Data Relay Research Articles

Behavioural ontogeny of bearded seals Erignathus barbatus through the first year of life

Pinniped pups face special ontogenetic challenges as they are born and receive maternal care on solid substrates (land or ice) but must transition to feeding aquatically following weaning. In this study, satellite relay data loggers were used to study behavioural ontogeny of bearded seal Erignathus barbatus pups (n = 13) through their first year in Svalbard, Norway. Pups occupied shallow, coastal habitats and were found in areas with intermediate ice concentrations (in seasons with sea ice: late-autumn/winter). Most pups showed exploratory movement patterns that peaked in the weeks following weaning; maximum home range size occurred at 31 to 60 d of age. Thereafter, home range size decreased with pups settling into areas along the coast. Time spent diving, dive duration, dive depth and time at the bottom of dives increased during the first weeks of independence, stabilizing when pups were ~50 d old. Dive depth subsequently decreased to depths comparable to adult bearded seals (by the time pups were ~175 d old). Record maximum dive depth (368 m) and duration (16.5 min) were performed by pups that were 66 and 224 d old, respectively. Time spent hauled out decreased after weaning, with pups hauling out only sporadically after they were 75 d old. Bearded seal pups seem to be physiologically and behaviourally well developed by the time they are 2 mo old. Pups did not display the individually specialized diving behaviour seen in adults, which suggests that they continue to fine-tune their aquatic and other life-skills well past the end of the first year of life.

Performance of Wireless Powered DF Relay System Under Nakagami-$m$ Fading: Relay Assists Energy-Constrained Source

We consider a two-hop decode-and-forward relay system with an energy-constrained source node. Relay node wirelessly powers the source and assists in forwarding the data to the destination. The direct link is considered to be deeply faded and other links are Nakagami- $m$ faded. Data at the source are transmitted in two time-slots. In the odd time slot, the source sends data to the relay node and in the even time slot, the relay node forwards the data. Since source and destination are in the coverage range of the relay node, both receive radio frequency signal transmitted by the node in even slot. The received signal is used simultaneously at the source to harvest energy and at the destination to detect the relayed data. Harvested energy at the source is used to transfer data to the relay node in the subsequent time slot. The average symbol error rate (SER) of the system is derived when data are 1) $M$ -ary phase-shift keying modulated with coherent detection and 2) orthogonal $M$ -ary frequency-shift keying modulated with noncoherent detection. The corresponding high-signal-to-noise ratio (SNR) approximations of the average SER are obtained. The effects of modulation order, channel conditions, and relay placement on the system’s performance are investigated.

Secure transmission line distance protection during wide area cascading events using artificial intelligence

The problem of distance protection misoperation has been a research priority recently because it was a major contributing factor in blackouts around the world such the 2003 US-Canada blackout and the 2015 Turkish blackout. In this paper, we propose a method that uses local relay data to enhance the security of zone 3 distance protection for transmission lines, even during wide area cascading events. Three k-nearest neighbor classifiers are trained using the details coefficients of discrete wavelet transform of the aerial mode currents without using any voltage signals altogether. The first classifier determines whether a fault has occurred. The second and third classifiers collectively determine whether this fault is within the zone 3 reach of the relay. If the second and third classifiers determine that the fault is outside the zone 3 reach of the relay, then a blocking signal will be sent to the relay to prevent operation even if the impedance falls within the operating characteristic of the relay. Alternatively, if the second and third classifiers determine that the fault is within zone 3 reach of the relay, a permissive trip signal will be sent to the relay only if the fault has not been cleared.

Ant-Based Automated Mission Planning for Data Relay Space Missions

The Earth observation (EO) market is rapidly growing due to technology miniaturization, cheaper launch opportunities, and a wider spectrum of EO applications. Along with an exponential growth of the ground-based users that can access low-Earth-orbit (LEO) spacecraft data, this growing community represents an important demand for data relay missions. LEO spacecraft have short visibility windows to the ground stations (GSs), which limits their throughput. Data relay missions comprise spacecraft at higher-altitude orbits (geostationary orbits) acting as relays of data among LEO spacecraft and GSs. Those missions are then able to offer more frequent data downlink opportunities to the LEO spacecraft, thus increasing the volume of the data reaching the ground and improving the responsiveness between users’ requests and downlink operations. Ground-based mission planning systems (MPSs) are commonly managing such complex missions, representing a large operational cost. In this paper, the application of a swarm intelligence algorithm to the design of an automated MPS for data relay missions is proposed. Automated MPSs have the potential to save operational costs while leaving the high-level decisions to human operators. This paper represents the first time that an ant colony optimization (ACO) algorithm is applied to this type of scheduling problem. This family of algorithms is generally found to offer a good level of efficiency and scalability. In this work, an ACO approach is compared against an algorithm that is popular in the literature, called Squeaky Wheel Optimization, outperforming it.

Correction and Accuracy of High- and Low-Resolution CTD Data from Animal-Borne Instruments

AbstractMost available CTD Satellite Relay Data Logger (CTD-SRDL) profiles are heavily compressed before satellite transmission. High-resolution profiles recorded at the sampling frequency of 0.5 Hz are, however, available upon physical retrieval of the logger. Between 2014 and 2018, several loggers deployed on elephant seals in the Southern Ocean have been set in continuous recording mode, capturing both the ascent and descent for over 60 profiles per day during several months, opening new horizons for the physical oceanography community. Taking advantage of a new dataset made of seven such loggers, a postprocessing procedure is proposed and validated to improve the quality of all CTD-SRDL data: that is, both high-resolution profiles and compressed low-resolution ones. First, temperature and conductivity are corrected for a thermal mass effect. Then salinity spiking and density inversion are removed by adjusting salinity while leaving temperature unchanged. This method, applied here to more than 50 000 profiles, yields significant and systematic improvements in both temperature and salinity, particularly in regions of rapid temperature variation. The continuous high-resolution dataset is then used to provide updated accuracy estimates of CTD-SRDL data. For high-resolution data, accuracies are estimated to be of ±0.02°C for temperature and ±0.03 g kg−1 for salinity. For low-resolution data, transmitted data points have similar accuracies; however, reconstructed temperature profiles have a reduced accuracy associated with the vertical interpolation of ±0.04°C and a nearly unchanged salinity accuracy of ±0.03 g kg−1.

Security Optimization of Two-Hop AF Cooperative Relay Network

In a two-hop cooperative relay network under eavesdropping environment, selecting the appropriate relay node forwarding information can improve the security performance of the system. Traditional relay selection depends on the channel condition of the two-hop link acquired through feedback to select the optimal relay node, ignoring the possible feedback delay of the system during relay selection moment and data transmission moment and inevitably causing the system security performance decline. With this in mind, this paper aims at improving the security transmission performance of the system, considering the condition of two-hop link channel of AF secure cooperative network combined with the maximum posterior probability criterion to weaken the influence of feedback delay to the relay selection, thus improving the security performance of the system. The simulation results shows that, with the improved optimal relay selection strategy based on the maximum posterior probability criterion, the reliability of relay selection is improved, and the system security performance is better.

Improved estimation of air pollutant emissions from landing and takeoff cycles of civil aircraft in China

Civil aircraft emissions during landing and takeoff (LTO) are important air pollutant sources, but have been given insufficient attention in China. Accurate estimation of these emissions is limited by a lack of important parameters, such as detailed flight information and the dynamic time in climb and approach modes during LTO that are dependent on mixing layer height (MLH). We developed a flight-time/flight-height relationship using real-time height information in Aircraft Meteorological Data Relay data, and then calculated the actual time for each flight in those two modes based on the actual MLH from meteorological observation. Hourly emissions of civil aircraft were then estimated based on the database of each flight. Total emissions of NOx, CO, SO2, HC and PM from LTO cycles of domestic flights in China during 2015 were 37.78 Gg, 30.25 Gg, 12.00 Gg, 2.38 Gg and 0.75 Gg, respectively. Substantial monthly, daily and hourly variations of emissions due to the flight schedule as well as MLH were calculated. Large differences were found between the new estimation and emissions calculated based on traditional method. Compared with the emissions estimated based on default parameter obtained from International Civil Aviation Organization, the average difference of annual emission among airports with new estimation for various pollutants was approximately 30.3% in climb mode and 81.4% in approach mode; compared with the emissions estimated based on the method proposed by China National Guide, the average difference of annual emission among airports were 37.4% (NOx), 8.4% (CO), 73.1% (HC) and 58.1% (PM) during LTO process. The monthly airport-specific emissions per LTO were also proposed. These can provide necessary and meaningful support for the revision of the values in National Guide.

Estimating Zero-Sequence Line Impedance and Fault Resistance Using Relay Data

Data recorded by intelligent electronic devices such as protective relays contain a wealth of valuable information that can be used beyond post-mortem analysis of fault events. The objective of this paper is to propose algorithms to estimate zero-sequence line impedance and fault resistance using protective relay data collected during short-circuit fault events. Protective relaying data may be available from one or both ends of the line. For the latter, they may be collected at different sampling rates with dissimilar fault time instants. Furthermore, they may be unsynchronized. This paper presents approaches which uses measurement data from one and both ends of the line. The efficacy of the proposed algorithms presented in this paper are demonstrated using a test case as well as field data. The error percentage of the zero-sequence line impedance magnitude estimated using the data from both ends of a two-terminal line was under 3% for all the test cases. The error percentage in estimating the fault resistance was less than 1% in the test cases presented.

Foraging behaviour of Weddell seals (Leptonychotes weddellii) in connection to oceanographic conditions in the southern Weddell Sea

The region of the Filchner Outflow System (FOS) in the southeastern Weddell Sea is characterized by intensive and complex interactions of different water masses. Dense Ice Shelf Water (ISW) emerging from beneath the ice shelf cavities on the continental shelf, meets Modified Warm Deep Water (MWDW) originating from the Antarctic Circumpolar Current at the sill of the Filchner Trough. These hydrographic features convert the FOS into an oceanographic key region, which may also show enhanced biological productivity and corresponding aggregations of marine top predators. In this context, six adult Weddell seals (Leptonychotes weddellii) were instrumented with CTD-combined satellite relay data loggers in austral summer 2014. By means of these long-term data loggers we aimed at investigating the influence of environmental conditions on the seals’ foraging behaviour throughout seasons, focussing on the local oceanographic features. Weddell seals performed pelagic and demersal dives, mainly on the continental shelf, where they presumably exploited the abundant bentho-pelagic fish fauna. Diurnal and seasonal variations in light availability affected foraging activities. MWDW was associated with increased foraging effort. However, we observed differences in movements and habitat use between two different groups of Weddell seals. Seals tagged in the pack ice of the FOS focussed their foraging activities to the western and, partly, eastern flank of the Filchner Trough, which coincides with inflow pathways of MWDW. In contrast, Weddell seals tagged on the coastal fast ice exhibited typical central-place foraging and utilized resources close to their colony. High foraging effort in MWDW and high utilization of areas associated with an inflow of MWDW raise questions on the underlying biological features. This emphasizes the importance of further interdisciplinary ecological investigations in the near future, as the FOS may soon be impacted by predicted climatic changes.

A Hybrid Unequal Clustering Based on Density with Energy Conservation in Wireless Nodes

The Internet of things (IoT) provides the possibility of communication between smart devices and any object at any time. In this context, wireless nodes play an important role in reducing costs and simple use. Since these nodes are often used in less accessible locations, recharging their battery is hardly feasible and in some cases is practically impossible. Hence, energy conservation within each node is a challenging discussion. Clustering is an efficient solution to increase the lifetime of the network and reduce the energy consumption of the nodes. In this paper, a novel hybrid unequal multi-hop clustering based on density (HCD) is proposed to increase the network lifetime. In the proposed protocol, the cluster head (CH) selection is performed only by comparing the status of each node to its neighboring nodes. In this new technique, the parameters involving energy of nodes, the number of neighboring nodes, the distance to the base station (BS), and the layer where the node is placed in are considered in CH selection. So, in this new and simple technique considers energy consumption of the network and load balancing. Clustering is performed unequally so that cluster heads (CHs) close to BS have more energy for data relay. Also, a hybrid dynamic–static clustering was performed to decrease overhead. In the current protocol, a distributed clustering and multi-hop routing approach was applied between cluster members (CMs), to CHs, and CHs to BS. HCD is applied as a novel assistance to cluster heads (ACHs) mechanism, in a way that a CH accepts to use member nodes with suitable state to share traffic load. Furthermore, we performed simulation for two different scenarios. Simulation results showed the reliability of the proposed method as it was resulted in a significant increase in network stability and energy balance as well as network lifetime and efficiency.

Understanding Probabilistic Cognitive Relaying Communication with Experimental Implementation and Performance Analysis.

Efficiently use of the limited wireless spectrum can be achieved by cooperative cognitive relaying, where secondary users (SUs), who do not pay for the licensed spectrum and have better channel condition to the primary users (PUs) destination, can help the PU by relaying their traffic. A systematic approach of implementing a Cooperative Cognitive Relaying framework using USRP2 is proposed in this paper, which could be used for practical experiments on cognitive radio applications. Two probabilities are introduced in the experiment in the paper and their effect on the PU and SU performance are studied and analyzed. The two probabilities are: (1) Probability of Admission, which controls the PU data that would be allowed by SU in their PU data queue (which could be relayed by SU later) and (2) Probability of Scheduling, which controls the selection of queue at the SU (PU relay data queue or the SU data queue) and the data of the selected queue would be relayed by SU during an idle time slot. Finally, the practical results from the varying of the introduced probabilities on the performance of PU and SU are verified with the simulation results. A very interesting result is found from the practical experiment where it is seen that increasing probability of scheduling of the PU packets at the SU is always in favor of the SU as opposed to the PU in terms of both throughput and delay.

Evaluation of Differential Protection in a Main Power Transformer: A Case Study in PT Pertamina Geothermal Energy Area of Kamojang

The electric power system consists of various components, ranging from the components of generation, transmission, and distribution. The systems are quite expensive, so that excellent, reliable, and economic protection is needed to avoid internal and external faults. The faults can trigger damage to components, especially on the main transformers in the Power Plant Geothermal Unit 4 of the Kamojang area managed by PT Pertamina Geothermal Energy. Disturbances that occur in the main transformers of various types so that the primary protection needed in the transformer is a differential relay to protect to avoid interference that occurs. This study discusses the comparison of theoretical differential relay calculation calculations with actual differential relay setting data in the Kamojang Unit 4 Geothermal Power Plant and simulates with ETAP 12.6 software. The problem that occurs in the main transformer of the Geothermal Power Unit Unit 4 Kamojang area is the difference in the slope 1 of the actual setting data with a mathematical calculation that is the actual setting data of 40% and the numerical calculation data worth 8.5%. Please note that the minimum slope one limit is 5%. PT Pertamina Geothermal Energy made slope one changes, so that differential relays are not too sensitive to the interference current that occurs within the protection zone of differential relays.

Barriers of Visceral Leishmaniasis reporting and surveillance in Nepal: comparison of governmental VL-program districts with non-program districts.

At the time when Nepal is on the verge of reaching the maintenance phase of the Visceral Leishmaniasis (VL) elimination program, the country is facing new challenges. The disease has expanded to 61 of the country's 75 districts including previously non-endemic areas where there is no control or patient management program in place. This study aimed to assess which elements of the surveillance and reporting systems need strengthening to identify cases at an early stage, prevent further transmission and ensure sustained VL elimination. In a cross-sectional mixed-method study, we collected data from two study populations in VL program and non-program districts. From February to May 2016, structured interviews were conducted with 40 VL patients, and 14 in-depth and semi-structured interviews were conducted with health managers. The median total delay from onset of symptoms to successful reporting to the Ministry of Health was 68.5days in the VL-program and 83days in non-program districts. The difference in patient's delay from the onset of symptoms to seeking health care was 3days in VL-program and 20days in non-program districts. The diagnostic delay (38.5days and 36days, respectively), treatment delay (1 vs. 1days) and reporting delay (45 vs. 36days) were similar in program and non-program districts. The diagnostic delay increased three-fold from 2012, while treatment and reporting delay remained unchanged. The main barriers to surveillance were: (i) lack of access and awareness in non-program districts; (ii) growing private sector not included in and not participating to referral, treatment and reporting; (iii) lack of cooperation and coordination among stakeholders for training and deployment of interventions; (iv) insufficient validation, outreach and process optimisation of the reporting system. Corrective measures are needed to maintain the achievements of the VL elimination campaign and prevent resurgence of the disease in Nepal. A clear patient referral structure, reinforcement of report notification and validation and direct relay of data by local hospitals and the private sector to the district health offices are needed to ensure prompt treatment and timely and reliable information to facilitate a responsive system of interventions.

High-Efficient Resource Allocation in Data Relay Satellite Systems With Users Behavior Coordination

In data relay satellite (DRS) systems, users compete for limited intersatellite link antenna beam (ILAB) resources of data relay satellites by submitting excessive service requests to the mission scheduling center (MSC), which leads to serious scheduling conflicts and considerably degrades the QoS (quality of service). Two key challenges, the effective mission scheduling, and the coordination of multiple users’ behaviors in submitting service requests, are involved in this issue. Most of the previous works have only focused on the mission scheduling issue, while neglecting the impact of users’ selfish behavior on the QoS. In this paper, we investigate the resource allocation problem in DRS systems from the perspective of users’ behavior analysis, i.e., joint coordination of users’ selfish behavior in submitting service requests and mission scheduling. Since those selfish users have no incentive to cooperate in the one-shot interaction, we construct a repeated game framework with a proper punishment and forgiveness strategy to maximize users’ payoffs and meanwhile to reduce the resource conflicts through a cooperative way. Moreover, an efficient cheat-proof mechanism is proposed to make users self-enforced to submit his/her actual resource requirement. Simulation results confirm that the proposed scheme can significantly improve the system operational performance. Compared with the payoffs under the Nash equilibrium in the one-shot game which is the main method of the current coordination scheme for DRS systems, our proposed joint method based on the repeated game framework can acquire 1.36 to 3.46 times gain in respect to 2 to 10 users, and also effectively decrease the resource conflicts.

Estimating zero-sequence impedance of three-terminal transmission line and Thevenin impedance using relay measurement data

Current and voltage waveforms recorded by intelligent electronic devices (IEDs) are more useful than just performing post-fault analysis. The objective of this paper is to present techniques to estimate the zero-sequence line impedance of all sections of a three-terminal line and the Thevenin equivalent impedance of the transmission network upstream from the monitoring location using protective relay data collected during short-circuit ground fault events. Protective relaying data from all three terminals may not be always available. Furthermore, the data from each terminal may be unsynchronized and collected at different sampling rates with dissimilar fault time instants. Hence, this paper presents approaches which use unsynchronized measurement data from all the terminals as well as data from only two terminals to estimate the zero-sequence line impedance of all the sections of a three-terminal line. An algorithm to calculate positive-, negative- and zero-sequence Thevenin impedance of the upstream transmission network has also been presented in this paper. The efficacy of the proposed algorithms are demonstrated using a test case. The magnitude error percentage in determining the zero-sequence impedance was less than 1% in the test case presented.

Breaking Bandwidth Limitation for Mission-Critical IoT Using Semisequential Multiple Relays

Most existing or currently developing Internet of Things (IoT) communication standards are based on the assumption that the IoT services only require low data rate transmission and therefore can be supported by limited resources such as narrow-band channels. This assumption rules out those IoT services with burst traffic, critical missions, and low latency requirements. In this paper, we propose to utilize the idle devices in mission-critical IoT networks to boost the transmission data rate for critical tasks through multiple concurrent transmissions. This approach virtually expands the existing narrow-band IoT protocols to break the bandwidth limitation in order to provide low latency services for critical tasks. In this approach, we propose the task-balance method and the first-link descending order to determine the relay order and data partition in a given relay set. We theoretically prove that the optimal relay configuration that minimizes the uploading latency in single source scenario can be derived by the proposed algorithms in polynomial time when we have sufficient number of available channels. We also propose a greedy algorithm to approximate the optimal solution within a 1/2 performance lower bound in general scenarios. The simulation results shows that the proposed approach can reduce the latency of critical tasks up to 76% comparing with traditional approaches.

Improved zone-3 distance protection based on adjacent relays data

Improved zone-3 distance protection based on adjacent relays data

Subglacial discharge plume behaviour revealed by CTD-instrumented ringed seals

Subglacial discharge plumes increase submarine melting of marine-terminating glaciers significantly; however, in-situ data on their properties and behaviour are limited. We present oceanographic data collected by ringed seals (Pusa hispida) instrumented with GPS-equipped conductivity-temperature-depth satellite relay data loggers (GPS-CTD-SRDLs) in Kongsfjorden, Svalbard, during 2012. The seals foraged just outside the plumes and collected hydrographic data from within the plumes’ upwelling cores as they returned to the surface. The seals encountered water with fractions of subglacial discharge as high as 27% at 60 m below the ocean surface. The ringed seals responded rapidly to spatial and temporal variations in subglacial discharge at the glacier terminus, suggesting that prey becomes available quickly following the appearance of plumes. The seals’ dive locations were used to monitor the presence of plumes over a four-month period. High surface runoff from Kronebreen catchment created strong plumes, but weak plumes were present even during periods of low surface runoff. The continued retreat of Kronebreen, and other tidewater glaciers, will lead to the loss of these marine-termini as the glaciers retreat onto land. The techniques presented here improve our understanding of the drivers of glacial retreat and the implications of future habitat loss for glacier-associated birds and mammals.

A tradeoff resource allocation based on MF‐TDMA scheme in the multibeam data relay satellite systems

SummaryA tremendous increase in the number of distributed satellite constellations with the unscheduled burst data traffic will impose addition and diverse requirements on the DRS (data relay satellite) systems, which increases the complexity for beam management and affects a real‐time data return and acquisition. In this paper, we suggested that a large capacity can be achieved by a multibeam DRS system based on multifrequency time division multiple access scheme providing multiaccess for the distributed satellite constellations. Because the space‐based information network is characterized by the limited on‐board resources, a highly dynamic topology and time‐varying intersatellite links, we designed a 2‐stage dynamic optimization approach to separate the multiobjective optimization for frequency/time blocks and power, aiming at the rapidly converging to the optimal solution and at the same time meeting the fairness resource allocation. In particular, a capacity‐fairness tradeoff algorithm is proposed based on hybrid the enhanced genetic algorithm and the particle swarm optimization. Simulation results show that the tradeoff between maximizing total capacity and providing proportional fairness allocation is well balanced. The proposed algorithm can rapidly converge to adapt to the highly dynamic topology in data relay satellite systems.

Social-Aware D2D Relay Networks for Stability Enhancement: An Optimal Stopping Approach

Device-to-device (D2D) relay network is regarded as a promising approach to extend the coverage area of cellular networks or improve the service quality for cell-edge users. However, the mobility of relay devices will negatively affect the stability of D2D communications. Aiming to improve the stability in mobile D2D communications and hence deliver more data traffic in D2D relay networks, in this paper, we exploit users’ social behaviors to dynamically detect better relay devices and substitute them for the existing ones. As the mobility of relays pose a critical challenge in achieving the tradeoff between the relay probing time and the optimality of relay selection, we propose the optimal stopping approach for mobile devices conducting the relay re-selection. Specifically, we embed social tie and centrality relationships between a potential relay and the end user to predict the date delivery performance of the potential relay in the D2D relay network. Our optimal stopping approach can be applied to different network topologies for mobile users with different social behaviors. The simulation results show that our proposed scheme can achieve the optimal tradeoff between the time used in relay probing and the optimality of the selected relay. Results also show that both short-term and long-term stability can be obtained and the amount of relayed data traffic can be maximized.