In the present work, a microchannel reactor for autothermal reforming of methanol using a synthesized catalyst porous alumina support-CuO/ZnO mixed with ZrO2 sol washcoat has been developed and its fine structure and inner surface characterized. Experimentally, CuO/ZnO and alumina support with ZrO2 sol washcoat catalyst (catalyst slurries) nanoparticles is the catalytically active component of the microreactor. Catalyst slurries have been dried at 298 K for 5 h and then calcined at 623 K for 2 h to increase the surface area and specific pore structures of the washcoat catalyst. The surface area of BET N2 adsorption isotherms for the as-synthesized catalyst and catalyst/ZrO2 sol washcoat samples are 62 and 108 ± 2 m2g−1, respectively. The intensities of Cu content from XRD and XPS data indicate that Al2O3 with Cu species to form CuAl2O4. The EXAFS data reveals that the Cu species in washcoat samples have Cu-O bonding with a bond distance of 1.88 ± 0.02 Å and the coordination number is 3.46 ± 0.05, respectively. Moreover, a hydrogen production rate of 2.16 L h−1 is obtained and the corresponding methanol conversion is 98% at 543 K using the CuO/ZnO with ZrO2 sol washcoat catalyst.
SUMMARYGiven a video/audio streaming system installed on a multichannel multiradio wireless mesh network, we are interested in a problem concerning about how to construct a delay‐constrained multicast tree to support concurrent interference‐free transmissions so that the number of serviced mesh clients is maximized. In this paper, we propose a heuristic approach called cross‐layer and load‐oriented (CLLO) algorithm for the problem. On the basis of the cross‐layer design paradigm, our CLLO algorithm can consider application demands, multicast routing, and channel assignment jointly during the formation of a channel‐allocated multicast tree. The experimental results show that the proposed CLLO outperforms the layered approaches in terms of the number of serviced mesh clients and throughputs. This superiority is due to information from higher layers can be used to guide routing selection and channel allocation at the same time. As a result, the CLLO algorithm can explore more solution spaces than the traditional layered approaches. In addition to that, we also propose a channel adjusting procedure to enhance the quality of channel‐allocated multicast trees. According to our simulations, it is proved to be an effective method for improving the performance of the proposed CLLO algorithm. Copyright © 2013 John Wiley & Sons, Ltd.
Given a video stream delivering system deployed on a multicast tree, which is embedded in a multi-channel multi-radio wireless mesh network, our problem is concerned about how to allocate interference-free channels to tree links and maximize the number of serviced mesh clients at the same time. In this paper, we propose a channel allocation heuristic algorithm based on best-first search and backtracking techniques. The experimental results show that our BFB based CA algorithm outperforms previous methods such as DFS and BFS based CA methods. This superiority is due to the backtracking technique used in BFB approach. It allows previous channel-allocated links to have feasibility to select the other eligible channels when no conflict-free channel can be found for the current link during the CA process. In addition to that, we also propose a tree refinement method to enhance the quality of channel-allocated trees by adding uncovered destinations at the cost of deletion of some covered destinations. Our aim of this refinement is to increase the number of serviced mesh clients. According to our simulation results, it is proved to be an effective method for improving multicast trees produced by BFB, BFS and DFS CA algorithms.
Wireless mesh networks (WMNs) have been increasingly used to carry multimedia traffic with flow requirements. The performance of multi-radio multi-channel (MRMC) WMNs largely depends on the routing and channel assignment. Because routing and channel decisions are coupled, they need to be jointly optimized to achieve the best performance. This is the so-called routing and channel assignment (RCA) problem, which is known to be NP-hard. There has not been sufficient consideration on joint RCA optimization which takes into account multimedia traffic demands in the network.In this paper, we propose and study CRAFT (Channel and Routing Assignment with Flow Traffic) for MRMC WMNs. CRAFT is distributed, cooperative, computationally efficient and simple to implement. It jointly optimizes routing and channel assignment by using a properly designed objective function to meet the flow demands of the mesh nodes. Simulation results based on NS3 show that CRAFT performs much better than other state-of-the-art schemes in terms of convergence, delay, loss rate and throughput.
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