esa-sceva/satcom-chunk-collection huggingface dataset:
# Query Processing in Blockchain Systems: Current State and Future Challenges
## 8 Conclusions  
Blockchains are considered the new go-to technology in many application domains to store data in an immutable and tamper-resistant manner while ensuring high availability. A blockchain, however, is rather a conceptual design than a specific embodiment of a technology. Therefore, there are different implementations of a blockchain, each with their respective advantages and disadvantages. To support query capabilities on blockchain data, there are currently two prevalent approaches:  
The first approach is to store all data in the blockchain and then execute the queries on it. The advantages of this approach are that the data history is fully available, and the data are protected by being immutable and tamper-resistant. The disadvantage of this approach is that query processing requires sequential traversal of the blocks, since there are no index structures to improve the efficiency of query processing.  
The second approach is to operate a database in parallel to the blockchain. This database maintains the world state. This way, SQL-like queries can be executed efficiently, which is this approach's advantage. Its disadvantage is that such a database does not provide the data history. As a consequence, temporal queries and state-based queries are not or at least insufficiently supported. Furthermore, the authenticity of this data is not guaranteed by the blockchain. To this end, an additional verification step is required.  
Therefore, to unlock the full potential of the blockchain technology (i.e., security and data history combined with comprehensive query capabilities), many research efforts are still needed (e.g., in terms of developing new index and data access structures forblockchains). In particular, we identified four categories of current research challenges in this regard: data models, data structures, block structures, and query processing.  
In summary, the importance of blockchain systems as a secure data store is undeniable for a digitized society. However, there are still many research questions to be addressed before blockchains can compete with traditional database systems in terms of query capabilities and efficiency.  
Conceptualization, C.G., D.P. and C.S.; methodology, D.P. and C.S.; software, D.P.; validation, C.G., D.P. and C.S.; formal analysis, D.P. and C.S.; investigation, D.P. and C.S.; resources, B.M.; data curation, D.P. and C.S.; writing--original draft preparation, D.P. and C.S.; writing--review and editing, C.G., B.M., D.P. and C.S.; visualization, D.P. and C.S.; supervision, B.M. and C.S.; project administration, B.M. and D.P.; funding acquisition, B.M. All authors have read and agreed to the published version of the manuscript.  
This research was funded by German Federal Ministry of Education and Research (BMBF) as part of the Software Campus program grant number 01 IS17051.  
Not applicable.  
We thank the anonymous reviewers for their valuable comments and suggestions which helped us to improve the content and presentation of this paper.  
The authors declare no conflict of interest.
## 2 Related Work and Technologies
### SigFox  
SigFox is an LPWAN network operator that offers a complete IoT connectivity solution based on its patented technologies. SigFox deploys its base stations with equipment previously configured with proprietary software and connects them to the back-end servers using an IP-based network. End devices are connected to these base stations using phase-shift keying (BPSK) modulation on an ultra-narrow band (100 Hz) sub-GHZ ISM carrier. Like LoRa technology, SigFox uses unlicensed ISM bands, for example, 868 MHz in Europe, 915 MHz in North America and 433 MHz in Asia. By using an ultra-narrow band, SigFox uses frequency bandwidth efficiently and achieves very low noise levels, leading to very low power consumption, ensuring the high sensitivity of the receiver and low cost antenna design at the expense of a maximum transfer rate of just 100 bps. SigFox initially supported only uplink communication, but later evolved into bidirectional technology with significant link asymmetry. Downlink communication, that is, data derived from base stations to end devices, can only occur after an uplink communication. The number of messages per uplink is limited to 140 messages per day. The maximum payload length for each uplink message is 12 bytes, but the number of messages in the downlink is limited to four per day, meaning that confirmation of each uplink message is not supported [38].  
In [39], the authors show the use of a system based on SigFox networks, with applications in agriculture, for monitoring environmental factors. In this article, they present SigFox technology, as well as how this type of communication would be integrated into precision agriculture, while referring to other technologies already in use in this field. The authors concluded that SigFox and LPWAN technologies represent the future of IoT. Regardless the domain in which it is used, the IoT finds its applicability, leading researchers and developers to find and implement new solutions in order to increase its performance, productivity, and market value.
## 5 Discussion
### What is the Infrastructure usually used in Deploying A-WSNs for Oceanographic Monitoring?
It is therefore desirable to use techniques that make it possible to monitor the status of the network and possible changes in its original (ideal) deployment. Several solutions have been proposed in the literature addressing these issues [24]. At the same time, considerable effort has been devoted to the design of energy efficient message delivery and data retrieval methods [25]. Theoretically, point-to-point systems are the most reliable because there is only one point of failure in the topology (the host). Moreover, the system can be made more robust by adding more hosts. However, if the signal range is too short it may be necessary to consider other topologies that offer wider coverage while minimizing the risks of system breakdown through the failure of a single node [19]. In all the cases reviewed, the design of the flotation device (buoy) was seen as crucial. Firstly, it is important to analyse the component elements of the node and their weights, since a given weight at a considerable distance from the buoy's line of flotation can cause instability, producing oscillations to avoid capsizing. Secondly, if such elements as batteries and electronics are close to the waterline, the space where they are contained requires more insulation. Then there is the Fresnel effect, which means that the communications antenna must be raised as high as possible to assure better robustness and quality of node communications. We identified a number of buoy implementations on the basis of the location of their components (electronics, radio, batteries, sensors) and mooring system. Figure 6 shows the most representative sensor locations identified in the survey. What is the Scope of the Projects in Terms of the Deployment, the Data Collected and the Deployment Time? Most of the A-WSNs reviewed cover relatively small marine areas only a few kilometres across (not more than 20), and the distance between nodes is in a range of 100-250 m. As to time resolution, in most of these cases the data were sampled every 5 to 10 min. This indicates a higher space-time resolution than can be achieved with the networks of buoys used in coastal oceanographic observatories. There, the spatial resolution is a matter of kilometres and the time resolution one of hours or days. On the other hand, coastal observatories normally cover a much larger area, as much as several hundred kilometres across. Lastly, it is worth noting that practically all of the deployments were implemented for a short period of time, lasting at most three weeks, except in the case of number 11 (GLUCOS Project), in which monitoring was carried on for whole semesters. What this shows is that most of these deployments  
Figure 6: Most representative configurations of buoys used in A-WSNs. were purely experimental and that there is still a long way to go before we can have more permanent facilities.
## 2 Materials and Methods
### Quantitative PCR Analysis of lys-7 in C. elegans  
The SYBR Green method and the SYBR Premix Ex TaqMan II kit (Takara, Beijing, China) were used for real-time RT-PCR. The _C. elegans_ gene-specific primers for _lys-7_ (40 cycles: 94 \({}^{\circ}\)C, 1 min; 60 \({}^{\circ}\)C, 1 min; 72 \({}^{\circ}\)C, 1 min) and the housekeeping gene _actin_ primers (40 cycles: 94 \({}^{\circ}\)C, 1 min; 55 \({}^{\circ}\)C, 1 min; 72 \({}^{\circ}\)C, 1 min) were combined with their PCR mix separately and at a predefined ratio. Amplification was followed by a melting curve analysis. The list of primers used in this study is provided in Table 2. The amplified specific genes were normalized with _C. elegans actin_. Fold changes were calculated using the \(2^{-\Delta\Delta\Delta\mathrm{ct}}\) method. The qPCR analysis was performed with three independent experimental samples in triplicates and gene expression level averages were plotted with the mean \(\pm\) SD. The level of significance was analyzed using one-way ANOVA [44].  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Name** & **Forward (5/-3/)** & **Reverse (5/-3/)** \\ \hline _lys-7_ & TTGTTGACTCATCCCTTCC & TGTCCTGGGTTGAT \\ _actin_ & AAGACCACGTCATAAAGG & TCTCCATATCATCCACGT \\ \hline \hline \end{tabular}
\end{table}
Table 2: Primers for real-time Polymerase Chain Reaction (PCR) used in this study.
## 3 Failure Mode  
For ice-rock, the distribution of the stress field is closely related to the material properties of the ice. If the modulus of elasticity of the ice is large, the displacement of the rock will be limited. If the modulus of elasticity of the ice is small, the rock will experience stress concentration. Under different conditions of ice modulus distribution, the stress distribution law of the rock changes. To examine the expansion of a crack under various stress distribution states, the extended finite element method (XFEM) was employed. The analysis focused on a crack with a half-length of 5 mm, located at an angle of 30\({}^{\circ}\) and inclined at an angle of 30\({}^{\circ}\). The crack expansion was studied under different elastic modulus ratios of 2, 1, and 0. The crack expansion is shown in Figure 6.  
As can be observed from the simulation cloud diagram of crack propagation, when the ice's modulus of elasticity is high, crack propagation becomes more stable. The crack then propagates along the original crack surface until it penetrates the rock, and the crack tip reaches the inner part of the ice before being deflected. At this point, the cracks always remain as shear cracks. If the model is homogeneous, the crack will first expand along the crack face and then deflect to the left or upwards. At this point, the crack type gradually changes from a shear crack to a tensile crack. If the modulus of elasticity of the ice is much smaller than that of the rock, stress concentration occurs in the rock. The cracks are deflected during the initial expansion, and the crack tip near the circular hole tends to propagate along the hole edge. Meanwhile, the crack at the end, away from the circular hole, rapidly develops into a wing crack.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{\(\theta(^{\circ})\)} & \multirow{2}{*}{\(\beta(^{\circ})\)} & \multicolumn{2}{c}{**XFEM**} & \multicolumn{3}{c}{**Analytic Solution**} \\ \cline{3-8}  & & \(K_{\Pi}(-)\) & \(K_{\Pi}(+)\) & \(K_{\Pi}(-)\) & **Error (\%)** & \(K_{\Pi}(+)\) & **Error (\%)** \\ \hline \multirow{8}{*}{0} & 0 & 0.00281 & 0.002251 & 0 & / & 0 & / \\  & 30 & 0.109355 & 0.09039 & 0.10139 & 7.856 & 0.14032 & 35.583 \\  
From the crack evolution law mentioned above, it is evident that incorporating ice with a higher modulus of elasticity into the rock matrix can effectively hinder the propagation of cracks into tensile cracks. As a result, this reduces the rate at which frozen rocks become destabilized. As the modulus of the elasticity of ice gradually decreases, the rate at which cracks develop into tensile cracks gradually accelerates, leading to an increase in the rate of the destabilization of ice-rock. In short, the state of damage and the rate of destabilization of the ice-rock are positively correlated with the modulus of the elasticity of the ice.
# Cooperation-Assisted Spectrum Handover Mechanism in Vehicular Ad Hoc Networks
## 4 Performance Evaluation  
This section contains three parts. The first part introduces the performance metrics, the second part describes the setting of simulation parameters and simulation environment, and the last part shows the simulation results. In addition, we will compare the performance of the following five spectrum handover methods.  
1. Full scan without the cooperation (\(SCAN_{Full}\)): When the SU enters a new BS, it starts to perform the full spectrum scanning method, and then selects the most idle spectrum to transmit.
2. Random access without the cooperation (\(SCAN_{Random}\)): When the SU enters a new BS, it does not perform scanning and directly uses the random access spectrum to transmit data.
3. Partial scan without the cooperation (\(SCAN_{Partial}\)): When SU enters a new BS, it adopts the partial spectrum scanning method to shorten the scanning time, and then the SU selects the idlest spectrum to transmit data according to the partial results of the scanning.
4. Full scan with the cooperation (\(SCAN_{Co-Full}\)): The cooperating SU will collect the usage status of all the spectrums of the new BS. Therefore, before entering a new BS, the SU can know the spectrum usage status of the new BS in advance through the  
Figure 12: The influence of different scanning modes on the transmission magnification within a fixed sensing time.  
* Partial scan with the cooperation (\(SCAN_{Co\_Partial}\)): The cooperating SU will collect the usage status of some spectrums of the new BS. Therefore, before entering a new BS, the SU can know in advance the usage status of the new BS's spectrum through the V2V message exchange. The BS can quickly decide which spectrum to use to transmit data.
# Approximate Image-Space Multidirectional Occlusion Shading Model for Direct Volume Rendering
## 4 Results and Discussion
For the quality comparison, we compare our hard shadow with the existing deep shadow map [27] in Figure 13. Local illumination in (a), ambient occlusion in (b), deep shadow map in (c), and our hard shadow by ISMOS in (d) are compared. As seen in the figure, our hard shadow is almost identical to the deep shadow map. Although our model supported various lighting models, indirect lighting was not achieved since indirect lighting was not interpreted within the model. However, it was possible to extend our model to support the enclosed volume with a partially opaque object and multiple objects with varying partial opacity by adding more buffers to store more precise transmittance. Figure 11: ISMOS applied to the carp data. (a) presents the direct volume rendering with the local illumination. The approximated opacity values are used for our ISMOS in (c,d). The image-space horizon-based ambient occlusion [5] is used in (b). (e) presents our spotlight model. Figure 10: ISMOS applied to the abdomen data. Opaque and transparent transfer function settings are used in (a–c) and (d–f), respectively. The image-space horizon-based ambient occlusion [5] is used in (b). The approximated opacity values are applied for our ISMOS in (e–f). PO indicates partial occlusion.
# Arabic Hate Speech Detection Using Deep Recurrent Neural Networks
## 4 Experimental Results and Discussion
### Hate Speech Detection from Positive and Negative Arabic Comments  
The second experiment was based on three classes of comments: negative, positive, or hate speech. Table 4 shows the results of using the DT, MLP, NB, and LR classifiers. It can be seen from Table 6 that the highest accuracy (56.192%) was achieved using DT. Again, this was still a very low percentage. The precision, recall, and F1 score were the highest for DT as well, with values of 0.56, 0.56, and 0.56, respectively.  
A repeat of the same experiment using the proposed deep RNN model (DRNN-2) showed a significant improvement in the classification of the three classes of Arabic comments, as shown in Table 7. The DRNN-2 results are shown because they are significantly better than those achieved by DRNN-1. With the use of DRNN-2, the training accuracy increased to 95.38%, with a training loss of 0.1391 and a validation loss and validation accuracy of 0.4148 and 86.40%, respectively. It can be observed that the proposed model showed better results than those listed in Table 6 as well as those listed in Table 1 from the extant literature while targeting the classification of Arabic comments into three classes.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Method** & **Accuracy** & **Precision** & **Recall** & **F1 Score** \\ \hline DT & 56.970\% & 0.57 & 0.57 & 0.59 \\ MLP & 57.576\% & 0.58 & 0.58 & 0.58 \\ NB & 62.810\% & 0.64 & 0.62 & 0.59 \\ LR & 63.937\% & 0.63 & 0.61 & 0.65 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Comparison of experimental results using typical classification methods for the two classes of Arabic comments.  
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Model** & **Iterations** & **Train Loss** & **Train Acc.** & **Val. Loss** & **Val. Acc.** \\ \hline Five deep layers with & 10 & 0.0709 & 98.28\% & 0.4815 & 75.17\% \\
231,841 parameters & 25 & 0.0074 & 99.78\% & 0.7993 & 81.88\% \\ (DRNN-1) & 50 & 0.0041 & 99.93\% & 0.9914 & 82.55\% \\  & Best & 0.0044 & 99.73\% & 0.9439 & 83.22\% \\ \hline
10 deep layers with & 10 & 0.0289 & 99.19\% & 0.8572 & 79.39\% \\
1,682,787 parameters & 25 & 0.0038 & 99.87\% & 1.1484 & 81.82\% \\ (DRNN-2) & 50 & 0.0073 & 99.80\% & 1.1335 & 83.64\% \\  & Best & 0.0578 & 98.18\% & 0.3574 & 90.30\% \\ \hline \hline \end{tabular}
\end{table}
Table 5: Experimental results using the proposed deep recurrent neural network model-based classification method for two classes of Arabic comments.  
Figure 5 shows the confusion matrix for the classification of Arabic comments into three classes. The diagonal squares indicate that the confusion was minimal when it came to normal positive and normal negative comments. However, with the hate speech class, the confusion matrix shows that there were abnormalities in the true identification of hate speech comments.
## 4 Conclusions  
Novel synthetic CaO-based sorbents were developed for CO\({}_{2}\) capture in the SESR process. Based on the experimental work carried out in this research, the following conclusions were drawn: For the preparation of the CaO-based sorbents, the adapted co-precipitation method from [PERSON], et al 2012 study [15] described in Sections 2.1 and 2.2, was used adding a drying step at 350 \({}^{\circ}\)C with continuous slight stirring inside a fume cupboard. The calcination of the samples at 650 \({}^{\circ}\)C successfully converted the nitrate precursors into oxide phases. MgO and CeO\({}_{2}\) maintained their inert nature as they did not take part in the carbonation reactions and did not change the crystalline structure of CaO. It has been found that the CO\({}_{2}\) uptake capacity and CaO utilization of the prepared samples depend on the MgO, CeO\({}_{2}\) and CaO ratio. Thus, controlling this ratio can result in improved CaO utilization and CO\({}_{2}\) uptake capacity. It was found that samples with CaO, MgO and CeO\({}_{2}\) molar ratios of 6:2:1 and 4:2:1 had CO\({}_{2}\) uptake capacities of 29 wt% and 25 wt%, respectively. These values fall within the accepted range of 20-40 wt% for application in SESR processes for CO\({}_{2}\) capture [15]. The characterization tests of the prepared samples confirmed that there was no clear correlation between CO\({}_{2}\) uptake and surface area. It was also concluded that the presence of MgO and CeO\({}_{2}\) as inert composites provided a well-dispersed skeleton (partition wall) that effectively prevented the agglomeration and size growth of CaO. They prevented CaO sorbent sintering and provided a porous surface structure that helps maintain their CO\({}_{2}\) uptake capacity during carbonation/decarbonation multi-cycles. Generally, based on the above conclusions, it may be concluded that sorbents' porous texture is the key parameter for stability over multiple carbonation/decarbonation cycles.  
Conceptualization, E.I.G.; Formal analysis, H.E.; Investigation, M.K.; Resources, G.W.; Writing--original draft, H.E.; Writing--review & editing, M.K.; Supervision, G.W. All authors have read and agreed to the published version of the manuscript.  
This study was financially supported by Islamic Development Bank (IDB) and University of Nottingham (Advanced Material Research Division).  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
Author [PERSON] was employed by the company Jacobs Engineering UK Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
# Feature Importances: A Tool to Explain Radio Propagation and Reduce Model Complexity
## 6 Conclusions and Future Work  
Our work highlighted the significance of feature importances, both as a tool to explain radio propagation, and a means to perform feature elimination and reduce model complexity. The emergence of different propagation mechanisms, for two different transmitter heights, was associated with the difference between the values of feature importances. Moreover, model reduction on the basis of the ranked feature importances was performed, leading to substantially faster, although equally accurate, predictions.  
The acquisition of more data regarding other transmitter heights, or frequencies, could pave the way to an extension of our work, through the incorporation of the aforementioned parameters as extra features. A single model would then be able to provide results for various propagation scenarios.  
Conceptualization, S.P.S.; methodology, K.S.; software, S.P.S.; writing--original draft preparation, S.P.S. and K.S.; writing--review and editing, S.K.G.; supervision, K.S. and S.K.G. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The authors declare no conflict of interest.
## 5 Discussion
### Effect of the End Plate and Shear Stiffness at the Bolt-Rock Interface  
The results with different shear stiffnesses and with or without end plates are plotted in Figure 12. In the case without an end plate, \(K_{cp}=0\) MN/m, while in the case with an end plate, \(K_{cp}=20\) MN/m. As shown by the black solid line in Figure 12a, the normalized displacement decreased with the increasing shear stiffness before a critical value (about 20 MPa in this case), beyond which, the normalized displacement was almost constant because the shear stress at the bolt-rock interface increased with the increasing shear stiffness (see Figure 12b), while the decoupling at the bolt-rock interface occurred when the shear stress exceeds its capability. Moreover, Figure 12b shows that the maximum shear stress was generated at the end of bolts; therefore, the failure of the bolt-rock interface was more likely to start from the tunnel perimeter.  
The red dashed line in Figure 12a illustrates that the end plate could effectively improve the reinforcement effectiveness of passive bolts by about 20% and avoids decoupling at the bolt-rockinterface, which was due to the interaction between the end plate and rock mass exerting a support pressure on the tunnel periphery (see Figure 12c) and decreasing the shear stress (see Figure 12b). Figure 12c shows that the maximum tensile force in the case with an end plate was significantly larger than that in the other case, which implies that the tension failure of the bolts was more likely to occur in the case with an end plate.