Physicshttp://etd.aau.edu.et/handle/123456789/492022-09-29T11:43:26Z2022-09-29T11:43:26ZVerification of Einstein General theory of Relativity with Gravitational WavesHabtie, Abelhttp://etd.aau.edu.et/handle/123456789/322252022-07-11T12:15:13Z2021-07-11T00:00:00ZVerification of Einstein General theory of Relativity with Gravitational Waves
Habtie, Abel
Gravitational wave science is one of direct observation of the waves predicted
by Einsteinâ€™s general theory of relativity and opening the exciting new field of
gravitational wave astronomy. In this thesis work we study gravitational waves
and we also present some of the general relativity test of gravitational wave such
as linear approximation of Einstein field equation which is Einstein equation for a
weak gravitational field simply _h__ = 0, thus, the metric perturbations satisfy
the flat space wave equation and the solutions can therefore be interpreted as
gravitational waves polarization(plus and cross polarization). In this thesisWe also
found that gravitational wave emites when BBHs are spiraling with each other. We
suggested that high amplitude of gravitational waves are formed around merger of
BBHs, the amplitude of GWs large for high masses and also the amplitude fails
when the waves moves away from the source like standard sirenâ€™s of h / 1
r . We
also checked that SEOBNR and IMRPhenom models are matched with pridiction
of GR simulated by NR and the waveform observed from LIGO. These waveform
comparison tells us Einstein general theory of relativity passes the test of GW.
2021-07-11T00:00:00ZSize Dependent Optical Properties of Spherical ZnO@Cu and ZnO@Au Core/Shell NanostructuresGizat, Tesfahunhttp://etd.aau.edu.et/handle/123456789/318562022-06-01T08:02:53Z2022-02-19T00:00:00ZSize Dependent Optical Properties of Spherical ZnO@Cu and ZnO@Au Core/Shell Nanostructures
Gizat, Tesfahun
In this work, we studies the effect of size and thickness variation on the optical
properties of a system that consists of spherical ZnO@Cu and ZnO@Au core-shell
composite nanostructures embedded in a dielectric host matrix. The effective dielectric
function, refractive index, and absorbance of the composite nanostructures are
determined using the Maxwell-Garnett effective medium theory within the framework
of the electrostatic approximation. The numerical simulation using nanoinclusions of
radii 30 nm shows interesting behavior in the optical responses of the ensemble. In
particular, it is shown that for different values of volume fraction and filling factor
the refractive index and optical absorbance of the ensemble exhibited two sets
of resonance peaks; the first set located around 515 nm and 490 nm and the second
set found above 635 nm and 605 nm spectral regions for a system of ZnO@Cu
and ZnO@Au nanoparticles, respectively. These peaks are attributed to the surface
plasmon resonance of copper and gold at the core@metal and metal@host-matrix interface.
Moreover, when the Cu and Au shell thickness is increased, the observed
resonance peaks are enhanced; accompanied with slight red shifts for the first set
of peaks and a blue shifts for the second set of peaks. In brief, it is seen that the
optical properties of spherical ZnO@Cu and ZnO@Au core-shell nanoinclusions embedded
in vacuum can be tuned by varying the shell thickness, filling factor, and/or
volume fraction of the nanocomposites. The results obtained may be used in various
applications such as sensors and nano-optoelectronics devices in optimizing material
parameters to the desired values.
2022-02-19T00:00:00ZThe Quantum Analysis of the Light Produced by Coherently Driven Degenerate Three-Level Atom in a Cavity Containing Parametric Amplifier and Coupled to a Vacuum ReservoirMekete, Antigegnhttp://etd.aau.edu.et/handle/123456789/318402022-06-01T13:21:53Z2022-04-18T00:00:00ZThe Quantum Analysis of the Light Produced by Coherently Driven Degenerate Three-Level Atom in a Cavity Containing Parametric Amplifier and Coupled to a Vacuum Reservoir
Mekete, Antigegn
In this thesis, we analyze the statistical and squeezing properties of the light produced by
a degenerate three-level atom, whose top and bottom levels are coupled by coherent light,
and available in a cavity containing degenerate parametric amplifier and coupled to a vacuum
reservoir via a port-mirror. Employing the master equation for the system under consideration,
we obtain the equations of evolution for the expectation value of atomic operators
and the quantum Langevin equation for the cavity mode operator. Using the steady-state
solutions of these equations and the large time approximation, we have determined the mean
and variance of photon number, the power spectrum of cavity mode, quadrature variance and
quadrature squeezing. We observe that the increase of the amplitude of the driving coherent
light and the presence of the parametric amplifier enhance the mean and variance of the
photon number. We have also established that the maximum quadrature squeezing is 61%
for _ = 0.03 and 70% for _ = 0.06 below the vacuum-state level. Thus, we note that the
presence of parametric amplifier has positive impact on the quadrature squeezing.
2022-04-18T00:00:00ZPhysics of Cloud and PrecipitationKuchi, Nigatuhttp://etd.aau.edu.et/handle/123456789/318272022-05-31T07:45:45Z2022-04-11T00:00:00ZPhysics of Cloud and Precipitation
Kuchi, Nigatu
In this project we present a review of the physics of clouds and precipitation in the atmosphere.
Thunderstorms are a global phenomenon in the mid-latitudes and tropics. They form
where and whenever the ingredients for their formation come together: instability, moisture
and lift. Especially upon interaction with vertical wind shear, they may develop in to wellorganized
systems that produce hazards such as large hail, severe winds, heavy precipitation,
and tornadoes.
We must look in to the processes by which the clouds are formed and precipitation is
produced in order to the meaning of clouds they related to weather. We will see how clouds
are classified and, named and what kinds of precipitation certain types of clouds produce. And
also in this project we study how to clouds form and precipitation develop in the atmosphere
must be saturated with moisture. As a cold air passes over warm water, rapid evaporation
takes places and the saturation is quickly reached.
Lifting of air, and the resulting adiabatic expansion, is the most important cooling method.
The lifting may be accomplished by thermal orographic or frontal action. It produces most
of the clouds and precipitation.
2022-04-11T00:00:00Z