esa-sceva/satcom-chunk-collection huggingface dataset:
# Channel Estimation Based on IOTA Filter in OFDM/OQPSK and OFDM/OQAM Systems
## 5 Simulation Results
### The Performance of the OFDM/QQAM System  
Figure 8 illustrates the BER performance of the proposed OFDM/QQAM system over Rayleigh fading channels with different Doppler spread. As shown in Figure 8, when the maximum Doppler spread increased from 20 Hz to 60 Hz, the proposed IOTA filter method demonstrates its advantage in tracking the channel variation. The BER curve gaps between the IOTA filter method with Doppler spread of 20, 40, and 80 Hz are about 1.8 and 3.5 dB at the target BER of \(10^{-4}\). In addition, the BER curve gaps between the ICE method with Doppler spread of 20, 40, and 80 Hz are about 2.0 and 3.1 dB at the target BER of \(10^{-4}\). The BER curves under Doppler spread of 40 and 60 Hz are very similar and the BER curves declined rapidly as the \(E_{\rm b}/N_{0}\) increased. It can be seen that AWGN is the main factor affecting the accuracy of channel estimation in the lower \(E_{\rm b}/N_{0}\) zone, but the IOTA filter can maintain orthogonality between subcarriers to counteract Rayleigh fading.  
Figure 9 presents the NMSE performance of the OFDM/QQAM system over Rayleigh fading channels with different Doppler spread. As shown in Figure 9, the channel estimation results can be accurately measured by the NMSE values. When the NMSE value is 0.02, the \(E_{\rm b}/N_{0}\) gaps between the NMSE performance curves of the proposed IOTA filter method with the Doppler spread of 20, 40, and 80 Hz are about 1.5 and 4.0 dB, respectively. The IOTA filter is a good choice that can be well adopted in the proposed OFDM/QQAM system. Under the maximum Doppler spread of 40 and 60 Hz, the NMSE curves almost overlap, but the IOTA method with a Doppler spread of 40 Hz still outperforms the Doppler spread of 60 Hz by about 0.03 dB.  
Figure 7: NMSE performance of the OFDM/QPSK system over Rayleigh fading channels with Doppler spread of 20, 40, 60, and 80 Hz.  
Figure 8: BER performance of the OFDM/OQAM system over Rayleigh fading channels with Doppler spread of 20, 40, 60, and 80 Hz.  
Figure 9: NMSE performance of the OFDM/OQAM system over Rayleigh fading channels with Doppler spread of 20, 40, 60, and 80 Hz.
## 1 Introduction
### IoT for 6G in Smart Cities  
A range of technologies that need to be described for the full-scale development of the 6G communication network. The study of [PERSON] et al. [5] highlighted different technologies that can be useful in 6G wireless communication. These technologies include the Internet of Things (IoT), virtual reality (VR), Terahertz (THz) communication, visible light communication, etc. IoT is also discussed by [PERSON] et al. [5], who states that the current state of communication networks, i.e., 5G, is relatively slow at keeping the billions of devices connected to IoT systems, as they require massive data processing and communication in real-time. As a result, scientists are already looking forward to a faster form of communication that can open up a new era in terms of connectivity.
## 4 Comparisons of Results for DFE, MLD Algorithms
### EVM Performance as a Function of Fiber Length  
Figure 6 illustrates the EVM performance as a function of fiber length for both QPSK and 16-QAM modulation schemes without equalization and after equalization with the MLD, DFE, and RDE algorithms. These results demonstrate the efficacy of MLD, DFE, and RDE techniques in compensating ISI within a converged mm-wave A-RoF system operating at 60 GHz. A comparative analysis of these two equalization algorithms (for QPSK and 16-QAM) reveals that the DFE slightly outperforms the MLD, as shown in Table 4, although RDE, as mentioned above, outperforms both of them.  
Figure 7 presents the EVM results versus the fiber length for 64-QAM and 128-QAM. A comparative analysis of these two equalization algorithms (for 64-QAM and 128-QAM) reveals that the DFE slightly outperforms the MLD, as shown in Table 4. In our proposed setup, RDE is working for higher-order (more than 16-QAM) modulation formats and thus is not plotted.  
Moreover, when we compare the two algorithms in terms of computational complexity, the DFE is performing better than the MLD because the latter assesses all potentially transmitted symbol sequences to identify the one that optimizes the likelihood of generating the observed received sequence, and MLD's complexity increases exponentially with the size of the signal constellation and the number of symbols in the sequence [41], rendering it less efficient for systems with high modulation orders.  
Figure 6: EVM results obtained before and after equalization vs. the fiber lengths for (**a**) QPSK constellations after MLD, DFE, and RDE equalization, and (**b**) 16-QAM constellations after MLD, DFE, and RDE equalization.
# Pattern and Analysis of Corrugation-Sand Retaining Seals for
## 6 Conclusions  
1. Based on the [PERSON] theory, the relevant formula for calculating the leakage of the corrugated main seal is deduced. The main factors affecting the leakage of the special-shaped seal ring are the seal compression state, the pressure difference \(\Delta P\) inside and outside the seal cavity, and the relevant parameters of the main seal sine wave, and the actual model is obtained.
2. Determine the compression state of the main seal and the contact gap of the sand retaining flap, and prove that the corrugated special-shaped sand retaining seal meets the design requirements. Calculate the leakage rate and draw the conclusion that the greater the contact width, the greater the leakage rate under the premise of the constant load.
3. The main structural parameter that affects the leakage of the main seal and the contact gap between the sand flap tip are obtained. Through the single-factor optimization method, the influence law of each structural parameter on the leakage and the contact  
Figure 14: Comparison of tip contact gap of sand flap: (**a**) Before optimization, and (**b**) Optimized.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Performance** & **Maximum Stress** & **Contact Pressure** & **Contact Width of** & **Main Seal** & **Main Seal** & **Sand Retaining Flap** \\  & **of Sealing Ring** & **of Main Seal** & **Main Seal** & **Bearing** & **Leakage** & **Tip Contact Gap** \\ \hline Not optimized & 7.774 MPa & 19.213 MPa & 2.45 mm & 550.3 N & 282.79 mg/h & 0.0039343 mm \\ Optimized & 4.526 MPa & 14.742 MPa & 0.86 mm & 499.2 N & 43.10 mg/h & 0.00019479 mm \\ \hline \hline \end{tabular}
\end{table}
Table 5: Performance changes of new sealing ring before and after optimization.  
gap is obtained, and a set of optimal structural parameter combinations suitable for 8 1/2 inch (215.9 mm) drill bits are obtained, the main seal contact pressure is reduced and the leakage is reduced by 85%; it takes 580 h for the grease to run out; and the contact gap is 0.00019479 mm, a decrease of 95%, the abrasive medium is separated from the main seal components, which can greatly reduce the wear of the main seal.  
Conceptualization, Y.Z.; methodology, W.Z.; software, W.Z.; validation, Y.Z.; formal analysis, W.Z.; investigation, Y.Z.; resources, Y.Z.; data curation, W.Z.; writing--original draft preparation, W.Z.; writing--review and editing, Y.Z. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The authors declare no conflict of interest.
## 2 Materials and Methods  
Data processing for the original detected MEG signal aims to remove noise, including line frequency noise, blink artifacts, eye movement artifacts, cardiac artifacts, etc. Blink artifacts are the noise that has the greatest influence on the original detected MEG signal. In order to remove the blink artifacts with the SSP and the ICA algorithm, the occurrence time of the blink artifacts should firstly be decided from the blink signals in the EOG. In this work, an ANN is utilized to recognize the spatial distribution characteristics of the blink artifacts, providing a new solution to automatically identify the blink artifacts from the original detected MEG data in real time. The process includes three sequential steps: obtaining the data, training the network, and testing the network.
## 2 Channel Reliability Modeling for 5G Communications
### Probability of Reliable Operation of Sectionalized Switches  
The telemetry of sectional switches is an important basis for fault area determination in distribution stations. If the monitoring information of a sectional switch is invalid, the control center can only use the monitoring information of its upstream sectional switches to determine the fault location, and the sectional switch can not act normally to isolate the fault, which leads to the extension of the fault isolation range. After completing the fault location decision, the control center will issue control commands to the switch with valid monitoring information that is closest to the fault point to isolate the fault area. At the same time, the control center will judge whether the fault isolation is successful or not through the control feedback information of the switch.  
If the control information or control feedback information is invalid, the control center will mistakenly believe that the fault has not been successfully isolated and send control commands to the upstream switch in turn until it is determined that the fault has been successfully isolated.  
Since the uploading of monitoring information, issuing of control instructions, and uploading of control feedback information are independent of each other, the probability that the faulty upstream switch can successfully act by the instructions of the control center and that the control center can confirm that the fault has been successfully isolated by the switch is  
\[p_{ICT,i}=R_{M,i}R_{C,i}R_{F,i} \tag{12}\]  
where \(R_{M,i}\) is the probability that the monitoring information of switch \(i\) is valid. \(R_{C,i}\) is the probability that the control information of switch \(i\) is valid. \(R_{F,i}\) is the probability that the control feedback information of switch \(i\) is valid. Also, \(i\in\mathbb{N}\).  
Consistent with the circuit breaker, due to the design defects of the switching element itself, there is still a certain probability of refusal to act after receiving the control command, so the probability of successful operation of the sectionalized switch is  
\[p_{sw,i}=p_{sw}p_{ICT,i} \tag{13}\]  
where \(P_{sw}\) is the probability of reliable operation of the sectionalized switch itself.
# Improving IoT Data Security and Integrity Using Lightweight Blockchain Dynamic Table
## 7 Evaluation and Analysis  
Three main security requirements must be addressed by any security design, namely confidentiality, integrity, and availability, otherwise known as CIA. Confidentiality makes sure that only an authorized user can read the message. Integration makes sure that the message sent at the destination is received without any change, and availability means that every service or data point is available to the user when they need it. To increase the availability of a smart home, devices are protected from malicious requests. This is achieved by limiting the accepted transactions to those entities with which each device has created a shared key. Transactions from the overlay are authorized by the miner before being forwarded to the devices. Furthermore, it can be argued that our BC-based framework offers only a marginal increase in transaction processing delays compared to current smart home gateway products. There is also an additional one-time delay during initialization for the generation and distribution of shared keys. In short, the additional delays are not significant and do not affect the availability of smart home devices.  
Figure 6: Z1 IoT device.
# Synthesis of Star Nanoparticles and Their Applications for Bioactive Compound Encapsulation
## 2 SNP Preparation Method
### Emulsion Cross-Linking  
Recently, the synthesis of SNPs by an emulsion-crosslinking technique has been reported. This technique involves mixing of an aqueous phase which contains cross-linking agents with another phase that contains dissolved starch. The mixture is then added into an oily or organic phase with the presence of emulsifying agents as can be seen in Figure 4. Through this W/O emulsion, small particles are generated by cross-linking reaction within the aqueous droplets. However, the particles obtained from this emulsion cross-linking approach are relatively large and on the microscale [32; 33].  
To reduce the size of these particles, the emulsion should contain nanoscale droplets, which means use a miniemulsion (also called nanoemulsions) instead of an emulsion [35]. [PERSON] et al. used retrograded starch (RS III) to synthesize SNPs through a high-speed shearing emulsification method using N,N\({}^{\prime}\)-methylenediacrylamide (MBAA) as the cross-linking agent and NaHSO\({}_{3}\) as an inducing agent in the aqueous phase which contained the dissolved starch in a potassium hydroxide solution. The oil phase was formed by mixing cyclohexane with a mixture of Span 80 and Tween 80 at an 84:16 proportion. The aqueous phase was added to the oil phase in order to form the microemulsion which was homogenized by a high-shear homogenizer to break the droplets and form the nanoemulsion. A small particle size distribution was obtained, and the average size was approximately 287 nm. The stability of the particles was studied, and it was shown that these nanoparticles were stable in neutral and alkaline pH or in low NaCl concentration [36].
# A Fast Approach to Optimize Trad Pattern Shape for Tire Noise Reduction
## 2 Tire-Pavement Interaction Noise  
### Mechanism of Tire Pattern Noise  
When a patterned tire rolls on a flat surface, the impact and release of the tread blocks on the pavement cause the vibration of the tire belt and tread surface, generating noise. Due to the high damping of the rubber material, these vibrational waves primarily remain concentrated near the impact area and do not propagate far. Consequently, acoustic sources located near the contact path are then amplified by the tire-pavement geometry, resulting in far-field noise, as shown in Figure 1. Finally, it is transmitted to the human ear through the air, resulting in perceptible noise.  
Tire noise is generated by various mechanisms, including tire surface vibration and the noise associated with aerodynamics, which are discussed in [35]. In general, tire surface vibration can be explained by the excitation force, transfer function, and acoustic field. The former is primarily affected by the tread pattern design, while the transfer function is related to tire structure, material, and boundary conditions. The transfer function can be mathematically represented as follows:  
\[H_{ij}(f)=\frac{X_{ij}(f)}{F_{ij}(f)} \tag{1}\]  
Figure 1: Mechanism of tire noise generation.  
where \(H_{ij}(f)\) is the vibration response transfer function in the frequency domain, being related to the tire structural design and material composition. \(F_{ij}(f)\) and \(X_{ij}(f)\) are the inputs of the exciting force and the response of vibration, respectively. Generally, \(X_{ij}(f)\) can be the displacement, velocity, or acceleration of the vibration. For a patterned tire, \(F_{ij}\) is mainly influenced by the tread pattern geometry and distribution on the tread. If we ignore the transfer characteristics of tires, that is, \(H_{ij}\) is constant, and Equation (1) can be simplified as:  
\[\frac{\left[X_{p}\right]_{ij}}{\left[F_{p}\right]_{ij}}=const \tag{2}\]  
where \(\left[X_{p}\right]\) and \(\left[F_{p}\right]\) are the vibration response of the tread surface and exciting force on the tread pattern. Equation (2) shows that the vibration response of the tread surface is directly proportional to the input force.
## 5 Optimal Sensor Placement and Validation Results Based on QR Pivoting  
### Criterions for Optimal Sensor Placement  
The optimal sensor placements are those that minimize the relative errors. From Equation (10), the problem of optimal placement of sensors is transformed into seeking rows of \(\Psi\) which optimally condition the inversion of the matrix \(\Theta\). Therefore, the condition number of the linear system can be improved by optimizing the spectral content of K using its determinant, trace, or spectral radius. Based on the criterion of spectral radius, the smallest singular value of K\({}_{\lambda}\) can be maximized by K\({}_{\lambda}^{-1}\).  
\[\lambda^{*}=\underset{\lambda,|\lambda|=r}{\text{argmin}}\|\text{K}_{\lambda} ^{-1}\|_{2}=\underset{\lambda,|\lambda|=r}{\text{argmax}}\,\sigma_{\text{min}} (\text{K}_{\lambda}) \tag{19}\]  
Likewise, the criteria of optimizing the trace or determinant of its eigenvalue or singular value spectrum are as follows:  
\[\lambda^{*}=\underset{\lambda,|\lambda|=r}{\text{argmax}}\text{tr}\Big{(} \text{K}_{\lambda,|\lambda|=r}\Big{)}=\underset{\lambda}{\text{argmax}}\underset {i}{\sum}\,\lambda_{i}(\text{K}_{\lambda}) \tag{20}\]  
\[\lambda^{*}=\underset{\lambda,|\lambda|=r}{\text{argmax}}|\text{det}\text{K} _{\lambda}|=\underset{\lambda,|\lambda|=r}{\text{argmax}}\,\prod_{i}\sigma_{ i}(\text{K}_{\lambda}) \tag{21}\]  
However, if the above criteria are used for optimization, a combinatorial search over \(\begin{pmatrix}n\\ r\end{pmatrix}\) is required, which is a brute-force search containing all possible sensor configurations and is hence computationally intractable. Recently, with the development of EIMs (Empirical Interpolation Methods), the study of Q-DEIMs has attracted the most attention, where \"Q\" stands for QR pivoting [28; 29; 30], which provides an optimal sampling method for nonlinear interpolation reconstruction in ROMs (Reduced-Order Models). Based on QR factorization and column pivoting of \(\Psi^{T}\) by the Q-DEIM method, an approximate greedy algorithm is proposed.
# Maritime Cyber Security: A Global Challenge Tackled through Distinct Regional Approaches
## 4 Findings and Discussion
Looking at the responses presented in Figure 10(a),b, an interesting realization that reaffirms what has been previously mentioned was identified. Asian maritime experts were more advanced in terms of security-minded technology solutions applied within their maritime transport organizations, compared to their European counterparts. As such, they were able to mitigate incoming malicious content. Having the appropriate measures  
Figure 4.3 Have you experienced a surge in cyber attacks in your organization during the pandemic? (**a**) Europe; (**b**) Asia. in place and not allowing an increased number of attacks to penetrate their organizations ecosystem justified the responses presented in Figure 11b. Similar to question 4, presented in Table 1 and analyzed above, the last question of the survey tried to identify the level of effectiveness of shipping companies in adapting to the new norm, due to the COVID-19 pandemic. This new norm entailed: (A) an increased number of employees working remotely (from home), (B) the adoption of digital solutions to facilitate this transition, and (C) uptake in number of cyber attacks affecting the industry. As demonstrated in Figure 13a,b, 86% of European participants mentioned that shipping companies were either very or somewhat effective in adapting to the new norm. In comparison, opinions on the same matter from Asian participants were limited to almost half of the percentage demonstrated above (46% were either very or somewhat effective). Overall, Figure 14 illustrates that a strong majority of industry practitioners (68%) believed that the industry was effective in adapting to the new norm due to the COVID-19 pandemic. Figure 4.4 How effective have shipping companies been in adapting to the new norm due to the COVID-19 Pandemic? (Asia and Europe). Figure 4.5 How effective have shipping companies been in adapting to the new norm due to the COVID-19 Pandemic? (**a**) Europe; (**b**) Asia. The difference in responses illustrated in Figure 13a,b reaffirms the trend identified throughout this survey regarding the level of maturity and understanding of what cyber security entails between the European and Asian participants. With reference to the findings of Figure 14, this comes as no surprise, as, unlike other industries, shipping, due to its nature, is used to having its most valuable assets operating remotely. Ships operating globally, thousand miles away from their shipping company's offices, have established procedures and technology solutions for decades. In this section, the findings of the survey were demonstrated and discussed. Section 5 summarizes the key points of this research.
# Closing Connectivity Gap: An Overview of Mobile Coverage Solutions for Not-Spots in Rural Zones
## 4 Discussion  
At this height, the rural zones have struggled to embrace fully fledged connectivity. Regarding Latin America's situation, three considerable constraints are in conflict with the ubiquitous rural coverage aim: First, MNOs do not furnish a suitable telecom infrastructure outside of urban environments. Secondly, rural settlements are concentrated but geographically sparse, occupying common hot spots. Finally, the studied strategies should be based on bespoke hardware requirements since uneven relief and ecosystem variation hapter the static estimation of channel parameters--the latter demands higher investment cost--which seems unprofitable for ISPs and MNOs.  
The not-spots affect directly rural inhabitants, especially those who attempt to foster rural businesses, which include mainly agricultural and new industrial activities in the countryside. Hence, Table 7 states the advantages and shortcomings of the studies solutions--in Section 3--while we spur ongoing research of UAV-assisted networks deployment driven by mobility, cost-effective, and the other leverages outlined in Table 7 that can bring networks to the uncovered regions. Further works include the analysis of dynamical propagation model and simulations of LTE--aiming for 5G-NR deployment--at incoming experimental stages.
# Rural Healthcare IoT Architecture Based on Low-Energy LoRa
## 3 Architectural Challenges
### Communication Synchronization  
A big challenge for devices that remain in sleep states for prolonged periods of time is communication synchronization. The energy constraints prohibit a device from having a complete picture of the state of the environment, the network, and other devices.  
Communication in the network is inherently sparse based on the assumption that energy is not reliable. Each IoT node and healthcare gateway should have a built-in real-time clock and calendar chip and a battery-powered circuit. If power is lost due to power grid blackout or bad conditions for renewable energy harvest, a timer-based battery switch starts the gateways at the predetermined communication time slot. A real-time clock or internal timer will also wake up IoT devices with buffered data to transmit to the network.