Studies in general aviation aerodynamics

The Department of Aerospace Engineering at the University of Maryland has completed a research study for NASA Langley on the application of drooped leading edges to high aspect wings. The experimental study conducted for this grant was a natural extension of work previously conducted at NASA Ames, the University of Michigan, NASA Langley and the University of Maryland. Previous research had shown that wing planform modifications (commonly referred to as drooped leading edge mods) could have a significant effect on reducing or eliminating the stall/spin characteristics of General Aviation (GA) aircraft. All aircraft studied in the earlier work had relatively low aspect ratio wings (AR = 6). Since future GA aircraft will feature higher aspect ratio wings, the obvious question was: how well will the dropped leading edge work on higher aspect ratio wings? The focus of the current study was to examine the effectiveness of the drooped leading edge modifications to higher aspect ratio wings with AR = 9 to 12

Consistent estimation of zero-inflated count models

Applications of zero-inflated count data models have proliferated in health economics. However, zero-inflated Poisson or zero-inflated negative binomial maximum likelihood estimators are not robust to misspecification. This paper proposes Poisson quasi-likelihood estimators as an alternative. These estimators are consistent in the presence of excess zeros without having to specify the full distribution. The advantages of the Poisson quasi-likelihood approach are illustrated in a series of Monte Carlo simulations and in an application to the demand for health services.Excess zeros, Poisson, logit, unobserved heterogeneity, misspecification

An experimental investigation of a two and a three-dimensional low speed turbulent boundary layer

Experimental studies of a two and a three-dimensional low speed turbulent boundary layer were conducted on the side wall of a boundary layer wind tunnel. The 20 ft. long test section, with a rectangular cross section measuring 17.5 in. x 46 in., produced a 3.5 in. thick turbulent boundary layer at a free stream Reynolds number. The three-dimensional turbulent boundary layer was produced by a 30 deg swept wing-like model faired into the side wall of the test section. Preliminary studies in the two-dimensional boundary layer indicated that the flow was nonuniform on the 46 in. wide test wall. The nonuniform boundary layer is characterized by transverse variations in the wall shear stress and is primarily caused by nonuniformities in the inlet damping screens

Reconsidering the analysis of longitudinal happiness data - with an application to the effect of unemployment

The paper reconsiders existing estimators for the panel data fixed effects ordered logit model, including one that has not been used in econometric studies before, and studies the small sample properties of these estimators in a series of Monte Carlo simulations. There are two main findings. First, we show that some of the estimators used in the literature are inconsistent. Second, the new estimator seems to be more immune to small sample bias than other consistent estimators and is easy to implement. The empirical relevance is illustrated in an application to the effect of unemployment on happiness. Choosing the right estimator avoids a bias of up to 30 percent in key parameters.Ordered response, panel data, correlated heterogeneity, incidental parameters

Relative status and satisfaction

This paper investigates the relationship between income satisfaction of adult children and their relative economic status, using data from the German Socio-Economic Panel and income rank as an indicator of status. The results show that children appear to compare their actual economic status with that of their parents, deriving large satisfaction gains from an income rank that is higher than that of their parents. The effect is asymmetric with regard to parents, as these seem not to be ifluenced by their children's income rank.happiness, income norm, subjective well-being

The Trade Effects of Endogenous Preferential Trade Agreements

Recent work by Anderson and van Wincoop (2003) establishes an empirical modelling strategy which takes full account of the structural, non-(log-)linear impact of trade barriers on trade in new trade theory models. Structural new trade theory models have never been used to evaluate and quantify the role of endogenous preferential trade agreement (PTA) membership for trade in a way which is consistent with general equilibrium. Apart from this gap, the present paper aims at delivering an empirical model which takes into account both that preferential trade agreement membership is endogenous and that the world matrix of bilateral trade flows contains numerous zero entries. These features are treated in an encompassing way by means of (possibly two-part) Poisson pseudo-maximum likelihood estimation with endogenous binary indicator variables in the empirical model.gravity model, endogenous preferential trade agreement membership, Poisson pseudo-maximum likelihood estimation with endogenous binary indicator variables

The Trade Effects of Endogenous Preferential Trade Agreements

Recent work by Anderson and van Wincoop (2003) establishes an empirical modeling strategy which takes full account of the structural, non-(log-)linear impact of trade barriers on trade in new trade theory models. Structural new trade theory models have never been used to evaluate and quantify the role of endogenous preferential trade agreement (PTA) membership for trade in a way which is consistent with general equilibrium. Apart from this gap, the present paper aims at delivering an empirical model which takes into account both that preferential trade agreement membership is endogenous and that the world matrix of bilateral trade flows contains numerous zero entries. These features are treated in an encompassing way by means of (possibly two-part) Poisson pseudo-maximum likelihood estimation with endogenous binary indicator variables in the empirical model.Gravity model, Endogenous preferential trade agreement membership, Poisson pseudo-maximum likelihood estimation with endogenous binary indicator variables

Project of a superfluid He3 detector for direct detection of non-baryonic dark matter : MACHe3

MACHe3 (MAtrix of Cells of superfluid Helium 3) is a project of non-baryonic Dark Matter search using superfluid He3 as sensitive medium. Simulations on a high granularity matrix show very good rejection against background events. First results on a prototype cell are very encouraging. Neutron detection has been highlighted as well as cosmic muon detection. A phenomenological study has been done with the DarkSUSY code to investigate complementarity of MACHe3 with existing Dark Matter detectors.Comment: 5 pages, 5 figures, to appear in Proceedings of the 4th Marseille International Cosmology Conferenc

Disquisition on material parameters and their influence on wear rates at high temperatures

The aim of this work is to find correlations of hard phase content and matrix type with hot hardness and wear rates in the cyclic impact abrasion test at high testing temperatures. Several materials with different matrix types and varying hard phase content have been investigated regarding their wear behaviour as well as their hot hardness up to 800°C. The hot hardness and hard phase content then was correlated to the wear rates using statistical methods. Materials with comparable matrix properties and higher hard phase content always have higher hot hardness and these parameters are statistically dependent so correlation of wear rate with hot hardness is statistically sufficient. It was found, that within the same material the wear rate is correlated to the hot hardness as long as there is no significant change in the wear mechanism. When the matrix of the material changes the hot hardness can not be directly correlated to the wear rate any more. It was also found that among all materials tested those with an austenitic matrix generally have higher wear resistance even if they have the same hot hardness

Hedonic Adaptation to Living Standards and the Hidden Cost of Parental Income

High parental income, while undeniably causing beneÞts for a child in terms of better access to education and more favorable labor market outcomes, may at the same time increase a childÕs income aspirations and thereby reduce Þnancial satisfaction, ceteris paribus. In this paper, we investigate the relationship between Þnancial satisfaction and parental income with data from the German Socio-Economic Panel. The results indicate that there is indeed a negative well-being externality of parental income, and that children appear to compare their actual income situation with the aspiration level acquired while growing up