bluuebunny/crossref_metadata_2025 huggingface dataset:
Self-consistent description of the halo nature of 31Ne with continuum and pairing correlations
Authors: Zhang S S , Zhong S Y , Shao B , Smith M S
Published: December 2021

Background: A relativistic structure model has previously been used to predict a halo structure for 31Ne (Zhang et al 2014 Phys. Lett. B 730 30), consistent with halo signatures from measured reaction cross sections of Ne isotopes bombarding Carbon targets. However, previous attempts to calculate those cross sections with reaction models were missing contributions from resonances and pairing correlations in their structure input. Purpose: Use a reaction model with our relativistic fully microscopic structure model input to predict these cross sections and momentum distributions and analyze for possible halo signatures. Methods: Structure input for exotic Ne isotopes were obtained via the analytical continuation of the coupling constant (ACCC) method based on the relativistic mean field (RMF) theory with Bardeen–Cooper–Schrieffer (BCS) pairing approximation, the RAB approach. Total reaction cross sections, one-neutron removal cross sections, and momentum distributions of breakup reaction products were calculated with a Glauber model using our relativistic structure input. Results: Our predictions of total reaction and one-neutron removal cross sections of 31Ne on a Carbon target were significantly enhanced compared with those of neighboring Neon isotopes, agreeing with measurements at 240 MeV/nucleon and consistent with a single neutron halo. Furthermore, our calculations of the inclusive longitudinal momentum distribution of the 30Ne and valence neutron residues from the 31Ne breakup reaction indicate a dilute density distribution in coordinate space, another halo signature. Conclusions: We give a full description of the halo nature of 31Ne that includes a self-consistent use of pairing and continuum contributions that makes predictions consistent with reaction cross section measurements. This approach can be utilized to determine the halo structure of other exotic nuclei.
Topological phase and thermoelectric properties of bialkali bismuthide compounds (Na, K)2RbBi from first-principles
Authors: Yalameha Shahram , Nourbakhsh Zahra , Vashaee Daryoosh
Published: December 2021

We report the topological phase and thermoelectric properties of bialkali bismuthide compounds (Na, K)2RbBi, as yet hypothetical. The topological phase transitions of these compounds under hydrostatic pressure are investigated. The calculated topological surface states and Z
2 topological index confirm the nontrivial topological phase. The electronic properties and transport coefficients are obtained using the density functional theory combined with the Boltzmann transport equation. The relaxation times are determined using the deformation potential theory to calculate the electronic thermal and electrical conductivity. The calculated mode Grüneisen parameters are substantial, indicating strong anharmonic acoustic phonons scattering, which results in an exceptionally low lattice thermal conductivity. These compounds also have a favorable power factor leading to a relatively flat p-type figure-of-merit over a broad temperature range. Furthermore, the mechanical properties and phonon band dispersions show that these structures are mechanically and dynamically stable. Therefore, they offer excellent candidates for practical applications over a wide range of temperatures.
Material–structure integrated design for ultra-broadband all-dielectric metamaterial absorber
Authors: Peng Mengyue , Qin Faxiang , Zhou Liping , Wei Huijie , Zhu Zihao , Shen Xiaopeng
Published: December 2021

Material and structure are the essential elements of all-dielectric metamaterials. Structure design for specific dielectric materials has been studied while the contribution of material and synergistic effect of material and structure have been overlooked in the past years. Herein, we propose a material–structure integrated design (MSID) methodology for all-dielectric metamaterials, increasing the degree of freedom in the metamaterial design, to comprehensively optimize microwave absorption performance and further investigate the contribution of material and structure to absorption. A dielectric metamaterial absorber with an ultra-broadband absorption from 5.3 to 18.0 GHz is realized. Theoretical calculation and numerical simulation demonstrate that the symphony of material and structure excites multiple resonance modes encompassing quarter-wavelength interference cancellation, spoof surface plasmon polariton mode, dielectric resonance mode and grating mode, which is essential to afford the desirable absorption performance. This work highlights the superiority of coupling of material and structure and provides an effective design and optimization strategy for all-dielectric metamaterial absorbers.
An improved posture evaluation method for cylindrical intersecting holes on large aerospace components based on monocular vision
Authors: Deng Zhengping , Sun Lili , Hao Fei , Zhang Bo , He Yujie
Published: December 2021

Cylindrical intersecting holes (CIHs) are common connection and location reference features in the assembly of large aerospace structures such as missiles and rocket cabins. The posture accuracy of assembly holes significantly impacts the relative position accuracy of joined parts and the fatigue strength of the finished product. At present, monocular vision measurement is widely used in the automatic drilling of assembly holes due to its integration simplicity and lower cost, but in most research, only the front face edge of the hole is used in the measurement model, and the hole end surface is usually assumed to be plane, which inevitably leads to precision loss. In this research, a novel posture measurement method for CIHs is proposed. Firstly, by introducing an ambiguity removal strategy, a coarse posture estimation method based on the plane hypothesis of the two end surfaces of CIHs is suggested. Secondly, considering that there is no simple explicit expression for a CIH’s edge, it is difficult to adopt the conventional model projection-based pose optimization method. In view of this, the 3D points corresponding to the edge pixels of the CIHs’ image are derived, and the pose optimization model is established by minimizing the deviations between the distance from the points to the CIHs’ axis and the hole radius. Moreover, to better control the direction parameters of CIHs during the global optimization process, the approximately perpendicular and intersection constraints between the CIHs’ axis and cylindrical component axis are involved in the solution. The effectiveness of the posture measurement method is verified by comparative experiments with current methods and coordinate measuring machine, which demonstrates improvements in both measurement accuracy and robustness.
The chiral coating on an achiral nanostructure by the secondary effect in focused ion beam induced deposition
Authors: Fang Chen , Chai Qing , Chen Ye , Xing Yan , Zhou Zaifa
Published: December 2021

Optical metamaterials are widely used in electromagnetic wave modulation due to their sub-wavelength feature sizes. In this paper, a method to plate an achiral nanopillar array with chiral coating by the secondary effect in focused ion beam induced deposition is proposed. Guided by the pattern defined in a bitmap with variable residence time, the beam scan strategy suppresses the interaction between adjacent nanostructures. A uniform chiral coating is formed on the target nanostructure without affecting the adjacent nanostructure, under carefully selected beam parameters and the rotation angle of the sample stage. Energy dispersive x-ray spectroscopy results show that the chiral film has high purity metal, which enables the generation of localized surface plasmon resonances and causes the circular dichroism (CD) under circularly polarized light illumination. Finally, the tailorable CD spectrum of the coated array is verified by the finite difference time domain method.
Weakly-supervised lesion analysis with a CNN-based framework for COVID-19
Authors: Wu Kaichao , Jelfs Beth , Ma Xiangyuan , Ke Ruitian , Tan Xuerui , Fang Qiang
Published: December 2021

Objective. Lesions of COVID-19 can be clearly visualized using chest CT images, and hence provide valuable evidence for clinicians when making a diagnosis. However, due to the variety of COVID-19 lesions and the complexity of the manual delineation procedure, automatic analysis of lesions with unknown and diverse types from a CT image remains a challenging task. In this paper we propose a weakly-supervised framework for this task requiring only a series of normal and abnormal CT images without the need for annotations of the specific locations and types of lesions. Approach. A deep learning-based diagnosis branch is employed for classification of the CT image and then a lesion identification branch is leveraged to capture multiple types of lesions. Main Results. Our framework is verified on publicly available datasets and CT data collected from 13 patients of the First Affiliated Hospital of Shantou University Medical College, China. The results show that the proposed framework can achieve state-of-the-art diagnosis prediction, and the extracted lesion features are capable of distinguishing between lesions showing ground glass opacity and consolidation. Significance. The proposed approach integrates COVID-19 positive diagnosis and lesion analysis into a unified framework without extra pixel-wise supervision. Further exploration also demonstrates that this framework has the potential to discover lesion types that have not been reported and can potentially be generalized to lesion detection of other chest-based diseases.
Building a precise machine-specific time structure of the spot and energy delivery model for a cyclotron-based proton therapy system
Authors: Zhao Lewei , Liu Gang , Zheng Weili , Shen Jiajian , Lee Andrew , Yan Di , Deraniyagala Rohan , Stevens Craig , Li Xiaoqiang , Tang Shikui , Ding Xuanfeng
Published: December 2021

Objective. We proposed an experimental approach to build a precise machine-specific beam delivery time (BDT) prediction and delivery sequence model for standard, volumetric, and layer repainting delivery based on a cyclotron accelerator system. Approach. Test fields and clinical treatment plans’ log files were used to experimentally derive three main beam delivery parameters that impacted BDT: energy layer switching time (ELST), spot switching time, and spot drill time. This derived machine-specific model includes standard, volumetric, and layer repainting delivery sequences. A total of 103 clinical treatment fields were used to validate the model. Main results. The study found that ELST is not stochastic in this specific machine. Instead, it is actually the data transmission time or energy selection time, whichever takes longer. The validation showed that the accuracy of each component of the BDT matches well between machine log files and the model’s prediction. The average total BDT was about (−0.74 ± 3.33)% difference compared to the actual treatment log files, which is improved from the current commercial proton therapy system’s prediction (67.22%±26.19%). Significance. An accurate BDT prediction and delivery sequence model was established for an cyclotron-based proton therapy system IBA ProteusPLUS®. Most institutions could adopt this method to build a machine-specific model for their own proton system.
An effort to enhance the threshold contrast index of gas Cherenkov detectors
Authors: Guan Xingyin , Sheng Liang , Hu Huasi , Chen Xiang
Published: December 2021

Because gas Cherenkov detectors can exclude most interference from secondary gamma rays, they have been the primary candidate for detection of fusion gamma rays. It is a goal worthy of long-term efforts to enhance the threshold contrast index used for evaluating the ability of gas Cherenkov detectors to exclude below-threshold interference. This paper presents a way of enhancing the index through ultraviolet reflection selective suppression of scintillation signals in the detectors. Both theoretical estimation and experimental verification demonstrate that the threshold contrast index can be enhanced by 5.5 times after applying this method. This provides possibilities of obtaining better fusion gamma-ray detection waveforms and higher confidence diagnostic information.
A simple and green photoreduction approach for synthesis of Au/g-C3N4 hybrid nanocomposites with high solar light photocatalytic activity
Authors: Linh Pham Hoai , Chung Pham Do , Oanh Le Thi Mai , Van Khien Nguyen , Bach Ta Ngoc , Thai Le Tien , Hang Lam Thi , Hung Nguyen Manh , Van Thanh Dang
Published: December 2021

In this study, we developed a green and easy to scale up approach for producing Au/g-C3N4 (Au/GCN) hybrid plasmonic photocatalyst without using the chemical reducing agents via the growing of Au nanoparticles (Au NPs) on the surface of GCN nanosheets under the photo-reduction of ultraviolet (UV)-radiation. Different characterization techniques were conducted for investigating the structure, morphology, surface chemistry and optical properties of the as-prepared catalysts. The scanning electron microscope image shows that the homogeneous Au NPs anchored on the surface of the GCN nanosheet increased with the UV illumination time. The x-ray photoelectron spectroscopy results prove the coexistence of GCN nanosheets with heptazine heterocyclic ring (C6N7) units and Au NPs in the Au/GCN. The photoluminescence intensity decreased sharply with the time of UV irradiation, indicating that the recombination rate of photogenerated electron–hole recombination decreased. The photocatalytic activity of the hybrid catalysts was evaluated by degrading rhodamine B (RhB) under simulated sunlight irradiation. The results show that the Au/GCN photocatalyst exhibits superior sunlight photocatalytic activity than that of bare GCN. The 6 h irradiated fabricating sample exhibited the strongest photocatalytic activity, completely decomposing the 10 ppm RhB in 30 min of irradiation. This report can provide the design of a simple and green synthesis method for the highly active Au/GCN photocatalyst.
Non-Hermiticity-induced reentrant localization in a quasiperiodic lattice
Authors: Wu Chaohua , Fan Jingtao , Chen Gang , Jia Suotang
Published: December 2021

In this paper, we demonstrate that the non-Hermiticity can induce reentrant localization in a generalized quasiperiodic lattice. Specifically, by considering a nonreciprocal dimerized lattice with staggered quasiperiodic disorder, we find that the localization transition can appear twice by increasing the disorder strength. We also unravel a multi-complex-real eigenenergy transition, whose transition points coincide with those in the localization phase transitions. Moreover, the impacts of boundary conditions on the localization properties have been clarified. Finally, we study the wavepacket dynamics in different parameter regimes, which offers an experimentally feasible route to detect the reentrant localization.
Modulational instability and rogue waves in one-dimensional nonlinear acoustic metamaterials: case of diatomic model
Authors: Joseph Mora , Justin Mibaile , David Vroumsia , Azakine Sindanne Sylvere , Betchewe Gambo
Published: December 2021

In this paper, by means of the expanded Taylor series and Lindstedt-Poincaré perturbation methods, the coupled nonlinear Schrödinger equations (CNLSE) modeling the propagation of acoustic waves in acoustic metamaterial is obtained. Using these equations, the Modulational Instability (MI) phenomenon is observed in disturbance mode. Manakov integrable system is derived with suitable parameters and we shown that the Rogue Waves (RWs) can propagate diatomic acoustic metamaterials.
Research on sensitivity analysis and traveling wave solutions of the (4 + 1)-dimensional nonlinear Fokas equation via three different techniques
Authors: Kaplan Melike , Akbulut Arzu , Raza Nauman
Published: December 2021

In the current manuscript, (4 + 1) dimensional Fokas nonlinear equation is considered to obtain traveling wave solutions. Three renowned analytical techniques, namely the generalized Kudryashov method (GKM), the modified extended tanh technique, exponential rational function method (ERFM) are applied to analyze the considered model. Distinct structures of solutions are successfully obtained. The graphical representation of the acquired results is displayed to demonstrate the behavior of dynamics of the nonlinear Fokas equation. Finally, the proposed equation is subjected to a sensitivity analysis.
On the possible influence of solar 11-year cycle on a climate of Southern Fennoscandia
Authors: Ogurtsov M G
Published: December 2021

Three proxy records of Southern Fennoscandia climate variability were analyzed. It was found that their decadal variations correlate significantly (p=0.961-0.993) with a quasi 11-year solar cycle of Schwabe during AD 1706-1990. But two proxy records have significant decadal correlation with the index of summer North-Atlantic Oscillation (SNAO) as well. Taking into account that decadal periodicity in the SNAO index also has some correlation with the solar cycle of Schwabe, the revealed relations could be a result of influence of solar activity on the Southern Fennoscandian climate realizing by the complicated way. Possible causes of such complexity are discussed.
Solar coronal rotation according to soft X-ray solar radiation during the 22nd, 23rd, and 24th solar cycles
Authors: Dmitriev P B
Published: December 2021

Using the developed method of combining numerous scattered time series of the same type of measurements into a single weighted average series, according to the data of the GOES series satellites, a single series of daily data was synthesized during the 22nd, 23rd and 24th solar cycles (1986 – 2019 years). The flare and background components were distinguished from this data series, which were investigated by means the method of constructing a composite spectral periodogram for the presence of quasiperiodic oscillations at various solar cycles. Some of these found quasiperiods may be explained by both synodic and sidereal rotation of the Sun, while others coincide with the average lifetime of the solar atmosphere active formations such as the sunspot groups and the facular plages. Special attention was paid to the study of the change over time the revealed quasiperiodic values over the course of solar cycles by calculating the sample normalized spectral density of the analyzed data in a sliding time window with a value of up to two years. Based on the revealed quasiperiodic value changes presented on the dynamic diagrams, it can be concluded that the differential rotation of the solar corona is unstable and manifests itself only at certain stages of the development and existence of solar activity cycles.
Generation of ultrashort pulses in the THz frequency range
Authors: Oparina Yu S , Savilov A V
Published: December 2021

There are results for the spontaneous coherent super-radiative undulator emission in the terahertz frequency range from a short (as compared to the wavelength of the radiated wave) dense electron bunch. If the group velocity of the wave is close to the bunch velocity, this is a process of spontaneous radiation followed by amplification of a single wave cycle. Despite the Coulomb repulsion of electrons inside the bunch, its compactness is provided by the compression of the bunch under the action of its own radiation fields. As a result, formation of an ultra-short (several cycles long) powerful wave packet occurs when the bunch moves through several undulator periods with high (∼20% in optimized systems) efficiency of extraction of the electron energy and high intensity (∼ 100 MV/m) of the peak wave field.
Kelvin-probe microscopy as a technique of estimation of the charge traps saturation time
Authors: Dementev P A , Dementeva E V
Published: December 2021

In this work, a method for estimating the saturation time of traps in dielectric layers based on the KPM is proposed. Using hafnium oxide layers as an example, it is shown that when charging with a series of points with different durations, a different dependence of the residual potential on time is observed. It is assumed that this technique makes it possible to evaluate the performance of devices based on dielectric layers.
Synthesis and structural characterization of Fe1-xMexBO3 (Me = Al, Sc) single crystals
Authors: Mogilenec Yu , Seleznyova K , Yagupov S , Seleznev K , Nauhatsky I , Maksimova E , Strugatsky M
Published: December 2021

Fe1-xMexBO3 (Me = Al, Sc) single crystals have been synthesized by flux growth technique using B2O3-PbO-PbF2 solvent and approach of identical synthesis conditions. The contents of the diamagnetic ions Me in the initial charge of both compositions were equal, xcharge=0.05. The exact contents and crystal lattice parameters of the synthesized crystals were determined by X-ray fluorescence analysis and X-ray diffraction, respectively.
Interaction of sulfur with impurities in bcc iron
Authors: Verkhovykh A V , Mirzoev A A , Okishev Yu K , Dyuryagina N S
Published: December 2021

In this work, the modeling of the sulfur interaction with substitutional impurities (Mn, P) and interstitial (C) has been carried out. All calculations were performed using the density functional theory in the WIEN2k software package. For the first two coordination spheres, there is a strong repulsion between carbon and sulfur, but in the third relative position, a slight attraction arises between the atoms. When sulfur interacts with manganese, attraction occurs only for the first coordination sphere, while the dissolution energy of both manganese and sulfur decreases. In the case of the S-P interaction, the binding energy is negative, and the dissolution energy of both sulfur and phosphorus decreases for all configurations, although the distance between phosphorus and sulfur increases. It can be assumed that the presence of phosphorus leads to the accumulation of sulfur in the material.
On quantum analogue of instable oscillating states of an inverted oscillator in external poly-harmonic field
Authors: Chistyakov V
Published: December 2021

Nonstationary Schroedinger equation (NSE) is solved analytically and numerically to study a phenomenon of dynamical stabilization of the inverted oscillator driven by polyharmonic in time and spatially uniform force with specially chosen phase shifts. It is shown that for Gaussian wave packet asymptotically fitting the initial condition (IC) it occurs temporary delay of the packet center about top of the parabolic potential for about 2 fundamental time periods followed by the center bifurcation.
The dependence of surface morphology on the growth temperature of the Pb0.7Sn0.3Te/Si(111) topological insulator thin films
Authors: Kaveev A K , Bondarenko D N , Tereshchenko O E
Published: December 2021

The possibility of epitaxial growth of Pb0.7Sn0.3Te crystalline topological insulator films on the Si(111) surface was shown and epitaxial relations were found. It was shown that, depending on the growth temperature, it is possible to control not only the character of the morphology, but also, to a significant extent, the smoothness of the epitaxial layer surface, which is extremely important for further transport measurements of the films. Analysis of the grown films surface morphology made it possible to establish the average value of the height and lateral size of the terraces and islands forming Pb0.7Sn0.3Te surface.
Mechanical frictional scanning probe lithography of TMDCs
Authors: Borodin B R , Benimetskiy F A , Alekseev P A
Published: December 2021

In this work, we investigate mechanical scanning probe lithography (SPL) of thick MoSe2 flakes. The conventional technique faces difficulties in processing the thick samples due to cantilever twisting that leads to the growth of a number of defects and artifacts that decrease spatial resolution. In course of this work, we proposed the approach of frictional-SPL based on small pressure force and many repetitions of lithographic patterns. This approach allows to avoid the formation of remarkable defects and maintain high spatial resolution. By frictional-SPL, we processed thick MoSe2 flakes (up to 40 nm thick) with the highest resolution down to 20 nm. The results of this work show that frictional-SPL is an effective method of resistless lithography suitable for fabricating nanodevices based on transition metal dichalcogenides (TMDC) materials.
Thermal conductivity of PCM materials based on a composite consisting of n-alkane and nanoscale additives
Authors: Borisov A K , Egorov V M , Marikhin V A , Myasnikova L P
Published: December 2021

Composites based on n-alkane and nanoscale additives were investigated to determine the efficiency of heat transfer during phase transitions in phase change materials. It was found that the thermal conductivity of composite materials is several times higher than the thermal conductivity of the initial n-alkane. The observed effect is due to the specificity of the supramolecular nanostructure of the composite, which differs from the supramolecular structure of the nonadecane.
Study of elastic deformations in tapered nanowires
Authors: Dunaevskiy M S , Alekseev P A
Published: December 2021

In this work, the calculation of the values of elastic deformations and stresses arising in tapered nanowires is carried out. It was found that in tapered nanowires the magnitude of deformations changes from the base of the nanowire to its tip not linearly (as would be the case in cylindrical nanowires), but in a more complex manner. The ranges of conicity angles at which an extended region of increased stresses can appear in tapered nanowires have been determined.
Investigation of HIT solar cells low frequency noise characteristics
Authors: Ermachikhin A V , Vorobyov Y V , Trusov E P , Litvinov V G
Published: December 2021

The effect of solar cell fragment annealing on its noise characteristics is shown. The calculated difference in relaxation times arising from the change in noise after annealing was 30%. Measurements of noise characteristics in the dark and under illumination with a red laser with different radiation power were carried out. Close to linear dependences of noise power reduction with increasing radiation power were obtained.
Study of the titanium VT1-0 surface degradation after cyclic loading in different structural states, including ones when coatings are formed by Micro-Arc Oxidation
Authors: Narykova M V , Kadomtsev A G , Betekhtin V I , Kolobov Yu R , Dvorak J , Sklenicka V
Published: December 2021

This article considers the results of the study of the titanium VT1-0 surface degradation (Grade-4 equivalent) for recrystallized- and ultrafine-grained states after fatigue testing. Comparative analysis of peculiarities of the titanium samples degradation was performed after coating formation by Micro-Arc Oxidation. It was found, that the coating formed by Micro-Arc Oxidation shows different degradation behaviors for recrystallized and ultrafine-grained states
Effect of heat treatment on the galvanomagnetic properties of bulk nanostructured samples of Bi85Sb15 solid solution
Authors: Tagiyev M M , Abdinova G D , Abdullayeva I A
Published: December 2021

Extruded bulk nanostructured samples of Bi85Sb15 solid solution from particles with average sizes ∼ 2.105; 950; 650; 380; 30 and 15 nm were obtained and investigated their galvanomagnetic properties in the range of ∼ 77-300 K. Were investigated samples that have not passed heat treatment, and the same samples that have passed heat treatment. It was found that the electrical and thermal properties of Bi85Sb15 solid solution samples significantly depend on the size of nanoparticles and post-extrusion heat treatment. Heat treatment leads to a decrease in the concentration of current carriers and to an increase in the mobility of current carriers and the total thermal conductivity of the samples under study, which is mainly due to the electronic component of thermal conductivity. The change in thermal parameters is satisfactorily explained by changes in occurring in the structure of samples during extrusion and heat treatment and correlates well with changes in the electrical parameters of these processes.
Multiphoton intersubband transitions in an armchair graphene nanoribbon
Authors: Monozon B S , Fedorova T A , Schmelcher P
Published: December 2021

We present an analytical approach to the problem of the interband transitions in an armchair graphene nanoribbon (AGNR), exposed to the time-periodic electric field of strong light wave, polarized parallel to the ribbon axis. The two-dimensional Dirac equation for the massless electron subject to the ribbon confinement is employed. In the resonant approximation the probability of the transitions between the valence and conduction size-quantized subbands are calculated in an explicit form. We trace the dependencies of the Rabi frequency for these transitions on the ribbon width and electric field strength for both the multiphoton-assisted and tunneling regimes relevant to the fast oscillating and practically constant electric field, respectively. Estimates of the expected experimental values for the typically employed AGNR and laser technique facilities show that the Rabi oscillations can be observed under laboratory conditions. The data, corresponding to the intersubband tunneling, makes the AGNR a 1D condensed matter analog, in which the quantum electrodynamic vacuum decay can be detected by the employment of the attainable electric fields.
Average SWCNT bundle length estimated by resistance measurement
Authors: Mitin D M , Vorobyev A.A. , Berdnikov Y S , Mozharov A M , Nasibulin A G , Mukhin I S
Published: December 2021

The length of single-walled carbon nanotubes (SWCNTs) affects the optoelectronic and mechanical properties of macroscopic SWCNT layers. Modern methods are capable to measure the length of short nanotubes, and also require complex sample preparation procedures. In this work we show that the average length of SWCNTs can be estimated by measuring the resistance of randomly oriented SWCNTs array. We observe the change in the slope of the resistance dependence on the distance between the contacts with the interval between 100 and 200 μm. The change of resistance slope indicates a change in the path of current flow through the SWCNT. The change in the conduction path can be associated with the “effective bundle length”, which should be related to the average nanotube length. Thus, we have demonstrated a simple and quick technique to measure SWCNT bundle length, which can be used in-situ and does not require special sample preparation.
144Ce - 144Pr spectrum measurement with 4π semiconductor β-spectrometer
Authors: Alekseev I E , Bakhlanov S V , Derbin A V , Drachnev I S , Kotina I M , Lomskaya I S , Mikulich M S , Muratova V N , Niyazova N V , Semenov D A , Trushin M V , Unzhakov E V
Published: December 2021

Precision β-spectra measurement always had a great importance in some fundamental physics problems including neutrino physics. Magnetic and electrostatic spectrometers have high resolution, but at the same time usage of such kinds of equipment involves the size and cost issues. Since electron mean free path at the energy of 3 MeV (which is basically the maximum energy of a β-transition for the long-lived nuclei) does not exceed 2 g/crn2
, electron registration could be effectively performed with the solid state scintillators and semiconductors. A strong probability of backscattering from detector surface is present in case of semiconductor detectors and is dependent upon the detector material. Such problem can be solved with 4π geometry detector development, which fully covers the radioactive source and is able to register the backscattered electrons. In this work we present the newly developed technology of 4π geometry β-spectrometer based on two semiconductor detectors. This spectrometer was used for measurement of the 144Ce - 144Pr spectrum, that is the perspective anti-neutrino source due to endpoint energy at 3 MeV and can be used for the sterile neutrino search experiments. The form-factor parameters that were obtained are: C(W) = 1 + (-0.02877 ± 0.00028)W + (-0.11722 ± 0.00297)W-1. The measurement accuracy was sufficiently enhanced with respect to the previous results.
Spectral studies of bismuth-containing pyrochlores
Authors: Nekipelov S V , Zhuk N A , Petrova O V , Sivkov D V , Bakina K A , Bogachuk D V , Skandakov R A , Sivkov V N
Published: December 2021

Thermal stable solid solutions of titanates, niobates, and tantalates of bismuth with a pyrochlore structure doped with 3d-metal atoms were studied using XPS and NEXAFS spectroscopy. Based on spectral studies, it was shown that the manganese, cobalt, nickel and copper atoms in these solid solutions have mainly charge state +2 and iron atoms – charge state +3.
A study of the influence of copper sulfate on the spectral properties of common buckwheat (Fagopyrum esculentum)
Authors: Goryainov V S , Buznikov A A
Published: December 2021

The influence of pollutants on the spectral properties of common buckwheat (Fagopyrum esculentum) has been investigated insufficiently, compared to the cereals from the Poaceae family. A two-stage spectral survey has been carried out, growing common buckwheat in containers with set concentrations of copper(II) sulfate in soil both in laboratory conditions and in the open air. Spectral distributions of diffuse reflectance of the plants were registered in the range of 400 – 1100 nm, and spectral indices were calculated, using wavelengths corresponding to spectral features of plant pigments. Simultaneously, digital photos were taken to account for projective cover of the plants. Four spectral indices were found to depend quantitatively on pollutant concentration, three of them taking extreme values at the time of maximal projective cover. When growing buckwheat in the open air, lower temperatures and higher irradiation lead to closer values of spectral indices corresponding to different copper concentration, than in laboratory conditions. The results show the usability of common buckwheat as an indicator of soil pollution by copper.
Interaction of an electromagnetic E-wave with a thin conducting film between two dielectric media in the case of an anisotropic isoenergetic surface and impurity scattering
Authors: Kuznetsova I A , Romanov D N , Yushkanov A A
Published: December 2021

The coefficients of reflection, transmission and absorption are calculated in the framework of the kinetic approach, when an electromagnetic E-wave interacts with a thin conducting film located between two dielectric media. To account for the surface scattering of charge carriers is used a model of mirror-diffuse boundary conditions, assuming that the specularity coefficients of the upper and lower surfaces of the film differ from each other. The electromagnetic wave falls on the upper surface of the film at an arbitrary angle. The case of an anisotropic isoenergetic surface of a conductor having the form of a three-axis ellipsoid, one of the main axes of which is parallel to the magnetic field strength of the wave, and the other is perpendicular to the film surfaces, is considered. The impurity scattering of electrons (holes) is dominated in the volume of the conductor. The dependence of the absorption coefficient on the parameters of the isoenergetic surface of the conductor is analyzed.
Development of a method for quantitative comparison of the luminance of self-glowing crystals – the basic elements of a low current source
Authors: Mjagkih M K , Dementev P A , Zamoryanskaya M V
Published: December 2021

This work is devoted to the development of a method for the quantitative comparison of the luminosity of weakly luminous samples, such as self-glowing crystals. A self-glowing crystal is an efficient scintillator, whose self-luminescence is due to the decay of a radioactive isotope introduced into the crystal matrix during its growth. Such crystals can be used as low current sources with a service life of 50 years or more. This technique takes into account the luminescence spectra of the samples under study, the spectral functions of the spectrometer and photodetector. Information on the luminescence spectra of samples can be obtained based on their cathodoluminescence spectra. Thanks to the calculations performed according to this technique, it becomes possible to estimate the optical radiation power of a self-glowing crystal, which can be converted into an electric current using a photodiode. Also, the proposed technique can be applied to assess the luminosities of any materials under the influence of radioactive radiation.
Spectral analysis of juvenile dentin biomaterials
Authors: Timchenko P E , Timchenko E V , Volova L T , Frolov O O , Vlasov M Y , Shipko S S
Published: December 2021

The experiments in optical evaluation of biomaterials taken from juvenile dentin have been made using the Raman spectroscopy method. It was shown that juvenile teeth lose their mineral components and preserve organic components in the process of demineralization with the use of hydrochloric acid.
Nonstationary holographic currents in a β-Ga2O3 crystal at wavelength λ = 457 nm
Authors: Bryushinin M A , Sokolov I A
Published: December 2021

We report the excitation of nonstationary holographic currents in a monoclinic gallium oxide crystal. Although the crystal is almost transparent and insulating for a visible light, the dynamic space-charge gratings are recorded and holographic currents are observed for both the diffusion and drift modes. The anisotropy along the [100] and [010] directions is revealed, namely, there is a small difference in the transport parameters and a pronounced polarization dependence of the signal. The crystal’s photoconductivity, responsivity and diffusion length of electrons are estimated for the light wavelength λ = 457 nm.
Determination of the refractive index profile and surface topography of optically smooth objects using interference of optical vortices
Authors: Sokolenko B V , Shostka N V , Poletaev D A
Published: December 2021

In this paper, we present the results of the propagational dynamics of vortex beams in the scope of their possible applications for interferometric non-contact robust and precision optical surface profilometry with nanoscale longitudinal resolution. The result of coaxial superposition of the reference plane wave with singly charged vortex beams represents a dynamically changing intensity distribution. The nature of this changes, namely, rotational effects of intensity zeros, allows to determine directly the optical path difference which is introduced by the surfaces and internal structure of test object. We have proposed the experimental setup for examination of reflecting and transmitting objects.
Influence of the aluminum content on the luminescent and electronic properties of β-Ga2O3
Authors: Dementeva E V , Dementev P A , Kremleva A V , Panov D Y , Romanov A E , Bugrov V E , Zamoryanskaya M V
Published: December 2021

In this work, we investigated bulk β-Ga2O3samples grown by the Czochralski method on Al2O3and β-Ga2O3seeds. The elemental composition of the samples and its effect on the luminescent and electrophysical properties of the samples were determined. The Kelvin probe microscopy was used to study the processes of localization and dissipation of charges in the samples. It was shown that in a β-Ga2O3sample grown on an Al2O3seed, the characteristic charge dissipation time is 10 times longer.
Modeling of plasmon resonance of silver nanoparticles on a silicon surface
Authors: Bolshakov V O , Ermina A A , Zharova Yu A , Tolmachev V A
Published: December 2021

Silver nanoparticles have unique optical properties due to resonance effects that arise due to the presence of conduction electrons in them. When these electrons interacte with photons, they can create localization of electric fields at the interfaces with the environment. Silver nanoparticles deposited on a transparent substrate are often used for research, while Ag nanostructures on Si are studied in this work. They have great potential for practical applications. The interaction of light with nanostructures can be described using various models (pseudo-dielectric functions, effective medium, thin-layer structures, etc.) and optical methods for the experimental determination of their parameters (refractometry, spectrophotometry). Bulk plasmon resonance is considered in this work, which is excited when plasmons are excited at their resonant frequency by an external electromagnetic wave. Calculations were performed for different diameters of silver nanoparticles on a silicon substrate with different structure periods. The calculated spectra are in good agreement with the experimental data of the obtained samples. As a result of the plasmon resonance modeling, the position of the plasmon resonance depends on the density of the arrangement of silver nanoparticles, with an increase in the displacement resonance towards the long-wavelength region.
Phase-sensitive amplification based on gradient Er:PPLN
Authors: Galutskiy V V , Puzanovskiy K V , Shmargilov S A , Stroganova E V
Published: December 2021

The present research focuses on the study of the phase-sensitive amplification based on periodically poled lithium niobate (PPLN) made from gradient Er doped lithium niobate. It is shown that the presence of a growing Er gradient increases the gain while maintaining phase sensitivity to the input signal.
Study of characteristics of LEDs based on InGaN/GaN quantum wells under short electric impacts accompanied by joule heating
Authors: Ivanov A M , Klochkov A V
Published: December 2021

Results are presented of a study of commercial blue and UV light-emitting diodes based on structures with InGaN/GaN quantum wells. An accelerated aging was provided by currents of 80 – 190 mA under a forward bias with duration not exceeding 3 h. The study demonstrated the possible rise in the external quantum efficiency by 20% relative to that in the starting samples. The possible physical mechanisms responsible for the rise in the quantum efficiency and for the formation of a low-frequency current noise are presented.
Influence of AlN/GaN interfacial non-idealities on the properties of two-dimensional electron gas in AlGaN/AlN/GaN heterostructures
Authors: Arteev D S , Sakharov A V , Lundin W V , Zavarin E E , Tsatsulnikov A F
Published: December 2021

The influence of two types of AlN/GaN interfacial non-idealities, namely unintentional Ga incorporation into AlN spacer and blurring of the spacer due to Al and/or Ga atomic diffusion on the mobility and density of two-dimensional electron gas in AlGaN/AlN/GaN heterostructure was studied theoretically. It was found that moderate amount of GaN in the nominal AlN spacer does not affect much the mobility and density of 2DEG as long as the interface is abrupt. In contrast, the blurring of AlN/GaN interface was found to have a significant impact on the mobility and sheet resistance of the structure since the GaN channel actually becomes AlGaN and alloy-disorder scattering takes place.
Direct Numerical Simulation of separated turbulent flow in axisymmetric diffuser
Authors: Stabnikov A S , Kolmogorov D K , Garbaruk A V , Menter F R
Published: December 2021

Direct numerical simulation (DNS) of the separated flow in axisymmetric CS0 diffuser is conducted. The obtained results are in a good agreement with experimental data of Driver and substantially supplement them. Along with other data, eddy viscosity extracted from performed DNS could be used for RANS turbulence model improvement.
Analysis of the applicability of the one-dimensional model for calculating thermal and thermoelectric processes in anisotropic bismuth thermoelements
Authors: Popov P A
Published: December 2021

The results of the temperature and electric potential numerical simulation in the model of an anisotropic thermoelement under thermal action typical for the experimental conditions on shock tubes are presented. The influence of the thermal conductivity anisotropy on the temperature distribution and the generated thermoelectric power is analysed. The results of solving the inverse problem - determining the heat flux from the calculated thermoelectric power are presented. The errors in calculating the heat flux on the basis of the one-dimensional model have been determined.
Modeling of weak shock waves propagation in aqueous foam layer
Authors: Bolotnova R Kh , Gainullina E F
Published: December 2021

Dynamics of low-intensity air shock waves in the shock tube containing an aqueous foam layer is theoretically investigated. Modeling of studied process is carried out using two-phase model of aqueous foam developed by the authors in single-pressure, single-speed and two-temperature approximations. The model takes into account the Ranz-Marshall interphase contact heat transfer, effective Herschel-Bulkley viscosity, which describes foam behavior as a non-Newtonian fluid, and elastic properties of aqueous foam under a weak shock impaction without destruction of foam structure. Properties of air and water as the foam components are described by realistic equations of state. Computer implementation of the aqueous foam model is carried out in the solver, developed by the authors in OpenFOAM software. The influence of aqueous foam viscoelastic properties on the intensity and structure of a shock wave has been investigated. When analyzing the obtained solutions, reliability of the proposed model and method of numerical modeling is estimated by comparative analysis of the found solutions and literature experimental data.
Electronic structure of thermally oxidized tungsten
Authors: Timoshnev S N , Dementev P A , Dementeva E V , Lapushkin M N , Smirnov D A
Published: December 2021

The electronic structure of thermally oxidized tungsten used as an emitter in thermal ionization of organic molecules is studied. Tungsten foil was thermally oxidized at oxygen pressure 1 Torr and temperature 950 K. The photoemission spectra from the valence band and O 2s and W 4f core levels are studied under synchrotron excitation with the photon energies 100 ÷ 600 eV. It is shown that thermal oxidation of tungsten leads to the formation in the W near-surface region various tungsten oxides with an oxidation state from 6+ to 4+. In this case, mainly tungsten oxides with an oxidation state of 6+ are formed on the surface, the proportion of which gradually decreases with distance from the surface with an increase in tungsten oxides with an oxidation state of 4+.
Effectiveness of Banana Trunk as Protection Wall from High Velocity Shrapnel During Detonation of Unexploded Ordnance (UXO)
Authors: Othman Abdul Rashid , Hilmi Ahmad Humaizi , Hamid Asna Rasyidah Abdul , Jun Wong Xian
Published: December 2021

This paper is to investigate banana trunk fibre to be constructed alternatively for the sand bag and high energy absorption. The aim of this study also for enhancing method of absorption velocity shrapnel during detonated of Unexploded Ordnance (UXO), Explosive Remnants of War (ERW) and Improvise Explosive Device (IED). The study involved blast test which is providing high energy impact based on the amount of explosive used. Type of explosive were used are Emulex 180 with velocity of detonation 4500m/s to 5700m/s, Explosive energy 4.17 MJ/kg, density 1.13g/cc to 1.21g/cc and initiation were used are No. 8 Detonator. The structure of specimen is analysed using Stereo Microscope Image Analyser (35x zoom) which is an optical instrument that can observe the structure of the fragments (banana fibre) after blast test. Results shows that banana trunk can become a protection wall as it can absorb the impact of blast from explosion.