bluuebunny/crossref_metadata_2025 huggingface dataset:
Visualization in models of transformation of social space of the Eurasian macroregion: the example of the Urals
Authors: Gordeev Sergey , Zyryanov Sergey , Sitkovskiy Arseniy
Published: December 2020

The relevance of the topic determines a lot of structural socio- economic changes associated with both globalization and crisis processes. Such changes affect various aspects of spatial development, including the transformation of social space. Prospects for research into the transformation of social space in such conditions are largely related to the development of complex problem-adapted systems of models and the use of computer technologies – visualization tools. These models consider the interconnected spatial objects most significant for transformation. Such objects include zones of transport corridors and agglomeration processes. The purpose of the research results presented in the article is to determine and approbate a number of provisions, the spatial development of the macroregion, as a complex heterogeneous multilevel socio-economic system. The key issues here are the construction of a multilevel framework of social space when adapting local models. In the study, the base was the territory of the macroregion of the “Big Urals”. The peculiarities of the methodology, first of all, are related to the issues: determination of the most significant elements of the structure and characteristics of the transformation of social space and building a system of information- adapted models. The following issues are considered here: problem- oriented zoning of territories, transformation of the settlement framework, integration of the most significant objects of social transformations. The main results of the research are related to the possibilities of significantly expanding the class of tasks for managing regional and municipal development, solving problems of strategic planning and forming programs for the development of territories.
Enterprise product sales market selection model
Authors: Anisimov Vladimir , Anisimov Evgeniy , Saurenko Tatyana
Published: December 2020

Efficient sales logistics is the foundation of sustainability of enterprises in the real economy. This is due to the fact that it is the closing link in the logistics system, production of goods and provides a choice of distribution channels and their participants. The choice of distribution channels, first of all, involves the determination of markets for the products manufactured by the enterprise. Due to the need to ensure the effectiveness of this choice of taking into account a large number of various factors, the solution to this problem involves the use of formalized models and techniques. The article proposes a model and methodology that provides a reasonable choice of markets for the products of an enterprise in the real sector of the economy at the initial stage of forming its marketing logistics strategy. The model is based on a formal apparatus of statistical conclusions based on nonparametric statistics. This made it possible to take into account the inherent uncertainty of the source information inherent in the considered selection problem. The proposed model may be useful for digitalization in the field of logistics management of enterprises in the real sector of the economy.
Synergy of interaction of control and supervisory structures in ensuring the stability of the socio-economic system: principles and organization
Authors: Bezdenezhnykh Vyacheslav , Bezdenezhnykh Anastasiya , Karanina Elena
Published: December 2020

The article examines the system of interaction of control and supervisory services and structures (CSS) in the process of managing the development of socio-economic systems (SES). The system of interaction of the CSS is considered as a complex independent dynamic regulated process. The new concept of “synergy management system (SMS) of interaction” of control and supervisory services of complex socio- economic systems is substantiated. The basic principles and structure of the organization of the system of management of synergy of interaction of CSS are proved. It is noted that in the theory of complex synergetic systems, an important place belongs to the processes of self-regulation in local areas. It is shown that the existence of mechanisms for implementing self-regulation indicates the maturity of synergy management systems. The essential functions and principles of the organization of the system of interaction between control and supervisory services are highlighted, and the concept of complexity and maturity of this system is revealed. Methods of reducing the risks of possible implementation of negative events when coordinating within a self-regulating system for managing the synergy of interaction of subsystems are indicated. It was also emphasized that a mandatory aspect aimed at establishing the work of the SMS is a methodically based assessment of the effectiveness of the management systems for the synergy of interaction between control and supervisory services.
Teaching technosphere safety and environmental culture at a technical university
Authors: Bazaliy R
Published: December 2020

The article discusses the psychological and pedagogical components of the environmental-cultural development of students of technical and humanitarian specialties, as well as cause-and-effect relationships of environmental problems of the largest industrial enterprises. The necessity of using control methods and modern technical means to ensure human security in the modern world is justified. The control effects on the elements of the technosphere space that support the biosphere and technosphere in a qualitative state are analyzed. The article reveals the prospects for common activities between the technical university and companies that are aimed at ensuring the necessary level of technosphere security.
Effectiveness of mergers and acquisitions for agribusiness companies
Authors: Aleksandrov Igor , Fedorova Marina , Parshukov Aleksey
Published: December 2020

This research is aimed at improving the efficiency of evaluating mergers and acquisitions for companies in the agro-industrial complex. When evaluating these transactions, it is necessary to take into account their impact on the environment. The paper analyzes the problems associated with the evaluation of these transactions and identifies ways to improve the evaluation methods. The authors ‘ approach to evaluating acquisitions based on the assessment of changes in the company’s potential is intended to improve the accuracy of the assessment and reduce the risks of revaluation of discounted cash flow from acquisitions. Assessment of potential changes as a result of the implementation of integration projects will allow assessing the economic impact of takeover options, taking into account the environmental consequences for the territory. The proposed approach is aimed at more accurate accounting for changes in intellectual capital of the combined company as a result of integration. Rationalization of the evaluation of the effectiveness of acquisitions will allow owners and management of agro-industrial companies to reduce the risks of making ineffective decisions.
The role of the organic farming system in the development of society
Authors: Kapov S , Kojukhov A , Orlyansky A , Petenev A , Khaustov P
Published: December 2020

The experience of the development and use of the system of dry farming in the Stavropol Territory is considered, the causes and prerequisites for the emergence of an adaptive-landscape farming system are identified. It is shown that the farming systems of the Stavropol Territory are in constant development, they function in conditions of the joint manifestation of water and wind erosion. As a result of degradation, a third of the arable land of the region is in the zone of erosion processes. The expediency of the development of a universal soil protection system of agriculture, aimed at protecting the soil from water and wind erosion, is substantiated.
Efficient land use in the Russian Federation
Authors: Shariapova Emma , Matveeva Marina , Shuvaev Andrei
Published: December 2020

Efficient land use has always been the key direction of Russia’s national policy. Land is the main source of wealth for any country. The idea of efficient land use has been perceived differently depending on a country and historical period. The authors of this paper assume that there are some blank spaces in modern understanding of land use efficiency in Russia. Start, development and termination of land relations are often hampered by the lack of conceptual and categorical framework, which is supposed to be the basis of the land law theory. The present study focuses on searching for weak spots in the land law of the Russian Federation and possible reasons of land misuse. The authors suggest several solutions for advancing the national policy in land matters.
Application of cluster models in forecasting housing construction economic potential in the region
Authors: Sievka Victoria , Shevchuk Igor , Stepanov Aleksey , Tykhankina Oksana
Published: December 2020

The article introduces the first econometric modeling of the needs in new housing construction, reconstruction, capital repairs and finishing of uncompleted construction objects in the region on the basis of cluster models. Forecasting diagrams of gaps between the existing economic potential of housing construction and a normative need in sector housing as well as the need in introducing sector housing to reach mean European standards of housing are plotted.
Auswirkungen der COVID-19-Pandemie auf die Versorgung von HNO-Tumoren – die Patientenperspektive
Authors: Büntzel Jens , Walter Stefanie , Hellmund Herbert , Klein Michael , Hübner Jutta , Vitek Petr , Büntzel Judith , Koscielny Sven , Sesterhenn Andreas M. , Büssing Arndt
Published: December 2020

Fragestellung Die COVID-19-Pandemie hat Auswirkungen auf die Versorgung von Tumorpatienten. Wie erleben Patienten mit Kopf-Hals-Tumoren (KHT) diese Situation und welche Coping-Strategien ergeben sich?

Material und Methode Wir befragten in Studie 1 während des Lockdowns (15.04.–15.05.2020) 433 Tumorpatienten nach ihren Eindrücken/Belastungen (online, standardisiert, anonym). In Studie 2 wurden 292 Patienten nach dem Lockdown (06.05.–10.06.2020) zu ihren wahrgenommenen Veränderungen, Perspektivwechseln und Coping-Strategien mit standardisierten Tools (WHO-5, MLQ-10, GrAw-7) befragt. Für beide Studien analysierten wir die KHT.

Ergebnisse An Studie 1 nahmen 91 Patienten mit KHT teil, in Studie 2 wurden 84 Patienten mit KHT aufgenommen. Studie 1 zeigte im Lockdown einen hohen Druck auf die Mehrheit der Patienten mit KHT (53,8 %). Es waren Ängste bezüglich der eigenen Krankheit (39,6 %), aber auch erwartete physische (24,7 %) und psychische Folgen (21,3 %) der Pandemie. Die soziale Isolation (Besuchsverbot) wurde als ein Hauptproblem (58,5 %) beschrieben. Studie 2 bestätigte diese Belastungen auch nach dem Lockdown. Intensivere Beziehungen in der Familie (60/100 Punkten) sowie eine Zuwendung zu Natur und Stille (58/100 Punkten) wurden als entlastend beschrieben. Eine hohe Inaktivität (MLQ-10) sowie ein vermindertes Wohlbefinden (WHO-5) und eine reduzierte Achtsamkeit (GrAw-7) waren Charakteristiken der KHT, die Ansatzpunkte für eine Stärkung der Resilienz sein können.

Schlussfolgerung Patienten mit KHT haben einen hohen mentalen und psychischen Druck durch die Pandemie. Ihr Blickwinkel ergänzt unsere bisherige Sicht und kann zu einer verbesserten Gesamtversorgung dieser Patienten beitragen.
Synthesis of Diarylethynes from Aryldiazonium Salts by Using Calcium Carbide as an Alkyne Source in a Deep Eutectic Solvent
Authors: Li Zheng , Ma Xiaolong
Published: December 2020

An efficient method for the synthesis of diarylethynes from aryldiazonium salts by using calcium carbide as an alkyne source at room temperature in a deep eutectic solvent is described. The salient features of this protocol are an inexpensive and easy-to-handle alkyne source, a nonvolatile and recyclable solvent, mild conditions, and a simple workup procedure.
Design and experimental validation of a magnetic device for stem cell culture
Authors: Salvador-Clavell Rubén , Rodríguez-Fortún José-Manuel , López Irene , Martín de Llano José Javier , Orús Javier , Sancho-Tello María , Carda Carmen , Doweidar Mohamed H.
Published: December 2020

Cell culture of bone and tendon tissues requires mechanical stimulation of the cells in order to mimic their physiological state. In the present work, a device has been conceived and developed to generate a controlled magnetic field with a homogeneous gradient in the working space. The design requirement was to maximize the magnetic flux gradient, assuring a minimum magnetizing value in a 15 mm × 15 mm working area, which highly increases the normal operating range of this sort of devices. The objective is to use the machine for two types of biological tests: magnetic irradiation of biological samples and force generation on paramagnetic particles embedded in scaffolds for cell culture. The device has been manufactured and experimentally validated by evaluating the force exerted on magnetic particles in a viscous fluid. Apart from the magnetic validation, the device has been tested for irradiating biological samples. In this case, viability of human dental pulp stem cells has been studied in vitro after electromagnetic field exposition using the designed device. After three days of irradiation treatment, cellular microtissues showed a 59% increase in the viable cell number. Irradiated cells did not show morphological differences when compared with control cells.
Noisy consensus dynamics in windmill-type graphs
Authors: Sun Weigang , Li Yifan , Liu Suyu
Published: December 2020

In the present study, two types of consensus algorithms, including the leaderless coherence and the leader–follower coherence quantified by the Laplacian spectrum, are applied to noisy windmill graphs. Based on the graph construction, exact solutions are obtained for the leader–follower coherence with freely assigned leaders. In order to compare consensus dynamics of two nonisomorphic graphs with the same number of nodes and edges, two generalized windmill graphs are selected as the network models and then explicit expressions of the network coherence are obtained. Then, coherences of models are compared. The obtained results reveal distinct coherence behaviors originating from intrinsic structures of models. Finally, the robustness of the coherence is analyzed. Accordingly, it is found that graph parameters and the number of leaders have a profound impact on the studied consensus algorithms.
Flywheel-based traveling-wave thermoacoustic engine
Authors: Biwa T. , Watanabe T. , Penelet G.
Published: December 2020

Motivated by the success of a traveling-wave thermoacoustic engine with a linear load, we built a thermoacoustic engine with a flywheel and a reciprocal piston. The engine has a looped tube with a regenerator and heat exchangers at the ends. When the temperature difference between the ends of the regenerator is increased above a threshold, the flywheel undergoes steady rotation. From simultaneous measurements of the pressure and velocity of the working gas, we demonstrated experimentally that this flywheel-based thermoacoustic engine is a kinematic Stirling engine.
Selective etching of hexagonal boron nitride by high-pressure CF4 plasma for individual one-dimensional ohmic contacts to graphene layers
Authors: Seo Yuta , Masubuchi Satoru , Watanabe Eisuke , Onodera Momoko , Moriya Rai , Watanabe Kenji , Taniguchi Takashi , Machida Tomoki
Published: December 2020

We describe a technique for fabricating one-dimensional Ohmic contacts to individual graphene layers encapsulated in hexagonal boron nitride (h-BN) using CF4 and O2 plasmas. The high etch selectivity of h-BN against graphene (>1000) is achieved by increasing the plasma pressure, which enables etching of h-BN, while graphene acts as an etch stop to protect underlying h-BN. A low-pressure O2 plasma anisotropically etches graphene in the vertical direction, which exposes graphene edges at h-BN sidewalls. Despite the O2 plasma bombardment, the lower h-BN layer functions as an insulating layer. Thus, this method allows us to pattern metal electrodes on h-BN over a second graphene layer. Subsequent electron-beam lithography and evaporation fabricate metal contacts at the graphene edges that are active down to cryogenic temperatures. This fabrication method is demonstrated by the preparation of a graphene Hall bar with a graphite backgate and double bilayer-graphene Hall bar devices. The high flexibility of the device geometries enabled by this method creates access to a variety of experiments on electrostatically coupled graphene layers.
A perspective on semiconductor-based superconducting qubits
Authors: Aguado Ramón
Published: December 2020

Following the demonstration of semiconductor-based Josephson junctions, which are fully tunable by electrical means, new routes have been opened for the study of hybrid semiconductor–superconductor qubits. These include semiconductor-based transmon qubits, single-spin Andreev qubits, and fault-tolerant topological qubits based on Majorana zero modes. In this perspective, we review recent progress in the path toward such hybrid qubit designs. After a short introduction and a brief digression about the historical roadmap that has led to the experimental state-of-the-art, the emphasis is placed on superconducting qubits based on semiconductor nanowires.
Light absorption and nanofocusing on a tapered magnetic metasurface
Authors: Wei Dong , Hu Chai , Chen Mingce , Shi Jiashuo , Luo Jun , Wang Haiwei , Xie Changsheng , Zhang Xinyu
Published: December 2020

A type of metasurface was constructed on a silicon wafer using a nanopatterned magnetic film to achieve ideal light absorption within a wide wavelength range of 3 μm–15 μm. Using the metasurface, the surface electrons could be localized efficiently into an arrayed planar magnetic nanotip and then modulated by configuring the surface architecture to produce remarkable infrared reflectivity variation. A theoretical analysis showed that the excited surface plasmon exhibit stronger electric field components at the common metal-to-air interface. The Tb14Fe68Co18 nanotip array provided more powerful nanofocusing and a lower infrared reflectivity than an array shaped on a traditional aluminum film. By adjusting the structural parameters of the nanorhombus array formed on the TbCo film system, the convergent light spot could be modulated to improve light absorption markedly.
Scenarios of hyperchaos occurrence in 4D Rössler system
Authors: Stankevich N. , Kazakov A. , Gonchenko S.
Published: December 2020

The generalized four-dimensional Rössler system is studied. Main bifurcation scenarios leading to a hyperchaos are described phenomenologically and their implementation in the model is demonstrated. In particular, we show that the formation of hyperchaotic invariant sets is related mainly to cascades (finite or infinite) of nondegenerate bifurcations of two types: period-doubling bifurcations of saddle cycles with a one-dimensional unstable invariant manifold and Neimark-Sacker bifurcations of stable cycles. The onset of the discrete hyperchaotic Shilnikov attractors containing a saddle-focus cycle with a two-dimensional unstable invariant manifold is confirmed numerically in a Poincaré map of the model. A new phenomenon, “jump of hyperchaoticity,” when the attractor under consideration becomes hyperchaotic due to the boundary crisis of some other attractor, is discovered.
Carrier recombination and diffusion in high-purity diamond after electron irradiation and annealing
Authors: Grivickas P. , Ščajev P. , Kazuchits N. , Lastovskii S. , Voss L. F. , Conway A. M. , Mazanik A. , Korolik O. , Bikbajevas V. , Grivickas V.
Published: December 2020

Carrier-transport mechanisms are studied in high-purity diamond irradiated with 6 MeV electrons in the dose range of 1012–1016 cm−2 and annealed at different temperatures up to 1450 °C. Lifetimes and diffusion coefficients are extracted using two pump–probe techniques based on free-carrier absorption and transient-grating principles and then correlated with the corresponding defect evolution from spectroscopic measurements. The neutral monovacancy is revealed as the main carrier recombination center in the as-irradiated diamond, providing bipolar carrier lifetimes of a few nanoseconds at the highest irradiation dose. Carrier-capture cross sections are reduced during annealing as vacancies aggregate into divacancies at ≤1000 °C and extended vacancy clusters at 1450 °C.
Electrical properties of GaN metal-insulator-semiconductor field-effect transistors with Al2O3/GaN interfaces formed on vicinal Ga-polar and nonpolar surfaces
Authors: Ando Yuto , Nagamatsu Kentaro , Deki Manato , Taoka Noriyuki , Tanaka Atsushi , Nitta Shugo , Honda Yoshio , Nakamura Tohru , Amano Hiroshi
Published: December 2020

GaN metal-insulator-semiconductor field-effect transistors (MISFETs) with Ni/Al2O3/GaN gate stack structures formed on a vicinal Ga-polar (c-plane) or nonpolar (m-plane) surface were fabricated. Current–voltage characteristics and carrier transport properties of the channels in the MISFETs with and without post-metallization annealing (PMA) were systematically investigated. GaN layers grown on freestanding substrates with vicinal surfaces led to good transistor behaviors for the m-plane as well as the c-plane. It was found that PMA improves the electron mobility in the MIS channel (μEFF) for both the c- and m-planes, and that μEFF for the m-plane is slightly higher than that for the c-plane both with and without PMA. Temperature dependences of μEFF clarified that μEFF for the m-plane is dominantly limited by phonon scattering, while both Coulomb and phonon scatterings are dominant for the c-plane. Consequently, we achieved high performance for the GaN MISFETs fabricated on the m-plane because of the reduced numbers of Coulomb scattering centers at the Al2O3/GaN interface.
Disorder dependent spin–orbit torques in L1 FePt single layer
Authors: Zheng S. Q. , Meng K. K. , Liu Q. B. , Chen J. K. , Miao J. , Xu X. G. , Jiang Y.
Published: December 2020

We report spin–orbit torques (SOT) in a L10-ordered perpendicularly magnetized FePt single layer, which is significantly influenced by disorder. Recently, self-induced SOT in the L10-FePt single layer has been investigated, which is ascribed to the composition gradient along the normal direction of the film. However, the determined mechanisms for magnetization switching have not been fully studied. With varying growth temperatures, we have prepared FePt single layers with the same thickness (3 nm) but with different disordering. We have found that nearly full magnetization switching only happens in more disordered films, and the magnetization switching ratio becomes smaller with increasing L10 ordering. The method for deriving effective spin torque fields in the previous studies cannot fully explain the spin current generation and self-induced SOT in the L10-FePt single layer. Combined with the magneto-optical Kerr effect microscopy and anomalous Hall effect measurements, we concluded that the disorder should determine the formation of domain walls, as well as the spin current generation.
A fast and large bandwidth superconducting variable coupler
Authors: Chang H.-S. , Satzinger K. J. , Zhong Y. P. , Bienfait A. , Chou M.-H. , Conner C. R. , Dumur É. , Grebel J. , Peairs G. A. , Povey R. G. , Cleland A. N.
Published: December 2020

Variable microwave-frequency couplers are highly useful components in classical communication systems and likely will play an important role in quantum communication applications. Conventional semiconductor-based microwave couplers have been used with superconducting quantum circuits, enabling, for example, the in situ measurements of multiple devices via a common readout chain. However, the semiconducting elements are lossy and furthermore dissipate energy when switched, making them unsuitable for cryogenic applications requiring rapid, repeated switching. Superconducting Josephson junction-based couplers can be designed for dissipation-free operation with fast switching and are easily integrated with superconducting quantum circuits. These enable on-chip, quantum-coherent routing of microwave photons, providing an appealing alternative to semiconductor switches. Here, we present and characterize a chip-based broadband microwave variable coupler, tunable over 4–8 GHz with over 1.5 GHz instantaneous bandwidth, based on the superconducting quantum interference device with two parallel Josephson junctions. The coupler is dissipation-free and features large on-off ratios in excess of 40 dB, and the coupling can be changed in about 10 ns. The simple design presented here can be readily integrated with superconducting qubit circuits and can be easily generalized to realize a four- or more port device.
First-principles study and experimental characterization of metal incorporation in germanium telluride
Authors: Cooley Kayla A. , Keilbart Nathan , Champlain James G. , Ruppalt Laura B. , Walter Timothy N. , Dabo Ismaila , Mohney Suzanne E.
Published: December 2020

Germanium telluride is a well-known phase change material (PCM) used in non-volatile memory cells and radio frequency switches. Controlling the properties of GeTe for improved PCM device performance has sometimes been achieved by doping and/or alloying with metals, often at concentrations greater than 10 at. % and using non-equilibrium methods. Since switching PCMs between the low-resistance crystalline and high-resistance amorphous states requires a heating cycle, the stability of metal-incorporated GeTe (Ge0.5−xMxTe0.5) films is also critical to practical implementation of these materials in electronic and optoelectronic devices. In this work, we use both density-functional theory and experimental characterization methods to probe the solubility and critical properties of Ge0.5−xMxTe0.5 films. Using first-principles calculations, we determine the enthalpy of formation for GeTe with 2.08, 4.17, and 6.25 at. % of Cu, Fe, Mn, Mo, and Ti and show trends between the stability of the Ge0.5−xMxTe0.5 systems and the atomic position, composition, and distribution of the metal atoms in the GeTe matrix. Out of all the studied systems, Mo was the only metal to cluster within GeTe. Analysis of the Ge–Te bond lengths and volumes of the Ge0.5−xMxTe0.5 supercells shows that increasing the atomic concentration (2.08, 4.17, 6.25 at. %) of the different metals causes varied distortions of the crystal structure of GeTe that are accompanied by significant changes in the projected density of states. Computational predictions concerning metal solubility and the effect of metal incorporation on critical properties of GeTe are compared to experimental results in the literature (Cu, Mn, Mo, and Ti) and to transmission electron microscopy and transport data from newly characterized co-sputtered Ge0.5−xFexTe0.5 films. The computational predictions of decreasing solubility (Mn > Cu, Fe > Ti, Mo) shows good agreement with experimental observations (Mn, Cu > Fe > Ti, Mo), and Ge0.5−xFexTe0.5 films exhibited increased crystallization temperatures from pure GeTe.
Ultra-thin Hf0.5Zr0.5O2 thin-film-based ferroelectric tunnel junction via stress induced crystallization
Authors: Goh Youngin , Hwang Junghyeon , Lee Yongsun , Kim Minki , Jeon Sanghun
Published: December 2020

We report on 4.5-nm-thick Hf0.5Zr0.5O2 (HZO) thin-film-based ferroelectric tunnel junctions (FTJs) with a tungsten (W) bottom electrode. The HZO on the W electrode exhibits stable ferroelectricity with a remanent polarization of 14 μC/cm2, an enhanced tunneling electroresistance of 16, and excellent synaptic properties. We found that a large tensile stress was induced on a HZO thin film, owing to a low thermal expansion coefficient of the W bottom electrode. The low thermal expansion coefficient results in the effective formation of an orthorhombic phase, even in an ultra-thin HZO film. This was verified by a comparative study of the electrical characteristics, grazing-angle incidence x-ray diffraction, and residual stress measurement of the HZO film on various bottom electrodes with different thermal expansion coefficients. In addition, this study demonstrates the suitable functions of the FTJ for electronic synapses, such as analog-like resistance transition under various pulse schemes. The fabricated stress-engineered FTJ exhibits an appropriate conductance ratio, linearly modulated long-term potentiation and depression characteristics, and excellent reliability. These characteristics render FTJs ideal electronic devices for neuromorphic computing systems.
Monte Carlo study on domain wall dynamics of J1–J2 triangular spin system
Authors: Liu Ju , Xie Yunlong , Li Xiang , Liu Meifeng , Liu Jun-Ming
Published: December 2020

Monte Carlo simulations are employed to study the model of a triangular Ising antiferromagnet with the next-nearest neighbor ferromagnetic interaction (TIAFF), which can be well mapped to a six-state clock model, and provide a new model to explore the excitation of a topological six-state domain vortex. The TIAFF model retains the symmetry of the lattice and provides more details of vortex excitations and micro dynamics. The crossover of the domain walls in three sub-lattices creates the topological six-state domain vortices. The attractive force between the vortex and the anti-vortex is proportional to the number of domain walls that connect them. The movement of the vortex in the lattice is along the domain walls to avoid creating new defects. Our simulation works reveal that vortices obeying Arrhenius law are difficult to excite at a low temperature. Therefore, the surviving vortices are generated through the Kibble–Zurek mechanism (KZM), which explains the formation of topological solitons in a nonequilibrium system. The existing vortices in the system go through a slow random walk and annihilate in the first-order kinetic process.
Chiroptical spectrophotometer and analytical method for optically anisotropic samples
Authors: Harada Takunori , Manabe Kazusa
Published: December 2020

A new dual-polarization-modulated comprehensive chiroptical spectrophotometer (D-CCS) was successfully developed for recording artifact-free chiroptical circular dichroism (CD) and circularly polarized luminescence (CPL) spectra of optically anisotropic samples on the basis of the Stokes–Mueller matrix approach. The D-CCS includes an additional second photoelastic modulator (PEM) set in front of the sample and a second PEM controller being driven independently of the first PEM driver, which are essential for obtaining artifact-free chiroptical signals of optically anisotropic samples containing non-chiral signals, i.e., linear birefringence, linear dichroism, and linearly polarized luminescence. The theory and implementation of the method are described, and examples of its application to CD and CPL samples with macroscopic anisotropies are provided. An important advantage of the developed D-CCS is that it reduces the essential step of sample rotation in the plane, including the gravitational axis, to obtain artifact-free CD signals. Consequently, this dual-polarization method shortens the time required to obtain artifact-free CD signals by half and could be very effective for samples, such as high fluidity samples, gels, liquid crystals, and supramolecules in solution, for which artifact-free chiroptical signals are difficult to obtain using conventional methods.
AC magnetometry with active stabilization and harmonic suppression for magnetic nanoparticle spectroscopy and thermometry
Authors: Bui Thinh Q. , Tew Weston L. , Woods Solomon I.
Published: December 2020

Magnetic nanoparticle (MNP) thermometry based on magnetic particle spectroscopy is explored as a potential approach for realizing in situ temperature measurement of 3D objects. MNP thermometry relies on the nonlinear magnetization response to an AC drive field. This nonlinear response has functional dependence on frequency and temperature, governed by the complex magnetization dynamics of MNPs suspended in solution. In this work, we introduce our approach for accurate and precise AC magnetization measurements using actively stabilized drive fields ranging from direct current to 10 kHz. To isolate the harmonic response of MNPs from the drive field, we also perform active cancelation to reach drive field suppression up to 120 dB. Active stabilization and cancelation are utilized for real-time, sensitive measurements of AC magnetization of commercial samples, with stability on the timescale of hours. Initial results for MNP thermometry are demonstrated using this technique, and we achieved a total temperature uncertainty of 410 mK and 170 mK at 100 ms and 10 s integration time, respectively.
Observation of quantum interference conductance fluctuations in metal rings with strong spin–orbit coupling
Authors: Ramos R. , Makiuchi T. , Kikkawa T. , Daimon S. , Oyanagi K. , Saitoh E.
Published: December 2020

We investigated the magnetotransport properties of mesoscopic platinum nanostructures (wires and rings) with sub-100 nm lateral dimensions at very low temperatures. Despite the strong spin–orbit interaction in platinum, oscillation of the conductance as a function of the external magnetic field due to quantum interference effects was found to appear. The oscillation was decomposed into Aharonov–Bohm periodic oscillations and aperiodic fluctuations of the conductance due to a magnetic flux piercing the loop of the ring and the metal wires forming the nanostructures, respectively. We also investigated the magnetotransport under different bias currents to explore the interplay between electron phase coherence and spin accumulation effects in strong spin–orbit conductors.
A ten-dimensional quantum dynamics model for the X + YCAB2 reaction: Application to H + CH4 reaction
Authors: Liu Rui , Song Hongwei , Qi Ji , Yang Minghui
Published: December 2020

The exact description of the prototypical X + CH4 reactions in the framework of quantum mechanics is a long-standing challenge in chemical reaction dynamics. A number of reduced-dimensional models have been developed and advanced our understanding of polyatomic chemical reactivity. Here, we propose a new ten-dimensional (10D) quantum dynamics model for the kind of X + YCAB2 reaction. The new model is an extension of our previous eight-dimensional (8D) model for the X + YCZ3 reaction. In this 10D model, AB2 holds C2v symmetry and the group CAB2 is assumed to keep Cs symmetry, which gives a better description of the rocking mode of methane than the previous 8D model. The reaction dynamics of H + CH4 → H2 + CH3 is first investigated using this model. The calculations showed that the rocking mode has a similar reaction efficiency to the umbrella mode. For the degenerate asymmetric stretching mode, the averaged efficiency is comparable to that of the symmetric stretching mode.
An AlGaN tunnel junction light emitting diode operating at 255 nm
Authors: Pandey A. , Gim J. , Hovden R. , Mi Z.
Published: December 2020

We report on the demonstration of high-performance tunnel junction deep ultraviolet (UV) light-emitting diodes (LEDs) by using plasma-assisted molecular beam epitaxy. The device heterostructure was grown under slightly Ga-rich conditions to promote the formation of nanoscale clusters in the active region. The device operates at ∼255 nm with a maximum external quantum efficiency of 7.2% and wall-plug of 4%, which are nearly one to two orders of magnitude higher than those of previously reported tunnel junction devices operating at this wavelength. The devices exhibit highly stable emission, with a nearly constant emission peak with increasing current, due to the strong charge carrier confinement related to the presence of Ga-rich nanoclusters. Efficiency droop, however, is observed at relatively low current densities. Detailed temperature-dependent measurements suggest that the presence of efficiency droop of deep UV LEDs is largely due to electron overflow.
Augmentation of Wind Farm Fault Ride Through by DFIG-based Variable Speed Wind Generator
Authors: Okedu Kenneth
Published: December 2020

Recent wind farm grid codes require wind generators to ride through voltage sags, which means that normal power production should be re-initiated once the nominal grid voltage has been recovered. This chapter proposes a new control strategy using DFIGs (Doubly Fed Induction Generators) for stabilizing a wind farm composed of DFIGs and IGs (Induction Generators). Simulation analysis by using Power System Computer Aided Design and Electromagnetic Transient Including DC (PSCAD/EMTDC) shows that the DFIGs can effectively stabilize the IGs and hence the entire wind farm through the proposed control scheme by providing sufficient reactive power to the system.
New Protection Scheme of DFIGs
Authors: Okedu Kenneth
Published: December 2020

This chapter proposes a control strategy of doubly fed induction generators (DFIGs) with new protection schemes for enhancing fault ride through capability of wind farms composed of DFIGs and induction generators (IGs). Since the DFIGs will be stressed or overloaded in the process of stabilizing the wind farm during a grid fault, it is paramount to consider a protection scheme for the DFIG, in order to protect its power converters. Two schemes, the DC-link chopper-controlled braking resistor with the supplementary rotor current (SRC) control of the rotor side converter of the DFIG and series dynamic braking resistor (SDBR) connected to the stator of the DFIG, are proposed. Merits and drawbacks of both schemes are highlighted and compared. The simulation results in Power System Computer Aided Design and Electromagnetic Transient Including DC (PSCAD/EMTDC) show that the two proposed schemes can eliminate the need for an expensive crowbar switch in the rotor circuit, because either could limit the rotor current of the DFIG within its nominal value during a grid fault. Finally, considering the overall system performance, the latter is recommended.
Stability Enhancement using a DC-Chopper, Crowbar, and FACTS Device
Authors: Okedu Kenneth
Published: December 2020

A fixed speed wind turbine generator system that uses induction generator as a wind generator has the stability problem similar to a synchronous generator. On the other hand, a doubly fed induction generator (DFIG) has the flexibility to control its real and reactive powers independently while being operated in variable speed mode. This chapter focuses on a scheme where an Induction Generator (IG) is stabilized by using DFIG during grid fault. In that case, DFIG will be heavily stressed and a remedy should be found to protect the frequency converter as well as to allow the independent control of real and reactive powers without losing the synchronism. For that purpose, a crowbar protection switch or DC-link protecting device can be considered. This chapter presents a comparative study between two protective schemes, a crowbar circuit connected across the rotor of the DFIG and a protective device connected in the DC-link circuit of the frequency converter. Simulation analysis by using Power System Computer Aided Design and Electromagnetic Transient Including DC (PSCAD/EMTDC) shows that both schemes could effectively protect the DFIG, but the latter scheme is superior to the former, because of less circuitry involved.
Parallel Integrated Capacitor and Modified Modulated Braking Resistor
Authors: Okedu Kenneth
Published: December 2020

Wind energy has a dilute, unpredicted nature, hence, it creates a challenge for effective and well managed operation of wind turbines connected to the grid network. There is a mandatory requirement for wind turbines to fulfil standard grid codes for stability control. In this chapter, a new scheme consisting of parallel connected capacitor with the DC-link scheme of the Doubly Fed Induction Generator (DFIG) wind turbine is proposed. Scenarios of integrating different sizes of the parallel capacitor at the grid side converter of the DFIG were investigated, in order to know the optimum size for better transient performance of the wind generator. For effective comparative study, the same constant wind speed was used for the considered scenarios in the investigation of the wind generator transient performance. The presented results in Power System Computer Design and Electromagnetic Transient Including DC show that the proposed parallel capacitor based DC-link scheme power converter improves the grid voltage response and the variables of the wind generator during severe grid fault condition. Furthermore, a proposed modulated series dynamic braking resistor (MSDBR) was used to improve the overall performance of the capacitor scheme. The results of the proposed MSDBR were compared to the traditional scheme.
Determination of the Most Effective Switching Signal and Position of Braking Resistor
Authors: Okedu Kenneth
Published: December 2020

The Series Dynamic Braking Resistor (SDBR) helps in the post fault recovery of the wind generator system. This chapter investigates the best location of the SDBR in the Doubly Fed Induction Generator (DFIG) architecture, considering the best switching signal of the SDBR. In this chapter, three signals were investigated in switching the SDBR during transient conditions of the DFIG wind generator; the DC-link voltage, rotor current and grid voltage respectively. Also, three locations were considered in connecting the SDBR in the DFIG system; the stator, rotor and grid side converter respectively. Furthermore, the optimum size and best insertion time of the SDBR were investigated based on the most effective performance of the SDBR scheme considering its switching signal and position in the DFIG system. Simulations were run in Power System Computer Aided Design and Electromagnetic Transient Including DC (PSCAD/EMTDC). The results show that when the SDBR is connected at the stator of the DFIG wind generator and a grid voltage signal is used in its actuation, considering a fast insertion time and short duration of operation, the DFIG wind generator variables were quickly recovered during transient conditions.
Effect of zeolite administration on nitrogen metabolism and excretion in lactating dairy cows offered pasture herbage
Authors: Stelwagen K. , Beukes P. C. , Hemmings C.
Published: December 2020

Context
Due to high protein concentrations in pastures, dairy cows offered a pasture-based diet often consume excess nitrogen (N), which leads to high ruminal ammonia concentrations and excessive urinary N excretion, thereby contributing to pasture N leaching.

Aims
To study the effect of administration of natural zeolite on ruminal pH and ammonia production and N excretion in lactating cows offered an all-pasture herbage diet.

Methods
In a metabolism stall trial using a crossover trial design, rumen-cannulated Friesian cows were administered either zero (Control, n = 16) or 400 g/day of zeolite (Zeolite; n = 16). Zeolite was divided into two equal portions and administered directly into the rumen before feeding fresh-cut ryegrass-clover herbage at 07:30 and 15:30 hours. Cows were kept in the metabolism stalls for two measurement periods of 5 days each, with each period preceded by an adaptation/washout period of 2 weeks. Feed intake, milk yield, total urine and faecal outputs were measured daily. During the last day of each measurement period ruminal fluid and blood were frequently sampled.

Key results
Zeolite administered at 2.2% of dry matter intake (DMI) did not affect daily DMI. Moreover, milk yield and milk composition, including milk urea, were not affected by zeolite administration. In cows administered zeolite the mean 24-h ruminal ammonia concentration was reduced by 1.5 mmol/L (9%) and the ruminal pH pattern in zeolite-administered cows over 24 h was above that of Control cows, but the overall effect on pH was not significant. Zeolite had no effect on plasma urea, total urinary N excreted or faecal N. Of the total N excreted across the groups, 21.7, 50.6 and 27.7% was excreted into milk, urine and faeces respectively.

Conclusions
Zeolite administration reduced ruminal ammonia concentration but this did not result in reduced urinary N excretion in dairy cows offered pasture.

Implications
Dietary supplementation with zeolite may help to improve aspects of ruminal function in cows consuming pasture, but is unlikely to be an effective tool for reducing N leaching from pastures.
Mitophagy-mediated adipose inflammation contributes to type 2 diabetes with hepatic insulin resistance
Authors: He Feng , Huang Yanrui , Song Zhi , Zhou Huanjiao Jenny , Zhang Haifeng , Perry Rachel J. , Shulman Gerald I. , Min Wang
Published: December 2020

White adipose tissues (WAT) play crucial roles in maintaining whole-body energy homeostasis, and their dysfunction can contribute to hepatic insulin resistance and type 2 diabetes mellitus (T2DM). However, the mechanisms underlying these alterations remain unknown. By analyzing the transcriptome landscape in human adipocytes based on available RNA-seq datasets from lean, obese, and T2DM patients, we reveal elevated mitochondrial reactive oxygen species (ROS) pathway and NF-κB signaling with altered fatty acid metabolism in T2DM adipocytes. Mice with adipose-specific deletion of mitochondrial redox Trx2 develop hyperglycemia, hepatic insulin resistance, and hepatic steatosis. Trx2-deficient WAT exhibited excessive mitophagy, increased inflammation, and lipolysis. Mechanistically, mitophagy was induced through increasing ROS generation and NF-κB–dependent accumulation of autophagy receptor p62/SQSTM1, which recruits damaged mitochondria with polyubiquitin chains. Importantly, administration of ROS scavenger or NF-κB inhibitor ameliorates glucose and lipid metabolic disorders and T2DM progression in mice. Taken together, this study reveals a previously unrecognized mechanism linking mitophagy-mediated adipose inflammation to T2DM with hepatic insulin resistance.
Determination of the reaction coefficient in a time dependent nonlocal diffusion process
Authors: Ding Ming-Hui , Zheng Guang-Hui
Published: December 2020

This paper investigates the inverse reaction coefficient problem for a time dependent nonlocal diffusion equation by utilizing the nonlocal flux measurement from an accessible part of region, which is a continuation and an extension of our recent work (Zheng and Ding 2020 Inverse Problems
36 035006). The uniqueness of inverse reaction coefficient problem is proved. The variational regularization method is proposed to overcome the ill-posedness of inverse problem, and an alternating iteration method is adopted to automatically select regularization parameters. Furthermore, we use Laplace approximation method to capture the statistics information of the solution. In particular, we prove the lower bound of confidence width is rigorously estimated to characterize the reliability of the method. Finally, numerical results indicate that the proposed method could yield an accurate estimate and efficient uncertainty quantification of the solution.
Effect of band bending on topological surface transport of Bi2Te3 single crystal
Authors: Kumar Devendra , Lakhani Archana
Published: December 2020

Understanding the effect of surface to bulk coupling on topological surface states is important for harnessing the topological insulators for low dissipation electronics and quantum technologies. Here we investigate this effect on a low bulk carrier density Bi2Te3 single crystal using magnetoresistance, Hall resistivity, and Shubnikov–de Haas oscillations. Our results show the presence of high mobility surface bands and low mobility bulk bands. The surface states exhibit ambipolar transport without any gating. The mobility of surface states strongly depend on the nature of band bending, the upward band bending with holes as surface charge carrier exhibit large mobility while the downward band bending with electrons as surface charge carriers exhibit low surface mobility. The large mobility of surface Dirac holes is related to low surface defect density and small cyclotron mass. We also observe large magnetoresistance ∼285% due to multichannel quantum coherent transport in the bulk.