22,126 research outputs found

    Tests on duralumin columns for aircraft construction

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    The following paper is based on the results of tests, upon duralumin columns, contained in two theses presented to the Department of Civil and Sanitary Engineering of the Massachusetts Institute of Technology

    Preliminary study of the damping factor in roll

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    This paper constitutes a general theoretical discussion of the damping factor in roll, together with the results of wind tunnel tests on the continuous rolling of U.S.A. 30 airfoil

    IMPORT RULES FOR FMD CONTAMINATED BEEF

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    Under the new WTO trading rules the United States is obligated to revise its beef import policy and has proposed barriers based on classifying nations according to livestock health risks. This research develops a model which captures the impact of various degrees of FMD risk from imports on setting import barriers. The results show that nations classified as high risk for FMD continue to face prohibitive barriers. As outbreak risk falls so does the level of the barrier levied against that exporter. The barrier levels are also sensitive to the expected social losses as influenced by alternative control strategies.Food Consumption/Nutrition/Food Safety, International Relations/Trade,

    Land Degradation in the Sahel: An Application of Biophysical Modeling in the Optimal Control Setting

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    Low-input farming practices in many parts of the developing world have pushed cultivation onto marginal lands. Sustainability of already fragile ecosystems is threatened. Farmers place a high priority on satisfying subsistence food needs with on-farm production. Population pressure is high throughout much of Sub-Saharan Africa. Farmers in those regions are challenged by the need to put continually more food on their table over the coming years. An optimal control model was developed to investigate alternative farming practices within this setting. Namely, whether farmers would choose continued land expansion of if they would adopt crop intensive practices. The model included an environmental subcomponent to estimate the degradation costs from continued expansion onto marginal areas. The modeling activities from the Sahel of West African reinforce farmers' observed propensity to clear new land in lieu of crop intensification. Model activities suggest an important role for crop intensification under adequate policy conditions as well as the need to introduce new technology before degradation erodes its potential.Land Economics/Use,

    INTEGRATED ASSESSMENT OF ENVIRONMENTAL EFFECTS FROM AGRICULTURAL PRODUCTION

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    Agriculture's impact on the environment is a complex research problem. A challenge to future economic research is to account for the interrelationship between agricultural production activities, soil productivity, erosion, and water quality. It will become increasingly important to determine not only the economic consequences, but also the environmental effectiveness of alternative policies aimed at improving resource use and quality. The application of biophysical simulation models to environmental quality problems provides a means to better understand the complex interaction between agricultural production and environmental quality.Environmental Economics and Policy,

    Improved Time-Domain Accuracy Standards for Model Gravitational Waveforms

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    Model gravitational waveforms must be accurate enough to be useful for detection of signals and measurement of their parameters, so appropriate accuracy standards are needed. Yet these standards should not be unnecessarily restrictive, making them impractical for the numerical and analytical modelers to meet. The work of Lindblom, Owen, and Brown [Phys. Rev. D 78, 124020 (2008)] is extended by deriving new waveform accuracy standards which are significantly less restrictive while still ensuring the quality needed for gravitational-wave data analysis. These new standards are formulated as bounds on certain norms of the time-domain waveform errors, which makes it possible to enforce them in situations where frequency-domain errors may be difficult or impossible to estimate reliably. These standards are less restrictive by about a factor of 20 than the previously published time-domain standards for detection, and up to a factor of 60 for measurement. These new standards should therefore be much easier to use effectively.Comment: 10 pages, 5 figure

    The long-term prognostic significance of 6-minute walk test distance in patients with chronic heart failure

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    Background. The 6-minute walk test (6-MWT) is used to assess patients with chronic heart failure (CHF). The prognostic significance of the 6-MWT distance during long-term followup ( > 5 years) is unclear. Methods. 1,667 patients (median [inter-quartile range, IQR]) (age 72 [65-77] ; 75% males) with heart failure due to left ventricular systolic impairment undertook a 6-MWT as part of their baseline assessment and were followed up for 5 years. Results. At 5 years' followup, those patients who died (n = 959) were older at baseline and had a higher log NT pro-BNP than those who survived to 5 years (n = 708). 6-MWT distance was lower in those who died [163 (153) m versus 269 (160) m; P 360 m. 6-MWT distance was a predictor of all-cause mortality (HR 0.97; 95% CI 0.96-0.97; Chi-square = 184.1; P < 0.0001). Independent predictors of all-cause mortality were decreasing 6-MWT distance, increasing age, increasing NYHA classification, increasing log NT pro-BNP, decreasing diastolic blood pressure, decreasing sodium, and increasing urea. Conclusion. The 6-MWT is an important independent predictor of all-cause mortality following long-term followup in patients with CHF. © 2014 Lee Ingle et al

    Proton - Lambda correlations in Au-Au Collisions at sNN=200\sqrt{s_{NN}} = 200 GeV from the STAR experiment

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    The space-time evolution of the source of particles formed in the collision of nuclei can be studied through particle correlations. The STAR experiment is dedicated to study ultra-relativistic heavy ions collisions and allows to measure non-identical strange particle correlations. The source size can be extracted by studying pΛp-\Lambda, pˉΛˉ\bar{p}-\bar{\Lambda}, pˉΛ\bar{p}-\Lambda and pΛˉp-\bar{\Lambda} correlation functions. Strong interaction potential has been studied for these systems using an analytical model. Final State Interaction (FSI) parameters have been determined and has shown a significant annihilation process present in pˉΛ\bar{p}-\Lambda and pΛˉp-\bar{\Lambda} systems not present in pΛp-\Lambda and pˉΛˉ\bar{p}-\bar{\Lambda}.Comment: contribution to the 20th Winter Workshop on Nuclear Dynamic

    The Pitfalls of Constructing Yield Maps

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    Crop Production/Industries,
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