esa-sceva/satcom-chunk-collection huggingface dataset:
## 5 Convergence of ML and Blockchain in IoV
### Prospects of ML and BC Convergence for IoV System
#### 5.1.5 Content Caching  
In the Cognitive Internet of Vehicles (CIoV), user experience is improved by means of content caching. It brough about added features such as vehicle-deployment monitoring and resource allocation. Through content caching, cognitive engines can gauge the content requirements of users and provide such content to requesters. In this application, privacy is paramount to both users and requesters as there is a possibility of data leakage. In a bid to address that, [PERSON] et al. [162] proposed a blockchain-based privacy-aware content caching approach in CIoV. ML provides the perception through deep learning by learning the need of the participating vehicles, analyzing such perceptual data and sending feedback to the system. Blockchain is used to ensure secured content sharing transactions. The authors analyzed the performance of their approach by the cache hit ratio under different Zipf parameters as well as under different vehicle requesters. They reported that the proposed approach's content caching was superior to the traditional content caching scheme. [PERSON] et al. [163] proposed a privacy-protecting predictive cache method based on blockchain and machine learning (BML-PPPCM). BML-PPPCM provides a method for obtaining services by broadcasting cached data via CPs to reduce query requests. In this study, the authors implemented a Bi-directional Long-Short Term Memory (Bi-LSTM) model is to enhance query prediction, before a deep Q-learning (DQN) was utilized to determine the optimal cache decision.  
Blockchain was used to improve system protection by securely storing the transaction and trust data. The authors compared simulated results with similar studies and found that the newly proposed BML-PPPCM achieved a higher cache hit ratio and a better malicious response than other similar schemes. By integrating BC and ML, this study showed improvement in the privacy protection and suppression of malicious and incentive denial of service attacks. A permissioned blockchain was employed to address the trust issues in content caching [164]. The authors applied a lightweight Proof-of-Utility (PoU) approach that served as block verifier selection metric while a e DRL provided the output for intelligent content caching. The results tested on an Uber dataset showed that the proposed scheme attained better performance when compared to existing approaches.
# Tracking and Monitoring System Based on LoRa Technology for Lightweight Boats
###### Abstract  
Maritime communications are really challenging due to the adverse transmission conditions and the lack of a pre-provided infrastructure for supporting long range connectivity with land. Communications in high seas are usually covered by satellite links that are expensive and lead to high power consumption by the terminals. However, in areas closer to the shore, other communication options have been adopted for different kinds of services such as boat tracking and telemetry, data collection from moored monitoring systems, etc. In these scenarios, technologies such as cellular communications or wireless sensor networks have been employed so far; nevertheless, all of them present different drawbacks mostly related with the coverage and energy-efficiency of the system. Recently, a novel communication paradigm, so-called Low Power-Wide Area Network (LP-WAN) has gained momentum due to its interesting characteristics regarding transmission distances and end-node's power consumption. The latter may be of great interest for ships with energetic restrictions such as small sailboats, recreational boats, or radio control ships. For that reason, in this work, we present a boat tracking and monitoring system based on LoRa (Long Range), one of the most prominent LP-WAN technologies. We provide a comprehensive overview of this communication solution as well as a discussion addressing its benefits when applied to maritime scenarios. We present the results extracted from a case of study, where real-training sessions of Optimist Class sailboats have been monitored by means of the presented architecture, obtaining good levels of coverage and link-reliability with limited power consumption. A transmission range study is also presented, demonstrating the validity of this proposal for monitoring activities inside the port or maneuvers close to the shore.  
maritime communications; intelligent transportation systems (ITS); LoRa; low power-wide area network (LP-WAN); internet of things (IoT); energy efficiency
# Effect of the Transition Points Mismatch on Quanta Image Sensors
## 2 The Transition Points Mismatch and Its Influence on the BER in a QIS  
In a single-bit QIS, jets have two binary states: \"0\" means the jet collects no photon; \"1\" means the jet collects at least one photon. So, the jet array outputs a bit cube and each bit plane in it represents a captured field. One pixel in the final image is reconstructed from a small \"cubic\" of bits from the jet data cube [16; 17], and an example is shown in Figure 1. The cubicle has two spatial dimensions (x, y) and one temporal dimension (t). The spatial oversampling factor is the product of the x-axis and y-axis values, and the temporal oversampling factor is the t-axis value. In Figure 1, they are 16 and 4, respectively. In a multi-bit QIS, one jet outputs \(n\)-bit data in one frame, which represents the number of photoinduced electrons. The number \(n\) is the bit depth of the multi-bit QIS.  
In the following discussion, we assume that the quantum efficiency of jets is 100%. The probability of receiving \(k\) photons by one jet in one frame follows a Poisson distribution:  
\[P[k]=\frac{e^{-H}H^{k}}{k!}, \tag{1}\]  
where \(H\) represents the average number of received photons.  
Figure 1: A \(4\times 4\times 4\) cubicle of jets bit data forms one pixel in the final image.  
Before ADC processing, the output signal is corrupted by root-mean-square (r.m.s.) read noise. We label the corrupted signal with \(V\) and the read noise with \(V_{n}\). By dividing \(V\) and \(V_{n}\) by the conversion gain (CG), they are normalized to the number of electrons. If we label the normalized signal and the read noise with \(U\) and \(U_{n}\), respectively, then \(U=V/CG\) and \(U_{n}=V_{n}/CG\). If the read noise follows a normal distribution, the probability density function (PDF) \(P\left[U,k\right]\) for the corrupted signal \(U\) and its relevant count of generated photoelectrons \(k\) is given by [11]:  
\[P[U,k]=\frac{P[k]}{U_{n}\sqrt{2\pi}}exp\left[-\frac{[U-k]^{2}}{2U_{n}^{2}} \right]. \tag{2}\]
## 3 Statistical Model-Based Ultrasound Envelope Statistics Parametric Imaging Techniques  
Ultrasound backscattered signals are essentially random signals. There is a correlation between the probability distribution pattern of the envelope of the backscattered signals and the tissue characteristics (Figure 3). If there are a large number of scatterers (\(\geq\)10) randomly distributed in the ultrasound resolution cell, the envelope statistics will obey Rayleigh distribution. In this case, the B-mode image speckle is called fully developed speckle. Considering the diversity of human tissue structure, the scatterer distribution in different tissues does not necessarily meet the conditions of fully developed speckle. Therefore, many researchers began to develop non-Rayleigh statistical models to describe envelope statistics. Among them, Nakagami and homodyned-K (HK) distributions are the two most important generalized models.  
In this section, three kinds of statistical model-based ultrasound envelope statistics parametric imaging techniques for characterizing hepatic steatosis are reviewed: acoustic structure quantification (ASQ) imaging which uses the Rayleigh model, ultrasound Nakagami parametric imaging which uses the Nakagami model, and ultrasound HK parametric imaging which uses the HK model. The theories  
Figure 2: Typical algorithmic steps for ultrasound envelope statistics parametric imaging.  
of these statistical models and the parameter estimation methods are introduced, followed by the applications of statistical model-based ultrasound envelope statistics parametric imaging to hepatic steatosis assessment.
# Indoor Vehicles Geolocalization Using LoRaWAN
## 6 Conclusions  
In this paper, we described our solution based on simple client devices and on the deployment of various LoRaWAN gateways to provide indoor localisation for vehicular applications. Through estimation of the behaviour of a LoRaWAN channel and using trilateration, the localisation of a vehicle can be obtained within a 20-30 m range. The main advantage of this solution is its low cost and clearly the possibility of operating indoors.  
We based our proposal on the use of the RSSI of the signal perceived by various surrounding gateways. The problem of using Time Difference Of Arrival (TDoA) for this goal is that not all devices nor all gateways can provide a proper estimation of these values, yet. In this sense, existing work fails to present results on the stability of the RSSI values over time and on the impact of the spreading factor on the quality of the obtained values. In this work, we particularly focus on these details using real devices.  
Our proposal properly fits the ITS world where various types of vehicles and even pedestrians must locate each other in any condition and in indoor conditions, like city tunnels, which cannot be covered by a GPS based solution. For example, we consider that it could be used to locate vehicles of any type in underground car parks, keep a platoon of trucks in formation or create geo-fences, that is, sending an alert if an object moves outside a defined area, like a bicycle being stolen. The routing of heavy vehicles within an industrial setting is another possibility.  
We think, therefore, that this work could be an advance in this direction, providing a useful starting point for the use of LoRaWAN for localisation in ITS. Our main goal in this paper was to clearly evaluate the actual contributions and possibilities that a LoRaWAN only solution could offer. We are anyway aware that the use of V2V communications or the integration with other systems or solutions could allow for better results. More work has to be done, since we consider that better precision can be obtained. Various parameters and factors are still to be investigated and the impact of mobility on this technique has to be thoroughly analysed. We left the evaluation of these alternatives for future work.  
Figure 11: The variation of the precision of the localisation in the scenario considered.  
**Author Contributions:** Conceptualisation, P.M.; Data curation, C.T.C.; Funding acquisition, C.T.C. and J.-C.C.; Investigation, P.M.; Methodology, P.M. and J.-C.C.; Software, C.T.C.; Visualisation, E.H.-O.; Writing--original draft, J.-C.C. and E.H.-O.; Writing--review & editing, P.M. and E.H.-O.  
**Funding:** This work was partially supported by the \"Ministerio de Ciencia, Innovacion y Universidades, Programa Estatal de Investigacion, Desarrollo e Innovacion Orientenda a los Retos de la Sociedad, Proyectos I+D+1 2018\", Spain, under Grant RTI2018-096384-B-I00.  
**Conflicts of Interest:** The authors declare no conflict of interest.
## 2 Existing Technology and Challenges  
### Satellite Constellations  
A satellite constellation is a group of coordinated satellites designed for specific tasks, like telecommunications or Earth observation. Recent interest in constellations for applications like these has led to plans by companies like SpaceX, OneWeb, and Amazon to develop and launch large constellations, with others in development [4]. Additionally, several other constellations are currently being considered and developed by government-backed research and defense organizations. These systems are typically placed in orbit either one by one on separate launch vehicles, or in batches on a single launch with additional propulsion for spreading them out later. For missions involving multiple satellites per launch, the usage of OTVs is an additional option to consider. Regardless, these options are costly in terms of finances, materials, and time, especially for smaller organizations and academia [2; 4; 5]. Each approach presents challenges for constellation operators with factors that can be complex to consider and settle on a solution for, and further become even more difficult to handle when dealing with logistics and execution. The ongoing research described in this article is primarily focused on constellations constructed from batches of smaller ride-sharing satellites as opposed to larger single satellites with dedicated launchers. Some challenges associated with ride-sharing satellite delivery for satellite operators include the following:  
* Flying with an OTV spacecraft offers much more flexibility, but also relies on interaction with the OTV provider, and can again be costly due to the inherent specialization of the orbit delivery process of multiple onboard spacecraft. If the propulsion system included onboard the OTV is electric based or some other low-thrust system, the time to fully deploy each constellation spacecraft can be lengthy due to the low acceleration and resultant time to achieve \(\Delta\)V to spread properly.
* Including onboard propulsion systems in a single-launch constellation offers more flexibility, but also comes with design and operation challenges. Some teams may not be able to handle the complexity, mass, and cost of these systems. Ensuring their reliability and on-orbit operation is another challenge on top of this.
* While chemical propulsion is impulsive and can be used for rapid deployments, their relatively inefficient usage of mass can make them incompatible with some small satellite designs.
* More efficient propulsion solutions like electric propulsion are available, and are more commonly used on constellations, but require more extensive dispersion times, typically in the order of months.
* For even smaller satellites where chemical and electric propulsion systems are too large, differential drag techniques can be used for dispersion, but this method's performance is irregular, limits application to low altitudes with enough atmospheric interaction, and contributes to orbit decay, reducing satellite lifetime.
# Broadband Spectral Domain Interferometry for Optical Characterization of Nematic Liquid Crystals
## 1 Introduction
In this paper, we propose exploiting a simple setup with single-shot acquisition for optical characterization of _MLC_2132 and comparison with \(E7\). The principle is based on Spectral Domain Interferometry (SDI). SDI combined with Fourier analysis is a powerful metrology tool, already developed for optical coherent tomography [26], bulk group index measurement [27], phase response of metasurfaces [28] or ultrashort pulse characterization [29; 30]. In previous publications, we have shown that common-path SDI performed with femtosecond pulses is suitable to achieve real-time tracking of the electro-optical changes in birefringence of nematics [3; 11]. Here, we demonstrate that such a method, combined with broad spectral bandwidth (above 200 nm) and a low-coherence Michelson interferometer, takes advantage of the high chromatic dispersion of thick nematics. It gives access to: (i) the chromatic dispersion parameters (group velocity dispersion and third-order dispersion) of the mixture, (ii) the extended Cauchy-model parameters knowing the optical index for one wavelength, and (iii) the thermo-optical coefficients of the _4 parameters parabolic_ equations to ascribe the dependence of the optical index with the inner temperature. The widely characterized \(E7\) mixture is first tested and the retrieved parameters are in good agreement with the data found in the literature, proving the relevance of the method [20; 31; 32]. Then, the _MLC_2132 preparation, about which little data is published to date, is characterized. For both nematics, the results are collected for the two polarization states. The results asset the interest of _MLC_2132 for applications for which a large dynamic range of phase change, either electro-optically or thermo-optically induced, is required.
## 1 Introduction
Their results showed that the populations did not show renal tubular or glomerular injury, which is explained by the role of Se in improving Cd induced nephrotoxicity by activating antioxidant enzymes systems. An effect of selenium (Se) on Cd toxicity was observed in a study of Bangladesh preschool children, aged 4.4-5.4 years [30]. The measured Cd effects were kidney volume, determined by ultrasonography, and estimated glomerular filtration rate (eGFR) calculated from serum cystatin C levels. Urinary Cd levels were inversely associated with eGFR, especially in girls. A beneficial effect of Se was suggested in a Chinese case-control study that included 240 invasive breast cancer cases and 246 age-matched non-cancer controls [31]. There was a 2.83-fold increase in breast cancer risk in women with urinary Cd in the highest tertile and urinary Se in the lowest tertile [31]. The risk of breast cancer was also reduced in women with urinary Se in the middle tertile [31]. Based on the information mentioned above, the authors focused on finding ecofriendly solutions to alleviate the toxic effects of Cd on kidneys. To date, there are several studies focused on ability of lactic bacteria or different nanoparticles to reduce the toxic effects of heavy metals [14; 32; 33], whereas only one referred to SeNPs-enriched probiotics in a murine model of Cd-induced renal toxicity [34]. The novelty of our study resulted from the use of endogenous nanoselenium biosynthesis by lactic acid bacteria (_L. casei_), in order to provide a possible functional food which is able to alleviate the toxic effect of cadmium on kidneys. In this study, SeNPs biosynthesis was produced by _L. casei_ and consequently two products were obtained: purified SeNPs (bacteria was removed by acidic hydrolysis) and Lact-SeNPs (bacteria enriched in SeNPs). These products where further tested in vivo for their ability to alleviate toxic effects induced by cadmium in kidneys. For this purpose, both SeNPs products were administered orally to mice for 30 days at three different concentrations (0.1, 0.2, and 0.4 mg/kg b.w.) and the creatinine (CREA), total antioxidant plasma (by TEAC assay), along with the histology, immunohistochemistry for mitochondrial apoptosis markers (_bcl-2, bax_), and gene expression of hepatic inflammatory markers (NF-kB, TNF\(\alpha\), and IL-6) were analyzed in terms of comparative evaluation of dose-dependent protective activity of SeNPs against cadmium intoxication.
# A Review: Factors Affecting Internal Two-Phase Flow-Induced Vibrations
## 1 Introduction
### Two-Phase External Flow
#### 1.1.1 Axial Flow  
External axial flow is defined as the flow of fluid parallel to the axial direction of pipe and it is also known as parallel flow, as shown in Figure 3a. Geometries, such as straight tubes or tube bundles, when subjected to axial flow at high velocities, may undergo some instabilities. These instabilities can be generated at low velocities due to pressure fluctuations. Vibrations due to external axial flow are usually smaller than in the case of external cross flow. Considerable studies have been performed on axial-flow-induced vibrations, especially since the surfacing of nuclear reactors in 1960s, focusing on systems, such as Boiling Water Reactor fuel bundles, are subjected to axial flow [22; 23]. The vibration due to axial flow is mainly due to vibration mechanisms, such as fluid elastic instabilities and random turbulence excitations [24; 25; 26; 27]. Void fraction fluctuations, flow velocity, pressure, and geometry are reported to be major influencing parameters. [PERSON] and [PERSON] [28] reported that based on their experimental work on BWR fuel rod under steam water flow, there is no effect on vibration due to nucleate boiling on the surface of the heated rod. [PERSON] et al. [18] proposed a model for axial-flow-induced vibrations to examine the effect of spring support on FIV for Pressurized Water Reactor fuel rods. The vibration response for both spring supported and simply supported rods was recorded. The displacement in the case of spring supported rod was larger than the simply supported rod, and vibration displacement decreased with the increasing spring constant for the spring supported rod. [PERSON] [29] reported from his experiments on BWR fuel rod vibrations that damping in axial flow is approximately four times higher compared to the single-phase flow. Moreover, the author reported that the highest amplitude of vibrations was observed for mass quality (vapor mass/total mass) range of 0.1 and 0.2. Later, [PERSON] and [PERSON] [30] also reported a peak amplitude at mass quality of 0.1-0.2 and 0.4-0.5, indicating the role played by flow regime on vibration amplitude, considering flow regime changes with the change in mass quality. The effect of flow regime was not properly explained, and it is hard to create a linkage of two-phase flow regime with axial FIV [31; 32].
## 4 Engineering Applications
### Modeling and Boundary Conditions  
The most important step in analyzing the movement and damage of jointed rock mass using 3 DEC discrete element modeling software is to establish a simplified, yet practical computational model. Based on the geological investigation of the slope, the actual geological conditions were reasonably simplified. In order to ensure that the computational boundaries do not affect the wedge area of interest, its width was extended to three times the width of the wedge during the modeling process. Based on the results of the geological survey, a complex 3D geologic model containing the major fissures was created using Rhino software 7.4 and exported as a 3 DEC 5.2 block file. By importing this file into 3 DEC software, the required computational model was finally obtained. Finally, the model created was 660 m \(\times\) 525 m \(\times\) 530 m at the maximum side length, respectively, as shown in Figure 7.  
Numerical simulations were performed using the Mohr-Coulomb principal model. All faces, except for the top face (slope face), are set as fixed faces. In the DEM modeling of the slope, all the blocks of the computational model are considered to be deformable and are modeled using the Mohr-Coulomb damage criterion. Based on the detailed site investigation and indoor straight shear test, the mechanical parameters of the rock and soil bodies were determined, as listed in Table 2. Since structural surfaces exist on the left and right sides of the wedge, the parameters for structural surfaces were used to characterize this part. The parameters of the weak interlayer were used at the bottom of the wedge and at the interface between the rock and soil bodies.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Geotechnical Name**} & \multirow{2}{*}{\(\rho\)/kg\(\cdot\)m\({}^{-3}\)} & \multirow{2}{*}{\(E_{\text{m}}\)/MPa} & \multicolumn{2}{c}{**Poisson’s**} & \multicolumn{2}{c}{**Natural Shear Strength**} & \multicolumn{2}{c}{**Saturated Shear Strength**} \\ \cline{5-8}  & & & **Ratio** & _c/kPa_ & _\(\varphi\)/(\({}^{\circ}\))_ & _c/kPa_ & _\(\varphi\)/(\({}^{\circ}\))_ \\ \hline silty clay & 1910 & 9 & 0.43 & 24.97 & 18.06 & 21.47 & 16.25 \\ clastic soil & 2200 & 22 & 0.4 & 44.73 & 44.26 & 26.8 & 32.61 \\ dolerite & 2360 & 300 & 0.3 & 13.5 & 33.4 & 11.7 & 29.8 \\ gabbro (geology) & 3130 & 5000 & 0.2 & \(3.66\times 10^{3}\) & 45.36 & \(2.42\times 10^{3}\) & 40.99 \\ structural plane & - & - & - & 1.13 & 28.81 & 2.11 & 27.52 \\ weak sandwich & & & & 92.2 & 10.65 & 72.5 & 4.11 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Calculation parameters.  
Figure 7: General slope discrete element calculation model (unit: m).