esa-sceva/satcom-chunk-collection huggingface dataset:
## 2 Fixed Tilt Angle System vs. Horizontal Single-Axis Tracker
### Technical Considerations for \(PV\) Module Mounting Systems
#### 2.1.1 Fixed Tilt Angle System  
The optimal orientation condition for a fixed tilt angle system is with a certain fixed tilt angle facing south (in the northern hemisphere) [33]. The tilt angle of the \(PV\) field depends on the location of the \(PV\) power plant [34].  
The structural system of a fixed tilt angle system is comprised of several elements: columns (1), beams (2), purlins (3), and braces (4) (see Figure 2). The column is embedded in the ground, using a suitable foundation, and it also serves as a seat for the beam. The beam supports the purlins, and the purlins are where the \(PV\) modules are fixed. Depending on the configuration used, a beam can be connected to one or two columns. Therefore, there are two types of configurations in relation to the number of columns [35]: (i) one-column mounted systems (see Figure 2a), and (ii) two-column mounted systems (see Figure 2b):
# Optical Pupil Shift Correction Method for Large Ground-Based Optical Telescopes
## 4 Simulation Analysis and Experimental Verification  
The 4 m telescope illustrated in Figure 11 was used as an example to validate the Hartmann-and-calibration dual detector optical-pupil calibration-compensation method based on the coma-free theory of the Cassegrain system. The optical axis deflection and optical pupil shift introduced through gravitational deformation and temperature change were analyzed. The shift error was actively compensated by secondary mirror positioning, attitude adjustment, and telescope pointing adjustment. Finally, the proposed model and compensation method were validated based on the number of effective sub-aperture points of the Hartmann detector in the actual calibration process of the adaptive optical imaging system.  
Figure 11: Deformation analysis model of the telescope. The node position information of primary and secondary mirrors was obtained via model node calculation.  
Figure 10: The change in coma and ast vs. the FOV of the telescope. The secondary mirror nodal displacement \(d_{y}\) is chosen as 0, 0.5, 1.0, 1.5, and 2.0 mm and the optical aberration is compensated for by the secondary mirror rotation \(t_{x}\).
# A Telepresence Wheelchair with 360-Degree Vision Using WebRTC
## 3 Results
### Experiment 2: QoE Estimation of Wireless Video Streaming Using Neural Networks
We used the trained NN to estimate the QoE for 100 test cases of video streaming. The estimated MOS is presented in Figure 12 in comparison with the measured MOS. The correlation between the estimated MOS and measured MOS is about 94%. The simulation results demonstrated that the proposed scheme provides good predictive accuracy (~94%) between the measured and estimated values. The results achieved reasonable prediction values from the neural network models. This work can potentially help in predicting the quality of service (QoS) in order to react in time for video streaming of a telepresence wheelchair over wireless networks. The measured MOS in Figure 13 demonstrated that the video transmission quality in our telepresence wheelchair is satisfactory. The results show that good estimation accuracy was obtained from the proposed prediction model. This study should help in the development of an estimation of the video quality of a telepresence wheelchair. Moreover, by observing the estimated MOS score, the remote user can navigate the wheelchair into the area, which can guarantee a continuous connection and provide good performance. Figure 12: The performance progress over epochs and regression plots for the training, validation, testing, and all data. Figure 13: Estimated MOS based on Artificial Neural Network (ANN) versus measured MOS.
# Albatross-Like Utilization of Wind Gradient for Unpowered Flight of Fixed-Wing Aircraft
## 1 Introduction
[36] in developing a bio-inspired Rayleigh cycle strategy that is more efficient in terms of computation time than the traditional optimization method. In addition, we developed a method for utilizing a wind gradient  
Figure 1: An albatross flying over the sea to obtain extra airspeed. Because the wind speed below the wave is nearly zero and the wind above the wave has a certain speed, the wind can be considered to comprise two layers with a wind shear between them. Suppose that the initial airspeed of the albatross is 17 m/s in the wind layer below the wave. If the wind speed above the wave is 7 m/s higher than that below the wave, when the albatross faces the wind and crosses the wind shear between the lower and upper wind layers, the airspeed would suddenly increase to 24 m/s. This sudden gain in speed is due to the lack of time for the albatross to change its ground speed. for sustainable climbing [39] in unpowered flight. Simulation experiments and analysis were used to verify the effectiveness of the proposed flight method. The results showed that the proposed method could be used to efficiently guide a micro fixed-wing aircraft through effortless soar in a shear wind. The rest of this paper is organized as follows. In Section 2, the problem of dynamic soaring is defined and the development of a dynamic model of the concept is described. In Sections 3 and 4, the criterion for sustainable climbing is derived, the Rayleigh cycle is explained from an energy viewpoint, and a bio-inspired strategy for implementing the cycle is proposed. In Section 4, the effects of different factors in the criterion are subsequently analyzed and discussed. The results of experimental simulations involving the bio-inspired strategy for implementing the Rayleigh cycle are then presented and validated by the traditional optimized trajectory. Finally, the conclusions drawn from the study are presented. The innovative ideas of this paper are as follows: On the basis of equilibrium theory, a novel criterion for sustainable climbing that is easily implemented for engineers is derived, and this criterion decouples the effects of aerodynamics, environment and wing loading. Moreover, a simple bio-inspired strategy is proposed to generate a Rayleigh cycle, which consumes much less time than the traditional numerical optimization method.
## 4 Test Results and Mechanism Analysis
### Mechanism of Superhydrophobic Nano-SiO\({}_{2}\) on the PSD of Soil Samples  
Montmorillonite is a 2:1-type mineral, and the C-axis of its unit crystal cell was variable owing to the different number of water layers between unit crystal layers, as shown in Figure 14. Generally, the number of the intercrystalline water layers is one, two, or three. The saturated soil samples had three stable water layers and the C-axis or crystal plane spacing was 18.5 A, as shown in Figure 14d. Montmorillonite lost part of its water owing to evaporation in the atmosphere. When the atmospheric relative humidity was more than 50%, the number of water molecular layers was stable at two, as shown in Figure 14c. When the atmospheric relative humidity was low, such as less than 50%, calcareous montmorillonite still had two water layers. Conversely, for sodic montmorillonite, only one water layer may be maintained, as shown in Figure 14b. When the montmorillonite was baked at 105 \({}^{\circ}\)C for 24 h, the water layer can be completely lost between the crystal layers; it shrank to about 9.6 A, as shown in Figure 14a. Except for the water layer, some cations balanced the positive charge of the crystal layer [33].  
In the hydraulic-conductivity test, water was filled between the soil particles. The volume of expansive soil expanded after absorbing water and appeared to have structure loosening, as shown in Figure 15. The loose structure of expansive soil resulted in increased pore size, which primarily affected the amount of capillary water and free water. To some extent, the hydrophobic surface hindered water absorption from soil. Compared with unmodified soil, the surface of modified soil was more hydrophobic. Results of TGA revealed that after adding nano-SiO\({}_{2}\), the content of interlayer water and adsorbed water decreased (Figure 13). Combined with the analysis of PSD obtained via NMR, after saturation, the expansion of montmorillonite crystal in the modified soil was smaller than that in the unmodified soil. Consequently, the crystal plane spacing of modified soil was smaller and the pore radius of micropores and medium pores was smaller, indicating that the volume change of samples was smaller.  
Figure 13: TGA curves of soil samples.
# Experimental and Empirical Study for Prediction of Blast Loads
## 2 Materials and Methods  
### Ideal Blast Wave Characteristics  
An explosion is a physical phenomenon in which there is a sudden, very rapid release of energy. The phenomenon lasts only some milliseconds, and it results in the production of very high temperatures and pressures. During detonation the hot gases that are produced expand in order to occupy the available space, leading to wave-type propagation through space that is transmitted spherically through an unbounded surrounding medium. Along with the produced gases, the air around the blast (for air blasts) also expands and its molecules pile-up, resulting in what is known as a blast wave and shock front. The blast wave contains a large part of the energy that was released during detonation and moves faster than the speed of sound [20].  
Figure 1 illustrates the idealised profile of the pressure in relation to time for the case of a free air blast wave, which reaches a point at a certain distance from the detonation. The pressure surrounding the element is initially equal to the ambient pressure \(P_{0}\), and it undergoes an instantaneous increase to a peak pressure \(P_{S0}\) at the arrival time \(t_{A}\), when the shock front reaches that point. The time needed for the pressure to reach its peak value is very small and for design purposes it is assumed to be equal to zero. The peak pressure  
\(P_{S0}\) is also known as side-on overpressure. The peak overpressure \(P_{S0}-P_{0}\) is marked as \(P_{ti}\) in the following sections. The value of the peak overpressure as well as the velocity of propagation of the shock wave decrease with increasing distance from the detonation centre. After its peak value, the pressure decreases with an exponential rate until it reaches the ambient pressure at \(t_{A}+t_{0}\), where \(t_{0}\) is called the positive phase duration. After the positive phase of the pressure-time diagram, the pressure becomes smaller (referred to as negative) than the ambient value, and finally returns to it. The negative phase is longer than the positive one, its minimum pressure value is denoted as \(P_{S0}{}^{-}\) and its duration as \(t_{0}{}^{-}\). During this phase the structures are subjected to suction forces, which is the reason why sometimes during blast loading glass fragments from failures of facades are found outside a building instead of in its interior. This specific type of failure is usually due to a primary failure of the glass filling by the positive phase, or a situation may occur where the negative phase has a significantly higher negative impulse value \(i_{s}{}^{-}\)[21].
# Wireless Caching: Making Radio Access Networks More than Bit-Pipelines
## 7 Edge Compression and Proactive Computation in Cache-Empowered RANs
### Preference-Aware Compression  
One of the key application-layer functions is to compress data. In cache-empowered RANs, user preferences can be exploited to improve the compression ratio of lossless and lossy data compression [44, 45], as in Figure 7. A user may prefer a certain subclass of data from a content provider. As a consequence, the symbol distribution of the user's requested data is different to that of data cached at the BS.  
Consider a toy example with an edge-cached website providing image download services. The pixel colors are assumed to obey a uniform distribution if pixels of all images in the website are counted. Therefore, when the website is transmitted to and cached at the BS, colors are mapped to equal-length codewords for maximizing the compression ratio. Consider a user preferring sightseeing pictures only, in which green pixels appear with a high probability. To reduce the bandwidth consumed in serving this particular user, the BS may re-map green pixels to a shorter codeword. This preference-aware approach is also referred to as edge compression. It will not incur much additional complexity by adopting universal source coding without the knowledge about symbol distributions.  
Classic data compression is source-specific, while edge compression is user-specific. It challenges the current protocol stack inspired by the source-channel separation theorem. More particularly, no application-layer function is performed at present-day BSs. By contrast, edge compression requires BSs to implement application-layer protocols. Other research opportunities include edge-compression-friendly recommendation and multicasting. RSs may change a user's preferences, thereby holding the promise of further improving the compression ratio at the edge. The existing physical-layer multicasting relies on using a common codebook of source coding, which is not compatible with user-specific compression. Further cross-layer design of edge compression and multicasting is desired.
# Theoretical Optimization of Trapped-Bubble-Based Acoustic Metamaterial Performance
## Problem Formulation
### Bubble Array with Reflector  
It is expected that the practical applications of the metascreens coupled with the metal reflector to increase the absorption of the incoming acoustic wave, as proposed in literature [20], can be limited due to relatively high total mass of the system. The system proposed in [20] operates in MHz range for the buubles trapped in cavities with square cross-section (\(14\times 14\)\(\upmu\)m). To address this issue, we propose to use lighter reflectors (e.g., machine wax, which has a mass density almost 10 times smaller than the steel). To reduce the transmission of the incoming wave, several layers of the metascreens can be stacked and coupled with the reflectors. The similar concept was proven to be beneficial in designing bubble phononic crystals [21] and resulted in existence of multiple bandgaps in relatively wide (MHz)frequency range [17]. This will allow both to reduce the total mass of the device and increase the number of the scatterers.  
Now, let us estimate an effect of presence of the reflector on the frequency dependence of the energy coefficients. [PERSON] et al. [20] demonstrated that, if the reflector is present near the bubble metascreen, the total amplitude transmission coefficient is given by:  
\[r_{tot}=r+\frac{t^{2}r_{0}e^{2 ikh}}{1-rr_{0}e^{2 ikh}} \tag{14}\]  
where \(r_{0}\) is a an amplitude reflection coefficient of the reflector. Introducing energy transmission coefficient, \(T_{ri}\) we obtain extremal problems:  
\[\frac{dT_{r}}{d\Omega}=0,\quad\frac{dT_{r1}}{d\Omega}=0,\quad\frac{dT_{r2}}{d \Omega}=0 \tag{15}\]  
for cases of absence of interface, 1- and 2-interface, respectively.
# Preliminary Seismic Hazard Analyses for the Ugandan Region
## 3 Materials and Methods
### Calculating the Hazard  
Once potential seismic source zones were identified and characterized, and GMPEs were selected, calculating the seismic hazard could commence. The Ugandan study region was discretized into sites at every 0.5\({}^{\circ}\) in latitude and longitude, which is about 50 km apart, resulting in 575 sites. The hazard integral was calculated for each site. However, since this study considers two GMPEs, the use of a logic tree was used in integrating them into the hazard calculation. A logic tree is basically a mathematical construct to help account for various options in a calculation. There was a root which describes the point of interest, nodes which branched off from the root or previous nodes, and the final products were the leaves. The root and leaves were also nodes. The branches connecting the nodes allowed the user to assign weights to different components used in calculations, thereby calculating a contribution to each seismic hazard calculation. The weights in each level of the logic tree summed to 1. If there was only one branch emanating from a node, then the weight of that branch was 1.  
An example logic tree used for this study is shown in Figure 2. The logic tree starts with each site in the Ugandan region, generally termed \"Uganda\" and suggests 4 seismic sources as zones with accompanying earthquake recurrence law parameters, as well as minimum and maximum moment magnitudes. Each branch then splits into two branches, each indicating the GMPE used. For this study, the weight assigned to the branch that utilizes the Toro [29] GMPE is 0.6 while the weight of the branch that utilizes the Idriss [30] GMPE is 0.4. Note that these weights sum to 1.  
Figure 1: Results from considered ground motion prediction equations in terms of PGA for \(M_{w}\) = 5, 6, and 7 [29; 30].  
The hazard calculation at each site will focus on PGA as it will better help compare to work by others as mentioned in the previous section. The mean annual rates of exceedance for PGA at each site will be compared to the hazard level, which from previous studies correspond to 10% exceedance in 5, 10, 20, 50, 100, and 500 years. As each site will have a PGA to a specific hazard level, seismic hazard maps can be constructed according to the hazard level, which can be used in infrastructure planning and design.
## 1 Introduction  
Virtual reality (VR) systems are continuously advancing, offering users increasingly realistic and immersive experiences through the stimulation of various senses. To increase the immersion, presence, and user experience, it is necessary to create a complementary multisensory experience in VR, allowing users to feel more physically engaged and deeply absorbed in the virtual world [1]. Haptic feedback, which stimulates the sense of touch, can significantly contribute to this. Numerous studies have demonstrated that the introduction of haptic feedback positively impacts both the subjective perception of presence and influence, as well as objective, task-related performance in immersive extended reality (XR) environments. Reported benefits include faster task completion times [2, 3, 4], improved accuracy [4], enhanced user experience [5, 6], more natural interaction [7, 8, 9], greater perceived realism [10], increased enjoyment [10], deeper immersion [10, 11, 12], a stronger sense of embodiment and ownership [13], and even the perception of improved task performance, including increased perceived performance and reduced perceived difficulty [10, 11].  
A systematic analysis of papers published from 2010 to 2024 found that haptic feedback enhances realism, modulates emotional responses, and influences behaviors such as compliance, decision-making, and social interaction in VR, which represents one of the most sophisticated aspects of interaction [14]. Moreover, research has shown that haptic feedback can be highly beneficial in both increasing the accessibility of existing applications for people with impaired vision and hearing, and in enabling the creation of new applications specifically designed for them. For example, gamepad vibration could be used for the development of audio-haptic maps [15; 16], more inclusive games [17; 18; 19], or specialized applications aimed at improving reality perception for individuals with sensory impairments [20]. These findings confirm the capability of haptic feedback to effectively stimulate the sense of touch.
## 2 The Experimental Campaign  
### Specim Geometry and Test Setup  
The overall morphology of the specimens (Figure 1) was chosen to allow cyclic shear to be imposed exactly at the interface (i.e., with no eccentricity). The interfaces were 500 mm long and 100 mm wide. The overall dimensions of the specimens were, however, significantly larger to allow for the positioning of the testing equipment within the testing frame and to ensure that the specimen was fixed in the testing position at a distance from the interface, to avoid the positive effect of restraining forces on the interface shear resistance. The two parts of the specimens were reinforced and designed to avoid the formation of cracks, not related to the interface behavior [22]. The interfaces were crossed by three (3) reinforcing bars 8 mm, 12 mm, or 16 mm in diameter. To avoid parasitic rotation of the specimens during testing, the decision was taken to use three reinforcing bars throughout the experimental campaign. Thus, to reach different reinforcing ratios, the diameter of the bars varied. The reinforcing bars were positioned at mid-width of the interface. The axial distance between consecutive bars was equal to 21.25, 14.17, or 10.63 times the bar diameter for the specimens with 8 mm, 12 mm, or 16 mm diameter bars, respectively (Figure 1). The distances between consecutive bars are within the prescriptions of the EOTA TR066 [23]. B500C-grade (EN 10080 [24]) deformed steel bars were used, with a mean yield strength equal to 560 N/mm\({}^{2}\). Class C steel (according to [24; 25]) is hot rolled and weldable. The bars have two longitudinal ribs, as well as transverse ribs of alternating direction on both sides. The specimens were constructed in two phases. Initially, block \"A\" corresponding to old concrete was constructed. When the concrete was mature enough, the surface of block \"A\" corresponding to the interface was roughened (chipped) using a pickaxe (Figure 1b). Approximately 28 days after the construction of block \"A\", the second block, \"B\", simulating new concrete, was cast against the old concrete. The reinforcing bars were (a) cast-in in both concrete blocks. The anchorage length was a parameter of the test (6.25 d\({}_{\text{b}}\), 12.5 d\({}_{\text{b}}\), or 20.0 d\({}_{\text{b}}\), Table 2) and it was the same for the two concrete blocks (Figure 1a), each side of the roughened interface. Alternatively, and depending on the test objective, (b) the reinforcing bars were post-installed initially in the first block, \"A\", using epoxy resin mortar to a depth (6.25 d\({}_{\text{b}}\) or 12.5 d\({}_{\text{b}}\)) that observed the manufacturer's specification. The epoxy resin mortar is a high-performance thixotropic adhesive of two components, solvent-free, conforming to the requirements of EN 1504-6:2006 [26]. The bars protruded to a length sufficient for full anchorage by bond in the second concrete block, \"B\" (Figure 1b). The purpose of this option was to study the behavior of interfaces governed by the post-installed portion of the reinforcing bars.
# Propagation Mechanism of Pressure Waves during Pulse Hydraulic Fracturing in Horizontal Wells
## 4 Results and Discussion
### Influence of Wellbore Section Length  
#### 4.3.1 Influence of Horizontal Section Length  
In order to investigate the influence of horizontal section length on pressure fluctuations at the downhole, a constant liquid injection scheme and vertical section length of the well tubing are maintained, while the horizontal section lengths are varied to 1000 m, 1500 m, and 2000 m.  
As evident from the simulation results in Figure 10, the downhole pressure and amplitude of pressure fluctuations gradually decrease with the increase in the horizontal section length of the well tubing. For every 500 m increase in the length of the horizontal section, the downhole pressure decreases by approximately 5 MPa, and the amplitude of pressure fluctuations reduces by 15% to 25%.