KUET Institutional Repository (Khulna University of Engineering & Technology)
Not a member yet
1045 research outputs found
Sort by
Synthesis of (1-x) [Bi0.9Eu0.1FeO3] + x [Ni0.6Zn0.4Fe2O3] Nanostructured Multiferroic Composites and Study of its Structural, Magnetic and Electrical Properties
No full textThis 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 Science in Physics, May 2018.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 72-81).Multiferroic Composites with different mass ratio of Europium doped Bismuth Ferrite
(BEFO) and Nickel Zinc Ferrite (NZF) with general formula (1-x) [Bi0.9Eu0.1FeO3] +
x [Ni0.6Zn0.4Fe2O4] for various x values (x=0, 0.1, 0.3, 0.5, 0.7 and 1) have been
prepared by the conventional solid-state reaction method aided with different
dispersion techniques like magnetic stirring, power ultrasonification and
centrifugation. Crystallinity and structure of the samples were investigated by powder
X-ray diffraction and distorted rhombohedral perovskite BEFO and cubic NZF has
been observed for x = 0.0 and x = 1.0. Mixed perovskite-spinel structure has been
observed for the composites which prove that in the composite BEFO and NZF
phases coexist together with no chemical reaction. The formation of nano is observed
through FESEM micrographs and the compositional purity of the prepared samples
has been confirmed by Energy dispersive x-ray Spectra (EDX). To understand the
temperature dependent grain growth of the samples, all the samples were heated at
3000 C, 4500 C, 6000 C, 7500 C and 8500 C and the average grain size has been
observed in between (65 ~ 75) nm, (65 ~ 70) nm, (55 ~ 70) nm, (350 ~ 400) nm and
(750 ~ 800) nm respectively. The ferromagnetic hysteresis behavior of the samples
have been obtained through vibrating sample magnetometer (VSM) and the magnetic
properties such as saturation magnetization (Ms), remanent magnetization (Mr),
coercive field (Hc), molecular magnetic moment (μB) and magnetic anisotropy
constant are calculated from it. It has been observed that Ms has increased with
increasing NZF content. The complex permeability (μ) of the prepared samples have
been measured and a fairly constant initial permeability (μ') has been observed over a
wide range of frequency (~108 Hz) region. Dielectric properties and AC conductivity
of the samples have been studied in a wide range of frequencies from 1Hz to 100MHz
at room temperature by impedance analyzer and found that x = 0.1 shows the
maximum dielectric constant. Dielectric dispersion has been observed at lower
frequency (< 105 Hz) and is attributed to the interfacial polarization. The complex
impedance spectroscopy is used to correlate between the electrical properties of the
studied samples with their microstructure. The optimum composition is observed for x
= 0.1 which possess the highest frequency dependent dielectric constant and
permeability with lower dielectric and magnetic loss.AL-MasudMaster of Science in Physic
Study of the Magnetic and Transport Properties of Ytterbium Doped Co-Zn Ferrites
No full textThis 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 Science in Physics, October 2018.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 69-75).The present research work is focused Ytterbium (Yb) doped Co-Zn ferrites. The
ferrite samples of the composition Co0.25Zn0.75YbxFe2-xO4 [where x = 0.00, 0.02, 0.04,
0.06 and 0.08] were prepared by standard solid state reaction technique. The samples
were pre-sintered at 850°C for 2 hours and sintered at 1150°C for 3 hours. The effect
of rare earth Yb3+ substitution on the structural, magnetic and electrical properties of
the Co-Zn ferrites was studied. The Phase identification and lattice parameter
determination were carried out by using X-ray diffraction (XRD). XRD patterns
showed that all the samples consisted of the singe phase cubic spinel structure with no
extra peak. The lattice parameters gradually increased with increasing Yb content.
The bulk density slightly decreased with increasing rare earth Yb3+ ion and the X-ray
density increased continuously with increasing x-content. The microstructural
analysis was done by Scanning Electron Microscopy (SEM). The SEM images
showed that the sample exhibit uniform surface morphology with well-defined
spherical grains. The average grain size was calculated using Image J software and
observed that the average grain size increases with Yb content. The complex
permeability, loss tangent and dielectric properties were investigated as a function of
frequency range 1 KHz to 120 MHz by using an impedance analyzer. The initial
permeability was found in steady state to a higher order of frequency range from
103Hz - 50 MHz. Continuous decrease of the dielectric constant with the increasing
frequency and remains almost constant at higher frequency range has been observed.
The magnetic properties have been studied by Vibrating Sample Magnetometer
(VSM). The saturation magnetization (Ms), coercivity (Hc), remanent magnetization
(Mr), Bhor magneton (μB), and anisotropy constant (Ku) have been calculated from the
M-H loop at room temperature. The values of Ms were decreased with increasing
Yb3+ content. Coercivity was increased with Yb content except for X = 0.08 where it
decreased. The values of μB were found to be decreased with increasing Yb3+content.
Doping of Yb ion lowers the conduction and subsequently an increase in resistivity is
observed. The characteristics of electromagnetism, excellent chemical stability,
mechanical hardness, high coercivity, and moderate saturation magnetization have
made Yb doped Co-Zn ferrite a good candidate for synthesizing and investigation to
contribute in science and technology.Md. Deloar HossainMaster of Science in Physic
A Study on Rule Based Reporting Systems
No full textThis thesis is submitted to the Department of Computer Science and Engineering, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Engineering in Computer Science and Engineering, December 2018.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 52-56).Government enacts rules & regulations. People are bound to follow those rules and regulations in
their everyday life. Human brains do the computation for generating conclusions to take decisions on
different circumstances applying those rules. A Human being does not need any external rule reasoner.
However, nowadays data is generated by different automated systems, and inserted, updated, deleted in
different database design formats. So, the decision-making becomes difficult by generating required
conclusions from large repositories of data having multiple formats. Therefore, artificial intelligence
in form of the Rule Based System can help to mitigate this problem by analyzing the conclusions from
the given facts. But, the existing Rule Based Systems processes the adverse events from only one data
sources at a single time and manually generates the facts. In this circumstance, the study proposes
an automated Rule Based System, which is capable of generating conclusions as output for the given
input queries. The study results in a database independent Rule Based method with dynamic predicate
generation & translation for analyzing the stored adverse events from multiple databases by applying
the predefined set of rules and regulations. The formal rules are generated using Defeasible Logic (DL)
to efficiently handle the logic-based implementation of the proposed methodology. In addition, the
proposed system includes SPINdle rule engine to generate required conclusions by loading the formal
rules that are generated using the DL. The resulting Rule Based Reporting System (RuleRS) integrates
simultaneous reasoning generation from the adverse events along with the existing Rule Based Systems
to get the argumentation from multiple relational databases. It also supports the easy integration of
additional data sources for generating assumptions. The output is sent to the I/O section for showing the
generated reports. The study also conducted an empirical evaluation for the single sources (i.e., FAERS
& ChildSafe database separately) and proposed RuleRS in reasoning simultaneously from multiple
sources of data (i.e., FAERS & ChildSafe database concurrently). The evaluation result is promising to
integrate the developed system with the existing RuleRS.Prodip Kumer DasMaster of Science in Engineering in Computer Science and Engineerin
