10,381 research outputs found

    Detonation interaction with an interface

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    Detonation interaction with an interface was investigated, where the interface separated a combustible from an oxidizing or inert mixture. The ethylene-oxygen combustible mixture had a fuel-rich composition to promote secondary combustion with the oxidizer in the turbulent mixing zone (TMZ) that resulted from the interaction. Sharp interfaces were created by using a nitro-cellulose membrane to separate the two mixtures. The membrane was mounted on a wood frame and inserted in the experimental test section at a 45° angle to the bulk flow direction. The membrane was destroyed by the detonation wave. The interaction resulted in a transmitted and reflected wave at a node point similar to regular shock refraction. A detonation refraction analysis was carried out to compare with the measured shock angles. It was observed that the measured angle is consistently lower than the predicted value. An uncertainty analysis revealed possible explanations for this systematic variation pointing to factors such as the incident wave curvature and the role of the nitro-cellulose diaphragm. Analysis of the TMZ and Mach stem formed from the reflection of the transmitted shock wave off the solid boundary were carried out and found to justify the size and strength of these features as a function of the test gas composition. The role of secondary combustion in the TMZ was also investigated and found to have a small influence on the wave structure

    Feasibility study of high performance hydrogen-oxygen fuel cells Final technical report

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    Engineering analysis for evaluating moving bed and mediator hydrogen-oxygen fuel cell conceptual design

    The ASL-CDI 2.0: an updated, normed adaptation of the MacArthur Bates Communicative Development Inventory for American Sign Language

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    Vocabulary is a critical early marker of language development. The MacArthur Bates Communicative Development Inventory has been adapted to dozens of languages, and provides a bird’s-eye view of children’s early vocabularies which can be informative for both research and clinical purposes. We present an update to the American Sign Language Communicative Development Inventory (the ASL-CDI 2.0, https://www.aslcdi.org), a normed assessment of early ASL vocabulary that can be widely administered online by individuals with no formal training in sign language linguistics. The ASL-CDI 2.0 includes receptive and expressive vocabulary, and a Gestures and Phrases section; it also introduces an online interface that presents ASL signs as videos. We validated the ASL-CDI 2.0 with expressive and receptive in-person tasks administered to a subset of participants. The norming sample presented here consists of 120 deaf children (ages 9 to 73 months) with deaf parents. We present an analysis of the measurement properties of the ASL-CDI 2.0. Vocabulary increases with age, as expected. We see an early noun bias that shifts with age, and a lag between receptive and expressive vocabulary. We present these findings with indications for how the ASL-CDI 2.0 may be used in a range of clinical and research settingsAccepted manuscrip

    Physical and geometric constraints explain the labyrinth-like shape of the nasal cavity

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    The nasal cavity is a vital component of the respiratory system that heats and humidifies inhaled air in all vertebrates. Despite this common function, the shapes of nasal cavities vary widely across animals. To understand this variability, we here connect nasal geometry to its function by theoretically studying the airflow and the associated scalar exchange that describes heating and humidification. We find that optimal geometries, which have minimal resistance for a given exchange efficiency, have a constant gap width between their side walls, but their overall shape is restricted only by the geometry of the head. Our theory explains the geometric variations of natural nasal cavities quantitatively and we hypothesize that the trade-off between high exchange efficiency and low resistance to airflow is the main driving force shaping the nasal cavity. Our model further explains why humans, whose nasal cavities evolved to be smaller than expected for their size, become obligate oral breathers in aerobically challenging situations.Comment: 7 pages, 4 figure

    Bringing Clean Energy to the Base of the Pyramid: The Interplay of Business Models, Technology, and Local Context

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    Social enterprises are providing affordable energy and environmentally sustainable energy to a small but growing percentage of the four billion people living on less than $2,000/year. Santa Clara University’s Global Social Benefit Incubator (GSBITM) has worked with over 60 of these enterprises and profiled them on its Energy Map website. Based on this direct experience and associated research, the authors conclude that it is the interplay among innovative business models, quality technologies tailored to localized energy markets, and appropriate interfacing with local ecosystems that allows social enterprises to go to scale. This conclusion is supported by a review of prominent enterprises including Shindulai, Solar Sister, Angaza Design, Potential Energy, Selco, Husk Power Systems, and Practical Action

    Fitting the Means to the Ends: One School’s Experience with Quantitative and Qualitative Methods in Curriculum Evaluation During Curriculum Change

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    Curriculum evaluation plays an important role in substantive curriculum change. The experience of the University of Texas Medical Branch (UTMB) with evaluation processes developed for the new Integrated Medical Curriculum (IMC) illustrates how evaluation methods may be chosen to match the goals of the curriculum evaluation process. Quantitative data such as ratings of courses or scores on external exams are useful for comparing courses or assessing whether standards have been met. Qualitative data such as students’ comments about aspects of courses are useful for eliciting explanations of observed phenomena and describing relationships between curriculum features and outcomes. The curriculum evaluation process designed for the IMC used both types of evaluation methods in a complementary fashion. Quantitative and qualitative methods have been used for formative evaluation of the new IMC courses. They are now being incorporated into processes to judge the IMC against its goals and objectives

    Carbon fiber plume sampling for large scale fire tests at Dugway Proving Ground

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    Carbon fiber sampling instruments were developed: passive collectors made of sticky bridal veil mesh, and active instruments using a light emitting diode (LED) source. These instruments measured the number or number rate of carbon fibers released from carbon/graphite composite material when the material was burned in a 10.7 m (35 ft) dia JP-4 pool fire for approximately 20 minutes. The instruments were placed in an array suspended from a 305 m by 305 m (1000 ft by 1000 ft) Jacob's Ladder net held vertically aloft by balloons and oriented crosswind approximately 140 meters downwind of the pool fire. Three tests were conducted during which released carbon fiber data were acquired. These data were reduced and analyzed to obtain the characteristics of the released fibers including their spatial and size distributions and estimates of the number and total mass of fibers released. The results of the data analyses showed that 2.5 to 3.5 x 10 to the 8th power single carbon fibers were released during the 20 minute burn of 30 to 50 kg mass of initial, unburned carbon fiber material. The mass released as single carbon fibers was estimated to be between 0.1 and 0.2% of the initial, unburned fiber mass
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