bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Model for Ionospheric Total Electron Content: The Impact of Solar Flux Proxies and Indices
Authors: Goncharenko Larisa P. , Tamburri Cole A. , Tobiska W. Kent , Schonfeld Samuel J. , Chamberlin Phillip C. , Woods Thomas N. , Didkovsky Leonid , Coster Anthea J. , Zhang Shun‐Rong
Published: January 2021

We present a new high‐resolution empirical model for the ionospheric total electron content (TEC). TEC data are obtained from the global navigation satellite system (GNSS) receivers with a 1° × 1° spatial resolution and 5‐min temporal resolution. The linear regression model is developed at 45°N, 0°E for the years 2000–2019 with 30‐min temporal resolution, unprecedented for typical empirical ionospheric models. The model describes dependency of TEC on solar flux, season, geomagnetic activity, and local time. Parameters describing solar and geomagnetic activity are evaluated. In particular, several options for solar flux input to the model are compared, including the 10.7 cm solar radio flux (F10.7), the Mg II core‐to‐wing ratio, and formulations of the solar extreme ultraviolet flux (EUV). Ultimately, the extreme ultraviolet flux presented by the Flare Irradiance Spectral Model, integrated from 0.05 to 105.05 nm, best represents the solar flux input to the model. TEC time delays to this solar parameter on the order of several days as well as seasonal modulation of the solar flux terms are included. The Ap3 index and its history are used to reflect the influence of geomagnetic activity. The root mean squared error of the model (relative to the mean TEC observed in the 30‐min window) is 1.9539 TECu. A validation of this model for the first 3 months of 2020 shows excellent agreement with data. The new model shows significant improvement over the International Reference Ionosphere 2016 (IRI‐2016) when the two are compared during 2008 and 2012.
A Mutual Information‐Based Likelihood Function for Particle Filter Flood Extent Assimilation
Authors: Dasgupta Antara , Hostache Renaud , Ramsankaran RAAJ , Schumann Guy J.‐P. , Grimaldi Stefania , Pauwels Valentijn R. N. , Walker Jeffrey P.
Published: January 2021

Accurate flood inundation forecasts have the potential to minimize socioeconomic losses, but uncertainties in inflows propagated from the precipitation forecasts result in large prediction errors. Recent studies suggest that by assimilating independent flood observations, inherent uncertainty in hydraulic flood inundation modeling can be mitigated. Satellite observations from Synthetic Aperture Radar (SAR) sensors, with demonstrated flood monitoring capability, can thus be used to reduce flood forecast uncertainties through assimilation. However, researchers have struggled to develop an appropriate cost function to determine the innovation to be applied at each assimilation time step. Thus, a novel likelihood function based on mutual information (MI) is proposed here, for use with a particle filter‐based (PF) flood extent assimilation framework. Using identical twin experiments, synthetic SAR‐based probabilistic flood extents were assimilated into the hydraulic model LISFLOOD‐FP using the proposed PF‐MI algorithm. The 2011 flood event in the Clarence Catchment, Australia was used for this study. The impact of assimilating flood extents was evaluated in terms of subsequent flood extent evolution, floodplain water depths, flow velocities and channel water levels (WLs). Water depth and flow velocity simulations improved by ∼60% over the open loop on an average and persisted for up to 7 days, following the sequential assimilation of two post‐peak flood extent observations. Flood extents and channel WLs also showed mean improvements of ∼10% and ∼80% in accuracy, respectively, indicating that the proposed MI likelihood function can improve flood extent assimilation.
Noradrenergic correlates of chronic cocaine craving: neuromelanin and functional brain imaging
Authors: Wang Wuyi , Zhornitsky Simon , Zhang Sheng , Li Chiang-shan R.
Published: January 2021

Preclinical studies have implicated noradrenergic (NA) dysfunction in cocaine addiction. In particular, the NA system plays a central role in motivated behavior and may partake in the regulation of craving and drug use. Yet, human studies of the NA system are scarce, likely hampered by the difficulty in precisely localizing the locus coeruleus (LC). Here, we used neuromelanin imaging to localize the LC and quantified LC neuromelanin signal (NMS) intensity in 44 current cocaine users (CU; 37 men) and 59 nondrug users (NU; 44 men). We also employed fMRI to investigate cue-induced regional responses and LC functional connectivities, as quantified by generalized psychophysiological interaction (gPPI), in CU. Imaging data were processed by published routines and the findings were evaluated with a corrected threshold. We examined how these neural measures were associated with chronic cocaine craving, as assessed by the Cocaine Craving Questionnaire (CCQ). Compared to NU, CU demonstrated higher LC NMS for all probabilistic thresholds defined of 50–90% of the peak. In contrast, NMS of the ventral tegmental area/substantia nigra (VTA/SN) did not show significant group differences. Drug as compared to neutral cues elicited higher activations of many cortical and subcortical regions, none of which were significantly correlated with CCQ score. Drug vs. neutral cues also elicited “deactivation” of bilateral parahippocampal gyri (PHG) and PHG gPPI with a wide array of cortical and subcortical regions, including the ventral striatum and, with small volume correction, the LC. Less deactivation of the PHG (r = 0.40, p = 0.008) and higher PHG-LC gPPI (r = 0.44, p = 0.003) were positively correlated with the CCQ score. In contrast, PHG-VTA/SN connectivity did not correlate with the CCQ score. Together, chronic cocaine exposure may induce higher NMS intensity, suggesting neurotoxic effects on the LC. The correlation of cue-elicited PHG LC connectivity with CCQ score suggests a noradrenergic correlate of chronic cocaine craving. Potentially compensating for memory functions as in neurodegenerative conditions, cue-elicited PHG LC circuit connectivity plays an ill-adaptive role in supporting cocaine craving.
Soil microbial legacies differ following drying-rewetting and freezing-thawing cycles
Authors: Meisner Annelein , Snoek Basten L , Nesme Joseph , Dent Elizabeth , Jacquiod Samuel , Classen Aimée T , Priemé Anders
Published: January 2021

Climate change alters frequencies and intensities of soil drying-rewetting and freezing-thawing cycles. These fluctuations affect soil water availability, a crucial driver of soil microbial activity. While these fluctuations are leaving imprints on soil microbiome structures, the question remains if the legacy of one type of weather fluctuation (e.g., drying-rewetting) affects the community response to the other (e.g., freezing-thawing). As both phenomenons give similar water availability fluctuations, we hypothesized that freezing-thawing and drying-rewetting cycles have similar effects on the soil microbiome. We tested this hypothesis by establishing targeted microcosm experiments. We created a legacy by exposing soil samples to a freezing-thawing or drying-rewetting cycle (phase 1), followed by an additional drying-rewetting or freezing-thawing cycle (phase 2). We measured soil respiration and analyzed soil microbiome structures. Across experiments, larger CO2 pulses and changes in microbiome structures were observed after rewetting than thawing. Drying-rewetting legacy affected the microbiome and CO2 emissions upon the following freezing-thawing cycle. Conversely, freezing-thawing legacy did not affect the microbial response to the drying-rewetting cycle. Our results suggest that drying-rewetting cycles have stronger effects on soil microbial communities and CO2 production than freezing-thawing cycles and that this pattern is mediated by sustained changes in soil microbiome structures.
Olfactory ecto-mesenchymal stem cell-derived exosomes ameliorate murine Sjögren’s syndrome by modulating the function of myeloid-derived suppressor cells
Authors: Rui Ke , Hong Yue , Zhu Qiugang , Shi Xiaofei , Xiao Fan , Fu Hailong , Yin Qing , Xing Yida , Wu Xinfeng , Kong Xiaodan , Xu Huaxi , Tian Jie , Wang Shengjun , Lu Liwei
Published: January 2021

Sjögren’s syndrome (SS) is a systemic autoimmune disease characterized by progressive inflammation and tissue damage in salivary glands and lacrimal glands. Our previous studies showed that myeloid-derived suppressor cells (MDSCs) exhibited impaired immunosuppressive function during disease progression in patients with SS and mice with experimental Sjögren’s syndrome (ESS), but it remains unclear whether restoring the function of MDSCs can effectively ameliorate the development of ESS. In this study, we found that murine olfactory ecto-mesenchymal stem cell-derived exosomes (OE-MSC-Exos) significantly enhanced the suppressive function of MDSCs by upregulating arginase expression and increasing ROS and NO levels. Moreover, treatment with OE-MSC-Exos via intravenous injection markedly attenuated disease progression and restored MDSC function in ESS mice. Mechanistically, OE-MSC-Exo-secreted IL-6 activated the Jak2/Stat3 pathway in MDSCs. In addition, the abundant S100A4 in OE-MSC-Exos acted as a key factor in mediating the endogenous production of IL-6 by MDSCs via TLR4 signaling, indicating an autocrine pathway of MDSC functional modulation by IL-6. Taken together, our results demonstrated that OE-MSC-Exos possess therapeutic potential to attenuate ESS progression by enhancing the immunosuppressive function of MDSCs, possibly constituting a new strategy for the treatment of Sjögren’s syndrome and other autoimmune diseases.
Correction: Revisiting gene delivery to the brain: silencing and editing
Authors: Conniot João , Talebian Sepehr , Simões Susana , Ferreira Lino , Conde João
Published: January 2021

Correction for ‘Revisiting gene delivery to the brain: silencing and editing’ by João Conniot et al., Biomater. Sci., 2021, DOI: 10.1039/D0BM01278C.
Insight into non-covalent interactions in two triamine-based mononuclear iron(iii) Schiff base complexes with special emphasis on the formation of Br⋯π halogen bonding
Authors: Basak Tanmoy , Frontera Antonio , Chattopadhyay Shouvik
Published: January 2021

The nature and characteristics of noncovalent interactions that play important roles in the crystal packing of two iron(iii) complexes have been discussed.
In silico approach of modified melanoma peptides and their immunotherapeutic potential
Authors: Pereira A. C. L. , Bezerra K. S. , Santos J. L. S. , I. N. Oliveira J. , Freire V. N. , Fulco U. L.
Published: January 2021

Our results showed the most relevant residue-residue interactions and the main HLAA*0201 amino acids for peptide-HLA binding.
Electron deficiency but semiconductive diamond-like B2CN originated from three-center bonds
Authors: Zhang Xinxin , Yu Guoliang , Chen Hui , Zhao Yu , Cheng Taimin , Li Quan
Published: January 2021

The high-pressure semiconductive C2 phase of B2CN with three-center bonds. (a) the electronic band structure and (b) the three-center bonds evidenced by the localized ELFs.
Complexity of a peroxidase–oxidase reaction model
Authors: Gallas Jason A. C. , Hauser Marcus J. B. , Olsen Lars F.
Published: January 2021

The peroxidase–oxidase reaction was he first (bio)chemical reaction to show chaotic dynamics. Here, we show that the rich complex dynamics observed in a detailed model of the reaction changes dramatically with changes in enzyme concentration.
Correction: Electrostatically modulated magnetophoretic transport of functionalised iron-oxide nanoparticles through hydrated networks
Authors: Lyons Stephen , Mc Kiernan Eoin P. , Dee Garret , Brougham Dermot F. , Morrin Aoife
Published: January 2021

Correction for ‘Electrostatically modulated magnetophoretic transport of functionalised iron-oxide nanoparticles through hydrated networks’ by Stephen Lyons et al., Nanoscale, 2020, 12, 10550–10558, DOI: 10.1039/D0NR01602K.
Modern approaches towards the synthesis of geminal difluoroalkyl groups
Authors: Carvalho Dayanne R. , Christian Alec H.
Published: January 2021

This review will cover the importance of and most recent approaches toward geminal difluoroalkyl groups using transition metal-mediated, photochemical, organocatalytic, and other methods.
Analgesic, anti-inflammatory and anti-ulcer properties of Thai Perilla frutescence fruit oil in animals
Authors: Paradee Narisara , Koonyosying Pimpisid , Kusirisin Winthana , Janthip Rattanaporn , Kanjanapothi Duangta , Pattanapanyasat Kovit , Srichairatanakool Somdet
Published: January 2021

Perilla frutescens fruit oil (PFO) is rich in α-linolenic acid (ALA) and exhibits biological activities. We aimed to investigate analgesic, anti-inflammatory and anti-ulcer activities of PFO and PFO-supplemented soybean milk (PFO-SM) in animal models. Analgesic activity was assessed in acetic acid-induced writhing in mice, while anti-inflammatory activity was performed in ethyl phenylpropiolate (EPP)-induced ear edema and carrageenan-induced hind paw edema in rats. Anti-ulcer effects were conducted in water immersion stress, HCl/ethanol and indomethacin-induced gastric ulcer in rats. Distinctly, PFO, containing 6.96 mg ALA and 2.61 mg LA equivalence/g, did not induce acute toxicity (LD50 > 10 mL/kg) in mice. PFO (2.5 and 5 mL/kg) and PFO-SM (0.05 mL PFO equivalence/kg) inhibited incidences of writhing (16.8, 18.0 and 32.3%, respectively) in acetic acid-induced mice. In addition, topical applications of PFO (0.1 and 1 mL/ear) significantly inhibited EPP-induced ear edema (59.3 and 65.7%, respectively) in rats, while PFO-SM slightly inhibited ear edema (25.9%). However, PFO and PFO-SM did not inhibit carrageenan-induced hind paw edema in rats. Indeed, PFO (2.5 and 5 mL/kg) significantly inhibited gastric ulcers in rats that induced by water immersion stress (92.4 and 96.6%, respectively), HCl/ethanol (74.8 and 73.3%, respectively) and indomethacin (68.8 and 88.9%, respectively), while PFO-SM did not. PFO displayed potent analgesic, anti-inflammatory and anti-ulcer properties, while PFO-SM exerted only analgesic properties. Thus, Thai PFO and its functional drink offer potential benefits in treatment of analgesic, inflammatory diseases and gastric ulcer.
Cryptanalysis and improvement of a user authentication scheme for wireless sensor networks using chaotic maps
Authors: Kumar Devender , Chand Satish , Kumar Bijendra
Published: January 2021

One of the challenging issues in wireless sensor networks (WSNs) is to provide secure communication as the channel used is wireless. User authentication is a mechanism that is used to provide secure communication. The authors analyse the security of a recent authentication scheme for WSNs and show that it is not resistant to smart card loss, insider, and denial of service attacks besides the user traceability problem. Here, they design an improved user authentication scheme using the chaotic maps for WSNs. The chaotic maps‐based public key cryptosystem helps a scheme to consider a large integer as the secret key rather than a large prime number and makes it fast. They show its formal security analysis using the random oracle model. They also analyse its security informally to show that it is resistant to various known attacks. They show that their scheme offers more security features than the existing schemes.
GI school projects and their value and transferability to Uzbekistan
Authors: Hennig Sabine , Vogler Robert
Published: January 2021

Geospatial technologies and spatial data have increasingly become a key issue in our world with regard to digitalization. The ability and capability to handle spatial data products is a key competence in the 21st century. Accordingly, school education is an important domain to address these skills, but still lacks behind its actual potential - even if numerous concepts and approaches already exist. A promising means of addressing this issue is to actively involve schools in real-world GI projects. This paper sums up relevant educational approaches and concepts that are important for such initiatives and briefly describes four selected projects that were carried out in Austria. Based on the knowledge gained in these projects, challenges and benefits are presented, and the transferability and the potential of carrying out such projects in Uzbekistan is discussed.
A Thermo-hydrodynamic lubrication model of a mechanical seal modified by equivalent film thickness
Authors: Wang Xiuying , Zhi Dapeng , Yu Chengtao , Chen Yu
Published: January 2021

An effective way to improve the combined performance of mechanical seals is to optimize their surface textures using multi-objective optimization method. For compatibility with the multi-objective optimization algorithm, the theoretical performance of a mechanical seal is often determined using the finite-difference method (FDM). However, compared with the finite-volume method (FVM) and finite-element method (FEM), FDM is weaker for dealing with the issue of discontinuous film thickness for a textured surface. In the present study, the thermo-hydrodynamic lubrication model of a mechanical seal is modified by means of an equivalent-thickness treatment, and the accuracy of the modified lubrication model is assessed by comparing its predictions for film pressure and temperature with published FVM and FEM results, showing that the equivalent-thickness lubrication model is effective for addressing the issue of discontinuous film thickness. The present work is important in that it improves the simulation accuracy of multi-objective optimization for textured mechanical seals.
Analytic insights into nonlocal energy transport. III. steady state Fokker Planck theory in spherical and planar geometry
Authors: Manheimer Wallace , Colombant Denis
Published: January 2021

This paper develops an approximate steady state Fokker Planck theory for energetic electron transport in a spherical laser fusion target. First, we apply the theory to only a small population of electrons, which is specified at the outset. Then, one determines the nonlocal electron energy flux of these electrons at a particular position. These energetic electrons may either come from the tail of the thermal distribution function or be generated by an instability. This paper develops two approximate methods of solution, which we call the “characteristic method” and “sparse eigenfunction.” The former works only in planar geometry and the latter in both planar and spherical geometry. Comparison of the two methods in planar geometry shows that even though the approximations are very different, they give about the same result, increasing their credibility. For the example we have chosen, spherical effects are not important for electrons from the tail of the distribution function but may well be for instability generated electrons, which have much higher energy. Comparing planar to spherical, one finds an additional spherical barrier protecting the fuel. It turns out that the associated fuel preheat a Fokker Planck model predicts is considerably less than that predicted by the Krook models as developed at both NRL and other places.
Features of the relativistic motion of a single electron entering a waveguide
Authors: Castillo A. J. , Milant'ev V. P.
Published: January 2021

Properties of the motion of an electron with relativistic energy entering an arbitrary Hmn-mode wave in a rectangular waveguide are considered. The derivation of the averaged motion is performed using the Krylov–Bogolyubov averaging method. The ratio of the amplitude of the quiver velocity of the particle in the wavefield to the speed of light is considered as the small parameter. The averaged equations of motion and the periodic additions to the smoothed variables are obtained up to second-order expansions over the small parameter. It is shown that the averaged (ponderomotive) force along the longitudinal axis of the waveguide is absent independent of the wave mode. Numerical solutions of both exact and averaged systems of equations are obtained, demonstrating an excellent agreement of the models. The importance of the correct setting of the initial conditions for the averaged equations based on the values of the periodic additions is emphasized. The conditions, under which the effect of reflection or refraction of the electron by the waveguide field takes place, are established in the case when the electron is injected transversely.
Numerical study of coronal plasma jet formation
Authors: Latham J. , Belova E. V. , Yamada M.
Published: January 2021

A new scenario for solar flare eruption in the coronal holes is analyzed by using MHD stability concepts for a spheromak configuration. The stability properties of a spheromak partially embedded into a conducting surface are studied using three dimensional MHD simulations. In agreement with the analytical theory, a large degree of line-tying stabilizes the spheromak's tilt instability, while the elongation has a destabilizing effect. High-resolution nonlinear simulations also demonstrate current sheet formation at the upper surface of the spheromak, where the tilted magnetic field of the spheromak reconnects with the background magnetic field. The calculated stability threshold and the observed magnetic reconnection support a model of coronal jet eruptions where a dome-like magnetic structure grows through flux emergence on the solar surface, tilts, reconnects, and erupts. Countering the effect from elongation, line-tying strongly stabilizes a spheromak growing from a flux-emergence process, suggesting that to accelerate the onset of eruptive coronal jets, there must be magnetic reconnection at the bottom of the spheromak to detach the structure from the solar surface.
Simplicity in mean-field phase behavior of two-component miktoarm star copolymers
Authors: Li Wei , Liu Yi-Xin
Published: January 2021

Using self-consistent field theory, we systematically explore the microphase separation in the class of two-component miktoarm star copolymers containing a single conjunction point between different blocks by considering an extended list of candidate microphases. We plot mean-field phase diagrams in the plane of segregation strength and composition for an array of representative star copolymers. Three principal phase diagram topologies, dictated by different phase stabilities, are exposed, displaying a hierarchy in complexity by increasing the molecular asymmetry. Our investigation indicates that the phase diagram topology depends on the ratios of arm numbers and Kuhn segment lengths, which highlights the role of the coordination number ratio between different polymers at the domain interface. These findings reveal the simplicity of the general phase behavior and suggest a complete list of stable microphases for the entire class, which provide useful insight into studying copolymers with more complicated architectures and conformational properties.
Tornado-inspired acoustic vortex tweezer for trapping and manipulating microbubbles
Authors: Lo Wei-Chen , Fan Ching-Hsiang , Ho Yi-Ju , Lin Chia-Wei , Yeh Chih-Kuang
Published: January 2021

Significance

The retention and accumulation of biotherapeutic agents within the circulatory system are difficult due to the high velocity of the blood flow, which limits drug leakage and drug concentration in the targeted region. Herein, we propose a tornado-inspired acoustic vortex tweezers to noninvasively collect microbubbles for improved local concentration of up to 1.7-fold in vitro and in vivo. This technique enables systemic drug administration with extremely low doses.
Exploring the learning burden and decay of foreign language vocabulary knowledge
Authors: Barclay Samuel , Pellicer-Sánchez Ana
Published: January 2021

Research has shown that several intralexical factors affect the learning burden of foreign language vocabulary (e.g.,Laufer, 1997) and that some accrued lexical knowledge is forgotten. It is often assumed that the lexical items most difficult to acquire are those easiest to forget. However, few studies have provided empirical evidence to support this claim. This study examined the effect of two intralexical factors, part of speech and word length, on the learning burden and decay of intentionally learned foreign language lexical knowledge, as well as the role that learning burden played in the decay process. Forty-eight learners of English studied words of various parts of speech and lengths using flashcard software. Knowledge (form recall and recognition) of target items was assessed immediately after learning and four weeks later. Results of mixed-effects models showed that part of speech and word length have differential impacts on learning burden and decay and that increased burden mitigated loss of form recognition knowledge.
Fabrication of mechanically reliable micrometric scale conductive pattern by direct pattern transfer using UV photopolymer penetration
Authors: Harisha Bairi Sri , Jeong Si Hun , Lee Min Seop , Yoo Kisoo , Lim Jiseok
Published: January 2021

A mechanically reliable micrometric scale conductive wire fabrication method was developed using silver paste. In order to increase the bonding strength between silver particles, a method was developed for filling the space between particles with UV photopolymer. The UV photopolymer covers the top of a mold filled with silver paste, after which vacuum forces are generated by the evaporation of the solvent in the silver paste and the density difference between the UV photopolymer and the solvent. This results in the penetration of UV photopolymer into the silver paste. The UV photopolymer fills the interparticle air gaps inside the silver paste and positively modifies the mechanical strength of the conductive pattern. A conductive wire with a minimum line width of 10 µm was successfully fabricated on a polyethylene terephthalate film using silver paste with a particle size of 300 nm. The height of the wire is defined by the penetration depth of the UV photopolymer into the silver paste, which is a function of the resting period between applying the UV photopolymer coating and UV illumination to induce UV photo-polymerization. The penetration affected the spreading of the silver paste, resulting in favorable resistance values. A numerical analysis of the UV photopolymer penetration depth was done for validation and was consistent with the experimental results. The developed method enables large-area replication of micrometric scale conductive wire on a flexible substrate using a simple process and instrumentation with improved conductivity per unit area.
Disalignment rate coefficient of argon 2p8 due to nitrogen collision
Authors: Bergert Roman , Isberner Leonard W , Mitic Slobodan , Thoma Markus H
Published: January 2021

Tunable diode laser induced fluorescence (TDLIF) measurements are discussed and quantitatively evaluated for nitrogen admixtures in argon plasma under the influence of a strong magnetic field. TDLIF measurements were used to evaluate light-transport properties in a strongly magnetized optically thick argon/nitrogen plasma under different pressure conditions. Therefore, a coupled system of rate balance equations was constructed to describe laser pumping of individual magnetic sub-levels of 2p8 state through frequency-separated sub-transitions originating from 1s4 magnetic sub-levels. The density distribution (alignment) of 2p8 multiplet was described by balancing laser pumping with losses including radiative decay, transfer of excitation between the neighboring sub-levels in the 2p8 multiplet driven by neutral collisions (argon and nitrogen) and quenching due to electron and neutral collisions. Resulting 2p8 magnetic sub-level densities were then used to model polarization dependent fluorescence, considering self-absorption, which could be directly compared with polarization-resolved TDLIF measurements. This enables to estimate the disalignment rate constant for the 2p8 state due to collisions by molecular nitrogen. A comparison to molecular theory description is given providing satisfactory agreement. The presented measurement method and model can help to describe optical emission of argon and argon–nitrogen admixtures in magnetized conditions and provides a basis for further description of optical emission spectra in magnetized plasmas.
A feasible process for lead-free Cs2SnI6 films using vapor-assisted deposition method with Sn and I2 powders as reactants
Authors: Wang Jiaming , Ullah Saad , Yang Peixin , Liu Linlin , Yang Shi-E , Xia Tianyu , Guo Haizhong , Chen Yongsheng
Published: January 2021

As potential candidates for organic–inorganic hybrid perovskite materials, Pb-free Cs2SnI6 has gained considerable attention because of their better stability under atmospheric conditions containing oxygen and water vapor. Herein, we fabricate Cs2SnI6 films using the vapor-assisted deposition method with Sn and I2 powders as reactants. To obtain uniform and pure Cs2SnI6 films, two different reaction systems are applied and the properties of the samples are characterized via x-ray diffraction, scanning electron microscopy, UV–vis spectrometer, photoluminescence, and Hall-effect measurements. All the results showed a strong dependency on the reaction temperature and fabrication approach. Based on the preparation process in a closed system, we successfully inhibited the high temperature decomposition of Cs2SnI6 even at 250 °C. However, in the open system, the reaction temperature of Cs2SnI6 films should not be higher than 200 °C. Finally, n-type semiconducting Cs2SnI6 films with bandgap (E
g) of 1.32–1.54 eV, carrier concentration of 1013–1016 cm−3, and carrier mobility above 100 cm2 V−1 s−1 are obtained due to the generated I-rich synthesis condition. We believe that our findings will provide beneficial guidance for the fabrication of Cs2SnI6 perovskite solar cells.
A structure scheme to reduce the influence of the accelerometer inner lever-arm effect on tri-axis inertial navigation systems
Authors: Yang Shenglin , Hu Xiaomao , Wang Xiaodan , Li Dechun
Published: January 2021

The accelerometer inner lever-arm effect is a significant error source for high-precision inertial navigation systems (INSs) and has a marked influence on the speed accuracy—a critical technical index of high-precision weapon systems. Rotation modulation technology is widely applied to reduce the errors of high-precision INS. However, this method fails to work for the inner lever-arm effect. Furthermore, variations in the rotation angular velocity and acceleration during modulation alter the inner lever-arm effect, further complicating the compensation of errors. System self-calibration is currently the principle method adopted to deal with the inner lever-arm effect, yet calculation errors result in residual estimations at the millimeter-level for the inner lever-arm. Such a residual will cause obvious speed errors for high-precision INS, which typically turns over the inertial measurement unit via the rotation modulation. This consequently makes it difficult to fully meet the requirements of high-precision weapon systems. In the current paper, we propose an accelerometer geometric space scheme based on the calculations and structural characteristics of a tri-axis INS. Through a simple structure arrangement, we demonstrate the complete theoretical elimination of the inner lever-arm effect in the absence of complex calibration and compensation processes. The only residual error of the inner lever-arm in the proposed scheme is the accumulated geometric tolerance with a value less than 0.2 mm. Semi-physical simulation results reveal the ability of our scheme to directly reduce the magnitude of the system speed error from 10−2 to 10−5. Moreover, the speed fluctuation disappears during the modulation rolling process, thus fully meeting the requirements of high-precision weapon systems.
A novel multi-adversarial cross-domain neural network for bearing fault diagnosis
Authors: Jin Guoqiang , Xu Kai , Chen Huaian , Jin Yi , Zhu Changan
Published: January 2021

Recently, deep neural networks have achieved great success in bearing fault diagnosis. Most existing methods are developed under the assumption that the bearing vibration signals are collected under the same machine operating conditions. However, bearing fault diagnosis under cross-domain conditions will suffer from domain shift problems if the neural network is only trained with the source domain data. Moreover, acquiring enough labeled data from the target domain will be expensive and time-consuming. To address the above problems, this paper proposes an end-to-end multi-adversarial cross-domain neural network for bearing fault diagnosis, which takes labeled source domain data and unlabeled target domain data to achieve the cross-domain bearing fault diagnosis under cross-load conditions and cross-machine conditions. The proposed method employs multi-adversarial training to automatically extract the domain-invariant features from source and target domains instead of manually designing features, which combines domain-adversarial learning and mini-max entropy adversarial learning to adversarially reduce the domain discrepancy between the source and target domains and alleviate the class misalignment problem. The results of the cross-load and the cross-machine experiments prove the effectiveness of the proposed method, and the proposed method provides a promising tool for cross-domain bearing fault diagnosis.
Giant energy storage effect in nanolayer capacitors charged by the field emission tunneling
Authors: Ilin Eduard , Burkova Irina , Colla Eugene V , Pak Michael , Bezryadin Alexey
Published: January 2021

We fabricate nanolayer alumina capacitor and apply high electric fields, close to 1 GV m−1, to inject charges in the dielectric. Asymmetric charge distributions have been achieved due to the selectivity of the quantum tunneling process. Namely, the electrons near the Fermi level cannot tunnel intoregions near the cathode, where the total energy would be less than the potential energy. This mechanism exhibits a strong tendency to populate charge traps located near the anode, i.e. the regions where their potential energy is the lowest. Such spatially selective charging of the dielectric allows a permanent bulk charge storage in the dielectric layer, even if the capacitor plates are short-circuited, provided that the temperature is sufficiently low so that the conductivity of the dielectric is negligible. The stored charge can be recovered if the temperature is increased above ~250 K for the dielectric tested, i.e. Al2O3. In our experiments, the total charge stored in the dielectric was up to seven and a half times higher than the charge stored on the capacitor plates. Also, measurements of the breakdown voltage show that the breakdown electric field, i.e. the dielectric strength, is independent of the thickness of the dielectric.
Correlative STEM-HAADF and STEM-EDX tomography for the 3D morphological and chemical analysis of semiconductor devices
Authors: Jacob Martin , Sorel Julien , Pinhiero Rafael Bortolin , Mazen Frederic , Grenier Adeline , Epicier Thierry , Saghi Zineb
Published: January 2021

3D analysis of an arsenic-doped silicon fin sample is performed in a transmission electron microscope (TEM). High angle annular dark-field scanning TEM (STEM-HAADF) and energy-dispersive x-ray spectroscopy (STEM-EDX) modes are used simultaneously to extract 3D complementary multi-resolution information about the sample. The small pixel size and angular step chosen for the STEM-HAADF acquisition yield reliable information about the sidewall roughness and the arsenic clusters’ average volume. The chemical sensitivity of STEM-EDX tomography gives insights into the 3D conformality of the arsenic implantation and its depth distribution. Non-negative matrix factorization method is employed to identify the chemical phases present in the sample automatically. A total variation minimization algorithm, implemented in 3D, produces high-quality volumes from heavily undersampled datasets. The extension of this correlative approach to electron energy-loss spectroscopy STEM tomography and atom probe tomography is also discussed.
Zero and first-degree spline multiwavelets and parallel computing
Authors: Shumilov B M
Published: January 2021

The paper considers the Haar-like multiwavelets of zero degree splines (step functions) and first-degree splines (broken lines). In contrast to the use of the wavelet transforms based on the Hermitian spline-multiwavelets, the approach proposed does not require the calculation of approximate values of derivatives. On the other hand, the parallelization effect does not rigidly relate to the degree of a spline. This can lead to a significant computation speedup due to the parallel processing of the measured values by several (instead of one) filters. The results of numerical calculations are compared to the known analogs.
Some properties of the classification algorithms using ensemble kernels
Authors: Odinokikh N , Berikov V
Published: January 2021

In this paper, we study the properties of the KCCE algorithm (Kernel-based Classification with Cluster Ensemble) proposed in our previous publication. Different strategies for choosing the ensemble weights are investigated from the point of view of their influence on the quality and speed of the algorithm. We perform numerical experiments with the algorithm on real datasets from the UCI repository under conditions of artificially added noise at different levels.
The development of a system for automated ontology building based on heterogeneous ontology design patterns
Authors: Zagorulko Y A , Borovikova O I , Zagorulko G B
Published: January 2021

Currently, ontologies have become the main means of formalizing and systematizing knowledge and data in scientific subject domains (SSDs). In this regard, there is an urgent need for the methods and software tools allowing to involve specialists from different scientific subject domains in the process of ontology building. A possible way to solve this problem is to use ontology design patterns (ODPs). The paper presents an approach to the development of a system supporting the automated construction of the SSD ontologies based on ontology design patterns, which are the formal descriptions of field-proven solutions to typical ontological modeling problems. The main components of this system are repositories of heterogeneous ODPs and basic ontologies, including concepts common to most SSDs, and editors of patterns and ontologies used to build and populate ontologies.
Numerical research of the influence of wall heating on the turbulent flow pattern in an idealized street canyon
Authors: Danilkin E A , Lechshinskiy D V , Starchenko A V
Published: January 2021

The work is aimed at the study of the flow structure and the distribution of impurities in an idealized street canyon, depending on the intensity of heating of the street canyon walls.
Data assimilation algorithm based on an approximate solution of the optimal nonlinear filtering problem
Authors: Klimova E G
Published: January 2021

In the ensemble Kalman filter, a currently popular data assimilation algorithm, it is assumed that the density of the estimation error distribution is a Gauss function, which is not fulfilled in the general case of a nonlinear model and a nonlinear observation operator. Statement of the optimal filtering problem in the general case is based on the Bayesian approach. One way to approximate the nonlinear optimal filtration problem is to represent the distribution density as a sum of Gaussian distributions with given mean values and covariance matrices. Then the optimal estimate is the weighted sum of estimates obtained in the Kalman filter for the corresponding parameters of the Gaussian distribution in this sum. The paper considers the algorithm for implementing this approach, which uses the previously developed effective local ensemble data assimilation algorithm (ensemble pi-algorithm). The results of numerical experiments to evaluate the properties of the proposed algorithm with the 1-dimensional nonlinear model are presented.
Eddy mixing of momentum and heat in stably stratified boundary layers: Numerical study
Authors: Kurbatskaya L I
Published: January 2021

The paper analyzes the features of turbulent momentum and heat transfer in a stably stratified atmospheric boundary layer (ABL), in the upper troposphere and lower stratosphere, and the possibility of taking them into account in RANS (Reynolds Average Navier Stokes) turbulence models. Such features, for example, include the transfer of momentum (but not heat) by internal gravitational waves under conditions of strong stability, the formation of a low-level jet. Models for the coefficients of eddy diffusion of momentum and heat were obtained by writing the differential equations for the Reynolds stresses and the turbulent heat flux vector in the weakly equilibrium approximation, in which the advection and diffusion of some dimensionless quantities are neglected. In the considered version of the algebraic model built on the physical principles of the RANS approximation for stratified turbulence, three prognostic equations are used: for the kinetic energy of turbulence, the rate of its spectral consumption and the dispersion of temperature fluctuations. It is shown that the profile of the vertical diffusivity for momentum, which was calculated using three-parametric turbulent model, is in agreement with data of direct measurements either within a stable stratified atmospheric boundary layer or beyond this layer in free atmosphere.
An algorithm for estimating greenhouse gas fluxes using satellite data for a global transport and diffusion model
Authors: Platonova M V , Klimova E G
Published: January 2021

The task of estimating the greenhouse gas fluxes in the atmosphere from satellite data is relevant. This problem is solved based on a data assimilation system using a model of transport and diffusion of an impurity in the atmosphere. The paper discusses an approach to solving the problem of estimating the greenhouse gas fluxes based on the use of the ensemble Kalman filter for the global model of transport and diffusion. The paper proposes a numerical algorithm based on the decomposition of the model domain. The originality of this work is the application of the local ensemble Kalman filter algorithm. The case of this study when the greenhouse gas fluxes are considered as a variable is discussed. Here are the results of the simulated numerical experiments on the implementation of the step of analyzing the data assimilation algorithm in the case of the global model of transfer and diffusion.
Numerical modeling of the liquid film flow with evaporation on the basis of the generalized interface conditions
Authors: Rezanova Ekaterina
Published: January 2021

A thin layer of a viscous incompressible liquid flowing down an inclined, non-uniformly heated substrate under conditions of a concomitant gas flow is studied. The flow is accompanied by evaporation at the thermocapillary interface. Dynamic processes in a gas are not taken into account (one-side model). The mathematical model of a thin liquid layer flow is based on the Navier-Stokes equation and the heat transfer equation, as well as generalized kinematic, dynamic and energetic conditions at the thermocapillary boundary. The local mass flux at the interface is determined using the Hertz-Knudsen equation. Analytical solutions of the problem are constructed for the zeroth-order terms of the expansions of the desired functions in powers of a small parameter of the problem. Parametric analysis of the problem is performed. An evolutionary equation for determining the thickness of the liquid layer is obtained. An algorithm for numerical solution of the evolutionary equation is constructed. The results of numerical studies of flows of a thin layer of ethanol and HFE-7100 with evaporation at the interface are obtained.
On solving the slice-by-slice three-dimensional 2-tensor tomography problems using the approximate inverse method
Authors: Louis A K , Maltseva S V , Polyakova A P , Schuster T , Svetov I E
Published: January 2021

A numerical solution of the problem of recovering the solenoidal part of a three-dimensional symmetric 2-tensor field using the incomplete tomographic data is proposed. The initial data of the problem are values of the ray transform for all straight lines, which are parallel to at least one of the planes from a finite set of planes. We consider two sets of planes, the number of planes in which are three and six. The recovery algorithms are based on the approximate inverse method.
An iterative algorithm for reconstructing a 2D vector field by its limited-angle ray transform
Authors: Maltseva S V , Svetov I E , Louis A K
Published: January 2021

In this paper, we consider problem of reconstructing a vector field in the unit disc by using the ray transform in a limited angular domain. We propose an approach to solving this problem. The approach is based on the Papoulis-Gerchberg algorithm. It is an iterative algorithm including iterations in the main space of vector fields and in the frequency domain. The results of numerical simulation are demonstrated.
On the problem of modeling the acoustic radiation pattern of source for the 2D first-order system of hyperbolic equations
Authors: Kabanikhin S I , Klyuchinskiy D V , Novikov N S , Shishlenin M A
Published: January 2021

In this paper the problem of modeling the acoustic radiation pattern of source is considered. The problem is formulated in the form of control problem for the 2D first-order system of hyperbolic equations. This problem is related to ultrasound tomography for early breast cancer detection. The modelling of the acoustic radiation patterns of sources allows us to improve the resolution of acoustic tomography.
Approximate filtered back-projection algorithm for plane curves in tomography problems
Authors: Pickalov V V
Published: January 2021

In previous works by the author and colleagues, it was proposed in some tomography problems to convert the fan-shaped projection measurement scheme into a system of parallel rays by deforming reconstructed image. The deformation of the tomogram for each direction of observation will be different, but the one-to-one nature of these deformations allows one to return back to the original coordinate system. Further, this method is generalized to a family of plane curvilinear trajectories that allow one-to-one transitions to parallel rays. For each back projection, the image is modulated by a known function following from the path differential of a given trajectory. Illustrations of the operation of this algorithm are given on examples of parabolic, sinusoidal and fan-beam paths of rays. The applicability of the algorithm in problems of visualization of discontinuities, in problems of ROI-tomography (local tomography) is shown.References
The singular value decomposition of the dynamic ray transforms operators acting on 2-tensor fields in ℝ2
Authors: Polyakova A P , Svetov I E
Published: January 2021

We consider the problem of the dynamic two-dimensional 2-tensor tomography. An object motion is a combination of rotation and shifting. Properties of the dynamic longitudinal, mixed and transverse ray transform operators are investigated. The singular value decompositions of the operators with usage of the classic orthogonal polynomials are constructed.
The approximation neural-network method for solving nonlinear multi-criteria inverse problems of geophysics
Authors: Shimelevich M I , Obornev E A , Obornev I E , Rodionov E A
Published: January 2021

A multi-criteria inverse problem is reduced to a system of operator equations on compact sets. It is shown that some a posteriori error estimates of solutions of the multi-criteria problem decrease with an increasing number of the criteria used. The approximation neural-network method for solving the multi-criteria inverse problem is presented. An example of a numerical solution of the two-criterion problem of geoelectrics is given, and the a posteriori error estimates are calculated.