A Versatile Active Block: DXCCCII and Tunable Applications

The study describes dual-X controlled current conveyor (DXCCCII) as a versatile active block and its application to inductance simulators for testing. Moreover, the high pass filter application using with DXCCCII based inductance simulator and oscillator with flexible tunable oscillation frequency have been presented and simulated to confirm the theoretical validity. The proposed circuit which has a simple circuit design requires the low-voltage and the DXCCCII can also be tuned in the wide range by the biasing current. The proposed DXCCCII provides a good linearity, high output impedance at Z terminals, and a reasonable current and voltage transfer gain accuracy. The proposed DXCCCII and its applications have been simulated using the CMOS 0.18 µm technology

The Effects of Shear and Rotation Anisotropy Upon the Process of Gravitational Instability

In this paper, we study the role of shear fields on the evolution of density perturbations embedded in a Friedmann flat background universe, by studying the evolution of a homogeneous ellipsoid model. In this context, we show that while the effect of the shear is that of increasing the growth rate of the density contrast of a mass element, the angular momentum acquired by the ellipsoid has the right magnitude to counterbalance the shear. Finally, our result show that initial asphericities and tidal interaction induce a slowing down of the collapse after the system has broken away from the general expansion, in perfect agreement with the previrialization conjecture (Peebles & Groth 1976; Davis & Peebles 1977)

Origin of gamma-ray emission in the shell of Cassiopeia A

Non-thermal X-ray emission from the shell of Cassiopeia A (Cas A) has been an interesting subject of study, as it provides information about relativistic electrons and their acceleration mechanisms in the shocks. Chandra X-ray observatory revealed the detailed spectral and spatial structure of this SNR in X-rays. The spectral analysis of Chandra X-ray data of Cas A shows unequal flux levels for different regions of the shell, which can be attributed to different magnetic fields in those regions. Additionally, the GeV gamma-ray emission observed by Large Area Telescope on board Fermi Gamma Ray Space Telescope showed that the hadronic processes are dominating in Cas A, a clear signature of acceleration of protons. In this paper we aim to explain the GeV-TeV gamma-ray data in the context of both leptonic and hadronic scenario. We modeled the multi-wavelength spectrum of Cas A. We use synchrotron emission process to explain the observed non-thermal X-ray fluxes from different regions of the shell. These result in estimation of the model parameters, which are then used to explain TeV gamma-ray emission spectrum. We also use hadronic scenario to explain both GeV and TeV fluxes simultaneously. We show that a leptonic model alone cannot explain the GeV-TeV data. Therefore, we need to invoke a hadronic model to explain the observed GeV-TeV fluxes. We found that although pure hadronic model is able to explain the GeV-TeV data, a lepto-hadronic model provides the best fit to the data.Comment: Accepted in A&

Migration of giant planets in planetesimal discs

Planets orbiting a planetesimal circumstellar disc can migrate inward from their initial positions because of dynamical friction between planets and planetesimals. The migration rate depends on the disc mass and on its time evolution. Planets that are embedded in long-lived planetesimal discs, having total mass of $10^{-4}-0.01 M_{\odot}$, can migrate inward a large distance and can survive only if the inner disc is truncated or because of tidal interaction with the star. In this case the semi-major axis, a, of the planetary orbit is less than 0.1 AU. Orbits with larger $a$ are obtained for smaller value of the disc mass or for a rapid evolution (depletion) of the disc. This model may explain several of the orbital features of the giant planets that were discovered in last years orbiting nearby stars as well as the metallicity enhancement found in several stars associated with short-period planets.Comment: 21 pages; 6 encapsulated figures. Accepted by MNRA

Professional Development Needs of Turkish Teachers in an Era of National Reforms

An emerging consensus in the teacher education literature confirms that supporting educational reforms and improving designs for national programs can be accomplished simply by maximizing the match between teachers’ expressed needs and the content by which those professional development needs are met. This paper presents an interpretation of findings on Turkish teachers’ in-service training needs during an era of massive reform. The findings indicate that teachers do not report a strong need for any professional development program content. Analyses are based on survey data from 1,730 Turkish teachers from 352 primary schools. The results raise the discussion of whether teachers simply do not want to participate or actually do not need to participate in any more training during this era of massive educational reforms. The paper concludes by outlining policy and practice implications arising from the research

Vibrations due to Dynamic Compaction

Ground vibrations due to dynamic compaction (DC), at a harbor site were measured to investigate whether the magnitude of vibrations were unacceptably strong to cause any damage to or increase existing damage on the surrounding structures experienced August 17, 1999 Kocaeli, Gölcük earthquake (M~7.4). The site is located in city of Kocaeli at the seaside of The Port of Derince. It was a reclaimed land formed with Hereke limestones. The measured data included vibrations induced by the tamping energy of DC both at the vicinity of nearby structures and within the DC site. The site was surrounded by a shallow isolation trench all along the land sides. This paper presents the case and the characteristics of vibration such as peak values of the records, Fourier spectrum and amplitude attenuations over distance. The predominant frequencies and amplitude of vibrations were compared to the related code limits to estimate the effect of vibrations on the existing structures

Efficacy of Hedonic Shopping Value in Predicting Word of Mouth

This research examines the efficacy of hedonic shopping value in predicting tourists’ satisfaction and word of mouth communication. The data were collected through face-to-face interviews of 506 tourists of whom 383 respondents indicated that they had shopped and made a purchase during their holidays in Turkey. A total of 345 completed interviews were used for analysis. Findings suggest that hedonic shopping value is strongly linked to tourists’ satisfaction and word of mouth. Theoretical and practical implications are discussed within the context of retailing industry in a maturing tourist destination