esa-sceva/satcom-chunk-collection huggingface dataset:
# Semantic Distributed Data for Vehicular Networks Using the Inter-Planetary File System
## 3 IPFS (Inter-Planetary File System)
This is the reason why this paper considers the usage of IPFS--mature and fully functional P2P software that could greatly facilitate the creation of a P2P network of vehicles, RSUs, and other IoT devices. IPFS software has been designed with large scalability and fast speed as main characteristics. The distribution and search of content in the P2P network is done using a DHT (distributed hash table) based on the Kademlia algorithm [32]. The DHT allows peers to find content stored in any other peer of the network using only the cryptographic hash of the content. For this task, IPFS supports multiple hash algorithms, although by default it uses 32 bytes SHA-256 hashes. A previous study by [PERSON] et al. demonstrated that the DHT algorithm can be used to find content in a P2P network with one million peers [33]. The DHT search uses a hash as input and the result is a list with the peers that currently hold content matching that hash. The interested peer can then select any peer from the list and establish a direct connection to download the content. As the content search is done by hash, IPFS guarantees that the original content has not been altered. If the content is modified, the hash is effectively changed, and the content is rejected. This is exactly the reason that IPFS does not support searching by content name or description, as it would allow peers to tamper with the content before sending it to others. However, this safety measure becomes an inconvenience for vehicle networks, given that the interested node would need to know the hash of the requested information prior to fetching it from the network. Figure 4 shows the process of sharing a file with other peers. Note from the figure that IPFS 32 bytes SHA-256 hashes are encoded as strings using Base58 and adding the prefix Qm. Although the example shows how to share a file, IPFS is not file-oriented but block-oriented. Each shared block has a maximum size of 256 kB and can be individually addressed using its hash. Content hashes are known as CIDs (content identifiers). When a large file is shared, IPFS splits it into multiple interlinked blocks. IPFS can also share complex file structures (such as Web pages). The interlinked blocks are stored using a Merkle tree [34], a structure that guarantees tamper proof storage and avoids data duplication. This technical solution is also used by Git version control software. Thanks to Merkle trees, nodes only need to know the CID of the root block of the tree to be able to download the whole structure with complete guarantee of integrity of all the downloaded blocks.
## 2 Background
### Innovations for Automated Air-to-Air Refueling (A3R)  
While no UA currently exists in the Department of Defense (DoD) that has been authorized to conduct the A3R portion of a mission, the task has been accomplished on both crewed aircraft and UA as a demonstration. Extensive research has been conducted on the algorithms required to complete the task from as a receiver, specifically the computer vision (CV) portion of A3R [19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36]. As ranges increase for UAs to travel to complete the mission, the demand for a UA capable of A3R will continue to increase as well.  
The first crewed aircraft to demonstrate A3R resulted from a combined research effort between the National Aeronautics and Space Administration (NASA) and the Defense Advanced Research Projects Agency (DARPA) in 2005 and 2006 [37]. Phase 1 of the program involved demonstrating A3R between a crewed F-18 aircraft acting as the receiver and a crewed Omega Air B707 tanker. In this case, the pilot in the receiver aircraft allowed the autonomous agent to control the flight path of the receiver aircraft to complete the engagement. For safety and risk mitigation, the pilot served as a human-on-the-loop (HOTL) and would be able to override the autonomy to safely separate the two aircraft in  
Figure 7: Visual depiction of right echelon formation (tanker at left; refueled aircraft at top right).  
the event that the approach became unsafe or the autonomous agent began to operate in an unsafe manner. At the completion of the research program, NASA/DARPA successfully designed, developed, and tested a prototype system that was capable of completing the A3R portion of a mission, however this capability was never integrated into a fielded platform.  
On 22 April 2015, the USN, using the Northrop Grumman built X-47B Unmanned Carrier Air Vehicle Demonstrator (UCAS-D), demonstrated the A3R portion of the mission using the X-47B as the receiver and an Omega Aerial Refueling Services Boeing 707 tanker [38]. The demonstration program was then discontinued and the X-47B demonstrators were relocated for storage and for public viewing in museums.  
Since the completion of the X-47B demonstration program, the USN has not conducted additional A3R testing with a UA acting as the receiver aircraft. In 2021, during the initial testing of the Boeing produced MQ-25, the USN did demonstrate the capability of a UA to serve as the tanker aircraft when a crewed F/A-18F [39], E-2D [40], and F-35C [40]. Flown by Air Test and Evaluation Squadron (VX) VX-23 and VX-20 test pilots, all completed successful engagements with the MQ-25. VX-23 [41] and VX-20 [42] are the Navy's developmental test squadrons charged with supporting Research, Development, Test and Evaluation of fixed wing aircraft at Naval Air Station (NAS) Patuxent River, Maryland. Given that the USN demonstrated the ability to receive fuel autonomously with the X-47B in 2015 and provide fuel as a tanker autonomously with the MQ-25A in 2021, a logical progression in capability would be to demonstrate a UA aircraft receiving fuel from a UA tanker in the future.
# Methods for Detecting Picric Acid--A Review of Recent Progress
## 2 Selected Fluorescence-Based PA Detection Mechanisms  
### Fundamentals of Fluorescence Quenching Methods  
Fundamentally, luminescence is the process of a molecule returning to a ground state from its excited state via the emission of electromagnetic radiation, with the emitted radiation typically being in the visible light range [23]. Depending on the mechanism by which the molecule achieves its excited state, various types of luminescence, for example, chemiluminescence, electroluminescence and fluorescence, can be differentiated. In the case of fluorescence, this excited state is brought about by the absorption of electromagnetic radiation, with the emitted radiation varying in energy from the absorbed radiation, typically the energy of the emitted radiation being lower than that of the absorbed radiation (Stokes shift) [24].  
The excited state of a molecule can, however, also decay through collisions and interactions with other molecules, leading to non-radiative transitions. Purposefully introducing substances interacting with fluorophores in such a way as to promote non-radiative transitions over fluorescence is the basis of all detection methods relying on the phenomenon of fluorescence quenching.  
Methods based on fluorescence quenching constitute the vast majority of methods for detecting picric acid (PA), however, several fluorescence enhancement mechanisms have also been described. Based on the interaction between the fluorophore and PA, the detection mechanisms can be divided into non-covalent interaction-based phenomena, which include resonance energy transfer (RET) and photo-induced electron transfer (PET) and interaction-free phenomena, which include, for example, the inner filter effect (IFE) phenomenon.
## 4 Results and Discussion
### Effect of Hydrostatic Pressure  
Underwater sensing and information transmission should be capable of working in deep water conditions. To determine the effect of the hydrostatic pressure exerted on the sensing performance of our device, a homemade high-pressure stainless-steel tank was employed to mimic the high hydrostatic pressure environment [23; 44]. The ionic current generated by contacting the gold sheet with the copper working electrode was measured and recorded in the high-pressure tank. The gauge pressure was adjusted from 0 MPa to 1 MPa. Figure 8 shows the dependence of the ionic current signals on the hydrostatic pressure (experimental data can be seen in Table A8 of Appendix A). It can be clearly seen that the magnitude of the ionic current signals was kept almost unchanged as the gauge pressure of the tank increased from 0 to 1 MPa. Therefore, the hydrostatic pressure showed little effect on the ionic current signals.  
Figure 8: Effect of hydrostatic pressure on ionic current.  
Figure 7: Effects of (**a**) working electrode surface area and (**b**) sensing electrode surface area on ionic current.
## 5 Conclusions  
The effective diffusion coefficients and permeability of different rank coals were theoretically deduced with the data from mercury porosimetry. Besides, we have explored the correlation of CH4 diffusivity to porosity and permeability of different rank coals. The conclusions are made as follows:  
1. The calculated effective diffusion coefficient (\(D_{e}\)) is slightly higher than measured results due to the existence of CH4 adsorption in pore surface. The theoretically deduced permeability (k) is similar to the experimental result. This supports the validity of the derivation method of determining effective diffusion coefficient and permeability by mercury porosimetry.
2. The coal composition and the maximum vitrinitere flectance (R\({}_{0,m}\)) exhibits no significant correlation with effective diffusion coefficient (\(D_{e}\)) and gas diffusivity (\(D^{\prime}\)) due to the limited coal samples. However, diffusivity, permeability and porosity present an obviously positive correlation.
3. A distinct power function relationship exists between gas diffusivity and porosity for coals and other rocks. The deduced cementation factors (m values) for coals show relatively high m values (from 2.03 to 2.46), which tends to exhibit a larger m value for coals compared with other rocks due to the unconsolidated nature of coals.  
Conceptualization, Y.C.; Funding acquisition, D.L.; Investigation, X.F.; Methodology, X.F.; Validation, Y.Z.  
This research was funded by the National Natural Science Fund of China (grant nos. 41602170 and 41772160), and the National Major Research Program for Science and Technology of China (2016 ZX05043-001). The authors declare no conflict of interest.
## 3 Results and Discussion
Because the morphologies of Au NPs are irregular, the polarization of electromagnetic wave reflected from Au NPs is randomly distributed. Therefore, the proportions for the Raman signal with different polarizations change as a result of the disturbed polarization of excitation light. Figure 4: Magnetic field–induced modulation of the Raman intensity in different polarization configurations. (**a–c**) Magnetic field–dependent polarized-Raman intensity of 2 LA(M), \(E^{\prime}\) and \(A^{\prime}_{1}\) modes for WS\({}_{2}\)/SiO\({}_{2}\), respectively. (**d–f**) Magnetic field–dependent polarized-Raman intensity of 2 LA(M), \(E^{\prime}\) and \(A^{\prime}_{1}\) modes for WS\({}_{2}\)/Au, respectively. Compared with previous literature, the low temperature magneto-optical Raman results obtained in this work exhibit significant difference in resonance magnetic field. Strikingly, the resonance field of monolayer WS\({}_{2}\) in this work (5 T or 5.5 T) is higher than that for the WS\({}_{2}\) grown on sapphire substrate using the CVD method (WS\({}_{2}\)/Al\({}_{2}\)O\({}_{3}\)) at room temperature (4 T) [24]. Based on previous reports, the resonant magnetic field strength is inversely proportional to optical mobility [22]. A smaller optical mobility was predicted for the WS\({}_{2}\) samples in our work according to the results shown in Figures 4 and 5. Normally, the mobility of mechanically exfoliated (ME) WS\({}_{2}\) is higher than that of CVD WS\({}_{2}\)[46]. In addition, as demonstrated on MoS\({}_{2}\), the amplitude of resonance magnetic field at low temperature is smaller than that at high temperature [22; 25]. Therefore, the primary origin for the discrepancy in the optical mobility (or resonance magnetic field) between our work and previous reports can be attributed to the different dielectric properties of the substrates used. As the magnetic field effect on Raman process is through the field-modulated motion of electrons [22], the change transfer from the substrate to WS\({}_{2}\) cannot be neglected. The sapphire substrate has a better electronic screening effect than SiO\({}_{2}\). It is assumed that more photon-induced charges can be evolved into the field-modulated Raman process. Moreover, the LSPR induced hot electrons transferred from Au NPs to WS\({}_{2}\), which disturbed the electronic motion under the magnetic fields. Therefore, the resonance magnetic field for WS\({}_{2}\)/Au is the highest as compared to WS\({}_{2}\)/SiO\({}_{2}\) and WS\({}_{2}\)/Al\({}_{2}\)O\({}_{3}\). These results suggest that a high-k substrate, such as HfO\({}_{2}\), would be helpful for reducing the resonance magnetic field.
## 4 Discussion  
The experimental results described above demonstrate the feasibility of the elimination of the edge part of an arc in the stitching process for the improvement of a cross-correlation coefficient. The modified workpiece-holding mechanism was also found to be effective in improving the quality of stitching between two neighboring arcs in the stitching linear-scan method. Meanwhile, cross-correlation coefficients were found to become smaller with the decrease in the workpiece diameter. The increase in the pressure angle of the stylus in the linear-scan surface profiler due to the decrease in the workpiece diameter is one of the main root causes of the degradation of the cross-correlation coefficients. The pressure angle \(\alpha\) of the stylus can be represented by the following equation:  
\[\alpha=\arcsin\sqrt{1-\left(\frac{x}{r}\right)^{2}} \tag{2}\]  
where \(r\) is the workpiece radius. As can be seen in the above equation, the decrease in the workpiece diameter increases the pressure angle of the stylus even though the same \(X\)-directional position on a workpiece surface is measured. Figure 23a,b summarize  
\begin{table}
\begin{tabular}{c c c} \hline  & **Diameter** & **Out-of-Roundness** \\ \hline Nominal value & 1.500 mm & \textless{}0.15 μm \\ Measured value & 1.497 mm & 0.12 μm \\ \hline \end{tabular}
\end{table}
Table 2: The diameter and out-of-roundness of the workpiece evaluated from the circumferential profile obtained by the stitching linear-scan method.  
Figure 21: Cross-correlation coefficients observed in the stitching operations of the arc-profiles obtained by measuring the workpiece with a diameter of 1.5 mm.  
Figure 22: The circumferential profile of the workpiece obtained through the stitching operation: (**a**) Before the filtering process; (**b**) After the filtering process.  
the differences in two neighboring arc-profiles in the overlapping regions obtained by measuring workpieces with diameters of 3.0 mm and 1.5 mm, respectively (shown in Figures 10 and 19). As can be seen in the figures, the well-matched region was found to become narrower with the decrease in the workpiece diameter. Although the increase in the eliminating region of the edge part of an arc-profile in the stitching process is expected to improve the cross-correlation coefficient, too much data elimination in an arc-profile could result in the degradation of the accuracy of stitching. It is, therefore, necessary to optimize the measurement conditions by the measurement uncertainty analysis based on GUM [21], while considering the number of arcs to reconstruct a whole circumferential profile, the eliminating region of the edge part of an arc-profile in the stitching process, as well as the measurement throughput.
## 4 Discussion
### Comparison of Segmentation Methods
#### 4.1.3 Cross-Resolution  
In this study, we approached remote sensing semantic segmentation by converting a pixel classification challenge into an image translation task. The focus of the model training was mainly on a pixel level, where the original full-view image was cropped to a size of 256 \(\times\) 256. Our experimental results show that different resolution images are used for forest identification, and long time series forest identification and monitoring can be performed by multi-source images, but the effect of data distribution differences on semantic segmentation needs further in-depth study in the future.
# Optical Design and Stray Light Analysis of Underwater Spectral Radiometer
## 3 Underwater Spectral Radiometer Design
### Front-End Optical System  
When a spectral radiometer is used to observe the bidirectional distribution of spectral radiation in the water body, different front-end optical systems need to be selected because of different observation targets. When observing the spectral radiance of the water body, the field of view of the radiance sensor is 2-18\({}^{\circ}\) according to the Marine optical specifications. In this paper, a Gershun tube (Diaphragm cylinder structure) is selected to limit the observation field of the instrument. The Gershun tube is a field-of-view regulating device that can be connected by optical fiber. In order to minimize the influence of stray light and eliminate the radiation from the light source outside the field of view, a stray light-blocking hole is installed inside the Gershun tube [16]. The observed field of view of the radiance sensor in this paper is 10\({}^{\circ}\).  
The cosine corrector is used as the light-collecting device of an underwater spectral radiometer to measure spectral irradiance. During observation, the spectral irradiance of the underwater sun is proportional to the cosine of its incident angle, and the energy intensity received by the detector should also exhibit cosine characteristics. In fact, there is a certain deviation between the observed spectral irradiance of the sun by the instrument and the theoretical value, known as cosine error. Therefore, only when the response of the detector and the angle of the incident light source strictly adhere to the cosine law can the actual situation of the radiation source be objectively characterized. The cosine corrector functions for optical homogenization and serves as a sampling element capable of collecting 180\({}^{\circ}\) spectral radiation, effectively eliminating issues arising from the geometric structure of optical interfaces during optical sampling. By using the cosine corrector as the irradiance observation window of the spectroradiometer, the effect of changes in the solar zenith angle on measurement results can be corrected, yielding the actual solar radiation intensity.
# Reflection Propagation Law of Electromagnetic Waves in U-Shaped Roadway
## 7 Conclusions  
For the electromagnetic reflection propagation law of a U-shaped roadway, a model based on the mirror image method was proposed, and the following conclusions were drawn.  
1. The distance from the transceiver point to the corner and the position of the transceiver point in the U-shaped roadway affect the number of valid reflection lines. When the distance from the transceiver point to the corner decreased, the number of valid reflection lines increased, and the change in the vertical position had a relatively small effect on the number of valid reflection lines compared to the change in the horizontal position of the transmitting point. When the transceiver point is located in the center of the roadway, it facilitates electromagnetic wave propagation.
2. The distance and height between the relay node and the receiving point in the U-shaped roadway affected the reflected field strength at the receiving point. As the distance between the relay node and the receiving point increased, the reflected field strength of the receiving point decreased, and the attenuation of the reflected field strength at the same height was less than that at the same height when the relay node and the receiving point was not at the same height.
3. The frequency of the antenna in the U-shaped roadway, the relative dielectric constant of the roadway walls, and the roadway width all affect the reflected field strength at the receiving point. As the distance between the relay node and the receiving point increases, the reflection field strength attenuation at the receiving point will decrease with a larger roadway width, a smaller relative permittivity of the roadway walls, and a lower transmitting frequency of the antenna.  
Conceptualization, L.G., X.L., X.S., L.M. and C.G.; Methodology, L.G. and X.L.; Software, L.G., X.L. and X.S.; Validation, L.G., X.L., X.S., L.M. and C.G.; Formal analysis, L.G., X.L. and X.S.; Investigation, L.G. and X.L.; Resources, L.G., X.L., X.S., L.M. and C.G.; Data curation, X.L.; Writing - original draft preparation, L.G. and X.L.; Writing - review and editing, L.G., X.L., X.S., L.M. and C.G.; Visualization, L.G. and X.L.; Supervision, L.G., X.L., X.S., L.M. and C.G.; Project administration, L.G., L.M. and C.G.; Funding acquisition, L.G., L.M. and C.G. All authors have read and agreed to the published version of the manuscript.  
Figure 23: Field strength of the receiving point as a function of the distance between the relay node and the receiving point for different roadway widths.  
**Funding:** The study was funded by the 14 th Five Year National Key R&D Program Project (Project Number: 2023 YFB3211001).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data supporting the results of this study are available from the corresponding author upon request.  
**Conflicts of Interest:** The authors declare no conflict of interest.