esa-sceva/satcom-chunk-collection huggingface dataset:
# NN-Based 8 FSK Demodulator for the Covert Channel
## 2 Model of the Cover Transmission
### Selection of the Modulation for Hidden Transmission  
[PERSON]'s ability (from Figure 1) to hide the fact of communication mainly depends on his ability to make covert signals look like noise. Therefore, the power of the covert signal should be kept as small as possible; in order to avoid detection by the outsider ([PERSON]) [18].  
Moreover, a covert waveform can be modified to impede steganalysis. So far, in the case of typical coherent transmission (QAM/PSK modulation), the covertness was increased by constellation point rotations [2,3]. The impact of the shape of the covert con-stellation points and resulting IQ histograms will be discussed in the next section.  
It is also worth considering receiver problems. From the demodulator point of view, non-coherent demodulators are simpler. This issue arises because the carrier phase can be altered by the channel and has an impact on the accuracy of the detection. If there is not a perfect phase coherence, the non-coherent demodulation constitutes a good solution and can make it easier to convert channel demodulation. In addition to the foregoing, it is worth noting that, in contrast to the typical communication model, a covert channel generally does not require a high data rate. The low variance of the covert signal is compensated by the increased duration of the symbol.  
These scenarios and assumptions lead us to the main assumptions for covert signal modulation:  
* No constant constellation points (higher immunity to steganalysis [2, 3, 4]);
* Non-coherent detection (easier detection, lack of expensive, and complex recovery circuit);
* Possible low BER (bit error rate) for given energy per symbol to noise power (reliable transmission).  
FSK modulation fulfills the first two of three criteria. The last criterion must be carefully analyzed. The best way to do this is as follows: BER curves are used for illustration of the modulation performance. Figure 2 shows the BER performance for coherent (QAM and PSK) and non-coherent demodulation (FSK), taking the different modulation orders into consideration.  
Figure 1: Scenarios for covert channel: (**a**) general model; (**b**) simplified model.  
The performance analysis of the two-ordered modulation under the minimum required \(E_{b}/N_{0}\)rate shows the superiority of 2 PSK modulation. The 2 FSK modulation required 4 dB more energy per bit. By increasing the order of the PSK/QAM modulation, the higher \(E_{b}\) that is required, the lower the bandwidth. In the case of FSK, the higher modulation order results in lower energy per bit and higher bandwidth. From a covert channel perspective, it is most important to choose a modulation scheme that has a lower required \(E_{b}/N_{0}\) for the given BER. This justifies the use of 2 PSK, 4 PSK, and QAM modulation in the previous papers of the author [2; 3; 4; 5].  
As was shown in Figure 2, 8 FSK provides similar results (in the sense of energy per bit), and that is why it became the waveform for the covert information and subject of our analysis.
# A Review of Methods and Applications for a Heart Rate Variability Analysis
## 5 Dimensionality Reduction Techniques
### Independent Component Analysis (ICA)
#### 5.3.3 Filtering  
The filtering-based preprocessing step is generally used depending on the application. For example, if the input is time-series data, then some band-pass filtering may be used. Even if we linearly filter the input signal \(x_{i}(t)\) and obtain a modified signal \(x_{i}\)*(\(t\)), the ICA model remains the same [74].
###### Abstract  
The rise in renewable energy has increased the use of DC/AC converters, which transform the direct current to alternating current. These devices, generally called inverters, are mainly used as an interface between clean energy and the grid. It is estimated that 21% of the global electricity generation capacity from renewable sources is supplied by photovoltaic systems. In these systems, a transformer to ensure grid isolation is used. Nevertheless, the transformer makes the system expensive, heavy, bulky and reduces its efficiency. Therefore, transformerless schemes are used to eliminate the mentioned disadvantages. One of the main drawbacks of transformerless topologies is the presence of a leakage current between the physical earth of the grid and the parasitic capacitances of the photovoltaic module terminals. The leakage current depends on the value of the parasitic capacitances of the panel and the common-mode voltage. At the same time, the common-mode voltage depends on the modulation strategy used. Therefore, by the manipulation of the modulation technique, is accomplished a decrease in the leakage current. However, the connection standards for photovoltaic inverters establish a maximum total harmonic distortion of 5%. In this paper an analysis of the common-mode voltage and its influence on the value of the leakage current is described. The main topologies and strategies used to reduce the leakage current in transformerless schemes are summarized, highlighting advantages and disadvantages and establishing points of comparison with similar topologies. A comparative table with the most important aspects of each converter is shown based on number of components, modes of operation, type of modulation strategy used, and the leakage current value obtained. It is important to mention that analyzed topologies present a variation of the leakage current between 0 to 180 mA. Finally, the trends, problems, and researches on transformerless grid-connected PV systems are discussed.  
DC/AC converter; modulation strategy; grid-connected; leakage current; PV systems
# High-Accuracy Clock Offsets Estimation Strategy of BDS-3 Using Using Multi-Source Observations
## 2 Materials and Methods
### The New Strategy  
From the above analysis, it can be seen that the reason why the accuracy of two-way clock offsets is poor is that the traditional strategy totally believes in the single two-way measurement and ignores that the errors of each measurement will also be superimposed in the final two-way clock offsets. All BDS-3 satellites are equipped with high-performance onboard atomic clocks [26; 27; 28], and the output signal has high stability in the short timescale. Therefore, the new strategy should believe in the ability of onboard atomic clocks instead of signal measurement. More importantly, unlike the traditional strategy, the new strategy abandons the C-band inter-station two-way clock offsets and L-band two-way clock offsets of MEOs and IGSOs, instead only using Ka-band inter-satellite between all satellites and L-band two-way clock offsets of GEOs. After the above changes, the new clock offsets estimated strategy includes three steps, shown in Figure 4.  
Firstly, the new strategy takes redundant Ka-band two-way inter-satellite clock offsets as the inputs and uses least square estimation to filter the noise and errors of the two-way clock offsets to estimate inter-satellite clock offsets with higher accuracy between all satellites, which is recorded as two-way estimated inter-satellite clock offsets. Then, taking the two-way estimated inter-satellite clock offsets between GEOs and their L-band two-way clock offsets as inputs, the new strategy further uses least square estimation to estimate one GEO's clock offsets with respect to BDT. Last, by making the differences between the ODTS clock offsets and two-way estimated clock offsets and averaging their differences, the bias between two kinds of clock offsets can be calibrated and thereby realize the alignment of the two-way estimated clock offsets to the ODTS clock offsets. The following subsection will introduce each step of the new clock offsets estimation strategy of BDS-3.
###### Abstract
An adaptive control with PI model was developed in [18] considering Riccati-like equation, sliding mode control and fuzzy model to enhance control robustness. It is evident from the above literature survey that adaptive control remains as a potential controller for various dynamic systems. In addition, the adaptive control can be easily combined with other control types such as sliding mode control, optimal control, fuzzy model and PID model for improving control robustness of many systems subjected to parameter uncertainty and external disturbance. Consequently, the main technical contribution of this work is to formulate a new robust adaptive controller which preserves merits of PID and fuzzy models, sliding mode control and prescribed performance. More specifically, the following contents are to be carried out in this work: (1) a new integration of conventional sliding surface and prescribed sliding surface for switching control is presented, (2) a novel modified Riccati-like equation with PID parameters is proposed for the design of a new robust control input, (3) a new selection methodology for system constraints adaptable to the change of magnitude of disturbance coupled with dynamic motion is proposed and (4) computer simulations are undertaken to validate the robust stability considering the vibration problem of a vehicle seat suspension equipped with a semi-active magnetorheological (MR) dampers. In the presentation of control performances, a comparison between the proposed controller and two other existing controllers is made to demonstrate some salient properties of the proposed controller showing less vibration magnitude and higher stability against external disturbances (road excitations). This article is organized as follows. After addressing the research background and motivation in Introduction, design procedures for the proposed controller are presented in Section 2 considering the robustness of input control. In Section 3, computer simulations are carried out for three controllers: the proposed controller and two compared existing controllers. After discussing on vibration control performances of three controllers, the conclusion is drawn in Section 4 validating that the proposed controller can provide better control performance with higher robustness against severe disturbances than two compared controllers.
## 4 Algorithms  
In a wireless system, at any moment nodes may leave or join a system and the Ganglia and NWS periodically collect network and node statuses, making the network connections between nodes and the MCI server very dynamic. Hence, the SePCS periodically, or on receiving a message issued by Calculator, updates the performance table to avoid Scheduler from using out-of-date information to allocate resource nodes to user requests. Figures 4-8 respectively list the algorithms of Collector, Front Unit, Calculator, and Resource Broker (named Semi-preemptive allocation algorithm, SPA algorithm for short) where SPA is run by Scheduler. The parameters and functions used in the following are defined below. (1) \(R_{x}\): Type of the request \(x\), \(x=1\), 2 or 3. (2) \(S\): A set of the resource-node candidates. (3) \(Size(x)\): The number of elements in set \(x\). (4) \(HS\): The candidate with the highest score in \(S\). (5) \(Priority(x)\): priority of \(x\) in its global queue. (6) \(GBQ(R_{x})\): The function returns the global queue of \(R_{x}\) type, \(R_{x}\) may be 1, 2, or 3. (7) _enqueueRequest_(x,GBQ(\(R_{x}\))): This function first increases \(x\)'s priority by one if priority(\(x\)) \(<\) 3, and then enqueues request \(x\) to the corresponding global queue GBQ of \(R_{x}\) type where \(R_{x}\) = 1, 2 or 3, and priority 0 (3) is the lowest (highest) priority. (8) \(Type(x)\): The function checks the type of request \(x\). (9) \(chooseCandidates(y\),\(R_{x})\): It chooses those resource-node candidates that can serve the request of \(R_{x}\) type from the designated set of resource nodes \(y\). (10) \(getMaxScoreCandidate(S)\): It returns the ID of the resource node with the highest score in \(S\). If several candidates are of the same score, the one with the smallest ID will be returned. (11) \(allocateRequest(x\),\(A)\): It allocates request \(x\) to resource node \(A\). In a global queue, the highest priority user request will be chosen by Scheduler for allocating resource nodes. (12) \(accessRequestType(i)\): Accessing the type of the request being executed by node \(i\). (13) \(job\): The corresponding job of a request to be executed.
# Influence of Stray Current on Fastening System Components in Urban Railway Tracks
## 2 Research Objectives  
Based on the state of the art, it can be concluded that previous studies are mostly focused on the following:  
* modeling of stray currents in track construction, especially in metro systems
* analysis of rail potential
* the effects of stray currents on endangered structures near the tracks, particularly pipelines
* analysis of methods for protecting buried pipelines from the effects of stray currents.  
However, previous research has not analyzed the effects of stray currents on rails and fastening systems in urban railway tracks, which are the main sources of stray currents. After identifying the damage caused by the stray currents in the track, effective measures to protect the track can be determined. This reduces the stray current and prevents damage to structures near the track.  
To define the negative effects of stray currents on urban railway tracks, the authors performed a laboratory simulation of stray currents on four real-scale samples of the entire rail with all the fastening components. The difference among these four samples was the type of fastening system used. The fastening systems used for this test are characteristic of the tramway infrastructure in the city of Zagreb, Croatia, which has one of the highest traffic loads in Europe and where the problem of stray currents has been recognized. The samples prepared for testing were placed in plastic tubs to allow the tests to be performed under dry conditions and at different water levels. Different water levels simulate different conditions that can occur in tracks when drainage is inadequate and water is retained in the track.
# Inactivation of Contaminated Fungi in Rice Grains by Dielectric Heating
## 2 Materials and Methods
### Measurement of Dielectric Properties of Fine Rice Powder and Aspergillus sp. BP17  
The fungal colony on PDA and 60 g of fine rice powder in a polystyrene Petri dish (diameter 100 mm and height 15 mm) were measured dielectric properties using a VNA (Agilent Technologies, Inc., Santa Clara, CA, USA) with an open-ended coaxial probe and a computer [39; 40]. The probe and the network analyzer were contacted using a highly flexible coaxial. The network analyzer measurement based on software (Keysight Materials Measurement Suit; Keysight Technologies Inc., Santa Rosa, CA, USA) was set from 40 to 8500 MHz and at 1001 discrete frequencies to measure the dielectric properties. The measurement set-up is shown in Figure 2.  
The measurement system was turned on and kept in a standby mode at room temperature for approximately 60 min. Then, the network analyzer and the open-end coaxial probe were calibrated at room temperature using air, short, and deionized water as the standard [41]. After that, the calibrated probe was dried and cleaned using 70% alcohol.  
For dielectric properties measurement, the samples (fungal colony on PDA and 60 g of fine rice powder) were placed on the laboratory jack and the sample surface was touched with the probe (Figure S1 in Supplementary Material). Then, the dielectric property values of each sample were measured with three replications, and the values were recorded and analyzed for optimal frequency ranges in dielectric heating experiments.
## 3 Results and Discussion
### NMR and HPLC-MS\({}^{n}\) Analysis of Secondary Metabolites
In their work, the authors reported 13 compounds that, in accordance with our results, were classified into flavonoids and phenolic acids [25]. Considering the single compounds, several were differ  
Figure 6: \({}^{1}\)H-NMR spectrum of the BUT fraction. ent from those reported in our work. Among the flavonoids, (epi)catechin, epigallocatechin, phlorizin, naringenin, and apigenin glucoside were not detected in our extract. Conversely, the presence of myricetin hexoside in _P. spinosa_ is reported for the first time in our work. Among the phenolic acids, several derivatives of caffe acid identified in our extract were lacking in the results presented by [PERSON] et al. [25]. These differences can be attributed to several factors. First of all, the different collection sites of the plants generally have a significant influence on the chemical properties of plant specimens. Secondly, the different extraction protocols lead to the enrichment of the extracts in compounds with different physical and chemical properties. Last but not least, the analytical method used for the chemical characterization of extracts. In Algeria, _P. spinosa_ is used as a medicinal remedy for several health disorders, especially microbial infections and inflammation. Although a bioactivity screening of extracts was not performed in this study, we could assess the presence of some secondary metabolites whose pharmacological properties have already been studied in vitro and in vivo. Among these are some of the most abundant constituents of the methanol extract of _P. spinosa_, such as chlorogenic acid and 3,5-dicaffeoylquinic acid, whose anti-inflammatory, antioxidant, and antibacterial activities have been reported in vivo. Other bioactive compounds were detected among the flavonoids, such as the well-known apigenin, quercetin, and kaempfer. Moreover, for these, literature data demonstrate their antioxidant, antimicrobial, anti-inflammatory, and antitumor effects in vivo. A summary of these data is reported in Table 4. Overall, these data will be useful as a starting point for further bioactivity assessments on _P. spinosa_ from Algeria.
# Evaluation of Multi-Beam Massive MIMO Considering MAC Layer Using IEEE802.11 ac and FDD-LTE
## 1 Introduction
We assessed the proposed method by evaluating the transmission rates it achieved using the IEEE802.11 ac and frequency division duplex (FDD)-LTE standards. In addition, we evaluated the throughput of the method under the MAC layer of each standard to consider overhead. The rest of this paper is organized as follows: The general massive MIMO transmission approach is described in Section 2. In Section 3, we describe the use of amplitude correlation for modulation and propose a simple adaptive modulation scheme for multi-beam massive MIMO. In Section 4, we present our simulation model and describe its application in evaluating simple adaptive modulation schemes. Then, we describe the results of the performance evaluation of the proposed multi-beam massive MIMO method through the computer simulation of the IEEE802.11 ac and FDD-LTE standard environments.
# End to End Delay and Energy Consumption in a Two Tier Cluster Hierarchical Wireless Sensor Networks
## 4 Communication
### The Communication Range  
The communication range required for both type of communication will dependent of the number of rings, \(r_{\max}\), that conforms the WSN. For a large value of \(r_{\max}\), the WSN shape looks like a hexagon, see Figure 1, with an area equal to \(3\sqrt{3}R_{HEX}^{2}/2\). If \(R_{WSN}\) is the radius of the circle with equal area to the hexagon, we have \(3^{3/4}R_{HEX}=(2\pi)^{1/2}R_{WSN}\). In our topology, the number of CH including the sink is given by \(N_{c}(r_{\max})=1+3\cdot r_{\max}(r_{\max}+1)\). Then, the area of a given cluster, a small hexagon, is \(A_{c}(r_{\max})=\pi R_{WSN}^{2}/N_{c}(r_{\max})\), all with the same size. Approximating the coverage area of a cluster by a circle, its radio \(R_{c}(r_{\max})\) is given by the equation \(\pi R_{c}^{2}(r_{\max})=A_{c}(r_{\max})\), so \(R_{c}(r_{\max})=R_{WSN}/\sqrt{N_{c}(r_{\max})}\). Hence, for intra-cluster communication, \(R_{C}=R_{c}(r_{\max})\) is the minimum communication range. For inter-cluster communication, assuming that the CHs are located in the center of the hexagon, the distance between two closest CHs is given by \(\sqrt{3}R_{h}(r_{\max})\) where \(R_{h}(r_{\max})=KR_{WSN}/\sqrt{N_{c}(r_{\max})}\) is the radius of a small hexagon (a cluster) and \(K=\sqrt{2\pi/3^{3/2}}\approx 1.0996\). Then, for inter-cluster communication, \(R_{T}=\sqrt{3}R_{h}(r_{\max})\) is the minimum communication range required. These parameters are used in Section 8.
# Multi-User Linear Equalizer and Precoder Scheme for Hybrid Sub-Connected Wideband Systems
## 3 Analog Precoder Design  
In this section, we design a low complexity analog precoder to be employed at the transmitters. These precoders are computed based on the knowledge of partial CSI, i.e., only a quantized version of the average AoD \(\theta_{q}^{u}\), \(q=1,\dots N_{cl}\) of each cluster is used. These angles estimated at the receiver are quantized as  
\[\widetilde{\theta}_{q}^{u}= f_{Q}\Big{(}\theta_{q}^{u}\Big{)}\,,q=1,\dots N_{cl}\,,u=1, \dots,U, \tag{9}\]  
and then sent to the transmitters. In this paper, for the sake of simplicity, we consider uniform quantizers, i.e., the uniform function \(f_{Q}\) has \(2^{n}\) (\(n\) is the number of quantization bits) levels equally spaced between clipping levels \(-A_{m}\) and \(A_{m}\).  
With the knowledge of these quantized angles, user \(u\) should start by computing the correlation matrix \(\mathbf{R}_{u}=\mathbf{\overline{A}}_{tx,u}\mathbf{\overline{A}}_{tx,u}^{H}\), where the overall matrix \(\mathbf{\overline{A}}_{tx,u}\in\mathbb{C}^{N_{tx}\times N_{cl}}\) is given as  
\[\mathbf{\overline{A}}_{tx,u}=\left[\mathbf{a}_{tx,u}(\widetilde{\theta}_{1}^{ u}),\dots,\mathbf{a}_{tx,u}(\widetilde{\theta}_{q}^{u}),\dots,\mathbf{a}_{ tx,u}(\widetilde{\theta}_{N_{cl}}^{u})\right], \tag{10}\]  
with \(\mathbf{a}_{tx,u}(\widetilde{\theta}_{q}^{u})\) computed from  
\[\mathbf{a}_{tx,u}(\widetilde{\theta}_{q}^{u})=\frac{1}{\sqrt{N_{tx}}}\bigg{[} 1,\mathrm{e}^{jkd\sin(\widetilde{\theta}_{q}^{u})},\dots,\mathrm{e}^{i(N_{tx} -1)kld\sin(\widetilde{\theta}_{q}^{u})}\bigg{]}. \tag{11}\]  
To compute the analog precoders, we first need to apply the eigenvalue decomposition to the correlation matrix \(\mathbf{R}_{u}\), i.e., \(\mathbf{R}_{u}=\mathbf{U}_{tx,u}\mathbf{A}_{tx,u}\mathbf{U}_{tx,u}^{H}\), where \(\mathbf{\overline{\Lambda}}_{tx,u}\) is a diagonal matrix whose elements are the matrix \(\mathbf{R}_{u}\) eigenvalues and \(\mathbf{U}_{tx,u}\) a square matrix where the \(i\)th column is the \(i\)th eigenvector of \(\mathbf{R}_{u}\). Finally, entry \(n_{tx}\) of the proposed analog precoders of the \(u\)th user is set as  
\[\mathbf{f}_{u,u}(n_{tx})=\frac{1}{\sqrt{N_{tx}}}\mathrm{e}^{i\mathrm{arg}\left( \mathbf{U}_{tx,u}(n_{tx},1)\right)}\,,n_{tx}=1,\dots,N_{tx}, \tag{12}\]where \(\arg(a)\) denotes the argument of complex number \(a\) and \(\mathbf{U}_{tx,u}(n_{tx},1)\),\(n_{tx}=1,\ldots,N_{tx}\) represents entry \(n_{tx}\) of the eigenvector corresponding to the largest eigenvalue of the correlation matrix \(\mathbf{R}_{u}\). Hence, the beam follows the best channel direction, improving the transmit/receive link reliability.