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961.
962.
The U.S. Departments of Agriculture and Energyjointly analyzed the economic potential for,and impacts of, large-scale bioenergy cropproduction in the United States. Anagricultural sector model (POLYSYS) wasmodified to include three potential bioenergycrops (switchgrass, hybrid poplar, and willow). At farmgate prices of US $2.44/GJ, anestimated 17 million hectares of bioenergycrops, annually yielding 171 million dry Mg ofbiomass, could potentially be produced at aprofit greater than existing agricultural usesfor the land. The estimate assumes highproductivity management practices are permittedon Conservation Reserve Program lands. Traditional crops prices are estimated toincrease 9 to 14 percent above baseline pricesand farm income increases annually by US $6.0billion above baseline.At farmgate prices of US $1.83/GJ, anestimated 7.9 million hectares of bioenergycrops, annually yielding 55 million dry Mg ofbiomass, could potentially be produced at aprofit greater than existing agricultural usesfor the land. The estimate assumes managementpractices intended to achieve highenvironmental benefits on Conservation ReserveProgram lands. Traditional crops prices areestimated to increase 4 to 9 percent abovebaseline prices and farm income increasesannually by US $2.8 billion above baseline.  相似文献   
963.
964.
Continental breakup, or compressive lithosphere scale faulting, requires a physical mechanism for wholesale faulting of the lithosphere. We compared numerical and experimental models for the nucleation of quasi-adiabatic shear bands in polyvinylchloride (PVC) with those in an idealized viscoelastoplastic mantle with olivine rheology. In both materials fault nucleation is caused by elastic stress concentration on pre-existing imperfections, with localized yielding confined to its vicinity. Faulting occurs rapidly after the initial elastic energy in the system is charged sufficiently to cause wholesale yielding. Propagation of the fault, monitored by looking at the dissipation of plastic energy, reveals migration of a sharp, thermal-mechanical “crack”- like instability, which appears in the temperature field as a slightly diffused signal. The initial temperature rise in the crack is subtle but increases suddenly when the plate is severed. This autocatalytic behavior has also been described in ductile polymers, which can be used as mechanical analogues. We suggest that elastoplastic coupling in quasi-adiabatic shear banding is a key for fast (< 1 Ma) nucleation of shear zones. These nonlinear phenomena will be illustrated for both experimental and numerical results by nine movies  相似文献   
965.
966.
Summary. Bick (1987,1990) and He and Leland (1993) demonstrated that not every arbitrage-free Markovian diffusion price process is consistent with an equilibrium approach. We propose a unified framework for these results and we derive a new martingale characterization of equilibrium.  相似文献   
967.
    
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968.
    
Agriculture remains sensitive to variation in rainfall and temperature. Fortunately, our ability to predict the lower frequency variation in the earth's atmosphere is increasing rapidly. While information cannot affect the underlying source of variability, it allows unexpected shocks to be anticipated and acted upon. This paper develops and analyzes an intertemporal Ricardian trade model with Bayesian beliefs. Results in this paper show that improved climate prediction reduces expected prices, but increases price variability. In addition, trade is crucial to realizing the potential benefits of climate prediction. The value of climate prediction is highest with both storage and trade, and falls by over 300% when a country is in autarky.  相似文献   
969.
    
John Caruthers (1836–1914), the Scottish civil engineer who built canals and railways many parts of the world, was a good friend of William Morris and an active supporter of the Scoialist League and then the Hammersmith Socialist Society. He advocated a non-bureaucratic socialism, which had only a limited state machinery and made considerable use of the market system, with money, banks and flexible prices. His ideas were elaborated in a long boon Communal and Commercial Economy (1883) and in a substantial article (1884) in To-Day (a leading London socialist periodical of the time) and elsewhere. The paper sets out his economic ideas in some detail, including his (implicit) emphasis on the Golden Rule in he choice of technique. These ideas were a considerale achievement for the early 1880s and it is perhaps unfortunate that they did not have a greater influence on the socialist movement.  相似文献   
970.
Abstract

The paper discusses Sraffa's consecutive attempts in the late 1920s and early 1940s to tackle a problem which endangered his objectivist, surplus-based approach to the theory of value and distribution aimed at reviving the standpoint of the classical economists. Whilst with circulating capital the value transfer to the product and the physical ‘destruction’ of the input are one and the same thing, with fixed capital this is not so. Sraffa eventually overcame the difficulty in terms of the joint products-method. This allowed him to explain relative prices and the rate of profits strictly in ‘material terms’.  相似文献   
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