1,721,106 research outputs found
Reliability Assessments of Lead-contained and Lead-free BGA Solder Joints under Cyclic Bending Loads
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EXPERIMENTAL-STUDY OF MASS-TRANSFER AROUND A TURBULENCE PROMOTER BY THE LIMITING CURRENT METHOD
No full textA MIMO antenna structure that combines transmit beamforming and spatial multiplexing
No full textWe propose a new closed-loop MIMO (Multiple-Input Multiple-Output) signal processing scheme that combines transmit beamforming and spatial multiplexing in Rayleigh frequency-flat fading channel environment. Diversity gain. achieved by beamforming, and multiplexing gain by spatial multi-IS plexing. The proposed scheme is particularly useful for downlink communication, where the number of transmit antennas at the base station is greater than the number of receive antennas at the mobile. Beamforming weight vectors are computed at the receiver using the estimated channel matrix and are sent to the transmitter. The computation is based on the mutual information maximization criterion which reduces to a symmetric eigenvalue problem. The BER (Bit Error Rate) performance comparisons with other known schemes are also presented for the cases of the AIL (Maximum Likelihood) decoding and the MMSE (Minimum Mean-Squared Error) nulling and ordered-cancellation decoding, through extensive-Monte-Carlo simulation. The simulation results show that the proposed scheme has lower BER than the other schemes
EFFECT OF YTTRIUM ON THE STABILITY OF ALUMINIDE YTTRIUM COMPOSITE COATINGS IN A CYCLIC HIGH-TEMPERATURE HOT-CORROSION ENVIRONMENT
No full textA composite coating of aluminide-yttrium has shown excellent corrosion resistance in a cyclic high-temperature hot-corrosion environment. To understand the effect of yttrium on the stability of the composite coating, the specimens were prepared with various coating parameters of Y thickhess, sequence of post heat treatment and surface condition before Y-ion plating, Performance of the composite coating was evaluated by isothermal oxidation and cyclic high-temperature hot corrosion. Isothermal-oxidation-test results show that the Y in the composite coating helps to form a thick and dense Al2O3 scale which is ductile and resistant to thermal stress. The Y in Al2O3 may act as a donor which leads to an increase in concentration of interstitial oxygen and, thus, increases in oxidation rate. The presence of Y2O3 and (Y, Al) O-type compounds in grain boundaries of Al2O3 and boundaries between the Al2O3 and NiAl effectively prohibits the fast diffusion of oxidants (such as O and S) and Al along grain boundaries, Consequently, it may induce slow diffusion through the matrix, and thus the corrosion resistance of the composite coating under cyclic hot corrosion increases substantially.11sciescopu
Investigation of applicability of electromagnetic energy harvesting system to inclined stay cable under wind load
No full textElectromagnetic-type energy harvesting systems utilizing wind or traffic induced vibration
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A comparative study of the fatigue Behavior of SnAgCu and SnPb solder joints
No full textFatigue behaviors of 63Sn37Pb and two types of lead-free solder joints were compared using pseudo-power cycling testing method, which provides more realistic load cycling to solder joints than chamber cycling method does. Pseudo-power cycling test was performed in various temperature ranges to evaluate the shear strain effect. A nonlinear finite element model was used to simulate the thermally induced visco-plastic deformation of solder joint in BGA packages. The results revealed that lead free solder joints have a good fatigue property in the low temperature condition, where a small strain was induced. In the high temperature condition where a large strain was induced, however, lead contained solder joints have a longer fatigue life
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