bluuebunny/crossref_metadata_2025 huggingface dataset:
Neue Operationstechnik: Weltweit modernster Herzkatheter-Roboter in Freiburg
Authors: Heeser Alexandra
Published: November 2021

Freiburgs Uniklinik hat als eine von sechs Kliniken in Europa einen Roboter, der bei Eingriffen an den Herzkranzgefäßen assistiert. Zusammen erreichen hier Mensch und Maschine eine extrem hohe Präzision – im Mikrometer-Bereich. Die neue Methode hat Vorteile für beide Seiten: Patienten und Behandelnde.
Electrical properties of high permittivity epitaxial SrCaTiO3 grown on AlGaN/GaN heterostructures
Authors: Jin Eric N. , Downey Brian P. , Gokhale Vikrant J. , Roussos Jason A. , Hardy Matthew T. , Growden Tyler A. , Nepal Neeraj , Katzer D. Scott , Calame Jeffrey P. , Meyer David J.
Published: November 2021

Epitaxial integration of perovskite oxide materials with GaN has unlocked the potential to improve functionality and performance in high-power RF and power-switching applications. In this work, we demonstrate structural and electrical properties of high dielectric constant Sr1−xCaxTiO3 epitaxial layers grown on AlGaN/GaN/4H-SiC high-electron-mobility transistor structures with compositions ranging from x = 0 to x = 0.53 and oxide film thicknesses ranging from 7 to 126 nm. We show (111) orientation in the SrCaTiO3 (SCTO) thin films using a 1 nm (100) TiO2 buffer layer grown by RF-plasma-assisted oxide molecular beam epitaxy. Current–voltage measurements show up to 5 orders of magnitude reduced leakage with SCTO films when compared to Schottky contacted samples. Capacitance–voltage measurements show minimal hysteresis, an extracted dielectric constant (κ) as high as 290, and a fixed positive interface charge density of 2.38 × 1013 cm−2 at the SCTO/AlGaN interface. The direct integration of the SCTO layer does not significantly affect the two-dimensional electron gas (2DEG) density or the channel mobility with the 2DEG density as a function of SCTO thickness having good agreement with 1D Poisson–Schrödinger simulations. RF characterization of interdigitated capacitors using the SCTO films on unintentionally doped GaN/SiC shows that the films maintain their high κ into microwave frequencies and only exhibit a slight reduction in κ with increased lateral electric fields. These results demonstrate that the integration of a high-κ oxide with GaN can potentially improve electric field management in RF high-electron-mobility transistors and increase the device breakdown voltage without significant degradation to channel transport properties.
Spatial evolution characteristics of ion and electron flow for 300 W class low-power Hall thruster
Authors: Chen Xinwei , Gao Jun , Gu Zuo , Guo Ning , Wang Shangmin , Yang Sanxiang , Ma Yifan , Shi Kai , Geng Hai , Zhang Hong , Pu Yanxu
Published: November 2021

The Faraday probe and cylindrical Langmuir probe were used to characterize the downstream ion and electron spatial evolution of a 300 W class low-power Hall thruster. The time-averaged ion current density, electron energy probability function, plasma potential, electron temperature, and electron density measurements were conducted at discharge voltages of 200–400 V and anode mass flow rates of 0.65 and 0.95 mg s−1 in the range of 100–500 mm axially and −100 to 100 mm radially downstream of the thruster. The results show that the ion and electron flows exhibit a bipolar diffusion characteristic along the radial direction. Meanwhile, the radial diffusion rate of ions in the plume is greater than the axial diffusion rate. The plasma potential decreases from 18 V at 100 mm axially from the thruster exit to 4 V at 500 mm axially and 100 mm radially. Correspondingly, the electron temperature decreases from 4.2 to 1.0 eV. The electron number density decreases from 2.6 × 1016 to 4 × 1014 m−3. A variable exponential relationship between electron temperature and electron density was observed from the measurements of electron energy probability distribution functions, with an adiabatic factor γ ranging between 1.3 and 1.4 (below the adiabatic value of 5/3). The adiabatic factor γ is considered to correlate with the anode mass flux and the spatial location of plasma, which suggests a possible dependence on the collision rate. These data are of great importance for plume model validation, improvement, plume effect evaluation, and protection mechanisms.
Atomic structure of liquid refractory Nb5Si3 intermetallic compound alloy based upon deep neural network potential
Authors: Wang Q. , Zhai B. , Wang H. P. , Wei B.
Published: November 2021

The knowledge of atomic structure for liquids, especially for liquid alloys with complex crystal structure and high liquidus temperatures, remains poorly understood. In this work, we have extended the development of deep neural network (DNN) potential for liquid Nb5Si3. The DNN potential captures the structural features of liquid alloys compared with ab initio results. The chemical short-range order parameter suggests that there exists strong affinity between Nb and Si atoms. The dynamic property was investigated, and the diffusion coefficient obeys the Arrhenius relationship. The atomic structure has been subsequently explored for normal and undercooled liquid Nb5Si3. Large amounts of fivefold symmetry Honeycutt–Andersen pairs have been identified in liquid Nb5Si3. However, due to the violent thermal motion in a high-temperature Nb5Si3 melt, icosahedral symmetry and distorted icosahedrons (ICOs) account for little proportion according to Voronoi polyhedron (VP) analysis. The effect of thermal motion on VPs has been discussed. Except from the well documented ⟨0,2,8,2⟩ and ⟨0,1,10,2⟩ distorted ICOs, six more quasi-ICOs (⟨0,1,9,3⟩, ⟨0,2,8,1⟩, ⟨0,2,8,4⟩, ⟨0,2,8,5⟩, ⟨0,1,10,3⟩, and ⟨0,1,10,4⟩) have been proven to deform from ICOs at high temperatures. The local environment motif obtained by the atomic cluster alignment method demonstrates the existence of dominant distorted ICOs. At last, the atomic structure during melting process is discussed by VP analysis. It is found that ⟨0,2,8,1⟩, ⟨0,2,8,2⟩, ⟨0,2,8,5⟩, and ⟨0,1,10,4⟩ prefer to form at the beginning of the melting but rapidly reduce when it is fully melted.
Dynamic strain evolution in an optically excited Pt thin film
Authors: DeCamp M. F. , DiChiara A. D. , Unruh K. M.
Published: November 2021

The structural evolution of a Pt thin film following photo-thermal excitation by 1 ps optical laser pulses was studied with a time resolution of 100 ps over a total time period of 1 ms. Laser pulse fluences below 50 mJ/cm2 were insufficient to relax the residual stress state of the as-prepared film even after 10 000 pulses. In this fluence regime, a rapid initial lattice expansion and a decrease in the lattice coherence length due to ultrafast photo-thermal heating were observed. The lattice expansion reached a maximum, and the coherence length reached a minimum, 100–200 ps after excitation before monotonically decaying back to their initial values in about 1 µs. Laser pulse fluences greater than 50 mJ/cm2 produced irreversible stress relaxation within the first 10 optical pulses. In this regime, the lattice expansion was qualitatively similar to that in the low fluence regime, except that the initial structural state was not recovered. The evolution in the coherence length, however, was more complex. Following an initial decrease similar to that observed at low fluence, the coherence length then increased to a broad maximum greater than the initial value, before recovery.
Reorganization of CDW stacking in 1T-TaS2 by an in-plane electrical bias
Authors: Li Weijian , Naik Gururaj V.
Published: November 2021

1T-TaS2 is a 2D quantum material supporting charge density waves (CDWs) at room temperature. The strong correlations in this material make its electrical properties extremely sensitive to external stimuli such as an electrical bias and illumination. Recently, we demonstrated that the optical properties of this material also considerably change with electrical bias and light. With light, we showed that the CDW domains across layers stack differently and thus result in a unity-order change in the refractive index. Here, we demonstrate that an in-plane electrical bias also changes the CDW stacking in 1T-TaS2. However, the stacking change with electrical bias opposes that with illumination. Our experiments at room temperature suggest that an in-plane electrical bias sets the CDWs sliding and making way for the higher energy stacking configurations to switch to the ground-state stacking. The demonstration here sheds light on the origin of the giant electro-optical effect previously observed in 1T-TaS2 and paves the way for low-power MHz-fast electrically tunable optical devices.
Evaluation of effective magnetic anisotropy constant of magnetic nanoparticles from coercive field of AC magnetization curve
Authors: Enpuku Keiji , Draack Sebastian , Ludwig Frank , Yoshida Takashi
Published: November 2021

Magnetic nanoparticles (MNPs) have been widely studied for use in biomedical application with the magnetic anisotropy constant K playing an important role in determining the performance. We estimated K near room temperature from the coercive field Hc of an AC magnetization (M–H) curve. First, we performed numerical simulation of the AC M–H curve of immobilized MNPs and clarified the dependencies of Hc on the MNP parameters and excitation conditions. Based on the simulation result, we obtained an analytical expression for Hc that was more general and included the previously obtained expression; and in addition, it could be applied to an MNP sample with a core-size distribution. Next, we measured the AC M–H curves of two commercial MNP samples and determined the dependencies of Hc on the amplitude and frequency of the excitation field. The dependencies agreed reasonably well with the analytical results. The K value was evaluated to obtain the best fit between the measured and analytical Hc, and the obtained K values were consistent with those estimated using other methods. The temperature dependence of K near room temperature was also determined. The present method will provide a useful tool to estimate the K value of MNPs.
Measurement of cell compressibility changes during epithelial–mesenchymal transition based on acoustofluidic microdevice
Authors: Fu Qibin , Zhang Yan , Huang Tuchen , Liang Ying , Liu Yang
Published: November 2021

Epithelial–mesenchymal transition (EMT) confers migratory and invasiveness abilities on cancer cells, as well as leading to changes in biomechanical properties and cytoskeletal structure. Cell mechanical properties are considered to be promising label-free markers for diagnosis of cancer metastasis. In this work, cell compressibility, a novel and important parameter of cell mechanical properties, was measured directly and quickly using a specially designed acoustofluidic microdevice. The compressibilities of cells with different metastatic potentials were investigated. Based on a comparison of the measurement results, non-metastatic cells exhibited lower compressibility than metastatic cells. The correlation between cell compressibility and EMT status was further studied; the results showed that the acquisition of mesenchymal status was accompanied by an increase in cell compressibility. These findings imply strong correlations among cell compressibility, EMT status, and invasiveness. Therefore, cell compressibility represents a novel biomechanical marker for evaluating malignant transformation and metastasis of cancer.
Effect of spraying power on the microstructure and wear behavior of the plasma-sprayed FeCoCrNiMo0.2 coating
Authors: Zhang Shitao , Li Wenge , Hu Yihuai , Jiang Tao , Guo Leyang , Zhang Yangyang , Zhao Yuantao
Published: November 2021

In this work, FeCoCrNiMo0.2 high-entropy alloy coatings were fabricated using the atmospheric plasma spraying technique. The dependence of the microstructure and wear property of the coatings on spraying power was explored. The results showed that with increasing spraying power, the streamlined structure of the coating was gradually disturbed, the content of the oxides in the coating was enhanced, and the distribution of oxides became relatively uniform. Meanwhile, the porosity in the coating was reduced due to the increased melting degree of feeding particles. As the spraying power increased from 25.5 to 45 kW, the micro-hardness of the coating was improved from 438 ± 15.27 to 558.73 ± 7.23 HV0.2 and the wear loss of the coating decreased from 2.05 × 10−4 to 1.18 × 10−4 mm3/nm. The synergistic effect of the dispersive oxides and the reduced porosity could account for the enhanced micro-hardness by the second phase strengthening mechanisms. Subsequently, the wear resistance of the coating prepared at a high spraying power was improved due to the increased micro-hardness and the reduced crack behaviors. In addition, the broken oxides of metal elements, especially Cr oxides, during wearing led to the abrasive wear behavior, and the broken oxides could work as a lubricant to decrease the wear coefficient of the coating. Finally, the FeCoCrNiMo0.2 coating prepared at a power of 45 kW had the best wear resistance.
The acquisition of verbal passives by Portuguese-speaking children
Authors: Agostinho Celina , Gavarró Anna
Published: November 2021

Previous cross-linguistic research showed that verbal passives are delayed in child grammar. Moreover, Maratsos et al. (1985) found that actional passives elicit more adult-like results than non-actional passives in child English. Hirsch & Wexler (2006) proposed that the adult-like results children achieved with actional passives are due to a resultative adjectival passive analysis, unavailable for non-actional verbs. Alternatively, Snyder & Hyams (2015) proposed that this delay is due to the need of semantic coercion to passivize non-actional verbs. Here we present an experiment testing children’s comprehension of short and long passives of actional and perception verbs in European Portuguese, a language with different auxiliaries for adjectival and verbal passives. The results replicate previous findings for English, despite the difference in auxiliary.
The interpretation of null subjects in Romanian
Authors: Frascarelli Mara
Published: November 2021

This chapter explores the ‘acceptability’ and ‘interpretation’ of referential null subjects in Romanian in different syntactic conditions and distinct clause types (matrix clauses, embedded under bridge verbs, embedded under factive verbs and adverbial clauses). Based on the results of an original online survey (carried out by almost 80 respondents), it is shown that Romanian is a consistent pro-drop language, in which no partial pro-drop properties can be found. Furthermore, the results emerged from the analysis provide significant support to the validity of an information-structure approach to the interpretation of null subjects, in which the Topic Criterion (Frascarelli 2007), the formation of Topic chains and the existence of silent Topics play a crucial role.
The effects of language ecology on syntactic structure
Authors: Laub Robert W.
Published: November 2021

Kristang and Makista are two related Portuguese-lexified creoles of southeast Asia. While they are generally mutually intelligible, there are differences between them. A look at the contact languages found in Malacca and Macau can give us ideas as to where these differences come from. Building on Ansaldo’s notion of language ecology, this study will look at the histories of Kristang and Makista, and the features that exhibit these differences. These histories will be taken into account when looking at the differences, and evidence suggesting the connection between language ecology and morphosyntactic structures will be presented. The two features discussed are genitive patterns, and cleft constructions.
Syntactic vs pragmatic passive
Authors: Vasilescu Andra
Published: November 2021

This chapter discusses the relationship between the two passive constructions in Romanian (se-passive and be-passive) in a twofold comparison: old Romanian vs present-day Romanian, and standard vs substandard present-day Romanian. Stipulating the distinction ‘syntactic passive’ vs ‘pragmatic passive’, I argue that the evolution of the two competing structures illustrates a typical case of convergence and I invoke the situation in present-day subdialectal Romanian as an additional proof. In old Romanian, se-structures functioned as syntactic passives under the Slav(on)ic influence, while be-structures had a temporal or copular meaning, pragmatically implying the passive meaning. In present-day standard Romanian, be-structures are grammaticalized for the passive meaning following the influence of Western Romance languages, while se-structures have acquired an impersonal-presentative meaning, continuing to pragmatically imply the passive meaning. The situation in present-day dialectal spoken varieties, more conservative compared to standard Romanian, reflects the grammaticalization/degrammaticalization processes that affected the evolution of the two structures: while se-structures followed the long-term evolution in standard Romanian and lost their grammaticalized passive function acquiring an impersonal-presentative meaning, the more recent grammaticalization process of be-structures as passives has not fully extended to subdialectal varieties. Hence, active constructions are the preferred option across subdialects, which currently lack a grammaticalized passive construction, as the passive meaning is pragmatically implied both by se-structures and be-structures.
Term distance, frequency and collocations
Authors: Johnsen Lars G.
Published: November 2021

In this paper I study two co-occurrence measures, local to a particular corpus, for constructing collocations or relevance relations between words or terms. One is a distance measure, while the other uses different co-occurrence windows, one contained in the other. Both are discussed with respect to the common method of comparing co-occurrence measures within a particular corpus to those of a reference corpus. A practical consequence of these measures is that they may relieve the burden of computing a reference statistic, which may incur a high computational cost. We also believe that distance, as a measure in itself, has a theoretical interest. Being different from frequency, it may add something new to collocation analysis.
Grammar efficiency and the One-Meaning–One-Form Principle
Authors: Vulanovic Relja
Published: November 2021

The more a linguistic system departs from the One-Meaning–One-Form Principle, the less efficient it is. This notion is used to simplify the previous approach to the evaluation of grammar efficiency. The recently proposed measure of the departure from the Principle is revisited and its simplified version is included in the formula for grammar efficiency. The new and the old grammar-efficiency formulas are compared when applied to parts-of-speech systems as defined by Hengeveld. It is shown that the number of calculations is considerably reduced in the new formula, while the results obtained by the two approaches correlate well.
The perils of big data
Authors: Embleton Sheila , Uritescu Dorin , Wheeler Eric S.
Published: November 2021

The use of large amounts of data and the technologies to process them are characteristic of modern research. However, such practices come with risks of misleading the researcher. While there is much that could be said on this topic, here briefly is our cautionary tale to others, based on our direct experiences.
From distinguishability to informativity
Authors: Konca Maxim , Mehler Alexander , Baumartz Daniel , Hemati Wahed
Published: November 2021

We present a study of the distinctiveness of random and non-random texts based on text characteristics of quantitative linguistics. We additionally experiment with text features that evaluate contiguity associations among sentences by means of BERT (Bidirectional Encoder Representations from Transformers). To this end, we experiment with generative models for random texts as currently discussed in the context of neural networks. The chapter contributes to the clarification of deficits of existing random text models and of the informativeness of quantitative text features.
Phonological properties as predictors of text success
Authors: Milička Jiří , Růžičková Alžběta Houzar
Published: November 2021

In this study, the relation of phoneme structure and success rate of Czech texts is investigated. The study is based upon two phenomena: (1) the beauty-in-averageness effect and (2) the euphony principle. The main objective is to examine whether one or the other prevails in the perception of written text, whether they interact in some way, or whether the phoneme structure has no major effect on the text’s appeal to the readers. Several phoneme groups, both vowel and consonant, are focused on.
Analysis of English text genre classification based on dependency types
Authors: Wang Yaqin
Published: November 2021

The present study aims to explore whether dependency type can be used as a distinctive text vector for classifying English genres. Three classification methods, namely principal component analysis, hierarchical clustering, and random forest were employed to investigate the clustering effect. Results show that dependency type is an effective measure in distinguishing text genres, especially between spoken genre and written genre.
Impact of climate change on pests of rice and cassava
Authors: Chaya Mona , Xiang Tao , Green Ashley , Gu Baogen
Published: November 2021

Climate change is exacerbating food insecurity, and its negative impacts will worsen over time. This is happening via several pathways, among which plant pests are a leading cause. To contribute to more evidence-based decisions and policies, a team from the Food and Agriculture Organization of the United Nations (FAO) carried out a comprehensive literature review on rice (
Oryza sativa
) and cassava (
Manihot esculenta
), the major pests and diseases affecting them, and the impact of climate change on the latter. Rice is the major staple crop for about half the world’s population. Most studies conclude that pest pressure will increase on rice under future climate change. There are a lot of pests of rice, among which brown planthopper (
Nilaparvata lugens
) is the most important pest. Leaf blast disease caused by fungus Magnaporthe grisea is the most significant disease, with losses of up to USD 66 billion dollars per year that are equivalent to the amount needed to feed 60 million people. Cassava is the major staple crop and crucial for food security in many countries of the world. A study has shown that cassava production will vary from −3.5% to +17.5% within Africa under 2030 climate projections. Unfortunately, as other crops, cassava will be vulnerable to pests and diseases. Over a third of attainable cassava yield is lost every year to pests and disease alone.
Highly sensitive fiber-optic SPR sensor with surface coated TiO2/MWCNT composite film for hydrogen sulfide gas detection
Authors: Chen Rong , Lan Guilian , Wang Ning , Yan Wenjing , Yi Jueming , Wei Wei
Published: November 2021

Hydrogen sulfide (H2S) gas has a severe effect on the respiratory system of the human body and ambient environment, necessitating development of on-line H2S gas sensors with high performance for safety and health concerns. Here, we proposed a fiber-optic surface plasmon resonance sensor for H2S detection employing TiO2 nanoparticles and multilayer carbon nanotubes composite (TiO2/MWCNT) as sensing film, featuring desirable advantages of high sensitivity, selectivity, and real-time detection. Benefiting from special structure and large specific surface area of MWCNTs, the adsorption capacity of sensing surface to gas molecules can be significantly enhanced. Moreover, the high carrier mobility of MWCNTs can further promote the charge transfer between TiO2 and H2S. These unique features of TiO2/MWCNT composite film result in an obvious improvement of sensitivity for H2S detection. Experimental results show that the maximum sensitivity of 21.76 pm ppm−1 (picometer/part-per-million) and detection limit of 0.2 ppm can be obtained by appropriately optimizing the componential constitutions of TiO2/MWCNT composite. Such detection limit is strikingly lower than the threshold concentrations in workplace set by Federal Institute for Occupational Safety (10 ppm). In addition, the favorable selectivity, response/recovery times, repeatability and stability were demonstrated as well. This facile and cost-effective work provides a novel strategy for constructing high performance H2S gas sensor with fast response and real-time detection, which has prospective application in the fields of human health and environmental conservation.
The effects of the driving frequencies on micro atmospheric pressure He/N2 plasma jets driven by tailored voltage waveforms
Authors: Hübner G , Bischoff L , Korolov I , Donkó Z , Leimkühler M , Liu Y , Böke M , Schulz-von der Gathen V , Mussenbrock T , Schulze J
Published: November 2021

Capacitively coupled micro atmospheric pressure plasma jets are important tools for the generation of radicals at room temperature for various applications. Voltage waveform tailoring (VWT), which is based on the simultaneous use of a set of excitation frequencies, has been demonstrated to provide an efficient control of the electron energy probability function (EEPF) in such plasmas and, thus, allows optimizing the electron impact driven excitation and dissociation processes as compared to the classical single-frequency operation mode. In this work, the effects of changing the driving frequencies on the spatio-temporally resolved electron power absorption dynamics, the generation of helium metastables and the dissociation of nitrogen molecules are investigated in He/N2 plasmas based on experiments and simulations. We find that under a single-frequency excitation, the plasma and helium metastable densities are enhanced as a function of the driving frequency at a fixed voltage. When using valleys-type driving voltage waveforms synthesized based on consecutive harmonics of the fundamental driving frequency, the spatial symmetry of the electron power absorption dynamics and of the metastable density profile is broken. Increasing the fundamental frequency at a constant voltage is found to drastically enhance the plasma and metastable densities, which is a consequence of the change of the EEPF. Finally, we compare the energy efficiency of the formation of radicals under single-frequency and VWT operation at different driving frequencies. For a given power dissipated in the plasma, VWT yields a higher helium metastable as well as electron density and a higher dissociation rate of N2.
Multi-robot cardinality-balanced multi-Bernoulli filter simultaneous localization and mapping method
Authors: Zhang Zijing , Zhang Fei , Ji Chuantang
Published: November 2021

In order to improve the simultaneous localization and mapping (SLAM) accuracy of mobile robots in complex indoor environments, the multi-robot cardinality-balanced multi-Bernoulli filter SLAM (MR-CBMber-SLAM) method is proposed. First of all, this method introduces a multi-Bernoulli filter based on the random finite set (RFS) theory to solve the complex data association problem. This method aims to overcome the problem that the multi-Bernoulli filter will overestimate the aspect of SLAM map feature estimation, and combines the strategy of balancing cardinality with a multi-Bernoulli filter. What is more, in order to further improve the accuracy and operating efficiency of SLAM, a multi-robot strategy and a multi-robot Gaussian information-fusion method are proposed. In the experiment, the MR-CBMber-SLAM method is compared with the multi-vehicle probability hypothesis density SLAM (MV-PHD-SLAM) method. The experimental results show that the MR-CBMber-SLAM method is better than MV-PHD-SLAM method. Therefore, it effectively verifies that the MR-CBMber-SLAM method is more adaptable to a complex indoor environment.
Tailoring the properties of Ni-Mn based NTC thermistors by Cu and Li addition
Authors: V K Haripriya , V S Sharon , K A Malini
Published: November 2021

The influence of Cu and Li doping in the structural and R-T characteristics of Ni-Mn-based spinel oxide negative temperature coefficient (NTC) thermistors prepared using the conventional solid-state synthesis method was investigated in this study. The doping of Cu and Li in nickel manganite plays an important role in tailoring the thermistor parameters. The structural characterization of the prepared samples using XRD revealed that the basic structure of the samples is not altered by the addition of the dopants Cu and Li. The particle size of the samples was obtained at less than 50 nm. R-T characteristics showed a decrease in resistance with temperature. It was observed that the addition of dopant Cu in a minimal amount helps to tune the resistance of the thermistor in the required range and Li addition, as a dopant, stabilized the thermistor parameters B and alpha.
Multilayer analysis of immiscible power-law fluids under magnetohydrodynamic and pressure-driven effects in a microchannel
Authors: Gómez J R , Escandón J P , Hernández C G , Vargas R O , Torres D A
Published: November 2021

In the present study, the combined magnetohydrodynamic and pressure-driven flow of multilayer immiscible fluids into a parallel flat plate microchannel is semi-analytically solved. Due to the handling of complex fluids in various microfluidic platform applications, the fluid transport reviewed here considers the power-law model. The movement of electrically conductive fluid layers is due to Lorentz forces that arise from the interaction between an electric current and a magnetic field. To find a solution for the flow field, the momentum equation and the rheological model for each fluid layer, together with the corresponding boundary conditions at the liquid-liquid and solid-liquid interfaces, are solved simultaneously through a closed system of nonlinear equations. The graphical results show the influence of the dimensionless parameters that arise from the mathematical modeling on the velocity profiles and flow rate. These are the magnetic parameters, the fluid layers thickness, the viscosity coefficients, the ratios between pressure forces and magnetic forces, and the flow behavior indexes. This theoretical work contributes to the design of microfluidic devices for flow-focusing tasks in chemical, clinical, and biological areas.
Nanotube formation from self-curling nanofilms driven by intrinsic surface-stress imbalance
Authors: Li Jiangang , Yao Haiyan , Xu Yaodong , Gao Zhixiang , Wang Hua , Shi Yunlong
Published: November 2021

The theoretical analysis for fabricating nanotubes from self-curling of nanofilms due to intrinsic surface stress imbalance was given in this paper. A nanofilm was curled into a nanotube along tangential direction, while the other in-plane direction (cylindrical direction) was only elongated but wasn’t curled or bent. Film bending behavior is usually described by using Stoney formula, but the Poisson’s effect of cylindrical direction should be considered for describing mechanical behavior of curling up phenomenon. Stoney formula assumes that the surface stress is isotropic and the bending is also isotropic, but the shape of nanotube is anisotropic. On the other hand, surface effects and symmetry lowering effect strongly affect the mechanical properties of nonafilms. Here, we gave a more accurate curling theory by including surface stress, surface elasticity, symmetry lowering and Poisson’s effect of cylindrical direction.
Scalar fields near compact objects: resummation versus UV completion
Authors: Davis Anne-Christine , Melville Scott
Published: November 2021

Low-energy effective field theories containing a light scalar field are used extensively in cosmology, but often there is a tension between embedding such theories in a healthy UV completion and achieving a phenomenologically viable screening mechanism in the IR.

Here, we identify the range of interaction couplings which allow for a smooth resummation of classical non-linearities (necessary for kinetic/Vainshtein-type screening), and compare this with the range allowed by unitarity, causality and locality in the underlying UV theory.
The latter region is identified using positivity bounds on the 2→2 scattering amplitude, and in particular by considering scattering about a non-trivial background for the scalar we are able to place constraints on interactions at all orders in the field (beyond quartic order).
We identify two classes of theories can both exhibit screening and satisfy existing positivity bounds, namely scalar-tensor theories of P(X) or quartic Horndeski type in which the leading interaction contains an odd power of X.
Finally, for the quartic DBI Galileon (equivalent to a disformally coupled scalar in the Einstein frame),
the analogous resummation can be performed near two-body systems and imposing positivity constraints introduces a non-perturbative ambiguity in the screened scalar profile.
These results will guide future searches for UV complete models which exhibit screening of fifth forces in the IR.
Dynamical screening effects on big bang nucleosynthesis
Authors: Hwang Eunseok , Jang Dukjae , Park Kiwan , Kusakabe Motohiko , Kajino Toshitaka , Balantekin A. Baha , Maruyama Tomoyuki , Ryu Chang-Mo , Cheoun Myung-Ki
Published: November 2021

A moving ion in plasma creates a deformed electric potential depending on the ion velocity, which leads to the distinct screening effect compared to the standard static Salpeter formula. In this paper, adopting the test charge method, we explore the dynamical screening effects on big bang nucleosynthesis (BBN). We find that the high temperature in the early universe causes the ion velocity to be faster than the solar condition so that the electric potential is effectively polarized. However, the low density of background plasma components significantly suppresses the dynamical screening effects on thermonuclear reaction rates during the BBN epoch. We compare our results with several thermonuclear reaction rates for solar fusion considering the dynamical screening effects. Also, we discuss the additional plasma properties in other astrophysical sites for the possible expansion from the present calculation in the future.
Organic electrolytic photocapacitors for stimulation of the mouse somatosensory cortex
Authors: Missey Florian , Botzanowski Boris , Migliaccio Ludovico , Acerbo Emma , Głowacki Eric Daniel , Williamson Adam
Published: November 2021

Objective. For decades electrical stimulation has been used in neuroscience to investigate brain networks and been deployed clinically as a mode of therapy. Classically, all methods of electrical stimulation require implanted electrodes to be connected in some manner to an apparatus which provides power for the stimulation itself. Approach. We show the use of novel organic electronic devices, specifically organic electrolytic photocapacitors (OEPCs), which can be activated when illuminated with deep-red wavelengths of light and correspondingly do not require connections with external wires or power supplies when implanted at various depths in vivo. Main results. We stimulated cortical brain tissue of mice with devices implanted subcutaneously, as well as beneath both the skin and skull to demonstrate a wireless stimulation of the whisker motor cortex. Devices induced both a behavior response (whisker movement) and a sensory response in the corresponding sensory cortex. Additionally, we showed that coating OEPCs with a thin layer of a conducting polymer formulation (PEDOT:PSS) significantly increases their charge storage capacity, and can be used to further optimize the applied photoelectrical stimulation. Significance. Overall, this new technology can provide an on-demand electrical stimulation by simply using an OEPC and a deep-red wavelength illumination. Wires and interconnects to provide power to implanted neurostimulation electrodes are often problematic in freely-moving animal research and with implanted electrodes for long-term therapy in patients. Our wireless brain stimulation opens new perspectives for wireless electrical stimulation for applications in fundamental neurostimulation and in chronic therapy.
On the dynamic effects of evaporation and boiling of drops on inhomogeneous graphene substrates for effective thermal management of energy devices
Authors: Babenko D D , Dmitriev A S , Mikhailova I A
Published: November 2021

This research examines thermal performance of metal-graphene nanocomposites for thermal management. Graphene nanoflakes and graphite microparticles were compressed with cooper meshes under different pressures. The prepared samples were characterized using optical microscopy. The fabricated samples of cooper-graphene composites were studied to determine the droplet evaporation rates and contact angles at different temperatures including film boiling.
Power spectra of pressure pulsations in the processes of evaporation/boiling of a liquid at low pressures
Authors: Brester A E , Zhukov V I , Shvetsov D A , Pavlenko A N
Published: November 2021

This paper presents experimental data on pressure fluctuations during evaporation/boiling of a thin liquid film under conditions of reduced pressure. The experimental data were obtained as a result of studying heat transfer on a smooth horizontal surface in a wide range of changes in the height of the liquid layer. Using the fast Fourier transform, the power spectra of pressure pulsations versus frequency were obtained. It was found that the power spectra of pressure pulsations differ depending on the mode of evaporation/boiling in the system.
Non-trivial capillary hydrodynamics and strong evaporative cooling in multilayer two-dimensional materials: application in thermal management systems of electronic and energy devices
Authors: Dmitriev A S
Published: November 2021

Studies of evaporation from graphene nanostructures with nontrivial capillary hydrodynamics are being carried out. Data were obtained for the rates of evaporation and heat fluxes during cooling of experimental heated cells. Models were built and compared with experimental data. It is shown that the existing models overestimate the evaporation rates and heat fluxes and heat transfer coefficients.
Modelling the hydrodynamics of a two-phase flow in the non-Newtonian fluid
Authors: Kozhukhova E A , Kozhukhov N N , Ryazhskikh V I , Naumov A M , Netreba A V
Published: November 2021

The paper presents the results of modelling the flow of droplets in the flow of a non-Newtonian fluid. The task is solved in a nonstationary formulation. We determined the time of stabilization of the speed profile of the droplets and the length of the initial hydrodynamic sector. We compared the specified characteristics for the main flow of the non-Newtonian fluid and for the set of droplets in the flow. We show the coincidence of the lengths of the initial hydrodynamic sections determined by the stabilization of speeds for the droplets and the non-Newtonian medium.
Modern approaches to the intensification of heat and mass exchange in multi-temperature condensation filters
Authors: Malevany M V , Konovalov D A
Published: November 2021

The article considers the problems and features of heat and mass exchange on developed surfaces in the conditions of both single-phase and vapour-liquid flow during its condensation. We give a brief analytical review of studies of hydrodynamics and heat exchange in such systems. We analyzed the efficiency of the working channel of the condensation filter and identified problematic points. We offer possible methods for intensifying heat and mass transfer on working surfaces.
Flow and heat transfer near a cylinders row
Authors: Mityakov A V , Gusakov A A , Grekov M A , Seroshtanov V V
Published: November 2021

The paper aims to investigate the dependence of heat transfer classification on the Reynolds number (Re) during flow around circular heated cylinders row. The investigated range of Re number varies from 4.5×103 up to 42×103. The distance between cylinders S was changed from 0.5d to 4d (where d is the cylinders dia). Cylinders surface temperature was kept constant. For each Re number, the case when the cylinders were mounted one after the other was investigated. To measure heat transfer and flow parameters (velocity, heat flux and heat transfer coefficient) near and at the cylinders surface, two experimental methods were used: gradient heatmetry and PIV. Heat flux and velocity fields were obtained from gradient heatmetry and PIV results, based on which the flow mode could be determined and compared with heat transfer mode. As a result, it was found that heat transfer is influenced by both the Reynolds number and the distance between the cylinders. The observed features are associated with influence on characteristics such as separation point location, boundary layer thickness, change in flow between the cylinders and vortices formation.
Investigation of the influence of narrowing annular channel and Reynolds number on formation of Tayler-Gortler vortexes
Authors: Pankratov E V
Published: November 2021

Abstract. The article investigates the Taylor-Gortler vortices arising in a swirling flow when the annular channel narrows. Several options for the geometry of the narrowed annular channel are researched. In the first case, the outer cylinder with a constant diameter and the inner cone with a variable cone angle are considered. In the second case, on the contrary an inner cylinder with a constant diameter and an outer cone with a variable cone angle are considered. All geometries were tested at different Reynolds numbers Re. = 8.3-103…21•103. As a result, the analysis of the propagation of secondary vortices along the length of the annular channel is presented.
Investigation of the influence of Taylor-Gortler vortexes on heat transfer of annular channel
Authors: Pankratov E V
Published: November 2021

This article is about the influence of Taylor-Gortler vortices on heat transfer in concentric annular channels with turbulent decaying swirling flows. The study shows that the occurrence and transformation of secondary vortex structures has a significant effect on the distribution of heat flux over the annular channel surface. An explicit is relationship between the radial velocity fluctuations and the heat flux density distribution. The highest intensity of heat transfer on the outer surface is observed in the areas of positive radial velocity values, while on the inner surface it is observed in the areas of negative radial velocity values.
Method for calculating the critical heat flux at pool boiling on structured surfaces
Authors: Stupakova A V , Dedov A V
Published: November 2021

A method of the critical heat flux enhancements at pool boiling using rough structures of various regular and irregular geometries is investigated. The experimental data are compared, and the critical heat flux is calculated since the V. V. Yagov model, which considers the additional inflow of liquid into the evaporation zone due to the action of capillary forces in the porous space. Based on the comparison of experimental and calculated data, it is concluded that the model is not universal for all microstructured surfaces. Recommendations for the calculation are given.
Modeling of vapor bubble growth at subatmospheric pressures
Authors: Vladyko I V , Malakhov I P , Surtaev A S , Pil’nik A A , Chernov A A
Published: November 2021

In this paper, the results of numerical calculations of a vapor bubble growth in superheated water at different pressures are presented. Modeling is based on a previously developed by the authors semi-analytical solution. The results are verified by experimental data obtained at atmospheric and subatmospheric pressures. The presented simulation results and experimental data are in good agreement. The advantage of the solution over the earlier ones (based on the thermal growth model) is shown.
Analytical solution to the problem of diffusion of the light component of the binary gas mixture in a plane channel
Authors: Popov V N , Popov I V
Published: November 2021

Within the framework of the kinetic approach, an analytical solution to the problem of diffusion of the light component of a binary mixture in a flat channel with infinite parallel walls is constructed. It is assumed that the mass of light component molecules and their concentration is much less than the mass of molecules and the concentration of heavy components. The flow rate of the heavy component is assumed to be zero. The change in the state of a light gas component is described on the basis of the BGK (Bhatnagar, Gross, Kruk) model of the Boltzmann kinetic equation. The diffuse reflection model is used as a boundary condition on the channel walls. The mass velocity profile of the light gas component is constructed. The flow rate of the light gas component per unit channel width is calculated. A comparison with similar results presented in open sources was done.
Simulation of a two-dimensional binary gas mixture outflow into vacuum through a thin slit on the basis of direct solution of the Boltzmann kinetic equation
Authors: Sitnikov S S , Tcheremissine F G , Sazykina T A
Published: November 2021

Two-dimensional binary gas mixture outflow from a vessel into vacuum through a thin slit is studied on the basis of direct solution of the Boltzmann kinetic equation. For evaluation of collision integrals in the Boltzmann equation a conservative projection method is used. Numerical simulation of a two-dimensional argon-neon gas mixture outflow from a vessel into vacuum was performed. Graphs of mixture components flow rate dependence on time during the flow formation, as well as fields of molecular density and temperature for steady-state regime, were obtained.
On reconstruction of the coefficient in complex Helmholtz’s equation
Authors: Malovichko M , Orazbayev A , Kloss Yu , Khokhlov N
Published: November 2021

This note summarizes some preliminary results on the fast solution of the coefficient inverse problem for the Helmholtz equation, given measured pressure in a set of observation points. The Helmholtz equation is the model PDE for the harmonic problem of the linear theory of elasticity, and this work is a move in that direction. The problem has been the primary focus for several research areas, most notably seismic exploration. Still, practical problems are very challenging because they are non-linear and large. In this paper, we develop a novel numerical method for seismic full-waveform inversion based on Newton iterations. Its distinctive future is that it does not require the Jacobian of the target functional. Thus, in certain scenarios, it will perform only a fraction of computations comparing to the conventional Gauss-Newton algorithm. We present some early results on the Helmholtz equation in two dimensions.
Determination of Reynolds shear stress from the turbulent mean velocity profile and spectral characteristics of Orr-Sommerfeld -Squire equations
Authors: Selim R. S.
Published: November 2021

Theoretically, based on a waveguide model, the expression of the tangential stress is formulated for steady, two-dimensional incompressible fluid flow over a flat plate in turbulent boundary layer. It is dependent on some factors, one of them, the behaviour of the last damping mode eigenvalues, and eigenfunctions, that are deduced from solution Orr-Sommerfeld equation by spectral Chebyshev collocation Method. Verification of the latter method is investigated by comparison the deduced formula of turbulent tangential stress with experimental data. In addition to, weight factors in this expression are connected to define the condition of dynamical system solution for multiple 3-wave resonance. This system is solved numerically, and the dynamic invariant is normalized to obtain the time average of the square modulus harmonic, and sub harmonics amplitudes by theorem Birkhoff-Khinchin. Comparison is made between the time-averaged and the phase average for the square modulus of harmonic, and sub harmonic amplitudes that defined on the unit sphere, in the state of multiple 3-wave resonance.