bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.
Towards threshold invariance in defining hippocampal ripples
Authors: Watanabe Yusuke , Okada Mami , Ikegaya Yuji 
Published: October 2021

Abstract

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

Abstract

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

Abstract
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

Abstract
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.
Physics design of new lower tungsten divertor for long-pulse high-power operations in EAST
Authors: Xu G.S. , Wang L. , Yao D.M. , Jia G.Z. , Sang C.F. , Liu X.J. , Chen Y.P. , Si H. , Yang Z.S. , Guo H.Y. , Du H.L. , Luo Z.P. , Li H. , Zhou Z.B. , Cao L. , Xu H.C. , Xu T.J. , Wang Z.L. , Zi P.F. , Li L. , Han L. , Xu J.C. , Liu J.B. , Li K.D. , Cao B. , Yu Y.W. , Ding F. , Ding R. , Yan N. , Meng L.Y. , Tao Y.Q. , Wang H.Q. , Zhang Y. , Shao L.M. , Zhang X.D. , Zhu S.Z. , Wan B.N. , EAST Team the 
Published: October 2021

Abstract
A new lower tungsten divertor has been developed and installed in the EAST superconducting tokamak to replace the previous graphite divertor with power handling capability increasing from <2 MW m−2 to ∼10 MW m−2, aiming at achieving long-pulse H-mode operations in a full metal wall environment with the steady-state divertor heat flux of ∼10 MW m−2. A new divertor concept, ‘corner slot’ (CS) divertor, has been employed. By using the ‘corner effect’, a strongly dissipative divertor with the local buildup of high neutral pressure near the corner can be achieved, so that stable detachment can be maintained across the entire outer target plate with a relatively lower impurity seeding rate, at a separatrix density compatible with advanced steady-state core scenarios. These are essential for achieving efficient current drive with low-hybrid waves, a low core impurity concentration and thus a low loop voltage for fully non-inductive long-pulse operations. Compared with the highly closed small-angle-slot divertor in DIII-D, the new divertor in EAST exhibits the following merits: (1) a much simpler geometry with integral cassette body structure, combining vertical and horizontal target plates, which are more suitable for actively water-cooled W/Cu plasma facing components, facilitating installation precision control for minimizing surface misalignment, achieving high engineering reliability and lowering the capital cost as well; (2) it has much greater flexibility in magnetic configurations, allowing for the position of the outer strike point on either vertical or horizontal target plates to accommodate a relatively wide triangularity range, δ
l = 0.4–0.6, thus enabling to explore various advanced scenarios. A water-cooled copper in-vessel coil has been installed under the dome. Five supersonic molecular beam injection systems have been mounted in the divertor to achieve faster and more precise feedback control of the gas injection rate. Furthermore, this new divertor allows for double null divertor operation and slowly sweeping the outer strike point across the horizontal and vertical target plates to spread the heat flux for long-pulse operations. Preliminary experimental results demonstrate the ‘corner effect’ and are in good agreement with simulations using SOLPS-ITER code including drifts. The EAST new divertor provides a test-bed for the closed divertor concept to achieve steady-state detachment operation at high power. Next step, a more closed divertor, ‘sharp-cornered slot’ divertor, building upon the current CS divertor concept, has been proposed as a candidate for the EAST upper divertor upgrade.
Study on the influence of geometric imperfections and welding deformation on the global stability of orthogonal mixed with oblique single-layer reticulated shell
Authors: Wang Y M , Zheng F H , Wang J , Ju J S , Sang X X 
Published: October 2021

Abstract
Using finite element method to study the influence of geometric imperfections and welding deformation on the global stability of orthogonal mixed with oblique single-layer reticulated shells. The initial imperfection values of different geometries and the effects of welding residual deformation on the global stability of the ultimate bearing capacity of the structure are compared, and the difference between the instability modes of the two kinds of reticulated shells in the structure is analysed. It is shown that the residual welding deformation almost has no impact on the ultimate bearing capacity of the structure, and the initial geometric imperfections with the first buckling mode have a more obvious effect on the stability of the shell. The rigidity of the orthogonal single-layer reticulated shell is greater than that of the oblique. The deformation of the oblique single-layer reticulated shell is always greater than that of the orthogonal shell in the middle of the shell span or the position of the support.