Air bearing Patent

Air bearings for near frictionless transfer of loads from one body to anothe

Chemical kinetic modeling of propane oxidation behind shock waves

The stoichiometric combustion of propane behind incident shock waves was studied experimentally and analytically over a temperature range from 1700 K to 2600 K and a pressure range from 1.2 to 1.9 atm. Measurements of the concentrations of carbon monoxide (CO) and carbon dioxide (CO2) and the product of the oxygen atom and carbon dioxide concentrations (O)(CO) were made after passage of the incident shock wave. A kinetic mechanism was developed which, when used in a computer program for a flowing, reacting gas behind an incident shock wave predicted experimentally measured results quite well. Ignition delay times from the literature were also predicted quite well. The kinetic mechanism consisted of 59 individual kinetic steps

A Chemical Kinetic Mechanism for the Ignition of Silane/Hydrogen Mixtures

A chemical kinetic reaction mechanism for the oxidation of silane/hydrogen mixtures is presented and discussed. Shock-tube ignition delay time data were used to evaluate and refine the mechanism. Good agreement between experimental results and the results predicted by the mechanism was obtained by adjusting the rate coefficient for the reaction SiH3 + O2 yields SiH2O + OH. The reaction mechanism was used to theoretically investigate the ignition characteristics of silane/hydrogen mixtures. The results revealed that over the entire range of temperature examined (800 K to 1200 K), substantial reduction in ignition delay times is obtained when silane is added to hydrogen

The Use of Sr/Ga Ratios in the Determination of Trophic Levels of Contemporary and Recent Human and Faunal Populations

Previous studies have shown that Sr/Ca ratios were good indicators of trophic levels of human and faunal populations in a given geographical region. These studies have operated under the assumption that removal of debris and post-depositional matter from the bone by using a wash protocol will bring the Sr/Ca ratios to their original state. this study concludes that that is an erroneous assumption. Wildebeest samples collected at death and ten years later were analyzed for Sr/Ca ratios and the results were negative for the return of the tenth-year sample to the ratios of the first-year sample after washing. Andrew Sillen\u27s recent Sr/Ca study is followed in this present study and his conclusions and assumptions are discussed

Ignition of mixtures of SiH sub 4, CH sub 4, O sub 2, and Ar or N sub 2 behind reflected shock waves

Ignition delay times in mixtures of methane, silane, and oxygen diluted with argon and nitrogen were measured behind reflected shock waves generated in the chemical kinetic shock tube at Langley Research Center. The delay times were inferred from the rapid increase in pressure that occurs at ignition, and the ignition of methane was verified from the emission of infrared radiation from carbon dioxide. Pressures of 1.25 atm and temperatures from 1100 K to 1300 K were generated behind the reflected shocks; these levels are representative of those occurring within a supersonic Ramjet combustor. Expressions for the ignition delay time as a function of temperature were obtained from least squares curve fits to the data for overall equivalence ratios of 0.7 and 1.0. The ignition delay times with argon as the diluent were longer than those with nitrogen as the diluent. The infrared wavelength observations at 4.38 microns for carbon dioxide indicated that silane and methane ignited simultaneously (i.e., within the time resolution of the measurement). A combined chemical kinetic mechanism for mixtures of silane, methane, oxygen, and argon or nitrogen was assembled from one mechanism that accurately predicted the ignition of methane and a second mechanism that accurately predicted silane hydrogen ignition. Comparisons between this combined mechanism and experiment indicated that additional reactions, possibly between silyl and methyl fragments, are needed to develop a good silane methane mechanism

Chemical kinetic modeling of benzene and toluene oxidation behind shock waves

The oxidation of stoichiometric mixtures of benzene and toluene behind incident shock waves was studied for a temperature range from 1700 to 2800 K and a pressure range from 1.1 to 1.7 atm. The concentration of CO and CO2 produced were measured as well as the product of the oxygen atom and carbon monoxide concentrations. Comparisons between the benzene experimental data and results calculated by use of a reaction mechanism published in the open literature were carried out. With some additional reactions and changes in rate constants to reflect the pressure-temperature range of the experimental data, a good agreement was achieved between computed and experimental results. A reaction mechanism was developed for toluene oxidation based on analogous rate steps from the benzene mechanism. Measurements of NOx levels in an actual flame device, a jet-stirred combustor, were reproduced successfully by use of the reaction mechanism developed from the shock-tube experiments on toluene. These experimental measurements of NOx levels were reproduced from a computer simulation of a jet-stirred combustor

Analysis of Volatile Organic Compounds in the Apollo Next Generation Sample Analysis (ANGSA) 73002 Core Sample

Understanding the organic content of lunar regolith was an early priority upon the return of Apollo samples, with amino acids being of special interest because of their importance to life on Earth and their astrobiological relevance. Many initial studies focused on the detection of amino acids in these samples and attempts to determine the origin of those compounds. Although no consensus on the origin of the amino acids was reached in those early studies, more recent work determined that the detected amino acids originated from both terrestrial contamination and meteoritic or cometary in fall to the lunar surface. A majority of the amino acids in the Apollo samples studied originated from precursor molecules, either indigenous to the lunar samples or contaminants, that reacted during the water extraction and acid hydrolysis process for analysis in the laboratory, but the identities of the amino acid precursors still remain poorly understood. Such precursors could include hydrogen cyanide (HCN) and other volatile organic compounds such as amines, carboxylic acids, or aldehydes and ketones. The identities of these compounds, as well as the effects of years of curation on their abundances in lunar regolith samples stored at ambient temperature under nitrogen gas purge, are not clear. The specially curated samples available through the Apollo Next Generation Sample Analysis (ANGSA) program provide a unique opportunity to use state-of- the-art analytical techniques to examine previously unstudied lunar materials. The ANGSA samples include three types of samples: 1) samples stored frozen since <1 month after Earth arrival; 2) samples stored under helium; and 3) a double drive tube collected by Apollo 17 astronauts, with the bottom portion of the drive tube sealed under vacuum on the Moon and never opened. In contrast to the typically curated Apollo samples that have been kept for decades at room temperature under flowing nitrogen purge that may have significantly reduced the abundance of volatiles, the vacuum-sealed and frozen samples may have enhanced preservation of these volatiles. Our initial investigation examines amino acids and their potential volatile precursors, including hydrogen cyanide (HCN), aldehydes, ketones, amines, and mono-carboxylic acids, in a sample from the top portion of the Apollo 17 double drive tube. These results will aid in understanding the lunar abundances of these molecules and will also be compared to future analyses of other drive tube and frozen ANGSA samples

Traditional tales and imaginary contexts in primary design and technology: a case study

Working with contexts is a key component to design and technology activity and education. The most recent iteration of the national curriculum programme of study for design and technology, in England, sets out that children between the ages of 5 and 7 “should work in a range of relevant contexts” (DfE, 2013: 193); suggested contexts including “home and school, gardens and playgrounds, the local community, industry and the wider environment”. Whilst these are real world and familiar contexts, fictional contexts also provide opportunities for developing “creative spaces” in which to speculate and discuss. This intrinsic case study explores the work of two primary teachers’ development of a design and technology activity, where traditional tales provide the context. Children explore design problems and opportunities through the eyes of the Billy Goats Gruff, as they seek assistance to cross the river. Data was gathered through semi-structured interviews and document analysis of children’s design work. The case study reveals how multidisciplinary and imaginative approaches to teaching and learning in the primary classroom simulate and nurture design thinking, dialogue and critique

Strengthening the Resiliency of Dryland Forest-Based Livelihoods in Ethiopia and South Sudan: A Review of Literature on the Interaction Between Dryland Forests, Livelihoods and Forest Governance

Dry forests account for nearly half of the world’s tropical and subtropical forests and provide a multitude of ecological services. They contribute to hydrological cycles and livestock and wildlife provisioning; and host pollinators and wild plants. They are also important ecological zones for dryland agriculture and pastoral livelihood strategies that support hundreds of millions of people around the world. Dry forests cover large areas and their biomass stores carbon and helps mitigate climate change. Dry forests are particularly important to people in Africa. They provide wood for construction and energy, contribute to local diets with wild fruits, vegetables, nuts, edible insects and bushmeat. Wild, edible plants provide essential nutrients, particularly during times of food scarcity. Yet dry forests are subject to high rates of deforestation and degradation driven mainly by agricultural expansion and growing energy demands. Other challenges include limited information on dry forests (their inventories, changes over time, major drivers of deforestation and recovery, etc.), their biophysical aspects and ecosystem services and the potential roles they could play in increasing the sustainability of crop and livestock farming. Governments, development partners and communities are looking for options to better manage these resources at the landscape level. Dry forests are complex ecosystems that are not fully understood. Scientific knowledge to better manage dry forests and sustain the livelihoods of people that depend on these ecosystems remains scanty as research to inform policy and practice is still very limited. The knowledge gap is even more pronounced in northeastern Africa, notably Ethiopia and South Sudan where these forest types are important in terms of areas coverage and in supporting rural livelihoods. Ethiopia and South Sudan share histories of political unrest and conflict that have contributed to famines; large-scale land acquisition for investment and agricultural expansion by smallholders are resulting in major and rapid land-use changes in their dry forested areas. Ethiopia’s two decades of peace and stability and its experience in managing its natural resources could inform post-conflict intervention measures in South Sudan. This study was conducted as an effort to help fill the knowledge gap in dry forest-based livelihoods through a critical review of the available literature. It used publications from CIFOR’s work on dry forests and product marketing in Ethiopia and from other sources, including gray literature. The study assessed the socio-ecological context, including relevant laws and strategies, with an emphasis on the biophysical characteristics of the dryland forests of Ethiopia and South Sudan and the major causes of deforestation and forest degradation. Using livelihood systems as an analytical framework, it examined (i) major livelihood strategies; (ii) the contribution of dry forests to livelihoods; (iii) forest product markets and value chains; and (iv) forest and land governance with an emphasis on the relationship between political, economic and resource management policies and the level of degradation of dry forests and their contributions to the livelihoods of forest-dependent communities in Ethiopia and South Sudan. It also identified major threats to dry, forest-based livelihoods and key issues for policy, research and practice that need to be addressed to maintain the multifunctionality of dryland forests while also ensuring the well-being of communities dependent on these landscapes