esa-sceva/satcom-chunk-collection huggingface dataset:
# Compact Design and Impact Ionization: Utilizing Small-Sized Thyristors in a 4-Stage Marx Generator
## 2 Materials and Methods
Our simulation models assume ideal closing switches for both SiC MOSFETs and thyristors, providing an approximate representation of the system rather than an exact prediction of the real setup. The primary objective is to gain an initial understanding of the circuit behavior, offering preliminary insights to guide the design process. No readily available simulation model accurately captures the performance of SiC MOSFETs in gate-boosted mode or thyristors in impact-ionization mode. Since precise modeling of their real behavior was not the priority at this stage, we opted to represent all switching components as ideal closing switches to focus on overall circuit operation. Stages 2-4 are represented by a dotted line, along  
Figure 5: Simulation model of the Marx generator, following the schematic in Figure 4.  
Figure 6: PCB 3D cut of the Marx generator setup. with their corresponding biasing voltage sources, for better visualization. The simulation was conducted under conditions representative of the actual operational environment of the circuit, aiming to indicate the effects of signal reflections and impedance mismatches on ideal switches. The transmission lines were modeled with varying impedances to compare the effects of controlled versus non-controlled impedance configurations following the values in Table 1, which also includes the corresponding calculated delay for each stage. To assess the impact of controlling the impedance of the transmission lines on the reflections, we positioned our test point at the first switch, S1, which represents the six parallel SiC MOSFETs. We compared the current passing through this switch in both the impedance-controlled model and the non-controlled model, where each stage was set to a uniform \(20\,\Omega\) impedance. This value is based on the approximate pad impedance of a D2 PAK casing, which is the minimal width suitable for the D2 PAK thyristors in our design. The simulation illustrates the voltage distribution across all stages in Figures 7 and 8, including the SiC MOSFETs (\(U_{SiCMOS}\)) and thyristors (\(U_{TP1}\) to \(U_{TP4}\)), providing insight into the system's behavior. While the simulation does not perfectly match reality, it effectively demonstrates the progressive voltage amplification and associated delay, as well as the reflections and their attenuation over time. It can be observed that the reflections in the controlled impedance case (Figure 8) demonstrate less amplitude than in the fixed \(20\,\Omega\) case (Figure 7). Additionally, the results in Figure 9 show that the \(20\,\Omega\) configuration causes higher peaks from the signal reflections, which can reach up to \(2\,\mathrm{kA}
## 3 Results
### Verification of Population Estimation Results  
The model trained using the XGBoost algorithm outputs population spatialization results at a resolution of 100 m \(\times\) 100 m, and we produced the population density spatial distribution. Based on the model's grid level population estimates, statistical calculations are performed for the estimated populations at the town and street administrative scales. We then conducted correlation and relative error analyses comparing these estimates with officially published statistical data at corresponding administrative levels. Furthermore, we compared and analyzed differences in correlation and relative error between WorldPop dataset values and the statistical data to validate the accuracy of our population spatialization estimates. Using the estimated population and the WorldPop population data for 214 towns and streets in Shanghai, we conducted correlation analyses with the obtained statistical data. The results (Figure 3) show that the discrete points of the estimated results closely follow the trend line, whereas the discrete points of the WorldPop dataset are relatively scattered. Linear regression analysis revealed an R\({}^{2}\) of 0.98 between the statistical population data and our XGBoost-based estimates at the administrative scale, compared to an R\({}^{2}\) of 0.78 for the WorldPop dataset. This demonstrates that the XGBoost model produces significantly more accurate population estimates than WorldPop, confirming the high precision of our method.  
Figure 3: Accuracy of population estimation results. (**a**) Correlation between census population and estimated population (**b**) Correlation between WorldPop and estimated population.  
Figure 2: SHAP values of main feature variables in different districts of Shanghai.  
Further analysis was conducted on the errors between the estimation results of the XGBoost model and the WorldPop population dataset in relation to the statistical population data at the town and street administrative scales (Table 2). The number of towns and streets with relative errors for the XGBoost model estimation results in the ranges of [0, 10%], (10%, 20%], (20%, 50%], (50%, 100%], and >100% is 194, seven, five, three, and five, respectively. Notably, the number of towns and streets with relative errors within 10% accounts for 90.9% of the total. In contrast, the number of towns and streets with relative errors in the corresponding ranges of the WorldPop population data is 33, 36, 89, 40, and 16, respectively. Only 15.4% of the total towns and streets in the WorldPop dataset have relative errors within 10%, while the number of towns and streets with relative errors greater than 50% reaches 56, accounting for 26.2% of the total. In addition, the MRE of the estimation results from the XGBoost model is 0.09, which is significantly lower than the MRE of the WorldPop dataset of 0.40. Overall, the XGBoost model demonstrates superior accuracy for population spatial estimation.
# GPS Results from Long Time Monitoring of Geodynamic Processes in South-Western Bulgaria
## 6 Conclusions  
The presented data result from two campaigns made in 1997 and 2000, that are enlarged by a third campaign from 2020 and supplemented by an extension and acquirement of new data in 2021. The results provide new data on a tectonically and seismically active area. Compared to the first published results of the network [5; 6; 21], the present results confirm that the general tendency of movement of the stations in the region of Central West Bulgaria is in the south direction with respect to stable Eurasia.  
The velocities are in the range of 1.5-2 mm/year to 3-4 mm/year. They increase generally from north to south. The change in the velocity field tends to be related to active faults. Extension is shown to be the main mechanism of deformation.  
The obtained results in a general way confirm previously data, but with much better accuracy and details at local level. This way, both the repeated measurements and extension of the geodynamic network prove to be a powerful tool for better understanding present-day geodynamics.  
Conceptualization, N.D.; Investigation, N.D. and R.N.; Writing--original draft, N.D. and R.N. All authors have read and agreed to the published version of the manuscript.  
This research was funded by National Science Fund, Bulgaria, Contract No KIT-06-H 34/1, project \"Monitoring of geodynamic processes in the area of Sofia\". Call identifier \"Competition for financial support of basic research projects--2019\".  
Not applicable.  
We are grateful to the staff of the project \"Monitoring of geodynamic processes in the area of Sofia\" for their hard work. We obtained global solution files and most of the IGS tracking data from the Scripps Orbit and Permanent Array Center (SOPAC) and Crustal Dynamics Data In-formation System (CDDIS). We thank [PERSON], for helpful advice and discussions. The maps in this paper were generated using the public domain Generic Mapping Tools (GMT) software [22]. For topography we used data from the General Bathymetric Chart of the Oceans (GEBCO). We thank three anonymous reviewers for comments that have improved the manuscript.  
The authors declare no conflict of interest.
# Reinforcement Learning Based Relay Selection for Underwater Acoustic Cooperative Networks
## 2 System Model
### UWA Channel with Long Transmission Delays  
The speed of UWA propagation is only about 1500 m/s, which leads to large delay of UWA signal during its transmission. The transmission delay of UWA communication is five orders of magnitude higher than that of land-based radio communication. The impact on UWA communication and network should not be ignored.  
On one hand, the location of the relay nodes are different, so that their transmission delays to the destination node are different either. According to the analysis in Section 1, the nodes with better channel quality may not be able to reach the destination node with the shortest access delay. From the perspective of system throughput, the channel quality and access delay should be comprehensively considered. Define access delay of one round in an UWA cooperative communication system as the sum of the transmission delay and the packet duration. The total access delay \(T_{S_{r}I,D}\) from source node to the destination node can be expressed as  
\[T_{S_{r}I,D}=(T_{S_{r}i}+T_{p})+(T_{r,D}+T_{p}) \tag{12}\]  
where \(T_{S_{r}i}\) is the transmission delay from the source node to the relay node \(r_{i}\), \(T_{r,D}\) is the transmission delay from the relay node \(r_{i}\) to the destination node, and \(T_{p}\) is the duration of the data packet. The source node can know the channel status and transmission delay information of each potential relay through the feedback of the destination node [47]. In RL based UWA relay selection, the influence of access delay will be designed in the expression of system reward.  
On another hand, the relay selection is decided according to the UWA feedback CSI. When the selected relay transmits data, it experiences a certain transmission delay after the time of feedback. That is to say, the actual transmission is decided by the feedback CSI one transmission round ago. The phenomenon of the outdated feedback CSI will be considered in the state design of RL based UWA relay selection.
## 3 Results and Discussion  
### Welding Results without Jigs  
Figure 10 shows the simulation results of Y-displacement deformation for GMAW without jigs after the workpiece cools to 25 \({}^{\circ}\)C. The deformation is large on both sides of the welding bead (see yellow). Figure 11 presents the Y-displacement deformation graph in 3D format and confirms that the overall deformation of the thin plates caused a vertical bulge in the center, front, and back, as well as horizontal twisting. This is quite a complicated deformation and causes major weakening in the welding bead. Considering that construction steel can sustain buckling damage under working stress, the amount of welding deformation that can occur is an important issue in the field of mechanical manufacturing. Figure 12 presents the simulation results for the equivalent von Mises stress situation in a 3D image, showing that the equivalent von Mises stress after welding is very large, even reaching the yield stress of SUS304 stainless steel plates. Since the heat source has the greatest effect at the welding bead and the surrounding area, this can be regarded as equaling the material's yield stress. Hence, the workpieces must go through a heat treatment procedure to reduce the residual stress. The suggested approaches are solid solution heat treatment for stainless steel and annealing heat treatment for carbon steel.
## 3 Performance Evaluation
### Latency  
We next study by simulation the average latency of one-way ATT communications and round-trip ATT dialogues between a master and a slave, as a function of the _connInterval_ parameter, and for various BER values. Examples of the one-way ATT communications considered include the following: (i) the master polls the slave and the slave replies with a notification or a command; (ii) the master sends a notification or a command, and the slave acknowledges the master's message at the Link Layer. The round-trip ATT dialogue considered is the same as that assumed in the energy consumption evaluation.  
The latency of each message exchange is measured as the difference of times between the start of the transmission of the first message and the end of the correct reception of the last message. We assume that a connection has been created between the two BLE devices before the ATT message exchange. Figure 6 illustrates the results, which are obtained as the average latency from ten million simulated message exchanges for each set of conditions. A _connSlaveLatency_ equal to 0 is assumed. The results do not include the latency for the first packet of the connection. In fact, the master has flexibility in selecting the start time of the first packet transmission, which can occur between 1.25 ms and 11.25 + _connInterval_ ms after the transmission of the Connection Request message.  
Figure 6: Average latency for one-way and round-trip message exchanges, for various _connInterval_ and BER values.  
For very low BER values (e.g., 10\({}^{-6}\)), the average latency of round-trip and one-way ATT message exchanges are smaller than 2 ms and 1 ms, respectively, for any _connInterval_ value. However, for greater BER values, the influence of _connInterval_ becomes significant, since on average more than a single connection event is required for successful transmission of each ATT message. For high BER values (e.g., 10\({}^{-3}\)), the average latency increases by up to three orders of magnitude.  
On the other hand, we have measured the latency of an error-free one-way ATT exchange during the experiments presented in Subsection 3.1. The latency value obtained is 676.7 \(\upmu\)s, which is consistent with the delay expected to transmit a maximum-sized notification, receive the corresponding acknowledgment and wait for two IFS intervals. The measurement has been performed on the basis of a CC2540 slave current consumption plot, which is illustrated in Figure 7.
## 3 Results and Discussion
### Rheological Experiment at High Temperatures and High Pressures  
The high-pressure high-temperature (HPHT) rheological characteristics of the fluid containing the tackifier are presented in Figure 6. Figure 6 indicate that the Bingham plastic model is suitable for the HPHT rheological curve of the fluid containing the tackifier.  
Figure 6 shows that the rheological parameters of the fluid treated with DT are favorable at temperatures of 120 \({}^{\circ}\)C, 150 \({}^{\circ}\)C, and 180 \({}^{\circ}\)C, indicating that DT exhibits good viscosity-increasing performance under HPHT conditions. The rheological parameters of the fluid containing the tackifier respond to temperature increases. In the case of fluid containing DT at temperatures between 150 \({}^{\circ}\)C and 180 \({}^{\circ}\)C, viscosity and yield stress tend to remain stable with the increasing temperature. This stability may be related to the formation of hydrophobic association microstructures with phenyl groups in the side chains, accompanied by changes in the hydrodynamic volume of polymer molecules in solution and a transformation from loose helices to network aggregates [20]. Additionally, phase separation is prevented by the hydrophilic main chain, which stabilizes the associated phase at the microscopic level. Microstructures play a minor role in crosslinking between polymer chains, which helps maintain or increase the viscosity.
# Flexural Behavior of a 30-Meter Full-Scale Simply Supported Prestressed Concrete Box Girder
## 5 Conclusions  
This paper reports destructive experiments on a 30-meter-long simply supported prestressed concrete box girder. A nonlinear numerical model was developed using the finite strip method (FSM) on the basis of the experiment. Parametric analyses were conducted, and the design was optimized. The following conclusions may be drawn:  
1. The failure mode of the tested girder was fracture of the prestressing tendon. The maximum compressive strain of concrete in the compression zone was only 1456\(\mu\varepsilon\), which is far less than the ultimate compressive strain (3300\(\mu\varepsilon\)). Therefore, the concrete in the top flange was not fully utilized.
2. The maximum deflection was 1/102 of the span, and the ductility index of the tested girder was 1.99. Therefore, the tested girder possessed good ductility.
3. The measured cracking load was 750 kN, which is 1.98 times the applied load corresponding to the designed ultimate state of bearing capacity. Moreover, the measured maximum load was 1872 kN, which is 2.50 times the cracking load. It can be seen that the tested girder had a sufficient safety margin.
4. A nonlinear analysis procedure was performed using the FSM. The analysis procedure was demonstrated to be effective by comparing the analytical results with those of the tested girder and a laboratory-scale model.
5. The ratio of reinforcement in the compression zone has no obvious influence on the failure mode of the tested girder and can be ignored. The reinforcement in the tensile zone has a small effect on the bearing capacity and deformation of the tested girder, but has a large effect on the ductility index.
6. The ratio of prestressing tendons has an obvious influence on the bearing capacity, deformation, and ductility index. Considering the influence on the bearing capacity and ductility index of the structure, it is suggested that the ratio of prestressing tendons be increased to 1.041%. The prestressing tendons should thus be increased from four strands to six strands in each duct of the tested girder. After optimization of the prestressed reinforcement, the girder is ductile and the bearing capacity can be increased by 44.3%.  
Conceptualization, J.W. and S.T.; methodology, J.W.; Validation, M.Z. and C.Z.; Formal analysis, H.Z. and M.Z.; Writing--original draft preparation, J.W. and T.S.; Writing--review and editing, J.W. and S.T.; Project administration, H.Z. and C.Z.; Funding acquisition, J.W. and S.T. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the National Natural Science Foundation of China (Grant No.: 51408218, 51508488, 51608189) and Hunan Education Department (Grant No.: 18A202).  
The authors declare no conflict of interest.
# FD-LTDA-MAC: Full-Duplex Unsynchronised Scheduling in Linear Underwater Acoustic Chain Networks
## 4 Results and Discussion
### Small Scale Scenarios: 2, 10, and 20 km Pipelines  
The simulation results for small scale scenarios considering short pipelines of few kilometres (2, 10 and 20 km) are presented here. It is important to firstly consider short pipelines with a different number of hops in order to understand the performance of the FD-LTDA-MAC protocol in simple situations where there is a limited opportunity for spatial reuse.  
The cumulative distributive function (cdf) plot of frame durations for FD-LTDA-MAC, LTDA-MAC, and LTDA-MAC in FD protocols in small scale scenarios are shown in Figures 9-11. The results for a 2 km pipeline configured with 2, 4, 10, and 20 hops can be seen in Figure 9, which shows that FD-LTDA-MAC can achieve shorter frame durations compared to the LTDA-MAC and LTDA-MAC with FD protocols. The frame duration is reduced on average by 29% and 9% against LTDA-MAC and LTDA-MAC in FD, respectively. Hence, this capability provides better packet schedules which translates into improvement in network throughput even with limited opportunity for spatial reuse.  
The frame durations obtained for 10 km and 20 km pipelines as shown in Figures 10 and 11 demonstrate a more significant performance improvement compared with 2 km pipeline scenarios. The FD-LTDA-MAC shortens the frame duration by 64% against LTDA-MAC protocol, whereas LTDA-MAC in FD improves by 53% against LTDA-MAC protocol. The significant improvement achieved by FD based protocols is because the search algorithm is able to better exploit longer pipelines.  
Figure 8: Zoomed in sections of Figure 7a,b. (**a**) LTDA-MAC. (**b**) FD-LTDA-MAC.  
Figure 9: Frame duration cdfs of LTDA-MAC with HD nodes, LTDA-MAC with FD nodes, and FD-LTDA-MAC for a 2 km pipeline.
## 2 Asymmetric Turbo Code (ATC)
### Code Matched Interleaver
Actually, only those input sequences whose weights are less than certain value \(\mathrm{w}_{\mathrm{max}}^{(\beta)}\ (\beta\ =\ 2,4)\) should be eliminated. The parameter \(\mathrm{w}_{\mathrm{max}}^{(\beta)}\) acts like a threshold [30]. By combining Equation (4) with \(\mathrm{w}_{\mathrm{max}}^{\beta=2}\), and integrating Equation (8) with \(\mathrm{w}_{\mathrm{max}}^{\beta=4}\), we obtained the following inequalities:  
\[6\ +\ c_{1}(\mathrm{l}_{\mathrm{min},1}\!-\!2)+\mathrm{c}_{2}(\mathrm{l}_{ \mathrm{min},2}\!-\!2)\ \leq\ \mathrm{w}_{\mathrm{max}}^{\beta=2},\ \ 12+(c_{1}^{\prime}+c_{2}^{\prime})(\mathrm{l}_{ \mathrm{min},1}\!-\!2)+(c_{3}^{\prime}+c_{4}^{\prime})(\mathrm{l}_{\mathrm{ min},2}\!-\!2)\ \leq\ \mathrm{w}_{\mathrm{max}}^{\beta=4}\,, \tag{11}\]  
If \(\mathrm{l}_{\mathrm{min},1}=\mathrm{l}_{\mathrm{min},2}=\mathrm{l}_{\mathrm{ min}}\), the above inequalities are equivalent to:  
\[\mathrm{c}_{1}\ +\ \mathrm{c}_{2}\ \leq\ \frac{\mathrm{w}_{\mathrm{max}}^{\beta=2 }-6}{\mathrm{l}_{\mathrm{min}}-2}\,,\ \ \ \ c_{1}^{\prime}+\ c_{2}^{\prime}+c_{3}^{\prime}+c_{4}^{\prime}\ \leq\ \frac{\mathrm{w}_{\mathrm{max}}^{\beta=4}-12}{\mathrm{l}_{\mathrm{min}}-2} \tag{12}\]  
The algorithm utilized in [28] for the interleaver design is described as follows:  
1. Let us randomly choose an integer from the finite set \(\mathrm{I}_{\mathrm{S}}=\ \{1,\ 2,\ \ldots,\ \mathrm{N}\}\), where N denotes the size of the interleaver. 2. Compare the selected integer with S previous selected integers, where \(\mathrm{S}\ <\sqrt{\mathrm{N}/2}\). If the absolute value of the difference between the current selected integer and any of the S previous selected integers is smaller than S [31], then go back to the first step and search for a proper integer. 3. Check whether the weight-2 and 4 mapping conditions are simultaneously satisfied by the current interleaver output. If they are not satisfied, then go back to the first step. 4. When a specified number of iterations is reached, if we do not find an integer from the set \(\mathrm{I}_{\mathrm{S}}\) to make it satisfy both the second and third steps simultaneously, then the value S is reduced by 1 and the process is restarted from the first step. 5. The selected integer is saved as the current interleaver output. Repeat the process until we obtain all N interleaver outputs.
# A Capacity Enhancement Method for Frequency-Hopping Anti-Jamming Communication Systems
## 3 Results
### BER Performance Analysis
#### 3.2.2 Information B BER Analysis  
After the FH capacity boost signal passes through the Gaussian white noise channel, the baseband Information B is recovered using envelope detection.  
To reduce the BER of Information B, two methods are used to reduce the information rate (joint multi-symbol judgement) in addition to channel coding.  
Multi-symbol joint judgement reduces the information rate to achieve a lower BER by sacrificing the transmission rate of Information B and estimating multiple symbols as one symbol. The Information B code element rates are 1000, 500, 250, 125, 62.5, and 31.25 bps for the code elements of joint judgement of 1, 2, 4, 8, 16, and 32, respectively. The BER improvement of Information B is shown in Figure 16. The more symbols that are united, the better the BER performance of Information B.  
Figure 16: Information B BER test data for different rates.  
Figure 15: Information A BER test data for different J values.  
To further reduce the bit error rate, the (2, 1) convolutional code is added at the Information B code element rate of 31.25 bps. A simulation verifies that the bit error rate reduces further as a result. When J = 32 and (2, 1) convolutional coding is used, the Information B BER is less than three orders of magnitude lower than the Information A BER.