esa-sceva/satcom-chunk-collection huggingface dataset:
## 4 Performance Analysis for Variable-Gain Relaying
### Ergodic Capacity  
The definition of ergodic capacity is \(\bar{C}=E[\log_{2}(1+\alpha_{t}\gamma)]\), where \(\alpha_{t}=1\) for HD and \(\alpha_{t}=e/2\pi\) for IM/DD [35]. With the help of the CCDF \(F_{\gamma}^{c}(\gamma)\), the ergodic capacity can be written as:  
\[\bar{C}=\frac{\alpha_{t}}{\ln 2}\int_{0}^{\infty}\frac{F_{\gamma}^{c}(\gamma)}{1 +\alpha_{t}\gamma}d\gamma \tag{38}\]  
Substituting (23) into (38), the ergodic capacity is expressed as:  
\[\bar{C}^{V} =\frac{\alpha_{t}}{\ln 2}\int_{0}^{\infty}\frac{1}{1+\alpha_{t} \gamma}\text{exp}\bigg{(}-\frac{\gamma}{\hat{\gamma}_{RF}}\bigg{)}d\gamma \tag{39}\] \[-\frac{\alpha_{t}m^{2}}{\ln 2\Gamma(a)\Gamma(b)}\int_{0}^{\infty} \frac{1}{1+\alpha_{t}\gamma}\text{exp}\bigg{(}-\frac{\gamma}{\hat{\gamma}_{ RF}}\bigg{)}\] \[\times G_{3,3}^{22}\bigg{[}\frac{\phi_{m}\gamma^{1/t}}{\hat{ \gamma}_{FSO}^{1/t}}\big{|}1-b,1,1+m^{2}\bigg{]}d\gamma\]  
Utilizing [31] (Equation (7.813.1)) and [33] (Equations (10) and (11)), and with the aid of the integral of the extended generalized bivariate Meijer's G function (EGBMGF) [36] (Equation (20)), the ergodic capacity expression for the variable-gain relay is derived as:  
\[\bar{C}^{V} =\frac{\alpha_{t}\hat{\gamma}_{RF}}{\ln 2}G_{2,1}^{1,2}\bigg{[} \alpha_{t}\hat{\gamma}_{RF}\big{|}\begin{matrix}0,0\\ 0\end{matrix}\bigg{]}-A_{1}\frac{\alpha_{t}}{\ln 2}\hat{\gamma}_{RF} \tag{40}\] \[\times\begin{matrix}0,1;1,2;2t,2t\\ 1,0;1,1;3t,3t\end{matrix}\bigg{[}-\big{|}\begin{matrix}1,0\big{|}Q_{1}\\ Q_{2}\big{|}a_{t}\hat{\gamma}_{RF},\phi_{m}^{t}\frac{\hat{\gamma}_{RF}}{\hat{ \gamma}_{FSO}}\end{matrix}\bigg{]}\]
## 5 3 GPP Standardization for URLLC  
To guarantee the desired reliability, 3 GPP and its allies are still working and planning for improvements at multiple aspects of 5G architecture. Some of the recent critical points highlighted by 3 GPP Release 16 [49] include the following:
# Around View Monitoring-Based Vacant Parking Space Detection and Analysis
## 3 Algorithm to Detect Vacant Parking Spaces
### Parking Space Detection Stage
#### 3.2.4 Space Type Determination  
The type of parking space must be identified before a parking strategy can be determined. Divider lines must be connected to the lane boundary line. Using this characteristic, we can assume a virtual lane boundary line in a binary image, scan d pixels to the right along the \(x\)-axis, and record accumulated pixels along the \(y\)-axis. The results of this scan are shown in Figures 10a and 11a. Because the scanning process can contain noise, such as parking space serial numbers, we firstly filtered accumulated pixels under a threshold (0.75\(d\))). Next, the line width, \(W_{line}\) (10 pixels = 13 cm) served as a criterion to eliminate errors in detection. The filtered results are shown in Figures 10b and 11b. By observing the distance between peaks \(W_{slot}\) (178 pixels = 231 cm in Figure 10b, 435 pixels = 566 cm in Figure 11b), the parking space can be classified as a perpendicular or parallel space.  
Figure 10: Perpendicular parking. (**a**) Scanned distribution; (**b**) Distribution after filtering.  
Figure 9: Lane boundary line recognition. (**a**) Algorithm; (**b**) Results.
# A Survey on Recent Advanced Research of CPS Security
## 5 Conclusions  
CPS security is a hot area of current security research, as it is closely related to real life. Although there are many studies on CPS security, more efforts are still needed to understand CPS security from a more comprehensive perspective. We provide a comprehensive survey based on 142 papers selected from A/B level conferences/journals recommended by the CCF and obtain a series of valuable conclusions. Technically, the current research hotspots of CPS security include authentication and access control schemes and analysis of firmware and apps. However, there are still many emerging fields, such as the security of CPS blockchains and cloud servers that require more research. Globally, the United States is in a leading position with respect to the most published papers, while China is catching up. In addition, the number of institutions/universities that contribute to CPS  
Figure 6: Main universities and labs studying the security of CPS and their cooperations.  
security research has increased from 10 in 2015 to 62 in 2019, and international academic communication is getting closer than ever. Therefore, we hope to provide more insight and ideas to the research community through this review.  
Conceptualization, Z.W. and W.X.; methodology, W.X.; software, Z.W.; validation, E.W., B.W. and J.T.; funding acquisition, B.W. All authors have read and agreed to the published version of the manuscript.  
The work was supported by the Natural Science Foundation of Hunan Province in China (2019J50729) and Natural Science Foundation of China (61902412, 61902416).  
The authors declare no conflict of interest.
## 4 Discussion
### Noise Attack Analysis  
In addition, a common noise attack in the field of image encryption needs to be discussed. Because there is noise in the process of ciphertexts transmission or hackers deliberately add noise to the ciphertexts to disturb the decrypted results, we add salt and pepper noise to the ciphertexts to test the anti-noise ability of the system. After adding salt and pepper noises with densities of 0.05, 0.1, and 0.2 to the four ciphertexts (which are proportional to the total number of pixels of the noise points), Figure 9 shows the four ciphertext images and the associated reconstructed images under different noise densities. The results show that even if significant salt and pepper noise is introduced, the original images can still be reconstructed from the decrypted QR codes, which shows that our system can effectively resist noise attacks.
# Behavior of Circular Hollow Steel-Reinforced Concrete Columns under Axial Compression
## 6 Calculations of Ultimate Strength  
### Proposed Design Procedures  
The axial compression bearing capacity of the circular HSRC columns can be divided into two components: the hollow steel tube and the hollow RC, based on the superposition principle. According to the limit equilibrium principle, the ultimate axial compression bearing capacity (\(N_{\text{uc}}\)) of circular HSRC columns can be calculated using the following expression:  
\[N_{\text{uc}}=N_{\text{uc}}^{\text{rc}}+N_{\text{uc}}^{\text{s}} \tag{3}\]  
where: \(N_{\text{uc}}^{\text{rc}}\) and \(N_{\text{uc}}^{\text{s}}\) represent the ultimate strength of the outer RC and the inner steel tube, respectively.  
Method 1 follows the Chinese codes T/CECS 188-2019 [22] and GB50010-2010 [23]. The normal-section bearing capacity of the RC part (\(N_{\text{uc1}}^{\text{rc}}\)) and the inner steel tube part (\(N_{\text{uc1}}^{\text{s}}\)) under axial compression can be determined with the axial compressive bearing capacity (\(N_{\text{uc1}}^{\text{rc}}\) and \(N_{\text{uc}}^{\text{s}}\)) of short columns corresponding to similar cross-sectional parameters using code GB50010-2010. The axial bearing capacity of the circular HSRC column can be obtained through the sum of the two components (\(N_{\text{uc1}}^{\text{rru}}\) and \(N_{\text{uc1}}^{\text{s}}\)), multiplying the stability coefficient provided in code T/CECS 188-2019 (see Table 1).  
According to AJJ [11], method 2 defines the \(H/D\) ratio, where \(H\) is the effective length of the member and \(D\) represents the section diameter of the column. Circular HSRC columns are categorized into short, medium-long, and long columns based on the \(H/D\) ratio, and the corresponding formulas are established. The specific provisions are as follows: \(H/D\leq 4\) denotes a short column, \(4<H/D\leq 12\) indicates a medium-long column, and \(H/D>12\) represents a long column, as presented in Figure 11. The formula for the bearing capacity of the columns under axial compression is based on the linear equation of the interpolation function at the boundary of the short column and long columns.  
Method 3 is according to Eurocode 4 [12]. The plastic compressive capacity (\(N_{\text{pl,Rd}}\)) of the loading cross-section is calculated by increasing the plastic bearing capacity of the components. As for the long column under axial compression in the European code, the elastic, critical load on the column is determined according to the analysis method in Eurocode 4 [12] and the design value of the effective bending stiffness determined by the member defects in which the second-order effect is not considered.
# A Novel Cell-Based Adaptive Cartesian Grid Approach for Complex Flow Simulations
## 2 Adaptive Cartesian Grid Generation Method
### Initial Uniform Grid Generation  
To define the computational domain, only the coordinates of two vertices, \((D_{\text{min}}^{x},D_{\text{min}}^{y},D_{\text{min}}^{z})\) and \((D_{\text{max}}^{x},D_{\text{max}}^{y},D_{\text{max}}^{z})\), in floating-point numbers (real) are required. Subsequently, the initial grid numbers in the \(xyz\) directions \((N^{x},N^{y},N^{z})\), in integer type, are determined. The mixed arithmetic formula for the grid sizes in the \(xyz\) directions \((L^{x},L^{y},L^{z})\) and the initial total number of grids \((N^{init})\) is as follows:  
\[\begin{array}{l}L^{x}=\text{real}\big{(}D_{\text{max}}^{x}-D_{\text{min}}^{x }\big{)}/\text{integer}(N^{x})\\ L^{y}=\text{real}\big{(}D_{\text{max}}^{y}-D_{\text{min}}^{y}\big{)}/\text{ integer}(N^{y})\\ L^{z}=\text{real}\big{(}D_{\text{max}}^{z}-D_{\text{max}}^{z}\big{)}/\text{ integer}(N^{z})\\ N^{init}=N^{x}\times N^{y}\times N^{z}\end{array} \tag{1}\]  
Using integer types to determine the number of grid divisions and subsequently calculating the initial grid sizes facilitates the initial grid partitioning and control of the computational domain size. In contrast, using floating-point types to determine grid sizes and then deriving the number of grids introduces rounding errors due to floating-point truncation. Additionally, considering that the grid sizes in the \(xyz\) directions are independent of each other, the initial uniform grid can be established with certain proportions. The determination of computational domain size and the generation of initial uniform grids are illustrated in Figure 2.  
Figure 1: Adaptive Cartesian grid generation process.
## 1 Introduction
Due to its remarkable tuning abilities such as high stability and fast switch speed [29; 30], GST has been applied in many novel tunable nano-photonic devices such as multi-wavelength duplex metalens, dipole-quadrupole (DQ) Fano resonance (FR) induced lateral force, beam steering, filter, color control, and ultraviolet/high-energy-visible resonances by combining with metasurfaces [20; 31; 32; 33; 34; 35; 36], which has proved to be the great potential of GST. Nevertheless, the research for tunable metalens array using phase change materials has not been explored yet. In this article, we designed an actively tunable metalens array at the mid-infrared (M-IR) wavelength based on patterned phase change material GST. Although many tunable nano-devices have been achieved by phase change materials, they use phase change materials as a dielectric layer, where the multi-layer design method increases the complexity of the system. Here, our proposed tunable metalens array is a single layer device directly constructed of patterned GST to make our devices go further in the way of the miniaturization of the systems. Benefiting from the Pancharatnam-Berry (P-B) phase shift, the metalens array has excellent broadband performance in the range from 4.5 \(\upmu\)m to 5.2 \(\upmu\)m. By changing the phase state of GST settled in different sections, the performance of the tunable metalens array can be actively controlled at the designed wavelength of 4.6 \(\upmu\)m. Completely switching on and off, focused letters, and symbols \"L\", \"H\", \"+\" and \"\(-\)\" will be demonstrated in the article. We believe our efforts will make some contributions to the application of tunable metalens arrays.
# Deep-Learning-Based Recovery of Frequency-Hopping Sequences for Anti-Jamming Applications
###### Abstract  
The frequency-hopping communication system has been widely used in anti-jamming communication due to its anti-interception and anti-jamming performance. With the increasingly complex electromagnetic environment, the frequency-hopping communication system needs more flexible frequency-hopping patterns to deal with interferences, which brings great challenges to the communication receiver. In this paper, an intelligent receiving scheme of frequency-hopping sequences is proposed, which combines time-frequency analysis with deep learning to realize an intelligent estimation of frequency-hopping sequences. A hybrid network module is designed by combining a convolutional neural network (CNN) with a gated recurrent unit (GRU). In the proposed network module, the combination of a residual network (ResNet) and squeeze and extraction (SE) improves the feature extraction and expression capabilities of the CNN network. The GRU network is proposed to solve the problem of dealing with signals with variant input lengths. A transfer learning scheme is further proposed to deal with communications systems with different frequency-hopping sets. Simulation results show that the proposed method has strong generalization ability and robustness, and the bit error rate (BER) performance of intelligent receiving is close to the receiving performance under ideal conditions.  
footnote: footnotetext: **Copyright** © 2023 by the authors. Liconse MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ([[https://creativecommons.org/licenses/py/4.0/](https://creativecommons.org/licenses/py/4.0/)]([https://creativecommons.org/licenses/py/4.0/](https://creativecommons.org/licenses/py/4.0/))).  
**Keywords:** frequency-hopping communication; anti-jamming; convolutional neural network; gated recurrent unit; transfer learning
# Clustering Smart City Services: Perceptions, Expectations, Responses
## 4 Reading the Outcomes of the Pilot Study
### Perceptions of Users for Technology Clusters Ratings  
In Figure 5, we present the average rating of users for each of the technology clusters. It is extremely interesting to elaborate on some of the key findings:  
* The average rating for the frequent use of diverse technologies for the provision of smart city services is ranging from 34% to 46%. This, in fact, provides a critical mass of users for smart city services. A question for future research is related to advanced policy-making: what are the required strategies and policies to support people who are concerned by the efficiency of services to adopt and to integrate into their lives.
* A significant part of responders ranging from 19% to 25%, defines themselves as users of smart cities applications with great motivation to adopt smart cities services, enabled by all the seven clusters of smart cities enabling technologies.
* As a direct interpretation of the above findings, it is evident from our empirical study that almost two-thirds of responders constitute a group of light and heavy smart cities services. In fact, it seems that the adoption of various services in the past years resulted in increased motivation and intention to use smart cities services.
* A significant part of responders is also skeptical about the use of ICTs for smart city services. Based on the findings of our research, this group of people is ranging from 11% to 13% of the total population. This is a key finding of our research and for sure, future research should analyze further the qualitative characteristics for their disposition to use smart services. In most of the cases, these are related to privacy and security concerns.
* One more key finding is that content management and networking services have currently the greater number of users with a strong outlook also for use in the near future.
## 4 SAR Raw Signal Processing
### Omega-k Algorithm for SAR System
#### 4.1.2 Reference Function Multiply  
The SAR raw data in the two-dimensional frequency domain are shown in Equation (29); therefore, we implemented general focus, which consists of multiplying the data by the reference function is shown in Equation (39).  
\[H_{ref}(f_{t},f_{n})=exp\Big{(}-j\psi_{ref}(f_{t},f_{n})\Big{)} \tag{39}\]  
where  
\[\psi_{ref}(f_{t},f_{n})=-\frac{4\pi\alpha R_{ref}}{c}\left(\sqrt{\left(f_{0}+f_ {t}\right)^{2}-\left(\frac{f_{n}c}{2\alpha V_{s}}+\frac{V_{s}}{c}(f_{0}+f_{t}) \right)^{2}}\right)-\frac{\pi f_{t}^{2}}{k_{r}} \tag{40}\]  
Then, the data are multiplied in the two-dimensional frequency domain \(S_{A}(f_{t},f_{n})\) with the reference function \(H_{ref}(f_{t},f_{n})\) in the following way.  
\[S_{A}(f_{t},f_{n})H_{ref}(f_{t},f_{n})=exp\Big{(}1j\Big{(}\psi(f_{t},f_{n})- \psi_{ref}(f_{t},f_{n})\Big{)}\Big{)} \tag{41}\]  
Then, the signal result phase \(S_{A}(f_{t},f_{n})\) is as follows:  
\[\psi_{RFM}(f_{t},f_{n})=-\frac{4\pi\alpha\Big{(}R_{0}-R_{ref}\Big{)}}{c}\left( \sqrt{\left(f_{0}+f_{t}\right)^{2}-\left(\frac{f_{n}c}{2\alpha V_{s}}+\frac{V _{s}}{c}(f_{0}+f_{t})\right)^{2}}\right) \tag{42}\]
# The Potential for the Use of Hydrogen Storage in Energy Cooperatives
## 5 Conclusions, Limitations and Future Research
### Conclusions
The stochastic nature of the operation of renewables through the use of hydrogen storage will effectively buffer generation, improve grid security, power balance and power spreads. This will enable a better use of the grid and should realistically result in a higher number of positively considered connection conditions for renewables, which will certainly have a positive environmental impact. To summarize the key and new research achievements of the authors, it is important to point out the following:  
* It has been proved technically feasible to build quasi-island energy independence at the local level using hydrogen storage and the efficiency of the power-to-power chain. * Algorithms have been developed to optimize generation capacity, source types and storage capacity to build independence for energy communities of different sizes and with different levels and profiles of energy consumption.
# Indoor Wavelet OFDM VLC-MIMO System: Performance Evaluation
## 4 Conclusions  
This paper suggests an indoor MIMO-VLC system based on the DWT-OFDM hybrid space-frequency domain pre-equalization technique instead of the traditional FFT-OFDM technique. Our proposed system contains Pre-FDE in addition to Pre-SDE in the transmitting corner and uses an imaging ImR and ImADR on the receiver side. The simulation results reveal that, the BER is improved by performing Pre-SDE in the space domain after  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Comparison Parameters** & **FFT-OFDM** & **DWT-OFDM** \\  & **(Ref. [22])** & **(Present Work)** \\ \hline \multirow{4}{*}{**Coverage contour**} & Diameter of the coverage contour employing only & 3.4 & 4 \\  & Pre-FDE ImADR (m) & (52.6\%) & (70\%) \\ \cline{2-4}  & Diameter of the coverage contour employing Pre-SDE & & \\  & after Pre-FDE ImADR (m) & 4.2 & 4.7 \\ \cline{2-4}  & Diameter of the coverage contour employing only & 2 & 2.3 \\  & Pre-FDE ImR (m) & (20\%) & (25\%) \\ \hline \multirow{4}{*}{**Bit rate**} & 983.6 Mbps & 1.049 Gbps \\ \cline{2-4}  & **BER (along X direction)** & Less than 10\({}^{-5}\) & Less than 5 \(\times\) 10\({}^{-6}\) \\ \hline \hline \end{tabular}
\end{table}
Table 4: Comparison between traditional FFT-OFDM as well as present work (DWT-OFDM) for N = 4.  
Pre-FDE at a target BER equal to \(10^{-3}\). The proposed system is evaluated and compared with the system based on the traditional-OFDM, in terms of the coverage contour and bit rate for various channels. The obtained results revealed that our proposed DWT-OFDM system is preferable over the FFT-OFDM, where the transmission distance and coverage contour are increased by an average of 20% over the FFT-OFDM technique, and the bit rate is increased to 1.049 Gbps. It is noted that, the suggested technique can be repeated for a large number of channels with different room dimensions. In addition, it is viable for the non-LOS channel. Furthermore, the pre-distortion can be used individually or with a pre-equalizer for more improvement. Moreover, the receiver locations can be changed to the center scenario. To conclude, the proposed system can be a good candidate for the indoor VLC applications. Implementing a hardware simulation and producing patents for the proposed system are a very good attempt for future work.  
Formal analysis, W.K.B. and M.G.E.-H.; Investigation, M.G.E.-H. and M.H.A.; Methodology, W.K.B.; Project administration, M.H.A.; Resources, W.K.B. and M.G.E.-H.; Software, M.G.E.-H.; Supervision, W.K.B. and M.H.A.; Writing--original draft, M.G.E.-H.; Writing--review & editing, M.H.A. 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.
## 3 Results
: _Let \(q_{0}(\mathbf{y})\in(\psi^{(-)}(\mathbf{y}),\psi^{(+)}(\mathbf{y}))\) be the unique solution to the equation \(H_{0}^{u}(q,\mathbf{y})=0\) and the function \(p_{0}(\mathbf{y})\in(\varphi^{(-)}(q_{0}(\mathbf{y}),\mathbf{y}),\varphi^{(+)}(q_{0}(\mathbf{y}),\mathbf{y})\,)\) be the unique solution to the equation \(H_{0}^{u}(p,q_{0}(\mathbf{y}),\mathbf{y})=0\)._  
_Let some vicinity of the function \(q_{0}(\mathbf{y})\) belongs entirely to the set \(K^{(-)}\cap K^{(+)}\), and let some vicinity of the function \(p_{0}(\mathbf{y})\) entirely belongs to the set \(P^{(-)}\cap P^{(+)}\). Then, the inequalities hold:_  
\[\frac{\partial H_{0}^{u}}{\partial q}(q_{0}(\mathbf{y}),\mathbf{y})\
eq 0,\ \text{(NP, PN)};\quad\frac{\partial H_{0}^{u}}{\partial q}(q_{0}(\mathbf{y}),\mathbf{y})>0,\ \text{(NN, PP)};\quad\frac{\partial H_{0}^{u}}{\partial p}(p_{0}(\mathbf{y}),q_{0}( \mathbf{y}),\mathbf{y})>0.\]  
**Remark 1**. : _The functions \(p_{0}(\mathbf{y}),\ q_{0}(\mathbf{y})\) in Proposition 4 are smooth with \(\mathbf{y}\in\gamma\) due to the properties of the functions \(\Phi^{(\mp)}\), \(\mathbf{\Psi}^{(\mp)}\) (see Equations (8) and (9))._  
**Remark 2**. : _The inequalities from Proposition 4 are equivalent to_  
\[ \begin{array}{c}h^{(-)}(q_{0}(\mathbf{y}),\mathbf{y})-h^{(+)}(q_{0}(\mathbf{y}),\mathbf{y}) \
eq 0,\ \text{(NP, PN)};\\ h^{(-)}(q_{0}(\mathbf{y}),\mathbf{y})-h^{(+)}(q_{0}(\mathbf{y}),\mathbf{y})>0,\ \text{(NN, PP)};\\ f^{(-)}(p_{0}(\mathbf{y}),q_{0}(\mathbf{y}),\mathbf{y},0)-f^{(+)}(p_{0}(\mathbf{y}),q_{0}(\mathbf{ y}),\mathbf{y},0)>0.\end{array} \]  
Furthermore, we introduce the functions  
\[\
u^{(\mp)}(v,\mathbf{x}):=g_{0}^{(\mp)}(\varphi^{(\mp)}(v,\mathbf{x}),v,\mathbf{x},0)+ \frac{f_{0}^{(\mp)}(\varphi^{(\mp)}(v,\mathbf{x}),v,\mathbf{x},0)}{f_{u}^{(\mp)}( \varphi^{(\mp)}(v,\mathbf{x}),v,\mathbf{x},0)}\cdot g_{u}^{(\mp)}(\varphi^{(\mp)}(v, \mathbf{x}),v,\mathbf{x},0), \tag{11}\]  
on the sets \((v,\mathbf{x})=I_{v}\times\overline{D}^{(-)}\) for functions with the superscript \({}^{\prime\prime}(-)\)\" and  
\((v,\mathbf{x})=I_{v}\times\overline{D}^{(+)}\) for functions with the superscript \({}^{\prime\prime}(+)\)\", and introduce the notation  
\[\bar{v}^{(\mp)}(\mathbf{x}):=\
u^{(\mp)}(\psi^{(\mp)}(\mathbf{x}),\mathbf{x}).\]  
**Proposition 5**.