Recently, wireless sensor networks have been widely discussed in many applications. In this paper, we propose a novel 3D emergency service that aims to guide people to safe places when emergencies happen. At normal time, the network is responsible for monitoring the environment. When emergency events are detected, the network can adaptively modify its topology to ensure transportation reliability, quickly identify hazardous regions that should be avoided, and find safe navigation paths that can lead people to exits. In particular, the structures of 3D buildings are taken into account in our design. Simulation results shows that our protocols can adapt emergencies quickly at low message cost and can find safer paths to exits than existing results.

We report a two-step dip-coating approach for the fabrication of self-assembled monolayers of platinum nanocrystals (SAM-Pt) with a particle size of B3 nm and that are uniformly deposited on a transparent conducting oxide (TCO) surface to serve as a counter electrode (CE) for dye-sensitized solar cells (DSSCs). In the first step, we prepared a polyol solution containing H 2 PtCl 6 and ethylene glycol at 110 1C, in which the reduction kinetics were controlled by adding various proportions of NaOH. In the second step, we immersed a thiol-modified TCO substrate into the polyol solution with monodispersed Pt nanoparticles prepared at pH 3.7 at approximately 295 K to complete the nanofabrication. The DSSC devices using Z907 dye as a photosensitizer and the CE prepared using this SAM-Pt approach attained notable photovoltaic performance (Z ¼ 9.2%) comparable with those fabricated using a conventional thermal decomposition method (Z ¼ 9.1%) or a cyclic electrodeposition method (Z ¼ 9.3%) under the same experimental conditions. We emphasize that the SAM-Pt films feature a clean surface, uniform morphology, narrow size distribution, small Pt loading and great catalytic activity; the present approach is hence not only suitable for DSSCs but also applicable for many other energy-related applications that require platinum as an efficient catalyst.

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A method for the synthesis of substituted quinolizinium salts from 2-ethylpyridines and alkynes is demonstrated. The transformation is conveniently achieved using 1 mol % of a Rh(III) catalyst along with an excess amount of copper(II) salt. The reaction gives high product yields with broad substrate scope and functional group tolerance. Detailed mechanistic studies suggest that 2-vinylpyridine is formed in situ from 2-ethylpyridine by a copperpromoted C(sp 3 )−H hydroxylation, followed by dehydration. Later, a Rh(III)-catalyzed pyridine-directed vinylic C(sp 2 )−H activation and annulation with alkynes provided the final product.

Power saving and query processing are two major concerns in a wireless sensor network. Each of these two issues has been intensively studied separately in the literature. In this work, we are interested in linking the asynchronous power-saving protocol and the continuous query-processing problem together. A cross-layer solution is proposed. On the MAC layer, we propose to use the grid-quorum system [25] to serve as the underlying power-saving framework. On the network layer, we propose to find query paths based on the power cost incurred by grid quorums used by nodes along a path. We show how these two layers interwork with each other to support continuous queries in an energy-efficient way.