A Distributed Scheduling Algorithm to Provide Quality-of-Service in Multihop Wireless Networks

Control of multihop Wireless networks in a distributed manner while providing end-to-end delay requirements for different flows, is a challenging problem. Using the notions of Draining Time and Discrete Review from the theory of fluid limits of queues, an algorithm that meets delay requirements to various flows in a network is constructed. The algorithm involves an optimization which is implemented in a cyclic distributed manner across nodes by using the technique of iterative gradient ascent, with minimal information exchange between nodes. The algorithm uses time varying weights to give priority to flows. The performance of the algorithm is studied in a network with interference modelled by independent sets

Neutron and X-ray diffraction studies on complex liquids

The above examples illustrate the extent to which present day neutron and X-ray diffraction methods are being used to determine interatomic structure in a wide range of liquid and amorphous systems. The determination of pair radial distribution functions not only offers a means to characterise different structures in liquids, but also provides theorists with information to construct realistic model potentials that can be used to calculate macroscopic behaviour and structural properties in regimes not currently accessible to experiment.\ud The well-established NDIS difference methods remain superior to all other methods for the determination of interatomic pairwise structure. The relatively new AXD (or DAS) difference methods have the potential to answer long-standing questions about the structure around species with mass number greater than about 30. However, the relatively low X-ray scattering power from light elements such as hydrogen, carbon, nitrogen etc. means that it will never be possible to resolve completely structures of biologically important liquids by X-ray methods alone. EXAFS spectroscopy has the distinct advantage over both diffraction techniques as it can be used to study local structure around particular species at high dilution. Therefore studies which combine reference data from AXD or NDIS, with extensive EXAFS data, are likely to be useful in studies of structure in regimes which prove difficult for AXD and NDIS. \ud It is clear that no one method will be sufficient to resolve structure at the required level of detail around all species in a complex liquid. Instead one must rely on a full complement of diffraction and other techniques including computer simulation to determine the complete atomic structure of a complex liquid or amorphous system.\ud On the technical front, the construction and commissioning of new neutron diffractometers with higher count rates, such as D20 and D4C at ILL, and GEM at ISIS with an optimised sample environment for work at non-ambient conditions, will enable new and more extensive research to be undertaken. Additionally, the new custom-built X-ray diffractometer for liquids proposed for the DIAMOND synchrotron being established at RAL will provide a much-needed boost for wide-ranging AXD and EXAFS investigations of complex liquids. \ud Besides the many studies of immediate interest suggested at the end of some sections, there are several investigations that will become feasible in the longer term as the technology develops. These include 1. the use of isotopes such as 12C and 13C and 33S and 32S which will enable detailed and extensive structural studies to be carried out on a wide range of biologically significant materials, and 2. the exploitation of higher neutron and X-ray count rates to facilitate real time experiments to investigate changes of structure as a chemical or biochemical reaction occurs. \ud The one strong theme which emerges from all the work described in this paper is that diffraction, especially that based on difference techniques, remains the best means to determine structure at atomic resolution in complex liquids

Wealth Accumulation by Farm Households: Evidence from a National Survey

Wealth affects the economic well-being of the farm households by enabling farm households to secure credit, facilitate intergenerational transfer, and provide for smoothing consumption expenditures in times of income shortfall. This paper examines the factors that are likely to influence wealth accumulation by farm households. Specifically, we use 2001 ARMS data and multivariate regression procedure to estimate two models; one for those farm households whose wealth originates primarily from the farm and another for households with both farm- and nonfarm wealth.Farm Management,

RISK MANAGEMENT THROUGH ENTERPRISE DIVERSIFICATION: A FARM-LEVEL ANALYSIS

Enterprise diversification is a self-insuring strategy used by farmers to protect against risk. This paper examines the impact of various farm, operator, and household characteristics on the level of on-farm diversification. Results provide evidence that larger farms are more specialized. Also, farmers who participate in off-farm income and farms located near urban areas are less likely to diversify. Additionally, results also show a significant positive relationship between diversification and farm/crop insurance and sole proprietorships. Finally, there is also evidence that farms that received government payments are more diversified than their counterparts.Farm Management, Risk and Uncertainty,

ADOPTION AND ECONOMIC IMPACT OF SITE-SPECIFIC TECHNOLOGIES IN U.S. AGRICULTURE

A Heckman's two-stage method is used in conjunction with data from the 1998 Agricultural Resource Management Study to estimate the likelihood of adopting a variable rate application technology (VRT) and the impact of such adoption on the per-acre costs of fertilizers and lime in cash grain production. Results highlight the importance of operator's level of human capital and attitude toward risk, along with size and location of farm in impacting VRT adoption decisions. Results also indicate no significant cost-savings attributable to VRT adoption.Farm Management, Research and Development/Tech Change/Emerging Technologies,

Vertical coordination in high-value commodities

"Rising per capita income, urbanization and globalization are changing the consumption basket in the developing countries towards high-value commodities (like fruits & vegetables, milk, meat, poultry, fish, etc.). This paper explores how smallholders can benefit from the emerging opportunities from a silent demand-driven changes in high-value agriculture in India. The study examines the institutional mechanisms adopted by different firms to integrate small producers of milk, broilers and vegetables in supply chain and their effects on producers' transaction costs and farm profitability. The study finds that the innovative institutional arrangements in the form of contract farming have considerably reduced transaction costs and improved market efficiency to benefit the smallholders. The study does not find any bias against smallholders in contract farming. Also, the study does not find that the relevant firms have exploited their monopsonistic position by paying lower prices to farmers. On the contrary, contract producers were found enjoying benefits of assured procurement of their produce and higher prices. The study lists policy hurdles in scaling up the innovative models of vertical coordination in high-value food commodities" Authors' AbstractHigh value commodities ,Urbanization ,High value agriculture ,Scaling up ,