esa-sceva/satcom-chunk-collection huggingface dataset:
# Design of a Digital Array Signal Processing System with Full Array Element
## 2 System Architectural Design
### System Hardware Architecture Design
#### 2.1.2 Hardware Design of the Transceiver Module  
The hardware architecture of the transceiver module, which integrates 2 RFSoC chips with 16 transmit channels and 16 receive channels, is shown in Figure 2.  
Figure 1: System hardware architecture.  
Figure 2: Hardware architecture of transceiver module.  
The RFSoC is an on-chip RF system developed by XILINX using 16 nm technology [13]. It integrates high-performance ADCs and DACs in the SoC, replaces discrete data converters with integrated direct RF sampling technology, and integrates high-speed data links on-chip, enabling a 50-75% reduction in power consumption and package size. Its 10 GSPS sampling rate DAC and 5 GSPS sampling rate ADC can realize broadband signal acquisition and transmission, and its 0-6 GHz wide analog bandwidth, on-chip digital up converter (DUC), and on-chip digital down converter (DDC) can realize direct RF input/output or HIF input/output [14]. Each RFSoC is connected to two DDR memory chips that can realize fast caching of large-capacity data. To achieve high-speed synchronization between the chips, the transceiver module uses a low-skew and low-jitter LMK04828 clock network to simultaneously provide clocks for both RFSoCs, providing clock synchronization as the hardware basis for the synchronization work between the channels of the whole system.  
The actual transceiver module is shown in Figure 3.  
The two RFSoC circuits use the same PCB layout and wiring, and the external interface of the IF signal uses arc lines, which can better ensure multi-channel consistency and isolation.  
The isolation between channels is simulated, and the isolations between ADC channels, DAC channels and clocks, and DAC channels and clocks are tested separately. The simulation results show that isolation between channels is better than \(-\)60 dB in the frequency range 0-10 GHz (Figure 4).  
The results of simulating and testing amplitude and phase consistency between ADC and DAC channels, respectively, are shown in Figure 5. The simulation input/output signal is a single frequency signal at 3 GHz. It can be seen from Figure 5 that the amplitude consistency of each channel is less than \(\pm\)0.3 V, and the time delay between channels is less than \(\pm\)5 ps.  
Figure 3: Physical receiving and sending modules.
## 3 Results and Discussion
### Analysis of Molecular Structural Characteristics  
#### 3.3.1 Molecular Weight  
The time of chitosan solution flowing through capillary tube was measured by Ubbelohde viscometer at 25 \(\pm\) 0.1 \({}^{\circ}\)C. According to the flow time, the specific viscosity (n\({}_{\text{ISP}}\)) of chitosan solution was calculated, and then the specific viscosity (n\({}_{\text{ISP}}\)/C) was obtained, the results were shown in Table 2. The relationship between the specific viscosity (n\({}_{\text{ISP}}\)) and the concentration (C) of three kinds of chitosan in 0.2 M sodium chloride/0.1 M acetic acid was shown in Figure 2. Under the same solvent and temperature, the intercept [n], which can directly show the difference of M\({}_{\text{W}}\), was obtained by extrapolating the straight line to intersect with the ordinate. The viscosity average M\({}_{\text{W}}\) obtained as a result of extrapolation according to the Mark-Houwink equation ([n] = K(M\({}_{\text{W}}\))\({}^{\alpha}\)) were shown in Table 3, and the data was consistent with its apparent viscosity. The highest M\({}_{\text{W}}\) of CS was 377.1 kDa, followed by CSC (249.8 kDa) and CSS (22.5 kDa). M\({}_{\text{W}}\) has an important impact on chitosan physiochemical properties and biological function. Chitosan M\({}_{\text{W}}\) can affect the viscosity of chitosan solution [35], the DD lower and the M\({}_{\text{W}}\) higher, the chitosan solution viscosity stronger. Chitosan with M\({}_{\text{W}}\) of 10 kDa has many excellent physiological functions, such as inhibiting the growth of tumor cells, reducing cholesterol, enhancing immunity [34]. The difference of M\({}_{\text{W}}\) of the three tested chitosan samples is due to the different sources of raw materials and treatment methods. It is obvious that high temperature and high pressure flash explosion is a controllable method to obtain low M\({}_{\text{W}}\) chitosan.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**C(g/100 mL)**} & \multicolumn{2}{c}{**CS**} & \multicolumn{2}{c}{**CSC**} & \multicolumn{2}{c}{**CSS**} \\ \cline{2-7}  & \(\mathbf{n_{\text{ISP}}}\) & \(\mathbf{n_{\text{ISP}}/C}\) & \(\mathbf{n_{\text{ISP}}}\) & \(\mathbf{n_{\text{ISP}}/C}\) & \(\mathbf{n_{\text{ISP}}}\) & \(\mathbf{n_{\text{ISP}}/C}\) \\ \hline
0.20 & 0.93 & 463.31 & 1.43 & 713.03 & 0.41 & 204.58 \\
0.13 & 0.55 & 413.22 & 0.82 & 616.22 & 0.21 & 153.86 \\
0.10 & 0.39 & 389.10 & 0.55 & 546.07 & 0.13 & 130.44 \\
0.07 & 0.24 & 367.25 & 0.33 & 490.28 & 0.07 & 105.21 \\
0.05 & 0.18 & 359.34 & 0.22 & 449.31 & 0.05 & 94.01 \\ \hline \end{tabular}
\end{table}
Table 2: Data of chitosan viscosity measurement.  
Figure 2: \(\eta_{\text{ISP}}\)/C-C diagram of chitosan.
# Mathematical Modeling of Screw Press Configuration for Processing Safflower Oil
## 2 Materials and Methods
### Description of the Press Equipment  
The oil press RAWMID Dream Modern was used to press safflower, which comprises a frame, pressing screw, cone-shaped pressing cage, pressure-regulating mechanism in the pressing chamber, and a loading hopper (Figures 1 and 2).  
Figure 1: Structural scheme of the press for safflower oil production. 1—frame; 2—screw; 3—pressing cage; 4—pressure regulator mechanism; 5—loading hopper.  
The screw is made of stainless steel with a total length of 0.20 m and a diameter of 0.16 m. The screw spiral has a constant spacing of 0.02 m, the coils have a constant thickness of 0.008 m, and the depth of the spacing is equal to a constant value (Figure 3).  
The design of the operating device is made with a regulating mechanism, which ensures optimum pressure delivery to each turn of the screw. In this mechanism, the screw press is designed as a back-and-forth motion. Based on the cone shape of the outer and inner diameters of the screw shaft, the reciprocating movement of the screw narrows parts of the gap between the pressing cage and the pressing screw. This design creates a condition for narrowing the section of each turn and at the same time provides a two-way side pressure on the raw material.  
The pressure control mechanism consists of a spring, a locking nut, a check nut, two sliding lugs and washers, and a rubber sealing ring (Figure 4).  
Figure 4: Pressure control mechanism: (**a**) pressure control spring; (**b**) lock nut; (**c**) sliding tip; (**d**) control nut; (**e**) washer; and (**f**) sealing ring.  
Figure 3: Pressing screw.  
The press works as follows: Peeled safflower seeds from the feed hopper enter the pressing chamber. The pressure rises as a result of the gradual reduction of the inner diameter of the pressing screw on the safflower. Oil is extracted through the cone-shaped openings of the pressing cage. The pressure required for oil separation is regulated on the basis of a specially designed pressure control mechanism.  
The following dependencies were investigated during the improvement of the pressing process:  
* Study of the effect of changing speeds (\(\omega\) = 5.2 rad/s; \(\omega\) = 6.2 rad/s; \(\omega\) = 6.8 rad/s; and \(\omega\) = 7.3 rad/s) on the duration of pressing;
* Study of the effect of changing the initial and final diaphragm gap between the screw and the pressing cage (\(\delta=1\times 10^{-3}\) m; \(\delta=3\times 10^{-3}\) m; \(\delta=5\times 10^{-3}\) m; and \(\delta=7\times 10^{-3}\) m) on the pressing pressure.
# Cooperative Downloading for LEO Satellite Networks: A DRL-Based Approach
## 3 Deep-Reinforcement-Learning-Based Cooperative Downloading Scheme
### MDP Formulation
#### 3.2.3 Reward  
According to the current state and the set of selected actions, the agent controls LEO satellites and receives an instantaneous reward. To obtain more rewards, we need to maximize the total amount of downloaded data during an episode. Let \(n_{l}^{D}(t)\) be the amount of downloaded data of satellite \(l\in\mathrm{L}\) at time slot \(t\). We assume that each satellite can transmit one data unit at each time slot. To transmit data to GS, satellite \(l\) has to have sensory data and its selected action needs to indicate one of the adjacent GSs. Therefore, \(n_{l}^{D}(t)\) can be expressed as  
\[n_{l}^{D}(t)=\delta[a_{l}(t)=k,A_{lk}(t)=1,\text{ and }m_{l}(t)\geq 1],k\in \mathrm{K}, \tag{5}\]where \(\delta[\cdot]\) denotes the delta function that returns 1 if the conditions in brackets are true; otherwise, it returns 0.  
Meanwhile, we need to avoid meaningless data exchange between satellites, which also affects the reward. Let \(n_{l}^{O}(t)\) be the amount of offloaded data of satellite \(l\in\mathrm{L}\) at time slot \(t\). Satellite \(l\) can offload data only when it has data and its selected action refers to one of the adjacent satellites. Therefore, \(n_{l}^{O}(t)\) can be expressed as  
\[n_{l}^{O}(t)=\delta[a_{l}(t)=l^{\prime},A_{ll^{\prime}}(t)=1,\text{ and }m_{l}(t)\geq 1],l^{\prime}\in \mathrm{L}\backslash\{l\}. \tag{6}\]  
To summarize, the instantaneous reward \(r_{t}{:=}r(s_{t},a_{t})\) at time slot \(t\) can be defined as  
\[r_{t}=\sum_{l\in\mathrm{L}}\{n_{l}^{D}(t)+\lambda\cdot n_{l}^{O}(t)\}, \tag{7}\]  
where \(\lambda{\leq}0\) denotes the weight of the offloading data.
# Hiding Stealth Optical CDMA Signals in Public BPSK Channels for Optical Wireless Communication
## 5 Conclusions  
The present study is preliminary research investigating the probability of applying other types of OCDMA in optical steganography. We have proposed a novel optical steganography transmission technique that conceals SPC-OCDMA signals in a public BPSK channel. A Walsh-Hadamard code is employed as a signature code for assigning a vertically or horizontally linear SOP to each specified wavelength. A CFBG provides considerable dispersion in a small size. The scale of the device is approximately 2000 times smaller compared with a single-mode fiber providing the same dispersion. Herein, the CFBG provides a dispersion of 1600 ps/nm and transforms the stealth signal into a noise-like signal so that it can be buried in the public channel.  
The results indicate that the security of the system is enhanced because no one except the intended recipient knows the existence of the stealth signal in either the spectral or time domain. The power of the public noise is proportional to the security of the system and inversely proportional to the performance of the stealth channel. That is, with larger public noise, the stealth signal can be hidden more efficiently but the BER is higher. We propose 1-Gbps stealth transmission with a FSO link.  
Furthermore, the pair of CFBGs adds another dimension to the key space of the stealth channel. An eavesdropper needs the correct dispersion compensator to detect the stealth signal. Even if the correct dispersion is obtained by using a tunable dispersion compensator, the eavesdropper cannot recover the data without the corresponding receiver.  
The results show that the stealth signal is favorably hidden in the public channel and that our proposed optical steganography system provides high security when the average power of the stealth signal, public signal, and public noise are \(-5\), \(0\), and \(-3\) dBm, respectively. A range of FSO transmission of up to 380 m can be achieved at a BER of \(1.62\times 10^{-9}\) under a clear sky and 320 m at a BER of \(2.4\times 10^{-9}\) on a rainy day. Since the system configuration is done in the study, the proposed stealth communication system can furthermore be used to investigate the hiding capacity, distortion measurement and impact on network performance in the future work.  
[PERSON] performed the simulations and algorithm analysis, and contributed to manuscript writing. [PERSON] and [PERSON] contributed in conceiving the experiment and the corresponding data analysis. All authors contributed to writing the paper.  
This research received no external funding.  
This study was supported in part by the Ministry of Science and Technology MOST 106-2622-E-150-018-CC3 and National Formosa University 106B096.  
The authors declare no conflict of interest.
# Efficient Capture of Sr\({}^{2+}\) Ions by a Layered Potassium Neodymium Phosphate
## 3 Results and Discussion
### Adsorption Mechanism Study  
The powder x-ray diffraction (PXRD) patterns of K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\) and its Sr\({}^{2+}\) adsorption product (K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\)-Sr) are shown in Figure 4a. By comparing the simulated pattern from K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\) single crystal diffraction data with the measured one of K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\) and K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\)-Sr, it was confirmed that the sample of K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\) was pure and K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\)-Sr maintained the layered structure of the pristine. The color of the pristine K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\) powder was light purple (Figure 4b(I)), while that of K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\)-Sr powder was white (Figure 4b(II), photos taken under the same light intensity). The UV-Vis spectra of K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\) and K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\)-Sr are shown in Figure S2. The band characteristics of K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\) are complex. The absorption peaks of K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\) are all specially owned to the f-f transition of 4f electrons of Nd\({}^{3+}\) ions from \({}^{4}\)I\({}_{9/2}\) ground level to excitation level [45; 66]. After adsorbing Sr\({}^{2+}\), no new absorption band appeared. This shows that Sr\({}^{2+}\) did not change the original coordination environment of Nd\({}^{3+}\) ions in the anion layer after adsorption. Energy dispersive X-ray spectroscopy (EDS) analysis of the adsorption product K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\)-Sr showed that Sr\({}^{2+}\) ions entered the structure of K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\), but there still existed the potassium element (Figure S3). This proves that K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\) has the ability to adsorb Sr\({}^{2+}\) in the solutions. By comparing the elemental distribution of K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\) and K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\)-Sr (Figure 4c), it was confirmed that the strontium was uniformly distributed on the K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\)-Sr sample. Scanning electron microscopy (SEM) images showed that the surfaces of the K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\)-Sr were no longer smooth, but they still retained the grain morphology (Figure S4). These prove that Sr\({}^{2+}\) ions are indeed successfully adsorbed by K\({}_{3}\)Nd(PO\({}_{4}\))\({}_{2}\).
## 8 Implementation and Performance Evaluation
### Implementation Notes and Challenges  
In our experiments, we used a custom ECC module written in C, adapted from the TinyECC codebase. As standard ECC libraries do not natively support point halving in \(\mathbb{F}_{2^{n}}\), we implemented it using the inverse of the doubling procedure over binary Koblitz curves.  
The point halving procedure implemented in our module is based on operations over binary fields \(\mathbb{F}_{2^{n}}\) and follows these main steps:  
* Take as input the point \(Q=(x_{Q},y_{Q})\) such that \(Q=2P\).
* Compute the slope \(\lambda\) as \(\lambda=x_{P}+y_{Q}/x_{Q}\).
* Derive the x-coordinate of \(P\) as \(x_{P}=\sqrt{x_{Q}+\lambda^{2}+a}\).
* Compute the y-coordinate as \(y_{P}=x_{P}\cdot(\lambda+1)\).
* Return the point \(P=(x_{P},y_{P})\).  
Implementing square roots and divisions in \(\mathbb{F}_{2^{n}}\) over constrained devices posed challenges due to limited memory and instruction sets. We used precomputed lookup tables for square roots and optimized division via shift-and-subtract loops.  
On the ATmega328P, we faced register pressure and had to inline some routines to reduce stack usage. On the Cortex-M4, code was optimized for constant-time execution, disabling hardware floating-point units to preserve deterministic timing.  
We ensured constant-time traversal of the DBC scalar representation by computing and executing a predetermined sequence of additions and halvings with no conditional branching. While randomized scalar blinding was not included in this version, our method is compatible with such techniques, and future work may explore their integration for increased side-channel resistance.  
Although our protocol is identity-based and does not rely on certificate chains, we briefly referenced X.509 and key management schemes to emphasize compatibility with hybrid environments where trust anchors and revocation strategies coexist. A full integration study is outside the scope of this work.  
\begin{table}
\begin{tabular}{l c c} \hline
**Platform** & **Original GN-AK** & **Improved GN-AK** \\ \hline ATmega328P & 8523 & 6411 \\ STM32F411 RE & 2181 & 1653 \\ \hline \end{tabular}
\end{table}
Table 1: Execution Time Comparison (\(\mu\)s).  
\begin{table}
\begin{tabular}{l c c} \hline
**Platform** & **Original GN-AK** & **Improved GN-AK** \\ \hline ATmega328P & 34.1 & 25.6 \\ STM32F411 RE & 19.6 & 14.2 \\ \hline \end{tabular}
\end{table}
Table 2: Estimated Energy Consumption (m)).
## 5 Conclusions  
An FSM with an 80 mm diameter mirror supported by a compact and simple magnetic suspension, allowing two-DOF lateral control of the mirror, and driven by four compact VCMs, allowing control in the tip-tilt and axial directions, was proposed, fabricated, and evaluated. The mirror was a dummy mirror made of aluminum alloy. Rapid positioning of the mirror was achieved by controlling the VCMs with simple PID compensators. The VCMs, which have inner and outer coils, and use the magnetic flux from permanent magnet, were designed and tested. The driving ranges of the mirror were \(\pm\)20 mrad and \(\pm\)500 \(\upmu\)m in the tip-tilt and axial directions, respectively. No large interference nor structural resonances, that would compromise the stability of the mirror, were not found. Servo bandwidths of more than 1 kHz and 200 Hz in the tip-tilt and axial directions of the mirror, respectively, were achieved. These ranges of movement and bandwidths satisfy the design targets for the mirror to be used on observation satellites.  
A comparative experiment between the magnetically suspended mirror and a gimbal guided mirrors showed the FSM dynamics using the magnetic suspension to be much simpler than those for the gimbal mechanism; thus, it was possible to show that the bandwidth could be easily widened, and that the axial positioning for focus correction could be implemented.  
In future work, in order to apply this method to an actual observation satellite, we need to develop a compact launch lock mechanism to withstand the vibration encountered during lunch and to have built-in displacement sensors for the FSM. Furthermore, in order to withstand long-time use in space, optimization of the material and structures, and durability and reliability tests under various conditions are necessary.  
Conceptualization, T.S. and K.K.; methodology, T.S. and D.S.; software, D.S.; validation, T.S. and K.F.; formal analysis, T.S. and D.S.; investigation, D.S.; resources, K.F.; data curation, D.S. and K.F.; writing--original draft preparation, T.S.; writing--review and editing, T.S.; visualization, T.S. and D.S.; supervision, T.S.; project administration, T.S.; funding acquisition, T.S. and K.K. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The authors declare no conflict of interest.  
Figure 14: Reference characteristic of the FSM using gimbal mechanism: (**a**) Bode plots in the \(\theta_{x}\) and \(\theta_{y}\) directions; (**b**) simulated vibration modes near the peak frequencies.
# An Efficient Internet-Wide Scan Approach Based on Location Awareness
## 5 Experiments
### Experimental Setup  
In our lab, we use global server resources deployed on AliCloud's international platform covering multiple countries and regions, totalling over 500 lightweight servers, each of  
Figure 4: Load-balancing process between scanner clusters.  
Figure 5: The process of executing a task by scanners inside a cluster.  
which can maintain direct communication with each other. These servers cover more than 50 countries with well-developed networks, such as the United States, China, the United Kingdom, France, Japan, and so on. Each country covers 5 major cities, with 2 servers in each city. Considering the variability of different geographical regions, we have chosen several countries with large geographical differences as the scanning origins of our experiments, namely TH, JP, DE, US, and AU. These countries not only are geographically dispersed but also have large variations in terms of network infrastructures, bandwidths, and latencies. As mentioned in the previous section, we mainly use Nmap as the main research tool, and hence Nmap is chosen as the scanning tool. In the algorithm, it is mentioned that we need to geolocate IP addresses; therefore, in the scanning dataset, we use IP2 Location [19] as the IP geolocation database. In the execution part of the algorithm, it is divided into two parts in total; the first part is the pre-scanning procedure; therefore, we need to cluster the scanners of the five countries first and then select 30 network segments of each country from the IP2 Location database as the initial task. In Figure 5(a), we show part of the scanning data, with rows representing the target countries and columns representing the starting countries. Each value represents the average scanning time. In Figure 5(b), we show the storage structure of the list. The lighter colours are the target geographic locations, and the darker colours are the geographic locations where the scanners are located. When there is a task to be assigned, the programme will first look for the lighter-coloured location and then sequentially look for the darker-coloured location to find a scanner that can be assigned.  
Figure 6: Constructing the similarity matrix: (**a**) the average time for similarity matrix scanning; (**b**) storage structure of the similarity matrix. **Note**: In picture (**b**), the ’...’ in the target region indicates the name of the other target region omitted, in the origin region the horizontal ’...’ indicates the name of the omitted origin region in the queue, and the vertical ’...’ indicates the omitted queue.
## 2 Preliminaries  
### Gfdm  
GFDM is one of the modulation models intended for the next-generation communication systems. It contains blocks of subcarriers and subsymbols, i.e., time slots [23; 24]. The space of the subcarriers on GFDM is more substantial than OFDM. The GFDM signal is given as:  
\[\mathbf{x}_{n}=\sum_{m=0}^{M-1}\sum_{k=0}^{K-1}d^{(k,m)}\mathbf{h}(n-mK)e^{(j2 \pi\frac{k}{k}n)}, \tag{1}\]  
where \(K\) is the subcarriers and \(M\) is the subsymbols. \(d^{(k,m)}\) is the transmitted symbol on the \(k\)th and \(m\)th subcarrier and subsymbol, respectively. Then, the symbols are filtered with \(\mathbf{h}(n)\) filter which is \(K\times M\) length [25].