esa-sceva/satcom-chunk-collection huggingface dataset:
## 2 Background
### Related Works  
Conceptually, blockchain is a decentralized, distributed digital ledger that verifies and stores transactions immutably and transparently, without relying on a third party or central authority. However, blockchain is not appropriate for storing a large number of data files. For that, IPFS offers a reasonable solution. This review discusses related research on blockchain-based platforms and the IPFS distributed file system. This section also reviews previous research on smart contracts and DApps.  
[PERSON] et al. [7] developed an off-chain communication exchange protocol to stabilize a secure channel for downloading digital content using Ethereum and IPFS.  
The integration of blockchain and IPFS technology was also undertaken, to form a framework for a secure, tamper-proof model for academic-research record-keeping with access control methods [6]. The framework utilized smart contracts for storing the metadata of research in the blockchain network and auditing purposes. To enhance file confidentiality, the researchers encrypted the files with the master key before they were uploaded into IPFS.  
[PERSON] et al. [8] tried to prove the integrity of videos on cloud services by calculating the hash of each frame and sending the hash to the blockchain, which is trusted by interested parties.  
To store large amounts of data on distributed storage systems using blockchain technology, one study [9] created the protocol for notarizing files over blockchain (NFB), to ensure communication between the hyperledger blockchain and OKORO (a secured centralized archiving document management system).  
The integration of Ethereum and IPFS has been applied in a social media application [10] for recording data in a distributed data storage service. The researchers developed a web-based, front-end interface and used Infura [11] IPFS API to bridge the communication between the main Ethereum network and the public IPFS.  
Research has also shown that DApps may be the solution for the single point of failure issue, as they have several advantages over traditional applications [12]. For instance, DApps are effective for payment processing because users can use cryptocurrencies for transactions. Users can use private and public keys to authenticate themselves and sign transactions. Moreover, transactions stored on a public ledger are transparent and, in turn, more trustworthy.  
Previous research [13] introduced the Ethereum-based Smart Home System (SMS) for distributing personal data for emergency calls via IPFS. The personal data were signed via the digital signatures of the users.  
These related works leverage the key features of blockchain and IPFS. Likewise, this solution will adopt some of the methods applied in these solutions with several modifications. For instance, instead of using a symmetric key, like a master key, to protect the confidentiality of files, this paper's proposed system relies on creating IPFS and Ethereum private networks. Moreover, in this case, users have to be registered in the private network before they can sign a transaction.
## 3 Results  
### Intra-Session Reliability  
Average values and standard deviations of peak and mean \(GRF\) and \(v\) variables at four different inertias can be found in Appendix A (rotary encoder) and Appendix B (force plates and linear encoder). The analysis of the rotary encoder variables revealed statistically significant bias (\(p<0.05\)) between sets for the following variables: concentric mean \(GRF\) at 0.225 and 0.25 kg\(\cdot\)m\({}^{2}\); eccentric mean \(GRF\) at 0.075, 0.225 and 0.25 kg\(\cdot\)m\({}^{2}\); eccentric peak \(GRF\) for all inertias; concentric mean \(v\) at 0.225 kg\(\cdot\)m\({}^{2}\), concentric peak \(v\) 0.225 and 0.25 kg\(\cdot\)m\({}^{2}\), and eccentric mean and peak \(v\) at 0.225 and 0.25 kg\(\cdot\)m\({}^{2}\). The analysis of the force plates and linear encoder variables (Appendix B) showed statistically significant inter-set bias for mean concentric \(GRF\) at 0.075, 0.225, and 0.25 kg\(\cdot\)m\({}^{2}\); peak concentric \(GRF\) at 0.225 and 0.25 kg\(\cdot\)m\({}^{2}\); mean and peak eccentric \(GRF\) at 0.025, 0.075 and 0.225 kg\(\cdot\)m\({}^{2}\); concentric peak \(v\) at 0.025 and 0.25 kg\(\cdot\)m\({}^{2}\), and eccentric mean \(v\) at 0.075, 0.225 and 0.25 kg\(\cdot\)m\({}^{2}\). ICC values for both criterion and direct measures showed excellent reliability with the exception of criterion measure eccentric mean \(GRF\) at 0.025 and 225 kg\(\cdot\)m\({}^{2}\) and peak \(GRF\) at 0.025 kg\(\cdot\)m\({}^{2}\) (good reliability) and direct measure eccentric peak at 0.025 and 0.225 kg\(\cdot\)m\({}^{2}\) (good reliability). CV variables were acceptable (CV \(<\) 10%) for all variables.  
Inter-set reliability of the \(F\)-\(v\)-\(P\) variables (Table 2) showed statistically significant bias considering V0 (direct measure) and F0, V0, and _Slope_ (criterion measure) (\(p<0.05\)). ICC values for criterion variables ranged from good (V0, \(P_{\rm max}\), slope) to excellent (F0), and for direct measure variables from moderate (V0, \(P_{\rm max}\), slope) to excellent (F0). Unacceptable CV values (\(>\)10%) were found for all the calculated variables, except for F0, regardless of the measure.
## 2 Decomposition of the Standard JRC Profile
### Standard JRC Profile Decomposition Method
#### 2.1.3 Criterion of Critical Decomposition Level  
Accurate decomposition of the waviness and unevenness from the joint surface is the premise for analyzing their mechanical contribution. This is significant to establish the roughness characterization formula which considering their mechanical contribution. The EEMD method only decomposes the standard JRC profile into the approximate component and detail component. In order to obtain the waviness and unevenness from the joint surface, the criterion of critical decomposition level is still needed. According to the qualitative description of waviness by the ISRM, it reflects the macroscopic fluctuation of the joint surface, which contains the main characteristics of the initial standard JRC profile. We speculated that the similarity between the waviness and the initial standard JRC profile would be high. With the increase in decomposition level, more and more detail components are separated from the initial standard JRC profile, which leads to a decrease in the similarity between the approximate components and the initial standard profile. Before reaching the critical decomposition level, the approximate components still contain waviness, and the approximate components can represent the macroscopic fluctuations of the initial standard JRC profile. Therefore, the approximate component has high similarity with the initial standard JRC profile. When the critical decomposition level is exceeded, part of the waviness component is decomposed into the detail component, which suddenly leads to the decrease in similarity between the approximate component and the initial standard JRC profile. Therefore, the similarity between the approximate component and the initial standard JRC profile can be treated as a parameter to determine the critical decomposition level. There are many methods to measure the similarity between two profiles; the cosine similarity criterion was chosen to evaluate the similarity in this study. The unevenness [57] can be regarded as a stationary random process following the Gaussian distribution. The Kolmogorov-Smirnov (K-S) test [72] was chosen to check the distribution characteristics of unevenness at the critical decomposition level.
## 5 Experimental Results and Discussions  
In this section, we evaluate the performance of the proposed method in the respect of IOD accuracy by using various CSI data measured in real-world experimental scenarios. For the experiments, we set \(h=20\), \(\tau=10\), and \(S=52\).
## 1 Introduction  
As the technology around us continues to evolve in size, portability, intelligence, and efficiency, the next logical thing is to find a new purpose for existing components to improve their usability. With the advent of LEDs, researchers have started exploring its properties for establishing data communication between devices which gave rise to the complete new domain of VLC. Increasing interest in VLC has led to a need to revamp the previously existing modulation techniques, posing more unique challenges specific to the nature of visible light. However, the receiver side adoption of VLC is strictly limited to implementation based on Photodiode or Camera. Photodiodes are inexpensive and provide low complexity implementation for VLC as the modulation techniques are based on light intensity. In this case, achieving higher data rates is constrained to the response time of the photodiode [1; 2; 3]. On the other side, exploration of other light properties such as color has shown promising results in terms of better data rate, Refs. [4; 5] but as photodiodes are limited to sensing only light intensities, other techniques had to be explored.  
OCC is considered one possible solution towards achieving a ready-to-use Li-Fi system by utilizing the camera's properties, computational capacity of mobile phones, and chromaticity of the light [6]. Since such systems use existing cameras integrated into mobile phones, they need not require additional dedicated hardware like photodiode [7; 8]. These systems can be used in vehicle-to-vehicle communication, indoor localization, indoor positioning, indoor navigation and augmented reality. In a typical indoor environment, VLC Systems can be deployed as Lamps or Ceiling Lights, as shown in Figure 1. However, other challenges related to the OCC-based Li-Fi System include identifying the Li-Fi access point, adjusting exposure, and video pre-processing. This paper proposes, implements, and evaluates a novel hybrid modulation technique and compares it with the existing two modulation techniques with similar implementational complexities. The objectives of this paper are  
* To study and experimentally evaluate thresholding techniques for On-Off Keying(OOK) and Frequency Shift Keying(FSK) modulation schemes under OCC.
* To propose and implement Hybrid Frequency Shift Pulse Duration Modulation scheme for OCC.
* To evaluate the performance of the proposed technique based on Bit Error Ratio (%), distance, and frames per bit.  
The remainder of the paper is organized as per the following structure. In Section 2, previous studies in the related domain are summarized. In Section 3, an overview of the OCC system is provided, with a basic design and description of other functional elements of the system. Section 4 discusses the design and implementation of reference modulation techniques such as OOK, FSK, and the proposed HFSPDM. Section 5 highlights the obtained experimental result of each modulation technique and provides comparative performance analysis.
## 6 Maintenance Improvement Brought about by DT with XR Devices
### Synchronous and Asynchronous Collaboration during Maintenance Procedures  
Thanks to the centralisation of data made possible using a DT, stakeholders can participate more actively in the different phases of the project, whether they are on-site or on remote platforms. If the data are correctly filtered [36], every stakeholder is allowed to access and analyse their related data. Even before a maintenance operation is planned, the stakeholders are able to monitor the various equipment of a system and provide their own feedback on it. This information can then be added to its related equipment and eventually be used for predictive or inspection purposes (e.g., knowledge from expertise on a similar building used to estimate the remaining life) [22; 43; 70; 72]. This _collaborative analysis_ is considered _asynchronous_ because it is carried out before the maintenance operations.  
Occasionally, during maintenance procedures, the operator may require some assistance in resolving certain issues he or she may encounter. Some complex procedures may require contacting a remote expert for deeper information. Collaboration then becomes _synchronous_ as it is carried out in parallel with maintenance operations. In the literature, there are multiple projects that promote this collaboration through the use of XR devices [22; 43; 69; 72]. Using AR or MR devices, a remote expert can use a shared video feed to obtain contextual information concerning the performed procedure. Then, through the use of a digital avatar and a graphic representation of the gaze direction, the remote expert may simulate his or her presence to the on-site operator and thus share more accurate and contextual information [72] (see Figure 11). This collaboration promotes the sense of telepresence of the remote expert on-site [70; 72; 78]. The communication between the remote expert and the on-site operator can be performed with the combined use of a video call and augmented virtual annotations. These augmentations could be created in real-time by the expert, or before the maintenance, and triggered to provide information to the operator [25; 43; 47; 55; 67; 68; 69; 72; 73].  
Once the maintenance is performed, the collaboration between the on-site operator and the remote expert could continue for deeper analysis. Thanks to the use of the centralised DT and augmentations through XR devices, inspection and maintenance reports could be shared between the on-site operator and multiple stakeholders [22; 72]. However, research is still needed to propose a methodology to improve the way these reports can be created and sent to the DT by the on-site operator [66].  
Figure 10: Inspection of a bridge 3D representation in a virtual environment [79].
# Technique for Searching Data in a Cryptographically Protected SQL Database
## 4 The Proposed Technique for Searching the Required Data
1.4: The application context attribute (atrc) is set to a value of \(K_{ss}\). 1.5: Using the value of the _atrc_1 application context attribute, the next module of special software is decrypted 1.6: Compiling and running some decrypted modules to extract \(K_{sec}\). 1.7: Extracting the key \(K_{sec}\) from the stegocontainer file\({}_{i}^{1}(K_{sec})\). 1.8: The atrc application context attribute is set to \(K_{sec}\). 2: Executing a search query \((Q_{M})\) over encrypted data. 2.1: Decryption of the remaining stored modules of special software, their compilation and execution. 2.2: The pre-decrypted software provides secure, hidden and automatic extraction and decryption (without displaying it in the clear) of the encrypted data required for searches. 2.3: Executing a search query \(Q_{M}\). 2.4: Removing decrypted stored modules of special software. 3: The DBMS server returns the result of the query \(Q_{M}\) to the database proxy server in encrypted form. 4: The database proxy decrypts the received encrypted data and returns to the application the result of the original user query Q. ```  
**Algorithm 2****Query Execution Algorithm (QEA)**  
Thus, in order for the initial request to be executed only by a legitimate user, the latter in an active session must present the corresponding keys stored on the security tokens he has. The corresponding data are decrypted using the legitimate user's key chain, including the \(K_{pd}\) key stored on the database proxy server. Examples of data search queries (SELECT statement). Pattern matching. Search for activities that were carried out using bank cards whose numbers start with '516'. A search query for appropriate activities with such bank cards may look like this:  
select id, at_1, at_2 from TABLE_1  
where get_decr_val(at_1, 'TABLE_1', 'at_1', 'AES128', 'CBC', id))  
Like  
(select get_decr_val('82C5218A798679 BB9C5 FC82B135D66 CD', 'TABLE_1', 'at_1', 'AES128', 'CBC', 272076869831384594639313635595876910277) from dual)  
order by id;  
where the value '82C5218A798679 BB9C5 FC82B135D66 CD' in the _get_decr_val function is the encrypted value \(w_{l}=\arcsin\)\({}^{\prime}\) 516%. Range search. Search for activities that were carried out using bank cards whose numbers range from '378282246310005' to '4454102135347018'.
## 3 Results
### Staged Deployment of LEO Constellation for MEO Navigation Satellite Failure  
#### 3.2.1 Failure Analysis of Single and Double Satellite in MEO Navigation Constellation  
Based on the number of satellites in failure, satellite failure modes are categorized as single-satellite failure, double-satellite failure, and three-satellite failure. They can also be classified according to the orbital plane of the failed satellite into coplanar and non-coplanar satellite failures [21]. In this study, failure mode \(mn\) denotes the \(m_{\text{th}}\) satellite failure on the \(n_{\text{th}}\) orbital plane; for example, failure mode 11 represents the first satellite failure on the first orbital plane.  
In this paper, a universal MEO global navigation constellation is presented. Using the Walker 24/3/1 global navigation constellation as a case study, the orbital altitude of the constellation satellites is 20,000 km with an inclination of 55\({}^{\circ}\). The PDOP \(\leq\) 4 criterion is applied along with the 2\(\sigma\) principle, with minimum observation elevation denoted as 5\({}^{\circ}\) and grid denoted as 5\({}^{\circ}\)\(\times\)5\({}^{\circ}\). Simulation analysis investigated the impact of partial satellite failures on global navigation service performance within a 24 h period.  
Assuming an equal failure probability for all satellites in the constellation, the minimum PDOP is 2.102, and the CV of the constellation is 100% when all satellites are operational, as depicted in Figure 10. The minimum CV of a single-satellite failure constellation is approximately 99.773%, while that of a double-satellite failure is about 93.193%. Single- and double-satellite failures exhibit negligible impact on constellation service performance, thus necessitating the simulation of three-satellite failure.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Parameter** & **Scheme 1** & **Scheme 2** & **Scheme 3** & **Scheme 4** & **Scheme 5** \\ \hline Altitude \(h\)/km & 1117 & 1136 & 1152 & 1176 & 1193 \\ Inclination \(i/^{\circ}\) & 88 & 87 & 86 & 85 & 87 \\ Number of coverage & 13.25 & 13.32 & 13.41 & 13.59 & 13.60 \\ PDOP & 1.9606 & 1.9091 & 1.8648 & 1.863 & 1.8115 \\ \hline \hline \end{tabular}
\end{table}
Table 2: LEO polar constellation scheme.  
Figure 10: Variation in CV following the failure of a single and double satellite: (**a**) single-satellite failure and (**b**) double-satellite failure.
# SD-BROV: An Enhanced BGP Hijacking Protection with Route Validation in Software-Defined eXchange
## 3 SD-BROV: An SDX-Based BGP Route Origin Validation
### Functionality of SDX-Based Route Validation  
To make SDX capable of managing route validation adaptively, the design principles of proposed idea are listed below:  
**SDX-based Route Validation Application:** In operation, the SDX controller application has to provide ROV service for SDX based on information from RPKI Validator. This application is responsible for checking each received route prefix from the BGP router of participating ASes with the latest ROA database. Meanwhile, in order to reduce verification time and increase the scalability, the application should not query to the RIR server directly for performance reasons. RPKI Validator is a local RPKI cache server (i.e., Routinator) that is used to offer such information. It will periodically synchronize with ROA database maintained by RIR, and the controller application counts on it to validate the originated route prefix and ASN.  
**Route-to-Intent/Flow Validation:** To optimize ROV progress, SDX should be designed to translate route prefix into a high-level of rules to be forwarding rules (i.e., flow rule) for SDN components (such as SDN switch). However, flow-level abstraction may not be scaled with the massive number of route prefixes. Intent-level abstraction is the best mechanism for representing route prefix into \"compiled\" flow-level rules in the forwarding path.  
**Policies for Valid, Unknown, and Invalid Routes:** To accommodate different route validation results from the RPKI validator, SDX application needs to define different actions for each prefix route. The mechanism logic of the application is shown in Figure 4. In development, intent with \"forwarding\" treatment is required to be applied as route entries. On the contrary, intent with \"blocking\" treatment is required to be setup an invalid prefix route. While for unknown prefix routes, depending on the SDX policy, different flow-based intent can be defined by the administrator. For example, if those need to be quarantined, the intent will be processed with \"change-next-hop\" treatment to a specific inspection device for investigation.
## 5 Conclusions  
In this paper, we propose a model degradation and iterative control strategy for a class of end-joint-failed PMLUM, considering the initial velocity non-zero and torque disturbance factors. Using the model degradation method, the PMLUM is degraded to a PVP, and an iterative controller is created to achieve the position control objective. Thus, the control process is divided into two stages: model degradation and stabilization control. The planar AAP and planar AAAP systems with end-joint failures are selected for the simulation experiments, and the proposed strategy is shown to be effective and universal based on the results of the numerical simulations. The strategy proposed in this paper can be applied to the fault-tolerant control of a fully driven manipulator when some of its actuators face damage in space exploration and ocean engineering.  
In future research, when establishing the dynamic model of the underactuated manipulator, the dissipation term can be considered from the perspective of energy, the influence of noise on the system can be considered from the perspective of noise measurability, and other model uncertainties can be considered. At the same time, the experimental simulation is built to consider the influence of more model uncertainties on the control effect.  
Conceptualization, Z.H. and Y.Z.; methodology, Z.H. and Y.Z.; software, W.W., B.Z. and C.Y.; validation, W.W., B.Z. and C.Y.; formal analysis, W.W., B.Z. and C.Y.; investigation, W.W., B.Z. and C.Y.; data curation, W.W., B.Z. and C.Y.; writing--original draft preparation, Y.Z.; writing--review and editing, Z.H.; supervision, Z.H. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China (no. 61773353), the Nature Science Foundation of Hubei Province (no. 2023 AFB380), the Graduate Innovative Fund of Wuhan Institute of Technology (no. CX2023550, no. CX2023566, and no. CX2023578), the Hubei Key Laboratory of Digital Textile Equipment (Wuhan Textile University) (no. KDTL2022003), and the Hubei Key Laboratory of Intelligent Robots (Wuhan Institute of Technology) (no. HBIRL202301 and no. HBIRL202302).  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
The authors declare no conflicts of interest.  
Figure 13: The planar AAAP system’s simulation results in case C (Second group). (**a**) Joint angle; (**b**) joint angular velocity; (**c**) joint torque; (**d**) endpoint coordinates.