esa-sceva/satcom-chunk-collection huggingface dataset:
## 2 Bidirectional DC-DC Converters
### Classification of Bidirectional DC-DC Converter
#### 2.1.2 Isolated Bidirectional \(DC\)-\(DC\) Converters (IBDCs)
Particularly, it is well suited to the integration of a two-switch buck-boost converter in the half-bridge side for obtaining a complete \(UPS\) topology. Other variations of this configuration have been proposed, such as a full-bridge-half-bridge bidirectional \(DC\)-\(DC\) converter paired with impedance networks to improve performance [70]. Figure 14: Isolated half-bridge–full-bridge bidirectional \(DC\)-\(DC\) converter [18]. Figure 13: Comparison of (**a**) full-bridge topology and (**b**) half-bridge technique [69]. In the case of the magnetic isolation requirement, the well-known flyback converter is realized when a transformer replaces the inductor of the buck-boost converter. A bidirectional isolated buck-boost converter can be constructed using the bidirectional evolution technique in non-isolated topologies, as shown in Figure 15. The gain of the converter in forward power flow is obtained by applying the volt-second and charge-second balancing, which is the same as the voltage gain ratio of the flyback converter as expected. It is worth noting that the transformer design technique must be considered, and a voltage clamp snubber is required to control the flyback transformer's leakage current [71]. Push-Pull Bidirectional _DC-DC_ Converter  
Based on the unidirectional push-pull converter, the bidirectional push-pull converter (see Figure 16) was suggested in order to allow power to flow in both directions. Same as unidirectional push-pull converters, bidirectional push-pull converters use a multi-winding transformer to convert the power. A three-phase bidirectional push-pull converter was also proposed to run this approach in high-power applications [73].
## 2 Synchronization and Reliability Provided by Power Supply System Design
### Traction Power Distribution System
#### 2.3.2 Distribution Traction System  
Single-end feed: In this system, the trains draw current from one direction by a TPS [13; 14; 21; 52; 53; 54; 55; 56]. The advantages of this network include its simplicity, ease of installing security devices, and uncomplicated operation. However, a disadvantage is that it experiences a significant voltage drop along the line, which reduces the passenger carry capacity.  
Double-end feed: In this system, trains draw current from the two directions by two adjacent TPSs [21; 52; 53; 54; 55; 56]. The benefits include a reduced voltage drop in the contact line, extended supply distance, and higher transport capacity. However, this network has a more intricate structure, necessitates the installation of intricate protection devices, and requires difficult maintenance.
## 3 Results
### Electric Machines and Their Role in Distributed Energy Systems  
#### 3.6.1 Current Developments  
The design and operation of electric machines have undergone significant advancements to address the evolving needs of DES. Modern designs increasingly prioritize flexibility, efficiency, and compatibility with distributed generation sources, such as solar and wind power. Synchronous machines and reluctance generators, among other types, are being optimized for integration into microgrids and nanogrids. For instance, advanced droop-controlled inverters interfaced with LC or LCL filters have been employed in autonomous nanogrids to maintain voltage and frequency stability during P2P energy trading. These systems ensure a robust control performance under variable generation conditions, enabling effective energy sharing and grid support [20].  
Reluctance generators, known for their simplicity and robustness, are being re-engineered to enhance their efficiency in renewable energy applications. Their adaptability to variable speed operations, particularly in wind energy systems, makes them well-suited for dynamic environments. Coupled with advanced power electronics and secondary control mechanisms, these machines can deliver a consistent performance while supporting energy trading in distributed networks [2]. Electric vehicles are also playing an important role in DES as mobile energy storage units. Integrating EV charging stations into microgrids has opened new opportunities for utilizing electric motors in V2G and V2V operations. This dual functionality of electric machines--both as energy converters and storage units--hassignificantly enhanced the flexibility and stability of distributed systems, particularly in urban transportation networks [95].
# Efficient Support Vector Regression for Wideband DOA Estimation Using a Genetic Algorithm
## 4 Performance Analysis
### Resolution Performance  
This experiment mainly analyzes the resolution performance of the proposed algorithm. Here, the definition of a successful resolution is as follows: a simulation trial is considered successful if the absolute error between all estimated signal angles and the true values remains within \({}_{1^{\circ}}\). Otherwise, it is regarded as a failure. In the case of two far-field wideband signals at \(SNR\) = 8 dB, the incident angle of the first signal is fixed at \(\theta_{1}=0^{\circ}\), while the angle of the second signal is set to \(\theta_{2}=\theta_{1}+\Delta\theta\). \(\Delta\theta\) is the interval between the two angles, where the angular separation is \(\Delta\theta\in(1^{\circ},2^{\circ},\cdots,20^{\circ})\). Each angular interval undergoes 200 Monte Carlo trials to derive the resolution probability versus the angular separation curve, as presented in Figure 7a. Additionally, with fixed signal positions \(\theta_{1}=0^{\circ}\) and \(\theta_{2}=7^{\circ}\), the SNR is systematically varied from \(-10\) dB to \(10\) dB in 2 dB increments, producing the corresponding resolution probability versus SNR curve shown in Figure 7b.  
As can be seen in Figure 7, with the increase in the angular interval and SNR, the resolution probability of all methods is in an increasing trend, and the successful resolution probability of the proposed algorithm is the first to reach 100%, which is higher than that of the other methods. The CWSVR method ranks second in performance. In the case of low SNR, the resolution performance of other methods is relatively poor, and the proposed method in this paper can still maintain a certain resolution probability. The L1-SVD method reaches 100% only when the angular separation exceeds \({}_{11^{\circ}}\). It can be seen that the probability of successful resolution is very low when the angular interval is \(\tau\), and there is no great improvement in the resolution probability even if the SNR is enlarged. The performance of the RSS-MUSIC method is highly sensitive to the predicted angle. When the predicted angle is inaccurate, the performance significantly degrades. It can be seen in Figure 7 that the RSS\(-\)MUSIC method is almost unable to successfully discriminate the signal under the same conditions.  
Figure 7: The resolution performance of two signals: (**a**) varying angular spacing; (**b**) varying SNR.
# Statistical Model for Mobile User Positioning Based on Social Information
###### Abstract
Thus, the main contribution of this work is  
* The finding of alternative data sources (i.e., social network information and user context information) for user positioning. * A complete methodology for user positioning merging classical (cell ID and Time Advance statistics) and novel data sources. User context is estimated from the connections Key Performance Indicators, KPIs, while the population distribution in the scenario is obtained from geo-positioned information of heavily used social networks. This paper is composed of four sections. To contextualize the algorithm, different contributions of interest in the field of user positioning are discussed in Section 2. Next, Section 3 presents the statistical distribution model of users in the network, while Section 4 contextualizes the data used for testing the model, in addition to showing the obtained results. To conclude the paper, Section 5 provides a series of conclusions drawn from the work.
## 3 Theoretical Background
### Sign of Induced Birefringence  
The sign of the induced birefringence (negative or positive) depends on which direction refractive index of the sample is higher (along or perpendicular to magnetic field direction). From the molecular description, this is given by the relative orientations of magnetic and electric susceptibility (polarizability) ellipsoids. By convention, if the direction of the highest magnetic polarizability coincides with direction of highest electric polarizability, the induced birefringence is positive [25].
## 1 Introduction
At present, SEY study on MgO are mostly limited to bulk material or thick film, and related SEY studies for nanoscale ultrathin MgO coatings are seldom reported, which makes the occasions employing ultrathin MgO films, such as the design of MCP functional layer, lack of experimental research and theoretical support. Therefore, further research is needed regarding the SEE characteristics of ultrathin MgO coatings. In this work, from both experimental and theoretical aspects, we systematically studied the SEE characteristics of the nanoscale MgO coatings (thickness ranges from 1 to 30 nm), and revealed the dependence of SEY on the coating thickness; finally, we obtained the quantified SEY regularities of MgO/Si double-layer structures. In the research, we prepared a series of ultrathin MgO coatings with increasing thickness by employing atomic layer deposition (ALD) technique, and characterized their SEE properties and electron spectra characteristics, as well as concluded the SEY evolution regularities with the variation of the coating thickness. By utilizing the SEE model developed for double-layer structures, we calculated the theoretical SEY values of MgO/Si double-layer structures and gave the quantified influence of coating thickness on SEY theoretically. In addition, for the purpose of quantifying the SEY contribution level of two layers, we broke down the calculated SEY curves, and extracted the SEY proportions contributed by the top layer and bottom layer, respectively, for the 1 nm and 20 nm MgO coating samples. The extracted SEY curves quantitatively interpreted the SEY dependence on the top and bottom layer with the change of the top coating's thickness. The results obtained via the theoretical calculation kept in well accordance with the experimental phenomena.
## 3 Results and Discussion
### Thermodynamics of Cr(VI) Adsorption. Results for Gibbs Free Energy  
By excluding the 5.23 ppm initial Cr(VI) concentration case, where the total dissolved Cr(VI) amount was adsorbed and no equilibrium stage was obtained, for initial concentrations of 20.94, 26.73, 35.40, and 54.14 ppm at which AC@SCF became saturated with Cr(VI), \(\Delta G^{0}\) was calculated as \(-\)24.1,  
Figure 6: (**a**) Predictions for maximum loading of Cr(VI) at equilibrium conditions on AC@SCF for different initial concentrations. (**b**) Initial rate estimation for different initial concentrations using the three different kinetic models (except the intraparticle diffusion model). (**c**) Intraparticle diffusion constant for different initial concentrations. (**d**) Diffusion–chemisorption constant for different initial concentrations.  
\(-\)22,7, \(-\)21.6, and \(-\)20.2 kJ/mol respectively. The negative values confirmed the spontaneous nature of the adsorption process, where the values of \(-\)20 \(>\)\(\Delta G^{0}\)\(>\)\(-\)80 kJ/mol were attributed to the transition stage from physisorption to chemisorption. Thus, both physisorption and chemisorption phenomena occurred, and ion exchange and/or surface complexion were likely the main mechanisms. This was inconsistent with the diffusion-chemisorption model, which is the preferable model for sorption kinetic studies. Moreover, such \(\Delta G^{0}\) values indicate that other mechanisms of adsorption (like ion exchange and/or surface complexation) mainly occur [56; 57].
## 6 Conclusions and Future Work
### Cooperation and Negotiation with Telecom Operators  
It is undoubtedly an excellent way to locate users through 5G, but how to carry out cooperation and profit distribution is another issue that is both practical and yet to be discussed. Since it is impossible for telecom operators to provide user positioning information for free, besides rental fees even discussing profit splitting or intermediary rental bargaining has become an interesting issue.  
For the advertising platform, the more telecom base station data, the more accurate the analysis and utilization will be. Of course, more base stations have to be rented, so the cost of obtaining audience location information will be higher. However, if the number of leased base stations is not enough, the data will be analyzed and the accuracy and the range of services provided will be limited. The advantage of renting is that it needn't invest a large amount of capital in the initial stage to collect audiences' geographic data and adjust the number of base stations rented according to the effectiveness anytime. If the business can obtain huge profits from it in the future, the renting cost also may not necessarily increase.  
To respond to government policies, telecom operators must invest a large amount of capital for base station construction in the early stage. After the completion of the construction, apart from being unable to directly recover a large amount of money invested in a short time, they must also pay regular maintenance fees to ensure the smooth operation of the base station system.  
For other operators who are willing to lease equipment, telecom operators will certainly be happy to cooperate. However, whether the two sides can profit or at least break even, it still relies on business negotiations or the mutual running-in to decide. Due to the huge investment cost and the fact that it is difficult to estimate the partner's profit, it will be more difficult for telecom operators to decide on the rental fee.  
Another critical reason for cooperating with telecom companies is that they have an important influence in dominating the market. All communication software and hardware will be replaced and updated with the progress of the times, whether it is the communication protocol or the service used in the user's mobile phone. Even if a user may be unwilling to update the software and hardware of the mobile phone due to cost considerations or other factors, it will eventually be forced to update due to the replacement of the telecom company's system.  
Telecom companies will also continue to provide various transitional technical solutions during the transitional period of technology replacement through online updates or technology compatibility. Thus, some old-style communication equipment can continue to operate, and it is why other companies cannot easily enter the communication service market and only telecom companies can stabilize the communication operations in these markets. That is also the value of the existence of telecom companies.
## 1 Introduction
[17], an investigation and proposal for a multi-layer array antenna are made. The THz antenna topologies presented herein enhance operational bandwidth in order to compensate for the larger antenna diameter. Wideband THz antennas were designed by researchers who published their results in peer-reviewed publications, with the intention of addressing the fading issue in high-speed, short-range wireless applications running at high frequencies in the THz spectrum. Use of multiple-input multiple-output (MIMO) antenna methods may minimize signal fading concerns in wireless networks. In this work, an ultra-wideband graphene-based circular patch-shaped Yagi-like MIMO antenna is numerically investigated for 1-30 THz of the band. The various parameters, such as return loss, directivity, peak gain, TARC, ECC, MEG, CCL, and DG are calculated for the 2 \(\times\) 2 MIMO antenna structure. The effect of the different antenna configurations--such as 1 \(\times\) 2, 2 \(\times\) 1 and 1 \(\times\) 1 structures--has also been calculated to identify the influential operating bands. This design provides promising results for all the antenna parameters, making it suitable for THz wireless communication applications. The highlights of the proposed UWB antenna are as follows:  
* Microstrip technology is used to design the graphene-based circular patch-shaped Yagi-like ultra-wideband MIMO antenna. Thus, it is smaller, lighter, easier to build, and more cost effective than other THz antennas. * The suggested antenna has a substantially broader bandwidth (10.96 THz). * The proposed MIMO structure offers better diverse performance parameters: DG \(\approx\) 10 dB, CCL \(<\) 0.5 bps/Hz/s, TARC \(\leq-\)10.0 dB, MEG \(\leq-\)3.0 dB, and ECC \(<\) 0.01). This helps to overcome the challenges associated with short-distance communication such as signal fading, multipath propagation, and increased interference.
# Internet of Things and Long-Range-Based Smart Lampposts for Illuminating Smart Cities
## 2 Related Works and Overview of IoT
### Overview of IoT  
According to GSM association (GSMA) intelligence forecasting, the number of IoT connections will reach 25 billion globally by 2025 [40]. The growth of IoT devices from 2015 to 2025 is presented in Figure 1.  
IoT is an interconnection of physical things with a virtual environment through internet protocol (IP) connectivity. In IoT, the physical things are embedded with sensors and actuators for sensing and controlling. A communication protocol is integrating with the sensors and actuators for updating and transmitting the sensory data to the server. Integration of sensor/actuators, connectivity, data processing, and user interface (UI) forms an IoT network. IoT comprises the four components that define the functionality and it is shown in Figure 2.  
A sensor is a device that senses and responds to the input from the physical environment. The output signal of the sensor is converted into a digital signal. Connectivity is necessary for the transmission of sensory data and they are different wireless protocols for establishing connectivity. The distinct kinds of wireless communication technologies are existing in the Internet of Things. GSM/global packet for radio service (GPRS), Zigbee, BLE (Bluetooth Low Energy), IPv6 over low -power wireless personal area networks (6 LoWPAN), radio frequency identification (RFID), LoRa, Sigfox, narrow band-IoT (NB-IoT), long term evolution (LTE), IEEE 802.11g Wi-Fi, near field communication (NFC), and Z-wave are the communication technologies. Zigbee, Z-wave, BLE, 6 LoWPAN, and IEEE 802.11 g are the short-range wireless communication technologies, and GSM/GPRS, LTE, LoRa, Sigfox, and NB-IoT are the communication technologies for the long-range distance. Generally, the transmission range of these communication technologies such as IEEE 802.11 Wi-Fi,  
Figure 1: Growth of IoT devices (2015–2025) [40]. IEEE 802.15.4 Zigbee, and IEEE 802.15.1 BLE is short-range; however, except IEEE 802.11 Wi-Fi, the remaining two wireless communication technologies consume low power for the data transmission. LoRa, NB-IoT, and Sigfox are emerging low power and long-range communication technologies that meet the goal of the IoT. Among the three low-power wide-area network (LPWAN) technologies, LoRa is the optimal communication system with secure bi-directional communication and free licensed band capabilities. RFID and NFC are identification technologies that work on radio waves. Both technologies communicate up to a range of 4 cm-10 cm. The data processing is one more component of the IoT, where the sensory data is converted to machine-readable form. Classification, sorting, and calculations are performed on the data for getting meaningful information. Different tools are existing for data processing in the IoT. The technical specifications of the communication technologies are briefly mentioned in Table 1.
## 3 PSO-Based Optimization of RIS Phase Shifts  
On the purpose of fulfilling the target to achieve the maximum average capacity, where the maximum SNR \(\gamma[n]\) should be reached. Then, the target translates to maximize the pointing error and atmospheric loss coefficients \(h_{a}[n]\) and \(h_{p}[n]\). Therefore, we exploit Particle Swarm Optimization (PSO) to optimize the pointing error loss within each position point of the UAV during its operation. Due to the UAV operating the 3D flight, the incident laser beam is not perpendicular to the PD, and the Gaussian profile beam footprint is an ellipse on the PD plane. Furthermore, we considered the pointing error loss \(h_{p}[n]\) in this work to model the effect of the fluctuation, which is equivalent to considering imperfect CSI at the PD. By iteratively adjusting leading angles of RIS in each iteration \(m\in\{1,2,\ldots,M\}\) of PSO, the number of \(h_{p}[n]\) will be maximized as a precondition in each UAV position, denoted as  
\[(\mathbf{P}2): \max_{\Phi,\mathbf{G}}h_{p}[n]\] (15) s.t. \[(1)(2).\]  
This method allows for the decoupling of the phase shifts optimization problem and the UAV trajectory optimization problem, which simplifies our optimization challenge into two independent yet separated problems. In this paper, the PSO algorithm was proposed for the purpose of obtaining high-precision continuous phase shifts leading angles for the most optimized RIS status. The steps of PSO are listed as:
# Shading on Photovoltaic Collectors on Rooftops
###### Abstract  
Rooftop photovoltaic (PV) systems in urban environments play an important role in solar electric energy generation. Shading on PV collectors, by self-shading, walls and fences on rooftops, affect negatively the output energy of the PV systems. Increasing the distance between the collector rows, and between the walls and fences near to the collectors, may minimize the shading losses. Practically, this option is usually limited, especially on rooftops. Rooftops may be of different types: horizontal, inclined, and saw-tooth, and may have obscuring structures like walls and fences. The distance between the shading objects and the PV collector rows determine the loss of energy due to shading. The study provides the PV system designer with mathematical expressions for distances from obscuring objects for the deployment of PV systems on rooftops. The optimal inclination and azimuths angles of a PV system on a triangular sloped rooftop are also illustrated.  
PV on rooftops; shading by walls and fences; row distance; shading losses +
Footnote †: journal: Applied Sciences