Decoding auditory brain responses with mutual information and the effects of aging

The ability to segregate and understand speech in complex listening scenarios is an inherent property of the human brain. However, this ability deteriorates as the brain ages. The underlying age-related alteration of neural mechanisms is still unclear. Understanding the subcortical and cortical neural mechanisms of auditory processes might be critical in order to get a better understanding of how they degraded by age. Importantly, the likely non-linearity nature of these auditory processes may conceal important internal mechanisms that might not be captured with traditional linear methodology. This thesis develops a novel non-linear approach based on information theory and investigates the non-linear representation of speech in both the midbrain and the cortex. In this dissertation, midbrain and cortical activities from younger and older listeners are noninvasively recorded with both clean speech (i.e. subjects listening to a single speaker) and with adverse listening conditions (i.e. two competing speakers). Additionally, the effect of informational masking is also investigated. Results from the mutual information analysis suggest an age-related deterioration of the response in the midbrain and a strong effect of the informational masking only in older adults. Conversely, the cortical analysis reveals an exaggerated response in older listeners. Interestingly, this exaggerated response is strongly correlated with behavioral measurements, such as speech-in-noise score and behavioral inhibitory control score. Further analysis also reveals that the exaggerated response in the aging cortex manifests only in the neural representation of the low-frequency speech envelope, while at higher frequencies (60-100 Hz) no differences were seen between younger and older listeners. However, the aging cortex demonstrates neural deficits, at such higher frequency, in suppression of the competing speech in challenging listening conditions, shown by an increasing trend of response level with increasing sound level of the competing speech. In summary, this dissertation develops a novel mutual information approach for analyzing neural recordings, and the results reveal new findings of age-related changes in auditory midbrain and cortical activities

Multi-Behavior Recommendation with Cascading Graph Convolution Networks

Multi-behavior recommendation, which exploits auxiliary behaviors (e.g., click and cart) to help predict users' potential interactions on the target behavior (e.g., buy), is regarded as an effective way to alleviate the data sparsity or cold-start issues in recommendation. Multi-behaviors are often taken in certain orders in real-world applications (e.g., click>cart>buy). In a behavior chain, a latter behavior usually exhibits a stronger signal of user preference than the former one does. Most existing multi-behavior models fail to capture such dependencies in a behavior chain for embedding learning. In this work, we propose a novel multi-behavior recommendation model with cascading graph convolution networks (named MB-CGCN). In MB-CGCN, the embeddings learned from one behavior are used as the input features for the next behavior's embedding learning after a feature transformation operation. In this way, our model explicitly utilizes the behavior dependencies in embedding learning. Experiments on two benchmark datasets demonstrate the effectiveness of our model on exploiting multi-behavior data. It outperforms the best baseline by 33.7% and 35.9% on average over the two datasets in terms of Recall@10 and NDCG@10, respectively.Comment: Accepted by WWW 202

Optimization of nano coating to reduce the thermal deformation of ball screws

To reduce the thermal deformation of ball screws, the process of nano coating preparation for coating on ball screws to reduce temperature rise and thereby thermal deformation was discussed in this article. Simultaneously, the cooling mechanism was presented. The thermal channels and the relatively even distribution of graphene in the nano coating were observed in scanning electron microscopic images. In terms of the preparation of nano coating, optimization design was carried out to obtain the optimized material ratio and nozzle flow through orthogonal experiment. The influence of design parameters of nano coating on reducing thermal deformation was also discussed. The experimental results show that the maximum temperature rise, thermal deformation, and time to reach thermal balance decreased by 12.5, 69.1, and 46.3%, respectively. The effectiveness of nano coating in reducing thermal deformation was validated experimentally

Simulation study of a high‐performance brain PET system with dodecahedral geometry

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145295/1/mp12996_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145295/2/mp12996.pd

A New Scheme on Synchronization of Commensurate Fractional-Order Chaotic Systems Based on Lyapunov Equation

This paper proposes a new fractional-order approach for synchronization of a class of fractional-order chaotic systems in the presence of model uncertainties and external disturbances. A simple but practical method to synchronize many familiar fractional-order chaotic systems has been put forward. A new theorem is proposed for a class of cascade fractional-order systems and it is applied in chaos synchronization. Combined with the fact that the states of the fractional chaotic systems are bounded, many coupled items can be taken as zero items. Then, the whole system can be simplified greatly and a simpler controller can be derived. Finally, the validity of the presented scheme is illustrated by numerical simulations of the fractional-order unified system

A New Scheme on Synchronization of Commensurate Fractional-Order Chaotic Systems Based on Lyapunov Equation

This paper proposes a new fractional-order approach for synchronization of a class of fractional-order chaotic systems in the presence of model uncertainties and external disturbances. A simple but practical method to synchronize many familiar fractionalorder chaotic systems has been put forward. A new theorem is proposed for a class of cascade fractional-order systems and it is applied in chaos synchronization. Combined with the fact that the states of the fractional chaotic systems are bounded, many coupled items can be taken as zero items. Then, the whole system can be simplified greatly and a simpler controller can be derived. Finally, the validity of the presented scheme is illustrated by numerical simulations of the fractional-order unified system