LAND TENURE INSECURITY AND LABOR ALLOCATION IN RURAL CHINA

Farmers' ability to leave agriculture is an important and debated topic in China and other countries. Many scholars believe China's unique land tenure policies prevent farmers from leaving agriculture. This paper examines the hypothesis that China's land tenure system deters exit from agriculture using household level data from Northeast China.Farm Management, Labor and Human Capital, Land Economics/Use,

The sweeping rate in diffusion-mediated reactions on dust grain surfaces

A prominent chemical reaction in interstellar clouds is the formation of molecular hydrogen by recombination, which essentially takes place on dust grain surfaces. Analytical approaches to model such a system have hitherto neglected the spatial aspects of the problem by employing a simplistic version of the sweeping rate of reactants. We show how these aspects can be accounted for by a consistent definition of the sweeping rate, and calculate it exactly for a spherical grain. Two regimes can be identified: Small grains, on which two reactants almost surely meet, and large grains, where this is very unlikely. We compare the true sweeping rate to the conventional approximation and find a characteristic reduction in both regimes, most pronounced for large grains. These effects can be understood heuristically using known results from the analysis of two-dimensional random walks. We finally examine the influence of using the true sweeping rate in the calculation of the efficiency of hydrogen recombination: For fixed temperature, the efficiency can be reduced considerably, and relative to that, small grains gain in importance, but the temperature window in which recombination is efficient is not changed substantially.Comment: 10 pages, 6 figure

CHINA'S AGRICULTURAL WATER SCARCITY : EFFECTS ON INTERNATIONAL MARKETS

Water shortages in important grain-producing regions of China may significantly affect China's agricultural production potential and international markets. This paper provides an overview of how water scarcity could affect China's agricultural production and trade. The paper identifies the areas where available water resources are most overexploited and the crops most vulnerable to reductions in irrigation. We present preliminary results from modeling a decline in irrigated land in water scarce areas in China and the effect this would have on China's production and trade. Wheat and cotton are most vulnerable to a decrease in irrigated area in water scarce regions, and production for these crops could fall by 7-10 percent under a severe cutback in irrigation. The effect this will have on international markets will depend largely on the openness of China's border to imports. In addition, we describe recent conservation policies and how these may affect crop production in China.Resource /Energy Economics and Policy,

Interactions between Resource Scarcity and Trade Policy: The Potential Effects of Water Scarcity on China’s Agricultural Economy under the Current TRQ Regime

International Relations/Trade, Resource /Energy Economics and Policy,

Accurate rate coefficients for models of interstellar gas-grain chemistry

The methodology for modeling grain-surface chemistry has been greatly improved by taking into account the grain size and fluctuation effects. However, the reaction rate coefficients currently used in all practical models of gas-grain chemistry are inaccurate by a significant amount. We provide expressions for these crucial rate coefficients that are both accurate and easy to incorporate into gas-grain models. We use exact results obtained in earlier work, where the reaction rate coefficient was defined by a first-passage problem, which was solved using random walk theory. The approximate reaction rate coefficient presented here is easy to include in all models of interstellar gas-grain chemistry. In contrast to the commonly used expression, the results that it provides are in perfect agreement with detailed kinetic Monte Carlo simulations. We also show the rate coefficient for reactions involving multiple species.Comment: 4 pages, 2 figure

LAND RENTAL MARKET DEVELOPMENT AND AGRICULTURAL PRODUCTION IN CHINA

The development of a land rental market in China may help stimulate further increases in agricultural production. This paper provides a description of land rental transactions in rural China, analyzes the determinants of land supply and demand and estimates the implications land rental activity has for increasing agricultural production.Land Economics/Use,

Diffusion-limited reactions on a two-dimensional lattice with binary disorder

Reaction-diffusion systems where transition rates exhibit quenched disorder are common in physical and chemical systems. We study pair reactions on a periodic two-dimensional lattice, including continuous deposition and spontaneous desorption of particles. Hopping and desorption are taken to be thermally activated processes. The activation energies are drawn from a binary distribution of well depths, corresponding to `shallow' and `deep' sites. This is the simplest non-trivial distribution, which we use to examine and explain fundamental features of the system. We simulate the system using kinetic Monte Carlo methods and provide a thorough understanding of our findings. We show that the combination of shallow and deep sites broadens the temperature window in which the reaction is efficient, compared to either homogeneous system. We also examine the role of spatial correlations, including systems where one type of site is arranged in a cluster or a sublattice. Finally, we show that a simple rate equation model reproduces simulation results with very good accuracy.Comment: 9 pages, 5 figure

Diffusion, Nucleation and Recombination in Confined Geometries

In this work we address several problems of surface physics which are all based on the transport mechanism of diffusion. Essential parts consider systems in which particles interact upon meeting, either by reaction or by nucleation. For the astrophysical problem of hydrogen recombination on interstellar dust, the previous analytical treatment is substantially improved upon: The parameter responsible for reaction is defined consistently, and in its calculation, we account for the nature of two-dimensional diffusion. Within several models that are also compared with each other, one obtains explicit results that excellently agree with Monte Carlo simulations. Special attention is given to the influence of the confined geometry, which is analytically examined and explained for a minimal model. We also deal with the role of disorder in the surface structure. A further section presents the closely related problem of nucleation at island edges, which, however, proves to be no longer tractable analytically even under moderate assumptions. Step growth under the effect of codeposited impurities is a technologically relevant process, which is examined in a one-dimensional random walk model. Using microscopic models for the resulting disorder on the surface, one finds interesting results that also bear implications for simulations. Those results concern the general influence on the speed and stability of step growth as well as the nature of boundary conditions in the corresponding continuum model. In the last part we thoroughly analyze a model to describe the diffusion field in desorption experiments, which can be made directly visible on a large scale and with real time resolution. The model agrees well with experimental data and hence constitutes an important step in understanding the fundamental processes involved. Based on this understanding, one can draw direct conclusions from the observation of a surface of complex morphology on its microscopic properties

THE RISE OF RURAL-TO-RURAL LABOR MARKETS IN CHINA

The continued transfer of agricultural labor into the industrial sector is crucial to China's transformation into an industrial economy. We argue in this paper that rural industry offers an alternative to urban industry for receiving agricultural labor from areas without off-farm employment opportunities. Characteristics of rural industry differ from their urban counterparts. These characteristics may serve to shape the growth in employment for incoming workers in rural areas, provide opportunities for certain types of workers, and affect the impacts these workers have on the local economy. In this paper we examine the features of China's rural-to-rural labor movement and the villages where these workers are employed. Using a nationally representative sample of 215 villages, we show that the growth in rural-to-rural labor movement between 1988 and 1995 has been much faster than in rural-to-urban movement or in local off-farm employment. The rapid growth in rural-to-rural commuting and migration has not negatively affected off-farm income earning opportunities for workers living in the receiving villages. Rural-to-rural labor movement also has many positive effects. Labor movement into rural villages provides opportunities for workers generally underrepresented in other parts of the off-farm labor market, appears to dampen upward pressure on wages that allows rural industry to maintain labor intensive practices, and promotes national economic integration.Labor and Human Capital,