34,549 research outputs found

    Computer program for calculating aerodynamic characteristics of upper-surface-blowing and over-wing-blowing configurations

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    The program is based on the inviscid wing-jet interaction theory of Lan and Campbell, and the jet entrainment theory of Lan. In the interaction theory, the flow perturbations are computed both inside and outside the jet, separately, and then matched on the jet surface to satisfy the jet boundary conditions. The jet Mach number is allowed to be different from the free stream value (Mach number nonuniformity). These jet boundary conditions require that the static pressure be continuous across the jet surface which must always remain as a stream surface. These conditions, as well as the wing-surface tangency condition, are satisified only in the linearized sense. The detailed formulation of these boundary conditions is based on the quasi-vortex-lattice method of Lan

    Radiolysis of Macromolecular Organic Material in Mars-Relevant Mineral Matrices

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    The fate of organic material on Mars after deposition is crucial to interpreting the source of these molecules. Previous work has addressed how various organic compounds at millimeter depths in sediments respond to ultraviolet radiation. In contrast, this study addressed how highenergy particle radiation (200MeV protons, simulating the effect of galactic cosmic rays and solar wind at depths of <45 cm) inuences organic macromolecules in sediments. Specically, we report the generation of organicacid radiolysis products after exposure to radiation doses equivalent to geological time scales (17 Myr). We found that formate and oxalate were produced from a variety of organic starting materials and mineral matrices. Unlike ultravioletdriven reactions that can invoke Fenton chemistry to produce organic acids, our work suggests that irradiation of semiconductor surfaces, such as TiO2 or possible clay minerals found on Mars, forms oxygen and hydroxyl radical species, which can break down macromolecules into organic acids. We also investigated the metastability of benzoate in multiple mineral matrices. Benzoate was added to samples prior to irradiation and persisted up to 500 kGys of exposure. Our ndings suggest that organic acids are likely a major component of organic material buried at depth on Mars

    Some factors influencing radiation of sound from flow interaction with edges of finite surfaces

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    Edges of surfaces which are exposed to unsteady flow cause both strictly acoustic effects and hydrodynamic effects, in the form of generation of new hydrodynamic sources in the immediate vicinity of the edge. An analytical model is presented which develops the explicit sound-generation role of the velocity and Mach number of the eddy convection past the edge, and the importance of relative scale lengths of the turbulence, as well as the relative intensity of pressure fluctuations. The Mach number (velocity) effects show that the important paramater is the convection Mach number of the eddies. The effects of turbulence scale lengths, isotropy, and spatial density (separation) are shown to be important in determining the level and spectrum of edge sound radiated for the edge dipole mechanism. Experimental data is presented which provides support for the dipole edge noise model in terms of Mach number (velocity) scaling, parametric dependence on flow field parameter, directivity, and edge diffraction effects

    WHOLESALE DEMAND FOR USDA QUALITY GRADED BOXED BEEF AND EFFECTS OF SEASONALITY

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    This study estimates wholesale demand for pork, chicken, and quality differentiated beef. We estimate meat retailer own- and cross-price demand elasticities for USDA Choice and Select boxed beef. Results indicate that meat retailers have more elastic demand for lower quality graded beef. Retail beef price has a strong positive relationship with Choice and Select boxed beef demand, and a strong negative relationship with wholesale pork and chicken demand. Seasonal analysis reveals demand for both beef quality grades becomes highly price inelastic during the summer months. The two beef quality grades are substitutes during the winter; however, Select beef is not a substitute for Choice beef in the spring and summer.Demand and Price Analysis,

    VADA: A transformation-based system for variable dependence analysis

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    Variable dependence is an analysis problem in which the aim is to determine the set of input variables that can affect the values stored in a chosen set of intermediate program variables. This paper shows the relationship between the variable dependence analysis problem and slicing and describes VADA, a system that implements variable dependence analysis. In order to cover the full range of C constructs and features, a transformation to a core language is employed Thus, the full analysis is required only for the core language, which is relatively simple. This reduces the overall effort required for dependency analysis. The transformations used need preserve only the variable dependence relation, and therefore need not be meaning preserving in the traditional sense. The paper describes how this relaxed meaning further simplifies the transformation phase of the approach. Finally, the results of an empirical study into the performance of the system are presented

    Learning about sustainability through experiencing complex, adverse conditions typical of the South : reflections from the African Catchment Games played in Finland 2008

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    The African Catchment Game is an innovative role playing game which was played twice in Finland in 2008 as part of the CIMO funded collaboration between Finland Futures Research Centre and Rhodes University. It simulates a "real imaginary country" and enables participants to explore and experience how southern countries may or may not develop scenarios of sustainable resource extraction and consumption. New processes modelling climatic variability, water management and consumption were introduced for these two game runs. This imaginary country has roles for an urban/industrial sector, the informal sector, trading intermediaries, overseas trade, a government comprised of a president and two ministers, peasant and commercial farmers. Chapman's original game, Green Revolution Game/Exaction, is based on systems and complexity theories from the 1970s and 1980s. Our modifications to Chapmanā€™s game are underpinned by theories of Complex Adaptive Systems and educational approaches based on constructivist, active/experiential learning models. The paper presents an analysis of the two Finnish games from the perspectives of the participants and the game managers. Participantsā€™ information came from pre and post game questionnaires and the focus group discussions that were part of the debriefing pro-cess. These two methods enabled us to examine the local and network processes which de-veloped during the games. Global scale processes of production, consumption, resource utilization, trading and water provision was collected by the game managers as part of their management processes throughout each game run. Our analysis shows that the par-ticipantsā€™ understanding altered and deepened as a result of playing the game. The nature of the game, as a Complex Adaptive System, and the constructivist learning approach through which the game is experienced means that lessons of a more universal nature cannot be extrapolated
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