Docking positrophilic electrons into molecular attractive potential of fluorinated methanes

The present study shows that the positrophilic electrons of a molecule dock into the positron attractive potential region in the annihilation process under the plane-wave approximation. The positron-electron annihilation processes of both polar and non-polar fluorinated methanes (CH4-nFn, n=0, 1,..., 4) are studied under this role. The predicted gamma-ray spectra of these fluorinated methanes agree well with the experiments. It further indicates that the positrophilic electrons of a molecule docking at the negative end of a bond dipole are independent from the molecular dipole moment in the annihilation process.Comment: 11 pages, 5 figure

Is Government Involvement Really Necessary: Implications for Systemic Risk and Crop Reinsurance Contracts

Agriculture is subject to substantial systemic risk of crop yield losses due to widespread natural disasters. The systemic risk has been a major obstacle for the development of private crop insurance markets. Driven by spatially correlated weather events, crop losses are highly correlated within a certain area. As a result, the portfolio insurance risk associated with the crop losses has been raised far above what it would be if individual losses were independent, as proposed by Miranda and Glauber (1997). For example, Miranda and Glauber (1997) find that the portfolio risk faced by U.S. crop insurers is about ten times larger than that of conventional insurance lines. Large portfolio risk requires high premium rates to cover the cost of bearing the systemic portfolio risk unless the cost is subsidized. Some national governments, such as the U.S., are willing to provide subsidies and reinsurance for crop insurance policies so that they are affordable to farmers. In this way, the cost of bearing the systemic risk has been transferred to governments. For those countries where there are no government subsidies, private crop insurers would have to charge high premiums, in order to hold large enough reserves for the potential systemic loss or purchase expensive international reinsurance. In this way, the cost of bearing the systemic risk is actually passed onto farmers eventually. Consequently, farmers are either buying extremely expensive insurance to get insured, or being exposed to huge crop loss risks

Robust Parameter Control based on Selecting Online Controllable Variables

AbstractRobust parameter design (RPD) is considered as a cost effective tool for reducing process variability. Robust parameter control, integrating RPD with automatic process control, will performance better than the traditional RPD approach. This paper proposed a strategy of robust process control based on selecting online controllable variables with consideration of generalized quality cost, which includes quality loss and manufacturing cost. Firstly, online controllable variables were selected and offline controllable variables were optimized in the design stage by minimizing the expectation of quality loss. Then, online controllable variables were adjusted during production according to the measurement of noise variables. Finally, the illustrative example showed that the proposed approach achieved lower quality cost

Diversifying Systemic Risk in Agriculture: A Copula-based Approach

One of the biggest obstacles for the development of private crop insurance markets is the systemic risk inherent in crop yields. Driven by spatially correlated weather events, crop losses are highly correlated within a certain area. As a result, the portfolio insurance risk has been raised prohibitively high for viable private crop insurance markets unless subsidized by the government. For example, the portfolio risk faced by U.S. crop insurers is about ten times larger than that of conventional insurance lines (Miranda and Glauber, 1997)

Vine-copula Based Models for Farmland Portfolio Management

U.S. farmland has achieved total returns of 10%-13% over the past decade with volatility of only 4%-5% (NCREIF Farmland Index). In addition, farmland returns have had low or negative correlation with traditional asset classes. These characteristics make farmland an attractive asset class for investors. Farmland, as a real asset, can also provide a hedge against inflation because farmland returns exhibit positive correlation with inflation. Over the past decade, annual U.S. farmland total return exceeds U.S. inflation rate by 3.55% (NCREIF Farmland Index and Consumer Price Index - Urban). With growing global demand for agricultural commodities and limited land to expand capacity, some investors expect that farmland will continue to generate superior returns for the foreseeable future