bluuebunny/crossref_metadata_2025 huggingface dataset:
Broadband waveguide-integrated superconducting single-photon detectors with high system detection efficiency
Authors: Wolff Martin A. , Beutel Fabian , Schütte Jonas , Gehring Helge , Häußler Matthias , Pernice Wolfram , Schuck Carsten
Published: April 2021

Fast and efficient detection of single photons with high timing accuracy is a crucial requirement in most quantum optics experiments and enables novel sensing and imaging solutions. Superconducting nanowire single-photon detectors (SNSPD) achieve technology-leading performance in terms of detection efficiency, dark count rate, timing jitter, and detector dead times. However, conventional SNSPDs with high system detection efficiency typically rely on resonant enhancement of the absorption efficiency, thus only achieving attractive detector benchmarks over narrow spectral windows. Waveguide-integrated SNSPDs allow for leveraging the wideband material absorption in superconducting nanowires by absorbing light in a traveling-wave geometry but have been limited to low system detection efficiencies due to interface losses when coupling to optical fibers. Here, we show how high system detection efficiencies of 22%–73% are realized over a broad wavelength range from 532 nm to 1640 nm in a single waveguide-integrated SNSPD device. We accomplish efficient coupling between optical fibers and waveguide-integrated nanowire detectors by employing a 3D interface, produced in direct laser writing, that relies on total internal reflection for achieving a broad transmission bandwidth. We further find low timing jitter of 25.7 ps and detector decay times of 9.8 ns, allowing for single-photon counting with high repetition rates up to 100 MHz. Our work paves the way for an efficient single-photon detector solution that combines the spectral requirements of an extremely wide range of quantum optics experiments in a single device. The coupling approach and SNSPD-integration with nanophotonic circuits are further well-suited for realizing large-scale detector arrays.
Vortex in a strongly coupled dusty plasma embedded in an external magnetic field
Authors: Dasgupta Chitrita , Maitra Sarit
Published: April 2021

Vortex motion of a dust fluid suspended in an argon rf power has been investigated for both the kinetic and hydrodynamic limit of a strongly coupled compressible dusty plasma below crystallization limit. Dust particles are confined by a radial weak electric field under the influence of a strong vertical magnetic field, dust-dust correlation, ion drag, particle attachment, grains drift, and diffusion. Radial distribution of different vortex properties is observed numerically. Modifications of those properties due to the variations in grain size and ion temperature are compared between hydrodynamic and kinetic limits and are found to be more prominent in the hydrodynamic regime. With the decreasing correlation among the grains, the range of radial distribution of dust particles expands and the influence of shear rotation increases. Moreover, vortex flow dissipation is found to be enhanced at a large rate in the case of hydrodynamic limit compared to the case of kinetic one.
Mixing and transport enhancement in microchannels by electrokinetic flows with charged surface heterogeneity
Authors: Guan Yifei , Yang Tianhang , Wu Jian
Published: April 2021

Electrokinetic flow in a microchannel driven by charged surface heterogeneity in the presence of an external electric field is investigated by three-dimensional simulations. A computational framework is developed coupling a two-relaxation-time lattice Boltzmann solver for the transport equations of fluids, charged species, and passive tracing scalars and a fast Poisson solver for the electric potential. The two-relaxation-time lattice Boltzmann method is used to resolve the spatiotemporal distribution of flow field, ion concentration, and two passive tracing scalars. The fast Poisson solver is used to solve the electric potential at every time step. Three charged surface patterns together with various external electric fields are investigated. The induced electrokinetic vortices contribute to the mixing and transport enhancement of the passive scalars, depending on the surface patterns and the external electric field. The transport enhancement is found to follow a power law with respect to the magnitude of the external electric field.
A near-wall predictive model for passive scalars using minimal flow unit
Authors: Zhang Bo-Yuan , Huang Wei-Xi , Xu Chun-Xiao
Published: April 2021

In the present study, direct numerical simulations (DNSs) are performed to the passive scalar transport in minimal flow units (MFUs) at Reτ=1000, 2000, and 4000 and in a full-sized channel at Reτ=1000 for comparison. The molecular Prandtl number ranges from 0.2 to 2.0. At each Prandtl number, the scalar intensities in MFUs at different Reynolds numbers agree well with each other, and with those at MFU-contained scales in the full-sized channel. This suggests that scalar transport in MFUs is Reynolds number independent and is able to represent that at small scales in the full-sized channel. A near-wall predictive model for passive scalars based on MFU data is proposed in the framework of superposition and modulation of the outer large-scale motions. The modulation coefficients at different Prandtl numbers are collapsed together under the presently proposed transforming. Both the scalar intensities and the joint probability density functions of the predicted results agree well with those of the DNS results. Furthermore, a predictive model for wall scalar-flux based on MFU data and the quasi-steady hypothesis is put forward and validated against the DNS results.
Antibubble formation by a single drop impact on a free surface
Authors: Wang Wei , Lin Fangye , Wei Xiaofeng , Zou Jun
Published: April 2021

An experimental study of the antibubble formation by a single drop impact on an identical liquid bath is presented. With the increase in the impact velocity, different phenomena are observed and classified into four regimes: No droplet, Single droplet, Double droplets, and Antibubble formation. In fact, the Antibubble formation is part of the Double droplets regime. A high-speed drop impact leads to the formation of a thick jet, which subsequently pinches into two main droplets named as the primary droplet and the secondary droplet. The secondary droplet first impacts on the liquid surface, while the primary droplet then falls back and pushes it into the liquid bath, generating an antibubble. The detailed dynamics is presented, and the critical conditions for antibubble formation are introduced. This work should benefit the controllable generation of antibubbles and stimulate the future applications in practice.
Electric-field effect on magnetic moments in Co ultra-thin films deposited on Pt
Authors: Obinata A. , Koyama T. , Matsukura F. , Nakamura K. , Chiba D.
Published: April 2021

This study investigates the electric-field effect on magnetic moments in perpendicularly magnetized Co ultra-thin films on a Pt underlayer. By applying electric fields to the Co surface through MgO/HfO2 insulating layers, we determined the change in the magnetic moment per one electrically increased electron. From systematic experiments at temperatures much below the Curie temperature, we found that the sign and the magnitude of the change depend on the nominal Co thickness tCo: the change nearly equals to −1 μB/electron for tCo ∼ 0.45 nm and more than +1 μB/electron at tCo ∼ 0.2 nm. The former value is consistent with the expectation from the celebrated Slater–Pauling curve. The latter value implies that one needs to consider some effects characteristic to Pt/Co system with extremely small tCo. The calculated band structures suggest that the intermixing between Co and Pt is related to the observed deviation from the Slater–Pauling curve with decreasing tCo.
On uniqueness of probability solutions of the Fokker-Planck-Kolmogorov equation
Authors: Bogachev V. I. , Krasovitskii T. I. , Shaposhnikov S. V.
Published: April 2021

The paper gives a solution to the long-standing problem of uniqueness for probability solutions to the Cauchy problem for the Fokker- Planck-Kolmogorov equation with an unbounded drift coefficient and unit diffusion coefficient. It is proved that in the one-dimensional case uniqueness holds and in all other dimensions it fails. The case of nonconstant diffusion coefficients is also investigated.

Bibliography: 70 titles.
Overexpression of
Authors: Rahman M. Anisur , Wu Wei , Yan Yanchun , Bhuiyan Shamsul A.
Published: April 2021

Sugarcane (Saccharum hybrid) is an important industrial crop worldwide. Its growth and sucrose contents are severely affected by drought stress. Genetic engineering offers a rapid solution to improve tolerance level of sugarcane against this stress. This study was designed to transform sugarcane with the Tomato ethylene responsive factor 1 (TERF1) gene through Agrobacterium. Embryogenic callus of sugarcane cv. XintaitangR22 was used for transformation with Agrobacterium strain LBA4404 harbouring the pROK2 vector containing the TERF1 gene driven by the CaMV 35S promoter. Highest regeneration efficiency (74%) was obtained with inoculum density (OD600) at 0.4 and co-cultivated for 4 days on MS-based medium; 5.4% transformation efficiency was acquired from the regenerated plants. Successful insertion of the TERF1 gene into sugarcane was indicated by PCR-positive plants (n = 4). Expression of TERF1 transcripts in transgenic lines at various levels was detected by reverse transcriptase-PCR. Under normal conditions, growth status of transgenic lines was similar to that of wild-type plants; by contrast, only transgenic lines were able to withstand water-deficit stress conditions, showing tolerance against drought stress. Physiological and biochemical assays revealed that TERF1-overexpressed plants showed not only increased accumulation of proline, soluble sugars and glycine betaine but also reduced malondialdehyde and H2O2 content in response to drought stress. Our results revealed that overexpression of TERF1 in sugarcane conferred drought tolerance through increased accumulation of osmo-protectant, decreasing reactive oxygen species and malondialdehyde content, which possibly resulted from activation of expression of stress-related genes by TERF1 under stress. These findings indicate that the gene might have a regulatory role in the response to drought stress in sugarcane.
Effects of feeding condition on the morphology, behaviour and nutritional status of
Authors: Llamazares Vegh Sabina , Lozano Ismael E. , Diaz Marina V. , Gómez María I. , Sánchez Sebastián , Fuentes Carlos M.
Published: April 2021

Early life stages of migratory fish in rivers rely on physical transport mechanisms to carry them from spawning sites to distant nursery areas where they find food and refuge conditions. Starvation after a prolonged downriver drift could severely affect the colonisation and predator evasion capabilities of the larvae. In this study we investigated differences in the external morphology, nutritional condition and swimming abilities of fed and unfed Prochilodus lineatus early larvae under experimental conditions. After yolk reabsorption on Day 6, larvae were either fed with nauplii of Artemia salina or left unfed for up to 10 days. Larvae from each feeding regime (i.e. fed and unfed) were sampled daily from three aquaria, and the morphometry and routine swimming activity were determined and analysed together with a previously published RNA/DNA ratio dataset. The results were in agreement with previous investigations that indicated that the larvae of this species have starvation endurance; however, prolonged food deprivation is associated with a smaller body, anal depth and head length, as well as lower RNA/DNA ratios and reduced swimming ability.
Predicting social tipping and norm change in controlled experiments
Authors: Andreoni James , Nikiforakis Nikos , Siegenthaler Simon
Published: April 2021

Significance

Social tipping—instances of sudden change that upend social order—is rarely anticipated and usually understood only in hindsight. The ability to predict when societies will reach a tipping point has significant implications for welfare, especially when social norms are detrimental. In a large-scale laboratory experiment, we identify a model that accurately predicts social tipping and use it to address a long-standing puzzle: Why do norms sometimes persist when they are detrimental to social welfare? We show that beneficial norm change is often hindered by a desire to avoid the costs associated with transitioning to a new norm. We find that policies that help societies develop a common understanding of the benefits from change foster the abandonment of detrimental norms.
A guideline to limit indoor airborne transmission of COVID-19
Authors: Bazant Martin Z. , Bush John W. M.
Published: April 2021

Significance

Airborne transmission arises through the inhalation of aerosol droplets exhaled by an infected person and is now thought to be the primary transmission route of COVID-19. By assuming that the respiratory droplets are mixed uniformly through an indoor space, we derive a simple safety guideline for mitigating airborne transmission that would impose an upper bound on the product of the number of occupants and their time spent in a room. Our theoretical model quantifies the extent to which transmission risk is reduced in large rooms with high air exchange rates, increased for more vigorous respiratory activities, and dramatically reduced by the use of face masks. Consideration of a number of outbreaks yields self-consistent estimates for the infectiousness of the new coronavirus.
Harnessing psilocybin: antidepressant-like behavioral and synaptic actions of psilocybin are independent of 5-HT2R activation in mice
Authors: Hesselgrave Natalie , Troppoli Timothy A. , Wulff Andreas B. , Cole Anthony B. , Thompson Scott M.
Published: April 2021

Significance

Psychedelic compounds, such as psilocybin, have beneficial actions in several psychiatric diseases. They also produce strong alterations of consciousness, which may be a barrier to their widespread use. We found that psilocybin has fast-acting antidepressant-like properties in mice. Using multiple assays of hedonic behavior and an antagonist of prohallucinatory 5-HT2A receptors, we further suggest that altered perception may not be necessary for its therapeutic actions. We also showed that psilocybin strengthens connections between brain cells in regions important for processing rewards and emotions. These experiments suggest that it may be possible to retain the beneficial actions of psilocybin while minimizing the alterations in consciousness, thereby accelerating its use in the clinic.
A translational riboswitch coordinates nascent transcription–translation coupling
Authors: Chatterjee Surajit , Chauvier Adrien , Dandpat Shiba S. , Artsimovitch Irina , Walter Nils G.
Published: April 2021

Significance

Transcription–translation coupling is critical for fast and efficient gene expression in many bacteria, yet how coupling between RNA polymerase (RNAP) and ribosome is established and maintained is poorly understood. Combining biochemical and single-molecule fluorescence approaches, we here uncover the roles of nascent mRNA structure and transcription factors in coupling. We find that the inherently paused RNAP facilitates 30S ribosomal subunit recruitment, whereas ligand-induced translational riboswitch folding in the 5′ untranslated region (5′ UTR) impedes it. Transcription factors NusG and RfaH distinctly enhance 30S recruitment and retention, respectively, and actively translating 70S ribosome accelerates the leading RNAP. Taken together, our data yield a unifying dynamic model of transcription–translation coupling, promising to inspire new approaches for the design of antibiotics.
Cardenolides, toxicity, and the costs of sequestration in the coevolutionary interaction between monarchs and milkweeds
Authors: Agrawal Anurag A. , Böröczky Katalin , Haribal Meena , Hastings Amy P. , White Ronald A. , Jiang Ren-Wang , Duplais Christophe
Published: April 2021

Significance

Interactions between plants and herbivores constitute a major pathway of energy transfer up the food chain. As a consequence, evolution by natural selection has honed the chemically mediated antagonistic interactions between these groups. Monarch butterflies and milkweeds serve as royal representatives in deciphering such coevolution, and our study takes a mechanistic and manipulative approach to understand how the tropical milkweed,
Asclepias
curassavica
, defends itself against monarch butterflies, which would seem to be impervious feeders. By directly observing plant–herbivore interactions and coupling this with experiments on isolated toxins and the monarch’s neural sodium-potassium pump enzymes, we show that tropical milkweed produces a burdensome cardenolide toxin, and monarchs convert it to less toxic compounds, the latter sequestered for their own benefit.
Modified empirical formulas and machine learning for α-decay systematics
Authors: Saxena G , Sharma P K , Saxena Prafulla
Published: April 2021

Latest experimental and evaluated α-decay half-lives between 82 ⩽ Z ⩽ 118 have been used to modify two empirical formulas: (i) Horoi scaling law (2004 J. Phys. G: Nucl. Part. Phys.
30 945), and Sobiczewski formula (2005 Acta Phys. Pol. B
36 3095) by adding asymmetry dependent terms (I and I
2) and refitting of the coefficients. The results of these modified formulas are found with significant improvement while compared with other 21 formulas, and, therefore, are used to predict α-decay half-lives with more precision in the unknown superheavy region. The formula of spontaneous fission (SF) half-life proposed by Bao et al (2015 J. Phys. G: Nucl. Part. Phys.
42 085101) is further modified by using ground-state shell-plus-pairing correction taken from FRDM-2012 and using the latest experimental and evaluated SF half-lives between 82 ⩽ Z ⩽ 118. Using these modified formulas, contest between α-decay and SF is probed for the nuclei within the range 112 ⩽ Z ⩽ 118 and consequently probable half-lives and decay modes are estimated. Potential decay chains of 286−302Og and 287−303119 (168 ⩽ N ⩽ 184: island of stability) are analyzed which are found to be in excellent agreement with available experimental data. In addition, four different machine learning models: XGBoost, random forest, decision trees, and multilayer perceptron (MLP) neural network are used to train a predictor for α-decay and SF half-lives prediction. The prediction of decay modes using XGBoost and MLP are found to be in excellent agreement with available experimental decay modes along with our predictions obtained by the above-mentioned modified formulas.
Comparing spontaneous and pellet-triggered ELMs via non-linear extended MHD simulations
Authors: Cathey A , Hoelzl M , Futatani S , Lang P T , Lackner K , Huijsmans G T A , Pamela S J P , Günter S
Published: April 2021

Injecting frozen deuterium pellets into an ELMy H-mode plasma is a well established scheme for triggering edge localized modes (ELMs) before they naturally occur. This paper presents non-linear simulations of spontaneous type-I ELMs and pellet-triggered ELMs in ASDEX Upgrade performed with the extended MHD code JOREK. A thorough comparison of the non-linear dynamics of these events is provided. In particular, pellet-triggered ELMs are simulated by injecting deuterium pellets into different time points during the pedestal build-up described in A Cathey et al (2020 Nuclear Fusion
60 124007). Realistic ExB and diamagnetic background plasma flows as well as the time dependent bootstrap current evolution are included during the build-up to accurately capture the balance between stabilising and destabilising terms for the edge instabilities. Dependencies on the pellet size and injection times are studied. The spatio-temporal structures of the modes and the resulting divertor heat fluxes are compared in detail between spontaneous and triggered ELMs. We observe that the premature excitation of ELMs by means of pellet injection is caused by a helical perturbation described by a toroidal mode number of n = 1. In accordance with experimental observations, the pellet-triggered ELMs show reduced thermal energy losses and a narrower divertor wetted area with respect to spontaneous ELMs. The peak divertor energy fluence is seen to decrease when ELMs are triggered by pellets injected earlier during the pedestal build-up.
Highly efficient few-cycle laser wakefield electron accelerator
Authors: Papp Daniel , Lécz Zsolt , Kamperidis Christos , Hafz Nasr A M
Published: April 2021

A significant part of the laser wakefield acceleration (LWFA) research effort focuses on studying high-energy, quasi-monoenergetic electron beams. For other applications, such as the production and application of intense betatron x-ray radiation, Bremsstrahlung γ-rays and positron beams, the beam’s spectral quality is secondary to the number of electrons produced. This work discusses 3D particle-in-cell simulations of a highly efficient LWFA acceleration process, generating a broad spectrum of electrons, driven by a 12 TW few-cycle laser on high-density gas targets. In some cases, laser absorption in plasma exceeds 80%, and up to 27% of the driving laser energy is transferred to electrons over 20 MeV leaving the plasma. We also observe a deceleration of the accelerated beam at the plasma downramp and plasma exit, which arises from transitioning from laser-driven to beam-dominated wake, and also from the induced axial electric field. This effect is similar to magnetic vortex acceleration, where the induced axial electric field, instead of accelerating plasma ions, would slow down the opposite-charged electron beam and also a strong return current and backward electron beam.
Single-shot electron imaging of dopant-induced nanoplasmas
Authors: Medina C , Schomas D , Rendler N , Debatin M , Uhl D , Ngai A , Ben Ltaief L , Dumergue M , Filus Z , Farkas B , Flender R , Haizer L , Kiss B , Kurucz M , Major B , Toth S , Stienkemeier F , Moshammer R , Pfeifer T , Krishnan S R , Heidenreich A , Mudrich M
Published: April 2021

We present single-shot electron velocity-map images of nanoplasmas generated from doped helium nanodroplets and neon clusters by intense near-infrared and mid-infrared laser pulses. We report a large variety of signal types, most crucially depending on the cluster size. The common feature is a two-component distribution for each single-cluster event: a bright inner part with nearly circular shape corresponding to electron energies up to a few eV, surrounded by an extended background of more energetic electrons. The total counts and energy of the electrons in the inner part are strongly correlated and follow a simple power-law dependence. Deviations from the circular shape of the inner electrons observed for neon clusters and large helium nanodroplets indicate non-spherical shapes of the neutral clusters. The dependence of the measured electron energies on the extraction voltage of the spectrometer indicates that the evolution of the nanoplasma is significantly affected by the presence of an external electric field. This conjecture is confirmed by molecular dynamics simulations, which reproduce the salient features of the experimental electron spectra.
Ion kinetic effects on the evolution of Richtmyer–Meshkov instability and interfacial mix
Authors: Yan X X , Cai H B , Yao P L , Huang H X , Zhang E H , Zhang W S , Du B , Zhu S P , He X T
Published: April 2021

Plasma effects, such as the multi-component kinetic diffusion and self-generated electromagnetic fields, are recognized as a pivotal key to understanding the physics of interface evolution in inertial confinement fusion and supernova remnants. In this work, a two-dimensional hybrid fluid-PIC code is used to investigate the ion kinetic effects of the single-mode Richtmyer–Meshkov instability (RMI) at the interface between hydrogen plasma and carbon plasma. After an electrostatic shockwave passing through the perturbed interface, the RMI, which reshapes the interface, grows via the vorticity depositing as well as the self-generated magnetic field. After scaling the growth of the interfacial mix region with time, the density transition layer has been found to exceed the disturbance wavelength and lead to a suppression of the instability evolution finally.
Study on NiO:Zn2+ films fabricated through dc magnetron reactive sputtering: substrate temperature-dependent microstructure pattern, optical and electrical properties
Authors: Meng Xue , Gao Xiaoyong , Li Binqi
Published: April 2021

Nickel oxide (NiO) films have potential applications in optical coatings, ultraviolet detectors, gas sensors and perovskite solar cells. The great improvement in electrical conduction is still critical for NiO films so far. NiO films are usually p-type conductive because of the native Ni vacancies and interstitials O. These native point defects make n-type NiO difficult to prepare. Even that, n-type NiO films with improved electrical conduction still need to be prepared for n-NiO-based heterojunction devices. Herein the face-centered cubic NiO:Zn2+ films are magnetron reactively sputtered on the glass substrates at different substrate temperatures (Tsub). The introduction of Zn2+ to NiO leads to the transition in conduction from p to n at 400 °C Tsub. The films are almost improved in crystallization with increase in Tsub, thereby reducing the point defect content i.e. the free carrier concentration. The resulting films are also improved in optical transmittance with increase in Tsub. The film’s optical energy gap is tunable in the range of 3.6 eV through 3.8 eV with Tsub.
Impact of thermophoretic particle deposition on heat and mass transfer across the dynamics of Casson fluid flow over a moving thin needle
Authors: Kumar R Naveen , Gowda R J Punith , Madhukesh J K , Prasannakumara B C , Ramesh G K
Published: April 2021

In this current study, the steady, two-dimensional flow of an incompressible Casson fluid along a horizontal thin moving needle is investigated. Influence of Soret/Dufour effect and thermophoretic particle deposition is considered to examine the heat and mass transport analysis. This model finds application in designing of new medical equipment’s for cell delivery to the central nervous system. The efficient Runge–Kutta Fehlberg fourth fifth order method by adopting shooting technique is employed to solve the reduced non-dimensional form of equations. The impact of several non-dimensional parameters on concentration, velocity and thermal fields are discussed with the help of suitable graphs. Also, friction factor, heat passage rate and thermophoretic particle deposition velocity are analyzed graphically. Results reveal that, increase in Dufour number declines heat transfer but opposite behaviour is depicted in mass transfer. The increasing values of thermophoretic parameter improves the mass transfer. Thermophoretic diffusive deposition velocity increases for rising values of thermophoretic parameter.
Probing the Atmospheric Precipitable Water Vapor with SOFIA, Part I, Measurements of the Water Vapor Overburden with FIFI-LS
Authors: Fischer C. , Iserlohe C. , Vacca W. , Fadda D. , Colditz S. , Fischer N. , Krabbe A.
Published: April 2021

We report on the measurements of telluric water vapor made with the instrument FIFI-LS on SOFIA. Since November 2018, FIFI-LS has measured the water vapor overburden with the same measurement setup on each science flight with about 10 data points throughout the flight. This created a large sample of 469 measurements at different locations, flight altitudes and seasons. The paper describes the measurement principle in detail and provides some trend analysis on the 3 parameters. This presents the first systematic analysis with SOFIA based on in situ observations.
Toroidal modeling of runaway avalanche in DIII-D discharges
Authors: Liu Yueqiang , Li L. , Paz-Soldan C. , Parks P.B. , Lao L.L.
Published: April 2021

A toroidal modeling tool is developed to study the runaway electron (RE) avalanche production process in tokamak plasmas, by coupling the Rosenbluth–Putvinski avalanche model (Rosenbluth and Putvinski 1997 Nucl. Fusion
37 1355) with an n = 0 magneto-hydrodynamic (MHD) solver. Initial value numerical simulations are carried out for two DIII-D discharges with different plasma shapes (one near circular, and the other with high elongation). It is found that, assuming the same level of about 1% seed current level, the Rosenbluth–Putvinski model somewhat underestimates the RE plateau current for the circular-shaped plasma, as compared with that measured in DIII-D experiments. For an elongated, higher current plasma, simulations find strong runaway current avalanche production despite the lack of measured plateau RE current in experiments. A possible reason for this discrepancy is a lack of additional RE dissipation physics in the present two-dimensional model. Systematic scans of the plasma boundary shape, at fixed pre-disruption plasma current, find that the plasma elongation helps to reduce the RE avalanche production, confirming recent results obtained with an analytic model (Fülöp et al 2020 J. Plasma Phys.
86 474860101). The effect of the plasma triangularity (either positive or negative), on the other hand, has a minor effect. On the physics side, the avalanche process involves two competing mechanisms associated with the electric field. On the one hand, a stronger electric field produces a higher instantaneous avalanche growth rate. On the other hand, a fast growing RE current quickly reduces the fraction of the conduction current together with the electric field, and hence a faster dissipation of the poloidal flux. As a final result of these two dynamic processes, the runaway plateau current is not always the largest with the strongest initial electric field. These results lay the foundation for future self-consistent inclusion of the MHD dynamics and the RE amplification process.
EGFET-based pH Sensor coupled with Low-cost Electrochemical Screen-printed Electrodes
Authors: Alvarez-Serna Bryan E , Ramírez-Chavarría Roberto G
Published: April 2021

In this paper, we present an attractive EGFET-based pH sensor that integrates a n-channel metal-oxide-semiconductor field-effect transistor (MOSFET) as the transducer and low-cost electrochemical screen-printed electrodes (SPE) as the sensitive element. Our sensor is based on a metallic silver/silver-chloride (Ag/AgCl) reference electrode and an indium-tin-oxide (ITO) sensitive electrode, operating in the pH range of 2 to 9. Results show that the proposed sensor can measure pH with acceptable sensitivity and resolution.
Overview of speech keyword recognition technology
Authors: Li Sixuan , Li Guanyu , Han Jiao , Zhi Tiankai
Published: April 2021

Since the 1990s, speech keyword recognition technology has gradually separated from speech recognition technology and officially become an important branch of speech recognition technology. In this paper, several speech keyword recognition technologies are studied and reviewed, including sample recognition methods, filler model methods, basic speech recognition systems based methods, neural network classifiers and end-to-end methods. Finally, the development prospect and advanced technology of speech keyword recognition will be discussed.
Analysis on Wireless Charging Technology of Electric Vehicle
Authors: Fang Deng , Yuanqing Zhang , Qiusheng Liu , Jianhe Xie , Jian Wang
Published: April 2021

With the progress of science and technology and the development of the times, people’s living standards are gradually improving, and the use of travel tools is becoming more and more frequent. However, due to the lack of fuel resources in China and the great environmental pollution caused by the use of fuel resources, the country is vigorously promoting the development of new energy to alleviate the domestic oil crisis, among which electric energy is the most widely used energy. Enterprises can use power resources to realize wireless charging technology of electric vehicles. As far as the wireless charging technology currently studied in China is concerned, many technologies are not perfect, which can not meet the needs of people and enterprises for the performance of the wireless charging automobile industry. Therefore, according to the problems existing in the development of the current wireless charging technology, this paper makes relevant analysis.
Application of Digital Twins in Port System
Authors: Yao Haiyuan , Wang Dachuan , Su Mengchao , Qi Yue
Published: April 2021

This article reviewed the concept, development history, technical characteristics, and application directions of the digital twin, concluding the port’s characteristics as an international trade hub window, and the construction decision-making problems faced by the government in management, and proposed the application of digital twins in the field of port construction and operation, which should focus on the needs of port digitization and integrated management, especially set up the research on infrastructure construction, data integration, information model construction, application service platform expansion, etc., then established a spatiotemporal correlation index system for infrastructure, simulate port construction and operation processes, to realize port’ infrastructure elements virtualized, real-time monitoring, and management collaborated. The full scene visualizes the port development process and ability to ensure the adaptation, thereby promoting the cost reduction and efficiency improvement of the entire logistics chain and value chain.
Numerical solution of Showalter–Sidorov and Cauchy problems of ion–acoustic waves propagation mathematical model
Authors: Bychkov E V , Zamyshlyaeva A A
Published: April 2021

The paper deals with the problem of numerical investigation of semilinear mathematical model of ion-acoustic waves propagation in plasma. The research is based on the previous study of solvability of the Cauchy problem for an abstract semilinear Sobolev type equation of higher order. The theory of relatively polynomially bounded operator pencils, the theory of differentiable Banach manifolds, and the phase space method are used for analytical study of the model. Projectors splitting spaces into direct sums of subspaces are constructed. Given equation is reduced to a system of two equations. One of them determines the phase space of the initial equation, and its solution is a function with values from the eigenspace of the operator at the highest time derivative. The solution of the second equation is the function with values from the image of the projector. Moreover, in the second section, the sufficient conditions for the solvability of the abstract problem under study are presented. These results are applied to the mathematical model of ion-acoustic waves in plasma which is based on the fourth-order equation with a singular operator at the highest time derivative. Reducing the matematical model to an abstract problem, we obtain sufficient conditions for the existence of unique solution. The results of analytical investigation of the Showalter – Sidorov problem which is more natural for Sobolev type equations are also presented in this section. The Galerkin method is used for numerical study of the model. An algorithm for the numerical solution of the Showalter – Sidorov problem for the model of ion-acoustic waves in plasma is described in the last section.
On a hyperbolic system of equations in the problem of unsteady fluid motion
Authors: Grazhdantseva E Y , Solodusha S V
Published: April 2021

We consider a nonlinear system of the first-order partial differential equations with constant coefficients admitting a solution of the traveling wave type. Such systems are used in applied research to describe the dynamics of unsteady water movement in a pressure pipeline. In this paper, we propose methods for obtaining exact solutions in the case of an inhomogeneous equation of fluid motion under restrictions on the right-hand side in the form of a function. A special feature of the present research is reduction of the problem under study to the equations integrable in elementary functions.
Integro-differential equation with fractional order Caputo operators and spectral parameters
Authors: Yuldashev T K
Published: April 2021

The questions of unique solvability of a boundary value problem for an integro-differential equation with two Caputo fractional operators and spectral parameters are considered. The fractional Caputo operator’s order is bigger than one and smaller than two. Using the method of Fourier series, countable systems of ordinary fractional integro-differential equations with degenerate kernel is obtained. Further, is used a method of degenerate kernel. To determine arbitrary integration constants, a system of algebraic equations is obtained. From this system the regular and irregular values of the spectral parameters were calculated. The solution of the problem under consideration is obtained in the form of Fourier series. The unique solvability of the problem for regular values of spectral parameters is proved. In proofing of the convergence of Fourier series the properties of the Mittag-Leffler function, Cauchy-Schwarz inequality and Bessel inequality are used. We also studied the continuous dependence of the solution of the problem on small parameter for regular values of spectral parameters. The results obtained in this paper are formulated as a theorem.
On one boundary control problem of string vibrations with given velocity of points at an intermediate moment of time
Authors: Barseghyan V R , Solodusha S V
Published: April 2021

The boundary control problem for the string vibration equation with given initial and final conditions, with the given velocity of the string points at an intermediate moment of time is considered. It is controlled by displacement of one end while the other end is fixed. A constructive approach for constructing the boundary control action is proposed, which is applied for given functions.
On approximate controllability of a class of degenerate fractional order distributed systems
Authors: Fedorov V E , Gordievskikh D M , Filin N V
Published: April 2021

The approximate controllability issues for a class of control systems, whose dynamics is described by an equation in a Banach space with a linear degenerate operator at the Riemann — Liouville fractional derivative, is investigated. Under the condition of p-boundedness of the pair of operators in the equation the control system is reduced to subsystems on two mutually complement subspaces. It was shown that the approximate controllability of the whole system is equivalent to the approximate controllability of the two subsystems. Criteria of the approximate controllability for the system and two subsystems are obtained. Analogous results are got on the approximate controllability for free time and for systems of the same form with a finite-dimensional input. The obtained criteria were applied to the investigation of the approximate controllability for a distributed system with polynomials of a differential with respect to the spatial variables self-adjoint elliptic operator and for a system of the Scott-Blair — Oskolkov type.
Approximate optimal synthesis of operational control systems for dynamic objects based on quasilinearization and sufficient optimality conditions
Authors: Khrustalev M M , Sizykh V N , Daneev A V
Published: April 2021

A new approach to the analytical design of linear and nonlinear integrated automatic control systems (ACS) of a real (accelerated) time scale, based on the joint use of dynamic programming technologies and the quasilinearization method, is presented. For continuous dynamic systems, the foundations of the theory of nonlinear synthesis in a degenerate (synergetic) formulation are given.
Discrete maximum principle in systems with a delay in control
Authors: Mardanov M J , Malik S T
Published: April 2021

In the paper, we consider a discrete optimal control problem with a delay in control. Taking into account the specificity of this problem, we offer a new research method. The essence of this method is that unlike previously known ones here we assume that the set of admissible speeds satisfies convexity type conditions at the moment t + h, but not at t, where h is time delay in the system. The discrete analog of Pontryagin’s maximum principle is obtained under weakened assumptions. An example showing the content-richness of the obtained result is given.
The method of parameterization in the quadratic optimal control problem
Authors: Srochko V A , Antonik V G , Aksenyushkina E V
Published: April 2021

In the framework of control parameterization method the optimization problem with respect to linear phase system with quadratic functional is considered. Approximation of the control is obtained in the class of piecewise constant functions. It is formed as a linear combination of a special set of support functions. Coefficients of this combination are variables of the finite-dimensional problem. To effectively solve this problem explicit expressions for the functional with respect to parameters of approximations are obtained. As a result the quadratic mathematical programming problem is formulated.
Mechanisms of polymorphic systematization of bioecological data within the BaikalIntelli platform for organizing computational models of population dynamics
Authors: Kedrin V S , Arguchintsev A V , Dobrinets I M
Published: April 2021

A conceptual model of the BaikalIntelli platform for universal storage, input and processing of arbitrary spatio-temporal databases of bioecological parameters is proposed. Information technologies that allow implementing the basic functionality of the universal metamechanism of data systematization are considered. The platform mechanism has been tested on the example of entering quantitative data of different types of oligochaetes, one of the mass groups of invertebrates of Lake Baikal. Web interface for the database “Spatio-temporal variability of oligochaete populations in the area of industrial wastewater discharge of the Baikal pulp and paper mill” is developed on the base of JavaScript.
Modelling of turbulent structure of plasma inhomogeneity according to decameter data transionospheric sensing
Authors: Afanasiev N T , Trofimov E A , Chudaev S O
Published: April 2021

A method for determining the parameters of the thin turbulent structure of a large-scale ionospheric irregularity from the trajectory characteristics of decametre radio signals emitted from the spacecraft is proposed. The spatial parameters of large-scale heterogeneity are determined by the results of numerical synthesis of the distance-frequency characteristics of radio signals. The statistical moments of signals’ trajectory characteristics at various operating frequencies, obtained by analytically solving stochastic ray equations, are used to diagnose the thin structure of the irregularity.
Reduced mathematical model of the flow in a deep extended natural channel
Authors: Nadolin K A
Published: April 2021

A slightly curved open stationary channel flow is considered. It is assumed that the flow bed is given by a sufficiently smooth function, and the flow itself is long and deep, i.e. the length of the section under consideration is much longer than its width and depth, which, in turn, have similar dimensions. Using the previously developed technique for obtaining reduced mathematical models for channel flows, it is possible, at constant viscosity, to reduce the solution of a complex three-dimensional problem to solving a sequence of standard two-dimensional problems on cross-sections.
The addition of ethylhydrazine to α,β- and β,γ-unsaturated ketones: a quantum-chemical modeling
Authors: Gnatovsky G R , Orel V B , Vitkovskaya N M
Published: April 2021

The reactivity of α,β- and β,γ-unsaturated ketones with respect to the nucleophilic attack by ethylhydrazine in one of the key stages of the formation of 4,5-dihydropyrazole has been studied. It is shown that the addition of the terminal nitrogen atom of ethylhydrazine to the carbonyl group of β,γ- and α,γ-unsaturated ketones with the formation of β,γ- and α,β-unsaturated hydrazones is energetically preferable with the participation of two water molecules. At the same time, the addition of the internal nitrogen of ethylhydrazine to the double C=C bond of the α,β-unsaturated ketone (which is preferable in the presence of one water molecule) to give β-ethylhydrazinyl ketone occurs with a lower activation barrier and is thermodynamically more favorable than the addition to the C=O bond.
Acetylene vs ketones on the route to base-promoted assembly of furans or 6,8-dioxabicyclo[3.2.1]octanes and cyclopentenols: a quantum-chemical study
Authors: Orel V B , Vitkovskaya N M
Published: April 2021

The electronic characteristics of substrates (α,β-unsaturated ketones) and reagents (carbanions of ketones and ethynide ions), as well as thermodynamic and kinetic characteristics both their interaction and the formation of final products have been evaluated using the B2PLYP/6-311+G**//B3LYP/6-31+G* and B3LYP/6-311++G**//B3LYP/6-31+G* quantum-chemical approaches. Reactivity indices that adequately describe the electrophilic and nucleophilic properties of the substrates and reagents are proposed. It has been shown that, regardless of the nature of substrates and reagents, the formation of cyclopentenols and furans is thermodynamically favorable, while the presence of bulky substituents leads to an increase in energy during the formation of 6,8-dioxabicyclo[3.2.1]octanes and explains in this case their absence in products. The calculated activation barriers of the competing reactions of the nucleophilic addition of ethynide ions and ketone carbanions to the double C=C bond of α,β-unsaturated ketones are correlated with the observed reaction direction and the proposed reactivity indices.
Research on transformer fault diagnosis based on genetic algorithm optimized neural network
Authors: Zhang Lei , Zeng Xianwen
Published: April 2021

Aiming at the problem of transformer fault diagnosis in power system, a fault diagnosis method based on genetic algorithm optimization BP neural network is proposed. The BP neural network structure was established based on the traditional three-ratio fault diagnosis method. The concentration of dissolved gas in transformer oil was taken as the input value of the neural network, and the fault working state of transformer was taken as the output value. The established neural network is used to diagnose transformer faults. In order to avoid BP neural network falling into the problem of local optimal value, the weights and thresholds of the neural network are optimized by genetic algorithm. By using the genetic algorithm toolbox in Matlab to establish the genetic algorithm network structure, the transformer fault data as input for the performance of the neural network test. The results show that the neural network optimized by genetic algorithm has a high classification effect on transformer fault types, and the neural network optimized by genetic algorithm has a higher diagnostic efficiency and accuracy than BP neural network.
Research on Docker Cluster Scheduling Based on Self-define Kubernetes Scheduler
Authors: Zheng Gengsheng , Fu Yao , Wu Tingting
Published: April 2021

To address the issue that native scheduler in kubernetes cannot realize load balancing and cannot give full play to the overall performance of the cluster, we put forward a scheduling strategy based on Docker cluster of self-define kubernetes scheduler. The kubernetes scheduler can improve the native kubernetes scheduling strategy using optimized predicate algorithm model and priority algorithm model. Moreover, it can also be used to conduct contrast experiment between the native scheduling strategy of kubernetes and that of self-define kubernetes scheduler. It is in VMware Workstation environment where Centos system is installed, and where Docker container service and kubernetes container orchestration engine are deployed to establish Docker container cluster. Experimental results show that cluster scheduling strategy of the self-define kubernetes scheduler is better than the native one, because it can save more system resources to improve the fairness of the cluster scheduling and the scheduling efficiency.