esa-sceva/satcom-chunk-collection huggingface dataset:
## 4 Conclusions  
The average concentrations of Hg, As, Cu, Pb, Cd, and Zn in surface sediments of the dumping area were 0.080, 15.1, 24.5, 30.8, 0.21, and 97.6 mg/kg, respectively. HMs in the surface sediments of the study area generally showed a trend of high in the northwest and central areas and low in the southeast of the dumping area. All HMs, except for Hg, met the class I standard for MSQS. The Nemerow index showed that sediments in the dumping area were at a light pollution level, and the polluted areas were mainly in the northwest and central areas with large dumping amounts. The values of \(I_{geo}\) showed that the dumping  
Figure 8: Cluster and n-MDS plots based on abundance of taxa, density, and diversity in each station.  
area was at a mild contamination level, and Hg and Cd were the major pollutants. The \(RI\) of the dumping area was relatively high. Hg and Cd are the main factors that cause the potential ecological risk of sediments. Areas with high potential ecological risk and high pollution levels were mainly those that undertake frequent and large dumping amounts of dredged materials.  
Benthos identified in this study include arthropods, chordates, annelids, mollusks, echinoderms, hermiteans, coelenterates, and echiurans. Among these groups, arthropods were the most abundant, accounting for 38.5% of all benthos, and chordate, annelid, and mollusks accounted for 25.0%, 15.4%, and 13.5%, respectively. The abundance of taxa and density of benthic organisms showed little difference among the stations within the dumping area but were significantly lower than those of the stations outside the dumping area. It can be inferred that dumping dredged materials in the Huangmao Island marine dumping area had a negative impact on the benthos.  
The assessment of HMs in the dumping area indicated that the pollutants in the dredged materials may have harmful effects on benthos. As, Hg, and Cd must be treated before dumping dredged materials. To study the impact of HMs more objectively in dumping dredged materials on marine organisms, metal concentration evaluation in benthic organisms and the toxicity test in sediments of dumping areas should be evaluated in further research. Additionally, the dumping area should be managed by zones to avoid intensive dumping in the northern part.  
Conceptualization, W.T. and Z.J.; methodology, W.T. and Z.J.; validation, X.P. and Z.Y.; investigation, Z.J.; data curation, H.Y. and J.Y.; writing--original draft preparation, W.T. and J.Y.; writing--review and editing, W.C. and W.T.; supervision, Z.J. and J.Y.; Funding acquisition, W.T. and J.Y. All authors have read and agreed to the published version of the manuscript.  
This research was funded by State Oceanic Administration, grant number DOMEP-01-03.  
Not applicable.  
Data employed in this study will be available on request to the corresponding authors.  
The authors would like to thank the technicians from South China Sea Environment Monitoring Center, China for sample collection and analysis.  
The authors declare no conflict of interest.
# Metasurface-Based Polarimeters
## 2 Fundamentals  
### Generalized Snell's Law  
The phase discontinuity or abrupt phase shift at the interface between two media was first introduced by [PERSON]'s group in 2011, resulting in a generalized [PERSON]'s laws of reflection and refraction [6]. Figure 1 schematically shows a one-dimensional (1D) system used to derive generalized [PERSON]'s laws, where the interface between two media consists of an artificial metasurface introducing a position-dependent phase shift \(\Phi(x)\)[6]. Considering a plane wave impinging at an angle of \(\theta_{t}\), generalized [PERSON]'s laws of reflection and refraction can be written as:  
\[\sin(\theta_{r})n_{i}-\sin(\theta_{i})n_{i} =\frac{\lambda_{0}}{2\pi}\frac{\mathrm{d}\Phi}{\mathrm{d}x} \tag{1}\] \[\sin(\theta_{t})n_{t}-\sin(\theta_{i})n_{i} =\frac{\lambda_{0}}{2\pi}\frac{\mathrm{d}\Phi}{\mathrm{d}x}, \tag{2}\]  
respectively. Here, \(n_{i}\) and \(n_{t}\) are the refractive indexes of the two media, \(\lambda_{0}\) is the wavelength in free space, and \(\theta_{r}\) and \(\theta_{t}\) are the reflected and refracted angles, respectively. From Equations (1) and (2), it is evident that the reflected/refracted beam can have an arbitrary direction, provided that a nonzero phase gradient (\(\mathrm{d}\Phi/\mathrm{d}x\)) along the interface is introduced. It should be noted that in the case of \(\mathrm{d}\Phi/\mathrm{d}x=0\), we recover the usual laws of reflection and refraction that imply the conservation of in-plane wave vectors.  
To realize metasurfaces with phase discontinuity, V-shaped antenna--which support symmetrical and antisymmetrical electric dipole resonance--were demonstrated to control the reflection and refraction of linearly polarized (LP) light in the infrared range, governed by generalized Snell's law [6; 25]. However, here \(2\pi\) phase control is achieved with the transmitted/reflected light polarized orthogonal to the incident wave because V-shaped antennae only support electric dipole resonance, which limits the available phase coverage to \(\pi\) due to its Lorentz-like polarizabilities [55; 56]. Additionally, the polarization conversion efficiency for such single non-magnetic metasurfaces is only 25% for the lossless case [57; 58]. To solve these problems, one can design gap-surface plasmon metasurfaces (GSPMs) [26; 27; 30; 59] or use all-dielectric meta-atoms [40; 41], which ensure the full control of the phase space with high efficiency while maintaining the polarization state.
# A Generalized Framework for the Estimation of Edge Infection Probabilities
## 2 Definitions  
The infection processes described in this paper take place in graphs. We will denote graph \(G\) as \(G(V,E)\), where \(V_{G}\) is the vertex and \(E_{G}\) is the edge set of \(G\). By default, we are going to consider these graphs to be connected and undirected, unless otherwise noted. The infection models require a real value \(w_{e}\in[0,1],e\in E\) (also denoted by \(w_{u,v}\in[0,1],v,w\in V\)) to be present on all edges of the graph; these are known as the edge infection probabilities. We will denote the surjective assignment of edge infection probabilities to the edges as \(W_{G}:E(G)\mapsto[0,1]\). The task of inverse infection is the estimation of these values.  
Among the most frequently used infection models present in the literature are the IC, SI, SIR and SEIR models [1; 2; 9]. These processes are iterative; events take place in discrete time steps, and the models terminate in finite steps.
# A Survey on Robust Video Watermarking Algorithms for Copyright Protection
## 3 Properties of Video Watermarking  
A video is composed of a series of temporally continuous images, but it is not just a simple combination of images, because adjacent frames not only have high correlation but also have a large amount of spatial and temporal redundancy. Therefore, video watermarking algorithms not only have some characteristics of image watermarking algorithms, such as imperceptibility, robustness, watermark capacity, and security, but also have their own unique characteristics, such as random detection, real-time processing, code rate constancy, and combination with video coding standards [18]. In different applications, watermarking algorithms need to meet different requirements. For general robust video watermarking algorithms, performance is usually evaluated by analyzing their imperceptibility, robustness, watermark capacity, and real-time processing. In addition,  
Figure 6: The basic model of watermark extraction.  
for watermarking algorithms in compressed domain, bit increase rate (BIR) may be measured as one of the performance metrics. Next, these properties and their evaluation indexes will be introduced.
# The Feasibility of Shadowed Image Restoration Using the Synthetic Aperture Focusing Technique
## 3 Results  
### Synthetic Simulation  
Taking the spreading attenuation into consideration, a synthetic profile of the pitch/catch scan obtained from the model is computed using the Levin equation [26]. At a sampling interval of 16 ns, a zero-phase Ricker wavelet is used to compute the synthetic profile using FORTRAN language. The velocity used is the same as the modeling material, i.e., 1450 m/s. Following the practical operation, the spacing interval of two successive traces is fixed at 2 mm. In the following paragraphs, the synthetic profile is used to assist image interpretation and serve as test data to evaluate the performance of SAFT in image restoration. Figure 3a shows the synthetic profile which is computed, based on the theoretical echo paths that respond from the \"eight targets\", i.e., the relative positions of  
Figure 2: A brief description of the SAFT process.  
T\({}_{\text{OBS}}\) and T\({}_{\text{N}}\) inside the created model. According to point diffraction theory, there should be eight hyperbolic trajectories showing up in the synthetic profiles, with the targets as the apexes. When the scan positions (SPs) move or are close to the projection of T\({}_{\text{OBS}}\), echo signals around the vicinity of the apexes T\({}_{1}\), T\({}_{2}\), and T\({}_{3}\) are purposely muted to simulate and demonstrate the shadowed images in an anechoic zone (Figure 3a). In the synthetic and the following images, echo signals are displayed using a linear grayscale from black (the smallest) to white (the largest).  
The synthetic profile is SAFT-processed; Figure 3b shows the output images of restoration. Even though part of the echo signals is purposely muted in the incomplete trajectories, T\({}_{1}\), T\({}_{2}\), and T\({}_{3}\) respond to the acoustic shadow. All the hyperbolic trajectories shown in Figure 3a are successfully refocused as eight spots and repositioned in Figure 3b. The apex positions of T\({}_{\text{OBS}}\) and T\({}_{4}\) that show up at 40.0 us and 43.6 us in Figure 3a are shifted upward to 37.6 us and 41.3 us, respectively, in Figure 3b, in response to the SAFT process. In other words, the events of T\({}_{\text{OBS}}\) and T\({}_{4}\) are not only successfully restored, but also relocated to a new position.
# An Efficient Single-Anchor Localization Method Using Ultra-Wide Bandwidth Systems
## 6 Conclusions  
In this paper, we proposed a high-efficiency SAL method, which serves multiple agents based on the single-anchor UWB system with minimum exchanges of signals. In such systems, the anchor equipped with an antenna array achieves localization of multiple agents by using range and AOA estimations. During the measurement process, the anchor only needs to turn on the receiver once to complete the measurement of all agents, which improves the measurement efficiency. We implemented our method on a single-anchor UWB system and evaluated the localization accuracy and measurement efficiency in two indoor environments. The results show that our system can achieve decimeter-level localization accuracy and the measurement time does not increase with the number of agents, within a certain number of agents.  
There are still several issues to be further studied, such as the effect of multi-path and NLOS propagation for the proposed SAL system. In future work, we will also conduct sufficient experiments in more complex environments, and design algorithms to improve system capacity and localization accuracy.  
**Author Contributions:** conceptualization, T.W. and Y.S.; methodology, T.W. and H.Z.; software, T.W.; validation, T.W.; formal analysis, T.W. and H.Z.; investigation, T.W.; resources, T.W., H.Z. and Y.S.; data curation, T.W.; writing--original draft preparation, T.W.; writing--review and editing, T.W., H.Z., and Y.S.; visualization, T.W.; supervision, H.Z. and Y.S.; project administration, T.W., H.Z and Y.S.; funding acquisition, Y.S. All authors have read and agree to the published version of the manuscript.  
**Funding:** This research was supported by the National Natural Science Foundation of China under Grant 61871256, 91638204, and 61811530329.  
**Acknowledgments:** Authors thank [PERSON] for providing technical support and practical comments on embedded development. Authors also thank [PERSON] for collecting experimental data used in the case study.  
**Conflicts of Interest:** The authors declare no conflict of interest.
# Review of Functionally Graded Thermal Sprayed Coatings
## 2 Spray Techniques and Feedstock Used to Deposit Functionally Graded Coatings
### Low Pressure Cold Spraying and High Pressure Cold Spraying
Figure 10: Methods of powders preparation in composite coatings deposition: mixture of powders (**left**), mechanically blended powders (**middle**), and cladded powders (**right**). Figure 9: The scheme and principle of high- (**up**) and low-pressure (**down**) cold spray systems. Many reports show advanced technology of functionalization of the coatings sprayed using mechanically alloyed powders. This powder production technology enables introducing the crystal refinement strengthening effects in the composite powders. [PERSON] et al. [127] found that the grain size of the NiCrAl matrix in the c-BN-NiCrAl composite powder prepared by mechanical alloying had a size of a few tens of nanometers. Cold spraying enables preserving these small crystal sizes in coatings. The contributions of the strengthening mechanisms including work hardening, dispersion strengthening, and crystal refinement enabled reaching the hardness of cold-sprayed coatings of 40 vol.% c-BN + NiCrAl as high as 1175 HV [128]. Finally, hardness and many other properties can be increased by using nanostructured coatings obtained from nano-structured powders. The mechanical alloying method of powder production renders more uniform distribution of ceramics in composite coatings. However, the spray process modifies the strength of the metal particles and its morphology which becomes more irregular and lowers the deposition efficiency. To resolve this problem an innovative process was developed. The process deals with the core-shell powders morphology. The core includes a reinforcing ceramic phase and shell is a ductile metal or alloy [129; 130]. [PERSON] et al. [130] compared a coatings properties obtained by spraying of powders obtained by mixing of ceramics and metallic powders with those obtained with powders having particles coated with CVD. The authors used Ni-coated B4C composite to deposit composite coatings. They found that coatings obtained by mixing the initial powders results in coatings having B4C content always smaller than 20 vol.%. Many B4C particles were fractured. The coatings sprayed with CVD-coated powders particles had higher content of entire B4C particles. Similarly, [PERSON] et al. [131] compared the coatings cold sprayed using powder with particles of diamond coated with Cu-Ni with the deposits obtained using diamond particles mixed with the Al ones. The authors found, that the core-shelled diamond particles were easier to spray than that of powders mixture.
## 2 Basic Theory of Signal Noise Reduction Method
### Wavelet Noise Reduction Principle
#### 2.1.4 Signal Reconstruction  
The reconstruction of smoothing signal after filtering is shown as Equation (4)  
\[c_{j-1,k}=\sum\limits_{n}\left[h_{k-2n}c_{j,n}+g_{k-2n}d_{j,n}\right] \tag{4}\]  
Firstly, the signal is decomposed into time-frequency domain using Equation (3). Then the reconstruction of denoised signal is realized by Equation (4).
## 4 Results
### Sequence Framework
#### 4.3.3 Cyclic Structure  
This study employs wavelet transform analysis to quantitatively resolve depositional cyclicity using the GR curve from three representative wells (T1, N2, and Z2), validating the established sequence stratigraphic framework and characterizing cyclic depositional patterns.  
Building on previous methodologies [35; 36; 69], Daubechies wavelet (db12) decomposition with 12 maximum decomposition levels optimally resolves hierarchical sequence units when calibrated with geological constraints. The d11 curve delineates two second-order sequence boundaries and the maximum flooding surface (MFS) of sequence I, defining one complete second-order sequence I and one incomplete sequence II (Figure 10). The d10 curve identifies ten third-order sequence boundaries partitioning nine third-order sequences (SQ1-SQ9), corroborating the proposed scheme of sequence stratigraphy (Figure 10). The d8 curve identifies forty-two fourth-order sequences in well T1.  
Figure 10: Sequence classification and wavelet analysis of the Lower–Middle Jurassic in the Kuqa depression.  
Sequence I comprises regional-scale transgressive hemicycles and rapid regressive hemicycles, with its MFS at the Yangxia Formation top marked by thick lacustrine mudstone (Figures 6 and 10). The Kezilenuer Formation constitutes the partial transgressive hemicycles of sequence II. Five third-order sequences (SQ1-SQ5) occur within sequence I, and four (SQ6-SQ9) within sequence II, each subdivided into lowstand (LST), transgressive (TST), and highstand (HST) systems tracts via cycle inflection points and flooding surfaces.
## 3 Database of Water Content and Hyperspectral Information
### Analysis of Hyperspectral Information  
Before data extraction, preprocessing processes to correct hyperspectral information, such as geometric and atmospheric correction, must be performed. The files obtained from the camera are image files and coordinate files containing hyperspectral information. First, geometric correction is performed to combine these two files. When this process is performed, the orthophoto files are rearranged according to latitude and longitude with the WGS-84 coordinate system. When this correction is completed, atmospheric correction is  
Figure 8: Results with oven-drying method: (**a**) Relationship between \(w_{s}\) and \(w_{in}\); (**b**) Comparison of \(w_{s}\) and \(w_{s}/w_{in}\).  
performed to extract accurate data. This is a process of correcting the reflectance to prevent hyperspectral information from being changed by environmental factors such as weather.
# A Proactive Approach to Extended Vehicle Routing Problem with Drones (EVRPD)
## 3 Problem Statement and Mathematical Model  
This study presented the main assumptions and features of the extended vehicle routing problem with drones (EVRPD) and the mathematical model for the EVRPD. Significant extensions of the presented problem in relation to the VRPD were marked. The proposed model could be the basis for building a decision support system or ad hoc decision support for both proactive and reactive decisions for deliveries within the last mile.
# PCONet: A Trainable Feedback Scheme of Precoder for the Uplink Multi-User MIMO Systems
## 2 System Model
### Channel Model  
The channels are assumed to be frequency flat and known at the receiver side. We consider multiple channel models such as the i.i.d. Rayleigh fading channel and the more realistic NAIE channel provided by Huawei Corporation [25]. The channel matrix \(h_{ij}^{k}=\left[\mathbf{H}_{k}\right]_{ij}\) represents the channel fading coefficient between the \(j\)-th transmit antenna of the \(k\)-th UE and the \(i\)-th received antenna of the BS. The i.i.d. Rayleigh channel matrix \(\mathbf{H}\) consists of independent and identically distributed (i.i.d.) \(\mathcal{CN}(0,1)\) elements. The NAIE MIMO channels are taken from the CDLB300_20 UE_4T32R dataset provided by the iMaster NAIE platform, which is a channel environment measured in practical scenarios.  
The parameters of the NAIE dataset are listed in Table 1. The dimension of the dataset matrices is \(\left[\mathcal{L},K,N_{k,t},N_{r},N_{f}\right]=\left[500,20,4,32,96\right]\), which represents the number of data frames, the number of UEs, the number of antennas for UE, the number of antennas for BS, and the number of carriers, respectively. When the testing and training datasets are generated for the NAIE channel, they are randomly picked from the 500 matrix elements  
Figure 2: Block diagram of the feedback link for the precoding matrices over an uplink MU-MIMO System.  
and then normalized to satisfy the power constraints. If the number of frames is less than 500, the data frames are randomly selected. Otherwise, the datasets will be reused when the number of data frames is larger than the dimension of the dataset \(\mathcal{L}=500\).
## 4 Methodologies Used  
The primary way to represent semantic information is a triplet--a syntactic structure consisting of three elements: subject, predicate, and object (Figure 1). A triplet can express a connection between two concepts, semantics which is defined by a predicate, for example \"Course-Require-Skill\". In addition, the subject property can act as a predicate, and the value of this property can act as an object, for example \"Course-Has-name-Java Script Programming\". Either an entity or a literal (numeric or string value) can act as an object.  
An essential part of the semantic model is the principle of the uniqueness of object names. In the Semantic Web concept, it is customary for these names to have the form URI (Uniform Resource Identifier).  
The most famous application of the ontological approach is the Semantic Web project--semantic web. This is a concept for the development of a web environment for the introduction of metadata into information that allows to store and process the semantics of documents. In addition, using special tools for data extraction will allow for not contextual but \"semantic search\", i.e., looking for an answer to a question and using logical inference. Semantic Web technologies can also be used in other areas--for system integration, de  
Figure 1: Triplet—the basic unit of semantic information representation.  
scription, the cataloguing of information resources, and the creation of intelligent software agents.  
The ontological approach has several advantages in the implementation of information models of poorly formalised subject areas, which include the content of the educational programme:  
* The \"transparency\" of the data model, which provides for its expansion by adding new concepts and relationships throughout the system's life cycle.
* The ability to model complex relationships and the use of logical inference.
* The usage of agreed (shared by all) terminology with precisely defined semantics.