http://hdl.handle.net/20.500.12228/52 2026-04-07T13:10:43Z 2026-04-07T13:10:43Z Debnath, Samir Kumar http://hdl.handle.net/20.500.12228/470 2018-12-23T21:00:17Z 2018-01-01T00:00:00Z

Sensitivity of Tropical Cyclone Mahasen to Physical Parameterization Schemes using Weather Research & Forecasting (WRF) model Debnath, Samir Kumar In this study, the sensitivity of numerical simulations of tropical cyclone to physical parameterizations is carried out with a view to determine the best set of physics options for prediction of cyclones originating in the north Indian Ocean. For this purpose, the tropical cyclone Mahasen that formed in the Bay of Bengal and crossed Bangladesh-Myanmar coast in the month of May, 2013 has been simulated by the advanced (or state of science) mesoscale Weather Research and Forecasting (WRF) model with the available physical parameterizations. To determine on the prediction of track and intensity of Tropical Cyclone Mahasen has been used single domain with latitude from 2.0450 N to 26.4800N and longitude from 73.960 E to 97.040E. Domain has been used 12 km horizontal resolution. Different run and different physical parameterizations have been used available in the model. The different physical parameterizations schemes are KF, BMJ , GF, OSAS and Grell-3 for Cumulus; YSU, MYJ, GBM, MYNN3, ACM2, MYNN2, BouLac, UW, TEMF and MRF for Planetary Boundary Layer; WSM6, Kessler, Purdue Lin, WSM3, WSM5, Eta, Thompson, Morrison 2-mom, CAM5.1, SBU-Ylin, WDM5, WDM6, NSSL 2-mom, NSSL 2-mom-CCN, NSSL 1-mom and NSSL 1-momlfo for Microphysics; UNLS, TDS, RUC, NLS, CLM4.0 and PXS for Land surface model; Dudhia, GSFC ARW+Chem(τ), CAM, RRTMG, New Goddard and FLG for Short Wave Radiation; RRTM, CAM Long wave (CAM), RRTMG, New Goddard FLG and Held-Suarez for Long Wave Radiation that have been used for the purpose to test the Sensitivity of Tropical Cyclone Mahasen to Physical Parameterization Schemes using Weather Research & Forecasting (WRF) model. Three parameters track, wind speed and CSLP has been used for calculating Root Mean Square Error (RMSE) to find the best physical made using parameterizations option with respect to observed. Finally Betts Miller Janjic (BMJ) for Cumulus, Medium Range Forecast Model (MRF) for Planetary Boundary Layer (PBL), WRF Single Moment 3-class simple ice scheme (WSM3) for Microphysics (MP), Unified Noah land-Surface Model (UNLS) for Land surface model (LSM), Dudhia (MM5) for Short Wave Radiation (SWR) and Rapid Radiative Transfer Model (RRTM) for Long Wave Radiation (LWR) were found the best among available physics option. This thesis is submitted to the Department of Physics, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Philosophy in Physics, January 2018.; Cataloged from PDF Version of Thesis.; Includes bibliographical references (pages 107-115).

2018-01-01T00:00:00Z Pervin, Shaheena http://hdl.handle.net/20.500.12228/441 2018-08-30T21:00:28Z 2005-10-01T00:00:00Z

Multiple Correlation Between Rainfall of Post-Monsoon Season and the Different Meteorological Parameters of the Monsoon Season Over Bangladesh Pervin, Shaheena In this thesis work attempt has been made to investigate the correlation between the monthly and seasonal rainfall of post monsoon with the dry bulb and wet bulb temperature and rainfall of different months of monsoon and the season itselt First of all the raw data, collected &oni BMD, has been processed to obtain monthly and seasonal average of them. Also the standard deviation in terms of months and seasons have been computed. Using the processed data the correlation coefficients have been computed. We have considered 30 stations all over Bangladesh under all 6 divisions during 1951 - 2000. The computations are made station wise. In this process we have analyzed the following topics: - Averages dry bulb temperature (DBT) and wet bulb temperature (WBT) of the month of June, July, August and September and of monsoon season. Average rainfall of the month of June, July, August, September, October and November and of monsoon and post monsoon season. • The Standard deviation of all the above mentioned cases. • Correlation coefficients between the monthly I seasonal rainfall of post monsoon and monthly / seasonal DBT, WBT and rainfall of monsoon season. Correlation coefficients between the monthly / seasonal rainfall of post monsoon and monthly / seasonal DBT & WBT, WBT & rainfall, DBT & rainfall of monsoon season. And finally correlation coefficients between the monthly / seasonal rainfall of post monsoon and monthly / seasonal DBT, WB'I' & rainfall of monsoon season. From the analysis we have found that in October the amount of rainfall at Sandwip and Patuakhali is the highest and that in the November is at Bhola and Cox's Bazar region. In November the Standard deviation of average rainfall is comparatively high in the southern region. We also observe that November rainfall and WBT of monsoon months are positively correlated except northeast-southern region in July and northeast and Bhola region in June and August of the country. Also regression equations have been developed on considering October and Novcmbcr rainthll as dependent variable and dry bulb temperature, wet bulb temperature and rainfall of monsoon as independent variables. Where the correlation coefficients are high, there these equations will be useful for the prediction purpose. This thesis is submitted to the Department of Physics, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Philosophy, October 2005.; Cataloged from PDF Version of Thesis.; Includes bibliographical references (pages 103-104).

2005-10-01T00:00:00Z Noor, Saroaut http://hdl.handle.net/20.500.12228/440 2018-08-30T21:00:28Z 2005-03-01T00:00:00Z

Effects of Two Step Annealing on Complex Permeability of Fe-Cu-Nb-Si-B Nanocrystalline Soft Magnetic Materials Noor, Saroaut The typical nanocrystalline alloy known as Finemet with the composition Fe73.5Cu jNb3Si135B9 has been studied for the soft magnetic properties. The crystalline phases that evolved after crystallization were studied by X-ray diffraction, crystallization temperature by DTA and magnetic properties by VSM and impedance analyzer. The change of magnetic properties with annealing temperature, Ta in the range 400-700°C and annealing time 1-60 minutes have been investigated. The effect of a two-step annealing on the permeability Fe735Cu)Nb3Si135B9 alloy has been studied. The grain size was determined from the line broadening of the fundamental peak using Scherrers method. Annealed at 555°C, the grain size, the solute silicon content of a-Fe(Si) grains and the improvement in magnetic softness saturate as a function of time. As compared to a nanocrystalline alloy obtained by conventional one-step annealing at around the crystallization temperature, the alloy subjected to preannealing at Ta = 400°C and subsequent high temperature annealing at Ta=555°C shows similar soft magnetic properties. An enhancement of initial permeability with increasing annealing temperature was observed until the annealing temperature TL = 475°C and corresponds to the amorphous relaxed structure. An abrupt deteroriation of permeability takes place at the beginning of crystalization beyond which permeability rises dramatically attaining a maximum value at Ta = 555°C which is attributed to the nanometri grain size effect as a result of averaging out of effective magnetic anisotropy by exchange interaction and decrease of magnetoelastic energy. A sharp decrease of permeability above 580°C is assumed to be connected with iron-boride phase at the beginning of second crystallization stage. The initial permeability for the optimum annealed sample has been found to be 20786 as compared with 284 for its amorphous counterpart. The behavior of very high permeability is explained on the basis of random anisotropy model. From the temperature dependence of magnetization the Curie temperature of the amorphous state and crystallized ferromagnetic phases like Fe(Si) and iron-boride phases and the onset of crystallization temperatures of these phases have been determined. Saturation magnetization measured on the amorphous and annealed samples at different annealing temperature gradually increases with Ta and show a maximum at the medium stage of nanocrysallization at Ta 525°C beyond which magnetization decreases. The results are interpreted on the basis of irreversible structural relaxation as well as enrichment of the nanograins with Si. This thesis is submitted to the Department of Physics, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Philosophy, March 2005.; Cataloged from PDF Version of Thesis.; Includes bibliographical references (pages 110-114).

2005-03-01T00:00:00Z Debnath, Nipa http://hdl.handle.net/20.500.12228/439 2018-09-05T03:58:34Z 2015-09-01T00:00:00Z

Synthesis and Characterization of MgFe204 Ferrite Nanoensemble for Biomedical Application Debnath, Nipa Magnetic nanoparticles have drawn tremendous attraction from both fundamental aspect as well as applications in biomedicine such as magnetic bio-separation, detection of biological entities, magnetic resonance imaging, magnetic fluid hyperthermia and targeted drug delivery due to their fascinating magnetic properties. Superparamagnetic nanoparticles have become the focus of this study because their superparamagnetic, biocompatible and hydrophilic properties would be revealed after modifying the particle surface by suitable surfactants. Considerable research in this area has provided valuable in sites; however, suitable magnetic materials that can be fulfill all the requirements of MRI and hyperthermia applications are still under investigation. This thesis reports on an investigation into the synthesis, control, and stabilization of high quality magnesium ferrite nanoparticles for biomedical application. A new understanding of the factors effecting nanoparticle growth in a coprecipitation methodology has been determined. Then the ferrimagnetic MgFe204 r nanoparticles were modified by annealed temperature from 200 to 1400°C using box furnace. The crystal structural, mean particle size and magnetic properties of the modified ferrimagnetic MgFe204 nanoparticles were measured to investigate the effect of each process on the synthesized nanoparticles. The structural, morphological, magnetic properties of these synthesized products were characterized by using X-ray diffraction (XRD), Vibrating sample magnetometer (VSM), Mössbauer spectroscopy and NMR analysis. XRD patterns of as-dried powder yielded single phase. No impurity peaks were detected. With the increase of annealing temperature, the width of peaks decreases which reflects the coarsening of particles. The smallest crystallite size about 3 nm was obtained for as-dried sample while the largest value 71.86 nm was obtained from the highest studied temperature 1400°C. The crystallite size of the nanoparticles abruptly increased with the annealing temperature. Magnetization measurements have been accomplished by VSM. It was found that saturation magnetization increases with the increase particle size. The small particles first exhibit superparamagnetic behavior at the early stage and then transform to ferromagnetic behavior when particle size passes the superparamagnetic limit. Interesting experimental results on the size dependent magnetic properties at different temperatures have been found. Other structural and magnetic properties such as chemical isomer shift, quadruple splitting and hyperfine IL field were determined by Mössbauer spectroscopy. Superparamagnetic/ferromagnetic transition with the increase of particle size has also confirmed by this analysis. Mössbauer spectroscopy measurements are shown to evidence collective inter-particle correlations between the nanoparticles. The magnesium ferrite nanoparticles were then coated with biocompatible Chitosan (CS) and Polyethylene glycol (PEG). NMR spectroscopy was studied to investigate the spin-spin or T2 relaxivity values to determine its applicability in magnetic resonance images as MRI contrast agents. This thesis is submitted to the Department of Physics, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Philosophy in Physics, Septmber 2015.; Cataloged from PDF Version of Thesis.; Includes bibliographical references (pages 122-136).

2015-09-01T00:00:00Z