esa-sceva/satcom-chunk-collection huggingface dataset:
## 2 Materials and Methods
### Sample Characterization
#### 2.2.2 Scanning Electron Microscope (SEM)  
The pyrophyllite samples were examined using a field emission scanning electron microscope FESEM Model (JSM-7600F, JEOL, Tokyo, Japan) combined with an energy dispersive X-ray (EDX) unit (Oxford Instruments, Abingdon, UK). SEM observations were conducted to detect changes in the phases before and after microwave treatment. The images were taken at a low voltage of 5 kV to avoid overcharging the sample. The intensity peaks of each element at specific energy levels were estimated by EDX.
## 3 MLE Parameter Estimation Model
### The Principle of MLE  
MLE is often used to estimate unknown non-random parameters. MLE is defined as the estimator of \(\theta\) value that maximizes the likelihood function. The estimated value is denoted as \(\theta_{MLE}(x)\). We take the MLE for a single-parameter \(\theta\) as an example. For an unknown non-random estimation \(\theta\), the probability density function \(p(x\,|\,\theta)\) of the observation vector (denotes as \(x\)) is called the likelihood function. The basic principle of MLE can be explained as follows: for a selected \(\theta\), MLE consider the probability \(p(x\,|\,\theta)dx\) that \(x\) falls in a small area, and take the corresponding \(\theta\) whose \(p(x\,|\,\theta)dx\) is the largest as the estimated \(\theta_{MLE}(x)\). As shown in Figure 3, the likelihood function is obtained after \(x=x_{0}\), then we can draw a curve between the likelihood function and the estimated value of \(\theta\). The value of \(p(x\,|\,\theta)dx\) for each \(\theta\) means the probability that \(x\) falls within \(\mathrm{d}x\), and \(\mathrm{d}x\) centered on \(x_{0}\) in the observation space R for \(\theta\). When \(x=x_{0}\), it can be seen that \(\theta=\theta_{1}\) is unreasonable, so we choose \(\theta=\theta_{2}\) as the estimation, and the \(\theta\) that maximizes \(p(x=x_{0}\,|\,\theta)\) is selected as the estimated value \(\theta_{MLE}(x)\) within a range allowed by the estimated \(\theta\).
## 4 Taxonomy of Cooperation in UASNs
### Game Theoretic-Based Cooperation
#### 4.3.1 Repeated Game or Decision Making-Based Games  
Game theory uses mathematics to express the phenomena of decision making among more than one agent [68]. It focuses on providing a mechanism for optimality in the network as well as providing reliability in the cooperative routing and forwarding the packets. All players in this type of game are usually assumed to be completely biased in that they only focus on their expected gain in the particular strategic game [72]. The authors in [73] use game theory to model the interactions between a society of agents as a repeated game. They analyzed distributed search for resources in networks where agents interact with each other and offer services and consume these services. They have associated a cost to every agent in a non-homogeneous manner to study which network structures are more appropriate to promote cooperation. These forms of security problems are mostly addressed in the forms of attacker (i.e., malicious node) and defender which can be either transceiver or the receiver using a repeated game. It is a decision-making (DM) game such that a DM has advantage or information about the opponent player. It can also be a collaboration toward achieving a particular target if the decision making cooperates in a coalitional or cooperative game. The game of interaction among players can be modeled in a way to improve the privacy of both players in the game. A game of incomplete information can be modeled to evaluate the issues of the repeated game, which can contain simultaneous movement of players. Because these incomplete information games are dynamic, there is always a trade-off in terms of privacy and trust in the game of theoretic concept which is based on the trust formulation [34]. Some forms of game classes can be applied to the dynamic uncertainty in which the domain of uncertainty can be modeled and represented as a decision process in the game [74]. An algorithm for path planning based on scheduling proposed in [75] overcomes the Traveling Salesperson Problem (TSP). It provides a multi-node communication and improves the performance of path selection. To achieve this, there is a need for a robust protocol for scheduling that solves the problem of channel interference and variation. Mathematical comparison of repeated games approaches is presented in Appendix A. Repeated games permit a drastic defect that allows the players to behave selfishly and obtain maximum payoff (Nash Equilibrium), and there is no sufficient punishment to the selfish participant, which makes it not suitable to encourage cooperation in UASNs.
## 3 Results and Discussion
### Nitrogen Removal Effect of Reed Carbon Source Constructed Wetland
#### 3.1.3 Removal Effect of NO\({}_{2}\)\({}^{-}\)-N  
In the process of microbial denitrification, NO\({}_{3}\)\({}^{-}\)-N must go through the reduction process of NO\({}_{3}\)\({}^{-}\)N \(\rightarrow\) NO\({}_{2}\)\({}^{-}\)N \(\rightarrow\) NO\(\rightarrow\) N\({}_{2}\)O \(\rightarrow\) N\({}_{2}\) and is finally converted into gaseous nitrogen, such as N\({}_{2}\)O or N\({}_{2}\), and discharged. However, if the organic carbon source in the wetland is insufficient, the nitrite reductase will be at a disadvantage in competing with the nitrate reductase for electron donors, so the reaction stops at the NO\({}_{2}\)\({}^{-}\)-N generation stage, resulting in the accumulation of NO\({}_{2}\)\({}^{-}\)-N [27]. Therefore, the NO\({}_{2}\)\({}^{-}\)-N concentration  
Figure 2: Changes of NH\({}_{4}\)\({}^{+}\)-N concentration and corresponding removal rate in influent and effluent of three groups of wetland systems.  
in wetland effluent is one of the important indicators for evaluating the denitrification stability of constructed wetlands.  
As shown in Figure 4, the influent water of RW, CW and N-RW did not contain NO\({}_{2}\)\({}^{-}\)-N; the effluent NO\({}_{2}\)\({}^{-}\)-N concentration was 0.01-0.02, 0.03-0.04 and 0.01-0.02 mg/L, and the corresponding mean values were 0.02 \(\pm\) 0.00, 0.03 \(\pm\) 0.00 and 0.02 \(\pm\) 0.00 mg/L. It was found that the NO\({}_{2}\)\({}^{-}\)-N concentration in the effluent of the three groups of constructed wetlands was at a low level. The reed carbon source in RW could provide a sufficient organic carbon source for denittifying bacteria. The denitrification reaction in RW was relatively thorough, and there was no accumulation of NO\({}_{3}\)\({}^{-}\)-N and NO\({}_{2}\)\({}^{-}\)-N, indicating that RW had high denitrification stability. Although the NO\({}_{2}\)\({}^{-}\)-N concentration in the CW effluent was only slightly higher than that of RW, the reduction rate of NO\({}_{3}\)\({}^{-}\)-N in the process of microbial denitrification was reduced due to the lack of organic carbon sources in the CW, resulting in the accumulation of a large amount of NO\({}_{3}\)\({}^{-}\)-N in the wetland [27]. Therefore, the TN-removing effect of CW was poor.  
Figure 4: Changes of NO\({}_{2}\)\({}^{-}\)-N concentration in influent and effluent of three groups of wetland systems.  
Figure 3: Changes of NO\({}_{3}\)\({}^{-}\)-N concentration and corresponding removal rate in influent and effluent of three groups of wetland systems.  
The comparison between RW and N-RW showed that reed planting had no significant effect on NO2-N removal in constructed wetlands (\(p>0.05\)). This may be due to the small number of reeds planted in RW in this experiment, which did not have a significant impact on NO2-N removal. The main limiting factor in the wetland denitrification process was still whether the organic carbon source was sufficient [28].
# Robustness Analysis for Multi-Agent Consensus Systems with Application to DC Motor Synchronization
###### Abstract  
DC motor speed synchronization is a critical problem in industrial and robotic applications. To tackle this problem, we propose to use a multi-agent consensus-based control scheme that guarantees the convergence of the DC motor speeds to either fixed or time-varying reference. A detailed robustness analysis considering parametric uncertainty and time delay in the multi-agent system is performed to guarantee the consensus on the speed of DC motors in actual practice. The results obtained concerning the robustness analysis allowed us to implement experimental tests on a three-motor system using a wireless communication system to achieve satisfactory performance.  
multi-agent systems; consensus; synchronization; DC motors; time delay systems; robust control +
Footnote †: journal: Applied Sciences
## 3 Cascade Experiments  
The linear cascade experiments provide a very good raw material to support the investigation of axial turbomachinery loss phenomena, although they are made of annular cascades, operating under three-dimensional flow. The linear cascade flow is essentially two-dimensional, making the measurement work much easier. Despite the absence of radial gradient, the linear cascade retains the dominant loss mechanism represented by the boundary layer growth along the blade surfaces. Furthermore, the linear cascade can properly represent the flow in a certain radial position of an annular cascade.  
In fact, a few research institutions in the world have developed technological capabilities to conduct such experiments [21; 22]. The hardware complexity, the precision of cascade angular setting and blade staggering, the manufacturing of static pressure taps along blade profile, the total pressure traverses and the high Mach number measurements are challenging aspects of building such test device. Special care must be taken in the cascade tunnel experiments to provide a two dimensional flow running into the specimen to be tested. For this purpose the tunnel boundary layers must be removed. Also, the blade chord dimension must be designed to keep the Reynolds number in a suited range, notably to avoid laminar separation during the tests.  
In these experiments the total pressure is measured pitch wise downstream the cascade, through an inserted rake, such way the wake pattern can be closely captured. Downstream flow angle, surface velocity distribution and a wake loss coefficient are also assessed from the cascade test measurements.  
The flow across an axial blade cascade is realized to be a superposition of a circulatory flow around the airfoil over the through-flow. Based on this argument, an interrelation between the maximum surface profile velocity and a circulation parameter is expected to be found. This parameter is suggested by the application of the Kelvin circulation theorem in the inter-blade channel. It follows that the product of the difference of downstream to upstream tangential velocities \(\Delta V_{u}\) by the blade spacing \(t\) can represent the circulation integral around one blade. By adopting the upstream velocity and the blade mean-line curvature length as the characteristic parameters for the turbine cascade flow problem, the non-dimensional circulation parameter \(\Delta V_{u}/(\sigma V_{1}/C)\) and the maximum surface velocity ratio \(V_{s,max}/V_{1}\) are obtained. A linearized correlation was first proposed by [PERSON] [12] for axial flow compressor cascades. Later, [PERSON] [11] proposed its generalized utilization for all kinds of axial cascades, although modifying the circulation parameter by an axial projection. When applying this method to turbine cascades, however, the loss estimation seems to be somewhat conservative. Taking advantage of this idea, the mentioned expression is revised in the next sections by analyzing the turbine blade cascade tests presented in [15].
## 5 Conclusions and Future Work  
In this study, we investigated the potential of both backbone-like and mesh-like clustering approaches to support low-latency communications through vehicle-to-vehicle exchanges for massively connected vehicles in the 6G era. In order to conduct a fair and accurate comparison between both approaches, we relied on two promising protocols. The first one is CBL-OLSR, a backbone-like clustering solution that has recently been shown to outperform most ad hoc routing protocol approaches. The other is TFD-OLSR, a variant of the well-known OLSR protocol, which is still widely referenced in the design of ad hoc routing protocols for vehicles. That OLSR variant was modified to perform in a single road traffic flow direction so that it could be compared fairly with CBL-OLSR on the basis of the same network node density and topology. Simulations conducted in medium and high node density networks and for various types of application traffic with different constraints showed that the CBL-OLSR backbone-like clustering solution always offers the best latency, while the TFD-OLSR mesh-like clustering always achieves the best packet delivery ratio. However, through a new metric introduced as the packet bit-delay, we observed that in medium node density networks, the global advantage is obtained with the mesh-like approach, whereas high node density scenarios favor the global performance offered by backbone-like clustering. Since real-world vehicular networks may involve both time-constrained applications and various node density scenarios, the best solution is probably a combination of both clustering approaches or at least an adaptation of one approach in order to reduce the gap on the metrics for which the other approach still offers better performance. In our future work, we plan to investigate the latency reduction in mesh-like clustering approaches. Another interesting direction could focus on the combination of backbone-like clustering in the nearest neighborhood, where time-constraint applications are more likely to be necessary, with a mesh-like clustering approach at the level of branch nodes where redundancy may bring alternative routes and improve packet delivery ratio in more than two-hop exchanges.  
Conceptualization, T.D., M.W. and P.S.; data curation, T.D.; resources, M.W. and P.S.; software, T.D., M.W. and P.S.; writing--original draft, T.D., M.W. and P.S.; writing--review and editing, T.D., M.W. and P.S. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding. The authors acknowledge the support of the CPER RITMEA, the European Regional Development Fund, and the Hauts-de-France Region Council.  
The algorithm specifying the modification of OLSR to create TFD-OLSR was detailed. The results obtained from simulation scenarios can be obtained upon request.  
The authors declare no conflicts of interest.  
Figure 13: Mean delivery ratio and end-to-end delay for the monodirectional videoconference application and two communicating nodes approximately 7 hops apart.
# Separable Data-Hiding Scheme for Encrypted Image to Protect Privacy of User in Cloud
## 3 Proposed Scheme  
In cloud computing, a user usually hopes to encrypt the image before transmission to protect the privacy of the image. Figure 2 shows that user A encrypted the private image, saved the encrypted key into his/her private cloud storage, and then embedded the hidden bits into the encrypted image by using the data-hiding key. So, the stego-image, i.e., the encrypted image that contained the hidden data, was saved in the public cloud. When user B wants to download user A's image, he/she must provide authentication information to the public cloud. User B must pass the authentication before he/she can download the stego-image and obtain the corresponding information according to the key that he/she has.  
Figure 3 shows the detailed process of the proposed system. First, a protected private image \(I\) is sampled by a data owner using BCS to obtain measurement values. Then, non-uniform quantization can be performed, and the data that are to be hidden are embedded into the coding of each measurement value. When the receiver possesses the encrypted image that contains hidden data, he/she can extract or decrypt the desired image in accordance with a different key.
## 3 Proposed Method
### SURF-Based Feature Extraction and Class Assignment  
As the first step of the proposed method, SURF digitizes a PCB image as a vector. SURF then detects the features and extracts the descriptors in the form of a vector as mentioned in the previous section. Figure 5a shows an example of an original PCB image. The circuits in the area inside the dotted line have a defective edge, whereas the other circuits have a normal edge. The extracted features are shown in the circles in Figure 5b. As Figure 5b illustrates, the features are obtained identically without discriminating between a defective edge and a normal edge. In other words, SURF cannot distinguish between a defective and a normal edge. Thus, we should learn the fault pattern of the features by setting the normal and fault areas and assigning classes to each feature.  
As shown in Figure 6a, we define a lozenge area with four points so that the fault area can be visually represented in the clearest manner. We can then consider the fault occurring in the lozenge area. We assign the features within the lozenge area in Figure 6b to the fault class. The remaining features from areas other than the lozenge area are designated as being of a normal class through Equation (8).  
\[c(x_{i})=\left\{\begin{array}{c}\begin{array}{c}\text{{Fault class},\,if \,x_{i}\in X_{L}}\\ \text{{Normal class},\,otherwise}\end{array}\end{array}\right., \tag{8}\]  
where \(x_{i}\) indicates each feature composed using a multivariate vector and \(X_{L}\) is a set of features within the lozenge area.  
Figure 5: An example of SURF-based feature extraction (**a**) Original image; (**b**) A resultant image after extracting the features of the PCB.  
Figure 6: An area selection for a class assignment: (**a**) A fault occurring in the lozenge area; (**b**) The features within the lozenge area are the fault class and the remaining features are the normal class.
## 4 Conclusions  
Based on the results, it can be concluded that the impregnation method applied in the synthesis of photocatalysts is effective and that the catalysts produced can be applied in the treatment of contaminants of emerging concern (such as SMX) in liquid effluents. Moreover, the preparation steps before and during the impregnation method are very relevant to increasing the amount of TiO\({}_{2}\) immobilized on the Leca surface. SEM images reveal the adhesion of TiO\({}_{2}\) films and high porosity of Leca(r) S before and after impregnation, as well as a varying thickness of the supported TiO\({}_{2}\) layer from 7.64 to 10.9 \(\upmu\)m. The increase of TiO\({}_{2}\) load in the suspension enhances the amount of impregnated TiO\({}_{2}\) onto the Leca surface. It also increases the loss of TiO\({}_{2}\) from the Leca at the end of the photocatalytic reactions.  
The performance of TiO\({}_{2}\) supported on Leca(r) S in the degradation of SMX in ultrapure water depends on the radiation time, and the concentration of TiO\({}_{2}\) supported in the reactor. The photocatalysts achieved a degradation rate of SMX in the order of 28 to 43% after 2 h of reaction, using 86.6 mg/L of 3.6%TiO\({}_{2}\)/Leca and 102.5 mg/L 5%TiO\({}_{2}\)/Leca, respectively.  
It is expected that the optimization of the photoreactor configuration may favor the yield of the degradation, namely by improving the photon absorption, agitation, and the type of radiation used.  
Conceptualization, S.D., R.C.M., M.M.J.Q. and J.G.; investigation, S.D. and C.O.; data curation, S.D., C.O. and R.S.; writing--original draft preparation, S.D. and C.O.; writing--review and editing, R.S., R.C.M., M.M.J.Q. and J.G.; supervision, R.C.M., M.M.J.Q. and J.G. All authors have read and agreed to the published version of the manuscript.  
Figure 10: (**a**) Cross-section of the 5%TiO\({}_{2}\)/Leca photocatalyst, (**b**) mapping of a pore of the 5%TiO\({}_{2}\)/Leca marking Ti in pink and Si in blue.  
**Funding:** This work was financially supported by Fundacao para a Ciencia e Tecnologia (FCT, Portugal), through the Project PEst-C/EQB/ UI0102/2019. Sadjo Dana acknowledges and gratefully the Camoes Institute of Portuguese Language for their financial support, within the scope of Portuguese cooperation, for training and valorization of the beneficiary countries. The authors of CIEPQPF were supported by Foundation Science and Technology--FCT (Portugal) UIDB/00102/2020. The authors also gratefully acknowledge Foundation for Science and Technology--FCT (Portugal) for the financial support (CEECIND/01207/2018).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest.
# Ultra-Low-Power Wide Range Backscatter Communication Using Cellular Generated Carrier +
###### Abstract  
With the popularization of Internet-of-things (IoT) and wireless communication systems, a diverse set of applications in smart cities are emerging to improve the city-life. These applications usually require a large coverage area and minimal operation and maintenance cost. To this end, the recently emerging backscatter communication (BC) is gaining interest in both industry and academia as a new communication paradigm that provides high energy efficient communications that may even work in a battery-less mode and, thus, it is well suited for smart city applications. However, the coverage of BC in urban area deployments is not available, and the feasibility of its utilization for smart city applications is not known. In this article, we present a comprehensive coverage study of a practical cellular carrier-based BC system for indoor and outdoor scenarios in a downtown area of a Helsinki city. In particular, we evaluate the coverage outage performance of different low-power and wide area technologies, i.e., long range (LoRa) backscatter, arrow band-Internet of Things (NB-IoT), and Bluetooth low energy (BLE) based BC at different frequencies of operation. To do so, we carry out a comprehensive campaign of simulations while using a sophisticated three-dimensional (3D) ray tracing (RT) tool, ITU outdoor model, and 3 rd generation partnership project (3 GPP) indoor hotspot model. This study also covers the energy harvesting aspects of backscatter device, and it highlights the importance of future backscatter devices with high energy harvesting efficiency. The simulation results and discussion provided in this article will be helpful in understanding the coverage aspects of practical backscatter communication system in a smart city environment.  
backscatter communication; LoRa backscatter; IoT; NB-IoT; BLE; ray tracing; low power wide area network; LPWAN; simulations; 3 GPP; macrocellular; smart city +
Footnote †: This paper is an extended version of our conference paper: [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON] \"Monostatic Backscatter Communication in Urban Microcellular Environment Using Cellular Networks.\" In Proceedings of the 2020 IEEE Wireless Communications and Networking Conference (WCNC), Seoul, Korea, 25-28 May 2020.