Parameter Dependence Research Articles

Twist corrections to exclusive vector meson production in a saturation framework

We develop a framework combining the higher-twist formalism of exclusive processes in the s channel with the semiclassical effective description of small-x physics in the t channel. We apply it to transversely polarized light vector meson production, γ*p→V(ρ,φ,ω)p, which starts at the next-to-leading power and for which a purely collinear treatment leads to end-point singularities. The result is obtained in the most general kinematics, including both forward and nonforward cases by preserving the full impact parameter dependence in the nonperturbative correlators, in both momentum and coordinate space representations. A systematic expansion of the Wilson lines in terms of Reggeized gluon fields is performed in order to obtain the results in the weak-field BFKL approximation. These new results will allow for investigating the dilute-to-dense regime transition of quantum chromodynamics for a wide class of observables. Published by the American Physical Society 2025

Domain wall constraints on the doublet left-right symmetric model from pulsar timing array data

Recent evidence of a stochastic gravitational wave (GW) background found by NANOGrav and other pulsar timing array (PTA) collaborations has inspired many studies looking for possible sources. We consider the hypothesis that the GW signature is produced by domain walls (DWs) arising in the doublet left-right symmetric model (DLRSM) due to the spontaneous breaking of the discrete parity symmetry. We show that the DW network consists of two types of DWs, namely Z2 and LR DWs, and solve the kink equations to obtain the parametric dependence of the surface tension in the two cases. We argue that the Z2 DWs are unstable due to higher surface tension, leading to a stable network consisting only of LR DWs. Considering the GW signal from the DLRSM DW model with and without the contribution from supermassive black hole binaries, we perform a Bayesian analysis using the PTA data to estimate the posterior distribution and identify best-fit parameter ranges. The PTA data favors a parity-breaking scale of O(105) GeV, and a biased potential Vbias∼(O(100) MeV)4. The model with only DLRSM DWs is slightly favored over the model where additional supermassive black hole binaries contribution is considered. Published by the American Physical Society 2025

Investigation of magnetic fluctuations in L-H and H-L transition dynamics on DIII-D

Abstract The dynamics of the L-H transition is not fully understood, with many parameters changing the threshold power to enter H-mode and the self-regulation between zonal flows and turbulence in the plasma edge. This paper presents power threshold analysis for DIII-
D L-H and H-L transitions, as well as measurements of pedestal temperatures for these transitions. A comparison is made between an L-H transition and H-L transition of comparable Psep exhibiting oscillatory behaviour, showing symmetry between forward and backward transition dynamics. Information geometry analysis has been performed on measurements of plasma density fluctuations, perpendicular plasma velocity fluctuations, and magnetic field fluctuations to investigate the self-regulation of these variables during the transitions. Perpendicular flow evolution is shown to dominate the transition dynamics in both directions, but self-regulation behaviour is observed between all three variables. A strong correlation between magnetic fluctuation information rate and density fluctuation information rate for these two shots indicates the strong influence of magnetic behaviour on both the L-H and H-
L transition, and that these transition dynamics have an electromagnetic contribution. Some parameter dependencies of the magnetic fluctuation activity are presented.

Reducing the Parameter Dependency of Phase-Picking Neural Networks with Dice Loss

Abstract Training a neural network for picking seismic phase arrivals has been commonly posed as a segmentation problem. It is a highly imbalanced segmentation problem in the sense that the background vastly dominates the foreground because we are trying to pick the optimal single sample point that represents the arrival of a seismic phase in a many seconds long time window. Here, we test the Dice loss, which is a preferred loss function for highly imbalanced image segmentation problems. We show that phase-picking neural networks trained on the Dice loss behave in a binary fashion for which the prediction output is almost always either nearly 1 or nearly 0. This feature removes the strong dependence of data processing workflows on the prediction score threshold, which is an otherwise critical parameter to determine when using neural networks trained on the cross-entropy loss. When strategically used, models trained on the Dice loss can reduce the parameter dependency of machine learning-based seismic monitoring.

Main Component in Altimetry-Observed Response to a Tropical Cyclone

Abstract The ocean response to a tropical cyclone (TC) generally consists of near-inertial and geostrophic components, and the geostrophic response is impliedly believed to be ignorable. This study divides and compares the geostrophic and near-inertial components in the sea surface height (SSH) response obtained by a two-layer theory and numerical experiments, revealing that the geostrophic component is dominant and the near-inertial component ignorable. This conclusion results from 1) the high ratios (approximately 70%–90%) of the geostrophic component in the upwelling where the geostrophic response occurs and/or 2) the small absolute near-inertial amplitudes, usually below 3 cm, which satellite altimeters cannot capture. The findings are first presented in a two-layer model and then confirmed to be robust using numerical experiments by considering the effects of the nonlinear process, vertical dispersion of near-inertial internal waves, and vertical structure of the geostrophic response. By testing parameter dependence, the findings are insensitive to ocean stratification and TC characteristics including moving speed, intensity, and latitude, thus being generally appropriate for any TC case. The generality is physically related to the nature of Rossby adjustment and the dispersion of TC-induced near-inertial internal waves. Finally, the evidences are provided by the SSH response to Typhoon Mawar (2023) captured by the Surface Water and Ocean Topography satellite, which demonstrates the main features of the geostrophic response and no near-inertial wavelike signals. This study lays a solid foundation for dynamically understanding altimetry-observed response, highlighting the vital role of the geostrophic response. Significance Statement The ocean response to a tropical cyclone generally consists of wave and quasi-steady components, and the quasi-steady component is impliedly believed to be ignorable. Based on the theory, numerical experiments, and altimetry observations, this study finds the high ratios of the quasi-steady component in sea surface height response and the relatively small wave amplitudes. Thus, the quasi-steady response is the main component, and the wave component is ignorable in the sea surface height response to a tropical cyclone observed by satellite altimeters. This study lays a solid foundation for dynamically understanding altimetry-observed response to a tropical cyclone and proves the vital importance of the quasi-steady response.

Zonal fields as catalysts and inhibitors of turbulence-driven magnetic islands

A novel coalescence process is shown to take place in plasma fluid simulations, leading to the formation of large-scale magnetic islands that become dynamically important in the system. The parametric dependence of the process on the plasma β and the background magnetic shear is studied, and the process is broken down at a fundamental level, allowing us to clearly identify its causes and dynamics. The formation of magnetic-island-like structures at the spatial scale of the unstable modes is observed quite early in the non-linear phase of the simulation for most cases studied, as the unstable modes change their structure from interchange-like to tearing-like. This is followed by a slow coalescence process that evolves these magnetic structures toward larger and larger scales, adding to the large-scale tearing-like modes that already form by direct coupling of neighboring unstable modes, but remain sub-dominant without the contribution from the smaller scales through coalescence. The presence of the cubic non-linearities retained in the model is essential in the dynamics of this process. The zonal fields are key actors of the overall process, acting as mediators between the competitive mechanisms from which turbulence-driven magnetic islands can develop. The zonal current is found to slow down the formation of large-scale magnetic islands, acting as an inhibitor, while the zonal flow is needed to allow the system to transfer energy to the larger scales, acting as a catalyst for the island formation process.

Analysis on thermo-mechanical reliability of laser-electricity converter

Thermal and mechanical responses of a typical Laser-Electricity Converter (LEC) used in laser power beaming to continuous wave (CW) Laser, as well as the damage behavior of key sensor illuminated by laser have been investigated to evaluate the reliability of the converter. Firstly, temperature elevation and thermal stress arising in the whole LEC are calculated and analyzed to find out the vulnerable parts, i.e., the infrared detectors for optical path alignment during wireless power transfer. Then, the parameter dependence of thermo-mechanical behaviors of the detector is revealed with a group of numerical simulations. Finally, the typical experimental tests are carried through to verify the theoretical analysis.

On the Exceptional Points effect in All-Dielectric Metasurface

All-dielectric non-Hermitian structures make it possible to obtain unique effect like the appearance of the exceptional points (EP). A system at EP is sensitive to a small perturbation of refractive index, which can be widely used in different ways, such as EP-based sensors, optical amplifiers, laser gyroscopes and other fields. In this study, we investigate an exceptional point in two-rectangle system with varying opening angle which can be defined as a structure with only in-plane symmetry breaking. Furthermore, the effect dependance of geometry parameters has been studied. The main advantage of our geometric approach is the simplified way to experimental control an EP. Consequently, this effect has the potential to significantly simplify the manufacturing process of photonic devices with diverse functionalities.

Assessment of the JET ICRH system performance since 2000

Abstract The paper provides an assessment of the ion-cyclotron resonance heating (ICRH) system performance on JET since the year 2000. The vast amount of collected data offer an insight into the historical challenges and trends in the ICRH system performance encompassing the transition from carbon (JET-C) to beryllium & tungsten ITER-like wall (JET-ILW) operations, the deuterium–tritium experiments (DTE2 & DTE3) and introduction of new RF antenna & matching systems. The best achieved operational parameters are reported and statistics on the RF plant reliability and performance is analysed. Antenna-plasma coupling is identified as the dominant factor critical to all the aspects of the ICRH system behaviour; parametric dependencies of coupling resistance on plasma parameters and the RF plant settings are discussed and the key role of local electron concentration profiles close to the antennas is highlighted. Following confident antenna performance at high RF voltages over the recent decade, observations are presented suggesting improved electrical strength of the RF vacuum components after the JET-C to JET-ILW transition; this is tentatively attributed to the reduction of dust levels in the JET vessel. Statistics on application rate and typical origins of the RF amplifier failures and protection power limits is presented indicating that the amplifier issues noticeably affected the high-power ICRH operations. Performance comparison is provided for different RF antenna & matching systems installed at JET since 2000 including the original system, two load-tolerant systems based on the 3 dB hybrid and external conjugate-T power-splitters, and the ITER-like antenna. The paper could be of interest both as a summary of technical challenges, constraints and achievements related to the ICRH application on JET and as a reference for design and operations of high-power RF systems in future fusion devices.

Reduced order modeling of blood perfusion in parametric multipatch liver lobules

In this paper, we present a computationally efficient reduced order model for obtaining blood perfusion profiles within parametric functional units of the liver called ‘lobules’. We consider Darcy’s equation in two-dimensional hexagonal lobule domains with six flow inlets and one outlet, whose positions are parameterized to represent varying lobule geometries. To avoid the meshing effort for every new lobule domain, we map the parametric domain onto a single reference domain. By making use of the contra-variant Piola mapping, we represent solutions of the parametric domains in the reference domain. We then construct a reduced order model via proper orthogonal decomposition (POD). Additionally, we employ the discrete empirical interpolation method (DEIM) to treat the non-affine parameter dependence that appears due to the geometric mapping. For sampling random shapes and sizes of lobules, we generate Voronoi diagrams (VD) from Delaunay triangulations and use an energy minimization problem to control the packing of the lobule structures. To reduce the dimension of the parameterized problem, we exploit the mesh symmetry of the full lobule domain to split the full domain into six rotationally symmetric subdomains. We then use the same set of reduced order basis (ROB) functions within each subdomain for the construction of the reduced order model. We close our study by a thorough investigation of the accuracy and computational efficiency of the resulting reduced order model.

Impurity transport driven by kinetic ballooning mode in the strong gradient pedestal of tokamak plasmas

Abstract The impurity transport driven by kinetic ballooning mode (KBM) is theoretically studied in the DIII-D H-mode strong gradient pedestal plasmas. From the electromagnetic gyrokinetic equation, including the correction of the strong radial electric field, the dispersion relationship of KBM instability with non-trace impurity is firstly derived. Then, the turbulent impurity flux and ion heat flux, as well as the associated transport coefficients, are further calculated. Through the parametric dependence analysis of analytical results, it is found that dilution effects of light fully ionized impurities can reduce the drive of KBM by affecting the kinetic pressure gradient parameter α and diamagnetic effects, thus leading to a decrease in both the absolute value of the real frequency | ω r ′ | and the growth rate γ k ′ of KBM instability. Stronger dilution effects by increasing the impurity charge number Z or steepening the impurity density profile correspond to stronger effects. Moreover, the removal efficiency of light fully ionized impurities, quantified by the ratio between the impurity diffusivity and effective ion heat conductivity D z χ i eff ≈ 1 − b z + 4 ω Dz / ω r ′ 3 ( 1 + 1 / η i ) / 2 , increases with an increase of Z mainly due to the smaller impurity finite Larmor radius (FLR) effects reflected by b z ∝ 1 / Z . Besides, the increase of the impurity density gradient can significantly enhance D z / χ i eff , and this is because stronger impurity dilution effects make a larger magnetic drift term | ω Dz | / | ω r ′ | ( ω Dz is the magnitude of impurity magnetic drift frequency) and η i (the ratio of ion density gradient scale length to ion temperature gradient scale length). For heavy metal impurities with a concentration of 10 − 4 , the peaking factor (PF) is positive, which means that its density profile is inwardly peaked, and the PF decreases with the enhancement of impurity FLR effects. These results may provide some theoretical reference on understanding the physical mechanism of impurity transport in the pedestal of H-mode plasmas.

Efficient Solution of Sequences of Parametrized Lyapunov Equations With Applications

ABSTRACTSequences of parametrized Lyapunov equations can be encountered in many application settings. Moreover, solutions of such equations are often intermediate steps of an overall procedure whose main goal is the computation of , where denotes the solution of a Lyapunov equation and is a given matrix. We are interested in addressing problems where the parameter dependency of the coefficient matrix is encoded as a low‐rank modification to a seed, fixed matrix. We propose two novel numerical procedures that fully exploit such a common structure. The first one builds upon the Sherman‐Morrison‐Woodbury (SMW) formula and recycling Krylov techniques, and it is well‐suited for small dimensional problems as it makes use of dense numerical linear algebra tools. The second algorithm can instead address large‐scale problems by relying on state‐of‐the‐art projection techniques based on the extended Krylov subspace. We test the new algorithms on several problems arising in the study of damped vibrational systems and the analyses of output synchronization problems for multi‐agent systems. Our results show that the algorithms we propose are superior to state‐of‐the‐art techniques as they are able to remarkably speed up the computation of accurate solutions.

Finite Control Set Model Predictive Control with Feedback‐Based Flux‐Weakening Operation for PMSM Drives

Finite control set model predictive control (FCS‐MPC) has gained widespread application in permanent magnet synchronous motor (PMSM) drives, especially for the operations below the base speed. In this paper, a novel voltage feedback‐based flux‐weakening control scheme is proposed to enable FCS‐MPC to extend its operation above the base speed. In this method, an extended state observer (ESO)‐based ultra‐local model is employed as the prediction model to reduce parameter dependence. To realize flux‐weakening operation, PMSM's steady‐state voltage drop is estimated using the information from ultra‐local model. And the magnitude of steady‐state voltage drop is then used as the feedback variable to reconstruct a novel voltage control loop. The output of voltage controller automatically modifies the d‐axis current reference when motor operates above the base‐speed. With the help of voltage control loop, a smooth and automatic flux‐weakening operation can be achieved without requiring the motor parameters. The proposed method is verified experimentally under various speed and load conditions. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

BEGAN: Boltzmann-Reweighted Data Augmentation for Enhanced GAN-Based Molecule Design in Insect Pheromone Receptors.

Identifying small molecules that bind strongly to target proteins in rational molecular design is crucial. Machine learning techniques, such as generative adversarial networks (GAN), are now essential tools for generating such molecules. In this study, we present an enhanced method for molecule generation using objective-reinforced GANs. Specifically, we introduce BEGAN (Boltzmann-enhanced GAN), a novel approach that adjusts molecule occurrence frequencies during training based on the Boltzmann distribution exp(-ΔU/τ), where ΔU represents the estimated binding free energy derived from docking algorithms and τ is a temperature-related scaling hyperparameter. This Boltzmann reweighting process shifts the generation process toward molecules with higher binding affinities, allowing the GAN to explore molecular spaces with superior binding properties. The reweighting process can also be refined through multiple iterations without altering the overall distribution shape. To validate our approach, we apply it to the design of sex pheromone analogs targeting Spodoptera frugiperda pheromone receptor SfruOR16, illustrating that the Boltzmann reweighting significantly increases the likelihood of generating promising sex pheromone analogs with improved binding affinities to SfruOR16, further supported by atomistic molecular dynamics simulations. Furthermore, we conduct a comprehensive investigation into parameter dependencies and propose a reasonable range for the hyperparameter τ. Our method offers a promising approach for optimizing molecular generation for enhanced protein binding, potentially increasing the efficiency of molecular discovery pipelines.

Time–frequency representation of adjacent multi-component signals driven by IVKF-MPRTF and its application for mechanical equipment fault diagnosis

Rotating machinery is characterized by time-varying operating conditions and complex structures. The balance of its internal structure gradually changes with the variation of external working conditions. The vibration signals of rolling bearings that are key components exhibit obvious nonstationary characteristics at low speeds and heavy loads. Furthermore, mixed faults and modulation phenomena will generate time-varying multicomponent signals with adjacent fault characteristic frequencies. The existing time–frequency representation (TFR) algorithms for processing nonstationary signals with adjacent frequencies have limitations such as low time–frequency resolution and excessive parameter dependence. Therefore, a novel time–frequency analysis (TFA) framework for adjacent multicomponent signals driven by improved Vold–Kalman filtering-modified parameterized resampling time–frequency (IVKF-MPRTF) transform is presented in this study. First, this article introduces multicomponent signal time–frequency curve extraction to obtain the initial frequency information of the measured vibration signal, which addresses the issue of Vold–Kalman filtration (VKF) relying on a priori frequency information, and thus forms the improved Vold–Kalman filtering (IVKF). Then, the vibration signal can be precisely decomposed into adjacent components by the presented IVKF. Second, this article introduces local maximum frequency allocation operator and synchroextracting operator to compensate for the blur time–frequency resolution by parameterized resampling time–frequency transform, thus forming a modified parameterized resampling time–frequency (MPRTF) transform. By MPRTF, high-resolution TFR of multiple sets of single components can be obtained, and thus an enhanced TFR of nonstationary multicomponent signals is achieved through time–frequency fusion. Finally, the superiority of the adjacent multicomponent signals identification by the proposed IVKF-MPRTF is verified through the experimental signal analysis.

Linear topological invariants for kernels of differential operators by shifted fundamental solutions

We characterize the condition (Ω) for smooth kernels of partial differential operators in terms of the existence of shifted fundamental solutions satisfying certain properties. The conditions (PΩ) and (PΩ¯¯) for distributional kernels are characterized in a similar way. By lifting theorems for Fréchet spaces and (PLS)-spaces, this provides characterizations of the problem of parameter dependence for smooth and distributional solutions of differential equations by shifted fundamental solutions. As an application, we give a new proof of the fact that the space {f∈E(X)|P(D)f=0} satisfies (Ω) for any differential operator P(D) and any open convex set X⊆Rd.

Parametric dependencies of ion temperature profile peaking in ASDEX Upgrade high-beta scenarios

Abstract Advanced Tokamak (AT) scenarios are attractive candidates for future nuclear fusion power plants. These scenarios often feature peaked temperature profiles, suggesting a local reduction of turbulent transport. The mechanisms behind this are, as yet, not fully understood. Parameters that are thought to be connected to these transport reductions include the q-profile and the ExB-shear ωExB. Another parameter considered to be important is the fast ion content, which can reduce transport in multiple different ways.
This work presents AT experiments performed at the ASDEX Upgrade tokamak (AUG) in which these three parameters are varied to investigate their respective effect on the observed peaked ion temperature profiles. To disentangle potentially competing effects, simulations using the codes GENE and TGLF have been performed. It is found that the ExB-shear does not play a role in the AT scenarios performed at AUG, which have relatively low rotation, with vtor=100-250km/h. Experimentally, a significant dependence of R/LTi on the electron cyclotron current drive (ECCD) settings was found, indicating that either the current profile (and, therefore, the q-profile) or Te/Ti has a significant impact on the observed suppression of turbulent transport. In support of the first option, both GENE and TGLF show a q-profile dependence of R/LTi. Furthermore, according to GENE, electromagnetic (EM) fast ion effects are essential in reproducing the experimental results. Scans with TGLF (which does not include such effects), suggest that these fast ion effects become relevant above a threshold of R/LTi= 4-5. In the presence of ICRF, additional electrostatic (ES) fast ion effects seem to come into effect, according to GENE, albeit to a smaller degree than the EM effects.

Is the Real Two-Higgs-Doublet Model Consistent?

We provide strong evidence that the widely studied real two-Higgs-doublet model is inconsistent under renormalization due to quark-induced divergent CP violation (CPV). We identify the necessary ingredients for the CPV to enter the renormalization-group equations based on symmetry proprieties of the divergent diagrams. We demonstrate that while these ingredients are present starting at six loops, the divergent CPV is zero at that order due to approximate symmetries. We show that these symmetries are broken at seven loops and determine the parameter dependence of the resulting divergent CPV.

Modeling of Lithium-Ion Batteries for Electric Transportation: A Comprehensive Review of Electrical Models and Parameter Dependencies

The power and transportation sectors contribute to more than 66% of global carbon emissions. Decarbonizing these sectors is critical for achieving a zero-carbon economy by mid-century and mitigating the most severe impacts of climate change. Battery packs, which enable energy storage in electric vehicles, are a key component of electrified transport systems. The production of these batteries has significantly increased in recent years to meet rising demand, and this trend is expected to continue. However, current traction batteries exhibit lower energy density compared to fossil fuels. As a result, accurate battery models that balance computational complexity and precision are essential for designing high-performance energy storage systems. This paper provides a comprehensive review of the most used electrical models for lithium-ion batteries in traction applications, as reported in the technical literature. By exploring the strengths and limitations of different modeling approaches, this paper aims to offer valuable insights into their practical applicability for the electrification of transportation systems. Additionally, this paper discusses the primary methods employed to derive the values of the electrical components within these models. Finally, it examines the key parameters—such as temperature, state of charge, and aging—that significantly influence the component values. Ultimately, it guides researchers and practitioners in selecting the most suitable modeling approach for their specific needs.

Mechanism of generating collisionless shock in magnetized gas plasma driven by laser-ablated target plasma

The mechanism of generating collisionless shock in magnetized gas plasma driven by laser-ablated target plasma is investigated by using one-dimensional full particle-in-cell simulation. The effect of finite injection time of target plasma, mimicking the finite width of laser pulse, is taken into account. It was found that the formation of a seed-shock requires a precursor. The precursor is driven by gyrating ions, and its origin varies depending on the injection time of the target plasma. When the injection time is short, the target plasma entering the gas plasma creates a precursor; otherwise, gas ions reflected by the strong piston effect of the target plasma create a precursor. The precursor compresses the background gas plasma, and subsequently, a compressed seed-shock forms in the gas plasma. The parameter dependence on the formation process and propagation characteristics of the seed-shock was discussed. It was confirmed that the seed-shock propagates through the gas plasma exhibiting behavior similar to the shock front of supercritical shocks.