

Semi organic crystals offer a variety of molecular structures by virtue of the changes brought out in selection of dopants. In the present work mechanical, thermal, dielectric, FTIR and UV studies of single crystals of ammonium teroxalate dihydrate (ATOXAL) doped with basic amino acid L-Lysine have been studied and compared. Fourier transform infrared (FTIR) spectroscopy study confirms the incorporation of L-Lysine into ATOXAL. Optical studies on L-Lysine doped ATOXAL (L-Lys doped ATOXAL) crystals reveal that these crystals are optically better and more transparent than the pure ones having wide transmission spectra lying in the entire visible and near infrared (NIR) regions. Optical band gap has been found to be 4.281 eV and the nonlinear index of refraction is 1.829. Negative photoconductivity has been exhibited by the crystal. TG / DTG and DSC analyses reveal that thermal anomalies occurr at 111.1 ° C and 231.8 ° C. Low dielectric constant and dielectric loss at higher frequency observed in L-Lys doped ATOXAL is a desirable property to enhance the NLO efficiency. Also, it is observed from the dielectric studies that the ferroelectric phase has higher activation energy than the paraelectric phase. Vickers’s micro hardness test reveals that dopant inclusion increased the mechanical strength of the crystals.

14 illus, 3 tables, 48 ref

025097   RAM I S, RAM J, SINGH K (Jawaharlal Nehru Univ, New Delhi - 110 067, Email: kedarbhp@rediffmail.com) : Carrier type reversal in Pb modified Se₈₀In₂₀ semiconducting glassy alloys. Indian J Pure Appl Phys 2018, 56(6), 440-3.

The effective thermal conductivity (λ_e), effective thermal diffusivity (χ_e) and specific heat per unit volume (ρC_p) of twin pellets of Se₈₀In₂₀-xPb_x (x = 0, 5, 10 and 15) glasses have been measured at room temperature by using transient plane source (TPS) technique. All three parameters have been varied with Pb content and show reversal trend for 5 at. wt. % of Pb. This reversal trend can be explained on the basis of carrier type reversal as a consequence of unpinning of the Fermi level due to incorporation of Pb in Se-In glassy system.

3 illus, 23 ref

025096   DRIZE A, SETTAOUTI A (Electrotechnic Dep, Sciences and Technology Univ, Oran, Algeria, Email: abbes.drize28@gmail.com) : Physical investigation of copper thin film prepared by sputtering. Indian J Pure Appl Phys 2018, 56(6), 434-9.

Copper thin films have been deposited by sputtering. The simulation results show that most of deposited atoms on the substrate have kinetic energy ranging between 1 and 1.5 eV which leads to the deterioration of the crystalline quality, the impact angle between 10°- 70° and 100°-160°, with a peak at 40° and 150°, the oblique incidences of sputtered atoms on the substrate give films with porous and columnar microstructures. For higher pressure theses distributions are more uniforms leading to the uniformity of the obtained thin film which paid a great attention in the industry. These results are in accordance with numerical and experimental ones obtained in others works.

5 illus, 44 ref

025095   BHAKAT D, BARIK P, BHATTCHARJEE A (Physics Dep, Vishva-Bharati Univ, Shantiniketan-731 235, Email: bhattacharjee@visva-bharati.ac.in) : Electrical conductive properties of some composites of gum arabic biopolymer and magnetite nanoparticles. Indian J Pure Appl Phys 2018, 56(6), 428-33.

DC electrical conductive properties of some composites of gum arabic biopolymer (host) and magnetite nanoparticles (guest) synthesized in different weight percentages have been studied as a function of temperature and applied bias voltage to explore the effect of the guest on the electrical conduction of the host. Two types of trap distributions (single discrete and exponential) have been found in these composites. The observed results show that the conductivity of the composites increases with increasing guest content along with a decrease in activation energy. Percolation theory has been employed for the analysis of the room temperature electrical conductivity enhancement with the variation of guest content. The activation energy and the pre-exponential factor values estimated following Arrhenius relation satisfies the compensation law.

4 illus, 1 table, 38 ref

025094   CHOUDHARY A R, WAGHULEY S A (Physics Dep, Sant Gadge Baba Amravati Univ, Amravati - 444 602, Email: sandeepwaghuley@sgbau.ac.in) : LPG sensing application of ex situ PPy-Bi₂O₃-MOX (MOX=ZrO₂, Ag₂O and TiO₂) nanocomposites. Indian J Pure Appl Phys 2018, 56(6), 423-7.

PPy-Bi₂O₃-MOX (MOX=ZrO₂, Ag₂O and TiO₂) nanocomposites have been synthesized by ex situ approach. PPy-Bi₂O₃- MOX (MOX=ZrO₂, Ag₂O and TiO₂) nanocomposites sensors have been fabricated for LPG sensing application. The nanocomposites have been characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), ultra violet visible spectroscopy (UV-Vis) and thermo gravimetric-differential thermal analyzer (TG-DTA) techniques. SEM micrograph exhibits irregular morphology, appropriate for gas sensing application. XRD reveals that all nanocomposites have amorphous nature. Among all the nanocomposites PBZr (PPy-Bi₂O₃-ZrO₂) nanocomposite sensor has found good LPG sensing performance. PBZr nanocomposite sensor also exhibits better selectivity and stability against LPG. This sensor has low operating temperature against LPG of the order of 323 K and fast response and recovery time.

4 illus, 1 table, 18 ref

025093   TAHIR M B, ULLAH S, ALI S, RAFIQUE M, RAFIQUE M S (Physics Dep, Gujrat Univ, Pakistan, Email: m.bilaltahir@uog.edu.pk) : Spectroscopic studies of laser generated plasma X-rays and their effects on polymeric materials. Indian J Pure Appl Phys 2018, 56(5), 392-8.

Surface modification of polymers by X-rays produced from laser plasma can put a wide range of changes and are magnificently used in effectively all industries ranging from coatings, semiconductors, household appliances, automotive, and biomedical implants. Polymeric materials commonly have outstanding bulk physical and chemical properties. Different properties like electrical, chemical and physical properties can be modify when an extreme dose of X-rays is exposed on the surface of polymers. Currently X-rays are irradiated on the surface of two different polymers including polypropylene and polyethylene. These X-rays are detected with pin photodiode (BPX-65), generated from laser generated Cu plasma where Nd: YAG laser (1064 nm, 10 mJ) is focused on copper. Polymer surface is exposed to X-rays by different shots of laser which are varied from 100 to 400 with a gap of 100. Morphological structure has been studied by using optical microscopy and four point probes are used for studying the resistivity and conductivity. It has been observed that irradiation of X-rays from laser produced plasma produce changes in the bonding structure of polymers due to cross linking and chain-seasoning which are highly responsible for breakage or formation of a bond. A similar type of a result is deduced from four-point probe method that the resistivity of polymers is decreased due to the breakage of the H-C bond.

8 illus, 29 ref