Elemental sulfur is not traditionally considered as an
afterglow
material, even though it can be endowed with fluorescence properties
through processing it into nanodots. Herein, we discovered that elemental
sulfur powder could emit room temperature phosphorescence (RTP) with
a lifetime of 3.7 ms. A long-lived (>12 s) afterglow emission at
77
K could also be observed by the naked eye. Detailed investigations
suggested that such a special phenomenon was attributed to impurity-related
traps coupled with conduction and valence bands. After the sulfur
is processed into nanodots, the rigid environment formed by the cross-linking
of the surface ligands could stabilize the excited charges from quenching.
This results in the promotion of RTP intensity and lifetime to achieve
an emission lifetime of 200 ms. These results confirm the unique RTP
of elemental sulfur powder, and also suggest the potential of sulfur-based
materials as versatile components for the development of RTP materials.
Water-environment monitoring network (WMN) is a wireless sensor network based real-time system, which collects, transmits, analyzes and processes water-environment parameters in large area. Both cluster selection mechanisms and energy saving strategies play an important role on designing network routing protocols for the WMN. Since those existing routing algorithms can not be used directly in the WMN, we thus propose an improved version of LEACH, a LEACH-Head Expected Frequency Appraisal (LEACH-HEFA) algorithm, for the WMN in this paper. Simulation results show that the LEACH-HEFA can balance the energy consumption of nodes, rationalize the clustering process and prolong the network lifetime significantly in the WMN. It indicates that the LEACH-HEFA is suitable to the WMN
Urban or regional disaster bearing capacity mainly depends on the disaster bearing capacity of lifeline systems. In the analysis of disaster bearing capacity evaluation of lifeline system, we should not only investigate the complexity, balance and reliability of network characteristics, but also consider the relation between each subsystem. A new brittleness entropy of city disaster vulnerability associated coupling analysis method is proposed based on the brittleness of complex system theory. Correlation characteristics are reflected and evaluated in the brittle link entropy and the whole lifeline system, and then the vulnerability of city lifeline system can be quantified in flood scenarios. As a result of the coupling analysis and calculation, power system has the greatest effect among other subsystems. Because the key factors and influence of water supply system are uncertainties, the water supply system work or supply should be restored first after the disaster. The results show that the method can provide the basis for the optimization of system management, and control the repair work after disaster and coordination between subsystems.
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