esa-sceva/satcom-chunk-collection huggingface dataset:
# Lightweight CoAP-Based Bootstrapping Service for the Internet of Things
## 3 The Bootstrapping Service: CoAP-EAP
### Additional Considerations
#### 3.6.5 Cryptographic Suite and Protection Selection  
In order to simplify the bootstrapping service, we assume a default cryptographic suite based on AES algorithm. We assume AES-CMAC-PRF-128 as the default KDF (see Section 3.4.3); AES-CMAC-128 to generate the new AUTH option (Section 3.4.2); and, when encryption and integrity protection are required at CoAP application level, we assume AES-CCM [91]. In any case, some sort of negotiation is important to support cryptographic agility [92].  
In our model, the controller is the entity which decides the cryptographic suite that must be used in the security domain. Thus, the information the controller needs to know about the Smart Object is the supported cryptosuite. Since our solution is AAA-centric, the IdP's AAA, where the smart object is registered, can provide this information to the Controller during the bootstrapping, so that it can finally decide what option to choose. Thus, this information is not sent over the constrained network reducing the CoAP message size of the bootstrapping service. Additionally, the IdP's AAA can inform if the smart object supports AUTH-based protection, DTLS-based protection or both.  
In contrast, the AAA protocol needs to carry this information. However, there are no standard attributes for this. It means defining several new attributes: _Encryption-Type_, _KDF-Type_, _Protection-Type_ and _MAC-Type_. These attributes would carry one octet specifying the algorithm (for example, using the value in [93]) for ciphering; the KDF to derive cryptographic material; the function to generate the AUTH option value, and the type of protection supported by the smart object, respectively.  
The IdP's AAA server may include an attribute of this type per each supported algorithm when sending the EAP Success to the Controller. For simplicity, if these attributes are not included, the Controller will assume that the default values are those supported by the smart object and that both AUTH-based protection or DTLS-based are supported.  
Finally, the smart object needs to be informed about the decision as well. This can be done in the last POST message containing the EAP Success (step **16**) through a new option _Crypto-Suite_ that contains 3 bytes (3-tuple) with: encryption, KDF and MAC algorithms. Nevertheless, to avoid increasing the message size, if this option is not included it is assumed that the default values will be the chosen ones. The use of AUTH-based or DTLS-based protection is determined because the Smart Object sees a message over the DTLS port and protected with DTLS or a message with AUTH option over the yet-to-be defined port for AUTH-based protection.
# Strain-Softening Analyses of a Circular Bore under the Influence of Axial Stress
## 3 Strain-Softening Analyses and Solution Procedure
### Solution Procedures  
As \(p_{in}\) is lower than critical pressure (\(p_{c}\)), the plastic region will develop in the surrounding rock mass. Assuming that the inner pressure reduces gradually from \(p_{c}\) to \(p_{in}\), the pressure decrease will be divided into \(n\) steps and denoted by \(\Delta p_{k}(k=1,n)\). After the \(n\) steps of the pressure decrease, the internal pressure \(p_{in(n)}=p_{c}-\sum\limits_{k=1}^{n}\Delta p_{k}\).  
If the inner pressure changes from \(p_{c}\) to \(p_{in(1)}=p_{c}-\Delta p_{1}\), a plastic annulus with thickness \(r_{1}-r_{0}\) appears as shown in Figure 6a.  
If the pressure decreases further from \(p_{in(1)}\) to \(p_{in(2)}=p_{c}-\Delta p_{1}-\Delta p_{2}\), plastic deformation will continue in the first plastic annulus (with thickness \(r_{1}-r_{0}\)). Meanwhile, a new plastic annulus with thickness \(r_{2}-r_{1}\) will appears as shown in Figure 6b.  
Figure 5: Schematic simplification of strain-softening process.  
By analogy, when the pressure decreases to \(p_{in(j)}=p_{c}-\sum\limits_{k=1}^{j}\Delta p_{k}\), there will be \(j\) annuli in the surrounding rock mass. The \(j\)th annulus, adjacent to the elastic zone and with inner radius \(r_{j-1}\) and outer radius \(r_{j}\), is illustrated in Figure 6c. Plastic deformation will go on in the other \(j\)\(-\)1 plastic annuli until the residual strength is reached during the pressure decrease.  
In each of the plastic annuli, incremental stress, displacement, et al. will be obtained, and the solution process will be discussed in detail later.  
Now, the \(i\)th load increment (or the \(i\)th pressure decrease \(\Delta p_{i}\)) is to be considered, I which \(\Delta\sigma_{r(i)}\) and \(\Delta\sigma_{\theta(i)}\) are the corresponding incremental radial and tangential stresses respectively, and \(\sigma_{r(i-1)}\) and \(\sigma_{\theta(i-1)}\) are the stress components at the end of the \(i\)\(-\)1 th load increment.  
The equilibrium equation for the incremental stresses is,  
\[\frac{d(\Delta\sigma_{r(i)})}{dr}+\frac{\Delta\sigma_{r(i)}-\Delta\sigma_{ \theta(i)}}{r}=0 \tag{8}\]  
but Equation (8) can be rewritten as  
\[\Delta\sigma_{\theta(i)}=r\frac{d(\Delta\sigma_{r(i)})}{dr}+\Delta\sigma_{r( i)} \tag{9}\]
## 8 Concluding Remarks  
Wireless Sensor Networks have the potential to revolutionize our everyday life, as they provide a flexible approach for us to observe the surrounding environment, and respond to events. The availability of tiny battery-powered sensor nodes, embedded with sensing, processing, and communication capabilities, which are wirelessly networked together via multi-hop communication, increase the opportunities for WSNs to find applications in a wide range of areas. Along with the opportunities, there are also challenges and requirements for the successful deployment and operations of WSNs. This survey has focused on the implications of the need for connectivity.  
Ensuring connectivity of a WSN is challenging when sensors have random locations, either because of mobility or initial random deployment. A substantial body of literature has been written on this problem, including deep theoretical results applied to simple models of i.i.d. uniformly distributed nodes with circular radio footprints. This model is widely accepted as it is analytically tractable. An important open research problem is to generalise these results to more realistic propagation models, including effects such as shadowing and non-uniform distribution of nodes, and to determine what engineering insights can be drawn from the theoretical asymptotic results.  
Connected subsets of nodes also play an important role in WSNs. As we have seen, cluster routing uses a connected \"backbone\" of nodes to simplify routing, and minimise the work required from the majority of sensor nodes. Finding the smallest such backbone is equivalent to finding a Minimum Connected Dominating Set in the corresponding graph, which is known to be NP-complete. Further research is needed both into finding more efficient, more accurate or simpler suboptimal solutions to the MCDS problem, and also into the benefits which can be obtained by using non-minimum backbones. Such benefits include reduced path lengths, and increased resilience. Such research will play an important part in bringing about the benefits that sensor networks have to offer.
# GoZone: A Numerical Model for Travelling Fires Based on Cellular Automata Concept
## 3 Ignition Strategy  
Unlike what has been done in previous travelling fire models [16; 18; 20], the fire dynamics in GoZone is not imposed by assigning a predefined fire velocity or fire path; instead, it is regulated by the ignition strategy that is presented here.  
Development and validation of this strategy was based on experimental data obtained on wood, first because wood-based products still represent a substantial fraction of the fire load in buildings, but also because of the wide availability of scientific data for this specific material. Conceptually speaking, it should be possible to adapt the model for other materials, assuming the availability of data on these materials. Application of the model in a compartment containing different materials would then require defining a combination rule, taking into account the proportion of each material present in the compartment. It will be shown in Section 5 that the proposed ignition strategy can be applied to replicate the global results in terms of ignition and propagation velocity as defined by a time constant linked to each type of occupation in EN1991-1-2,without any reference to the types of material that are present in the compartment.  
Theories and models about the ignition of wood have evolved since the first studies started more than one century ago [29] from a concept of critical oven temperature [30] to the introduction of the time of exposure [31] and surface temperature [32; 33; 34], then to the idea of a constant incident heat flux [14; 15; 35; 36; 37; 38; 39; 40]. To study materials under constant incident heat flux exposure, a concept of critical heat flux \"\(q_{cr}\)\" was introduced: a constant flux level below which ignition cannot be obtained in practical conditions. However, this concept is based on a constant applied heat flux, not representative of a real fire. An ignition strategy considering a non-constant heat flux would thus probably be more appropriate to represent a real fire. One of the first works on time varying heat flux is from [PERSON] et al. [41], who were still using a time decreasing heat flux, which is not representative of the first growing phase in a compartment fire. In 2006, [PERSON] et al. [42] proposed a simple method to derive the time of wood ignition based on linearly increasing heat flux exposition.  
The ignition strategy proposed here is based on the notion of critical energy (i.e., the minimum energy needed to be accumulated by a specific material to get ignited) and has been developed from a material characterisation in terms of ignitability, accounting for several kinds of time varying heat flux exposures. The concept is similar to the one used in the cumulative flux method [43] or in the flux time product (FTP) developed mainly for constant heat flux exposure [37].  
Figure 1: Smoke layer discretisation.
# Node Screening Method Based on Federated Learning with IoT in Opportunistic Social Networks
## 5 Conclusions  
In summary, when studying the data transmission problem in the opportunistic social network, this paper communicates the social network of opportunities, and proposes an effective node selection scheme based on federated learning, which greatly improves the transmission efficiency and improves the reliability of data transmission. On the Reality Mining dataset, this paper compares the FABD algorithm with four existing algorithms, and the results show that FADB has the highest delivery rate, the lowest energy consumption, and the lowest average overhead, although the end-to-end delay of FADB is not the lowest, it can be concluded that its comprehensive performance is excellent.  
Figure 14: The energy consumption of FABD under different mobile models.  
Figure 15: The average delay of the FABD algorithm under the three mobile models.  
In the 5G era, IoT technology is developing rapidly, and good data transmission capabilities have become an important factor in improving user experience and network stability. In the future, the FABD algorithm proposed in this paper will have broad application prospects in improving data transmission efficiency and reducing node energy consumption. In future work, as the number of terminals in the opportunistic social network increases and computing power increases, our FABD algorithm will have greater practical advantages. We will also collect real data sets in social scenarios, optimize and improve them, and continue to improve the performance of the algorithm.  
Writing--original draft, Y.S.; Writing--review & editing, F.G. and J.W. All authors designed this works. All authors have read and agreed to the published version of the manuscript.  
This work was supported in The Hunan Provincial Natural Science Foundation of China (2018)[3299, 2018]J3682).  
Not applicable.  
The authors declare no conflict of interest.
# An Overview of Key Technologies in Physical Layer Security
## 4 Challenges and Promising PLS Solutions
### Promising PLS Solutions
#### 4.2.5 Visible Light Communication (VLC)  
VLC is one of the technologies which has emerged with the potential of providing omnipresent access to wireless broadband for indoor settings [10; 112]. This is enabled by some of its unique characteristics, which include line-of-sight propagation, inability of light waves to penetrate opaque surface, technological advancements, and economical costs of lighting equipment such as solid-state light-emitting diodes (LEDs). The aforementioned characteristics are highly useful in PLS since VLC signals are confined inside the building's walls, hence an inherently secure communication which prevents eavesdropping for outdoor eavesdroppers. VLC schemes are realized through the use of a number of LED arrays and photodetectors (PDs). The LED arrays serve a dual purpose of offering illumination and data transmission simultaneously while the PDs are used as receivers. The most common method of modulation in VLC is the intensity modulation and direct detection (IM/DD). Unlike in RF systems, the modulating signals in VLC systems must have real, non-negative values [113]. To show the concept of VLC, Figure 21 depicts the illumination and power distribution using various arrays made up of red-green-blue (RGB) LEDs.  
Horizontal illuminance of a light fixture made up of an LED array of \(50\times 50\) RGB LED chips with a semi-angle of \(60^{\circ}\) is depicted in Figure 21a. Each LED chip has a Lambertian radiation pattern and total  
Figure 20: Secrecy rate vs distance.  
luminous intensity of 33.74 cd. As seen in Figure 21, increasing the number of LED arrays leads to an increased intensity and luminescence at all points of the room. Consequently, this results in elevated optical power, as seen in Figure 21. Optical power is crucial for data transmission because direct detection depends on the amount of power which impinges the PD. Due to incoherently distributed light intensity, the amount of optical power produced by the LED arrays decreases logarithmically with increasing distance.
# Data-Decoupled Scattering Imaging Method Based on Autocorrelation Enhancement
## 2 Materials and Methods
### Model and Data Design
#### 2.2.2 Neural Network Model
It is used to achieve recovery of the target details by calculating the average of the sum of the squared errors of the corresponding points of the predicted and original data. \[MSE=\frac{1}{M\times N}\sum_{i=1}^{M\times N}\left(x_{i}-x_{i}^{\prime}\right)^ {2}, \tag{7}\]  
where \(x_{i}\) and \(x_{i}^{\prime}\) are the first \(i(i=1,2,3\cdots,M\times N)\) pixel values on the target image and corresponding recovered image, respectively.
# Evaluation of Waste Blends with Sewage Sludge as a Potential Material Input for Pyrolysis
## 3 Results and Discussion  
### Analysis of Input Waste  
The analytical results of input waste are summarized in Table S1. Bulk density was an important parameter in waste blend preparation. The plastics, paper rejects and tire waste ash yields were much lower than that of the sewage sludge (49 wt. %). Typical raw sewage sludge has a high moisture content, in our case 72 wt. %, but the samples were analyzed after drying. The SS had a low carbon content (approximately 28 wt. % in dry matter), and a high oxygen content. There were relatively high values for nitrogen and sulfur in SS. The nitrogen in SS has its origin in the microorganisms used for water purification. The sewage sludge is characterized by a much lower HHV than other waste inputs, because of the higher inorganic content and because of the high oxygen content. The composition of SS differs within the literature; however, the authors of Refs. [44; 45], for instance, showed comparable values for the chemical composition of sewage sludge.  
A higher ash content and lower HHV means less efficient fuel [46]. In Figure 4, the highest ash content and the lowest HHV were determined for SS; on the other hand, RDF has the lowest ash content and the second highest HHV. Mixing the plastics with SS may improve the characteristics of oil and char derived from pyrolytic treatment [10].  
Certain studied plastics, such as RDF, TP and LDPE, have higher volatile matter and weight loss than PR, PES and SS, so there is more chance of the decomposition of volatile matter, and in turn high oil and gas yields (Figure 5) [10].  
It is apparent from Figure 6 that the combustible matter of SS is the lowest in quantity, while the highest amount of combustible matter with the highest C/H ratio is in TP and PES. The C/H ratio in biomass affects the yields of char, tar, and gas [47]. A higher C/H content means a higher production of char and a lower production of tar, and the opposite holds for lower C/H content. A comparison with pyrolytic products is the aim of future investigations.
# Organic Crystals for THz Photonics
## 3 THz-Wave Generation and Detection via NLO Processes
### Difference-Frequency Generation
For difference-frequency generation in case of perfect phase-matching and neglecting the pump-light absorption, the visible-to-THz conversion efficiency is given by [20]  
\[\eta_{\rm THz}=\frac{\omega_{\rm THz}^{2}d_{\rm THz}^{2}L^{2}l_{0}}{2\varepsilon _{0}c^{3}n_{0}^{2}n_{\rm THz}}\exp(-\alpha_{\rm THz}L/2)\,\left(\frac{\sinh( \alpha_{\rm THz}L/4)}{(\alpha_{\rm THz}L/4)}\right)^{2}, \tag{16}\]  
where  
\[d_{\rm THz}=\frac{1}{4}n_{o}^{4}r \tag{17}\]  
is the NLO coefficient for THz-wave generation that scales with the electro-optic coefficient \(r\), \(L\) the length of the NLO material, \(l_{0}\) the pump intensity, \(\alpha_{\rm THz}\) the absorption coefficient at the THz frequency, \(n_{o}\) and \(n_{\rm THz}\) the refractive indices at the pump optical and the generated THz frequencies,respectively. Equation (16) shows that, besides phase-matching and minimal THz absorption \(\alpha_{\rm THz}\), the main material figure of merit for THz-wave generation FM\({}_{\rm THz}\) can be defined as [6]  
\[{\rm FM}_{\rm THz}=\frac{d_{\rm THz}^{2}}{n_{o}^{2}n_{\rm THz}}=\frac{n_{o}^{6} r^{2}}{16n_{\rm THz}}. \tag{18}\]  
Table 2 shows these parameters for several inorganic and organic NLO crystals at a wavelength that is as close as possible to phase matching. Conventional inorganic semiconducting crystals used for THz-wave generation and detection such as ZnTe and GaP have much lower electro-optic coefficients compared to best inorganic electro-optic crystals such as LiNbO\({}_{3}\), but are anyway widely used because of the possibility for phase matching that is not directly possible with LiNbO\({}_{3}\) and other inorganic crystals with a high electro-optic coefficient. The organic crystals DAST, DSTMS, and OH1 show the largest figures of merit and they can be phase matched using pump lasers at telecommunication wavelengths in the range of 1300-1560 nm. The particular phase matching properties at different pump wavelengths and the generated THz frequencies are discussed for these crystals in details in Section 3.4 and examples of THz sources based on difference-frequency generation in organic crystals are given in Section 4.1.
## 4 Dispersing the Light
### Arrayed Waveguide Gratings (AWGs)  
#### 4.1.1 The Concept  
Arrayed waveguide gratings are a widely used technology in the telecommunication industry and a direct photonic analogue of a conventional diffraction grating spectrograph, as shown in Figure 4. The concept of AWGs, first presented in 1988, is based on a phased array of channels/antennae in radio receivers and transmitters [58; 59]. A single-mode fiber couples to a single-mode waveguide on the chip. The input waveguide illuminates an array of single-mode waveguides through a slab waveguide, called a free propagation region (FPR). Each waveguide in the array has an identical path difference, \(m\lambda_{0}\) with respect to its adjacent waveguide, where \(m\) is the central spectral order and \(\lambda_{0}\) is the central wavelength. The emergent light interferes in the output FPR and forms constructive interference fringes of different wavelengths within a spectral order (where free spectral range \(\sim\)\(\lambda/\,m\)) at different locations on the Rowland circle. Thus, the wavelengths within a spectral order are dispersed horizontally. The discrete resolving elements can then be sampled by output waveguides.  
However, different spectral orders overlap at the focal plane (see Figure 2). Essentially, all wavelengths the same value of \(m\lambda\) will overlap. Hence, for a complete spectrum, the spectral orders need to be separated using a cross disperser (i.e., an order sorter) or a set of secondary AWGs (called tandem AWGs) [60]. For continuous sampling of wavelengths, as is often required in astronomical spectrographs, the chip is cleaved at the focal plane and cross-dispersed in the perpendicular direction to get a full spectrum with the orders separated vertically (see Figure 2). In the design of AWGs, especially at high spectral resolution (\(R\)), the AWG does the heavy-lifting with finer dispersion (\(\delta\lambda\sim\lambda/R\)), and the cross-dispersive optics do a coarse dispersion (\(\Delta\lambda\sim\lambda/\,m\)) [61].  
Figure 3: A simple schematic of the full setup of an integrated photonic spectrograph specifically designed for low-resolution exoplanet spectroscopy by integrating nulling interferometer and AWGs on one chip. The two arms of the nulling interferometer have a phase difference of \(\pi\). The two AWGs are fed the outputs of the nulling interferometer to acquire separate spectra of star\(+\)planet and planet only (coming from the null output). Additional processing of the spectra will be required to eliminate residual starlight (say, from diffraction speckles) in the planet only spectrum.
# Binaural Rendering with Measured Room Responses: First-Order Ambisonic Microphone vs. Dummy Head
###### Abstract  
To improve the limited degree of immersion of static binaural rendering for headphones, an increased measurement effort to obtain multiple-orientation binaural room impulse responses (MOBRIRs) is reasonable and enables dynamic variable-orientation rendering. We investigate the perceptual characteristics of dynamic rendering from MOBRIRs and test for the required angular resolution. Our first listening experiment shows that a resolution between 15\({}^{\circ}\) and 30\({}^{\circ}\) is sufficient to accomplish binaural rendering of high quality, regarding timbre, spatial mapping, and continuity. A more versatile alternative considers the separation of the room-dependent (RIR) from the listener-dependent head-related (HRIR) parts, and an efficient implementation thereof involves the measurement of a first-order Ambisonic RIR (ARIR) with a tetrahedral microphone. A resolution-enhanced ARIR can be obtained by an Ambisonic spatial decomposition method (ASDM) utilizing instantaneous direction of arrival estimation. ASDM permits dynamic rendering in higher-order Ambisonics, with the flexibility to render either using dummy-head or individualized HRIRs. Our comparative second listening experiment shows that 5 th-order ASDM outperforms the MOBRIR rendering with resolutions coarser than 30\({}^{\circ}\) for all tested perceptual aspects. Both listening experiments are based on BRIRs and ARIRs measured in a studio environment.  
binaural synthesis; dynamic binaural rendering; BRIR measurements; head-tracked binaural; psychoacoustics Article