Higher-order Response Research Articles

Experimental study on vortex-induced vibration of rough and smooth risers under variable incident angles arrangement

The interference effect between adjacent risers in a riser group has been an important research topic for a long time. To investigate the VIV responses of rough and smooth risers in a double riser system, and elucidate the impact of interference effect on rough and smooth risers. VIV experiments were conducted in a flume for rough and smooth risers under variable incident angles. The results indicate that the wake interference has the most significant impact on "lock-in" displacement when the roughness of the rough riser is lowest within the sub-critical Reynolds number range. The wake interference effect is more likely to exacerbate the vibration displacement of rough risers in the IL direction as the reduced velocity increases. Furthermore, the smooth riser at an incident angle of 0° is significantly excited by the wake from the rough riser, resulting in an expanded "lock-in" region, a shift in the dominant mode, and the excitation of higher-order frequency responses. The displacement response of the smooth riser at an incident angle of 90° is akin to that of an isolated smooth riser.

Investigation of linear and microscopic nonlinear optical responses of 1-indanone compounds in different environments based on polarity models

Molecular spectroscopic and nonlinear features can indicate positive changes by solvent molecules. In this work, DFT and spectroscopic techniques were used to study the polarity effects of different solvent environments. Polarity-based models were used for studying solvent induced interactions on the optical features of new groups of biomolecules. Despite the significant contribution of general effects on the molecular absorption spectra, there is considerable competition between general and specific environmental effects on the molecular emission properties. Under this condition, strong hydrogen bonds tend to increase molecular nonlinear responses. The same results were observed for the low order (first and second order) nonlinearity of biomolecules. Therefore, the studies on the environment effects on the biomolecules’ first order nonlinearity can give valuable information about higher-order optical responses. Moreover, 1-Indanone compounds with high nonlinearity can be considered as an effective element in designing optical devices.

Application of a novel higher-order stretchable kinematic model for electro-elastic response analysis of constrained cylindrical shell

This article investigates impact of initial electric potential and parameters of Pasternak’s foundation on the higher-order electroelastic responses of cylindrical shell rested on the Pasternak’s foundation subjected to electromechanical loads. The mathematical modeling is performed using the higher-order thickness stretchable model including bending and shear parameters of deformation. The virtual work principle is used to derive governing equations. The results are analytically obtained in terms of main parameters of the shell. A verification study is presented before presentation of numerical results. The results are presented with changes of initial electric potential and two parameters of Pasternak’s foundation.

Crystallographic and Optical Spectroscopic Study of Metal–Organic 2D Polymeric Crystals of Silver(I)– and Zinc(II)–Squarates

Metal–organic framework materials, as innovative functional materials for nonlinear optical technologies, feature linear and nonlinear optical responses, such as a laser damage threshold, outstanding mechanical properties, thermal stability, and optical transparency. Their non-centrosymmetric crystal structure induces a higher-order nonlinear optical response, which guarantees technological applications. ZnII– and AgI–squarate complexes are attractive templates for these purposes due to their good crystal growth, optical transparency, high thermal stability, etc. However, the space group type of the catena-((μ2-squarato)-tetra-aqua-zinc(II)) complex ([Zn(C4O4)(H2O)4]) is debatable, (1) showing centro- and non-centrosymmetric monoclinic C2/c and Cc phases. The same is valid for the catena-((μ3-squarato)-(μ2-aqua)-silver(I)) complex (Ag2C4O4), (2) exhibiting, so far, only a C2/c phase. This study is the first to report new crystallographic data on (1) and (2) re-determined at different temperatures (293(2) and 300(2)K) and the non-centrosymmetric Cc phase of (2), having different numbers of molecules per unit cell compared with the C2/c phase. There are high-resolution crystallographic measurements of single crystals, experimental electronic absorption, and vibrational spectroscopic data, together with ultra-high-resolution mass spectrometric ones. The experimental results are supported for theoretical optical and nonlinear optical properties obtained via high-accuracy static computational methods and molecular dynamics, using density functional theory as well as chemometrics.

Person explanatory multidimensional item response theory with the instrument package in R.

We present the new R package instrument to perform Bayesian estimation of person explanatory multidimensional item response theory. The package implements an exploratory multidimensional item response theory model and a higher-order multidimensional item response theory model, a type of confirmatory multidimensional item response theory. Explanation of person parameters is accomplished by fixed and random effect linear regression models. Estimation is carried out using Hamiltonian Monte Carlo in Stan. In this article, we provide a detailed description of the models; we use the instrument package to demonstrate fitting explanatory item response models with fixed and random effects (i.e., mixed modeling) of person parameters in R; and, we perform a simulation study to evaluate the performance of our implementation of the models.

A simplified approach for judging and evaluating the contribution of higher-order modes to the wind-induced acceleration of high-rise buildings

Acceleration is the control parameter for the occupant comfort, often solved in the frequency domain with modal decomposition. In general, the first-order mode response is adopted to represent the total acceleration in practice. However, considering only the first-order mode has been demonstrated to yield underestimated results up to 20 %, while no exact criterion exists to determine whether higher-order modes require to be considered or not. Hence, underlying factors, like the structural natural frequencies, the excitation dominant frequencies, and the distributions of building masses/stiffness, which may significantly affect the contribution of higher-order modes to the acceleration, are analyzed first. Notably, the ratio of the natural frequency of the higher-order mode to that of the first-order mode plays a decisive role in the contribution of the higher-order mode's acceleration. Moreover, the third-order and beyond modes can be largely disregarded. Subsequently, an empirical approach is introduced to determine the need for considering high-order modes. Finally, a simplified formula for estimating acceleration response in the frequency domain is derived to consider second-order modal response. This study provides a method for determining the contribution of higher-order vibration modes to acceleration and a simplified formula to consider the higher-order modal response.

Highly selective microstrip bandpass filters using dual-mode patch resonator loaded with short via

In this paper, highly selective dual-mode microstrip bandpass filters (BPFs) are presented utilizing novel square patch resonator loaded with short via and periodic metallic vias array. Characteristics of the patch resonator are studied, and a new nondegenerate dual-mode patch resonator operating with the second and third higher-order modes is proposed. A two-pole BPF based on one dual-mode patch cavity is analyzed, and two transmission zeros (TZs) are produced. To realize higher-order filtering responses, four-pole BPFs with two cascaded dual-mode patch resonators are proposed, and different cascaded methods of two dual-mode patch resonators by a λg/4 microstrip connecting line (MCL) are analyzed and compared to maintain high selectivity and small size. For the demonstration, two four-pole filters with the center frequency at 3.3 GHz and five transmission zeros is designed, fabricated and measured.

Enhancing higher-order modal response in multifrequency atomic force microscopy with a coupled cantilever system.

Multifrequency atomic force microscopy (AFM) utilizes the multimode operation of cantilevers to achieve rapid high-resolution imaging and extract multiple properties. However, the higher-order modal response of traditional rectangular cantilever is weaker in air, which affects the sensitivity of multifrequency AFM detection. To address this issue, we previously proposed a bridge/cantilever coupled system model to enhance the higher-order modal response of the cantilever. This model is simpler and less costly than other enhancement methods, making it easier to be widely used. However, previous studies were limited to theoretical analysis and preliminary simulations regarding ideal conditions. In this paper, we undertake a more comprehensive investigation of the coupled system, taking into account the influence of probe and excitation surface sizes on the modal response. To facilitate the exploration of the effectiveness and optimal conditions for the coupled system in practical applications, a macroscale experimental platform is established. By conducting finite element analysis and experiments, we compare the performance of the coupled system with that of traditional cantilevers and quantify the enhancement in higher-order modal response. Also, the optimal conditions for the enhancement of macroscale cantilever modal response are explored. Additionally, we also supplement the characteristics of this model, including increasing the modal frequency of the original cantilever and generating additional resonance peaks, demonstrating the significant potential of the coupled system in various fields of AFM.

Prediction model and optimization of energy consumption, cutting force, and surface roughness during machine tool cutting process based on high-order response surface methodology

Prediction model and optimization of energy consumption, cutting force, and surface roughness during machine tool cutting process based on high-order response surface methodology

Graphene-Based Artificial Dendrites for Bio-Inspired Learning in Spiking Neuromorphic Systems.

Analog neuromorphic computing systems emulate the parallelism and connectivity of the human brain, promising greater expressivity and energy efficiency compared to those of digital systems. Though many devices have emerged as candidates for artificial neurons and artificial synapses, there have been few device candidates for artificial dendrites. In this work, we report on biocompatible graphene-based artificial dendrites (GrADs) that can implement dendritic processing. By using a dual side-gate configuration, current applied through a Nafion membrane can be used to control device conductance across a trilayer graphene channel, showing spatiotemporal responses of leaky recurrent, alpha, and Gaussian dendritic potentials. The devices can be variably connected to enable higher-order neuronal responses, and we show through data-driven spiking neural network simulations that spiking activity is reduced by ≤15% without accuracy loss while low-frequency operation is stabilized. This positions the GrADs as strong candidates for energy efficient bio-interfaced spiking neural networks.

Seismic Response of the Continuous Rigid-Framed Bridge with Super-High Piers Based on Shaking Table Tests

Continuous rigid-framed bridges with super-high piers (CRFB-HP) have been widely applied in mountain areas. However, their seismic performance is still urgently to be clarified. In this study, the refined finite element model (FEM) of a CRFB-HP was constructed and verified according to the shaking table test results of its scaled model. On this basis, systematic elastic-plastic time history analysis of the CRFB-HP was conducted to investigate the influence of parameters on their seismic performance, including main bridge span, pier height and number of tie beams. The results show that CRFB-HP have the characteristic of long vibration periods and are more sensitive to long-period ground motions. Along the longitudinal and transverse directions, the peak pier top displacement and pier bottom bending moment of CRFB-HP are both relatively large under NLPL (+20~+70%) and NFPT (TP ≈ T1, +50~+120%) excitations. For the same span, the peak pier top displacement increases with the pier height increasing, while the peak pier bottom bending moment decreases with the pier height increasingFor the same pier height, the peak pier top displacement and peak pier bottom bending moment both increase with the span length increasing. Moreover, the pier height change has a greater effect on the pier top displacement than that of the span change. CRFB-HP show obvious high-order response participation (HRP) under different ground motions. The NFPT (TP ≈ T1), ground motions can significantly increase HRP. Moreover, compared with cast-in-place CRFB-HP, the HRP of a fabricated super-high pier is greater (+20~+30%). The peak pier top displacement and pier bottom bending moment both decrease with the increase in the number of tie beams. The reasonable arrangement of tie beams can improve the lateral seismic performance of CRFB-HP. However, compared to the cast-in-place CRFB-HP, the peak pier top displacement is larger, and the peak pier bottom bending moment is smaller, for the fabricated CRFB-HP.

Introducing high-order response surface method for improving scour depth prediction downstream of weirs

Scour depth downstream of weirs is considered one of the most important hydraulic problems, which greatly influences the stability of weirs. Recently, artificial intelligence (AI) methods have become increasingly popular in modeling hydraulic variables, especially scour depth, because they can capture nonlinear relationships between input variables and their associated objectives. Despite their importance, these models have problems with hyperparameter tuning in scour depth modeling due to their structures, so algorithms must be used to tune the hyperparameters. Moreover, these algorithms are usually tuned by using the trial-and-error method to select the hyperparameters such as the number of hidden nodes, transfer function, and learning rate, and in this case, the main problem is overfitting during the training phase. To solve these problems, the high-order response surface method (HORSM), an improved version of the response surface method (RSM), is used as an alternative approach for the first time in this study to predict the scour depth. The HORSM model is based on high-order polynomial functions (from two to six) compared with the artificial neural network model (ANN). The findings indicate that the fifth order of the HORSM polynomial function yields the most precise predictions, with a higher coefficient of determination (R2) of 0.912 and Willmott Index (WI) of 0.972 compared to the values obtained using ANN (R2 = 0.886 and WI = 0.927). Moreover, the accuracy of the predictions is represented by a reduction of the mean square error by up to 44.17 and 29.01% compared to the classical RSM and ANN, respectively. The suggested model established an excellent correlation and accuracy with experimental values.

FE Model Updating of Continuous Beam Bridge Based on Response Surface Method

In this paper, A high-order response surface method is proposed for finite element model updating of continuous beam bridges. Firstly, based on visual inspection and environmental vibration testing, the peak picking (PP) method and random subspace identification (SSI) method are used to identify the dynamic characteristic parameters of the structure. Then, the finite element model of the continuous beam bridge is updated based on the third-order response surface method. It can be concluded that the results of the updated finite element model are in good agreement with the test results, and the maximum error between the calculated and measured frequency is less than 3%, with MAC values greater than 85%. Moreover, the updated finite element model can reflect the current situation of real bridges and serve as the basis for bridge health monitoring, damage detection, and safety assessment.

Comparisons for Global Dynamics of a Geometrically Nonlinear Oscillator among Single-, Double- and Quadruple-Well Configurations

This paper conducts a comparative analysis of the global dynamics of a harmonically excited oscillator with geometrical nonlinearities. Static analysis of the oscillatory system shows that adjusting the horizontal distance ratio from 1 to 0 can lead to single, double and quadruple well configurations successively. Intra-well and inter-well resonant responses are deduced analytically. Qualitative and quantitative results both reveal that the oscillator displays the stiffness–softening characteristic in cases of double and quadruple wells and the stiffness–hardening characteristic in the case of a single well. The initial-sensitive phenomenon jump is performed via fractal basins of attraction. Complex dynamical behaviors, including higher-order periodic responses and chaos, are also exhibited. The results demonstrate that the oscillator with a double or quadruple well configuration can achieve the inter-well response with large displacement, thus confirming its desirability in engineering applications of geometrically nonlinear oscillators.

Damage detection based on accelerometers and computer vision measurements of moving load-induced structural responses

Damage identification is an important and challenging issue in structural health monitoring to prevent sudden structural failures. This study introduces a novel damage detection method for beams associated with the cross-correlation function of the moving load-induced full-field displacements. Firstly, through theoretical derivation, the structural responses of a single-span beam under arbitrary boundary conditions subjected to a moving concentrated force were investigated, both before and after damage occurred. The changes in structural responses due to local stiffness damage were analyzed from a theoretical perspective. Then, a method is introduced to extract high-resolution mode shapes, which represent the true state of the structure, from the computer vision-based displacements and accelerations measured at limited locations. These mode shapes were then used for full-field displacement reconstruction, and the changes in the cross-correlation function of these reconstructed displacements were employed for damage detection. The proposed method can obtain the higher-order responses compared to the traditional vision-based methods, and the displacements at the acceleration-unmeasured locations can be improved compared to the conventional data fusion method. Finally, the proposed method was validated both in numerical simulations and experimental tests on a beam model with multiple damage scenarios. The results have demonstrated the capability of the proposed method in mode shape extraction, full-field displacement reconstruction, and damage detection.

Behaviors of higher-order modes in I.H.P. SAW devices and discussion of their suppression

In this work, behaviors of higher-order modes in an I.H.P. SAW device with a layered LiTaO3/SiO2/SiN/Si substrate are investigated, and techniques for their suppression are discussed. First, variation of the higher-order mode responses with structural parameters are analyzed using two-dimensional FEM. Then, on the basis of the calculated data, structural parameters are determined for higher-order modes suppression while retaining the main mode characteristics. In addition, the effectiveness of the optimized structure is confirmed using measured data from a fabricated one-port resonator and filters. In the measured data, it is shown that higher-order modes in a specific frequency range are successfully suppressed, while the main made characteristics, such as Bode-Q, bandwidth, and TCF, are almost equivalent to those of conventional I.H.P. SAW resonators and filters.

Acoustic and language-specific sources for phonemic abstraction from speech

Spoken language comprehension requires abstraction of linguistic information from speech, but the interaction between auditory and linguistic processing of speech remains poorly understood. Here, we investigate the nature of this abstraction using neural responses recorded intracranially while participants listened to conversational English speech. Capitalizing on multiple, language-specific patterns where phonological and acoustic information diverge, we demonstrate the causal efficacy of the phoneme as a unit of analysis and dissociate the unique contributions of phonemic and spectrographic information to neural responses. Quantitive higher-order response models also reveal that unique contributions of phonological information are carried in the covariance structure of the stimulus-response relationship. This suggests that linguistic abstraction is shaped by neurobiological mechanisms that involve integration across multiple spectro-temporal features and prior phonological information. These results link speech acoustics to phonology and morphosyntax, substantiating predictions about abstractness in linguistic theory and providing evidence for the acoustic features that support that abstraction.

On the Evaluation of Higher-Harmonic-Current Responses for High-Field Spectroscopies in Disordered Superconductors

We discuss a formalism that allows for the calculation of a higher-harmonic-current response to a strong applied electric field for disordered superconducting systems described on the basis of tight-binding models with on- and/or intersite interactions. The theory is based on an expansion of the density matrix in powers of the field amplitudes, where we solve the equation of motion for the individual components. This allows the evaluation of higher-order response functions on significantly larger lattices than one can achieve with a previously used approach, which is based on a direct temporal integration of the equation of motion for the complete density matrix. In the case of small lattices, where both methods can be applied by including also the contribution of collective modes, we demonstrate the agreement of the corresponding results.

Three-dimensional sound recording using directional beams

The recording of three-dimensional spatial audio is typically carried out using microphone arrays that produce higher-order B-format responses, which are defined by spherical harmonics. Spherical harmonics provide a compact, orthonormal representation of the sound field, but can be intuitively challenging for general users because they do not have a direction, as opposed to typical microphones used in the audio industry. Furthermore, spherical microphone arrays typically use microphone angles based on Platonic solids which do not have intuitive directions such as front, rear, left, right, up, and down. This paper considers the use of sets of directional beams that have orthonormal properties in a similar manner to spherical harmonics. Sets of angles that have intuitive directions are used, and a method of approximating orthonormal beams is developed. The approach can also be applied to angles obtained from Platonic solids. Finally, a prototype microphone array that implements the directional recording format is described.

QuDPy: A Python-based tool for computing ultrafast non-linear optical responses

Nonlinear Optical Spectroscopy is a well-developed field with theoretical and experimental advances that have benefited multiple disciplines, including chemistry, biology, and physics. However, for the accurate interpretation of the corresponding multi-dimensional spectra, there is a need for precise quantum dynamical simulations based on model Hamiltonians. In this article, we present the initial release of our code, QuDPy (Quantum Dynamics in Python), which provides a robust numerical platform for performing quantum dynamics simulations based on model systems, including open quantum systems. A distinguishing feature of our approach is the ability to specify various high-order optical response pathways in the form of double-sided Feynman diagrams through a straightforward input syntax. This syntax outlines the time-ordering of ket-sided or bra-sided optical interactions acting on the time-evolving density matrix of the system. We utilize the quantum dynamics capabilities of QuTip to simulate the spectral response of complex systems, allowing us to compute virtually any n-th order optical response of the model system. To illustrate the utility of our approach, we provide a series of example calculations. Program summaryProgram Title:QuDPyCPC Library link to program files:https://doi.org/10.17632/5xm9pm24cz.1Developer's repository link:https://github.com/sa-shah/QuDPyLicensing provisions: MIT LicenseProgramming language: Python (v3.7)Supplementary material: Available as Google Colab Files.Example 1: https://tinyurl.com/y3j5jmmrExample 2: https://tinyurl.com/37vwntn5External packages:•QuTip (v.4.7) and dependencies i.e. Numpy, Matplotlib (https://qutip.org/)•UFSS Automatic Diagram Generator (https://github.com/peterarose/ufss)Nature of problem: Accurate quantum simulations of complex systems are required in order to understand and interpret multi-dimensional ultrafast spectroscopic signals. This code provides an open-source/multi-platform method that facilitates the generation of higher-order non-linear optical responses for an arbitrary molecular or material system given a model input Hamiltonian and bath model.Solution method: We use the double-sided Feynman diagram method [1, 2] to generate (symbolically) a set of response functions corresponding to the nth order non-linear response of the system to a series of laser pulses using the UFSS package [3] We then perform a series of accurate quantum dynamics calculations using the QuTip package [4] to generate the numerical response and spectra which correspond to specific experimental conditions.