Search Results (642)

This paper presents the design process and resulting technical concept for an integrated hyperloop system, aimed at realizing efficient high-speed ground transportation. This study integrates various functions into a coherent and technically feasible solution, with key design decisions that optimize performance and cost-efficiency. An iterative design process with domain-specific experts, regular reviews, and a dataset with a single source of truth were employed to ensure continuous and collective progress. The proposed hyperloop system features a maximum speed of 600 $\frac{\mathrm{km}}{h}$ and a capacity of 21 passengers per pod (vehicle). It employs air docks for efficient boarding, electromagnetic suspension (EMS) combined with electrodynamic suspension (EDS) for high-speed lane switching, and short stator motor technology for propulsion. Cooling is managed through water evaporation at an operating pressure of 10 $\mathrm{m}$$\mathrm{bar}$, while a 300 $\mathrm{k}$$\mathrm{W}$ inductive power supply (IPS) provides onboard power. The design includes a safety system that avoids emergency exits along the track and utilizes separated safety-critical and high-bandwidth communication. With prefabricated concrete parts used for the tube, construction costs can be reduced and scalability improved. A dimensioned cross-sectional drawing, as well as a preliminary pod mass budget and station layout, are provided, highlighting critical technical systems and their interactions. Calculations of energy consumption per passenger kilometer, accounting for all functions, demonstrate a distinct advantage over existing modes of transportation, achieving greater efficiency even at high speeds and with smaller vehicle sizes. This work demonstrates the potential of a well-integrated hyperloop system to significantly enhance transportation efficiency and sustainability, positioning it as a promising extension to existing modes of travel. The findings offer a solid framework for future hyperloop development, encouraging further research, standardization efforts, and public dissemination for continued advancements. Full article

With the success and commercialization of 5G, 3GPP has started working toward the sixth generation of communication systems. While 5G explored the concept of non-terrestrial networks like satellites and unmanned aerial vehicles working alongside terrestrial networks, 6G is expected to take this integration a step further, aiming to achieve a more coherent network where satellites and terrestrial infrastructure work together seamlessly. However, the complexity and uniqueness of such networks create numerous attack surfaces that make them vulnerable to cyberattacks. The solution to such cyberattacks can be addressed by encryption and other upper-layer authentication methods. However, with the move to higher-frequency bands, such encryption techniques are difficult to scale for low-latency networks. In addition, the recent progress in quantum computing will make networks more vulnerable. To address such challenges, physical layer security (PLS) is proposed as a secure and quantum-resistant way to implement security by taking advantage of the physics of the channel and transceiver. This article reviews the latest trends and progress in PLS in integrated satellite–terrestrial networks (ISTNs) from a signal processing perspective. This work provides a comprehensive survey of the state-of-the-art research conducted, challenges, and future directions in the PLS of ISTNs. Full article

The outbreak at the end of February 2022 of the Russian invasion of Ukraine—and the Russian–Ukrainian hostilities that began in 2014 with the Euromaidan—has led to numerous dramatic episodes from both a humanitarian and an informative perspective. In this context, social media have been filled with rhetoric and narrative mechanisms, both from civil society organisations and from European media and institutions, in their eagerness to define their position within the dialectical battle. This research aims to address organisational communication in the European Union during the first year after the invasion, taking as its object of study the publications of four institutional bodies: European Commission, European Parliament, European Council, and European External Action Service. For this purpose, a content analysis of tweets was carried out, as well as in-depth interviews with specialised actors in institutional communication and disinformation at the EU level. Overall, the results show that the parallel narrative of the Commission, the Parliament, the Council, and the EEAS has been quite similar and lacks significant divergences, reflecting coherence and coordination in the communication strategies around the Ukrainian war, although there are interesting findings on the interaction of the institutions with the media and other civil society actors in communicating this international crisis via social media. Full article

Tourism development has a significant contribution to the sustainable development of countries and regions through job creation, infrastructure development, cultural preservation, community empowerment, and revenue increase. Within this context, digitalization in the different facets of the tourism marketspace is a powerful tool that promotes competitiveness and economic growth, sustainability, innovation, and regional coherence. Digitalization also calls for the industry actors to have meaningful integration of novel technologies and practices in their operations and strategy. Despite the importance of digital technologies as a competitive antecedent for hospitality ventures, the extant research is mainly anchored on digital marketing and its associations with traditional mass tourism activity. Evidence on other facets of digitalization is far less appreciated, especially in the niche segment of the alternative tourism marketspace. Considering the above developments, our research aim is to assess the contribution of a digital business ecosystem, including a wide array of digital applications, to the competitiveness of the hospitality industry in Greece, with a focus on alternative tourism activities. Our research draws on data collected from a sample of local ventures to investigate the impact of digital technologies on tourists’ attraction and company growth. In the main, our findings record the positive impacts of digitalization, with internet-based technologies standing out as the most influential medium to boost growth and hotels’ sustainability. We contribute by showing that in cases where hospitality ventures remain digitally illiterate, they will most probably face severe competition losses. Full article

Neovascular age-related macular degeneration (nAMD) is one of the major causes of vision impairment that affect millions of people worldwide. Early detection of nAMD is crucial because, if untreated, it can lead to blindness. Software and algorithms that utilize artificial intelligence (AI) have become valuable tools for early detection, assisting doctors in diagnosing and facilitating differential diagnosis. AI is particularly important for remote or isolated communities, as it allows patients to endure tests and receive rapid initial diagnoses without the necessity of extensive travel and long wait times for medical consultations. Similarly, AI is notable also in big hubs because cutting-edge technologies and networking help and speed processes such as detection, diagnosis, and follow-up times. The automatic detection of retinal changes might be optimized by AI, allowing one to choose the most effective treatment for nAMD. The complex retinal tissue is well-suited for scanning and easily accessible by modern AI-assisted multi-imaging techniques. AI enables us to enhance patient management by effectively evaluating extensive data, facilitating timely diagnosis and long-term prognosis. Novel applications of AI to nAMD have focused on image analysis, specifically for the automated segmentation, extraction, and quantification of imaging-based features included within optical coherence tomography (OCT) pictures. To date, we cannot state that AI could accurately forecast the therapy that would be necessary for a single patient to achieve the best visual outcome. A small number of large datasets with high-quality OCT, lack of data about alternative treatment strategies, and absence of OCT standards are the challenges for the development of AI models for nAMD. Full article

This study examined the emotional reactions and coping resources of Bedouin teenagers (ages 12–18) following the events of 7 October 2023 and the subsequent Iron Swords War between Israel and Hamas forces in Gaza. This study focused on the relationships between subjective exposure, personal sense of coherence, community resilience, and the use of different coping strategies, on the one hand, and anxiety, anger, and psychological distress, on the other. During 2024, 762 participants completed the study questionnaire, which addressed the different study variables. The findings revealed significant differences between the boys and the girls. Specifically, the girls reported higher levels of subjective exposure and emotional reactions. Personal sense of coherence was found to be a significant protective factor. In contrast, the use of nonproductive coping strategies increased distress. This study underscores the need for intervention programs tailored for this society and by gender, as well as training for educational professionals, to help them to identify and treat emotional reactions to stress in ways that take into consideration the Bedouin cultural context. This study enhances our understanding of how Bedouin teenagers cope with stressful situations and crises. Full article

The health of road transport workers is affected by working conditions and life. However, there is a lack of studies on the level of stress and health of the families of these workers. This study aimed to evaluate the perceived stress level and family effectiveness of family members of road transport workers. A quantitative study was carried out with the family members of road transport workers in the southern region of Brazil. For data collection, a sociodemographic form, the Perceived Stress Scale (PSS), and the Evaluation of Family Effectiveness Strategies were used. The data were analyzed by simple frequency, Spearman correlation coefficient (ρ) (p < 0.05), and descriptive analysis from the perspective of Systemic Organization. The sample was composed of 49 family members of road transport workers. Perceived stress was higher in family members who had more than nine years of education (p = 0.0403). Family members who scored higher in Family Effectiveness scored high on the targets of Control (p = 0.0353) (Control aims to reduce anxiety and prevent and eliminate events that threaten family stability) and Growth (p = 0.0360) (represented by attitudes that promote new roles in response to critical situations experienced by families, which require re-adaptation processes and adjustments). The Control target was significant (p = 0.0353) in families that had more than three people. The Coherence dimension (concerning self-esteem, body image, personal identity, self-confidence, and sexual identity) presented positive significance (p = 0.0244) in families with health problems and whose income was less than USD 792.00 per month (p = 0.0072). The Individuation dimension (including functions and responsibilities, where talents are reinforced, as well as initiatives that allow for the incorporation of knowledge to assume behaviors against personal/family and environmental pressures), was significant (p = 0.0138) in families with incomes over USD 792.00. The Maintenance System (strategies for decision-making, problem negotiation, ritual and traditional roles, communication patterns, standards, financial management, and approaches to maintaining family harmony) presented positive significance (p = 0.0151) in families where drivers worked as intercity drivers, as did the Stability target (p = 0.0196) (concerning the continuity of routines, structure, organization, traditions, and values assumed by the family and transmitted from generation to generation, which promote unity and the development of values, attitudes, and beliefs). In conclusion, social factors, such as education, income, diseases, type of worker activity in road transport, and number of people in the family, influenced perceived stress and family effectiveness, which demonstrates the need to increase the promotion of health care for the families of road transport workers. Full article

In this paper, we skillfully utilize the discriminative ability of the discriminator to construct a conditional generative adversarial network, and propose a scheme that uses few symbols to achieve high accuracy recognition of modulation formats under low signal-to-noise ratio conditions in coherent optical communication. In the one thousand kilometres G.654E optical fiber transmission system, transmission experiments are conducted on the PDM-QPSK/-8PSK/-16QAM/-32QAM/-64QAM modulation format at 8G/16G/32G baud rates, and the signal-to-noise ratio parameters are traversed under experimental conditions. As a key technology in the next-generation elastic optical networks, the modulation format recognition scheme proposed in this paper achieves 100% recognition of the above five modulation formats without distinguishing signal transmission rates. The optical signal-to-noise ratio thresholds required to achieve 100% recognition accuracy are 12.4 dB, 14.3 dB, 15.4 dB, 16.2 dB, and 17.3 dB, respectively. Full article

To detect moving weak targets in the dual function radar communication (DFRC) system of an orthogonal frequency division multiplexing (OFDM) waveform, a modified hybrid integration method is addressed in this paper. A high-speed aircraft can cause range walk (RW) and Doppler walk (DW), rendering traditional detection methods ineffective. To overcome RW and DW, this paper proposes an integration approach combining DFRC and OFDM. The proposed approach consists of two primary components: intra-frame coherent integration and hybrid multi-inter-frame integration. After the echo signal is re-fragmented into multiple subfragments, the first step involves integrating energy across fixed situations within intra-frames for each subcarrier. Subsequently, coherent integration is performed across the subfragments, followed by the application of a Radon transform (RT) to generate frames based on the properties derived from the coherent integration output. This paper provides detailed expressions and analyses for various performance metrics of our proposed method, including the communication bit error ratio (BER), responses of coherent and non-coherent outputs, and probability of detection. Simulation results demonstrate the effectiveness of our strategy. Full article

(1) Background: The significant progress observed over the last two decades in coherent beam combining (CBC) technology has mainly focused on its applications in high-energy physics and laser weapons. This work provides insight into the basic principles of CBC and the search for an alternative, namely optical angular momentum (OAM) generation using CBC. (2) Methods: A semi-analytical model based on the paraxial wave equation was explored, generating OAM-CBC beams by manipulating the tilts and phases of the CBC (T&P-CBC) of hexagonal architecture. (3) Results: The specially arranged T&P-CBC shows typical properties of OAM, such as annular profiles for the zero diffraction order and 1st-order replicas in the far field and correlation coefficients of 1% between different OAM-CBC fields. (4) Conclusions: The differences between classical OAM beams and OAM-CBC are substantial due to hexagonal lattice properties. Moreover, applications in free space optical communications are feasible as T&P CBC fulfills the main conditions and requirements for OAM generation. Full article

To effectively mitigate the effects of atmospheric turbulence in free space optical (FSO) communication, we propose a parallel carrier frequency offset estimation (FOE) scheme based on time-tagged QPSK partitioning (TTQP). This scheme can be applied to spatial diversity polarization multiplexing (PM) coherent FSO communication systems. Specifically, the TTQP scheme performs QPSK partitioning by time-tagging signal points, accurately recording the time intervals between signals, and significantly reducing implementation complexity through a modified Mth power algorithm. The simulation results for the PM 16-quadrature amplitude modulation (QAM) validate the effectiveness of the proposed scheme. Compared to traditional QPSK partitioning algorithms, the TTQP algorithm achieves high accuracy, low complexity, and multi-format versatility in high-speed coherent FSO communication. Full article

Light intensity flicker is the most basic and important effect of turbulence. Fiber coupling efficiency is the primary parameter that ensures the system’s communication quality. The light intensity flicker effect caused by atmospheric turbulence significantly affects the coupling efficiency of space light in a single-mode optical fiber. Based on the principle of fiber coupling efficiency, this paper first establishes the relationship between light intensity flicker and spatial coherence radius, then analyzes the influence of light intensity flicker on fiber coupling efficiency through the spatial coherence radius. A laser communication system was built, and real-time measurement experiments on atmospheric light intensity flicker and optical fiber coupling efficiency at different transmission distances and altitudes above the ground were completed. The experimental results show that the constructed experimental system can simultaneously measure the scintillation index and fiber coupling efficiency. When the communication distance is 12,000 m and the height is 600 m above the ground, the scintillation index is measured to be 0.63, and the coupling efficiency is 0.05. The results of the study provide an experimental and theoretical basis and data support to promote the development of atmospheric laser communications. Full article

In underwater communications for 6G, Doppler effects cause the coherent time to become similar to or shorter than the orthogonal frequency division multiplexing (OFDM) symbol length. Conventional time and frequency synchronization methods require additional training symbols for synchronization, which reduces the traffic data rate. This paper proposes the Zadoff–Chu sequence (ZCS) pilot-based OFDM for time and frequency synchronization. The proposed method transmits ZCS as a pilot for OFDM symbols and simultaneously transmits traffic data to increase the traffic data rate while estimating the CFO at each coherence time. For time–frequency synchronization, the correlation of the ZCS pilot is used to perform coarse and fine time and frequency synchronization in two stages. Since the traffic data cause interference with the correlation of ZCS pilots, we theoretically analyzed the relationship between the amount of traffic data and interference and verified it through computer simulations. The synchronization and BER performance of the proposed ZCS pilot-based OFDM were evaluated by conduction computer simulations and a practical ocean experiment. Compared to the methods of Ren, Yang, and Avrashi, the proposed method demonstrated a 6.3% to 14.3% increase in traffic data rate with similar BER performance and a 2 dB to 3.8 dB SNR gain for a 14.3% to 23.8% decrease in traffic data rate. Full article

This paper presents a case study on integrating Agile Systems Engineering methodologies in the preliminary design phase of satellite systems, focusing on the ³ColStar satellite mission. Through Model-Based Systems Engineering (MBSE), technical consistency was rigorously managed across various architectural documents, ensuring coherency and minimizing errors. Furthermore, the preliminary design was developed, with the implementation of the Arcadia Method, supported by the Capella modeling tool. This allowed the digitalization of the system, which was represented by models that contain requirements, architecture, and interfaces between the different parts of the system. At the same time, the preliminary design process was streamlined and completed within an accelerated time frame of 4 months, with weekly sprints driving progress based on the scrum methodology. This case study highlights the effectiveness of Agile Systems Engineering principles to improve the team communication accuracy, communication, and efficiency of satellite systems preliminary design, providing valuable insights for future missions. Full article

Thin film lithium niobate (TFLN) has become a promising material platform for large scale photonic integrated circuits (PICs). As an indispensable component in PICs, on-chip electrically tunable narrow-linewidth lasers have attracted widespread attention in recent years due to their significant applications in high-speed optical communication, coherent detection, precision metrology, laser cooling, coherent transmission systems, light detection and ranging (LiDAR). However, research on electrically driven, high-power, and narrow-linewidth laser sources on TFLN platforms is still in its infancy. This review summarizes the recent progress on the narrow-linewidth compact laser sources boosted by hybrid TFLN/III-V semiconductor integration techniques, which will offer an alternative solution for on-chip high performance lasers for the future TFLN PIC industry and cutting-edge sciences. The review begins with a brief introduction of the current status of compact external cavity semiconductor lasers (ECSLs) and recently developed TFLN photonics. The following section presents various ECSLs based on TFLN photonic chips with different photonic structures to construct external cavity for on-chip optical feedback. Some conclusions and future perspectives are provided. Full article