Mode Splitting Research Articles

On-chip microresonator dispersion engineering via segmented sidewall modulation

Microresonator dispersion plays a crucial role in shaping the nonlinear dynamics of microcavity solitons. Here, we introduce and validate a method for dispersion engineering through modulating a portion of the inner edge of ring waveguides. We demonstrate that such partial modulation has a broadband effect on the dispersion profile, whereas modulation on the entire resonator’s inner circumference leads to mode splitting primarily affecting one optical mode. The impact of spatial modulation amplitude, period, and number of modulations on the mode splitting profile is also investigated. Through the integration of four modulated sections with different modulation amplitudes and periods, we achieve mode splitting across more than 50 modes over a spectral range exceeding 100 nm in silicon nitride resonators. These results highlight both the simplicity and efficacy of our method in achieving flatter dispersion profiles.

Modal Split and Cost-Sensitivity Analysis for Various Travel Modes Using Calibrated Parameters in NL Modeling

Modal Split and Cost-Sensitivity Analysis for Various Travel Modes Using Calibrated Parameters in NL Modeling

The role of the (e-)bike: a mode choice model for short distances

The bicycle is a very important mode for travel in various countries, particularly in the Netherlands. However, it is in practice often modelled with less detail than other urban modes, such as the car and public transport. Moreover, the increasing use of e-bikes and the differences with conventional bikes show that more research into this transport mode is needed. E-bikes require less physical effort and allow higher speeds, making the e-bike suitable for longer distances. The goals of this research are to (1) create a mode choice model that predicts an accurate modal split for urban areas in the Netherlands and this model is used to (2) find significant factors that influence the modal split, in order to support municipalities of Dutch urban areas to stimulate the use of the (e-)bike. Within both goals, potential differences between conventional bikes and e-bikes are considered. A conceptual model, following from the literature, describes the assumed modal choice including factors relevant to cycling. Data was used mainly from the Dutch National Travel Survey (ODiN). Discrete choice models, a multinomial logit and a nested logit, are estimated to identify significant influencing factors. Results show that a nested logit model is the most explanatory one compared to the other models, with a rho-square-bar of 0.469. The model includes 15 main variables, 3 quadratic components and 4 interaction effects. The nested structure is formed by a correlation between the bike and the e-bike. The factors that show to be generally highly influential for the bike and the e-bike are the travel distance, owning a driver’s license and street density. The model is practically applicable for municipalities to form expectations in the modal shift for changes in their networks or policies. However, modelling these changes has not been validated and thus needs further research.

Investigation of NWC and Structural LWC Using Local Material in the UAE Exposed to Elevated Temperatures

In response to the rapid urbanization and local boom in UAE’s development and real estate industry, concrete is continuously in demand in alarming amounts contributing to the climate change effect. Research has continuously shown that lightweight concrete (LWC) is a potential sustainable alternative for normal weight concrete (NWC) due to incorporation of cement alternatives within the mix, higher resource efficiency, and enhanced thermal insulation. This paper investigates the residual properties of NWC and structural LWC at room temperature and when exposed to the following steady-state temperatures: 100°C, 200°C, 400°C, 600°C, and 800°C. Results show that LWC exhibit higher fire performance than NWC. At failure, NWC specimens majorly reported cone and split failure modes. The LWC specimens displayed mostly columnar failure modes. Spalling of concrete was first reported at 600°C on LWC at the corners of the specimens. At 800°C, surface spalling was reported on NWC only, indicating the higher fire resistive property of LWC. After heat exposure, discoloration was first observed in all specimens at 400°C. The compressive strength of both types of concrete initially increased after high-temperature exposure. Residual strength reported increase up to 200°C and 400°C for NWC and LWC, respectively. Consequently, significant decrease in compressive strength reaching around 20% of the original compressive strength when exposed to 800°C. Results showed that NWC experiences more reduction in residual strength than LWC, supporting that LWC is a promising construction material in enhancing structural fire safety.

Complex network analysis of fossil fuel functional regions in the United States during the period 2017 to 2022

In this paper we use complex network analysis to describe fossil fuel spatial flows among 132 places covering the entire United States in 2017 and in 2022. These spatial flows are for crude petroleum, gasoline, and oil fuels. The analysis shows that all three fuels have different network topology. For all six networks we find major hubs of crude petroleum and its products, gasoline and fuel oils, concentrated in areas with large reserves such as the south-central part of the US. Using modularity, a network cluster identification metric, we show that spatial interactions can be used to delineate functional regions and their differences across fuel types. These functional regions evolve over time in response to the shifting US role as a major producer and net exporter of fossil fuels, expansion of the domestic pipeline network, and increases in fuel production and refinement locations. The modal split of the fuels examined in this paper shows the dominant role pipelines play for crude petroleum, transporting approximately 83 % of tonnage in 2017 and increasing to almost 89 % in 2022. In contrast, gasoline and oil fuels modal split hovers at around 60 % of tonnage transported by tanker truck followed by other modes including pipelines. Our analysis shows geographic clustering of major hubs and their functional regions along the Gulf Coast in Texas and Louisiana. These are in places that are often the locations of natural disasters. This together with the rapid increase of a few hubs as gateways to fossil fuel US exports makes them prime candidates in disrupting fossil fuel supply chains worldwide and amplifies vulnerability of fossil fuel supply chains. The spatial clustering trends shown in this paper provide added evidence of the source of short-term negative impacts in places such as Chicago in Illinois and Corpus Christi in Texas. This offers added information for government intervention.

Entropy-driven DNA nanomachine with magnetic assistance manipulating the aggregation of Au nanoparticles for label-free photothermal Aptasensing

Photothermal sensing has attracted increasing attention as a fast and portable detection method. However, photothermal sensors with excellent comprehensive performance still face challenges. Herein, a unique photothermal biosensor for bisphenol A as a model target is successfully constructed based on aptamer recognition coupled with the programmable entropy-driven DNA nanomachine cascaded strand displacement manipulating the aggregation of gold nanoparticles. In this protocol, the exposed bases of two DNA probes released from the DNA amplification network can anchor gold nanoparticles by van der Waals attraction. This allows gold nanoparticles to resist aggregation induced by a certain concentration of sodium chloride. Based on this exclusive mechanism, target-induced visual detection can be achieved by reading temperature changes. The two probes that are fully utilized to improve the atomic economy of the reaction and enhance the detection sensitivity. Also, label-free gold nanoparticles save time in the fabrication of the photothermal sensor. Moreover, visualized photothermal sensors with multi-color gradients enable self-verification of detection results, increasing sensor reliability. In particular, the splitting mode of magnetic-assisted extraction gives the designed photothermal sensor excellent specificity, which can meet the needs of real sample detection with high background noise. Additionally, this programmable and robust photothermal sensor has advantages of portability, replicability, rapid response, and simple operation.

Evidence for a Close-in Tertiary Orbiting around the Algol-type System HZ Dra with Tidal Splitting and Spots Activities

We report a cyclic variation of the O − C diagram with a semiamplitude of 0.0033 days and a period of 1.05 yr for the pulsating eclipsing binary HZ Dra. The cyclic variation can be explained by the light travel-time effect via the presence of a close-in third body orbiting around HZ Dra in an elliptical orbit with a maximum semimajor axis of 0.89 au. Based on the Wilson–Devinney code, the contribution of the third light to the total system is determined to be 29.0%, which is in agreement with the estimated value. Our light-curve modeling indicates an evolving hot and cool spot on the surface of the primary and secondary components, respectively. Their positions are roughly symmetrical to the inner Lagrangian point L1, which could be used to explain the variation in the O'Connell effect. Our frequency analysis detects one radial p-mode, seven nonradial p-modes, and one nonradial g-mode. In addition, a total of six multiplets are identified, spaced by the orbital frequency, which can be explained as a tidally split mode caused by the equilibrium tides of the close binary system with a circular orbit. These pulsating features suggest that the primary of HZ Dra is a δ Scuti star, pulsating in both p- and g-mode and influenced by tidal forces.

A linear model to estimate modal split in international freight transport, based on revealed preferences about cost and time saving

We present a new model for estimating the distribution of international freight transport over transport modes that is directly applicable to aggregated data, allows estimations and predictions also when some modes are infeasible on some routes, and requires few processing time and memory space. It builds on the assumption that demand for transport by a given mode is driven by trading firms’ and consumers’ preferences about saving transport costs and time. In contrast to conventional mode-choice models, it is linear and grounded on consumer demand theory. Applying the model to international freight transport as recorded in the latest upgrade of UN Comtrade reveals an average cost elasticity of transport demand of − 0.32 and an average time elasticity of − 0.18. In addition, we find significant independent mode-specific effects. Cost and time elasticities are highly dependent on the type of commodity transported. The cost elasticity ranges from zero to − 1.9 and the time elasticity from zero to − 3.3 across commodity groups defined at the four-digit level of the Harmonized System classification. These findings suggest that policy measures, exogenous shocks or other events that change the relative transport costs and transit times across modes can cause modal shifts—for some commodities more than for others—thereby mitigating the loss in welfare.

Oscillation frequencies of moderately rotating delta scuti stars: asymmetric mode splittings due to non-spherical distortion

ABSTRACT We find that the observed pressure-mode rotational splittings of slowly/moderately rotating $\delta$ Scuti stars and $\beta$ Cephei stars mostly have a positive asymmetry. That is, the left frequency spacing is larger than the right spacing in the dipole mode splitting triplets and the $l=2$ mode splitting multiplets (considering $m=1, 0, -1$ modes only). This is in agreement with the second-order perturbative effect of the rotational non-spherical distortion: both the prograde and retrograde modes have their frequencies shifted towards lower values relative to the $m=0$ modes. We thus study the rotational perturbation both in the first and second order, as well as the near-degeneracy mode coupling effect in MESA models representing $\delta$ Scuti stars. For faster rotators, the near-degeneracy mode coupling between the nearest radial and quadrupole modes can significantly shift the $m=0$ modes, reduce the splitting asymmetry, and even change its sign. We find the theoretical splitting asymmetry from the second-order non-spherical distortion can explain the observed asymmetry quantitatively. To facilitate future detections, we predict correlations between splitting asymmetry, splitting amplitude, and pulsation frequency. We also discuss additional factors that can influence splitting asymmetry, including embedded magnetic fields, resonant mode coupling, and binarity.

Dual-Band Polarization Control with Pairwise Positioning of Polarization Singularities in Metasurfaces.

Emerging applications of metasurfaces in classical and quantum optics are driving the need for precise polarization control of nearly-degenerate, high quality (Q)-factor modes. However, current approaches to creating specifically polarized pairs of modes force a trade-off between maintaining high Q factors and robustness. Here, we solve this challenge by employing pairwise generation, annihilation, and positioning of polarization singularities, derived from symmetry-guaranteed pairs of symmetry-protected bound states in the continuum. We experimentally demonstrate this design paradigm in silicon metasurfaces with mode splittings of ≈20 nm, mode splitting deviations as low as 1nm, and Q factors up to 200. This approach opens new avenues for enhancing metasurface performance across a diverse range of applications, including sensing, modulating, nonlinear mixing, and generating quantum light.

Splitting behavior of lamella

Lamella is a unique microstructure in matters that possesses special properties. The formation and evolution of lamellar microstructures are crucial for achieving super abilities, while the mechanisms of lamellar formation and evolution at the nanoscale are unclear. Driving by the interesting while uncovered micromechanism in lamellar microstructure evolution, we performed the phase-field simulation and experiment to investigate the multiple splitting behaviors of lamellar Ti-Al alloys. The splitting mode of lamella is discovered, inner splitting (IS) and outside splitting (OS). The originations of splitting are found to come from the high interfacial energy of step-like interface between γ variants for the IS, and the stress concentration at α2/γ interface drives step-like interface for the OS. The lamellar splitting is complied with the energy change in matter, decreasing in total free energy and elastic energy, while increasing in interfacial energy. These findings provide the new mechanisms of internal lamellar interface breaking driven by the interfacial energy. Therefrom, the expected matter features will be achieved by the strategy of microstructure modulation and optimization.

A Diachronic Agent-Based Framework to Model MaaS Programs

In recent years, mobility as a service (MaaS) has been thought as one of the opportunities for shifting towards shared travel solutions with respect to private transport modes, particularly owned cars. Although many MaaS aspects have been explored in the literature, there are still issues, such as platform implementations, travel solution generation, and the user’s role for making an effective system, that require more research. This paper extends and improves a previous study carried out by the authors by providing more details and experiments. The paper proposes a diachronic network model for representing travel services available in a given MaaS platform by using an agent-based approach to simulate the interactions between travel operators and travelers. Particularly, the diachronic network model allows the consideration of both the spatial and temporal features of the available transport services, while the agent-based framework allows the representation of how shared services might be used and which effects, in terms of modal split, could be expected. The final aim is to provide insights for setting the architecture of an agent-based MaaS platform where transport operators would share their data for providing seamless travel opportunities to travelers. The results obtained for a simulated test case are promising. Particularly, there are interesting findings concerning the traffic congestion boundary values that would move users towards shared travel solutions.

Linear and nonlinear coupling of light in twin-resonators with Kerr nonlinearity

Nonlinear effects in microresonators are efficient building blocks for all-optical computing and telecom systems. With the latest advances in microfabrication, coupled microresonators are used in a rapidly growing number of applications. In this work, we investigate the coupling between twin-resonators in the presence of Kerr nonlinearity. We use an experimental setup with controllable coupling between two high-Q resonators and discuss the effects caused by the simultaneous presence of linear and nonlinear coupling between the optical fields. Linear-coupling-induced mode splitting is observed at low input powers, with the controllable coupling leading to a tunable mode splitting. At high input powers, the hybridized resonances show spontaneous symmetry breaking (SSB) effects, in which the optical power is unevenly distributed between the resonators. Our experimental results are supported by a detailed theoretical model of nonlinear twin-resonators. With the recent interest in coupled resonator systems for neuromorphic computing, quantum systems, and optical frequency comb generation, our work provides important insights into the behavior of these systems at high circulating powers.

Natural mode splitting of a rotating disc in water at different wall distances as a model for high-head francis runners

Francis turbines are essential equipments in the realm of sustainable energy production. However, their complex dynamics, particularly in the presence of fluid-structure interaction, pose significant challenges to optimising design and enhancing performance. This study focuses on the phenomenon of frequency splitting of a simplified rotating disc submerged in water, serving as a representative model for high-head Francis runners. The primary objective is to gain a deep understanding of how proximity to surrounding walls affects modal parameters of the rotating runner. This research employs both analytical and numerical methods. For cases characterised by significant asymmetry in wall distances on either side of the disc, we have refined the analytical model for frequency splitting based on the assumed mode method and potential flow theory. Additionally, we have developed a numerical model for predicting modal parameters of underwater rotating discs, building upon the imposed modal motion approach. These methods are validated using existing experimental results, demonstrating excellent consistency. The research indicates that for underwater rotating discs, frequency splitting occurs simultaneously with damping splitting. In general, as wall distances decrease, the degree of splitting increases, and the sensitivity of splitting to changes in wall distance also rises. This comprehensive study provides profound insights into the dynamic behavior of high-head Francis runners, highlighting the pivotal role played by wall proximity in shaping their vibrational behavior.

Double-slot micro-ring resonators with trapezoidal subwavelength grating as ultra-sensitive biochemical sensors

Silicon-based refractive index sensors are of significance in the detection of gases, biological substances and chemical compounds. Among these, optical microcavities can confine the optical field to the micrometre-scale region, and possess the advantages of high Q factor, small size and easy integration. In this paper, a trapezoidal subwavelength grating (SWG) is introduced into a slot micro-ring resonator, and the mode splitting is employed to enrich the supported standing wave modes and optimize the spatial profiles of the resonant modes. The modes’ Q factor is improved and the high sensitivity and low detection limit is achieved. The optimal trapezoidal subwavelength grating double slot micro-ring resonator (T-SWGDSMRR) structure is obtained by designing the structural parameters and analyzing their effects on the sensing performance parameters and spectral characteristics. The T-SWGDSMRR, designed for detecting the glucose solution, demonstrated a low detection limit of 3.3×10−5 RIU and an ultra-high Q factor of up to 100825, accompanied by a refractive index sensitivity of 424 nm/RIU. Finally, a cascaded double micro-ring sensor is proposed using the vernier effect, through cascading the T-SWGDSMRR with a referential ring, the sensitivity is enhanced to 12828 nm/RIU, and the limit of detection is 3.12×10−6 RIU.

Incorporating policy mixes to multimodal network capacity considering second-best constraints

In the pursuit of capacity-oriented urban sustainable development (SD), this study aims to enhance the multimodal transport network by making it more accessible, efficient, and environmentally friendly. A sustainable framework combining policy mixes and second-best constraints is developed as a multimodal transportation network capacity (TNC) model with the bi-level programming (BLP) formulation. The upper-level model is to maximise the total origin-destination (OD) demand with considering second-best constraints. The lower-level model is a combined mode split and traffic assignment with elastic demand (CMSTA-ED) model which considers policy mixes. Numerical experiments are conducted to demonstrate the effectiveness of the hybrid PSO–GWO algorithm, the synergy of the method for selecting and mixing policy instruments based on the proposed assessment system, and a methodology to establish a policy mix. The findings of this research offer practical guidance for formulating well-informed and no-redundant policy mixes, contributing to the improvement of sustainable multimodal transportation network performance.

Estimation of frequencies and Q-factors of Earth’s low-frequency toroidal normal modes using strain data

In the study, estimations of the parameters of three low-frequency toroidal modes 0T2, 0T3, and 0T4, excited by the 13 largest earthquakes of the 21st century, were carried out. The etimations were obtained using the data from the Baksan Laser Interferometer–Strainmeter of SAI MSU. Using an adaptive spectral algorithm, estimates of the modes’ frequencies were obtained, and they were compared with the PREM model. Significant deviations in the frequency estimates of the 0T4 mode for a series of earthquakes were found, showing their possible connection with local inhomogeneities in the values of the speed of shear waves and the Earth’s density in the upper mantle. The splitting of the 0T2 mode due to Earth’s ellipticity and rotation was studied, with frequency estimates of singlets excited after catastrophic earthquakes in Sumatra, Japan, and Chile obtained. An evaluation of the Q-factors of the low-frequency toroidal modes was performed using three different methods.

Synthesis, crystal structure and properties of μ-tetra-thio-anti-monato-bis-[(cyclam)zinc(II)] perchlorate 0.8-hydrate.

The reaction of Zn(ClO4)2·6H2O with Na3SbS4·9H2O in a water/aceto-nitrile mixture leads to the formation of the title compound, (μ-tetra-thio-anti-monato-κ2 S:S')bis-[(1,4,8,11-tetra-aza-cyclo-tetra-decane-κ4 N)zinc(II)] perchlorate 0.8-hydrate, [Zn2(SbS4)(C10H24N4)2]ClO4·0.8H2O or [(Zn-cyclam)2(SbS4)]+[ClO4]-·0.8H2O. The asymmetric unit consists of two crystallographically independent [SbS4]3- anions, two independent perchlorate anions and two independent water mol-ecules as well as four crystallographically independent Zn(cyclam)2+ cations that are located in general positions. Both perchlorate anions and one cyclam ligand are disordered and were refined with a split mode using restraints. The water mol-ecules are partially occupied. Two Zn(cyclam)2+ cations are linked via the [SbS4]3- anions into [Zn2(cyclam)2SbS4]+ cations that are charged-balanced by the [ClO4]- anions. The water mol-ecules of crystallization are hydrogen bonded to the [SbS4]3- anions. The cations, anions and water mol-ecules are linked by N-H⋯O, N-H⋯S and O-H⋯S hydrogen bonds into a three-dimensional network. Powder X-ray diffraction proves that a pure sample had been obtained that was additionally investigated for its spectroscopic properties.

Metal–to–particle charge transfer invoked photoelectrochemistry on ferroelectric SrTiO3 for split–mode and high–throughput aptasensing

Split–mode aptasensing is highly desirable in photoelectrochemistry because of its distinctive advantages of high-throughput, avoided damage to biomolecules, and increased sensitivity and selectivity. However, the currently available photoelectrochemical (PEC) strategy conducible to split–mode aptasensing is still limited to the bioreaction mediated generation of photoactive species, in which a low photocurrent was usually attained, rending this strategy impotent for attaining high sensitivity. As a result, to explore new strategies that are amendable to highly efficient, split-mode PEC aptasensing are still challenging but demanding. Herein, ferrocyanide mediated metal–to–particle charge transition (MPCT) on ferroelectric strontium titanate (SrTiO3) was explored as an innovative signal transduction strategy and was validated for high-performance aptasensing. By taking the 17β–Estradiol (E2) as a model analyte, the recognition between the target (E2) and its aptamer anchored on the Fe3O4@Au (named as Fe3O4@Au/Apt) destroyed the beforehand formed assembly between the Fe3O4@Au/Apt and the ssDNA labeled liposome encapsulated with [Fe(CN)6]4- (named as DLL–FeCN), which resulted in the release of the beforehand encapsulated [Fe(CN)6]4- into solution. The released [Fe(CN)6]4- then coordinated onto the surface of SrTiO3 nanoparticles consisted photoelectrode, forming the MPCT process from metal ion (iron (II) in [Fe(CN)6]4-) to the conduction band (CB) of SrTiO3 for anodic photocurrent signal output. The detection achieved linear range of 1.0 pM–100 nM, with a detection limit of 0.3 pM for E2. Benefiting from the cooperative effects of the MPCT process and the ferroelectric polarization in bulk SrTiO3 for achieving highly efficient photocurrent generation capability, the developed split–type detection had the advantage of high sensitivity/selectivity and high throughput. This work not only opens up the MPCT process for innovative PEC sensing strategy but also blazes a new road for high performance PEC aptasensing.

Atomic-Scale Mechanism of Enhanced Electron-Phonon Coupling at the Interface of MgB2 Thin Films.

In conventional Bardeen-Cooper-Schrieffer (BCS) superconductors, electron-phonon coupling is the fundamental mechanism of superconductivity. For instance, the superconductivity of magnesium diboride (MgB2) comes from the coupling between E2g modes (in-plane boron-boron bond vibrations) and self-doped charge carriers. In thin films and ceramics of BCS superconductors, interfaces with discontinuous chemical bonds may alter the local electron-phonon coupling. However, such effects remain largely unexplored. Here, we investigate the heterointerface of the MgB2 film on the SiC substrate at the atomic scale using electron microscopy and spectroscopy. We detect the presence of a thin MgO layer with a thickness of ∼1 nm between MgB2 and SiC. Atomic-level electron energy loss spectra (EELS) show MgB2-E2g mode splitting and softening near the MgB2/MgO interface, which enhances electron-phonon coupling at the interface. Our findings highlight the potential of interface engineering to enhance superconductivity via modulating local phonon states and/or electron states.