esa-sceva/satcom-chunk-collection huggingface dataset:
# User-Information-Aware D2D Multicast File Distribution Mechanism
## 1 Introduction
In order to solve the above problem and further reduce the redundant transmission, the user-information-aware D2D multicast file distribution mechanism is designed in this paper, and then the corresponding clustering and cluster head selection algorithms are proposed. The main contributions of this work are summarized as follows. * This paper proposes a user-information-aware D2D multicast file distribution mechanism, the video is pushed to potential service requester when distributing video for service requesters, the energy and spectrum efficiency can been improved dramatically by increasing the number of D2D multicast receivers. * To guarantee the quality of experience (QoE) of potential service requesters, the willingness of potential requesters to accept the pushed video was calculated by considering users' interest and the status information about user's device, and then a clustering algorithm based on the user's willingness is developed. * The utility metric of D2D multicast communication is proposed to evaluate the D2D multicast content distribution service. Meanwhile, the link quality information and social relationships among users are taken into the calculation in the utility value to suit the actual communication environment. * A cluster head selection algorithm is developed to maximize the utility value of D2D multicast communication. The rest of this paper is organized as follows: the related works are introduced in Section 2. The system model is given in Section 3. A user-demand-aware method and a clustering algorithm based on the user's willingness are proposed in Section 4. The social information awareness method is introduced in Section 5. The cluster head selection algorithm that maximizes the utility value of D2D multicast communication is proposed in Section 6. Simulation results are analyzed in Section 7. Lastly, the conclusions are given in Section 8.
## 5 Numerical Experiments
### Comparison between \(\Lambda_{1}\) and the Estimate in [12]  
Under the same assumptions of Theorem 2, the authors in [12] proved that the solution \(x(t)\) of the \(VI(F,K(t))\) is Lipschitz continuous with a constant equal to  
\[\Lambda_{0}=\inf_{(\varepsilon,\lambda)}\left\{\frac{M+\sqrt{ \frac{\lambda^{2}+\lambda}{\varepsilon}+\lambda^{2}}}{1-\sqrt{1+\lambda^{2}(1 +\varepsilon)-\lambda(2\widetilde{\alpha}-\varepsilon)}}:\ \ 0<\varepsilon<2 \widetilde{\alpha},\ 0<\lambda(1+\varepsilon)+\varepsilon<2\widetilde{ \alpha}\right\}, \tag{39}\]  
where \(\widetilde{\alpha}=\alpha/L\). Since it is not easy to write the estimates \(\Lambda_{0}\) and \(\Lambda_{1}\) in closed form, we decided to compare them numerically. We considered the following grid for the parameters \((\widetilde{\alpha},M)\): \(\widetilde{\alpha}\) varies from 0.01 to 1 with a step equal to 0.01, while \(M\) varies from 0 to 10 with step equal to 0.01. For any value of \((\widetilde{\alpha},M)\) in the considered grid, we computed the values of \(\Lambda_{0}\) and \(\Lambda_{1}\): the minimum value in \(\Lambda_{0}\) was numerically approximated (due to the non-convexity of the objective function and constraints), while the minimum value in \(\Lambda_{1}\) was computed by exploiting the MATLAB function fminbnd. The results show that the new estimate \(\Lambda_{1}\) definitely improves \(\Lambda_{0}\). In fact, \(\Lambda_{1}\) is always less than \(\Lambda_{0}\) and the relative improvement in \(\Lambda_{1}\) compared to \(\Lambda_{0}\), i.e., \((\Lambda_{0}-\Lambda_{1})/\Lambda_{0}\), is about 42% on average with a minimum of 13% and a maximum of 99%.
# Multi-Objective Task Scheduling Optimization in Spatial Crowdsourcing
## 4 Performance Evaluation
### The Performance of the Ranking Strategy Algorithm
Figure 5 shows that using the output of the ranking strategy as the particle's position in the first iteration (the percentage of randomness is 0%) improves the fitness value to approximately 82% and 86% in case 1 and case 2, respectively, and to approximately 89% in the real dataset compared to initializing the positions of all particles randomly. Due to the huge search space included in our research (i.e., consisting of hundreds or thousands of available workers and spatial tasks), the ranking strategy improves the convergence of the particles to the best solution regarding the objectives of the MOTSO model. There is a big difference in both the number of completed tasks and the total travel costs, as shown in Figure 6, when the positions of all particles are initialized from the output of the ranking strategy in the first iteration, as mentioned in Section 3. The number of completed tasks can be improved by the ranking strategy to approximately 90% in case 1, 92% in case 2, and 93% in Gowalla. The total travel costs can be reduced when using the ranking strategy to approximately 93%, 95%, and 96% in case 1, case 2, and Gowalla, respectively, compared to the random initialization of particles under the same parameter settings. Otherwise, there are no important differences in WLB. The reason behind these improvements in only two objectives is because the ranking strategy contains two main tables. The first table is the TED table, which positively affects the reduction of travel costs, where the best worker is selected to perform a specific task based on who is closest to this task's location. The second table is the TE table, where the task entropy helps to maximize the number of completed tasks.
# Determination of Geometrical REVs Based on Volumetric Fracture Intensity and Statistical Tests
## 5 Discussion  
### Investigation of the REV Size  
Many methods have been developed for the REV research of fractured rock masses, which can be divide into three categories in terms of the research viewpoints of relevant parameters: the geometrical parameters of discontinuities and rock blocks, and the mechanical and hydraulic parameters of the fractured rock mass. The quantitative indicators of geometrical REVs mainly focus on the geometrical parameters, such as trace length, fracture orientation, fracture intensity, and fracture connectivity [1; 17; 19; 21; 23; 32; 33; 34; 35; 36]. Based on the aforementioned geometrical parameters, many statistical methods have been used to estimate the geometrical REV sizes. The mechanical REVs mainly focus on the mechanical parameters of the fractured rock mass, such as elastic modulus, Poisson's ratio, stiffness modulus, and damage coefficient [15; 19; 23]. However, due to the limitation of site conditions and high costs of large in situ test, the laboratory rock mechanics test and numerical simulation technology are always used to determine mechanical REVs of fractured rock masses using numerical software, such as PFC application [19; 22; 23]. The REVs obtained from hydraulic parameters mainly focus on the hydraulic properties of the fractured rock mass, such as hydraulic conductivity and equivalent permeability tensor [4; 5; 63; 64]. Based on the aforementioned methods, it can be seen that the different methods focus on different aspects, and the REVs obtained from different methods are not identical [19; 23; 64]. Even though we employed the same method to estimate the REVs, the REV values obtained from different parameters are not exactly the same [32; 35; 36]. Therefore, it is necessary to consider comprehensive difference and to determine a more reasonable REV size by using different methods. Generally, it is relatively simple and feasible to calculate REV size by using the geometrical parameter and several different statistical methods. However, it is relatively complex to calculate REV values by using the mechanical and hydraulic parameters. Especially, multiple parameters are considered at the same time. Therefore, in future research, we still need to further explore the REVs by considering different aspects.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Cube Size of Sample (m)**} & \multirow{2}{*}{**Cube Size of Sample 20 (m)**} & \multicolumn{2}{c}{**Likelihood Ratio Test**} & \multicolumn{2}{c}{**Wald–Wolfowitz Runs Test**} \\ \cline{3-5}  & & \(\mathbf{p}\) **Value** & **Result** & \(\mathbf{p}\) **Value** & **Result** \\ \hline  
\hline \hline \end{tabular}
\end{table}
Table 4: Results of the likelihood ratio test and Wald–Wolfowitz runs test.
## 3 Experiments
### Results
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Model**} & \multicolumn{3}{c}{**CMeIE**} & \multicolumn{3}{c}{**CEMR**} \\ \cline{2-7}  & _Precision (\%)_ & _Recall (\%)_ & _F1 (\%)_ & _Precision (\%)_ & _Recall (\%)_ & _F1 (\%)_ \\ \hline CopyRe & 45.81 & 36.50 & 40.63 & 51.05 & 47.50 & 49.21 \\ GraphRel & 53.26 & 50.02 & 51.59 & 56.86 & 53.52 & 55.14 \\ HRL & 58.93 & 52.32 & 55.43 & 62.33 & 58.57 & 60.39 \\ ETL-Span & 66.59 & 52.50 & 58.71 & 72.93 & 55.37 & 62.95 \\ WDec & **68.05** & 56.37 & 61.66 & **77.04** & 61.04 & 68.11 \\ RSAN & 65.02 & 61.44 & 63.18 & 73.05 & 69.80 & 71.39 \\ BERT-JEORE & 66.21 & 63.31 & 64.73 & 72.53 & 74.33 & 73.42 \\ \hline SRAGNNs(\#layers = 2) & 67.58 & **64.77** & **66.14** & 76.44 & **74.35** & **75.30** \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Results on CEMR and CMeIE. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Element** & _Precision (\%)_ & _Recall (\%)_ & _F1 (\%)_ \\ \hline H & 84.49 & 85.98 & 85.23 \\ T & 83.86 & 85.29 & 84.57 \\ R & 88.02 & 88.80 & 88.41 \\ (H, T) & 75.26 & 84.76 & 79.73 \\ (H, R) & 77.28 & 80.38 & 78.80 \\ (R, T) & 74.53 & 84.58 & 79.24 \\ (H, R, T) & 76.44 & 74.35 & 75.30 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Results for relational triplet elements. The advantages of the SRAGNNs model are as follows: for Chinese medical texts, the model uses a combination of pre-trained medical character and word embedding as an input form, which avoids the problem of word segmentation errors. At the same time, the addition of segmentation features can make good use of the boundary information of characters and words. The model pays attention to the correlations and dependencies between relations, while capturing and sharpening the fine-grain features in the relations and Chinese characters and words. Our model can effectively capture the overlapping triplets.
## 3 Model Construction and Research Assumptions
### Research Hypotheses
It enhances learners' sense of community, perceived usefulness, and sustained engagement, positively influencing satisfaction, learning outcomes, and experience flow. Therefore, interactivity is crucial in user behavior and significantly affects the flow experience. Based on this, the following hypothesis is proposed:  
**H10**. : _IN has a positive effect on the flow experience._  
The concept of presence (PR), initially proposed by [PERSON] et al. [48], refers to the subjective experience where a user feels the presence of another entity while interacting with a medium. In virtual environments, presence is recognized as a complex psychological phenomenon. [PERSON] [49] developed a framework integrating presence, interaction, and flow, highlighting that presence and mindfulness are essential for a positive VE experience. [PERSON] et al. [50] found a positive correlation between presence and enjoyment in virtual museum settings, indicating that a heightened sense of presence enhances engagement. Furthermore, [PERSON] et al. [51] confirmed that presence positively influences user behavior, emphasizing its significance in improving the enjoyment of virtual environments, particularly in cultural heritage meta-universe experiences. Based on these findings, the following hypothesis is proposed:  
**H11**. : _PR has a positive effect on the experience of flow._  
According to [PERSON]'s [52] research, things and environments are viewed as more natural, and the narrative experience is more thrilling and captivating when people are in immersive and narrative states. The study indicates that story improves mediating presence and participants' cognitive abilities. Participants remembered more details and wanted the experience to continue when asked to complete tasks in contextualized virtual reality situations. To see how narrativity plays a constructive and active part in users' usage patterns and affects each person's flow experience, the following hypothesis is proposed in this paper:  
**H12**. : _Narrativity (NA) has a positive effect on the experience of flow._  
More studies have revealed that users' usage behavior during moments of flow is especially noticeable in virtual environments. Users' propensity to use virtual environments is influenced by their flow experience, according to research by [PERSON] et al. [53]. Furthermore, virtual cultural heritage excursions involve a mediation role in the flow experience [54]. Based on this, this paper proposes the following hypothesis:  
**H13**. : _Flow experience has a positive effect on the willingness of users to use the cultural education meta-universe system._
# A Time-Varying Filter for Doppler Compensation Applied to Underwater Acoustic OFDM
## 5 Conclusions  
In this work, a Doppler compensation technique was developed, modelled and tested in realistic environments. Doppler shift is included in the channel model by introducing a time-variant time-scaling factor. A low-complexity implementation of the model that uses a time-variant fractional delay line (TVFDL) custom filter realization is also described.  
At the OFDM receiver, estimation and tracking of the filter is realized by minimizing the error between the OFDM symbol and its estimate. To improve communication reliability, the Doppler effect during the transmission of a frame is corrected by interpolating the time-scaling estimate between the symbols.  
While the TVFDL filter developed in this work can realize real-time Doppler compensation, an estimate of the Doppler scaling factor at the OFDM receiver can only be produced at the OFDM symbol rate, and as such it is required to buffer the content of consecutive symbols to interpolate the time-scaling factor between OFDM symbols. Therefore, an algorithm that can estimate the Doppler scaling factor in the time domain is highly desirable to maintain real-time operation.  
The algorithm was tested in realistic conditions for two extreme applications and the output of the simulator was compared to that of the measured results. The channel prediction and BER estimator provided by the model were in close agreement with the measured results. For a short range telemetry application, a 2.4 kbps link was established, and a bit error rate of 0.03 was measured at 5.5-dB SNR. In addition, a 16-bps link was measured for a distance as long as 10 km. For fixed platforms, the BER was below \(10^{-3}\). When the receiver was mobile, BER improvements were demonstrated when the Doppler correction filter was enabled. For example, when the receiver was moving at 1 knot, two iterations of the Doppler compensation filter improved the bit error rate from 0.2 to 0.06. It can be expected that, for both applications, an efficient error correcting coding technique across the subcarriers will provide significant performance improvement.  
Formal analysis, H.R.M.; Investigation, J.-F.B.; Methodology, H.R.M.; Supervision, J.-F.B.; Validation, H.R.M. and J.-F.B.; Writing--original draft, H.R.M.; and Writing--review and editing, J.-F.B.  
This work was funded by NSERC CRDPJ #468580 and a Mitacs Accelerate.  
The authors would like to thank Ultra Electronics Maritime Systems and InnovaSea Marine Systems Canada for their technical and financial support.  
The authors declare no conflict of interest.
## 3 Case Studies  
### Carbon Monoxide: Preliminary Considerations  
As a precaution, it should be noticed that CO is a very poisonous colourless, odourless and non-itching gas, which can be produced by incomplete combustion of fossil fuels, and hence inadvertent exposure to CO can occur when domestic fuels, such as gas or charcoal, are burned in a poorly ventilated room; exposure to car engine exhaust is another main source of concern (specially in parking garages). Carbon monoxide is very dangerous because when inhaled it binds tightly to haemoglobin, thus reducing the amount of oxygen carried by the blood stream, which can lead to severe hypoxia and, eventually, death [73,74].  
As already mentioned in the Introduction section, hydrogen obtained from syngas or from steam reforming of hydrocarbons usually contains traces of CO, and has to be purified before using it in proton exchange membrane fuel cells (PMFCs), because otherwise the carbon monoxide poisons the platinum catalyst. Note that PMFCs could be used in fuel cell powered vehicles, which are a potential alternative to the current hybrid electric vehicle [75, 76, 77].  
Aside from that, detailed studies on carbon monoxide adsorption are also highly valuable in the context of zeolite characterization, since CO is a probe molecule very frequently used for IR spectroscopic studies on the nature (and location) of the gas adsorption sites in zeolites and other porous adsorbents [65,78, 79, 80, 81, 82] as well as for ranking Bronsted acidity of protonic zeolites [83,84]. The early IR spectra of CO adsorbed in alkaline zeolites, usually recorded at a fixed (low) temperature, were frequently analysed assuming that the adsorption sites consisted of an extra-framework alkali-metal cation and the nearby oxygen atoms of the zeolite framework, as shown in Figure 1. More recently, however, a fruitful combination of VTIR spectroscopy with DFT calculations on periodic zeolite models [71,85] led to an increasing awareness that, often, the adsorption site involves more than a single cation. Moreover, the adsorbed molecule, being confined inside intrazeolite voids (channels and cages) that have molecular dimensions can also be subject to (non-negligible) weak host-guest interactions (frequently referred to as _the confinement effect_) [86, 87, 88, 89] that can affect till some extent, both the stability of gas-solid adsorption complexes and the vibrational dynamics of the adsorbed molecule [90,91].
## 3 Results and Discussion
### Structure and Surface  
Sulfur copolymers are completely amorphous materials. Nevertheless, the polymer networks can show slight crystalline reflections in the PXRD. The detected attenuated crystalline reflections are in agreement with the powder X-ray diffractogram of crystalline elemental sulfur. In the case of low residual elemental sulfur in all sulfur copolymers, the respective monomers have not been converted completely and the depolymerization occurs with a temporal dependence. The small quantities of sulfur have no influence on thermal or mechanical properties. S\({}_{8}\) can be qualitatively detected in the first heating phase of the DSC measurement and, in very small amounts, in the SEM images and PXRD diffractograms.  
SEM-images of sulfur copolymers show sulfur microcrystals (Figure 3b). These are characterized by an angular shape (Figure 3b) with a plain surface showing little spherical dots (Figure 3c). The microcrystals form agglomerates (Figure 3a). The image shows exemplarily a section with an S\({}_{8}\) that remains on the polymer and is not distributed over the entire surface of the copolymers. This observation is confirmed by [PERSON] et al. [28].  
The sulfur copolymer films exhibit a plain surface, partly with unevenly distributed holes to rod-shaped notches (Figure 4a,d). The holes are probably the remainders of sulfur-occupied gaps (Figure 4b,e). After usage of the hot press, elemental sulfur almost disappears, probably by post cross-linking (virtually full conversion of sulfur). The sulfur copolymers show thin cracks when using the hot press (Figure 4c,f).  
Figure 2: Illustrations of pS-DVB- (**above**) and pS-DIB-films (**below**) obtained by hot press treatment with varying incorporated monomer content.  
Consequently, the structure appears slightly inhomogeneous due to residual elemental sulfur, holes, pores and cracks. The linking agents DVB and DIB seem to be incorporated completely into the polymer network because no residual monomer is detected in the gas chromatography. However, low double bonds are available (solid-state NMR), which show the presence of a few non-converted double bonds, so probably only one functional group of the divinyl monomers is affected. This observation of incomplete conversion of double bonds of the vinyl monomers agrees with the investigations of [PERSON] using larger reaction scales [10]. Despite the same conditions for each reaction and thus similar conversion values of double bonds, other effects (gel effect, post cross-linking) have an additional influence on the properties, possibly with no linear correlation.
## 3 Methodology
### Point Features Extraction
#### 3.1.3 Intensity Coefficient of Variation (\(Icov\))  
Intensity Coefficient of Variation is calculated by dividing the standard deviation by the mean of the intensity values. The water points were assumed to have \(ICOV^{\text{C1 or C2 or C3}}\) greater than those of land objects. The reason for this is the intensity variation in water bodies is relatively high as a result of different incidence angles. For each LiDAR point in any channel, the \(ICOV^{\text{C1 or C2 or C3}}\) can be calculated from Equation (5), where \(I_{j}\) is the point's intensity value and \(\overline{I}\) is the mean of the intensity values.  
\[ICOV^{\text{C1 or C2 or C3}}_{p_{i}}=\frac{\sqrt{\frac{1}{n-1}\sum\limits_{j=1}^ {n}{\left({I_{j}-\overline{I}}\right)^{2}}}}{\frac{1}{n}\sum\limits_{j=1}^{n}{ I_{j}}} \tag{5}\]
## 2 System and Channel Model  
### Basic Principles of the Investigated THz System  
The typical multi-hop LOS THz system under consideration comprises the transmitter node, the receiver node and the \(N\)-1 serially connected decode-and-forward (DF) relay nodes along the propagation channel, with \(N\geq 1\). Therefore, \(N\) distinct intermediate THz links, commonly known as hops, are created along the total propagation path. Each relay node decodes the signal after direct detection, remodulates it and retransmits it to the next relay node, provided that it exceeds a given appropriate decoding intensity threshold. This process continues until the source's data arrives at the receiver destination node [56]. Without loss of generality, these intermediate links can be assumed to be of equal length. Additionally, the investigated system is considered to employ the On-Off Keying (OOK) modulation format which is commonly utilized in both commercial and industrial fields, mainly due its simplicity among the rest of the alternative modulation schemes. Under these assumptions, the THz signal that arrives at the \(n\)-th node, where \(1\leq n\leq N\), is expressed as:  
\[y_{n}=h_{n}x_{n-1}+n_{n} \tag{1}\]  
where \(h_{n}\) is the total corresponding channel state due to atmospheric turbulence, total attenuation and generalized pointing errors, \(x_{n-1}=\{0\text{ or }2P_{t}\}\) is the corresponding emitted information signal according to the OOK modulation format with \(P_{t}\) being the average transmitted signal power and \(n_{n}\) represents the corresponding additive Gaussian white noise with variance \(\sigma_{n}^{2}\)[19].
# A Design of a Time Synchronization Protocol Based on Dynamic Route and Forwarding Certification
## 3 Design of a Time Synchronization Protocol Based on Dynamic Routing and Forwarding Certification  
The proposed time synchronization protocol DRFC-TSP is composed of two processes: the time synchronization process during which the node modifies its clock according to the reference information, and the forwarding certification process during which certain nodes are authorized to conduct forward certification. Two process phases are initiated by the root node, and the other nodes accomplish the corresponding process. The realization of DRFC-TSP is shown in Figure 3.