esa-sceva/satcom-chunk-collection huggingface dataset:
# Real-Time Traffic Sign Detection and Recognition Method Based on Simplified Gabor Wavelets and CNNs
###### Abstract  
Traffic sign detection and recognition plays an important role in expert systems, such as traffic assistance driving systems and automatic driving systems. It instantly assists drivers or automatic driving systems in detecting and recognizing traffic signs effectively. In this paper, a novel approach for real-time traffic sign detection and recognition in a real traffic situation was proposed. First, the images of the road scene were converted to grayscale images, and then we filtered the grayscale images with simplified Gabor wavelets (SGW), where the parameters were optimized. The edges of the traffic signs were strengthened, which was helpful for the next stage of the process. Second, we extracted the region of interest using the maximally stable extremal regions algorithm and classified the superclass of traffic signs using the support vector machine (SVM). Finally, we used convolution neural networks with input by simplified Gabor feature maps, where the parameters were the same as the detection stage, to classify the traffic signs into their subclasses. The experimental results based on Chinese and German traffic sign databases showed that the proposed method obtained a comparable performance with the state-of-the-art method, and furthermore, the processing efficiency of the whole process of detection and classification was improved and met the real-time processing demands.  
simplified Gabor wavelets; MSERs; regions of interest; SVM; CNN +
Footnote †: journal: Sensors
# _photonics_
## 2 QKD Protocol and Architecture Assumptions in the LEO  
### System Architecture, Satellite, and Ground Stations  
The presented work focuses on the use of LEO satellite-to-ground QKD links for delivering quantum keys on the ground segment of the network. The orbit altitude of LEO satellites is lower than 2000 km, thereby allowing for much higher signal-to-noise ratio (SNR) values and lower free-space loss compared to geostationary Earth orbit (GEO) satellites, which are positioned in a height of about 35,000 km. On the other hand, in contrast with GEO satellites that are at a fixed position in the sky, LEO satellites are visible by OGSs only a few minutes each day, if the atmospheric conditions allow it.  
Through our analysis, we considered the satellite-to-ground scenario (downlink) assuming the cloud-free line of sight conditions and links with elevation angle higher than 20 degrees. In the case of downlink transmission, the attenuation caused by atmospheric turbulence is lower compared to that of the uplink, since the laser beam has already expanded before it comes into contact with the atmosphere [23; 32]. Aside from the attractive transmission features, the downlink scenario is compatible with the strict requirements of satellite system architectures. More specifically, it allows the implementation of a compact quantum sender station based on a highly attenuated coherent source and simple optics for the encoding of quantum information, being also controlled by simple electronics [33]. In this way, complex single-photon counters which require advanced cooling mechanisms are located at the ground stations where there are not any strict requirements on footprint and energy consumption. Moreover, by implementing the satellite-to-ground scenario, large apertures for the single-photon detection can be placed in astronomical observatories. In this way, smaller, lighter apertures can be employed on board in space.  
Through our analysis, we assumed that three astronomical observatories in Greece communicate with the LEO satellite constellation. The first is located in Skinakas (South, longitude: 35.2118\({}^{\circ}\), latitude: 24.8981\({}^{\circ}\)) at a height of 1750 m, the second in Helmos (Middle, longitude: 37.9855\({}^{\circ}\), latitude: 22.1984\({}^{\circ}\)) is at a height of 2340 m, and the third in Cholomondas (North, longitude: 40.3419\({}^{\circ}\), latitude: 23.5060\({}^{\circ}\)) is at a height of 850 m. These three observatories are involved in Greek QCI, which aims to build a secure communication infrastructure by exploiting the terrestrial fiber segments for quantum key delivery in users [31]. The location of each OGS is shown in Figure 1.  
The quantum key sifting is assumed to be implemented via a public optical channel. For this purpose, different wavelengths within the standard bands will be available for classical data channel and quantum channel. Uplink beacon and other service channels for the QKD link establishment can be also implemented within the available bands [34].
## 4 Factors Affecting the Quality of User Experience
### Technological-Process Factors of Network Services/Applications  
Technological-process factors affecting the quality of user experience (\(QoE\)) are directly related to QoS parameters and their objective measurements. According to [43; 45], QoS parameters enable the quantification of the quality of user experience. They are often labeled with KPI, and are under the control of the service provider [49]. The authors in the paper [31], based on a review of published relevant research, classified factors related to QoS parameters into a group of system factors, such as: transmission speed, frame rate, packet loss, resolution, codec, jitter, quantization level, delay, packet error rate, spatial degradation, compression level, encoding, quality degradation, throughput, etc. In addition, a similar list of system parameters is given in the paper [25]. The basic criterion on the basis of which the classification is made into conversational, streaming, interactive and background traffic is sensitivity to delay [24]. According to [46], the term System Quality of Service (SQoS) refers to network indicators-attributes that are defined from the perspective of the service provider, not the user, and that directly affect \(QoE\). The technical report [46] defines another term arising from QoS, which is end-to-end service quality of service (ESQoS). It describes the overall level of QoS, end-to-end. The parameters through which SQoS and ESQoS can be evaluated are defined by the service provider.
## 6 Conclusions  
In this research, 54 GALs in the Lengqu River section were identified based on RRIM transformation, the relationships between GALs, resurgent GALs, inactive GAL depositions and excess topography were quantitatively analyzed, and the following conclusions were obtained:1. The RRIM method used in the Lengqu River section makes visible the morphology and color features of the landslide occurrence that are obviously different from the surrounding areas, which provides good technical support for the census of GALs.
2. A total of 77.75% of the GALs in the Lengqu River section are still on excess topography, which means that the vast majority of the GALs are still at risk of new landslides; 68.38% of the 5 resurgent GALs, which are almost unaffected by human activities in the Lengqu River section, are on excess topography, 62.21% of the inactive GAL depositions are on the non-excess topography, and these results all indicate that the excess topography has an indicative effect on GAL resurrection in the natural state to a certain extent.
3. In the future, the RRIM method can be used to interpret smaller landslides with a higher-resolution DEM. At the same time, we can try to conduct quantitative analysis on the relationship between landslides in different regions, resurgent landslides and excess topography for further assessment of landslide risk with the help of the concept of excess topography. However, the decoding laws for smaller landslides based on the RRIM need to be recapitulated, and how to select the appropriate threshold hillslope for a new study area is also important.  
Conceptualization, X.W. and S.B.; Data curation, X.W. and S.B.; Formal analysis, X.W.; Funding acquisition, S.B.; Investigation, X.W. and S.B.; Methodology, S.B.; Project administration, S.B.; Resources, X.W. and S.B.; Software, X.W.; Supervision, S.B.; Validation, X.W. and S.B.; Visualization, X.W.; Writing--original draft, X.W.; Writing--review and editing, S.B. All authors have read and agreed to the published version of the manuscript.  
This study was supported by the National Natural Science Foundation of China (grant nos. 41941017 and 41877522).  
Not applicable.  
The authors declare no conflict of interest.
# Efficient Crowd Anomaly Detection Using Sparse Feature Tracking and Neural Network
## 3 Materials and Methods
### Crowd Representation and Behaviour Descriptors
#### 3.1.3 Spatial Representation Using Delaunay Triangulation  
To encapsulate the spatial interactions between reliable tracklets, we employ Delaunay triangulation as a spatial representation technique [37]. Tracklets, which are short sequences of object locations in consecutive frames, are crucial in our approach. The terminal location of each tracklet is considered as a vertex in a graph. These vertices are then interconnected using the Delaunay triangulation graph. The Delaunay graph facilitates the exploration of neighbouring nodes in any direction, thereby accurately representing both local and spatial interactions. It is denoted as \(g^{k}\Big{(}\theta^{k},\varepsilon^{k},\ \mathrm{F}^{k}\Big{)}\), defined by the list of node connections \(\varepsilon^{k}\) and the list of triple indices \(\left(\mathrm{F}^{k}\right)\), where each triplet represents a triangle. This graph effectively captures topological changes over time, preserving the overall shape of the graph despite noise or partial occlusion. From the constructed graph \(g^{k}\), local entities called cliques can be extracted, which are groups of points connected by edges \(\left(\varepsilon^{k}\right)\) and are defined around a seed point \(V_{i}^{k}\)\(C^{k}=\left\{C\Big{(}V_{1}^{k}\Big{)},\ldots C\Big{(}V_{m_{k}}^{k}\Big{)}\right\}\). Each seed point possesses a unique local configuration, forming a first-order clique, as represented in Equation (5):  
\[C\Big{(}V_{i}^{k}\Big{)}=\Big{\{}V_{i}^{k}\Big{\}}\cup\Big{\{}V_{j}^{k},\forall \Big{(}V_{i}^{k},V_{j}^{k}\Big{)}\in\mathcal{E}^{k}\Big{\}}. \tag{5}\]  
Higher-order connections can be extrapolated by considering indirect neighbours, thereby forming larger cliques, as in Equation (6) [38]  
\[C_{n}\Big{(}V_{i}^{k}\Big{)}=C_{n-1}\Big{(}V_{i}^{k}\Big{)}\cup\Big{\{}C_{1} \Big{(}V_{j}^{k}\Big{)},\forall V_{j}^{k}\in C_{n-1}\backslash C_{n-2}\Big{\}} \tag{6}\]  
with \(C_{0}\Big{(}V_{i}^{k}\Big{)}=\Big{\{}V_{i}^{k}\Big{\}}\) and \(C_{1}\Big{(}V_{i}^{k}\Big{)}=C\Big{(}V_{i}^{k}\Big{)}\). The local features are temporally interconnected through trajectories, capturing short-term and long-term patterns. Spatially, they are connected through cliques of varying order. By leveraging low-level features, a dynamic graph is constructed that illustrates the temporal and spatial distributions of individuals within the crowd. This comprehensive, localised scene model facilitates the measurement of diverse crowd attributes.
## 4 System Design and Goals
### Message Sequence
#### 4.2.5. HI Message State  
Nodes that received or heard a HELLO broadcast will use this state to:  
Broadcast a HI message with the addresses of all nodes whose HELLO messages were received, as shown in Figure 7.  
* Here, EMERGENCY_HELLO is set to 1 or a value that is greater than zero. This will enable the node to broadcast a HELLO message before the next LISTEN state. Nodes that broadcasted the initial HELLO message are mandated to equally broadcast a HI message for the following reasons:
* To determine the symmetric connection between nodes.
* To prevent a break in the message sequence; for example, when all nodes broadcast a HELLO message concurrently, all nodes must therefore respond with a HI message to maintain the message sequence.  
The three nodes (green, brown, and cyan) that heard or received the initial HELLO broadcast responded with a HI message after the expiration of the DB_NIEGHBORS_RCVD state. Broadcasts from the three nodes are received by both the node that initiated the HELLO message (red) and the nodes that were outside the range of the initial HELLO broadcast (black). Nodes that received or heard the HI message will update their Link and Neighbor Sets. R1 will set the symmetric status of links R2-R4 to 1 since they all responded to its initial HELLO message, while nodes R5 and R6 will set the symmetric status of links R2-R4 to 0 (asymmetric) because the ability of those nodes to respond to the broadcasts is still uncertain.  
Figure 6. Neighbor Set after HELLO broadcast.  
Figure 7. HI message broadcast and sample Neighbor Set after broadcast.  
Any node that did not broadcast a HELLO message but received a HI message must do the following:  
* Set EMERGENCY_HELLO to 1 or a value that is greater than zero. This will enable the node to broadcast a HELLO message before the next LISTEN state. The HI message process or state is summarized in the flowchart in Figures 8 and 9 below.
# BBSF: Blockchain-Based Secure Weather Forecasting Information through Routing Protocol in Vanet
## 3 Methodology
### Routing Strategy  
The primary goal of this work was to establish effective routing for secure weather forecasting information distribution. The chosen routing algorithm aimed to achieve high packet delivery rates while minimizing end-to-end delays. System analysis was conducted to address the network design and operational challenges. Two primary challenges for efficient routing were node connectivity and channel reliability.  
In terms of the node connectivity, we considered two devices in the network to be active, and the other as a dumb type. Smart devices are referred to as such in the case of providing access to the data and onboard sensors of the vehicles, and others are transmitted toward less accessible devices. The ratio of message exchange in low mobility networks is very high compared to the risks associated with packet drops due to low network performance. Due to packet drops, the waiting time of the network performance expired due to network connectivity issues and performance enhancements.  
Channel reliability is another factor in network routing. Whenever the network density is high, limited medium bandwidth is caused. Messaging is another issue which is faced due to the overwhelming of network performance parameters. Due to the high availability of the network parameters, the channel coverage and bandwidth performance enhancements are limited due to the limited packet rates. The channel topology is flexible due to the wireless activity and performance enhancements. The channel's reliability is maximum with the maximum availability of network parameters. For instance, vehicles may not be able to receive GPS signals in certain areas, beacon messages may collide with other messages, and vehicles may be selfish and refuse to broadcast the message.
## 3 Simulation and Result
The simulation results indicate that the proposed method and the conventional indirect FOC exhibit comparable performance in terms of dynamic response. Following step changes in either the speed command or the load torque, both control strategies successfully converge to the new steady-state operating point. However, under steady-state conditions, the proposed method yields significantly lower stator current magnitudes compared to the conventional FOC approach, indicating improved efficiency. This improvement is particularly evident in Figure 13d,h.
## 4 Discussion
### Fractal Dimension Parameter  
The fractal dimension, derived from the fractal theory in geometry, serves as a crucial parameter for describing the complexity and heterogeneity of pore structures in coal. Studying the fractal dimension of coal samples allows for further quantification of the roughness of pore surfaces and the complexity of their spatial distribution, reflecting the heterogeneity of the pore system. Previous research has shown that the fractal dimension of samples is influenced by numerous factors, including coal quality parameters, pore structure parameters, and metamorphic grade. [PERSON] et al. [47], when studying lignite from the Hailar Basin, found a positive correlation between the fractal dimension of coal pore surfaces and ash yield, as well as a \"U\"-shaped relationship with fixed carbon content. [PERSON] et al. [48], in their study of the fractal characteristics of adsorption pores in coal from the Fukang mining area in Xinjiang, discovered a negative correlation between the fractal dimension and pore diameter and a positive correlation with pore specific surface area and pore volume. [PERSON] et al. [49], taking the Xishan coalfield as their research object, analyzed the factors influencing the fractal dimension of coal samples and found that as metamorphic grade and burial depth increase, the fractal dimension of coal surfaces also increases, leading to a more complex pore surface.  
To explore the extent to which volatiles affect the fractal dimension of coal samples, Figure 8 illustrates the correlation between the fractal dimensions and the volatile content of the selected samples using different analysis methods. As the volatile content increases, the fractal dimensions exhibit a linear downward trend to varying degrees, indicating that as the volatile content increases, the morphology of nanopores tends to become more complex. High-volatile coals have larger average pores, predominantly macropores with a uniform scale and regular shape, sparse microcracks and nanopores, and poor pore connectivity, resulting in lower fractal dimensions. As volatiles escape, pores are compressed or reconstructed into branched channels, increasing the pore surface roughness and making the structure of pores at different scales more complex, leading to an increase in the fractal dimension.
###### Abstract  
Recently, there has been significant interest in the thermal performance of parabolic trough collectors. They are capable of operating and generating highly variable temperature ranges, which can be used in various applications. This paper, therefore, addressed the thermal performance model of using a parabolic trough collector under the radiation intensity level found in Budapest city, as well as the effect of inserting a hybrid nanofluid as the thermal fluid. First, a new modified hybrid nanofluid of alumina and tungsten oxide-based Therminol VPI is used to enhance the thermal properties of the thermal fluid to be more efficient to use. This enhancement is performed under various volume concentrations and has a volume fraction of 50:50. Second, in order to demonstrate the effectiveness of the thermal element, mathematical energy balance equations were solved and simulated using MATLAB Symbolic Tools. The simulation is presented for two cases: one under a constant radiation intensity and the other under the radiation intensity level of Budapest. For both cases, the results of the dimensionless Nusselt number, heat transfer coefficient, pressure drop, exergy efficiency, and energy efficiency are described. The major findings show that a volume concentration of 4% (Al\({}_{2}\)O\({}_{3}\) and WO\({}_{3}\)) based Therminol VPI was the most efficient volume concentrations in both cases. For the first case, the maximum enhancement of the Nusselt number and the heat transfer coefficient are 138% and 169%, respectively. These results enhanced the thermal and exergy efficiencies by 0.39% and 0.385% at a temperature 600 K, flow rate of 150 L/min, and radiation intensity of 1000 W/m\({}^{2}\). For the second case, the maximum exergy and energy values are recorded at midday under Budapest's summer climatic conditions and reach 32.728% and 71.255%, respectively, under the optimum temperature of 500 K and flow rate of 150 L/min. Accordingly, the mean improvement in thermal and exergy efficiencies approximately equal to 0.25% at a high concentration, regardless of the season (summer or winter).  
solar energy; parabolic trough collector; thermal performance enhancement; radiation intensity; hybrid nanofluid; thermal efficiency; Budapest +
Footnote †: journal: Applied Sciences
## 1 Introduction
In what way the working fluids affect the pump performance is the key consideration in this study. The vast majority of papers about Roots pump are related to applications such as air blowers and vacuum pumps. Nevertheless, all these studies provided invaluable insights and helpful information for theoretical modeling the performance of Roots pump for hydrogen recirculation. For example, it has been shown that the performance of the Roots pump can be calculated by thermo-fluid modeling based on one-dimensional chamber modeling with lumped parameters [24; 25]. Moreover, it has also been indicated that the CFD simulation is more accurate and more detailed for predicting the performance of Roots machine, because it can simulate the velocity and pressure fields within the pump chamber and the leakage clearances [26; 27; 28; 29; 30]. Regretfully, as of the present study, simulations of a hydrogen pump [20; 21] were based on pure hydrogen, and only together with water vapor considered for ejector [12; 31; 32]. These research results indicated that water vapor could apparently influence the entertainment performance of the ejector. Thus, there is still a big difference from real applications. As mentioned above, the hydrogen recirculated by the Roots pump is associated with impurities including water vapor and nitrogen. The objective of this study is to find out the effects of these impurities on the performance of the Roots pump and to evaluate the performance of this kind of hydrogen pump under various operating conditions in the PEM fuel cell system. The investigation is performed by the simulation based on CFD modeling of the three-lobe Roots pump with helical rotors developed specifically for fuel cell systems between 60 to 110 kW. Furthermore, abundant verification experiments are conducted via running with air and helium. Based on this, the prediction of the flow rate and power consumption of this Roots hydrogen pump are carried out numerically under various operating conditions. The effects of water vapor and nitrogen that remained in the recirculated hydrogen on the pump performance are discussed in detail for the first time. In the end, correlations of volumetric efficiency and isentropic efficiency are given based on simulation results to show the general pattern of this kind of hydrogen pump. It is believed that these equations are very helpful to the design and operation control of the PEM fuel cell system.