esa-sceva/satcom-chunk-collection huggingface dataset:
## 2 Numerical Calculation Model of Four-Tooth Three-Stage Brush Seal  
### Geometric Structure and Calculation Domain  
The brush seal consists of an annular high-pressure side baffle, a brush bundle, and a low-pressure side baffle welded to the outside. The brush bundle is formed by a fine high-temperature alloy filament tilted in a circumferential direction. The inner side of the brush bundle adheres to the rotor, and the high-pressure gas flows through the brush bundle to produce a pressure drop to achieve the seal. The brush bundle exhibits flexibility, allowing it to absorb the radial runout of the rotor and maintain stable sealing performance [21]. Multi-stage brush seals and grate-brush combination seals are gradually being designed and applied to aircraft engines to achieve sealing under megapascal differential pressure conditions. The four-tooth three-stage brush seal described in this paper adopts a one-piece manufacturing method, in which the three-stage brush seal and the four-stage beveled grate-tooth seal are axially combined and welded together, as shown in Figure 1. The seal has compact dimensions, a high pressure limit, and good sealing performance. Because the geometric model has asymmetry, the computational domain is selected as the arc segment region with a 1\({}^{\circ}\) circumferential direction, removing the solid region and the brush bundle welding region, and the cross-section schematic of the topological fluid domain is shown in Figure 2.  
Figure 1: Schematic diagram of four-tooth three-stage brush combination seal structure.  
The structural parameters of the combined seal prototype (basic type) used in this paper are as follows: an inside diameter of 138.0 mm, an outside diameter of 158 mm, an axial thickness of 32.0 mm, a thickness of the brush bundle of 2.2 mm, an axial distance of the brush bundle of 1.8 mm, a height of the backplane of the brush bundle of 1.0 mm, an inclination angle of the grate teeth of 50.0\({}^{\circ}\), a distance of the grate teeth of 2.0 mm, and a radial clearance at the top of the grate teeth of 0.3 mm. To investigate the influence of different structural parameters on the unevenness of the interstage pressure drop and sealing characteristics, the axial distance of the brush bundle, the thickness of the brush bundle, the radial clearance of the brush bundle, the height of the backplate, and the number of teeth, the radial clearance of the grate teeth, and the inclination angle of the grate teeth of the combined seal were modified; a series of sealing geometrical models with different structural parameters were composed; and the list of the specific parameters is shown in Table 1.
## 4 Discussion
[2], which showed notable differences between the right and left upper impacted canines in terms of their angulation with the midline and occlusal plane. Regarding the inclination angle of the canine, we observed that canines with a greater buccopalatal diameter showed a greater angulation relative to the occlusal plane. In this way, we observed that lateral incisors with a shorter root and crown, as well as a smaller mesiodistal size, presented a greater angulation of the canine in relation to the palatal suture. Similarly, we noted a greater angulation of the canines in reference to the midline in cases where the root and crown length of the lateral incisors was shorter. [PERSON] et al. [47] discovered that the distance from the tip of the canine cusp to the occlusal plane became the strongest predictor of maxillary canine impaction. In our study, we found that the canines were larger when located in sector 1 compared to the lateral incisor. [PERSON] et al. [31] suggested that the angulation of the canine towards the lateral incisor is a key predictor of canine impaction, highlighting the importance of assessing this factor in future research endeavors. [PERSON] et al. [30] concluded that the volume of the lateral incisor, the mesiodistal and buccolingual width of the lateral incisor crown and root, the total length of the lateral incisor, and the lateral incisor angulation to the midline and the axis of the adjacent canine were found to be strong predictors of maxillary canine impaction. Based on the results, the null hypothesis stating that there is no association between the spatial position of the impacted maxillary canine and the dimensions or resorption of the adjacent lateral incisor was rejected. The findings demonstrated significant associations between canine position and the morphology of adjacent lateral incisors, thereby supporting the alternative hypothesis. One of the main limitations of this study is its cross-sectional design, which allows for the identification of associations but does not establish causality. This inherent limitation suggests that any relationships observed between the positioning of the maxillary canine and the dimensions of the lateral incisor should be interpreted with caution. Longitudinal studies are necessary to explore causal relationships more thoroughly and to track changes over time. Additional limitations include the fact that the sample size calculation was done for a different outcome, as this study shows secondary data of a larger project. This may have limited the capacity to obtain statistically significant differences. Further studies are needed to determine the relationship of the maxillary lateral incisor in the impaction of the maxillary canine. There is a potential selection bias, as this is not a random sample. Future studies are needed with a segmentation of the sample by gender in order to eliminate confounding factors.
# Feature Fusion Graph Consecutive-Attention Network for Skeleton-Based Tennis Action Recognition
## 5 Materials and Methods
### Datasets
#### 5.1.1 Thetis  
The THEIS (Three dimEnsional Tennis Shot) dataset was created in 2013 [33]. Twelve tennis strokes were registered by Microsoft's Kinect motion capture system. They were performed by thirty-one amateurs and twenty-four professional tennis players. The data collection included twelve movements: backhand (one-handed, two-handed, slice), volley (backhand and forehand), forehand (flat, open stands, slice), service (flat, kick, slice) and smash. The following data formats are available in the dataset: ONI files, depth and RGB videos, silhouette, skeleton 2D and 3D videos, and skeleton joints. THEITS is a very well-known dataset that has been incorporated in many papers recently. In this study, the authors focus on ONI files that reflect a model of the tennis player. The model involves 15 points (Figure 1).
## 4 Results: Analysis of the Integration of VR, AR, and MR in the Design Process
### Results of Usability Indicator Analysis
#### 4.1.1 Dimensional Accuracy  
One of the most notable features of immersive technologies applied to design is the ability to sketch and model directly within a three-dimensional environment. This allows the user to interact with the product model from multiple perspectives in real time. Controllers function as drawing tools, capable of adopting roles equivalent to pencils, pens, digital rulers, or compasses, depending on the software used [101]. In VR environments, spatial selection of points achieves higher dimension accuracy thanks to controllers with position and orientation tracking. This contrasts with traditional paper sketching, where accuracy depends on the graphic skills of the designer, or traditional 3D modelling using peripherals such as mouse and keyboard. Specific tools, such as the digital pen in Gravity Sketch, enable reaching dimensional accuracy levels comparable to those achieved with a mouse in CAD environments but with greater gestural freedom. To empirically evaluate the accuracy of geometric dimensions in immersive environments, specific tests were carried out in Design Units 1 (ring) and 2 (candle holder).  
To evaluate dimensional accuracy in VR, the design and modelling of a ring was performed using the freehand drawing function of the 'Gravity Sketch' controllers, adjusting the anthropometric dimensions with a female hand model (Figure 4a). The model was exported in OBJ format, processed with the software 'Ultimaker Cura' (UtiMaker B.V., Utrecht, Netherlands), and manufactured using 3D printing (Figure 4b). The final model showed an absolute error of 0.1 mm (0.55% relative error), which is considered acceptable for conceptual prototyping tasks in immersive environments (Figure 4c).  
To analyse dimensional accuracy in the use of AR, the design and direct modelling of the product from Design Unit 2 (candle holder) were carried out on a physical element (candle). First, the scale of the augmented environment was validated (Figure 4d). Next, a three-dimensional model was developed, adjusted to the real geometry (Figure 4e), by modelling the surface wrap and editing the thickness of the candle holder; the design was manufactured using 3D printing (Figure 4f) and validated dimensionally by fitting it onto the candle (Figure 4g). The absence of deviation in measurements (absolute error of 0.0 mm and 0.0% relative error) indicates a complete match between the AR design and the physical result (Figure 4h), demonstrating that immersive tools can maintain high dimensional accuracy in modelling tasks involving real elements.  
Figure 3: Comparative analysis of usability indicators of Design Units.
# Wildlife Monitoring Using a Multi-UAV System with Optimal Transport Theory
## 3 Method
### OT-Based Multi-UAV Exploration: Time-Invariant Case
#### 3.2.2 Algorithm  
The formal algorithm of the OT-based multi-UAV exploration strategy is presented in Algorithm 1.  
```
1:initialize \(x_{1}^{k}\), \(y_{j}\), \(M_{a}\), \(N\), \(r_{0}\), \(\delta\), \(h\), \(n_{a}\), \(T\gets 1\)
2:while\(T\leq M_{a}\)do
3:each agent implements the following
4:for\(k\gets 1\) to \(n_{a}\)do
5: initialize circle's radius by \(r\gets r_{0}\)
6:while\(\#\mathcal{R}(x_{T}^{k},r)\leq h\) and \(n_{T}^{k}(y_{j})>0\)do
7:\(r\gets r+\delta\)
8:endwhile
9: calculate the cost function \(C^{k}(l)\) associated with all possible candidate trajectories \({}^{c}x_{T+1:T+h}^{k}(l)\)
10: obtain \({}^{g}x_{T+1}^{k}\) from (6)
11: update the UAV position \(x_{T}^{k}\) with the given UAV dynamics with the calculated next goal position \(s_{T+1}^{k}\)
12: update the individual weight \(n_{T}^{k}(y_{j})\) by (7)
13:endfor
14:the central agent
15:receives information about \(n_{T}^{k}(y_{j})\) from all agents
16: updates the common weight \(n_{T}(y_{j})\) from (10)
17: transmits \(n_{T}(y_{j})\) to all corresponding agents
18:each agent receives \(n_{T}(y_{j})\) from the central agent and \(n_{T}^{k}(y_{j})\gets n_{T}(y_{j})\)
19:\(T\gets T+1\)
20:endwhile
```  
**Algorithm 1** Multi-Agent Exploration Algorithm  
At the beginning of the exploration, all parameters are initialized as in the first line of Algorithm 1. At any time \(T\leq M_{a}\), each agent creates a circle centered at the current UAV position \(x_{T}^{k}\) and increases the circle radius \(r\) by \(\delta\) until there are \(h\) number of sample points with positive weight in \(\mathcal{R}(x_{T}^{k},r)\), which denotes the set of sample points located within the search circle centered at \(x_{T}^{k}\) and radius \(r\). Next, a tree structure is generated by each agent for all possible trajectories connecting the sample points with positive weight located in the search circle, starting from the current UAV position \(x_{T}^{k}\). Then, the cost for each trajectory is calculated from (5) and the next goal position \(s_{T+1}^{k}\) is determined using (6). Once the next goal point is determined, the agent heads towards its corresponding goal point using its motion controller and moves to a new location \(x_{T+1}^{k}\). After reaching a new location, each agent distributes \(\frac{1}{M_{a}}\) amount to weight to the sample points \(\{y_{j}\}_{j=1}^{N}\) and updates the weight information \(n_{T}^{k}(y_{j})\) using (7). Then, the central agent receives the updated individual weight information \(n_{T}^{k}(y_{j})\) from other agents, updates the common weight information \(n_{T}(y_{j})\) from (10), and transmits the common weight information to all agents. These procedures are performed in every time step \(T\) until the current time step \(T\) becomes \(M_{a}\).
# How Can Radiomics Help the Clinical Management of Patients with Acute Ischemic Stroke?
## 3 Discussion
With regard to the radiomics models reviewed, the studies that used a combined radiomics and clinical model showed better results than the isolated radiomics or clinical models. For this reason, we think that the first steps of radiomics in the routine clinical management of patients with AIS will be in the form of support for clinical criteria currently used for certain diagnoses. Segmentation is a fundamental point in radiomics, and manual segmentation is still considered the gold standard; however, the major drawback of this method is the waste of time for the neuroradiologist. Segmentation software is now available that allows semi-automated and 3D segmentation to be performed quickly and easily, which we believe will replace the manual method as the gold standard in the coming years [65]. In terms of feature extraction, we found that this varied from study to study. Heterogeneity in imaging acquisition and feature extraction is a classic problem in radiomic studies and one that initiatives such as the Radiomics Quality Score (RQS) are trying to standardize [66]. Finally, in the studies included in this article, we can see that radiomics provides valuable information that can complement the information provided by conventional imaging studies. The future of radiomics is promising, we may be at a tipping point that will change the paradigm of diagnostic imaging, but we believe that prospective studies are needed to demonstrate that radiomic analysis of an image adds specific diagnostic value.
## 4 Simulation Results and Discussion
### The Proposed Model  
In the next experiment, we compared our proposed model to the MVA. To implement the MVA [12], we had to first determine the interference coefficient \(\varepsilon_{VA}\). Here, we fixed SNR = 15 dB and simulated the BER performance according to \(\varepsilon_{VA}\). Based on the results in Figure 13, we chose \(\varepsilon_{VA}\) = 0.25 for the MVA in [12].  
In our algorithm, we will calculate the \(\varepsilon\) coefficient in (51). As the \(\varepsilon\) coefficient is the channel's ITI factor, this means that the coefficient is equal to \(h_{1,0}\) or \(h_{-1,0}\). In practice, however, we are not able to determine the values for \(h_{1,0}\) and \(h_{-1,0}\). As an alternative, we can use the target factor \(\alpha_{1}\) or \(\alpha_{2}\) instead of the interference factor. This is possible because the \(\alpha_{1}\) or \(\alpha_{2}\) in the GPR target is an estimation of \(h_{1,0}\) or \(h_{-1,0}\). In addition, this helps in avoiding the simulation for finding the optimum coefficient \(\varepsilon\) unlike finding \(\varepsilon_{VA}\).  
In Figure 14, the two-way GPR target and four-way MVA is the MVA in [12], whereas the two-way GPR target and two-way MVA is the conventional VA in [12]. Based on the results shown in Figure 14, the three-way GPR target and three-way MVA with feedback indicate that our proposed algorithm can be improved with a more accurate estimation of the ITI coefficient. The results also show that our proposed algorithm has an approximately 1 dB gain compared to the MVA at \(10^{-5}\) BER.
## Materials and Methods
### Experiment Design  
To evaluate the use of the devised VRMT as a support tool in training design from a TP perspective, a user study was arranged as follows. The two most experienced trainers of the Piedmont Region Coordination body of Civil Protection Volunteering, with a background in real-world exercise and training preparation for the HCP procedure, took on the roles of TPs. Firstly, they were asked to participate as a team in a DP session (following the steps described in Section 2.2; in the session, they were requested to provide a revised training procedure as an outcome. Subsequently, three trainees from the participating Civil Protection bodies with different levels of expertise in the HCP procedure were invited to engage in the VRMT experience (one at a time), whereas TPs were asked to analyze their behavior. TPs were allowed to take notes and talk to each other as well as to the trainees while observing the HMD's first-person perspective through a projected screen (110\" diagonal, 6 m distant). In the following, the two TPs will be referred to as TP 1 and TP 2.  
Feedback from the TPs was collected through a structured interview by means of a questionnaire arranged in three sections. The first section included items adapted from the Instructional Materials Motivation Survey (IMMS) [37] and was devoted to the evaluation of the trainees' performance from the TPs's viewpoint based on the expected learning objectives. In the second section, items were designed to gather general feedback on the suitability of the VRMT as a mock-up tool. The aspects investigated included, for instance, the capability to identify training flaws, the easiness to spot potential equipment misuse and risk-exposure, the foreseeable real-world deployability, etc. Statements belonging to both the first and second section had to be rated on a scale ranging from \"totally disagree\" (1) to \"totally agree\" (5). Finally, in the third section, TPs were asked to express their preference by scoring in favor of the DP (1) or the VRMT (5) in seven dimensions.
# Secure D2D Group Authentication Employing Smartphone Sensor Behavior Analysis
## 4 Proposed Secure Certificateless Group Authentication Scheme for D2D Communication
### Group Key Updating Strategy  
In the proposed centralized scheme, group key updating is provided in an efficient way, which requires comparatively small efforts in the SN side. Note that further communication rounds with the participating devices are not required. Respectively, let \(ID_{r}\) denote the UE identity to be revoked, \(ID_{j}\) denote the newly joining device identity. The key updating involving multiple UEs can be achieved in the following step:  
For device revocation, SN removes the related \(\varphi_{r}\) from the stored set \(\{\varphi_{1},\ldots,\varphi_{t}\}\) and choose a new group key \(\gamma_{r}^{new}\). Hence the \(f(x)\) function is built as  
\[f(x)=(x-\varphi_{1})\ldots(x-\varphi_{r-1})(x-\varphi_{r+1})\ldots(x-\varphi_ {t})+\gamma_{r}^{new} \tag{17}\]  
In this way, \(f(\varphi_{r})\
eq\gamma_{r}^{new}\), indicating that the revoked device cannot acquired the updated group key. For \(i\in[1,t]\backslash\{r\}\), \(f(\varphi_{i})=\gamma_{r}^{new}\) holds. Hence the remaining UEs can directly derive the updated group key with the current \(\varphi_{i}\). Extra information for key distribution is not required for SN and all the legitimate UEs.  
The process for newly joining UE is similar. After successful authentication, SN computes the corresponding \(\varphi_{i}\) related to \(ID_{j}\) and adds it to the set \(\{\varphi_{1},\ldots,\varphi_{t}\}\), Hence the new function \(f(x)\) is built as  
\[f(x)=\prod_{i=1}^{t}(x-\varphi_{i})(x-\varphi_{j})+\gamma_{j}^{new}, \tag{18}\]  
where \(\gamma_{j}^{new}\) denotes the newly generated group key. Obviously, for \(i\in[1,t]\cap\{j\}\), \(f(\varphi_{i})=\gamma_{j}^{new}\) holds. All the valid UEs can acquire the update group key in this case.  
It is worth nothing that the presented key updating strategy is able to provide efficient group key updating involving multiple UEs simultaneously. That is, SN organizes the newly generated key information with only one broadcasting. The revoked UEs cannot acquire the updated key according to the keying message due to the removal of \(\varphi_{i}\) from \(f(x)\) function. Similarly, the newly joining UEs can acquire the updated group key using the computed \(\varphi_{i}\).
# The Polar Code Construction Method in Free Space Optical Communication
## 5 Simulation Analysis of Polar Code Construction
In order to further prove the feasibility of STPO in strong turbulence channels, considering that the different effects of different degrees of turbulence intensity on communication performance are different, Figure 8 shows that the length was 1024, the code rate was 0.5, and SC decoding was adopted at different turbulence intensities and the performance of constructing polar code with STPO and MC was compared. From Figure 8, we can see that these two construction methods generated almost the same BER in low SNR. Moreover, in high SNR, when turbulence intensity was  
Figure 6: Reliability of each sub-channel when \(N=1024\). Figure 7: Comparison of bit error rate under different code lengths and code rates. \(\sigma_{R}^{2}=2.3\), two construction methods still had similar error performances. When turbulence intensity was \(\sigma_{R}^{2}=5.2\), BER was \(10^{-4}\), STPO was compared with MC, and a loss of about 0.05 dB was produced, which was nearly the same in the condition that \(\sigma_{R}^{2}=3.5\). Therefore, it is feasible for STPO to be used in FSO to construct polar code in strong turbulence, and it had a better performance at a lower turbulence intensity. Based on the above simulation results and analysis it can be seen that the STOP and MC methods had similar performances. The system BER curves of the STOP method at different transmission distances are given in Figure 9. It can be seen from the figure that the system performance decreased as the transmission distance increased. There was a significant decrease in the system performance when the distance increased from 1 km to 3 km, while the system performance did not decrease significantly when the transmission distance increased from 3 km to 5 km. This is because as the distance continued to increase, the flicker of the received optical signal at the receiver side entered a saturation state. Although the communication performance decreased with increasing distance, we can see from the figure that we could improve the communication performance by appropriately increasing the SNR. Figure 8: Comparison of bit error rate under different turbulence intensities. Figure 9: System BER performance for different transmission distances. STPO was used to construct polar code in an offline operation mode, in which a small number of calculations were required in actual polar code construction, and STPO had an error performance similar to MC in a strong turbulence channel. The application of STPO in the strong turbulence channel greatly improved the transmission performance of the FSO system and had important practical significance for the practical application of the FSO system.