Using Numerical Dynamic Programming to Compare Passive and Active Learning in the Adaptive Management of Nutrients in Shallow Lakes

This paper illustrates the use of dual/adaptive control methods to compare passive and active adaptive management decisions in the context of an ecosystem with a threshold effect. Using discrete-time dynamic programming techniques, we model optimal phosphorus loadings under both uncertainty about natural loadings and uncertainty regarding the critical level of phosphorus concentrations beyond which nutrient recycling begins. Active management is modeled by including the anticipated value of information (or learning) in the structure of the problem, and thus the agent can perturb the system (experiment), update beliefs, and learn about the uncertain parameter. Using this formulation, we define and value optimal experimentation both ex ante and ex post. Our simulation results show that experimentation is optimal over a large range of phosphorus concentration and belief space, though ex ante benefits are small. Furthermore, realized benefits may critically depend on the true underlying parameters of the problem.adaptive control, adaptive management, dynamic programming, value of experimentation, value of information, nonpoint source pollution, learning, decisions under uncertainty, Resource /Energy Economics and Policy,

A Comparison of Methodologies for Valuing Decreased Health Effects from Wildfire Smoke

Wildfire seasons are becoming longer and more intense throughout the world, making it increasingly important to monetize the full damages caused by wildfires when analyzing various fire management policies. We estimate the economic costs of the health effects associated with exposure to wildfire smoke using a simple cost of illness approach and for the first time to our knowledge we estimate willingness-to-pay (WTP) for a decrease in symptom days from wildfire smoke using the contingent valuation method and the averting behavior method. Comparing estimates across all three common approaches for estimating the economic cost of exposure to an air pollutant is an important contribution to the literature. This study uses data from the largest wildfire in Los Angeles County’s modern history, the Station Fire of 2009. Our results show that a simple cost of illness estimate is about $3 per day of symptoms, the averting behavior method results in a WTP value of$43 or $94 to avoid one day of wildfire-smoke induced symptom days, depending on the model used, and the contingent valuation method results in a WTP estimate of$74 - $98 to avoid one day of wildfire-smoke induced symptom days, depending on model specification.averting behavior method, contingent valuation method, cost of illness, wildfire smoke, health, morbidity, Environmental Economics and Policy, Health Economics and Policy, Q,

IRRIGATION WATER DEMAND: A META ANALYSIS OF PRICE ELASTICITIES

Meta-regression models are estimated to investigate sources of variation in empirical estimates of the price elasticity of irrigation water demand. Elasticity estimates are drawn from mathematical programming, econometric and field experiment studies reported in the United States since 1963. Explanatory variables include method of analysis, water price, time-frame of analysis, farmers' adjustment options, type of data, and climate. Results indicate that the magnitudes of elasticity estimates are affected by the method of analysis. When separate regressions are performed for the estimates from each method, the price of water at which an elasticity is estimated as well as the time-frame of analysis are found to influence price elasticities.Resource /Energy Economics and Policy,

Integral throat entrance development, qualification and production for the Antares 3 nozzle

Although design analyses of a G-90 graphite integral throat entrance for the Antares 3 solid rocket motor nozzle indicated acceptable margins of safety, the nozzle throat insert suffered a thermostructural failure during the first development firing. Subsequent re-analysis using properties measured on material from the same billet as the nozzle throat insert showed negative margins. Carbon-carbon was investigated and found to result in large positive margins of safety. The G-90 graphite was replaced by SAI fast processed 4-D material which uses Hercules HM 10000 fiber as the reinforcement. Its construction allows powder filling of the interstices after preform fabrication which accelerates the densification process. Allied 15V coal tar pitch is then used to complete densification. The properties were extensively characterized on this material and six nozzles were subjected to demonstration, development and qualification firings

SWELLING OF ALUMINUM-CLAD ALUMINUM-PLUTONIUM ALLOYS ON POSTIRRADIATION ANNEALING. Final Report

The changes in density and hardness as a result of annealing at temperatures up to 600 deg C are reported for and aluminum-clad Al-5 wt% Ra andd Al-10 wt% Pu alloy in which 89.3% andd 75.6%, respectively, of the plutonium atoms were fissioned. The density of the irradiated specimens at room temperature decreased after pulse anneals of 15-min duration at temperatures above 525 deg C, whereas for lower andnealing temperatures the density of the specimens increased. The hardness of the specimens at room temperature decreased substantially after annealing at temperatures between 275 deg C andd 360 deg C. A specimen of 1100 aluminum which was heavily deformed by rolling was also annealed in a manner similar to the irradiated materials. The density of the aluminum at room temperature increased after pulse anneals at temperatures up to 600 deg C, and the hardness decreased after annealing at temperatures above 300 deg C. (auth

Comparison of swelling for structural materials on neutron and ion irradiation

The swelling of V-base alloys, Type 316 stainless steel, Fe-25Ni-15Cr alloys, ferritic steels, Cu, Ni, Nb-1% Zr, and Mo on neutron irradiation is compared with the swelling for these materials on ion irradiation. The results of this comparison show that utilization of the ion-irradiation technique provides for a discriminative assessment of the potential for swelling of candidate materials for fusion reactors

Latitudinal variation of freeze tolerance in intertidal marine snails of the genus melampus (Gastropoda: Ellobiidae)

Low temperatures limit the poleward distribution of many species such that the expansion of geographic range can only be accomplished via evolutionary innovation. We have tested for physiological differences among closely related species to determine whether their poleward latitudinal ranges are limited by tolerance to cold. We measured lower temperature tolerance (LT50) among a group of intertidal pulmonate snails from six congeneric species and nine locales. Differences in tolerance are placed in the context of a molecular phylogeny based on one mitochondrial (cytochrome oxidase subunit I) and two nuclear (histone 3 and a mitochondrial phosphate carrier protein) markers. Temperate species from two separate lineages had significantly lower measures of LT50 than related tropical species. Range differences within the temperate zone, however, were not explained by LT50. These results show that multiple adaptations to cold and freezing may have enabled range expansions out of the tropics in Melampus. However, northern range limits within temperate species are not governed by cold tolerance alone. © 2014 by The University of Chicago. All rights reserved

Effects of Heavy-Ion Irradiation on Microstructure of V-4Cr-4Ti Alloy at Moderate Temperatures

V-4Cr-4Ti is promising for first-wall and structural applications in magnetic fusion reactors. Fast neutron sources were used to evaluate postirradiation properties of fusion candidate materials, but FFTF and EBR-II have been shutdown. Under these circumstances, heavy-ion irradiation is an attractive alternative. We used 3-MeV V{sup +} and 4.5-MeV Ni{sup 2+} ions to investigate effects of irradiation on microstructure of V-4Cr-4Ti at 200-420 C. This paper report results of ion irradiation experiments and compare with fast-neutron irradiation data. From TEM, the dominant feature of postirradiation microstructure was a high density of dislocation loops and point- defect clusters. Density and defect size depend on irradiation dose and temperature. Precipitates and voids/bubbles were not observed, even in specimens simultaneous injected with he and exposed to heavy ions. Increased transport of point defects to internal interfaces was observed, as manifested by defect denuded zones along grain boundaries. Defect denuded zones along grain boundaries could lead to segregation of impurities and solutes and formation of precipitates on grain boundaries