esa-sceva/satcom-chunk-collection huggingface dataset:
## 5 Discussion
### Comparison with Other Positioning Technologies
However, these technologies still face challenges in dynamic environments and in optimizing cost and power consumption for certain applications. In contrast, the proposed ultrasound-based system offers a cost-effective alternative, as the main investment is made in the installation of the beacons, while the robots only require low-cost receivers. This is particularly advantageous for scenarios involving a fleet of robots, where equipping each robot with expensive sensors can be cost-prohibitive. Despite its limitations in sampling rate and range compared to some other technologies, the ultrasound-based system provides a balanced solution that is especially suitable for controlled indoor environments. In these settings, factors such as cost-effectiveness, robustness, and simplicity often take precedence over high-speed tracking or large-scale mapping capabilities. The proposed system's ability to provide accurate, absolute positioning with minimal computational overhead and power consumption makes it an attractive choice for a wide range of indoor applications. Ultimately, the choice between these technologies depends on the specific requirements of the application. Factors to consider include the type of environment (e.g., indoor, outdoor, and dynamic), accuracy requirements, update rate needs, available computational resources, power constraints, and budget. The ultrasound-based isochrone method presented in this paper offers a unique combination of benefits that make it particularly well suited for indoor applications demanding accurate and efficient localization. By leveraging the advantages of ultrasound technology, such as its robustness to lighting conditions and low computational requirements, the proposed system fills a crucial gap in the spectrum of localization solutions. It provides a cost-effective and reliable alternative for applications where the operating environment is well defined, and the primary focus is on achieving precise positioning without the need for complex, resource-intensive algorithms or expensive sensor suites.
## 3 Velocity Obstacle Model for MASS
### Building the VO Model  
An MASS is generally equipped with different kinds of sensors, including camera, laser radar, and ultrasound radar. The MASS can obtain its own location from GPS and the locations of surrounding ships from AIS. The radar system also detects static objects. Based on this information, an MASS can generate the VO model of surrounding objects in its own configuration space.  
Suppose the location of the MASS is at \(X_{t}\) and with velocity vector \(v_{t}\). There are \(K\) objects detected, which are denoted by \(\{B_{1},\cdots,B_{k}\}\). The contours of these objects can be detected by the radar system installed on the MASS. We denote the contours of these objects by \(\{Y_{1},Y_{2},\cdots,Y_{K}\}\). The velocity vectors of the surrounding objects (including static ones) are denoted by \(\{v_{B_{1}},v_{B_{2}},\cdots,v_{B_{K}}\}\). Based on this information, the extended contours of surrounding objects can be calculated by shrinking the original contours by a radius \(r_{A}\), which is the radius of the MASS. Using this information, the VO model for the MASS at a time instant \(t\) can be built by Algorithm 1. The algorithm processes each mobile object once and calculates VO for time \(t\) by the union VOs of all the surrounding objects.  
```
Input:\(X_{t},v_{t},\{Y_{1},\cdots,Y_{K}\},\{v_{Y_{1}},\cdots,v_{Y_{K}}\}\), interval length \(\Delta_{t}\) Output:\(VO\), i.e., the velocity obstacle regions generated by surrounding objects
1 Initialize \(VO=\emptyset\) ;
2 for\(i\)do
3 Generate extended contours \(\{Y^{\prime}_{i}\}\). \(\{Y^{\prime}_{i}\}\) is generated by shrinking the contour \(Y_{i}\) with radius \(r_{x}\);
4 Calculate \(CC_{X,Y_{i}}=\{v_{t}|\lambda_{X,Y_{i}}\cap Y^{\prime}_{i}\
eq\emptyset\}\), i.e., the cone region centered at \(X_{t}\) and tangent to \(Y^{\prime}_{i}\);
5 Calculate \(VO_{i}=CC_{X,Y_{i}}\oplus v_{Y_{i}}\), where \(\oplus\) is the Minkowski vector sum operator. ;
6\(VO_{B_{i},H}=\left\{v_{t}|v_{t}\in VO_{i},\left\|v_{X,Y_{i}}\right\|\leq\frac{ d_{X,Y_{i}}}{\Delta_{t}}\right\}\) ;
7\(VO_{B_{i}}=VO_{B_{i}}\setminus VO_{B_{i},H}\);
8\(VO=VO\cup VO_{B_{i}}\);
```  
**Algorithm 1**Building the VO model from sensor readings.
# Energy Recovery via Thermal Gasification from Waste Insulation Electrical Cables (WIEC)
## 4 Results
### Controlled Gasification Theoretical Parameters  
Regarding theoretical parameters, the cold gas efficiency (CGE) is a function of LHV, syngas, and fuel flow. The LHV is influenced by the ER, i.e., when ER decreases, the LHV tends to increase, and gasification efficiency also increases. In order to maintain the ideal operating conditions of a commercial gasifier, it is normally operated with an equivalence ratio of 0.25 [38]. Air intakes in the reduction zone increase the rate of the devolatilization reaction due to pyrolysis and heterogeneous oxidative reactions.  
Figure 2: Syngas composition.  
However, when the ER increases, the concentration of CO\({}_{2}\) present in syngas tends to increase, while the concentrations of CO and H\({}_{2}\) decrease. The gasification temperature is mainly responsible for the directional change in the balance of gasification reactions. For example, endothermic reactions tended to change directly with increasing temperature or indirectly with decreasing temperature. Therefore, when there is an increase in ER, the conversion of carbon into CO and H\({}_{2}\) is highly reduced, favoring other products, mainly CO\({}_{2}\)[39]. Although the rate of gas production increases and the CGE increases, the calorific value of syngas decreases, and the efficiency of gasification also decreases (Figure 3), with steam responsible for contributing to the water-gas reaction and the greater the value, the lower the conversion to synthesis gas [40]. For comparison of the different operating temperatures, the yield of synthesis gas decreased with an increase in temperature, indicating that the high temperature may not have been as beneficial for the production volume as for the quality of the syngas. An increase in ER leads to a poorer syngas composition, because of the N\({}_{2}\) dilution effect, and also because the H\({}_{2}\) and CO contents decrease. With high ER, more oxidizing agent enters in the process, therefore, higher CO\({}_{2}\) content is observed, and it can be concluded that combustion reactions are dominant over gasification reactions.  
For the study carried out, the highest CGE was 80.1, with an ER of 0.28 to 100% pine chip, and the minimum was obtained in the 80:20 test, i.e., a CGE of 53.7 and a 0.24 ER. Regarding the effect of ER on CGE, it is not relevant since the concentration of CO, H\({}_{2}\), and CH\({}_{4}\) contributes to an increase in the HHV of syngas and ER close to 0.2 [41]. In addition to this point, since the yield of the products above decreased and the consumption of biomass increased as WIEC was added, CGE follows a downward trend.
# Reducing Forecast Errors of a Regional Climate Model Using Adaptive Filters
## 5 Experiments
### Results
There is a 6-h interval between each value of the time series; therefore, the four-coefficient filter, comprising a 24-h time period, removes the diurnal cycle, which is a strong signal in meteorological time series. The 6-h interval is the sampling interval availability of the Eta RCM forecasts data set. It should be noted that a four-coefficient filter refers to a one-day forecast. Moreover, the NMSE leads to a larger MER centroid and smaller dispersion than \(e_{\text{max}}\) and \(e_{\text{NR}}\). This is expected given that the filter is adapted in the least-square sense for the whole time series length, i.e., on average. Figure 9: Effectiveness rate of RCM forecast deviation reduction at 500 hPa with different filter orders (above), and a larger view with values greater than 50%. From the preceding results, we now fix the filter order at \(N=4\) and the number of clusters at \(K=19\) and evaluate the MER with respect to the error metrics NMSE, \(e_{\text{max}}\), and \(e_{\text{NR}}\), separating the analysis into climate variables: meridional wind, zonal wind, and geopotential height. The results are shown in Table 3. At 250 hPa, meridional wind provides the best MER performance with respect to the three forecast deviation metrics. At 500 hPa, all studied climate variables show equivalent MER performance with respect to NMSE and \(e_{\text{NR}}\), whereas for the geopotential height, one achieves the best MER performance with respect to \(e_{\text{max}}\).
# Security Scheme Based on Parameter Hiding Technic for Mobile Communication in a Secure Cyber World
###### Abstract  
Long Term Evolution (LTE) and Long Term Evolution-Advanced (LTE-A) support a better data transmission service than 3G dose and are globally commercialized technologies in a cyber world that is essential for constructing a future mobile environment, since network traffics have exponentially increased as people have started to use more than just one mobile device. However, when User Equipment (UE) is executing initial attach processes to access LTE networks, there is a vulnerability in which identification parameters like International Mobile Subscriber Identity (IMSI) and Radio Network Temporary Identities (RNTI) are transmitted as plain texts. It can threat various services that are commercialized therewith in a cyber world. Therefore, a security scheme is proposed in this paper where identification parameters can be securely transmitted and hidden in four cases where initial attach occurs between UE and Mobility Management Entity (MME). The proposed security scheme not only supports encrypted transmission of identification parameters but also mutual authentication between Evolved Node B (eNB) and MME to make a secure cyber world. Additionally, performance analysis results using an OPNET simulator showed the satisfaction of the average delay rate that is specified in LTE standards.  
Keywords:initial attach; mutual authentication; LTE; hiding technic; session management +
Footnote †: journal: Computer Science and Engineering
# Improved Hierarchical Adaptive Deep Belief Network for Bearing Fault Diagnosis
## 1 Introduction
[23] comprehensively reviewed contemporary rolling bearing fault detection, diagnostic and prediction techniques, which referred to DBN-based prognostics and health management (PHM). By utilizing the DBN's learning ability, [PERSON] et al. [24] presented a method using multivibration signals to identify various bearing faults. The direction of mechanical equipment fault diagnosis presents a trend of big data. For high-dimensional or large-volume samples, the conventional deep learning model faces difficulty in effectively guaranteeing operational efficiency [25]. As one of the classic models of deep learning neural networks, DBN voluntarily extracts the intrinsic features of data through greedy layer-by-layer unsupervised learning, avoiding the complexity and uncertainty caused by artificial extraction of features, and improving classification accuracy. In the present research, the bearing fault identification is realized on the basis of the proposed hierarchical optimization DBN algorithm. The presented method is derived by Nesterov momentum (NM) and adjusted by an independent adaptive learning rate algorithm, which aims to improve the convergence and fault diagnosis performance. First, the signals are converted to a frequency domain for the input of the deep learning model. Then, a hierarchical deep learning structure is constructed to recognize the bearing fault type and degree. NM compensates to infer the location of the parameter drop and control the speed of parameters to reach the optimal solution, thereby avoiding missing optimal point caused by the traditional momentum method. Furthermore, a learning rate adjustment strategy is presented, to adaptively set the gradient descent step size, to accelerate the model learning and enhance the generalizability of the model. Finally, global fine-tuning is completed by Softmax classifier to constitute the entire model. Bearing signals from various fault conditions are analyzed to prove the satisfactory performance. In terms of the diagnostic accuracy, the proposed method achieves the highest accuracy for bearing fault identification compared with support vector machines and the standard deep belief network. As for the operational efficiency, the optimized model can accelerate the model training speed, improve the generalization ability of the deep belief network, and realize bearing fault diagnosis effectively. The structure of this paper is presented as follows. Section 2 explains the basic theory of DBN. Section 3 illustrates a hierarchical model based on the improvement of DBN to recognize the bearing fault type and degrees. Section 4 describes experimental information and validates the performance of the raised method. Finally, Section 5 concludes this paper.
## 4 Parametric Studies
### Embankment Height and Pile Spacing  
Figure 12 shows the vertical stress distribution on rigid floating piles with a pile spacing of 2.5 m under embankments of heights 2.0 m, 4.0 m, and 6.5 m. It has been observed that as the embankment height increases, the self-weight stress of the embankment continuously increases, leading to a corresponding increase in the vertical stress within the embankment. With the increase in embankment height from 2.0 m to 6.5 m, both the outer and inner arch heights of the soil arch increase, accompanied by an increase in the  
Figure 11: Variation in settlement with embankment height for different bearing capacities of subsoil.  
thickness of the soil arch. The stress above the piles increases by 392%, and the pile-soil stress ratio increases from 6.59 to 16.2, highlighting the enhanced soil arching effect.  
As shown in Figure 13, there is no variation in the stress distribution in the upper area of the embankment as the pile spacing increases, which is equal to the embankment load. It signifies that the upper soil of the embankment remains undisturbed. However, the vertical stress above the piles gradually decreases at the bottom of the embankment, while the vertical stress above the subsoil gradually increases. With an increase in pile spacing from 2.0 m to 3.0 m, the pile top stress decreases from 596 kPa to 412 kPa, and the surface stress of the subsoil increases from 39.05 kPa to 57.24 kPa. Furthermore, as the pile spacing increases, the height of the soil arch progressively increases. However, the pile-soil stress ratio decreases from 15.26 to 7.21, reducing load transfer to the piles.  
Figure 12: Variation in vertical stress with different embankment heights.  
Figure 13: Variation in vertical stress with different amounts of pile spacing.  
Figure 14 presents the variation in the earth pressure coefficient in the embankment as a function of the embankment height normalized by the net pile spacing (\(s\) - \(a\)). It has been found that when \(H/(s\) - \(a)\geq 1.6\), the earth pressure coefficient at the top of the embankment still approaches \(K_{0}\), indicating the onset of the soil arching effect. Even if the \(H/(s\) - \(a)\) reaches 3.25, the maximum value of \(K\) at the bottom of the embankment does not reach \(K_{\rm p}\), implying the absence of plastic failure. It has been concluded that the soil arching effect in the embankment supported by rigid floating piles does not fully develop due to the weaker foundation. With an increase in \(H/(s\) - \(a)\), the value of \(K\) gradually increases. When \(H/(s\) - \(a)\) is 3.25, the peak value of \(K\) in the embankment reaches 2.84, representing a 60% increase compared to \(H/(s\) - \(a)\) = 1.6. For the embankment with \(H/(s\) - \(a)\) = 1, however, the variation in \(K\) along the height of the embankment follows an \"s\" shape without the occurrence of soil arching. Additionally, it has been found that with an increase in pile spacing, both the inner and outer arch heights in the embankment gradually increase.
## 1 Introduction
After the nozzle was additively manufactured by powder-bed fusion of metals using a laser beam (PBF-LB/M), small cubes of a Mo-Si-B alloy could be built without extensive oxidation. [PERSON] et al. [19] developed a dedicated shielding gas nozzle for the powder-based LMD of large structural space components made of titanium alloys. A honeycomb-like structure was applied in conjunction with a faster outer flow curtain to prevent turbulence in the shielding gas flow and, thus, mixing with the atmosphere. Cooling channels were introduced into the nozzle to counteract overheating due to reflected laser radiation. The complex nozzle design was realized by additive manufacturing through PBF-LB/M. Using this system, mostly oxide-free components made of Ti-6 Al-4V with good mechanical properties could be produced. In the existing studies, various shielding gas concepts for several DED processes were developed, and the effects of the shielding gas atmosphere on the process as well as on the resulting material properties were investigated. For LMD with coaxial wire feeding, depending on the system used, both off-axis [8; 37; 38] and simple coaxial [3; 9; 39; 40; 41; 42] approaches exist for the local shielding gas supply. However, in contrast to powder-based LMD, no in-depth investigations have been carried out with regard to adapted nozzle geometries and the resulting shielding gas coverage. Since wire-based LMD lacks the carrier gas flow of the powder-based process variant and the geometric constraints due to the conical shape of the laser beam have to be taken into account, the nozzle concepts presented for powder-based LMD are not directly transferable. Therefore, the objective of this work was to design a dedicated shielding gas nozzle for LMD with coaxial wire feeding and to investigate its performance thoroughly. So far, a similar concept has not been realized in the literature. For this purpose, a direction-independent shielding gas device was designed based on various methods of fluid mechanics and iteratively improved by means of 3D CFD simulations. Based on the flow studies, a prototype with additional integrated cooling channels was manufactured using PBF-LB/M. The shielding gas concept was validated based on deposition experiments. For individual weld beads, the influence of the shielding gas flow rate on the geometrical properties as well as the melt pool temperature was evaluated. Moreover, a defect-free multi-track multi-layer cuboid was built with close to no oxidation.
## 3 Results and Discussion  
### X-ray Diffraction (XRD) Analysis  
Figure 1a,b represents the XRD pattern of the as synthesized CuFe\({}_{2}\)O\({}_{4}\) and ZnFe\({}_{2}\)O\({}_{4}\) nanoparticles. Respective diffraction peaks of hydrothermally synthesized CuFe\({}_{2}\)O\({}_{4}\) sample peaks were observed and exactly coincide with the reported values (JCPDS file No.: 34-0425). The exhibited reflection peaks of diffraction planes were indexed from ZnFe\({}_{2}\)O\({}_{4}\) (JCPDS 82-1042). The crystal size of the as synthesized powder samples was measured by using [PERSON]'s formula:  
\[(D=(\frac{(0.9\lambda)}{\beta\cos(\theta)}) \tag{3}\]  
where \(D\) is the average crystalline size of the particle, \(\lambda\) is the incident wavelength, \(\theta\) is the Bragg angle and \(\beta\) is the diffracted full width at half maxima. The CuFe\({}_{2}\)O\({}_{4}\) sample (Figure 1a) crystal-line size was calculated for the seven most intensely marked diffraction peaks (\(\theta\) = 15.216, 16.602, 17.916, 21.790, 27.045, 28.802, 31.654), and the corresponding calculated values are 16.20, 35.55, 42.66, 35.82, 36.18, 31.25, and 22.47 nm, respectively. The ZnFe\({}_{2}\)O\({}_{4}\) samples (Figure 1b) crystal-line size was calculated for the six most intensely marked diffraction peaks (\(\theta\) = 15.153, 17.824, 21.651, 26.879, 28.601, 31.402), and the corresponding calculated values are 42.95, 32.32, 32.51, 10.96, 43.93, and 21.77 nm, respectively. The average crystalline size of CuFe\({}_{2}\)O\({}_{4}\) and ZnFe\({}_{2}\)O\({}_{4}\) was found to be about 31.42 nm and 30.74 nm, respectively. Clearly broadened X-ray diffraction peaks indicate that the prepared particles are small in size.
# Image Dehazing Enhancement Strategy Based on Polarization Detection of Space Targets
### Contributions  
A space target polarization dehazing image processing strategy is proposed in our paper, which divides the space target polarization dehazing into three steps, namely preprocessing, polarization dehazing, and image enhancement. In the preprocessing process, a hybrid multi-channel interpolation method based on regional correlation analysis is proposed to reduce the influence of the instantaneous field of view error on image quality and improve the accuracy of polarization information solution before image dehazing. In the polarization dehazing stage, a space target polarization image inversion method based on full polarization information inversion is proposed to restore the target polarization information to the greatest extent. In the image enhancement stage, the method based on discrete cosine transformation is used to fuse the dehazed intensity image with the degree of polarization image obtained by inversion. Through the above methods, the polarization information is added on the basis of the intensity information, and the contrast of the image is significantly improved. Finally, simulated space target images and real space target images were used to verify the effectiveness of the proposed strategy.  
In Section 2, the basic principles of space target polarization detection and the optical system used in subsequent experiments were introduced. In Section 3, the preprocessing methods for space target polarization images were introduced to improve the accuracy of polarization information calculation. After completing the preprocessing of the image, the necessity of the space target polarization dehazing method is verified, and the space target polarization dehazing is introduced in Sections 4 and 5, respectively. In Section 6, the effectiveness of the proposed method was verified using actual measured space target images. In Section 7, a summary and outlook of our work in this paper is presented.
# Real-Time Terrain-Following of an Autonomous Quadrotor by Multi-Sensor Fusion and Control
## 3 Quadrotor Integrated Control
### Height and Vertical Velocity Based on a Cascade PID Controller  
The cascade control system is one of the effective methods to improve the control quality and it has been widely used in process controls. The cascade PID controller is composed of a single loop PID regulator (as the main regulator) and an external set regulator (as a secondary regulator) connected in series to form a dual loop regulation system. The control output of the main regulator is used as the external set regulator and the control output of the external set regulator is sent to the control regulation structure.  
In order to improve the quality of height control effectively, a cascade PID based height controller system is designed as follows. The error between the expected height and the height measured by the range-finder is set as the outer loop feedback of the cascade PID controller, the expected vertical speed is obtained after the outer loop PID controller and then the difference between the expected vertical velocity and the actual vertical speed is set as the inner loop feedback input to accomplish the adjustment of the vertical speed, which finally realizes the dual loop control of the height and vertical speed. The control structure and Simulink are shown in Figures 6 and 7.  
Figure 5: Simulink structures of the integrated control of the autonomous quadrotor.