Constant Coupling Research Articles

Feasibility study of a touch-enabled active sensing approach to inspecting subsea bolted connections using piezoceramic transducers

Pipelines that stretch on for miles and miles are linked together through a multitude of bolted connections. However, each bolted connection represents a point of vulnerability that can suffer from leakage. In subsea environments, leakage can spread farther and cause even more disastrous to both economy and environment. A number of structural health monitoring methods have been proposed and explored. However, most monitoring methods require permanent installation of sensors on the structures to be monitored, which can be difficult for subsea locations. In this paper, a piezoceramic transducer enabled touch-based active sensing approach is proposed to inspect subsea bolted connections without the requirement of permanent installation of sensors on the structures. The proposed approach also aims for an easy integration with a subsea robotic system, such as a remotely operated vehicle (ROV) for bolted connection inspection. To study the feasibility of the proposed approach, a spring-loaded C-clamp shaped device that mimics two robotic fingers equipped with a pair of piezoceramic transducers is designed and fabricated. Two piezoceramic transducers are mounted on the inner surfaces of the two robotic fingers. In addition, a pair of permanent magnets are employed to ensure a temporary while constant coupling between the transducers and the both surfaces of the bolt connection, upon touching. In this way, one piezoceramic transducer generates stress waves that propagate across the connection interface, and the other PZT transducer detects the propagating stress wave. By analyzing the received stress wave signals via spectrograms and wavelet packet transformation, the status of the connection can be derived. Experimental investigations are performed on a bolted connection with different applied torques in air and in salt water (3.5% salinity), and results demonstrate effectiveness of the proposed touch-enabled active sensing for inspection of submerged bolted connection.

Axionlike Origin of the Primordial Density Perturbation

We show that an axionlike field coupled to a new confining gauge group can generate the primordial density perturbation in the postinflation Universe. The axion decay constant and strong coupling scale are uniquely determined by observations of the density perturbation, which further suggest a temporal deconfinement of the gauge group after inflation. The resulting temperature-dependent axion potential, together with its periodic nature, gives rise to the red-tilted density perturbation, with a positive local-type non-Gaussianity of order unity.

Update on coupled dark energy and the H0 tension

In this work we provide updated constraints on coupled dark energy (CDE) cosmology with Peebles-Ratra (PR) potential and constant coupling strength $\beta$. This modified gravity scenario introduces a fifth force between dark matter particles, mediated by a scalar field that plays the role of dark energy. The mass of the dark matter particles does not remain constant, but changes with time as a function of the scalar field. Here we focus on the phenomenological behavior of the model, and assess its ability to describe updated cosmological data sets that include the Planck 2018 cosmic microwave background (CMB) temperature, polarization and lensing, baryon acoustic oscillations, the Pantheon compilation of supernovae of Type Ia, data on $H(z)$ from cosmic chronometers, and redshift-space distortions. We also study which is the impact of the local measurement of $H_0$ from SH0ES and the strong-lensing time delay data from the H0LICOW collaboration on the parameter that controls the strength of the interaction in the dark sector. We find a peak corresponding to a coupling $\beta > 0$ and to a potential parameter $\alpha > 0$, more or less evident depending on the data set combination. We show separately the impact of each data set and remark that it is especially CMB lensing the one data set that shifts the peak the most towards $\Lambda$CDM. When a model selection criterion based on the full Bayesian evidence is applied, however, $\Lambda$CDM is still preferred in all cases, due to the additional parameters introduced in the CDE model.

Dilute magnetic ions mediated magneto-dielectric, optical and ferroelectric response of MgAl2O4 spinels

Magnesium aluminate (MgAl2O4) commonly termed as spinel has been a subject of intense research due to its excellent thermal, optical and dielectric characteristics. These properties in such compounds can efficiently be tuned by introducing small contents of different transition metals. In this work, dilute contents of transition metals (Mn, Fe, Co, and Ni) are incorporated in MgAl2O4 to produce the dilute magnetic compositions of these aluminates. Crystallographic information reveals the formation of spinel cubic crystal structure with Fd−3m space group. Magnetic measurements demonstrate a clear magnetization response to an external magnetic field establishing dilute magnetic behavior of these spinels. The increase in ferroelectric characteristics with the incorporation of transition elements suggests that these materials are quite suitable for energy storage devices. A sharp variation in dielectric constant and magneto-dielectric coupling with the response to the external magnetic field, further exposes them as an excellent candidate for magneto-dielectric applications.

Reduction of electron-phonon coupling in warm dense iron

The electron-ion relaxation dynamics in warm dense iron were investigated by time-resolved x-ray absorption near-edge spectroscopy (XANES). A novel analysis, combining ab initio density functional theory (DFT) and two temperature model (TTM) simulations, was developed to calculate the x-ray absorption spectra as a function of delay time. Here we present experimental evidence of changes at the XAS L3 edge of iron that are consistent with the reduction of the electron-phonon coupling under warm dense matter conditions. The experimental results are in agreement with the model that takes both the electron (${T}_{e}$) and the ion temperature (${T}_{i}$) dependence of the thermophysical properties into consideration, while models where either constant electron-phonon coupling factor (G) or only ${T}_{e}$-dependent G are used do not agree with the observed relaxation dynamics of iron.

A dS obstruction and its phenomenological consequences

In this note we observe that positive runaway potentials can generically be stabilized by abelian p-form fluxes, leading to parametrically controlled de Sitter solutions after compactification to a lower dimension. When compactifying from 4d to 2d the dS solutions are metastable, whereas all higher dimensional cases are unstable. The existence of these dS solutions require that a certain inequality involving the derivatives of the potential and p-form gauge coupling is satisfied. This inequality is not satisfied in simple stringy examples (outside of the scope of Maldacena-Nuñez), which unsurprisingly avoid this route to dS solutions. We can apply our techniques to construct dS2 solutions in the Standard Model plus an additional runaway scalar such as quintessence. Demanding that these are avoided leads to (weak) phenomenological constraints on the time variation of the fine structure constant and QCD axion-photon coupling.

Phononic loss in superconducting resonators on piezoelectric substrates

We numerically and experimentally investigate the phononic loss for superconducting resonators fabricated on a piezoelectric substrate. With the help of finite element method simulations, we calculate the energy loss due to electromechanical conversion into bulk and surface acoustic waves. This sets an upper limit for the resonator internal quality factor Qi. To validate the simulation, we fabricate quarter wavelength coplanar waveguide resonators on GaAs and measure Qi as function of frequency, power and temperature. We observe a linear increase of Qi with frequency, as predicted by the simulations for a constant electromechanical coupling. Additionally, Qi shows a weak power dependence and a negligible temperature dependence around 10 mK, excluding two level systems and non-equilibrium quasiparticles as the main source of losses at that temperature.

The Extended Manifold for Antenna Arrays

The paper investigates a general parametric model for the manifold of polarization sensitive arrays based on representing each antenna by a collection of short dipoles. The manifold has a simple form consisting of an extended isotropic manifold, vertical and horizontal direction vectors and a constant non-square coupling matrix. The resulting manifold captures the effects of coupling, polarization and antenna characteristics. It provides an accurate representation of the analytic manifold which is based on electromagnetic theory. Three methods for computing the Coupling Matrix are described based on: (i) the current distributions in the antennas, (ii) its approximation by a sum of Kronecker products, and (iii) least-squares fit of the analytic and extended manifolds. The accuracy of these manifolds is illustrated by numerical examples.

Controllable quantum interface between itinerant optical photon and microwave photonic memory

We propose a scheme for controlling the quantum interface between the travelling optical wave packet and microwave photonic memory. The effective coupling between the optical and microwave modes is mediated by the rare earth doped crystal as first proposed by Williamson et al. [L.A. Williamson, Y.H. Chen, J.J. Longdell, Phys. Rev.Lett. 113, 203601 (2014)], and can be modulated by a time-dependent coherent driving field. With the effective model, we obtain the fidelity of the write process for arbitrary input wave packet as well as driving field, and investigate its optimization in two cases. In the first case of constant coupling, the optimal input wave packet is analytically derived to maximize the fidelity, while in the latter case of tunable coupling, the sequence of coherent driving field is numerically optimized for arbitrary given input wave packet. The write process for the Gaussian input wave packet can be explicitly characterized in the tunable parameter regime of real experiments, revealing that the fidelity can reach 0.974η (η being the coupling efficiency of the optical cavity). Based on these advantages, the proposal will have potential applications for the investigation of quantum networks.

Research and analysis of electromagnetic systems with constant flow coupling using a physical model

Research and analysis of electromagnetic systems with constant flow coupling using a physical model

Simulation of Synchronized-Switching Method Energy Harvester Including Accurate Piezoceramic Nonlinear Behavior

Synchronized-switching techniques have significantly enhanced the harvested energy from semipassive and active surrounding ambient mechanical vibration harvesters. They have allowed a large improvement of vibration-control efficiency using piezoelectric devices. Unfortunately, for such techniques, dielectric limitations appear as soon as the piezoceramic operates under external solicitation of higher amplitudes and frequencies. Under extreme conditions, active materials exhibit nonlinear behavior related to dielectric hysteresis that significantly reduces their performance. In this work, we focus on this nonlinear behavior and its consequences in terms of system efficiency. We apply a realistic model including accurate material laws. In such models, a constant piezoelectric coupling d 31 is not suitable as a coefficient anymore and it should be replaced by a function depending on the polarization level through the active material. The response of more realistic systems including hysteresis was taken into account and compared with the basic model, where a constant d 31 was considered.

Circulation Cooling in Continuous Skin Sonoporation at Constant Coupling Fluid Temperatures

Exposure of the skin to low-frequency ultrasound in the Franz diffusion cell has been found to increase the permeability of the skin to molecular transport. In many cases, significant heating of the coupling fluid requires the use of duty cycles that extend the total experimental time. This is a methodological study in which the coupling fluid is circulated between a modified Franz diffusion cell and a heat exchanger to allow for the continuous application of low-frequency ultrasound while the coupling fluid temperature is held constant. Dermatomed porcine skin was exposed to continuous ultrasound at 20 kHz for 10 min at an intensity of 55 W/cm2 while the coupling fluid was maintained at one of three target temperatures (13°C, 33°C or 46°C). Foil pitting and passive cavitation detection revealed that inertial cavitation activity decreased with increasing coupling fluid target temperature. Transport measurements revealed an increase in mean donor calcein concentration with increasing coupling fluid temperature, though these were not statistically significant. Taken together these findings suggest that the weakened stratum corneum lipid structure at higher temperatures is more susceptible to the introduction of defects from the jetting of cavitation.

Locally Strong-Coupled Microwave Resonator Using PEMC Boundary for Distant Sensing Applications

This research study reports on a new coupling structure to demonstrate a constant coupling strength for longer distances in planar microwave sensors. It is shown that there is a positive correlation between the gap size in a pair of gap-coupled transmission lines (GCTLs) and the effective distance of reader and sensing resonators in a planar microwave sensor. On the other hand, the coupling strength in a pair of GCTLs is negatively correlated to the gap size between the two lines, where the larger gap sizes result in weaker coupling strength or vice versa. A technique is introduced to make the coupling strength partially independent of the gap size in GCTLs. The technique enables a sensor designer to increase the gap size, and subsequently, the distance between the reader and sensing resonators of a sensor. Strong electromagnetic coupling is locally demonstrated between a pair of GCTLs using a new artificial perfect electromagnetic conductor (PEMC) boundary, which does not allow electromagnetic power reflect toward the source over larger gap sizes in GCTLs. The concept is experimentally verified with a gap size up to 10 mm between GCTLs with a constantly measured insertion loss of 0.9 dB. Moreover, the structure is employed to design distant microwave resonator for humidity sensing applications. The design has demonstrated the ability of sensing, while the sensing resonator is placed at 35-mm distance from the readout circuitry. The structure is reported to increase the sensing distance with a ratio of about 12 (36:3) compared to the conventional microwave sensors.

Super heat kernel of general second order operators in N=1 superspace and one-loop divergence of dilaton-coupled SYM theory

We shall develop a general technique to obtain the super heat kernel coefficients of an arbitrary second order operator in $N=1$ superspace. We focus on the space of conformal supergravity here but the method presented is equally applicable for other types of superspace. The first three coefficients which determine the one-loop divergence of the corresponding quantum theory will be calculated. As an application we shall present the one-loop logarithmic divergence of super Yang-Mills theory coupled to a string dilaton $S$. This is the first superfield calculation for SYM with a non-trivial gauge kinetic function, which generalize the previous result with a constant coupling strength. We also demonstrate that the method presented can be extended to the case of third order operators, with the restriction that its third order part is composed of only spinor derivatives.

Design, Analysis, and Experimental Verification of a Ball-Joint Structure With Constant Coupling for Capacitive Wireless Power Transfer

This article presents the design, analysis, and verification of a ball-joint structure suitable for capacitive wireless power transfer (WPT) for a consumer electronic lighting system. The WPT structure consists of a ball-joint component rotatable inside a spherical socket. Conductive surfaces are used to form equivalent plates so that the capacitive WPT can be achieved through electric field coupling. One unique feature of this novel structure is that the mutual capacitance remains almost constant in the rotatable angular range. The design and theoretical analysis are included and practical results obtained from a 7-W prototype are included to confirm the theory.

Influence of polymer insertion on the dielectric, piezoelectric and acoustic properties of 1-0-3 polyurethane/cement-based piezo composite

Cement/polyurethane based piezo composite was fabricated with 1-0–3 connectivity. Microstructural analysis shows that polyurethane (PU) acts as a binder, reducing the porosity and improving the matrix adhesion to the piezoelectric phase. Dielectric characterisation shows that PU strongly reduces both the interfacial polarisation process and the ionic mobility in the matrix, thus decreasing the dielectric constant and increasing the values of voltage constant (g33) and electromechanical coupling coefficient (kt). The composite was surface mounted on a porous concrete bar and evaluated as an acoustic emission sensor (AE). The results show that this material is a highly sensitive sensor for AE detection in the frequency range 50–220 kHz.

Real and imaginary energy gaps: a comparison between single excitation Superradiance and Superconductivity and robustness to disorder

A comparison between the single particle spectrum of the discrete Bardeen-Cooper-Schrieffer (BCS) model, used for small superconducting grains, and the spectrum of a paradigmatic model of Single Excitation Superradiance (SES) is presented. They are both characterized by an equally spaced energy spectrum (Picket Fence) where all the levels are coupled between each other by a constant coupling which is real for the BCS model and purely imaginary for the SES model. While the former corresponds to the discrete BCS-model describing the coupling of Cooper pairs in momentum space and it induces a Superconductive regime, the latter describes the coupling of single particle energy levels to a common decay channel and it induces a Superradiant transition. We show that the transition to a Superradiant regime can be connected to the emergence of an imaginary energy gap, similarly to the transition to a Superconductive regime where a real energy gap emerges. Despite their different physical origin, it is possible to show that both the Superradiant and the Superconducting gaps have the same magnitude in the large gap limit. Nevertheless, some differences appear: while the critical coupling at which the Superradiant gap appears is independent of the system size $N$, for the Superconductivity gap it scales as $(\ln N)^{-1}$. The presence of a gap in the imaginary energy axis between the Superradiant and the Subradiant states shares many similarities with the "standard" gap on the real energy axis: the superradiant state is protected against disorder from the imaginary gap as well as the superconducting ground state is protected by the real energy gap. Moreover we connect the origin of the gapped phase to the long-range nature of the coupling between the energy levels.

Dynamical and static spin structure factors of Heisenberg antiferromagnet on honeycomb lattice in the presence of Dzyaloshinskii-Moriya interaction

We have theoretically studied the spin structure factors of Heisenberg model on honeycomb lattice in the presence of longitudinal magnetic field, i.e. magnetic field perpendicular to the honeycomb plane, and Dzyaloshinskii-Moriya interaction. The possible effects of next nearest neighbor exchange constant are investigated in terms of anisotropy in the Heisenberg interactions. This spatial anisotropy is due to the difference between nearest neighbor exchange coupling constant and next nearest neighbor exchange coupling constant. The original spin model hamiltonian is mapped to a bosonic model via a hard core bosonic transformation where an infinite hard core repulsion is imposed to constrain one boson occupation per site. Using Green's function approach, the energy spectrum of quasiparticle excitation has been obtained. The spectrum of the bosonic gas has been implemented in order to obtain two particle propagator which corresponds to spin structure factor of original Heisenberg chain model Hamiltonian. The results show the position of peak in the dynamical transverse spin structure factor at fixed value for Dzyaloshinskii Moriya interaction moves to higher frequency with magnetic field. Also the intensity of dynamical transverse spin structure factor is not affected by magnetic field. However the Dzyaloshinskii Moriya interaction strength causes to decrease the intensity of dynamical transverse spin structure factor. The increase of magnetic field does not varied the frequency position of peaks in dynamical longitudinal spin susceptibility however the intensity reduces with magnetic field. Our results show static transverse structure factor is found to be monotonically decreasing with magnetic field and temperature for different values of next nearest neighbor coupling exchange constant.

Generation of new structured beams via spatially dependent transparency

We propose a new scheme for generating new structured beams via spatially dependent transparency in a three-level atomic system. Due to the joint quantum interference induced by Laguerre–Gaussian (LG) field and constant coupling field, we can achieve different spatially dependent beams by measuring the probe absorption intensity profiles. The proposed scheme may provide potential applications in optics and novel quantum technologies.

Can the symmetry breaking in the SM be determined by the “second minimum” of the Higgs potential?

The possibility that the spontaneous symmetry breaking in the Standard Model (SM) may be generated by the Top-Higgs Yukawa interaction (which determines the so called ``second in the SM) is investigated. A former analysis about a QCD action only including the Yukawa interaction of a single quark with a scalar field is here extended. We repeat the calculation done in that study of the two loop effective action for the scalar field of the mentioned model. A correction of the former evaluation allowed to select a strong coupling $\alpha $($\mu,\Lambda_{QCD})=0.2254$ GeV at an intermediate scale $\mu=11.63$ GeV, in order to fix the minimum of the potential at a scalar mean field determining $175$ GeV for the single quark mass. Further, a scalar field mass $m=44$ GeV is evaluated, which is also of the order of the experimental Higgs mass. The work is also considering the effects of employing a running with momenta strong coupling. For this purpose, the finite part of the two loop potential contribution determined by the strong coupling, was represented as a momentum integral. Next, substituting in this integral the experimental values of the running coupling, the potential curve became very close to the one for constant coupling. This happened after simply assuming that the low momentum dependence of the coupling is saturated to a constant value being close to its lowest experimental value.