A comparison of six farrowing house slat materials

There were 410 crossbred Duroc, Hampshire, Landrace and Yorkshire sows and their litters used in this study to compare the self-cleaning properties of six different slat types and to relate slat cleanliness to pig performance. Each litter was raised to weaning (about 5 weeks of age) in a 24-crate environment controlled confinement farrowing house. Each partially slatted farrowing crate utilized one of six different slat types in the rear 30 inches of the crate. The slat materials, #9 expanded metal, Behlen stainless steel, round rods, flat steel, plastic and aluminum, were evaluated for cleanliness by objective numeric scoring of the slatted area at weekly intervals. Slat cleanliness was primarily related to percent void (slot) space in the slat section. Expanded metal, Behlen stainless steel and round rod slats had a greater percent void space and scored significantly cleaner than flat steel, aluminum and plastic slats. The slats constructed of materials more readily available for on-farm construction such as expanded metal, round rods and flat steel self-cleaned more effectively than the specialty slat materials such as stainless steel, plastic and aluminum. The age and number of pigs in the litter had little influence on slat cleanliness. Year and season of year differences affected the cleanliness of all slat types but did not affect the differences among slat types. Slat cleanliness had little influence on the percentage of pigs weaned of those born alive; however, the slat material itself significantly affected the percentage weaned. Expanded metal, round rods, Behlen stainless steel and flat steel slat materials were those associated with the lower weaning percentages of 74.3 and 69.5, respectively. There were no significant differences in adjusted 35-day pig weaning weight

Estimating firm technical efficiency using alternative frontier function approaches: an application to farrow to finish hog production units

The purpose of this study was to estimate the relative technical efficiency of individual farrow-to-finish swine production units and to analyze the relationship between firm technical efficiency and selected swine production practices. Study areas included 11 states in the North Central region and seven states in the Southeast region of the U.S. hog enterprise production data were obtained from a cross-sectional cost of production study conducted by the Economic Research Service, U.S.D.A. in 1981. Information available for 216 farrow-to-finish swine units in the North Central region and 339 farrow-to-finish swine units in the Southeast region was used to derive the empirical data on annual output and resource use of each swine unit. Technical efficiency was estimated for each firm using alternative frontier production function approaches. The frontier function approaches used were (1) the Farrell linear programming approach to estimating multifactor productivity measures of technical, scale, and input congestion efficiency, and (2) a statistical composed error frontier approach to measuring technical efficiency relative to a random stochastic frontier. The resulting estimates of technical efficiency were used as dependent variables in explanatory regression models which related technical efficiency among firms to specified production characteristics. Production characteristics specified as independent variables were sow herd production intensity, level of confinement, type of management,type of farm business organization, type of manure handling practices, and type of feed and feed processing practices. Linear programming measures of technical efficiency permitted the derivation of estimates of scale efficiency and congestion efficiency for each hog unit. Mean technical efficiency for hog units in each sample was higher as the frontier function was altered to allow variable returns to scale and weak input disposability in the frontier relation-ship. Results showed scale and congestion inefficiency to be minor compared to technical inefficiency among swine units in each regional sample. The statistical, stochastic frontier approach gave results showing that technical efficiency was higher for larger size hog units and the estimates of the parameters of the frontier indicated the elasticity of production was less than one for each factor and for all factors collectively. Results derived from regression models using the deterministic measure of technical efficiency showed very little explanatory power and in many instances the signs, magnitude of the coefficients obtained for explanatory variables were contrary to expectations. Estimates from the regression models using the stochastic frontier indicated a moderate degree of explanation for the variation in technical among firms and estimated coefficients were more plausible. The existence of technical inefficiency in the hog production process seems quite well documented, but the determinants of hog farm technical efficiency are still unclear based on the results of this study

Landing impact studies of a 0.3-scale model air cushion landing system for a Navy fighter airplane

An experimental study was conducted in order to determine the landing-impact behavior of a 0.3-scale, dynamically (but not physically) similar model of a high-density Navy fighter equipped with an air cushion landing system. The model was tested over a range of landing contact attitudes at high forward speeds and sink rates on a specialized test fixture at the Langley aircraft landing loads and traction facility. The investigation indicated that vertical acceleration at landing impact was highly dependent on the pitch angle at ground contact, the higher acceleration of approximately 5g occurring near zero body-pitch attitude. A limited number of low-speed taxi tests were made in order to determine model stability characteristics. The model was found to have good pitch-damping characteristics but stability in roll was marginal

Experimental and analytical dynamic flow characteristics of an axial-flow fan from an air cushion landing system model

An investigation was conducted to compare the steady-state and dynamic flow characteristics of an axial-flow fan which had been used previously as the air supply fan for some model air cushion landing system studies. Steady-state flow characteristics were determined in the standard manner by using differential orifice pressures for the flow regime from free flow to zero flow. In this same regime, a correlative technique was established so that fan inlet and outlet pressures could be used to measure dynamic flow as created by a rotating damper. Dynamic tests at damper frequencies up to 5 Hz showed very different flow characteristics when compared with steady-state flow, particularly with respect to peak pressures and the pressure-flow relationship at fan stall and unstall. A generalized, rational mathematical fan model was developed based on physical fan parameters and a steady-state flow characteristic. The model showed good correlation with experimental tests at damper frequencies up to 5 Hz

Conservation Reserve and Conservation Compliance Programs: Implications for Resource Adjustment

Conservation Titles of the 1985 Food Security Act lead to agricultural market and resource use adjustments. This study explores how the Conservation Reserve Program (CRP) and the Conservation Compliance (CC) Program influence land use, commodity markets, input and technology use, production costs, and the environment. In the case of the Conservation Reserve Program, CARD/FAPRI commodity models are used to generate a baseline and to evaluate the impacts of increasing the amount of land in the reserve. In the case of the Conservation Compliance Program, the CARD ARIMS model is used to generate a baseline without the program and then to evaluate the impacts of imposing erosion restrictions consistent with the conservation compliance provisions. Lower stocks and higher commodity prices would be consequences of expanding the CRP. Resource adjustment associated with conservation compliance can be protracted and may be costly. Insofar as CRP reduces production and strengthens prices, it also can have the effect of increasing the intensity of input use in the remaining planted area. Conservation compliance clearly influences cropping patterns and choices of technology, as well as rates of soil erosion. While production cost increases of 2-4 percent seem relatively small, this could mean as much as 6-15 percent decline in net farm income

Analysis of 1990 Farm Bill Conservation Options

This report summarizes the ARIMS analysis for the 1990 Farm Bill Conservation Initiatives Work Group. Three major tasks were completed. First, ARIMS was updated to reflect the short-run nature of possible 1990 farm bill policies. Specifically, ARIMS now incorporates a more differentiated set of land resources and crop production technology to match the requirements of the 1985 Food Security Act. Second, baseline solutions for 1990, 1995, and 2000 were estimated. The solutions included the conservation titles of the 1985 Food Security Act. The baselines differed in the specification of acres in the Conservation Reserve Program (CRP) and in conservation compliance provisions. The 1990 baseline had a 40-million-acre CRP requirement; the 1995 baseline has a 40-million-CRP plus conservation compliance; and the 2000 baseline has an eight-million CRP with conservation compliance. Third, two alternative farm bill policy options were evaluated. The water quality option involved adding 10 million acres to the 40-million-acre CRP enrollment in the 1995 baseline. The selection of the 10 million acres was based on potential water quality impacts. The Trees for the U.S. program evaluated the conversion to tress of 37 million targeted acres of cropland and marginal pasture land

National and Regional Implications of Conservation Compliance

Soil erosion as an on-site problem received much attention in the 1985 Food Security Act (FSA), which established programs for the Conservation Reserve and conservation compliance. The 1985 FSA explicitly linked farmers\u27 resource use and conservation activities to benefits received from commodity programs. Much debate has ensued on erosion standards for compliance and farm income trade-offs. Farm-level uncertainties about meeting conservation compliance standards and about the trade-offs between limiting soil loss and maintaining farm income are evident. The objective of the analysis described herein was to provide information on national and regional implications of conservation compliance

National and Regional Implications of Targeting the Conservation Reserve

Within the Conservation Reserve (CR) program, a change in program criteria could reduce the amount of erosion material entering our nation\u27s waterways. The inclusion of land adjacent to water bodies, flowing streams, and river waterways may reduce erosion from these lands and improve water quality. These buffer strip areas, removed from production and placed in the reserve with a vegetative cover, would limit sedimentation and act to prevent upland erosion materials from reaching waterway channels, thus enhancing the programs\u27 environmental benefits. This paper analyzes the economic benefits of including buffer strups as eligible CR land, and it reviews the problems of identifying such areas

Prevalence and Correlates of Overweight and Obesity among Preschool-Aged Children in San Luis Obispo County, 2006-2014

Background and Purpose: National prevalence of overweight and obesity (OW/OB) among children remains high; surveillance of OW/OB at state- and local-levels is needed. This study determines the prevalence and sociodemographic predictors of OW/OB among preschool-age children in San Luis Obispo (SLO) County. Methods: Cross-sectional convenience samples of Head Start, California State, and private preschools were surveyed in 2006 (n=482), 2009/10 (n=559), and 2014 (n=442). At all waves, preschool children aged 3-5 years were measured for height and weight using standardized stadiometer and digital scale protocols. In 2014, parents completed a demographics questionnaire. Results: Children assessed in 2009/10 and 2014 were more likely to be OW/OB than those assessed in 2006 (p=0.016). Unadjusted, bivariate odds ratios illustrated increased risk for OW/OB was associated with Hispanic ethnicity, residing in a lower income household, attending preschool in southern SLO County, and participation in a Head Start preschool. In the adjusted, multivariable model, increased risk for OW/OB was associated with attending preschool in SLO City and participation in a California State or Head Start preschool. Conclusion: OW/OB trends in SLO County are similar to national trends. Programs to continue to monitor and reduce socioeconomic disparity in OW/OB prevalence among young children are needed

Large Scale Cross-Correlations in Internet Traffic

The Internet is a complex network of interconnected routers and the existence of collective behavior such as congestion suggests that the correlations between different connections play a crucial role. It is thus critical to measure and quantify these correlations. We use methods of random matrix theory (RMT) to analyze the cross-correlation matrix C of information flow changes of 650 connections between 26 routers of the French scientific network `Renater'. We find that C has the universal properties of the Gaussian orthogonal ensemble of random matrices: The distribution of eigenvalues--up to a rescaling which exhibits a typical correlation time of the order 10 minutes--and the spacing distribution follow the predictions of RMT. There are some deviations for large eigenvalues which contain network-specific information and which identify genuine correlations between connections. The study of the most correlated connections reveals the existence of `active centers' which are exchanging information with a large number of routers thereby inducing correlations between the corresponding connections. These strong correlations could be a reason for the observed self-similarity in the WWW traffic.Comment: 7 pages, 6 figures, final versio