Металлизация поверхности керамики В4С комбинированным электронно-ионно-плазменным методом

Объектом исследования является керамика В4С с металлизированной поверхностью. Цель работы – исследование структуры и свойств систем «пленка (Ti)/(В4С-керамика) подложка» и «пленка (Cu)/(В4С-керамика) подложка», обработанных интенсивным импульсным электронным пучком. В процессе исследования проводились рентгенофазовые исследование; исследование поверхности и излома образцов методом сканирующей электронной микроскопии; исследование микротвердости и коэффициента вязкости разрушения образов. В результате исследования установлено формированию в поверхностном слое толщиной (5-7) мкм многофазной структуры эвтектического типа, состоящей из кристаллитов карбида бора, диборида титана и титана; снижение микротвердости модифицированных образцов керамики Ti/В4С в ≈1,2 раза относительно микротвёрдости исходных образцов. Основные конструктивные, технологические и технико-эксплуатационные характеристики: температура разложения >2450 °C; плотность 2,52 г/см³; теплопроводность 121 Вт/(мК) при 300 °К; микротвёрдость 49,1 ГПа; модуль упругости 450 ГПа; полупроводник p-типа.The object of the research is B4C ceramics with metallized surface. Objective - to study the structure and properties of systems "film (Ti) / (B4C-ceramic) substrate" and "film (Cu) / (B4C-ceramic) substrate" treated with intense pulsed electron beam. The study carried out X-ray phase study; study the surface and break the samples by scanning electron microscopy; study of microhardness and fracture toughness ratio images. The study showed the formation of a surface layer (5-7) m multiphase eutectic structure consisting of crystallites of boron carbide, titanium diboride, and titanium; decrease in microhardness modified ceramic samples Ti / B4C in ≈1,2 times the microhardness of the initial samples. The basic constructive, technological and technical and operational characteristics: the decomposition temperature of> 2450 ° C; density 2.52 g / cm³; thermal conductivity of 121 W / (mK) at 300 ° K; microhardness 49.1 GPa; modulus 450 GPa; p-type semiconductor

Impacts of a large Sahelian city on groundwater hydrodynamics and quality : example of Niamey (Niger)

The management of groundwater resources is very important in the semiarid Sahel region, which is experiencing rapid urban development. Impacts of urbanization on groundwater resources were investigated in the unconfined aquifer of the Continental Terminal beneath the city of Niamey, Niger, using water level and chemical data. Hydrodynamic and chemical changes are best described by a combination of factors including the historical development of the city, current land use, water-table depth and topography. Seasonal groundwater recharge occurs with high spatial variability, as indicated by water-level monitoring in all wells, but there was no interannual trend over the 5-year study period. Groundwater salinity shows high spatial variability and a minor rising trend. The highest salinity is in the old city centre, with Na-NO3 dominant, and it increases seasonally with recharge. Salinity is much lower and more variable in the suburbs (Ca-HCO3, Ca-NO3, and Na-NO3 dominant). Nitrate is the main ionic contaminant and is seasonally or permanently above the international guidelines for drinking water quality in 36 % of sampled wells, with a peak value of 112 mg L-1 NO3-N (8 meq L-1). Comparison of urban and rural sites indicates a long-term increase in groundwater recharge and nitrate enrichment in the urban area with serious implications for groundwater management in the region

Task design and interaction in collaborative writing: the students’ story

This article investigates student behaviour on collaborative assignments, looking at the relationship between task type and interaction, and considers the implications for task design. Students reported on interactions in a year-long workplace-focussed group communication project, comparing these with interactions on other academy based group assignments. Differences were seen in the amount of brainstorming, the criteria for dividing up work, the intensity of editing, and how conflict was managed. Contributing factors to these differences included the presence or absence of a creative element, the instrumental nature of the task, and the need for a collective approach inherent in the task design

Defining Expressive Language Benchmarks for Children with Down Syndrome.

Establishing expressive language benchmarks (ELBs) for children with Down syndrome (DS), as developed by Tager-Flusberg et al. for children with autism, is critically needed to inform the development of novel treatments, identify individualized treatment targets, and promote accurate monitoring of progress. In the present study, we assessed ELB assignments in three language domains (phonology, vocabulary, and grammar) for 53 young children with DS (CA range: 2.50-7.99 years) using standardized assessments. The participants were classified into one of four ELB levels (preverbal, first words, word combinations, and sentences) in each language domain. Associations with additional measures of language, chronological age, nonverbal cognition, and verbal short-term memory were considered. Analyses of individual ELB profiles indicated substantial variability across the three language domains, with six different patterns of variation across domains emerging. At the same time, the ELB categories were significantly associated with independent language measures and broader developmental domains. Moreover, ELB changes were observed in a small sample of children with DS reassessed 18-24 months after the initial visit. Results from the present study suggest the procedures outlined by Tager-Flusberg et al. for defining ELBs are a potentially useful tool for describing the language abilities of children with DS

Defining Expressive Language Benchmarks for Children with Down Syndrome

Establishing expressive language benchmarks (ELBs) for children with Down syndrome (DS), as developed by Tager-Flusberg et al. for children with autism, is critically needed to inform the development of novel treatments, identify individualized treatment targets, and promote accurate monitoring of progress. In the present study, we assessed ELB assignments in three language domains (phonology, vocabulary, and grammar) for 53 young children with DS (CA range: 2.50–7.99 years) using standardized assessments. The participants were classified into one of four ELB levels (preverbal, first words, word combinations, and sentences) in each language domain. Associations with additional measures of language, chronological age, nonverbal cognition, and verbal short-term memory were considered. Analyses of individual ELB profiles indicated substantial variability across the three language domains, with six different patterns of variation across domains emerging. At the same time, the ELB categories were significantly associated with independent language measures and broader developmental domains. Moreover, ELB changes were observed in a small sample of children with DS reassessed 18–24 months after the initial visit. Results from the present study suggest the procedures outlined by Tager-Flusberg et al. for defining ELBs are a potentially useful tool for describing the language abilities of children with DS