esa-sceva/satcom-chunk-collection huggingface dataset:
## 3 Results and Discussion
### EDX Analysis  
Elemental analyses of the adsorbents are shown in Table 1. The EDS measurements focused on different areas of the composites. Biochar showed the contents of carbon, oxygen, and calcium. The O/C ratio shows the polarity and oxygen-containing surface functional groups in biochar; the higher the ratio, the more polar the functional groups [18]. The DES-CTAB and DES-glycerol-modified adsorbents showed a higher O/C ratio than the composite material (biochar/rGO), indicating that biochar/rGO/DES-CTAB and biochar/rGO/DES-glycerol are more hydrophilic. than biochar/rGO. Both materials also showed no detectable hydrogen. The composite biochar/rGO introduced silicon into the mixture and increased the carbon content by 3.84% resulting in a carbon content of 89.3%. This is due to rGO being a carbon-rich material. Further modification of the material by introducing DES-CTAB added aluminum and chlorine to the mixture.  
Figure 3: XRD profile of biochar, biochar/rGO, biochar/rGO/DES-CTAB, and biochar/rGO/DES-glycerol.  
The final modified material (biochar/rGO/DES-CTAB) contained C, O, Al, and Cl at quantities of 80.90%, 13.01%, 2.52%, and 3.58%, respectively. A slight carbon content reduction of 8.9% and an increased oxygen content of 3.14% were observed.  
On the other hand, further modification occurred by introducing DES-glycerol, which added calcium and chlorine to the mixture. The final modified material contained C, O, Ca, and Cl at quantities of 84.92%, 13.95%, 0.31%, and 0.82%, respectively. A slight carbon content reduction of 4.45% and an increased oxygen content of 4.08% were noticed. This is assumed to come from the introduction of DES-glycerol. All the materials were further characterized with SEM.
## 3 Results and Discussion
### Determination of Zeta Potential  
The role of electrostatic interaction is recognized as significant in the non-productive binding process between lignin and enzymes. As the pH of the solution employed in this experiment exceeded the isoelectric point (PI) of the cellulase utilized, the cellulase surface was negatively charged. The zeta potential of the lignin surface was examined in order to investigate the impact of ozone pretreatment on the charge properties of the lignin surface. The findings revealed that the negative zeta potential of MWL exhibited an increase following ozone pretreatment, with values of \(-11.8\) mV and \(-15.5\) mV for OL60 and OL120, respectively, representing a respective increase of 14.6% and 50.5% (Table 5). This increase can be attributed to the rise in the number of carboxyl groups and other groups in the lignin, resulting from ozone pretreatment [41]. Consequently, the electrostatic repulsion increased between ozone-pretreated MWL and cellulase, and effectively reduced the ineffective adsorption of cellulase onto lignin [42; 43; 44].
# Practical Application of Mesh Opportunistic Networks
## 5 Discussion
### Mesh OppNets as an Emergent Technology in Future Smart City  
In the future, it is likely that devices will be available that facilitate mesh communication without the need for a phone terminal. Moreover, further research should assess the value of mesh OppNets in smart cities in the advent of this post-pandemic society, where internal electronic communication flows will have to adapt more quickly to a new way of consuming geolocated content more locally and on a daily basis. In this context, Wi-Fi direct-based protocols should be taken into account, and further research should be done to determine if their limitations (such as scalability or routing) [39] could make this technology suitable for practical mesh networks such as the one described here.  
The increased spread of mesh OppNets is a phenomenon that will become important in areas with poor mobile coverage, in states of emergency, and in military use. Indeed, they are already becoming evident in urban settings and for informal conversations. As such, communication studies and smart city designers must pay attention to community implantation experiments and it will be necessary in subsequent studies to understand their use in informal networks within cities, paying attention to the content that early adopters of this technology implement in these communications. Electronic commerce research must be alert to this new method of electronic communication  
**Author Contributions:** Conceptualization, M.A.M.-P. and C.A.-S.; methodology, M.A.M.-P. and C.A.-S.; software, M.A.M.-P. and C.A.-S.; validation, M.A.M.-P. and C.A.-S.; formal analysis, M.A.M.-P. and C.A.-S.; investigation, M.A.M.-P. and C.A.-S.; resources, M.A.M.-P.; data curation, M.A.M.-P.; writing--original draft preparation, M.A.M.-P. and C.A.-S.; writing--review and editing, M.A.M.-P. and C.A.-S.; visualization, M.A.M.-P. and C.A.-S.; supervision, M.A.M.-P.; project administration, M.A.M.-P.; funding acquisition, M.A.M.-P. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by Department of Technological Innovation of Institute RTVE (Spanish Public Television, RTVE), the Almagro Classical Theater Festival and Observatory for Innovation in News for the Digital Society (OI2).  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.  
**Acknowledgments:** We acknowledge the logistic assistance of the City Council and the Almagro Classical Theater Festival, and the participation of students from the Autonomous University of Barcelona (UAB) and the University of Castilla La Mancha (UCLM), within the framework of the Chair of the Observatory for Innovation in News from the Digital Society (OI2) of the UAB and RTVE. We thank [PERSON], [PERSON] and [PERSON] from Video Stream Networks (VSN), and [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON] from RTVE. We thank [PERSON] for his support with the English language editing.  
**Conflicts of Interest:** The authors declare no conflict of interest.
## 2 Energy Model  
### Constellation Topology  
There are two commonly symmetric constellation topologies, namely the walker-delta and walker-polar. Due to the stability and periodicity, they are particularly suitable for NTSN applications. In former topology, there are multiple inclined orbits distributed evenly over the equator. The low and mid latitudes regions are covered better by it, but the pole regions are missed. Starlink is the most typical application. In the later topology, there are multiple vertical orbits distributed over a half equator. The global coverage can be achieved by it, but the traffic hotspot problem cannot be solved. OneWeb and Iridium are the most typical applications.  
To study mega NTSN and routing scheme, a walker-delta constellation is the best research object. A walker-delta constellation consisting of 48 orbits and 1152 satellites is proposed, as shown in Figure 1. In this constellation, there are four connectable satellites for a single ground user at any time. Two of them are ascent links (the connected satellites move from South Pole to North Pole) and other two are descent links (the connected satellites move from North Pole to South Pole).  
The basic parameters of the specific constellation are inclination and altitude. They are defined as 55 degrees and 550 km in this paper. The orbit period is about 90 min. To simplify the research objectives, a satellite can be defined as (\(O\), \(S\)), where \(O\) is the orbit factor and \(S\) is the satellite phase factor. The range of \(O\) is from 1 to 48, and the range of \(S\) is from 1 to 24. There are four inter-satellite-links (ISL) for each satellite.
# A Two-Stage Kalman Filter-Based Carrier Tracking Loop for Weak GNSS Signals
## 3 Conventional Two-Stage Carrier Tracking Strategy
### Coarse Tracking Design
#### 3.1.2 FLL-Assisted-PLL Tracking Loop Design  
To track the dynamic signals, the FLL-assisted-PLL tracking loop is selected. Figure 3 shows the block diagram of the second-order FLL assisting the third-order PLL tracking loop, as described in [1].  
Figure 3: Block diagram of the second-order FLL assisting third-order PLL tracking loop. (NCO: numerically controlled oscillator; FLL: frequency-locked loop; PLL: phase-locked loop).  
Figure 2: Block diagram of the frequency pulling algorithm.  
In Figure 3, the updated tracking loop can be calculated as:  
\[\left\{\begin{array}{l}S_{0}=S_{0}+(\delta\varphi\!\cdot\!P_{0}+\delta f\!\cdot \!F_{1})\!\cdot\!T\\ S_{1}=S_{1}+(\delta\varphi\!\cdot\!P_{1}+S_{0}+\delta f\!\cdot\!F_{0})\!\cdot\!T \\ f_{c}=S_{1}+\delta\varphi\!\cdot\!P_{2}\\ f_{carrier}=f_{ref}+f_{c}\end{array}\right. \tag{8}\]  
where \(\delta\varphi\) and \(\delta f\) are the outputs of the PLL and FLL discriminators, respectively; \(F_{0}\), \(F_{1}\), \(P_{0}\), \(P_{1}\), and \(P_{2}\) are the coefficients of the FLL and PLL tracking loops; \(T\) is the updated period of the tracking loop, which is typically the same as the predetection integration time; \(f_{c}\) is the carrier frequency error after the update; and \(f_{carrier}\) is the local carrier frequency after adjustment. The discriminator results, \(\delta\varphi\) and \(\delta f\), are computed as described in Table 1.
## Materials and Methods
### Retrieval Algorithm
#### 2.3.3 Assessment of Algorithm Performance  
The assessment of the proposed physically-based grassland AGB retrieval method was conducted in the two following aspects:  
Comparison with reference AGB map: The reference AGB map upscaled directly from the field measurements was seen as the proxy of 'true values' to assess the accuracy of the AGB map generated from the physically-based method. The reference AGB was aggregated to the same spatial resolution (500 m) as the MCD43A4 product before validation. We used the reference AGB map rather than the field measurements per se because there is obvious scale difference between sampling plots and MCD43A4 pixels (100 m vs. 500 m), and the spatial heterogeneity within the MCD43A4 pixel would cause scale error [40; 41; 42]. As recommended by the Committee Earth Observing Satellites' Working Group on Calibration and Validation (CEOS WGCV), the 'bottom-up' validation approach through reference maps could significantly immediate the uncertainty caused by scale discrepancy, and provide more objective validation results [43]. A pixel-by-pixel comparison was conducted to calculate the RMSE and relative RMSE (RRMSE) between the reference and estimated AGB, as indicators representing the absolute and relative accuracy. The spatial distribution of the reference and estimated AGB maps was also compared to check whether the physically-based method can reproduce the spatial pattern of the 'true' case.  
Temporal dynamic analysis: 46 AGB maps covering our study area in 2017 was generated. The temporal distribution of the AGB maps corresponds to that of our downloaded MCD43A4 (Section 2.2.2). The mean of each AGB map was calculated, and its temporal profile was analyzed to check that whether the estimated AGB time series can capture the grassland phenology. Moreover, the time series of estimated LAI and Cm, as elements to calculate AGB (see Equation (2)), was also analyzed.
## 4 Experiments
### Positioning Accuracy Experiment  
In the entire set of image samples, the theoretical pixel center coordinates of the road stud are determined by taking the mean of multiple manual annotations, denoted as (\(x_{0}\), \(y_{0}\)). The pixel center coordinates of the road stud obtained by the positioning algorithm are denoted as (\(x,y\)). Additionally, multiple annotations yield a pixel diameter of the road stud, \(D_{i}=54.45\) pixels. The actual diameter of the road stud is \(D_{r}=24\) mm. Thus, the scale factor \(\lambda_{i-r}=D_{i}/D_{r}=2.3\) pixels/mm. The positioning error, \(E_{rr}\), can be calculated using the distance between two points and the scale factor. \(E_{rr}\) is a performance metric for algorithm evaluation and positioning accuracy analysis. Given the constraints of the railway environment, the vertical position of the rail spike in the image changes very little. However, with the movement of the robot, the horizontal position of the rail spike in the image changes significantly. Therefore, in the experiment, the horizontal position of the rail spike in the image is taken as the X-axis to represent the image samples captured at different moments during the robot's movement. The positioning error, Err, is taken as the Y-axis for the quantitative analysis of positioning accuracy. The positioning error distribution of all rail spike samples is shown in Figure 15. The red areas indicate regions where the positioning error is too large, exceeding a positioning error of 3 mm.  
The graph shows that the positioning error is distributed from 0 mm to 2 mm, with an overall mean positioning error of 0.9 mm. A tiny fraction of the positioning errors exceed 3 mm, primarily due to severe oil contamination. In the railway environment, the loss of surface features of spiral rails due to severe oil contamination is only an isolated case; therefore, the positioning error demonstrated by the algorithm in this paper meets the requirements for robotic operations under railway environmental conditions. Additionally, the experimental results indicate that the positioning remains accurate even when the positions of the rail spikes are constantly changing.  
Figure 14: Number of failed filtering of different-sized increment values.
## 3 Probabilistic Numerical Model of SFRC Beam Flexural Behavior
### Defining Characteristic Points of Beam Flexural Behavior  
Three characteristic points in the flexural behavior of beams are identified in this study: the point when the first crack appears (i.e., the first-crack point); the point when longitudinal reinforcement starts to yield (i.e., the yield point) and the point when the beam collapses (i.e., the collapse point). Characteristic points are identified by following the stresses and strains in concrete and longitudinal reinforcement. Figure 2 illustrates how the characteristic points are defined. The appearance of the first crack in the beam is defined as the point when the concrete reaches its residual tensile strength. The yield point is defined as the point when the longitudinal reinforcement reaches its yield strength.  
Different collapse definitions have been suggested in the literature. Some researchers define collapse by comparing the post-peak and peak loads (e.g., [32; 33]). Such a definition is valid for structural elements that exhibit deflection-softening behavior. An alternative is to define maximal allowable strain values. This study uses one such criteria, as proposed by fib Model Code 2010 [34; 35]. According to fib Model Code 2020 [34] bending failure (i.e., collapse) of an SFRC beam occurs when one of the following conditions is met:  
* Attainment of the ultimate compressive strain in the SFRC;
* Attainment of the ultimate tensile strain in the longitudinal reinforcement;
* Attainment of the ultimate tensile strain in the SFRC.  
The ultimate compressive strain for the adopted bilinear concrete stress-strain relation is between 2.4% and 3.5%, depending on the concrete compressive strength. The ultimate tensile strain in the longitudinal reinforcement is assumed to be 10% and the ultimate tensile  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Model Input** & **Probability Distribution** & **CoV** \\ \hline Concrete compressive strength \(f_{ck}\) & Lognormal & 12\% \\ Concrete tensile strength \(f_{t}\) & Lognormal & 20\% \\ Concrete elastic modulus \(E_{c}\) & Lognormal & 8\% \\ Concrete residual tensile strength \(f_{t,res}\) & Lognormal & 35\% \\ Steel yield strength \(f_{y}\) & Lognormal & 5\% \\ Steel elastic modulus \(E_{y}\) & Normal & 4\% \\ \hline \hline \end{tabular}
\end{table}
Table 1: Probability distribution of material properties.  
Figure 2: Identifying characteristic points of beam bending using the stresses and strains in fiber cross-sections. The collapse point is represented in red, yield point in orange and first-crack point in green for the case of a beam cross-section exposed to pure bending. The bottom side is in tension, and the top side is compressed.  
strain in SFRC is equal to 2% for variable strain distribution along the cross-section [34]. Beam shear failure is not considered in this study.
## 3 Methods and Materials
### Methodology
#### 3.2.2 Image Pre-Processing  
After the data collection stage, we moved on to the preprocessing stage where three main concepts were applied to obtain uniform data in terms of size, pixel values, and array dimensions. The following three methods were applied: converting to NumPy arrays, normalization, and resizing images.  
1. Converting to NumPy arrays In this step, all of the used images for training, validation, and testing were converted into NumPy arrays, which means each pixel in the image will typically be represented as a NumPy array of shape (3 matrix).  
The first framework addresses the force of the red channel. The second addresses the force of the green channel. The third network addresses the power of the blue channel.  
Converting data to NumPy arrays enhances performance, simplifies code, and facilitates interoperability with other numerical computing libraries. In detail, they allow for faster operations and utilize less memory, providing a wide range of mathematical functions that operate on entire arrays of data without the need for explicit loops, making code concise and easier to read.  
2. Normalization In this applied step, the data values (pixels) were adjusted to a common scale by dividing by 255 without distorting differences in the ranges of values. The purpose of this method is to improve convergence and accuracy and avoid numerical instability.  
3. Resizing images In this study, the data images were resized to 100 \(\times\) 100 pixels to facilitate easier handling and processing, especially when dealing with large datasets where images might vary in size, as in our case. Additionally, resizing helps reduce the computational load and memory requirements during model training and prediction. While VGG16 typically requires input data of 416 \(\times\) 416 pixels, resizing to 100 \(\times\) 100 pixels helps avoid session crashes in Google Collab due to memory limitations.
## 3 Results and Discussion
### Properties in Fresh Condition
#### 3.2.2 Setting  
The test was carried out on cement pastes with substitutions that have been proposed and the setting time was determined with the Vicat needle. Waste added to the cement paste generated a parabolic tendency of increase in the water demand for a normal consistency. The higher demand for water corresponds to the higher specific surface area and the finer size distribution in some wastes that are added to the cement, which hinders the fluidity of the cement paste. As shown in Figure 1, more water is required to wet the entire surface of the cement, as it is larger.  
The smallest setting times correspond to the larger waste substitutions in the cement. The justification for this process may be related to the particle size: the finer particles will serve as crystallization nuclei that help in hydrated phase formation [39].  
The reaction products obtained in the waste/cement system, in all cases and additions studied, are, above all, layered double hydroxide (LDH) compounds, whose concentrations increase with setting time, in addition to portlandite and amorphous material. LDH compounds presence reduces the carbonation of the cement. All of these products enhance their formation when the substitution is 20% waste and, therefore, they are directly linked to the setting time. In an inverse relationship: higher concentration of reaction products, shorter setting time [40].
# Aluminum-Based Plasmonic Photodetector for Sensing Applications
###### Abstract  
Plasmonic sensors have great potential for widespread usage. However, the prohibitive cost of noble metals restrains the wider adoption of these devices. The aim of our study is to develop a cost-effective Al-based alternative to common noble metal-based plasmonic detectors. We considered a structure consisting of an n-type doped Si wafer with a shallow p-n junction and an overlying Al grating with a trapezoidal groove profile. The RCWA (rigorous coupled-wave analysis) method was used to numerically calculate the distribution of absorbed light energy in the plasmonic detector layers and to optimize the grating parameters. Based on the simulation results, experimental samples of plasmonic photodetectors with optimal grating parameters (period--633 nm, relief depth--50 nm, groove filling factor--0.36, and thickness of the intermediate Al layer--14 nm) were manufactured, and their properties were studied. For these samples, we obtained a polarization sensitivity value of \(\mathrm{I}_{\mathrm{P}}/\mathrm{I}_{\mathrm{s}}=8\), an FWHM of the resonance in the photocurrent spectrum ranging from 50 to 100 nm, a sensitivity at the resonance maximum of \(\mathrm{I}_{\mathrm{ph}}=0.04\)-0.06 A/W, and an angular half-width of photocurrent resonance of \(\Delta\Theta=5^{\circ}\), which are comparable to noble metal-based analogs. Our results may be used for creating cost-effective high-sensitivity plasmonic sensors.  
plasmon-polariton photodetectors; surface plasmon resonance; diffraction gratings; optochemical sensors +
Footnote †: journal: Medical Physics
## 5 Conclusions  
This works extends the utilization of SISO IRC, originally introduced in [34], to a MIMO IRC configuration. This extension has considered the general framework outlined in [35] and the MIMO IRC proposed in [36]. The resulting MIMO IRC keeps the main advantages of the IRC proposed in [34], but in a MIMO configuration. The main advantages are as follows:  
* The controller's resilience against spillover effects, which has been tested in experiments by impact perturbation, which excites higher vibration modes.
* The robustness to system variations, which has been illustrated in the simulation results.  
With respect to the stability, the section \"Robust Analysis: Simulation Results\" also shows that the stability depends on the ration between the first vibration mode and the natural frequency of the actuator. The same conclusion, for SISO IRC, was shown in [34], but here, it has been extended to the MIMO case. Thus, if the natural frequency decreases with respect to the model considered for the controller designed, the closed-loop system might be degraded. Future work will focus on deducing the stability conditions for the novel IRC scheme, incorporating elements such as the Negative Imaginary Frequency Response property and the Small-Gain theorem [45].  
Finally, this work has a big practical application to the active vibration control of civil structures, where non-resonant structural responses and resonant vibrations must be attenuated [23].  
Conceptualization, E.P., S.S.A., E.P. and I.M.D.; software, I.M.D. and X.W.; validation, X.W., I.M.D. and E.P.; formal analysis, E.P. and S.S.A.; investigation, E.P., I.M.D. and S.S.A.; resources, E.P., I.M.D. and S.S.A.; data curation, E.P. and X.W.; writing--review and editing, I.M.D. and S.S.A.; visualization, X.W.; supervision, E.P.; project administration, I.M.D.; funding acquisition, E.P. and I.M.D. All authors have read and agreed to the published version of the manuscript.  
This research was funded by PID2022-140117 NB-I00 (Spanish Government) and the National Natural Science Foundation of China (No. 52308220).  
Figure 12: Magnitude (in dB) plot of the open-loop (black) and closed-loop (grey) FRFs of the laboratory-based floor structure, clearly depicting the efficacy of the proposed control scheme in imparting multimode damping.  
Data Availability StatementThe original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
The authors declare no conflicts of interest.