esa-sceva/satcom-chunk-collection huggingface dataset:
## 1 Introduction
As a result, a DoS attack effectively degrades the performance of the cooperation, but it cannot prevent to continue the mission with a limited number of cooperating nodes, or at the very least with all the nodes acting individually. In practical situations, if a DoS persists, as an extreme measure, an underwater node may surface and communicate with a land station using standard radio communication technologies. It is finally remarked that the tools proposed can be easily generalized to other underwater applications, though in the rest of the paper the reference applicative scenario is that of underwater surveillance. In the paper, we report some results to characterize the application level performance of an underwater acoustic network including the cooperative strategy and the security suite proposed in the paper. Raw data were obtained during the experimental campaign UAN11 held in May 2011, within the Underwater Acoustic Network (UAN) project [14]. Field data show that the security solution is efficient in terms of number of messages and message size, reducing the time and the energy of the transmission. The paper is organized as follows: in the next section the problem setting is described, defining in general terms the secure cooperative problem addressed. Section 3 describes the adaptive/cooperative algorithm for a team of autonomous underwater vehicles, abstracting from the specific network architecture chosen. Area coverage performance is described and the main algorithm limitations discussed. In Section 4 the secure communication procedures are presented. In Section 5 we report the result from the application of the algorithms during the UAN11 sea trial. Finally, conclusions are given in Section 6.
## 2 Materials and Methods
### GEDI Level 4A Data  
The GEDI sensor is installed on the International Space Station and is equipped with a geodetic-class laser altimeter/waveform lidar composed of three lasers that produce eight transects of structural information, providing 25-m resolution measurements of forest height in temperate and tropical forests (between 51.6\({}^{\circ}\) N and 51.6\({}^{\circ}\) S latitude). GEDI data are released with different products corresponding to different preprocessing levels [36]. In this study, we used the highest level of GEDI products, Level 4A, which predicts--in tons per hectare (t ha\({}^{-1}\))--the aboveground biomass density (AGBD) for each sampled geolocated laser pulse [35]. AGBD predictions were derived from parametric models linking simulated relative height (RH) metrics from Level 2A to field plot estimates of AGBD. A calibration dataset of RH metrics and field estimates of AGBD were generated for multiple world regions and plant functional types (PFT) to train different models representing the combinations of regions and PFTs. With each footprint are associated a set of ancillary data such as uncertainty metrics, quality flags, and model inputs (land cover input data including PFTs and the world region identifiers). For details on the procedure used to generate Level 4A data, please refer to [PERSON] et al. [36].
## 4 Field Application and Results
### SQp and SQs Attributes  
The outcomes of pre-stack simultaneous inversion, Vp/Vs, and density 3D cubes are implemented to generate SQp and SQs through mathematical equations. As discussed earlier, the SQp attribute has a similar log response to the gamma-ray log, and SQs is close to the resistivity log response. They are proven to be effective in litho-fluid delineation.  
The hydrocarbon-bearing zones and their continuity can be identified in SQp and SQs sections (Figure 21a,b). The reservoir target between Top H and H60 horizon demonstrates low SQp and high SQs values. The SQp values range between 0.0021 and 0.04, and SQs values range from 0.62 to 0.73 in possible hydrocarbon-bearing sands intervals.  
Figure 21a,b show the distribution and changes of SQp and SQs attributes' values within the interval between Top H and H60 horizons. The SQp attributes delineated the distribution of sand (green colour) and shale (violet colour) lithology. The area of interest (dotted line in Figure 22a) responded as a low value of the SQp attribute, indicating the presence of sand lithology. The dotted line in Figure 22b exhibited a high SQs value, indicating the sand porosity is filled by hydrocarbons. From the horizon slices generated at Top H to H 60 horizons of the study area, it can be summarised that the west of the study area is sand-prone and filled by hydrocarbons.  
Figure 21: (**a**) Inverted SQp crossline section containing XD-2 well; (**b**) Inverted SQs crossline section containing XD-2 well.
# A Novel Channel Calibration Method for Bistatic ISAR Imaging System
## 1 Introduction
The channel calibration method is proposed in Section 3, the accumulation method of multi-period echoes in time domain are provided, the calibration coefficient is constructed and the calibration process for bistatic ISAR imaging system is presented. The experimental results are presented to validate the effectiveness of proposed method in Section 4, and finally, conclusions are drawn in Section 5.
# A Split Ring Resonator-Based Metamaterial for Microwave Impedance Matching with Biological Tissue
## 2 Recall of Theory
\right) \tag{9}\]When the antenna radiation frequency is within the range for which the permeability element \(\mu_{\text{reff}}(\omega)<0\), the \(x\)-axis wave vector component is imaginary \(k_{x}=\omega\sqrt{\varepsilon_{y}\mu_{z}}\), and therefore the component of the electromagnetic field parallel to SRRs plane is evanescent and the sideward radiation forbidden. Consequently, the main lobe of antenna radiation pattern will be improved while the side lobe is attenuated, and there is an overall improvement in terms of directivity and gain [15]. The metamaterial lens placed on the antenna, in addition to the electromagnetic field focusing properties, allowing the gain increasement, can be used as impedance matching layer. When the radiated electromagnetic waves propagate through media with different permittivity and permeability values an impedance mismatch occurs. The scheme of the normal wave propagation through the two layers sandwiched between two semi-infinite media is illustrated in Figure 1, where the SRR metamaterial layer is placed at distance \(t_{2}\) from the biological layer to be matched. The metamaterial lens, if properly designed, can minimize the mismatch and maximize the energy transmission. With reference to Figure 1, the general form of wave matrices is given by (10). \[\left[ \begin{array}{c}E^{i}\\ E^{r}\end{array} \right]=\prod_{n=1}^{3}\frac{1}{T_{n}}\left( \begin{array}{cc }e^{i\gamma_{n}t_{n}}&\Gamma_{n-1}e^{-i\gamma_{n}t_{n}}\\ \Gamma_{n-1}e^{i\gamma_{n}t_{n}}&e^{-i\gamma_{n}t_{n}}\end{array} \right)\left[ \begin{array}{c}E^{t}\\ 0\end{array} \right]=\left( \begin{array}{cc}a_{11}&a_{12}\\ a_{21}&a_{22}\end{array} \right)\left[ \begin{array}{c}E^{t}\\ 0\end{array} \right] \tag{10}\]  
\[\Gamma_{in}=\frac{E^{r}}{E^{i}}=\frac{a_{21}}{a_{11}} \tag{11}\]  
where \(T_{n}\), \(\gamma_{n}\) and \(t_{n}\) are the transmission coefficient, propagation constant and thickness of the layer \(n\), and \(\Gamma_{n-1}\) is the reflection coefficient at the \((n-1)-n\) layers interface. The total reflection coefficient of the multiple layers \(\Gamma_{in}\), given by (11), is zero for a 'perfect' impedance match. By considering (11), the total reflection coefficient is a function of frequency and can be minimized by appropriately planning the effective magnetic permeability of the metamaterial and by adjusting the distance from the medium to be matched.
# Direct-Write Spray Coating of a Full-Duplex Antenna for E-Textile Applications
## 3 Results and Discussion
### Characterization of the Printed Textile-Based Antenna  
The dielectric-ink-sprayed knit fabric is very flexible, as can be observed in Figure 4a. Figure 4b shows the BT nanoparticles deposited on the textile fiber after spraying. Nonwoven fabric screen printed with silver conductive ink is shown in Figure 4c,d. The silver conductive ink was successfully deposited on the nonwoven fabric and forms a uniform layer around 40 \(\upmu\)m thick.  
The buckling analysis of the antenna substrate under compression was executed to compare the flexibility of the nonwoven substrate (eight layers of nonwoven fabric), knit substrate (eight layers of knit fabric), and combination substrate (two layers of nonwoven fabric and six layers of knit fabric spray coated with BT dielectric ink). Figure 5a displays the shape of the fabric deflection during the test  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Fabric Assembly** & **Dielectric Constant** & **Dielectric Loss** & **Thickness (mm)** \\ \hline Knit Fabric, six Layers & 1.43 & 0.009 & 1.68 \\ Knit Fabric, six Layers w/BT & 1.61 & 0.013 & 1.60 \\ Dielectric Ink & 1.78 & 0.021 & 1.97 \\ Nonwoven Fabric & 1.75 & 0.008 & 1.94 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Fabric dielectric properties.  
Figure 4: (**a**) Flexibility of the knit fabric assembly with BT dielectric ink and (**b**) an SEM image of the BT with acrylate and urethane UV-curable dielectric ink coated on a single fiber within the fabric after UV curing for 5 min (10,000\(\times\), 350 nm of scale bar). (**c**) Cross-sectional microscope image of Ag screen-printed patch section of the antenna (20\(\times\), 100 \(\upmu\)m of scale bar). (**d**) Cross-sectional SEM image of Ag screen-printed patch section of the antenna (150\(\times\), 120 \(\upmu\)m of scale bar).  
The buckling of the fabric under the continuously increasing compression loading force was recorded in Figure 5b. A total of 4 N is needed to cause 30 mm displacement for the nonwoven fabric assembly, while only 0.7 N is necessary for the knit fabric substrate. The larger force required to deform the nonwoven fabric by 30 mm indicates that the nonwoven fabric is more rigid than the knit fabric, since it takes more mechanical energy to displace the nonwoven fabric. Regarding the combination substrate (two layers of nonwoven fabric and six layers of knit fabric spray coated with BT dielectric ink), only 2 N was required. The lower force required for the amalgamated substrate indicates that it behaves like a composite structure and demonstrates superior flexibility compared to the nonwoven substrate.
## 3 Methodology and Comparative Experimental Setup
### Methodology
#### 3.1.3 Quantile Mapping for Post-Processing  
Quantile Mapping is a widely used bias-correction method. The statistical transformation process of the distribution-mapping method is to determine a statistical distribution in advance so that the distribution fitted by the observations is mapped to the distribution fitted by the predicted values by quantile with minimum error [37]. The method corrects the simulated runoff depth by establishing a transfer function between the simulated runoff depth and the observed runoff depth. The principle schematic of the quantum mapping method is shown in Figure 5, and the specific correction method is as follows: calculate the cumulative distribution function (CDF); construct the transfer function (TF); correct the model runoff depth for the validation period for each grid using the transfer function at the time of modeling; and obtain the correct results for the whole watershed [38].
# Convert a Strongly Connected Directed Graph to
###### Abstract  
In a previous paper we defined the black and white SAT problem which has exactly two solutions, where each variable is either true or false. We showed that black and white 2-SAT problems represent strongly connected directed graphs. We presented also the strong model of communication graphs. In this work we introduce two new models, the weak model, and the Balatonboglar model of communication graphs. A communication graph is a directed graph, where no self loops are allowed. In this work we show that the weak model of a strongly connected communication graph is a black and white SAT problem. We prove a powerful theorem, the so called transitions theorem. This theorem states that for any model which is between the strong and the weak model, we have that this model represents strongly connected communication graphs as black and white SAT problems. We show that the Balatonboglar model is between the strong and the weak model, and it generates 3-SAT problems, so the Balatonboglar model represents strongly connected communication graphs as black and white 3-SAT problems. Our motivation to study these models is the following: The strong model generates a 2-SAT problem from the input directed graph, so it does not give us a deep insight how to convert a general SAT problem into a directed graph. The weak model generates huge models, because it represents all cycles, even non-simple cycles, of the input directed graph. We need something between them to gain more experience. From the Balatonboglar model we learned that it is enough to have a subset of a clause, which represents a cycle in the weak model, to make the Balatonboglar model more compact. We still do not know how to represent a SAT problem as a directed graph, but this work gives a strong link between two prominent fields of formal methods: the SAT problem and directed graphs.  
SAT problem; directed graph; strongly connectedness +
Footnote †: journal:
## 6 Conclusions  
This paper presents a motion planning and coordinated control scheme for the trajectory tracking of the UVMS. A new secondary task with a nonlinear coefficient for redundancy resolution of the UVMS is proposed. In this way, the interactive effects between the vehicle and the manipulator can be minimized and the energy consumption of the UVMS is reduced. Simulation results show that the energy consumption based on the proposed redundancy resolution technique (proposed control\({}_{\text{c1}}\)) is reduced by 48% (in the linear trajectory tracking) and 6% (in the circular trajectory tracking), compared with the comparative redundancy resolution technique (proposed control\({}_{\text{c2}}\)). The proposed redundancy resolution technique is simple in design and easy to implement. Furthermore, a control scheme including a fuzzy compensator and a tracking control with joint-space errors, end-effector errors and inertial delay control (IDC) is proposed. The proposed control scheme ensures precise and robust tracking performance in the presence of model uncertainties, time-varying ocean currents, payload and sensory noises. Simulation results show that the position and orientation tracking precisions based on the proposed control\({}_{\text{c1}}\) are reduced by 57.7% and 24.4% (in the linear trajectory tracking) and 65.6% and 36.5% (in the circular trajectory tracking), compared with the H\({}_{\infty}-\)EKF\({}_{\text{c1}}\) method [23]. Even though the effectiveness of the proposed redundancy resolution technique and coordinated motion control scheme were validated through numerical simulations, experiments should be carried out on the real UVMS to further enhance the computer simulation results, which will be done in the future.  
Conceptualization, H.H., Y.W. and X.Y.; data curation, H.H.; formal analysis, H.H.; funding acquisition, Y.W. and X.Y.; investigation, H.H.; methodology, H.H.; project administration, Y.W. and X.Y.; resources, Y.W. and W.L.; software, H.H.; supervision, Y.W., X.Y. and W.L.; validation, H.H., Y.W., X.Y. and W.L.; visualization, H.H.; writing--original draft, H.H.; writing--review editing, Y.W. and X.Y. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the National Natural Science Foundation of China under grant number 41876100, in part by the National key research and development program of China under grant number 2017 YFC0306001, in part by the Heilongjiang Natural Science Foundation under grant number E2017024 and in part by the Key Program for International S and T Cooperation Projects of China under grant number 2014 DFR10010.  
The authors would like to thank [PERSON], [PERSON] and [PERSON], who provided insight and expertise that greatly assisted the writing of this manuscript.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
# Modeling the Submergence Depth of Oil Well States and Its Applications
## 2 Materials and Methods
### Submergence Depth Model Construction
#### 2.1.2 Oil Well Nonfull-Pumping State Model  
In the nonfull-pumping state, the pumping speed corresponding to the full-pumping state speed \(v\) is \(\left(h/h_{p}\right)v\). Formula (1) is thus satisfied during the pumping process:  
\[\frac{KA\rho g}{\mu L}(h_{E}-h)-\frac{h}{h_{p}}v=S\frac{dh}{dt}. \tag{6}\]Thus, the following holds:  
\[\frac{dh}{dt}+\bigg{(}C_{f}+\frac{v}{S\cdot h_{p}}\bigg{)}h=C_{f}\cdot h_{E}. \tag{7}\]  
It is assumed that \(C_{n}=C_{f}+v/\big{(}S\cdot h_{p}\big{)}\); then, the differential equation in Formula (7) can be solved to obtain the oil well nonfull-pumping state model:  
\[h=h_{0}+\bigg{[}h_{E}\bigg{(}1-\frac{v}{C_{n}\cdot S\cdot h_{p}}\bigg{)}-h_{0} \bigg{]}\Big{(}1-e^{-C_{n}t}\Big{)}. \tag{8}\]  
When the oil well is in the nonfull-pumping state, the submergence depth must satisfy \(h<h_{p}\) and \(h_{0}<h_{p}\).  
The change in parameter \(C_{n}\) in Formula (8) (also called the nonfull-pumping state model (8)) is related to the comprehensive seepage parameter \(C_{f}\) and the oil well pumping speed \(v\). Assuming that the pumping speed \(v=0\), when the time \(t\) approaches infinity, the submergence depth tends to be the greatest; that is, the submergence depth \(h\) tends to \(h_{E}\). Assuming that the pumping speed \(v>0\), when the time \(t\) approaches infinity, \(h_{E}\) tends to \(0\).  
In summary, for the constructed submergence depth models of Formulas (5) and (8) of oil wells in full and nonfull-pumping states, the change in the submergence depth (except at time \(t\)) is mainly related to the change in the oil well's comprehensive seepage parameter \(C_{f}\) and pumping speed \(v\). Especially for the nonfull-pumping model, the change trend of the submergence depth is more sensitive to the pumping speed because of the small liquid reserves in the oil well.
## 6 Evaluation and Security
### Threat Mitigation  
The proposed protocol incorporates a variety of targeted mechanisms to neutralize potential threats and ensure the security of the system. One of the primary concerns is the risk of replay attacks, where an attacker might capture and resend valid messages to illicitly repeat transactions or commands. To counter this, each authentication attempt within the protocol is tagged with a unique nonce and an accompanying session token. These elements ensure that every transaction is unique; even if an attacker intercepts a message, it cannot be reused because the system will recognize it as a duplicate and subsequently reject it.  
Another significant threat is posed by Sybil attacks, where a malicious actor creates multiple fake identities to overwhelm or manipulate the network. The protocol defends against this by leveraging the inherent properties of blockchain consensus mechanisms. These mechanisms, such as Proof-of-Stake or other decentralized algorithms, make it computationally and economically prohibitive for an attacker to flood the network with fraudulent identities. As a result, the network remains resilient and resistant to domination by any single entity attempting to subvert the system.  
Insider threats, which involve malicious actions by authorized users or compromised accounts, are addressed through robust access control measures. The protocol employs Role-Based Access Control (RBAC) to ensure that every user is granted only the permissions necessary for their role. This minimizes the potential damage that could be caused by an insider. Furthermore, regular security audits and the continuous monitoring of user activities help detect any anomalous behavior early on, allowing for prompt intervention to prevent potential security breaches.  
Finally, to protect against data theft, the protocol utilizes the Ascon encryption algorithm to secure all sensitive data during transmission. This means that even if an attacker manages to intercept the communication channel, the captured data remain encryptedand indecipherable without their corresponding decryption key. By ensuring that data are always encrypted while in transit, the protocol effectively safeguards sensitive information from being extracted or misused by unauthorized parties.
# Vibration Reduction of a Timoshenko Beam with Multiple Parallel Nonlinear Energy Sinks
## 5 Conclusions  
A simply supported beam coupled with distributed NESs is investigated, and the responses are investigated based on Timoshenko beam theory. Numerical simulation verified the accuracy of the analytical results based on the harmonic balance method. The effects of the NES parameters on vibration reduction were discussed. The parameters and locations of NESs were optimized with the genetic algorithm method, and several optimized parallel NESs were investigated. The conclusions can be drawn as follows:  
1. For a short beam coupled with NESs, it is necessary to establish dynamic models with Timoshenko beam theory. The errors of the first four resonance frequencies based on Timoshenko beam theory were within 1%, while those based on Euler beam theory exceeded 69%. With the same total mass, the multiple parallel nonlinear energy sinks achieved better vibration reduction performance than a single nonlinear energy sink, and the first resonant peak was reduced by 54.55%.
2. When increasing the mass ratio and damping ratio of NESs, better performance at the first two resonance frequencies can be obtained. When adjusting the cubic stiffness of NESs, effective vibration reduction is obtained within a certain range. Unstable responses occur when the value of cubic stiffness exceeds a threshold.
3. The optimal locations of multiple parallel NESs are related to low-order modal shapes, and the optimal locations and cubic stiffness are different for different numbers of nonlinear energy sinks. In the studied case, when the number of parallel NESs equaled two, the best performance was obtained. A further increase in the number of NESs may lead to declining effective performance.  
W.-Y.Z.: conceptualization, methodology, software, writing--original draft, visualization. M.-Q.N.: conceptualization, resources, writing--review and editing, supervision, funding acquisition. L.-Q.C.: conceptualization, resources, writing--review and editing, supervision, funding acquisition. 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] grant number [11872159, 11902097, 12132002, and 62188101] and [Guangdong Basic and Applied Basic Research Foundation] grant number [2022A1515012054].  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
The authors would like to thank all the peer reviewers and editors for their valuable contribution to this work.  
The authors declare no conflict of interest.