617 research outputs found

    Abelian monopoles in finite temperature lattice SU(2) gluodynamics: first study with improved action

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    The properties of the thermal Abelian color-magnetic monopoles in the maximally Abelian gauge are studied in the deconfinement phase of the lattice SU(2) gluodynamics. To check universality of the monopole properties we employ the tadpole improved Symanzik action. The simulated annealing algorithm combined with multiple gauge copies is applied for fixing the maximally Abelian gauge to avoid effects of Gribov copies. We compute the density, interaction parameters, thermal mass and chemical potential of the thermal Abelian monopoles in the temperature range between Tc and 3Tc. In comparison with earlier findings our results for these quantities are improved either with respect to effects of Gribov copies or with respect to lattice artifacts.Comment: 11 pages, 14 figures, 5 tables; substantially changed version, title change

    Optoelectronic properties and characteristics of doping superlattices

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    Optical and electric properties of doping superlattices, or n-i-p-i crystals, can be varied in a wide range under excitation and through the choice of the thicknesses and doping of the crystal layers. Some basic results concerned the transformation of the electron energy spectrum of doping superlattices are summarized. Parameters and characteristics of doping superlattices related to optoelectronics devices, such as photodetectors, laser diodes, and optical modulators, are presented

    Nonlinear optical processes in doped semiconductor superlattices

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    For doped semiconductor superlattices we have analyzed the effects of absorption saturation and change in the refractive index depending on the level of their excitation and structure parameters. The calculations were carried out with account for the tails of the density of states and screening of the electrostatic potential. It is shown that doped superlattices may display "shading," i.e., the increase in the absorption coefficient at a fixed frequency with increase in light intensity. For δ-doped superlattices a stronger nonmonotonicity of the change in the refractive index with increase in the excitation level in comparison with typical structures can manifest itself

    Auger Recombination Processes and Threshold Conditions in Asymmetric-Multiple-Quantum-Well Heterostructure Lasers

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    Different possible processes of non-radiative Auger recombination which occur in the active region of quantum-well lasers are analyzed and the temperature dependence of the lasing threshold in the GaInAs-GaInAsP-InP bi-quantum-well heterolasers with different widths of the quantum wells (4 and 9 nm) is determined. Activated behavior of the Auger recombination is mentioned and respective effective parameters of the processes are calculated. For described asymmetric quantum-well heterostructure lasers, it is shown that the influence of the Auger recombination processes on the temperature behavior of the lasing threshold is not essential until the temperature of the active region is lower than 360 K and the cavity losses do not exceed 80 cm-

    Temperature dependence of the threshold and Auger recombination in asymmetric quantum-well heterolasers

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    The temperature dependence of the lasing threshold in the GaInAs-GaInAsP-InP bi-quantum-well heterolasers with different widths of the quantum wells (4 and 9 nm) has been determined. Processes of non-radiative Auger recombination which occur in the active region of the quantum-well lasers have been included into consideration. The analytical approach for the evaluation of the characteristic temperature of the lasing threshold is presented. For described asymmetric quantumwell heterostructure lasers, it is shown that the influence of Auger recombination processes on the temperature behavior of the lasing threshold is not essential until the temperature of the active region is lower than 360 K and the cavity losses do not exceed 80 cm-

    How to restrain Auger recombination predominance in the threshold of asymmetric bi-quantum-well lasers

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    Both radiative and nonradiative processes which occur in the active region of GaInAs–GaInAsP–InP asymmetric multiple quantum-well (AMQW) heterolasers with two quantum wells of different width (4 and 9 nm) are described. Several possible processes of non-radiative Auger recombination which affect the temperature sensitivity of the lasing threshold are analyzed and the temperature dependencies of the investigated processes are presented. For the above-mentioned AMQW heterostructure, it is shown that the influence of the Auger recombination processes on the temperature behaviour of the lasing threshold can be restrained by operation at temperatures lower than 340 K and the cavity losses which do not exceed 60 cm-1

    Low risk of hypoglycemia and high efficacy of gliclazide MB: results of recent studies

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    Sulfonylureas are widely prescribed all over the world, mainly because of their high effectiveness. At the same time, the heterogeneity of the group is obvious, primarily in relation to the effect of drugs on the risk of developing hypoglycemic events. The review presents the results of new studies, including «Comparative effectiveness of gliclazide modified release versus sitagliptin as second-line treatment after metformin monotherapy in patients with uncontrolled type 2 diabetes» and results of a model-based meta-analysis of 24 antihyperglycemic drugs for type 2 diabetes, confirming the higher efficacy of modified release gliclazide (gliclazide MB) compared to DPP-4, as well as a low risk of hypoglycemic conditions. The results of recent studies, as well as the results of the ADVANCE and ADVANCE-ON studies, suggest that gliclazide MB is safe to use as a second-line drug, especially in patients with chronic kidney disease

    Asymmetric multiple-quantum-well heterostructure laser systems: conception, performance, and characteristics

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    A new type of laser diodes and amplifiers based on asymmetric quantum-well heterostructures having active layers of different thickness and/or compositions has been considered. Bistable switching and regimes of regular radiation pulsation at two or three remote wavelengths in the range of 790 to 850 nm in the GaAs-AlGaAs bi- and triple-quantum-well heterostructures are described. Influence of non-linear processes including gain suppression due to carrier heating on lasing regimes has been examined. Transformation of gain bands for TE and TM modes in dependence on the pump current has been studied for asymmetric four-quantum-well structures. The interval of tuning amplification wavelengths in the system reaches up to 70 nm. Keywords: quantum-well laser diodes, non-linear effects, bistability, regular pulsation, gain spectra

    РОЗРОБКА ТА ЗАСТОСУВАННЯ ПРОГРАМНОГО ЗАБЕЗПЕЧЕННЯ ДЛЯ БАГАТОКРИТЕРІАЛЬНОЇ ОПТИМІЗАЦІЇ ЗМІСТУ ПРОЕКТУ

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    Software for solving the problem of multi-criteria project scope optimization is proposed with constraints and given alternatives of works presented in the form of network models. The problem of determining the optimal project scope application on the site of the machinery plant application of ion-plasma coatings in terms of profit, time, cost, quality and risks of its implementation within the constraints of quality, cost and timing of the project is solved.Запропоновано програмне забезпечення для розв'язання задачі багатокритеріальної оптимізації змісту проекту за наявності обмежень і заданих альтернативних варіантів виконання робіт, наведених у вигляді мережевих моделей. Вирішено задачу визначення оптимального змісту проекту зі створення ділянки машинобудівного заводу з нанесення іонно-плазмового покриття з точки зору прибутку, часу, вартості, якості та ризиків його виконання з урахуванням обмежень щодо якості, вартості та термінів виконання проекту

    Tunable photoluminescence spectra of doped semiconductor superlattices

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    Taking into account the density state tails appearing due to fluctuations of impurity concentrations, the spontaneous emission spectra of doped semiconductor superlattices are calculated. In the framework of the model developed, the explanation of the experimentally observed longwave edge and the shift of the photoluminescence spectra with increase in the excitation level and temperature is given. The role of the defects formed on α-irradiation is discussed, and the lifetime of current carriers is evaluated depending on the design parameters and excitation conditions of the GaAs doped superlattices
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