20 research outputs found
Towards Efficient Record and Replay: A Case Study in WeChat
WeChat, a widely-used messenger app boasting over 1 billion monthly active
users, requires effective app quality assurance for its complex features.
Record-and-replay tools are crucial in achieving this goal. Despite the
extensive development of these tools, the impact of waiting time between replay
events has been largely overlooked. On one hand, a long waiting time for
executing replay events on fully-rendered GUIs slows down the process. On the
other hand, a short waiting time can lead to events executing on
partially-rendered GUIs, negatively affecting replay effectiveness. An optimal
waiting time should strike a balance between effectiveness and efficiency. We
introduce WeReplay, a lightweight image-based approach that dynamically adjusts
inter-event time based on the GUI rendering state. Given the real-time
streaming on the GUI, WeReplay employs a deep learning model to infer the
rendering state and synchronize with the replaying tool, scheduling the next
event when the GUI is fully rendered. Our evaluation shows that our model
achieves 92.1% precision and 93.3% recall in discerning GUI rendering states in
the WeChat app. Through assessing the performance in replaying 23 common WeChat
usage scenarios, WeReplay successfully replays all scenarios on the same and
different devices more efficiently than the state-of-the-practice baselines
Active Fault Tolerance Control Based on Consistent Matrix for Multimotor Synchronous System
This paper presents an active fault-tolerant method to mitigate sensor failures in multimotor synchronous control. First, inspired by the construction of the coupling matrix in complex network synchronous output, a consistent matrix is designed based on structural redundancy in synchronous control. This consistent matrix has two advantages: one is that it can reflect different sensor output similarities and the other one is that it can detect, locate, and estimate the sensor fault. Then, the fault information is integrated into the design of tolerance control with an improved mean feedback mechanism. The proposed method is suitable for both single and multiple fault situations, and its effectiveness is finally verified by both MATLAB simulation and the ABB semiphysical experimental platform
Subtidal Flow Reversal Associated With Sediment Accretion in a Delta Channel
In branching delta channel networks, tides intrude into parallel river outlets causing complex tidal behavior. The tidal motion can impact the division of river discharge over distributary channels. Under some circumstances, the discharge averaged over a tidal cycle may even reverse, drawing ocean water intox the delta, such as observed in the Yangtze Delta, the Fly Delta and the Colorado Delta. Here, we study the flow reversal associated with sediment accumulation of a distributary channel in terms of tidal propagation and subtidal discharge dynamics, by focusing on the Yangtze Delta. The Yangtze Delta channel configuration represents a deep and wide main channel and a smaller side channel that has rapidly accreted over the past decades. A new mechanism is presented, which results in seawater transport across the shallow side channel, posing a risk to freshwater availability. The shallowest section in the side channel nearly acts as a tidal divide. In this section, the tide has the character of a standing wave, which implies that Stokes transport converges from opposite sides of the channel. This leads to significant variation of the total water storage in the side channel and subtidal water levels in the side channel being elevated above that in the main channel. The bulge of water that is stored during spring tide leaves the side channel toward neap tide, explaining reversal of the tide-averaged discharge and seawater intrusion when the river discharge is low.</p
Tidal impacts on the subtidal flow division at the main bifurcation in the Yangtze River Delta
Flow division at bifurcations in the Yangtze Estuary has received ample attention, since it may control the pathways of terrestrial sediments over downstream river branches including the 12.5 m Deepwater Navigation channel. While some efforts have been made to interpret flow division at the bifurcations of the Yangtze Estuary, little attention has been paid to the role of tides. Flow division at estuarine bifurcations is made complicated by tides that propagate from the outlet of the tidal channels into the delta. To quantify the tidal influence on the distribution of river discharge, and more generally, to understand the mechanisms governing the subtidal flow division at the tidally affected bifurcation in the Yangtze River Delta, a two-dimensional hydrodynamic model is employed. In this model, the landward boundary is chosen beyond the tidal limit, where the tidal motion has faded out entirely. The seaward boundary is chosen such that the river discharge does not influence the water level. Subtidal discharges are decomposed using the method of factor separation, to distinguish between the effects of tides, river discharge and river-tide interactions on the subtidal flow division. Results indicate that tides modify the river discharge distribution over distributary channels in the Yangtze River Delta, particularly in the dry season. A significant difference in the subtidal flow division during spring tide and neap tide shows that the tidally averaged flow division over the distributaries in the delta greatly depends on tidal amplitude. By varying the river discharge at the landward boundary and amplitudes and phases of the principal tidal constituents at the seaward boundary of the established model, the sensitivities of the subtidal flow division to the river discharge and tidal amplitude variation were investigated in detail. Generally, the tidal impacts on the subtidal flow division are around 12% to 22%, with river discharge varying from 30,000 m3s-1 to 20,000 m3s-1. This effect on the flow distribution can even overwhelm the effects induced by river discharge based on geometry only, when the flow discharge is lowest. Furthermore, the fortnightly tidal cycle plays an important role in enhancing the inequality of the subtidal flow division caused by the M2 tidal component solely at the tidal bifurcation in the Yangtze River Delta during low flow
Deterioration of organic coatings on concrete under artificial aging
The deterioration of organic coatings on concrete is closely linked to the efficiency in the protection process of reinforced structures. In the present work, polyurea resin and epoxy resin, which are widely used engineering coatings, were selected to measure and compare the performance under artificial aging. Fourier Transform infrared spectroscopy, water contact angle and scanning electron microscope were used to determine the deterioration of coatings. X-ray fluorescence method was used to measure chloride content passing through the coatings, which represent the efficiency of protection. Test results demonstrate that both deterioration and resistance to corrosion are important in assessment of the organic coatings under aging
MLCV: Bridging Machine-Learning-Based Dimensionality Reduction and Free-Energy Calculation
Full spectrum core-shell phosphors under ultraviolet excitation
Full spectrum core-shell phosphors under ultraviolet excitatio
Massive red-shifting of Ce3+ emission by Mg2+ and Si4+ doping of YAG:Ce transparent ceramic phosphors
Massive red-shifting of Ce3+ emission by Mg2+ and Si4+ doping of YAG:Ce transparent ceramic phosphor
Spectrum regulation of YAG:Ce transparent ceramics with Pr, Cr doping for white light emitting diodes application
YAG:Ce transparent ceramics with high luminous efficiency and color render index were prepared via a solid state reaction-vacuum sintering method. Cr3+ and Pr3+ were applied to expand the spectrum of YAG:Ce transparent ceramics. As prepared ceramics exhibit luminescence spectrum ranging from 500 nm to 750 nm, which almost covers full range of visible light. After the concentration optimization of Ce3+, Pr3+ and Cr3+, high quality white light was obtained by coupling the YAG:Ce,Pr,Cr ceramics with commercial blue LED chips. Color coordinates of the YAG:Ce,Pr,Cr ceramics under 450 nm LED excitation vary from cold white light to warm white light region. The highest luminous efficiency of WLEDs encapsulated by transparent YAG:Ce,Pr,Cr ceramic was 89.3 Im/W, while its color render index can reach nearly 80. Energy transfers between Ce3+ -> Pr3+ and Ce3+ -> Cr3+ were proved in co-doped ceramic system. Transparent luminescence ceramics accomplished in this work can be quite prospective for high power WLED5 application. (C) 2017 Elsevier Ltd. All rights reserved