DEVELOPING AND PRICING PRECIPITATION INSURANCE

Production agriculture and agribusiness are exposed to many weather-related risks. Recent years have seen the emergence of an increased interest in weather-based derivatives as mechanisms for sharing risks due to weather phenomena. In this study, a unique precipitation derivative is proposed that allows the purchaser to specify the parameters of the idemnity function. Pricing methods are presented in the context of a cotton harvest example from Mississippi. Our findings show a potential for weather derivatives to serve niche markets within U.S. agriculture.Risk and Uncertainty,

Linearized large signal modeling, analysis, and control design of phase-controlled series-parallel resonant converters using state feedback

This paper proposes a linearized large signal state-space model for the fixed-frequency phase-controlled series-parallel resonant converter. The proposed model utilizes state feedback of the output filter inductor current to perform linearization. The model combines multiple-frequency and average state-space modeling techniques to generate an aggregate model with dc state variables that are relatively easier to control and slower than the fast resonant tank dynamics. The main objective of the linearized model is to provide a linear representation of the converter behavior under large signal variation which is suitable for faster simulation and large signal estimation/calculation of the converter state variables. The model also provides insight into converter dynamics as well as a simplified reduced order transfer function for PI closed-loop design. Experimental and simulation results from a detailed switched converter model are compared with the proposed state-space model output to verify its accuracy and robustness

The association between retinal vein ophthalmodynamometric force change and optic disc excavation

Aim: Retinal vein ophthalmodynamometric force (ODF) is predictive of future optic disc excavation in glaucoma, but it is not known if variation in ODF affects prognosis. We aimed to assess whether a change in ODF provides additional prognostic information. Methods: 135 eyes of 75 patients with glaucoma or being glaucoma suspects had intraocular pressure (IOP), visual fields, stereo optic disc photography and ODF measured on an initial visit and a subsequent visit at mean 82 (SD 7.3) months later. Corneal thickness and blood pressure were recorded on the latter visit. When venous pulsation was spontaneous, the ODF was recorded as 0 g. Change in ODF was calculated. Flicker stereochronoscopy was used to determine the occurrence of optic disc excavation, which was modelled against the measured variables using multiple mixed effects logistic regression. Results: Change in ODF (p=0.046) was associated with increased excavation. Average IOP (p=0.66) and other variables were not associated. Odds ratio for increased optic disc excavation of 1.045 per gram ODF change (95% CI 1.001 to 1.090) was calculated. Conclusion: Change in retinal vein ODF may provide additional information to assist with glaucoma prognostication and implies a significant relationship between venous change and glaucoma patho-physiology

Damage spreading in two dimensional geometrically frustrated lattices: the triangular and kagome anistropic Heisenberg model

The technique of damage spreading is used to study the phase diagram of the easy axis anisotropic Heisenberg antiferromagnet on two geometrically frustrated lattices. The triangular and kagome systems are built up from triangular units that either share edges or corners respectively. The triangular lattice undergoes two sequential Kosterlitz-Thouless transitions while the kagome lattice undergoes a glassy transition. In both cases, the phase boundaries obtained using damage spreading are in good agreement with those obtained from equilibrium Monte Carlo simulations.Comment: 7 pages, 4 figure

The Predictability of Commodity Trading Advisor Returns

This study investigates the performance and predictability of returns generated by advisors to Commodity Trading Funds from 1979 through 1989. Rates of return and Sharpe Ratios show evidence of predictability from one year to the next for all Commodity Trading Advisors (CTAs). Returns for the top one-third and top 5 performing CTAs show more predictability than for all CTAs

Impact of fill factor on input current ripple of photovoltaic system

This paper discusses the impact of fill factor on the input current ripple of the photovoltaic module and the loss effect on power extracted. Photovoltaic module's P-V curve produces exponential curve. The curvature of this curve indicates the fill factor of the particular cell; hence, by increasing the fill factor, the available extracted power increases. Yet, this paper states that losses due to photovoltaic current increases by increasing the fill factor

A framework of environmental mitigation for the convention and exhibition centers in the China greater Bay area

The numerous participants in convention and exhibition (C&E) events and the consequently huge consumption of direct and indirect resources have increased the environmental pressure on C&E centers to implement environmentally friendly practices and procedures. This paper explores the innovative methods adopted by green-certified C&E centers and synthesizes a reference framework of environmental mitigation practices for the C&E sector in the Greater Bay Area, which was recently designated as a major regional development area in China. Eleven green-certified C&E centers were selected to establish a comprehensive and indicative framework containing 59 actual environmental practices in three major categories. Suggestions made by 12 experts for modifying the fit of the constructed framework to suit the local geographical and climatic situations of C&E centers in the China Greater Bay Area were examined

Book Reviews

Reviews of the following books: History of Belfast in the 20th Century: by Jay David and Tim Hughes, with Megan Pinette; At Home With The General: A Visit to the Joshua L. Chamberlain Museum by Allan M. Levinsky; “Do Your Job!” An Illustrated Bicentennial History of the Portsmouth Naval Shipyard, 1800-2000 by Richard E. Winslow, III; Super U: The History and Politics of the University of Maine System by James Libb

Magnetic Energy and Helicity Budgets in the Active-Region Solar Corona. I. Linear Force-Free Approximation

We self-consistently derive the magnetic energy and relative magnetic helicity budgets of a three-dimensional linear force-free magnetic structure rooted in a lower boundary plane. For the potential magnetic energy we derive a general expression that gives results practically equivalent to those of the magnetic Virial theorem. All magnetic energy and helicity budgets are formulated in terms of surface integrals applied to the lower boundary, thus avoiding computationally intensive three-dimensional magnetic field extrapolations. We analytically and numerically connect our derivations with classical expressions for the magnetic energy and helicity, thus presenting a so-far lacking unified treatment of the energy/helicity budgets in the constant-alpha approximation. Applying our derivations to photospheric vector magnetograms of an eruptive and a noneruptive solar active regions, we find that the most profound quantitative difference between these regions lies in the estimated free magnetic energy and relative magnetic helicity budgets. If this result is verified with a large number of active regions, it will advance our understanding of solar eruptive phenomena. We also find that the constant-alpha approximation gives rise to large uncertainties in the calculation of the free magnetic energy and the relative magnetic helicity. Therefore, care must be exercised when this approximation is applied to photospheric magnetic field observations. Despite its shortcomings, the constant-alpha approximation is adopted here because this study will form the basis of a comprehensive nonlinear force-free description of the energetics and helicity in the active-region solar corona, which is our ultimate objective.Comment: 44 pages, 8 figures, 2 tables. The Astrophysical Journal, in pres