esa-sceva/satcom-chunk-collection huggingface dataset:
# Axial-Symmetric Diffraction Radiation Antenna with a Very Narrow Funnel-Shaped Directional Diagram
## 5 Conclusions  
The paper briefly describes rigorous models of the method of exact absorbing conditions, enabling the study and analysis of the effects of diffraction radiation (wave analogs of the effects of SPR) in axially symmetric electrodynamic structures such as 'a finite segment of an open radial guiding line installed near a finite concentric reflective or semitransparent grating'. These mathematical models, implemented in a complex of original authentic algorithms and codes, were used to study the physics of the processes of transformation of eigen surface waves of the corresponding open waveguides into waves propagating infinitely far in free space. The primary attention was paid to emitters--prototypes of practical antennas, capable of forming a funnel-shaped radiation pattern with a very narrow 'throat'. The results discussed in the paper confirm the possibility to construct such well-directed antennas, implementing the wave analog of the Smith-Purcell coherent radiation. The presented results also prove the correctness of our ideas about how, in what way, and due to what physical principals the proposed for implementing non-standard transformations of electromagnetic waves structure should work. It has been shown how and within what limits the characteristics of the corresponding devices can be changed in a controlled manner. In particular, this may be performed by the optimal selection of the parameters of the open waveguide line (due to the change in the parameters of the surface waves directed by such a line) and/or by choosing the geometric and material parameters of the grating, as only gratings propagating spatial harmonics determine all the features of the radiation field.  
Conceptualization, Y.S. and S.S.; methodology, Y.S.; software, M.S.; formal analysis, N.B. and A.B.; investigation, Y.S., S.S. and N.Y.; writing--original draft preparation, Y.S. and N.Y.; writing--review and editing, Y.S. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan, grant number AP08855557. And The APC was funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan too.  
Not applicable.  
The authors declare that there is no conflict of interests regarding the publication of this paper.
# A Smart Collaborative Routing Protocol for Reliable Data Diffusion in IoT Scenarios
## 2 Related Work
### Routing Protocols Based on Geographic Location
Although the EBGR protocol showed longer network latency, it was still acceptable in the wide-area agricultural environments. The simulation results illustrated that the proposed protocol had less computational complexity. Unlike the terrestrial WSN, radio waves cannot be applied in the communications of Underwater Wireless Sensor Network (UWSN). However, the acousticchannels can be used for it. In [22], three main location-based routing protocols (i.e., VBF, HH-VBF and FBR) in UWSN were compared on the basis of data delivery ratio, the quantity of live nodes, end-to-end delay and total energy consumption. For the end-to-end delay and data delivery ratio, the HH-VBF was superior to other protocols. In terms of the alive nodes quantity and total energy consumption, the VBF was outperforming the other two protocols. [PERSON] et al. [23] introduced a novel position-based routing protocol named Speed Up-Greedy Perimeter Stateless Routing (SU-GPSR) protocol in WSN. The main idea was to combine the speed-up mode with the greedy mode to provide a solution in data transmission. Moreover, the proposed next hop selection could be applied to both still and mobile nodes considering energy consumption. Finally, the end-to-end delay, hop counts and packet delivery rate were optimized respectively.
## 2 Design and Methods
### Deep Learning Surrogate Model  
The data generated in Ansys, namely the resultant equivalent stress, were exported to a comma-separated value (CSV) file. These data were then imported into MATLAB (Version 24.2.0.2806996 (R2024b), MathWorks, accessed on 5 April 2024) as a table, where a DL network was trained to predict the equivalent stress distributions over the geometry based on the X-, Y-, and Z-coordinates of the mesh. A linear regression algorithm was used to develop the neural network to ensure continuity over the entire geometry. The model architecture included the following:  
Figure 7: Loading scenarios for gait analysis. Model was subjected to four loading scenarios: (1) loading phase (foot flat), (2) terminal stance (heel off), (3) stair ascent, and (4) stair descent.  
* Input: X-, Y-, Z-coordinates of the mesh;
* Hidden layers: fully connected layers with ReLU activation;
* Output: predicted stress values;
* Training: 80% of the data were used for training, 10% for validation, and 10% for testing.  
The network was iterated for 200 epochs, with a sampling size of 10,000 entries for the table.  
Once the network was trained, the test data were used to evaluate the mean squared error (MSE) of the network's predictions. If the MSE calculated from the data was less than 5%, the model was considered sufficient for use in other cases. However, if the MSE was greater than 5%, the network was retrained. Once the network achieved an MSE below 5%, it was deemed ready for use as a DL-FEA surrogate to calculate the equivalent stress distributions over the entire geometry. The diagram in Figure 8 summarizes this process.
# Capturing a Space Target Using a Flexible Space Robot
## 3 Contact Model  
This section presents the contact model between the robot and the target. Today there are two main methods to analyze impact and contact between contact objects. One is the momentum method. In this method, impact impulse is used instead of contact force in impact analysis. The contact process is considered as a discontinuous process divided into two phases: pre-contact and post-contact. Comparatively, in the other method, the contact process is considered as a continuous process, and contact force acts on the contact objects until they separate. Compared with the first method, the second method gives a better description of the real contact behavior. More importantly, the second method can be applied to complex contact problems such as multi-object contact. The Hertz contact theory is a typical example of the second method and has had many applications in practice [35].  
In this paper, the Hertz contact theory is used to model the contact dynamics of the robot system, and computer graphics are employed to detect the interference between the end effector and the target object. For simplicity of description, the target object is modeled as a rigid cylinder, as shown in Figure 1, it may simulate the handle of a target spacecraft or other structures with a similar shape which are captured.
## 3 General Opportunities, Challenges, and Applications
### Main Challenges
#### 3.3.1 Communication and System Heterogeneity  
Communication is fundamental to every distributed system, including federated learning (FL). In the age of big data and artificial intelligence, FL stands out due to its ability to protect data privacy while minimizing the need to transfer and process massive volumes of data, all while maintaining the advantages of machine learning. Unlike typical centralized training, FL uses collaborative model training to share parameter updates. However, its wider implementation is hampered by the significant communication and processing overheads resulting from the high computing demands and huge parameter updates sent. This problem is particularly acute in Internet of Things (IoT) applications, where edge and fog devices frequently have limited computing power, bandwidth, and data capacities. This study aims at filling this gap by providing a number of recent works conducted to improve the communication and/or computational efficiency in FL [6; 44].  
Communication costs are the primary restriction, and demonstrate a 10-100\(\times\) reduction in communication rounds compared to synchronized stochastic gradient descent. However, FL operates in an environment marked by diverse systems and protocols. Managing the complicated process of interaction within such a heterogenous landscape is challenging. The variabilities in storage, processing power, and communication capabilities among federated components add to this complexity. Each system might have its own limitations, capacities, and peculiarities, which can affect the overall synchronization and efficiency. While solutions like model compression and decentralized training [45] provide some benefit, implementing these solutions seamlessly across a diverse network remains a challenge.
# Cutting Force Estimation Using Milling Spindle Vibration-Based Machine Learning
## 2 Relationship Between Tool Wear and Cutting Force  
As tool wear progresses, cutting forces typically increase; however, relying solely on changes in cutting forces to precisely determine the optimal timing for tool replacement presents inherent limitations. While an increase in cutting forces indicates greater cutting resistance caused by wear, these variations are influenced by complex interactions between tool conditions and machining parameters, making quantitative evaluation challenging.  
Furthermore, changes in cutting forces due to tool wear often display non-linear characteristics, complicating accurate estimations of tool wear based solely on simple fluctuations in force magnitude. To address these challenges, this chapter aims to experimentally and quantitatively investigate the relationship between changes in cutting forces and machined surface quality, thereby establishing a foundation for determining the optimal timing for tool replacement.
## 5 Conclusions  
A VLC system for V2V communication by modulating the taillights of a car using an improved version of the UDPSOOK modulation method by [PERSON] et al. [3] is proposed. On the receiving side of the system, a DSLR camera is used for capturing the scene with 30 FPS. As the system is intended to be used in traffic, where there is a distance of 30 m to 80 m between two cars, i.e., the transmitter and receiver, adjustments to the original UDPSOOK modulation methods were necessary, to optimize it in terms of applicability and bit error rate. With the adjustment of the chosen phase of the modulation signal of \(\pi/2\) and \(3\times\pi/2\) for the inverted signal, it was possible to modulate a light source without visible flickering. This first improvement was crucial for this application, as flickering would distract other drivers on the road.  
In this system, the first step on the receiving side is to detect the car in front and its taillights to recognize the states of the taillights. As it is difficult to decide exactly which pixel in the image needs to be analyzed to see the taillight state, a region of interest containing each taillight is selected. However, the problem is that in such a region the captured taillight might be ON, OFF or have an ambiguous state. Such an ambiguous state occurs if the taillight in the camera's view is captured at the exact time when its state is changed. This results in an image where, e.g., the top of the taillight is ON and the bottom  
Figure 18: Error distribution for different qualities of synchronization.  
of the taillight is OFF. Such a scenario always results in bit errors and hence, the modulation method was optimized to get as few as possible bit errors caused by such ambiguous states in the communication. The best bit error rate of 0.48% was achieved by setting the exposure time to 1/4000 s, the pulse width ratio to 47.6% and the modulation frequency to 120 Hz using the best possible loose synchronization. This is a major improvement compared to the results of previous research that was publish in [1]. In this first concept of the visible light vehicle-to-vehicle communication system using modulated taillights, an average BER of 3.46% was achieved. This means by optimizing the modulation method, the proposed system now is not only applicable for the usage in traffic, but also the BER is reduced by 86%.  
The proposed system is not quick enough to transmit time-sensitive data between two cars driving on the road. However, the optical data transmission using a camera as receiver is very hard to manipulate for a third party and therefore could be used to verify the identity of another car. This information can be used to establish a fast and encrypted connection between two cars driving in succession, where, e.g., 5G or 802.11p is used for the main communication channel, and the slow but secure optical channel is only used to exchange data for the identity verification of the cars.
## 2 Analytical Model and Equations
### Theoretical Verification of Automatic Correction
When \(Q_{0}\
eq 0\), \(N_{1}\
eq 0\), \(N_{2}\
eq 0\), the corresponding length of cantilever beam is \(L_{0}\). To make it satisfy the Equation (16), \(Q=0\), indicating that the state is the critical state for the change of \(Q\) direction. 3. When \(Q_{0}\
eq 0\), \(N_{1}\
eq 0\), \(N_{2}\
eq 0\), if its corresponding cantilever beam length \(L>L_{0}\), it shows that the cantilever beam line stiffness decreases, resulting in the increased deformation, or obvious load and unload effect; let \(Q_{0}+N_{1}\sin\alpha+N_{2}\sin\beta>P\), according to Equation (16), \(Q>0\), showing that the direction of the \(Q\) is right. 4. When \(Q_{0}\
eq 0\), \(N_{1}\
eq 0\), \(N_{2}\
eq 0\), if its corresponding cantilever beam length \(L<L_{0}\), showing that the stiffness of the beam line increases, leading to the reduced deformation, thus reducing the unloading effect; make \(Q_{0}+N_{1}\sin\alpha+N_{2}\sin\beta<P\), according to Equation (16), \(Q<0\), showing that the direction of the \(Q\) is left. Based on the above analysis, when the cantilever beam is under the horizontal load \(P\), the direction of the top shear force is mainly related to the initial tension of the structure and the linear stiffness of the cantilever beam. When the initial tension or the structure line stiffness changes, all of the above four situations may occur. Accordingly, only when the direction of \(Q\) changes to the critical state, the horizontal impact on tower deviation can be eliminated. By comparison, the active control method can achieve the real-time dynamic adjustment of tower deviation to the target state, making tower under the condition of changing the horizontal force reach a critical state through the feedback control system, eventually eliminates the impact of horizontal force, and keeps the structure in vertical state. Therefore, the feasibility of the active control is theoretically proved.
# A Location and Velocity Prediction-Assisted FANET Networking Scheme for Highly Mobile Scenarios
## 4 Network Clustering
### \(k\)-means+ Clustering Algorithm  
Since the \(k\)-means algorithm is sensitive to the initialization of the centroids, we utilize the \(k\)-means++ to overcome this drawback. The \(k\)-means++ algorithm mainly contains the following three steps [23].  
1. Choose a node from the set \(\mathcal{X}\) randomly as the centroid of the 1 st cluster, marked as \(c_{1}\).
2. For a node marked as \(n_{i}(i\in\mathcal{X})\), calculate its distance from the nearest previously chosen centroids and obtain the distance vector. It can be expressed as \[D(i)=\min_{k\in\mathcal{K}}\{D(i,k)\},\] (16) where \(\mathcal{K}\) is a set containing all previously chosen centroids.
3. Choose a node \(n_{j}\in\mathcal{X}\) as the centroid of next cluster with a probability of \[P(j)=\frac{D^{2}(j)}{\sum_{n_{j}\in\mathcal{X}}D^{2}(j)},\] (17) This formula implies that the probability of a node being selected as the next centroid is highly related to its separation from the nearest, previously chosen centroid.
4. Repeat Step 2 and Step 3 until \(K\) centroids have been determined.
5. Use the \(k\)-means algorithm to cluster all nodes and obtain the centroids.
6. For the \(k\)-th cluster, search a CM from the assigned CMs \(\mathcal{X}_{k}\) with the nearest distance to the centroid \(c_{k}\) and take it as the CH, i.e., \[CH_{k}=\arg\min_{k\in\mathcal{X}_{k}}\{\|\mathbf{p}(k)-c_{k}\|\}.\] (18)  
It is noteworthy that the distance between any two nodes, namely \(n_{i}\) and \(n_{j}\), during the clustering procedure not only depends on their relative positions but also is related to their relative speed differences, which can be expressed as  
\[D(i,j)=\|\mathbf{p}_{i}-\mathbf{p}_{j}\|+\Delta t\|\mathbf{v}_{i}-\mathbf{v}_{j}\|, \tag{19}\]where symbol \(\|\cdot\|\) calculates the 2-norm, i.e., the 3-D Euclidean distance. The second part of this equation indicates a possible separation distance at a short update interval \(\Delta t\). Hence, this equation implies that a higher speed difference should not be ignored even under the case of close position distance.  
As for the convergence condition, it contains the judgment of maximal iteration and CH position difference, which proceeds as follows: (1) If current iteration reaches the pre-set maximal iterations, then it will stop regardless of the position difference. This condition is set to cater to the requirement of low computational time for highly mobile scenarios. (2) If the cluster head position differences between the pre-iteration and current iteration are smaller than the given threshold, then it will stop.
# Data Compression with a Time Limit
## 5 Conclusions  
In this paper, we first explore a framework (closely aligned with the one proposed in [1]) for determining the optimal selection of compression algorithms in order to achieve the best allocation of computing resources in large-scale data storage environments. This approach is experimentally validated through the lossless compression of one-dimensional and two-dimensional data. We then extended this technique for lossy compression, and we successfully tested it on the lossy compression of bidimensional data.  
The results of our experiments demonstrate that the proposed framework is highly efficient for compressing large quantities of images within a specified time budget. Across all input scenarios, it was observed that, compared to a traditional strategy, the optimized compression approach, that is based on identifying an optimal combination of algorithms, effectively eliminated idle periods in the system. By doing so, it maximized the use of the allocated time budget, leading to more efficient processing.  
The algorithm performed reliably with all types of images (both animated and non-animated), regardless of whether the scenes were similar or varied. Additionally, the algorithm was evaluated in scenarios where the time budget was set very close to the runtime of one of the two optimal compression algorithms. Even in these cases, the algorithm performed correctly, distributing files among the compressors to ensure that the entire time budget was utilized effectively.  
However, a key challenge remains in calculating the metrics of individual algorithms. If we assume that this activity can be performed once for a document and then the metrics can be reused for all future similar documents, then the proposed framework remains highly effective. On the other hand, if metrics have to be recalculated for each new document, it will be necessary to develop a method to estimate them as quickly as possible, which warrants further investigation.  
Future research will focus on extending the algorithm's experimentation to other types of digital data, such as medical or hyperspectral images (see [22, 23]), or even to hybrid situations in which different types of digital data must be compressed together: sometimes using lossless compression, and at other times using lossy compression. The ability to handle a broad range of data types in an efficient and adaptive manner will be a valuable addition to this framework. In addition, as in [4], it could be interesting to study a mechanism that involves frequent sampling of the data stream to detect changes in its characteristics.  
This work was partially supported by project SERICS (PE00000014) under the NRRP MUR program funded by the EU--NGEU.  
No new data were created or analyzed in this study. Data sharing is not applicable to this article.  
The author wishes to thank his students [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON] who developed, at different times, preliminary versions of the software that was used for the experimental tests in this paper.  
The author declares no conflict of interest.
# An Improved Dual-Sorting NSGA-II Method for Optimal Radiation Shielding Design
## 4 Conclusions  
The NSGA-II-based radiation shielding optimization method effectively constructs the Pareto front; however, it experiences a decline in evolutionary pressure beyond the early stages of evolution, primarily due to difficulties in selecting optimal solutions. To overcome this limitation, this study introduces a novel fitness value and its corresponding crowding distance, leveraging the concave function properties of the Pareto front in radiation shielding optimization. Accordingly, a dual-sorting NSGA-II method is proposed, integrating both \(O\)-based and \(R\)-based sorting mechanisms to refine Pareto front identification. This approach retains the \(R\)-based sorting method's ability to preserve a diverse solution set while significantly enhancing efficiency in locating optimal solutions.  
To assess the effectiveness of the dual-sorting NSGA-II method, this study applies it to a simplified multilayer flat plate shielding optimization problem and compares its performance against the classical NSGA-II method. Repeated computational experiments demonstrate that the dual-sorting NSGA-II method markedly improves the selection probability of optimal solutions. As a result, it achieves superior optimization efficiency, notably in the middle and late evolutionary stages, with performance improvements exceeding 40% in certain phases. This enhanced efficiency underscores the practical advantages of the dual-sorting NSGA-II method in radiation protection design, enabling a more effective determination of shielding configurations while reducing computational time and resource consumption.  
Conceptualization, Z.C.; methodology, S.C.; validation, Y.L.; formal analysis, S.C. and Y.Y.; investigation, W.J. and P.H.; writing--original draft preparation, S.C.; writing--review and editing, Z.C. and T.P.; visualization, S.C. and Y.L. All authors have read and agreed to the published version of the manuscript.  
This study is funded by Institute of Nuclear Physics and Chemistry. Funding number is not available.  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
The authors declare no conflict of interest.