Khalifa, United Arab Emirates
Khalifa, United Arab Emirates

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Buyukcakir O.,Korea Advanced Institute of Science and Technology | Je S.H.,Korea Advanced Institute of Science and Technology | Choi D.S.,Korea Advanced Institute of Science and Technology | Talapaneni S.N.,Korea Advanced Institute of Science and Technology | And 5 more authors.
Chemical Communications | Year: 2016

Porous cationic polymers (PCPs) with surface areas up to 755 m2 g-1 bearing positively charged viologen units in their backbones and different counteranions have been prepared. We have demonstrated that by simply varying counteranions both gas sorption and catalytic properties of PCPs can be tuned for metal-free capture and conversion of CO2 into value-added products such as cyclic carbonates with excellent yields. © The Royal Society of Chemistry.

Jishi H.Z.,Khalifa UniversityAbu Dhabi | Umer R.,Khalifa UniversityAbu Dhabi | Cantwell W.J.,Khalifa UniversityAbu Dhabi
Polymer Composites | Year: 2015

Techniques for enhancing the interfacial fracture properties of foam-based sandwich structures are investigated. Prior to manufacture, holes were drilled into a PET foam core in order to facilitate resin flow during the subsequent resin-infusion process. Glass fibers were then inserted into the perforations in an attempt to increase the interfacial fracture toughness of the sandwich structure. The results from these tests are compared to data generated from similar tests on a plain PET core, as well as on samples in which no fiber reinforcement was incorporated into the vertical holes. The inclusion of fibers in the through-thickness holes served to increase the skin-core interfacial fracture toughness of the sandwich structures. Here, it was noted the highest values of fracture toughness were more than three times the value measured on the plain foam system. © 2015 Society of Plastics Engineers.

Talapaneni S.N.,Korea Advanced Institute of Science and Technology | Buyukcakir O.,Korea Advanced Institute of Science and Technology | Je S.H.,Korea Advanced Institute of Science and Technology | Srinivasan S.,Korea Advanced Institute of Science and Technology | And 3 more authors.
Chemistry of Materials | Year: 2015

Postcombustion CO2 capture and the conversion of captured CO2 into value added chemicals are integral part of today's energy industry mainly due to their economic and environmental benefits arising from the direct utilization of CO2 as a sustainable source. Sterically confined N-heterocyclic carbenes (NHCs) have played a significant role in organocatalysis due to their air-stability, super basic nature, and strong ability to activate and convert CO2 gas. Here, we report a new class of nanoporous polymer incorporating sterically confined N-heterocyclic carbenes (NP-NHCs) that exhibit exceptional CO2 capture fixation efficiency of 97% at room temperature, which is the highest ever reported for carbene based materials measured in the solid state. The NP-NHC can also function as a highly active, selective, and recyclable heterogeneous nanoporous organocatalyst for the conversion of CO2 into cyclic carbonates at atmospheric pressure with excellent yields up to 98% along with 100% product selectivity through an atom economy reaction by using epoxides. Narrow pore size distribution of NP-NHC also allowed us to introduce a unique substrate selectivity based on size, just like enzymes, for the corresponding epoxides. This metal-free two in one approach for the CO2 gas fixation/release and conversion provides a new direction for the cost-effective, CO2 capture and conversion processes. © 2015 American Chemical Society.

Marshoud H.,Khalifa UniversityAbu Dhabi | Kapinas V.M.,Khalifa UniversityAbu Dhabi | Kapinas V.M.,Aristotle University of Thessaloniki | Karagiannidis G.K.,Khalifa UniversityAbu Dhabi | And 3 more authors.
IEEE Photonics Technology Letters | Year: 2016

The main limitation of visible light communication (VLC) is the narrow modulation bandwidth, which reduces the achievable data rates. In this letter, we apply the non-orthogonal multiple access (NOMA) scheme to enhance the achievable throughput in high-rate VLC downlink networks. We first propose a novel gain ratio power allocation (GRPA) strategy that considers the users' channel conditions to ensure efficient and fair power allocation. Our results indicate that the GRPA significantly enhances the system performance compared with the static power allocation. We also study the effect of tuning the transmission angles of the light emitting diodes and the field of views of the receivers, and demonstrate that these parameters can offer new degrees of freedom to boost the NOMA performance. The simulation results reveal that NOMA is a promising multiple access scheme for the downlink of VLC networks. © 2015 IEEE.

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