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Evaluation of methods for gravity wave extraction from middle-atmospheric lidar temperature measurements
摘要： This study evaluates commonly used methods of extracting gravity-wave-induced temperature perturbations from lidar measurements. The spectral response of these methods is characterized with the help of a synthetic data set with known temperature perturbations added to a realistic background temperature profile. The simulations are carried out with the background temperature being either constant or varying in time to evaluate the sensitivity to temperature perturbations not caused by gravity waves. The different methods are applied to lidar measurements over New Zealand, and the performance of the algorithms is evaluated. We find that the Butterworth filter performs best if gravity waves over a wide range of periods are to be extracted from lidar temperature measurements. The running mean method gives good results if only gravity waves with short periods are to be analyzed.
关键词： running mean,sliding polynomial fit,lidar,extraction methods,temperature perturbations,spectral response,gravity waves,Butterworth filter
更新于2025-09-23 15:23:52
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New Interior Transmission Problem Applied to a Single Floquet-Bloch Mode Imaging of Local Perturbations in Periodic Media
摘要： This paper considers the imaging of local perturbations of an infinite penetrable periodic layer. A cell of this periodic layer consists of several bounded inhomogeneities situated in a known homogeneous media. We use a differential linear sampling method to reconstruct the support of perturbations without using the Green’s function of the periodic layer nor reconstruct the periodic background inhomogeneities. The justification of this imaging method relies on the well-posedeness of a nonstandard interior transmission problem, which until now was an open problem except for the special case when the local perturbation did not intersect the background inhomogeneities. The analysis of this new interior transmission problem is the main focus of this paper. We then complete the justification of our inversion method and present some numerical examples that confirm the theoretical behavior of the differential indicator function determining the reconstructable regions in the periodic layer.
关键词： Local Perturbations,Imaging,Floquet-Bloch Mode,Inverse Problems,Interior Transmission Problem,Periodic Media
更新于2025-09-23 15:21:01
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Human sensitivity to perturbations constrained by a model of the natural image manifold
摘要： Humans are remarkably well tuned to the statistical properties of natural images. However, quantitative characterization of processing within the domain of natural images has been difficult because most parametric manipulations of a natural image make that image appear less natural. We used generative adversarial networks (GANs) to constrain parametric manipulations to remain within an approximation of the manifold of natural images. In the first experiment, seven observers decided which one of two synthetic perturbed images matched a synthetic unperturbed comparison image. Observers were significantly more sensitive to perturbations that were constrained to an approximate manifold of natural images than they were to perturbations applied directly in pixel space. Trial-by-trial errors were consistent with the idea that these perturbations disrupt configural aspects of visual structure used in image segmentation. In a second experiment, five observers discriminated paths along the image manifold as recovered by the GAN. Observers were remarkably good at this task, confirming that observers are tuned to fairly detailed properties of an approximate manifold of natural images. We conclude that human tuning to natural images is more general than detecting deviations from natural appearance, and that humans have, to some extent, access to detailed interrelations between natural images.
关键词： natural images,image recognition,noise perturbations,artificial neural networks,generative adversarial nets
更新于2025-09-23 15:21:01
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Side chain torsion dictates planarity and ionizability of Green fluorescent protein’s chromophore leading to spectral perturbations.
摘要： Spectral characteristics of Fluorescent Proteins (FP) are well studied and through protein engineering, several FP variants constituting entire visible spectrum have been created. One of the most common mechanisms attributed to spectral shifts in FP are excited state proton transfer (ESPT), hydroxyl moiety protonation and deprotonation, along with chromophore Cis-Trans isomerism. Most widely studied FPs are those derived from avGFP (Aequorea victoria GFP) and Dsred (Discosoma coral). Apart from the above mechanism, certain interacting residues are said to play a vital role in altering the proton transfer pathway shift. The torsional changes of wild avGFP, S65T avGFP, and Dsred has been studied to van der Waals packing in Dsred is more compact than that of avGFP, thus creating a low solvent occupiable environment and reduced solvent interactions having higher red spectral hypothesize the torsional landscape and altered residual interactions are prominent factors for the spectral shifts. Through our 200 ns molecular dynamics investigation we prospect that leading to numerous spectral variants. Similarly, the hydrogen-bonded networks solely cannot dictate the energy landscape of FPs. Non-bonded interactions also can create secondary harmonic shifts by dipole-dipole inductions. Side chain contacts tend to alter the topological and torsional geometry, thereby disturbing the chromophore’s planarity. Side chain torsional variations have almost been unaccounted for their distortions in FP’s. We comprehend the inter-residual contact distance and the geometrical descriptors.
关键词： Green fluorescent protein,spectral perturbations,Sidechain torsional variations,Residual accessible area,Chromophore planarity
更新于2025-09-23 15:21:01
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[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Active Modulation of EIT-like Response with a Metal-graphene Hybrid Metasurface in Microwave Regime
摘要： Bipedal locomotion is a popular area of study across multiple fields (e.g., biomechanics, neuroscience, and robotics). Different hypotheses and models have tried explaining how humans achieve stable locomotion. Perturbations that produce shifts in the nominal periodic orbit of the joint kinematics during locomotion could inform about the manner in which the human neuromechanics represent the phase of gait. Ideally, this type of perturbation would modify the progression of the human subject through the gait cycle without deviating from the nominal kinematic orbits of the leg joints. However, there is a lack of publicly available experimental data with this type of perturbation. This paper presents the design and validation of a perturbation mechanism and an experimental protocol capable of producing phase-shifting perturbations of the gait cycle. The effects of this type of perturbation on the gait cycle are statistically quantified and analyzed in order to show that a clean phase shift in the gait cycle was achieved. The data collected during these experiments will be publicly available for the scientific community to test different hypotheses and models of human locomotion.
关键词： phase-dependent behavior,perturbations,Gait analysis,locomotion control
更新于2025-09-23 15:19:57
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Optical Pooled Screens in Human Cells
摘要： A screening approach that combines high-content imaging with in situ sequencing can identify genes that affect spatially and temporally defined phenotypes like morphology and subcellular localization, expanding the list of scientific questions that can be asked with genetic tools.
关键词： genetic perturbations,in situ sequencing,high-content imaging,optical pooled screens,cellular phenotypes
更新于2025-09-19 17:13:59
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Asymptotics of Eigenvalues in Spectral Gaps of Periodic Waveguides with Small Singular Perturbations
摘要： The asymptotics of eigenvalues appearing near the lower edge of a spectral gap of the Dirichlet problem is studied for the Laplace operator in a d-dimensional periodic waveguide with a singular perturbation of the boundary by creating a hole with a small diameter ε. Several versions of the structure of the gap edge are considered. As usual, the asymptotic formulas are di?erent in the cases d ≥ 3 and d = 2, where the eigenvalues occur at distances O(ε2(d?2)) or O(ε2d) and O(| ln ε|?2) or O(ε4), respectively, from the gap edge. Other types of singular perturbation of the waveguide surface and other types of boundary conditions are discussed, which provide the appearance of eigenvalues near both edges of one or several gaps. Bibliography: 51 titles.
关键词： eigenvalues,spectral gaps,periodic waveguides,asymptotics,singular perturbations
更新于2025-09-16 10:30:52
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Relativistic Evaluation Models of Laser Time Transfer between Satellites Resulting from Orbit Perturbations and Attitude Jitters
摘要： The realization of picosecond level laser time transfer between satellites plays a key role in microgravity scientific missions, such as gravitational wave detection, next generation GNSS (Global Navigation Satellite System), deep space exploration, testing general relativity and searching for dark matter. In picosecond or higher level, a deep insight of relativistic error of laser time transfer between satellites induced by orbit perturbations and attitude jitters is urgently needed, which contributes to the compensation of relativistic error. Firstly, this paper points out the problem of orbit perturbations and attitude jitters. Then, the relativistic evaluation models of one-way laser time transfer and two-way laser time transfer resulting from orbit perturbations and attitude jitters are investigated. The relativistic evaluation models are proposed with incorporation of attitude dynamics and orbit dynamics of satellites, as well as relativistic models of one-way laser time transfer and two-way laser time transfer. Simulation studies are carried out to analyze the effect of orbit perturbations and attitude jitters on the relativistic error. Simulation results show that the relativistic error induced by orbit perturbations increases with time and the relativistic error induced by attitude jitters displays periodic variation. Furthermore, the relativistic error of two-way laser time transfer is less than one-way laser time transfer.
关键词： Laser time transfer,Relativistic evaluation models,Gravitational wave detection,Orbit perturbations,Attitude jitters
更新于2025-09-16 10:30:52
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Spurious harmonic suppression in compact coupled-line bandpass filter with asymmetric perturbations
摘要： Present article exhibits the design of a third-order compact parallel-coupled line bandpass filter at 5.25 GHz having asymmetric perturbations to suppress the second harmonic. Initially, the effects of compactness on filter characteristics have been studied by synthesising the distributed filter network into its equivalent circuit model. The design has been initiated by computing the unit cell model, which leads to the first-order and third-order design instances with an improvement in compactness over the traditional parallel-coupled line filter. In contrary, compactness in the filter characteristics degrades the second harmonic level subject to enhanced imbalances among the odd- and even-mode velocities at the coupled lines. Subsequently, the improvement in the harmonic suppression of 53 dB and 58 dB has been achieved by incorporating different non-uniform perturbations to the outer and coupled edges of the compact filters. Accordingly, compactness of 58% and 71% have been obtained subject to the folded and in-line designs over the conventional layout.
关键词： harmonic suppression,compactness,Bandpass filter,parallel-coupled lines,perturbations
更新于2025-09-16 10:30:52
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Waveguide dispersion curves identification at low-frequency using two actuators and phase perturbations
摘要： Dispersion curves of fluid-filled elastic-tubes are used for non-destructive measurement of material acoustic properties. The underlying physics leads to a singular numerical procedure when several modes or long-wavelength scenarios take part in the tube dynamics. The literature describes several methods to identify dispersion curves that require a large ratio of samples per length. Described is a method to enrich the amount of available information of an otherwise ill-posed problem, by multiple boundary phase perturbations at each excitation frequency. The method uses two actuators, one at either end of the waveguide to produce different relative phases, followed by a nonlinear model fitting procedure. Presented are a model-based derivation and experimental verification of the proposed approach on an air-filled elastic-tube. The latter shows the capability of the method to recover the dispersion curves even for very weak structural-acoustic coupling and at low frequencies. The portrayed scheme can be applied on various waveguides by using two actuators and only a single sensor, and hence makes dispersion curve estimation realistic in formerly inaccessible cases.
关键词： non-destructive measurement,phase perturbations,nonlinear model fitting,dispersion curves,acoustic properties,fluid-filled elastic-tubes
更新于2025-09-11 14:15:04