esa-sceva/satcom-chunk-collection huggingface dataset:
## 5 Discussion
### Limitations and Future Directions
#### 5.6.1 Limitations  
Variability in time measurements, stemming from factors such as ambient noise and fluctuations in acoustic signals, presents a significant challenge to achieving absolute precision within methodologies. Mitigating these variations holds promise for enhancing the reliability of the methodology. Moreover, the accuracy of audio-based measurements is subject to potential inaccuracies due to environmental noise interference or limitations in the sensitivity of smartphone microphones. Exploring improvements in audio signal processing or alternative validation methods could effectively address these concerns. Additionally, while this study was conducted under controlled laboratory conditions, extending the methodology to real-world environments introduces additional variables that may impact measurement accuracy. Thus, it is imperative to carefully consider these external factors to ensure broader applicability and robustness of the methodology. Furthermore, it is imperative to consider that sound waves possess a finite velocity and are subject to variation with temperature, pressure, and humidity. Under standard conditions, typically defined as at sea level with a temperature of 20 \({}^{\circ}\)C or 68 \({}^{\circ}\)F, the speed of sound in dry air is approximately 343 m per second. This velocity exhibits an upward trend with elevated temperatures and conversely declines at greater altitudes. Consequently, there may exist temporal disparities between the occurrences of actual events and the instances of the corresponding sound waves recorded by the smartphone. These temporal disparities are anticipated to escalate with increasing distances between the ball, mechanical switches, and the smartphone. To mitigate this issue, meticulous attention should be directed toward aligning the positions of the smartphone, mechanical switches, and the point of ball descent in close proximity.
## 4 Hardware Architecture
### The Microcontroller  
The microcontroller is the _STMMicroelectronics(tm) STM32F429 IIH_ (Geneve, Switzerland), which belongs to the ARM-Cortex(tm)-M family and represents a tradeoff between processing power and power consumption. Therefore, the selection of the core was influenced by the requirements of compactness and low energy consumption and by the adopted peripherals for the sensors' data transmission and reception. It is a 32 bit ARM Cortex(tm) for microcontroller applications equipped with 176 pins and high-speed memories [15].  
Low power of the embedded microprocessor is essential for a wireless device to increase battery lifetime, reduce the device size, and simplify the power supply.  
The voltage domain range for the battery is [1.65 V \(\div\) 3.6 V], whereas the power supply range is [1.7 V \(\div\) 3.6 V] [16; 17].  
Figure 3: MSP hardware prototype.
# CKGAT: Collaborative Knowledge-Aware Graph Attention Network for Top-N Recommendation
## 5 Experiments
### Experimental Results
#### 5.4.2 Recommendation Diversity (RQ2)  
The notion of diversity means that the set of items within a single recommended list should be as diverse as possible [53]. Even if the accuracy of a recommendation method is high, it may not be able to generate diversified recommendations for users. The diversity of recommended results can prevent users from getting bored because of many non-diversified items being recommended. Therefore, the diversity of recommendation results is also an important evaluation aspect to measure recommendation performance. Our experiment used the DIV@N metric [55] to evaluate the diversity of recommendation results. The total number of all possible recommendation pairs \((\mathcal{R}_{i},\mathcal{R}_{j})\), \(i\
eq j\) in \(M\) top-N recommendations is \(M(M-1)/2\), the overlap rate of a recommendation pair is \(\left|R_{i}\cap R_{j}\right|/\left|R_{i}\cup R_{j}\right|\). The DIV@N metric measures the mean non-overlap ratio of all recommendation pairs, which is defined in Equation (16) [55].  
\[\text{DIV@N}=\frac{2}{M(M-1)}\sum_{i,j\in\{1,2,\ldots,M\};i\
eq j}\left(1- \frac{\left|R_{i}\cap R_{j}\right|}{\left|R_{i}\cup R_{j}\right|}\right) \tag{16}\]where \(M=100\) because we randomly generate top-N recommendations for 100 users during the test.  
Figure 7 shows the DIV@10 and DIV@20 results of CKGAT and the four propagation-based methods (KGNN-LS, KGAT, CKAN and KGIN) on the Movielens 20M dataset. We have the following observations from the results:  
1. The diversity of CKGAT's recommendation results is significantly better than that of KGNN-LS, KGAT, CKAN, and KGIN, although the recommendation accuracy of CKGAT on the MovieLens 20M dataset is slightly better than these four methods.
2. The diversity of KGIN's recommendation results is slightly better than that of CKAN, KGAT and KGNN-LS. This may be due to the fact that KGIN handles user intent at a more fine-grained level, and considers multiple aspects of user intent.
3. The diversity of CKAN's recommendation results is slightly better than that of KGNN-LS and KGAT. This may be due to the fact that CKAN can extract a variety of user preferences and various item features in the process of heterogeneous propagation.
4. The diversity of KGAT's recommendation results is better than that of KGNN-LS. This may be because KGAT uses a collaborative knowledge graph containing user-item interaction information, which contains a wealth of user preference information.
## 3 Materials and Methods
### Digitalizing Calibration Data Exchange and Management
#### 3.3.2 Calibration Customer  
On the industrial level, the calibration orders are typically based on a service contract that includes all the calibrations and services that the parties have agreed to be carried out over a defined period, e.g., a calendar year. In the manufacturing industry's end of the calibration chain, especially in non-accredited field calibrations, the calibration request has a significant role in the calibration processes as the requests or contracts include the instructions for the calibration procedures as mandated by the quality management regulations. For accredited laboratories, this is not a significant issue as their procedures are audited as a part of the accreditation process, based on which they are also compliant with the quality system regulations. In the field calibration cases, it is mostly up to the manufacturing companies to audit the service providers that they use and ensure that the calibrations are performed correctly.  
The correct interpretation of the exchanged data in this kind of setting is heavily dependent on the format in which the data are exchanged and their harmonized use by the parties involved. This is why it is necessary for the receiver to have the means to validate that the received certificate uses the correct format in a correct manner, to make sure that the data can be interpreted and used correctly when they are uploaded to the CMS. Due to the use of digital signatures, validation also includes authenticating the source of the certificate and checking that it is unaltered to ensure its data integrity.  
Long-term storing and archiving of calibration certificates is required for investigating any measurement-related quality issues and for auditing purposes. For electronic records and documents, the storage can be implemented with relative ease with conventional cloud storage applications. In addition to maintaining the records over the required period, they also need to be easily accessible and viewable, especially for auditing purposes, which can be implemented in the calibration management systems with relative ease.  
The availability of calibration data in a machine-interpretable and processable format is one of the cornerstones for the use of the data in Industry 4.0 applications. For example, the data could be used to analyze the performance of individual devices, device models, or types over time to predict the optimal calibration intervals and select the devices used for controlling and processing the manufacturing processes. These kinds of features have already been available in commercial calibration management systems that have been developed for use in the industry, where field calibrations are common. However, the use of the features is limited to certificate formats used by collaborating instrument and system providers, meaning that a significant amount of the data is not usable without manually importing the data, which is an issue in terms of data integrity.
## 3 Proposed Model
### Verification of Academic Information
#### 3.2.2 Case 2: The Holder Only Wants to Share Parts of the Academic Information  
This is a different case in which the holder \(H\) wants to share with a third-party \(T\) only some academic information from the whole certificate (\(c\)), unveiling some data to preserve their privacy. To achieve, \(H\) sends to \(T\) using a secure channel only some data contained in the certificate (\(c\)), the calculated Merkle paths of the shared information, the manifest (\(m\)), the blockchain transaction \(id\), and adds \(T\)'s account in the _SCAccess_ (\(aa\)) to grant access indicating use case number two. When \(T\) requests the encrypted root of the Merkle tree \(h\) from _SCData_, it queries _SCAccess_ to check that is allowed and logs in _SCLog_ that the data of the holder will be accessed by \(T\) (or not, if access is not granted). \(T\) recuperates if data are valid and \(h\), decrypts \(h\) with the organization's public key and compares the result with the calculated root of the Merkle tree and paths from the received information to confirm that it is valid and not revoked.  
The sequence diagram that represents the flow of information and interactions among actors and related smart contracts is graphically represented in Figure 4.  
Figure 3: Overview of the process in case 1.  
2.3 Case 3: The Holder Allows a Third Party to Receive the Certificate Directly from the Academic Institution  
In this use case, the holder \(H\) needs a third-party \(T\) to obtain the whole certificate (\(c\)) directly from the issuing entity \(E\) instead of sending it directly (to give more confidence because the holder no longer has the academic information, etc.). To achieve this, the holder \(H\) transmits to \(T\) the blockchain transaction \(id\) and adds \(T\)'s address in _SCAccess_ (\(aa\)) indicating use case number three. \(T\) requests the record id of the academic information in the database (\(idp\)) and the database server access point (\(se\)) from SCData, which after checking \(T\)'s permissions in _SCAccess_, sends it to \(T\). When \(T\) obtains these data and asks _SCService_ for the certificate (\(c\)), which, after verifying \(T\)'s authorization (in _SCAccess_), queries the information in the local database and sends to \(T\) the data using a secure channel. Both _SCData_ and _SCService_ log in _SCLog_ that \(T\) has tried to access or actually accessed the record. If necessary, \(T\) could confirm the authenticity and validity of (\(c\)) following the first procedure (case 1). The whole sequence diagram for this case is depicted in Figure 5, which depicts the interactions among holder, third party, and institution through the different smart contracts.  
If academic records published in the consortium blockchain contain other public nonsensitive personal data, such as the type of academic information, degree, or category of the certificate, this could be used to anonymously generate statistics, learning analytics data, or trends relevant to the education domain.
# Nanofiber-Based Materials for Persistent Organic Pollutants in Water Remediation by Adsorption
## 4 Persistent Organic Pollutants
### Polychlorinated Biphenyls (PCBs) and Polyaromatic Hydrocarbons (PAHs)  
#### 4.2.1. Adsorbate Properties  
Table 17 presents the different molecular structures for the selected polychlorinated biphenyls PCBs in this study, which are namely 2 to 6 -PCB, PCB 28 and PCB 77. PCBs are polycyclic aromatic organochlorines of chemical formula C\({}_{12}\)H\({}_{10-x}\)Cl\({}_{x}\). The PCB structure is composed of two benzene rings, thus sharing the aromatic structure of phenols molecules, and decorated by a number of chlorine groups. PCBs 2 and 3, also called 2- and 3-chlorobiphenyls, possess one chlorine group attached on position 2 and 3, respectively, on one of the benzene rings. Sharing a molecular weight of 188.7 g/mol, water solubility was determined at 1.45 mg/L (25 \({}^{\circ}\)C), corresponding to a Log K\({}_{\rm{ow}}\) of 4.54. PCBs 4-6 possess two chlorine groups, for a weight of 223.1 g/mol. Their chemical names are 2,2\({}^{\prime}\)- 2,3- and 2,3\({}^{\prime}\)-dichlorobiphenyls, respectively, corresponding to the chlorine groups' respective positions on one or both benzene rings. PCB 28, called 2,4,4\({}^{\prime}\)-trichlorobiphenyl, possesses three chlorine groups for a weight of 257.5 g/mol. PCB 77, called 3,3\({}^{\prime}\),4\({}^{\prime}\)-tetrachlorobiphenyl, possesses four chlorine group for a weight of 292.0 g/mol. Compared to monochloro-biphenyls, PCB 77 water solubility decreased to 0.18 mg/L (25 \({}^{\circ}\)C, log K\({}_{\rm{ow}}\) 6.72). All molecules are apolar.  
Table 18 presents selected characteristics of the Phenantrene molecule, non-POP-classified, from the family of polycyclic aromatic hydrocarbon compounds. Of a molecular weight in the same order as monochlorinated biphenyls, its water solubility was determined to be 1.15 mg/L (25 \({}^{\circ}\)C). An apolar molecule, Phenantrene is composed of three fused benzene rings.
## 4 Stereoselective Analytical Methods in the Study of Pharmacokinetics of \(\beta\)-Blockers  
Stereoselective analytical methods for determination of the respective enantiomers in biological materials, especially in urine and plasma, are indispensable for the evaluation of pharmacokinetics and metabolism of \(\beta\)-blockers. At present, modern analytical techniques such as liquid chromatography with mass detection (LC-MS, LC-MS/MS) are used. Enantioseparation is carried out by means of chiral chromatographic stationary phases. In the case of \(\beta\)-blockers, chiral stationary phases based on macrocyclic antibiotics (teicoplanin and vancomycin) are often employed. Teicoplanin-based chiral phase (Chirobiotic T) was applied successfully in the analysis of enantiomers of metoprolol. Ion trap with electrospray (ESI) ionization in positive mode was used for the MS ion detection [133].  
Chiral stationary phase Chirobiotic T and polar mobile phase (methanol/acetic acid/triethylamine) were employed in the pharmacokinetic studies of carvedil [134] and acebutolol [135]. Chiral stationary phase containing vancomycin (Chirobiotic V) demonstrated efficiency in enantioseparation of atenol, labetalol, and nebivolol [127; 136; 137].  
Stereoselective analysis of acebutolol and its active metabolite diacetol in human plasma was accomplished by means of HPLC on a chiral phase containing cellobihydrolase, in combination with quadrupole tandem mass spectrometry as the detector [138].  
Other frequently used chiral phases employed in stereoselective bioanalyses of \(\beta\)-blockers encompass especially the polysaccharide-based stationary phases containing derivatives of cellulose and amylose [139; 140].
# Exploring Residual Clays for Low-Impact Ceramics: Insights from a Portuguese Ceramic Region
###### Abstract  
This study investigates the potential of residual clays from a traditional ceramic-producing region in southern Portugal as raw materials for red ceramic applications. This work aims to support more sustainable ceramic practices through the local valorization of naturally available, underutilized clay resources. A multidisciplinary approach was employed to characterize clays, integrating mineralogical (XRD), chemical (XRF), granulometric, and thermal analyses (TGA/DTA/TD), as well as technological tests on plasticity, extrusion moisture, shrinkage, and flexural strength. These assessments were designed to capture both the intrinsic properties of the clays and their behavior across key ceramic processing stages, such as shaping, drying, and firing. The results revealed a broad diversity in mineral composition, particularly in the proportions of kaolinite, smectite, and illite, which strongly influenced plasticity, water demand, and thermal stability. Clays with higher fine fractions and smectite content exhibited excellent plasticity and workability, though with increased sensitivity to drying and firing conditions. Others, with coarser textures and illitic or feldspathic composition, demonstrated improved dimensional stability and lower shrinkage. Thermal analyses confirmed expected dehydroxylation and sintering behavior, with the formation of mullite and spinel-type phases contributing to densification and strength in fired bodies. This study highlights that residual clays from varied geological settings can offer distinct advantages when matched appropriately to ceramic product requirements. Some materials showed strong potential for direct application in structural ceramics, while others may serve as additives or tempering agents in formulations. These findings reinforce the value of integrated characterization for optimizing raw material use and support a more circular, resource-conscious approach to ceramic production.  
2025
## 1 Introduction
They focused on investigation for structural conformity of the bearing concept with the actuator activation, via an experimental approach to measure the inner shape of a deformed bearing. [PERSON] and [PERSON] [15] presented a controllable GFB concept that can control mechanical preloads as well as the bearing clearance via PZT actuators. The bearing consists of nine actuators located in the bearing housing in the circumferential direction and bearing guides that support the foil structures connected to the PZTs. The authors established an analytical model of the PZTs using the inverse piezoelectric effect. They applied it to the traditional prediction model of the GFB based on the Reynolds equation. They observed that in terms of bearing performance, the clearance control of the bearing significantly affected the variation in the direct stiffness and damping coefficients. Meanwhile, the preload control affected the cross-coupling effect considerably. [PERSON] et al. [11] introduced PZT actuators into GFBs to control mechanical preloads. A proposed bearing concept comprises six PZTs located in the bearing cartridge to produce deformation in their thickness directions, and three lever amplifiers to amplify the deformation of the actuators. A static load test on the bearing indicated that PZT control could produce mechanical preloads in tens of micrometers depending on the driving voltage of the actuators. Finally, the authors revealed that PZT control could alter the journal equilibrium position and dynamic force coefficients of the fluid film. After that, [PERSON] et al. [12] applied the identical bearing concept to an impulse turbine and performed experiments to investigate the effect of PZT control on the amplitudes of oil whirl and oil whip vibrations. The results indicate that an increase in the driving voltage results in remarkably suppressed subsynchronous motions of the system. This work aims to evaluate the feasibility and effectiveness of controllable gas foil bearings' (C-GFB) control performance in real time. The PZT actuators are used as active mechatronic elements to control the mechanical preloads of the C-GFB. The equivalent spring model for PZT actuators and foil structures is introduced to predict top foil shape depending on the driving voltages of the actuators. The spring model is then coupled with a theoretical analysis model of GFBs for evaluating the effects of PZT actuator activations on bearing performance. Finally, nonlinear orbit simulation with the real-time PZT control is performed. In addition, the effectiveness and feasibility of the C-GFB for stabilizing the subsynchronous motions of the journal are discussed.
# Denoising Directional Room Impulse Responses with Spatially Anisotropic Late Reverberation Tails
## 3 Plane Wave Decomposition and Spatial Analysis
This separation describes the resolution limit of the beamformer; any adjacent look directions \(\Omega_{d}\) and \(\Omega_{d^{\prime}}\) closer than this will result in a combined directivity whose peaks are no longer centered on the original targets (see Figure 1c). In the context of a PWD performed over \(D\) look directions, each resulting signal will overlap with every one of the other \(D-1\) directions, leading to a total combined directivity of [20]  
\[W(\Omega)=\sum_{d=1}^{D}w_{d}^{2}(\Omega). \tag{13}\]  
If any look directions are less than \(\Theta_{\text{PN}}\) apart, we therefore risk the loss of their individual directivity peaks, thereby compromising the independence between the corresponding signals. Although the optimal arrangement of points on the surface of a sphere is a vast research topic that is beyond the scope of this article, the considerations detailed above will allow us to choose, with respect to the problem at hand, the most appropriate among various known solutions (e.g., Sloan-Womersley hyperinterpolation grids [21], Fliege t-designs [22]). For a given grid solution of \(D=(L+1)^{2}\) look directions, the central angles between all nearest neighbors can be calculated and compared to \(\Theta_{\text{PN}}\) to assess the risk of \"fusing\" directivity peaks, as in Figure 1c, and the variance (or standard deviation) in the total coverage \(W(\Omega)\) can be calculated to ensure that the spatial analysis is as \"flat\" as possible. Indeed, since we have assumed our anisotropic late reverberation field to be made up of an infinity of incident plane waves under an arbitrary spatial power distribution, this \"flatness\" in \(W(\Omega)\) is necessary in order to avoid any subspaces of the sphere being privileged over others. Note that the \"flat coverage\" condition can be fulfilled exactly using t-designs with \(D>(L+1)^{2}\)[20], but these would break the linear independence conditions described above. Figure 1: 4 th-order combined directivity patterns for two plane-wave decomposition (PWD) directions \(\Delta\Omega\) apart, in terms of the relative angle \(\Theta\) along the great circle joining them on the unit sphere.