Fractography of Fatigue Fracture Surface in Silumin Subjected to Electron-Beam Processing

The surface modification of the eutectic silumin with high-intensity pulsed electron beam has been carried out. Multi-cycle fatigue tests were performed and irradiation mode made possible the increase in the silumin fatigue life more than 3.5 times was determined. Studies of the structure of the surface irradiation and surface fatigue fracture of silumin in the initial (unirradiated) state and after modification with intense pulsed electron beam were carried out by methods of scanning electron microscopy. It has been shown, that in mode of partial melting of the irradiation surface the modification process of silicon plates is accompanied by the formation of numerous large micropores along the boundary plate/matrix and microcracks located in the silicon plates. A multi-modal structure (grain size within 30-50 μm with silicon particles up to 10 [mu]m located on the boundaries) is formed in stable melting mode, as well as subgrain structure in the form of crystallization cells from 100 to 250 [mu]m in size). Formation of a multi-modal, multi-phase, submicro- and nanosize structure assisting to a significant increase in the critical length of the crack, the safety coefficient and decrease in step of cracks for loading cycle was the main cause for the increase in silumin fatigue life

Effects of Size Polydispersity on the Extinction Spectra of Colloidal Nanoparticle Aggregates

We investigate the effect of particle polydispersity on the optical extinction spectra of colloidal aggregates of spherical metallic (silver) nanoparticles, taking into account the realistic interparticle gaps caused by layers of stabilizing polymer adsorbed on the metal surface (adlayers). The spectra of computer-generated aggregates are computed using two different methods. The coupled-multipole method is used in the quasistatic approximation and the coupled-dipole method beyond the quasistatics. The latter approach is applicable if the interparticle gaps are sufficiently wide relative to the particle radii. Simulations are performed for two different particle size distribution functions (bimodal and Gaussian), varying the number of particles per aggregate, and different distribution functions of the interparticle gap width. The strong influence of the latter factor on the spectra is demonstrated and investigated in detail

Degradation of structure and properties of rail surface layer at long-term operation

The microstructure evolution and properties variation of the surface layer of rail steel after passed 500 and 1000 million tons of gross weight (MTGW) have been investigated. The wear rate increases to 3 and 3.4 times after passed 500 and 1000 MTGW, respectively. The corresponding friction coefficient decreases by 1.4 and 1.1 times. The cementite plates were destroyed and formed the cementite particles of around 10-50 nm in size after passed 500 MTGW. The early stage dynamical recrystallization was observed after passed 1000 MTGW. The mechanisms for these have been suggested. The large number of bend extinction contours is revealed in the surface layer. The internal stress field is evaluated

Жизнь напоказ: почему сегодня важно выставлять свои действия в социальной сети

Social networks have emerged relatively recently in human life, but have already become an integral part of it. Companies tell about themselves, their activities, innovations, promotions and events in their profiles. This helps increase audience coverage, tell more about your brand, products, services. People in personal accounts have the opportunity to share their lives and creativity through photos, videos and texts. Now it is not necessary to receive higher education to become an operator, director or actor whose talent is recognized by society. It is enough to start a page on the social network and start sharing your knowledge and creativity.To find out why people post photos, videos and write texts on their social networks, a pilot sociological study was carried out. The method of deep interview with active users of social networks was chosen to carry out the study. The interview allowed getting unique information, to learn the opinion of users about social networks, the impact of the new way of communication on their life, to identify the reasons why users start and maintain profiles.The respondents were 20 users of social networks between the ages of 19 and 22. Interviewees have profiles on the most popular Instagram and Vkontakte networks. As a result of the analysis of the interview, a tendency was revealed to differ in the perception of users of their actions on the social network and similar actions of other users. Their content is perceived by them as opportunities to be in sight, as a resource to form their social status and an element of influence on their reference group. And the same content published by others is perceived as boasting. Социальные сети появились в жизни человечества сравнительно недавно, но уже стали неотъемлемой ее частью. Компании рассказывают о себе, своей деятельности, новинках, акциях и мероприятиях в своих профилях. Это помогает увеличить охват аудитории, больше рассказать о своем бренде, продуктах, услугах. У людей в личных аккаунтах появилась возможностью делиться своей жизнью и творчеством с помощью фотографий, видео и текстов. Теперь не обязательно получать высшее образование, чтобы стать оператором, режиссером или актером, чей талант признает общество. Достаточно завести страницу в социальной сети и начать делиться своими знаниями и творчеством.Чтобы выяснить, зачем люди выкладывают фотографии, видео и пишут тексты в своих социальных сетях, было проведено пилотное социологическое исследование. Для проведения исследования был выбран метод глубинного интервью с активными пользователями социальных сетей. Интервью позволило получить уникальную информацию, узнать мнение пользователей о социальных сетях, влиянии нового способа коммуникации на их жизнь, выявить причины, по которым пользователи завели и ведут профили.Респондентами стали 20 пользователей социальных сетей в возрасте с 19 до 22 лет. Опрошенные имеют профили в наиболее популярных сетях Instagram и Вконтакте. В результате анализа интервью была выявлена тенденция различия в восприятии пользователями своих действий в социальной сети и аналогичных действий других пользователей. Свой контент воспринимается ими как возможности быть на виду, как ресурс формирования своего социального статуса и элемент влияния на свою референтную группу. А тот же контент, опубликованный другими, воспринимается как хвастовство и понты