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Contour interaction under photopic and scotopic conditions
摘要： In the present study, we asked whether contour interaction undergoes significant changes for different luminance levels in the central and peripheral visual field. This study included nine normal observers at two laboratories (five at Palacky University Olomouc, Czech Republic and four at the University of Houston, USA). Observers viewed a randomly selected Sloan letter surrounded by four equally spaced bars for several separations measured edge-to-edge in min arc. Stimuli were viewed foveally under photopic and mesopic luminances and between 5° and 12° peripherally for four different background luminances of the display monitors, corresponding to photopic, mesopic, scotopic, and dim scotopic levels. The extent of the contour interaction in the fovea is approximately 20 times smaller than in the periphery. Whereas the magnitude of foveal contour interaction markedly decreases with decreasing luminance, no consistent luminance-induced change occurs in peripheral contour interaction. The extent of contour interaction does not scale with the size of the target letter, either in the fovea or peripherally. The results support a neural origin of contour interaction consistent with the properties of center-surround antagonism.
关键词： contour interaction,photopic,crowding effect,mesopic,scotopic,luminance,peripheral vision
更新于2025-09-23 15:22:29
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Four-Wave Mixing in Metamaterials
摘要： Interaction of four counterpropagating waves in a cubic medium being “left” for the signal wave is considered in the constant-intensity approximation. Analytical expression for the signal wave intensity is derived for the general case of four-wave interaction in a metamaterial. The influence of different parameters on the signal wave amplification coefficient, efficiency of conversion into the signal wave, and the reflection coefficient of the mirror whose role is played by the metamaterial is analyzed. It has been obtained for the first time that the determining role in the backward signal wave amplification is played by the total length of the metamaterial and the intensities of all three forward waves. An analysis has shown that the optimal thickness of the metamaterial depends not only on the phase mismatch and the strong coherent pump field intensity, as in the constant-field approximation, but also on the intensity of the weak wave at the frequency ω2. It has been demonstrated for the first time that the efficiency of frequency conversion in metamaterials depends on the total metamaterial length, input intensities of all four interacting waves, phase mismatch, and losses in the medium. It is established that the maxima of the reflection coefficient of the metamaterial depend on the total metamaterial length and the intensities of all three forward waves.
关键词： metamaterial,negative refraction,four-wave interaction,constant-intensity approximation
更新于2025-09-23 15:22:29
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Skin Friction Measurements Using Oil Film Interferometry in a 3-D Supersonic Flowfield
摘要： The application of oil film interferometry (OFI) for the measurement of global skin friction on the surface beneath a complex three-dimensional supersonic flow is explored in this study. The flowfield is produced by a fin-generated oblique shock interacting with a compressible turbulent boundary layer. Measurements were obtained by modifying a comprehensive acquisition and processing software, previously developed for two-dimensional, low-speed flows, to measure skin friction distributions underneath such flows. This approach required the local flow direction on the surface, and therefore traditional oil flow visualization was coupled with OFI measurements. A cross-correlation-based algorithm was incorporated to extract flow direction from sequences of oil flow visualization images. Photogrammetry was used with both surface oil flow and OFI to ensure proper spatial overlap for the two measurements. Results from this study demonstrate the capability of the approach in a complex, supersonic flow field that contains regions of both separation and reattachment concomitant with a wide range of skin friction values. The skin friction results show excellent homogeneity, standard deviation of 5.1% of the mean, in the undisturbed boundary layer upstream of the interaction and capture well-resolved high shear gradients in the interaction region. A comparison to legacy data from a similar interaction shows matching trends within the developed flow.
关键词： three-dimensional flow,shock boundary-layer interaction,supersonic flow,oil film interferometry,skin friction
更新于2025-09-23 15:22:29
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Spin-orbit interaction of Tm3+ - ground level and crystal field strength
摘要： The ground level 3H6 of Tm3+ ions in a number of crystals has been examined through the matrix elements of spin – orbit interaction. The latter have been determined comparable with the separation between 3H6 and the first excited level 3F4. The normalized ratios of spin – orbit interactions relative to the free ion value of Tm IV as a function of the scalar crystal field parameter Nv have been found to vary analogous to the nephelauxetic effect. The relationships between maximum splitting of 3H6, spin-orbit coupling constant, crystal-field parameters and the Nv have been also studied for the presented 42 stoichiometric or doped crystals containing Tm3+. The compounds include halogenides, organic complexes, oxides, oxohalides, and semiconductors.
关键词： Thulium (3+),Crystal field strength,Spin-orbit interaction,Ground level
更新于2025-09-23 15:22:29
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Hand Gesture Recognition in Automotive Human–Machine Interaction Using Depth Cameras
摘要： In this review, we describe current Machine Learning approaches to hand gesture recognition with depth data from time-of-flight sensors. In particular, we summarise the achievements on a line of research at the Computational Neuroscience laboratory at the Ruhr West University of Applied Sciences. Relating our results to the work of others in this field, we confirm that Convolutional Neural Networks and Long Short-Term Memory yield most reliable results. We investigated several sensor data fusion techniques in a deep learning framework and performed user studies to evaluate our system in practice. During our course of research, we gathered and published our data in a novel benchmark dataset (REHAP), containing over a million unique three-dimensional hand posture samples.
关键词： time-of-flight sensors,hand gesture recognition,automotive,human–machine interaction,neural networks
更新于2025-09-23 15:22:29
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Nonlinear Analytic Solution of Eulerian Beam-Wave Interaction Theory Considering Harmonic Interaction of Traveling-Wave Tube Amplifiers
摘要： In this paper, a novel Eulerian nonlinear beam-wave interaction (BWI) theory considering harmonic interaction of a helix traveling-wave tube (TWT) is developed. Derived from this Eulerian model, the novel Eulerian nonlinear analytic solutions (the fourth-order analytic solution of fundamental and the second-order analytic solution of harmonic) are first obtained by the method of successive approximation. The analytic relationships between electric fields of fundamental/harmonic frequencies and electron phases are also found. Then, the Eulerian nonlinear analytic solutions and Eulerian nonlinear BWI theory are compared to a Lagrangian theory. C-band and Ku-band helix TWTs based on a single pitch section are included in the simulation. It is found that the Eulerian nonlinear analytic solutions and Eulerian nonlinear BWI theory agree well with the Lagrangian theory at 1-dB gain compression point. Interestingly, the saturation effects caused by electron overtaking cannot be found by the traditional Eulerian analysis but can be described by the Eulerian nonlinear analytic solutions and Eulerian nonlinear BWI theory. Moreover, Eulerian nonlinear analytic solutions are simpler and more accurately than existing approaches and, thus, allow analytical progress. This paper confirms that the Eulerian nonlinear analytic solutions can outperform the previous proposals.
关键词： analysis,nonlinear,traveling-wave tubes (TWTs),Eulerian,Analytic solution,beam-wave interaction (BWI),harmonic
更新于2025-09-23 15:22:29
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<i>N</i> -soliton solutions for the nonlocal two-wave interaction system via the Riemann–Hilbert method
摘要： In this paper, a nonlocal two-wave interaction system from the Manakov hierarchy is investigated via the Riemann–Hilbert approach. Based on the spectral analysis of the Lax pair, a Riemann–Hilbert problem for the nonlocal two-wave interaction system is constructed. By discussing the solutions of this Riemann–Hilbert problem in both the regular and non-regular cases, we explicitly present the N-soliton solution formula of the nonlocal two-wave interaction system. Moreover, the dynamical behaviour of the single-soliton solution is shown graphically.
关键词： N-soliton solutions,Riemann–Hilbert problem,nonlocal two-wave interaction system
更新于2025-09-23 15:22:29
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Influence of the capping layer material on the interfacial Dzyaloshinskii-Moriya interaction in Pt/Co/capping layer structures probed by Brillouin light scattering<sup></sup>
摘要： Influence of the capping layer material on the interfacial Dzyaloshinskii-Moriya interaction in Pt/Co/capping layer structures probed by Brillouin light scattering. Co ultrathin films, of various thicknesses (0.8 nm ≤ tCo ≤ 2.5 nm), have been grown by sputtering on Si substrates, using Pt buffer layers and different capping layers (Cu, Ir, MgO and Pt). The x-ray diffraction revealed that our films have a (111) out-of-plane texture with various degrees of strains. Their magnetic properties have been studied by vibrating sample magnetometry (VSM) and Brillouin light scattering (BLS) in the Damon-Eshbach geometry. VSM characterizations revealed that films with Co thickness below (above) the spin reorientation transition thickness, which is capping layer dependent, are perpendicularly (in-plane) magnetized, suggesting the existence of an interface anisotropy. The magnetic dead layer has been taken into account to precisely determine the surface anisotropy constant was found to be 1.42 ± 0.02 erg/cm2 and of 1.33 ± 0.02 erg/cm2 for the Pt/Co/Cu and Pt/Co/Ir samples, respectively, suggesting that it is due to the Pt/Co interface and that the top Co/Cu or Co/Ir interfaces have a negligible contribution. A lower value of 1.07 ± 0.02 erg/cm2 has been obtained for Pt/Co/MgO most probably due to over-oxidation of Co at the Co/MgO interface. The BLS measurements revealed a pronounced nonreciprocal spin waves propagation, due to the interfacial Dzyaloshinskii-Moriya interaction (iDMI) induced by Pt interface with Co, which increases with decreasing Co thickness. The surface iDMI constant Ds estimated at -0.8 pJ/m, -1.05 pJ/m and –0.95 pJ/m, respectively for Pt/Co/Ir, Pt/Co/Cu and Pt/Co/MgO for the samples where a linear thickness dependence of the effective iDMI constant has been observed.
关键词： Dzyaloshinskii-Moriya interaction,Brillouin light scattering,spin waves and Perpendicular magnetic anisotropy,Interface effects
更新于2025-09-23 15:22:29
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Towards a physical model for energy deposition via cosmic rays into sub-K bolometric detectors
摘要： Cosmology space missions have been known to be particularly sensitive to systematic effects arising from the interaction between cosmic rays and highly sensitive detectors below 200 mK. To remove this signal, one must first understand the deposition and dissipation of energy into these detectors. Using a well-known NTD germanium composite bolometer, we simulate the effect of cosmic rays using a radioactive source in the laboratory. Through analysis of experimental data, we find that the glitch signal shape is a function of incoming particle position, as well as the incoming particle energy. We report also on nonlinear effects in the fit, in order to lay the groundwork towards a new physical model for this energy propagation in the bolometer.
关键词： Interaction of radiation with matter,Cryogenic detectors,Systematic effects,Space instrumentation
更新于2025-09-23 15:22:29
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Quantum-dot circuit-QED thermoelectric diodes and transistors
摘要： Recent breakthroughs in quantum-dot circuit-quantum-electrodynamics systems are promising both from fundamental perspectives and from the point of view of quantum photonic devices. However, understanding such setups as potential thermoelectric devices has been missing. In this paper, via the Keldysh nonequilibrium Green’s function approach, we show that cavity-coupled double quantum-dots can serve as excellent quantum thermoelectric diodes and transistors. Using an enhanced perturbation approach based on the exact polaron transformation, we find dependencies of thermoelectric transport properties on the electron-photon interaction beyond the predictions from the conventional second-order perturbation theory. In particular, strong light-matter interaction leads to pronounced rectification effects for both charge and heat, as well as thermal transistor effects in the linear transport regime, which opens up a cutting-edge frontier for quantum thermoelectric devices.
关键词： rectification,light-matter interaction,circuit-QED,diode,transistor,thermoelectric,thermal transistor,quantum-dot
更新于2025-09-23 15:22:29