Thermal elastohydrodynamic lubrication of spur gears

An analysis and computer program called TELSGE were developed to predict the variations of dynamic load, surface temperature, and lubricant film thickness along the contacting path during the engagement of a pair of involute spur gears. The analysis of dynamic load includes the effect of gear inertia, the effect of load sharing of adjacent teeth, and the effect of variable tooth stiffness which are obtained by a finite-element method. Results obtained from TELSGE for the dynamic load distributions along the contacting path for various speeds of a pair of test gears show patterns similar to that observed experimentally. Effects of damping ratio, contact ratio, tip relief, and tooth error on the dynamic load were examined. In addition, two dimensionless charts are included for predicting the maximum equilibrium surface temperature, which can be used to estimate directly the lubricant film thickness based on well established EHD analysis

NormFace: L2 Hypersphere Embedding for Face Verification

Thanks to the recent developments of Convolutional Neural Networks, the performance of face verification methods has increased rapidly. In a typical face verification method, feature normalization is a critical step for boosting performance. This motivates us to introduce and study the effect of normalization during training. But we find this is non-trivial, despite normalization being differentiable. We identify and study four issues related to normalization through mathematical analysis, which yields understanding and helps with parameter settings. Based on this analysis we propose two strategies for training using normalized features. The first is a modification of softmax loss, which optimizes cosine similarity instead of inner-product. The second is a reformulation of metric learning by introducing an agent vector for each class. We show that both strategies, and small variants, consistently improve performance by between 0.2% to 0.4% on the LFW dataset based on two models. This is significant because the performance of the two models on LFW dataset is close to saturation at over 98%. Codes and models are released on https://github.com/happynear/NormFaceComment: camera-ready versio

Network performance isolation for latency-sensitive cloud applications

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Direct CP violation in two-body hadronic charmed meson decays

Motivated by the recent observation of CP violation in the charm sector by LHCb, we study direct CP asymmetries in the standard model (SM) for the singly Cabibbo-suppressed two-body hadronic decays of charmed mesons using the topological-diagram approach. In this approach, the magnitude and the phase of topological weak annihilation amplitudes which arise mainly from final-state rescattering can be extracted from the data. Consequently, direct CP asymmetry $a_{dir}^{\rm (tree)}$ at tree level can be reliably estimated. In general, it lies in the range $10^{-4}<a_{dir}^{\rm (tree)}<10^{-3}$. Short-distance QCD penguins and penguin annihilation are calculated using QCD factorization. Their effects are generally small, especially for $D\to VP$ modes. Since weak penguin annihilation receives long-distance contributions from the color-allowed tree amplitude followed by final-state rescattering, it is expected to give the dominant contribution to the direct CP violation in the decays $D^0\to K^+K^-$ and $D^0\to \pi^+\pi^-$ in which $a_{dir}^{\rm (tree)}$ is absent. The maximal $\Delta a_{CP}^{\rm dir}$, the direct CP asymmetry difference between the above-mentioned two modes, allowed in the SM is around -0.25%, more than $2\sigma$ away from the current world average of $-(0.645\pm 0.180)$.Comment: 19 pages, 2 figures; typos correcte

Flow transitions and combined free and forced convective heat transfer in rotating curved channels: The case of positive rotation

The simultaneous effects of curvature, rotation and heating/cooling in channel flow complicate the flow and heat transfer characteristics beyond those observed in the channels with simple curvature or rotation. The phenomena encountered are examined for steady, hydrodynamically and thermally fully developed flow in square channels. The governing equations are solved numerically by using a finite-volume method. Certain hitherto unknown flow patterns are found. And the results show both the nature of the flow transition and the effect of this transition on the distributions of temperature, friction factor and Nusselt number in a square channel. © 1996 American Institute of Physics.published_or_final_versio

Visualization of flows in curved channels with a moderate or high rotation speed

Flows in channels with streamwise curvature and spanwise rotation are visualized in terms of end-view near the exit of the test sections through injecting smoke into the flows. Two test sections are used, i.e. the rectangular channels with the aspect ratio of 1 and 10, respectively. The work focuses on visualization of Dean and Coriolis vortices under the effects of secondary instabilities and flows in the region with a relatively high rotation speed. The results show that the secondary instabilities cause the Dean and Coriolis vortices oscillating in various forms and the flows at high rotation speeds are controlled by the secondary instabilities rather than the primary instability. In particular, the secondary instabilities lead the flows to be unsteady and turbulent somewhat like the bursting flow in the turbulent boundary layers. © 1997 OPA (Overseas Publishers Association) Amsterdam B.V.published_or_final_versio