1,077 research outputs found
On the topological pressure of random bundle transformations in sub-additive case
In this paper, we define the topological pressure for sub-additive potentials
via separated sets in random dynamical systems and we give a proof of the
relativized variational principle for the topological pressure.Comment: 16page
Graph Analysis in Decentralized Online Social Networks with Fine-Grained Privacy Protection
Graph analysts cannot directly obtain the global structure in decentralized
social networks, and analyzing such a network requires collecting local views
of the social graph from individual users. Since the edges between users may
reveal sensitive social interactions in the local view, applying differential
privacy in the data collection process is often desirable, which provides
strong and rigorous privacy guarantees. In practical decentralized social
graphs, different edges have different privacy requirements due to the distinct
sensitivity levels. However, the existing differentially private analysis of
social graphs provide the same protection for all edges. To address this issue,
this work proposes a fine-grained privacy notion as well as novel algorithms
for private graph analysis. We first design a fine-grained relationship
differential privacy (FGR-DP) notion for social graph analysis, which enforces
different protections for the edges with distinct privacy requirements. Then,
we design algorithms for triangle counting and k-stars counting, respectively,
which can accurately estimate subgraph counts given fine-grained protection for
social edges. We also analyze upper bounds on the estimation error, including
k-stars and triangle counts, and show their superior performance compared with
the state-of-the-arts. Finally, we perform extensive experiments on two real
social graph datasets and demonstrate that the proposed mechanisms satisfying
FGR-DP have better utility than the state-of-the-art mechanisms due to the
finer-grained protection
NADiffuSE: Noise-aware Diffusion-based Model for Speech Enhancement
The goal of speech enhancement (SE) is to eliminate the background
interference from the noisy speech signal. Generative models such as diffusion
models (DM) have been applied to the task of SE because of better
generalization in unseen noisy scenes. Technical routes for the DM-based SE
methods can be summarized into three types: task-adapted diffusion process
formulation, generator-plus-conditioner (GPC) structures and the multi-stage
frameworks. We focus on the first two approaches, which are constructed under
the GPC architecture and use the task-adapted diffusion process to better deal
with the real noise. However, the performance of these SE models is limited by
the following issues: (a) Non-Gaussian noise estimation in the task-adapted
diffusion process. (b) Conditional domain bias caused by the weak conditioner
design in the GPC structure. (c) Large amount of residual noise caused by
unreasonable interpolation operations during inference. To solve the above
problems, we propose a noise-aware diffusion-based SE model (NADiffuSE) to
boost the SE performance, where the noise representation is extracted from the
noisy speech signal and introduced as a global conditional information for
estimating the non-Gaussian components. Furthermore, the anchor-based inference
algorithm is employed to achieve a compromise between the speech distortion and
noise residual. In order to mitigate the performance degradation caused by the
conditional domain bias in the GPC framework, we investigate three model
variants, all of which can be viewed as multi-stage SE based on the
preprocessing networks for Mel spectrograms. Experimental results show that
NADiffuSE outperforms other DM-based SE models under the GPC infrastructure.
Audio samples are available at: https://square-of-w.github.io/NADiffuSE-demo/
Applicability of magnetic force models for multi-stable energy harvesters
Multi-stable piezoelectric energy harvesters have been exploited to enhance performance for extracting ambient vibrational energy from a broadband energy source. Since magnetic force plays a significant role in enhancing the dynamic behavior of harvesters, it is necessary to model and understand the significant influencing of structural parameters on magnetic force. Recently, several theoretical modeling methods, including magnetic dipole, improved dipole, magnetic current, and magnetic charge models, have been developed to calculate the magnetic force in multi-stable energy harvesters. However, the influence of structural parameters and magnet dimensions on the accuracy of magnetic force calculation for these methods has not been analyzed. Therefore, it is necessary to investigate the applicability of these methods under a range of operating conditions. New insights into the accuracy and application constraints of these methods are presented in this paper to calculate the impact of magnetic force on multi-stable energy harvesters. From the theoretical derivation of models and numerical results obtained, a quantitative assessment of errors under different structural parameters and magnet sizes is presented and compared to evaluate the application constraints. Moreover, experimental measurements are performed to verify the applicability of these modeling methods for bi-stable and tri-stable energy harvesters with different structural parameters.</p
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