esa-sceva/satcom-chunk-collection huggingface dataset:
# Joint Task Offloading and Power Allocation for Satellite Edge Computing Networks
## 5 Performance Analysis
### Delay Performance with Different Computation Resources and Different Bandwidths  
We choose different bandwidths from [200 MHz, 500 MHz, 800 MHz] and compute the delay under the condition of different main frequencies. The result is shown in Figure 9, which indicates that a 4 kW elevation in transmission power threshold achieves 24.89% total delay reduction, confirming the critical relationship between power configuration and latency performance.
## 2 BDS-3 SAIM Monitoring Method
### Current Monitoring Methods
#### 2.1.1 Signal Power Monitoring  
In the front of the downlink navigation transmitting antenna of the navigation satellite, the low power signal is obtained by coupling as the input signal of the SAIM function unit. Based on the power monitoring information collected by the signal processing module, the navigation signal's quality is monitored and evaluated by the power of the satellite's signal. Normally, the signal power monitored for a satellite should fluctuate within a certain range around the mean value. Once the navigation signal's power drops beyond the alarm threshold, SAIM will issue an alarm. The SAIM alarm threshold usually has an initial empirical value. Under normal signal conditions, the on-orbit signal power monitoring data should have high stability.
# Aerodynamic Modeling and Performance Analysis of Variable-Speed Coaxial Helicopter
## 2 Establishment of an Aerodynamic Model
### Rotor Aerodynamic Model
#### 2.1.2 Rotor Aerodynamic Force  
In this paper, the blade element method will be used to model the aerodynamic forces of the upper and lower rotors, but the expression variables derived from the original blade element method include the total pitch angle. However, the total pitch angle of the coaxial unmanned helicopter in this paper remains unchanged, and the speed changes. Therefore, the dimensionless blade element theoretical expression should be transformed into the blade element theoretical expression whose variable is the speed.  
Through the blade element theory, the forces and moments of the upper and lower rotors in the rotor coordinate system can be deduced. Due to the complexity of the final expressions of these forces and moments, only the more characteristic expressions of lower rotor tension are described, and the expressions of other forces and moments can be obtained one by one by this method. The pull force of the lower rotor can be expressed as [17]:  
\[\begin{array}{l}T_{1}=\frac{1}{4}N_{b}\rho ac\varepsilon\Omega^{2}R^{3}\big{\{} (\theta_{0}+\theta_{01})\big{(}\frac{2}{3}+{\mu_{1}}^{2}-\varepsilon{\mu_{1}}^{ 2}\big{)}\\ +\theta_{t}[\frac{1}{2}-\frac{2}{3}\varepsilon+\frac{1}{2}{\mu_{1}}^{2}\big{(}1 -\varepsilon^{2}\big{)}]\\ -B_{1}\mu_{1}\big{(}1-\varepsilon^{2}\big{)}+\lambda_{1}\big{(}1-\varepsilon^ {2}\big{)}+a_{1}\varepsilon\mu_{1}(1-\varepsilon)\big{\}}\end{array} \tag{3}\]  
where \(N_{b}\) is the number of blades, \(\rho\) is the air density, \(a\) is the lift line slope, \(c\) is the blade chord length, \(\Omega\) is the rotor speed, \(\theta_{0}\) is the blade installation angle, \(\theta_{01}\) is the heading differential angle of the lower rotor, \(\theta_{t}\) is the blade torsion angle, \(\varepsilon\) is the dimensionless swing hinge offset, \(\mu_{1}\) is the forward ratio of the lower rotor, \(\lambda_{1}\) is the inflow ratio of the lower rotor, \(B_{1}\) is the longitudinal periodic pitch of the upper and lower rotors, and \(a_{1}\) is the rear chamfer of the lower rotor.  
In the expressions of all forces and moments, the inflow ratio and forward ratio are with speed variables. The inflow ratio and forward ratio can be expressed as:  
\[\mu_{1}=\frac{\sqrt{V_{x}^{2}+V_{y}^{2}}}{\Omega R} \tag{4}\]  
\[\lambda_{1}=\frac{V_{z}-(v_{1}+\delta_{1}v_{2})}{\Omega R} \tag{5}\]  
where \(v_{1}\) and \(v_{2}\) are the induced velocities of the lower and upper rotors, respectively, and \(V_{X}\), \(V_{Y}\) and \(V_{Z}\) are the components of the incoming flow along each axis of the rotor coordinate system. \(\delta_{1}\) is the interference coefficient between the upper rotor and the lower rotor. See the induced velocity model for the specific calculation method.
# Guided Self-Accelerating Airy Beams--A Mini-Review
## 2 Results and Discussion
### Nonlinear Guidance  
Based on the above analysis, one finds that the properties of Airy beams are stable in free space. Naturally, one wonders whether these concepts can be extended to inhomogeneous or nonlinear media. Indeed, it has been confirmed that Airy beams can exist in photonic lattices and give rise to interesting phenomena, such as accelerating lattice solitons [53]. Furthermore, we have investigated the interactions of Airy beams in different NL media [34; 35]. The governing nonlinear Schrodinger equation (NLSE) can now be written as  
\[i\frac{\partial\psi}{\partial z}+\frac{1}{2}\frac{\partial^{2}\psi}{\partial x ^{2}}+\delta n\psi=0, \tag{9}\]  
where \(\delta n\)--a function of the intensity \(|\psi(x)|^{2}\)--is the refractive index change. It acts as a potential in the Schrodinger equation. The index change depends both on the light and the material, and it may vary widely. In Kerr media, for example, this change is proportional to \(n_{2}I\), where \(n_{2}\) is the second-order nonlinear index and \(I\) is the intensity of the wave. For most materials, the value of \(n_{2}\) is rather small, e.g., between \(10^{-16}\) and \(10^{-14}\) cm\({}^{2}\)/W for glasses and transparent crystals, but in liquid crystals it can reach \(10^{-4}\) cm\({}^{2}\)/W. Thus, with a laser of 1 GW/cm\({}^{2}\), these nonlinear effects are easily observable over relatively short propagation distances (km in fibers and mm in liquid crystals).  
For the sake of obtaining an accelerating solution of NLSE--a nonlinear accelerating beam--one introduces \(x-z^{2}/4\) as a new variable, instead of \(x\) in Equation (9), to end up with  
\[i\frac{\partial\psi}{\partial z}-i\frac{z}{2}\frac{\partial\psi}{\partial x} +\frac{1}{2}\frac{\partial^{2}\psi}{\partial x^{2}}+\delta n\psi=0. \tag{10}\]  
Assuming the solution of Equation (10) of the form \(\psi(x,z)=u(x)\exp[i(xz/2+z^{3}/24)]\), allows Equation (10) to be recast into  
\[\frac{\partial^{2}u}{\partial x^{2}}+2\delta nu-xu=0, \tag{11}\]  
which is simpler than Equation (9). We treat it as an initial value problem with a required asymptotic behavior \(u(x)=\alpha\text{Ai}(x)\) and \(u^{\prime}(x)=\alpha\text{Ai}^{\prime}(x)\) for large \(x>0\); here \(\alpha\) represents the strength of the nonlinearity induced by the assumed solution. Similar to the ordinary Airy beams, the nonlinear accelerating beams are accelerating along parabolic trajectories.  
To investigate the interaction of Airy beams, we take the initial beam as a superposition of two Airy components  
\[\psi(x)=A_{1}\text{Ai}[(x-B)]\exp[a(x-B)]+\exp(il\pi)A_{2}\text{Ai}[-(x+B)]\exp[-a (x+B)], \tag{12}\]  
where \(B\) is the transverse position shift and \(l\) controls the phase shift. If \(l=0\), the two components are in-phase, while if \(l=1\), they are out-of-phase.
# A Review: Sample Preparation and Chromatographic Technologies for Detection of Aflatoxins in Foods
## 1 Introduction
Development of sample preparation and detection techniques has been influenced by these properties. For example, selection of extraction solvents should be based on the polarity and solubility of aflat. Detection and quantitation of aflat could be achieved using their UV and fluorescence spectrum. Molecular ions and structurally specific fragments of aflat are often used to achieve unambiguous identification in mass spectrometry analysis. Over the years, numerous methods have been developed to address challenges including heterogeneous distribution, difficulties in cleanup strategies for diverse matrices, laborious steps during extraction and matrix effects. By retrospectively comparing different techniques and evaluating their potentials and limitations, we can understand and appreciate how important discoveries in the past have led to our current aflatoxin analysis procedures and the challenges we need to address now and the directions we want to take in the future. So, it would be worthwhile to provide a comprehensive summary of developed sample preparation and analytical technologies for the determination of aflat. In brief, this review not only outlines the significant advances in sample preparation, and analytical strategies in the area of aflatoxin analysis in a wide range of food matrices, namely cereals, peanut, spices and dairy products, but also illuminates existing and emerging challenges that should be addressed presently and in the foreseeable future from a practical standpoint.
# Temperature Condition Analysis for Freezing on Tunnel Lining Back Side According to Tunnel Length
###### Abstract  
Railway mountain tunnels were constructed in cold regions of Korea recently, and freezing has been generated. Most mountainous railway tunnels are designed with waterproofing membranes since groundwater exists on the backside of the tunnels. The lower air temperature inside the tunnel is transferred to the back of the tunnel lining as the outside air temperature drops below zero in winter, causing the groundwater behind the waterproofing membrane to freeze. There have been cases of freezing-related damage, such as the obstruction of drainage flow and freezing groundwater leakage. Therefore, the freezing conditions inside the tunnel should be analyzed by each tunnel length after the air temperature variation in the tunnel is measured. In this study, the air temperature inside a railway tunnel located in a cold region was measured using thermometers. The inside air temperature over time was changed by the DTR (diurnal temperature range) every 24 h. The DTR inside the tunnel was also reduced far from the entrance. Heat transfer analysis was implemented considering the air temperature variation inside the tunnel. Assuming that the minimum air temperature freezing inside the tunnel lasts seven days, the higher the minimum air temperature the longer the tunnel length. The research results show that the freezing inside a tunnel can be estimated from the tunnel length and the minimum air temperature inside the tunnel.  
railway tunnel; back of waterproofing membrane freezing; heat transfer; tunnel length; minimum temperature; diurnal temperature range +
Footnote †: journal: Applied sciences
###### Abstract  
Solar energy has attracted the attention of researchers around the world due to its advantages. However, photovoltaic (PV) panels still have not attained the desired efficiency and economic mature. PV tracking techniques can play a vital role in improving the performance of the PV system. The aim of this paper is to evaluate and compare the technical and economic performance of grid-connected hybrid energy systems including PV and fuel cells (FC) by applying major types of PV tracking technique. The topology and design principles and technical description of hybrid system components are proposed in this paper. Moreover, this paper also introduces economic criteria, which are used to evaluate the economy of different PV tracking techniques and seek the optimal configuration of system components. In the case study, the results show that the vertical single axis tracker was ranked 1 st in terms of highest PV generation, penetration of renewable energy to the grid, lowest CO\({}_{2}\) emission, highest energy sold to the grid and lowest purchased, and lowest net present cost (NPC) and levelized cost of energy (LCOE). The study found that the optimal design of a grid-connected hybrid energy system (PV-FC) was by using a vertical single axis tracker which has the lowest NPC, LCOE.  
Keywords:optimal configuration; techno-economic analysis; PV tracking techniques; fuel cell; hybrid systems +
Footnote †: journal: Applied Sciences
# Cooperative Jamming-Based Physical-Layer Group Secret and Private Key Generation
## 5 Numerical Results
One can observe that the key rates of SK and PK are notably large in the high SNR regime, which makes the gap negligible at high SNRs. Therefore, the proposed CJ-based physical layer group SK and PK generation scheme has a performance that is close to optimal bound. Figure 8 compares the security performance among the proposed CJ-based, SNC-based [16] key generation (KG) schemes, and the traditional pairwise KG scheme [11; 12; 13; 14; 22], where \(d=100\) m and \(P=30\) dBm. As depicted in the figure, the SK rate of the CJ-based scheme equals that of the SNC-based scheme, both surpassing the pairwise scheme. Additionally, as the group size increases, the disparity in SK rates among the three schemes decreases gradually. This trend stems from the fact that when the group size is \(N\), both the CJ-based and SNC-based schemes require a coherence time of \(NT_{0}\), whereas the pairwise scheme necessitates \((N+1)T_{0}\). Consequently, the SK rates of the CJ-based and SNC-based schemes are \(\frac{N+1}{N}\) times that of the pairwise scheme, with the rate gap narrowing as \(N\) increases. However, as the group size expands, the number of key agreements for the pairwise scheme also increases, leading to diminished key generation efficiency. Conversely,  
Figure 6: The achievable key rates of SK and PK as functions of group size \(N\). Figure 7: The SK/PK upper and lower bounds versus the transmit power \(P\). the key agreement times of the CJ-based and SNC-based schemes remain unaffected by group size expansion. Specifically, the CJ-based scheme requires two key agreements, while the SNC-based scheme requires only one key agreement. Moreover, the first key agreement stage of the CJ-based scheme plays a similar role to the secret sharing stage in the SNC-based scheme; thus, the key generation efficiency of the two schemes is similar. However, the distinction lies in the fact that the second key agreement stage of the CJ-based scheme can generate both an SK and a PK, while the key agreement of the SNC-based scheme solely generates SK. Similarly, the pairwise scheme can only generate the SK. Therefore, the PK rate of the SNC-based scheme and the pairwise scheme is always 0.
## 4 Conclusions  
Concerning the main achievement in this article the following conclusions can be drawn:  
1. The obtained results showed good correlations between the SCC compressive strength and the NDT test readings. However, some differences were observed, when comparing with the correlations obtained for NVC, being more evident for the surface hardness test and the pull-out test. Thus, when testing SCC with NDT, general correlation should be used with precaution.
2. Surface hardness of SCC seems to be lower than that measured in NVC for the same level of concrete compressive strength, and this can be attributed to differences in mixture proportions and the used method to densify the concrete. The absence of vibration in SCC (it compacts by its self-weigh), the higher cement paste dosage, lower volume of coarse aggregates, and lower maximum aggregate size, together with the wall effect, can introduce differences near to the concrete surface. External vibration used to compact NVC specimens certainly have contributed to densify the near surface area of concrete.
3. Pull-out force measured in SCC was lower than that measured in NVC for the same level of concrete compressive strength, and this can be attributed to the same causes reported for surface hardness. In fact, both methods evaluate the concrete in the surface or near to the surface.
4. The analysis of the within-test variability allows to conclude that the standard deviation (\(S_{d}\)) and the coefficient of variation (\(C_{v}\)) which could be expected in a location of SCC with compressive strength up to 97 MPa, when using surface hardness test (9 readings), ultrasonic pulse velocity test (4 readings), and pull-out test (5 readings) are quite similar to that obtained in a location of NVC of compressive strengths up to 82 MPa, when using the same type of equipment and number of individual readings, respectively.  
[PERSON] supervised the experimental tests, processed the recorded data, and performed the comparative analyzes. [PERSON] and [PERSON] wrote the paper. This work was financed by Portuguese national funds through FCT--Foundation for Science and Technology, IP, within the research unit C-MADE, Centre of Materials and Building Technologies (UID/ECI/04082/2019 project), University of Beira Interior, Portugal.  
The authors would like to thank [PERSON]. [PERSON] for his support in laboratory tests.  
The authors declare no conflict of interest.
# Estimation of Optimal Speed Limits for Urban Roads Using Traffic Information Big Data
###### Abstract  
The use of an inconsistent speed limit determination method can cause low speed limit compliance. Therefore, we developed an objective methodology based on engineering judgment considering the traffic accident rate in road sections, the degree of roadside development, and the geometric characteristics of road sections in urban roads. The scope of this study is one-way roads with two or more lanes in cities, and appropriate sections were selected among all roads in Seoul. These roads have speed limits of the statutory maximum speed of 80 km/h or lower and are characterized by various speeds according to the function of the road, the roadside development, and traffic conditions. The optimal speed limits of urban roads were estimated by applying the characteristics of variables as adjustment factors based on the statutory maximum speed limit. As a result of investigating and testing various influence variables, the function of roads, the existence of median, the level of curbside parking, the number of roadside access points, and the number of traffic breaks were selected as optional variables that influence the operating speed. The speed limit of one-way roads with two or more lanes in Seoul was approximately 10 km/h lower than the current speed limit. The existing speed limits of the roads were applied uniformly considering only the functional road class. However, considering the road environment, the speed limit should be applied differently for each road. In the future, if the collection scope and real-time collection of road environment information can be determined, the GIS visualization of traffic safety information will be possible for all road sections and the safety of road users can be ensured.  
speed limit model; application data; GIS; traffic information; big data +
Footnote †: journal: Applied Sciences
# Application of FBG Based Sensor in Pipeline Safety Monitoring
## 1 Introduction
However, few studies about corrosion monitoring have been conducted, despite having the advantage of high measurement accuracy. Moreover, the existing optic fiber based monitoring technique cannot conduct corrosion monitoring and leakage monitoring simultaneously. In this paper, an FBG hoop strain sensor is proposed to monitor pipeline corrosion and leakage simultaneously. Two model experiments were conducted to test the performance of an FBG strain hoop sensor. To verify the correctness of the monitoring theory, a numerical analysis was also carried out using SAP2000 software (V15, Computers and Structures, Inc., New York, NY, USA).
# An Asymmetric Encryption-Based Key Distribution Method for Wireless Sensor Networks
## 1 Introduction
A lightweight password-authenticated key exchange scheme was proposed by [PERSON] et al. for heterogeneous wireless sensor networks [24]. Three 3-PAKE protocols were analyzed, and the vulnerabilities of the protocols were proposed. The new protocol provided good security features with high flexibility and efficiency. In this paper, we present a security key management scheme for cluster-based wireless sensor networks. In our scheme, session keys can be safely distributed and updated among all sensors with the help of the base station. Both static and dynamic scenarios are studied over the hierarchical networks. In particular, in our proposed scheme, the efficient encrypting algorithm makes it possible to adopt asymmetric encryption to guarantee authentication and confidentiality during data transmission. The rest of our paper is organized as follows: Section 2 introduces security features and design constraints in WSNs; Section 3 exhibits the details of the security key management scheme; Section 4 evaluates the performance of the proposed security protocols; and Section 5 presents the conclusion and perspectives.
## 4 Experimental Results and Comparative Analyses
### Datasets and Experimental Setup
#### 4.1.1 Datasets  
To explore the technological evolution in the domain-specific fields in 6G, we collected the datasets of five emerging fields in 6G using a carefully crafted search query developed by domain experts. These fields include new spectrum technologies (NSTs), reconfigurable intelligent surfaces (RISs), integrated sensing and communication (ISAC), integrated space-air-ground-sea communication (ISAGSC), and enhanced air interfaces (EAIs). The detailed statistics of the datasets are illustrated in Table 1. Given the restricted number of topics suitable for modeling in the early years, the time period from 2016 to 2024 was selected for performing the DTM. This time frame provides a more comprehensive and representative data source for the research, compensating for the limitations in the initial stages and enabling a more in-depth exploration of the technological evolution in these 6G fields.
## 4 Optimization of Measurement Parameters
### Frequency and Depth of Laser Modulation  
We use the finite element software \"COMSOL Multiphysics\" to simulate the resonant frequency and obtain the calculated result of about 800 Hz. The frequency scan experiment shows that the resonance frequency is located at 710 Hz (Figure 4), and the quality factor is calculated to be Q = 6.70. Because the quality factor Q of the photoacoustic cell used in this paper is small, the frequency response curve is somewhat asymmetrical [37]. The distance between the two microphones located at the center of the two main tubes is far less than the wavelength of the acoustic wave at the resonance frequency (0.49 m). There is in-phase acoustical noise in each cell as the gas passes through both tubes identically, but this noise can be significantly suppressed by differentiating the signals of the measuring channel and the reference channel (Figure S1 and Table S1).  
The amplitude of the laser modulation wave, i.e., the modulation depth, will directly affect the strength and the profile of the photoacoustic signal, and should be optimized experimentally.  
In this paper, the photoacoustic signal of 57 ppm methane at different modulation depths is measured at the resonance frequency (710 Hz) of the photoacoustic cell, as shown in Figure 5.  
Figure 3: Schematic of the experimental workflow. (MFC: Mass flow controller; ICL: Interband cascade laser; PA cell: Photoacoustic cell; DAQ card: Data acquisition card; PC: Personal computer).  
It can be seen from Figure 5b that when the modulation depth is low, the photoacoustic signal increases with the increase of depth, reaches the maximum value when the amplitude is 12 mA, and then begins to decline slowly. This is because the modulation depth will affect the instantaneous power of the laser, and the greater the amplitude, the greater the output power. However, when the modulation depth is too large, wavelength shift and spectral line broadening will occur, as shown in Figure 5a. When the modulation depth is 10 mA, there is not much difference (>99%) with the maximum modulation depth of the signal at 12 mA (Figure 5b). Therefore, the modulation depth is comprehensively selected as 10 mA. Although the optimal modulation depth may depend on the gas molecules and pressure, for simplicity, we choose this value for all gases to be analyzed. It was demonstrated that ethane and ethylene can also show sufficient signal intensity at this modulation depth and meet the experimental requirements.