esa-sceva/satcom-chunk-collection huggingface dataset:
# Characterization of the Body-to-Body Propagation Channel for Subjects during Sports Activities
###### Abstract  
Body-to-body wireless networks (BBWNs) have great potential to find applications in team sports activities among others. However, successful design of such systems requires great understanding of the communication channel as the movement of the body components causes time-varying shadowing and fading effects. In this study, we present results of the measurement campaign of BBWN during running and cycling activities. Among others, the results indicated the presence of good and bad states with each state following a specific distribution for the considered propagation scenarios. This motivated the development of two-state semi-Markov model, for simulation of the communication channels. The simulation model was validated using the available measurement data in terms of first and second order statistics and have shown good agreement. The first order statistics obtained from the simulation model as well as the measured results were then used to analyze the performance of the BBWNs channels under running and cycling activities in terms of capacity and outage probability. Cycling channels showed better performance than running, having higher channel capacity and lower outage probability, regardless of the speed of the subjects involved in the measurement campaign.  
b 2018; 18, 620; doi:10.3390/s1802062018 February 2018
## 4 Conclusions  
This study addresses the existing issues and limitations of traditional methods in bolt loosening detection for steel truss structures. It focuses on acoustic signal recognition technology and proposes an innovative bolt loosening damage identification strategy based on MFCC-WPES feature fusion and an optimized Random Forest algorithm. The research process involves frame segmentation, windowing preprocessing of acoustic signals, feature extraction using MFCC and WPES, fusion of these features to construct an MFCC-WPES combined feature training set, and training an RF classifier for sensitive feature selection and effective damage signal identification. A genetic algorithm is employed to optimize key parameters of the Random Forest model, aiming to construct an identification model with optimal performance. The results demonstrate that the proposed method accurately identifies bolt loosening damage signals and exhibits strong robustness to environmental noise. Compared to methods relying on single features and traditional machine learning models, this method shows significant advantages in core performance indicators.  
Future research directions will focus on testing the model under more complex environments and a wider range of damage conditions, with plans to conduct field measurements on large-scale truss steel structures under actual working conditions to further validate and optimize the practical application effectiveness of the proposed method.  
Conceptualization, D.Z.; methodology, D.Z.; software, Z.Z.; validation, Z.J.; formal analysis, Z.J.; investigation, Z.J.; resources, Z.Z.; data curation, Z.Z.; writing--original draft preparation, Z.Z.; writing--review and editing, D.Z.; visualization, Z.Z.; supervision, D.Z.; project administration, D.Z.; funding acquisition, D.Z. All authors have read and agreed to the published version of the manuscript.  
This research was funded by National Natural Science Foundation of China (Grant number 52268049) and the Hunan Provincial Natural Science Foundation (Grant number 2021 JJ30557).  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
The authors declare no conflicts of interest.
## 3 Methodology
### GitHub Modeling Using DTMC
#### 3.2.3. Property Specification Using PCTL  
In this research, we employ PCTL to express and verify various properties related to participant behavior within GitHub repositories. These properties capture aspects such as activity frequency, PR handling, and collaboration patterns. A total of 12 key independent variables are defined using PCTL specifications. Each variable represents a specific participant behavior or system state, as outlined in Table 1. In this case, _pLabel_ means the participant's label. The probability that a PR submitted by a participant will be processed immediately. act_level: A variable indicating how often the participant is active in the project, with smaller values indicating more frequent activity. merge: A variable that indicates how often a participant engages in the activity of merging PRs on GitHub. Merge activity plays an important role in project maintenance and management. A variable that indicates how often a participant submits PRs. participants who submit PRs more frequently are more likely to be active participants to the project and stay active for a longer period of time. p1_merge: A variable representing the probability that the first participant (p1) will merge another participant's PR. The first participant is often the leader of the project, and their active participation in merging PRs can be interpreted as an important contribution to the overall management of the project. create_to_pr: The average time step it takes for a participant to submit a PR after creating a branch. pr_to_processing: The average time step it takes for the PR to be processed (accepted or rejected). pr_to_create: The average time step it takes to create a new branch after submitting a PR. alone: A variable that measures the amount of time a participant has been working alone, with a high amount of alone time indicating a lack of collaboration. commit_to_commit: The probability of a participant performing consecutive commits. prRate: The percentage of branches created that actually lead to a PR.
## 4 Experimental Environment and Results
### Design Framework Results  
#### 4.1.1 Literature Analysis Findings  
Based on our systematic analysis of the literature, this study identified three core dimensions that need to be considered in designing technology products for the elderly.  
From the perspective of human-computer interaction, [PERSON]'s [PERSON] (2016) ecological approach theory emphasizes that environments or objects should naturally guide users' interactive behaviors. When [PERSON] (2017) applied this theory to human-computer interaction design, the findings revealed that the learning threshold decreases significantly when the interface design aligns with the user's natural perceptual patterns. This finding supports our design approach of using daily objects as interactive interfaces.  
Regarding intergenerational interaction research, [PERSON] et al. (2015) demonstrated that elderly users exhibit stronger motivation to use technological products when engaging in activities with their grandchildren. Additionally, physical interactive interfaces and puzzle-type activities help elderly users to interact in a joyful atmosphere while enhancing their social capabilities.  
In terms of sensing technology applications, Project Jacquard Jacquard (2018) confirms that interactive materials must be more closely aligned with daily life and possess the characteristics of warmth, comfort, and flexibility to facilitate more fluid user operation.
###### Abstract  
This study aims to investigate the ultimate bearing capacity of a novel tubular K-joint used for light-steel structures consisting of thin-walled square hollow section members, a U-shape connector and self-drilling screws, and the effect of three patterns of stamping indentation fabricated on the U-shape connector on the ultimate bearing capacity of the proposed K-joint. Firstly, a total of 12 K-joint specimens were tested to failure under monotonic brace axial compressive loading. Secondly, failure mode and the ultimate bearing capacity of each specimen were investigated and analyzed. Finally, finite element analyses were carried out to study the effect of three key parameters, including chord axial stress ratio, half width-to-thickness ratio of the chord and brace-to-chord wall thickness ratio, on the ultimate bearing capacity of the proposed K-joints using the recommended U-shape connector. It was found that failure mode of the proposed K-joint is governed by both the deformation of the U-shape connector and the chord local plastification. Besides, the K-joint specimen using a U-shape connector with the strip stamping grooves in the horizontal direction generally has a higher bearing capacity and a much smaller connector deformation. Similar to the welded tubular joints, chord axial stresses may also significantly reduce the ultimate bearing capacity of the proposed K-joint.  
light-steel structure; novel tubular K-joint; U-shape connector; pattern of stamping indentation; chord axial stress +
Footnote †: journal: Applied Sciences
# The PIV Measurements of Time-Averaged Parameters of the Synthetic Jet for Different Orifice Shapes
## 3 Results and Discussion
### The Turbulent Kinetic Energy of the Synthetic Jet
#### 3.3.2 Impact of the Dimensionless Stroke Length on the Time-Averaged Vorticity Field  
The SJ vorticity filed at \(L_{0}=10\) had a lower dissipation rate than the vorticity at \(L_{0}=2\). It is especially visible in Figures 19 and 20, where the radial vorticity profiles at a distance of \(x/d=10\) were presented. The maximal value of dimensionless vorticity at \(L_{0}=2\) was aproximetely equal to 0.35, and at \(L_{0}=10\), it was approximately equal to 0.6. It indicates the slower disappearance of the vortex structure. However, the vorticity at a low distance from the orifice \(x/d<4\) was higher at \(L_{0}=2\), and a fields area of very high vorticity (\(\omega d/U_{e}>|3.5|\)) was also higher at \(L_{0}=2\). The faster disappearance of the vortex ring is caused by the higher value of the normal stress. [PERSON] and [PERSON] [11] showed that the increased dimensionless stroke length caused a decrease in the time-averaged normal stress near the orifice.  
As was mentioned in Section 3.3.1, the decrease in vorticity can be identified with the vortex ring coalescing. This is indicated by the visualizations carried out by [PERSON] and [PERSON] [15] and [PERSON] et al. [25]. [PERSON] et al. [41] visualized the SJ at \(L_{0}=3.29\); \(2.33\); \(1.75\) and \(Re=17\),\(000\); \(12\),\(000\); \(9000\), respectively. The vortex ring coalescing was not observed only at \(L_{0}=3.29\) and \(Re=17,000\). The SJ coalesced at a distance of \(x/d=4\) and \(3\) at \(L_{0}=2.33\) and \(1.75\), respectively. On the other hand, [PERSON] et al. [25] observed the vortex ring coalescing at \(Re=199\) and \(St=0.22\) (\(L_{0}=4.55\)) and at a distance of approximately \(x/d=3\), and [PERSON] and [PERSON] [15] at \(Re=7784\) and \(St=0.012\) (\(L_{0}=83.3\)). [PERSON] et. al [12] did not recognize the distance and parameter at which the vortex ring coalescing occurred. However, the slot SJ visualization presented in their article showed that the SJ coalesced at a distance of \(x/d=4\) at \(Re\geq 332\) and \(L_{0}=2.3\). [PERSON] et al. [23] did not observe the vortex ring coalescing at \(Re=890;900\) and \(L_{0}=2.2\); \(10\), respectively.  
A visualization made by [PERSON] and [PERSON] [11] showed that the value of phase-averaged dimensionless vorticity below 0.5 results in the loss of the SJ's coherent structure. However, [PERSON] et al. [23] showed that the coherent structure of the SJ can be preserved even for the value of a time-averaged dimensionless vorticity field equal to approximately 0.25 for the SJ at \(Re=900\) and \(L_{0}=10\).
## 5 Simulation Results and Discussions  
To compare the performance of the considered systems, BER, received power and Q-factor are taken as metrics with the following parameters listed in Table 2. As indicated by the above figures, the transmitter side started by pseudo-random bit sequence generator with a rate 1 Gbps followed by a line coding technique (NRZ or RZ or PSK), then the modulator stage. We consider LASER as a light source with a wavelength of 700 nm and power 10 dBm. The data bits and laser light are received through a Mach-Zehnder (MZ) modulator. Two ambient light noise sources are considered with a wavelength of 550 nm. The channel may be SISO or MIMO according to the considered system. At the receiver side, the optical signal is recovered by PIN photodiode, which is then passed through a low-pass Bessel filter. A BER analyzer is utilized to calculate the BER.  
In Table 2, an attenuation value of 25 dB/km was chosen to represent a worst-case or highly lossy channel condition that may arise in realistic free-space optical (FSO) or long-range VLC scenarios, particularly under adverse environmental factors such as heavy ambient interference, fog, rain, or aerosol-dense atmospheres. This value allows the system's performance to be evaluated under challenging outdoor conditions, ensuring that the proposed MIMO-VLC system is assessed in severe yet plausible attenuation scenarios.  
Figure 5: SISO–VLC with ambient light noises and different line coding techniques.  
Figure 6: MIMO–VLC with ambient light noises and different line coding techniques.
# Compact Planar Super-Wideband Monopole Antenna with Four Notched Bands
## 2 Antenna Design
### Parametric Studies of Antenna Performance  
The effects of the ground plane length, U-shaped slots, meandered slot, and SRR on the proposed antenna are studied.  
The gap between the ground plane and the radiating element is mainly responsible for impedance matching. Figure 6 shows the simulated reflection coefficients of the proposed SWB antenna when the ground plane length (\(l_{1}\)) is varied. The length \(l_{1}\) is varied from 5.65 mm to 6.65 mm, while the other dimensions of the antenna are kept fixed. When the length \(l_{1}\) is increased or decreased, the impedance matching becomes poorer in the higher frequency bands. On the other hand, when \(l_{1}\) is increased to 6.65 mm, the antenna shows resonance only for the UWB range. However, a longer ground plane results in a long feed line, which increases the size of the antenna.  
To study further the behavior of the notch bands, a parametric analysis on the length of the U-shaped slots, meandered slot, and SRR is performed, as illustrated in Figure 7. In Figure 7a, the changes of the reflection coefficients as varying the SRR length (\(b_{1}\)) are shown. It is noticed that as the value of \(b_{1}\) increases, the notch band moves towards the lower frequency side. Whereas, when the length of the SRR is decreased, the notch band shifts towards the higher frequency side.  
Figure 5: Simulated current distribution at frequency: (**a**) 10.5 GHz, (**b**) 7.5 GHz, (**c**) 5.5 GHz, (**d**) 3.5 GHz.  
Figure 6: Simulated reflection coefficients of the antenna when the ground plane length (\(l_{1}\)) is varied.  
Figure 7: \(Cont\).  
In Figure 7b,c, the variations of the reflection coefficients of the U-slot lengths (\(l_{3}\) and \(l_{4}\)) are shown. It is observed that as the value of \(l_{3}\) increases from 4.6 mm to 5.2 mm, the center frequency of the notch band shifts towards the lower frequency range. In the same way, the notch band shifts towards the lower frequency range, when the length \(l_{4}\) of the larger U-slot varies from 4.05 mm to 4.65 mm. Hence, the center frequency of the notch band can be easily tuned by changing the length of the U-shaped slot. The effect of varying the length (\(l_{9}\)) of the meandered slot is shown in Figure 7d. On varying the length \(l_{9}\) from 2.6 mm to 3.2 mm, the notch center frequency shifts towards the lower side. Considering, the available patch space and the required notch band frequencies, the optimized values are chosen for designing the proposed antenna.
## 3 Results and Discussion
### Content of Total Phenolic Compounds (TPC)  
Phenolic compounds are very important plant-derived antioxidants. A total phenolic compound (TPC) analysis conducted by the Folin-Ciocaltau method has been widely used to assess and compare their content in different food matrices. Figure 3 shows the effect of the addition of chokeberry pomace to green tea leaves and hibiscus flowers on the content of total phenolic compounds in infusions.  
The content of phenolic compounds in green tea leaf infusions was significantly higher (23 mg GAE/100 mL) than in hibiscus flower infusions (2.3-3.6 mg GAE/100 mL). [PERSON] et al. [46] determined the content of phenols in green tea leaf infusions at a level of 57-84 mg of catechin equivalents/100 mL. However, they prepared infusions with 1.5 g of dried leaves and used different phenolic standards. In turn, [PERSON] et al. [47] optimized the conditions for the preparation of infusions with calves hibiscus (tested ranges: calves/water ratio of 1-20 g/100 mL; temperature of 7-100 \({}^{\circ}\)C; and brewing time of 1-1200 min) and determined phenolic compounds from 5.48 to 21.47 mg GAE/100 mL. The content of phenols determined in our studies was lower, which may be related to both the method of flower drying and the brewing conditions [48]. The addition of dried pomace to green tea leaves or hibiscus flowers, regardless of the proportion, increased the content of phenols by an average of 16 mg/100 mL-23 mg/100 mL. The highest content was found in infusions of green tea leaves, although greater increases were noted for infusions of hibiscus. This suggested better extractability of pomace phenolics in the presence of compounds from hibiscus flowers. A greater increase in the content of phenolic compounds in hibiscus infusion may be associated with a significantly lower pH of this solution compared to green tea leaf infusions. Also, [PERSON] and [PERSON] [49] determined the effect of pH in the range of 3 to 6 on the stability of chlorogenic and caffeic acids. They found that an increase in pH value causes a decrease in absorbance in spectrophotometric assays; however, they did not identify the nature of these changes.  
An increase in the addition of chokeberry pomace (x) to hibiscus flowers, irrespective of their type (red or white), resulted in an increase in total polyphenol levels (y) according to the equation \(y=7.5x+3.9667\) (R\({}^{2}\) = 0.889).
## 3 Finite Element Analyses
### Domain Discretization of UC1 and UC2  
The geometry models of the UC1 and UC2 were established based on the CAE (computer-aided engineering) software SolidWorks (Version 2016, Dassault Systemes, Massachusetts, MA, USA, 2016). In this work, UC2 is one-fourth of the size of UC1. As seen in Figure 11, the UC1 is prescribed as a cube by the domain \(0\leq x\leq l\), \(0\leq y\leq w\), \(0\leq z\leq h\). \(l\) and \(w\) are the length and width of the UC1, respectively, \(h\) is the height of UC1 and UC2, \(d_{fr}\) is the diameter of carbon fiber rod, \(h_{fb}\) and \(l_{fb}\) represent the height and length of carbon fiber bundle, respectively, and \(g\) is the distance between the carbon fiber bundle and the carbon fiber rod. For the unit cells discussed above, these parameters are fixed as follows, \(l=5.54\) mm, \(w=3.2\) mm, \(h=3.3\) mm, \(d_{fr}=1.2\) mm, \(h_{fb}=0.9\) mm, \(l_{fb}=0.9\) mm, \(g=0.34\) mm.  
In addition, three additional diameters (\(d_{fr}=1.4\) mm, \(1.6\) mm, \(1.8\) mm) of carbon fiber rods are set in order to observe the effect of fiber rod diameter on the thermal conductivities while the value of \(g\) is fixed. As discussed above, the thermal conductivities of carbon fiber bundles and carbon fiber rods are used as inputs for calculating the thermal conductivities of 4D C/C composites, so local coordinates are required to define the axes of carbon fiber bundles and carbon fiber rods. UC1 and UC2 are both meshed by the C3D8R element, which imposed the temperature boundary conditions discussed in Sections 2.2 and 2.3, respectively. The meshed models of UC1 and UC2 can be seen in Figure 11, and the corresponding number of elements of the two-unit cells with carbon fiber rods of different diameters are shown in Table 3.
# Clinical Brain Monitoring with Time Domain NIRS: A Review and Future Perspectives
## 5 Current Developments in TD-NIRS and Clinical Pertinence
### Development of New Methodologies
The method has been tested on piglet with promising results. As hypothermic therapy is now the standard treatment for neonates, but optimal protocols are yet to be established (i.e., in terms of duration and depth of treatment, for example) [138], the ability to monitor brain temperature non-invasively at the bedside would certainly be another argument in favour of the clinical use of TD-NIRS. The last big methodological development, which was discussed in an earlier section, was the ability to measure brain perfusion. It has been shown that the use of TD-NIRS in combination with DCS could improve the data quality of the BFI retrieved by the DCS. However, the current DCS measurement suffers from the same drawback as CW-NIRS, being the contamination of the signal by extracerebral layers. [PERSON] and colleagues in 2015 used a combination of short and long source-detector distance DCS with pressure modulation (head blood pressure cuff) to remove extracerebral contributions in the DCS signal [139]. However, a recent development called TD-diffuse correlation spectroscopy (TD-DCS) has been reported, allowing DCS measurement in the TD regime [137]. Thus, through the use of time gating, an in-depth measurement of the BFI became possible, improving the accuracy of the measurement of the cerebral blood flow [138]. Finally, it is also worth mentioning that while most of the DCS systems reported in the literature only have one channel, [PERSON] and colleagues have recently demonstrated a dual channel DCS allowing bi-hemispheric measurements in stroke patients [140]. This illustrates the potential development of multi-channel DCS. Finally, as seen in this review, imaging patients differs from imaging healthy subjects because normal tissue configuration cannot always be assumed. A recent study by [PERSON] and colleagues [141] showed that it might be possible to use TD-NIRS to evaluate the progression of brain atrophy in patients. Indeed, the late photons of the TPSF seems to be sensitive to the thickness of the CSF layer. However, this simulation study showed that this technique would require the acquisition of photons with very long arrival time (\(>\)2.5 ns) with a good enough SNR. In that sense, the newly developed detector might help to push this methodology forward. On the other hand, the structural changes consecutive to some pathologies also suggests that classical models might not work in all cases. However, as it has been seen, NIRS is extremely well-suited for multimodal imaging. Therefore, combining anatomical imaging with NIRS allows for model-patient specific geometry that will increase the NIRS accuracy [142]. Here, the progress being done in terms of Monte-Carlo modelling, especially in terms of calculation speed [143], unlock new possibilities for it to be used in real-time at the bedside.