Spiral Structure in Galaxies – A Density Wave Theory
On a splendid star night, when you look at the sky, facing bling bling stars, you will remember many ancient myths. The modern scientific discovery proves that the Earth where we are is in the Milky Way galaxy. In a deep universe, there are many galaxies, like Milky Way galaxy. Astro-observation finds that most of galaxies outside the Milky Way show a spiral shape, known as spiral galaxy. Why do many spiral galaxies take on double arm symmetric spiral shape on a large length scale? Why do they take on the legendary flying saucer shape from the side? What is a mysterious force to play a role in the back? ...... Many problems trouble us and attract the curious physicists to image and explore. In a word, the experiment is the sole criterion for testing truth. This new theory has a big impact not only on astrophysics and cosmic evolution , but also on the reconstruction and development of relativity theory and the whole basic physics theory and is particularly important to breaking through the difficulty in the research of graviton nature faced at present.
The linear theory of electromagnetic radiation from a plasma-loaded sinusoidally corrugated backward wave oscillator driven by intense relativistic electron beam has been developed and analyzed numerically as well as analytically. A beam-plasma waveguide model has been proposed and studied analytically with an aim to give a guideline to achieve an optimally designed backward wave oscillator in the X-band frequency range. First, the dispersion relation for TM01 mode in absence of electron beam has been analyzed numerically for different structure-size parameters and plasma density. Then, developing the analytical dispersion relation, the effects of variation of structure parameters and plasma density on the spatial and temporal growth rates for TM01 mode are investigated. Here, the analytical investigation, have been carried out by absolute instability analysis. It is observed that the variation of structure-size parameters and filled-plasma density modify the dispersion curves of the backward wave oscillator significantly and affect the beam-wave interaction frequency, the temporal and spatial growth rates and thus the signal strengths considerably.
This book is concerned with simulation of non-stationary wave for aseismic check of nonlinear structures, in which simulated earthquake, referred to as critical earthquake, causes greater response on a given nonlinear structure than that of an observed record of an actual earthquake, referred to as target. The critical earthquake is simulated in such a way that satisfies amplitude and frequency restriction conditions. Critical earthquake is simulated by three numerical methods, all followed by an application on a given structure. In the first method, the simulation is carried out by modifying power spectral density (PSD) function of target at several consecutive time intervals. The modification of PSD function is dealt with the natural period of considered structure which might be prolonged at some time interval(s). The latter two methods based on drift of specified component(s) of non-stationary PSD function, which is determined using a narrow band filter, and multi-filter function of target to the peak acceleration time of target. The specified components correspond to and around the natural frequency of considered structure.
Compton Scattering has become a standard tool to study the electron momentum densities in materials because the momentum distribution of valence electrons in a solid can be measured through the Doppler shift of Compton scattered photons by electrons in motion. This book details how the Compton scattering experiments are performed, data are analyzed, and results are interpreted and provides fundamental understanding of the electronic structure and momentum density of some Ti-based alloys and semiconductors compounds.
Borides of transition metals are rather attractive materials for wide scale application in various fields of machine-building, metallurgy, instrument-making, chemical industry, etc. In this work, structural parameters and electronic properties of Tantalum diboride (TaB2) compound have been calculated and investigated in hexagonal phase with p6/mmm space group. The calculations have been performed with ultrasoft pseudopotential in the frame work of Density Functional Theory (DFT). Density functional theory provides a powerful tool for computations of the quantum state of atoms, molecules and solids, and of ab-initio molecular dynamics. These calculations have been done by using the plane waves (pw) method that implemented in Quantum Espresso package.
Theory & Structure in International Political Economy – An International Organization Reader
A consideration has been given to dynamic models of formation of martensite plates with a fine structure of transformation twins, which are compatible with the supersonic growth rate of martensite crystals. Along with relatively long quasi-longitudinal waves, which determine the orientation of the habit plane, the control wave process includes relatively short longitudinal waves, which act in synchronism and control the growth of the main component of a regular twin structure. Preference is given to a model containing, at the initial moment of time, the only active dynamic cell capable of periodic reproduction in the interphase region at the stage of the martensite crystal growth. The calculated macroscopic morphological attributes, which were deduced from dynamic considerations, have been compared with the experimental data and crystallogeometrical calculation. Discussion of results and conclusions in a final part of the monography represent the independent interest. For scientific employees and experts in the field of metallography and physics of metals and alloys, as well as teachers, post-graduate students and the students who are specializing in materials technology.
This book consists of two parts. In the first part, we investigate the superconducting proximity effect in a clean magnetic structure consisting of two ferromagnetic layered domains with antiparallel magnetizations in contact with a superconductor. Within the quasiclassical Green''s function approach we find that the penetration of the superconducting correlations into the magnetic domains can be enhanced as compared to the corresponding single domain structure. This enhancement depends on an effective exchange field which is determined by the thicknesses and exchange fields of the two domains. In the second part, we study the superconducting proximity effect in a clean nonmagnetic metal in contact with a ferromagnetic superconductor which has a nonunitary f-wave triplet order parameter. Using the quasiclassical Green''s function approach, we solve the Eilenberger equation analytically in a non-self-consistent form. The density of states is obtained in the bulk of the ferromagnetic superconductor and it is plotted versus the energy. We have compared energy-dependence of density of states with the corresponding dependences for s-wave and d-wave superconductors.
This book is about the international political structure of the world after the Cold War. It focuses on how the international political scene at the time influenced Japan's nuclear policy. The book is based on the theory of International Relations scholar from the Neorealist school of thought, Kenneth Waltz. His theory posits that, in an international political structure, the behavior of a state is influenced by the behavior of other states. And that these states tend to behave in a similar manner. Waltz refers to this as the, Theory of International Politics. The main aim of this book was to challenge Waltz' theory by giving evidence that state behavior is not always influenced on a structural level but on a unit(state) level. This was carried out by using Japan as a case study and analyzing its behavior after the Cold War and comparing its policies with those of other states during that period.
This book aims to show how the Maximum Entropy (MaxEnt) approach has changed deeply the traditional research methods in regional and urban geography as the result of paradigm shifts occurred during the last 50 years. MaxEnt method as pioneered by A. Wilson (1967,1970) and “Spatial Entropy” concept by M. Batty (1974) have been based on the Information Theory that was founded by Shannon (1948), E.T.Jaynes (1957) and Kullback (1959) and others. Information Theory has provided the theoretical foundation for challenging the uncertainty and incomplete information issues concerning the complex urban structure. MaxEnt, as a new logic, aims to assign probabilities “maximally noncommittal” with respect to the missing information. This dissertation applies Spatial Entropy measures to Ankara 1970 and 1990 census data by 34 zones and compares the population density changes during the two decades. This book shall not only guide young generations to understand the past contributions but also encourage them to make further researches under the information-theoric Weltanschauung.
This book inquires about the poetics and politics of the Post/Humanities.In doing so, it is intended to investigate the nature of interrelationship and tension between humanism and posthumanism; to evaluate whether posthumanities can be an academic possibility or not; to explore into the queered state of human-nonhuman binary because of the emergence of transhuman, cyborg and other posthuman identities; to understand how these identities are represented in the contemporary Hollywood films; to comprehend what these selected films want us to think about our future world.
Seyfert galaxies are a subclass of active galaxies and are categorized as nearby, low luminosity, radio-quiet Active Galactic Nuclei (AGN) hosted in spiral or lenticular galaxies. Seyfert galaxies are classified mainly into two subclasses named as `type 1' and `type 2' based on the presence and absence of broad permitted emission lines in their optical spectra, respectively. Seyfert unification scheme hypothesizes that Seyfert type 1s and type 2s belong to the same parent population and appear different solely due to the differing orientations of the obscuring material having a torus-like geometry around the AGN. The primary objective of this work is to examine the validity and limitations of the orientation and obscuration based Seyfert unification scheme using multiwavelength (mainly X-ray and radio) observations. It has been emphasized that the key issue in testing the Seyfert unification scheme is acquiring a well defined Seyfert sample. The statistical comparisons of X-ray, radio and IR properties of the two Seyfert subtypes have been discussed in the framework of the unification scheme.
Aurorae often break down into elongated, cylindrically symmetric space-charge filaments (with radius r) parallel to the local uniform geomagnetic field. We study the ion kinetic theory in auroral plasmas in the presence of the strong electric field (E) produced by the filaments. A method of characteristics is used to solve both the collision-free and collisional Boltzmann equation under different E and initial ion density (n). If E is constant in time (t) but proportional to r and n is uniform, the collision-free ion distribution function (f) pulsates in t and transport properties oscillate. If collisions are introduced, f takes a horseshoe shape symmetric to the E direction while the bulk parameters evolve from pulsating to steady states. When E changes radially, the collision-free f has various shapes and bulk parameters change accordingly. Results are also obtained in the presence of collisions and initial density inhomogeneities when E is constant in t and proportional to r. Finally, when E is unable to stay constant and is modulated by in-coming charged particles (i.e., the Bolzmann-Vlasov problem), several plasma wave modes are excited under different initial conditions.