Savings and technology choice for risk averse farmers

Farmers in developing countries have limited opportunities for borrowing to even out variability associated with risky farm income, but they can save. A dynamic programming model of savings is presented in the current paper which examines optimal savings strategies for farmers, using a case study of integrated rice-shrimp farms in Vietnam. It is shown that when savings are accounted for, the expected utility ranking of different risky farm choices may not differ that much between farmers with different levels of risk aversion.Farm Management, Risk and Uncertainty,

The economics of land degradation and technological change: a case study in Vietnam

This paper explores the economics of land degradation in the rice-shrimp system in the Mekong Delta of Vietnam. A bioeconomic NPV model was developed to evaluate and compare the long-term benefits of alternative production choices and farm technologies. There is an alternative rice-shrimp technology emerging in Vietnam that does not have the same land degrading impacts as the 'traditional' system, however the high capital outlay and risk associated with such technology presents its own problems. In the paper the economic incentives for adoption of the non-land degrading rice-shrimp technology are explored. Conclusions are drawn with regard to the opportunity cost of land degradation and technological change. Some conclusions are also provided on the policy implications arising from the results presented.land degradation, technological change, Vietnam, Environmental Economics and Policy,

Theoretical and material studies on thin-film electroluminescent devices

A theoretical study of resonant tunneling in multilayered heterostructures is presented based on an exact solution of the Schroedinger equation under the application of a constant electric field. By use of the transfer matrix approach, the transmissivity of the structure is determined as a function of the incident electron energy. The approach presented is easily extended to many layer structures where it is more accurate than other existing transfer matrix or WKB models. The transmission resonances are compared to the bound state energies calculated for a finite square well under bias using either an asymmetric square well model or the exact solution of an infinite square well under the application of an electric field. The results show good agreement with other existing models as well as with the bound state energies. The calculations were then applied to a new superlattice structure, the variablly spaced superlattice energy filter, (VSSEP) which is designed such that under bias the spatial quantization levels fully align. Based on these calculations, a new class of resonant tunneling superlattice devices can be designed

The Design of an Uncertainty Model For The Tidal Constituent and Residual Interpolation (TCARI) Method for Tidal Correction of Bathymetric Data

Recent advances in processing multibeam sonar data brought about by the Combined Uncertainty and Bathymetric Estimator (CUBE) [1] have demonstrated the value of identifying and tracking survey uncertainties. Most of these uncertainties were outlined in Hare, Godin, and Mayer uncertainty model developed in 1995 [2]. That report identified the uncertainties in the various electronic systems used to acquire the bathymetric data. However, one of the largest contributors to the overall error budge t in a near coastal hydrographic survey is that contributed by water level uncertainty. As the ocean mapping industry pushes for ever finer spatial details in its data, the traditional method of discrete tide zoning [3] must be abandoned for a more robust method that can match the requirements of the data. The method currently under investigation by the National Oceanic and Atmospheric Administration is the Tidal Constituent And Residual Interpolation (TCARI) method [4]. TCARI has the ability to interpolate the water level at a vessel’s position for any location and instance in time. It can also produce a gridded water level surface of the entire survey area. While the potential of this method is encouraging, a rigorous investigation of the uncertainties associated with it has yet to be completed. This research seeks to close that gap by examining the uncertainties in this method, using both observed water level information from around the country as well as data acquired during the original 1995 NOS Kinematic GPS experiment in Galveston Bay, Texas [5]

The welfare costs of urban outdoor water restrictions

Outdoor water restrictions are usually implemented as bans on a particular type of watering technology (sprinklers), which allow households to substitute for labour-intensive (hand-held) watering. This paper presents a household production model approach to analysing the impact of sprinkler restrictions on consumer welfare and their efficacy as a demand management tool. Central to our empirical analysis is an experimentally derived production function which describes the relationship between irrigation and lawn quality. We demonstrate that for a typical consumer complete sprinkler bans may be little more effective than milder restrictions policies, but are substantially more costly to the household.household model, urban water demand, urban water restrictions, Resource /Energy Economics and Policy,

Valuing Urban Wetlands of the Gnangara Mound: A Hedonic Property Price Approach in Western Australia

Up to 60% of potable water supplied to Perth in Western Australia is extracted from the Gnangara mound. Many of the urban wetlands above the Mound are groundwater-dependent. Excessive groundwater extraction and climate change have resulted in a decline in water levels in the wetlands. This study estimates the value of urban wetlands in three local government districts in the Perth metropolitan region using the hedonic property price approach. Preliminary results found that proximity to wetlands influences the sales prices of properties. The marginal implicit price of reducing the distance to the nearest wetland by 1 metre, evaluated at the mean sales value, is AU$463. If there is more than one wetland within 1.5 kilometres of a property, the second wetland will help increase the property price by AU$6,081. For a 50 ha wetland, we estimate the total premium of on sales due to wetland proximity is AU$220 million, based on average property characteristics and medium house density. These results will help inform policy makers and land developers on the value of conserving existing urban wetlands, creating new wetland areas and urbanising rural wetlands.groundwater, housing development, aquifer, marginal implicit price, Land Economics/Use,

Cavitation Scaling Experiments With Headforms: Bubble Acoustics

Recently Ceccio and Brennen [1][2][3] have examined the interaction between individual traveling cavitation bubbles and the structure of the boundary layer and flow field in which the bubble is growing and collapsing. They were able to show that individual bubbles are often fissioned by the fluid shear and that this process can significantly effect the acoustic signal produced by the collapse. Furthermore they were able to demonstrate a relationship between the number of cavitation events and the nuclei number distribution measured by holographic methods in the upstream flow. Kumar and Brennen [4][5] have further examined the statistical properties of the acoustical signals from individual cavitation bubbles on two different headforms in order to learn more about the bubble/flow interactions. All of these experiments were, however, conducted in the same facility with the same size of headform (5.08cm in diameter) and over a fairly narrow range of flow velocities (around 9m/s). Clearly this raises the issue of how the phenomena identified change with speed, scale and facility. The present paper will describe further results from experiments conducted in order to try to answer some of these important questions regarding the scaling of the cavitation phenomena. These experiments (see also Kuhn de Chizelle et al. [6][7]) were conducted in the Large Cavitation Channel of the David Taylor Research Center in Memphis Tennessee, on similar Schiebe headforms which are 5.08, 25.4 and 50.8cm in diameter for speeds ranging up to 15m/s and for a range of cavitation numbers

Memantine for prevention of migraine: a retrospective study of 60 cases.

The objective was to retrospectively characterise the efficacy of memantine as preventive therapy in a series of patients with frequent migraine. Patients in a university headache clinic completed a survey regarding their experience with memantine, and medical records were reviewed. All patients who received memantine as preventive therapy for migraine over a 15-month period were mailed surveys and consent forms for record review. Patients were treated with memantine beginning at a dose of 5 mg/day, increasing if needed by 5 mg/week up to 10 mg twice a day. The majority of patients (36 out of 54) treated with memantine for at least 2 months reported a significant reduction in estimated headache frequency, and improved function. Side effects were uncommon and generally mild. This limited retrospective case review suggests that memantine may be an effective preventive therapy for patients with frequent migraine. A prospective trial is warranted