bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrolyte-gated transistors for synaptic electronics, neuromorphic computing, and adaptable biointerfacing
Authors: Ling Haifeng , Koutsouras Dimitrios A. , Kazemzadeh Setareh , van de Burgt Yoeri , Yan Feng , Gkoupidenis Paschalis
Published: January 2020

Functional emulation of biological synapses using electronic devices is regarded as the first step toward neuromorphic engineering and artificial neural networks (ANNs). Electrolyte-gated transistors (EGTs) are mixed ionic–electronic conductivity devices capable of efficient gate-channel capacitance coupling, biocompatibility, and flexible architectures. Electrolyte gating offers significant advantages for the realization of neuromorphic devices/architectures, including ultralow-voltage operation and the ability to form parallel-interconnected networks with minimal hardwired connectivity. In this review, the most recent developments in EGT-based electronics are introduced with their synaptic behaviors and detailed mechanisms, including short-/long-term plasticity, global regulation phenomena, lateral coupling between device terminals, and spatiotemporal correlated functions. Analog memory phenomena allow for the implementation of perceptron-based ANNs. Due to their mixed-conductivity phenomena, neuromorphic circuits based on EGTs allow for facile interfacing with biological environments. We also discuss the future challenges in implementing low power, high speed, and reliable neuromorphic computing for large-scale ANNs with these neuromorphic devices. The advancement of neuromorphic devices that rely on EGTs highlights the importance of this field for neuromorphic computing and for novel healthcare technologies in the form of adaptable or trainable biointerfacing.
Time delay effects in the control of synchronous electricity grids
Authors: Böttcher Philipp C. , Otto Andreas , Kettemann Stefan , Agert Carsten
Published: January 2020

The expansion of inverter-connected generation facilities (i.e., wind and photovoltaics) and the removal of conventional power plants is necessary to mitigate the impacts of climate change, whereas conventional generation with large rotating generator masses provides stabilizing inertia, inverter-connected generation does not. Since the underlying power system and the control mechanisms that keep it close to a desired reference state were not designed for such a low inertia system, this might make the system vulnerable to disturbances. In this paper, we will investigate whether the currently used control mechanisms are able to keep a low inertia system stable and how this is affected by the time delay between a frequency deviation and the onset of the control action. We integrate the control mechanisms used in Continental Europe into a model of coupled oscillators which resembles the second order Kuramoto model. This model is then used to investigate how the interplay of changing inertia, network topology, and delayed control affects the stability of the interconnected power system. To identify regions in the parameter space that make stable grid operation possible, the linearized system is analyzed to create the system’s stability chart. We show that lower and distributed inertia could have a beneficial effect on the stability of the desired synchronous state.
Brain-inspired computing with memristors: Challenges in devices, circuits, and systems
Authors: Zhang Yang , Wang Zhongrui , Zhu Jiadi , Yang Yuchao , Rao Mingyi , Song Wenhao , Zhuo Ye , Zhang Xumeng , Cui Menglin , Shen Linlin , Huang Ru , Joshua Yang J.
Published: January 2020

This article provides a review of current development and challenges in brain-inspired computing with memristors. We review the mechanisms of various memristive devices that can mimic synaptic and neuronal functionalities and survey the progress of memristive spiking and artificial neural networks. Different architectures are compared, including spiking neural networks, fully connected artificial neural networks, convolutional neural networks, and Hopfield recurrent neural networks. Challenges and strategies for nanoelectronic brain-inspired computing systems, including device variations, training, and testing algorithms, are also discussed.
Backward volume vs Damon–Eshbach: A traveling spin wave spectroscopy comparison
Authors: Bhaskar U. K. , Talmelli G. , Ciubotaru F. , Adelmann C. , Devolder T.
Published: January 2020

We compare the characteristics of electrically transduced Damon–Eshbach spin-wave (DESW) and backward volume spin-wave (BVSW) configurations within the same, 30 nm thick, ferromagnetic, CoFeB waveguide. Sub-micrometer U-shaped antennas are used to deliver the necessary in-plane and out-of-plane RF fields. We measure the spin-wave transmission with respect to in-plane field orientation, frequency, and propagation distance. Unlike DESW, BVSWs are reciprocally transduced and collected for either direction of propagation, but their ability to transport energy is lower than DESWs for two reasons. This arises first because BVSWs are inductively transduced less efficiently than DESWs. Also, in the range of wavevectors (∼5 rad μm−1) typically excited by our antennas, the group velocity of BVSWs stays lower than that of DESW, which leads to reduced propagation ability that impact transmission signals in an exponential manner. In contrast, the group velocity of DESWs is maximum at low fields and decreases continuously with the applied field. The essential features of the measured SW characteristics are well reciprocated by a simple, 1D analytical model, which can be used to assess the potential of each configuration.
Disorder and critical current variability in Josephson junctions
Authors: Sulangi Miguel Antonio , Weingartner T. A. , Pokhrel N. , Patrick E. , Law M. , Hirschfeld P. J.
Published: January 2020

We investigate theoretically the origins of observed variations in the critical currents of Nb/Al-AlOx/Nb Josephson junctions in terms of various types of disorder. We consider the following disorder sources: vacancies within the Al layer, thickness variations in the AlOx layer, and “pinholes” (i.e., point contacts) within the AlOx layer. The calculations are all performed by solving the microscopic Bogoliubov–de Gennes Hamiltonian self-consistently. It is found that a small concentration of vacancies within the Al layer is sufficient to suppress the critical current, while the presence of a small number of thick regions of the oxide layer induces a similar effect as well. The pinhole scenario is found to result in anomalous behavior that resembles neither that of a pure tunnel junction nor that of a superconductor–normal–superconductor junction but a regime that interpolates between these two limits. We comment on the degree to which each of the three scenarios describes the actual situation present in these junctions.
Understanding size dependence of phase stability and band gap in CsPbI3 perovskite nanocrystals
Authors: Yang Ruo Xi , Tan Liang Z.
Published: January 2020

Inorganic halide perovskites CsPbX3 (X = Cl, Br, I) have been widely studied as colloidal quantum dots for their excellent optoelectronic properties. Not only is the long-term stability of these materials improved via nanostructuring, their optical bandgaps are also tunable by the nanocrystal (NC) size. However, theoretical understanding of the impact of the NC size on the phase stability and bandgap is still lacking. In this work, the relative phase stability of CsPbI3 as a function of the crystal size and the chemical potential is investigated by density functional theory. The optically active phases (α- and γ-phase) are found to be thermodynamically stabilized against the yellow δ-phase by reducing the size of the NC below 5.6 nm in a CsI-rich environment. We developed a more accurate quantum confinement model to predict the change in bandgaps at the sub–10 nm regime by including a finite-well effect. These predictions have important implications for synthesizing ever more stable perovskite NCs and bandgap engineering.
Influence of A-Site cation size-disorder on the magnetocaloric response of La0.6CaxSr0.4-xMnO3 nanoparticles
Authors: Hunt C. S. M. , Barua R. , Carpenter E. E.
Published: January 2020

Building on previous work finding a significant magnetocaloric effect (MCE) in manganite nanoparticles having the formula La0.60Cax Sr0.40-xMnO3 (0<x<0.4), which show promise for application in magnetic refrigeration systems. These were synthesized via a Pechini sol-gel method, as verified by powder x-ray diffraction and laser ablation-inductively coupled plasma-mass spectrometry. The temperature-dependence of the magnetic entropy change between 200K and 320K in a magnetic field of μH=3T was evaluated by means of Maxwell’s relations and isothermal MH curves. The reported values of ΔSmax increase from 1.5 J kg-1K-1 to 5.6 J kg-1K-1 as x increases from 0 to 0.4. Ms; crystallite size and b and c lattice parameters increase with x. The results show a clear positive correlation between calcium concentrations and the value of -ΔS, suggesting that a larger atom at the calcium site negatively impacts the magnetocaloric effect, thereby decreasing magnetic refrigeration viability.
Production of anisotropic SmFe3 magnets by hot deformation
Authors: Saito Tetsuji , Ogawa Yusuke , Nishio-Hamane Daisuke
Published: January 2020

In this study, we investigated the production of anisotropic SmFe3 magnets by the hot deformation of hot-pressed SmFe3 magnets. Hot-pressed SmFe3 magnets were able to be hot-deformed at 973–1073 K into hot-deformed SmFe3 magnets. Although the hot-deformed SmFe3 magnet produced at 973 K was magnetically isotropic, the specimen produced at 1023 K was magnetically anisotropic. The specimen produced at 1073 K was also slightly anisotropic. This indicates that anisotropic SmFe3 magnets were successfully produced by the hot deformation of hot-pressed magnets, as has been reported in the case of hot-deformed Nd-Fe-B magnets. However, the highest coercivity obtained by these anisotropic SmFe3 magnets was only 1.5 kOe, which is insufficient in comparison with rare-earth permanent magnets. Further work is therefore necessary to increase the coercivity of these magnets.
Domain decomposition with subdomain pre-processing for finite element modelling of transformers with stranded conductors
Authors: Gürbüz Ismet Tuna , Lehikoinen Antti , Aydin Ugur , Rasilo Paavo , Takala Eelis , Belahcen Anouar
Published: January 2020

Finite element analysis of transformers with stranded conductors can be computationally heavy due to the fine mesh required for winding domains. In this paper, a domain decomposition method with subdomain pre-processing is proposed to overcome with this problem. In order to solve the field-circuit problem with finite element analysis, the winding domain is modelled initially. Next, the reduced matrix system is obtained from the winding domain formulation. The solution of the entire problem is obtained by solving the winding domain formulation and the reduced matrix system separately. The method is tested on a transformer model in no load operation. Accurate solutions are obtained in both frequency and time domains 7-9 times faster than when using brute-force method.
Determination of fine magnetic structure of magnetic multilayer with quasi antiferromagnetic layer by using polarized neutron reflectivity analysis
Authors: Zhong Yongshi , Kurokawa Yuichiro , Nagashima Gen , Horiike Shu , Hanashima Takayasu , Schönke Daniel , Krautscheid Pascal , Reeve Robert M. , Kläui Mathias , Yuasa Hiromi
Published: January 2020

We carried out polarized neutron reflectivity (PNR) analysis to determine the fine magnetic structure of magnetic multilayers with quasi-antiferromagnetic (quasi-AFM) layers realized by 90-deg coupling using two Co90Fe10 layers, and quantitatively evaluated the magnetization of quasi-AFM layers. Two types of samples with different buffer layers, Ru buffer and a NiFeCr buffer, were investigated and the average angles between the respective magnetization of the two Co90Fe10 layers were estimated to be +/− 39 degrees and +/− 53 degrees. In addition, less roughness was found in the NiFeCr buffer sample resulting stronger 90-deg coupling. A perfect quasi-AFM is expected to be realized by a flat interface of the magnetic multilayer.
Structural and magnetic properties of Mn3Ge films with Pt and Ru seed layers
Authors: Kobayashi A. , Higo T. , Nakatsuji S. , Otani YoshiChika
Published: January 2020

The Mn-Ge binary system has been intensively studied because of a variety of phases with intriguing magnetic properties. Here, we report the thin film fabrication of two types of Mn3Ge by employing Pt and Ru seed layers. Our structural analysis, in addition to magnetic and transport measurements, have revealed that the Mn3Ge film with the Pt layer has γ-Mn type cubic structure. This is in contrast to the Mn3Ge film with Ru seed layer, which posseses D022 tetragonal structure. Pt/Mn3Ge also exhibits antiferromagnetic properties, including the exchange bias effect with the blocking temperature of TB ∼ 350 K.
Electronic transport characterization of B+ ion-implanted silicon wafers with nonlinear photocarrier radiometry
Authors: Lei Xiaoke , Li Bincheng , Sun Qiming , Wang Jing , Gao Chunming
Published: January 2020

A nonlinear photocarrier radiometry (PCR) based quantitative defect characterization method is applied to determine the electronic transport parameters of the implantation layer of B+ ion-implanted silicon wafers with different implantation doses. A rigorous two-layer nonlinear PCR model is employed to fit the experimental modulation frequency dependences of PCR amplitude and phase to determine the transport parameters, that is, the carrier lifetime, carrier diffusion coefficient, and front surface recombination velocity of the implantation layer via multiparameter fitting. In the multiparameter fitting, the effects of the implantation layer thickness determination on the extraction of the electronic transport properties of the implantation layer are discussed via setting the thickness as a free parameter in the multiparameter fitting and fixed parameters determined by Monte Carlo based TRIM calculation. The fitted implantation layer thicknesses are in good agreement with that determined via TRIM calculation with a modified electronic damage threshold. Monotonic dependences of the transport properties of the implantation layers on the implantation dose are observed, and the effects of impurity density on the transport properties of the implantation layers are discussed. Good agreements between the experimental implantation dose dependence of the nonlinearity coefficient and corresponding theoretical calculations with the determined transport parameters are obtained. These results show that the two-layer nonlinear PCR model is accurate for quantitatively characterizing the transport properties and thickness of the ion-implantation layers of silicon wafers, and the nonlinear PCR technique is appropriate for precise defect characterization in the semiconductor manufacturing processes.
On the origin of the sharp, low-field pinning force peaks in MgB2 superconductors
Authors: Koblischka Michael R. , Wiederhold Alex , Koblischka-Veneva Anjela , Chang Crosby , Berger Kévin , Nouailhetas Quentin , Douine Bruno , Murakami Masato
Published: January 2020

Various MgB2 thin films and single crystals were found in the literature to exhibit a sharp, narrow peak at low fields in the volume pinning force, Fp(H)-diagrams. The origin of this peak is associated with a steep drop of the current density when applying external magnetic fields and is ascribed to sample purity. We show here that bulk MgB2 prepared by spark-plasma sintering also shows the sharp, narrow peak in Fp. The peak is also seen in the volume pinning force scaling, Fp/Fp,max vs h = H/Hirr. Furthermore, polycrystalline bulk MgB2 samples prepared close to the optimum reaction temperature reveal this peak effect as well, but other samples of the series show a regular scaling behavior. The combination of magnetization data with data from electric transport measurements on the same samples demonstrates the origin of this peak effect. On increasing preparation temperature, the pinning force scaling changes from grain boundary pinning to point pinning and the grain connectivity gets worse. Hence, the sharp, low-field peak in Fp vanishes. Therefore, the occurrence of the peak effect in Fp gives important information on the grain coupling in the MgB2 samples.
The multi-configurational time-dependent Hartree approach in optimized second quantization: Imaginary time propagation and particle number conservation
Authors: Weike Thomas , Manthe Uwe
Published: January 2020

The multilayer multiconfigurational time-dependent Hartree (MCTDH) in optimized second quantization representation (oSQR) approach combines the tensor contraction scheme of the multilayer MCTDH approach with the use of an optimized time-dependent orbital basis. Extending the original work on the subject [U. Manthe and T. Weike, J. Chem. Phys. 146, 064117 (2017)], here MCTDH-oSQR propagation in imaginary time and properties related to particle number conservation are studied. Differences between the orbital equation of motion in real and imaginary time are highlighted and a new gauge operator, which facilitates efficient imaginary time propagation, is introduced. Studying Bose-Hubbard models, particle number conservation in MCTDH-oSQR calculations is investigated in detail. Interesting properties of the single-particle functions used in the multilayer MCTDH representation are identified. Based on these results, a tensor contraction scheme, which explicitly utilizes particle number conservation, is suggested.
Productivity and bioactivity of enokipodins A–D of Flammulina rossica and Flammulina velutipes
Authors: Tabuchi Akiko , Fukushima-Sakuno Emi , Osaki-Oka Kumiko , Futamura Yushi , Motoyama Takayuki , Osada Hiroyuki , Ishikawa Noemia Kazue , Nagasawa Eiji , Tokimoto Keisuke
Published: January 2020

Enokipodins are antimicrobial sesquiterpenes produced by Flammulina velutipes in a mycelial culture medium. To date, enokipodin production has not been reported in other members of the genus Flammulina. Hence, in this study, the production of enokipodins A, B, C, and D by F. velutipes and F. rossica was investigated. Some strains of F. rossica were confirmed to produce at least one of the four enokipodins in the culture medium. However, some strains of F. velutipes did not produce any of the enokipodins. In an antibacterial assay using liquid medium, enokipodin B showed the strongest growth inhibitory activity against Bacillus subtilis among the four types of enokipodins. Enokipodin B inhibited the spore germination of some plant pathogenic fungi. Enokipodins B and D exerted moderate anti-proliferative activity against some cancer cell lines, and enokipodins A and C inhibited the proliferation of the malarial parasite, Plasmodium falciparum.
Investigation of the effects of indoxyl sulfate, a uremic toxin, on the intracellular oxidation level and phagocytic activity using an HL-60-differentiated human macrophage cell model
Authors: Tsutsumi Shuhei , Tokunaga Yuki , Shimizu Shunsuke , Kinoshita Hideki , Ono Masateru , Kurogi Katsuhisa , Sakakibara Yoichi , Suiko Masahito , Liu Ming-Cheh , Yasuda Shin
Published: January 2020

Indoxyl sulfate (IS), a uremic toxin, is a sulfate-conjugated metabolite originated from tryptophan. Accumulating uremic toxins may worsen renal diseases and further complicate related disorders including impaired immune functions under oxidative stress conditions. However, it has remained unclear whether or not IS can directly cause the cellular immune dysfunction. We investigated the effects of IS on the intracellular oxidation level and phagocytic activity in a HL-60-differantiated human macrophage cell model. Incubation of the cells in the presence of IS resulted in increasing intracellular oxidation level and decreasing phagocytic activity. In addition to inhibitors for NADH oxidase (NOX), organic anion transporting polypeptide2B1 (OATP2B1), protein kinase C (PKC), and phosphoinositide 3-kinase (PI3K), a representative antioxidant Trolox, was also shown to significantly relieve the IS-induced oxidation and restore weakened phagocytosis. Collectively, IS may directly down-regulate the phagocytic immune function of macrophages through the oxidation mechanisms including OATP2B1, PKC, PI3K, and NOX pathways.

Abbreviations

CKD: Chronic kidney disease; IS: Indoxyl sulfate; ROS: Reactive oxygen species; NOX: NADH oxidase; OATP2B1: Organic anion transporting polypeptide2B1; PKC: Protein kinase C; PI3K: Phosphoinositide 3-kinase; 2-APT: 2-acetylphenothiazine
Evaluating the influence of differences in methodological approach on metabolic thresholds and fat oxidation points relationship
Authors: Nikolovski Zoran , Barbaresi Silvia , Cable Tim , Peric Ratko
Published: January 2020

In this study, we aimed to determine the exercise intensities eliciting the highest (FATmax) and the lowest (FATmin) fat oxidation rate in male cyclists and to compare these intensities with their individual aerobic (AeT) and anaerobic (AnT) thresholds, respectively. Twenty‐two moderately trained male cyclists performed a 2‐min stage graded exercise test until exhaustion using breath‐by‐breath gas analysis to determine maximal oxygen consumption (VO2max). The fat oxidation rate was calculated using a stoichiometric equation, with metabolic thresholds being determined by ventilatory gas analysis. In the present group of subjects, FATmax was found at a 21.34 ± 3.64 ml·kg−1·min−1 corresponding to 45.05 ± 7.68% VO2max. AeT occurred at an exercise intensity of 22.15 ± 4.84 ml·kg−1·min−1, matching 46.76 ± 10.24% VO2max. AnT and FATmin were located at intensities equivalent to 32.56 ± 5.52 ml·kg−1·min−1 and 32.30 ± 5.35 ml·kg−1·min−1 which corresponded to 68.74 ± 11.65 and 68.19 ± 11.29% VO2max, respectively. The correlation between FATmax and AeT was strong (r = 0.80, p < 0.05). No statistical difference was observed between FATmin and AnT (r = 0.99, p < 0.05). The strong relationship between observed indices can be used to provide a more tailored exercise approach.
Channel integrated optoelectronic tweezer chip for microfluidic particle manipulation
Authors: Witte Christian , Reboud Julien , Cooper Jonathan M , Neale Steven L
Published: January 2020

Light patterned electrical fields have been widely used for the manipulation of microparticles, from cells to microscopic electronic components. In this work, we explore a novel electromechanical phenomenon for particle focusing and sorting where the electrical field patterns are shaped by a combination of the light patterned photoconductor and the channel geometry. This effect results from the combination of particle polarisation described by the Clausius–Mossotti relation and the engineering of large electric gradients produced by choosing the channels height to suit the size of the particles being manipulated. The matched geometry increases the distortion of the field created by a combination of the illuminated photoconductor and the particles themselves and hence the non-uniformity of the field they experience. We demonstrate a new channel integration strategy which allows the creation of precisely defined channel structures in the OET device. By defining channels in photoresist sandwiched between upper and lower ITO coated glass substrates we produce robust channels of well controlled height tailored to the particle. Uniquely, the top substrate is attached before photolithographically defining the channels. We demonstrate versatile control using this effect with dynamically reconfigurable light patterns allowing the retention against flow, focusing and sorting of micro particles within the channels. Contrary to traditional designs, this channel integrated device allows patterned micro channels to be used in conjunction with conductive top and bottom electrodes producing optimal conditions for the dielectrophoretic manipulation as demonstrated by the rapid flow (up to 5 mm s−1) in which the particles can be focused.
Applicability of coupling strength estimation for linear chains of restricted access*
Authors: Feng He , Yan Tian-Min , Jiang Yuhai
Published: January 2020

The characterization of an unknown quantum system requires the Hamiltonian identification. The full access to the system, however, is usually restricted, hindering the direct retrieval of the relevant parameters, and a reliable indirect estimation is usually required. In this work, based on the reformulated form of the original algorithm of Burgarth et al. [Phys. Rev. A
79 020305 (2009)], the robustness of the estimation scheme against numerous sources of errors during the actual measurement is analyzed. The scheme is numerically studied for sites with a chain structure, exploring its applicability against observational errors including the limited signal-noise ratio and the finite spectral width. The spectral distribution of the end site is shown to determine the applicability of the method, and reducing the influence from truncated spectral components is critical to realize the robust reconstruction of the coupling strengths.
Quantum speed limit time of a non-Hermitian two-level system
Authors: Wang Yan-Yi , Fang Mao-Fa
Published: January 2020

We investigated the quantum speed limit time of a non-Hermitian two-level system for which gain and loss of energy or amplitude are present. Our results show that, with respect to two distinguishable states of the non-Hermitian system, the evolutionary time does not have a nonzero lower bound. The quantum evolution of the system can be effectively accelerated by adjusting the non-Hermitian parameter, as well as the quantum speed limit time can be arbitrarily small even be zero.
Vibronic spectra of aluminium monochloride relevant to circumstellar molecule*
Authors: Xu Jian-Gang , Zhang Cong-Ying , Zhang Yun-Guang
Published: January 2020

The A1Π → X1 Σ+ transition system of aluminium monochloride is determined by using ab initio quantum chemistry. Based on the multi-reference configuration interaction method in conjugate to the Davidson correction (MRCI + Q), the potential energy curves (PECs) of the three electronic states are obtained. Transition dipole moments (TDMs) and the vibrational energy levels are studied by employing the aug-cc-pwCV5Z-DK basis set with 4220-active space. The rovibrational constants are first determined from the analytic potential by solving the rovibrational Schrödinger equation, and then the spectroscopic constants are determined by fitting the vibrational levels, and these values are well consistent with the experimental data. The effect of spin–orbit coupling (SOC) on the spectra and vibrational properties are evaluated. The results show that the SOC effect has almost no influence on the spectroscopic constants of AlCl molecules. For the A1Π → X1 Σ+ transition, the highly diagonalized Frank–Condon factor (FCF) is f
00 = 0.9988. Additionally, Einstein coefficients and radiative lifetimes are studied, where the vibrational bands include ν″ = 0–19 → ν′ = 0–9. The ro-vibrational intensity is calculated at a temperature of 296 K, which can have certain astrophysical applications. At present, there is no report on the calculation of AlCl ro-vibrational intensity, so we hope that our results will be useful in analyzing the interstellar AlCl based on the absorption from A1Π → X1 Σ+.
Precise measurement of a weak radio frequency electric field using a resonant atomic probe*
Authors: Hao Liping , Xue Yongmei , Fan Jiabei , Bai Jingxu , Jiao Yuechun , Zhao Jianming
Published: January 2020

We present a precise measurement of a weak radio frequency electric field with a frequency of ≲ 3 GHz employing a resonant atomic probe that is constituted with a Rydberg cascade three-level atom, including a cesium ground state |6S1/2⟩, an excited state |6P3/2⟩, and Rydberg state |nD5/2⟩. Two radio frequency (RF) electric fields, noted as local and signal fields, couple the nearby Rydberg transition. The two-photon resonant Rydberg electromagnetically induced transparency (Rydberg-EIT) is employed to directly read out the weak signal field having hundreds of kHz difference between the local and signal fields that is encoded in the resonant microwave-dressed Rydberg atoms. The minimum detectable signal fields of E
Smin
= 1.36 ± 0.04 mV/m for 2.18 GHz coupling |68D5/2⟩ → |69P3/2⟩ transition and 1.33 ± 0.02 mV/m for 1.32 GHz coupling |80D5/2⟩ → |81P3/2⟩ transition are obtained, respectively. The bandwidth dependence is also investigated by varying the signal field frequency and corresponding −3 dB bandwidth of 3 MHz is attained. This method can be employed to perform a rapid and precise measurement of the weak electric field, which is important for the atom-based microwave metrology.
Low-temperature plasma enhanced atomic layer deposition of large area HfS2 nanocrystal thin films*
Authors: Chang Ailing , Mao Yichen , Huang Zhiwei , Hong Haiyang , Xu Jianfang , Huang Wei , Chen Songyan , Li Cheng
Published: January 2020

Hafnium disulfide (HfS2) is a promising two-dimensional material for scaling electronic devices due to its higher carrier mobility, in which the combination of two-dimensional materials with traditional semiconductors in the framework of CMOS-compatible technology is necessary. We reported on the deposition of HfS2 nanocrystals by remote plasma enhanced atomic layer deposition at low temperature using Hf(N(CH3)(C2H5))4 and H2S as the reaction precursors. Self-limiting reaction behavior was observed at the deposition temperatures ranging from 150 °C to 350 °C, and the film thickness increased linearly with the growth cycles. The uniform HfS2 nanocrystal thin films were obtained with the size of nanocrystal grain up to 27 nm. It was demonstrated that higher deposition temperature could enlarge the grain size and improve the HfS2 crystallinity, while causing crystallization of the mixed HfO2 above 450 °C. These results suggested that atomic layer deposition is a low-temperature route to synthesize high quality HfS2 nanocrystals for electronic device or electrochemical applications.
fNIRS-GANs: data augmentation using generative adversarial networks for classifying motor tasks from functional near-infrared spectroscopy
Authors: Nagasawa Tomoyuki , Sato Takanori , Nambu Isao , Wada Yasuhiro
Published: January 2020

Objective. Functional near-infrared spectroscopy (fNIRS) is expected to be applied to brain–computer interface (BCI) technologies. Since lengthy fNIRS measurements are uncomfortable for participants, it is difficult to obtain enough data to train classification models; hence, the fNIRS-BCI accuracy decreases. Approach. In this study, to improve the fNIRS-BCI accuracy, we examined an fNIRS data augmentation method using Wasserstein generative adversarial networks (WGANs). Using fNIRS data during hand-grasping tasks, we evaluated whether the proposed data augmentation method could generate artificial fNIRS data and improve the classification performance using support vector machines and simple neural networks. Main results. Trial-averaged temporal profiles of WGAN-generated fNIRS data were similar to those of the measured data except that they contained an extra noise component. By augmenting the generated data to training data, the accuracies for classifying four different task types were improved irrespective of the classifiers. Significance. This result suggests that the artificial fNIRS data generated by the proposed data augmentation method is useful for improving BCI performance.
Simulation of Alfvén eigenmodes destabilized by energetic electrons in tokamak plasmas
Authors: Wang Jialei , Todo Yasushi , Wang Hao , Wang Zheng-Xiong
Published: January 2020

Alfvén eigenmodes (AEs) driven by energetic electrons were investigated via hybrid simulations of an MHD fluid interacting with energetic electrons. The investigation focused on AEs with the toroidal number n = 4. Both energetic electrons with centrally peaked beta profile and off-axis peaked profile are considered. For the centrally peaked energetic electron beta profile case, a toroidal Alfvén eigenmode (TAE) propagating in the electron diamagnetic drift direction is found. The mode is mainly driven by deeply trapped energetic electrons. It is also found that a few passing energetic electrons spatially localized around rational surfaces can resonate with the mode. For the off-axis peaked energetic electron beta profile case, an AE propagating in the ion diamagnetic drift direction is found when a

q

−
p
r
o
f
i
l
e

with weak magnetic shear is adopted. The destabilized mode is an elliptical-Alfvén-eigenmode-type (EAE-type) mode which has a spatial profile peaking at the rational surface and a frequency close to the second Alfvén frequency gap. It is found that passing energetic electrons and barely trapped energetic electrons are responsible for this EAE-type mode destabilization. The saturation levels are compared for a TAE with the same linear growth rate among energetic electron driven mode and energetic ion driven mode with isotropic and anisotropic velocity space distributions. The saturation level of TAE driven by trapped energetic electrons is comparable to that driven by energetic electrons with isotropic velocity space distribution where the contribution of trapped particles is dominant. It is found that the trapped energetic ion driven TAE has a larger saturation level than the passing energetic ion driven TAE, which indicates the difference in particle trapping by the TAE between trapped and passing energetic ions.
Dislocation dipole in graphene at finite temperatures
Authors: Klyavlina A I , Rysaeva L Kh , Murzaev R T
Published: January 2020

In the present work, the evolution of defect structure of graphene with dislocation dipole of three types in thermal equilibrium is studied by molecular dynamics simulations. The presence of defects can considerably reduce the temperature at which graphene remains stable in thermal equilibrium. It is found, that at elevated temperatures, there is a movement of dislocations in a dipole with arm equal to 7 Å, so that a new dipole with the arm 3 Åis formed with the further transformation to the Stone-Wales defect. This reveals that dipole arm is less than annihilation distance for dislocation dipole. Again, the Stone–Wales defect at elevated temperatures disappears as a result of the rotation of the C–C bond. The obtained results will allow describing the dynamics of defects in graphene in thermal equilibrium, which can be helpful to analytically describe dislocation dynamics in graphene.
Hydrostatic compression as the way of property improvement of crumpled graphene: atomistic simulation
Authors: Krylova K. A. , Safina L. R.
Published: January 2020

In the present work, crumpled graphene is considered under hydrostatic tension by molecular dynamics simulation. Here hydrostatic compression is used in two variants: to obtain composite from crumpled graphene combined with Ni nanoparticles and to serve hydrogen inside crumpled graphene. Pressure-strain curves and structural transformations during hydrostatic compression in both cases are discussed. It is found, that hydrostatic compression at high temperatures can be very effective for Ni-graphene composite formation. The possibility of application of compressive strain to make crumpled graphene better media for hydrogen storage is discussed. It is observed that at 77 K and 300 K compression results in the considerable increase of hydrogen sorption capacity.
Total fission energy depending on VVER-1000 fuel burnup
Authors: Bahdanovich R , Gerasimov A , Tikhomirov G
Published: January 2020

To calculate the energy deposition in a nuclear reactor’s core, it is necessary to calculate the value of the energy released per one fission act. Simplified methods for calculating the total fission energy are still used in many computer codes. They do not take into detailed account some of the physical phenomena occurring in nuclear fission and their time dependence. In this work, we used a calculation method that takes into account these physical features in order to obtain the dependence of the total fission energy and its components on the fuel burnup of VVER-1000. The calculation for the model of 16ZSH type fuel assembly using the methodology of the Fisencor.pl program (based on the MCU-PTR code) demonstrated that total fission energy increases with the fuel burnup. During the interval between refuelling, total fission energy increases by 3% from 199.7 to 206.4 MeV per one fission. Application of the proposed method for calculating the total fission energy will allow to enhance the precision of nuclear fuel isotopic composition calculations.
Analysis of the methods for group constants generation for calculation of a large SFR core using Serpent 2 and CriMR codes
Authors: Akpuluma D A , Smirnov A D , Pugachev P A , Tikhomirov G V , Gerasimov A S
Published: January 2020

This work aimed at generating homogenized group constants using the Serpent code and then using the CriMR diffusion code to model the large SFR OECD 3600 MWth MOX core. The results were compared with a full core reference Monte Carlo solution by Serpent. Reactivity feedback parameters were also considered. Generating the group constants from separate fuel assemblies allows for simultaneously carrying out calculations and then using the results as input in diffusion codes rather than waiting so long for a 3D full core Monte Carlo calculation to be completed. From the results of the integral parameters we see a close agreement in the calculation codes. The differences can be attributed to the errors that could arise from generating the constants from individual sub-assemblies. The differences in the underlying physics and approximations used in development of the codes could also be a factor. Another way the errors could be reduced is by checking to see that the sub-assembly configurations used in the non-multiplying zones are as close as possible to the real layout in a full 3D core.
Study of the trigger on nucleus-nucleus interactions for the BM@N experiment using a Geant4 + QGSM software package
Authors: Lashmanov N A , Sedykh S A , Yurevich V I
Published: January 2020

Monte-Carlo simulation was used to study the background conditions which affect the performance of the trigger system of the BM@N experiment. A GEANT4 + QGSM software package was used for the simulation. The influence of the background from δ-electrons was estimated and measures to minimize this background were evaluated. Addition of lead shielding and a small change in the geometry of the target zone allow to reduce the background. The efficiency of the modified trigger system was calculated for Au+Au collisions as a function of the impact parameter. The efficiency is 100% for central and semi-central collisions.
GEANT4 simulation of energy resolution of the SPACAL electromagnetic calorimeter
Authors: Shmanin E
Published: January 2020

Geant4 based simulation study of energy resolution is performed for Spaghetti electromagnetic calorimeter module (SPACAL). Several configurations of SPACAL module, with different fiber pitch and scintillation material, were simulated. For each configuration, the energy and angular dependencies of energy resolution were determined. The sampling fraction for electromagnetic showers for the selected SPACAL configuration was also determined
Problems with experimental observation of violation of Wigner inequalities in a system of neutral kaons
Authors: Anna Efimova
Published: January 2020

In the current work we add background to a system of neutral kaons using a Werner state. We show that the violation of Wigner inequalities is only observervable in experiment in case when the background contribution is less than 1%.
Pressure drop in valve for different open flow areas
Authors: Laouar Soufiane , Sakib Md Nazmus , Muqit Al Sazid , Navasardyan Manuk V. , Kutsenko Kirill V.
Published: January 2020

In any piping system different types of regulating components (valves) are used. To determine the pressure drop of the liquid in these components, it is necessary to know the exact values of the local loss coefficients, which depend on their design and manufacturer. The calculations of local loss coefficients of the valves are usually carried out according to engineering methods using design handbooks. However, the large design diversity of the valves does not allow an accurate assessment of the local loss coefficient for a particular product (using handbooks). There are two ways to solve this problem. The first way is experimental determination; the second is calculation using CFD modelling. This article presents the results of CFD simulation of the pressure drop of liquid through valves and a comparison with experimental data obtained from the thermal hydraulic test bench.
Development of a method for determining corrosion damage of fuel element claddings of a nuclear power unit by using acoustic resonance method in a hot chamber environment
Authors: Rodko I I , Moshev A A , Bozhko Yu V , Yudin I A , Tokarev A N , Biryukov A P , Chernykh P O , Tolstov M S
Published: January 2020

As part of the strategic research program of state corporation Rosatom, carried out by the Technological Platform “Closed Nuclear Fuel Cycle with Fast Neutron Reactors”, a research to equip protective cells with original equipment, including ultrasonic flaw detectors for primary post-reactor non-destructive research of the properties of critical materials of fast neutron reactors, is being performed. In this paper, we present a method developed for determining corrosion damage of fuel claddings by the acoustic resonance method in hot chamber conditions, and a description of the experimental installation.
Determination of types and degree of corrosion damage of fuel cladding by informative ranges of divergences of their natural oscillation frequencies
Authors: Moshev A A , Rodko I I , Berestov A V , Yudin I A , Tokarev A N , Biryukov A P , Ocheretko V E , Gavrilyuk M Yu
Published: January 2020

The urgency of the work consists in using a new approach to the definition of informative frequencies for the identification of corrosion damage. The aim of the work is to determine the discrepancies between the resonance frequencies of the oscillations of the fuel casing segments of the factory geometry and with various types of corrosion damage obtained by modelling defects in the casings of fuel casing segments. As a result of the analysis, informative ranges of ordinal numbers were revealed, which allow to determine the following corrosion damages: thinning from the outer and inner sides of the fuel casing, pitting corrosion, fretting corrosion.
The synchronous movement of mechanisms taking into account forces of the different nature
Authors: Misyurin S Yu , Kreinin G V , Nelubin A P , Nosova N Yu
Published: January 2020

In the work the method of transition to dimensionless parameters is presented on the example of movement by two synchronously working piston hydraulic engines of a heavy object with use of the theory of similarity and analogousness. Advantage of such approach is shown in limit simplification of dimensionless model, its universality and efficiency of search of an optimal solution in the choice of parameters of the real device.

Methods of dimension and the theory of similarity are successfully applied in a research of dynamic systems of various classes. The problems arising at the same time are connected generally with the choice of a rational combination of the main units of measure of physical quantities, with transition to dimensionless models and with formation basic criterion of similarity. The specified problems are solved by the researcher, as a rule, on the basis of own intuition and experience. The systematized approaches to the solution of similar problems based on a method of the theory of analogousness are meanwhile known.
E-beam longitudinal pumped semiconductor laser based on ZnCdS/ZnSSe type-II multi quantum well structure
Authors: Butaev M R , Kozlovsky V I , Sannikov D A , Skasyrsky Y K
Published: January 2020

A ZnCdS/ZnSSe multi quantum well structure was grown by metal-organic vapor phase epitaxy on GaAs substrate. The structure is consisted of the 45 ZnCdS layers of 5 nm in thickness separated by the 100 nm thin ZnSSe barrier layers and was the type-II heterostructure. A microresonator was produced from this structure for scanning electron beam longitudinal pumping. Lasing with output power up to 2W at 478 nm was achieved at room temperature.
Enhancement of the photoluminescence of semiconductor nanocrystals in transfer-printed microcavities based on freestanding porous silicon photonic crystals
Authors: Kryukova I S , Dovzhenko D S , Rakovich Yu P , Nabiev I R
Published: January 2020

Today, lots of research address the phenomenon of interaction between light and matter. In particular, it is of a special interest to investigate light–matter interaction in one-dimensional resonators based on porous materials. In this case, one can embed emitting semiconductor particles into the porous resonator, where the excitons of these particles couple to the resonator eigenmode and luminescence intensity of the emitters is enhanced, allowing an increase in the sensitivity of optical sensors, detectors, and photonic diagnostic assays. A particular challenge is to place the emitters directly in the antinode region of the resonator eigenmode in order to maximize the coupling strength, which is sometimes a problem due to the spatial distribution of emitters away from the eigenmode localization region. Here, we have shown that the transfer-printing technique can be used to obtain structures based on freestanding porous silicon photonic crystals capable of precisely controlling the emitter spatial distribution about the eigenmode localization region. This, as well as the porosity of these structures and high adsorption capacity of porous silicon, allows the light–matter interaction in these hybrid structures to be used in sensing applications. We have shown that the transfer-printing method does not worsen the optical properties of the microcavities compared to the conventional electrochemical etching of the whole microcavity at a time. Furthermore, we have observed slightly better coupling of the exciton of the emitter to the eigenmode of the transfer-printed microcavity in the weak coupling regime.
Acoustical monitoring of laser-matter interaction using nanosecond radiation pulses with periodically modulated intensity
Authors: Zubko A E , Samokhin A A , Shashkov E V , Vorob’ev N S
Published: January 2020

Nanosecond laser ablation of metal target under the action of radiation pulses with periodically modulated intensity is investigated. Generated pressure pulses are detected by piezo-transducer (lithium niobate) on the back target side. Such approach permits to measure simultaneously recoil pressure behavior and calculate the irradiated surface displacement during laser action by comparison modulated parts of laser and acoustic signals. Nanosecond laser pulses contain 10–15 short peaks of 60 ps duration (1.08 μm wavelength) which provide fluence values up to 30 J cm−2 in the pulse. Plasma light emission is also registered with the help of photodiode. At the considered fluences surface displacement during the pulse turns out to be considerably smaller than theoretical estimation for free vacuum vaporization and measured experimental displacement which follows from the arrival time delay of another pressure signals generated with subsequent laser pulse directed to the same spot. Such behavior can be evidence that crater formation in the considered irradiation regime occurs after the pulse end.
Influence of ZnGeP2 crystal temperature on broadband cascaded frequency conversion (numerical study)
Authors: Ionin A A , Kinyaevskiy I O , Sagitova A M
Published: January 2020

Broadband three-stage frequency conversion of multiline CO laser radiation in a single sample of ZnGeP2 crystal was numerically studied at various crystal temperatures. Decrease of the ZnGeP2 crystal temperature resulted in enhancement of efficiency for each frequency conversion stage due to phase-matching shifting. The third stage efficiency at liquid-nitrogen crystal temperature was 1.7-fold higher as compared to one at the room temperature. Also, the crystal temperature decrease resulted in spectral broadening of frequency converted radiation.