arXiv subjects

Dimitri O. Ledenyov

Publications and source records attributed to Dimitri O. Ledenyov.

23 records · Page 2Linked to original sources

arXiv2012

Lumped element modeling of nonlinear properties of high temperature superconductors in a dielectric resonator

Microwave properties of High Temperature Superconductors (HTS) exhibit dependence on RF power levels. Effects of nonlinear phenomena causing this dependence can be modelled using lumped element circuits. Several RLC circuits to model the surface impedance of HTS were investigated (with equations expressing transmitted power derived) and assessed. Linear, quadratic and exponential dependences of surface resistance RS and inductance LS on the RF power for the model chosen as the best have been examined and used in simulations of electromagnetic responses of superconducting films in a Hakki-Coleman dielectric resonator.

cond-mat.supr-con↗

arXiv2012

Features of oxygen and its vacancies diffusion in YBa2Cu3O7-δ thin films near to magnetic quantum lines

The temperature dependence of the real and imaginary parts of magnetic susceptibility of YBa2Cu3O7-δ superconducting thin films were researched at the electron irradiation with the energy of 2{\cdot}10<4> eV in the magnetic field of -2.4{\cdot}10<4> A/m at the temperature T=77 K. It is retrieved that the nonequilibrium distribution of atoms of oxygen, originating at the operation of an electron beam, reduces in the change of a sort of dependence of the complex magnetic susceptibility of YBa2 Cu3O7-δ thin films on the temperature T. The diffusion relaxation of a none equilibrium distribution of oxygen atoms and its vacancies, generated at the application of electron irradiation, results in an appearance of pinning centers with the reduced contents of the oxygen in the normal cores of the Abricosov magnetic vortices. The increase of pinning forces results in the increase of critical current density, having an effect on the magnetic susceptibility of YBa2Cu3O7-δ thin films. The proposed theoretical mechanism on the oxygen and its vacancies diffusion in YBa2Cu3O7-δ superconducting thin films near to the centers of Abricosov magnetic vortices cores at the action of the superconducting electron pair potential gradient explains the observed physical properties.

cond-mat.supr-con↗

arXiv2012

Designing the new architecture of international financial system in era of great changes by globalization

We present a broad agenda for meaningful banking regulation reform aiming the creation of evolutive competitive environment to maximize the effectiveness of international financial system through the introduction of fair competition process among the banks in free market capitalism. We assume that the international financial system may evolve or decline within the evolutive competitive environment depending on both the environmental regulation policies as well as the competition between the banks. We present the commonly known definition of competition and apply the conceptual collateral thinking to identify the source of competitive strengths of financial institutions in free market capitalism. We explore how the banks conduct a search for competitive strategies. We show that the root cause of crisis in finances is hidden in the very wrong regulation policies and ideas behind these policies, which failed to create the evolutive competitive environment for effective, profitable, responsible and sustainable bank operation within existing international financial system. We review a number of initiatives on meaningful banking regulation reform proposed by central bankers from the G20 nations. We propose to introduce the Random Tax and the Quantum Tax. We argue that the introduction of the Random Tax and the Quantum Tax may compensate for the negative effects commonly associated with the existing banking regulation limitations imposed on the international financial system. We believe that the Random Tax and the Quantum Tax will improve the evolutive competitive environment and make it possible for the management teams at financial institutions to search for and to execute the winning virtuous business strategies toward the effective, profitable, responsible and sustainable banks operation.

q-fin.GN↗

arXiv2012

Shaping the international financial system in century of globalization

We educe a perspective on how best to regulate the bank of tomorrow in frames of debate launched by the International Centre for Financial Regulation and Financial Times. Our goal is to create a conceptual framework for policymakers and regulators to shape the international financial system in century of globalization using the 1888 FT's motto: "Without fear and without favour." Our prospect employs an analytical approach, which focuses on the origins and evolution of banking system, its transformation over the recent decades, subsequent encountering the limits to growth and redefinition of new strategic boundaries of emerging financial industry. We identify the main reasons and limitations, which led to the global financial crisis. We propose the new research agendas with the aim to understand the situation in finances, evaluate the created systemic damages, and find the possible ways to resolve the existing problems through introduction of new banking regulation. We think that the global economic and financial systems are highly nonlinear systems. In our opinion, the frequency, phase and amplitude modulation during the mixing of waves, which characterize the Kitchin, Juglar, Kuznets, Kondratiev economic cycles, may result in origination of strong nonlinear dynamics in financial system, accompanied by chaos- induced phenomena. These nonlinear effects have to be taken to the account, when adding the liquidity to the financial system in small quantas in series over time period during the Quantitative Easing policy execution by central banks. We propose the Random Tax to be selectively imposed on the profits, obtained by market agents during high-risk high-profit speculative transactions. We expect that the Random Tax will stabilize the financial system in conditions of free market capitalism.

q-fin.GN↗

arXiv2012

Influence by proximity effect on ultrasound attenuation in Cu-Nb composite system at low temperatures

The attenuation of longitudinal ultrasonic wave with the frequency of 30 MHz in Cu-Nb copper-niobium (40 vol%) composite system at low temperatures from 0.35 K up to 2 K is researched. It was found that the ultrasonic attenuation decreases in a Cu-Nb multi-filamentary composite sample at low temperatures in distinction to the pure Cu copper or Nb niobium homogeneous bulk samples. It is well known that the contact between the normal metal N and the superconductor S is characterized by an appearance of superconducting properties in the thin surface layer of normal metal N, because of the presence of proximity effect at low temperatures T. This phenomenon is observed on the temperature dependent distance ξ_N(T) in the normal metal N at the normal metal - superconductor NS boundary. It is assumed that the transition from the normal state N to the superconducting state S must be accompanied by the decrease of magnitude of ultrasonic wave's electronic energy absorption in normal metal N. The experimental results show that the superconducting electron coherence length in the normal thin layer is temperature dependent ξ_N(T). The electron mean free path l, which is dependent on the impurity scattering in volume and near Cu-Nb interfaces, was measured by the three independent methods at low temperatures. It is understood that the Andreev reflections are present in S-N-S structure, making some influence on the measured ultrasonic longitudinal wave attenuation in Cu-Nb composite samples at ultra low temperatures. The measured experimental results of ultrasonic longitudinal wave attenuation in Cu-Nb composite samples at low temperatures are in good agreement with the theoretical modeling data, obtained in case of dirty local limit.

cond-mat.supr-con↗