esa-sceva/satcom-chunk-collection huggingface dataset:
# An Adaptive Launch Control for Balloon-Borne UAVs with Large Wingspans
## 6 Evaluation
### Experiment Results  
The results of simulation experiment when using the proposed algorithm are shown in Figures 12-16. Figure 12 describes the tracking of the pitch angle's command. Overall, we can see that two curves indicating the pitch command and the pitch angle fit well. Concretely, at the initial time, the elevator control surface's efficiency is low due to its low airspeed, and then it increases until at eighth second. After the 8 th second, the aircraft has negative angular rate movements until pulls up at about 13 th second. These results demonstrates that the control strategy can track the pitch command well and realize the pull-up of the UAV.  
Figures 13 and 14 provide changes in the airspeed and altitude during the pull-up process. The initial vertical velocity is \(3\) m/s and its direction is upward; then, its velocitysharply increases from \(-3\) m/s under the action of gravity, and the maximum true airspeed of the aircraft is 49.42 m/s. The altitude drops by 147.3 m during the launching process.  
Figure 14: Altitude in the pull-up process.  
Figure 12: Pitch angle command tracking in the pull-up process.  
Figure 13: Airspeed in the pull-up process.  
Figures 15 and 16 represent the response of the roll angle and yaw angle. For the initial rotation speed of 3 degree per second of the aircraft and the balloon, there is an initial roll rate and an yaw rate after launch. The roll angle changes between \(-3.23\) deg and \(2.66\) deg, the yaw angle changes from \(-192.3\) deg to \(-180.2\) deg, and both of them gradually stabilize after \(8\) s.  
In addition, we also provide results from the comparison of the simulation experiment when using the latest control algorithm in the pull-up process for UAVs with large wingspans, as shown in Figure 17. Here, the blue dotted line is the result of the proposed control algorithm, and the blue solid line represents the algorithm used in the latest implementation. We can see that the \(\delta\) of the pitch angle when using the proposed control algorithm is smaller than that of the latest algorithm. This demonstrates that the proposed pull-up control algorithm is better than the state-of-the-art pull-up control algorithm. We still record changes in the pitch angle when performing flight tests with the latest algorithm, as shown in Figures 18 and 19. Here, Figure 18 represents the rising process of the balloon-borne solar-powered UAV, and Figure 19 illustrates the pitch angle and pitch angle command. From Figure 19, we can see that the UAV was launched at the time of \(217.3\) s, and the strategy proposed could realize pull-up before \(221\) s. However, the fuselage was damaged and the UAV failed to pull up. This probably is due to the elastic deformation and insufficient structural strength of the fuselage.  
Figure 16: Yaw angle in the pull-up process.  
Figure 15: Roll angle in the pull-up process.  
By comparing flight tests and evaluating simulation tests, we demonstrate our dynamic model, and the pull-up control model could be applied to solar-powered UAVs with large wingspans.
# Correlation Analysis and Its Application on an Asymmetry
## 5 Discussion and Conclusions  
For a rotor without overhang, many balancing methods have been proposed to identify the imbalance distribution. However, for an overhang rotor, methods are seldom proved to be suitable. In the field of engineering, rotors with long overhangs are considered impossible to balance. Most of the time, to suppress the vibration of this kind of rotor, the rotor structure or the position of support are adjusted. According to the correlation analysis, a rotor with overhang can be easily balanced. Compared with the modal based balancing method, the correlation analysis are simple and implementable.  
In this work, modeling, dynamical simulation, correlation analysis and experiment of an overhang rotor are carried out. Based on the rules found, we could conclude that (1) The critical speeds of the first and the second orders are substantially affected by support stiffnesses and the coupling effect of the bearing and support stiffnesses, while the third order is less affected by the reasonable stiffness range; and (2) By introducing a correlation parameter, which is defined by imbalance mass and amplitude of the particular nodes, the most influenced nodes can be found. With the rotor model adopted in this work, the overhang node is most influential.  
Based on the findings, by choosing the overhang node to add trial weight, an overhang rotor is easily balanced. Through experimental testing, this analysis has significant meaning in terms of controlling the vibration of the overhang rotor. The theory provides an alternative approach to modal analysis which needs more knowledge of the system.  
Conceptualization, S.Z. ([PERSON]), S.Z. ([PERSON]); methodology, S.Z. ([PERSON]), J.Y. and Y.Z.; software, S.Z. ([PERSON]); validation, S.Z. ([PERSON]), J.Y. and Y.Z.; formal analysis, S.Z. ([PERSON]); investigation, [PERSON] ([PERSON]), J.Y. and Y.Z.; writing--original draft preparation, [PERSON] ([PERSON]), writing--review and editing, [PERSON] ([PERSON]); visualization, [PERSON] ([PERSON]); supervision, [PERSON] ([PERSON]); project administration, [PERSON] ([PERSON]); funding acquisition, [PERSON] ([PERSON]). 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 nos. 51479136,12102234, 11902184, 11502161),the Project of Tianjin Municipal Transportation Commission (2019-15), and the Project of Tianjin Natural Science Foundation (17)CYBJC18700).  
Not applicable.  
Restrictions apply to the availability of these data. Data was obtained from Hebei Ruizhao Laser Remanufacturing Technology Stock Co., Ltd and are available from [PERSON] with the permission of Hebei Ruizhao Laser Remanufacturing Technology Stock Co., Ltd.  
On behalf of all authors, the corresponding author states that there is no conflict of interest.
# Nodal Accuracy Improvement Technique for Linear Elements with Application to Adaptivity
## 5 Numerical Examples  
In this section, the first two subsections, i.e., Sections 5.1-5.3, are dedicated to verifying the convergence orders of the FE solution \(u^{h}\), EEP solution \(u^{*}\), improved FE solution \(\widetilde{u}^{h}\) and improved EEP solution \(\widetilde{u}^{*}\) based on the linear element results on a sequence of uniformly refined meshes. The maximum norm on the domain \(\Omega\) is adopted, and on each element, 10 grid points for 1D problems, \(10\times 10\) grid points for 2D problems and \(10\times 10\times 10\) grid points for 3D problems are taken as sampling points for calculating the errors of interior displacements. Effective index \(\theta\) is defined as the ratio of the estimated error value to the real error value [16]. For an effective error estimator, it is expected that the value of \(\theta\) tends to 1 as the mesh refines, as \(\theta>1\) means overestimation of the error and \(\theta<1\) means underestimation of the error.  
For the subsequent three subsections, i.e., Sections 5.4-5.6, three representative examples of the adaptive FE analyses based on the adaptive algorithm proposed in Section 4 are presented. For comparison, the results from the uniform mesh refinement of linear elements and the adaptive mesh refinement of cubic elements [22] are also included, and the total number of degrees of freedom (DOFs), which is denoted by \(N_{\text{dof}}\), is counted to evaluate their performance on the final mesh.  
In adaptivity examples, to facilitate the pointwise error estimation and checking, the error ratio, i.e., the error divided by the given tolerance \(T_{l}\), is used to normalize the error expressions so that the adaptivity criterion in Equation (15) and stopping criterion in Equation (16) can be equivalently rewritten as  
\[-1<(u-u^{h})/T_{l}<1\qquad\qquad\text{on }\Omega \tag{18}\]  
\[-1<(\widetilde{u}^{*}-u^{h})/T_{l}<1\qquad\qquad\text{on }\Omega \tag{19}\]  
Therefore, as long as the pointwise error ratios \((u-u^{h})/T_{l}\) are bounded by \([-1,\ 1]\), the adaptivity analysis achieves full success.
###### Abstract  
Sign language recognition is one of the most challenging applications in machine learning and human-computer interaction. Many researchers have developed classification models for different sign languages such as English, Arabic, Japanese, and Bengali; however, no significant research has been done on the general-shape performance for different datasets. Most research work has achieved satisfactory performance with a small dataset. These models may fail to replicate the same performance for evaluating different and larger datasets. In this context, this paper proposes a novel method for recognizing Bengali sign language (BSL) alphabets to overcome the issue of generalization. The proposed method has been evaluated with three benchmark datasets such as '38 BdSL', 'KU-BdSL', and 'Ishara-Lipi'. Here, three steps are followed to achieve the goal: segmentation, augmentation, and Convolutional neural network (CNN) based classification. Firstly, a concatenated segmentation approach with YCbCr, HSV and watershed algorithm was designed to accurately identify gesture signs. Secondly, seven image augmentation techniques are selected to increase the training data size without changing the semantic meaning. Finally, the CNN-based model called BenSignNet was applied to extract the features and classify purposes. The performance accuracy of the model achieved 94.00%, 99.60%, and 99.60% for the BdSL Alphabet, KU-BdSL, and Ishara-Lipi datasets, respectively. Experimental findings confirmed that our proposed method achieved a higher recognition rate than the conventional ones and accomplished a generalization property in all datasets for the BSL domain.  
Bengali sign language (BSL); Convolutional neural network (CNN); 38-BdSL; Ishara-Lipi; KU-BdSL; concatenated segmentation; Luminance blue red (YCbCr); Hue saturation value (HSV) +
Footnote †: journal: Applied Sciences
# Cutting Force and Cutting Quality during Tapered Milling of Glass Magnesium Board
## 3 Results and Discussion
### Research on Cutting Force Based on ANOVA (Analysis of Variance)  
ANOVA and F tests were carried out to prove the significance of each factor. As listed in Table 5, the ANOVA analysis was adopted for a significance level of \(\alpha=0.05\), namely, 95% confidence level. By comparing the F value of each factor with F\({}_{0.05}=19.00\), if the F value of a factor was higher than the value of F\({}_{0.05}\), namely, 19.00, the contribution of that factor was significant, otherwise it was insignificant [20; 21]. In this work, the contributions of the taper angle (F\({}_{0.05}=19.00<\) F\({}_{\lambda}=60.726\)) and cutting depth (F\({}_{0.05}=19.00<\) F\({}_{\lambda}=513.136\)) to the cutting force were significant, while the contribution of the spindle speed was insignificant (F\({}_{\rm n}=2.162<\) F\({}_{0.05}=19.00\)).
# Versatile Video Coding-Post Processing Feature Fusion:
## 4 Experimental Evaluations and Discussion
### Qualitative Analysis  
Figures 7 and 8 illustrate a visual comparison of the reconstructed frames between the VVC-compressed content and the proposed network output, with a high QP value of 42. The network output in Figure 7 demonstrates less distortion than the reconstructed frame and a 0.18 dB luma PSNR improvement for the DaylightRoad2 sequence. In Figure 8, the LD configuration preserves clearer details of the FourPeople sequence, with a 0.51 dB luma PSNR gain. Notably, the CNN-post-processed frames exhibit fewer artifacts and higher subjective quality compared to the original VVC decoder output for both RA and LD scenarios.
## 3 Simulation and Experimental Validation
### Controller Optimization and Validation
The simulated results shown in Figure 8a suggest that method 1 will have a relatively serious waterbed effect and stability risk at high frequencies (as indicated by the arrows), while the results in Figure 8c suggest that method 2 will have a relatively mild waterbed lift (controlled within 5 dB) under all measured secondary paths. This comparison indeed underscores the advantages of method 2 in noise reduction and system stability. It also showcases method 2's robustness and adaptability, as it maintains consistent effectiveness even with the addition of new subjects who were not included in the initial controller design. Subsequently, the noise reduction is also measured with the controllers optimized using method 1 and method 2, and the results are shown in Figure 8b,d, respectively. The overall measured results are generally in agreement with the simulation predictions, indicating a strong correlation between theoretical predictions and practical outcomes. Across all subjects, method 2 has demonstrated stable performance with a moderate waterbed lift; this suggests that method 2 offers a reliable approach to commercial ANC headphones.
# Spatial Data-Based Automatic and Quantitative Approach in Analyzing Maintenance Reachability
###### Abstract  
Reachability, as a vital parameter in product maintainability design, exerts a tremendous influence in practical maintenance, especially in the usage stage. To decrease subjectivity in maintenance reachability analysis, this study proposes an automatic and quantitative approach based on the spatial data of the human arm to implement maintenance reachability analysis. The approach focused on two aspects, namely, accuracy and efficiency. In terms of accuracy, the presented methodology starts from the maintenance spot where the human hand is attached. An original global data sequence set was generated, including the wrist, elbow, and shoulder joints, under the constraints of kinematics, in which a data sequence represents an arm motion. Moreover, the surrounding objects are represented by their geometric data, in which each data sequence is analyzed to judge whether collision occurs between arm segments and surrounding objects. In this filtering process, the data sequence is retained if the aforementioned collision does not occur. In terms of efficiency, owing to the large number of global data sequences, the efficiency of the interval selection in collision calculation is also taken into consideration in this methodology. Unlike the traditional methods in the virtual environment, the starting point is the maintenance spot, rather than the human body. Hence, nearly all possibilities of arm postures are considered in a global perspective with little subjective involvement, which enhances the automation and objectivity in maintenance reachability analysis to a certain extent. The case study shows the usability and feasibility by a practical maintenance scene.  
maintainability; maintenance reachability; quantitative analysis +
Footnote †: journal: Applied  
doi: 10.3390/APPL122412804
###### Abstract  
Many factors can influence the displacements of a dam, including water level variability and environmental temperatures, in addition to the dam composition. In this work, optical-based classification, thermal diachronic analysis, and a quasi-PS (Persistent Scatter) Interferometric SAR technique have been applied to determine both forcing factors and resulting displacements of the crest of the Castello dam (South Italy) over a one-year time period. The dataset includes Sentinel-1A images acquired in Interferometric Wide swath mode using the Terrain Observation with Progressive Scans SAR (TOPSAR); Landsat 8 Thermal Infrared Sensor (TIRS) thermal images, and Global Navigation Satellite System (GNSS) for interpreting the motion of the top of the dam retrieved via interferometry. Results suggest that it is possible to monitor both dam water level and temperature periodic forcing factors and resulting displacements via a synergistic use of different satellite images.  
dam displacements; GNSS; Sentinel-1A TOPSAR; Landsat TIRS; PS-InSAR; full graph 10.390/rs13081543
# Evaluation and Improvement of Lidar Performance Based on Temporal and Spatial Variance Calculation
## 4 Optimization of Data Acquisition Parameters and Calibration of Lidar Data  
A Licel transient recorder provides two detection modes simultaneously for PMT application: one is the analog detection mode, which uses the A/D card; the other is the PC detection mode, which uses the PC system. The high voltages applied in PMTs must be set in the linear working range to get the  
Figure 4: Example of the calculation results of spatial variance for both (**a**) analog data and (**b**) photon-counting data. Every group of 30 consecutive bins in a single probing profile from the measurement of the ultraviolet elastic scanning lidar was selected to construct the sample distribution for calculating the spatial variance. The event shown in Figure 2 was selected as the study object. A green line \(\mu=\sigma^{2}\) is plotted to show the necessary condition of Poisson property.  
Figure 5: Statistics of the number of non-zero distributions from the scatter plots of spatial variance and temporal variance shown in Figures 3 and 4.  
optimal gain for enhancing the performance of the lidar system, and the working range is influenced by weather conditions or specifications of lidar system. The evaluation of the linear working range of PMT is meaningful in the calibration of lidar data.  
Moreover, the PC detection system comprises a discriminator and a counter. The discriminator is used to discriminate the voltage level of the pulse height of the PMT output, while the counter is to count the number of effective light pulse signals. Therefore, the preset threshold voltage of the discriminator is important in data acquisition procedures, as the final results of PC data is determined by this preset threshold voltage. Meanwhile, with the increase of the light intensity, the response of the PC system becomes nonlinear, because the output count rate is no longer proportional to the incident light intensity [25]. The estimation of the dead time plays an important role in the correction of pile-up effects in PC data.  
Finally, a novel technique based on variance calculation for data gluing between analog data and PC data is presented in order to produce a uniform expression of a lidar trace.
# Lithological Discrimination of Khyber Range Using Remote Sensing and Machine Learning Algorithms
## 2 Regional Geology and Tectonics  
### Study Area  
The study area lies in the Khyber district between 71\({}^{\circ}\)9\({}^{\prime}\)0\({}^{\prime\prime}\) E and 71\({}^{\circ}\)22\({}^{\prime}\)0\({}^{\prime\prime}\) E longitude and between 33\({}^{\circ}\)56\({}^{\prime}\)0\({}^{\prime\prime}\) N and 34\({}^{\circ}\)12\({}^{\prime}\)0\({}^{\prime\prime}\) N latitude within the tribal belt of northwestern Pakistan. The Orakzai district lies to its south, the Kurram district to the southwest, and Peshawar to the east, whereas the Mohammad district lies to its north. It also borders the Nangarhar province of Afghanistan in the west.
# Toward the Utilization of 3D Blading in the Cantilevered Stator from Highly Loaded Compressors
## 2 Research Object and Investigation Methodology
### Numerical Simulation Method  
The cantilevered stator to be investigated comes from the aft stage of a highly loaded high-pressure compressor, whose hub clearance is constant at 1% blade height. As shown in Figure 2, The numerical simulation is performed under the stage environment, with the simulation domain containing three blade rows: the IGV, the rotor, and the stator. The domain inlet is 2.0 times the chord length upstream of the IGV, while the domain outlet is 3.5 times the chord length downstream of the stator blade. The structured grid was generated using NUMECA Autogrid5; the main blade region and the clearances adopt the O4H topology and the H-O topology, respectively. Moreover, the grid is clustered at the near-wall region to satisfy the requirements of the turbulent model; y+ of the first grid off wall is about 2.5 in the region close to the transition position, and the number is smaller near the trailing edge. After grid independence analysis with grid density, the total grid number for the rotor and stator blade rows was 1.28 million and 1.45 million, respectively [31; 32]. For a 1.5-times finer mesh, the variation of the loss, the static pressure rise coefficient, and the flow angle compared with the selected mesh is less than 0.1%.  
This paper uses the commercial software ANSYS CFX 18.0 to explore the effects of the 3D blading techniques; previous studies have found that the two-equation eddy-viscosity models could simulate the complex vortex flows in the low-speed compressor with satisfying accuracy [33; 34]. As a low-speed compressor (\(Ma\sim 0.2\)), the atmospheric condition (101,325 Pa, 288.15 K) was imposed at the domain inlet, where the total pressure was specified using a circumferential averaged radial profile obtained from experimental results. The mass flow rate was given at the outlet. Rotational periodic conditions were applied to the side walls, whereas the solid walls were defined as the adiabatic non-slip walls. The rotating speed of the rotor was 1100 rpm, and the interface between the rotor and the stator was modeled as the mixing plane. As for the turbulent model, the standard k-\(\omega\) model was chosen, as it can capture more accurate 3D flow details than the standard  
Figure 1: Definitions of 3D blade design in the orthogonal coordinates.  
Figure 2: Model configuration and simulation grid.  
k-\(\varepsilon\) model, while obtaining a better convergence than the SST model [19; 35]. A combination of the second-order spatial and temporal numerics are selected for the transport equations.  
To ensure calculation accuracy, in addition to the default parameters, self-defined parameters, including the compressor pressure ratio, efficiency, and the inlet/outlet mass flow rate, were monitored during the simulation process. The flow field was considered converged when the mass flow discrepancy at the domain inlet and outlet was smaller than 0.1%.
# Analysis and Reduction of Nonlinear Effects in Optical Fiber Frequency Transfer
## 4 Experimental Verification  
### Stimulated Brillouin Scattering  
As depicted in Figure 8, we compared the calculated threshold powers for generating Brillouin scattering with experimental results. These experimental results include values from the published literature as well as our own measurements. The threshold powers for Brillouin scattering in optical fibers with lengths of 1 km, 2 km, 3 km, and 4 km are obtained from ref. [34]. For optical fiber lengths ranging from 5 km to 17 km, we cite the measured threshold powers from ref. [35]. In our laboratory, we conducted experiments using a 120 km single mode fiber to determine the threshold power for generating Brillouin scattering. Our experimental results indicate that the threshold power for a 120 km length optical fiber is approximately 8 mW.  
Overall, the calculated threshold powers for generating Brillouin scattering align well with the experimental measurements. On average, there is a difference of about 4.5% between the experimental and calculated values. The largest discrepancy, about 34%, is observed at a fiber length of 3 km, while the smallest difference of approximately 1% is observed at a length of 13 km. Notably, for fiber lengths ranging from 2 km to 7 km, the experimental threshold powers for generating Brillouin scattering are higher than the calculated values. However, for fiber lengths ranging from 11 km to 120 km, the experimental results are lower than the calculated values. For instance, at a fiber length of 2 km, the experimental and calculated threshold powers for generating Brillouin scattering are approximately 30 mW and 25.5 mW, respectively. The experimental results show that the threshold powers for generating Brillouin scattering are approximately 9.2 mW, which is slightly higher than the calculated values. This experiment is conducted using an optical fiber length of 11 km.