13,442 research outputs found
A Mass-Spring-Damper Model of a Bouncing Ball (Conference proceeding)
The mechanical properties of a vertically dropped ball, represented by an equivalent mass-spring-damper model, are related to the coefficient of restitution and the time of contact of the ball during one bounce with the impacting surface. In addition, it is shown that the coefficient of restitution and contact time of a single bounce are related to the total number of bounces and the total time elapsing between dropping the ball and the ball coming to rest. For a ball with significant bounce, approximate expressions for model parameters, i.e., stiffness and damping or equivalently natural frequency and damping ratio, are developed. Experimentally based results for a bouncing pingpong ball are presented
Ubiquitination accomplished: E1 and E2 enzymes were not necessary
Qiu et al. (2016) show that a mono-ADP-ribosyltransferase, SdeA, from Legionella pneumophila catalyzes ADP-ribosylation of ubiquitin, allowing SdeA to modify substrate with ubiquitin in the absence of E1 and E2 enzymes
A Mass-Spring-Damper Model of a Bouncing Ball
The mechanical properties of a vertically dropped ball, represented by an equivalent mass-spring-damper model, are shown to be related to impact parameters. In particular, the paper develops relationships connecting the mass, stiffness and damping of a linear ball model to the coefficient of restitution and the contact time of the ball with the surface during one bounce. The paper also shows that the ball model parameters are functions of quantities readily determined in an experiment: (i) the height from which the ball is dropped from rest, (ii) the number of bounces, and (iii) the time elapsing between dropping the ball and the ball coming to rest. For a ball with significant bounce, approximate expressions are derived for the model parameters as well as for the natural frequency and damping ratio. Results from numerical and experimental studies of a bouncing ping-pong ball are presented
Climate Change, Cooperation, and Moral Bioenhancement
The human faculty of moral judgment is not well suited to address problems, like climate change, that are global in scope and remote in time. Advocates of ‘moral bioenhancement’ have proposed that we should investigate the use of medical technologies to make human beings more trusting and altruistic, and hence more willing to cooperate in efforts to mitigate the impacts of climate change. We survey recent accounts of the proximate and ultimate causes of human cooperation in order to assess the prospects for bioenhancement. We identify a number of issues that are likely to be significant obstacles to effective bioenhancement, as well as areas for future research
The equivariant K-theory of toric varieties
This paper contains two results concerning the equivariant K-theory of toric
varieties. The first is a formula for the equivariant K-groups of an arbitrary
affine toric variety, generalizing the known formula for smooth ones. In fact,
this result is established in a more general context, involving the K-theory of
graded projective modules. The second result is a new proof of a theorem due to
Vezzosi and Vistoli concerning the equivariant K-theory of smooth (not
necessarily affine) toric varieties.Comment: 12 page
Convolutional Gated Recurrent Neural Network Incorporating Spatial Features for Audio Tagging
Environmental audio tagging is a newly proposed task to predict the presence
or absence of a specific audio event in a chunk. Deep neural network (DNN)
based methods have been successfully adopted for predicting the audio tags in
the domestic audio scene. In this paper, we propose to use a convolutional
neural network (CNN) to extract robust features from mel-filter banks (MFBs),
spectrograms or even raw waveforms for audio tagging. Gated recurrent unit
(GRU) based recurrent neural networks (RNNs) are then cascaded to model the
long-term temporal structure of the audio signal. To complement the input
information, an auxiliary CNN is designed to learn on the spatial features of
stereo recordings. We evaluate our proposed methods on Task 4 (audio tagging)
of the Detection and Classification of Acoustic Scenes and Events 2016 (DCASE
2016) challenge. Compared with our recent DNN-based method, the proposed
structure can reduce the equal error rate (EER) from 0.13 to 0.11 on the
development set. The spatial features can further reduce the EER to 0.10. The
performance of the end-to-end learning on raw waveforms is also comparable.
Finally, on the evaluation set, we get the state-of-the-art performance with
0.12 EER while the performance of the best existing system is 0.15 EER.Comment: Accepted to IJCNN2017, Anchorage, Alaska, US
Power properties if invariant tests for spatial autocorrelation in linear regression
This paper derives some exact power properties of tests for spatial autocorrelation in the context of a linear regression model. In particular, we characterize the circumstances in which the power vanishes as the autocorrelation increases, thus extending the work of Krämer (2005). More generally, the analysis in the paper sheds new light on how the power of tests for spatial autocorrelation is affected by the matrix of regressors and by the spatial structure. We mainly focus on the problem of residual spatial autocorrelation, in which case it is appropriate to restrict attention to the class of invariant tests, but we also consider the case when the autocorrelation is due to the presence of a spatially lagged dependent variable among the regressors. A numerical study aimed at assessing the practical relevance of the theoretical results is include
Attention and Localization based on a Deep Convolutional Recurrent Model for Weakly Supervised Audio Tagging
Audio tagging aims to perform multi-label classification on audio chunks and
it is a newly proposed task in the Detection and Classification of Acoustic
Scenes and Events 2016 (DCASE 2016) challenge. This task encourages research
efforts to better analyze and understand the content of the huge amounts of
audio data on the web. The difficulty in audio tagging is that it only has a
chunk-level label without a frame-level label. This paper presents a weakly
supervised method to not only predict the tags but also indicate the temporal
locations of the occurred acoustic events. The attention scheme is found to be
effective in identifying the important frames while ignoring the unrelated
frames. The proposed framework is a deep convolutional recurrent model with two
auxiliary modules: an attention module and a localization module. The proposed
algorithm was evaluated on the Task 4 of DCASE 2016 challenge. State-of-the-art
performance was achieved on the evaluation set with equal error rate (EER)
reduced from 0.13 to 0.11, compared with the convolutional recurrent baseline
system.Comment: 5 pages, submitted to interspeech201
- …