4,218 research outputs found
Static inconsistencies in certain axiomatic higher-order shear deformation theories for beams, plates and shells
AbstractStatic inconsistencies that arise when modelling the flexural behaviour of beams, plates and shells with clamped boundary conditions using a certain class of axiomatic, higher-order shear deformation theory are discussed. The inconsistencies pertain to displacement-based theories that enforce conditions of vanishing shear strain at the top and bottom surfaces a priori. First it is shown that the essential boundary condition of vanishing Kirchhoff rotation perpendicular to an edge (w,x=0 or w,y=0) is physically inaccurate, as the rotation at a clamped edge may in fact be non-zero due to the presence of transverse shear rotation. As a result, the shear force derived from constitutive equations erroneously vanishes at a clamped edge. In effect, this boundary condition overconstrains the structure leading to underpredictions in transverse bending deflection and overpredictions of axial stresses compared to high-fidelity 3D finite element solutions for thick and highly orthotropic plates. Generalised higher-order theories written in the form of a power series, as in Carrera’s Unified Formulation, do not produce this inconsistency. It is shown that the condition of vanishing shear tractions at the top and bottom surfaces need not be applied a priori, as the transverse shear strains inherently vanish if the order of the theory is sufficient to capture all higher-order effects. Finally, the transverse deflection of the generalised higher-order theories is expanded in a power series of a non-dimensional parameter and used to derive a material and geometry dependent shear correction factor that provides more accurate solutions of bending deflection than the classical value of 5/6
To Claim or Not to Claim: Estimating Non-take-up of Social Assistance in Germany and the Role of Measurement Error
Using representative micro data from the German Socio-Economic Panel Study (SOEP) for the year 2002, we analyse non-take-up behaviour of Social Assistance (SA) inGermany. According to our simulation as much as 67 percent of the eligible population did not claim SA in that year which is slightly higher than reported in previous work. We particularly emphasize the role of measurement error in estimating non-take-up. First, we consider misspecifications of the simulation model due, e.g., to households claiming to have received SA although not simulated as eligible ("beta-error"). Second, we employ sensitivity analyses revealing the impact of measurement errors in reported household income and wealth as well as in simulated needs. Misreported household incomes appear to have the greatest impact on the estimated non-take-up rates, as shown in Monte-Carlo-type simulations. Regression analysis of the potential determinants of non-take-up behaviour confirm that rational motives - i.e., the expected net utility from claiming - as well as stigma and other barriers play a crucial role in explaining the puzzle of large non-take-up rates of SA.Non-take-up, social assistance, measurement error, microsimulation, SOEP
Shape Control for Experimental Continuation
An experimental method has been developed to locate unstable equilibria of
nonlinear structures quasi-statically. The technique involves loading a
structure by application of either a force or a displacement at a main
actuation point, while simultaneously controlling the overall shape using
additional probe points. The method is applied to a shallow arch, and unstable
segments of its equilibrium path are identified experimentally for the first
time. Shape control is a fundamental building block for the experimental---as
opposed to numerical---continuation of nonlinear structures, which will
significantly expand our ability to measure their mechanical response.Comment: Updated Figure 6 experimental results with correct calibration factor
for linear transducer. Updated Figure 6 finite element results with correct
load multiplier for half-model. Updated paper text to reflect these changes.
5 pages, 6 figure
Crystal structures and freezing of dipolar fluids
We investigate the crystal structure of classical systems of spherical
particles with an embedded point dipole at T=0. The ferroelectric ground state
energy is calculated using generalizations of the Ewald summation technique.
Due to the reduced symmetry compared to the nonpolar case the crystals are
never strictly cubic. For the Stockmayer (i.e., Lennard-Jones plus dipolar)
interaction three phases are found upon increasing the dipole moment:
hexagonal, body-centered orthorhombic, and body-centered tetragonal. An even
richer phase diagram arises for dipolar soft spheres with a purely repulsive
inverse power law potential . A crossover between qualitatively
different sequences of phases occurs near the exponent . The results are
applicable to electro- and magnetorheological fluids. In addition to the exact
ground state analysis we study freezing of the Stockmayer fluid by
density-functional theory.Comment: submitted to Phys. Rev.
Dealing with Incomplete Household Panel Data in Inequality Research
Population surveys around the world face the problem of declining cooperation and participation rates of respondents. Not only can item nonresponse and unit nonresponse impair important outcome measures for inequality research such as total household disposable income; there is also a further case of missingness confronting household panel surveys that potentially biases results. The approach commonly used in such surveys of interviewing all adult household members and aggregating their individual incomes to yield a final outcome measure for welfare analyses often suffers from partial unit non-response (PUNR), i.e., the non-response of at least one unit, or member, of an otherwise participating household. In these cases, the aggregate income of all household members lacks at least one individual's income. These processes are typically not random and require appropriate correction. Using data from more than twenty waves of the German Socio-Economic Panel (SOEP) we evaluate four different strategies to deal with this phenomenon: (a) Ignorance, i.e., assuming the missing individual's income to be zero. (b) Adjustment of the equivalence scale to account for differences in household size and composition. (c) Elimination of all households observed to suffer PUNR, and re-weighting of households observed to be at risk of but not affected by PUNR. (d) Longitudinal imputation of the missing income components. The aim of this paper is to show how the choice of technique affects substantive results in the inequality research. We find indications of substantial bias on income inequality and poverty as well as on income mobility. These findings are obviously even more important in cross-national comparative analyses if the data providers in the individual countries deal differently with PUNR in the underlying data.Household Panel Surveys, Partial Unit Non-Response, Inequality, Mobility, Imputation, SOEP
Economic Gains from Publicly Provided Education in Germany
The aim of this paper is to estimate income advantages arising from publicly provided education and to analyse their impact on the income distribution in Germany. Using representative micro-data from the SOEP and considering regional and education-specific variation, from a cross-sectional perspective the overall result is the expected levelling effect. When estimating the effects of accumulated educational transfers over the life course within a regression framework, however, and controlling for selectivity of households with children as potential beneficiaries of educational transfers, we find evidence that social inequalities are increasing from an intergenerational perspective, reinforced in particular by public transfers for non-compulsory education, thus negating any social equalisation effects achieved within the compulsory education framework.Education, Public Transfers, Income Distribution, Economic Wellbeing, SOEP
The Impact of Home Production on Economic Inequality in Germany
Using representative income and time use-data from the German Socio-Economic Panel (SOEP), we estimate non-monetary income advantages arising from home production and analyse their impact on economic inequality. As an alternative to existing measures, we propose a predicted wage approach based on a bias-adjusted measure of hours spent on home production. Sensitivity analyses comparing results obtained from different approaches provide indications of methodological effects arising from the choice of method. Although the substantive notion of reduced inequality is stable, the degree of variation in our findings underscores the need for a harmonized approach in cross-nationally comparative research.home production, non-cash incomes, economic inequality, well-being, SOEP
Dealing with Incomplete Household Panel Data in Inequality Research
Population surveys around the world face the problem of declining cooperation and participation rates of respondents. Not only can item nonresponse and unit nonresponse impair important outcome measures for inequality research such as total household disposable income; there is also a further case of missingness confronting household panel surveys that potentially biases results. The approach commonly used in such surveys of interviewing all adult household members and aggregating their individual incomes to yield a final outcome measure for welfare analyses often suffers from partial unit non-response (PUNR), i.e., the non-response of at least one unit, or member, of an otherwise participating household. In these cases, the aggregate income of all household members lacks at least one individual's income. These processes are typically not random and require appropriate correction. Using data from more than twenty waves of the German Socio-Economic Panel (SOEP) we evaluate four different strategies to deal with this phenomenon: (a) Ignorance, i.e., assuming the missing individual's income to be zero. (b) Adjustment of the equivalence scale to account for differences in household size and composition. (c) Elimination of all households observed to suffer PUNR, and re-weighting of households observed to be at risk of but not affected by PUNR. (d) Longitudinal imputation of the missing income components. The aim of this paper is to show how the choice of technique affects substantive results in the inequality research. We find indications of substantial bias on income inequality and poverty as well as on income mobility. These findings are obviously even more important in cross-national comparative analyses if the data providers in the individual countries deal differently with PUNR in the underlying data.Household Panel Surveys, Partial Unit Non-Response, Inequality, Mobility, Imputation, SOEP
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