Effects of asymmetric coupling and boundary on the dynamic behaviors of a random nearest neighbor coupled system

This study investigates the dynamical behaviors of nearest neighbor asymmetric coupled systems in a confined space.First, the study derivative analytical stability and synchronization conditions for the asymmetrically coupled system in an unconfined space, which are then validated through numerical simulations. Simulation results show that asymmetric coupling has a significant impact on synchronization conditions. Moreover, it is observed that irrespective of whether the system is confined, an increase in coupling asymmetry leads to a hastened synchronization pace. Additionally, the study examines the effects of boundaries on the system's collective behaviors via numerical experiments. The presence of boundaries ensures the system's stability and synchronization, and reducing these boundaries can expedite the synchronization process and amplify its effects. Finally, the study reveals that the system's output amplitude exhibits stochastic resonance as the confined boundary size increases.

InGaAs/InAlAs Five Layer Asymmetric Coupled Quantum Well (FACQW) for Ultra-Wideband Ultrafast Optical Modulators

An InGaAs/InAlAs five-layer asymmetric coupled quantum well (FACQW) is expected to show very large electrorefractive index change . n in a wideband transparency region. Band structures of the FACQW are analyzed with Luttinger-Kohn Hamiltonian. The electrorefractive characteristics of the FACQW are discussed.

Transportation of Two Coupled Particles in an Asymmetric Saw-Tooth Potential

Based on a simple model, we theoretically show the transport behaviors of two harmonically coupled Brownian particles in an asymmetric saw-tooth potential with two slopes. The coupled particles are subject to stochastic fluctuations. It is found that when the equilibrium distance of the coupled particles is between the two slopes of the potential, the transport direction of the coupled particles will be reversed with a certain harmonic coupling strength. This current reversal can be easily understood with the near rigid approximation, where the two coupled particles can be regarded as a single particle in an effective potential. Compared with the original saw-tooth potential, the asymmetry of the effective potential could be reversed when the equilibrium distance is between the two slopes of the original potential, which results in the current reversal.

A High-Sensitivity Refractive-Index Sensor Based on Plasmonic Waveguides Asymmetrically Coupled with a Nanodisk Resonator

A high-sensitivity plasmonic refractive-index sensor based on the asymmetrical coupling of two metal-insulator- metal waveguides with a nanodisk resonator is proposed and simulated in the finite-difference time domain. Both analytic and simulated results show that the resonance wavelengths of the sensor have an approximate linear relationship with the refractive index of the materials which are filled into the slit waveguides and the disk- shaped resonator. The working mechanism of this sensor is exactly due to the linear relationship, based on which tile refractive index of the materials unknown can be obtained from the detection of the resonance wavelength. The measurement sensitivity can reach as high as 6.45 × 10-7, which is nearly five times higher than the results reported in the recent literature [Opt. Commun. 300 （2013） 265]. With an optimum design, the sensing value can be further improved, and it can be widely applied into the biological sensing. Tile sensor working for temperature sensing is also analyzed.

ADAPTIVE PINNING SYNCHRONIZATION OF COUPLED NEURAL NETWORKS WITH MIXED DELAYS AND VECTOR-FORM STOCHASTIC PERTURBATIONS

In this article, we consider the global chaotic synchronization of general cou- pled neural networks, in which subsystems have both discrete and distributed delays. Stochastic perturbations between subsystems are also considered. On the basis of two sim- ple adaptive pinning feedback control schemes, Lyapunov functional method, and stochas- tic analysis approach, several sufficient conditions are developed to guarantee global syn- chronization of the coupled neural networks with two kinds of delay couplings, even if only partial states of the nodes are coupled. The outer-coupling matrices may be symmetric or asymmetric. Unlike existing results that an isolate node is introduced as the pinning target, we pin to help the network realizing synchronization without introducing any iso- late node when the network is not synchronized. As a by product, sufficient conditions under which the network realizes synchronization without control are derived. Numerical simulations confirm the effectiveness of the obtained results.

Network dynamics and its relationships to topology and coupling structure in excitable complex networks

All dynamic complex networks have two important aspects, pattern dynamics and network topology. Discovering different types of pattern dynamics and exploring how these dynamics depend or/network topologies are tasks of both great theoretical importance and broad practical significance. In this paper we study the oscillatory behaviors of excitable complex networks （ECNs） and find some interesting dynamic behaviors of ECNs in oscillatory probability, the multiplicity of oscillatory attractors, period distribution, and different types of oscillatory patterns （e.g., periodic, quasiperiodic, and chaotic）. In these aspects, we further explore strikingly sharp differences among network dynamics induced by different topologies （random or scale-free topologies） and different interaction structures （symmetric or asymmetric couplings）. The mechanisms behind these differences are explained physically.

A high Q terahertz asymmetrically coupled resonator and its sensing performance

A terahertz asymmetrically coupled resonator （ACR） consisting of two different split ring resonators （SRRs） was designed. Using finite difference time domain （FDTD）, the transmission of ACR and its refractive-index- based sensing performaance were simulated and analyzed. Results show that the ACR possesses a sharp coupled transparent peak or high quality factor （Q）, its intensity and bandwidth can be easily adjusted by spacing the two SRRs. Furthermore, the resonator exhibits high sensitivity of 75 GHz/RIU and figure of merit （FOM） of 4.4, much higher than the individual SRR sensors. The ACR were fabricated by using laser-induced and chemical non-electrolytic plating with copper on polyimide substrate, the transmission of which measured by terahertz time-domain spectroscopy system is in good agreement with simulations.

Enantioselective Pinacol Coupling of Aromatic Aldehydes Induced by Chiral Titanium Complexes

Asymmetric pinacol coupling of aromatic aldehydes with TiCl4-Zn in the presence of enantiopure squaric acid amidoalcohols afforded 1, 2-diols in excellent yields with high dl- diastereoselectivities and enantioselectivities in the range of 46-89% ee. Some factors influencing dl-diastereoselectivity and enantioselectivity were discussed.

Synthesis of a Soluble Diacetylene with Phenylimidazole Ring

6-(2-Methyl-4-phenyl)-N-imidazole-2, 4-hexadiyn-1-ol was synthesized in a good yield by asymmetric coupling, and the corresponding intermediates were also prepared. The diacetylene monomer could be dissolved in common organic solvents. In addition, all kinds of conditions were also discussed effectively improving the formation of the diacetylene monomer.

热扩散系统中非厄米趋肤效应的观测

The paradigm shift of Hermitian systems into the non-Hermitian regime profoundly modifies inherent property of the topological systems, leading to various unprecedented effects such as the nonHermitian skin effect(NHSE). In the past decade, the NHSE has been demonstrated in quantum, optical and acoustic systems. Beside those wave systems, the NHSE in diffusive systems has not yet been observed, despite recent abundant advances in the study of topological thermal diffusion. In this work,we design a thermal diffusion lattice based on a modified Su-Schrieffer-Heeger model and demonstrate the diffusive NHSE. In the proposed model, the asymmetric temperature field coupling inside each unit cell can be judiciously realized by appropriate configurations of structural parameters. We find that the temperature fields trend to concentrate toward the target boundary which is robust against initial excitation conditions. We thus experimentally demonstrated the NHSE in thermal diffusion and verified its robustness against various defects. Our work provides a platform for exploration of non-Hermitian physics in the diffusive systems, which has important applications in efficient heat collection, highly sensitive thermal sensing and others.

Luminescence distribution and hole transport in asymmetric InGaN multiple-quantum well light-emitting diodes

Asymmetric InGaN/GaN multiple-quantum well（MQW） light-emitting diodes were fabricated to expose the luminescence distribution and explore the hole transport.Under electrical injection,the sample with a wNQW active region in which the first QW nearest the p-side（QW1） is wider than the subsequent QWs shows a single long-wavelength light-emission peak arising from QW1.The inverse nWQW sample with a narrow QW1 shows one short-wavelength peak and one long-wavelength peak emitted separately from QW1 and the subsequent QWs.Increasing the barrier thickness between QW1 and the second QW（QWB1） in the nWQW structure,the long-wavelength peak is suppressed and the total light-emission intensity decreases.It was concluded that the nWQW and thin-QWB1 structure can improve the hole transport,and hence enhance the light-emission from the subsequent QWs and increase the internal quantum efficiency.

Asymmetric Pinacol Coupling of Aromatic Aldehydes Catalyzed by TiCl_4(THF)_2-Zn/Chiral Diamines

Asymmetric pinacol coupling of aromatic aldehydes catalyzed by chiral diamines/low valent titanium complexes gave corresponding pinacols in good yields with high diastereoselectivity and moderate enantioselectivities.

Boosting Electrocatalytic Urea Production via Promoting Asymmetric C–N Coupling

Electrocatalytic C–N coupling shows great potential in direct and sustainable urea synthesis.However,the mechanism of interaction between catalytic sites and intermediate species is currently unclear,and exploring corresponding strategies to boost urea synthesis is urgent.Herein,we demonstrated that a multihole structure could preserve the Cu^(+)component of Cu_(2)O spheres under electrochemical reduction conditions.An in situ formed Cu^(0)–Cu^(+)site thermodynamically and kinetically promoted the asymmetric coupling process of^(*)CO and^(*)NO,thereby boosting the urea production.The impressive urea yield rates of 29.2 and 114.0 mmol h^(−1)g^(−1)were realized for electrochemical coupling of CO_(2)with nitrate and nitrite,respectively.The multihole-Cu_(2)O exhibits both superior activity and long-term stability compared to the electrocatalysts with a reconstructed Cu^(0)-dominated surface.This work provides insights into the identification and design of the active site for C–N coupling and urea synthesis.

Strain effects on performance of electroabsorption optical modulators

This paper reports a detailed theoretical investigation of strain effects on the performance of electroabsorption optical modulators based on the asym- metric intra-step-barrier coupled double strained quantum wells （AICD-SQWs） active layer. For this purpose, the electroabsorption coefficient was calculated over a range of AICD-SQWs strain from compressive to tensile strain. Then, the extinction ratio （ER） and insertion loss parameters were evaluated from calculated electroabsorp- tion coefficient for transverse electric （TE） input light polarization. The results of the simulation suggest that the tensile strain from 0.05% to 0.2% strain in the wide quantum well has a significant impact on the ER and insertion loss as compared with compressive strain, whereas the compressive strain of the narrow quantum well from -0.5% to -0.7% strain has a more pronounced impact on the improvement of the ER and insertion loss as compared with tensile strain.

SYNCHRONIZATION STABILITY OF COMPLEX CONNECTED NETWORKS WITH DELAYS

Recently, much work has been devoted to the study of a large-scale complex system described by a network or a graph with complex topology, whose nodes are the elements of the system and whose edges represent the interactions among them. On the other hand, realistic modelling of many large networks with nonlocal interaction inevitably requires connection delays to be taken into account, since they naturally arise as a consequence of finite information transmission and processing speeds among the units. This paper gives the sufficient conditions guaranteeing the local and global synchronization stability of the complex connected networks by using Lyapunov functional.

Enantioselective Pinacol Coupling of Aromatic Aldehydes Mediated by TiCl_4(THF)_2/Zn with Tartaric Ester

Asymmetric pinacol coupling of aromatic aldehydes mediated by low valent titanium complexes of chiral ligands derived from natural tartaric acid provided corresponding pinacols in good yields with excellent diastereo-selectivities and moderate enantioselectivities.