Fall Prediction for New Sequences of Motions

Abstract. Motions reinforce meanings in human-robot communication, when they are relevant and initiated at the right times. Given a task of using motions for an autonomous humanoid robot to communicate, different sequences of relevant motions are generated from the motion library. Each motion in the motion library is stable, but a sequence may cause the robot to be unstable and fall. We are interested in predicting if a sequence of motions will result in a fall, without executing the sequence on the robot. We contribute a novel algorithm, ProFeaSM, that uses only body angles collected during the execution of single motions and interpolations between pairs of motions, to predict whether a sequence will cause the robot to fall. We demonstrate the efficacy of ProFeaSM on the NAO humanoid robot in a real-time simulator, Webots, and on a real NAO and explore the trade-off between precision and recall

State-dependent potentials for the 1S0^1\text{S}_{0} and 3P0^3\text{P}_{0} clock states of neutral ytterbium atoms

We present measurements of three distinctive state-(in)dependent wavelengths for the $^1\text{S}_{0}-^3\text{P}_{0}$ clock transition in $^{174}\text{Yb}$ atoms. Specifically, we determine two magic wavelengths at $652.281(21)\,$THz and $542.50205(19)\,$THz, where the differential light shift on the $^1\text{S}_{0}-^3\text{P}_{0}$ clock transition vanishes, and one tune-out wavelength at $541.8325(4)\,$THz, where the polarizability of the $^1\text{S}_{0}$ ground state exhibits a zero crossing. The two new magic wavelengths are identified by spectroscopically interrogating cold $^{174}\text{Yb}$ atoms on the clock transition in a one-dimensional optical lattice. The ground-state tune-out wavelength is determined via a parametric heating scheme. With a simple empirical model, we then extrapolate the ground and excited state polarizability over a broad range of wavelengths in the visible spectrum

Atomic scale analysis of the GaP Si 100 heterointerface by in situ reflection anisotropy spectroscopy and ab initio density functional theory

A microscopic understanding of the formation of polar on nonpolar interfaces is a prerequisite for well defined heteroepitaxial preparation of III V compounds on 100 silicon for next generation high performance devices. Energetically and kinetically driven Si 100 step formations result in majority domains of monohydride terminated Si dimers oriented either parallel or perpendicular to the step edges. Here, the intentional variation of the Si 100 surface reconstruction controls the sublattice orientation of the heteroepitaxial GaP film, as observed by in situ reflection anisotropy spectroscopy RAS in chemical vapor ambient and confirmed by benchmarking to surface science analytics in ultrahigh vacuum. Ab initio density functional calculations of both abrupt and compensated interfaces are carried out. For P rich chemical potentials at abrupt interfaces, Si P bonds are energetically favored over Si Ga bonds, in agreement with in situ RAS experiments. The energetically most favorable interface is compensated with an intermixed interfacial layer. In situ RAS reveals that the GaP sublattice orientation depends on the P chemical potential during nucleation, which agrees with a kinetically limited formation of abrupt interface

Light trapping gratings for solar cells an analytical period optimization approach

Solar cells can harvest incident sunlight very efficiently by utilizing grating based light trapping. As the working principle of such gratings strongly depends on the number as well as the propagation directions of the diffraction orders, the grating period is a key parameter. We present an analytical model for optimizing the grating period, focusing on its impact on light path enhancement and outcoupling probability. Based on the presented model, we formulate guidelines to maximize light trapping in state of the art high end solar cells. The model increases the understanding of the grating performance in systems like the III V Si triple junction solar cell achieving record efficienc

Nonradiative lifetime extraction using power-dependent relative photoluminescence of III-V semiconductor double-heterostructures

A power-dependent relative photoluminescence measurement method is developed for double-heterostructures composed of III-V semiconductors. Analyzing the data yields insight into the radiative efficiency of the absorbing layer as a function of laser intensity. Four GaAs samples of different thicknesses are characterized, and the measured data are corrected for dependencies of carrier concentration and photon recycling. This correction procedure is described and discussed in detail in order to determine the material's Shockley-Read-Hall lifetime as a function of excitation intensity. The procedure assumes 100% internal radiative efficiency under the highest injection conditions, and we show this leads to less than 0.5% uncertainty. The resulting GaAs material demonstrates a 5.7 ± 0.5 ns nonradiative lifetime across all samples of similar doping (2–3 × 10^(17) cm^(−3)) for an injected excess carrier concentration below 4 × 10^(12) cm^(−3). This increases considerably up to longer than 1 μs under high injection levels due to a trap saturation effect. The method is also shown to give insight into bulk and interface recombination

Twenty-five years of two-dimensional rational conformal field theory

In this article we try to give a condensed panoramic view of the development of two-dimensional rational conformal field theory in the last twenty-five years.Comment: A review for the 50th anniversary of the Journal of Mathematical Physics. Some references added, typos correcte

Civil Society, Everyday Life and the Possibilities for Development Studies

Civil society is one of the most contentious terms in political thought. There is considerable, and highly significant, difference between academic debate about the meaning of ‘civil society’ and the way the term is mobilized in international development discourse. In particular, narratives of civil society in international development are often dominated by reference to organizational descriptions and measurability. But I would like to suggest here that the term should be reclaimed as a way of giving meaning to the stories of the everyday lives of the people who create, shape and embody civil society. Used in this way, the idea of civil society can be understood as intersecting emotions, discourses and practices and can add to the body of scholarly work that nurtures and values everyday life as a lens through which to view wider social processes. Paying attention to the everyday life of civil society may have implications for that way the civil society is engaged with academically, and also has the potential to refresh how civil society is thought about in development practice

Improved Upper Limit on the Neutrino Mass from a Direct Kinematic Method by KATRIN.

We report on the neutrino mass measurement result from the first four-week science run of the Karlsruhe Tritium Neutrino experiment KATRIN in spring 2019. Beta-decay electrons from a high-purity gaseous molecular tritium source are energy analyzed by a high-resolution MAC-E filter. A fit of the integrated electron spectrum over a narrow interval around the kinematic end point at 18.57 keV gives an effective neutrino mass square value of (-1.0_{-1.1}^{+0.9})  eV^{2}. From this, we derive an upper limit of 1.1 eV (90% confidence level) on the absolute mass scale of neutrinos. This value coincides with the KATRIN sensitivity. It improves upon previous mass limits from kinematic measurements by almost a factor of 2 and provides model-independent input to cosmological studies of structure formation