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In recent years, unmanned aerial vehicle(UAV) has been developing rapidly which is also widely concerned in the military field, but the research on the communication services for the battlefield is seriously lack of development. Multi-UAV cooperative applications have better performance than single UAV, but the cooperative communication problems between UAVs need to be solved urgently. Therefore,...
High pressure air blowing liquid solder and synchrotron radiation x-ray real-time imaging technology were used to study the interface reactions of Sn-XAg/Cu (X=0, 1, 3) joints during reflow with various soldering time under temperature of 250/275/300°C. This experiment allows us in-situ observe the interfacial IMCs growth and completely avoids Cu6Sn5 precipitation from the solder in cooling stage...
The interfacial reactions in Cu/Sn-9Zn/Ni micro solder joints during reflow under temperature gradient was investigated in this study. And corresponding isothermal reflow of the micro solder joints as a reference experiment was also conducted. The results indicate that the Cu atoms can migrate to the opposite Ni side even against the temperature gradient while the Ni atoms can only migrate to the...
Synchrotron radiation x-ray real-time imaging technology was used to study the interface reactions of Sn/Cu and Sn0.7Cu/Cu joints during reflow with soldering time of 1h under temperature of 300/350 °C. This experiment allows us in-situ observe the interfacial IMCs growth and completely avoids Cu6Sn5 precipitation from the solder in cooling stage to affect the morphology and thickness of interfacial...
The anisotropic behaviors of micro solder interconnects have been recognized as a crucial reliability concern due to the continuous trend of miniaturization in high-performance electronic devices. The hexagonal structure η-Cu6Sn5 with highly anisotropic phase structure has considerable influence on its growth behavior during soldering and performance in service. In the present work, synchrotron radiation...
The Modified Ashworth Scale (MAS) is the gold standard in clinical for grading spasticity. However, its results greatly depend on the physician evaluations and are subjective. In this study, we investigated the feasibility of using support vector machine (SVM) to objectively assess elbow spasticity based on both surface electromyography (sEMG) and mechanomyography (MMG). sEMG signals and tri-axial...
This paper proposes a new delay HIV (Human Immunodeficiency Virus) epidemic model with switching parameters and pulse control. We investigate the global attractivity of infection-free periodic solution and the persistence of the disease. Furthermore, two thresholds which govern the extinction and the persistence of the epidemic disease are derived. Numerical simulations are performed to illustrate...
This paper is concerned with the problem of the exponential passive filter design for neutral-type neural networks with time-varying mixed delays. First, a Luenberger-type filter is designed for estimating the network states. Second, by constructing an appropriate Lyapunov-Krasovskii functional and using the so-called Wirtinger-based integral inequality to estimate its derivative, a delay-range-dependent...
Development of low temperature wafer level hybrid bonding process using Cu/SnAg bump and photosensitive adhesive was reported. Two kinds of photosensitive adhesives, i.e., polyimide and dry film, were selected for adhesive bonding. The proposed hybrid bonding method has been successfully applied to 8 inch wafer to wafer bonding. Hybrid bonding using both polyimide and dry film achieved seam-free bonding...
Queueing models can be used to evaluate the performance of manufacturing systems. Due to the emergence of cluster tools in contemporary production systems, proper queueing models have to be derived to evaluate the performance of machines with complex configurations. Job cascading is a common structure among cluster tools. Because of the blocking and starvation effects among servers, queue time analysis...
A tunable liquid antenna is designed and analyzed. The ability of adjustment is realized with the help of a thin post penetrating the solid dielectric and the liquid layers. The influence of the thickness and parameters of the substrate is investigated. The performance of different liquid materials including sea water, oil and distilled water is analyzed as well. The influence of the distribution...
Positioning of wireless sensor network node is essentially an optimization problem of measurements based on different distance or path. In the discussion of simulated annealing algorithm and node location of wireless sensor networks, proposed localization algorithm and its realization based on simulated annealing combined with the objective function. Simulation results show that the algorithm achieved...
Based on MCGS (Monitor and Control Generated System) software a training diagnosis system for a certain kind of equipment is designed and developed. Through analysis of the structure of the equipment composition and working principles of the process a two-dimensional simulation model is established. The model can achieve simple operation training. Using common equipment for fault modeling, a fault...
An antenna with both solid dielectric and liquid materials is designed and analyzed. The influence of the thickness and parameters of the substrate is investigated. The performance of different liquid materials including sea water, oil and distilled water is analyzed. The influence of the distribution of the liquid and other relevant factors are studied. The simulation results revealed the validity...
The influence of season and terrain on the performance of the scene matching end guidance is studied, respectively. Seasonal changes would result in the regular transformation of surface vegetation, especially the ratio of water, which could change the electromagnetic characteristics of the ground. Complex permittivity changes regularly according to the liquid water storage per unit, while the quantity...
As bubbles on the solder/copper interface can seriously decrease the joint reliability of lead-free soldering in electronic packaging industry, the research of interfacial bubbles is extremely imperative. In the local area around an interfacial bubble, the Cu atoms tend to migrate towards the gas/solid interface, providing the copper element to form the interfacial intermetallic compounds (IMCs)....
Synchrotron radiation x-ray imaging technique was applied for in-situ observation of interfacial bubbles in Cu/molten Sn-3.5Ag/Cu joint undergoing thermomigration. The heating plate temperature was maintained at 350 °C and reflow time of 1 h was considered. Interfacial bubbles at hot side, favoured by wetting transition for growth, increase the effective thermal gradient in the solder medium. The...
This study investigated the interfacial reaction of Ni/Sn-9Zn/Ni solder joints undergoing liquid-solid thermomigration by reflowing the solder joints on a hot plate. The simulated working temperature and temperature gradient across the liquid solder layer were about 240 °C and 976 °C/cm, respectively. Zn and Ni atoms were forced to migrate towards the cold end by temperature gradient, which resulted...
With rising concerns on energy and environment, the energy-efficient operation techniques in railway systems are paid more attention in recent years. The metro-transit system has some distinguishing features like short headway and a high number of stations with short interstation distance, which makes effectively using regenerative energy becoming more significant in the energy-saving study. This...
One approach to reduce energy consumption in railway systems is to implement optimised train trajectories. These are speed profiles that reduce energy consumption without foregoing customer comfort or running times. This is achieved by avoiding unnecessary braking and running at reduced speed whilst maintaining planned arrival times. An optimised train trajectory can be realised using a driver advisory...
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