Journal of Nepal Physical Society 2021-08-06T10:20:44+00:00 Dr. Binod Adhikari Open Journal Systems <p>Official journal of the Nepal Physical Society.</p> Editorial Vol.7(2) 2021-07-28T02:37:02+00:00 Binod Adhikari <p>No abstract available.</p> 2021-06-30T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Structural, Electronic and Magnetic Properties of Impurities Defected Graphene/MoS2 Van Der Waals Heterostructure: First-principles Study 2021-07-26T01:44:24+00:00 H. K. Neupane N. P. Adhikari <p>Two-dimensional (2D) pristine and defected van der Waals (vdW) heterostructure (HS) materials open up fortune in nanoelectronic and optoelectronic devices. So, they are compatible for designing in the fields of device applications. In the present work, we studied structural, electronic and magnetic properties of vdW (HS) graphene/MoS<sub>2</sub> ((HS)G/MoS<sub>2</sub>), Nb impurity defect in vdW (HS) graphene/MoS<sub>2</sub> (Nb-(HS)G/MoS<sub>2</sub>), and Tc impurity defect in vdW (HS) graphene/MoS<sub>2</sub> (Tc-(HS)G/MoS<sub>2</sub>) materials by using spin-polarized DFT-D2 method. We examined the structure of these materials, and found that they are stable. Based on band structure analysis, we found that (HS)G/MoS<sub>2</sub>, Nb-(HS)G/MoS<sub>2</sub> and Tc-(HS)G/MoS<sub>2</sub> have metallic characteristics. Also, (HS)G/MoS<sub>2</sub> and Tc-(HS)G/MoS<sub>2</sub> materials have n-type Schottky contact, while Nb-(HS)G/MoS<sub>2</sub> material has p-type Schottky contact. To understand the magnetic properties of materials, we have used DoS, IDoS and PDoS calculations. We found that (HS)G/MoS<sub>2</sub> is a non-magnetic material, but Nb-(HS)G/MoS<sub>2</sub> and Tc-(HS)G/MoS<sub>2</sub> are magnetic materials. Magnetic moment of Nb-(HS)G/MoS<sub>2</sub> and Tc-(HS)G/MoS<sub>2</sub> materials are -0.24 μ<sub>B</sub>/cell and +0.07μ<sub>B</sub>/cell values respectively from DoS/PDoS calculations, and 0.26 μ<sub>B</sub>/cell and 0.08μ<sub>B</sub>/cell values respectively from IDoS calculations. Up-spin and down-spin states of electrons in 2p orbital of C atoms, 3p orbital of S atoms, 4d orbital of Mo atoms, 4d orbital of Tc atom in Tc-(HS)G/MoS<sub>2</sub>, and 2p orbital of C atoms, 3p orbital of S atoms, 4p &amp; 4d orbitals of Mo atoms, 4p &amp; 4d orbitals of Nb atom in Nb-(HS)G/MoS<sub>2</sub> have major contribution for the development of magnetic moment.</p> 2021-06-30T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Improving Tribological Behavior of ICE’s Cylinder Surface by Laser Surface Texturing (LST) 2021-07-26T03:10:37+00:00 K. Tripathi S. W. Lee <p>This study investigates the effect of laser surface texturing (LST) on the friction and wear behavior of grey cast iron (GCI) of internal combustion engine (ICE) cylinder in lubricated conditions. The dimples having diameter of about (58-60) μm and depth of about 10 μm were created on the surface with various dimple densities ranging from 5 to 50%. A ball-on-disc friction tests were performed for all the specimens under 5W30 and 15W50 oils with different viscosities. The tests were carried out at a load of 5N and speed of 5cm/s. The coefficient of friction of the dimpled specimen was reduced significantly by approximately 32% as compared to the polished speciemen. Specimen with 15% dimples exhibits the lowest coefficient of friction of all the dimpled specimens in both low and high viscous oils. The high viscous oil found to be more efficient regarding coefficeint of friction compared to the low viscous oil. The degree of wear of the specimens was analyzed on the basis of wear scar developed on the counter surface as it supplements the wear during the friction tests. The resistance to wear of the sliding specimens was found to be increased in high viscous oil compared to that in low viscous oil.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Study of Structural Behavior of Cadmium Based Alloys at Molten State 2021-07-27T09:55:44+00:00 G. Shrestha I. Koirala <p>The simple statistical model or simple theory of mixing has been used to study the structural behavior of cadmium based alloys at their molten state at a temperature of 800 K by computing thermodynamic functions and structural functions. The thermodynamic functions include free energy of mixing (G<sub>M</sub>), activity (a), the heat of mixing (H<sub>M</sub>), and the entropy of mixing (S<sub>M</sub>). The structural functions include concentration fluctuation in the long-wavelength limit (S<sub>GG</sub>(0)) and Warren-Cowley short-range order parameter (α<sub>1</sub>). Interchange energy or interaction energy or ordering energy (ω) was calculated for the respective alloys system and found to be positive and temperature-dependent. Based on interchange energy (ω) and coordination number (Z), theoretical values of all the functions are calculated by applying the grand partition function. All the computed values for the mentioned functions are in good agreement with experimental values. For the cadmium based alloys, viz., Cd-Zn &amp; Cd-In, both show the segregating in nature at temperature 800 K for the concentration of range 0.1 to 0.9, however, Cd-Zn is more segregating than Cd-In.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Structural, Morphological, and Magnetic Properties of Nickel Substituted Cobalt Zinc Nanoferrites at Different Sintering Temperature 2021-07-27T10:07:23+00:00 D. Parajuli N. Murali K. Samatha <p>Co-precipitation was used for the preparation of Co<sub>0.5-x</sub>Ni<sub>x</sub>Zn<sub>0.5</sub>Fe<sub>2</sub>O<sub>4</sub> (x = 0 to 0.3) nanoferrites. The inverse spinel structure of the samples was clearly shown by the structural analysis of X-ray Diffractometer (XRD) and Fourier Transform Infrared (FTIR) Spectroscopy. We have studied the effect of sintering temperature (500<sup>o</sup>C) on the lattice constant and particle size using XRD. The average lattice parameters for the non-sintered and sintered samples were 8.377 Å and 8.354 Å respectively. For the non-sintered sample, the nickel concentration decreases the lattice parameter from 8.354 Å to 8.310 Å due to its smaller ionic radii than that of cobalt. While for a sintered sample at 500<sup>o</sup>C, the lattice parameter increases for concentration x=0.3 due to the thermal effect. The particle size calculated by Transmission Electron Microscope (TEM) agrees well with that of XRD. The morphological and compositional analysis was done with the help of Scanning Electron Microscopy (SEM) and the attached Energy Dispersive X-ray (EDX) Analyzer. The increasing percentage of nickel with decreasing percentage of cobalt shows that the cobalt is substituted by Nickel. The magnetic properties were studied by Vibrational Spectrometer (VSM). The value of saturation magnetization is higher for x=0.1 but lower for x=0.2 and 0.3 due to their particle size. The hysteresis loop of the samples their superparamagnetic behavior at room temperature.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Substitutional Lithium Doping on Germanene: A First-principles Study 2021-07-27T10:26:08+00:00 J. Basel N. Pantha <p>The density functional theory (DFT) based first-principles calculations have been adopted for the study of structural, electronic and magnetic properties of pure and single Lithium (Li) atom doped germanene monolayer. Due to the higher intrinsic carrier mobilities and large spin orbit gap, germanene has great possibility of being integrated into the silicon based semiconductor industry. Different studies have been done to change the band gap value from its’ pristine zero band gap state. We have doped the single Li atom into the germanene system with the intention of tuning the band gap and other electronic and magnetic properties. Band structure calculations show pristine germanene is semi-metallic in nature whereas the Li doped system is fully metallic with the overlapping of the conduction and valance bands in the Fermi level. Under density of states (DOS) calculations, it is evident that both pristine and doped system are non-magnetic in nature with symmetric DOS plot.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Estimation of Solar Energy Using Different Empirical Models at Mid Hill, Nepal 2021-07-27T10:34:50+00:00 U. Joshi P. M. Shrestha S. Maharjan B. Maharjan N. P. Chapagain I. B. Karki K. N. Poudyal <p>Accurate knowledge of global solar radiation distribution is essential for designing, sizing, and performing an evaluation of solar energy system in any part of the world. However, it is not available in many sites of Nepal due to the high expense of the technical process. This study is focused on the performance of different models based on daily global solar radiation, sunshine hour, temperature, and relative humidity at mid-hill region Lumle, (lat. 28.29650N, long. 83.8179oE, and Alt. 1740.0 m.a.s.l.). This study is carried for the year 2018 to 2020. The performance of different models based on sunshine hour, temperature, and relative humidity were analyzed using the regression technique and statistical tools such as Root Mean Square Error (RMSE), Mean Bias Error (MBE), Mean Percentage Error (MPE), and Coefficient of determination (R2). After the analysis, the modified Angstrom model (M-9) based on temperature difference and relative humidity was found to be the best in terms of accuracy of least RMSE value and highest coefficient of determination. Finally, the empirical constants for model m-9 are a = 0.003, b = 0.523, c = 0.118 and, d = 0.002 obtained. The calculated empirical constants can be utilized for the prediction of GSR at similar geographical locations of Nepal.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society SDSS J114818.18-013823.7: Forming Compact Dwarf Galaxy through the Dwarf-Dwarf Merger 2021-07-27T10:48:18+00:00 D. N. Chhatkuli S. Paudel A. K. Gautam B. Aryal <p>We studied the spectroscopic properties of the low redshift (z = 0.0130) interacting dwarf galaxy SDSS J114818.18-013823.7. It is a compact galaxy of half-light radius 521 parsec. It’s r-band absolute magnitude is -16.71 mag. Using a publicly available optical spectrum from the Sloan Sky Survey data archive, we calculated star-formation rate, emission line metallicity, and dust extinction of the galaxy. Star formation rate (SFR) due to H<sub>α</sub> is found to be 0.118 M<sub>ʘ</sub> year<sup>-1</sup> after extinction correction. The emission-line metallicity, 12+log(O/H), is 8.13 dex. Placing these values in the scaling relation of normal galaxies, we find that SDSS J114818.18-013823.7 is a significant outlier from both size-magnitude relation and SFR-B-band absolute relation. Although SDSS J114818.18-013823.7 possess enhance rate of star-formation, the current star-formation activity can persist several Giga years in the future at the current place and it remains compact.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Seismic phases of 25 April 2015 (Mw 7.8) Earthquake and 12 May 2015 (Mw 7.3) Earthquake Predicted by AK135 Model - A comparison 2021-07-27T11:05:07+00:00 R. K. Tiwari H. Paudyal <p>A strong Mw 7.8 (depth = 8.2 km) earthquake initiated ~80 km northwest of the Kathmandu on 25 April of 2015 was followed by the Mw 7.3 (depth = 15 km) earthquake on 12 May. The seismic phases of these earthquakes were predicted at Kakani, Kathmandu seismic station (27.80°N and 85.28°E) using software model AK135 . The model predicts 21 arrivals for Gorkha earthquake with first p phase arriving at incident angle 82.65° in 11.516 seconds and final phase SKIKSSKIKS in 3270.791 seconds with incident angle 0.02°. Similarly, for the Dolakha earthquake 27 arrivals are predicted with the first arrival p phase at incident angle 74.35° in 14.504 seconds and final arrival SKIKSSKIKS phase at incident angle 0.03° in 3268.823 seconds. The 5 depth phases and 8 core phases predicted are similar for both the earthquakes while 8 and 12 mantle phases are predicted for Gorkha earthquake and Dolakha earthquake respectively. In addition, two crustal phases (Pn, Sn) were predicted only for Dolakha earthquake. The additional phases are critically refracted seismic phases indicating the existence of the Moho discontinuity between the crust and upper mantle. Their existence for Dolakha earthquake could be the indication of different geological provinces of the source region of the earthquakes, differing in age, crustal thickness, temperature, and tectonic stress. The ratio of P wave ad S wave velocity is found to be 1.67 for the regions. These seismic phases reflect their sensitivity to different layers of the earth and carry information about the geometrical and physical properties of discontinuities inside the earth.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Muonium and Water in Histidine Amino Acid 2021-07-27T11:12:50+00:00 A. D. Pant <p>In order to apply muon spin rotation and relaxation method for study of life sciences like electron transfer process, detection of molecular concentration, photosynthesis process, etc., theoretical study to understand the stopping sites of muon and its charge species in the macromolecules is necessary. In the systematic theoretical study to know the behaviour of muon and muonium in water hydrated biological macromolecules like protein and DNA through the first-principles approach, the behaviour of a water molecule in the presence of muonium in histidine amino acid with extended main chain is presented here. The sites of a water molecule and a muonium in histidine amino acid are estimated. Two possible sites with potential energy 0.3 eV (approximately) for water molecule in the optimized structure of muonium in extended main chain histidine were estimated. Water in the sites is expected to contribute to enhance the intra- and inter-chain electron transfer in the system as reported experimentally.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Solvation Free Energy of Protonated Lysine: Molecular Dynamics Study 2021-07-27T11:19:28+00:00 S. P. Khanal B. Poudel R. P. Koirala N. P. Adhikari <p>In the present work, we have used an alchemical approach for calculating solvation free energy of protonated lysine in water from molecular dynamics simulations. These approaches use a non-physical pathway between two end states in order to compute free energy difference from the set of simulations. The solute is modeled using bonded and non-bonded interactions described by OPLS-AA potential, while four different water models: TIP3P, SPC, SPC/E and TIP4P are used. The free energy of solvation of protonated lysine in water has been estimated using thermodynamic integration, free energy perturbation, and Bennett acceptance ratio methods at 310 K temperature. The contributions to the free energy due to van der Waals and electrostatics parameters are also separately computed. The estimated values of free energy of solvation using different methods are in well agreement with previously reported experimental value within 14 %.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Measurement of Plasma Potential, Ion Saturation Current and Mach number using Retarding Field Energy Analyzer 2021-07-27T11:37:47+00:00 L. N. Mishra Å. Fredriksen <p>This article deals about the experimental measurement of plasma potential, ion saturation current and Mach number obtained with the variation of power, operating gas pressure and radial position using retarding field energy analyzer. We employed a retarding field energy analyzer by rotating with different angles such as 0° (facing toward source), 90° (facing side walls) and 180° (facing opposite the source). The coil current is varied from 0 to 15 A to produce the magnetic field which is used to confine the plasma. The flow of plasma has been characterized which was found to be subsonic. The low-temperature plasma is produced by means of a 13.56 MHz helicon plasma source at 300-1000 kW radio frequency power. The plasma is expanding from 13.8 cm diameter source into a 150 cm long diffusion chamber of 60 cm diameter.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Spatial Orientations of Angular Momentum Vectors of Galaxies in Supercluster S [195+027+0022] and Substructure 2021-07-27T11:44:51+00:00 J. R. Malla W. Saurer B. Aryal <p>This paper presents an analysis of the spin vector orientations of SDSS (Sloan Digital Sky Survey) galaxies in the Supercluster S [195+027+0022] using the seventh data release (2008 October). By using the spectroscopic database of galaxies, identified number density map in the region of Superclusters. Several density enhancements are observed, suggesting the possibility of substructure in the Supercluster. Two-dimensional observed parameters that we received from the database are used to compute three-dimensional galaxy rotation axes by applying `position angle-inclination' method. Apply the selection effects by performing the random simulation method. The expected distribution curves are obtained from the simulation. Chi-square, auto-correlation, and Fourier tests are used to examine non-random effects in the polar and azimuthal angle distributions of the galaxy rotation axes. To check these results with the different galaxy evolution models namely Hierarchy, Primordial, and Pancake model. The result supports the Hierarchy model.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Assessment of Environmental Radioactivity in Soil Samples from Kathmandu Valley, Nepal 2021-07-27T11:53:13+00:00 P. Lamichhane B. Rijal P. Shrestha B. R. Shah <p>This study was conducted to determine the amount of naturally occurring radioactivity in the soil of Nepal's Kathmandu valley. The activity of naturally occurring radionuclides was determined in these soil samples using a sodium iodide detector. Activity concentrations of <sup>238</sup>U, <sup>232</sup>Th, and <sup>40</sup>K were found in the range: 32.00-111.38 Bq kg<sup>-1</sup>, 33.52-130.04 Bq kg<sup>-1</sup>, and 342.50-897.71 Bq kg<sup>-1</sup>, respectively. These values are well within the permissible range as recommended by UNSCEAR. The soil samples with the highest activity concentrations were primarily found in the valley's northern region. The activity concentrations were also used to calculate the radiation hazard indices: the mean value obtained were 96.63 nGy hr<sup>-1</sup> for Absorbed Gamma Dose Rate in Air, 200.04 Bq kg<sup>-1</sup> for Radium Equivalent Activity, the 0.12 mSv yr<sup>-1</sup> for Annual Effective Dose, and 0.55 for External Hazard Index. These calculated hazard indices were used to estimate the potential radiological health risk from the soil, and the dose rates associated with it were significantly less than their permissible limit. The overall findings indicate no radiological threat to the population's health in the study area. Additionally, the findings of this study provide baseline information on potential radionuclides that contribute mostly for radiation exposure from natural sources.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Numerical Modelling on the Influence of Source in the Heat Transformation: An Application in the Metal Heating for Blacksmithing 2021-07-27T11:59:28+00:00 H. P. Kandel J. Kafle L. P. Bagale <p>Many physical problems, such as heat transfer and wave transfer, are modeled in the real world using partial differential equations (PDEs). When the domain of such modeled problems is irregular in shape, computing analytic solution becomes difficult, if not impossible. In such a case, numerical methods can be used to compute the solution of such PDEs. The Finite difference method (FDM) is one of the numerical methods used to compute the solutions of PDEs by discretizing the domain into a finite number of regions. We used FDMs to compute the numerical solutions of the one dimensional heat equation with different position initial conditions and multiple initial conditions. Blacksmiths fashioned different metals into the desired shape by heating the objects with different temperatures and at different position. The numerical technique applied here can be used to solve heat equations observed in the field of science and engineering.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Analysis of Tec Variations over Nepal Obtained from GPS Data on Geo-Magnetically Quiet and Disturbed Days of the Year 2015 2021-07-27T12:04:54+00:00 B. D. Ghimire N. P. Chapagain V. Basnet B. Khadka <p>Dual frequency Global Positioning System (GPS) receiver in two nearby stations i.e. BESI (28.228 °N, 84.739 °E) and GHER (28.375 °N, 84.739 °E) located at almost same latitude and longitude are used to measure ionospheric total electron content (TEC) for the year 2015. Since Year of 2014- 2016 have been known as most active years in terms of geomagnetic events, the year 2015 shows some abnormal results. Diurnal, monthly and seasonal variations of GPS TEC have been studied. The difference in the value of TEC is observed between quiet and disturbed days. Moreover, the correlation between GPS-data of each month with solar activities parameters such as Kp index, disturbance storm time (Dst) index, and Solar Flux index (F10.7 cm) have been studied, separately for quiet and disturbed days for each station. In case of diurnal variation, mean TEC varies from 0100 UT (LT= UT+5:45) to maximum from 0900 UT to 1100UT. The value of TEC is observed higher on quiet days than disturbed days. For seasonal variation, local seasons i.e. autumn, Spring, Summer and Winter is taken and, the value of TEC is found to be higher in Spring (March, April and May) in both stations in quiet and disturbed days. The difference in value of quiet and disturbed days of GPS-TEC explained the geomagnetic phenomena difference in these days in ionosphere. This study can be useful to calculate the water vapor concentration in the atmosphere which is useful for weather prediction and meteorological department.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Study of Dust Cavity around the White Dwarf WD 0352-049 in Infrared Astronomical Satellite Map 2021-07-27T12:16:07+00:00 M. S. Paudel P. Bhandari S. Bhattarai <p>In this work, we have studied the far-infrared images of the dust cavity around the White Dwarf WD 0352-049 available in Infrared Astronomical Satellite Map from Sky View Observatory. The size of the cavity is 24.48 pc × 8.10 pc. We have studied the relative infrared flux density and calculated the dust color temperature and dust mass. The temperature of the whole cavity structure lies between a maximum value 24.09 ± 0.50 K to a minimum 21.87 ± 0.61K with fluctuation of 2.22 K and an average value of 23.09 ± 1.11 K. The small fluctuation of dust color temperature suggests that the dust in cavity structure is evolving independently and less disturbed from background radiation sources. The color map shows the identical distribution of flux at 60 μm and 100 μm and the inverse distribution of dust color temperature and dust mass. There is a Gaussian-like distribution of relative flux density, dust color temperature and dust mass. The Gaussian distribution of temperature suggests that the dusts in cavity are in local thermodynamic equilibrium. The study of relative flux density and dust color temperature along the major and minor axis shows there is a sinusoidal fluctuation of flux and temperature, which might be due to the wind generated by White Dwarf located nearby the center of the cavity structure. The total dust mass of the dust is found to be 0.07 M<sub>ʘ</sub> and that of gas is 13.66 M<sub>ʘ</sub>. The Jeans mass of the structure is less than the total mass of gas in the structure, suggesting the possibility of star formation activity by gravitational collapse in the future. Also, the study of inclination angle suggests that the three-dimensional shape of the structure is uniform and regularly shaped.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Determination of Optical Constants and Thickness of Nanostructured ZnO Film by Spin Coating Technique 2021-07-27T12:27:15+00:00 R. R. Ghimire Y. P. Dahal K. B. Rai S. P. Gupta <p>In this report, we have investigated optical constants and thickness of nanostructured ZnO films grown on a glass substrate by sol-gel spin coating technique using zinc acetate as precursor. Optical constants such as complex refractive index <em>ñ</em> and dielectric constant <em>ϵ</em> determined from the transmittance spectrum in the ultraviolet, visible, near infrared (UV-VIS, NIR) region by envelope method. The value of refractive index decreases from 2.34 to 1.86 and extinction coefficient increases from 0.28 to 0.64 with increasing wavelength. The decreasing behavior of refractive index is attributed due to the increase in transmission and decrease in absorption coefficient with increasing wavelength. The film exhibits reasonably high transmittance (&gt;80%) in the visible region. Absorbance coefficient α and film thickness (d) were calculated from the interference of fringes of transmittance spectrum. The band gap and thickness of the film were found 3.02 eV and 275nm, respectively. The thickness of the film measured by envelope method is validated with cross-section micrograph of SEM images which is about 285 nm. The real part of the dielectric function of nanostructured ZnO decreases with increasing wavelength where as the imaginary part of dielectric constant increases with increasing wavelength. The observed high value of refractive index n and real part of dielectric constant <em>ϵ</em> at lower wavelength is due to band edge absorption of carriers. The dispersion relation shows the increase of complex refractive index and dielectric constant at the high frequency regime is due to the discharging of defect levels using optical excitation of carriers in the visible region.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Geomagnetically Quiet Period Analysis of Relativistic Electrons, Auroral Precipitation, Joule Heating, and Ring Current During the Years of 1999, 2000 and 2004 2021-07-27T12:37:02+00:00 R. K. Mishra A. Gautam P. Poudel N. Parajuli A. Silwal B. Adhikari B. R. Tiwari S. P. Gautam <p>This work presents the study of the quietest time variation in relativistic electrons, auroral precipitation, ring current, and joule heating during 1999, 2000, and 2004. Geostationary Operational Environmental Satellite (GOES) data on relativistic electrons with energies above 0.6 MeV, 2 MeV, and 4 MeV were analyzed. The time-series analysis of the relativistic electrons over a 24-hour averaged interval reveals a precise 24-hour modulation of the relativistic electron population during all seasons for energies above 0.6 MeV and 2 MeV, and during the winter season for higher energies above 4 MeV. In addition, relativistic electron fluxes at energies above 0.6 MeV and above 2 MeV were higher during the descending phase of the solar cycle compared to the ascending and solar-maximum phases. The cross-correlation analysis presented a strong correlation of Joule heating, ring current, and auroral precipitation with the relativistic electron population in three energy bands considered, as indicated by the zero-time lag. Studying the quiet time variation of relativistic electrons will lead to more complete ionospheric models, which were previously limited to the geomagnetically disturbed period.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Temporal Ion Velocity Variation with Obliqueness in Magnetized Plasma Sheath 2021-07-27T12:47:56+00:00 B. R. Adhikari R. Khanal <p>A narrow region having sharp gradients in physical parameters is formed whenever plasma comes into contact with a material wall. In this work, the temporal velocity variation of ions in such a sheath has been studied in the presence of an external oblique magnetic field. The Lorentz force equation has been solved for the given boundary conditions using Runge-Kutta method. In order to satisfy the Bohm criterion, ions enter the sheath region with ion acoustic velocity. It is observed that all components of the velocity waves are damped in plasma in the time scale of one second. The computed oscillatory part of ion velocity match with the equation of the damped harmonic oscillator. Thus obtained damping constants as well as the frequency of all three components are nearly equal for obliqueness less than 600 after which they are distinctly different. This is due to the fact that the magnetic field becomes almost parallel to the wall. In earlier studies, only the final velocity profiles are reported and hence this study is useful in understanding how the ion velocities evolve in time as they move from sheath entrance towards the wall.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society Preperation of Thin Film of Tin Oxide (SnO2) by Spray Pyrolysis Method and Study its Application as Gas Sensor 2021-07-27T12:53:51+00:00 R. Chalise P. K. Thakur J. J. Nakarmi S. P. Shrestha <p>In this article SnO<sub>2</sub> thin films have been deposited onto glass substrates by Spray Pyrolysis Method. Tin chloride dihydrate (SnCl<sub>2</sub>.2H<sub>2</sub>O) and Copper nitrate (Cu (NO<sub>3</sub>)<sub>2</sub> .3H<sub>2</sub>O) were used as source of Sn and Cu respectively. The structural, optical and gas sensing properties of Undoped and copper doped by (vol. %) SnO<sub>2</sub> film have been investigated. XRD of film shows structure of films. Also result so obtained from XRD spectroscopy shows that these layers have the tetragonal polycrystalline tinoxide structure. The optical transmission was found to decrease with addition of copper as dopant on SnO<sub>2</sub> with the addition of Cu except for 5% Cu-Doped. The reponse of these layers have been investigated for different concentrations of butane gas by static gas sensing system. The results of this investigation show that the Cu-Doped SnO<sub>2</sub> nanostructure layer compared with the pure SnO<sub>2</sub> nanostructure layer has showed the better response for butane gas. Among Cu-Doped SnO<sub>2</sub> thin film layer 4% (by vol.) copper doped thin film layer has showed higher response toward the Butane gas with less response and recovery time than other films.</p> 2021-08-06T00:00:00+00:00 Copyright (c) 2021 Journal of Nepal Physical Society