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Room-temperature wettability of a single graphene sheet has long been a controversial subject. To gain a better understanding of the problem, temperature dependence of the contact angle (CA) of water nanodroplets with the surface of suspended graphene bilayers was investigated by extensive molecular dynamics (MD) simulations. We also estimated the macroscopic CA Θ M and its dependence on temperature. Four popular Lennard-Jones (LJ) energy parameters ϵ CO for water oxygen−carbon pair interactions, corresponding to Θ M = 23 ± 2, 64 ± 4, 87 ± 3, and 127 ± 2°at 300 K, were utilized in the MD simulations in order to cover a broad range of possible roomtemperature wettability. The MD simulations indicate that for the first three cases with Θ M < 90°, a wetting transition occurs at both nano-and macroscales at a characteristic temperature T w below the water critical temperature T c . The general trends of the dependence of Θ M on the temperature T and the estimate of T w for the third case (Θ M = 87 ± 3°) are in good agreement with the experimental data for water on highly oriented pyrolytic graphite surface. In the case of Θ M = 127°, water nanodroplets detach from the surface at a temperature T d < T c , signaling a drying transition. The extrapolated values of Θ provide evidence for the drying transition at the macroscale as well. This is in contrast to three-dimensional materials for which the drying transition is believed to occur either for ϵ CO = 0 or if weak water−surface interactions are truncated at short distances. The robustness of the results for both drying and wetting transitions is demonstrated by increasing the LJ cutoff radius r c up to the values that further truncation of the potential produces negligible error. In addition, the occurrence of wetting or drying transition at the macroscale was also studied by MD simulation in a slab-like system, for which the macroscopic CA was estimated by calculating it for a thin but long water droplet that is almost free of the line tension effect.

In IEEE 802.16 standard, the performance of the Subscriber Station (SS) MAC has to meet the timing constraints for the uplink and downlink transmissions. This requirement implies hardware acceleration of some protocol components through a precise hardware-software partitioning. In this paper, we first model the behavior of the system through high level Specification and Description Language (SDL). After automatic translation of the SDL model into a true C model, a SoPC platform is used for prototype implementation. Analysis and HW/SW partitioning of the generated model is performed to meet 75Mbps throughput required for OFDM-PHY. The proposed hardware accelerator in this paper has been implemented using a 0.13um CMOS technology in order to perform more detailed analysis on the performance of design which is targeted for ASIC applications. Analysis results show efficiency of our proposed design in terms of area and timing while achieving the required throughput on a low-cost embedded-processor based platform.

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