esa-sceva/satcom-chunk-collection huggingface dataset:
## 1 Introduction  
The shape and material nature of Cu foil, which affects the energy deposition, plasma output ability and flyer velocity, is the most researched topic on exploding foil detonators [1, 2, 3], which are considered as the key materials for electronic safe and arm systems for rocket motor ignition, fuzing, ammunition, and flight termination applications [4, 5, 6, 7, 8, 9, 10, 11, 12]. The velocity and shape of the flyer are two key factors that affect the energy-output effect of exploding foil initiators. They are the most important characterization indexes for exploding foil initiators and have shown some important referenced values for the design of the reliability, evaluation, and performance optimization of exploding foil initiators [13, 14]. At present, the theoretical and experimental researches on the flyer velocity of exploding foil initiators is relatively mature, and a variety of velocity testing techniques of small flyers have been mastered. Moreover, the various parameters of the exploding foil initiator on the flyer velocity have also been investigated from a macro point of view [15, 16, 17]. The macroscopic properties of materials depend not only on their chemical composition, but also, to a greater extent, on their micromorphology and grain size [18, 19].  
Usually, the film grown by various atomic deposition techniques is generally polycrystalline with a strong texture. The texture characteristics have a great influence on the magnetic properties, electrical properties, and microstructure density of the film, which often directly affects the physical properties, surface, and interface structures of the devices [20, 21]. As a new kind of metal film, Cu foil is considered as a potential core energy converter of next-generation exploding foil detonators. Although, Cu foils have attracted much attention in the fields of fuse, initiators, and pyrotechnics, unfortunately, the influence of the micromorphology and grain size of Cu foils on the velocity and morphology of the flyer has not been reported [22; 23; 24; 25]. However, systematically studying the effect of different characteristics of the Cu foil on the velocity of the flyer is of great significance.  
In this paper, the flyer velocity of Cu foils with different micromorphologies and grain sizes was studied during an electric explosion. The Cu foils with different parameters were prepared by the physical vapor deposition sputtering method. In addition, the morphology of the flyer was observed and collected. The influence of the micromorphology and grain size of the Cu foil on the flyer velocity and flyer morphology was investigated. This study will provide the technical support and theoretical basis for the preparation of Cu foil and for the reliability of exploding foil detonators.
## 3 Results and Analysis of Influencing Factors
### The Influence of Helical Loop Position  
The position of the helical loop antenna has a certain degree of uncertainty, and we need to investigate its relationship with signal transmission. By calculating the amplitude of the received magnetic field and the signal attenuation, it is found that the length of the drill string below the helical loop has a significant impact on signal reception as shown in Figure 13. Specifically, when the lengths of the drill string below the helical loop are 1 m, 5 m, and 10 m, respectively, the amplitude of the received signal at the same transmission distance shows an increasing trend. Notably, when the length of the drill string is increased to 10 m, the amplitude of the received signal reaches its maximum. It is important to note that when the helical loop is moved further up, the amplitude of the received signal no longer changes significantly.  
The result of this study suggests that increasing the length of the drill string within a certain range below the helical loop has a positive effect on signal reception. Therefore, in practical applications, to optimize the transmission and reception quality of the signal, it is recommended to set the length of the drill string below the helical loop to more than 10 m.
# Mechanical Properties and Microstructure of Polyvinyl Alcohol (PVA) Modified Cement Mortar
## 2 The Experiment
### Testing Methods  
The flow table test was carried out on the freshly prepared mortars as described by GB/T2419-2005 [24]. The jumping table beats 25 times in 15 s and measures the average diameter of the fresh mortar on two mutually perpendicular sides.  
The hardened density of the specimens was determined by using a water displacement method according to GB/T 11970-1997 [25].  
The capillary water absorption test on cement mortar was conducted after 28-day standard curing and determined according to DIN 52617 [26]. Fifteen samples of size \(40\times 40\times 80\) mm\({}^{3}\) were adopted in this test, and the surface of samples was wax-sealed, and then the molded surface was immersed in water, the distance between the height of the water surface and the bottom edge of the test piece was 5 mm, the schematic diagram is shown in Figure 3. The results are the average values of three specimens.  
An electronic universal testing machine (CMT-5105, China) was used to measure flexural strength and compression strength of the composites (three samples of size \(40\times 40\times 160\) mm\({}^{3}\) were adopted in this test). The flexural strength was tested at 3 days, 7 days, 14 days, and 28 days using a three-point method in accordance with GB/T 17671-1999 [27]. The broken pieces (portions of the prisms broken in the flexural strength test) were used to determine the cube compressive strength of the mortar samples in accordance with GB/T 17671-1999 [27].  
Differential thermal analysis was using a Shimadzu DSC 50 thermal analyzer at a heating rate of 20 \({}^{\circ}\)C/min. The samples chamber was purged with nitrogen at a flow rate of 40 cc/min.  
FT-IR spectra were carried out using a MAUNA-IR 750 spectrometer manufactured by Nikolai, USA. Powdered samples were mixed with KBr and pressed into pellets. The analyses were carried out in the frequency range of 500-4000 cm\({}^{-1}\).  
Figure 3: Capillary water absorption test schematic diagram (**a**) and measured diagram (**b**).  
Figure 2: Illustration of the PVA modified cement mortar fabrication process.  
The microstructures of the cement mortar were observed using a scanning electron microscope (SEM, SU3500) at an accelerating voltage of 10 kV. The sample was coated with a thin layer of gold before observation.
# Analysis and Research on Secondary LT Coding Anti-Eavesdropping Scheme Based on LT Code Degree-1
## 4 Simulation Results and Discussion
### Eve Untranslated Rate and Erase Channel Relationship  
The scheme of this paper is compared with LT codes, in the literature [21, 22], respectively, to observe the change in the eavesdropper \(P_{\text{{\rm{rev\_undecode}}}}\) under different schemes.  
1. Comparison of the effect of simultaneous changes in the main channel and the eavesdropping channel on the eavesdropper untranslated probability.  
Compare the change in the eavesdropper \(P_{\text{{\rm{rev\_undecode}}}}\) under different schemes when \(P_{AB}=P_{AE}\) is increased simultaneously.  
From the experimental results in Figure 4, it can be seen that the probability of deletion in the channel is smaller as \(P_{AB}=P_{AE}\) increases, and all four schemes increase with \(P_{AB}=P_{AE}\). When the probability of deletion in the channel then reaches a certain value, the \(P_{\text{{\rm{rev\_undecode}}}}\) of the four schemes begins to have a decreasing trend. When \(P_{AB}=P_{AE}>0.18\), the \(P_{\text{{\rm{rev\_undecode}}}}\) of this paper's scheme is larger than in the literature [21] and LT codes, but smaller than the literature [21].  
2. Comparison of the effect of the main channel change for the eavesdropper untranslated probability.  
When \(P_{AE}=0.3\), \(P_{AB}\) increases, comparing the change in the eavesdropper \(P_{\text{{\rm{rev\_undecode}}}}\) under different schemes.  
As can be seen from the experimental results in Figure 5, all four schemes decrease with increasing \(P_{AB}\). The \(P_{\text{{\rm{rev\_undecode}}}}\) of the scheme in this paper is greater than the LT codes. Compared with the other three schemes, \(P_{AB}\leq 0.28\) and the \(P_{\text{{\rm{rev\_undecode}}}}\) of this paper is smaller than the literature [21, 22]; at \(0.28<P_{AB}<0.32\), the \(P_{\text{{\rm{rev\_undecode}}}}\) of this  
Figure 4: The effect of changes in the main channel and the eavesdropping channel on \(P_{\text{{\rm{rev\_undecode}}}}\).  
Figure 3: Effect of \(P_{AB}\) variation on the number of encoded symbols sent by the source.  
for decoding also increases substantially, as can be seen in Figure 3. Double LT requires a relatively low number and complexity of encoded symbols to be sent by the source for decoding since only degree-1 symbols are encoded for the second time. Compared with [21; 22] schemes, although Eve's \(P_{\text{eve\_undecode}}\) is not the highest, when the eavesdropping channel deletion probability is low and the eavesdropping channel is better than the main channel, then the double LT scheme can enable Eve to achieve a high untranslated rate. Therefore, this paper's scheme, double LT, also has a high application value.
## 4 Discussion
### The Enzyme Activity as Affected by Soil Horizons and Microsites
In mineral soils though (AB or B horizon), numerous enzymes (AG, CBH, XYL, POX, PER, and NAG) exhibited higher activity when normalized by unit mass of SOC or MBC in the drained wetland compared to the natural wetland, which is more consistent with previous findings of the positive effects of drainage on decomposition. This may be driven by several factors: (1) the positive effects of a lower water table and increased soil aeration on enzyme activity at depth; (2) greater supply of root-derived organic C from deep rooted pines to microbes in the subsurface soil horizons thereby enhancing enzyme activities targeting organic C and N compounds with faster turnover time (AG, CBH, and XYL) [53; 60], and slower turnover time (POX and PER) [61]; and (3) higher pH in the AB and B mineral soil horizons (pH 5.4) of the drained wetland compared to that of the natural wetland (pH 4.8) [16] enhancing microbial enzyme activity [49]. Indeed, we found that enzyme activity tended to be positively correlated with pH when normalized per unit mass of SOC or MBC, particularly for the drained wetland. In support of higher microbial activity in mineral soils of the drained wetland, previous work at our sites showed that SOC in the mineral soil horizons of the drained forested wetland was enriched in \({}^{13}\)C compared to the natural wetland [16], suggesting that this C has been subjected to a greater degree of microbial degradation. While enzyme rates normalized per unit mass of SOC and/or MBC showed significant differences in organic and mineral soil horizons between the natural wetland and the drained wetland, enzyme activity rates normalized by soil weight showed few differences between sites. Estimating specific enzyme activity rates (either per unit mass of SOC or MBC) has been shown to be more sensitive to management than those expressed per dry soil weight [33; 35]. Our study also found that C-degrading enzyme activities normalized per unit mass of SOC and MBC were more sensitive to drainage and soil depth compared to when normalized by soil weight. For enzyme activity normalized by SOC or MBC, enzymes targeting C compounds with fast (AG and BG) and slow (PER) turnover rates tended to be higher in the Oi and Oa organic soil horizons in the natural wetland compared to the drained wetland. This pattern likely relates to the presence of plant litter in a less decomposed state [16], and therefore containing greater amounts of glucosic and cellulosic substrates compared to SOC in a more decomposed state [62]. Alternatively, the N degrading enzyme NAG was higher in the Oi horizons of the drained wetland compared to the natural wetland, which may reflect the need of microbes to acquire more N from N-poor pine litter compared to more N-rich hardwood litter [63; 64; 65].
# Design of Time-Synchronized Switch Based on Zynq
## 2 WR Technology
### Precision Clock Protocol (PTP)  
PTP is a high-precision time synchronization protocol based on the IEEE 1588 standard, designed to provide solutions for applications that require synchronization at the sub-microsecond level. Compared to the traditional Network Time Protocol (NTP), the main advantage of PTP lies in its ability to achieve higher precision in time synchronization. PTP achieves nanosecond-level time precision in wired networks by generating timestamps at the hardware level, thereby eliminating delays and inaccuracies introduced by the operating system and software processing [19]. This high-precision synchronization capability makes PTP particularly suitable for fields with extremely strict time requirements, such  
Figure 1: Standard Ethernet and synchronous Ethernet.  
as industrial automation, power systems, and financial market trading. In addition, PTP employs a master-slave structure for clock synchronization in the network [20; 21]. The master clock is responsible for transmitting time information to the slave clocks by continuously exchanging message packets that contain timestamps of the sent and received times. The slave clocks then calculate the time deviation based on the synchronization algorithm and perform self-adjustments to achieve synchronization with the master clock. The synchronization process of PTP is illustrated in Figure 2.  
(1) At time \(t_{1}\), the master clock sends a Sync message, placing the timestamp information in the Follow_Up message.  
(2) At time \(t_{2}\), the slave clock receives the message and obtains the timestamp from time \(t_{1}\).  
(3) At time \(t_{3}\), the slave clock sends a Delay_Req message.  
(4) At time \(t_{4}\), the master clock receives the message and then sends a Delay_Resp message. The slave clock records the four timestamps.  
According to the PTP, the one-way transmission delay (\(\delta_{MS}\)) and the offset between the master and slave clocks (\(offset_{MS}\)) can be calculated, assuming that the round-trip delay of the messages between the master and slave clocks is symmetrical, as shown in Formulas (1) [9] and (2) [22].  
\[\delta_{MS}=\frac{t_{4}-t_{3}+t_{2}-t_{1}}{2} \tag{1}\]  
\[offset_{MS}=t_{2}-t_{1}+\delta_{MS} \tag{2}\]
## 5 Case Studies, Including Impact on the Ecosystem
### Development of Freshwater Systems  
Nowadays, artificial reefs are commonly used in warm, salty waters. The benefits of their use include new habitats for organisms, from sessile forms to fish, protection of the shoreline, reduction in the effects of anthropogenic impacts by increasing spatial complexity, and development of tourism [1,8,92]. Artificial reefs mainly act at a local scale, acting as a refuge in the system and increasing spatial heterogeneity in the reservoir [4,8].  
In this case, the use of these structures in inland reservoirs becomes particularly important. Despite the high demand, few studies have been conducted on the use of artificial reefs in freshwater lakes [3,93]--Table 1. Among them, there is a lack of additive manufacturing applications for this type of water.  
The analysis of the research conducted to date, presented in Table 1, shows that the currently used solutions for artificial reefs in freshwater reservoirs are characterized by a high degree of primitivism, both in terms of the materials used and the technologies applied. There is a lack of previous research connected with the usage of 3D printing technologies for designing freshwater artificial reefs. Meanwhile, the need to optimize this kind of construction for freshwater ecosystems seems to be even larger than for marine ones.  
Previous studies have shown the important role of microhabitats in the lifecycle of lake fauna, with particular emphasis on selected freshwater fish species. The artificial structures in these studies supported freshwater species, helping to reduce the negative impacts of environmental pressures and playing a key role in the successful colonization of these areas by several species. Additionally, these structures promoted the protection of juveniles, reducing the effectiveness of predators as the availability of shelters increased. The studies show that artificial reefs in freshwater can significantly support the maintenance of biodiversity by increasing the spatial complexity of the environment [8].
## 3 Measurement Setup
### Measurement Scenarios  
Two primary measurement scenarios were selected, which can be described as a flat concrete road and flat grass. The flat concrete road scenario was a straight cement concrete road, which was fairly flat and wide. There were several trees and buildings at the end of the road, but they were rather far away from the measurement field. The flat grass scenario was a nearly flat large lawn, with sparsely scattered bushes and trees nearby. Moreover, two derived scenarios were measured to further investigate the effect of other terrain factors. In the \"undulating grass\" scenario, the surrounding environment was similar to that of \"flat grass\", except that the grass was on wavy terrain. Under this scenario, the transmitter and receiver could only have non-line-of-sight (NLOS) communication unless they were adjacent to each other. The \"flat grass with obstacles\" scenario was flat grass with bushes between two nodes. Figure 1 shows the four scenarios.
# A Low-Power ECG Processor ASIC Based on an Artificial Neural Network for Arrhythmia Detection
## 5 Conclusions  
This paper proposes an ECG processor ASIC based on ANN, which integrates heart rate monitoring and arrhythmia detection functions. Thanks to the proposed hardware efficient R-peak detector and the lightweight classification engine based on feedforward ANN, this design achieves a prediction accuracy of 96.69% with only 4.5 kB of memory overhead. The proposed algorithm model with low computation complexity, combined with the hardware reuse strategy applied to the ECG pre-processing engine and classification engine, significantly reduces the chip area overhead and improves energy efficiency. By utilizing a configurable parameter buffer, this ASIC can easily update the NN model to adapt to application differences. The implementation results indicate that the proposed design has a comparable performance with state-of-the-art ECG processors, achieving a good compromise between performance and cost. Thus, it can be stated that this ECG processor can be integrated in ultralow power healthcare devices for detecting arrhythmia efficiently.  
Conceptualization, C.Z. and X.W.; methodology, C.Z.; software, C.Z. and Y.G.; validation, C.Z., J.C. and Y.G.; formal analysis, C.Z.; investigation, J.C.; resources, J.C. and X.W.; data curation, C.Z. and Y.G.; writing--original draft preparation, C.Z.; writing--review and editing, X.W. and X.Z.; visualization, C.Z.; supervision, Q.L. and X.W.; project administration, Q.L.; funding acquisition, J.C., X.W. and X.Z. All authors have read and agreed to the published version of the manuscript.  
This research was supported by a fundamental research grant from the Shenzhen Science and Technology Innovation Commission, grant number KQTD20200820113105004.  
Not applicable.  
The authors declare no conflict of interest.
## 4 Network Communication
### Trends and Challenges  
There are still many issues that need to be further studied in BSN communication. Minimizing power consumption as well as ensuring quality of communication links is a long-term objective, and energy-efficient MAC and routing protocol remain to be developed [54]. IEEE 802.15.6 has defined many BSN band standards, so developing many upper layer protocols which support a variety of physical layer channel is an inevitable trend [35]. Besides, in some medical applications, the key information should be sent out in time when a medical emergency occurs, but BSN data correlations often cause network congestion which makes network protocol design that supports emergency communication become a major challenge in further BSN development. Finally, the deployment of BSNd is different from that of traditional sensor network applications. They should be able to deal with topology changes and adapt to conversion between in-body and on-body. Besides, nodes should be ready to join or withdraw from network, so node context awareness and network configuration is also a trend in future studies [34].  
There are still many challenges in the BSN network communication research field. First of all, experimental channel models which are significantly simplified fail to take full account of human motion and environmental changes. At the same time, as personal safety issues it involved, it is really difficult to apply implantable or wearable devices to applications. There are still many factors which can affect channel characteristics, such as the electrical characteristics of the human body, human mobility, and energy restrictions. Accurate description of channel characteristics and channel prediction are very difficult too. Secondly, for MAC layer protocols in BSNs, TDMA is obviously more suitable than CSMA/CA [31], but the time synchronization mechanism is still a weakness of TDMA. Thirdly, because BSNd have the features of small scale and low-power transmission, a simple human body action will cause a relatively big change of topology with old connections being disconnected or new connections built, which is a challenge for the routing protocol designer. Moreover, although cryptography technology can achieve better security performance, due to limited sensor resources and the fact that pre-deployed secret keys are hard to replace, many existing key management and distribution algorithms are not suitable for BSNs. Therefore, designing efficient key management, distribution and agreement schemes in BSNs is still challenging [97]. Finally, the trade-off between energy efficiency and the complexity of fast routing algorithms also needs to be figured out [35]. All of above are big challenges for BSN topology design.