esa-sceva/satcom-chunk-collection huggingface dataset:
# Beam Training for Millimeter-Wave Communication Based on Tabu Table Enhanced Rosenbrock Algorithm
## 1 Introduction  
In recent years, to meet the higher requirements on transmission rate and signal bandwidth, millimeter-wave (mm Wave) has been widely concerned because of its widely available bandwidth, strong anti-interference ability and short-wavelength [1]. Although mm Wave wireless communication has great application value, it faces many difficulties in practical applications due to its serious problems such as small coverage limited by severe path loss, intermittent transmission interrupted by human blockage and extra link budget due to absorption of the atmosphere [2]. To solve this problem, antenna array can be used to obtain remarkable processing gain, this technology can effectively compensate path loss and enhance the signal-noise ratio (SNR) of the receivers [3]. Concurrently, it can mitigate interference among users through directional transmission. In addition, multiple antennas can be expediently implemented on miniature portable devices, thanks to the millimeter wavelength. Usually, on the basis of the usage of the spatial domains, traditional multi-antenna technologies can be divided into two types, the spatial multiplexing and beamforming (BF). In order to easily implement and effectively improve the link budgets, it is widely believed that BF-based directional transmission is more appealing for mm Wave communications [4]. Therefore, BF has been adopted into the mmWave wireless communications related standards. On the other side, to establish and maintain the directional communication link between transmitter and receiver, beam search at both ends of the link is required, which always is much more time consuming and incurs a big burden on the system in terms of signaling overhead.
## 2 Materials and Methods
### Statistical Analysis  
For the descriptive analysis, we computed the means of absolute and relative frequencies for categorical variables of interest, and measures of central tendency and statistical dispersion for numeric variables.  
To analyze survival times among NBA players, we studied two different response variables. First, survival time was defined as the time elapsed from the end of the NBA career until death. Players who were active on 15 April 2015 were excluded from this analysis, and the survival times of former players alive on 15 April 2015 were treated as right-censored. We estimated survival probabilities and median survival time using the Kaplan-Meier method [25]. We conducted multivariate analysis using the Cox proportional hazards model [26], whose measure of effect size is the hazard ratio, i.e., the ratio of instantaneous risk functions, which is assumed to be constant over time. The potential predictors were the players' physical characteristics and NBA career-related variables. In addition, the model was adjusted for age and year of the players' retirement from the NBA. For the second objective, age at death was modeled as the response variable; this analysis included both active and former players. The survival times of players who were alive on 15 April 2015 were treated as right-censored, and all survival times were treated as left-truncated at the age of the corresponding NBA debut. As before, survival probabilities were estimated using the Kaplan-Meier method and the multivariate analysis was conducted using the Cox proportional hazards model. The potential model predictors were the players' characteristics. In addition, the model was adjusted for the year of the players' first NBA season. Studying age at death permits us to estimate LE as the model-based estimate of the median. For both models, only African-American and white players were considered, and the proportional hazard assumptions of both models were checked using the Schoenfeld residuals [27].  
Moreover, to compare the mortality of African-American and white NBA players with that of the general African-American and white US populations, respectively, we computed standardized mortality ratios (SMRs) for the years 2000 through 2014. This measure is the ratio of the observed to the expected number of deaths in the study population, where the yearly expected number of deaths was calculated based on the players' ages on January 1, and the survival probabilities of the same year in the corresponding population.  
All analyses were conducted using version 3.4.4 of the R statistical software (Vienna, Austria; [[http://www.rproject.org/](http://www.rproject.org/)]([http://www.rproject.org/](http://www.rproject.org/))). Specifically, we used the R packages survival [28] and epitools [29] to analyze the survival times and to compute the SMRs, respectively. The R code of the analyses carried out and the data are available as Supplemental Material. This work fulfils the transparency and reproducibility of scientific research.
# Neural-Network-Based Synchronization Acquisition with Hankelization Preprocessing
## 4 Simulation Results
### Performance for Detecting Synchronization Signal Under Practical Channel Condition  
In this subsection, we evaluate the performance of the proposed method in a practical channel environment to assess its robustness under realistic conditions. To this end, we incorporate the tap delay line-B (TDL-B) channel model, which effectively captures multipath fading effects encountered in wireless communication systems [27]. The simulation parameters related to the channel configuration are summarized in Table 2, while the NN architecture remains consistent with the configuration presented in Table 1.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Values** \\ \hline Carrier frequency & 3.5 GHz \\ \hline Sampling frequency & 15.36 MHz \\ \hline Subcarrier spacing & 15 kHz \\ \hline Number of paths & 6 \\ \hline Path gain and delay & TDL-B [27] \\ \hline \hline \end{tabular}
\end{table}
Table 2: Default configuration for practical channel experiments.  
Figure 7: Detection error rate for the synchronization signal using m-sequences according to SNR. (**a**) length = 63. (**b**) length = 127.  
Figure 8 shows the detection error rate of the proposed method in comparison to various baseline approaches under different SNR conditions within a practical channel setting. The results demonstrate that the proposed method consistently outperforms conventional techniques, maintaining a significantly lower detection error rate. In particular, while the baseline methods experience some performance degradation due to multipath fading, the proposed approach maintains enhanced resilience, achieving reliable synchronization detection even in low-SNR environments. These findings suggest the effectiveness of the Hankelization-based preprocessing technique in ensuring reliable synchronization detection, even in the presence of multipath fading.
the direct imaging of implanted microspheres [9; 10]. Different studies have demonstrated the feasibility of 90Y PET/CT for post-injection treatment monitoring and its advantages over bremsstrahlung SPECT scanning [10; 11]. For this reason, there is a growing interest in investigating 90Y quantification, based on phantom and post-radioembolization patient studies, to evaluate the 90Y-PET/CT performance, improving its accuracy and defining a standard protocol for image acquisition and reconstruction with PET/CT scanners [12; 13]. The new generation of PET-CT scanners with Time-of-Flight (ToF) technology has improved performances, allowing for the implementation of volumetric 90Y-dosimetry techniques and for the investigation of tumor dose-response directly based on 3D 90Y-activity distribution [14; 15; 16]. Many authors have tried to establish a routine protocol for 90Y-PET/CT in terms of bed-time acquisition, matrix size, the number of Equivalent Iterations (EI), defined as the product of iterations and subsets, and the post-reconstruction Gaussian filter [17; 18; 19; 20; 21]. [PERSON] et al. [21] recently presented an approach to optimization that also involves the evaluation of Dose Volume Histograms (DVH) and absorbed dose distribution. In particular, they used the Root Mean Square Error (RMSE) extracted from integral DVHs (iDVHs) as a metric to evaluate the best 90Y-PET/CT reconstruction parameters. The aim of this study was to perform an up-to-date evaluation of the optimal 90Y PET-CT reconstruction parameters (in terms of Matrix Size, EI and Gaussian Filter) to improve the accuracy of quantification and dosimetry, combining old metrics (RC convergence and CoV evaluation) with new ones, involving a dosimetric approach. In addition to RMSE metric, we proposed the use of Full Width at Half Maximum (FWHM), extracted from the analysis of differential DVHs (dDVHs), as a second complementary metric.
## 2 Algorithm for Optimal Deployment
### Communication Performance Surface Algorithm  
As described in the previous section, the process to estimate the communication performance is complex and time-consuming. If the process is repeated on candidate positions in the targeted area in the computation loop in order to search for optimal sensor positions, it will take too long to find the optimal solution. Here, the communication PS for the targeted area is constructed based on the BER performance estimated in Section 2.2, and then it is used for rapid computation of the search process to find the optimal positions. The communication PS represents the spatial distribution of the relative performance of the underwater communication system, which varies temporally and spatially in the ocean [18].  
The BER estimates as a function of the source-receiver range for the eight azimuthal angles of each grid point were made to obtain the communication PS of the targeted area. Figure 5a,b show the interpolation of the BER performances for the eight azimuthal angles of each grid point predicted using the mean sound speed profiles in February and August, respectively. The difference between the sound speed profiles in the two seasons produces the difference of channel impulse response, which ultimately produces the difference in BER performance. Note that the BER may vary with the types of equalizer and receiver used in the UWASN. Here, a BER of 2% is chosen as a criterion of tolerance for communication, and the range corresponding to this criterion is defined as a communication range. Figure 6 shows an example of the BER performance estimated as a function of range. In this case, the communication range is determined to be 1.8 km.  
Now, the communication ranges for the eight azimuthal angles are averaged to represent the communication radius at the grid point. The minimum or maximum communication range can also be chosen optionally by a user as a representation of the communication radius at the grid point.  
Figure 4: Block diagram of the single-input multiple-output (SIMO) communication receiver system.  
The communication radii estimated for every grid point are interpolated to create the communication PS of the targeted area. Figure 7 shows an example of the communication PS simulated using a three-channel vertical array for the two different seasons ((a) in February and (b) in August). In our simulation case, the overall communication radii in February are longer than those in August, which means that the communication environment in February is better than that in August.  
Figure 5: Communication bit error rate (BER) performance fields of 100 grid points obtained by interpolation of the BER estimate as a function of range for the eight azimuthal angles predicted using the mean sound speed profiles in (**a**) February and (**b**) August.  
Figure 6: Example of the BER performance as a function of range. A BER of 2% is used as a criterion of tolerance for communication in this paper.  
Figure 7: Communication performance surface (PS) simulated for the targeted area in (**a**) February and (**b**) August.
# Marginal Contribution-Based Distributed Subchannel Allocation in Small Cell Networks
###### Abstract  
The paper presents a game theoretic solution for distributed subchannel allocation problem in small cell networks (SCNs) analyzed under the physical interference model. The objective is to find a distributed solution that maximizes the welfare of the SCNs, defined as the total system capacity. Although the problem can be addressed through best-response (BR) dynamics, the existence of a steady-state solution, i.e., a pure strategy Nash equilibrium (NE), cannot be guaranteed. Potential games (PGs) ensure convergence to a pure strategy NE when players rationally play according to some specified learning rules. However, such a performance guarantee comes at the expense of complete knowledge of the SCNs. To overcome such requirements, properties of PGs are exploited for scalable implementations, where we utilize the concept of marginal contribution (MC) as a tool to design learning rules of players' utility and propose the marginal contribution-based best-response (MCBR) algorithm of low computational complexity for the distributed subchannel allocation problem. Finally, we validate and evaluate the proposed scheme through simulations for various performance metrics.  
Keywords:small cells; distributed subchannel allocation; game theory; best-response; potential games; marginal contribution +
Footnote †: journal:
# HVdc Circuit Breakers: Prospects and Challenges
## 2 High Voltage Direct Current Networks
Numerous challenges need to be dealt with before M-HVdc grid becomes a reality, which are: Communication between converter stations [64; 65; 66; 67; 68], control [69; 70], and primary and back-up protection schemes [71; 72; 73; 40; 74; 75; 76; 77; 78; 79; 80; 81; 82; 83; 84;  
same rating. So, initially ac breakers and isolators were employed on ac side of converters as substitute of dc breakers in point-point HVdc configuration [76]. In a medium or low voltage dc applications, various techniques based on solid-state switches or switching arcs have been developed to interrupt the short circuit current [73]. The major problem encountered in the development of DCCBs is the absence of the usual zero-crossing phenomenon in the dc system [77; 78; 79]. The basic requirements which must be accomplished by the breakers are;  
1. Develop a zero-crossing current to interrupt the fault current
2. Must dissipate the stored energy of the inductance
3. Able to hold the voltage profile of the system after the interruption of fault current  
The first two conditions form the dc circuit breaker basis, and the third particular attribute distinguishes them from ac breakers. Secondary requirements of the dc breaker in addition to the features mentioned above are as follows [80];  
1. The dc breaker must interrupt the fault current, as mentioned earlier, in the VSC-based M-HVdc system. 2. The maximum voltage produced across the breaker must be within safe limits to coordinate with the system's insulation. This is of prime importance when the system operates at a nominal voltage to switch heavy load currents. Excessive developments and researches are being conducted on HVdc breakers from six decades [57; 58; 59], but interest in DCCBs is dropped significantly after 1985 due to no success in developing a fast and short interruption mechanism. However, new studies on DCCB appeared [80; 81; 82; 83] recently boomed the interest in HVdc grids. Developments are made in technologies, which ultimately improve the DCCB design and configuration [84; 85]. This paper focuses on the more recent dc breaker field developments, special attention to the latest VSC/MMC-based M-HVdc grids.
# Validation Analysis of Drought Monitoring Based on FY-4 Satellite
## 4 Discussion
### Differences between FY-4A and Other Satellites
#### 4.3.2 Differences in FY Series Geostationary Meteorological Satellites  
FY-4B is new generations satellites after FY-4A. They share the same band lengths in the NIR and IR spectra. However, due to their different positions in space (FY-4A at 104.7\({}^{\circ}\) E and FY-4B at 133\({}^{\circ}\) E), variations in viewing angles and sampling frequencies can result in different values. As a result, the area of drought detected by FY-4A may be larger than that detected by FY-4B, but the spatial distribution patterns remain consistent. The overall differences between these two satellite products are controllable but require further discussion.  
The FY-4 satellite series offers a greater number of channels compared to its predecessor, the FY-2 satellite series. The earlier FY-2 satellites have only one visible light band. The deployment of a sole visible light channel in FY-2 imposes constraints on the computation of the NDVI and restricts the monitoring of land-based ecosystems [65]. In contrast, the multi-band advantage of FY-4A enables it to capture and monitor aerosols, snow cover, and drought conditions effectively. Moreover, FY-4A exhibits the capability to differentiate various cloud phases and detect high and mid-level atmospheric water vapor with enhanced clarity. The FY-4 satellites exhibit higher spatial resolution and observation frequency compared to the FY-2 satellites. This enables them to capture more detailed and frequent data, enhancing their capabilities for various applications, including drought monitoring.
_applied_  
_sciences_  
_Article_  
**Age Estimation Based on Pulp-Tooth Volume Ratio of Anterior Teeth in Cone-Beam Computed Tomographic Images in a Selected Population: A Cross-Sectional Study**  
[PERSON] 1, [PERSON] 2, [PERSON] 2, [PERSON] 3, [PERSON] 1,* and [PERSON] 3,*\({}^{\text{\textregistered}}\)  
\begin{tabular}{r p{341.4 pt}}  & \\ \end{tabular}  
**Featured Application: Based on the findings of this study, pulp-tooth volume ratio of mandibular central incisors, maxillary lateral incisors, and maxillary canines can be used for age estimation in males. Pulp-tooth volume ratio of maxillary and mandibular central incisors, maxillary lateral incisors, and maxillary and mandibular canines can be used for age estimation in females. Additionally, age estimation was most accurate among females using the maxillary central incisors and among males using the mandibular central incisors and maxillary canines.**  
**Abstract: The present study aimed to investigate the correlation between chronological age and pulp-tooth volume ratio in anterior teeth using cone beam computed tomographic (CBCT) images and provide equations for age estimation based on pulp-tooth volume ratio. In this cross-sectional study, CBCT images of 312 anterior teeth of the maxilla and mandible were examined. The chronological age and the sex of the patients were recorded. Tooth volume and pulp volume of the anterior teeth were measured using Mimics software, and then tooth-pulp volume ratio was calculated. Statistical analysis of data was performed using chi-square test, independent T-test, Pearson's correlation, and linear regression (\(\alpha\) = 0.05). Finally, equations were made based on the results of the regression analysis for age estimation in general and for males and females. The age of the subjects ranged between 16 and 69 years (mean 40.6 \(\pm\) 12.74). The pulp-tooth volume ratio of the maxillary teeth was generally higher than the mandibular teeth. A significant inverse relationship between age and pulp-tooth volume ratio was observed for all anterior teeth. (\(p\) < 0.05). The strongest correlation between age and pulp-tooth volume ratio was reported for mandibular central incisor (r = \(-\)0.58, \(p\) < 0.001) and the weakest was for mandibular lateral incisor (r = \(-\)0.36, \(p\) = 0.012). Age estimation was most accurate among females using the maxillary central incisors (\(p\) < 0.001) and among males using the mandibular central incisors and maxillary canines (\(p\) = 0.003). Pulp-tooth volume ratio of mandibular central incisors, maxillary lateral incisors, and maxillary canines in males and maxillary and mandibular central incisors, maxillary lateral incisors, and maxillary and mandibular canines in females can be used for age estimation.  
**Keywords:** cone beam computed tomography; age estimation; pulp-tooth volume ratio; cross-sectional study
# Integrity Monitoring of GNSS Constellations with Only LEO-PNT Satellites +
## 1 Introduction  
The current navigation systems providing integrity services to GNSS users rely on ground infrastructure to elaborate the integrity information that is broadcasted to the user. LEO (Low-Earth-Orbit) mega-constellations provide a unique infrastructure that could be leveraged to provide alternative navigation systems, such as the LEO-PNT initiative by the ESA. In this paper, we explore options for exploiting the LEO-PNT to deliver new high-integrity navigation systems with no infrastructure on ground, providing time to alarms (TTAs) shorter than 6 s. The LEO-PNT satellites (here called LEOs for short) are used as integrity monitors of the GNSS satellites flying above the GNSS users and transmit integrity information directly to them, thus significantly improving their time to alarm performance.  
The bare minimum integrity required is that the LEOs provide information to GNSS users in such a way that they can determine their PVT solution with a bounded error that is not exceeded with a given probability.
# An AUV-Aided Cross-Layer Mobile Data Gathering Protocol for Underwater Sensor Networks +
## 4 Description of Our Proposed Cross-Layer Mobile Data-Gathering Protocol
### Neighbor Discovery Phase  
Sensors exchange a few short control packets to discover one-hop neighboring nodes and update the neighboring table, \(N_{t}\). Each sensor selects its transmission time randomly within the discovery phase interval which is set to a predefined constant value. The discovery phase should be long enough to allow tables formation. This phase is fully explained in our previous works [6; 29; 30].