bluuebunny/crossref_metadata_2025 huggingface dataset:
Laplacian on fuzzy de Sitter space
Authors: Brkić Bojana , Burić Maja , Latas Duško
Published: March 2022

We study details of geometry of noncommutative de Sitter space: we determine the Riemann and Ricci curvature tensors, the energy and the Laplacian. We find, in particular, that fuzzy de Sitter space is an Einstein space, R

ab
= −3ζη

ab
. The Laplacian, defined in the noncommutative frame formalism, is not Hermitian and gives nonunitary evolution. When symmetrically ordered, it has the usual quadratic form Δ = Π
a
Π
a
(when acting on functions in representation space,

Ψ
∈
H

): we find its eigenstates and discuss its spectrum. This result is a first step in a study of the scalar field Laplacian, Δ = [Π
a
, [Π
a
, ]], and its propagator.
Using zero-energy states to explore how external boundaries affect the number of bound states in a quantum well
Authors: Timberlake Todd K , Babione Sarah E
Published: March 2022

We use the condition for the existence of zero-energy eigenstates to examine how the number of bound (negative energy) states in a finite-width one-dimensional quantum well is altered by the introduction of boundaries outside of the well. We consider a variety of quantum wells including a finite square well, a triangular well, and sets of two to five Dirac delta wells. Each of these quantum wells is placed at the center of an infinite square well with variable width and the conditions for the existence of zero-energy eigenstates are determined analytically. The zero-energy conditions (ZEC) form curves in the parameter space that separate regions with different numbers of bound states. Moving across one of these curves changes the number of bound states by one. We find that, for the systems studied, introducing external boundaries changes the number of bound states by at most two. This work illustrates the usefulness of the ZEC as a tool for studying how the number of bound states in a quantum well depends on the system parameters.
Development of a piezoelectric pump with unfixed valve
Authors: Fan Yiwen , Zhao Weixian , Zhang Xinfeng , Yu Xingjian , Luo Xiaobing
Published: March 2022

Piezoelectric pump, driven by piezoelectric actuator, is one of the most promising micropumps in compact system. However, the application of piezoelectric pump is limited by the check valve, which is not efficient enough and needs careful fixation. This work presents a novel design with unfixed check valve, which greatly simplifies the assembly of valve-based piezoelectric pump and improves the output performance. The valve is unfixed with a small gap to obtain variable stiffness at different working stages, making it open more quickly. The piezoelectric pumps with three different valve gaps were designed, fabricated, and tested. The pump with the unfixed valve shows a 25.6% flow rate improvement compared with the fixed check valve without reducing the output pressure. To reveal the mechanism of the flow rate improvement, we investigated the flow resistance and the volumetric efficiency of the piezoelectric pump. The results show that the unfixed valve increases the volumetric efficiency of the piezoelectric pump, which improves the flow rate. The prototype pump achieved the maximum output performance of 162 ml min−1 and 33 kPa. The power consumption was less than 100 mW, reaching a pump efficiency of 21.7%.
Unveiling ferromagnetism and antiferromagnetism in two dimensions at room temperature
Authors: Araujo Ravel de Moraes Telles , Zarpellon Juliana , Mosca Dante Homero
Published: March 2022

The aim of this work is to present an overview and a critical discussion on two-dimensional materials and functional nanostructures exhibiting ferromagnetic and antiferromagnetic long-range ordering at or above room temperature (RT). We specially describe and discuss the series of results concerning two-dimensional magnetism originated from intrinsic and induced d magnetic moments in low-dimensional nanostructured materials. Selected materials showing two-dimensional magnetic properties close to RT are classified as atomic monolayers, natural and artificial van der Waals layers, magneto-lamellar intermetallic compounds, and nanostructured materials containing native and artificially created defects that originate magnetic moments in networks with two-dimensional interconnectivity. To make the point on these materials, we describe their atomic and electronic structures as well as magnetic interaction mechanisms responsible for magnetic behavior. Theoretical backgrounds for understanding the correlations between structure and magnetic properties are examined. Special emphasis on the possible applications of two-dimensional magnetism for developments of new devices in the fields of spintronics, spin-orbitronics, magnonics, valleytronics and twistronics, among other emergent technologies are discussed.
A novel multivariate signal processing-based fault diagnosis approach of rotating machinery under various operating conditions
Authors: Lv Yong , Yang Di , Yuan Rui , Yang Ke , Zhong Hongyu
Published: March 2022

Compared with signals collected by the single sensor, the collected multivariate signals contain more information to reflect the state of mechanical equipment, which has a positive effect on fault diagnosis. However, different acquisition channels and various operating conditions interfere with the extraction of fault features of rotating machinery. To solve this problem, taking rolling bearings as an example in this paper, a novel method is adopted to alleviate these interferences and combined with an improved extreme learning machine (ELM) to achieve intelligent fault diagnosis of rolling bearings under various operating conditions. First, adaptive projection intrinsically transformed multivariate empirical mode decomposition is used to decompose multivariate signals and obtain intrinsic mode functions of each channel to construct feature matrices. Then, nuisance attribute projection (NAP) is employed to alleviate the interference components in the feature matrix, which are originated from different channels and operating conditions. Finally, vectors belonging to the processed feature matrix as samples are input into the proposed weighted extreme learning machine (WELM) for intelligent fault classification. The weighted matrix of the WELM can compress the dimension of the sample and extract sensitive features, and the effectiveness of the proposed fault diagnosis model via the above methods is verified by experiments. Furthermore, comparative experiments show that the proposed fault diagnosis model has higher accuracy than the model combined with NAP and traditional single-hidden layer feedforward neural network or ELM. Therefore, the proposed fault diagnosis model may potentially aid experts on fault diagnosis of rotating machinery under various operating conditions.
Phosphorene grain boundary effect on phonon transport and phononic applications
Authors: Wang Xujun , Wang Quanjie , Liu Xinyu , Huang Zixuan , Liu Xiangjun
Published: March 2022

Grain boundaries (GBs) widely exist in black phosphorene (BP), which plays a vital role in determining the properties of 2D materials. Significant GB effect on the thermal boundary resistance in BP structures is found by using molecular dynamics calculations and lattice dynamic analysis. A remarkably high interface thermal resistance is observed. By analyzing the strain distribution and phonon vibrational spectra, we reveal this high thermal resistance originates from phonon localization and strong phonon boundary scattering induced by the local stress at the GB area. Particularly, it is interesting to find that the partial phonon modes display weak localization when GBs present. The fraction of atoms participating in a particular phonon vibrational mode has been quantified through the calculation of phonon participation ratio. In addition, the thermal boundary resistance is found size-dependent, which further induces interesting thermal rectification effect in the BP structures. A high rectification ratio is obtained by adjusting the structural length and temperature bias. These findings provide a through insight into the GB effects on individual phonon mode transmission across the GBs, and highlight that the GB effect is an important factor and should be taken into account for the applications of BP-based phononic devices.
Offline and online LSTM networks for respiratory motion prediction in MR-guided radiotherapy
Authors: Lombardo Elia , Rabe Moritz , Xiong Yuqing , Nierer Lukas , Cusumano Davide , Placidi Lorenzo , Boldrini Luca , Corradini Stefanie , Niyazi Maximilian , Belka Claus , Riboldi Marco , Kurz Christopher , Landry Guillaume
Published: March 2022

Objective. Gated beam delivery is the current clinical practice for respiratory motion compensation in MR-guided radiotherapy, and further research is ongoing to implement tracking. To manage intra-fractional motion using multileaf collimator tracking the total system latency needs to be accounted for in real-time. In this study, long short-term memory (LSTM) networks were optimized for the prediction of superior–inferior tumor centroid positions extracted from clinically acquired 2D cine MRIs. Approach. We used 88 patients treated at the University Hospital of the LMU Munich for training and validation (70 patients, 13.1 h), and for testing (18 patients, 3.0 h). Three patients treated at Fondazione Policlinico Universitario Agostino Gemelli were used as a second testing set (1.5 h). The performance of the LSTMs in terms of root mean square error (RMSE) was compared to baseline linear regression (LR) models for forecasted time spans of 250 ms, 500 ms and 750 ms. Both the LSTM and the LR were trained with offline (offline LSTM and offline LR) and online schemes (offline+online LSTM and online LR), the latter to allow for continuous adaptation to recent respiratory patterns. Main results. We found the offline+online LSTM to perform best for all investigated forecasts. Specifically, when predicting 500 ms ahead it achieved a mean RMSE of 1.20 mm and 1.00 mm, while the best performing LR model achieved a mean RMSE of 1.42 mm and 1.22 mm for the LMU and Gemelli testing set, respectively. Significance. This indicates that LSTM networks have potential as respiratory motion predictors and that continuous online re-optimization can enhance their performance.
Effects of humidity on the dynamics and electron recombination of a pin-to-pin discharge in He + H2O at atmospheric pressure
Authors: Brisset Alexandra , Harris Benjamin , Dickenson Aaron , Niemi Kari , Walsh James , Wagenaars Erik
Published: March 2022

Control of the plasma chemistry is essential for the effectiveness of atmospheric pressure plasmas in many applications. For this, the effects of the humidity of the feed gas on the discharge chemistry need to be considered. Detailed studies are scarce and many of them are dominated by surface interactions, obscuring any volume effects. Here, a negative nanosecond pulsed discharge is generated in a pin–pin 3 mm gap geometry in He + H2O that enables the study of volume kinetics due to minimal surface area. The effect of humidity on the discharge development, electric field and electron density is investigated through experiments and modelling. It is found that the presence of water vapour affects both the electron density at the start of the pulse (remaining from the previous pulse) and the ionisation rates during the ignition phase, leading to a complex dependence of the discharge development speed depending on the water concentration. The electron decay is studied using the 0D global kinetics model GlobalKin. The dominant reactions responsible for the electron decay depending on the concentration of water vapour are determined by comparing experimental and simulated results and these reactions are grouped in simplified kinetic models. It is found that with water concentrations increasing from 0 to 2500 ppm, the complexity of the dominant reactions increases with in particular O2
+, H2O3
+ and water clusters becoming important for high water concentrations. This work also provides experimental data for validation of kinetic models of plasmas in controlled environments.
Opto-electronic, thermodynamic and charge carriers transport properties of Ta2FeNiSn2 and Nb2FeNiSn2 double half-Heusler alloys
Authors: Berarma Khadidja , Essaoud Saber Sâad , Mousa Ahmad A , Azar Said M , Al-Reyahi Anas Y
Published: March 2022

A computational research study of the structural, electronic, and optical characteristics of double half-Heusler alloys Ta2FeNiSn2 and Nb2FeNiSn2 is presented by performing ab initio calculations. The density functional theory framework employs the full-potential linearized augmented plane wave method to solve Kohn–Sham equation as implemented in the Wien2k code. The exchange-correlation potential is processed by using the local density approximation and the generalized gradient approximation–Perdew, Burke, and Ernzerhof approximations to calculate the total energy and other physical properties. The obtained results showed that both alloys possess high cohesive energies, where Nb2FeNiSn2 (7.213 eV atom−1) is more consistent than Ta2FeNiSn2 (6.249 eV atom−1), these remarkable results support the structural stability for both alloys. Also, the thermodynamic stability of both compounds was confirmed through calculating the formation energy as the obtained results were close to the results obtained in as well as given the Open Quantum Materials Database. Electronic characteristics and chemical bonding are illustrated and discussed by computing the electron charge density, density of states, and band structure. Both alloys show semiconductor behavior with (∼0.5 eV) indirect energy bandgap. Also, we have calculated and analyzed the complex dielectric function, absorption coefficient, as well as, reflectivity spectra for both compounds. The semi local Boltzmann transport theory has been employed to treat temperature effect on thermoelectric properties of Ta2FeNiSn2 and Nb2FeNiSn2 compounds where the obtained results appears that both compounds have high coefficient at the normal condition, and they also have a good power factor at the Fermi level, which emphasizes that the thermoelectric efficiency of the two compounds is good and does not require doping. Also, depending on quasi-harmonic model was used for estimating the heat capacity, the lattice thermal conductivity, the thermal expansion and the Debye temperature under the pressure effects.
Photon-pair blockade in a Josephson-photonics circuit with two nondegenerate microwave resonators
Authors: Ma Sheng-li , Xie Ji-kun , Ren Ya-long , Li Xin-ke , Li Fu-li
Published: March 2022

We propose to generate photon-pair blockade in a Josephson-photonics circuit that consists of a dc voltage-biased Josephson junction in series with a superconducting charge qubit and two nondegenerate microwave resonators. The two-level charge qubit is utilized to create anticorrelations of the charge transport; that is, the simultaneous Cooper pair tunneling events are inhibited. When the Josephson frequency matches the sum of resonance frequencies of the charge qubit and the two resonators, we demonstrate that the two resonators can release their energies in the form of antibunched pairs of two strongly correlated photons. The present work provides a practical way for producing a bright microwave source of antibunched photon pairs, with potential applications ranging from spectroscopy and metrology to quantum information processing.
Compton profile and charge density reconstruction by the maximum entropy method
Authors: Aguiar Julio C , Di Rocco Héctor O
Published: March 2022

The aim of this work is to propose a theoretical procedure to determine the electron momentum density and Compton profile of valence electrons in solids. The procedure consists in a hybrid methodology that combines the maximum entropy method and Dirac-Hartree–Fock formalism, which allows including exchange and correlation effects on valence electrons for distances near the atomic nucleus and that are approximated using the Breit-Wigner distribution function. This technique can be applied for a wide range of crystalline solids. The results and comparisons reported here are for: lithium, beryllium, aluminum, silicon and copper. The application of the model only requires prior knowledge of the Fermi momentum values. In addition, a reconstruction of the valence electron charge density distribution via simple expression of the Compton profile is derived.
Cross-polarization ratio analysis of digital speckle patterns applied to teeth demineralization diagnosis
Authors: Castilho V M , Nunes A M , de Abreu L G , Balthazar W F , da Silva L , O Huguenin J A
Published: March 2022

We propose using the cross-polarization ratio (CPR) of the digital speckle pattern as a parameter to detect enamel erosion. We applied such analysis to successfully detect enamel erosion caused by teeth demineralization. The speckle patterns were produced using an in vitro study in human teeth where the erosion was produced artificially by acid attack. Our result is a proof of principle of the viability to apply CPR in the characterization of enamel erosion, which can be a powerful instrument for early diagnosis of teeth demineralization. This approach proved to be very sensitive to variation in speckle patterns compared with other traditional speckle patterns analyses.
Comparisons between high power fiber systems in the presence of radiation induced photodarkening
Authors: Tao Mengmeng , Chen Hongwei , Feng Guobin , Wang Lijun , Ye Jingfeng , Wang Yamin , Ye Xisheng , Chen Weibiao
Published: March 2022

Performance of high power fiber lasers and amplifiers with different pump sources are evaluated in the presence of radiation induced photodarkening in post-irradiated active fibers. Evolutions of output power and thermal mode instability threshold under different radiation doses are examined and analyzed. Severe degradation in both output power and thermal mode instability threshold is recorded for high power fiber systems with their active fibers exposed to radiations. Comparisons show that, amplifiers present a relatively better performance than lasers in adverse environments. Besides, 976 nm pump source is more favorable for high power laser sources in radioactive applications, even though 915 nm pump ensures a much lower temperature profile inside the active fiber.
A neurostimulator system for real, sham, and multi-target transcranial magnetic stimulation
Authors: Memarian Sorkhabi Majid , Denison Timothy
Published: March 2022

Objective. Transcranial magnetic stimulation (TMS) is a clinically effective therapeutic instrument used to modulate neural activity. Despite three decades of research, two challenging issues remain, the possibility of changing the (a) stimulated spot and (b) stimulation type (real or sham) without physically moving the coil. In this study, a second-generation programmable TMS device with advanced stimulus shaping is introduced that uses a five-level cascaded H-bridge inverter and phase-shifted pulse-width modulation. The principal idea of this research is to obtain real, sham, and multi-locus stimulation using the same TMS system. Approach. We propose a two-channel modulation-based magnetic pulse generator and a novel coil arrangement, consisting of two circular coils with a physical distance of 20 mm between the coils and a control method for modifying the effective stimulus intensity, which leads to the live steerability of the target and type of stimulation. Main results. Based on the measured system performance, the stimulation profile can be steered ±20 mm along a line from the centroid of the coil locations by modifying the modulation index. Significance. The proposed system supports electronic control of the stimulation spot without physical coil movement, resulting in tunable modulation of targets, which is a crucial step towards automated TMS machines.
Evaluating the clinical benefit of brain-computer interfaces for control of a personal computer
Authors: Fry Adam , Chan Ho Wing , Harel Noam Y , Spielman Lisa A , Escalon Miguel X , Putrino David F
Published: March 2022

Brain-computer interfaces (BCIs) enabling the control of a personal computer could provide myriad benefits to individuals with disabilities including paralysis. However, to realize this potential, these BCIs must gain regulatory approval and be made clinically available beyond research participation. Therefore, a transition from engineering-oriented to clinically oriented outcome measures will be required in the evaluation of BCIs. This review examined how to assess the clinical benefit of BCIs for the control of a personal computer. We report that: (a) a variety of different patient-reported outcome measures can be used to evaluate improvements in how a patient feels, and we offer some considerations that should guide instrument selection. (b) Activities of daily living can be assessed to demonstrate improvements in how a patient functions, however, new instruments that are sensitive to increases in functional independence via the ability to perform digital tasks may be needed. (c) Benefits to how a patient survives has not previously been evaluated but establishing patient-initiated communication channels using BCIs might facilitate quantifiable improvements in health outcomes.
Based on RBF Neural Network of Hypersonic Re-entry Vehicle Attitude Control
Authors: Chang Shunzhang , Liu Shiyue , Chen Jiabin
Published: March 2022

In this paper, an attitude control method combining radial basis (RBF) neural network with integral sliding mode control is proposed for the re-entry stage of hypersonic vehicle with uncertain aerodynamic parameters and atmospheric density. Firstly, the Time-scale separation model of nonlinear equations for aircraft is established. Meanwhile, the feedback linearization method is used to linearize the time scale separation model. For fast and slow control subloops, a global sliding mode variable structure control was designed, and the stability of the closed-loop system was verified by Lyapunov theory. Finally, RBF neural network online regulation law is designed to adjust the controller parameters online to reduce chattering. The simulation results show that the controller can maintain good dynamic characteristics even when the aerodynamic data are greatly deviated.
Robust Decentralized Fuzzy Controller Design for Nonlinear Large-Scale Interconnected Descriptor Systems
Authors: Chang Wen-Jer , Su Che-Lun , Pen Chin-Lin , Lin Zi-Yao
Published: March 2022

This paper dealt with the robust control problem for fuzzy large-scale descriptor systems (FLSDS) with uncertainties. First, each nonlinear subsystem of the large-scale descriptor system was described as a FLSDS with interconnectivity and uncertainty. Based on the proportional-plus-derivative state feedback (PD) method, the decentralized fuzzy controller in each subsystem was designed to stabilize the whole system. In order to solve the uncertainties problem in the control system simply, a benefits robust approach has been proposed. The final stability conditions can be recast into the linear matrix inequality (LMI) problem by the Schur complement. At last, a numerical example was given to illustrate the control design procedure and its effectiveness.
Study on the Morphology Characteristics of Epoxy Resin of Composite Insulator under Acid-heat Condition
Authors: Pan Wenwu , Zhang Dandan , Lu Ming , Li Zhenbiao , Gao Chao , Wan Zhiyu
Published: March 2022

Whether epoxy resin is degraded or not in composite insulators is the most direct criterion to distinguish Decay-like fracture from brittle fracture and normally mechanical fracture. During the actual operation of composite insulators, the nitric acid produced by partial discharge and abnormal heating will accelerate the degradation and deterioration of epoxy resin of composite insulators. In this paper, the experimental platform under acid-heat condition is built by using heating furnace, grinding bottle and serpentine condensation tube, and the acid-heat deterioration experiments are carried out under 60 °C (3 mol/L and 5 mol/L) and 80 °C (3 mol/L and 5 mol/L) condition. The macroscopic and microscopic morphologies of epoxy resin after acid-heat deterioration are analyzed, and the morphology changes of epoxy resin under the influence of acid-heat coupling field are studied. Firstly, it is concluded that the epoxy resin changes directly from colorless to light yellow, and then from light yellow to dark yellow under the influence of acid-heat deterioration. In addition, in the early stage of deterioration, the bulge on the surface of epoxy resin decreases gradually. Meanwhile, the maximum height difference and standard deviation of the surface profile of epoxy resin also gradually decreases, and the roughness decreases. In the later stage of deterioration, cracks appear on the surface of epoxy resin and some epoxy resins fall off. At the same time, the maximum height difference and standard deviation of surface profile of epoxy resin increases.
Research on Micro-motion Modeling and Feature Extraction of Passive Bistatic Radar Based on CMMB Signal
Authors: Xia Saiqiang , Jiang Haiman , Cai Wanyong , Yang Jun , Zhang Chaowei , Chen Wenfeng
Published: March 2022

Passive bistatic radar has unique advantages in studying Micro-Doppler effect because of its system characteristics. China Mobile Multimedia Broadcasting (CMMB) as a broad range of radio and television signal, its signal adopts multi-carrier Orthogonal Frequency Division Multiplexing (OFDM) technology, can be used as a good illuminator. Based on the CMMB signal, the scattering point model of helicopter’s echo is established, and the influencing factors of Micro-Doppler frequency are analyzed. On this basis, the Singular-spectrum Analysis combined with Time-frequency analysis and autocorrelation method is used to extract the target micro-motion characteristics. The simulation results verify the rationality of the micro-motion model and the effectiveness of the feature extraction method in this paper.
Development of an Integrated Simulation Platform for Modelling and Simulation of the Energy Consumption of a Multi-zone Building
Authors: Zhang Jie , Liu-Henke Xiaobo , Vietor Thomas
Published: March 2022

This paper focuses on a simulation platform to model and simulate the energy consumption of a building with multiple zones under the influence of daily and seasonal environmental factors, as well as the impact of the HVAC system and human activities. By using model-based requirements engineering (MBRE), the requirements of the simulation platform are hierarchically derived and specified. On this basis, the simulation platform is designed and developed. With the help of the simulation platform, it is possible to obtain a mathematical model for a realistic description of the thermodynamics and energy consumption of the individual zones of a building, which can be used as a basis for the model-based development of the energy management system, e.g. intelligent energy dispatch strategy. In the following, the concept of the simulation platform and the process will be demonstrated and validated with an application example of the research building Open Mobility Lab (OML).
Study on the Adaptive Test Modelling Based on Knowledge Graph in the Domain of Substation
Authors: Weizhou WANG , Xilan ZHAO , Qi GAO , Lu LIU , Changnian LIN
Published: March 2022

Traditional tests in the substation training fail to fit the ability of the operation and maintenance personnel and precisely describe their weakness. In this paper, an adaptive test model based on the knowledge graph in the domain of substation is constructed. With the help of the knowledge point correlations in the knowledge graph, the model updates the knowledge level of the testee in real time according to the response of each question, and automatically selects the next question that fits the individual. In cases where the test question covers different knowledge amount, the model constructs the knowledge state space or the adjacency/reachability matrix to infer the knowledge mastery, which improves the test efficiency and quality by reasonably reducing the number of questions during the test. Calculation results demonstrate that the model can accurately capture the weakness the substation personnel and has broad application prospects on evaluations in the vocational education.
Quantitative Influence of Wind Farm Reactive Power and Voltage Control Capability on Hunan Power Grid Thermal Power Spinning Reserve
Authors: Wang Ding , Xu Ming , Hu Zhen , Shen Yangwu , Hao Luxi , Zuo Jian
Published: March 2022

Affected by factors such as the inverse distribution of power sources and loads in the province, and the mismatch between the construction of load center power sources and load growth, the problem of voltage stability in central and southern Hunan is prominent, which mainly restricts the thermal power maximum operating capacity of the Hunan Power Grid. Under the heavy load mode, the hydro power units and thermal power units operating in the province need to reserve a certain amount of spinning reserve to response the voltage stability problems in central and southern Hunan. Thus, it leads to insufficient power supply during peak load periods. In recent years, the grid load has maintained rapid growth, and the increase in power sources is mainly the wind power. Affected by the anti-peak-shaving characteristics of wind power, the lack of wind power has aggravated the problem of insufficient power supply. Actually, the wind turbine is in a hot standby state during standby/backup, and its grid-connected converter is still in a grid-connected state within four hours. Besides, the continuous running SVG in the wind farm booster station can still be used temporarily. The above devices can provide reactive power support to the power grid during the transient process. Therefore, this paper takes the southern Hunan region as an example, and quantified the reduced thermal power requirement reserve by analyzing the reactive power support effect of the grid-connected wind farms. In this way, the power supply capacity can be improved.
Study on Galvanic Corrosion Characteristics of the Ground Grid with Different Metal Conductors in the Converter Station
Authors: Lu Yuxin
Published: March 2022

The galvanic corrosion of grounding net in converter station seriously affects its dispersion performance. However, the corrosion potential difference between different metal conductors will aggravate the corrosion speed of the converter station grounding network. In this paper, the variation of corrosion potential difference and corrosion current of dissimilar metals in water medium and soil medium is analyzed by experiments. In the two media, when the circuit resistance is high, the galvanic corrosion is mainly affected by ohmic polarization. Then, CDEGS simulation was used to obtain the change rule of corrosion current under different circuit resistance, and the simulation results are compared with the experimental results. The results show that with the increase of circuit resistance, the corrosion potential difference is basically unchanged, while the corrosion current decreases gradually, and when the circuit resistance increases to a certain margin, the corrosion current decreases gently. When the current density is less than 0.47A/m2, ohmic polarization can be used to approximate analyze the galvanic corrosion of dissimilar metal connections.
Research on Decoupling Simulation of Electric Platform System Based on ADAMS
Authors: Zhao Yulong , Zhang Yuan , Wang Yan , Liu Haiyang
Published: March 2022

Aiming at the problem that the cross-linking coupling between the electric cylinders affects the stable operation of the six-degree-of-freedom electric platform, the decoupling design and co-simulation verification of the electric platform are carried out. First, considering the integrity of the platform, the inertial coupling matrix of the electric platform and its characteristics are analysed; further, the overall decoupling system of the electric platform is designed based on the fuzzy decoupling network; finally, the electric platform model is constructed based on ADAMS, and the virtual platform is constructed. A co-simulation analysis was carried out to verify the effectiveness of the decoupling design of the electric platform system.
A Novel DC Circuit Breaker with Fast Breaking Capability in Full Current Range
Authors: Zhao Xiaomin , Wang Jun , Wang Yawen , Kang Qiong , Long Chen , Shen Jaming
Published: March 2022

With the rapid development of DC power system in recent years, more stringent requirements have been put forward for the rapid reliability of DC circuit breakers. At present, most hybrid circuit breakers widely used create artificial zero crossing by injecting current opposite to short-circuit current. However, when it comes to the small current, the injected current may reverse puncture the contacts of the high-speed mechanical switch. And this results in the difficulty of extinguishing the arc between the contacts of the high-speed mechanical switch during disconnection, prolonging the disconnection time and adversely affecting the system. This paper presents a double break DC circuit breaker structure based on double capacitor structure. In the process of current breaking, the capacitor with small capacitance is used to commutate for small current, and the double capacitor parallel method is used to complete the current transfer for large current. The working principle of the circuit breaker is analysed, and the appropriate parameters are selected through simulation.
Research on Detection Method of Insulator Image Based on Improved Faster R-CNN
Authors: Pha Samphors , Zheng Hanbo , Sun Yonghui
Published: March 2022

This study proposes the use of Improved Faster Region-Convolutional Neural Network (R-CNN) in target detection for insulator images in power systems. Faster R-CNN is essentially a combination of the Fast R-CNN and the Regional Proposal Network (RPN). The Faster R-CNN method, which is being used today, is an extension and improvement of the Fast R-CNN. The Improved Faster R-CNN is particularly highly effective in the detection of occluded targets and those with different aspect ratios and scales. Through the various experiments conducted in the study, it has been demonstrated that the improved Faster R-CNN is highly effective in detecting insulator images with different scales and with different aspect ratios. Furthermore, the improved Faster R-CNN is also very effective in detecting mutually occluded insulator images.
The radiation tolerance of a low voltage LDO developed for the CMS HGCAL on-detector electronics system
Authors: Irshad A. , Ceard L.
Published: March 2022

The CMS detector will undergo the replacement of its current endcap calorimeter by a new high granularity calorimeter (HGCAL). The new HGCAL will need to withstand much higher radiation levels than the present endcaps. This poses tight requirements on the front-end electronics, including the powering chain. As part of this chain, a low-dropout linear regulator (LDO) has been designed and prototyped for post-regulation for HGCAL, providing extremely low noise and stable power to the analog front-end. We present results from tests of the LDO, including from a detailed irradiation campaign.
Optofluidic conical microresonator for precise displacement sensing
Authors: Mohammadfam B. , Mahdieh M.H. , Veladi H.
Published: March 2022

In the present work we report fabrication of a compact
optical displacement sensor based on whispering gallery mode with
common materials on Polydimethylsiloxane (PDMS) medium with mold
master technique. Conical and hollow geometry of microcavity filled
with Rhodamine B-doped Glycerol as active medium. The fabricated
device can be utilized for sensing applications. Coupling junction
can be tuned so that moving the conical microcavity of about
100 μm in the axial direction is equivalent to ∼1.5 nm
shift in resonant wavelength. Also, a small change in concentration
of active medium results in a shift in the resonant wavelength which
provides the feasibility of sensing the refractive index. The
proposed structure demonstrates the ability of considerably
high-resolution sensing for fine displacement steps which is limited
by the resolution of the spectrometer (0.6 nm).
Nitrogen cycle impacts on CO2 fertilisation and climate forcing of land carbon stores
Authors: Huntingford Chris , Burke Eleanor J , Jones Chris D , Jeffers Elizabeth S , Wiltshire Andrew J
Published: March 2022

Anthropogenic fossil fuel burning increases atmospheric carbon dioxide (CO2) concentration, which is adjusting the climate system. The direct impact of rising CO2 levels and climate feedback alters the terrestrial carbon stores. Land stores are presently increasing, offsetting a substantial fraction of CO2 emissions. Less understood is how this human-induced carbon cycle perturbation interacts with other terrestrial biogeochemical cycles. These connections require quantification, as they may eventually suppress land fertilisation, and so fewer emissions are allowed to follow any prescribed future global warming pathway. Using the new Joint UK Land Environment Simulator-CN large-scale land model, which contributed to Coupled Model Intercomparison Project Phase 6 as the land component of the UK Earth System Model v1 climate model, we focus on how the introduction of the simulated terrestrial nitrogen (N) cycle modulates the expected evolution of vegetation and soil carbon pools. We find that the N-cycle suppresses, by approximately one-third, any future gains by the global soil pool when compared to calculations without that cycle. There is also a decrease in the vegetation carbon gain, although this is much smaller. Factorial simulations illustrate that N suppression tracks direct CO2 rise rather than climate change. The finding that this CO2-related effect predominantly influences soil carbon rather than vegetation carbon, we explain by different balances between changing carbon uptake levels and residence times. Finally, we discuss how this new generation of land models may gain further from emerging point knowledge held by the detailed ecological modelling community.
Seasonality of inundation in geographically isolated wetlands across the United States
Authors: Park Junehyeong , Kumar Mukesh , Lane Charles R , Basu Nandita B
Published: March 2022

Inundation area is a major control on the ecosystem services provisioned by geographically isolated wetlands. Despite its importance, there has not been any comprehensive study to map out the seasonal inundation characteristics of geographically isolated wetlands over the continental United States (CONUS). This study fills the aforementioned gap by evaluating the seasonality or the long-term intra-annual variations of wetland inundation in ten wetlandscapes across the CONUS. We also assess the consistency of these intra-annual variations. Finally, we evaluate the extent to which the seasonality can be explained based on widely available hydrologic fluxes. Our findings highlight significant intra-annual variations of inundation within most wetlandscapes, with a standard deviation of the long-term averaged monthly inundation area ranging from 15% to 151% of its mean across the wetlandscapes. Stark differences in inundation seasonality are observed between snow-affected vs. rain-fed wetlandscapes. The former usually shows the maximum monthly inundation in April following spring snowmelt (SM), while the latter experiences the maximum in February. Although the magnitude of inundation fraction has changed over time in several wetlandscapes, the seasonality of these wetlands shows remarkable constancy. Overall, commonly available regional hydrologic fluxes (e.g. rainfall, SM, and evapotranspiration) are found to be able to explain the inundation seasonality at wetlandscape scale with determination coefficients greater than 0.57 in 7 out of 10 wetlandscapes. Our methodology and presented results may be used to map inundation seasonality and consequently account for its impact on wetland functions.
Diffusion-mediated surface reactions and stochastic resetting
Authors: Bressloff Paul C
Published: March 2022

In this paper, we investigate the effects of stochastic resetting on diffusion in

R

d

\
U

, where

U

is a bounded obstacle with a partially absorbing surface

∂
U

. We begin by considering a Robin boundary condition with a constant reactivity κ
0, and show how previous results are recovered in the limits κ
0 → 0, ∞. We then generalize the Robin boundary condition to a more general probabilistic model of diffusion-mediated surface reactions using an encounter-based approach. The latter considers the joint probability density or generalized propagator P(x, ℓ, t|x
0) for the pair (X

t
, ℓ

t
) in the case of a perfectly reflecting surface, where X

t
and ℓ

t
denote the particle position and local time, respectively. The local time determines the amount of time that a Brownian particle spends in a neighborhood of the boundary. The effects of surface reactions are then incorporated via an appropriate stopping condition for the boundary local time. We construct the boundary value problem satisfied by the propagator in the presence of position resetting, and use this to derive implicit equations for the marginal density of particle position and the survival probability. We highlight the fact that these equations are difficult to solve in the case of non-constant reactivities, since resetting is not governed by a renewal process. We then consider a simpler problem in which both the position and local time are reset. In this case, the survival probability with resetting can be expressed in terms of the survival probability without resetting, which considerably simplifies the analysis. We illustrate the theory using the example of a spherically symmetric surface. In particular, we show that the effects of a partially absorbing surface on the mean first passage time (MFPT) for total absorption differs significantly if local time resetting is included. That is, the MFPT for a totally absorbing surface is increased by a multiplicative factor when the local time is reset, whereas the MFPT is increased additively when only particle position is reset.
Edge-mode polariton chains in the dielectric whispering gallery modes and two-dimensional material’s topological system
Authors: Chai Zhen , Wang Weiyi , Tian Zhongxing , Xu Yuting
Published: March 2022

Topological polaritons are a new topological phenomenon that has a combination of advantages such as strong nonlinearity, low effective mass, and topological invariants. However, the actual configurations of topological polaritons based on two-dimensional materials have not been discussed yet. In this paper, we theoretically demonstrate a Su-Schrieffer-Heeger (SSH) model (Sinev et al 2015 Nanoscale
7 11904; Dobrykh et al 2018 Phys. Rev. Lett.
121 163901; Qi et al 2020 Phys. Rev. A 102 022404) with topological polaritons by TiO2 whispering gallery modes and nanodisk arrays coupled with two-dimensional transition metal dichalcogenides (TMDCs) exciton materials. The transverse electric-polarized strong evanescent fields around the TiO2 nanodisks coupled with the TMDCs excitons for each atom can construct strong coupling between exciton-polaritons with a distinct resonant Rabi splitting dispersion of approximately 14 nm. By changing the distance between adjacent nanodisks, we observed obvious edge states for the SSH polariton chain at the wavelength of polaritons. This study paves the way toward new topological polaritons in large nonlinear devices with an edge transport based on two-dimensional materials.
Facile synthesis of Veitchia merilli coir-based porous carbon using combined chemical and physical activation routes as electrode material for energy storage
Authors: Farma R , Anugrah A P , Apriyani I , Awitdrus A
Published: March 2022

This study aimed to prepareVeitchia merillicoir (VMC) through pre-carbonisation process, followed by chemical activation using potassium hydroxide as an activating agent. The experiment was conducted under different pyrolytic physical activation temperatures of 650, 700, and 750 °C with the code VMS-650, VMS-700, and VMS-750 for each sample. Physical activation methods develop or modify the pore structure, specific surface area, and microstructure of activated carbon. Furthermore, the prepared VMCs were characterised using X-ray diffraction, Fourier transform infrared, scanning electron microscope, energy dispersive X-ray, and cyclic voltammetry with a symmetrical two-electrode system in 1 M H2SO4solution. The microstructure analysis showed that the VMC carbon electrode has an amorphous structure with two broad peaks at 2θangles around 26° and 44° corresponding to the (002) and (100) planes, with theLcVMS-700 having a value of 16.007 nm. The VMC electrode has a C≡C carbon bond as a functional group, which extends in bands from 2311.79 to 2373.51 cm−1. Meanwhile, the VMS-700 electrode shows a combined surface morphology of nanofibers as well as mesopores, and the energy dispersive X-ray results showed carbon content of 92.83%. The electrochemical properties of supercapacitor cells indicated this electrode had the highest specific capacitance value of 264.2 F g−1. From the obtained results, the respective physical and electrochemical properties of the carbon electrodes and supercapacitor cells showed that the activated VMC-700 at 700 °C is the optimum temperature to produce the best performance compared to 650 and 750 °C.
Spectroscopic studies on reduced graphene oxide behaviour in multi-step thermal reduction
Authors: Aditya Dominico Michael , Hardiansyah Andri
Published: March 2022

Graphene’s excellent electrical, mechanical, thermal and optical properties make it one of the most desirable materials for diverse applications. Nevertheless, mass producing graphene has been a challenge since the first discovery in 2004. Here, we conducted a fast, green and safe method: multi-step thermal reduction (MSTR) process combining the use of commercial microwave and conventional furnace as the first and second steps, respectively to reduce graphene oxide (GO). Both steps used common tools in a short time to minimise investment. By evaluating several characterisation methods, we show that the first step partially reduces GO by decomposing most hydroxyls, creating a double interlayer spacing distance of 9.381 Å and 3.590 Å with retained hydrophilic property. Meanwhile, the second step further decomposes oxygen functional groups, recovers structural defects and creates a porous layered structure with an average interlayer spacing distance of 3.504 Å, 3.413 Å and 3.393 Å for temperatures of 500, 650 and 800 °C, respectively. In short, MSTR is a viable option to mass produce graphene-based material with desired properties.