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

A System Complexity Approach to Swarm Electrification

The study investigates a bottom-up concept for microgrids. Financial analysis is performed through a business model approach to test for viability when replacing a researched energy expenditure baseline in Bangladesh. A literature review compares the approach to current trends in microgrids. A case study of Bangladesh illustrates the potential for building on the existing infrastructure base of solar home systems. Opportunities are identified to improve access to reliable energy through a microgrid approach that aims at community-driven economic and infrastructure development by building on network effects generated through the inclusion of localized economies with strong producer-consumer linkages embedded within larger systems of trade and exchange. The analysed approach involves the linking together of individual stand-alone energy systems to form a microgrid that can eventually interconnect with present legacy infrastructure consisting of national or regional grids. The approach is likened to the concept of swarm intelligence, where each individual node brings independent input to create a conglomerate of value greater than the sum of its parts

Magnetization of ferrofluids with dipolar interactions - a Born--Mayer expansion

For ferrofluids that are described by a system of hard spheres interacting via dipolar forces we evaluate the magnetization as a function of the internal magnetic field with a Born--Mayer technique and an expansion in the dipolar coupling strength. Two different approximations are presented for the magnetization considering different contributions to a series expansion in terms of the volume fraction of the particles and the dipolar coupling strength.Comment: 19 pages, 11 figures submitted to PR

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

Mass Optimisation of Variable Angle Tow, Variable Thickness Panels with Static Failure and Buckling Constraints

By taking advantage of curved fiber paths, Variable Angle Tow (VAT) laminates increase the design space for tailoring the structural behavior of thin-walled aerospace structures. In recent years, advancements in Automated Fiber Placement (AFP) and Continuous Tow Shearing (CTS) have facilitated the manufacture of these laminates. The CTS technique holds the advantage of reducing many of the manufacturing defects characteristic of the AFP process such as fiber wrinkling, tow gaps and tow overlaps, while also allowing for tighter steering radii. On the other hand, the CTS process features added complexity due to the coupling of fiber steering angle with tow thickness. In this study, a minimum- mass design of a typical aircraft wing panel under end-compression subject to pre-defined manufacturing, static failure and buckling load constraints is sought. The geometric effects of the asymmetric thickness distribution of the CTS panel on the critical buckling loads, postbuckling paths and static failure behavior are captured for the first time. A hybrid optimization scheme that couples a genetic algorithm with a pattern-search algorithm is used to define a VAT laminate that reduces the mass of both square and rectangular aircraft panels by 31% compared to a baseline straight fiber design. The optimization of the fiber paths is driven by two distinct requirements, namely local and global stiffness tailoring that inuence the buckling performance and static strength, respectively. Finally, the initial postbuckling behavior of the optimized designs is investigated using Koiter's perturbation approach, which reveals that postbuckling stability should be considered when optimizing VAT panels manufactured by the CTS technique.</p

Virtual Testing of Experimental Continuation

We present a critical advance in experimental testing of nonlinear structures. Traditional quasi-static experimental methods control the displacement or force at one or more load-introduction points on a structure. This approach is unable to traverse limit points in the control parameter, as the immediate equilibrium beyond these points is statically unstable, causing the structure to snap to another equilibrium. As a result, unstable equilibria---observed numerically---are yet to be verified experimentally. Based on previous experimental work, and a virtual testing environment developed herein, we propose a new experimental continuation method that can path-follow along unstable equilibria and traverse limit points. To support these developments, we provide insightful analogies between a fundamental building block of our technique---shape control---and analysis concepts such as the principle of virtual work and Galerkin's method. The proposed testing method will enable the validation of an emerging class of nonlinear structures that exploit instabilities for novel functionality

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

Leukocyte sequestration in pulmonary microvessels and lung injury following systemic complement activation in rabbits

Inflammatory reactions are associated with sequestration of leukocytes in the lung. Complement activation leads to accumulation of leukocytes in alveolar septa and alveoli, to lung edema and hemorrhage. Although in organs other than the lung leukocytes interact with the vascular endothelium only in postcapillary venules, alveolar capillaries are considered to be the site of leukocyte sequestration in the lung. However, pulmonary venules and arterioles have not been investigated systematically after complement activation so far, A closed thoracic window was implanted in anesthetized rabbits; leukocytes and red blood cells were stained, and the movement of these cells was measured in superficial pulmonary arterioles, venules and alveolar capillaries using fluorescence video microscopy before and 30 and 60 min after infusion of cobra venom factor (CVF). Erythrocyte velocity and macrohemodynamic conditions did not change after CVF infusion and were not different from the sham-treated controls. The number of sticking leukocytes increased significantly compared to baseline and control: by 150% in arterioles and in venules and by 740% in alveolar capillaries within 60 min after CVF infusion. The width of alveolar septa in vivo was significantly enlarged after CVF infusion, indicating interstitial pulmonary edema. At the end of the experiments, myeloperoxidase activity was higher in the CVF group, showing leukocyte sequestration in the whole organ. It is concluded that complement activation by CVF induces leukocyte sequestration in lung arterioles, venules and alveolar capillaries and leads to mild lung injury

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 $\sim r^{-n}$. A crossover between qualitatively different sequences of phases occurs near the exponent $n=12$. 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.

Observed crustal uplift near the Southern Patagonian Icefield constrains improved viscoelastic Earth model

Thirty‒one GPS geodetic measurements of crustal uplift in southernmost South America determined extraordinarily high trend rates (> 35 mm/yr) in the north‒central part of the Southern Patagonian Icefield. These trends have a coherent pattern, motivating a refined viscoelastic glacial isostatic adjustment model to explain the observations. Two end‒member models provide good fits: both require a lithospheric thickness of 36.5 ± 5.3 km. However, one end‒member has a mantle viscosity near η =1.6 ×1018 Pa s and an ice collapse rate from the Little Ice Age (LIA) maximum comparable to a lowest recent estimate of 1995–2012 ice loss at about −11 Gt/yr. In contrast, the other end‒member has much larger viscosity: η = 8.0 ×1018 Pa s, half the post–LIA collapse rate, and a steadily rising loss rate in the twentieth century after AD 1943, reaching −25.9 Gt/yr during 1995–2012.Fil: Lange, H.. Technische Universitaet Dresden; AlemaniaFil: Casassa, G.. Centro de Estudios Cientificos; Chile. Universidad de Magallanes; ChileFil: Ivins, E. R.. Institute of Technology. Jet propulsion Laboratory; Estados UnidosFil: Schroeder, L.. Technische Universitaet Dresden; AlemaniaFil: Fritsche, M.. Technische Universitaet Dresden; AlemaniaFil: Richter, Andreas Jorg. Technische Universitaet Dresden; Alemania. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Astrometría; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Groh, A.. Technische Universitaet Dresden; AlemaniaFil: Dietrich, R.. Technische Universitaet Dresden; Alemani