esa-sceva/satcom-chunk-collection huggingface dataset:
# Long Time Simulation Analysis of Geometry Dynamics Model under Iteration
## 7 Conclusions  
From the simulation results of a planer pendulum and a 3D pendulum, the conclusions can be summarized as follows.  
1. In the long simulation, the influence of error accumulation on the dynamics was not only reflected in the amplitude, but also in the periodic law of the system.
2. The reduced attitude model of planer pendulum can conserve the long simulation characteristic with a special time step. If the time step is not suitable, the error accumulation may lead to the hysteresis of simulation. Thus, the error accumulation speed is obviously influenced by the time step.
3. The complete Lie group dynamics model has similar simulation characteristics with different time steps, which means that the error accumulation is not sensitive to the time step. The simulation results using Lie algebra do not have this advantage.
4. In the simulation of a 3D pendulum, the reduced attitudes and complete Lie group also had low sensitivity to the time step in the dynamics calculations. The simulation results for the time steps of 0.1 and 0.01 s are not obviously distinguishable.
5. The dynamics results for the 3D pendulum lost their conservation under the Lie algebra model, which is determined by Cardan rotation, which means that the custom expression of rotation in space does not have the desired long simulation characteristics.  
According to the above conclusions, the long simulation characteristic is influenced by the expression of the model and the time step simultaneously. The complete Lie group expression has the best long simulation characteristics and has the least sensitivity to the  
Figure 27: The attitude results under Lie algebra expression.  
time step for both planer and 3D pendulum simulations, because it conserves the complete geometry characteristics of the system.  
Conceptualization, X.G. and L.B.; methodology, L.B.; software, W.S.; validation, W.S.; formal analysis, L.B.; investigation, L.X.; resources, L.X.; data curation, W.S.; writing--original draft preparation, W.S.; writing--review and editing, L.B.; visualization, L.B.; supervision, L.X.; project administration, L.X.; funding acquisition, L.B. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Youth Fund of National Natural Science Foundation of China, grant number 11802035; National Natural Science Foundation of China, grant number 12072041; Major project of National Natural Science Foundation of China, grant number 11732005; General project of Science and Technology Plan of Beijing Municipal Education Commission, grant number KM201911232022; Talent support program of BISTU, grant number 511211110.  
Not applicable.  
The funders had no role in the design of the study; in the collection, analyses or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
# A Survey on Swarm Robotics for Area Coverage Problem
## 3 Algorithms and Methods for Swarm Robotics
### Classical Algorithms
#### 3.2.3 The Force Vector Algorithm  
The general force vector algorithm was designed for most swarm robotics applications with few requirements to solve area coverage problems. This algorithm works efficiently and gets good results; it is considered an alternative to many complex algorithms for effectively covering an environment. Many simple robots are required for implementation with more capabilities, enabling the algorithm to cover specific areas [62].
###### Abstract  
In order to solve the problems of multiple process parameters, difficult control and high process requirements in laser first/second scribing of aerospace chemical milling thin-wall parts, a laser scribing depth model based on thermal energy balance was established, and the relationship between laser power and speed was established with scribing depth as a target. Using AC850 laser scribing maskant as coating material, the effects of laser power, scribing speed, laser frequency, forward angle and side slope angle on the scribing depth were studied by single factor experiment. Experimental results show that the theoretical model is in good agreement with experimental data. The laser scribing depth is positively proportional to the laser power and inversely proportional to the laser speed and has little relationship with the laser frequency. The predicted accuracy of the mathematical equations regarding the laser power density and scribing depth, calculated by the laser power, speed and scribing depths experimental data, are 88.53% and 90.79%. The laser scribing depth at a forward angle of 6\({}^{\circ}\) and a side slope angle of 7\({}^{\circ}\) is deeper compared with the vertical incident scribing depth, and the angle is also the recommended angle of laser scribing. Based on the simplified regression model, the laser scribing depth model can be directly used in the laser NC system to realize the adaptive adjustment and accurate control of laser energy according to the actual laser speed.  
laser scribing; chemical milling; depth model; univariate linear regression; incident angle
# Can the WiMAX IEEE 802.16 Standard Be Used to Resolve Last-Mile Connectivity Issues in Botswana?
## 4 Material and Methods
### WiMAX IEEE 802.16e Performance Metrics Used
#### 4.1.4 Traffic Dropped  
Traffic dropped (packet lost) is the number of packets that failed to reach their destination, as a result of network interference and network congestion. To measure the traffic/packet dropped we use the packet loss rate formula [27].  
\[PLR=\frac{N^{tx}-N^{rx}}{N^{tx}}\times 100 \tag{4}\]  
where:  
\(PLR\) = Packet loss rate  
\(N^{tx}\) = total number of transmitted packets  
\(N^{rx}\) = total number of received packets
# Underwater Acoustic Target Tracking: A Review
## 5 Classification Underwater Acoustic Target Tracking Algorithms
### Classification Based on Tracking Optimization Method  
According to the tracking instrument and tracking mode, researchers have proposed numerous algorithms to improve the tracking accuracy and stability. However, other optimization methods have also been investigated for further improvement. Here, we take the filtering techniques, arithmetic average, and Sage-Husa model as the tracking optimization methods driven by the noise. The filtering techniques such as KF, EKF, UKF, and PF are used to estimate the state of the target and decrease the interference of noise on the tracking performance. That's why we take the filtering techniques as the tracking optimization methods. The sensor scheduling strategies and quantized methods are the subcategories of the tracking optimization methods driven by the limited source.
## 4 Conclusions  
In conclusion, we demonstrated frequency down-conversion of an SF pump laser from the near-infrared to mid-infrared region based on intracavity DFG for the first time. By building a parametric oscillation of the high-power 1018 nm fiber source, a high intracavity signal power was achieved. The phase-matching conditions were met by setting the temperature to 20 \({}^{\circ}\)C. Then the 1064 nm SF pump beam was converted to the 3.7 \(\upmu\)m mid-infrared radiation. Utilizing the high-power intracavity signal power, the maximum pump-to-idler conversion efficiency reaches 21.6%, which to the best of our knowledge, is the highest DFG conversion efficiency for SF lasers. The maximum power of the low-power 1064 nm SF pump source was as low as 340 mW, which showed great advantages compared to other methods requiring high-power pump sources. Meanwhile, the narrow linewidth of 271 pm (5.9 GHz) in the mid-infrared region was achieved without adding any extra devices in the cavity. The experiment results reveal great potential in using this method to achieve frequency down-conversion of low-power special laser sources like frequency-swept lasers and generate special mid-infrared sources with great values.  
Conceptualization, X.L., X.C. and J.F.; methodology, X.L., X.C. and J.F.; validation, J.F. and X.C.; investigation, J.F. and X.C.; data curation, J.F. and X.C.; writing--original draft preparation, J.F. and X.C.; writing--review and editing, X.L., P.W., W.H. and K.H.; supervision, X.L. and W.H.; project administration, X.L., P.W., W.H. and K.H.; funding acquisition, X.L., P.W. and W.H. 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 under Grant 61975236, and Open Research Fund of State Key Laboratory of Pulsed Power Laser Technology, Electronic Countermeasure Institute, National University of Defense Technology under grant SKL2020 ZR03. The authors thank Nanjing University, Zhejiang University and Fujian Institute of Research on the Structure for their offer of nonlinear crystals. The authors thank [PERSON] and [PERSON] for their technical support in the experiment. The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
# An Experimental and Numerical Study on Reduction of Generated Axial Force
## 1 Introduction  
A constant velocity joint (CVJ) is a component to transmit power from the powertrain to the driving wheels. There are generally inboard and outboard types [1]. An inboard type located at the inner end of the drive shaft connects the drive shaft to the powertrain. It allows angular and axial displacements to the drive shaft so that the drive shaft can axially move when a plunge force is applied. An outboard type located at the outer end of the drive shaft connects the drive shaft to the wheel. It allows large articulation angles to the drive shaft so that it enables the wheel to steer. Typically, a tripod CVJ is adopted for the inboard type and a ball CVJ is adopted for the outboard type [2].  
Figure 1 shows a tripod type. It has three spherical rollers--the key feature that distinguishes the tripod from the ball type. Each spherical roller is fixed on the arm of the spider (trunion) so they maintain a \(120^{\circ}\) angle difference with each other [3]. In the tripod type, nine contact points occur between the components, and generated axial force (GAF) is induced by the internal friction at the contact points [4]. This causes lateral vibration called'shudder effect' in the vehicle when the vehicle starts to accelerate.  
Figure 1: Exploded view of tripod-type constant velocity joint.  
Many studies have been performed to theoretically analyze and reduce the GAF. [PERSON] studied kinematics and statics of tripod CVJs [5]. In his study, the closed-loop equations of three spherical rollers, three spider ends and the housing of the CVJ were deduced as spatial mechanism. [PERSON] proposed analytical and sophisticated GAF models using Adams software [6]. The results were compared with the measurement results. For a further study, [PERSON] also studied the internal friction of ball CVJs [7]. [PERSON] developed a physics-based phenomenological dynamic friction model of a CVJ [8]. The experimental data and physical parameters were used to develop the model. [PERSON] developed mechanical models for tripod and ball CVJs [9]. Along with the friction between the rollers and tulip ramps, the friction between the spherical rollers and trunnions was also modeled using viscous and Coulomb friction approaches.  
[PERSON] developed a GAF model of a tripod CVJ with theoretical and experimental approaches [10]. The kinematics and friction characteristics were analyzed, and the results were used for the GAF model. In the study, the pure sliding and rolling-sliding friction models were employed to find accurate friction coefficients. Based on the GAF model, the GAF of a CVJ is estimated, and the results are verified by experimental results.  
This study proposes a theoretical approach that optimizes design parameters of a CVJ to reduce the GAF. Key design parameters can be found by analyzing the sensitivity of the design parameters on the GAF, and then they are optimized to reduce the GAF. Based on the developed model, the GAF with the optimized parameters is estimated. Then, the estimated results with the optimized parameters are verified by experimental results.
## 3 Results  
Of the 1012 records identified, 256 met all eligibility criteria. Of these, 212 studies were classified as either clinical (\(n=96\)) or nonclinical (\(n=116\)). The number of telemedicine and eHealth publications has grown steadily over the past decade, with significant increases observed during the COVID-19 pandemic (2020-2022). The analysis of temporal trends and themes (captured by thematic codes) examined the evolution of telemedicine and eHealth in Poland across three phases: (1) the Pre-Pandemic Foundations Phase (2014-2019), (2) the Pandemic Catalyst Phase (2020-2022), and (3) the Post-Pandemic Maturation Phase (2023-2024).  
In the first phase (2014-2019), Polish law formally recognized and accepted telemedicine in December 2015, and e-prescriptions, e-referrals, and online patient accounts (IKP) were gradually implemented [23; 24]. The initial clinical focus during this period was on psychiatry, cardiology, and dermatology. In the second phase (2020-2022), teleconsultations will be mandatorily implemented, accounting for up to 80% of primary care visits and 79% of specialist visits. In this phase, e-prescriptions became mandatory, with 67% of usersaccessing them independently. The scope of the national pilot programs for remote monitoring, including heart failure and geriatrics, has expanded. The third phase (2023-2024) witnessed the implementation of AI-based diagnostics in cardiology [48] and mental health as well as the emergence of cross-sector partnerships, including collaborations with the space industry and EU agencies. A strategic focus is placed on digital skills, interoperability, and sustainability.
## 3 The Proposed Method  
Our method is primarily based on searching for Finder Patterns and utilizes their characteristic feature--1:1:3:1:1 black and white point ratio in any scanning direction. The basic steps are indicated in the flowchart in Figure 4.  
Figure 4: The flow chart of proposed algorithm.  
Before searching for a QR Code, the original image (maybe colored) is converted to a gray scale image using Equation (1), because the color information does not bear any significant additional information that might help in QR Code recognition.  
\[I=\frac{77R+151G+28B}{256} \tag{1}\]  
where \(I\) stands for gray level and \(R\), \(G\), \(B\) for red, green, and blue color intensities of individual pixels in the RGB model, respectively. This RGB to gray scale conversion is integer approximation of widely used luminance calculation as defined in recommendation ITU-R BT.601-7:  
\[I=0.299R+0.587G+0.114B \tag{2}\]  
Next, the gray scaled image is converted to a binary image using modified adaptive thresholding (with the size of window 35--the window size we choose to be at least five times the size of expected size of QRC module) [19]. We expect that black points, which belong to QRC, will become foreground points.  
We use the modification of the well-known adaptive thresholding technique (Equation (3)), which calculates individual threshold for every point in the image. This threshold is calculated using average intensity of points under a sliding window. To speed up the thresholding we pre-calculate the integral sum image and we also use the global threshold value (points with intensity above 180 we always consider as background points). Adaptive thresholding can successfully threshold also uneven illuminated images.  
\[B(x,y)=\left\{\begin{array}{lcl}0&\leftarrow&I(x,y)>180\\ 0&\leftarrow&I(x,y)>=T(x,y)\\ 1&\leftarrow&I(x,y)<T(x,y)\end{array}\right. \tag{3}\]  
\[T(x,y)=m(x,y)-\frac{I(x,y)}{10}-10\]  
\[m(x,y)=\frac{1}{35\times 35}\sum_{i=-17}^{17}\sum_{j=-17}^{17}I(x+i,y+j)\]  
where \(I\) is gray scale (input) image, \(B\) is binary (output) image, \(T\) is threshold value (individual for each pixel at coordinates \(x,y\)), and \(m\) is average of pixel intensities under sliding window of the size \(35\times 35\) pixels.  
In order to improve adaptive thresholding results, some of the image pre-processing techniques, such as histogram equalization, contrast stretching or deblurring, are worth to consider.
# _electronics_
## 2 Waveguide Design
Under the loss criterion of 0.1 dB/mm, the transmission bandwidths are 0.278-0.289 THz (bandwidth of 11 GHz, relative value of 3.9%) and 0.242-0.267 THz (bandwidth of 25 GHz, relative value 9.8%) for the forward and backward topological modes, respectively. Although the topological bandgap has a wide relative bandwidth of 16.1% (corresponding to 44 GHz), it could not be entirely occupied--81.8% of the bandgap was utilized for the two topological mode propagations (total transmission bandwidth of two modes is 36 GHz). Furthermore, the frequencies offering the lowest loss and zero GVD for the two modes are indicated in Figure 4, which will be used for the link budget model later.
## 5 Case Study: Propose Three Different Designs
### Second Design: Broadcasting Design  
In this design, the nodes are informed whom the SCHs are through a new broadcast message sent during the \"Schedule Creation Phase\"; therefore, it is called Broadcasting design. Thus, a new message type has been introduced in this design, which the \"SCH Broadcast Message\". The message is sent by the CHs to their joined nodes, so the nodes only know the SCH of their CH. To clarify it more, Figure 7 illustrates the broadcast design.  
Figure 6: Scheduling design process.
## 2 Literature Review  
This literature review followed the recommendations from [14] to thoroughly investigate the current state of DC in education concerning their measurement and assessment supported by ICT. All studies satisfied one of the set criteria:  
* Indicate a lack of DC in children;
* Describe systems for assessment and certification of DC;
* Describe the acquisition of DC through the curriculum.  
First, it is interesting to report that various studies dealt with teachers' competences [4; 15; 16; 17; 18; 19; 20] and the ways they adopted the technology in their classes [21; 22]. One of the possible reasons is that teachers are considered responsible for students' DC assessment and acquisition at all levels of education [23]. In contrast, numerous studies discussed the lack of and need for developing DC among university students [8; 23; 24]. A smaller number of studies included primary and secondary students [25; 26], as confirmed by recent research [11; 27]. Several authors [3; 4; 5; 9] suggested that the acquisition and assessment of DC should start early in primary schools as a part of the formal curriculum.  
Our literature review revealed only a few examples of tools for competence development or assessment (e.g., [28; 29]). Identified tools are implemented as a part of formal education, employment training, or life-long learning for citizens. Neither of those tools was assessed for its exploitation and successful implementation to the best of our knowledge. However, their further development is expected in the future [30]. From a theoretical point of view, the findings from the authors of [31] are very substantial. They analyzed 32 different frameworks for 21 st-century competences and indicated that competences must be operationally defined and embedded within and across core subjects to facilitate competence implementation in schools. However, in terms of interdisciplinarity, \"... intentions and practice seemed still far apart\" [31] (p. 299).  
It can be concluded that there is a lack of assessment instruments and tools for education based on competence [32]. According to gathered information [33], there is a need for such instruments to optimize students' learning and inform them about their progress. Moreover, ref. [34] recognized that it is necessary to develop the assessment criteria for each competence based on which students' progress at an individual or group level could be tracked. Based on the described literature review, we could conclude the following:  
1. A modest number of studies deal with the DC acquisition and certification in primary and secondary schools in a way of only indicating its importance without providing an implementation solution.
2. None of the studies tried to assess the implementation of the systems for DC acquisition.
3. There seems to be a need to start with DC education and assessment from the earliest age and integrate it into the formal curriculum.
# The Design of a Long-Distance Signal Transmission System in a Bistatic RCS Testing System
## 3 System Testing
### Phase Stability and Group Delay Testing  
A principle diagram and the testing environment for system phase stability testing are shown in Figure 17. The system was connected to a vector network analyzer, and the S21 parameter of the network analyzer was used to obtain the group delay and the phase variation of the system over 8 h of continuous operation at different frequencies. The system group delay was determined to be 1503 ns.  
During testing, the system needed to operate for 1 h to reach a stable state. Using the phase at the 1 h mark as a reference, the subsequent hourly phase changes relative to the 1, h, mark were recorded. The results are shown in Table 4.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Frequency** \\ **(GHz)** \\ \end{tabular} } & \multicolumn{8}{c}{**Continuous Operation Time**} \\ \cline{2-9}  & **1H** & **2H** & **3H** & **4H** & **5H** & **6H** & **7H** & **8H** \\ \hline
2 & \(0^{\circ}\) & \(-0.01^{\circ}\) & \(0.11^{\circ}\) & \(0.09^{\circ}\) & \(0.01^{\circ}\) & \(0.07^{\circ}\) & \(0.18^{\circ}\) & \(0.37^{\circ}\) \\
5 & \(0^{\circ}\) & \(0.02^{\circ}\) & \(0.25^{\circ}\) & \(-0.05^{\circ}\) & \(-0.28^{\circ}\) & \(-0.19^{\circ}\) & \(0^{\circ}\) & \(0.45^{\circ}\) \\
10 & \(0^{\circ}\) & \(-0.22^{\circ}\) & \(0.19^{\circ}\) & \(-0.45^{\circ}\) & \(-0.95^{\circ}\) & \(-0.84^{\circ}\) & \(-0.53^{\circ}\) & \(0.35^{\circ}\) \\
20 & \(0^{\circ}\) & \(0.2^{\circ}\) & \(1.08^{\circ}\) & \(-0.49^{\circ}\) & \(-1.3^{\circ}\) & \(-1.05^{\circ}\) & \(-0.49^{\circ}\) & \(1.18^{\circ}\) \\
30 & \(0^{\circ}\) & \(0.18^{\circ}\) & \(1.45^{\circ}\) & \(-0.45^{\circ}\) & \(-1.8^{\circ}\) & \(-1.45^{\circ}\) & \(-0.59^{\circ}\) & \(2.05^{\circ}\) \\
39 & \(0^{\circ}\) & \(-0.13^{\circ}\) & \(1.7^{\circ}\) & \(1.38^{\circ}\) & \(-0.28^{\circ}\) & \(-0.15^{\circ}\) & \(0.35^{\circ}\) & \(3.37^{\circ}\) \\ \hline \hline \end{tabular}
\end{table}
Table 4: Phase stability test results.  
Figure 16: Power response curve with different frequencies.  
Figure 17: Diagram and test setup of the phase stability and group delay test.  
The testing results indicate that the system meets the functional requirements: clutter and high-order harmonics are within acceptable limits, with no need for additional filtering; the gain levels satisfy the RCS testing criteria; and the phase stability is adequate for both one-dimensional and two-dimensional imaging. Overall, the system performs as required for practical applications.