Journal of Nepal Physical Society <p>Official journal of the Nepal Physical Society.</p> <p>Journal of Nepal Paediatric Society is included on <a title="DOAJ" href="" target="_blank" rel="noopener">DOAJ</a>.</p> en-US <p>©2019 Journal of Nepal Physical Society.</p> <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 Gopi Chandra Kaphle) (Sioux Cumming) Sun, 29 Dec 2019 13:29:53 +0000 OJS 60 Editorial Vol.5(1) <p>Not available.</p> Vinaya Kumar Jha ##submission.copyrightStatement## Thu, 26 Dec 2019 00:00:00 +0000 White Painting Pigment as a Low-Cost Light Scattering Material for Bilayer Photoelectrodes of Dye-Sensitized Solar Cells <p>White pigment (DuPont R902+) has been used as a light scattering material in the preparation of bilayerphotoelectrodes of dye-sensitized solar cells (DSCs). The X-ray diffraction (XRD) pattern of the white pigment revealed that the material consists of rutile phase of titanium dioxide. The light scattering layer prepared from the white pigment was coated onto the main-layer of the photo electrodes of DSCs. The solar cells with and without light scattering layer were tested in the simulated light of 100 mW/cm<sup>2</sup>. The DSCs with the light scattering layer generated more current density than the DSCs without scattering layer and the overall light to electric power conversion efficiency of DSCs with the light scattering layer was ~4.00 % compared with 3.25 % efficiency of the DSCs without the scattering layer.</p> P. Joshi ##submission.copyrightStatement## Thu, 26 Dec 2019 05:59:36 +0000 Estimation of Monthly Average Daily Diffuse Solar Radiation using Empirical Models For Kathmandu Nepal <p>An accurate knowledge and data of solar radiation and its component are indispensable for the utilization of solar energy. However radiation data are often inaccessible. In this regard, the empirical models are reliable tools. This paper aims to develop and evaluate three simple empirical models (linear, quadratic, and cubic) for estimation of monthly average daily diffuse solar radiation of Kathmandu. Developed Models correlates diffuse fraction with clearness index are based on the satellite data from the NASA Langley Research Center. The performance of models is found to be statistically significant which has been analyzed in terms of statistical indicators like RMSE, MBE and R<sup>2</sup>. Among the three models, the cubic model is best fit on the basis of statistical parameters. So that cubic model is recommended for the estimation of monthly average daily diffuse radiation at Kathmandu and similar climatic sites of Nepal.</p> B. Pandey, R. P. Aryal, C. L. Gnawali, K. N. Poudyal, I. B. Karki, I. Koirala ##submission.copyrightStatement## Thu, 26 Dec 2019 06:21:25 +0000 Spatial Orientation of Galaxies in Supercluster S[195+027+0022] <p>We present a study of spin vector orientation of 1198 SDSS (Sloan Digital Sky Survey) galaxies in Super cluster S[195+027+0022] having red shift 0.07 to 0.09. The databases of these galaxies are taken from SDSS (Sloan Digital Sky Survey) 7th and 9th data release. We have converted two dimensional data to three-dimensional by Godlowskian Transformation using position angle-inclination angle method. We intend to find non-random effects in the spatial orientation of galaxies in Super cluster. No preferred alignment of angular momentum vectors (spin vector) is noticed, supporting Hierarchy model of galaxy formation.</p> J. R. Malla, B. Aryal, W. Saurer ##submission.copyrightStatement## Thu, 26 Dec 2019 06:49:42 +0000 First-Principles Study of Van Der Waals Interactions between Halogen Molecules (Cl2 and I2) <p>Density Functional Theory (DFT) based first-principles calculations have been performed to investigate vander Waals (vdW) interactions in between halogen atoms/molecules —Cl-Cl, I-I, Cl<sub>2</sub>-Cl<sub>2</sub>, Cl<sub>2</sub>-I<sub>2</sub>, I<sub>2</sub>-I<sub>2</sub>—via with and without a non-local exchange-correlation (XC) functional (vdW-DF) using Quantum ESPRESSO codes. The non-polar covalent bond length between atomic halogens (Cl-Cl and I-I) is not observed to be affected by vdW interactions and agrees well with experimental values. The binding energy between theatomic halogens, on the other hand, is slightly corrected by vdW interactions. However, the role of vdW interactions is observed to be crucial to bind molecular halogens. The molecules are weakly bound in the presence of vdW interactions and not correlated (bound) in the absence of them.</p> S. Neopane, N. Pantha ##submission.copyrightStatement## Thu, 26 Dec 2019 08:28:52 +0000 Energy Loss of Proton Beam on Ovary Tumor <p>Proton beam therapy is more effective method than most common radiation (x-rays or photons) therapy and is a new type of irradiation that destroys the tumor or cancer cells in the human body. In the proton therapy, the beam consists of charged nuclei of hydrogen atoms i.e. hydrogen ions or protons. The beam of proton loses the most of its energy to the targeted tissue like ovary tumor cells, with less impact of healthy tissues and organs. This property of a proton beam makes it ideal for clinical applications. When organ safe keeping is our priority then proton beam therapy is the most effective tool to damage nearby affected tissues. For efficient treatment planning in ovary tumor, the maximal energy loss of proton beam in its tissues must be exactly calculated. The method of computer simulation, SRIM is employed for the calculation of energy loss by energized proton beam irradiation on ovary tumor at a depth of 43.3 mm. The stopping power and range data agrees with standard reference data. 65 Mev energy loss is caused by ionization and the energy loss in various layers viz. skin, adipose tissue, soft muscle and ovary are approximately 2.6 MeV, 15 MeV, 7 MeVand 40 MeV respectively, ensuring less injury to healthy cells.</p> K Giri, R. Khanal ##submission.copyrightStatement## Thu, 26 Dec 2019 08:43:26 +0000 Theoretical Study of Plasma Using Different Dimension of Hollow Cathode <p>This article deals about the theoretical study on DC hollow cathode glow discharge using different hollow cathode geometry. The mechanism of discharge is analyzed at various gas pressure and radial configuration. The dependence of temperature on gas pressure has been elucidated with the help of Scotty limit. Discharge behavior with radius has also been explained. It is revealed that floating potential increases as gas pressure increases whereas plasma potential decreases as gas pressure increases. This theoretical work resembles with the experimentally measured results. This work might be useful for the plasma processing for industrial purposes.</p> L. N. Mishra, K. Khanal ##submission.copyrightStatement## Thu, 26 Dec 2019 09:29:53 +0000 Study of a Far Infrared Cavity around an AGB Star under Iras Survey at Galactic Latitude -1.6° <p>In this paper, we discuss about the physical properties of the dusty environment around the AGB star located at R.A. (J2000) = 06h 42m 02s and Dec (J2000) = 00° 53’ 00”, in the far infrared (60 and 100μm) IRAS maps. A cavity like structure (major diameter ∼ 2.5 pc &amp; minor diameter ∼0.9 pc) is found to lie at R.A. (J2000) = 06h 41m 43.03s and DEC (J2000) = 01° 09’ 22.8”, located at a distance ∼ 405 pc from the star. By using contour map diagram, we studied the distribution of flux density, dust color temperature, dust mass and outflow mass in the cavity. The dust color temperature is found to lie in the range 21.4K to 21.9 K which shows the cavity is isolated and independently evolved. Such a low offset temperature variation shows that the star is stable and its life is long. Dust particles are less interacting and mean free path is large. The cavity may be in thermally pulsating phase. Product of dust color temperature and visual extinction is found to be less than one. A possible explanation of the results will be discussed.</p> A. K. Gautam, B. Aryal ##submission.copyrightStatement## Sun, 29 Dec 2019 04:32:37 +0000 First-Principles Study of Electronic and Magnetic Properties of Anatase and its Role in Anatase-Mxene Nanocomposite <p>The electronic and magnetic properties of Titanium and one of its oxide Anatase are calculated by using Tight Binding Linear Muffin-Tin Orbital Atomic Sphere Approximation (TB-LMTO-ASA) method under Density Functional Theory (DFT). The lattice parameter, band structure, Density of States (DOS) and charge density distributions of Ti and TiO<sub>2</sub> (Anatase) required for electronic structure are calculated respectively. The orbital contribution is analyzed by fat band structure; the d- orbital on conduction band and, s and p orbitals on valance bands. Consequently, their magnetic properties are checked. From our study, we found that the magnetic moments of Ti and TiO<sub>2</sub> are found to be 2.2 μB and 0 respectively. The total Density of States for spin up and down electron have smaller difference in Ti and symmetric in TiO<sub>2</sub> indicates that Ti slightly paramagnetic and Anatase is non magnetic in nature. The charge density plots reveals the concentration of electrons at the site under study. Anatase can be deposited onto Mxene to form Mxene-Anatase nanocomposite which has several excellent applications in the field of biosensors, biocompatible materials, energy storage devices, topological insulators etc.</p> D. Parajuli, G. C. Kaphle, K. Samatha ##submission.copyrightStatement## Sun, 29 Dec 2019 09:18:09 +0000 A Study of Far Infrared Cavity At -3.6° Galactic Latitude <p>We have present properties like inclination angle, dust color temperature and dust mass of core region in far infrared located nearby White dwarf WD2236+541.The size of cavity is 0.84 pc×0.51 pc. The cavity is formed by high pressure at the time of white dwarf formation. The dust color temperature varies from 22.42K to 27.43 K. The inclination angle of cavity is 54.2°. The position of white dwarf is found at R.A. J (2000)= 22<sup>h</sup>38<sup>m</sup>24<sup>s</sup> and Dec. J (2000)= +54°26<sup>m</sup>19<sup>s</sup>.</p> B. B. Sapkota, B. Aryal ##submission.copyrightStatement## Sun, 29 Dec 2019 06:15:00 +0000 Study of Total Electron Content and Electron Density Profile from Satellite Observations During Geomagnetic Storms <p>Total Electron Content (TEC) and electron density profile are the key parameters in the mitigation of ionospheric effects on radio wave communication system. In this study, the variations of TEC and electron density profile have been analyzed using satellite data from four different latitude-longitude sectors (13°N -17°N, 88°E - 98°E), (30°N - 50°N, 95°W - 120°W), (26°S - 29°S, 163°W - 167°W,) and (45°S - 60°S, 105°W-120°W) during different geomagnetic storms. The interplanetary magnetic field (Bz), solar wind velocity (Vsw), solar wind pressure (Psw) and geomagnetic indices, aurora index -AE, Kp and disturbed stormed time index (Dst) are also analyzed to distinguish their effects on TEC and electron density. The geomagnetic indices and solar wind parameters are correlated with the TEC and electron density. The study showed that the value of TEC and electron density vary significantly with different latitude, longitude, altitude and solar activities. The result also concludes that the electron density profile increases with the altitude, acquired peak value around 250km-300km and decreased beyond the altitude of 300 km.</p> B. B. Rana, N. P. Chapagain, B. Adhikari, D. Pandit, K. Pudasainee, S. Chapagain, D. Chhatkuli ##submission.copyrightStatement## Sun, 29 Dec 2019 06:45:26 +0000 Empirical Models for the Evaluation of Global Solar Radiation in the Different Sites of Nepal <p>To operate many phenomenon’s on the earth surface such as physical, chemical and biological process solar radiation plays vital role. A common practice is to estimate average daily global solar radiation (GSR) using appropriate empirical models for the areas lacking the actual measured values. In this context several single and multiple meteorological parameters were selected to estimate the GSR for Jumla, Nepalgunj and Kathmandu. In order to validate the selected models various statistical test were employed. The selected models were compared on the basis of statistical errors. In the statistical analysis the value of root mean square error (RMSE) and coefficient o determination R<sup>2</sup> is found to, 0.26 and 0.98, 0.96, 0.96 respectively for Jumla, Nepalgunj and Kathmandu in Samuel model. These values were comparatively better than other models. It is concluded that Samuel model (order three) is the best among the used models. The established result uncover that there is a good possibility of solar energy as a alternative energy source in Nepal.</p> B. P. Pant, K. N. Poudyal, B. Acharya, B. Budha ##submission.copyrightStatement## Sun, 29 Dec 2019 07:03:07 +0000 An Infrared Survey of Isolated Nebular Structures at Galactic Latitudes 16.98° & 1.98° in ARAS map <p>Two isolated far infrared dust structures (∼2.61pc × 1.57pc and ∼82.99pc × 39.99pc) at galactic coordinates: (353.01°, 16.98°) and (18.42°, 1.98°), were selected. We adopted the distance of the first structure to be about 139 pc and that of the second structure to be 2.6 kpc. In this present work we have studied the flux density variation and calculated dust color temperature and mass profile of the dust and Jeans mass of the structures using the data reduction software ALADIN v9. Our aim was to test whether this region is star forming or not. We also calculated the size and inclination angle of our structures. The dust color temperature is found to lie in the range 20.75 K to 35.90 K for the first region and 22.52 K to 45.63 K for the second region. The total mass of gas for the first structure is found to be about 20.99 M<sub>☉</sub> and Jeans mass is found to be 180.9 M<sub>☉</sub>, which is significantly greater than the total mass of the structure, suggesting no possibility of star formation activity for the first region. For the second region, the total mass of gas and the Jeans mass are found to be 5621.61 M<sub>☉</sub> and 6005.04 M<sub>☉</sub> respectively. The mass of the region is still significantly lesser than the Jeans mass. Thus, we conclude that this region is also probably not a star forming region. Also the study of inclination angle suggests that the three-dimensional shape of structures is non uniform and regularly shaped.</p> A. S. Thapa, M. S. Paudel, B. Pant ##submission.copyrightStatement## Sun, 29 Dec 2019 07:16:25 +0000 Electrical Characterization of an Atmospheric Pressure Plasma Jet <p>In this work, a plasma jet has been generated with capillary tube having external diameter 4.0 mm and thickness 1.0 mm. Argon has been used as a working gas. The electrical characteristics of this device like instantaneous power, and discharge current have been measured. The effects of applied voltage on the dissipated power of the device have been investigated. The current is measured with the current probe whereas the voltage is measured from the locally fabricated voltage divider having ratio 1201:1. The electron density has been found out using power balance method. In addition, the power consumption during the discharge has also been studied with the help of Lissajous Figures. The calculated power consumption has been compared with other manual as well as I-V plots.</p> S. K. KC, S. Sharma, R. Shrestha, D. P. Subedi ##submission.copyrightStatement## Sun, 29 Dec 2019 08:31:58 +0000 Theoretical Study of Absorption of Light Due to Effect of Ponderomotive Force <p>Absorption of light due to effect of ponder motive force in laser plasma interaction which has seen that the nonlinear interaction results from rigorous application of the ponder motive force description based on Lorentz’s theory. The deduced equation of motion is more general than that of the two–fluid model of the plasma and that used in the theory of microwave interaction with plasma. As might be expected, the forces are only in the direction of lower plasma densities and tangential forces vanish only with the general equation of two–fluid model. This result has been verified up to the third order in the spatial variation of the electron density. In addition it is seen that the collision frequency decreases continuously with the increase in temperature. From these results, it is concluded that the absorption coefficient decreases continuously with the increase in temperature. Furthermore, this work describes the variation of the absorption coefficient with laser light frequency and shows that the absorption coefficient depends on the frequency of light.</p> P. K. Thakur, J. J. Nakarmi ##submission.copyrightStatement## Sun, 29 Dec 2019 08:41:47 +0000 Structural, Electronic and Magnetic Properties of XYZ Type Half-Heusler Alloys <p>The spintronic devices have played an important role in modern technological era. Heusler alloys have attracted lot of interest in spintronic applications due to their half-metallic properties predicted by band structure calculations. We investigate the electronic, magnetic and structural properties of half-Heusleralloys FeMnGe and CoMnSb using first principles based density functional theory (DFT) implemented on Tight Binding Linear Muffin-Tin Orbital within Atomic Sphere Approximation (TB-LMTO-ASA) code. The calculation reveal that CoMnSb and FeMnGe are half-metallic Ferro-magnet in nature of with magnetic moment 1.00 μB and 2.99 μB per formula unit at equilibrium lattice parameter respectively. The magnetic moment mainly originates from the strong spin polarization of d electrons of X atom and partial contribution of p electrons of Y atom. The half metallic gap of FeMnGe and CoMnSb is found to be 0.38 eV and 0.95 eV respectively. This shows that these alloys are very promising spintronic functional materials.</p> R. Dahal, G. C. Kaphle ##submission.copyrightStatement## Sun, 29 Dec 2019 08:51:10 +0000 Damage Formation and Calculation of Energy Loss during Implantation of Antimony and Boron Ion in Silicon Target <p>The aim of this research work is a computational study of damage profile and visualization of the ion implantation graph obtained from the simulation method using SRIM-2013 software. SRIM (Stopping and Range of Ions in Matter) helps in calculating the energy required for an ion to obtain maximum concentration for desirable range and TRIM (Transport of Ions in Matter) is used to calculate doping statistics and calculation of energy loss. The main objective of this work is to get knowledge about the graphical study of ion range, distribution, stopping power and energy loss during implantation of antimony and boron ion on the silicon target within 0 to 3500 Å target depth. The implantations of 10,000 antimony and boron ions are accelerated by 350 keV and 45 keV energy in silicon monolayer target to obtain maximum defects concentration. The result of the ionization process indicates that 11.68% of the total energy of antimony ion and 65.25% of the total energy of boron ion are lost during the ionization process. This indicates that lighter boron ion causes more ionization than the heavier antimony ion for the same projected range.</p> G. P. Adhikari, H. K. Limbu ##submission.copyrightStatement## Sun, 29 Dec 2019 09:01:46 +0000