Localized Modes Research Articles

Technological search strategy and breakthrough innovation: An integrated approach based on main-path analysis

The significance of breakthrough innovations is not only reflected in their technological novelty but also in their impacts on the evolution of industrial technology paths. In the context of accelerating digitalization and industrial upgrading, it is particularly important to investigate how can firms manage their technological search strategies to generate breakthrough outputs. We develop a main-path-based approach to complement the existing method of breakthrough innovations in terms of their impact on industrial technology evolution. Besides, based on a sample of 29,620 USPTO patents of the electric communication industry, for the period 1976–2021, we further link firms' technological search strategies of local and distant modes to their breakthrough innovation and find that the two search modes have respective and joint effects on firms' breakthrough performance concerning both technological novelty and industrial impact. This paper not only provides a more integrated approach to identifying breakthrough innovations but also explores the impact of a firm's technological search strategy on them.

Two-dimensional symbiotic solitons and quantum droplets in a quasi-one-dimensional optical lattice

Symbiotic solitons (SS) and quantum droplets (QD) are self-trapped localized modes emerging in binary Bose-gas mixtures with intra-component repulsion and inter-component attraction. We have shown that two-dimensional (2D) SS can be stabilized against collapse or decay by means of a quasi-one-dimensional optical lattice (OL). Mobility of SSs along the free direction of the potential allows us to explore interactions and collisions of SSs moving in the same channel and neighboring channels of the quasi-1D OL. For the case of equal atom numbers in both components of the binary Bose–Einstein condensate (BEC) we have developed a variational approach that showed the stability of SS. For parameter settings when the SS stays on the verge of collapse/decay instability we take into account the Lee–Huang–Yang quantum fluctuations (QF) term in the coupled Gross–Pitaevskii equations (GPE). The QF term in the 2D GPE has the form of nonlinearity with a logarithmic factor, which is repulsive for large amplitude waves and attractive for opposite situations. This property of the governing equation supports stable QDs immersed in a gaseous phase of the larger component in particle-imbalanced Bose-gas mixtures. We explore the peculiar properties of QD such as incompressibility and surface tension, which are inherent to liquids. The proposed model of binary BEC loaded in a quasi-1D OL allows us to demonstrate the manifestations of the incompressibility and surface tension of 2D QDs.

A new hybrid model for monthly runoff prediction using ELMAN neural network based on decomposition-integration structure with local error correction method

The important foundation for water resource management and utilization is effective monthly runoff prediction. In this study, a new coupled model for predicting monthly runoff is proposed. In order to predict the decomposed subsequences separately using an ELMAN neural network optimized by the sparrow search algorithm (SSA), this model first decomposes the original runoff series using robust local mean decomposition (RLMD) and complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) predicts the decomposed subsequences separately using an ELMAN neural network optimized by the sparrow search algorithm (SSA), and reconstructs the results to get initial prediction results. To acquire the final prediction result, local error correction (LEC) is used to perform error correction on the initial prediction model. Five evaluation indicators are used to assess the performance of the suggested coupling model on monthly runoff data from three experimental stations in China. After having analyzed the error correction capability of LEC model, it is found that CEEMDAN-RLMD-SSA-ELMAN-LEC decreases root mean square error (RMSE) values of Manwan Hydropower, Jiayuguan Station, and Yingluoxia Station by 18.52%, 21.78%, and 38.80%, respectively, and increases Nash-Sutcliffe efficiency coefficient (NSEC) values by 2.11%, 4.49%, and 5.43% compared to CEEMDAN-RLMD-SSA-ELMAN without error correction. Therefore, by incorporating error correction, the proposed coupled model is a trustworthy and beneficial means for forecasting monthly runoff.

Land Financing Model and Local Government Debt Governance: An Empirical Study of Prefecture-Level Cities in China

This paper addresses the lack of comprehensive research on land financing in relation to local government debt governance. It examines two land financing methods: "Getting revenue by selling land" and "land finance," using an endogenetic approach. The study analyzes the interactive relationship between local government debt expansion and land financing modes using panel data from Chinese prefecture-level cities. Key findings include: (1) Land financing methods significantly increase local government debt leverage, with varying performance levels. (2) Regional economic competition and financial status influence the interaction between land financing and local debt risk. (3) Fiscal and financial policies regulate local government's land financing behavior, leading to diverse approaches. To achieve effective fiscal and financial governance, it is crucial to establish a strong connection between local government debt risk prevention/control and land use mode. Implementing differentiated systems can enhance land use efficiency.

Dynamic modeling and analysis of hanger cables with spacers and dampers for vibration mitigation

Many suspension bridges are designed with hangers composed of pairs of cables. The hanger cables are featured by low fundamental frequencies and extremely low inherent damping, and thus subjected to various wind-induced vibrations, typically including wake-induced and vortex-induced vibrations. Spacers are required to connect the cables for suppressing wake-induced vibrations, which nevertheless provide nearly no additional damping. Damping devices are also required to suppress other types of vibrations, e.g., vortex-induced vibrations. A combination of spacers and dampers for vibration mitigation of hanger cables leads to a complex dynamic system. This paper focuses on modeling dynamic behaviors of such a system. A generalized and dimensionless numerical model is first established. Parametric analysis is then conducted to investigate the influences of spacers and dampers on system frequency and damping. It is found that equally distributed spacers with a dimensionless stiffness coefficient larger than 102 can be considered as rigid and further increasing stiffness cannot increase the system frequencies but leads to increased number of localized modes. A combination of near-anchorage dampers and viscoelastic spacers can provide adequate damping to both in-phase and out-of-phase cable vibrations. Variation in tension, mass and length ratios of the two cables is not effective in improving damping provided by viscoelastic spacers to in-phase vibrations.

Optimization as generator of structural instability: Koiter’s worst imperfection

This paper is focused on the interaction of local modes in pin-jointed structures, with the aim to present an algorithm for the appraisal of the lowest critical load characterizing the structure under the effect of small imperfections. This interaction phenomenon is framed within Koiter’s theory of elastic instability as a quartic system. First of all, the paper discusses the theoretical results of Koiter’s theorem about the determination of the worst imperfection with respect to the critical load. In doing this, the characterization of the fold lines in the modal space is recalled and used for the purposes of the reformulation of the theorem. Then, a FEM code aimed at the determination of the most dangerous shape of the imperfection, and at performing the related sensitivity analysis, is presented. The basis of the code is a nonlinear model of a 3D rod equipped with a planar flexural deformation, within the context of Eulerian instability. Some numerical results having a practical interest are discussed.

The Management Mode of Subway Localization in China

Subway gains more attention from the herds than before for the simple reason that the growth of fast food is regarded as an essential part in catering services. In that case, there are a myriad of risks in the process of Chinese indigenization. Based on the theoretical support of management theory and SWOT analysis, the management problems of Subway in the localization of China are analyzed. The study found that Subway had three problems after entering China, namely product innovation, operation procedure and advertising. Suggestions on these obvious problems will be given to provide reference for Subway in the future.

Kinetic study of the bifurcation of resonant magnetic perturbations for edge localized mode suppression in ASDEX Upgrade

The correlation between the bifurcation of resonant magnetic perturbations (RMPs) to the unshielded state and edge localized mode (ELM) suppression in ASDEX Upgrade is studied using a kinetic plasma response model numerically and analytically. For the numerical studies, the linear kinetic Maxwell solver KiLCA for cylindrical geometry and the quasilinear transport code QL-Balance are used in combination with the ideal MHD solver GPEC to account for realistic tokamak geometry. Based on this modelling, a numerical local bifurcation criterion is introduced which estimates the effect of RMP-induced temperature plateau formation in the resonant layer. Its analytical form is derived in constant-psi approximation. The kinetic model reproduces the known gyrocenter resonance, Er=0 , and the electron fluid resonance. In contrast to MHD theory, the latter is located at the zero of the perpendicular electron fluid velocity computed only with half of the electron temperature gradient. The application of the criterion to experimental data shows a correlation between bifurcation and the ELM suppression phase. Moreover, an electron density limit is found resembling the one observed in experiments.

Distributed Generation Based WADC for Inter-Area Oscillations Considering Unknown Inputs

Inter-area oscillations (IAOs) are one of the main problems for contemporary power systems because of their low-damping characteristics. Additionally, the damping behaviors of IAOs might be further deteriorated by the addition of low inertial distributed generation (DG) to the power system. Therefore, a novel wide-area damping controller (WADC) for DG-integrated power systems is developed utilizing a modal linear quadratic regulator (LQR) technique that only targets essential IAOs without degrading other local modes. The states participated in linear combination from modal LQR are generally unavailable and need to be estimated. Full order observers are frequently used in literature, although they may not function if some inputs are unavailable. Hence, an unknown input observer (UIO) is suggested in this paper to estimate the states despite certain inputs being unknown. The proposed methodology is then tested on a DG-integrated 4-machine, 11-bus system and 10-machine, 39-bus system to validate the overall proposed design process. Results show that the proposed WADC successfully dampens the crucial IAO modes by 10% and 15% while not degrading other modes of the system.

Systematic Assessment of Phonon and Optical Characteristics for Gas-Source Molecular Beam Epitaxy-Grown InP1−xSbx/n-InAs Epifilms

Experimental and theoretical assessments of phonon and optical characteristics are methodically accomplished for comprehending the vibrational, structural, and electronic behavior of InP1−xSbx/n-InAs samples grown by Gas-Source Molecular Beam Epitaxy. While the polarization-dependent Raman scattering measurements revealed InP-like doublet covering optical modes (ωLOInP~350 cm−1, ωTOInP~304 cm−1) and phonons activated by disorders and impurities, a single unresolved InSb-like broadband is detected near ~195 cm−1. In InP1−xSbx, although no local vibrational (InSb:P; x → 1) and gap modes (InP:Sb; x → 0) are observed, the Raman line shapes exhibited large separation between the optical phonons of its binary counterparts, showing features similar to the phonon density of states, confirming “two-mode-behavior”. Despite the earlier suggestions of large miscibility gaps in InP1−xSbx epilayers for x between 0.02 and 0.97, our photoluminescence (PL) results of energy gaps insinuated achieving high-quality single-phase epilayers with x ~ 0.3 in the miscibility gap. Complete sets of model dielectric functions (MDFs) are obtained for simulating the optical constants of binary InP, InSb, and ternary InP1−xSbx alloys in the photon energy (0 ≤ E ≤ 6 eV) region. Detailed MDF analyses of refractive indices, extinction coefficients, absorption and reflectance spectra have exhibited results in good agreement with the spectroscopic ellipsometry data. For InP0.67Sb0.33 alloy, our calculated lowest energy bandgap E0 ~ 0.46 eV has validated the existing first-principles calculation and PL data. We feel that our results on Raman scattering, PL measurements, and simulations of optical constants provide valuable information for the vibrational and optical traits of InP1−xSbx/n-InAs epilayers and can be extended to many other technologically important materials.

Organic cross-linking decreases the thermal conductivity of calcium silicate hydrates

We study the conductive heat transport through calcium silicate hydrate (C-S-H) and organically cross-linked C-S-H via experiments, micromechanical homogenization theory, and molecular simulations. We find that C-S-H's intrinsic thermal conductivity falls below its amorphous limit when cross-linked with short-chain organosilanes. The observed reduction correlates with the alkyl chain length of the bis-organosilane molecule. To understand the underlying fundamental molecular processes accountable for such a reduction, we construct realistic molecular structures of cross-linked C-S-H and validate them against the spectroscopic and pycnometery measurements. The atomistic simulations indicate that the reduction in the contribution of propagons (propagating heat carriers) and diffusons (diffusive heat carriers) to heat transport, and the amplification of locons (localized vibrational modes), are the main driving factors allowing to limit the heat conduction in C-S-H. Presented findings offer new potential directions to nanoengineering novel admixtures for cement composites and resilient lightweight cementitious mesostructures for thermally efficient building envelopes.

Design of steel-concrete composite panels under low-velocity impact: Local punching failure

Steel-concrete composite panels (SC panels), consisting of two layers of steel plates and one layer of in-filled concrete, have excellent impact resistance. Currently, the proposed impact-resistant design methods of SC panels under low-velocity impact only consider the overall bending failure mode, but are unsuitable for the more common local punching failure mode. This study establishes an ideal tri-fold line resistance function and theoretically derives the stiffness and resistance of SC panels for the local punching failure mode. Furthermore, from the energy perspective, a design method is proposed in the study with impact-side steel plate tearing and SC panel penetration as safety criteria, and a design process covering two types of failure modes is provided. The design process is applied to the SC panel of the AP1000 nuclear station, and its practicality is validated, providing a simple tool for researchers and engineers.

Localized defect modes’ tunability by Octonacci photonic bandgap structures with thin high-Tc superconductors

The reflectance spectrum, through 1D superconducting photonic bandgap structures organized following the Octonacci sequence, is studied by employing a theoretical calculation based on the transfer-matrix method and the two-fluid Gorter–Casimir theory. The proposed hetero-structures are made up of Yttrium oxide (A) and YBa2Cu3O7 (B) materials. We report the localization of modes for specific generations of the Octonacci sequence and TEM mode. We discuss the field-localization properties for different Octonacci sequences. It is noticed that localized defect modes of intensity scale up to 99% are sensitive to the wave-incident-angle and the TEM wave polarizations. The lateral position of the localized defect mode can be notably adjusted by the operating superconductor’s temperature (T), by applying a structural strain along the stacks, and by specific thicknesses of the used superconductor. The spectra exhibit forbidden wavelength zones around the localized defect modes in which the bandwidths increase with the strain coefficient h and under critical superconductor temperatures. The given structure has potential applications in tunable localized defect modes and is very useful in optical resonators.

Theoretical and Experimental Study of Optical Losses in a Periodic/Quasiperiodic Structure Based on Porous Si-SiO2

This study investigates the reduction of optical losses in periodic/quasiperiodic structures made of porous Si-SiO2 through a dry oxidation process. Due to their unique optical properties, these structures hold great promise for various optoelectronic applications. By carefully engineering the composition and geometry of the structures, we fabricate periodic/quasiperiodic structures on a quartz substrate using an electrochemical anodization technique and subsequently subject them to dry oxidation at two different temperatures. The structure exhibits two localized modes in the transmission and reflection spectra. Unoxidized and oxidized structures’ complex refractive index and filling factors are determined theoretically and experimentally. Optical characterization reveals that the porous Si-SiO2 structures exhibit lower absorption losses and improved transmission than the pure porous silicon structures. Additionally, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) confirm the presence of porous Si-SiO2 and reduced silicon content. Our study demonstrates that dry oxidation effectively decreases Rayleigh scattering losses, leading to enhanced optical performance and potential applications in efficient optoelectronic devices and systems based on silicon. For instance, periodic/quasiperiodic structures could soon be used as light-emitting devices inside the field of optoelectronics, adding photoluminescent nanoparticles to activate the localized modes.

Experimental recognition of seismic performance of simple bolt-connected precast frame by comparing with equal stiffness cast-in-situ frame

Multi-story industry buildings composed of precast concrete members and simple bolt-type connections are widely constructed in the world, and there is enormous need for future construction market. Based on the equal stiffness and stiffness distribution along the height, a 1/5-scale precast RC frame utilizing simple bolt-type connections and a reference cast-in-situ monolithic RC frame were designed and constructed to conduct shaking table tests. According to the test results, the seismic responses, failure modes and energy dissipation behaviors of the two models were analyzed and compared. The vibration modes of the precast frame performed bending deformation pattern, while the cast-in-situ one presented shear deformation pattern. The damage and inter-story drift of the precast frame was comparatively uniformly distributed along the stories, whereas that of the cast-in-situ frame was concentrated in the first story. The energy dissipation capacity of the precast frame was inferior to that of the reference frame, as the bolt-type connections couldn't have plastic damages and plastic hinges that occurred in the cast-in-situ joint zones. In general, the global seismic performance of the precast frame was close to the reference frame and its collapse resisting capacity under severe earthquakes was reliable. Some serious local failure modes and less of energy dissipation capacity of the precast frame should be concerned in high seismic regions.

Efficient second harmonic generation at quasi-bound states in the continuum in hybrid nanostructures of 2D plasmonic array and waveguide

We numerically investigate the second harmonic generation (SHG) in hybrid plasmonic–photonic structures consisting of an array of periodic gold nanodisks covered by a nonlinear dielectric layer. In the designed hybrid systems, symmetry-protected bound states in the continuum (BICs) at normal incidence, and Friedrich–Wintgen BICs due to the coupling between localized surface plasmon resonances (LSPRs) and waveguide modes at oblique incidence, are observed under both transverse-electric (TE) and transverse-magnetic (TM) polarized illuminations. SHG near the BICs is studied, and the dramatically enhanced nonlinear optical response at quasi-BICs is obtained. Such enhancement is ascribed to the enhanced local field due to hybrid modes of LSPRs and photonic modes. The results indicate that hybrid plasmonic-dielectric systems supporting BICs at both TE- and TM-polarized incidences are promising platforms for linear and nonlinear photonic devices.

Buckling-induced transmission switching in phononic waveguidesa).

On-chip phononic circuits tailor the transmission of elastic waves and couple to electronics and photonics to enable new signal manipulation capabilities. Phononic circuits rely on waveguides that transmit elastic waves within desired frequency passbands, which are typically designed based on the Bloch modes of the constitutive unit cell of the waveguide, assuming periodicity. Acoustic microelectromechanical system waveguides composed of coupled drumhead resonators offer megahertz operation frequencies for applications in acoustic switching. Here, we construct a reduced-order model (ROM) to demonstrate the mechanism of transmission switching in coupled drumhead-resonator waveguides. The ROM considers the mechanics of buckling under the effect of temperature variation. Each unit cell has two degrees of freedom: translation to capture the symmetric bending modes and angular motion to capture the asymmetric bending modes of the membranes. We show that thermoelastic buckling induces a phase transition triggered by temperature variation, causing the localization of the first-passband modes, similar to Anderson localization caused by disorders. The proposed ROM is essential to understanding these phenomena since Bloch mode analysis fails for weakly disordered (<5%) finite waveguides due to the disorder amplification caused by the thermoelastic buckling. The illustrated transmission control can be extended to two-dimensional circuits in the future.

Evaluation of impact response of thermal-damaged FRP-RC slabs: Effects of FRP bar type and concrete cover thickness

The purpose of present study is to investigate the impact response of FRP-RC slabs under elevated temperatures. Considering the high-temperature degradation effect and strain rate enhancement effect of FRP bars and concrete materials, a numerical model for studying the fire and impact resistance of FRP-RC slabs was established and verified. The impact failure mechanism of in-fire thermal-damaged FRP-RC slabs was analyzed. The influence of the type of FRP bars, concrete cover thickness and fire duration on the in-fire impact resistance of FRP-RC slabs was revealed. Ultimately, the post-fire residual bearing capacity of the slabs after elevated temperature and impact was obtained. The results show that the typical local punching failure mode is not affected by thermal damage while energy dissipated by concrete accounts for most of the impact energy absorbed by the slabs. When exposed to fire for 60 min, the elevated temperature significantly deteriorates the impact resistance of FRP-RC slabs with a cover thickness of 15 mm. At this time, the greater the concrete cover thickness, the better the impact resistance of FRP-RC slabs. Under the combined action of elevated temperature and impact, Carbon FRP-RC slabs have greater stiffness, lower deflection, greater impact plateau value, less impact duration and lower energy consumption than Aramid FRP, Basalt FRP and Glass FRP-RC slabs. Moreover, the damage index of the slab based on residual bearing capacity and peak displacement is approximately linearly positively correlated. The influence of the concrete cover thickness is more prominent on the damage index based on the peak displacement.

Metallic and All‐Dielectric Metasurfaces Sustaining Displacement‐Mediated Bound States in the Continuum

AbstractBound states in the continuum (BICs) are localized electromagnetic modes within the continuous spectrum of radiating waves. Due to their infinite lifetimes without radiation losses, BICs are driving research directions in lasing, non‐linear optical processes, and sensing. However, conventional methods for converting BICs into leaky resonances, or quasi‐BICs, with high‐quality factors typically rely on breaking the in‐plane inversion symmetry of the metasurface and often result in resonances that are strongly dependent on the angle of the incident light, making them unsuitable for many practical applications. Here, an emerging class of BIC‐driven metasurfaces is numerically analyzed and experimentally demonstrated, where the coupling to the far field is controlled by the displacement of individual resonators. In particular, both all‐dielectric and metallic as well as positive and inverse displacement‐mediated metasurfaces sustaining angular‐robust quasi‐BICs are investigated in the mid‐infrared spectral region. Their optical behavior with regard to changes in the angle of incidence is investigated and experimentally shows their superior performance compared to two conventional alternatives: silicon‐based tilted ellipses and cylindrical nanoholes in gold. These findings are anticipated to open exciting perspectives for bio‐sensing, conformal optical devices, and photonic devices using focused light.

Active control of localized mode and transmission in topological phononic waveguides by non-Hermitian modulation

We demonstrate the switching behavioral differences between lossy and nearly lossless edge-mode propagation by non-Hermitian modulation based on the phononic band design of a C 3v symmetric, two-dimensional phononic crystal with a unit cell composed of three air-filled circular holes in polydimethylsiloxane. We numerically show that strong loss effects lead to the extinction of the localized modes. This mechanism is analogous to the bound-to-unbound transition in non-Hermitian quantum systems. This result suggests that large variations in non-Hermitian modulation can be used for the active control of edge-mode propagation along topological interfaces.