Detailed Investigation of Breakdown Prediction Models for High Voltage Circuit Breakers

Although studied for several decades, detailed knowledge on the leader mechanism conducting to a dielectric breakdown seems to be still insufficient. For this reason, based on home-made 2D-Euler CFD code, the present study handles the pressure and temperature as controlling parameters to consider for the efficient prediction of the dielectric breakdown. Moreover, it presents the limits of the suggested theoretical approach. This theoretical and numerical investigation is correlated with corresponding power test results on HV mock-ups

An Efficient Implementation of the Finite-volume Method For the Solution of Radiation Transport in Circuit Breakers

In this paper, we propose to revisit the method to solve the radiation transport equation in circuit breakers to reduce the computation time. It is based on an explicit approach using a space marching algorithm. The method can further be accelerated using a Cartesian grid and using the axisymmetric assumption. Comparisons performed in terms of accuracy and efficiency between the P1 model, the implicit finite-volume discrete ordinate method and the space-marching finite-volume discrete ordinate method show that the explicit approach is more that an order of magnitude faster than the implicit approach, for the same accuracy

Quantized conductance in a one-dimensional ballistic oxide nanodevice

Electric-field effect control of two-dimensional electron gases (2-DEG) has enabled the exploration of nanoscale electron quantum transport in semiconductors. Beyond these classical materials, transition metal-oxide-based structures have d-electronic states favoring the emergence of novel quantum orders absent in conventional semiconductors. In this context, the LaAlO3/SrTiO3 interface that combines gate-tunable superconductivity and sizeable spin-orbit coupling is emerging as a promising platform to realize topological superconductivity. However, the fabrication of nanodevices in which the electronic properties of this oxide interface can be controlled at the nanoscale by field-effect remains a scientific and technological challenge. Here, we demonstrate the quantization of conductance in a ballistic quantum point contact (QPC), formed by electrostatic confinement of the LaAlO3/SrTiO3 2-DEG with a split-gate. Through finite source-drain voltage, we perform a comprehensive spectroscopic investigation of the 3d energy levels inside the QPC, which can be regarded as a spectrometer able to probe Majorana states in an oxide 2-DEG

Competition between electron pairing and phase coherence in superconducting interfaces

In LaAlO3/SrTiO3 heterostructures, a gate tunable superconducting electron gas is confined in a quantum well at the interface between two insulating oxides. Remarkably, the gas coexists with both magnetism and strong Rashba spin–orbit coupling. However, both the origin of superconductivity and the nature of the transition to the normal state over the whole doping range remain elusive. Here we use resonant microwave transport to extract the superfluid stiffness and the superconducting gap energy of the LaAlO3/SrTiO3 interface as a function of carrier density. We show that the superconducting phase diagram of this system is controlled by the competition between electron pairing and phase coherence. The analysis of the superfluid density reveals that only a very small fraction of the electrons condenses into the superconducting state. We propose that this corresponds to the weak filling of high- energy dxz/dyz bands in the quantum well, more apt to host superconductivity

Обнаружение автомобильных номерных знаков с использованием предварительной обработки кандидатов

Статья посвящена проблеме ускорения процесса поиска объектов на изображениях, основанного на использовании мультимасштабного сканирования. Для решения этой задачи предлагается использовать\ud предварительную обработку кандидатов с использованием интегральных характеристик, которая реализуется как первый этап каскада классификаторов смешанного типа. В качестве тестовой задачи выбрана задача обнаружения на цифровых изображениях номерных знаков автомобилей. Полученный каскад классификаторов позволил увеличить быстродействие обработки изображений при обнаружении номерных знаков в 1.6 раза по сравнению с каскадом линейных классификаторов, полученным с помощью алгоритма AdaBoost. Результаты проведенных экспериментов могут быть распространены на задачи поиска других объектов на изображениях.Стаття присвячена проблемі прискорення процесу пошуку об'єктів на зображеннях, заснованого на використанні мультимасштабного сканування. Для вирішення цього завдання пропонується використати попередню обробку кандидатів, що реалізується як перший етап каскаду класифікаторів змішаного типу. Як тестове завдання обрана задача виявлення на цифрових зображеннях номерних знаків автомобілів. Отриманий каскад класифікаторів дозволив збільшити швидкодію обробки зображень при виявленні номерних знаків в 1.6 рази в порівнянні з каскадом лінійних класифікаторів, отриманим за допомогою алгоритму AdaBoost. Результати проведених експериментів можуть бути поширені на завдання пошуку інших об'єктів на зображеннях.The article is devoted to a problem of acceleration of objects detection process on the images, the multiscale scanning based on use. For the solution of this task it is offered to use preliminary processing of candidates with use of integrated characteristics which is realized as the first stage of the classifiers cascade of the mixed type. As a test task the problem of detection on digital images of cars registration plates is chosen. The received cascade of classifiers allowed to increase computational performance of images processing at detection of registration plates by 1.6 times in comparison with the cascade of linear classifiers received by means of AdaBoost algorithm. Results of the made experiments can be extended to problems of search of other objects on images

Effect of the deposition conditions of NiO anode buffer layers inorganic solar cells, on the properties of these cells

tNiO thin films deposited by DC reactive sputtering were used as anode buffer layer in organic photovoltaiccells (OPVs) based on CuPc/C60planar heterojunctions. Firstly we show that the properties of the NiOfilms depend on the O2 partial pressure during deposition. The films are first conductive between 0 and2% partial oxygen pressure, then they are semiconductor and p-type between 2 and 6% partial oxygenpressure, between 6 and 9% partial oxygen pressure the conduction is very low and the films seem to be n-type and finally, for a partial oxygen pressure higher than 9%, the conduction is p-type. The morphology ofthese films depends also on the O2 partial pressure. When the NiO films is thick of 4 nm, its peak to valleyroughness is 6 nm, when it is sputtered with a gas containing 7.4% of oxygen, while it is more than double,13.5 nm, when the partial pressure of oxygen is 16.67%. This roughness implies that a forming process,i.e. a decrease of the leakage current, is necessary for the OPVs. The forming process is not necessary ifthe NiO ABL is thick of 20 nm. In that case it is shown that optimum conversion efficiency is achievedwith NiO ABL annealed 10 min at 400◦C

Field-effect control of superconductivity and Rashba spin-orbit coupling in top-gated LaAlO3/SrTiO3 devices

The recent development in the fabrication of artificial oxide heterostructures opens new avenues in the field of quantum materials by enabling the manipulation of the charge, spin and orbital degrees of freedom. In this context, the discovery of two-dimensional electron gases (2-DEGs) at LAlO3/SrTiO3 interfaces, which exhibit both superconductivity and strong Rashba spin-orbit coupling (SOC), represents a major breakthrough. Here, we report on the realisation of a field-effect LaAlO3/SrTiO3 device, whose physical properties, including superconductivity and SOC, can be tuned over a wide range by a top-gate voltage. We derive a phase diagram, which emphasises a field-effect-induced superconductor-to-insulator quantum phase transition. Magneto-transport measurements indicate that the Rashba coupling constant increases linearly with electrostatic doping. Our results pave the way for the realisation of mesoscopic devices, where these two properties can be manipulated on a local scale by means of top-gates