Fuel containment, lightning protection and damage tolerance in large composite primary aircraft structures

The damage-tolerance characteristics of high strain-to-failure graphite fibers and toughened resins were evaluated. Test results show that conventional fuel tank sealing techniques are applicable to composite structures. Techniques were developed to prevent fuel leaks due to low-energy impact damage. For wing panels subjected to swept stroke lightning strikes, a surface protection of graphite/aluminum wire fabric and a fastener treatment proved effective in eliminating internal sparking and reducing structural damage. The technology features developed were incorporated and demonstrated in a test panel designed to meet the strength, stiffness, and damage tolerance requirements of a large commercial transport aircraft. The panel test results exceeded design requirements for all test conditions. Wing surfaces constructed with composites offer large weight savings if design allowable strains for compression can be increased from current levels

EFFECT OF A MASS MERCHANDISER ON TRADITIONAL FOOD RETAILERS

Non-traditional retailers such as warehouse club stores, discount drug stores, and discount mass merchandisers are new competitors for traditional food retailers. It is expected that non-traditional retailers will account for roughly 14 percent of total grocery sales by the turn of the century. The impact of a particular discount mass merchandiser (Wal-Mart) on the sales of a conventional retail grocery outlet (David's Supermarket, Inc.) located in the rural areas surrounding the Dallas/Ft. Worth metroplex is analyzed. In this case study, Wal-Mart alone is responsible for about a 21 percent reduction in sales.Agribusiness,

California’s Solar Rooftop Experience: An Update

An earlier Takeaway focusing on 2010 showed the necessity of state and federal subsidies to support the adoption of residential solar rooftops. Back then, the environmental bang for the buck was poor. But now, steeply falling solar costs have changed the picture. As before, this update looks not only at the costs and benefits to the solar adopters, but also to the investor-owned electric utilities, to the government, and to the environment. Cost reductions in solar panels now make subsidies unnecessary, but electric utilities continue to face a difficult situation. The author argues that wo big policy changes are needed

Estimation of Standardized Effort in the Heterogeneous Gulf of Mexico Shrimp Fleet

In this paper we estimate nominal and standardized shrimping effort in the Gulf of Mexico for the years 1965 through 1993. We accomplish this by first developing a standardization method (model) and then an expansion method (model). The expansion model estimates nominal days fished for noninterview landings data. The standardization model converts nominal days fished to standard days fished. We then characterize the historical trends of the penaeid shrimp fishery byvessel configuration, relative fishing power, and nominal and standardized effort. Wherever possible, we provide comparison with previous estimates by the National Marine Fisheries Service, NOAA

Homogeneous, heterogeneous or shrinkage estimators? Some empirical evidence from French regional gasoline consumption

This paper contrasts the performance of heterogeneous and shrinkage estimators versus the more traditional homogeneous panel data estimators. The analysis utilizes a panel data set from 21 French regions over the period 1973-1998 and a dynamic demand specification to study the gasoline demand in France. Out-of-sample forecast performance as well as the plausibility of the various estimators are contrasted.Panel data; French gasoline demand; Error components; Heterogeneous estimators; Shrinkage estimators

Impact of Automated Guidance for Mechanical Control of Herbicide-Resistant Weeds in Corn

This study evaluated the feasibility of reintroducing mechanical weed control as an alternative for herbicide-resistance weed infestations. The production practice tested included row cultivation with a separate banded spray application using high-accuracy automated guidance systems. A range of ground speeds were tested for the row cultivation operation, each with a different per acre cost and timeliness penalty. A typical eastern Corn Belt farm with a rotation of corn and soybean served as the base for the linear programming model. It was found that if the farmer was willing to reintroduce tillage, row cultivation conducted at higher operating speeds in conjunction with separate banded application could be justified under a range of relatively inexpensive herbicide costs as low as $7 per acre. When effective herbicides were relatively expensive at$30 per acre, the optimal decision would be to use row cultivation and reduce herbicides via banding. At faster ground speeds, the majority of hours devoted to row cultivation shifted to earlier time periods so that yield penalties were avoided

ESTIMATED COSTS AND RETURNS FOR CATFISH FARMS WITH RECIRCULATING PONDS ALONG THE UPPER TEXAS COAST

Cost, returns, and economies of scale for small, medium and large catfish farms with recirculating ponds are presented for the upper Texas coast. Internal rates of return are 0.150, 0.183 and 0.219, respectively. Total investment is higher than farms with static ponds but investment per unit production capacity is 7 percent to 16 percent lower. Average total cost per pound is between $0.565 and$0.541, (11 percent –20 percent lower than farms using current technology). These results have implications for regional comparative advantage of catfish production as well as incentive for adoption of new technology in conventional ponds.Aquaculture, Catfish, Economics, Off-flavor, Livestock Production/Industries,

A Smart, Price-Based Energy Policy

Energy policy in the United States is fatally flawed both in the process by which problems are identified and in the solutions that are chosen. It relies too heavily on subsidies, tax credits, grants, and mandates, when what is needed are price-based policies that encourage technological innovation and will achieve the goals of keeping energy reasonably cheap, but also reasonably clean and secure