444 research outputs found
Microstructure-property relaltionship in silicon carbide armor ceramics
No full textDefects are one of the factors that show a negative effect on the ballistic performance. Uniform microstructures with a low percentage of well distributed porosity could possibly demonstrate high ballistic strength; therefore, it is of interest to estimate the parameters that define the spatial arrangement of defects. This aspect of microstructures was investigated in a variety of silicon carbide ceramics ranging from off-density sintered samples to high density hot-pressed armor grade samples.
The spatial distribution of defects was examined by various techniques including nearest neighbor distance distributions, tessellation analysis, and pair correlation functions. Random distributions were observed for most of the samples with some degree of clustering. Hardness was selected as a mechanical property to correlate with microstructural findings. Hardness contour maps were constructed by indenting samples with a statistically significant number of indents per load to see the variation in terms of location. The large number of indents allowed for Weibull analysis to be used to examine the spread in the data and to test spatial variability. A high degree of correlation was obtained between microstructural parameters and hardness/Weibull modulus values. Smaller defect sizes and homogenous distribution of defects were shown to provide higher hardness values.
A sintered SiC tile was examined using ultrasound to determine high and low amplitude regions in C-scan image maps. Serial sectioning was performed on diced samples from these two regions. Although no significant difference was observed in terms of density and average defect size, statistical tests showed that the difference in the largest defect size detected in low amplitude and high amplitude regions was significant. Clusters of defects were also identified in the samples from the low amplitude regions. The signal loss that was observed in C-scans maps could partially be attributed to these results.
A particularly high degree of correlation was shown between average defect size, spatial distribution parameters and hardness data. These findings exhibit the strong effect of microstructure on the quasi-static properties and may affect ballistic performance.Ph.D.Includes bibliographical references (p. 210-219)
EFFECTS OF AN Al2O3 NANO-ADDITIVE ON THE PERFORMANCE OF CERAMIC COATINGS PREPARED WITH MICRO-ARC OXIDATION ON A TITANIUM ALLOY
No full textIn this research, nano-sized Al2O3 particles were added to silicate-based coatings and the effect of these particles on the microstructure, composition and properties of the coatings was investigated. The effects of the nano-additive on the structure, phase composition and hardness of the micro-arc oxidation (MAO) coatings were analysed using scanning electron microscopy (SEM), X-ray diffraction and micro-hardness testing. The SEM showed that the coatings with a nano-additive have lower porosities than those without a nano-additive. XRD results showed that the coatings with nano-additives contain more oxide when compared to those without nano-additives. The results showed that the nanoparticle additions improve the hardness of the MAO coatings
Transport and energy in India. Energy used by Indian transport systems and consequent emissions: the need for quantitative analyses (Well-to-Wheel, Lifecycle)
No full textThe purpose of this work is, at first, a general overview on the state-of-art of the transportation system in India outlining the related energy consumption, for the different transport modes, with consequent estimated emissions. These elements are essential for the preparation of a high-level strategic transport planning on the whole energy issue, to help India in the choices of most suitable transportation systems, according to the well-to-wheel analysis (WTW). Pursuing a WTW global index for India that takes into account both the energy and environmental aspects on a uniform basis is an important aim: it allows the best choices to be made as well as enabling the comparison between some of the most important powertrain and fuel options on the Indian market, the results are discussed from three different points of view: energy, environmental and economic impac
Review of \u3ci\u3eGasoline, Diesel, and Ethanol Biofuels from Grasses and Plants\u3c/i\u3e, by Ram B. Gupta and Ayhan Demirbas.
No full textA new book on the production of biofuels by Gupta and Demirbas provides technical insight into the conversion processes that could provide a range of domestic fuels from plant materials to substitute for foreign oil. It focuses primarily on conversion processes for production of cellulosic ethanol, Fischer-Tropsch diesel, pyrolysis bio-oil, and hydrothermal biocrude from biomass resources, as well as first-generation grain ethanol and biodiesel from vegetable oil. In addition to a detailed summary of these chemical processes, the book provides a briefer treatment of related matters such as biofuel policy, economics, and environmental issues
Rent-Seeking in Developed and Developing Countries: Cross Section and Time Series Studies
No full textThe property rights issue is one of the most important institutional differences between developed/developing countries. The violation of the property rights results with rentseeking. In order to see if the extent of rent-seeking differs significantly between developed and developing countries, I applied a cross section and a time series study with the intention to measure rent-seeking. I found that rent-seeking is low in developed countries whilst it is high in developing counterparts. Turkey, as a developing country was my special case to apply time series study to see if rentseeking vary over the years. In my additional work for Turkey, I found that there is a cointegrating relationship between rent- seeking as a percentage of the budget LnRt and government size ( LnGYt ), and GNP per capita income ( LnGNPCt ).Rent-Seeking; Budgetary Allocation; Cross Section Study; Time Series Study
Diagrammatic guide used to visually quantify spermathecal fill in females 24 h post-copulation.
No full textImage generated by Dr. Güler Demirbas-Uzel. (TIF)</p
Pathologies sexuelles et moeurs féminines : du regard des "Archives d'Anthropologie criminelle, de criminologie et de psychologie normale et pathologique" (1886-1914)
No full textEg er den eg er og det er meg. Bruk av flerspråklige praksiser i en ungdomsskoleklasse.
No full textI denne masteroppgaven utforskes bruken av språkportrett som et pedagogisk verktøy. Vi planla og gjennomførte et undervisningsopplegg i en 8. klasse der vi ønsket å undersøke hvordan elever uttrykker sine meninger og anvender sitt språklige repertoar. Oppgaven har derfor følgende problemstilling:
Hvordan kan språkportrett brukes som pedagogisk verktøy for å inspirere elever på ungdomsskolen til å uttrykke sine meninger og anvende sitt språklige repertoar?
Studien vår benytter en tilnærming basert på mixed-methods research, hvor både kvalitative og kvantitative forskningsmetoder kombineres. Vårt innsamlede materiale tar utgangspunkt i elevenes utfylling av språkportrett, spørreskjema og egenprodusert tekst. Materialet i sin helhet er tilgjengelig på en sikker nettsky. For å få tilgang, vennligst kontakt [email protected]. Tilgang vil bli gitt for en begrenset periode på 14 dager. Dette tiltaket er ment for å sikre at materialet ikke er tilgjengelig på en åpen plattform, og at vi kan ha kontroll over hvem som får tilgang og hvorfor de ønsker det.
For å analysere materialet anvendte vi semiotiske ressurser og diskursanalytiske verktøy utviklet av James Paul Gee. Våre funn viser at elevene var ivrige etter å fylle ut og fremføre sine språkportrett, og klassen inkluderte til sammen 31 ulike språk og dialektvariasjoner. Elevtekstene avslørte transspråking, hvor språk ble brukt om hverandre, og noen tekster viste også intertekstualitet ved å integrere allerede eksisterende sanger samt egen stemme og identitet. Ved å se språkportrettene og tekstene sammen, fikk vi utvidet informasjon om elevenes identitet, språk og kulturer.
Spørreskjemaene avdekket at elevene ikke hadde arbeidet på en flerspråklig måte som dette i norsktimen tidligere. Vi mener dette kan skyldes utdaterte holdninger eller manglende kunnskap. En annen mulig forklaring er at helhetlig transspråking som pedagogisk praksis, kan virke abstrakt og udefinert uten et tilstrekkelig begrepsapparat. Vår studie foreslår at bruk av diskursanalyse og semiotiske ressurser sammen med «innhold» som språkportrett og elevtekster, kan være en effektiv måte å identifisere og forstå elevers nye måter å skape mening på
- …
