Effectiveness Based Design of a Tactical Tanker Aircraft

An approach to drive conceptual aircraft design using mission effectiveness parameters is described and applied to an operational scenario. The scenario includes traditional aircraft refueling tankers and a proposed tactical tanker concept supporting fighter aircraft conducting offensive (OCA) and defensive (DCA) counter air patrols. Traditional conceptual design methodologies were used to generate a baseline design for a tactical tanker aircraft, which was evaluated using a MATLAB-based model to investigate Measures of Effectiveness (MOE). The model holds the traditional tanker and fighter capabilities constant, while varying the tactical tanker\u27s specific fuel consumption, lift-to-drag ratio, fuel payload, mass fraction, and proximity to contested airspace. A sensitivity analysis was conducted to show the effect of technology variations on MOEs. Results show with a minimum of 45000 lb fuel payload, the tactical tanker can increase the fighter OCA penetration radius by 57%, and the DCA loiter time by 48%. However; optimal size is heavily dependent on gameboard layout, fighter size, and number of aircraft tasked to the tanker. Sensitivity analysis and full factorial trade space exploration show the MOEs are most sensitive to changes in proximity and mass fraction. These results provide recommendations for the prioritization of research efforts if the US Air Force decides to develop a tactical tanker aircraft in the future

Responses to 19 generations of litter size selection in the Nebraska Index line. I. Reproductive responses estimated in pure line and crossbred litters

Our objective was to estimate responses in reproductive traits in the Nebraska Index line (I) after 19 generations of selection for increased litter size. Responses were estimated in dams producing pure line, F1, and three-way cross litters. A total of 850 litters were produced over six year-seasons, including 224 pure line litters, 393 F1 litters produced from I and C females mated with DanbredNALandrace (L) or Duroc- Hampshire (T) boars, and 233 litters by F1 L x I and L x C females mated with T boars. Contrasts of means were used to estimate the genetic difference between I and C and interactions of line differences with mating type. Farrowing rates of lines I (û = 91.0%) and C (û = 92.8%) did not differ. Averaged across all genetic groups, mean number born alive per litter was 10.1 pigs, and number and weight of pigs weaned per litter, both adjusted for number nursed and weaning age of 12 d, were 9.7 pigs and 34.4 kg, respectively. Averaged across mating types, direct genetic effects of I were greater than C (P \u3c 0.05) for total born (3.53 pigs), number born alive (2.53 pigs), number of mummified pigs (0.22 pig), and litter birth weight (2.14 kg). The direct genetic effect of line I was less than C (P \u3c 0.05) for litter weaning weight (-1.88 kg). Interactions of line effects with crossing system were significant (P \u3c 0.05) for total number born, number of stillborn pigs, number weaned, and litter weaning weight. In pure line litters, I exceeded C by 4.18 total pigs and 1.76 stillborn pigs per litter, whereas the estimate of I–C in F1 litters was 2.74 total pigs and 0.78 stillborn pig per litter. The contrast between I and C for number weaned and litter weaning weight in pure litters was 0.32 pig and -0.28 kg, respectively, compared with 0.25 pig and -2.14 kg in F1 litters. Crossbreeding is an effective way to use the enhanced reproductive efficiency of the Index line

Promoting Active Studying: The Study Challenge

We explore using a “Study Challenge” to help students become active studiers in mathematics courses. We describe how a Study Challenge works and how we implemented it in calculus and differential equations courses. We discuss qualitative reactions from students who accepted the Study Challenge, which suggest that this might be a useful tool for students’ to add to their examination preparation toolbox. Finally, we offer some suggestions for implementing a Study Challenge within the mathematics classroom

Relativistic quark models of baryons with instantaneous forces

This is the first of a series of three papers treating light baryon resonances (up to 3 GeV) within a relativistically covariant quark model based on the three-fermion Bethe-Salpeter equation with instantaneous two- and three-body forces. In this paper we give a unified description of the theoretical background and demonstrate how to solve the Bethe-Salpeter equation by a reduction to the Salpeter equation. The specific new features of our covariant Salpeter model with respect to the usual nonrelativistic quark model are discussed in detail. The purely theoretical results obtained in this paper will be applied numerically to explicit quark models for light baryons in two subsequent papers

PAYLEAN® Improves Growth and Carcass Merit of Pigs with 25% and 50% Nebraska Index Line Genes

The Nebraska Index Line excels in reproduction and is being used in industry breeding programs. However, because it has been selected only for litter size since 1981, growth and carcass merit of pure-line pigs are below industry standards. The objectives of this experiment were 1) to compare growth and carcass traits of Index cross pigs with either 50% or 25% Line I genes in a crossbreeding system typical of how the line is used in the industry and 2) to determine the effects of feeding 18 g PAYLEAN® per ton during the last 28 days of the feeding period on Index cross pigs. Line I was crossed with Danbred® USA Landrace (L) boars and Duroc-Hampshire terminal boars to produce F1 pigs with 50% Line I genes and terminal cross pigs with 25% Line I genes. Pigs with 25% Line I genes grew faster (2.03 vs. 1.97 lb/d) from 65 days of age to approximately 240 lb than pigs with 50% Line I genes (P \u3c 0.05). They also ate more feed per day although the difference was not significant (5.82 vs 5.76 lb per d). Thus, the difference between groups in feed conversion was small and not significant. Terminal cross pigs with 25% Line I genes had only 0.02 in less backfat at the end of the experiment than F1 pigs with 50% Line I genes, but they had significantly larger longissimus muscle area (6.42 vs 6.10 in2) and greater percentage carcass lean (52.4 vs 51 %). Pigs of both genetic groups and both barrows and gilts responded similarly to a diet with 18 g PAYLEAN® per ton. Feeding PAYLEAN® at 18 g/ton for 28 days significantly increased growth rate (2.19 vs. 1.80 lb/d), reduced feed intake (6.49 vs. 6.81 lb/d) improved efficiency of growth (0.33 vs 0.26 gain/ feed ratio, corresponding with 3.03 and 3.85 feed/gain ratios), increased carcass weight (185.4 vs 177.2 lb), increased dressing percentage (75.2 vs 74.3%), and increased carcass lean (53.6 vs 49.9%). Performance and carcass merit of pigs with 25% Line I genes were greater than for F1 pigs with 50% Line I genes, and feeding PAYLEAN® at the rate of 18 g per ton produced similar increases in performance and carcass merit of both groups

Scaling unreinforced masonry for reduced-scale seismic testing

When testing multi-storey structures, most testing facilities require the testing of a reduced-scale model. A literature review on tests of scaled masonry structural components revealed that scaling of masonry was rather challenging and often significant differences in stiffness, strength and failure mechanisms between the different sized masonry were reported. This paper addresses the scaling of hollow clay brick masonry with fully mortared head and bed joints. We investigate different choices of scaling brick units and mortar joints. Based on the results of an extensive test programme including standard material tests and quasi-static cyclic tests on masonry walls subjected to horizontal and axial loads, we formulate recommendations for the production of a half-scale model of unreinforced masonry structures. The experimental results show a good match between full-scale and half-scale masonry. We discuss the differences in material properties that remained and compare the force-displacement hystereses obtained for the wall tests

Associations between Maternal Iron Supplementation in Pregnancy and Changes in Offspring Size at Birth Reflect Those of Multiple Micronutrient Supplementation.

It was previously observed that in a population of a high-income country, dietary multiple micronutrient supplementation in pregnancy was associated with an increased risk of gestational diabetes (GDM) and increased offspring size at birth. In this follow-up study, we investigated whether similar changes are observed with dietary iron supplementation. For this we used the prospective Cambridge Baby Growth Study with records of maternal GDM status, nutrient supplementation, and extensive offspring birth size measurements. Maternal iron supplementation in pregnancy was associated with GDM development (risk ratio 1.67 (1.01-2.77), p = 0.048, n = 677) as well as offspring size and adiposity (n = 844-868) at birth in terms of weight (β' = 0.078 (0.024-0.133); p = 0.005), head circumference (β' = 0.060 (0.012-0.107); p = 0.02), body mass index (β' = 0.067 (0.014-0.119); p = 0.01), and various skinfold thicknesses (β' = 0.067-0.094; p = 0.03-0.003). In a subset of participants for whom GDM statuses were available, all these associations were attenuated by adjusting for GDM. Iron supplementation also attenuated the associations between multiple micronutrient supplementation and these same measures. These results suggest that iron supplementation may mediate the effects associated with multiple micronutrient supplementation in pregnancy in a high-income country, possibly through the increased risk of developing GDM