Relay Capability Research Articles

Dual-stage polyporate framework with redox mediator for high loading lithium sulfur batteries

Realizing a high sulfur loading cathode is a necessary measure for assembling a high actual energy density lithium sulfur battery, which requires consideration of conductivity, reaction interface, confinement of lithium polysulfide, and redox kinetics. Herein, a pomegranate-inspired dual-stage porous graphene foam with large cavity skeletons and submicron small cavity carriers is obtained by combining the bubble-template and the flash-freezing ice-template. Furthermore, the redox mediator of poly (1-aminoanthraquinone) is electropolymerized onto it to obtain a sulfur host with high specific surface area and strong confinement capability. The nanosized sulfur deposition behavior and the rich electronic relay capability of the sulfur host are analyzed by the independent gradient model combined with in-situ Raman spectroscopy. Besides, a few of electro-depolymerization products of poly (1-aminoanthraquinone) are confirmed to be able to migrate to the anode surface to stabilize lithium deposition. With these merits, the assembled lithium sulfur batteries exhibit a discharge capacity of 1214 mAh g−1 and a high capacity retention rate of 75.1 % after 800 cycles at a sulfur loading of 10.0 mg cm−2, and provide an excellent areal capacity of 17.5 mAh cm−2 (867 mAh g−1) even at an ultra-high sulfur loading of 20.1 mg cm−2.

Multiplexed DNA and Protease Detection with Orthogonal Energy Transfer on a Single Quantum Dot Scaffolded Biosensor.

Almost all pathogens, whether viral or bacterial, utilize key proteolytic steps in their pathogenesis. The ability to detect a pathogen's genomic material along with its proteolytic activity represents one approach to identifying the pathogen and providing initial evidence of its viability. Here, we report on a prototype biosensor design assembled around a single semiconductor quantum dot (QD) scaffold that is capable of detecting both nucleic acid sequences and proteolytic activity by using orthogonal energy transfer (ET) processes. The sensor consists of a central QD assembled via peptidyl-PNA linkers with multiple DNA sequences that encode complements to genomic sequences originating from the Ebola, Influenza, and COVID-19 viruses, which we use as surrogate targets. These are hybridized to complement strands labeled with a terbium (Tb) chelate, AlexaFluor647 (AF647), and Cy5.5 dyes, giving rise to two potential FRET cascades: the first includes Tb → QD → AF647 → Cy5.5 (→ = ET step), which is detected in a time-gated modality, and QD → AF647 → Cy5.5, which is detected from direct excitation. The labeled DNA-displaying QD construct is then further assembled with a RuII-modified peptide, which quenches QD photoluminescence by charge transfer and is recognized by a protease to yield the full biosensor. Each of the labeled DNAs and peptides can be ratiometrically assembled to the QD in a controllable manner to tune each of the ET pathways. Addition of a given target DNA displaces its labeled complement on the QD, disrupting that FRET channel, while protease addition disrupts charge transfer quenching of the central QD scaffold and boosts its photoluminescence and FRET relay capabilities. Along with characterizing the ET pathways and verifying biosensing in both individual and multiplexed formats, we also demonstrate the ability of this construct to function in molecular logic and perform Boolean operations; this highlights the construct's ability to discriminate and transduce signals between different inputs or pathogens. The potential application space for such a sensor device is discussed.

Across the Board: Rui Cao on Electrocatalytic CO2 Reduction.

In this series of articles, the Board Members of ChemSusChem review recent research articles that they consider of exceptional quality and importance for sustainability. This entry features Prof. Rui Cao, who discusses how tuning the second-sphere environments of Fe porphyrins can improve the activity and selectivity for CO2 reduction. Substituents with proton relay capability, hydrogen-bonding, and electrostatic features have significant impact on the efficiency of Fe porphyrins for the electrocatalytic CO2 reduction reaction.

Understanding Self-Assembled Pseudoisocyanine Dye Aggregates in DNA Nanostructures and Their Exciton Relay Transfer Capabilities

Progress has been made using B-form DNA duplex strands to template chromophores in ordered molecular aggregates known as J-aggregates. These aggregates can exhibit strong electronic coupling, extended coherent lifetimes, and long-range exciton delocalization under appropriate conditions. Certain cyanine dyes such as pseudoisocyanine (PIC) dye have shown a proclivity to form aggregates in specific DNA sequences. In particular, DX-tiles containing nonalternating poly(dA)-poly(dT) dinucleotide tracks (AT-tracks), which template noncovalent PIC dye aggregates, have been demonstrated to exhibit interesting emergent photonic properties. These DNA-based aggregates are referred to as J-bits for their similarity to J-aggregates. Here, we assemble multifluorophore DX-tile scaffolds which template J-bits into both contiguous and noncontiguous linear arrays. Our goal is to understand the relay capability of noncontiguous J-bit arrays and probe the effects that orientation and position have on the energy transfer between them. We find that linearly contiguous J-bits can relay excitons from an initial AlexaFluor 405 donor to a terminal AlexaFluor 647 acceptor across a distance of up to 16.3 nm. We observed a maximum increase in energy transfer of 41% in the shortest scaffold and an 11% increase in energy transfer across the maximum distance. However, in nonlinear arrays, exciton transfer is not detectable, even when off-axis J-bit-to-J-bit transfer distances were <2 nm. These results, in conjunction with the previous work on PIC-DNA systems, suggest that PIC-DNA-based systems may currently be limited to simple 1-D designs, which prevent isolating J-bits for enhanced energy-transfer characteristics until further understanding and improvements to the system can be made.

Exploring our solar system with CubeSats and SmallSats: the dawn of a new era

We are on the threshold of a new era in robotic exploration of our solar system, one in which CubeSats and SmallSats will play an important role. As the National Aeronautics and Space Administration (NASA)’s lead center for robotic solar system exploration, JPL has a strategic interest in these new capabilities that enable planetary scientists to expand our knowledge of how our solar system formed, how it works, and even how life originated. In November 2018, JPL’s two Mars Cube One (MarCO) spacecraft, launched with the InSight Discovery mission, made history as they flew past Mars. This first pair of interplanetary CubeSats navigated their way independently to Mars to provide a relay capability for the InSight lander back to Earth. Lunar Flashlight and Near-Earth Asteroid Scout, two CubeSats that are currently under development, will form part of the ‘swarm’ of CubeSats escorted onto a lunar trajectory by NASA’s Artemis-1 mission—the first launch of its new Space Launch System (SLS) rocket. This paper provides an overview of these and other CubeSat and SmallSat mission developments at JPL from the author’s perspective. It is intended to inspire others to follow the trail blazed by these pioneering missions.

Performance of Bundle Protocol (BP) for deep space communications with long link disruptions

Near Earth missions and deep space missions will continue to be a major future space mission. A long link disruption is inevitable in space communications because of spacecraft rotation, planetary bodies and limited relay capability. A few works have been done with delay/disruption tolerant networking (DTN) technology for deep space communications and provided feasibility for its adoption in LEO- space and deep space missions. However, not much work has been done to fully evaluate the performance of DTN in such an environment, especially in the presence of custody and long link transfer. In this article, we present an experimental performance evaluation of DTN architecture and protocol stack with DTN custody transfer and long link break underneath bundle protocol (BP), in typical LEO-satellite and deep space communication infrastructures accompanied. The experiment was conducted by performing realistic file transfers over a PC-based test-bed.

Towards Plug-and-Play Protection for Meshed Distribution Systems With DG

Future distribution systems are expected to display increased complexity, mainly due to looped/meshed operation, switch between grid-connected and islanded mode and considerable integration of distributed generation. This paper investigates a plug-and-play protection solution for overhead distribution systems with such variable operation conditions, employing existing numerical relay capabilities. This solution is applied by designing plug-and-play, communication-assisted, multifunctional relays with integrated protection element settings, which apply universally to all distribution system conditions, rendering the protection scheme independent of a specific system. Hence, the need for user-defined settings or future revisions due to system changes is eliminated. The scheme ensures coordination between main line relays and backup protection of laterals, without a coordination study. There is no need to replace or modify existing lateral protection means for this purpose; only their known time-overcurrent curves are uploaded to the relays by the user. The scheme is described and evaluated through simulations in two test systems. Meaningful conclusions are finally derived.

Intelligent Symbiotic Relay Selection Technique for 5G Networks

The growing demand for bandwidth and spectrum has inspired the ongoing efforts to establish the future 5G network supporting vertical sectors such as cyber-physical systems (CPS). Cooperative communication is one of the requisite techniques to improve coverage, network capacity and reduce power consumption in the network. In this paper, a symbiotic two-phase intelligent transmission is considered. The first phase occurs between the source and the candidate relays, and involves the selection of a set of “reliable relays”. The second phase occurs between the reliable relays and the destination, and involves the selection of the “best relay” for transmission. Dynamic relay selection using k-means clustering is used to detect the most significant correlation between all the channel state information (CSI) attributes in the system. The work identified the reliable relays while reducing the number of relay nodes for the second transmission phase. Contextual scenarios are created with typical network configuration using three geographical locations Coventry, Birmingham and London. An experimental validation is done with Omnet++ environment for the scenarios of three geographical locations. A natural grouping of mobile users is carried out leveraging the relay capabilities. The results are validated using support vector machine (SVM) classification algorithm. Considering urban environment deployment of relay nodes, metrics such as signal-to-noise-plus-interference ratio (SINR), attenuation, signal to noise ratio (SNR), link quality, k-means clustering, accuracy, and root mean square error (RMSE) are investigated for the Direct-2-Direct (D2D) capable relays. It was observed that the proposed technique both outperforms the other fixed-parameter relay selection techniques and improves with larger datasets unlike the other techniques.

Utilizing HomoFRET to Extend DNA‐Scaffolded Photonic Networks and Increase Light‐Harvesting Capability

AbstractDNA‐based photonic wires that exploit Förster resonance energy transfer (FRET) between pendant fluorophores to direct and focus excitonic energy have high research interest due to their potential applications in light harvesting, biocomputing, and biosensing. One important goal with these structures is to increase their ability to harvest energy and then transfer it over multiple steps both across extended portions of the spectra and physical space. Toward these goals, incorporating extended homogeneous or homoFRET sections into three unique FRET cascade DNA dendrimer architectures are explored. The effects of inserting increasingly longer homoFRET modules into assemblies based on AF488→Cy3→Cy3.5→Cy5→Cy5.5 dye‐displaying four‐arm, eight‐arm, and 2:1 dendrimeric DNA photonic wires are evaluated to understand what these hybrid structures may offer toward increased efficiency. Each structure incorporates an extendable Cy3 homoFRET region capable of incorporating one to six Cy3 repeats. Steady‐state and time‐resolved fluorescence measurements along with detailed analysis and simulations reveal that despite their modest relay capabilities, the structures are capable of acting as efficient antennas, with the dendrimeric structure manifesting a remarkably high sixfold gain. Moreover, an energy transfer efficiency of ≈3% is possible over nine sequential FRET steps.

Delay Insertion Based P2PTV Traffic Localization Considering Peer's Relaying Capability

Recently, P2PTV is a popular application to deliver video streaming data over Internet network. On the overlay network, P2PTV applications create the logical links between pairs of peers considering round trip time (RTT) without physical network consideration. P2PTV packets are shared over a network without localization awareness which is the serious problem for Internet Service Providers (ISPs). The delay-insertion-based traffic localization scheme was proposed for solving this problem. However, this scheme sometimes leads the newly joining peer to download streaming traffic from a local neighbor peer which has only scarce upload bandwidth. This paper proposes a novel scheme of delay-insertion-based traffic localization in which the router estimates relay capability to each relay peer candidate and leads the newly joining peer to connect to a neighbor peer with sufficient performance for relaying video data. Parameters were evaluated for the optimized condition in the relay capability estimation process. In addition, experiments conducted on a real network show that our proposed scheme can lead the newly joining peer to avoid downloading video data from insufficient relay capability peers and maintain video quality close to normal P2PTV system while efficient traffic localization in level of Autonomous System (AS) network.

Tuning the Photocycle Kinetics of Bacteriorhodopsin in Lipid Nanodiscs

Monodisperse lipid nanodiscs are particularly suitable for characterizing membrane protein in near-native environment. To study the lipid-composition dependence of photocycle kinetics of bacteriorhodopsin (bR), transient absorption spectroscopy was utilized to monitor the evolution of the photocycle intermediates of bR reconstituted in nanodiscs composed of different ratios of the zwitterionic lipid (DMPC, dimyristoyl phosphatidylcholine; DOPC, dioleoyl phosphatidylcholine) to the negatively charged lipid (DOPG, dioleoyl phosphatidylglycerol; DMPG, dimyristoyl phosphatidylglycerol). The characterization of ion-exchange chromatography showed that the negative surface charge of nanodiscs increased as the content of DOPG or DMPG was increased. The steady-state absorption contours of the light-adapted monomeric bR in nanodiscs composed of different lipid ratios exhibited highly similar absorption features of the retinal moiety at 560 nm, referring to the conservation of the tertiary structure of bR in nanodiscs of different lipid compositions. In addition, transient absorption contours showed that the photocycle kinetics of bR was significantly retarded and the transient populations of intermediates N and O were decreased as the content of DMPG or DOPG was reduced. This observation could be attributed to the negatively charged lipid heads of DMPG and DOPG, exhibiting similar proton relay capability as the native phosphatidylglycerol (PG) analog lipids in the purple membrane. In this work, we not only demonstrated the usefulness of nanodiscs as a membrane-mimicking system, but also showed that the surrounding lipids play a crucial role in altering the biological functions, e.g., the ion translocation kinetics of the transmembrane proteins.

고고도 장기체공 무인기 구조 설계 및 해석

Research is being carried out at Korea Aerospace Research Institute with aim of design a HALE UAV(High Altitude Long Endurance Unmanned Air Vehicle). HALE UAVs are ideally suited to provide surveillance, remote sensing and communication relay capabilities for both military and civilian applications. HALE UAVs typically cruise at an altitude between 15 km and 20 km, travelling at low speed and circling specific area of interest. Airframe structural point of view, weight reduction of the airframe structure is the most important method to improve the flight efficiency. High modulus CFRP(Carbon Fiber Reinforced Polymer) has been used in designing the structure in order to minimize the airframe weight. With respect to structural design and analysis, the key question is to decide an adequate airworthiness certification base to define suitable load cases for sizing of various structural components. In this study, FAR(Federal Aviation Regulation) 23 have constituted the guidance and benchmark throughout all structural studies. And the MSC/FlightLoads was introduced to analyze the flight loads for the HALE UAV. The MSC/FlightLoads can compute the flexible air load and analyzed loads are distributed on structural model directly. A preliminary structural concept was defined in accordance with the estimated inertial and aerodynamic loads. A FEM analysis was carried out using the MSC/Nastran code to predict the static and dynamic behaviour of UAV structure.

Verification of heterogeneous multi-agent system using MCMAS

The focus of the paper is how to model autonomous behaviours of heterogeneous multi-agent systems such that it can be verified that they will always operate within predefined mission requirements and constraints. This is done by using formal methods with an abstraction of the behaviours modelling and model checking for their verification. Three case studies are presented to verify the decision-making behaviours of heterogeneous multi-agent system using a convoy mission scenario. The multi-agent system in a case study has been extended by increasing the number of agents and function complexity gradually. For automatic verification, model checker for multi-agent systems (MCMAS) is adopted due to its novel capability to accommodate the multi-agent system and successfully verifies the targeting behaviours of the team-level autonomous systems. The verification results help retrospectively the design of decision-making algorithms improved by considering additional agents and behaviours during three steps of scenario modification. Consequently, the last scenario deals with the system composed of a ground control system, two unmanned aerial vehicles, and four unmanned ground vehicles with fault-tolerant and communication relay capabilities.

Model-based rational feedback controller design for closed-loop deep brain stimulation of Parkinson's disease

Objective. To explore the use of classical feedback control methods to achieve an improved deep brain stimulation (DBS) algorithm for application to Parkinson's disease (PD). Approach. A computational model of PD dynamics was employed to develop model-based rational feedback controller design. The restoration of thalamocortical relay capabilities to patients suffering from PD is formulated as a feedback control problem with the DBS waveform serving as the control input. Two high-level control strategies are tested: one that is driven by an online estimate of thalamic reliability, and another that acts to eliminate substantial decreases in the inhibition from the globus pallidus interna (GPi) to the thalamus. Control laws inspired by traditional proportional-integral-derivative (PID) methodology are prescribed for each strategy and simulated on this computational model of the basal ganglia network. Main Results. For control based upon thalamic reliability, a strategy of frequency proportional control with proportional bias delivered the optimal control achieved for a given energy expenditure. In comparison, control based upon synaptic inhibitory output from the GPi performed very well in comparison with those of reliability-based control, with considerable further reduction in energy expenditure relative to that of open-loop DBS. The best controller performance was amplitude proportional with derivative control and integral bias, which is full PID control. We demonstrated how optimizing the three components of PID control is feasible in this setting, although the complexity of these optimization functions argues for adaptive methods in implementation. Significance. Our findings point to the potential value of model-based rational design of feedback controllers for Parkinson's disease.

Using a hybrid neuron in physiologically inspired models of the basal ganglia

Our current understanding of the basal ganglia (BG) has facilitated the creation of computational models that have contributed novel theories, explored new functional anatomy and demonstrated results complementing physiological experiments. However, the utility of these models extends beyond these applications. Particularly in neuromorphic engineering, where the basal ganglia's role in computation is important for applications such as power efficient autonomous agents and model-based control strategies. The neurons used in existing computational models of the BG, however, are not amenable for many low-power hardware implementations. Motivated by a need for more hardware accessible networks, we replicate four published models of the BG, spanning single neuron and small networks, replacing the more computationally expensive neuron models with an Izhikevich hybrid neuron. This begins with a network modeling action-selection, where the basal activity levels and the ability to appropriately select the most salient input is reproduced. A Parkinson's disease model is then explored under normal conditions, Parkinsonian conditions and during subthalamic nucleus deep brain stimulation (DBS). The resulting network is capable of replicating the loss of thalamic relay capabilities in the Parkinsonian state and its return under DBS. This is also demonstrated using a network capable of action-selection. Finally, a study of correlation transfer under different patterns of Parkinsonian activity is presented. These networks successfully captured the significant results of the originals studies. This not only creates a foundation for neuromorphic hardware implementations but may also support the development of large-scale biophysical models. The former potentially providing a way of improving the efficacy of DBS and the latter allowing for the efficient simulation of larger more comprehensive networks.

Cooperative diversity performance of selection relaying over correlated shadowing

The study of relaying systems has found renewed interest in the context of cooperative diversity for communication channels suffering from fading. In particular, dual-hop relaying with diversity combining of the relayed and direct path at the receiver has practical importance and can be considered as a building block for forming larger communication systems. This paper presents novel analytical expressions and numerical results on cooperative diversity performance using selection relaying over correlated lognormal channels for both SC and MRC techniques at the receiver. In addition, an exact framework for comparing the performance and efficiency of the medium access protocol and relay capabilities (TDMA/half-duplex, SDMA/full-duplex) is proposed. Finally, based on the analysis and novel mathematical expressions for the outage probability, we investigate the impact of the lognormal parameters (including correlation) on the cooperative system performance and its efficiency.

Security Issues and Solutions of the Key Management Protocols in IEEE 802.16j Multi-Hop Relay Network

The recent IEEE 802.16j-2009 adds multi-hop relay capabilities to IEEE 802.16 systems, which aims to offer improved coverage and capacity over single-hop radio access systems. In this paper, we point out several security issues, including non-authenticated privacy and key management messages, insecure relay multicast rekeying algorithm and insecure Multicast and Broadcast Rekeying Algorithm (MBRA), of the key management protocols in IEEE 802.16j-2009 and give some solutions. In particular, we propose a new Secure MBRA (SMBRA) based on identity and logical key tree to solve the security issues of MBRA. SMBRA can not only provide backward and forward secrecy of communications but also avoid key forgery. Furthermore, our theoretical analysis and simulation indicate that SMBRA is much more efficient and adequate, especially in a large group.

Correlation transfer from basal ganglia to thalamus in Parkinson’s disease

There is much experimental evidence that neurons located in the basal ganglia of parkinsonian primates show increased pairwise correlations, oscillatory activity, and burst rate compared to normal brain activity. Past computational work has suggested that such changes in the firing pattern of neurons in the globus pallidus internus (GPi), the main output nucleus of the basal ganglia, may compromise thalamocortical relay capabilities. To understand how changes in the patterns of basal ganglia activity affect correlation transfer, we study pairs of realistic models of thalamocortical (TC) relay neurons receiving correlated inhibitory input from the GPi, as well as uncorrelated excitatory signals from cortex. We observe that bursty firing patterns such as those seen in the parkinsonian GPi allow for stronger transfer of correlations and higher correlation susceptibility than do firing patterns found under normal conditions. We also show that removing the T-current in the TC neurons does not significantly affect the correlation transfer, despite its pronounced effects on the spiking of the neurons. Oscillatory firing patterns in GPi are shown to affect the time scale at which correlations are best transferred through the system. We obtain the same results using an integrate-and-fire-or-burst (IFB) model of TC neurons as we do with a more realistic conductance-based model of the TC neurons, suggesting that the IFB model is a good reduced model for studying correlation transfer. In a reduced point process model, we derive analytic calculations of the spike count correlation coefficient for the time-inhomogeneous case. The analysis indicates that the rhythms seen in the transfer of correlations at varying time scales are very robust to different levels of spike correlations and rate correlations between the neurons. It also points to the fact that these rhythms can be seen because of differences in instantaneous spike correlations, even when the long time scale rhythmic modulation of the neurons in identical. Overall, these results show that parkinsonian firing patterns in GPi do indeed affect the way that correlations are transferred to the thalamus.

The future of WiMAX: Multihop relaying with IEEE 802.16j

Relaying and cooperation have re-emerged as important research topics in wireless communication over the past half-decade. Although multihop relaying for coverage extension in wireless networks is an old concept, it became practical only recently. Nowhere is this better illustrated than in the IEEE 802.16 working group, which has devoted a task group to incorporating relay capabilities in the foundation of mobile WiMAX-IEEE 802.16e-2005. Currently, this task group is in the process of finishing IEEE 802.16j, the multihop relay specification for 802.16. This amendment will be fully compatible with 802.16e-2005 mobile and subscriber stations, but a BS specific to 802.16j will be required for relays to operate. This article presents an introduction to the upcoming IEEE 802.16j amendment and provides insight about the obstacles that practical system designers face when incorporating relaying into a wireless broadband network.

Solid oxide fuel cell/gas turbine hybrid system analysis for high-altitude long-endurance unmanned aerial vehicles

High-altitude long-endurance (HALE) unmanned aerial vehicles (UAVs) are ideally suited to provide surveillance, remote sensing and communication relay capabilities for both military and civilian applications. HALE UAVs typically cruise at an altitude between 15 km and 20 km, travelling at low speed and circling specific areas of interest. The work reported aims to investigate alternative power system architectures that enable an efficiency increase and consequent fuel consumption reduction to realise a one-week endurance target. Specifically, the application of a solid oxide fuel cell combined with a gas turbine is considered; with different system configurations modelled with a view to maximising overall efficiency. It is found that modularising the fuel cell capacity into a number of discrete stacks such that the fuel is distributed in parallel and air is fed in series results in an increased system efficiency compared with a single-stack design. An overall system efficiency of 66.3% (LHV) when operating on hydrogen is predicted for a three-stack system.