Luminescent properties of fine-dispersed ZnS:Cu prepared using self-propagating high-temperature synthesis

Fine-dispersed ZnS doped with Cu was prepared using self-propagating hightemperature synthesis. In the photoluminescence excitation spectra, the blue shift of the host lattice excitation peak is observed for powder ZnS:Cu that contains nano- and mesosized (submicron) particles. The obtained spectra indicate that radiative recombination in meso-sized particles is significantly reduced as compared to micro-sized particles, which can be caused by the increase of non-radiative relaxation processes in surface states

Influence of the presence of a fluxing agent and its composition on the spectral characteristics of ZnS(Cu) obtained by self-propagating high-temperature synthesis

Investigated in this work were the photoluminescence spectra and luminescence excitation spectra of powered ZnS:Cu, obtained using the method of selfpropagating high-temperature synthesis (SHS) with addition of NaCl and MgCl₂ as a fluxing agent into the charge and without them. It was shown that increasing the amount of fraction with the particle sizes ≤5 nm in powdered ZnS:Cu-SHS, where fluxing agents are present in the charge, is caused by the decrease in temperature inside the reactor in the course of the synthesis reaction. Besides, related increasing the intensity of the PL blue band with λmax ~ 450…465 nm in powdered ZnS:Cu-SHS/MgCl₂, which is associated with redistribution of the copper impurity in the bulk of microcrystals, probably, occurring as a result of increasing the partial pressure of Cl during synthesis

Electroluminescence powdered ZnS:Cu obtained by one-stage synthesis

Photo- and electroluminescence properties of ZnS obtained using selfpropagating high-temperature synthesis and doped with Cu were studied in this work. It has been shown that high-temperature one-stage synthesis enables to obtain two-phase system ZnS-Cu₂₋xS with the maximum radiation 515 nm for photo- and electroluminescence. Since the synthesis process is non-equilibrium, impurities distribute nonuniformly in the bulk of microcrystals. Additional annealing and introducing the Ga coactivator lead to more non-uniform distribution of impurities in the bulk of microcrystals. It causes the increase in the intensity of the blue band in photoluminescence spectra and shift of the maximum of electroluminescence toward longer wavelengths. It is probable that this increase in the intensity of the blue band in photoluminescence spectra is caused by formation of the radiative centers Cui₋CuZn

Detection of explosives

The extensive literature on the methods of detection of explosives under the stationary and field conditions is reviewed. Today, there are hundreds of publications on detectability of explosives by different methods, but none of the methods gives a 100% guarantee of explosives detection. Consideration has been given to advanced high-technology methods of explosives detection: nuclear quadrupole resonance method, nuclear physics methods (slow and fast neutrons, gamma-quanta), biological methods. Notice that the danger of newly created explosives, including land mines, increases. The actuation systems are also constantly improved. Most difficulties with detection, extraction and deactivation of explosive devices can be overcome with the help of updated methods and techniques. The present review calls attention primarily to the possibility of solving the pressing and complicated problems using charged particle accelerators.Проведен обзор литературы по методам детектирования взрывчатых веществ (ВВ) в стационарных и полевых условиях. В настоящее время имеются сотни публикаций по возможности детектирования ВВ различными методами, но 100% гарантии их обнаружения нет. Внимание уделено современным высокотехнологическим методам обнаружения ВВ: ядерному квадрупольному резонансу, ядерно-физическим (медленные и быстрые нейтроны, гамма-кванты) и биологическим. Следует отметить, что опасность вновь создаваемых ВВ, в том числе и полевых мин, увеличивается. Совершенствуются и системы их срабатывания. Большинство трудностей по детектированию, извлечению и деактивации взрывных устройств может быть преодолено с помощью современных методов и технологий. Данный обзор, прежде всего, обращает внимание на возможность решения этой острой и сложной проблемы с помощью ускорителей заряженных частиц.Проведено огляд літератури по методах детектування вибухових речовин (ВР) у стаціонарних і польових умовах. На даний час є сотні публікацій по можливості детектування ВР різними методами, але 100% гарантії їх виявлення немає. Увага приділена сучасним високотехнологічним методам виявлення ВР: ядерному квадрупольному резонансу, ядерно-фізичним (повільні й швидкі нейтрони, гамма-кванти) і біологічним. Слід зазначити, що небезпека створюваних ВР, у тому числі польових мін, збільшується. Удосконалюються й системи їхнього спрацьовування. Більшість труднощів по детектуванню, добуванню і деактивації вибухових пристроїв може бути подолане за допомогою сучасних методів і технологій. Даний огляд, насамперед, звертає увагу на можливість рішення цієї гострої і складної проблеми за допомогою прискорювачів заряджених частинок

The factors influencing luminescent properties of ZnS:Mn obtained by the method of one-stage synthesis

Considered in this paper is the model that combines appearance of defects responsible for self-activated (SA) emission in ZnS with its piezoelectric properties. Being based on analysis of the luminescence spectrum, the authors demonstrate the influence of mechanical destruction, impact of ultrasound, microwave radiation and pulsed magnetic field on the emission efficiency for centers of luminescence connected with intrinsic defects in ZnS:Mn prepared using the method of self-propagating hightemperature synthesis (SHS). It has been shown that downsizing the ZnS:Mn crystals prepared according to the above method as well as more discrete differentiation of phases present in this material due to development and growth of inner boundaries and surface under external actions leads to quenched SA-photoluminescence with λ ~ 400–525 n

Effect of heating rate on oxidation process of fine-dispersed ZnS:Mn obtained by SHS

The influence of annealing at 350 °C in air atmosphere on the luminescent characteristics of powdered ZnS: Mn obtained by self-propagating high-temperature synthesis has been studied. It was shown that variation in material heating rate due to changes in the annealing temperature results in different behavior of oxidative processes. It has been ascertained that the slow heating of powdered ZnS:Mn, compared with the rapid one in the presence of oxygen, promotes active oxidation of ZnS and formation of Frenkel pairs, increases mileage of defects acting as sensitizers, and their localization near Mn²⁺. The model which explains the observed changes in the luminescence and PLE spectra has been presented

METHOD OF ADAPTIVE CHOOSING NUMBER CHANNELS IN MIMO SYSTEM

В роботі запропоновано методику адаптивного вибору числа каналів системи МІМО при збереженні ймовірності бітової помилки нижче заданої межі. Методика дозволяє працювати при низьких значеннях відношення сигнал/шум в режимах з обмеженою кількістю паралельних каналів передачі.В работе предложена методика адаптивного выбора количества каналов системы МІМО при сохранении вероятности битовой ошибки ниже заданной границы. Методика позволяет работать при низких значениях отношения сигнал/шум в режимах с ограниченным количеством параллельных каналов передачи.In article offer method of adaptive choosing number channels in mimo system with saving bit error probability under specified border. Method allow to work with small attitude signal oise in mode with limited number parallel channels transfer

Luminescent properties of fine-dispersed self-propagating high-temperature synthesized ZnS:Cu,Mg

The influence of magnesium impurities on luminescent properties of ZnS:Cu,Mg using obtained by self-propagating high-temperature synthesis (SHS) has been investigated. Special attention was paid to changes of photoluminescence spectra caused by relaxation processes in ZnS:Cu,Mg-SHS. It was shown that introduction of magnesium into ZnS:Cu-SHS leads to a change in symmetry of ZnS crystal lattice. It leads to relaxation quenching the photoluminescence bands caused by presence of copper impurities in ZnS

Selective introduction of Cu impurity into fine-dispersed ZnS obtained during the process of one-stage synthesis

Abstract Fine ZnS:Cu, obtained by method of self-propagating high-temperature synthesis was investigated. As flux in the mixture NaCl was used, Zn and S were taken in stoichiometric ratio; Cu concentration in charge consisted ~1.5 wt.%. Using SEM data, it was established that obtained ZnS:Cu consists from two fractions—first with particles sizes ~10 μm and more, and other with sizes 50–500 nm. It was established that composition of ZnS:Cu fractions was essentially different. According to EDS data, Cu concentration in particles of fraction with 50–500 nm sizes consists ~2 wt.%, and in particles with sizes ~10 μm and more the presence of Cu was not detected. The reasons that lead to the selective doping of particles in dependence on their size and also the role of NaCl in processes undergoing during synthesis of material are discussed

METHOD OF ADAPTIVE MANAGEMENT PARAMETERS MIMO APSAA

В роботі запропоновано методику адаптивного управління параметрами багатоантенних систем військового радіозв’язку з активними фазованими антенними решітками. Методика дозволяє зберігати працездатність багатоантенних систем військового призначення за рахунок сумісного адаптивного управління параметрів багатоантенних систем військового радіозв’язку та активних фазованих антенних решіток.В работе предложена методика адаптивного управления параметрами многоантенных систем радиосвязи военного назначения с активными фазированными антенными решетками. Методика позволяет сохранять работоспособность многоантенных систем военного назначения за счет совместного адаптивного управления параметрами многоантенных систем военной радиосвязи и активных фазированных антенных решеток.In article offered method of adaptive management parameters multiantenna systems military radio communication with active phased antenna arrays. Method allow to save performance multiantenna systems military appointment due to the joint adaptive management parameters multiantenna systems military radio communication and active phased antenna arrays