Moderate Coupling Research Articles

Dissipative Josephson vortices in annular polariton fluids

We consider two concentric rings formed by bosonic condensates of exciton-polaritons. A circular superfluid flow of polaritons in one of the rings can be manipulated by acting upon the second annular polariton condensate. The complex coupling between the rings with different topological charges triggers nucleation of stable Josephson vortices (JVs) which are revealed as topological defects of the angular dependence of the relative phase between rings. Being dependent on the coupling strength, the structure of the JV governs the difference of the mean angular momenta of the inner and the outer rings. At the vanishing coupling the condensates rotate independently demonstrating no correlations of their winding numbers. At the moderate coupling, the interaction between two condensates tends to equalize their mean angular momenta despite of the mismatch of the winding numbers demonstrating the phenomenology of a drag effect. Above the critical coupling strength the synchronous rotation is established via the phase slip events.

Dynamical Jahn-Teller effects on the generation of electronic ring currents by circularly polarized light

The generation of electronic ring currents in ring-shaped molecules by photo-excitation with circularly polarized laser light is considered in the presence of vibronic coupling effects. $(E\times e)$ Jahn-Teller distortions, unavoidable by symmetry in the $(E)$ subset of electronic states supporting the ring current, mix the clockwise and anti-clockwise circulation directions of the electrons and can suppress the maximum achievable current by at least one order of magnitude, already for moderate vibronic coupling strengths, as compared to the Born-Oppenheimer limit of fixed atomic positions. The circulation direction of the electrons is found to depend on the spectral region of the $(E\times e)$ Hamiltonian. This fact results in the surprising effect that the same polarization direction of the laser pulse can trigger either clockwise or anti-clockwise electronic dynamics depending on the wavelength of the photons. These findings are illustrated in a model of the triazine molecule.

The relationship between coupling open innovation and innovation performance: the moderating effect of platform openness

ABSTRACT With the deepening of economic globalisation and the rapid development of the Internet, open innovation has become the main innovation paradigm for enterprises to win a competition. There are three modes of open innovation: inbound, outbound, and coupling. Among them, coupling open innovation can better meet the innovation needs of enterprises. This paper takes the survey data of 421 enterprises in 10 cities in East China as samples, and uses a neural network model to explore the relationship between coupling open innovation and innovation performance, as well as the moderating effect of open innovation platforms. The study found that for enterprises in the start-up, growing and transition stages, the proportion of inbound open innovation positively affects innovation performance; for enterprises in the mature stage, the proportion of outbound open innovation positively affects innovation performance. At the same time, there are peak points for both. The breadth of platform openness does not significantly moderate coupling open innovation and innovation performance, while the depth of platform openness has a significant moderating effect on coupling open innovation and innovation performance.

On the Global and Local Decoding of q-Ary SC-LDPC Codes With Moderate Coupling Length

This letter discusses a special type of q-ary spatially coupled low-density parity-check (SC-LDPC) codes with the potential for local decoding (LD). We demonstrate that q-ary SC-LDPCL (suffix “L” stands for locality) code ensembles have better decoding thresholds than the corresponding binary ensembles. We also develop local window decoding (LWD) to improve local decoding performance. The q-ary codes are constructed from low-order finite fields that guarantees relatively low complexity. The provided examples show that q-ary SC-LDPCL codes outperform the corresponding binary codes in both global and local decoding.

Vulnerability assessment of China–Europe Railway Express multimodal transport network under cascading failures

Transshipment and transnational long-haul transport make the multimodal transport network (MTN) vulnerable when subjected to unexpected disturbances, which may cause cascading failures. Therefore, this paper presents a dynamic layered road–rail MTN to measure the vulnerability of China–Europe Railway Express (CR Express) MTN. The statistical analysis of the topological characteristics and the final simulation results show that the layered road–rail MTN with priority connection mechanism exhibits power-law distribution characteristics. The final simulation results reveal that the road–rail MTN shows a better ability to suppress the risk cascading propagation when the transshipment coupling enhances the dynamic flexibility of the network. Although the optimal inter-layer transshipment coupling changes positively with the external disturbance and negatively with the intra-layer coupling in special cases, the moderate inter-layer coupling is still the most effective in improving the anti-cascading ability of general MTN. These findings provide recommendations for the CR Express MTN to suppress the cascading failures.

Temporal variations of ambient air pollutants and meteorological influences on their concentrations in Tehran during 2012–2017

BACKGROUND AND AIM: In 2015, air pollution exposure was responsible for approximately nine million premature deaths; 16% of all deaths globally. In this study, we examined long-term air quality status in Tehran. METHODS: Here the temporal variations (hourly, daily, monthly, seasonal, and annual) of key criteria air pollutants (PM2.5, PM10 NO2, O3, SO2, CO) concentration and their relation to metrological parameters, as well as annual trends of air quality index (AQI) were investigated based on real-time hourly measurements of twenty-one air quality monitoring stations (AQMSs). RESULTS:Tehran citizens were consistently exposed to annual PM2.5, PM10 and NO2 approximately 3.0–4.5, 3.5–4.5 and 1.5–2.5 times higher than the World Health Organization air quality guideline levels during the period. Except for O3, all air pollutants demonstrated the lowest and highest concentrations in summertime and wintertime, respectively. The highest O3 concentrations were found on weekend (weekend effect), whereas other ambient air pollutants had statistically significant (P 0.05) daily variations in which higher concentrations were observed on weekdays compared to weekend (holiday effect). Hourly O3 concentration reached its peak at 3.00 p.m., though other air pollutants displayed two peaks; morning and late night. Approximately 45% to 65% of AQI values were in the subcategory of unhealthy for sensitive groups and PM2.5 was the responsible air pollutant in Tehran. Amongst meteorological factors, temperature was the key influencing factor for PM2.5 and PM10 concentrations, while nebulosity and solar radiation exerted major influences on ambient SO2 and O3 concentrations. Additionally, there is a moderate coupling between wind speed and NO2 and CO concentrations. CONCLUSIONS:Despite years of efforts for air quality improvement in Tehran, our results clearly confirm that ambient PM2.5 and PM10 are still the most notable air pollutants in this city. This represents that traffic-related policy measures for air quality improvement were not sufficiently efficacious in Tehran, particularly concerning reducing PM2.5 and PM10. KEYWORDS: Temporal trends, Criteria air pollutants, Meteorological parameters, AQI

Ethereal Hydroperoxides: Powerful Reagents for S-Oxygenation of Bridging Thiophenolate Functions

S-Oxygenation of thiophenolate bridges by ethereal hydroperoxides was studied. [NiII2LS(PhCO2)]+ (1), where LS = macrocyclic aminethiolate supporting ligand, is S-oxygenated readily in a mixed methanol/acetonitrile solution with ether/dioxygen at room temperature in the presence of daylight. The reactions were found to depend strongly on the choice of the ether. Uptake of two O atoms occurs in dioxane to give a mixed thiolate/sulfinate complex [NiII2LSO2(PhCO2)]+ (2) containing the rare five-membered Ni(μ1,1-S)(μ1,2-OS)Ni core. In tetrahydrofuran, four O atoms are taken up by 1 to generate the bis(sulfinate) species [NiII2LSO4(PhCO2)]+ (3). A mono-S-oxygenated sulfenate intermediate can be detected by electrospray ionization mass spectrometry. The oxygenation reactions proceed in high yields without complex disintegration and invariably provide μ1,2-bridging sulfinates as established by spectroscopy (IR and UV/vis), X-ray crystallography, and accompanying density functional theory calculations. The oxygenation of the S atoms has a strong impact on the electronic structures of the nickel complexes. The monosulfinate complex 2 has an S = 2 ground state resulting from moderate ferromagnetic exchange coupling interactions (J = +15.7 cm-1; H = -2JS1S2), while an antiferromagnetic exchange interaction in 3 shows the presence of a ground state with spin S = 0 (J = -0.56 cm-1).

Lattice dynamics and magnetic exchange interactions in GeCo2O4 : A spinel with S=12 pyrochlore lattice

${\mathrm{GeCo}}_{2}{\mathrm{O}}_{4}$ is a unique system in the family of cobalt spinels $A{\mathrm{Co}}_{2}{\mathrm{O}}_{4}$ ($A$= Sn, Ti, Ru, Mn, Al, Zn, Fe, etc.) in which magnetic Co ions stabilize on the pyrochlore lattice exhibiting a large degree of orbital frustration. Due to the complexity of the low-temperature antiferromagnetic (AFM) ordering and long-range magnetic exchange interactions, the lattice dynamics and magnetic structure of a ${\mathrm{GeCo}}_{2}{\mathrm{O}}_{4}$ spinel have remained puzzling. To address this issue, here we present theoretical and experimental investigations of the highly frustrated magnetic structure, and the infrared (IR) and Raman-active phonon modes in the spinel ${\mathrm{GeCo}}_{2}{\mathrm{O}}_{4}$, which exhibits an AFM ordering below the N\'eel temperature ${T}_{N}\ensuremath{\sim}21$ K and an associated cubic ($Fd\overline{3}m$) to tetragonal ($I{4}_{1}/amd$) structural phase transition whose location at ${T}_{N}$ vs at a lower ${T}_{S}\ensuremath{\sim}16$ K is controversial. Our density functional theory ($\mathrm{DFT}+U$) calculations reveal that one needs to consider magnetic-exchange interactions up to the third-nearest neighbors to get an accurate description of the low-temperature AFM order in ${\mathrm{GeCo}}_{2}{\mathrm{O}}_{4}$. At room temperature, three distinct IR-active modes (${T}_{1\mathrm{u}}$) are observed at frequencies 680, 413, and 325 ${\mathrm{cm}}^{\ensuremath{-}1}$ along with four Raman-active modes ${A}_{1\mathrm{g}}, {T}_{2\mathrm{g}}$(1), ${T}_{2\mathrm{g}}$(2), and ${E}_{\mathrm{g}}$ at frequencies 760, 647, 550, and 308 ${\mathrm{cm}}^{\ensuremath{-}1}$, respectively, which match reasonably well with our $\mathrm{DFT}+U$ calculated values. All the IR-active and Raman-active phonon modes exhibit signatures of moderate spin-phonon coupling. The temperature dependence of various parameters, such as the shift, width, and intensity, of the Raman-active modes is also discussed. Noticeable changes around ${T}_{N}\ensuremath{\sim}21$ K and ${T}_{S}\phantom{\rule{4pt}{0ex}}\ensuremath{\sim}16$ K are observed in the Raman line parameters of the ${E}_{\mathrm{g}}$ and ${T}_{2\mathrm{g}}$(1) modes, which are associated with the modulation of the Co-O bonds in ${\mathrm{CoO}}_{6}$ octahedra during the excitations of these modes.

Massive electrons and unconventional room-temperature superconductivity in superhydrides

The search for room-temperature superconducting materials has been at the center of modern research for decades. The recent discovery of high-temperature superconductivity, under extreme pressure in hydrogen-rich materials, is a tremendous achievement in this research front. This discovery offers a route in the search for room temperature superconductivity at ambient pressure. The superconductivity of these hydrogen-rich materials was confirmed by the observation of zero-resistance, isotope effects, effect of magnetic field, and other standard properties. However, some of the experimental features were puzzling as they were not consistent with the known superconductivity theories. These debatable features have lead to a series of recent publications downplaying the existence of superconductivity in these superhydrides. Here we propose a concept of massive electrons under pressure and successfully explain all non-standard experimental observations. Our massive electron concept explains the large effective mass of the quasiparticles, the reason for the high critical temperatures for moderate electron-phonon couplings, and a 3-5 orders of magnitude larger conductivity causing a narrow resistivity broadening at the transition in the presence of magnetic field. We anticipate our findings will lead to a new directions and tweaks in current research in the search for ambient-pressure, room-temperature superconductors.

Corporate Leadership Strategy Management Based on Entropy Coupling Algorithm

With the continued economic downturn, coupled with the slowdown of domestic economic development and fierce market competition, the development of small and medium-sized enterprises has become more and more difficult. Because the financial background and operating strength of small and medium-sized enterprises are far inferior to large-scale enterprises, coupled with the influence of global economic integration, many small and medium-sized enterprises have gradually closed down. Therefore, exploring the entropy coupling algorithm is of great significance to the role of corporate leadership strategy management. This paper studies the coupling conditions and coupling process of corporate strategy and business model, builds a new coupling model, and goes deep into the coupling model to study the cooperation mechanism between its internal modules and initially builds the company to break through the two major dilemmas at the same time. This paper uses entropy theory to evaluate corporate leadership strategy, constructs an evaluation index system based on entropy, determines the weight of each index, and calculates the entropy value. This paper uses the alpha coefficient to test the reliability of the questionnaire. The value range of α coefficient is [0, 1], and different values represent different reliability. Large enterprises as a whole are mostly in the highly coupled (41.80%) and moderately coupled (27.34%) stages; medium-sized enterprises as a whole are mostly in the highly coupled (39.50%) and moderately coupled (31.50%) stages; small enterprises as a whole are mostly in the moderately coupled (39.50%) and moderately coupled (40.72%), low coupling (33.20%), and high coupling (25.9%) stages; microenterprises as a whole are mostly in the low coupling (43.70%), moderate coupling (36.41%), and high coupling (30.51%) stages. The results show that the entropy coupling algorithm can improve the deficiencies in the leadership strategy and provide a practical and reliable path for carrying out leadership development projects.

Exploring the potential benefits of using metasurface for galloping energy harvesting

Inspired by the successful applications of metasurfaces in many other fields, this paper aims to explore the potential application of metasurfaces in designing aerodynamic systems. Bluff bodies are proposed to be wrapped in metasurfaces for improving galloping energy harvesting. Three different metasurfaces with convex cylinder, tri-prim, and wedge ornaments are designed. A general aeroelastic model for a galloping energy harvester is developed. The aerodynamic force is represented by a polynomial function with its coefficients being determined from three-dimensional CFD simulations. Subsequently, physical prototypes of the proposed galloping piezoelectric energy harvesters are fabricated, and experimental tests are conducted. The theoretical model is validated by the experimental results. The analytical method and three-dimensional CFD simulation are combined to predict the dynamic responses of the metasurface-wrapped GPEHs. Besides, the results show that the metasurface can significantly change the aerodynamic characteristics of the bluff body, and it is learned that a bluff body wrapped in convex cylinder metasurface could bring benefits for promoting galloping energy harvesting performance. Further experimental studies are conducted to reveal the effects of convex ornament parameters on the galloping energy harvesting performance. It is found that using the metasurface distributed with convex cylinder ornaments of diameter 6 mm and height 9 mm leads to the largest vibration displacement and largest voltage output. Compared to the typical GPEH, the maximum vibration displacement and maximum output voltage of the proposed galloping piezoelectric energy harvester can be increased by 26.81% and 26.14%, respectively. The vortex shedding processes around the wind flow fields near the bluff bodies wrapped in metasurfaces are simulated. The underlying aerodynamic mechanism of the influence of the metasurfaces is unveiled. Finally, based on the validated theoretical model, a parametric study is carried out to investigate the effects of the load resistance and electromechanical coupling strength on the galloping energy harvesting performance. It is concluded that increasing the coupling strength to a certain level and tuning the load resistance to the optimal value could further improve the power output. However, when the electromechanical coupling strength increases to a certain extent, the power output will reach the saturation state, and the coupling strength is extremely large. Therefore, a piezoelectric element with a moderate coupling coefficient is recommended for practical applications from the perspective of economic benefit.

Empirical Analysis of the Influence of Green Credit on the Industrial Structure: A Case Study of China

In order to explore the influence of green credit on the optimization and rationalization of the industrial structure in China, based on the relevant data of the green credit balance, interest expenditure in six high-energy-consuming industries, and industrial structure in China from 2007–2019, the paper first measured the green credit index and the index of industrial structure optimization and rationalization by the methods of entropy weight and Theil index. Then, the coupling model was adopted to study the coupling degree and the coupling coordination degree between them, and the regression model was employed to further study the influence coefficient of green credit on the optimization and rationalization of industrial structure. Research showed that the degree of coupling between green credit and industrial structure rationalization presents three stages—extremely low coupling, low coupling, and moderate coupling—and the degree of coupling coordination presents two stages—extremely low coordination and low coordination. Similarly, the degree of coupling between them presents two stages—extremely low coupling and low coupling—and the degree of coupling coordination presents two stages—extremely low coordination and low coordination. Regression analysis showed that the influence coefficients of the green credit index on rationalization and optimization of industrial structure were 0.56 and 0.03, respectively, which supported the conclusion that the coupling degree between the former two is higher than that between the latter two on the one hand, and made it clear that green credit positively and effectively guides the rational allocation of resources and promotes secondary and tertiary industries on the other hand.

Dust-Acoustic Wave Dispersion in Thermal Dusty Plasmas at Weak and Moderate Couplings

The dispersion of dust-acoustic waves (DAWs) in weakly and moderately coupled thermal dusty plasmas is studied in the framework of the linear density-response formalism with the static local-field correction for interdust interactions. The plasma medium composition and the charge of dust particles are simultaneously determined within a recently developed chemical model (Physical Review E, vol. 101, 063203, 2020) based on minimizing the Helmholtz free energy of the system under investigation. Stemming from the generalized Poisson-Boltzmann equation, the renormalization procedure is consistently applied to derive an interdust screened potential that takes into account the finiteness of dust grains. Within the framework of the Ornstein-Zernike relationship in the hypernetted chain approximation, the static structure factor of the dust component is evaluated to manifest the appearance of local extrema on its wavenumber dependence, thereby indicating the short-range order formation in the arrangement of dust particles with respect to one another. It is shown that the DAW dispersion law is completely governed by the static structure factor and, therefore, exhibits a nonmonotonic dependence on the wavenumber as well. In the long-wavelength limit, the acoustic-like behavior of the DAW dispersion is strictly confirmed and the corresponding phase speed, reduced in units of the dust thermal velocity, is ultimately expressed via the static structure factor at zero wavenumber.

On the use of single-frequency versus double-frequency satellite-transition pulses for MQMAS

It has been shown recently that a rotor-period long pulse applied at a frequency selective to the satellite-transitions of half-integer quadrupole nuclei can efficiently interconvert central-transition (CT) and triple-quantum (TQ) coherences for the acquisition of MQMAS spectra [I. Hung, Z. Gan, J. Magn. Reson. 324 (2021) 106913; doi: https://doi.org/10.1016/j.jmr.2021.106913]. By using a pair of such pulses and selecting opposite changes in coherence order, the anisotropic phase of the effective rf field can be refocused. Efficient multiple-quantum interconversion has led to low-power MQMAS pulse sequences capable of obtaining isotropic NMR spectra for the largest quadrupolar couplings to date. In this work, we extend the satellite-transition selective pulses from single- to double-frequency (or cosine) irradiation. By applying average Hamiltonian theory in the quadrupolar jolting frame, it is shown that the phase for TQ/CT conversion converges when the double-frequency irradiation matches the mirror-image symmetry of the satellite-transitions. The coherent conversion explains the mechanism behind the double-frequency sweep (DFS) and fast amplitude modulation (FAM) methods used for MQMAS. However, the strict matching condition limits the bandwidth of such double-frequency pulses to less than one spinning frequency. The use of a pair of identical cosine satellite-transition pulses is proposed to refocus the residual anisotropic phase spread. The refocusing leads to a more efficient MQMAS pulse sequence with a broader bandwidth suitable for large quadrupolar couplings and chemical shift ranges. Comparisons with the recently presented single-frequency lpMQMAS and other MQMAS pulse schemes show that cos-lpMQMAS is more efficient, less susceptible to fluctuations in spinning frequency, and suffers from less distortion in quadrupolar line shapes, as demonstrated with model compounds of moderate and large quadrupolar couplings, 87RbNO3 and β-71Ga2O3. In particular, the results for β-71Ga2O3 show an order of magnitude increase in MQMAS efficiency.

Thermal effects in field electron emission from idealized arrangements of independent and interacting micro-protrusions

Modelling studies of thermo-field electron emission (TFE) from protrusions at a cathode surface usually use simulations in 2D axial symmetry. Indeed, time-dependent simulations in 3D are very demanding in computation time. Often, 3D simulations have been restricted to stationary pure field electron emission to account for the drastic current decrease caused by electric field screening when the emitters are close. Little interest has therefore been granted to the heat exchanges occurring between nearby emitters. Although the temperature is a second-order parameter in TFE compared to the electric field, thermal effects become non-negligible in high current density regimes, where self-heating is well established. The present study focuses on the thermal effects occurring during the TFE from micro-protrusions. Our model considers a DC voltage but solves in time the temperature evolution coupling the heat equation and the current continuity equation. The protrusions are modelled as hemiellipsoids with 2D axial symmetry. Emission enhancement due to the increase of the temperature in the thermo-field regime compared to the pure field regime is detailed as a test case for isolated protrusions. Then, full 3D simulations are used to investigate the thermal coupling between multiple neighbouring protrusions via their outwards heat fluxes inside the cathode. The results show a higher current increase due to thermal coupling for dome-like protrusions with a low field enhancement factor. The current increases up to 13% of the total current for aspect ratios of 1, but this value is reached for an extreme applied electric field, hardly reachable in experiments. For sharper protrusions with higher field enhancement, the interaction range through the cathode being shorter, the thermal coupling is suppressed by electrostatic screening. Nevertheless, in arrangements of densely distributed field emitter, when the screening is compensated by a higher voltage, our model predicts the possibility of a moderate but noticeable thermal coupling even for sharp protrusions: a parametric study indicates up to 14.5% of the emitted current being caused by a thermal coupling through the cathode bulk, for protrusions with an aspect ratio of 10 under a fixed applied electric field of 0.4 GV m−1 in DC mode.

The 22 July 2020 MW 7.8 Shumagin seismic gap earthquake: Partial rupture of a weakly coupled megathrust

The earthquake potential of the Shumagin seismic gap along the Alaska Peninsula (∼162°W to ∼158.5°W) has been debated for more than 40 years. On 22 July 2020, the eastern half of the gap hosted an MW 7.8 earthquake involving a patchy rupture of the megathrust in the depth range of 20 to 45 km. The space-time slip distribution is determined by joint inversion of teleseismic P and SH waves and static displacements from regional GPS stations. The event initiated near the epicenter of the 10 November 1938 (MW 8.2) event, and ruptured westward, with little/no overlap with the 1938 rupture zone. The main slip patch has peak slip of ∼3.8 m below the Shumagin Islands, and produced ∼30 cm uplift and ∼25 cm SSE horizontal displacement on Chernabura Island. The slip model predicts well the small (<1 cm) tsunami signals persisting for more than ten hours observed at deep-water DART seafloor pressure recordings along the Alaska-Aleutian arc. Aftershocks with depths from 20 to 40 km fringe the large-slip patches, and show westward concentration during the first month after the mainshock. Aftershocks up-dip of the 1948 MW 7.1 event contribute to the high level of modest-size background seismicity extending to the trench in the region of very low seismic coupling (0.0–0.1) in the western Shumagin gap east of the 1 April 1946 (MW 8.6) rupture zone. The 31 May 1917 event is the last major earthquake to rupture the eastern half of the Shumagin gap, and has a lower surface wave magnitude (MSG-R 7.4, horizontal components) compared to the 2020 event (MSG-R 7.7, vertical components). Comparison of instrument-equalized waveforms for the 1917 and 2020 events indicates similar size contrast and differences in overall rupture duration and slip complexity. The 2020 rupture has average slip of ∼1.9 m over the 3600 km2 region with co-seismic slip ≥1 m. This is much less than the ∼6.7 m of potentially accumulated slip deficit since 1917, consistent with geodetic estimates of low average seismic coupling coefficient of 0.1–0.4. The megathrust seaward of the 2020 event has low seismicity and may either be aseismic or capable of comparable size ruptures. Comparisons are made with other subduction zones that have experienced relatively deep megathrust slip in regions with moderate seismic coupling.

Coupling Coordination and Prediction Research of Tourism Industry Development and Ecological Environment in China

Based on the data relevant to China’s tourism industry and ecological environment from 2005 to 2018, the entropy method and the coupling coordination degree model were used to analyze the coupling degree and coupling coordination degree of the tourism industry’s development and the ecological environment, and the GM (1.1) gray model was used to predict these values in the future. The model provided predictions and illustrated the trend in the changes in the degree of coordination between the development of China’s tourism industry and the ecological environment for the next five years. The results show the following. (1) The coupling degree between China’s tourism industry and the ecological environment was between 0.3 and 0.5. It was in the low-level coupling stage in 2005 and 2006 and generally low in 2005–2009, lower than the average level of 0.4204. In 2018, the coupling degree between the development of China’s tourism industry and the ecological environment was mainly in a stage of antagonism, reaching a peak of 0.4998 in 2013. The coupling degree declined slightly from 2013 to 2015 and then began to show an upward trend again in 2016. (2) The average coupling coordination level of China’s tourism industry development and ecological environment was 0.4266, which is in the medium coupling coordination stage. From 2007 to 2013, it was mainly in the phase of moderate coupling and coordination and high coupling and coordination from 2014 to 2018. (3) From the prediction results, the coupling degree will enter the coupling degree running-in stage in 2021 and the extreme coordination stage in 2023, but the coupling growth level during the running-in period will be significantly lower than the coupling coordination degree. Coordinated development of the two systems will take a long time, and active economic policies need to be adopted to promote their coordinated development.

On the use of metasurface for Vortex-Induced vibration suppression or energy harvesting

This paper explores the use of metasurface in designing an aerodynamic system for potential vortex-induced vibration (VIV) suppression or energy harvesting. Four kinds of metasurface patterns are designed to decorate an ordinary cylinder bluff body for modifying its aerodynamic characteristics. A theoretical model is developed for the VIV system by describing the wake as a van der Pol oscillator. The aerodynamic parameters, i.e., the lift and drag coefficients, used in the theoretical model, are determined from three-dimensional CFD simulations. A wind tunnel experiment is conducted to validate the theoretical model and investigate the aerodynamic behaviors of the VIV systems with different bluff bodies. It is found that the metasurface pattern has a significant influence on the aerodynamic characteristics of the bluff body. Using different metasurface patterns to decorate the bluff body, the vortex-induced vibration of the system could be either enhanced or suppressed, compared with the baseline reference using an ordinary bluff body with a smooth surface. Furthermore, the vortex shedding processes are simulated to give further insights into the wake oscillating motions. The roles of the metasurface in suppressing or enhancing the vortex-induced vibration are reasonably explained: the existence of metasurfaces could alter the flow field around the bluff bodies and consequently the aerodynamic force. In addition, based on the validated theoretical model, it is learned from a parametric study that the power output reaches saturation when the electromechanical coupling strength is increased to a certain level. Therefore, piezoelectric transducers with moderate coupling coefficients are recommended for practical applications from the cost-effective perspective.

Fully gapped superconductivity in centrosymmetric and noncentrosymmetric Re-B compounds probed with μSR

We present a comprehensive study on superconducting properties of Re$_7$B$_3$ and Re$_3$B through specific heat, magnetic susceptibility, resistivity, and transverse and zero-field muon spin rotation/relaxation ($\mu$SR) experiments on polycrystalline samples. Re$_7$B$_3$ (T$_C$ = 3.2~K) is a non-centrosymmetric type-II ($\kappa$ $\approx$ 9.27) superconductor in the weak coupling ($\lambda_{e-ph}$ = 0.54) regime. On the other hand, Re$_3$B (T$_C$ = 5.19~K) is a centrosymmetric type-II ($\kappa$ $\approx$ 34.55) superconductor in the moderate coupling ($\lambda_{e-ph}$ = 0.64) regime. Our transverse-field $\mu$SR measurements show evidence for isotropically gapped BCS type superconductivity with normalized gap ($\Delta_0/k_BT_C$) values of 1.69 (Re$_7$B$_3$) and 1.75 (Re$_3$B).

Description of longitudinal modes in moderately coupled Yukawa systems with the static local field correction

In moderately coupled Yukawa fluids, longitudinal mode dispersion is determined by the competition between kinetic and potential effects. In a recent paper [S. Khrapak and L. Couëdel, Phys. Rev. E 102, 033207 (2020)], a semi-phenomenological dispersion relation was constructed by the ad hoc addition of the Bohm–Gross kinetic term to the generalized instantaneous excess bulk modulus, which showed very good agreement with simulations. In this paper, a nearly identical dispersion relation is derived in a rigorous manner based on a dielectric formulation with static local field corrections. At moderate coupling, this formalism is revealed to be more accurate than other successful theoretical approaches.