Thermosetting materials are widely used as encapsulation in the electrical packaging to protect the core electronic components from external force, moisture, dust, and other factors. However, the spreading and curing behaviors of such kind of fluid on a heated surface have been rarely explored. In this study, we experimentally and numerically investigated the spreading and curing behaviors of the silicone(OE6550 A/B, which is widely used in the light-emitting diode packaging) droplet with diameter of ~2.2 mm on a heated surface with temperature ranging from 25 ℃ to 250 ℃. For the experiments, we established a setup with high-speed camera and heating unit to capture the fast spreading process of the silicone droplet on the heated surface. For the numerical simulation, we built a viscosity model of the silicone by using the Kiuna's model and combined the viscosity model with the Volume of Fluid(VOF) model by the User Defined Function(UDF) method. The results show that the surface temperature significantly affected the spreading behaviors of the silicone droplet since it determines the temperature and viscosity distribution inside the droplet. For surface temperature varied from 25 ℃ to 250 ℃, the final contact radius changed from ~2.95 mm to ~1.78 mm and the total spreading time changed from ~511 s to ~0.15 s. By further analyzing the viscosity evolution of the droplet, we found that the decreasing of the total spreading time was caused by the decrease of the viscosity under high surface temperature at initial spreading stage, while the reduction of the final contact radius was caused by the curing of the precursor film. This study supplies a strategy to tuning the spreading and curing behavior of silicone by imposing high surface temperature, which is of great importance to the electronic packaging. 相似文献
In graph-based linear dimensionality reduction algorithms, it is crucial to construct a neighbor graph that can correctly
reflect the relationship between samples. This paper presents an improved algorithm called fuzzy local maximal marginal embedding
(FLMME) for linear dimensionality reduction. Significantly differing from the existing graph-based algorithms is that two
novel fuzzy gradual graphs are constructed in FLMME, which help to pull the near neighbor samples in same class nearer and
nearer and repel the far neighbor samples of margin between different classes farther and farther when they are projected
to feature subspace. Through the fuzzy gradual graphs, FLMME algorithm has lower sensitivities to the sample variations caused
by varying illumination, expression, viewing conditions and shapes. The proposed FLMME algorithm is evaluated through experiments
by using the WINE database, the Yale and ORL face image databases and the USPS handwriting digital databases. The results
show that the FLMME outperforms PCA, LDA, LPP and local maximal marginal embedding. 相似文献
This paper deals with a combined test rig for a traction system in the laboratory environment. An experimental system was designed and implemented to verify the performance of the traction system for a metro train. For a highly accurate control of the system, a hybrid control algorithm combining vector control and slip frequency control was applied to control the traction inverter. The design method of the flywheels, which represent the equivalent model of the train moment inertia, was elaborated. A train runtime diagnosis system was completed by adopting the multifunction vehicle bus (MVB) protocol. The dynamic performance of the metro power traction system was emulated under the control of the train runtime diagnosis system. Using the combined test rig, the performances of the traction system in traction, braking, temperature rise, etc., were verified through traction and breaking experiments.
Electric load simulator (ELS) is an important equipment to exert aerodynamic load to actuation system according to flight condition. The key issue of ELS is how to eliminate the influence of extra torque caused by actuation system, parametric uncertainties and uncertain nonlinearities. In order to overcome these difficulties, this paper proposes a powerful model-based adaptive robust torque control (ARTC) algorithm which transfers external disturbance elimination problem to a performance-oriented problem under uncertainties and nonlinearities. A discontinuous projection-based online parameter adaptation is employed to reduce the effect of various parameter uncertainties. Instead of discontinuous friction model, a continuous friction model based on smooth shape function is applied for friction compensation. The estimated velocity of actuator is utilized in ARTC controller for eliminating extra torque. The backstepping design via adaptive robust control Lyapunov function is employed to construct ARTC control law for ELS. Extensive comparative results indicate that the proposed ARTC controller is effective to achieve a guaranteed transient as well as final tracking accuracy in the presence of both parametric uncertainties and uncertain nonlinearities. 相似文献
Smart grid has drawn a lot of attention and investment in recent years, which not only helps the modern generation and distribution of traditional power but also highly widens the application of renewable energy sources. However, the main challenges in the application of smart grid are 1. the privacy preservation of users' information and 2. the trustful transmission channel among peers. In order to solve these problems, VPN and blockchain can be considered since they have some features perfectly suitable for these situations. In this paper, we propose a smart grid system based on WireGuard and Hyperledger Fabric to solve the problems mentioned above. And we also implement the whole system and give a view by web application. What's more, all the functionalities are displayed and tested, including building a smart device simulator, deploying data visualization and making some performance evaluations about transactions and WireGuard communication. Experiment results show that the introduction of WireGuard into network infrastructure does not cause too much loss of bandwidth and delay, but it ensures a certain degree of communication security. And Fabric provides the consistency and traceability of transactions in smart grid system. 相似文献
Robust predictive control handles constrained systems that are subject to stochastic uncertainty but propagating the effects of uncertainty over a prediction horizon can be computationally expensive and conservative. This paper overcomes these issues through an augmented autonomous prediction formulation, and provides a method of handling probabilistic constraints and ensuring closed loop stability through the use of an extension of the concept of invariance, namely invariance with probability p. 相似文献