Notes

Belowground feedbacks because owners associated with spatial self-organization and also neighborhood construction.
Optical coherence tomography angiography (OCTA) images suffer from inevitable micromotion (breathing, heartbeat, and blinking) noise. These image artifacts can severely disturb the visibility of results and reduce accuracy of vessel morphological and functional metrics quantization. Herein, we propose a multiple wavelet-FFT algorithm (MW-FFTA) comprising multiple integrated processes combined with wavelet-FFT and minimum reconstruction that can be used to effectively attenuate motion artifacts and significantly improve the precision of quantitative information. We verified the fidelity of image information and reliability of MW-FFTA by the image quality evaluation. The efficiency and robustness of MW-FFTA was validated by the vessel parameters on multi-scene in vivo OCTA imaging. Compared with previous algorithms, our method provides better visual and quantitative results. Therefore, the MW-FFTA possesses the potential capacity to improve the diagnosis of clinical diseases with OCTA.We discover the quantum analog of the well-known classical maximum power transfer theorem. Our theoretical framework considers the continuous steady-state problem of coherent energy transfer through an N-node bosonic network coupled to an external dissipative load. We present an exact solution for optimal power transfer in the form of the maximum power transfer theorem known in the design of electrical circuits. Furthermore, we introduce the concept of quantum impedance matching with Thevenin equivalent networks, which are shown to be exact analogs to their classical counterparts. Our results are applicable to both ordered and disordered quantum networks with graph-like structures ranging from nearest-neighbor to all-to-all connectivities. This work points towards universal design principles adapting ideas from the classical regime to the quantum domain for various quantum optical applications in energy-harvesting, wireless power transfer, and energy transduction.We propose a weakly guiding graded-index ring-core fiber (RCF) with trench-assisted structure. The simulation analysis indicates that such a special fiber design is able to support 8 orbital angular momentum (OAM) mode groups (MGs) with low inter-group crosstalk ( less then -25 dB/km) and low intra-group differential mode delay (DMD) ( less then 125 ps/km) for higher order OAM MGs with topological charge |l| = 4, 5, 6, 7. The designed RCF also shows favorable tolerance characteristics to ellipticity and bending. Moreover, stable and distinguished broadband performance of proposed RCF is verified over the whole C band ranging from 1530 nm to 1565 nm. This kind of fiber design could be employed in small-scale multiple-input multiple-output digital signal processing (MIMO-DSP) intra-group modes multiplexing transmission combined with MIMO-free inter-group mode multiplexing transmission. The simulated results of the designed RCF show its great potential of the 16-channel long-distance mode division multiplexing (MDM) transmission with low MIMO-DSP complexity.We propose to use a calibration target with a narrow spectral color range for the background (e.g., from blue) and broader spectral color range for the feature points (e.g., blue + red circles), and fringe patterns matching the background color for accurate phase extraction. Since the captured fringe patterns are not affected by the high contrast of the calibration target, phase information can be accurately extracted without edging artifacts. Those feature points can be clearly "seen" by the camera if the ambient light matches the feature color or without the background color. We extract each calibration pose for three-dimensional coordinate determination for each pixel, and then establish pixel-wise relationship between each coordinate and phase. Comparing with our previously published method, this method significantly fundamentally simplifies and improves the algorithm by eliminating the computational framework estimate smooth phase near high-contrast feature edges. Experimental results demonstrated the success of our proposed calibration method.Neutron irradiation induced degradation of porous silica film is studied by Molecular Dynamics and Density-Functional theory-based methods. The degradation of microscopic structure, thermal property, and optical property of porous silica film are systematically investigated. Low-energy recoil is used to simulate the neutron irradiation effect. The pair and bond angle distributions, and coordination number distributions reveal that, under neutron irradiation, the microscopic structure of porous silica film is obviously modified, and the coordination defects are induced. We find that the higher recoil energy, the more coordination defects are formed in the film. The increased defects lead to a decrease in thermal conductivity. In addition, neutron irradiation induces additional optical absorption peaks in UV region and increasement in refractive index, resulting in a noticeable reduction in light transmittance. The detailed calculation of density of states reveals that these optical absorption peaks originate from the irradiation induced defect states in band gap. Our work shows that low-energy neutron irradiation can induce obvious defect density and degrade thermal and optical properties of porous silica film, which are responsible for subsequent laser-induced damage.The beam spatial intensity distribution is critical to laser applications both in the scientific and the industrial fields. Here, a method for beam spatial intensity modification based on stimulated Brillouin amplification (SBA) is proposed, which provides an alternative approach of laser beam shaping accompanied by efficient energy amplification. Three beam shaping schemes based on SBA has been demonstrated and evaluated in theoretical simulation and experiments with pulsed laser. The results indicate that the spatial distribution can be modified by manipulation of the beam polarization and the intensity. Finally, the shaped Stokes beam has been modified into the flat-top distribution with the output pulse energy increasing to 4.43 times of the input energy, proving the feasibility of SBA spatial shaping method.Since inverse design is an ill-conditioned problem of mapping from low dimensions to high dimensions, inverse design is challenging, especially for design problems with many degrees of freedom (DOFs). Traditional deep learning methods and optimization methods cannot readily calculate the inverse design of meta-atoms with high DOFs. In this paper, a new method combining deep learning and genetic algorithm (GA) methods is proposed to realize the inverse design of meta-atoms with high DOFs. In this method, a predicting neural network (PNN) and a variational autoencoder (VAE) generation model are constructed and trained. The generative model is used to constrain and compress the large design space, so that the GA can jump out of the local optimal solution and find the global optimal solution. The predicting model is used to quickly evaluate the fitness value of each offspring in the GA. With the assistance of these two machine learning models, the GA can find the optimal design of meta-atoms. This approach can realize, on demand, inverse design of meta-atoms, and opens the way for the optimization of procedures in other fields.The polarization based phase shifting method is an effective way for dynamic measurements. However, when this technique is applied to the measurements of large optics, the interferometric results are easily limited by the birefringence of large optics. The birefringence changes the polarization states of reference light and test light, and brings constant polarization aberrations into the measurement results independent of the phase shifting procedure. In this article, the detailed theoretical analysis on the mechanism of polarization aberration is presented. Afterwards, we propose a new interferometric method to determine the birefringence effects by measuring the transmitted wavefronts of the large optics, which are considered as birefringent samples. Theoretical analysis shows that the polarization error in the linearly polarized system can be corrected by two independent measurements with orthogonal polarization states. The phase retardance can be obtained from the wavefront difference of the transmitted wavefronts when switching the polarization states of the incident lights. The birefringence distribution obtained is used to calibrate the polarization aberrations in the measurement result of a homemade large aperture measurement platform and the correction result is compared with the result via the wavelength tuning phase shifting method. The elimination of the polarization aberrations can be observed in the final results.Graphene is a two-dimensional material with unique physical and chemical properties, whose excellent biocompatibility has also attracted widespread attention in the field of biosensing and medical detection. Graphene provides a novel solution for dramatically improving the sensitivity of terahertz metasurface sensors, since the electrical conductivity can be modified by contact with biomolecules. In this paper, a metal-graphene hybrid metasurface is proposed and demonstrated for high-sensitive nortriptyline sensing based on the plasmon-induced transparency (PIT) resonances. The π-π stacks between nortriptyline and graphene lead to an increase in the Fermi level of graphene and a decrease in the conductivity, thus enhancing the PIT resonance. Experimental results show that the peak-to-peak amplitude magnitude of the PIT window is enhanced up to 3.4-fold with 1 ng nortriptyline analyte, and the minimum detection limit is extended down to 0.1 ng. But no significant change is observed from the samples without graphene as a comparative experiment, which demonstrates that the presence of graphene greatly enhances the bonding to the drug molecules and improves the sensing sensitivity. This metasurface sensor has the advantages of high sensitivity, fast detection speed, label-free and steady properties, which has potential applications in the fields of trace molecular sensing and disease diagnosis.Vernier-effect has been widely employed in interferometer-based optical fiber sensors to improve the sensitivities greatly. However, the influence of the Vernier-effect on detection limit (DL) that is more important for evaluating the actual performance of the sensor has not been discussed. Two gas pressure fiber sensors (a typical Fabry-Perot interferometer-based sensor and a Vernier sensor) are used to compare the DL of them by experiments. Both the theoretical analysis and the experimental results show that, though the Vernier-effect magnifies the spectrum shift sensitivity, it also magnifies the value of the smallest detectable wavelength shift. As a result, the actual DL of the sensor is not improved by employing the Vernier-effect. If the contrast ratio of the Vernier envelope is not optimized enough for most of the reported sensors, the DL can even degenerate greatly.In a traveling-wave resonant tunneling diode oscillator, the gain medium is encapsulated in a metallic waveguide. The geometrical parameters of the system and the skin penetration depth in the metal layers are of similar length scales. It confirms the need for a full-wave simulation, where the impedance boundary conditions can not be applied in a straightforward manner. In this work, a method of moments-based electromagnetic wave solver was developed and used to illustrate different traveling-wave RTD oscillator structures.
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