5,580 research outputs found
Effects of Climate Change on Water Resources
Environmental Economics and Policy, Resource /Energy Economics and Policy, Q25, Q54,
The persistence of drought impacts across growing seasons: a dynamic stochastic analysis
Agricultural producers throughout much of the United States experienced one of the most severe droughts in the last 100 years during the years 1999-2006. The prolonged nature of this drought highlights a need to better understand the impacts and management of drought across growing seasons, rather than just within a growing season. Producers express specific concern about the tendency of drought impacts to persist even after drought itself has subsided. The persistence of drought impacts has received limited attention in the economics literature. The objectives of this study are two-fold: 1) to determine whether inter-year dynamics, in the form of agronomic constraints and financial flows, can cause persistence of a drought's impact in years subsequent to the drought, and 2) to determine whether the impact of one year of drought can alter the impact of a subsequent year of drought. A multi-year, dynamic and stochastic decision model is developed in a discrete stochastic programming framework and solved to address the objectives. The structure and parameters of the farm-level model are based on irrigated row crop farms in eastern Oregon, USA. Analysis of the model's solution reveals the following results: 1) the impact of a drought can persist long after the drought subsides, and 2) the impact of one year of drought can alter the impact of a subsequent year of drought. Potential implications for the administration of drought-related assistance are discussed briefly.Drought, preparedness, response, uncertainty, dynamics, discrete stochastic programming, agriculture, irrigation, eastern Oregon, row crops, crop rotation, Crop Production/Industries, Risk and Uncertainty,
LES of an Inclined Jet into a Supersonic Turbulent Crossflow
This short article describes flow parameters, numerical method, and
animations of the fluid dynamics video "LES of an Inclined Jet into a
Supersonic Turbulent Crossflow"
(http://ecommons.library.cornell.edu/bitstream/1813/14073/3/GFM-2009.mpg
[high-resolution] and
http://ecommons.library.cornell.edu/bitstream/1813/14073/2/GFM-2009-web.m1v
[low-resolution] video). We performed large-eddy simulation with the sub-grid
scale (LES-SGS) stretched-vortex model of momentum and scalar transport to
study the gas-dynamics interactions of a helium inclined round jet into a
supersonic () turbulent (\Reth) air flow over a flat
surface. The video shows the temporal development of Mach-number and magnitude
of density-gradient in the mid-span plane, and isosurface of helium
mass-fraction and \lam_2 (vortical structures). The identified vortical
structures are sheets, tilted tubes, and discontinuous rings. The vortical
structures are shown to be well correlated in space and time with helium
mass-fraction isosurface ().Comment: 7 pages, 1 figure, 1 table, article describing fluid dynamics video
submitted to Gallery of Fluid Motion, APS-DFD 200
Flight investigation of the effect of a local change in wing contour on chordwise pressure distribution at high speeds
Technology Policy: A Fixture on the National Agenda
Federal government research and development priorities have shifted in recent years away from areas of national security and agency missions, and toward the enhancement of industrial competitiveness in the global economy. This shift has stirred ideological controversy over whether the federal government should be in the business of picking winners and losers, even prompting some to label this practice “corporate welfare.” Rycroft, Kash, and Adams suggest that the central issues at stake have little to do with ideological differences and a great deal to do with whether the U.S.will continue to lead the world in technological innovation. They describe a new economic reality, driven by technology, that calls for basic changes to our national technology policy
Development of Design Criteria for Sensitizer Photooxidation Treatment Systems
Sensitized photooxidation is a physicochemical process that can degrade many toxic and refractory organic pollutants. A trace quantity of sensitizer added to the waste absorbs visible light; electronically excited intermediates then transfer the energy to decompose the waste. Engeineering design criteria were developed for industrial waste treatment lagoons that would use sensitized photooxidation. Design criteria were developed regarding optimum lagoon pH, optimum sensitizer concentration, depth and sizing of lagoons, dissolved oxygen requirements, and effect of temperature on photooxidation rate. Treatment of the refractory pesticides bromacil, terbacil, and fluometuron was investigated using methylene blue and riboflavin as sensitizers. Methylene blue-sensitized photooxidation of the three pesticides was most efficient at basic pH. The optimum pH of riboflavin-sensitized photooxidaction varied and was substrate-dependent. A model was developed to predict sensitized photooxidation rate as a function of lagoon depth. The model is based on light intesnity, sensitizer extinction coefficient, and an applied quantum yeirld, all of which are integrated over wavelengths of visible light. The model serves as the basis of sizing photooxidation lagoons. A dissolved oxygen residual of 1 mg/1 was required to maintain maximum methylene blue-sensitized photooxidation rate. At least 4 mg/1 dissolved oxygen was necessary to maintain riboflavin-sensitized phooxidation at maximum levels. Oxygen uptake rates in sensitized phooxidation reactions were proportional to the concentration of substrate. Temperatures from 10 degrees to 35 degreees Celcius had no significant effect on sensitized photooxidation rates. Using the model developed, a methylene blue-sensitized phooxidation pilot lagoon was designed to treat a 30 mg/1 bromacil influent concentraion to 0.1 mg/1 bromacil in the effluent. For an influent flow of 0.263 m^3/min (0.1 MGD) waste, a 0.1 mg/1 methylene blue concentration, 36 cm depth, and 1870 m^2 surface area are required. A cost analysis was performed which indicated that sensitized photooxidation lagoons appear to be cost-compentitive with other industrial waste treatement systems
SBSI:an extensible distributed software infrastructure for parameter estimation in systems biology
Complex computational experiments in Systems Biology, such as fitting model parameters to experimental data, can be challenging to perform. Not only do they frequently require a high level of computational power, but the software needed to run the experiment needs to be usable by scientists with varying levels of computational expertise, and modellers need to be able to obtain up-to-date experimental data resources easily. We have developed a software suite, the Systems Biology Software Infrastructure (SBSI), to facilitate the parameter-fitting process. SBSI is a modular software suite composed of three major components: SBSINumerics, a high-performance library containing parallelized algorithms for performing parameter fitting; SBSIDispatcher, a middleware application to track experiments and submit jobs to back-end servers; and SBSIVisual, an extensible client application used to configure optimization experiments and view results. Furthermore, we have created a plugin infrastructure to enable project-specific modules to be easily installed. Plugin developers can take advantage of the existing user-interface and application framework to customize SBSI for their own uses, facilitated by SBSI’s use of standard data formats
Utilization of Corn Co-Products in the Beef Industry
Corn milling co-products are expected to increase dramatically in supply. Two primary types of milling processes currently exist, resulting in quite different feed products. The dry milling process produces distillers grains plus solubles, and the wet milling process produces corn gluten feed. These feeds can be marketed as wet feed, or they can be dried and marketed as either dry corn gluten feed or dry distillers grains with or without solubles. For the purposes of this article, only wet corn gluten feed (WCGF) and wet distillers grains plus solubles (WDGS) will be discussed. The majority of plant expansions are dry milling plants that produce WDGS; however, an increase in supply of WCGF is also expected. Therefore, these feeds may be very attractive for beef producers to use as an energy source. This article will focus on the production, composition of these feeds, energy values, and economics of using WDGS. Some other management issues will be discussed as well including grain processing when these co-products are used in feedlot diets, roughage level when these co-products are used, and feeding combinations of WDGS and WCGF. Forage fed situations will be covered with dried co-products as this will be the most common application for both energy and protein supplementation in many forage feeding situations
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