esa-sceva/satcom-chunk-collection huggingface dataset:
# Spintronic RF-Direct on-off Keying Modulation Using a Frequency Division Multiplex
## 3 Design of the Spin Modulator
### Biasing and Modulation on STNOs  
An oscillation signal is generated by the current flowing through the STNO. Current can be supplied via a current mirror circuit as a bias for a stable current supply. Figure 6 shows the schematic of biasing an STNO and modulating data through the current mirror circuit including the T-junction matching circuit on the two STNOs of the array structure.  
We designed a current mirror circuit as a circuit supplying current with two PMOS transistors (M1, M2, M4, and M5), as shown in Figure 6. The ratio of the transistor width for the current mirror circuit must be set at 1:8 to reduce the leakage current to 1/8 th of the current flowing through the STNO.  
The STNO is easily broken by the breakdown current, as the magnetic tunnel junction (MTJ) is operated with a tunneling effect in the inserted insulator as a non-magnetic layer. A variable resistor (VR1 or VR2) is added in the current mirror circuit to limit the current for safe operation together with R3 and R4. The value of VR1 or VR2 is set for the current flowing through STNO to flow as around 1.5 mA in this work.  
The supplied current drives the STNO to generate oscillation. We then modulate the STNO with the OOK method, where the current supplied from the current mirror circuit is  
Figure 5: Matching results of the T-junction matching circuit.  
Figure 6: The schematics of the biasing an STNO and modulating a data through the current mirror circuit including the T-junction matching circuit on the two STNOs of the array structure.  
switched on/off. This function is executed through a NMOS transistor (M3 or M6) switch that enables operation of the current mirror circuit.
## 7 Net Axial Stress  
The net axial stress at a length position, \(z\), is the sum of the bending stresses due to moments \(M_{x}=F_{y}(L-z)\) and \(M_{y}=F_{x}(L-z)\), taken from Equation (1a\(-\)c), added to the axial stress at that position induced by constraining all warping displacement at the fixed end (\(z=0\)). Bending stresses under \(M_{x}\) and \(M_{y}\) in Figure 7a are aligned with the length direction \(z\). Figure 7b shows how \(\sigma_{z}\) is distributed linearly over the section's depth \(d\), under \(M_{x}\). Under \(M_{y}\) a linear distribution in \(\sigma_{z}\) applies across the flange width, \(b\). Both distributions are zero, i.e.,' neutral' to stress at their intersections with centroidal co-ordinates \(x\) and \(y\).  
The signs of bending stresses \(\sigma_{z}\) in Equation (7) complies with a hogging moment producing tension (\(y\) positive) and sagging moment compression (\(y\) negative). Signs of \(\sigma_{z}\), denoting tension (\(+\)) and compression (\(-\)), are referred to the section's quadrants whose centroidal axes \(x\) and \(y\) carry hogging moments \(M_{x}\) and \(M_{y}\) as shown. Conveniently, here, forces \(F_{x}\) and \(F_{y}\) applied to G in negative \(x\) and \(y\) directions each produce hogging moments in the first quadrant, i.e., \(1(+,+)\). In the remaining quadrants, their respective signs are: \(2(+,-)\), \(3(-,-)\) and \(4(-,+)\).  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Point** & **1** & **2** & **3** & **4** & **5** & **6** & **7** \\ \hline \(D_{y}/d^{3}\) & 0 & \(8.88\times 10^{-4}\) & \(8.333\times 10^{-4}\) & 0 & \(-8.333\times 10^{-3}\) & \(-8.88\times 10^{-4}\) & 0 \\ \hline \(D_{x}/d^{3}\) & 0 & \(33.33\times 10^{-4}\) & \(41.7\times 10^{-4}\) & \(72.92\times 10^{-4}\) & \(41.7\times 10^{-4}\) & \(33.33\times 10^{-4}\) & 0 (check) \\ \hline \(\times I_{y}/I_{x}\) & 0 & \(2.311\times 10^{-4}\) & \(2.892\times 10^{-4}\) & \(5.056\times 10^{-4}\) & \(2.892\times 10^{-4}\) & \(2.311\times 10^{-4}\) & 0 \\ \hline \(\sum D/d^{3}\) & 0 & \(11.191\times 10^{-4}\) & \(11.225\times 10^{-4}\) & \(5.056\times 10^{-4}\) & \(-5.441\times 10^{-4}\) & \(-6.569\times 10^{-4}\) & 0 \\ \hline \(q_{x}+q_{y}\) & 0 & 5.4218 & 5.4383 & 2.4495 & \(-2.6361\) & \(-3.1826\) & 0 \\ \hline \(q_{T}\) & 0 & 1.23 & 1.23 & 0 & \(-1.23\) & \(-1.23\) & 0 (check) \\ \hline \(\sum q\) & 0 & 6.652 & 6.668 & 2.450 & \(-3.866\) & \(-4.413\) & 0 \\ \hline \(\tau=\sum q/t\) & 0 & 5.587 & 5.60 & 2.458 & \(-3.247\) & \(-2.707\) & 0 \\ \hline \end{tabular}
\end{table}
Table 6: Net shear flow \(\sum q\), (N/mm) for channel section C with transverse forces \(F_{x}=F_{x}=100\) N applied to centroid G.  
Figure 7: Channel (**a**) with linear distribution in (**b**) under bending stress under \(M_{x}\) and \(M_{y}\).
# Urban Seismic Networks: A Worldwide Review
## 2 USN Catalogue  
We collected information about 105 different USNs. The collection criteria were basically two: (i) the earthquake network should mainly cover an urbanized area (town, city, or metropolitan area) and (ii) it should have been active at least for some months. Moreover, measurements encompassing the systematic repositioning of sensors rather than their simultaneous recording as a proper network were excluded. We did not include deployments of sensors in different non-contiguous urban areas. Such situations do not describe independent and complete networks with characteristics that can be easily quantified (e.g., number of sensors or covered area). As an example, what are often referred as citizen-based or community-based networks usually show a patchy distribution over many different urban areas and even different countries [9; 10; 11].  
Several characteristics are reported in this review paper to characterize the purposes related to the deployment of each USN: the position, number of nodes, area covered, main objective, and secondary objectives (where indicated). Moreover, specific network-related characteristics such as the timing (start, duration, and end of recording), type of sensors, and transmission system were summarized.  
It is worth pointing out that all information was retrieved as-is from the listed references without making any critical interpretations of the details provided by the authors. All the desires information was retrieved from the paper(s) or websites describing the networks. Unfortunately, sometimes details about the data transmission were not reported (16% of the USNs). Furthermore, certain USNs evolved over time, in these cases, we report the most up-to-date information available.  
To provide a detailed framework of the USNs, general information, i.e., location, objectives, and sources, are reported in Table 1, whereas specific characteristics such as operating time, coverage, density, and technical features of the instruments are reported in Table 2. Moreover, in the following sub-paragraphs we describe and analyze each of these aspects characterizing the USNs.
## 4 Node Importance Evaluation Model
### Comprehensive Evaluation Based on the Variation Coefficient-VIKOR Method  
Multiple criteria decision-making (MCDM) is an important technique that presents a systematic approach to helping decision-makers in this field [48]. The MCDM method includes AHP, TOPSIS, VIKOR, and PROMETHEE, among others. Among these, the basic idea of the VIKOR method is to normalize the original data, construct the initial matrix, select the optimal and the worst solution in the whole solution set, and determine the comprehensive ranking results according to the distance between the optimal and the worst solution between different values, that is, the criterion that the optimal solution is the closest, and the worst solution is the furthest [49]. The method is often a compromise between the attributes so that the feasible solution can ensure the maximum benefit of the group but also take into account the individual loss, which can effectively deal with the problem of urban rail transit station importance based on the evaluation of a number of indicators and make full use of the original data in the calculation process. Therefore, the VIKOR method is selected in this paper for the comprehensive evaluation of station importance.  
However, the VIKOR method defaults to equal weighting of all evaluation indicators, which is not consistent with the actual situation. This paper adopted the coefficient of variation method, which is an objective weighting method, to enhance the VIKOR comprehensive evaluation method. The improved method evaluates the degree of the data dispersion of indicators as an assignment criterion, assigning higher weights to indicators with greater variation dispersion [38]. The specific evaluation process is as follows.
# On the Rate-Distortion Theory for Task-Specific Semantic Communication
## Appendix A Proof of Theorems 1 and 2  
To begin with, we note that the mutual information between two Gaussian distributions is independent of their means. Therefore, without loss of generality, we may assume that the recovery source \(\hat{S}\) and the semantic source \(S\) share the same mean. Specifically, we let \(\hat{S}\sim\mathcal{N}(0,\sigma^{2})\) for analytical convenience.  
We first discuss the case where the constraint on Wasserstein distance is not active, i.e.,  
\[d_{WD}(p_{S},p_{S})=(1-\sigma)^{2}<P. \tag{1}\]  
In this case, based on the Wyner-Ziv theorem, we have  
\[R_{\kappa}(D,P)=\frac{1}{2}\log\frac{1-\eta^{2}}{D}, \tag{2}\]  
with  
\[\sigma=1-D. \tag{3}\]  
Taking (3) back into (1), we have  
\[0\leq D<\sqrt{P}=D_{1}^{L}. \tag{4}\]  
When the constraint on Wasserstein distance is active, i.e.,  
\[d_{WD}(p_{S},p_{\hat{S}})=(1-\sigma)^{2}=P, \tag{5}\]  
we have  
\[\sigma=1-\sqrt{P}=\sigma_{1}. \tag{6}\]  
Then, define the following coding schemes  
\[(Y,S,\hat{S})=(\eta S^{\prime}+\sqrt{1-\eta^{2}}Y^{\prime},S^{\prime},bS^{ \prime}+\sqrt{1-b^{2}}\hat{S}^{\prime}), \tag{7}\]where \((Y^{\prime},S^{\prime},\hat{S}^{\prime})\) is standard normal and  
\[b=\sqrt{\frac{\kappa^{2}-\eta^{2}}{1+\eta^{2}\kappa^{2}-2\eta^{2}}}, \tag{111}\]  
which gives us \(E[E[S|\hat{S},Y]^{2}]=\kappa^{2}\). Let \(\hat{S}=\sigma_{1}\kappa^{-1}E[S|\hat{S},Y]\) with \(\kappa=(1+\sigma_{1}^{2}-D)/2\sigma_{1}\), we then have  
\[E[d(S,\hat{S})]=E[(S-\kappa^{-1}E[S|\hat{S},Y])^{2}]\] \[= E[S^{2}]+(\sigma_{1}^{2}\kappa^{-2}-2\sigma_{1}\kappa^{-1})E[E[ S|\hat{S},Y]^{2}]\] \[= 1+\sigma_{1}^{2}-2\sigma_{1}\kappa=D, \tag{112}\]  
which is equivalent to \(E[d(S,\hat{S})]=D\). The mutual information term is then written as  
\[I(S;\hat{S}|Y)=h(S|Y)-h(S|\hat{S},Y)=\frac{1}{2}\log\frac{1-\eta^{2}}{1-\kappa ^{2}}. \tag{113}\]  
The mutual information \(I(S;\hat{S}|Y)\) equals zero when \(\kappa=\eta\), i.e.,  
\[(1+\sigma_{1}^{2}-D)/2\sigma_{1}=\eta\] \[\Leftrightarrow D=1+\sigma_{1}^{2}-2\eta\sigma_{1} \tag{114}\]  
This concludes the proof of Theorem 1. By replacing the constraint on Wasserstein distance with the following KL divergence  
\[d_{KL}(p_{S},p_{\hat{S}})=\frac{1}{2}(\ln\sigma^{2}+\frac{1}{\sigma^{2}}-1) \leq P, \tag{115}\]  
and reverse KL divergence  
\[d_{RKL}(p_{S},p_{\hat{S}})=\frac{1}{2}(-\ln\sigma^{2}+\sigma^{2}-1)\leq P, \tag{116}\]  
and repeating the same steps of the proof of Theorem 1, we conclude the proof of Theorem 2.
# Research on a Decoupling Algorithm for the Dual-Deformable-Mirrors Correction System
## 6 Conclusions  
This article presents a decoupling algorithm for a dual-deformable-mirrors wavefront correction system. The algorithm utilizes Zernike coefficients to directly represent the compensating ability of the DM and enables independent correction of each order of aberration. Based on the expression formula of the coupling coefficient in a typical dual-deformable-mirrors wavefront correction system, this study analyzes the coupling effect of correcting different aberrations and draws the following conclusions:  
1. The utilization of a typical dual-deformable-mirrors wavefront correction system can achieve independent correction of various order aberrations and targeted correction of specific aberrations in different scenes, effectively suppressing the coupling effect between deformable mirrors.
2. The algorithm studied in this paper is simple and feasible, and it has been verified that the algorithm can be applied to the feasibility of the dual-deformable-mirrors wavefront correction system with a wavefront sensor. This research holds great practical significance in engineering and provides an important reference basis for its practical applications.  
Conceptualization, X.K.; methodology, J.L. and H.W.; software, H.W.; validation, J.L., H.W., M.H. and X.K.; formal analysis, X.K.; investigation, M.H.; resources, J.L.; data curation, J.L., M.H. and H.W.; writing--original draft preparation, H.W.; writing--review and editing, J.L. and H.W.; supervision, X.K.; project administration, H.W. All authors have read and agreed to the published version of the manuscript.  
The Key Industrial Innovation Chain Project of Shaanxi Province [grant number 2017 ZDCALGY-06-01]; the General Project of National Natural Science Foundation of China [grant number 61377080]; the Xi'an Science and Technology Planning Project [grant number 2020 KJRC0083]; and the Xi'an Science and Technology Plan (22 GXFW0115).  
The study did not require ethical approval.  
Figure 8: Curves. (**a**) Coupling coefficient curve. (**b**) Saturation margins of DM actuators.  
Data Availability Statement: The data or code cannot be made publicly available. Data sharing is not applicable to this article because of the limitations of our patent work.  
The authors declare no conflict of interest.
# Robust Bluetooth AoA Estimation for Indoor Localization Using Particle Filter Fusion
###### Abstract  
With the growing demand for positioning services, angle-of-arrival (AoA) estimation or direction-finding (DF) has been widely investigated for applications in fifth-generation (5G) technologies. Many existing AoA estimation algorithms only require the measurement of the direction of the incident wave at the transmitter to obtain correct results. However, for most cellular systems, such as Bluetooth indoor positioning systems, due to multipath and non-line-of-sight (NLOS) propagation, indoor positioning accuracy is severely affected. In this paper, a comprehensive algorithm that combines radio measurements from Bluetooth AoA local navigation systems with indoor position estimates is investigated, which is obtained using particle filtering. This algorithm allows us to explore new optimized methods to reduce estimation errors in indoor positioning. First, particle filtering is used to predict the rough position of a moving target. Then, an algorithm with robust beam weighting is used to estimate the AoA of the multipath components. Based on this, a system of pseudo-linear equations for target positioning based on the probabilistic framework of PF and AoA measurement is derived. Theoretical analysis and simulation results show that the algorithm can improve the positioning accuracy by approximately 25.7% on average.  
indoor localization; particle filter (PF); angle of arrival (AoA); Bluetooth direction finding; robust beam weighting +
Footnote †: journal: Applied sciences
###### Abstract
Additionally, due to their high aspect ratio and lack of flaps for lift enhancement, BWB aircraft commonly experience issues such as descent and altitude loss during deceleration and landing. The traditional solution to this is to adjust the thrust by regulating the flow rate of the BLI fans, but this reduces the boundary-layer ingestion effect, leading to a loss of lift and affecting the pitch moment in BWB aircraft, which have short lever arms. As a result, maintaining additional lift and pitch moment during landing is crucial to improving the stability and safety of these aircraft during the landing phase. To address the issue of descent and altitude loss in BWB aircraft with distributed electric BLI propulsors during the landing phase, this paper proposes a novel thrust control configuration located behind the BLI propulsors, based on a comparison of various thrust control schemes. The core concept is to maintain the lift and pitch moment while simultaneously reducing the thrust. This is achieved through a series of thrust control cascades that function similarly to spoilers. These cascades alter the direction of the airflow at the fan exit, increasing aerodynamic drag and reducing the aircraft's speed without changing the flow rate of the BLI fans. By maintaining the speed of the BLI fans, the boundary-layer ingestion effect remains constant, preserving the additional lift and thereby enhancing the stability of BWB aircraft with short lever arms during landing. This study involves a comparative analysis, numerical simulations, and ground tests, culminating in a thrust control configuration that maintains lift across all operational conditions, particularly improving the landing stability of BWB aircraft.
## 4 Experimental Setup
### The Statistical Analysis Methods  
The statistical analysis methods are based on the computational and experimental outcomes derived from 15 independent runs of each algorithm. Specifically, the reported results include the best solution (Best), worst solution (Worst), median (Median), mean (Average), and standard deviation (StdDev) obtained across these 15 runs. Here, is a detailed explanation of each statistical indicator:  
* Best: This represents the best performance achieved by the algorithm across the 15 runs. It indicates the highest level of performance that the algorithm can reach under the given experimental conditions. A higher best value generally suggests that the algorithm is capable of finding very high-quality solutions, even if it is not consistent every time.
* Worst: This represents the worst performance observed among the 15 runs. It provides insight into the least favorable outcome that the algorithm might produce. A higher worst value is preferable as it indicates that even in the least favorable scenario, the algorithm still performs relatively well.
* Median: This is the middle value of the performance results when they are sorted in ascending order. It gives an indication of the typical performance of the algorithm, minimizing the impact of outliers. The median is particularly useful in understanding the central tendency of the algorithm's performance.
* Mean (Average): This represents the mean performance across all 15 runs. It is calculated by summing all the performance values and dividing by the number of runs. The average provides a general idea of the algorithm's overall performance.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Instance** & \(n^{\prime}\) & \(Q\) & **Knapsack Type** & **R** \\ \hline _el151\_n50_ & 50 & 4029 & bsc & 01 \\ _el151\_n250_ & 250 & 22,832 & usw & 05 \\ _el151\_n500_ & 500 & 22,486 & unc & 10 \\ _el150\_n149_ & 149 & 12,310 & bsc & 01 \\ _ch150\_n1395_ & 745 & 68,034 & usw & 05 \\ _ch150\_n1490_ & 1490 & 1,262,022 & unc & 10 \\ _a280\_n279_ & 279 & 25,936 & bsc & 01 \\ _a280\_n1395_ & 1395 & 637,010 & usw & 05 \\ _a280\_n2790_ & 2790 & 1,262,022 & unc & 10 \\ \hline \hline \end{tabular}
\end{table}
Table 5: The Bi-objective Traveling Thief Problem (BITTP) test instances.  
* Standard Deviation (StdDev): This measures the amount of variation or dispersion in the performance results. A lower standard deviation is preferable as it indicates that the algorithm's performance is more consistent across different runs. This means that the algorithm is reliably achieving similar results, which is a desirable characteristic in optimization algorithms.  
Each of these statistical indicators provides a different perspective on the algorithm's performance. By considering them together, we can gain a comprehensive understanding of the strengths and limitations of each algorithm under different conditions. The performance metrics are chosen to ensure that the analysis is thorough and that the best algorithm can be identified based on a balanced consideration of all relevant factors.
# Incorporation of Torsion Springs in a Knee Exoskeleton for Stance Phase Correction of Crouch Gait
## 1 Introduction
Often, rigid ankle-foot orthoses (AFOs) are used to aid in the rehabilitation of people affected by gait deviation. [PERSON] et al. studied the effects of using torsional springs in the ankles in stroke and multiple sclerosis patients [22] to achieve an energy efficient gait. Some AFOs incorporating torsion springs in the ankles show improvement of moments and flexion in the knee; however, these did not improve knee angles to normal values [23]. Robotic or powered exoskeletons have the potential to improve gait movement and the overflexion of the knee [4]. [PERSON] et al. described the benefit of a motorized version of a lower-extremity assistance device through strengthening the knee extensors and improving posture during the gait cycle that encouraged broader participation of the knee extensors throughout the stance phase of the gait cycle. While strength training of the knee extensors [24], especially in those with a hamstring length within the range for normal walking, has the potential for gait improvement, motorized assistive devices throughout the gait cycle provide for a more optimum improvement in these muscle functions [4]. Figure 1: Normal knee angle (red curve) by phase of gait cycle with respect to proportion of gait cycle. The black arrows represent the duration of the stance phase from 0.0 to 0.6 proportion of the gait cycle, and the swing phase from 0.6 to 1.0 of the gait cycle. The majority of noninvasive, nonsurgical correction is through motorized lower limb exoskeletons that reduce the overall flexion of the knee in the stance phase of gait, while encouraging a greater range of motion. The objective of this project is to develop a lower limb exoskeleton for rehabilitative purposes, and to perform a comparative dynamic analysis on the functionality of the exoskeleton with applied forces and torques as a result of several crouch gaits. We seek to develop a passive model rather than a motorized exoskeleton, using torsional springs, to off-load excessive forces [25] generated during the stance phase of gait. While research indicates that most complications occur at the ankle, and ideally, an entire lower limb exoskeleton would be preferential, the objective is to analyze the results of offloading forces in a small portion of the leg, to be less invasive on the overall lower extremity [26], and to reduce the risk of abandonment of the device [27]. A comparative analysis between the passive and motorized knee exoskeleton is conducted. This paper focuses on developing the mathematical model for determining segmental moments and applying data obtained through biomechanical human modeling software of crouch gait, to determine the effectiveness of a passive knee exoskeleton in the correction of four different crouch gaits.