Coupling Distance Research Articles

Spin–Flip Relaxation Between the Landau Levels in Gapped Graphene

Within the frame of the Huang–Rhys’s lattice relaxation model, we theoretically investigate the spin–flip relaxation assisted by two-phonon processes between the zeroth and first-excited Landau level in gapped graphene on different polar substrates. We give the comparisons between the spin-conserving and the spin–flip of two-phonon processes, which are composed of the surface-optical phonons and longitudinal acoustic phonons. The dependences of two-phonon processes on the energy separation, temperature and polarizability of substrates are discussed. Moreover, we find that the relaxation time of spin–flip can be tuned on a large scale by adjusting the Rashba spin–orbital coupling and internal distance between the graphene and the polar substrate.

Herring–Flicker coupling and thermal quantum correlations in bipartite system

In this paper, we study thermal quantum correlations as quantum discord and entanglement in bipartite system imposed by external magnetic field with Herring–Flicker coupling, i.e., $$J(R)=1.642 e^{-2 R} R^{5/2}+O(R^{2}e^{-2R})$$ . The Herring–Flicker coupling strength is the function of R, which is the distance between spins and systems carry XXX Heisenberg interaction. By tuning the coupling distance R, temperature and magnetic field quantum correlations can be scaled in the bipartite system. We find the long sustainable behavior of quantum discord in comparison with entanglement over the coupling distance R. We also investigate the situations, where entanglement totally dies but quantum discord exists in the system.

Absorptivity enhancement of higher-order electric sextupole plasmonic modes by the outer-square inner-ring coupled resonators

Plasmonic resonances in metal-dielectric-metal structures have shown strong electric and magnetic fields enhancement in the sub-wavelength region, which can significantly boost the performance of plasmon-based metamaterial absorbers. Square resonators (SR) and ring resonators (RR) are both the most common blocks for designing metamaterial perfect absorbers (MPAs) by exciting fundamental electric dipole plasmonic modes. Actually, they can also excite the higher-order electric sextupole plasmonic modes but the absorptivity is very low, which are not available for the design of MPAs. In this paper, the near-field-coupling idea is introduced to enhance the absorptivity of higher-order electric sextupole modes. We propose the outer-square inner-ring coupled resonators (OSIRCR) made of the Ag and ZnS. When the coupling distance has decreased from 70 to 10 nm, the electric field intensity has increased 10.8 times from 55 to 594, which leads to a 5.4 times increase in absorptivity of higher-order electric sextupole modes of the outer-square from 17.6% to 95.3%. In addition to the higher-order electric sextupole modes, the OSIRCR can also excite the fundamental electric dipole modes of the outer-square and the inner-ring. Then a six-band polarization-independent MPA in the infrared range is designed with an average absorptivity of 91.5% utilizing two different sized OSIRCRs.

High transmission of negative permittivity materials based on strong magnetic field coupling

Materials with negative permittivity are opaque for electromagnetic wave such that the transmitted signal cannot travel through them. To combat this phenomenon, we propose a novel high transmission mechanism using periodic placed split-ring resonators and metallic wires to construct a transparent sandwich structure. This structure consists of three layers of materials, where the material with negative permittivity is sandwiched between the materials with high permittivity. With the given frequency, we firstly exploit the metallic wires and split-ring resonators to attain non-transparent negative permittivity and high permittivity, respectively. By effective medium theory, effective relative permittivity retrieved from these materials’ S parameters is verified to be negative or high. Then a resonant tunneling of electromagnetic fields occurs in the proposed three-layer sandwich structure. Simulated and measured results show that this structure fulfills high transmission, although each single material layer is nearly opaque. In addition, this high transmission mechanism is characterized by strong magnetic field coupling and an optimized coupling distance. The high transmission phenomenon and resonant tunneling mechanism provide an idea of reference to realize perfect transmission through opaque materials, which is also realizable in infrared or optical regimes with appropriate designs.

Quantitative Harris-type theorems for diffusions and McKean–Vlasov processes

We consider ℝd-valued diffusion processes of type dXt = b(Xt)dt+dBt. Assuming a geometric drift condition, we establish contractions of the transitions kernels in Kantorovich (L1 Wasserstein) distances with explicit constants. Our results are in the spirit of Hairer and Mattingly's extension of Harris' Theorem. In particular, they do not rely on a small set condition. Instead we combine Lyapunov functions with reflection coupling and concave distance functions. We retrieve constants that are explicit in parameters which can be computed with little effort from one-sided Lipschitz conditions for the drift coefficient and the growth of a chosen Lyapunov function. Consequences include exponential convergence in weighted total variation norms, gradient bounds, bounds for ergodic averages, and Kantorovich contractions for nonlinear McKean-Vlasov diffusions in the case of sufficiently weak but not necessarily bounded nonlinearities. We also establish quantitative bounds for sub-geometric ergodicity assuming a sub-geometric drift condition.

Theoretical Reveal of Intriguing Standing Wave Modes of Carrying Space Beat-Frequency Phenomenon in Nanopillar Arrays

In this work, we demonstrate a kind of new standing wave modes of carrying space beat-frequency effect in an optimized nanopillar array, which can greatly reshape the electric filed distribution and result in high-quality biosensors. The in-depth theoretical research reveals that the mismatch of SPP wave vector and the light wave vector of high-order modes in medium is the crucial factors. The coupling distance, the SPP propagation distance, and the structure parameters also have been systematically investigated. Our results enrich the standing wave modes in nanostructures and give new insights into the fundamental understanding of the standing wave modes.

Understanding the Capacitive Coupling with Influence Factors and Applications

After the concept of electromagnetic fields was summarized by scientists, a new technique called capacitive coupling was invented. This technique is a way to transmit signals. The front-end circuit and back-end circuit may be connected together by a capacitive coupling to eliminate physical contact. Such a capacitive coupling minimizes the possibility of poor physical contact between two circuits due to vibration, corrosion and the like. Thus, the reliability and stability of data between the two circuits are improved. It can be applied to many practical aspects. At the same time, the application of capacitive coupling electrode has its limitations. The limitations come from the coupling area and distance, electrode materials and other influencing factors. There are many problems in the application process. Scientists have come up with a number of solutions. This paper summarizes the information about capacitive coupling electrode. Then this paper lists some factors that influence capacitive coupling as well as some practical applications of it.

Influence of the alkyl chain lengths in perylenetetracarboxylic diimide (PTCDI) derivatives on the photovoltaic properties of planar organic solar cells

Abstract Control of the lowest unoccupied molecular orbital (LUMO) energy offset between an electron-donating polymer (D) and electron-accepting molecule (A) is important for the efficient dissociation of photo-induced excitons into free carriers and for improving the power conversion efficiencies (PCEs) of organic photovoltaics (OPVs). The distance between D and A also affects the dissociation of charge transfer (CT) excitons into free carriers, because the exciton binding energy is inversely proportional to the spatial separation in electron-hole coupling. In addition, the distance between D and A influences the probability that photo-induced excitons in the D (or A) domain become CT excitons through the D/A interface. In this study, the influence of D-A separation on OPV characteristics was investigated by fabricating planar OPVs composed of perylenetetracarboxylic diimide derivatives with different alkyl chain lengths (PTCDI-Cn) as A and a low band-gap polymer (PTB7) as D. The D-A separation distance was controlled by the alkyl chain length of the PTCDI-Cn, which functions as a spacer separating D and A. The open-circuit voltage (Voc) improved at the expense of short-circuit current densitie (Jsc) with increasing alkyl chain length in PTCDI-Cn. To examine the electron-hole coupling between A and D, the electroluminescence (EL) from CT states was measured. A flat CT EL was observed for the OPVs with PTCDI-C3 (perylenetetracarboxylic diimide with propyl groups), while the maxima of CT EL bands were clearly seen for other PTCDI-Cn-based OPVs. This result indicates the existence of CT excitons with different electron-hole coupling distances at the PTB7/PTCDI-C3 interface, suggesting the existence of a variety of molecular orientations of PTCDI-C3 on the surface of PTB7. This may be the origin of the increased PCE for the PTCDI-C3-based OPVs compared to other PTCDI-Cn-based OPVs.

Physical mechanisms and factors influencing inductive pulsed plasma thruster performance: a numerical study using an extended magnetohydrodynamic model

The inductive pulsed plasma thruster (IPPT) is a sort of spacecraft propulsion device. To promote the development of IPPTs, the working process and performance influencing factors are investigated in this study, using a novel magnetohydrodynamic model, with an exterior circuit coupled and extended magnetic field involved in the computation.By exploring the spatial distributions of different physical fields and the global properties of the thruster, a comprehensive physical picture of the operation process is illustrated, which is comprised of the structure evolution of the plasma current sheet, the relationship between thrust force and circuit current, the coupling effect that derives from plasma back to the circuit, and the energy deposition and conversion process of the system. Besides, the positive contribution of the secondary current sheet to the ultimate thrust performance is also confirmed.Further investigations discuss the impacts of varied factors including the operating parameters, initial gas distributions, and metal structures nearby. The results indicate that by adjusting propellant mass to achieve identical specific energy, the specific impulse and efficiency of the thruster can remain almost constant under varied discharge energy. Both compressing the initial gas against the face of coil, and ameliorating its radial uniformity, can help enhance the coupling between the plasma and drive-coil. Conductive structures nearby, especially the grounded metal plate that mounts the capacitors, can impair the acceleration of the plasma, unless it is located out of the electromagnetic coupling distance of the drive-coil.This study may help to reveal the underlying physical mechanisms and improve the designs of IPPTs.

Jupiter Lightning‐Induced Whistler and Sferic Events With Waves and MWR During Juno Perijoves

AbstractDuring the Juno perijove explorations from 27 August 2016 through 1 September 2017, strong electromagnetic impulses induced by Jupiter lightning were detected by the Microwave Radiometer (MWR) instrument in the form of 600‐MHz sferics and recorded by the Waves instrument in the form of Jovian low‐dispersion whistlers discovered in waveform snapshots below 20 kHz. We found 71 overlapping events including sferics, while Waves waveforms were available. Eleven of these also included whistler detections by Waves. By measuring the separation distances between the MWR boresight and the whistler exit point, we estimated the distance whistlers propagate below the ionosphere before exiting to the magnetosphere, called the coupling distance, to be typically one to several thousand of kilometers with a possibility of no subionospheric propagation, which gives a new constraint on the atmospheric whistler propagation.

Hydrodynamic coupling distance between a falling sphere and downstream wall

In solid-liquid two phase flow, the knowledge of how descending solid particles affected by the presence of downstream wall is important. This work studies at what interstitial distance the velocity of a vertically descending sphere is affected by a downstream wall as a consequence of wall-modified hydrodynamic forces through a validated dynamic model. This interstitial distance-the hydrodynamic coupling distance Sc-is found to decay monotonically with the approach Stokes number St which compares the particle inertia to viscous drag characterized by the quasi-steady Stokes\' drag. The scaling relation Sc-St-1 decays monotonically as literature below the value of St equal to 10. However, the faster diminishing rate is found above the threshold value from St=10-40. Furthermore, an empirical relation of Sc-St shows dependence on the drop height which clearly indicates the non-negligible effect of unsteady hydrodynamic force components, namely the added mass force and the history force. Finally, we attempt a fitting relation which embedded the particle acceleration effect in the dependence of fitting constants on the diameter-scaled drop height.

Regulation of synaptic release-site Ca2+ channel couplingas a mechanism to control release probability and short-term plasticity.

Synaptic transmission relies on the rapid fusion of neurotransmitter-containing synaptic vesicles (SVs), which happens in response to action potential (AP)-induced Ca2+ influx at active zones (AZs). A highly conserved molecular machinery cooperates at SV-release sites to mediate SV plasma membrane attachment and maturation, Ca2+ sensing, and membrane fusion. Despite this high degree of conservation, synapses - even within the same organism, organ or neuron - are highly diverse regarding the probability of APs to trigger SV fusion. Additionally, repetitive activation can lead to either strengthening or weakening of transmission. In this review, we discuss mechanisms controlling release probability and this short-term plasticity. We argue that an important layer of control is exerted by evolutionarily conserved AZ scaffolding proteins, which determine the coupling distance between SV fusion sites and voltage-gated Ca2+ channels (VGCC) and, thereby, shape synapse-specific input/output behaviors. We propose that AZ-scaffold modifications may occur to adapt the coupling distance during synapse maturation and plastic regulation of synapse strength.

Effect of jumping current on corrosion behaviors of stainless-steel and steel water pipeline separated by insulating joint

Abstract Corrosion behaviors of intrinsic jumping current in “pipe-in-pipe method”, a trenchless pipeline renewal techniques, were studied. Laboratory demonstration clearly showed that the current was generated by an electromotive force derived from environmental difference at joint section among soil and water, and that the amount of current was determined by sum of various resistance components involved in electrochemical current pathway. Value of the current decreased as the coupling distance increased. In the case of using stainless steel new pipe, almost no distance dependence was observed and the current was considerably small because of its high corrosion resistance.

The Microbead: A Highly Miniaturized Wirelessly Powered Implantable Neural Stimulating System.

An implant that can electrically stimulate neurons across different depths and regions of the brain currently does not exist as it poses a number of obstacles that need to be solved. In order to address the challenges, this paper presents the concept of "microbead," a fully integrated wirelessly powered neural device that allows for spatially selective activation of neural tissue. The prototype chip is fabricated in 130-nm CMOS technology and currently measures 200μm × 200 μm, which represents the smallest remotely powered stimulator to date. The system is validated experimentally in a rat by stimulating the sciatic nerve with 195-μs current pulses. To power the ultrasmall on-silicon coil, 36-dBm source power is provided to a highly optimized transmitter (Tx) coil at a coupling distance of 5 mm. In order to satisfy the strict power limit for safe use in human subjects, a pulsed powering scheme is implemented that enables a significant decrease in the average power emitted from the Tx.

A correlation-hole approach to the electric double layer with counter-ions only

ABSTRACTWe study a classical system of identically charged counter-ions near a planar wall carrying a uniform surface charge density. The equilibrium statistical mechanics of the system depends on a single dimensionless coupling parameter. A new self-consistent theory of the correlation-hole type is proposed which leads to a modified Poisson–Boltzmann integral equation for the density profile, convenient for analytical progress and straightforward to solve numerically. The exact density profiles are recovered in the limits of weak and strong couplings. In contrast to previous theoretical attempts of the test-charge family, the density profiles fulfil the contact-value theorem at all values of the coupling constant and exhibit the mean-field decay at asymptotically large distances from the wall, as expected. We furthermore show that the density corrections at large couplings exhibit the proper dependence on coupling parameter and distance to the charged wall. The numerical results for intermediate values of the coupling provide accurate density profiles which are in good agreement with those obtained by Monte Carlo simulations. The crossover to mean-field behaviour at large distance is studied in detail.

Plasmonic nano-sensor based on metal-dielectric-metal waveguide with the octagonal cavity ring

In this paper, a refractive index plasmonic sensor including a waveguide of metal–insulator–metal with side coupled octagonal cavity ring has been suggested. The sensory and transmission feature of the structure has been analyzed numerically using Finite Element Method numerical solution. The effect of coupling distance and changing the width of metal–insulator–metal waveguide and refractive index of the dielectric located inside octagonal cavity—which are the effective factors in determining the sensory feature—have been examined so completely that the results of the numerical simulation show a linear relation between the resonance wavelength and refractive index of the liquid/gas dielectric material inside the octagonal cavity ring. High sensitivity of the sensor in the resonance wavelength, simplicity and a compact geometry are the advantages of the refractive plasmonic sensor advised which make that possible to use it for designing high performance nano-sensor and bio-sensing devices.

Active Zone Scaffold Protein Ratios Tune Functional Diversity across Brain Synapses

High-throughput electron microscopy has started toreveal synaptic connectivity maps of single circuitsand whole brain regions, for example, in the Drosophila olfactory system. However, efficacy, timing, and frequency tuning of synaptic vesicle release are also highly diversified across brain synapses. These features critically depend on the nanometer-scale coupling distance between voltage-gated Ca2+ channels (VGCCs) and the synaptic vesicle release machinery. Combining light super resolution microscopy with invivo electrophysiology, we show here that two orthogonal scaffold proteins (ELKS family Bruchpilot, BRP, and Syd-1) cluster-specific (M)Unc13 release factor isoforms either close (BRP/Unc13A) or further away (Syd-1/Unc13B) from VGCCs across synapses of the Drosophila olfactory system, resulting in different synapse-characteristic forms of short-term plasticity. Moreover, BRP/Unc13A versus Syd-1/Unc13B ratios were different between synapse types. Thus, variation in tightly versus loosely coupled scaffold protein/(M)Unc13 modules can tune synapse-type-specific release features, and "nanoscopic molecular fingerprints" might identify synapses with specific temporal features.

Distance Entropy Cartography Characterises Centrality in Complex Networks.

We introduce distance entropy as a measure of homogeneity in the distribution of path lengths between a given node and its neighbours in a complex network. Distance entropy defines a new centrality measure whose properties are investigated for a variety of synthetic network models. By coupling distance entropy information with closeness centrality, we introduce a network cartography which allows one to reduce the degeneracy of ranking based on closeness alone. We apply this methodology to the empirical multiplex lexical network encoding the linguistic relationships known to English speaking toddlers. We show that the distance entropy cartography better predicts how children learn words compared to closeness centrality. Our results highlight the importance of distance entropy for gaining insights from distance patterns in complex networks.

A Circuit Model-Based Analysis of Magnetically Coupled Resonant Loops in Wireless Power Transfer Systems

DOI: 10.26650/electrica.2018.55345 Magnetically coupled resonant loops can be represented by a lumped element circuit model. Each parameter in the lumped element model can be expressed as a function of loop geometry and the separation between the loops; therefore, the geometry can be systematically changed, and the power transfer efficiency of the coupled loops can be predicted. This paper presents a simulation-based efficiency analysis for wireless power transfer systems utilizing magnetically coupled resonant loops. The behavior of power transfer efficiency is studied for various loop geometry parameters, and the simulation results are presented in detail. These results clearly show that there is a trade-off between peak efficiency and critical coupling distance, both of which depend on the loop size, frequency of operation, and source-load impedances. To verify the accuracy model, two identical circular loops are fabricated and measured, and the measurement results agree well with the model.

Multistage Coupling of Laser-Wakefield Accelerators with Curved Plasma Channels.

Multistage coupling of laser-wakefield accelerators is essential to overcome laser energy depletion for high-energy applications such as TeV-level electron-positron colliders. Current staging schemes feed subsequent laser pulses into stages using plasma mirrors while controlling electron beam focusing with plasma lenses. Here a more compact and efficient scheme is proposed to realize the simultaneous coupling of the electron beam and the laser pulse into a second stage. A partly curved channel, integrating a straight acceleration stage with a curved transition segment, is used to guide a fresh laser pulse into a subsequent straight channel, while the electrons continue straight. This scheme benefits from a shorter coupling distance and continuous guiding of the electrons in plasma while suppressing transverse beam dispersion. Particle-in-cell simulations demonstrate that the electron beam from a previous stage can be efficiently injected into a subsequent stage for further acceleration while maintaining high capture efficiency, stability, and beam quality.