Comparison of Constrained Parameterisation Strategies for Aerodynamic Optimisation of Morphing Leading Edge Airfoil

In the context of ambitious targets for reducing environmental impact in the aviation sector, dictated by international institutions, morphing aircraft are expected to have potential for achieving the required efficiency increases. However, there are still open issues related to the design and implementation of deformable structures. In this paper, we compare three constrained parameterisation strategies for the aerodynamic design of a morphing leading edge, representing a potential substitute for traditional high-lift systems. In order to facilitate the structural design and promote the feasibility of solutions, we solve a multi-objective optimisation problem, including constraints on axial and bending strain introduced by morphing. A parameterisation method, inherently producing constant arc length curves, is employed in three variants, representing different morphing strategies which provide an increasing level of deformability, by allowing the lower edge of the flexible skin to slide and the gap formed with the fixed spar to be closed by a hatch. The results for the optimisation of a baseline airfoil show that the geometric constraints are effectively handled in the optimisation and the solutions are smooth, with a continuous variation along the Pareto frontier. The larger shape modification allowed by more flexible parameterisation variants enables an increase of the maximum lift coefficient up to 8.35%, and efficiency at 70% of stall incidence up to 4.26%

Two essays on individual preferences toward means-tested income transfers.

This thesis examines public preferences toward the structure of means-tested income transfer programs using nationally representative survey data on individuals' expressed preferences revealed through experimental methods and measures of their economic and demographic characteristics. In the first essay I relate the cash public assistance awards of respondents to characteristics of hypothetical recipient families to examine benefit targeting and adequacy. Measured demographic and financial dimensions indicating need and "deservingness" often have large effects on transfers. Most important for the young recipients are the number of young children and the labor force status of the mother or father. For the elderly recipients, large asset holdings in the form of savings or home equity and the presence of financially well-off children are determinants of transfers. Preferred income guarantees are more generous than officially defined poverty thresholds for most families by type and size, except for the largest families. Income guarantees and benefit reduction rates are quite high for the elderly. Guarantees and benefit reduction rates for young recipients are lower relative to the elderly, but still appear higher than those advocated by commentators who stress the importance of low guarantees and benefit reduction rates to encourage labor supply for working age recipients. In the second essay I relate cash transfers to characteristics of respondents to examine the insurance motive of dem and s for income transfers. I construct and analyze models in which the individual's economic problem is to choose the benefits he would like to see the government transfer to low-income households given he views such cash assistance as an insurance policy in the event his own family income falls to some low level making him eligible for welfare payments. Respondent income guarantees are then related to calculated measures of expected benefits and costs likely received and paid by respondents. Responses of the nonelderly toward the young recipients were consistent with the self-insurance motive: income guarantees increased with the ratio of expected benefits to expected costs. However, there was no evidence supportive of self-interest as an explanation of transfers to elderly woman recipients by the elderly and near-elderly.Ph.D.Labor economicsPublic policyUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/161962/1/8821637.pd

Factors Associated With School Meal Participation and the Relationship Between Different Participation Measures

This study investigated factors that infl uence students’ participation in the National School Lunch Program (NSLP) and School Breakfast Program (SBP). The analysis used recently collected data on a large, nationally representative sample of students certifi ed for free and reduced-price meals during the 2005–06 school year. Results show that, although eligible students are very likely to participate in the programs (i.e. pick up the meal offered that day), eligible elementary school students are more likely to participate than are middle or high school students. Likewise, students who like the taste of the meals are more likely to participate than are students who do not like the taste. In addition, if students now eligible for reduced-price lunches were instead given free lunches, they would participate more than they do now. The same was not strictly the case, however, for breakfast. Finally, the study suggests that analysts should use caution in relying on parents’ reports of a student’s participation to estimate yearly school meal participation. Parental reports of the previous day’s or previous week’s participation tend to overstate participation, which results in higher reported annual participation rates than is true according to administrative data

A Longitudinal Analysis of White Women's Wages

According to human capital theory, women's work participation decisions will strongly affect their wages and wage growth. We test human capital predictions about how labor force withdrawals, both past and prospective, part-time work experience, and working in "male" rather than in "female" jobs affect wages and wage growth for white women. We do this by estimating a wage change model for the years 1967-1979 for a national sample of white women. We find that wages drop immediately following withdrawals, but that this is followed by a rapid wage growth so that the net loss in wages from dropping out of the labor force is small. We further find that wage growth is not significantly lower in "female" than in "male" jobs, but that part-time work experience does not lead to significant wage growth, in either "male" or "female" jobs.

The effects of cashing-out food stomps on household food use and the cost of issuing benefits

The recent report produced by Vice President Gore's committee on government efficiency highlights the importance of streamlining government operations. But often there are trade-offs between administrative streamlining and accomplishing substantive program objectives. This article examines these tradeoffs in the context of the Food Stamp Program, an important component of the United States' safety net for providing low-income assistance. We estimate impacts on both administrative costs and substantive outcomes (participant food expenditures) resulting from issuing program benefits in the form of checks rather than the usual food coupons. The findings, which are based on experimental tests of the cashout approach in parts of Alabama and California, suggest that significant cost savings can be attained through cashout but that these savings may be achieved at the cost of weakening the program's ability to achieve its substantive objective of encouraging food use.