esa-sceva/satcom-chunk-collection huggingface dataset:
# Flexible Wearable Heart Rate Monitoring System and Low-Power Design: A Review
## 4 Design of the Flexible Wearable Heart Rate Signal Preprocessing Module
### Low-Power Algorithm Design of Flexible Wearable Heart Rate Signal Preprocessing Module
The algorithm employs low-power optimization strategies at multiple stages: in the candidate peak selection stage, it can effectively filter out redundant PPG signals collected by flexible wearable systems, thus significantly reducing computational overhead and power consumption; in the feature extraction stage, it accurately identifies key features while eliminating redundant information; and compared with complex architectures, the three-layer multi-layer perceptron (MLP) network minimizes the consumption of computational resources while ensuring high accuracy. By optimizing the computational process to reduce power consumption, this algorithm lays a solid foundation for subsequent research. In summary, in the preprocessing of heart rate signals acquired by flexible wearable systems, whether it is the adaptive filtering algorithms for ECG signals, such as the LMS algorithm and its optimized version, the NLMS algorithm, the classic algorithms for PPG signal processing, like the CurToSS and TAPIR algorithms, or the emerging deep learning algorithms, they all focus on improving performance metrics such as accuracy while attaching great importance to low-power optimization. By means of improving calculation methods, streamlining parameter adjustment, and optimizing network structures and processes, these algorithms strive to achieve efficient and low-power heart rate signal preprocessing in resource-constrained flexible wearable systems. This not only ensures effective signal processing but also lays a solid foundation for long-term and stable heart rate monitoring as well as subsequent medical applications.
# Seismic Coherent Noise Removal of Source Array in the NSST Domain
###### Abstract  
The technique of the source array based on the vibroseis can provide the strong energy of a seismic wave field, which better meets the need for seismic exploration. The seismic coherent noise reduces the signal-to-noise ratio (SNR) of the source array seismic data and affects the seismic data processing. The traditional coherent noise removal methods often cause some damage to the effective signal while suppressing coherent noise or cannot suppress the interference wave effectively at all. Based on the multi-scale and multi-direction properties of the non-subsampled Shearlet transform (NSST) and its simple mathematical structure, the seismic coherent noise removal method of source array in NSST domain is proposed. The method is applied to both the synthetic seismic data and the filed seismic data. After processing with this method, the coherent noise of the seismic data is greatly removed and the effective signal information is greatly protected. The analysis of the results demonstrates the effectiveness and practicability of the proposed method on coherent noise attenuation.  
source array; NSST; seismic coherent noise removal; seismic data analysis +
Footnote †: journal: Applied  
1
Footnote 1: [[https://www.mdpi.com/journal/applsci](https://www.mdpi.com/journal/applsci)]([https://www.mdpi.com/journal/applsci](https://www.mdpi.com/journal/applsci))
## 3 Material and Methods
### Data Collection Tools
#### 3.2.3 Tobii Pro Glasses 2  
For collecting eye-tracking data during the near-miss recognition experiment, we employed Tobii Glasses 2 (manufactured by Tobii AB Company, Danderyd Municipality, Sweden) to monitor participants' visual behavior (see Figure 1c). This device has been previously utilized in construction safety research and is effective in quantifying visual sensing. Using wearable eye-tracking technology, we captured and analyzed two-dimensional eye-movement information related to participants' attention allocation within areas of interest (AOIs). The device features a gaze sampling frequency of 100 Hz with a horizontal camera angle of 82\({}^{\circ}\) and a vertical angle of 52\({}^{\circ}\).
# Advanced Technologies in Optical Wireless Communications
## 5 Modulation and Multiplexing Techniques  
Similarly to strategies used in fiber optics and RF wireless communications, one of the most effective approaches to increasing the transmission data rate of OWC is the use of multiplexing techniques. In OWC, since light carries the transmitted data, many multiplexing methods commonly used in fiber optics can potentially be adapted for OWC. These methods include wavelength-division multiplexing (WDM) [12], polarization-division multiplexing (PDM) [13], and orbital angular momentum (OAM) multiplexing [14]. Moreover, because the OWC channel is wireless, multiplexing techniques from RF wireless systems can also be applied. Examples include multiple-input multiple-output (MIMO) [15, 16], non-orthogonal multiple access (NOMA) [17], and orthogonal frequency-division multiple access (OFDMA) [18]. These multiplexing techniques are summarized in Figure 1. Despite the many possible ways to implement transmission multiplexing in OWC, a key challenge lies in managing crosstalk and interference between channels, which increase as the number of multiplexed channels increases.  
This Special Issue includes four articles in the category of modulation and multiplexing techniques. In Contribution 12, an OWC system that combines MIMO with Faster-than-Nyquist (FTN) signaling is studied. This approach aims not only to increase the transmission data rate, but also to improve spectral efficiency. However, in this case, crosstalk occurs between different MIMO channels, and FTN introduces strong interference. To overcome this issue, a machine learning-based approach combining a convolutional  
Figure 1: A wide range of transmission multiplexing techniques used in fiber optics and RF wireless communications can potentially be applied to OWC to achieve high-dimensional multiplexing.  
neural network (CNN) and a bidirectional long short-term memory (Bi-LSTM) network is proposed for interference mitigation. Contribution 13 focuses on the study of NOMA in OWC. In particular, NOMA is integrated with the concept of cognitive radio (CR) to achieve high spectral efficiency.  
Regarding modulation methods, OFDM is often considered in OWC as it is already widely used in many existing wireless communication standards [18]. However, because of the high peak-to-average power ratio (PAPR) of OFDM signals, clipping noise often occurs [19]. Contribution 14 investigates a receiver-based signal processing method designed to mitigate clipping noise in optical OFDM systems. In Contribution 15, the use of code shift keying (CSK) in an intensity modulation/direct detection (IM/DD)-based OWC system is studied. Unlike conventional CSK, which is based on orthogonal codes, this work focuses on the use of non-orthogonal codes to improve the transmission efficiency of OWC systems.
# Eight Element Wideband Antenna with Improved Isolation for 5G Mid Band Applications
## 1 Introduction
It is evident that there is a technical requirement for a low-profile multi-port flexible antenna that can accommodate a greater number of users and at the same time, exhibits a wider bandwidth, high efficiency, gain, and excellent MIMO diversity metrics. Addressing the above-mentioned limitations, a flexible, eight-element antenna is proposed for the 5G mid-band. The antenna is fabricated on a PET substrate which makes the antenna highly flexible. To the authors' best knowledge, an article that communicates the development and detailed study of a fabricated flexible eight-element antenna for the specific band is lacking in the literature. Being a part of the C-band spectrum, this band finds application in several communication infrastructures that includes the development of RF devices [25], resonators and filters [26], smartphone applications [27; 28], and so on. The antenna has a footprint of 83 \(\times\) 129 \(\times\) 0.1 mm\({}^{3}\) and a 4.5-5.5 GHz bandwidth with an average 4 dBi gain and 90% radiation efficiency throughout the operating range. Novelty and Contributions:  
* The proposed CPW-fed eight-element antenna consists of a self-isolating structure with a connected ground plane that offers isolation of 24 dB across the operating band. * The antenna has a great bending profile with minimal influence on antenna properties, and it is validated using conformal analysis in both the x and y planes along a radius of 50 mm. * Diversity performance of the proposed eight-element antenna is examined, and the results show good diversity values with ECC \(<\) 0.07, DG-10, MEG ratio-0, TARC \(<-\)10 dB, and ME \(<-\)0.5 that proves the appropriateness of the antenna for real-time diversity environments. * Additionally, the proposed antenna's ergodic channel capacity is investigated and compared with the ideal 8 \(\times\) 8 MIMO antenna. The suggested antenna has a channel capacity ranging from 41.8 to 42.6 bps/Hz across its operational range. This is close to the optimum value, demonstrating the antenna's benefits for high-quality MIMO performance. The overall framework of this paper is as follows: A summary of the single-element design is given in Section 2. The dual and quad-element antenna are explained in Section 3. The proposed eight-element antenna and the associated analysis are elaborated on in Section 4. Sections 5 and 6 include the results and discussion of the antenna and a conclusion, respectively.
# Experimental Study on the Near-Red Flow Characteristics of Alluvial Channel with Seepage
###### Abstract  
This paper aims to analyze the turbulent structure of flows over beds undergoing downward seepage under clear-water conditions. Laboratory experiments in this regard were carried out in a straight rectangular channel that was 17.20 m long and 1.00 m wide. A sandy bed with median grain size \(d_{50}=0.50\) mm and sediment gradation \(\sigma_{g}=1.65\) (i.e., slightly non-uniform sediment) was used for the channel bed. The 3D instantaneous velocities of water were measured with an Acoustic Doppler Velocimeter (ADV) at the working test section. In the vicinity of the bed surface with seepage, measurements revealed that the flow longitudinal velocities (i.e., velocities in \(x\) direction) were higher than those in the case of a bed without seepage. Moreover, the variations inthe Reynolds shear stresses increased for the bed with seepage, indicating a higher exchange of flow energy towards the boundary and vice versa. Therefore, it was found that seepage processes influence the turbulence intensity, with a prominent magnitude in the streamwise and vertical directions. The paper also focuses on the third-order moment (skewness) and the kurtosis of velocity fluctuations and the governance of sweep events within the near-bed flow in cases where seepage was observed.  
clear-water regime; higher-order moments of velocity fluctuations; near-bed turbulence characteristics; seepage flow +
Footnote †: journal: Applied Sciences
## 4 Experiments
### Experimental Details  
The proposed method is running in Pytorch (2.0.0), with an NVIDIA 3090 Ti GPU (NVIDIA, Santa Clara, CA, USA) and i9-12900 KF CPU (Intel Corporation, Santa Clara, CA, USA) equipped with 24 GB of video memory. The AdamW optimizer is used with an initial learning rate of 1 \(\times\) 10\({}^{-3}\), \(\beta_{1}=0.9\), \(\beta_{2}=0.999\), and the learning decay is 0.9. The model is trained for 100 epochs with a batch size of 1 until convergence. Also, we adopted three dual cross-attention blocks to construct the MMFIM. In addition, we conducted experiments on the knee and brain datasets of fastMRI [54; 55]. On the knee dataset, we first applied a one-dimensional Cartesian random sampling pattern and conducted experiments under the conditions of 10\(\times\) and 12\(\times\) acceleration factors. Then, on the brain dataset, we adopted two sampling patterns: one-dimensional Cartesian random and equispaced, and conducted experiments under the acceleration factors of 4\(\times\), 8\(\times\), and 12\(\times\). We also compared our method with six state-of-the-art methods, including three single-modality MRI reconstruction methods: U-Net [51], STUN [15], and PC-UNet [47], and three multi-modality MRI reconstruction methods: MINet [49], DuDoCAF [27], and DuDoRNet [14].
## 2 Results and Discussion
### In Vitro Biological Evaluation
#### 2.2.1 Antimicrobial Activity
_N_-Methylated indolylbenzimidazole **3b** exhibited moderate antimicrobial activity against _C. albicans_; _S. aureus_, including MRSA; and _M. smegmatis_. The closest structural analogue **3 ag**, containing methyl in the imidazole fragment, demonstrated significantly higher bacteriatic and mycostatic activity: the MIC against _S. aureus_ decreased by 2 times, against MRSA it decreased by 4 times, against mycobacteria it decreased by 16 times, and against _C. albicans_ it decreased by 32 times. However, in this case, improving the ability to inhibit bacterial growth was not accompanied by an increase in the bactericidal effect. On the contrary, a strong increase in mycostatic activity (MIC reduced by 32 times) coincided with an increase in lethal activity against _C. albicans_ (MFC reduced by 32 times). Comparing the antimicrobial activity in the group of 5,7-disubstituted 2-(1\(H\)-indol-3-yl)-1\(H\)-benzo[\(d\)]imidazoles **3z-ad**, it should be noted that the 7-bromo-2-(1\(H\)-indol-3-yl)-5-methyl-1\(H\)-benzo[\(d\)]imidazole (**3 ab**) demonstrated higher antimicrobial activity against _C. albicans_; _S. aureus_, MRSA; and _M. smegmatis_ than 7-bromo-2-(1\(H\)-indol-3-yl)-5-methoxy-1\(H\)-benzo[\(d\)]imidazole (**3 ac**). An increase in antistaphylococcal activity was observed for 7-bromo-5-chloro-2-(1\(H\)-indol-3-yl)-1\(H\)-benzo[\(d\)]imidazole (**3 aa**): the MIC against _S. aureus_ ATCC 25923 was 7.8 \(\upmu\)g/mL and MRSA was 3.9 \(\upmu\)g/mL. At the same time, the replacement of a chlorine atom with bromine also led to an increase in the antimicrobial activity of the compound **3 ad**. Interestingly, the furo- and thieno-derivatives **3 at** and **3 au**, respectively, of benzimidazoles show a decrease in activity against all studied microorganisms, with the exception of _E. coli_ in the case of **3 at**, where we observed a slight increase in bacteriostatic action. We also analyzed the antimicrobial properties of the target molecule after replacing the imidazole cycle with a thiazole cycle. Replacement of the imidazole fragment in compound **3a** with a thiazole one, **3 az**, led to a significant increase in inhibitory but not bactericidal activity against staphylococci (16- and 8-times decrease in MIC against _S. aureus_ ATCC 25923 and MRSA, respectively). The inhibitory and fungicidal activities against _C. albicans_ were not changed in this case. 2-(5-Iodo-1\(H\)-indol-3-yl)-1\(H\)-benzo[\(d\)]imidazole (**3n**) can be compared with the structurally close 2-(5-iodo-1\(H\)-indol-3-yl)quinazolin-4(3\(H\))-one [25] that has a pyrimidinone cycle instead of imidazole ring and similar spectrum of antimicrobial activity. The antimy-cobacterial activity of compound **3n** was higher than in its nearest homolog.
# On the Issues of \(\mathbf{NO_{x}}\) as Greenhouse Gases: An Ongoing Discussion...
## 4 Dualistic Nature of NO\({}_{x}\) Impact on the Greenhouse Effect
### Cooling Nature  
It was previously mentioned that the presence of NO\({}_{\rm x}\) can lead (in some specific conditions) to global cooling. This is why the GWP values are sometimes negative. Furthermore, NO\({}_{\rm x}\) are sometimes termed as cooling gases [7; 45; 50; 54]. It was proven that the presence of NO can influence the increase in the concentration of OH radicals in the atmosphere, and OH radicals contribute to destroying methane, according to the following reactions [50]:  
\[\rm{HO_{2}+NO\leftrightarrow OH+NO_{2}} \tag{7}\]  
\[\rm{OH+CH_{4}\leftrightarrow H_{2}O+CH_{3}} \tag{8}\]  
Here, CH\({}_{4}\) belongs to the direct group of GHGs, thus destroying it causes a cooling effect. Moreover, CH\({}_{4}\) reduction results in a long-term reduction in tropospheric O\({}_{3}\), and a long-term reduction in stratospheric water vapor from the reduced oxidation of CH\({}_{4}\). Both of these phenomena are recognized as negative radiative forcing effects [39]. It should be explained that the cooling effect of NO\({}_{\rm x}\) depends on the impact of other compounds existing in the atmosphere. Namely, the presence of CO can contribute to a decrease in the concentration of OH radicals. Consequently, the cooling effect of NO\({}_{\rm x}\) can be inhibited, and the GWP for NO\({}_{\rm x}\) is positive (a warming effect). Furthermore, the decrease in the OH concentration inhibits CH\({}_{4}\) destruction (being a direct GHG). If the impact of NO\({}_{\rm x}\) is considered without reference to the CO contribution, it would only be assumed that the cooling effect of NO\({}_{\rm x}\) is from surface sources. The increase in the CO concentration in the atmosphere causes NO\({}_{\rm x}\) to convert from cooling gases to warming gases with a positive GWP [54]. We can have reasonable hope that the development of combustion technology by increasing the combustion efficiency and decreasing CO emissions will inhibit NO\({}_{\rm x}\) from having an effect as a warming gas.  
Another phenomenon responsible for the cooling effect of NO\({}_{\rm x}\) is the formation of aerosols (dispersion of very fine liquid droplets) in the atmosphere. Increased aerosol formation and cloud reflectivity cause a decrease in sunlight radiation and enhance the cooling effect [7; 38]. The main process responsible for aerosol formation is the conversion of SO\({}_{2}\) into H\({}_{2}\)SO\({}_{4}\) formations, which condensate as very fine droplets (aerosols). The contribution of NO\({}_{\rm x}\) in this process relies on OH formation. It has already been explained that an increase in NO concentration causes an increase in OH radical concentration in the atmosphere. Moreover, the presence of OH radicals intensifies SO\({}_{2}\) conversion into aerosols, thus directly causing a cooling effect [7].
# Underwater Communications for Video Surveillance Systems at 2.4 GHz
## 5 RTT Measurements for Each Modulation at Several Temperatures
### Average RTT for 26 \({}^{\circ}\)C  
Figure 19 shows the RTT values and their typical errors in ms as a function of working frequency for all data transfer rates at 26 \({}^{\circ}\)C.  
Figure 17: Values of RTT in ms for 20 \({}^{\circ}\)C.  
Figure 18: Values of RTT in ms for 22 \({}^{\circ}\)C.  
As Figures 8-10 showed previously, this temperature permits the lowest values of maximum distance. It this case, there are great changes in RTT values. On the one hand, frequencies of 2412 MHz and 2427 MHz (using 1 Mbps as data transfer rate) present the lowest values (about 6 ms). On the other hand, the highest frequency analyzed for this temperature, i.e., 2442 MHz presents the greatest values of RTT.  
At 26 \({}^{\circ}\)C, the best combination of parameters would be working at 2412 MHz at 1 Mbps. However it is a situation of best combinations which offers the worst results.  
As a summary of this section, we can conclude that the temperature slightly affects the value of RTT. We can observe that the lowest frequencies present smallest RTT values, but it is difficult to relate the RTT values with the network performance. This is because the line between whether an underwater network using EM waves works or not, in the case of the aquatic environment, is very subtle and therefore a gradual deterioration in terms of network performance is hardly observable.
# Graphene-Based Flexible Electrode for Electrocardiogram Signal Monitoring
## 2 Research on Graphene-Based Flexible ECG Electrodes
### Fabric-Based Graphene ECG Electrodes  
A smart way to improve the wearable comfort of contact electrodes and make them suitable for long-term wear is to make functional daily-wear clothes or fabrics. Recently, with the rapid progress of fiber electronics, many fabric ECG electrodes have been developed [44]. Compared to conventional Ag/AgCl gel ECG electrodes, fabric electrodes have intrinsic advantages, including light weight, high gas permeability, and low cost, which make them more acceptable to the consumer market. However, most clothing fibers are electrically insulated and do not closely adhere to skin, which results in high contact impedance between electrode and skin, large motion artifact caused by relative movement between electrode and skin, and serious noise problems of collected ECG signal. Facing these challenges, much work has been carried out by combining graphene materials with fibers to endow the fabric ECG electrodes with high electrical conductivity without affecting its other advantages [45; 46; 47; 48; 49; 50; 51; 52; 53]. Meanwhile, some research on adhesive fabrics and electrode-wearing methods have been developed to improve contact between the fabric ECG electrode and skin. In this section, we will introduce several typical fabric ECG electrodes proposed in recent years, and discuss their characteristics.  
Figure 1: Bionic graphene ECG electrodes. (**a**) Gecko-inspired ECG electrodes. Reprinted with permission from Ref. [36]. Copyright 2016, American Chemical Society. (**b**) Photo of the strong adsorption of the CDA electrode (**left**) and liquid droplets on the gecko-inspired CDA electrode (**right**). Reprinted with permission from Ref. [36]. Copyright 2016, American Chemical Society. (**c**) Amphibian- and octopus-inspired hierarchical hexagonal microstructures for ECG monitoring. Reprinted with permission from Ref. [40]. Copyright 2016, American Chemical Society. (**d**) An avian-nest-inspired ECG electrode and its preparation process. Reprinted with permission from Ref. [42]. Copyright 2020, American Chemical Society. (**e**) Schematic of the preparation process (**left**) and the ultra-fast self-healing ability (**right**) of the PC/rGO/PVA hydrogel ECG electrode. Reprinted with permission from Ref. [43]. Copyright 2020, Elsevier. (**f**) The self-healing ECG electrode is used to detect ECG signals. Reprinted with permission from Ref. [43]. Copyright 2020, Elsevier.
## 3 Method
### Network Structure
#### 3.3.4 Loss Function  
The loss function determines the performance of the model to a certain extent because the model prediction is often different from the real value, and the magnitude of this difference is measured by the loss function. In BT-YOLO, the loss was divided into three types: classification loss, localization loss, and confidence loss. Adding these three losses together gave us the loss of the entire model. Considering the mismatch between the prediction box and the desired prediction box, we redefined the penalty metric, where the localization loss was calculated using SloU, which contained the angle loss, distance loss, shape loss, and IoU loss. In Equation (1), we defined the way of computation as follows:  
\[L_{box}=1-IoU+\frac{\Delta+\Omega}{2} \tag{1}\]  
where \(\Delta\) denoted the distance loss after taking into account the angular loss, which was calculated as:  
\[\Delta=\sum_{t=x,y}{(1-e^{-Ypt})} \tag{2}\]  
\[\rho_{x}=(\frac{B_{cx}^{gt}-B_{cx}}{C_{w}}),\rho_{y}=(\frac{B_{cy}^{gt}-B_{cy}} {C_{h}}),Y=2-\Lambda \tag{3}\]  
Figure 4: Three-dimensional weights in SimAM.  
In Figure 5 below, we showed some notation in the calculation formula. Angle cost \(\Lambda\) can be calculated using Equation (4).  
\[\Lambda=1-2\times\sin^{2}(\arcsin(x)-\pi/4) \tag{4}\]  
\[x=\frac{C_{h}}{\sigma}=\sin(\alpha) \tag{5}\]  
\[\sigma=\sqrt{\left(B_{cx}^{gt}-B_{cx}\right)^{2}+\left(B_{cy}^{gt}-B_{cy} \right)^{2}} \tag{6}\]  
\[C_{h}=\max(B_{cy}^{gt},B_{cy})-\min(B_{cy}^{gt},B_{cy}) \tag{7}\]  
It is clear from Equation (5) that the closer \(\alpha\) is to \(\frac{\pi}{4}\), the larger the contribution of distance loss.  
Equation (8) denotes the shape loss, which is calculated as:  
\[\Omega=\sum_{t=w,h}\left(1-e^{-\omega t}\right)^{\theta} \tag{8}\]  
\[\omega_{w}=\frac{\left|w-w^{gt}\right|}{\max(w,w^{gt})},\omega_{h}=\frac{ \left|h-h^{gt}\right|}{\max(h,h^{gt})} \tag{9}\]