esa-sceva/satcom-chunk-collection huggingface dataset:
## 3 Path Loss Models
### COST-231 Hata Model
#### 3.1.2 Current Empirical Models  
In light of new standards (such as new frequency bands and beamforming antennas), the propagation modeling for 5G has been updated, establishing new empirical path loss models. Some of these empirical models include the Close-In (CI) reference model [23], Alpha-Beta-Gamma (ABG) model [23], 3 GPP model [39], and Float Intercept (FI) model [43]. These models are briefly discussed below, concerning the illustration of important parameters in Figure 3.  
3 GPP TR 38.901 Model [39] This model is considered in two scenarios: LOS and NLOS [44].
4. For the urban macro and line-of-sight (LOS) scenario, the model expression is written as follows [44; 45]: \[PL_{UMA-LOS}=\begin{cases}PL_{1}&\quad 10\;m\leq d_{2D}\leq d_{BP}^{\prime},\\ PL_{2}&\quad d_{BP}^{\prime}\leq d_{2D}\leq 5\;km^{\prime},\end{cases}\] (9) \[PL_{1}=28.0+22\text{log}_{10}(d_{3D})+20\text{log}_{10}(f_{c}),\] (10) \[PL_{2}=28.0+40\text{log}_{10}(d_{3D})+20\text{log}_{10}\left(f_{c}\right)-9 \text{log}_{10}\Big{(}\big{(}d_{BP}^{\prime}\big{)}^{2}+\left(h_{BS}-h_{UT} \right)^{2}\Big{)},\] (11) \[Elevation\;angle,\;\theta=tan^{-1}\bigg{(}\frac{\left(h_{BS}-h_{UT} \right)}{d_{2D}}\bigg{)}.\] (12)
5. For the NLOS scenario [45], the path loss expression is thus written as follows [45]: \[PL_{UMA-NLOS}=max\big{(}PL_{UMA-LOS},\;\;PL_{UMA-NLOS}^{\prime}\big{)}\;for\; \;10m\leq d_{2D}\leq 5\;km,\] (13) \[PL_{UMA-NLOS}^{\prime}=13.54+39.08\text{log}_{10}\left(d_{3D}\right)+20\text{ log}_{10}\left(f_{c}\right)-0.6(h_{UT}-1.5).\] (14)
6. Close-In (CI) Free Space Reference Distance Path Loss Model [23] For a single frequency, the CI free space reference distance model can thus be written as follows [23]: \[P_{L}^{CI}(f,d)[dB]=P_{L}(f,d_{0})|_{1\;m}+10n\text{log}\left(\frac{d}{d_{0}} \right)+W_{\sigma}^{CI},\] (15) where \(P_{L}(f,d_{0})\), \(f\), \(n\), \(d_{0}\), and \(W_{\sigma}^{CI}\) are the free space path loss at a T-R separation distance of 1 m, carrier frequency, path loss exponent, initial separating path, and zero-mean Gaussian-distributed random variable, respectively. Shadow fading standard deviation, \(\sigma_{SF}\) is set to 6 dB, and the range of applicability includes default antenna heights of \(1.5\;m\leq h_{UT}\leq 22.5\;m\) and \(h_{BS}=25\;m\), which are valid for (14) and (15), respectively.  
Figure 3: Definition of \(d_{2D}\) and \(d_{3D}\) for outdoor \(UT_{S}\).
# Multi-Pass Stamping Forming a Concave Ring
## 1 Introduction
[PERSON] and [PERSON] [14] proposed an analytical model and finite element model to study the incremental air bending process. They used FEM to simulate and analyze the influence of tool parameters on the forming shape, air bending forming force and workpiece warpage. [PERSON] et al. [15] studied the air bending of structured sheet metal. A numerical model was developed to predict the process safety and bend line form. [PERSON] and [PERSON] [16] analyzed the importance of metal sheet bending under tension. An analytical model has been developed for metal sheet to plane strain bending under tension. This model has been used to describe the effect of tension on the bending moment in a linear elastic work-hardened sheet. [PERSON] and [PERSON] [17] studied the energy parameters, material parameters and geometric parameters for the laser bending of metal sheet. [PERSON] and [PERSON] [18] presented a finite element simulation of a temperature field during the laser forming. These current studies focus on the establishment of a numerical model of sheet metal bending process, springback prediction and new processing methods. There are few studies on the forming process of the complex bending parts. Based on the characteristics of sheet metal bending and the limit value of bending, a set of multi-pass stamping dies for the forming of the concave ring is designed. Through simulation, the stress-strain fields during the forming process are analyzed. Finally, the rationality of the die design is verified through experiments.
## 4 Mechanism
### Suppression of Electron-hole Recombination  
The lifetime of photogenerated carriers affects photocatalysis significantly. The trapped e\({}^{-}\) and h\({}^{+}\) transferred immediately to the surface and reacted with adsorbed oxygen and water molecules to generate free radicals. However, the lifetime is generally nanosecond, and the electron-hole pairs recombine instantly and induce deactivation.  
Carbonaceous materials enhance the electrons-holes separation owing to the excellent double conductivity. [PERSON] et al. [55] prepared TiO\({}_{2}\)-CuO/BC (hemp stem) under different calcination temperature (500, 600 and 700\({}^{\circ}\)C). They found the enhanced removal of ammonia was owing to the retardation of e\({}^{-}\)/h\({}^{+}\) pairs. Moreover, the BC formed a mid-gap energy state above the VB of TiO\({}_{2}\) (Figure 6A). [PERSON] et al. [38] synthesized BC/Fe\({}_{3}\)O\({}_{4}\)/Bi\({}_{2}\)O\({}_{3}\) composite via a solvothermal method. The electrons in Bi\({}_{2}\)O\({}_{3}\) were transported to the BC/Fe\({}_{3}\)O\({}_{4}\), thus inhibiting the recombination of h\({}^{+}\) and e\({}^{-}\) pairs. The magnetic nanoparticles (BC/Fe\({}_{3}\)O\({}_{4}\)) acted as an electron storage center, which was beneficial to transfer the electron from Bi\({}_{2}\)O\({}_{3}\) and reduce the probability of electron return to Bi\({}_{2}\)O\({}_{3}\) (Figure 6B). [PERSON] et al. [92] suggested the synergistic effect between biochar and g-C\({}_{3}\)N\({}_{4}\) resulted in a longer lifetime of excited electrons of semiconductor and hindered photo-induced electron-hole recombination. [PERSON] et al. [63] also found that photodegradation was sensitive to the loading concentration of TiO\({}_{2}\) onto  
Figure 5: Schematic illustration of the proposed mechanism for facilitating electron transport. Reproduced with permission from reference [93].  
biochar. The photodegradation efficiency was enhanced owing to the reduced charge recombination. [PERSON] et al. [91] fabricated biochar-based g-C\({}_{3}\)N\({}_{4}\) for 2-Mercaptobenzothiazzole degradation. They proposed that the introduction of biochar can produce more active sites and result in highly efficient of electron-hole pairs separation. Furthermore, BC can significantly inhibit the g-C\({}_{3}\)N\({}_{4}\) reunion and stacking.
###### Abstract  
This paper discusses the influence of vehicle parameters on the identification accuracy of bridge fundamental frequency from a passing vehicle and validates such influence through laboratory tests. In the process of theoretical derivation, the interaction between a vehicle and bridge is no longer ignored to uncouple the equation group and the stepwise integration method is used to solve the equation group. Key parameters such as the vehicle speed \(\alpha_{v}\), vehicle-to-bridge mass ratio \(\alpha_{mv}\), and frequency ratio \(\mu_{1}\), are dimensionless. Based on the simplified vehicle-to-bridge system model, the numerical analysis method is used to analyze their influence on the identified bridge frequency. Through parameter analysis, it is found that the vehicle-to-bridge mass ratio and vehicle speed have a great impact on the patterns of identified bridge frequency; and when the vehicle frequency is greater than or less than the bridge frequency, the identified bridge frequency exhibits different patterns. The bridge frequency deviation rate can be greater than 20% when the vehicle speed and vehicle-to-bridge mass ratio increases. In order to ensure the accuracy of bridge frequency identification, it is recommended that the vehicle-bridge mass ratio should not exceed 10%. Besides, appropriately increasing the vehicle-to-bridge mass ratio will increase the probability of accurately identifying the bridge frequency under certain conditions. In addition, a novel frequency extraction method was proposed to more accurately filter out the frequency from the vehicle acceleration spectrum.  
bridge; fundamental frequency; vehicle mass; frequency deviation; vehicle-bridge interaction; laboratory test +
Footnote †: journal: Applied
# Multi-Lens Array Full-Field X-ray Microscopy
## 2 Materials and Methods  
### Multi Full-Field Microscopy  
To decrease exposure times, it could be an option to increase the aperture of the objective CRL. Unfortunately, increasing the effective aperture is limited due to absorption at the outer parts of a CRL. Analogous arguments exist for other kinds of X-ray optics. As an alternative, we suggest using an array of CRLs to reduce the exposure time of cone-beam sources. In this case, the optical axes of the individual CRLs are not parallel to each other but slightly tilted in such a way that they meet in the center point of the FoV. Thus, the same part of the sample is imaged several times from slightly different directions. The multi full-field microscopy principle is shown in Figure 1, assuming proper sample illumination. A 3 \(\times\) 3 array of slightly tilted objective lenses, a so-called multi-focus CRL (MFCRL), is imaging the FoV to the scintillator plane. The scintillator converts the X-rays to visible light, and this visible image is detected via a microscope objective on a CCD-detector (not shown in Figure 1). The multi full-field microscopy principle has obvious similarities with approaches towards tomography, where the sample has to be projected simultaneously from various different directions [13; 14], which results in a decrease of the total exposure time for one tomograph [15]. In contrast to these methods, in multi full-field microscopy, the imaging objective lens is positioned between the sample and the detector, and the angles should be as small as possible to position as many images as possible side by side on the detector.  
Due to small angles in X-ray optics, the Scheimpflug effect [16] can be neglected in the first approximation. The Scheimpflug effect describes the tilt of the focus plane when the objective plane and detector plane are not parallel to each other. For hard X-ray full-field microscopy at laboratory sources, this principle could reduce the necessary exposure times drastically. In the case of moderate magnifications, typically the complete detector area is not used in these setups. Thus, applying the multi full-field principle is feasible even with the detector existing in the system. Often 3 \(\times\) 3 or even more images could be placed beside each other on the detector. Using multi full-field microscopy instead of conventional full-field microscopy, the number of photons gathered can be increased by a factor of \(n^{2}-1\) when using an \(n\times n\) lens array. Thus, the signal to noise ratio (SNR) can be increased drastically.  
Figure 1: Sketch of the multi full-field microscopy principle. The multi-focus CRL (MFCRL) images the sample with a certain magnification to the scintillator plane.
## 3 Results and Discussions
### Flow Pattern Evolutions in Evaporator and Condenser
#### 3.3.1 Flow Pattern Evolutions in Evaporator  
In order to observe the flow patterns evolutions in the evaporator, the insulation box is opened in some experimental cases for visualization. As shown in Figure 6, when the working fluid in the evaporator is heated to reach the saturation state, nucleate boiling appears, and some dispersed small bubbles are produced, flowing up quickly due to the buoyancy and driving pressure difference between the hot and cold ends of the OHP. Meanwhile, the dispersed bubbles grow up or coalesce into the bigger ones and even the vapor slugs, which triggers the transition from bubbly flow to the slug flow. It can be clearly seen from the comparison among the flow pattern evolutions in the evaporators with different inner diameters that the transition from the bubbly flow to the slug flow is mainly dependent on the self-growth of the dispersed bubbles in the evaporator with \(D_{\text{i}}=1\) mm, rather than the coalescence among them in the evaporators with diameter of 2 mm and 3 mm. Furthermore, less dispersed bubbles are produced by the nucleate boiling with the decreasing inner diameter, which further explains the characteristics of bubbly flow in the OHP with \(D_{\text{i}}=1\) mm as discussed in the above section.
# A Communication-Efficient Secure Routing Protocol for IoT Networks +
## 7 Conclusions  
To improve the communication efficiency of cryptography-based secure routing, we have proposed a secure routing protocol that enables the relay node to initiate an RREP. Our proposed method enables an intermediate node to prove to a third party that it has a possible route to the destination by disclosing the previous route information received from the destination, significantly reducing the number of hops required for route establishment compared with existing methods. Furthermore, we have performed an emulation-based routing overhead analysis assuming multi-hop IoT networks. The emulation results demonstrate that the proposed method improves communication efficiency in IoT systems that operate in environments where communication failure due to signal interference is a concern, such as congested ISM bands.  
Finally, we summarize the limitations of the proposed method and discuss future works. The proposed method increases the packet length hop-by-hop, which degrades the routing overhead in end-to-end communication. Introducing efficient authentication schemes, such as physical layer authentication [34], is a possible future direction. Furthermore, the routing performance degrades under heterogeneous computing and communication capabilities. Because this heterogeneity sometimes behaves as an attack on routing, improving these effects should be discussed as a next step. Finally, the integrated design of low-latency routing and novel applications in distributed networks is a possible direction. For example, recent demands for big data analysis have attracted considerable attention for FL [6]. FL is expected to be a privacy-preserving machine learning scheme, and can extend its training scale based on multi-hop communications; however, it should be performed with high security and communication efficiency. Thus, the design of routing for FL over large-scale wireless networks represents an interesting research topic.  
Conceptualization, K.S.; methodology, Y.S. and K.S.; software, Y.S.; validation, K.I.; formal analysis, Y.S.; investigation, Y.S. and K.I.; resources, Y.S.; data curation, Y.S.; writing--original draft preparation, K.S.; writing--review and editing, K.S.; visualization, Y.S.; supervision, K.S.; project administration, K.S.; funding acquisition, K.S. All authors have read and agreed to the published version of the manuscript.  
Part of this work was supported by JST SICORP Grant Number JPMJSC20C1, Japan.  
Not applicable.  
The authors declare no conflict of interest.
## 3 Results and Discussion  
### Lattice Structure and Electronic Properties  
Figure 1 illustrates the energy-minimized P-TpG monolayer with a hexagonal lattice. The DFT algorithm employs electronic relaxation and optimized geometry structures. The hexagonal lattice parameter and the C-P bond's average lengths are 14.41 A and 1.74-1.78 A, respectively. Unit-cell optimization results indicate the varying bond length of 1.23-1.44 A for C-C bonds. The spatial-dependent electron localization function (ELF) [63] qualitatively describes the chemical bonding nature. We illustrated the ELF for the pristine nanosheet in Figure 1. It takes values between 0 and 1, indicating delocalized electrons (0), electron gas-like behavior (0.5), and localized electron regions (1). The electron localization intensity in the middle of the C-C bonds shows the covalent bonding features. However, the electron localization of the C-P bonds occurs mostly around the P atoms due to the higher electronegativity of the P atoms than C atoms.  
Theoretical studies confirmed the lattice stability of novel nitrogenated-, phosphorylated-, and arsenicated-TpG (N-TpG, P-TpG, As-TpG) nanosheets. According to reported PBE results, the band-gaps of TpG, As-TpG, N-TpG, and P-TpG monolayers have been predicted as \(\sim\)1.26 eV, \(\sim\)0.47 eV, \(\sim\)1.24 eV, and \(\sim\)1.00 eV, respectively, which makes them attractive  
Figure 1: The atomic lattice of P-TpG monolayer. Color contours refer to electron localization function in unit-cell.  
semiconductor for the application as an electrode in rechargeable batteries [37; 52]. The electronic properties of the single-layer pristine P-TpG can be found in Figure 2. It shows the band structure along with the high symmetry \(\Gamma\)-M-K-\(\Gamma\) directions in the irreducible Brillion zone. The atoms' contribution to the band structure and electronic density of states (DOS) have been predicted by the PBE method. The results show that the top/bottom of the valence/conduction bands occurs at the \(\Gamma\)-point, leading to direct band-gaps of \(\sim\)0.982 eV. P-TpG monolayer has shown a smaller band-gap value than N-TpG with \(\sim\)0.982 eV and 1.24 [37; 52] using the PBE method, respectively, which implies better semiconducting electronic characteristics of the P-TpG monolayer.
# Recovery of Polyphenols from Agri-Food By-Products: The Olive Oil and Winery Industries Cases
## 2 Polyphenols from Olive Oil Production Wastes: Source and Applications
### Applications of Polyphenols from Olive Oil Industrial Wastes  
Research into the application of olive by-products and/or their bioactive compounds is growing [22], aimed to improve the nutritional profile of food products, to improve food properties, to obtain innovative natural additives for cosmetics, etc.  
As stated previously, hydroxytrosol is widely present in olive oil by-products, and its antioxidant and antimicrobial properties have been widely demonstrated [1; 5; 12; 13; 18]. In this sense, [PERSON] et al. [23] tested the extract from olive waste, rich in hydroxytrosol, as a potential substitute for sulfur dioxide in winemaking. After verifying that the most important odorants present in the extract were also present in wines, they observed that the extract showed antimicrobial activity against _Hanseniuspora uwarum_, _Candidia stellata_, _Lactobacillus plantarum_, _Pediococcus damosus_, _Acetobacter aceti_, _Oenococcus oeni_, _Dekrera bruxellensis_, and _Botryotinia fuckeliana_ microorganisms.  
On the other hand, the food industry is interested in adding natural antioxidants to packaging materials to preserve food products and extend their shelf-life, while maintaining the organoleptic properties. In this sense, the food packaging sector is developing active materials based, for instance, on by-products of agribusiness, such as lignocellulosic fibers from olive pomace [18]. Instead, [PERSON] et al. [24] developed ternary films for food active packaging, using polyvinyl alcohol as a polymeric matrix, nanostructured starch as reinforcement phase, and hydroxytrosol as an antioxidant agent. Experimental data showed a prolonged release of hydroxytrosol from ternary films with strong antioxidant activity, showing favorable results for active food packaging. [PERSON] et al. [25] used an olive leaf extract as the active component in polyethylene terephthalate/polypropylene films, oleuppein and luteolin-7-glucose being the main phenolic antioxidants. The effectiveness of the film against lipid oxidation was evaluated during the storage of sunflower seeds, obtaining, as a result, the delaying of lipid oxidation.  
As a matter of example, focusing on the cosmetic industry, [PERSON] et al. [26] studied the application of different concentrations of phenolic compounds, such as hydroxytrosol, tyrosol, or oleuppein, recovered from olive mill wastewater as boosters of UV filters. Absorption of synthetic UV filters increased as a function of olive phenols concentration, while the entrapment of olive phenols in silica particles, improved their water resistance.
# Design, Challenges and Developments for 5G Massive MIMO Antenna Systems at Sub 6-GHz Band: A Review
## 4 Challenges and Future Directions
Spatial diversity and polarization techniques are used with a mMIMO switchable frame antenna array as a decoupling technique to reduce the coupling effects and enhance isolation [63]. Inverted-F, T-shapeddecoupling stub, self-decoupling, defective ground structure, and other techniques are also used as decoupling methods. As a future direction, to face the challenges of the hardware, the characteristics of the components, and their modification and enhancement, a metamaterial technique with unique properties will used as isolation, which is attributed effectively to the enhancement in the size, gain, efficiency, bandwidth, and other aspects. In smartphones, maintaining the SAR within the predetermined limits is difficult since MIMO systems have an increasing number of antennas [119]. Several techniques in design antennas are used to reduce the SAR results to <2, which is very safe for user applications. Furthermore, increasing the bandwidth is a much more important goal to decrease the SAR and high efficiency to ensure safe user handling of the mobile device. Low-cost hardware is considered as the upcoming demand for 5G systems since it requires an economy of scale in manufacturing. Despite the fact that the BS has numerous antennas deployed, a high array gain can still be attained due to hardware shortcomings, which might result in channel estimate error and a capacity ceiling. The user side will experience severe hardware impairments compared to the BS side [120]. The high cost of mMIMO in smartphones also faces a challenge that affects the price of the devices on the market. Therefore, a reasonable cost and effective technical equipment can achieve perfect results. Finally, the selection type of the application is relative to the environment surrounding the application and the ways to use it. The environment must provide the optimal propagation conditions for mMIMO systems to function well. As a future direction, a three-dimensional massive MIMO array of the base station for maximum coverage and low SAR for a smartphone with a flexible spectrum band ensures good implementation for mixture (5G/6G) and 6G networks, whereas a metamaterial is a good choice to improve the overall performance [121].