Experimental Study of Two-Phase Thermosyphons of the Thermoelectric Cooling Unit

Проведены экспериментальные исследования теплопередающей способности двухфазных термосифонов, заправленных фреоном 134А. Термосифоны изготовлены из нержавеющей стали, имеют длину 400 мм и внутренний диаметр 10,5 мм, протяженность зоны испарения составляла 200 мм, а длина конденсатора – 60 мм. Приведены данные измерений температурного состояния и теплопередающих характеристик термосифонов в зависимости от передаваемого теплового потока, угла наклона от вертикали и температуры теплоносителя системы теплоотводаExperimental studies of the heat transfer capacity of two- phase thermosiphons filled with Freon 134A have been carried out. Thermosyphons are made of stainless steel, have a length of 400 mm and an internal diameter of 10.5 mm, the length of the evaporation zone was 200 mm, and the length of the condenser was 60 mm.The data of measurements of the temperature state and heat transfer characteristics of thermosiphons depending on the transferred heat flux, the angle of inclination from the vertical and the temperature of the coolant of the heat removal system are give

Eurasian-Scale Experimental Satellite-based Quantum Key Distribution with Detector Efficiency Mismatch Analysis

The Micius satellite is the pioneering initiative to demonstrate quantum teleportation, entanglement distribution, quantum key distribution (QKD), and quantum-secured communications experiments at the global scale. In this work, we report on the results of the 600-mm-aperture ground station design which has enabled the establishment of a quantum-secured link between the Zvenigorod and Nanshan ground stations using the Micius satellite. As a result of a quantum communications session, an overall sifted key of 2.5 Mbits and a total final key length of 310 kbits have been obtained. We present an extension of the security analysis of the realization of satellite-based QKD decoy-state protocol by taking into account the effect of the detection-efficiency mismatch for four detectors. We also simulate the QKD protocol for the satellite passage and by that validate our semi-empirical model for a realistic receiver, which is in good agreement with the experimental data. Our results pave the way to the considerations of realistic imperfection of the QKD systems, which are important in the context of their practical security.Comment: 8+2 pages, 5+2 figure

Runways ground monitoring system by phase-sensitive optical-fiber OTDR

Runways monitoring in civil airports is typically performed by enhanced radar surveillance systems operating in the so-called Precision Runway Monitor (PRM) system that provides position of airplanes and information on their trajectories. In this paper, we propose an additional measurement system that can be used jointly with the conventional PRM approach to monitor aircrafts position on land without using the radar approach or requiring visual inspection of the lanes. We propose a system made of ground-based distributed optical fiber sensors (OFSs), to be placed below the concrete floor of the take-off and landing lanes as well as along the different roads and intersections within the airport. OFSs will be read by a phase-sensitive OTDR (Φ-OTDR) driven by low-noise narrow-linewidth 1.55 mm laser. The laser field is used to inject the optical fiber with a pulsed signal and to read the phase shifts arising from vibrations and pressure waves produced by aircrafts moving, or even still with engines turned on, along the lanes. An absolute localization of different planes, with a few meters resolution and accuracy across the whole airport, would be possible after installing OFSs and adjustment of the detection system. The proposed ground monitoring system, in addition to the ones currently available, offers information redundancy at a promising low-cost and a backup aircraft-positioning tool in case of failure or malfunctioning of the existing video-or radio-based systems. Furthermore, the proposed system is inherently immune to e.m. interference and also to intentional disturbance or intrusion. Design of the laser source and of the Φ-OTDR measurement system is underway with the aim of precise and continuous monitoring of the on-land position and movement of different aircrafts or vehicles within the airport

Synthesis of Co-Ni Alloy Particles with the Structure of a Solid Substitution Solution by Precipitation in a Supercritical Carbon Dioxide

Mixed Co-Ni bimetallic systems with the structure of a solid substitution solution have been synthesized using the supercritical antisolvent precipitation (SAS) method, which uses supercritical CO2 as an antisolvent. The systems obtained have been characterized in detail using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier-transform infrared (FTIR) spectroscopy, and magnetostatic measurements. It has been found that Co-enriched systems have a defective hexagonal close-packed (hcp) structure, which was described by a model which embedded cubic fragments of packaging into a hexagonal close-packed (hcp) structure. It has been shown that an increase in water content at the precipitation stage leads to a decrease in the size of cubic fragments and a more uniform distribution of them in Co-enriched systems. It has also been shown that mixed systems have the greatest coercivity in the line of samples. Ni-enriched bimetallic systems have a cubic close-packed (ccp) structure with modified crystal lattice parameters

Experimental Study of Frost Formation in a Plate Heat Exchanger

Представлены результаты исследования инееобразования на поверхности ребер теплообменника при обтекании потоком влажного воздуха. Приведено описание экспериментального стенда и методики проведения экспериментов. Влияние инееобразования на эффективность теплопередачи оценивалось по временным температурным зависимостям в различных точках поверхности ребра. В ходе экспериментов толщина слоя инея и степень перекрытия межреберных промежутков контролировались визуально и с помощью анемометра. Анализ экспериментальных данных выявил особенности образования инея в зависимости от геометрических параметров ребер. Полученные результаты могут быть использованы при разработке и проектировании теплообменников холодильного оборудованияThe paper presents the results of a study of frost formation on the surface of the heat exchanger fins when a moist air flow is flown around. The description of the experimental stand and the experimental procedure are given. The effect of frost formation on the efficiency of heat transfer was estimated from the time temperature dependences at various points of the fin surface. During the experiments, the thickness of the frost layer and the degree of overlap of the intercostal spaces were monitored visually and using an anemometer. Analysis of the experimental data revealed the features of frost formation depending on the geometric parameters of the ribs. The results obtained can be used in the development and design of heat exchangers for refrigeration equipmen

Multipurpose monitoring system for icebreakers: Development, implementation, and testing

We demonstrate the results of a project on implementing a complete and practical multipurpose monitoring system for icebreakers. We describe the basic principles of operating the developed monitoring system. We present a 3D finite element analysis of the ship model to optimise the sensor arrangement. We also present the benchmarks and test results of the system during an expedition on the Russian scientific research vessel Akademik Tryoshnikov

Multipurpose monitoring system for icebreakers: Development, implementation, and testing

We demonstrate the results of a project on implementing a complete and practical multipurpose monitoring system for icebreakers. We describe the basic principles of operating the developed monitoring system. We present a 3D finite element analysis of the ship model to optimise the sensor arrangement. We also present the benchmarks and test results of the system during an expedition on the Russian scientific research vessel Akademik Tryoshnikov