An Unsupervised Port Detection Method in Polarimetric SAR Images Based on Three-Component Decomposition and Multi-Scale Thresholding Segmentation

It is difficult to detect ports in polarimetric SAR images due to the complicated components, morphology, and coastal environment. This paper proposes an unsupervised port detection method by extracting the water of the port based on three-component decomposition and multi-scale thresholding segmentation. Firstly, the polarimetric characteristics of the port water are analyzed using modified three-component decomposition. Secondly, the volume scattering power and the power ratio of the double-bounce scattering power to the volume scattering power (PRDV) are used to extract the port water. Water and land are first separated by a global thresholding segmentation of the volume scattering power, in which the sampling region used for the threshold calculation is automatically selected by a proposed homogeneity measure. The interference water regions in the ports are then separated from the water by segmenting the PRDV using the multi-scale thresholding segmentation method. The regions of interest (ROIs) of the ports are then extracted by determining the connected interference water regions with a large area. Finally, ports are recognized by examining the area ratio of strong scattering pixels to the land in the extracted ROIs. Seven single quad-polarization SAR images acquired by RADARSAT-2 covering the coasts of Dalian, Zhanjiang, Fujian, Tianjin, Lingshui, and Boao in China and Berkeley in America are used to test the proposed method. The experimental results show that all ports are correctly and quickly detected. The false alarm rates are zero, the intersection of union section (IoU) indexes between the detected port and the ground truth can reach 75%, and the average processing time can be less than 100 s.

Derivation of the set of the fundamental interactions from first principles

Global conservation laws require the fundamental interactions to be processes which transfer information from one particle to another. Therefore, in order to show what types of interactions may exist, we derive from the very first principles a set of the most fundamental information transfers and their basic properties. Within these information transfers, we identify candidates for gravitational, electromagnetic and strong scattering, and also for weak decay. We do it by taking the characteristic properties of each fundamental interaction, such as confinement or parity violation, and by using them to rule out information transfers without these properties. The found mapping then makes possible to study the information transfers in order to get knowledge about the corresponding fundamental interactions.

First Space-VLBI Observations of Sagittarius A*

We report results from the first Earth-space VLBI observations of the Galactic Center supermassive black hole, Sgr A*. These observations used the space telescope Spektr-R of the RadioAstron project together with a global network of 20 ground telescopes, observing at a wavelength of 1.35 cm. Spektr-R provided baselines up to 3.9 times the diameter of the Earth, corresponding to an angular resolution of approximately 55 μas and a spatial resolution of 5.5R Sch at the source, where R Sch ≡ 2GM/c 2 is the Schwarzschild radius of Sgr A*. Our short ground baseline measurements ( ≲ 80 Mλ) are consistent with an anisotropic Gaussian image, while our intermediate ground baseline measurements (100–250 Mλ) confirm the presence of persistent image substructure in Sgr A*. Both features are consistent with theoretical expectations for strong scattering in the ionized interstellar medium, which produces Gaussian scatter-broadening on short baselines and refractive substructure on long baselines. We do not detect interferometric fringes on any of the longer ground baselines or on any ground–space baselines. While space-VLBI offers a promising pathway to sharper angular resolution and the measurement of key gravitational signatures in black holes, such as their photon rings, our results demonstrate that space-VLBI studies of Sgr A* will require sensitive observations at submillimeter wavelengths.

Seismic Response of 2D Topographic Profiles for Incident SH Waves: Iterative Solution and Comparison of Direct and Indirect BEM

ABSTRACT The scattering and diffraction of waves by irregular surface profiles is of interest in seismology and in many other areas. Diverse techniques have been proposed to quantitatively study the problem. Among them, domain approaches such as finite differences, spectral elements and finite elements have been used. Because the reduction of dimensionality boundary formulations is widely used. Recently, the direct boundary-element method has been applied using some series approximations for surface scattering, including the preconditioned splitting series, for the numerical description of rough surface scattering. Extending further and simplifying this approach, we use the indirect boundary-element method. The ensuing Fredholm integral equation of the second kind that arises in IBEM leads to a very efficient iterative scheme based on the classical Jacobi method. A discussion of direct and indirect approaches is presented. Assuming incident SH waves, results are obtained with the various approaches and compared among them for both a canyon and a hill, both of semicircular shape. Besides, an example is presented of a surface profile that produces strong scattering. This was inspired by the diverse problems that arise in the emerging field of metamaterials.

Phonons, electrons and thermal transport in Planckian high Tc materials

The room-temperature thermal diffusivity of high Tc materials is dominated by phonons. This allows the scattering of phonons by electrons to be discerned. We argue that the measured strength of this scattering suggests a converse Planckian scattering of electrons by phonons across the room-temperature phase diagram of these materials. Consistent with this conclusion, the temperature derivative of the resistivity of strongly overdoped cuprates is noted to show a kink at a little below 200 K that we argue should be understood as the onset of a high-temperature Planckian T-linear scattering of electrons by classical phonons. This kink continuously disappears toward optimal doping, even while strong scattering of phonons by electrons remains visible in the thermal diffusivity, sharpening the long-standing puzzle of the lack of a feature in the T-linear resistivity at optimal doping associated with the onset of phonon scattering.

Detection of Scratch on Transparent Plate with Strong Scattering Noise by Digital Holographic Technique

We applied a digital holographic detection technique to detect the scratches on glass surfaces with scattering noise. In the experiment, scratches with widths of 1.67 µm were generated on the front sides of the glass slides, and three different gray levels were painted on the back sides of the glass slides to generate the scattering noise. It demonstrated that the digital holographic detection method can enhance the image contrast of the scratch under high scattering noise. The high defocus tolerance promises a detection process without optical focusing and thus benefits the high-speed automatic optical inspection.

Modeling with Multiple Correlated Spectral Data Based on Approximating the Nonlinear Spectrum Induced by Scattering

In the spectral quantitative analysis of scattering solution, the improvement of accuracy is seriously restricted by the nonlinearity caused by scattering, and even the measurement will fail due to the influence of scattering. The important reasons are that the modeling variables are greatly affected by nonlinearity, and the information contained in the modeling data cannot represent the scattering characteristics. In this paper, a method is proposed, in which the spectral data of several optical pathlengths with equal space are combined as the modeling data set of a sample. These highly correlated spectral data contain relatively nonlinear information. The addition of the spectral data provides more options for the selection of principal components in modeling with PLS method. By giving lower weight to the corresponding wavelength which is greatly affected by scattering, the model is insensitive to scattering and the prediction accuracy is improved. Through the spectral quantitative analysis experiment on strong scattering material, the prediction accuracy of the model was 61.7% higher than that of the traditional method and was 58.5% higher than that of the variable sorting for normalization method. The feasibility of the method is verified.