ABSTRACT
Room-temperature gas sensors have emerged as effective platforms for sensing explosive or toxic gases in ambient environment. However, room-temperature gas sensor usually suffers from extremely poor sensitivity and sluggish response/recovery characteristics due to the low reacting activity at low temperature. Herein, we present a room-temperature NO2 sensor with greatly enhanced sensitivity and rapid response/recovery speed under ultraviolet (UV) illumination. The sensor based on In2O3/ZnO yolk-shell nanofibers exhibits remarkable sensitivity (Rg/Ra = 6.0) to 1 ppm NO2 and rapid response/recovery time (≤36, 68 s) under UV illumination, obviously better than negligible sensing performance and inefficient response/recovery properties in dark condition. Such excellent gas sensing properties of the In2O3/ZnO yolk-shell nanofibers were not only attributed to the improved photo-generated charge separation efficiency derived from the effect of heterojunction, but also related to the enhanced receptor function towards NO2 endowed by increased reactive sites and gas adsorption. These proposed strategies will provide a reference for developing high-performance room-temperature gas sensors.
ABSTRACT
We report on a modulated coherent state in a ring of nonlocally coupled oscillators. Although the identical oscillators are all synchronized under the symmetric coupling, the phase configuration has an inhomogeneous structure. This symmetry-broken coherent state exists only for a nonlocal coupling with both attracting and repulsive interactions, depending on the distance between oscillators, and emerges via a continuous bifurcation from a uniformly coherent state. We analyze the existence and stability of the modulated coherent states on the basis of Ott-Antonsen equations for the local order parameter. Our theoretical results are verified using the numerical simulations.
ABSTRACT
We consider a ring of phase oscillators with nonlocal coupling strength and heterogeneous phase lags. We analyze the effects of heterogeneity in the phase lags on the existence and stability of a variety of steady states. A nonlocal coupling with heterogeneous phase lags that allows the system to be solved analytically is suggested and the stability of solutions along the Ott-Antonsen invariant manifold is explored. We present a complete bifurcation diagram for stationary patterns including the uniform drift and modulated drift states as well as chimera state, which reveals that the stable modulated drift state and a continuum of metastable drift states could occur due to the heterogeneity of the phase lags. We verify our theoretical results using the direct numerical simulations of the model system.
ABSTRACT
We suggest a site disorder model that describes the population of identical oscillators with quenched random interactions for both the coupling strength and coupling phase. We obtain the reduced equations for the suborder parameters, on the basis of Ott-Antonsen ansatz theory, and present a complete bifurcation analysis of the reduced system. New effects include the appearance of the incoherent chimera and glassy state, both of which are caused by heterogeneity of the coupling phases. In the incoherent chimera state, the system displays an exotic symmetry-breaking behavior in spite of the apparent structural symmetry where the oscillators for both of the two subpopulations are in a frustrated state, while the phase distribution for each subpopulation approaches a steady state that differs from each other. When the incoherent chimera undergoes Hopf bifurcation, the system displays a breathing incoherent chimera. The glassy state that occurs on a surface of three-dimensional parameter space exhibits a continuum of metastable states with zero value of the global order parameter. Explicit formulas are derived for the system's Hopf, saddle-node, and transcritical bifurcation curves, as well as the codimension-2 crossing points, including the Takens-Bogdanov point.
