71 research outputs found
Historiaurrearen, Antzinaroaren eta Erdi Aroaren historia euskaraz. Historia ala fikzioa?
No full textEl objeto del presente artículo es efectuar un breve repaso de la historia e historiografía de la Prehistoria, Antigüedad y Edad Media producidas en euskara. Igualmente, la autora expone brevemente sus reflexiones sobre los problemas y dificultades que supone escribir y trabajar en euskara sobre estos temas.Euskaraz idatzi den Historiaurrearen, Antzinaroaren eta Erdi Aroaren historiari eta historiografiari errepaso labur bat egitea da artikulu honen helburua. Aldi berean, euskaraz arlo hauetan idazteak eta lana egiteak dituen arazo eta zailtasunei buruz, egileak bere gogoetak azaldu ditu laburki.Le but de cet article est d'effectuer une brève révision de l'histoire et de l'historiographie de la Préhistoire, de l'Antiquité et du Moyen Age produites en euskara. De même, l'auteur expose brièvement ses réflexions sur les problèmes et les difficultés que suppose écrire et travailler en euskara sur ces thèmes.The aim of this article is to make a summary about the Prehistory, Antique and Medieval History's historiography written in Basque language. The author gives also her thoughs and experiences about writing and working in Basque about those periods of the History
Synthesis and Characterization of Hydroxyapatite Powders From Eggshell For Functional Biomedical Application
No full textBulus, Erdi (Arel Author), İsmik, Deniz (Arel Author), Mansuroğlu, Demet Sezgin (Arel Author), Şahin, Yeşim Müge (Arel Author)Apatitic phosphates are considered within the category of bioceramics. HA and its derives are used of in the fields of medicine, orthopedics and dentistry in order to support a grow up of new bone cells. HA structures have a high biocompability and are widely in biomedical applications. On the other hand, synthesis of HA structures necessitates complex technologies (microwave sintering, hydrothermal synthesis etc.) and their production costs high. This study aims the production of nano apatitic structures with great biocompability from a natural material. Simple hotplate method was used to obtain natural, nano scale HA from eggshells. After calcination and sintering processes at different temperatures, the obtained apatitic phosphate powders have been structurally characterized by infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). Morphological investigation has been conducted by FEG-SEM images. Biological investigations have been carried out for the produced nanosized bioceramics and the results reveal that these nanomaterials are promising for tissue engineering purposes
Thermochemistry of N-heterocyclic carbenes with 5-, 4-, 3-, and 2-membered rings
No full text#nofulltext# Bleda, Erdi A. (Arel Author)N-heterocyclic carbenes (NHCs) based on imidazole-2-ylidene (1) or the saturated imidazolidine-2-ylidene (2) scaffolds are long-lived singlet carbenes. Both benefit from inductive stabilization of the sigma lone pair on carbon by neighboring N atoms and delocalization of the N pi lone pairs into the nominally vacant p-pi atomic orbital at the carbene carbon. With thermochemical schemes G4 and CBS-QB3, we estimate the relative thermodynamic stabilization of smaller ring carbenes and acyclic species which may share the keys to NHC stability. These include four-membered ring systems incorporating the carbene center, two trivalent N centers, and either a boron or a phosphorus atom to complete the ring. Amino-substituted cyclopropenylidenes have been reported but three-membered rings containing the carbene center and two N atoms are not known. Our calculations suggest that amino-substituted cyclopropenylidenes are comparable in stability to the four-membered NHCs but that diazacyclopropanylidenes would be substantially less effectively stabilized. Concluding the series are acyclic carbenes with and without neighboring N atoms and a series of “two-membered ring” azapropadienenylidene cations of form :C[DOUBLE BOND]N[DOUBLE BOND]W with W = an electron-withdrawing agent. We have studied W = NO2, CH2(+), CF2(+), and (CN)2C(+). Although these systems display a degree of stabilization and carbene-like electronic structure, the stability of the NHCs is unsurpassed
High-order harmonic generation from Rydberg states at fixed Keldysh parameter
No full textBleda, Erdi A. (Arel Author)Because the commonly adopted viewpoint that the Keldysh parameter ? determines the dynamical regime in strong field physics has long been demonstrated to be misleading, one can ask what happens as relevant physical parameters, such as laser intensity and frequency, are varied while ? is kept fixed. We present results from our one- and fully three-dimensional quantum simulations of high-order harmonic generation (HHG) from various bound states of hydrogen with n up to 40, where the laser intensities and the frequencies are scaled from those for n = 1 in order to maintain a fixed Keldysh parameter ?< 1 for all n. We find that as we increase n while keeping ? fixed, the position of the cut-off scales in well defined manner. Moreover, a secondary plateau forms with a new cut-off, splitting the HHG plateau into two regions. First of these sub-plateaus is composed of lower harmonics, and has a higher yield than the second one. The latter extends up to the semiclassical Ip + 3.17Up cut-off. We find that this structure is universal, and the HHG spectra look the same for all n & 10 when plotted as a function of the scaled harmonic order. We investigate the n-, l- and momentum distributions to elucidate the physical mechanism leading to this universal structure
Phase-dependent interference fringes in the wavelenght scaling of harmonic efficiency
No full textBleda, Erdi A. (Arel Author)We describe phase-dependent wavelength scaling of high-order harmonic generation efficiency driven by ultra-short laser fields in the mid-infrared. We employ both numerical solution of the time-dependent Schr¨odinger equation and the Strong Field Approximation to analyze the fine-scale oscillations in the harmonic yield in the context of channel-closing effects. We show, by varying the carrier-envelope phase, that the amplitude of these oscillations depend strongly on the rescattering electron trajectory counts. Furthermore, the peak positions of the oscillations vary significantly as a function of the carrier-envelope phase. Owing to its significant practical applications, we also investigate the wavelength dependence of harmonic yield in the single-cycle limit, finding that scaling near the cut-off region departs from the commonly observed ? -x behavior. For a fixed spectral range, we identify a surprisingly smooth behavior of x in ? -x as a function of the ionization potential in the single-cycle limit, which shows suppression of the oscillations in the overall wavelength-scaling. Moreover, we observe that the harmonic efficiency scales as ? -x with x = 5.2, independent from the target atom, and in reasonable agreement with the semi-classical x = 5 scaling
Reset Control for Vibration Isolation
No full textFloor vibrations are a common problem in high tech engineering where good tracking, precision and bandwidth have utmost importance. They are mainly present at low frequencies, and they need to be suppressed. PID control is the go-to controller in the industry because of its ease of design, simple implementation and good performance. However, PID is subjected to the fundamental limitations of linear control theory - the waterbed effect and bode's gain-phase relationship. Therefore, it is not possible to improve one performance criterion, like stability, without negatively influencing the other. The need for overcoming the fundamental limitations of linear control initiates research towards nonlinear controllers. Reset control is a type of nonlinear controller as a solution to overcome the limitations of a linear control. It reduces phase lag within the system, gives the advantage to reach higher bandwidth and results in lower overshoot or a faster settling time compared to linear controllers. However, using reset control comes with a price of unwanted dynamics due to the higher order harmonics. The main focus of this thesis is to improve disturbance rejection performance against floor vibrations by attenuating the power of high order harmonics. This problem has been tackled within the thesis, and a band-pass reset control is proposed.Proposed reset controller applies reset only within the frequency range where floor vibrations are present, and it uses integrator as a reset variable. Results show reset controller that has a broadband phase compensation, like CgLp, is more advantageous towards phase lag reduction methods. CgLp is a reset element, which is an abbreviation of Constant-Gain Lead Phase. It gives broadband phase compensation within the desired range of frequencies by using generalized first order reset element. Also, CgLp controller achieved disturbance rejection performance of PI\textsuperscript{2}D with the phase behavior of Clegg.Mechanical Engineering | Mechatronic System Design (MSD
Turkish foreign policy and ontological (in)security: historical trajectories, contemporary dynamics, and theoretical reflections
No full textSince the foundation of the Republic in 1923, Turkish foreign policy has been shaped by not only material interests and geopolitical calculations but also by deeper existential anxieties surrounding national identity and recognition. This article explores Turkey’s foreign policy through the conceptual framework of ontological (in)security, particularly during the Justice and Development Party (AKP) era. Drawing upon historical trajectories, theoretical insights, and empirical case studies, the paper analyzes how identity-based insecurities influence Turkey’s international behavior. The article further discusses how Turkey’s ambivalent positioning between East and West, its evolving regional aspirations, and its self-claimed middle power status generate a unique ontological dynamic. The contributions to this special issue adopt a multidisciplinary lens to assess how these identity tensions have manifested in strategic decision-making, foreign policy rhetoric, and domestic–international linkages. Ultimately, the issue offers a comprehensive reflection on the existential underpinnings of contemporary Turkish foreign policy
Recombination rate coefficients of boron-like Ne
No full textBleda, Erdi A. (Arel Author)Recombination of Ne5+ was measured in a merged-beam type experiment at the heavy-ion storage ring CRYRING. In the collision energy range 0–110 eV resonances due to 2s22p › 2s2p2 (?n = 0) and 2s22p › 2s23l (?n = 1), core excitations were observed. The experimentally derived rate coefficients agree well with the calculations obtained using AUTOSTRUCTURE. At low energies, recombination is dominated by resonances belonging to the spinforbidden 2s2p2(4PJ)nl series. The energy-dependent rate coefficients were convoluted with a Maxwell–Boltzmann electron energy distribution to obtain plasma recombination rate coefficients. The data from the literature deviate from the measured results at low temperature
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