Arbitrary Structure Research Articles

Vibration damping by maximizing the reactive power of an inertial shaker

Passive and active vibration control is required to reduce noise, prevent damage, or maintain the stability of a structure. Active measures are of particular importance due to their narrowband performance. They use inverted or phase shifted signals to shift the kinetic energy of the vibrating structure to frequency bands where it does not have a negative effect on the sound emission and auditory sensation. In this paper, an active-mass-damper is realized by an inertial shaker as actuator by controlling its current. The power that the active-mass-damper transmits to the vibrating structure is measured by the transmitted force and the acceleration of the point of force application. The control system maximizes the reactive power and, therefore, acts as an active-mass-damper to minimize the vibration of a structure. An arbitrary structure represented by a single DOF mass-spring-damper system which is excited by a modal shaker. An electromechanical model of the inertial shaker is formulated, and a control system is designed. The simulation is validated with laboratory experiments. The experimental results show that the vibration of the structure can be minimized by increasing the reactive power transmitted by the active-mass-damper to the structure.

Fiber-optic temperature sensor based on glass Fabry–Perot interferometer

The paper presents a theoretical and experimental study of a fiber-optic all-glass microthermometer based on a Fabry–Perot interferometer. The interferometer is fabricated by applying borosilicate glass to the cleaved end of a standard telecom single-mode optical fiber using a microforge. According to the results of experimental studies, the spectral sensitivity of the fabricated interferometer was about 40 pm/°C. A mathematical model of the Fabry–Perot interferometer based on the method of scattering and transfer matrices is presented and verified, which makes it possible to calculate the spectral response of an interferometer with arbitrary structure parameters.

A novel spatial–temporal generative autoencoder for wind speed uncertainty forecasting

Wind speed interval prediction is one of the most long-standing challenges because of the high uncertainty and the complex spatial–temporal correlation between wind turbines. In this paper, based on variational Bayesian inference, we propose a novel spatial–temporal generative autoencoder (STGAE) model to capture the continuous probability distribution of each wind turbine on an arbitrary graph structure. In the encoding process, a parameterization strategy is used to expand the hypothesis space of the adjacency matrix rather than being limited by the distance between nodes. The multiple graph convolution layers with kernels approximated by Chebyshev polynomials adjust the collecting scope of spatial information. The bi-directional dependency is modeled by the multi-head attention to tap correlations of different time horizons effectively. The interval prediction at each node is yielded based on the probability densities of generated samples produced by the decoder. Using publicly available wind data from the Global Energy Forecasting Competition 2014, numerical experiments are conducted to compare the prediction reliability and accuracy between the proposed model and the recent state-of-the-art models. The forecasting results suggest that the proposed model significantly improves performance, especially the strong generalization ability makes it practical under different weather conditions.

Strain experimental modal analysis of an Euler–Bernoulli beam based on the thermoelastic principle

The strain mode shapes can be utilized as an indicator of vibration fatigue-hotspots and are utilized for predicting the distribution of damage intensity. However, the conventional approach for measurement, which involves using strain sensors, does not offer the necessary high spatial density required for accurately identifying critical locations or creating a comprehensive map of damage intensity. Non-contact methods have been employed to indirectly determine the full-field strain shapes, but when measuring kinematic quantities, a relation between kinematics and stress/strain must be known. For Euler–Bernoulli beam, the double spatial derivative is required which introduces a significant uncertainty. In contrast, by leveraging the thermoelastic principle, the full-field stress/strain response of an arbitrary structure can be directly measured using a high-speed infrared (IR) camera. The thermoelastic principle has not been extensively researched for strain experimental modal analysis (EMA). In this study, the hybrid EMA (based on one high-dynamic range sensor) was researched for thermoelastic identification of an Euler–Bernoulli beam. The minimum stress/temperature variation required to achieve accuracy comparable to scanning-laser kinematics-based strain mode shapes was investigated. The findings demonstrate that even when the noise floor is significantly higher than the signal, full-field strain mode shapes can be identified using IR cameras and the hybrid EMA method. By considering the minimum stress/temperature variation determined in this research (for aluminum and steel), the accuracy of thermoelasticity-based strain shapes can be evaluated during the experiment-design stage. While this research is theoretically and experimentally based on Euler–Bernoulli beam, generalization of the thermoelastic principle to arbitrary structure is feasible.

Vibrations of Periodic Systems Consisting of Identical Subsystems of an Arbitrary Structure

Vibrations of Periodic Systems Consisting of Identical Subsystems of an Arbitrary Structure

Chiroptical interactions between an achiral T-shaped gold nanoparticle and chiral media in the strong coupling regime

The research on the interactions between plasmon and chiral materials is fundamental to the understanding of chiroptical effects and the designs of chiroptical devices. Some theories have been developed to explain the strong interactions between simple nanoparticles and chiral media, but it is difficult to apply to complicated systems. In this paper, we developed an effective method, which utilizes the chiral constitutive relations and finite element method (FEM) simulation, to investigate strong interactions between arbitrary structure and chiral media. To demonstrate the feasibility of our method, we designed a hybrid system by homogeneously coating a layer of chiral medium on achiral T-shaped gold nanoparticle (TGNP). By calculating the circular dichroism (CD) and absorption spectra of the system, we observed a large mode splitting in the CD/absorption spectra, which indicated the system achieves a strong coupling regime. Furthermore, we discovered that the CD spectra of the system can be decomposed into three curves, which are contributed by the chiral media, TGNP, and the optical chirality (OC) density. The chiroptical response of the achiral TGNP is induced by the chiral media and exhibits a strong anti-crossing behavior. The phenomenon can be explained by using the chiral Poynting’s theorem and FEM. Our research has wide potential applications in chiroptical manipulation and chiral quantum optics.

Суперэллипсоидальные аппроксимации в задаче быстродействия для двумерной линейной дискретной системы с ограниченным управлением

<p>The paper considers a two-dimensional linear discrete system with bounded control. For the system, the problem of speed is solved, that is, the construction of a control process that transfers the system from the initial state to the origin in the minimum number of steps. If the set of acceptable control values has a superellipse structure, then the problem of calculating optimal control can be reduced to solving a system of algebraic equations. A superellipsoidal approximation method has been developed for sets of arbitrary structure. Examples are considered in the paper.</p>

Interpolating Graph Pair to Regularize Graph Classification

We present a simple and yet effective interpolation-based regularization technique, aiming to improve the generalization of Graph Neural Networks (GNNs) on supervised graph classification. We leverage Mixup, an effective regularizer for vision, where random sample pairs and their labels are interpolated to create synthetic images for training. Unlike images with grid-like coordinates, graphs have arbitrary structure and topology, which can be very sensitive to any modification that alters the graph's semantic meanings. This posts two unanswered questions for Mixup-like regularization schemes: Can we directly mix up a pair of graph inputs? If so, how well does such mixing strategy regularize the learning of GNNs? To answer these two questions, we propose ifMixup, which first adds dummy nodes to make two graphs have the same input size and then simultaneously performs linear interpolation between the aligned node feature vectors and the aligned edge representations of the two graphs. We empirically show that such simple mixing schema can effectively regularize the classification learning, resulting in superior predictive accuracy to popular graph augmentation and GNN methods.

The importance of flavor in SMEFT Electroweak Precision Fits

Effective field theory tools are essential for exploring non-Standard Model physics at the LHC in the absence of the discovery of new light particles. Predictions for observables are typically made at the lowest order in the QCD and electroweak expansions in the Standard Model effective field theory (SMEFT) and often ignore the effects of flavor. Here, we present results for electroweak precision observables (EWPOs) at the next-to-leading order QCD and electroweak expansions (NLO) of the SMEFT with an arbitrary flavor structure for the fermion operators. Numerical NLO SMEFT fits to EWPOs have a strong dependence on the assumed flavor structures and we demonstrate this using various popular assumptions for flavor symmetries.

Andreev Reflection in Scanning Tunneling Spectroscopy of Unconventional Superconductors.

We evaluate the differential conductance measured in an STM setting at arbitrary electron transmission between STM tip and a 2D superconductor with arbitrary gap structure. Our analytical scattering theory accounts for Andreev reflections, which become prominent at larger transmissions. We show that this provides complementary information about the superconducting gap structure beyond the tunneling density of states, strongly facilitating the ability to extract the gap symmetry and its relation to the underlying crystalline lattice. We use the developed theory to discuss recent experimental results on superconductivity in twisted bilayer graphene.

EFT analysis of New Physics at COHERENT

Using an effective field theory approach, we study coherent neutrino scattering on nuclei, in the setup pertinent to the COHERENT experiment. We include non-standard effects both in neutrino production and detection, with an arbitrary flavor structure, with all leading Wilson coefficients simultaneously present, and without assuming factorization in flux times cross section. A concise description of the COHERENT event rate is obtained by introducing three generalized weak charges, which can be associated (in a certain sense) to the production and scattering of νe, νμ and {overline{nu}}_{mu } on the nuclear target. Our results are presented in a convenient form that can be trivially applied to specific New Physics scenarios. In particular, we find that existing COHERENT measurements provide percent level constraints on two combinations of Wilson coefficients. These constraints have a visible impact on the global SMEFT fit, even in the constrained flavor-blind setup. The improvement, which affects certain 4-fermion LLQQ operators, is significantly more important in a flavor-general SMEFT. Our work shows that COHERENT data should be included in electroweak precision studies from now on.

Flexible, long cycle-life micro-supercapacitor with polypyrrole@Ag-wall interdigitated electrodes fabricated by micro-3D printing and electrochemical polymerization

Conductive polymers (CPs) have been widely used as electrode materials in supercapacitors because of their facile synthesis, low cost, and high capacitance. However, their practical application in micro-supercapacitors (MSCs) has been hindered by the manufacturing complexity and dimensional limits due to their low processability, and the very poor cycle-life due to its volumetric change in the charge-discharge process. Here, we present CPs-based MSCs with a unique structure of polypyrrole (PPy)@Ag-wall interdigitated electrodes fabricated by combing micro-3D printing Ag-wall and electrochemical polymerization of PPy. Benefiting from the unique structure and effective interface of PPy@Ag-wall interdigitated electrodes, these all-solid-state MSCs (S < 0.25 cm2) offer an area capacitance (C/A) up to 90 mF cm−2, coupled with a long cycle-life (capacitance remains 109 % after 10,000 cycles), great flexibility (capacitance remains 95 % after bending for 1000 times), and a very low interfacial resistance (2.88 Ω). In conclusion, this unique design of the PPy@Ag-wall interdigitated electrode structure not only achieves the formation of the arbitrary structure of CPs, but also greatly improves its cycle-life, promoting the CPs-based MSCs for the future miniature energy storage device.

Computer Simulation of the Effect of Coherent Dynamical Diffraction of Synchrotron Radiation in Crystals of Arbitrary Shape and Structure

Computer Simulation of the Effect of Coherent Dynamical Diffraction of Synchrotron Radiation in Crystals of Arbitrary Shape and Structure

Carbon quantum initiators enabled direct laser writing: A technique for fabrication of dielectric, all-carbon chiral metasurfaces

Chiral metasurfaces exhibit extraordinary capabilities of steering polarization of electromagnetic waves; and hence offering enormous potential in development of ultrathin components for advanced photonic technologies such as quantum computing and communication, imaging, optical memories and logics. These structures are realized by periodically arranged subwavelength resolved artificial elements (metaelements). Metaelements are mainly metallic, dielectric or metal-dielectric based and their fabrication is a daunting task due to the associated complex fabrication methodologies involving serial, time-consuming processes and sophisticated instrumentation, hence limiting the growth, and application of these metasurfaces to its true potential. To mitigate these issues, we exploited the single-step fabrication capabilities of two-photon polymerization based lithography to generate a range of all-carbon-based dielectric chiral metasurfaces in a carbon-polymer nanocomposite resin. Additionally, theoretical responses of these structures are also calculated. These structures derive their responses from structural chirality. With the advantages of single-step fabrication of any arbitrary structure with sub-wavelength resolved features, along with the capability of rapid prototyping in the proposed material system; this work holds a great potential towards generation of all-carbon metamaterials and 3D metasurfaces for several advanced photonic and optical technologies.

Drell-Yan tails beyond the Standard Model

We investigate the high-pT tails of the pp → ℓν and pp → ℓℓ Drell-Yan processes as probes of New Physics in semileptonic interactions with an arbitrary flavor structure. For this purpose, we provide a general decomposition of the 2 → 2 scattering amplitudes in terms of form-factors that we match to specific scenarios, such as the Standard Model Effective Field Theory (SMEFT), including all relevant operators up to dimension-8, as well as ultraviolet scenarios giving rise to tree-level exchange of new bosonic mediators with masses at the TeV scale. By using the latest LHC run-II data in the monolepton (eν, μν, τν) and dilepton (ee, μμ, ττ, eμ, eτ, μτ) production channels, we derive constraints on the SMEFT Wilson coefficients for semileptonic four-fermion and dipole operators with the most general flavor structure, as well as on all possible leptoquark models. For the SMEFT, we discuss the range of validity of the EFT description, the relevance of mathcal{O} (1/Λ2) and mathcal{O} (1/Λ4) truncations, the impact of d = 8 operators and the effects of different quark-flavor alignments. Finally, as a highlight, we extract for several New Physics scenarios the combined limits from high-pT processes, electroweak pole measurements and low-energy flavor data for the b → cτν transition, showing the complementarity between these different observables. Our results are compiled in HighPT (https://highpt.github.io), a package in Mathematica which provides a simple way for users to extract the Drell-Yan tails likelihoods for semileptonic effective operators and for leptoquark models.

Is a black hole shadow a reliable test of the no-hair theorem?

Capturing the image of the shadow cast by the event horizon of an illuminated black hole is, at the most basic level, an experiment of extreme light deflection in a strongly curved spacetime. As such, the properties of an imaged shadow can be used to probe the general relativistic Kerr nature of astrophysical black holes. As an example of this prospect, it is commonly asserted that a shadow can test the validity of the theory's famous ``no hair theorem'' for the black hole's mass and spin multipole moments. In this paper, we assess this statement by calculating the shadow's equatorial radius in spacetimes with an arbitrary multipolar structure and within a slow rotation approximation. We find that when moments higher than the quadrupole are taken into account, the shadow acquires a high degree of degeneracy as a function of the deviation from the Kerr multipole moments. The results of our analysis suggest that dark objects with strongly non-Kerr multipolar structure could nevertheless produce a Kerr-like shadow with its characteristic quasicircular shape.

Analytic solution on force analysis of tripod in arbitrary space

Tripod is a common support structure. The key to tripod design is to accurately analyze the force, select appropriate materials, and design the angle according to the size of the axial force. To study the stress condition and application performance of a tripod, this paper takes any tripod in space as the research object, through the combination of mathematics and mechanics, establishes a space rectangular coordinate system, solves the internal force of the tripod member, and verifies the correctness of the solution results. The evolution from arbitrary tripod structure to special tripod structure demonstrates the correctness of the reasoning method from general to special. An arbitrary space tripod is a common engineering application structure. Taking it as the research object, mechanical analysis has certain practical significance.

Обобщенная задача динамического уравновешивания и перспективные направления ее применения

The paper considers the generalized problem of the machines and mechanisms dynamic balance in terms of ensuring the given laws of altering reactions in the selected links. Representation of equations of the mechanical systems dynamics in the form of differential algebraic equations was used making it possible to obtain mathematical models of the nonlinear mechanical systems dynamics with the arbitrary structure of kinematic and force connections. With this approach, the constraint reactions are determined by algebraic equations from the system coordinates. The problem solution is based on changing the bonds selected reactions due to the impact on reactions in the other selected bonds by adding non-stationary terms to the selected bonds equation. Conditions for rigorous solution of the optimal control problem for a mechanical system are shown for the integral quality criterion not explicitly containing the control functions. The method is aimed at numerical models of the mechanical systems widely used in the programs for dynamic analysis of the coupled systems of bodies. Test examples are provided for manipulator, anthropomorphic robot and controlled suspension of a transport vehicle. The method was realized in the software package for simulating the controlled motion dynamics of the coupled systems of bodies.

COMPUTER SIMULATION OF THE EFFECT OF COHERENT DYNAMICAL DIFFRACTION OF SYNCHROTRON RADIATION IN CRYSTALS OF ARBITRARY SHAPE AND STRUCTURE

A new scheme for the numerical solution of Takagi–Taupin equations, which makes it possible to simulate the effect of synchrotron radiation diffraction in crystals of arbitrary structure, is described in detail. The new scheme is convenient to perform calculations for crystals of arbitrary shape. The rectangular coordinate system and the algorithm for calculating derivatives at half of step have proven their efficiency and are used, but the recurrence equations of this algorithm have been modified towards simplification. The boundary conditions are in no way related to the crystal boundaries. A computer program is developed, and two examples are considered for the cases of diffraction in the Laue and Bragg geometries, for which the analyticl solutions are known. The calculation results are in complete agreement with these solutions.

그래프 트랜스포머 기반 농가 사과 품질 이미지의 그래프 표현 학습 연구

Recently, a convolutional neural network (CNN) based system is being developed to overcome the limitations of human resources in the apple quality classification of farmhouse. However, since convolutional neural networks receive only images of the same size, preprocessing such as sampling may be required, and in the case of oversampling, information loss of the original image such as image quality degradation and blurring occurs. In this paper, in order to minimize the above problem, to generate a image patch based graph of an original image and propose a random walk-based positional encoding method to apply the graph transformer model. The above method continuously learns the position embedding information of patches which don`t have a positional information based on the random walk algorithm, and finds the optimal graph structure by aggregating useful node information through the self-attention technique of graph transformer model. Therefore, it is robust and shows good performance even in a new graph structure of random node order and an arbitrary graph structure according to the location of an object in an image. As a result, when experimented with 5 apple quality datasets, the learning accuracy was higher than other GNN models by a minimum of 1.3% to a maximum of 4.7%, and the number of parameters was 3.59M, which was about 15% less than the 23.52M of the ResNet18 model. Therefore, it shows fast reasoning speed according to the reduction of the amount of computation and proves the effect.