Resonant forcing of nonlinear systems of differential equations

We study resonances of nonlinear systems of differential equations, including but not limited to the equations of motion of a particle moving in a potential. We use the calculus of variations to determine the minimal additive forcing function that induces a desired terminal response, such as an energy in the case of a physical system. We include the additional constraint that only select degrees of freedom be forced, corresponding to a very general class of problems in which not all of the degrees of freedom in an experimental system are accessible to forcing. We find that certain Lagrange multipliers take on a fundamental physical role as the effective forcing experienced by the degrees of freedom which are not forced directly. Furthermore, we find that the product of the displacement of nearby trajectories and the effective total forcing function is a conserved quantity. We demonstrate the efficacy of this methodology with several examples.Comment: 9 pages, 3 figure

Employment Adjustments on the Internal and External Labour Market: An Empirical Study with Personnel Records of a German Company

Firms are affected by the product demand. This leads to employment adjustments. In the literature we find only very few contributions investigating the issue whether internal adjustments are linked and which relationships exist with external adjustments. Are they of a complementary or substitutive nature? Furthermore, it is of interest to find out, whether we can observe an obvious trend and whether the adjustments are driven by cyclical movements. For this study we have an extensive data set of a large German manufacturing company, which supplies innovative products for the domestic and international market, provided on a monthly base from January 1999 to December 2005. The empirical analysis starts with descriptive statistics. We find that the employment adjustment cycle coincides only to a certain degree with the macroeconomic cycle. Internal and external adjustments are more characterized by complementarity than by substitution. Over the observed period we cannot detect analogous wage adjustments. It is noticeable that in 2003 compared with the years before the number of employees is substantially reduced. The econometric investigation is based on a two-stage approach. We start with a bivariate probit estimation in order to extract the relationship between the probability of overtime and of promotion. Unobserved variables have opposite effects on the former and the latter adjustment instrument. Furthermore, we detect a negative trend of internal employment adjustments. Cyclical effects are ambiguous. The next step, the determination of external adjustments with respect to overtime and promotion adjustments, is split into two estimates. On the one hand we do not distinguish between the type of external employment adjustment and on the other hand we use this information separating between quits, layoffs, workers with a cancellation agreement and with a transition into a transfer organisation. The first approach demonstrates that a promotion reduces the probability to leave the firm while overtime is positively associated with an external job change. This pattern holds generally speaking in the second, more detailed estimates. Quits are the exception. In this case we observe opposite effects. Finally, we cannot detect any influences of promotions on cancellation agreements. --Personnel records,overtime,promotion,job mobility,cancellation agreement,transfer organisation

Do Women Manage Smaller Funds?

Based on a sample of 467 asset managers from four countries we robustly find that women manage smaller funds than men, despite tough competition in this industry. Interestingly, the gender gap exists only for managers of smaller funds, i.e. at the lower end of the hierarchy, as quantile regressions show. This is inconsistent with the glass ceiling hypothesis. Going further, this gender gap is limited to large firms. Explanations may refer to large firms using market power in the area of smaller funds or to "visibility" among top asset managers protecting against unequal treatment of the sexes.segregation, asset managers, gender, attitudes, qualification

Heritability of time preference: evidence from German twin data

Intergenerational correlations of time preference are well documented. However, there is still limited empirical evidence about the role of genetics in this transmission process. In our paper, we use data on roughly 3,000 twins from the German TwinLife project to estimate the heritability of time preference. We rely on an experimentally validated survey measure of temporal discounting, namely, self-assessed patience. The analysis of monozygotic and dizygotic twins enables us to apply standard biometric models. We find that genetic differences explain up to 23 percent of individual variation in patience. Whereas the additive genetic effect and common environmental effects are of minor importance, a major dominant genetic effect is present. These results indicate a notable degree of genetic influence on economic time preferences

Enhanced Strength and Ductility in Magnesium Matrix Composites Reinforced by a High Volume Fraction of Nano- and Submicron-Sized SiC Particles Produced by Mechanical Milling and Hot Extrusion

In the present study, Mg nanocomposites with a high volume fraction (10 vol %) of SiC particles were fabricated by two approaches: mechanical milling and mixing, followed by the powder consolidation steps, including isostatic cold pressing, sintering, and extrusion. A uniform distribution of the high content SiC particles in a fully dense Mg matrix with ultrafine microstructure was successfully achieved in the mechanically milled composites. The effect of nano- and submicron-sized SiC particles on the microstructure and mechanical properties of the nanocomposites was evaluated. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), and X-ray diffractometry (XRD) were used to characterize microstructures of the milled and mixed composites. Mechanical behavior of the Mg composites was studied under nanoindentation and compressive loading to understand the effects the microstructural modification on the strength and ductility of the Mg/SiC composites. The mechanical properties of the composites showed a significant difference regarding the size and distribution of SiC particles in the Mg matrix. The enhanced strength and superior ductility achieved in the mechanically milled Mg composites are mainly ascribed to the effective load transfer between matrix and SiC particles, grain refinement of the matrix, and strengthening effects of the nano- and submicron-sized SiC particles.DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli

South-North convergence from a new perspective

This North-South model of Schumpeterian endogenous growth combines a market, productivity and knowledge effect. A set of various convergent and divergent growth paths is derived that is much richer than in the literature so far. South-North convergence based on North-South technology diffusion through intermediate goods trade is guaranteed if the knowledge effect dominates the productivity effect. Moreover, a larger Southern market expands the area of convergence and can prevent divergence. Not only a larger Southern market size, but also a higher Southern steady state growth rate benefit the North so that convergence is desirable for both, the South and the North

Evolutionary dynamics of structural features

Structural features have the potential to push the time barrier, after which we cannot test hypotheses about relatedness of languages, back in time. However, we have to know the stability of structural features in order to be able to apply them for such purposes. In this thesis I describe the typological profile of the Transeurasian languages, which serve as a data sample for the analysis of stability, build a phylogenetic tree with these languages, measure the stability of structural features as phylogenetic signal and evolutionary rate, reconstruct ancestral states of structural features and apply an admixture model from population genetics to test the performance of phonological, morphological and syntactic features in assigning languages to their respective language families and to investigate the level of diffusion in these three feature sets. More than half of structural features appear to have a high phylogenetic signal and evolve at a slow rate. I compare the stability across functional categories, parts of speech and language levels and come to a conclusion that argument marking (flagging and indexing), derivation and valency are the most stable functional categories, pronouns and nouns the most stable parts of speech and phonology and morphology the most stable language levels. The admixture model as implemented in STRUCTURE is able to correctly identify Turkic, Mongolic and Tungusic language families at the levels of morphology and syntax, whereas Japonic and Koreanic languages are assigned to the same ancestry. We see the least amount of admixture at the level of morphology and the highest level of admixture in syntactic features. One of the most important insights is that morphological features carry the most genealogical information, and these features could be used in the future to test relationships above the language family level

Phylogenetic signal and rate of evolutionary change in language structures

Within linguistics, there is an ongoing debate about whether some language structures remain stable over time, which structures these are and whether they can be used to uncover the relationships between languages. However, there is no consensus on the definition of the term ‘stability’. I define ‘stability’ as a high phylogenetic signal and a low rate of change. I use metric D to measure the phylogenetic signal and Hidden Markov Model to calculate the evolutionary rate for 171 structural features coded for 12 Japonic, 2 Koreanic, 14 Mongolic, 11 Tungusic and 21 Turkic languages. To more deeply investigate the differences in evolutionary dynamics of structural features across areas of grammar, I divide the features into 4 language domains, 13 functional categories and 9 parts of speech. My results suggest that there is a correlation between the phylogenetic signal and evolutionary rate and that, overall, two-thirds of the features have a high phylogenetic signal and over a half of the features evolve at a slow rate. Specifically, argument marking (flagging and indexing), derivation and valency appear to be the most stable functional categories, pronouns and nouns the most stable parts of speech, and phonological and morphological levels the most stable language domains