Journal of Nepal Physical Society <p>Official journal of the Nepal Physical Society.</p> en-US <p>All right reserved. No part of this Journal may be reproduced in any form or by any electronic or mechanical means, including information storage and retrieval system, without permission in writing from the publisher, except by a reviewer who may quote brief passage in a review. The views and interpretation in this journal are those of author(s) and they are not attributable to the NPS.</p> (Dr. Hom Bahadur Baniya) (Sioux Cumming) Fri, 30 Dec 2022 00:00:00 +0000 OJS 60 Application of Absorption Spectra to Study Order of Sequence in Intersecting Printed and Pen Strokes <p>This work is performed to establish chronological order in crossing strokes between printed stroke and pen strokes. Nine different types of pens including cello maxriter pen (black and blue), pilot pen (red and black), cello pointec pen (black and blue) and cello techno tip pen (red, black and blue) are used to produce pen strokes and for printed stroke Canon LBP 3300 printer is used. In the case of printed stroke, only black color stroke is applied. As a result, samples of both homogeneous and heterogeneous intersecting strokes are prepared. This work is based on the assumption that nature and peak characteristics of absorption spectra from crossing stroke should be similar to that of second stroke. Here, absorption spectra is generated by Video Spectral Comparator-6000 by using light of wavelength ranging from 400 nm to 1000 nm. From this experiment, it is found to be possible to find chronological order for heterogeneous crossing strokes (crossing stroke of different colors) only if printed stroke is over pen stroke. It means, only if print is done over writing strokes from red and blue pen, then order of sequence of writing can be determined whereas in other cases it is not possible.</p> R. Giri, S. P. Chimouriya, B. R. Ghimire Copyright (c) 2022 Journal of Nepal Physical Society Fri, 30 Dec 2022 00:00:00 +0000 Free Energy of Mixing, Heat of Mixing and Viscosity of Na-K Liquid Alloy at Different Temperatures <p>The Free energy of mixing, Heat of mixing and Viscosity of Na-K alloy are investigated theoretically at different temperatures using the Regular solution model. The interaction energy is temperature dependent. The theoretical values of interchange energy at different temperatures are obtained by best fit parameter approximation with the help of experimental values at 384K. The properties have been studied with the help of computed theoretical interchange energy at different temperatures using interchange energy and temperature relation. A comparison of theoretical and experimental values at 384K shows that they are in good agreement and using this basis we have computed the values at different temperatures.</p> H. K. Limbu, G. P. Adhikari, K. K. Mishra, K. Neupane, I. S. Jha Copyright (c) 2022 Journal of Nepal Physical Society Fri, 30 Dec 2022 00:00:00 +0000 Comparative Study of Fire-Gilded and Electroplated Gold Films on Copper Substrates <p>We compared the structural and optical properties of the gold films deposited on copper substrates by the traditional fire-gilding method and electroplating method which are being adopted by the craftsmen in the Kathmandu valley, Nepal. Atomic force microscopy (AFM) and reflectance spectroscopy were employed to characterize the surface morphology and optical reflectance of the samples, respectively. In the AFM images of the surface of the gold films, we observed that the surfaces of the fire-gilded films not only are smoother but also have higher reflectance than that of the electroplated gold films. In the corrosion experiment by chemical etching of the gold films, fire-gilded samples showed superior corrosion resistance than electroplated gold films.</p> P. Joshi, N. Maharjan, M. L. Nakarmi Copyright (c) 2022 Journal of Nepal Physical Society Fri, 30 Dec 2022 00:00:00 +0000 Estimation of Direct and Diffuse Solar Radiation on Bode, Bhaktapur <p>The main objective of the study is to estimate direct solar radiation (I<sub>B</sub>) and diffuse solar radiation (I<sub>D</sub>) on Bode, Bhaktapur (27.68° N, 85.39° E, 1297 m a. s. l.) for a period of one year (2013). Daily data of Aerosol optical depth (AOD), total ozone column are derived from NASA website. The maximum and minimum monthly average of diffuse solar radiation values were found 318±95 W/m<sup>2</sup> in April and 108 ± 20 W/m<sup>2</sup> in August respectively. The maximum and minimum monthly average of direct solar radiation values were found 975±74 W/m<sup>2</sup> in February and 748 ± 126 W/m<sup>2</sup> in March respectively. The annual average of diffuse solar radiation and direct solar radiation are found 216 ± 88 W/m<sup>2</sup> and 864 ± 125 W/m<sup>2</sup> respectively. Result of this research work is beneficial for the further identification, impact and analysis of direct solar radiation diffuse solar radiation at different places.</p> P. M. Shrestha, S. P. Gupta, U. Joshi, N. P. Chapagain, I. B. Karki, K. N. Poudyal Copyright (c) 2022 Journal of Nepal Physical Society Fri, 30 Dec 2022 00:00:00 +0000 Fabrication of Gas Sensor Based on Graphene for the Adsorption of Gases Produced from Waste Material in Kitchen and its Surrounding <p>Graphene attracted to the researcher with huge attention due to their unique physicochemical properties including high specific surface area and high-speed electron mobility at room temperature. The graphene with several layers was synthesized through liquid phase exfoliation method using high shear force of the magnetic stirrer. This process was performed about 6 hour on the graphite powder and dimethyl-formamide solvent of 0.25 M, 0.5 M and 1 M concentration solution following the microwave treatment for 30 second and sonication for 2 hour at room temperature. The drop-casted exfoliated graphene into glass substrate had G peak and 2D peak. The graphene from 1M concentration had the better quality as compared to the graphene obtained from 0.25M and 0.5M concentration solution. The fabricated gas sensor device with two contact electrodes using exfoliated graphene as a channel material produced the different current (I)–voltage (V) characteristics. The current vs. voltage of bare graphene film without filling of waste harmful gases had the current shifted from 0 mA to 0.0652 mA when the maximum voltage was applied. The current increased nearly from 0.0652 mA to 0.2391 mA after harmful waste gases adjustment at maximum applied voltage. The current through few layers graphene channel after harmful gases filled was found 3.6 times higher than that of the current through the graphene channel without harmful waste gases. This result was due to the adsorption/absorption and interaction of more quantity of harmful waste gases by the exfoliated graphene. So, the device showing some current variation informed that the graphene gas sensor was sensitive to waste gases produced from home kitchen and its surrounding.</p> K. B. Rai, R. P. Yadav, P. M. Shrestha, S. P. Gupta, R. Neupane, R. R. Ghimire Copyright (c) 2022 Journal of Nepal Physical Society Fri, 30 Dec 2022 00:00:00 +0000 Post Monsoon Season Spatial Distribution of Groundwater Depth over the Low-Lands of Sunsari District of Eastern Nepal <p>The knowledge and an accurate representation of the spatial distribution of groundwater depth of an area are very important to realize sustainable use of groundwater resource, protection of ecosystem and for the development of adaptation policies in the changing climate. The present study has, thus, developed a groundwater depth distribution map of southern low-lands of the Sunsari District at the horizontal grid resolution of 3 km × 3 km. The groundwater depths were surveyed at predefined 82 numbers of geo-referenced grid points scattered over the region during the post monsoon season of the year 2019. Referencing the sampled depths, spatial distribution of the groundwater depth over the area has been predicted using the Ordinary Kriging Method. Three widely used Semivariogram modules such as Spherical, Exponential, and Gaussian were implemented. The Gaussian model of Semivariogram outperformed the other methods with <em>R<sup>2</sup></em> of 0.336, <em>RMSE </em>of 2.591, and <em>MAE </em>of 1.946. The predicted spatial distribution of groundwater depth reasonably well correlated with the observed distribution. The spatial distribution of groundwater level suggests that 12.36% the total area, particularly, over the western, southwestern and northern parts hold groundwater at much shallower depth (&lt; 5 m). Over 51.59 % of the total area in the southeastern and northeastern parts, the groundwater level remained below 8 m from the ground and the rest of the total area holds the groundwater deeper than 8 m.</p> D. Ghimire, D. R. Dhakal, G. Bhusal, A. K. Khadka, S. Shrestha, R. P. Regmi Copyright (c) 2022 Journal of Nepal Physical Society Fri, 30 Dec 2022 00:00:00 +0000 Spatial Distribution of Groundwater Level over Lowlands of Morang District of Eastern-Nepal <p>A better understanding of spatial distribution of groundwater level is necessary for the development of groundwater development strategies and sustainable use of available resources. The present study evaluates the spatial distribution of groundwater level over the Morang Administrative District of Eastern Nepal and the groundwater accessibility over the area. The study was realized by performing an extensive field survey of groundwater level during the post-monsoon season over 126 sites. The study area of 1224.80 <em>km</em><sup>2</sup> was gridded at 3 km x 3 km horizontal grid resolution and at least one survey was ensured for each grid point. Downscaled spatial distribution of groundwater level was achieved by interpolating the observed data using the Inverse Distance Weighting (IDW) with different weighting parameters available with the geostatistical module of ArcGIS. The performances of the interpolation methods were evaluated based on the cross-validation of results characterized by the statistical parameters RMSE, <em>R</em><sup>2</sup> and MAE and optimal power (α) for weighting function. The IDW (with α=4) appears to perform well for the study area with Coefficient of Determination (<em>R</em><sup>2</sup>) and Root Mean Square Error (RMSE) and Mean Absolute Error (MAE) values of 0.336, 4.750 and 2.967, respectively. The spatial distribution of groundwater level over the low-lands of Morang District mapped with the IDW interpolation method, revealed that the ground water level is maximum in south-western part of the district. The depth to groundwater lies between the ranges of 4.5 to 10 meters covering almost 67.47% of the total study area.</p> A. Bhattarai, S. Shrestha, R. P. Regmi Copyright (c) 2022 Journal of Nepal Physical Society Fri, 30 Dec 2022 00:00:00 +0000 Electrical Properties of Cobalt Substituted NZCF and ZNCF Nanoparticles Prepared by the Soft Synthesis Method <p>The soft chemical method was adopted for the synthesis of cobalt substituted nickel-zinc and zinc-nickel ferrites (Ni<sub>0.95-x</sub>Zn<sub>0.05</sub>Co<sub>x</sub>Fe<sub>2</sub>O<sub>4</sub> and Zn<sub>0.95-x</sub>Ni<sub>0.05</sub>Co<sub>x</sub>Fe<sub>2</sub>O<sub>4</sub> for x= 0.01, 0.02, 0.03, 0.04, 0.05, and 0.06. We have recently studied the structural, morphological, magnetic properties, initial permeability, and dielectric constant of the samples. They are found with cubic ferromagnetic spinel structure along with the morphology suitable for high-density recording media. The effective initial permeability μi (μ<sub>eff</sub>) is found to depend on magnetocrystalline anisotropy constant K<sub>1</sub> and grain size D. From this present study, the dc resistivity is found to increase linearly with Co<sup>2+</sup> substitution for both ZNCF and NZCF ferrites up to x=0.04. After that, the material changes its ferromagnetism to paramagnetism thereby increasing the activation energy. The difference between the two magnetic states (Ferro and para) in NZCF is found to be greater than in ZNCF. The phase transition helps to determine the Curie temperature. The ac conductivity takes place by the hopping of charge carriers called polarons. The conductivity is enhanced with frequency.</p> D. Parajuli, V. K. Vagolu, K. Chandramoli, N. Murali, K. Samatha Copyright (c) 2022 Journal of Nepal Physical Society Fri, 30 Dec 2022 00:00:00 +0000 Analysis of Proton Flux with Solar Wind Parameters, Symmetric (SYM) and Asymmetric (ASY) H-indices <p>After significant solar eruptions, protons are fired at extremely high speeds, sometimes reaching several thousand kilometer per second (km/s), resulting in solar radiation storms. Solar particle events can be found all around the heliosphere. The cross-correlation analysis along with time series analysis is used to look at how the solar wind and proton flux are related. The parameters used in this work are flux of Solar Energetic Protons (SEP) ranging from &gt;10 MeV to &gt;60 MeV along with speed, density, and pressure of the solar wind parameters. The findings indicate that proton flux (E&gt;10 MeV) shows significant changes just before the storm while flux (E&gt;30 MeV) and (E&gt;60 MeV) doesn’t correlate with solar parameters although during quiet day no significant changes were observed. These finding suggested that SEP can be used as precursor of CME driven storms.</p> A. Giri, A. D. Lama, B. Adhikari, S. Rimal, S. Khatri Copyright (c) 2022 Journal of Nepal Physical Society Fri, 30 Dec 2022 00:00:00 +0000 Discharging Phenomena in different types of Lightning <p>There are two charge regions and charges can transfer from one region to another region. For lightning discharging process, the centers of two charges are separated by different distances and air as an insulator between them. The methods of the process of charge formation in differ-ent types of lightning are different. In volcanic lightning, it form closer to the ground and dis-charging process occurs between the two charge regions as the normal thunderstorm lightning does. The steeped leader starts at the structure and propagates upward in nuclear lightning. Their direction of branching is also upward and the return strokes do not initiate from upward moving leaders. It is similar to upward initiated thunderstorm lightning flashes from tall struc-tures and forms in several kilometers. In Earthquake lightning, a shifting of the positive and negative charge centers in the material, which then results in an external electric field. Even the different lightning signatures have been observed in our scientific community, the thunderstorm lightning is frequently observed and measured by the different methods such as electric field measurement, magnetic field measurement, photography and so on. Here, the method of elec-tric field measurement is used to measure the thunderstorm lightning. In all cases of lightning, the discharge phenomena take place between two different charged regions. The two regions of positive charges and negative charges are separated by a certain distance and the air between them is an insulator. When the sufficient charges store in the two charge regions, voltage is de-veloped between them. If the potential developed is sufficient for the electric breakdown of the air, then lightning phenomena occur. Hence, the discharging phenomena occur between the positive and negative charge regions for the different types of lightning.</p> P. B. Adhikari Copyright (c) 2022 Journal of Nepal Physical Society Fri, 30 Dec 2022 00:00:00 +0000 Monitoring Linear Accelerator Output Constancy and Overall Performance Using the PTW Quickcheckwebline <p>Daily morning quality assurance (QA) for all available beams using conventional phantom measures only output and beam quality. PTW QUICKCHECK<sup>webline</sup> (PTW QCw) is a compact movable light-weight dosimetry equipment used for daily QA, capable of measuring flatness, symmetry, beam quality and output constancy of a given beam in a single exposure. The purpose of this study was to analyze and monitor the output constancy of a medical linear accelerator using PTW QCw and assess the overall performance of the PTW QCw. The output parameters of 4, 6 and 15 MV photon beams and 4, 6, 8, 10, 12 and 15 MeV electron beams of the Elekta Synergy linear accelerator in Kathmandu Cancer Center were analyzed. It was found in the study that all the parameters were well within the recommended tolerance limit of ±3%. Some known modifications in the settings of the linear accelerator gantry, couch, and collimator were introduced separately during the exposures, and the percentage variations from the baseline values were noted to check the sensitivity of the PTW QCw using 6 MV photon beam. The PTW QCw was able to detect the deviations introduced to the external irradiation conditions for both photon and electron beams under daily testing conditions. The results from this study suggest that daily dosimetric consistency measurements using the PTW QCw helps to monitor the overall performance of the linear accelerator.</p> K. S. Nyaichyai, D. Jha, K. P. Adhikari, R. Prajapati, R. Neupane Copyright (c) 2022 Journal of Nepal Physical Society Fri, 30 Dec 2022 00:00:00 +0000 Electronic and Magnetic Properties of K2Mn3S4 <p>Many opto-electronic and energy efficient devices depend on semiconductors’ direct as well as indirect band gap. Using spin-polarized density functional theory approach, we calculate the electronic structure and magnetic properties of K<sub>2</sub>Mn<sub>3</sub>S<sub>4</sub>. We found that this system has a ferrimagnetic ground state with a saturated magnetic moment of 10<em>μ<sub>B</sub></em> per unit cell. This was mostly caused by the antiferromagnetic interaction between the Mn (I) and Mn (II) atoms, with individual magnetic moment of 4.2<em> μ<sub>B</sub></em> and 4.1 <em>μ<sub>B</sub></em>, respectively. More significantly, from the density of states and band structure calculations, K<sub>2</sub>Mn<sub>3</sub>S<sub>4</sub> is noted as a semiconductor with an indirect band gap of 1.1 eV between the top of the valence band of spin up channel and bottom of the conduction bands of spin down channel, indicating the material as a promising candidate for photovoltaic and opto-electronic devices.</p> G. B. Acharya, M. P. Ghimire Copyright (c) 2022 Journal of Nepal Physical Society Fri, 30 Dec 2022 00:00:00 +0000 Comparative Study of Dust Properties around White Dwarf PG 1225-079 in IRIS, AKARI and WISE Data <p>In this work, dust properties around the White Dwarf PG 1225-079 located at RA (J2000): 12<sup><em>h </em></sup>27<sup><em>m </em></sup>47.35<sup><em>s</em></sup>, DEC(J2000): -08° 14’ 37.97” is studied extensively using the publicly available data from Improved Reprocessing of IRAS Survey (IRIS), AKARI infrared survey and Wide field Infrared Survey Explorer (WISE). The bipolar dust structure hardly resolved in IRIS (60 <em>μ</em>m and 100 <em>μ</em>m) is clearly resolved in AKARI (90 <em>μ</em>m and 140 <em>μ</em>m) and WISE (12 <em>μ</em>m and 22 <em>μ</em>m) images. The dust color temperature and dust mass are calculated from the infrared flux density. The average value of dust color temperature in isolated dust structure is 27.57 K for IRIS (I1). For isolated upper and lower dust clouds the average temperatures are; 22.64 K and 22.63 K for AKARI (A1 and A2), 295.34 K and 296.85 K in WISE (W1 and W2) data. A wide range of temperatures suggests the bipolar dust structure is dynamically active. The mass of dust is found to be 3.44 × 10<sup>25</sup> kg in IRIS (I1), 1.82 × 10<sup>26</sup> kg and 5.89×10<sup>26</sup> kg in two bipolar regions in AKARI (A1 and A2) and 1.12 ×10<sup>26</sup> kg and 1.14×10<sup>26</sup> kg in WISE (W1 and W2). A good relation is found between the infrared flux in all survey data with <em>r</em><sup>2</sup> value 0.83 in IRIS (I1) and more than 0.90 in AKARI (A1, A2) and WISE (W1, W2) data. SIMBAD database explore some sources including Supernova Remnants nearby the dust which might be the progenitor of dust as well as the contributor of energetic radiation. The Gaussian modeling of temperature is found to be deviated from normal shape. The contour plot of dust color temperature and dust mass shows non uniform variation among the IRIS, AKARI and WISE survey. The relation between infrared flux, dust color temperature and dust mass within the dust clouds are presented.</p> S. Sigdel, S. Rijal, M. S. Paudel Copyright (c) 2022 Journal of Nepal Physical Society Fri, 30 Dec 2022 00:00:00 +0000 Editorial Vol.8(3) <p>No abstract available.</p> Hom Bahadur Baniya Copyright (c) 2022 Journal of Nepal Physical Society Fri, 30 Dec 2022 00:00:00 +0000