24,101 research outputs found

    Electrostatic forces for personnel restraints

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    The feasibility of utilizing electrostatic forces for personnel retention devices on exterior spacecraft surfaces was analyzed. The investigation covered: (1) determination of the state of the art; (2) analysis of potential adhesion surfaces; (3) safety considerations for personnel; (4) electromagnetic force field determination and its effect on spacecraft instrumentation; and (5) proposed advances to current technology based on documentation review, analyses, and experimental test data

    "Willingness to Pay for Electric Vehicles and their Attributes"

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    This article presents a stated preference study of electric vehicle choice using data from a national survey. We used a choice experiment wherein 3029 respondents were asked to choose between their preferred gasoline vehicle and two electric versions of that preferred vehicle. We estimated a latent class random utility model and used the results to estimate the willingness to pay for five electric vehicle attributes: driving range, charging time, fuel cost saving, pollution reduction, and performance. Driving range, fuel cost savings, and charging time led in importance to respondents. Individuals were willing to pay (wtp) from 35to35 to 75 for a mile of added driving range, with incremental wtp per mile decreasing at higher distances. They were willing to pay from 425to425 to 3250 per hour reduction in charging time (for a 50 mile charge). Respondents capitalized about 5 years of fuel saving into the purchase price of an electric vehicle. We simulated our model over a range of electric vehicle configurations and found that people with the highest values for electric vehicles were willing to pay a premium above their wtp for a gasoline vehicle that ranged from 6000to6000 to 16,000 for electric vehicles with the most desirable attributes. At the same time, our results suggest that battery cost must drop significantly before electric vehicles will find a mass market without subsidy.Electric Vehicles, Stated Preference, Discrete Choice

    "Can Vehicle-to-Grid Revenue Help Electric Vehicles on the Market?"

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    Vehicle-to-grid (V2G) electric vehicles can return power stored in their batteries back to the power grid and be programmed to do so at times when power prices are high. Since providing this service can lead to payments to owners of vehicles, it effectively reduces the cost of electric vehicles. Using data from a national stated preference survey (n = 3029), this paper presents the first study of the potential consumer demand for V2G electric vehicles. In our choice experiment, 3029 respondents compared their preferred gasoline vehicle with two V2G electric vehicles. The V2G vehicles were described by a set of electric vehicle attributes and V2G contract requirements such as “required plug-in time” and “guaranteed minimum driving range”. The contract requirements specify a contract between drivers and a power aggregator for providing reserve power to the grid. Our findings suggest the V2G concept is mostly likely to help EVs on the market if power aggregators operate on pay-as-you-go-basis or provide consumers with advanced cash payment (upfront discounts on the price of EVs) in exchange for V2G restrictions.electric vehicles, vehicle-to-grid, stated preference, latent-class model

    Galaxy Morphology from NICMOS Parallel Imaging

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    We present high resolution NICMOS images of random fields obtained in parallel to other HST observations. We present galaxy number counts reaching H=24. The H-band galaxy counts show good agreement with the deepest I- and K-band counts obtained from ground-based data. We present the distribution of galaxies with morphological type to H<23. We find relatively fewer irregular galaxies compared to an I-band sample from the Hubble Deep Field, which we attribute to their blue color, rather than to morphological K-corrections. We conclude that the irregulars are intrinsically faint blue galaxies at z<1.Comment: 13 pages, including 4 figures. Accepted for publication in ApJ Letter

    Using practice architectures theory to compare consecutive offerings of the same subject

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    CONTEXT Two consecutive offerings (2015 and 2016) of the same subject, Concrete Technology and Practice, prompted opposite reactions from students. The academics involved in 2015 and/or 2016 sought to explore the similarities and differences between these consecutive offerings in reflecting on the learning and teaching practices in their classroom. PURPOSE Practice architectures theory provides a framework for examining and understanding the differences between these consecutive offerings of ostensibly the same subject. This paper also provides an example of how a theoretical framework can be used to examine teaching practices – even our own by practitioners who are also acting as researchers in this context. APPROACH Evidence used in comparing the 2015 and 2016 offerings of this subject is drawn from focus group discussions with students and observations of each of the researcher/practitioners involved. Additional data includes the end of semester Student Feedback Survey results including written responses to open-ended questions. RESULTS Differences in aspects of the cultural-discursive, material-economic and socio-political arrangements of the 2015 and 2016 offerings of Concrete Technology and Practice became apparent from the analysis. CONCLUSIONS Using the theory of practice architectures gave us insights into the inter-relationships between the different arrangements inherent in teaching and learning practices. It also highlighted the resilience of ‘taken for granted’ practices

    Optimally adapted multi-state neural networks trained with noise

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    The principle of adaptation in a noisy retrieval environment is extended here to a diluted attractor neural network of Q-state neurons trained with noisy data. The network is adapted to an appropriate noisy training overlap and training activity which are determined self-consistently by the optimized retrieval attractor overlap and activity. The optimized storage capacity and the corresponding retriever overlap are considerably enhanced by an adequate threshold in the states. Explicit results for improved optimal performance and new retriever phase diagrams are obtained for Q=3 and Q=4, with coexisting phases over a wide range of thresholds. Most of the interesting results are stable to replica-symmetry-breaking fluctuations.Comment: 22 pages, 5 figures, accepted for publication in PR

    Current legal and institutional issues in the commercialization of phosphoric acid fuel cells

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    Legal and institutional factors affecting the development and commercial diffusion of phosphoric acid fuel cells are assessed. Issues for future research and action are suggested. Perceived barriers and potential opportunities for fuel cells in central and dispersed utility operations and on-site applications are reviewed, as well as the general concept of commercialization as applied to emerging energy technologies

    Bistability in a simple fluid network due to viscosity contrast

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    We study the existence of multiple equilibrium states in a simple fluid network using Newtonian fluids and laminar flow. We demonstrate theoretically the presence of hysteresis and bistability, and we confirm these predictions in an experiment using two miscible fluids of different viscosity--sucrose solution and water. Possible applications include bloodflow, microfluidics, and other network flows governed by similar principles
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