PAPR suppressing matrix transform and dual layered phase sequencing design for a chaos-based multi-carrier CDMA VLC system.

In this paper, we propose a chaos-based visible light communication system, wherein multiple users can access the network via the multi-carrier code division multi-access (MC-CDMA). By utilizing the high security property of chaotic sequences being aperiodic and sensitive to initial values, secure access can be achieved. However, the multi-carrier transmission suffers from high peak to average power ratio (PAPR) due to the superposition of multiple carriers, which reduces the lifetime of the light-emitting diodes (LEDs). In order to suppress the PAPR, we propose a joint matrix transform and dual layered phase sequencing (MT-DLPS) scheme. By reducing the autocorrelations of signals, the PAPR can be reduced. Moreover, the computation complexity is analyzed. Simulations are then conducted to validate that the PAPR is effectively reduced while maintaining satisfactory bit error rate (BER) performances.

Application of recycled carbon-fibre-reinforced polymers as reinforcement for epoxy foams.

The ever-increasing demand for carbon fibre reinforced polymers (CFRP) and stringent environmental legislation have driven the research into recycling and reusing the CFRP waste. This paper presents a mechanical recycling process of CFRP and the application of the recyclates as reinforcement for epoxy foams. The CFRP was mechanically processed using a jet mill. Up to 10 wt% of the CFRP recyclates, without separation of fibre-rich portion and resin-rich portion, was added into epoxy foams. The compressive modulus and strength of the epoxy foams increased from 288 MPa and 7.0 MPa, respectively, to 1060 MPa and 22.8 MPa, respectively, accompanied with an increase in foam density from 0.37 g cm-3 to 0.68 g cm-3. Consequently, the specific compressive modulus and strength (normalised against density) increased from 789 MPa cm3 g-1 and 19.1 MPa cm3 g-1 for unreinforced foam to 1563 MPa cm3 g-1 and 33.5 MPa cm3 g-1 for CFRP recyclates reinforced foam, representing a 98% and 75% improvement, respectively. These results demonstrate that the CFRP recyclates have excellent reinforcing ability for epoxy foams.