Магнитные свойства высококоэрцитивных ферритов Sr1-xGdxFe12-xCoxO19 (0 ≤ x ≤ 0,5)

Sr1-xGdxFe12-xCoxO19 ( x = 0; 0.1; 0.2; 0.3; 0.4; 0.5) ferrites have been prepared by solid-state method under air at 1473 K. It has been found that increasing the value of x first leads to a slight decrease in the Curie temperature, from 727 K for the base ferrite SrFe12O19 to 725 K of solid solution Sr0.9Gd0.1Fe11.9Co0.1O19, but with x further increasing, the Curie temperature rises reaching 745 K at x=0.5. It has been found that at 5 K and 300 K, spontaneous magnetization (no) values are respectively 4.2 and 3.7 % higher for solid solution Sr0.9Gd0.1Fe11.9Co0.1O19 than for the base ferrite SrFe12O19.Твердофазным методом на воздухе при температуре 1473 K получены образцы ферритов Sr1-xGdxFe12-xCoxO19 ( x = 0; 0,1; 0,2; 0,3; 0,4; 0,5). Рентгенофазовый анализ показал, что образцы с x≥0,2, кроме основной фазы со структурой магнетоплюмбита, содержали примесные фазы α-Fe2O3, Gd3Fe5O12, в образцах с x=0,3; 0,4; 0,5 присутствовали фазы GdFeO3, CoFe2O4, а в образцах с x=0,4; 0,5 - фаза Gd2O3. Установлено, что увеличение параметра состава x сначала приводит к незначительному уменьшению температуры Кюри от 727 K для SrFe12O19 до 725 K для феррита с x=0,1, а при дальнейшем увеличении x до 0,5 она немного возрастает и для образцов с x=0,5 составляет 745 K. Установлено, что твердый раствор феррита Sr1-xGdxFe12-xCoxO19 с x=0,1 при 5 и 300 K имеет значения самопроизвольной намагниченности (и0) больше, чем у феррита SrFe12O19 на 4,2 и 3,7 % соответственно

Botnet detection techniques: review, future trends, and issues

NoIn recent years, the Internet has enabled access to widespread remote services in the distributed computing environment; however, integrity of data transmission in the distributed computing platform is hindered by a number of security issues. For instance, the botnet phenomenon is a prominent threat to Internet security, including the threat of malicious codes. The botnet phenomenon supports a wide range of criminal activities, including distributed denial of service (DDoS) attacks, click fraud, phishing, malware distribution, spam emails, and building machines for illegitimate exchange of information/materials. Therefore, it is imperative to design and develop a robust mechanism for improving the botnet detection, analysis, and removal process. Currently, botnet detection techniques have been reviewed in different ways; however, such studies are limited in scope and lack discussions on the latest botnet detection techniques. This paper presents a comprehensive review of the latest state-of-the-art techniques for botnet detection and figures out the trends of previous and current research. It provides a thematic taxonomy for the classification of botnet detection techniques and highlights the implications and critical aspects by qualitatively analyzing such techniques. Related to our comprehensive review, we highlight future directions for improving the schemes that broadly span the entire botnet detection research field and identify the persistent and prominent research challenges that remain open.University of Malaya, Malaysia (No. FP034-2012A