bluuebunny/crossref_metadata_2025 huggingface dataset:
Generation of single-cycle relativistic infrared pulses at wavelengths above 20 µm from density-tailored plasmas
Authors: Zhu Xing-Long , Liu Wei-Yuan , Weng Su-Ming , Chen Min , Sheng Zheng-Ming , Zhang Jie
Published: December 2021

Ultra-intense short-pulse light sources are powerful tools for a wide range of applications. However, relativistic short-pulse lasers are normally generated in the near-infrared regime. Here, we present a promising and efficient way to generate tunable relativistic ultrashort pulses with wavelengths above 20 µm in a density-tailored plasma. In this approach, in the first stage, an intense drive laser first excites a nonlinear wake in an underdense plasma, and its photon frequency is then downshifted via phase modulation as it propagates in the plasma wake. Subsequently, in the second stage, the drive pulse enters a lower-density plasma region so that the wake has a larger plasma cavity in which longer-wavelength infrared pulses can be produced. Numerical simulations show that the resulting near-single-cycle pulses cover a broad spectral range of 10–40 µm with a conversion efficiency of ∼2.1% (∼34 mJ pulse energy). This enables the investigation of nonlinear infrared optics in the relativistic regime and offers new possibilities for the investigation of ultrafast phenomena and physics in strong fields.
Spin Seebeck effect driven by thermal flux in two-dimensional ferromagnets
Authors: Li Guang-Qing , Zhu Zhen-Gang , Su Gang
Published: December 2021

The spin Seebeck effect is a novel indirect thermoelectric conversion phenomenon, in which magnetic materials play an important role, that is distinct from the traditional direct thermoelectric conversion method. In this paper, we studied the spin Seebeck effect driven by thermal flux in two-dimensional ferromagnets and derived the spin-dependent Seebeck coefficient and the spin Seebeck coefficient contributed by conduction electrons in a ferromagnet based on the non-equilibrium linear irreversible thermodynamics and the Boltzmann linear theory. The spin Seebeck coefficients of six two-dimensional ferromagnetic materials (including manganese halides and transition metal chalcogenides) were numerically calculated. A largest spin Seebeck coefficient is found for MnCl3 to be 1600 μV/K in the range of temperature from 50 to 120 K, which is even larger than that of known CrI3 and CrGeTe3. The present study on the heat flow-spin current transport properties of ferromagnets could have great significance for the thermoelectric applications in spintronics.
Grading your models: Assessing dynamics learning of models using persistent homology
Authors: Tan Eugene , Corrêa Débora , Stemler Thomas , Small Michael
Published: December 2021

Assessing model accuracy for complex and chaotic systems is a non-trivial task that often relies on the calculation of dynamical invariants, such as Lyapunov exponents and correlation dimensions. Well-performing models are able to replicate the long-term dynamics and ergodic properties of the desired system. We term this phenomenon “dynamics learning.” However, existing estimates based on dynamical invariants, such as Lyapunov exponents and correlation dimensions, are not unique to each system, not necessarily robust to noise, and struggle with detecting pathological errors, such as errors in the manifold density distribution. This can make meaningful and accurate model assessment difficult. We explore the use of a topological data analysis technique, persistent homology, applied to uniformly sampled trajectories from constructed reservoir models of the Lorenz system to assess the learning quality of a model. A proposed persistent homology point summary, conformance, was able to identify models with successful dynamics learning and detect discrepancies in the manifold density distribution.
Transcriptome-wide development and utilisation of novel intron-length polymorphic markers in common vetch (
Authors: Wei Xingyi , Ma Yitong , Wang Qiuxia , Li Yanpeng , Liu Wenxian
Published: December 2021

Common vetch (Vicia sativa subsp. sativa) is one of the most economically important forage legumes, with high nutritional value and multiple uses. Although microsatellite markers have been developed and applied on a large scale for evaluation of common vetch germplasm, intron-length polymorphic (ILP) markers have not been systematically investigated and exploited. In this study, introns within the common vetch genome were located by aligning the RNA-Seq sequences of common vetch with barrel medic (Medicago truncatula), soybean (Glycine max) and Arabidopsis thaliana genome sequences, and then used for VsILP marker development. In total, 10 400 markers were generated from 44 582 common vetch unigenes. Of 300 randomly selected VsILP markers, 283 were successfully amplified in common vetch. Among these markers, 40 produced length variation in 30 accessions of common vetch, collectively yielding 166 alleles with an average of 4.0 alleles per locus. The polymorphic information content values extended from 0.06 to 0.81 with a mean of 0.49. Of the 283 VsILP markers, 84.8% exhibited transferability to other species, both leguminous (common vetch, lucerne (Medicago sativa), barrel medic, soybean, yellow sweet clover (Melilotus officinalis), Lotus corniculatus and Sophora alopecuroides) and non-leguminous (rice (Oryza sativa), Arabidopsis and tobacco (Nicotiana tabacum)). Here, we present the first large-scale development of ILP markers in common vetch and their utility in germplasm evaluation and transferability, which will be valuable for further comparative genomic studies, genetic relationship assessments, and marker-assisted breeding of leguminous and non-leguminous species.
The hippocampus as the switchboard between perception and memory
Authors: Treder Matthias S. , Charest Ian , Michelmann Sebastian , Martín-Buro María Carmen , Roux Frédéric , Carceller-Benito Fernando , Ugalde-Canitrot Arturo , Rollings David T. , Sawlani Vijay , Chelvarajah Ramesh , Wimber Maria , Hanslmayr Simon , Staresina Bernhard P.
Published: December 2021

Significance

How do we adaptively switch from perceiving the external world to retrieving goal-relevant internal memories? To tackle this question, we used—in a cued-recall paradigm—direct intracranial recordings from the human hippocampus complemented by high-density scalp electroencephalography (EEG). We found that a hippocampal signal ∼500 ms after a perceptual cue marks the conversion from external (perceptual) to internal (mnemonic) representations. This sets in motion a recall cascade involving posterior parietal and medial prefrontal cortex, revealed via source-localized and time-resolved EEG alpha power. Together, these results unveil the hippocampal–cortical dynamics supporting rapid and flexible memory recall.
Daily monitoring of scattered light noise due to microseismic variability at the Virgo interferometer
Authors: Longo Alessandro , Bianchi Stefano , Valdes Guillermo , Arnaud Nicolas , Plastino Wolfango
Published: December 2021

Data acquired by the Virgo interferometer during the second part of the O3 scientific run, referred to as O3b, were analysed with the aim of characterising the onset and time evolution of scattered light noise in connection with the variability of microseismic noise in the environment surrounding the detector. The adaptive algorithm used, called pytvfemd, is suitable for the analysis of time series which are both nonlinear and nonstationary. It allowed to obtain the first oscillatory mode of the differential arm motion degree of freedom of the detector during days affected by scattered light noise. The mode’s envelope i.e. its instantaneous amplitude, is then correlated with the motion of the West end bench, a known source of scattered light during O3. The relative velocity between the West end test mass and the West end optical bench is used as a predictor of scattered light noise. Higher values of correlation are obtained in periods of higher seismic noise in the microseismic frequency band. This is also confirmed by the signal-to-noise ratio (SNR) of scattered light glitches from GravitySpy for the January–March 2020 period. Obtained results suggest that the adopted methodology is suited for scattered light noise characterisation and monitoring in gravitational wave interferometers.
Target signatures for thin surfaces
Authors: Cakoni Fioralba , Monk Peter , Zhang Yangwen
Published: December 2021

We investigate an inverse scattering problem for a thin inhomogeneous scatterer in

R

m

, m = 2, 3, which we model as an m − 1 dimensional open surface. The scatterer is referred to as a screen. The goal is to design target signatures that are computable from scattering data in order to detect changes in the material properties of the screen. This target signature is characterized by a mixed Steklov eigenvalue problem for a domain whose boundary contains the screen. We show that the corresponding eigenvalues can be determined from appropriately modified scattering data by using the generalized linear sampling method. A weaker justification is provided for the classical linear sampling method. Numerical experiments are presented to support our theoretical results.
RF MEMS electrostatically actuated tunable capacitors and their applications: a review
Authors: Khan Fahimullah , Younis Mohammad I
Published: December 2021

This paper reviews the recent developments of micro-electromechanical system (MEMS) based electrostatically actuated tunable capacitors. MEMS based tunable capacitors (MBTCs) are important building blocks in advanced radio frequency communication systems and portable electronics. This is due to their excellent performance compared to solid state counterpart. Different designs, tuning mechanisms, and performance parameters of MBTCs are discussed, compared, and summarized. Several quantitative comparisons in terms of tuning range, quality factor (Q factor), and electrodes configurations are presented, which provide deep insight into different design studies, assists in selecting designs, and layouts that best suit various applications. We also highlight recent modern applications of tunable capacitors, such as mobile handsets, internet of things, communication sensors, and 5G antennas. Finally, the paper discusses different design approaches and proposes guidelines for performance improvement.
Charge carrier dynamics and photovoltaic properties of near-infrared absorbing squaraine incorporated solution-processed additive-free PTB7:PCBM based ternary solar cells
Authors: Anitha B , Joseph Alvin , Alexander Akhil , Vijith K P , Varun Srivastava , Namboothiry Manoj A G
Published: December 2021

The introduction of a third component vehemently modifies the morphology and charge carrier dynamics in the blend of a donor–acceptor pair, thereby affecting the photovoltaic properties of organic solar cells (OSCs). Combining steady-state, impedance, and transient spectroscopic measurements, photovoltaic properties of 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl] squaraine (SQ) incorporated additive-free PTB7:PC70BM OSCs are assessed. As observed from steady-state measurements, concomitant enhancement in open-circuit voltage (VOC) and short-circuit current density (JSC) has caused a 33% enhancement in power conversion efficiency (PCE) with good reliability and reproducibility. On introducing 25 wt.% SQ to the OSCs, V
OC has increased from 0.74 to 0.80 V, while J
SC has improved from 11.3 to 13.9 mA cm−2 with an increment in exciton dissociation probability rate from 81.5% to 94.9%. However, the fill factor values show inconsistent marginal variations with SQ addition. Equivalent circuit modeling of bias-voltage dependent impedance spectra along with transient photovoltage measurements reveal an improvement in effective charge carrier lifetime for the SQ incorporated OSCs, in comparison to the binary device. The addition of SQ also ensures better charge transport and extraction, as evidenced by photo-CELIV and transient photocurrent analysis. Atomic force microscopy (AFM) images confirm the effective tuning of the morphology of the active layer when SQ is introduced into the binary blend, favoring efficient charge dissociation and transport. The possible operation mechanism of SQ incorporated ternary OSCs is proposed based on photoluminescence and AFM measurements. Moreover, the un-encapsulated OSC with 25 wt.% SQ has retained 91% of the initial PCE, while for the binary device the PCE declined to ∼75% of the initial value after 200 h of continuous 1 sun illumination from a white LED in ambient atmosphere.
Complex band structure with non-orthogonal basis set: analytical properties and implementation in the SIESTA code
Authors: Bosoni E , Sanvito S
Published: December 2021

The complex band structure (CBS), although not directly observable, determines many properties of a material where the periodicity is broken, such at surfaces, interfaces and defects. Furthermore, its knowledge helps in the interpretation of electronic transport calculations and in the study of topological materials. Here we extend the transfer matrix method, often used to compute the complex bands, to electronic structures constructed using an atomic non-orthogonal basis set. We demonstrate that when the overlap matrix is not the identity, the non-orthogonal case, spurious features appear in the analytic continuation of the band structure to the complex plane. The properties of these are studied both numerically and analytically and discussed in the context of existing literature. Finally, a numerical implementation to extract the CBS from periodic calculations carried out with the density functional theory code siesta is presented. This is constructed as a simple post-processing tool, and it is therefore amenable to high-throughput studies of insulators and semiconductors.
Thermal transport in beta-gallium oxide thin-films using non-gray Boltzmann transport equation
Authors: Kumar Nitish , Barry Matthew C , Kumar Satish
Published: December 2021

Phonon transport in β-Ga2O3 thin films and metal-oxide field effect transistors (MESFETs) are investigated using non-gray Boltzmann transport equations (BTEs) to decipher the effect of ballistic-diffusive phonon transport. The effects of domain size, and energy dissipation to various phonon modes and subsequent phonon–phonon energy exchange on the thermal transport and temperature distribution is investigated using non-gray BTE. Our analysis deciphered that domain size plays a major role in thermal transport in β-Ga2O3 but energy dissipation to various phonon modes and subsequent phonon–phonon energy exchange does not affect the temperature field significantly. Phonon transport in β-Ga2O3 MESFETs on diamond substrate is investigated using coupled non-gray BTE and Fourier model. It is established that the ballistic effects need to be considered for devices with β-Ga2O3 layer thickness less than 1 μm. A non-gray phonon BTE model should be used near hotspot in the thin β-Ga2O3 layer as the Fourier model may not give accurate temperature distribution. The results from this work will help in understanding the mechanism of phonon transport in the β-Ga2O3 thin films and energy efficient design of its FETs.
Instability of Majorana states in Shiba chains due to leakage into a topological substrate
Authors: Sedlmayr Nicholas , Bena Cristina
Published: December 2021

We revisit the problem of Majorana states in chains of scalar impurities deposited on a superconductor with a mixed s-wave and p-wave pairing. We also study the formation of Majorana states for magnetic impurity chains. We find that the magnetic impurity chains exhibit well-localized Majorana states when the substrate is trivial, but these states hybridize and get dissolved in the bulk when the substrate is topological. Most surprisingly, and contrary to previous predictions, the scalar impurity chain does not support fully localized Majorana states except for very small and finely tuned parameter regimes, mostly for a non-topological substrate close to the topological transition. Our results indicate that a purely p-wave or a dominant p-wave substrate are not good candidates to support either magnetic or scalar impurity topological Shiba chains.
Pressure driven long wavelength MHD instabilities in an axisymmetric toroidal resistive plasma
Authors: Graves J P , Coste-Sarguet M , Wahlberg C
Published: December 2021

A general set of equations that govern global resistive interchange, resistive internal kink and resistive infernal modes in a toroidal axisymmetric equilibrium are systematically derived in detail. Tractable equations are developed such that resistive effects on the fundamental rational surface can be treated together with resistive effects on the rational surfaces of the sidebands. Resistivity introduces coupling of pressure driven toroidal instabilities with ion acoustic waves, while compression introduces flute-like flows and damping of instabilities, enhanced by toroidal effects. It is shown under which equilibrium conditions global interchange, internal kink modes or infernal modes occur. The m = 1 internal kink is derived for the first time from higher order infernal mode equations, and new resistive infernal modes resonant at the q = 1 surface are reduced analytically. Of particular interest are the competing effects of resistive corrections on the rational surfaces of the fundamental harmonic and on the sidebands, which in this paper is investigated for standard profiles developed for the m = 1 internal kink problem.
Experimental and numerical investigation of Poole–Frenkel effect on dynamic R
ON transients in C-doped p-GaN HEMTs
Authors: Zagni Nicolò , Cioni Marcello , Iucolano Ferdinando , Moschetti Maurizio , Verzellesi Giovanni , Chini Alessandro
Published: December 2021

In this paper, we investigate the influence of Poole–Frenkel effect (PFE) on the dynamic R
ON transients in C-doped p-GaN HEMTs. To this aim, we perform a characterization of the dynamic R
ON transients acquired during OFF-state stress (i.e. V
GS,STR = 0 V < V
T, V
DS,STR = 25–125 V) and we interpret the results with the aid of numerical simulations. We find that dynamic R
ON transients at room temperature accelerate with V
DS,STR
1/2, which is signature of PFE, as further confirmed by the simultaneous decrease of the activation energy (E
A) extracted from the Arrhenius plot of the dynamic R
ON transients at V
DS,STR = 50 V and T = 30 °C–110 °C. Results obtained by means of calibrated numerical simulations reproduce the exponential dependence of transients time constants (τ) on V
DS,STR
1/2 and consequent E
A reduction only when including the PFE-enhancement model of hole emission from dominant acceptor traps in the buffer related to C doping. This result is consistent with the ‘hole-redistribution’ model that considers hole emission from acceptor traps (rather than electron capture) as the mechanism underlying dynamic R
ON increase during OFF-state stress.
Shadow surface states in topological Kondo insulators
Authors: Ghazaryan Areg , Nica Emilian M , Erten Onur , Ghaemi Pouyan
Published: December 2021

The surface states of 3D topological insulators in general have negligible quantum oscillations (QOs) when the chemical potential is tuned to the Dirac points. In contrast, we find that topological Kondo insulators (TKIs) can support surface states with an arbitrarily large Fermi surface (FS) when the chemical potential is pinned to the Dirac point. We illustrate that these FSs give rise to finite-frequency QOs, which can become comparable to the extremal area of the unhybridized bulk bands. We show that this occurs when the crystal symmetry is lowered from cubic to tetragonal in a minimal two-orbital model. We label such surface modes as ‘shadow surface states’. Moreover, we show that the sufficient next-nearest neighbor out-of-plane hybridization leading to shadow surface states can be self-consistently stabilized for tetragonal TKIs. Consequently, shadow surface states provide an important example of high-frequency QOs beyond the context of cubic TKIs.
Kinetic theory of instability in the interaction of an electron beam and plasma with an arbitrary anisotropic electron velocity distribution function
Authors: Sukhomlinov Vladimir S , Mustafaev Alexander S , Koubaji Hend , Timofeev Nikolay A , Murillo Oscar
Published: December 2021

Based on the kinetic approach, this work investigates the stability of the system consisting of a fast electron beam and a dense plasma at an arbitrary (anisotropic) electron velocity distribution function. It is shown that during the interaction of a fast electron beam with a cold plasma, both the conditions for losing stability and the growth rate of disturbances do not depend on the form of the electron distribution function (EDF) of a plasma and are determined only by the ratio of the electron beam energy to the mean energy in a plasma. With an increase in the mean electron energy in the plasma, it becomes necessary to take into account the following energy moments of the EDF. It was found that the plasma anisotropy has a significant effect on both the stability loss conditions and the growth rate. The physical reason for this effect is the shift in the plasma frequency due to the Doppler effect caused by the plasma anisotropy in the coordinate system moving along with the beam. Other findings include a region of anomalous dispersion of the electron beam–plasma system and regions of negative group velocity of perturbations in such system. Physical interpretations are proposed for all the observed effects.
Study of the influence of MoO3 concentration on the chemical structure, physical properties, and radiation absorption prowess of alumino lead borate glasses
Authors: Al-Buriahi M S , Alrowaili Z A , Kebaili Imen , Al-Baradi Ateyyah M , Wahab E A Abdel , Olarinoye I O , Sriwunkum Chahkrit , Shaaban Kh S
Published: December 2021

The present study presents the preparation of a glass system with composition of 55B2O3 - 30Pb3O4-

(
15
−
x
)

Al2O3-

x

MoO3, where

x
:

(
0
≤
x
≤
5

mol

%
)

by melt quenching conventional method. The structure of the synthesized samples was examined by XRD and FT-IR techniques. It was found that the molybdenum acts as a modifier and enhances the change between BO3 and BO4 structural units. Increasing MoO3 in the sample improved the glass network compactness. The influence of MoO3 content was studied on several physical parameters such as inter-ionic distance (Ri), the polaron radius (rp) and internuclear distance (ri), B—B separation (dB-B) average coordination number, number of bonds, field strength of (Mo+3), and the floppy modes. Increasing MoO3 doping concentration from 0–5 mol % produced corresponding increase in fast neutron effective removal cross section

Σ

R

from 0.07127–0.10825 cm−1, total cross section for thermal neutrons

σ

T

from 68.35875–105.7526 cm−1, and an increment in the cold neutron scattering cross section. Furthermore, the influence of MoO3 doping in the glasses was such that the stopping powers

(

S

p

)

and ranges RCSDA /Rp of electrons, proton, alpha particles, and carbon ion follows the trend:

(

S

p

)

BPAM-G1 > 

(

S

p

)

BPAM-G2 > 

(

S

p

)

BPAM-G3 > 

(

S

p

)

BPAM-G4 > 

(

S

p

)

BPAM-G5, and (RCSDA /Rp)BPAM-G1 > (RCSDA /Rp)BPAM-G2 > (RCSDA /Rp)BPAM-G3 > (RCSDA /Rp)BPAM-G4 > ((RCSDA /Rp)BPAM-G5 respectively. On the other hand, the doping produced no noticeable differences in the equivalent atomic number and the exposure buildup factor of the glasses.
Nonclassicality of photon–modulated spin coherent states in the Holstein-Primakoff realization
Authors: Zhang Xiaoyan , Wang Jisuo , Wang Lei , Meng Xiangguo , Liang Baolong
Published: December 2021

Two new photon-modulated spin coherent states (SCSs) are introduced by operating the spin ladder operators J
± on the ordinary SCS in the Holstein–Primakoff realization and the nonclassicality is exhibited via their photon number distribution, second-order correlation function, photocount distribution and negativity of Wigner distribution. Analytical results show that the photocount distribution is a Bernoulli distribution and the Wigner functions are only associated with two-variable Hermite polynomials. Compared with the ordinary SCS, the photon-modulated SCSs exhibit more stronger nonclassicality in certain regions of the photon modulated number k and spin number j, which means that the nonclassicality can be enhanced by selecting suitable parameters.
Superconductivity in octagraphene
Authors: Li Jun , Yao Dao-Xin
Published: December 2021

This article reviews the basic theoretical aspects of octagraphene, an one-atom-thick allotrope of carbon, with unusual two-dimensional (2D) Fermi nesting, hoping to contribute to the new family of quantum materials. Octagraphene has an almost strongest sp2 hybrid bond similar to graphene, and has the similar electronic band structure as iron-based superconductors, which makes it possible to realize high-temperature superconductivity. We have compared various possible mechanisms of superconductivity, including the unconventional s± superconductivity driven by spin fluctuation and conventional superconductivity based on electron–phonon coupling. Theoretical studies have shown that octagraphene has relatively high structural stability. Although many 2D carbon materials with C4 carbon ring and C8 carbon ring structures have been reported, it is still challenging to realize the octagraphene with pure square-octagon structure experimentally. This material holds hope to realize new 2D high-temperature superconductivity.
Quantum private comparison of arbitrary single qubit states based on swap test
Authors: Huang Xi , Chang Yan , Cheng Wen , Hou Min , Zhang Shi-Bin
Published: December 2021

By using swap test, a quantum private comparison (QPC) protocol of arbitrary single qubit states with a semi-honest third party is proposed. The semi-honest third party (TP) is required to help two participants perform the comparison. She can record intermediate results and do some calculations in the whole process of the protocol execution, but she cannot conspire with any of participants. In the process of comparison, the TP cannot get two participants’ private information except the comparison results. According to the security analysis, the proposed protocol can resist both outsider attacks and participants’ attacks. Compared with the existing QPC protocols, the proposed one does not require any entanglement
swapping technology, but it can compare two participants’ qubits by performing swap test, which is easier to implement with current technology. Meanwhile, the proposed protocol can compare secret integers. It encodes secret integers into the amplitude of quantum state rather than transfer them as binary representations, and the encoded quantum state is compared by performing the swap test. Additionally, the proposed QPC protocol is extended to the QPC of arbitrary single qubit states by using multi-qubit swap test.
Preemptive RMP-driven ELM crash suppression automated by a real-time machine-learning classifier in KSTAR
Authors: Shin Giwook , Han H. , Kim M. , Hahn S.-H. , Ko W.H. , Park G.Y. , Lee Y.H. , Lee M.W. , Kim M.H. , Juhn J.-W. , Seo D.C. , Jang J. , Kim H.S. , Lee J.H. , Kim H.J.
Published: December 2021

Suppression or mitigation of edge-localized mode (ELM) crashes is necessary for ITER. The strategy to suppress all the ELM crashes by the resonant magnetic perturbation (RMP) should be applied as soon as the first low-to-high confinement (L–H) transition occurs. A control algorithm based on real-time machine learning (ML) enables such an approach: it classifies the H-mode transition and the ELMy phase in real-time and automatically applies the preemptive RMP. This paper reports the algorithm design, which is now implemented in the KSTAR plasma-control system, and the corresponding experimental demonstration of typical high-δ KSTAR H-mode plasmas. As a result, all initial ELM crashes are suppressed with an acceptable safety factor at the edge (q
95) and with RMP field adjustment. Moreover, the ML-driven ELM crash suppression discharges remain stable without further degradation due to the regularization of the plasma pedestal.
First plasma exposure of a pre-damaged ITER-like plasma-facing unit in the WEST tokamak: procedure for the PFU preparation and lessons learned
Authors: Richou Marianne , Corre Yann , Loewenhoff Thorsten , Diez Mathilde , Martin Céline , Aretz Anke , Coenen Jann Willem , Firdaouss Mehdi , Giacometti Gregory , Grosjean Alex , Pintsuk Gerald , Roche Hélène , Spähn Michael , De Temmerman Gregory , Tsitrone Emmanuelle , Wirtz Marius , WEST Team the
Published: December 2021

The evaluation of the impact of plasma-facing components damage on subsequent plasma operation is an important issue for ITER. During the first phase of the operation of WEST, a few ITER-like divertor plasma-facing units (PFUs) have been installed on the lower divertor. One PFU was pre-damaged under electron beam gun thermal loading, before its installation in WEST, and the subsequent evolution of the damage was studied after the WEST plasma exposure. This paper presents the procedure followed to get the pre-damaged PFU. It consists of the characterization of the response of tungsten samples representative of WEST PFU under high heat flux (HHF) loading, the selection of damage (namely, small cracks, crack network, crack network, and W melt droplets). Finally, according to the WEST plasma loading conditions, the blocks with damage within the PFU and the position of the pre-damaged PFU on the WEST lower divertor are attributed. The first results obtained after an initial plasma exposure in WEST lead to the assessment, as expected with regard to the heat loading conditions, that no major surface aspect modification was found. This result emphasized the possibility of implementing as pre-damaged small droplets of melted tungsten in a high heat-loaded zone for a future WEST experimental campaign.
Initiation of the plasma jet of the magneto-plasma compressor by the external plasma source
Authors: Brovkin V G , Klimov A I , Mashek I Ch , Pashchina A S , Ryazansky N M , Vedenin P V
Published: December 2021

The results of a preliminary study of the interaction of supersonic gas-plasma flows created by a magneto-plasma compressor and a pulsed erosion plasma jet are presented. Stable initiation of the MPC discharge at atmospheric pressure was achieved for the first time. The advantage of using the coaxial arrangement of plasma jets sources for MPC discharge initiation is shown. A noticeable change in the shock wave front velocity and pressure (up to 20%), created during the MPC discharge and dispersed powders and liquid mixtures interaction, is discovered.
The pre -breakdown characteristics of weakly ionized media in the high non-uniform electric field using calculations with refined grid cells
Authors: Apfelbaum M S , Doludenko A N
Published: December 2021

The theoretical model of a pre-breakdown ions formation in a liquid dielectric and their flows, caused by high non-uniform electric field is represented. The 3D system of the macroscopic pre-breakdown electrohydrodynamic equations is written. Influence of the electric field on the molecule dissociation rate is taken into account. The system includes the Poison equation for electric field potential, the equation of ions formation and the Navier-Stokes equations with electric force. In addition, results of modelling using refined mesh are presented.
To on-board MHD power generation
Authors: Bityurin V A , Bocharov A N , Popov N A , Kuznetsova T N , Baranov D S
Published: December 2021

The electric power generation in on-board MHD generator is considered under conditions of vehicle’s flight in Earth atmosphere. The physical and computational model of on-board MHD power generation is presented. It is shown that electric power of order of 18 – 20 MW (or ∼ 100 W/cm3) can be extracted in ordinary Faraday-type segmented MHD generator. This high level of electric power is achieved at magnetic field about 0.3 – 0.4 tesla and constitutes nearly 9.5% of total enthalpy flux. The main factor limiting the rise of extracted power is a stall of flow due to MHD deceleration.
High-current arc discharge in air
Authors: Bocharov A N , Mareev E A , Popov N A
Published: December 2021

Computational model of high-current pulsed arc discharge in air is proposed. This is, in general, two-dimensional model with taking into account gas dynamics of the discharge channel, real air thermodynamics in a wide range of pressure and temperature, electrodynamics of the discharge including pinch effect, and radiation. The developed model was applied to simulate the electric discharge in air for the currents of 1 - 250 kA and characteristic rise times in 13 - 25 µs, and results of calculations were compared with experimental ones. It was concluded that most of characteristics of the discharge are predicted well. Namely, arc column radius and shock wave position agree well with experimental data for all current amplitudes and rise times considered. Radial distributions of temperature and electron density also satisfactorily agree with experimental data. It was found that pinch effect should be considered for currents higher than 100 kA.
Droplet sweeping to enhance heat transfer during dropwise condensation
Authors: Tancon M , Mirafiori M , Bortolin S , Martucci A , Del Col D
Published: December 2021

It is well known that dropwise condensation (DWC) can achieve heat transfer coefficients (HTCs) up to 5-8 times higher as compared to filmwise condensation (FWC). The interaction between the condensing fluid and the surface defines the condensation mode. Coatings that present low surface energy and high droplet mobility are a solution to promote DWC instead of FWC on metallic substrates. In the present paper, the effect of vapor velocity during DWC has been investigated over a sol-gel coated aluminum surface and a graphene oxide coated copper surface. Heat transfer coefficients and droplets departing radii have been measured at constant saturation temperature and heat flux, with average vapor velocity ranging between 3 m s−1 and 11 m s−1. A recent method developed by the present authors to account for the effect of vapor velocity on the droplet departing radius is here presented. The results of the proposed method, when coupled with the Miljkovic et al. [1] heat transfer model, are compared against experimental data.
Numerical analysis of the solidification process of water used as PCM in a rectangular latent heat thermal storage unit
Authors: Dekhil M A , Simo Tala J V , Bulliard-Sauret O , Bougeard D
Published: December 2021

A numerical analysis of the solidification process of water used as phase change material (PCM) has been carried out in a rectangular latent heat thermal storage unit. The major heat transfer phenomena involved in such a process were numerically characterized using the CFD code Star CCM+. During the solidification process, the flow and heat transfer were analysed through vector field, temperature and solid fractions contours. Quantitative global results such as the temporal evolution of the average temperature of the PCM were also provided during the solidification process. The present study shows that the natural convection plays an important role in heat transfer kinetics during solidification process.
Preliminary thermal characterisation of an active latent thermal energy storage system using PCM
Authors: Egea A , García A , Herrero-Martín R , Pérez-García J
Published: December 2021

Preliminary results of energy charging/discharging processes in a latent thermal energy storage system are reported. A novel design of a rotative scrapper heat exchanger has been studied. Paraffin RT44HC is employed as a phase change material. A Coriolis flowmeter is employed for measuring the mass flow through the prototype, and PT100 temperature sensors are used for measuring the inlet and exit temperature of the heat transfer fluid.
Effect of input parameters on energy requirements of phase change material integrated local heating system
Authors: Shukla Pushpendra Kumar , Kishan Pydi Anil
Published: December 2021

The space heating in residential buildings in winter accounts for a considerable amount of conventional energy. Therefore, improving the performance of space heating systems with the inclusion of renewable energy sources like solar becomes crucial in order to have better occupant’s comfort while reducing energy use. Phase change material (PCM) is one of the best solutions for renewable energy, especially solar, which is intermittently available. PCM stores energy when surplus energy is available and delivers whenever it is required. It is integrated with the current system for energy storage as well as availing heat at a constant temperature. The present study will try to demonstrate the energy-saving by implementing the local heating with a spiral latent heat thermal energy storage system, when only a particular (local) space heating is of interest. In this work, an experimental as well as the numerical study of a dome over a bed was performed. Various heating coil configurations, namely floor coil, roof zig-zag, and roof spiral, were constructed to find the best configuration for the localized space heating. Experiments and simulations with the variable flow rate (0.25, 0.50, and 0.75 m/s) and varying inlet temperatures (55, 60, and 65°C) of the heat transfer fluid were carried out. It was found that the floor coil heating gives better results as compared with the other two. It was also seen that the effect of mass flow rate and inlet temperature was not that much significant after a limit. A temperature difference of 20°C was maintained between the space under consideration with the surrounding room.
Conceptual design and performance evaluation of an innovative high temperature ceramic heat exchanger
Authors: Zavattoni S A , Cornolti L , Arrivabeni E , Puragliesi R , Ortona A , Barbato M C
Published: December 2021

The development of an innovative and highly efficient heat exchanger (HE) solution for gas-gas heat recovery is one of the major objectives of the HYDROSOL-beyond project which aims at enhancing the process efficiency for producing H2 from water dissociation with concentrated sunlight. Because of the very high temperature level of the process (up to 1’400°C), an innovative ceramic HE was proposed with an integrated lattice structure, as secondary surface, to maximize the heat transfer. To assist the design of the HE, a multiscale approach was adopted: a 1D model based on global correlations was developed and a 3D computational fluid dynamics model of the secondary surfaces were generated. The former was applied to assess the performance of the entire HE; while, the latter was exploited to study in detail the thermo-fluid dynamics behavior of a HE core element and to provide the global correlations to be integrated into the 1D model. The effect of the number of lattice layers, located into each channel, on the HE effectiveness was evaluated showing that reducing the height of the secondary structure allows to improve the HE effectiveness from 72% up to 94%.
Composite Decoupling Control of PMSM Based on Extended State Observer
Authors: Yan Hongliang , Geng Yan , Zhai Weizhi
Published: December 2021

In order to solve the problem that the dynamic decoupling performance of the traditional decoupling method is reduced due to the parameter disturbance of permanent magnet synchronous motor (PMSM), a composite decoupling control method based on extended state observer (ESO) is proposed in this paper. In this method, voltage drop across stator resistance, cross coupling terms, internal uncertains and external load torque are taken as disturbances. The disturbance is observed in real time by using the extended state observer and compensated to the output end of the current controller, so as to realize the current decoupling control of the system and achieve the purpose of precise control of the current loop. The results of theoretical analysis show and simulation show that the composite decoupling control strategy based on extended state observer has better dynamic decoupling effect.
Design and Prototype Test of key components of Segmented Ligusticum wallichii Harvester
Authors: Yang Yajun , Liao Min , Su Chao , Zhang Qiang
Published: December 2021

According to the harvest demand of Ligusticum wallichii, a segmented Ligusticum wallichii harvester was designed. The crushing device was set in the front end of tractor and the vibrating harvester was mounted in the rear end of tractor. Firstly, the strength test of Ligusticum wallichii stalks was carried out, and the basic parameters of the crushing device were determined. The results showed that the minimum required speed of the crushing device was 3880r/min. Secondly, the vibration structure was modeled and analyzed by vector equation, and the vibration structure was simulated and analyzed by ADAMS, and the parameters of the vibration structure were determined. The results showed that when the crank angle was 22~100°, the Ligusticum wallichii-soil mixture was thrown backward away from the vibration steel bar, and throw away distance was 88.42mm. Finally, the field prototype test was carried out. During the test, the crushing device could crush the stems of Ligusticum wallichii normally. The rotational speed was measured at 4020r/min. The obvious rate, loss rate and damage rate of Ligusticum wallichii stem were calculated. The stems obvious rate was 95%, loss rate was 4.5% and damage rate was 0.4%, which met the harvest requirements of Ligusticum wallichii.
Micro pin header defect detection system based on OpenCV
Authors: Yang Houcheng , Yan Yinxin , Yu Zhangsi , Ning Zhang
Published: December 2021

In order to solve the problems of low detection efficiency and large detection error in the process of manual quality inspection, a full-automatic defect detection system is built. The system uses an industrial camera, selects a suitable light source for image acquisition, uses the open source OpenCV visual library for image processing and defect contour recognition, and sets the screening conditions for unqualified products. The system can detect whether the needle arrangement has defects in real time and classify them according to different defect categories, It can greatly improve the detection efficiency of needle arranging production enterprises. Through a large number of experimental tests, the detection success rate can reach 98.67%, which shows that the system is feasible.
Design of Refrigeration Control System for Parallel Refrigerator Unit Based on PLC
Authors: Tian Jinyu , Feng Lijie , Liu Hai
Published: December 2021

In order to improve the refrigeration control efficiency and reduce the temperature fluctuation in the cold storage. In this paper, the refrigeration control system of the parallel unit of the cold storage is designed based on the upper and lower computers. The lower computer uses PLC to monitor the field parameters and control the execution of the field equipment. The upper computer uses HMI to realize the real-time monitoring, parameter display and alarm function during the operation of the cold storage, and uses the slide valve to adjust the energy of the compressor. The results show that the control system runs reliably and meets the control requirements of large cold storage.
A Data Mining Method For Improving the Prediction Of Bioinformatics Data
Authors: Wang Tong , Tan Wenan , Xue Jianxin
Published: December 2021

The composition of proteins nearly correlated with its function. Therefore, it is very ungently important to discuss a method that can automatically forecast protein structure. The fusion encoding method of PseAA and DC was adopted to describe the protein features. Using this encoding method to express protein sequences will produce higher dimensional feature vectors. This paper uses the algorithm of predigesting the characteristic dimension of proteins. By extracting significant feature vectors from the primitive feature vectors, eigenvectors with high dimensions are changed to eigenvectors with low dimensions. The experimental method of jackknife test is adopted. The consequences indicate that the arithmetic put forwarded here is appropriate for identifying whether the given protein is a homo-oligomer or a hetero-oligomer.
Artificial Thermal Decay: Influence of Mineralogy and Microstructure of Sandstone, Calcarenite and Marble
Authors: Aquino Andrea , Pagnotta Stefano , Lezzerini Marco
Published: December 2021

Within a major framework of studies around artificial weathering and its effects on different lithotypes, in this work we study the effects of thermal stresses after artificial thermal decay on different types of stones used in historical buildings: a sandstone, a calcarenite and a marble. The sandstone belongs to the so called “Macigno” Formation and mainly outcrops along the northern Apennine (North Western Tuscany) and it has been widely used around Tuscany for building purposes (e.g., in Florence, Lucca, Pisa, Pistoia, etc.); the analysed calcarenite (Gravina) comes from the surrounding of Matera Town and has been deeply used for the construction of the ancient buildings of the town itself; and the marble comes from the Carrara marble district (Northern Tuscany), a highly used stone throughout the centuries as ornamental stone. All these types of stone for their physical and mechanical properties, and aesthetic appearance, have been extensively used as both ornamental stones and as construction materials. To reproduce a plausible effect of natural thermal decay of the stones due to day-to-night and season-to-season fluctuations, we subjected the samples to artificial thermal decay. We carried out different thermal cycles on the samples by using a stove at 150°C and a muffle furnace at 300°C and 450°C. We analysed the physical and mechanical properties before and after each cycle to compare and evaluate the effects of thermal stresses on the stones. Among the different analyses: mass and volume measurements, water absorption tests, mercury intrusion porosimetry, thin-section observations and determination of chromatic alterations through image analysis and Munsell charts method. It was then possible to evaluate the influence of both mineralogy and microstructures on thermal decay of the studied stones (variations in fabric and modifications on physical and mechanical properties).
Allelopathic potential of siam weed (Chromolaena odorata L.) extract for enhancing soybean productivity
Authors: Hasanuddin H , Hafsah S , Erida G , Marliah A , Bahri H , Zainabun  , Bobihoe J , Aryani D S
Published: December 2021

Many tropical invasive species have strong allelopathic effects. Chromolaena odorata is reported to have the best potential to act as bioherbicide against several weeds on crops. This research was conducted in May-September 2019 to evaluate the efficacy of C. odorata extract on soybean plant. This study employed Randomized Block Design (RBD) Factorial with two factors. The first factor was 4 different doses of C. odorata extracts: 0, 8, 16 and 24 tons ha−1. The second factor was 3 different times of application: 0, 7 and 14 days after planting. Variables observed were number of pods per plant, seed weight per plant, weight of 100 seeds and dry seed yield. The findings indicated that the extract did have effect on seed weight per plant, weight of 100 seeds and yield of dry seeds. The application of extract 16-24 tons ha−1 has improved the seed weight per plant, weight of 100 seeds, and yield of dry seeds. There was no interaction between siam weed extract and time of application in all variables observed.