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Graphene nanosheets are widely employed for fabricating high-dielectric-constant polymer nanocomposites for energy storage. However, severely reduced electric breakdown strengths of composites with increasing graphene content limit their high-field applications. To improve breakdown strengths of polyvinylidene fluoride/graphene composites without sacrificing dielectric constants, in this work, we proposed a rational strategy of constructing MXene quantum dot inter-layers for preparing ternary composites with desirable electric properties, owing to inter-layer induced quantum confinement and Coulomb blockade effects. Graphene oxide@nitrogen-doped Ti3C2 MXene quantum-dot hybrid nanoparticles were synthesized via hydrogen-bond induced self-assembly route. Binary polymer/graphene and ternary polymer/hybrid-particle nanocomposite films were fabricated by solution cast process. Compared with binary composites, ternary counterparts have synergistically improved dielectric constants and breakdown strengths. Repeated disorder-bounce of electrons and strong coupling between electrons and holes, inside each quantum dot, might be responsible for superior electric performances of ternary composites. High dielectric constant (~53@1 kHz) and breakdown strength (~205 MV m−1) were realized in ternary composite with 0.12 wt % of nanoparticles. This work might pave a road for large-scale fabrication of high-performance nanocomposite dielectrics for energy storage.

To investigate the influence of nitrogen injection and sealing (N2 I S) on the fracture and permeability of coal reservoirs, two low-rank coal samples from the Fukang (FK) and Wudong (WD) mining areas in the southern margin of the Junggar Basin, China, were collected and used for N2 I S experiments. A Chandler Model 6100 Formation Response Tester (FRT) from the Chandler Company was used for N2 I S experiments with sealing times of 6, 18 and 36 h and a sealing pressure of 584 psi for the samples, and the real-time permeability changes were monitored during the N2 I S process. An NDP-605 NanoDarcy Permeameter was used to test the permeability with different effective stresses before and after N2 I S, and the difference in pore distribution before and after N2 I S was determined by low-field nuclear magnetic resonance (NMR) for the samples. X-ray CT (μCT) was used to observe the changes in the distribution of fractures before and after N2 I S. The results showed that the permeability of FK increased by 43.75%, 91.67% and 162.99% and that of WD increased by 13.96%, 49.92% and 73.68% after 6, 18 and 36 h of sealing time, respectively. For each N2 I S period, the permeability increased with increasing sealing time, while the change rate gradually decreased, as demonstrated by a curve similar to the “Langmuir isotherm adsorption” curve. The stress sensitivity of permeability increased after N2 I S, and the decrease in permeability with increasing effective stress was greater than that of non-N2 I S-treated samples. Low-field NMR showed that the amplitude of 100% water saturation had no obviously changes after N2 I S, which means that no new fracture formed after that. Meanwhile, X-ray CT images also showed that no new fracture formed after N2 I S, but the connectivity is enhanced. Further analysis showed that N2 I S dispersed fracture fillers and opened up the fractures of the coal reservoir, resulting in an enhancement in permeability, but also increased the degree of fracture closure, which caused an increase in the stress sensitivity of the permeability.

The impacts of ambient PM2.5 on public health have become great concerns worldwide, especially in the developing countries. Epidemiological and toxicological studies have shown that PM2.5 does not only induce cardiopulmonary disorders and/or impairments, but also contributes to a variety of other adverse health effects, such as driving the initiation and progression of diabetes mellitus and eliciting adverse birth outcomes. Of note, recent findings have demonstrated that PM2.5 may still pose a hazard to public health even at very low levels (far below national standards) of exposure. The proposed underlying mechanisms whereby PM2.5 causes adverse effects to public health include inducing intracellular oxidative stress, mutagenicity/genotoxicity and inflammatory responses. The present review aims to provide an brief overview of new insights into the molecular mechanisms linking ambient PM2.5 exposure and health effects, which were explored with new technologies in recent years.

With the rapid development of information technology, network security issues become increasingly serious. Forwarding and Control Elements Separation (ForCES) architecture advanced by ForCES working group of IETF routing area can solve network security problems well, which has become an important research direction of next generation Internet. This paper first illustrates the design of stateful packet inspection firewall (SPIF) based on ForCES architecture, and then focuses on the implementation based on network processor. Finally, we test our work and the result verifies the correctness and feasibility of SPIF based on ForCES architecture.

Load-Capacity models are usually used for analyzing the network fault-tolerance and survivability. The node's capacity reflects its redundant resources. We propose an evolutionary algorithm to search an optimized capacity allocation strategy, which makes the network achieve optimal robustness with the same resources. Our algorithm is implemented by the following two steps repeatedly: (1) Construct a new capacity allocation strategy by transferring the capacity among network nodes; and (2) Evaluate the network robustness and then decide whether or not to accept this strategy. It can be considered as a process of simulated annealing. We find that the Load-Capacity relationship seems to be neither the linear nor the preferential-attachment relation. Our works can provide algorithm support for trustworthy network design and the information security emergency response.

'Robust yet fragile (RYF)' is a major feature of Internet survivability. The cascading failure, which is caused by attacks or configuration mistakes, is one of the most serious incidents impact on the network survivability. Taking aim at this incident, this paper proposes a simple 'load-capacity' model based on the 'self-organized criticality' and the 'highly optimized tolerance' theories in complex system. The model is the abstract of the network topology, the dynamics in network protocols and the complex patterns of network behaviors (load). In this model, the network capacity reflects the expectation of survivability. Our research shows that the RYF nature in network is closely related to abnormal network load pattern.