A subwavelength MIM waveguide resonator with an outer portion smooth bend structure

We systematically investigate bends in metal–insulator–metal (MIM) subwavelength plasmonic waveguides resonator, realized in a two-dimensional (2D) plasmon polariton metal using a finite-difference time-domain (FDTD) method with perfectly matched layers (PMLs) boundary conditions. We apply the outer portion of the bend structure in resonator which can lead to remarkably good bending transmission characteristics. We discuss the existence conditions of different modes which affect the device performance, and analyze coupling efficiency of the outer portion of the bend structure resonator in detail. Meanwhile, we find that the first dip of the outer portion smooth bend resonator nearly linear shifts toward longer wavelengths with the increase of the effective waveguiding length. In addition, add/drop directional couplers are realizable using the present resonator structure.     

Ferroelectric and magnetic properties of ferroelectromagnetic PbFe1/2Nb1/2O3 type ceramics

PbFe_1/2Nb_1/2O₃ (PFN) ceramics, to which an admixture of manganese oxide (MnO₂) was added, was obtained by calcination of the powder in a single stage synthesis. Compacting was made by a free sintering method. Results of investigations of microstructure, magnetic, magnetoelectric, dielectric and piezoelectric properties and electric conductivity vs. temperature are presented. The influence of manganese admixture on the physical properties of the PFN ceramics is presented. The admixtures decrease the electric conduction of the PFN ceramic specimens.     

Transition metals on the (0 0 0 1) surface of graphite: Fundamental aspects of adsorption,diffusion, and morphology

In this article, we review basic information about the interaction of transition metal atoms with the (0 0 0 1) surface of graphite, especially fundamental phenomena related to growth. Those phenomena involve adatom-surface bonding, diffusion, morphology of metal clusters, interactions with steps and sputter-induced defects, condensation, and desorption. General traits emerge which have not been summarized previously. Some of these features are rather surprising when compared with metal-on-metal adsorption and growth. Opportunities for future work are pointed out.     

Unidirectional synchronization of Hodgkin–Huxley neurons exposed to ELF electric field

In this paper, a hybrid control strategy, H_∞ variable universe adaptive fuzzy control, is derived and applied to synchronize two Hodgkin–Huxley (HH) neurons exposed to external electric field. Firstly, the modified model of HH neuron exposed to extremely low frequency (ELF) external electric field is established and its periodic and chaotic dynamics in response to sinusoidal electric field stimulation are described. And then the statement of the problem for unidirectional synchronization of two HH neurons is given. Finally H_∞ variable universe adaptive fuzzy control is designed to synchronize the HH systems and the simulation results demonstrate the effectiveness of the proposed control method.     

Coupling commutator pairs and integrable systems

According to classification of the matrix Lie algebras, a type of explicit Lie algebras are constructed which can be decomposed into a few Lie subalgebras. These subalgebras constitute several coupling commutator pairs from which some continuous multi-integrable couplings could be generated if the proper isospectral Lax pairs could be set up. Then the above Lie algebras are again decomposed into a kind of Lie algebras which are also closed under the matrix multiplication. From such the Lie algebras, some discrete multi-integrable couplings could be worked out. Finally, a few examples are given. However, the Hamiltonian structures of the (continuous and discrete) integrable couplings obtained by the above Lie algebras cannot be computed by using the trace identity or the quadratic-form identity, which is a strange and interesting problem. The phenomenon indicates that the importance of the Lie-algebra classification. The problem also needs us to try to find an efficient scheme to deal with.     

Travelling wavefronts of a generalized Fisher equation with spatio-temporal delay

We discuss a generalized Fisher equation with a convolution term which introduces a time-delay in the nonlinearity. Special attention is paid to the existence and the asymptotic behavior of travelling wavefronts connecting two uniform steady states.     

An unstructured mesh finite element method for solving the multi-term time fractional and Riesz space distributed-order wave equation on an irregular convex domain

In this paper, the numerical analysis for a multi-term time fracstional and Riesz space distributed-order wave equation is discussed on an irregular convex domain. Firstly, the equation is transformed into a multi-term time-space fractional wave equation using the mid-point quadrature rule to approximate the distributed-order Riesz space derivative. Next, the equation is solved by discretising in time using a Crank–Nicolson scheme and in space using the finite element method (FEM) with an unstructured mesh, respectively. Furthermore, stability and convergence are investigated by introducing some important lemmas on irregular convex domain. Finally, some examples are provided to show the effectiveness and correctness of the proposed numerical method.     

Large deviations of Markov chains with multiple time-scales

For Markov processes evolving on multiple time-scales a combination of large component scalings and averaging of rapid fluctuations can lead to useful limits for model approximation. A general approach to proving a law of large numbers to a deterministic limit and a central limit theorem around it have already been proven in Kang and Kurtz (2013) and Kang et al. (2014). We present here a general approach to proving a large deviation principle in path space for such multi-scale Markov processes. Motivated by models arising in systems biology, we apply these large deviation results to general chemical reaction systems which exhibit multiple time-scales, and provide explicit calculations for several relevant examples.     

Measurement and evaluation of the metabolic capacity of an urban ecosystem

Cities as superorganisms confront disturbances from their metabolic processes, including large metabolic fluxes, low stocks of resources and products, and a low efficiency of the urban material metabolism. Based on ecological thermodynamics, an indicator system is established in this paper to evaluate the fluxes, stocks, and effiency of the urban material metabolism using emergy analysis. Also, a new model for the urban material metabolism is proposed to define the production possibility curve using a wealth index (WI) and an ecological effiency index (EEI). Then, six large Chinese cities including Beijing, Shanghai, Tianjin, Chongqing, Guangzhou, and Shenzhen are selected as typical cases to validate the proposed model. The results show that Shenzhen has the highest metabolic capacity, followed by Beijing, Shanghai, Guangzhou, Tianjin, and Chongqing. It is also reflected that different urban material metabolisms of the six cities are resulted from the varied regional metabolic capacities, thus providing insights into how cities improve their metabolic capacities. Meanwhile, Shenzhen has the highest WI and EEI, Chongqing has the lowest WI and EEI, and Beijing, Shanghai, Tianjin, and Guangzhou has low WI and high EEI. It is also shown that the sustainable operation of the urban material metabolism reflects the mutualism and symbiosis between socioeconomic development and ecological environment protection.     

Electro-photo modulation of the fermi level in WSe2/graphene van der Waals heterojunction

We report an electro-photo double modulation of the fermi level in a WSe₂/graphene heterojunction. The heterojunction exhibits high I_ON/I_OFF ratio (~10³) in transfer characteristic in dark and distinct rectification behavior in output characteristic under light illumination, respectively. Time-dependent photoresponse reveals that the heterojunction has a considerable potential in the application of photodetection. Interestingly, an exotic current peak is observed in transfer characteristic under light illumination. This novel behavior is attributed to the tunable fermi level at the WSe₂/graphene heterojunction by electro-photo double modulation. The results may be helpful to develop tunable photovoltaic optoelectronics based on van der Waals heterojunctions.