Effect of plasma resonances on dynamic characteristics of double graphene-layer optical modulator

We analyze the dynamic operation of an optical modulator based on double graphene-layer(GL) structure utilizing the variation of the GL absorption due to the electrically controlled Pauli blocking effect. The developed device model yields the dependences of the modulation depth on the control voltage and the modulation frequency. The excitation of plasma oscillations in double-GL structure can result in the resonant increase of the modulation depth, when the modulation frequency approaches the plasma frequency, which corresponds to the terahertz frequency for the typical parameter values.Comment: 8 pages, 4 figure

Flux Penetration in Superconducting Strip with Edge-Indentation

The flux penetration near a semicircular indentation at the edge of a thin superconducting strip placed in a transverse magnetic field is investigated. The flux front distortion due to the indentation is calculated numerically by solving the Maxwell equations with a highly nonlinear $E(j)$ law. We find that the excess penetration, $\Delta$, can be significantly ($\sim$ 50%) larger than the indentation radius $r_0$, in contrast to a bulk supercondutor in the critical state where $\Delta=r_0$. It is also shown that the flux creep tends to smoothen the flux front, i.e. reduce $\Delta$. The results are in very good agreement with magneto-optical studies of flux penetration into an YBa$_2$Cu$_3$O$_x$ film having an edge defect.Comment: 5 pages, 7 figure

УПРАВЛІННЯ ПРОЦЕСОМ ОЦІНЮВАННЯ ЗНАНЬ ПРИ ПІДГОТОВЦІ РЯ- ТУВАЛЬНИКІВ З ВИКОРИСТАННЯМ ОНТОЛОГІЇ НАВЧАЛЬНИХ КУРСІВ

In connection with the expansion of distance education there is a necessity of the development and use of computer-aided learning and knowledge control. The main attention is paid to the peculiarities of software development and the problems of optimization of the educational material structure, and the development of a methodology of knowledge testing and methods of verification remain on the sidelines. This article proposes a new approach to the development of automated control systems of knowledge based on ontology of subject areas, which in this case are the training courses. The formation of ontology and logic scheme of control of knowledge allows structuring the learning material, to identify topics and issues that represent challenges for the cadets (students), as well as to develop a software wrapper for uniform formation of control systems of knowledge of various training courses.У зв'язку з поширенням дистанційної освіти виникає необхідність розробки і використання засобів автоматизованого навчання і контролю знань. При цьому головну увагу звертають на особливості розробки програмного забезпечення, а проблеми оптимізації структури навчального матеріалу, а також розробки методології тестування знань і методів її верифікації залишаються осторонь. Запропоновано новий підхід до розробки автоматизованих систем контролю знань, заснований на онтологіях предметних областей, якими в даному випадку є навчальні курси. Формування онтології та логічної схеми контролю знань дозволяє структурувати навчальний матеріал, визначити теми і питання, які становлять труднощі для курсантів (студентів), а також розробити програмну оболонку для уніфікованого формування систем контролю знань з різних навчальних курсів

Practical thermodynamics of Yukawa systems at strong coupling

Simple practical approach to estimate thermodynamic properties of strongly coupled Yukawa systems, in both fluid and solid phases, is presented. The accuracy of the approach is tested by extensive comparison with direct computer simulation results (for fluids and solids) and the recently proposed shortest-graph method (for solids). Possible applications to other systems of softly repulsive particles are briefly discussed.Comment: Published in J. Chem. Phy

Mechanism for flux guidance by micrometric antidot arrays in superconducting films

A study of magnetic flux penetration in a superconducting film patterned with arrays of micron sized antidots (microholes) is reported. Magneto-optical imaging (MOI) of a YBCO film shaped as a long strip with perpendicular antidot arrays revealed both strong guidance of flux, and at the same time large perturbations of the overall flux penetration and flow of current. These results are compared with a numerical flux creep simulation of a thin superconductor with the same antidot pattern. To perform calculations on such a complex geometry, an efficient numerical scheme for handling the boundary conditions of the antidots and the nonlocal electrodynamics was developed. The simulations reproduce essentially all features of the MOI results. In addition, the numerical results give insight into all other key quantities, e.g., the electrical field, which becomes extremely large in the narrow channels connecting the antidots.Comment: 8 pages, 7 figure

Biliary stent placement specialities in endoscipic treatment of common bile duct stones

The article is devoted to palliative treatment of mechanical jaundice, caused choledocholitiasis, get having patients with high operating risk and hemostasissystemdisturbances, by means for endobiliary stenting. Authors have researched reasons of efficacy decreasing and suggested original ways to elaborate that, after that have carried outcomparing the results in the groupofcomparison