Estimation of operating modes of the self-excited current inverter with use SFI-wavelet transformation

Abstract: Application of the SFI-wavelet transformation for fault isolation in self-excited current inverter consider in this paper. Definition of the fault type based on the analysis of current and voltage spectrum constructed with the use of SFI-wavelet transformation

Biocomposite Materials Based on Poly(3-hydroxybutyrate) and Chitosan: A Review

One of the important directions in the development of modern medical devices is the search and creation of new materials, both synthetic and natural, which can be more effective in their properties than previously used materials. Traditional materials such as metals, ceramics, and synthetic polymers used in medicine have certain drawbacks, such as insufficient biocompatibility and the emergence of an immune response from the body. Natural biopolymers have found applications in various fields of biology and medicine because they demonstrate a wide range of biological activity, biodegradability, and accessibility. This review first described the properties of the two most promising biopolymers belonging to the classes of polyhydroxyalkanoates and polysaccharides—polyhydroxybutyrate and chitosan. However, homopolymers also have some disadvantages, overcome which becomes possible by creating polymer composites. The article presents the existing methods of creating a composite of two polymers: copolymerization, electrospinning, and different ways of mixing, with a description of the properties of the resulting compositions. The development of polymer composites is a promising field of material sciences, which allows, based on the combination of existing substances, to develop of materials with significantly improved properties or to modify of the properties of each of their constituent components

Хаотична розширювальна послідовність лінійної частотної модуляції

У наведеній статті запропоновано використання хаотичних сигналів як розширювальних послідовностей при лінійно-частотній модуляції. Наведено приклад схеми генератора хаотичного сигналу, побудованого на основі лінійних та перемикаючих елементів, а також рівняння, що описують роботу схеми. Показано результати розрахунку та моделювання процесів із конкретними заданими параметрами схеми. Наведено біфуркаційну діаграму та функції відображення для процесів з двома та трьома точками тяжіння. Показано, що при формуванні діапазону зміни частоти необхідно враховувати наявність «мертвої зони». Наведено формулу для розрахунку та графік зміни коефіцієнта кореляції. Для процесу з двома точками тяжіння наведено приклад цілочисельних послідовностей, які пропонується використовувати для ідентифікації виду хаотичного процесу. Бібл. 7, рис. 4, табл. 1

Collagen/Chitosan Gels Cross-Linked with Genipin for Wound Healing in Mice with Induced Diabetes

Diabetes mellitus continues to be one of the most common diseases often associated with diabetic ulcers. Chitosan is an attractive biopolymer for wound healing due to its biodegradability, biocompatibility, mucoadhesiveness, low toxicity, and hemostatic effect. A panel of hydrogels based on chitosan, collagen, and silver nanoparticels were produced to treat diabetic wounds. The antibacterial activity, cytotoxicity, swelling, rheological properties, and longitudinal sections of hydrogels were studied. The ability of the gels for wound healing was studied in CD1 mice with alloxan-induced diabetes. Application of the gels resulted in an increase in VEGF, TGF-b1, IL-1b, and TIMP1 gene expression and earlier wound closure in a comparison with control untreated wounds. All gels increased collagen deposition, hair follicle repair, and sebaceous glands formation. The results of these tests show that the obtained hydrogels have good mechanical properties and biological activity and have potential applications in the field of wound healing. However, clinical studies are required to compare the efficacy of the gels as animal models do not reproduce full diabetes pathology