42,519 research outputs found
Applications of remote sensing to estuarine management
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Foreign Direct Investment and Relative Wages: Evidence from Mexico's Maquiladoras
In this paper, we examine the increase in the relative wages of skilled workers in Mexico during the 1980s. We argue that rising wage inequality in Mexico is linked to capital inflows from abroad. The effect of these capital inflows, which correspond to an increase in outsourcing by multinationals from the United States and other Northern countries, is to shift production in Mexico towards relatively skill-intensive goods thereby increasing the relative demand for skilled labor. We study the impact of foreign direct investment (FDI) on the share of skilled labor in total wages in Mexico using state-level data on two-digit industries from the Industrial Census for the period 1975 to 1988. We measure the state- level growth in FDI using data on the regional activities of foreign- owned assembly plants. We find that growth in FDI is positively correlated with the relative demand for skilled labor. In the regions where FDI has been most concentrated, growth in FDI can account for over 50 percent of the increase in the skilled labor share of total wages that occurred during the late 1980s.
A rapid method for optimization of the rocket propulsion system for single-stage-to-orbit vehicles
A rapid analytical method for the optimization of rocket propulsion systems is presented for a vertical take-off, horizontal landing, single-stage-to-orbit launch vehicle. This method utilizes trade-offs between propulsion characteristics affecting flight performance and engine system mass. The performance results from a point-mass trajectory optimization program are combined with a linearized sizing program to establish vehicle sizing trends caused by propulsion system variations. The linearized sizing technique was developed for the class of vehicle systems studied herein. The specific examples treated are the optimization of nozzle expansion ratio and lift-off thrust-to-weight ratio to achieve either minimum gross mass or minimum dry mass. Assumed propulsion system characteristics are high chamber pressure, liquid oxygen and liquid hydrogen propellants, conventional bell nozzles, and the same fixed nozzle expansion ratio for all engines on a vehicle
Productivity Measurement and the Impact of Trade and Technology on Wages: Estimates for the U.S., 1972-1990
We develop an empirical framework to assess the importance of trade and technical change on the wages of production and nonproduction workers. Trade is measured by the foreign outsourcing of intermediate inputs, while technical change is measured by the shift towards high-technology capital such as computers. In our benchmark specification, we find that both foreign outsourcing and expenditures on high-technology equipment can explain a substantial amount of the increase in the wages of nonproduction (high-skilled) relative to production (low-skilled) workers that occurred during the 1980s. Surprisingly, it is expenditures on high-technology capital other than computers that are most important. These results are very sensitive, however, to our benchmark assumption that industry prices are independent of productivity. When we allow for the endogeneity of industry prices, then expenditures on computers becomes the most important cause of the increased wage inequality, and have a 50% greater impact than does foreign outsourcing.
Intermediaries in Entrepot Trade: Hong Kong Re-Exports of Chinese Goods
In this paper, we examine Hong Kong's role in intermediating trade between China and the rest of the world. Hong Kong distributes a large fraction of China's exports. Net of customs, insurance, and freight charges, re-exports of Chinese goods are much more expensive when they leave Hong Kong than when they enter. Hong Kong markups on re-exports of Chinese goods are higher for differentiated products, products with higher variance in export prices, products sent to China for further processing, and products shipped to countries which have less trade with China. These results are consistent with quality-sorting models of intermediation and with the outsourcing of production tasks from Hong Kong to China. Additional results suggest that Hong Kong traders price discriminate across destination markets and use transfer pricing to shift income from high-tax countries to Hong Kong.
Ownership and Control in Outsourcing to China: Estimating the Property-Rights Theory of the Firm
In this paper, we develop a simple model of international outsourcing and apply it to processing trade in China. We observe China's processing exports broken down by who owns the plant and by who controls the inputs the plant processes. Multinational firms engaged in export processing in China tend to split factory ownership and input control with managers in China: the most common outcome is to have foreign factory ownership but Chinese control over input purchases. To account for this organizational arrangement, we appeal to a property-rights model of the firm. Multinational firms and the Chinese factory managers with whom they contract divide the surplus associated with export processing by Nash bargaining. Investments in input search, production, and marketing are partially relationship specific. In our benchmarks estimates, this relationship specificity is lowest in southern coastal provinces, where export markets are thickest, and highest in interior and northern provinces. The probability contracts are enforced has a similar pattern and is the lowest along the southern coast and the highest in the north.
Transport in ultradilute solutions of He in superfluid He
We calculate the effect of a heat current on transporting He dissolved in
superfluid He at ultralow concentration, as will be utilized in a proposed
experimental search for the electric dipole moment of the neutron (nEDM). In
this experiment, a phonon wind will generated to drive (partly depolarized)
He down a long pipe. In the regime of He concentrations and temperatures K, the phonons comprising the heat current
are kept in a flowing local equilibrium by small angle phonon-phonon
scattering, while they transfer momentum to the walls via the He first
viscosity. On the other hand, the phonon wind drives the He out of local
equilibrium via phonon-He scattering. For temperatures below K, both
the phonon and He mean free paths can reach the centimeter scale, and we
calculate the effects on the transport coefficients. We derive the relevant
transport coefficients, the phonon thermal conductivity and the He
diffusion constants from the Boltzmann equation. We calculate the effect of
scattering from the walls of the pipe and show that it may be characterized by
the average distance from points inside the pipe to the walls. The temporal
evolution of the spatial distribution of the He atoms is determined by the
time dependent He diffusion equation, which describes the competition
between advection by the phonon wind and He diffusion. As a consequence of
the thermal diffusivity being small compared with the He diffusivity, the
scale height of the final He distribution is much smaller than that of the
temperature gradient. We present exact solutions of the time dependent
temperature and He distributions in terms of a complete set of normal
modes.Comment: NORDITA PREPRINT 2015-37, 9 pages, 6 figure
Low Temperature Transport Properties of Very Dilute Classical Solutions of He in Superfluid He
We report microscopic calculations of the thermal conductivity, diffusion
constant and thermal diffusion constant for classical solutions of He in
superfluid He at temperatures T \la 0.6~K, where phonons are the dominant
excitations of the He. We focus on solutions with He concentrations
\la \,10^{-3}, for which the main scattering mechanisms are phonon-phonon
scattering via 3-phonon Landau and Beliaev processes, which maintain the
phonons in a drifting equilibrium distribution, and the slower process of
He-phonon scattering, which is crucial for determining the He
distribution function in transport. We use the fact that the relative changes
in the energy and momentum of a He atom in a collision with a phonon are
small to derive a Fokker-Planck equation for the He distribution function,
which we show has an analytical solution in terms of Sonine polynomials. We
also calculate the corrections to the Fokker-Planck results for the transport
coefficients.Comment: 29 pages, 2 figure
Transport in very dilute solutions of He in superfluid He
Motivated by a proposed experimental search for the electric dipole moment of
the neutron (nEDM) utilizing neutron-He capture in a dilute solution of
He in superfluid He, we derive the transport properties of dilute
solutions in the regime where the He are classically distributed and rapid
He-He scatterings keep the He in equilibrium. Our microscopic
framework takes into account phonon-phonon, phonon-He, and He-He
scatterings. We then apply these calculations to measurements by Rosenbaum et
al. [J.Low Temp.Phys. {\bf 16}, 131 (1974)] and by Lamoreaux et al.
[Europhys.Lett. {\bf 58}, 718 (2002)] of dilute solutions in the presence of a
heat flow. We find satisfactory agreement of theory with the data, serving to
confirm our understanding of the microscopics of the helium in the future nEDM
experiment.Comment: 10 pages, 5 figures, v
Applications of remote sensing to estuarine management
Remote sensing was used in the resolution of estuarine problems facing federal and Virginia governmental agencies. A prototype Elizabeth River Surface Circulation Atlas was produced from photogrammetry to aid in oil spill cleanup and source identification. Aerial photo analysis twice led to selection of alternative plans for dredging and spoil disposal which minimized marsh damage. Marsh loss due to a mud wave from a highway dyke was measured on sequential aerial photographs. An historical aerial photographic sequence gave basis to a potential Commonwealth of Virginia legal claim to accreting and migrating coastal islands
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