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

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

Projecting Supply and Demand for Land in the Long Run

The goal of this work is to investigate land-use change at the global scale over the long run particularly in the context of analyzing the fundamental drivers behind land-use related GHG emissions. For this purpose, we identify the most important drivers of supply and demand for land. On the demand side, we begin with a dynamic general equilibrium (GE) model that predicts economic growth in each region of the world, based on exogenous projections of population, skilled and unskilled labor and technical change. Economy-wide growth is, in turn, translated into consumer demand for specific products using an econometrically estimated, international cross-section, demand system that permits us to predict the pattern of future consumer demands across the development spectrum. This is particularly important in the fast-growing, developing countries, where the composition of consumer demand is changing rapidly. These countries also account for an increasing share of global economic growth and greenhouse gas emissions. Consumer demand is translated into derived demands for land through a set of sectoral production functions that differentiate the demand for land by Agro-Ecological Zone (AEZ). The paper devotes considerable attention to modeling the supply of land to different land-using activities in the economy. In order to represent the competition for land among different sectors in the model, we disaggregated the land endowment in each region into Agro-Ecological Zones, drawing on the data base of Lee et al. (2005), to reflect the fact that land is heterogeneous endowment. To further restrict land mobility across uses, land supply within an AEZ is constrained via a nested Constant Elasticity of Transformation (CET) frontier. In the nested structure, land owner of particular type of land (AEZ) first decides on the allocation of land between agriculture and forestry to maximize the total returns from land. Then, based on the relative returns to land in crop and livestock production, the land owner decides on the allocation of land between these two broad types of agricultural activities. A soft link between our GE model and an intertemporal forestry model is included for better representation of forestry sector in GE model. To reflect the real world fact that deforestation represents an important source of land supply in the face of high demand, we also introduce the possibility of conversion of unmanaged forest land to land used in production. This is treated as an investment decision whereby new land is accessed only when present value of returns on land in a given region is high enough to cover the costs of accessing the new land. In equilibrium, the supply of land to each land-using activity adjusts to meet the derived demand for land. A set of projections for the long run supply and demand for land obtained with this model is a useful input to improving our understanding of land-related GHG emissions in the future.land use, climate change policy, baseline, general equilibrium, agro-ecological zones, C68, R14, Q24, Land Economics/Use,

Electronic structure and dynamics of optically excited single-wall carbon nanotubes

We have studied the electronic structure and charge-carrier dynamics of individual single-wall carbon nanotubes (SWNTs) and nanotube ropes using optical and electron-spectroscopic techniques. The electronic structure of semiconducting SWNTs in the band-gap region is analyzed using near-infrared absorption spectroscopy. A semi-empirical expression for $E_{11}^{\rm S}$ transition energies, based on tight-binding calculations is found to give striking agreement with experimental data. Time-resolved PL from dispersed SWNT-micelles shows a decay with a time constant of about 15 ps. Using time-resolved photoemission we also find that the electron-phonon ({\it e-ph}) coupling in metallic tubes is characterized by a very small {\it e-ph} mass-enhancement of 0.0004. Ultrafast electron-electron scattering of photo-excited carriers in nanotube ropes is finally found to lead to internal thermalization of the electronic system within about 200 fs.Comment: 10 pages, 10 figures, submitted to Applied Physics

Poverty analysis using an international cross-country demand system

This paper proposes a new method for ex ante analysis of the poverty impacts arising from policy reforms. Three innovations underlie this approach. The first is the estimation of a global demand system using a combination of micro-data from household surveys and macro-data from the International Comparisons Project (ICP). Estimation is undertaken in a manner that reconciles these two sources of information, explicitly recognizing that per capita national demands are an aggregation of the disaggregated, individual household demands. The second innovation relates to a methodology for post-estimation calibration of the global demand system, giving rise to country-specific demand systems and an associated expenditure function which, when aggregated across the expenditure distribution, reproduce observed per capita budget shares exactly. This leads to the third innovation, which is the establishment of a unique poverty level of utility and an appropriately modified set of Foster-Greer-Thorbecke poverty measures. With these tools in hand, the authors are able to calculate the change in the head-count of poverty, poverty gap, and squared poverty gap arising from policy reforms, where the poverty measures are derived using a unique poverty level of utility, rather than an income or expenditure-based measure. They use these techniques with a demand system for food, other nondurables and services estimated using a combination of 1996 ICP data set and national expenditure distribution data. Calibration is demonstrated for three countries for which household survey expenditure data are used during estimation-Indonesia, the Philippines and Thailand. To show the usefulness of these calibrated models for policy analysis, the authors assess the effects of an assumed 5 percent food price rise as might be realized in the wake of a multilateral trade agreement. Results illustrate the important role of subsistence expenditures at lowest income levels, but of discretionary expenditure at higher income levels. The welfare analysis underscores the relatively large impact of the price hike on poorer households, while a modified Foster-Greer-Thorbecke poverty measure shows that the 5 percent price rise increases the incidence and intensity of poverty in all three cases, although the specific effects vary considerably by country.Markets and Market Access,Economic Theory&Research,Population Policies,Rural Poverty Reduction,Poverty Lines

Three-dimensional magnetic flux-closure patterns in mesoscopic Fe islands

We have investigated three-dimensional magnetization structures in numerous mesoscopic Fe/Mo(110) islands by means of x-ray magnetic circular dichroism combined with photoemission electron microscopy (XMCD-PEEM). The particles are epitaxial islands with an elongated hexagonal shape with length of up to 2.5 micrometer and thickness of up to 250 nm. The XMCD-PEEM studies reveal asymmetric magnetization distributions at the surface of these particles. Micromagnetic simulations are in excellent agreement with the observed magnetic structures and provide information on the internal structure of the magnetization which is not accessible in the experiment. It is shown that the magnetization is influenced mostly by the particle size and thickness rather than by the details of its shape. Hence, these hexagonal samples can be regarded as model systems for the study of the magnetization in thick, mesoscopic ferromagnets.Comment: 12 pages, 11 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,

The Effect of Carbon Payments on Deforestation Rates and Carbon Sequestration: Estimates from a Global Forestry and Agricultural Model.

Environmental Economics and Policy,

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,