esa-sceva/satcom-chunk-collection huggingface dataset:
# Investigation of Load Environment and Bending Load Capacities of Aged Prestressed Concrete Sleepers
## 2 Investigation of Load Environment of PC Sleepers
### Investigation Methods
#### 2.1.4. Material Constants and Analysis Cases for Numerical Analysis  
Table 1 shows the material constants in the numerical analysis. These constants were based on the Design Standards for Railway Structures and Commentary and nominal values [24; 25].  
In track maintenance in Japan, as shown in Figure 5a, the center sections of PC sleepers are generally not supported by ballasts (rail seat (center void) support) to reduce the reaction force from the ballast. However, in this study, assuming that a certain amount of time had passed since the latest track maintenance activity, the support conditions of the PC sleepers were assumed to be uniform rather than hollow (Figure 5b). Uniform support was set as the basic case.  
Table 2 shows the analysis cases. We focused on the parameters for which constant fluctuations were assumed, specifically, the train speed, vehicle occupancy rate, rail surface irregularity, track pad spring constant, and ballast support spring constant. According to previous research, each value was set assuming its deterioration over time. Regarding the support conditions of the PC sleepers (last row of Table 2), as shown in Figure 5c, the support spring constant of an entire PC sleeper was reduced for only one evaluation sleeper, and the support spring constant under the rail was reduced (the range of the center support of 600 mm at the center did not reduce the spring constant). The underlined constants constituted the basic case. A total of 14,400 cases were analyzed.  
\begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**Material Constants**} \\ \hline Rail & 60 kg rail (JIS E 1101; Young’s modulus \(E_{\text{S}}\) = 200 GPa) \\ Track gauge = 1435 mm \\ \hline Track pad & Spring constant \(D_{\text{P}}\) = 50 MN/m \\ \hline \multirow{4}{*}{Sleeper} & Type 3T (JIS E 1201), PC steel strand = \(\varphi\) 2.9 mm, N = 16 \\  & Length \(L_{\text{P}}\) = 2400 mm \\ \cline{1-1}  & Bottom width \(B_{\text{P}}\) = 283 mm (rail seat section), 230 mm (center section) \\ \cline{1-1}  & Height \(H_{\text{P}}\) = 190 mm (rail seat section), 175 mm (center section) \\ \cline{1-1}  & Young’s modulus \(E_{\text{C}}\) = 33 GPa \\ \hline \multirow{2}{*}{Ballast} & Ballast thickness \(h\) = 250 mm \\  & Support spring constant \(D_{\text{B}}\) = 200 MN/m (per rail) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Material constants used in numerical analysis.  
Figure 5: Support conditions of PC sleepers: (**a**) rail seat (central void) support; (**b**) uniform support; (**c**) center support.  
As shown in Table 3, the rail surface roughness (Figure 6; 2500 \(\upmu\)m maximum amplitude), measured at the rail joint of a conventional line, was set. The reason for this setting was that although this condition is unlikely to occur under general use conditions in Japan, it was established to verify the effect of its occurrence on the bending moments of PC sleepers.
###### Abstract
The antenna is designed to fit into commercially available 1U and 2U nanosatellites to avoid deployment complexity and to mitigate power scarcity. As the antenna structure is stable and, unlike the conventional deployable antenna, it does not require deployment, this antenna addresses the risk of mission failure due to antenna deployment. Moreover, as the proposed antenna provides space for additional placement of a solar panel, it helps to address the power scarcity in a nanosatellite. The proposed approach is a viable alternative based on the above-mentioned circumstances.
# Trusted GNSS-Based Time Synchronization for Industry 4.0 Applications
## 4 Trusted Computing
### Secure Boot  
The Secure Boot portion can be implemented by means of a combination of the (full) disk encryption with the TPM sealing of the encryption/decryption key to a specific set and configuration of the components loaded and executed before mounting the encrypted partition. Therefore, the availability of the encryption/decryption key is bound to specific values of a set of PCRs containing the accumulated measurements of the loaded components. If such components (and/or their configurations) are different from the expected ones, this is reflected into the PCR values different from those stored along with the encryption/decryption key in a Non-Volatile (NV) storage index. Indeed, it is possible to associate a set of PCRs and their values representing a specific configuration to the disk encryption/decryption key when the data is protected (sealing). The complementary operation is the unsealing when the TPM checks whether the current PCR values meet the values' set stored along with the disk encryption/decryption key. If they differ, the TPM does not release the encryption/decryption key (it does the Trust Decision) and, since the encrypted partition cannot be mounted, the bootstrap process gets stopped, thus implementing the Secure Boot. In our prototype, we implemented the Secure Boot using a modified version of Cryptsetup [49] that uses a NV storage index to protect the encryption/decryption phase.
# An Adaptive and Secure Holographic Image Watermarking Scheme
## 5 Experiments and Results
### Test for the Effectiveness of Our Watermarking Scheme  
A series of experiments were carried out to evaluate the imperceptibility and the robustness, which are two main requirements of the watermarking system according to the proposed method. The peak signal to noise ratio (PSNR) [26] was employed to measure the quality of the watermarked images. The watermarked image is within the acceptable degradation level if _PSNR_ is larger than 30 dB. Another metric normalized correlation (NC) [26], which is used to estimate the similarity between the original watermark and the extracted watermark, is utilized to evaluate the correctness of the extracted watermark. \(NC\in[0,1]\). Usually, it can be considered acceptable if \(NC\) is greater than 0.7. Higher NC value indicates good quality of extracted watermark. Bit error rate (BER) [27] is employed to calculate the difference between the reconstructed images of the embedded and extracted holograms. \(BER\in[0,1]\). The smaller the BER is, the better reconstructed image quality is. Experiments demonstrate the reconstructions obtained from the extracted watermarks cannot be recognized when their \(BER\) values are larger than 0.3. Ideally, \(NC=1\) and \(BER=0\).  
The encrypted CGH in Figure 2b was used as the watermark in the tests. Four \(1024\times 1024\) grayscale images Elaine, Goldhill, Peppers and Crane given in Figure 3 were the host images. The quantization step \(q\) is 45 and \(z=8\). In terms of imperceptibility and robustness, the PSNR, NC and BER of our scheme are compared those of three other adaptive methods in [2; 4; 7]. For a fair comparison, the encrypted binary CGH in Figure 2b was adopted as the watermark in these four algorithms.
applied sciences  
Technical and Economic Evaluation of Bioactive Compounds from _Schinus treehithifolius_ Using Supercritical Carbon Dioxide  
**[PERSON] 1,2,*(r)**, [PERSON] 3, [PERSON] 3, [PERSON] 4, [PERSON] 4, [PERSON] 5,**  
**[PERSON] 6 and [PERSON] 1,3**  
1 Engineering of Chemical and Biochemical Processes, Chemistry School, Federal University of Rio de Janeiro, Rio de Janeiro 21941-902, RJ, Brazil  
2 Institute of Technology in Foods and Beverages, University Center SENAI/CIMATEC, Salvador 41650-010, BA, Brazil  
3 Computational Modeling and Industrial Technology, University Center SENAI/CIMATEC, Salvador 41650-010, BA, Brazil; [EMAIL_ADDRESS] (A.B.)  
4 Institute of Innovation in Health Advanced Systems (CIMATEC ISI SAS), University Center SENAI/CIMATEC, Salvador 41650-010, BA, Brazil; [EMAIL_ADDRESS] (B.M.)  
5 Pharmaceutical Sciences Department, Federal Rural University of Rio de Janeiro, Seropedica 23897-000, RJ, Brazil  
6 Chemical Engineering Department, Federal Rural University of Rio de Janeiro, Seropedica 23897-000, RJ, Brazil; [EMAIL_ADDRESS]  
*Correspondence: [EMAIL_ADDRESS]  
This study evaluated the technical and economic feasibility of using supercritical CO\({}_{2}\) extraction for the production of bioactive compounds from _Schinus treehithifolius_. Supercritical fluid extraction techniques employing carbon dioxide were employed to extract valuable compounds from _S. treehithifolius_. The extraction was performed under different operating conditions, showing an increase in yield with higher pressures and temperatures. The bioactive compounds in the extract demonstrated significant potential in terms of their antioxidant and antimicrobial properties, making them valuable for applications in food preservation. The economic evaluation revealed a positive net present value (NPV) and favorable return on investment (ROI) within a two-year timeframe. The break-even point was determined to be below 25% production capacity, supporting the economic feasibility of the process. Overall, the utilization of supercritical CO\({}_{2}\) extraction for bioactive compounds from _S. treehithifolius_ offers a sustainable and environmentally friendly extraction method while ensuring the extract's integrity and quality. Although the operational costs and extractor contributions require consideration, the findings support the economic viability and commercial potential of this technique. Further research and development can enhance the efficiency and cost-effectiveness, making it an attractive option for various commercial applications.  
bioactive compounds; _Schinus treehithifolius_ extract; supercritical fluid extraction (SFE); techno-economic analysis
# An Energy Efficient Sink Location Service for Continuous Objects in Wireless Sensor Networks
## 3 Proposed Scheme
### Origin-Based Continuous Object Tracking(Ocot)
#### 3.2.3 Location Update and Data Report  
As an integrated location update scheme, in OCOT, the location update message from the mobile sink is delivered to the origin node through the grid structure as shown in Figure 13 left. The mobile sink sends a location update message to 1-hop neighboring sensor nodes. Because the nodes aware their cluster head, the location update message is delivered to closest cluster head. The cluster head forward this message to its upstream grid point, eventually the message reaches the origin node. The origin node is responsible for passing the location update messages to the boundary cluster heads. The origin node delivers the message to its four neighboring grid points. The location update message is propagated by the same way with grid construction messages. The difference is that the location update message is not propagated to all grid  
Figure 11: Boundary detection and tracking in OCOT.  
Figure 12: The state transition diagram of cluster heads.  
points, but to boundary and cluster heads. Unlike location update massage, data reporting does not use the grid structure like in Figure 13 right. The boundary cluster head receiving a location update message sends collected data to the location in the message directly. This separation between data reporting and location updating contributes to avoidance of concentration to the grid structure. The movement of a mobile sink during the message and data are delivered is filled by progressive foot-print chaining [30].
# Key Issues on the Design of an Offshore Wind Farm Layout and Its Equivalent Model
## 5 Collector System in a Wind Farm  
The internal electrical system of an offshore wind farm and its connection to the main power system pose special challenges. Electrical power losses affect the economics of wind farm operation. Investments to reduce losses can provide substantial returns in the long run. Electrical collector systems can normally be designed with various layouts, depending on the size of the wind farm and the desired collector reliability [37; 38; 39; 40]. Possible configurations of electrical collector systems include radial, single-sided ring, single return, star, double-sided ring, multiple rings, and multi-hub ring configurations [41].  
The simplest arrangement of a collector system in wind farms is radial. The main advantages of such a layout are the low cable costs and the simplicity of the control algorithms. The disadvantage is the relatively poor reliability. The ring layout uses a redundant connection between the strings of wind turbines, but the use of longer cables with higher cable ratings increases the expense. Generally, a ring arrangement performs better in large offshore wind system as it provides fewer losses than the radial system in both normal and contingency operations. It also provides larger grid security. The star design enables cable ratings to be reduced and provides a high level of security throughout the wind farm. This design is also likely to support better voltage regulation along the cables between wind turbines. The aforementioned configurations of electrical collector systems all have advantages and disadvantages. However, the basic designs of current offshore wind farms are radial and ring designs [41]. For example, the radial design was used for the 160 MW Horns Rev offshore wind farm in Denmark, and this design has been proposed for many other offshore wind farms that are in the planning stage, including the 640 MW Krieger's Flak wind farm in Sweden and the 420 MW Cape Wind offshore wind farm in the USA.  
The IEEE PES Wind Plant Collector System Design Working Group has addressed the issues related to the design of collector systems for offshore wind farms [42], and they have summarized some important design considerations, such as the topology of feeders, the design of collector systems, interconnect, and NESC/NEC requirements. They have also provided design guidelines that are based on reliability, economics, and redundancy.
# Novel Extensions to Enhance Scalability and Reliability of the IEEE 802.15.4-DSME Protocol
## 3 Shareable D-DSME Extension
### Plain DSME Allocation Procedure  
The GTSs in the CFP are allocated using a distributed procedure [1], suitable for operating in a mesh network. In order to support the operation, each node maintains two items in memory:  
* the _macDSMEACT table_, which contains all the slots in the multi-superframe in which the node is source or destination;
* the _macDSMESAB mask_, which contains all the slots in the multi-superframe that the node knows to be busy.  
When a node X needs to allocate a slot to transmit to a destination node Y, it sends to Y a _DSME_GTS_REQUEST_ message (hereinafter named \(M_{req}\)) containing:  
* the item macDSMESAB(X), i.e., the current _macDSMESAB mask_ of node X;
* the identifier of the slot that node X requests to allocate.  
The node Y performs the OR operation between its own current macDSMESAB(Y) mask and the macDSMESAB(X) field in the received \(M_{req}\). If the bit corresponding to the required slot in the OR-ed result is unset, there is no conflict (at least, in the knowledge of X and Y) and Y can allocate the slot to X. In such a case, the destination node Y updates its local _macDSMESAB(Y)_ mask and sends in broadcast a _DSME_GTS_RESPONSE_ message (hereinafter named \(M_{\textit{resp}}\)) to all the other nodes, indicating the address of the source node X and the id of the newly allocated slot.  
When the node X receives \(M_{\textit{resp}}\) from Y, updates its local _macDSMESAB(X) mask_ and _macDSMEACT(X) table_. Next, the node X sends a _DSME_GTS_NOTIFY_ message (hereinafter named \(M_{\textit{not}}\)) in broadcast to all the other nodes, indicating the address of Y and the id of the newly allocated slot.  
The \(M_{\textit{resp}}\) and \(M_{\textit{not}}\) messages are sent broadcast. This way, all the neighbours of the nodes X and Y are informed that a new slot was allocated, so they can mantain a consistent view of the busy slots. When a node Z in the neighbourhood of X and Y receives \(M_{\textit{resp}}\) or \(M_{\textit{not}}\), it verifies that there is no conflict on the assigned slot using its local _macDSMESAB(Z) mask_. If no conflict is detected, the mask is updated. Otherwise, the node Z sends a message to the other nodes and starts a new procedure to handle the conflict.
## 2 Description of [PERSON]'s attack and its properties
### Extending the attack to multiple qubits -- the collective attack  
For each qubit \(j\in[1\ \ldots\ 2n]\), [PERSON] applies the unitary \(U_{j}\) on the space \(\mathcal{H}_{j}^{E}\otimes\mathcal{H}_{2}\) where \(\mathcal{H}_{j}^{E}\) is her probe space and \(\mathcal{H}_{2}\) is the qubit space. [PERSON]'s view expressed with respect to basis \(b_{j}\) is obtained by tracing out [PERSON] from the states \(|\phi_{0}^{b_{j}}\rangle_{j}\) and \(|\phi_{1}^{b_{j}}\rangle_{j}\), resulting with the respective density matrices  
\[(\rho_{0}^{b_{j}})_{j}=|E_{00}^{b_{j}}\rangle_{j}\langle E_{00}^{b_{j}}|+|E_{ 01}^{b_{j}}\rangle_{j}\langle E_{01}^{b_{j}}| \tag{6}\] \[(\rho_{1}^{b_{j}})_{j}=|E_{10}^{b_{j}}\rangle_{j}\langle E_{10}^ {b_{j}}|+|E_{11}^{b_{j}}\rangle_{j}\langle E_{11}^{b_{j}}|. \tag{7}\]  
If [PERSON] sends the string \(\mathbf{i}\) using bases \(\mathbf{b}\), then [PERSON]'s global state is the tensor product of all those states \((\rho_{ij}^{b_{j}})_{j}\). After the test bits are revealed, [PERSON] needs only those \((\rho_{ij}^{b_{j}})_{j}\) for which \(s_{j}=1\). The set \(\{j\ |\ s_{j}=1\}\) has \(n\) elements; let us denote it \(\{j_{1},\ldots,j_{n}\}\), so that \(s_{j_{l}}=1\) for \(1\leq l\leq n\). [PERSON]'s global state corresponding to \(\mathbf{s}\), \(\mathbf{b}\) and \(\mathbf{x}\) can now be written  
\[\rho_{\mathbf{x}}^{\mathbf{b_{s}}}=(\rho_{i_{j_{1}}}^{b_{j_{1}}})_{j_{1}} \otimes\ldots\otimes(\rho_{i_{j_{n}}}^{b_{j_{n}}})_{j_{n}}=\bigotimes_{l=1}^{ n}\left(\rho_{i_{j_{l}}}^{b_{j_{l}}}\right)_{j_{l}}. \tag{8}\]  
We can rewrite Eq. (8) using the \(n\)-bit strings \(\mathbf{x}\) and \(\mathbf{b^{\prime}}=\mathbf{b_{s}}\) with the index \(l\) running from \(1\) to \(n\) (instead of the \(2n\) strings \(\mathbf{i}\) and \(\mathbf{b}\) indexed by \(\{j_{1},\ldots,j_{n}\}\)),  
\[\rho_{\mathbf{x}}^{\mathbf{b_{s}}}=\rho_{\mathbf{x}}^{\mathbf{b^{\prime}}}= \rho_{x_{1}}^{b^{\prime}_{1}}\otimes\ldots\otimes\rho_{x_{n}}^{b^{\prime}_{n} }=\bigotimes_{l=1}^{n}\rho_{x_{l}}^{b^{\prime}_{l}}. \tag{9}\]It is the state \(\rho_{\mathbf{x}}^{\mathbf{b_{s}}}\) (or a mixture of such states) that [PERSON] measures collectively to guess the string \(\mathbf{x}\) (or directly the final key \(\mathbf{k}\)) once \(\mathbf{b}\), \(\mathbf{s}\) and the information for error correction and privacy amplification is known to her.
## 2 Proposed ISAC System
### Spread Spectrum Signal  
Figure 2 shows an example of a DSSS signal, where a binary phase-shift keying (BPSK) signal is transmitted at a data rate of \(R_{b}\), with a bit duration of \(T_{b}=1/R_{b}\). The channel bandwidth is assumed to be \(W\) Hz. To spread the signal across the entire bandwidth, a pattern generator is used to produce a PN sequence at a rate of \(W\) pulses/s (chips/s), where \(T_{c}\) represents the pulse duration or chip interval. This modulation can be achieved using modulo-2 addition or multiplication operations [11]. The number of chips (\(N_{c}\)) per information bit is determined by the ratio of \(T_{b}\) to \(T_{c}\) (\(N_{c}=T_{b}/T_{c}\)). The time-domain representation of the BPSK signal, PN sequence, and the spread spectrum signal is shown in Figure 2 for \(T_{b}=6T_{c}\), or in other words, six chips within a single bit.  
On the other side, the DSSS receiver can be implemented using either matched filtering (MF) or correlator techniques. In the case of a matched filter-based receiver, as shown in Figure 3, the receiver's matched filter output samples are multiplied by the same PN sequence used in the transmitter. The resulting values are then summed together to recover the original transmitted bits. It is important to note that accurate time synchronization is necessary between the PN sequence generated at the receiver and the PN sequence of the incoming signal to ensure proper operation.  
Figure 2: Information data, PN sequence, and the resulting DSSS signal.  
A common method for generating maximal-length PN sequences is utilizing a \(q\)-stage shift register with linear feedback employing a modulo-2 adder, as depicted in Figure 4. The resulting sequence has a length of \(L=2^{q}-1\) bits. The characteristics of the maximal-length sequence are determined by the logic feedback connection described by a generator polynomial over a binary field, the initial states of the shift register, and its length \(q\). The PN sequence exhibits periodicity with a period of \(L\). The maximum period achievable by a PN sequence produced by a \(q\)-length shift register is \(2^{q}-1\). When the period reaches this maximum length, the PN sequence is referred to as a maximal-length sequence, wherein the number of ones exceeds the number of zeros by one.  
The periodic autocorrelation function of a maximal-length sequence is given by [14]:  
\[R(j)=\begin{cases}L,&\text{for }j=0\\ -1,&\text{for }1\leq j\leq q-1\end{cases} \tag{1}\]  
This indicates that the ratio of the off-peak values \(R(j)\) to the peak value \(R(0)\) (i.e., \(R(j)/R(0)=-1/L\)) is small when \(L\) is large. Consequently, the maximal-length sequences are nearly ideal in terms of their autocorrelation function, but they exhibit relatively large cross-correlation peaks when compared to any two other maximal-length sequences.
# A Novel Covert Channel for IEEE 802.11 Networks Utilizing MAC Address Randomization
## 5 Covert Channel Performance Evaluation
### Scenario 2--Periodic Transmission with Retransmission
To address the challenges posed by external traffic, especially in dense environments, we propose the adaptation of the modified selective repeat (SR) ARQ (automatic repeat request) protocol called in our paper SWP (sliding window protocol) [47]. This protocol allows the covert stations to monitor the channel's state and transmit frames only under favorable conditions. Consequently, the adoption of this protocol leads to linear throughput growth, improved frame efficiency, and reduced overall delay and jitter within the covert channel. The operation of the covert channel, following the adoption of SWP, is depicted in Figure 15. The window size refers to the number of frames an STA can transmit consecutively without receiving acknowledgment. Each probe request is assigned a unique sequence number and has an associated timeout. The first probe request, which does not contain a covert message, utilizes a customized MAC address content to signal the readiness  
Figure 14: Covert channel jitter as a function of transmission interval in scenario with retransmission enabled. Figure 13: Covert channel delay as a function of transmission interval in scenario with retransmission enabled. of the STA for covert communications. Upon receiving a probe response, subsequent frames transmitted by the STA are interpreted as covert messages. When an STA sends a covert message, it decrements the window size by one and sets a timeout for the corresponding probe response. Upon receiving a response, the window size is incremented by one (sliding the window). If the probe response timeout event is triggered, the STA checks whether it has received the expected probe response. If no probe response is detected, the STA considers the frame lost and schedules a retransmission event (note that retransmission does not decrement the window size). The protocol proposed by us differs from the original SR ARQ protocol in that both the sender and receiver's windows can be discontinuous, meaning that only the maximum number of sent and unacknowledged frames is important, which cannot exceed the window size. This implies that the transmission process continues constantly, as long as the number of received acknowledgments is not less than the total number of sent frames minus the window size. The algorithm used during the simulation to implement the scheme in Figure 15 is also demonstrated in Algorithm 2. Figure 15: Adoption of sliding window protocol into the covert channel.