bluuebunny/crossref_metadata_2025 huggingface dataset:
Blockchain‐enabled balise data security for train control system
Authors: Muniandi Ganesan
Published: May 2021

The train control system is the railway system's brain, ensuring the train protection and the railway network's operating performance. This control system relies on the balise data received via near‐field wireless communication to localize the train and update real‐time operating conditions and constraints. The attackers can capture these data through their balise antenna and corrupt them through replay or false data injection attacks. This corrupted data can compromise train safety and jeopardize the entire train fleet operations. To overcome these attacks and to ensure the trustworthiness of balise and data integrity, this study proposes the permissioned blockchain‐enabled two novel architectures for data transactions. Besides, each balise is equipped with a novel built‐in blockchain cryptography algorithm to create its secret and public keys to provide the key integrity without needing third‐party Certification Authority of conventional Public‐Key Infrastructure based security systems. Each balise can create the unique signature using a ‘nonce’ signal sent by the train control system in the static architecture or using a self‐generated ‘k‐once’ secret key per train control system in dynamic architecture. Finally, the case studies are carried out to confirm the security sufficiency of the proposed architectures.
Study of blockchain's consensus mechanism based on score
Authors: Cai Shaobin , Han Tangxuan , Wang Yuhao , Zhang Hu
Published: May 2021

The consensus mechanism is a key technology to achieve state consistency among distributed nodes and it determines the consensus efficiency and stability of the blockchain system. If the consensus efficiency and stability are improved, that can promote the development of the entire society. Therefore, it is necessary to improve the consensus efficiency and stability of the blockchain system. However, there are many disadvantages in the existing consensus mechanism, such as high communication complexity, low throughput, and poor scalability. For solving these disadvantages, a blockchain consensus mechanism Score‐Based Byzantine Fault Tolerance (SBBFT) is proposed. First, the score of nodes are obtained by Analytical Hierarchy Process (AHP) and SBBFT uses the score of the node to choose a node to be the primary node and acknowledgment node. Second, SBBFT selects acknowledgment nodes to be an acknowledgment node subset. This subset can change the communication of nodes from all‐to‐all to all‐to‐c. Moreover, the view change of acknowledgment node subset can make the system resistant to attacks from more malicious nodes. According to the experiment, 900,000 transactions from Ethereum, the result demonstrates SBBFT can significantly reduce the communication complexity, improve the consensus efficiency and stability of the system.
Hybrid piezo/triboelectric nanogenerator for stray magnetic energy harvesting and self‐powered sensing applications
Authors: Yang Aijun , Wang Chaoyu , Ma Jing , Fan Chengyu , Lv Pinlei , Bai Yuchen , Rong Yiming , Wang Xiaohua , Yuan Huan , Rong Mingzhe
Published: May 2021

Stray magnetic fields with a fixed frequency of 50/60 Hz are ubiquitous in buildings, factories, and power system equipment. Researchers are increasingly focusing on harvesting electrical energy from stray magnetic fields to provide sustainable energy for the Internet of Things (IoT) devices. Magneto‐mechano‐electric energy conversion is the most efficient way to convert low‐frequency stray magnetic fields into electricity. In this study, we proposed a hybrid piezo/triboelectric nanogenerator (HP/TENG) on the basis of a cantilever beam to use stray magnetic fields from the surrounding environment. The hybrid nanogenerator provided high output voltage/current and power of ∼176 V/375 μA and 4.7 mW (matched impedance of 20 kΩ) in a magnetic field environment of 4 Oe. The device provided a stable 3.6 V direct current output by incorporating energy management circuitry to sustainably drive power to commercial wireless temperature/humidity sensors. The HP/TENG has a significant application potential in IoT, which can use stray magnetic energy and a power wireless sensor system.
Simulation and Experimental Research on Overvoltage Measurement of Hybrid CVT
Authors: Nie Yu , Zhang Guoqing , Song Jiakuo , Wang Guizhong
Published: May 2021

The CVT equipment running on site is slightly modified to form a hybrid CVT to achieve transient overvoltage measurement, which is theoretically feasible and practical. In order to study the voltage division method based on the hybrid CVT to measure the overvoltage of the power system, that is, the low voltage capacitor C3 is connected in series between the low voltage terminal of the medium voltage capacitor C2 of the traditional CVT and the ground, and the transient overvoltage measurement is realized through C3. This article uses ATP-EMTP to establish its high-frequency transient model for simulation analysis. For further verification, a power frequency voltage test and an impulse voltage test were carried out on the 110kV hybrid CVT produced by Taikai Transformer Factory, focusing on the analysis of the partial voltage characteristics of the capacitor C3. The simulation results show that the C3 partial pressure method can achieve a relatively accurate measurement of the transient overvoltage. The test results show that the voltage across C3 is affected by uncertain factors and has an impact phenomenon. The above analysis process and results have certain practical value for designing actual products.
A Current-Commutation DC Circuit Breaker with Adaptive Reclosing Capability
Authors: Jiang Chunbing , Zhao Chengyong
Published: May 2021

DC faults are critical events in a flexible high-voltage dc (HVDC) grid. Thus, ensuring that the power system returns to normal operation rapidly and reliably after fault isolation is very important. This requires a HVDC breaker. In overhead line systems under temporary faults, reclosing is often required. However, once the dc circuit breaker (DCCB) is reclosed directly, the large second overcurrent may occur which could damage the power electronic devices. To avoid this problem, a current-commutation DC circuit breaker with adaptive reclosing capability is proposed. Compared with the traditional auto-reclosing strategy, the second damage under permanent fault condition can be avoided by the proposed DCCB, which can identify the fault property. Compared with the hybrid DCCB, the power electronic breaking branch composed of lots of IGBTs is replaced by the current-commutation branch, which is employed to interrupt bi-directional dc fault current. Moreover, bypassing branch is configured to reduce the energy dissipation of arrester and shorten the fault isolation time effectively. Finally, simulation cases in PSCAD /EMTDC verify the effectiveness and superiorities of the proposed DCCB.
Research on Two-stage Game Strategy of Virtual Power Plant in Deep Peak Regulation Auxiliary Service Market
Authors: Guili Yuan , Sixuan Chen , Xiaoxuan Dou
Published: May 2021

There is a large number of combined heat and power units in northern China, and due to the limit of heating demand, the operating mode of setting electricity by heat of combined heat and power units has seriously took over the consumption space of other energy, resulting in severe wind power curtailment and rationing situation in some areas, so this paper studies the deep peak regulation bidding strategy problem considering multiple uncertainties on virtual power plants, and established a two-staged optimization model of virtual power plant to maximize the net revenue, then introduced the Shapely value method with correction coefficient redistribute the peak regulation revenue. The simulation results showed that the two-stage bidding model can not only improve the market competitiveness of the virtual power plant, but also promote the consumption of renewable energy and reduce the market peak regulation service cost. Meanwhile, the improved apportion method can effectively guarantee the enthusiasm of all kinds of units to participate in the deep peak regulation market.
Research on Comprehensive Evaluation Method of Distribution Automation Equipment Testing Results Based on Analytic Hierarchy Process and CRITIC Method
Authors: Zheng Youzhuo , Fu Yu , Xiao Xiaobing
Published: May 2021

To utilize the objective information of index data and consider the important role of subjective judgment in the evaluation of distribution automation equipment testing results, a comprehensive evaluation method based on AHP (Analytic Hierarchy Process) and CRITIC (CRiteria Importance Through Intercriteria Correlation) method is proposed. Firstly, an evaluation index system of distribution automation equipment testing results considering seven big indicators and thirty-six small indicators is established. Secondly, AHP and CRITIC method are adopted to solve a practical evaluation problem of distribution automation equipment testing results. The subjective weights of each evaluation index are calculated by AHP, the objective weights of each evaluation index are calculated by the CRITIC method. Then, to achieve the sorting of distribution automation equipment testing results accurately, the comprehensive weights are obtained by combining the two weights. Finally, the analysis and comparison of case studies show that the proposed evaluation index system can accurately reflect the performance of distribution automation equipment and the comprehensive evaluation method of distribution automation equipment testing results which comprehensively considers the subjective comprehensive evaluation results.
Development of Smart Distribution Transformer Terminal Based on Software Defined Technology
Authors: Wu Hai , Teng Xianliang , Zhou Cheng , Hu Guo , Zhou Hualiang , Dai Shenjian
Published: May 2021

In order to cope with the development trend of distribution network, the demand for terminal to have the ability of IoT has become increasingly prominent. This paper firstly expounds the development trend of low-voltage distribution network, and emphasizes the technical transformation of the core equipment of low-voltage distribution network-smart terminal; secondly, it puts forward the software and hardware architecture of smart terminal suitable for the IoT, and emphasizes the cooperative capability of the software and hardware platform; and then it introduces the key technologies of the smart terminal, integrates model standardization and virtualization technologies, realizes the plug and play of information flow, and supports application through engineering; finally, it analyzes the work plan of the next stage, and designs to improve the functions of the smart terminal.
Design of Distributed Electricity Trading Mechanism Based on Contract for Difference
Authors: Long Li , Yang Tianhai , Li Qifen , Yang Yongwen , Song Lifei , Wu Tianjiao
Published: May 2021

A contract for difference is a medium and long-term financial contract, which can be used in the electricity market to lock the electricity price in advance and avoid the risk of electricity price fluctuations in the spot market. The construction of the domestic power spot market has just started. With the release of relevant policies and the gradual improvement of the market structure, it is urgent to design a corresponding trading mechanism to ensure the smooth transition of the market. The current day-ahead transactions, real-time transactions and other short-term transactions for distributed power generation, on the one hand power load forecasting, electricity price demand response and other related technologies need to be further improved, on the other hand due to the randomness and uncertainty of distributed energy, participating in the short-term spot market has large price fluctuations, which is not conducive to the stability of the electricity market, and it is also not conducive to the consumption of distributed energy. Aiming at the above problems, this paper uses the characteristics of CFDs to restrain market power to design a distributed energy trading mechanism to achieve the purpose of energy saving and emission reduction.
Power Identification of Distributed Generation Based on Back-Propagation Neural Network
Authors: Peng Fang , Liu Yang , Wang Feng , Li Chong , Wang Luhao , Cheng Xingong , Zong Xiju
Published: May 2021

Distributed generator (DG) is widely used and applied due to the energy and environment issues. Distributed photovoltaic generation is a typical kind of DG. Its output power is random and fluctuant, which has great influence on the safe, stable and economic operation of power system. Thus it is necessary to identify the power generated by the distributed photovoltaic generation. This paper proposes a power identification method based on BP Neural Network. The sample data comes from simulation by PSCAD and consists of current and active power that are measured in the branch of distributed network connected with DG and active power generated by the DG. The training is based on Matlab. Simulation results verify that the BP Neural Network can identify active power of DG accurately.
Position Sensorless Control of Switched Reluctance Motor under Magnetic Field Saturation
Authors: Qiu Chunyuan , Sun Baojiang
Published: May 2021

When the switched reluctance motor is running, as the motor phase current increases, the magnetic circuit of the motor will gradually saturate, which affects the estimation of the special position of the motor rotor. Aiming at the above problems, this paper proposes a positionless control method for switched reluctance motors under the condition of magnetic field saturation. Firstly, the Fourier phase inductance function of switched reluctance motor is established, and then the component of Fourier phase inductance function affected by magnetic field saturation is eliminated mathematically. Research the method of estimating the position and angle of the rotor based on the inductance positioning point. This paper takes a 12\8 motor as an example to verify the effectiveness of the method by simulation.
Technology and application of high speed fault location,isolation and self-healing in DC distribution network
Authors: Tan Kuo , Hu Guo , Wu Hai , Huang Feng
Published: May 2021

With the continuous increase of DC load, the research of DC distribution network has been developed rapidly. Compared with the traditional AC distribution network, DC distribution network has the advantages of less conversion times, high efficiency, low cost, simple control structure, no need to consider the frequency and phase and reactive power compensation equipment. Compared with AC distribution network, DC distribution network has more flexible operation mode and less power supply points However, the more flexible operation mode of DC distribution network also brings the problem of fault location and self-healing. The fault location, isolation and self-healing control strategy of AC distribution network can not be applied to DC distribution network. In this paper, a high-speed fault location, isolation and self-healing method for DC distribution network is proposed. Based on high-speed goose communication, a comprehensive evaluation is carried out according to the fault status of the power grid, and the millisecond level fault location, isolation and self-healing of DC distribution network are completed. The coordinated control equipment based on this method is successfully applied in Tongli integrated energy service center. When the fault occurs in this area, uninterrupted power supply is realized in the non fault area, which verifies the correctness and practicability of this method.
The Online Path Planning Method of UAV Autonomous Inspection in Distribution Network
Authors: Li Li , Zhan Hong , Hao Yongjing
Published: May 2021

In this paper, the problem of online path planning for autonomous inspection of distribution network lines by UAV is studied. Because the distribution lines are mostly distributed around cities, counties and mountainous areas, the lines and their surrounding environment are uncertain and dynamic. These factors will affect the safety of UAV inspection, making the off-line pre-planned path for UAV unavailable. This paper designs an improved iteration random tree algorithm (IRRT) algorithm, which can quickly plan the path of UAV in dynamic environment.
Short term Load Forecasting Considering Demand Response under virtual power plant mode
Authors: Du Zhendong , Wu Di , Bai Hua , Wang Zhengyong , Guo Yizong , Guo Chuangxin
Published: May 2021

In order to better manage demand response resources of user side and reduce short-term load forecasting error, a short-term load forecasting method considering demand response in virtual power plant mode is proposed. Firstly, the demand response mechanism of the virtual power plant is analyzed. Taking the maximum profit of the virtual power plant as the goal, considering the user’s energy consumption habits, self built photovoltaic, energy storage behavior and thermal electric coupling, the optimization model is established for each type of demand response resources. The CPLEX solver is called to solve the mixed integer linear programming problem after the model transformation, and the sub signals of each resource participating in the demand response are obtained. Then, based on this model, a long-term and short-term memory network model considering demand response signals is established to predict load power iteratively. At the same time, the long-term and short-term memory network model considering the demand response signals effectively makes up for the shortcomings of the traditional forecasting model without considering the demand response, and is more accurate in predicting the future trend of load change.
Overload Control Strategy Based on Triangular Fuzzy Analytic Hierarchy Process
Authors: Wang Heng
Published: May 2021

After the high-voltage transmission line is cut off due to a fault, the bearing transmission power will be transferred, which may cause overload. If overload cannot be eliminated quickly and scientifically, it is very likely that the line backup protection will be activated, which will trigger chain trip or even blackout accidents. In view of this, this paper proposed a cross-voltage level optimization load shedding control strategy based on fuzzy analytic hierarchy process. Through step-by-step progression in the three indexes of line overload degree, load importance degree, and unit load shedding cost, the lower-level lines of the overload line are selected for optimal line removal, thus achieving the goal of optimizing load shedding across voltage levels.
A Multi-objective Optimal Dispatch Method for Integrated Energy System Considering Multiple Loads Variations
Authors: Lv Dong , Tang Jun , Yang Chen
Published: May 2021

This paper proposes a multi-objective optimization dispatching method for the Integrated Energy System (IES), in which cooling/heating/electricity multi-load demand are included, and IES’s requirements in terms of energy efficiency, economy, and emissions are considered. We established an IES model for multi-objective optimal dispatch, and simulated cooling/heating/electric multiple load variations in it; then we established multiple objective functions based on IES’s scheduling requirements in terms of energy efficiency, economy, environmental issues. The model is solved by finding the pareto front based on genetic algorithm (GA), so that the decision makers can filter out the scheduling plan based on their preference, in which single-objective optimization is used first to find out the initial population for GA. Finally, the proposed method’s effectiveness is verified by case studies.
Feasibility Analysis of EV+X Storage to Support Power System Frequency
Authors: Deng Zhe , Wang Zengping , Li Ran
Published: May 2021

With the fast growth of renewable energy generation, the power system faces the challenge of low inertia. Lower system inertia makes it more challenging to keep the frequency stable, and the conventional frequency response mechanism is not capable of ensuring frequency within the limit. In this paper, a new frequency response mechanism is proposed to help to improve the frequency performance, where electric vehicles (EV) are used as energy storage, and they will cooperate with existing primary frequency response (PFR) to form an EV+X storage supporting power system frequency. This approach is proposed based on rigorous mathematical derivation, where the relationship between frequency and active power is quantitively analysed. To validate the new mechanism’s feasibility, simulation models are built to simulate the frequency behaviour after a big disturbance, and a series of tests are conducted. Both technical and economic benefits are investigated, considering the difference in EV control strategies and the proportion of EV responses. The result shows that EV+X storage can be a promising solution to the frequency stability problem.
An Improved Specific Harmonic Detection Method Based on Adaptive Cancellation Principle
Authors: Wang Lei , Pan Sun , Jun Sun , Yan Liang , Lang Xie Hai , Sheng Xiong
Published: May 2021

When the active power filter (APF) and the tunable filter are used for specific harmonic suppression, the accurate single harmonic current detection module is one of the key links to ensure its harmonic suppression effect. An improved single harmonic detection method based on the principle of adaptive cancellation has been proposed, which does not have some of the problems of traditional algorithms, for instance the feedback error is not accurate enough, and the contradiction between tracking speed and steady-state accuracy. This method can accurately and quickly detect the harmonic amplitude and phase angle, and can be flexibly applied to the harmonic detection of three-phase and single-phase systems. Through theoretical analysis and MATLAB simulation, it is proved that the method can guarantee a higher steady-state accuracy and a faster tracking speed.
20 Years of Forging N-Heterocycles from Acrylamides through Domino/Cascade Reactions
Authors: Comesse Sébastien , Alahyen Ismail , Benhamou Laure , Dalla Vincent , Taillier Catherine
Published: May 2021

Acrylamides are versatile building blocks that are easily obtained from readily available starting materials. During the last 20 years, these valuable substrates bearing a nucleophilic nitrogen atom and an electrophilic double bond have proven to be efficient domino partners, leading to a wide variety of complex aza-heterocycles of synthetic relevance. In this non-exhaustive review, metal-free and metal-triggered reactions followed by an annulation will be presented; these two approaches allow good modulation of the reactivity of the polyvalent acrylamides.

1 Introduction

2 Metal-Free Annulations

2.1 Domino Reactions Triggered by a Michael Addition

2.2 Domino Reactions Triggered by an Aza-Michael Addition

2.3 Domino Processes Triggered by an Acylation Reaction

2.4 Domino Reactions Triggered by a Baylis–Hillman Reaction

2.5 Cycloadditions and Domino Reactions

2.6 Miscellaneous Domino Reactions

3 Metal-Triggered/Mediated Annulations

3.1 Zinc-Promoted Transformations

3.2 Rhodium-Catalyzed Functionalization/Annulation Cascades

3.3 Cobalt-Catalyzed Functionalization/Annulation Cascades

3.4 Ruthenium-Catalyzed Functionalization/Annulation Cascades

3.5 Iron-Catalyzed Functionalization/Annulation Cascades

3.6 Palladium-Catalyzed Functionalization/Annulation Cascades

3.7 Copper-Catalyzed Transformations

3.8 Transition Metals Acting in Tandem in Domino Processes

4 Radical Cascade Reactions

5 Conclusion
Arterial Thrombosis in Patients with Antiphospholipid Syndrome: A Review and Meta-Analysis
Authors: Aibar Jesus , Schulman Sam
Published: May 2021

There is a scarcity of high-quality randomized controlled trials (RCTs) comparing antithrombotic regimens for secondary prevention of arterial thrombosis (AT) in antiphospholipid syndrome (APS). We reviewed different antithrombotic regimens used for this purpose. We searched for studies on management of AT in APS on PubMed and Web of Science. Eleven studies (5 RCTs, 3 prospective, and 3 retrospective cohort studies) comparing different regimens and reporting outcomes specifically for patients with index AT events were identified. Treatments were vitamin K antagonists (VKA; 9 studies), non-VKA oral anticoagulant (NOAC; 3 studies), single antiplatelet therapy (SAPT; 7 studies), dual antiplatelet therapy (DAPT; 2 studies), and VKA combined with SAPT (4 studies). We performed a meta-analysis for the outcomes: recurrent AT, any (arterial or venous) recurrent thromboembolism, and major bleeding. Recurrent AT was reduced with VKA plus SAPT versus VKA (risk ratio [RR]: 0.43; 95% confidence interval [CI]: 0.22–0.85) and with DAPT versus SAPT (RR: 0.29; 95% CI: 0.09–0.99). Any recurrent thromboembolism was reduced with VKA plus SAPT versus VKA alone (RR: 0.41; 95% CI: 0.24–0.69) and versus SAPT alone (RR: 0.36; 95% CI: 0.13–0.96). There were no significant differences between other treatments for thromboembolism and for none of the comparisons regarding major bleeding. In a sensitivity analysis, excluding low-quality studies, VKA was more effective than NOAC to prevent recurrent AT (RR: 0.25; 95% CI: 0.07–0.93). Combined antithrombotic therapy might be more effective than single agents as secondary prophylaxis in APS with AT, and does not seem to compromise with safety, but the quality of evidence is generally low. NOACs should be avoided for patients with APS and AT.
Vascularized Rib Bone Grafting: Indications, Techniques, and Clinical Outcomes
Authors: Winocour Sebastian J. , Agrawal Nikhil , Wagner Kathryn M. , Davis Matthew J. , Abu-Ghname Amjed , Shekher Rohil , Raber Michael R. , Bohl Michael A. , Ropper Alexander E. , Reece Edward M.
Published: May 2021

Pseudarthrosis is a difficult complication often seen in patients with complex spinal pathology. To supplement existing neurosurgical approaches to cervicothoracic spinal instrumentation and fusion, novel vascularized rib bone grafts can be utilized in patients at high risk for failed spinal fusion. In this article, we discuss the indications, benefits, surgical technique, feasibility, and limitations of using rib vascularized rib bone grafts to augment spinal fusion.
Scoping study of detecting high harmonic fast waves in NSTX-U hot core plasma directly using beam emission spectroscopy
Authors: Rutherford Grant , Shiraiwa Syun’ichi , Smith David R. , Bertelli Nicola
Published: May 2021

In this paper, we used radio frequency (RF) full wave simulation to explore the feasibility of generating a density beat oscillation formed by high harmonic fast waves (HHFWs) in the National Spherical Tokamak Experiment-Upgrade (NSTX-U) and of measuring it numerically with 2D beam emission spectroscopy (BES). This oscillation is of interest as it can be used to determine the injected RF fields. We began by computing HHFW fields in NSTX-U under a variety of experimental conditions and antenna configurations with Petra-M, a 3D RF wavefield solver. These fields were then used to evaluate the amplitude of δne,beat/ne0 in the volume of measurement, which we predict to be between 5 × 10−10 and 10−9, although it is highly dependent on plasma parameters. Trends in magnetic field, core temperature, core density, and antenna phasing are presented, and the parameters most suitable to this measurement are identified. Finally, we developed a synthetic BES diagnostic to compare the experimental BES signal against.
Insight into plasma degradation of paracetamol in water using a reactive molecular dynamics approach
Authors: Brault Pascal , Abraham Mado , Bensebaa Aïda , Aubry Olivier , Hong Dunpin , Rabat Hervé , Magureanu Monica
Published: May 2021

Plasma-produced reactive oxygen and nitrogen species are expected to promote micropollutant degradation in water and more generally in liquids. Among these species, the hydroxyl radical (HO•) is recognized as being the most efficient. Molecular dynamics simulations were carried out to determine the reaction steps of HO• interaction with the paracetamol molecule in water, a pharmaceutical residue that is frequently detected in surface and tap water and is well documented. Calculations were performed at various temperatures to determine the oxidation pathways, and the intermediate and final products were identified. Assuming a ratio of 10% HO• in water, it was found that a local temperature of 2500 K is required to decompose paracetamol to CO, H2O, NH3, and C2H2.
Laser-induced breakdown in liquid water: Influence of repeated laser pulses on plasma formation and emission
Authors: Young A. , Graham W. G. , Morgan T. J. , Hüwel L.
Published: May 2021

We have experimentally investigated the influence of repeated laser pulses on laser-induced breakdown (LIB) in water following a focused 1064 nm laser pulse, for repetition rates between 0.5 and 20 Hz and up to 100 pulses. LIB plasma image data are collected as a function of repetition rate and laser pulse number, using an intensified CCD camera with sub-nanosecond camera-laser timing. Each pulse induces multiple breakdowns, shockwaves, and macroscopic cavitation bubbles. These effects disappear by the time the next pulse arrives. Even so, we find that the water target retains effects from previous pulses that persist up to roughly a second and that modify subsequent LIB properties including plasma location, spatial extension, and total emission intensity. We quantify the effects by tracking the first moment of the plasma emission intensity, which we call the “center of intensity” (CoI). Three distinct reproducible repetition-rate-dependent phases are identified with repeated pulses. In particular, (1) with initial pulses, emission intensity decreases and the CoI broadens and propagates downstream from the laser focus reaching a maximum axial distance away from the focal point, (2) with additional pulses, the CoI narrows and travels back upstream toward the laser, and (3) with continued pulses, the plasma gains back a portion of the lost intensity and the CoI reaches a steady state position, not at the focal point. Two possible causal effects are highlighted; particle inclusion concentration changes and microbubbles in the laser path.
Effect of ligand binding on riboswitch folding: Theory and simulations
Authors: Sharma Shivangi , Singh Vishal , Biswas Parbati
Published: May 2021

The effect of ligand binding on the conformational transitions of the add A-riboswitch in cellular environments is investigated theoretically within the framework of the generalized Langevin equation combined with steered molecular dynamics simulations. Results for the transition path time distribution provide an estimate of the transit times, which are difficult to determine experimentally. The time for the conformational transitions of the riboswitch aptamer is longer for the ligand bound state as compared to that of the unbound one. The transition path time of the riboswitch follows a counterintuitive trend as it decreases with an increase in the barrier height. The mean transition path time of either transitions of the riboswitch in the ligand bound/unbound state increases with an increase in the complexity of the surrounding environment due to the caging effect. The results of the probability density function, transition path time distribution, and mean transition path time obtained from the theory qualitatively agree with those obtained from the simulations and with earlier experimental and theoretical studies.
Energy localization and topological protection of a locally resonant topological metamaterial for robust vibration energy harvesting
Authors: Lan Chunbo , Hu Guobiao , Tang Lihua , Yang Yaowen
Published: May 2021

During the past decade, metamaterial-based vibration energy harvesters (meta-VEHs) have been increasingly developed owing to the extraordinary characteristics of metamaterials, such as locally resonant bandgap, defect state, and wave focusing features. In this paper, the interface state, a feature recently found in topological metamaterials, is exploited for low-frequency vibration energy harvesting. The topological meta-VEH consists of two kinds of locally resonant metamaterials with different topological phases and a piezoelectric transducer being installed at the interface between these two metamaterials. First, the governing equations of the topological meta-VEH are established based on the mass–spring model. Subsequently, the dispersion relation of such a one-dimensional topological meta-VEH is obtained by applying Bloch's theorem. It is revealed that the interface mode can be attained in the low-frequency range through the band folding of the locally resonant metamaterial. Moreover, the finitely long model of this topological meta-VEH is built, and the transmittance response is calculated both analytically and numerically. Subsequently, the potential benefits of topological metamaterial, including wave localization and topological protection, are thoroughly investigated. It is found that the elastic energy in the interface state is localized at the interface position, resulting in a significant improvement in output power. Meanwhile, the topological protection property can significantly improve the robustness of the interface mode, thus achieving outstanding energy harvesting performance. Finally, to further enhance the energy harvesting performance, the stiffness tuning method and the defect enhancement method are proposed. It is found that integrating the defect mode and interface mode not only improves the output voltage but also achieves the capability of a highly robust energy harvesting.
The effects of air flow on the nanosecond pulsed pin-to-pin discharge dynamics in atmosphere-pressure air
Authors: Lei XinYu , Nie LanLan , Xian YuBin , Lu XinPei
Published: May 2021

Investigation of the breakdown phase of a nanosecond pulsed pin-to-pin discharge in air at atmosphere pressure with different gas flow rates is carried out. The experimental results show that the air flow leads to increase in the breakdown delay time. The effect of air flow rate on the current growth rates and streamer channel appearance at the beginning of breakdown is observed, which indicates that the redistribution and decrease in the densities of reactive species produced by previous discharges are playing the main role in the discharge delay time. When 15 standard liters per minute (slm) air flow is used and pulse frequency is 1 kHz, the discharge current reaches a peak of about 0.5 A, then it decreases to 0.4 A and lasts for about 70 ns, and then the discharge current starts to increase rapidly at a rate of >0.1 A/ns. For pulse frequency of 8 kHz or nitrogen as working gas, the discharge current increases monotonically. Besides, the difference of the gas temperature for the cases of 0 and 15 slm is measured, and the result indicates that the difference of the gas temperature should not be the main contributor to the difference of the breakdown delay time. Detailed analysis shows that the appearance of the first current peak is due to the fast detachment of O2−. Finally, simulation results show that the ionization rate for the case of 15 slm is also more significantly delayed than the case of 0 slm, which is consistent with the measured discharge current waveform.
How sensitive are physical properties of choline chloride–urea mixtures to composition changes: Molecular dynamics simulations and Kirkwood–Buff theory
Authors: Celebi Alper T. , Dawass Noura , Moultos Othonas A. , Vlugt Thijs J. H.
Published: May 2021

Deep eutectic solvents (DESs) have emerged as a cheaper and greener alternative to conventional organic solvents. Choline chloride (ChCl) mixed with urea at a molar ratio of 1:2 is one of the most common DESs for a wide range of applications such as electrochemistry, material science, and biochemistry. In this study, molecular dynamics simulations are performed to study the effect of urea content on the thermodynamic and transport properties of ChCl and urea mixtures. With increased mole fraction of urea, the number of hydrogen bonds (HBs) between cation–anion and ion–urea decreases, while the number of HBs between urea–urea increases. Radial distribution functions (RDFs) for ChCl–urea and ChCl–ChCl pairs shows a significant decrease as the mole fraction of urea increases. Using the computed RDFs, Kirkwood–Buff Integrals (KBIs) are computed. KBIs show that interactions of urea–urea become stronger, while interactions of urea–ChCl and ChCl–ChCl pairs become slightly weaker with increasing mole fraction of urea. All thermodynamic factors are found larger than one, indicating a non-ideal mixture. Our results also show that self- and collective diffusivities increase, while viscosities decrease with increasing urea content. This is mainly due to the weaker interactions between ions and urea, resulting in enhanced mobilities. Ionic conductivities exhibit a non-monotonic behavior. Up to a mole fraction of 0.5, the ionic conductivities increase with increasing urea content and then reach a plateau.
Should deep eutectic solvents be treated as a mixture of two components or as a pseudo-component?
Authors: Zhang Huan , Lu Xuejun , González-Aguilera Laura , Ferrer M. Luisa , del Monte Francisco , Gutiérrez María C.
Published: May 2021

Deep eutectic solvents (DESs) and dilutions thereof (mainly in H2O but also in many other non-aqueous solvents and co-solvent mixtures) have recently attracted great attention. It is well known that DES dilutions exhibit deviations from ideality. Interestingly, the treatment of DES as a mixture of two components or a pseudo-component is by no means trivial when determining deviations in density and, mainly, in viscosity. Herein, we studied aqueous dilutions of one of the most widely studied DES, this is, that composed of choline chloride and urea in a 1:2 molar ratio (e.g., ChCl2U). Using density and viscosity data reported in previous works, we calculated the excess molar volumes (VE) and excess viscosities (ln ηE) considering ChCl2U as either a mixture of two components or a pseudo-component, that is, taking the DES molecular weight as MChCl2U = fChClMChCl + fUMU = 86.58 g mol−1 (with fChCl = 1/3 and fU = 2/3) or as M*ChCl2U = MChCl + 2 MU = 259.74 g mol−1. We found that neither the sign of VE and VE* nor their evolution with temperature was influenced by the use of either MChCl2U or M*ChCl2U, and only the absolute magnitude of the deviation and the DES content (in wt. %) at which the minimum appears exhibited some differences. However, ln ηE and ln ηE* exhibited opposite signs, negative and positive, respectively. The odd achievement of negative ln ηE in aqueous dilutions of ChCl2U characterized by the formation of HB networks suggest the treatment of ChCl2U as a pseudo-component as more appropriate. Moreover, the role played by the presence of U in the evolution of ln ηE* with temperature was also discussed.
The Einstein effective temperature can predict the tagged active particle density
Authors: Shakerpoor Alireza , Flenner Elijah , Szamel Grzegorz
Published: May 2021

We derive a distribution function for the position of a tagged active particle in a slowly varying in space external potential, in a system of interacting active particles. The tagged particle distribution has the form of the Boltzmann distribution but with an effective temperature that replaces the temperature of the heat bath. We show that the effective temperature that enters the tagged particle distribution is the same as the effective temperature defined through the Einstein relation, i.e., it is equal to the ratio of the self-diffusion and tagged particle mobility coefficients. This result shows that this effective temperature, which is defined through a fluctuation–dissipation ratio, is relevant beyond the linear response regime. We verify our theoretical findings through computer simulations. Our theory fails when an additional large length scale appears in our active system. In the system we simulated, this length scale is associated with long-wavelength density fluctuations that emerge upon approaching motility-induced phase separation.
Thermoelectric properties of p-type polycrystalline Bi0.8Sb0.8In0.4Se3
Authors: Jiang Feng , Xia Chengliang , Zhu Yongbin , Han Zhijia , Liu Chengyan , Xia Jiating , Chen Yue , Liu Weishu
Published: May 2021

Achieving both n-type and p-type performance in one thermoelectric material family is of great benefit for the thermoelectric device due to the comparable mechanical properties. Bi2Se3 shows strong n-type behavior due to the intrinsic Se vacancy. Herein, we reported a p-type poly-crystalline Bi0.8Sb0.8In0.4Se3 material, which has the same crystalline structure as Bi2Te3, with an intrinsic Seebeck coefficient of 500 μV K−1 at room temperature. It is found that Mn is a good p-type charge carrier provider in the as-fabricated Bi0.8Sb0.8In0.4Se3 thermoelectric material. An optimized power factor of ∼420 μW m−1 K−2 and a low thermal conductivity of 0.51 W m−1 K−1 result in a ZT of 0.48 at 350 °C in Mn0.03Bi0.77Sb0.8In0.4Se3. Our work provides an incisive insight into the manipulation of the intrinsic defects via high entropy strategy.
Scanning triboelectric nanogenerator as a nanoscale probe for measuring local surface charge density on a dielectric film
Authors: Lin Shiquan , Wang Zhong Lin
Published: May 2021

Inspired by the contact-separation mode triboelectric nanogenerator (TENG), we propose a technique for local surface charge density measurement based on atomic force microscopy. It is named as scanning TENG, in which a conductive tip tapping above a charged dielectric surface produces an AC between the tip and the dielectric bottom electrode due to electrostatic induction. The Fourier analysis shows that the amplitude of the first harmonic of the AC is linearly related to surface charge density. The results demonstrate that the scanning TENG is a powerful tool for probing nanoscale charge transfer in contact-electrification.
Confinement and complex viscosity
Authors: Coombs S. J. , Giacomin A. J. , Pasquino R.
Published: May 2021

Whereas much is known about the complex viscosity of polymeric liquids, far less is understood about the behavior of this material function when macromolecules are confined. By confined, we mean that the gap along the velocity gradient is small enough to reorient the polymers. We examine classical analytical solutions [O. O. Park and G. G. Fuller, “Dynamics of rigid and flexible polymer chains in confined geometries. II. Time-dependent shear flow,” J. Non-Newtonian Fluid Mech. 18, 111–122 (1985)] for a confined rigid dumbbell suspension in small-amplitude oscillatory shear flow. We test these analytical solutions against the measured effects of confinement on both parts of the complex viscosity of a carbopol suspension and three polystyrene solutions. From these comparisons, we find that both parts of the complex viscosity decrease with confinement and that macromolecular orientation explains this. We find the persistence length of macromolecular confinement, Lp, to be independent of both λω and λγ̇0.
Combined microwave and laser Rayleigh scattering diagnostics for pin-to-pin nanosecond discharges
Authors: Wang Xingxing , Patel Adam , Shashurin Alexey
Published: May 2021

In this work, the temporal decay of electrons produced by an atmospheric pin-to-pin nanosecond discharge operating in the spark regime was measured via a combination of microwave Rayleigh scattering (MRS) and laser Rayleigh scattering (LRS). Due to the initial energy deposition of the nanosecond pulse, a variation in the local gas density occurs on the timescale of electron decay. Thus, the assumption of a constant collisional frequency is no longer applicable when electron number data are extracted from MRS measurements. To recalibrate MRS measurements throughout the electron decay period, temporally resolved LRS measurements of the local gas density were performed over the event duration. The local gas density was calculated to be 30% of the ambient level during the later stages of electron decay, and it recovers at about 1 ms after discharge. A shock front traveling approximately 500 m/s was additionally observed. Coupled with plasma volume calibration via temporally resolved intensified charge-coupled device imaging, the corrected decay curves of the electron number and electron number density are presented with a measured peak electron number density of 4.5 × 1015 cm−3 and a decay rate of ∼(0.1–0.35) × 107 s−1. A hybrid MRS and LRS diagnostic technique can be applied for a broad spectrum of atmospheric-pressure microplasmas where a variation in the gas number density is expected due to energy deposition in the discharge.
Tracking the recruitment and evolution of snake toxins using the evolutionary context provided by the
Bothrops jararaca
genome
Authors: Almeida Diego Dantas , Viala Vincent Louis , Nachtigall Pedro Gabriel , Broe Michael , Gibbs H. Lisle , Serrano Solange Maria de Toledo , Moura-da-Silva Ana Maria , Ho Paulo Lee , Nishiyama-Jr Milton Yutaka , Junqueira-de-Azevedo Inácio L. M.
Published: May 2021

Significance

The jararaca lancehead genome provides a comprehensive road map of the genomic context of pitviper toxin genes. Comparisons of these genomic segments across the phylogeny revealed an unexpectedly high number of toxin families that originated via the direct co-option of preexisting nontoxin genes, indicating that the snake toxin arsenal was mostly assembled from local elements of the ancestral genome. These results support a new perspective in venom evolution in which gene duplications in most toxin families occurred after, rather than before, initial toxin recruitment from nontoxin genes, contributing to the evolutionary optimization of snake venoms. They also emphasize the importance of correctly identifying orthologous loci to accurately trace the genomic pathways that lead to the evolutionary origination of new traits.
Responsive manipulation of neural circuit pathology by fully implantable, front-end multiplexed embedded neuroelectronics
Authors: Zhao Zifang , Cea Claudia , Gelinas Jennifer N. , Khodagholy Dion
Published: May 2021

Significance

We introduce a multiplex-then-amplify (MTA) scheme that requires only one amplifier per multiplexer, significantly reducing the number of components in multichannel acquisition systems while enabling arbitrary waveform stimulation independently on all channels. Based on this scheme, we developed a fully implantable, miniaturized, responsive embedded system that can acquire neural oscillations and action potentials using conformable conducting polymer-based electrodes as well as perform real-time onboard processing, low-latency arbitrary waveform stimulation, and local data storage. MTA devices enabled development of a protocol for suppression of pathologic coupling within an epileptic network. These devices will allow application of targeted high-spatiotemporal resolution responsive neurostimulation approaches to a variety of brain functions, broadening our ability to chronically modify neural networks in health and disease.
Hierarchical transitions and fractal wrinkling drive bacterial pellicle morphogenesis
Authors: Qin Boyang , Fei Chenyi , Wang Bruce , Stone Howard A. , Wingreen Ned S. , Bassler Bonnie L.
Published: May 2021

Significance

Multicellular bacterial communities called biofilms and pellicles significantly influence medical infections and industrial biofouling. Biofilms and pellicles often act as reservoirs of toxigenic bacteria. Here, we report a fractal wrinkling morphogenesis program that underlies pellicle formation in the model biofilm former and global pathogen,
Vibrio cholerae
. Pellicle morphogenesis is marked by the emergence of a cascade of self-similar structures with fractal-like scaling in wavelength, which increases surface area and presumably enhances nutrient transport and signaling among community members. This morphogenesis program can be altered by varying the spatial heterogeneity of the community. Thus, bacterial pellicles could provide tractable model systems to understand overarching principles driving morphogenesis and for engineering of functional soft biomaterials.