bluuebunny/crossref_metadata_2025 huggingface dataset:
Stirling Engine and oil-free compressors
Authors: Raballand Thierry
Published: October 2021

Refering to figure 1 [Fig.1], an oscillating « flipper » piston (1) and its associated chamber (2) are maintained without reciprocal contact. No oil is required because there is no contact and so no friction. An oscillating shaft (22) maintains the oscillating « flipper »piston (1). Around shaft (22), a twisting seal (8) allows for absolute sealing. This characteristic is important for Stirling engines and oil-free compressors. Referring to figure 4 [Fig.4], the two oscillating « flipper » pistons on the left belong to a Stirling-Franchot engine, more particularly to a Stirling-Franchot engine with two oscillating « flipper » pistons and so with two quadric crank mechanisms. The oscillating « flipper » piston on the right belongs to an oil-free compressor. The Stirling engine shaft (11), which is in alternative rotation, directly powers the oil-free compressor shaft (22). This prevents the use of a third quadric crank mechanism from shaft (33) to shaft (22). A Stirling engine connected to an oilfree compressor is useful when the fluid is precious or dangerous. A French patent was taken out on Februar 1st, 2020.
Stirling-powered solar dish collector with compressed air energy storage system
Authors: Ricco Giovanni
Published: October 2021

At present time, the SE applied to solar dish reflectors is not competitive compared to other concentrated solar power technologies because Stirling CSP equipment has complex and expensive engines and does not have a proper energy storage system. This paper introduces Stirling solar dish technology, proposes a layout of a simple SE with compressed air storage system, and examines the total performance of the equipment.
A method for evaluating the heat rejection efficiency in a Lunar power plant consisting of a free-piston Stirling engine (FPSE)
Authors: Smirnov Sergey , Sinkevich Mikhail , Antipov Yuri , Khalife Hassan
Published: October 2021

A method for evaluating the heat rejection efficiency in a Lunar power plant consisting of a free-piston Stirling engine FPSE is proposed. The waste heat from the FPSE is absorbed by the refrigerant circulating in a closed pumped loop and then rejected through a radiator into space. The magnitude of the heat flux rejected through the radiator is determined by the temperature difference between the radiator fins and surrounding environment, as well as the surface areas of the radiator and the emissivity coefficient. The method developed is used to qualitatively evaluate the refrigerant efficiency based on calculating the average temperature of the radiator fin which is established during the heat exchange process in the radiator. The method allowed us to determine the most efficient refrigerant in terms of maximum heat rejection at a given operating temperature range without the need of detailed calculations like in the previous works of the authors. Computational studies in a two-dimensional formulation of the radiator, using helium or liquid ammonia as a refrigerant, to determine the quantitative characteristics of the heat rejection process and overall dimensions of the radiator were performed, and a comparative analysis of the results is presented.
Demonstration of flywheel-based travelling-wave thermoacoustic engine
Authors: Watanabe Takumaru , Shoji Eita , Biwa Tetsushi , Penelet Guillaume
Published: October 2021

We report test results on a thermoacoustic engine having a piston-crank-flywheel assembly. The engine maintained steady rotation states when the heating temperature was increased more than 114°C. The rotation frequency increased with the higher heating temperature and reached 14.5 Hz when it was 296°C. The pressure versus volume diagram was created to deduce the power delivered to the piston-crank-flywheel assembly from measurements of the pressure of the working gas and the rotation angle of the flywheel.
Stirling Thermodynamics using Phasor Notation
Authors: Berchowitz David M.
Published: October 2021

Phasor mathematics is used to develop the isothermal Stirling cycle and extended to the ideal adiabatic Stirling cycle. The results are developed for piston – piston (alpha) machines and displacer – piston (beta and gamma) machines. The effect of non-ideal regeneration is handled by defining a regenerator effectiveness ratio. The importance of the amplitude pressure ratio (pressure amplitude to the mean pressure) is developed and shown to be a useful parameter when evaluating the effect of dead volume or when applying simple cycle analyses. The analysis is developed for both power producing and cooling engines. The utility of these analyses is discussed with respect to calibrated results of real machines.
Weight restrictions for the DEA model in the presence of dual-role factors: An application to the Iranian banking sector
Authors: Ghazi Amineh , Lotfi Farhad Hosseinzadeh
Published: October 2021

A production process transforming multiple inputs to different outputs is considered in conventional data envelopment analysis (DEA) models. In various settings, however, there are factors that simultaneously play the roles of both input and output called dual-role factors. In some situations, additional information is available to impose on a DEA model with dual-role factors, or the decision maker is forced to impose some restrictions regarding the importance of dual-role factors on the model. Toward this end, the current research employs two different weighting methods to introduce various weighted DEA models in the presence of dual-role factors. To strengthen the accuracy of the new models, their properties are discussed. Then, each new model is illustrated in details by a numerical example. Moreover, to show that the new models are applicable, they are applied to the Iranian banking sector. To do this, 20 bank branches which have dual-role factors are assessed. At last, to show the outcome of weight restrictions, the results obtained by each new model are compared with those from Cook and Zhu’s model [Eur. J. Oper. Res. 180 (2007) 692–699].
Rotational and reflectional equivariant convolutional neural network for data-limited applications: Multiphase flow demonstration
Authors: Siddani B. , Balachandar S. , Fang R.
Published: October 2021

This article deals with approximating steady-state particle-resolved fluid flow around a fixed particle of interest under the influence of randomly distributed stationary particles in a dispersed multiphase setup using convolutional neural network (CNN). The considered problem involves rotational symmetry about the mean velocity (streamwise) direction. Thus, this work enforces this symmetry using SE(3)-equivariant, special Euclidean group of dimension 3, CNN architecture, which is translation and three-dimensional rotation equivariant. This study mainly explores the generalization capabilities and benefits of a SE(3)-equivariant network. Accurate synthetic flow fields for Reynolds number and particle volume fraction combinations spanning over a range of [86.22, 172.96] and [0.11, 0.45], respectively, are produced with careful application of symmetry-aware data-driven approach.
Formation, lithium storage properties, and mechanism of nanoporous germanium fabricated by dealloying
Authors: Wang Shengzhen , Ma Wensheng , Yang Wanfeng , Bai Qingguo , Gao Hui , Peng Zhangquan , Zhang Zhonghua
Published: October 2021

Germanium (Ge) has become a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity and decent electron/ion conductivity, but it exhibits inferior lifespan caused by dramatic volume variations during the (de)lithiation process. Herein, hierarchically, nanoporous Ge (np-Ge) was fabricated by the combination of selective phase corrosion with chemical dealloying. As an anode for LIBs, the np-Ge electrode exhibits marvelous cycling stability with capacity retentions of 1060.0 mA h g−1 at 0.2 A g−1 and 767.1 mA h g−1 at 1 A g−1 after 100 cycles. Moreover, the electrode shows excellent rate capability with a capacity retention of 844.2 mA h g−1 at 5 A g−1. Noticeably, the (de)lithiation mechanisms of np-Ge and porous Si–Ge (p-Si6Ge4) were unveiled by operando X-ray diffraction.
Kinetic theory of polydisperse gas–solid flow: Navier–Stokes transport coefficients
Authors: Zhao Bidan , Wang Junwu
Published: October 2021

The particulate phase stress and solid–solid drag force in the multifluid modeling of polydisperse gas–solid flows are usually closed using kinetic theory. This research aims to establish the hydrodynamic equations and constitutive relations of the multifluid model for polydisperse systems via species kinetic theory, in which the non-equipartition of energy and interphase slip velocity between different species are considered. Whereas previous studies have used approximations, such as Taylor series expansions, to simplify the calculation of collision integrals, the present study, for the first time, solves the collision integrals analytically without any approximations to obtain accurate constitutive relations. Explicit expressions for the constitutive laws are obtained, including the particle stress tensor, solid–solid drag force, heat flux, and energy dissipation rate up to the Navier–Stokes order. The present study offers more complete and mathematically rigorous constitutive laws for the multifluid modeling of polydisperse gas–solid flows.
Melatonin treatment during late gestation of undernourished ewes: lamb body temperature and mother–young behaviours after birth
Authors: Freitas-de-Melo A. , Sales F. , Ungerfeld R. , Parraguez V. H.
Published: October 2021

Context In extensive grazing sheep systems, pregnant ewes undergo periods of undernutrition because gestation coincides with winter when natural pasture is of lowest quantity and poorest quality. The lamb’s weight and thermoregulatory capacity, and the ewe–lamb bond at birth, may be compromised. Maternal melatonin treatment during gestation may reverse these effects. Aim The aim was to determine the effects of melatonin treatment of single-lambing, undernourished ewes during the last third of gestation on lamb birthweights and body temperatures, and on ewe–lamb interactive behaviour after birth. Methods At Day 100 of gestation, 39 single-bearing ewes received a subcutaneous melatonin implant, and 54 ewes served as controls with no implant. Throughout gestation, the ewes remained under extensive conditions grazing on natural pasture. Measurements were made of lamb birthweight, body temperatures (surface temperature by infrared thermography and rectal temperature), and ewe–lamb behaviours during a handling test at 6–17 h after lambing. Key results There was no effect of melatonin treatment on lamb birthweight or rectal temperature, or on ewe–lamb interaction behaviours. Hip minimum surface temperature was greater in lambs from melatonin-treated ewes than lambs from control ewes (21.2°C ± 0.9°C vs 18.8°C ± 0.8°C; P = 0.05), and there was a similar trend for hip mean surface temperature (24.6°C ± 0.9°C vs 22.3°C ± 0.7°C; P = 0.06). Rump surface temperatures were greater in male than female lambs: maximum (27.9°C ± 1.2°C vs 22.9°C ± 1.2°C; P = 0.01), minimum (22.2°C ± 1.5°C vs 16.7°C ± 1.5°C; P = 0.02) and mean (25.4°C ± 1.3°C vs 20.5°C ± 1.3°C; P = 0.02). Conclusion Melatonin treatment during the last third of ewe pregnancy slightly enhanced the surface temperature of lambs at birth but did not influence ewe–lamb interaction behaviour after birth (i.e. after establishment of the ewe–lamb bond). Implications Further study in more depth is warranted into the possible effects of maternal supplementation with commercial melatonin implants on lamb development, thermoregulatory capacity, behaviour and survival rates in extensive grazing systems, including the effect on ewe–lamb behaviours immediately after birth for both singletons and twins.
Effects of different concentrations of eugenol in maturation medium on bovine oocytes, oxidative status and preimplantation embryos
Authors: de Oliveira Lhara Ricarliany Medeiros , Aquino Leonardo Vitorino Costa de , Santos Maria Valéria de Oliveira , Freitas Vicente José de Figueirêdo , Bertini Luciana Medeiros , Pereira Alexsandra Fernandes
Published: October 2021

Context Eugenol is a bioactive compound with defined attributes, including a role in reducing oxidative stress. Therefore, it is an interesting candidate for in vitro embryo production that has an environment that favours the formation of reactive oxygen species. Aim The objective of the study was to evaluate different concentrations of eugenol in bovine oocytes during in vitro maturation to observe the oxidative status and embryonic development. Methods Oocytes were allocated into five groups: control (without antioxidant), 100 μM cysteamine, 83 μM eugenol (E83), 100 μM eugenol and 120 μM eugenol. Three experiments were performed with 23 replicates. Oocytes were evaluated for metaphase II, first polar body, cytoplasmic maturation, cumulus cell expansion and viability. Oxidative status was measured by mitochondrial membrane potential, reactive oxygen species and glutathione. Oocytes were artificially activated and cultured in vitro. Key results The presence of eugenol at 83 μM improved the metaphase II rate compared with all treatments (P < 0.05). E83 and 100 μM cysteamine improved first polar body extrusion, cumulus cell expansion, viability and mitochondrial aggregation rates (P < 0.05). All antioxidant treatments resulted in increased cytoplasmic maturation and decreased mitochondrial membrane potential (P < 0.05). Reactive oxygen species levels decreased, and glutathione levels increased with E83 and 100 μM cysteamine treatments (P < 0.05). Finally, the E83 group increased the cleavage rates, embryo development, number of expanded blastocysts and number of blastomeres (P < 0.05). Conclusions A low concentration of eugenol (83 μM) is sufficient to generate a significant effect, attenuating the oxidative status and optimising i n vitro maturation and embryo development. Implications This study provides information of a new natural antioxidant with defined concentration, 83 μM eugenol, representing a lower cost alternative capable of improving the efficiency of in vitro embryo production in cattle.
Dynactin 1 negatively regulates HIV-1 infection by sequestering the host cofactor CLIP170
Authors: Shanmugapriya Shanmugapriya , Santos da Silva Eveline , Campbell Jackson A. , Boisjoli Marie-Philipe , Naghavi Mojgan H.
Published: October 2021

Significance

While HIV type 1 (HIV-1) is known to exploit host microtubules and motors to reach the nucleus and establish infection, our understanding of the precise factors involved and underlying mechanisms remains limited. In particular, why HIV-1 does not rely upon the core dynein adaptor subunit dynactin-1 (DCTN1) is unclear. Here, we reveal that beyond its motor–adaptor functions, DCTN1 acts as a negative regulator of early HIV-1 infection by competitively binding and sequestering the host cofactor cytoplasmic linker protein 170 that regulates the stability of incoming viral particles. Our findings provide insights into DCTN1 function and offer a rationale for why HIV-1 might have evolved away from DCTN1 in favor of BICD2-based engagement of dynein.
Collapse of complexity of brain and body activity due to excessive inhibition and MeCP2 disruption
Authors: Li Jingwen , Kells Patrick A. , Osgood Ayla C. , Gautam Shree Hari , Shew Woodrow L.
Published: October 2021

Significance

How does brain function falter when inhibition is not properly balanced by excitation in cerebral cortex? Here we show in rats that excessive inhibition leads to stereotyped, low-complexity relationships among neurons in motor cortex and body movements. We observed similar phenomena in rats with disrupted MeCP2 function, suggesting that imbalanced inhibition may contribute to motor dysfunction in Rett syndrome.
Curial e Güelfa
Authors: Soler Molina Abel
Published: October 2021

Resum

L’anònima novel·la cavalleresca Curial e
Güelfa (Nàpols-Milà?, ca. 1445–1448)
es considera, juntament amb el Tirant lo Blanc, de
Joanot Martorell, una de les obres mestres de les lletres catalanes
del segle XV. Tanmateix, el fet que l’anònim –procedent de València,
però culturalment italianitzat– emprara el català com a vehicle
d’expressió literària no és cap obstacle per a catalogar el llibre,
per la seua modernitat (influx de l’ideari humanístic i del
neoplatonisme, sàtira llucianesca, ironia metaliterària…), com una
obra de “recepció” de la cultura del Quattrocento
italià per part d’algú format en la tradició medieval (llibres de
cavalleria, lírica trobadoresca, amor cortés), però que pretén
emular el Boccaccio napolità, concertant armes i amors en una àgil
narrativa de ficció. S’acaba el secolo senza poesia
i s’enceta amb el Curial un gènere de gust
aristocràtic, que hom sol denominar umanesimo
cavalleresco o, més pròpiament dit, cavalleria
humanística. El nou gènere florirà a la Florència dels Mèdici uns
anys després.
Derivational morphology in Croatian child language
Authors: Hržica Gordana
Published: October 2021

Few studies have analysed derivation in languages other
than English, including Croatian. This study shows that by the age of three
years, Croatian children already use a high number of derived words,
especially prefixed verbs. Both the number of acquired affixes and
proportion of derived words increase with age. Verbs are mainly prefixed and
nouns suffixed. The most prevalent semantic categories in nouns are objects
and instruments, and derivation in verbs marks differences in aspect and/or
Aktionsart. Later child speech shows productive usage
of derivation, including derivational pairs and mini-paradigms, neologisms
and neosemantism. The frequency of derived words in child-directed speech
influences their frequency in child language. Compared to children, adults
employ a broader repertoire of derivational patterns.
Acquisition of derivational morphology in Russian
Authors: Kazakovskaya Victoria , Voeikova Maria D.
Published: October 2021

The chapter examines the onset of derivational morphology
in the speech production of two Russian boys (aged between 1;5–2;8 and
1;8–3;0). This process involves early nouns, verbs and adjectives built by
different derivation methods. Suffixation is typical for nouns and
adjectives, whereas new verbs are mostly built by prefixation. Derived verbs
and nouns belong to the same grammatical class as the originals and
adjectives are formed from nouns. Productive use of derivation was
registered several months after the first derivatives occur. The differences
between adult-child dyads relate to the set of semantic categories of derived words and
the proportion of derivatives belonging to different grammatical classes.
Further development of derivation (4;2 to 5;10) in one of the boys was
tracked.
Nutritional value of
Cyperus esculentus
L. (Neglected and Underutilized Crop Species): implication for valorization
Authors: Palanga Koffi Kibalou , Akabassi Ghislain Comlan , Padonou Elie Antoine , Dagnon Yao Dodzi , Tozo Koffi , Assogbadjo Achille Ephrem
Published: October 2021

The investigation of the nutritional value of Neglected and Underutilized Crop Species is essential for their valorization. This global systematic review aimed at investigating the nutritional value of tigernut to highlight the importance of the species in the fight against malnutrition. Extensive searches were carried out through three databases (ScienceDirect, Google Scholar, and African Journal Online) from March to April 2021, and studies were screened and extracted using the established systematic review methods. A total of 36 papers from Africa, America, Asia, and Europe met the inclusion criteria. Thematic synthesis was used to synthesize data, and findings were presented under three framework aspects (biochemical, mineral composition, and vitamin content). About 63.88% of the papers included in this global review were published from 2010 to 2020. The highest number of papers (
n
 = 14) was recorded between 2015 and 2020, and most of the publications were from Europe (
n
 = 13). The review showed that tigernut contained alkaloids, cyanogenic glycosides, resins, tannins, sterols, and saponins. It was very rich in potassium (K), followed by phosphorus (P), magnesium (Mg), calcium (Ca) sodium (Na), iron (Fe), zinc (Zn), copper (Cu), and vitamins A, B, C, D, and E. The review has also revealed that biochemical composition and vitamin content of tigernut depend on its geographical origin. Overall, the results highlighted the nutritional values of tigernut. Its valorization in foodstuffs could increase the profitability of this crop and contribute to the fight against malnutrition in Africa.
Manipulation of optical nonreciprocity in hot atom-cavity system
Authors: Zhou Hai-Tao , Xie Shu-Yun , Li Xin , Wang Dan , Yang Bao-Dong , Zhang Jun-Xiang
Published: October 2021

Hot atoms can exhibit non-magnetic optical non-reciprocal transmission due to their chiral properties, which are characteristic of most alkali metal atoms. In fact, the nonreciprocity in hot atoms depends on the propagation direction of the coupling field due to the Doppler effect. Herein, the reciprocal to non-reciprocal conversion based on the single- and double-dark states is realized by controlling the bidirectional coupling fields in a three-level electromagnetically induced transparent medium coupled with a ring cavity. Tuning the frequency difference between the two coupling fields causes the multi-frequency-channel reciprocity and nonreciprocity manipulation to occur. The experimental proof can be applied to quantum communications and quantum networks, such as optical transistors, all-optical switching or routing and logic gate operation.
Recent progress and applications of terahertz metamaterials
Authors: He Jingwen , He Xunjun , Dong Tao , Wang Sen , Fu Maixia , Zhang Yan
Published: October 2021

Metamaterials are an artificial electromagnetic material composed of periodic/non-periodic subwavelength micro-/nanostructures, i.e. meta-atoms. The meta-atom interacts with the incident electromagnetic wave and introduces electromagnetic resonance, which makes the metamaterial exhibit the desired electromagnetic characteristics. Therefore, the electromagnetic wave can be controlled by changing the geometry, configuration and distribution of the meta-atoms. Due to their flexible electromagnetic manipulation ability, metamaterials have attracted great interest in many fields, such as super-resolution imaging, high-sensitive detection, aerocraft stealth and laser-machining. A planar metamaterial with one or a few layers of meta-atoms is called a metasurface. The metasurface can not only manipulate the amplitude, phase and polarization of the electromagnetic waves, but also has the advantages of being ultra-thin, ultra-light and easy to process. In the terahertz (THz) region, more and more devices based on metasurfaces have been proposed for spectrum modulation and wavefront shaping, which has contributed to the rapid development of THz technology. This paper reviews the design principles and research progress of metamaterials/metasurfaces for spectrum modulation, wavefront shaping, polarization conversion and surface wave manipulation in the THz region. Active metamaterials can be used to manipulate electromagnetic waves dynamically, and this will become a research field with great application potential. In this review, the implementation schemes and research results of various active THz metamaterial devices are reviewed in detail. Furthermore, the potential applications of metamaterials/metasurfaces in security, high-capacity communication, biomedicine and other fields are analyzed. Finally, we discuss the future developments and challenges of THz metamaterials.
New and old probes of dark matter scenarios on galactic and sub-galactic scales
Authors: Mayer Lucio
Published: October 2021

This review focuses on novel astrophysical probes of dark matter at galactic and sub-galactic scales. After reviewing classical tests of cold dark matter (CDM) in galaxy formation, we discuss them in light of recent results from increasingly detailed simulations and observations, and then shift our attention to more recent, less explored tests in the context of the most popular and most studied dark matter scenarios alternative to CDM. Among them, there are warm dark matter (WDM) scenarios, arising, for example, from sterile neutrinos, as well as self-interacting dark matter (SIDM) scenarios , mixed models that combine WDM and SIDM, and Bose–Einstein condensate/fuzzy dark matter scenarios (FDM/BECDM) originating from ultra-light bosons such as axions. The hypothesis that primordial black holes constitute all or most of the dark matter is also revisited in light of the LIGO/Virgo discovery of massive black holes together with very recent constraints from the internal structure of nearby ultra-faint dwarf galaxies. The important role of baryonic physics in the interpretation of various probes of dark matter, especially how it affects the ability to infer dark matter properties from observational diagnostics, is emphasized and reviewed. The effect of baryons blurs, in many cases, the underlying differences in the properties of dark matter halos arising in various dark matter models. Nevertheless, baryons can potentially be a useful tracer of such differences, for instance during the earliest phases of star formation in the lowest mass galaxies. New promising probes which will be delivered by future gravitational wave experiments are discussed, such as the occurrence rate of gravitational wave signals from merging intermediate mass black holes in dwarf galaxies tracing the inner structure of dark halos. Recent observational discoveries and analysis methods, such as the tentative detection of dark subhalos through the analysis of stellar tidal streams in the Milky Way halo, and the prospects of gravitational lensing analysis to directly detect dark substructure down to the relevant small scales, are also illustrated.
Theory of unidirectional magnetoresistance and nonlinear Hall effect
Authors: Freimuth Frank , Blügel Stefan , Mokrousov Yuriy
Published: October 2021

We study the unidirectional magnetoresistance (UMR) and the nonlinear Hall effect (NLHE) in the ferromagnetic Rashba model. For this purpose we derive expressions to describe the response of the electric current quadratic in the applied electric field. We compare two different formalisms, namely the standard Keldysh nonequilibrium formalism and the Moyal–Keldysh formalism, to derive the nonlinear conductivities of UMR and NLHE. We find that both formalisms lead to identical numerical results when applied to the ferromagnetic Rashba model. The UMR and the NLHE nonlinear conductivities tend to be comparable in magnitude according to our calculations. Additionally, their dependencies on the Rashba parameter and on the quasiparticle broadening are similar. The nonlinear zero-frequency response considered here is several orders of magnitude higher than the one at optical frequencies that describes the photocurrent generation in the ferromagnetic Rashba model. Additionally, we compare our Keldysh nonequilibrium expression in the independent-particle approximation to literature expressions of the UMR that have been obtained within the constant relaxation time approximation of the Boltzmann formalism. We find that both formalisms converge to the same analytical formula in the limit of infinite relaxation time. However, remarkably, we find that the Boltzmann result does not correspond to the intraband term of the Keldysh expression. Instead, the Boltzmann result corresponds to the sum of the intraband term and an interband term that can be brought into the form of an effective intraband term due to the f-sum rule.
The activity evidence of Ti defect towards electrocatalytic N2 reduction
Authors: Wu Tongwei , Ma Chao , Wang Pai , Zhao Haitao , Zhang Yanning
Published: October 2021

Electrochemical N2 reduction reaction (NRR) for NH3 synthesis, which usually needs highly-efficient electrocatalysts for N2 activation, is a carbon-neutral alternation compared to the traditional Haber–Bosch process. Although Ti-based compounds is widely used as electrocatalysts, what Ti defect affects NRR activity is still illusive. In this work, our systematic density functional calculations on Ti defect-decorated titanium oxide disclose that the unsaturated-Ti with the orbital splitting of defect electron states is the necessary feature for N2 binding and activation, which can be further enhanced by increasing the splitting degree. The bonding/antibonding orbital population and projected density of states indicate that the nature of N2 binding and activation on Ti-defect site is attributed to the elimination of the bonding orbital population in the conduction bands and the formation of *
π back-bonding in the valence bands. For the whole NRR process, the synergy of Ti-defect and oxygen vacancy (VO) promotes N2 reduction, and the required maximum energy input scales quite well with the adsorption strength of *NNH. Finally, the formed volcano shape successfully predicts new candidate catalysts for ammonia synthesis, such as TiO2 combined VO with Ti interstitial or H atom. This work provides disclosure of the key elements on the rational design of Ti-based nanomaterial electrocatalysts for artificial N2 fixation.
Analytical solutions of some model cases of piston-cylinder assemblies
Authors: Pražák Dominik , Hajduk Tomáš , Krajíček Zdeněk , Šafaříková-Pštroszová Markéta , Tesař Jiří
Published: October 2021

Pressure balances are an important part of the sets of primary pressure standards in many national metrology institutes. The most critical factor determining their accuracy is the effective area of their piston-cylinder assemblies (PCAs). This can be determined (for PCAs with undistorted pressure) by applying a numerical procedure based on a theory by Dadson while knowing a gapprofile (of an axisymmetric PCA approximation). The pressure balances are also a basis for the primary pressure scale of the Czech Metrology Institute. Hence, we wanted to test our programme by computing the effective area from the geometrical data. Therefore, we solved the analytical formulae of Dadson et al (1982) The Pressure Balance—Theory and Practice (London: Her Majesty’s Stationery Office) for several simple geometries with a constant gap width, which are easy to calculate analytically. It is shown that the analytical results always agreed perfectly with the results of our programme. This success confirmed the correctness of our programme. However, it also pointed out a problem of discretization which can be non-negligible, even in the case of relatively simple geometries. We assume that the analytical formulae obtained can be of practical use for any other pressure metrology laboratory requiring an independent way to confirm their own PCA-modelling software.
Depth measurement based on a convolutional neural network and structured light
Authors: Jia Tong , Liu Yizhe , Yuan Xi , Li Wenhao , Chen Dongyue , Zhang Yichun
Published: October 2021

Depth measurement methods based on structured light are popular due to their advantages of low cost, good portability and ease of implementation. Depth information for the object is obtained based on the geometric relationship of the imaging system and triangulation theory, which usually requires local stereo matching operations. However, this is computationally intensive, resulting in reduced depth accuracy and worse depth maps. To address these problems, this paper proposes a novel depth measurement method based on a convolutional neural network (DMCNN), which is cast as a pixel-wise classification–regression task without matching. Firstly, the DMCNN network is designed as an encoder–decoder structure. A feature pyramid is adopted in the encoder to extract multi-scale fusion features, and parallel classification and regression branches are constructed at the end of the decoder to achieve depth prediction from coarse to fine. Secondly, we use a four-step phase shift algorithm to generate ground truth depth maps and build a dataset containing a large number of speckle distortion images and their corresponding depth maps to train our network. The algorithm runs on an RTX 2080Ti graphics processing unit (GPU) using 20 000 training images. Experimental results show that our method can achieve higher accuracy than alternative depth measurement methods.
Novel nitrogen plasma doping on CdS/GO compounds and their photocatalytic assessment
Authors: Ramos-Corona A , Rangel R , Lara J , Trejo-Tzab R , Bartolo P , Alvarado-Gil J J
Published: October 2021

Nitrogen-doping of cadmium sulfide nanostructured compounds was carried out under a nitrogen plasma source to produce CdS-N compounds. Once prepared, it was supported on graphene oxide sheets for producing CdS-N/GO photocatalysts, which were tested in the degradation of lignin and methylene blue (MB) molecules. Photocatalytic reactions were carried out under UV and visible (vis) energy irradiation. To provide insight on the catalytic behavior the CdS, CdS-N, GO, and CdS-N/GO compounds were characterized using different techniques including x-ray diffraction, scanning electron microscopy, Raman, and UV–vis diffuse reflectance spectroscopy. X-ray photoelectron spectroscopy allowed determining the chemical composition in samples. It was observed an outstanding performance in photocatalytic activity tests, attributed to the extended response towards the visible light regime, and the synergistic effect between CdS-N and GO particles. The catalytic activity tests, reveal that the CdS-N/GO compound achieved over 90% lignin degradation and 100% of MB degradation. In addition, a remarkable performance is observed in the CdS-N/GO compound which exhibited stability after performing several reaction cycles.
Dependence of nitrogen vacancy color centers on nitrogen concentration in synthetic diamond
Authors: Li Yong , Chen Xiaozhou , Ran Maowu , She Yanchao , Xiao Zhengguo , Hu Meihua , Wang Ying , An Jun
Published: October 2021

Crystallization of diamond with different nitrogen concentrations was carried out with a FeNiCo–C system at pressure of 6.5 GPa. As the nitrogen concentration in diamond increased, the color of the synthesized diamond crystals changed from colorless to yellow and finally to atrovirens (a dark green). All the Raman peaks for the obtained crystals were located at about 1330 cm−1 and contained only the sp3 hybrid diamond phase. Based on Fourier transform infrared results, the nitrogen concentration of the colorless diamond was < 1 ppm and absorption peaks corresponding to nitrogen impurities were not detected. However, the C-center nitrogen concentration of the atrovirens diamond reached 1030 ppm and the value of A-center nitrogen was approximately 180 ppm with a characteristic absorption peak at 1282 cm−1. Furthermore, neither the NV0 nor the NV− optical color center existed in diamond crystal with nitrogen impurities of less than 1 ppm by photoluminescence measurement. However, Ni-related centers located at 695 nm and 793.6 nm were observed in colorless diamond. The NE8 color center at 793.6 nm has more potential for application than the common NV centers. NV0 and NV− optical color centers coexist in diamond without any additives in the synthesis system. Importantly, only the NV− color center was noticed in diamond with a higher nitrogen concentration, which maximized optimization of the NV−/NV0 ratio in the diamond structure. This study has provided a new way to prepare diamond containing only NV− optical color centers.
Majorana fermions induced fast- and slow-light in a hybrid semiconducting nanowire/superconductor device
Authors: Chen Hua-Jun , Zhu Peng-Jie , Chen Yong-Lei , Hou Bao-Cheng
Published: October 2021

We investigate theoretically Rabi-like splitting and Fano resonance in absorption spectra of quantum dots (QDs) based on a hybrid QD-semiconducting nanowire/superconductor (SNW/SC) device mediated by Majorana fermions (MFs). Under the condition of pump on-resonance and off-resonance, the absorption spectrum experiences the conversion from Fano resonance to Rabi-like splitting in different parametric regimes. In addition, the Fano resonances are accompanied by the rapid normal phase dispersion, which will indicate the coherent optical propagation. The results indicate that the group velocity index is tunable with controlling the interaction between the QD and MFs, which can reach the conversion between the fast- and slow-light. Fano resonance will be another method to detect MFs and our research may indicate prospective applications in quantum information processing based on the hybrid QD-SNW/SC devices.
Optimal control strategy for COVID-19 concerning both life and economy based on deep reinforcement learning*
Authors: Deng Wei , Qi Guoyuan , Yu Xinchen
Published: October 2021

At present, the global COVID-19 is still severe. More and more countries have experienced second or even third outbreaks. The epidemic is far from over until the vaccine is successfully developed and put on the market on a large scale. Inappropriate epidemic control strategies may bring catastrophic consequences. It is essential to maximize the epidemic restraining and to mitigate economic damage. However, the study on the optimal control strategy concerning both sides is rare, and no optimal model has been built. In this paper, the Susceptible-Infectious-Hospitalized-Recovered (SIHR) compartment model is expanded to simulate the epidemic’s spread concerning isolation rate. An economic model affected by epidemic isolation measures is established. The effective reproduction number and the eigenvalues at the equilibrium point are introduced as the indicators of controllability and stability of the model and verified the effectiveness of the SIHR model. Based on the Deep Q Network (DQN), one of the deep reinforcement learning (RL) methods, the blocking policy is studied to maximize the economic output under the premise of controlling the number of infections in different stages. The epidemic control strategies given by deep RL under different learning strategies are compared for different reward coefficients. The study demonstrates that optimal policies may differ in various countries depending on disease spread and anti-economic risk ability. The results show that the more economical strategy, the less economic loss in the short term, which can save economically fragile countries from economic crises. In the second or third outbreak stage, the earlier the government adopts the control strategy, the smaller the economic loss. We recommend the method of deep RL to specify a policy which can control the epidemic while making quarantine economically viable.
On chip chiral and plasmonic hybrid dimer or tetramer: Generic way to reverse longitudinal and lateral optical binding forces
Authors: Biswas Sudipta , Rumi Roksana Khanam , Raima Tasnia Rahman , Das Saikat Chandra , Mahdy M R C
Published: October 2021

For both the longitudinal binding force and the lateral binding force, a generic way of controlling the mutual attraction and repulsion (usually referred to as reversal of optical binding force) between chiral and plasmonic hybrid dimers or tetramers has not been reported so far. In this paper, by using a simple plane wave and an onchip configuration, we propose a possible generic way to control the binding force for such hybrid objects in both the near-field region and the far-field region. We also investigate different inter-particle distances while varying the wavelengths of light for each inter-particle distance throughout the investigations. First of all, for the case of longitudinal binding force, we find that chiral-plasmonic hybrid dimer pairs do not exhibit any reversal of optical binding force in the near-field region nor in the far-field region when the wavelength of light is varied in an air medium. However, when the same hybrid system of nanoparticles is placed over a plasmonic substrate, a possible chip, it is possible to achieve a reversal of the longitudinal optical binding force. Later, for the case of lateral optical binding force, we investigate a setup where we place the chiral and plasmonic tetramers on a plasmonic substrate by using two chiral nanoparticles and two plasmonic nanoparticles, with the setup illuminated by a circularly polarized plane wave. By applying the left-handed and the right-handed circular polarization state of light, we also observe the near-field and the far-field reversal of lateral optical binding force for both cases. As far as we know, so far, no work has been reported in the literature on the generic way of reversing the longitudinal optical binding force and the lateral optical binding force of such hybrid objects. Such a generic way of controlling optical binding forces can have important applications in different fields of science and technology in the near future.
Towards threshold invariance in defining hippocampal ripples
Authors: Watanabe Yusuke , Okada Mami , Ikegaya Yuji
Published: October 2021

Objective. Hippocampal ripples are transient neuronal features observed in high-frequency oscillatory bands of local field potentials (LFPs), and they occur primarily during periods of behavioral immobility and slow-wave sleep. Ripples have been defined based on mathematically engineered features, such as magnitudes, durations, and cycles per event. However, the ‘ripple’ could vary from laboratory to laboratory because their definition is subject to human bias, including the arbitrary choice of parameters and thresholds. In addition, LFPs are often influenced by myoelectric noise arising from animal movement, making it difficult to distinguish ripples from high-frequency noises. These problems have to be overcome. Approach. We extracted ripple candidates under few constraints and labeled them as binary or stochastic ‘true’ or ‘false’ ripples using Gaussian mixed model clustering and a deep convolutional neural network (CNN) in a weakly supervised fashion. Main results. Our automatic method separated ripples and myoelectric noise and was able to detect ripples even when the animals were moving. Moreover, we confirmed that a CNN detected ripples defined by our method. Leave-one-animal-out cross-validation estimated the accuracy, the area under the precision-recall curve, the receiver operating characteristic curve to be 0.88, 0.99 and 0.96, respectively. Significance. Our automatic ripple detection method will reduce time spent on performing laborious experiments and analyses.
Deep brain stimulation: is it time to change gears by closing the loop?
Authors: Marceglia Sara , Guidetti Matteo , Harmsen Irene E , Loh Aaron , Meoni Sara , Foffani Guglielmo , Lozano Andres M , Volkmann Jens , Moro Elena , Priori Alberto
Published: October 2021

Objective. Adaptive deep brain stimulation (aDBS) is a form of invasive stimulation that was conceived to overcome the technical limitations of traditional DBS, which delivers continuous stimulation of the target structure without considering patients’ symptoms or status in real-time. Instead, aDBS delivers on-demand, contingency-based stimulation. So far, aDBS has been tested in several neurological conditions, and will be soon extensively studied to translate it into clinical practice. However, an exhaustive description of technical aspects is still missing. Approach. in this topical review, we summarize the knowledge about the current (and future) aDBS approach and control algorithms to deliver the stimulation, as reference for a deeper undestending of aDBS model. Main results. We discuss the conceptual and functional model of aDBS, which is based on the sensing module (that assesses the feedback variable), the control module (which interpretes the variable and elaborates the new stimulation parameters), and the stimulation module (that controls the delivery of stimulation), considering both the historical perspective and the state-of-the-art of available biomarkers. Significance. aDBS modulates neuronal circuits based on clinically relevant biofeedback signals in real-time. First developed in the mid-2000s, many groups have worked on improving closed-loop DBS technology. The field is now at a point in conducting large-scale randomized clinical trials to translate aDBS into clinical practice. As we move towards implanting brain-computer interfaces in patients, it will be important to understand the technical aspects of aDBS.
Non-resonant global mode in LHD partial collapse with net toroidal current
Authors: Ichiguchi K. , Suzuki Y. , Todo Y. , Sakakibara S. , Ida K. , Takemura Y. , Sato M. , Sugiyama L.E. , Carreras B.A.
Published: October 2021

A transition from an interchange mode to a non-resonant mode is found in the nonlinear magnetohydrodynamic simulation for the partial collapse in a large helical device (LHD) plasma with a net toroidal current. This transition can occur when the magnetic shear is weak and the rotational transform is close to unity in the core region. In this transition, the mode number of the dominant Fourier component is reduced. As a result of the nonlinear evolution, the (m, n) = (1, 1) component can be dominant, where m and n are the poloidal and the toroidal mode numbers, respectively. This transition is considered to be a candidate to explain the observation in the LHD experiments with the net toroidal current that show partial collapses are caused by the (1, 1) mode.
A dimensionality reduction algorithm for mapping tokamak operational regimes using a variational autoencoder (VAE) neural network
Authors: Wei Y. , Levesque J.P. , Hansen C.J. , Mauel M.E. , Navratil G.A.
Published: October 2021

A variational autoencoder (VAE) is a type of unsupervised neural network which is able to learn meaningful data representations in a reduced dimensional space. We present an application of VAE in identifying the operational stability boundary of tokamak plasma discharges. This model was implemented using a dataset of over 3000 discharges from the high beta tokamak-extended pulse (HBT-EP) device. We found the VAE model to be capable of forming a continuous low-dimensional operational space map and identifying the operational boundaries using a specified warning time window. By projecting the operational parameters onto the same reduced space, this provides an intuitive way for the machine operator or an automated control system to perform disruption avoidance using a relevant control actuator as a discharge approaches a boundary. Pre-programmed GPU control experiments were conducted to demonstrate this control technique using HBT-EP’s saddle control coils as a horizontal position actuator, showing the ability to avoid the oncoming disruptive event and extend the duration of the discharge.