Damped Response Research Articles

Design and real-time implementation of a wireless autopilot using multivariable predictive generalized minimum variance control in the state-space

The contribution of this work is the numerical simulation and the experimental assessment of a network distributed control system using an unmanned aerial vehicle and a remote master controller connected by a wireless network. A novel multi-input multi-output long-range predictive horizon minimum variance control approach is developed and implemented in altitude, heading, lateral and longitudinal velocities control problems under the influence of process noise, measurement noise and time-delay. The proposed autopilots exhibited damped and fast response speeds with optimal control and output variance minimization, outperforming a classic model predictive control approach in convincing experimental field tests in real-world environments and scenarios.

A simple molecular orbital picture of RIXS distilled from many-body damped response theory.

Ab initio calculations of resonant inelastic x-ray scattering (RIXS) often rely on damped response theory, which prevents the divergence of response solutions in the resonant regime. Within the damped response theory formalism, RIXS moments are expressed as the sum over all electronic states of the system [sum-over-states (SOS) expressions]. By invoking resonance arguments, this expression can be reduced to a few terms, an approximation commonly exploited for the interpretation of computed cross sections. We present an alternative approach: a rigorous formalism for deriving a simple molecular orbital picture of the RIXS process from many-body calculations using the damped response theory. In practical implementations, the SOS expressions of RIXS moments are recast in terms of matrix elements between the zero-order wave functions and first-order frequency-dependent response wave functions of the initial and final states such that the RIXS moments can be evaluated using complex response one-particle transition density matrices (1PTDMs). Visualization of these 1PTDMs connects the RIXS process with the changes in electronic density. We demonstrate that the real and imaginary components of the response 1PTDMs can be interpreted as contributions of the undamped off-resonance and damped near-resonance SOS terms, respectively. By analyzing these 1PTDMs in terms of natural transition orbitals, we derive a rigorous, black-box mapping of the RIXS process into a molecular orbital picture. We illustrate the utility of the new tool by analyzing RIXS transitions in the OH radical, benzene, para-nitroaniline, and 4-amino-4'-nitrostilbene. These examples highlight the significance of both the near-resonance and off-resonance channels.

Localizing Ground-Motion Models in Volcanic Terranes: Shallow Events at Mt. Etna, Italy, Revisited

ABSTRACTWe present a set of revised ground-motion models (GMMs) for shallow events at Mt. Etna Volcano. The recent occurrence of damaging events, in particular two of the strongest earthquakes ever instrumentally recorded in the area, has required revising previous GMMs, as these failed to match the observations made for events with local magnitude ML>4.3, above all for sites situated close to the epicenter. The dataset now includes 49 seismic events, with a total of 1600 time histories recorded at distances of up to 100 km, and ML ranging from 3.0 to 4.8. The model gives estimates of peak ground acceleration (both horizontal and vertical), peak ground velocity (both horizontal and vertical), and 5% damped horizontal pseudoacceleration response spectral ordinates up to a period of 4 s. GMMs were developed using the functional form proposed by Boore and Atkinson (2008). Furthermore, with a slightly modified approach, we also considered a regression model using a pseudodepth (h) depending on magnitude according to the scaling law by Azzaro et al. (2017). Both models were applied to hypocentral distance ranges of up to 60 km and up to 100 km, respectively. From the statistical analysis, we found that reducing the maximum distance from the event up to 60 km and introducing a magnitude-dependent pseudodepth improved the model in terms of total error. We compared our results with those derived using the GMMs for shallow events at Mt. Etna found by Tusa and Langer (2016) and for volcanic areas by Lanzano and Luzi (2019). The main differences are observed at short epicentral distances and for higher magnitude events. The use of variable pseudodepth avoids sharp peaks of predicted ground-motion parameters around the epicenter, preventing instabilities when using a GMM in probabilistic seismic hazard analysis.

Ground motion prediction equation for crustal earthquakes in Taiwan

We develop a ground motion prediction equation (GMPE) for estimating horizontal ground motion amplitudes caused by crustal earthquakes, based on an integrated data set that includes strong motion recordings mainly from Taiwan earthquakes and only from large magnitude earthquakes in the NGA-West2 database. This GMPE is developed for probabilistic seismic hazard analysis study, which is introduced as a part of Taiwan Senior Seismic Hazard Analysis Committee Level 3 projects. The functional form developed by Chiou and Youngs was carefully studied to determine the key modeling parameters needed to regress against ground motion in the target region. Using this functional form, the GMPE achieves considerable improvement over previously developed Taiwan GMPEs. In particular, the use of a high-order function in magnitude scaling enables representation of the saturation effects of large earthquakes. Moreover, consideration of focal mechanisms, depth effects, and dip effects are used to correct the magnitude scaling; consideration of nonlinear site amplification is conditioned on VS30 and reference ground motion on rock; and consideration of basin depth effect is a function of Z1.0 in correlation with VS30. In addition, ground motion data used in this study are not only expanded by more than three times as many earthquakes and records compared with a previous Taiwan model but also provide the metadata of these records that were not available or were previously incomplete. In this study, we compare the proposed model with the NGA-West2 models and discuss the regional difference in ground motion in terms of spectral shape, magnitude scaling, distance scaling, depth scaling, style of faulting, and site effects. We provide median and single standard deviations of peak ground acceleration and 5% damped pseudospectral acceleration response ordinates of the orientation-independent average horizontal component of ground motion (RotD50) for the spectral period of 0.01–10 s.

Nonlinear free vibration and damping analysis of a microbeam with pseudoelastic shape memory alloy layer based on the modified couple stress theory

The aim of this investigation is to evaluate the size effects on the nonlinear free vibration of the sandwich composite microbeam with an extensible shape memory alloy layer in the midplane. A one-dimensional constitutive model is considered to simulate the pseudoelastic behavior of the shape memory alloy layer. The governing equation of motion is derived using the Euler–Bernoulli beam theory together with the modified couple stress theory through the Hamilton’s principle. Midplane stretching and phase transformation of the shape memory alloy which are sources of nonlinearity were considered, and a numerical solution method is presented. A damped response of the sandwich composite microbeam is observed because of the hysteresis behavior of the extensible shape memory alloy layer in the midplane. Results are appraised by comparing with the available literature. The influence of material length scale, temperature, and initial velocity on the loss factor and other pivotal vibrational behavior is evaluated. Results show that increasing the material length scale to thickness ratio has a decreasing effect on damping capacity.

Magnetic circular dichroism in plasmonic Ag–Au core–shell nanoparticles: how does the magneto-optical activity tune?

Magnetic circular dichroism (MCD) is demonstrated for plasmonic bimetallic nanoparticles. They have an Ag–Au core–shell configuration, which can be synthesized using a seeded growth technique. In the seeded growth process, when the amount of Au (as coating metal) added to the Ag core is small, both ordinary (lower-energy) and extraordinary (higher-energy) modes of localized surface plasmon resonance (LSPR) are detected in optical extinction spectra, suggesting successful formation of well-defined core–shell morphology with a rather thin shell (= AgAu alloy) thickness. Interestingly, the related MCD, showing a typical bisignate magnetoplasmonic response, is more distinct than the extinction signal in the ordinary LSPR mode, but strong damping is found upon thin shell formation. Hence, such bimetallic nanosystems have an advantage of systematic tuning of their magnetoplasmonic behavior, but may not be favorable to obtaining large magneto-optical (MO) activity or MCD amplitudes. The damped MCD response is discussed from a viewpoint of spectral inhomogeneity.

Construction of a Site- and Period-Specific Seismic Hazard Map for the Korean Peninsula

The 2016 Gyeongju and 2017 Pohang earthquakes caused casualties and economic damage in the surrounding areas. Therefore, the importance of earthquake damage prediction and seismic design in the Korean peninsula has increased. Probabilistic seismic hazard analysis (PSHA) is one of the well-known methods for predicting earthquake damage. The objective of this study is to construct Korean Peninsula seismic hazard maps of 5% damped response spectrum acceleration and peak ground acceleration, using PSHA. To consider the local effects for each site's classification, seismic hazard maps were constructed by considering the site amplification model. To conduct seismic design, uniform hazard response spectra (UHRS) were also constructed for the Korean peninsula.

Behavior Stability and Individual Differences in Pavlovian Extended Conditioning.

How stable and general is behavior once maximum learning is reached? To answer this question and understand post-acquisition behavior and its related individual differences, we propose a psychological principle that naturally extends associative models of Pavlovian conditioning to a dynamical oscillatory model where subjects have a greater memory capacity than usually postulated, but with greater forecast uncertainty. This results in a greater resistance to learning in the first few sessions followed by an over-optimal response peak and a sequence of progressively damped response oscillations. We detected the first peak and trough of the new learning curve in our data, but their dispersion was too large to also check the presence of oscillations with smaller amplitude. We ran an unusually long experiment with 32 rats over 3,960 trials, where we excluded habituation and other well-known phenomena as sources of variability in the subjects' performance. Using the data of this and another Pavlovian experiment by Harris et al. (2015), as an illustration of the principle we tested the theory against the basic associative single-cue Rescorla–Wagner (RW) model. We found evidence that the RW model is the best non-linear regression to data only for a minority of the subjects, while its dynamical extension can explain the almost totality of data with strong to very strong evidence. Finally, an analysis of short-scale fluctuations of individual responses showed that they are described by random white noise, in contrast with the colored-noise findings in human performance.

Approximate versus Exact Embedding for Chiroptical Properties: Reconsidering Failures in Potential and Response.

We investigate the suitability of subsystem time-dependent density-functional theory (sTDDFT) for describing chiroptical properties with a focus on optical rotation parameters. Our starting point is a new implementation of the recently proposed projection-based, coupled frozen-density embedding (FDEc) framework. We adapt the generalized, non-Hermitian formulation of TDDFT and derive corresponding expressions for regular and damped response properties from subsystem TDDFT. We verify that our implementation of this "exact" formulation allows to reproduce supermolecular results of electronic circular dichroism (ECD) spectra, of optical rotatory dispersion, and of polarizabilities. We present a systematic test of the main approximations typically introduced in practical frozen-density embedding (FDE) calculations of response properties: (i) the use of approximate nonadditive kinetic-energy (NAKE) functionals, which can be avoided through projection techniques, (ii) the use of monomer (subsystem) basis sets rather than supersystem basis sets, and (iii) the neglect of intersubsystem response coupling within the so-called uncoupled FDE (or FDEu) approximation. While approximation (i) is known to generally lead to large errors for covalently bound subsystems, we present cases in which either the basis set or the coupling step are similarly or even (much) more important. In particular, we explicitly demonstrate by comparison to a fully coupled calculation that missing intersubsystem response couplings are responsible for the failure of FDE reported in a previous study [ J. Chem. Theory Comput. 2015, 11, 5305-5315]. We show that good agreement with reference results can be obtained in this case even with standard NAKE approximations for the FDE potentials and efficient monomer basis sets, making calculations for larger systems well accessible.

Watts Bar Nuclear Power Plant Strong-Motion Records of the 12 December 2018 M 4.4 Decatur, Tennessee, Earthquake

Abstract The moment magnitude M 4.4 on 12 December 2018 Decatur, Tennessee, earthquake occurred in the eastern Tennessee seismic zone. Although the causative fault is not known, the earthquake had a predominantly strike-slip mechanism with an estimated hypocentral depth of about 8 km. It was felt over a distance of 500 km stretching from Southern Kentucky to Georgia. Strong shaking, capable of causing slight damage, was reported near the epicenter. The Watts Bar nuclear power plant (NPP) is only 4.9 km from the epicenter of the earthquake and experienced only slight shaking. The earthquake was recorded by the plant’s seismic strong-motion instrumentation installed at four different locations. Near-real-time calculations by the plant operators indicated that the operating basis earthquake (OBE) ground motion was not exceeded during the earthquake. We obtained and processed the recorded motions to calculate corrected accelerations, velocities, and displacements. In addition, we computed the Fourier and 5% damped response spectra to compare them with the plant’s OBE. Comparisons of the ground-motion prediction models with the digital recordings at the plant site indicated that recorded ground motions were significantly below the predicted results calculated using the ground-motion prediction models approved for regulatory use. Availability of high-quality, digital recordings in this case helped make a quick decision about the ground motions not exceeding the OBE and hence prevented unnecessary shutdown of the NPP. Availability of earthquake recordings from the four locations in the NPP also presented an opportunity to analyze the linear response of plant structures.

A new class of hyperbolic variational–hemivariational inequalities driven by non-linear evolution equations

The aim of the paper is to introduce and investigate a dynamical system which consists of a variational–hemivariational inequality of hyperbolic type combined with a non-linear evolution equation. Such a dynamical system arises in studies of complicated contact problems in mechanics. Existence, uniqueness and regularity of a global solution to the system are established. The approach is based on a new semi-discrete approximation with an application of a surjectivity result for a pseudomonotone perturbation of a maximal monotone operator. A new dynamic viscoelastic frictional contact model with adhesion is studied as an application, in which the contact boundary condition is described by a generalised normal damped response condition with unilateral constraint and a multivalued frictional contact law.

Development of the corticosterone stress response differs among passerine species

Glucocorticoids are steroid hormones which increase dramatically in response to a physical or perceived stressor. However, developing young of altricial species typically have a damped glucocorticoid stress response. The developmental hypothesis posits that the physiological stress response should develop concurrently with an individual’s ability to respond to a challenge. The dampened response may benefit an organism, as chronic exposure to glucocorticoids can have short- and long-term detrimental effects, and altricial young are unable to escape most stressors. However, we do not know if or why species with similar ontogeny vary in their development of the physiological stress response. We assessed levels of baseline and stress-induced corticosterone (the main avian glucocorticoid) in six passerine species with varying life-history strategies, including a brood parasite, the brown-headed cowbird (Molothrus ater). Circulating baseline corticosterone levels increased with nestling age for all species. Stress-induced corticosterone levels sampled at 15-min post-capture significantly increased with nestling age at a similar rate and magnitude in brown-headed cowbirds, eastern phoebes (Sayornis phoebe), hooded warblers (Setophaga citrina), red-winged blackbirds (Agelaius phoeniceus), and song sparrows (Melospiza melodia). However, gray catbird (Dumetella carolinensis) nestlings showed an extremely dampened elevation in corticosterone in response to stress, even near fledge. Gray catbirds are unusual among songbirds, as they are open-ended song learners. Stress during development can profoundly influence avian song learning and performance abilities. However, further study is necessary to determine if there is a relationship between nestling adrenocortical activity and open- versus closed-ended song learning.

How do conservative backbone curves perturb into forced responses? A Melnikov function analysis

Weakly damped mechanical systems under small periodic forcing tend to exhibit periodic response in a close vicinity of certain periodic orbits of their conservative limit. Specifically, amplitude-frequency plots for the conservative limit have often been noted, both numerically and experimentally, to serve as backbone curves for the near resonance peaks of the forced response. In other cases, such a relationship between the unforced and forced response was not observed. Here, we provide a systematic mathematical analysis that predicts which members of conservative periodic orbit families will serve as backbone curves for the forced–damped response. We also obtain mathematical conditions under which approximate numerical and experimental approaches, such as energy balance and force appropriation, are justifiable. Finally, we derive analytic criteria for the birth of isolated response branches (isolas) whose identification is otherwise challenging from numerical continuation.

Experiment study of characteristics of powder pneumatic filling

Powder engine is one kind of new concept engines with multiple ignition capability and thrust modulation function. Powder filling is an important process of the powder engine tests. The powder pneumatic filling experiments were carried out to investigate the effects of the filling position of the powder collection box and the mass flow rate of fluidization gas on the stability and performance of powder pneumatic filling. It’s found that large mass flow rate of fluidization gas contributes to stability of powder pneumatic filling, but its volume efficiency of powder filling is the lowest, only 68.1%, but it’s 93.9% when the mass flow rate of fluidization gas is small. Compared with the vertical inlet of end cap, tangential inlet on the cylinder wall makes the powder uniformity better. In the pneumatic filling mode, the powder bulk density in the collection box is greater than the bulk density in the powder tank. In addition, the mass of powder calculated by position displacement is always larger than the mass of powder measured by the electronic balance. It indicates powder bulk density in tank is constantly changing during the powder pneumatic filling experiments. The actual powder bulk density in the powder tank is calculated by a model established in this paper, it’s found that when the mass flow rate of fluidization gas is low, the bulk density of the powder in the tank is increased first and then decreased, and the final bulk density is less than the initial value. While the mass flow rate of fluidization gas is high, powder bulk density in the tank is first increased, then decreased, then increased and then decreased, and the final bulk density is greater than the initial value. The compression mechanism of powder bulk density in the tank is similar to the motion law of the damper spring vibrator when it is forced to vibrate. It can be described by the damped second-order system response function. When the mass flow rate of fluidization gas is small, the damping coefficient of the system is smaller. While the mass flow rate of fluidization gas is large, the damping coefficient is larger and is variable.

СООТНОШЕНИЯ МЕЖДУ АМПЛИТУДНЫМИ СПЕКТРАМИ ФУРЬЕ И СПЕКТРАМИ МАКСИМАЛЬНЫХ РЕАКЦИЙ (СПЕКТРАМИ ОТВЕТОВ) НА ЗЕМЛЕТРЯСЕНИЯ

The paper notes the relevance of introducing into practice the calculations of structures on seismic effects of methodologically sound initial data - reaction spectra. In the course of the work, the concepts of pseudo-spectra of responses in displacements, speeds, and accelerations are formulated. The results of determining the relationship between the amplitude Fourier spectra and the spectra of the maximum reactions of systems with damping equal to zero are presented. Relations between the spectra Fourier and response spectra for systems with viscous damping are obtained, similar to the dependences between the Fourier spectra and the response spectrum for non-damped systems (Kawasumi, 1956; Rubin, 1961; Hudson, 1962; Jennings, 1972). In contrast to the work “Damped Fourier Spectrum and Response Spectra” (Idvadia and Trifunak, 1973), the functional Damped Fourier spectrum is not used in our work. The classic Fourier transform is used.

Correction: How to stay out of trouble in RIXS calculations within equation-of-motion coupled-cluster damped response theory? Safe hitchhiking in the excitation manifold by means of core-valence separation.

Correction for 'How to stay out of trouble in RIXS calculations within equation-of-motion coupled-cluster damped response theory? Safe hitchhiking in the excitation manifold by means of core-valence separation' by Kaushik D. Nanda et al., Phys. Chem. Chem. Phys., 2020, 22, 2629-2641, DOI: .

How to stay out of trouble in RIXS calculations within equation-of-motion coupled-cluster damped response theory? Safe hitchhiking in the excitation manifold by means of core-valence separation.

We present a novel approach for computing resonant inelastic X-ray scattering (RIXS) cross sections within the equation-of-motion coupled-cluster (EOM-CC) framework. The approach is based on recasting the sum-over-states expressions for RIXS moments into closed-form expressions by using damped response theory. Damped response formalism allows one to circumvent problems of divergent behavior of response equations in the resonant regime. However, the convergence of response equations in the X-ray frequency range is often erratic due to the electronically metastable (i.e., resonant) nature of the virtual core-excited states embedded in the valence ionization continuum. We circumvent this problematic behavior by extending the core-valence separation (CVS) scheme, which decouples the valence-excited and core-excited configurations of the excitation manifold, into the response domain. The accuracy of the CVS-enabled damped response theory, implemented within the EOM-EE-CCSD (EOM-CC for excitation energies with single and double excitations) framework, is assessed by comparison against standard damped EOM-EE-CCSD response calculations. The capabilities of the new approach are illustrated by calculations of RIXS cross sections for benzene and benzene radical cation.

Relativistic four-component linear damped response TDDFT for electronic absorption and circular dichroism calculations.

We present a detailed theory, implementation, and a benchmark study of a linear damped response time-dependent density functional theory (TDDFT) based on the relativistic four-component (4c) Dirac-Kohn-Sham formalism using the restricted kinetic balance condition for the small-component basis and a noncollinear exchange-correlation kernel. The damped response equations are solved by means of a multifrequency iterative subspace solver utilizing decomposition of the equations according to Hermitian and time-reversal symmetry. This partitioning leads to robust convergence, and the detailed algorithm of the solver for relativistic multicomponent wavefunctions is also presented. The solutions are then used to calculate the linear electric- and magnetic-dipole responses of molecular systems to an electric perturbation, leading to frequency-dependent dipole polarizabilities, electronic absorption, circular dichroism (ECD), and optical rotatory dispersion (ORD) spectra. The methodology has been implemented in the relativistic spectroscopy DFT program ReSpect, and its performance was assessed on a model series of dimethylchalcogeniranes, C4H8X (X = O, S, Se, Te, Po, Lv), and on larger transition metal complexes that had been studied experimentally, [M(phen)3]3+ (M = Fe, Ru, Os). These are the first 4c damped linear response TDDFT calculations of ECD and ORD presented in the literature.

Estimation of Strong Motion Generation Area for the 2004 Parkfield Earthquake Using Empirical Green’s Function Method

The empirical Green’s function (EGF) method is used to simulate the 2004 Parkfield earthquake (Mw = 6.1). The strong motion generation areas (SMGA) are estimated to reproduce near-source ground motions in a broadband frequency range of 0.25–10 Hz. In this simulation, the EGF uses the small events that occurred in 2005 (Mw = 4.5), 2012 (Mw = 4.4), 2010 (Mw = 4), and 2007 (Mw = 4). The source spectral ratio estimates the seismic moment ratio between large and small events whose corner frequencies obey the omega-squared scaling law. The estimated SMGA is 12 km in length by 8 km in width and is located near the large slip area of the waveform inversion. The result shows that the rupture propagates radially from the southeastern bottom part of the SMGA toward the northwestern shallow direction. In addition, a characterized source model comprising two asperities and a background slip area is proposed. The rupture propagates from asperity1 toward asperity2 with 2 s time delay. The characterized source model simulates more accurately than the single SMGA. The comparison between the 5% damped pseudo acceleration response spectra of our simulations verifies a better compatibility for more than 2 Hz.

A dsPIC based optimal sizing of solar PV plant using ultra capacitors for transient power delivery

Solar PV sources are being increasingly implemented in many applications due to the growing concern of environmental pollution. The capacity of solar PV depends both on the transient power and nominal power required by any type of motor loads. The present investigation reports on a method to optimize the required capacity of Solar Panel by augmenting an Ultra capacitor bank for powering the transient needs of BLDC Motor. A PID based high quality dynamic response characteristics controller was designed to improve the speed transient response of the BLDC motor thereby reducing the transient energy requirement of the BLDC Motor. Tuning of PID parameters is critical to optimise the transient behaviour of the motor. The under damped step response tuning method has achieved an optimal PID parameters without any loss in speed transients when compared with other major tuning methods. PID controller is programmed in dsPIC controller that has high-resolution control and minimal control loop delays, thereby reduces torque ripples, harmonics and improves the dynamic behaviour in all speed ranges. The proposed optimal design of PV system augmented with Ultra capacitor for transient power delivery has been modelled and simulated in MATLAB/Simulink, which resulted in a reduction of plant size by 50 percent. The results obtained in simulation are verified experimentally.