Research of electrical characteristics of increased uniformity LAN-cables

Formulation of the problem. At present, symmetric LAN cables are widely used in structured cabling systems (SCS) and fixed broadband access (BBA) networks in the world and in Russia. Practical experience of using LAN cables on real broadband access networks shows that high-quality transmission can only be achieved using high-quality highly uniform cables.Objective. Study of the dependence of the quality of LAN-cables on technological equipment and the quality of materials, which provide increased cable uniformity.Results. Based on the experimental studies carried out with the use of a modern measuring system, the main electrical characteristics of the transmission and the mutual influence of the most popular four-pair LAN-cable of the 5e category of the U/UTP4×2×0.52 type in the frequency range up to 100 MHz are determined. It is shown that to ensure high and stable transmission characteristics and mutual influence, modern technological equipment must be equipped with cable quality parameters automatic control systems and it is necessary to choose reliable suppliers when using domestic production materials.Practical significance. For the effective practical use of LAN cables on fixed broadband access networks and in SCS, it is very important to have high stability of electrical characteristics and their compliance with rather high established standards. This is possible only by ensuring high geometric and structural homogeneity of the structural elements of LAN cables

Лазерное формообразование конструкций из упрочненных сплавов аллюминия

У роботі проаналізовані технології виготовлення крупно габаритних конструкцій з зістареного сплаву Д16. Показано, що метод лазерного формоутворення має ряд переваг в порівнянні з способом дробоударного формоутворення, який в даний час застосовується у авіабудівній промисловості. Приведено результати дослідження структури та механічних властивостей зони термічного впливу сплаву Д16 після лазерної обробки. Показано, що при великих кутах згину у зоні термічного впливу проходять процеси знеміцнення. Запропонована схема лазерного формоутворення з охолодженням заготовки парами рідкого азоту. Доказано, що вказана технологія більш продуктивна та дозволяє зберігати у зоні термічного впливу вихідну структуру.This paper analyzes methods of obtaining thin-walled sheet structures from the pre-heat-treatable aluminum alloys. These drawbacks technology Drobotenko of shaping, which is currently widely used in aircraft industry. It is proved that the method of laser forming a more flexible and productive compared with the specified technology. On the basis of literary data analysis determined that for aged alloys barrier to introducing the technology of laser forming could be a weakening of the alloy in the heat affected zone as a result of dissolution or coagulation of strengthening phases. According to the traditional scheme of Dogville laser forming on samples of alloy D16 at CO2 - laser with radiation power P =1 kW, focal spot diameter d=4 mm, a speed of movement of the beam V=6.0 m/min. Determined the microhardness, yield stress, and strength parameters of the substructure and the residual stresses in the heat affected zone. It is shown that the processes of softening are not recorded up to angles of ≈30°. To obtain structures with large bend angles is proposed and implemented scheme of laser forming with cooling of the workpiece in pairs of liquid nitrogen. According to this technology held laser bending samples. Characterization of strength and substructure of heat affected zone. It is shown that the yield and strength of the alloy in the heat affected zone increases with the number of passes by increasing the dislocation density. The latter is a result of plastic deformation of the alloy when the relaxation time of thermal stresses on the heating stage of the thermal cycle. It is proved that laser forming with cooling of the workpiece is more productive in comparison with the traditional scheme due to the increase of bending moment in consequence of the increase of the temperature gradient normal to the sample surface. It is experimentally shown and theoretically proved that the laser forming leads to the appearance in the surface layers of the workpiece residual compressive stress. The latter should substantially increase the fatigue strength of the structure.В работе проанализированы технологии изготовления крупно габаритных конструкций из состаренного сплава Д16. Показано, что метод лазерного формообразования имеет ряд преимуществ в сравнении с способом дробоударного формообразования, который в настоящее время применяется в авиастроительной промышленности. Приведены результаты исследования структуры и механических свойств зоны термического влияния сплава Д16 после лазерной обработки. Показано, что при больших углах сгиба в зоне термического влияния проходят процессы разупрочнения. Предложена схема лазерного формообразования с охлаждением заготовки парами жидкого азота. Доказано, что указанная технология более производительна и позволяет хранить в зоне термического влияния исходную структуру