esa-sceva/satcom-chunk-collection huggingface dataset:
## The Problem Formulation
### The Complex Model with User Rate Proportionality Constraints  
Based on the practical scenario discussed above for the basic OFDM power allocation model in CRNs, instead of considering the primary interference constraints, we considered the fairness of channel resource allocation among secondary users. Then, the capacity of different secondary users needs to meet the certain rate proportional constraint, as follows [39].  
\[R_{1}:R_{2}:\cdots:R_{K}=\alpha_{1}:\alpha_{2}:\cdots:\alpha_{K}, \tag{8}\]  
\[R_{k}=\sum_{n=1}^{N}\lambda_{k,n}b_{k,n},\ \ k=1,2,\cdots,K \tag{9}\]  
\[R_{k}>0,\ \ k=1,2,\cdots,K \tag{10}\]  
In Equation (8), \(\alpha_{k}\left(k=1,2,\cdots,K\right)\) is a predefined constant, representing the rate proportional constraint that needs to be met by secondary users. Different users' capacity is defined in Equation (9), and it can be further calculated with Equation (3). In addition, Equation (10) is a non-negative constraint on users' capacity, which is implicitly indicated by Equation (8). In this model, we still strive for the maximum value of the defined function in Equation (3). The interference constraint, Equation (6), in the previous model is ignored, and we add constraints from Equations (8)-(10) to further limit the capacity of different secondary users.
# Dynamic Stall Mechanisms of Pitching Airfoil: IDDES Study Across Different Mach Numbers
## 5 Conclusions  
The aerodynamic characteristics of a pitching airfoil are investigated using the IDDES method, with a focus on airload distributions, vortex characteristics, and aerodynamic damping. The key findings are summarized as follows:  
1. At the low Mach number of 0.283, the oscillatory motion induces a pronounced stall delay. The dynamic stall is characterized by a leading-edge stall caused by strong adverse pressure gradients, resulting in rapid variations in aerodynamic loads. The formation of a secondary LEV and TEV during the pitching-down stroke contributes to significant fluctuations in aerodynamic loads.
2. At the high Mach number of 0.5, the dynamic stall is dominated by shock-induced separation. The LEV shows a distinct structure characterized by dispersed, small vortices. The loss of leading-edge suction and circulation is moderate, leading to relatively mild variations in aerodynamic loads during stall.
3. The analysis of aerodynamic damping reveals that negative damping is primarily attributed to stall delay. The convection of LEV stabilizes the pitching motion during the pitching-up stage but destabilizes it during the pitching-down stage. Notably, the pitching motion indicates greater stability at the higher Mach number due to reduced stall delay effects and the dispersed stall vortices.
4. Increasing the reduced frequency delays the aerodynamic response of the pitching airfoil, thereby postponing dynamic stall. Specifically, at low Mach numbers, increasing the reduced frequency significantly delays dynamic stall and enhances the tendency for oscillatory motion to diverge. At high Mach numbers, although the delaying effect of increased reduced frequency on dynamic stall is relatively weak, it induces a more pronounced hysteresis effect in pitching moment and contributes to greater stability in oscillatory motion.  
Data curation, S.J.; funding acquisition, G.Z. and Q.Z.; validation, F.L. and L.M.; writing--original draft, S.J.; writing--review and editing, G.Z. and Q.Z. All authors have read and agreed to the published version of the manuscript.  
This research is supported by the National Natural Science Foundation of China under Grant Number 12032012, China Postdoctoral Science Foundation under Grant Number 2024M764240, and Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions.  
Not applicable.  
Figure 27: Aerodynamic damping of airfoil pitching motion for different reduced frequencies at \(Ma=0.5\): (**a**) cycle-averaged damping; (**b**) time-resolved damping.  
**Data Availability Statement:** The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
**Conflicts of Interest:** The authors declare no conflicts of interest.
## 2 Related Work
### Classification of Multicast Protocols
MCMP (multicast core-based mesh protocol) distributes data through multiple paths centered around a core node [17]. The core node serves as the central point of the multicast tree, facilitating the establishment of multicast paths between the source and destination nodes. Each destination node receives data via the core node and utilizes multiple mesh paths for delivery. The path configuration by the core node allows efficient management of mesh paths. Hybrid multicast protocol is a technique that combines tree-based and mesh-based protocols to achieve both performance and robustness [18; 19]. Similar to the mesh-based approach, multiple paths are configured to deliver data packets to the destination. Tree-based approach is used in the routing process to ensure multicast efficiency. HMMP (hybrid multicast routing protocol) initially employs tree-based routing to establish efficient paths [20]. If a problem arises along the path, it switches to mesh-based routing to ensure stability. By combining tree and mesh structures, HMMP enables flexible path adjustments. CBT-MR (core-based tree with mesh routing) transmits multicast data centered on the core, which acts as the root node of the tree. If the transmission path is disrupted, the protocol utilizes the mesh structure to deliver data through alternative routes [21]. Core-assisted mesh protocol (CAMP) supports multicast routing by constructing a mesh structure [22]. All nodes in the network maintain tables with membership and routing information. Each member node also retains a cache set composed of previous data packets and unacknowledged membership requests. CAMP consists of mesh creation and maintenance processes. To join a multicast mesh, a node first checks its table to verify whether an existing mesh member is a neighbor. If found, the node declares its membership using a CAMP UPDATE. Otherwise, the node forwards a JOIN REQUEST to one of the multicast groups. All members of the node respond with a JOIN ACK, which propagates back to the requesting source. PAST-DM (progressively adapted sub-tree in dynamic mesh) was proposed to avoid the inefficiency caused by the generation of a fixed virtual mesh in the AMRoute technique, and a periodic virtual mesh reconstruction method was applied [23]. That is, it collects information about all nodes in the multicast group and uses it to collect the entire topology information of the virtual mesh. Then it creates several subgroups, creates a subtree in each subgroup, and delivers data to child nodes by unicast.
## 5 Experiments and Discussions
### Comparisons with Related Work  
In this section, we make some comparisons with other compressed wideband spectrum sensing hardware, mainly focusing on the performance and actual hardware complexity. As for performance, we compare with the first reported practical hardware that performs sub-Nyquist sampling based on MWC in [20]. From Table 2, we can see the most significant difference is compression ratio, that means we make it possible to use one low rate ADC to detect the whole sensing bandwidth. Also, the signal  
Figure 16: (**a**) The input signal and (**b**) Samples after LPF. (**c**) Detected power spectrum and (**d**) probability of detection.  
bandwidth is a little lower than that of MWC, which means the estimation accuracy improves a little to some extent.  
Another comparison is concerned about hardware complexity in actual design. As shown in Table 3, SCMWC has a big advantage over MWC. In detail, SCMWC only needs one frond-end and most importantly, in designing the periodic sequences generator, we introduced to use GTX, which can highly reduce the complexity and size of the hardware. However, in MWC, two boards is used. One is called digital board aiming to produce sequences with a lot of shift registers (SR) on it. Another one is called analog board with the purpose of power allocation, mixing, low-pass-filtering and so on. It is apparent that SCMWC based spectrum sensing hardware has a simpler structure which makes it more suit for CR systems.
# Microwave Photonic Frequency Conversion Based on a Wavelength Swept Laser
## 4 Conclusions  
We have proposed and experimentally demonstrated an all optical new microwave photonic conversion interrogation with flexible tunability and a simple structure based on a WSL. The frequency conversion system uses the combination of a WSL and a dispersion control device to realize the up-down conversion of the input signal. In the proposed frequency conversion system, the WSL is used as the optical carrier to sample the input signal. We simulated the influence of the WSL to the conversion system and found that the input microwave signal can be arbitrarily converted up and down by adjusting the value of the dispersion control device. As shown in the experiment, the 5 GHz microwave signal can be up-converted to 5.577 GHz and down-converted to 4.936 GHz by switching the sign of the chirp rate and adjusting the length of the SMF array. The 16 GHz high frequency microwave signal can be up-converted to 16.62 GHz. The conversion spectrum has multi-longitudinal modes due to the low duty cycle of the WSL pulse. The conversion performance could be further improved by introducing a WLS with a high duty cycle.  
Writing--original draft preparation, investigation, validation, Y.K.; writing--review and editing, methodology, Y.C.; validation, formal analysis, L.W. and G.W.; conceptualization, methodology, X.F.; project administration and supervision, X.F. and B.-O.G. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China (NSFC), (No. 61771221, No.61860206002 and No. 61701193) and Basic and Applied Basic Research Foundation of Guangdong Province (2019A1515110946).  
The authors declare no conflict of interest.
# Comprehensive Survey on VLC in E-Healthcare: Channel Coding Schemes and Modulation Techniques
## 3 Modulation Techniques for VLC in E-Healthcare Systems
### Modulation Techniques for MIMO Approaches in VLC  
Multiple-input multiple-output (MIMO) techniques have been shown to significantly enhance the data rate and spectral efficiency in VLC systems, which is particularly beneficial in healthcare environments where multiple devices may need to communicate simultaneously [56]. In VLC, MIMO uses multiple LEDs and photodiodes to transmit and receive data across multiple channels, effectively multiplying the available data throughput. For example, spatial multiplexing (SMP) has been used to improve performance in VLC systems using imaging receivers, resulting in significant improvements in signal reception and data transmission [57; 58; 59]. These techniques are particularly useful in healthcare settings where large amounts of data, such as high-resolution medical images, need to be transferred quickly and efficiently.  
Additionally, the use of imaging receivers with specialized lenses, such as convex or fish-eye lenses, plays a crucial role in improving the performance of MIMO VLC systems. These lenses focus the incoming light more precisely onto the photodetectors, which helps maximize the received signal's intensity and reduce signal loss. By using these lenses, the light beam can be better concentrated, allowing for more efficient use of the available light and improving the overall quality of the received signal. This is particularly beneficial in environments where light reflections or diffusions might otherwise scatter the signal, such as in healthcare settings where equipment and personnel may obstruct direct line-of-sight communication. Specialized lenses enable the VLC system to maintain high performance even in challenging conditions, ensuring that data such as patient monitoring information or medical imaging can be transmitted reliably across the hospital or clinical environment [58; 59].  
A study specifically examining GSM, QCM, and DCM modulation techniques with convex lens-based image receivers demonstrated substantial improvements in SNR and BER when using these specialized lenses [60]. The lenses' ability to focus light more accurately onto the photodetectors enhanced signal reception and contributed to more stable data transmission, especially in multi-user scenarios where multiple VLC systems operate simultaneously. These improvements in SNR and BER are critical for applications that require high data integrity and minimal interference, such as real-time patient monitoring or the transfer of large medical datasets like MRI scans or X-rays. By using convex or fish-eye lenses, the system can effectively handle larger volumes of data with fewer errors, ensuring reliable and efficient communication in complex healthcare environments. This highlights the potential of integrating imaging receivers with advanced lens technology, to optimize further the performance of MIMO VLC systems in medical and other high-demand settings.
# Calculation of Intracoronary Pressure-Based Indexes with JLabChart
## 3 Results and Discussion
Irregular cycles were found in nine patients (data points shown in Figure 12). Furthermore, for these patients, new values of iFR were calculated (indicated as iFR*) removing the irregular cycles. Figure 12 shows the correlation plot and the Bland-Altman plot generated for iFR, considering all the cycles, and for iFR*, considering only the regular cycles, respectively. The experimental results show that the correlation between the values measured with JLabChart and the commercial software was higher when the irregular cycles were eliminated from the dataset (iFR: \(R_{p}=0.9784\), \(R_{IC}=0.9876\); iFR*: \(R_{p}=0.9814\), \(R_{IC}=0.9898\)). Finally, the tool was tested with synthetic vessels generated using the Comsol [43] software tool. The vessel images were designed with several known measures regarding stenosis, blood flow pressures, and so on. Figure 1 shows one of the 55 Comsol syntetic images used to measure iFR and FFR values. The JLabChart was used on such images, which simulated patients, and the resulting measurements demonstrated that the tool is reliable in terms of measurement and evaluation of iFR and FFR even on synthetic images. Indeed, we performed measurements using both JLabChart and Comsol (latter as correct and. thus, used as the reference) obtaining an average error of 0.05661818 and a standard deviation of 0.07071159, thereby proving JLabChart's reliability. Figure 12: Correlation plot and Bland–Altman for iFR and iFR*. (**a**) Correlation plot for iFR. (**b**) Bland–Altman plot for iFR. (**c**) Correlation plot for iFR*. (**d**) Bland–Altman plot for iFR*. The performance improved after the exclusion of the irregular cycles. The correlation plot showed an increased correlation coefficient \(R_{p}\) and intraclass correlation coefficient \(R_{IC}\) nearer to one. By the Bland-Altman plot, the values of the confidence interval were adjacent to the mean value, and the confidence interval was limited, which implies that the percentage differences are constant and the difference in the values is moderate.
# A Spatial 4-DOF Laser Collimation Measurement System
## 6 Conclusions  
The 4-DOF measuring system in this paper uses the laser collimation method, which has the characteristics of miniaturization, a low cost, and high precision. Three CMOS were used, which can reduce the crosstalk caused by the results of the distance measurement and angle measurement. According to the system design scheme, an engineering prototype was built to carry out experiments with a target measured distance of 500 mm. The measuring range in the X direction was \(\pm\)2.0 mm, the measuring range in the Y direction was \(\pm\)1.6 mm, the linearity in the X direction was better than 0.99997, and the linearity in Y direction was better than 0.99999. The stability of the distance measurements in the X direction reached  
Figure 18: Article’s technical route.  
\(1.11\) um and the stability in the Y direction reached \(0.94\) um. The pitch angle measuring range in the X direction was \(\pm 1.9^{\circ}\); the yaw angle measuring range in the Y direction was \(\pm 1.4^{\circ}\); the linearity of the pitch angle in the X direction was better than \(0.99987\); the linearity of the yaw angle in the Y direction was better than \(0.99998\); the stability of the pitch angle in the X direction was \(0.91\) arcsec; the stability of the yaw angle in the Y direction was \(0.90\) arcsec. At present, the index meets the requirements of the optical load ground test.  
The system has good reference value for machine tool precision measurements and other industrial fields, and is also suitable for high-altitude space precision measurements of optical load.  
Conceptualization, H.J. and L.J.; methodology, K.Z. and C.H.; software, H.J.; validation, H.J., L.J. and C.H.; formal analysis, H.J. and K.Z.; investigation, H.J. and L.J.; resources, C.H., K.Z. and L.J.; data curation, H.J.; writing--original draft preparation, H.J.; writing--review and editing, H.J., R.Z., K.Z. and C.H; visualization, R.Z.; supervision, R.Z.; project administration, H.J. and L.J.; funding acquisition, C.H. and K.Z. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding authors.  
The authors declare no conflicts of interest.
## 3 Results and Discussion  
### Adsorbent Characterisation  
#### 3.1.1 X-ray Diffraction (DRX)  
The crystalline structure of ACSCGs-activated carbon and CAC was characterised by DRX analysis. The diffractograms are shown in Figure 2. In general, the XRD spectra of the different samples are amorphous; nevertheless, we observe a weak crystallinity in the range from 20 to 50\({}^{\circ}\) for the two activated carbons. We note that the spectra show the same appearance and present the same diffraction peaks. On the other hand, we observe after activation of the SCGs the appearance of new peaks at 29.6\({}^{\circ}\) and at 43.3\({}^{\circ}\), the displacement of the main peak from 19.6\({}^{\circ}\) to 24.3\({}^{\circ}\), and the decrease of its intensity. This is attributed to the structural modifications resulting from the activation, indicating the formation of a non-uniform lattice strain in the activated carbon [63, 64] and showing that the activation process was well undertaken. The peaks at 29.6\({}^{\circ}\) and at 43.3\({}^{\circ}\) are attributed to the (002) and (100) reflections of graphite, respectively [65, 66].
# Edge-Driven Multiple Trajectory Attention Model for Vehicle Routing Problems
## 2 Related Work  
### Traditional Methods  
Traditional methods for solving VRPs can be broadly divided into exact methods, approximation methods, and heuristic methods. Exact methods, such as Branch-and-Bound [28] and Concorde [29], are prominent solvers specifically designed for the TSP. Although these methods guarantee optimal solutions, they become computationally expensive for large-scale problems due to their exponential time complexity. In contrast, heuristic methods are commonly employed for their practical efficiency, delivering satisfactory solutions within reasonable time constraints. [PERSON] et al. [30] propose a genetic algorithm combined with simulated annealing to address the optimal waiting time and path planning problem, enhancing solution quality for time-varying networks. [PERSON] et al. [31] propose an improved genetic algorithm based on fuzzy C-means clustering to solve the vehicle routing problem with capacity constraints. [PERSON] et al. [32] propose a mixed integer programming formulation and an ant colony optimization algorithm to solve the vehicle routing problem with a drone (VRPD), achieving significant cost savings and efficiency improvements in parcel delivery. [PERSON] et al. [33] propose a dynamical artificial bee colony algorithm to address the VRPD, achieving new best solutions and demonstrating promising advantages in operational cost minimization. However, these methods often depend on domain-specific customization and expert knowledge [19], and their lack of a solid theoretical foundation can lead to unpredictable performance, making it challenging to generalize across different problem contexts.
# Optimization of Acoustic Communication Links for a Swarm of AUVs: The COMET and NEMOSENS Examples
## 5 Physical Layer
### Optimization Evaluation  
For assessing the performance of this optimization method, we compared its results with a genie-aided modem. This latter approach selects the parameters pair \((N_{\text{sub}},T_{\text{CP}})\) which leads to the minimum measured bit-error rate (BER). For this case, we utilized the previously described modem. All the tested cases considered a D-BPSK constellation and a sampling rate \(f_{s}=192\) kHz. We utilize the Watermark simulator [34; 35] for replaying the underwater channel. This simulator provides real measurements of the channels, which have a time-varying impulse response. Performance is first evaluated without channel coding and without noise in the channel. Results with coding and noise are then discussed in Section 5.5. The Matlab program was utilized for performing all these simulations.
# A ResNet1D-AttLSTM-Based Approach for Ship Trajectory Classification
###### Abstract  
To improve the feature extraction method for ship trajectories and enhance trajectory classification performance, this paper proposes a ship trajectory classification model that combines a one-dimensional residual network (ResNet1D) and an attention-based Long short-term memory network (AttLSTM). The model aims to address the limitations of traditional methods in extracting feature patterns jointly represented by non-adjacent local regions in ship trajectories, optimized through the introduction of a self-attention mechanism. Specifically, the model first utilizes the ResNet1D module to progressively extract implicit motion pattern features from local to global levels, while the AttLSTM module captures temporal sequence features of ship trajectories. Finally, the fusion of these two types of features generates a more comprehensive and rich spatiotemporal motion feature representation, enabling accurate classification of five types of ship trajectories, including towing vessels, fishing vessels, sailing vessels, passenger ships, and tankers. Experimental results show that this model excels on extensive real-world trajectory datasets, achieving a classification accuracy of 89.7%, significantly outperforming models relying solely on single feature sets or lacking integrated attention mechanisms. This not only validates the model's superior performance in ship trajectory classification tasks but also demonstrates its potential and effectiveness for practical applications.  
Keywords:ship trajectory classification; residual neural network (ResNet); long short-term memory network (LSTM); self-attention mechanism +
Footnote †: journal: Applied sciences