esa-sceva/satcom-chunk-collection huggingface dataset:
# Random Segmentation: New Traffic Obfuscation against Packet-Size-Based Side-Channel Attacks
## 4 Materials and Methods
### Practical Considerations  
To change the standard packet sizing enforced by underlying protocols controlled by the operating system, we initially considered changing the MTU. Dynamic modification of the MTU value will directly impact the packet size, breaking larger packets into smaller ones to fit within the new limit. However, MTU is a system-wide parameter, and such modification will not affect our program but the entire system, which is undesirable. In addition, smaller MTUs increase packet fragmentation, leading to adverse consequences for the system's performance. Assembling fragments at the destination adds extra burden and reduces the overall efficiency. Further delay can also occur when a fragment is missed or corrupted. In this case, the receiver cannot read partial data, and the whole data frame must be retransmitted. On the other hand, our approach does not fragment packets but divides TCP segments into separate IP packets. Hence, we avoid the drawbacks associated with packet fragmentation.  
The main challenge in applying our idea is that applications do not have direct packet abstraction to control packet lengths. We could work around this technical obstacle by modifying two parameters on a per-socket basis, thus not affecting other programs.  
First, we disable [PERSON]'s algorithm Nagle (1966) using the TCP_NODELAY option. [PERSON]'s algorithm avoids sending small TCP segments by introducing a time delay to collect more data so that it sends full segments. Since we aim to send data in predetermined sizes, this data aggregation contradicts our purpose and needs to be disabled.  
Second, in the case of intensive traffic, we limit the amount of data that can be pushed out of a socket at the initial stage of the communication. TCP begins with a small congestion window to assess the network condition and find the optimal window size. As we turn off [PERSON]'s algorithm, many small packets can be sent immediately. As a result, the operating system overrides our program and accumulates the data into larger packets to improve efficiency, rendering our defense ineffective. To avoid this problem, we decrease the send socket buffer to less than the receive buffer.  
As stated, our traffic-shaping technique masks the packet length without adding noisy data. Thus, the data rate remains unchanged (i.e., the amount of transmitted data is the same). Therefore, we added another module to select the amount of covered traffic as needed. In our approach, we inject a certain amount of traffic to make one device similar to another in terms of the data rate.
# Mapping Surface Flow Velocity of Glaciers at Regional Scale Using a Multiple Sensors Approach
## Data and Methods
### Post-Processing: Time-Averaged Ice Velocity Maps  
Time-averaged glacier surface velocity fields are computed on the geo-cubes previously described by doing first a pixel-by-pixel filtering and then a weighted average of the filtered layers. For the filtering part, we compute the median and standard deviation separately for x- and y-component and then remove outlier measurements that are more than one standard deviation from the median either for the x- or y-component. We compared filtering results using 0.5, 1, 2 and 3 \(\sigma\) threshold and found that 1-sigma seems to provide the best balance between filtering and preserving a reasonable amount of values (\(\sim\)40%) as illustrated for the Mont-blanc area in Figure S1. Then, on the filtered values, we compute the weighted standard deviation, weighted standard error of the mean and weighted average. The weights are taken as \(1/\epsilon^{2}\) where \(\epsilon\) is the error on the velocity assuming a sub-pixel matching precision of 0.1 pixel [29]. Effective precision on glacier surface velocity mapping is discussed later in the manuscript and justifies our assumption. For efficiency reasons, the code that performs post-processing has been developed in Fortran-90 (integrated in Python using f2 py). Each geo-cube can also be processed independently of the others so that the averaging of maps can be done on high-performance clusters.  
The code returns six output parameters for each component (x and y) of the ice flow: (1, 2) the number of values before and after filtering (Figure S4); (3) the weighted standard deviation after filtering (Figures 1B and 2B); (4) the standard error of the weighted mean on the filtered data; (5, 6) the mean before and after filtering. This post-treatment algorithm is used in this study to form time-averaged maps of glacier surface velocity using all measurements obtained for the years 2017 and 2018 with Sentinel-2, Landsat 8 or Venus. Using the same algorithm, we can also create time-averaged maps on a shorter time scale to capture seasonal speed fluctuations. We illustrate it for New Zealand where we assemble late winter-spring (September to December) and late summer-fall (March to July) velocity maps by successively averaging the measurements with a repeat cycle time between 10 and 80 days. It should be noted that in New Zealand the seasons are reversed compared to the northern hemisphere. Finally, the maps are compared by simple subtraction to display variations in glacier surface velocity between the two seasons (Figure 3B).
# A Robust Security Architecture for SDN-Based 5G Networks
## 2 Background  
### SDN Based 5G Network Architecture  
In this subsection section, we first illustrate the concept of SDN based network architecture. Here, the SDN is an approach to improve the scalability of the traditional network and to provide the unified interface to the upper applications and terminal devices. In a traditional network architecture, the applications need to program the network hardware devices when communicating with the terminal devices. If the hardware devices are changed (e.g., is provided by a new manufacturer), the original upper applications may not be able to control them since these devices often use a different Application Programming Interface (API), making the network hard to be programmed as a consequence. The SDN architecture is just designed to handle this problem. For better understanding of this technique, we show a typical SDN architecture in Figure 2. As we can see, the SDN architecture is made up of three components: the application layer, the control layer and the data layer. Comparing with traditional network architecture separates the data and control into two planes instead of exposing all of them to the upper application plane. Since the control plane will automatically manage the network hardware devices, this separation can help the application to directly control the network with a unit interface given by the control plane and do not need to consider the hardware changes as we mentioned in the traditional network. Similarly, when the terminal devices in the network attempt to send their message to the applications, the SDN architecture will also provide the unified interface to overcome the bad scalability cased by hardware difference. Considering the significant advantage of SDN architecture, it becomes a key design concept in the 5G Network architecture.
## 2 Materials and Methods
### Road DEM Construction Method
#### 2.3.2 Local Shape Control  
In early DEM research, smoothness was used as a criterion for evaluating the quality of the DEM. Therefore, mathematical methods with better smoothness, such as polynomial interpolation, were also used to realize DEM elevation interpolation. Later on, with the development of earth observation technology, people began needing high-resolution DEM extraction. At this time, because it is difficult to ensure a smooth terrain at the micro scale, the smoothness of DEM results is no longer emphasized in DEM construction. However, as a kind of artificial terrain providing vehicle-driving function, smoothness is an important morphological feature of the road surface. Among DEM construction methods, the DEM constructed by the high-accuracy surface modeling method (HASM) proposed by a research team of Chinese scholar [27; 28; 29] has good smoothness and has been successfully applied in DEM construction in different regions and at different scales. However, the HASM method is more suitable for large-scale natural terrain DEM construction, and has the best effect for terrain modeling, with multilevel undulation characteristics. For the road, although its surface smoothness is good, its undulation form is too simple, and it generally presents a quadratic parabola type, which tends to be lower on both sides with a slight bulge in the middle in the transverse direction. The undulation, for a short distance in the longitudinal direction, can also be simulated with a quadratic equation. Therefore, this study has made corresponding improvements to the original HASM method: the second derivative of the surface in the local area was 0, that is, for the local 3 \(\times\) 3, the central grid point in the window was analyzed, and the following equations were established:  
\[f_{p0}^{\prime\prime}=\frac{f_{p3}-2f_{p0}+f_{p2}}{2h}=0 \tag{1}\]  
\[f_{p0}^{\prime\prime}=\frac{f_{p4}-2f_{p0}+f_{p1}}{2h}=0 \tag{2}\]  
We traversed each grid within the range of the road surface, formulated Equations (1) and (2), and then combined the corresponding equations of each point into the equation set:  
\[\mathrm{AF}=\mathrm{p} \tag{3}\]  
\[\mathrm{BF}=\mathrm{q} \tag{4}\]  
where the precision control equation could be established from the nodes that had been assigned elevation values on the road sideline and the road centerline:  
\[fp_{i}=k_{i} \tag{5}\]  
All precision control equations were combined into the equation set:  
\[\mathrm{SF}=\mathrm{K} \tag{6}\]  
Referring to the calculation process of the HASM method, Equations (3), (4), and (6) were combined as a minimum extremum problem:  
\[\mathrm{min}\left\| \begin{bmatrix}A\\ B\\ S\end{bmatrix} .F- \begin{bmatrix}p\\ q\\ k\end{bmatrix}
## 4 Discussion
### Non-Targeted LC-QTOF-MS Based Metabolomics Data Analysis
#### 4.2.2 Phenolic Compounds: Polyphenols, Phenylpropanoids, Flavonoids  
More than 10,000 different structures related to phenolic compounds have been identified [7]. Forty-two phenolic compounds have been identified in _C. sativa_[78], of which twenty-six different flavonoids have been identified [8; 16], belonging mainly to two classes, flavonoids and favones [79]. The seven chemical structures of the flavonoid aglycones are orientin, vitexin, isovitexin, apigenin, luteolin, kaempfer, and quercetin.  
These phenolic compounds share precursors with compounds derived from the nitrogenous pathways and include enzymes such as phenylalanine-ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H, a cytochrome P450) and 4-comamate-CoA ligase (4 CL) (Figure 6). These enzymes transform the aromatic amino acids phenylalanine and tyrosine into coenzyme A-activated 4-comamaric acid via the phenyl-propanol pathway [53]. 4-Coumaroyl-CoA gives rise to many different natural products. These include flavones, aglycones in the form of O- and C-glycosids such as apigenin-8-C-glucose [80], cannabis A produced by enzymatic precursors such as caffeoyl CoA and feruloyl CoA, and ligands such as secoisolariciresinol, cannabis D.  
Data extracted from LC-QTOF-MS described some of the unique metabolites of the species, such as cannflavin A (Table 3). Cannaflavins come from the condensation of three malonyl molecules to form naringenin chalcone. When the ring is closed, it forms naringenin and thanks to the action of flavone synthase, it is possible to produce apigenin, which is a derivative of luteonyl [16]. Among the reported benefits of flavonoids and particularly cannabis are their antioxidant and anti-inflammatory activity, and cardioprotective, neuroprotective, hepatoprotective, and immunomododulatory effects [80]. Other properties of flavonoids are their flavor, color, and aroma, as well as anti-diabetic and neuroprotective activities thanks to the modulation of the number of cellular cascade signals [11].  
However, there are gaps in our knowledge of the biosynthesis of flavonoids and therefore the means by which some esters, lignins, flavonoids, and coumarins are formed is unknown [7].
# Passive Sampling and Analysis of Naphthalene
## 1 Introduction
### Methods for PAHs Quantification  
Quantification of PAHs is a complex, time-consuming, and costly process considering their hydrophobicity, low water solubility, and propensity for low recoveries due to their losses during sampling and sample preparation. Many established quantification techniques focus on PAHs recovery from PM, an airborne carrier for sorbed PAHs. They have disadvantages such as a multistep sampling and sample preparation process requiring specialized equipment (pumps and gas sampling calibration), use of toxic solvents, and significant analytical skills.  
Gas-phase PAHs sampling and sample preparation is typically completed by trapping on a different type of sorbents and filters (polyurethane foam (PUF) [21,22], XADs [23], Teflon [24] and Carbopack C [25]) by subsequent extraction with organic solvent. As an alternative to using organic solvent-based methods, thermal desorption or solid phase microextraction (SPME) are widely used.  
SPME was applied in conjunction with sampling of gas-phase PAHs on sorbents such as XAD-2 [26]. PAHs were collected from the indoor air on XAD-2 sorbent and were mixed with 10 mL extraction solution (ethylene glycol mol\(\cdot\)L\({}^{-1}\) NaCl, 7:3) in a 25 mL flask with the ground-glass joint. Then, microwave-assisted thermal desorption (MAD) coupled to headspace SPME (exposed mode) was applied [26]. Another SPME-based method involves capturing of 16 U.S. EPA priority PAHs (adsorbed on diesel particulate matters) on glass microfiber filters, following thermal extraction of analytes by using the thermogravimetric analyzer to Tedlar bags and determination of concentration by SPME in a conventional exposed fiber coating mode [27]. Also, exposed SPME fibers were used for determination of PAHs directly in exhaust pipes [28,29].  
Passive sampling offers an alternative for gas-phase PAHs while addressing many deficiencies for conventional methods. Many methods for long-term monitoring of exposure to environmental pollutants use passive sampling to estimate TWA concentration. The time-weighted averaging (TWA)approach to sampling could be a useful way to \"even out\" these variations during sampling from vehicle exhaust gases, i.e., a source that is inherently variable [30]. Passive sampling is based on the diffusion of the analyte, either into a large sorbent bed (e.g., passive badges) or onto the retracted SPME fiber. The relatively large size of typical passive badges (10 to 40 mm I.D.) limits their applicability for vehicle tailpipe emissions. The small size of SPME needle (0.64 mm O.D.) is suitable for insertion in narrow conduits with minimal practical considerations.
# Experimental Flow Performance Investigation of Francis Turbines from Model to Prototype
## 4 Conclusions  
The experimental findings in this study demonstrate a correlation between the efficiency and power output of the Francis turbine, and this relationship is attributed to fluctuations in flow rates and rotational speeds from 50% to 100% load. The model turbine consistently maintains acceptable efficiency levels across different operational conditions, showcasing its adaptability and stability in varying loads.  
The hill chart demonstrated that the parameters of the model Francis turbine including flow rates, speed, guide vane openings, and design head achieve maximum torque and power output. This validates the design and performance of the prototype Francis turbine under various load conditions. The model tests have shown that rapid changes in fluctuating pressure in the flow below vapor pressure can lead to the formation and collapse of bubbles in the fluid in various areas of the turbine flow passages. This study also revealed that at various loads from 50% to 100%, cavitation tendencies show a sigma cavitation factor (\(\sigma\)) greater than the critical cavitation factor (\(\sigma_{c}\)).  
The measured pressure pulsations and frequency amplitudes at four monitoring points at the spiral case inlet, head cover, draft tube cone, and draft tube elbow, as well as the vortex rope, were consistent with the performance of the model runner under different operating  
Figure 11: Frequency spectrum at the (**a**) spiral case inlet, (**b**) head cover, (**c**) draft tube cone, and (**d**) draft tub elbow for the model runner with the head of 38.50 m.  
Figure 12: Frequency spectrum at the (**a**) spiral case inlet, (**b**) head cover, (**c**) draft tube cone, and (**d**) draft tub elbow for the model runner with the head of 37.50 m.  
conditions. Furthermore, no turbulence, vibration, or acoustic noise anomalies were detected at different loads, while the model turbine reached peak efficiency at full load. This experimental study provides important insights for engineers and researchers aiming to optimize Francis turbine designs, improve operational strategies, and promote sustainable hydropower utilization. The conclusions and model test approach of this investigation can be extended to other prototype Francis turbine prototypes where experimental results are lacking.  
Conceptualization, B.M.U. and X.H.; methodology, B.M.U. and X.H.; software, B.M.U.; validation, B.M.U.; investigation, B.M.U.; writing--original draft preparation, B.M.U.; writing--review and editing, X.H.; supervision, Z.W. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the Research and Development Foundation of China (No. 014120208001).  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.
# The Development of a Spaceborne SAR Based on a Reflector Antenna
## 3 Reflector Antenna Configurations in Spaceborne SAR Systems
### Reflector Antenna Configurations in Representative SAR Systems  
Reflector antennas have been widely adopted in a variety of spaceborne SAR missions due to their high gain and beam shaping flexibility. Depending on specific mission objectives, different reflector structure types and feed configurations have been developed. This section summarizes the reflector antenna configurations of selected current and upcoming SAR systems, categorized according to the reflector deployment mechanisms and feed types, as defined in Section 2. Specifically, three classes of deployable reflectors--radial rib deployable antennas, framework deployable antennas, and perimeter truss deployable antennas--are identified, along with three types of feed systems: single-beam feed, multi-beam feeds, and phased array feed. Table 4 provides an overview of representative SAR missions and highlights their antenna configurations and system characteristics.  
Overall, the adoption of different reflector structures and feed types reflects the trade-offs between system complexity, imaging performance, and deployment constraints. Scientific missions tend to favor advanced configurations such as perimeter truss deployable antennas and multi-beam feeds to achieve wide-swath and high-resolution capabilities, while commercial systems often prioritize compactness and cost-effectiveness through simpler designs.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Feed Type** & **Characteristics** & **Spaceborne SAR Applications** \\ \hline Single-Beam Feed & Simple design, cost-effective & Qilu-1 (China, 2021) \\ \hline Multi-Beam Feeds & Enables beam scanning and reconfiguration, but with limited and discontinuous scanning angles & TecSAR (Israel, 2008), RISAT-2 (India, 2009), HJ-1-C (China, 2012) \\ \hline \multirow{4}{*}{Phased Array Feed (PAF)} & Provides larger scanning angles, continuous beam steering, and higher flexibility and reliability than multi-beam feeds & HJ-2-E/F (China) \\ \cline{1-1} \cline{2-3}  & & multi-beam feeds \\ \hline \hline \end{tabular}
\end{table}
Table 3: Summary of reflector antenna feed forms.
## 3 Research Methods
### Questionnaire  
Early studies screened and reorganized the items in the safety climate scale into a scale to measure PSC. This contains 26 questions covering the relevant PSC dimensions. [PERSON] et al. [10] combined the literature relating to stress prevention intervention theory and safety research and divided PSC into four dimensions of management support, management priority, organizational communication, and organizational participation (e.g., [PERSON] and [PERSON] [36]; [PERSON] [35]; [PERSON] and [PERSON] [9]; [PERSON] et al. [37]; [PERSON] et al. [44]; [PERSON] et al. [45]; [PERSON] [40]; [PERSON] and [PERSON] [39]; see Table 1) to develop and adopt the the psychosocial safety climate scale (PSC-12) [10] scale based on 26 questions. This tool is a Likert 5-point scoring method from 1 (strongly disagree) to 5 (strongly agree). The score range of each item is, therefore, 1-5 points, with a range for each dimension of 3-15 points, making a total PSC score range of 12-60 points. As indicated in Table 2, PSC scores of 41 and over are taken to indicate that the perceived PSC level is high (low risk), belonging to an organization that is performing well. [PERSON] et al.'s [10] empirical work indicates that the PSC-12 scale has good reliability and validity with a 0.88 management commitment reliability, 0.90 management priority reliability, 0.77 organizational communication reliability, 0.80 organization participation reliability, and a 0.95 overall reliability score.  
The scale's extensive use in related research also justifies its good reliability and validity [10]. It has been widely used worldwide and is suitable for a variety of organizations and industries. The design of the questions is very simple and clear, which facilitates the ease of understanding of respondents. It can be used directly. [PERSON] et al. [15] developed a Chinese version of the PSC-12 scale and conducted an empirical test with 405 nurses as samples, confirming that the PSC-12 scale is also applicable in domestic studies in China. Therefore, no further validity analysis of the scale is needed.  
The questionnaire used is based on PSC-12, with statements scored on a 5-point Likert scale from 1 (strongly disagree) to 5 (strongly agree). This includes four demographic questions concerning the position, age, gender, and marital status of construction employees added to form the 'Questionnaire on Psychosocial Safety Climate of Construction Industry' (see Appendix A).
## 3 Network Architecture and Topology
### Network Architecture Classification
#### 3.5.3 Heterogeneous Networks
Another typical scheme is done by placing the gateways in vehicles, which have greater energy availability [12, 14], as opposed to placing them on the roadside [40]. The drawbacks of this option though, are, firstly, that it requires an extra investment since the potential number of vehicles may be greater than the number of static nodes and, secondly, that the interconnection between vehicles and static nodes is accomplished using WSN communication standards which are not specifically designed for vehicular applications, thus offering worst mobility  
Figure 5: VANET-centric application. Data Interchange between disconnected vehicles: (1) source vehicle detection, (2) notification to Cluster Head, (3) data request to vehicle, (4) data reply (stored at the Cluster Head), (5) destination vehicle detection, (6) notification to Cluster Head, (7) data delivery to destination vehicle. support, radio coverage and throughput. However, standards such as 802.15.4 and B-MAC [53] have been used in applications involving vehicles traveling at low to medium speeds [14, 40]. As pointed in [40] the coexistence of both approaches in a same system can be desirable, providing a compromise between costs and achieved performance according to the road operator's needs.