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Flying ad hoc network (FANET) is a new technology, which creates a self-organized wireless network containing unmanned aerial vehicles (UAVs). In FANET, routing protocols deal with important challenges due to limited energy, frequent link failures, high mobility of UAVs, and limited communication range of UAVs. Thus, a suitable path is always essential to transmit data between UAVs. In this paper, a local filtering-based energy-aware routing scheme (LFEAR) is proposed for FANETs. LFEAR improves the template of the route request (RREQ) packet by adding three fields, namely the energy, reliable distance, and movement similarity of the relevant route to create stable and energy-efficient paths. In the routing process, LFEAR presents a local filtering construction technique to avoid the broadcasting storm issue. This filter limits the broadcasting range of RREQs in the network. Accordingly, only UAVs inside this local filtered area can rebroadcast RREQs and other UAVs must eliminate these packets. After ending the route discovery process, the destination begins the route selection phase and extracts information about each discovered route, including the number of hops, route energy, reliable distance, and movement similarity. Then, the destination node calculates a score for each path based on the extracted information, selects the route with the highest score, and sends a route reply (RREP) packet to the source node through this route. Finally, the simulation process of LFEAR is performed using the NS2 simulator, and two simulation scenarios, namely change in network density and change in the speed of UAVs, are defined to evaluate network performance. In the first scenario, LFEAR improves energy consumption, packet delivery rate, network lifespan, and delay by 1.33%, 1.77%, 6.74%, and 1.71%, while its routing overhead is about 16.51% more than EARVRT. In the second scenario, LFEAR optimizes energy consumption and network lifetime by 5.55% and 5.67%, respectively. However, its performance in terms of routing overhead, packet delivery rate, and delay is 23%, 2.29%, and 6.67% weaker than EARVRT, respectively.
- Klíčová slova
- Artificial intelligence (AI), Flying ad hoc networks (FANETs), Mobility, Routing, Unmanned aerial vehicles (UAVs),
- Publikační typ
- časopisecké články MeSH
BACKGROUND: Intense fear of flying, called aviophobia, is a highly prevalent psychological phenomenon, afflicting (in some estimates) up to 40% of the population of industrialized countries and although aviophobia is a highly prevalent mental health problem, published studies about its epidemiology and treatment are rare. METHODS: In this study, including 61 participants (28 males and 33 females; mean age 26.85) engaged in business related travels in the last two years, we assessed relationships of fear of flying problems with symptoms of stress also reflecting childhood traumatic stress experiences and its influences on brain sensitization and epileptic-like symptoms. In this assessment we also studied fear of flying symptoms and work related psychological problems described as burnout. RESULTS: The results show that the participants who manifest higher levels of stress symptoms have higher levels of aviophobic experiences. Stress symptoms measured by TSC-40 manifested significant correlations with aviophobic experiences measured by Flight Anxiety Modality Questionnaire (FAS) (Spearman R=0.46, p<0.01). Other correlations were found between FAS and Limbic System Checklist (LSCL-33) (Spearman R=0.39, p<0.01) and FAS and Burnout Measure (BM) (Spearman R=0.30, p<0.01). CONCLUSION: The results of this study indicate that the experience of fear of flying is related to past and recent stressful events and also to levels of work related problems described and experienced as burnout.
- Klíčová slova
- anxiety, aviophobia, epileptic-like symptoms, sensitization, stress,
- Publikační typ
- časopisecké články MeSH
The amount of internet traffic generated during mass public events is significantly growing in a way that requires methods to increase the overall performance of the wireless network service. Recently, legacy methods in form of mobile cell sites, frequently called cells on wheels, were used. However, modern technologies are allowing the use of unmanned aerial vehicles (UAV) as a platform for network service extension instead of ground-based techniques. This results in the development of flying base stations (FBS) where the number of deployed FBSs depends on the demanded network capacity and specific user requirements. Large-scale events, such as outdoor music festivals or sporting competitions, requiring deployment of more than one FBS need a method to optimally distribute these aerial vehicles to achieve high capacity and minimize the cost. In this paper, we present a mathematical model for FBS deployment in large-scale scenarios. The model is based on a location set covering problem and the goal is to minimize the number of FBSs by finding their optimal locations. It is restricted by users' throughput requirements and FBSs' available throughput, also, all users that require connectivity must be served. Two meta-heuristic algorithms (cuckoo search and differential evolution) were implemented and verified on a real example of a music festival scenario. The results show that both algorithms are capable of finding a solution. The major difference is in the performance where differential evolution solves the problem six to eight times faster, thus it is more suitable for repetitive calculation. The obtained results can be used in commercial scenarios similar to the one used in this paper where providing sufficient connectivity is crucial for good user experience. The designed algorithms will serve for the network infrastructure design and for assessing the costs and feasibility of the use-case.
- Klíčová slova
- 5G, FBS, UAV base station, flying base station, location covering problem, location optimization, network coverage capacity, on-demand,
- MeSH
- algoritmy * MeSH
- teoretické modely * MeSH
- Publikační typ
- časopisecké články MeSH
Relativistic flying forcibly oscillating reflective diffraction gratings are formed by an intense laser pulse (driver) in plasma. The mirror surface is an electron density singularity near the joining area of the wake wave cavity and the bow wave; it moves together with the driver laser pulse and undergoes forced oscillations induced by the field. A counterpropagating weak laser pulse (source) is incident at grazing angles, being efficiently reflected and enriched by harmonics. The reflected spectrum consists of the source pulse base frequency and its harmonics, multiplied by a large factor due to the double Doppler effect.
- Publikační typ
- časopisecké články MeSH
- MeSH
- farmakoterapie * MeSH
- letecké a kosmické lékařství * MeSH
- lidé MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Československo MeSH
Insects are the only arthropod group to achieve powered flight, which facilitated their explosive radiation on land. It remains a significant challenge to understand the evolutionary transition from nonflying (apterygote) to flying (pterygote) insects due to the large gap in the fossil record. Under such a situation, ontogenic information has historically been used to compensate for fossil evidence. Recent evo-devo studies support and refine a paleontology-based classical hypothesis that an ancestral exite incorporated into the body wall contributed to the origin of insect wings. The modern hypothesis locates an ancestral precoxa leg segment with an exite within the hexapod lateral tergum, reframing the long-standing debate on the insect wing origin. A current focus is on the contributions of the incorporated exite homolog and surrounding tissues, such as the pleuron and the medial bona fide tergum, to wing evolution. In parallel, recent analyses of Paleozoic fossils have confirmed thoracic and abdominal lateral body outgrowths as transitional wing precursors and suggested their possible role as respiratory organs in aquatic or semiaquatic environments. These recent studies have revised our understanding of the transition to flying insects. This review highlights recent progress in both evo-devo and paleontology, and discusses future challenges, including the evolution of metamorphic development.
Flying Gaussian method simulates multiple replicas of the studied system and enhances sampling by disfavoring replicas to simultaneously sample similar states. The bias potential used for this enhancement is highly dynamic when looking at individual replica, which raises concerns about the accuracy of free-energy surfaces predicted by reweighing methods. Here we show that the bias potential can be considered as static when looking at the simulation from a multisystem perspective. We present two equations that can be used to predict the free-energy surface, and we demonstrate their convergence.
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Flying ad-hoc networks (FANETs) include a large number of drones, which communicate with each other based on an ad hoc model. These networks provide new opportunities for various applications such as military, industrial, and civilian applications. However, FANETs have faced with many challenges like high-speed nodes, low density, and rapid changes in the topology. As a result, routing is a challenging issue in these networks. In this paper, we propose an energy-aware routing scheme in FANETs. This scheme is inspired by the optimized link state routing (OLSR). In the proposed routing scheme, we estimate the connection quality between two flying nodes using a new technique, which utilizes two parameters, including ratio of sent/received of hello packets and connection time. Also, our proposed method selects multipoint relays (MPRs) using the firefly algorithm. It chooses a node with high residual energy, high connection quality, more neighborhood degree, and higher willingness as MPR. Finally, our proposed scheme creates routes between different nodes based on energy and connection quality. Our proposed routing scheme is simulated using the network simulator version 3 (NS3). We compare its simulation results with the greedy optimized link state routing (G-OLSR) and the optimized link state routing (OLSR). These results show that our method outperforms G-OLSR and OLSR in terms of delay, packet delivery rate, throughput, and energy consumption. However, our proposed routing scheme increases slightly routing overhead compared to G-OLSR.
- Publikační typ
- časopisecké články MeSH
We demonstrate the capability of flying focus (FF) laser pulses with ℓ=1 orbital angular momentum (OAM) to transversely confine ultrarelativistic charged particle bunches over macroscopic distances while maintaining a tight bunch radius. A FF pulse with ℓ=1 OAM creates a radial ponderomotive barrier that constrains the transverse motion of particles and travels with the bunch over extended distances. As compared with freely propagating bunches, which quickly diverge due to their initial momentum spread, the particles cotraveling with the ponderomotive barrier slowly oscillate around the laser pulse axis within the spot size of the pulse. This can be achieved at FF pulse energies that are orders of magnitude lower than required by Gaussian or Bessel pulses with OAM. The ponderomotive trapping is further enhanced by radiative cooling of the bunch resulting from rapid oscillations of the charged particles in the laser field. This cooling decreases the mean-square radius and emittance of the bunch during propagation.
- MeSH
- nízká teplota * MeSH
- normální rozdělení MeSH
- pohyb těles MeSH
- srdeční frekvence MeSH
- změna skupenství MeSH
- Publikační typ
- časopisecké články MeSH
The growing availability of virtual cranial endocasts of extinct and extant vertebrates has fueled the quest for endocranial characters that discriminate between phylogenetic groups and resolve their neural significances. We used geometric morphometrics to compare a phylogenetically and ecologically comprehensive data set of archosaurian endocasts along the deep evolutionary history of modern birds and found that this lineage experienced progressive elevation of encephalisation through several chapters of increased endocranial doming that we demonstrate to result from progenetic developments. Elevated encephalisation associated with progressive size reduction within Maniraptoriformes was secondarily exapted for flight by stem avialans. Within Mesozoic Avialae, endocranial doming increased in at least some Ornithurae, yet remained relatively modest in early Neornithes. During the Paleogene, volant non-neoavian birds retained ancestral levels of endocast doming where a broad neoavian niche diversification experienced heterochronic brain shape radiation, as did non-volant Palaeognathae. We infer comparable developments underlying the establishment of pterosaurian brain shapes.
- MeSH
- aligátoři a krokodýli anatomie a histologie genetika MeSH
- biologická evoluce * MeSH
- fylogeneze MeSH
- lebka anatomie a histologie MeSH
- let zvířat MeSH
- mozek anatomie a histologie růst a vývoj MeSH
- ptáci anatomie a histologie genetika MeSH
- zkameněliny anatomie a histologie MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
