Stereo electro-optical tracker study for the measurement of model deformations at the National Transonic Facility

The effects of model vibration, camera and window nonlinearities, and aerodynamic disturbances in the optical path on the measurement of target position is examined. Window distortion, temperature and pressure changes, laminar and turbulent boundary layers, shock waves, target intensity and, target vibration are also studied. A general computer program was developed to trace optical rays through these disturbances. The use of a charge injection device camera as an alternative to the image dissector camera was examined

Biofuels for all? Understanding the Global Impacts of Multinational Mandates

The recent rise in world oil prices, coupled with heightened interest in the abatement of greenhouse gas emissions, has led to a sharp increase in domestic biofuels production around the world. Previous authors have devoted considerable attention to the impacts of these policies on a country-by-country basis. However, there are also strong interactions among these programs, as they compete in world markets for feedstocks and ultimately for a limited supply of global land. In this paper, we evaluate the interplay between two of the largest biofuels programs, namely the renewable fuel mandates in the US and the EU. We examine how the presence of each of these programs influences the other, and also how their combined impact influences global markets and land use around the world. We begin with an analysis of the origins of the recent bio-fuel boom, using the historical period from 2001-2006 for purposes of model validation. This was a period of rapidly rising oil prices, increased subsidies in the EU, and, in the US, there was a ban on the major competitor to ethanol for gasoline additives. Our analysis of this historical period permits us to evaluate the relative contribution of each of these factors to the global biofuel boom. We also use this historical simulation to establish a 2006 benchmark biofuel economy from which we conduct our analysis of future mandates. Our prospective analysis of the impacts of the biofuels boom on commodity markets focuses on the 2006-2015 time period, during which existing investments and new mandates in the US and EU are expected to substantially increase the share of agricultural products (e.g., corn in the US, oilseeds in the EU, and sugar in Brazil) utilized by the biofuels sector. In the US, this share could more than double from 2006 levels, while the share of oilseeds going to biodiesel in the EU could triple. Having established the baseline 2006-2015 scenario, we proceed to explore the interactions between the US and EU policies. This involves decomposing the contributions of each set of regional policies to the global changes in output and land use. The most dramatic interaction between the two sets of policies is for oilseed production in the US, where the sign of the output change is reversed in the presence of EU mandates (rising rather than falling). In other sectors, the interaction is more modest. However, when it comes to the impacts of these combined mandates on third economies, the two policies combine to have a much greater impact than just the US or just the EU policies alone.Resource /Energy Economics and Policy,

Magnetization structure of a Bloch point singularity

Switching of magnetic vortex cores involves a topological transition characterized by the presence of a magnetization singularity, a point where the magnetization vanishes (Bloch point). We analytically derive the shape of the Bloch point that is an extremum of the free energy with exchange, dipole and the Landau terms for the determination of the local value of the magnetization modulus.Comment: 4 pages, 2 figure

Biofuel Growth: Global Greenhouse Gas Emissions Impacts from Changes in Forest Carbon Stocks

There is significant policy interest in liquid biofuels with appealing prospects for energy security, farm security, poverty alleviation, and climate change. Large-scale commercial biofuel production could have far reaching implications for regional and global markets – particularly those related to energy and land use. As such, large-scale biofuels growth is likely to have significant impacts on global greenhouse gas (GHG) emissions. This paper utilizes a CGE model with explicit biofuel, land, and energy markets. The model is able to estimate the effects on the broad range of input and output markets potentially affected globally by biofuels policies. One of the most controversial issues within the biofuels debate is potential indirect changes in land use and, in particular, the resulting changes in forest carbon stocks. To uncover consequences of biofuel policies for forest carbon, we link our CGE model with a dynamic forward looking model of the forest sector. Within this framework, we evaluate the potential effects of US and multinational biofuels growth on changes in land use and emissions from changes in forest carbon stocks.land use change, biofuels, CGE model, forest carbon stocks, GHG emissions, Resource /Energy Economics and Policy,

Ammonia emissions from deciduous forest after leaf fall

The understanding of biochemical feedback mechanisms in the climate system is lacking knowledge in relation to bi-directional ammonia (NH3) exchange between natural ecosystems and the atmosphere. We therefore study the atmospheric NH3 fluxes during a 25-day period during autumn 2010 (21 October to 15 November) for the Danish beech forest Lille Bøgeskov to address the hypothesis that NH3 emissions occur from deciduous forests in relation to leaf fall. This is accomplished by using observations of vegetation status, NH3 fluxes and model calculations. Vegetation status was observed using plant area index (PAI) and leaf area index (LAI). NH3 fluxes were measured using the relaxed eddy accumulation (REA) method. The REA-based NH3 concentrations were compared to NH3 denuder measurements. Model calculations of the atmospheric NH3 concentration were obtained with the Danish Ammonia MOdelling System (DAMOS). The relative contribution from the forest components to the atmospheric NH3 flux was assessed using a simple two-layer bi-directional canopy compensation point model. A total of 57.7% of the fluxes measured showed emission and 19.5% showed deposition. A clear tendency of the flux going from deposition of −0.25 ± 0.30 μg NH3-N m−2 s−1 to emission of up to 0.67 ± 0.28 μg NH3-N m−2 s−1 throughout the measurement period was found. In the leaf fall period (23 October to 8 November), an increase in the atmospheric NH3 concentrations was related to the increasing forest NH3 flux. Following leaf fall, the magnitude and temporal structure of the measured NH3 emission fluxes could be adequately reproduced with the bi-directional resistance model; it suggested the forest ground layer (soil and litter) to be the main contributing component to the NH3 emissions. The modelled concentration from DAMOS fits well the measured concentrations before leaf fall, but during and after leaf fall, the modelled concentrations are too low. The results indicate that the missing contribution to atmospheric NH3 concentration from vegetative surfaces related to leaf fall are of a relatively large magnitude. We therefore conclude that emissions from deciduous forests are important to include in model calculations of atmospheric NH3 for forest ecosystems. Finally, diurnal variations in the measured NH3 concentrations were related to meteorological conditions, forest phenology and the spatial distribution of local anthropogenic NH3 sources. This suggests that an accurate description of ammonia fluxes over forest ecosystems requires a dynamic description of atmospheric and vegetation processes

Global Implications of U.S. Biofuels Policies in an Integrated Partial and General Equilibrium Framework

With the increasing research interests in biofuels, global implications of biofuels production have been generally examined either in a partial equilibrium (PE) or general equilibrium (GE) frameworks. Though both of these approaches have unique strengths, they also suffer from many limitations due to complexity of addressing all the relevant aspects of biofuels. In this paper we have exploited the strengths of both PE and GE approaches for analyzing the economic and environmental implications of the U.S. policies on corn-ethanol and biodiesel production. In this study, we utilize the Forest and Agricultural Sector Optimization Model (FASOMGHG: Adams et al. 1996, 2005; Beach et al. 2009), a non-linear programming, PE model for the United States. We also use the GTAP-BIO model (Birur et al. 2008), a multi-region, multi-sector CGE model for global-scale assessment of biofuels policies. Following Britz and Hertel (2009), we link the GTAP-BIO model through a static, quadratic restricted revenue function obtained from perturbing crop prices from the FASOMGHG model. With this linkage we implement the U.S. Corn ethanol and biodiesel scenarios in the GTAP-BIO model and obtain the FASOMGHG-consistent, global land use changes. The resulting crop price changes from the GE model are fed back into the FASOMGHG model to obtain the disaggregated impacts in the U.S.Biofuels, Indirect land use change, Land use emissions, Partial Equilibrium, Computable General Equilibrium, Land Economics/Use, Resource /Energy Economics and Policy,

Bonuses and Bribes: Mood Effects in Memory

Free recall of emotionally positive, neutral, and negative adjectives was used as an indirect assessment of the effects of reward on expectations about intrinsic interest. Reward for performing later activities described as interesting (a bonus orientation) produced recall of a greater number of emotionally positive adjectives, whereas reward for the same activities described as boring (a bribe orientation) produced recall of a larger number of negative adjectives. A cued-expectancy analysis suggests that reward serves to polarize initial attitude about forthcoming tasks; these polarized attitudes, like moods, influence the nature of words retrieved from memory

The Relative Role of Land in Climate Policy

Replaced with revised version of paper 06/26/09.Climate policy, land use related emissions, carbon forest sequestration, CGE, Environmental Economics and Policy,

Collisionless energy absorption in the short-pulse intense laser-cluster interaction

In a previous Letter [Phys. Rev. Lett. 96, 123401 (2006)] we have shown by means of three-dimensional particle-in-cell simulations and a simple rigid-sphere model that nonlinear resonance absorption is the dominant collisionless absorption mechanism in the intense, short-pulse laser cluster interaction. In this paper we present a more detailed account of the matter. In particular we show that the absorption efficiency is almost independent of the laser polarization. In the rigid-sphere model, the absorbed energy increases by many orders of magnitude at a certain threshold laser intensity. The particle-in-cell results display maximum fractional absorption around the same intensity. We calculate the threshold intensity and show that it is underestimated by the common over-barrier ionization estimate.Comment: 12 pages, 13 figures, RevTeX