esa-sceva/satcom-chunk-collection huggingface dataset:
# Non-Mechanical Beam Steering with Polarization Gratings: A Review
###### Abstract  
Polarization gratings (PCs) enable a novel architecture for dynamic non-mechanical steering of light over large angles and with large clear apertures. This beam steering approach has many applications in active sensing and optical communications. In this review, we describe some of the defining characteristics of this beam steering architecture and highlight several applications of the technology.  
polarization gratings; non-mechanical; beam steering; lidar 1
## 4 Discussion
### Analysis of the Relationship between Preprocessing and Clustering Results  
In general, data preprocessing serves for clustering, and the smoothed data set makes the clustering results more accurate and closer to the actual clustering center. In the case of this paper, the value of the clustering center of the preprocessed wind speed data is smaller than that of the original data because the outliers of the original data are mostly higher than the average data. The appearance of continuous outliers may indicate the overall fluctuation of the air volume state.  
There may be errors in the clustering process in two cases: one is that when the wind volume fluctuates as a whole, at the connection of the two, data preprocessing often generates new outliers in the smoothing process, and second, when outliers appear densely, some abnormal data are not identified as outliers and can not be eliminated smoothly. When these outliers appear densely near a specific value, the algorithm will identify them as a single cluster and list them separately, which will be confused with average wind speed clustering. This is related to the robustness of data preprocessing and clustering validity function. Therefore, it is necessary to set the smoothing process at the connection of the air volume state separately to reduce the generation of new outliers and identify the intensive outliers in the data set to enhance the algorithm's applicability.
# CFD Based Non-Dimensional Characterization of Energy Dissipation Due to Verticle Slosh
## 5 Scaling of Violent Sloshing Systems
### Practical Considerations  
As a direct consequence of Table 3, using the same fluid for a reduced-scale experiment leads to differences in the Reynolds and Weber numbers to the full scale. In addition, there are no practical constraints in enforcing equality for the other \(\pi\) groups.  
\[\begin{split}\frac{Re}{Re_{fs}}&=\lambda^{1.5}\
eq 1 \\ \frac{We}{We_{fs}}&=\lambda^{2}\
eq 1\end{split} \tag{26}\]  
By way of example, for 1:5 scale (\(\lambda=0.2\)), Equation (26) imply viscous effects approximately ten times greater (\(\lambda^{1.5}\approx 0.1\)) and surface tension effects approximately twenty-five times greater (\(\lambda^{2}\approx 0.04\)) than those at full scale. An alternative could be to engineer a fluid with the same density as full scale and the appropriate scaling for viscosity and surface tension. The associated time and cost (if at all possible) however make the use of validated numerical models instead ideal.  
In practice, even exact Froude scaling is not always feasible due to budget and time constraints. As shown in Table 4, the Protospace experiment did not achieve the required \(Fr\) number. With the available materials, it was not possible to reach a closer similarity, as this would have required a bespoke cantilever design. The lower natural frequency of 3.35 Hz would have implied a greater initial displacement of the free-end, possibly leading to a geometrically non-linear oscillation of the beam. Further, the fact that the characteristic velocity achieved is higher than that required by \(Fr\) similarity could indicate that the dissipative effects due to liquid impact are overestimated experimentally if compared to an ideally Froude scaled experiment. All of the aforementioned point to the use of CFD to quantify the effect of the various non-dimensional numbers on all key physical characteristics (forces, damping, etc.) of interest. This will result in so-called non-dimensional scaling-laws, from which experimental data may be used to estimate the flow physics of the full-scale tank. This is the objective of the sections to follow and indeed a key contribution of this article.
# Performance of Communication- and Computation-Intensive SaaS on the OpenStack Cloud
## 4 Results and Discussion
### Overhead of Cloud Infrastructure
The background processes of the OpenStack service Zun for Docker containers required more CPU time and produced a larger load imbalance than those of the OpenStack service Nova for KVM-based VMs, probably because Zun processes run on nodes together with Nova processes, using part of their functionality. The CPU time required by Zun and Nova background processes can be short, but the processes have a significant influence on the load balance of the communication- and computation-intensive SaaS based on MPI. Moreover, the load imbalance grows with the number of employed MPI processes and multicore nodes.
## 5 Conclusions  
In this paper, the analysis of shielding properties of improvised head covers made of conductive materials (\"tinfoil hats\") is presented. The results of computer simulations of a human head exposed to an EM wave similar to fields generated by 5G systems are given. The power density and \(SAR\) parameters were obtained for the case where no cover was used and the model of an improvised conductive cover was applied. For the 3600 MHz band the frequency, a selective shielding structure based on vertical wires was proposed.  
In the case of the wave illuminating the face, no significant reduction in power density was observed in the area of the face and eyes for a head covered with an improvised electromagnetic shield (i.e., full metal shield). Placing the conducting surface close to the body changes the power distribution in the head region. It reduces the power density in the back side of the head, but for some configurations, it may increase power density in the eye lens region.  
In the case of conductive screens, which were tested in this study, a limited degree of reduction of the average value of energy absorbed by tissues was observed. This effect, examined with an average value of the \(SAR\) parameter, depends on the angle of wave propagation. The maximum reduction factor, equal to approximately 50%, was obtained for the metal surface shield for a wave directed to the side of the head. The application of the metal surface shield increases the maximum value of \(SAR\) compared to the unshielded case.  
To a limited extent, the simple dipole-based structure proposed in this paper can be used for frequency selective shielding of the head. For wave propagation in the horizontal plane, its performance is comparable to the tinfoil-like structure, but its design makes it much more comfortable for the user. Such shields that are not fabricated with metal foil do not limit the transfer of heat and water from the body, which is important for any material located close to the skin surface.  
Further research will be carried out to investigate different application scenarios, which will include the analysis of shielding performance in other systems such as DVB-T or DAB. Additionally, the shielding of mobile terminal radiation will be investigated.  
\begin{table}
\begin{tabular}{c  
The initial results presented here on a wire-based shield motivate additional investigations on these structures. Owing to it simple design, that is, a set of conducting wires, the shield can be manufactured with textile technologies, such as printing with conductive ink or embroidery with conductive yarns. These shielding materials could then be integrated with clothing.  
In further research, a multilayer configuration of a wire shield with rotated elements will also be developed, thereby providing shielding properties for waves of different polarizations (current design is effective only for vertical polarization).  
This research received no external funding.  
All simulation results are available upon request ([EMAIL_ADDRESS]).  
The author declares no conflict of interest.  
Human Body Model Properties  
Human body model parameters.
# Worldwide Coverage Mobile Systems for
## 2 Satellites Constellations
### Worldwide Coverage Developments  
In this section, we introduce the main features of each constellation and compare them. Worldwide mobile coverage is generating high expectation to potential users, and three main projects have been identified to compete in this market: OneWeb (Ku&Ka-band System), SpaceX (Ku&Ka-bands System), and Telesat (Ka-band System). Table 8 shows and compares the main features of the three constellations.
# Cross-Attention U-Net for Elastic Wavefield Decomposition in Anisotropic Media
###### Abstract
Recent deep learning (DL) advances have provided useful tools for seismic wavefield processing, addressing challenges in wave mode separation and vector decomposition. U-Net-based convolutional neural networks (CNNs) have emerged as a common approach. [PERSON] et al. (2021) [9] developed a U-Net model to separate qP and qS wavefields in anisotropic media. By incorporating techniques such as dilated convolutions and anti-aliasing, the model effectively handled complex anisotropic wavefields while maintaining the spatial resolution. [PERSON] et al. (2023) [10] introduced a U-ConvNeXt architecture that integrates ConvNeXt blocks--known for their enhanced feature extraction and representation capabilities--into a U-Net framework. This architecture enabled cleaner separation of P- and S-wave components, reduced artifacts, and showed computational efficiency suitable for large-scale seismic data analysis. Generative Adversarial Networks (GANs) have also been applied to wave mode separation. [PERSON] et al. (2021) [11] proposed a CycleGAN framework to decouple qP and qS wavefields in anisotropic media. This method eliminated the need for solving the computationally intensive Christoffel equation and achieved reliable separation of wave modes in highly anisotropic environments. While previous deep learning methods [9; 10; 11] have shown promise in wavefield decomposition, they do not incorporate mechanisms to explicitly capture the interactions between P- and S-wave components. To address this limitation, this study proposes a U-Net-based architecture enhanced with cross-attention mechanisms for elastic wavefield vector decomposition in anisotropic media. The model employs a dual-branch encoder to process horizontal and vertical displacement components separately, while the cross-attention enables dynamic feature exchange between them. This structure allows the network to preserve the physical characteristics of each wave mode and to focus on the most relevant features across components, thereby improving the decomposition accuracy and efficiency. The cross-attention mechanism is particularly effective in capturing the complex inter-mode relationships that are inherent to anisotropic wavefields.
###### Abstract  
The presentation of X-ray fluorescence data (XRF) assays is commonly restricted to tables or graphical representations. While the latter may sometimes be in a 3D format, they have yet to incorporate the actual objects they are from. The presentation of multiple XRF assays on a 3D model allows for more accessible presentation of data, particularly for composite objects, and aids in their interpretation. We present a method to display and interpolate assay data on 3D models using the PyVista Python package. This creates a texture of the object that displays the relative differences in elemental composition. A crested helmet from Tomb 1036 from the Casale del Fosso necropolis, Veii, Italy, is used to exemplify this method. The results of the analysis are presented and show variation in composition across the helmet, which also corresponds with macroscopic and decorrelation stretching analyses.  
bronze analysis; pXRF; photogrammetry; interpolation; PyVista; decorrelation stretching; crested helmet; Casale del Fosso
# Research on Lazy Theta+
## 6 Simulation Experiment and Analysis
### Route Planning Algorithm Comparison Experiment
#### 6.2.2 Grid Point-Based Lazy Theta* Route Planning at Different Grid Levels  
This section carries out simulation tests and analyzes the outcomes of grid point-based Lazy Theta* algorithm planning at various grid levels. The route planning utilizes the grid levels ranging from \(N=3\) to \(N=9\), and compares the path length, path cost, maximum pitch angle, and maximum turning angle of the planned route. The grid level that is most suitable for route planning is selected.  
1. Simulation  
Figure 21 illustrates the route planning results for grid point Lazy Theta* at grid levels 3 and 7.  
Figure 20: Route planning algorithm data comparison chart. (**a**) Path length comparison, (**b**) Path cost comparison, (**c**) Maximum pitch angle comparison, (**d**) Maximum turning angle comparison, and (**e**) Running time comparison.  
The route planning simulation results at other grid levels are shown in Figure 14 of Appendix B. Next, the data obtained from this simulation experiment are analyzed and compared.  
2 Analysis of results  
The experimental data are reported in Table 3, and the corresponding trend of the data change is depicted in Figure 22.  
Figure 21: Lazy Theta* route planning at different grid levels. (**a**) Grid level \(N=3\), and (**b**) \(N=7\).  
Figure 22: _Cont._  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Algorithm** & **Grid Level** & **Path Length** & **Path Cost** & **Max Pitch Angle** & **Max Turn Angle** & **Running Time** \\ \hline \multirow{6}{*}{Grid point Lazy Theta*} & 3 & 105.02 & 86.39 & 2.86 & 63.64 & 1.25 \\  & 4 & 91.26 & 74.01 & 1.99 & 36.87 & 2.02 \\  & 5 & 87.90 & 68.01 & 1.46 & 16.58 & 2.38 \\ \cline{1-1}  & 6 & 83.67 & 66.58 & 4.04 & 4.62 & 4.45 \\ \cline{1-1}  & 7 & 79.45 & 64.75 & 2.70 & 2.29 & 6.85 \\ \cline{1-1}  & 8 & 78.36 & 63.82 & 8.05 & 7.44 & 13.45 \\ \cline{1-1}  & 9 & 78.94 & 63.25 & 5.11 & 18.82 & 58.64 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Lazy Theta* route planning data of different grid levels.  
By analyzing the above experimental results, it can be seen that with an increase in the grid level, the path length and path cost of the planning algorithm show a downtrend. After level 7, the decrease is minimal, and the maximum pitch angle is the smallest at level 5, which then gradually increases. The maximum turn angle is the smallest at level 7 and then gradually increases. The running time always increases; it grows slowly at levels 3-7 and grows very quickly after level 7. The algorithm has lost its timeliness when at level 9. Since the increase in the grid level will lead to an exponential increase in the number of calculations, according to the data analysis, the path length, path cost, maximum pitch angle, and maximum turning angle can be guaranteed to be as small as possible at the seventh level, while ensuring the calculation efficiency. Therefore, grid level 7 is the most appealing grid level for route planning, this conclusion is also similar to that of the eighth level grid obtained in Experiment 1.
## 4 Experiments and Results
### Results Analysis
#### 4.3.1 Wormhole Implementation  
Wormhole initially acts in a trustworthy manner for the first five to ten seconds during an experiment. However, after this period, it starts to behave maliciously by discarding data packets received from nearby nodes instead of forwarding them to their intended destinations. As a result, the RPL-based network experiences significant degradation because the nodes continue to transmit data packets to the malicious wormhole node.
## 2 Applications of Nanotechnology in the Petroleum Industry
### Drilling and Completion
#### 2.2.2 Cement Additives  
Nanoparticles also exhibit many advantages for cement additives. Many types of NPs such as nano-clay [31], silica [29; 59], alumina [29], and magnesium oxide [60] have been studied as cement additives. Silica NP has proved to improve cement slurry stability, rheology, and hydration degree by acting as both an accelerator and mechanical properties enhancer [29; 59]. The nanoparticle can also improve flexibility, reducing the permeability and compressive strength of the cement [31; 61]. In particular, a carbon nanotube (CNT) has been shown to significantly improve cement compressive strength in HPHT conditions [32]. [PERSON] et al. [33] combined cellulose nanofibers (CNF) and graphene nano-platelets (GNP) for oil well cement additives and concluded that the addition increased yield stresses and degree of hydration, which enhanced both the flexural and compressive strength of the cement.
## 1 Introduction
In this paper, we propose an optimized scheduling cell allocation algorithm (OSCAR), which is an autonomous scheduling TSCH cell allocation algorithm based on Orchestra to address the aforementioned issues. This new design differs from Orchestra by allocating slots according to the location of the node relative to the root. The goal of this algorithm is to allocate slots to nodes according to their needs. Indeed, Orchestra determines the TSCH schedule for each node regardless of its traffic load, which can significantly affect communication latency and energy consumption. There is therefore an accumulation of packets in the queues of nodes close to the root due to their high load, which can lead to a loss of packets induced by an overflow of the buffer memory. OSCAR is characterized by the classification of nodes according to the distance from the root. Each node is assigned a class ID, representing the layer it occupies based on the geographic location relative to the root. Moreover, OSCAR provides a method to adjust the radio duty cycle of each node and improve energy efficiency by turning off the radio when no packets are received. In this work, OSCAR is validated through simulations and experimentation. The performance analysis is first carried out on a test bench composed of 11 CC2650 Launchpad nodes and then a simulation is used to evaluate its performance in a larger-scale network. The contributions of this work are summarized as follows. * A classification architecture for the nodes allowing better distribution of allocated cells according to their position. * A system to reduce the cells allocated to inactive nodes. These contributions allow an improvement of the energy and latency metrics of the nodes in the considered scenarios. The remainder of this paper is organized as follows. Section 2 provides an overview of related works. Section 3 presents the high traffic load issues in convergecast traffic and Orchestra limitations. Section 4 describes the detailed design and implementation of OSCAR. In Section 5, we evaluate the performance of OSCAR and compare it to Orchestra using a test bench and the scenarios considered. Section 6 provides a discussion of the results and future research directions. Finally, the conclusion is presented.
# Design of Typhoon Detection Downcast Device Based on Four-Arm Helical Antenna Structure
## 4 Analysis and Improvement
### HFSS Simulation Results  
Therefore, the simulation was re-run with HFSS, and the previous scheme was replaced with a dielectric-loaded printed antenna. The modeled four-armed helical antenna was swept and simulated. The antenna simulation focused on a few results, namely the return loss, voltage standing-wave ratio, antenna directional maps, and axial ratio, as shown in Figures 13-16, respectively.  
Figure 12: Overall schematic of the improved droppable sounding system.  
Figure 13: Return loss.  
Analyzing the simulation results and observing Figures 13-16, it can be seen that the resonance frequency is near 403 MHz; the return loss reaches \(-\)17.9 dB at 403 MHz; and the voltage VSWR is 1.29, which is less than 1.5. The maximum gain of the antenna's directional map reaches 6.3 dB, and it can reach a gain effect in all directions and meet the requirements of the cardioid directional map. Therefore, the performance indicators meet the requirements for use. The antenna's axial ratio is less than or equal to 3 dB, so it is a good circularly polarized antenna in the main direction. The ECC between the antenna ports is 0.007361 between 1 and 2, 0.026491 between 2 and 3, 0.006164 between 3 and 4, and 0.000762 between 4 and 1, so the coupling between the antenna elements is low. The  
Figure 16: Axial ratio.  
Figure 14: Voltage VSWR.  
Figure 15: Radiation pattern.  
dimensions of the antenna are reported as follows. The height of the spiral arm in the vertical direction is \(L_{z}=22.7\) cm, which is shortened by about 12 cm compared with the previous one; the radius of the spiral is \(r=3.2\) cm, corresponding to a reduction by about 2 cm compared with the previous one; and the volume is obviously smaller. The overall schematic diagram is presented in Figure 12, which shows that printing the four-arm spiral antenna with flexible material on the outside can avoid direct contact with space probes and improve the stability of the antenna's structure and performance.
# Application of Molecularly Imprinted Polymers in the Analysis of Waters and Wastewaters
## 3 Synthesis of Molecularly Imprinted Polymers
### Emulsion Polymerization  
Emulsion polymerization is a biphasic system [17]. The technique involves emulsifying the cross-linkers, template, and functional monomers in an aqueous solution. Stabilizers are added to the non-aqueous phase to give small, stabilized, homogeneous-sized emulsion droplets. Water-soluble redox initiator is commonly used in emulsion polymerization. The initiator decomposes under the condition of illumination or heating to generate free radicals. The functional monomers and the template molecules are first pre-polymerized, and the pre-polymerization time is generally 12 h. In order to improve the pre-polymerization effect, ultrasonic assistance can be used. Then, cross-linking agents and initiators are added to carry out a polymerization reaction under suitable conditions. Finally, the obtained polymers are eluted under appropriate conditions to elute the template molecules.  
This method forms homogeneous particle sizes but has a lot of disadvantages, such as requiring complicated conditions, which makes it difficult and expensive, showing low performance of the product, and having a water phase in the system, which might have a negative effect on the performance of the resulting polymers that are supposed to be based on favorable hydrogen bonding to the template rather than water being present in the synthesis process [18; 19].
# A Multilayer Data Processing and Aggregating Fog-Based Framework for Latency-Sensitive IoT Services
###### Abstract  
This study proposes a Client-Fog-Cloud (CFC) multilayer data processing and aggregation framework that is designed to promote latency-sensitive applications in an IoT context. The framework is designed to address the current IoT-based challenges: wide distribution, massive uploading, low latency, and real-time interaction. The proposed framework consists of the device gateway, the fog server and the cloud. The device gateway collects data from clients and uploads it to the nearest fog node. Received data will be pre-processed and filtered by the fog server before being transferred to the cloud for further processing or storage. An abduction alert fog-based service was implemented to evaluate the proposed framework. Performance was evaluated by comparing the response time and the delay time of the proposed architecture with the traditional cloud computing architecture. Additionally, the aggregation rate was evaluated by simulating the speed of bike riding as well as the walking speed of young adults and elderly. Results show that comparing with the traditional cloud, our proposal noticeably reduces the average response time and the delay time (i.e., whether the newest data or the historical data are being queried). Results indicate the capability of the proposed framework to reduce the response time by 32% and the data transferred to the cloud by 30%.  
f +
Footnote †: journal: Applied Statistics and Applications  
doi: 10.3390/app11041374