Functional Gradient Material of Ti-6Al-4V and γ-TiAl Fabricated by Electron Beam Selective Melting

Additive Manufacturing (AM) technologies are very promising in fabricating functionally graded materials. Electron Beam Selective Manufacturing (EBSM) is one widely used AM technology capable of fabricating a variety of materials especially titanium alloys. Previous studies on EBSM process were focused on the manufacturing of one single material. In this study, a novel EBSM process capable of building gradient structures with dual metal materials was developed. Ti6Al4V powders and Ti47Al2Cr2Nb powders were used to fabricate Ti3Al/TiAl and Ti6Al4V/Ti3Al dual metal structures. The chemical compositions, microstructure and micro-hardness of the dual material samples were investigated employing Optical Microscope (OM), Scanning Electronic Microscope (SEM), Electron Probe Micro-Analyzer (EPMA). Results showed that the thickness of the transition zone was about 300μm. The transition zone was free of cracks, and the chemical compositions exhibited a staircase-like change. The microstructure and chemical compositions in different regions were studied. Microhardness was affected by the microstructure. The microstructures turned out to be full lamellar at the TiAl region and basket-weave structure at the Ti3Al and Ti6Al4V region.Mechanical Engineerin

Filter Band Multicarrier Based Transmission Technology for Clinical EEG Signals

A transmission scheme is proposed based on filter band multicarrier (FBMC) transmission technology for clinical electroencephalogram (EEG) signals. The proposed scheme integrates binary phase shift keying (BPSK) and offset quadrature amplitude modulation (OQAM), an FBMC transmission mechanism, and low-density parity-check code (LDPC) error protection in an FBMC-based EEG mobile communication system. The proposed EEG mobile communication system employs high-speed transmission, with schemes providing significant error protection for mobile communication of clinical EEG signals requiring a stringent bit-error rate (BER). The performances of BERs and mean square errors (MSEs) of the proposed EEG mobile communication system were explored. Simulation results show that the proposed scheme is a superior transmission platform as compared to existing schemes for clinical EEG signals