Coupling Perturbation Research Articles

Additively manufactured electromagnetic based planar pressure sensor using substrate integrated waveguide technology

This paper proposes an electromagnetic based planar pressure sensor using a substrate integrated waveguide (SIW). The proposed pressure sensor is inspired by a rectangular SIW cavity and is additively manufactured using 3D printed dielectric material with inkjet printed conductive pattern. Since the resonance frequency depends on the SIW centre in transverse electrical mode, a circular cylinder with four bridges is placed at the SIW centre for perturbation. We inserted meshed material at the SIW centre, to facilitate soft pressing, and simplify producing frequency shifts due to capacitive coupling perturbation from different pressure levels. The proposed concept was numerically and experimentally verified, reducing resonance frequency from 4.28 to 3.71 GHz by increasing the pressure from 0 to 2.4 kPa. Device sensitivity = 2.4 × 108 Hz/kPa, and stable frequency change was observed over 100 repeats.

Continuous Integral Terminal Sliding Mode Control for Double-Layer Peltier System Based on Finite-Time Observer

This paper addresses the finite-time tracking problem for the double-layer Peltier system. Peltier is a semiconductor thermoelectrical transform device. It is widely used in the thermal tactile reappearance area. To expand temperature differences, Peltier is usually used in the form of double layers. There are some uncertain factors such as state coupling, external disturbance, and parameter perturbation in double-layer Peltier. Therefore, it is of great theoretical and practical significance to design a controller with superior performance. To this end, a compound continuous integral terminal sliding mode control strategy is proposed here. Firstly, finite-time disturbance observers are designed for feedforward compensation and evaluating the external disturbances. Secondly, the strong robustness of the sliding mode control enhances the disturbance rejection of the system. The continuous integral sliding mode makes the input continuous and weakens the chattering. Also, the terminal sliding mode improves the convergence speed of the system on the sliding surface significantly. The performance of the proposed method is analyzed through Lyapunov stability analysis, simulations, and experiments. Compared to nonsmooth finite-time control, the continuous integral terminal sliding mode control achieves rapid temperature stability and better disturbance rejection under the same condition of finite-time convergence.

Coupled gravitational and electromagnetic perturbations of Reissner–Nordström spacetime in a polarized setting

Coupled gravitational and electromagnetic perturbations of Reissner–Nordström spacetime in a polarized setting

Impedance modeling and stability analysis of PV grid-connected inverter system considering frequency coupling

Impedance analysis is an effective method to analyze the oscillation issue associated with grid-connected photovoltaic systems. However, the existing impedance modeling of a grid-connected photovoltaic inverter usually only considers the effect of a single perturbation frequency, ignoring the coupling frequency response between the internal control loops of a grid-connected inverter, which severely affects the accuracy of the stability analysis. Hence, a method of impedance modeling and stability analysis for grid-connected photovoltaic inverters considering cross-coupling frequency is proposed in this paper. First, the generation mechanism of frequency coupling in grid-connected photovoltaic inverters, and the relationship between the coupling frequency and perturbation frequency are analyzed. Secondly, a sequence impedance model of grid-connected photovoltaic systems considering the coupling frequency is established by using the harmonic linearization method. The impact of DC bus voltage control strategy on frequency coupling characteristics of a grid-connected photovoltaic system is evaluated, and the impact of a coupling frequency term on system stability is quantitatively analyzed. Finally, the advantages of the proposed method are verified by several simulations. The results show that the proposed impedance model can accurately predict the potential resonance points of the system, and the coupling frequency characteristics will become much stronger with smaller DC bus capacitance or larger bandwidth of the DC bus controller.

Instability of a Reissner–Nordström–AdS Black Hole from a Derivative Coupling Perturbation

Instability of a Reissner–Nordström–AdS Black Hole from a Derivative Coupling Perturbation

Synthesis and electronic structure of a mononuclear copper(II) complex supported by tris(2-hydroxyliminopropyl)amine

The blue-green, mononuclear copper complex [CuL(NO3)]NO3, (1), was synthesized by reacting copper(II) nitrate with L = tris(2-hydroxyliminopropyl)amine in methanol. The structure of 1 was determined by single-crystal X-ray diffraction, which revealed a copper(II) ion that exhibits a pseudo-octahedral coordination geometry. While one of the nitrate anions is coordinated in an η2 fashion, the other is non-coordinated and is involved in intra- and inter-molecular hydrogen bonds. The nitrate-promoted intermolecular hydrogen bonding is supported by the protonated ligand and leads to the formation of supramolecular undulating chains. The electronic structure of 1 was investigated using Electron Paramagnetic Resonance (EPR) measurements performed at cryogenic temperatures on both neat powders and frozen solutions. In the solid state we observe a quasi-axial S = 1/2 signal described by gz = 2.256, gy = 2.086, and gx = 2.048. These values were rationalized using coupled-perturbed (CP) Density Functional Theory (DFT) and CASSCF/NEVPT2 calculations. The computational investigation of 1 suggests an (x2 − y2)-type ground state and a g -tensor dominated by the (xy) → (x2 − y2) transition. EPR investigation of frozen solution samples revealed the presence of two similar spectral components indicating that upon dissolution the nitrate anion is displaced from the coordination sphere and 1 speciates into six- and five-coordinated complex-cations. The cyclic voltammograms of 1 revealed a quasi-reversible Cu(I)/Cu(II) redox couple, E1/2 = +0.26 V vs. SHE, and that 1 functions as a precursor for electrodeposited Cu(0)/Cu2O films.

Modified adaptive second order sliding mode control: Perturbed system response robustness

Sensitivity to parameters, which is negative for any system; for an aircraft is destructive. In this respect, an Adaptive Second-order Sliding Mode Control (AS-SMC) is proposed to manage the unknown time-varying aircraft parameter uncertainty and un-modeled coupling perturbations. The employed adaptivity relaxes the required knowledge of the perturbation bound, the suggested sliding surface improves the system stability and bypassing the SMC reaching phase enhances the performance robustness. The effectiveness of the scheme in providing low tolerance responses with respect to the basic controller is illustrated through extensive simulations. The response is more appreciated when the system operates in a high angle of attack/sideslip conditions.

Coupled Perturbation Theory Approach to Dual Basis Sets for Molecules and Solids. 1. General Theory and Application to Molecules.

We present a new coupled Hartree-Fock(HF)/Kohn-Sham DFT perturbation method that accounts for the effect of enlarging the basis set in electronic structure calculations. In contrast with previous approaches, our dual basis set treatment yields not only a correction for the total energy but also for the orbital eigenvalues and density. The zeroth order solution is obtained from the projection of the small basis set coefficients. Diagonalization of the full Fock matrix in the large basis set is avoided. In this first paper of a series, we develop the theoretical foundations of our approach for molecules, including the coupled-perturbed equations through second order and the energy expressions through fourth order-as our method complies with Wigner's 2n + 1 rule. The first-order perturbation equation turns out to be uncoupled, and odd-order terms in the energy expansion vanish. In calculations on simple molecules, our method recovers over 93% (84%) of the missing DFT(HF) energy when going from the cc-pVDZ to the aug-cc-pVDZ basis, and over about 95% in all cases if an energy extrapolation formula is used. Mulliken charges, the orbital eigenvalue spectrum, and HOMO-LUMO gaps of the large basis are well reproduced. Charge density maps show that the differences between the perturbatively corrected density and the reference nearly vanish through second-order.

Non-equatorial equilibrium points around an asteroid with gravitational orbit-attitude coupling perturbation

A recently proposed orbital dynamics model in the close proximity of an asteroid, which is called “attitude-restricted orbital dynamics”, includes the perturbation caused by the spacecraft’s gravitational orbit–attitude coupling. This orbital model improves the precision of classical point-mass orbital model with only the non-spherical gravity. Equatorial equilibrium points have been investigated in the previous paper. In this paper, the in-plane non-equatorial equilibrium points, which are outside the asteroid’s equatorial plane but within its longitudinal principal plane, are further studied for a uniformly-rotating asteroid. These non-equatorial equilibrium points are more diverse than those in the classical point-mass orbital dynamics without gravitational orbit–attitude coupling perturbation (GOACP). Two families of them have been found. The equatorial equilibrium points studied before and the non-equatorial ones studied here give a complete map of equilibrium points in the asteroid’s principal planes. Compared with the classical point-mass orbital dynamics without GOACP, the equatorial equilibrium points have extended the longitude range of equilibrium points around an asteroid, while the non-equatorial ones studied here will extend the latitude range. These equatorial and non-equatorial equilibrium points provide natural hovering positions for the asteroid close-proximity operations.

Natural Z′ -portal Majorana dark matter in alternative U(1) extended standard model

We consider a non-exotic gauged U(1)$_X$ extension of the Standard Model (SM), where the U(1)$_X$ charge of a SM field is given by a linear combination of its hypercharge and Baryon-minus-Lepton ($B-L$) number. All the gauge and mixed gauge-gravitational anomalies are cancelled in this model with the introduction of three right-handed neutrinos (RHNs). Unlike the conventional minimal U(1)$_X$ model, where a universal U(1)$_X$ charge of $-1$ is assigned to three RHNs, we consider an alternative charge assignment, namely, two RHNs ($N_R^{1,2}$) have U(1)$_X$ charge $-4$ while one RHN ($N_R$) has a $+5$ charge. With a minimal extension of the Higgs sector, the three RHNs acquire their Majorana masses associated with U(1)$_X$ symmetry breaking. While $N_R^{1,2}$ have Yukawa coupling with the SM lepton doublets and play an essential role for the 'minimal seesaw' mechanism, $N_R$ is isolated from the SM particles due to its U(1)$_X$ charge and hence it is a natural candidate for the dark matter (DM) without invoking additional symmetries. In this model context, we investigate the $Z^\prime$-portal RHN DM scenario, where the RHN DM communicates with the SM particles through the U(1)$_X$ gauge boson ($Z^\prime$ boson). We identify a narrow parameter space by combining the constraints from the observed DM relic abundance, the results of the search for a $Z^\prime$ boson resonance at the Large Hadron Collider Run-2, and the gauge coupling perturbativity up to the Planck/Grand Unification scale. For a special choice of U(1)$_X$ charges for the SM fields allows us to extend the model to SU(5)$\times$U(1)$_X$ grand unification. In this scenario, the model parameter space is more severely constrained, which will be explored at future high energy collider experiments.

Deriving models for the Kitaev spin-liquid candidate material α−RuCl3 from first principles

We use the constrained random phase approximation (cRPA) to derive from first principles the Ru-$t_{2g}$ Wannier function based model for the Kitaev spin-liquid candidate material $\alpha$-RuCl$_3$. We find the non-local Coulomb repulsion to be sizable compared to the local one. In addition we obtain the contribution to the Hamiltonian from the spin-orbit coupling and find it to also contain non-negligible non-local terms. We invoke strong coupling perturbation theory to investigate the influence of these non-local elements of the Coulomb repulsion and the spin-orbit coupling on the magnetic interactions. We find that the non-local Coulomb repulsions cause a strong enhancement of the magnetic interactions, which deviate from experimental fits reported in the literature. Our results contribute to the understanding and design of quantum spin liquid materials via first principles calculations.

Compact Triple-Mode Bandstop Ceramic Cavity Filters Using Parallel Coupled Resonators

Triple-mode bandstop ceramic cavity filters utilizing parallel-coupled resonators are presented. A transmission line, etched onto the face of a silver-plated ceramic cube, couples to three modes in parallel, avoiding any interresonator coupling perturbations. By varying only a few structural parameters, the coupling strengths into each mode can be controlled, and highly flexible bandstop filtering functions are demonstrated. A 30-MHz bandstop filter at 1800 MHz, from a roughly 27 mm3 ceramic block mounted to a copper base, is fabricated and measured. It achieves 26 dB of attenuation, with less than 0.3 dB of insertion loss 20 MHz away from the stopband, and less than 0.3 dB of reflection loss in the stopband, closely matching the simulation.

Preheating after Higgs inflation: Self-resonance and gauge boson production

We perform an extensive analysis of linear fluctuations during preheating in Higgs inflation in the Einstein frame, where the fields are minimally coupled to gravity, but the field-space metric is nontrivial. The self-resonance of the Higgs and the Higgsed gauge bosons are governed by effective masses that scale differently with the nonminimal couplings and evolve differently in time. Coupled metric perturbations enhance Higgs self-resonance and make it possible for Higgs inflation to preheat solely through this channel. For $\xi\gtrsim 100$ the total energy of the Higgs-inflaton condensate can be transferred to Higgs particles within $3$ $e$-folds after the end of inflation. For smaller values of the nonminimal coupling preheating takes longer, completely shutting off at around $\xi\simeq 30$. The production of gauge bosons is dominated by the gauge boson mass and the field space curvature. For large values of the nonminimal coupling $\xi \gtrsim 1000$, it is possible for the Higgs condensate to transfer the entirety of its energy into gauge fields within one oscillation. For smaller values of the nonminimal coupling gauge bosons decay very quickly into fermions, thereby shutting off Bose enhancement. Estimates of non-Abelian interactions indicate that they will not suppress preheating into gauge bosons for $\xi \gtrsim 1000$.

Nonperiodically intermittent pinning synchronization of complex-valued complex networks with non-derivative and derivative coupling

Considering the fact that time delays in practical systems are unavoidable and cannot be ignored, this paper studies nonperiodically intermittent pinning synchronization of delayed complex-valued complex dynamical networks with derivative coupling and parameters perturbation, in which the considered node systems have bounded parametric uncertainties. Different from previous works, the time-varying delays exist in the complex-valued node dynamics and non-derivative coupling forms. A nonperiodically intermittent pinning control scheme is proposed to stabilize the error system of drive–response complex-valued dynamical networks. By taking the advantage of Lyapunov method in complex field and utilizing inequality technology, firstly, the sufficient condition is derived, where the free time delay is considered; secondly, the synchronization condition is obtained, where we take into account the constrained time delay. Finally, numerical examples are given to illustrate the correctness of the obtained results and the theoretical analysis.

Temporal Coherence for Sound Transmission Through Fluctuating Deep Water with Adiabatic Perturbed Modes

Adiabatic approximation (AP) combined with perturbation theory gives a fast normal-mode solution of temporal coherence for sound field in a two-dimensional deep water with time-varying random internal waves. Internal waves induced mode changes are deduced using the first-order perturbation theory [C. T. Tindle, L. M. O’Driscoll and C. J. Higham, Coupled mode perturbation theory of range dependence, J. Acoust. Soc. Am. 108(1) (2000) 76–83]. And mode perturbations in amplitude are neglected by the adiabatic method with wavenumber perturbations in phase merely considered. The AP expression of temporal coherence function is theoretically identical to the adiabatic transport equation theory [J. A. Colosi, T. K. Chandrayadula, A. G. Voronovich and V. E. Ostashev, Coupled mode transport theory for sound transmission through an ocean with random sound speed perturbations: Coherence in deep water environments, J. Acoust. Soc. Am. 134(4) (2013) 3119–3133]. Numerical results of the adiabatic temporal coherence function for several low frequencies and ranges up to 1000[Formula: see text]km are calculated. Then the coherence time scales obtained from the calculations are examined by a one-way coupled theory considering forward scattering [A. G. Voronovich, V. E. Ostashev and J. A. Colosi, Temporal coherence of acoustic signals in a fluctuating ocean, J. Acoust. Soc. Am. 129(6) (2011) 3590–3597]. Comparisons demonstrate that the range and frequency dependence of coherence time for both methods are quite close. And this shows good agreement with the well-known inverse frequency and inverse square root range laws. In addition, the internal wave energy dependence of coherence time is also studied.

Micromachined Filters at 450 GHz With 1% Fractional Bandwidth and Unloaded <italic>Q</italic> Beyond 700

This letter presents two silicon-micromachined narrowband fourth-order waveguide filter concepts with center frequency of 450 GHz, which are the first narrowband submillimeter-wave filters implemented in any technology with a fractional bandwidth as low as 1%. Both filters designs are highly compact and have axial port arrangements, so that they can be mounted directly between two standard waveguide flanges without needing any split-block interposers. The first filter concept contains two TM110 dual-mode cavities of circular shape with coupling slots and perturbations arranged in two vertically stacked layers, while the second filter concept is composed of four TE101 series resonators arranged in a folded, two-level topology without crosscouplings. Prototype devices are fabricated in a multilayer chip platform by high-precision, low-surface roughness deep-silicon etching on silicon-on-insulator wafers. The measured passband insertion loss of two prototype devices of the dual-mode circular-cavity filters is 2.3 dB, and 2.6 dB for three prototypes of the folded filter design. The corresponding extracted unloaded quality factors of the resonators are 786 ± 7 and 703 ± 13, respectively, which are the best so far reported for submillimeter-wave filters in any technology. The presented filters are extremely compact in terms of size; their footprints have areas of only 0.53 and 0.55 mm2, respectively, and the thickness between the waveguide flanges is 0.9 mm.

Strong-coupling perturbative study of the disordered Hubbard model on the honeycomb lattice

We study the Anderson disordered Hubbard model on the honeycomb lattice. The Hubbard term is han- dled with strong-coupling perturbation theory which encodes the Mott transition physics into a rich dynamical structure of a local self-energy. The local nature of self-energy allows us to combine it with kernel polynomial method and transfer matrix methods. The locality of self-energy combined with the analytic nature of the strong- coupling perturbation theory enables us to study lattices with millions of sites. The transfer matrix method in the ribbon geometry is essentially free from finite size errors and allows us to perform a careful finite size scaling of the width of the ribbon. This finite size scaling enables us to rule out the possibility of metallic phase in between the Mott and Anderson insulating phases. We therefore find a direct transition between Anderson and Mott insulators when the disorder strength W is comparable to the Hubbard interaction U . For a fixed disorder W , we obtain an interaction dependent nonmonotonic behavior of the localization length which reflects interac- tion induced enhancement of the localization length for weak and intermediate interaction strengths. Eventually at strong interactions U, the Mott localization takes over and the localization length becomes comparable to the lattice scale. This is reminiscent of the holographic determination of the Mott state where the system at IR recognizes its UV lattice scale.

12. SYNAPTIC DYSFUNCTION IN SCHIZOPHRENIA: EXPLORATION OF NOVEL HYPOTHESES AND PROMISING NEW LEADS

Overall : Accumulating evidence suggests that bioenergetic function is impaired in the brain in schizophrenia. In normal brain, glucose is metabolized to lactate and pyruvate, which are monocarboxylate intermediates that serve as the primary energy source for neurons. Working memory and other cognitive domains are dependent on the shuttling of lactate from astrocytes to neurons. Defects in this complex pathway may underlie cognitive dysfunction in schizophrenia. The focus of this symposium is to present evidence of such defects, and to identify substrates that may be targeted for the development of new treatment strategies. Dr. Laura Rowland (University of Maryland, Baltimore, Maryland, USA) will present evidence of bioenergetic dysfunction in living subjects with schizophrenia. Increased levels of lactate (P < 0.05) were present in the ACC in schizophrenia (n = 27) compared to controls (n = 29). Higher lactate levels were associated with lowers scores on the MATRICS Consensus Cognitive Battery. These data establish a direct link between cognition and bioenergetic function in vivo in schizophrenia. Dr. Robert McCullumsmith (University of Cincinnati, Cincinnati, Ohio, USA) will present evidence of alterations in the lactate shuttle and glycolytic enzymes in postmortem samples from schizophrenia (n = 20) and control subjects (n = 20). Cell-subtype specific changes (P < 0.05) in transcripts include increased levels of the lactate transporter MCT4, decreased levels of the glycolytic enzymes PFK1 and hexokinase, and decreased levels of the glucose transporters Glut1 and Glut3. These data suggest attenuated glycolysis in pyramidal neurons, with a shift towards pathways that boost protection from oxidative stress. The last two speakers will present data that address mechanisms related to these findings, using animal models with behavioral endophenotypes of schizophrenia. Dr. Eduard Bentea (Free University of Brussels (VUB), Brussels, Belgium) will present data from the xCT knockout mouse showing that disruption of system xc-, which supports oxidative stress buffering mechanisms, leads to synaptic dysfunction. Specifically, electron microscopy studies indicate depletion of both pre-and post-synaptic glutamate, while electrophysiological studies show diminished excitatory postsynaptic potentials. These findings directly connect oxidative balance and extracellular glutamate levels with development of “broken” synapses, highlighting a potential mechanism for perturbation of bioenergetic coupling between astrocytes and neurons. Dr. Amy Ramsey (University of Toronto, Toronto, Canada) will present evidence from an animal model of synaptic dysfunction, the GluN1 knockdown mouse. These mice show a bioenergetic defect similar to schizophrenia, with decreased expression of glycolytic enzymes and glucose transporters. These translational findings indicate that genetic risk for schizophrenia may lead to an intermediate bioenergetic phenotype, where diminished supply of lactate and other energetic molecules to neurons could contribute to cognitive dysfunction. Taken together, the work presented by these speakers will provide a fresh look at the bioenergetic defects in schizophrenia, establishing that 1) metabolic perturbations in the brain are prominent and not just an effect antipsychotic treatment, 2) altered neuron-astrocyte coupling leads to synaptic dysfunction, and 3) genetic risk for “broken” synapses disrupts metabolic function.

Coupling based estimation approaches for the average reward performance potential in Markov chains

Performance potential is an important concept in the sensitivity analysis of Markov chains. The estimation of performance potential provides the basis for the simulation-based optimization and sensitivity analysis of Markov chains. In this study, we present novel estimation approaches for the average reward (or cost) performance potential by combining perturbation realization factors and coupling techniques for Markov chains with finite state space. These approaches can effectively implement estimation with geometric variance reduction for average reward performance potential. Meanwhile, a number of coupling methods, including two optimal coupling methods, can be applied to further reduce estimation variance or simulation time. The numerical tests show that our approaches can significantly enhance the simulation efficiency.

Robust Adaptive Synchronization of Ring Configured Uncertain Chaotic FitzHugh-Nagumo Neurons under Direction-Dependent Coupling.

This paper exploits the dynamical modeling, behavior analysis, and synchronization of a network of four different FitzHugh–Nagumo (FHN) neurons with unknown parameters linked in a ring configuration under direction-dependent coupling. The main purpose is to investigate a robust adaptive control law for the synchronization of uncertain and perturbed neurons, communicating in a medium of bidirectional coupling. The neurons are assumed to be different and interconnected in a ring structure. The strength of the gap junctions is taken to be different for each link in the network, owing to the inter-neuronal coupling medium properties. Robust adaptive control mechanism based on Lyapunov stability analysis is employed and theoretical criteria are derived to realize the synchronization of the network of four FHN neurons in a ring form with unknown parameters under direction-dependent coupling and disturbances. The proposed scheme for synchronization of dissimilar neurons, under external electrical stimuli, coupled in a ring communication topology, having all parameters unknown, and subject to directional coupling medium and perturbations, is addressed for the first time as per our knowledge. To demonstrate the efficacy of the proposed strategy, simulation results are provided.