Edge Stations Research Articles

GP4ESP: a hybrid genetic algorithm and particle swarm optimization algorithm for edge server placement

Edge computing has attracted wide attention due to its ultra-low latency services, as well as the prevalence of smart devices and intelligent applications. Edge server placement (ESP) is one of the key issues needed to be addressed for effective and efficient request processing, by deciding which edge stations to equip with limited edge resources. Due to NP-hardness of ESP, some works have designed meta-heuristic algorithms for solving it. While these algorithms either exploited only one kind of meta-heuristic search strategies or separately perform two different meta-heuristic algorithms. This can result in limit performance of ESP solutions due to the “No Free Lunch” theorem. In addition, existing algorithms ignored the computing delay of edge servers (ESs) on request process, resulting in overestimation of the service quality. To address these issues, in this article, we first formulate ESP problem with the objective of minimizing the overall response time, considering heterogeneous edge servers with various service capacity. Then, to search effective or even the best ESP solutions, we propose a hybrid meta-heuristic algorithm (named GP4ESP) by taking advantage of both the powerful global search ability of genetic algorithm (GA) and the fast convergence of particle swarm optimization (PSO). GP4ESP effectively fuses the merits of GA and PS by integrating the swarm cognition of PSO into the evolutionary strategy of GA. At last, we conducted extensive simulation experiments to evaluate the performance of GP4ESP, and results show that GP4ESP achieves 18.2%–20.7% shorter overall response time, compared with eleven up-to-date ESP solving algorithms, and the performance improvement is stable as the scale of ESP is varied.

Physical optima for nitrogen fixation in cyclonic eddies in the Subtropical Northwestern Pacific

Nitrogen fixation is a vital new nitrogen source in the oligotrophic ocean. Although our knowledge of the controlling factors of marine nitrogen fixation have increased rapidly, the physical controls, particularly eddies-induced upwelling and light intensity, remain elusive. In this study, conducted in the Subtropical Northwestern Pacific, we measured nitrogen fixation rates (NFR) in two cyclonic eddies (CEs). Our observations in one CE revealed that depth-integrated NFR (INFR) in core stations were significantly higher than in edge stations, indicating that CEs-induced upwelling might enhance nitrogen fixation. However, more intense upwelling in another CE resulted in lower INFR in core stations compared to edge stations. The INFR distributions in CEs were driven by the upwelling intensity, showing a unimodal response, i.e., the maximum INFR appeared at optimal upwelling intensity. This finding reconciles the debate about whether CEs inhibit nitrogen fixation. Additionally, results from light manipulation incubations proved that light intensity is a key driver for the vertically unimodal pattern of NFR, i.e., peaks at the subsurface layer with an optimum light intensity of 20% to 50% of surface PAR. Furthermore, molecular evidence showed that UCYN-A dominated in the upwelling area, while UCYN-B dominated in the non-upwelling area, indicating that CEs-induced physical perturbation regulates the niches of diazotrophs. Taken together, these results suggest that physical dynamics exert profound controls on the spatial heterogeneity of diazotrophic distribution and activity in the Subtropical Northwestern Pacific, providing new insights into the physical drivers of nitrogen fixation on mesoscale hydrodynamics..

A hierarchical federated learning incentive mechanism in UAV-assisted edge computing environment

Federated learning can utilize the local resources of user devices for model training while protecting their private security. Combining edge computing with federation learning can migrate computational tasks to the network edge, reducing communication latency and overhead. However, traditional edge stations are fixed in location and costly to deploy, making it difficult to cope with traffic surges, infrastructure failures, and device migration. Therefore, we introduce flexible and low-cost UAVs into federated learning, which can establish line-of-sight transmission paths with user devices and receive data for local aggregation. In federated learning, user devices need to contribute their own resources, and without sufficient rewards they may not be willing to participate, so we proposes a hierarchical federated learning incentive mechanism, which is designed based on contract theory considering data volume, data quality and cost input in an information asymmetry scenario. The experimental results compared with other benchmark schemes verify that the contractual design of this paper satisfies incentive compatibility and maximizes the utility of model owners.

Influence of tree-fall gaps on directional seed dispersal by small mammals in Central Panama

Small mammals, particularly rodents, are often important seed-dispersal agents in Neotropical forests. Directional seed dispersal into tree-fall gaps may enhance seedling survival of light-demanding species and thus influence forest regeneration. To examine this proposition, we tracked seeds of a light-demanding palm (Attalea butyracea), with a focus on spiny rats (Proechimys semispinosus), the most-likely seed-removal agents. We established seed-removal stations at three distances relative to 28 gaps (gap center, gap edge, and intact forest 10 m from a gap edge) in a lowland forest in Central Panama. We placed five fresh fruits (with their seed) in semi-permeable exclosures to exclude larger mammals at each station and tracked the directions in which seeds were moved and deposited intact. More seeds were moved toward or into gaps when removed from gap center or edge stations; however, seeds dispersed from intact forest stations showed no such directionality. Small mammals may have dispersed seeds into and within tree-fall gaps because they favored caching seeds in areas that offered increased cover, which is typical of gaps, and consequently protection from predation. The lack of directional dispersal from intact forest stations may have been because spiny rats were able to find sufficient cover in the young intact forest that was closer than the gaps. In older forest, the contrast between intact forest and gaps may be greater, resulting in directed dispersal into gaps.

Scatter-GNN: A Scatter Graph Neural Network for Prediction of High-Speed Railway Station—A Case Study of Yinchuan–Chongqing HSR

The Yinchuan–Chongqing high-speed railway (HSR) is one of the “ten vertical and ten horizontal” comprehensive transportation channels in the National 13th Five-Year Plan for Mid- and Long-Term Railway Network. However, the choice of node stations on this line is controversial. In this paper, the problem of high-speed railway station selection is transformed into a classification problem under the edge graph structure in complex networks, and a Scatter-GNN model is proposed to predict stations. The article first uses the Node2vec algorithm to perform a biased random walk on the railway network to generate the vector representation of each station. Secondly, an adaptive method is proposed, which derives the critical value of edge stations through the pinching rule, and then effectively identifies the edge stations in the high-speed railway network. Next, the calculation method of Hadamard product is used to represent the potential neighbors of edge sites, and then the attention mechanism is used to predict the link between all potential neighbors and their corresponding edge sites. After the link prediction, the final high-speed railway network is obtained, and it is input into the GNN classifier together with the line label to complete the station prediction. Experiments show that: Baoji and Hanzhong are more likely to become node stations in this north–south railway trunk line. The Scatter-GNN classifier optimizes the site selection strategy by calculating the connection probabilities between two or more candidate routes and comparing their results. This may reduce manual selection costs and ease geographic evaluation burdens. The model proposed in this paper can be used as an auxiliary strategy for the traditional route planning scheme, which may become a new way of thinking to study such problems in the future.

Preliminary Study on Long Period Ground Motion in the Eskişehir Basin, Turkey

Effects of a basin structure on long period ground motion generation in Eskişehir region are studied by investigating the observed features of the 2011 Simav Earthquake (Mw:5.9) accelerograms. Spectral values and significant duration of ground motion at the basin center is much higher than the predicted mean values obtained by empirical models. 3-D wave propagation simulation of a small magnitude local event is accomplished utilizing a finite difference method and experimental velocity models. Simulation results indicate that the basin model produces more realistic waveforms than the flat layered model. Synthetic velocities agree with observed ones at two basin-center stations but considerable discrepancies exit at basin edge stations. These findings suggest that more careful definitions of basin boundaries are necessary for future models.

Extraction kits could affect the interpretation of metabarcoding results of sediment samples taken around salmon farms

Differences in PCR strategies and errors, sequencing errors and methods used for extractions affect sequence data and potentially its interpretation. These effects could vary based on the target fragments, which are also influenced by limitations of incomplete databases. In this study, we tested the effects of two different proprietary DNA extraction kits on sediment samples, for the purposes of benthic monitoring of salmon farms. The levels of organic enrichment at farms show a gradient from cage edge to more distant locations. The effects of enrichment on benthic communities can be established with metabarcoding. We collected samples at three salmon farms in Scotland, at varying distances from cage edge. The sediments underneath two of the farms was fine while the sediment under the other was coarse, with a larger mean particle size. We extracted the samples with two different kits, each using a different mass of sediment – Qiagen DNeasy PowerSoil Pro (0.5 g) and Qiagen DNeasy PowerMax (5 g). We then subjected each extract to three independent PCRs targeting 16S (bacterial) and CO1 (eukaryotic) fragments. The PCR products of samples and blanks were sequenced with an Illumina MiSeq instrument on a single run. We denoised the sequenced data using DADA2 and rarefied it before analysis (Callahan et al. 2016). The 16S data was annotated against the seven-level SILVA database (Quast 2012). We collated this data at ‘Family’ level. The CO1 data was filtered to remove Amplicon Sequence Variants (ASVs) present in only one sample and ASVs with a frequency of less than ten reads across all samples. The read count data of family level 16S and ASVs of CO1 were transformed and converted to Bray-Curtis dissimilarity matrices (Bray and Curtis 1957). A permutational multivariate analysis of variance was carried out. We also ordinated these data with non-metric multi-dimensional scaling. 474 bacterial families and 3380 eukaryotic ASVs were included in the analysis. The samples extracted with both kits demonstrated a gradient based on distance from cage edge. This gradient in sampling stations was observed with both the 16S and CO1 markers. Data from both markers and kits showed a greater distinction between cage edge stations and more distant stations in the farms characterised by fine sediment. The two extraction kits showed similar trends but differed in their results. The 16S data showed a separation of samples by extraction kit along the y-axis. PowerMax extractions were associated with higher values on the y-axis (Fig. 1). The multivariate analysis of variance of the 16S data showed that extraction kit contributes to approximately 7% (p<0.001) of variation in data. The CO1 ASV data also showed a grouping of samples of both kits along the x-axis on the basis of distance from the farm (Fig. 1). The CO1 data showed that extraction kits contribute to about 5% (p<0.001) of the variation. The results of the two extraction kits were more similar to each other with the CO1 marker than with 16S. The greater axes values and grouping in the CO1 ordination, indicate that it is able to split farms and distances better than 16S. We show that both extraction kits demonstrated a gradient according to distance from the cage edge. However, there was a systematic difference between the extraction kits. Variability due to kit was greater with the 16S marker despite it including fewer bacterial families than CO1 ASVs. We recommend that the same extraction kit be used to develop protocols for monitoring of fish farms with metabarcoding. Though both kits demonstrate the same major trend, subtle differences may not be distinguished. These variations between the kits could influence the results and interpretation of metabarcoding.

An efficient blockchain-based privacy preserving scheme for vehicular social networks

In vehicular social networks (VSNs), edge stations or cloud service provider can support the traffic services or location services to vehicles. Moreover, the information sharing among vehicles can assist vehicles to avoid traffic accidents and guarantee driving safety. However, it is easy to be threatened in the communication of vehicle-to-edge station, vehicle-to-cloud service provider and vehicle-to-vehicle in VSNs, which leads to the vehicle’s privacy leakage easily. Besides, some malicious users may provide untrustworthy information to mislead others just for its selfishness. Hence, in this paper, we propose an efficient, reliable and privacy-preserving scheme based on blockchain for VSNs. In our scheme, pseudonym mechanism is employed to achieve individual anonymization by concealing the vehicles’ identity. Moreover, to encourage vehicles to report trustworthy information, incentive-punishment mechanism is proposed. Meanwhile, we propose multi-factors and single-factor weight-based evaluation mechanism to evaluate the reliability of message. Additionally, Practical Byzantine Fault Tolerance (PBFT) and blockchain are also employed to achieve consensus and store the records respectively, which can prevent malicious entities from manipulating on vehicles’ reward scores and credit scores. Finally, we analyze the security of the proposed scheme in terms of external attacks, internal attacks, collusion attacks etc. The relevant experimental results are shown that our scheme is feasible and efficient.

Controls on the shuttling of manganese over the northwestern Black Sea shelf and its fate in the euxinic deep basin

Manganese (Mn) is an essential micronutrient for phytoplankton and its cycling interacts with that of iron (Fe). Continental shelf sediments are a key but poorly quantified source of Mn to marine waters. In this study, we investigate Mn release from shelf sediments, its lateral transport (“shuttling”) in the oxic water column over the northwestern Black Sea shelf and its fate in the adjacent euxinic deep basin. We find a high release of Mn from organic-rich, bioirrigated coastal sediments, but negligible mobilization and release of Mn from sediments in offshore shelf regions, because of a low input of organic matter. Most Mn in the water column is present in dissolved form. We suggest that this dissolved Mn is released from coastal sediments and subsequently transported offshore through physical processes. Surface sediments at open shelf and shelf edge stations are highly enriched in Mn when compared to coastal and deep basin stations. Only part of the surface enrichment can be explained by oxidation of porewater Mn. The remainder of this enrichment is likely the result of oxidative removal of dissolved Mn from the water column and deposition as Mn oxides. Using X-ray spectroscopy we show that Mn in surface sediments in this area predominately consists of Mn(IV) oxides (phyllo- and/or tectomanganates). A key difference between Mn versus Fe shuttling is the form in which the metal is transported: while dissolved Mn dominates in the water column over the shelf, most Fe is present in particulate form. Sediment trap data indicate that the vertical transport of both Mn and Fe through the euxinic water column is correlated and is associated with the sinking flux of biogenic particulate matter following the spring and fall phytoplankton blooms. In the sediments of the euxinic basin, Mn is enriched when compared to a detrital Mn background and its burial correlates with that of Fe. This suggests that Mn could be incorporated in pyrite in the euxinic water column. Our results highlight the critical role of organic matter input as a driver of Mn and Fe shuttling over the Black Sea continental shelf and particulate matter as the carrier of Mn and Fe into the euxinic basin.

Mesopelagic fish composition and diets of three myctophid species with potential incidence of microplastics, across the southern tropical gyre

The species occurrence of mesopelagic fish collected in the scattering layers was studied across the Indian Ocean subtropical gyre during the dry season (2015). Ocean eddies can retain zooplankton and plastic debris, and determine biological composition through advection. The conditions inside the gyre were stabilised by low chlorophyll-a concentrations and a deep nutricline. A diverse assemblage of mesopelagic fish, dominated by myctophids, exhibited diel migrations to the upper water layers for feeding since the early night. Myctophids were concentrated ca. 100 m depth, where the deep chlorophyll maximum was located, and coinciding with the nutricline. Another group of mesopelagic fish remained in deeper waters during the daytime, with a higher occurrence of Stomiiformes (Phoshycthyidae and Sternoptychidae) at the 500–600 m Deep Scattering Layer. Moreover, the diets of 220 myctophid specimens belonging to the species Ceratoscopelus warmingii, Diaphus effulgens, and Symbolophorus evermanni, were investigated based on stomach content analysis. Calanoid copepods, mainly Pleuromamma abdominalis, made up 30% of the diet in the three myctophid species, with interspecific differences in the preferred second item: C. warmingii preferred ostracods, D. effulgens, non-calanoid copepods, and S. evermanni, euphausiids. Thus, partial dietary segregation was observed among the three species. We hypothesized that these myctophid diets differed between stations located at the gyre core and its outer edge. Any dietary pattern indicating aggregation of food resources, or an enhancement of the foraging opportunities for myctophids, was discerned as an effect of the gyre advection. However, prey composition diverged between the core and the outer edge stations regardless of the fish species, with a higher dietary representation of P. abdominalis and euphausiids (migratory zooplankton) in the individuals collected in the core-influenced area. A total of six plastic pieces were present in the stomachs of D. effulgens and S. evermanni, in contrast with the high presence of plastic particles found at the surface in most sampling stations (average number of plastic pieces was 41 per hour). The selected myctophid species did not appear to be important transport vectors for microplastics in comparison with species from other oceans.

Station avenue: high-speed rail’s missing link. Assessing pedestrian city-station routes for edge stations in Spanish small cities

High-speed rail edge stations, which are located within the urban fabric limits of a city, have generally a good access through motorised transportation modes while the pedestrian/bicycle access becomes, in many cases, very difficult. This paper assesses the quality of pedestrian routes linking high-speed rail edge stations to the city centre, considering physical aspects such as footpaths width, characteristics of the built environment or detours at street crossings. The assessment demonstrates that a pedestrian route could be redesigned to minimise discontinuities and to improve walkability, extending the walkable distance threshold through an adequate design. The proposed methods could provide a useful tool for cities to identify the most appropriate footpath to create convenient and legible pedestrian routes with walkable promenades for edge stations, because, in general, there are no specific strategies or policies to favour these walkable connections. In many cases, these edge stations are hidden city gates and the station-city pedestrian connection is the missing link in this intermodal transport chain.

A digital quadrature modulator with on-chip d/a converter

The first analog IF mixer stage of a transmitter can be replaced with this digital quadrature modulator. The modulator interpolates orthogonal input carriers by 16 and performs digital quadrature modulation at carrier frequencies f/sub s//4, -f/sub s//4,f/sub s//2 (f/sub s/ is the sampling frequency). A 12-b digital-to-analog (D/A) converter is integrated with the digital quadrature modulator. A segmented current source architecture is combined with a proper switching technique to reduce spurious components and to enhance dynamic performance. The digital quadrature modulator is designed to fulfill the spectral, phase, and EVM specifications of GSM, EDGE, and WCDMA base stations. The die area of the chip is 27.09 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (0.35-μm CMOS technology) and the total power consumption is 1.02 W with 2.8 V at 500-MHz output sampling rate (0.78-W digital modulator, 0.24-W D/A converter).

Microbial community composition and growth dynamics in the Antarctic Polar Front and seasonal ice zone during late spring 1997

Abstract The microbial community between the Antarctic Polar Front region (APFr) and the seasonal ice edge at 170°W was examined as part of the US JGOFS AESOPS Process 1 Study during late spring (December) 1997. Water-mass identities of the sampled stations were determined based on physical properties, with three regions identified: the APFr, the South ACC region (SACCr), and the southern region of the ACC near the ice edge (SACCr-IE). The APFr (60.1–60.5°S) was dominated by centric diatoms, with mixed-layer communities tending toward single genera (i.e., Chaetoceros and Corethron ). Stations in the SACCr (61.4–63.0°S) were also characterized by large centric diatoms, but no single genus dominated. In contrast, the SACCr-IE stations (64.1–64.4°S), positioned near the retreating ice edge, were dominated by colony-forming Phaeocystis . A seasonal succession in phytoplankton is proposed, with the youngest communities near the ice edge and the most “mature” in the polar front region. We found an inverse relationship between chlorophyll a values and phytoplankton growth rates. Phytoplankton growth rates were the highest (up to 1 d −1 ) in the APFr, despite relatively low chlorophyll a values. Microzooplankton grazing accounted for ∼50% of phytoplankton growth. The SACCr stations had intermediate chlorophyll a concentrations and phytoplankton growth rates (0.5–0.9 d −1 ), with grazing consuming ∼50–70% of growth. The SACCr-IE stations had the highest chlorophyll a values and the lowest phytoplankton growth rates (0.2 d −1 ) of the transect, while grazing accounted for ∼70% of growth in the one dilution experiment that gave a significant result. Given these growth and grazing estimates, a higher proportion of production in the northern diatom-dominated regions was available for export than in the Phaeocystis -dominated ice edge stations. However, since microzooplankton produce small fecal debris, the bulk of the consumed production was more likely remineralized in the upper water column.

In situ ingestion rates of appendicularian tunicates in the Northeast Water Polynya (NE Greenland)

We report in situ ingestion rates of individual oikopleurid appendicularians from the Northeast water Polynya (NEW) determined by a modification of the gut pigment technique. Appendicularians were most abundant at ice edge stations and were rare at open water stations in the centre of the polynya. Gut passage time (GPT), which was determined in experiments onboard ship, was not related to body size (mean ± SD = 74 ± 23 min). Gut chlorophyll content (GCC) excluding phaeopigments (i.e. GCC = chlorophyll a + b + c), averaged 4.06 ng ind.-1, with quartiles of 1.20 to 4.73 ng ind.-1. There was no evidence of a diel feeding rhythm. GCC was higher and more variable at non-bloom (i.e. at chlorophyll concentrations 5 μm in size. This suggests inhibition of ingestion rates at ice edge stations with diatom blooms. The ingestion rate (IR, ng chlorophyll ind.-1 d-1) of individual appendicularians in the NEW can be predicted by IR = 2.5 BL:BT-0.41 TL2.14 (r2 = 0.43) where BL:BT is the ratio of chlorophyll a in particles >5 μm in diameter to the total chlorophyll biomass, and TL (mm) is the trunk length.

Abundance and distribution of tintinnid ciliates in an ice edge zone during the austral autumn

Tintinnid ciliates were present throughout the upper (100m) water column of the ice-edge zone when sampled in autumn 1986 in the Weddell Sea. Biomass ranged from 0.02 μgC1−1 under the sea-ice to 1.3 μgC1−1 in the ice-free water column. Cymatocylis, Codonellopsis, Laackmaniella and a small Salpingella were the most abundant and/or largest biomass contributors. The under ice assemblage was characterized by low biomass and dominated by small species (Salpingella and Codonellopsis); the ice edge stations were dominated by these same taxa but in higher abundances while the open water assemblage was characterized by high biomass and dominated by Cymatocylis, the largest taxa. All taxa exhibited maximum concentrations in the upper 50m of the water column. Both krill and salps grazed upon the Cymatocylis and Codonellopsis without preference in both the ice covered and open water regimes.