411 research outputs found

    High performance implementation of 3D FEM for nonlocal Poisson problem with different ball approximation strategies

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    Nonlocality brings many challenges to the implementation of finite element methods (FEM) for nonlocal problems, such as large number of queries and invoke operations on the meshes. Besides, the interactions are usually limited to Euclidean balls, so direct numerical integrals often introduce numerical errors. The issues of interactions between the ball and finite elements have to be carefully dealt with, such as using ball approximation strategies. In this paper, an efficient representation and construction methods for approximate balls are presented based on combinatorial map, and an efficient parallel algorithm is also designed for assembly of nonlocal linear systems. Specifically, a new ball approximation method based on Monte Carlo integrals, i.e., the fullcaps method, is also proposed to compute numerical integrals over the intersection region of an element with the ball

    SGLD-Based Information Criteria and the Over-Parameterized Regime

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    Double-descent refers to the unexpected drop in test loss of a learning algorithm beyond an interpolating threshold with over-parameterization, which is not predicted by information criteria in their classical forms due to the limitations in the standard asymptotic approach. We update these analyses using the information risk minimization framework and provide Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) for models learned by stochastic gradient Langevin dynamics (SGLD). Notably, the AIC and BIC penalty terms for SGLD correspond to specific information measures, i.e., symmetrized KL information and KL divergence. We extend this information-theoretic analysis to over-parameterized models by characterizing the SGLD-based BIC for the random feature model in the regime where the number of parameters pp and the number of samples nn tend to infinity, with p/np/n fixed. Our experiments demonstrate that the refined SGLD-based BIC can track the double-descent curve, providing meaningful guidance for model selection and revealing new insights into the behavior of SGLD learning algorithms in the over-parameterized regime

    Content Creator versus Brand Advertiser? The Effect of Inserting Advertisements in Videos on Influencers Engagement

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    Influencer advertising has become an indispensable component of online marketing due to the exponential growth of social influencers and their influence. Whereas the effectiveness of using influencer endorsements is well studied from the brand or company perspective, how the commercial endorsements affect influencers themselves is an important yet unrevealed question. We empirically examine the instantaneous (measured using live comment sentiment) and longer-term (measured using video feedback and follower number change) influence of inserting advertisements in videos on influencers’ reputation. We further investigate how this effect can be moderated when influencers demonstrate stronger endorsement by showing their faces during advertisements. Our result suggests that inserting advertisements have a negative impact on both instantaneous and longer-term viewer engagement; advertisements with influencers’ face showing moderate the negative effect of advertisements on viewers’ instantaneous response, while the different impact between advertisements with/out influencers showing their faces is not significant in the longer term

    On the Active Components in Crystalline Li-Nb-O and Li-Ta-O Coatings from First Principles

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    Layered-oxide LiNixMnyCo1xyO2\mathrm{LiNi_xMn_yCo_{1-x-y}O_2} (NMC) positive electrodes with high Nickel content, deliver high voltages and energy densities. However, a high nickel content, e.g., xx = 0.8 (NMC 811), can lead to high surface reactivity, which can trigger thermal runaway and gas generation. While claimed safer, all-solid-state batteries still suffer from high interfacial resistance. Here, we investigate niobate and tantalate coating materials, which can mitigate the interfacial reactivities in Li-ion and all-solid-state batteries. First-principles calculations reveal the multiphasic nature of Li-Nb-O and Li-Ta-O coatings, containing mixtures of LiNbO3\mathrm{LiNbO_3} and Li3NbO4\mathrm{Li_3NbO_4}, or of LiTaO3\mathrm{LiTaO_3} and Li3TaO4\mathrm{Li_3TaO_4}. The concurrence of several phases in Li-Nb-O or Li-Ta-O modulates the type of stable native defects in these coatings. Li-Nb-O and Li-Ta-O coating materials can form favorably lithium vacancies VacLi\mathrm{Vac^{'}_{Li}} and antisite defects NbLi\mathrm{Nb^{\bullet \bullet \bullet \bullet}_{Li}} (TaLi\mathrm{Ta^{\bullet \bullet \bullet \bullet}_{Li}}) combined into charge-neutral defect complexes. Even in defective crystalline LiNbO3\mathrm{LiNbO_3} (or LiTaO3\mathrm{LiTaO_3}), we reveal poor Li-ion conduction properties. In contrast, Li3NbO4\mathrm{Li_3NbO_4} and Li3TaO4\mathrm{Li_3TaO_4} that are introduced by high-temperature calcinations can provide adequate Li-ion transport in these coatings. Our in-depth investigation of the structure-property relationships in the important Li-Nb-O and Li-Ta-O coating materials helps to develop more suitable calcination protocols to maximize the functional properties of these niobates and tantalates
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